JPH1129879A - Antibacterial treated metallic material and the antibacterial treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain high antibacterial characteristic for a long period without changing characteristics inherent in a material and to provide high antibacterial characteristic without deteriorating a metallic material nor raising the price of the metallic material. SOLUTION: The metallic material contains Ag only in the vicinity of the surface. An Ag layer is formed on the surface of a metallic material, such as stainless steel and Al, and then this metallic material is rolled, preferably, heat-treated in vacuum or in inert gas, or, as another method, a naturally occurring oxide film is removed from the surface of a metallic material and, after or during the formation of an Ag layer on the above surface of the metallic material from which the naturally occurring oxide film is removed, the metallic material is heat-treated in vacuum or in inert gas. By this method, the Ag layer is allowed to diffuse in the surface of the metallic material, and antibacterial treatment for the metallic material can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal material for a metal product used in an environment where bacteria can easily propagate, and a method for antibacterial treatment of the surface of the metal material.

[0002]

2. Description of the Related Art Bath products such as bathtubs, soap boxes, cups, etc.
Sinks, drainage garbage, triangle corners, kitchen utensils such as cooking utensils, washing tubs for washing machines, heat exchangers for home and automotive air conditioners, metal parts for personal accessories such as watches, glasses, accessories, medical equipment, etc. Is mentioned. Conventionally, in this kind of antibacterial treatment of a metal material, an antibacterial agent or a fungicide containing Ag or Cu is applied to the surface of the metal material. However, in this method, since the antibacterial layer and the antifungal layer are easily peeled off, a method of adding Ag or Cu during the production of the metal material and alloying the material has been adopted.

[0003]

In this antibacterial treatment method,
Cu is inexpensive compared to Ag, but has poor antibacterial properties and must be added in large quantities, which may alter the metal material. On the other hand, Ag which exerts antimicrobial properties in a small amount is more expensive than general metal materials, and for alloying Ag, it is necessary to include Ag even in metal materials that do not require antimicrobial performance. A lot of Ag is used, which may increase the price of the metal material.

[0004] An object of the present invention is to provide a metal material which has been subjected to antibacterial treatment and which maintains high antibacterial properties for a long period of time without changing the intrinsic properties of the material. Another object of the present invention is to provide an antibacterial treatment method for a metal material that can impart high antibacterial properties to the metal material without changing the characteristics of the metal material and without increasing the price of the metal material.

[0005]

The invention according to claim 1 is
It is an antibacterial-treated metal material containing Ag only in the vicinity of the surface. Since Ag having a high antibacterial property is contained at a low concentration only in the vicinity of the surface of the metal material, a metal material having high antibacterial property for a long period of time can be obtained without changing the intrinsic properties of the material.

The invention according to claim 2 or claim 8 is the invention according to claim 1 or claims 3 to 7, which is a metal material whose metal material is stainless steel or Al, or an antibacterial treatment method thereof. Stainless steel, A as metal material
By selecting 1, Al alloy or Zn plated steel,
Ag can be appropriately diffused inside the surface.

[0007] The invention according to claim 3 is that the metal material surface has A
An antibacterial treatment method for a metal material, comprising rolling the metal material after forming the g layer. By rolling, A
The g layer extends together with the metal material, becomes a very thin layer, spreads over the entire surface of the metal material, and diffuses inside. In many cases, the surface of a metal material is covered with a natural oxide film, and in this case, this method is effective. This is because the natural oxide film has poor ductility and is finely divided at the time of rolling and does not hinder the diffusion of the Ag layer into the metal material. According to this method, even if a natural oxide film exists on the surface of the metal material, it is not necessary to remove it.

[0010] The invention according to claim 4 is the invention according to claim 3, which is an antibacterial treatment method for a metal material, wherein the metal material is rolled and then heat-treated in a vacuum or an inert gas. is there. By performing the heat treatment after the rolling, the Ag atoms constituting the Ag layer are surely diffused into the metal material.

According to a fifth aspect of the present invention, there is provided a metal material having a natural oxide film on its surface, wherein the natural oxide film is removed and an Ag layer is formed on or after the surface of the metal material from which the natural oxide film has been removed. An antibacterial treatment method for a metal material, wherein the metal material is heat-treated in a vacuum or in an inert gas. Since the Ag layer is formed on the surface of the metal material after the removal of the natural oxide film, the natural oxide film does not hinder the diffusion of Ag into the metal material. Diffuses uniformly and smoothly throughout the material. By performing the heat treatment in a vacuum or in an inert gas, no altered layer due to the atmosphere is formed on the surface of the Ag layer or the metal material.

The invention according to claim 6 is the invention according to claim 5, which is an antibacterial treatment method for a metal material in which a natural oxide film is removed by wet etching or dry etching. By performing wet or dry etching of the metal material, most of the natural oxide film present on the surface of the metal material can be removed.

The invention according to claim 7 is the invention according to claim 3 or 5, wherein the Ag layer is formed by physical vapor deposition (PVD: Physic).
al Vapor Deposition) is an antibacterial treatment method for a metal material formed by the above method. By forming the Ag layer by a physical vapor deposition method, the Ag layer can be formed with a thickness of about several atomic layers.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The metal material of the present invention is a metal material other than Ag, and is preferably stainless steel or Al. Other than this, an Al alloy, Zn-plated steel, or the like may be used. SUS301 (composition: 17Cr-7
Ni), SUS303 (composition: 18Cr-8Ni-high S), SUS304 (composition: 18Cr-8
Ni), SUS304L (composition: 18Cr-9Ni-low C), SUS310S (composition: 25Cr)
-20Ni), SUS316 (composition: 18Cr-12Ni-2.5Mo), SUS321 (composition:
18Cr-9Ni-Ti), SUSXM7 (Composition: 18Cr-9Ni-3.5Cu), SUSXM15
Austenitic JIS stainless steel such as J1 (composition: 18Cr-13Ni-4Si), SUS410L (composition: 13Cr-low C), SUS430 (composition: 18
Cr), SUS430F (composition: 18Cr-high S), SUS434 (composition: 18Cr-1Mo)
Ferritic JIS stainless steel, SUS410 (composition: 13
Cr), SUS420J1 (composition: 13Cr-0.2C), SUS420J2 (composition: 13Cr-
0.3C), SUS440A (composition: 18Cr-0.7C), SUS440B (composition: 18Cr-
0.8C), martensitic J such as SUS440C (composition: 18Cr-1C)
IS stainless steel, SUS630 (composition: 17Cr-4Ni-4Cu-Nb), SU
Precipitation hardening JIS stainless steel such as S631 (composition: 17Cr-7Ni-1Al) is exemplified.

The first method for antibacterial treatment of a metal material according to the present invention is a method of rolling a metal material after forming an Ag layer on the surface of the metal material. The rolling breaks the natural oxide film on the surface of the metal material, and Ag diffuses into the metal material. Thus, a metal material containing Ag only in the vicinity of the surface and having antibacterial properties can be obtained without performing a treatment for removing a natural oxide film on the surface of the metal material. After rolling this metal material, heat treatment of the metal material in a vacuum or an inert gas,
It is preferable because Ag atoms constituting the Ag layer are surely diffused into the metal material. The second method of antibacterial treatment of a metal material of the present invention is a method of removing a natural oxide film on the surface, forming an Ag layer on the surface of the metal material, and performing a heat treatment. The distribution of Ag in the vicinity of the surface of the metal material subjected to the antibacterial treatment by this method depends on the Ag layer thickness and the heat treatment conditions. The distribution state of Ag near the surface of the metal material is expressed by the following equations (1) and (2). The x-axis is perpendicular to the surface of the metal material, and the surface of the metal material is x = 0, and the inside of the metal material is positive.

[0014]

(Equation 1)

C: A at a distance x from the metal material surface
g concentration (g / cm ³ ) α: The total amount of Ag diffused per rod when the metal material is divided into rods having a cross-sectional area of 1 cm ² perpendicular to the surface (A
g Depends on layer thickness)

[0016]

(Equation 2)

D: Diffusion coefficient of Ag in the metal material (depends on the heat treatment temperature) t: Heat treatment time Using this relationship, the Ag distribution near the metal material surface can be controlled. That is, by controlling the Ag layer thickness and the heat treatment conditions, the Ag having a desired concentration can be formed at a desired depth.
Can be obtained.
As an example, several antimicrobial treatment conditions for obtaining an antimicrobial Al material having an Ag weight concentration of 1 ppb at a depth of 50 μm from the surface are shown.

(A) Ag layer thickness: 10 ° Heat treatment temperature: 400 ° C. Heat treatment time: 1.5 hours (b) Ag layer thickness: 50 ° Heat treatment temperature: 400 ° C. Heat treatment time: 1.3 hours (c) Ag layer thickness: 10 ° Heat treatment temperature: 500 ° C. Heat treatment time: 4.3 minutes However, since the Ag concentration in the metal material is small, the Ag weight concentration = C / pure Al density. A at 400 ° C.
The diffusion coefficient of Ag in 1 is 1 × 10 ⁻¹⁰ cm ² / sec,
The diffusion coefficient of Ag in Al at 500 ° C. is 2 × 10
^-9 cm ² / sec, the density of Ag is 10.5 g / cm ³ ,
A value of 2.7 g / cm ³ was used for the density of Al.

Bathroom supplies such as bathtubs, soap boxes, cups, etc., kitchen utensils such as sinks, drainage garbage, triangular corners, cooking utensils, metal parts of accessories such as washing tubs of washing machines, watches, glasses, accessories, etc. When the metal material according to claim 1 is used for a tool or the like, a sufficient concentration of the metal material from the surface of the metal material to a deep position in advance is prevented so that the antibacterial property is not lost even if the metal material is scratched or worn during use. Ag needs to be diffused.

When this metal material is usually left in the air, it reacts with oxygen in the air to form a natural oxide film on the surface. As a method for removing the natural oxide film, wet etching or dry etching is preferable. When removing the natural oxide film by wet etching, a mixed acid of hydrochloric acid and nitric acid is used as an etchant for stainless steel, and sodium hydroxide or hydrochloric acid is used for Al, and the natural oxide film is removed by dry etching. In this case, a reverse sputtering method, a plasma etching method, or the like is used. It is preferable to perform ultrasonic cleaning with an organic solvent before performing these etchings. The formation of the Ag layer is preferably performed by a physical vapor deposition method. The physical vapor deposition method includes vacuum vapor deposition, ion plating, sputtering and the like. A in these ways
After evaporating g, it is condensed on the surface of the metal material to form an Ag layer. The formation of the Ag layer is not limited to the physical vapor deposition method, but may be a plating method such as electrolytic plating, electroless plating, or the like.
The liquid containing g may be coated. The Ag layer is formed to an appropriate thickness depending on the required thickness of the antibacterial layer, the strength of the antibacterial activity, and the like.

[0021]

Next, examples of the present invention will be described together with comparative examples. <Example 1> 30 mm x 30 mm x 0.
A 3 mm SUS304 substrate was prepared. This substrate (metal material) is immersed in an isopropyl alcohol solution and subjected to ultrasonic cleaning, and then 36% HCl: 60% HNO ₃ : H ₂ O = 1:
The substrate was immersed in a 1: 3 room temperature etchant for 10 minutes to perform wet etching. After the etching, the substrate was washed with distilled water and dried. Next, the substrate was placed in a sputtering apparatus using pure Ag as a target.
× 10 ⁻⁶ Torr. With this sputtering apparatus, the distance between the target and the substrate was set to 9 cm, and Ar (2 × 10
^-3 Torr) as a sputtering gas, and high-frequency sputtering is performed at a target power of 100 W to a thickness of about 5
A 0 Å Ag layer was formed. The substrate (metal material) during sputtering was maintained at 400 ° C. After forming the Ag layer, the substrate (metal material) is kept at 400 ° C. for 30 minutes while maintaining the above-mentioned degree of vacuum in the same sputtering apparatus.
Was heat treated.

<Embodiment 2> 25 mm × 2 as a metal material
Using a 5 mm x 2 mm Al substrate, 36 as an etchant
% HCl: H ₂ O = 1: 4, and wet etching was performed in the same manner as in Example 1 except that the immersion time of this etchant was set to 30 minutes. Thereafter, an Ag layer was formed in the same manner as in Example 1. Then, the substrate was heat-treated.

Example 3 An Al substrate of the same shape and size as in Example 2 was used as a metal material, and 10 wt% N was used as an etchant.
The wet etching was performed in the same manner as in Example 1 except that the aOH solution was used. After the wet etching, sputtering was performed in the same manner as in Example 1 except that the temperature of the substrate (metal material) during sputtering was set to room temperature, to form an Ag layer having a thickness of 1000 Å. The heat treatment after the formation of the Ag layer was not performed. After the formation of the Ag layer, rolling was performed until the thickness of the Al substrate became 0.5 mm.

Example 4 A metal material was treated in the same manner as in Example 3 except that an Al substrate having the same shape and the same size as that of Example 2 was used as the metal material and wet etching was not performed.

<Comparative Example 1> The same metal material as in Example 1 in which no etching, Ag layer formation, or heat treatment was performed was used as Comparative Example 1. <Comparative Example 2> A metal material was treated in the same manner as in Example 1 except that wet etching was not performed. <Comparative Example 3> A metal material was treated in the same manner as in Example 1 except that the temperature of the metal material (substrate) was set to room temperature during sputtering.

<Test for Confirming Antibacterial Activity> Using the antibacterial-treated or untreated metal materials of Examples 1 to 4 and Comparative Examples 1 to 3 as samples, the antibacterial activity was determined according to the following bacteria count method. A confirmation test was performed. That is, 10 ⁶
A sample / ml of Staphylococcus aureus solution was dropped, and the sample was brought into contact with the bacteria at 30 ° C. for 17 hours. Thereafter, the bacteria were cultured, collected with distilled water, and the number of each bacteria was measured. 17 at 30 ° C
Table 1 shows the viable cell count after contact for an hour.

<Confirmation of Ag Diffusion Layer on Metal Material Surface> The samples of Example 1 and Comparative Example 2 were prepared separately from the samples for the antibacterial confirmation test. The surface of these samples was wiped with a soft cloth to remove the Ag layer remaining on the surface without diffusing into the metal material. Next, each sample was subjected to ultrasonic cleaning with distilled water and dried, and the composition distribution in the depth direction from the surface of the sample was examined by Auger analysis, which is a surface analysis method. The result is shown in FIG. 1 (Example 1),
The results are shown in FIG. 2 (Comparative Example 2) and Table 1. 1 and 2, the horizontal axis represents the sputtering time by Ar gas, and the vertical axis represents the element concentration (atomic%).

<Confirmation of Ag Distribution on Metal Material Surface after Rolling> Samples of Examples 3 and 4 were prepared separately from the samples for the antibacterial confirmation test. The metal material after rolling was approximately 100 mm × 25 mm × 0.5 mm. The presence or absence of Ag was analyzed by XPS analysis (X-ray photoelectron analysis) at a total of three points at both ends and the center of the surface of these metal materials, and whether or not the Ag layer was stretched together with the metal material by rolling and spread over the entire surface of the metal material. It was confirmed. Table 1 shows the results.

[0029]

[Table 1]

From Table 1, in Comparative Examples 1 to 3, 10 per ml was used.
^{About 5} bacteria were measured and had no antibacterial activity, whereas no bacteria were observed in Examples 1 and 2 and it was found that they had antibacterial activity. Also, from the Auger analysis result, A
Ag concentration (atomic%) in the vicinity of the sample surface for r sputtering time of 0 to 2 minutes is compared between FIG. 1 and FIG.
FIG. 1 shows that the Ag concentration is higher and the Ag diffusion layer is formed at a concentration sufficient to impart an antibacterial effect to the metal material.

Further, from the XPS analysis results, by rolling,
It was found that the Ag layer was stretched together with the metal material and spread over the entire surface of the metal material, so that the entire surface of the metal material had antibacterial properties.
Further, by comparing Example 3 with Example 4, the rolling method is effective as an antibacterial treatment method regardless of the presence or absence of the natural oxide film on the surface of the metal material. It was determined that there was no need to remove any, if any.

[0032]

As described above, according to the present invention, Ag having a high antibacterial property is contained only in the vicinity of the surface of a metal material at a low concentration, so that a high antibacterial property can be obtained without changing the original properties of the material. A long-lasting metal material is obtained. Further, according to the antibacterial treatment method of the present invention, unlike a conventional antibacterial treatment method, it is not necessary to add a large amount of Ag or Cu, so that the metal material is not deteriorated. Further, since antibacterial Ag is diffused at a low concentration only in the vicinity of the surface of the metal material required to have antibacterial action, it is not necessary to alloy the entire metal material with Ag, and a large amount of Ag is not used. Therefore, high antibacterial properties can be imparted to the metal material without increasing the price of the metal material. In addition, since the Ag atoms are diffused into the material and the interface between the antibacterial layer and the metal material is not present, the metal product is manufactured by processing the antibacterial-treated metal material or when the metal product is used for a long time. Also, there is an advantage that the antibacterial property does not deteriorate.

[Brief description of the drawings]

FIG. 1 is a diagram showing Auger analysis results of a sample after heat treatment in Example 1.

FIG. 2 is a diagram showing Auger analysis results of a sample after heat treatment of Comparative Example 2.

Claims (8)

[Claims] 1. An antibacterial metal material containing Ag only near its surface. 2. The metal material according to claim 1, wherein the metal material is stainless steel or Al. 3. An antibacterial treatment method for a metal material, comprising forming an Ag layer on the surface of the metal material and then rolling the metal material. 4. The antibacterial treatment method for a metal material according to claim 3, wherein after the metal material is rolled, the metal material is heat-treated in a vacuum or in an inert gas. 5. After removing the natural oxide film of the metal material having a natural oxide film on the surface, and forming the Ag material on or during the formation of the Ag layer on the surface of the metal material from which the natural oxide film has been removed, An antibacterial treatment method for a metal material, wherein the heat treatment is performed in a vacuum or an inert gas. 6. The method according to claim 5, wherein the natural oxide film is removed from the metal material by wet etching or dry etching. 7. The method according to claim 3, wherein the Ag layer is formed by physical vapor deposition. 8. The antibacterial treatment method for a metal material according to claim 3, wherein the metal material is stainless steel or Al.