Antibacterial ceramic film and method for producing the same

Abstract

To provide an antibacterial ceramic film that exhibits antibacterial properties and superior durability, and to provide a method for producing the same.SOLUTION: An antibacterial ceramic film 1 is disposed on a surface of a substrate 2 and composed of cubic-phase TiON, with a plurality of columnar porous segments 10 that are erected in a thickness direction of the film. Each columnar porous segment 10 has a conical top portion 11, with a plurality of spiny portions 12 on a surface thereof. A method for producing the antibacterial ceramic film 1 includes forming a TiON film by growing a plurality of columnar porous segments by irradiating titanium, which is an evaporation source, with an electron beam from an electron gun under reduced pressure in a nitrogen gas atmosphere containing a trace amount of oxygen gas, at a temperature of 500°C or higher and lower than 700°C, and by depositing the evaporated titanium onto the surface of the substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an antibacterial ceramic film for use in antibacterial products such as bioimplants, and a method for producing the same. [Background technology]

[0002] Implants implanted in the body must satisfy biocompatibility and corrosion resistance. Titanium forms a strong passive film (Ti-O) and has excellent biocompatibility and corrosion resistance, making it an ideal base material for implants. For example, in dental implants, peri-implantitis, a condition similar to periodontal disease in natural teeth, is known to occur after treatment. Peri-implantitis is also caused by oral bacteria, which invade the gap between the gums and the implant and induce inflammation through the action of toxins produced by the bacteria. It is also known that bacteria can proliferate on the surface of implants other than dental implants, leading to postoperative infections. For this reason, various methods have been proposed to impart antibacterial properties to implants.

[0003] For example, Patent Document 1 describes a biological implant having a thermal spray coating formed by high-velocity flame spraying of a powder containing brookite-type titanium oxide as a main component on at least a portion of a substrate made of metal, etc. Patent Document 2 describes a biological implant having a calcium phosphate coating containing silver and having a crystallinity of more than 90% on the surface of the substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-65304 [Patent Document 2] Patent Publication No. 2021-40972 [Patent Document 3] JP 2019-72475 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the bioimplants described in Patent Documents 1 and 2, bacterial growth is suppressed by forming an antibacterial coating on the surface of the implant. In this method, it is desirable to improve not only the antibacterial properties of the coating but also its adhesion to the substrate and durability. On the other hand, as described in Patent Document 3, it has been reported that the microstructures of insect wings, such as those of cicadas, which are composed of numerous nanometer-order columnar protrusions, have bactericidal properties. If such microstructures could be realized on the surface of implants, revolutionary antibacterial properties without the use of drugs could be realized. However, nanometer-order minute protrusions are easily worn or chipped when subjected to external loads. Therefore, for example, when applied to dental implants, there is a concern that they may be easily worn away due to stress concentration associated with repeated occlusion, such as chewing.

[0006] The present disclosure has been made in view of the above circumstances, and aims to provide an antibacterial ceramic film that has antibacterial properties and excellent durability, as well as a method for producing the same. [Means for solving the problem]

[0007] (1) In order to solve the above problems, the antibacterial ceramic film of the present disclosure is an antibacterial ceramic film placed on the surface of a substrate, which is made of cubic TiON and has a plurality of columnar porous segments arranged in the thickness direction of the film, each of which has a conical top and a plurality of spiky portions on its surface.

[0008] The antibacterial ceramic film of the present disclosure (hereinafter, sometimes simply referred to as "ceramic film") is a titanium-based TiON film, and therefore has excellent biocompatibility. Furthermore, when the substrate is made of a titanium-based material, it also has high affinity with the substrate. The ceramic film of the present disclosure has multiple columnar segments extending in the thickness direction of the film. The segments are porous, with numerous nanometer-order voids inside. Because of the presence of minute gaps between adjacent segments, the rigidity in the direction intersecting the thickness direction of the film is lower than that of dense films with accumulated particles, etc. As a result, the ceramic film of the present disclosure has high deformation tolerance against external loads and is less susceptible to mechanical damage. Furthermore, each columnar porous segment has a conical top and multiple spiky portions on its surface. When bacteria attach to the spiky portions or other minute protrusions, the cell membrane is destroyed and the bacteria are killed. As a result, bacterial growth is suppressed. Thus, the ceramic film of the present disclosure exhibits excellent antibacterial activity. Therefore, when used on dental implants, it is effective in preventing peri-implantitis. Furthermore, because the thorns are formed on the surface of each individual columnar porous segment, they are resistant to wear even when subjected to repeated loads such as bites, making the thorns highly durable and maintaining their antibacterial properties.

[0009] (2) In the above configuration, the (111) plane of the TiON may be oriented in the extending direction of the surface of the substrate. TiON has a sodium chloride (rock salt) type crystal structure. The (111) plane of TiON is composed of atoms of the same type and has high surface energy. As will be described later, when the antibacterial ceramic film of the present disclosure is formed by electron beam physical vapor deposition, crystals can be grown preferentially in the (111) plane direction, which has high surface energy.

[0010] (3) In any of the above configurations, the nitrogen atom content in the TiON may be 15 atomic % or more and 30 atomic % or less. According to this configuration, by doping TiO with an appropriate amount of nitrogen atoms (N), covalent bonding can be strengthened and surface diffusion can be suppressed. This makes the tops of the columnar porous segments conical and facilitates the formation of multiple spiky portions on the surface.

[0011] (4) In any of the above configurations, the maximum width of the top of the columnar porous segment may be 100 nm or more and 500 nm or less. This configuration allows the columnar porous segment to have both durability against a compressive load in the membrane thickness direction and the formation of spiky portions on the surface.

[0012] (5) In any of the above configurations, the substrate may have a bonding layer containing TiO, and the antibacterial ceramic film may be disposed on the surface of the bonding layer. With this configuration, the ceramic film is disposed via the bonding layer, which improves adhesion between the substrate and the ceramic film and is effective in improving durability.

[0013] (6) In any of the above configurations, the antibacterial ceramic film may be used in a biological implant, which allows the ceramic film to fully exhibit its biocompatibility, antibacterial properties, and durability.

[0014] (7) In any of the above configurations, the substrate may be made of titanium or a titanium alloy, and the antibacterial ceramic film may be used for a dental implant. This configuration allows the ceramic film to fully exhibit its biocompatibility, antibacterial properties, and durability. Specifically, even when subjected to repeated loads such as chewing, the film is less likely to suffer mechanical damage, and the spines are less likely to wear. Therefore, the antibacterial properties are sustained, making it effective in preventing peri-implantitis.

[0015] (8) One embodiment of the method for producing an antibacterial ceramic film of the present disclosure is characterized by comprising a film-forming step of irradiating an electron beam from an electron gun onto a titanium evaporation source under reduced pressure in a nitrogen gas atmosphere containing a trace amount of oxygen gas at a temperature of 500°C or higher but lower than 700°C, and depositing the evaporated titanium on the surface of the substrate, thereby growing a plurality of the columnar porous segments and forming a film made of the TiON.

[0016] In the method for producing an antibacterial ceramic film of the present disclosure (hereinafter sometimes simply referred to as the "production method of the present disclosure"), a TiON film is formed by electron beam physical vapor deposition (EB-PVD). The EB-PVD method melts and vaporizes titanium, an evaporation source, by irradiating it with a high-power electron beam, enabling nanometer-order structural control, thereby enabling the ceramic film of the present disclosure to be produced with high precision and relatively quickly. In the production method of the present disclosure, a TiON film in which TiO is appropriately doped with N is formed by film formation in a nitrogen gas atmosphere containing a trace amount of oxygen gas. This strengthens covalent bonding and suppresses surface diffusion of film components. Furthermore, surface diffusion of film components can also be suppressed by film formation at a relatively low temperature below 700°C. As a result, flattening of the tops of the resulting columnar porous segments is suppressed, facilitating the formation of multiple spiky portions on the surface of the columnar porous segments.

[0017] (9) The film-forming step of the manufacturing method (8) may be configured to deposit the evaporated titanium on the surface of the substrate while rotating the substrate relative to the deposition source. The crystals that form the columnar porous segments grow in the direction of the deposition particles. In this configuration, the substrate is rotated relative to the deposition source, which changes the direction of the deposition particles incident on the substrate. For example, if the deposition particles are incident obliquely to the crystal growth direction, the deposition particles are blocked by already formed crystals, creating shadow areas where the deposition particles cannot reach. This shadowing effect can change the crystal growth direction or create voids between the crystals. As a result, a conical top and multiple spiky portions are likely to form on the columnar porous segments. [Effects of the Invention]

[0018] The antibacterial ceramic membrane of the present disclosure has excellent antibacterial properties, high tolerance for deformation under external loads, and excellent durability. Furthermore, the manufacturing method of the present disclosure enables the accurate production of the antibacterial ceramic membrane of the present disclosure having the desired columnar porous segment structure. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view showing an embodiment of the antibacterial ceramic film of the present disclosure. FIG. [Figure 2] FIG. 2 is an enlarged view of two pillar-shaped porous segments in FIG. 1. [Figure 3] FIG. 1 is a cross-sectional schematic diagram illustrating one embodiment of an electron beam physical vapor deposition (EB-PVD) apparatus. [Figure 4] 1 is an SEM image of the surface of a Ti substrate before heat treatment. [Figure 5A] 1 is an SEM image of the surface of a Ti substrate after heat treatment. [Figure 5B] This is an SEM image of a cross section of the substrate in the thickness direction. [Figure 6] FIG. 1 shows XRD patterns of the surface of a Ti substrate before and after heat treatment. [Figure 7] FIG. 1 shows XRD patterns of the surfaces of samples A and B. [Figure 8A] 1 is an SEM image of the surface of the film of sample A. [Figure 8B] This is an SEM image of the cross section of the film in the thickness direction. [Figure 9] This is a TEM image of the cross section of the film in the thickness direction. [Figure 10A] 1 is an SEM image of the surface of the film of sample B. [Figure 10B] This is an SEM image of the cross section of the film in the thickness direction. [Figure 11] Fluorescence micrographs of the culture medium surface corresponding to the Ti substrate. [Figure 12] Fluorescence micrographs of the culture surface corresponding to the pre-oxidized Ti substrate. [Figure 13] 1 is a fluorescence microscope photograph of the medium surface corresponding to sample A. [Figure 14] 1 is a fluorescence microscope photograph of the medium surface corresponding to sample B. DETAILED DESCRIPTION OF THE INVENTION

[0020] The following describes embodiments of the antibacterial ceramic film and its manufacturing method according to the present disclosure. However, the embodiments are not limited to the following embodiments, and various modifications and improvements that can be made by those skilled in the art can be made.

[0021] <Antibacterial ceramic film> The antibacterial ceramic film of the present disclosure is disposed on the surface of a substrate. The type of substrate is not particularly limited as long as a TiON film can be formed, and examples include metals and ceramics. Metals include titanium, titanium alloys, stainless steel alloys, and cobalt-chromium alloys. Ceramics include alumina, zirconia, and alumina-zirconia composite ceramics. For example, when used as a biological implant, titanium or a titanium alloy is preferred from the viewpoints of biocompatibility and safety. Metals added to titanium alloys include aluminum, tin, zirconium, molybdenum, nickel, palladium, tantalum, niobium, vanadium, and platinum.

[0022] The antibacterial ceramic film of the present disclosure may be disposed so as to cover the entire surface of the substrate, or may be disposed on only a portion of the surface of the substrate. The surface of the substrate (film-forming surface) may be the substrate itself, or may be subjected to a surface treatment to form a different layer. The layer formed may be one layer or two or more layers. For example, when titanium or a titanium alloy is used as the substrate, a TiO film can be formed on the surface by prior heat treatment. The TiO film is reduced to a TiO film during the formation of the ceramic film. When a ceramic film is formed on the surface of the TiO film, the TiO film acts as a bonding layer, improving the adhesion between the substrate and the ceramic film.

[0023] The antibacterial ceramic film of the present disclosure is made of cubic TiON. TiO is doped with an appropriate amount of N [TiO x N 1-xBy setting it to (0 < x < 1), the covalent bond strength is enhanced and the surface diffusion of the film components is suppressed. As a result, the flattening of the top of the columnar porous segment is suppressed, and it becomes easier to form a plurality of spiky portions on the surface. In the ceramic film, a form in which the (111) plane of TiON is oriented in the extending direction of the surface of the base material is desirable. In this case, it is desirable that the top of the columnar porous segment is formed of the (110) plane and the (100) plane having a smaller surface energy than the (111) plane. By doing so, the surface diffusion of the film components is suppressed, and the top of the columnar porous segment can be made conical.

[0024] The content of nitrogen atoms in TiON may be determined in consideration of the formation of spiky portions in the columnar porous segment. For example, the content of nitrogen atoms may be set to 15 atomic % or more and 30 atomic % or less. If the content of nitrogen atoms is less than 15 atomic %, the covalent bond strength is weakened and the surface diffusion of the film components is promoted, so that it becomes difficult to form the top of the columnar porous segment into a conical shape. On the other hand, if the content of nitrogen atoms exceeds 30 atomic %, the biocompatibility may decrease.

[0025] The antibacterial ceramic film of the present disclosure has a plurality of columnar porous segments erected in the thickness direction of the film. Hereinafter, the columnar porous segment will be described using a schematic diagram. FIG. 1 shows a schematic cross-sectional view of an embodiment of the antibacterial ceramic film of the present disclosure. As shown in FIG. 1, the base material 2 has a base material main body 20 and a bonding layer 21. The antibacterial ceramic film 1 is disposed on the surface of the bonding layer 21. The antibacterial ceramic film 1 is composed of a plurality of columnar porous segments 10 (hereinafter, simply referred to as "segment 10") extending from the surface of the bonding layer 21 in the thickness direction of the film (upward in FIG. 1). The segments 10 are each disposed substantially perpendicular to the surface of the base material 2. The top 11 of the segment 10 has a conical shape with a triangular cross-section and forms the surface of the antibacterial ceramic film 1. The maximum width W (the length in the horizontal direction in FIG. 1) of the top 11 is about 200 nm.

[0026] Figure 2 shows an enlarged view of two columnar porous segments in Figure 1. As shown in Figure 2, multiple thorns 12 are formed on the surface of the segment 10. The width of the thorns 12 is approximately 20 nm. There are also tiny gaps between adjacent segments 10. This provides high deformation tolerance to external loads. The segment 10 has a cone-shaped apex 11, and its surface is covered with fine thorns 12, which can be called a feather-like structure. When bacteria attach to the thorns 12, their cell membranes are destroyed and they die. In this way, bacterial growth is inhibited, and the antibacterial properties of the antibacterial ceramic film 1 are exerted.

[0027] In this embodiment, the columnar porous segments are arranged perpendicular to the surface of the substrate, but this does not necessarily have to be perpendicular. The columnar porous segments may be arranged at an angle to the surface of the substrate. The length of the columnar porous segments determines the thickness of the antibacterial ceramic film. The thickness of the ceramic film may be determined appropriately depending on the application. For example, when used for dental implants, it is recommended that the thickness be 1 μm or more and 50 μm or less.

[0028] As shown in the examples below, the columnar porous segments tend to become thicker from the substrate side toward the membrane surface. From the viewpoint of increasing durability against compressive loads in the thickness direction of the membrane, the maximum width of the apex of the columnar porous segment is preferably 100 nm or more. Furthermore, from the viewpoint of facilitating the formation of spiky portions on the surface, the maximum width of the apex is preferably 500 nm or less. Herein, the width of the apex of the columnar porous segment refers to the radial length, i.e., the length perpendicular to the extension direction of the columnar porous segment. The size of the spiky portions formed on the surface of the columnar porous segment is not particularly limited as long as antibacterial properties are exhibited. For example, from the viewpoint of fully exhibiting antibacterial activity, the width of the spiky portions is preferably less than 50 nm. Furthermore, from the viewpoint of reducing wear due to compressive loads in the thickness direction, the width of the spiky portions is preferably 10 nm or more. Herein, the width of the spiky portions of the columnar porous segment refers to the radial length, i.e., the length perpendicular to the extension direction of the spiky portions. The thickness of the antibacterial ceramic film, the shape and size of the columnar porous segments, etc. can be measured using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0029] <Method for manufacturing antibacterial ceramic film> The method for producing an antibacterial ceramic film according to the present disclosure, which is one embodiment of the method for producing an antibacterial ceramic film according to the present disclosure, includes a film formation step of forming a TiON film by electron beam physical vapor deposition (EB-PVD). Hereinafter, as one embodiment of the film formation step by EB-PVD, a film formation method using a single electron beam PVD apparatus (hereinafter simply referred to as "EB-PVD apparatus") will be described. First, the configuration of the EB-PVD apparatus according to this embodiment will be described. FIG. 3 shows a schematic cross-sectional view of the EB-PVD apparatus. As shown in FIG. 3, the EB-PVD apparatus 5 includes a chamber 50, an electron gun 51, a deposition source (target) 52, a support member 53, a semiconductor laser 54, and a gas supply device 55.

[0030] The chamber 50 is connected to a vacuum pumping device (not shown) to adjust the internal pressure. A gas supply device 55 is connected to the left wall of the chamber 50 and supplies nitrogen gas containing 0.1 vol% oxygen gas (N2 + 0.1 vol% O2) into the chamber 50. An electron gun 51 is connected to the top wall of the chamber 50 and irradiates an electron beam toward a vapor deposition source 52 (see the dashed-dotted downward arrow in Figure 3). The vapor deposition source 52 is made of titanium. A substrate 60, on which a film is to be formed, is attached to a support member 53 on the vapor deposition source 52 side. The support member 53 is rotatably installed by a rotation shaft 530. A semiconductor laser 54 is connected to the bottom wall of the chamber 50 and irradiates a laser toward the substrate 60 to heat it (see the dashed-dotted upward arrow in Figure 3). A laser shielding plate 540 is installed inside the top wall of the chamber 50.

[0031] Next, the film formation method will be described. First, the pressure inside the chamber 50 is reduced to 0.1 to 1 Pa, and nitrogen gas containing 0.1 volume % oxygen gas is supplied from the gas supply device 55. Next, the substrate 60 is heated using a semiconductor laser 54 until its surface temperature reaches 550°C, and the electron gun 51 irradiates the deposition source 52 with an electron beam. During this process, the support member 53 is rotated in one direction at 30 rpm, and the evaporated titanium is evaporated onto the surface of the substrate 60 (see the dotted upward arrow in Figure 3). Because the substrate 60 also rotates together with the support member 53, the incident direction of the evaporated titanium relative to the substrate 60 changes. In this way, columnar porous segments grow on the surface of the substrate 60, forming a TiON film.

[0032] In this embodiment, the film was formed while rotating the substrate in one direction, but the film may also be formed without rotating the substrate. When rotating the substrate, the rotation angle, rotation direction, rotation speed, etc. are not particularly limited. For example, the rotation direction may be periodically reversed, such as by rotating the substrate at an angle of ±90° around the normal line of the substrate. The film formation conditions can also be appropriately changed. The pressure in the chamber during film formation should be reduced to approximately 0.1 to 10 Pa. The volume ratio of oxygen gas in the supplied nitrogen gas can be determined taking into account the nitrogen atomic weight in the film, and is preferably, for example, 0.01% by volume or more and 1% by volume or less. The substrate surface temperature should be 500°C or more and less than 700°C. If the substrate surface temperature is too low, the growth rate of the columnar porous segments will be slow and they will become amorphous. Conversely, if the substrate surface temperature is too high, the film components will be more likely to diffuse over the surface, making it difficult to form conical tops of the columnar porous segments or desired spiky portions on the surface. The film formation time may be appropriately determined depending on the thickness of the ceramic film to be formed, and can be, for example, from 500 seconds to 2000 seconds. [Example]

[0033] Next, the present disclosure will be described more specifically with reference to examples.

[0034] <Sample production> [Pre-oxidation process] A Ti substrate (disk shape, 10 mm in diameter, 3 mm in thickness) with a mirror-finished film surface was heat-treated in a nitrogen gas atmosphere from which oxygen had been removed using an oxygen pump, to form a rutile-type TiO2 (R-TiO2) film as a bonding layer on the surface of the Ti substrate. The oxygen partial pressure (P O2 ) is 10 -17 Pa, and the flow rate of nitrogen gas is 300×10 -6 m 3 The heat treatment was carried out at 700°C for 1 hour.

[0035] FIG. 4 shows an SEM image of the surface (film-formed surface) of the Ti substrate before heat treatment. FIG. 5A shows an SEM image of the surface of the Ti substrate after heat treatment, and FIG. 5B shows an SEM image of a cross section of the same substrate in the thickness direction. FIG. 6 shows diffraction patterns obtained by X-ray diffraction (XRD) measurement of the surface of the Ti substrate before and after heat treatment. In FIG. 6, the lower side shows the diffraction pattern before heat treatment, and the upper side shows the diffraction pattern after heat treatment. As shown in FIG. 6, an R-TiO2 peak appears in the diffraction pattern after heat treatment, confirming that an R-TiO2 film was formed on the surface of the Ti substrate after heat treatment. A Ti substrate on which an R-TiO2 film (bonding layer) is formed is included in the concept of a substrate in this disclosure.

[0036] [Film forming process] The film was formed on the bonding layer surface of the Ti substrate using the electron beam physical vapor deposition (EB-PVD) method. The film was formed using the EB-PVD apparatus shown in Figure 3, and two types of film formation were performed under different conditions.

[0037] (1) Sample A First, the Ti substrate on which the bonding layer was formed was attached to the support member of the EB-PVD device. Then, under reduced pressure of 0.1 to 1 Pa, an electron beam was irradiated onto the Ti targets (two types) using an electron gun (output 12 kW), and a rock salt type TiON film with a thickness of approximately 2 μm was formed on the bonding layer surface of the Ti substrate while rotating the support member at 30 rpm. The film was formed by irradiating 100 × 10 nitrogen gas containing 0.1% by volume of oxygen gas onto the Ti substrate and the target, respectively. -6 m 3 The Ti substrate was heated with a semiconductor laser so that the surface temperature reached 550°C while being sprayed at a flow rate of 1 / min. The film formation time was 900 seconds. The sample obtained in this manner is referred to as Sample A.

[0038] (2) Sample B A rock salt type TiO film with a thickness of approximately 2 μm was formed by changing the type of gas used and the film formation time among the film formation conditions of Sample A. The obtained sample is called Sample B. The film formation of Sample B was carried out by supplying oxygen gas to the Ti substrate and the target at 100×10 -6 m 3While spraying at a flow rate of / min, laser heating was performed so that the surface temperature of the Ti substrate reached 550°C. The film formation time was 120 seconds. Table 1 summarizes the film formation conditions for Samples A and B.

[0039]

Table 1

[0040] Figure 7 shows the diffraction patterns obtained by XRD measurement of the surfaces of Samples A and B. In Figure 7, the lower side shows the diffraction pattern of Sample A, and the upper side shows the diffraction pattern of Sample B. As shown in Figure 7, a peak of R-TiO2 appears in the diffraction pattern of Sample B, while a peak of TiO x N 1-x (0 < x < 1) appears, and it was confirmed that the film of Sample A is strongly oriented in the

[0111] direction with respect to the surface of the Ti substrate.

[0041] Figure 8A shows the SEM image of the surface of the film of Sample A, and Figure 8B shows the SEM image of the cross-section in the thickness direction of the same film. Further, Figure 9 shows the TEM image of the cross-section in the thickness direction of the same film. Figure 9 corresponds to an enlarged view of Figure 8B. Also, Figure 10A shows the SEM image of the surface of the film of Sample B, and Figure 10B shows the SEM image of the cross-section in the thickness direction of the same film. In the cross-sectional SEM images of Figure 8B and Figure 10B, the outermost layer of the film that appears white is a platinum deposition film deposited on the sample surface during imaging. In the cross-sectional TEM image of Figure 9, the outermost layer of the film that appears white is a carbon deposition film deposited on the sample surface during imaging.

[0042] As shown in Figures 8B and 9, the film of Sample A was confirmed to be composed of numerous columnar porous segments extending approximately vertically from the bonding layer (the TiO film was reduced during film formation to form a TiO film) toward the surface. As shown in Figure 8A, each columnar porous segment had a cone-shaped apex, and the TEM image in Figure 9 reveals that the cross section of the apex was triangular. Furthermore, numerous spiky portions, exhibiting shapes such as flakes and needles, were formed on the surface of each segment. Many of the segments had increasing widths toward the surface. The maximum width of the segment apex measured in the TEM image in Figure 9 was between 100 nm and 500 nm, and the width of the spiky portions was between 10 nm and 50 nm.

[0043] In contrast, in the film of Sample B, as shown in Figures 10A and 10B, columnar segments extending almost perpendicularly from the bonding layer toward the surface were formed, but the individual segments were thicker than those of Sample A and had rounded, flat tops. Furthermore, no spiky portions were observed on the surface of the segments.

[0044] The films of Samples A and B were analyzed by X-ray photoelectron spectroscopy (XPS), and their compositions were analyzed based on the binding energy values ​​obtained from the photoelectron spectra. As a result, the composition of the film of Sample A was Ti 45.2 O 31.8 N 23.0 The composition of the film of sample B is Ti 33.7 O 66.3 It was found that...

[0045] <Sample evaluation> The antibacterial properties of the films of Samples A and B were evaluated by fluorescent staining. For comparison, the antibacterial properties of the Ti substrate used as the base material and the pre-oxidized Ti substrate (with the R-TiO2 film as the bonding layer) were also evaluated in the same way.

[0046] [Test method (fluorescent staining method)] Four types of test specimens were prepared: Ti substrate, pre-oxidized Ti substrate, sample A, and sample B. One specimen each was prepared and subjected to antibacterial evaluation using fluorescent staining. These specimens were sterilized by ultrasonic cleaning, first in acetone for 5 minutes twice, then in sterilized ultrapure water for 5 minutes twice. Finally, the front (test surface) was irradiated with ultraviolet light for 30 minutes and the back surface for 5 minutes. The sterilized test specimens were placed test-side up in a petri dish, and a bacterial solution of Escherichia coli (JCM 5491) was dropped onto them. The top surfaces of the test specimens were covered with a sterilizing film, and the petri dish was then capped and incubated in an incubator at 35°C and 90% relative humidity for 24 hours. The test specimens were then transferred to a new petri dish, the sterilizing film was removed, and the specimens were washed with ultrapure water. The specimens were then immersed in a staining solution (Cellstain® AO solution) and fluorescently stained for 15 minutes at 37°C while shielded from light. After staining, the specimens were observed under an inverted fluorescence microscope.

[0047] [Test Results] Figures 11 to 14 show photographs of the culture medium surface observed with a fluorescence microscope. Figure 11 corresponds to the Ti substrate, Figure 12 corresponds to the pre-oxidized Ti substrate, Figure 13 corresponds to sample A, and Figure 14 corresponds to sample B. In each photograph, the scale bar at the bottom right is 200 μm long. As shown in Figure 13, brightly shining particles (viable bacteria) were hardly observed in the film of sample A, and the number of viable bacteria was significantly reduced compared to the other three (Figures 11, 12, and 14). This confirmed that the film of sample A has antibacterial properties against E. coli. [Industrial Applicability]

[0048] The antibacterial ceramic film of the present disclosure can be widely used in products requiring antibacterial properties. For example, antibacterial products in the medical field include medical instruments, surgical instruments, and biological implants. Examples of biological implants include artificial bones, artificial joints, various fixation devices, and artificial dental roots. In particular, the film is suitable for use in dental implants because of its high durability against repeated compressive loads. [Explanation of symbols]

[0049] 1: antibacterial ceramic membrane, 10: columnar porous segment, 11: top portion, 12: spiky portion, 2: substrate, 20: substrate body, 21: bonding layer, 5: EB-PVD apparatus, 50: chamber, 51: electron gun, 52: deposition source, 53: support member, 530: rotating shaft, 54: semiconductor laser, 540: laser shielding plate, 55: gas supply device, 60: substrate, W: maximum width of top portion.

Claims

1. An antibacterial ceramic film disposed on a surface of a substrate, It is made of cubic TiON, a plurality of columnar porous segments extending in the thickness direction of the membrane; The antibacterial ceramic membrane is characterized in that the columnar porous segment has a conical top and a plurality of spiky portions on its surface.

2. 2. The antibacterial ceramic film according to claim 1, wherein the (111) plane of the TiON is oriented in the extending direction of the surface of the substrate.

3. 2. The antibacterial ceramic film according to claim 1, wherein the content of nitrogen atoms in the TiON is 15 atomic % or more and 30 atomic % or less.

4. 2. The antibacterial ceramic film according to claim 1, wherein the maximum width of the top of the columnar porous segment is 100 nm or more and 500 nm or less.

5. 2. The antibacterial ceramic film according to claim 1, wherein the substrate has a bonding layer containing TiO, and the antibacterial ceramic film is disposed on a surface of the bonding layer.

6. The antibacterial ceramic film according to claim 1, which is used for a biological implant.

7. The antibacterial ceramic film according to claim 1, wherein the substrate is made of titanium or a titanium alloy and is used for a dental implant.

8. 2. A method for producing the antibacterial ceramic film according to claim 1, A method for producing an antibacterial ceramic film, comprising a film-forming step of irradiating an electron beam from an electron gun onto a titanium evaporation source under reduced pressure in a nitrogen gas atmosphere containing a trace amount of oxygen gas at a temperature of 500°C or higher but lower than 700°C, and depositing the evaporated titanium on the surface of the substrate, thereby growing a plurality of the columnar porous segments and forming a film made of TiON.

9. 9. The method for producing an antibacterial ceramic film according to claim 8, wherein in the film-forming step, the evaporated titanium is deposited on the surface of the substrate while the substrate is rotated relative to the deposition source.

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