JPWO2007013232A1 - Pre-coated metal plate and manufacturing method thereof - Google Patents

Abstract

The present invention provides a precoated metal sheet that is excellent in corrosion resistance and has excellent design in appearance because a vivid color can be expressed even if the coating thickness is reduced in order to prevent occurrence of boiling defects, and a method for producing the same. The pre-coated metal plate is a multi-layer pre-coated metal plate in which a multi-layer coating film is formed by sequentially laminating a primer coating layer, an intermediate coating layer film and a top coating layer on one side or both sides of a metal plate, The primer coating layer contains one or both of Si and P, and there is a liquid interface trace interface between the intermediate coating layer and the top coating layer in the multilayer coating, and the liquid interface trace The size of the fine irregularities at the interface is 0.3 to 0.8 μm expressed by the center line average roughness (Ra), and the intermediate coating layer contains a Ti-based additive.

Description

  The present invention relates to a pre-coated metal plate excellent in design and corrosion resistance and a method for producing the same, and in particular, has a bright red, yellow, and orange design appearance, and is used for home appliances, building materials, and civil engineering. The present invention relates to a precoated metal sheet that is excellent in corrosion resistance and excellent in workability of a coating film in applications such as machinery, automobiles, furniture, and containers.

Conventionally, post-painted products that have been painted after processing have been used in applications such as home appliances, building materials, and automobiles. Instead of these post-painted products, pre-coated metal sheets coated with a colored coating film are used. Are beginning to be used. This metal plate is obtained by coating a metal plate that has been subjected to a metal pretreatment, and is generally used after being molded and then processed.
In the industry, as a general method for mass-producing pre-coated metal sheets, a continuous coating facility called a coil coating line having a coating facility called a roll coater or a curtain coater is known. However, in a coil coating line, it is common to paint on a metal plate at a relatively high speed and to bake and harden it in a short time. A coating defect called “boiling” is likely to occur. For this reason, in the case of a conventional precoated metal plate, the film thickness is generally about 1 to 25 μm in the case of a single layer, and the film thickness of each layer is generally about 1 to 25 μm in the case of multiple layers.
The technology relating to these pre-coated metal plates is disclosed in, for example, “Technical Trends of Pre-Coated Metal Plates” by Ueda et al. (Coloring Materials, 1999, 72 (8), p. 51).
By the way, when the coating color of the pre-coated metal plate is colored to a color other than white and black, the color other than white and black has low concealability. It becomes a blackish color. In particular, when red, yellow and orange colors are colored, this tendency is generally strong. In order to conceal these colors and develop vivid colors, thick films (generally over 50 μm) must be applied. However, if this pre-coated metal sheet is produced on a coil coating line, it will boil. There was a problem that defects would occur.
On the other hand, in post-coating, in which a metal plate used for automobiles, etc. is formed and then applied by spraying, etc., an electrodeposition coating with a corrosion resistance function is applied, and then a highly concealed base coat called a surfacer is applied, In addition, there is a technology for expressing vivid colors by applying a colored top coating on top of it. However, these paints for automobiles are generally baked after being processed, and if the paint is processed after painting, coating film cracks and peeling occur at the processed part. It was difficult to apply. In addition, a pre-coated metal sheet is prepared by using the same coating material for a pre-coated metal sheet, which is generally known as a three-coat specification in which a corrosion-resistant coating film, an intermediate coating film, and a colored top coating film are laminated. However, precoated metal sheets are baked in a short time unlike automotive paints, so it is difficult to coat each layer with a thick film like automotive paints in order to prevent the occurrence of “boiling” defects. Therefore, it must be painted with a thin film, and when painted with a thin film, a vivid appearance cannot be expressed, so it is difficult to achieve both appearance and corrosion resistance with a pre-coated metal plate.
Therefore, the present invention has been made in view of such problems, and is excellent in corrosion resistance and can exhibit a vivid color even if the coating film thickness is reduced in order to prevent the occurrence of the above-described boiling defects. An object of the present invention is to provide a new and improved pre-coated metal sheet having excellent design properties and a method for producing the same.

In order to solve the above-mentioned problems, the present inventors have intensively studied to develop a vivid color on a pre-coated metal sheet having a thin coating thickness, and as a result, a colored coating layer (hereinafter referred to as a top coating layer). By providing a coating layer containing a large amount of Ti in the lower layer (hereinafter referred to as an intermediate coating layer), it is possible to conceal the color of the base metal plate in the intermediate coating layer. It is possible to vividly express the color of the top coating layer coated on the surface, and furthermore, at least the intermediate coating layer and the top coating layer are simultaneously coated in multiple layers to form the intermediate coating layer and the top coating layer. The liquid-liquid interface trace interface is located at the interface between and the liquid-liquid interface trace interface, and the fine irregularities of the center-line average roughness (Ra) are 0.3 to 0.8 μm. Visible light is more diffusely reflected at the interface with the coating film, so it reaches the metal plate. To become Nikuku, more hiding the color of the metal plate, it was found that it is possible to more vividly expressed the color of the top coating layer. However, since the corrosion resistance of the pre-coated metal sheet cannot be ensured only by the intermediate coating layer and the top coating layer, the present inventors added either one or both of Si and P to the lower layer of the intermediate coating layer. It has been found that by providing a coating layer (hereinafter referred to as a primer coating layer), a pre-coated metal plate can be obtained that has excellent corrosion resistance and can express the primary color of the top coating layer vividly.
The present invention has been completed based on such findings, and the gist of the present invention is as follows.
(1) A multi-layer pre-coated metal plate in which a multi-layer coating film is formed by sequentially laminating a primer coating layer, an intermediate coating layer and a top coating layer on one side or both sides of a metal plate:
The primer coating layer includes one or both of Si and P,
There is a liquid interface trace interface between the intermediate coating layer and the top coating layer in the multilayer coating film, and the size of the fine irregularities of the liquid interface trace interface is the centerline average roughness (Ra). Expressed as 0.3 to 0.8 μm,
The pre-coated metal sheet having a vivid color tone, wherein the intermediate coating layer contains a Ti-based additive.
(2) The precoated metal sheet having a vivid color tone according to (1), wherein the top coating layer contains a color pigment other than a Ti-based additive and does not contain a Ti-based additive.
(3) The intermediate coating film layer has a vivid color tone as described in (1) or (2) above, which contains a coloring pigment other than the Ti-based additive in addition to the Ti-based additive Pre-coated metal plate.
(4) The vivid color tone according to any one of (1) to (3) above, wherein the additive amount of the Ti-based additive contained in the intermediate coating layer is 40 mass% or more. A pre-coated metal plate.
(5) The precoated metal sheet having a vivid color tone according to any one of (1) to (4), wherein the Ti-based additive is titanium oxide.
(6) The above-mentioned (1) to (5), wherein the colored pigment other than the Ti-based additive in the top coating layer is a pigment of any color of red, yellow or orange The precoat metal plate which has the vivid color tone in any one of.
(7) The top coating layer is colored with a pigment of any color of red, yellow or orange, and in addition to the Ti-based additive in the intermediate coating layer, red, The pre-coated metal plate having a vivid color tone according to any one of the above (1) to (6), characterized in that it has a yellow or orange color (containing a pigment.
(8) When the liquid-liquid interface trace interface is observed at a magnification of 500 times, the maximum height from the center line of the waviness of the interface is 50% measured from the center line of the layer located on the interface The precoated metal sheet having a vivid color tone according to any one of the above (1) to (7), which is as follows.
(9) Each film thickness of the primer coating film layer, the intermediate coating film layer, and the top coating film layer is in the range of 1 to 30 μm, and the total film thickness of the multilayer coating film is 50 μm or less. The precoated metal sheet having a vivid color tone according to any one of (1) to (7), wherein
(10) The precoat metal having a vivid color tone according to any one of (1) to (9) above, wherein the elongation at break of each coating layer is 100% or more when it is 23 ° C. Board.
(11) The outermost coating film has (A) a glass transition temperature of 5 to 30 ° C., and (B) a hardness at 23 ° C. of 2.5 N / mm ² or more in terms of universal hardness under a load of 5 mN. (C) The elongation at break at 23 ° C. is 100% or more, and (D) the specular gloss of the coating film on the outermost layer is 60% when the incident angle and the light receiving angle are each measured at 60 °. It is the above, The precoat metal plate which has the vivid color tone in any one of said (1)-(10) characterized by the above-mentioned.
(12) The precoated metal sheet having a vivid color tone according to (11), which is deep-drawn to a molding height of 25 mm or more.
(13) The precoated metal sheet having a vivid color tone according to any one of (1) to (12) above, wherein a particle diameter of the Ti-based additive is 0.2 to 0.3 μm.
(14) The precoated metal sheet having a vivid color tone according to any one of (1) to (13) above, wherein the particle size of the particles contained in the top coating layer is 0.1 μm or less. .
(15) A method for producing a precoated metal sheet according to any one of (1) to (14) above:
A precoat having a vivid color tone, wherein at least two layers of a primer coating layer, an intermediate coating layer and a top coating layer are applied to one or both surfaces of a metal plate by a multilayer simultaneous coating method. A method for producing a metal plate.
(16) A leveler is added to the upper paint layer of two adjacent layers to be applied by the multi-layer simultaneous application method, and the difference in surface tension between the intermediate paint layer paint and the top paint layer paint is 1.2 mN / m or more and less than 5 mN / m, and as the coating material for each layer, use a coating material whose difference between the maximum value and the minimum value obtained is less than 2 mN / m when the surface tension is measured 5 times. The manufacturing method of the precoat metal plate which has the vivid color tone as described in said (15) characterized by the above-mentioned.
(17) A leveler is added to both the top coating layer and the intermediate coating layer of the two adjacent layers to be applied by the simultaneous coating method, so that the intermediate coating layer coating and the top coating layer coating are added. When the surface tension is measured five times as a coating material for each layer, the difference between the surface tensions is 0.3 mN / m or more and less than 3.7 mN / m. The method for producing a precoated metal sheet having a vivid color tone as described in (15) above, wherein a paint having a difference of less than 2 mN / m is used.
ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the precoat metal plate which is excellent in corrosion resistance, and is excellent in the designability, and its manufacturing method. Therefore, if the pre-coated metal plate according to the present invention is used, it becomes possible to manufacture metal parts having bright primary colors that could only be handled by post-coating so far.

FIG. 1 is a schematic cross-sectional view of a precoated metal plate of the present invention.
2A and 2B are diagrams for explaining the interface between the lower coating layer and the upper coating layer of the precoated metal sheet according to the present invention.
FIG. 3 is a diagram for explaining a method for evaluating Ra of the coating film interface of the precoated metal sheet.
FIG. 4 is a diagram for explaining the interface when the lower layer of the multilayer simultaneous coat contains a pigment.
FIG. 5 is a schematic perspective view of a slide hopper type curtain coating apparatus.
FIG. 6 is an explanatory view showing the bending method of the method for measuring the elongation at break of the coating film of the precoated metal sheet.
FIG. 7 is a schematic diagram for explaining a pre-coated metal plate manufacturing process line.
FIG. 8 is a diagram showing a draw bead test method for evaluating the coating caulking property of the pre-coated metal plate.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.
  In the present invention, referring to FIG. 1, a primer coating layer 12, an intermediate coating layer 13, and a top coating layer 14 are sequentially laminated on one side or both sides of the metal plate 11 (only on one side in FIG. 1). Even if the top coating layer is colored with a color other than white or black, the primer coating layer is either Si or P. Or both, and there is a liquid-liquid interface trace interface between the intermediate coating layer and the top coating layer in the multilayer coating, and the size of the fine irregularities of the interface is the centerline average roughness The thickness of the metal plate can be concealed when the intermediate coating film layer contains a Ti-based additive. In particular, when the top coating layer does not contain a Ti-based additive, or when the coating color is colored with any of red, yellow, or orange colors, the effect of concealing the color of the metal plate is more effective. To do.
  As a metal plate used as the base of the precoat metal plate of this invention, a steel plate, an aluminum plate, a titanium plate etc. can be used, for example, However, A metal plate is not limited to these.
  Examples of usable steel sheets include cold-rolled steel sheets, hot-rolled steel sheets, galvanized steel sheets, galvanized steel sheets, zinc-iron alloy-plated steel sheets, zinc-aluminum alloy-plated steel sheets, aluminum-plated steel sheets, chrome-plated steel sheets, nickel Examples of the steel sheet include a plated steel sheet, a zinc-nickel alloy plated steel sheet, and a tin plated steel sheet. The steel sheet can be subjected to a base treatment (pre-painting treatment) as necessary. Examples of the base treatment include water washing, hot water washing, pickling, alkali degreasing, grinding, polishing, chromate treatment, zinc phosphate treatment, composite oxide film treatment and other non-chromate treatments. These can be used alone or in combination for pre-coating of the steel sheet.
  In addition, the primer coating film layer in this invention is a coating film layer coated directly on a metal plate, or directly on the metal plate which gave chemical conversion treatment. The intermediate coating film is a coating layer applied on the primer coating layer, and the top coating layer is a coating layer applied on the intermediate coating layer. In the present invention, the top coating layer may be one layer or two or more layers. When the top coating layer is a single layer, only a coating layer colored with a color other than white or black can be applied. When there are two or more layers, a metallic pigment is applied on the colored layer. It is possible to laminate a clear coating layer containing a clear coating layer or a clear coating layer containing no pigment.
  The primer coating layer of the present invention needs to contain either one or both of Si and P. In the present invention, one of the features is that the primer coating layer is provided with a rust prevention function of the metal plate. Since the compound containing Si and P has a rust prevention function and the color of the compound is white, an intermediate coating film layer and a top coating layer colored in a vivid primary color are formed thereon. When applied in a thin film, the color of the colored layer becomes vivid. As a method of including Si or P in the primer coating layer, there is a method of adding a compound containing Si or P into the primer coating layer.
  As the compound containing Si or P, generally known compounds, for example, compounds containing Si or P such as silica, Ca ion exchange silica, zinc phosphate, aluminum tripolyphosphate, and the like can be used. These compounds may be those commercially available as reagents or those commercially available as industrial products such as pigments. These compounds may be added in combination. In particular, Ca ion-exchanged silica or aluminum dihydrogen tripolyphosphate is particularly suitable because it has a beautiful coating appearance and excellent corrosion resistance. As the Ca ion exchange silica, “SHIELDEX (registered trademark)” manufactured by GRACE, and “K-WHITE” manufactured by Teika Co., etc., can be used as the aluminum tripolyphosphate.
  The addition amount of Si compound or P compound can be changed as necessary, but the addition amount of Si compound or P compound, and when these are used in combination or in combination, the total addition amount is in the dry coating film. 5 to 60 mass% is more preferable. If it is less than 5 mass%, the corrosion resistance is inferior. If it exceeds 60 mass%, the coating film becomes brittle and the workability may be inferior. In addition, you may add another pigment and a compound in a primer coating film layer as needed.
  The precoated metal sheet of the present invention has a liquid-liquid interface trace interface between the intermediate coating layer and the top coating layer in the multilayer coating. The liquid-liquid interface trace interface is a unique interface that is formed because a liquid-liquid interface is formed between the liquid layers of the multi-layer when the multi-layer liquid layers are simultaneously applied by the multi-layer simultaneous application method adopted by the present invention. Yes, this is a unique interface that is never seen when the upper layer is applied after the lower layer is applied (dried, baked). When observing the cross section of the multi-layer coating film of the pre-coated metal plate, the swell is seen at the interface between the upper and lower coating films in the low magnification magnified photograph of about 500 times, and when observed at a high magnification of about 5000 times There are fine wavy irregularities formed by the upper and lower layers penetrating each other when they are in the liquid phase. These undulations and the shape of fine irregularities are unique to the liquid-liquid interface. The unique fine irregularities derived from the liquid-liquid interface contribute to the concealing action by irregular reflection.
  When the cross section of the pre-coated metal sheet of the present invention produced by multi-layer simultaneous coating is observed at a magnification of 500 times, as shown schematically in FIG. 2A, undulation is present at the interface 105 between the lower coating layer 101 and the upper coating layer 103. Is recognized. Generally, the pitch of the undulation (distance P in the figure) is about 0.5 to 1 mm. When the coating layer interface 105 is further observed at a high magnification of 5000 times, the interface 105 is derived from the liquid-liquid interface as schematically shown in FIG. 2B corresponding to the enlarged view of the portion indicated by B in FIG. 2A. Fine irregularities with a unique shape are observed.
  The precoated metal sheet of the present invention has a liquid interface trace interface derived from multilayer simultaneous coating between the intermediate coating layer and the top coating layer in the multilayer coating, and the liquid By measuring the size of the fine irregularities of the interface trace interface by the centerline average roughness (Ra) method to 0.3 to 0.8 μm (hereinafter simply referred to as “interface centerline average roughness (Ra) )), Visible light is more diffusely reflected at the interface between the intermediate coating layer and the top coating layer, so that a more vivid color of the top coating can be expressed. If Ra at the interface between each coating layer intermediate coating layer and the top coating layer is less than 0.3 μm, it becomes difficult to express the vivid coating color without completely concealing the color of the original plate, resulting in blackening. It becomes a cloudy paint color. Moreover, since the adhesiveness of the interface of both coating layers improves also by Ra of the interface of an intermediate coating film layer and a top coating film layer being 0.3-0.8 micrometer, it is more suitable. When Ra of the interface is less than 0.3 μm, the adhesion at the coating film interface may be lowered. In general, when the coating films are laminated, the adhesion of the coating films is maintained by physical bonds such as chemical bonds, hydrogen bonds, and van der Waals forces between the coating films. By setting it as the above, in addition to these adhesion forces, the adhesion force by an anchor effect is provided. However, if it exceeds 0.8 μm, the appearance when the top paint is applied is affected, and the gloss may be lowered.
  Here, in the present invention, the fine unevenness at the interface between the upper and lower coating layers formed by the simultaneous multilayer coating obtains the centerline average roughness Ra (JIS B 0601) used to represent the surface roughness of the material. This can be specified. That is, Ra can be obtained by regarding the curve of the interface 105 when observed at a magnification of 5000 as a roughness curve.
  For example, a coated metal plate is cut and embedded in a resin and then polished, so that the cross section perpendicular to the surface of the coating film is smoothed and photographed with a 5000 × scanning microscope. Can be sought. Specifically, the Ra of the interface is covered with a transparent sheet used for OHP on the photo, and the unevenness of the interface is traced precisely, and then the area of the vertical line is processed as shown in FIG. It can be determined from the following equation as an average value measured by an apparatus.
        Ra = (∫₀ ^l| F (x) | dx) / l
In the equation, l is the measured length in the direction of the center line shown in FIG.
  In order to more easily measure Ra of the interface, cover the photograph with a transparent sheet used for OHP, trace the unevenness of the interface precisely, and draw an average line corresponding to the center line in FIG. Then, the transparent sheet may be cut out, the weights of the top and bottom peaks and troughs of the average line may be measured, and the weight may be converted into an average length to determine Ra.
  When the fine irregularities at the interface of the coating layer formed by multilayer simultaneous coating are examined in this way, the value of the center line average roughness Ra is generally 0.3 μm or more, and it is at least about 0.25 μm. As can be seen, the upper limit was generally about 0.7 to 0.8 μm. This relationship is also recognized in the case of three or more coating films formed by multi-layer simultaneous coating. In this case, the centerline average roughness Ra observed at a high magnification of 5000 times at the interface between two adjacent layers is Again, it was generally 0.3 μm or more and at least about 0.25 μm, and the upper limit was generally about 0.7 to 0.8 μm. On the other hand, in the case of a multilayer coating film in which the coating layers formed by the conventional single layer coating method are stacked, the Ra of the interface is about 0.15 to 0.25 μm. The difference from the coating layer according to the invention was clear.
  2A, the maximum height H measured from the center line C of the undulation peaks 111 and the valleys 113 of the interface 105 shown in FIG. It is desirable not to exceed 50% of the thickness t of the top coating layer expressed as the distance from the top surface of the top coating layer. This is because when this value exceeds 50%, color unevenness may be observed.
  In the present invention, the thickness t expressed as the distance from the center line of the wavy interface to the upper surface of the top coating layer as described above is defined as the average thickness of the top coating layer. Similarly, the thickness expressed as the distance from the lower surface of the intermediate coating layer to the center line of the interface with the top coating layer is taken as the average thickness of the intermediate coating layer. When two or more top coating layers are applied, it is more preferable that t be the thickness of the top coating layer that is simultaneously applied immediately above the intermediate coating layer.
  As shown in FIG. 4, when the intermediate coating layer 101 includes the pigment 107 and a part of the pigment 107 exists in the ridge 111 of the wavy interface 105, the upper part of the pigment 107 is the interface 111. Or may protrude from the interface 111 to the top coating layer 103. The maximum height H when the pigment 107 protrudes from the interface 111 is determined by regarding the contour 107a of the portion protruding from the interface 111 of the pigment 107 as the interface.
  In order to give Ra in the above range to the interface between the coating layers, it can be achieved by multilayer simultaneous application. Multi-layer simultaneous coating (multi-layer simultaneous coating) is a method of applying multiple layers of coating liquid, such as a slot die coater or slide hopper type curtain coater, to the substrate in a state of being laminated simultaneously, and then applying the multiple layers of coating liquid Are simultaneously dried and baked. In this way, by laminating the coating liquids in the undried state and applying them simultaneously, the coating liquids of each layer are mixed slightly in the vicinity of the interface of the laminated coating film, thereby forming a trace interface originating from the liquid-liquid interface at the interface. Fine irregularities (that is, Ra) can be generated. In general, when two or more coating layers are applied by simultaneous multi-layer coating, the Ra at the coating interface becomes 0.3 to 0.8 μm.
  The coating film of the precoated metal sheet of the present invention is formed using a multilayer simultaneous coating apparatus. FIG. 5 shows a schematic perspective view of a slide hopper type curtain coating apparatus which is a representative of such an apparatus.
  Referring to FIG. 5, the slide hopper 1 is provided with a paint supply hole 8 and a slit 6 through which three layers of paint are quantitatively sent out by a gear pump (not shown) or the like. A chain-like curtain guide 3 is provided so as to be in contact with both end portions of the lip portion 7A of the slide surface 7. A paint pan 5 is installed below the lip 7 </ b> A, and the curtain guide 3 hangs down to the bottom of the paint pan 5. The paint P is uniformly supplied to the slide surface 7 through the slit 6 from each paint supply hole 8 of the slide hopper 1, and is laminated on the slide surface 7. Since the laminated paint is spread by the curtain guide 3 when falling from the tip (lip 7A) of the slide surface 7 to the paint pan 5, it flows down as a uniform liquid film in the width direction as the paint curtain 4. By passing a strip-shaped metal plate such as the steel strip 2 through this liquid film, a plurality of layers of paint can be applied simultaneously on the surface of the steel strip 2.
  When a slide hopper type curtain coating apparatus is used, simultaneous coating of a plurality of layers is performed in a non-contact manner with the metal plate surface, so that roping that cannot be avoided with a roll coater does not occur. In addition, since the coating film is a multi-layer (laminated body) curtain 4, if the total film thickness of the curtain 4 is equal to or greater than the stable film thickness, that is, about 20 μm in dry film thickness, the coating film thickness of one layer is Even a few μm can be painted. Therefore, by coating the coating film of the intermediate coating film layer and the coating film of the top coating layer at the same time, it is possible to obtain a coated metal plate having a beautiful appearance without causing roping.
  In order to generally describe the simultaneous multilayer coating, the top coating layer is referred to as the upper layer, the intermediate coating layer is referred to as the lower layer, and the top coating layer or the intermediate coating layer may be composed of two or more layers. Considering the lower layer and the upper layer in consideration, it is preferable to add a leveler to the upper layer because the Ra of the interface between the upper layer and the lower layer can be controlled. In particular, the surface tension of the paint is adjusted by adding a leveler to the upper layer coating film, and the degree of color tone is improved as compared with the case where no leveler is added to the upper layer. And when adding a leveler only to an upper layer, when the difference in surface tension between the upper layer and the lower layer is 1.2 mN / m or more and less than 5 mN / m, it is suitable for achieving both prevention of color tone deterioration and adhesion. is there. The reason is not limited, but the following hypothesis can be considered. In order for the upper-layer paint to spread on the lower-layer paint, it is considered necessary to hold the relationship of the following equation based on the balance of the interface forces.
      S = σ (lower layer) −σ (upper layer) −γ (upper layer and lower layer)> 0
Here, σ represents surface tension, and γ represents interfacial tension.
  Therefore,
      σ (lower layer) −σ (upper layer)> γ (upper layer and lower layer)
In other words, if the surface tension of the lower layer is not higher than the surface tension of the upper layer than the surface tension of the upper layer, it is considered that the upper layer coating does not spread on the lower layer coating. It is thought that the force that the upper layer paint wets and spreads acts to suppress the force that disturbs the interface between the upper layer and the lower layer due to Marangoni convection and widens the interface. When the difference in surface tension between the upper layer and the lower layer paint is 1.2 mN / m or more and less than 5 mN / m, the Ra of the interface between the upper layer and the lower layer coating after baking is 0.3 to 0. The inventors have found that the thickness is preferably 8 μm.
  The effect of adding a leveler as a surface conditioner to the upper layer of the multilayer coating film to improve the color tone is considered to be due to the uniform reduction of the surface tension of the upper layer and the suppression of non-uniform evaporation of the solvent.
  Moreover, when a leveler is put not only in the upper layer (top coating layer) but also in the lower layer (intermediate coating layer), the upper layer after baking the coating layer when the surface tension of the upper layer is lower than the surface tension of the lower layer, There is a condition that Ra of the interface of the lower layer coating film can be controlled to 0.3 to 0.8 μm. This phenomenon makes it easier for the lower layer paint to spread on the lower layer (another paint layer that is formed together in the multi-layer simultaneous coating, or the steel plate or the primer layer thereon), and the lower layer paint is locally spread. It is presumed that the phenomenon of excitement is suppressed. When a leveler is added to the upper layer (top coating layer) and the lower layer (intermediate coating layer), the difference in surface tension between the upper layer (top coating layer) and the lower layer (intermediate coating layer) is 0.3 mN. The inventors have found that the Ra of the interface between the upper layer and the lower layer is 0.3 to 0.8 μm, which is suitable when it is / m or more and less than 3.7 mN / m.
  In the present invention, the leveler is a kind of paint surface conditioner, which is also called a leveling agent, and is an additive having the property of making the paint surface uniform. Examples of the leveler that can be used in the present invention include an acrylic leveler and a silicone leveler. For example, homogenol L18, homogenol L95, homogenol L1820 (Kao Co., Ltd.), BYK057, BYK051, BYK052, BYK053, BYK055, BYK077 (BYK-Chemie), etc., as non-silicone series, homogenol L100 (Kao Corporation), BYK080, BYK141, BYK065, BYK066, BYK070, BYK088 (BYK-Chemie).
  The leveler in the coating film of the product pre-coated steel plate manufactured by multilayer simultaneous coating peels off the coating film of the product, extracts the unreacted polymer in the solvent, heats and concentrates the extracted solvent, and then absorbs the infrared light. Can be detected by analysis.
  The precoated metal sheet of the present invention needs to contain a Ti-based additive in the intermediate coating layer. Ti compounds as Ti-based additives, especially titanium oxide, when added to the coating film, have high concealability of the coating film and high effect of concealing the color of the base plate (metal plate). By coating this under the coating layer, the color of the coating can be made more vivid. As the Ti compound contained in the intermediate coating layer, for example, titanium oxide, barium titanate, strontium titanate, or the like can be used. A commercially available product may be used. A type in which the surface of these titanium compounds is coated with another metal or resin may be used. As the commercially available titanium oxide, “Taipeku” manufactured by Ishihara Sangyo Co., Ltd., “TITANIX” manufactured by Teika Co., Ltd., or the like can be used.
  The particle size of the Ti-based additive in the intermediate coating film is preferably 0.1 to 0.3 μm, more preferably 0.2 to 0.3 μm. If the particle size of the Ti-based additive is smaller than 0.1 μm, the concealing effect may be unexpected, and if it is larger than 0.3 μm, Ra at the interface between the top coating and the intermediate coating may be increased more than necessary. Because there is. However, the particle size of the Ti-based additive in the intermediate coating film is not particularly limited. For example, considerably large particles can be used, and those having a particle size outside the above range can be used as necessary.
  The addition amount of the Ti-based additive in the intermediate coating film can be appropriately selected as necessary, but is preferably 40 mass% or more, more preferably 40-60 mass% in the dry coating film. . If it is less than 40 mass%, the concealability is insufficient, so that there is a possibility that a vivid primary color will not be expressed when the top coating is applied. In addition, when a paint in which a Ti-based additive of 40 mass% or more is added to the intermediate coating in the dry coating and the top coating are applied by multilayer simultaneous coating, a Ti-based coating is formed at the interface between the intermediate coating layer and the top coating layer. Additives tend to thicken, so that visible light is more easily diffusely reflected in the vicinity of the interface, so that concealability is increased and a more vivid primary color is developed. However, if it exceeds 60 mass%, the coating film becomes brittle and the workability may be inferior. In addition, you may further add another pigment and a compound in an intermediate coating film layer as needed.
  The top coating layer of the precoated metal sheet of the present invention is colored with a color other than white or black, particularly when it does not contain a Ti additive, or is red, yellow or orange. It is more effective if it is colored with the color of. Furthermore, if the Ti-based additive is not included and the material is colored in any one of red, yellow, or orange colors, a very vivid color tone can be expressed. Titanium oxide is a typical pigment containing Ti. However, since these have very high whiteness, when they are included in the top layer, the colors of primary colors such as colored red, orange, and yellow are pale. There is a risk that it will become a system color and vivid colors will not be expressed. Furthermore, when the top coating layer of the pre-coated metal plate of the present invention is colored with any of red, yellow or orange, the intermediate coating layer is also red-based in addition to the Ti-based additive. , It is preferable to be colored in either a yellow or orange color because a vibrant primary color is developed even if the amount of Ti additive added is less than 40 mass%. When the intermediate coating film is colored with any of red, yellow or orange colors, the additive of Ti is added by the synergistic effect of the masking effect of the original plate and the Ti additive of these colors. Even if the amount is less than 40 mass%, a vivid primary color is developed. In addition, when the intermediate coating layer is colored with any of red, yellow, or orange in addition to the Ti-based additive, this intermediate coating and top coating can be applied simultaneously in multiple layers or wet-on. When wet coating is applied, the Ti-based additive in the intermediate coating slightly diffuses into the top coating when wet, so there is a Ti-based additive at the interface between the intermediate coating layer and the top coating layer. It is easy to thicken, so that visible light is more easily diffused and reflected near the interface, so that the concealing property is increased and a more vivid primary color system is developed. In addition to the Ti-based additive in the intermediate coating layer, the addition amount of the Ti-based additive is not particularly specified when it is colored in any of red, yellow or orange colors, 5-60 mass% is suitable. If it is less than 5 mass%, if it is less than 40 mass%, the concealability is insufficient, so that there is a possibility that a vivid primary color will not be expressed when the top coating is applied. If it exceeds 60 mass%, the coating film becomes brittle and the workability may be inferior.
  When the top coating is colored with a color other than white and black, it can generally be colored with a known pigment. For example, in order to give a red, orange or yellow color, each color pigment or color dye can be added to the coating film. Generally known color pigments and colored dyes can be used. A commercially available product may be used. For example, examples of red pigments include inorganic red pigments such as cadmium red and silver vermilion, organic soluble azo red pigments such as carmine 6B, lake red C, and watching red, permanent red, lake red 4R, and naphthol red. Organic insoluble azo red pigments, condensed azo red pigments such as chromoftal red, etc., yellow pigments include, for example, inorganic yellow pigments such as yellow lead, yellow iron oxide, cadmium yellow, disazo yellow, Organic yellow pigments such as monoazo yellow and condensed azo yellow can be used, and as orange pigments, for example, inorganic orange pigments such as molybdenum orange, organic orange pigments such as disazo orange and permanent orange can be used. . About the kind and addition amount of a pigment, it can select suitably as needed. For the top coating layer, a commercially available paint that has already been colored may be used.
  The particle size of the pigment used for the top coating is not limited, but is preferably smaller than Ra and more preferably 0.3 μm or less. When the particle size of the pigment of the top coating film is small, particularly 0.1 μm or less is preferable for obtaining a deep color tone.
  As the binder for all coating layers of the precoated metal sheet of the present invention, generally known resins can be used. For example, polyester resin, epoxy resin, urethane resin, acrylic resin, fluorine resin, melamine resin, etc. can be used. These resins may be thermoplastic or thermosetting. However, the thermosetting type is more suitable from the viewpoint of the scratch resistance of the coating film. In the case of a thermosetting resin, a generally known crosslinking agent, for example, an aminoplast resin such as melamine, isocyanate or the like may be added to the above known resin.
  Each coating layer of the precoated metal sheet of the present invention, that is, each of the primer coating layer, the intermediate coating layer and the top coating layer is in the range of 1 to 30 μm, and each coating layer It is more preferable that the total film thickness of the multilayer coating film including the film layer is 50 μm or less. If the film thickness of each of the primer film, intermediate coating film and top coating film is less than 1 μm, the primer coating film has corrosion resistance, and the intermediate coating film has concealment property. In the case of a film, the color tone may be inferior. Further, when the film thickness of each of the primer coating film, the intermediate coating film, and the top coating film exceeds 30 μm, a coating defect called boiling may occur. Furthermore, even when the total film thickness of the primer coating, intermediate coating, and top coating exceeds 50 μm, there is a possibility that a coating defect called boiling occurs.
  When the elongation at break of all the coating layers applied to the precoated metal sheet of the present invention is 23% or higher, the degree of freedom for forming into various shapes is more preferable. The elongation referred to in the present invention is [elongation] = {[elongation (ΔL)] / [initial length (L₀)]} × 100 (%). The elongation rate is defined differently depending on the literature, and is described below to avoid confusion. The method for measuring the elongation at break of each coating film is a coating film obtained by peeling each coating layer coated on a pre-coated metal plate from the metal plate, or a substrate having peelability such as a Teflon (registered trademark) sheet in advance. Furthermore, after the coating film is coated and baked under the same conditions as the precoated metal plate, a coating film prepared by peeling the coating film from the substrate can be used. The elongation at break can be measured by pulling the coated film thus prepared until it breaks in a 23 ° C. atmosphere using a tensile tester.
  As another method, a metal plate that has already been coated is tightly bent 180 ° in an atmosphere of 23 ° C. with the coating layer side facing outward, and the presence or absence of cracks in the coating film at the curvature portion is observed with a microscope. If crack generation is not observed, it can be determined that the elongation at break of the coating film is 100% or more (hereinafter, this method is referred to as a bending method). As shown in FIG. 6, when the material (pre-coated metal plate) 10 that is tightly bent by 180 ° is viewed from the cross-sectional direction, the neutral portion in which no distortion occurs at the central portion in the thickness direction of the bent portion of the material. A part called a surface occurs. It is known that tensile strain occurs outside the bend from the neutral plane and compressive strain occurs inside. Here, assuming that the outermost surface of the bent portion of the metal plate is a semicircle having a radius of curvature of the thickness t of the metal plate, the metal plate is bent tightly using Equation (I). Elongation rate of outermost surface (ε_s) And can be calculated to be 100%. As is clear from FIG. 1 and formula (I), in the case of the technique for obtaining the elongation percentage of the coating film by the bending method, the thickness of the metal plate as the base material is theoretically any plate. Even if a thick metal plate is used, the value obtained is the same and there is no problem.
ε_s= (2πt−2π (t / 2)) × 100 / 2π (t / 2)
    = 100% (I)
  This concept is based on K.K. Ueda et al. Progress in Organic Coatings (2001), 43 (4), p. 233-242, and in order to derive this idea, reference is made to literatures on general material mechanics, for example, Terufumi Machida “Easy to understand material strength”, Ohm Publishing Co., Ltd., 1999, etc. be able to.
  Therefore, when the pre-coated metal sheet is bent 180 ° so that the coating film side is on the outside, it can be assumed that the elongation rate of the coating film has reached 100%, and cracks are recognized in the coating film at this time. If not, it can be considered that the elongation at break of the coating film is 100% or more. Microscopic observation of the occurrence of cracks in the coating film of the coated metal plate bent 180 ° closely may be observed from the surface of the coating film, or the coating film may be observed from a cross section.
  As a method for measuring the elongation at break of the coating film in the present invention, either a method obtained by a tensile test of a coating film or a method of observing the occurrence of cracks by tightly bending a coated metal plate by 180 ° is adopted. You may do it. When the elongation at break of any one of the coating films to be coated on the precoated metal sheet of the present invention is less than 100%, cracks and peeling of the coating film occur in the processed part when processed into a strict shape. There is a risk of poor appearance and poor corrosion resistance at the machined part.
  In order to set the elongation at break of the coating film used in the present invention to 100% or more, it can be achieved by controlling the type, Tg, molecular weight, and crosslinking density of the binder resin of the coating film. The type of coating resin is more preferable because polyester resin is highly flexible and the elongation at break tends to be high. A lower Tg of the coating resin is more suitable because the elongation at break tends to be higher. A higher molecular weight is more preferable because the elongation at break tends to be higher. A lower crosslink density is more preferable because the elongation at break tends to be higher. In addition, a crosslinking density can be adjusted by changing the addition amount and kind of hardening | curing agent. In general, when the addition amount is small, the crosslinking density is low, and as the number of functional groups of the crosslinking agent is small, the crosslinking density is low.
  As a knowledge obtained by the inventors, it is preferable to use a polyester / melamine system or a polyester / isocyanate system as a binder resin in order to make the elongation at break of the coating film 100% or more. Furthermore, it is more preferable to use the following specifically exemplified resins. In a polyester resin, the number average molecular weight of the polyester resin is more preferably 10,000 to 50,000. If the number average molecular weight is less than 10,000, the processability may be inferior, and if it exceeds 50,000, it may be difficult to form a paint by dissolving in a solvent. Further, the glass transition temperature (hereinafter referred to as Tg) of the polyester resin is more preferably 30 ° C. or less. In addition, when a plurality of polyester resins are mixed, it is preferable that the number average molecular weight of the entire mixed polyester resin is 10,000 to 50,000. When using a commercially available polyester, it is more possible to use “Byron (registered trademark)” manufactured by Toyobo Co., Ltd. or “Desmophen (registered trademark)” manufactured by Sumika Bayer Urethane Co., Ltd. Is preferred. A plurality of these may be mixed and used.
  When a melamine resin is used as a crosslinking agent, generally known melamine resins such as fully alkyl methylated melamine, butylated melamine, and imino group mixed alkylated melamine can be used, and commercially available products such as Mitsui Cytec “Cymel (registered trademark)”, “My Coat (registered trademark)” manufactured by Dainippon Ink & Chemicals, Inc., “Super Becamine (registered trademark)”, and the like can be used. Further, two or more kinds of these resins may be mixed and used. Moreover, the addition amount of a melamine resin is more suitable in a melamine solid content being 5-30 mass parts with respect to 100 mass parts of polyester resin solid content. If the melamine solid content is less than 5 parts by mass with respect to 100 parts by mass of the polyester resin solid content, the amount of the crosslinking agent is too small, and the coating film may not be cured and may not form a film even after dry baking. If the amount of melamine solid content exceeds 30 parts by mass, the coating film is too hard and hard, so the elongation at break of the coating film at 23 ° C is less than 100% and the moldability may be inferior. is there.
  When an isocyanate is used as the cross-linking agent, commercially available isocyanates such as “Sumijour (registered trademark)” and “Desmodur (registered trademark)” manufactured by Sumika Bayer Urethane can be used. It is preferable that the amount of isocyanate added is within the range of 0.8 to 1.2 in terms of the equivalent ratio of the OH number of the polyester resin and the NCO number of the isocyanate. Outside this range, the coating film may be in an uncured state and may be in a so-called “stickiness” state in which the coating film has viscosity.
  Furthermore, in the precoated metal sheet of the present invention, the outermost coating film of the coating layers has (A) a glass transition temperature of 5 to 30 ° C. and (B) a hardness at 23 ° C. under a load of 5 mN. Universal hardness 2.5N / mm²(C) The elongation at break at 23 ° C. is 100% or more, and (D) the specular gloss of the outermost coating film is measured under the conditions of an incident angle and a light receiving angle of 60 °, respectively. Is preferably 60% or more. By satisfying these conditions, it is possible to provide a high-gloss deep-drawing pre-coated metal sheet that does not easily lose its gloss even when deep drawing is performed.
  In the case of a coating film containing a pigment or a curing agent, the Tg of the coating film on the outermost surface in the preferred pre-coated metal plate is Tg as the bulk of the coating film after adding these. The Tg of the coating film may be measured using a differential scanning calorimeter (generally referred to as DSC) after peeling off the coating film applied to the pre-coated metal plate, or in a state where it is applied as a pre-coated metal plate The measurement may be performed using a thermomechanical analyzer (generally called TMA). Moreover, you may measure by a generally well-known method. In addition, it is known that the Tg of the coating film has some errors depending on the measuring equipment and measurement conditions. Therefore, in the present invention, the coating film Tg is 5 to 30 ° C. when measured by any one of a plurality of generally known Tg measuring methods, that is, a method using DSC or a method using TMA. If it is in the range, it is included in the present invention. Since the Tg of the coating film is mainly governed by the Tg of the binder resin, the coating film Tg can be adjusted by controlling the Tg of the binder resin. Since it may be considered that the Tg of the binder resin substantially correlates with the Tg of the coating film, the binder resin used preferably has a Tg of 5 to 30 ° C. Alternatively, a plurality of resins having different Tg may be mixed and the Tg of the entire mixed resin may be set to 5 to 30 ° C.
  If the coating film Tg is less than 5 ° C, the hardness of the entire coating film is too low, and the universal hardness under a load of 23 ° C and 5 mN is 2.5 N / mm.²It is not suitable because it is difficult to secure the above. On the other hand, if the coating film Tg is higher than 30 ° C., when the precoated metal sheet is formed, the gloss of the coating film is reduced in the processed portion, which is not suitable. The coating film Tg is more preferably 10 to 28 ° C.
  The coating hardness of the pre-coated metal sheet can be adjusted mainly by the type and amount of the crosslinking agent contained in the coating, but the universal hardness is the coating hardness described in DIN 50359-1 of Germany. Refers to the measurement method, where a square pyramid made of diamond with a 136 ° facing angle (same as the indenter used in the Vickers hardness test described in JIS-Z-2244) is pressed against the surface of the material and is acting The hardness is calculated from the indentation depth at. The universal hardness in the present invention is measured under the conditions of a temperature of 23 ° C. and an indentation load of 5 mN and using a micro hardness meter described in this DIN standard.
  Addition of generally known curing agents such as melamine resin, isocyanate, etc. is more preferable because the coating film hardness increases. As the type of curing agent, melamine resin or isocyanate is effective, and the universal hardness increases as the amount of these added increases. Universal hardness tends to be higher for melamine curing agents than for isocyanate curing agents. The addition amount of the melamine resin is more preferably 5 to 120 parts by mass with respect to 100 parts by mass of the main resin solid content. When the addition amount of the melamine resin is less than 5 parts by mass with respect to 100 parts by mass of the main resin solid content, the universal hardness at 23 ° C. is 2.5 N / mm.²If the added amount of melamine resin exceeds 120 parts by mass, the elongation at break may be less than 100%. The universal hardness at 23 ° C is 2.5 N / mm.²If it is less than 1, it is not suitable because galling of the coating film is likely to occur when press molding is performed under severe conditions.
  Moreover, since the universal hardness may change depending on the type and amount of pigment added, the universal hardness of the coating film may be adjusted by controlling these.
  If the elongation at break of the coating film on the precoated metal sheet is less than 100% at 23 ° C., cracks are likely to occur from the bent portion during press working, particularly during deep drawing with a forming height of 25 mm or more. The elongation rate was explained earlier.
  In the above-mentioned preferable precoated metal sheet of the present invention, the specular gloss of the coating film is 60% or more when measured in an unprocessed state at an incident angle and a light receiving angle of 60 °. When the specular gloss at 60 ° is less than 60%, the reduction in gloss of the coating film at the molded portion is hardly noticeable, and this aspect is meaningless. When the specular gloss is 80% or more, the effect of this aspect is more exerted, and therefore, it is more preferable. The mirror gloss of the coating film is JIS. K. 5600.4.7: 1999, which means the specular gloss. The gloss of the coating film is generally 80% or more unless adjusted using a matting agent or the like. When adjusting the gloss to a low level, it can be adjusted using a matting agent such as silica. In addition, it can be adjusted using other generally known gloss adjusting agents.
  In addition to the interface between the intermediate coating film layer and the top coating film layer, the precoated metal sheet of the present invention further includes an interface other than the interface between the intermediate coating film layer and the top coating film layer, such as a primer coating film layer. Between the intermediate coating layer and the intermediate coating layer, when there are a plurality of top coating layers, the size of the fine irregularities of at least one interface such as the top coating layer is 0. It is more preferable that it is 3 to 0.8 μm. If the size of the fine irregularities at the interface between the coating film layers is less than 0.3 μm in Ra, the adhesion at the coating film interface may be lowered. In general, when a coating film is laminated, the adhesion of the coating film is maintained by a physical bond such as a chemical bond, a hydrogen bond, or a van der Waals force between the coating films. By setting the thickness to 3 μm or more, in addition to these adhesion forces, adhesion force due to the anchor effect is imparted. However, if it exceeds 0.8 μm, the appearance when the top paint is applied is affected, and the gloss may be lowered. Since the primer coating layer is generally in contact with the base metal plate and the intermediate coating layer or the top coating layer is generally coated thereon, the metal plate or intermediate coating layer, Since a resin with excellent adhesion such as an epoxy resin is used so as to be in close contact with the top coating film, or added as one of the components in the primer coating layer, the primer coating layer and these coating films A certain degree of adhesion is ensured even when the size of the fine irregularities at the interface is outside the range of 0.3 to 0.8 μm in Ra. However, in the case of the intermediate coating layer or the top coating layer, if adhesion is imparted to the coating film itself, there is a possibility that other coating film performance may be deteriorated. Therefore, since the intermediate coating layer and the top coating layer tend to be inferior in adhesion as compared with the primer coating layer, it is preferable that the Ra of these interfaces is in the above range because the adhesion is further improved. . It should be noted that the interface between the primer coating layer and the intermediate coating layer also has an advantage that, when Ra is within the above range, the adhesion is improved, or a resin that does not consider the adhesion can be used. Is more preferable.
  Here, in the present invention, the centerline average roughness (Ra) representing the size of the fine irregularities at the interface is measured by the following method (that is, a method basically according to JIS-B-0601-1982). can do.
  That is, after photographing a vertical cross section of the interface whose surface roughness Ra is to be measured with a micrograph, the unevenness (roughness curve) of the interface is traced, and a predetermined formula defined by JIS-B-0601-1982 (below) According to the example), the centerline average roughness Ra of this interface can be determined.
  In order to give Ra in the above range to the interface between the coating layers, it can be achieved by multilayer simultaneous application. Multi-layer simultaneous coating is applied to a substrate in a state where multiple layers of coating liquid such as a slot die coater or slide hopper type curtain coater are laminated simultaneously, and then the applied multiple layers of coating liquid are simultaneously dried and baked. Is the method.
  As described above, simultaneous multi-layer coating allows the coating liquid of each layer to be slightly mixed in the vicinity of the interface of the laminated coating film, thereby generating irregularities (that is, Ra) at the interface. In general, when two or more coating films are applied by simultaneous multi-layer coating, the size Ra of the fine irregularities at the coating film interface is 0.3 to 0.8 μm.
  As a multilayer simultaneous application method, a method of applying by coating different paints from two or more parallel slits, such as a slide hopper curtain coater, can be used.
  FIG. 7 shows an example in which a multilayer film is curtain-coated on a steel strip as a pretreatment metal plate production processing line.
  In the facility shown in FIG. 7, the steel strip wound around the coil is unwound by an uncoiler 41 and passed through an accumulator 42, a chemical conversion treatment device 47, a prime coater 45, and an induction heating furnace 43. A slide type slide hopper type curtain coating device 49 is arranged at a subsequent position, and a multilayer film is applied on the surface of the traveling steel plate 11 by curtain coating. An induction heating furnace 51 is provided downstream of the curtain coating device 49 as equipment for drying and baking the applied paint. Thereafter, the steel sheet is wound up by the recoiler 44 as a steel strip that has been processed through the accumulator 53.
  In the slide hopper type curtain coating apparatus 49, two layers are simultaneously coated. As for the size of the slide hopper type curtain coating apparatus, for example, the slit width on the coater is 200 mm, the slit interval is 500 μm, and the height to the steel plate to be coated is 150 mm. The steel sheet moves under the multilayer slide coater, and a multilayer coating film is formed on the steel sheet. After simultaneous two-layer coating, drying and baking are performed in an induction heating furnace. The thickness of the coating film is, for example, 2-15 μm for the intermediate coating layer and 0.5-15 μm for the top coating layer. The heating rate in the induction heating furnace is, for example, 2 to 10 ° C./s, and the ultimate temperature of the steel plate after baking is 200 to 230 ° C.
  The pre-coated metal sheet of the present invention is a roll coater coating, dip coating, curtain flow coater, roller curtain coater, slide hopper type curtain, except that at least the intermediate coating layer film and the top coating layer are coated and baked by a multilayer simultaneous coating method. The coating may be performed by a generally known coating method such as a flow coater, and by repeating the method of coating and baking each layer one layer at a time. The baking method is more suitable because it can be applied on the current 2-coat 2-bake coating line.
  That is, a general pre-coated metal sheet production line (generally called a coil coating line or CCL) is generally used for two-coat coating, so it is difficult to apply three or more layers. Also, in order to modify the line so that three or more layers can be painted, it was necessary to increase the number of painting equipment and baking furnaces, which required a large amount of capital investment. For this reason, it has been considered difficult to develop vivid colors on precoated metal sheets.
  However, in the present invention, the above problem can also be solved by using the multi-layer simultaneous coating method.
  Moreover, generally known drying baking methods, such as a hot air oven, a direct-fired oven, a far-infrared oven, and an induction heating oven, can be used as a drying baking method in coating.
  Generally known additives such as antifoaming agents, leveling agents, slip agents, waxes, matting agents, etc. are added to the primer, intermediate coating and top coating used in the present invention as necessary. May be.
  As the metal plate used in the present invention, generally known metal materials can be used. The metal material may be an alloy material. For example, a steel plate, a stainless steel plate, an aluminum plate, an aluminum alloy plate, a titanium plate, a copper plate, and the like can be given. The surface of these materials may be plated. Examples of plating types include zinc plating, aluminum plating, copper plating, and nickel plating. These alloy platings may be used. In the case of steel plates, generally known steel plates and plated steel plates such as hot-dip galvanized steel plates, electrogalvanized steel plates, zinc-nickel alloy plated steel plates, hot-dip galvanized steel plates, aluminum-plated steel plates, aluminum-zinc alloyed steel plates, etc. Applicable.
  If the surface of the metal plate used in the present invention is generally subjected to a known chemical conversion treatment, the adhesion between the metal plate and the coating layer is improved, which is more preferable. As the chemical conversion treatment, zinc phosphate chemical conversion treatment, coating chromate treatment, electrolytic chromic acid treatment, reaction chromate treatment, chromate-free chemical conversion treatment, or the like can be used. As the non-chromate chemical conversion treatment, those treated with an aqueous solution containing a silane coupling agent, a zirconium compound, a titanium compound, tannin or tannic acid, a resin, silica and the like are known, and Japanese Patent Application Laid-Open No. 53-9238 is known. JP-A-9-241576, JP-A-2001-89868, JP-A-2001-316845, JP-A-2002-60959, JP-A-2002-38280, JP-A-2002-266081, You may use the well-known technique described in Kaikai 2003-253464 etc. These chemical conversion treatments are commercially available, for example, chromate treatment “ZM-1300AN” manufactured by Nihon Parkerizing Co., Ltd., chromate-free chemical conversion treatment “CT-E300N” manufactured by Nihon Parkerizing Co., Ltd., and trivalent chromium-based chemical conversion manufactured by Nippon Paint Co., Ltd. The treatment “Surfcoat ™ NRC1000” or the like can be used.

次に，本実施例に用いたプレコート金属板について詳細を説明する。
新日本製鐵株式会社製の亜鉛−ニッケル合金めっき鋼板「ジンクライト」（以下，ＺＬと称す）と新日本製鐵株式会社製の電気亜鉛めっき鋼板「ジンコート」（以下，ＥＧと称す）と新日本製鐵株式会社製の溶融亜鉛めっき鋼板「シルバージンク」（以下，ＧＩと称す）を原板として準備した。板厚は０．６ｍｍのものを使用した。本実験で用いたＺＬのめっき付着量は片面２０ｇ／ｍ^２，めっき層中のニッケル量は１２ｍａｓｓ％であった。また，ＥＧのめっき付着量は片面２０ｇ／ｍ^２のものを、ＧＩのめっき付着量は片面６０ｇ／ｍ^２のものを用いた。
次に，準備した原板を日本パーカライジング社製のアルカリ脱脂液「ＦＣ−４３３６」の２質量％濃度，５０℃水溶液にてスプレー脱脂し，水洗後，乾燥した後に，日本パーカライジング社製のクロメートフリー化成処理である「ＣＴ−Ｅ３００Ｎ」をロールコーターにて塗布し，熱風オーブンにて乾燥させた。熱風オーブンでの乾燥条件は，金属板の到達板温で６０℃とした。クロメートフリー処理の付着量は，全固形分で２００ｇ／ｍ^２付着するように塗装した。
次に，化成処理を施した金属板の片方の面に，作製したプライマー塗料を，他方の面に日本ファインコーティングス社製の裏面塗料である「ＦＬ１００ＨＱ」のグレー色をロールコーターにてそれぞれ塗装し，熱風を吹き込んだ誘導加熱炉にて金属板の到達板温が２１０℃となる条件で乾燥硬化した。そして乾燥焼付後に，塗装された金属板へ水をスプレーにて拭きかけ，水冷した。
次に，中塗り塗料とトップ塗料を図５に示す如きスライドホッパー式のカーテンコーターにて同時に積層塗装し，熱風を吹き込んだ誘導加熱炉にて金属板の到達板温が２３０℃となる条件で積層した塗膜を同時に乾燥硬化した。そして，乾燥焼付後に，塗装された金属板へ水をスプレーにて拭きかけて水冷することで，３層のプレコート金属板を得た（本手順での塗装方法を「塗装方法（ｉ）」と称す）。
また，プライマー塗膜の上に，中塗り塗料とトップ塗料，トップクリヤー塗料をスライドホッパー式のカーテンコーターにて同時に３積層塗装し，熱風を吹き込んだ誘導加熱炉にて金属板の到達板温が２３０℃となる条件で積層した塗膜を同時に乾燥硬化した。そして乾燥焼付後に，塗装された金属板へ水をスプレーにて拭きかけて水冷することで，４層のプレコート金属板を得た（本手順での塗装方法を「塗装方法（ｉｉ）」と称す）。
更には，プライマー塗料を塗装する工程で，プライマー塗料，中塗り塗料，トップ塗料の３層をスライドホッパー式のカーテンコーターにて同時に３積層塗装し，熱風を吹き込んだ誘導加熱炉にて金属板の到達板温が２３０℃となる条件で積層した塗膜を同時に乾燥硬化した。そして，乾燥焼付後に，塗装された金属板へ水をスプレーにて拭きかけて水冷することで，３層のプレコート金属板も得た（本手順での塗装方法を「塗装方法（ｉｉｉ）」と称す）。
また，プライマー塗膜上にロールコーターにて中塗り塗料を１層のみ塗装し，上述の要領で焼付けた後に，中塗り塗膜上に再度ロールコーターにてトップ塗料を１層塗装し焼き付けた３層のプレコート金属板も作製した（本手順での塗装方法を「塗装方法（ｉｖ）」と称す）。
プライマー塗膜上にロールコーターにてトップ塗料のみを１層塗装し焼き付けた２層のプレコート金属板も作製した（本手順での塗装方法を「塗装方法（ｖ）」と称す）。
作製したプレコート金属板の各塗膜厚については，ロールコーターの場合にはロールの回転周速や塗料粘度を，スライドホッパー式のカーテンコーターの場合は塗料の塗出圧力や塗料粘度を調整することで，制御した。なお，裏面塗料の膜厚は乾燥膜厚で５μｍとした。なお，各膜厚はＫＥＴ社製の電磁膜厚計「ＬＥ−２００Ｊ」にて測定し，更に，各サンプルの垂直切断面を顕微鏡にて観察し，求める膜厚となっているかを再確認した。
表２に，作製したプレコート金属板の詳細を記載する。

以下，作製したプレコート金属板の評価方法の詳細を記載する。
１．プレコート金属板の外観観察
作製したプレコート金属板のトップ塗膜を施した面の外観を目視及び１０倍ルーペにて観察して評価した。外観評価は，色調と沸き欠陥の発生度との両者に着目して行った。色調については，塗膜の色が明らかに黒ずんで見えた場合，または，明らかに白味を帯びており淡色系に見えた場合をそれぞれ×，僅かに黒ずんで見えた場合を△，黒ずみが殆ど無く鮮やかに見えた場合を○、黒ずみが全くなく鮮やかに見えた場合を◎と評価した。また、前記評価で○と△の中間レベルのものを○△と評価した。
沸き欠陥については，目視でもルーペでも全く沸き欠陥が認められない場合には○，目視では認められないがルーペにて極小さな沸き欠陥が認められる場合には△，目視でも明らかな沸き欠陥が認められる場合は×と評価した。
２．耐食性試験
作製したプレコート金属板のトップ塗膜を施した面にカット傷を入れて，ＪＩＳ Ｋ ５４００．９．１記載の方法で塩水噴霧試験を実施した。塩水は，試験片のクロスカットを入れた面に噴霧した。試験時間は２４０時間とした。そして，表面側のカット部からの塗膜膨れ幅を測定し，カット部膨れ幅が片側３ｍｍ以下の場合を○，カット部膨れ幅が片側３ｍｍ超５ｍｍ以下の場合を△，カット部膨れ幅が片側５ｍｍ超の場合を×と評価した。
３．塗膜界面のＲａ測定
プレコート金属板を塗膜断面が観察できるように垂直に切断し，切断したプレコート金属板を樹脂に埋め込んだ後に断面部を研磨して，３５００倍の走査型電子顕微鏡による塗膜の断面写真を撮影した。次に，透明の樹脂シート（市販のＯＨＰシートを使用）を写真上にかぶせて，塗膜界面の凹凸を正確にトレースした。そして，図２に示すように，縦線の部分の面積を画像処理装置で測定して，その平均値として下記式（ＩＩ）からＲａを算出した。
Ｒａ＝（∫_０ ^ｌ｜ｆ（ｘ）｜ｄｘ）／ｌ・・・（ＩＩ）
４．塗膜破断伸び率測定
作製したプレコート金属板を，２３℃の雰囲気中にてトップ塗膜を施した面が外側となるように１８０°折り曲げ加工（密着曲げ加工）した。次に，加工部を１０倍顕微鏡にて観察し，塗膜の割れ発生の有無を調査した。更には，加工したプレコート金属板の加工部の中心付近を断面が観察できるように垂直に切断し，切断したプレコート金属板を樹脂に埋め込んだ後に断面部を研磨して，１０倍及び５００倍の顕微鏡にて断面を観察した。そして，各塗膜層の亀裂発生の有無を観察した。このようにして各塗膜層を観察し，５００倍の顕微鏡で観察して全ての塗膜層に亀裂が入っていなかった場合を塗膜の破断伸び率が１００％以上として○，１層以上の塗膜に１０倍の顕微鏡で極僅かに亀裂が確認され，５００倍の顕微鏡で明らかに亀裂が確認される場合は，判断伸び率が僅かに１００％未満であるとして△，１層以上の塗膜に１０倍の顕微鏡で明らかな亀裂が発生していた場合を塗膜の破断伸び率が明らかに１００％未満として×と評価した。
５．塗膜密着性評価
上記の塗膜破断伸び率測定で折り曲げ加工したプレコート金属板の加工部の塗膜表面に粘着テープを貼り付け，これを勢い良く剥離したときの塗膜の残存状態を目視にて観察した。塗膜剥離の評価は，塗膜剥離の全くない場合を○，塗膜に僅かな剥離が認められる場合を△，塗膜に明確な大きな剥離がある場合を×として評価した。
６．プレコート金属板の塗膜のガラス転移温度の測定
セイコー電子社製の熱機械分析装置「ＳＳＣ５２００シリーズＴＭＡ／ＳＳ１２０Ｃ」にて塗膜のＴｇを測定した。なお，測定時のプローブは，針入プローブを用いた。
７．プレコート金属板の塗膜のユニバーサル硬度測定
フィッシャー・インストルメンツ社製の微小硬度計「フィッシャースコープ（登録商標）Ｈ１００」を用いて測定した。測定時の雰囲気温度は２３℃とし，押付け荷重５ｍＮのときのユニバーサル硬度（ＨＵ（Ｎ／ｍｍ^２））を本測定機器にて測定した。
８．プレコート金属板の塗膜の鏡面光沢度測定
スガ試験機社製の「デジタル変角光沢計」を用いて，入射角と受光角が６０°の条件で鏡面光沢度を測定した。
９．プレコート金属板加工後の鏡面光沢度測定
幅５０ｍｍの短冊状に切断したプレコート金属板を引張り試験機に治具間距離１００ｍｍとなるようにセットして，引っ張り速度２００ｍｍ／ｍｉｎの条件で，治具間距離が１１０ｍｍとなるまで引っ張った。そして，引っ張り加工後のサンプルを取り出し，サンプルの中央部の鏡面光沢度を，スガ試験機社製の「デジタル変角光沢計」を用いて，入射角と受光角が６０°の条件で測定した。そして，測定結果より光沢保持率（＝［加工後の鏡面６０°光沢］×１００／［加工前の鏡面６０°光沢］）を算出した。そして６０°鏡面光沢の光沢保持率が８５％以上のものを○、８５％未満のものを×評価した。
なお，本実験において，治具間距離１００ｍｍのサンプルを治具間距離１１０ｍｍまで引っ張った時の鏡面光沢を測定した理由は，経験的に，この条件で加工した時の６０°鏡面光沢の光沢保治率が８５％以上であると，深絞り成形部での光沢低加が目立ち難いことを本発明者らが知見したためである。
１０．ドロービード試験
プレス成形時の摺動性や金型による材料のキズ付き性を評価する試験方法として，ドロービード試験が知られている。本実験方法にて，プレコート金属板を評価すると，プレス成形で発生する塗膜の型カジリが再現され，プレス成形にて塗膜の型カジリが発生し易いプレコート金属板は，本試験方法でも塗膜の型カジリによる剥離が観察される。本実験は，図８に示すように，図８に示す形状および寸法の凸金型６１と凹金型６２との間にサンプル６３を挟み込み，押付け荷重Ｆを０．６ｔ及び１．０ｔで金型に荷重をかけた状態で，サンプルを２００ｍｍ／ｍｉｎの速度で引き抜いたときの塗膜の外観を観察することで実施した。なお，金型の表面粗度はＲａ＝０．８μｍに調整したものを用いた。また，本試験を実施する際には，サンプル塗膜表面に日本工作油社製の揮発性潤滑油「Ｇ−６２１５ＦＳ」を塗布し，評価面（裏面塗料を塗布していない面）が凹金型側となるように金型を押付けた。そして，引き抜いた後のサンプルの塗膜表面のキズ発生有無を調査し，次の基準で評価した。押し付け加重０．６ｔの条件でも１．０ｔでの条件でも塗膜の剥離が観察されない場合を○，０．６ｔの押し付け荷重条件では塗膜の剥離が認められないが，１．０ｔの条件で塗膜剥離が認められる場合を△，押し付け加重０．６ｔの条件でも１．０ｔでの条件でも塗膜の剥離が観察される場合を×と評価した。
１１．角筒成形試験
作製したプレコート金属板を評価面（裏面塗膜を施していない面）が成形物の外側となるように角筒形状に深絞り成形した。角筒成形時の金型は次の条件のものを用いた。即ち，ポンチサイズが４０ｍｍ角，ポンチコーナーＲが５ｍｍ，ポンチ肩Ｒが５ｍｍ，ダイス肩Ｒが５ｍｍの条件とした。また，金型の表面粗度はＲａで０．１μｍ以下の鏡面仕上げとした。また，材料のブランクサイズはφ１００ｍｍの円形とし，しわ押さえ圧を０．８ｔとした。成形高さは２０ｍｍと２５ｍｍと３０ｍｍの３水準実施した。また，成形加工後は，プレコート金属板の加工された部分の塗膜剥離もしくは亀裂の発生有無（以降，加工性と称す）を目視と１０倍顕微鏡で観察し，目視と顕微鏡いずれの方法で観察しても剥離や亀裂の発生が認められない場合は○，顕微鏡では剥離や亀裂の発生が認められるが，目視ではこれらが認められない場合を△，目視でも剥離や亀裂の発生が認められた場合は×と評価した。また，成形物の光沢度を目視観察し，加工部で光沢の低下が認められない場合は○，明らかに光沢の低下が認められる場合は×と評価した。
（角筒成形物の光沢測定）
上記「１１．角筒成形試験」で得た成形高さ２５ｍｍと３０ｍｍの角筒成形物底面の鏡面光沢度を，スガ試験機社製の「デジタル変角光沢計」を用いて，入射角と受光角が６０°の条件で測定した。
（角筒成形物の塗膜界面のＲａ測定）
上記「１１．角筒成形試験」で得た成形高さ２５ｍｍと３０ｍｍの角筒成形物底面の任意の部分を切り出し，この部分の塗膜断面が観察できるように垂直に切断し，切断した塗装金属板を樹脂に埋め込んだ後に断面部を研磨して，３５００倍の走査型電子顕微鏡による塗膜の断面写真を撮影した。次に，透明の樹脂シート（市販のＯＨＰシートを使用）を写真上にかぶせて，塗膜界面の凹凸を正確にトレースした。そして，図３に示すように，縦線の部分の面積を画像処理装置で測定して，その平均値として上記式２からＲａを算出した。なお，成形物の断面観察した部位の金属板が，成形により曲がっていた場合，塗膜界面の粗さ中心に，金属板の表面もしくはその上に被覆された塗膜の最表面に対して平行な線を引き，これを界面の中心線とした。

以下，評価結果について詳細を説明する。
表３〜表５に作製したプレコート金属板の評価結果を示す。表３において、本発明のプレコート金属板（実施例ＰＣＭ−Ｎｏ．１〜２０、２２〜３０）は，いずれも中塗り塗膜層とトップ塗膜層の界面に液々界面痕跡界面が観察されたが、赤系，黄系，オレンジ系の色に着色したときに，黒味がかったり，白味がかったりすることなしに，鮮やかな色を発現することができ，且つ，沸き欠陥の発生も無く，良好な意匠外観であった。特に従来の各層を塗装するごとに焼付ける方法で塗装し、中塗り塗膜層とトップ塗膜層との界面の微細凹凸のＲａが０．３μｍ未満のもの（比較例ＰＣＭ−２１）より、他の多層同時塗布によって塗装し、中塗り層とトップ層と界面に液々痕跡界面を有しその界面の微細凹凸のＲａを０．３〜０．８μｍにしたもの（実施例ＰＣＭ−Ｎｏ．１〜２０、２２〜３０）は、より鮮やかな外観を発現している。
中塗り塗膜中に含まれるチタン系顔料の添加量が４０ｍａｓｓ％未満であると（実施例ＰＣＭ−Ｎｏ．９），トップ塗膜の塗装外観が若干黒味を帯びてくる傾向であり，６０ｍａｓｓ％超であると（実施例ＰＣＭ−Ｎｏ．９），破断伸びが１００％を僅かに下まわる傾向であり，加工性に劣る懸念があるため，中塗り塗膜のチタン系顔料の添加量は４０〜６０ｍａｓｓ％がより好適である。また，塗膜の破断伸びが１００％未満のもの（実施例ＰＣＭ−Ｎｏ．１２，１６〜１８）は，加工性に劣る懸念があるため，本発明のプレコート金属板に用いる塗膜は，破断伸び率が１００％以上のものがより好適である。
本発明のプレコート金属板は，中塗り塗膜とトップ塗膜との界面の微細凹凸のＲａが０．３〜０．８μｍの範囲外であると（実施例ＰＣＭ−Ｎｏ．２１），厳しい加工を施した時に塗膜密着性が損なわれるため，界面の微細凹凸のＲａは０．３〜０．８μｍがより好適である。本実験でも明らかなように，多層同時塗布による塗装を行なうことで、各塗膜界面の微細凹凸のＲａを０．３〜０．８μｍとすることができる。
本発明のプレコート金属板で，プライマー塗膜の薄いもの（実施例ＰＣＭ−Ｎｏ．２２）は耐食性が若干劣る傾向であった。中塗り塗膜の膜厚が薄いもの（実施例ＰＣＭ−Ｎｏ．２３）は，原板の色を隠蔽しきれないため，この上にトップ塗膜を塗装した時の外観が若干黒味を帯びる傾向であった。トップ塗膜の膜厚が薄いもの（実施例ＰＣＭ−Ｎｏ．２４）は，意匠外観的にトップ塗膜の色が薄く，中塗り塗膜の白色が若干透けて見える傾向であった。一方，各塗膜層の膜厚が厚いもの（実施例ＰＣＭ−Ｎｏ．２５，２６，２７）は，極微細な沸き欠陥が発生する傾向であった。したがって，本発明のプレコート金属板の各塗膜の膜厚は，それぞれの膜厚が１〜３０μｍで，且つ，全塗膜厚が５０μｍ未満であることがより好適であった。
また，原板はＺＬでもＥＧも塗膜性能（塗膜の素地色調隠蔽性等）に大きな差は無かったため（実施例ＰＣＭ−Ｎｏ．２とＰＣＭ−Ｎｏ．２８との比較），本発明のプレコート金属板の原板は，公知の金属板であれば，どのようなものを使用しても構わないことが判った。
本発明のプレコート金属板のプライマー塗膜中にＳｉ，Ｐ以外の防錆顔料，例えば，Ｃｒ系防錆顔料を含む場合（比較例ＰＣＭ−Ｎｏ．３１）や中塗り塗膜にＴｉ系添加剤を含まないものも（比較例ＰＣＭ−Ｎｏ．３２）は，トップ塗膜まで塗装した時の色調が悪く，鮮やかな色を発現できないため，不適であった。また，トップ塗膜にＴｉ系添加剤を含むもの（実施例ＰＣＭ−Ｎｏ．２９）は，若干白味を帯びた色調となってしまったため，鮮やかな赤系，オレンジ系，黄系の色を発現させるためには，トップ塗膜にはＴｉ系添加剤を含まない方がより好適である。Ｔｉ系添加剤を含む中塗り塗膜を塗装せず，且つ，トップ塗膜を比較的薄膜で塗装したもの（比較例ＰＣＭ−Ｎｏ．３３〜３５）も，求める意匠外観（鮮やかな赤，黄，オレンジ系の色）を得ることができないため，不適であった。一方，Ｔｉ系添加剤を含む中塗り塗膜を塗装しない場合で，トップ塗膜を厚膜で塗装したもの（比較例ＰＣＭ−Ｎｏ．３６）は，激しい沸き欠陥が発生したため，不適であった。プライマー塗膜を塗装せずに，中塗り塗膜とトップ塗膜のみを塗装したもの（比較例ＰＣＭ−Ｎｏ．３７）は，良好な外観を得られたものの，耐食性が劣るため，不適であった。
なお，本発明のプレコート金属板のプライマー塗料，中塗り塗料，トップ塗料には市販の塗料をベースに，プライマー塗膜層中にはＳｉ，Ｐのいずれか一方，もしくは，両方を含むものを用い，且つ，中塗り塗膜層中にＴｉ系添加剤を含むものを用い，且つ，トップ塗膜層が白系，黒系以外の色に着色されているもの（実施例ＰＣＭ−Ｎｏ．１５，１６）を用いても効果を発揮する。特に，中塗り塗料とトップ塗膜とを多層同時塗布で塗装し，これら界面のＲａを０．３〜０．８μｍとすると塗膜密着性に優れより好適である。
なお，プレコート金属板を使用することで，ポストコート塗装で課題となっていた揮発性有機溶剤（ＶＯＣ）の問題を解決することができるだけではなく，ユーザーでの塗装設備撤廃によるコストダウン，工場小スペース化等も達成される。
また，従来では多層プレコート金属板を製造するためには，積層した塗膜層の数だけオーブン等の焼付け乾燥設備が必要であったが，本願発明の多層同時塗布やウェットオンウェット塗装にて塗装することで，これら焼付け乾燥設備の数を減らすことができるため，コンパクトな設備で低コストの製造方法を提供することが可能となる。したがって，本発明は，産業上の極めて価値の高い発明であると言える。
また、表４において、本発明の実施例に係るプレコート金属板（ＰＣＭ−２，ＰＣＭ−１７，ＰＣＭ−４５〜ＰＣＭ−４９）は、高い光沢を有しているにもかかわらず、深絞り加工した時の加工部での光沢低下が小さく、更には、連続プレス時の塗膜カジリを再現するドロービード試験においても塗膜カジリが発生し難く、且つ、加工部での塗膜の剥離や亀裂の発生がなく、良好であった。
ただし、中塗り塗膜層とトップ塗膜層との界面のＲａが０．３〜０．８から外れるもの（ＰＣＭ−４８、ＰＣＭ−４９）は、ドロービード試験で塗膜が剥離し易い傾向である。
一方、塗膜のＴｇが３０℃超のもの（ＰＣＭ−１７、ＰＣＭ−４８、ＰＣＭ−４９）は加工後の光沢保持率が低く、角筒成形しても目視で明らかに光沢低下が認められるため、塗膜のＴｇは３０℃以下が好適である。
次に、プレコート粉金属板ＰＣＭ−２、ＰＣＭ−１７、ＰＣＭ−４５〜ＰＣＭ−４９を用いて、成形加工した成形物の評価結果を表５に示す。本発明で期待した範囲内のプレコート金属板を用いて、成形した成形物は、いずれも６０°鏡面光沢で６０％以上の外観を有しており、また、加工部で塗膜の亀裂や剥離の発生も無く、優れた外観であった。ただし、Ｔｇが３０℃超のもの（ＰＣＭ−１７）は加工後の光沢保持率が他のものと比べて低く、僅かに６０％を超えるレベルであるため、塗膜のＴｇは３０℃以下がより好適である。一方、塗膜のＴｇが３０℃超であり、且つ、トップ塗膜層との界面のＲａが０．３〜０．８から外れるもの（ＰＣＭ−４８、ＰＣＭ−４９）はいずれも６０°鏡面光沢で６０％未満と著しく光沢が低くなるため、不適である。
以上，添付図面を参照しながら本発明の好適な実施形態について説明したが，本発明はかかる例に限定されないことは言うまでもない。当業者であれば，特許請求の範囲に記載された範疇内において，各種の変更例または修正例に想到し得ることは明らかであり，それらについても当然に本発明の技術的範囲に属するものと了解される。   Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.
  Hereinafter, the details of the test material used in this example will be described.
  First, the details of the paint used will be described.
  “Byron (registered trademark) 63CS” (Tg: 7 ° C., number average molecular weight: 20000) which is an amorphous polyester resin manufactured by Toyobo Co., Ltd. and “Byron (registered trademark)” which is an amorphous polyester resin manufactured by Toyobo Co., Ltd. ) 200 "(Tg: 67 ° C, number average molecular weight: 17000)," Byron (registered trademark) 220 "(Tg: 53 ° C, number average molecular weight: 3000)," Byron (registered trademark) GK890 "(Tg: 17 ° C) , Number average molecular weight: 11000) was used as the binder resin. Since “Byron (registered trademark) 200” and “Byron (registered trademark) 220” are in the form of pellets or flakes, they are used as an organic solvent (mixed in a mass ratio of cyclohexanone: solvesso 150 = 1: 1). Used by dissolving. Further, “Byron (registered trademark) 63CS” was used as it was because the polyester resin was already dissolved in an organic solvent (mixed in a mass ratio of cyclohexanone: solvesso 150 = 1: 1).
  Next, as a cross-linking agent, “Cymel (registered trademark) 303” which is a fully alkyl methylated melamine resin (hereinafter referred to as melamine resin) manufactured by Mitsui Cytec Co., Ltd. is used. Mixed. The mixing amount was such that the mass ratio of each resin solid was [polyester: melamine = 85: 25]. Further, “Catalyst 602” manufactured by Mitsui Cytec Co., Ltd. was added as a reaction catalyst in an amount of 1.0 mass% based on the total resin solid content. The clear paint used for the experiment was prepared by the above procedure. In the following text, a paint made using a polyester resin “Byron (registered trademark) 63CS” is referred to as a polymer low Tg paint, a paint using “Byron (registered trademark) 220” is referred to as a polymer high Tg paint, The paint using "Byron (registered trademark) 200" is referred to as a low molecular high Tg paint, and the paint using "Byron (registered trademark) GK890" is referred to as a medium molecular low Tg paint.
  Next, a necessary amount of titanium oxide “Taipeku CR95” (hereinafter referred to as Ti-based) manufactured by Ishihara Sangyo Co., Ltd. was added to the clear paint produced above to produce an intermediate coating. In addition, a clear coating of “Flex Coat 200HQ” (hereinafter referred to as a commercially available high-working intermediate coating) manufactured by Nippon Fine Coatings and a “Nippe Super Coat 200HQ” (manufactured by Nippon Fine Coatings), which are commercially available coatings. Hereinafter, a commercially available clear coating (referred to as a low-process intermediate coating) was prepared by adding 50 mass% of the above-described titanium oxide. Details of the prepared intermediate coating are shown in Table 1.
  Next, red, yellow, and orange color pigments were added to the clear paint produced to produce a top paint. Commercially available naphthol red was used for red pigments, commercially available disazo yellow was used for yellow pigments, and commercially available disazopyrazolone orange was used for orange pigments. In addition to these colored pigments, a titanium oxide “Taipeku CR95” manufactured by Ishihara Sangyo Co., Ltd. was also added as a comparison. Also, a red paint of “Flexcoat 200HQ” (hereinafter referred to as a commercially available high-processing top paint) and “Nippe Super Coat 200” (hereinafter referred to as “pre-coated metal plate paints” manufactured by Nippon Fine Coatings, Inc., which are commercially available paints. , Also called a commercially available low-process top paint). Furthermore, as required, a clear paint without any pigment was also used as a top clear paint to be coated on these colored coating layers.
  As for the primer paint, a clear paint of FL641EU primer manufactured by Nippon Fine Coatings Co., Ltd., which is a commercially available primer paint, was prepared, and a primer paint was prepared by adding a necessary amount of a rust preventive pigment thereto. The rust preventive pigment used in this experiment is “Topol C” (hereinafter referred to as “Cr-based”), a chromium-based rust preventive pigment manufactured by Toho Pigment, and K-WHITE #, a tripolyaluminum dihydrogen phosphate manufactured by Teika. 105 "(hereinafter referred to as P-based)," SHIELDEX (registered trademark) C303 "(hereinafter referred to as Si-based), which is a calcium ion exchange silica manufactured by GRACE, was used. Moreover, what added the titanium oxide "Taipeku CR95" (Ti system pigment) by Ishihara Sangyo Co., Ltd. as needed was also produced. Details of the prepared primer coating are shown in Table 1.
  In addition, no leveler is added to all intermediate coatings, and an acrylic leveler manufactured by Nippon Paint Co., Ltd. is used as the leveler in all top coatings. The difference in surface tension between the intermediate coating and top coating is 1. Appropriately added to each paint so that the difference between the maximum and minimum values obtained is less than 2 mN / m when the surface tension is measured 5 times between 2 mN / m and 5 mN / m. The amount was adjusted.
  Furthermore, BYK-Chemie's silicone additive BYK141 is added to all of the top clear paints, and the difference in the surface tension of the top paint to which the leveler used for coating is added is 0.3 mN / m or more. Appropriately so that the difference between the maximum value and the minimum value of the obtained measurement value is less than 2 mN / m when the surface tension is measured 5 times as the paint of each layer, and less than 3.7 mN / m The amount added was adjusted.
  The amount of the leveler added is determined by measuring the surface tension of the paint five times using a dynamometer (by BYK-Chemie GmbH) every time a drop of the leveler is dropped into the paint with a dropper, and repeating this operation until it falls within the above range. Went the way.

  Next, the details of the precoated metal plate used in this example will be described.
  Zinc-nickel alloy-plated steel sheet "Zinclite" (hereinafter referred to as ZL) manufactured by Nippon Steel Corporation and electro-galvanized steel sheet "JINCOAT" (hereinafter referred to as EG) manufactured by Nippon Steel Corporation A hot-dip galvanized steel sheet “Silver Zinc” (hereinafter referred to as GI) manufactured by Nippon Steel Co., Ltd. was prepared as an original sheet. A plate thickness of 0.6 mm was used. The amount of ZL plating used in this experiment was 20 g / m on one side.²The amount of nickel in the plating layer was 12 mass%. The EG plating adhesion amount is 20 g / m on one side.²GI plating coverage is 60g / m on one side²The thing of was used.
  Next, the prepared original plate is spray degreased with 50% aqueous solution of 2% by weight of alkaline degreasing solution “FC-4336” manufactured by Nihon Parkerizing Co., Ltd., washed with water, dried, and then chromate-free formed by Nihon Parkerizing Co., Ltd. The treatment “CT-E300N” was applied with a roll coater and dried in a hot air oven. The drying conditions in the hot air oven were set to 60 ° C. at the ultimate temperature of the metal plate. The amount of chromate-free treatment is 200 g / m in total solids.²Painted to adhere.
  Next, paint the primer coating on one side of the chemical-treated metal plate, and apply the gray color of “FL100HQ”, a back coating made by Nippon Fine Coatings, on the other side using a roll coater. Then, it was dried and hardened under the condition that the ultimate plate temperature of the metal plate was 210 ° C. in an induction heating furnace in which hot air was blown. After drying and baking, water was sprayed on the painted metal plate and cooled.
  Next, the intermediate coating and the top coating are simultaneously laminated and coated with a slide hopper type curtain coater as shown in FIG. 5, and the ultimate temperature of the metal plate is 230 ° C. in an induction heating furnace in which hot air is blown. The laminated coating film was simultaneously dried and cured. Then, after drying and baking, water was sprayed onto the coated metal plate and water-cooled to obtain a three-layer pre-coated metal plate (the coating method in this procedure is referred to as “painting method (i)”) Called).
  In addition, on the primer coating, intermediate coating, top coating, and top clear coating are simultaneously laminated in a slide hopper type curtain coater, and the ultimate temperature of the metal plate is measured in an induction heating furnace blown with hot air. The coating films laminated at 230 ° C. were simultaneously dried and cured. Then, after drying and baking, water was sprayed onto the coated metal plate with water spray to obtain a four-layer pre-coated metal plate (the coating method in this procedure is referred to as “painting method (ii)”). ).
  Furthermore, in the process of painting the primer paint, three layers of primer paint, intermediate paint, and top paint are applied simultaneously in three layers using a slide hopper type curtain coater, and the metal plate is coated in an induction heating furnace blown with hot air. The coating films laminated under the condition that the ultimate plate temperature was 230 ° C. were simultaneously dried and cured. After drying and baking, water was sprayed onto the coated metal plate and cooled with water to obtain a three-layer pre-coated metal plate (the coating method in this procedure is referred to as “painting method (iii)”) Called).
  In addition, only one layer of the intermediate coating was applied on the primer coating with a roll coater, baked as described above, and then one layer of the top coating was again applied on the intermediate coating with a roll coater and baked. A pre-coated metal plate with a layer was also prepared (the coating method in this procedure is referred to as “painting method (iv)”).
  A two-layer pre-coated metal sheet was also produced by coating only one layer of the top coating on the primer coating with a roll coater and baking it (the coating method in this procedure is referred to as “coating method (v)”).
  Regarding the coating thickness of the pre-coated metal sheet, the roll peripheral speed and paint viscosity should be adjusted in the case of roll coaters, and the paint application pressure and paint viscosity should be adjusted in the case of slide hopper type curtain coaters. And controlled. The film thickness of the back coating was 5 μm in terms of dry film thickness. Each film thickness was measured with an electromagnetic film thickness meter “LE-200J” manufactured by KET, and the vertical cut surface of each sample was observed with a microscope to reconfirm that the film thickness was as required. .
  Table 2 shows the details of the prepared precoated metal sheet.

  The details of the evaluation method for the prepared precoated metal sheet are described below.
1. Appearance observation of pre-coated metal plate
  The appearance of the surface of the prepared precoated metal plate on which the top coating film was applied was evaluated by visual observation and observation with a 10-fold magnifier. Appearance evaluation focused on both the color tone and the occurrence of boiling defects. As for the color tone, when the color of the coating film was clearly darkened, or when it was clearly white and light-colored, x, when it looked slightly dark, Δ The case where it appeared vivid with no darkness was evaluated as ◯, and the case where it looked vivid without any darkening was evaluated as ◎. Moreover, the thing of the intermediate level of (circle) and (triangle | delta) by said evaluation was evaluated as (circle) (triangle | delta).
  Regarding boiling defects, ◯ when no boiling defects are observed visually or with a loupe, △ when no extremely small boiling defects are observed with a loupe, and obvious boiling defects are observed visually. When evaluated, it was evaluated as x.
2. Corrosion resistance test
  Cut scratches were made on the surface of the prepared precoated metal sheet on which the top coating film had been applied, and a salt spray test was performed by the method described in JIS K 5540.9.1. Salt water was sprayed on the surface of the test piece with the cross cut. The test time was 240 hours. Then, the film swollen width from the cut portion on the surface side is measured, ○ when the cut portion swollen width is 3 mm or less on one side, Δ when the cut portion swollen width is more than 3 mm and less than 5 mm on one side, and the cut portion swollen width is The case of more than 5 mm on one side was evaluated as x.
3. Ra measurement of paint film interface
  Cut the pre-coated metal plate vertically so that the cross-section of the coating film can be observed, embed the cut pre-coated metal plate in the resin, polish the cross-section, and take a cross-sectional picture of the coating film with a scanning electron microscope of 3500 times did. Next, a transparent resin sheet (using a commercially available OHP sheet) was placed on the photograph to accurately trace the unevenness at the coating film interface. Then, as shown in FIG. 2, the area of the vertical line portion was measured by an image processing apparatus, and Ra was calculated from the following formula (II) as the average value.
        Ra = (∫₀ ^l| F (x) | dx) / l (II)
4). Measurement of elongation at break of coating film
  The prepared pre-coated metal sheet was subjected to 180 ° bending (adhesion bending) in a 23 ° C. atmosphere so that the surface to which the top coating film was applied was on the outside. Next, the processed part was observed with a 10 × microscope, and the presence or absence of cracks in the coating film was investigated. Furthermore, the vicinity of the center of the processed part of the processed precoated metal plate is cut vertically so that the cross section can be observed, the cut precoated metal plate is embedded in the resin, and then the cross section is polished to obtain 10 times and 500 times. The cross section was observed with a microscope. And the presence or absence of the crack generation of each coating film layer was observed. In this way, each coating layer is observed, and when all the coating layers are not cracked by observing with a 500 × microscope, the breaking elongation of the coating is 100% or more. If a very slight crack is confirmed with a 10 × microscope and a clear crack is confirmed with a 500 × microscope, it is assumed that the judged elongation is slightly less than 100%, and one or more layers When a clear crack was generated in the coating film with a 10-fold microscope, the elongation at break of the coating film was clearly less than 100% and evaluated as x.
5). Coating film adhesion evaluation
  The adhesive tape was affixed to the coating film surface of the processed part of the pre-coated metal sheet that was bent by the above-described measurement of elongation at break of the coating film, and the remaining state of the coating film was visually observed when it was peeled off vigorously. In the evaluation of coating film peeling, the case where there was no coating film peeling was evaluated as ◯, the case where slight peeling was observed in the coating film was evaluated as Δ, and the case where the coating film had clear large peeling was evaluated as x.
6). Measurement of glass transition temperature of precoated metal sheet
  The Tg of the coating film was measured with a thermomechanical analyzer “SSC5200 series TMA / SS120C” manufactured by Seiko Denshi. The probe used for the measurement was a needle probe.
7. Universal hardness measurement of pre-coated metal sheet
  The measurement was performed using a microhardness meter “Fischerscope (registered trademark) H100” manufactured by Fischer Instruments. The ambient temperature during measurement is 23 ° C, and the universal hardness (HU (N / mm²)) Was measured with this measuring instrument.
8). Mirror gloss measurement of precoated metal sheet
  The specular glossiness was measured using a “digital variable angle gloss meter” manufactured by Suga Test Instruments Co., Ltd. under the conditions of an incident angle and a light receiving angle of 60 °.
9. Mirror gloss measurement after pre-coated metal sheet processing
  A pre-coated metal plate cut into strips having a width of 50 mm was set on a tensile tester so that the distance between jigs was 100 mm, and was pulled until the distance between jigs became 110 mm under the condition of a pulling speed of 200 mm / min. Then, the sample after the pulling process was taken out, and the specular gloss at the center of the sample was measured using a “digital gonio-gloss meter” manufactured by Suga Test Instruments Co., Ltd. under the conditions of an incident angle and a light receiving angle of 60 °. . The gloss retention (= [mirror surface 60 ° gloss after processing] × 100 / [mirror surface 60 ° gloss before processing]) was calculated from the measurement result. Then, 60 ° specular gloss gloss retention of 85% or more was evaluated as ○, and less than 85% was evaluated as ×.
  In this experiment, the reason why the specular gloss was measured when a sample with a distance between jigs of 100 mm was pulled to a distance between jigs of 110 mm was empirically determined to be 60 ° specular gloss when processed under these conditions. This is because the present inventors have found that when the rate is 85% or more, it is difficult to reduce the gloss at the deep-drawn formed part.
10. Draw bead test
  A draw bead test is known as a test method for evaluating the slidability during press molding and the scratching property of a material by a mold. When the pre-coated metal sheet is evaluated by this experimental method, mold galling of the paint film that occurs during press forming is reproduced, and a pre-coated metal sheet that is prone to galling of the paint film during press forming is also coated by this test method. Peeling due to film galling is observed. In this experiment, as shown in FIG. 8, a sample 63 is sandwiched between a convex mold 61 and a concave mold 62 having the shape and dimensions shown in FIG. 8, and the pressing load F is 0.6 t and 1.0 t. It was carried out by observing the appearance of the coating film when the sample was pulled out at a speed of 200 mm / min with a load applied to the mold. The surface roughness of the mold was adjusted to Ra = 0.8 μm. Also, when carrying out this test, apply volatile lubricant “G-6215FS” manufactured by Nippon Kogyo Oil Co., Ltd. to the surface of the sample coating film, and the evaluation surface (the surface to which the back coating is not applied) is indented. The mold was pressed so as to be on the mold side. And the presence or absence of the crack generation | occurrence | production of the coating-film surface of the sample after drawing was investigated, and the following reference | standard evaluated. The case where the peeling of the coating film is not observed even under the condition of the pressing load of 0.6 t or the condition of 1.0 t, the peeling of the coating film is not recognized under the pressing load condition of 0.6 t, but the condition of 1.0 t The case where peeling of the coating film was observed was evaluated as Δ, and the case where peeling of the coating film was observed under the condition of a pressing load of 0.6 t or 1.0 t was evaluated as x.
11. Square tube forming test
  The prepared pre-coated metal plate was deep-drawn into a rectangular tube shape so that the evaluation surface (the surface not provided with the back coating film) was outside the molded product. The mold used for the rectangular tube molding was as follows. That is, the punch size was 40 mm square, the punch corner R was 5 mm, the punch shoulder R was 5 mm, and the die shoulder R was 5 mm. The surface roughness of the mold was Ra with a mirror finish of 0.1 μm or less. The blank size of the material was a circle of φ100 mm, and the wrinkle holding pressure was 0.8 t. The molding height was implemented at three levels of 20 mm, 25 mm and 30 mm. In addition, after the forming process, the presence or absence of coating film peeling or cracking (hereinafter referred to as processability) of the processed part of the precoated metal sheet is observed visually and with a 10 × microscope, and observed with either the visual or microscopic method. Even when peeling or cracking was not observed, ○, peeling or cracking was observed with a microscope, but when these were not visually observed, Δ was observed, and peeling or cracking was also observed visually. The case was evaluated as x. Further, the glossiness of the molded product was visually observed, and it was evaluated as ◯ when no gloss reduction was observed in the processed part, and × when the gloss reduction was clearly observed.
(Gloss measurement of square tube molding)
  The specular glossiness of the bottom of the square tube molded product with a molding height of 25 mm and 30 mm obtained in the above “11. Square tube molding test” was measured using the “Digital Variable Glossmeter” manufactured by Suga Test Instruments Co., Ltd. Measurement was performed under a condition where the light receiving angle was 60 °.
(Ra measurement at the coating film interface of the rectangular tube molding)
  Cut out any part of the bottom of the square tube molding with the molding height of 25mm and 30mm obtained in the above "11. Square tube forming test", cut vertically so that the coating cross section of this part can be observed, and cut the coating After embedding the metal plate in the resin, the cross section was polished, and a cross-sectional photograph of the coating film was taken with a scanning electron microscope of 3500 times. Next, a transparent resin sheet (using a commercially available OHP sheet) was placed on the photograph to accurately trace the unevenness at the coating film interface. Then, as shown in FIG. 3, the area of the vertical line portion was measured by the image processing apparatus, and Ra was calculated from the above equation 2 as the average value. If the metal plate observed at the cross section of the molded product is bent by molding, it is parallel to the surface of the metal plate or the outermost surface of the coating film coated on the metal plate. A straight line was drawn and used as the center line of the interface.

  Details of the evaluation results will be described below.
  The evaluation result of the precoat metal plate produced in Table 3-Table 5 is shown. In Table 3, as for the precoat metal plate (Example PCM-No. 1-20, 22-30) of this invention, the liquid interface trace interface was observed in the interface of an intermediate coating film layer and a top coating film layer all. However, when it is colored red, yellow, or orange, it can produce a vivid color without being blackish or white, and also has boiling defects. There was no good design appearance. In particular, it is applied by a baking method every time each conventional layer is applied, and the Ra of the fine irregularities at the interface between the intermediate coating layer and the top coating layer is less than 0.3 μm (Comparative Example PCM-21), Coated by other simultaneous multi-layer coating, with an intermediate coating layer and a top layer, and a liquid-liquid trace interface at the interface, and Ra of fine irregularities at the interface of 0.3 to 0.8 μm (Example PCM-No. 1-20, 22-30) expresses a more vivid appearance.
  When the addition amount of the titanium pigment contained in the intermediate coating film is less than 40 mass% (Example PCM-No. 9), the coating appearance of the top coating film tends to be slightly blackish, and 60 mass. When the content exceeds 100% (Example PCM-No. 9), the elongation at break tends to be slightly below 100%, and there is a concern that the processability is inferior. 40-60 mass% is more suitable. Moreover, since there exists a possibility that the elongation at break of a coating film is less than 100% (Example PCM-No.12, 16-18) may be inferior in workability, the coating film used for the precoat metal plate of this invention is a fracture. Those having an elongation of 100% or more are more suitable.
  When the pre-coated metal sheet of the present invention has a Ra of fine unevenness at the interface between the intermediate coating film and the top coating film outside the range of 0.3 to 0.8 μm (Example PCM-No. 21), severe processing Since the coating film adhesion is impaired when the coating is applied, the Ra of the fine irregularities at the interface is more preferably 0.3 to 0.8 μm. As is apparent from this experiment, the Ra of the fine unevenness at each coating film interface can be set to 0.3 to 0.8 μm by performing coating by multilayer simultaneous application.
  The precoated metal plate of the present invention having a thin primer coating (Example PCM-No. 22) tended to have slightly inferior corrosion resistance. When the film thickness of the intermediate coating film is thin (Example PCM-No. 23), the color of the original plate cannot be completely concealed, so the appearance when the top film is painted on this tends to be slightly blackish Met. When the film thickness of the top coating film was thin (Example PCM-No. 24), the color of the top coating film was thin in appearance and the white color of the intermediate coating film tended to be seen through slightly. On the other hand, when the thickness of each coating layer was thick (Examples PCM-No. 25, 26, 27), extremely fine boiling defects tended to occur. Therefore, the film thickness of each coating film of the precoated metal plate of the present invention is more preferably 1-30 μm and the total coating thickness is less than 50 μm.
  In addition, since there was no significant difference in coating film performance (background color tone concealment property, etc.) of the original plate ZL and EG (comparison between Example PCM-No. 2 and PCM-No. 28), the pre-coating of the present invention It has been found that any metal plate can be used as long as it is a known metal plate.
  When the primer coating of the precoated metal sheet of the present invention contains a rust preventive pigment other than Si and P, for example, a Cr rust preventive pigment (Comparative Example PCM-No. 31), or a Ti additive in the intermediate coating Those which do not contain (Comparative Example PCM-No. 32) were unsuitable because the color tone was poor when the top coating was applied, and vivid colors could not be expressed. In addition, the one containing Ti-based additive in the top coating (Example PCM-No. 29) has a slightly whitish color tone, so it has vivid red, orange and yellow colors. In order to express it, it is more preferable that the top coating does not contain a Ti-based additive. The appearance of the desired design (brilliant red, yellow), which is not coated with an intermediate coating film containing a Ti-based additive and the top coating film is coated with a relatively thin film (Comparative Example PCM-No. 33 to 35). , Orange color) is not suitable. On the other hand, in the case where the intermediate coating film containing the Ti-based additive was not applied and the top coating film was coated with a thick film (Comparative Example PCM-No. 36), a severe boiling defect occurred, which was not suitable. . A coating with only an intermediate coating and a top coating (Comparative Example PCM-No. 37) without a primer coating (Comparative Example PCM-No. 37) was not suitable because of its poor corrosion resistance. It was.
  The primer coating, intermediate coating, and top coating of the pre-coated metal plate of the present invention are based on commercially available coatings, and the primer coating layer contains one or both of Si and P. In addition, an intermediate coating layer containing a Ti-based additive is used, and the top coating layer is colored in a color other than white or black (Examples PCM-No. 15, 16) ) Is also effective. In particular, when the intermediate coating and the top coating are applied by simultaneous multilayer coating and Ra of the interface is 0.3 to 0.8 μm, the coating film adhesion is excellent and more preferable.
  The use of pre-coated metal plates not only solves the problem of volatile organic solvents (VOC) that has been a problem in post-coating, but also reduces costs by eliminating user equipment and reduces the size of the plant. Space can be achieved.
  Conventionally, in order to produce a multi-layer pre-coated metal plate, baking and drying facilities such as ovens were required for the number of laminated coating layers. By doing so, since the number of these baking and drying facilities can be reduced, it is possible to provide a low-cost manufacturing method with a compact facility. Therefore, it can be said that the present invention is an industrially extremely valuable invention.
  Moreover, in Table 4, although the precoat metal plate (PCM-2, PCM-17, PCM-45-PCM-49) which concerns on the Example of this invention has high gloss, deep drawing processing In the draw bead test that reproduces coating galling at the time of continuous press, coating galling is difficult to occur, and coating film peeling and cracks in the processing portion are less likely to occur. There was no generation and it was good.
  However, those in which Ra at the interface between the intermediate coating layer and the top coating layer deviates from 0.3 to 0.8 (PCM-48, PCM-49) tend to peel off easily in the draw bead test. is there.
  On the other hand, when the Tg of the coating film exceeds 30 ° C. (PCM-17, PCM-48, PCM-49), the gloss retention after processing is low, and even when the rectangular tube is molded, a gloss reduction is clearly observed visually. Therefore, the Tg of the coating film is preferably 30 ° C. or less.
  Next, Table 5 shows the evaluation results of molded products molded using the precoated powder metal plates PCM-2, PCM-17, and PCM-45 to PCM-49. Each molded product formed using a precoated metal plate within the range expected in the present invention has a 60 ° specular gloss and an appearance of 60% or more. The appearance was excellent with no occurrence of. However, the Tg of more than 30 ° C (PCM-17) has a low gloss retention after processing, which is slightly higher than 60%, so the Tg of the coating is 30 ° C or less. More preferred. On the other hand, Tg of the coating film exceeds 30 ° C., and Ra whose interface with the top coating layer deviates from 0.3 to 0.8 (PCM-48, PCM-49) is 60 ° mirror surface. The gloss is less than 60%, and the gloss is extremely low.
  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are of course within the technical scope of the present invention. Understood.

  The present invention can be applied to a precoated metal plate excellent in design and corrosion resistance and a method for producing the same, and in particular, has a bright red, yellow, or orange design appearance, and is used for home appliances and building materials. Applicable to pre-coated metal plates with excellent corrosion resistance, coating processability, and scratch resistance in applications such as industrial use, civil engineering, machinery, automobiles, furniture, and containers It is.

Claims (17)

A multi-layer pre-coated metal plate in which a multi-layer coating film is formed by sequentially laminating a primer coating layer, an intermediate coating layer and a top coating layer on one or both sides of a metal plate:
The primer coating layer includes one or both of Si and P,
There is a liquid interface trace interface between the intermediate coating layer and the top coating layer in the multilayer coating film, and the size of the fine irregularities of the liquid interface trace interface is the centerline average roughness (Ra). Expressed as 0.3 to 0.8 μm,
The pre-coated metal sheet having a vivid color tone, wherein the intermediate coating layer contains a Ti-based additive. The pre-coated metal plate having a vivid color tone according to claim 1, wherein the top coating layer contains a coloring pigment other than a Ti-based additive and does not contain a Ti-based additive. The pre-coated metal sheet having a vivid color tone according to claim 1 or 2, wherein the intermediate coating film layer contains a color pigment other than the Ti-based additive in addition to the Ti-based additive. The pre-coated metal sheet having a vivid color tone according to any one of claims 1 to 3, wherein an addition amount of the Ti-based additive contained in the intermediate coating layer is 40 mass% or more. The precoated metal sheet having vivid color tone according to any one of claims 1 to 4, wherein the Ti-based additive is titanium oxide. The colored pigment other than the Ti-based additive in the top coating layer is a pigment of any color of red, yellow, or orange, according to any one of claims 1 to 5. Pre-coated metal plate with vivid colors. The top coating layer is colored with a pigment of any color of red, yellow or orange, and in addition to the Ti additive in the intermediate coating layer, a red, yellow or The pre-coated metal sheet having a vivid color tone according to any one of claims 1 to 6, wherein the pre-coated metal sheet includes any one of orange-based pigments. When the liquid-liquid interface trace interface is observed at a magnification of 500 times, the maximum height from the center line of the waviness of the interface is 50% or less when measured from the center line of the layer located on the interface The precoated metal sheet having vivid color tone according to any one of claims 1 to 7, Each film thickness of the primer coating film layer, the intermediate coating film layer and the top coating film layer is in the range of 1 to 30 μm, and the total film thickness of the multilayer coating film is 50 μm or less. The precoated metal sheet having a vivid color tone according to any one of claims 1 to 7, The precoated metal sheet having a vivid color tone according to any one of claims 1 to 9, wherein the coating film layer has a breaking elongation of 100% or more when it is 23 ° C. The outermost coating layer has (A) a glass transition temperature of 5 to 30 ° C., (B) a hardness at 23 ° C. of 2.5 N / mm ² or more in terms of universal hardness under a load of 5 mN, and (C ) The elongation at break at 23 ° C. is 100% or more, and (D) the specular gloss of the outermost layer coating film is 60% or more when the incident angle and the light receiving angle are each measured at 60 °. The precoated metal sheet having a vivid color tone according to any one of claims 1 to 10, wherein The precoated metal sheet having a vivid color tone according to claim 11, which is deep-drawn to a forming height of 25 mm or more. The precoated metal sheet having a vivid color tone according to any one of claims 1 to 12, wherein a particle diameter of the Ti-based additive is 0.2 to 0.3 µm. The precoated metal sheet having a vivid color tone according to any one of claims 1 to 13, wherein the particle size of the particles contained in the top coating layer is 0.1 µm or less. It is a manufacturing method of the precoat metal plate in any one of Claims 1-14, Comprising:
A precoat having a vivid color tone, wherein at least two layers of a primer coating layer, an intermediate coating layer and a top coating layer are applied to one or both surfaces of a metal plate by a multilayer simultaneous coating method. A method for producing a metal plate. A leveler is added to the upper layer of the two adjacent layers to be applied by the multi-layer simultaneous application method, and the difference in surface tension between the intermediate coating layer coating and the top coating layer coating is 1.2 mN / m to 5 mN Less than / m, and when the surface tension is measured five times, a paint whose difference between the maximum value and the minimum value obtained is less than 2 mN / m is used. The manufacturing method of the precoat metal plate which has the vivid color tone of Claim 15. Leveler is added to both the top coating layer and the intermediate coating layer of the two adjacent layers applied by the simultaneous coating method, and the surface tension of the coating of the intermediate coating layer and the coating of the top coating layer The difference between the maximum value and the minimum value obtained is 2 mN when the surface tension of the paint of each layer is measured five times as the difference of 0.3 mN / m or more and less than 3.7 mN / m. The method for producing a pre-coated metal sheet having a vivid color tone according to claim 15, wherein the paint is less than / m.

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