Antibacterial sheet and method for producing the same

Abstract

The present invention provides an antibacterial sheet which includes a resin film and a copper film formed on at least one surface of the resin film. The copper film contains copper oxide and non-copper oxide. Moreover, the content of non-copper oxide in the copper film is less than the content of copper forming copper oxide and is 0.04 g / m<supgt;2< / supgt> or less.

Description

Technical Field

[0001] The invention relates to an antibacterial sheet and a method for making the same. Background Art

[0002] In recent years, the use of electronic devices such as personal computers has been promoted in medical facilities and food processing facilities. In medical facilities, it is required to suppress the growth of harmful microorganisms such as pathogens in the room and keep the room clean. At present, in such facilities, various methods such as cleaning by wiping with water or sterilization using chemicals are used to maintain the cleanliness of the room. In order to maintain the cleanliness of the room by cleaning or sterilization, it is necessary to clean or sterilize regularly.

[0003] However, the interfaces of electronic devices such as keyboards, operation panels, and touch panels are easily damaged because they are frequently touched by many people. In order to keep these parts clean, it is ideal to clean or sterilize them every time they are used, but cleaning them every time they are used is very troublesome. Therefore, it is required to reduce the frequency of cleaning or sterilization.

[0004] In response to this problem, a method of reducing the frequency of cleaning or sterilization by covering the interface with a sheet or film having an antibacterial effect, that is, an effect of inhibiting the growth of bacteria, has attracted much attention. For example, Patent Document 1 describes an antibacterial film, which has at least one layer of antibacterial metal film formed on at least one surface of a flexible polymer film substrate, and the metal film is composed of a vapor-deposited film formed by a vacuum vapor deposition method by heating and melting a metal evaporation source.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2010-247450 Summary of the invention

[0008] Problems to be solved by the invention

[0009] When the antibacterial film is used for display objects such as interfaces or printed materials, a transmittance (visible light transmittance) that can easily distinguish the display content is required. However, since the required transmittance varies depending on the display method or usage environment of the display object, it is expected that the transmittance of the antibacterial film can be easily adjusted. However, in the structure disclosed in Patent Document 1, the antibacterial film cannot easily adjust the transmittance while maintaining the antibacterial effect, and there is room for improvement.

[0010] The present invention has been made in view of this background, and an object of the present invention is to provide an antibacterial sheet capable of easily adjusting light transmittance.

[0011] Technical solutions to solve problems

[0012] One aspect of the present invention is an antibacterial sheet comprising: a resin film;

[0013] a copper film formed on at least one side of the resin film and containing oxidized copper and non-oxidized copper,

[0014] The content of the non-oxidized copper in the copper film was less than the content of the copper forming the oxidized copper, and was 0.04 g / m 2 the following.

[0015] Effects of the Invention

[0016] According to the antibacterial sheet, the content of non-oxidized copper in the copper film is 0.04 g / m 2 Within this range, there is a correlation between the content of non-oxidized copper in the copper film and the light transmittance of the antibacterial sheet, and in the region where the content of non-oxidized copper is small, there is a tendency that the light transmittance changes greatly with respect to the change of the content of non-oxidized copper. Therefore, by adjusting the content of non-oxidized copper within the above range, when the antibacterial sheet is used for a display, the light transmittance can be easily adjusted while maintaining a light transmittance that allows easy identification of the displayed content.

[0017] Furthermore, since the copper film is composed of copper oxide and non-copper oxide, the antibacterial sheet exhibits copper or brass color. 2 The intensity of the copper color tone can be adjusted by adjusting the non-oxidized copper contained in the copper film within the following range. For example, by setting the antibacterial sheet to a moderately copper color, it is easy to identify that it is a sheet with antibacterial effect, so the part where the antibacterial sheet is provided can also obtain a sense of security that the growth of bacteria is suppressed.

[0018] As described above, according to the present invention, an antibacterial sheet capable of easily adjusting light transmittance can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a diagram showing the analysis results of the O1s spectrum by XPS of the Example.

[0020] Figure 2 It is a diagram showing the analysis results of the Cu 2p spectrum by XPS in Examples.

[0021] Figure 3 It is a diagram showing the analysis results of the Cu LMM spectrum based on XPS of the Example.

[0022] Figure 4 This is a conceptual diagram showing the existence ratio of Cu and Cu2O based on the chemical bonding state of the embodiment.

[0023] Figure 5This is a graph showing the relationship between the amount of non-oxidized copper and the amount of light transmittance reduction in Examples.

[0024] Figure 6 (a) is a photograph in lieu of a drawing showing a state where a test material B4 and a printed matter are overlapped, and (b) is a photograph in lieu of a drawing showing a state where a test material A6 and a printed matter are overlapped. DETAILED DESCRIPTION

[0025] The copper film is preferably composed of a sputtered film containing the copper oxide and the non-oxidized copper. In this case, compared with the case where the copper film is composed of a vapor-deposited film, since it is densely formed, the film thickness can be reduced without reducing the copper content. Furthermore, the thin film composed of copper oxide has high transmittance because it transmits visible light, especially long-wavelength light. As a result, the light transmittance can be improved while maintaining the antibacterial effect. In addition, a copper film containing a desired amount of non-oxidized copper can be easily formed.

[0026] The total content of copper forming the copper oxide and the content of the non-oxidized copper is preferably 0.04 g / m 2 In this case, since the copper film formed on the resin film achieves a sufficient antibacterial effect, the antibacterial effect of the antibacterial sheet can be ensured.

[0027] In the antibacterial sheet, a resin film transparent to visible light can be used as the resin film. The resin film preferably contains one or more resins selected from polyester, polyolefin, polycarbonate, polyurethane, polyvinyl chloride and silicone. These resins have a high refractive index, and the copper film containing copper oxide also has a high refractive index. Therefore, by using a film containing these resins as the resin film, the interface reflectivity of the copper film containing copper oxide can be reduced, and the transmittance of visible light of the antibacterial sheet can be further improved. In addition, because these resins have high heat resistance, the degradation of the resin film during sputtering can be suppressed during the manufacture of the antibacterial sheet.

[0028] Examples of polyesters include polyethylene terephthalate, polymethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate. Examples of polyolefins include homopolymers of olefins such as polyethylene and polypropylene, and copolymers containing olefins such as ethylene-propylene copolymers.

[0029] The thickness of the resin film can be set to 5 to 250 μm, for example. If the thickness of the resin film is less than 5 μm, handling of the resin film during the manufacturing process tends to become difficult. On the other hand, if the thickness of the resin film exceeds 250 μm, the transmittance of visible light may decrease.

[0030] The antibacterial sheet may also have an anchor coating (AC) layer between the resin film and the copper film. In this case, the adhesion between the resin film and the copper film can be further improved, and the peeling of the copper film from the resin film can be suppressed for a longer period of time. As a result, the antibacterial effect of the antibacterial sheet can be maintained for a longer period of time.

[0031] For example, a resin coating agent having high adhesion to both the resin film and the copper oxide can be used as the anchor coating. Examples of the resin coating agent include resins such as polyamide resins, polyolefin resins, epoxy resins, polyester resins, polyurethane resins, acrylic resins, and nitrocellulose resins.

[0032] In addition, an adhesive layer for pasting the antibacterial sheet to the object to be protected can also be provided on the back side of the resin film in the antibacterial sheet, that is, on the side without the copper film. The material of the adhesive layer is not particularly limited as long as it is transparent. For example, as the adhesive layer, acrylic adhesives, rubber adhesives, polyurethane adhesives, silicone adhesives, etc. can be used. In addition, when the adhesive layer is provided, a protective adhesive layer and a diaphragm that can be easily peeled off when the antibacterial sheet is pasted to the object can also be stacked on the adhesive layer. In this case, the handling of the antibacterial sheet with an adhesive layer becomes easy, and the convenience of use is improved. As the diaphragm, as long as it is a material that can be easily peeled off from the adhesive layer, for example, a diaphragm with a peeling layer consisting of a silicone peeling agent, etc., can be used on a substrate consisting of a polyester resin or a polyolefin resin, etc.

[0033] As a method for manufacturing the antibacterial sheet, for example, the following method can be used: the copper film is formed on the resin film by sputtering while controlling the amount of oxygen introduced in a mixed gas atmosphere containing an inert gas and oxygen. By this manufacturing method, a copper film consisting of a sputtered film containing copper oxide and non-oxide copper can be formed on the resin film. Furthermore, according to the amount of oxygen introduced in the mixed gas, the ratio of copper oxide to non-oxide copper in the copper film is adjusted, and the content of non-oxide copper is set to 0.04 g / m 2 the following.

[0034] In the manufacturing method, the resin film may be pre-treated as needed after the resin film is prepared and before the sputtering. As the pre-treatment, for example, a treatment for normalizing the surface of the resin film may be performed. Specifically, surface treatments such as corona discharge treatment, plasma treatment, and glow discharge treatment may be used.

[0035] Example

[0036] use Figure 1 to Figure 6The specific aspects of the antibacterial sheet and the method for producing the same are not limited to the following aspects, and the structure can be appropriately changed within the scope of not impairing the gist of the present invention.

[0037] The antibacterial sheet of this example comprises a resin film and a copper film formed on at least one side of the resin film. The copper film contains copper oxide and non-oxide copper. Moreover, the content of non-oxide copper in the copper film is less than the content of copper forming copper oxide, which is 0.04 g / m 2 Below, can also be 0.03g / m 2 Below, preferably 0.02g / m 2 the following.

[0038] It is not clear how the copper and copper oxide particles in the copper film exist, but it is presumed that oxidized copper particles, partially oxidized copper particles, and unoxidized copper particles exist in a mixture. In addition, the copper oxide in the copper film does not contain substances caused by natural oxidation or unavoidable impurities. In addition, the copper particles may be composed of pure copper or copper alloys. In the case where the copper particles are composed of copper alloys, from the viewpoint of fully exerting the antibacterial effect brought by copper, the copper content in the copper alloy is preferably 60% by mass or more.

[0039] The ratio of the content of copper forming copper oxide to the amount of Cu in the copper film (the total of the content of copper forming copper oxide and the content of non-oxidized copper) is 40% or more, for example, 85% or more, and preferably 90% or more.

[0040] The antibacterial sheet of this example is described in detail below. In addition, test materials A2 to A7, A12 to A18 shown in Table 1 below were prepared as test materials for the antibacterial sheet of this example. In addition, test materials A1, A8 to A11, B1 to B8 shown in Table 1 below were prepared as sheets of comparative examples.

[0041] Each test material can be produced by the following method.

[0042] First, a resin film was prepared. As shown in the "Base Material" column of Table 1 below, a transparent film with a thickness of 50 μm containing polyethylene terephthalate was prepared in test materials A1 to A10 and B1 to B8, a transparent film with a thickness of 50 μm containing polyurethane was prepared in test materials A11 to A17, and a transparent film with a thickness of 25 μm containing polyethylene was prepared in test material A18.

[0043] Moreover, in test materials A2 to A10, A12 to A18, and B1 to B8, a copper film is formed on one side of the resin film. In test materials A2 to A10 and A12 to A18, a copper film consisting of a sputtered film containing copper oxide and non-copper oxide is formed by sputtering. As a sputtering gas used for sputtering, a mixed gas in which oxygen (O2) is added in a range of 10 to 50% to pure argon (Ar purity: 99.999%) can be used. Sputtering is performed by magnetron sputtering with the vacuum degree set to 0.12 Pa. In addition, as a target material in sputtering, oxygen-free copper with a purity of 99.9% by mass or more can be used. In addition, test materials A1 and A11 are not sputtered, and no copper film is formed on the resin film.

[0044] The above-mentioned sputtering can be performed, for example, as follows. First, a resin film is placed on a cooling roller in a sputtering device. Then, the pressure in the sputtering device is reduced by a vacuum pump, and Ar gas or a mixed gas of Ar and O2 is introduced. Then, sputtering is performed while the resin film is cooled by the cooling roller. In this way, by performing sputtering while cooling the resin film, it is possible to suppress the thermal shrinkage, wrinkles, deformation, etc. of the resin film.

[0045] The oxygen introduction amount in the above-mentioned sputtering device is set to four levels of "high", "medium", "low" and "none" as shown in the "oxygen introduction amount" column of Table 1 below. In addition, by controlling the oxygen introduction amount within the range shown in Table 1 and appropriately changing the sputtering speed and film formation time to perform sputtering, the antibacterial sheets (test materials A1 to A18) shown in Table 1 were obtained. The setting value of the film thickness of the copper film during sputtering is recorded in the "target film thickness" column of Table 1.

[0046] [Table 1]

[0047]

[0048] In the test materials B1 to B8 as comparative examples, a copper film was formed on a resin film by vacuum deposition, and oxygen-free copper having a purity of 99.9 mass % or more was used as a deposition source.

[0049] The amount of oxidized copper and the amount of non-oxidized copper in each test material were measured as follows.

[0050] First, the amount of Cu (the total amount of copper that forms copper oxide and non-oxidized copper) in the copper film of each test material was measured by atomic absorption spectrometry. In this atomic absorption analysis, a polarized Zeeman atomic absorption spectrophotometer (manufactured by Hitachi High-Technologies Corporation, ZA3000) was used to steadily heat each test material formed with a copper film in (1+1) hydrochloric acid to melt Cu, and the mass of Cu, i.e., the amount of Cu, was measured by an atomic absorption spectrometer. The measurement results are recorded in the "Cu amount" column of Table 1. In addition, an X-ray fluorescence analyzer (manufactured by Rigaku Corporation, ZSX PrimusIV) was used to measure the fluorescence X-ray intensity of the Cu-Kα line on the surface of each test material formed with a copper film, and the Cu film thickness of each test material was measured based on a calibration curve of the fluorescence X-ray intensity of a known Cu film thickness, and the measurement results are recorded in the "Cu film thickness (XRF)" column of the following Table 2.

[0051] The abundance ratio of copper oxide and copper non-oxide in the film of each of the test materials A2, A4 to A6, A8 to A10, and B3 was measured by X-ray photoelectron spectroscopy (XPS). The apparatus and analysis conditions used for XPS are as follows.

[0052] (XPS apparatus and XPS analysis conditions)

[0053] XPS equipment: PHI5000 VersaprobeIII manufactured by ULVAC PHI Co., Ltd.

[0054] X-ray source: Al-Kα (monochromatization)

[0055] Output: 25W, 15kV

[0056] Spot diameter: 100μm

[0057] Take-out angle: 45 degrees

[0058] Pass Energy: 55eV

[0059] Time step: 20ms

[0060] Sweep times: five times

[0061] In XPS, first, in the copper films of test materials A2, A4-A6, A8-A10 and B3, the surface organic film of several nm was removed by Ar sputtering. Then, the O1s spectrum, Cu 2p spectrum and Cu LMM spectrum were measured under the above conditions. Figure 1 to Figure 3 The measurement results of test materials A9, A10, A5 and B3 are shown in FIG.

[0062] according to Figure 1The results of O1s spectrum measurement shown above show that in test material B3, in which the copper film was formed by oxygen-free evaporation, the amount of oxygen in the copper film was very small and Cu was 0 valent. In test materials A9, A10, and A5, it was confirmed that the amount of oxygen in the copper film increased as the amount of oxygen introduced increased.

[0063] according to Figure 2 The results of the measurement of the Cu 2p spectrum shown in FIG. 1 show that in any of the test materials, the main peak is Cu or Cu2O, and the proportion of the satellite peaks derived from the Cu2 valence is very small. Figure 3 The measurement results of the Cu LMM spectrum shown in FIG. 1 show that in the test material A5 with a large amount of oxygen introduction, the peak is converted to Cu 1 valence, while in the test material A10 with a medium amount of oxygen introduction and the test material A9 with a small amount of oxygen introduction, the peak becomes a mixture of Cu and Cu 1 valence. Furthermore, in the test materials A9, A10, A5 and B3, the peaks of Cu 1 valence and Cu 1 valence are mixed. Figure 2 The measurement results of the Cu2p spectrum shown are as follows: the peak of CuO and the peaks of Cu and Cu2O are separated, and the atomic weight ratio of CuO to Cu and Cu2O is calculated based on the areas of the two peaks.

[0064] like Figure 2 , Figure 3 As shown in the figure, since it is difficult to separate the peaks of Cu and Cu2O into waveforms, it is considered that O other than O contained in CuO is combined with Cu, and the atomic weight ratio of Cu and Cu2O is calculated based on the semi-quantitative value. Figure 4 The calculation results are shown in . In addition, the atomic weight ratios of test materials A2, A4, A6 and A8 were calculated in the same manner and are shown in the above column of Table 2 below.

[0065] [Table 2]

[0066]

[0067] According to the XPS analysis results shown in Table 2, the comparison test materials A2 to A6 all have a "large" oxygen introduction amount and are of the same degree, and the ratio of the non-oxidized copper amount in the copper film is the same regardless of the film thickness. On the other hand, the comparison test materials A5, A8 to A10 have a copper film thickness of the same degree, and the ratio of the non-oxidized copper amount in the copper film increases as the oxygen introduction amount increases. Therefore, the ratio of the non-oxidized copper amount shows a tendency to be dependent on the oxygen introduction amount when the copper film is formed, rather than on the film thickness.

[0068] Furthermore, based on the above calculation results, in the test materials A2, A4 to A6, A8 to A10 and B3, the atomic weight ratio of copper oxide (CuO + Cu2O) and non-oxidized copper (Cu) constituting the copper film was calculated, and the ratio of the copper oxide (CuO + Cu2O), i.e., (CuO + Cu2O) / (CuO + Cu2O + Cu), was recorded in the "CuO + Cu2O ratio" column of Table 1. Furthermore, based on the mass of Cu measured by the above-mentioned atomic absorption spectrometry, i.e., the amount of Cu, and the above-mentioned atomic weight ratio of copper oxide and non-oxidized copper, the mass of the non-oxidized copper in the film was calculated, and the calculation results were recorded in the "non-oxidized copper amount" column of the above-mentioned Table 1.

[0069] As described in the "CuO+Cu2O ratio" column of Table 1 above, in the test materials A2 and A4 to A6, the amount of copper that forms copper oxide relative to the amount of Cu (the total amount of copper that forms copper oxide and non-oxidized copper) is 90% or more. Furthermore, as described in the "Non-oxidized copper amount" column of Table 1 above, in the test materials A2 and A4 to A6, the amount of non-oxidized copper is 0.04 g / m 2 In the above test material, the amount of Cu in the copper film is 0.04 g / m 2 In addition, the numerical values ​​recorded in the "Non-oxidized copper amount" column of the test materials A3, A7, A12 to A18 are not the estimated values ​​of the non-oxidized copper amount calculated based on the "CuO + Cu2O ratio" in the test material A5 shown in Table 1, but the actual measured values. Similarly, the numerical values ​​recorded in the "Non-oxidized copper amount" column of the test materials B1, B2, B4, and B5 are not the estimated values ​​of the non-oxidized copper amount calculated based on the "CuO + Cu2O ratio" in the test material B3 shown in Table 1, but the actual measured values.

[0070] Next, the light transmittance, insulation properties, and antibacterial effect of each test material were evaluated as follows.

[0071] (Evaluation of light transmittance)

[0072] The total light transmittance (light source: D65) of each test material was measured using a haze meter ("NDH-2000" manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7361-1:1997, and recorded in the "Light Transmittance" column of Table 1. In addition, as the amount of light transmittance reduction, the difference in light transmittance relative to the test material A1 without a copper film was calculated for test materials A2 to A10 and test materials B1 to B8, and the difference in light transmittance relative to the test material A11 without a copper film was calculated for test materials A12 to A17, and recorded in the "Light Transmittance Reduction" column of the above Table 1. Figure 5 The relationship between the amount of non-oxidized copper and the amount of light transmittance reduction is shown in FIG.

[0073] like Figure 5As shown, the amount of non-oxidized copper indicated by arrow A is 0.04 g / m 2 In the following range, the correlation between the amount of non-oxidized copper and the amount of light transmittance reduction is significant. In the lower region of light transmittance reduction of about 10 to 60%, that is, the region of high light transmittance, the correlation is significant. In this region, the change in the amount of non-oxidized copper is sensitively reflected in the change in the amount of light transmittance reduction, and it becomes a relationship that if the amount of non-oxidized copper increases, the amount of light transmittance reduction increases accordingly (that is, the light transmittance decreases). On the other hand, when the amount of non-oxidized copper is greater than 0.04 g / m 2 Within the range of , the change in the amount of non-oxidized copper is difficult to reflect the change in the amount of transmittance reduction.

[0074] As shown in Table 1, in terms of light transmittance, when comparing the test material A7 with the test materials B5 (no oxygen introduction) and B8 (large oxygen introduction) having the same target film thickness, the test material A7 having a copper film composed of a sputtered film has a higher light transmittance than the test materials B5 and B8 having a copper film composed of a vapor-deposited film. Similarly, in the test materials A3 to A6 and the test materials B1 to B4, if the target film thickness is the same, the test materials A3 to A6 having a copper film composed of a sputtered film have a higher light transmittance.

[0075] In this example, the visibility of the printed content when the printed material printed in monochrome by a laser printer and the test material are superimposed is also evaluated. Figure 6 (a) shows an example of a state where the test material B4 and the printed material P are overlapped. Figure 6 (b) shows an example of a state where the test material A4 is overlapped with the printed matter P. In the "Visibility" column of Table 1, when each test material is overlapped with the printed matter P, the case where the printed content can be recognized without light passing through from the back is recorded as "A". In addition, the case where the printed content can be recognized if light passes through from the back is recorded as "B". On the other hand, the case where the printed content cannot be recognized even if light passes through from the back is recorded as "C".

[0076] As shown in Table 1, in the test materials A9, B5 to B8, the light transmittance is less than 20%, and the printed content cannot be recognized even if light is transmitted from the back, and the visibility of the printed matter P is poor. On the other hand, in A1 to A7, A11 to A18, and B1 to B3, the light transmittance exceeds 30%. Figure 6 As shown in (a), the printed content can be identified without light passing through from the back, and the visibility is good. In addition, in the test materials A8, A10, and B4, the light transmittance is more than 20% and less than 30%, and the printed content can be identified if light passes through from the back. Figure 6 (a) and Figure 6As shown in (b), test materials A2 to A7, A10, and A12 to A18 all have a moderate copper or brass color. Since they are all identified in a moderate copper color, it is easy to identify the area where the test materials overlap. Figure 5 As shown by arrow A, at 0.04g / m 2 By adjusting the non-oxidized copper within the following range, the intensity of the copper color tone can be adjusted.

[0077] (Evaluation of insulation properties)

[0078] The surface resistivity of the copper film surface of each test material was measured using a low resistivity meter ("Loresta GP" manufactured by Mitsubishi Analytech Co., Ltd.) by a method based on JIS K7194: 1995. The measurement results are described in the "Surface Resistivity" column of Table 1. In addition, as an evaluation of the electrostatic capacitive touch panel, each test material was placed on an electrostatic capacitive touch panel monitor to evaluate whether the touch panel reacts normally. In the evaluation method, if the touch panel reacts normally, it is set as good (0), and if the touch panel reacts abnormally or reacts at a location different from the touched location, it is set as bad (×), and the evaluation results are recorded in the "Electrostatic Capacitive Touch Panel Property" column of Table 1.

[0079] As shown in Table 1, the surface resistivity of the test materials A1 to A7, A11 to A18 is OL (1×10 6 Ω / □ or more), cannot be measured, very high. Moreover, in the above-mentioned test materials, the electrostatic capacitive touch panel properties are all good. In addition, in test material A10, the surface resistivity is 988 (Ω / □), which is high enough, and the electrostatic capacitive touch panel properties are good. On the other hand, in test materials A8 and A9, the surface resistivity is low, and the electrostatic capacitive touch panel properties are poor. In addition, test materials B1 to B8 all have low surface resistivity and poor electrostatic capacitive touch panel properties. It is inferred that if the surface resistivity is a high value above 950 (Ω / □), the electrostatic capacitive touch panel properties are good.

[0080] (Evaluation of antibacterial effect)

[0081] The antibacterial effect was evaluated as follows. First, antibacterial processed test pieces in a square shape with a side of 40 mm were taken from each test material A12 to A16 and B1 to B5. In addition, unprocessed test pieces in a square shape with a side of 40 mm were taken from the resin film before the copper film was formed. Using these test pieces, an antibacterial test was performed according to the method specified in JIS Z2801:2010. The bacteria used in the test were Staphylococcus aureus and Escherichia coli, and the culture time was set to 24 hours.

[0082] Based on the number of viable bacteria in each test piece after 24 hours of culture, the antibacterial activity value indicating the magnitude of the antibacterial effect was calculated, and the calculation results were recorded in the "Antibacterial Activity Value" column of Table 1. Specifically, the antibacterial activity value R was calculated by the following formula. In addition, the symbol Ut in the following formula is the average value of the common logarithm of the number of viable bacteria in the unprocessed test piece after 24 hours of culture, and At is the average value of the common logarithm of the number of viable bacteria in the antibacterial processed test piece after 24 hours of culture.

[0083] R=Ut-At

[0084] In the evaluation of the antibacterial effect, for both Staphylococcus aureus and Escherichia coli, the case where the antibacterial activity value R is 2.0 or more is judged as qualified, and the case where at least one of them is less than 2.0 is judged as unqualified. As shown in Table 1, in test material B1, because the antibacterial activity value against Escherichia coli is less than 2.0, it is unqualified, but in other test materials A12 to A16 and B2 to B5, the antibacterial activity values ​​are all above 2.0, which are qualified. In addition, test materials A2 to A6 have a different structure of the resin film from test materials A12 to A16, but the structure of the copper film is the same, and the copper film contains 0.04g / m 2 Therefore, in the test materials A2 to A10, A17, and A18, it is estimated that the antimicrobial activity values ​​equivalent to those of the test materials A12 to A16 are obtained.

[0085] Hereinafter, the effects of the antibacterial sheet of this example will be described in detail.

[0086] In the antibacterial sheet of this example, as in the above-mentioned test materials A2 to A7 and A12 to A18, the copper film contains 0.04 g / m 2 The following non-oxidized copper. The content of non-oxidized copper is 0.04g / m 2 In the following range, there is a correlation between the content of non-oxide copper and the light transmittance of the antibacterial sheet, and in the region where the content of non-oxide copper is small, there is a tendency that the light transmittance changes greatly with respect to the change of the content of non-oxide copper. Therefore, by adjusting the content of non-oxide copper in the above range, when the antibacterial sheet is used for an interface, the light transmittance can be maintained at a level that allows the display content of the interface to be easily discerned, and the light transmittance can be easily adjusted.

[0087] In addition, the antibacterial sheet is composed of copper oxide and non-copper oxide, and has a copper or brass color. 2The intensity of the copper color tone can be adjusted by adjusting the non-oxidized copper contained in the copper film within the following range. For example, by setting the antibacterial sheet to a moderately copper color, it is easy to identify the sheet 1 having an antibacterial effect, so the portion provided with the antibacterial sheet can also obtain a sense of security that bacterial growth is suppressed.

[0088] In addition, since the antibacterial metal thin film in the existing antibacterial film is composed of highly conductive metals such as copper, silver or their alloys, it is difficult to use it in electrostatic capacitive touch panels commonly used as touch panels of smartphones, etc. or electrostatic capacitive touch sensors used for various operation panels. In contrast, in the antibacterial sheet of this example, as in the above-mentioned test materials A2 to A7 and A12 to A18, since the copper film attached to at least one side of the resin film shows an antibacterial effect and the copper oxide constituting the copper film has low conductivity, it can be used in electrostatic capacitive touch panels or touch sensors.

[0089] In addition, in this example, the copper film is composed of a sputtered film containing copper oxide and non-oxide copper. Therefore, compared with the case where the copper film is composed of a vapor-deposited film, since it is densely formed, the film thickness can be reduced without reducing the copper content. In addition, the film composed of copper oxide has high transmittance because it transmits visible light, especially long-wavelength light. As a result, the light transmittance can be increased while maintaining the antibacterial effect. In addition, a copper film containing a desired amount of non-oxide copper can be easily formed.

[0090] In this example, the total content of copper forming copper oxide and the content of non-oxidized copper is 0.04 g / m 2 As a result, since the copper film formed on the resin film achieves a sufficient antibacterial effect, the antibacterial effect in the antibacterial sheet can be ensured.

[0091] In addition, in this example, a resin film transparent to visible light is used as the resin film. The resin film preferably contains one or more resins selected from polyester, polyolefin, polycarbonate, polyurethane, polyvinyl chloride and silicone. In this example, the resin film is composed of polyethylene terephthalate contained in polyester. Because the resin film has a high refractive index, it can reduce the interface reflectivity of the copper film with a high refractive index, and further improve the visible light transmittance of the antibacterial sheet. In addition, because the resin has high heat resistance, it can suppress the degradation of the resin film during sputtering in the manufacturing process of the antibacterial sheet.

[0092] The thickness of the resin film can be set to 5 to 250 μm, for example, and is set to 50 μm or 25 μm in this example. This makes it easier to handle the resin film during the manufacturing process, and reduces the reduction in the transmittance of visible light.

[0093] In addition, the surface resistivity of the antibacterial sheet can be set to 950Ω / □ or more, for example, and in this example, it is set to 988Ω / □ or more. Therefore, because the surface resistance of the antibacterial sheet is high enough, when the electrostatic capacitive touch panel is covered by the antibacterial sheet, the touch panel can be normally operated through the antibacterial sheet, and when the touch sensor is covered by the antibacterial sheet, the touch sensor can be normally operated through the antibacterial sheet. Therefore, it becomes an antibacterial sheet suitable for covering an electrostatic capacitive touch panel or a touch sensor for use.

[0094] As described above, according to this example, an antibacterial sheet with easily adjustable light transmittance can be provided. The antibacterial sheet of this example can be used to cover the interface or printed matter of electronic devices such as keyboards, operation panels, and touch panels, or to cover indoor walls or furniture.

Claims

1. An antibacterial sheet, comprising: Resin film; a copper film formed on at least one side of the resin film and containing oxidized copper and non-oxidized copper, The content of the non-oxidized copper in the copper film was less than the content of the copper forming the oxidized copper, and was 0.04 g / m 2 the following, The total content of copper forming the copper oxide and the content of the non-oxidized copper is 0.04 g / m 2 above, The copper oxide is CuO and Cu2O, and the non-oxidized copper is Cu. The surface resistivity of the antibacterial sheet is greater than 950Ω / □.

2. The antibacterial sheet according to claim 1, wherein: The copper film is composed of a sputtered film containing the copper oxide and the non-oxide copper.

3. The antibacterial sheet according to claim 1 or 2, wherein: The resin film contains one or more resins selected from polyester, polyolefin, polycarbonate, polyurethane, polyvinyl chloride and silicone.

4. The antibacterial sheet according to claim 1 or 2, wherein: The resin film has a thickness of 5 to 250 μm.

5. A method for producing an antibacterial sheet, comprising producing the antibacterial sheet according to any one of claims 1 to 4, wherein: The copper film is formed on the resin film by performing sputtering in a mixed gas atmosphere containing an inert gas and oxygen while controlling the amount of oxygen introduced.

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