Antibacterial metal materials and antibacterial articles

Abstract

This antibacterial metal material has a surface which has a roughness index of 4.0 or higher. The roughness index is obtained by dividing the real surface area (m2), which is measured by the krypton adsorption method, by the geometric surface area (m2).

Description

[Technical Field]

[0001] The present disclosure relates to antimicrobial metallic materials and antimicrobial articles. [Background technology]

[0002] There is an increasing demand for antibacterial articles with antibacterial properties in many applications, including pharmaceutical and medical fields, housing, etc. For example, Patent Document 1 discloses an antibacterial article provided with an antibacterial resin film. The antibacterial article disclosed in Patent Document 1 includes an antibacterial resin film containing a specific polymer and a substrate to which the antibacterial resin film is bonded.

[0003] Patent Document 1: International Publication No. 2016 / 051444 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology described in Patent Document 1, there is a possibility that the antibacterial resin film may peel off from the substrate, and there is a concern that chemical substances contained in the antibacterial resin film may leach out. The antibacterial properties of the antibacterial resin film may not be sufficient.

[0005] The present disclosure has been made in light of these circumstances, and the problem that one embodiment of the present disclosure aims to solve is to provide an antibacterial metal material that has excellent antibacterial properties. Another problem to be solved by another embodiment of the present disclosure is to provide an antibacterial article using the above antibacterial metallic material. [Means for solving the problem]

[0006] The present disclosure includes the following aspects. <1> An antibacterial metal material having a surface with a roughness index of 4.0 or more, obtained by dividing the true surface area (m2) by the geometric surface area (m2) measured by the krypton adsorption method. <2> The surface has a porous structure. <1> The antibacterial metallic material according to claim 1. <3> having a plating layer, the surface is the surface of the plating layer; <2> The antibacterial metallic material according to claim 1. <4> The diameter of the opening of at least some of the holes is smaller than the maximum inner diameter of the holes. <2> or <3> The antibacterial metallic material according to claim 1. <5> The surface satisfies at least one of the following (1) to (3): <2> ~ <4> The antibacterial metallic material according to any one of the above. (1) The average value of the arithmetic mean roughness (Ra) is 0.2 μm to 20 μm. (2) The average value of the ten-point mean roughness (Rz) is 2 μm to 100 μm. (3) The average value of the mean length of the roughness profile element (RSm) is 10 μm to 400 μm. <6> The average value of the arithmetic mean roughness (Ra) is 3 μm or more, The average value of the ten-point average roughness (Rz) is 20 μm or more, The average value of the average length (RSm) of the roughness profile elements is 100 μm or more. <5> The antibacterial metallic material according to claim 1. <7> the surface has a concave-convex structure layer with an average thickness of 10 nm to 5000 nm; <1> ~ <6> The antibacterial metallic material according to any one of the above. <8> The concave-convex structure layer is a dendritic layer or a mesh-like layer. <7> The antibacterial metallic material according to claim 1. <9> the average thickness is greater than 200 nm; <7> or <8> The antibacterial metallic material according to claim 1. I've got it. <10> The average thickness is 350 nm or more. <7> or <8> The antibacterial metallic material according to claim 1. <11> The material includes at least one selected from the group consisting of aluminum, magnesium, silver, copper, iron, titanium, an alloy, and a plating material; The alloy includes at least one selected from the group consisting of aluminum, magnesium, silver, copper, iron, and titanium. <1> ~ <10> The antibacterial metallic material according to any one of the above. <12> The roughness index is 95.0 or more. <1> ~ <11> The antibacterial metallic material according to any one of the above. <13> The aforementioned <1> ~ <12> An antibacterial article comprising the antibacterial metallic material according to any one of the above. [Effects of the Invention]

[0007] According to one embodiment of the present disclosure, an antibacterial metallic material with excellent antibacterial properties is provided. According to another embodiment of the present disclosure, there is provided an antibacterial article using the above antibacterial metallic material. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view schematically showing an example of a dendritic layer of an antibacterial metallic material. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the present disclosure, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced by the upper or lower limit value of another numerical range described in stages, or may be replaced by a value shown in an example. In this disclosure, when a material contains multiple substances corresponding to each component, the amount of each component in the material means the total amount of the multiple substances present in the material unless otherwise specified. In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. When embodiments are described with reference to the drawings in this disclosure, the configuration of the embodiment is not limited to the configuration shown in the drawings. The sizes of the components in each drawing are conceptual, and the relative size relationships between the components are not limited to these.

[0010] <Antibacterial metal material> The antibacterial metallic material according to the present disclosure has a true surface area (m 2 ) to the geometric surface area (m 2 ) has a surface with a roughness index of 4.0 or more. This allows the antibacterial metallic material to exhibit excellent antibacterial properties.

[0011] When describing the antibacterial metal material according to the present disclosure, the term "antibacterial" means having at least one of antibacterial properties and virus inactivation properties. In the present disclosure, the term "microorganisms" is a concept that includes bacteria and viruses. Bacteria for which the antibacterial metal material of the present disclosure exhibits antibacterial properties include Staphylococcus aureus. Viruses for which the antibacterial metal material of the present disclosure exhibits virus inactivation properties include influenza A H3N2 and feline calicivirus. Based on the estimated mechanism below, bacterial species for which the antibacterial properties are exhibited are not limited to Staphylococcus aureus, and virus species for which the antibacterial metal material of the present disclosure exhibits virus inactivation properties are not limited to influenza A H3N2 and feline calicivirus. The antibacterial metallic material of the present disclosure includes a first configuration and a second configuration. The first configuration consists solely of a member made of a metal or alloy, as described below. The second configuration has a member made of a metal or alloy and a plating layer laminated on the member. In the first configuration, the "surface" of the antibacterial metallic material refers to the surface of the member made of a metal or alloy. In the second configuration, the "surface" of the antibacterial metallic material refers to the surface of the plating layer.

[0012] The mechanism by which antibacterial metal materials exhibit excellent antibacterial properties by having a surface roughness index (hereinafter simply referred to as the "roughness index") of 4.0 or more is not clear, but is presumed to be as follows. The surface of an antibacterial metal material with a roughness index of 4.0 or more has a finely textured structure, and therefore, when bacteria adhere to the surface of the antibacterial metal material (i.e., the textured structure), it is thought that the bacteria are damaged by the textured structure and, in a preferred embodiment, are killed. When a virus adheres to the uneven structure of the antibacterial metallic material, it is believed that at least a portion of the virus is captured by the uneven structure, weakening the activity of the virus and, in a preferred embodiment, inactivating the virus. The scope of the present disclosure is not limited in any way by the above speculation.

[0013] As will be described in detail below, antibacterial metal materials can be produced by roughening the surface of a metal material, which forms a fine uneven structure on the surface of the metal material. That is, the surface of the metal material itself is roughened to form an uneven structure with antibacterial properties. Therefore, the peeling described above in the technology described in Patent Document 1, which uses an antibacterial resin film, does not occur, and the elution of chemical substances is suppressed. Furthermore, in a mode in which the antibacterial properties of the metal itself are exhibited, the antibacterial properties of the antibacterial metal material can be further improved.

[0014] From the viewpoint of further enhancing antibacterial properties, the roughness index is preferably 10.0 or more, more preferably 25.0 or more, even more preferably 50.0 or more, and particularly preferably 95.0 or more. A roughness index of 95.0 or more provides superior antibacterial performance against Staphylococcus aureus and superior viral inactivation performance against Influenza A H3N2, and is capable of damaging Staphylococcus aureus more and weakening the activity of Influenza A H3N2 and feline calicivirus in a relatively short period of time (e.g., 30 minutes after inoculation with the bacteria or virus). As a result, the antibacterial properties of the antibacterial metal material are superior and the immediate effect is also excellent. The upper limit of the roughness index is not particularly limited, but from the viewpoint of further enhancing antibacterial properties, it may be 150.0 or less, 125.0 or less, or 110.0 or less.

[0015] In this disclosure, the true surface area is the specific surface area (m 2 / g) by the mass of the sample. The specific surface area is determined by measuring the adsorption isotherm using the BET method after vacuum-heating and degassing the sample (antibacterial metal material) at liquid nitrogen temperature (77 K) using the krypton adsorption method. The adsorption isotherm can be measured using a gas adsorption measurement device. For example, a BELSORP-max (manufactured by Microtrack-Bell Corporation) can be used as the gas adsorption measurement device. The mass of the antibacterial metallic material may be the mass of the metallic material after the roughening treatment. Since the change in mass before and after the roughening treatment is very small, the mass of the metallic material before the roughening treatment may be used as the mass of the antibacterial metallic material.

[0016] In this disclosure, the geometric surface area is a value calculated from the dimensions of the object to be measured. For example, if the object to be measured is a rectangular parallelepiped with length X, width Y, and height Z, the geometric surface area S can be calculated as S = 2XY + 2YZ + 2ZX. The geometric surface area is measured for a portion or the entire surface of the antibacterial metallic material. The geometric surface area may be measured on a metal material after roughening treatment, or on a metal material before roughening treatment because the change in geometric surface area before and after roughening treatment is very small.

[0017] The type of metal contained in the antibacterial metallic material is not particularly limited, and examples of the metal include aluminum, iron, copper, nickel, gold, silver, platinum, cobalt, zinc, lead, tin, zirconium, titanium, niobium, chromium, aluminum, magnesium, manganese, alloys containing the above metals, and plated materials of the above metals and alloys.

[0018] For example, the antibacterial metallic material may include at least one selected from the group consisting of aluminum, magnesium, silver, copper, iron, titanium, an alloy, and a plating material. The alloy includes at least one selected from the group consisting of aluminum, magnesium, silver, copper, iron, and titanium. The alloy may include aluminum, magnesium, silver, copper, iron, and titanium as main components. The main component indicates that the proportion of aluminum, magnesium, silver, copper, iron, and titanium is 50 mass% or more relative to the total amount of the alloy. The plating material includes aluminum, magnesium, copper, iron, titanium, and the above-mentioned alloy. In particular, silver and copper can further improve the antibacterial properties of the antibacterial material due to their own antibacterial properties.

[0019] Examples of the alloy include brass, phosphor bronze, steel (for example, stainless steel), brass, etc. Examples of the plated material include plated steel, etc.

[0020] The surface of the antibacterial metallic material may have a porous structure (hereinafter, sometimes referred to as a "first microstructure").

[0021] In the present disclosure, the term "porous structure" refers to a structure having a plurality of pores. Specifically, the term "porous structure" refers to a structure in which pores are present when observing a cross section obtained by cutting the antibacterial metallic material horizontally relative to the surface of the antibacterial metallic material. In this disclosure, "pore" means an open pore (a pore connected to the outside air). The pore diameter is a value measured at the entrance of the pore.

[0022] The porous structure can be confirmed by observing the surface and a cross section perpendicular to the surface of the antibacterial metallic material using an electron microscope or a laser microscope.

[0023] The antibacterial metallic material preferably has a plating layer, and the surface of the porous structure is the surface of the plating layer. Examples of materials for the plating layer include zinc, nickel, and chromium. Hereinafter, a plating layer whose surface has a porous structure may be referred to as a "porous plating layer."

[0024] The antibacterial metallic material may have a porous structure in which the diameter of the openings of at least some of the pores is smaller than the maximum inner diameter of the pores (hereinafter, sometimes referred to as a "specific structure"), which may make it easier to enhance the antibacterial properties of the antibacterial metallic material.

[0025] In this disclosure, the "opening diameter" of a hole is the value measured at the entrance of the hole.

[0026] The specific structure can be confirmed by observing a cross section perpendicular to the surface of the antibacterial metallic material using an electron microscope or a laser microscope.

[0027] The surface of the antibacterial metallic material may have a porous structure and may also satisfy at least one of the following (1) to (3). (1) The average value of the arithmetic mean roughness (Ra) is 0.2 μm to 20 μm. (2) The average value of the ten-point mean roughness (Rz) is 2 μm to 100 μm. (3) Average length of roughness curve element (RS m ) is 10 μm to 400 μm in average. By providing such a roughened surface to the antibacterial metallic material, it may be easier to enhance the antibacterial properties of the antibacterial metallic material. Below, the average value of the arithmetic mean roughness (Ra), the average value of the ten-point mean roughness (Rz), and the average length of the roughness curve element (RS m ) are sometimes collectively referred to as "macroscopic surface texture."

[0028] The arithmetic mean roughness (Ra) is a value measured in accordance with JIS B 0601:2001 (corresponding international standard: ISO4287). The average value of the arithmetic mean roughness (Ra) may be 0.2 μm to 10 μm, may be 0.3 μm to 7 μm, or may be 3 μm to 6 μm.

[0029] The ten-point average roughness (Rz) is a value measured in accordance with JIS B 0601:2001 (corresponding international standard: ISO4287). The average value of the ten-point mean roughness (Rz) may be 5 μm to 100 μm, 6 μm to 80 μm, 8 μm to 50 μm, or 20 μm to 35 μm.

[0030] Average length of roughness curve element (RS m ) is a value measured in accordance with JIS B 0601:2001 (corresponding international standard: ISO4287). Average length of roughness curve element (RS m The average value of the thickness of the film may be 50 μm to 350 μm, 80 μm to 250 μm, 90 μm to 150 μm, or 100 μm to 130 μm.

[0031] Among them, the surface of the antibacterial metal material has an average value of arithmetic mean roughness (Ra) of 3 μm or more, an average value of ten-point mean roughness (Rz) of 20 μm or more, and an average length of roughness curve element (RS m ) is preferably 100 μm or more. This allows the antibacterial metal material to have better antibacterial performance against Staphylococcus aureus and better viral inactivation performance against Influenza A H3N2, and to damage Staphylococcus aureus and weaken the activity of Influenza A H3N2 and feline calicivirus in a relatively short time (for example, 30 minutes after inoculation with the bacteria or virus). As a result, the antibacterial performance of the antibacterial metal material is better and also has excellent immediate effect.

[0032] The surface of the antibacterial metallic material may have a concavo-convex structure layer (hereinafter, sometimes referred to as "second microstructure") with an average thickness of 10 nm to 5000 nm. By providing such a roughened surface to the antibacterial metallic material, it may be easier to enhance the antibacterial properties of the antibacterial metallic material.

[0033] The average thickness of the second microstructure may be 20 nm or more but less than 4000 nm, 30 nm to 2000 nm, 50 nm to 800 nm, 100 nm to 700 nm, 150 nm to 600 nm, more than 200 nm but not more than 600 nm, or 350 nm to 600 nm. When the average thickness of the second microstructure exceeds 200 nm, the antibacterial metal material has better antibacterial properties against Staphylococcus aureus and better viral inactivation properties against Influenza A H3N2, and can damage Staphylococcus aureus and weaken the activity of Influenza A H3N2 and feline calicivirus in a relatively short time (e.g., 30 minutes after inoculation with the bacteria or virus).As a result, the antibacterial properties of the antibacterial metal material are better and have an immediate effect. When the average thickness of the second microstructure is 350 nm or more, the antibacterial metal material has better antibacterial performance against Staphylococcus aureus and is more effective immediately than when the average thickness of the second microstructure is more than 200 nm and less than 350 nm.

[0034] The average thickness of the second microstructure is calculated from the cross-sectional profile taken with a scanning electron microscope (SEM). Specifically, SEM photographs are taken at 10 randomly selected points on the antibacterial metallic material using a scanning electron microscope (SEM). After that, the average thickness at 1 μm length is measured at two random spots on each photograph, and similar measurements are made at the other nine points. The average value of the measurements at a total of 20 points is then taken as the average thickness of the second microstructure.

[0035] The second microstructure (i.e., the uneven structure layer) may be a dendritic layer, a mesh-like layer (sometimes called a "spongy layer"), or a pinholder-like layer, which makes it easier to enhance the antibacterial properties of the antibacterial metallic material.

[0036] The dendritic layer is a layer consisting of trunks growing from the surface of the metal material, originating from the metal material portion that has been subjected to the roughening treatment. The trunks may have branches branching off from the trunks, and the branches may have side branches branching off from the branches. The mesh layer refers to a layer having a mesh or sponge-like shape derived from the metal material portion that has been subjected to a roughening treatment. The pinholder-shaped layer refers to a layer having sharp, irregularly shaped projections and depressions that originate from the plated portion that has been subjected to a roughening treatment. The dendritic layer or mesh-like layer may be an aluminum oxide layer or an aluminum hydroxide layer. From the viewpoint of extending the life of the surface irregularities of the metal component in a high-temperature and high-humidity environment, it is preferable that the second microstructure includes a dendritic layer made of aluminum oxide.

[0037] FIG. 1 shows an antibacterial metallic material 100, which is an example of the antibacterial metallic material of the present disclosure. The antibacterial metallic material 100 may be, for example, a metallic material 10 having a dendritic layer 30 formed on the surface thereof, as shown in FIG.

[0038] The dendritic layer and the network layer can be confirmed by observing the surface and a cross section perpendicular to the surface of the antibacterial metallic material using an electron microscope or a laser microscope.

[0039] The antibacterial metallic material can have various structures due to the above-mentioned configuration. For example, the surface of the antibacterial metallic material may have only a porous structure (first microstructure), only a concave-convex structure layer (second microstructure), or both the first microstructure and the second microstructure.

[0040] For example, the surface of the antibacterial metallic material may have a porous structure, and the porous structure (first microstructure) may further have a fine uneven structure layer (second microstructure) on at least one of the inside and outside of the pores, which may facilitate further enhancing the antibacterial properties of the antibacterial metallic material.

[0041] For example, the surface of the antibacterial metallic material may have a porous structure, and further, a dendritic layer (second microstructure) may be formed on at least one of the inside and outside of the pores. In this case, the antibacterial metallic material may have, for example, Ra of 4 μm to 6 μm, Rz of 20 μm to 35 μm, and RS of 90 μm to 120 μm. mand a concave-convex structure layer having an average thickness of several nm to several hundred nm, which can make it easier to further improve the antibacterial properties of the antibacterial metallic material.

[0042] Presence or absence of porous structure (first microstructure), presence or absence of specific structure, Ra range, Rz range, RS m The range of the second microstructure, the presence or absence and thickness of the second microstructure, and the presence or absence of the dendritic layer are preferably selected appropriately depending on the type of bacteria and viruses for which antibacterial properties are to be exerted. For example, bacteria are generally several hundred nanometers to several tens of micrometers in size, and viruses are several nanometers to several hundred nanometers in size. Taking these sizes into consideration, it is preferable to control the surface structure of the antibacterial metal material (i.e., the presence or absence of a porous structure, the range of Ra, etc., the presence or absence of the second microstructure, etc., as described above) so that the antibacterial properties of the antibacterial metal material are more suitably exerted. For example, an antibacterial metal material with a relatively thick second microstructure may be more effective in inactivating small viruses.

[0043] <Method of manufacturing antibacterial metal material> The antibacterial metallic material can be produced by roughening the surface of a metallic material. The roughening method is not particularly limited as long as it can provide the antibacterial metallic material with a roughness index of 4.0 or more. For example, a method using a laser as disclosed in Japanese Patent No. 4020957; a method of immersing the surface of a metal material in an aqueous solution of an inorganic base such as NaOH or an inorganic acid such as HCl or HNO3; a method of treating the surface of a metal material by anodic oxidation as disclosed in Japanese Patent No. 4541153; a displacement crystallization method (hereinafter referred to as "roughening treatment method 1") in which etching is performed with an acid-based etching agent aqueous solution containing an acid-based etching agent (preferably an inorganic acid, ferric ions or cupric ions) and, if necessary, manganese ions, aluminum chloride hexahydrate, sodium chloride, etc. as disclosed in International Publication No. 2015-8847. Examples of such roughening treatments include: a method of immersing the surface of a metal material in an aqueous solution of one or more selected from hydrazine hydrate, ammonia, and a water-soluble amine compound, as disclosed in International Publication No. 2009 / 31632 (hereinafter referred to as "roughening treatment method 2"); a method of chemically roughening the surface of a metal material by contacting it with an oxidizing acidic aqueous solution containing a specific metal cation, as disclosed in International Publication No. 2020 / 158820 (hereinafter referred to as "roughening treatment method 3"); a hot water treatment method, as disclosed in Japanese Patent Application Laid-Open Nos. 2008-162115 and 2019-018547; and roughening treatments such as blasting. The roughening treatment method can be selected depending on the quality of the metal material, the desired roughness index, the desired average pore size, etc.

[0044] Among the above roughening treatment methods, from the viewpoint of achieving a surface roughness index of 4.0 or more for the metal material, roughening treatment methods 1 to 3 can be preferably used. Furthermore, a treatment combining two or more of these roughening treatment methods (for example, a roughening treatment method combining roughening treatment methods 1 and 3) can also be preferably used. These treatments will be specifically described below.

[0045] [Roughening treatment method 1] An example of the roughening treatment method 1 is a method in which the following steps (1) to (4) are carried out in this order.

[0046] (1) Pretreatment process In step (1), a pretreatment is carried out to remove a coating made of oxides or hydroxides present on the surface of the metal material. Mechanical polishing or chemical polishing is usually used as the pretreatment. If the surface of the metal material is significantly contaminated with machine oil or the like, treatment with an alkaline aqueous solution such as a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution, or degreasing may be carried out.

[0047] (2) Treatment with alkaline aqueous solution containing zinc ions In step (2), an alkali hydroxide (MOH or M(OH)) and zinc ions (Zn 2+ ) and the mass ratio ((MOH or M(OH)2) / Zn 2+ The pretreated metal material is immersed in an aqueous alkaline solution containing zinc ions, the aqueous solution containing zinc ions in a ratio of 1 to 100. In the above MOH and M(OH), M is an alkali metal or alkaline earth metal.

[0048] (3) Treatment process using acid etching agent In step (3), after carrying out step (2), the metal material is treated with an acid-based etching agent containing at least one of ferric ions and cupric ions and an acid. By carrying out step (3), the zinc-containing coating on the surface of the metal material is eluted, and, for example, Ra of 4 μm to 6 μm, Rz of 20 μm to 35 μm, and RS of 90 μm to 120 μm is obtained. m It is possible to form a porous structure (first microstructure) having at least one of the above.

[0049] (4) Post-processing In step (4), the metal material is washed after step (3) is performed. The method for washing the metal material is not particularly limited, and typically comprises water washing and drying. The method for washing the metal material may also include ultrasonic washing to remove smut.

[0050] [Roughening treatment method 2] In roughening treatment method 2, a metal material is pretreated with hydrochloric acid, sodium hydroxide, nitric acid, or the like, and then immersed in an aqueous solution of a weakly basic amine such as hydrazine hydrate, followed by rinsing with water and drying at, for example, 70° C. or less. The immersion temperature and immersion time may be adjusted as appropriate depending on the desired roughness index, desired average pore size, etc.

[0051] This makes it possible to form, for example, a first microstructure, which is a porous structure of several hundred nanometers, and a second mesh-like microstructure with an average thickness of several tens of nanometers, which is further applied on top of the first microstructure, on the surface of the metal material.

[0052] [Roughening treatment method 3] As an example of the roughening treatment method 3, there is a method in which a metal material is brought into contact with a specific oxidizing acidic aqueous solution. The specific oxidizing acidic aqueous solution has a standard electrode potential E 0 It contains a metal cation having a value of more than -0.2 and not more than 0.8, preferably more than 0 and not more than 0.5. The oxidizing acidic aqueous solution is 0 It is preferable that the metal cations contained therein do not have a value of -0.2 or less.

[0053] Standard electrode potential E at 25°C 0 The metal cations for which the value is greater than -0.2 and less than 0.8 are Pb 2+ , Sn 2+ , Ag + , Hg 2+ , Cu 2+ Among these, Cu is the most popular from the viewpoint of the scarcity of metals and the safety and toxicity of the corresponding metal salts. 2+ is preferred.

[0054] Cu 2+ Examples of compounds that generate copper include inorganic compounds such as copper hydroxide, copper (II) oxide, copper (II) chloride, copper (II) bromide, copper sulfate, copper nitrate, copper gluconate, etc. Among these, copper oxide is preferred from the viewpoints of safety, toxicity, and the efficiency of providing a dendritic layer.

[0055] Examples of the oxidizing acidic aqueous solution include nitric acid, mixed acids, and aqueous percarboxylic acid solutions (e.g., peracetic acid, performic acid, etc.). Mixed acids are obtained by mixing nitric acid with any of hydrochloric acid, hydrofluoric acid, and sulfuric acid. When nitric acid is used as the oxidizing acidic aqueous solution and cupric oxide is used as the metal cation generating compound, the nitric acid concentration constituting the aqueous solution is, for example, 10% by mass to 40% by mass, preferably 15% by mass to 38% by mass, and more preferably 20% by mass to 35% by mass. The copper ion concentration constituting the aqueous solution is, for example, 1% by mass to 15% by mass, preferably 2% by mass to 12% by mass, and more preferably 2% by mass to 8% by mass.

[0056] The temperature when the metal material is brought into contact with the oxidizing acidic aqueous solution is not particularly limited, but in order to complete the roughening at an economical speed while controlling the exothermic reaction, it is, for example, room temperature to 60° C., preferably 30° C. to 50° C. The treatment time is, for example, in the range of 1 minute to 15 minutes, preferably 2 minutes to 10 minutes.

[0057] In this manner, by roughening treatment method 3, a dendritic layer (second microstructure) having an average thickness of, for example, several nm to several hundred nm can be formed on the surface of the metal material.

[0058] The above-described dendritic layer can also be formed by the hot water treatment method disclosed in JP 2019-018547 A.

[0059] [Combination of roughening treatment method 1 and roughening treatment method 3] In the combination of the roughening treatment methods 1 and 3, for example, a metal material that has been roughened by the roughening treatment method 1 may be further subjected to the roughening treatment method 3. This results in, for example, Ra of 4 μm to 6 μm, Rz of 20 μm to 35 μm, and RS of 90 μm to 120 μm. m It is possible to provide the surface of the metal material with a porous structure (first microstructure) having at least one of the above, and further with a dendritic layer (second microstructure) having an average thickness of several nm to several hundred nm.

[0060] <Antibacterial articles> An antibacterial article according to the present disclosure includes an antibacterial metallic material according to the present disclosure.

[0061] Antibacterial articles are not particularly limited and can be used in a wide variety of applications, such as medical and pharmaceutical-related (e.g., medical pads, surgical instruments, medicine bottle caps, dental materials, etc.); housing-related (e.g., doorknobs, handrails, etc.); food and cooking-related (e.g., tableware, cooking utensils, sinks, faucets, serving trays); infrastructure-related (e.g., water treatment, piping used in factory facilities, etc.); automobile-related (e.g., doorknobs, etc.); miscellaneous goods-related (e.g., pencil cases, rulers, mechanical pencils, calculators, etc.); IT-related (e.g., casings for personal computers, smartphones, etc.); and entertainment-related (e.g., medals used in gaming machines, etc.).

[0062] The method for producing the antibacterial article is not particularly limited, and the antibacterial article may be produced by a conventional method using the antibacterial metallic material according to the present disclosure. [Example]

[0063] The present disclosure will be described in more detail below with reference to examples, although the present disclosure is not limited to these examples.

[0064] Example 1 Metal materials used to prepare antibacterial metal materials for antibacterial tests and metal materials used to prepare antibacterial metal materials for virus inactivation tests were prepared as follows. (Antibacterial test) The metal material was prepared by cutting an aluminum alloy (thickness: 0.2 cm) with alloy number A5052 specified in JIS H 4000:2014 into a length of 4.5 cm and a width of 2.0 cm. The geometric surface area of ​​this metal material (sample) was 20.6 cm. 2 and the density is 2.68 g / cm 3 and the volume is 1.8cm 3 and the mass was 4.8 g. (Virus inactivation test) The metal material was prepared by cutting an aluminum alloy (thickness: 0.2 cm) with alloy number A5052 specified in JIS H 4000:2014 into a length of 3.5 cm and a width of 2.4 cm. The geometric surface area of ​​this metal material (sample) was 19.2 cm. 2 and the density is 2.68 g / cm 3 and the volume is 1.7 cm 3 and the mass was 4.5 g.

[0065] (Degreasing treatment) The metal material was degreased under the following conditions. Composition: 5% by mass of Aluminum Cleaner "NE-6" manufactured by Meltex Co., Ltd., 95% by mass of water ·Temperature: 60℃ Soaking time: 5 minutes

[0066] (roughening treatment) The degreased metal material was immersed in an aqueous solution of hydrochloric acid, an aqueous solution of sodium hydroxide, and an aqueous solution of nitric acid under the following conditions, and then washed with water to obtain a first microstructure.

[0067] <Hydrochloric acid aqueous solution> Composition: Hydrochloric acid 1% by mass, water 99% by mass ·Temperature: 40℃ Soaking time: 1 minute <Sodium hydroxide solution> Composition: Sodium hydroxide 1.5% by mass, water 98.5% by mass ·Temperature: 40℃ Soaking time: 4 minutes <Nitric acid aqueous solution> Composition: Nitric acid 3% by mass, water 97% by mass ·Temperature: 40℃ Soaking time: 3 minutes

[0068] Next, the metal material on which the first microstructure was formed was immersed in aqueous solution A containing hydrazine hydrate and aqueous solution B containing hydrazine hydrate under the following conditions, and then washed with water and dried at 70°C or less to produce antibacterial metal material 1 of Example 1. Note that the antibacterial metal material for antibacterial testing and the antibacterial metal material for virus inactivation testing will be referred to as antibacterial metal material 1 without distinction.

[0069] <Aqueous solution A containing hydrazine hydrate> Composition: Hydrazine hydrate 3.5% by mass, water 96.5% by mass ·Temperature: 60℃ Soaking time: 1 minute <Aqueous solution B containing hydrazine hydrate> Composition: Hydrazine hydrate 0.5% by mass, water 99.5% by mass ·Temperature: 40℃ Soaking time: 5 minutes

[0070] (Structural observation) A scanning electron microscope "Regulus8220" manufactured by Hitachi High-Technologies Corporation was used to observe the surface and a cross section perpendicular to the surface of the antibacterial metal material 1. The antibacterial metal material 1 had a porous structure (first microstructure) and a fine uneven structure layer (second microstructure), but did not have a specific structure.

[0071] (Roughness index) After vacuum heating and degassing the antibacterial metal material 1 (100°C), the adsorption isotherm was measured by the krypton adsorption method at liquid nitrogen temperature (77K) using a BELSORP-max (Microtrac-Bell Corporation), and the specific surface area was calculated by the BET method. The specific surface area was multiplied by the mass of the antibacterial metal material to obtain the true surface area (m 2 ) was calculated. 2 ) to the geometric surface area (m 2 ) to obtain the roughness index of antibacterial metallic material 1. In addition, since the change in geometric area and mass before and after the roughening treatment was very small and the impact on the calculated roughness index was negligible, the geometric surface area and mass of the metal material were used as those of the antibacterial metal material 1.

[0072] (arithmetic mean roughness, ten-point mean roughness, average length of roughness curve elements) Macroscopic surface quality (i.e., the average value of the arithmetic mean roughness (Ra), the average value of the ten-point mean roughness (Rz), and the average value of the mean length of the roughness curve element (RS) of the first microstructure) m )) was measured using a surface roughness measuring device "Surfcom 1400D" manufactured by Tokyo Seimitsu Co., Ltd. in accordance with JIS B 0601:2001.

[0073] (Average thickness of the second microstructure) The average thickness of the second microstructure was calculated from the cross-sectional profile taken with a scanning electron microscope (SEM). Specifically, a Hitachi High-Technologies Corporation scanning electron microscope, Regulus 8220, was used to take SEM photographs of 10 randomly selected points on the antibacterial metallic material. Then, the average thickness over a 1 μm length was measured at two randomly selected spots on each photograph, and similar measurements were made at the other nine points. The average value of the measurements at a total of 20 points was taken as the average thickness of the second microstructure.

[0074] <Example 2> An antibacterial metal material 2 of Example 2 was prepared in the same manner as in Example 1, except that the roughening treatment method was changed as follows, and structural observation was performed. The antibacterial metal material 2 had a dendritic layer (second microstructure) and did not have a porous structure (first microstructure) or a specific structure. The roughness index, macroscopic surface properties (i.e., arithmetic mean roughness, ten-point mean roughness, and average length of roughness curve elements), and average thickness of the second microstructure (dendritic layer) were determined for the antibacterial metal material 2 in the same manner as in Example 1. The antibacterial metal material for the antibacterial test and the antibacterial metal material for the virus inactivation test are referred to as antibacterial metal material 2 without distinction.

[0075] (roughening treatment) Under the following conditions, the metal material is Cu2+ The antibacterial metallic material 2 of Example 2 was prepared by contacting the metal with an oxidizing acidic aqueous solution containing the compound and rinsing it with water.

[0076] <Cu 2+ Oxidizing acidic aqueous solution containing Composition: Copper sulfate 5.03% by mass, nitric acid 30% by mass, water 64.97% by mass ·Temperature: 40℃ Soaking time: 5 minutes

[0077] Example 3 An antibacterial metal material 3 of Example 3 was prepared in the same manner as in Example 1, except that the roughening treatment method was changed as follows, and its structure was observed. The antibacterial metal material 3 had a porous structure (first microstructure), a dendritic layer (second microstructure), and a specific structure. The roughness index, macroscopic surface properties (i.e., the average value of arithmetic mean roughness, the average value of ten-point mean roughness, and the average length of roughness curve elements), and the average thickness of the second microstructure (dendritic layer) were determined for the antibacterial metal material 3 in the same manner as in Example 1. The antibacterial metal material for the antibacterial test and the antibacterial metal material for the virus inactivation test are referred to as the antibacterial metal material 3 without distinction. In the specific structure of the antibacterial metal material 3, the diameter of the openings was approximately 10 μm, and the maximum inner diameter of the pores was approximately 15 μm.

[0078] (roughening treatment) The metal material was degreased in the same manner as in Example 1, and then treated with alkali hydroxide (MOH) and zinc ions (Zn 2+ ) and the mass ratio (MOH / Zn 2+ The degreased metal material was immersed in an aqueous alkaline solution containing zinc ions, the aqueous solution containing zinc ions in a ratio of 1 to 100, to form a zinc-containing coating on the surface. Next, the metal material was treated with an acid-based etching agent containing at least one of ferric ions and cupric ions and an acid under the following conditions to elute the zinc-containing coating on the surface of the metal material, and then washed with water. Then, the metal material was mixed with Cu under the following conditions: 2+ The antibacterial metallic material 3 of Example 3 was prepared by contacting the metal with an oxidizing acidic aqueous solution containing the compound (II) and rinsing with water.

[0079] <Zinc ion-containing alkaline aqueous solution> Composition: Sodium hydroxide 19% by mass, zinc oxide 3.2% by mass, water 77.8% by mass ·Temperature: 30℃ Soaking time: 2 minutes <Acid etching agent> Composition: sulfuric acid 4.1% by mass, ferric chloride 3.9% by mass, cupric chloride 0.2% by mass, water 91.8% by mass ·Temperature: 30℃ Immersion time: 250 seconds <Cu 2+ Oxidizing acidic aqueous solution containing Composition: Nitric acid 30% by mass, cupric oxide 6.3% by mass, water 63.7% by mass ·Temperature: 40℃ Soaking time: 5 minutes

[0080] Example 4 Cu 2+ Antibacterial metal material 4 of Example 4 was prepared in the same manner as in Example 3, except that the oxidizing acidic aqueous solution containing copper sulfate was replaced with an aqueous solution containing copper sulfate under the following conditions, and its structure was observed. Antibacterial metal material 4 had a porous structure (first microstructure), a dendritic layer (second microstructure), and a specific structure. The roughness index, macroscopic surface properties (i.e., arithmetic mean roughness, ten-point mean roughness, and average length of roughness curve elements), and the average thickness of the second microstructure (dendritic layer) were determined for antibacterial metal material 4 in the same manner as in Example 1. The antibacterial metal material for antibacterial testing and the antibacterial metal material for virus inactivation testing are referred to as antibacterial metal material 4 without distinction. In the specific structure of antibacterial metal material 4, the diameter of the openings was approximately 10 μm, and the maximum inner diameter of the pores was approximately 15 μm.

[0081] <Aqueous solution containing copper sulfate> Composition: Nitric acid 30% by mass, copper sulfate 5.03% by mass, water 64.97% by mass ·Temperature: 40℃ Soaking time: 5 minutes

[0082] <Example 5> An aluminum plate serving as a substrate was degreased in the same manner as in Example 1, and an undercoat nickel plating layer having a thickness of approximately 3 μm to 4 μm was formed on the surface. The undercoat nickel plating layer was formed using an aqueous solution containing nickel sulfate (280 g / L), nickel chloride (45 g / L), and boric acid (40 g / L) at a solution temperature of 50°C, pH 4.3, and a cathode current density of 3 A / dm 2 The experiment was carried out under the following conditions. Next, a nickel plating layer having a porous structure and a thickness of about 1 μm to 5 μm was formed on the base nickel plating layer. The nickel plating layer with a porous structure was formed using a plating solution containing nickel sulfate (280 g / L), nickel chloride (45 g / L), and boric acid (40 g / L) to which dodecyltrimethylammonium chloride (10 ml / L) was added as a substance to inhibit the growth of the plating layer. The plating solution was set at a solution temperature of 50°C, pH 4.3, and a cathode current density of 3 A / dm 2 The experiment was carried out under the following conditions. The aluminum plate on which the nickel plating layer having a porous structure was formed was subjected to an etching treatment by immersing it for 3 minutes in an aqueous solution (40° C.) containing 0.6 mass % of nitric acid and 7.5 mass % of phosphoric acid. In this way, the antibacterial metal material 5 of Example 5 was produced, and its structure was observed. The antibacterial metal material 5 had a porous structure (first microstructure), a pin-holder-shaped layer (second microstructure), and a specific structure. The roughness index, macroscopic surface properties (i.e., arithmetic mean roughness, ten-point mean roughness, and average length of roughness curve elements), and average thickness of the second microstructure (pin-holder-shaped layer) were determined for the antibacterial metal material 5 in the same manner as in Example 1. The antibacterial metal material for antibacterial testing and the antibacterial metal material for virus inactivation testing are referred to as the antibacterial metal material 5 without distinction. In the specific structure of the antibacterial metal material 5, the diameter of the openings and the maximum inner diameter of the holes were both approximately 2 μm, and locations where the diameter of the openings was smaller than the maximum inner diameter of the holes were confirmed.

[0083] <Comparative Example 1> The metal material used in Example 1 before the roughening treatment was degreased in the same manner as in Example 1 and used as Comparative Example 1, and the roughness index and macroscopic surface properties (i.e., arithmetic mean roughness, ten-point mean roughness, and average length of roughness curve elements) were determined in the same manner as in Example 1. When the structure of the antibacterial metal material 4 of Comparative Example 1 was observed in the same manner as in Example 1, neither the first microstructure nor the second microstructure was observed.

[0084] <Antibacterial test> Antibacterial tests were conducted in accordance with ISO 21702:2019 using antibacterial metal materials that had been sterilized with ethanol. The test bacteria was one species of Staphylococcus aureus, and the test bacteria inoculation concentration was 2.5 x 10 5 pieces / mL~10 6 The test bacterial culture medium is 1 / 25NB. In the antibacterial test, the antibacterial metallic material 1 was inoculated with a test bacterial solution, and the percentage of viable bacteria was measured 30 minutes and 24 hours later.

[0085] The percentage of viable bacteria after 30 minutes (%) indicates the ratio of the number of viable bacteria 30 minutes after the antibacterial metal material 1 is inoculated with the test bacterial liquid to the number of viable bacteria at the time the antibacterial metal material 1 is inoculated with the test bacterial liquid. The percentage of viable bacteria after 24 hours (%) indicates the ratio of the number of viable bacteria 24 hours after the antibacterial metal material 1 is inoculated with the test bacterial liquid to the number of viable bacteria at the time the antibacterial metal material 1 is inoculated with the test bacterial liquid. The lower the percentage of viable bacteria (%), the more bacteria are damaged.

[0086] Antibacterial tests were carried out in the same manner as above for the antibacterial metallic materials of Examples 1, 2, 4, and 5, and the antibacterial metallic material of Comparative Example 1. The results are shown in Table 1.

[0087] <Virus inactivation test> A virus inactivation test was conducted using an antibacterial metal material in accordance with ISO 21702:2019. In the virus inactivation test, the antibacterial metal material was inoculated with a test virus solution, and the virus inactivation rate and infectivity titer were measured 30 minutes and 24 hours later. The infectivity titer is an index that represents the degree of virus inactivation. Two types of viruses were used: Influenza A H3N2 (size: 80 nm to 120 nm, enveloped) and feline calicivirus (size: 27 nm to 32 nm, non-enveloped).

[0088] A virus inactivation test was carried out in the same manner as above for the antibacterial metal materials of Examples 1, 3, 4, and 5, and the metal material of Comparative Example 1. Note that the virus inactivation rate after 24 hours and the infectivity titer for Influenza A H3N2 were not evaluated for antibacterial metal material 1 of Example 1. The results are shown in Table 2.

[0089] The virus inactivation rate after 30 minutes indicates the ratio of the infectivity titer 30 minutes after the antibacterial metal material 1 is inoculated with the test virus fluid to the infectivity titer at the time the antibacterial metal material 1 is inoculated with the test virus fluid. The virus inactivation rate after 24 hours indicates the ratio of the infectivity titer 24 hours after the antibacterial metal material 1 is inoculated with the test virus fluid to the infectivity titer at the time the antibacterial metal material 1 is inoculated with the test virus fluid. The higher the virus inactivation rate, the more the virus activity has been weakened. The viral infectivity was measured by TCID50 (50% tissue culture infectious dose).

[0090] [Table 1]

[0091] [Table 2]

[0092] The roughness index of Comparative Example 1 was less than 4.0. Therefore, the viable cell count rate after 24 hours of the antibacterial metal material of Comparative Example 1 was 17%. The virus inactivation rate of feline calicivirus after 24 hours of the antibacterial metal material of Comparative Example 1 was 99.991%. On the other hand, the roughness index of Examples 1 to 5 was 4.0 or more. Therefore, the percentage of viable bacteria after 24 hours for the antibacterial metal materials of Examples 1, 2, 4, and 5 was 0.202% or less, which was lower than that of Comparative Example 1. In other words, it was found that the antibacterial metal materials of Examples 1, 2, 4, and 5 had antibacterial properties. The virus inactivation rates of the antibacterial metal materials of Examples 1 and 3 to 5 against feline calicivirus after 24 hours were 99.999% or higher, which was higher than that of Comparative Example 1. In other words, it was found that the antibacterial metal materials of Examples 1 and 3 to 5 have virus inactivation performance. These results demonstrate that Examples 1 to 5 have at least one of antibacterial and virus inactivation properties, ie, the antibacterial metallic materials of Examples 1 to 5 have excellent antibacterial properties.

[0093] As shown in Table 1, the antibacterial metal materials of Examples 1, 2, and 4 had a low percentage of viable bacteria and excellent antibacterial properties. In particular, 24 hours after inoculation with the test bacterial solution, the percentage of viable bacteria was significantly reduced to 0.202% or less. On the other hand, the metal material of Comparative Example 1 had a high percentage of viable bacteria and poor antibacterial properties.

[0094] As shown in Table 2, the antibacterial metal materials of Examples 1, 3, and 4 had high virus inactivation rates, low infectivity titers, and excellent antibacterial properties. In particular, 24 hours after inoculation with the test virus solution, the virus inactivation rate for feline calicivirus was significantly increased to 99.999% or more, and the infectivity titer was significantly reduced to 2.28 LogTCID50mL or less. On the other hand, the metal material of Comparative Example 1 had a low virus inactivation rate for influenza A H3N2 after 30 minutes, indicating poor antibacterial properties.

[0095] Furthermore, among the antibacterial metallic materials of Examples 1, 3, and 4 having the first microstructure and the second microstructure layer, the Ra, Rz, and RS m The antibacterial metal materials of Examples 3 and 4, which had larger second microstructures and thicker second microstructures, showed higher inactivation rates even 30 minutes after inoculation with the test virus fluid, demonstrating superior antibacterial properties compared to antibacterial metal material 1 of Example 1. For influenza A H3N2, 24 hours after inoculation with the test virus fluid, the virus inactivation rate was significantly increased to 99.997% or more, and the infectivity titer was significantly reduced to 2.28 LogTCID50mL or less.

[0096] The disclosure of Japanese Patent Application No. 2021-129074, filed on August 5, 2021, is incorporated herein by reference in its entirety. All publications, patent applications, and technical standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. The true surface area (m ２ ) to the geometric surface area (m ２ ) has a surface having a roughness index of 4.0 or more, the surface has a concave-convex structure layer with an average thickness of 10 nm to 5000 nm, the concave-convex structure layer is a dendritic layer or a pinholder-shaped layer, The surface has a porous structure, An antibacterial metallic material having a structure in which the diameter of the openings of at least some of a plurality of holes is smaller than the maximum inner diameter of the interior of the holes.

2. The antibacterial metallic material according to claim 1, wherein the surface satisfies at least one of the following (1) to (3): (1) The average value of the arithmetic mean roughness (Ra) is 0.2 μm to 20 μm. (2) The average value of the ten-point mean roughness (Rz) is 2 μm to 100 μm. (3) The average value of the average length of the roughness curve elements (RSm) is 10 μm to 400 μm.

3. The average value of the arithmetic mean roughness (Ra) is 3 μm or more, The average value of the ten-point average roughness (Rz) is 20 μm or more, The antibacterial metallic material according to claim 2, wherein the average value of the average length (RSm) of the roughness curve elements is 100 μm or more.

4. The true surface area (m ２ ) to the geometric surface area (m ２ ) has a surface having a roughness index of 4.0 or more, the surface has a concave-convex structure layer with an average thickness of 10 nm to 5000 nm, the concave-convex structure layer is a dendritic layer or a pinholder-shaped layer, The surface has a porous structure, The surface of the antibacterial metallic material satisfies at least one of the following (1) to (3): (1) The average value of the arithmetic mean roughness (Ra) is 3 μm to 20 μm. (2) The average value of the ten-point mean roughness (Rz) is 20 μm to 100 μm. (3) The average value of the average length of the roughness curve elements (RSm) is 100 μm to 400 μm.

5. having a plating layer, The antibacterial metallic material according to any one of claims 1 to 4, wherein the surface is the surface of the plating layer.

6. The antibacterial metallic material according to any one of claims 1 to 4, wherein the concave-convex structure layer is a dendritic layer.

7. The antibacterial metallic material according to any one of claims 1 to 4, wherein the average thickness is greater than 200 nm.

8. The antibacterial metallic material according to any one of claims 1 to 4, wherein the average thickness is 350 nm or more.

9. The material includes at least one selected from the group consisting of aluminum, magnesium, silver, copper, iron, titanium, an alloy, and a plating material; The antibacterial metallic material according to any one of claims 1 to 4, wherein the alloy contains at least one selected from the group consisting of aluminum, magnesium, silver, copper, iron, and titanium.

10. The antibacterial metallic material according to any one of claims 1 to 4, wherein the roughness index is 95.0 or more.

11. An antibacterial article comprising the antibacterial metallic material according to any one of claims 1 to 4.

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