Painted metal sheet and method for manufacturing a painted metal sheet

Abstract

To provide a painted metal sheet in which the possibility of the synthetic resin layer being destroyed by a photocatalytic reaction is further reduced. [Solution] The painted metal plate 30 comprises a metal base 40, a synthetic resin layer 44, a protective layer 46, and a photocatalytic reaction layer 48. The synthetic resin layer 44 is formed on any surface of the metal base 40. The protective layer 46 is formed on the surface of the synthetic resin layer 44. The photocatalytic reaction layer 48 contains a photocatalytic material. The photocatalytic reaction layer 48 is formed on the surface of the protective layer 46. The protective layer 46 contains at least one of silicon dioxide and silicon dioxide hydrate. The concentration of a component in the protective layer 46 that is different from both silicon dioxide and silicon dioxide hydrate is 150 PPM or less.

Description

[Technical Field]

[0001] This invention relates to painted metal sheets and methods for manufacturing painted metal sheets. [Background technology]

[0002] Photocatalytic materials have recently attracted attention as inorganic antibacterial and antifungal agents. Practical applications of photocatalytic materials are progressing in areas such as cleaning, deodorizing, and antibacterial action on painted steel surfaces. Photocatalytic reactions are caused by excited electrons and holes. These excited electrons and holes are generated when photocatalytic metal compounds, such as titanium dioxide, absorb light. The specific antibacterial action in photocatalytic reactions is thought to be as follows: Excited electrons and holes undergo oxidation-reduction reactions with oxygen and water adsorbed on the surface of the photocatalytic metal compound. The reactive species generated by this oxidation-reduction reaction cause damage to the cell membranes of microorganisms. Microorganisms with damaged cell membranes die. The reactive species continue to act for a longer period, eventually leading to the decomposition of the microorganisms. This completes the antibacterial action described above. Because antibacterial action is produced in this way, photocatalytic materials can exert their effects against a wide variety of microorganisms, including mold. The possibility of resistant bacteria developing that can withstand the antibacterial action of photocatalytic materials is low. Furthermore, photocatalytic materials exhibit almost no degradation over time. These are the strengths of photocatalytic materials.

[0003] Patent Document 1 discloses a photocatalytic coating solution. The photocatalytic coating solution disclosed in Patent Document 1 contains dispersed photocatalytic particles. The photocatalytic coating solution disclosed in Patent Document 1 contains 0.01 to 100% by mass of water-soluble cage-type silsesquioxane relative to the photocatalytic solid content. The photocatalytic coating solution disclosed in Patent Document 1 maintains its hydrophilicity even in the dark. The photocatalytic coating solution disclosed in Patent Document 1 does not experience a decrease in self-cleaning properties.

[0004] However, the photocatalytic reaction is caused by irradiation with ultraviolet light (wavelength 10 to 400 nanometers) or visible light (wavelength 400 to 800 nanometers). Therefore, simply coating the surface of a painted steel sheet with a paint containing a photocatalytic material will cause the synthetic resin layer on the surface of the painted steel sheet to be destroyed by the photocatalytic reaction caused by natural light or artificial light irradiation.

[0005] Patent Document 2 discloses a painted steel sheet that solves the problem of "the synthetic resin layer on the surface of the painted steel sheet being destroyed by the photocatalytic reaction". The painted steel sheet disclosed in Patent Document 2 has a zinc-based plated steel sheet, a chemical conversion coating formed on at least one side thereof, and a synthetic resin coating formed thereon. In this painted steel sheet, the synthetic resin coating consists of a primer layer (A), a synthetic resin layer (B), a clear coating layer (C), and a clear coating layer (D). The primer layer is made of a thermosetting resin containing a rust preventive pigment. The clear coating layer (C) contains a silicon compound as a main component. The film thickness of the clear coating layer (C) is 0.2 micrometers or more. The clear coating layer (D) contains titanium oxide particles. The titanium oxide particles have photocatalytic activity. The adhesion amount per side of the clear coating layer (D) is 10 milligrams to 2000 milligrams per square meter in terms of titanium dioxide.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, the invention disclosed in Patent Document 2 has a problem that the reduction of the possibility of the synthetic resin layer being destroyed by the photocatalytic reaction is still insufficient.

[0008] The present invention solves the above-described problems. Its object is to provide a coated metal plate in which the possibility that the synthetic resin layer is destroyed by a photocatalytic reaction is further reduced.

Means for Solving the Problems

[0009] The coated metal plate and the method for manufacturing the coated metal plate of the present invention will be described with reference to the drawings. The reference numerals in the drawings are used in this section to assist in understanding the content of the invention, and are not intended to limit the content to the illustrated scope.

[0010] In order to solve the above-described problems, according to an aspect of the present invention, the coated metal plate 30 includes a metal base 40, a synthetic resin layer 44, a protective layer 46, and a photocatalytic reaction layer 48. The synthetic resin layer 44 is formed on one of the surfaces of the metal base 40. The protective layer 46 is formed on the surface of the synthetic resin layer 44. The photocatalytic reaction layer 48 contains a photocatalytic material. The photocatalytic reaction layer 48 is formed on the surface of the protective layer 46. The protective layer 46 contains at least one of silicon dioxide and a hydrate of silicon dioxide. The concentration of components different from both silicon dioxide and the hydrate of silicon dioxide in the protective layer 46 is 150 PPM or less.

[0011] When the concentration of components different from both silicon dioxide and the hydrate of silicon dioxide in the protective layer 46 is 150 PPM or less, even if an organic substance is contained in the protective layer 46, the influence of the destruction of the organic substance by the photocatalytic reaction can be greatly suppressed. Since the influence is greatly suppressed, the possibility that the function of the protective layer 46 deteriorates due to the influence is significantly reduced. Since the possibility that the function of the protective layer 46 deteriorates is significantly reduced, the possibility that the synthetic resin layer 44 is destroyed by the photocatalytic reaction is significantly reduced. As a result, a coated metal plate in which the possibility that the synthetic resin layer is destroyed by the photocatalytic reaction is further reduced is provided.

[0012] Furthermore, it is desirable that the recessed water contact angle of the portion of the synthetic resin layer 44 that is in direct contact with the protective layer 46 be less than 40 degrees. When the recessed water contact angle at that portion is less than 40 degrees, the water containing silicon dioxide and silicon dioxide hydrate (protective layer forming liquid) spreads more easily across the surface of the synthetic resin layer 44. This makes it easier to apply the protective layer forming liquid to the surface of the synthetic resin layer 44. As a result, the formation of the protective layer 46 becomes easier.

[0013] Furthermore, it is desirable that the arithmetic mean roughness of the portion of the synthetic resin layer 44 that is in direct contact with the protective layer 46 be between 1.00 micrometers and 10.00 micrometers. In this case, it is desirable that the ten-point average roughness of the portion of the synthetic resin layer 44 that is in direct contact with the protective layer 46 be between 10.00 micrometers and 60.00 micrometers. When these requirements are met, the possibility of the painted metal plate 30 exhibiting a rainbow pattern is suppressed.

[0014] Furthermore, it is desirable that the material of the metal base 40 described above be one of the following: steel with zinc plating on the surface, steel with zinc-aluminum alloy plating on the surface, steel with zinc-aluminum-magnesium alloy plating on the surface, steel with aluminum plating on the surface, steel with zinc-nickel alloy plating on the surface, steel with zinc-iron alloy plating on the surface, aluminum alloy, or stainless steel.

[0015] According to another aspect of the present invention, a method for manufacturing a painted metal plate 30 comprises a protective layer forming liquid coating step S504, a protective layer forming liquid drying step S506, a photocatalytic reaction layer forming liquid coating step S508, and a photocatalytic reaction layer forming liquid drying step S510. In the protective layer forming liquid coating step S504, a protective layer forming liquid containing at least one of silicon dioxide and silicon dioxide hydrate and water is coated onto the surface of a synthetic resin layer 44 formed on the surface of a metal base 40. In the protective layer forming liquid drying step S506, the protective layer forming liquid coated onto the surface of the synthetic resin layer 44 is dried. In the photocatalytic reaction layer forming liquid coating step S508, a photocatalytic reaction layer forming liquid containing a photocatalytic material is coated onto the surface of a protective layer 46 formed by the drying of the protective layer forming liquid. In the photocatalytic reaction layer forming liquid drying step S510, the photocatalytic reaction layer forming liquid coated onto the surface of the protective layer 46 is dried. The proportion of the component that is neither silicon dioxide, silicon dioxide hydrate, nor water in the total of the components of the protective layer forming liquid, which are either silicon dioxide or silicon dioxide hydrate, and the component that is neither silicon dioxide, silicon dioxide hydrate, nor water, is 150 PPM or less. [Effects of the Invention]

[0016] According to the present invention, a painted metal sheet and a method for manufacturing a painted metal sheet are provided in which the possibility of the synthetic resin layer being destroyed by a photocatalytic reaction is further reduced. [Brief explanation of the drawing]

[0017] [Figure 1] This is a partial cross-sectional view of a painted metal plate according to one embodiment of the present invention. [Figure 2] This is a flowchart illustrating a method for manufacturing a painted metal sheet according to one embodiment of the present invention. [Figure 3] This figure shows the manufacturing conditions for a painted metal sheet according to one embodiment and a comparative example of the present invention. [Figure 4] This figure shows test results relating to painted metal sheets according to certain embodiments and comparative examples of the present invention. [Figure 5]This figure shows the surface of a painted metal plate according to Embodiment 1 of the present invention. [Figure 6] This figure shows the photodegradation effect on a painted metal plate immediately after completion according to one embodiment and a comparative example of the present invention. [Figure 7] This figure shows the photodegradation effect on a painted metal plate immediately after a cyclic corrosion test according to one embodiment of the present invention. [Figure 8] This figure shows the photodegradation effect on a painted metal plate immediately after a weathering test according to one embodiment and a comparative example of the present invention. [Figure 9] This figure shows the surface of a painted metal plate immediately after an exposure test according to one embodiment and a comparative example of the present invention. [Figure 10] This figure shows the surface of a painted metal plate according to Embodiment 4 of the present invention. [Modes for carrying out the invention]

[0018] Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are the same. Therefore, detailed descriptions of them will not be repeated.

[0019] <Composition of painted metal sheet> Figure 1 is a partial cross-sectional view of the painted metal plate 30 according to this embodiment. The configuration of the painted metal plate 30 according to this embodiment will be explained based on Figure 1.

[0020] As is clear from Figure 1, the painted metal plate 30 according to this embodiment comprises a metal base 40, a primer layer 42, a synthetic resin layer 44, a protective layer 46, and a photocatalytic reaction layer 48.

[0021] The metal base 40 serves as the base of the painted metal plate 30 according to this embodiment. The metal base 40 according to this embodiment can be a metal plate. Examples of materials for such a plate include steel with a zinc-aluminum alloy plating on its surface, steel with a zinc plating on its surface, steel with a zinc-aluminum-magnesium alloy plating on its surface, steel with an aluminum plating on its surface, steel with a zinc-nickel alloy plating on its surface, steel with a zinc-iron alloy plating on its surface, aluminum alloy, and stainless steel. Among these materials, steel may be subjected to a well-known chemical conversion treatment on at least one of its front or back surfaces.

[0022] The primer layer 42 is formed on the surface of the metal base 40. The primer layer 42 in this embodiment is formed by the drying of a well-known primer coating. Needless to say, the specific composition of the primer layer 42 in the painted metal plate 30 according to this embodiment is not particularly limited. The primer layer 42 is not a layer that must be provided in the painted metal plate 30 according to this embodiment.

[0023] In this embodiment, the synthetic resin layer 44 is formed on the surface of the primer layer 42. It goes without saying that the synthetic resin layer 44 may also be formed directly on the surface of the metal base 40. In this embodiment, the synthetic resin layer 44 is formed by the drying of a paint mainly composed of synthetic resin. However, the specific means for forming the synthetic resin layer 44 in this embodiment are not limited thereto.

[0024] In the painted metal plate 30 according to this embodiment, the specific composition of the paint used to form the synthetic resin layer 44 is not particularly limited. Examples of such paints include polyester-based paints and acrylic-based paints. As a result, the surface of the synthetic resin layer 44 according to this embodiment can take on various forms. Examples of these forms include those with a well-known uneven surface called a "wrinkled pattern," those that are opaque and flat called a "solid type," and those that are matte and flat.

[0025] In addition, the color of the synthetic resin layer 44 according to this embodiment is not particularly limited. The synthetic resin layer 44 according to this embodiment may be transparent or opaque. Naturally, the synthetic resin layer 44 according to this embodiment may be colored and transparent.

[0026] In manufacturing the painted metal sheet 30 according to this embodiment, a material that satisfies the following requirements may be used. These requirements concern the roughness of the portion of the synthetic resin layer 44 that is in direct contact with the protective layer 46. These requirements are based on the arithmetic mean roughness R specified in Japanese Industrial Standard (hereinafter referred to as "JIS") B 0601 (2013). a The roughness is between 0.10 micrometers and 10.00 micrometers, with a ten-point average roughness R ZJIS The requirement is that it is between 1.00 micrometers and 60.00 micrometers. a R is between 1.00 micrometers and 10.00 micrometers. ZJIS It is more desirable that the thickness is between 10.00 micrometers and 60.00 micrometers. When a synthetic resin layer 44 satisfying these requirements is used in the manufacture of the painted metal plate 30 according to this embodiment, the possibility of the painted metal plate 30 exhibiting a rainbow pattern due to light interference is reduced. a R is between 2.60 micrometers and 8.80 micrometers. ZJISIt is even more desirable that the thickness is between 15.70 micrometers and 31.10 micrometers. When a synthetic resin layer 44 satisfying these requirements is used in the manufacture of the painted metal plate 30 according to this embodiment, the possibility of the painted metal plate 30 exhibiting a rainbow pattern due to light interference is further reduced. An example of a specific procedure for forming a synthetic resin layer 44 satisfying these requirements is that a well-known commercially available paint that forms a wrinkled pattern is applied to the surface of the metal base 40, and then the paint is dried using a well-known procedure suitable for that paint. The selection of such paint and the specific procedure for drying such paint are well-known. Therefore, a detailed explanation will not be repeated here. Alternatively, instead of a metal base 40 in which a primer layer 42 is formed on the surface and a synthetic resin layer 44 is formed on the surface of the primer layer 42, a well-known painted metal plate with a similar configuration may be used.

[0027] Furthermore, in this embodiment, the synthetic resin layer 44 may be subjected to known surface modification such as corona discharge. However, the inventors have found that when the synthetic resin layer 44 satisfies the following requirements, it becomes easy to apply the protective layer forming liquid described later to the surface of the synthetic resin layer 44 even without the application of known surface modification such as corona discharge. The requirement is that the receding water contact angle of the synthetic resin layer 44, measured by the shrinkage method, is less than 40 degrees (2π / 9 radians). It is more desirable that the subsequent receding water contact angle be 33 degrees (11π / 60 radians) or less. When these requirements are met, the protective layer forming liquid described later can be easily applied to the surface of the synthetic resin layer 44 even if it does not contain surfactants or alcohol. This makes it possible to apply the liquid using equipment such as a roll coater. As a result, large-scale equipment, such as that used when performing corona discharge, becomes unnecessary.

[0028] The protective layer 46 is formed on the surface of the synthetic resin layer 44. The protective layer 46 contains at least one of silicon dioxide and silicon dioxide hydrate. The inventors have found that by suppressing the concentration of organic substances such as surfactants and alcohols in the protective layer 46, the possibility of the synthetic resin layer 44 being destroyed by the photocatalytic reaction can also be suppressed. This is because the protective function of the protective layer 46 to protect the synthetic resin layer 44 is maintained for a long time. This function is maintained for a long time because the destruction of the protective layer 46 by the photocatalytic material contained in the photocatalytic reaction layer 48 is avoided. The destruction of the protective layer 46 is avoided because the concentration of organic substances that are targeted for destruction by the photocatalytic reaction of the photocatalytic material is suppressed. As far as the inventors have confirmed, when the concentration of components other than silicon dioxide and silicon dioxide hydrate in the protective layer 46 is 150 PPM or less, the destruction of the protective layer 46 by the photocatalytic material contained in the photocatalytic reaction layer 48 is sufficiently avoided. In the following description, components that are different from both silicon dioxide and silicon dioxide hydrate in the protective layer 46, and components that are different from both silicon dioxide, silicon dioxide hydrate, and water in the protective layer forming solution, are referred to as "non-silicon dioxide components." It goes without saying that it is desirable for these non-silicon dioxide components to be so-called unavoidable impurities. In this invention, unavoidable impurities refer to substances that are inevitably mixed into the painted metal plate 30 during the manufacturing process of this embodiment. Substances that are inevitably mixed into the protective layer 46 during its formation are naturally unavoidable impurities. One example of a cause of contamination is contamination as an impurity in the protective layer forming solution. It should be noted that the inventor's confirmation results described above do not mean that the protective layer 46 will immediately become easily destroyed when the concentration of non-silicon dioxide components in the protective layer 46 exceeds 150 PPM.

[0029] The amount of silicon dioxide per unit square meter in the protective layer 46 is not particularly limited. The amount of silicon dioxide hydrate per unit square meter in the protective layer 46 is also not particularly limited. For example, it may be 30 milligrams or more and 150 milligrams or less per unit square meter. The sum of the amount of silicon dioxide and the amount of the silicon dioxide hydrate excluding water molecules may be 30 milligrams or more and 150 milligrams or less per unit square meter of the protective layer 46. The amount of silicon dioxide per unit square meter in the protective layer 46 may be 50 milligrams or more and 100 milligrams or less per unit square meter. The sum of the amount of silicon dioxide and the amount of the silicon dioxide hydrate excluding water molecules may be 50 milligrams or more and 100 milligrams or less per unit square meter of the protective layer 46.

[0030] The photocatalytic reaction layer 48 is formed on the surface of the protective layer 46. The photocatalytic reaction layer 48 contains a well-known photocatalytic material. An example of a well-known photocatalytic material is titanium dioxide. Aside from this, the specific composition of the photocatalytic reaction layer 48 is not particularly limited.

[0031] <Method for manufacturing painted metal sheets> Figure 2 is a flowchart showing the manufacturing method of the painted metal sheet 30 according to this embodiment. The manufacturing method of the painted metal sheet 30 according to this embodiment will be explained based on Figure 2.

[0032] The method for manufacturing the painted metal plate 30 according to this embodiment comprises a synthetic resin-containing paint coating step S500, a synthetic resin-containing paint drying step S502, a protective layer forming liquid coating step S504, a protective layer forming liquid drying step S506, a photocatalytic reaction layer forming liquid coating step S508, and a photocatalytic reaction layer forming liquid drying step S510.

[0033] In the synthetic resin-containing paint application process S500, a topcoat paint is applied to the surface of the plate material that will become the metal base 40. In this embodiment, the plate material is a zinc-aluminum alloy plated steel sheet with a primer layer 42 formed on its surface. In this embodiment, the surface of the steel sheet is subjected to a well-known chemical conversion treatment. The primer layer 42 described above is obtained by applying a well-known undercoat paint to the surface of the chemically treated steel sheet and drying the undercoat paint under conditions appropriate to the undercoat paint. Of course, instead of a zinc-aluminum alloy plated steel sheet with a primer layer 42 formed on its surface, a steel sheet with zinc plating on its surface, a steel sheet with zinc-aluminum-magnesium alloy plating on its surface, a steel sheet with aluminum plating on its surface, a steel sheet with zinc-nickel alloy plating on its surface, a steel sheet with zinc-iron alloy plating on its surface, an aluminum alloy sheet, or a stainless steel sheet may be used.

[0034] In the synthetic resin-containing paint drying process S502, the topcoat paint applied on the primer layer 42 is dried. The topcoat paint, along with the metal base 40 and the primer layer 42, is dried by a drying device. Once the topcoat paint is dry, a synthetic resin layer 44 is formed on the surface of the primer layer 42.

[0035] In the protective layer forming liquid coating step S504, a protective layer forming liquid is applied onto the synthetic resin layer 44. This protective layer forming liquid is a liquid containing at least one of silicon dioxide and silicon dioxide hydrate and water. The proportion of the components of the protective layer forming liquid described below is 150 PPM or less. This proportion is the ratio of the non-silicon component to the total of the components that are either silicon dioxide or silicon dioxide hydrate and the non-silicon component.

[0036] In the protective layer forming liquid drying step S506, the protective layer forming liquid applied to the synthetic resin layer 44 is dried. The protective layer forming liquid, along with the metal base 40, primer layer 42, and synthetic resin layer 44, is dried together by a drying apparatus. Once the protective layer forming liquid is dry, a protective layer 46 is formed on the surface of the synthetic resin layer 44. The conditions for drying are not particularly limited, but for example, it is desirable that the temperature of the metal base 40 be 180 degrees Celsius (453.15 Kelvin) or lower. It is even more desirable that the temperature of the metal base 40 be between 100 degrees Celsius (373.15 Kelvin) and 160 degrees Celsius (433.15 Kelvin).

[0037] In the photocatalytic reaction layer forming solution coating step S508, the photocatalytic reaction layer forming solution is coated onto the protective layer 46. The photocatalytic reaction layer forming solution contains a photocatalytic material.

[0038] In the photocatalytic reaction layer forming liquid drying step S510, the photocatalytic reaction layer forming liquid applied on the protective layer 46 is dried. The photocatalytic reaction layer forming liquid, along with the metal base 40, primer layer 42, synthetic resin layer 44, and protective layer 46, is dried together in a drying apparatus. Once the photocatalytic reaction layer forming liquid is dry, a photocatalytic reaction layer 48 is formed on the surface of the protective layer 46. The drying conditions are not particularly limited, but it is desirable, for example, that the temperature of the metal base 40 be between 100 degrees Celsius (373.15 Kelvin) and 230 degrees Celsius (503.15 Kelvin).

[0039] <How to use painted metal sheets> The method of using the painted metal plate 30 according to this embodiment is the same as that known. Therefore, a detailed explanation will not be repeated.

[0040] <Description of the Examples> The following are examples of the present invention, but the present invention is not limited to the following examples.

[0041] (Preparation of the metal base) To prepare the metal base 40, the worker performed a well-known chemical conversion treatment on a zinc-aluminum alloy plated steel sheet. The thickness of the zinc-aluminum alloy plated steel sheet was 0.4 millimeters. The size of the zinc-aluminum alloy plated steel sheet was 210 mm x 297 mm. This size is equivalent to the "A4" size specified in JIS P 0138 (1998). Twenty-eight such zinc-aluminum alloy plated steel sheets were prepared (4 sheets / Example-Comparative Example x 7 Examples-Comparative Example = 28 sheets). There were no differences between these zinc-aluminum alloy plated steel sheets. These zinc-aluminum alloy plated steel sheets will become the metal base 40 in Examples 1 to 4 and Comparative Examples 1 to 3 below. That is, the metal base 40 in Examples 1 to 4 and Comparative Examples 1 to 3 below are exactly the same.

[0042] (Formation of primer layer) The worker applied a well-known primer to the surface of each of the 28 zinc-aluminum alloy plated steel sheets described above. The amount of primer applied was the same for all zinc-aluminum alloy plated steel sheets. After the primer was applied to the surface of the zinc-aluminum alloy plated steel sheets, the worker heated them. A well-known hot air drying oven was used for heating. The heating conditions were common and suitable for drying the primer. Through this heating, the zinc-aluminum alloy plated steel sheets became metal bases 40 with a primer layer 42 formed on their surface. As a result, 28 identical metal bases 40 with a primer layer 42 formed on their surface were obtained. That is, the primer layer 42 is also exactly the same in Examples 1 to 4 and Comparative Examples 1 to 3 below.

[0043] [Example 1] (Manufacturing conditions) The worker applied a topcoat paint to the surface of one of the 28 metal bases 40 described above, so as to completely cover its primer layer 42 (S500). This topcoat paint was a polyester-based paint. In Figure 3, the term "polyester" in the "coating film resin system" column of the "synthetic resin layer" column refers to this. Once the topcoat paint was applied, the worker heated the metal base 40 (S502). This heating formed a synthetic resin layer 44 on top of the primer layer 42 of the metal base 40. In this embodiment, the synthetic resin layer 44 had a wrinkled pattern. In Figure 3, the term "hydrophilic wrinkled coating film" in the "coating film characteristics" column of the "synthetic resin layer" column refers to this and indicates that the synthetic resin layer 44 is hydrophilic.

[0044] The worker measured the static contact angle of the synthetic resin layer 44 by the following procedure: the worker dropped a single drop of water onto the surface of the synthetic resin layer 44. Once the water droplet was placed, the worker measured the angle between the synthetic resin layer 44 and the edge of the water droplet. The angle measured in this way is the static contact angle. In this embodiment, the static contact angle was 37.0 degrees (37π radians / 180). The value "37.0" in the "Static Contact Angle (degrees)" column of the "Synthetic Resin Layer" column shown in Figure 3 represents this static contact angle.

[0045] Next, the worker measured the receding water contact angle of the synthetic resin layer 44 using the shrinkage method. The specific procedure of the shrinkage method is well known, so a detailed explanation will not be repeated here. The receding water contact angle of the synthetic resin layer 44 in this embodiment was 21.1 degrees (21.1π radians / 180). The value "21.1" in the "Receding Water Contact Angle (degrees)" column of the "Synthetic Resin Layer" column shown in Figure 3 represents its static contact angle.

[0046] After the receding water contact angle is measured, the ten-point average roughness R shown in JIS B0601 (2013) is measured. ZJIS When the worker measured it, the value was 31.09 micrometers. In the "Synthetic Resin Layer" column shown in Figure 3, "R ZJIS The value "31.09" in the "(μm)" column represents that value. Similarly, the arithmetic mean roughness R shown in JIS B0601 (2013)a When the operator measured it, the value was 8.76 micrometers. The value "8.76" in the "R a (μm)" column in the "Synthetic Resin Layer" column shown in Figure 3 means that value.

[0047] The operator formed a synthetic resin layer 44 on the surfaces of three more metal bases 40 by the same procedure as described above.

[0048] After that, the operator applied the protective layer forming liquid described below to the surface of the synthetic resin layer 44 (S504). The protective layer forming liquid was a mixture of silicon dioxide mixed with water. In that water, silicon dioxide may have existed as a hydrate. The ratio of the non-silicon dioxide component to the total of the component that is either silicon dioxide or a hydrate of silicon dioxide among the components of the protective layer forming liquid was 150 PPM or less. There was no substance intentionally mixed into the water other than silicon dioxide in the protective layer forming liquid. The application amount of the protective layer forming liquid was adjusted so that the amount of silicon dioxide after evaporation of the water contained in the protective layer forming liquid would be 65 milligrams per square meter of the metal base 40. The value "65" in the "SiO2 Adhesion Amount (mg / m 2 )" column in the "Protective Layer" column shown in Figure 3 means that amount of silicon dioxide. The protective layer forming liquid was applied so as to cover all of the synthetic resin layer 44. The protective layer forming liquid spread well on the surface of the synthetic resin layer 44. The circled mark in the "Coatability" column in the "Protective Layer" column shown in Figure 3 means that the protective layer forming liquid spread well on the surface of the synthetic resin layer 44. The application of the protective layer forming liquid to the surface of the synthetic resin layer 44 was performed for all of the four metal bases 40 described above. In the following examples and comparative examples, the same protective layer forming liquid was used.

[0049] When the protective layer forming liquid was applied to the surface of the metal base 40 on which the synthetic resin layer 44 was formed, the worker heated the metal base 40 (S506). The hot air drying oven described above was used for heating. The maximum plate temperature reached during heating was 160 degrees Celsius (433.15 Kelvin). The heating time was 30 seconds. The water contained in the protective layer forming liquid evaporated as a result of the evaporation of the water. The protective layer 46 was formed on top of the synthetic resin layer 44. The formation of the protective layer 46 was performed on all four of the metal bases 40 described above.

[0050] Once a protective layer 46 was formed on the synthetic resin layer 44 of the metal base 40, the worker applied the photocatalytic reaction layer forming liquid described below onto the protective layer 46 (S508). The photocatalytic reaction layer forming liquid was a mixture of silicon dioxide and titanium dioxide in water. In the water, silicon dioxide was sometimes present as a hydrate. Of the components of the photocatalytic reaction layer forming liquid, the proportion of components other than silicon dioxide, silicon dioxide hydrate, titanium dioxide, and water, in the total of components that are either silicon dioxide or silicon dioxide hydrate, titanium dioxide, and water, was 150 PPM or less. In other words, most of the components of the photocatalytic reaction layer forming liquid were either silicon dioxide, silicon dioxide hydrate, titanium dioxide, or water. In the photocatalytic reaction layer forming liquid, there were no substances other than silicon dioxide and titanium dioxide that were intentionally mixed into the water. The amount of photocatalytic reaction layer forming solution applied was adjusted so that the amount of silicon dioxide after evaporation of the water contained in the photocatalytic reaction layer forming solution was 25 milligrams per square meter of the metal base 40. The "SiO2 / TiO2 adhesion amount (mg / m²)" is shown in the "Photocatalytic Reaction Layer" column of Figure 3. 2 The value "25" in the column ")" represents the amount of silicon dioxide. The photocatalytic reaction layer forming solution was applied so as to completely cover the protective layer 46. The application of the photocatalytic reaction layer forming solution to the surface of the protective layer 46 was performed on all four of the metal bases 40 described above. In the following examples and comparative examples, the same photocatalytic reaction layer forming solution was used.

[0051] After the photocatalytic reaction layer forming liquid was applied to the protective layer 46 of the metal base 40, the worker heated the metal base 40 (S510). The hot air drying oven described above was used for heating. The maximum plate temperature reached during heating was 200 degrees Celsius (473.15 Kelvin). The heating time was 30 seconds. This heating formed a photocatalytic reaction layer 48 on the surface of the metal base 40. The formation of the photocatalytic reaction layer 48 was performed on all four of the metal bases 40 described above. This completed the four painted metal plates 30 according to this embodiment.

[0052] (Observation of rainbow patterns and methylene blue decolorization test) Five evaluators observed the surface of one of the painted metal plates 30 according to this embodiment from various angles outdoors in clear weather. Based on the results of their observations and the following criteria, each evaluator set a score for the painted metal plate 30 according to this embodiment. Rating 3: No rainbow pattern is visible from any angle. Rating 2: The rainbow pattern is not visible when viewed from a certain angle. Rating 1: The rainbow pattern is visible from any angle. The average of the scores set by the five evaluators was used as the score for the painted metal plate 30 in this embodiment. The average value was "3". The value "3" in the "Interference Color Presence / Absence Score" column in the "Immediately After Painting" column shown in Figure 4 represents that average value. Figure 5 shows the surface of the painted metal plate 30 that was the subject of observation.

[0053] After the evaluation score for the painted metal plate 30 according to this embodiment was obtained, the worker applied methylene blue to a portion of the painted metal plate 30 that was the subject of observation. A well-known spray was used to apply the methylene blue. The methylene blue was applied to the painted metal plate 30 until it was clearly colored. Once the methylene blue was applied, the worker covered a portion of the area where the methylene blue had been applied. Once the portion of the area where the methylene blue had been applied was covered, the worker irradiated the area with ultraviolet light. The output of the ultraviolet light was 35 watts. The distance from the area where the methylene blue had been applied to the ultraviolet light source was 10 centimeters. The irradiation time was 24 hours (86,400 seconds). After the ultraviolet light was irradiated, the worker removed the covering described above. In this case, the color of the covered (non-irradiated with ultraviolet light) portion of the area where the methylene blue had been applied remained dark blue. On the other hand, if the methylene blue was decomposed by the photocatalytic material, the color of the uncoated (UV-irradiated) areas would lighten. Therefore, five evaluators assessed the effect of the photocatalytic material on the uncoated (UV-irradiated) areas of the methylene blue-coated surface based on the following criteria. Circled area: The color of the uncoated (UV-irradiated) area was the same as the color of the area where methylene blue was not applied. Triangle mark: A faint trace of methylene blue remained in the areas that were not covered (UV irradiation). X mark: The color of the uncoated (UV-irradiated) areas was the same as the color of the coated (non-UV-irradiated) areas.

[0054] The effect of the photocatalytic material in this embodiment was indicated by a circle. This is shown in the "Methylene Blue Discoloration Test" column in the "Immediately After Painting" column of Figure 4. Figure 6 also shows the color of the areas that were coated (not irradiated with ultraviolet light) and the areas that were not coated (irradiated with ultraviolet light) where methylene blue was applied.

[0055] (Cycle corrosion test) The worker performed a cyclic corrosion test on one of the painted metal plates 30 according to this embodiment. The test was carried out in accordance with JIS K 5600-7-9 "Cyclical corrosion test method - Salt spray / drying / wetting". Spraying and drying were repeated according to "Annex 1 (Normative) Cycle D" of the "Cyclical corrosion test method - Salt spray / drying / wetting". In the cyclic corrosion test, spraying and drying were repeated for 1500 hours. The test apparatus used for the test was a combined cyclic testing machine (model: CYP-90L) manufactured by Suga Test Instruments Co., Ltd. In the following embodiments and comparative examples, this combined cyclic testing machine was also used for the cyclic corrosion tests. After the cyclic corrosion test, the amount of silicon dioxide remaining on the surface of the painted metal plate 30 was 72 milligrams per square meter. The amount of residual silicon dioxide was measured using a wavelength-dispersive compact X-ray fluorescence analyzer (model: Supermini200) manufactured by Rigaku Corporation. In the following examples and comparative examples, this wavelength-dispersive compact X-ray fluorescence analyzer was used to measure the amount of residual silicon dioxide. The column "After 1500 Hr of Cyclic Corrosion Test (CCT)" in Figure 4 shows the "Total amount of residual SiO2 (mg / m³)". 2 The value "72" in the ")" column represents the amount of silicon dioxide. The amount of silicon dioxide in protective layer 46 was 65 milligrams per square meter. The "SiO2 amount (mg / m)" in the "Immediately after painting" column shown in Figure 4 represents the amount of silicon dioxide. 2 The value "65" in the "Protective Layer" column of the ")" column represents the amount of silicon dioxide. The amount of silicon dioxide in the photocatalytic reaction layer 48 was 25 milligrams per square meter. The "SiO2 amount (mg / m)" in the "Immediately after painting" column shown in Figure 4 represents the amount of silicon dioxide. 2 The value "25" in the "Photocatalytic Reaction Layer" column of the ")" section represents the amount of silicon dioxide. This means that before the cycle corrosion test, 90 milligrams of silicon dioxide per square meter were present on the surface of the painted metal plate 30. As a result, the residual rate of silicon dioxide after the cycle corrosion test was 80.0%. The value "80.0" in the "SiO2 Residual Rate (%)" column of the "After Cycle Corrosion Test (CCT) 1500 Hr" section shown in Figure 4 represents that residual rate.

[0056] Furthermore, the worker applied methylene blue and irradiated the painted metal plate 30, which had completed the cycle corrosion test, with ultraviolet light using the same procedure as that used for the painted metal plate 30 used for observing the rainbow pattern. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as those used for the painted metal plate 30 used for observing the rainbow pattern. The effect of the photocatalytic material in this embodiment at the end of the cycle corrosion test was indicated by a circle. This is shown in the "Methylene Blue Discoloration Test" column of the "Cycle Corrosion Test (CCT) 1500 Hr" column in Figure 4. Also, Figure 7 shows the color of the areas where methylene blue was applied that were covered (not irradiated with ultraviolet light) and the areas that were not covered (irradiated with ultraviolet light).

[0057] (Weather resistance test) In accordance with JIS B 7753, the worker tested the weather resistance of one of the painted metal plates 30 according to this embodiment. The test was continued for 1500 hours. The test apparatus used for the test was a sunshine weather meter (model: S80DBH) manufactured by Suga Test Instruments Co., Ltd. This sunshine weather meter was also used for the weather resistance tests in the following examples and comparative examples. After the test, the amount of silicon dioxide remaining on the surface of the painted metal plate 30 was 78 milligrams per square meter. In the "Weather Resistance Test (SWOM) After 1500 Hr" column shown in Figure 4, the "Total Remaining SiO2 Amount (mg / m²)" is shown. 2 The value "78" in the "( ) " column represents the amount of silicon dioxide. As mentioned above, before the test, 90 milligrams of silicon dioxide per square meter were present on the surface of the painted metal plate 30. As a result, the residual silicon dioxide after the test was 86.7%. The value "86.7" in the "SiO2 residual rate (%)" column of the "Weathering test (SWOM) after 1500 hours" column shown in Figure 4 represents that residual rate.

[0058] Furthermore, the worker applied methylene blue and irradiated the painted metal plate 30 with ultraviolet light using the same procedure as that used for the painted metal plate 30 used for observing the rainbow pattern, after the weathering test was completed. Subsequently, five evaluators evaluated the effect of the photocatalytic material using the same criteria as those used for the painted metal plate 30 used for observing the rainbow pattern. The effect of the photocatalytic material in this embodiment at the end of the weathering test was indicated by a circle. This is shown in the "Methylene Blue Discoloration Test" column of the "Weathering Test (SWOM) 1500 Hr" column in Figure 4. Also, Figure 8 shows the color of the areas where methylene blue was applied that were covered (not irradiated with ultraviolet light) and the areas that were not covered (irradiated with ultraviolet light).

[0059] (Exposure test) The worker left one of the painted metal plates 30 according to this embodiment outdoors for 1500 hours. After the exposure, the painted metal plate 30 according to this embodiment showed no dirt compared to the painted metal plate 30 according to Comparative Example 1 described later. This situation is shown in Figure 9. The circles in the "Raindrop Stain Test Evaluation" column of the "After 1500 Hr Exposure Test" column shown in Figure 4 indicate that no dirt was observed compared to the painted metal plate 30 according to Comparative Example 1.

[0060] Furthermore, the worker applied methylene blue and irradiated the painted metal plate 30 after the exposure test using the same procedure as that used for the painted metal plate 30 used for observing the rainbow pattern. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as those used for the painted metal plate 30 used for observing the rainbow pattern. The effect of the photocatalytic material in this embodiment at the end of the exposure test was indicated by a circle. This is shown in the "Methylene Blue Discoloration Test" column under the "After 1500 Hr of Exposure Test" column in Figure 4.

[0061] [Example 2] (Manufacturing conditions) The painted metal plate 30 according to this embodiment differs from the painted metal plate 30 according to Embodiment 1 in the following respects.

[0062] The first point is that a different topcoat paint was used than the one used in Example 1. This topcoat paint was also a polyester-based paint, similar to that used in Example 1. A wrinkled pattern was also formed on the synthetic resin layer 44 in this example. The worker measured the static contact angle and the receding water contact angle of the synthetic resin layer 44 in this example using the same procedure as in Example 1. The static contact angle of the synthetic resin layer 44 in this example was 47.1 degrees (157π radians / 600). The receding water contact angle of the synthetic resin layer 44 in this example was 17.8 degrees (89π radians / 900). These values ​​are shown in the "Static Contact Angle (degrees)" and "Receding Water Contact Angle (degrees)" columns in the "Synthetic Resin Layer" column shown in Figure 3. The ten-point average roughness R of this synthetic resin layer 44 ZJIS The arithmetic mean roughness R of this synthetic resin layer 44 was 15.72 micrometers. a The value was 2.69 micrometers. These values ​​are shown in the "R" column of the "Synthetic Resin Layer" section in Figure 3. ZJIS (μm)" column and "R a This is shown in the "(μm)" column.

[0063] The second point concerns the amount of protective layer forming solution applied. In this embodiment, the amount of protective layer forming solution applied was adjusted so that the amount of silicon dioxide (including hydrates if present) after evaporation of the water contained in the protective layer forming solution was 75 milligrams per square meter of the metal base 40. The "SiO2 adhesion amount (mg / m²)" in the "Protective Layer" column shown in Figure 3 is indicated. 2 The value "75" in the ")" column represents the amount of silicon dioxide.

[0064] The third point concerns the amount of photocatalytic reaction layer forming solution applied. In this embodiment, the amount of photocatalytic reaction layer forming solution applied was adjusted so that the amount of silicon dioxide (including hydrates if present) after evaporation of the water contained in the photocatalytic reaction layer forming solution was 70 milligrams per square meter of the metal base 40. The "SiO2 / TiO2 adhesion amount (mg / m²)" in the "Photocatalytic Reaction Layer" column shown in Figure 3 is indicated. 2 The value "70" in the ")" column represents the amount of silicon dioxide.

[0065] (Observation of rainbow patterns and methylene blue decolorization test) In the same manner as in Example 1, five evaluators assigned scores to the painted metal plate 30 according to this example. The average score was "3". The worker applied methylene blue and irradiated with ultraviolet light using the same procedure as in Example 1. Subsequently, five evaluators evaluated the effect of the photocatalytic material using the same criteria as in Example 1. The effect of the photocatalytic material according to this example was indicated by a circle at the time of observation of the rainbow pattern. This is shown in the "Methylene Blue Discoloration Test" column in the "Immediately After Painting" column of Figure 4. Figure 6 also shows the color of the areas where methylene blue was applied that were covered (not irradiated with ultraviolet light) and the areas that were not covered (irradiated with ultraviolet light).

[0066] (Cycle corrosion test) The operator performed a cycle corrosion test on one of the painted metal plates 30 according to this embodiment, in the same manner as in Example 1. After the cycle corrosion test, the amount of silicon dioxide remaining on the surface of the painted metal plate 30 was 108 milligrams per square meter. In the column "After Cycle Corrosion Test (CCT) 1500 Hr" shown in Figure 4, the "Total Remaining SiO2 Amount (mg / m²)" is indicated. 2 The value "108" in the "( ) " column represents the amount of silicon dioxide. The amount of silicon dioxide in the protective layer 46 was 75 milligrams per square meter, and the amount of silicon dioxide in the photocatalytic reaction layer 48 was 70 milligrams per square meter. This means that before the cycle corrosion test, there was 145 milligrams of silicon dioxide per square meter on the surface of the painted metal plate 30. As a result, the residual silicon dioxide rate after the cycle corrosion test was 74.5%. The value "74.5" in the "SiO2 residual rate (%)" column in the "Cycle Corrosion Test (CCT) 1500 Hr" column shown in Figure 4 represents that residual rate.

[0067] Furthermore, the worker applied methylene blue and irradiated the painted metal plate 30, which had completed the cycle corrosion test, with ultraviolet light using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. The effect of the photocatalytic material in this example at the end of the cycle corrosion test was indicated by a circle. This is shown in the "Methylene Blue Discoloration Test" column of the "After 1500 Hr of Cycle Corrosion Test (CCT)" section in Figure 4. Also, Figure 7 shows the color of the areas where methylene blue was applied that were covered (not irradiated with ultraviolet light) and the areas that were not covered (irradiated with ultraviolet light).

[0068] (Weather resistance test) The worker tested the weather resistance of one of the painted metal plates 30 according to this embodiment in the same manner as in Example 1. After these tests, the amount of silicon dioxide remaining on the surface of the painted metal plate 30 was 118 milligrams per square meter. As mentioned above, before these tests, there was 145 milligrams of silicon dioxide per square meter on the surface of the painted metal plate 30. As a result, the residual silicon dioxide rate after these tests was 81.4%. The value "81.4" in the "SiO2 amount remaining rate (%)" column of the "Weather resistance test (SWOM) after 1500 Hr" column shown in Figure 4 represents this residual rate.

[0069] Furthermore, the worker applied methylene blue and irradiated with ultraviolet light using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. At the end of the weathering test, the effect of the photocatalytic material in this example was indicated by a circle. This is shown in the "Methylene Blue Discoloration Test" column of the "Weathering Test (SWOM) 1500 Hr" column in Figure 4. Also, Figure 8 shows the color of the areas where methylene blue was applied that were covered (not irradiated with ultraviolet light) and the areas that were not covered (irradiated with ultraviolet light).

[0070] (Exposure test) The worker left one of the painted metal plates 30 according to this embodiment outdoors for 1500 hours. After the exposure, the painted metal plate 30 according to this embodiment showed no dirt compared to the painted metal plate 30 according to Comparative Example 1 described later. This situation is shown in Figure 9. Also, the circles in the "Raindrop Stain Test Evaluation" column of the "After 1500 Hr Exposure Test" column shown in Figure 4 indicate that no dirt was observed compared to the painted metal plate 30 according to Comparative Example 1.

[0071] Furthermore, the worker applied methylene blue and irradiated the painted metal plate 30 after the exposure test using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. The effect of the photocatalytic material in this example at the end of the exposure test was indicated by a circle. This is shown in the "Methylene Blue Discoloration Test" column under the "After 1500 Hr of Exposure Test" column in Figure 4.

[0072] [Example 3] (Manufacturing conditions) The painted metal plate 30 according to this embodiment differs from the painted metal plate 30 according to Embodiment 1 in the following respects.

[0073] The first point is that a different topcoat paint was used than the one used in Example 1. This topcoat paint was also a polyester-based paint, similar to that used in Example 1. A wrinkled pattern was also formed on the synthetic resin layer 44 in this example. The worker measured the static contact angle and the receding water contact angle of the synthetic resin layer 44 in this example using the same procedure as in Example 1. The static contact angle of the synthetic resin layer 44 in this example was 83.2 degrees (104π radians / 225). The receding water contact angle of the synthetic resin layer 44 in this example was 30.5 degrees (61π radians / 360). These values ​​are shown in the "Static Contact Angle (degrees)" and "Receding Water Contact Angle (degrees)" columns in the "Synthetic Resin Layer" column shown in Figure 3. The ten-point average roughness R of this synthetic resin layer 44 ZJIS The arithmetic mean roughness R of this synthetic resin layer 44 was 26.25 micrometers. aIt was 6.67 micrometers. These values ​​are shown in the "R" column of the "Synthetic Resin Layer" section in Figure 3. ZJIS (μm)" column and "R a This is shown in the "(μm)" column.

[0074] The second point concerns the amount of protective layer forming solution applied. In this embodiment, the amount of protective layer forming solution applied was adjusted so that the amount of silicon dioxide (including hydrates if present) after the evaporation of water contained in the protective layer forming solution was 80 milligrams per square meter of the metal base 40. The "SiO2 adhesion amount (mg / m²)" in the "Protective layer" column shown in Figure 3 is indicated. 2 The value "80" in the ")" column represents the amount of silicon dioxide.

[0075] The third point concerns the amount of photocatalytic reaction layer forming solution applied. In this embodiment, the amount of photocatalytic reaction layer forming solution applied was adjusted so that the amount of silicon dioxide (including hydrates if present) after evaporation of the water contained in the photocatalytic reaction layer forming solution was 35 milligrams per square meter of the metal base 40. The "SiO2 / TiO2 adhesion amount (mg / m²)" in the "Photocatalytic Reaction Layer" column shown in Figure 3 is indicated. 2 The value "35" in the ")" column represents the amount of silicon dioxide.

[0076] (Observation of rainbow patterns and methylene blue decolorization test) In the same manner as in Example 1, five evaluators assigned scores to the painted metal plate 30 according to this embodiment. The average score was "3". The worker applied methylene blue and irradiated with ultraviolet light using the same procedure as in Example 1. Subsequently, five evaluators evaluated the effect of the photocatalytic material using the same criteria as in Example 1. The effect of the photocatalytic material according to this embodiment at the time of observation of the rainbow pattern was indicated by a circle. This is shown in the "Methylene Blue Discoloration Test" column in the "Immediately After Painting" column of Figure 4.

[0077] (Cycle corrosion test) The operator performed a cycle corrosion test on one of the painted metal plates 30 according to this embodiment, in the same manner as in Example 1. After the cycle corrosion test, the amount of silicon dioxide remaining on the surface of the painted metal plate 30 was 90 milligrams per square meter. In the column "After Cycle Corrosion Test (CCT) 1500 Hr" shown in Figure 4, the "Total Remaining SiO2 Amount (mg / m²)" is indicated. 2 The value "90" in the "( ) " column represents the amount of silicon dioxide. The amount of silicon dioxide in the protective layer 46 was 80 milligrams per square meter, and the amount of silicon dioxide in the photocatalytic reaction layer 48 was 35 milligrams per square meter. This means that before the cycle corrosion test, there was 115 milligrams of silicon dioxide per square meter on the surface of the painted metal plate 30. As a result, the residual rate of silicon dioxide after the cycle corrosion test was 78.3%. The value "78.3" in the "SiO2 residual rate (%)" column in the "Cycle Corrosion Test (CCT) 1500 Hr" column shown in Figure 4 represents that residual rate.

[0078] Furthermore, the worker applied methylene blue and irradiated the painted metal plate 30, which had completed the cycle corrosion test, with ultraviolet light using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. The effect of the photocatalytic material in this example at the end of the cycle corrosion test was indicated by a circle. This is shown in the "Methylene Blue Discoloration Test" column of the "After 1500 Hr of Cycle Corrosion Test (CCT)" section in Figure 4. Also, Figure 7 shows the color of the areas where methylene blue was applied that were covered (not irradiated with ultraviolet light) and the areas that were not covered (irradiated with ultraviolet light).

[0079] (Weather resistance test) The worker tested the weather resistance of one of the painted metal plates 30 according to this embodiment in the same manner as in Example 1. After these tests, the amount of silicon dioxide remaining on the surface of the painted metal plate 30 was 98 milligrams per square meter. As mentioned above, before these tests, there was 115 milligrams of silicon dioxide per square meter on the surface of the painted metal plate 30. As a result, the residual silicon dioxide rate after these tests was 85.2%. The value "85.2" in the "SiO2 amount remaining rate (%)" column of the "Weather resistance test (SWOM) after 1500 Hr" column shown in Figure 4 represents this residual rate.

[0080] Furthermore, the worker applied methylene blue and irradiated with ultraviolet light using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. At the end of the weathering test, the effect of the photocatalytic material in this example was indicated by a circle. This is shown in the "Methylene Blue Discoloration Test" column of the "Weathering Test (SWOM) 1500 Hr" column in Figure 4. Also, Figure 8 shows the color of the areas where methylene blue was applied that were covered (not irradiated with ultraviolet light) and the areas that were not covered (irradiated with ultraviolet light).

[0081] (Exposure test) The worker left one of the painted metal plates 30 according to this embodiment outdoors for 1500 hours. After the exposure, the painted metal plate 30 according to this embodiment showed no dirt compared to the painted metal plate 30 according to Comparative Example 1 described later. This situation is shown in Figure 9. The circles in the "Raindrop Stain Test Evaluation" column of the "After 1500 Hr Exposure Test" column shown in Figure 4 indicate that no dirt was observed compared to the painted metal plate 30 according to Comparative Example 1.

[0082] Furthermore, the worker applied methylene blue and irradiated the painted metal plate 30 after the exposure test using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. The effect of the photocatalytic material in this example at the end of the exposure test was indicated by a circle. This is shown in the "Methylene Blue Discoloration Test" column under the "After 1500 Hr of Exposure Test" column in Figure 4.

[0083] [Example 4] (Manufacturing conditions) The painted metal plate 30 according to this embodiment differs from the painted metal plate 30 according to Embodiment 1 in the following respects.

[0084] The first point is that a different topcoat paint was used than the one used in Example 1. Unlike the one in Example 1, this topcoat paint contained a large amount of acrylic resin in addition to polyester. The "Acrylic + Polyester" in the "Coating Film Resin System" column of the "Synthetic Resin Layer" column shown in Figure 3 indicates this. The surface of the synthetic resin layer 44 in this example was of the solid type. The "Hydrophilic Solid Coating" in the "Coating Film Characteristics" column of the "Synthetic Resin Layer" column shown in Figure 3 indicates this and that the synthetic resin layer 44 is hydrophilic. The operator measured the static contact angle and the receding water contact angle of the synthetic resin layer 44 in this example using the same procedure as in Example 1. The static contact angle of the synthetic resin layer 44 in this example was 38.2 degrees (191π radians / 900). The receding water contact angle of the synthetic resin layer 44 in this example was 33.0 degrees (11π radians / 60). These values ​​are shown in the "Static Contact Angle (degrees)" and "Receding Water Contact Angle (degrees)" columns of the "Synthetic Resin Layer" column in Figure 3. The ten-point average roughness R of this synthetic resin layer 44 ZJIS The arithmetic mean roughness R of this synthetic resin layer 44 was 1.00 micrometer. a It was 0.12 micrometers. These values ​​are shown in the "R" column of the "Synthetic Resin Layer" section in Figure 3. ZJIS (μm)" column and "R a This is shown in the "(μm)" column.

[0085] The second point concerns the amount of protective layer forming solution applied. In this embodiment, the amount of protective layer forming solution applied was adjusted so that the amount of silicon dioxide (including hydrates if present) after evaporation of the water contained in the protective layer forming solution was 75 milligrams per square meter of the metal base 40. The "SiO2 adhesion amount (mg / m²)" in the "Protective Layer" column shown in Figure 3 is indicated. 2 The value "75" in the ")" column represents the amount of silicon dioxide.

[0086] The third point concerns the amount of photocatalytic reaction layer forming solution applied. In this embodiment, the amount of photocatalytic reaction layer forming solution applied was adjusted so that the amount of silicon dioxide (including hydrates if present) after evaporation of the water contained in the photocatalytic reaction layer forming solution was 50 milligrams per square meter of the metal base 40. The "SiO2 / TiO2 adhesion amount (mg / m)" in the "Photocatalytic Reaction Layer" column shown in Figure 3 is indicated. 2 The value "50" in the ")" column represents the amount of silicon dioxide.

[0087] (Observation of rainbow patterns and methylene blue decolorization test) In the same manner as in Example 1, five evaluators assigned scores to the painted metal plate 30 according to this embodiment. The average score was "1". The value "1" in the "Interference Color Presence / Absence Score" column of the "Immediately After Painting" section shown in Figure 4 represents this average value. Figure 10 shows the surface of the painted metal plate 30 according to this embodiment. In Figure 10, a rainbow pattern was observed where linear variations in shade appeared. That is, a rainbow pattern was observed on the painted metal plate 30 according to this embodiment. Subsequently, the five evaluators evaluated the effect of the photocatalytic material using the same criteria as in Example 1. The effect of the photocatalytic material according to this embodiment at the time of observation of the rainbow pattern was indicated by a circle. This is shown in the "Methylene Blue Discoloration Test" column of the "Immediately After Painting" section shown in Figure 4.

[0088] (Cycle corrosion test) The operator performed a cycle corrosion test on one of the painted metal plates 30 according to this embodiment, in the same manner as in Example 1. After the cycle corrosion test, the amount of silicon dioxide remaining on the surface of the painted metal plate 30 was 75 milligrams per square meter. In the column "After Cycle Corrosion Test (CCT) 1500 Hr" shown in Figure 4, the "Total Remaining SiO2 Amount (mg / m²)" is indicated. 2 The value "75" in the "(CCT) 1500Hr" column represents the amount of silicon dioxide. The amount of silicon dioxide in the protective layer 46 was 75 milligrams per square meter, and the amount of silicon dioxide in the photocatalytic reaction layer 48 was 50 milligrams per square meter. This means that before the cycle corrosion test, there was 125 milligrams of silicon dioxide per square meter on the surface of the painted metal plate 30. As a result, the silicon dioxide residue rate after the cycle corrosion test was 60.0%. The value "60.0" in the "SiO2 residue rate (%)" column in the "Cycle Corrosion Test (CCT) 1500Hr" column shown in Figure 4 represents that residue rate.

[0089] Furthermore, the worker applied methylene blue and irradiated the painted metal plate 30, which had completed the cycle corrosion test, with ultraviolet light using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. The effect of the photocatalytic material in this example at the end of the cycle corrosion test was indicated by a circle. This is shown in the "Methylene Blue Decolorization Test" column of the "After 1500 Hr of Cycle Corrosion Test (CCT)" section in Figure 4.

[0090] (Weather resistance test) The worker tested the weather resistance of one of the painted metal plates 30 according to this embodiment in the same manner as in Example 1. After these tests, the amount of silicon dioxide remaining on the surface of the painted metal plate 30 was 75 milligrams per square meter. As mentioned above, before these tests, there was 125 milligrams of silicon dioxide per square meter on the surface of the painted metal plate 30. As a result, the residual silicon dioxide rate after these tests was 60.0%. The value "60.0" in the "SiO2 amount remaining rate (%)" column of the "Weather resistance test (SWOM) after 1500 Hr" column shown in Figure 4 represents this residual rate.

[0091] Furthermore, the worker applied methylene blue and irradiated with ultraviolet light using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. At the end of the weathering test, the effect of the photocatalytic material in this example was indicated by a circle. This is shown in the "Methylene Blue Discoloration Test" column of the "Weathering Test (SWOM) 1500 Hr" column in Figure 4. Also, Figure 8 shows the color of the areas where methylene blue was applied that were covered (not irradiated with ultraviolet light) and the areas that were not covered (irradiated with ultraviolet light).

[0092] (Exposure test) The worker left one of the painted metal plates 30 according to this embodiment outdoors for 1500 hours. After the exposure, the painted metal plate 30 according to this embodiment showed no dirt compared to the painted metal plate 30 according to Comparative Example 1 described later. The circles in the "Raindrop Stain Test Evaluation" column of the "After 1500 Hr Exposure Test" column shown in Figure 4 indicate that no dirt was observed compared to the painted metal plate 30 according to Comparative Example 1.

[0093] Furthermore, the worker applied methylene blue and irradiated the painted metal plate 30 after the exposure test using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. The effect of the photocatalytic material in this example at the end of the exposure test could be described as either a triangle or a circle. That is, the color of the areas coated with methylene blue was dark blue, while the color of the areas that were not coated was light blue. This is shown in the "Methylene Blue Discoloration Test" column in the "After 1500 Hr of Exposure Test" column in Figure 4.

[0094] [Comparative Example 1] (Manufacturing conditions) The painted metal sheet 30 in this comparative example differs from the painted metal sheet 30 in Example 1 in the following respects.

[0095] The first point is that a different topcoat paint was used than the one used in Example 1. This topcoat paint was also a polyester-based paint, similar to that used in Example 1. A wrinkled pattern was also formed on the synthetic resin layer 44 in this example. The "Normal Wrinkled Coating" in the "Coating Film Characteristics" column of the "Synthetic Resin Layer" column shown in Figure 3 refers to this and the fact that the synthetic resin layer 44 is not hydrophilic. The operator measured the static contact angle and the receding water contact angle of the synthetic resin layer 44 in this comparative example using the same procedure as in Example 1. The static contact angle of the synthetic resin layer 44 in this comparative example was 97.8 degrees (163π radians / 300). The receding water contact angle of the synthetic resin layer 44 in this comparative example was 61.5 degrees (41π radians / 120). These values ​​are shown in the "Static Contact Angle (degrees)" column and the "Receding Water Contact Angle (degrees)" column of the "Synthetic Resin Layer" column shown in Figure 3. The ten-point average roughness R of this synthetic resin layer 44 ZJIS The arithmetic mean roughness R of this synthetic resin layer 44 was 22.3 micrometers. a It was 4.1 micrometers. These values ​​are shown in the "R" column of the "Synthetic Resin Layer" section in Figure 3. ZJIS (μm)" column and "R a This is shown in the "(μm)" column.

[0096] The second point is that the protective layer forming solution was not applied. In this comparative example, the synthetic resin layer 44 repelled the protective layer forming solution, so the worker was unable to apply the solution to the synthetic resin layer 44. As a result, no protective layer 46 was formed on the painted metal plate in this comparative example. The "SiO2 adhesion amount (mg / m²)" in the "Protective layer" column shown in Figure 3 is incorrect. 2 The "Processing Impossible" column indicates that the protective layer forming liquid could not be applied to the synthetic resin layer 44. The "Coating Properties" column indicates that the synthetic resin layer 44 repelled the protective layer forming liquid, resulting in poor coating properties.

[0097] The third point is that the photocatalytic reaction layer forming solution was not applied. In this comparative example, since the protective layer 46 was not formed, the worker could not apply the photocatalytic reaction layer forming solution to the protective layer 46. As a result, the photocatalytic reaction layer 48 was not formed on the painted metal plate in this comparative example. In the "Photocatalytic Reaction Layer" column shown in Figure 3, the "SiO2 / TiO2 Adhesion Amount (mg / m²)" is shown. 2 The entry "Processing impossible" in the ) column means that the photocatalytic reaction layer forming solution could not be applied to the synthetic resin layer 44.

[0098] (Observation of rainbow patterns and methylene blue decolorization test) For the painted metal plate 30 in this comparative example, it was not possible to assign a score similar to that in Examples 1 to 4. This is indicated by the "Interference Color Presence / Absence Score" column in the "Immediately After Painting" section shown in Figure 4, which shows "Unprocessable." The worker applied methylene blue and irradiated with ultraviolet light using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. At the time of observation of the rainbow pattern, the effect of the photocatalytic material in this comparative example was marked with an "X." This is indicated in the "Methylene Blue Discoloration Test" column in the "Immediately After Painting" section shown in Figure 4.

[0099] (Cycle corrosion test) The operator performed a cycle corrosion test on one of the painted metal plates 30 in this comparative example in the same manner as in Example 1. In this comparative example, the amount of silicon dioxide remaining on the surface of the painted metal plate 30 was not measured. In the column "After Cycle Corrosion Test (CCT) 1500 Hr" shown in Figure 4, the "Total amount of remaining SiO2 (mg / m²)" is calculated. 2 The "---" in the ")" column and the "SiO2 remaining amount (%)" column means the same thing.

[0100] Furthermore, the worker applied methylene blue and irradiated the painted metal plate 30, which had completed the cycle corrosion test, with ultraviolet light using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. The effect of the photocatalytic material in this comparative example at the end of the cycle corrosion test was marked with an "X". This is shown in the "Methylene Blue Decolorization Test" column under the "After 1500 Hr of Cycle Corrosion Test (CCT)" section in Figure 4.

[0101] (Weather resistance test) The operator tested the weather resistance of one of the painted metal plates 30 in this comparative example in the same manner as in Example 1. In this comparative example, the amount of silicon dioxide remaining on the surface of the painted metal plate 30 was not measured. In the "Weather Resistance Test (SWOM) 1500 Hr" column shown in Figure 4, the "Total amount of remaining SiO2 (mg / m²)" is calculated. 2 The "---" in the ")" column and the "SiO2 remaining amount (%)" column means the same thing.

[0102] Furthermore, the worker applied methylene blue and irradiated with ultraviolet light using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. At the end of the weathering test, the effect of the photocatalytic material in this comparative example was marked with an "X". This is shown in the "Methylene Blue Discoloration Test" column of the "Weathering Test (SWOM) 1500 Hr" column in Figure 4.

[0103] (Exposure test) The worker left one of the painted metal plates 30 according to this comparative example outdoors. The leaving time was 1500 hours. After leaving it outdoors, rain streaks and discoloration were observed on the painted metal plate 30 according to this comparative example. This situation is shown in Figure 9. The "X" mark in the "Rain streak stain test evaluation" column of the "After 1500 Hr exposure test" column shown in Figure 4 means that there was staining on the surface of the painted metal plate 30 according to this example after leaving it outdoors.

[0104] Furthermore, the worker applied methylene blue and irradiated the painted metal plate 30 after the exposure test using the same procedure as in Example 1. Subsequently, five evaluators evaluated the effect of the photocatalytic material using the same criteria as in Example 1. The effect of the photocatalytic material in this comparative example at the end of the exposure test was marked with an "X". This is shown in the "Methylene Blue Discoloration Test" column under the "After 1500 Hr of Exposure Test" column in Figure 4.

[0105] [Comparative Example 2] (Manufacturing conditions) The painted metal sheet 30 in this comparative example differs from the painted metal sheet 30 in Example 1 in the following respects.

[0106] The first point is that a different topcoat paint was used than the one used in Example 1. This topcoat paint was also a polyester-based paint, similar to that used in Example 1. The surface of the synthetic resin layer 44 in this comparative example was matte. The "Normal matte finish" in the "Coating characteristics" column of the "Synthetic resin layer" column shown in Figure 3 refers to this and the fact that the synthetic resin layer 44 is not hydrophilic. The operator measured the static contact angle and the receding water contact angle of the synthetic resin layer 44 in this comparative example using the same procedure as in Example 1. The static contact angle of the synthetic resin layer 44 in this comparative example was 81.4 degrees (407π radians / 900). The receding water contact angle of the synthetic resin layer 44 in this comparative example was 74.7 degrees (83π radians / 200). These values ​​are shown in the "Static contact angle (degrees)" and "Receding water contact angle (degrees)" columns of the "Synthetic resin layer" column shown in Figure 3. The ten-point average roughness R of this synthetic resin layer 44 ZJIS The arithmetic mean roughness R of this synthetic resin layer 44 was 6.7 micrometers.a It was 0.95 micrometers. These values ​​are shown in the "R" column of the "Synthetic Resin Layer" section in Figure 3. ZJIS (μm)" column and "R a This is shown in the "(μm)" column.

[0107] The second point is that the protective layer forming solution was not applied. In this comparative example, the synthetic resin layer 44 repelled the protective layer forming solution, so the worker was unable to apply the solution to the synthetic resin layer 44. As a result, no protective layer 46 was formed on the painted metal plate in this comparative example. The "SiO2 adhesion amount (mg / m²)" in the "Protective layer" column shown in Figure 3 is incorrect. 2 The "Processing Impossible" column indicates that the protective layer forming liquid could not be applied to the synthetic resin layer 44. The "Coating Properties" column indicates that the synthetic resin layer 44 repelled the protective layer forming liquid, resulting in poor coating properties.

[0108] The third point is that the photocatalytic reaction layer forming solution was not applied. In this comparative example, the synthetic resin layer 44 repelled the photocatalytic reaction layer forming solution in addition to the protective layer forming solution, so the worker was unable to apply the photocatalytic reaction layer forming solution to the synthetic resin layer 44. As a result, the photocatalytic reaction layer 48 was not formed on the painted metal plate in this comparative example. The "SiO2 / TiO2 adhesion amount (mg / m²)" in the "Photocatalytic Reaction Layer" column shown in Figure 3 is shown. 2 The entry "Processing impossible" in the ) column means that the photocatalytic reaction layer forming solution could not be applied to the synthetic resin layer 44.

[0109] (Observation of rainbow patterns and methylene blue decolorization test) For the painted metal plate 30 in this comparative example, it was not possible to assign a score similar to that in Examples 1 to 4. This is indicated by the "Interference Color Presence / Absence Score" column in the "Immediately After Painting" section shown in Figure 4, which shows "Unprocessable." The worker applied methylene blue and irradiated with ultraviolet light using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. At the time of observation of the rainbow pattern, the effect of the photocatalytic material in this comparative example was marked with an "X." This is indicated in the "Methylene Blue Discoloration Test" column in the "Immediately After Painting" section shown in Figure 4.

[0110] (Cycle corrosion test) The operator performed a cycle corrosion test on one of the painted metal plates 30 in this comparative example in the same manner as in Example 1. In this comparative example, the amount of silicon dioxide remaining on the surface of the painted metal plate 30 was not measured. In the column "After Cycle Corrosion Test (CCT) 1500 Hr" shown in Figure 4, the "Total amount of remaining SiO2 (mg / m²)" is calculated. 2 The "---" in the ")" column and the "SiO2 remaining amount (%)" column means the same thing.

[0111] Furthermore, the worker applied methylene blue and irradiated the painted metal plate 30, which had completed the cycle corrosion test, with ultraviolet light using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. The effect of the photocatalytic material in this comparative example at the end of the cycle corrosion test was marked with an "X". This is shown in the "Methylene Blue Decolorization Test" column under the "After 1500 Hr of Cycle Corrosion Test (CCT)" section in Figure 4.

[0112] (Weather resistance test) The operator tested the weather resistance of one of the painted metal plates 30 in this comparative example in the same manner as in Example 1. In this comparative example, the amount of silicon dioxide remaining on the surface of the painted metal plate 30 was not measured. In the "Weather Resistance Test (SWOM) 1500 Hr" column shown in Figure 4, the "Total amount of remaining SiO2 (mg / m²)" is calculated. 2 The "---" in the ")" column and the "SiO2 remaining amount (%)" column means the same thing.

[0113] Furthermore, the worker applied methylene blue and irradiated with ultraviolet light using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. At the end of the weathering test, the effect of the photocatalytic material in this comparative example was marked with an "X". This is shown in the "Methylene Blue Discoloration Test" column of the "Weathering Test (SWOM) 1500 Hr" column in Figure 4.

[0114] (Exposure test) The worker left one of the painted metal plates 30 according to this comparative example outdoors. The leaving time was 1500 hours. After leaving the plate, the painted metal plate 30 according to this comparative example showed the same type of staining as in Comparative Example 1. The "X" mark in the "Raindrop stain test evaluation" column of the "After 1500 Hr exposure test" column shown in Figure 4 indicates that there was staining on the surface of the painted metal plate 30 according to this example after leaving the plate.

[0115] Furthermore, the worker applied methylene blue and irradiated the painted metal plate 30 after the exposure test using the same procedure as in Example 1. Subsequently, five evaluators evaluated the effect of the photocatalytic material using the same criteria as in Example 1. The effect of the photocatalytic material in this comparative example at the end of the exposure test was marked with an "X". This is shown in the "Methylene Blue Discoloration Test" column under the "After 1500 Hr of Exposure Test" column in Figure 4.

[0116] [Comparative Example 3] (Manufacturing conditions) The painted metal sheet 30 in this comparative example differs from the painted metal sheet 30 in Example 1 in the following respects. Otherwise, the painted metal sheet in this comparative example is identical to the painted metal sheet 30 in Example 1.

[0117] The first point is that, for comparison with the painted metal plate 30 of Example 1, the protective layer forming liquid was not applied. As a result, the protective layer 46 was not formed on the painted metal plate of this comparative example. The "SiO2 adhesion amount (mg / m²)" in the "Protective layer" column shown in Figure 3 is shown. 2The entry "Untreated" in the ) column means that the protective layer forming liquid was not intentionally applied to the synthetic resin layer 44.

[0118] The second point is that, for comparison with the painted metal plate 30 of Example 1, the photocatalytic reaction layer forming solution was not applied. As a result, the photocatalytic reaction layer 48 was not formed on the painted metal plate of this comparative example. The "---" indicated in the "Coatingability" column of the "Protective Layer" column in Figure 3 means that the protective layer forming solution was intentionally not applied.

[0119] (Observation of rainbow patterns and methylene blue decolorization test) In this comparative example, no rainbow pattern was observed. This is indicated by the "No Treatment" column in the "Immediately After Painting" section of Figure 4. The worker applied methylene blue and irradiated with ultraviolet light using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. At the time of rainbow pattern observation, the effect of the photocatalytic material in this comparative example was marked with an "X". This is indicated in the "Methylene Blue Discoloration Test" column in the "Immediately After Painting" section of Figure 4. Figure 6 also shows the color of the areas where methylene blue was applied that were covered (not irradiated with ultraviolet light) and the areas where it was not covered (irradiated with ultraviolet light). In this comparative example, the areas where methylene blue was applied that were covered were reddish-purple, while the areas where it was not covered were a slightly lighter reddish-purple than the covered areas.

[0120] (Cycle corrosion test) The operator performed a cycle corrosion test on one of the painted metal plates related to this comparative example in the same manner as in Example 1. In this comparative example, the amount of silicon dioxide remaining on the surface of the painted metal plate 30 was not measured. In the column "After Cycle Corrosion Test (CCT) 1500 Hr" shown in Figure 4, the "Total amount of remaining SiO2 (mg / m²)" is calculated. 2 The "---" in the ")" column and the "SiO2 remaining amount (%)" column means the same thing.

[0121] Furthermore, the worker applied methylene blue and irradiated the painted metal plate 30, which had completed the cycle corrosion test, with ultraviolet light using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. The effect of the photocatalytic material in this comparative example at the end of the cycle corrosion test was marked with an "X". This is shown in the "Methylene Blue Decolorization Test" column under the "After 1500 Hr of Cycle Corrosion Test (CCT)" section in Figure 4.

[0122] (Weather resistance test) The operator tested the weather resistance of one of the painted metal plates in this comparative example in the same manner as in Example 1. In this comparative example, the amount of silicon dioxide remaining on the surface of the painted metal plate 30 was not measured. In the "Weather Resistance Test (SWOM) After 1500 Hr" column shown in Figure 4, the "Total Remaining SiO2 Amount (mg / m²)" is shown. 2 The "---" in the ")" column and the "SiO2 remaining amount (%)" column means the same thing.

[0123] Furthermore, the worker applied methylene blue and irradiated with ultraviolet light using the same procedure as in Example 1. Subsequently, five evaluators assessed the effect of the photocatalytic material using the same criteria as in Example 1. At the end of the weathering test, the effect of the photocatalytic material in this comparative example was marked with an "X". This is shown in the "Methylene Blue Discoloration Test" column of the "Weathering Test (SWOM) 1500 Hr" column in Figure 4.

[0124] (Exposure test) The worker left one of the painted metal plates related to this comparative example outdoors for 1500 hours. After the period of exposure, the painted metal plate 30 related to this comparative example showed no dirt compared to the painted metal plate 30 related to comparative example 1. The circles in the "Raindrop stain test evaluation" column of the "After 1500 hours of exposure test" column shown in Figure 4 indicate that no dirt was observed compared to the painted metal plate 30 related to comparative example 1.

[0125] Furthermore, the worker applied methylene blue and irradiated the painted metal plate 30 after the exposure test using the same procedure as in Example 1. Subsequently, five evaluators evaluated the effect of the photocatalytic material using the same criteria as in Example 1. The effect of the photocatalytic material in this comparative example at the end of the exposure test was marked with an "X". This is shown in the "Methylene Blue Discoloration Test" column under the "After 1500 Hr of Exposure Test" column in Figure 4.

[0126] [Explanation of effects] Since the non-silicon dioxide component is suppressed in the protective layer 46, even if organic matter is present in the protective layer 46, the impact of that organic matter being destroyed by the photocatalytic reaction is greatly reduced. Because this impact is greatly reduced, the risk of deterioration of the function of the protective layer 46 due to this impact is greatly reduced. Because the risk of deterioration of the function of the protective layer 46 is greatly reduced, the possibility of the synthetic resin layer 44 being destroyed by the photocatalytic reaction is greatly reduced. As a result, in the painted metal plate 30 according to this embodiment, the possibility of the synthetic resin layer 44 being destroyed by the photocatalytic reaction is greatly reduced.

[0127] Furthermore, according to Examples 1 to 4 and Comparative Examples 1 to 3, when the receding water contact angle of the synthetic resin layer 44 exceeded 40 degrees (2π / 9 radians), the protective layer-forming liquid did not wet and spread. Therefore, it was difficult to apply the protective layer-forming liquid to the surface of the synthetic resin layer 44. On the other hand, when the receding water contact angle was 40 degrees (2π / 9 radians) or less, the protective layer-forming liquid could be applied to the surface of the synthetic resin layer 44 without any problems.

[0128] Furthermore, according to Examples 1 to 4 and Comparative Examples 1 to 3, if a protective layer 46 with suppressed non-silicon dioxide components was provided, the photocatalytic activity in the photocatalytic reaction layer 48 persisted even after the cyclic corrosion test. The same was true after the weathering test.

[0129] Furthermore, according to Examples 1 to 4 and Comparative Examples 1 to 3, when a wrinkled pattern was formed on the synthetic resin layer 44, the occurrence of rainbow patterns on the painted metal plate 30 was suppressed. In addition, the effect of the photocatalytic material after the exposure test was superior compared to when the synthetic resin layer 44 was smooth. When the synthetic resin layer 44 was smooth, rainbow patterns occurred.

[0130] [Explanation of variations] The painted metal plate 30 described above is an example provided to embody the technical concept of the present invention. The shape and structure of the metal base 40, the composition of the primer layer 42, the composition of the synthetic resin layer 44, and the composition of the photocatalytic reaction layer 48 are not limited to those described above. Various modifications can be made to them. [Explanation of symbols]

[0131] 30…Painted metal plate 40…Metal base 42…Primer layer 44…Synthetic resin layer 46...Protective layer 48…Photocatalytic reaction layer

Claims

1. A metal base and A synthetic resin layer formed on any surface of the aforementioned metal base, A protective layer formed on the surface of the synthetic resin layer, A painted metal plate comprising a photocatalytic reaction layer formed on the surface of the protective layer and containing a photocatalytic material, The protective layer contains at least one of silicon dioxide and silicon dioxide hydrate. A painted metal sheet characterized in that the concentration of a component in the protective layer that is different from both silicon dioxide and silicon dioxide hydrate is 150 PPM or less.

2. The painted metal plate according to claim 1, characterized in that the recessed water contact angle of the portion of the synthetic resin layer that is in direct contact with the protective layer is less than 40 degrees.

3. The arithmetic mean roughness of the portion of the synthetic resin layer that is in direct contact with the protective layer is 1.00 micrometers or more and 10.00 micrometers or less. The painted metal plate according to claim 2, characterized in that the ten-point average roughness of the portion of the synthetic resin layer that is in direct contact with the protective layer is 10.00 micrometers or more and 60.00 micrometers or less.

4. The painted metal plate according to claim 1, characterized in that the material of the metal base is any of the following: steel with zinc plating on the surface, steel with zinc-aluminum alloy plating on the surface, steel with zinc-aluminum-magnesium alloy plating on the surface, steel with aluminum plating on the surface, steel with zinc-nickel alloy plating on the surface, steel with zinc-iron alloy plating on the surface, aluminum alloy, and stainless steel.

5. A protective layer forming liquid coating step is performed in which a protective layer forming liquid containing at least one of silicon dioxide and silicon dioxide hydrate and water is applied to the surface of a synthetic resin layer formed on the surface of a metal base, A protective layer forming liquid drying step is performed in which the protective layer forming liquid applied to the surface of the synthetic resin layer is dried. A photocatalytic reaction layer forming liquid coating step is performed in which a photocatalytic reaction layer forming liquid containing a photocatalytic material is applied to the surface of the protective layer formed when the protective layer forming liquid dries, A method for manufacturing a painted metal plate, comprising a photocatalytic reaction layer forming liquid drying step in which the photocatalytic reaction layer forming liquid applied to the surface of the protective layer is dried, A method for manufacturing a painted metal sheet, characterized in that, among the components of the protective layer forming liquid, the proportion of the component that is neither silicon dioxide nor silicon dioxide hydrate nor water to the total of the component that is neither silicon dioxide nor silicon dioxide hydrate nor water is 150 ppm or less.

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