Plant cultivating container

Abstract

To provide a coated steel sheet from which adhered algae can be easily removed and which can maintain corrosion resistance.SOLUTION: The coated steel sheet 1 includes a steel sheet 2 and a coating film layer 3 disposed on the steel sheet 2. The contact angle of the surface of the coating film layer 3 to water is 82 ° or more and 130 ° or less, and the contact angle to ethylene glycol is 70 ° or more and 120 ° or less. The ten point average roughness of the surface is more than 0 μm and 20 μm or less. The coating film layer 3 contains a fluorine-containing polysiloxane (A). The fluorine-containing polysiloxane (A) is a reaction product of reactive components including a fluorine-containing resin (A1) and a polysiloxane (A2). The fluorine resin (a1) has a structural unit (a1) bonded by a urethane bond, and the structural unit (a1) contains a structural unit (a11) having a radically polymerizable unsaturated group. The polysiloxane (A2) has radically polymerizable unsaturated bonds at one end of the molecular chain.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a coated steel sheet and a plant cultivation container, and more particularly to a coated steel sheet and a plant cultivation container having a coating film formed by a paint containing a resin. [Background technology]

[0002] Patent Document 1 discloses a coated metal plate comprising a metal plate and a coating layer covering the metal plate, the coating layer containing a pyrithione compound. It is disclosed that this coated metal plate has high anti-algae properties and is resistant to algae adhesion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-90102 Summary of the Invention [Problem to be solved by the invention]

[0004] It is difficult to completely prevent algae from adhering to a coated metal sheet. Moreover, the attached algae can become fixed on the surface of the coated metal sheet. Therefore, it is difficult to remove the algae once attached to the surface of the coated metal sheet.

[0005] An object of the present disclosure is to provide a coated steel sheet and a plant cultivation container that can easily remove attached algae and maintain corrosion resistance. [Means for solving the problem]

[0006] The coated steel sheet of the present disclosure comprises a steel sheet and a coating layer disposed on the steel sheet. The coating layer has a surface with a contact angle to water of 82° or more and 130° or less, and a contact angle to ethylene glycol of 70° or more and 120° or less. The ten-point average roughness of the surface is greater than 0 μm and less than 20 μm.

[0007] The coated steel sheet of the present disclosure comprises a steel sheet and a coating layer disposed on the steel sheet. The coating layer contains a fluorine-containing polysiloxane (A). The fluorine-containing polysiloxane (A) is a reaction product of reactive components including a fluororesin (A1) and a polysiloxane (A2). The fluororesin (A1) has structural units (a1) bonded by urethane bonds, and the structural units (a1) contain structural units (a11) having a radically polymerizable unsaturated bond. The polysiloxane (A2) has a radically polymerizable unsaturated bond at one end of the molecular chain.

[0008] The plant cultivation container of the present disclosure includes a container portion for holding a culture solution, at least a portion of which is made from the above-described coated steel sheet. [Effects of the Invention]

[0009] It is possible to provide a coated steel sheet and a plant cultivation container that can easily remove attached algae and maintain corrosion resistance. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view showing a coated steel sheet according to one embodiment of the present disclosure. [Figure 2] FIG. 1 is a schematic diagram illustrating a method for cultivating plants using a plant cultivating container made from a coated steel sheet according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Embodiment] Embodiments of the present disclosure will be described. Note that the following embodiments are merely a portion of various embodiments of the present disclosure. Furthermore, the following embodiments can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Furthermore, the mechanism of action described below is speculated, and the present disclosure is not bound by the explanation of the mechanism of action below.

[0012] 1. Overview When cultivating plants, algae that inhibit plant growth can grow. If the algae grow in large quantities, the plants may suffer from nutrient deficiencies due to the algae growth. This can lead to problems with plants not growing efficiently. Therefore, a method for preventing algae from attaching is desired.

[0013] For example, algae adhesion can be suppressed by forming a coating film containing a component capable of suppressing algae adhesion on the surface of a container used for cultivating plants. However, in practice, it is difficult to completely suppress algae adhesion. Moreover, attached algae can adhere to the surface of the container. Therefore, removing algae once attached to the surface of the container is difficult. Furthermore, if the container is rubbed hard in an attempt to thoroughly remove algae attached to the surface of the container, the container may be scratched. If chemicals come into contact with the scratches, corrosion may occur in the container. Therefore, removing algae attached to the container may impair the corrosion resistance of the container. Therefore, as a result of extensive research and development, the inventor completed a coated steel sheet 1 that allows easy removal of attached algae while maintaining corrosion resistance, and conceived of applying it to containers for cultivating plants.

[0014] The inventors have found that by providing a coated steel sheet 1 with a coating layer 3 having a specific surface condition, it is possible to remove algae adhering to the coated steel sheet 1 and maintain the corrosion resistance of the coated steel sheet 1. That is, the inventors have completed a coated steel sheet 1 comprising a steel sheet 2 and a coating layer 3 disposed on the steel sheet 2, in which the surface of the coating layer 3 has a contact angle with water of 82° or more and 130° or less, and a contact angle with ethylene glycol of 70° or more and 120° or less, and the ten-point average roughness (Rzjis) of the surface is more than 0 μm and 20 μm or less.

[0015] The inventors also found that by providing a coated steel sheet 1 with a coating layer 3 containing a specific component, algae adhering to the coated steel sheet 1 can be easily removed and the corrosion resistance of the coated steel sheet 1 can be maintained. That is, the inventors also completed a coated steel sheet 1 comprising a steel sheet 2 and a coating layer 3 disposed on the steel sheet 2, the coating layer 3 containing a fluorine-containing polysiloxane (A), the fluorine-containing polysiloxane (A) being a reaction product of reactive components including a fluororesin (A1) and a polysiloxane (A2), the fluororesin (A1) having structural units (a1) bonded by urethane bonds, the structural unit (a1) including a structural unit (a11) having a radically polymerizable unsaturated bond, and the polysiloxane (A2) having a radically polymerizable unsaturated bond at one end of the molecular chain.

[0016] The inventors have also found that a coated steel sheet 1 having a coating layer 3 that combines both the above-described surface condition and components can easily remove algae adhering to the coated steel sheet 1 and can further maintain the corrosion resistance of the coated steel sheet 1. Such a coated steel sheet 1 will be described below as the present embodiment.

[0017] 2.Details 2.1 Painted steel sheets FIG. 1 shows a coated steel sheet 1 according to this embodiment. In this embodiment, the coated steel sheet 1 includes a steel sheet 2 and a coating layer 3 disposed on the steel sheet 2. The contact angle of the surface of the coating layer 3 with water is 82° or more and 130° or less, and the contact angle with ethylene glycol is 70° or more and 120° or less. The ten-point average roughness (Rzjis) of the surface is greater than 0 μm and 20 μm or less. The coating layer 3 contains a fluorine-containing polysiloxane (A). The fluorine-containing polysiloxane (A) is a reaction product of reactive components including a fluororesin (A1) and a polysiloxane (A2). The fluororesin (A1) has structural units (a1) bonded by urethane bonds, and the structural unit (a1) contains a structural unit (a11) having a radically polymerizable unsaturated bond. The polysiloxane (A2) has a radically polymerizable unsaturated bond at one end of the molecular chain.

[0018] As described above, the coating layer 3 has a specific surface condition or contains specific components. This allows algae adhering to the coated steel sheet 1 to be easily removed and maintains the corrosion resistance of the coated steel sheet 1. For example, the coating layer 3 is disposed on the outermost side of the coated steel sheet 1. In this case, algae adhering to the coated steel sheet 1 can be particularly easily removed. For this reason, in this embodiment, the coating layer 3 is disposed on the outermost side of the coated steel sheet 1.

[0019] The method for forming the coating layer 3 is not particularly limited. For example, the coating layer 3 can be formed by applying a resin coating containing a resin component such as a fluorine-containing polysiloxane (A) and baking it to harden it. The maximum plate temperature is, for example, 210°C to 250°C, and the coating is baked for 20 to 60 seconds. The thickness of the coating layer 3 is not particularly limited as long as there are no problems such as peeling, but it is preferably, for example, 1 μm to 20 μm. A resin coating is applied so that the thickness falls within this range, and the coating is then baked to harden it to form the coating layer 3. If the thickness of the coating layer 3 falls within the above range, the workability of the coated steel sheet 1 can be improved.

[0020] In this embodiment, the coated steel sheet 1 further includes a plating layer 5 covering the surface of the steel sheet 2 on the coating layer 3 side. The plating layer 5 is interposed between the steel sheet 2 and the coating layer 3. In other words, the steel sheet 2 is a plated steel sheet. The thickness of the plating layer 5 is, for example, 5 μm or more and 30 μm or less. The plating layer 5 contains, for example, at least one selected from the group consisting of zinc and aluminum. In other words, the plated steel sheet is preferably a hot-dip plated steel sheet, and examples of the hot-dip plated steel sheet include a zinc-plated steel sheet and a Zn-Al alloy-plated steel sheet.

[0021] Furthermore, in this embodiment, the coated steel sheet 1 further includes an intermediate layer 4 between the steel sheet 2 and the coating layer 3. The intermediate layer 4 can be formed, for example, by applying a resin paint or the like to the steel sheet 2. Examples of resin paints include polyester-based resin paints and epoxy-based resin paints. The use of such resin paints can improve adhesion between the intermediate layer 4 and the steel sheet 2 and the coating layer 3. In this embodiment, when the coated steel sheet 1 includes the intermediate layer 4, the coating layer 3 can correspond to the top coat layer. The intermediate layer 4 may be composed of one layer or two or more layers. For example, when the intermediate layer 4 is composed of only a primer layer, a resin paint for primer coating (primer paint) is applied to the steel sheet 2 and baked to harden. In this manner, the intermediate layer 4 is formed. When the intermediate layer 4 is composed of two layers, a primer layer and a middle coat layer, a primer paint is applied to the steel sheet 2 and baked to harden to form the primer layer. Next, a resin paint for intermediate coating (intermediate coating paint) is further applied on the undercoat layer and baked to harden, thereby forming the intermediate layer 4.

[0022] 2.2 Surface condition of the coating layer The surface state of the coating layer 3 will be described in detail below.

[0023] The contact angle of the surface of the coating layer 3 with water is 82° or more and 130° or less. Algae are compatible with water and grow easily in the presence of water. However, if the contact angle of the surface of the coating layer 3 with water is within the above range, the coating layer 3 is less compatible with water, and water is less likely to penetrate the coating layer 3. In other words, if the contact angle of the surface of the coating layer 3 with water is within the above range, the coating layer 3 can have an adequately high water repellency. Accordingly, algae are less likely to grow by eroding from the surface of the coating layer 3 inward, and therefore the algae are less likely to adhere to the coating layer 3. As a result, even if algae adhere to the surface of the coated steel sheet 1, the algae can be easily removed. Furthermore, the attached algae can be removed without rubbing the surface of the coated steel sheet 1 too hard, thereby reducing damage to the surface of the coated steel sheet 1. If the coated steel sheet 1 is scratched and a chemical solution comes into contact with the scratch, corrosion can occur. However, the coated steel sheet 1 of this embodiment can prevent such scratches, thereby reducing the occurrence of corrosion, i.e., maintaining corrosion resistance. This contact angle with water is more preferably 84° or more, even more preferably 85° or more, particularly preferably 86° or more, and even more preferably 90° or more. This contact angle with water is more preferably 120° or less, even more preferably 115° or less, and particularly preferably 110° or less. Furthermore, the contact angle with ethylene glycol on the surface of the coating layer 3 is 70° or more and 120° or less. If the contact angle with ethylene glycol on the surface of the coating layer 3 is within the above range, the oil repellency of the coating layer 3 can be appropriately enhanced. This makes it difficult for algae to adhere to the coating layer 3. As a result, even if algae adhere to the surface of the coated steel sheet 1, the algae can be easily removed and corrosion resistance can be maintained. The contact angle with ethylene glycol is more preferably 71° or more, even more preferably 72° or more, and particularly preferably 73° or more. The contact angle with ethylene glycol is more preferably 110° or less, even more preferably 100° or less, and particularly preferably 93° or less. The contact angle of a droplet of water or ethylene glycol can be confirmed using a contact angle meter.

[0024] The surface free energy of the coating layer 3 is 5 mJ / m 2 More than 23mJ / m2 In this case, it is possible to more easily remove algae adhering to the surface of the coated steel sheet 1, and also to maintain corrosion resistance. This surface free energy is preferably 8 mJ / m 2 More preferably, it is 11 mJ / m or more. 2 More preferably, the surface free energy is 21.5 mJ / m or more. 2 More preferably, it is 20.5 mJ / m or less. 2 It is more preferable that:

[0025] The surface free energy value of the coating layer 3 can be calculated from the measured values ​​of the contact angles of water and ethylene glycol based on the Owens-Wendt equation and the Young equation.

[0026] The ten-point mean roughness (Rzjis) of the surface of the coating layer 3 is more than 0 μm and not more than 20 μm. In this case, the smoothness of the coating layer 3 is appropriately increased, making it difficult for algae to adhere to the coating layer 3. This makes it easier to remove algae that have adhered to the surface of the coated steel sheet 1. This ten-point mean roughness (Rzjis) is preferably not more than 15 μm, and more preferably not more than 7 μm. This ten-point mean roughness (Rzjis) may be, for example, not less than 0.5 μm. Note that, in accordance with JIS B 0601-2001, measurements are taken at three locations using a roughness measuring device, and the average of the measurements can be used as the ten-point mean roughness (Rzjis).

[0027] 2.3 Coating layer composition The components of the coating layer 3 will be described in detail below.

[0028] The coating layer 3 contains a fluorine-containing polysiloxane (A). This makes it easier to remove algae that adhere to the surface of the coated steel sheet 1. The fluorine-containing polysiloxane (A) also makes it possible to impart chemical resistance to the coating layer 3. Therefore, a coated steel sheet 1 having a coating layer 3 containing the fluorine-containing polysiloxane (A) can have high corrosion resistance. The content of the fluorine-containing polysiloxane (A) in the coating layer 3 is preferably 4% by mass or more and 40% by mass or less. In this case, it is easier to remove algae that adhere to the surface of the coated steel sheet 1. This content is more preferably 10% by mass or more, and even more preferably 30% by mass or more.

[0029] The fluorine-containing polysiloxane (A) contains, as its constituent components, a fluororesin (A1) component and a polysiloxane (A2) component. That is, the fluorine-containing polysiloxane (A) is a reaction product of reactive components including the fluororesin (A1) and the polysiloxane (A2). For example, the fluorine-containing polysiloxane (A) can be produced by graft polymerization of the fluororesin (A1) and the polysiloxane (A2). In other words, the fluorine-containing polysiloxane (A) can contain a graft polymer having a main chain derived from the fluororesin (A1) and a graft chain derived from the polysiloxane (A2). In this case, algae attached to the surface of the coated steel sheet 1 can be more easily removed. Although the exact reason for this is not clear, it is presumed to be due to the following reason. That is, the graft chains derived from the polysiloxane (A2) are aligned along the main chain derived from the fluororesin (A1), thereby forming a polymer brush structure having a brush-like morphology. The polymer brush structure formed by this polysiloxane (A2) can increase the water repellency and oil repellency of the coating layer 3, thereby making it more difficult for algae to adhere to the coated steel sheet 1. As a result, it becomes easier to remove algae that have adhered to the surface of the coated steel sheet 1.

[0030] The reaction product that produces the fluorine-containing polysiloxane (A) will now be described in detail.

[0031] As described above, the fluorine-containing polysiloxane (A) contains a fluororesin (A1) as a constituent. The fluororesin (A1) has structural units (a1) bonded by urethane bonds, and the structural units (a1) contain structural units (a11) having a radically polymerizable unsaturated bond. For example, the fluororesin (A1) can be obtained by reacting a fluororesin (A11) having a hydroxyl group with a radically polymerizable monomer (A12) having an isocyanate group. In other words, the fluororesin (A1) is a reaction product of reactive components including a fluororesin (A11) having a hydroxyl group and a radically polymerizable monomer (A12) having an isocyanate group. In this case, the radically polymerizable unsaturated bond in the structural unit (a11) can be derived from the radically polymerizable unsaturated bond in the radically polymerizable monomer (A12) having an isocyanate group.

[0032] The fluororesin (A11) having a hydroxyl group has, for example, at least one of a structural unit represented by the formula (1) and a structural unit represented by the formula (2).

[0033] [ka]

[0034] In formula (1), R1 and R2 are each independent of each other for each structural unit and are each a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 8 carbon atoms, a haloalkyl group having 1 to 10 carbon atoms substituted with one or more halogen atoms, or a haloaryl group having 6 to 8 carbon atoms substituted with one or more halogen atoms.

[0035] [ka]

[0036] In formula (2), R3 is independent for each structural unit. R3 is a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 8 carbon atoms, a haloalkyl group having 1 to 10 carbon atoms substituted with one or more halogen atoms, or a haloaryl group having 6 to 8 carbon atoms substituted with one or more halogen atoms. X is independent for each structural unit. X is OR4, CH2OR4, or COOR4. Examples of R4 include an alkylene group having 1 to 10 carbon atoms, a cycloalkylene group having 6 to 10 carbon atoms, and an alkylidene group having 2 to 10 carbon atoms.

[0037] The hydroxyl value of the hydroxyl group-containing fluororesin (A11) is 5 mgKOH / g or more and 250 mgKOH / g or less. If the hydroxyl value is 5 mgKOH / g or more, the hydroxyl group-containing fluororesin (A11) can have an appropriate amount of hydroxyl groups, and the reaction between the hydroxyl group-containing fluororesin (A11) and the radically polymerizable monomer (A12) having an isocyanate group can proceed efficiently. If the hydroxyl value is 250 mgKOH / g or less, the compatibility between the fluororesin (A1) and the polysiloxane (A2) can be improved. Therefore, the polymerization between the fluororesin (A1) and the polysiloxane (A2) can proceed efficiently. The hydroxyl value is preferably 10 mgKOH / g or more, more preferably 20 mgKOH / g or more. The hydroxyl value is preferably 200 mgKOH / g or less, more preferably 120 mgKOH / g or less.

[0038] The hydroxyl group-containing fluororesin (A11) contains at least one selected from the group consisting of, for example, vinyl ether-based fluororesins, allyl ether-based fluororesins, vinyl carboxylate / acrylic ester-based fluororesins, and vinyl ether / vinyl carboxylate-based fluororesins.

[0039] The hydroxyl group-containing fluororesin (A11) may be, for example, a commercially available product. Examples of commercially available products include Lumiflon (registered trademark) LF-100, LF-200, LF-300, LF-400, LF-554, LF-600, and LF986N manufactured by Asahi Glass Co., Ltd.; Cerafulcoat (registered trademark) PX-40, A606X, A202B, and CF-803 manufactured by Central Glass Co., Ltd.; Zaflon (registered trademark) FC-110, FC-220, FC-250, FC-275, FC-310, FC-575, and XFC-973 manufactured by Toagosei Co., Ltd.; Zeffle (registered trademark) GK-510 manufactured by Daikin Industries, Ltd.; and Fluonate (registered trademark) K-700, K-702, K-703, K-704, and K-705 manufactured by DIC Corporation.

[0040] The radically polymerizable monomer (A12) having an isocyanate group contains, for example, at least one of a compound represented by formula (3) and a compound represented by formula (4).

[0041] [ka]

[0042] In formula (3), R5 is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. Examples of the aryl group include a phenyl group. Examples of the cycloalkyl group include a cyclohexyl group. R6 is an oxygen atom, an alkylene group having 1 to 10 carbon atoms, an alkylidene group having 1 to 10 carbon atoms, an arylene group having 1 to 10 carbon atoms, or a cycloalkylene group having 1 to 10 carbon atoms.

[0043] [ka]

[0044] In formula (4), R7 is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. Examples of the aryl group include a phenyl group. Examples of the cycloalkyl group include a cyclohexyl group. R8 is an oxygen atom, an alkylene group having 1 to 10 carbon atoms, an alkylidene group having 1 to 10 carbon atoms, an arylene group having 1 to 10 carbon atoms, or a cycloalkylene group having 1 to 10 carbon atoms.

[0045] Furthermore, the radical polymerizable monomer (A12) having an isocyanate group may contain, as a specific compound, at least one selected from the group consisting of methacryloyl isocyanate, 2-isocyanatoethyl methacrylate, m-isopropenyl-α,α-dimethylbenzyl isocyanate, p-isopropenyl-α,α-dimethylbenzyl isocyanate, and the like.

[0046] The radical polymerizable monomer (A12) having an isocyanate group is preferably reacted with the fluororesin (A11) having a hydroxyl group in an amount of 0.001 mol or more and 0.1 mol or less per equivalent of hydroxyl group. If the amount is 0.001 mol or more, the graft copolymerization of the fluororesin (A1) with the polysiloxane (A2) proceeds easily. If the amount is 0.1 mol or less, gelation that occurs during the graft polymerization of the fluororesin (A1) with the polysiloxane (A2) can be suppressed.

[0047] As described above, the fluorine-containing polysiloxane (A) contains the polysiloxane (A2) as a constituent component. The polysiloxane (A2) has a radically polymerizable unsaturated bond at one end of the molecular chain. Examples of the radically polymerizable unsaturated bond include an acrylic group, a methacrylic group, a vinyl group, and an allyl group.

[0048] The polysiloxane (A2) contains, for example, at least one of a compound represented by formula (5) and a compound represented by formula (6).

[0049] [ka]

[0050] In formula (5), R9 is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms. Examples of this hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a phenyl group, and a cyclohexyl group. R9 is preferably a hydrogen atom or a methyl group. In formula (5), R10, R11, R12, R13, and R14 may be the same or different and are each a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms. Examples of the hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a phenyl group, and a cyclohexyl group. It is preferable that R10, R11, R12, and R13 are each a methyl group or a phenyl group, and that R14 is a methyl group, a butyl group, or a phenyl group. In formula (5), n is an integer of 2 or greater, preferably an integer of 10 or greater, and more preferably an integer of 30 or greater.

[0051] [ka]

[0052] In formula (6), R15 is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms. Examples of the hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a phenyl group, and a cyclohexyl group, and preferably a hydrogen atom or a methyl group. R16, R17, R18, R19, and R20 may be the same or different and are each a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms. Examples of the hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a phenyl group, and a cyclohexyl group, and preferably R16, R17, R18, and R19 are each a methyl group or a phenyl group, and R20 is a methyl group, a butyl group, or a phenyl group. Furthermore, p is an integer of 0 to 10, and preferably 3. Furthermore, q is an integer of 2 or greater, preferably an integer of 10 or greater, and more preferably an integer of 30 or greater.

[0053] Commercially available polysiloxanes (A2) can be used, such as Silaplane (registered trademark) FM-0711 (number average molecular weight 1000), FM-0721 (number average molecular weight 5000), and FM-0725 (number average molecular weight 10000) manufactured by Chisso Corporation; and X-22-174DX (number average molecular weight 4600) manufactured by Shin-Etsu Chemical Co., Ltd.

[0054] The reactive components forming the fluorine-containing polysiloxane (A) may contain, in addition to the fluororesin (A1) and the polysiloxane (A2), at least one component selected from the group consisting of a monomer (A3) having an alkoxysilyl group, a monomer (A4) having a hydroxyl group, and other monomers (hereinafter, referred to as monomers (A5)).

[0055] The alkoxysilyl group-containing monomer (A3) may be, for example, a compound having a dialkoxysilyl group or a trialkoxysilyl group and a radically polymerizable unsaturated bond. Specifically, the alkoxysilyl group-containing monomer (A3) may contain at least one selected from the group consisting of γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane.

[0056] The hydroxyl group-containing monomer (A4) may be a compound having a hydroxyl group and a radically polymerizable unsaturated bond. Specifically, the hydroxyl group-containing monomer (A4) may contain at least one selected from the group consisting of 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0057] The monomer (A5) is a monomer different from the fluororesin (A1), the polysiloxane (A2), the monomer (A3) having an alkoxysilyl group, and the monomer (A4) having a hydroxyl group. The monomer (A5) may contain, for example, at least one selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, and n-butyl (meth)acrylate.

[0058] The fluorine-containing polysiloxane (A) can be obtained by polymerizing reactive components including the above-mentioned fluororesin (A1), polysiloxane (A2), alkoxysilyl group-containing monomer (A3), hydroxyl group-containing monomer (A4), and monomer (A5). The content of the fluororesin (A1) in the reactive components is preferably 2% by mass or more and 70% by mass or less. This content is more preferably 10% by mass or more. This content is more preferably 40% by mass or less. The content of the polysiloxane (A2) in the reactive components is preferably 5% by mass or more and 40% by mass or less. This content is more preferably 10% by mass or more. This content is more preferably 30% by mass or less. The content of the alkoxy group-containing monomer (A3) in the reactive components is preferably 5% by mass or more and 55% by mass or less. This content is more preferably 10% by mass or more. This content is more preferably 40% by mass or less. Furthermore, the content of the hydroxyl group-containing monomer (A4) relative to the reactive components is preferably 3% by mass or more and 50% by mass or less. This content is more preferably 20% by mass or more. This content is even more preferably 30% by mass or less. Furthermore, the content of the monomer (A5) relative to the reactive components is preferably more than 0% by mass and 85% by mass or less. This content is even more preferably 30% by mass or less. When these contents are within the above ranges, algae adhering to the coated steel sheet 1 can be more easily removed, and corrosion resistance can be improved.

[0059] The coating layer 3 can contain, in addition to the fluorine-containing polysiloxane (A), a resin different from the fluorine-containing polysiloxane (A) (hereinafter also referred to as resin (B)). The resin (B) can contain at least one resin selected from the group consisting of acrylic silicone resins, urethane silicone resins, fluorosilicone resins, etc. The content of resin (B) in the coating layer 3 is preferably 30 mass % or less. In this case, algae attached to the coated steel sheet 1 can be more easily removed.

[0060] The coating layer 3 may contain a filler. If the coating layer 3 contains a filler, the filler preferably has an average particle size of 20 μm or less. In this case, the durability of the coating layer 3 can be improved while maintaining the enhanced smoothness of the coating layer 3. The average particle size is more preferably 10 μm or less, even more preferably 8 μm or less, and particularly preferably 7 μm or less. The filler may contain at least one type selected from the group consisting of silica, glass beads, nylon beads, and acrylic beads. The filler content in the coating layer 3 is preferably 10% by mass or less. In this case, the enhanced smoothness of the surface of the coating layer 3 can be more easily maintained. This content is more preferably 1% by mass or less. Furthermore, it is particularly preferable that the coating layer 3 does not contain a filler. In this case, the enhanced smoothness of the surface of the coating layer 3 can be particularly maintained. This makes it difficult for algae to adhere to the coating layer 3.

[0061] 3. Characteristics of coated steel sheets The coated steel sheet 1 can have high corrosion resistance. More specifically, the coated steel sheet 1 can have high acid resistance and high alkali resistance. The corrosion resistance can be confirmed by the following method. First, a test piece measuring 50 mm x 120 mm is cut out from the coated steel sheet 1. Next, the cut end surface of this test piece is protected with PTFE tape or the like and immersed in a chemical solution. The corrosion resistance of the coated steel sheet 1 can be confirmed by visually checking the degree of corrosion. Examples of the chemical solution include hydrochloric acid, sulfuric acid, phosphoric acid, and an aqueous solution of sodium hydroxide.

[0062] The coated steel sheet 1 allows easy removal of algae attached to its surface. The following method can be used to confirm whether algae can be easily removed, i.e., algae removal performance. First, the coated steel sheet 1 is immersed in a culture solution for one month to allow algae to grow on the surface of the coated steel sheet 1. The algae attached to the surface are then dried and wiped off with a cloth in one stroke. After performing the same procedure three times (over three months), the appearance of the wiped area is visually inspected, and the degree of remaining algae is observed to confirm the algae removal performance. The culture solution used may contain at least one component selected from the group consisting of NO3, PO4, SO4, Na, K, Mg, Ca, NH4, etc.

[0063] 4. Application examples of coated steel sheets The coated steel plate 1 allows for easy removal of algae attached to its surface. Therefore, it can be suitably used to fabricate a plant cultivation container 10 for cultivating plants PL (see FIG. 2). When fabricating the coated steel plate 1, its size can be designed appropriately. Therefore, by using the coated steel plate 1 when fabricating the plant cultivation container 10, the plant cultivation container 10 can be made larger or longer.

[0064] The plant cultivation container 10 includes a container portion 11 that holds a culture solution 12. That is, the plant cultivation container 10 has a tray-like shape that is open at the top, and can store and hold the culture solution 12 in the container portion 11. The plant cultivation container 10 may also include a lid 14 that covers the container portion 11, thereby enabling the container portion 11 to be covered.

[0065] When a plant PL is cultivated using the plant cultivation container 10, the plant PL is accommodated in the container portion 11. For example, the plant cultivation container 10 is provided with a holding material 13 for holding the plant PL. The holding material 13 has holes so that the plant PL can be held, and the plant PL can be held by passing the plant PL through the holes. The holding material 13 is preferably formed from a material that is flexible and water-permeable. Note that the plant cultivation container 10 does not necessarily have to be provided with the holding material 13. In other words, the plant PL may be placed in the plant cultivation container 10 without being held by the holding material 13.

[0066] At least a portion of this container portion 11 is made from the coated steel plate 1. For example, the plant cultivation container 10 can be formed by folding the coated steel plate 1 so as to have the container portion 11 capable of holding the culture solution 12. In this embodiment, the coating layer 3 of the coated steel plate 1 can be exposed on the inner surface of the container portion 11, i.e., the surface facing the space that holds the culture solution 12.

[0067] When cultivating plants PL using the plant cultivation container 10, algae may grow in the container portion 11. However, because at least a portion of the container portion 11 is made of a coated steel plate 1, the attached algae can be easily removed by wiping it off with a rag or the like. This allows the plants PL to be cultivated efficiently. Furthermore, since excessive force is not required when wiping off attached algae with a rag or the like, the plant cultivation container 10 is less likely to be damaged. This allows the corrosion resistance of the plant cultivation container 10 to be maintained.

[0068] The culture solution 12 is a liquid containing nutrients necessary for cultivating the plant PL. For example, the culture solution 12 contains a fertilizer. The fertilizer contains at least one element selected from the group consisting of phosphorus, magnesium, nitrogen, etc.

[0069] The pH of the culture solution 12 is maintained at approximately 5.5 to 7.0 from the viewpoint of growth management of the plant PL. However, this may fluctuate within a range of 3 to 9 during the cultivation of the plant PL. Therefore, appropriate chemicals may be added to the culture solution 12 as needed to adjust the pH. The chemicals include at least one selected from the group consisting of sulfuric acid, phosphoric acid, nitric acid, sodium hydroxide, potassium hydroxide, etc.

[0070] In this way, although the culture solution 12 may contain fertilizers and chemicals, the plant cultivation container 10 has high chemical resistance because it is made from the coated steel plate 1. Therefore, even if the plant cultivation container 10 comes into contact with the culture solution 12 containing chemicals such as acids and alkalis, it is less likely to deteriorate, such as corrosion and cracks or holes caused by corrosion, and the burden of removing algae can be reduced over a long period of time.

[0071] Next, a method for cultivating a plant PL using the plant cultivation container 10 will be described. First, a culture solution 12 is stored in the container portion 11 of the plant cultivation container 10. An acid or alkali is added to the culture solution 12 so that the pH thereof is adjusted to a predetermined value (approximately 5.5 to 7.0 in this embodiment). Note that the pH of the culture solution 12 may fluctuate from the predetermined value during the cultivation of the plant PL. Therefore, the pH of the culture solution 12 is checked from time to time to maintain the pH of the culture solution 12 at the predetermined value. If it is determined that the pH of the culture solution 12 is outside the range of 5.5 to 7.0, the pH is maintained within the range by appropriately adding the above-listed acid or alkali.

[0072] Subsequently, the plant PL is held in the container portion 11 of the plant cultivation container 10 so that the roots of the plant PL are immersed in the culture solution 12. The plant PL is not particularly limited, but examples thereof include lettuce, herbs, strawberries, cilantro, edible flowers, medicinal plants, spinach, kale, Japanese mustard spinach, parsley, ice plant, arugula, celery, and mizuna. As already mentioned, when holding the plant PL in the container portion 11, a holding material 13 may be used, and it is preferable to hold the plant PL by passing the plant through holes in the holding material 13.

[0073] When cultivating the plants PL, light is emitted from the light source LS, thereby promoting the growth of the plants PL. The light source LS is specifically an LED, a fluorescent lamp, or the like, and is installed on the upper side of the plant cultivation container 10. For example, the light source LS may be installed on the surface of the coated steel sheet 1 opposite to the surface on which the coating film layer 3 is arranged (hereinafter also referred to as the back surface).

[0074] During the process of cultivating the plants PL, algae may grow in the plant cultivation container 10, and this algae is removed by wiping it off with a rag or the like. By doing so, the plant cultivation container 10 can be kept clean, and the growth of the plants PL is less likely to be inhibited by the algae. Furthermore, as described above, algae attached to the plant cultivation container 10 made from the coated steel sheet 1 can be easily removed. This reduces the time and effort required to remove the algae.

[0075] By using such a method, the plant PL can be cultivated using the plant cultivation container 10. For example, the plant cultivation container 10 can be suitably used when cultivating the plant PL in a plant factory. Note that the above-described plant cultivation method is merely an example. In other words, the method for cultivating the plant PL using the plant cultivation container 10 is not limited to the above-described method.

[0076] 5. Variations The coated steel sheet 1 described in the above embodiment further includes a plating layer 5 covering the surface of the steel sheet 2 facing the coating film layer 3, with the plating layer 5 being interposed between the steel sheet 2 and the coating film layer 3, but this is not limiting. In other words, the coated steel sheet 1 does not have to include the plating layer 5 covering the surface of the steel sheet 2 facing the coating film layer 3. The coated steel sheet 1 may also further include a chemical conversion treatment layer interposed between the coating film layer 3 and the plating layer 5. In this case, the corrosion resistance of the coated steel sheet 1 can be improved.

[0077] In the above embodiment, the coated steel sheet 1 includes the intermediate layer 4, but the present invention is not limited to this. In other words, the coated steel sheet 1 does not necessarily have to include the intermediate layer 4.

[0078] In the above embodiment, the coated steel sheet 1 is used to fabricate the plant cultivation container 10, but the present invention is not limited to this.

[0079] 6. Aspects As is apparent from the above embodiments, the present disclosure includes the following aspects.

[0080] A coated steel sheet (1) according to a first aspect of the present disclosure comprises a steel sheet (2) and a coating layer (3) disposed on the steel sheet (2). The surface of the coating layer (3) has a contact angle with water of 82° or more and 130° or less, and a contact angle with ethylene glycol of 70° or more and 120° or less. The ten-point average roughness (Rzjis) of the surface of the coating layer (3) is more than 0 μm and 20 μm or less.

[0081] According to this embodiment, it is possible to provide a coated steel sheet (1) from which attached algae can be easily removed.

[0082] A coated steel sheet (1) according to a second aspect of the present disclosure is the first aspect, wherein the coating layer (3) contains a fluorine-containing polysiloxane (A). The fluorine-containing polysiloxane (A) is a reaction product of reactive components including a fluororesin (A1) and a polysiloxane (A2). The fluororesin (A1) has structural units (a1) bonded by urethane bonds, and the structural units (a1) contain structural units (a11) having a radically polymerizable unsaturated bond. The polysiloxane (A2) has a radically polymerizable unsaturated bond at one end of the molecular chain.

[0083] A coated steel sheet (1) according to a third aspect of the present disclosure comprises a steel sheet (2) and a coating layer (3) disposed on the steel sheet (2). The coating layer (3) contains a fluorine-containing polysiloxane (A). The fluorine-containing polysiloxane (A) is a reaction product of reactive components including a fluororesin (A1) and a polysiloxane (A2). The fluororesin (A1) has structural units (a1) bonded by urethane bonds, and the structural units (a1) contain structural units (a11) having a radically polymerizable unsaturated bond. The polysiloxane (A2) has a radically polymerizable unsaturated bond at one end of the molecular chain.

[0084] According to this embodiment, it is possible to provide a coated steel sheet (1) from which attached algae can be easily removed.

[0085] The coated steel sheet (1) according to a fourth aspect of the present disclosure is any one of the first to third aspects, in which the coating layer (3) does not contain a filler, or the coating layer (3) contains a filler, and the average particle size of the filler is 20 μm or less.

[0086] The coated steel sheet (1) according to a fifth aspect of the present disclosure is any one of the first to fourth aspects, further comprising an intermediate layer (4) between the steel sheet (2) and the coating layer (3).

[0087] A coated steel sheet (1) according to a sixth aspect of the present disclosure is any one of the first to fifth aspects, further comprising a plating layer (5) covering the surface of the steel sheet (2) on the coating layer (3) side. The plating layer (5) is interposed between the steel sheet (2) and the coating layer (3). The plating layer (5) contains at least one of zinc and aluminum.

[0088] A plant cultivation container (10) according to a seventh aspect of the present disclosure includes a container portion (11) that holds a culture solution (12). At least a portion of the container portion (11) is made from the coated steel sheet (1) according to any one of the first to sixth aspects. [Example]

[0089] More specific examples of this embodiment will be presented below, but this embodiment is not limited to the following examples.

[0090] [How to prepare coated steel sheets] Examples 1 to 10 A polyester resin paint (Dainippon Toryo Co., Ltd., product number "V Knit #156N") was applied as a primer to the surface of a 0.35 mm thick steel plate and baked for 30 seconds at a maximum temperature of 200°C to form a primer layer. Next, a polyester resin paint (Dainippon Toryo Co., Ltd., product number "V Knit #7520", containing a high molecular weight polyester with a molecular weight of 12,000) was applied as an intermediate coat on top of the primer layer and baked for 30 seconds at a maximum temperature of 220°C to dry and harden the applied paint, forming an intermediate coat. In this way, an intermediate layer 4 consisting of the primer layer and intermediate coat layer was formed. The polyester resin paint contained in the intermediate coat may contain a filler as needed.

[0091] Next, a paint containing fluorine-containing polysiloxane (product number "V Magic #10" manufactured by Dai Nippon Toryo Co., Ltd.) was applied as a top coat to the surface of the intermediate layer 4 (primer layer and intermediate layer), and the paint was dried and cured for 40 seconds at a maximum temperature of 230°C to form a coating layer 3 (top coat layer). A coated steel plate 1 was produced using this procedure.

[0092] In Example 8 only, coated steel plate 1 was produced without forming an intermediate coating layer.

[0093] <Method for preparing a coating material containing fluorine-containing polysiloxane> The paint containing fluorine-containing polysiloxane used in the above top coat paint (product number "V Magic #10" manufactured by Dai Nippon Toryo Co., Ltd.) can be prepared by the following method.

[0094] A glass reactor equipped with a stirrer, thermometer, condenser, and dry nitrogen gas inlet was charged with 1,554 parts of Cefralcoat CF-803, 233 parts of xylene, and 6.3 parts of 2-isocyanatoethyl methacrylate, and heated to 80°C under a dry nitrogen gas atmosphere. The reaction was carried out at 80°C for 2 hours, and after confirming that the absorption of the isocyanate group had disappeared by infrared absorption spectroscopy of a sample of the reaction liquid, the reaction mixture was removed and a component with a nonvolatile content of 50% was obtained.

[0095] Next, 40 parts of the above components and 80 parts of butyl acetate were placed in a glass reactor equipped with a stirrer, thermometer, condenser, and dry nitrogen gas inlet and heated to 90°C in a nitrogen gas atmosphere. A premixed mixture of 20 parts of methyl methacrylate, 7 parts of 2-ethylhexyl methacrylate, 23 parts of 2-hydroxyethyl methacrylate, 10 parts of FM-0721, 20 parts of γ-methacryloxypropyltrimethoxysilane, 2 parts of Perbutyl O, and 22 parts of xylene was added dropwise at the same temperature over 2 hours. After maintaining the temperature for 2 hours, 1 part of Perbutyl O was added, and the mixture was further maintained at 90°C for 5 hours, yielding a solution containing the desired fluorine-containing polysiloxane with a nonvolatile content of 45% and a weight-average molecular weight of 58,000.

[0096] Then, 1 equivalent of Coronate (registered trademark) hx was added to the fluorine-containing polysiloxane relative to the hydroxyl group equivalent of the fluorine-containing polysiloxane, and the mixture was further diluted with butyl acetate so that the non-volatile content of the paint was 35% by weight. In this way, a paint containing fluorine-containing polysiloxane was prepared. Then, a top coat paint was prepared by blending a filler into this paint containing fluorine-containing polysiloxane as necessary.

[0097] The materials used in the above preparation method are as follows:

[0098] Fluorine resin having hydroxyl groups: Cerafulcoat (registered trademark) CF-803. Manufactured by Central Glass Co., Ltd. Hydroxyl value: 60. Number average molecular weight: 15,000.

[0099] Radically polymerizable monomer having an isocyanate group: 2-isocyanatoethyl methacrylate.

[0100] Polysiloxane: Silaplane (registered trademark) FM-0721, manufactured by Chisso Corporation. Number average molecular weight: 5000.

[0101] Radical polymerization initiator: Perbutyl (registered trademark) O. t-butylperoxy-2-ethylhexanoate, manufactured by Nippon Oil & Fats Corporation.

[0102] Hardener: Coronate® HX. Polyisocyanurate based on hexamethylene diisocyanurate. Manufactured by Tosoh Corporation.

[0103] Example 11 A coated steel sheet 1 was produced in a manner similar to that of Example 2, except that a fluororesin paint (product number "V Flon #5000" manufactured by Dai Nippon Toryo Co., Ltd., containing an isocyanate-crosslinked trifluoride type (FEVE) fluororesin) was used as the topcoat paint. This trifluoride type fluororesin differs from the fluorine-containing polysiloxane of Example 1, etc., in that it does not have polysiloxane or the like in its functional groups.

[0104] Example 12 A coated steel plate 1 was produced in a manner similar to that of Example 1, except that a polyester resin paint (product number "FLC5100" manufactured by Nippon Paint Industrial Coatings) was used as the topcoat paint. The topcoat paint was baked and dried for 30 seconds.

[0105] (Comparative Example 1) A coated steel plate 1 was produced in a manner similar to that of Example 1, except that a polyester resin paint (product number "200HQ" manufactured by Nippon Paint Industrial Coatings) was used as the topcoat paint and no intermediate coat layer was provided. The topcoat paint was baked and dried to a maximum temperature of 220°C for 30 seconds.

[0106] (Comparative Example 2) Coated steel plate 1 was produced in a manner similar to that of Example 1, except that a fluororesin paint (product number "Dickflow C", difluoride type, manufactured by Nippon Paint Industrial Coating) was used as the topcoat paint and no intermediate coat layer was provided. The topcoat paint was baked and dried to a maximum temperature of 250°C for 45 seconds. This difluoride type fluororesin differs from the fluorine-containing polysiloxane of Example 1, etc., in that it does not have polysiloxane or the like in its functional groups.

[0107] (Comparative Example 3) An acrylic resin plate was used instead of a steel plate with a coating film formed thereon.

[0108] [Ingredients] Regarding the components contained in the primer layer, the resin components contained in the paint are shown in Tables 1 to 3.

[0109] Regarding the components contained in the intermediate coating layer, Tables 1 to 3 show the resin components contained in the paint, the presence or absence of filler, the type of filler, the average particle size of the filler, and the filler content.

[0110] Regarding the components contained in the topcoat layer, Tables 1 to 3 show the resin components contained in the paint, the presence or absence of filler, the type of filler, the average particle size of the filler, and the filler content.

[0111] [About the characteristics] Regarding the characteristics of the undercoat layer, the film thickness is shown in Tables 1 to 3.

[0112] Regarding the properties of the intermediate layer, the film thickness is shown in Tables 1 to 3.

[0113] The properties of the topcoat layer, such as film thickness, ten-point average roughness (Rzjis), contact angle with water, contact angle with ethylene glycol, and surface free energy, are shown in Tables 1 to 3.

[0114] The film thickness, surface roughness (Rzjis), contact angle with water, contact angle with ethylene glycol, and surface free energy were measured by the following methods.

[0115] (film thickness) The coated steel sheet 1 was cut along the direction in which the layers overlapped. Next, five points were selected at random from the cross section of the obtained coated steel sheet 1, and each point was observed using a scanning electron microscope (SEM) to measure the film thickness of the coating layer 3. The values ​​calculated by averaging the measurements at the five points are shown in the table.

[0116] (surface roughness) The ten-point average roughness Rzjis of the coating layer 3 was measured at three points using a roughness measuring device in accordance with JIS B 0601-2001, and the average value was taken as the ten-point average roughness Rzjis.

[0117] (contact angle with water) Water was dropped onto the surface of the coating layer 3, and the contact angle of the coating layer 3 with the water was measured using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd.).

[0118] (Contact angle to ethylene glycol) Ethylene glycol was dropped onto the surface of the coating layer 3, and the contact angle of the coating layer 3 with the ethylene glycol was measured using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd.).

[0119] (surface free energy) The surface free energy value of the coating layer 3 was calculated from the obtained measured values ​​of the contact angles of water and ethylene glycol based on the Owens-Wendt equation and the Young equation.

[0120] [evaluation] (Corrosion resistance (chemical resistance)) A 50 mm × 120 mm test piece was cut out from the coated steel sheet 1. The cut end surface of the test piece was then protected with PTFE tape and immersed in a chemical solution for 72 hours. The area of ​​paint blistering at this time was visually confirmed, and the corrosion resistance of the coated steel sheet 1 was evaluated according to the following criteria. 5% hydrochloric acid was used as the chemical solution.

[0121] A: There is no swelling of the coating film in the immersed area, or swelling of the coating film in the immersed area is less than 10% of the area B: The swelling of the coating film in the immersed area is 10% or more but less than 50% of the area. C: The immersed area has blistered more than 50% of the coating.

[0122] (Algae removal performance) A plant PL (spinach) was cultivated for 30 days using a plant cultivation container 10 in which part of the container portion 11 was made of a painted steel plate 1. After drying the algae adhering to the plant cultivation container 10, the container was rubbed back and forth once with a dry cloth. The same procedure was carried out three times (i.e., for a total of 90 days) on the same spot, and the ease of removing the algae when rubbed the third time (on the 90th day) and the appearance of the rubbed area were visually observed to observe the degree of remaining algae, and the results were evaluated according to the following criteria.

[0123] A: When wiping off the algae, there is no resistance and more than 90% of the algae attached to the wiped area can be removed. B: Although there is some resistance, wiping the algae with a little force can remove more than 90% of the algae attached to the wiped area. C: There is some resistance, but wiping the algae with some force removes 70% to less than 90% of the algae adhering to the wiped area. D: There is some resistance, but by wiping the algae with force, 70% to less than 90% of the algae attached to the wiped area can be removed. E: There is some resistance, but by wiping the algae with force, 40% to less than 70% of the algae attached to the wiped area can be removed. F: Vigorous wiping of the algae removes less than 40% of the algae present in the wiped area.

[0124] [Table 1]

[0125] [Table 2]

[0126] [Table 3] [Explanation of symbols]

[0127] 1. Painted steel plate 2 steel plate 3 Coating layer 4. Middle class 5 plating layer 10 Plant cultivation containers 11 Container section 12 Culture solution 13 Retaining material 14 Lid PL plant LS light source

Claims

1. A steel plate and a coating layer disposed on the steel plate, the contact angle of the surface of the coating layer with water is 82° or more and 130° or less, and the contact angle with ethylene glycol is 70° or more and 120° or less; The ten-point average roughness of the surface is more than 0 μm and 20 μm or less. Painted steel plate.

2. the coating layer contains a fluorine-containing polysiloxane (A), The fluorine-containing polysiloxane (A) is a reaction product of reactive components including a fluorine-containing resin (A1) and a polysiloxane (A2), the fluororesin (A1) has structural units (a1) bonded by urethane bonds, the structural units (a1) contain structural units (a11) having a radically polymerizable unsaturated bond, The polysiloxane (A2) has a radically polymerizable unsaturated bond at one end of the molecular chain. The coated steel sheet according to claim 1.

3. A steel plate and a coating layer disposed on the steel plate, the coating layer contains a fluorine-containing polysiloxane (A), The fluorine-containing polysiloxane (A) is a reaction product of reactive components including a fluorine-containing resin (A1) and a polysiloxane (A2), the fluororesin (A1) has structural units (a1) bonded by urethane bonds, the structural units (a1) contain structural units (a11) having a radically polymerizable unsaturated bond, The polysiloxane (A2) has a radically polymerizable unsaturated bond at one end of the molecular chain. Painted steel plate.

4. the coating layer does not contain a filler, or the coating layer contains a filler, and the average particle size of the filler is 20 μm or less; The coated steel sheet according to any one of claims 1 to 3.

5. An intermediate layer is further provided between the steel plate and the coating layer. The coated steel sheet according to any one of claims 1 to 3.

6. The steel sheet further includes a plating layer covering a surface of the steel sheet on the coating layer side, the plating layer being interposed between the steel sheet and the coating layer, The plating layer contains at least one of zinc and aluminum. The coated steel sheet according to any one of claims 1 to 3.

7. A container for holding a culture solution is provided. At least a part of the container part is made from the coated steel plate according to any one of claims 1 to 3. Plant cultivation container.

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