Hydrophilic coating film and method for forming coating film of hydrophilic coating film

Abstract

[Problem] To provide: a hydrophilic coating film which is capable of preventing the occurrence of cracks even when compressive force, tensile force, or shearing force due to thermal expansion or thermal contraction of a metal substrate acts thereon; and a method for forming a coating film of the hydrophilic coating film. [Solution] This hydrophilic coating film 10A is formed of: an inorganic porous coating film 13a which has an inorganic nanoporous structure wherein inorganic fine particles 14 adjacent to each other among a large number of inorganic fine particles 14 are partially connected to each other, and in which a large number of nano-sized voids 15 are formed between the inorganic fine particles 14 that form the inorganic nanoporous structure; and a hydrophilic organic polymer 16 which enters the voids 15 of the inorganic porous coating film 13a and is cured in the voids 15 so as to be bonded to the inorganic fine particles 14. The hydrophilic organic polymer 16 is firmly bonded to a coating surface 12 of a metal substrate 11, and even if there is a difference in thermal expansion or thermal contraction due to a temperature change between the hydrophilic coating film 10A and the metal substrate 11, the occurrence of cracks in the hydrophilic coating film 10A can be prevented.

Description

Hydrophilic coating film, method for forming a hydrophilic coating film.

[0001] The present invention relates to a hydrophilic coating film applied to the coated surface of a metal substrate, and to a method for forming a coating film to form a hydrophilic coating film on the coated surface of a predetermined metal substrate.

[0002] A coating film is disclosed which has a visible light transmittance of 85% or more, a water contact angle of 5° or less after 24 hours of black light irradiation, and is formed from at least one binder component selected from alkoxysilane, its partially hydrolyzed condensate, and its hydrolysis product, and a photocatalyst (see Patent Document 1). Because this coating film is formed from inorganic components, it has high hardness, and the surface on which the coating film is formed is covered and protected by the coating film.

[0003] Japanese Patent Publication No. 2008-100122

[0004] The coating disclosed in Patent Document 1, when formed on the surface of a metal plate, cannot follow the thermal expansion or contraction of the metal plate due to the difference in thermal expansion coefficients between the coating and the metal plate, when the metal plate undergoes thermal expansion or contraction due to temperature changes. Compressive, tensile, and shear forces due to the thermal expansion or contraction of the metal plate act on the coating, which may cause cracks to form in weak areas of the coating.

[0005] The object of the present invention is to provide a hydrophilic coating film and a method for forming such a coating film that can follow the thermal expansion or contraction of a metal substrate and prevent the occurrence of cracks even when compressive, tensile, or shear forces are applied due to the thermal expansion or contraction of the metal substrate. Another object of the present invention is to provide a hydrophilic coating film and a method for forming such a coating film that has excellent hydrophilicity and can quickly and easily wash away or wipe away dirt such as dust adhering to the surface.

[0006] The first premise of the present invention for solving the aforementioned problems is a hydrophilic coating film that is coated on the coating surface of a predetermined metal substrate.

[0007] The hydrophilic coating film of the present invention, as described in the first premise above, is characterized in that the hydrophilic coating film is formed from an inorganic porous coating film having an inorganic nanoporous structure in which adjacent inorganic nanoparticles among a large number of inorganic nanoparticles are partially connected to each other, and a large number of nano-sized voids are formed between these inorganic nanoparticles that make up the inorganic nanoporous structure, and a hydrophilic organic polymer that penetrates into these voids of the inorganic porous coating film, hardens in those voids, and bonds to the inorganic nanoparticles, and the hydrophilic organic polymer is firmly bonded to the coating surface of the metal substrate, and even if there is a difference in thermal expansion or contraction due to temperature changes between the hydrophilic coating film and the metal substrate, it is possible to prevent the occurrence of cracks in the hydrophilic coating film.

[0008] As an example of a hydrophilic coating film according to the present invention, in a hydrophilic coating film, the hydrophilic organic polymer cured in the voids has a predetermined flexibility, the hydrophilic organic polymer can change shape in the voids, and when a difference in thermal expansion or contraction occurs between the hydrophilic coating film and the metal substrate due to temperature changes, the hydrophilic organic polymer freely changes shape in the voids, and the hydrophilic coating film follows the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate, thereby preventing the occurrence of cracks in the hydrophilic coating film when thermal expansion or contraction occurs in the hydrophilic coating film and the metal substrate.

[0009] Another example of the hydrophilic coating film according to the present invention is a metal substrate which is any of the following: iron plate, various stainless steel plates, copper plate, copper alloy plate, aluminum plate, aluminum alloy plate, magnesium alloy plate, duralumin plate, tin alloy plate, steel plate, nickel plate, or zinc plate.

[0010] Another example of a hydrophilic coating film according to the present invention is one in which the water contact angle of the hydrophilic coating film, as measured according to JIS R3257, is 40° or less.

[0011] Another example of a hydrophilic coating film according to the present invention is an ionic polymer in which the hydrophilic organic polymer contains at least one of a betaine moiety, a cationic moiety, and an anionic moiety.

[0012] Another example of a hydrophilic coating film according to the present invention is one in which the hydrophilic organic polymer contains metal ions.

[0013] Another example of a hydrophilic coating film according to the present invention is made by impregnating a hydrophilic organic polymer into numerous nano-sized voids of an inorganic porous coating film, which is produced by a sol-gel method using at least one of silica sol, alumina sol, zirconia sol, titania sol, and ceria sol in which inorganic nanoparticles are dispersed.

[0014] Another example of a hydrophilic coating film according to the present invention is one in which a hydrophilic organic polymer penetrates into the voids of an inorganic porous coating film while coating the surface of the inorganic porous coating film.

[0015] Another example of a hydrophilic coating film according to the present invention is one in which the uppermost layer of the hydrophilic organic polymer is located slightly below the surface of the inorganic porous coating film, and the portion of the inorganic porous coating film that is exposed above the uppermost layer of the hydrophilic organic polymer forms fine irregularities on the surface of the hydrophilic coating film and is coated with an ultrathin film of hydrophilic organic polymer.

[0016] As another example of a hydrophilic coating film according to the present invention, when the hydrophilic coating film is 1. exposed to a high temperature atmosphere of 250°C and 2. rapidly cooled to room temperature, no cracks occur in the hydrophilic coating film.

[0017] Another example of a hydrophilic coating film according to the present invention is one in which the film thickness of the hydrophilic coating film is in the range of 0.01 to 5 μm.

[0018] Another example of a hydrophilic coating film according to the present invention is one in which the film thickness of the hydrophilic coating film is in the range of 0.1 to 0.6 μm.

[0019] Another example of a hydrophilic coating film according to the present invention is a hydrophilic organic polymer containing metal ions Ag. ＋ Ions and Cu ２＋ Ions and Zn ２＋ It is at least one of the ions.

[0020] A second premise of the present invention for solving the aforementioned problems is a method for forming a coating film that forms a hydrophilic coating film on the coating surface of a predetermined metal substrate.

[0021] The first feature of the coating film formation method of the present invention in the second premise described above is that the coating film formation method comprises a coating step of coating the coating surface of a metal substrate with at least one of silica sol, alumina sol, zirconia sol, titania sol, and ceria sol, which contains a large number of nano-sized inorganic fine particles dispersed in it; a film formation step of drying the silica sol, alumina sol, zirconia sol, titania sol, and ceria sol coated on the coating surface of the metal substrate to form an inorganic porous coating film in which adjacent inorganic fine particles are partially connected to each other and a large number of nano-sized voids are formed between the inorganic fine particles; an infiltration step of infiltrating the voids of the inorganic porous coating film with a hydrophilic organic polymer (ionic polymer); and a drying and bonding step of drying the hydrophilic organic polymer infiltrated into the voids of the inorganic porous coating film to cure the hydrophilic organic polymer in the voids and bond the hydrophilic organic polymer to the inorganic fine particles.

[0022] The second feature of the coating film formation method of the present invention, as described in the second premise above, is that the coating film formation method comprises a coating step of coating the coating surface of a metal substrate with a coating liquid containing at least one of silica sol, alumina sol, zirconia sol, titania sol, and ceria sol, in which a large number of nano-sized inorganic fine particles are dispersed, and a hydrophilic organic polymer (ionic polymer); and a drying and bonding step of drying the coating liquid, partially linking adjacent inorganic fine particles among the large number of inorganic fine particles to form a large number of nano-sized voids between the inorganic fine particles, and curing the hydrophilic organic polymer that has penetrated the large number of nano-sized voids formed between the inorganic fine particles to bond the hydrophilic organic polymer to the inorganic fine particles.

[0023] The hydrophilic coating film according to the present invention is formed from an inorganic porous coating film having an inorganic nanoporous structure in which adjacent inorganic nanoparticles among a large number of inorganic nanoparticles are partially connected, and a large number of nano-sized voids are formed between these inorganic nanoparticles that make up the inorganic nanoporous structure, and a hydrophilic organic polymer that penetrates into these voids of the inorganic porous coating film, hardens in these voids, and bonds to the inorganic nanoparticles. The hydrophilic organic polymer is firmly bonded to the coating surface of the metal substrate, and the hydrophilic organic polymer is able to change shape (elastically deform) in these voids, so the hydrophilic coating film exhibits excellent flexibility, and even if thermal expansion or contraction occurs in the hydrophilic coating film and the metal substrate due to temperature changes, the hydrophilic coating film can follow the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate, and even if compressive, tensile, or shear forces act on the hydrophilic coating film due to the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate, it is possible to prevent the occurrence of cracks in the hydrophilic coating film, and the covering state of the hydrophilic coating film on the surface of the metal substrate can be maintained for a long period of time. The hydrophilic coating film possesses excellent hydrophilicity due to the hydrophilic organic polymer, allowing for quick and reliable washing or wiping away of dust and other dirt adhering to its surface. The bonding between inorganic fine particles and the hydrophilic organic polymer includes ionic bonds, covalent bonds, hydrogen bonds, and intermolecular forces such as polar attractive forces and van der Waals forces.

[0024] In a hydrophilic coating film, the hydrophilic organic polymer, which has hardened in numerous nano-sized voids between the inorganic nanoparticles that form an inorganic nanoporous structure, possesses a predetermined flexibility. Because the hydrophilic organic polymer can change shape in these voids between the inorganic nanoparticles, the hydrophilic coating film exhibits excellent flexibility. Even if thermal expansion or contraction occurs in the hydrophilic coating film and the metal substrate due to temperature changes, the hydrophilic organic polymer can freely change shape in these voids. The hydrophilic coating film can follow the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate. Even if compressive, tensile, or shear forces act on the hydrophilic coating film due to the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate, crack formation in the hydrophilic coating film can be prevented, and the coating state of the hydrophilic coating film on the surface of the metal substrate can be maintained for a long period of time.

[0025] The hydrophilic coating film is formed on iron plates, various stainless steel plates, copper plates, copper alloy plates, aluminum plates, aluminum alloy plates, magnesium alloy plates, duralumin plates, tin alloy plates, steel plates, nickel plates, and zinc plates. Even if thermal expansion or contraction occurs in the hydrophilic coating film and these various metal substrates due to temperature changes, the hydrophilic organic polymer can freely change shape in the voids between the inorganic fine particles. The hydrophilic coating film can follow the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate. Even if compressive, tensile, or shear forces act on the hydrophilic coating film due to the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate, crack formation in the hydrophilic coating film can be prevented, and the coating state of the hydrophilic coating film on the surface of these various metal substrates can be maintained for a long period of time.

[0026] The hydrophilic coating film has a water contact angle of 40° or less as measured according to JIS R3257. Therefore, the hydrophilic coating film has excellent hydrophilicity, and even if dirt such as dust adheres to its surface, the dirt can be quickly and easily washed away or wiped off, keeping the surface clean.

[0027] Because the hydrophilic coating film is an ionic polymer in which the hydrophilic organic polymer contains at least one of the betaine, cationic, and anionic moieties, the hydrophilic coating film exhibits excellent hydrophilicity and antifouling properties, reliably reduces the contact angle of water with the surface of the hydrophilic coating film, reliably increases the contact area of ​​water with the surface of the hydrophilic coating film, and when the hydrophilic coating film is washed with water, the water comes into contact with a wide area of ​​the surface of the hydrophilic coating film, making it easy to wash away dirt attached to the hydrophilic coating film with water.

[0028] Because hydrophilic coating films contain metal ions in a hydrophilic organic polymer, these metal ions exhibit excellent antiviral, antibacterial, and antifungal functions. This allows for the rapid elimination of viruses, bacteria, and mold that adhere to the hydrophilic coating film. Furthermore, the metal ions are not lost from the hydrophilic coating film prematurely, enabling the antiviral, antibacterial, and antifungal functions of the hydrophilic coating film to be maintained for a long period.

[0029] Hydrophilic coating films are made by impregnating an inorganic porous coating film, which is created by the sol-gel method using at least one of silica sol, alumina sol, zirconia sol, titania sol, or ceria sol containing dispersed inorganic nanoparticles, with hydrophilic organic polymers (ionic polymers). Therefore, they have an inorganic nanoporous structure created by the sol-gel method, and the hydrophilic organic polymers penetrate into numerous nanoscale fine voids in the inorganic nanoporous structure, and the hydrophilic organic polymers (hydrophilic organic films) bond to the voids of the inorganic porous coating film, while also undergoing shape changes within those voids. As a result, the hydrophilic coating film exhibits excellent flexibility, and even if thermal expansion or contraction occurs in the hydrophilic coating film and the metal substrate due to temperature changes, the hydrophilic organic polymer freely changes shape in the voids between them, allowing the hydrophilic coating film to follow the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate. Even if compressive, tensile, or shear forces act on the hydrophilic coating film due to the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate, crack formation in the hydrophilic coating film can be prevented, and the coating state of the hydrophilic coating film on the surface of the metal substrate can be maintained for a long period of time. The hydrophilic organic polymer does not peel off or disappear from the hydrophilic coating film prematurely due to stress from the usage environment, and the hydrophilic organic polymer remains in the hydrophilic coating film for a long period of time, preventing a decrease in hydrophilicity and antifouling properties in the hydrophilic coating film, and maintaining the hydrophilic and antifouling functions of the hydrophilic coating film for a long period of time. When a hydrophilic coating film contains metal ions in the hydrophilic organic polymer, it can prevent a decrease in its antiviral, antibacterial, and antifungal functions, thus maintaining these functions for a long period of time. The bonding between the inorganic porous coating film and the hydrophilic organic polymer (hydrophilic organic film) includes ionic bonds, covalent bonds, hydrogen bonds, and intermolecular forces such as polar attractive forces and van der Waals forces.

[0030] In a hydrophilic coating film, hydrophilic organic polymers penetrate into the voids of an inorganic porous coating film while covering its surface. The hydrophilic organic polymers change shape within the numerous nano-sized voids of the inorganic nanoporous structure, resulting in a hydrophilic coating film exhibiting excellent flexibility. Even if thermal expansion or contraction occurs in the hydrophilic coating film and metal substrate due to temperature changes, the hydrophilic organic polymers freely change shape within these voids, allowing the hydrophilic coating film to follow the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate. Even if compressive, tensile, or shear forces act on the hydrophilic coating film due to the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate, crack formation in the hydrophilic coating film can be prevented, and the coating state of the hydrophilic coating film on the surface of the metal substrate can be maintained for a long period of time. When a hydrophilic coating film contains metal ions in the hydrophilic organic polymer, the antiviral, antibacterial, and antifungal functions of the metal ions are rapidly activated, allowing for the rapid elimination of viruses, bacteria, and mold that adhere to the hydrophilic coating film. Furthermore, the metal ions are not lost prematurely from the hydrophilic coating film, allowing the antiviral, antibacterial, and antifungal functions of the hydrophilic coating film to be maintained for a long period of time. The hydrophilic coating film possesses excellent hydrophilicity due to the hydrophilic organic polymer covering the surface of the inorganic porous coating film, allowing for the rapid and reliable washing or wiping away of dust and other dirt adhering to its surface.

[0031] In the hydrophilic coating film, the uppermost layer of the hydrophilic organic polymer is located slightly below the surface of the inorganic porous coating film. The portion of the inorganic porous coating film exposed above the uppermost layer of the hydrophilic organic polymer forms fine irregularities on the surface of the hydrophilic coating film. Furthermore, the hydrophilic organic polymer changes shape within the numerous nano-sized voids of the inorganic nanoporous structure, resulting in the hydrophilic coating film exhibiting excellent flexibility. Even if thermal expansion or contraction occurs in the hydrophilic coating film and the metal substrate due to temperature changes, the hydrophilic organic polymer freely changes shape within these voids, allowing the hydrophilic coating film to follow the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate. Even if compressive, tensile, or shear forces act on the hydrophilic coating film due to the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate, crack formation in the hydrophilic coating film can be prevented, and the coating state of the hydrophilic coating film on the surface of the metal substrate can be maintained for a long period of time. When a hydrophilic coating film contains metal ions in the hydrophilic organic polymer, the antiviral, antibacterial, and antifungal functions of the metal ions are rapidly activated, allowing for the rapid elimination of viruses, bacteria, and mold that adhere to the hydrophilic coating film. Furthermore, the metal ions are not lost prematurely from the hydrophilic coating film, allowing the antiviral, antibacterial, and antifungal functions of the hydrophilic coating film to be maintained for a long period of time. The surface of the hydrophilic coating film becomes uneven due to the portion of the hydrophilic organic polymer that is exposed above the top layer of the inorganic porous coating film. This unevenness, along with the hydrophilic organic polymer, gives the hydrophilic coating film excellent hydrophilicity, allowing for the rapid and reliable washing or wiping away of dust and other dirt adhering to its surface.

[0032] When a hydrophilic coating film is subjected to 1. exposure to a high temperature of 250°C and 2. rapid cooling to room temperature, no cracks occur in the hydrophilic coating film. Therefore, even if compressive, tensile, or shear forces act on the hydrophilic coating film due to the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate, the hydrophilic coating film has excellent durability and can adequately protect the surface of the metal substrate to which it is coated, and the coating state of the hydrophilic coating film on the surface of the metal substrate can be maintained for a long period of time. It has been found that coating films that do not crack in this thermal shock test will not crack under outdoor use conditions, and coating films that crack in this thermal shock test will crack under outdoor use conditions.

[0033] Because the hydrophilic coating film has a thickness in the range of 0.01 to 5 μm, the hydrophilic coating film maintains a predetermined strength and can adequately protect the surface of the metal substrate to which it is coated. In the hydrophilic coating film, the hydrophilic organic polymer can change shape in the numerous nano-sized fine voids of the inorganic nanoporous structure, giving the hydrophilic coating film excellent flexibility. Even if thermal expansion or contraction occurs in the hydrophilic coating film and the metal substrate due to temperature changes, the hydrophilic organic polymer can freely change shape in those voids, allowing the hydrophilic coating film to follow the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate. Even if compressive, tensile, or shear forces act on the hydrophilic coating film due to the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate, crack formation in the hydrophilic coating film can be prevented, and the coating state of the hydrophilic coating film on the surface of the metal substrate can be maintained for a long period of time.

[0034] Because the hydrophilic coating film has a thickness in the range of 0.1 to 0.6 μm, the hydrophilic coating film maintains a predetermined strength and can adequately protect the surface of the metal substrate to which it is coated. In the hydrophilic coating film, the hydrophilic organic polymer can change shape in the numerous nano-sized fine voids of the inorganic nanoporous structure, giving the hydrophilic coating film excellent flexibility. Even if thermal expansion or contraction occurs in the hydrophilic coating film and the metal substrate due to temperature changes, the hydrophilic organic polymer can freely change shape in those voids, allowing the hydrophilic coating film to follow the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate. Even if compressive, tensile, or shear forces act on the hydrophilic coating film due to the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate, crack formation in the hydrophilic coating film can be prevented, and the coating state of the hydrophilic coating film on the surface of the metal substrate can be maintained for a long period of time.

[0035] The hydrophilic coating film contains metal ions (Ag) within the hydrophilic organic polymer. ＋ Ions and Cu ２＋ Ions and Zn ２＋ Since it is at least one of the ions, these metal ions provide excellent antiviral, antibacterial, and antifungal functions, allowing for the rapid elimination of viruses, bacteria, and mold that adhere to the hydrophilic coating film. Furthermore, the metal ions are not lost from the hydrophilic coating film prematurely, allowing the antiviral, antibacterial, and antifungal functions of the hydrophilic coating film to be maintained for a long period of time.

[0036] The present invention provides a coating film formation method comprising: a coating step of coating the coating surface of a metal substrate with at least one of silica sol, alumina sol, zirconia sol, titania sol, and ceria sol, which contains a large number of nano-sized inorganic fine particles dispersed in it; a film formation step of drying the silica sol, alumina sol, zirconia sol, titania sol, and ceria sol coated on the coating surface of the metal substrate to form an inorganic porous coating film in which adjacent inorganic fine particles are partially linked and a large number of nano-sized voids are formed between the inorganic fine particles; an impregnation step of impregnating these voids of the inorganic porous coating film with a hydrophilic organic polymer (ionic polymer); and a drying and bonding step of drying the hydrophilic organic polymer impregnated into these voids of the inorganic porous coating film to cure the hydrophilic organic polymer in those voids and bond the hydrophilic organic polymer to the inorganic fine particles. This method makes it possible to create a hydrophilic coating film in which the hydrophilic organic polymer can change shape in the large number of nano-sized voids, and to create a hydrophilic coating film that exhibits excellent flexibility. The coating film formation method allows the hydrophilic organic polymer to freely change shape in the voids between the hydrophilic coating film and the metal substrate, even if thermal expansion or contraction occurs due to temperature changes. This allows the hydrophilic coating film to follow the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate. Even if compressive, tensile, or shear forces act on the hydrophilic coating film due to the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate, it is possible to prevent the occurrence of cracks in the hydrophilic coating film and to create a hydrophilic coating film that can maintain its coverage on the surface of the metal substrate for a long period of time. The coating film formation method also allows for the creation of a hydrophilic coating film that possesses excellent hydrophilicity due to the hydrophilic organic polymer, and can quickly and reliably wash away or wipe away dirt such as dust adhering to its surface.The coating film formation method, when using a hydrophilic organic polymer containing metal ions, can impart the antiviral and antibacterial functions of the metal ions, enabling the creation of a hydrophilic coating film that exhibits excellent antiviral, antibacterial, and antifungal functions, and that can reliably kill various viruses, bacteria, and fungal hyphae that adhere to the film in a short time after attachment. In this coating film formation method, because the hydrophilic organic polymer (ionic polymer) containing metal ions penetrates the voids of the porous film, the antiviral, antibacterial, and antifungal functions of the metal ions can be rapidly expressed, and the metal ions are not lost prematurely, allowing for the creation of a hydrophilic coating film that can maintain its antiviral, antibacterial, and antifungal functions for a long period of time. The bonding between inorganic fine particles and the hydrophilic organic polymer includes ionic bonds, covalent bonds, hydrogen bonds, and intermolecular forces such as polar attraction and van der Waals forces.

[0037] According to the coating film formation method of the present invention, which comprises a coating step of coating the coating surface of a metal substrate with a coating liquid containing at least one of silica sol, alumina sol, zirconia sol, titania sol, and ceria sol in which a large number of nano-sized inorganic fine particles are dispersed, and a hydrophilic organic polymer (ionic polymer), and a drying and bonding step of drying the coating liquid, partially linking adjacent inorganic fine particles among the large number of inorganic fine particles to form a large number of nano-sized voids between the inorganic fine particles, and curing the hydrophilic organic polymer that has penetrated the large number of nano-sized voids formed between the inorganic fine particles to bond the hydrophilic organic polymer to the inorganic fine particles, a hydrophilic coating film can be made in which the hydrophilic organic polymer can change shape in the large number of nano-sized voids, and a hydrophilic coating film exhibiting excellent flexibility can be made. The coating film formation method allows the hydrophilic organic polymer to freely change shape in the voids between the hydrophilic coating film and the metal substrate, even if thermal expansion or contraction occurs due to temperature changes. This allows the hydrophilic coating film to follow the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate. Even if compressive, tensile, or shear forces act on the hydrophilic coating film due to the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate, it is possible to prevent the occurrence of cracks in the hydrophilic coating film and to create a hydrophilic coating film that can maintain its coverage on the surface of the metal substrate for a long period of time. The coating film formation method also allows for the creation of a hydrophilic coating film that possesses excellent hydrophilicity due to the hydrophilic organic polymer, and can quickly and reliably wash away or wipe away dirt such as dust adhering to its surface. The coating film formation method, when a hydrophilic organic polymer contains metal ions, can impart the antiviral and antibacterial functions of the metal ions, enabling the creation of a hydrophilic coating film that exhibits excellent antiviral, antibacterial, and antifungal functions, and that can reliably kill various viruses, bacteria, and fungal hyphae that adhere to the film in a short time after contact.In this coating film formation method, a hydrophilic organic polymer (ionic polymer) containing metal ions penetrates the voids of a porous membrane. This allows the antiviral, antibacterial, and antifungal functions of the metal ions to be rapidly expressed, and the metal ions are not lost prematurely. As a result, a hydrophilic coating film can be created that maintains these antiviral, antibacterial, and antifungal functions for a long period of time.

[0038] An illustrative diagram showing an example of an inorganic porous coating film formed on the coated surface of a metal substrate. An illustrative diagram showing an example of a hydrophilic coating film formed from the inorganic porous coating film of Figure 1 and a hydrophilic organic polymer. An illustrative diagram showing another example of a hydrophilic coating film formed from the inorganic porous coating film of Figure 1 and a hydrophilic organic polymer. An illustrative diagram showing another example of an inorganic porous coating film formed on the coated surface of a metal substrate. An illustrative diagram showing an example of a hydrophilic coating film formed from the inorganic porous coating film of Figure 4 and a hydrophilic organic polymer. Ag to betaine polymer ＋ Figure illustrating the introduction of ions. An illustrative diagram showing an example of shape change (plastic deformation) of a hydrophilic organic polymer (hydrophilic organic film) in the hydrophilic coating film shown in Figure 2. An illustrative diagram showing an example of shape change (plastic deformation) of a hydrophilic organic polymer (hydrophilic organic film) in the hydrophilic coating film shown in Figure 3. An illustrative diagram showing an example of shape change (plastic deformation) of a hydrophilic organic polymer (hydrophilic organic film) in the hydrophilic coating film shown in Figure 5. An illustrative diagram showing an example of shape change (plastic deformation) of a hydrophilic organic polymer (hydrophilic organic film) in the hydrophilic coating film shown in Figure 6. A diagram showing the contact angle of a water droplet dropped onto the hydrophilic coating film shown in Figure 2. A diagram showing the contact angle of a water droplet dropped onto the hydrophilic coating film shown in Figure 3. A diagram showing the contact angle of a water droplet dropped onto the hydrophilic coating film shown in Figure 5. A diagram showing the contact angle of a water droplet dropped onto the hydrophilic coating film shown in Figure 6. A flowchart showing an example of a method for forming a hydrophilic coating film. A flowchart showing another example of a method for forming a hydrophilic coating film.

[0039] Referring to the attached drawings, the details of the hydrophilic coating film and the coating film forming method for forming the hydrophilic coating film according to the present invention will be described below. FIG. 1 is a schematic diagram showing an example of an inorganic porous coating film 13a formed on a coating surface 12 of a metal substrate 11, and FIG. 2 is a schematic diagram showing an example of a hydrophilic coating film 10A formed from the inorganic porous coating film 13a of FIG. 1 and a hydrophilic organic polymer 16. FIG. 3 is a schematic diagram showing another example of a hydrophilic coating film 10B formed from the inorganic porous coating film 13a of FIG. 1 and the hydrophilic organic polymer 16, and FIG. 4 is a schematic diagram showing another example of an inorganic porous coating film 13b formed on the coating surface 12 of the metal substrate 11. FIG. 5 is a schematic diagram showing an example of a hydrophilic coating film 10C formed from the inorganic porous coating film 13b of FIG. 4 and the hydrophilic organic polymer 16, and FIG. 6 is a schematic diagram showing an example of a hydrophilic coating film 10D formed from the inorganic porous coating film 13b of FIG. 4 and the hydrophilic organic polymer 16. In FIGS. 1 to 6, the inorganic fine particles 14 and the voids 15 in the inorganic porous coating films 13a and 13b are illustrated as visually recognizable images, but the inorganic fine particles 14 and the voids 15 cannot be visually observed in practice.

[0040] The hydrophilic coating films 10A to 10D are formed (deposited) on the coating surface 12 (surface) of the metal substrate 11 to be coated. The hydrophilic coating films 10A to 10D are composed of the inorganic porous coating films 13a and 13b and the hydrophilic organic polymer 16. For forming the hydrophilic coating films 10A to 10D, an aqueous solution (inorganic coating liquid) for forming the inorganic porous coating films 13a and 13b is coated (applied) onto the coating surface 12 of the metal substrate 11. After forming the inorganic porous coating films 13a and 13b on the coating surface 12 of the metal substrate 11, an aqueous solution (organic coating liquid) containing a hydrophilic organic polymer (ionic polymer), or a hydrophilic organic polymer (ionic polymer) and a metal ion (Ag ＋ ion and Cu ２＋ ion and Zn２＋ It is made by coating (applying) an aqueous solution (organic coating solution) containing at least one of the ions.

[0041] Alternatively, the hydrophilic coating films 10A to 10D form inorganic porous coating films 13a and 13b on the coating surface 12 of the metal substrate 11, and also contain an aqueous solution (organic coating solution) containing a hydrophilic organic polymer (ionic polymer), or a hydrophilic organic polymer (ionic polymer) and metal ions (Ag ＋ Ions and Cu ２＋ Ions and Zn ２＋ It is made by coating (applying) an aqueous solution (organic coating solution) containing at least one of the following ions. The hydrophilic coating films 10A to 10D have hydrophilic and antifouling functions due to the inclusion of hydrophilic organic polymers, and have antiviral, antibacterial, antifungal, and deodorizing functions due to the inclusion of metal ions.

[0042] The metal substrate 11 on which the hydrophilic coating films 10A to 10D are formed is one of the following: iron plate, various types of stainless steel plate, copper plate, copper alloy plate, aluminum plate, aluminum alloy plate, magnesium alloy plate, duralumin plate, tin alloy plate, steel plate, nickel plate, or zinc plate. Stainless steel plates (SUS plates) include currently manufactured stainless steel plates such as SUS304, SUS430, SUS303, SUS310, and SUS316, as well as all stainless steel plates to be developed in the future. Copper plates include tough pitch copper plates, oxygen-free copper plates, and deoxidized copper plates. Copper alloy plates include currently manufactured copper alloy plates such as brass plate, cupronickel plate, bronze plate, high copper alloy plate, and copper-nickel alloy plate, as well as all copper alloy plates to be developed in the future.

[0043] Aluminum alloy sheets include currently manufactured aluminum alloy sheets such as 1000 series aluminum (pure aluminum) non-heat-treatable alloy sheets, 2000 series alloy (Al-Cu) heat-treatable alloy sheets, 3000 series alloy (Al-Mn) non-heat-treatable alloy sheets, 4000 series alloy (Al-Si) non-heat-treatable alloy sheets, 5000 series alloy (Al-Mg) non-heat-treatable alloy sheets, 6000 series alloy (Al-Mg-Si) heat-treatable alloy sheets, and 7000 series alloy (Al-Zn-Mg) heat-treatable alloy sheets, as well as all aluminum alloy sheets to be developed in the future.

[0044] Magnesium alloy sheets include currently manufactured magnesium alloy sheets such as Mg-Al alloy sheets, Mg-Al-Zn alloy sheets, and Mg-Zn-Zr alloy sheets, as well as all magnesium alloy sheets to be developed in the future. Tin alloy sheets include currently manufactured tin alloy sheets such as tin-lead alloy (Sn-Pb) sheets, tin-copper alloy (Sn-Cu) sheets, tin-silver alloy (Sn-Ag) sheets, tin-bismuth alloy (Sn-Bi) sheets, tin-indium alloy (Sn-In) sheets, tin-zinc alloy (Sn-Zn) sheets, tin-cobalt alloy (Sn-Co) sheets, tin-nickel alloy (Sn-Ni) sheets, tin-copper-zinc alloy (Sn-Cu-Zn) sheets, and tin-copper-silver alloy (Sn-Cu-Ag) sheets, as well as all tin alloy sheets to be developed in the future.

[0045] The inorganic porous coating film 13a shown in Figure 1 has an inorganic nanoporous structure in which adjacent inorganic nanoparticles 14 among a large number of approximately spherical, nano-sized inorganic nanoparticles 14 are partially connected to each other, and a large number of nano-sized fine voids 15 (spaces) are formed between these inorganic nanoparticles 14. The inorganic porous coating film 13b shown in Figure 4 has an inorganic nanoporous structure in which irregularly shaped, nano-sized, approximately columnar inorganic nanoparticles 14 are partially connected (linked) to each other, and a large number of nano-sized fine voids 15 are formed between these inorganic nanoparticles 14.

[0046] In the hydrophilic coating film 10A shown in Figure 2, the hydrophilic organic polymer 16 (hydrophilic organic film) penetrates into numerous nanoscale fine voids 15 of the inorganic porous coating film 13a having the inorganic nanoporous structure shown in Figure 1. The hydrophilic organic polymer 16 (hydrophilic organic film) is bonded (joins) to the inorganic fine particles 14 forming the inorganic porous coating film 13a and the coating surface 12 of the metal substrate 11. Furthermore, the hydrophilic organic polymer 16 covers the surface of the inorganic porous coating film 13a, and the inorganic porous coating film 13a is embedded in the hydrophilic organic polymer 16 (hydrophilic organic film).

[0047] In the hydrophilic coating film 10B shown in Figure 3, the hydrophilic organic polymer 16 (hydrophilic organic film) penetrates into numerous nanoscale fine voids 15 of the inorganic porous coating film 13a having the inorganic nanoporous structure shown in Figure 1. The hydrophilic organic polymer 16 (hydrophilic organic film) is bonded (joins) to the inorganic fine particles 14 forming the inorganic porous coating film 13a and the coating surface 12 of the metal substrate 11. Furthermore, the uppermost layer of the hydrophilic organic polymer 16 is located slightly below the surface of the inorganic porous coating film 13a, and the uppermost layer of the inorganic porous coating film 13a (inorganic fine particles 14) is exposed above the uppermost layer of the hydrophilic organic polymer 16 (hydrophilic organic film). In Figure 3, the hydrophilic coating film 10B has a portion of the hydrophilic organic polymer 16 (hydrophilic organic film) within the inorganic porous coating film 13a (inorganic fine particles 14) that is exposed upward from the top layer (top layer), forming fine irregularities on the surface of the hydrophilic coating film 10B. Furthermore, the portion that forms the irregularities (top layer) is coated with an ultrathin film of the hydrophilic organic polymer 16 (hydrophilic organic film).

[0048] In the hydrophilic coating film 10C shown in Figure 5, the hydrophilic organic polymer 16 (hydrophilic organic film) penetrates into numerous nanoscale fine voids 15 of the inorganic porous coating film 13b having the inorganic nanoporous structure shown in Figure 4. The hydrophilic organic polymer 16 (hydrophilic organic film) is bonded (joins) to the inorganic fine particles 14 forming the inorganic porous coating film 13a and the coating surface 12 of the metal substrate 11. Furthermore, the hydrophilic organic polymer 16 covers the surface of the inorganic porous coating film 13b, and the inorganic porous coating film 13b is embedded in the hydrophilic organic polymer 16 (hydrophilic organic film).

[0049] In the hydrophilic coating film 10D shown in Figure 6, the hydrophilic organic polymer 16 (hydrophilic organic film) penetrates into numerous nanoscale fine voids 15 of the inorganic porous coating film 13b having the inorganic nanoporous structure shown in Figure 4. The hydrophilic organic polymer 16 (hydrophilic organic film) is bonded (joins) to the inorganic fine particles 14 that form the inorganic porous coating film 13a and the coating surface 12 of the metal substrate 11. Furthermore, the uppermost layer of the hydrophilic organic polymer 16 is located slightly below the surface of the inorganic porous coating film 13b, and the uppermost layer of the inorganic porous coating film 13b (inorganic fine particles 14) is exposed above the uppermost layer of the hydrophilic organic polymer 16 (hydrophilic organic film). In Figure 6, the hydrophilic coating film 10D has a portion of the hydrophilic organic polymer 16 (hydrophilic organic film) within the inorganic porous coating film 13b (inorganic fine particles 14) that is exposed upward from the top layer (top layer), forming fine irregularities on the surface of the hydrophilic coating film 10D. Furthermore, the portion that forms the irregularities (top layer) is coated with an ultrathin film of the hydrophilic organic polymer 16 (hydrophilic organic film).

[0050] The aqueous solution (inorganic coating solution) that forms the inorganic porous coating films 13a and 13b contains multiple fine silicon dioxide (SiO₂) particles. ２ A silica sol in which nano-sized inorganic fine particles (colloidal particles) consisting of ) are dispersed in a dispersion medium, and multiple fine aluminum oxides (Al ２ O ３ Nano-sized inorganic fine particles 14 (colloidal particles) consisting of ) are dispersed in a dispersion medium as alumina sol, and multiple fine zirconium oxide (ZrO)２ A zirconia sol in which nano-sized inorganic fine particles 14 (colloidal particles) consisting of ) are dispersed in a dispersion medium, and multiple fine titanium dioxide (TiO) ２ A titania sol, consisting of nano-sized inorganic fine particles 14 (colloidal particles) and multiple fine cerium oxide (CeO) particles, is dispersed in a dispersion medium. ２ One or more of the ceria sols in which nano-sized inorganic fine particles 14 (colloidal particles) consisting of ) are dispersed in a dispersion medium are used. The dispersion medium can be water or alcohol such as ethyl alcohol, n-propyl alcohol, isopropyl alcohol, or n-butanol, but is not limited to this method.

[0051] Silica sol is produced by the water glass method or the alkoxide method. However, it is not limited to these methods; silica sol can also be produced by other methods. The water glass method uses sodium silicate (Na) ２ O.Sio ２ Dilute the solution by adding water to a few percent to create an aqueous solution, and then add this aqueous solution little by little to a preheated sodium hydroxide solution to allow it to react. After the reaction, boil under reflux for several hours and then ultrafiltration is performed to produce an alkaline silica sol. Next, ion exchange is performed to remove impurities, and then a stabilizer is added to stabilize it and produce a silica sol (silica colloid solution).

[0052] The alkoxide method involves adding pure water to alkyl silicate (tetraalkoxysilane) to induce a hydrolysis reaction, then removing the alcohol produced by distillation, and finally adjusting the pH to a predetermined level by adding a pH adjuster (such as an alkali like tetraalkylammonium hydroxide or an acid like hydrochloric acid). After adjusting the pH, the solution is concentrated by reflux to produce silica sol (silica colloid solution).

[0053] One method for producing alumina sol involves neutralizing a water-soluble aluminum salt with an alkali to obtain an alumina gel, which is then hydrothermally treated in the presence of an organic acid to produce alumina sol (alumina colloid solution). Another method involves hydrothermally treating an alumina gel obtained by a liquid-phase neutralization reaction between an acidic aluminum compound and an alkaline substance in the presence of a monovalent inorganic acid to produce alumina sol (alumina colloid solution). Yet another method involves reacting a water-soluble aluminum salt with carbonic acid or a carbonate to obtain an alumina hydrate, which is then hydrothermally treated and mixed with a monovalent acid to produce alumina sol (alumina colloid solution).

[0054] Another example of a method for producing alumina sol is to react a water-soluble aluminum salt with carbonic acid or carbonate to obtain an alumina hydrate, then hydrothermally treat the hydrate and mix it with a monovalent acid to produce alumina sol (alumina colloid solution). Another example of a method for producing alumina sol is to hydrolyze aluminum alkoxide with a dilute acid aqueous solution to obtain an alumina hydrate, then add a new acid and hydrothermally treat it to gelatinize it, thereby producing alumina sol (alumina colloid solution). Another example of a method for producing alumina sol is to treat aluminum oxide powder in an aqueous phase in the presence of acid with a strongly acidic cation exchange resin, then remove the ion exchange resin and cool to room temperature to produce alumina sol (alumina colloid solution). It should be noted that alumina sol can be produced by other methods, not limited to these methods.

[0055] One example of a method for producing zirconia sol is to add an alkali to an aqueous solution containing a water-soluble zirconium salt such as zirconium oxychloride to produce zirconium hydroxide, and then hydrolyze the produced zirconium hydroxide to produce zirconia sol (zirconia colloid solution). Another example of a method for producing zirconia sol is to hydrolyze the reaction product of ammonium zirconium carbonate and a chelating agent (for example, oxyphenols, amino alcohols, oxy acids, polycarboxylic acids, oxyaldehydes, amino acids, and β-diketones) to produce zirconia sol (zirconia colloid solution). Another example of a method for producing zirconia sol involves heating an aqueous suspension containing zirconium hydroxide at a temperature of 80°C or higher to create an aqueous suspension containing crystallized zirconia with a crystallinity of 80% or higher, and then adding nitrogen-containing basic compounds (primary amines, secondary amines, quaternary ammonium hydroxides), alkali metals, or alkaline earth metal hydroxides to the aqueous suspension containing crystallized zirconia to produce a basic zirconia sol (zirconia colloid solution).

[0056] Another example of a method for producing zirconia sol is to add a base to an aqueous solution of zirconium salt to precipitate it, add an alkaline earth metal hydroxide or an aqueous solution thereof, and heat and age the resulting suspension at a temperature of 90 to 200°C to produce zirconia sol (zirconia colloid solution). Another example of a method for producing zirconia sol is to heat an aqueous solution of zirconium salt having a molar ratio of anion to metal of 0.5:1 to 4:1 to 120 to 300°C, then cool it to room temperature and adjust the pH to 2 to 6 to produce zirconia sol (zirconia colloid solution). Another example of a method for producing zirconia sol is to add an amount of hydrogen peroxide equal to or greater than 1 / 2 the amount of zirconium in the solution to an aqueous solution of zirconium salt with a concentration of 0.05 to 2.0 mol / liter, heat it to 80 to 300°C, and then add a base such as ammonia, or treat it with an ion exchange resin, to produce zirconia sol (zirconia colloid solution). Furthermore, zirconia sol can be manufactured using methods other than those mentioned above.

[0057] One method for producing titania sol involves adding an alkali to an aqueous solution of a water-soluble titanium salt such as titanium tetrachloride or titanium sulfate to precipitate titanium hydroxide, and then dissolving the precipitated titanium hydroxide with a strong acid such as hydrochloric acid or nitric acid to produce titania sol (titania colloid solution). Another method involves hydrolyzing a water-soluble titanium salt with an alkali to obtain a titanic acid gel, which is then subjected to hydrothermal treatment in the presence of quaternary ammonium hydroxide to produce titania sol (titania colloid solution). Yet another method involves reacting a water-soluble titanium compound with an alkali metal hydroxide, carbonate, or ammonium compound to obtain a gel, to which alkali metal hydroxides, ammonium hydroxide, methylamine, trimethylamine, ethylenediamine, ethanolamine, or other organic amines are added, and the gel is subjected to hydrothermal treatment at 100°C or higher to produce titania sol (titania colloid solution). It should be noted that the methods are not limited to these, and titania sol can also be produced by other methods.

[0058] One example of a ceria sol manufacturing method involves reacting cerium salt compounds such as ceric sulfate, ceric ammonium nitrate, ceric ammonium sulfate, cerium acetate, cerium chloride, cerium ammonium nitrate, cerium nitrate, and cerium nitrate with alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide, or ammonia, at 10°C to 90°C to form a gel. After that, an acid such as hydrochloric acid, nitric acid, acetic acid, formic acid, lactic acid, or glycolic acid is added, and the sol is produced by hydrothermal treatment at a temperature of 100°C or higher. The acid may be added after the hydrothermal treatment.

[0059] Another example of a method for producing ceria sol involves dispersing cerium hydroxide or hydrated cerium hydroxide in water, stirring, and then adding HNO ３ The reaction dispersion is prepared by adding [the substance]. The resulting reaction dispersion can also be produced by heating it to approximately 80-150°C and heat-treating it for about 6 hours. However, the production method is not limited to these methods, and ceria sol can also be produced by other methods.

[0060] Inorganic coating liquids include silicon dioxide (SiO ２ ), aluminum oxide (Al ２ O ３), zirconium oxide (ZrO ２ ), titanium oxide (TiO ２ ), ceria oxide (CeO ２ The material contains one or more types of inorganic fine particles 14 (inorganic nanoparticles) from the following: silica sol, alumina sol, zirconia sol, titania sol, and ceria sol. By coating (applying) silica sol, alumina sol, zirconia sol, titania sol, and ceria sol onto the surface 12 of a metal substrate 11, inorganic porous coating films 13a and 13b are formed by the sol-gel method, which have an inorganic nanoporous structure with numerous nano-sized fine voids 15 as shown in Figures 1 and 4.

[0061] Inorganic fine particles 14 (silicon dioxide (SiO₂) in an inorganic coating liquid ２ ), aluminum oxide (Al ２ O ３ ), zirconium oxide (ZrO ２ ), titanium oxide (TiO ２ ), ceria oxide (CeO ２ The solid content concentration of silicon dioxide (SiO₂) in the inorganic coating solution is in the range of 0.3 wt% to 50 wt% relative to the total mass of the inorganic coating solution. ２ If the solid content concentration of the inorganic fine particles 14 in the inorganic coating liquid is less than 0.3 wt%, the amount of silicon dioxide that readily bonds with the hydrophilic organic polymer 16 becomes insufficient, making it difficult for the hydrophilic organic polymer 16 that has penetrated the numerous fine voids 15 described below in the inorganic porous coating films 13a and 13b to bond to the voids 15 containing silicon dioxide, and thus preventing the hydrophilic organic polymer 16 (hydrophilic organic film) from being firmly bonded to the voids 15 in the inorganic porous coating films 13a and 13b. ２ Since the solid content concentration of the inorganic fine particles 14 is within the aforementioned range, the hydrophilic organic polymer 16 (hydrophilic organic film) that has penetrated into the numerous fine voids 15 of the inorganic porous coating films 13a and 13b easily bonds to the voids 15 containing silicon dioxide, and the hydrophilic organic polymer 16 can be firmly bonded to the voids 15 of the inorganic porous coating films 13a and 13b.

[0062] Aluminum oxide (Al) in inorganic coating solutions２ O ３ If the solid content concentration of the inorganic fine particles 14 in the inorganic coating liquid is less than 0.3 wt%, the amount of aluminum oxide that readily binds to the hydrophilic organic polymer 16 becomes insufficient. As a result, the hydrophilic organic polymer 16 (hydrophilic organic film) that has penetrated into the numerous fine voids 15 of the inorganic porous coating films 13a and 13b does not readily bind to the voids 15 containing aluminum oxide. Consequently, the hydrophilic organic polymer 16 cannot be firmly bound to the voids of the inorganic porous coating films 13a and 13b. Furthermore, the ability of aluminum oxide to remove salts such as magnesium, calcium, sodium, and silicon is reduced, making it impossible to prevent contamination of the hydrophilic coating films 10A to 10D due to the adhesion of salts such as magnesium, calcium, sodium, and silicon. ２ O ３ Since the solid content concentration of the inorganic fine particles 14 is within the range described above, the hydrophilic organic polymer 16 (hydrophilic organic film) that has penetrated into the numerous fine voids 14 of the inorganic porous coating films 13a and 13b can be firmly bonded to the voids 14 containing aluminum oxide. Furthermore, the aluminum oxide makes it difficult for salts such as magnesium, calcium, sodium, and silicon to adhere to the hydrophilic coating films 10A to 10D, thus preventing contamination of the hydrophilic coating films 10A to 10D due to the adhesion of salts such as magnesium, calcium, sodium, and silicon.

[0063] Zirconium oxide (ZrO) in inorganic coating solutions ２ If the solid content concentration of the inorganic fine particles 14 is less than 0.3 wt%, the hardness of the inorganic porous coating films 13a and 13b cannot be increased, and the rigidity of the hydrophilic coating films 10A to 10D cannot be increased. Zirconium oxide (ZrO) in the inorganic coating liquid ２ Since the solid content concentration of the inorganic fine particles 14 is within the above range, the hardness of the inorganic porous coating films 13a and 13b can be increased, and the rigidity of the hydrophilic coating films 10A to 10D can be increased.

[0064] Titanium oxide (TiO) in inorganic coating solutions ２ If the solid content concentration of the inorganic fine particles 14 in the inorganic coating solution is less than 0.3 wt%, the amount of titanium dioxide will be insufficient, and the self-cleaning effect cannot be imparted to the hydrophilic coating films 10A to 10D. ２ Since the solid content concentration of the inorganic fine particles 14 of titanium dioxide is within the above range, when light and water strike the inorganic fine particles 14 of titanium dioxide, the surfaces of the hydrophilic coating films 10A to 10D are covered with hydrophilic groups, and the hydrophilic coating films 10A to 10D can be given an excellent self-cleaning effect.

[0065] Cerium oxide (CeO) in inorganic coating solutions ２ If the solid content concentration of the inorganic fine particles 14 is less than 0.3 wt%, the hardness of the inorganic porous coating films 13a and 13b cannot be increased, and the rigidity of the hydrophilic coating films 10A to 10D cannot be improved. Furthermore, sufficient ultraviolet absorption function cannot be obtained. Cerium oxide (CeO) in inorganic coating liquid ２ Since the solid content concentration of the inorganic fine particles 14 is within the above range, the hardness of the inorganic porous coating films 13a and 13b can be increased, the rigidity of the hydrophilic coating films 10A to 10D can be increased, and the ultraviolet absorption effect of the hydrophilic coating films 10A to 10D can be obtained.

[0066] Inorganic fine particles 14 (silicon dioxide (SiO₂) in an inorganic coating liquid ２ ), aluminum oxide (Al ２ O ３ ), zirconium oxide (ZrO ２ ), titanium oxide (TiO ２ ), ceria oxide (CeO ２If the solid content concentration of the inorganic coating liquid exceeds 50 wt%, a large number of inorganic fine particles 14 come into contact with each other over a wide area, causing the inorganic fine particles 14 to become densely packed and preventing the formation of numerous fine voids 15. Since the solid content concentration of the inorganic fine particles 14 in the inorganic coating liquid is within the above range, inorganic porous coating films 13a and 13b having a predetermined strength and an inorganic nanoporous structure with numerous nano-sized fine voids 15 can be formed on the coating surface 12 of the metal substrate 11.

[0067] The average particle size of the inorganic fine particles 14 contained in the inorganic coating liquid is 1 μm or less. If the average particle size of the inorganic fine particles 14 exceeds 1 μm, the volume of the voids 15 increases, making it impossible to form inorganic porous coating films 13a and 13b with an inorganic nanoporous structure having numerous fine voids 15 on the coating surface 12 of the metal substrate 11. Because the average particle size of the inorganic fine particles 14 is 1 μm or less, numerous fine inorganic fine particles 14 are partially connected to each other, allowing inorganic porous coating films 13a and 13b with an inorganic nanoporous structure having numerous nano-sized fine voids 15 to be formed on the coating surface 12 of the metal substrate 11.

[0068] The hydrophilic organic polymer 16 is an ionic polymer containing at least one of the following: a betaine moiety (betaine polymer), a cationic moiety (cationic polymer), and an anionic moiety (anionic polymer). The hydrophilic organic polymer 16 contains Ag ＋ Ions (silver ions) and Cu ２＋ Ions (copper ions) and Zn ２＋ It contains at least one metal ion (zinc ion). The metal ion contained in the hydrophilic organic polymer 16 is Ag. ＋ Ions are preferred. Furthermore, the hydrophilic organic polymer 16 does not necessarily need to contain metal ions.

[0069] The content of betaine moieties (betaine polymer), cationic moieties (cationic polymer), and anionic moieties (anionic polymer) in the hydrophilic organic polymer 16 is in the range of 0.1 wt% to 20 wt% relative to the total weight of the hydrophilic organic polymer 16. If the content of betaine moieties, cationic moieties, and anionic moieties in the hydrophilic organic polymer 16 is less than 0.1 wt%, the content of betaine moieties, cationic moieties, and anionic moieties in the hydrophilic organic polymer 16 is low, and the hydrophilic organic polymer 16 cannot exhibit sufficient hydrophilicity and antifouling properties, and excellent hydrophilicity and antifouling properties cannot be imparted to the hydrophilic coating films 10A to 10D made from the inorganic porous coating films 13a and 13b and the hydrophilic organic polymer.

[0070] Since the hydrophilic organic polymer 16 contains betaine moieties (betaine polymer), cationic moieties (cationic polymer), and anionic moieties (anionic polymer) within the aforementioned range, the hydrophilic organic polymer 16 contains a sufficient amount of betaine moieties, cationic moieties, and anionic moieties, giving the hydrophilic organic polymer 16 excellent hydrophilicity and antifouling properties. This allows the hydrophilic coating films 10A to 10D, made from the inorganic porous coating films 13a and 13b and the hydrophilic organic polymer 16 (hydrophilic organic film), to be imparted with excellent hydrophilicity and antifouling properties, and the hydrophilic coating films 10A to 10D exhibit excellent hydrophilicity and antifouling properties.

[0071] The hydrophilic organic polymer 16 (ionic polymer) contains metal ions (Ag ＋ Ions and Cu ２＋ Ions and Zn ２＋ If at least one of the ions is included, the hydrophilic organic polymer 16 comprising at least one of the betaine moiety, cationic moiety, and anionic moiety and a metal ion (Ag ＋ Ions and Cu ２＋ Ions and Zn ２＋The weight ratio of the metal ion to at least one of the ions is 0.1 or more per 1 part of the hydrophilic organic polymer 16 (ionic polymer). Preferably, the weight ratio of the metal ion to the hydrophilic organic polymer 16 (ionic polymer) is 0.5 or more per 1 part of the hydrophilic organic polymer 16 (ionic polymer). More preferably, the weight ratio of the metal ion to the hydrophilic organic polymer 16 (ionic polymer) is 1 or more per 1 part of the hydrophilic organic polymer 16 (ionic polymer).

[0072] Ag ＋ Silver ions utilize oxidation catalyst action to convert oxygen into reactive oxygen species, thereby providing a bactericidal effect. They also pass through bacterial cell membranes, inhibiting the function of intracellular enzymes and leading to cell death. (Ag) ＋ Ions possess high bactericidal properties, high deodorizing effects, and excellent antiviral, antibacterial, antifungal, and deodorizing functions. Cu ２＋ Ions (copper ions) bind to oxygen and proteins, reducing their activity and inhibiting metabolic functions. ２＋ Through the catalytic action of ions, some of the oxygen in the air and water is converted into reactive oxygen species, which then decompose organic matter by microorganisms. Cu ２＋ Ions (copper ions 12b) have high bactericidal properties and excellent antiviral, antibacterial, and antifungal functions. Zn ２＋ Ions (zinc ions) possess photocatalytic properties, exhibiting strong oxidizing power on their surfaces when exposed to light. ２＋ Ions (zinc ions) have a strong bactericidal effect and possess excellent antiviral, antibacterial, and antifungal properties.

[0073] Ag ＋ Ions (silver ions) and Cu ２＋ Ions (copper ions), Zn ２＋ Because the metal ion (zinc ion) is in an unstable state (positively charged), it tries to combine with oxygen in microorganisms (viruses, bacteria, fungi, mold hyphae, etc.) and is taken into the microbial cell, and the taken-in Ag ＋ Ion, Cu ２＋ Ions, Zn ２＋Ions bind to proteins and other substances, inhibiting their function and preventing cell division. This protein dysfunction generates reactive oxygen species, leading to the death of microbial cells.

[0074] When the hydrophilic organic polymer 16 (ionic polymer) contains metal ions, if the weight ratio of the hydrophilic organic polymer 16 (ionic polymer) containing at least one of the betaine moiety, cationic moiety, and anionic moiety to the metal ions is less than 0.1 for every 1 part hydrophilic organic polymer 16 (ionic polymer), the amount of metal ions in the hydrophilic organic polymer 16 is low, and the hydrophilic organic polymer 16 cannot exhibit sufficient antiviral, antibacterial, and antifungal functions. As a result, the hydrophilic coating films 10A to 10D made from the inorganic porous coating films 13a and 13b and the hydrophilic organic polymer 16 (hydrophilic organic film) cannot be given excellent antiviral, antibacterial, antifungal, and deodorizing functions.

[0075] When the hydrophilic organic polymer 16 (ionic polymer) contains metal ions, the weight ratio of the hydrophilic organic polymer 16 to the metal ions is within the aforementioned range, so the hydrophilic organic polymer 16 contains a sufficient amount of metal ions, and the hydrophilic organic polymer 16 has excellent antiviral, antibacterial, antifungal, and deodorizing functions. This imparts excellent antiviral, antibacterial, antifungal, and deodorizing functions to the hydrophilic coating films 10A to 10D made from the inorganic porous coating films 13a and 13b and the hydrophilic organic polymer 16 (hydrophilic organic film), and the hydrophilic coating films 10A to 10D exhibit excellent antiviral, antibacterial, antifungal, and deodorizing functions.

[0076] Sulfoxybetaine, carboxybetaine, and phosphobetaine are used as betaine moieties (betaine polymers). An example of a betaine polymer is a sulfobetaine + silane compound. These polymers may also be obtained by copolymerizing multiple monomers. For example, monomers having alkyl groups to an extent that does not impair hydrophilicity, monomers having fluorine-containing alkyl groups, monomers having silicone moieties, and monomers having alkylene glycol moieties can be copolymerized. An example of the structural formula of a sulfobetaine + silane compound is shown in (Chemical Formula 1).

[0077] (Chem.1) Another example of a betaine moiety (betaine polymer) is sulfobetaine. An example of a sulfobetaine structural formula is shown in (Chemical Formula 2).

[0078] (Case 2) Another example of a betaine moiety (betaine polymer) is phosphobetaine. An example of a phosphobetaine structure is shown in (Chemical Formula 3).

[0079] (Case 3) The cationic moiety (cationic polymer) has the molecular formula NR ４ ＋ A quaternary ammonium group (quaternary ammonium cation), a positively charged polyatomic ion represented by (R refers to an alkyl group or aryl group), with molecular formula C ３ H ４ N ２ One example is a polymer containing imidazolium, a type of heterocyclic aromatic compound amine with nitrogen atoms at the 1st and 3rd positions on a five-membered ring with a molecular weight of 68.08. These polymers may also be obtained by copolymerizing multiple monomers. For example, monomers having alkyl groups to an extent that does not impair hydrophilicity, monomers having fluorine-containing alkyl groups, monomers having silicone moieties, and monomers having alkylene glycol moieties can also be copolymerized.

[0080] The anionic moiety (anionic polymer) is a sulfo group (-SO ３A sulfoxy group is a compound substituted with an H group, a carboxyl group is a functional group consisting of a carbonyl group (RR'C=O) and a hydroxyl group, a chemical ion or radical (P ＋ O ３ ２－ ) a phosphonyl group containing phosphorus and oxygen, and a monovalent substituent -NO that serves as a characteristic group ２ Polymers containing nitro groups are one example. These polymers may be obtained by copolymerizing multiple monomers. For example, monomers having alkyl groups to an extent that does not impair hydrophilicity, monomers having fluorine-containing alkyl groups, monomers having silicone moieties, monomers having alkylene glycol moieties, etc., can be copolymerized.

[0081] An example of the structural formula of the anionic moiety (anionic polymer) is shown in (Chemical Formula 4).

[0082] (Case 4) As an example of a hydrophilic organic polymer, a coating solution is used in which a polymer capable of forming a high-density polymer brush (surface graft polymer) shown in the following structural formula (1) is dispersed and mixed in a water-soluble solvent or an ester-based solvent. An example of the structural formula of a polymer capable of forming a high-density polymer brush is shown in (Chemical Formula 5).

[0083] (C5)

[0084] The polymer capable of forming the high-density polymer brush shown in the structural formula of (Chemical Formula 5) is a polymer brush of carboxybetaine monomer having a silanol group at one end, and uses γ-mercaptopropyltrimethoxysilane as a chain transfer agent. This polymer capable of forming a high-density polymer brush can be used to create a polymer thin film resembling a carpet by growing polymer chains.

[0085] In addition to polymers capable of forming the high-density polymer brushes (surface graft polymers) described above, hydrophilic organic polymers 16 can also use brush microparticles or bottle brushes. Furthermore, betaine polymers that do not contain silanol groups or alkoxysilyl groups in their terminals or polymer chains can also be used. By using betaine polymers that do not contain silanol groups or alkoxysilyl groups, reactions in solution do not occur, and long-term changes over time can be suppressed. Examples of other hydrophilic organic compounds that can be used in combination with the betaine polymer of the hydrophilic organic polymer include coating solutions in which polymers capable of forming PHEMA polymer brushes, PHEMA polymer, PPEGMA polymer, PNIPAM polymer, PMTAC polymer, PMTAC polymer, PSPMK polymer, and PSPMK polymer are dispersed and mixed in a water-soluble solvent or an ester-based solvent. Furthermore, other betaine polymers may be mixed in with the betaine polymer shown in the structural formula of (Chemical Formula 5), ​​and a coating liquid containing dispersed polymers that can form PMAPS polymer brushes, PMAPS polymers, PMPC polymer brushes, and PMPC polymers, as shown as another example, can also be used. These polymers may be obtained by copolymerizing multiple monomers. The structural formula of the PHEMA polymer is shown in (Chemical Formula 6), but it may have a silanol group or an alkoxysilyl group at one end, or it may contain a silanol group or an alkoxysilyl group in the polymer chain.

[0086] (C6) The structural formula of the PPEGMA polymer is shown in (Chemical Formula 7), but it may have a silanol group or alkoxysilyl group at one end, or it may contain a silanol group or alkoxysilyl group in the polymer chain.

[0087] (Chem.7) The structural formula of the PNIPAM polymer is shown in (Chemical Formula 8), but it may have a silanol group or an alkoxysilyl group at one end, or it may contain a silanol group or an alkoxysilyl group in the polymer chain.

[0088] (Chem.8) The structural formula of PMTAC polymer is shown in (Chemical Formula 9), but it may have a silanol group or alkoxysilyl group at one end, or it may contain a silanol group or alkoxysilyl group in the polymer chain.

[0089] (C9) The structural formula of the PSPMK polymer is shown in (Chemical Formula 10), but it may have a silanol group or alkoxysilyl group at one end, or it may contain a silanol group or alkoxysilyl group in the polymer chain.

[0090] (Chem.10) The structural formula of the PMAPS polymer is shown in (Chemical Formula 11), but it may have a silanol group or alkoxysilyl group at one end, or it may contain a silanol group or alkoxysilyl group in the polymer chain.

[0091] (Chem.11) The structural formula of the PMPC polymer is shown in (Chemical Formula 12), but it may have a silanol group or alkoxysilyl group at one end, or it may contain a silanol group or alkoxysilyl group in the polymer chain.

[0092] (Chem.12) Water-soluble solvents include pure water, primary alcohol solvents, secondary alcohol solvents, tertiary alcohol solvents, ether solvents, ester solvents, and ketone solvents. Primary, secondary, or tertiary alcohol solvents include iso-propanol, sec-butyl alcohol, tert-butyl alcohol, and propylene glycol monomethyl ether. Ether solvents include tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, triethylene glycol butyl methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol isopropyl methyl ether, ethylene glycol diethyl ether, ethylene glycol dimethyl ether, propylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tripropylene glycol dimethyl ether, diethylene glycol butyl methyl ether, diethylene glycol dibutyl ether, and dipropylene glycol dimethyl ether.

[0093] Ester solvents include methyl acetate, ethyl acetate, ethylene glycol monomethyl acetate, ethylene glycol monoethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether propionate, and γ-butyrolactone. Ketone solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, diisopropyl ketone, and cyclohexanone. Aprotic solvents include dimethyl sulfoxide, N,N-dimethylformamide, and N-methylpyrrolidone.

[0094] As another example of a betaine moiety (betaine polymer) contained in the hydrophilic organic polymer 16, the following betaine moieties (betaine polymers) can also be used. One example of a betaine moiety (betaine polymer) is a polymer containing 2-methacryloyloxyethyl phosphorylcholine as a component. An example of its structural formula is shown in (Chemical Formula 13), but it may have a silanol group or an alkoxysilyl group at one end, or it may contain a silanol group or an alkoxysilyl group in the polymer chain.

[0095] (Chem.13) Another example of a betaine moiety (betaine polymer) contained in the hydrophilic organic polymer 16 is polycarboxybetaine polymer. An example of the structural formula of a polycarboxybetaine polymer is shown in (Chemical Formula 14), but it may have a silanol group or alkoxysilyl group at one end, or it may contain silanol groups or alkoxysilyl groups in the polymer chain.

[0096] (Chem.14) The monomers that make up the betaine moiety (betaine polymer) include sulfobetaine monomer, carboxybetaine monomer, phosphobetaine monomer, dimethylamine oxide monomer, and dimethyl sulfoniopropionate. The general formula for sulfobetaine monomer is shown in (Chemical Formula 15), and its specific structural formulas are shown in (Chemical Formulas 15) to (Chemical Formulas 22).

[0097] (Chem.15)

[0098] (Chemical Formula 16) 3-{[2-(methacryloyloxy)ethyl]dimethylammonio}propane-1-sulfonic acid

[0099] (Chemical Formula 17) 4-[(3-methacrylamidopropyl)dimethylammonio]butane-1-sulfonic acid

[0100] (Chemical Formula 18) 3-{[2-(acryloyloxy)ethyl]dimethylammonio}propane-1-sulfonic acid

[0101] (Chemical Formula 19) 3-[(3-acrylamidopropyl)dimethylammonio]propane-1-sulfonic acid

[0102] (Chemical Formula 20) 4-{[2-(methacryloyloxy)ethyl]dimethylammonio}butane-1-sulfonic acid

[0103] (Chemical Formula 21) Bis[2-(methacryloyloxy)ethyl](methyl)ammonio]propane-1-sulfonic acid

[0104] (Chemical Formula 22) 3-[3-(methacrylamidopropyl)dimethylammonio]propane-1-sulfonic acid The general formula for carboxybetaine monomer is shown in (Chemical Formula 23), and its specific structural formulas are shown in (Chemical Formulas 24) to (Chemical Formulas 26).

[0105] (Case 23)

[0106] (Chemical Formula 24) 2-{[2-(methacryloyloxy)ethyl]dimethylammonioacetic acid}acetic acid

[0107] (Chemical Formula 25) 3-{[3-(methacryloyloxy)ethyl]dimethylammonio}propionate

[0108] (Chemical Formula 26) 3-[(3-acrylamidopropyl)dimethylammonio]propanoate The general formula for phosphobetaine monomer is shown in (Chemical Formula 27), and its specific structural formula is shown in (Chemical Formula 28).

[0109] (Case 27)

[0110] (Chemical Formula 28) 2-(methacryloyloxy)ethyl 2-(trimethylammonio)ethyl phosphate The structural formula of dimethylamine oxide is shown in (Chemical Formula 29).

[0111] (Chem.29) The structural formula of methylsulfoniocarboxylate is shown in (Chemical Formula 30).

[0112] (Chemical 30) Figure 7 is a diagram illustrating the introduction of Ag ＋ ions into a betaine site (betaine polymer). In the hydrophilic organic polymer 16, metal ions (Ag ＋ ions, Cu ２＋ ions, Zn ２＋ ions) are introduced into betaine sites (betaine polymer), anion sites (anionic polymer), and cation sites (cationic polymer) through ion exchange. For an example of introducing Ag ＋ ions into a betaine site (betaine polymer), when a betaine site (betaine polymer) and silver nitrate are dissolved in an aqueous solution (pure water), potassium ions with weak binding force detach from the betaine site (betaine polymer), and ion exchange occurs where silver ions from silver nitrate with stronger binding force bind to the betaine site (betaine polymer), and as shown in Figure 7, silver ions are introduced into the betaine site (betaine polymer).

[0113] Ag ＋ An example of the structural formula of a betaine site (betaine polymer) before ions are introduced is shown in (Chemical 31), and Ag is introduced into the betaine site (betaine polymer) having the structural formula of (Chemical 31) ＋ An example of the structural formula of a betaine site (betaine polymer) after ions are introduced is shown in (Chemical 32). An example of the structural formula of a betaine site (betaine polymer) after Cu ２＋ ions are introduced into the betaine site (betaine polymer) having the structural formula of (Chemical 31) is shown in (Chemical 33).

[0114] (Chemical 31)

[0115] (Chemical 32)

[0116] (Chemical 33) Ag ＋ Another example of the structural formula of a betaine site (betaine polymer) before ions are introduced is shown in (Chemical 34), and Ag is introduced into the betaine site (betaine polymer) having the structural formula of (Chemical 34) ＋An example of the structural formula of the betaine site (betaine polymer) after ions are introduced is shown in Chemical Formula 35. To the betaine site (betaine polymer) having the structural formula of Chemical Formula 34, Cu ２＋ An example of the structural formula of the betaine site (betaine polymer) after ions are introduced is shown in Chemical Formula 36.

[0117] (Chemical Formula 34)

[0118] (Chemical Formula 35)

[0119] (Chemical Formula 36) Ag ＋ Another example of the structural formula of the betaine site (betaine polymer) before ions are introduced is shown in Chemical Formula 37, and to the betaine site (betaine polymer) having the structural formula of Chemical Formula 37, Ag ＋ An example of the structural formula of the betaine site (betaine polymer) after ions are introduced is shown in Chemical Formula 38. To the betaine site (betaine polymer) having the structural formula of Chemical Formula 37, Cu ２＋ An example of the structural formula of the betaine site (betaine polymer) after ions are introduced is shown in Chemical Formula 39.

[0120] (Chemical Formula 37)

[0121] (Chemical Formula 38)

[0122] (Chemical Formula 39) Ag ＋ Another example of the structural formula of the anion site (anionic polymer) before ions are introduced is shown in Chemical Formula 40, and to the anionic polymer having the structural formula of Chemical Formula 40, Ag ＋ An example of the structural formula of the anionic polymer after ions are introduced is shown in Chemical Formula 41. To the anionic polymer having the structural formula of Chemical Formula 40, Cu ２＋ An example of the structural formula of the anionic polymer after ions are introduced is shown in Chemical Formula 42.

[0123] (Chemical Formula 40)

[0124] (Chemical Formula 41)

[0125] (Chemical Formula 42) The inorganic coating liquid used to create the inorganic porous coating films 13a and 13b is composed of silicon dioxide (SiO₂). ２ ), aluminum oxide (Al ２ O ３ ), zirconium oxide (ZrO ２ ), titanium oxide (TiO ２ ), cerium oxide (CeO ２ The inorganic coating solution contains at least one type of inorganic fine particles 14, and the solid content concentration of the inorganic fine particles 14 in the inorganic coating solution is 0.3 to 50 wt%, so it is possible to create inorganic porous coating films 13a and 13b with sufficient strength in which a large number of fine voids 15 are formed by the inorganic fine particles 14, and it is possible to create hydrophilic coating films 10A to 10D in which a hydrophilic organic polymer 16 (hydrophilic organic film) is firmly bonded (joined) to the voids 15 (inorganic fine particles 14) and the coating surface 12 of the metal substrate 11.

[0126] The inorganic coating liquid used to create the inorganic porous coating films 13a and 13b is composed of silicon dioxide (SiO₂). ２ When the inorganic fine particles 14 are included, by utilizing the ease with which the hydrophilic organic polymer 16 and silicon dioxide bond, the hydrophilic organic polymer 16 that has penetrated into the numerous fine voids 15 of the inorganic porous coating films 13a and 13b easily bonds to the voids 15 containing silicon dioxide, and hydrophilic coating films 10A to 10D can be made in which the hydrophilic organic polymer 16 (hydrophilic organic film) is firmly bonded (joined) to the voids 15 (inorganic fine particles 14) of the inorganic porous coating films 13a and 13b and the coating surface 12 of the metal substrate 11.

[0127] The inorganic coating liquid used to create the inorganic porous coating films 13a and 13b is aluminum oxide (Al ２ O ３When the inorganic fine particles 14 of ) are included, by utilizing the ease with which the hydrophilic organic polymer 16 and aluminum oxide bond, hydrophilic coating films 10A to 10D can be made in which the hydrophilic organic polymer 16 (hydrophilic organic film) that has penetrated into the numerous fine voids 15 of the inorganic porous coating films 13a and 13b is firmly bonded to the voids 15 (inorganic fine particles 14) of the inorganic porous coating films 13a and 13b containing aluminum oxide and to the coating surface 12 of the metal substrate 11. Furthermore, since salts such as magnesium, calcium, sodium, and silicon are less likely to adhere to the hydrophilic coating films 10A to 10D due to the adhesion of salts such as magnesium, calcium, sodium, and silicon, hydrophilic coating films 10A to 10D can be made in which contamination caused by the adhesion of salts such as magnesium, calcium, sodium, and silicon can be prevented.

[0128] The inorganic coating liquid used to create the inorganic porous coating films 13a and 13b is made of zirconium oxide (ZrO ２ When it contains inorganic fine particles 14 of ), the hardness can be increased by zirconium oxide, and hydrophilic coating films 10A to 10D with increased rigidity can be made. The inorganic coating liquid that makes the inorganic porous coating films 13a and 13b is made of titanium oxide (TiO ２ When the inorganic fine particles 14 of titanium dioxide are included, the surface of the inorganic fine particles 14 of titanium dioxide is coated with hydrophilic groups when exposed to light and water, so that hydrophilic coating films 10A to 10D with excellent self-cleaning effect can be made. The inorganic coating liquid that makes the inorganic porous coating films 13a and 13b is made of cerium oxide (CeO2). ２ When inorganic fine particles 14 of ) are included, the hardness can be increased by cerium oxide, and ultraviolet absorption ability can also be obtained, making it possible to create hydrophilic coating films 10A to 10D with increased rigidity and ultraviolet absorption ability.

[0129] The porosity of the voids 15 formed in the inorganic porous coating films 13a and 13b is in the range of 20% to 70% of the volume of the inorganic porous coating films 13a and 13b. If the porosity of the voids 15 is less than 20%, there are few voids 15 formed in the inorganic porous coating films 13a and 13b, and the hydrophilic organic polymer that penetrates these voids 15 cannot sufficiently change shape (plastic deformation) in these voids. When thermal expansion or contraction occurs in the metal substrate due to temperature changes, the hydrophilic organic polymer cannot change shape (plastic deformation) in these voids. Furthermore, the hydrophilicity and antifouling properties of the hydrophilic organic polymer 16 that penetrates the voids 15 of the inorganic porous coating films 13a and 13b cannot be fully utilized, and excellent hydrophilicity and antifouling properties cannot be imparted to the hydrophilic coating films 10A to 10D formed from the inorganic porous coating films 13a and 13b and the hydrophilic organic polymer 16 (hydrophilic organic film). If the porosity of the voids 15 exceeds 70%, the inorganic porous coating films 13a and 13b become weak, reducing the strength of the hydrophilic coating films 10A to 10D formed from the inorganic porous coating films 13a and 13b and the hydrophilic organic polymer 16 (hydrophilic organic film), and the hydrophilic coating films 10A to 10D cannot adequately protect the coated surface 12 of the metal substrate 11.

[0130] Since the hydrophilic coating films 10A to 10D have a porosity within the aforementioned range of the voids 15 formed in the inorganic porous coating films 13a and 13b, a necessary and sufficient number of fine voids 15 are formed in the inorganic porous coating films 13a and 13b, and the hydrophilic organic polymer (ionic polymer) that penetrates these voids 15 can sufficiently change shape (plastic deformation) within these voids. When thermal expansion or contraction occurs in the metal substrate due to temperature changes, the hydrophilic organic polymer can freely change shape (plastic deformation) within these voids. Furthermore, the hydrophilic organic polymer 16 penetrates these voids 15, and the excellent hydrophilicity and antifouling properties of the hydrophilic organic polymer 16 (hydrophilic organic film) can be fully utilized, thereby imparting excellent hydrophilicity and antifouling properties to the hydrophilic coating films 10A to 10D, and the hydrophilic coating films 10A to 10D have sufficient strength, and the coated surface 12 of the metal substrate 11 can be sufficiently protected by the hydrophilic coating films 10A to 10D.

[0131] In hydrophilic coating films 10A to 10D, the proportion of betaine moieties (betaine polymer), cationic moieties (cationic polymer), and anionic moieties (anionic polymer) contained in the hydrophilic organic polymer 16 that constitutes them is 20% or more of the total mass of the hydrophilic organic polymer. If the proportion of betaine moieties (betaine polymer), cationic moieties (cationic polymer), and anionic moieties (anionic polymer) to the total mass of the hydrophilic organic polymer 16 is less than 20%, the content of betaine moieties, cationic moieties, and anionic moieties in the hydrophilic organic polymer 16 is low, and the hydrophilic function of the betaine moieties, cationic moieties, and anionic moieties cannot be fully utilized. Therefore, hydrophilic coating films 10A to 10D cannot exhibit sufficient hydrophilicity or antifouling properties, and excellent hydrophilicity or antifouling properties cannot be imparted to the hydrophilic coating films 10A to 10D formed from inorganic porous coating films 13a, 13b and hydrophilic organic polymer 16 (hydrophilic organic film).

[0132] In the hydrophilic coating films 10A to 10D, the proportion of betaine moieties (betaine polymer), cationic moieties (cationic polymer), and anionic moieties (anionic polymer) relative to the total mass of the hydrophilic organic polymer 16 is 20% or more. Therefore, the hydrophilic organic polymer 16 contains a sufficient amount of betaine moieties, cationic moieties, and anionic moieties, allowing the excellent hydrophilicity of the betaine moieties, cationic moieties, and anionic moieties to be fully utilized. As a result, the hydrophilic organic polymer 16 exhibits sufficient hydrophilicity and antifouling properties, and the hydrophilic coating films 10A to 10D formed from the inorganic porous coating films 13a, 13b and the hydrophilic organic polymer 16 (hydrophilic organic film) can be given excellent hydrophilicity and antifouling properties.

[0133] The hydrophilic coating films 10A to 10D have a film thickness in the range of 0.01 μm to 5 μm, preferably in the range of 0.1 μm to 0.6 μm. If the film thickness of the hydrophilic coating films 10A to 10D is less than 0.01 μm, the strength of the hydrophilic coating films 10A to 10D decreases, and the coating surface of the metal substrate 11 cannot be adequately protected by the hydrophilic coating films 10A to 10D. If the film thickness of the hydrophilic coating films 10A to 10D exceeds 5 μm, the film thickness becomes unnecessarily thick, reducing the flexibility of the hydrophilic coating films 10A to 10D, and the hydrophilic organic polymer 16 cannot adequately change shape (plastic deformation) in the numerous nano-sized fine voids 15 of the inorganic nanoporous structure, and the hydrophilic coating films 10A to 10D cannot follow the deformation of the coating surface 12 of the metal substrate 11.

[0134] Since the hydrophilic coating films 10A to 10D have a film thickness within the aforementioned range, the hydrophilic coating films 10A to 10D maintain a predetermined strength, and the hydrophilic coating films 10A to 10D can adequately protect the coated surface 12 of the metal substrate 11. Furthermore, the hydrophilic coating films 10A to 10D have excellent flexibility, and the hydrophilic organic polymer 16 can sufficiently change shape (plastic deformation) in the numerous nano-sized fine voids 15 of the inorganic nanoporous structure. As a result, the hydrophilic coating films 10A to 10D can follow the deformation of the coated surface 12 of the metal substrate 11, and the covering state of the hydrophilic coating films 10A to 10D on the coated surface 12 of the metal substrate 11 can be maintained.

[0135] The hydrophilic coating films 10A to 10D are composed of inorganic porous coating films 13a and 13b made of silicon dioxide (SiO₂ ２ ), aluminum oxide (Al ２ O ３ ), zirconium oxide (ZrO ２ ), titanium oxide (TiO ２ ), cerium oxide (CeO ２ The hydrophilic coating films 10A to 10D contain at least one type of inorganic fine particles 14 from among the following. The inorganic porous coating films 13a and 13b contain silicon dioxide (SiO ２ When the inorganic fine particles 14 are included, the hydrophilic organic polymer 16 readily bonds with silicon dioxide, and the hydrophilic organic polymer 16 that penetrates into the numerous fine voids of the inorganic porous coating films 13a and 13b readily bonds to the voids containing silicon dioxide, allowing the hydrophilic organic polymer 16 (hydrophilic organic film) to be firmly bonded (joined) to the voids 15 (inorganic fine particles 14) of the inorganic porous coating films 13a and 13b and the coating surface 12 of the metal substrate 11.

[0136] The hydrophilic coating films 10A to 10D consist of inorganic porous coating films 13a and 13b made of aluminum oxide (Al ２ O ３When the inorganic fine particles 14 are included, the hydrophilic organic polymer 16 readily bonds with aluminum oxide, allowing the hydrophilic organic polymer 16 (hydrophilic organic film) that has penetrated into the numerous fine voids 15 of the inorganic porous coating films 13a and 13b to be firmly bonded (joined) to the voids 15 (inorganic fine particles 14) containing aluminum oxide and the coating surface 12 of the metal substrate 11. Furthermore, the aluminum oxide makes it difficult for salts such as magnesium, calcium, sodium, and silicon to adhere to the hydrophilic coating films 10A to 10D, thus preventing contamination of the hydrophilic coating films 10A to 10D due to the adhesion of salts such as magnesium, calcium, sodium, and silicon.

[0137] The hydrophilic coating films 10A to 10D consist of inorganic porous coating films 13a and 13b made of zirconium oxide (ZrO ２ When inorganic fine particles 14 of ) are included, the hardness of the inorganic porous coating films 13a and 13b can be increased, and the rigidity of the hydrophilic coating films 10A to 10D can be increased. The hydrophilic coating films 10A to 10D are made of inorganic porous coating films 13a and 13b containing titanium dioxide (TiO ２ When the inorganic fine particles 14 of titanium dioxide are included, when light and water strike the inorganic fine particles 14 of titanium dioxide, the surface of the hydrophilic coating films 10A to 10D is coated with hydrophilic groups, and the hydrophilic coating films 10A to 10D can be given an excellent self-cleaning effect. The hydrophilic coating films 10A to 10D are made of inorganic porous coating films 13a and 13b which contain cerium oxide (CeO2). ２ When inorganic fine particles 14 of ) are included, the hardness can be increased by cerium oxide, and ultraviolet absorption ability can also be obtained, thereby increasing the rigidity of the hydrophilic coating films 10A to 10D and enabling ultraviolet absorption ability.

[0138] Figure 8 is an illustrative diagram showing an example of shape change (plastic deformation) of the hydrophilic organic polymer 16 (hydrophilic organic film) in the hydrophilic coating film 10A of Figure 2, and Figure 9 is an illustrative diagram showing an example of shape change (plastic deformation) of the hydrophilic organic polymer 16 (hydrophilic organic film) in the hydrophilic coating film 10B of Figure 3. Figure 10 is an illustrative diagram showing an example of shape change (plastic deformation) of the hydrophilic organic polymer 16 (hydrophilic organic film) in the hydrophilic coating film 10C of Figure 5, and Figure 11 is an illustrative diagram showing an example of shape change (plastic deformation) of the hydrophilic organic polymer 16 (hydrophilic organic film) in the hydrophilic coating film 10D of Figure 6.

[0139] The metal substrates 11 (iron plate, various stainless steel plates, copper plates, copper alloy plates, aluminum plates, aluminum alloy plates, magnesium alloy plates, duralumin plates, tin alloy plates, steel plates, nickel plates, zinc plates) on which the hydrophilic coating films 10A to 10D are formed undergo thermal expansion or contraction due to temperature changes. There is a difference in the thermal expansion coefficients between the hydrophilic coating films 10A to 10D and the metal substrates 11, and the degree of thermal expansion or contraction of the hydrophilic coating films 10A to 10D due to temperature changes is different from that of the metal substrates 11 due to temperature changes.

[0140] When the metal substrate 11 (iron plate, various stainless steel plates, copper plates, copper alloy plates, aluminum plates, aluminum alloy plates, magnesium alloy plates, duralumin plates, tin alloy plates, steel plates, nickel plates, zinc plates) on which the hydrophilic coating film 10A is formed expands or contracts due to temperature changes, as shown in Figure 8, the hydrophilic organic polymer 16 (ionic polymer) bonded to the voids 15 (inorganic fine particles 14) and the coating surface 12 of the metal substrate 11 undergoes shape deformation (plastic deformation), following the thermal expansion or contraction of the metal substrate 11 and absorbing the expansion and contraction of the metal substrate 11 due to thermal expansion or contraction. The hydrophilic coating film 10A exhibits excellent flexibility and absorbs compressive, tensile, and shear forces due to the thermal expansion or contraction of the metal substrate 11, so the hydrophilic coating film 10A is not unintentionally damaged by the thermal deformation of the metal substrate 11.

[0141] When the metal substrate 11 (iron plate, various stainless steel plates, copper plates, copper alloy plates, aluminum plates, aluminum alloy plates, magnesium alloy plates, duralumin plates, tin alloy plates, steel plates, nickel plates, zinc plates) on which the hydrophilic coating film 10B is formed expands or contracts due to temperature changes, as shown in Figure 9, the hydrophilic organic polymer 16 (ionic polymer) bonded to the voids 15 (inorganic fine particles 14) and the coating surface 12 of the metal substrate 11 undergoes shape deformation (plastic deformation), following the thermal expansion or contraction of the metal substrate 11 and absorbing the expansion and contraction of the metal substrate 11 due to thermal expansion or contraction. The hydrophilic coating film 10B exhibits excellent flexibility and absorbs compressive, tensile, and shear forces due to the thermal expansion or contraction of the metal substrate 11, so the hydrophilic coating film 10B is not unintentionally damaged by the thermal deformation of the metal substrate 11.

[0142] When the metal substrate 11 (iron plate, various stainless steel plates, copper plates, copper alloy plates, aluminum plates, aluminum alloy plates, magnesium alloy plates, duralumin plates, tin alloy plates, steel plates, nickel plates, zinc plates) on which the hydrophilic coating film 10C is formed expands or contracts due to temperature changes, as shown in Figure 10, the hydrophilic organic polymer 16 (ionic polymer) bonded to the voids 15 (inorganic fine particles 14) and the coating surface 12 of the metal substrate 11 undergoes shape deformation (plastic deformation), following the thermal expansion or contraction of the metal substrate 11 and absorbing the expansion and contraction of the metal substrate 11 due to thermal expansion or contraction. The hydrophilic coating film 10C exhibits excellent flexibility and absorbs compressive, tensile, and shear forces due to the thermal expansion or contraction of the metal substrate 11, so the hydrophilic coating film 10C is not unintentionally damaged by the thermal deformation of the metal substrate 11.

[0143] When the metal substrate 11 (iron plate, various stainless steel plates, copper plates, copper alloy plates, aluminum plates, aluminum alloy plates, magnesium alloy plates, duralumin plates, tin alloy plates, steel plates, nickel plates, zinc plates) on which the hydrophilic coating film 10D is formed expands or contracts due to temperature changes, as shown in Figure 11, the hydrophilic organic polymer 16 (ionic polymer) bonded to the voids 15 (inorganic fine particles 14) and the coating surface 12 of the metal substrate 11 undergoes shape deformation (plastic deformation), following the thermal expansion or contraction of the metal substrate 11 and absorbing the expansion and contraction of the metal substrate 11 due to thermal expansion or contraction. The hydrophilic coating film 10D exhibits excellent flexibility and absorbs compressive, tensile, and shear forces due to the thermal expansion or contraction of the metal substrate 11, so the hydrophilic coating film 10D is not unintentionally damaged by the thermal deformation of the metal substrate 11.

[0144] Furthermore, in the case of hydrophilic coating films 10A to 10D, when the hydrophilic coating films 10A to 10D are subjected to 1. exposure to a high temperature atmosphere of 250°C and 2. rapid cooling to room temperature, no cracks are observed in the hydrophilic coating films 10A to 10D.

[0145] The hydrophilic coating films 10A to 10D are formed from inorganic porous coating films 13a and 13b, which have an inorganic nanoporous structure in which adjacent inorganic nanoparticles 14 among a large number of inorganic nanoparticles are partially connected to each other, and a large number of nano-sized voids 15 are formed between these inorganic nanoparticles 14 that make up the inorganic nanoporous structure, and hydrophilic organic polymers 16 (hydrophilic organic films) that penetrate into these voids 15 of the inorganic porous coating films 13a and 13b, harden in these voids 15 and bond to the inorganic nanoparticles 13a and 13b. Since the hydrophilic organic polymers 16 (hydrophilic organic films) can change shape (elastically deform) in these voids 15, the hydrophilic coating films 10A to 10D exhibit excellent flexibility, and the hydrophilic coating films 10A to 10D and the metal substrate 11 (iron plate, various stainless steel plates, copper plate, copper) are affected by temperature changes. Even if thermal expansion or contraction occurs in alloy plates, aluminum plates, aluminum alloy plates, magnesium alloy plates, duralumin plates, tin alloy plates, steel plates, nickel plates, or zinc plates, the hydrophilic organic polymer 16 can freely change shape (elastically deform) in those voids 15, and the hydrophilic coating films 10A to 10D can follow the difference in thermal expansion or contraction between the hydrophilic coating films 10A to 10D and the metal substrate 11. Even if compressive, tensile, or shear forces act on the hydrophilic coating films 10A to 10D due to the difference in thermal expansion or contraction between the hydrophilic coating films 10A to 10D and the metal substrate 11, the occurrence of cracks in the hydrophilic coating films 10A to 10D can be reliably prevented, and the covering state of the hydrophilic coating films 10A to 10D on the coated surface 11 of the metal substrate 11 can be maintained for a long period of time.

[0146] Figure 12 shows the contact angle of a water droplet W dropped onto the hydrophilic coating film 10A in Figure 2, and Figure 13 shows the contact angle of a water droplet W dropped onto the hydrophilic coating film 10B in Figure 3. Figure 14 shows the contact angle of a water droplet W dropped onto the hydrophilic coating film 10C in Figure 5, and Figure 15 shows the contact angle of a water droplet W dropped onto the hydrophilic coating film 10D in Figure 6.

[0147] The hydrophilic coating films 10A to 10D shown in Figures 2 and 3, and Figures 5 and 6 have a contact angle θ of 40° or less, preferably 20° or less, for water droplets W. The contact angle θ of water droplets W in the hydrophilic coating films 10A to 10D was measured according to JIS R3257 (Test method for wettability of substrate glass surfaces). The contact angle θ of the hydrophilic coating films 10A to 10D measured according to JIS R3257 was 40° or less (20° or less). For the wettability test according to JIS R3257, a test piece, a sample stage, an illumination device (light source), an optical reader, and a syringe were prepared. The sample stage is equipped with a mechanism to move the position of the sample stage up and down and left and right so that the water droplet placed on the test piece is at the center of the optical axis between the illumination device and the optical reader. The illumination device causes the image of the water droplet on the test piece to be placed within the field of view of the optical reader. The capacity of the syringe barrel is 1 ml or less.

[0148] The conditions for the wettability test are: room temperature: 25±5℃, humidity: 50±10%, water droplet volume: 1 μl, measurement time: 30 seconds, water used: distilled water. The procedure for the wettability test is as follows: (1) Calibrate the test apparatus using the prescribed method. (2) Place the test specimens with hydrophilic coating films 10A to 10D on the test stand. (3) Pour distilled water into a clean glass beaker and collect this distilled water into the syringe. (4) Allow the distilled water in the syringe to stand as a water droplet W on the test specimen on the sample stand. Quickly measure the r and h of the water droplet W. Alternatively, read θ / 2. (5) Measurements should be taken at a minimum of 5 locations.

[0149] Wettability was expressed as the average value and standard deviation of five or more data points for the contact angle θ calculated based on the following (Equation 1), or for the contact angle θ obtained from the direct reading of θ / 2.

[0150] (Equation 1): θ = 2tan －１ h / r

[0151] In equation (1), r is the radius (mm) of the surface of the water droplet W in contact with the test specimen, and h is the height (mm) from the surface of the test specimen to the top of the water droplet W.

[0152] The hydrophilic coating films 10A to 10D have a contact angle θ of 40° or less (20° or less) with water droplets W measured according to JIS R3257, thus possessing excellent hydrophilicity and antifouling properties. The small contact angle of water with the surface of the hydrophilic coating films 10A to 10D allows for a large contact area of ​​water with the surface of the hydrophilic coating films 10A to 10D. When the hydrophilic coating films 10A to 10D are washed with water, the water comes into broad contact with the surface of the hydrophilic coating films 10A to 10D. Therefore, even if dirt such as dust adheres to the surface of the hydrophilic coating films 10A to 10D, the dirt can be easily washed off or wiped away with water, keeping the surface clean.

[0153] Furthermore, in the hydrophilic coating films 10B and 10D, the portion of the hydrophilic organic polymer 16 (hydrophilic organic film) within the inorganic porous coating film 13b (inorganic fine particles 14) that is exposed upward from the uppermost layer (uppermost layer) forms fine irregularities on the surface of the hydrophilic coating film 10D. These irregularities further increase the water contact area, making it possible to easily and reliably wash or wipe away dirt adhering to the hydrophilic coating films 10B and 10D with water.

[0154] The hydrophilic coating films 10A to 10D have an inorganic nanoporous structure in which the inorganic porous coating films 13a and 13b are made by the sol-gel method using at least one of silica sol, alumina sol, zirconia sol, titania sol, and ceria sol, and the hydrophilic organic polymer 16 penetrates into numerous fine voids 15 of the inorganic porous coating films 13a and 13b, and the hydrophilic organic polymer 16 (hydrophilic organic film) penetrates into the voids 15 (inorganic fine particles) of the inorganic porous coating films 13a and 13b. 14) Since it is bonded (joined) to the coating surface 12 of the metal substrate 11, the hydrophilic organic polymer 16 will not peel off or disappear prematurely from the hydrophilic coating films 10A to 10D due to stress from the usage environment, and a decrease in the hydrophilicity, antifouling, antiviral, antibacterial, and antifungal properties of the hydrophilic coating films 10A to 10D can be prevented, and the hydrophilic function, antifouling function, antiviral function, antibacterial function, antifungal function, and deodorizing function of the hydrophilic organic polymer 16 can be maintained for a long period of time.

[0155] The hydrophilic coating films 10A to 10D are characterized by the hydrophilic organic polymer 16 (hydrophilic organic film) containing at least one of a betaine portion (betaine polymer), a cationic portion (cationic polymer), and anionic portion (anionic polymer), thereby enabling the hydrophilic organic polymer 16 to exhibit excellent hydrophilicity and antifouling properties, thereby reliably reducing the contact angle of water with the film surface of the hydrophilic coating films 10A to 10D, reliably increasing the contact area of ​​water with the film surface of the hydrophilic coating films 10A to 10D, and allowing dirt adhering to the hydrophilic coating films 10A to 10D to be easily washed away with water when the hydrophilic coating films 10A to 10D are washed with water.

[0156] The hydrophilic coating films 10A to 10D have a surface resistance value of 10 at room temperature. ７ ~10 １１The surface resistance values ​​are within the range of (Ω / □) (ohms per square). The surface resistance values ​​of the hydrophilic coating films 10A to 10D were measured in accordance with ANSI / EDS STM 11.13. The surface resistance values ​​were measured using a two-contact probe and the two-terminal method, and calculated using the following (Equation 2).

[0157] (Equation 2): Calculated using the formula ρS = (V / I) × (W / L).

[0158] In equation (2), V is the voltage applied to the surface between the two electrodes, I is the current flowing between the electrodes, W is the width of the electrodes, and L is the distance between the electrodes.

[0159] The hydrophilic coating films 10A to 10D have a surface resistance value (Ω / □) within the aforementioned range at room temperature. The surface resistance value of the hydrophilic coating films 10A to 10D is low, making it difficult for the hydrophilic coating films 10A to 10D to become charged. Furthermore, even if the hydrophilic coating films 10A to 10D become charged, they discharge easily, thus preventing the adhesion of dust and other dirt due to static electricity.

[0160] The hydrophilic coating films 10A to 10D have a light transmittance of 85% or more at 550 nm when deposited on glass. The light transmittance was determined by using a visible light transmittance meter to measure the transmitted light flux and incident light flux of glass (test specimens) coated with the hydrophilic coating films 10A to 10D, and expressing the ratio of the two as a percentage. Since the hydrophilic coating films 10A to 10D have a light transmittance of 85% or more at 550 nm when deposited on glass, the hydrophilic coating films 10A to 10D have excellent transparency and do not interfere with the output of various images, allowing the outputted images to be clearly viewed. When the hydrophilic coating films 10A to 10D are coated on the coating surface 12 of a metal substrate 11, characters, symbols, patterns, colors, etc. displayed on the coating surface 12 can be clearly viewed.

[0161] Figure 16 is a flowchart showing an example of a method for forming hydrophilic coating films 10A to 10D. An example of a method for forming hydrophilic coating films 10A to 10D based on Figure 16 is as follows. The method for forming hydrophilic coating films shown in Figure 16 creates hydrophilic coating films 10A to 10D formed from inorganic porous coating films 13a and 13b having numerous nano-sized fine voids 15 and a hydrophilic organic polymer 16 (hydrophilic organic film).

[0162] An example of a method for forming hydrophilic coating films 10A to 10D includes a cleaning step (P-1), a coating step (P-2), a film formation (inorganic porous coating film formation) step (P-3), an immersion step (P-4), a drying step (hydrophilic organic film formation) step (P-5), and a water cleaning step (P-6). By performing these steps (P-1) to (P-6), hydrophilic coating films 10A to 10D are formed on the coated surface 12 of a metal substrate 11 (iron plate, various stainless steel plates, copper plates, copper alloy plates, aluminum plates, aluminum alloy plates, magnesium alloy plates, duralumin plates, tin alloy plates, steel plates, nickel plates, zinc plates).

[0163] The cleaning process (P-1) involves first performing a cleaning treatment to blow away dust from the coated surface 12 of the metal substrate 11 using an air jet means such as an air gun, and then cleaning the coated surface 12 with an alkaline detergent. After cleaning with the alkaline detergent, the coated surface 12 is cleaned with an acidic liquid. The alkaline detergent can be any alkaline substance and is not limited to a specific detergent, and the acidic liquid can be any acidic substance and is not limited to a specific liquid. In the cleaning process, the coated surface 12 of the metal substrate 11 is cleaned with an alkaline detergent and then cleaned with an acidic liquid, ensuring that dirt such as dust, oil, and organic matter adhering to the coated surface 12 is reliably removed.

[0164] The coating step (P-2) involves coating (applying) a coating liquid (inorganic coating liquid) (at least one of silica sol, alumina sol, zirconia sol, titania sol, and ceria sol) containing a large number of nano-sized inorganic fine particles 14 onto the coating surface 12 of the metal substrate 11 after cleaning. The coating method for the coating liquid (inorganic coating liquid) on the coating surface 12 in the coating step (P-2) is one of the following: a wiping coating method in which the inorganic coating liquid is soaked into a soft cloth made of microfiber or nonwoven fabric and the inorganic coating liquid is coated onto the coating surface 12 of the metal substrate 11 with the cloth; a spin coating method in which the inorganic coating liquid is dripped near the center of the coating surface of the metal substrate 11 using a spin coater, and the metal substrate (inorganic coating liquid) is rotated at high speed to create a thin film of inorganic coating liquid by the centrifugal force generated; or a spray coating method in which the inorganic coating liquid is coated onto the coating surface 12 of the metal substrate 11 using a spray can or spray gun containing the inorganic coating liquid. Furthermore, as coating methods, brush coating is performed by applying an inorganic coating solution to the coating surface 12 of the metal substrate 11 using a brush, and a roll coater is used to apply the inorganic coating solution to the coating surface 12 of the metal substrate 11 using a roll coated with the inorganic coating solution. Prior to the coating process (P-2), an inorganic coating solution preparation process is carried out in which at least one of silica sol, alumina sol, zirconia sol, titania sol, and ceria sol is dissolved in an aqueous solution (for example, pure water) to create an inorganic coating solution.

[0165] In the film formation process (P-3), the coating liquid (inorganic coating liquid) applied to the coated surface 12 of the metal substrate 11 is dried, and inorganic porous coating films 13a and 13b are formed on the coated surface 12 by the sol-gel method. These inorganic porous coating films 13a and 13b have an inorganic nanoporous structure with a void ratio of 20% to 70% and a large number of nano-sized fine voids 15. The inorganic porous coating films 13a and 13b shown in Figure 1 or Figure 4 are formed on the coated surface 12 of the metal substrate 11.

[0166] In the film formation process (P-3), as previously described, silicon dioxide (SiO ２ ), aluminum oxide (Al ２ O ３ ), zirconium oxide (ZrO ２ ), titanium oxide (TiO ２ ), cerium oxide (CeO ２ The aforementioned coating solution (inorganic coating solution) containing at least one type of inorganic fine particles 14 (inorganic nanoparticles) is used. In the film formation process (P-3), after coating the coating surface 12 of the metal substrate 11 with the inorganic coating solution, the dispersion medium (water or alcohol) contained in the inorganic coating solution volatilizes, and the inorganic fine particles 14 are partially linked together. The inorganic porous coating films 13a and 13b formed in the film formation process (P-3) have an inorganic nanoporous structure having a large number of nano-sized fine voids 15, as shown in Figures 1 and 3.

[0167] The method for forming a hydrophilic coating film involves coating the coating surface 12 of the metal substrate 11 with at least one of silica sol, alumina sol, zirconia sol, titania sol, or ceria sol in the coating step using one of the following methods: spin coating, spray coating, or wiping coating. This allows the coating liquid (inorganic coating liquid) to be evenly coated (applied) to the coating surface 12, and ensures the formation of inorganic porous coating films 13a and 13b having numerous nano-sized fine voids 15.

[0168] In the penetration step (P-4), after inorganic porous coating films 13a and 13b having an inorganic nanoporous structure with numerous fine voids 15 are formed on the coating surface 12 of the metal substrate 11, a coating liquid (hydrophilic organic polymer coating liquid) containing a hydrophilic organic polymer 16 (ionic polymer), or metal ions (Ag) is applied to the coating surface 12 from above the inorganic porous coating films 13a and 13b. ＋ Ions (silver ions), Cu ２＋ Ions (copper ions), Zn ２＋A coating solution (hydrophilic organic polymer coating solution) containing a hydrophilic organic polymer 16 (ionic polymer) having at least one of the following ions (zinc ions) is applied. The coating solution (hydrophilic organic polymer coating solution) penetrates into numerous fine voids 15 formed in the inorganic porous coating films 13a and 13b.

[0169] Furthermore, if the hydrophilic organic polymer (ionic polymer) contains metal ions, before the infiltration step (P-4), the hydrophilic organic polymer 16 (ionic polymer) containing at least one of the betaine moiety (betaine polymer), cationic moiety (cationic polymer), and anionic moiety (anionic polymer) is dissolved in an aqueous solution (e.g., pure water), and the metal ions (Ag) are transferred to the betaine polymer, anionic polymer, or cationic polymer by ion exchange. ＋ Ion, Cu ２＋ Ions, Zn ２＋ A metal ion introduction process is carried out to introduce at least one of the ions.

[0170] In the penetration process (P-4), the coating method for the coating liquid (hydrophilic organic polymer coating liquid) on the inorganic porous coating films 13a and 13b (the coated surface 12 of the metal substrate 11) is one of the following: a wiping coating method in which the inorganic coating liquid is soaked into a soft cloth made of microfiber or nonwoven fabric and the hydrophilic organic polymer coating liquid is coated onto the coated surface 12 of the metal substrate 11 with the cloth; a spin coating method in which the hydrophilic organic polymer coating liquid is dripped onto the center of the coated surface 12 of the metal substrate 11 using a spin coater, and the metal substrate (hydrophilic organic polymer coating liquid) is rotated at high speed to create a thin film made of the hydrophilic organic polymer coating liquid by the centrifugal force generated; or a spray coating method in which the hydrophilic organic polymer coating liquid is coated onto the coated surface 12 of the metal substrate 11 using a spray can or spray gun containing the hydrophilic organic polymer coating liquid. Furthermore, as coating methods, a brush coating method is used to apply the hydrophilic organic polymer coating liquid to the coating surface 12 of the metal substrate 11, and a roll coater is used to apply the hydrophilic organic polymer coating liquid to the coating surface 12 of the metal substrate 11 using a roll coated with the hydrophilic organic polymer coating liquid.

[0171] In the penetration process (P-4), the coating liquid is applied to the inorganic porous coating films 13a and 13b (inorganic fine particles 14) to a predetermined coverage dimension so that the inorganic porous coating films 13a and 13b (inorganic fine particles 14) are not exposed from the surface of the coating liquid (hydrophilic organic polymer coating liquid), thereby covering the surface of the inorganic porous coating films 13a and 13b with the coating liquid. Alternatively, the coating liquid is applied to the inorganic porous coating films 13a and 13b so that the uppermost layer of the inorganic porous coating films 13a and 13b (inorganic fine particles 14) is exposed from the surface of the coating liquid (hydrophilic organic polymer coating liquid).

[0172] The drying (hydrophilic organic compound formation) step (P-5) dries the coating liquid (hydrophilic organic polymer coating liquid) that has penetrated the voids 15 formed in the inorganic porous coating films 13a and 13b (natural drying or heat drying). In the drying step (P-5), the solvent in the hydrophilic organic polymer coating liquid that has penetrated the voids 15 of the inorganic porous coating films 13a and 13b volatilizes, the hydrophilic organic polymer 16 hardens, and the hydrophilic organic polymer 16 (hydrophilic organic film) bonds (bonds) to the voids 15 (inorganic fine particles 14) of the inorganic porous coating films 13a and 13b and the coating surface 12 of the metal substrate 11, forming hydrophilic coating films 10A to 10D consisting of the inorganic porous coating films 13a and 13b and the hydrophilic organic polymer 16 (hydrophilic organic film).

[0173] During the formation of hydrophilic coating films 10A and 10C in the drying process (P-5), the inorganic porous coating films 13a and 13b are not exposed from the surface of the hydrophilic organic polymer 16 (hydrophilic organic film). Instead, the hydrophilic organic polymer 16 covers the surface of the inorganic porous coating films 13a and 13b (inorganic fine particles 14), and the inorganic porous coating films 13a and 13b (inorganic fine particles 14) are embedded in the hydrophilic organic polymer film (hydrophilic organic film) (see Figures 2 and 5). Alternatively, during the formation of hydrophilic coating films 10C and 10D in the drying process (P-5), the uppermost layer of the hydrophilic organic polymer 16 (hydrophilic organic film) is located slightly below the surface of the inorganic porous coating films 13a and 13b, the uppermost layer of the inorganic porous coating films 13a and 13b (inorganic fine particles 14) is exposed above the uppermost layer of the hydrophilic organic polymer 16, and the portion of the inorganic porous coating films 13a and 13b (inorganic fine particles 14) that is exposed above the uppermost layer of the hydrophilic organic polymer 16 (uppermost layer) forms fine irregularities on the surface of the hydrophilic organic polymer 16, and the portion that forms the irregularities (uppermost layer) is coated with an ultrathin film of the hydrophilic organic polymer 16 (hydrophilic organic film) (see Figures 3 and 6).

[0174] The water washing step (P-6) involves flowing water over the surface of the hydrophilic coating films 10A to 10D, which are formed from inorganic porous coating films 13a and 13b and hydrophilic organic polymers 16 (hydrophilic organic films), and washing the hydrophilic coating films 10A to 10D using water. In the water washing step (P-6), excess hydrophilic organic polymers 16 that are weakly bound to the inorganic porous coating films 13a and 13b are washed away with water, excluding the hydrophilic organic polymers 16 that are strongly bound to the inorganic porous coating films 13a and 13b, thereby removing hydrophilic organic polymers 16 that do not contribute to hydrophilicity from the hydrophilic coating films 10A to 10D.

[0175] Figure 17 is a flowchart showing another example of a hydrophilic coating film formation method for creating hydrophilic coating films 10A to 10D. Another example of a hydrophilic coating film formation method for creating hydrophilic coating films 10A to 10D based on Figure 13 is as follows. The hydrophilic coating film formation method shown in Figure 12 creates hydrophilic coating films 10A to 10D formed from inorganic porous coating films 13a, 13b having numerous nano-sized fine voids 15 and a hydrophilic organic polymer 16 (hydrophilic organic film).

[0176] Another example of a hydrophilic coating film formation method includes a cleaning step (P-1), a coating step (P-2), a film formation step (inorganic porous coating film and hydrophilic organic film formation) (P-3), and a water cleaning step (P-4). By performing these steps (P-1) to (P-4), hydrophilic coating films 10A to 10D are formed on the coated surface 12 of a metal substrate 11 (iron plate, various stainless steel plates, copper plates, copper alloy plates, aluminum plates, aluminum alloy plates, magnesium alloy plates, duralumin plates, tin alloy plates, steel plates, nickel plates, zinc plates). The cleaning step (P-1) is the same as that of the hydrophilic coating film formation method shown in Figure 16.

[0177] The coating step (P-2) involves a coating solution (inorganic and hydrophilic organic polymer coating solution) containing at least one of silica sol, alumina sol, zirconia sol, titania sol, and ceria sol in which a large number of nano-sized inorganic fine particles 14 are dispersed, and a hydrophilic organic polymer 16 (ionic polymer), or a coating solution containing at least one of silica sol, alumina sol, zirconia sol, titania sol, and ceria sol in which a large number of nano-sized inorganic fine particles 14 are dispersed, and a metal ion (Ag ＋ Ions (silver ions), Cu ２＋ Ions (copper ions), Zn ２＋ A coating solution (inorganic and hydrophilic organic polymer coating solution) containing a hydrophilic organic polymer 16 (ionic polymer) having at least one of the following ions (zinc ions) is coated (applied) to the coating surface 12 of the metal substrate 11 after cleaning.

[0178] The coating method for the coating solution (inorganic and hydrophilic organic polymer coating solution) on the coating surface 12 of the metal substrate 11 in the coating step (P-2) is the same as that for forming a hydrophilic coating film shown in Figure 16. Prior to the coating step (P-2), a coating solution preparation step is performed in which at least one of silica sol, alumina sol, zirconia sol, titania sol, and ceria sol, which are dispersed in an aqueous solution (e.g., pure water) with a hydrophilic organic polymer (ionic polymer) to create a coating solution (inorganic and hydrophilic organic polymer coating solution). Alternatively, at least one of silica sol, alumina sol, zirconia sol, titania sol, and ceria sol, which are dispersed in an aqueous solution (e.g., pure water) with a metal ion (Ag ＋ Ions (silver ions), Cu ２＋ Ions (copper ions), Zn ２＋ A coating solution preparation process is carried out to create a coating solution (inorganic and hydrophilic organic polymer coating solution) by dissolving a hydrophilic organic polymer (ionic polymer) containing at least one of the ions (zinc ions).

[0179] In the film formation process (P-3), the coating liquid (inorganic coating liquid among inorganic and hydrophilic organic polymer coating liquids) applied to the coated surface 12 of the metal substrate 11 is dried, and inorganic porous coating films 13a and 13b are formed on the coated surface of the metal substrate by the sol-gel method, creating an inorganic nanoporous structure with numerous nano-sized fine voids 15 in the range of 20% to 70% void ratio, and the coating liquid (hydrophilic organic polymer coating liquid among inorganic and hydrophilic organic polymer coating liquids) that has penetrated into the voids 15 formed in the inorganic porous coating films 13a and 13b is dried. In the film formation process (P-3), hydrophilic coating films 10A to 10D, consisting of the inorganic porous coating films 13a and 13b shown in Figure 1 or Figure 4 and a cured hydrophilic organic polymer 16 (hydrophilic organic film), are formed on the coated surface 12 of the metal substrate 11. The hydrophilic organic polymer 16 (hydrophilic organic film) is bonded (joins) to the voids 15 (inorganic fine particles 14) of the inorganic porous coating films 13a and 13b and to the coating surface 12 of the metal substrate 11.

[0180] In the film formation process (inorganic porous coating film and hydrophilic organic film formation) (P-3), silicon dioxide (SiO ２ ), aluminum oxide (Al ２ O ３ ), zirconium oxide (ZrO ２ ), titanium oxide (TiO ２ ), cerium oxide (CeO ２ A coating liquid (inorganic and hydrophilic organic polymer coating liquid) comprising at least one type of inorganic fine particles 14 (inorganic nanoparticles) and a hydrophilic organic polymer 16 (ionic polymer), or an inorganic fine particles 14 (inorganic nanoparticles), a hydrophilic organic polymer 16 (ionic polymer), and a metal ion (Ag ＋ Ions (silver ions), Cu ２＋ Ions (copper ions), Zn ２＋After coating the coating surface 12 of the metal substrate 11 with a coating solution (inorganic and hydrophilic organic polymer coating solution) containing at least one of the ions (zinc ions), the dispersion medium (water or alcohol) contained in the inorganic and hydrophilic organic polymer coating solution volatilizes, causing the inorganic fine particles 14 to be partially linked together to form an inorganic nanoporous structure having numerous nanoscale fine voids 15, and forming a hydrophilic organic polymer 16 (hydrophilic organic film) that penetrates these voids 15 and bonds (bonds) to the inorganic fine particles 14 and the coating surface 12 of the metal substrate 11. The water washing step (P-4) is the same as that of the hydrophilic coating film formation method shown in Figure 16.

[0181] The method for forming a hydrophilic coating film involves using a coating solution containing numerous inorganic fine particles 14 in the film formation (inorganic porous coating film formation) step (P-3) and drying (hydrophilic organic film formation) step (P-5) shown in Figure 16, and in the film formation (inorganic porous coating film and hydrophilic organic film formation) step (P-3) shown in Figure 17, and forming inorganic porous coating films 13a and 13b with an inorganic nanoporous structure having numerous nano-sized fine voids 15 by the sol-gel method, as well as a coating solution containing a hydrophilic organic polymer 16 (ionic polymer), or a coating solution containing a hydrophilic organic polymer 16 (ionic polymer) and metal ions. By using a coating solution, the hydrophilic organic polymer 16 is allowed to penetrate into the numerous fine voids 15 of the inorganic porous coating films 13a and 13b, forming a hydrophilic organic polymer 16 (hydrophilic organic film) on the coating surface 12 of the metal substrate 11. This makes it possible to create hydrophilic coating films 10A to 10D that have excellent hydrophilicity and antifouling properties (and even better antiviral, antibacterial, and antifungal properties if metal ions are included), as well as a small contact angle with the film surface and a large contact area with water on the film surface. This makes it possible to create hydrophilic coating films 10A to 10D that can easily wash away attached dirt with water.

[0182] In the method for forming the hydrophilic coating film, the hydrophilic organic polymer 16 penetrates into the numerous fine voids 15 of the inorganic porous coating films 13a and 13b, and the hydrophilic organic polymer 16 (hydrophilic organic film) bonded to the voids 15 (inorganic fine particles 14) of the inorganic porous coating films 13a and 13b and the coating surface 12 of the metal substrate 11. By combining these components, the hydrophilic organic polymer 16 will not peel off or disappear prematurely from the hydrophilic coating films 10A to 10D due to stress from the usage environment. Therefore, it is possible to create hydrophilic coating films 10A to 10D that can prevent a decrease in hydrophilicity and antifouling properties (and further antiviral, antibacterial, and antifungal properties if metal ions are included), and hydrophilic coating films 10A to 10D that can maintain their hydrophilic function and antifouling function (and further antiviral, antibacterial, antifungal, and deodorizing function if metal ions are included) for a long period of time.

[0183] The method for forming a hydrophilic coating film involves cleaning the coating surface 12 of the metal substrate 11 using an alkaline detergent (for example, an alkaline detergent with a pH of 8 to 9) in the cleaning step (P-1) shown in Figures 16 and 17, and then cleaning the coating surface 12 using an acidic liquid (for example, an acidic liquid with a pH of 1 to 2). This ensures that dirt such as dust, oil, and organic matter adhering to the coating surface 12 of the metal substrate 11 is reliably removed, and a hydrophilic coating film 10A to 10D with excellent hydrophilicity, antifouling, antiviral, antibacterial, and antifungal properties can be created on the coating surface 12 after the dirt has been removed.

[0184] The method for forming the hydrophilic coating film involves forming inorganic porous coating films 13a and 13b having an inorganic nanoporous structure by a sol-gel method using at least one of silica sol, alumina sol, zirconia sol, titania sol, and ceria sol. Therefore, inorganic coating films 10A to 10D having numerous nano-sized fine voids 15 can be reliably formed on the coating surface 12 of the metal substrate 11.

[0185] In the method for forming the hydrophilic coating film, the excess hydrophilic organic polymer 16 (hydrophilic organic film) that is weakly bonded to the voids 15 (inorganic fine particles 14) of the inorganic porous coating film 13a, 13b and the coating surface 12 of the metal substrate 11 is washed away with water, thereby removing the hydrophilic organic polymer 16 (hydrophilic organic film) that does not contribute to hydrophilicity from the hydrophilic coating films 10A to 10D.

[0186] The method for forming a hydrophilic coating film is such that the surface resistance value at room temperature is 10 ７ ~10 １１ It is possible to create hydrophilic coating films 10A to 10D in the range of (Ω / □) (ohms per square), which have low surface resistance, are difficult to charge, and even if they do charge, they discharge easily, thus preventing the adhesion of dust and other dirt due to static electricity.

[0187] The method for forming a hydrophilic coating film can produce hydrophilic coating films 10A to 10D with a light transmittance of 85% or more at 550 nm when deposited on glass, possessing excellent transparency, not hindering the output of various images, allowing for clear viewing of the outputted images, and enabling the clear viewing of characters, symbols, patterns, colors, etc. displayed on the coated surface 12 of the metal substrate 11.

[0188] Examples 1 to 5 of the hydrophilic coating films 10A to 10D according to the present invention will be described below, along with Comparative Examples 1 to 2 of the hydrophilic coating films 10A to 10D according to the present invention. The preparation methods for the inorganic coating solutions 1 to 7 used in these examples and comparative examples are as follows. The inorganic porous coating films were prepared by applying the inorganic coating solutions to a substrate.

[0189] In an inorganic coating solution 1: 4 g of ethanol, 11.6 g of water, 0.4 g of 1N-HCl, and 2 g of tetraethoxysilane were added to a 50 ml screw-cap tube and stirred at room temperature for at least 2 hours. In another 50 ml screw-cap tube, 8 g of isopropyl alcohol, 1 g of Nissan Chemical's IPA-ST (silica 30 wt%), and 1 g of the above solution were added and stirred at room temperature to obtain inorganic coating solution 1.

[0190] Inorganic coating solution 2: 10 g of ethanol, 5.6 g of water, 0.4 g of 1N-HCl, and 4 g of Colcoat ethyl silicate 40 were added to a 50 ml screw-cap tube and stirred at room temperature for at least 2 hours. In another 50 ml screw-cap tube, 8 g of isopropyl alcohol, 1 g of Nissan Chemical's IPA-ST (silica 30 wt%), and 1 g of the above solution were added and stirred at room temperature to obtain inorganic coating solution 2.

[0191] Inorganic coating solution 3: 16 g of ethanol, 1.6 g of water, 0.4 g of 1N-HCl, and 2 g of tetraethoxysilane were added to a 50 ml screw-cap tube and stirred at room temperature for at least 2 hours. In another 50 ml screw-cap tube, 7.5 g of isopropyl alcohol, 2 g of Nissan Chemical's IPA-ST-UP (silica 15 wt%), and 0.5 g of the above solution were added and stirred at room temperature to obtain inorganic coating solution 3.

[0192] Inorganic coating solution 4: 4 g of ethanol, 11.6 g of water, 0.4 g of 1N-HCl, and 2 g of tetraethoxysilane were added to a 50 ml screw-cap tube and stirred at room temperature for at least 2 hours. In another 110 ml screw-cap tube, 79 g of water, 20 g of Nissan Chemical's AS-520-A (alumina 20 wt%), and 1 g of the above solution were added and stirred at room temperature to obtain inorganic coating solution 4.

[0193] Inorganic coating solution 5: Merck's Durazane 2800-15 was used as inorganic coating solution 5.

[0194] Inorganic coating solution 6: Inorganic coating solution 6 was prepared by diluting Merck's Durazane 2400-15 with dibutyl ether 10-fold.

[0195] Inorganic coating solution 7: 4 g methanol, 11.6 g water, 0.4 g 1N HCl, and 2 g tetramethoxysilane were added to a 50 ml screw tube and stirred at room temperature for at least 2 hours. 9 g isopropyl alcohol was added to obtain inorganic coating solution 7.

[0196] The preparation methods for hydrophilic organic polymer solutions 1 to 4 used in the examples and comparative examples are as follows.

[0197] Hydrophilic organic polymer solution 1: Under nitrogen, 10 mmol of 2-{[2-(methacryloyloxy)ethyl]dimethylammonio}acetic acid and water were added to a round-bottom flask to make a 20 wt% solution. Next, 0.1 mmol of 2,2'-azobis-2-methyl-N-2-hydroxyethylpropionamide was added and heated with stirring at 75°C for 3 hours, after which water was added to obtain a 1 wt% hydrophilic organic polymer solution 1.

[0198] Hydrophilic Organic Polymer Solution 2: Under nitrogen, 10 mmol of 3-{[2-(methacryloyloxy)ethyl]dimethylammonio}propane-1-sulfonic acid and water were added to a round-bottom flask to make a 20 wt% solution. Next, 0.16 mmol of 2,2'-azobis-2-methyl-N-2-hydroxyethylpropionamide was added, and the mixture was heated with stirring at 75°C for 3 hours. After that, water was added to obtain a 1 wt% hydrophilic organic polymer solution 2.

[0199] Hydrophilic Organic Polymer Solution 3: Under nitrogen, 10 mmol of 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonic acid and water were added to a round-bottom flask to make a 20 wt% solution. Next, 0.16 mmol of 2,2'-azobis-2-methyl-N-2-hydroxyethylpropionamide was added and heated with stirring at 75°C for 3 hours, after which water was added to obtain a 1 wt% hydrophilic organic polymer solution 3.

[0200] Hydrophilic organic polymer solution 4: Under nitrogen, 10 mmol of potassium 3-sulfopropyl methacrylate and water were added to a round-bottom flask to make a 20 wt% solution. Next, 0.16 mmol of 2,2'-azobis-2-methyl-N-2-hydroxyethylpropionamide was added and heated with stirring at 75°C for 3 hours, after which water was added to obtain a 1 wt% hydrophilic organic polymer solution 4.

[0201] In Examples 1 to 5 and Comparative Examples 1 to 2, the inorganic coating solutions 1 to 7 and hydrophilic organic polymer solutions 1 to 4 were applied to the coating surface of metal substrates by microfiber cloth coating or spray coating. The film thickness of the hydrophilic coating films in Examples 1 to 5 and Comparative Examples 1 to 2 was measured by cross-sectional observation using a scanning electron microscope (SEM) either the XVision200TB manufactured by SII Nanotechnology Co., Ltd. or the JSM-5500 manufactured by JEOL Ltd. The contact angle of the hydrophilic coating films in Examples 1 to 5 and Comparative Examples 1 to 2 was measured using a Nick LSE-ME5. A Keyence VK-X3000 laser microscope was used.

[0202] In Example 1, an inorganic coating solution 1 was applied to the coated surface of a SUS304 substrate (metal substrate), which had been thoroughly cleaned with ethyl alcohol, using a microfiber cloth coating. After drying for 30 minutes, a hydrophilic organic polymer solution 1 was applied using a microfiber cloth coating and dried for 3 hours. Subsequently, the surface was washed with water using a sponge to remove any excess hydrophilic organic polymer 1, obtaining a hydrophilic coating film formed on the coated surface of the SUS304 substrate. The film thickness of the hydrophilic coating film formed on the coated surface of the SUS304 substrate, as observed by SEM in cross-section, was 248 nm. The contact angle of this hydrophilic coating film was measured to be 7.2°. The hydrophilic coating film of Example 1 was subjected to a thermal shock test by exposing it to a high temperature atmosphere of 250°C and then rapidly cooling it to room temperature. No cracks were observed in the hydrophilic coating film, neither visually nor under a laser microscope.

[0203] In Example 2, an inorganic coating solution 2 was spray-coated onto the coated surface of an aluminum substrate (metal substrate) that had been thoroughly cleaned with ethyl alcohol. After drying for 30 minutes, a hydrophilic organic polymer solution 2 was spray-coated and dried for 3 hours. Subsequently, the surface was washed with water using a sponge to remove any excess hydrophilic organic polymer 2, obtaining a hydrophilic coating film formed on the coated surface of the aluminum substrate. The film thickness of the hydrophilic coating film formed on the coated surface of the aluminum substrate, as observed by SEM, was 417 nm. The contact angle of this hydrophilic coating film was measured to be 6.2°. The hydrophilic coating film of Example 2 was subjected to a thermal shock test by exposing it to a high temperature atmosphere of 250°C and then rapidly cooling it to room temperature. No cracks were observed in the hydrophilic coating film, neither visually nor under a laser microscope.

[0204] In Example 3, an inorganic coating solution 3 was spray-coated onto the coated surface of an A5052 aluminum-magnesium alloy substrate (metal substrate) that had been thoroughly cleaned with ethyl alcohol. After drying for 30 minutes, a hydrophilic organic polymer solution 3 was spray-coated and dried for 3 hours. Subsequently, the surface was washed with water using a sponge to remove any excess hydrophilic organic polymer 3, obtaining a hydrophilic coating film formed on the coated surface of the A5052 aluminum-magnesium alloy substrate. The film thickness of the hydrophilic coating film formed on the coated surface of the A5052 aluminum-magnesium alloy substrate, as observed by SEM, was 251 nm. The contact angle of this hydrophilic coating film was measured to be 3.8°. The hydrophilic coating film of Example 3 was subjected to a thermal shock test by exposing it to a high temperature atmosphere of 250°C and then rapidly cooling it to room temperature. No cracks were observed in the hydrophilic coating film, neither visually nor under a laser microscope.

[0205] In Example 4, an inorganic coating solution 4 was applied to the coated surface of a duralumin substrate (metal substrate), which had been thoroughly cleaned with ethyl alcohol, using a microfiber cloth coating. After drying for 30 minutes, a hydrophilic organic polymer solution 3 was applied using a microfiber cloth coating and dried for 3 hours. Subsequently, the surface was washed with water using a sponge to remove any excess hydrophilic organic polymer 4, obtaining a hydrophilic coating film formed on the coated surface of the duralumin substrate. The film thickness of the hydrophilic coating film formed on the coated surface of the duralumin substrate, as observed by SEM, was 251 nm. The contact angle of this hydrophilic coating film was measured to be 15.6°. The hydrophilic coating film of Example 4 was subjected to a thermal shock test by exposing it to a high temperature atmosphere of 250°C and then rapidly cooling it to room temperature. No cracks were observed in the hydrophilic coating film, neither visually nor under a laser microscope.

[0206] In Example 5, an inorganic coating solution 2 was spray-coated onto the coated surface of a magnesium alloy substrate (metal substrate) whose surface had been thoroughly cleaned with ethyl alcohol. After drying for 30 minutes, a hydrophilic organic polymer solution 3 was spray-coated and dried for 1 hour. Subsequently, the surface was washed with water using a sponge to remove any excess hydrophilic organic polymer 3, obtaining a hydrophilic coating film formed on the coated surface of the magnesium alloy substrate. The film thickness of the hydrophilic coating film formed on the coated surface of the magnesium alloy substrate, as observed by SEM, was 311 nm. The contact angle of this hydrophilic coating film was measured to be 4.9°. The hydrophilic coating film of Example 5 was subjected to a thermal shock test by exposing it to a high temperature atmosphere of 250°C and then rapidly cooling it to room temperature. No cracks were observed in the hydrophilic coating film, neither visually nor under a laser microscope.

[0207] In Examples 1 to 5, the hydrophilic coating films were found to be able to prevent crack formation in the hydrophilic coating films. This is because the hydrophilic organic polymer penetrates the voids of the inorganic porous coating film, and the hydrophilic organic polymer (ionic polymer) bonded to the voids (inorganic fine particles) and the coating surface of the metal substrate undergoes shape deformation (plastic deformation). As a result, the hydrophilic coating films follow the thermal expansion or contraction of the metal substrates and absorb the expansion and contraction of the substrates due to thermal expansion or contraction. Even if compressive, tensile, or shear forces are applied to each hydrophilic coating film due to the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate, it is possible to prevent crack formation in the hydrophilic coating films.

[0208] In Comparative Example 1, an inorganic coating solution 5 was applied to the coated surface of a SUS304 plate (metal substrate) that had been thoroughly cleaned with ethyl alcohol, using a microfiber cloth. After application, it was dried at room temperature for one day. The film thickness of the coating film formed on the coated surface of the SUS304 plate, as observed by SEM of the cross section, was 239 nm. The contact angle of this coating film was measured to be 32°. A thermal shock test was performed on the coating film formed on the coated surface of the SUS304 plate by exposing it to a high temperature atmosphere of 250°C and then rapidly cooling it to room temperature. Cracks were observed in the coating film both visually and under a laser microscope.

[0209] In Comparative Example 2, an inorganic coating solution 6 was applied to the coated surface of an aluminum substrate (metal substrate) that had been thoroughly cleaned with ethyl alcohol, using a microfiber cloth coating. After application, it was heated and dried at 100°C for 3 hours. The film thickness of the coating film formed on the coated surface of the aluminum substrate, as observed by SEM, was 65 nm. The contact angle of this coating film was measured to be 25°. A thermal shock test was performed on the coating film formed on the coated surface of the aluminum substrate by exposing it to a high temperature atmosphere of 250°C and then rapidly cooling it to room temperature. Cracks were observed in the coating film both visually and under a laser microscope.

[0210] In Comparative Example 3, an inorganic coating solution 7 was applied to the coated surface of an A5052 aluminum-magnesium alloy substrate (metal substrate), which had been thoroughly cleaned with ethyl alcohol, using a microfiber cloth coating. After application, it was heated and dried at 300°C for 6 hours. The film thickness of the coating film formed on the coated surface of the A5052 aluminum-magnesium alloy substrate, as observed by SEM, was 151 nm. The contact angle of this coating film was measured to be 16.2°. A thermal shock test was performed on the coating film formed on the coated surface of the A5052 aluminum-magnesium alloy substrate by exposing it to a high temperature atmosphere of 250°C and then rapidly cooling it to room temperature. Cracks were observed in the coating film visually and with a laser microscope.

[0211] The coating films of Comparative Examples 1 to 3 were inorganic porous coating films made from inorganic coating solutions and did not contain hydrophilic organic polymers. It was found that the coating films could not follow the thermal expansion or contraction of the metal substrates, and that when compressive, tensile, or shear forces were applied to each coating film due to the difference in thermal expansion or contraction between the coating film and the metal substrate, cracks were generated in the coating films.

[0212] 10A-10D Hydrophilic coating film 11 Metal substrate 12 Coating surface 13a, 13b Inorganic porous coating film 14 Inorganic fine particles (inorganic nanoparticles) 15 Void 16 Hydrophilic organic polymer (hydrophilic organic film)

Claims

In a hydrophilic coating film applied to the coating surface of a predetermined metal substrate, The hydrophilic coating film is formed from an inorganic porous coating film having an inorganic nanoporous structure in which adjacent inorganic nanoparticles among a large number of inorganic nanoparticles are partially connected to each other, and in which a large number of nano-sized voids are formed between the inorganic nanoparticles that make up the inorganic nanoporous structure, and a hydrophilic organic polymer that penetrates into the voids of the inorganic porous coating film, hardens in those voids and is bonded to the inorganic nanoparticles, wherein the hydrophilic organic polymer is firmly bonded to the coating surface of the metal substrate, and even if a difference in thermal expansion or contraction occurs between the hydrophilic coating film and the metal substrate due to temperature changes, it is possible to prevent the occurrence of cracks in the hydrophilic coating film. 　 The hydrophilic coating film according to claim 1, wherein the hydrophilic organic polymer hardened in the voids has a predetermined flexibility, the hydrophilic organic polymer is shape-changeable in the voids, and when a difference in thermal expansion or contraction occurs between the hydrophilic coating film and the metal substrate due to a temperature change, the hydrophilic organic polymer freely changes shape in the voids, and the hydrophilic coating film follows the difference in thermal expansion or contraction between the hydrophilic coating film and the metal substrate, thereby preventing the occurrence of cracks in the hydrophilic coating film when thermal expansion or contraction occurs in the hydrophilic coating film and the metal substrate. 　 The hydrophilic coating film according to claim 1 or claim 2, wherein the metal substrate is any of the following: an iron plate, various stainless steel plates, copper plates, copper alloy plates, aluminum plates, aluminum alloy plates, magnesium alloy plates, duralumin plates, tin alloy plates, steel plates, nickel plates, or zinc plates. 　 The hydrophilic coating film according to claim 1, wherein the water contact angle of the hydrophilic coating film, as measured according to JIS R3257, is 40° or less. 　 The hydrophilic coating film according to claim 1, wherein the hydrophilic organic polymer is an ionic polymer comprising at least one of a betaine moiety, a cationic moiety, and an anionic moiety. 　 The hydrophilic coating film according to claim 5, wherein the hydrophilic organic polymer contains metal ions. 　 The hydrophilic coating film according to claim 5 or claim 6, wherein the hydrophilic coating film is made by impregnating and infiltrating the numerous nano-sized voids of the inorganic porous coating film, which is made by a sol-gel method using at least one of silica sol, alumina sol, zirconia sol, titania sol, and ceria sol in which inorganic nanoparticles are dispersed, with the hydrophilic organic polymer. 　 The hydrophilic coating film according to claim 1, wherein the hydrophilic organic polymer penetrates into the voids of the inorganic porous coating film and coats the surface of the inorganic porous coating film. 　 The hydrophilic coating film according to claim 1, wherein the uppermost layer of the hydrophilic organic polymer is located slightly below the surface of the inorganic porous coating film, and the portion of the inorganic porous coating film that is exposed above the uppermost layer of the hydrophilic organic polymer forms fine irregularities on the surface of the hydrophilic coating film, and is coated with an ultrathin film of the hydrophilic organic polymer. 　 The hydrophilic coating film according to claim 1, wherein when the hydrophilic coating film is 1. exposed to a high temperature atmosphere of 250°C and 2. rapidly cooled to room temperature, no cracks occur in the hydrophilic coating film. 　 The hydrophilic coating film according to claim 1, wherein the thickness of the hydrophilic coating film is in the range of 0.01 to 5 μm. 　 The hydrophilic coating film according to claim 11, wherein the thickness of the hydrophilic coating film is in the range of 0.1 to 0.6 μm. 　 The metal ions contained in the aforementioned hydrophilic organic polymer are Ag ＋ Ions and Cu ２＋ Ions and Zn ２＋ The hydrophilic coating film according to claim 6, which is at least one of the ions. 　 A method for forming a coating film in which a hydrophilic coating film according to any one of claims 1 to 12 is formed on the coating surface of a predetermined metal substrate, The coating film formation method is characterized by comprising: a coating step of coating the coating surface of a metal substrate with at least one of silica sol, alumina sol, zirconia sol, titania sol, and ceria sol, which contains a large number of nano-sized inorganic fine particles dispersed in it; a film formation step of drying the silica sol, alumina sol, zirconia sol, titania sol, and ceria sol coated on the coating surface of the metal substrate to form an inorganic porous coating film in which adjacent inorganic fine particles are partially connected to each other and a large number of nano-sized voids are formed between the inorganic fine particles; an impregnation step of impregnating the voids of the inorganic porous coating film with a hydrophilic organic polymer (ionic polymer); and a drying and bonding step of drying the hydrophilic organic polymer impregnated into the voids of the inorganic porous coating film to cure the hydrophilic organic polymer in the voids and bond the hydrophilic organic polymer to the inorganic fine particles. 　 A method for forming a coating film in which a hydrophilic coating film according to any one of claims 1 to 12 is formed on the coating surface of a predetermined metal substrate, The coating film formation method is characterized by comprising: a coating step of coating the coating surface of a metal substrate with a coating liquid containing at least one of silica sol, alumina sol, zirconia sol, titania sol, and ceria sol, in which a large number of nano-sized inorganic fine particles are dispersed, and a hydrophilic organic polymer (ionic polymer); and a drying and bonding step of drying the coating liquid, partially linking adjacent inorganic fine particles among the large number of inorganic fine particles to form a large number of nano-sized voids between the inorganic fine particles, and curing the hydrophilic organic polymer that has penetrated the large number of nano-sized voids formed between the inorganic fine particles to bond the hydrophilic organic polymer to the inorganic fine particles.

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