Guide wire and manufacturing method of guide wire

Abstract

To provide a guide wire having a core wire having an excellent tensile strength while maintaining a high flexibility at a tip part and a high rigidity at a base end part of the core wire.SOLUTION: A guide wire includes a core wire. The core wire includes: a first wire made of a nickel titanium alloy; and a second wire with a tip end thereof being bonded to a base end of the first wire and made of a cobalt-chromium alloy. In a vertical cross-section including a bonding face between the first wire and the second wire, the core wire includes a projection that projects toward the tip end of the core wire from the bonding face. The projection is made of an alloy containing at least one element composing the nickel titanium alloy and at least one element composing the cobalt-chromium alloy.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] TECHNICAL FIELD The technology disclosed herein relates to guidewires and methods of making guidewires. [Background technology]

[0002] In a guidewire to be inserted into a biological lumen such as a blood vessel, a technique has been proposed in which a core wire is formed by joining two wires made of different materials to increase the flexibility of the distal end of the core wire and the rigidity of the proximal end of the core wire. For example, Patent Document 1 discloses a guidewire in which a distal wire made of a relatively flexible Ni-Ti alloy and a proximal wire made of a relatively hard Co-Cr-Ni alloy are joined together to form a core wire. Patent Document 1 also describes that when different metal materials are joined together through a thermal history that melts the metal materials, an intermetallic compound is formed at the joint between the two, making the joint brittle, and therefore the thickness of the joint between the distal wire and the proximal wire is preferably 1 μm or less. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-113267 A Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, the tensile strength of the core wire constituting the guidewire was not sufficiently considered, and there was room for improvement. The technology disclosed in this specification aims to provide a guidewire having a core wire with excellent tensile strength while ensuring high flexibility at the tip end and high rigidity at the base end of the core wire.

[0005] This specification discloses a technique that can solve the above-mentioned problems. [Means for solving the problem]

[0006] The technology disclosed in this specification can be realized, for example, in the following forms.

[0007] (1) The guidewire disclosed in the present specification includes a core wire. The core wire includes a first wire made of a nickel-titanium alloy and a second wire made of a cobalt-chromium alloy, the tip of which is joined to the base end of the first wire. In a longitudinal section including a joining surface between the first wire and the second wire, the core wire has a protrusion that protrudes from the joining surface toward the tip side of the core wire. The protrusion is made of an alloy including at least one element constituting the nickel-titanium alloy and at least one element constituting the cobalt-chromium alloy.

[0008] Conventionally, it was believed that when different metal materials are joined through a thermal history that melts each metal material, an intermetallic compound is formed at the joint between the two, making the joint brittle and reducing the joint strength. However, the present inventors have conducted intensive research and have newly discovered that when the core wire has a protrusion made of an alloy containing at least one element constituting the nickel-titanium alloy, which is the material for forming the first wire, and at least one element constituting the cobalt-chromium alloy, which is the material for forming the second wire, at the joint between the first wire and the second wire, the tensile strength of the joint is improved. This is believed to be because the protrusion partially penetrates into the nickel-titanium alloy side, increasing the contact area and generating an anchor effect. Therefore, according to this guide wire, it is possible to provide a guide wire having a core wire with excellent tensile strength while ensuring high flexibility at the tip end (the part formed by the first wire) and high rigidity at the base end (the part formed by the second wire).

[0009] (2) In the above guidewire, the core wire may have the protrusions, which have a length of 2 μm or more along the axial direction of the core wire in the longitudinal cross section. By adopting this configuration, the anchor effect of the protrusions can be increased, and the tensile strength of the core wire can be effectively improved.

[0010] (3) In the above guidewire, the alloy constituting the protrusions may contain Ni, Ti, Co, and Cr. By adopting this configuration, it is possible to improve the bond between the protrusions and the nickel-titanium alloy and the cobalt-chromium alloy, and it is possible to further effectively improve the tensile strength of the core wire.

[0011] (4) In the above guidewire, the core wire may have the protrusions such that, in the longitudinal cross section, the contour of the protrusions includes a portion that extends toward the outer periphery of the protrusions as it approaches the distal end of the core wire. By adopting this configuration, the anchor effect of the protrusions can be further increased, and the tensile strength of the core wire can be further effectively improved.

[0012] (5) In the above guidewire, the core wire may have two or more protrusions that are substantially not continuous with each other in the longitudinal cross section due to the alloy constituting the protrusions. By adopting this configuration, the tensile strength of the core wire can be further effectively improved by the presence of two or more protrusions that are substantially not continuous with each other.

[0013] (6) In the above guidewire, the alloy constituting the protrusions may be harder than the nickel-titanium alloy and the cobalt-chromium alloy, and this configuration can increase the anchor effect by the relatively hard protrusions, thereby more effectively improving the tensile strength of the core wire.

[0014] (7) A method for producing a guidewire disclosed in this specification includes the steps of controlling the roughness of an end face of a first wire made of a nickel-titanium alloy so that the arithmetic mean height Sa is 0.01 μm or more and 0.5 μm or less, and butting the end face of the first wire and the end face of a second wire together to join them, thereby producing a core wire including the first wire and the second wire. According to this method for producing a guidewire, a protrusion can be formed at the joint between the first wire and the second wire, and a guidewire having a core wire with excellent tensile strength can be produced.

[0015] The techniques disclosed in this specification can be realized in various forms, for example, in the form of a guidewire, a medical system including a guidewire, a manufacturing method thereof, etc. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is an explanatory diagram illustrating a schematic configuration of a guidewire 100 according to an embodiment of the present invention. [Diagram 2] FIG. 1 is an explanatory diagram showing a configuration of a joint portion X1 between a first wire 11 and a second wire 12. [Diagram 3] FIG. 1 is an explanatory diagram showing a configuration of a joint portion X1 between a first wire 11 and a second wire 12. [Figure 4] Flowchart showing an example of a method for manufacturing the guidewire 100 [Diagram 5] FIG. 1 is an explanatory diagram showing an example and a comparative example of the core wire 10 constituting the guide wire 100. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] A. Embodiment: A-1. Configuration of guidewire 100: FIG. 1 is an explanatory diagram that shows a schematic configuration of a guidewire 100 in this embodiment. FIG. 1 shows a longitudinal section (YZ section) of the guidewire 100. In FIG. 1, the positive Z-axis direction side is the tip end side (distal side) that is inserted into the body, and the negative Z-axis direction side is the base end side (proximal side) that is operated by an operator such as a doctor. In FIG. 1, a part of the guidewire 100 is omitted. Also, FIG. 1 shows a state in which the central axis AX of a core wire 10 of the guidewire 100, which will be described later, is linear and parallel to the Z-axis direction, but the guidewire 100 has flexibility to the extent that it can be curved. These points are the same in the subsequent figures.

[0018] In this specification, the distal end of the guidewire 100 and each of its constituent members is referred to as the "distal end," the distal end and its vicinity are referred to as the "distal portion," the proximal end is referred to as the "proximal end," and the proximal end and its vicinity are referred to as the "proximal portion." Additionally, the outer diameter of the guidewire 100 and each of its constituent members refers to the size along a direction perpendicular to the central axis AX. Additionally, the longitudinal cross section of the guidewire 100 and each of its constituent members refers to a cross section including the central axis AX, and the transverse cross section of the guidewire 100 and each of its constituent members refers to a cross section perpendicular to the central axis AX.

[0019] The guidewire 100 is a medical device that is inserted into a biological lumen such as a blood vessel. The guidewire 100 is used, for example, to guide another medical device such as a catheter to a desired position in a biological lumen. The total length of the guidewire 100 is, for example, about 1500 mm to 2000 mm.

[0020] The guidewire 100 includes a core wire 10, a coil body 20, a distal joint portion 30, and a proximal joint portion 40. At least a portion of the guidewire 100 may be coated with, for example, a hydrophilic resin.

[0021] The core wire 10 is an elongated member extending along the central axis AX and is made of a metal wire. The core wire 10 has a first wire 11 made of a nickel-titanium alloy and a second wire 12 made of a cobalt-chromium alloy. The tip of the second wire 12 is joined to the base end of the first wire 11, for example, by welding. The distance from the tip of the core wire 10 to the joint X1 between the first wire 11 and the second wire 12 along the central axis AX is, for example, about 50 mm to 500 mm. In this embodiment, the joint X1 between the first wire 11 and the second wire 12 is located on the base end side relative to the base end of the coil body 20. The configuration of the joint X1 between the first wire 11 and the second wire 12 will be described in detail later.

[0022] The nickel-titanium alloy, which is the material for forming the first wire 11, is an alloy containing at least Ni and Ti. The nickel-titanium alloy is a softer material than the cobalt-chromium alloy, which is the material for forming the second wire 12. The nickel-titanium alloy preferably contains 40% by mass or more and 60% by mass or less of Ni and 40% by mass or more and 60% by mass or less of Ti.

[0023] The cobalt chromium alloy, which is the material for forming the second wire 12, is an alloy containing at least Co and Cr. The cobalt chromium alloy is, for example, a Co-Ni-Cr alloy, a Co-Cr-Ni-Mo alloy, a Co-Cr-W-Ni alloy, a Co-Cr-Mo alloy, a Co-Ni-Cr-Mo-W-Fe alloy, or the like. The cobalt chromium alloy is preferably an alloy containing at least Co, Cr, and Ni. For example, the cobalt chromium alloy is preferably an alloy having a composition of 9-40 mass% Ni-10-30 mass% Cr-balance Co, or an alloy having a composition in which a part of the balance Co in the composition is replaced with another element. The content of Co may be, for example, 20-78 mass%. When the cobalt chromium alloy contains elements other than Co, Cr, and Ni, the total content of the elements other than Co, Cr, and Ni is preferably 30 mass% or less. It is also preferable to include Mo as an element other than Co, Cr, and Ni, and the content of Mo is, for example, 3-15 mass%.

[0024] As shown in FIG. 1, the first wire 11 has a thin diameter portion 13, a tapered portion 14, and a thick diameter portion 15. The thin diameter portion 13 is a portion including the tip of the core wire 10. The thick diameter portion 15 is located on the proximal side of the thin diameter portion 13. The outer diameter of the thick diameter portion 15 is larger than the outer diameter of the thin diameter portion 13, for example, about 0.1 mm to 1.0 mm. The tapered portion 14 is located between the thin diameter portion 13 and the thick diameter portion 15. The outer diameter of the tapered portion 14 gradually increases from the boundary position with the thin diameter portion 13 toward the boundary position with the thick diameter portion 15. The second wire 12 has a substantially constant outer diameter. The outer diameter of the second wire 12 is substantially the same as the outer diameter of the thick diameter portion 15 of the first wire 11. The cross-sectional shape at each position of the core wire 10 may be any shape, for example, a circle or a rectangle.

[0025] The coil body 20 is a hollow cylindrical coil-shaped member in which one or more wires are wound in a spiral shape. Each wire constituting the coil body 20 may be composed of a single wire, or may be a twisted wire in which a plurality of wires are twisted together. The coil body 20 is disposed so as to surround the outer periphery of the tip portion of the core wire 10 (specifically, the thin-diameter portion 13, the tapered portion 14, and a part of the thick-diameter portion 15 of the first wire 11). The total length of the coil body 20 is, for example, about 10 mm to 500 mm, and the outer diameter of the coil body 20 is, for example, about 0.2 mm to 1.2 mm.

[0026] The coil body 20 may be made of a radiotransparent material such as stainless steel (SUS302, SUS304, SUS316, etc.), Ni-Ti alloy, or piano wire, or a radiopaque material such as platinum, gold, tungsten, or an alloy of these metals.

[0027] The distal joint 30 (distal tip) joins the distal end of the core wire 10 and the distal end of the coil body 20. The distal outer peripheral surface of the distal joint 30 is a smooth surface (e.g., a substantially hemispherical surface). The proximal joint 40 joins the core wire 10 and the proximal end of the coil body 20. Examples of materials that can be used to form the distal joint 30 and the proximal joint 40 include metal solder (Au-Sn alloy, Sn-Ag alloy, Sn-Pb alloy, Pb-Ag alloy, etc.), brazing material (aluminum alloy brazing, silver brazing, gold brazing, etc.), adhesive (epoxy adhesive, etc.), etc.

[0028] Next, a detailed configuration of the joint X1 between the first wire 11 and the second wire 12 of the core wire 10 will be described. Figures 2 and 3 are explanatory diagrams showing the configuration of the joint X1 between the first wire 11 and the second wire 12. Figure 2 shows an SEM photograph (1000x) of a vertical cross section of the joint X1 between the first wire 11 and the second wire 12, and Figure 3 shows a schematic configuration of the joint X1.

[0029] As shown in Figures 2 and 3, the core wire 10 has multiple projections 16 that protrude from the joint surface S1 between the first wire 11 and the second wire 12 toward the tip side of the core wire 10 (the side of the first wire 11).

[0030] The protrusion 16 is made of an alloy containing at least one element constituting the nickel-titanium alloy which is the material for forming the first wire 11, and at least one element constituting the cobalt-chromium alloy which is the material for forming the second wire 12. The alloy constituting the protrusion 16 is preferably an alloy containing Ni, Ti, Co, and Cr. The alloy constituting the protrusion 16 may be, for example, an alloy in which the elements constituting the nickel-titanium alloy are solid-dissolved in the crystal structure of the cobalt-chromium alloy, or conversely, an alloy in which the elements constituting the cobalt-chromium alloy are solid-dissolved in the crystal structure of the nickel-titanium alloy, or an intermetallic compound composed of the elements constituting the nickel-titanium alloy and the cobalt-chromium alloy. The content of Ni in the alloy constituting the protrusion 16 is preferably higher than the content of Ni in the cobalt-chromium alloy. The composition of the alloy constituting the protrusion 16 can be confirmed by composition analysis using EDX (Energy Dispersive X-ray Spectroscopy).

[0031] The alloy constituting the protrusion 16 is preferably a material harder than the nickel-titanium alloy and the cobalt-chromium alloy. The hardness of each alloy is measured, for example, by measuring the nanoindentation hardness with a diamond Berkovich indenter using a nanoindenter (iMicro) manufactured by KLA Corporation under the condition of a maximum indentation load of 30 mN.

[0032] It is considered that the core wire 10 has the protrusions 16 at the joint X1 between the first wire 11 and the second wire 12, and the protrusions 16 partially penetrate into the nickel-titanium alloy side, thereby increasing the contact area with the nickel-titanium alloy and generating an anchor effect, thereby improving the tensile strength at the joint X1 between the first wire 11 and the second wire 12. From the viewpoint of effectively improving the tensile strength at the joint X1, the core wire 10 preferably has the protrusions 16 with a length L of 2 μm or more, more preferably has the protrusions 16 with a length L of 3 μm or more, and further preferably has the protrusions 16 with a length L of 5 μm or more. In addition, since the protrusions 16 can be the starting point of fracture, the core wire 10 preferably does not have the protrusions 16 with a length L of more than 100 μm, and more preferably does not have the protrusions 16 with a length L of more than 50 μm.

[0033] The length L of the protrusion 16 is the length along the direction of the central axis AX of the core wire 10. The length L of the protrusion 16 is specified as follows. A surface analysis of the composition by EDX is performed on the longitudinal section of the core wire 10, and the interface at which an element (e.g., Ti) contained in the nickel-titanium alloy is not detected for the first time when moving from the first wire 11 along the central axis AX to the base end side is defined as the joint surface S1. For each protrusion 16, the interface at which an element (e.g., Co) contained in the cobalt-chromium alloy is not detected for the first time when moving from the joint surface S1 along the central axis AX to the tip end side is defined as the boundary surface between the protrusion 16 and the nickel-titanium alloy. The length along the central axis AX from the joint surface S1 to the boundary surface is defined as the length L of the protrusion 16.

[0034] In addition, in this specification, among the convex portions protruding from the joint surface S1 between the first wire 11 and the second wire 12 toward the tip side, the portion in which the ratio of width W to length L (W / L) is 3.0 or more (a very gentle convex portion) is not considered to be a protrusion 16.

[0035] Fig. 3 shows examples of the shapes of the protrusion 16. The protrusion 16a shown in Fig. 3 does not include a portion where the contour line 18 extends toward the outer periphery of the protrusion 16 as it approaches the tip side (left side in the figure) of the core wire 10. On the other hand, the protrusions 16b, 16c, and 16d shown in Fig. 3 include a portion where the contour line 18 extends toward the outer periphery of the protrusion 16 as it approaches the tip side of the core wire 10 (hereinafter referred to as a "returned portion 18X"). In order to generate a strong anchor effect by the protrusion 16, it is preferable that the core wire 10 has a protrusion 16 whose contour line 18 includes the turned portion 18X.

[0036] The core wire 10 preferably has two or more protrusions 16 that are not substantially continuous with each other in the longitudinal section due to the alloy constituting the protrusions 16. In this specification, the fact that the two protrusions 16 are not substantially continuous with each other due to the alloy means that the thickness of the alloy layer between the two protrusions 16 is 1 μm or less. That is, the configuration in which the two protrusions 16 are not substantially continuous with each other due to the alloy includes a form in which the alloy layer is not present between the two protrusions 16, as well as a form in which the alloy layer is present between the two protrusions 16 but has a thickness of 1 μm or less. The thickness of the alloy layer between the two protrusions 16 is preferably 0.5 μm or less.

[0037] A-2. Method of manufacturing guidewire 100: The guidewire 100 of this embodiment can be manufactured, for example, by the following method. Fig. 4 is a flow chart showing an example of a method for manufacturing the guidewire 100.

[0038] First, a first wire 11 made of a nickel-titanium alloy is prepared, and the roughness of the end face on the base end side of the first wire 11 is controlled (S110). More specifically, the arithmetic mean height Sa of the end face on the base end side of the first wire 11 is set to 0.01 μm or more and 0.5 μm or less. The control of the surface roughness can be realized by, for example, polishing, blasting, plating, etching, electrolytic polishing, thermal spraying, etc. For example, the roughness of the end face of the first wire 11 can be controlled by performing a polishing process using an abrasive. At this time, polishing with a fine-grained abrasive may be performed, and then polishing with a coarse-grained abrasive may be performed. In addition, the control of the roughness of the end face of the first wire 11 may be performed simultaneously with the cutting process of the first wire 11. For example, the cutting process of the first wire 11 and the polishing process of the end face may be performed simultaneously using a cutting machine capable of simultaneously performing cutting and polishing of the wire.

[0039] Next, the tip of the second wire 12 is joined to the base end of the first wire 11 to prepare the core wire 10 (S120). For example, the first wire 11 and the second wire 12 are held by a pair of left and right clamps so that the end face of the base end side of the first wire 11 and the end face of the tip side of the second wire 12 face each other. At this time, the clamps hold the first wire 11 and the second wire 12 at positions a predetermined distance away from each end face. The clamps are moved in a direction approaching each other to butt the end face of the base end side of the first wire 11 and the end face of the tip side of the second wire 12 together. One of the pair of left and right clamps is fixed and the other clamp is made movable relative to the fixed clamp, so that the end faces of the first wire 11 and the second wire 12 can be butted together with high precision. Next, the first wire 11 and the second wire 12 held by the clamps are energized (heated) while being pressurized. The current conditions (current, time, etc.) are appropriately selected so that at least one of the end faces of the first wire 11 and the second wire 12 melts. The end faces of the first wire 11 and the second wire 12 may melt entirely or partially. By applying pressure to the first wire 11 and the second wire 12 while applying current, the end faces of both wires soften and melt, and the end faces of both wires are deformed so as to expand toward the outer periphery by pressing against each other, and the end faces of both wires are joined together. By joining in this manner, the above-mentioned protrusion 16 is formed at the joint X1 between the first wire 11 and the second wire 12.

[0040] Thereafter, other members are attached to the core wire 10 (S130). For example, the coil body 20 is joined to the core wire 10. The guide wire 100 of this embodiment can be produced mainly through the above steps.

[0041] The length L of the projection 16 formed can be adjusted by adjusting the roughness of the end face on the base end side of the first wire 11. For example, polishing the end face of the first wire 11 with coarse sandpaper tends to shorten the length L of the projection 16, whereas polishing with fine sandpaper tends to lengthen the length L of the projection 16.

[0042] A-3. Advantages of this embodiment: As described above, the guide wire 100 of this embodiment includes the core wire 10. The core wire 10 includes the first wire 11 made of a nickel-titanium alloy, and the second wire 12 made of a cobalt-chromium alloy and whose tip is joined to the base end of the first wire 11. The core wire 10 has a protrusion 16 in a longitudinal section including a joining surface S1 between the first wire 11 and the second wire 12. The protrusion 16 is a portion that protrudes from the joining surface S1 toward the tip side of the core wire 10, and is made of an alloy containing at least one element constituting the nickel-titanium alloy that is the material for forming the first wire 11, and at least one element constituting the cobalt-chromium alloy that is the material for forming the second wire 12.

[0043] Conventionally, it was believed that when different metal materials are joined through a thermal history that melts each metal material, an intermetallic compound is formed at the joint between the two, making the joint brittle and reducing the joint strength. However, the inventor of the present application conducted intensive research and newly found that when the core wire 10 has a protrusion 16 made of an alloy containing at least one element constituting the nickel-titanium alloy that is the material for forming the first wire 11 and at least one element constituting the cobalt-chromium alloy that is the material for forming the second wire 12 at the joint X1 between the first wire 11 and the second wire 12, the tensile strength of the joint X1 is improved. This is believed to be because the protrusion 16 partially penetrates into the nickel-titanium alloy side, increasing the contact area and generating an anchor effect. Therefore, according to the guide wire 100 of this embodiment, it is possible to provide a guide wire 100 having a core wire 10 with excellent tensile strength while ensuring high flexibility of the tip end (the part formed by the first wire 11) of the core wire 10 and high rigidity of the base end (the part formed by the second wire 12).

[0044] Furthermore, in the guidewire 100 of this embodiment, the core wire 10 preferably has, in the longitudinal section, the projections 16 having a length L of 2 μm or more along the direction of the central axis AX of the core wire 10. By adopting such a configuration, the anchor effect of the projections 16 can be increased, and the tensile strength of the core wire 10 can be effectively improved.

[0045] In the guidewire 100 of the present embodiment, the alloy constituting the projections 16 preferably contains Ni, Ti, Co, and Cr. By adopting such a configuration, it is possible to improve the bondability between the projections 16 and the nickel-titanium alloy and the cobalt-chromium alloy, and it is possible to further effectively improve the tensile strength of the core wire 10.

[0046] In the guidewire 100 of this embodiment, the core wire 10 preferably has, in the longitudinal section, the protrusions 16 including return portions 18X in which the contour lines 18 of the protrusions 16 extend toward the outer periphery of the protrusions 16 as they approach the distal end of the core wire 10. By adopting such a configuration, the anchor effect of the protrusions 16 can be further increased, and the tensile strength of the core wire 10 can be further improved effectively.

[0047] Furthermore, in the guidewire 100 of this embodiment, the core wire 10 preferably has, in the longitudinal section, two or more protrusions 16 that are substantially discontinuous with each other due to the alloy that constitutes the protrusions 16. By adopting such a configuration, the tensile strength of the core wire 10 can be further effectively improved by the presence of two or more protrusions 16.

[0048] In the guidewire 100 of this embodiment, the alloy constituting the protrusions 16 is preferably a material harder than a nickel-titanium alloy and a cobalt-chromium alloy. By adopting such a configuration, the anchor effect of the relatively hard protrusions 16 can be increased, and the tensile strength of the core wire 10 can be further effectively improved.

[0049] The method for producing the guidewire 100 of this embodiment includes a step of controlling the roughness of the end face of the first wire 11 made of a nickel-titanium alloy so that the arithmetic mean height Sa is 0.01 μm or more and 0.5 μm or less, and a step of butting the end face of the first wire 11 and the end face of the second wire 12 and joining them to produce a core wire 10 including the first wire 11 and the second wire 12. According to the method for producing the guidewire 100 of this embodiment, the protrusion 16 can be formed at the joint X1 between the first wire 11 and the second wire 12, and the guidewire 100 including the core wire 10 having excellent tensile strength can be produced. EXAMPLES

[0050] FIG. 5 is an explanatory diagram showing an example and a comparative example of the core wire 10 constituting the guide wire 100. When producing the core wire 10 of the example and the comparative example, a nickel-titanium alloy wire having a diameter of 0.42 mm (composition (mass%): Ni: 56.1%, C: 0.032%, O: 0.025%, Ti: remainder) was prepared as the first wire 11, and a cobalt-chromium alloy wire having a diameter of 0.42 mm (composition (mass%): Cr: 20%, Ni: 36.5%, Mo: 10%, Mn: <0.01%, C: 0.002%, Co: remainder) was prepared as the second wire 12. The end surface of the nickel-titanium alloy wire was polished with an abrasive having a grain size shown in FIG. 5 to obtain a nickel-titanium alloy wire having an end surface with a surface roughness (arithmetic mean height Sa) shown in FIG. 5. Thereafter, the first wire 11 and the second wire 12 were joined together by the method described in the above embodiment to prepare a core wire 10, and the tensile strength of the core wire 10 was evaluated. To evaluate the tensile strength of the core wire 10, a sample was set with a chuck interval of 100 mm and the joint was located at the center, and the breaking load was measured when the sample was pulled at a speed of 10 mm / min. In addition, the core wire 10 prepared under the same conditions was cut along a plane passing through the central axis AX of the core wire 10 to represent a longitudinal section, and the longitudinal section was observed with a scanning electron microscope (SEM) to confirm the presence or absence of a protrusion 16 at the joint X1 between the first wire 11 and the second wire 12, and to measure the length L of the protrusion 16.

[0051] 5, in Examples 1 to 3 in which the protrusions 16 were found at the joint X1 between the first wire 11 and the second wire 12 of the core wire 10, the breaking load of the core wire 10 was relatively high at 168.4 N or more. On the other hand, in the Comparative Example in which the protrusions 16 were not found at the joint X1 between the first wire 11 and the second wire 12 of the core wire 10, the breaking load was relatively low at 155.3 N. In Examples 1 to 3, it is considered that the protrusions 16 formed at the joint X1 between the first wire 11 and the second wire 12 of the core wire 10 partially penetrate into the nickel-titanium alloy side, thereby increasing the contact area and generating an anchor effect, thereby improving the tensile strength of the core wire 10.

[0052] B. Variations: The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0053] In the above embodiment, the core wire 10 is composed of the first wire 11 and the second wire 12, but the core wire 10 may also have another wire arranged on the proximal side of the second wire 12.

[0054] In the above embodiment, the core wire 10 has multiple protrusions 16, but the core wire 10 may have a single protrusion 16.

[0055] In the above embodiment, the joint X1 between the first wire 11 and the second wire 12 of the core wire 10 is located closer to the base end than the base end of the coil body 20, but the joint X1 may also be located closer to the tip end than the base end of the coil body 20.

[0056] The materials of the components in the above embodiment are merely examples and may be modified in various ways. Furthermore, the method of manufacturing the guidewire 100 in the above embodiment is merely an example and may be modified in various ways. [Explanation of symbols]

[0057] 10: Core wire 11: First wire 12: Second wire 13: Thin section 14: Tapered section 15: Thick section 16: Projection 18: Contour line 18X: Returned section 20: Coil body 30: Distal joint 40: Base joint 100: Guide wire AX: Central axis S1: Joint surface X1: Joint

Claims

1. A guidewire, A core wire includes a first wire made of a nickel-titanium alloy and a second wire made of a cobalt-chromium alloy, the second wire having a distal end joined to the proximal end of the first wire; A guide wire in which the core wire has, in a longitudinal section including the joint surface between the first wire and the second wire, a protrusion protruding from the joint surface toward the tip side of the core wire and made of an alloy containing at least one element constituting the nickel-titanium alloy and at least one element constituting the cobalt-chromium alloy.

2. 2. The guidewire of claim 1, The core wire has the protrusions, the length of which along the axial direction of the core wire is 2 μm or more in the longitudinal cross section.

3. The guide wire according to claim 1 or 2, A guide wire, wherein the alloy constituting the protrusions includes Ni, Ti, Co and Cr.

4. The guide wire according to claim 1 or 2, The core wire has the protrusion such that, in the longitudinal cross section, the contour line of the protrusion includes a portion that extends toward the outer periphery of the protrusion as it approaches the tip side of the core wire.

5. The guide wire according to claim 1 or 2, A guidewire, wherein the core wire has two or more protrusions that are substantially not continuous with each other in the longitudinal cross section due to the alloy that constitutes the protrusions.

6. The guide wire according to claim 1 or 2, A guide wire, wherein the alloy constituting the protrusion is a material harder than the nickel-titanium alloy and the cobalt-chromium alloy.

7. A method for manufacturing a guidewire, comprising: a step of controlling the roughness of the end surface of the first wire made of nickel-titanium alloy so that the arithmetic mean height Sa is 0.01 μm or more and 0.5 μm or less; a step of butting the end surface of the first wire and an end surface of a second wire together to form a core wire having the first wire and the second wire; A method for manufacturing a guidewire, comprising:

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