Antibacterial molded body and its manufacturing method

Abstract

To provide an antibacterial molding capable of heightening antibacterial performance.SOLUTION: An antibacterial molding has an antibacterial region formed by combining a plurality of independent antibacterial surfaces having different heights. The plurality of antibacterial surfaces have a first antibacterial surface having a highest height, a second antibacterial surface having a lowest height, and an intermediate antibacterial surface having an intermediate height between the height of the first antibacterial surface and the height of the second antibacterial surface. Among the plurality of antibacterial surfaces, all of an average value of the first antibacterial surface, the average value of the second antibacterial surface and the average value of the intermediate antibacterial surface are 35.0 μm2 or more. 95.0 μm2 or less, and all of the difference of the most frequent value of a height distribution between the first antibacterial surface and the intermediate antibacterial surface and difference of most frequent value of a height distribution between the intermediate antibacterial surface and second antibacterial surface are 1.70 μm or more and 10.0 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an antibacterial molded article and a method for producing the same. [Background technology]

[0002] Due to increasing consumer awareness, many antibacterial products are available on the market. In many cases, the antibacterial properties are imparted to the surface of the product by coating it with an antibacterial agent or embedding silver nanoparticles into it.

[0003] In recent years, attempts have been made to physically achieve antibacterial effects by providing a fine uneven structure on the surface of an article (for example, Patent Documents 1 and 2). Many of these attempts aim to pierce and kill bacteria or inhibit bacterial movement by providing fine protrusions on the surface of the article. Therefore, sharp protrusions designed to pierce and kill bacteria or protrusions spaced at approximately the same intervals as the bacteria have been provided. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-132916 [Patent Document 2] Japanese Patent Application Publication No. 2019-151614 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the effectiveness of the above-mentioned antibacterial agents and antibacterial articles containing silver nanoparticles may disappear over time, and there have been concerns about safety to living organisms. This has resulted in limitations on their applications and usage environments. The methods described in Patent Documents 1 and 2, which provide a finely textured structure on the surface of an article, address these concerns. However, the methods described in Patent Documents 1 and 2 have the problem of not enhancing antibacterial activity as much as expected.

[0006] The present invention has been made in view of the above-mentioned problems, and aims to provide an antibacterial molded article having an antibacterial activity imparted to the surface of the article by providing a fine uneven structure, and having enhanced antibacterial activity, and a method for producing the same. [Means for solving the problem]

[0007] The antibacterial molded article for solving the above problems has an antibacterial region formed by combining a plurality of independent antibacterial surfaces of different heights. The plurality of antibacterial surfaces include a first antibacterial surface having the highest height, a second antibacterial surface having the lowest height, and an intermediate antibacterial surface having a height intermediate between the heights of the first antibacterial surface and the second antibacterial surface. The plurality of antibacterial surfaces have an average surface area of ​​the first antibacterial surface, an average surface area of ​​the second antibacterial surface, and an average surface area of ​​the intermediate antibacterial surface all of 35.0 μm. 2 95.0μm or more 2 or less, and the difference in the mode of the height distribution between the first antibacterial surface and the intermediate antibacterial surface, and the difference in the mode of the height distribution between the intermediate antibacterial surface and the second antibacterial surface are both 1.70 μm or more and 10.0 μm or less.

[0008] In addition, a method for manufacturing an antibacterial molded body to solve the above problem is a method for manufacturing an antibacterial molded body, in which the antibacterial region is formed on the surface of a molded body, or a molded body having the antibacterial region on its surface is molded. [Effects of the Invention]

[0009] According to the present invention, an antibacterial molded article is provided in which a fine uneven structure is provided on the surface of the article to impart antibacterial activity, and the antibacterial activity is enhanced. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a laser microscope photograph showing an example of an antibacterial region according to one embodiment of the present invention. [Figure 2] FIG. 2 is a plan view schematically illustrating the antibacterial region shown in FIG. [Figure 3]Figure 3A is a schematic diagram showing the antibacterial region cut along imaginary line AA shown in Figure 2 when viewed in the direction of the arrow in the figure, and Figure 3B is a schematic diagram showing the antibacterial region cut along imaginary line BB shown in Figure 2 when viewed in the direction of the arrow in the figure. [Figure 4] FIG. 4 is a schematic plan view showing an antibacterial region having only a first antibacterial surface with the highest height and a second antibacterial surface with the lowest height. [Figure 5] FIG. 5 is a plan view schematically illustrating another example of an antibacterial region according to one embodiment of the present invention. [Figure 6] FIG. 6 is a plan view schematically illustrating yet another example of an antibacterial region according to one embodiment of the present invention. [Figure 7] Figure 7 shows an example of a height distribution spectrum obtained by observing the antibacterial region with a laser microscope. [Figure 8] FIG. 8 shows an example of a contour curve obtained for a profile line arbitrarily set in the antibacterial region. DETAILED DESCRIPTION OF THE INVENTION

[0011] An antibacterial molded article according to one embodiment of the present invention has an antibacterial region on at least a portion of its surface that is imparted with antibacterial activity. The antibacterial region is formed by combining and arranging a plurality of antibacterial surfaces having different heights.

[0012] [Antibacterial area] FIG. 1 is a laser microscope photograph showing an example of the antibacterial region. FIG. 1 shows a photograph in which the surface height of the antibacterial region was measured using a laser microscope and different colors were assigned to different heights. FIG. 2 is a plan view schematically showing the antibacterial region shown in FIG. 1. FIG. 3A is a schematic diagram showing the antibacterial region cut along imaginary line AA in FIG. 2, viewed in the direction of the arrow (in FIG. 3A, the cross-sectional shape of the antibacterial region located one layer further back is shown by a dotted line). FIG. 3B is a schematic diagram showing the antibacterial region cut along imaginary line BB in FIG. 2, viewed in the direction of the arrow.

[0013] 1, 2, 3A, and 3B, antibacterial region 100 has first antibacterial surface 110, which has the highest height, second antibacterial surface 120, which has the lowest height, and intermediate antibacterial surface 130, which has an intermediate height. Antibacterial region 100 is formed by combining and arranging these multiple antibacterial surfaces of different heights.

[0014] Many bacteria inherently have a mechanism that slows growth and dies when their density increases. Individual bacteria also release attractants and recognize their density by sensing these attractants. In other words, as the amount of attractant increases, bacterial growth is suppressed, and as the bacteria die, the density decreases. Since each of the above antibacterial surfaces has a surface area set within a predetermined range, even with a relatively small amount of bacteria, the concentration of the attractant released by the bacteria increases sufficiently. As a result, growth stops and the bacteria die in a relatively short time, before they can grow significantly. Therefore, the amount of bacteria is unlikely to increase beyond a certain level over a long period of time, and a low bacterial population can be maintained.

[0015] By reducing the average surface area of ​​each antibacterial surface, the antibacterial effect due to the density of bacteria can be more fully exerted. On the other hand, by increasing the average surface area of ​​each antibacterial surface to a certain extent, a certain amount of bacteria can be present on the antibacterial surface, allowing each antibacterial surface to exert the antibacterial effect due to the density of bacteria. From the viewpoint of balancing these, the first antibacterial surface 110, the second antibacterial surface 120, and the intermediate antibacterial surface 130 all have an average surface area of ​​35.0 μm 2 95.0μm or more 2 Less than or equal to 35 μm 2 More than 70μm 2 Preferably, it is 35 μm or less. 2 More than 50μm 2 More preferably, it is:

[0016] Increasing the height difference between adjacent antibacterial surfaces to a certain extent makes it difficult for bacteria to overcome the barrier between the adjacent antibacterial surfaces and migrate to a higher antibacterial surface. On the other hand, limiting the height difference between adjacent antibacterial surfaces to a predetermined range can inhibit bacterial growth on the barrier between the antibacterial surfaces. From the viewpoint of achieving a balance between these two factors, the difference between the mode of the height distribution of the first antibacterial surface 110 and the mode of the height distribution of the intermediate antibacterial surface 130, and the difference between the mode of the height distribution of the intermediate antibacterial surface 130 and the mode of the height distribution of the second antibacterial surface 120 are both 1.70 μm or more and 10.0 μm or less, preferably 1.70 μm or more and 8.00 μm or less, and more preferably 2.00 μm or more and 3.00 μm or less. While the difference in the modes of these height distributions does not directly reflect the difference in height between adjacent antibacterial surfaces, it is estimated that if the difference in the modes of these height distributions is within the above range, the height difference between adjacent antibacterial surfaces will be within a sufficient range for many antibacterial surfaces.

[0017] Because the first antibacterial surface 110, the second antibacterial surface 120, and the intermediate antibacterial surface 130 all have surface areas set within a predetermined range, bacteria are unlikely to overcome the barrier between adjacent antibacterial surfaces and migrate to higher antibacterial surfaces. Therefore, bacteria present on each antibacterial surface can only remain on that antibacterial surface or migrate to an adjacent antibacterial surface with a lower height. If bacteria remain on that antibacterial surface, even a small amount of bacterial growth can sufficiently increase the bacterial density (attractant concentration), causing the bacteria to stop growing and die. If bacteria migrate to a lower antibacterial surface, the bacterial density (attractant concentration) on the destination antibacterial surface increases sufficiently, causing the bacteria to stop growing and die. Thus, by preventing bacteria from migrating to higher antibacterial surfaces, the spread of bacteria can be prevented, thereby preventing or eliminating the growth of the bacteria on each antibacterial surface.

[0018] As shown in FIG. 1 , in this embodiment, each of the multiple first antibacterial surfaces 110 is disposed independently, with no other first antibacterial surfaces 110 disposed adjacent to its periphery. More specifically, each first antibacterial surface 110 is only contacted at its periphery by the second antibacterial surface 120 and the intermediate antibacterial surface 130, with no other first antibacterial surfaces 110 disposed adjacent to its periphery. Therefore, bacteria present on each first antibacterial surface 110 cannot migrate to other first antibacterial surfaces 110 and can only remain on that first antibacterial surface 110. As a result, when the density of the bacteria (concentration of attractant) on that first antibacterial surface 110 increases, the bacteria stop growing and die out.

[0019] Furthermore, as shown in FIG. 1 , in this embodiment, each of the multiple second antibacterial surfaces 120 is disposed independently, with no other second antibacterial surfaces 120 disposed adjacent to its periphery. More specifically, each second antibacterial surface 120 is only contacted by the first antibacterial surface 110 and the intermediate antibacterial surface 130 at its periphery, with no other second antibacterial surfaces 120 disposed adjacent to its periphery. Therefore, bacteria present on each second antibacterial surface 120 cannot migrate to other second antibacterial surfaces 120, but can only remain on that second antibacterial surface 120 or migrate to an adjacent antibacterial surface with a lower height. As a result, the density of the bacteria (concentration of attractant) on that second antibacterial surface 120 or an adjacent antibacterial surface becomes sufficiently high, causing the bacteria to stop growing and die.

[0020] In this embodiment, antibacterial region 100 has first antibacterial surface 110, which has the highest height, and second antibacterial surface 120, which has the lowest height, as well as intermediate antibacterial surface 130, which has an intermediate height. By arranging intermediate antibacterial surface 130 and combining multiple antibacterial surfaces with at least three different heights, it is possible to make it difficult for other first antibacterial surfaces 110 and second antibacterial surfaces to be arranged in positions adjacent to the outer periphery of first antibacterial surface 110 and second antibacterial surface.

[0021] FIG. 4 is a schematic plan view showing a region 400 having only a first surface 410 with the highest height and a second surface 420 with the lowest height. In the region 400 shown in FIG. 4, a first surface 410a contacts an adjacent first surface 410b at point P. If bacteria move and spread from first surface 410a to first surface 410b via point P, the bacterial density (attractant concentration) on first surface 410 may not be sufficiently high, and bacterial growth may not be stopped or the bacteria may not be sufficiently killed. If smaller first surfaces 410 are arranged in the same position so that adjacent first surfaces 410 do not contact each other, adjacent second surfaces 420 will connect at the bottom of region 400, causing bacteria to move and spread from one second surface 420 to the adjacent second surface 420. As a result, the bacterial density (concentration of attractants) on second surface 420 (bottom surface) may not be sufficiently high, and bacterial growth may not be stopped or killed sufficiently. In contrast, in this embodiment, by providing intermediate antibacterial surface 130, adjacent first antibacterial surfaces 110 and adjacent second antibacterial surfaces 120 can be arranged so that they do not come into contact with each other (see FIG. 2), and the recent increase in bacterial density on each antibacterial surface can more fully inhibit bacterial growth and kill them (antibacterial effect).

[0022] From the viewpoint of more effectively inhibiting the movement of bacteria between first antibacterial surfaces 110 arranged in different positions, between second antibacterial surfaces 120 arranged in different positions, and between intermediate antibacterial surfaces 130 arranged in different positions, it is preferable that the distance between different first antibacterial surfaces 110, the distance between different second antibacterial surfaces 120, and the distance between different intermediate antibacterial surfaces 130 be as large as possible. On the other hand, from the viewpoint of keeping the average value of the surface area of ​​each antibacterial surface within the above-mentioned range, it is preferable not to make the distance between each first antibacterial surface 110, each second antibacterial surface 120, and each intermediate antibacterial surface 130 too large. From the viewpoint of balancing these factors, the average value of the distance between a first antibacterial surface 110 and the nearest first antibacterial surface 110, the average value of the distance between a second antibacterial surface 120 and the nearest second antibacterial surface 120, and the average value of the distance between an intermediate antibacterial surface 130 and the nearest intermediate antibacterial surface 130 are all preferably 0.5 μm or more and 95 μm or less, more preferably 1.5 μm or more and 45 μm or less, and even more preferably 2.0 μm or more and 14 μm or less.

[0023] When forming each antibacterial surface by forming convex portions on the surface of the base material, the surface tends to have multiple convex portions protruding from the surface with the lowest height (bottom surface), and in such a shape, the bottom surface becomes continuous, making it easy for bacteria to grow on the bottom surface. When forming each antibacterial surface, the formation conditions are adjusted so that the bottom surface becomes a shape that is not continuous, and the average surface area of ​​the second antibacterial surface 120 with the lowest height is 35.0 μm 2 95.0μm or more 2 Less than or equal to 35 μm, preferably 2 More than 70μm 2 Less than or equal to 35 μm, more preferably 2 More than 50μm 2 Similarly, it is desirable to adjust the formation conditions so that the average distance between one first antibacterial surface 110 and the nearest first antibacterial surface 110 is 0.5 μm or more and 95 μm or less, preferably 1.5 μm or more and 45 μm or less, and more preferably 2.0 μm or more and 14 μm or less.

[0024] Furthermore, the first antibacterial surface 110, which has the highest height, is prone to bacterial migration between adjacent antibacterial surfaces, and therefore is prone to bacterial proliferation. Therefore, the formation conditions are adjusted so that the average surface area of ​​the first antibacterial surface 110 is 35.0 μm 2 95.0μm or more 2 Less than or equal to 35 μm, preferably 2 More than 70μm 2 Less than or equal to 35 μm, more preferably 2 More than 50μm 2 Similarly, it is desirable to adjust the formation conditions so that the average distance between a given second antibacterial surface 120 and the nearest second antibacterial surface 120 is 0.5 μm or more and 95 μm or less, preferably 1.5 μm or more and 45 μm or less, and more preferably 2.0 μm or more and 14 μm or less.

[0025] Similarly, the formation conditions were adjusted to obtain an intermediate antibacterial surface 130 with an average surface area of ​​35.0 μm 2 95.0μm or more 2 Less than or equal to 35 μm, preferably 2 More than 70μm 2 Less than or equal to 35 μm, more preferably 2 More than 50μm 2 Similarly, it is desirable to adjust the formation conditions so that the distance between one intermediate antibacterial surface 130 and the nearest intermediate antibacterial surface 130 is 0.5 μm or more and 95 μm or less, preferably 1.5 μm or more and 45 μm or less, and more preferably 2.0 μm or more and 14 μm or less.

[0026] In this embodiment, first antibacterial surface 110, second antibacterial surface 120, and intermediate antibacterial surface 130 are arranged in a square lattice pattern with the lines of each antibacterial surface intersecting perpendicularly in the vertical and horizontal directions, with first antibacterial surface 110 and intermediate antibacterial surface 130 arranged alternately in one row ( FIG. 3A ), and second antibacterial surface 120 and intermediate antibacterial surface 130 arranged alternately in another adjacent row ( FIG. 3B ), and the arrangement of second antibacterial surface 120 is offset between the first row and the other row ( FIGS. 3A and 3B ). However, the arrangement of each antibacterial surface is not limited to this and may be irregular or regular.

[0027] Even when the antimicrobial surfaces are regularly arranged, the arrangement of the antimicrobial surfaces is not limited to that shown in Figures 1 and 2. For example, first antimicrobial surface 510, second antimicrobial surface 520, and intermediate antimicrobial surface 530 may be arranged on two non-orthogonal straight lines that intersect at a predetermined angle (Figure 5). Furthermore, first antimicrobial surface 610, second antimicrobial surface 620, and intermediate antimicrobial surface 630 may be arranged in a shape other than a square lattice, such as a triangular lattice (Figure 6).

[0028] In this embodiment, the first antibacterial surface 110 is composed of multiple antibacterial surfaces of the same height, but the antibacterial region 100 may have only one first antibacterial surface 110 with the highest height. Furthermore, the second antibacterial surface 120 is composed of multiple antibacterial surfaces of the same height, but the antibacterial region 100 may have only one second antibacterial surface 120 with the lowest height. Furthermore, in this embodiment, the intermediate antibacterial surface 130 is composed of multiple antibacterial surfaces of the same height, but the antibacterial region 100 may have multiple intermediate antibacterial surfaces 130 with different heights. When the antibacterial region 100 has multiple intermediate antibacterial surfaces 130 with different heights, it is preferable that each intermediate antibacterial surface 130 of each height satisfies the average surface area value described above, and that the height difference between the intermediate antibacterial surface 130 and the other intermediate antibacterial surface with the closest height satisfies the condition for the difference in the mode of the height distribution described above for the first antibacterial surface 110, the intermediate antibacterial surface 130, and the second antibacterial surface 120. To facilitate the fabrication of the antibacterial region 100, it is preferable that all intermediate antibacterial surfaces in the antibacterial region 100 have approximately the same height. When intermediate antibacterial surfaces of different heights are present, it is desirable to have two to five different heights, preferably two to three different heights, and more preferably two different intermediate antibacterial surfaces. The presence of "intermediate antibacterial surfaces of different heights" means that there is a clear difference between the most frequent values ​​of the height distribution, and two or more groups of intermediate antibacterial surfaces can be identified, allowing a threshold value (described below) to be set between each of the intermediate antibacterial surfaces. In this case, the average surface area of ​​the intermediate antibacterial surfaces, the most frequent value of the height distribution, and the distance between the nearest intermediate antibacterial surface are the average surface area, the most frequent value of the height distribution, and the distance between the nearest intermediate antibacterial surface, measured for each of the multiple intermediate antibacterial surfaces that make up a predetermined group of heights.

[0029] The first antibacterial surface 110, the second antibacterial surface 120 and the intermediate antibacterial surface 130 may have the same average surface area as described above, or the average surface area may differ for each antibacterial surface within the range described above.

[0030] The average surface area of ​​each antibacterial surface can be calculated using the following method. First, the antibacterial region is observed with a laser microscope to obtain a height distribution spectrum showing the distribution (frequency) of measurement points relative to height. Figure 7 shows an example of the height distribution spectrum obtained. Figure 7 shows three peaks: peak 710 (corresponding to the first antibacterial surface 110), peak 720 (corresponding to the second antibacterial surface 120), and peak 730 (corresponding to the intermediate antibacterial surface 130). The height distribution spectrum shown in Figure 7 is assumed to be a collection of normal distributions corresponding to these peaks, and the intersection of adjacent normal distributions (or, if there is no intersection, the point where the normal distribution with the lower height becomes 0) is set as the threshold. Figure 7 also shows threshold 740 between peak 710 and peak 730, and threshold 750 between peak 730 and peak 720. The total area of ​​the regions with the highest height higher than threshold 740 is then calculated, and the resulting total area is divided by the number of regions with the highest height higher than threshold 740 to calculate the average surface area of ​​the first antibacterial surface with the highest height. Next, the total area of ​​regions with heights higher than the next highest threshold value 750 is calculated, and the total area of ​​regions with heights higher than threshold value 740 is subtracted from the total area. The area thus obtained (corresponding to intermediate antibacterial surface 130) is divided by the number of regions with heights higher than threshold value 750 but lower than threshold value 740 to calculate the average surface area of ​​the intermediate antibacterial surface. Finally, the total area of ​​regions with heights higher than threshold value 750 is subtracted from the surface area of ​​the entire antibacterial region. The area thus obtained (corresponding to second antibacterial surface 120) is divided by the number of regions with heights lower than threshold value 750 to calculate the average surface area of ​​the second antibacterial surface with the lowest height. Note that when the antibacterial region has multiple intermediate antibacterial surfaces with different heights, more peaks and threshold values ​​can be set in the height distribution spectrum. By repeatedly calculating the average surface area of ​​the intermediate antibacterial surface based on these peaks and threshold values, the average surface area of ​​each intermediate antibacterial surface can be calculated. The number of regions corresponding to each peak can be measured using known image analysis software, etc.

[0031] Additionally, the difference between the mode of the height distribution of first antibacterial surface 110 and the mode of the height distribution of intermediate antibacterial surface 130 can be the difference in height between peak 710 and peak 730 in Figure 7. Similarly, the difference between the mode of the height distribution of intermediate antibacterial surface 130 and the mode of the height distribution of second antibacterial surface 120 can be the difference in height between peak 730 and peak 720 in Figure 7.

[0032] The average distance between a given first antibacterial surface 110 and its nearest first antibacterial surface 110 can be calculated from the cross-sectional curve obtained by observing the antibacterial region with the laser microscope. Figure 8 shows an example of a cross-sectional curve obtained for a profile line arbitrarily set in the antibacterial region. This cross-sectional curve shows the first antibacterial surface 110, the second antibacterial surface 120, and the intermediate antibacterial surface 130. Virtual lines are set on this cross-sectional curve, indicating heights corresponding to the thresholds 740 and 750 set in the measurement of the average surface area. For a pair of first antibacterial surfaces 110 set so that no other first antibacterial surfaces are sandwiched between them, the distance D1 between the intersection of the virtual line corresponding to threshold 740 and the cross-sectional curve is calculated and used as the distance between these antibacterial surfaces 110. In this way, the distance between one first antibacterial surface 110 is calculated for each of the ten arbitrarily set profile lines, and the arithmetic average of these values ​​is used as the average distance between a given first antibacterial surface 110 and its nearest first antibacterial surface 110. The same applies to the average value of the distance D2 between a given second antibacterial surface 120 and the nearest second antibacterial surface 120, and the average value of the distance D3 between a given intermediate antibacterial surface 130 and the nearest intermediate antibacterial surface 130. Note that although the distance between intermediate antibacterial surfaces 130 is taken as the distance between the cross-sectional curves at a height of threshold value 750 in Fig. 8, when a first antibacterial surface 110 is placed between intermediate antibacterial surfaces 130, the distance can be calculated based on the virtual line that intersects with each intermediate antibacterial surface 130, such as the distance between the cross-sectional curves at a height of threshold value 740.

[0033] These measurements and calculations can be performed using, for example, a laser microscope, VK-X250 manufactured by Keyence Corporation, and a multi-file analysis application, VK-HIXM, as analysis software.

[0034] The antibacterial region may be formed over the entire surface of the antibacterial molded article, or may be formed only in the area where bacteria are likely to adhere. Alternatively, the antibacterial region may be dispersed in part of the area where bacteria are likely to adhere.

[0035] [Material and shape of antibacterial molded body] The material of the antibacterial molded body is not particularly limited and can be appropriately selected depending on the application of the antibacterial molded body. As long as it has the above-mentioned antibacterial region, the same effect can be obtained regardless of the material of the antibacterial molded body. Here, the material of the antibacterial molded body may be, for example, an inorganic material such as metal or ceramic, an organic material such as resin, or a composite of these. It is preferable that the surface does not contain an antibacterial agent or silver nanoparticles.

[0036] Examples of metals include stainless steel, aluminum, copper, silver, iron, and titanium. Examples of ceramics include silicon carbide and lead zirconate titanate. The resin may be a thermoplastic resin or a thermosetting resin. The resin may be a crystalline resin or a non-crystalline resin. The resin may be rubber, such as synthetic rubber or natural rubber.

[0037] Examples of the resins include polyolefin resins such as polyethylene and polypropylene; cyclic olefin resins; halogenated hydrocarbons such as polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), perfluoroethylenepropene copolymer (FEP), polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), and polyvinylidene chloride (PVDC); polyamide; polyimide; polyacetal (POM); polyurethane; ethylene-vinyl alcohol copolymer (EVOH); acrylic polymer; ethylene-vinyl acetate copolymer (EVA); polylactic acid (PLA); polycaprolactone (PCL); polyglycolic acid (PGA); polystyrene (P Polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polybutylene naphthalate (PBN); polyphenylene sulfide (PPS); polyether ether ketone (PEEK); acrylonitrile-styrene copolymer (AS); acrylonitrile-butadiene-styrene copolymer (ABS); polycarbonate (PC); polyarylate (PAR); polyphenylene ether (PPE); polyphenolic resins; epoxy resins; rubbers such as isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), and ethylene-propylene rubber (EPM); etc.

[0038] Among the above, stainless steel, polycarbonate, and cyclic olefin resins are preferred from the viewpoints of processability, versatility, etc. Polycarbonate and cyclic olefin resins are preferred because they can form transparent films and can provide good appearances as packaging materials or protective sheets for electronic devices.

[0039] The shape of the antibacterial molded article is not particularly limited as long as it has the above-mentioned antibacterial region, and can be any shape depending on the application of the antibacterial molded article, etc. The antibacterial molded article can be formed into any desired shape, such as a film, sheet, tube, ring, bulk (cube, rectangular parallelepiped, cylinder, sphere, etc.), plate, bag, or a three-dimensional structure obtained by processing any of these.

[0040] [Uses of antibacterial molded products] The uses of the antibacterial molded article are not particularly limited, and it can be used in a wide range of applications, including packaging materials, medical instruments, home appliances, building equipment, space suits, spacecraft interiors, electronic devices and their peripherals, automobile parts, agricultural supplies, stationery, and body accessories, etc. The use modes of the antibacterial molded article include the antibacterial molded article being an article used for these applications, or the antibacterial molded article being incorporated as a part of these articles, etc.

[0041] Examples of packaging materials include films, sheets, boxes, cases, decorative items, etc. In this case, the antibacterial region of the antibacterial molded article may be disposed on either the surface that contacts the packaged item or the surface that does not contact the packaged item. By using the antibacterial molded article in a packaging material, bacterial growth in the packaged item can be prevented and the shelf life of the packaged item can be improved.

[0042] Among packaging materials, food packaging materials require high antibacterial properties. Therefore, the antibacterial molded body is particularly suitable as a food packaging material, and in this case, it is preferable to arrange an antibacterial region on the surface that comes into contact with food. As described above, the antibacterial molded body does not need to contain an antibacterial agent or silver nanoparticles, and therefore is highly safe. Furthermore, the antibacterial molded body kills bacteria by concentrating the attractant substances released by the bacteria. Therefore, it is more likely to be effective in an environment where a specific type of bacteria is present than in an environment where many types of bacteria are present. Therefore, for example, using the antibacterial molded body inside a food packaging material used to seal food can suppress the growth of specific bacteria and extend the expiration date, etc.

[0043] On the other hand, examples of medical instruments include forceps, syringes, stents, artificial blood vessels, catheters, wound dressings, scaffolding materials for regenerative medicine, anti-adhesion materials, and pacemakers. Among these, the antibacterial molded article is particularly useful as a component of in-vivo indwelling devices such as pacemakers. While bacteria do not normally enter or leave the body, they can sometimes enter the body via surgical instruments and the like. In response to this, the use of the antibacterial molded article as a part of an in-vivo indwelling device can inhibit bacterial growth in the body.

[0044] Examples of the home appliances include rice cookers, microwave ovens, refrigerators, irons, hair dryers, and filter parts of air conditioners and air purifiers.

[0045] Examples of the above-mentioned building equipment include toilets and toilet seats, vanities, water and sewage pipes, foot mats, interior materials, bathtub handrails and exterior parts, the bathtub itself, bathtub covers, door handles, handrails, switches, and other items that people touch on a daily basis.

[0046] The antibacterial molded article is also useful for the interior of spacesuits and spacecraft, as well as electronic devices and various devices brought into spacecraft. In outer space, the only bacteria present are those brought in from objects brought in from Earth or through the human body. However, in outer space, human immunity is weakened, so bacterial proliferation poses a major risk. Therefore, by using the antibacterial molded article in various components, bacterial proliferation can be effectively suppressed.

[0047] Examples of electronic devices and their peripherals include laptops, smartphones, tablets, digital cameras, medical electronic devices, POS systems, printers, televisions, mice and keyboards, etc.

[0048] Examples of the above automotive parts include steering wheels, seats, shift levers, and various types of piping.

[0049] Examples of the agricultural products include stretch films for agricultural greenhouses.

[0050] Examples of the body accessories include clothing including outerwear and underwear, hats, shoes, gloves, diapers, napkins and storage bags thereof.

[0051] Among the above, food packaging materials in which at least a part of the surface that comes into contact with food is the antibacterial region, or devices to be placed in a living body such as pacemakers are preferred.

[0052] [Method for manufacturing antibacterial molded body] The method for forming the antibacterial molded article is not particularly limited, and may be appropriately selected depending on the material, application, shape, etc. of the antibacterial molded article.

[0053] For example, when forming the antibacterial region on the surface of an antibacterial molded article, recesses having the desired depth and opening area can be formed at the desired intervals by laser processing or the like. For example, in the shape shown in Figure 2, recesses can be formed by scanning the laser vertically and then horizontally. The area processed by both vertical and horizontal scanning can be designated the second antibacterial surface with the lowest height, the area processed by only vertical or horizontal scanning can be designated the intermediate antibacterial surface, and the area not irradiated with the laser can be designated the first antibacterial surface with the highest height. It is desirable to control the laser irradiation conditions so that the first, second, and intermediate antibacterial surfaces satisfy the above-mentioned conditions. Furthermore, by changing the laser scanning direction, antibacterial regions with shapes such as those shown in Figures 5 and 6 can also be formed.

[0054] Alternatively, the antibacterial region may be formed by molding a resin or metal using a mold having protrusions on its inner surface that will form the shape of the antibacterial region, or by additive shaping to form the antibacterial region. Alternatively, the antibacterial region may be formed on the surface of a molded article that has been molded to suit the intended use by nanoimprinting, etching, or the like.

[0055] The antibacterial region may be formed in a coating layer such as a plating layer or film formed on the surface of the molded body, or a coating having the antibacterial region may be formed by a printing method such as an inkjet method. [Example]

[0056] Specific examples of the present invention will be described below together with comparative examples, but the present invention is not limited to these.

[0057] 1. Preparation of antibacterial molded body [Example 1] The surface of a stainless steel (material) metal plate was irradiated with a laser, adjusting the irradiation conditions and number of irradiations to create a shape 10 μm wide and 2 μm deep, to form groove-like depressions in both the vertical and horizontal directions (the angle between the vertical and horizontal depressions was 90°). The distance between each depression was 1.5 μm. Figure 1 shows a micrograph of the metal plate surface after laser irradiation. Note that because the laser was more intense in the center and the number of irradiations required to form depressions of the above depth was small, the edges irradiated with the laser were not sufficiently processed, and the distance between the depressions was wider than 1.5 μm. The resulting processed area is designated antibacterial region 1.

[0058] [Example 2] The surface of the metal plate was irradiated with a laser under the same conditions as in Example 1, except that the interval between each recess was set to 5.0 μm, to form groove-like recesses vertically and horizontally. The resulting processed area is referred to as antibacterial region 2.

[0059] [Comparative Example 1] The surface of the metal plate was irradiated with a laser under the same conditions as in Example 1, except that the width of each recess was set to 20 μm, to form groove-like recesses vertically and horizontally. The obtained processed areas were designated as antibacterial regions 3.

[0060] 2. Surface profile measurement Antibacterial regions 1 to 3 were observed with a laser microscope, and height distribution spectra were obtained, showing the distribution (frequency) of measurement points relative to height. Three peaks were confirmed in the height distribution spectra obtained from each antibacterial region (designated Peak 1, Peak 2, and Peak 3, in descending order). The height distribution spectrum was assumed to be a set of normal distributions corresponding to these three peaks, and the intersections of adjacent normal distributions were defined as thresholds (designated Threshold 1 and Threshold 2, in descending order). The total area of ​​regions higher than Threshold 1 was calculated, and the average surface area of ​​the second antibacterial surface with the highest height was calculated by dividing this total area by the number of regions corresponding to Peak 1. Next, the total area of ​​regions higher than Threshold 2 was calculated, and the total area of ​​regions higher than Threshold 1 was subtracted from the total area, and the resulting area was divided by the number of regions corresponding to Peak 2 to calculate the average surface area of ​​the intermediate antibacterial surface. Finally, the average surface area of ​​the first antibacterial surface with the lowest height was calculated by dividing the total area of ​​the areas higher than threshold 2 from the surface area of ​​the entire antibacterial area and dividing the resulting area by the number of areas corresponding to peak 3.

[0061] Furthermore, in the height distribution spectrum, the difference in height between Peak 1 and Peak 2 in Figure 7 was calculated and used as the difference between the mode of the height distribution of the first antibacterial surface and the mode of the height distribution of the intermediate antibacterial surface. Also, the difference in height between Peak 2 and Peak 3 was calculated and used as the difference between the mode of the height distribution of the intermediate antibacterial surface and the mode of the height distribution of the first antibacterial surface.

[0062] These measurements and calculations were performed using a laser microscope, VK-X250, manufactured by Keyence Corporation, and the multi-file analysis application VK-HIXM as analysis software.

[0063] Furthermore, ten profile lines were arbitrarily set in the antibacterial region observed by the laser microscope so as to include a certain first antibacterial surface and the first antibacterial surface closest to it, and in the cross-sectional curve obtained from each profile line, the distance between a certain first antibacterial surface and the first antibacterial surface closest to it was calculated from the distance between these antibacterial surfaces at the height of the threshold value 1. The distance between one antibacterial surface was calculated for each profile line, and the arithmetic mean value of these was used as the average value of the distance between a certain first antibacterial surface and the first antibacterial surface closest to it.

[0064] Ten profile lines were arbitrarily set in the antibacterial region observed by the laser microscope so as to include a certain second antibacterial surface and the second antibacterial surface closest to it, and in the cross-sectional curve obtained from each profile line, the distance between a certain second antibacterial surface and the second antibacterial surface closest to it was calculated from the distance between these antibacterial surfaces at the height of the threshold value 2. The distance between one antibacterial surface was calculated for each profile line, and the arithmetic mean value of these was used as the average value of the distance between a certain second antibacterial surface and the second antibacterial surface closest to it.

[0065] Ten profile lines were arbitrarily set in the antibacterial region observed by the laser microscope so as to include a certain intermediate antibacterial surface and the nearest intermediate antibacterial surface, and in the cross-sectional curve obtained from each profile line, the distance between a certain intermediate antibacterial surface and the nearest intermediate antibacterial surface was calculated from the distance between these antibacterial surfaces at the height of the threshold value 1 or threshold value 2. The distance between one antibacterial surface was calculated for each profile line, and the arithmetic mean of these values ​​was used as the average distance between a certain intermediate antibacterial surface and the nearest intermediate antibacterial surface.

[0066] 3. Evaluation of antibacterial activity The antibacterial activity of each antibacterial region against E. coli was evaluated according to the method described in JIS Z 2801 (2012). Specifically, the following E. coli strains were inoculated onto each antibacterial region and cultured for 24 hours under the following conditions. As a comparison sample, the surface of a sample without a surface treatment was also inoculated with the following E. coli strains and cultured for 24 hours under the following conditions.

[0067] (bacterial species) Escherichia coli, NBRC No. 3972 (Culture conditions) Temperature: 35℃±1℃ (Measurement of viable bacteria count) Media used: Standard agar medium

[0068] Immediately after inoculation and 24 hours after inoculation, the viable cell count was measured according to the method described in JIS Z 2801 (2012), and the Δlog cell count (logarithm of the viable cell count in the comparison sample after 24 hours - logarithm of the viable cell count in the evaluation sample after 24 hours) was calculated.

[0069] The shape of each antibacterial region, as well as the Δlog number of bacteria (antibacterial activity) and antibacterial properties are shown in Table 1. Those that show high antibacterial properties (Δlog number of bacteria of 2.0 or more) are marked with "Good", and those that show insufficient antibacterial properties (Δlog number of bacteria of less than 2.0) are marked with "Poor".

[0070] [Table 1]

[0071] As shown in Table 1, the average surface area was 35.0 μm 2 95.0μm or more 2 Good antibacterial activity was obtained in antibacterial region 1 and antibacterial region 2 forming the first antibacterial surface, intermediate antibacterial surface, and second antibacterial surface, where the difference in the mode of the height distribution was 1.70 μm or more and 10.0 μm or less.

[0072] On the other hand, in antibacterial region 3, where the average surface area of ​​the first antibacterial surface was large, the antibacterial activity was not so high. This is thought to be because bacteria were more likely to be scattered on the first antibacterial surface, making it difficult for the concentration of the attractant to increase, and therefore the bacteria were more likely to multiply. [Industrial Applicability]

[0073] The antibacterial molded article of the present invention provides high antibacterial properties. It also does not require the use of antibacterial agents or silver nanoparticles, and is therefore excellent in safety. Furthermore, it does not require the provision of protrusions on the surface, and the antibacterial region is less likely to wear out. Therefore, since high antibacterial properties are maintained for a long period of time, the article can be used in a variety of applications, such as food packaging materials and in-vivo indwelling devices. [Explanation of symbols]

[0074] 100, 500, 600 antibacterial area 110, 510, 610 1st antibacterial surface 120, 520, 620 Second antibacterial surface 130, 530, 630 Intermediate antibacterial surface 400 Antibacterial area 410 1st surface 420, 420a, 420b 2nd surface 710, 720, 730 peak 740, 750 threshold

Claims

1. An antibacterial molded body having an antibacterial region formed by combining a plurality of independent antibacterial surfaces having different heights, the plurality of antimicrobial surfaces include a first antimicrobial surface having the highest height, a second antimicrobial surface having the lowest height, and an intermediate antimicrobial surface having a height intermediate between the height of the first antimicrobial surface and the height of the second antimicrobial surface; The plurality of antibacterial surfaces have an average surface area of ​​the first antibacterial surface, an average surface area of ​​the second antibacterial surface, and an average surface area of ​​the intermediate antibacterial surface, all of which are 35.0 μm ２ 95.0 μm or more ２ or less, and the difference in the mode of the height distribution between the first antibacterial surface and the intermediate antibacterial surface and the difference in the mode of the height distribution between the intermediate antibacterial surface and the second antibacterial surface are both 1.70 μm or more and 10.0 μm or less, when the antibacterial molded article is viewed from above, the first antibacterial surface is in contact with its outer periphery only by the second antibacterial surface and the intermediate antibacterial surface, and the second antibacterial surface is in contact with its outer periphery only by the first antibacterial surface and the intermediate antibacterial surface, Antibacterial molded body.

2. The antibacterial molded article according to claim 1 , wherein the plurality of antibacterial surfaces are regularly arranged.

3. The antibacterial molded article according to claim 1 or 2, wherein the plurality of antibacterial surfaces are arranged in a lattice pattern.

4. The antibacterial molded article according to any one of claims 1 to 3, wherein the first antibacterial surface is positioned such that the distance between the first antibacterial surface and the nearest other first antibacterial surface is 0.5 μm or more and 95 μm or less.

5. The antibacterial molded article according to any one of claims 1 to 4, wherein the second antibacterial surface is positioned such that the distance between the second antibacterial surface and the nearest other second antibacterial surface is 0.5 μm or more and 95 μm or less.

6. The antibacterial molded article according to any one of claims 1 to 5, which is a food packaging material.

7. The antibacterial molded article according to any one of claims 1 to 6, which is an in-vivo indwelling device.

8. A method for producing an antibacterial molded article, comprising forming an antibacterial region possessed by the antibacterial molded article according to any one of claims 1 to 7 on the surface of the molded article, or molding a molded article having an antibacterial region possessed by the antibacterial molded article according to any one of claims 1 to 7 on its surface.

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