Medical device

Abstract

A medical device (100) is flexible, is excellent in terms of hygiene and, as a single use product, is highly safe when processed after disposal. The medial device comprises: an elastic layer (10) comprising an electroconductive polyurethane; and a first electrode layer (20) that includes silver, silver chloride, and a resin, and that is disposed on at least a part of a first surface of the elastic layer (10). It is possible to cause an electrical current to flow between a surface of the first electrode layer (20) and a second surface of the elastic layer (10).

Description

Medical Devices

[0001] The present invention relates to medical devices.

[0002] To date, laminated structures with a resin or paper sheet as one layer have been developed as bioelectrodes or devices equipped with such electrodes. In addition to the selection of the type or material of the layer, several techniques for improving the conductivity from both sides of the resin layer have been disclosed in the prior art (Patent Documents 1 to 3).

[0003] JP 2013-202336 A JP 5-95922 A JP 2016-67722 A

[0004] However, it can be said that the development and realization of a medical device for living organisms having a laminated structure using a material (typically, a material as a substrate) having all of the characteristics shown in (a1) to (f1) below is still in the early stages.

[0005] (a1) Disposable medical devices are widely used from a hygienic standpoint, but they are environmentally friendly, for example, by making it easier to ensure safety in post-disposal disposal (e.g., incineration) and / or by enabling the recycling of silver.

[0006] (b1) Low odor for patients who are sensitive to odors.

[0007] (c1) Having flexibility that is not easily affected by the temperature during use, and for example, when placed in contact with or attached to a part of a human body (for example, the skin), it can easily conform to the curves of parts of the human body such as the head, neck, arms, chest, abdomen, thighs, and feet, or can easily follow the movements of each part of the body even when they move.

[0008] (d1) It is easy to use for patients with sensitive skin, such as children, women, or the elderly.

[0009] (e1) It has good breathability and can be easily used even in humid environments.

[0010] (f1) It can be manufactured at low cost.

[0011] Furthermore, when a medical device having the above-described laminated structure is used as an electrode, there is still much room for research and development into materials or structures that have all of the characteristics shown in (a2) to (b2) below.

[0012] (a2) Low electrical resistance.

[0013] (b2) Even if an electrical signal (typically a biological signal) is weak, it can be detected with high accuracy.

[0014] By solving several of the technical problems described above, the present invention can greatly contribute to the realization of medical devices for living organisms that can also be used as components of electrodes.

[0015] The present inventors conducted extensive research and analysis to create materials and structures that can solve the above-mentioned technical problems. Specifically, the present inventors discovered that in manufacturing a medical device as a laminated structure, the material and structure that primarily serves as the substrate can have a significant impact on solving the above-mentioned technical problems. As a result of further research and development, the present inventors discovered that a urethane resin (polyurethane) that has been imparted with electrical conductivity is the most appropriate material to primarily serve as the substrate.

[0016] Furthermore, the inventors have discovered that in order to enable a medical device to properly function as an electrode, it is possible to overcome the above-mentioned technical challenges by appropriately selecting particles of metal (including said metal covering at least a portion of the core material) that can contribute to the detection of electrical signals (typically, biological signals) and that are placed on or above the above-mentioned substrate, and by devising the shape and / or aspect ratio of the metal particles.

[0017] Further research by the inventors has led to the interesting finding that, when the aspect ratio exceeds a predetermined value, even if a certain bending force is applied to the medical device as a laminated structure, the deviation from the value indicating the electrical conductivity when not bent can be suppressed with high certainty. The present invention was created based on the above-mentioned viewpoints.

[0018] One medical device of the present invention comprises an elastic layer made of conductive polyurethane, and a first electrode layer containing silver, silver chloride, and a resin on at least a portion of a first surface of the elastic layer, and is capable of passing an electric current between a surface of the first electrode layer and a second surface of the elastic layer.

[0019] This medical device employs an elastic layer made of conductive polyurethane as a material that mainly serves as a substrate, and has a structure in which the elastic layer is laminated with a first electrode layer containing silver, silver chloride, and resin. Therefore, of the above-mentioned technical problems, at least problems (a1), (b1), and (c1) can be solved.

[0020] In the above-mentioned invention, the silver is preferably in the form of whisker-like silver particles, since this can significantly contribute to solving the above-mentioned technical problems, particularly problems (a2) and (b2).

[0021] Another medical device of the present invention includes an elastic layer made of conductive polyurethane, and a first electrode layer on at least a portion of one first surface of the elastic layer, the first electrode layer including silver covering a core material, silver chloride, and a resin. Additionally, this medical device is capable of passing an electric current between a surface of the first electrode layer and the other second surface of the elastic layer, and the aspect ratio of the core material or the silver covering the core material is 10 to 240, and at least one portion of the silver covering the core material is embedded in the elastic layer.

[0022] This medical device employs an elastic layer made of conductive polyurethane as a material that primarily serves as a substrate, and has a structure in which a first electrode layer containing silver, silver chloride, and a resin covering a core material is laminated with the elastic layer, thereby solving at least problems (a1), (b1), and (c1) among the above-mentioned technical problems. Furthermore, as described above, in this medical device, the aspect ratio of the core material is 10 to 240, and at least one portion of the silver covering the core material is embedded in the elastic layer. Therefore, when the medical device is placed in contact with a part of a human (e.g., skin), even if a bending force is applied to the medical device due to movement of each part, it is possible to highly reliably suppress deviations from the conductivity when unbent.

[0023] Furthermore, the thickness of each of the elastic layer and the first electrode layer is not limited as long as the electrical conductivity in the thickness direction of each of the elastic layer and the first electrode layer is at least as high as useful for a medical device. In addition, the type of the resin is not limited as long as the electrical conductivity in the thickness direction of each of the elastic layer and the first electrode layer is at least as high as useful for a medical device.

[0024] In this application, the terms "layer" and "film" have the same meaning. Furthermore, the term "layer" in this application is not limited to a continuous layer of uniform thickness. Therefore, the term "layer" in this application includes continuous layers of different thicknesses. Furthermore, the term "layer" in this application includes, for example, a layer in which the target material is formed on a substrate in a discontinuous state, so to speak, in the form of multiple islands of approximately the same thickness or different thicknesses. Furthermore, the term "covering the core material" in this application does not necessarily mean that the shell completely covers the surface of the core material. Even if only a portion of the surface of the core material is not covered, the term "covering the core material" is included in the meaning of the term.

[0025] According to one medical device of the present invention, at least the above-mentioned problems (a1), (b1) and (c1) can be solved.

[0026] 1 is a cross-sectional view showing the configuration of a medical device 100 according to a first embodiment; FIG. 2 is a cross-sectional view showing the configuration of a medical device 100a according to a modified example of the first embodiment; FIG. 3 is a configuration diagram showing a manufacturing apparatus 900 for a part of the manufacturing process for the medical device 100 according to the first embodiment; FIG. 4 is a cross-sectional view showing the configuration of a medical device 200 according to a second embodiment; FIG. 5 is a cross-sectional view showing the configuration of a medical device 300 according to a third embodiment; FIG. 6 is a cross-sectional view showing the configuration of a medical device 300a according to a modified example of the third embodiment; FIG. 7 is an example of a cross-sectional SEM photograph showing a laminate structure of an elastic layer made of conductive polyurethane and a first electrode layer containing silver, silver chloride, and a resin; FIG. 8 is another example of a cross-sectional SEM photograph showing a laminate structure of an elastic layer made of conductive polyurethane and a first electrode layer containing silver, silver chloride, and a resin; FIG. 9 is an SEM (scanning electron microscope) image of an example of "silver covering a core material" having an aspect ratio of approximately 60, corresponding to sample (SP1); and FIG. 10 is an SEM (scanning electron microscope) image of an example of "silver covering a core material" having an aspect ratio of approximately 12, corresponding to sample (SP2). 1 is a scanning electron microscope (SEM) image of an example of approximately spherical (hence, aspect ratio of approximately 1) silver particles as a reference example, which corresponds to sample (SP3). FIG. 2 is a schematic diagram showing a method for measuring the surface resistance values ​​of samples (SP1) to (SP3).

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this description, common parts are designated by common reference numerals throughout the drawings unless otherwise specified. In addition, in the drawings, elements of the present embodiment are not necessarily drawn to scale. In addition, some symbols and shapes may be omitted to make each drawing easier to understand.

[0028] First Embodiment [Configuration of Medical Devices of the Present Embodiment and Modification (1) Thereof] Fig. 1 is a cross-sectional view showing the configuration of a medical device 100 of the present embodiment. As shown in Fig. 1, the medical device 100 is a laminated structure of an elastic layer 10 made of conductive polyurethane and a first electrode layer 20 containing silver (Ag), silver chloride (AgCl), and a resin. Fig. 2 is a cross-sectional view showing the configuration of a medical device 100a, which is a modification (1) of the medical device 100 of the present embodiment. Note that the medical device 100a, which is modification (1), has the same configuration as the medical device 100, except that the arrangement of the first electrode layer 20 differs from that of the medical device 100 of the present embodiment, and therefore redundant description may be omitted.

[0029] As shown in FIG. 1, the medical device 100 is shown in a state in which the first electrode layer 20 is arranged uniformly and to approximately the same thickness so as to substantially cover the entire surface of the elastic layer 10 (first surface 12 in FIG. 2).

[0030] On the other hand, as shown in Figure 2, on the elastic layer 10 of the medical device 100a of the modified example (1), the first electrode layer 20 is formed so as to cover a portion of the surface (first surface 12) of the elastic layer 10 in the form of one or more islands of approximately the same thickness.

[0031] From the viewpoint of ease of processing into a shape that can follow the shape or movement of human skin or each part, it is a preferred embodiment that the first electrode layer 20 is disposed uniformly and to have substantially the same thickness so as to cover the entire surface of the elastic layer 10, as in the medical device 100. On the other hand, from the viewpoint of preventing tears or fissures from occurring in the first electrode layer 20 when it follows the shape or movement of human skin or each part, it is a preferred embodiment that the first electrode layer 20 is disposed so that a portion of the surface of the elastic layer 10 is not covered, as in the medical device 100a of the modified example (1).

[0032] Next, the elastic layer 10 and the first electrode layer 20 constituting the medical device 100 of this embodiment and the medical device 100a of the modified example (1) thereof will be described.

[0033] Polyurethane, which is the main material of the elastic layer 10 that serves as the base material in the medical device 100 and the medical device 100a, has high flexibility, which allows it to conform to the curved surfaces of parts of a person's body, such as the head, neck, arms, chest, abdomen, thighs, and feet, when placed in contact with or attached to a part of the body (e.g., the skin), or to follow the movements of each part of the body and conform to the curved surfaces.

[0034] Therefore, when the medical device 100 is used as an electrode, in order to take advantage of its high flexibility, it is a preferred embodiment that the first electrode layer 20 disposed on the elastic layer 10 has approximately the same thickness. Another embodiment that can be adopted is that the first electrode layer 20 is formed so that part or all of the surface (first surface 12) of the elastic layer 10 is covered in a discontinuous state with the first electrode layer 20 having different thicknesses.

[0035] Furthermore, adjusting the amount of carbon blacks (including conductive carbon black, ketjen black, graphite, and mesoporous carbon), carbon nanotubes, graphene, graphene meso-sponge, or acetylene black, which are the conductive materials contained in the polyurethane, so that the surface resistance of the elastic layer 10 is 0.1 Ω or more and 100 Ω or less (more preferably 5 Ω or more and 70 Ω or less) is a preferred embodiment from the viewpoint of detecting electrical signals (typically, biological signals) with high sensitivity at a level useful as a medical device.

[0036] In addition, adjusting the amount of each of the above-mentioned conductive materials contained in the polyurethane so that the resistance value of the elastic layer 10 in the thickness direction is 0.1 Ω or more and 1000 Ω or less (more preferably 1 Ω or more and 100 Ω or less) is a preferred embodiment from the viewpoint of obtaining conductivity in the thickness direction that is at least useful as a medical device, and as a result, detecting electrical signals (typically, biological signals) with high sensitivity.

[0037] Furthermore, as described above, since the main material of the elastic layer 10 of this embodiment is polyurethane, for example, when the elastic layer 10 is placed in contact with human skin, it can achieve high moisture absorption for human sweat, and therefore using an elastic layer 10 made of conductive polyurethane is a preferred embodiment from the viewpoint of easily maintaining its functionality as a medical device. Furthermore, having a tensile elongation of the elastic layer 10 of 50% or more (more preferably, 70% or more, and even more preferably, 100% or more) and / or a glass transition temperature (Tg) of the elastic layer 10 of less than 70°C (more preferably, 50°C or less) is a preferred embodiment from the viewpoint of achieving an elastic layer 10 with higher flexibility and conformability.

[0038] Furthermore, from the viewpoint of realizing more reliably that the medical device 100, 100a conforms to the curved surfaces of each part of a human body, it is preferable that the resin, which is one of the materials constituting the first electrode layer 20, is a resin having flexibility and conformability, similar to the polyurethane that is responsible for the flexibility and conformability of the elastic layer 10. Representative examples of such a resin (hereinafter referred to as the "first resin") include acrylic resin, acrylic copolymer, epoxy resin, urethane resin, silicone resin, and polyester resin. Note that an acrylic resin or acrylic copolymer having a molecular weight of 5,000 to 300,000 and / or a glass transition temperature (Tg) of 100°C or less is a preferred embodiment from the viewpoint of realizing more reliably a first electrode layer 20 having flexibility and conformability.

[0039] The thickness of the elastic layer 10 is not limited as long as it exhibits the required conductivity or purpose of the medical device. For example, when placed in contact with or attached to a part of a human body (e.g., skin), the thickness is preferably 250 μm or less (more preferably 100 μm or less) in order to accurately conform to the undulations, irregularities, rotations, flexions, or extensions of the human skin surface. This is because if the thickness of the elastic layer 10 exceeds 250 μm, tears may form in the elastic layer 10 when it is caused to conform to the movements of parts of the human body, such as the head, neck, arms, chest, abdomen, thighs, and feet. On the other hand, the thickness of the elastic layer 10 that can serve as a substrate is preferably 40 μm or more in order to obtain sufficient strength as a medical device.

[0040] Next, the mass ratio of the total of silver (Ag) and silver chloride (AgCl) to the resin in the first electrode layer 20 is not limited as long as the required conductivity or the intended purpose of the medical device can be exhibited. From the viewpoint of reducing the burden on the environment or realizing cost reduction, it is a preferred embodiment that the ratio of the total mass of silver (Ag) and silver chloride (AgCl) to the mass of the resin is 0.05 or more and 0.45 or less (more preferably 0.15 or more and 0.25 or less) when the total mass is 1.

[0041] Furthermore, the mass ratio of silver (Ag) to silver chloride (AgCl) in the first electrode layer 20 is not limited as long as the required or intended conductivity of the medical device can be exhibited. As described above, from the viewpoint of reducing the burden on the environment or reducing costs, or from the viewpoint of accurately and sensitively detecting electrical signals (typically, biological signals) even when the medical device is bent, it is a preferred embodiment that the mass ratio of silver (Ag) to silver chloride (AgCl) is 0.05 or more and 2.5 or less (more preferably 0.1 or more and 1.6 or less) when silver (Ag) is 1.

[0042] Similarly to the thickness of the elastic layer 10, the thickness of the first electrode layer 20 is not limited as long as it exhibits the required conductivity or purpose of the medical device. From the viewpoint of detecting electrical signals (typically, biosignals) with high sensitivity, the thickness is preferably 2 μm or more (more preferably 3 μm or more, and even more preferably 3.5 μm or more). On the other hand, from the viewpoint of easily following the undulations, irregularities, rotations, flexions, or extensions of the surface of a human body (e.g., skin) when placed in contact with the body or attached to the skin, the thickness is preferably 30 μm or less (more preferably 15 μm or less). This is because if the thickness of the first electrode layer 20 exceeds 30 μm, there is a possibility that cracks or fissures may form in the first electrode layer 20 when the first electrode layer 20 is caused to follow the movements of the human body, such as the head, neck, arms, chest, abdomen, thighs, or feet.

[0043] <Modification (2) of the First Embodiment> The shape of the silver (Ag) in the first electrode layer 20 is not limited to a substantially spherical shape, and flake-shaped particles are also a suitable embodiment that can be adopted. Therefore, in this modification, the silver (Ag) can include flaky silver particles. A typical example of the average particle diameter (D50) of the flaky particles that can be adopted in this modification is from about 2 μm to about 7 μm (more narrowly, from about 3.5 μm to about 5 μm). In this embodiment, the average particle diameter is the cumulative median diameter at which a cumulative curve reaches 50% by volume when the total volume of the powder population is set to 100%. The average particle diameter can be measured using dynamic light scattering. Furthermore, when the silver (Ag) is in the form of flake particles, an aspect ratio (the value obtained by dividing the average particle diameter (D50) of the flaky silver particles by the plate thickness of the silver particles) of 3 or more and 100 or less (more preferably 20 or more and 60 or less) can greatly contribute to increasing the conductivity of the first electrode layer 20, i.e., enabling electrical signals (typically, biological signals) to be detected with high sensitivity.

[0044] In addition, a suitable embodiment of the silver (Ag) in the first electrode layer 20 is silver particles that can form a relatively high aspect ratio, such as rod-shaped, needle-shaped, cone-shaped, or wire-shaped particles, in addition to flake-shaped particles. In particular, the inclusion of silver particles in the first electrode layer 20 with an aspect ratio of 10 to 240 (more preferably 15 to 100) can significantly contribute to increasing the conductivity of the first electrode layer 20, i.e., enabling detection of electrical signals (typically, biological signals) with high sensitivity.

[0045] Furthermore, silver (Ag) is not limited to being present as simple silver (Ag). For example, one embodiment in which silver (Ag) covers at least a portion of the core material (hereinafter referred to as "silver covering the core material") can be adopted. Therefore, in this embodiment, silver plays the role of the shell of a "core-shell structure." An example of a core material is potassium titanate. Therefore, in this modification, the silver (Ag) can include silver covering the potassium titanate. The core material covered with silver (potassium titanate in this modification) or the "silver (Ag) covering the core material" has a whisker-like structure with a predetermined aspect ratio (typically, 10 to 240 (more narrowly, 15 to 100)). This can significantly contribute to increasing the conductivity of the first electrode layer 20, i.e., enabling highly sensitive detection of electrical signals (typically, biological signals). In this embodiment, the silver covering at least a part of the potassium titanate as the core material having the above-mentioned predetermined aspect ratio is referred to as "silver covering whisker-like potassium titanate."

[0046] Here, the inclusion of at least one type of silver particles selected from the group consisting of silver particles having an aspect ratio within the above-mentioned range, flaky silver particles having an aspect ratio within the above-mentioned range, and silver particles covering whisker-like potassium titanate, which may be employed in this modification, means that, compared to approximately spherical silver (Ag) particles, even if silver chloride (AgCl) particles are in a granular shape such as a spherical shape, the surface of the first electrode layer 20 will have a higher degree of irregularities, in other words, more irregularities with large height differences will be formed. As a result, the surface area of ​​the first electrode layer 20 as a whole will be substantially larger.

[0047] As a result, even if the area of ​​the elastic layer 10, which primarily serves as a substrate, is the same, the area in contact with human skin is substantially larger than that of a medical device 100, 100a that does not contain at least one selected from the group consisting of silver particles having an aspect ratio within the above-mentioned numerical range, flaky silver particles within the above-mentioned numerical range, and silver coated with the above-mentioned whisker-like potassium titanate. As a result, it is noteworthy that electrical signals (typically, biosignals) can be acquired with greater accuracy. Furthermore, the fact that the above-mentioned first electrode layer 20 contains silver coated with whisker-like potassium titanate can reduce the overall amount of silver used in the first electrode layer 20, which can significantly contribute to reducing the overall cost of the medical device.

[0048] Representative potassium titanate that can be used in this modification has a generally cylindrical, generally conical, generally polygonal truncated pyramid, or generally polygonal prism shape, a maximum diameter (maximum width) of about 0.1 μm to about 1 μm (more narrowly, about 0.2 μm to about 0.6 μm), and a length (height) of about 8 μm to about 24 μm (more narrowly, about 10 μm to about 20 μm). In addition, the thickness of the silver (Ag) film covering the potassium titanate is about 0.05 μm to about 0.3 μm (more narrowly, about 0.08 μm to about 0.26 μm).

[0049] In addition, the first electrode layer 20 is not limited to containing only one of flaky silver particles or silver particles of other shapes (e.g., substantially spherical) (hereinafter referred to as "flaky silver particles, etc.") within the above-mentioned numerical range, silver particles having an aspect ratio within the above-mentioned numerical range, and silver covering the above-mentioned whisker-like potassium titanate. For example, another suitable embodiment that can be adopted is one in which the first electrode layer 20 contains both silver particles having an aspect ratio within the above-mentioned numerical range and silver covering the above-mentioned whisker-like potassium titanate, or both the above-mentioned flaky silver particles and silver covering the above-mentioned whisker-like potassium titanate. Similarly, other examples of combinations selected from the above-mentioned three types are also other suitable embodiments that can be adopted.

[0050] Another suitable embodiment that can be adopted is one in which the above-mentioned silver is an approximately spherical silver (Ag) particle, and at least one of the approximately spherical silver (Ag) particles is partially embedded in the elastic layer 10.

[0051] Furthermore, the above-mentioned silver being in the following states (P), (Q) and / or (R) is a preferred embodiment, since it can greatly contribute to increasing the conductivity of the first electrode layer 20, that is, to enabling detection of electrical signals (typically, biological signals) with high sensitivity. (P) Silver particles having the above-mentioned aspect ratio, with at least one flake-shaped silver particle or the like being partially embedded in the elastic layer 10; (Q) The above-mentioned flake-shaped silver particles or the like, with at least one flake-shaped silver particle or the like being partially embedded in the elastic layer 10; (R) Silver (Ag) covering the above-mentioned core material (in this modified example, silver covering potassium titanate (particularly, silver covering whisker-shaped potassium titanate)), with at least one silver (Ag) covering the core material (in this modified example, silver covering the potassium titanate (particularly, silver covering the whisker-shaped potassium titanate)) being partially embedded in the elastic layer 10.

[0052] With regard to the above (P), it is an even more preferred embodiment that the first electrode layer 20 contains silver particles having an aspect ratio of 3 or more and 100 or less (more preferably 20 or more and 60 or less), since this is more likely and makes it easier for at least one portion of the flaky silver particle to be embedded in the elastic layer 10. With regard to the above (Q), it is an even more preferred embodiment that the first electrode layer 20 contains silver particles having an aspect ratio of 3 or more and 100 or less (more preferably 20 or more and 60 or less), since this is more likely and makes it easier for at least one portion of the flaky silver particle to be embedded in the elastic layer 10. Furthermore, with regard to the above (R), it is an even more preferred embodiment that the first electrode layer 20 contains a "core material" or "silver (Ag) covering the core material" having an aspect ratio of 10 or more and 240 or less, since this is more reliable and makes it easier for at least one portion of the "silver (Ag) covering the core material" to be buried in the elastic layer 10.

[0053] As described above, the silver particles having the above-mentioned aspect ratio, the approximately spherical silver (Ag) particles, the flake-shaped silver particles having the above-mentioned aspect ratio, and / or silver (Ag) covering the core material having the above-mentioned aspect ratio (for example, silver covering the potassium titanate (particularly, silver covering whisker-shaped potassium titanate)) act as a ``bond'' between the elastic layer 10 and the first electrode layer 20, thereby increasing the integrity (bonding strength) between the elastic layer 10 and the first electrode layer 20 and further increasing the conductivity of the medical device 100, 100a as a whole.

[0054] In particular, focusing on the flaky silver particles or the silver covering the core material (for example, the silver covering the potassium titanate) in this modified example, if we consider the flaky silver particles or the silver covering the core material dynamically, it is worth noting that when the flaky silver particles or the silver covering the core material have the above-mentioned aspect ratio, it becomes easier to more reliably form a state in which the silver covering the potassium titanate is, so to speak, piercing the elastic layer 10.

[0055] The core material in this modification is not limited to potassium titanate, as long as it is a material having appropriate rigidity that allows at least a portion of the core material to be embedded in the elastic layer 10. For example, in one preferred embodiment of this modification, the core material is at least one material selected from the group consisting of potassium titanate, titanium oxide, zinc oxide, aluminum oxide, silicon oxide, carbon fiber, and metal wire (excluding silver).

[0056] 7 and 8 are examples of cross-sectional SEM photographs showing a laminate structure of an elastic layer made of conductive polyurethane and a first electrode layer containing silver, silver chloride, and resin (acrylic resin in this example). In Fig. 7 and Fig. 8, "A" represents silver chloride (AgCl), "B" represents approximately spherical silver (Ag) particles, and "C" represents silver covering whisker-like potassium titanate.

[0057] 7 and 8, it can be observed that some of the approximately spherical silver (Ag) particles and / or some of the silver covering the potassium titanate penetrate into the elastic layer side of the interface between the first electrode layer and the elastic layer. Therefore, since some of the approximately spherical silver (Ag) particles and / or some of the silver covering the potassium titanate are embedded in the elastic layer, it can be seen that some of the approximately spherical silver (Ag) particles and / or some of the silver covering the potassium titanate can serve as a "bridge" between the elastic layer and the first electrode layer.

[0058] 7 and 8 show that when the first electrode layer contains substantially spherical silver (Ag) particles and / or silver covering potassium titanate, the distribution of the substantially spherical silver (Ag) particles and / or silver covering the potassium titanate in the thickness direction of the first electrode layer is not localized. Furthermore, when other examples are analyzed, it can be observed that when the first electrode layer contains flaky silver particles, the distribution of the flaky silver particles in the thickness direction of the first electrode layer is not localized.

[0059] [Experiment to Investigate the Effect of Differences in Aspect Ratio on Conductivity] The following describes an experiment to investigate the effect of differences in aspect ratio on conductivity in this modified example, and the results thereof. More specifically, the present inventors investigated the effect on conductivity of differences in aspect ratio of the core material itself or the silver covering the core material, representing the flaky silver particles and the silver covering the core material in this modified example.

[0060] In this experiment, since the thickness of the silver covering the core material is very thin compared to the cross-sectional diameter of the core material, it is considered that the aspect ratio of the core material itself is substantially the same as the aspect ratio of the silver covering the core material, and since there are cases where not all core materials are completely covered with silver (in other words, there are cases where some remain almost entirely as core material), the aspect ratio of this modified example applies to both the core material and the silver covering the core material.

[0061] In this experiment, the inventor measured the surface resistance values ​​of the three samples (SP1) to (SP3) shown in Table 1 in the three states (x1), (x2), and (x3) shown below.

[0062] Table 1 shows the mass ratios of materials constituting the first electrode layer 20 of three samples of this modified example with different aspect ratios. Note that silver (Ag) B1 in Table 1 is amorphous silver. Silver (Ag) C1 is silver covering whisker-shaped potassium titanate with an aspect ratio of approximately 60, which was used in sample (SP1). Silver (Ag) C2 is silver covering whisker-shaped potassium titanate with an aspect ratio of approximately 12, which was used in sample (SP2). Silver (Ag) B2 is approximately spherical silver particles.

[0063] FIG. 9 is a scanning electron microscope (SEM) image of an example of "silver covering potassium titanate" ("silver (Ag) C1" in Table 1) having an aspect ratio of approximately 60, which corresponds to the above-mentioned sample (SP1). FIG. 10 is a scanning electron microscope (SEM) image of an example of "silver covering potassium titanate" ("silver (Ag) C2" in Table 1) having an aspect ratio of approximately 12, which corresponds to the above-mentioned sample (SP2). FIG. 11 is a scanning electron microscope (SEM) image of an example of approximately spherical (hence, aspect ratio of approximately 1) silver particles ("silver (Ag) B2" in Table 1) as a reference example, which corresponds to the above-mentioned sample (SP3).

[0064]

[0065] <Measurement objects> (x1) Surface resistance value when the first electrode layer 20 is "flat (in other words, no bending force is applied)" (x2) Surface resistance value when the first electrode layer 20 is bent so as to be convex (x3) Surface resistance value when the first electrode layer 20 is bent so as to be concave

[0066] The structure employed in this experiment corresponds to that shown in Figure 1. The first electrode layer 20 is formed through the following steps (S1) to (S2): (S1) In an environment not exposed to ultraviolet light, an acrylic resin dissolved in a solvent (specifically, propylene glycol monomethyl ether) is mixed with particles of silver (Ag) B1, particles of silver chloride A, and particles of silver (Ag) C1, silver (Ag) C2, or silver (Ag) B2, which correspond to each of the above-mentioned samples (SP1) to (SP3), and the mixture is then dispersed using a three-roll mill to form three types of mixtures corresponding to each of the above-mentioned samples (SP1) to (SP3). (S2) Thereafter, each of the three types of mixtures was applied onto the elastic layer 10 using a bar coater method, and a heating and drying process (solvent removal and film formation process) was carried out in which the mixture was heated to about 80°C using a commercially available drying oven (manufactured by Yamato Scientific Co., Ltd., model DNE600), so that the final thickness of the first electrode layer 20 corresponding to each of the samples (SP1) to (SP3) was adjusted to about 3 μm.

[0067] In this experiment, the surface resistance was measured when the first electrode layer 20 was flat and when the first electrode layer 20 was curved so as to be concave or convex. Fig. 12 is a schematic diagram showing a method for measuring the surface resistance of samples (SP1) to (SP3).

[0068] 12, the surface resistance values ​​of each of samples (SP1) to (SP3) were measured using a surface resistance meter (manufactured by Nitto Seiko Analytech Co., Ltd., Model Loresta GXII MCP-T710) when the two terminals were spaced apart by 157 mm. Note that the surface resistance value when the first electrode layer 20 was convex or concave was a value measured when the first electrode layer 20 was placed along the semicircular surface of a cylinder with a diameter of 100 mm and the two terminals were spaced apart by 157 mm.

[0069] Table 2 shows the measurement results of the surface resistance values ​​of samples (SP1) to (SP3) in three states (x1), (x2), and (x3). Note that the values ​​in parentheses in Table 2 represent the rate of increase in the surface resistance value when the first electrode layer 20 is convex or concave, with the surface resistance value when the first electrode layer 20 is flat taken as the reference.

[0070]

[0071] As shown in Table 2, regardless of whether the first electrode layer 20 is flat or convex or concave, the absolute values ​​of the first electrode layer 20 in samples (SP1) and (SP2) are significantly smaller than the absolute value of the first electrode layer 20 in sample (SP3).

[0072] In addition, it was very interesting to find that the difference (increase rate) between the surface resistance value when the first electrode layer 20 in sample (SP1) and sample (SP2) was flat and the surface resistance value when the first electrode layer 20 was convex or concave was significantly smaller than the aforementioned difference (increase rate) in sample (SP3).

[0073] The inventors do not believe that the surface resistance values ​​of sample (SP3) are so high as to cause the medical device of this modified example to lose its function. However, it is noteworthy that the absolute values ​​of the surface resistance values ​​of the first electrode layer 20 in samples (SP1) and (SP2) are low, and that the surface resistance values ​​are not easily affected by the shape (flat, convex, concave) of the first electrode layer 20, in other words, that fluctuations in the surface resistance values ​​due to changes in the shape are small.

[0074] Furthermore, as a result of further research and analysis, the inventors have found that when the silver (Ag) particles contained in the first electrode layer 20 have some or all of the following two types (EB1) to (EB2), the technical effect of this modification can be enhanced if the aspect ratio of the silver (Ag) particles is 10 or more and 240 or less (more preferably 15 or more and 100 or less). Specifically, the inventors have found that the inclusion of silver (Ag) particles having the above aspect ratio in the first electrode layer 20 can make it easier for at least one of the silver (Ag) particles to be partially embedded in the elastic layer 10, thereby increasing the conductivity of the first electrode layer 20 and significantly contributing to the ability to detect electrical signals (typically, biological signals) with high sensitivity. (EB1) Rod-shaped, needle-shaped, cone-shaped, or wire-shaped (EB2) Silver (Ag) covering a core material

[0075] <Other Modifications of First Embodiment> Incidentally, with regard to the flaky silver particles or the like in the above-described modifications, a suitable embodiment that can be adopted is that the thickness of the first electrode layer 20 is 2 μm or more (more preferably 3 μm or more, and even more preferably 3.5 μm or more), and that the mass ratio of the flaky silver particles or the like to the above-described silver chloride (AgCl) is 0.25 or more and 0.95 or less, when the total amount of the flaky silver particles or the like and the silver chloride (AgCl) is 1. The first electrode layer 20 having this characteristic can, for example, sensitively detect electrical signals (typically, biological signals) that may be generated by undulations, irregularities, and movement of rotations, flexions, or extensions on the surface of human skin when the medical device 100, 100a is placed so as to come into contact with the skin.

[0076] Similarly, the thickness of the first electrode layer 20 when silver covering the potassium titanate (particularly, silver covering the whisker-like potassium titanate) in the above-described modified example is employed is not limited, as is the thickness of the elastic layer 10, as long as the required conductivity for the medical device or the intended purpose can be exhibited. From the viewpoint of detecting electrical signals (typically, biological signals) with high sensitivity, the thickness is preferably 2 μm or more (more preferably 3 μm or more, and even more preferably 3.5 μm or more). Furthermore, a preferred embodiment is one in which the mass ratio of the silver covering the potassium titanate (particularly, the silver covering the whisker-like potassium titanate) to the total amount of the silver covering the potassium titanate (particularly, the silver covering the whisker-like potassium titanate) is 0.25 or more and 0.95 or less, when the total amount of the silver covering the potassium titanate (particularly, the silver covering the whisker-like potassium titanate) and the silver chloride (AgCl) is taken as 1. More specifically, one suitable embodiment that can be adopted is one in which the mass ratio of the total amount of the core material and the silver covering the core material (potassium titanate) (particularly the silver covering the whisker-like potassium titanate) is 0.25 or more and 0.95 or less, when the total amount of the silver covering the potassium titanate core material, the silver covering the core material (potassium titanate) (particularly the silver covering the whisker-like potassium titanate), and the above-mentioned silver chloride (AgCl) is 1. The first electrode layer 20 having this characteristic can, for example, sensitively detect electrical signals (typically, biological signals) that may be generated by undulations, irregularities, and movement of rotations, flexions, or extensions on the surface of human skin when the medical device 100 of this modified example or the medical device 100a of the modified example is placed in contact with the skin.

[0077] Furthermore, the silver in the first electrode layer 20 in the above-described modified example is silver covering flaky silver particles and / or potassium titanate, and the distribution of the silver in the thickness direction of the first electrode layer 20 is approximately (almost) uniform, which can also contribute to improving the conductivity of the first electrode layer 20 and, ultimately, the conductivity of the medical device 100, 100a.

[0078] In addition, the average particle size (D50) of silver chloride (AgCl) in the above-described modified example is, for example, from about 1 μm to about 6 μm (more narrowly, from about 1.5 μm to about 4.5 μm).

[0079] [Method of Manufacturing Medical Device of This Embodiment and Each Modification Thereof] Next, a method of manufacturing the medical device 100 of this embodiment and the medical device 100a of the modifications thereof will be described.

[0080] [Step of Forming Elastic Layer 10 Made of Conductive Polyurethane] First, a description will be given of a method for manufacturing the elastic layer 10. In order to incorporate the above-mentioned conductive material (typically, conductive carbon black) into the polyurethane that mainly serves as the base material of the elastic layer 10, a method can be employed in which a composition for forming the polyurethane (typically, an organic polyisocyanate, a polyol, and a catalyst) and the conductive material are mixed by mechanical stirring.

[0081] [Step of Forming First Electrode Layer 20] There are no particular limitations on the method for forming the first electrode layer 20 on one surface (first surface 12) of the elastic layer 10. For example, after dissolving the above-mentioned silver (Ag), silver chloride (AgCl), and resin (typically, the first resin) in a glycol-based or ketone-based solvent, various coating or printing methods such as screen printing, spin coating, roll coating, knife coating, reverse roll coating, bar coating, blade coating, and spray coating can be employed.

[0082] As an example, a method for forming the first electrode layer 20 on the elastic layer 10 will be specifically described. Fig. 3 is a configuration diagram showing a manufacturing apparatus 900 for part of the manufacturing process of the medical device 100 of this embodiment. The manufacturing apparatus 900 shown in Fig. 3 is an example of an apparatus for forming the first electrode layer 20 of approximately the same thickness on the elastic layer 10.

[0083] As shown in FIG. 3 , a manufacturing apparatus 900 according to an embodiment of the present invention employs a film-forming method known as a knife coating method. The manufacturing apparatus 900 includes a knife roll 93, a rotatable coating roll 92, and a storage unit 91 for storing a slurry 20a, which is a raw material for the first electrode layer 20 and is composed of silver (Ag), silver chloride (AgCl), and a resin (typically, a first resin) mixed in the solvent described above. According to the manufacturing apparatus 900, as indicated by the dotted arrow, a layer of the slurry 20a is formed on one surface (first surface 12) of the elastic layer 10, which is continuously fed by the rotation of the coating roll 92, by utilizing the gap between the knife roll 93 and the coating roll 92, which is set to form the first electrode layer 20 of a predetermined thickness. The slurry 20a is then subjected to a heating and drying process (solvent removal and film-forming process) to form the first electrode layer 20. The slurry 20a is supplied to the storage unit 91 in proportion to its consumption, as indicated by the open arrow.

[0084] In addition, when forming the first electrode layer 20 on the elastic layer 10 in the form of one or more islands as a part of the manufacturing process of the medical device 100a of variant example (1) of this embodiment, one possible embodiment is to use, for example, a screen printing method utilizing a high-precision screen mask instead of the knife coating method described above.

[0085] Second Embodiment A medical device 200 of this embodiment is similar to the medical device 100 of the first embodiment, except that the second electrode layer 30 is disposed uniformly and to approximately the same thickness so as to substantially cover the entire surface (second surface 14 in FIG. 2 ) of the elastic layer 10 different from the first surface 12 of the medical device 100 of the first embodiment. Therefore, descriptions that overlap with those of the first embodiment may be omitted.

[0086] Fig. 4 is a cross-sectional view showing the configuration of a medical device 200 of this embodiment. As shown in Fig. 4, the medical device 200 includes a first electrode layer 20 on one surface (first surface 12) of the elastic layer 10, and a second electrode layer 30 on the other surface (second surface 14) of the elastic layer 10. A typical example of the second electrode layer 30 is a layer made of silver (Ag).

[0087] The thickness of the layer made of silver (Ag) as the second electrode layer 30 is not limited as long as it does not substantially impair the flexibility and conformability of the elastic layer 10. From the viewpoint of preventing interference caused by external electromagnetic waves, significantly increasing the electrical conductivity of the medical device 100, particularly in the thickness direction of the elastic layer 10, and / or reducing the manufacturing cost of the medical device 200, it is a preferred embodiment that the thickness of the layer is 2 μm or more and 30 μm or less, more preferably 3 μm or more and 15 μm or less.

[0088] As another example of the second electrode layer 30, the material of the second electrode layer 30 or the material contained in the second electrode layer 30 is not limited as long as it does not substantially impair the conductivity of the elastic layer 10 and does not substantially impair the flexibility and conformability of the elastic layer 10. Therefore, for example, in another aspect of this embodiment, copper (Cu) or nickel (Ni) is used instead of the thin layer made of silver (Ag).

[0089] Third Embodiment The medical device 300 of this embodiment is similar to the medical device 200 of the second embodiment, except that a conductive gel layer 40 (e.g., a gel-like layer containing an alkali metal halide, such as sodium chloride (NaCl) or potassium chloride (KCl), as an electrolyte) is further disposed or formed on the first electrode layer 20 in the medical device 200 of the second embodiment. A medical device 300a of one modification of this embodiment is similar to the medical device 100 of the first embodiment, except that a conductive gel layer 40 is further disposed or formed on the first electrode layer 20 in the medical device 100 and medical device 100a of the first embodiment or its modifications. Therefore, descriptions that overlap with those of the first or second embodiment may be omitted.

[0090] Fig. 5 is a cross-sectional view showing the configuration of a medical device 300 of this embodiment. Fig. 6 is a cross-sectional view showing the configuration of a medical device 300a of one modified example of this embodiment.

[0091] First, as shown in Figures 5 and 6, medical devices 300, 300a have a configuration in which a conductive gel layer 40 (for example, the conductive gel disclosed in Japanese Patent Laid-Open No. 06-181894) is disposed on a first electrode layer 20.

[0092] It is a preferred embodiment to use a physiologically acceptable (particularly suitable for contact with human skin) self-adhesive conductive gel as the conductive gel layer 40. It is also a preferred embodiment to use a physiologically acceptable (particularly suitable for contact with human skin) conductive gel that removably adheres to human skin as the conductive gel layer 40. The above-mentioned self-adhesive conductive gel or detachable conductive gel can serve as the conductive adhesive portion of the medical device.

[0093] In addition, in one example of this embodiment, similar to the formation of the first electrode layer 20, the conductive gel layer 40 can be arranged on the first electrode layer 20 by employing various coating methods, laminating methods, transfer methods, pasting methods, or printing methods.

[0094] In the medical devices 300 and 300a, the first electrode layer 20 described in the first embodiment employs at least one selected from the group consisting of the flake-shaped silver particles and the silver coated with whisker-like potassium titanate. This results in a more accurate formation of irregularities on the surface of the first electrode layer 20, even if silver chloride (AgCl) were in a roughly spherical or other granular form, compared to roughly spherical silver (Ag) particles. In particular, the use of silver coated with whisker-like potassium titanate results in a more accurate formation of irregularities on the surface of the first electrode layer 20, i.e., a greater number of irregularities with large height differences. As a result, the area of ​​contact between the conductive gel layer 40 and human skin is substantially increased.

[0095] As a result, the surface area of ​​the first electrode layer 20 as a whole is substantially increased, making it easier to perform electrolysis within the conductive gel layer 40, i.e., convert ion signals into electronic signals, which is a preferred aspect as it makes it possible to acquire even weaker biological signals with high accuracy.

[0096] Furthermore, since the first electrode layer 20 contains at least one type selected from the group consisting of the flake-like silver particles and the silver covering the whisker-like potassium titanate (particularly silver covering the whisker-like potassium titanate), it is possible to use a conductive gel that is less irritating to the skin, and therefore the elderly, children, women, or patients with sensitive skin can continue to use it for relatively long periods of time.

[0097] The disclosure of the above-mentioned embodiments and examples has been provided for the purpose of explaining the embodiments and examples, and is not intended to limit the present invention. In addition, other modifications within the scope of the present invention, including other combinations of the embodiments and examples, are also included in the scope of the claims.

[0098] The medical device of the present invention can be widely applied to medical purposes.

[0099] REFERENCE SIGNS LIST 10 Elastic layer 12 First surface 14 Second surface 20 First electrode layer 20a Slurry 30 Second electrode layer 40 Conductive gel layer 91 Storage section 92 Coating roll 93 Knife roll 100, 100a, 200, 300, 300a Medical device 900 Manufacturing apparatus for part of the manufacturing process of a medical device

Claims

1. A medical device comprising an elastic layer made of conductive polyurethane and a first electrode layer containing silver, silver chloride, and resin on at least a portion of a first surface of the elastic layer, wherein an electric current can be passed between the surface of the first electrode layer and the second surface of the elastic layer.

2. The medical device according to claim 1, wherein the silver is silver covering at least a portion of a core material, the aspect ratio of the core material or the silver covering at least a portion of the core material is 10 or more and 240 or less, and at least one portion of the silver covering at least a portion of the core material is buried in the elastic layer.

3. The medical device according to claim 1, wherein the silver comprises silver particles having an aspect ratio of 3 to 100, and at least one of the silver particles is partially embedded in the elastic layer.

4. The medical device according to claim 2, wherein the core material is at least one selected from the group consisting of potassium titanate, titanium oxide, zinc oxide, aluminum oxide, silicon oxide, carbon fiber, and metal wire (excluding silver).

5. The medical device according to any one of claims 1 to 3, further comprising a second electrode layer made of silver on at least a portion of the other second surface of the elastic layer.

6. The medical device according to any one of claims 1 to 3, wherein the first electrode layer further comprises an adhesive portion for removably adhering to the skin.

7. The medical device according to claim 2, wherein the thickness of the first electrode layer is 2 μm or more and 30 μm or less, and the mass ratio of the total amount of the core material and the silver covering at least a portion of the core material to the total amount of the core material, the silver covering at least a portion of the core material, and the silver chloride is 0.25 or more and 0.95 or less, when the total amount of the core material, the silver covering at least a portion of the core material, and the silver chloride is 1.

8. The medical device according to claim 2, wherein the distribution of the core material and the silver covering at least a portion of the core material in the thickness direction of the first electrode layer is not localized.

9. The medical device according to any one of claims 1 to 3, wherein the elastic layer has a tensile elongation of 50% or more.

10. The medical device according to any one of claims 1 to 3, wherein the elastic layer has a glass transition temperature (Tg) of less than 70°C.

Images