Manufacturing method and mold for antibacterial member

Abstract

To provide a production method and a mold for producing a member having an antibacterial effect in which countless fine irregularities are randomly formed on a surface using the mold.SOLUTION: A production method for an antibacterial member according to the present invention comprises transferring from a mold to produce the antibacterial member having an irregular surface in which a shape of the irregularity is reversed from a surface of the mold, wherein the mold has an irregularity pitch ranging from a minimum value of 0.4 μm to a maximum value of 7.3 μm, and has a surface on which an infinite number of fine irregularities are randomly formed, the depth of which is in a range from the minimum value of 0.04 μm to the maximum value of 1.0 μm. Further, in the present invention, the fine irregularities formed on the surface of the mold are formed by any one of shot material projection treatment, chemical etching, and plasma treatment, or a combination of at least two or more thereof.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a technology for imparting antibacterial or bacterial growth inhibitory effects (antibacterial effect or bacterial growth / biofilm formation inhibitory effect) to the surface of a component by performing a process to randomly form countless minute irregularities on the surface of the component.

[0002] To date, the present applicants have taken various approaches to explore the possibility of applying surface modification technology that uses dimple-shaped micro-irregularities to various fields, such as by confirming the effects of forming countless micro-irregularities on the surface of a member that comes into contact with the object to be treated (a member that comes into contact with the object to be treated) in various fields.In the process, the present applicants discovered that, as described in Patent Document 1, micro-irregularities of a predetermined size that are formed on the surface of a member by shot projection processing or the like exhibit antibacterial effects. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6695558 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, shot material projection processing (such as fine particle projection processing) in which shot material is projected is known as a surface treatment method for randomly forming countless minute irregularities on the surface of a component. In shot material projection processing, shot material (fine particle media) is sprayed together with compressed air from a relatively small nozzle toward a specific area of ​​the component to perform the treatment, and the nozzle is moved to gradually expand the treatment area until the entire component is treated. For this reason, depending on the size of the component, the processing time may be relatively long.

[0005] For this reason, in order to reduce processing time and manufacturing costs, it is conceivable to use a method in which shot projection processing is performed on the surface of a mold (such as a metal mold) and then the mold is used to transfer the shot onto the surface of a component.

[0006] In addition, to produce a transfer mold for reproducing the surface shape formed by the shot material projection process (also referred to as the shot material projection surface shape), two transfers are required, and in order to produce a mold for obtaining the final antibacterial product (a mold having a surface with an inverted uneven shape relative to the shot material projection surface shape), a one-time transfer mold (a mold having a surface with the same uneven shape (orientation) as the fine particle projection surface shape) is required to transfer this inverted uneven shape (orientation) of the shot material projection surface shape.

[0007] This is because the concave portions of the unevenness formed by the shot projection process are formed by the dimple-shaped concave portions being raised around the periphery, as shown in Figure 7, and therefore the concave portions and convex portions of the unevenness formed by the shot projection process are not symmetrical in the vertical direction (front-to-back direction). As shown in Figures 6(A) and (B), this is due to the characteristic unique to processing methods that randomly form random shapes, such as shot projection processing, in which the shape of the concave portions and convex portions is reversed with a single transfer.

[0008] Recently, the present inventors have gained new knowledge in the process of conducting various antibacterial tests on members produced using a mold.

[0009] The present invention has been made in light of the above-mentioned circumstances, and aims to provide a manufacturing method and mold for producing a member having antibacterial properties, in which a countless number of minute irregularities are randomly formed on the surface, using a mold. [Means for solving the problem]

[0010] The method for producing an antibacterial member according to the present invention comprises the steps of: The pitch of the concave-convex structure is in the range of a minimum of 0.4 μm to a maximum of 7.3 μm, and the depth of the concave portion associated with the pitch of the concave-convex structure is in the range of a minimum of 0.04 μm to a maximum of 1.0 μm., by shot material projection processing, The antibacterial member is characterized in that it is transferred from a mold having a surface with countless randomly formed projections and recesses, and has a textured surface in which the textured shape is the inverse of that of the surface of the mold.

[0012] In the present invention, the antibacterial member may be a resin member.

[0013] The mold according to the present invention is The pitch of the concave-convex structure is in the range of a minimum of 0.4 μm to a maximum of 7.3 μm, and the depth of the concave portion associated with the pitch of the concave-convex structure is in the range of a minimum of 0.04 μm to a maximum of 1.0 μm. , by shot material projection processing, It is characterized by having a surface on which countless random patterns are formed on the transfer surface. [Effects of the Invention]

[0015] According to the present invention, a manufacturing method and mold can be provided for manufacturing a component having antibacterial properties with countless randomly formed minute irregularities on the surface using a mold, thereby contributing to reducing the manufacturing time and manufacturing costs of antibacterial components. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a graph showing the results of an antibacterial test (the number of viable bacteria after 8 hours of testing) according to one embodiment of the present invention. [Figure 2] 10A to 10C are diagrams showing an example of a method for producing a resin test piece by transfer according to the embodiment of the present invention. [Figure 3] (A) is a 3D image of the surface of the "Control" (comparison control) "SUS304 #700 polished mirror surface" (untreated with shot projection treatment), (B) is a 3D image of the surface of a resin test piece onto which the surface of (A) has been transferred once, (C) is a 3D image of the surface (antibacterial MD-treated surface) of "SUS304 #700 polished mirror surface" that has been subjected to antibacterial MD treatment (shot projection treatment), and (D) is a 3D image of the surface (antibacterial MD-treated transferred surface) of a resin test piece onto which the antibacterial MD-treated surface of (C) has been transferred once. [Figure 4] This is a diagram showing surface shape data obtained by observing the pitch of minute irregularities on a surface (antibacterial MD-treated surface) that has been subjected to antibacterial MD treatment on "SUS304 #700 polished mirror surface." [Figure 5] FIG. 5 is a diagram showing surface shape data obtained by observing the pitch of minute irregularities on the surface of a resin test piece onto which the antibacterial MD treated surface of FIG. 4 has been transferred once (antibacterial MD treated transferred surface). [Figure 6] (A) is a cross-sectional view showing a schematic example of an uneven shape formed by a shot projection process, and (B) is a cross-sectional view showing a schematic example of an uneven shape transferred once using a mold having the uneven shape of (A). [Figure 7] This is a cross-sectional SEM image of a single micro-depression formed experimentally by a single shot of media used in fine particle peening, an example of shot projection processing. DETAILED DESCRIPTION OF THE INVENTION

[0017] An embodiment of the present invention will be described below with reference to the accompanying drawings. However, the present invention is not limited to the embodiment described below.

[0018] In Patent No. 6695558, the applicant proposed that a surface on which countless randomly formed minute irregularities (a minutely irregular surface) has an antibacterial effect. However, from the viewpoint of productivity, it is also conceivable that an antibacterial effect can be imparted by forming a minutely irregular surface using a transfer mold. For this reason, a test to confirm the antibacterial effect was also conducted using a resin part (a micro-irregular surface in which the shape (orientation) of the irregularities is the same as the shape (orientation) of the irregularities formed by the shot projection process) that had been transferred twice from the surface of a part on which countless micro-irregularities of a size that would provide an antibacterial effect had been formed randomly using a shot projection process, and it was confirmed that a good antibacterial effect could be obtained even with a resin part that had been transferred in this way. Note that the antibacterial effect (or action) here can also be expressed, for example, as a bacterial growth inhibitory effect (or action), a biofilm inhibitory effect (or action), etc. (the same applies below).

[0019] Incidentally, to reproduce the minute unevenness that is believed to have antibacterial effects by transfer, as mentioned above, two transfers are required. That is, to produce a transfer mold for reproducing the surface shape formed by shot blasting (shot material projection surface shape), for example, two transfers are required, and to obtain a mold (two-transfer mold) for obtaining the final antibacterial product (a mold in which the shape (orientation) of the unevenness is inverted relative to the shot material projection surface shape), another mold (single-transfer mold) (a mold in which the shape (orientation) of the unevenness is the same as that of the shot material projection surface shape) is required to transfer this inverted unevenness.

[0020] When conducting a confirmation test of the antibacterial effect of a part having a shot material projected surface shape obtained by this double transfer (obtained from a mold in which the shape (direction) of the concaves and convexes is reversed relative to the shot material projected surface shape), the surface of a part (a surface in which the shape (direction) of the concaves and convexes is reversed relative to the shot material projected surface shape) formed using a mold in which a single transfer was performed (a mold in which the shape (direction) of the concaves and convexes is the same as the shot material projected surface shape) was also subjected to a confirmation test of the antibacterial effect.

[0021] The test was carried out in the same manner as described in Japanese Patent No. 6695558. That is, the test was carried out at the Kanagawa Prefectural Industrial Technology Research Institute, a local independent corporation. The test method was to conduct an antibacterial activity evaluation test using the film adhesion method on samples (test pieces) with different surface treatments (surface textures).

[0022] The test conditions are as follows: Test strain: Escherichia coli NBRC3972 strain Inoculum solution concentration: 4.9×10 5 CFU / mL Bacterial solution inoculation volume: 0.4 mL (contains 0.05 w / v% Tween 80) Test area: 40 x 40 mm square Covering film: Esclinica Pack L, manufactured by Sekisui Chemical Co., Ltd. Test temperature: 35°C Exam duration: 8 hours A coliform microbial culture medium sheet (manufactured by JNC Corporation) was used to measure the viable cell count. The viable cell count was measured by washing the sample with 9.6 mL of sterile saline and measuring the viable cell count concentration in the washed-out liquid.

[0023] As a result, it was confirmed that even a surface with a single transfer (transfer using a mold with the same irregularities as the shot projection surface shape), in other words, a surface with countless randomly formed minute irregularities with inverted irregularities, had an antibacterial effect (see Figure 1). Figure 1 shows the results of an antibacterial test against E. coli (viable bacteria count after 8 hours of testing), and it was confirmed that the viable bacteria count on the single-transfer antibacterial MD-treated transferred surface (antibacterial shot projection treated transferred surface) was reduced by more than 90% compared to the comparison test piece (test piece with a mirror-transferred surface).

[0024] In Figure 1, which shows the results of the antibacterial test, the "Control" (comparison) is a resin test piece to which "SUS304 #700 polished mirror surface" (untreated for shot projection treatment) was transferred once, and the viable count of E. coli (CFU / cm 2 ) was 10,000. The "SUS304 #700 Polished Mirror Finish" is a stainless steel plate made of SUS304 that has been polished with a P700 buff, resulting in a semi-mirror finish with high reflectivity (some streaky polishing marks remain), as shown in Figure 3(A).

[0025] The 3D images, surface shapes, and surface shape data in this embodiment, including those described below, were acquired using a shape measurement laser microscope VK-X100 manufactured by KEYENCE Corporation.

[0026] In Figure 1, the "antibacterial MD treated surface" is a resin test piece with a surface that has been subjected to antibacterial MD treatment (shot projection treatment) transferred once onto a "SUS304 #700 polished mirror surface." The number of viable E. coli bacteria (CFU / cm) 2 ) was less than 1000. In the antibacterial MD treatment according to this embodiment, an abrasive manufactured by Fuji Manufacturing Co., Ltd. (product name "Fuji Random C (Carborundum)", SiC (silicon carbide) with particle number C#400 (maximum particle size 75 μm or less, particle size at 50% of cumulative height 30.0±2.0 μm)) was sprayed from a spray nozzle onto "SUS304 #700 polished mirror surface" (the surface of a stainless steel plate) together with compressed air of about 1 / several (for example, 0.3) MPa, and a projection treatment (projection processing) was performed on the processed surface. This type of shot projection processing (micro-irregularity formation processing, microdimple (MD) processing) is referred to here as antibacterial MD treatment.

[0027] In this embodiment, the resin test piece was prepared by the method shown in FIG. First, in step 1, an antibacterial MD treated substrate 1 (a metal plate on which countless minute irregularities are randomly formed by shot projection processing) is prepared, and then the antibacterial MD treated substrate is used as a mold to coat (apply) a UV curable resin 2 onto the antibacterial MD treated surface.

[0028] In step 2, the prepared quartz glass 3 is used to sandwich the UV curable resin 2 against the antibacterial treated surface of the antibacterial MD treated substrate (mold) 1, and pressure is applied.

[0029] In step 3, UV is irradiated onto the UV curable resin to cure it, whereby the uneven shape of the antibacterial treated surface of the antibacterial MD treated substrate (mold) 1 is transferred to the surface of the UV curable resin 2.

[0030] In step 4, the UV curable resin 2 is removed (released) from the antibacterial MD treated substrate (mold) 1. This results in a UV curable resin 2 with a one-time transferred textured surface in which the shape (direction) of the textured surface of the antibacterial MD treated substrate (mold) 1 is reversed. The resin used for the transfer was PAK-01, a UV nanoimprint resin manufactured by Toyo Gosei Co., Ltd., which is capable of nano-sized fine transfer. For details, please refer to the URL (https: / / www.toyogosei.co.jp / rd / uv-feature.html).

[0031] In this embodiment, a UV-curable resin 2 having a one-time transfer textured surface in which the textured shape (orientation) is the reverse of the textured shape of the antibacterial treated surface confirmed to have antibacterial effects in Patent No. 6695558 was subjected to an antibacterial test, and as a result, it was confirmed that the resin has antibacterial effects as described above (see Figure 1).

[0032] Here, the uneven surface of the UV curable resin 2, which has an uneven surface formed by one transfer, in which the uneven shape (direction) of the uneven surface is the reverse of that of the antibacterial treated surface, was observed. Figure 3(A) is a 3D image of the surface of the "Control" (SUS304 #700 polished mirror surface) (untreated with shot projection), and Figure 3(B) is a 3D image of the surface of a resin test piece onto which the "Control" (Control) was transferred once. In addition, Figure 3(C) is a 3D image of the surface (antibacterial MD-treated surface) of "SUS304 #700 polished mirror surface" that has been subjected to antibacterial MD treatment (shot material projection treatment), and Figure 3(D) is a 3D image of the surface (antibacterial MD-treated transferred surface) of a resin test piece to which this antibacterial MD-treated surface has been transferred once.

[0033] Figure 4 shows surface shape data obtained by observing the pitch of minute irregularities on a surface (antibacterial MD-treated surface) that was subjected to antibacterial MD treatment (shot projection treatment) on "SUS304 #700 polished mirror surface." As shown in Figure 4, the range (μm) of the irregularity pitch (spacing between convex parts) of the test piece was approximately 2.5 to 7.1 μm, and the average irregularity pitch (spacing between convex parts) was approximately 4.565 μm. Furthermore, the range of the depth of the concave parts related to the irregularity pitch was approximately 0.3 to 1.0 μm, and the average concave part depth was approximately 0.557 μm. The unevenness pitch and recess depth of the minute unevenness are within the range of antibacterial effect specified in Patent No. 6695558 (maximum unevenness pitch of 7.3 μm or less and minimum of 0.4 μm or more, and maximum recess depth of 1.0 μm or less and minimum of 0.04 μm or more) (i.e., the unevenness pitch range is 0.4 to 7.3 μm, and the recess depth related to the unevenness pitch range is 0.04 to 1.0 μm).

[0034] FIG. 5 shows surface shape data obtained by observing the pitch of minute irregularities on the surface of a resin test piece onto which the antibacterial MD-treated surface of FIG. 4 was transferred once (antibacterial MD-treated transferred surface). As shown in Figure 5, the unevenness pitch (the distance between convex portions) range (μm) of the test specimen was approximately 2.5 to 9.5 μm, and the average unevenness pitch (the distance between convex portions) was approximately 5.123 μm. The depth of the concave portions related to the unevenness pitch ranged approximately 0.3 to 0.9 μm, and the average depth of the concave portions was approximately 0.490 μm. It was confirmed that the unevenness pitch and the depth of the concave portions of the minute unevennesses were within the ranges for antibacterial effect specified in Japanese Patent No. 6695558 (the unevenness pitch range was 0.4 to 7.3 μm, and the depth of the concave portions related to the unevenness pitch range was 0.04 to 1.0 μm).

[0035] That is, according to this embodiment, it was confirmed that the surface (antibacterial MD treatment transferred surface) of a resin test piece onto which a surface that has been subjected to antibacterial MD treatment (antibacterial MD treatment surface) has been transferred once, and the shape (orientation) of the countless randomly formed minute irregularities is inverted relative to the antibacterial MD treatment surface, has an antibacterial effect.

[0036] Until now, it was thought that two transfers were required to reproduce the minute unevenness formed by shot projection processing, which is believed to have antibacterial effects, but this experiment showed that antibacterial effects can be achieved even with a single transfer.

[0037] As described above, according to this embodiment, even a transfer surface formed using a mold produced by a single transfer (a component surface in which the shape (orientation) of the unevenness is reversed relative to the shot material projection surface shape) can be imparted with an antibacterial effect equivalent to that of an uneven surface obtained by two transfers or an uneven surface directly subjected to shot material projection processing. Therefore, there is no need to prepare (manufacture) a final mold obtained by two transfers (a mold in which the shape (orientation) of the unevenness is reversed relative to the shot material projection surface shape) in order to reproduce the surface shape formed by shot material projection processing (shot material projection surface shape). This reduces the manufacturing costs, including the molds for two transfers, and also suppresses deterioration of the uneven shape due to an increase in the number of transfers. Therefore, even when an uneven surface is formed by a single transfer, it is possible to maintain a high level of antibacterial effect while achieving low costs.

[0038] As described above, according to the present embodiment, it is possible to provide a manufacturing method and mold for manufacturing a component having antibacterial properties in which a countless number of minute irregularities are randomly formed on the surface using a mold, thereby contributing to reducing the manufacturing time and manufacturing costs of antibacterial components.

[0039] Here, the shot projection process according to this embodiment (also referred to as fine particle projection process, micro-roughness formation process, micro-dimple process (MD process), etc.) can be carried out by using a known injection device to inject media (shot material, abrasive particles) such as those described above and collide them against the surface of the component.

[0040] For example, a blasting device can be used as the injection device, and an example of the blasting device is the "PNEUMA BLASTER" (models: SC series, SG series, etc.) manufactured by Fuji Manufacturing Co., Ltd. Also, for example, the device described in JP 2019-25584 A can be used.

[0041] More specifically, as an injection device for injecting the injected particles toward the surface of the component, a known blasting device (blasting processing device) that injects abrasives (fine particles) together with compressed gas (air, argon, nitrogen, etc.) can be used.

[0042] As for blast processing equipment (blast processing devices), various types are commercially available, including suction-type blast processing equipment that uses the negative pressure generated by the injection of compressed gas to inject abrasives, gravity-type blast processing equipment that injects abrasives that have fallen from an abrasive tank, carried on the compressed gas, direct pressure-type blast processing equipment that introduces compressed gas into a tank containing abrasives and combines the abrasive flow from the abrasive tank with the compressed gas flow from a separately provided compressed gas supply source and injects the abrasives, and blower-type blast processing equipment that injects the direct pressure-type compressed gas flow carried on a gas flow generated by a blower unit, all of which can be used to inject the aforementioned injection particles. Alternatively, a water jet can be used, which sprays a shot at high pressure along with a liquid such as water.

[0043] Although the present embodiment has been described using antibacterial MD treatment as an example, the present invention is not limited to this, and as long as it is a shot material projection treatment that can form a surface with antibacterial effects, there are no particular limitations on the size and type of media, other specifications, specifications of the injection device, injection conditions, etc.

[0044] Furthermore, in this embodiment, it has been described that countless dimple-shaped minute recesses are formed randomly on the surface of the mold by shot projection processing, but it is also possible to form countless minute recesses and projections randomly by subjecting the surface of the member to chemical polishing (chemical etching) or plasma treatment (e.g., argon bombardment treatment). However, the present invention is not limited to this, and the minute recesses and projections formed on the surface of the mold in the present invention can also be formed by at least one of chemical etching, plasma treatment, shot projection processing, etc., or by an appropriate combination of these. For chemical polishing (chemical etching), it is expected that an aqueous solution of, for example, acidic agents such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, or iron (III) chloride may be prepared in any ratio and used.

[0045] Furthermore, in this embodiment, the transfer method has been exemplified as transferring onto a resin member, but the present invention is not limited to this and can also be applied to methods of transferring onto the surface of stainless steel or other metal members using a press or the like.

[0046] The present invention is not limited to the above-described embodiment of the invention, and various modifications can be made without departing from the spirit of the present invention. [Explanation of symbols]

[0047] 1. Antibacterial MD-treated substrate 2 UV curable resin 3. Quartz glass

Claims

1. A method for manufacturing an antibacterial member, characterized in that an antibacterial member is manufactured by transferring, from a mold having a surface on which countless randomly formed micro-concaves have been formed by a shot projection process, micro-concaves having a pitch ranging from a minimum of 0.4 μm to a maximum of 7.3 μm, and the depth of the recesses associated with the pitch ranging from a minimum of 0.04 μm to a maximum of 1.0 μm, with the result that the antibacterial member has a convex-concave surface in which the shape of the convex-concave shapes is the inverse of that of the surface of the mold.

2. 2. The method for manufacturing an antibacterial member according to claim 1, wherein the antibacterial member is a resin member.

3. A mold characterized by having a surface on a transfer surface on which countless minute irregularities are randomly formed by a shot projection process, with the irregularity pitch ranging from a minimum of 0.4 μm to a maximum of 7.3 μm, and the depth of the recesses associated with the irregularity pitch ranging from a minimum of 0.04 μm to a maximum of 1.0 μm.

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