JP6659838B2 - Painted metal plate - Google Patents

Description

  The present invention relates to a coated metal plate, and more particularly to a coated metal plate capable of increasing whiteness while suppressing a decrease in glossiness. This application claims priority based on Japanese Patent Application No. 2017-003484 for which it applied to Japan on January 12, 2017, and uses the content here.

  Painted metal sheets are used for electric machinery and building materials. In recent years, pre-coated steel sheets that have been colored before processing are often used instead of post-coated steel sheets that are painted after processing. In a general pre-coated steel sheet, a zinc-plated steel sheet is used as an original sheet, and the original sheet is subjected to various processes such as pretreatment (chemical conversion treatment, etc.), lower layer paint application, baking, upper layer paint application, baking, etc. A coating is formed.

  Conventionally, in a precoated steel sheet, a chromium compound has been added to a chemical conversion treatment film or a lower layer coating film in order to improve corrosion resistance. However, due to recent environmental regulations, switching to a chromate-free precoated steel sheet that does not use a chromium compound at all is progressing. In this chromate-free precoated steel sheet, a rust-preventive pigment is added to the lower coating film of the coating film having a plurality of layers in order to improve corrosion resistance without containing a chromium compound. Searches for useful compounds, mainly inorganic compounds, as rust preventives, and studies on their practical use are underway. Examples of the rust preventive include calcium-modified silica, aluminum phosphate, and magnesium phosphate.

  Further, different performances are required for each layer of the chemical conversion coating and the coating film of the precoated steel sheet. For example, the chemical conversion coating has good adhesion, the lower coating has good adhesion and corrosion resistance, and the upper coating has good design, scratch resistance, stain resistance, chemical resistance, solvent resistance, etc. Required respectively.

  In addition, a precoated steel sheet is generally manufactured by a painting process that involves many steps to form a coating film, as described above, unlike a process of forming a plating layer. In recent years, with regard to pre-coated steel sheets, studies have been made on thinning the coating film, reducing the number of coating layers, or reducing the number of coating layers to one layer from the viewpoint of reducing manufacturing costs and manufacturing steps.

  For example, Patent Literature 1 discloses a resin-coated metal sheet having a predetermined composite plating film layer, a chemical conversion coating layer, and a resin coating layer and having excellent corrosion resistance and workability.

  Patent Document 2 discloses a precoated steel sheet having a base treatment layer containing at least one surface of an organic resin, titanium oxide and tannin or tannic acid, and a coating layer containing titanium oxide as a white pigment on at least one surface of the steel sheet. .

  Patent Literature 3 discloses a precoated steel sheet having a zinc-based plating layer, a chemical conversion coating, and a white coating film, wherein the white coating film contains titanium oxide and calcium-modified silica as a rust preventive pigment.

JP-A-8-49084 Japanese Patent Laid-Open No. 2000-212767 International Publication No. 2014/175420

  The coated metal plates described in Patent Documents 1 to 3 described above have been studied on the assumption that the coating film is white. A white pigment represented by titanium oxide generally increases the whiteness of a coating film by irregularly reflecting incident light. On the other hand, these white pigments reduce the specular reflection component with respect to incident light, so that the glossiness of the coating film tends to decrease. Thus, whiteness and glossiness are usually in a trade-off relationship.

  Further, as described above, in the production of a precoated steel sheet, thinning of the coating film on the precoated steel sheet and reduction in the number of coating layers are being studied from the viewpoint of omitting processes and costs. However, when the thickness of the coating film is reduced or the number of layers of the coating film is reduced, it is difficult to conceal the underlying color by the coating film, so that the whiteness of the precoated steel sheet is reduced. In particular, when the base color is a color that easily absorbs incident light, both the irregular reflection component and the regular reflection component with respect to the incident light become small, so that it is difficult to simultaneously increase whiteness and glossiness as a precoated steel sheet.

  Further, even in the case of a precoated steel sheet having a colored coating film instead of a white coating film, a white pigment may be added for the purpose of toning, so as to increase the whiteness of the coating film. Even in such a case, when a white pigment is added to the coating film, the glossiness of the coating film is reduced for the above-described reason.

  The present invention has been made in view of the above problems, and has as its object to provide a coated metal plate that can increase whiteness while suppressing a decrease in gloss.

  The present inventors have conducted intensive studies to solve the above-described problems, and as a result, by arranging a flat portion and a plurality of concave portions on the surface of the coating film, to increase the whiteness of the coating film while suppressing a decrease in glossiness. I found that I can do it.

The gist of the present invention is as follows.
(1) A coated metal plate according to one embodiment of the present invention includes a metal plate and a coating film located on at least one plate surface of the metal plate, wherein the coating film is disposed on an outermost surface. , and having a flat portion and a plurality of recesses on its surface, the average diameter of the recess is a 0.20～4.0Myuemu, average depth of the recess, Ri 20~200nm der, the coating the number density of the recesses relative to the surface of the membrane, a 1 × ¹⁰ 4 ~1 × ^{10 6} cells / mm ^2, the average surface roughness Ra of the flat portion, Ru der less than 20 nm.
( 2 ) In the coated metal plate according to the above (1) , an area ratio of the concave portion to the surface of the coating film may be 1 to 40%.
( 3 ) In the coated metal plate according to any one of (1) to ( 2 ), an area ratio of the concave portion to the surface of the coating film may be 20 to 40%.
(4) In the coated metal plate according to any one of the above (1) to (3), when viewed the coating film from a thickness direction, the contour length L ₁ of the concave portion, the circle of the recess The number of the concave portions satisfying 1.0 ≦ L ₁ / L ₂ ≦ 3.0 with the circumferential length L ₂ obtained from the equivalent diameter may be 95% or more in number%.
( 5 ) In the coated metal plate according to any one of (1) to ( 4 ), the concave portion may have a convex portion on an inner surface thereof.
( 6 ) In the coated metal plate according to the above ( 5 ), the average diameter of the projections may be 0.1 to 1.5 μm, and the average height of the projections may be 5 to 90 nm. .
The coated metal plate according to any one of (7) above (1) to (6), the flat portion area ratio of with respect to the surface of the coating film may be 60 to 99%.
( 8 ) In the coated metal plate according to the above ( 7 ), an area ratio of the flat portion to the surface of the coating film may be 60 to 80%.
( 9 ) In the coated metal plate according to any one of (1) to ( 8 ), the thickness of the coating film may be 8.0 to 30 μm.
( 10 ) In the coated metal plate according to any one of the above (1) to ( 9 ), the coating has a white pigment, and the content of the white pigment with respect to the coating is 40 to 70% by mass. It may be.
( 11 ) In the coated metal plate according to any one of the above (1) to ( 10 ), the coating film has a phosphoric acid-based rust-preventive pigment, and the phosphoric acid-based rust-proofing pigment with respect to the coating film. The content may be 1 to 15% by mass.
( 12 ) In the coated metal plate according to any one of the above (1) to ( 11 ), a chemical conversion treatment layer may be further provided between the metal plate and the coating film.

  According to the above aspect of the present invention, it is possible to provide a coated metal plate capable of increasing whiteness while suppressing a decrease in glossiness.

It is a cross section showing a painted metal plate concerning one embodiment of the present invention. FIG. 2 is a schematic plan view of a coated metal plate according to the embodiment. It is a cross section showing a modification of a painted metal plate concerning this embodiment. It is a cross section showing a modification of a painted metal plate concerning this embodiment. It is a mimetic diagram about a manufacturing method of a paint metal plate concerning this embodiment, and is a mimetic diagram showing a method of forming a coat by making a solvent and paint contact. It is a graph which shows the relationship between the whiteness and glossiness of the white coating film of a coating metal plate. It is a scanning electron micrograph of the surface of the coating metal plate which has a concave part in a coating film. It is an atomic force microscope image of the surface of the coating metal plate which has a concave part in a coating film. It is an atomic force microscope image of the surface of the coating metal plate which has a concave part in a coating film. It is a scanning electron micrograph of the surface of the coating metal plate which does not have a recess in a coating film.

  Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to only the configuration disclosed in the present embodiment, and various changes can be made without departing from the spirit of the present invention. Further, the numerical limit range described below includes a lower limit value and an upper limit value. Numerical values indicating “exceeding” or “less than” do not fall within the numerical range.

  In the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted. Further, in the drawings used in the following description, for the sake of simplicity, in order to make the characteristics of the present embodiment easy to understand, a portion that is a main part may be enlarged and shown, and the dimensional ratio of each component may be different from the actual one. Not necessarily the same.

<1. Painted metal plate>
First, a painted metal plate according to the present embodiment will be described with reference to FIGS. FIG. 1 is a schematic cross-sectional view of a coated metal plate according to the present embodiment, and FIG. 2 is a schematic plan view of the coated metal plate.

  FIG. 1 shows a cut surface in which the plate thickness direction and the cutting direction are parallel. The coated metal plate 1 shown in FIG. 1 includes a metal plate 11, a chemical conversion treatment layer 13 disposed on one surface of the metal plate 11, and a coating film 15 disposed on the chemical conversion treatment layer 13. The metal plate 11 is a substrate of the painted metal plate 1. Examples of the metal plate 11 include various metal plates such as steel (iron-based alloy), aluminum and its alloys, and magnesium and its alloys.

(Metal plate 11)
Examples of the steel sheet used for the metal sheet 11 include well-known plated steel sheets such as a zinc-based plated steel sheet and an aluminum-based plated steel sheet. The base steel sheet of the plated steel sheet may be a normal steel sheet (carbon steel) or a steel sheet (alloy steel) containing an additional element such as chromium. However, in the case of press forming, the base material steel sheet is preferably a steel sheet in which the type and amount of the added element and the metal structure are appropriately controlled so as to have a desired formability.

  Examples of the zinc-based plating layer of the zinc-based plated steel sheet include, for example, a plating layer made of zinc, zinc, and at least one of aluminum, cobalt, tin, nickel, iron, chromium, titanium, magnesium, manganese, zirconium, and vanadium. Known plating layers such as a composite plating layer and various zinc-based alloy plating layers containing other metal elements or nonmetal elements (for example, a quaternary alloy plating layer with zinc, aluminum, magnesium, and silicon) can be given. . However, other alloy components are not particularly limited, except that the zinc-based plating layer contains most zinc.

  In addition, these zinc-based plating layers further include, as a small amount of different metal elements or impurities, cobalt, molybdenum, tungsten, nickel, titanium, chromium, aluminum, manganese, iron, magnesium, lead, bismuth, antimony, tin, It may contain copper, cadmium, arsenic, etc., or may contain inorganic substances such as silica, alumina, titania and the like. When the zinc-based plating layer is formed by an electroplating method, a plating solution for forming the plating layer may contain an organic additive (for example, diallylamine polymer or diallyldialkylammonium), and the formed plating layer It may contain carbon originating from these organic additives.

  Specifically, examples of the galvanized steel sheet used for the metal sheet 11 include a galvanized steel sheet, an electrogalvanized steel sheet, a zinc-nickel alloy-coated steel sheet, and an alloyed hot-dip galvanized steel sheet.

  Examples of the aluminum-based plating layer of the aluminum-based plated steel sheet include a plating layer made of aluminum, an alloy plating layer of aluminum and at least one of silicon, zinc, and magnesium (for example, an alloy plating layer of aluminum and silicon, aluminum Known plating layers such as an alloy plating layer of zinc, and a ternary alloy plating layer of aluminum, silicon, and magnesium). However, other alloy components are not particularly limited except that the aluminum-based plating layer contains aluminum most.

  In addition, the zinc-based steel sheet and the aluminum-based steel sheet used for the metal sheet 11 are combined with other types of plating layers (for example, an iron plating layer, an alloy plating layer of iron and phosphorus, a nickel plating layer, a cobalt plating layer, and the like). It may be a multi-layer plated steel sheet.

  The method for forming the plating layer of the plated steel sheet is not particularly limited. For example, in forming a plating layer, electroplating, electroless plating, hot-dip plating, vapor deposition plating, dispersion plating, or the like can be used. The formation of the plating layer can be performed by any of a continuous method and a batch method. Further, after the plating layer is formed, a process such as a zero spangle process which is a process for uniform appearance, an annealing process which is a process for modifying the plating layer, and a temper rolling for adjusting the surface state or the material may be performed.

(Chemical conversion treatment layer 13)
The chemical conversion treatment layer 13 may be disposed so as to be interposed between the metal plate 11 and the coating film 15 as necessary. The chemical conversion treatment layer 13 is a film formed by performing a chemical conversion treatment on the surface (plate surface) of the metal plate 11. The chemical conversion treatment layer 13 improves the adhesion between the metal plate 11 and the coating film 15 by being interposed between the metal plate 11 and the coating film 15.

  Such a chemical conversion treatment layer 13 is not particularly limited, for example, silica, a silane coupling agent, tannin, tannic acid, a zirconium compound, and at least one selected from the group consisting of a titanium compound, a polyester resin, A film formed using a composition (chemical conversion treatment solution) containing at least one selected from the group consisting of urethane resins, epoxy resins, and acrylic resins. The chemical conversion treatment layer 13 composed of such a film is particularly excellent in the adhesion between the metal plate 11 and the coating film 15.

The attached amount of the chemical conversion treatment layer 13 is not particularly limited, and is preferably 10 to 800 mg / m ² , and more preferably 100 to 700 mg / m ² . When the adhesion amount of the chemical conversion treatment layer 13 is within the above range, it is possible to prevent the chemical conversion treatment layer 13 from cohesion failure while sufficiently improving the corrosion resistance and the coating film adhesion. Further, the thickness of the chemical conversion treatment layer 13 is not particularly limited, and may be, for example, 0.005 to 0.7 μm.

(Coating film 15)
The coating film 15 is a film which is located on at least one plate surface of the metal plate 11 and forms the outermost surface of the coated metal plate 1. As shown in FIGS. 1 and 2, the coating film 15 has a flat portion 151 and a plurality of concave portions 153 on the surface (film surface). As shown in FIG. 2, the plurality of recesses 153 are irregularly formed on the surface of the coating film 15, forming so-called substantially circular dimples.

  Since the coating film 15 has a plurality of concave portions 153 that contribute to whiteness in addition to the flat portion 151 that contributes to glossiness, it is possible to increase whiteness while suppressing a decrease in glossiness. In particular, when the coating film 15 is a white coating film, the glossiness and whiteness of the coating film 15 can be made sufficiently high.

  The reason why the above-described effect is obtained by the coating film 15 is unknown at present, but the following effects are considered.

  First, a conventional coating film will be described. In a coating film having a flat portion without a concave portion, a specular component with respect to incident light is large due to the flat portion, and thus the glossiness is a high value. However, since the irregular reflection component is reduced accordingly, the whiteness becomes a low value. On the other hand, if a white pigment is added to the coating film in order to increase the whiteness of such a coating film, the diffuse reflection component with respect to the incident light increases over the entire surface (film surface) of the coating film. Has a high value. However, along with this, the specular reflection component becomes small in the entire region of the film surface, so that the glossiness becomes a low value. As described above, conventionally, whiteness and glossiness have a trade-off relationship.

  Next, the coating film 15 of the coated metal plate 1 according to the present embodiment will be described. The coating film 15 has a flat portion 151 and a plurality of concave portions 153. In the concave portion 153, incident light can be irregularly reflected by the geometrical action of the concave portion 153. Therefore, separately from the function of irregularly reflecting the incident light by the white pigment, the presence of the concave portion 153 can increase the whiteness of the coating film 15. In addition, in the coated metal plate 1 according to the present embodiment, it is not necessary to excessively add a white pigment in order to increase the whiteness of the coating film 15, so that the incident light is corrected in the flat portion 151 of the coating film 15. The effect of reflecting can be maintained. Therefore, in the coated metal plate 1 according to the present embodiment, the whiteness of the coating film 15 can be increased by the presence of the concave portion 153, and the glossiness of the coating film 15 can be maintained by the presence of the flat portion 151. As a result, the coating film 15 is a coating film in which the whiteness is increased and the decrease in gloss is suppressed, as compared with the conventional coating film in which the concave portions 153 are not present.

  In the coated metal plate 1 according to the present embodiment, the color of the coating film 15 is not particularly limited. For example, when the coating film 15 is a white coating film, the whiteness and glossiness of the coating film 15 can be simultaneously increased. On the other hand, when the coating film 15 is a colored coating film, the presence of the concave portions 153 makes the coating film 15 white without adding a white pigment excessively, that is, while avoiding a decrease in the glossiness of the coating film 15. Can be given.

  The average diameter of the recess 153 is set to 0.20 to 4.0 μm. When the average diameter of the concave portion 153 is less than 0.20 μm, the amount of light incident on the concave portion 153 is reduced, so that the incident light cannot be sufficiently diffused. The lower limit of the average diameter of the concave portion 153 is 0.7 μm, and preferably 0.9 μm. On the other hand, when the average diameter of the concave portion 153 exceeds 4.0 μm, the geometrical effect of the concave portion 153 is reduced, so that the incident light cannot be sufficiently diffusely reflected. The upper limit of the average diameter of the recess 153 is 3.0 μm, and preferably 2.5 μm.

  In addition, the concave portion 153 can be specified as follows. First, using an atomic force microscope (AFM), the height data of surface irregularities in a 10 × 10 μm sample area including the entire contour of the concave portion 153 is 512 points in a horizontal direction × 512 points in a vertical direction (a total of 262144 points). ) Measure and record. The data of 110 points is extracted from the highest of the height data, and the arithmetic mean value of 100 points excluding the top 10 points (10 points of high data) is set as the reference height. It is classified into a point where the depth distance from the reference height toward the metal plate 11 is 10 nm or less and a point where the depth distance exceeds 10 nm. Then, an aggregated region in which a point exceeding 10 nm is formed in 99% or more is defined as a concave portion 153. It is to be noted that the aggregation region that is the concave portion 153 may include less than 1% of points having a depth distance of 10 nm or less as abnormal points. In addition, the concave portion 153 is a collective region including at least 60 points having a size exceeding 10 nm.

Among the recesses 153 specified as described above, the area S of the recess 153 including the entire contour is obtained by image processing. The area S is the area of the concave portion 153 when the coating film 15 is viewed from the thickness direction. Using the area S, the diameter D (circle equivalent diameter) of the concave portion 153 when the concave portion 153 is regarded as a perfect circle is obtained by the following equation.
D = 2 × (S / π) ^0.5 (π: Pi)
The above-mentioned 10 × 10 μm AFM observation is performed at least 20 places at the center of the plate surface excluding a range of 100 mm from the outermost edge (outer edge in the plate width direction) of the coated metal plate 1, and each obtained from each observation surface The arithmetic average value of the diameter D of the concave portion 153 is defined as the average diameter of the concave portion 153.

  The average depth of the recess 153 is set to 20 to 200 nm. If the average depth of the concave portion 153 is less than 20 nm, the geometrical effect of the concave portion 153 will be small, so that the incident light cannot be sufficiently diffusely reflected. The lower limit of the average depth of the recess 153 is 40 nm, and preferably 70 nm. On the other hand, when the average depth of the concave portion 153 exceeds 200 nm, the emission of light from the inside of the concave portion 153 to the outside is restricted in shape, so that the incident light cannot be sufficiently diffusely reflected. The upper limit of the average depth of the recess 153 is 150 nm, and preferably 120 nm.

  The depth of each recess 153 is calculated by extracting 110 data from the deepest of the depth data in the recess 153 specified by the above-described method, and excluding the top 10 points (10 deep data points). It can be determined by the height difference between the arithmetic average value and the reference height. In addition, the above-mentioned 10 × 10 μm AFM observation was performed at at least 20 places at the center of the plate surface excluding the range of 100 mm from the outermost edge of the coated metal plate 1, and the depth of each recess 153 obtained from each observation surface Is defined as the average depth of the concave portion 153.

  Further, as shown in FIG. 1, the concave portion 153 may have a convex portion 155 on an inner surface thereof. When the concave portion 153 has the convex portion 155, incident light can be preferably diffusely reflected by the geometrical action of the convex portion 155. Therefore, it is possible to preferably impart whiteness to the coating film 15 without excessively adding the white pigment, that is, while avoiding a decrease in the glossiness of the coating film 15. In FIG. 2, illustration of the protrusion 155 is omitted to make the drawing easier to see.

  The average diameter of the protrusion 155 is not particularly limited. For example, when the average diameter of the protrusions 155 is 0.1 to 1.5 μm, it is more preferable that the incident light can be irregularly reflected. The lower limit of the average diameter of the protrusion 155 is 0.2 μm, and preferably 0.3 μm. In addition, the upper limit of the average diameter of the protrusion 155 is 1.0 μm, and preferably 0.7 μm.

  Further, the average diameter of the convex portions 155 is preferably 1.5 to 60% of the average diameter of the concave portions 153. The lower limit of the ratio of the average diameter of the convex portions 155 to the average diameter of the concave portions 153 is 10%, and preferably 20%. The upper limit of the ratio of the average diameter of the convex portions 155 to the average diameter of the concave portions 153 is 50%, and preferably 40%. By controlling the ratio of the average diameter of the convex portion 155 to the average diameter of the concave portion 153, the arrangement of the inner surface of the concave portion 153 and the projection surface of the convex portion 155 becomes appropriate, and more preferably, the incident light can be diffusely reflected. .

  The average height of the protrusion 155 is not particularly limited. For example, when the average height of the protrusions 155 is 5 to 90 nm, more preferably, the incident light can be irregularly reflected. The lower limit of the average height of the projection 155 is 15 nm, and preferably 25 nm. In addition, the upper limit of the average height of the projection 155 is 70 nm, and preferably 50 nm.

  Note that the protrusion 155 can be determined as follows. First, the center of gravity (geometric center) of the concave portion 153 when the coating film 15 is viewed from the plate thickness direction is obtained based on the shape of the concave portion 153 specified by the above method. While rotating about the center of gravity by 18 degrees, ten cut surfaces parallel to the thickness direction of the coated metal plate 1 are obtained. The two-dimensional profile of the concave portion 153 and the convex portion 155 appearing on each cut surface is divided into two-dimensional profiles on the left and right sides based on the center of gravity of the concave portion 153. From the minimum points included in the two-dimensional profile on the left side, one point having the deepest depth (a large difference in height from the reference height) is specified, and similarly, the minimum point from the minimum points included in the two-dimensional profile on the right side is specified. One minimum point having a large depth (a large difference in height from the reference height) is specified. That is, two minimum points are specified for one cut surface. Two minimum points are specified on each of the ten cut surfaces. By connecting two minimum points (a total of 20 data) specified on each cut surface with a straight line in the rotation direction based on the coordinates of the two-dimensional profile, obtaining a octagon that approximately represents the contour of the convex portion 155 Can be. The area surrounded by the octagon is referred to as a convex 155.

The area s of the convex portion 155 including the entire contour among the convex portions 155 (20-sided) specified as described above is obtained by image processing. The area s is the area of the projection 155 when the coating film 15 is viewed from the thickness direction. Using this area s, the diameter d (circle equivalent diameter) of the convex portion 155 when the convex portion 155 is regarded as a perfect circle is obtained by the following equation.
d = 2 × (s / π) ^0.5 (π: Pi)
AFM observation of 10 × 10 μm described above was performed at at least 20 places at the center of the plate surface excluding the range of 100 mm from the outermost edge of the coated metal plate 1, and the diameter d of each convex portion 155 obtained from each observation surface was measured. The arithmetic average value is defined as the average diameter of the protrusion 155.

  Further, the height of the convex portion 155 is obtained from the above-mentioned ten cut surfaces. From the two-dimensional profiles appearing on the cut surface, one maximum point having the highest height (smallest difference from the reference height) is specified from the maximum points included in the area of the convex portion 155. One maximum point is specified on each of the ten cut surfaces. The highest point among the local maximum points (total 10 data) specified on each cut surface is defined as the top of the convex portion 155. On the other hand, among the minimum points (20 data in total) on each cut surface specified by the above method, the lowest point is defined as the deepest part of the convex portion 155. The difference (distance along the thickness direction) between the top and the deepest part is defined as the height of the convex part 155. In the central portion of the plate surface excluding the range of 100 mm from the outermost edge of the coated metal plate 1, the above-mentioned 10 × 10 μm AFM observation was performed at at least 20 places, and the height of each convex portion 155 obtained from each observation surface was measured. The arithmetic average value is defined as the average height of the convex portions 155.

  Although the concave portions 153 are arranged irregularly in FIGS. 1 and 2, the plurality of concave portions 153 formed in the coating film 15 may be aligned in the coated metal plate 1 according to the present embodiment. .

The density of the recess 153 is not particularly limited. For example, when the number density of the concave portions 153 with respect to the surface of the coating film 15 is 1 × 10 ⁴ to 1 × 10 ⁶ / mm ² , the whiteness can be increased while suppressing a decrease in glossiness. The lower limit of the number density of the concave portions 153 is 3 × 10 ⁴ / mm ² , and preferably 9 × 10 ⁴ / mm ² . The upper limit of the number density of the concave portions 153 is 1.5 × 10 ⁵ / mm ² , and preferably 1.2 × 10 ⁵ / mm ² .

  The density of the concave portions 153 is the number density of the concave portions 153 with respect to the surface of the coating film 15 when the coating film 15 is viewed from the thickness direction. The number density is obtained based on the concave portion 153 specified by the above method. At the central portion of the plate surface excluding the range of 100 mm from the outermost edge of the coated metal plate 1, the above-described 10 × 10 μm AFM observation was performed at at least 20 places so that the observation field of view was continuous. The number of existing portions is obtained, and the value obtained by dividing the existing number by the observation area is defined as the density of the concave portion 153.

  The area ratio of the concave portion 153 is not particularly limited. For example, when the area ratio of the concave portion 153 to the surface of the coating film 15 is 1 to 40%, the whiteness can be increased while suppressing a decrease in glossiness. The lower limit of the area ratio of the concave portion 153 is preferably 5%, 8%, or 20%. The upper limit of the area ratio of the concave portion 153 is 35%, and preferably 25%.

  The area ratio of the concave portion 153 is a ratio of the concave portion 153 to the surface of the coating film 15 when the coating film 15 is viewed from the thickness direction. The area ratio of the concave portion 153 is obtained by image processing based on height data of surface irregularities using AFM. The above-mentioned 10 × 10 μm AFM observation was performed at at least 20 places at the center of the plate surface excluding the range of 100 mm from the outermost edge of the coated metal plate 1 so that the observation field of view was continuous. And the arithmetic average value is defined as the area ratio of the concave portion 153.

The recess 153 preferably has a substantially circular outline. Specifically, the circumference when viewed coating 15 from a thickness direction, to all of the recesses 153, the contour length L ₁ of the recess 153 is determined from the diameter D of the recess 153 (circle equivalent diameter) the length _{L 2 is, 1.0 ≦ L 1 / L 2} ≦ 3.0 recesses 153 are satisfied it is preferably in number% 95% (and less than 100%). It is more preferable that the concave portion 153 satisfies the above condition, and it is possible to increase whiteness while suppressing a decrease in glossiness.

When the lower limit of L ₁ / L ₂ is 1.0, it means that the concave portion 153 is a perfect circle. However, since it is industrially difficult to control the concave portion 153 to be a perfect circle, the lower limit of L ₁ / L ₂ may be 1.2, 1.4, or 1.6. On the other hand, in order to preferably achieve both high whiteness and high gloss, the upper limit of L ₁ / L ₂ may be 2.8, 2.6, 2.4, or 2.0.

Incidentally, the contour length L ₁ and the circumferential length L ₂ of the recessed portion 153 can be specified as follows. Based on the recess 153 identified as described above, to identify the contour of the recess 153, obtaining the contour length L ₁ of the recessed portion 153 by the image processing. The contour length L ₁ is the length of the contour of the recess 153 when viewed coating 15 from a thickness direction. Further, based on the diameter D of the recess 153, when regarded recesses 153 and perfect circle, the circumferential length L ₂ of the recessed portion 153 obtained by the following equation.
L ₂ = π × D (π: pi)
The above-mentioned 10 × 10 μm AFM observation was performed at at least 20 places in the center of the plate surface excluding the range of 100 mm from the outermost edge of the coated metal plate 1, and 95% in terms of the number% of the concave portions 153 including the entire contour. The recess 153 preferably satisfies 1.0 ≦ L ₁ / L ₂ ≦ 3.0.

  Further, the flat portion 151 on the surface of the coating film 15 contributes to the glossiness. In order to preferably increase the specular reflection component with respect to the incident light, the average surface roughness Ra of the flat portion 151 is preferably less than 20 nm. The lower limit of the average surface roughness Ra of the flat portion 151 is not particularly limited, and is preferably as small as possible. For example, if necessary, the lower limit of the average surface roughness Ra of the flat portion 151 may be 1 nm. The upper limit of the average surface roughness Ra of the flat portion 151 is 18 nm, preferably 16 nm.

  The flat portion 151 is a region on the surface of the coating film 15 other than the concave portion 153 specified as described above. The surface roughness Ra of the flat portion 151 is obtained based on a two-dimensional profile of the flat portion 151 appearing on a cut surface parallel to the thickness direction of the coated metal plate 1. The surface roughness Ra is determined from at least a reference length of 3 μm or more. The above-mentioned 10 × 10 μm AFM observation was performed in at least 20 places at the center of the plate surface excluding the range of 100 mm from the outermost edge of the coated metal plate 1, and the surface roughness of each flat portion 151 obtained from each observation surface The arithmetic average value of Ra is defined as the average surface roughness Ra of the flat portion 151.

  The area ratio of the flat portion 151 is not particularly limited. For example, when the area ratio of the flat portion 151 to the surface of the coating film 15 is 60% to 99%, the whiteness can be increased while suppressing a decrease in glossiness. The lower limit of the area ratio of the flat portion 151 is 65%, and preferably 75%. The upper limit of the area ratio of the flat portion 151 is preferably 95%, 92%, or 80%.

  Note that the area ratio of the flat portion 151 is a ratio of the flat portion 151 to the surface of the coating film 15 when the coating film 15 is viewed from the thickness direction. The area ratio of the flat portion 151 is obtained by image processing based on height data of surface irregularities using AFM. The above-mentioned 10 × 10 μm AFM observation was performed at at least 20 places so that the observation field of view was continuous at the center of the plate surface excluding the range of 100 mm from the outermost edge of the coated metal plate 1, and a flat portion was formed on each observation surface. The area ratio of the flat portion 151 is determined, and the arithmetic average value is set as the area ratio of the flat portion 151.

  The thickness (film thickness) of the coating film 15 is not particularly limited. For example, when the thickness of the coating film 15 is 8.0 to 30 μm, it is more preferable, and both high whiteness and high gloss can be preferably achieved. When the base color is a color that easily absorbs incident light, the diffuse reflection component and the specular reflection component for the incident light are both small, so it is difficult to simultaneously increase whiteness and glossiness. When the thickness is 8.0 μm or more, the underlying color can be preferably hidden. The lower limit of the thickness of the coating film 15 is 10 μm, preferably 13 μm. On the other hand, from an industrial viewpoint, the upper limit of the thickness of the coating film 15 is 25 μm, and preferably 20 μm.

  The constituent material of the coating film 15 is not particularly limited as long as it can form the above-described surface shape. The coating film 15 can include, for example, a pigment and a resin.

  Examples of the pigment include a white pigment, a colored pigment, and an antirust pigment. In particular, when the coating film 15 contains a relatively large amount of a white pigment, the coating film 15 becomes a white coating film. Generally, in a metal plate having a white coating film, high whiteness is required, and high glossiness is required from the viewpoint of use and design. On the other hand, it has been conventionally difficult to achieve both high whiteness and high gloss. However, in the coated metal plate 1 according to the present embodiment, as described above, since the coating film 15 has the flat portion 151 and the plurality of concave portions 153, it is possible to achieve both high whiteness and high gloss.

The white pigment is not particularly limited. For example, examples of the white pigment include rutile-type or anatase-type titanium oxide (TiO ₂ ), CaSO ₄ , MgSO ₄ , BaSO ₄ , Al ₂ O ₃ , Sb ₂ O ₃ , and ZnO. These white pigments may be used alone or in combination of two or more. Further, as the white pigment, titanium oxide whose surface is coated with Al ₂ O ₃ , Sb ₂ O ₃ , ZnO or the like can also be used. Among the above, as the white pigment, BaSO ₄ , Al ₂ O ₃ and titanium oxide are preferable from the viewpoint of concealing properties and high whiteness.

  When the coating film 15 is a white coating film, the content of the white pigment in the coating film 15 is not particularly limited. For example, the coating 15 preferably has a white pigment, and the content of the white pigment with respect to the coating 15 is preferably 40 to 70% by mass. The lower limit of the content of the white pigment is preferably 40% by mass, 45% by mass, or 50% by mass based on the total mass of the coating film 15. The upper limit of the content of the white pigment is preferably 70% by mass, 65% by mass, or 60% by mass based on the total mass of the coating film 15.

  The colored pigment is not particularly limited. Known pigments can be appropriately selected according to the color of the target coating film 15. For example, examples of the colored pigment include red iron, aluminum, mica, carbon black, and cobalt blue. Also, the content of the colored pigment in the coating film 15 is not particularly limited, and can be appropriately selected according to the intended color of the coating film 15.

  Further, the coating film 15 preferably contains a rust preventive pigment as a pigment. When the coating film 15 contains the rust-preventive pigment, the corrosion resistance of the entire coated metal plate 1 can be improved.

  The rust preventive pigment is not particularly limited. For example, examples of the rust preventive pigment include a phosphoric acid rust preventive pigment and a silica rust preventive pigment. In particular, a phosphoric acid-based rust-preventive pigment is preferable because the corrosion resistance of the coated metal plate 1 can be sufficiently improved while preventing a decrease in glossiness.

  Examples of the phosphoric acid-based rust preventive pigment include phosphates, orthophosphates, and polyphosphates of metals such as magnesium and aluminum. Examples of the phosphoric acid-based rust preventive pigment containing magnesium include magnesium dihydrogen phosphate (for example, manufactured by Junsei Chemical Co., Ltd.).

  Examples of the phosphoric acid-based rust preventive pigment containing aluminum include aluminum dihydrogen tripolyphosphate and a surface-treated product thereof with magnesium, calcium, or zinc. For example, “K-WHITE” (trademark), which is aluminum dihydrogen tripolyphosphate manufactured by Teica, “K-WHITE / # 105” (zinc-treated), and “K-WHITE / Ca650” (calcium-treated), manufactured by Teika ), “K-WHITE / K-G105” (magnesium treatment) and the like.

  Among the above, phosphoric acid-based rust preventive pigments, particularly phosphoric acid-based rust preventive pigments containing magnesium, are preferable since the decrease in glossiness due to the addition is small.

  The content of the phosphoric acid-based rust preventive pigment in the coating film 15 is not particularly limited. For example, it is preferable that the coating film 15 has a phosphoric acid-based rust-preventive pigment, and the content of the phosphoric acid-based rust-proof pigment is 1 to 15% by mass based on the coating film 15. The lower limit of the content of the phosphoric acid-based rust preventive pigment is preferably 1% by mass, 2% by mass, or 3% by mass based on the total mass of the coating film 15. The upper limit of the content of the phosphoric acid-based rust preventive pigment is preferably 15% by mass, 10% by mass, or 8% by mass based on the total mass of the coating film 15.

  The resin functions as a binder for binding each component such as a pigment. The resin constitutes the surface of the coating film 15. The resin is not particularly limited. For example, examples of the resin include an epoxy resin, a polyester resin, an acrylic resin, a urethane resin, a vinyl chloride resin, a fluorine resin, and a melamine resin. Examples of the melamine resin include an alkylated melamine resin such as a methylated melamine resin and a butylated melamine resin. These resins may be used alone or in combination of two or more. Among the above, from the viewpoint of smoothing the coating film 15, the resin preferably contains an alkylated melamine resin, particularly a methylated melamine resin.

  When the coating film 15 is a white coating film, it is preferable to use a polyester resin as the main resin in order to improve whiteness, adhesion, chemical resistance, and corrosion resistance. The polyester resin preferably has a number average molecular weight of 3,000 to 30,000 and a glass transition temperature Tg of about 0 to 80 ° C. The lower limit of the number average molecular weight is 5000, preferably 9000. The upper limit of the number average molecular weight is 25,000, and preferably 23,000. The lower limit of the glass transition temperature Tg is 10 ° C, preferably 20 ° C. The upper limit of the glass transition temperature Tg is 70 ° C., preferably 60 ° C.

  The content of the resin in the coating film 15 is not particularly limited. For example, the lower limit of the resin content is preferably 30% by mass, 35% by mass, or 40% by mass with respect to the total mass of the coating film 15. The lower limit of the resin content is preferably 60% by mass, 55% by mass, or 50% by mass based on the total mass of the coating film 15.

  In addition, as a hardening | curing agent, a melamine resin, especially a methylated melamine is preferable. Isocyanates can also be used as curing agents. The ratio of the curing agent to the main resin is preferably in a ratio by mass of main resin: curing agent = 100: 25 to 100: 70. More preferably, the ratio of the main resin to the curing agent is 100: 30 to 100: 60.

  The coating film 15 may further include a lubricant. When the coating film 15 contains a lubricant, effects such as improvement in press workability due to reduction in the friction coefficient of the coating film surface and reduction in handling scratches can be obtained. Examples of the lubricant include polyethylene, polypropylene, and fluorine compounds. These can be used alone or in combination of two or more, depending on the processing application.

  The content of the lubricant is preferably 0.5 to 20% by mass, more preferably 1.0 to 10% by mass, based on the total mass of the coating film 15. By controlling the content of the lubricant, it is possible to obtain sufficient lubricity and to prevent problems caused by the paint such as stagnation and foaming caused by the lubricant.

  The coating film 15 may further include a coupling agent. When the coating film 15 contains a coupling agent, it is possible to prevent a decrease in processing adhesion due to the addition of a rust preventive pigment. Examples of such a coupling agent include a Si-based coupling agent and a Ti-based coupling agent. The addition amount of the Si-based and / or Ti-based coupling agent in the coating film 15 is not particularly limited. For example, the addition amount of the coupling agent can be 0.2 to 5.0 parts by mass with respect to 100 parts by mass of the resin.

  Since the coated metal plate 1 according to the present embodiment described above has the flat portion 151 and the plurality of concave portions 153 on the surface of the coating film 15, the whiteness can be increased while suppressing the decrease in gloss. Such a coated metal plate 1 is particularly useful as a coated metal plate that requires both high whiteness and high gloss.

  In addition, the coated metal plate 1 toned so as to increase the whiteness while increasing the glossiness of the surface as described above can be used, for example, in electric machine appliances such as household electric machine appliances (home appliances) and building materials. Can be used. Therefore, the painted metal plate 1 can be a painted metal plate for electric machine equipment, particularly a painted metal plate for household electric machine appliance, or a painted metal plate for building material. In other words, the electromechanical device may have the above-mentioned painted metal sheet 1 and the building material may have the above-mentioned painted metal sheet 1.

<2. Modification>
The preferred embodiment of the present invention has been described above in detail. Hereinafter, some modified examples of the above embodiment will be described. In addition, each modification described below may be applied to the above-described embodiment by itself, or may be applied to the above-described embodiment in combination. Further, each modification may be applied instead of the configuration described in the above embodiment, or may be additionally applied to the configuration described in the above embodiment.

(First Modification)
FIG. 3 is a schematic cross-sectional view of a coated metal plate 1A according to a modification of the above embodiment. In the above-described embodiment, the chemical conversion treatment layer 13 is disposed between the metal plate 11 and the coating film 15, but the chemical conversion treatment layer 13 may be omitted as shown in FIG.

(Second Modification)
FIG. 4 is a schematic cross-sectional view of a coated metal plate 1B according to a modification of the above embodiment. The coated metal plate 1B includes a primer (undercoat film) 17 between the chemical conversion treatment layer 13 and the coating film 15. The primer 17 improves the adhesion between the chemical conversion treatment layer 13 and the coating film 15 and, for example, improves the corrosion resistance of the coated metal plate 1B by including a rust preventive pigment or the like.

  When the primer 17 contains a rust preventive pigment, the rust preventive pigment in the coating film 15 can be omitted or reduced. In this case, the coating film 15 is composed of a composition for the purpose of design such as toning, and the primer 17 is composed of a composition for the purpose of improving corrosion resistance, so that the function of each layer can be separated.

  In addition, the material constituting the primer 17 is not particularly limited. For example, as the primer 17, various materials exemplified for the coating film 15 can be used.

(Other modifications)
In addition, for example, the coated metal plate may have a chemical conversion treatment layer on the side where the coating film is not formed. Further, the coated metal plate may have a coating film on both sides.

<3. Manufacturing method of painted metal sheet>
Next, a method for manufacturing the coated metal sheet 1 according to the present embodiment will be described in detail.

The method for manufacturing the coated metal sheet 1 according to the present embodiment includes:
A first step of applying a paint containing a resin and a liquid medium on the metal plate 11 (paint application step);
A second step (coating film forming step) of forming a coating film while removing a part or the entirety of the liquid medium from the coating material and bringing an atmosphere containing a solvent (liquid medium) into contact with the coating material. Have
The absolute value of the difference between the solubility parameter of the resin and the solubility parameter of the solvent is 0.5 or more and less than 2.0,
The partial pressure of the solvent in the atmosphere is 0.005 to 0.2 atm.

  In addition, the method for manufacturing the coated metal sheet 1 according to the present embodiment may include a chemical conversion treatment step of forming a chemical conversion treatment layer 13 on at least one surface of the metal plate 11 prior to the first step. . Hereinafter, a method for manufacturing the coated metal sheet 1 according to the present embodiment will be described step by step.

  First, the metal plate 11 is prepared. As the metal plate 11, those described above can be used.

  Next, a chemical conversion treatment is performed on at least one plate surface of the metal plate 11 to form a chemical conversion treatment layer 13. In the chemical conversion treatment, a composition (chemical conversion treatment solution) containing the constituent material of the chemical conversion treatment layer 13 described above is applied on the surface of the metal plate 11, and the liquid medium is removed by heating or the like, and the chemical conversion treatment layer 13 is formed. Can be performed by fixing.

  Examples of the chemical conversion treatment liquid include a liquid in which the above constituent materials are dispersed or dissolved in a liquid medium. For example, the content of the resin in the chemical conversion treatment liquid may be 1.0 to 100 g / L. The lower limit of the resin content is 2.0 g / L, and preferably 5.0 g / L. The upper limit of the content of the resin is 80 g / L, and preferably 60 g / L. The total content of at least one selected from the group consisting of silica, a silane coupling agent, tannin, tannic acid, a zirconium compound, and a titanium compound in the chemical conversion treatment solution is 0.01 to 100 g / L. I just need. The lower limit of this content is 0.1 g / L, and preferably 0.5 g / L. The upper limit of this content is 80 g / L, preferably 60 g / L. The chemical conversion treatment liquid described above makes it possible to sufficiently enhance the corrosion resistance and the coating film adhesion of the chemical conversion treatment layer 13 and to sufficiently enhance the stability of the chemical conversion treatment liquid.

  Further, the liquid medium of the chemical conversion treatment liquid is not particularly limited. For example, various known organic solvents and water can be used as the liquid medium. In particular, when the liquid medium of the chemical conversion treatment liquid is water, handling of the chemical conversion treatment liquid is easy.

  The method of applying the chemical conversion treatment liquid to the metal plate 11 is not particularly limited. For example, as a coating method, a roll coat, a ringer roll coat, an air spray, an airless spray, an immersion method, a curtain coat, and the like can be adopted.

  Further, the removal of the liquid medium in the chemical conversion treatment liquid and the formation and fixing of the chemical conversion treatment layer 13 are not particularly limited. For example, the chemical conversion treatment layer 13 can be formed by heating. The heating method is not particularly limited. For example, as the heating method, a known method such as a hot air heating method, an induction heating method, or a near infrared heating method can be used. The heating temperature may be, for example, 40 to 200 ° C. The lower limit of the heating temperature is preferably 50 ° C, and the upper limit of the heating temperature is preferably 180 ° C. The heating time may be, for example, 0.5 to 20 seconds. The lower limit of the heating time is preferably 1 second, and the upper limit of the heating time is preferably 15 seconds.

  Next, a coating film 15 is formed on the metal plate 11 on which the chemical conversion treatment layer 13 is formed, that is, on the chemical conversion treatment layer 13. First, a paint containing a resin and a liquid medium is applied on the metal plate 11 (first step).

  The paint only needs to contain a resin and a liquid medium, and preferably contains each component of the coating film 15 described above. The mixing ratio of each component in the paint can be appropriately selected and changed according to the composition of the coating film 15 to be formed and physical properties such as a viscosity range necessary for coating.

  The liquid medium contained in the paint is not particularly limited. For example, as the liquid medium, various organic solvents such as ketone solvents such as cyclohexanone and methyl ethyl ketone, aromatic hydrocarbon solvents such as xylene, ether solvents such as dioxane, alcohol solvents such as n-butanol and ethanol, and water. Is mentioned. These liquid media can be used alone or in combination of two or more.

  In this embodiment, the absolute value of the difference between the solubility parameter of the liquid medium and the solubility parameter of the resin is 0.5 or more and less than 2.0. As a result, an organic solvent having a predetermined difference in solubility parameter can be brought into contact with the paint in a second step described later. The lower limit of the absolute value of the difference between the solubility parameters is 0.6, and preferably 0.7. The upper limit of the absolute value of the difference between the solubility parameters is less than 1.8, and preferably less than 1.5.

  The solubility parameter of the liquid medium (solvent) and the solubility parameter of the resin (SP value: Solvity Parameter) can be experimentally obtained based on the following turbidity titration method.

  First, a poor solvent having a high SP value and a poor solvent having a low SP value are dropped into a sample solution, and the amount of the poor solvent required until turbidity occurs is determined. At this time, the above operation is performed using two types of poor solvents having different SP values, and the amount (volume) of the poor solvent required until turbidity is generated for each of them. Then, by substituting the obtained volume of the poor solvent required until the turbidity occurs and the SP value of the poor solvent into the following equation 1, the SP value δ of the solution can be obtained.

_{^{δ = (VmL 0.5 δ mL +}} Vmh 0.5 δ mh) / (VmL 0.5 + Vmh 0.5) ··· ( Equation 1)
The symbols in the formula are defined as follows.
VmL: volume of the poor solvent having a low SP value Vmh: volume of the poor solvent having a high SP value δ _mL : SP value of the poor solvent having a low SP value δ _mh : SP value of the poor solvent having a high SP value When the SP value is obtained, a liquid medium is used as the sample solution, and when the SP value of the resin is obtained, a resin solution is used as the sample solution.

  The method of applying the paint to the metal plate 11 is not particularly limited. For example, as a coating method, a roll coat, a ringer roll coat, an air spray, an airless spray, a dipping method, a curtain coat, an electrostatic coating method, or the like can be adopted.

  Next, at least a part of the liquid medium is removed from the paint while the solvent is in contact with the paint to form the coating film 15 (second step). Here, the absolute value of the difference between the solubility parameter of the resin and the solubility parameter of the solvent is 0.5 or more and less than 2.0. By controlling the solubility parameter, a flat portion 151 and a plurality of concave portions 153 are formed on the surface of the coating film 15.

  The reason why the plurality of recesses 153 are formed on the surface of the coating film 15 is unknown at present, but is presumed as follows.

  The resin contained in the paint greatly contributes to the formation of the surface shape of the coating film 15 as a binder. Then, when the liquid medium in which the resin is dissolved and dispersed is removed from the paint, the viscosity of the paint greatly increases. At this time, when a solvent having appropriate solubility for the resin comes into contact with the surface of the paint, the paint containing the resin repels the solvent at a part of the contact surface, and comes into contact with the solvent at another local part. Dissolve. Then, the portion dissolved by contact with the solvent becomes the concave portion 153. In the method for manufacturing the coated metal sheet 1 according to the present embodiment, the projections 155 are also formed in the depressions 153 at the same time as the depressions 153 are formed. If necessary, the protrusion 155 may be mechanically or chemically removed from the recess 153.

  If the absolute value of the difference between the solubility parameter of the resin and the solubility parameter of the solvent is less than 0.5, the solvent uniformly contacts the paint surface and dissolves the paint uniformly. The recess 153 is not formed. On the other hand, when the absolute value of the difference between the solubility parameter of the resin and the solubility parameter of the solvent is 2.0 or more, the surface of the paint repels the solvent too much, and the solvent is too concentrated locally. Coarse concave portions are formed on the surface of the coating film 15.

  As described above, the absolute value of the difference between the solubility parameter of the resin and the solubility parameter of the solvent may be 0.5 or more and less than 2.0. The lower limit of the absolute value of the difference between the solubility parameters is 0.6, and preferably 0.7. The upper limit of the absolute value of the difference between the solubility parameters is less than 1.8, and preferably less than 1.5. By controlling the solubility parameter, the shape of the concave portion 153 on the surface of the coating film 15 can be made preferable. The solubility parameters of the resin and the solvent may be determined based on the above-mentioned turbidity titration method.

  The contact between the paint (resin) and the solvent is performed by a method as shown in FIG. FIG. 5 is a schematic diagram showing a method of making contact between the paint and the solvent in the second step of the method for manufacturing the coated metal sheet 1 according to the present embodiment.

  The metal plate 11 coated with the paint 15A is heated by an arbitrary heating method such as a hot air heating method, an induction heating method, a near-infrared heating method, and the like, and then introduced into a baking furnace 100 shown in FIG. Will be The baking furnace 100 has a chamber 101, and the chamber 101 forms a space 103 therein. Further, the chamber 101 is provided with an inlet 105 and an outlet 107 for the metal plate 11, an air supply port 109, and an exhaust port 111.

  Further, a heating blower 113 is disposed in the upper portion of the chamber 101 on the space 103 side, and an air supply port 109 is connected to the heating blower 113. The heating blower 113 sucks ambient air from the air supply port 109, heats the air, and sends hot air in the direction of the arrow in the drawing. Thereby, the paint 15A carried on the metal plate 11 is heated, and at least a part of the liquid medium is removed from the paint 15A. Here, when the metal plate 11 coated with the paint 15A is continuously passed through the baking furnace, the vapor of the liquid medium stays in the space 103. Then, when the vapor of the liquid medium comes into contact with the paint 15A as a solvent, the coating film 15 in which the concave portions 153 are formed as described above is obtained. Part of the excessively retained liquid medium vapor is discharged from the exhaust port 111 to the outside.

  In particular, in the method for manufacturing the coated metal sheet 1 according to the present embodiment, the solvent partial pressure in the space 103 of the chamber 101 is controlled when forming (curing) the coating film 15 in order to form the plurality of recesses 153. . Under conventional manufacturing conditions, the solvent partial pressure was less than 0.005 atm. In the method for manufacturing the coated metal sheet 1 according to the present embodiment, the amount of hot air supplied from the air supply port 109, the amount of outside air flowing in from the inlet 105, the amount of exhaust air from the exhaust port 111, the amount of leakage from the outlet 107, By changing the heating temperature of the heating blower 113 from the conventional condition, the partial pressure of the solvent in the space 103 (atmosphere) is intentionally controlled to 0.005 to 0.2 atm. By controlling the partial pressure of the solvent in the space 103 (atmosphere), the paint 15A (resin) and the solvent are preferably in contact with each other, so that the concave portion 153 is preferably formed. At this time, the smoothness of the flat portion 151 also increases. As a result, a flat portion 151 and a plurality of concave portions 153 are formed on the surface of the coating film 15.

  The lower limit of the partial pressure of the solvent in the space 103 is preferably 0.008 atm, 0.010 atm, or 0.015 atm. The upper limit of the partial pressure of the solvent in the space 103 is preferably 0.15 atm, 0.12 atm, or 0.1 atm. The partial pressure of the solvent in the space 103 is determined by the amount of hot air supplied from the air supply port 109, the amount of outside air flowing in from the inlet 105, the amount of exhaust air from the exhaust port 111, the amount of leakage from the outlet 107, Control is performed by changing the heating temperature at 113. The amount of hot air supplied from the air supply port 109, the amount of outside air flowing in from the inlet 105, the amount of exhaust air from the exhaust port 111, the amount of leakage from the outlet 107, and the heating temperature in the heating blower 113 are determined for each manufacturing facility. Since these values change, each condition may be appropriately adjusted so that the solvent partial pressure in the space 103 according to the purpose is obtained.

  The temperature in space 103 in baking furnace 100 is not particularly limited. For example, the ultimate temperature of the metal plate may be 100 to 300 ° C. as the ambient temperature in the space 103. The lower limit of the temperature reached by the metal plate is 150 ° C, preferably 200 ° C. The upper limit of the temperature reached by the metal plate is 270 ° C., preferably 250 ° C. By controlling the ultimate temperature of the metal plate, the liquid medium can be efficiently transformed into vapor and used as a solvent.

  In addition, the heating time of the metal plate 11 supporting the paint 15A (the time required for the metal plate 11 to pass through the baking furnace) is not particularly limited. For example, the heating time of the metal plate 11 may be set to 10 to 120 seconds. The lower limit of the heating time of the metal plate 11 is 12 seconds, and preferably 15 seconds. The upper limit of the heating time of the metal plate 11 is 90 seconds, and preferably 60 seconds. By controlling the heating time of the metal plate 11, the vapor of the liquid medium can appropriately contact the paint 15 </ b> A as a solvent to form the recess 153 preferably.

  Through the above steps, the coated metal plate 1 having the flat portion 151 and the plurality of concave portions 153 on the surface of the coating film 15 is obtained. In addition, you may perform each said process continuously. Each of the above-described steps can be performed in a continuous coating line equipped with an apparatus corresponding to the above-described steps, for example, a coil coating line or a sheet coating line. As a result, the production efficiency of the coated metal plate 1 is improved.

  In addition, the manufacturing method of the coated metal sheet 1 according to the present embodiment is not limited to the above-described method. For example, the solvent to be brought into contact with the paint need not be derived from the liquid medium contained in the paint. For example, a solvent to be brought into contact with the paint can be separately supplied and brought into contact with the paint. In addition, the solvent to be brought into contact with the paint is not limited to a vapor solvent, and for example, a liquid or solid solvent can be appropriately used. Further, when a liquid solvent is used, the solvent can be brought into contact with the coating film 15 (paint 15A) using a droplet applying device such as a spray atomizer or an inkjet device.

  Next, the effects of one embodiment of the present invention will be described in more detail with reference to examples. The conditions in the examples are examples of one condition adopted to confirm the operability and effects of the present invention. Yes, the present invention is not limited to this one condition example. The present invention may employ various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

(1. Production of painted metal plate)
(I) Metal plate As a metal plate used for manufacturing a coated metal plate, an electrogalvanized steel (EG: Electro Galvanized Steel) having a thickness of 0.5 mm was used. The plating adhesion amount was 20 g / m ² on one side.

(Ii) Formation of chemical conversion treatment layer A chemical conversion treatment layer was formed on one plate surface of the above metal plate by the following method. First, a chemical conversion treatment liquid was applied to one plate surface of a metal plate using a roll coater. Thereafter, the metal plate was heated so that the ultimate temperature (PMT: Peak Metal Temperature) became 60 ° C. The applied amount of the chemical conversion treatment liquid on the application surface was applied such that the attached amount of the entire dried film was 300 mg / m ² . The amount of each chemical conversion coating was measured by X-ray fluorescence. As the chemical conversion treatment solution, a chromate-free chemical conversion treatment solution “CT-E300N” manufactured by Nippon Parkerizing Co., Ltd. was used.

(Iii) Formation of White Coating A white coating was formed on the chemical conversion treatment layer of the metal plate by the following method.
First, white paints (paints 1 to 18) each containing 17% by mass of a resin, 50% by mass of a liquid medium, 3.0% by mass of a rust preventive pigment, and 30% by mass of a white pigment as shown in Table 1 were prepared. Here, the solid content in the white paint was 50% by mass. Titanium oxide was used as the white pigment, and the content of titanium oxide in the total solid content was 60% by mass. In addition, in Table 1, the compounding ratio described in the column of the resin and the liquid medium indicates the compounding ratio of each component in the resin and the liquid medium, respectively.

  In Table 1, "Polyester" refers to a polyester resin "GK-140" manufactured by Toyobo Co., Ltd., "Methylated melamine" refers to a methylated melamine resin "Cymel 303" manufactured by Cytec Corporation, and "butylated melamine". Is a butylated melamine resin "Super Peckamine J-820-60" manufactured by DIC Corporation, "magnesium phosphate" is magnesium dihydrogen phosphate manufactured by Junsei Chemical Co., Ltd., and calcium-modified silica is W.M. R. "Sealdex C303" manufactured by Grace Co., Ltd. is shown. “Solvesso 100” is a solvent sold by ExxonMobil, “cyclohexanone” is “Anon” manufactured by Sankyo Chemical Co., and “Dioxane” is “1,4-dioxane” manufactured by Sankyo Chemical. Where “methyl ethyl ketone” is “MEK” manufactured by Sankyo Chemical Co., Ltd., “o-xylene” is “ortho xylene” manufactured by Mitsubishi Gas Chemical Company, and “ethanol” is “ethanol manufactured by Sankyo Chemical Co., Ltd.” And "n-butanol" is "butanol" manufactured by Sankyo Chemical Co., Ltd.

The SP value (solubility parameter) of the resin or liquid medium shown in Table 1 was experimentally obtained as follows. Each test temperature was 20 ° C.
<SP value measurement of resin>
0.5 g of the resin and cyclohexanone (manufactured by Kanto Chemical Co., Ltd.) were mixed to make 10 mL. The mixture was stirred with a stirrer to dissolve the resin in the mixture to obtain a sample solution. Next, poor solvents having different SP values were added dropwise until the sample solution became turbid.
<In the case of liquid medium>
10 mL of various liquid media was used as a sample solution. Next, poor solvents having different SP values were added dropwise until the sample solution became turbid.

  Then, the SP value δ of the sample solution was determined by substituting the obtained volume of the poor solvent required until the occurrence of turbidity and the SP value of the poor solvent into the above-described equation 1. In addition, n-hexane (manufactured by Kanto Chemical Co., Ltd.) was used as a poor solvent having a low SP value, and water (manufactured by Wako Pure Chemical Industries, Ltd.) was used as a poor solvent having a high SP value. As the SP values of n-hexane and water, the values described in the literature (CM Hansen et. Al: J. Paint Tech., 39 [505], 104-117 (1967)) were used.

  Next, for each of the invention examples and the comparative examples, paints 1 to 18 shown in Table 1 were applied to the surface of a zinc-based plated steel sheet having a chemical conversion coating by a slide curtain coater so as to have a predetermined dry film thickness. Then, after baking in a hot-air heating type baking furnace as shown in FIG. 5 so that the PMT becomes 220 ° C., water-cooling treatment is performed, and drying is performed by air blow to obtain a pre-coated steel sheet (coated metal sheet) having a target white coating film. ) Got. The passing speed (LS: Line Speed) was 80 m to 200 m per minute, and the heating time in the baking furnace (the passing time in the baking furnace) was 10 to 30 seconds.

  When baking was performed using a baking furnace as shown in FIG. 5, the liquid medium in the white paint volatilized to become a solvent and stayed in the internal space of the baking furnace chamber. At this time, in order to control the partial pressure of the solvent in the internal space of the chamber, the amount of hot air supplied from the supply port, the amount of outside air flowing in from the metal plate inlet, the amount of exhaust air from the exhaust port, and the amount And the heating temperature of the heating blower were adjusted. This enabled the solvent to contact the white coating film.

(2. Evaluation)
A white coating film on the outermost surface of the obtained coated metal plate was observed. As features of the recess, the presence or absence of the recess, the average diameter, the average depth, the number density, the area ratio, and the contour shape were measured. The average height and average diameter were measured as characteristics of the convex portion on the inner surface of the concave portion. Further, as features of the flat portion, the area ratio and the average surface roughness Ra were measured. Further, the thickness (film thickness) of the white coating film was measured.

  Specifically, the surface of the white coating film of the coated metal plate was scanned using an atomic force microscope (NanoScope IIIa, manufactured by Digital Instruments). As the cantilever, an SPM (Scanning Probe Microscope) sensor made of Si was used. The measurement range was 10 μm × 10 μm, and was 2.5 × 2.5 μm as needed. And the flat part, the concave part, and the convex part were specified by the above-mentioned method, and the above-mentioned feature was evaluated.

In addition, as the contour shape of the concave portion, L ₁ / L ₂ was calculated for each concave portion from the contour length L ₁ of the concave portion and the circumferential length L ₂ obtained from the equivalent circle diameter of the concave portion. Then, with respect to all the observed concave portions, the concave portions satisfying 1.0 ≦ L ₁ / L ₂ ≦ 3.0 were evaluated as number%.

  Further, the white coating film of the obtained coated metal plate was peeled off using a coating film release agent (“Neoriver SP751”, manufactured by Sansai Kako Co., Ltd.), and the film thickness was calculated by a gravimetric method.

Further, whiteness and glossiness of the obtained coated metal plate were measured. Regarding whiteness, L ^* value was measured using CR-400 manufactured by Konica Minolta. The glossiness was measured at 60 ° gloss using Multi Gloss 268 manufactured by Konica Minolta.

When the thickness of the white coating film was less than 10 μm, the whiteness was judged to be acceptable when the L ^* value was 87.0 or more, and the gloss was judged to be acceptable when the 60 ° gloss was 71 or more. When the thickness of the white coating film was 10 µm or more, the whiteness was judged to be acceptable when the L ^* value was 89.5 or more, and the gloss was judged to be acceptable when the 60 ° gloss was 72 or more. Table 2 shows the evaluation results of the manufactured coated metal plates having the white coating films. In addition, the average surface roughness Ra of the flat part was less than 20 nm in any of the coated metal plates.

  As shown in Table 2, the coated metal plates of Invention Examples 1 to 13 simultaneously satisfied whiteness and glossiness. On the other hand, the coated metal plates of Comparative Examples 1 to 11 had insufficient whiteness or gloss. Comparative Examples 1, 2, 5, and 6 did not have sufficient whiteness because no concave portions were formed on the surface of the white coating film. In Comparative Examples 3 and 4, the average depth of the concave portions was too large, and the whiteness and glossiness were not sufficient. In Comparative Example 7, the average diameter of the concave portions was too small, and the whiteness was not sufficient. In Comparative Example 8, the average depth of the concave portions was too small, and the whiteness was not sufficient. In Comparative Examples 9 and 10, since the solvent partial pressure in the chamber was low, the whiteness was not sufficient. Comparative Example 11 had insufficient whiteness and glossiness because the solvent partial pressure in the chamber was high.

  In general, the whiteness and glossiness of a coated metal plate having a white coating film are greatly affected by the thickness of the white coating film, and the whiteness and glossiness decrease as the thickness of the white coating film decreases. Here, comparing Invention Example 12 and Comparative Example 6 in which the thickness of the white coating film is 8.0 μm, Invention Example 12 exhibits higher whiteness while exhibiting the same glossiness as Comparative Example 6. did.

FIG. 6 is a graph showing the relationship between whiteness (L ^* value) and glossiness (60 ° gloss) for the inventive examples and comparative examples in which the thickness of the white coating film is the same (16 μm). As shown in FIG. 6, it is clear that the invention example achieves both high gloss and whiteness in comparison with the comparative example.

  FIG. 7 shows a scanning electron microscope (SEM) photograph of the surface of the white coating film of Inventive Example 1 observed. 8 and 9 show an atomic force microscope image (obliquely 45 °) of the surface of the white coating film of Inventive Example 1. FIG. 10 shows a scanning electron microscope (SEM) photograph in which the surface of the white coating film of Comparative Example 1 was observed.

  As shown in FIGS. 7 and 8, a plurality of concave portions were formed in the white coating film of Inventive Example 1. Further, as shown in FIG. 9, a convex portion was observed near the center of the concave portion. On the other hand, as shown in FIG. 10, no concave portion was observed in the white coating film of Comparative Example 1.

(3. Production of painted metal plate)
(I) Metal plate As a metal plate used for manufacturing a coated metal plate, an electrogalvanized steel plate (EG) having a thickness of 0.5 mm was used. The coating weight was 20 g / m ^{2 on} one side.

(Ii) Formation of chemical conversion treatment layer A chemical conversion treatment layer was formed on one plate surface of the above metal plate by the following method. The chemical conversion solution was applied to one surface of the metal plate by a roll coater. Then, it heated so that PMT might be set to 60 ° C. The applied amount of the chemical conversion treatment liquid on the application surface was applied such that the attached amount of the entire dried film was 300 mg / m ² . The amount of each chemical conversion coating was measured by X-ray fluorescence.

(Iii) Formation of Colored Coating A colored coating was formed on the chemical conversion treatment layer of the metal plate by the following method.
First, a colored paint (paints 19 to 27) containing 32.3% by mass of a resin, 65% by mass of a liquid medium, 0.9% by mass of a rust preventive pigment, and 1.8% by mass of a black pigment as shown in Table 3 was prepared. Prepared. The solid content in each colored paint was 35% by mass. Carbon black was used as the black pigment, and the content of carbon black in the total solid content was 5% by mass. In addition, about the description method of each component in Table 3, it is the same as that of Table 1. The SP values in the table were obtained by the above-described method.

  Next, for each of the invention examples and the comparative examples, paints 19 to 27 shown in Table 3 were applied to the surface of a zinc-based plated steel sheet having a chemical conversion coating so as to have a predetermined dry film thickness using a slide curtain coater. Then, after baking in a hot-air heating type baking furnace as shown in FIG. 5 so that the PMT becomes 220 ° C., water-cooling treatment is performed, and drying is performed by air blow to obtain a pre-coated steel sheet having a desired colored coating film (a coated metal sheet). ) Got. The passing speed was 120 m / min, and the heating time in the baking furnace was 15 seconds.

  In addition, when baking was performed using a baking furnace as shown in FIG. 5, the liquid medium in the colored paint volatilized to become a solvent and stayed in the internal space of the baking furnace chamber. At this time, in order to control the partial pressure of the solvent in the internal space of the chamber, the amount of hot air supplied from the air supply port, the amount of outside air flowing in from the metal plate inlet, the amount of exhaust air from the exhaust port, the metal plate outlet And the heating temperature of the heating blower were adjusted. This enabled the solvent to come into contact with the colored coating film.

(4. Evaluation)
The colored coating film on the outermost surface of the obtained coated metal plate was observed. The flat part, the concave part, and the convex part were specified by the same method as described above, and each characteristic was evaluated. Further, the thickness of the colored coating film was calculated in the same manner as described above.

Further, whiteness (L ^* value) and gloss (60 ° gloss) of the obtained coated metal plate were measured in the same manner as described above. As the whiteness, an L ^* value of 27.0 or more was judged as acceptable, and as the gloss, a 60 ° gloss of 50 or more was judged as acceptable. Table 4 shows the evaluation results of the coated metal sheets having the produced colored coating films. In addition, the average surface roughness Ra of the flat part was less than 20 nm in any of the coated metal plates.

  As shown in Table 4, the coated metal plates of Invention Examples 14 to 19 were whitened and had high glossiness. On the other hand, in the coated metal plates of Comparative Examples 12 to 17, the whiteness was not sufficiently imparted, or the glossiness was significantly reduced. In Comparative Example 12, since no concave portion was formed on the surface of the colored coating film, the whiteness was not sufficient. In Comparative Examples 13 and 14, the average depth of the concave portions was too large, and the glossiness was not sufficient. In Comparative Examples 15 and 16, the whiteness was not sufficient because the solvent partial pressure in the chamber was low. In Comparative Example 17, since the solvent partial pressure in the chamber was high, the whiteness and glossiness were not sufficient.

  According to the above aspect of the present invention, it is possible to provide a coated metal plate that can increase whiteness while suppressing a decrease in glossiness, and thus has high industrial applicability.

DESCRIPTION OF SYMBOLS 1, 1A, 1B Painted metal plate 11 Metal plate 13 Chemical conversion treatment layer 15 Coating 15A Paint 151 Flat part 153 Concave part 155 Convex part 17 Primer 100 Baking furnace 101 Chamber 103 Space 105 Inlet 107 Outlet 109 Air supply port 111 Exhaust port 113 Heating Blower

Claims (12)

A metal plate,
Having a coating film located on at least one plate surface of the metal plate,
The coating film is disposed on the outermost surface, and has a flat portion and a plurality of concave portions on the surface,
The average diameter of the concave portion is 0.20 to 4.0 μm,
The average depth of the recess, Ri 20~200nm der,
The number density of the concave portions with respect to the surface of the coating film is 1 × 10 ⁴ to 1 × 10 ⁶ / mm ² ,
The coated metal plate, wherein the flat portion has an average surface roughness Ra of less than 20 nm . The coated metal plate according to claim 1 , wherein an area ratio of the concave portion to the surface of the coating film is 1 to 40%. The coated metal plate according to claim 2 , wherein an area ratio of the concave portion to the surface of the coating film is 20 to 40%. When viewed the coating film from a thickness direction, the contour length L ₁ of the recess, the circumferential length L ₂ which is obtained from the circle equivalent diameter of the recess, 1.0 ≦ L _{1 /} L ₂ ≦ 3 4. The coated metal sheet according to any one of claims 1 to 3 , wherein the number of the concave portions satisfying 0.0 is 95% or more in number%. The said concave part has a convex part on the inner surface, The coating metal plate as described in any one of Claims 1-4 characterized by the above-mentioned. The average diameter of the protrusions is 0.1 to 1.5 μm,
The coated metal plate according to claim 5 , wherein an average height of the protrusions is 5 to 90 nm. The coated metal plate according to any one of claims 1 to 6 , wherein an area ratio of the flat portion to the surface of the coating film is 60 to 99%. The coated metal sheet according to claim 7 , wherein an area ratio of the flat portion to the surface of the coating film is 60 to 80%. The coated metal sheet according to any one of claims 1 to 8 , wherein the thickness of the coating film is 8.0 to 30 µm. The coated metal sheet according to any one of claims 1 to 9 , wherein the coating film has a white pigment, and the content of the white pigment with respect to the coating film is 40 to 70% by mass. The said coating film has a phosphoric acid type rust preventive pigment, and content of the said phosphoric acid type rust preventive pigment with respect to the said coating film is 1-15 mass%, The any one of Claims 1-10 characterized by the above-mentioned. The painted metal sheet according to the item. The coated metal sheet according to any one of claims 1 to 11 , further comprising a chemical conversion treatment layer between the metal sheet and the coating film.