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DESCRIPTION PRECOATED METAL SHEET AND MANUFACTURING METHOD FOR SAME
TECHNICAL FIELD
[0001]
The present invention relates to a precoated metal sheet precoated with a coating material that is mainly used in home appliances, construction materials, civil engineering applications, mechanical applications, automobiles, furniture or containers and the like and is premised on being shaped after coating, and to a production method thereof, and more particularly, relates to a precoated metal sheet having a superior designability, and a production method thereof.
BACKGROUND ART
[0002]
Precoated metal sheets covered with a colored coating film have recently come to be widely used in place of post-coated products, which are coated following shape forming of a metal material, as metal materials used in home appliances, construction materials, civil engineering applications, mechanical applications, automobiles, furniture or containers and the like. Precoated metal sheets are typically coated with a coating material after chemical conversion treatment has been carried out on the surface of the metal sheet, and are typically used after having been cut and press-formed in a state of being coated with a coating material. The use of such precoated metal sheets enables a coating step carried out by a user to be omitted, and since this contributes to improved productivity and reduced costs, the use of precoated metal sheets in industry has recently been increasing.
[0003]
On the other hand, there has recently been a growing demand for coatings having a design appearance featuring

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superior luster and an appearance of depth (which may hereinafter be referred to as a "high design appearance") primarily in the home appliance and automobile fields. Such coatings having a high design appearance are normally applied by spray coating. Coatings having a high design appearance have improved luster and an appearance of depth by repeatedly applying or coating a thick film of a coating material containing various types of luster pigments such as metallic flakes, mica, pearl or glass. [0004]
As has been described above, there has recently been a growing demand for a precoated metal sheet having a high design appearance featuring superior luster and an appearance of depth as well as high productivity to a greater degree than in the past. [0005]
As an example of a technology for expressing a high design appearance in a precoated metal sheet. Patent Document 1 discloses a technique in which a coated film having high luster and a three-dimensional design (solidity) is formed by coating a colored base coated film, containing organic resin fine particles of 5 \im to 80 |xm and a coloring pigment, and a clear coated film onto a metal sheet by wet-on-wet coating. In addition. Patent Document 2, for example, discloses a technique in which a coated film having high luster and a three-dimensional design is formed by coating a colored base coated film, containing organic resin fine particles of 5 [xm to 80 ^m and a coloring pigment^ and a clear coated film, containing a luster pigment, onto a metal sheet by wet-on-wet coating. Prior Art Documents Patent Documents [0006]
Patent Document 1: JP 11-19584 A

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Patent Document 2: JP 11-19581 A
SUMMARY OF THE INVENTION Problems to be Solved by the Invention [0007]
However, in the technique of Patent Documents 1 and 2 in which organic resin fine particles and a coloring pigment are added to a colored base coated film, although appearance of solidity is increased due to an increase in the number of surface irregularities in the coated film surface when the amount of the organic resin fine particles added is increased, hiding power decreases and an appearance of depth is lost since it is no longer possible to add a large amount of coloring pigment. On the other hand, if the amount of coloring pigment added is increased, although the appearance of depth increases due to an increase in hiding power, the appearance of solidity ends up being lost since it is no longer possible to add a large amount of organic resin fine particles. In other words, regardless of which of the techniques of Patent Documents 1 and 2 is used, there was the problem of it being difficult to provide a precoated metal sheet having a high design appearance having both appearance of solidity and appearance of depth. [0008]
With the foregoing in view, an object of the present invention is to provide a precoated metal sheet provided with both appearance of solidity and appearance of depth and having superior designability that has luster, appearance of solidity and appearance of depth greater than those in the past, and a production method thereof. Means for Solving the Problems [0009]
As a result of conducting extensive studies to solve the aforementioned problems, the inventors found that when a coating material containing fine particles such as a pigment in an amount that exceeds the amount of closest packing in a resin coated film (typically roughly 20% by

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volume to 30% by volume results in closest packing, although varying according to the shape of the fine particles), and a coating material containing a luster pigment are coated onto a base by simultaneous multilayer coating or a wet-on-wet method by controlling the physical properties of the coating materials such as the viscosity of the coating materials, the center line average roughness (Ra) of the boundary surface between coated films formed by both coating materials increases, and as a result thereof, a precoated metal sheet is obtained that has luster and an appearance of depth as well as an appearance of solidity. In addition, the inventors also found that by providing a prescribed amount of voids in a coated film containing fine particles, the precoated metal sheet has adequate hiding power and the design sense thereof is further increased. The technique of the invention of the present application is particularly effective when the coated film coated onto the precoated metal sheet is a white series color. [0010]
In general, hiding power is a property by which a color of the original sheet is optically hidden when coated with a colored coated film layer, and hiding power becomes inferior in the case where the original sheet is not completely hidden and the color of the original sheet can be seen through the colored coated film layer. In general, the color of the original sheet can be seen when visible light radiated onto the coated film surface layer reaches the original sheet at the bottom surface of the coated film and is reflected thereby, and this reflected light escapes outside the coated film from the coated film surface layer. Hiding power becomes lower in the case where a large amount of visible light reflected by the original sheet escapes outside the coated film. In order to enhance hiding power, it is necessary to release visible light entering from the coated film surface layer outside the coated film before reaching the original

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sheet. In general, hiding power of a coated film is secured by adding fine particles such as a pigment to a coated film to thereby allow visible light entering from the coated film surface layer to be reflected and released outside the coated film. The hiding power of a coated film is dependent on the pigment concentration in the coated film. Although hiding power increases if the pigment concentration is increased, there is a limit on the maximum pigment concentration, and hiding power is known to decrease if the pigment concentration exceeds a certain point. It is described in the Coloring Material Handbook edited by the Japan Society of Color Materials, issued on May 25, 1967 and published by Asakura Publishing Co., Ltd. that hiding power reaches a maximum in the vicinity of a pigment volume concentration of 20% to 30%. When fine particles such as pigment are added to a coated film, light is reflected due to a difference in interfacial refractive indices between a binder resin and the fine particles. If the pigment concentration is high, interface reflection caused by this difference in interfacial refractive indices increases, a large amount of light entering from the coated film surface layer is reflected before reaching the original sheet and is released outside the coated film, thereby increasing hiding power. However, if the concentration of pigment contained in the coated film increases further, the interval between particles narrows, and when this interval becomes equal to or less than about 1/2 of the wavelength of light, hiding power is said to typically decrease since the scattering efficiency at the pigment surface (interface between the pigment and binder resin) decreases. Consequently, in order to impart high hiding power to a coated film, the pigment volume concentration is typically made to be 20% to 30%. For example, in the case where the fine particles are anatase-type titanium dioxide particles, the specific gravity of the binder resin is 1.2 and the specific gravity of the anatase-type

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titanium dioxide is 4.2, a pigment volume concentration of 20% to 30% converts to a pigment weight concentration of 46.7% to 60%, and the amount of anatase-type titanium dioxide pigment is equivalent to 87.6 to 150 parts by weight relative to 100 parts by weight of the binder resin. [0011]
When a coating material to which fine particles have been added in an amount that exceeds the amount of closest packing in the coated film is dried and cured, since the amount of binder resin in the coated film ends up being less than the amount required to fill the gaps between the fine particles, voids form in the gaps between the fine particles in the coated film. It was found by the inventors that, when voids are formed, since a different interface forms with the resin and pigment in contact with the voids (interface between the resin and voids and interface between the pigment and voids), the degree of light scattering increases and hiding power also increases. In addition, it was found that when a coating material to which these fine particles have been added and a coating material containing a luster pigment are applied by simultaneous multilayer coating or by a wet-on-wet method so that the former is coated on the base sheet and the latter is coated on the surface layer, and are then simultaneously dried and cured, fine particles in the coating material to which fine particles were added diffuse into the coating material layer containing the luster pigment in the drying and curing step, and this serves as a driving force that greatly disorders the interfaces between the coated films resulting in increased interface Ra. Moreover, as a result of employing this type of composition for the coated film layers of a precoated metal sheet, it was found that luster and an appearance of depth are realized while having adequate hiding power. The reasons for this are as follows. (1) Visible light radiated onto the

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surface of a coated film is reflected by a luster pigment contained in the coated film at the surface side, and a portion thereof escapes outside the coated film from the coated film surface layer in the form of scattered light.
(2) Light that has not collided with the luster pigment in (1) above is diffused and reflected at the interface with the underlying coated film layer having a large Ra.
(3) Scattered light that has been diffused and reflected in (2) above is further diffused as a result of being reflected by the luster pigment. (4) Light that has entered the underlying coated film by being transmitted without being reflected at the interface between the coated films in (2) above is repeatedly diffused and reflected at the large number of pigment/binder resin interfaces, pigment/void interfaces and binder resin/void interfaces contained in the underlying coated film. (5) Visible light that has undergone repeated diffuse reflection in (4) above escapes from the underlying coated film to the surface coated film before reaching the original sheet, is again reflected by luster pigment in the surface coated film, and escapes from the coated film surface layer while these are repeated. (6) Light that has entered the surface coated film repeatedly undergoes the diffusion and reflection in the processes of (1) to (5) above, the degree of light scattering increases with each reflection, and since this scattered light coexists with light that escapes from the surface layer to outside the coated film without ultimately reaching the original sheet and is visible to the human eye, the precoated metal sheet appears to have greater luster to the human eye. (7) In addition to (6) above, since light that immediately escapes to the surface layer after entering in the process of step (1) above coexists with light that escapes outside the coated film from the surface layer after the passage of a certain amount of time as a result of being repeatedly reflected while going through the various processes of (2) to (5) above.

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the precoated metal sheet appears to have a greater appearance of depth to the human eye.
The present invention was completed on the basis of the findings described above. [0012]
In other words, according to the present invention, a precoated metal sheet is provided that has at least two or more coating layers, comprising a first coated film layer containing a coloring pigment and a second coated film layer containing a luster pigment laminated on the surface of the first coated film layer, on a portion or all of the surface of a metal sheet, wherein the center line average roughness Ra of the boundary surface between the first coated film layer and the second coated layer
is 0.8 |im or more. [0013]
The first coated film layer contains fine particles having a mean particle diameter of 100 nm to 2000 nm, and when the volume of the fine particles is taken to be VI and the volume of the binder resin is taken to be V2, the solid volume ratio between the fine particles and the binder resin in the first coated film layer is preferably such that V1/V2 = 30/70 to 95/5. [0014]
Voids are preferably present in the first coated film layer. [0015]
The content of the voids is preferably 3% by volume to 40% by volume relative to the sum of the total volume of the solid in the first coated film layer and the volume of the voids. [0016]
In addition, in the case of smoothing a cross-section perpendicular to the surface of the first coated film layer and capturing an image thereof with a scanning microscope at a magnification factor of 10,000X, the ratio of the surface area occupied by the portion in

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which the voids are present to the area of the entire
cross-section is preferably 1% to 40%.
[0017]
The fine particle is preferably a coloring pigment. [0018]
An example of the coloring pigment is a white pigment. [0019]
An example of the white pigment is titanium oxide. [0020]
The coating layers may further include a third coated film layer arranged on the surface of the second coated film layer. [0021]
In addition, the coating layers may further include a fourth coated film layer arranged between the first coated film layer and the metal sheet. [0022]
The metal sheet may be subjected to chemical conversion treatment. [0023]
In addition, according to the present invention, a production method of a precoated metal sheet is provided, comprising coating a first coating material containing a coloring pigment and a second coating material containing a luster pigment onto a portion or all of the surface of a metal sheet by simultaneous multilayer coating or a wet-on-wet method so that the second coating material is closer to the surface layer side than the first coating material, and simultaneously drying and curing the undried first coating material and second coating material coated on the surface of the metal sheet to thereby form a first coated film layer containing the coloring pigment and a second coated film layer containing the luster pigment so that the center line average roughness Ra of the boundary surface between the first coated film layer and the second coated film layer

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is 0.8 |jin or more. [0024]
According to the present invention, a precoated metal sheet superior in designability provided with both appearance of solidity and appearance of depth as well as having luster, appearance of solidity and appearance of depth greater than that in the past, and a production method thereof, can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS [0025]
FIG. 1 shows an example of the state of irregularities on a coated film boundary surface.
EMBODIMENTS FOR CARRYING OUT THE INVENTION [0026]
The following provides a detailed explanation of preferred embodiments of the present invention while referring to the attached drawings. [0027]

First, a detailed explanation is provided of the composition of a precoated metal sheet according to an embodiment of the present invention. [0028]
The precoated metal sheet according to the present embodiment is a metal sheet that is able to be shaped after coating, and has at least two coating layers on a portion or all of the surface of a metal material serving as a base. More specifically, these coating layers have a laminated structure consisting of two or more layers at least including a first coated film layer containing a coloring pigment (hereinafter referred to as a "colored coated film layer") and a second coated film layer containing a luster pigment laminated on the surface of the first coated film layer (hereinafter referred to as a "design coated film layer"). In addition, the precoated metal sheet according to the present embodiment may further have a third coated film layer (hereinafter

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referred to as a "clear coated film layer") further laminated on the surface of the design coated film layer as a coating layer, and may further have a fourth coated film layer (hereinafter referred to as a "primer coated film layer") at the inner side of the colored coated film layer (namely, between the metal sheet and the colored coated film layer). [0029]
[Roughness of Interface Between Colored Coated Film
Layer and Design Coated Film Layer]
In the precoated metal sheet according to the present embodiment, the center line average roughness Ra of the boundary surface between the colored coated film layer and the design coated film layer is required to be 0.8 i^m or more. By increasing the Ra of the boundary surface between the colored coated film layer and the design coated film layer in this manner, since the precoated metal sheet is made to have adequate luster and appearance of depth, and also has appearance of solidity, the designability of the precoated metal sheet can be remarkably improved. If the Ra of the boundary surface between the colored coated film layer and the design coated film layer is less than 0.8 |j,m, the effect of improving designability as described above cannot be adequately obtained. The value of Ra is more preferably 1.0 fjm or more since the designability as described above is further improved. [0030]
(Method for Controlling Boundary Surface Ra)
The Ra of the boundary surface between the colored coated film layer and the design coated film layer can be controlled by, for example, the coaling method of the colored coated film layer and the design coated film layer, the concentration of fine particles (such as pigment) in the colored coated film layer, or the viscosity at low shear or surface tension of the coatings

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used to form the colored coated film layer and the design coated film layer. For example, a precoated metal sheet in which the value of Ra of the boundary surface between the colored coated film layer and the design coated film layer is 0.8 |am or more can be obtained by laminating two layers of a coating material for the colored coated film layer (hereinafter referred to as a "colored coating material") and a coating material for the design coated film layer (hereinafter referred to as a "design coating material"), the surface tensions of which are controlled, in an undried state prior to drying and bake-curing when laminating the two layers consisting of the colored coated film layer and the design coated film layer, and then simultaneously drying and bake-curing the laminated, undried colored coating material and design coating material. [0031]
Although surface tension of each coating material can be adjusted by adding a prescribed amount of an additive typically referred to as a surfactant, such as a leveling agent or antifoaming agent, to the coating material, surface tension can also be adjusted by changing the type of solvent in the coating material. When the difference in surface tension between the colored coating material and design coating material becomes small, the value of Ra of the boundary surface formed between the colored coated film layer and the design coated film layer tends to become large. However, if the surface tension of the colored coating material coated at the inner side is smaller than the surface tension of the design coating material coated at the surface side, since the coated film of the lower layer tends to migrate towards the upper layer while the coated film of the upper layer tends to migrate towards the lower layer, there is increased susceptibility to the occurrence of a phenomenon in which the lower coated film partially rises up and protrudes to the surface layer or

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the upper coated film becomes thin causing the raised lower coated film to be visible therethrough, or in other words, a coating defect referred to as mixing of the two layers. Consequently, the surface tension of the colored coating material is preferably greater than the surface tension of the design coating material. Since a preferable value for the difference in surface tension between the colored coating material and the design coating material varies according to differences in the type of resin and type of solvent of each coated film layer, it cannot be comprehensively defined, and it is necessary to determine the optimum value by investigating each coating material in advance. According to findings obtained by the inventors, the optimum value is preferably 10.0 mN/m > ([surface tension of colored coating material]-[surface tension of design coating material]) > 0 mN/m. If the value of ([surface tension of colored coating material]-[surface tension of design coating material]) exceeds 10.0 mN/m, the value of Ra of the boundary surface tends to be less than 0.8 fJin, while if that value is less than 0 mN/m, the components of the colored coated film layer and the components of the design coated film layer end up mixing, and a tendency towards inferior designability of the appearance of the precoated metal sheet is observed. The value of
([surface tension of colored coating material]-[surface tension of design coating material]) is preferably 0.5 mN/m to 10 mN/m.
[0032]
An example of the most effective method for making the value of Ra of the boundary surface between the colored coated film layer and the design coated film layer 0.8 |am or more consists of adding fine particles having a particle diameter of 100 nm to 2000 nm to the colored coated film layer so as to be equal to or greater than the amount of closest packing relative to the volume

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of the binder resin in the coated film after drying, laminating the colored coating material and the design coating material in an undried state, and then simultaneously drying and curing them in a laminated state. As a result of adding fine particles such as coloring pigment in an amount equal to or greater than the amount of closest packing in the colored coated film layer and laminating with the design coated film layer in an undried state, a concentration gradient occurs in the fine particles between the coated film layers, and an action occurs in which fine particles in the colored coated film layer attempt to diffuse into the design coated film layer. Moreover, since heat is applied in the drying and curing step, this heat serves as a driving force that causes the action of the diffusion of fine particles to become remarkable. On the other hand, since a crosslinking reaction occurs in the resin that forms the coated films when heat is applied in the drying and curing step, an action occurs that inhibits the action of interlayer diffusion of the fine particles. Consequently, the boundary surface between the colored coated film layer and the design coated film layer becomes rough and the value of Ra becomes larger. [0033]
Addition of fine particles so as to be equal to or greater than the amount of closest packing relative to the volume of the binder resin in the coated film after drying refers to the volume of voids between fine particles such as pigment that have been filled in the closest packing amount in the coated film being greater than the volume of the binder resin in the coated film after drying. Thus, in the present embodiment, since all of the voids between fine particles present in the coated film are not filled by the binder resin, voids are present in the coated film. [0034]
Controlling the value of Ra of the boundary surface

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between the colored coated film layer and the design coated film layer by mixing fine particles into the colored coated film layer can be carried out by controlling the viscosity or each coating material or the reaction rate of a crosslinking agent added to each coating material. If the viscosity of each coating material is low, the fine particles in the colored coating material easily diffuse into the design coating material, and the value of Ra of the boundary surface between the colored coated film layer and the design coated film layer tends to increase. According to findings obtained by the inventors, a coating material to which fine particles (such as coloring pigment) has been added at a concentration so as to be equal to or greater than the closest packing amount in a coated film after drying and curing becomes a non-Newtonian fluid typically referred to as a thickly dispersed coating material, and when the viscosity thereof is measured with a rotational viscometer, viscosity increases at low rotating speeds and decreases at high rotating speeds, thus becoming a coating material having so-called shear thinning properties. Viscosity at high rotating speeds has a considerable effect on coating workability when coating such a coating material on a base, while viscosity at low rotating speeds has a considerable effect on intrafilm flow of the coating material in the drying and bake-curing step after coating. Thus, it is important to adjust coating material viscosity at low shear in order to control the value of Ra of the boundary surface between the colored coated film layer and the design coated film layer. More specifically, in the present embodiment, the viscosity of the colored coating material at a rotating speed of 5 rpm as determined with a rotational viscometer is preferably 500 mPa to 4000 mPa. If the viscosity of the colored coating material at a rotating speed of 5 rpm as determined with a rotational viscometer exceeds 4000 mPa, there is the risk of the

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value of Ra of the boundary surface being less than 0.8 |j,m, while if the viscosity is less than 500 mPa, the coloring pigment in the colored coating material easily diffuses into the design coating material while the luster pigment in the design coating material easily diffuses into the colored coating material, the interface between the two layers is no longer visible, and the two layers end up becoming the same layer containing the luster pigment and the coloring pigment, thereby resulting in the risk of inadequate designability of the appearance of the precoated metal sheet. The viscosity of the colored coating material at a rotating speed of 5 rpm as determined with a rotational viscometer is preferably 700 mPa to 4000 mPa and more preferably 700 mPa to 1000 mPa. [0035]
Coating material viscosity can be adjusted by altering the amount of solvent in the coating material and the storage conditions of the coating material (storage temperature and storage period). With respect to coating material storage conditions, since dispersion of pigment in the coating material is accelerated and thixotropy decreases the higher the storage temperature and the longer the storage period, coating material viscosity at low shear decreases. Moreover, coating material viscosity can also be adjusted by adding an additive such as a dispersant or thixotropic agent to the coating material. [0036]
Next, a detailed explanation is provided of the composition of each coated film layer in the order of the colored coated film layer, design coated film layer, clear coated film layer and primer coated film layer. [0037]
[Colored Coated Film Layer]
(Summary)
The colored coated film layer of the present

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embodiment is a coated film layer that contains a coloring pigment and a binder resin as essential components thereof, and is located inside than the design coated film layer, namely at the side closer to the metal material serving as the base. However, in the case where the coating layers have a three-layer structure or four-layer structure that includes one or both of a clear coated film layer and primer coated film layer in addition to the colored coated film layer and the design coated film layer, the colored coated film layer is a layer located in a portion interposed between and in contact with the primer coated film layer and the design coated film layer. In addition, in the case where the coating layers include another layer other than the colored coated film layer, design coated film layer, clear coated film layer and primer coated film layer, all layers located between the design coated film layer and the primer coated film layer and containing a coloring pigment serve as colored coated film layers. [0038]
(Coloring Pigment)
Colored organic fine particles may be used or a commonly known inorganic coloring pigment may be used for the coloring pigment contained in the colored coated film layer. Examples of organic fine particles that can be used include fine particles of colored acrylic-based resin, polystyrene-based resin and polyurethane-based resin. Examples of inorganic coloring pigment that can be used include white pigments such as titanium oxide, zinc oxide, alumina, barium sulfate and calcium carbonate, as well as cuprous oxide, molybdate orange, yellow iron oxide, iron black, red iron oxide, Prussian blue and ultramarine. If the coloring pigment is a white pigment, particularly titanium oxide having a high degree of whiteness, a white precoated metal sheet superior in designability can be obtained that has a high degree of whiteness and both luster and appearance of depth.

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thereby making this more preferable. A white coated appearance having superior designability that has both luster and appearance of depth is currently popular, and was conventionally only able to be realized by subsequent spray coating (post-coating). Consequently, being able to achieve such a coated appearance with a precoated metal sheet is preferable since productivity is significantly improved. [0039]
Furthermore, although titanium oxide consists of rutile-type titanium oxide and anatase-type titanium oxide, anatase-type titanium oxide has higher photocatalytic properties. Thus, since a coated film layer containing anatase-type titanium oxide has the possibility of the binder resin decomposing when light is received from the outside, in the present embodiment, rutile-type titanium oxide is preferably used for the titanium oxide. A commercially available product may be used for the rutile-type titanium oxide, examples of which include members of the Tipaque® series manufactured by Ishihara Sangyo Kaisha Ltd., members of the TA series manufactured by Fuji Titanium Industry Co., Ltd., and members of the Titanix® series manufactured by Tayca Co., Ltd. Moreover, the titanium oxide particles used in the present embodiment may be single titanium oxide particles or may be coated with silica, alumina, zirconia, zinc oxide, antimony oxide or an organic substance or the like. There are no particular limitations on the organic substances used to coat titanium oxide, and examples thereof include polyol-based compounds such as pentaerythritol and trimethylolpropane, alkanolamine-based compounds such as organic acid salts of triethanolamine and trimethylolamine, and silicon-based compounds such as silicon resins and alkylchlorosilanes. [0040]
(Fine Particles)
The colored coated film layer of the present

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embodiment preferably contains fine particles having a mean particle diameter of 100 nm to 2000 nm. As a result of containing fine particles having the aforementioned particle diameter in the colored coated film layer, a coated appearance superior in designability can be obtained. If the particle diameter of the fine particles of the present embodiment is less than 100 nm, the value of Ra at the boundary surface between the colored coated film layer and the design coated film layer becomes less
than 0.8 |Jin, appearance of solidity and appearance of depth are diminished, and there is a risk of inferior designability. On the other hand, if the particle diameter of the fine particles exceeds 2000 nm, the volume of the gaps (voids) present between the fine particles becomes excessively large, the binder resin for forming the design coated film layer easily diffuses into the colored coated film layer during drying and bake-curing and enters the void portions between the fine particles in the colored coated film layer. Consequently, since a state results in which the design coated film layer and the colored coated film layer are intermixed, a well-defined boundary surface no longer is present between the two layers, and there is the risk of a decrease in designability of the appearance. The particle diameter of the fine particles is preferably 200 nm to 1000 nm and more preferably 250 nm to 300 nm. [0041]
The mean particle diameter of the fine particles in the present embodiment is obtained by observing five arbitrary portions of a coated film with an electron microscope at a magnification of 10,000X, measuring the arithmetic mean of the particle diameter of those fine particles depicted in the field of view for each portion that remain after subtracting 20% of the fine particles having the smallest particle diameter and 5% of the fine particles having the largest particle diameter, and then averaging the resulting five values.

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[0042]
The ratio between the aforementioned fine particles and a binder resin (to be subsequently described in detail) in the colored coated film layer is preferably such that, when the volume of the fine particles is taken to be VI and the volume of the binder resin is taken to be V2, V1/V2 is 30/70 to 95/5 in terms of the solid volume ratio. If V1/V2 is less than 30/70, there is the risk of the value of Ra at the boundary surface between the colored coated film layer and the design coated film layer being less than 0.8, while if V1/V2 exceeds 95/5, the coating of the colored coated film layer becomes brittle resulting in the risk of inferior processing adhesion. From the viewpoint of more reliably making the value of Ra at the boundary surface between the colored coated film layer and the design coated film layer to be 0.8 or more, V1/V2 is preferably 35/65 or more, while from the viewpoint of making the coated film layers flexible and further improving processing adhesion, V1/V2 is preferably 50/50 or less. [0043]
The "solid volume" mentioned here refers to the total volume of the solids including the resin (binder) component, the pigment component and the fine particle component in the coated film of the colored coated film layer, and is obtained by subtracting the volume occupied by voids present in the coated film from the total volume of the coating. [0044]
The solid volume ratio in the colored coated film layer in the present embodiment is the same as that of the composition of the coating material used for coating, and can be calculated by using the ratio of the pigment, and fine particles added to the coating material and the binder resin. Furthermore, in the case where the fine particles are particles of inorganic pigment, the solid volume ratio in the colored coated film layer can also be

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determined according to the method described below. [0045]
First, the colored coated film layer targeted for measurement is scraped from a sample followed by measuring the weight Ml of the scraped coated film. Next, the scraped coated film is heated for 1 hour at 500°C to decompose the resin component. Since the portion that remains without decomposing can be considered to be fine particles, the weight M2 of that remainder is measured. When the density of the fine particles is taken to be pi, then the volume VI of the fine particles can be determined to be VI = M2/pl, and when the density of the resin is taken to be p2, then the volume V2 of the resin can be determined to be V2 = (iyil-M2)/p2. The solid volume ratio V1/V2 can then be determined from the volume VI of the fine particles and the volume V2 of the binder resin determined in this manner. [0046]
There are no particular limitations on the fine particles contained in the colored coated film layer of the present embodiment having a particle diameter of 100 nm to 2000 nm, and commonly known inorganic pigment, resin beads or the like can be used. If the fine particles of the present embodiment are particles of a coloring pigment, this is advantageous for obtaining designability with respect to luster and an appearance of depth, thereby making this preferable. Transparent fine particles and coloring pigment both having a particle diameter of 100 nm to 2000 nm may be used in combination as fine particles of the present embodiment. However, if the total amount of transparent fine particles and coloring pigment added is excessively large, the coated film easily becomes brittle. Consequently, since the amounts of fine particles and coloring pigment added are restricted in order to secure processing adhesion, there is the possibility of designability of the coated

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appearance being impaired. From this viewpoint, all of the fine particles contained in the colored coated film layer are preferably particles of coloring pigment. The coloring pigment used as fine particles is the same as that described in the examples of coloring pigment previously described, and colored organic fine particles or commonly known inorganic coloring pigments can be used. The fine particles are more preferably particles of titanium oxide having a high degree of whiteness in particular. [0047]
(Coated Film Voids)
It is more preferred that voids are present in the colored coated film layer of the present embodiment since appearance of solidity and an appearance of depth are demonstrated thereby and designability is further improved. In order to allow voids to be present in the colored coated film layer, the fine particles are contained at a high concentration so that fine particles having a particle diameter of 100 nm to 2000 nm are present in the coated film after drying and curing in an amount equal to or greater than the closest packing amount. As a result of containing the fine particles in the colored coated film layer at a high concentration, the volume of voids formed between the fine particles becomes greater than the volume of the binder resin. Consequently, differing from a coated film in which pigment is contained at a concentration that is less than the closest packing amount, portions where binder resin is not present are able to be present in the colored coated film layer as voids. [0048]
More specifically, voids can be provided in the colored coated film layer by adding fine particles to a colored coating material so that the solid volume ratio V1/V2 of fine particles having a particle diameter of 100 nm to 2000 nm to binder resin in the colored coated film

- 23 -
layer is 30/70 to 95/5 as previously described. [0049]
The content of voids in the colored coated film layer (hereinafter referred to as "porosity" or "void volume ratio") is preferably 3% by volume to 40% by volume relative to the sum of the total volume of the solids (coated film components) and the volume of the voids in the colored coated film layer for the purpose of improving designability. If the porosity is less than 3% by volume, there is the risk of a decrease in designability with respect to appearance of solidity and an appearance of depth, while if the porosity exceeds 40% by volume, the coated film becomes brittle and there is the risk of a great decrease in processability. The void volume ratio is preferably 25% to less than 35%. [0050]
Porosity in the colored coated film layer can be controlled by adjusting the particle diameter and amount of fine particles added in the colored coated film layer. More specifically, if the particle diameter of the fine particles exceeds 2000 nm, an appearance results that has irregularities at the surface of the coated film thereby leading to a poor appearance or leading to the risk of inferior processability due to the porosity being excessively large. On the other hand, if the particle diameter of the fine particles is less than 100 nm, porosity becomes excessively low, leading to the risk of inferior designability. Also, if the solid volume ratio V1/V2 between the fine particles and the binder resin is less than 30/70, porosity decreases, leading to the risk of inferior designability, while if V1/V2 exceeds 95/5, porosity becomes excessively high, leading to the risk of the coated film becoming brittle and inferior processing adhesion. [0051]
In addition to adjusting the particle diameter and amount of the fine particles added, porosity in the

- 24 -
colored coated film layer can also be controlled by, for example, adjusting the dispersed state of the coating material used to form the colored coated film layer. More specifically, since more of the binder resin is adsorbed by the pigment and efficiently fills in the voids between the pigment particles as the dispersed state of the pigment in the coating material becomes more favorable (becomes more uniform), porosity decreases. Thus, in order to obtain higher designability, it is preferable to limit the coating material to the minimally dispersed state within a range that does not cause problems with respect to coatability or stability of the coating material (the coating material is as non-uniform as possible within a range that does not cause problems with respect to coatability and stability of the coating material).
[0052]
Porosity (volume ratio) in the colored coated film layer can be calculated from the volume of deposit per unit area as calculated from the actual film thickness of the colored coated film layer obtained with an electromagnetic coating thickness meter or microscopic observation of a vertical cross-section of the coated film (hereinafter referred to as "actual volume of deposit per unit area"), and the volume calculated from weight of deposit obtained by cutting out only the colored coated film layer per unit area from a precoated metal sheet and weighing it, using the average dry coated film specific gravity of the colored coated film
(hereinafter referred to as "volume of coated film components per unit area"), according to the equation:
[Porosity] = ([volume of deposit per unit area] - [volume of coated film components per unit area]) x 100/[volume of deposit per unit area]. Values calculated for five arbitrary locations in the colored coated film layer are averaged and the resulting value is used as the porosity in the colored coated film layer. The calculated

- 25 -
specific gravity calculated from the added amounts of respective components contained in the colored coated film layer and the specific gravities of respective components can be used for the dry coated film specific gravity of the colored coated film layer. [0053]
In addition, in the case of smoothing a cross-section perpendicular to the surface of the colored coated film layer and capturing an image thereof with a scanning microscope at a magnification factor of 10,000X, the porosity of the colored coated film layer can also be confirmed according to the ratio of the area occupied by the portion in which the voids are present to the total area of the cross-section (hereinafter referred to as the "void area ratio"). In the case of expressing the porosity of the colored coated film layer in terms of the void area ratio, the average void area ratio as determined from arbitrary fields measuring 10 |jm x 10 |am of cross-sectional images captured at five arbitrary locations is preferably 1% to 40%. If the void area ratio is less than 1%, there is the risk of decrease in design in terms of appearance of solidity and an appearance of depth of a coated film decreasing, while if the void area ratio exceeds 40%, the coated film becomes brittle and there is the risk of a considerable decrease in processability. The void area ratio is more preferably 20% to 35%. [0054]
(Binder Resin)
There are no particular limitations on the binder resin used in the colored coated film layer of the present embodiment, and a commonly used binder resin can be used, such as a polyester resin, urethane resin, epoxy resin, acrylic resin, silicone resin or fluorocarbon resin. However, since fine particles are added to the colored coated film layer of the present embodiment in an amount that is equal to or greater than the closest

- 26 -
packing amount as necessary, to thereby easily render the coated film brittle, a resin having superior processability and adhesion is preferably used for the binder resin used in the colored coated film layer. More specifically, the use of, for example, a polyester resin having a glass transition temperature of 0°C to 40°C, a number average molecular weight of 10,000 to 30,000 and a hydroxyl value of less than 10 KOH-mg/g (hereinafter referred to as a "high molecular weight polyester resin") is preferable in terms of improving processability. [0055]
If the added amount of the high molecular weight polyester resin as described above is such that the concentration of the high molecular weight polyester resin relative to the entire binder resin is 14% by weight or more, a thick film can be applied without the occurrence of popping, thereby making it possible to realize both coatability and processability. Conseguently, the concentration of the high molecular weight polyester resin relative to the entire binder resin is preferably 14% by weight or more. [0056]
In addition, the addition of a polyfunctional resin having a number average molecular weight of 1,000 to 7,000 and a hydroxy value of 15 KOH-mg/g or more (hereinafter referred to as a "low molecular weight polyfunctional resin") in addition to the aforementioned high molecular weight polyester resin is more preferable since adhesion between coloring pigments can be enhanced. This is considered to be due to that, although in the case of using the high molecular weight polyester resin alone, the resin is unable to adeguately penetrate into the gaps (voids) between pigment particles present at a high concentration in the colored coated film layer, resulting in the possibility of a slight decrease in processability due to inadequate function as a binder, as a result of using the high molecular weight polyester

- 27 -
resin in combination with the low molecular weight polyfunctional resin, the low molecular weight polyfunctional resin penetrates between pigment particles that were unable to be penetrated by the high molecular weight polyester resin and functions as a binder between the pigments or between the pigment and the high molecular weight polyester resin, thereby improving strength and adhesion of the entire coating layer and allowing the obtaining of superior processability. In addition, as the hydroxyl value of the low molecular weight polyfunctional resin becomes higher, it is able to retain a larger number of crosslinking sites, thereby allowing the obtaining of higher coating adhesion. Although the polyfunctional group in the present embodiment is a hydroxyl group, there are no particular limitations on the polyfunctional resin provided it has a number average molecular weight of 1,000 to 7,000 and a hydroxyl value of 15 KOH-mg/g or more, and a commonly known resin can be used, such as a polyester resin, acrylic resin, urethane resin or epoxy resin. [0057]
Commercially available resins may be used for the binder resins serving as the high molecular weight polyester resin and low molecular weight polyfunctional resin described above. More specifically, examples of high molecular weight polyester resins that can be used include "Vylon® 300" polyester resin manufactured by Toyobo Co., Ltd., while examples of low molecular weight polyfunctional resins that can be used include "Vylon® GK680" polyester resin manufactured by Toyobo Co., Ltd. Moreover, a commonly known curing agent such as melamine resin or isocyanate is more preferably added to these binder resins as a curing agent. If the amount of curing agent added is 5 parts by weight to 30 parts by weight based on a value of 100 parts by weight for the total weight of binder resin, both processability and adhesion can be secured, thereby making this preferable.

- 28 -
Commercially available products may be used for these curing agents, examples of which include "Cymel® 303" melamine resin manufactured by Mitsui Cytec Ltd. [0058]
If the mixing ratio between the high molecular weight polyester resin and the low molecular weight polyfunctional resin is, in terms of the weight ratio thereof, such that 0.25 < (low molecular weight polyfunctional resin)/(high molecular weight polyester resin) < 4, superior adhesion and processability can be obtained. If the weight ratio of (low molecular weight polyfunctional resin)/(high molecular weight polyester resin) is less than 0.25, expression of the function of the low molecular weight polyfunctional resin becomes inadequate, thereby resulting in the risk of a decrease in adhesion, while if the ratio of (low molecular weight polyfunctional resin)/(high molecular weight polyester resin) exceeds 4, expression of function by the high molecular weight polyester resin becomes inadequate, thereby resulting in the risk of a decrease in processability. The mixing ratio of the low molecular weight polyfunctional resin and the high molecular weight polyester resin is preferably 0.5 to 2.0 and more preferably 0.8 to 1.2. [0059]
(Film Thickness)
The film thickness of the colored coated film layer of the present embodiment is preferably 10 ^m or more in order to obtain superior designability, and in cases requiring higher designability, the film thickness is more preferably 13 |^m or more. On the other hand, since there is the risk of a decrease in processability of the coated film if the film thickness of the colored coated film layer exceeds 80 )im, the film thickness of the colored coated film layer is preferably 80 |j,m or less, and in cases requiring higher processability, is more

- 29 -
preferably 60 |xm or less. [0060]
[Design Coated Film Layer]
Next, an explanation is provided of the design coated film layer of the present embodiment. [0061]
(Summary)
The design coated film layer of the present embodiment is a coating layer laminated on the surface of the aforementioned colored coated film layer, i.e., farther from the metal material serving as the base that contains a luster pigment. In the case the coating layers have a 2-layer structure comprised of a colored coated film layer and a design coated film layer, in the case of having a 3-layer structure that further comprises a primer coated film layer, and in the case of having a structure consisting of four or more layers in which a plurality of design coated film layers are present, the design coated film layer is located on the outermost layer among the plurality of coating layers. However, if the design coated film layer is laminated directly on the surface of the colored coated film layer, it is not necessarily required to be located on the outermost layer, but rather as will be subsequently described, a separate coating layer such as a clear coated film layer may be further laminated on the surface of the design coated film layer. [0062]
(Luster Pigment)
A luster pigment contained in the design coated film layer of the present embodiment refers to a pigment having luster such as a pearl pigment, glass flake pigment or metallic pigment, and a commonly known luster pigment can be used. More specifically, a commonly known pearl pigment such as mica or synthetic mica can be used for the pearl pigment, or a commercially available product may be used. An example of commercially

- 30 -
available mica is "PEARL-GLAZE" sold by Nihonkoken Co., Ltd. An example of commercially available synthetic mica is "ULTIMICA" sold by Nihonkoken Co., Ltd. composed of aluminum oxide, magnesium oxide, silicon dioxide and a fluorine compound. Glass flake pigment refers to glass particles in the form of flakes, and that coated with a metal or metal oxide on the surface thereof may also be used. A commercially available product may be used for the glass flake pigment, an example of which is "METASHINE" manufactured by Nippon Sheet Glass Co., Ltd. In addition, fine particles of a metal such as aluminum or silver or fine particles in the form of flakes can be used for the metallic pigment. From the viewpoint of improving the luster of the coated film, the amount of luster pigment added is preferably 3% by weight or more relative to the weight of the binder resin of the design coated film layer, while from the viewpoint of preventing the coated film from becoming brittle and improving processability, the amount of luster pigment added is preferably 30% by weight or less. [0063]
(Binder Resin)
There are no particular limitations on the binder resin used in the design coated film layer of the present embodiment, and a commonly used binder resin can be used, such as a polyester resin, urethane resin, epoxy resin, acrylic resin, silicone resin or fluorocarbon resin. However, from the viewpoint of adhesion to the colored coated film layer and sharing coating material raw materials, it is preferable to use the same resin as that of the colored coated film layer for all or a portion of the resin of the design coated film layer. More specifically, the use of the same resin as that of the colored coated film layer, namely a high molecular weight polyester resin having a glass transition temperature of 0°C to 40°C, a number average molecular weight of 10,000 to 30,000 and a hydroxyl value of less than 10 KOH-mg/g,

- 31 -
for all or a portion of the binder resin used in the design coated film layer is preferable since this results in improvement in processability and adhesion with the colored coated film layer. In addition, a commonly known curing agent such as melamine resin or isocyanate is more preferably added to the binder resin, as a curing agent. If the amount of curing agent added is 5 parts by weight to 30 parts by weight based on 100 parts by weight for the total weight of binder resin, both processability and adhesion can be secured, thereby making this preferable. Commercially available products may also be used for the curing agent, examples of which include "Cymel® 303" melamine resin manufactured by Mitsui Cytec Ltd. [0064]
(Film Thickness)
Since a luster pigment is added to the design coated film layer, greater luster is obtained as the film thickness of the design coated film layer increases. However, if the film thickness of the design coated film layer exceeds 30 |am, popping easily occurs during coating, thereby causing deterioration of coatability as well as being undesirable in terms of coating costs. On the other hand, if the film thickness of the design coated film layer is less than 3 |j,m, since the effect of improving luster demonstrated by the design coated film layer is diminished, the film thickness of the design coated film layer is preferably 3 )j,m to 30 |^m. More preferably, the thickness of the design coated film layer is 5 |im to 20 (im from the viewpoint of securing stable luster and coatability. [0065]
[Clear Coated Film Layer]
(Summary)
The coating layers possessed by the precoated metal sheet of the present embodiment may further include a clear coated film layer laminated onto the surface of the

- 32 -
previously described design coated film layer. The clear coated film layer of the present embodiment is a transparent coated film layer that does not contain pigment. As a result of further coating the clear coated film layer on the design coated film layer, the gloss of the precoated metal sheet increases, luster is enhanced and designability can be further improved. [0066]
(Binder Resin)
There are no particular limitations on the binder resin used in the clear coated film layer of the present embodiment, and a commonly used binder resin can be used, such as a polyester resin, urethane resin, epoxy resin, acrylic resin, silicone resin or fluorocarbon resin. However, from the viewpoint of adhesion to the design coated film layer and sharing coating material raw materials, it is preferable to use the same resin as that of the design coated film layer for all or a portion of the resin of the clear coated film layer. More specifically, the use of the same resin as that of the design coated film layer, namely a high molecular weight polyester resin having a glass transition temperature of 0°C to 40°C, a number average molecular weight of 10,000 to 30,000 and a hydroxyl value of less than 10 KOH-mg/g, for the binder resin used in the clear coated film layer is preferable since this results in improvement of processability and adhesion with the design coated film layer. In addition, a commonly known curing agent such as melamine resin or isocyanate is more preferably added to the binder resin, as a curing agent. If the amount of curing agent added is 5 parts by weight to 30 parts by weight based on 100 parts by weight for the total weight of binder resin, both processability and adhesion can be secured, thereby making this preferable. Commercially available products may also be used for the curing agent, examples of which include "Cymel® 303" melamine resin manufactured by Mitsui Cytec Ltd.

- 33 -
[0067]
(Film Thickness)
In order to obtain superior designability, the film thickness of the clear coated film layer of the present embodiment is preferably 3 jjiti or more, while in the case of requiring even higher designability, the film thickness is more preferably 10 |jin or more. On the other hand, if the film thickness of the clear coated film layer exceeds 20 |am, since there is the risk of popping easily occurring in the coated film, the film thickness of the clear coated film layer is preferably 20 ^m or less, while a film thickness of 15 |^m or less is preferable due to being able to further suppress popping. [0068]
[Primer Coated Film Layer]
(Summary)
The coating layers possessed by the precoated metal sheet of the present embodiment may also include a primer coated film layer in addition to the previously explained colored coated film layer, design coated film layer and clear coated film layer. This primer coated film layer is a coated film layer that is formed between the metal sheet and the colored coated film layer, and in the case where the coating layers are composed of three layers consisting of the design coated film layer, the colored coated film layer and the primer coated film layer, or are composed of four layers that include the clear coated film layer in addition to these coated film layers, the primer coated film layer is the coated film layer closest to the metal sheet serving as the base. In this case, however, even if a coating layer is the layer closest to the metal sheet, the coating layer having a film thickness of less than 1 f^m provided for the purpose of improving adhesion between the metal sheet and the coated film as well as corrosion resistance, is not equivalent to the primer coated film layer of the present

- 34 -
embodiment, but rather a coating layer closer to the surface layer side than the coating layer having a film thickness of less than 1 |im is the primer coated film layer. In this manner, coated film adhesion can be further improved by further coating the primer coated film layer at the inner side of the colored coated film layer. [0069]
(Binder Resin)
There are no particular limitations on the binder resin used for the binder of primer coated film layer, and a commonly used binder resin can be used, such as a polyester resin, urethane resin, epoxy resin, acrylic resin, silicone resin or fluorocarbon resin. However, from the viewpoint of adhesion to the colored coated film layer and sharing coating material raw materials, it is preferable to use the same resin as that of the colored coated film layer for all or a portion of the resin of the primer coated film layer. More specifically, the use of the same resin as that of the colored coated film layer, namely a high molecular weight polyester resin having a glass transition temperature of 0°C to 40°C, a number average molecular weight of 10,000 to 30,000 and a hydroxyl value of less than 10 KOH-mg/g, for all of a portion of the binder resin used in the primer coated film layer is preferable since this results in improvement of processability and adhesion with the colored coated film layer. [0070]
In addition, a commonly known additive for imparting adhesion, such as an epoxy resin or silane coupling agent, may also be added as necessary to the binder resin of the primer coated film layer. An example of an epoxy resin added to the primer coated film layer is a commonly known epoxy resin for coating applications, such as a condensation product of epichlorohydrin and bisphenol A. Examples of silane coupling agents added to the primer

- 35 -
coated film layer include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, dimethoxydiethoxysilane and dimethoxydipropoxysilane. There are no particular limitations on the added amounts of these epoxy resins and silane coupling agents, and the added amounts can be suitably determined as required. For example, in the case of using a polyester resin for the binder resin, the amount of epoxy resin or silane coupling agent added is preferably 1% by weight to 30% by weight in terms of solid concentration based on the solid resin of the primer coated film layer. If the amount of epoxy resin or silane coupling agent added is 1% by weight or more, the effects of adding the epoxy resin or silane coupling agent are adequately demonstrated and adhesion can be secured, while if the added amounts are 30% by weight or less, processability of the coated film can be secured. [0071]
(Pigment)
A pigment may also be added to the primer coated film layer of the present embodiment, and from the viewpoint of enhancing corrosion resistance, a rust-preventive pigment is added preferably. A commonly known rust-preventive pigment can be used for the rust-preventive pigment added to the primer coated film layer, examples of which include chromium-based rust-preventive pigments such as strontium chromate and potassium chromate, phosphate-based rust-preventive pigments such as aluminum dihydrogen tripolyphosphate, zinc phosphate and zinc phosphite, and silica-based rust-preventive pigments such as silica and Ca ion-adsorbed silica. However, since chromium-based rust-preventive pigments contain hexavalent chromium that places a burden on the environment, a rust-preventive pigment other than a chromium-based pigment such as a phosphate-based rust-

- 36 -
preventive pigment or silica-based rust-preventive pigment is preferable. Commercially available products may be used for the rust-preventive pigment, and examples of commercially available rust-preventive pigments that can be used include the aluminum dihydrogen tripolyphosphate "K-WHITE® #105" manufactured by Tayca Corp., and the Ca ion-adsorbed silica "Shieldex C303" manufactured by W.R.Grace & Co. [0072]
In addition, if a commonly known white pigment such as titanium oxide or zinc oxide is added to the primer coated film layer in order to obtain a white precoated metal sheet, whiteness of the precoated metal sheet is increased and designability is further improved, thereby making this preferable. [0073]
(Film Thickness)
Since greater processability and adhesion are obtained as the film thickness of the primer coated film layer is increased, in consideration of these performance aspects, it is not necessary to set an upper limit value for the film thickness of the primer coated film layer. However, the film thickness of the primer coated film layer exceeds 30 |j.m is undesirable, since unlike the colored coated film layer, there is increased susceptibility to the occurrence of popping during coating and coatability becomes inferior due to the low pigment concentration in the coating material, as well as in terms of coating costs. Accordingly, the film thickness of the primer coated film layer is preferably 30 )jin or less. On the other hand, since the effects of the primer coated film layer of improving processability and adhesion diminish if the film thickness of the primer coated film layer is less than 1 i^m, the film thickness of the primer coated film layer is preferably 1 )a,m or more. From the viewpoint of securing stable

- 37 -
processability, adhesion and coatability, the film thickness of the primer coated film layer is more preferably 3 |ain to 20 |Jin. [0074]
[Base (Metal Sheet)]
A commonly known steel sheet, stainless steel sheet, aluminum sheet, copper sheet, aluminum alloy sheet or titanium sheet and the like can be used for the metal sheet used for the base of the precoated metal sheet of the present embodiment. The surface of these metal sheets may be plated. Examples of types of plating include zinc plating, aluminum plating, copper plating, nickel plating and plating composed of an alloy thereof. In the present embodiment, a steel sheet is preferably used for the metal sheet due to its superior shaping processability. If a zinc-plated steel sheet is used for the steel sheet, corrosion resistance can be further improved, thereby making this more preferable. A commonly known zinc-plated steel sheet can be used, examples of which include a galvanized steel sheet, electro-zinc-plated steel sheet, iron-zinc alloy-plated steel sheet, aluminum-zinc alloy-plated steel sheet and zinc-aluminum-magnesium alloy-plated steel sheet. [0075]
In addition, the surface of the metal sheet used for the base of the precoated metal sheet of the present embodiment is more preferably subjected to chemical conversion treatment since this improves adhesion between the metal sheet and the coated film layer as well as corrosion resistance. Commonly employed chemical conversion treatment can be used for this chemical conversion treatment. Specific examples of chemical conversion treatment that can be used include zinc phosphate-based chemical conversion treatment, chromate-free chemical conversion treatment, dry-in-place chromate treatment, electrolytic chromate treatment and reactive chromate treatment. Among these, dry-in-place chromate

- 38 -
treatment, electrolytic chromate treatment and reactive chromate treatment are not very desirable since they use hexavalent chromium that places a burden on the environment. In addition, zinc phosphate-based chemical conversion treatment also has the risk of inferior processing adhesion in comparison with other treatment. Thus, chromate-free treatment is preferably used for the chemical conversion treatment performed on the metal material of the present embodiment. [0076]
Chromate-free treatment consists of that which uses an inorganic chemical conversion treatment agent and that which used an organic chemical conversion treatment agent, either type of which may be used. More specifically, known examples of chromate-free chemical conversion treatment include treatment that uses an aqueous solution containing a silane coupling agent, a zirconium compound, a titanium compound, tannin or tannic acid, a resin and silica. The known chromate-free chemical conversion treatment technique described in, for example, Japanese Unexamined Patent Publications No. 53-9238, 9-241576, 2001-89868, 2001-316845, 2002-60959, 2002-38280, 2002-266081 or 2003-253464 may be used. In addition, a commercially available chemical conversion treatment agent can also be used for this chemical conversion treatment, examples of which include the chromate treatment agent "ZM-1300AN" manufactured by Nihon Parkerizing Co., Ltd., the chromate-free chemical conversion treatment agent "CT-E300N" manufactured by Nihon Parkerizing Co., Ltd., and the trivalent chromium-based chemical conversion treatment agent "Surfcoat® NRCIOOO" manufactured by Nippon Paint Co., Ltd. [0077]
In the present embodiment, a chemical conversion treatment for which processing adhesion and corrosion resistance have been confirmed to be superior in advance can be used for the chemical conversion treatment

- 39 -
performed on the metal sheet. According to findings obtained by the inventors, the addition of at least one of silica, silane coupling agent, tannic acid and zirconium oxide to a water-soluble resin is preferable since this results in superior processing adhesion and corrosion resistance. [0078]

Next, an explanation is provided of a production method of a precoated metal sheet having a composition as previously described. [0079]
The production method of a precoated metal sheet of the present embodiment is a method for forming at least two coating layers comprising a colored coated film layer containing a coloring pigment and a design coated film layer containing a luster pigment laminated onto the surface of the colored coated film layer, so that the center line average roughness Ra of the boundary surface between the colored coated film layer and the design coated film layer is 0.8 (xm or more. The following provides a detailed explanation of the production method of a precoated metal sheet of the present embodiment. [0080]
The precoated metal sheet of the present embodiment can be produced by using an ordinary continuous coating line (CCL) or coating line for cut sheets, suitably selecting the required treatment, and carrying out the selected treatment. Although typical production steps of a coating line consist of cleaning -^ drying -^ chemical conversion treatment —> drying —> coating -^ drying/baking -^ cooling -^ drying, the production steps of the precoated metal sheet in the present embodiment are not limited thereto. [0081]
The precoated metal sheet of the present embodiment

- 40 -
may be produced by repeatedly carrying out coating, drying and baking each coating layer as is normally carried out. Alternatively, it may also be produced by coating a coating material for forming the colored coated film layer and a coating material for forming the design coated film layer onto all or a portion of the surface of a metal material by wet-on-wet or simultaneous multilayer coating, and then simultaneously drying, baking and curing them. Wet-on-wet or simultaneous multilayer coating enable the precoated metal sheet to be produced without having to additionally install an oven for drying, baking and curing the coating materials on an existing continuous coating line (CCL) used to produce precoated metal sheets, and is also preferable since it results in improved productivity as a result of reducing the number of drying steps and the like. [0082]
In the case of forming a clear coated film layer, a coating material for the clear coated film layer (hereinafter referred to as a "clear coating material") may be coated and then cured by baking and drying after having cured the colored coated film layer and the design coated film layer by drying and baking. Alternatively, the clear coating material may be coated with the colored coating material and the design coating material by wet-on-wet or simultaneous multilayer coating, followed by simultaneously drying, baking and curing the three laminated layers. The use of wet-on-wet or simultaneous multilayer coating is more preferable since the number of production steps can be further reduced. [0083]
Furthermore, in the case where the metal material of the present embodiment is a steel sheet having zinc-based plating, by producing the precoated metal sheet on a line having wet-on-wet coating equipment or simultaneous multilayer coating equipment installed after the plating step in continuous electroplated steel sheet equipment or

- 41 -
continuous galvanized steel sheet equipment, coating can be carried out before an oxide film is formed on the plated metal surface, thereby making it possible to prevent cissing defects in the appearance caused by the oxide film. [0084]
Simultaneous multilayer coating refers to a method whereby a plurality of coating liquids are simultaneously coated onto a base in a laminated state followed by simultaneously drying and baking the laminated coating liquids by using an apparatus capable of discharging different coating materials from two or more parallel slits or the like so as to laminate the coating materials, examples of which include a slot die coater and slide hopper-type curtain coater. [0085]
Wet-on-wet coating refers to a method whereby a coating liquid is coated onto a base followed by additionally coating another coating liquid thereon before the first coating liquid has dried and is still wet, and simultaneously drying and baking the multiple layers of laminated coating liquids. Specific examples of wet-on-wet coating methods include a method in which after coating a first coated film layer by a coating method such as roll coating, dip coating, curtain flow coating or roller curtain coating, a second layer is coated thereon before the first coated film layer is dried and baked, using a method that enables coating without contacting the base, such as curtain flow coating, roller curtain coating, sliding hopper-type curtain coating or slot die coating, followed by simultaneously drying and baking the laminated coated films while still laminated in the wet state. [0086]
In the present embodiment, a commonly known oven for baking a coating material, such as a hot air drying oven, direct type heating oven, induction heating oven.

- 42 -
infrared heating oven or heating oven consisting of a combination thereof, can be used to simultaneously dry, bake and cure the coated films coated by simultaneous multilayer coating or wet-on-wet coating. [0087]
As a result of simultaneously laminating and coating undried coating liquids in this manner, drying steps that conventionally were carried out separately for each layer can be carried out collectively, which offers the advantage of being able to reduce the amount of drying equipment, in addition to being advantageous in terms of productivity and production cost. [0088]
(Conclusion)
As has been explained above, a precoated metal sheet superior in designability having increased luster, appearance of solidity and an appearance of depth as compared with the prior art, and a production method thereof, can be provided by the present embodiment. Thus, products having superior designability can be produced and assembled by using precoated metal sheets demonstrating high productivity instead of post-coated materials having low productivity in fields such as home appliances, construction materials, civil engineering applications, mechanical applications, automobiles, furniture or containers, and advantageous effects such as improved work efficiency are provided. Thus, the precoated metal sheet and the production method thereof of the present embodiment can be said to have an extremely high degree of industrial value. Examples [0089]
Although the following provides a more detailed explanation of the present invention using examples thereof, the present invention is not limited to the following examples. [0090]

- 43 -
First, an explanation is provided of a precoated metal sheet used in the examples. [0091]
1. Metal Sheet
A galvanized steel sheet having a thickness of 0.5 mm was used for the metal sheet serving as the base of the precoated metal sheet. The amount of zinc deposited on the galvanized steel sheet used was 45 g/m^ per side. [0092]
2. Chemical Conversion Treatment Solution
An aqueous solution containing 5 g/1 of a silane coupling agent, 1.0 g/1 of water-dispersed silica (fine particles) and 25 g/1 of an aqueous acrylic resin was prepared, and used for the chemical conversion treatment solution used in the examples. y-
glycidoxypropyltrimethoxysilane was used for the silane coupling agent, "Snowtex N" manufactured by Nissan Chemical Industries Ltd. was used for the water-dispersed silica, and polyacrylic acid was used for the aqueous acrylic resin. [0093]
3. Primer Coating Material
The polyester resin "Vylon® 290" manufactured by
Toyobo Co., Ltd. (glass transition temperature: 72°C, number average molecular weight: 22,000, hydroxyl value: 5 KOH-mg/g) was dissolved in a mixed solvent obtained by mixing cyclohexanone and Solvesso 150 at a weight ratio of 1/1 (hereinafter referred to as the "mixed solvent"). The melamine resin "Cymel® 303" manufactured by Mitsui Cytec Ltd. was added to this solution at a weight ratio of the solid resin of 10 parts by weight to 100 parts by weight of the solid polyester resin. Moreover, the acidic catalyst "Catalyst® 600" manufactured by Mitsui Cytec Ltd. was added at 0.5% by weight to this mixed solution of polyester resin and melamine resin to prepare a clear coating material for a primer coated film layer.

- 44 -
[0094]
Next, the titanium oxide "Tipaque® CR-95" manufactured by Ishihara Sangyo Kaisha Ltd. was added to the clear coating material for the primer coated film layer in an amount of 100 parts by weight relative to 100 parts by weight of the total solid resin of the polyester resin and melamine resin to prepare a primer coating material (hereinafter referred to as the "white primer"). In addition, a rust-preventive pigment-containing primer coating material (hereinafter referred to as the "rust-preventive primer") was prepared by adding 30 parts by weight of the aluminum dihydrogen tripolyphosphate "K-
WHITE® #105" manufactured by Tayca Corp., 30 parts by weight of the Ca ion-adsorbed silica "Shieldex C303" manufactured by W.R.Grace & Co., and 40 parts by weight of the titanium oxide "Tipaque® CR-95" manufactured by Ishihara Sangyo Kaisha Ltd., based on a value of 100 parts by weight for the total solid resin of the polyester resin and the melamine resin, to the clear coating material.
[0095]
4. Colored Coating Materials
The polyester resin "Vylon® 300" manufactured by Toyobo Co., Ltd. (glass transition temperature: 7°C, number average molecular weight: 23,000, hydroxyl value: 5 KOH-mg/g) (subsequently referred to as the "high molecular weight resin") was dissolved in the mixed solvent. The melamine resin "Cymel® 303" manufactured by Mitsui Cytec Ltd. was added to this solution at a weight ratio of the solid resin of 10 parts by weight to 100 parts by weight of the solid polyester resin. Moreover, the acidic catalyst "Catalyst® 600" manufactured by Mitsui Cytec Ltd. was added at 0.5% by weight to this mixed solution of polyester resin and melamine resin to prepare a high molecular weight clear coating material.
[0096]

- 45 -
In addition, a 1:1 (weight ratio) mixture of the polyester resins "Vylon® 300" (glass transition temperature: 7°C, number average molecular weight: 23,000, hydroxyl value: 5 KOH-mg/g) and "Vylon® GK680" (glass transition temperature: 6°C, number average molecular weight: 6,000, hydroxyl value: 21 KOH-mg/g) manufactured by Toyobo Co., Ltd. (subsequently referred to as the "combined high molecular weight/low molecular weight resin") were dissolved in the mixed solvent. The melamine resin "Cymel® 303" manufactured by Mitsui Cytec Ltd. was added to this solution at a weight ratio of the solid resin of 10 parts by weight to 100 parts by weight of the solid polyester resin. Moreover, the acidic catalyst "Catalyst® 600" manufactured by Mitsui Cytec Ltd. was added at 0.5% by weight to this mixed solution of polyester resin and melamine resin to prepare a combined high molecular weight/low molecular weight clear coating material. [0097]
Next, colored coating materials were prepared by adding the respective required amounts of titanium oxide fine particles having a particle diameter of 280 nm, alumina fine particles having particle diameters of 700 nm, 1000 nm and 4000 nm, and silica particles having a particle diameter of 40 nm to these clear coating materials. [0098]
"Tipaque® CR-95" manufactured by Ishihara Sangyo Kaisha Ltd. was used for the titanium oxide fine particles having a particle diameter of 280 nm, "A33F", "A32" and "A34" manufactured by Nippon Light Metal Co., Ltd. were respectively used for the alumina fine particles having particle diameters of 700 nm, 1000 nm and 4000 nm, and "Aerosil 200" manufactured by Nippon Aerosil Co., Ltd. was used for the silica particles having a particle diameter of 12 nm.

- 46 -
[0099]
The fine particles were added by converting their added amounts relative to the solid content of resin indicated by the volume ratios in Table 1 to weight ratios based on the specific gravity of each resin and each fine particle. Since titanium oxide fine particles constitute a coloring pigment per se, other coloring pigments were not added to those coating materials to which titanium oxide fine particles had been added as fine particles contained in the colored coated film layer. On the other hand, the carbon black "TOKABLACK #7300" manufactured by Tokai Carbon Co., Ltd. was added as coloring pigment to coating materials to which alumina or silica had been added as fine particles, at 3 parts by weight based on 100 parts by weight for the total amount of the entire solid resin and the fine particles. [0100]
In addition, when coating each of the coating materials onto the metal sheet, viscosity thereof was adjusted by diluting each coating material with the mixed solvent as necessary, and surface tension of the colored coating material was adjusted by adding the surfactant BYK-333 manufactured by BYK Corp. as necessary. Viscosities of the coating materials were measured in compliance with JIS Z 8803.9 entitled "Method for Measuring Viscosity by Cone-Plate Rotational Viscometer". More specifically, viscosity was measured using the "RSF-II" rotational viscosity measuring device manufactured by Rheometrics Inc. Surface tension of coating materials was measured in compliance with JIS K 3362.8.4.2 entitled "Ring Method" using the "Dynometer" platinum ring method surface tension measuring device manufactured by BYK Corp. Required amounts of the mixed solvent for dilution (diluting thinner) and the surfactant were added while adjusting to the target viscosity and surface tension based on these measurements. A mixture of cyclohexanone and Solvesso 150 mixed at a weight ratio of 1:1 was used

- 47 -
for the diluting thinner. [0101]
The details of the colored coating materials prepared in the manner described above are shown in Table 1.
[0102]
Table 1
Coating Added Resin Added Fine Particles
Material Resin Type Blended Type Particle Blended
Amt. of Diameter Amt.
Solid Resin (nm) (parts by
(parts by volume of
volume of solid)
solid)
Colored HMW resin 70 Titanium 280 30
Coating oxide
Material 1
Colored HMW resin 60 Titanium 280 40
Coating oxide
Material 2
Colored HMW resin 20 Titanium 280 80
Coating oxide
Material 3
Colored HMW resin 5 Titanium 280 95
Coating oxide
Material 4
Colored HMW resin 60 Alumina 700 40 Coating
Material 5
Colored HMW resin 60 Alumina 1000 40 Coating
Material 6
Colored Combined 70 Titanium 280 30
Coating HMW/LMW oxide
Material 7 resin
Colored Combined 60 Titanium 2^0 40
Coating HMW/LMW oxide
Material 8 resin
Colored Combined 5 Titanium 280 95
Coating HMW/LMW oxide
Material 9 resin
Colored HMW resin 80 Titanium JSO " 20 ~
Coating oxide
Material 10
Colored HMW resin 3 Titanium 280 97
Coating oxide
Material 11
Colored HMW resin 60 Silica 12 40 Coating
Material 12
Colored HMW resin 60 Alumina 4000 40 Coating Material 13 0103]

- 48 -
5. Design Coating Materials
The polyester resin "Vylon® 300" manufactured by Toyobo Co., Ltd. (glass transition temperature: 7°C, number average molecular weight: 23,000, hydroxyl value: 5 KOH-mg/g) was dissolved in the mixed solvent. The melamine resin "Cymel® 303" manufactured by Mitsui Cytec Ltd. was added to this solution at a weight ratio of the solid resin of 10 parts by weight to 100 parts by weight of the solid polyester resin. Moreover, the acidic catalyst "Catalyst® 600" manufactured by Mitsui Cytec Ltd. was added at 0.5% by weight to this mixed solution of polyester resin and melamine resin to prepare a high molecular weight clear coating material. [0104]
Each of luster pigments in the form of mica, aluminum flakes and glass flakes (silver-coated) was added to the high molecular weight clear coating material at 5 parts by weight relative to 100 parts by weight of the solid resin. "Pearl Glaze" sold by Nihonkoken Co., Ltd. was used for the mica, Non-Filling Aluminum Paste #7100 manufactured by Toyo Aluminum K.K. was used for the aluminum flakes, and "METASHINE" manufactured by Nippon Sheet Glass Co., Ltd. was used for the glass flakes. In the following descriptions, the design coating material containing mica is referred to as the "mica coating material", the design coating material containing aluminum flakes is referred to as the "aluminum flake coating material", and the design coating material containing glass flakes is referred to as the "glass flake coating material". [0105]
The coating material viscosity of the design coating materials was measured using the "RSF-II" rotational viscosity measuring device manufactured by Rheometrics Inc. while diluting with a diluting thinner as necessary to adjust to a viscosity of 450 mPa. A mixture of

- 49 -
cyclohexanone and Solvesso 150 mixed at a weight ratio of
1:1 was used for the diluting thinner.
[0106]
6. Back Coating Material
The back coating material, Orga 100 (color: beige), manufactured by Nippon Fine Coatings Inc. was prepared for use as a back coating material to be coated onto the back of the metal sheet, namely the opposed side of the surface thereof coated with the colored coating material, design coating material and the like. [0107]
7. Production of Precoated Steel Sheet
The metal sheet prepared in 1 above was degreased by immersing it for 10 seconds in an aqueous solution at a temperature of 60°C containing FC-4336 (Nihon Parkerizing Co., Ltd.) at a concentration of 2% by weight, followed by rinsing with water and drying. Next, the chemical conversion treatment solution prepared in 2 above was applied to both sides of the degreased metal sheet with a roll coater followed by drying in a hot air drying oven to obtain a chemical conversion treated coating layer. The chemical conversion treatment solution was applied so that the amount of the entire coated film deposited after drying was 100 mg/m^. The peak material temperature when drying the chemical conversion treatment solution was 60°C. Next, the primer coating material prepared in 3 above was coated onto the surface of the chemical conversion treated metal sheet with a roll coater to a dry film thickness of 5 \xm, while the back coating material prepared in 6 above was coated onto the other side with a roll coater to a dry film thickness of 5 |im, followed by drying and baking under conditions of a peak metal temperature of 210°C in an induction heating oven into which hot air was blown to form a primer coated film layer. Following drying and baking, the coated metal sheet was cooled by spraying with water.

- 50 -
[0108]
Next, the colored coating material produced in 4 above and the design coating material produced in 5 above were simultaneously coated in two layers onto the primer coated film layer with a slide hopper-type curtain coater, and the laminated coating materials were simultaneously dried and baked under conditions of a peak metal temperature of 230°C in an induction heating oven into which hot air was blown to form a colored coated film layer and a design coated film layer on the primer coated film layer. Following drying and baking, the coated metal sheet was cooled by spraying with water to obtain a precoated metal sheet for use in testing (this method is hereinafter referred to as "3-coating, 2-baking" or "3C2B"). [0109]
In addition, in the case of having formed a clear coated film layer (uppermost coated film layer) on the design coated film layer, a colored coating material, a design coating material and a clear coating material were simultaneously coated in three layers on the primer coated film layer with a slide hopper-type curtain coater, and the laminated coating materials were simultaneously dried and baked under conditions of a peak metal temperature of the metal sheet of 230°C in an induction heating oven into which hot air was blown to form a colored coated film layer, a design coated film layer and a clear coated film layer on the primer coated film layer. Following drying and baking, the coated metal sheet was cooled by spraying with water to obtain a precoated metal sheet for use in testing (this method is hereinafter referred to as "4-coating, 2-baking" or 'MC2B") . [0110]
In addition, a metal sheet not provided with a primer coated film layer was also prepared for use in testing as necessary. In other words, a precoated metal

- 51 -
sheet having only a colored coated film layer and a design coated film layer, a precoated metal sheet for use in testing, was obtained by simultaneously coating two layers of the colored coating material produced in 4 above and the design coating material produced in 5 above directly on the surface of the chemical conversion treated metal sheet with a slide hopper-type curtain coater, followed by simultaneously drying and baking the laminated coating materials under conditions of a peak metal temperature of 230°C in an induction heating oven into which hot air was blown and cooling with water (this method is hereinafter referred to as "2-coating, 1-baking" or "2C1B"). [0111]
In addition, for a comparative example, a colored coating material was coated onto the primer coated film layer with a roll coater followed by simultaneously drying and baking it under conditions of a peak metal temperature of 230°C in an induction heating oven into which hot air was blown and cooling with water to form a colored coated film layer, after which a design coating material was coated onto the dried and baked colored coated film layer with a roll coater followed by simultaneously drying and baking it under conditions of a peak metal temperature of 230°C in an induction heating oven into which hot air was blown to form the colored coated film layer and a design coated film layer on the primer coated film layer. Following the drying and baking, the coated metal sheet was cooled by spraying with water to obtain a precoated steel sheet for use in testing (this method is hereinafter referred to as "3-coating, 3-baking" or "3C3B"). [0112]
Since the line used to produce the precoated metal sheets used in testing in the examples was a so-called 2-bake line having only two heating ovens, when producing

- 52 -
the 3C3B sample, the sample was produced by passing the metal sheet through the production line twice. [0113]
Details of the precoated metal sheets produced in the manner described above are shown in Table 2. The low shear viscosity of the colored coating materials shown in Table 2 refers to values measured at a rotating speed of 5 rpm, while the value of Ay during coating refers to the difference in surface tension between the colored coating material and the design coating material.

- 53 -
[0114]
Table 2
No. I Primer Coated I Colored Coated I Design I Clear I Low Shear Ay Coating Film Layer Film Layer Coated Coated Viscosity of During Method
Film Film Colored Coating Coating Layer Layer Material during (mN/m)
Coating (mPa)
~1 White primer Colored coating Glass None 1000 1.5 3C2B
material 1 flakes
2 White primer Colored coating Glass None 1000 1.5 3C2B material 2 flakes
3 White primer Colored coating Glass None 1000 1.5 3C2B material 3 flakes
4 White primer Colored coating Glass None 1000 1.5 3C2B material 4 flakes
5 White primer Colored coating Glass None 1000 1.5 3C2B material 5 flakes
6 White primer Colored coating Glass None 1000 1.5 3C2B
material 6 flakes
T~ White primer Colored coating Glass None 1000 1.5 3C2B
material 7 flakes
8 White primer Colored coating Glass None 1000 1.5 3C2B
material 8 flakes
9 White primer Colored coating Glass None 1000 1.5 3C2B
material 9 flakes
10 White primer Colored coating Mica None 1000 1.5 3C2B material 8
11 White primer Colored coating Aluminum None 1000 1.5 3C2B material 8 flakes
12 White primer Colored coating Glass Coated 1000 1.5 4C2B material 8 flakes
13 White primer Colored coating Glass None 700 1.5 3C2B material 8 flakes
14 White primer Colored coating Glass None 4000 1.5 3C2B material 8 flakes
15 White primer Colored coating Glass None 1000 0.5 3C2B material 8 flakes
16 White primer Colored coating Glass None 1000 10 3C2B material 8 flakes
17 Rust-preventive Colored coating Glass None 1000 1.5 3C2B
primer material 1 flakes
18 Rust-preventive Colored coating Glass None 1000 1.5 3C2B primer material 2 flakes
19 Rust-preventive Colored coating Glass None 1000 1.5 3C2B primer material 3 flakes
20 Rust-preventive Colored coating Glass None 1000 1.5 3C2B
primer material 4 flakes
21 Rust-preventive Colored coating Glass None 1000 1.5 3C2B primer material 5 flakes
22 Rust-preventive Colored coating Glass None 1000 1.5 3C2B primer material 6 flakes
23 Rust-preventive Colored coating Glass None 1000 1.5 3C2B primer material 7 flakes
24 Rust-preventive Colored coating Glass None 1000 1.5 3C2B primer material 8 flakes
25 Rust-preventive Colored coating Glass None 1000 1.5 3C2B primer material 9 flakes
2 6 Rust-preventive Colored coating Glass None 1000 1.5 3C2B
primer material 8 flakes
27 None Colored coating Glass None 1000 1.5 2C1B
material 8 flakes
28 White primer Colored coating Glass None 300 1.5 3C2B material 10 flakes
29 White primer Colored coating Glass None 300 1.5 3C2B material 11 flakes
30 White primer Colored coating Glass None 300 1.5 3C2B material 12 flakes
31 White primer Colored coating Glass None 300 1.5 3C2B material 13 flakes
32 White primer Colored coating Glass None 200 0.5 3C2B material 2 flakes
33 White primer Colored coating Glass None 5000 1.5 3C2B material 2 flakes
34 White primer Colored coating Glass None 1000 -0.5 3C2B material 2 flakes
35 White primer Colored coating Glass None 1000 15 3C2B material 2 flakes
36 White primer Colored coating Glass None 1000 1.5 3C3B material 2 flakes

- 54 -
[0115]
The following evaluation tests were carried out on the precoated metal sheets produced in the manner described above. In each of the tests, testing was carried out using the surface on which the colored coated film and design coated film were coated as the evaluated surface. [0116]
1. Measurement of Center Line Average Roughness Ra
of Boundary Surface between Colored Coated Film
Layer and Design Coated Film Layer
The center line average roughness Ra of the boundary surface between the colored coated film layer and the design coated film layer was measured in the manner indicated below in compliance with JIS B 6061.
The precoated metal sheets were cut vertically so as to be able to observe a cross-section of the coated films, and after embedding the sectioned precoated metal sheets in resin, the cross-sections were polished and cross-sectional micrographs were taken with a light microscope at a magnification factor of lOOOX. Next, a transparent resin sheet (a commercially available OHP sheet was used) was placed over the micrographs, and surface irregularities at the interface of the coated films were accurately traced. Next, as shown in FIG. 1, a sample of a boundary surface curve was taken over a standard length 1 in the direction of the average line thereof, and when the direction of the average line of this sampled portion was taken to be the X axis, the direction of vertical magnification was taken to be the Y axis, and the interface curve is represented by y = f(x), the value determined according to the following equation (I) was calculated as the value of Ra. The average of five measurements was used as the value of the center line average roughness Ra of the boundary surface between the colored coated film layer and the design coated film layer of the precoated metal sheets.

- 55 -
[0117]
Samples in which Ra of the boundary surface was 1.0
l^m or more were evaluated as o, those in which Ra of the
boundary surface was 0.8 ^im or more were evaluated as A,
and those in which the Ra of the boundary surface was
less than 0.8 |Jin were evaluated as x.
[0118]
1 f^ I
Ra = - f(x) dx (I)
^ Jo I I
[0119]
2. Measurement of Void Volume Ratio of Colored
Coated Film Layer
Each precoated metal sheet produced was observed from the direction of vertical cross-section thereof with a light microscope followed by measurement of actual film thickness and calculation of volume of deposit per unit area on the basis thereof. [0120]
Next, precoated metal sheets were respectively produced by coating only a colored coated film in a single layer on a galvanized steel sheet under the coating conditions used when coating the colored coated films of each metal sheet. Next, the sheets were cut to a specific surface area to cut out a sample, and after determining the weight thereof, only the coated film was removed with a coated film remover followed by determining the weight of the sample after removal of the coated film. Moreover, the value obtained by dividing the difference in weight before and after removing the coated film by the area of the sample was then used as the weight of deposit per unit area, whereby the volume of deposit per unit area was then calculated using the dry coated film specific gravity (calculated value) of each coated film, and the value obtained was then used as the volume of coated film components per unit area. The void volume ratio in the colored coated film layer was

- 56 -
then calculated using the following equation (II).
[Void volume ratio] = ([volume of deposit per unit
area] - [volume of coated film components per unit
area]) x 100/[volume of deposit per unit area] (II) The average of values obtained at five locations on each of the precoated metal sheets was then used as the void volume ratio of the colored coated film layer of each precoated metal sheet. [0121]
Samples in which the void volume ratio as measured in the manner described above was 25% to less than 35% were evaluated as o, those in which void volume ratio was 3% to less than 25% were evaluated as A(-), those in which void volume ratio was 35% to less than 40% were evaluated as A(+), those in which void volume ratio was less than 3% were evaluated as x(-) and those in which void volume ratio exceeded 40% were evaluated as x(+). [0122]
3. Measurement of Void Area Ratio of Colored Coated
Film Layer Cross-Section
Each of the precoated metal sheets produced was cut in the direction of a vertical cross-section, and the cross-section perpendicular to the surface of the coated film layer was smoothened followed by taking a micrograph with a scanning electron microscope at a magnification factor of lOOOOX. The void area ratio in the cut cross-section was measured by image analysis. The average of values at five locations on each precoated metal sheet was used as the void area ratio of a cross-section of the colored coated film layer of each precoated metal sheet. [0123]
Samples in which the void area ratio as measured in the manner described above was 20% to less than 35% were evaluated as o, those in which void area ratio was 1% to less than 20% were evaluated as A(-), those in which void area ratio was 35% to less than 40% were evaluated as

- 57 -
A(+), those in which void area ratio was less than 1%
were evaluated as x(-) and those in which void area ratio
exceeded 40% were evaluated as x(+). [0124]
4. Processability Test
The evaluated surfaces of the precoated metal sheets produced were processed so as to have protrusions using a cupping testing apparatus in compliance with JIS K 5600.5.2 (typically also referred to as an Erichsen cupping testing machine), and tape was adhered to a coated film of the protrusions processed in compliance with the coated film removal method using tape described in section 7.2.6 of "Adhesion" of JIS K 5600.5.6 (typically referred to as a tape peeling test), followed by peeling off the tape and observing the degree of separation of the coated film at the protrusions with a lOX magnifying glass. [0125]
Those samples in which there was no separation of the coated film observed were evaluated as o, those in which the coated film partially separated at the protrusion were evaluated as A, and those in which the entire coated film had separated were evaluated as x. [0126]
5. Corrosion Resistance Test
Samples were prepared in which scratches were made in a coated film on the evaluated surface of each of the precoated metal sheets produced that reached to the material of the metal sheet with a cutter knife, and these samples were then investigated for neutral salt water spray resistance described in JIS K 5600.7.1. The salt water was sprayed for 240 hours. [0127]
The creep width of corrosion of the coated film from the scratched portion of the samples following testing was measured, and samples in which the maximum creep

- 58 -
width was within 3 mm were evaluated as o, those in which the maximum creep width was from more than 3 mm to 10 mm were evaluated as A, and those in which maximum creep width exceeded 10 mm were evaluated as x. [0128]
6. Gloss Measurement
Specular gloss of the evaluated surface of the precoated metal sheets produced was measured with a testing apparatus that complied with JIS K 5600.4.7. The axis of incident light was set to an angle of 60° relative to the normal of the sample surface. The average of values obtained at five locations on each precoated metal sheet was used as the value of specular gloss of the precoated metal sheets. [0129]
Those samples in which specular gloss as measured in the manner described above was 80% or more were evaluated as o, those in which specular gloss was 50% to less than 80% were evaluated as A, and those in which specular
gloss was less than 50% were evaluated as x. [0130]
7. Examination of Designability
Since the designability of a coated film is a sensory indicator, sensory evaluations were carried out by five randomly selected evaluators. The following parameters were scored by each evaluator, and samples in which the average score per evaluator for the total of (a) to (c) was 2.5 points or more were evaluated as o, samples in which the average score was 1.5 points to less than 2.5 points were evaluated as A, and those in which the average score was less than 1.5 points were evaluated as x. When the evaluators were requested to make these evaluations, white coating samples and black coating samples were prepared, and the evaluators were requested to make sensory evaluations while comparing with these coating samples.

- 59 -
[0131]
(a) Luster
Extremely high degree of luster: 3 points Some degree of luster: 2 points No luster: 1 point
(b) Appearance of Solidity
Extremely high degree of appearance of solidity: 3 points
Some degree of appearance of solidity: 2 points No appearance of solidity: 1 point
(c) Appearance of Depth
Extremely high degree of appearance of depth: 3 points
Some degree of appearance of depth: 2 points
No appearance of depth: 1 point [0132]
The white coating sample sheets and black coating sample sheets used for comparison when evaluating designability were produced in the manner described below. [0133]
(White Coating Sample Sheets Used for Comparison
when Evaluating Designability)
Using a clear coating material produced using the high molecular weight resin used in the colored coating material of the examples and titanium oxide, a coating material in which titanium oxide was added to the clear coating material, in an amount of 100 parts by weight of titanium oxide relative to 100 parts by weight of solid resin of the clear coating material, was provided. This coating material was coated only in a single layer onto the galvanized steel sheet used in the examples at a dry film thickness of 20 [im with a wire bar, followed by drying and baking under conditions of a peak metal temperature of 230° in a hot air drying oven to produce a white coating sample sheet. [0134]

- 60 -
(Black Coating Sample Sheets Used for Comparison
when Evaluating Designability)
Using a clear coating material produced using the high molecular weight resin used in the colored coating material of the examples and carbon black, a coating material in which carbon black was added to the clear coating material, in an amount of 5 parts by weight of carbon black relative to 100 parts by weight of solid resin of the clear coating material, was provided. This coating material was coated only in a single layer onto the galvanized steel sheet used in the examples at a dry
film thickness of 20 )im with a wire bar, followed by baking under conditions of a peak metal temperature of 230° in a hot air drying oven to produce a black coating sample sheet. [0135]
The results of the evaluation tests carried out in the manner described above are shown in Table 3 along with the details of the evaluation results.

- 61 -
[0136]
^ Table 3
No. Boundary Void Void Process- Corrosion Gloss Design- Remarks
Surface Volume Area ability Resistance ability
Ra Ratio Ratio
^ A A(-) A(-) O A A A Example
2ooo^ AA° Example
3ooo^ AAO Example
__^ o A( + ) A( + ) A A A o Example
5^00 0 AAA Example
6^ OO o ^ AA Example
"^ A A(-) A(-) O A A A Example
80000 AA° Example
9 A A(-) A(-) A A A A Example
lOo 00 O ^ A° Example
llo 00 O ^ A° Example
12 o 00 O ^ 00 Example
13 o 00 o ^ A° Example 14^ 00 o A AA Example 15o 00 o A A° Example I60 00 o A A° Example
17 A A(-) A(-) o o A A Example
I80 00 A ° A° Example
19o 00 A ° A° Example
~^0~ O A( + ) A( + ) A ° A o Example
21A 00 O O AA Example
22A 00 O O AA Example
23 A A( + ) A( + ) O ^ A A Example
24O 00 O O A° Example
~^^ A A( + ) A( + ) A o A A Example
26o 00 O O A° Example
27o 00 A A A° Example
28 X x(-) X(-) O A A X Comp.Ex.
29 O x( + ) X( + ) X A A O Comp.Ex.
30 X x(-) x(-) A A Ax Comp.Ex.
31 X x(-) x(-) A A A X Co"^P • Ex.
32 No x(-) X(-) A A A X Comp.Ex.
interface
33j^ 00 A A Ax Comp.Ex.
34 Layer O O A A A x Comp.Ex.
mixing
defect
35 X x(-) X(-) A A A X Comp. Ex.
36^ 00 X A Ax Comp. Ex.

- 62 -
[0137]
As shown in Table 3, examples in which Ra of the boundary surface between the colored coated film layer and the design coated film layer was 0.8 \xm more that satisfy the requirement of the precoated metal sheet of the present invention (Examples 1 to 27) were preferable as a result of having superior designability. On the other hand, examples in which Ra of the boundary surface was less than 0.8 |4m (Comparative Examples 28, 30, 31, 33, 34 and 35) were unsuitable due to inferior designability. Examples in which Ra of the boundary surface is 1.0 (jm or more (such as Examples 2 to 4, 8 and 10 to 13) were more preferable as a result of having particularly superior designability. [0138]
Examples in which the void volume ratio of the colored coated film layer was 3% to 40% or the void area ratio of a cross-section was 1% to 40% (Examples 1 to 27) were more preferable since designability thereof was superior to that of those examples demonstrating values outside these ranges (Comparative Examples 28, 30 to 32 and 35). Moreover, examples in which void volume ratio was 25% to less than 35% or examples in which void area ratio was 25% to less than 35% were more preferable as a result of having even more improved designability. [0139]
Examples in which the ratio of blended amounts of resin and fine particles contained in the colored coated film layer of the precoated metal sheets was 30/70 to 95/5 in terms of the solid volume ratio in the colored coated film layer when represented as (fine particle volume)/(binder resin volume) (Examples 1 to 27) were more preferable since the boundary surface Ra was 0.8 fom or more and as a result of demonstrating superior designability. The example in which the ratio of (fine particle volume)/(binder resin volume) was less than

- 63 -
30/70 (Example 28) was not preferable since the boundary surface Ra was less than 0.8 [xm and designability was inferior. The example in which the ratio of (fine particle volume/binder resin volume) exceeded 95/5 (Example 29) demonstrated a somewhat brittle coating and shape formability tended to be inferior. [0140]
The particle diameter of fine particles contained in the colored coated film layer is preferably 100 nm to 2000 nm. In examples in which particle diameter was less than 100 nm (Comparative Example 30) and in which particle diameter exceeds 1000 nm (Comparative Example 31), boundary surface Ra between the colored coated film layer and the design coated film layer was less than 0.8 )Lim. [0141]
The example in which clear coating was further carried out on the colored coated film layer (Example 12) demonstrated particularly superior gloss, thereby making this more preferable. Precoated metal sheets having a primer coated film layer beneath the colored coated film layer were preferable, while the example not provided with a primer coated film layer (Example 27) tended to have inferior processability. In addition, since those examples that contains a rust-preventive pigment in the primer coated film layer (Examples 17 to 26) demonstrated more superior corrosion resistance in comparison with examples in which no rust-preventive pigment was contained (Examples 1-16), it was found that it is preferable to add a rust-preventive pigment to the primer coated film layer in order to improve corrosion resistance. On the other hand, although not shown in Table 3, those examples that combined a primer coated film layer containing a white pigment in the form of titanium oxide with a colored coated film layer in which titanium oxide was used for the fine particles (Examples 1 to 4 and 7 to 11) demonstrated a high degree of

- 64 -
whiteness, and were particularly preferable from the viewpoint of superior designability. [0142]
When producing a precoated metal sheet, it is preferable to employ a method in which a colored coating material and a design coating material are laminated and coated in an undried state to form a laminated film in an undried state, followed by simultaneous drying and curing. As indicated by Comparative Example 36, in the case of producing a precoated metal sheet by repeatedly coating, drying and curing, the Ra value of the boundary surface between the colored coated film layer and the
design coated film layer becomes less than 0.8 |^m,
thereby making this undesirable.
[0143]
Although the above has provided an explanation of preferred embodiments of the present invention with reference to the appended drawing and examples, it goes without saying that the present invention is not limited to these embodiments. It is self-evident that a person with ordinary skill in the art would be able to conceive of various modifications or improvements within the range described in the scope of the claims, and it is understood that these are also included in the technical scope of the present invention.

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CLAIMS
1. A precoated metal sheet that has at least two
or more coating layers, comprising a first coated film
layer containing a coloring pigment and a second coated
film layer containing a luster pigment laminated on the
surface of the first coated film layer, on a portion or
all of the surface of a metal sheet,
wherein the center line average roughness Ra of the boundary surface between the first coated film layer and the second coated layer is 0.8 \xm or more.
2. The precoated metal sheet according to claim 1,
wherein the first coated film layer contains fine particles having a mean particle diameter of 100 nm to 2000 nm,
and wherein when the volume of the fine particles is taken to be VI and the volume of the binder resin is taken to be V2, the solid volume ratio between the fine particles and the binder resin in the first coated film layer is such that V1/V2 = 30/70 to 95/5.
3. The precoated metal sheet according to claim 1 or 2, wherein voids are present in the first coated film layer.
4. The precoated metal sheet according to claim 3, wherein the content of the voids is 3% by volume to 40% by volume relative to the sum of the total volume of the solid in the first coated film layer and the volume of the voids.
5. The precoated metal sheet according to claim 3, wherein in the case of smoothing a cross-section perpendicular to the surface of the first coated film layer and capturing an image thereof with a scanning microscope at a magnification factor of 10,000X, the ratio of the surface area occupied by the portion in which the voids are present to the area of the entire cross-section is 1% to 40%.
6. The precoated metal sheet according to any one of claims 2 to 5, wherein the fine particle is a coloring

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pigment.
7. The precoated metal sheet according to any one of claims 1 to 6, wherein the coloring pigment contained in the first coated film layer is a white pigment.
8. The precoated metal sheet according to claim 7, wherein the white pigment is titanium oxide.
9. The precoated metal sheet according to any one of claims 1 to 8, wherein the coating layers further include a third coated film layer arranged on the surface of the second coated film layer.
10. The precoated metal sheet according to any one of claims 1 to 9, wherein the coating layers further include a fourth coated film layer arranged between the first coated film layer and the metal sheet.
11. The precoated metal sheet according to any one of claims 1 to 10, wherein the metal sheet is subjected to chemical conversion treatment.
12. A production method of a precoated metal sheet, comprising: coating a first coating material containing a coloring pigment and a second coating material containing a luster pigment onto a portion or all of the surface of a metal sheet by simultaneous multilayer coating or a wet-on-wet method so that the second coating material is closer to the surface layer side than the first coating material, and simultaneously drying and curing the undried first coating material and second coating material coated on the surface of the metal sheet to thereby form a first coated film layer containing the coloring pigment and a second coated film layer containing the luster pigment so that the center line average roughness Ra of the boundary surface between the first coated film layer and the second coated film layer is 0.8 [Jin or more.
Dated this 16/03/2012
HRISnmESH RAYcQm)HURY OFREMFRY& SAfiAR ATTORNEY FOR THE ApfeflclSTS