- 1 - DESCRIPTION TITLE OF THE INVENTION COATED METAL MATERIAL AND PROCESS FOR PRODUCING THE SAME TECHNICAL FIELD [0001] The present invention relates to a coated metal material having a high reflectance and a process for producing such a material. BACKGROUND ART [0002] Various devices utilizing visible ray (such as illuminators, audiovisual equipment, electronic apparatuses, mobile computing devices, liquid crystal televisions, and plasma displays) emit visible rays so that they have functions of brightening their surroundings with light, transmitting optical signals, projecting optical images or the like. Some of these apparatuses have a reflective plate disposed around or behind a light source thereof, and have a function of improving the luminance of the light or changing the direction of the light, etc., by reflecting the light by using the reflective plate. In this case, in order to avoid a decrease in the quantity of light when light is reflected by a reflective plate, the surface of the reflective plate is required to have a high-visible ray reflectance. Accordingly, as a measure for improving the reflectance on the surface of a reflective plate, for example, a metal has heretofore been polished so as to provide a mirror plane, or a metal has been coated with a white coating material having a high reflectance. [0003] As a measure for enhancing such a reflectance. Patent Document 1, for example, discloses a technique relating to a light-reflecting film comprising a substrate film, a thin metal film layer disposed on one - 2 - side of the substrate film, and a fine inorganic particle-containing resin layer disposed on the thin metal film layer, wherein the thin metal film layer is made of aluminum, and the reflective indices nf and n^ satisfy the relationship nf-nb>0.4 in which nf is the refractive index of the fine inorganic particle constituting the fine inorganic particle-containing resin layer and nt is the refractive index of the resin constituting that layer. [0004] Patent Document 2, for example, discloses a technique relating to a highly diffusing reflective coated metal sheet to be used as a reflective plate for the back light of a liquid crystal display, and the metal sheet comprises an aluminum plate, a primer coating layer disposed on the aluminum plate, and an upper coating film disposed on the primer coating layer, wherein the primer coating layer contains 100 parts by mass of a resin and 150 to 300 parts by mass of a titanium oxide pigment, and has a film thickness of 50 to 100 )j.m, and the upper coating film contains 100 parts by mass of a resin and 100 to 250 parts by mass of a titanium oxide pigment and has a gloss of not more than 15 and a film thickness of 10 to 30 i^m. [0005] In addition. Patent Document 3, for example, discloses a technique relating to a coating material having a highly diffused reflectance, comprising a high-density pigment layer and at least one low-density layer, in which the high-density pigment layer contains 100 parts by volume of a binder and 150 or more and less than 1500 parts by volume of a white pigment, and the low-density layer contains a binder and a white pigment and the porosity of the coating layer is 5% by volume or more and less than 35% by volume. [0006] - 3 - Further, Patent Document 4, for example, discloses a technique relating to a coating material having a highly diffused reflectance, comprising a visible light reflective layer, wherein the layer comprises a binder, rutile titanium oxide and particles having a refractive index which is lower than that of the rutile titanium oxide, and the concentration of the rutile titanium oxide is 35% by volume or more and 70% by volume or less. PRIOR ART DOCUMENTS PATENT DOCUMENT [0007] [Patent Document 1] JP-A (Japanese Unexamined Patent Publication; KOKAI) No. 10-730 [Patent Document 2] JP-A No. 2002-172735 [Patent Document 3] JP-A No. 2006-192660 [Patent Document 4] JP-A No. 2008-145942 SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION [0008] In recent years, there have been increasing needs for forming a light reflective plate to be used for an electric apparatus such as illuminator and liquid crystal display, into various shapes prior to the use of the light reflective plate, along with the recent complicated structure and design of such an electric apparatus. Further, there is a growing trend for reflective plates which are capable of reflecting light more strongly and evenly. [0009] Under these circumstance, when a film is used as a substrate as described in the above Patent Document 1, it is difficult to form the film into an intended shape, after the film is laminated with a metal thin film layer or a resin layer containing therein fine inorganic particles. Therefore, it is necessary to form the film - 4 - into the intended shape in advance, before the lamination thereof with the metal thin film layer or with the resin layer containing fine inorganic particles. However, when the shape of the light reflective plate is complicated, it is difficult to laminate the shaped portion of the reflective plate with a coating having a uniform thickness. [0010] In addition, in the technique disclosed in Patent Document 2, it is possible to form the aluminum plate into an intended shape after the aluminum plate is coated with a primer coating layer and an upper coating film beforehand. However, it is very difficult to coat the aluminum plate with a primer coating having such a thickness (i.e., 50 to 100 jam) in one operation at a common precoating line, and accordingly it is necessary to conduct the coating operation two or more times, to thereby cause a defect such as low productivity, etc. [0011] Further, in the technique disclosed in Patent Documents 3 and 4, it is possible to obtain a highly diffused reflectance even if the coating layer is thin, and also to obtain a precoated metal sheet having a highly diffused reflectance by a one-time coating operation at a common precoating line. However, the technique has a drawback such that the amount of the binder contained in the coating layer is too small to obtain good formability and adhesion. [0012] Under these circumstances, there has been studied a technique for enhancing the formability and adhesion by forming a low-pigment concentration layer as an upper or lower layer, with respect to the high-pigment concentration layer, a low-density layer, and the visible light reflective layer, as described above. In addition, there has also been studied a technique for enhancing the formability and adhesion by using a high-molecular weight - 5 - polyester resin as the binder resin. [0013] However, any of the above techniques cannot produce satisfactory results in terms of the formability and adhesion, so that they only can insufficiently cope with shaping processes for providing various shapes along with recent complicated structure and design of electric appliances. In addition, the total luminous reflectance of the coated metal materials, which have been produced by using these techniques, are still insufficient with respect to demands for the reflective plate to be used for the electric appliances. [0014] As described above, for the reasons of the structure and design of the electric appliances, the complicated shaping of the reflective plate is required in some cases. In such a case, the coated metal material for the electric appliance is required to have a high formability, a high total luminous reflectance and a high productivity, etc. In the coated metal materials disclosed in the above Patent Documents 1 to 4, however, the performances thereof such as formability (i.e., formability and adhesion) and total luminous reflectance are not satisfactory. [0015] The present invention has been accomplished in view of the above circumstances, and an object of the present invention is to provide a coated metal material having a total luminous reflectance which is higher than that of the conventional material and has an excellent formability, and also to provide a process for producing such a coated metal material. MEANS FOR SOLVING THE PROBLEM [0016] As a result of earnest study for the purpose of solving the above problem, the present inventors have - 6 - found that both of the high total luminous reflectance and a high formability can be obtained by providing a coated metal material such that two or more coating films disposed on a portion or the entirety of the surface of a metal material, which comprises a first coating film containing rutile titanium oxide in a high concentration, and a second coating film disposed thereon, and the roughness of the interface between the first and second coating films is increased. Based on such a discovery, the present inventors have completed the present invention. [0017] More specifically, according to the present invention, there is provided a coated metal material having at least two coating films comprising a first coating film containing rutile titanium oxide in a solid volume concentration of 35% or more and 70% or less, and a second coating film disposed on the surface side of the first coating film, on a portion or the entirety of the surface of a metal material, wherein the centerline average roughness Ra of the interface between the first coating film and the second coating film is 0.8 |j,m or more. [0018] In a preferred embodiment of the present invention, in the boundary portion between the first coating film and the second coating film, there is present a mixed layer in which a component in the first coating film and a component in the second coating film are mixed, and the mixed layer has a thickness of 3 |im or more and 12 |a,m or less. [0019] In the coated metal material, the filtered centerline waviness WCA at the outermost surface of coating film may preferably be 2 )u,m or less. [0020] - 7 - In the coated metal material, the outermost coating film among the coating films may contain a silicone resin or a fluorine resin. [0021] In the coated material according to any one of claims 1 to 3, wherein the outermost coating film among the coating films contains a -Si-O-Si- bond in the resin skeleton constituting the coating film. [0022] In the coated material, the rutile titanium oxide may preferably have an average particle size of 200 nm or more and 400 nm or less. [0023] In the coated material, the first coating film cmay further contain particles having a particle size larger than that of the rutile titanium oxide and a refractive index lower than that of the rutile titanium oxide. [0024] In the coated material, voids may preferably be present in the first coating film, and the content of the voids may preferably be 0.05 to 0.9 times the amount of the solid volume content in the first coating film. [0025] In the coated material, the film thickness of the first coating film may preferably be 10 )am or more and 80 |j,m or less. [0026] In the coated material, the film thickness of the second coating film may preferably be 5 |am or more and 30 \im or less. [0027] In the coated material, the coating films may further contain a third coating film disposed between the metal material and the first coating film. [0028] In the coated material, the film thickness of the - 8 - third coating film may preferably be 5 |am or more and 30 )am or less. [0029] Further, according to the present invention, there is provided a process for producing the above coated material, the process comprising: applying a coating material for forming a first coating film and a coating material for forming a second coating film on a portion or the entirety of the surface of a metal material by a multilayer simultaneous coating or a wet-on-wet method. [0030] Further, according to the present invention, there is provided an illuminator using the above coated material, as an illumination reflective plate. [0031] Further, according to the present invention, there is provided an electronic appliance using the above coated material, as a reflective plate for an illuminating component or a reflective plate for an image display component. EFFECT OF THE INVENTION [0032] According to the present invention, there is provided a coated metal material having a total luminous reflectance which is higher than that of the conventional material and has an excellent formability, and also to provide a process for producing such a coated metal material. BRIEF EXPLANATION OF THE DRAWINGS [0033] Fig. 1 is a cross-sectional view of an example of the luminance measuring device to be used in a specific example of the present invention appearing hereinafter. Fig. 2 is a schematic top view of the luminance measuring device shown in Fig. 1. - 9 - Fig. 3 is a view showing an example of the roughness of an interface between coating films. MODE FOR CARRYING OUT THE INVENTION [0034] Hereinbeow, preferred embodiments of the present invention will be explained in detail, with reference to the accompanying drawings. An element or part having substantially the same function and structure will be denoted by the same reference numeral in the present specification and the accompanying drawings, so as to omit the redundant explanation relating to such an element or part. [0035] First, the constitution of the coated metal material according to an embodiment of the present invention will be explained. [0036] The coated metal material according to this embodiment of the present invention has a coating layer of at least two coating films on a portion or the entirety of the surface of a metal material as a substrate. More specifically, the coating films has a laminated structure comprising: at least, a first coating film (hereinafter referred to as "high-density pigment film") containing rutile titanium oxide in a high concentration, and a second coating film (hereinafter referred to as "upper coating film") disposed on the surface side of the first coating film. Further, the coated metal material according to this embodiment of the present invention may also have a third coating film (hereinafter referred to as "primer coating film") on the inner side of the high-density pigment film, i.e., between the m.etal material and the high-density pigment film, and may further have another coating film (e.g., a coating film disposed on the surface side of the upper - 10 - coating film). Hereinbelow, the constitution of each of the coating films will be explained in detail, in the order of the high-density pigment film, the upper coating film and the primer coating film. [0037] [High-density pigment film] (Outline) In this embodiment of the present invention, the high-density pigment film contains rutile titanium oxide as a white pigment in a concentration of 35% or more and 70% or less in terms of a solid volume content, and the high-density pigment film is positioned at the inner side of the upper coating film, i.e., at a side thereof which is closer to the substrate metal material. However, when the coating layer has a three-layer structure comprising a primer coating film, a high-density pigment film and an upper coating film, the high-density pigment film is positioned at a portion in contact with, and sandwiched between the primer coating film and the upper coating film. In addition, when the coating film has a multilayer structure of 4 layers or more, which contains one or more layers in addition to the above three layers of the primer coating film, the high-density pigment film and the upper coating film, the high-density pigment film are all the layers which are positioned between the upper coating film and the primer coating film, an contains rutile titanium oxide in a solid volume concentration of 35% or more and 70% or less. Further, when, in the coating layer, the concentration of the rutile titanium oxide is continuously changed, and the boundary of the respective layers is not clear, the entire range of a portion which satisfies the condition of a solid volume concentration of rutile titanium oxide being 35% or more and 70% or less is considered as the "high-density pigment film". [0038] As used herein, the term "solid volume concentration of rutile titanium oxide" refers to the ratio of the - 11 - volume occupied by rutile titanium oxide, with respect to the volume occupied by the entire solid contents including the resin (binder) component and the pigment component in the coating film of the high-density pigment film, and the volume occupied by the voids in the coating film has been subtracted (the method of determining the "solid volume concentration of rutile titanium oxide" will be explained hereinbelow). [0039] In the high-density pigment film according to this embodiment of the present invention, the volume of the voids which have formed between the particles of rutile titanium oxide, becomes greater than the volume of the binder resin, by allowing rutile titanium oxide to be contained in a high concentration in the dried and cured coating film so that the particles of rutile titanium oxide may be present in an amount corresponding to the closest packing thereof or more. Accordingly, in the high-density pigment film according to this embodiment of the present invention, unlike in the case of a coating film in which the pigment is contained in a concentration not reaching the closest packing, regions in which no binder resin is present can be provided as voids in the coating film. Herein, since the refractive index of air is generally smaller than that of a resin used as the binder, the difference in refractive index between rutile titanium oxide and air is greater than the difference between the rutile titanium oxide and the resin. In the high-density pigment film according to this embodiment of the present invention, even the interface between the binder resin and the voids can reflect the light which has been received by the high-density pigment film. Accordingly, in the high-density pigment film according to this embodiment of the present invention, the difference in refractive index at the interface where light is reflected is greater than in the coating film in which the pigment is contained in a concentration not - 12 - reaching the closest packing of the pigment, and the area of the interface which can reflect light becomes greater, and therefore a high total luminous reflectance can be obtained. [0040] Hereinbelow, each of the components contained in the high-density pigment film is explained in more detail. [0041] (Rutile titanium oxide) According to this embodiment, rutile titanium oxide is used as a pigment to be contained in the high-density pigment film. It is because, by use of this pigment, the refractive index of rutile titanium oxide is greater than that of the other commonly used white pigments, and the difference in refractive index with a resin to be used as the binder or with air present in voids in the coating film can be made greater, and accordingly the total luminous reflectance at the interface between the pigment and the resin and between the pigment and air can be enhanced. In connection this, anatase titanium oxide may also have a relatively high refractive index, but it may not be preferred since it has a high photocatalytic activity, and there is a risk such that the binder resin may be decomposed when exposed to light such as fluorescent light. [0042] In the coated metal material according to this embodiment of the present invention, the main purpose thereof is to reflect visible light, and therefore it is important that the coated metal material has a high reflectance of light in the wavelength range to which the human eye has a high sensitivity. Although there is a certain individual difference, the human eye can perceive light in the wavelength range of 380 nm to 780 nm and with the peak of the sensitivity is in the vicinity of 555 nm. Accordingly, the coated metal material according to this embodiment of the present invention may - 13 - preferably reflect light of wavelength in the range around the center of 555 nm, and accordingly, the particle size of the pigment (rutile titanium oxide) to be used in the high-density pigment film may preferably be selected in this viewpoint. [0043] The smaller the average particle size of rutile titanium oxide to be used as a pigment is, the surface area per unit volume thereof becomes greater and the area of the interfaces between the particles and the resin or air, which is light reflective surfaces becomes greater, and accordingly the total luminous reflectance becomes higher. However, when the average particle size of the pigment is too small, light of long wavelength will only pass thereby, so as to decrease the total luminous reflectance. Herein, it is generally known that in the particle size range comparable to the wavelength, there is the so-called Mie scattering region in which light is highly scattered, and that light scattering is at an maximum when the particle size is about 1/2 of the wavelength. Based on this, it is preferred in this embodiment of the present invention that the average particle size of rutile titanium oxide to be used as the pigment may be about half the wavelength of the visible light, i.e., 200 nm or more and 400 nm or less, and more preferably 250 nm or more and 350 nm or less. [0044] The average particle size of rutile titanium oxide on this embodiment of the present invention refers to the arithmetic mean which has been obtained from the particle size of the rutile titanium oxide particles, which will remain after the subtraction of the number of particles corresponding to 20% of the total number of the particles counted from the smallest particle size in the particle size distribution, and of 5% of the total number of the particles counted from the largest particle size in the particle size distribution from the total number of the - 14 - particles, wherein the total number of the particles is that of the rutile titanium oxide particles which are projected on the viewing field of a scanning electron microscope (SEM) in the case of the observation of a portion of the coating film to be confirmed at a magnification of 10,000. Method of preparing a sample to be observed: A sample is embedded in a resin, and the vertical cross section of the sample was polished. Viewing field to be observed: The sample is observed with an optical microscope at a magnification of about 500 to 1000, or a scanning electron microscope (SEM) in advance, and an area of the layer corresponding to the high-density pigment film is selected. Method of selecting the rutile titanium oxide particles for determining the arithmetic mean: The viewing field which has been selected in the above manner is observed with a scanning electron microscope (SEM) at a magnification of 10,000, and the image is photographed. The particle sizes of the entirety of the rutile titanium oxide particles contained in the resultant photograph are determined. Method of determining the particle sizes of individual rutile titanium oxide particles: In the determination of the particle sizes of rutile titanium oxide particles, the lengths of the maximum major axis and minimum minor axis of each of the particles are measured, and the particle size of the rutile titanium oxide particle is determined according to the formula: Particle size of rutile titanium oxide particle = (maximum, major axis + minimum minor axis)/2. Average of arithmetic means: Three "viewing field to be observed" are arbitrarily selected from the above plurality of "viewing fields to be observed" in the above manner, and the three "arithmetic mean" values obtained from the above three "viewing field to be observed" are - 15 - further subjected to the calculation of an arithmetic mean, to thereby determine the average of the arithmetic means. [0045] The rutile titanium oxide particles according to this embodiment of the present invention may be used without specific limitation, as long as they satisfy the conditions as described above. The rutile titanium oxide particles to be used in this embodiment of the present invention may be rutile titanium oxide particle as a simple substance, or rutile titanium oxide coated with another substance such as: silica, alumina, zirconia, zinc oxide, antimony oxide, and any of various organic substances. Specific examples of the organic substances to be used for coating rutile titanium oxide may include for example, but not limited to: a polyol-based compound such as pentaerythritol and trimethylolpropane, an alkanolamine-based compound such as organic acid salt of triethanolamine and trimethylolamine, and a silicone-based compound such as alkylchlorosilane. [0046] In this embodiment of the present invention, it is also possible to use any of commercially available products as the rutile titanium oxide. Specific examples thereof may include: for example, "TIPAQUE (registered trademark)" series mfd. by Ishihara Sangyo Kaisha, Ltd.; "TA" series mfd. by Fuji Titanium Industry Co., Ltd.; and "TITANIX (registered trademark)" series mfd. by Tayca Corporation. [0047] The rutile titanium oxide as described above may have a solid volume concentration of 35% or more in the high-density pigment film. If the solid volume concentration of rutile titanium oxide is 35% or more, as described above, the particles of rutile titanium oxide may be densely present in the dried and cured coating film so as to provide packing of the closest packing or - 16 - more, and accordingly voids can be present in which no binder resin is present in the coating film. This allows to increase the total luminous reflectance of the high-density pigment film. When a higher reflection performance is desired for a coated metal material, the solid volume concentration of the rutile titanium oxide having an average particle size of 200 nm to 400 nm described above may be adjusted to be 50% or more. In this case, the interface between the rutile titanium oxide and the void, the interface between the rutile titanium oxide and the resin and the interface between the resin and the void in the coating film may effectively contribute to the total luminous reflectance, and accordingly a high total reflection may preferably be obtained. [0048] On the other hand, if the solid volume concentration of rutile titanium oxide in the high-density pigment film exceeds 70%, the ratio of the portion occupied by rutile titanium oxide and voids in the coating film may become too high, which makes it difficult to secure the continuity (i.e., to maintain the form of a film) of the coating film based on the binder resin, whereby the high-density pigment film per se is liable to be brittle. Accordingly, the solid volume concentration of rutile titanium oxide in the high-density pigment film may preferably be set to 70% or less. From the viewpoint of securing a stable strength of the coating film, a more preferred range of the solid volume concentration of rutile titanium oxide may be 65% or less. [0049] Herein, the method of determining the solid volume concentration in a coating film according to this embodiment of the present invention may be explained. As an example, there is explained a method of determining a solid volume concentration of rutile titanium oxide, in a case wherein the coating layer has a three-layered - 17 - structure comprising an upper coating film, a high-density pigment film and a primer coating film. [0050] (Method of determining solid volume concentration of rutile titanium oxide) First, each layer of the coating film, which is the measurement target, such as upper coating film, high-density pigment film and primer coating film is sliced off from the sample to be measured. For the sliced coating film, the area Al thereof and the mass Ml thereof are measured. Next, the sliced coating film is heated in a crucible at 500°C for 1 hour so to decompose the resin components contained therein. The residue which has not been decomposed may be considered to be rutile titanium oxide, and accordingly the mass M2 of the residue is measured. Since the density of common rutile titanium oxide pigment is about 3800-4200 kg-m~^, the density of the rutile titanium oxide pigment is assumed to be 4000 kg-m~^. In addition, since the density of common polyester resin is about 1150-1250 kg-m~^, the density of the polyester resin is assumed to be 1200 kg-m . The volume VI of the polyester resin may be determined from the formula: Vl=(M1-M2)/1200 kg-m"^ and volume V2 of the rutile titanium oxide may be determined from the formula:V2=M2/4000 kg-m'^ From the volume VI of the polyester resin and the volume V2 of the rutile titanium oxide, the volume concentration Cl of the rutile titanium oxide can be determined by using the formula: C1=V2/(V1+V2)xlOO (volume %). The above Cl is determined three times for each of the samples to be measured (for example, with respect to the high-density pigment film), and its arithmetic mean can be determined from the thus obtained three values. [0051] (Addition of other particles) - 18 - In the high-density pigment film according to this embodiment of the present invention, particles (hereinafter referred to as "low-refractive index particles" in some cases) having a particle size larger than, and a refractive index smaller than those of the above-mentioned rutile titanium oxide may be used in combination with rutile titanium oxide, the resultant total luminous reflectance can efficiently be enhanced, and accordingly such an embodiment may be preferred. When particles having a particle size larger than those of rutile titanium oxide are further added, voids between the particles present in the high-density pigment film may become larger and a larger number of voids can be contained therein, to thereby enhance the total luminous reflectance. In addition, since the particles having a particle size to be used together with the rutile titanium oxide are low-refractive index particles, light can be reflected even at the contacting interface where these low-refractive index particles and the rutile titanium oxide particles are in contact with each other, to thereby contribute to an increase in the total luminous reflectance. [0052] If the particle size of the above low-refractive index particles is excessively larger than that of rutile titanium oxide, it is difficult to exhibit the effect of effectively allowing voids to be contained in the high-density pigment film and further of efficiently reflecting light at the contacting interface between the low-refractive index particles and titanium oxide. In this point of view, the average particle size of the low-refractive index particles may preferably be 1 (im or more and 10 |jin or less, and more preferably 3 )am or more and 8 |am or less. The ratio RL of the arithmetic mean of low-refractive index particles to that of rutile titanium oxide, i.e., RL - 19 - = (arithmetic mean diameter of the low-refractive index particles)/(arithmetic mean diameter of rutile titanium oxide) may preferably be 1/40 or more, and more preferably 1/40 to 12/40 (particularly 3/40 to 10/40). The average particle size of the low-refractive index particles according to this embodiment of the present invention refers to, in the same manner as in the case of the rutile titanium oxide, the arithmetic mean which has been obtained from the particle size of the low-refractive index particles, which will remain after the subtraction of the number of particles corresponding to 20% of the total number of the particles counted from the smallest particle size in the particle size distribution, and of 5% of the total number of the particles counted from the largest particle size in the particle size distribution from the total number of the particles, wherein the total number of the particles is that of the low-refractive index particles which are projected on the viewing field of an electron microscope in the case of the observation of a portion of the coating film to be confirmed with the electron microscope at a magnification of 10,000. That is, the arithmetic mean of particle size of the low-refractive index particles can also be determined in a similar manner to that of the "rutile titanium oxide" as described hereinabove. [0053] The low-refractive index particles described above may not be specifically limited, as long as they have a refractive index smaller than that of the rutile titanium oxide, and the difference in refractive index with rutile titanium oxide may preferably be 1 or more, and may preferably have no strong absorption of light in the visible light region, and may preferably exhibit a white color at the powder state thereof. More specifically, as the low-refractive index particles described above, it is possible to use inorganic particles such as silica. - 20 - calcium carbonate, barium sulfate and zinc oxide. In addition, as the low-refractive index particles described above, resin powders can also be used. The type of resin powders is not specifically limited, and as the resin powder, acrylic resin powder, polyester resin powder, PTFE (polytetrafluoroethylene) powder etc., can be used. [0054] The role of the above low-refractive index particles is, as described above, to efficiently incorporate voids into the high-density pigment film, further to cause light to reflect at the contacting interface between the low-refractive index pigment and the titanium oxide, to thereby obtain a high reflectance. Accordingly, even if the amount of the low-refractive index particles to be added is small, the lower limit concentration of the low-refractive index particles need not be specifically limited, since they can exhibit a effect thereof which is commensurate with the amount thereof contained in the high-density pigment film. However, if (the volume of the low-refractive index particles/the volume of rutile titanium oxide) is less than 0.05, the effect of enhancing the total luminous reflectance due to the addition of the low-refractive index particles is small. Accordingly, the lower limit concentration of the low-refractive index particles may preferably be such that (the volume of the low-refractive index particles/the volume of rutile titanium oxide) may become 0.05 or more. [0055] On the other hand, with respect to the upper limit concentration of the low-refractive index particles, if (the volume of the low-refractive index particles/the volume of rutile titanium oxide) is in the range of 0.2 or less, the reflectance of light is increased as the amount of the low-refractive index particles to be added is increased, and the effect of adding the low-refractive index particles can be observed, but if the amount thereof to be added exceeds the above range, the - 21 - performance (formability, corrosion resistance, etc.) of the low-refractive index particles other than light reflectance tends to be decreased. Accordingly, the upper limit of the low-refractive index particles is such that (the volume of the low-refractive index particles/the volume of rutile titanium oxide) may become 0.2 or less. [0056] In addition to the role of enhancing the total luminous reflectance, the above low-refractive index particles also have a role of controlling the roughness of the interface between the high-density pigment film and the upper coating film. The latter role will be explained hereinbelow. [0057] (Voids in coating film) The content of the voids in the high-density pigment film may preferably be 0.05 times or more and 0.9 times or less of the solid volume content in the high-density pigment film. It is because if the content of the voids is less than 0.05 times of the solid volume content, the effect of enhancing the total luminous reflectance based on the inclusion of voids is small, and if the content of voids exceeds 0.9 times of the solid volume content, the high-density pigment film may become brittle (mechanical strength thereof is decreased), and the formability and adhesion thereof tend to be decreased. The "content of the voids" can be measured by a method as described below. [0058] The content of the voids in the high-density pigment film can be controlled, as described above, by controlling the content of a pigment such as rutile titanium oxide and the low-refractive index particles. In addition, the content of the voids can be controlled by adjusting the dispersion state of the pigment to be used for forming the high-density pigment film. More - 22 - specifically, the better (the more homogeneous) the dispersion state of the pigment in the coating material is, the binder resin is adsorbed to the pigment, and the resin efficiently fills the voids between the pigment particles, whereby the content of the voids becomes smaller. Accordingly, in order to obtain a higher total luminous reflectance, it may be preferred to maintain the lowest dispersed state, unless the coating performance and coating material stability become problematic (i.e., it is preferred to make the pigment as heterogeneous as possible, unless the coating performance and coating material stability become problematic). The dispersed state of the pigment in the coating material can be regulated by adjusting the type of the dispersion machine, dispersion time, the type of the dispersing agent, the amount thereof to be added, and the like. [0059] The size of the voids in the high-density pigment film is not specifically limited. However, an extremely large size thereof is not be preferred because of a risk of inducing a defective coating film to thereby decrease the performance such as formability and corrosion resistance of the coating film. Further, the extremely large size is not preferred, because the surface area per unit volume of void may become smaller and the effect of enhancing the total luminous reflectance may not be obtained. On the other hand, the smaller the size of the voids is, the surface area per unit volume of the voids may become larger and the area of the light-reflecting interface may become larger, whereby the total luminous reflectance may become higher. However, if the size of the voids is extremely small, light having a longer wavelength may pass by the voids, to thereby cause a risk of decreasing the total luminous reflectance. Therefore, from the viewpoint of enhancing the reflectance of light, the size of the voids in the high-density pigment film may preferably be about half of the - 23 - wavelength of the visible light, i.e., 200 nm or more and 400 nm or less, and more preferably 250 nm or more and 350 nm or less. However, it is difficult to regulate the void size, particularly to obtain uniformly sized voids, and therefore the void size is not taken into account, unless they cause problems of the defective coating film etc., or an extreme effect thereof on reflectance. In this embodiment of the present invention, as the size of the voids, there is used an equivalent sphere diameter, i.e., the diameter of a sphere having the same volume as that of the void. In practice, the equivalent sphere diameter can be determined by using a method wherein an arbitrary portion on a vertical cross section in the high-density pigment film is photographed with a scanning electron microscope (SEM) at a magnification of 10,000, an arbitrary void observed in the photograph is selected, and the diameter of a circle having the same area as that of the selected void is defined as the "diameter of a sphere having the same volume as the void". Among the voids observed in the electron micrograph, diameters are calculated with respect to randomly selected 10 voids, and the arithmetic mean may be considered to be the diameter of the void. [0060] Herein, there is described a method of determining the volume of the voids in the coating film according to this embodiment of the present invention. [0061] First, each of the layers of the coating film, which is the target to be measured, is sliced off from a sample, and then the coating film is cut along a plane perpendicular to the coated plane (i.e., a plane parallel to the surface of the metal material). The film thickness Tl is determined by observing the cross section with an optical microscope, an electron microscope, or the like, or by using an electromagnetic coating thickness meter. In a manner similar to the - 24 - determination of the volume concentration of rutile titanium oxide, the area Al of the sliced coating film, the volume VI of the binder resin (for example, a polyester resin), and the volume V2 of the pigment are measured (for example, rutile titanium oxide). From the thus obtained values Al, VI and V2, a film thickness T2 of the coating film when voids were not present is determined according to the formula: T2=(V1+V2)/Al. From the thus obtained values VI, V2, Tl and T2, the volume V3 of the voids can be determined from the equation: V3 =(Vl+V2)x(Tl-T2)/(T1+T2). From, the viewpoint of precision in the measurement, the above method of determining Tl may preferably be carried out by using an optical microscope or a scanning electron microscope (SEM). In addition, the void volume as described above may be determined for five times with respect to the same sample (i.e., the coating film), and the arithmetic mean may be calculated therefrom. [0062] (Binder resin) In this embodiment of the present invention, the binder resin to be used in the high-density pigment film is not specifically limited, and a commonly used binder resin such as polyester resin, urethane resin, epoxy resin, acrylic resin, silicone resin, fluorinated resin, etc., may be used. However, since the high-density pigment film according to this embodiment of the present invention may contain rutile titanium oxide particles for providing the closest-packed or more density, the coating film tends to be brittle. Accordingly, as the binder resin to be used in the high-density pigment film, a resin having excellent formability and adhesion may preferably be used. More specifically, as the binder resin, polyester resin A having a number-average molecular weight of 19000 or more and 28000 or less may be used for the following reasons. [0063] - 25 - In this embodiment of the present invention, an object of the coated metal material is to obtain a high total luminous reflectance, and accordingly rutile titanium oxide particles to be added as a white pigment to a high-density pigment film is at a high density of 35% to 70%, in terms of solid volume concentration. Therefore, depending on the type of the binder resin to be used in the coating material, there have caused problems such that the performance as the binder of binding the pigments with each other may be insufficient in some cases, and thereby the formability of the coated metal material is reduced. Accordingly, as a result of earnest study on the constitution of a coating film for securing the formability with a small amount of the binder resin, the present inventors have found that the polyester resin having an excellent adhesion with pigment particles and a substrate metal material may be most suitable, and that good formability can be obtained by using polyester resin A having a number-average molecular weight of 19000 or more and 28000 or less, since the use of the polyester resin A having a number-average molecular weight of 19000 or more and 28000 or less exhibits excellent performance of balanced ductility and strength. The number-average molecular weight of a polyester resin can be measured by "GPC". When a commercially available polyester resin is used, the value of number-average molecular weight indicated by the manufacturer can used as the above number-average molecular weight. [0064] In general, a coating material which uses a high molecular weight polyester resin having a molecular weight of 19000 or more as a binder tends to be highly viscous, and accordingly the solid content concentration in the coating material should be minimized in order to secure the viscosity suitable for a coating operation. Accordingly, when the present invention is used in the - 26 - main application relating to thick coating, a defective coating called "bubbles" tended to occur, and therefore the application of the polyester resin to the thick coating has been considered to be difficult. In this embodiment of the present invention, however, rutile titanium oxide as a white pigment is added in a large amount, and accordingly the concentration of the binder resin is relatively reduced. As a result, it becomes possible to secure the viscosity suitable for coating even without significantly keeping the solid content concentration in the coating material at a low level. Accordingly, even when a high-molecular weight polyester resin A is used as the binder in the high-density pigment film according to this embodiment of the present invention, a thick coating without bubbles can be realized, whereby both of coating performance and formability can be realized at the same time. [0065] If the number-average molecular weight of the polyester resin A is less than 19000, it may become difficult to secure the formability. Therefore, in consideration of the reasons as described above in combination, the preferred range of the number-average molecular weight of the polyester resin A used as the binder resin in the high-density pigment film according to this embodiment of the present invention has been set at 19000 or more. [0066] On the other hand, if the number-average molecular weight of the polyester resin A exceeds 28000, there is a risk such that the surface of a coating film becomes too soft and scratch resistance thereof may be decreased. Therefore, according to this embodiment of the present invention, the preferred range of the number-average molecular weight of the polyester resin A to be used as the binder resin in the high-density pigment has been set at 28000 or less. - 27 - [0067] As to the amount to be added of the above polyester resin A, when the concentration of the polyester resin A with respect to the entire binder resin is 20% by mass or more, a thick coating without bubbles can be realized, to thereby obtain both of coating performance and formability at the same time. Therefore, the concentration of the polyester resin A with respect to the entire binder resin may preferably be 20% by mass or more. [0068] The present inventors also have found that a further excellent formability can be obtained when, in addition to the above polyester resin A, the binder resin in the high-density pigment film contains polyester resin B having a number-average molecular weight of 2000 or more and 6000 or less and a hydroxyl value of 20 or more, and the weight ratio of the polyester resin A and polyester resin B is 0.25<(polyester resin B)/(polyester resin A)<4. [0069] As described above, a high molecular weight polyester resin A having a number-average molecular weight of 19000 or more and 28000 or less has an excellent formability. However, the high-density pigment film according to this embodiment of the present invention contains a high concentration of pigment such as rutile titanium oxide, and accordingly, it is considered that the high-density pigment film has a structure wherein the binder resin is dispersed in the pigment. In such a structure, its formability may tend to become low as compared to that of a coating film having a low concentration of the pigment, even if the coating film contains the high molecular weight polyester resin A. Accordingly, a further enhancement in the formability may be desired. [0070] Under these circumstances, as a result of earnest - 28 - study on further enhancement of the formability, the present inventors have found that, by using a high-molecular weight polyester resin A and a low-molecular weight polyester resin B in combination, an excellent formability can be obtained than that in a case where a high-molecular weight polyester resin A is used alone. More specifically, when a high-molecular weight polyester resin A is used alone, the resin cannot permeate into the voids in the pigment which is present in a high concentration, and the function as the binder may become insufficient, to thereby slightly reduce the formability. In contrast thereto, by using a high-molecular weight polyester resin A and a low-molecular weight polyester resin B in combination, the low-molecular weight polyester resin B can permeate into voids between the pigment particles, into which polyester resin A cannot permeate, whereby polyester resin B can function as the binder between the pigment particles, or between the pigment and the high-molecular weight polyester resin A. As a result, the strength and adhesion of the entire coating film becomes enhanced, so as to provide an excellent formability. The higher the hydroxyl value of the low-molecular weight polyester resin B is, the more crosslinking points in the resin can be obtained, and accordingly a higher adhesion of the coating film can be obtained. [0071] Based on the point of view, the low-molecular weight polyester resin B may preferably have a number-average molecular weight of 2000 or more and 6000 or less and a hydroxyl value of 20 or more. If the number-average molecular weight of the polyester resin B is less than 2000, the strength of the coating film may be insufficient and the formability may be decreased, whereas if it exceeds 6000, it may become difficult for polyester resin B to permeate into regions between the pigment particles, whereby a risk of decreasing the - 29 - effect of enhancing adhesion can be caused. If the hydroxyl value of the polyester resin B is less than 20, the crosslinking points between the pigments may be decreased, whereby a risk of decreasing the effect of enhancing adhesion can be caused. Further, from the viewpoint of coating film performance, the upper limit of the hydroxyl value of the polyester resin B need not be defined specifically, but from the viewpoint of easy availability of the resin and the stability of the coating material, the hydroxyl value of the polyester resin B may preferably be 200 or less. [0072] When the mixing ratio of the polyester resin A and polyester resin B is 0.25<(polyester resin B)/(polyester resin A)<4 in terms of mass ratio, excellent adhesion and formability can be obtained. If the mass ratio of (polyester resin B)/(polyester resin A) is less than 0.25, the polyester resin B may not fully exhibit its function, and accordingly the resultant adhesion may be decreased, whereas if the ratio of (polyester resin B)/(polyester resin A) is greater than 4, the polyester resin A may not fully exhibit its function, whereby a risk of decreasing the formability can be caused. [0073] (Film thickness) In order to obtain a high total luminous reflectance, the film thickness of the high-density pigment film according to this embodiment of the present invention may preferably be 10 )j,m or more, and in order to obtain a further higher total luminous reflectance, the film thickness may be more preferably 40 \xm or more. On the other hand, if the film thickness of the high-density pigment film exceeds 80 )am, the formability of the coating film may be decreased, and accordingly a film thickness of 100 |am or less may be preferred, and in order to obtain a further higher formability, a film - 30 - thickness of 15 |am or less may be more preferred. Herein, the film thickness of the high-density pigment film according to this embodiment of the present invention can be measured in the following manner. Thus, a sample to be measureed is cut along a plane perpendicular to the coated plane of each of the coating films. By observing the cross section with an optical microscope, an electron microscope or the like, the film thickness of the coating film can be determined. In the measurement of the "film thickness", the (arithmetic) mean which has been obtained by determining five arbitrary portions, is used as the film thickness. The film thicknesses of the upper coating film and primer coating film can also be measured in a manner similar to that of the high-density pigment film. In a case wherein a mixed layer is formed in the boundary portion between the respective coating films, such an embodiment will be explained hereinbelow. [0074] [Upper coating film] The high-density pigment film according to this embodiment of the present invention has been explained in detail as above, and next, the upper coating film according to this embodiment of the present invention will be explained. [0075] (Outline) The upper coating film according to this embodiment of the present invention is a coating film which is disposed on the surface side of the above high-density pigment film, i.e., on a side of the high-density pigment film which is farther from the substrate metal material. When the coating layer has a 2-layered structure comprising a high-density pigment film and an upper coating film, a 3-layered structure further comprising a primer coating film in addition to the above two coating films, or a 4-layered structure in which a plurality of - 31 - coating films are present as the high-density pigment film, the upper coating film may be positioned as the outermost coating film. However, when the upper coating film is disposed directly on the surface side of the high-density pigment film, it is not necessarily be positioned at the outermost layer, and an additional coating film may further be disposed on the surface side of the upper coating film. [0076] (Binder) A resin to be used as the binder for the upper coating film may not be specifically limited, but from the viewpoint of adhesion of the high-density pigment film, of the formation of a mixed layer as described below, of the use of common raw material for the coating material etc., the upper coating film may preferably contain the same resin as that of the high-density pigment film. The use of the polyester resin A having a number-average molecular weight of 19000 or more and 28000 or less may be preferred as the binder of the high-density pigment film, and accordingly the polyester resin A may also preferably be used as the binder for the upper coating film as well. If the number-average molecular weight of the polyester resin to be used as the binder for the upper coating film is less than 19000, there is a risk such that formability and adhesion may be decreased. If it exceeds 28000, there is a risk such that the surface of a coating film may become too soft and the scratch resistance and performance concerning the blocking may be decreased. [0077] As to the amount of the polyester resin A to be added to the upper coating film, when the concentration of the polyester resin A with respect to the entire binder resin is 80% by mass or more, the effect of enhancing the formability and adhesion can be exhibited, and accordingly the concentration of the polyester resin - 32 - A with respect to the entire binder resin may preferably be 80% by mass or more. [0078] (Pigment) Unlike the high-density pigment film, the upper coating film may not require the addition of a pigment. The intended reflective characteristics and other features may be imparted thereto by adjusting the presence or absence of pigment to be added thereto, depending on the intended use, the type of the pigment to be added, the concentration of the pigment, and the like. [0079] First, there is described a case in which a pigment such as rutile titanium oxide, is added to the upper coating film. By adding rutile titanium oxide to the upper coating film, the total luminous reflectance thereof can be enhanced, and a higher concentration of rutile titanium oxide may be more advantageous to the reflective performance. However, since the main role of the upper coating film is to protect the entire coating layer, a too brittle coating film may not be preferred. Accordingly from the viewpoint of securing the flexibility of the coating film, the concentration of rutile titanium oxide in the upper coating film may preferably be 35% or less in terms of the solid volume concentration. On the other hand, the lower limit of the rutile titanium oxide concentration in the upper coating film need not be specifically limited, and a case of containing no rutile titanium oxide may be included in this embodiment. Accordingly, the concentration of rutile titanium oxide in the upper coating film according to this embodiment of the present invention may preferably be 0% or more and 35% or less, in terms of the solid volume concentration. Further, when a further higher total luminous reflectance may be desired, the concentration of rutile titanium oxide in the upper coating film according to this embodiment of the present - 33 - invention may be adjusted to be 20% to 30% in terms of the solid volume concentration so that both of the function of protecting the entire coating layer due to the upper coating film and a high reflective performance can be realized to a higher level. [0080] As used herein the term "the solid volume concentration of rutile titanium oxide" refers to the ratio of the volume occupied by rutile titanium oxide with respect to the volume occupied by the entire solid comprising the resin (binder) component and the pigment component in the coating film in the upper coating film. [0081] When the average particle size of the rutile titanium oxide when it is used as a pigment is small, the surface area per unit volume may become larger and the area of the interface between the resin or voids and the pigment particles, as a reflective plane may become larger, whereby the total luminous reflectance may become higher. However, if the average particle size of the pigment is too small, light of a longer wavelength may pass by and accordingly the total luminous reflectance may be decreased. Therefore, in the same manner as in the case of the high-density pigment film, the average particle size of rutile titanium oxide to be used as the pigment in the upper coating film may preferably be 200 nm or more and 400 nm or less, and more preferably 250 nm or more and 350 nm or less. [0082] (Components to be added other than pigment) In addition to rutile titanium oxide, a delustering agent, for example, may be added to the upper coating film. By adding a delustering agent to the upper coating film in a solid volume concentration of 3% or more and 15% or less, a reflective characteristic substantially free of the specular reflection component can be obtained, while maintaining the total luminous - 34 - reflectance which is equal to that in a case where no delustering agent is used. When a coated metal material having such a reflective characteristic is used as the reflective plate for illuminators, a constant reflective light can be obtained regardless of the distance or the angle from the light source. Accordingly, even when the number of light sources was small or the interval between the light sources is large, a uniform reflective light can be obtained. However, the addition of a delustering agent can provide the formation of minute unevenness on the surface of the upper coating film. On such minute unevenness, staining substances tend to be deposited, and the staining substances cannot be easily removed even by wiping, and accordingly the addition of a delustering agent has a risk of decreasing the stain resistance. Accordingly, in the case of the addition of a delustering agent, it may be desired that an appropriate amount should be determined in consideration of its effect on the uniformity of the reflective light and a decrease in the stain resistance. [0083] The delustering agent to be used according to this embodiment of the present invention may not be specifically limited, but silica having a particle size of 3 |am to 9 |am may be preferred. [0084] (Film thic]<;ness) When rutile titanium oxide is added to the upper coating film, the thicker the film thickness of the upper coating film is, the higher formability, adhesion and total luminous reflectance can be obtained. However, if the film thickness of the upper coating film exceeds 30 \im, bubbles may easily occur at the time of coating operation, so as to provide a poor coating performance, and it may not be preferred in terms of costs for coating, either. On the other hand, if the film - 35 - thickness the upper coating film is less than 5 f^m, the effect of enhancing the formability, adhesion and total luminous reflectance by the upper coating film may become small, and accordingly the film thickness of the upper coating film may preferably be 5 f^m or more and 30 i^m or less. From the viewpoint of securing the stable formability, adhesion, total luminous reflectance and coating performance, the more preferred film thickness of the upper coating film may be 10 )Lim or more and 25 |am or less. [0085] When a delustering agent having a solid volume concentration of 3% or more and 15% or less is added to the upper coating film, the range of film thickness of the upper coating film may preferably be 5 |j.m or more and 30 |am or less, similarly as in the case of rutile titanium oxide to be added to the upper coating film. If the film thickness of the upper coating film exceeds 30 |j,m, bubbles may easily occur at the time of the coating operation so as to provide a poor coating performance, and it may not be preferred in terms of cost for coating, either. On the other hand, if the film thickness is less than 5 [ua, the effect of enhancing the formability and adhesion and of obtaining the reflective characteristic substantially free of the specular reflection component due to the upper coating film may be hardly obtained. From the viewpoint of securing the stable formability, adhesion, reflective characteristic and coating performance, the more preferred film thickness of the upper coating film containing the delustering agent may be 10 pm or more and 25 j^m or less. [0086] [Regarding roughness of interface between high-density pigment film and upper coating film] In the coated metal material according to this embodiment of the present invention, the centerline - 36 - average roughness Ra of the interface between the above high-density pigment film and the upper coating film may be required to be 0.8 |jjn or more. Accordingly, by increasing Ra of the interface between the high-density pigment film and the upper coating film, the interface between the high-density pigment film and the upper coating film becomes rough, whereby diffuse reflectance can be enhanced. If Ra of the interface between the high-density pigment film and the upper coating film is less than 0.8 j^m, the above effect of enhancing the adhesion and reflectance cannot be fully obtained. If it is 0.9 jam or more, the reflectance may become higher, and accordingly may be more preferred. Ra of the interface of 2.0 |am or more may be more preferred. Ra of the interface between the middle coating film and the upper coating film is evaluated by using a photograph which has been taken with a scanning electron microscope (magnification: 1000 fold) in which the coating film of each example is cut, embedded in a resin and then the resultant product is polished, and the plane perpendicular to the surface of the coating film is smoothed. The photograph is covered with a transparent sheet to be used for OHP and the roughness of the interface is precisely traced on the transparent sheet. Then, as shown in Fig. 3, a reference length L is extracted in the direction of an average line of the interface curve. When X axis is taken in the direction of an average line of the thus extracted section, Y axis is taken in the vertical magnification direction and the interface curve is expressed by a formula of y=f(x), the value determined by the following formula (1) is treated as Ra of the interface. In the present invention, there is used the average of Ra which has been determined by using the method described above with respect to arbitrary 5 points on the cross section in the coating film. - 37 - Ra = - \^\f{x)\ d^ (1) L J 0 ' ' [0087] (Method of regulating Ra of interface) Ra of the interface between the above high-density pigment film and the upper coating film may be regulated by using the method of applying the high-density pigment film and the upper coating film, the concentration of the pigment (rutile titanium oxide) in the high-density pigment film, the type of the pigment (rutile titanium oxide and low-refractive index particles such as silica), the viscosity and surface tension at a low shear of the coating material for forming the high-density pigment film and the upper coating film, and the like. As used herein, the interface between the above high-density pigment film and the upper coating film refers to the interfacial boundary (or interfacial boundary line) which can be visually observed, when the cross section of the coating film is photographed with an optical microscope or an electron microscope. [0088] More specifically, specific examples of the method of increasing Ra of the interface between the high-density pigment film and the upper coating film may include: (1) the so-called wet-on-wet method or the multilayer simultaneous coating method in which a coating material for forming a high-density pigment film and a coating material for forming the upper coating film are laminated while they are in an undried state; (2) a method of increasing the concentration of the pigment (rutile titanium oxide, etc.) in the high-density pigment film higher than that in the upper coating film; (3) a method of adding particles (silica, etc.) having a large particle size in the high-density pigment film; - 38 - (4) a method of decreasing the viscosity of a coating material for forming the high-density pigment film at a low shear; (5) a method of reducing the difference in surface tension between a coating material for forming the high-density pigment film and a coating material for forming the upper coating film; and the like. [0089] First, with respect to the above method (1), by laminating a coating material for forming the high-density pigment film and a coating material for forming the upper coating film while they are in an undried state, a force for driving the diffusion of rutile titanium oxide particles from the high-density pigment film toward the upper coating film may be exerted on the interface, to thereby increase Ra of the interface of the coating film. At this time, as in the method (2), by increasing the concentration of rutile titanium oxide in the high-density pigment film (particularly to a concentration higher than that at the closest packing), the difference in concentration with that in the upper coating film coating film may become larger, and accordingly a strong force may be exerted for driving the diffusion of rutile titanium oxide into the upper coating film, to thereby further increase Ra of the interface. [0090] With respect to method (3), by adding particles having a large particle size to the high-density pigment film and allowing them to be present in the vicinity of the interface between the high-density pigment film and the upper coating film, unevenness may be provided by the large-particle size particles in the interface, to thereby increase Ra of the interface. At this time, as in the method (1), by laminating a coating material for forming the high-density pigment film and a coating material for forming the upper coating film while they are in an undried state, particles having a large - 39 - particle size may be diffused from the high-density pigment film to the upper coating film, and accordingly it becomes easier for large-particle size particles to be present in the vicinity of the interface between the high-density pigment film and the upper coating film. [0091] With respect to method (4), by lowering the viscosity of a coating material for forming the high-density pigment film at a low shear, rutile titanium oxide in the high-density pigment film can more easily be diffused into the upper coating film, to thereby increase Ra of the interface. More specifically, according to the discovery by the present inventors, a coating material in which particles (in this case, rutile titanium oxide) have been added in a concentration higher than that of the close packing after drying and curing becomes a non-Newtonian fluid which is generally referred to as "a highly dispersed-type coating material". This means that, when the viscosity is measured by using a rotation viscometer, the viscosity of such a coating material becomes high at a low-speed rotation, and becomes low at a high-speed rotation, i.e., it becomes a coating material having a so-called shear-thinning characteristic. In the highly dispersed-type coating material, due to the short distance between the pigment particles, an intermolecular force may be exerted between the particles. Accordingly, at a low-speed rotation, a small shear force may be applied to the coating material, and due to the above intermolecular force, the viscosity thereof may become high. On the other hand, at a highspeed rotation, a large shear force may be applied to the coating material, and due to the intermolecular force, the viscosity becomes low. The coating processability at the time at which such a coating material is applied onto a substrate, is highly susceptible to the viscosity thereof at a high-speed rotation, whereas the flow of the coating material in the coating film after the drying and - 40 - baking-curing step is highly susceptible to the viscosity thereof at a low-speed rotation. Therefore, in the regulating of Ra of the interface between the high-density pigment film and the upper coating film, it is important to adjust the viscosity of the coating material at a low speed. [0092] The viscosity of the coating material at a low speed can be adjusted by changing the amount of a solvent in the coating material and the storage condition (storage temperature and period) for the coating material. With regard to the storage condition for the coating material, the higher the storage temperature and the longer the storage period are, the lower the thixotropy thereof becomes, to thereby increase the viscosity of the coating material at a low shear. This is because in a prolonged period of storage, the wettability of the surface of the pigment with the coating material becomes higher, a larger amount of the resin may be adsorbed to the surface of the pigment, and the intermolecular force between the pigment particles becomes weakened, to thereby reduce the thixotropy. Further, the viscosity of the coating material at a low shear can also be adjusted by adding an additive such as dispersant to the coating material. [0093] Further, with respect to the method (5), Ra of the interface may become large by reducing the difference in surface tension between a coating material for forming the high-density pigment film and a coating material for forming the upper coating film, and laminating these coating materials while they are in an undried state, and simultaneously drying, baking and curing these coating films. However, an appropriate value for the difference in surface tension between the coating material for forming the high-density pigment film and the coating material for forming the upper coating film may be - 41 - changed with the type of resin and solvent of each of the layers, and therefore the difference in surface tension cannot be determined unconditionally, and accordingly, an optimum value thereof should be determined for each of the coating materials by investigating them in advance. The surface tension of a coating material can be adjusted by using an additive generally called a surfactant such as leveling agent and antifoaming agent, and can also be adjusted by changing the type of a solvent. [0094] In the coated metal material according to this embodiment of the present invention, the centerline average roughness Ra of the interface between the high-density pigment film and the upper coating film should be 0.8 [rni or more. Specific examples of the effective method of achieving such a value may include a method in which rutile titanium oxide having a particle size of 200 nm to 400 nm is added to the high-density pigment film, so as to provide to a concentration which is higher than that at the closest packing or more, with respect to the volume of the coating film after the drying, and the coating material for forming the high-density pigment film and the coating material for forming the upper coating film are laminated while they are in an undried state, and the resultant product is simultaneously dried and cured at the laminated state. By adding rutile titanium oxide to the high-density pigment film so as to provide a concentration higher than that at the closest packing or more, and laminating the high-density pigment film with the upper coating film in an undried state, a concentration gradient of rutile titanium oxide particles between the respective coating films may be formed, and a force may be generated such that it drives the diffusion of the rutile titanium oxide particles from the high-density pigment film toward the upper coating film side, and further heat may be added during the drying and curing step, whereby the heat function as a driving force - 42 - so that a force for diffusing rutile titanium oxide becomes significant. On the other hand, when heat is applied during the drying and curing step, the crosslinking reaction of the resin is caused so as to form a coating film, to thereby generate a force for suppressing the diffusion movement of the rutile titanium oxide particles between the coating films. As a result, the interface between the high-density pigment film and the upper coating film becomes coarser, and the Ra between the coating films may become higher. [0095] Ra of the interface between the high-density pigment film and the upper coating film can be made 0.8 [m. or more by providing a high-density pigment film according to this embodiment of the present invention as a lower coating film, with respect to the upper coating film. Further, as in the above method (4), the regulation of Ra of the interface between the high-density pigment film and the upper coating film may be significantly affected by the viscosity of the coating material at a low shear, and Ra of the interface between the high-density pigment film and the upper coating film can be further increased by lowering the viscosity of the coating material at a low shear. [0096] [Mixed layer] In a coated metal material according to this embodiment of the present invention, by applying a coating material for forming the high-density pigment film and a coating material for forming the upper coating film by using the so-called wet-on-wet method or multilayer simultaneous coating method, rutile titanium oxide in the coating material for forming the high-density pigment film may be diffused beyond the interface of the coating films into the coating material for forming the upper coating film, to thereby form a layer having a concentration gradient of rutile titanium oxide - 43 - in the vicinity of the interface between the high-density pigment film and the upper coating film. As used herein, the concentration gradient layer of titanium oxide may be called a "mixed layer". In this case, due to the presence of the mixed layer at the interface between the high-density pigment film and the upper coating film, the adhesion between the high-density pigment film and the upper coating film can be enhanced. In the case of a precoated metal material, the forming to be conducted after the coating can sometimes lower the total luminous reflectance of the coated metal material. However, due to the presence of the mixed layer, the above adhesion can be enhanced and hence the reduction in the total luminous reflectance after the post-coat forming can also be prevented. [0097] (Definition of mixed layer) As used herein the term "mixed layer" refers to a layer in which the concentration of rutile titanium oxide is changed so as to provide a gradient thereof, since rutile titanium oxide in the high-density pigment film is diffused into the upper coating film. More specifically, according to this embodiment of the present invention, in view of rutile titanium oxide, when the amount of Ti in the high-density pigment film is denoted by "x" and that in the upper coating film is denoted by "y", the portion satisfying the formula: [x-0.05x(x-y)] to [y+0.05x(x-y)] is defined as the "mixed layer". The amount of each of the amounts of Ti can be determined by using analytical method as described below, and can be calculated by treating the thus measured intensity as the amount of Ti, when the intensity is measured by using each analytical instrument. [0099] A mixed layer may sometimes be formed in a region between the primer coating film as described below and the high-density pigment film. Also in this case, the - 44 - definition of the mixed layer and that of the interface are the same as those for the mixed layer between the high-density pigment film and the upper coating film. [0100] When low-refractive index particles are contained in the high-density pigment film, the volume ratio of the low-refractive index particles to rutile titanium oxide may be determined in a manner similar to that for determining the volume concentration of rutile titanium oxide, when the low-refractive index particles are for example an inorganic pigment. The particles can be differentiated from rutile titanium oxide for example, by using a method employing a chemical such as acid which is capable of dissolving only the low-refractive index particles, but is not capable of dissolving rutile titanium oxide. In this case, the low-refractive index particles contained in the high-density pigment film are selectively dissolved, and the mass of the low-refractive index particles can be calculated from the mass difference of the residue remaining after the dissolution and the residue remaining after the heating. Further, from the thus obtained mass and the density of the low-refractive index particles, the volume of the low-refractive index particles can be obtained. [0101] On the other hand, when the low-refractive index particles such as resin beads for example, have a transmissivity for electron beam which is utterly different from that of rutile titanium oxide, it is possible to use a method in which the cross section of the coating film is examined by using a scanning electron microscope or a method in which the coating film is sliced into a thin section with a microtome, etc., and the section is examined with a transmission electron microscope (magnification: about 10000 fold). More specifically, the number of rutile titanium oxide particles and the number of the low-refractive index - 45 - particles which are observed in the viewing field of the electron microscope may be counted selectively. If the number of the particles is small, however, the resultant error may be relatively large, and accordingly it is preferred that particles may be counted in a range, in which 100 or more rutile titanium oxide particles are present. [0102] When the electron beam transmittance of the low-refractive index particles is not so different from that of rutile titanium oxide and when the scanning electron microscope or the optical microscope cannot clearly differentiate the low-refractive index particles from rutile titanium oxide, the elementary composition in the cross section of a coating film is confirmed, and based on the confirmed composition, the ratio of rutile titanium oxide to the other low-refractive index particles can be determined. The elementary composition can be confirmed by using EPMA (electron probe microanalyzer), GDS (glow discharge spectroscopic instrument), etc. [0103] (Thickness of mixed layer) In this embodiment, when the above mixed layer is present, the mixed layer may preferably have a thickness of 3 fom or more and 12 |Jin or less. If the thickness of the mixed layer is less than 3 |am, the effect of enhancing the adhesion between the high-density pigment film and the upper coating film due to the mixed layer may not be stably obtained. On the other hand, if the thickness of the mixed layer exceeds 12 [ua, it may be difficult to sufficiently secure the thickness of the coating film of the high-density pigment film and the upper coating film, each of which is responsible for necessary functions. Accordingly, when the upper coating film is the outermost layer, the maintenance of - 46 - performance of the high-density pigment film and the upper coating film per se may become difficult such that, for example, a defective outer appearance may arise due to the insufficient thickness of the outermost layer, and the mixed layer may have substantially the same performance as that of a coating film which has been formed from the coating material obtained by mixing those for the high-density pigment film and the upper coating film, to thereby the performance originally required for the high-density pigment film and the upper coating film cannot be obtained. In addition, it is substantially difficult to regulate the thickness of the mixed layer so as to provide a thickness exceeding 12 |am. [0104] (Method of determining thickness of mixed layer) The thickness of the mixed layer can be determined by analyzing the distribution state along the direction of film thickness with respect to a component which is contained in only one of the high-density pigment film and the upper coating film. For the analysis, a known method can be used. For example, the element concentration in the direction of depth of the coating film can be analyzed, by using X-ray probe microanalyzer, electron beam microanalyzer (EPMA), X-ray photoemission spectroscopy (XPS), Auger electron spectroscopy (AES), glow discharge spectroscopy (GDS), etc. Alternatively, by use of the component analysis on the cross section of the coating film, the film thickness of the mixed layer can be determined from the concentration distribution of the target component. The type and/or method to be applied to the component analysis may be selected, as appropriate, depending on the film thickness, the amount of the component, etc. Any method other than the above EPMA, XPS, AES and GDS can also be used, as long as it can conduct the component analysis in the direction of depth. A component other than Ti can also be used as a component to be used in the analysis of the mixed layer. - 47 - Among these analytical methods, GDS may be preferred since it can conduct the analysis while sputtering with argon ion from the surface of the coating film in the direction of depth, and permits the precise comparison of the concentration in the direction of depth of the element to be measured. The film thickness of the mixed layer of the present invention refers to the average of film thickness values which have been measured at five arbitrary points. [0105] (Method of regulating thickness of mixed layer) The thickness of the mixed layer can be mainly regulated by the application method and the baking time. With respect to the application method, the wet-on-wet method or the multilayer simultaneous coating method permit the easy formation of a mixed layer. In addition, by increasing the baking time, a longer time can be allowed for mixed layer formation, and accordingly the thickness of the mixed layer can be thickened. More specifically, by setting the baking time at about 60 to 180 seconds, the thickness of the mixed layer can be adjusted to 3 |J.m or more and 12 )im or less. [0106] It is preferred that, in order to form a stable mixed layer, the difference (Aa=a2-al) of the surface tension (al) of a coating material for forming the high-density pigment film and the surface tension (a2) of a coating material for forming the upper coating film, each of which can contribute to the formation of the mixed layer, may be controlled to be 0.5 to 8 mN/m, and the difference (A(j)=(j)2-(j)l) of the viscosity ((j)!) of a coating material for forming the high-density pigment film and the viscosity ((j)2) of a coating material for forming the upper coating film, each of which can contribute to the formation of the mixed layer, may be controlled to be -100 to 4000 mPa•s. Accordingly, by also adjusting, as - 48 - appropriate, the relationship between the surface tension and viscosity of a coating material for forming the high-density pigment film and a coating material for forming the upper coating film to an appropriate value in the above condition, depending on the type of the coating material and coating condition as well, the formation of a stable mixed layer, the control of the film thickness, and further the control of the shape of the outermost surface can be attained. [0107] More specifically, since ACT is 8 mN/m or less or A^ is 4000 mPa-s or less, a mixed layer with a sufficient thickness can be formed and accordingly the adhesion between the layers can be further enhanced. On the other hand, since ACT is 0.5 mN/m or more or A(j) is -100 mPa-s or more, sufficient film thickness of the high-density pigment film and the upper coating film can be obtained, and the shape of the outermost surface can be appropriately provided, and accordingly a further stable performance can be secured. In this embodiment of the present invention, the surface tension of a coating material can also be measured by using the platinum ring-lifting method at 20 °C (with respect to the details of such a measurement of surface tension, JIS. K. 3362. 8.4.2 "Ring method" may be referred to). In addition, the viscosity of a coating material can be measured by using the type B viscometer at 20 °C and 6 rpm (with respect to the details of such a measurement of viscosity, JIS.Z.8803.8 "Method of measuring viscosity with a single cylindrical rotational viscometer" may be referred to). [0108] In order to adjust the surface tension of a coating material, a surfactant (also including an antifoaming agent and a leveling agent) can be used. A known surfactant can be used. Commercially available - 49 - surfactants may include, for example, BYK-333 and BYK-307 mfd. by BYK Corporation; Emulgen mfd. by Kao Corporation, and many of other surfactants, which may be added as desired, depending on the coating material components. The surface tension of a coating material may also be adjusted by using a method other than that using a surfactant, such as method of diluting the coating material, or mixing the same with another solvent. If the surface tension is too large, the coating performance may be decreased, and accordingly the surface tension of both of the high-density pigment film and the upper coating film may preferably be 40 mN/m or less. [0109] For the purpose of adjusting the viscosity of a coating material, a thickening agent (including a rheological modifier and a viscosity modifier) may preferably be used. A known thickening agent can be used, and commercially available thickening agents may include, for example, BYK-411 and BYK-425 mfd. by BYK Japan KK, and many other thickening agents, which may be added as desired, depending on the coating material components. The viscosity of a coating material may also be adjusted by using a method other than that using a thickening agent such as method of diluting the coating material, or method of mixing the same with another solvent, or by increasing the ratio of the solid components. [0110] Further, the thickness of the mixed layer can also be regulated by adjusting the difference between the pigment concentration in the high-density pigment film and the pigment concentration in the upper coating film. More specifically, if the difference in the pigment concentrations becomes large, the diffusion speed of the pigment from the high-density pigment film to the upper coating film becomes higher, and accordingly it is possible to form a mixed layer having a sufficient - 50 - thickness, before the high-density pigment film and the upper coating film become dried and cured. [0111] (Regarding waviness of outermost surface) In the coated metal material according to this embodiment of the present invention, the filtered center line waviness WCA of the outermost surface of the coating layer may preferably be 2 )im or less. In this way, by making the WCA of the outermost surface of the coating layer smaller, it is possible to improve the image clarity of the coated metal material. Further, a smooth surface free of fine unevenness can be obtained. Therefore, the coated metal material surface is resistant to buildup of stain substance, so the stain resistance thereof can be improved. If the WQA of the outermost surface of the coating layer exceeds 2 ^m, the image clarity and stain resistance are liable to be decreased. On the other hand, the preferable lower limit value of the WCA of the outermost surface of the coating layer does not have to be particularly defined, but the control of WCA of the outermost surface of the coating layer to less than 0.2 \\m is substantially difficult. In this point of view, WCA at the outermost surface of the coating layer may preferably be 2 \xm or less. WQA of the present invention refers to the average of measured values which have been obtained by measuring five arbitrary points, [0112] The "outermost surface of coating film" as used herein refers to the surface of the outermost coating film among the coating films. The "outermost coating film" refers to the upper coating film in this embodiment of the present invention, or, when a further coating film is laminated at the surface side of the upper coating film, the "outermost coating film" refers to the further coating film. [0113] - 51 - (Method of controlling WCA of outermost surface) The WcA of the outermost surface of the coating layer is changed due to the effect of the Ra of the interface between the high-density pigment film and the upper coating film. Therefore, the WCA of the outermost surface of the coating layer can be mainly controlled by the coating method and the coating viscosity at a low shear. Specifically, by using, as the coating method, the wet-on-wet method or the multilayer simultaneous coating method, rutile titanium oxide is diffused from the high-density pigment film to the upper coating film, so that the Ra of the interface between the high-density pigment film and the upper coating film becomes larger and the WQA of the outermost surface of the coating layer also becomes larger. Further, by lowering the low shear viscosity of the coating material for forming the high-density pigment film, the rutile titanium oxide in the high-density pigment film may easily be diffused to the upper coating film, so the Ra of the interface becomes larger and the WCA of the outermost surface of the coating layer also becomes larger. [0114] As explained above, it is preferable to increase the Ra of the interface between the high-density pigment film and the upper coating film and to reduce the WCA of the outermost surface of the coating layer, so it is preferable to consider the balance of the two values and determine a suitable value of the low shear viscosity of the coating material for forming the high-density pigment film. [0115] (Impartation of water repellency and oil repellency to outermost coating film) In the coated metal material according to this embodiment of the present invention, the outermost coating film of the coating layer formed on the metal material may contain a silicone resin or fluorocarbon - 52 - resin. The "outermost coating film" as used herein refers to the upper coating film when that upper coating film is formed at the outermost layer, and refers to a further coating film when the further coating film is formed on the surface side of the upper coating film. When this embodiment of the present invention is applied to a precoated metal sheet, the possibility of a decrease in the total light reflectance due to deposition of stain substance, etc., at the time of forming thereof is conceivable. In this connection, by using a silicone resin or fluorocarbon resin as portion or the entirety of the binder of the outermost coating film of the coated metal material according to this embodiment of the present invention, it is possible to impart oil repellency and water repellency to the coating film surface. In this way, by making the surface of the outermost coating film oil repellent and water repellent, the surface of the coating film becomes resistant to stain substance and a decrease in the total light reflectance can be suppressed, so this is preferred. [0116] As the method of introducing a silicone resin or fluorocarbon resin to the outermost coating film, there may be used a method of adding the silicone resin or fluorocarbon resin to the outermost coating film, and a method of using a resin containing a silicone resin or fluorocarbon resin as the main resin. [0117] As the silicone resin to be added to the outermost coating film, among the commercially available resins, for example, "BYK (registered trade marlc)-306", "BYK (registered trade mark)-378", etc. made by BYK are known, while as the fluorocarbon resin added to the outermost coating film, among the commercially available resins, for example, "BYK (registered trade mark)-340" etc., mfd. by BYK Corporation are known, but there are many other types as well. These may be suitably added in - 53 - accordance with the coating components. [0118] As the main resin containing the silicone resin or fluorocarbon resin, a commercially available silicone-acryl copolymer resin (for example, the "Symac (registered trade mark)" series or "Reseda (registered trade mark)" series mfd. by Toagosei, "SQ (registered trade mark)100", etc., mfd. by Tokushiki) or commercially available silicone-fluorocarbon copolymer resin (for example, "ZX-001", etc., mfd. by Fuji Kasei Kogyo) may be used. [0119] The above silicone-acryl copolymer resin or silicone-fluorocarbon copolymer resin may, as desired, be cross-linked by a generally known cross-linking agent, for example, isocyanate or melamine resin. In this case, as the isocyanate, a generally available one, for example, the "Sumidur (registered trade mark)" series or "Desmodur (registered trade mark)" series mfd. by Sumika Bayer, the "Takenate (registered trade mark)" series mfd. by Mitsui Takeda Chemical, etc., may be used. As the melamine resin, a generally commercially available one, for example, the "Cymel (registered trade mark)" series and "Mycoat (registered trade mark)" series mfd. by Mitsui Cytec, the "Beckamine (registered trade mark)" series and the "Supper Beckamine (registered trade mark)" series mfd. by Dainippon Ink & Chemicals, etc. may be used. [0120] As described above, a coated metal material including a silicone resin or fluorocarbon resin in the outermost coating film is suitable for not only applications for reflectors of lighting apparatuses, but also applications such as ceilings, wall materials, etc., of rooms. When a coated metal material including a silicone resin or fluorocarbon resin in the outermost coating film is applied to applications such as ceilings. - 54 - wall materials, etc., of rooms, it is possible to brighten the insides of the rooms with less light, since the ceilings and wall materials themselves in the rooms can perform the role of reflectors. [0121] (Imparting hydrophilicity to outermost coating film) In the coated metal material according to this embodiment of the present invention, the outermost coating film of the coating layer formed on the metal material may have -Si-O-Si- bonds in the resin skeleton for forming the coating film. The "outermost coating film" refers to the upper coating film when the upper coating film is formed at the outermost layer, and refers to a further coating film when the further coating film is laminated on the surface side of the upper coating film. Further, the Si atoms in the -Si-O-Si- bonds are derived from an alkoxysilane or a hydrolyzed condensate of alkoxysilane. [0122] When a coated metal material according to this embodiment of the present invention is applied to a precoated metal sheet, there may be the possibility of a decrease in total light reflectance due to the adhesion of stain substance at the time of forming, etc. In this connection, by forming -Si-O-Si- in the outermost coating film of the coated metal material according to this embodiment of the present invention, that is, by including therein Si atoms derived from an alkoxysilane or a hydrolyzed condensate of alkoxysilane, it is possible to impart hydrophilicity to the coating film surface without impairing the surface luster or the formability. In this way, by making the surface of the outermost coating film hydrophilic, wiping off foreign matter stuck on the coating film surface by water etc., becomes easier, and the decrease in total light reflectance can be suppressed, so this is preferred. [0123] - 55 - To incorporate -Si-O-Si- bonds in the resin skeleton for forming the coating film, it is sufficient to add an alkoxysilane or a hydrolyzed condensate of alkoxysilane into the coating material for forming the outermost coating film. Specific examples of the alkoxysilane used therefor, may include: generally known ones, for example, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, dimethoxydiethoxysilane, dimethoxydipropoxysilane, etc. Further, as the hydrolyzed condensate of alkoxysilane, for example, hydrolyzed condensates of the above-exemplified alkoxysilanes may be used. [0124] As described above, a coated metal material in the outermost coating film in which -Si-O-Si- bonds are formed is suitable for not only applications for reflectors of lighting apparatuses, but also applications such as ceilings, wall materials, etc., of rooms. When a coated metal material in the outermost coating film in which -Si-O-Si- is incorporated is applied to applications such as ceilings, wall materials, etc., of rooms, it is possible to brighten the insides of the rooms with less light since the ceilings and wall materials themselves in the rooms perform the role of reflectors. [0125] (Thickness of outermost coating film) When the coated metal material according to this embodiment of the present invention further has an outermost coating film (for example, the above-mentioned coating film containing a silicone resin or fluorocarbon resin, or coating film having -Si-O-Si- bonds in the resin skeleton for the coating film) at the surface side of the upper coating film, the thickness of this outermost coating film is not particularly limited as - 56 - long as the thickness is in an extent which can give the above-mentioned water repellency, oil repellency, hydrophilicity, or other characteristics. However, the thickness of the outermost coating film may preferably be 1 |am or more and 25 |im or less. If the thickness of the outermost coating film is less than 1 |am, there is a possibility of the water repellency, oil repellency, and hydrophilicity becoming insufficient, while if it exceeds 25 |im, there is a possibility of the formability decreasing. Further, this is not preferable from the viewpoint of costs. [0126] [Primer coating film] (Outline) A coating film of the coated metal material according to this embodiment of the present invention may contain a primer coating film, in addition to the high-density pigment film and the upper coating film as explained above. The primer coating film is a coating film to be formed between the metal material and the high-density pigment film, and when the coating layer has three layers comprising the upper coating film, the high-density pigment film and the primer coating film, it is a coating film closest to the substrate metal material. In this case, however, even if it is a layer closest to the substrate metal material, a coating film having a film thickness of less than 1 pm which is provided for the purpose of enhancing the adhesion and corrosion-resistance between the metal material and the coating film does not correspond to the "primer coating film" according to this embodiment of the present invention. Accordingly, a coating film at the further surface side than that of the coating film having a film thickness of less than 1 (j,m is considered to be a primer coating film. [0127] (Binder) A resin to be used as the binder for the primer - 57 - coating film may not be specifically limited, but from the viewpoint of adhesion of the high-density pigment film, or of the use of common raw material for the coating material etc., the primer coating film may preferably contain the same resin as that of the high-density pigment film. The use of the polyester resin A having a number-average molecular weight of 19000 or more and 28000 or less may be preferred as the binder of the high-density pigment film, and accordingly the polyester resin A may also preferably be used as the binder for the primer coating film as well. If the number-average molecular weight of the polyester resin to be used as the binder for the primer coating film is less than 19000, there is a risk such that formability and adhesion may be decreased. If it exceeds 28000, there is a risk such that the surface of a coating film may become too soft and the scratch resistance and performance concerning the blocking may be decreased. [0128] As to the amount of the polyester resin A to be added to the primer coating film, when the concentration of the polyester resin A with respect to the entire binder resin is 80% by mass or more, the effect of enhancing the formability and adhesion can be exhibited, and accordingly the concentration of the polyester resin A with respect to the entire binder resin may preferably be 80% by mass or more. [0129] (Pigment) The addition of rutile titanium oxide in a solid volume concentration of 20% or more and 35% or less as the pigment to the primer coating film can enhance the reflectance and accordingly may be preferred. The reason why rutile titanium oxide may be preferred as the pigment to be added to the primer coating film is that, as in the case of the high-density pigment film, the refractive index of rutile titanium oxide is higher than that of - 58 - other commonly used pigments, and accordingly a difference in refractive index from that of the resin used as the binder and the air in the voids present between pigment particles can be increased, to thereby enhance the reflectance of light at the interface of the pigment and the resin, and at the interface of the pigment and air. [0130] When the average particle size of rutile titanium oxide when it is used as a pigment is small, the surface area per unit volume may become larger and the area of the interface, which is a reflective plane, between the resin or voids and the pigment particles may become larger, to thereby enhance total luminous reflectance. However, if the average particle size of the pigment is too small, light of long wavelength may only pass by and accordingly the total luminous reflectance may be decreased. Therefore, similarly as in the case of the high-density pigment film, the average particle size of rutile titanium oxide to be used as the pigment in the primer coating film may be preferably 200 nm or more and 400 nm or less, and more preferably 250 nm or more and 350 nm or less. [0131] (Film thickness) With respect to the film thickness of the primer coating film, the thicker the film thickness is, higher formability, adhesion and total luminous reflectance can be obtained. Further, when rutile titanium oxide is added as the pigment, thicker film thickness is advantageous in terms of reflective performance as well, there is no need to set the upper limit for the film thickness of the primer coating film. However, if the film thickness of the primer coating film exceeds 30 |am, unlike in the case of the high-density pigment film, bubbles may easily occur during the coating operation, which leads to poor coating performance and it may not be - 59 - preferred in terms of cost, either. Accordingly the film thickness of the primer coating film may preferably be 30 |4,m or less. On the other hand, if the film thickness of the primer coating film is less than 5 ^.m, the effect of enhancing the formability, adhesion and reflective performance by the primer coating film may become small, and accordingly the film thickness of the primer coating film may preferably be 5 }4,m or more. From the viewpoint of securing the stable formability, adhesion, reflective characteristic and coating performance, the more preferred film thickness of the primer coating film may be 10 lam or more and 25 fim or less. [0132] (Substrate material (Metal material)) For the metal material used as a substrate material in this embodiment of the present invention, a generally known metal material may be used. The metal material may also be an alloy material. For example, steel sheet, stainless steel sheet, aluminum sheet, aluminum alloy sheet, titanium sheet, copper sheet, etc., may be mentioned. These materials may be plated on their surfaces. As the types of plating, galvanization, aluminum plating, copper plating, nickel plating, etc., may be mentioned. Alloy plating is also possible. In the case of steel sheet, hot dip galvanized steel sheet, electrolytic galvanized steel sheet, zinc-nickel alloy plated steel sheet, hot dip galvannealed steel sheet, aluminum plated steel sheet, aluminum-zinc alloy plated steel sheet, and other generally known steel sheet and plated steel sheet may be used. [0133] If the surface of the metal material to be used in this embodiment of the present invention is treated by a chemical conversion treatment, the adhesion between the metal material and the coating film may be improved, so this is more preferable. As the chemical conversion - 60 - treatment, it is possible to use any of generally known chemical conversion treatment. Specific examples thereof may include: zinc phosphate treatment, chromate-free treatment, coated chromate treatment, electrolytic chromate treatment, reaction chromate treatment, etc. Among these, the applied chromate treatment, the electro chromate treatment and the reactive chromate treatment include the use of hexavalent chromium, which is a burden on the environment, and accordingly may not be favorable. In addition, the zinc phosphate conversion treatment may provide a poorer process adhesion, as compared to other treatments. Accordingly, as the chemical conversion treatment according to this embodiment of the present invention, a chromate-free treatment may be preferred. [0134] The chromate-free conversion treatment may include one using an inorganic chemical conversion agent and one using an organic chemical conversion agent, either of which may be used. More specifically, as the chromate-free conversion treatment, there is known a treatment by an aqueous solution containing silane coupling agent, zirconium compound, titanium compound, tannin or tannic acid, resin, and silica, etc. It is also possible to use any of known techniques as described in JP-A No. 53-9238, JP-A No, 9-241576, JP-A No. 2001-89868, JP-A No. 2001-316845, JP-A No. 2002-60959, JP-A No. 2002-38280, JP-A No. 2002-266081, JP-A No. 2003-253464, etc. For such a treatment, a commercially available treatment agent, for example, the chromate treatment agent "ZM-1300AN" mfd. by Nihon Perkerizing Co., Ltd., the chromate-free treatment gent "CT-E300N" mfd. by Nihon Perkerizing Co., Ltd., the trivalent chrome-based treatment agent "Surfcoat (registered trade mark) NRCIOOO" mfd. by Nippon Paint, etc., may be used. [0134] (Regarding Post-Coated Metal Material) In the above explanation, the present invention has - 61 - mainly been explained based on the example of application to a precoated metal material, but the present invention is not limited to a precoated metal material and may also be applied to a post-coated metal material. In the case of a post-coated metal material, unlike the precoated metal material, the formability, adhesion, etc., are not necessarily required, but when used as a reflector, a high total luminous reflectance is required. [0135] In the case of a post-coated metal material, by adding low refractive index particles having a larger particle size than rutile titanium oxide in the high-density pigment film, if the solid content concentration of the low refractive index particles is high, the Ra of the interface between the high-density pigment film and the upper coating film can be made 0.8 |Jin or more. Alternatively, by forming a high-density pigment film on a processed metal material, then physically scratching the surface of the thus formed high-density pigment film, etc., to roughen the surface to an Ra of 0.8 )am or more, and then applying thereon an upper coating film, it is possible to make the Ra of the interface between the high-density pigment film and the upper coating film 0.8 |j,m or more. [0137] In the foregoing, the constitution of a coated metal material according to this embodiment of the present invention has been explained in detail. Next, a process for producing a coated metal material having the constitution as described above will be explained in detail. [0138] The process for producing a coated metal material according to this embodiment of the present invention is a process in which at least two coating films comprising - 62 - a high-density pigment film containing rutile titanium oxide in a solid volume concentration of 35% or more and 70% or less, and an upper coating film disposed on the surface side of the high-density pigment film are formed so that the centerline average roughness Ra of the interface between the high-density pigment film and the upper coating film becomes 0.8 [xm or more. The process for producing the coated metal material according to this embodiment of the present invention will be explained in detail below for a case in which the coated metal material is a precoated metal material and a case in which the coated metal material is a post-coated metal material, separately. [0139] [In the case of a precoated metal material] First, the process for producing a coated metal material according to this embodiment of the present invention will be explained for the case in which the coated metal material is a precoated metal material. The coated metal material according to this embodiment of the present invention may be produced in a common continuous coating line (referred to as "CCL") or a cut sheet coating line by selecting a necessary treatment as desired, and carrying out the selected treatment. A representative production process of the coating line may comprise "washing" —> "drying" -^ "chemical conversion" ^• "drying" —>• "coating" —> "drying/baking" —>■ "cooling" -^ "drying". However, the production process of a coated metal material according to this embodiment of the present invention is not limited to such a process. [0140] A coated metal material according to this embodiment of the present invention may also be produced by repeating coating and drying/baking for each coating film as may be usually carried out, but it may be preferred in terms of performance and productivity to produce the - 63 - material by coating a coating material for forming the high-density pigment film and a coating material for forming the upper coating film on a portion or the entirety of the surface of a metal material by using the multilayer simultaneous coating or the wet-on-wet method. Similarly, when a coated metal material according to this embodiment of the present invention has a further outermost coating film (for example, a coating film having the above-mentioned silicone resin or a fluorine resin) on an surface side of the upper coating film, it may be preferred to coat a coating material for forming the high-density pigment film, a coating material for forming the upper coating film and a coating material for forming the outermost coating film on the surface of a metal material by using the multilayer simultaneous coating or the wet-on-wet method. [0141] When the metal material according to this embodiment of the present invention is a zinc-based plated steel sheet, it may be produced by a plating step in a continuous electro-galvanized steel sheet facility or a continuous hot-dip galvanized steel sheet facility followed by producing in a wet-on-wet method facility or a simultaneous multilayer coating facility, and in this process, coating may be effected before an oxide film is formed on the surface of the plated metal. By so doing, a defective cissing appearance of the oxide film can be prevented. [0142] As used herein, the multilayer simultaneous coating is a method in which a plurality of coating liquids are applied simultaneously to the substrate at a laminated state by using an instrument which can discharge different coating materials from two or more parallel slits of a slot die coater or a slide hopper curtain coater or the like, so as to provide a laminated state, and the laminated coating liquids are simultaneously - 64 - dried and baked. [0143] In addition, the wet-on-wet method is a method in which after applying once a coating liquid onto the substrate and while the solution is still wet before drying, another coating liquid is further applied thereon, and the laminated multilayer coating liquids are simultaneously dried and baked. More specifically, after one coating film may be coated by using, as the wet-on-wet method, a coating method such as a roll coater, dipping, a curtain flow coater, a roller curtain coater, etc., and before drying and baking the coating film, further thereon, a second coating may be applied by a method that permits coating without contacting the substrate such as a curtain flow coater, a roller curtain coater, a slide hopper curtain coater, a slot die coater, etc., and then the multilayer coating film at the wet laminated form may be simultaneously dried and baked. [0144] In this embodiment of the present invention, as a method of simultaneously baking a coating film that has been coated by the multilayer simultaneous coating or the wet-on-wet method, there can be used a publicly known baking furnace for coating material, such as a hot-air drying furnace, a direct heating furnace, an induction heating furnace, an infrared heating furnace, or a combination thereof. [0145] Thus, in the simultaneous application by laminating an undried coating liquid, the coating liquid of each layer can slightly mix with each other at the boundary portion of the coating liquids so that a mixed layer in which the components of each layer are mixed can be formed, whereby the adhesion between the layers can be enhanced. In this method, the drying step which conventionally has been carried out layer by layer can be conducted at one time, and accordingly it is advantageous - 65 - in terms of productivity and production costs, and it also has a merit in that only a few drying facilities may be needed. [0146] [In the case of post-coated metal material] Next, a process for producing a coated metal material according to this embodiment of the present invention will be explained for the case in which the coated metal material is a post-coated metal material. [0147] A coated metal material produced by post-coating according to this embodiment of the present invention can be produced in a method in which a metal material, after subjected to chemical conversion as described above, may be formed into a shape of an illuminator reflective plate, a reflective plate for illuminating components, a reflective plate for image display components, or the like, and then coated by post coating. A method used for forming a metal material may be any of known methods. As the post-coating method, there can be used a known method such as spray coating, immersion coating, coating with a curtain flow coater, brush coating and electrostatic coating. In the case of a post-coated metal material as well, wet-on-wet method by spray coating, for example, may be carried out. [0148] (Summary) In electronic appliances that employ a coated metal material according to this embodiment of the present invention as described above, this coated metal material has both of excellent total luminous reflectance and excellent formability, and accordingly an enhanced brightness can be obtained with the same light source, and it is possible to secure equivalent brightness as that in the prior art, even by reducing the number of light sources or the input electric power. Further, since a coated metal material according to this - 66 - embodiment of the present invention has a characteristic that it can be easily formed into a variety of shapes or into more comiplicated shapes, the effect of expanding applicable electronic appliance targets and of enhancing productivity of applicable components can be expected. [0149] Electronic appliances which can make use of such a characteristic may include, but not limited to: an illuminator reflective plate, a reflective plate for illuminating components, a reflective plate for image display components, and the like. More specific examples thereof may include: an illuminator, illumination, audiovisual equipment, mobile devices, various displays, and the like, and they may preferably be used in illuminator reflective plates, reflective plates in electrically decorated panels, backlight reflective plate in liquid crystal displays, and the like. EXAMPLES [0150] The present invention will now be explained with reference to examples, but it should be noted that the present invention is not limited to them in any way. [0151] [Coating material] First, the coating materials used in the present examples are explained in detail. In the present examples, as a coated metal material, a precoated steel sheet in which a coating film having a 3-layered structure comprising a primer coating film, a high-density pigment film (middle coating film) and an upper coating film, or a 4-layered structure comprising a primer coating film, a middle coating film and two upper coating films were coated in this order from the steel sheet side on a the surface of a galvanized steel sheet which was a substrate. Below, a coating material for the primer coating film (referred to as "primer coating - 67 - material"), a coating material for the high-density pigment film (middle coating film) (referred to as "middle coating material") and a coating material for the upper coating film (referred to as "upper coating material") are explained in this order for the coating material components used. [0152] (Primer coating material) For the primer coating material, as shown in the following Table 1, "Vylon (registered trademark) 630" (number-average molecular weight: 23000, hydroxyl value: 5), an amorphous polyester resin mfd. by TOYOBO Co., Ltd., was used as the binder, and "Tipaque (registered trademark) CR95" (refractive index: 2.5), rutile titanium oxide having an average particle size of 280 nm mfd. by Ishihara Sangyo Kaisha Ltd., was used as the pigment, and rutile titanium oxide was mixed with the binder so as to provide a solid volume concentration of rutile titanium oxide of 25%, to thereby prepare a primer coating material (primer coating-1). [0153] Table 1 Binder Pigment Kind of Average ^ , . , , ^. , Solid volume Coating ^,. ^ „ ^,. _, particle . , Kind Tar°C Kind • concentration material ^^ •' size ( "6 } im) Primer Vylon Titanium Tipaque _ coating -1 630 oxide CR95 [0154] (Middle coating material) As the middle coating material, as shown in Table 2, "Vylon (registered trademark)" series, an amorphous polyester resin mfd. by TOYOBO Co., Ltd., and "Desmophen (registered trademark)" series, an amorphous polyurethane resin mfd. by Sumika Bayer Urethane Co., Ltd., were used as the base resin. For example, in the middle coating-1 to 20, "Vylon (registered trademark)" (number- - 68 - average molecular weight: 23000, hydroxyl value: 5) and "Desmophen (registered trademark)" (number-average molecular weight: 3500, hydroxyl value: 46), an amorphous polyurethane resin mfd. by Sumika Bayer Urethane Co., Ltd., were dissolved in an organic solvent (1:1 mixture of Solvesso 150 and cyclohexanone) at a mass ratio of 1:1. As a crosslinking agent, "Cymel (registered trademark) 303", a commercially available hexa-methoxy-methylated melamine mfd. by Mitsui Cytec Ltd., was added at 15 parts by mass with respect to 100 parts by mass of solid content of the polyester resin, and further 0.5 part by mass "Catalyst (registered trademark) 6003B", a commercially available acid catalyst mfd. by Mitsui Cytec Ltd., was added thereto, to thereby obtain a polyester-based clear coating material. [0155] As rutile titanium oxide, "Tipaque (registered trademark) CR95" (refractive index: 2.5), rutile titanium oxide having an average particle size of 280 nm mfd. by Ishihara Sangyo Kaisha Ltd., was used. [0156] As the low-refractive index particles to be contained in the middle coating film, "Sunsphere (registered trademark) H-31" (average particle size: 3 ^m), silica mfd. by Asahi Glass Co., Ltd., was used. [0157] Further, as a comparative material of a pigment to be contained in the middle coating film, "BARIACE (registered trademark) B-30" (refractive index: 1.6), barium sulfate having an average particle size of 300 nm mfd. by Sakai Chemical Industry Co., Ltd., and "Fine zinc oxide" (refractive index: 2.0), zinc oxide having an average particle size of 290 nm mfd. by Sakai Chemical Industry Co., Ltd., were used. [0158] Further, the viscosity of the coating material at a low shear of the middle coating material was adjusted by - 69 - changing the amount of solvent, the storage temperature and storage period for the coating material. The viscosity at a low shear was measured by using a type-B viscometer (model: B-8L) mfd. by Tokyo Keiki Co., Ltd. at a number of revolutions of 6 rpm. [0159] The details of the middle coating materials prepared are shown in the following Table 2. [0160] - 70 - 'TI n "^ OOOOOOOO O OOOOOOoOO„„ O OOOOO O OO O OOOOOOOOO r\ \7 ITI OOOOOOOO O OOOOOOOOOiX^ O OOOOO O OO O OOOOOOOOO filoA OOOOOOOO O OOOOOOOOO,7; )X O OOoOO O 00 O OOOOOOOOO UjOg 'J'-^'a-'^T-^'^'^ ^ ■ H -H>i ^_,^^^^_,^ . ^^^^_j^n'^r-Om O OOoOO O OO O OOOOOOOOO J, MiO n-<.-i.-ir-i.-ir-i.-ir-( .-( l-l^-^'-^^-^.-^T-^u)^^^~|^^^ jv^ p-jp^i^j^i^ j^ (v^p^ P-, rnror^mmrocnrorn "■a ^ " 0 f" u ^ 1 Su OOOOOOOO O 00000000000 O OOoOO O 00 O OOOOOOOOO "^ oJ?— CNCSjr-]CNJCM(Njr\J(N (N (Nr>JC\JCs)CNjrsJCsliDcu(DiD m JOJ(NJ cDci):x't-i 13 xxxxxxxxxxx x; xxxxx x xx x xxxxxxx? -U -P-t-) 4-J JJ^J-U-P-l-J-l-IJ-J-P-P H^H^HH^m HF'tHP'^HHE-iHE-'H ^ H £-■ F^ H H H E-- ^ H E-'HHtHF-'^HE-'H CQ r-I.H.-l.-H^rH^,-| ^ rH.HrH.-H^^^.-l.-HrHf-l O OOOOO ^ >H.-H ^ •H^rH^fOCNt^r-'a* '^ Ol O^p* l£)VDVDi,DkDli)'^l£) IX) SiJiXii£)VCi',Dii)kDl£liX)VOl£> '^ ^O O rHOCri'X)>0'.0^U3'^ -_— . I* m '^ ,,00000000000000000000 OOOO OOOOOOOOO f i^r^t^ OOOOOOOO O OOOOOOOOOOO , . , , , , O OO O OOOOOOOOO n, m'r^'^'^Ln'^''^"^'^^ ^ mmminunLnmLDmmu-) ' ' ' ' ' ' m oo LD oooinminmLnm 2- (0 o OJ g_^ OOOOOOOOOOOOOOOOOOOO rH OOOOOO ^7^ali) 1^ OJ CO ^ dGCGCGGGCGCGdGGCGCGG j::indtNJX:cN^:;!N:^CdGdi::G M ajajQ)fUQ)(U(Da) tu ajuudjajaiaJOJciiiiiai Q. r~- o) p. i^ C) oa'a>a)0a)(i! .^ jd^j::^x:j:;j:::j::x:x:x:j:;£:4:^^x:4:^x:i^x:t or-xiGoiN G ^jii^xij:;^; ,a)HM>^eE£EeE -H (Uii)ajQja)a)a)aja)a)(u QJ > >ai CD ^B-^^^^~^ Q ^^^^^_Q_Q Q '^^Q .5 Q Q Q Q _Q Q ">, t^ S 3 Di ^ > O ;E ^ TTc ' ' ^ TJC.-I OOOOOOOO O OOOOOOOOOOO O OOOOO O OO O OOOOOOOOO f rtJui+j OOOOOOOO o oooooooioocDo o ooooo o oo o ooooooooo i-(U^ oooooocDo o OOOOOOOOOOO o cDoooc) o CIO CD ooooooooo ajQjCnrnnmrot^mnro ro rnmrnr^cnrocncncnmm r- a\ o en as o o oo o ooooooooo ^>^-H {NjrMoJCMtNfMCNjfsj CM cM(Mcsj(M(Njr-i(Nf\JCN)CNJCN >^ ^CNjcNOjm ro mro m nrot^nrororoo^ro '^ (0 O 01 E_3 ^^_ OOOOOOOO O OOOOOOOOOOO OOOOy^ '^ •^ KD l£> VDlO'X)'X)W3tD—I'-H'H.-HI—II-H"-) T_, ^o^Diii>i3tD\o>i)\o li) uj^i^ickDViiki^ixitDVDiDUJGoLniiJkDinLn in LDuo in iriiOLninininLnmin ri O m ■H SSSSSSgC d GCdCGCGCGdG--ifOdGCGd d Gd G GGCGdGdCd v; OOOOOOOO O OOOOOOOOOOO > t£; OOOOO O OO O OOOOOOOOO >>>>>>>> > >>^>>>>>>>> >>>>> > >> > t->>>>>>>> Cn ■-HtNjm^j'in'iJr-co en o^(\jfO'TLr)ix>r-coaio ^H o-i m •=!• m "^ r~ COCTI O rMCNro^rm'^r-coa) c; I I I I J I I I I >HrH.-H,H^r-i.-HtH^>HCN] c^j CMtNjtNjcvjCNj CM CNjc-j (^ ^o^o^om^onc^mr) •0';^ -a.H.!H-H.lH.!^-H.r, -H GGGGGGGGGGG C GdGdG C dG d GdGdGdGdG '^ Url m(o1o^ttrafaro 1o ■lj4-'-t->4-iJ-l4Jj-l+J-t-'-l->-P -U 4-l-t-)4->-l-IJJ -U -MJ-I -t-> 4J4-I4-JJ-'4-J-I-I-P-4-J4J nl '4H,'^ UUUUOUUU U OOOOOOOOOOO O ooooo O oo O OOOOOOOOO ^ otj QjajQjajaJajajm OJ UUUUUUUUUUU U UUUUU U UU U UOOUUOUUU 1—i 2 ^^^^^^,_,^^ (iia)iDa)O(i}iva) XlX3T)X)X3X)XiX)Xl H 1 ^ I s I s I s I a I s I s I a I s I g: | g [ g | g | E | "is | s | s | K ] s | a 1 s | "g 1 s l ^ | s j a | s | a | s | s | s | ":s | s 1^ | a | is j s | s | s | is - 71 - [0161] (Upper coating material) As the upper coating material, as shown in the following Table 3, "Vylon (registered trademark) 630" (number-average molecular weight: 23000, hydroxyl value: 5), an amorphous polyester resin mfd. by Toyobo Co., Ltd., was dissolved in an organic solvent (1:1 mixture of Solvesso 150 and cyclohexanone). As the crosslinking agent, "Cymel (registered trademark) 303", a commercially available complete alkyl-type methylated melamine resin (hereinafter referred to as methylated melamine) mfd. by Mitsui Cytec Ltd., was added at 15 parts by mass with respect to 100 parts by mass of solid of the polyester resin, and further 0.5 part by mass of "Catalyst (registered trademark) 6003B", a commercially available acid catalyst mfd. by Mitsui Cytec Ltd., was added thereto obtain a clear coating material. Using this clear coating material, "Tipaque (registered trademark) CR95" (refractive index: 2.5), rutile titanium oxide having an average particle size of 280 nm mfd. by Ishihara Sangyo Kaisha Ltd., was used as the pigment, and rutile titanium oxide was mixed with the binder so as to provide a solid volume concentration of rutile titanium oxide of 25%, to thereby prepare an upper coating material (upper coating-1). [0162] Using a binder resin same with the above upper coating-1 and a pigment, a coating material (upper coating-2) in which one part by mass of BYK-306, a silicone-based additive of BYK Japan KK, was added and a coating material (upper coating-3) in which 0.5 part by mass of BYK-340, a fluorine-based additive of BYK Japan KK, was added, with respect to 100 parts by mass of the total amount of the binder resin and the pigment, were prepared. [0163] As the base resin for a binder, a commercially - 72 - available silicone acrylic copolymer resin "Cymac (registered trademark) US-380", a silicone-denatured acrylic resin mfd. by Toa Gosei Co., Ltd., was used, and as the crosslinking agent, "Supperbeccamine (registered trademark) J830", a butylated melamine resin mfd. by Dainippon Ink Co., Ltd., and "Cymel (registered trademark) 303", methylated melamine mfd. by Mitsui Cytec Ltd., were mixed at a mass ratio of 1:1. These binder resins and the crosslinking agent were mixed at a solid mass ratio of 100:30 to obtain a clear coating material (upper coating-4). Further, using this clear coating material, in a similar manner upper coating-1, "Tipaque (registered trademark) CR95" mfd. by Ishihara Sangyo Kaisha Ltd. was used as the pigment, and rutile titanium oxide was mixed with the binder to a solid volume concentration of rutile titanium oxide of 25%, to thereby prepare an upper coating material (upper coating-5). [0164] Except that "Desmodur BL3175 (registered trademark)" (hereinafter referred to as HDI) mfd. by Sumika Bayer Urethane Co., Ltd. was used as the crosslinking agent, coating materials (upper coating-6,7) were also prepared in a manner similar to that for upper coating-4,5. [0165] Except that "ZX-001", a silicone/fluorine copolymer resin mfd. by Fuji Chemical Industry Co., Ltd., was used as the base resin of the binder, coating materials (upper coating-8,9) were also prepared in a manner similar to that for upper coating-4,5. [0166] Using a binder resin and a pigment in the same manner as in the above upper coating-1, a coating material (upper coating-10) was also prepared in which 20 parts by mass of tetraethoxysilane was added to 100 parts by mass of the total amount of the binder resin and the pigment. [0167] - 73 - In the above upper coating-1 to 10, a 1:1 mixture of cyclohexanone and Sorbesso 150 in terms of mass ratio was used as the dilution solvent. 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