Guide wire and method for producing same

Abstract

Provided are a guide wire having high torque transmission and rotational operability while being pushable by a core wire containing stainless steel and able to support a catheter, and a method for producing the same.　In a guide wire (10) provided with a long core wire (20), the core wire (20) contains stainless steel containing 6.0-8.0 wt% of nickel and having a processing-induced martensite phase of 84 vol% or more.

Description

Guide wire and method for manufacturing the same

[0001] The present invention relates to a guide wire to be inserted into a lumen such as a blood vessel, and a method for manufacturing the same

[0002] A guide wire is a device inserted into a blood vessel to guide a catheter or stent for intravascular treatment to a target position

[0003] An operator first inserts a guide wire into a blood vessel and passes the distal end portion of the guide wire through a stenotic site of the blood vessel. Next, the operator inserts a catheter along the guide wire to the stenotic site to perform diagnosis and treatment. For this reason, guide wires are required to have properties such as vessel selectivity at vessel bifurcations, passability through stenotic sites, pushability, and torque transmissibility

[0004] As a material for forming the core wire of a guide wire, austenitic stainless steel with high rigidity is used from the viewpoint of excellent pushability and high catheter supportability (see, for example, Patent Document 1)

[0005] In recent years, procedures have been performed to treat lesions in blood vessels of the lower extremity region by inserting a device into a blood vessel through the radial artery. In such procedures, since the distance from the insertion position of the device into the blood vessel to the lesion position is long, a longer guide wire than conventional ones is required

[0006] Japanese Patent Laid-Open No. 2024-89900

[0007] For a long guide wire used in a procedure for treating a lesion in a blood vessel of the lower extremity region that is inserted into a blood vessel through the radial artery, the length from the position operated by the operator to the distal end is also long, so that the pushing force and rotation operation applied by the operator on the proximal end side are less likely to be transmitted to the distal end of the guide wire. In addition, in the above-mentioned procedure, the guide wire is located in a sharply bent blood vessel such as the junction between the subclavian artery and the aortic arch or the iliac artery. In this case, if the stainless steel used for the core wire undergoes plastic deformation, the guide wire will develop a bending habit, resulting in decreased torque transmissibility and an increased load required for rotation

[0008] The present invention was made to solve the above-mentioned problems, and aims to provide a guide wire and a method for manufacturing the same that have high torque transmission and rotational operability, while also possessing pushability and catheter support due to a core wire containing stainless steel.

[0009] The above objective is achieved by the invention described in (1) below.

[0010] (1) The guide wire according to the present invention is a guide wire having a long core wire, wherein the core wire contains stainless steel having 6.0 wt% to 8.0 wt% nickel and a processing-induced martensite phase of 84 vol% or more.

[0011] The guidewire described in (1) above uses stainless steel with a low nickel content for the core wire, which allows for the inclusion of a large amount of work-induced martensite phase through processing, thus making it less susceptible to plastic deformation. As a result, the guidewire has excellent torque transmission and rotational maneuverability while also possessing excellent pushability and catheter support.

[0012] (2) In the guide wire described in (1) above, the stainless steel may contain at least 0.15 wt% or more of solid solution elements. As a result, the solid solution elements accumulate around dislocations in the strain of the lattice in the metal crystal of the core wire, effectively suppressing the movement of dislocations and making plastic deformation less likely to occur. As a result, the guide wire is less likely to develop a bend even in curved blood vessels, and high torque transmission performance can be obtained.

[0013] (3) In the guide wire described in (2) above, the solid solution elements may consist of C in the range of 0.08 wt% to 0.11 wt% and N in the range of 0.04 wt% to 0.07 wt%. This allows the guide wire to have both appropriate strength and corrosion resistance.

[0014] (4) In the guide wire described in any one of (1) to (3) above, the stainless steel may have a shear modulus of 82 GPa or more. As a result, the guide wire containing this stainless steel has improved torsional rigidity, and thus high torque transmission performance can be obtained.

[0015] (5) In the guide wire described in any one of (1) to (4) above, the stainless steel may be selected from the SUS301 series. By using a SUS301 series stainless steel having a composition with a low nickel content and a high content of carbon, which is a solid solution element, a core wire suitable for a guide wire can be easily obtained.

[0016] (6) In the guide wire described in any one of (1) to (5) above, the core wire may include a second wire made of a superelastic alloy joined to the tip of the first wire made of stainless steel. This allows the guide wire to have a tip portion that has appropriate flexibility and resilience against bending, which is necessary when selecting blood vessels or passing through sharply curved blood vessels, and a proximal portion that has high rigidity, which is necessary for improving pushability, torque transmission, and support for therapeutic devices such as catheters.

[0017] (7) The present invention relates to a method for manufacturing a guidewire, comprising a long core wire, wherein the core wire is formed by heat-treating stainless steel containing 6.0 to 8.0 wt% nickel and at least 0.15 wt% solid solution elements, and is characterized by containing a work-induced martensite phase of 84 vol% or more. The method for manufacturing a guidewire allows for the inclusion of a large amount of work-induced martensite phase by drawing stainless steel with a low nickel content, and therefore enables the production of a guidewire with high pushability, high torque transmission, and high catheter support.

[0018] (8) In the guide wire manufacturing method described in (7) above, the heat treatment may be performed at a temperature of 300°C to 500°C for 1 to 60 minutes. This makes it possible to manufacture a guide wire 10 that is resistant to plastic deformation because the stainless steel undergoes a strain aging effect.

[0019] (9) In the method for manufacturing a guide wire described in (7) or (8) above, the solid solution element may consist of C in the range of 0.08 to 0.11 wt% and N in the range of 0.04 to 0.07 wt%. This makes it possible to manufacture a guide wire 10 that has appropriate strength and corrosion resistance.

[0020] This is a cross-sectional view showing a guide wire according to an embodiment. This is a graph showing the measured outer diameter of the guide wire from the tip to a predetermined position on the base end side. This is a graph showing the measured outer diameter of the range including the base end joint of the guide wire. This is a graph showing the measured outer diameter of the range including the tip joint of the guide wire. This is a graph showing the measured outer diameter of the range including the tip joint of the core wire. This is a graph showing an enlarged portion of Figure 5. This is a cross-sectional view of the range including the base end joint of the core wire. This is a cross-sectional view showing the measurement position of the core wire in the hardness measurement test. This is a plan view showing the jigs for bending strength tests 1, 2 and 3. This is a plan view showing the state of measuring the bending height in bending strength test 2. This is a graph showing the hardness and outer diameter of the core wire. This is a graph showing an enlarged portion of Figure 11. This is a plan view showing the stiffness modulus measuring instrument. This shows a transmission electron microscope image showing a longitudinal section of a SUS301 stainless steel wire. This shows a transmission electron microscope image showing a longitudinal section of a SUS304 stainless steel wire. This shows a scanning electron microscope image of a cross-section of a SUS301 stainless steel wire. This shows a scanning electron microscope image of a cross-section of a SUS304 stainless steel wire. This is a plan view of a tube used for torque transmission testing. This is a graph showing the tip rotation angle relative to the base rotation angle.

[0021] Embodiments of the present invention will be described below with reference to the drawings. Note that the dimensions in the drawings may be exaggerated for illustrative purposes and may differ from the actual dimensions. In addition, in this specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals to avoid redundant explanations. In this specification, the side of the guidewire that is inserted into the blood vessel will be referred to as the "tip side," and the side that is operated will be referred to as the "proximal side." The direction in which the guidewire extends in its natural state (without applying external force and in a straight state) will be referred to as the "long axis direction." The direction perpendicular to the long axis direction of the guidewire will be referred to as the "radial direction."

[0022] The guidewire 10 is used to guide the catheter into blood vessels in the heart, brain, lower limbs, liver, prostate, uterus, etc.

[0023] As shown in Figures 1 to 7, the guide wire 10 according to this embodiment comprises a long core wire 20, a coil 70 surrounding the tip of the core wire 20, a covering layer 90, and a cylindrical member 110.

[0024] The core wire 20 comprises a base core 40, an intermediate core 50 joined to the tip of the base core 40, and a tip core 60 joined to the tip of the intermediate core 50.

[0025] The base core 40 is a long member that constitutes the base end of the core wire 20. The base core 40 comprises a first constant outer diameter section 41, a first reduced diameter section 42, and a first expanded diameter section 43, extending from the base end toward the tip. The first constant outer diameter section 41 has a constant outer diameter from the base end toward the tip of the base core 40. The first reduced diameter section 42 has a reduced outer diameter from the tip of the first constant outer diameter section 41 toward the tip. The first expanded diameter section 43 has a expanded outer diameter from the tip of the first reduced diameter section 42 toward the tip. In this specification, the terms "constant" or "approximately equal" outer diameter may include differences of a manufacturing tolerance. If the difference in outer diameter is 0.003 mm or less, the outer diameter is considered constant or approximately equal.

[0026] The intermediate core 50 is a long member that constitutes the intermediate portion of the core wire 20. The intermediate core 50 comprises a second reduced diameter portion 51, a second expanded diameter portion 52, a second constant outer diameter portion 53, a third reduced diameter portion 54, a third constant outer diameter portion 55, a fourth reduced diameter portion 56, and a third expanded diameter portion 57, extending from the tip of the base core 40 toward the tip. The second reduced diameter portion 51 has an outer diameter that decreases from the tip of the base core 40 toward the tip. The second expanded diameter portion 52 has an outer diameter that increases from the tip of the second reduced diameter portion 51 toward the tip. The second constant outer diameter portion 53 has an outer diameter that remains constant from the tip of the second expanded diameter portion 52 toward the tip. The outer diameter of the second constant outer diameter portion 53 is approximately equal to the outer diameter of the first constant outer diameter portion 41 of the base core 40, but may be different. The third reduced diameter section 54 has an outer diameter that decreases from the tip of the second constant outer diameter section 53 toward the tip. The third constant outer diameter section 55 has a constant outer diameter from the tip of the third reduced diameter section 54 toward the tip. The outer diameter of the third constant outer diameter section 55 is smaller than the outer diameter of the second constant outer diameter section 53. The fourth reduced diameter section 56 has an outer diameter that decreases from the tip of the third constant outer diameter section 55 toward the tip. The third expanded diameter section 57 has an outer diameter that expands from the tip of the fourth reduced diameter section 56 toward the tip. The fourth reduced diameter section 56 and the third expanded diameter section 57 are connected by a curved surface 58 (see Figure 6) that is smooth and concave in a longitudinal section containing the central axis X that passes through the radial center of the core wire 20 and extends in the longitudinal direction. Note that the fourth reduced diameter section 56 and the third expanded diameter section 57 may be connected by a portion with a constant outer diameter. The fourth reduced-diameter section 56 may be formed by combining two or more tapers in which the taper angle changes midway (see the dotted line in Figure 5).

[0027] The tip core 60 is a long member that constitutes the tip of the core wire 20. The tip core 60 comprises a fourth enlarged diameter section 61, a fifth reduced diameter section 62, a fourth constant outer diameter section 63, a sixth reduced diameter section 64, and a fifth constant outer diameter section 65, extending from the tip of the intermediate core 50 toward the tip. The fourth enlarged diameter section 61 has an enlarged outer diameter extending from the tip of the intermediate core 50 toward the tip. The fifth reduced diameter section 62 has an enlarged outer diameter extending from the tip of the fourth enlarged diameter section 61 toward the tip. The fourth constant outer diameter section 63 has a constant outer diameter extending from the tip of the fifth reduced diameter section 62 toward the tip. The outer diameter of the fourth constant outer diameter section 63 is approximately equal to the outer diameter of the third constant outer diameter section 55 of the intermediate core 50, but may be different. The sixth reduced diameter section 64 has an enlarged outer diameter extending from the tip of the fourth constant outer diameter section 63 toward the tip. The fifth constant outer diameter section 65 has a constant outer diameter from the tip of the sixth reduced diameter section 64 toward the tip. The outer diameter of the fifth constant outer diameter section 65 is smaller than the outer diameter of the fourth constant outer diameter section 63.

[0028] The proximal core 40, intermediate core 50, and tip core 60 are formed of metal. Preferably, the material forming the proximal core 40 and intermediate core 50 has higher rigidity than the material forming the tip core 60. This allows the guidewire 10 to have appropriate flexibility and resilience against bending at the tip, which is necessary when selecting blood vessels or passing through sharply curved blood vessels, and the proximal end to have high rigidity, which is necessary for improving pushability, torque transmission, and support for therapeutic devices such as catheters.

[0029] The material forming the base core 40 and the intermediate core 50 is stainless steel, preferably SUS301 series stainless steel as defined in JIS standards. Compared to SUS304 series and SUS316 series stainless steels commonly used as the core wire 20 of the guide wire 10, SUS301 series stainless steel has a lower nickel content that stabilizes the austenite phase. Therefore, the austenite phase of SUS301 series stainless steel is unstable and prone to work-induced martensitic transformation due to wire drawing and straightening processes. When work-induced martensitic transformation occurs in stainless steel, high-density lattice defects are introduced into the metal crystal, and the dislocation density in the metallic material increases with increasing plastic strain. These increased accumulated dislocations suppress the movement of dislocations through interaction with moving dislocations, making it less likely for the metal to undergo plastic deformation. For this reason, SUS301 series stainless steel is less prone to plastic deformation compared to SUS304 series and SUS316 series stainless steels. Furthermore, the material forming the base joint 21 and the intermediate joint is not limited to SUS301 series stainless steel, but may be, for example, stainless steel of the SUS302, SUS304, SUS303, SUS316, SUS316L, SUS316J1, SUS316J1L, SUS405, SUS430, SUS434, SUS444, SUS429, SUS430F series, etc. The base core 40 and the intermediate core 50 may be formed from the same material or from different materials.

[0030] The amount of nickel contained in the stainless steel used for the base core 40 and the intermediate core 50 is preferably 6.0 wt% to 8.0 wt%, and more preferably 6.0 wt% to 7.0 wt%.

[0031] The stainless steel forming the base core 40 and the intermediate core 50 preferably contains at least 0.15 wt% of solid solution elements. SUS301 stainless steel has a higher amount of carbon in its composition compared to SUS304 and SUS316 stainless steels. Generally, atoms with small atomic radii, such as C, N, and Si, penetrate the lattice of metal atoms, gather around dislocations, and fix the dislocations, creating a Cottrell atmosphere. As a result, the metal becomes less resistant to deformation because dislocations are less likely to move, and plastic deformation is less likely to occur. There are various types of solid solution elements, but C and N are generally mentioned. Adding carbon to stainless steel can improve its hardness, yield strength, and tensile strength, but if the amount of carbon is excessive, corrosion resistance may decrease or brittleness may increase. Therefore, by adding a combination of C and N, stainless steel can have a combination of appropriate hardness, yield strength, tensile strength, and corrosion resistance. The amount of carbon (C) in the stainless steel used for the base core 40 and intermediate core 50 is preferably 0.08 wt% to 0.11 wt%, and more preferably 0.9 wt% to 0.11 wt%. Furthermore, the amount of nitrogen (N) in the stainless steel used for the base core 40 and intermediate core 50 is preferably 0.04 wt% to 0.07 wt%, and more preferably 0.5 wt% to 0.7 wt%.

[0032] The stainless steel forming the base core 40 and the intermediate core 50 is preferably heat-treated. It is known that stainless steel undergoes a strain aging effect when heat-treated at low temperatures. The strain aging effect occurs when carbon and nitrogen in a metal structure with many dislocations are fixed in place by room temperature and low-temperature heat treatment. As a result, the stainless steel becomes less susceptible to plastic deformation.

[0033] The proximal core 40 and intermediate core 50 are made of stainless steel that is less prone to plastic deformation compared to general stainless steel, so they are less likely to develop a bend even when positioned in a sharply curved blood vessel. As a result, the guidewire 10 provides excellent torque transmission and excellent rotational operability.

[0034] The material forming the tip core 60 is a superelastic alloy, such as a nickel-titanium alloy. However, the material forming the tip core 60 is not particularly limited and may be other superelastic alloys such as Cu-Al-Ni alloy or Cu-Zn-Al alloy. A superelastic alloy as used here is generally called a shape memory alloy and is a material whose transformation point is at least below the biological temperature (around 37°C).

[0035] The core wire 20 comprises a base joint 21 where the base core 40 and the intermediate core 50 are joined, and a tip joint 30 where the intermediate core 50 and the tip core 60 are joined. The base joint 21 and the tip joint 30 are joined by solid-state bonding. Solid-state bonding is a method of joining materials in a solid state without melting them. Examples of solid-state bonding include butt resistance welding, friction welding, and ultrasonic bonding, but butt resistance welding is preferred. By joining solid-state cores together by butting them, high dimensional accuracy and high joint strength can be obtained.

[0036] As shown in Figures 1, 3, and 7, the base joint portion 21 includes a base joint surface 22 which is the interface between the base core 40 and the intermediate core 50, a base projection 23 that protrudes radially outward, a base recess 24 which is recessed radially inward on the base side of the base projection 23, and a tip recess 25 which is recessed radially inward on the tip side of the base projection 23. The base recess 24 and the tip recess 25 are formed when the base joint portion 21 is ground after the base core 40 and the intermediate core 50 are joined.

[0037] The base projection 23 is the portion that protrudes radially outward from the first constant outer diameter portion 41 and the second constant outer diameter portion 53. The base projection 23 is formed by the tip portion of the first enlarged diameter portion 43 and the base end portion of the second reduced diameter portion 51. The most protruding apex of the base projection 23 is located on or near the base joint surface 22.

[0038] The base-side recess 24 and the tip-side recess 25 are portions that are recessed radially inward from the first constant outer diameter portion 41 and the second constant outer diameter portion 53. The base-side recess 24 is formed by the first reduced diameter portion 42 and the base-side portion of the first expanded diameter portion 43. The tip-side recess 25 is formed by the tip-side portion of the second reduced diameter portion 51 and the second expanded diameter portion 52.

[0039] The base joint portion 21 has a low-hardness portion 26 in which the hardness is lower than that of the first constant outer diameter portion 41 and the second constant outer diameter portion 53. The low-hardness portion 26 has a base-end hardness reduction starting point 34, a base-end transition portion 27, a constant hardness portion 28, a tip transition portion 29, and a tip hardness reduction starting point 35. The base-end hardness reduction starting point 34 is located on the base end side of the constant hardness portion 28 and is the point where the hardness begins to decrease from the base end side toward the tip end. The base-end transition portion 27 is located on the base end side of the constant hardness portion 28 and is the portion in which the hardness decreases and the outer diameter increases from the base end side toward the tip end. The tip hardness reduction starting point 35 is located on the tip side of the constant hardness portion 28 and is the point in which the hardness begins to decrease from the tip end side toward the base end. The tip transition portion 29 is located on the tip side of the constant hardness portion 28 and is the portion in which the hardness decreases and the outer diameter increases from the tip end side toward the base end. The constant hardness portion 28 is located between the base end transition portion 27 and the tip transition portion 29, and is a portion of the low-hardness portion 26 where the hardness is approximately constant. The constant hardness portion 28 includes the base end joint surface 22. The constant hardness portion 28 ranges from the point with the lowest hardness to the point with a Vickers hardness of +100 HV. Note that the base end joint portion 21 does not necessarily have to have a constant hardness portion 28.

[0040] The base joint 21 is formed by directly contacting the base end of a stainless steel wire with an outer diameter of 0.44 mm, which will become the intermediate core 50, with the tip of a stainless steel wire with an outer diameter of 0.44 mm, which will become the base core 40, and solid-state bonding. In other words, the base joint 21 is formed by joining the same type of metal. Solid-state bonding is a method of joining materials in a solid state without melting them. Examples of solid-state bonding include butt resistance welding, friction welding, and ultrasonic bonding, but butt resistance welding is preferred. Burrs generated by solid-state bonding are removed by grinding.

[0041] The distal joint portion 30 is formed by a third constant outer diameter portion 55 of the intermediate core 50, a fourth reduced diameter portion 56 of the intermediate core 50, a third enlarged diameter portion 57 of the intermediate core 50, a fourth enlarged diameter portion 61 of the distal core 60, and a fifth reduced diameter portion 62 of the distal core 60.

[0042] The distal joint portion 30 includes, as shown in FIGS. 1, 2, and 4 to 6, a distal joint surface 31 which is a boundary surface between the intermediate core 50 and the distal core 60, and a distal protruding portion 32 protruding radially outward. The distal protruding portion 32 is a portion protruding radially outward from a fourth constant outer diameter portion 63 of the distal core 60. The distal protruding portion 32 is formed by a distal-side portion of the third enlarged diameter portion 57, the fourth enlarged diameter portion 61, and the fifth reduced diameter portion 62. Note that the third enlarged diameter portion 57 may not be included in the distal protruding portion 32. Further, for the fourth enlarged diameter portion 61, only the distal-side portion may be included in the distal protruding portion 32, and the proximal-side portion may not be included in the distal protruding portion 32. The distal joint surface 31 is located on the proximal side relative to a portion having the maximum outer diameter of the distal joint portion 30. Since the distal joint portion 30 includes the distal protruding portion 32 whose outer diameter is larger than that of the fourth constant outer diameter portion 63, the area of the distal joint surface 31 between the distal core 60 and the intermediate core 50 can be secured, and thus high joint strength can be obtained.

[0043] The distal joint portion 30 is formed by directly bringing the proximal end of a nickel-titanium alloy wire rod having an outer diameter of 0.400 mm to 0.410 mm to serve as the distal core 60 into contact with the distal end of a stainless steel wire rod having an outer diameter of 0.400 mm to 0.405 mm to serve as the third constant outer diameter portion 55 of the intermediate core 50, and performing solid-phase bonding on the contact. That is, the distal joint portion 30 is formed by bonding dissimilar metals. Burrs generated by the solid-phase bonding are removed by grinding.

[0044] At the tip joint 30, the intermediate core 50, formed from stainless steel on the proximal end side, is machined to have a smaller outer diameter than the tip core 60, formed from a nickel-titanium alloy on the tip side, flanking the tip joint surface 31. Since the tip joint 30 joins the tip core 60, which is made of a nickel-titanium alloy and has low rigidity, with the intermediate core 50, which is made of stainless steel and has high rigidity, if the tip core 60 and the intermediate core 50 have the same diameter, the rigidity along the long axis of the tip joint 30 will change abruptly. As a result, the guidewire 10 may kink at the tip joint 30, or when passing the guidewire through a point where the angle of the blood vessel branching is 90° or more, the guidewire may locally bend and deviate as if pushed deeper into the main vessel when the tip is inserted into the branching point of the blood vessel, potentially causing a prolapse and reducing the ability to follow the blood vessel. The tip joint 30 is formed from a material with higher rigidity than the tip core 60 on the tip side, with the tip joint surface 31 in between. By reducing the outer diameter of the intermediate core 50 on the base side, the change in rigidity along the long axis direction in the tip joint 30 becomes more gradual, improving kink resistance.

[0045] The distal joint portion 30 has the third constant outer diameter portion 55 on the proximal end side of the fourth reduced diameter portion 56 of the intermediate core 50. For this reason, the outer diameter of the distal end portion of the intermediate core 50 gradually decreases from the distal end of the second constant outer diameter portion 53 toward the proximal end of the third enlarged diameter portion 57 having a smaller outer diameter or the curved surface 58. The longer the length of the reduced diameter portion that reduces the outer diameter from the outer diameter of the distal end of the second constant outer diameter portion 53 to the outer diameter of the proximal end of the third enlarged diameter portion 57, the more the change in rigidity along the longitudinal direction can be reduced. On the other hand, if the length of the reduced diameter portion is too long, the length of the portion with low rigidity near the joint becomes longer, so prolapse may occur. Since the distal joint portion 30 has the third constant outer diameter portion 55 on the proximal end side of the fourth reduced diameter portion 56 of the intermediate core 50, compared with the case where the outer diameter is continuously reduced from the distal end of the second constant outer diameter portion 53 toward the proximal end of the third enlarged diameter portion 57 without providing the third constant outer diameter portion 55, it is possible to suppress an abrupt change in rigidity of the core wire 20 along the longitudinal direction caused by the difference in rigidity between the distal core 60 and the intermediate core 50 while shortening the length of the portion having low rigidity near the proximal end of the distal joint portion 30. Therefore, the guide wire 10 can suppress the occurrence of prolapse in the vicinity of the distal joint portion 30.

[0046] As shown in FIGS. 1 to 6, an appropriate length can be selected for the longitudinal length L1 of the proximal core 40 depending on the total length of the guide wire 10, for example, 1040 mm to 1060 mm, 1540 mm to 1560 mm, or 2040 mm to 2060 mm can be selected. The outer diameter of the first constant outer diameter portion 41 of the proximal core 40 is, for example, 0.43 to 0.45 mm, preferably 0.435 mm to 0.440 mm. The longitudinal length of the proximal joint portion 21 is, for example, 0.5 mm to 2.0 mm, preferably about 1 mm. The outer diameter of the proximal joint portion 21 is, for example, 0.43 to 0.47 mm, preferably 0.44 mm to 0.46 mm.

[0047] The length L2 in the longitudinal direction of the portion of the intermediate core 50 from the base end joint surface 22 to the tip of the second constant outer diameter portion 53 is, for example, 2500 mm to 2600 mm. The outer diameter of this portion is, for example, 0.435 mm to 0.440 mm. The length L3 in the longitudinal direction of the third reduced diameter portion 54 of the intermediate core 50 is, for example, 60 mm to 80 mm. The outer diameter of the third reduced diameter portion 54 is, for example, 0.40 mm to 0.44 mm. The length L4 in the longitudinal direction of the third constant outer diameter portion 55 of the intermediate core 50 is, for example, 20 mm to 50 mm. The outer diameter of the third constant outer diameter portion 55 is, for example, 0.40 mm to 0.41 mm. The length L5 in the longitudinal direction of the fourth reduced diameter portion 56 of the intermediate core 50 is, for example, 5 mm to 25 mm. The outer diameter of the fourth reduced diameter portion 56 is, for example, 0.31 mm to 0.41 mm. The length L6 in the longitudinal direction of the portion from the base end of the third enlarged diameter portion 57 of the intermediate core 50 to the tip of the fifth reduced diameter portion 62 of the tip core 60 is, for example, 1 mm to 17 mm. The outer diameter of the portion from the base end of the third enlarged diameter portion 57 of the intermediate core 50 to the tip of the fifth reduced diameter portion 62 of the tip core 60 is, for example, 0.31 mm to 0.46 mm, and the outer diameter of the base end of the third enlarged diameter portion 57 of the intermediate core 50 is, for example, 0.31 mm to 0.33 mm.

[0048] The length L7 in the long axis direction of the fourth constant outer diameter portion 63 of the tip core 60 is, for example, 190 mm to 210 mm. The outer diameter of the fourth constant outer diameter portion 63 is, for example, 0.40 mm to 0.41 mm. The length in the long axis direction of the tip joint portion 30 is, for example, 1 mm or less. The outer diameter of the tip joint portion 30 is, for example, 0.41 mm to 0.46 mm. The length L8 in the long axis direction of the sixth reduced diameter portion 64 of the tip core 60 is, for example, 50 mm to 70 mm. The outer diameter of the base end of the sixth reduced diameter portion 64 is, for example, 0.39 mm to 0.41 mm. The outer diameter of the tip of the sixth reduced diameter portion 64 is, for example, 0.06 mm to 0.10 mm. The length L9 in the long axis direction of the fifth constant outer diameter portion 65 of the tip core 60 is, for example, 0 to 10 mm. The outer diameter of the fifth constant outer diameter portion 65 is, for example, 0.06 mm to 0.10 mm.

[0049] The SUS301 stainless steel that forms the intermediate core 50 and the base core 40 is a material that is resistant to plastic deformation. The resistance of SUS301 stainless steel to plastic deformation is due to its ease of phase transformation to the work-induced martensite phase and the influence of interstitial solid solution elements such as C and N.

[0050] As shown in Figure 1, the coil 70 surrounds substantially the entire fifth constant outer diameter portion 65 of the tip core 60 and the tip end portion of the sixth reduced diameter portion 64, and is fixed to the tip core 60. The tip of the coil 70 may coincide with the tip of the tip core 60 in the longitudinal direction, or it may be located closer to the tip or base end than the tip of the tip core 60. The wire of the coil 70 is tightly wound so as to have no gaps. The outer diameter of the wire of the coil 70 is, for example, 50 μm to 100 μm.

[0051] The coil 70 is preferably formed from a wire made of a radiopaque material. This allows the coil 70 to provide visibility under fluoroscopy to the tip of the guidewire 10. The coil 70 is formed from, for example, metallic materials such as gold, platinum, and tungsten, and alloys such as platinum-nickel alloys containing these materials.

[0052] The coil 70 is fixed to the core wire 20 by a fixing member 80. The fixing member 80 comprises a tip fixing member 81 and a base fixing member 82. The tip fixing member 81 fixes the tip portion of the coil 70 near the tip of the tip core 60. The base fixing member 82 fixes the base portion of the coil 70 to the sixth reduced diameter portion 64 of the tip core 60. The tip fixing member 81 and the base fixing member 82 are formed from, for example, an ultraviolet-curing adhesive, but other adhesives, brazing materials, solder, etc. may also be used.

[0053] The coating layer 90 comprises a base coating layer 91 that covers the base core 40, an intermediate coating layer 92 that covers the intermediate core 50, and a tip coating layer 93 that covers the tip core 60.

[0054] The tip coating layer 93 has a flexible tip resin layer 94 that covers the portion of the tip core 60 closer to the tip than the cylindrical member 110, the coil 70, the tip fixing member 81, and the base end fixing member 82, and a tip lubrication layer 95 that covers the tip resin layer 94. The tip resin layer 94 covers the tip of the core wire 20, thereby forming the rounded tip of the guide wire 10.

[0055] The material forming the tip resin layer 94 is, for example, urethane resin. The thickness of the tip resin layer 94 is, for example, 1.0 μm to 30.0 μm.

[0056] The tip lubrication layer 95 is preferably formed of a hydrophilic polymer. Examples of hydrophilic polymers that form the tip lubrication layer 95 include cellulose-based polymers, polyethylene oxide-based polymers, maleic anhydride-based polymers (e.g., maleic anhydride copolymers such as methyl vinyl ether-maleic anhydride copolymer), acrylamide-based polymers (e.g., polyacrylamide, block copolymer of polyglycidyl methacrylate-dimethylacrylamide (PGMA-DMAA)), water-soluble nylon, polyvinyl alcohol, and polyvinylpyrrolidone. Hydrophilic polymers exhibit high lubricity through wetting (water absorption). The thickness of the tip lubrication layer 95 is, for example, 0.4 μm to 2.5 μm.

[0057] The intermediate coating layer 92 has an intermediate resin layer 96 that covers the intermediate core 50 and linear bodies 97 arranged spirally on the outer surface of the intermediate resin layer 96. The base end of the intermediate resin layer 96 is located near the base end of the second constant outer diameter portion 53 of the intermediate core 50, and the tip of the intermediate resin layer 96 is located at the third constant outer diameter portion 55 of the intermediate core 50.

[0058] The intermediate resin layer 96 comprises an inner layer 98 that covers the intermediate core 50 and an outer layer 99 that covers the inner layer 98.

[0059] The material forming the inner layer 98 is preferably a fluororesin material. The inner layer 98 contains two types of fluororesin materials with different compositions, for example, one of which may be polytetrafluoroethylene (PTFE) and the other may be fluoroethylene propylene (FEP). The inner layer 98 may also contain a pigment and a binder to improve adhesion with the intermediate core 50. The thickness of the inner layer 98 is not particularly limited, but is preferably 1.0 μm to 15.0 μm, and more preferably 1.0 μm to 3.0 μm.

[0060] The outer layer 99 is formed on the inner layer 98. Preferably, the outer layer 99 is made of a material containing, for example, a resin and a pigment.

[0061] The material forming the outer layer 99 is preferably a fluororesin material, similar to the inner layer 98. Examples of fluororesin materials that can be used include polytetrafluoroethylene (PTFE) and fluoroethylene propylene (FEP). The outer layer 99 may also contain a pigment. The thickness of the outer layer 99 is not particularly limited, but is preferably 2.0 μm to 15.0 μm, and more preferably 2.0 μm to 4.5 μm.

[0062] The linear body 97 is arranged over substantially the entire length of the intermediate core 50, and is formed by winding the wire that forms the linear body 97 in a spiral manner such that adjacent windings are spaced apart. In a longitudinal section including the central axis X of the guide wire 10, the linear body 97 has a convex shape that protrudes radially outward from the outer surface of the intermediate resin layer 96. In a longitudinal section including the central axis X of the guide wire 10, the height of the convex shape formed by the linear body 97 from the outer surface of the intermediate resin layer 96 is 0.5 μm to 3.0 μm, preferably 1.0 μm to 2.0 μm. The width of the wire that forms the linear body 97 is 0.1 mm to 1.0 mm, preferably 0.15 to 0.50 mm. The spiral pitch is 0.5 mm to 2.0 mm, preferably 0.8 to 1.0 mm.

[0063] The material forming the linear body 97 is preferably a fluorine-based resin material such as polytetrafluoroethylene (PTFE) or fluoroethylene propylene (FEP), similar to the inner layer 98 and outer layer 99. The linear body 97 may also contain a pigment. The thickness of the linear body 97 is, for example, 1.0 μm to 2.0 μm.

[0064] The middle portion of the guidewire 10, when inserted into the lumen of the catheter, has a portion that is located within the lumen of the catheter and in contact with the inner surface of the catheter, and a portion that extends from the proximal end of the catheter toward the proximal end and is located outside the catheter and is grasped by the operator. Because the guidewire 10 has a linear body 97 in its intermediate coating layer 92, the contact area with the inner surface of the catheter is reduced in the portion located within the lumen of the catheter, thereby reducing frictional resistance during operations such as movement and rotation of the guidewire 10. As a result, the guidewire 10 can improve the delivery of the catheter. Furthermore, in the portion of the guidewire 10 located outside the catheter, the operator's fingers can get into the uneven shape formed by the linear body 97, thereby improving the operator's gripping strength. Consequently, the guidewire 10 has improved operability.

[0065] The base end coating layer 91 covers from the base end of the base end core 40 to the base end of the intermediate core 50. The tip of the base end coating layer 91 covers the base end of the intermediate coating layer 92 that covers the intermediate core 50, and together with the intermediate coating layer 92, it forms an overlapping portion 100.

[0066] The proximal coating layer 91 has an overlapping portion 100, which allows it to continuously cover the proximal core 40 to the proximal end of the intermediate core 50. As a result, the proximal coating layer 91 eliminates any exposed portion of the core wire 20 in the region from the proximal end to the intermediate end of the core wire 20, thereby suppressing an increase in the insertion resistance of the catheter inserted from the proximal end of the guide wire 10. Furthermore, since the overlapping portion 100 covers the proximal end of the intermediate coating layer 92, it prevents the tip of the catheter from getting caught on the proximal end of the intermediate coating layer 92 when inserting the catheter from the proximal end of the guide wire 10 toward the tip. As a result, the guide wire 10 can prevent the intermediate coating layer 92 from peeling and damage to the catheter inserted from the proximal end. Moreover, the overlapping portion 100 can be easily formed by covering the proximal end of the intermediate coating layer 92 with the proximal coating layer 91.

[0067] The base end coating layer 91 is preferably formed of a hydrophobic material. The material forming the base end coating layer 91 is, for example, a reaction-curing silicone oil or a composite material containing the same. In addition, the base end coating layer 91 may be formed of a lubricating oil containing hydrocarbons, esters, ethers, fluorine, etc., or a composite material thereof. The thickness of the base end coating layer 91 is preferably 0.001 μm to 1.0 μm, and more preferably 0.005 μm to 0.010 μm.

[0068] The length of the base coating layer 91 in the longitudinal direction is, for example, 1080 mm to 2080 mm. The length of the intermediate coating layer 92 in the longitudinal direction is, for example, 2590 mm to 2640 mm, preferably 2597 mm to 2633 mm. The length of the overlapping portion 100 in the longitudinal direction is, for example, 100 mm to 250 mm, preferably 150 mm to 200 mm. The length of the tip coating layer 93 in the longitudinal direction is, for example, 230 mm to 270 mm, preferably 240 mm to 260 mm.

[0069] The cylindrical member 110 is a cylindrical member that suppresses the peeling of the tip coating layer 93 that covers the tip core 60. The cylindrical member 110 contacts the base end of the tip coating layer 93 and is arranged coaxially with the tip core 60 on the radially outer side of the tip core 60. Preferably, the tip lubrication layer 95 is not coated on the outer surface of the cylindrical member 110. The cylindrical member 110 is fixed to the outer surface of the base end of the fourth constant outer diameter portion 63 of the tip core 60 by a cylindrical fixing member 111 arranged on the base end side. The material forming the cylindrical member 110 is, for example, a platinum-iridium alloy, but is not particularly limited as long as it is a thin cylindrical shape, and may be other metal materials or resin materials. The material forming the cylindrical fixing member 111 is, for example, solder, but is not particularly limited as long as it can fix the cylindrical member 110 to the tip core 60, and may be, for example, brazing material or adhesive.

[0070] The cylindrical member 110 and the cylindrical fixing member 111 are ground so that the corners on the base end are chamfered, and they are inclined to be smoothly continuous with respect to the tip core 60.

[0071] The length of the cylindrical member 110 in the longitudinal direction is, for example, 0.79 mm to 0.81 mm, and the length of the cylindrical fixing member 111 in the longitudinal direction is, for example, 0.2 mm to 2.0 mm. The outer diameter of the cylindrical member 110 is, for example, 0.45 mm to 0.46 mm.

[0072] The total length of the guide wire 10 in the longitudinal direction is 3000 mm to 6000 mm, for example, 3950 mm to 4050 mm, 4450 mm to 4550 mm, or 4950 mm to 5050 mm. The guide wire 10 has an exposed portion 33 that is exposed to the outside between the tip coating layer 93 and the intermediate coating layer 92. In this embodiment, the exposed portion 33 is exposed to the outside between the tip of the intermediate coating layer 92 and the base end of the cylindrical fixing member 111. The tip of the guide wire 10 may be straight or it may be shaped and bent at a predetermined angle. The bent shape may be, for example, J-shaped.

[0073] Figures 2-4 show the outer diameter of the guide wire 10 at various positions along its long axis. Figures 5-6 show the outer diameter of the core wire 20 at various positions along its long axis.

[0074] The core wire 20 of the guide wire 10 is formed by joining a base core 40, an intermediate core 50, and a tip core 60. Therefore, by appropriately selecting and combining the materials that form the base core 40, the intermediate core 50, and the tip core 60, and the material that forms the coating layer 90, a guide wire 10 with desired physical properties and surface characteristics along the long axis can be easily obtained. In addition, by processing the outer shape of the base joint 21 and the tip joint 30 of the guide wire 10 into a desired shape, it is easy to adjust the change in stiffness along the long axis near the joint.

[0075] Furthermore, the core wire 20, formed by joining a proximal core 40, an intermediate core 50, and a tip core 60, is useful in the manufacture of a guidewire 10 used in a procedure to treat lesions in blood vessels of the lower limb region, which is inserted into the blood vessel from the radial artery in the wrist. In this procedure, when the guidewire 10 is used with an over-the-wire type catheter, the guidewire 10 needs to be kept exposed from the proximal end of the catheter to the proximal end, without being fully inserted into the lumen of the catheter, in order to withdraw the catheter while leaving the tip inside the blood vessel. Therefore, the operator needs to use a guidewire 10 in which the length of the guidewire 10 extending from the proximal end of the catheter to the proximal end is greater than or equal to the length of the catheter, and this length may be more than twice the length of the catheter. In manufacturing such a long guide wire 10, the core wire 20 is formed by joining a base core 40, an intermediate core 50, and a tip core 60. As a result, the lengths of each of the base core 40, intermediate core 50, and tip core 60 can be shorter than when the core wire 20 is formed from a single continuous wire. Therefore, even if the total length of the guide wire 10 is long, it can be manufactured in a small space.

[0076] [Hardness Measurement Test] Multiple core wires 20 were prepared for testing, and the hardness of the base end joint 21 of the core wires 20 was measured. For hardness measurement, a microhardness tester (HM-211, manufactured by Mitutoyo Corporation) was used, and the Vickers hardness was measured with a load of 0.3 N and an approach speed of 60 μm / s.

[0077] To prepare a test specimen for hardness measurement, a section of the core wire 20 to be tested, including the base end joint 21, was cut out. The cut-out piece was laid flat (with the central axis X of the core wire 20 horizontal) and covered with epoxy resin, which was then allowed to harden. Next, the resin-embedded cut-out piece was mechanically polished together with the resin to a mirror finish, resulting in a test specimen in which the longitudinal section including the central axis X of the core wire 20 was exposed.

[0078] Next, as shown in Figure 8, the point through which the center line X of the core wire 20 passes on the base end joint surface 22 was used as the starting point P. Measurements were taken at two points ±0.05 mm radially outward from the starting point P, shifted by 0.1 mm on both sides in the longitudinal direction. The average of the measurements taken at the two points separated by ±0.05 mm radially outward was taken as the measurement result at that position in the longitudinal direction.

[0079] The range from the point with the lowest Vickers hardness to the point with a hardness of +100 HV was defined as the constant hardness section 28, and the width W1 of the constant hardness section 28, which is the length along the long axis from the tip end to the base end, was calculated. In addition, the range from the base end reduction point 34 to the tip end reduction point 35 was defined as the low hardness section 26, and the width W2 of the low hardness section 26, which is the length along the long axis, was calculated. Furthermore, the hardness reduction rate was calculated, which is the percentage decrease in Vickers hardness of the base end joint surface 22 relative to the Vickers hardness of the first constant outer diameter section 41 and / or the second constant outer diameter section 53.

[0080] [Bending Strength Test 1] A bending strength test was performed on the guide wire 10 in the area including the base end joint 21. As shown in Figure 9, multiple cylindrical fixtures 200 with radii R that changed in steps at 2.5 mm intervals were prepared for the test. First, using the fixture 200 with the largest radius R, the guide wire 10 was brought into contact with half the circumference of the outer surface of the fixture 200, and bent 180° with the base end joint 21 as the apex, and a bending load F was applied for 5 seconds. After this, the guide wire 10 was removed from the fixture 200, and the bending angle of the guide wire 10 was measured. The test was performed by gradually decreasing the radius of the fixture 200, and the radius R of the fixture 200 at which the bending angle first exceeded 3° was recorded as an index representing the bending strength of the guide wire 10.

[0081] [Bending Strength Test 2] A bending strength test was performed on the guide wire 10 in the area including the base end joint 21. For the test, as shown in Figure 9, a cylindrical jig 200 with a radius R of 15 mm, which was used in Bending Strength Test 1, was prepared. A bending load F was applied to the guide wire 10 for 5 seconds in the same manner as in Bending Strength Test 1. After this, as shown in Figure 10, the guide wire 10 was removed from the jig 200, and with the portion on the base end side of the base end joint 21 straightened, the bending height h, which is the distance from the extension line extending from the portion on the base end side of the base end joint 21 perpendicular to the portion 50 mm from the base end joint 21 toward the tip, was recorded as an index representing the bending strength of the guide wire 10.

[0082] [Bending Strength Test 3] A bending strength test was performed on the guide wire 10, including the base end joint 21. As shown in Figure 9, a cylindrical jig 200 with a radius R of 5 mm, which was used in Bending Strength Test 1, was prepared for the test. A bending load F was applied to the guide wire 10 for 5 seconds in the same manner as in Bending Strength Test 1. Whether or not fracture occurred at the joint was recorded as an indicator of the bending strength of the guide wire 10.

[0083] [Tensile Strength Test] A tensile strength test was performed on the base end joint 21 of the guide wire 10. The tensile strength test was conducted using an autograph with a distance of 150 mm between the two gripping chucks and a test speed of 10 mm / min. The guide wire 10 was fixed to the chucks so that the base end joint 21 was positioned in the center of the two chucks, and the tensile test was performed until it broke.

[0084] <Core Wire Test Results> Core wires 20 were prepared according to Examples 1 to 5, and the hardness measurement test, bending strength test 1, bending strength test 2, bending strength test 3, and tensile strength test described above were performed. The results are shown in Table 1. Note that the results of bending strength test 1 are shown as the range of variation of the five samples, and the results of bending strength test 2 and tensile strength test are shown as the average values ​​of the five samples. In bending strength test 3, a fracture was indicated if one or more of the five samples fractured.

[0085]

[0086] The results of bending strength tests 1 and 2 showed that Example 2 had a higher bending strength than Examples 1 and 3. The results of bending strength test 3 showed that no fracture occurred in Examples 1 to 4, while fracture occurred in Example 5. Furthermore, tensile strength tests showed that Example 2 had a higher tensile strength than Examples 1, 3, and 4.

[0087] In Examples 2, 4, and 5, where high bending strength was confirmed, the calculated hardness reduction rates were 46%, 21%, and 47%, respectively, all below 50%.

[0088] Figure 11 shows the outer diameter and hardness measurement results of one of the samples from Example 2 (constant hardness section width W1: 0.5 mm), and Figure 12 shows an enlarged view thereof. From the hardness measurement test results, a low-hardness section 26 was confirmed in the base end projection 23, where the Vickers hardness was lower than that of the first constant outer diameter section 41 and the second constant outer diameter section 53. In addition, a constant hardness section 28 with approximately constant hardness, a base end transition section 27 on the base end side of the constant hardness section 28, and a tip transition section 29 on the tip side of the constant hardness section 28 were confirmed in the low-hardness section 26. Furthermore, it was confirmed that the Vickers hardness of the base end recessed section 24 was approximately equal to that of the first constant outer diameter section 41 and approximately constant along the long axis, and the Vickers hardness of the tip recessed section 25 was approximately equal to that of the second constant outer diameter section 53 and approximately constant along the long axis.

[0089] <Compositional Analysis Results of Base Core and Intermediate Core Materials> Compositional analysis was performed on SUS301 stainless steel (Examples 6-8) used in the base core 40 and intermediate core 50, and SUS304 stainless steel (Reference Example 1) used in the core wire of a guide wire with a different configuration. C and S were analyzed by combustion-infrared absorption spectroscopy. Si was analyzed by silicon dioxide gravimetric method in Example 7, and by ICP emission spectroscopy in Examples 6, 8, and Reference Example 1. N was analyzed by inert gas fusion-thermal conductivity method. Other elements (Mn, P, Cu, Cr, Ni) were analyzed by ICP emission spectroscopy. The results are shown in Table 2. The compositions of SUS301 and SUS304 stainless steel as specified in JIS standards are also shown in Table 3. As a result, it was confirmed that the stainless steel used in the base core 40 and intermediate core 50 contained 6.0 wt% to 8.0 wt% nickel (Ni), 0.08 wt% to 0.11 wt% carbon (C), and 0.04 wt% to 0.07 wt% nitrogen (N). The total amount of C and N that could become solid solution elements was 0.15 wt% or more.

[0090]

[0091] <Analysis Results of Processing-Induced Martensite Phase in the Base Core and Intermediate Core Materials> SUS301 stainless steel (Examples 9-11) used in the base core 40 and intermediate core 50, and SUS304 stainless steel (Reference Example 2) used in the core wire of a guide wire with a different configuration were cut out, and X-ray diffraction measurements were performed to obtain diffraction peaks for the austenite phase and martensite phase. The analysis was performed by X-ray diffraction using an X-ray diffractometer (RINT2500H / PC: manufactured by Rigaku Corporation). Co Kα (30kV, 100mA) was used as the X-ray source, and the measurement range was set to 10° to 105°. Using XRD analysis software, the peaks of the martensite phase [(110) plane, (200) plane, (211) plane] and the austenite phase [(111) plane, (200) plane, (220) plane] were separated, and the ratio of the martensite phase to the austenite phase was calculated theoretically using the integrated intensity, and this was expressed as the amount of work-induced martensite (vol%). The results are shown in Table 3. As a result, it was confirmed that Examples 9 to 11 had a higher amount of work-induced martensite than Reference Example 2. Furthermore, it was confirmed that the amount of work-induced martensite in the SUS301 stainless steel used in the base core 40 and intermediate core 50 was 84 vol% or more.

[0092]

[0093] <Measurement Results of Shear Modulus (Shear Modulus) of Base Core and Intermediate Core Materials> The shear modulus was measured for the wire rods of SUS301 series stainless steel (Examples 12-14) used in the base core 40 and intermediate core 50, and for the wire rods of SUS304 series stainless steel (Reference Example 3) used in the core wires of guide wires with different configurations. The measurement was performed using the stiffness modulus measuring instrument 210 shown in Figure 13. The stiffness modulus measuring instrument 210 connects a cylindrical weight 211 to the lower part of the wire rod 215 via a chuck, and the upper part of the wire rod is connected to a suspension part 212 via a chuck and suspended. The suspension part 212 is rotated to give the wire rod 215 a 90° twist, and the rotation period of the weight 211 is detected by a sensor 213. The rotation period was measured, and the shear modulus was calculated from the average period every 10 cycles. When the mass of the weight 211 is W, the diameter of the weight 211 is D, the distance between the chucks is L, the radius of the wire is R, and the period is T, the shear modulus G was calculated using the following equations (1) and (2). In the examples and reference examples, the number of samples was 3 each. The calculated shear moduli are shown in Table 4. As a result, it was confirmed that SUS301 stainless steel has a shear modulus of 82 GPa or higher.

[0094] I = W × D ２ / 8...Formula (1) G=8πLI / R ４ T ２ ...Formula (2)

[0095]

[0096] <Analysis Results of Crystal Structure of Base Core and Intermediate Core Materials> The crystal structure of the longitudinal and transverse sections of the wire rod made of SUS301 stainless steel (Example 15) used in the base core 40 and intermediate core 50 was analyzed. In addition, as Reference Example 4, the crystal structure of the wire rod made of SUS304 stainless steel (Reference Example 4) used in the core wire of a guide wire with a different configuration was also analyzed.

[0097] The longitudinal sections of the wires were analyzed using a transmission electron microscope (TEM). Microscope samples were prepared using a focused ion beam processing and observation system (FB-2000A: Hitachi, Ltd.) and a Dual Beam (FIB / SEM) system (Nova200: FE-I Japan Co., Ltd.), with an acceleration voltage of 10 kV and a Ga ion source. First, each sample was embedded in resin and polished together with the resin to make the longitudinal section discernible. Next, a carbon film was coated to protect the surface of the embedded sample. Then, a tungsten film was coated using the focused ion beam processing and observation system, targeting a position 1 / 4 of the diameter of the longitudinal section of the wire (midway between the center of the longitudinal section and the outer surface of the wire). After that, a sample fragment was extracted by microsampling using the focused ion beam processing and observation system. Subsequently, the extracted fragment was thinned to a thickness suitable for TEM observation using the focused ion beam processing and observation system.

[0098] Next, using a field emission transmission electron microscope (Talos F200X: manufactured by FE-I Japan Co., Ltd.) and a camera system (Ceta 16M: manufactured by FE-I Japan Co., Ltd.), each sample was observed with an acceleration voltage of 200 kV and acquisition angles set to (HAADF: 59-200 mrad, DF4: 23-55 mrad, DF2: 12-20 mrad, BF: ~9 mrad). The observed microscopic images of the longitudinal section of the SUS301 stainless steel wire are shown in Figure 14, and the microscopic images of the longitudinal section of the SUS304 stainless steel wire are shown in Figure 15. In the longitudinal section of the core wire 20, it was confirmed that the crystal grains of the metallic structure have a fibrous structure that extends in the longitudinal direction of the core wire 20 and is arranged in layers.

[0099] The thickness of the crystal grain layers was calculated from the obtained microscope images. First, boundary lines were drawn at the boundaries of the crystal grains in each image. The multiple boundary lines were aligned approximately parallel to the central axis X of the core wire 20. The average distance between adjacent boundary lines was then calculated from the image and used as the thickness of the crystal grain layer. The thickness of the crystal grain layer and its standard deviation are shown in Table 5. As a result, in Example 15, it was confirmed that the thickness of the crystal grain layer forming the fibrous structure was 60 nm, and the standard deviation was 41 nm or less. It was also confirmed that more than 50% of the crystal grains forming the fibrous structure had a layer thickness of less than 50 nm.

[0100]

[0101] Cross-sectional analysis of the wire was performed using an electrolytic emission scanning electron microscope (FE-SEM). Microscope samples were prepared using a cross-section polisher (CP) (SM-09010: JEOL Ltd.), with an acceleration voltage of 5.0 kV and an argon ion source. After CP processing, osmium coating was applied.

[0102] Next, using a field emission transmission electron microscope (JSM-IT800: manufactured by Nippon FE-I Co., Ltd.), each sample was observed with an acceleration voltage of 5.0 kV and the imaging method being backscattered electron imaging. The microscopic images of the cross-sections of the SUS301 stainless steel wire are shown in Figure 16, and the microscopic images of the cross-sections of the SUS304 stainless steel wire are shown in Figure 17. As a result, in Example 15, it was confirmed that the crystal grains of the metal structure had an irregularly arranged irregular structure in the cross-section perpendicular to the central axis X of the core wire 20. In the cross-section of Example 15 shown in Figure 16, there were no lines extending in a specific direction, and a homogeneous mixed structure was confirmed overall. In the cross-section of Reference Example 4 shown in Figure 17, multiple lines extending in a specific direction (up and down in the figure) were confirmed.

[0103] <Evaluation of Torque Performance> The torque transmission performance and torque force, which is the load required to rotate the wire, were evaluated for the SUS301 series stainless steel wire (Examples 16-17) used in the base core 40 and intermediate core 50, and for the SUS304 series stainless steel wire (Reference Example 5) used in the core wire of a guide wire with a different configuration. Measurements were performed using a PT-8000G (manufactured by Protec Co., Ltd.). Each wire was inserted into a tube having multiple curved sections of R20 mm and R30 mm as shown in Figure 18, and one end (input side) was gripped and the wire was twisted and rotated by a motor at a base rotation angle of 0 to 720°. The tip rotation angle (helix angle) and torque force at the other end (output side) were measured. Figure 19 shows the tip rotation angle relative to the base rotation angle, and the closer to an ideal straight line the wire has superior torque transmission performance. Examples 16 and 17 showed behavior along an ideal straight line compared to Reference Example 5, confirming that they have superior torque transmission performance. Table 6 shows the results of torque force measurement. Since the torque force values ​​in Examples 16 and 17 were smaller compared to Reference Example 5, it was confirmed that the load required to rotate the wire was smaller and the rotation operation was easier.

[0104]

[0105] <Measurement of Wire Stiffness> The three-point bending stiffness of the SUS301 series stainless steel wire (Examples 18 and 19) used in the proximal core 40 and intermediate core 50, and the SUS304 series stainless steel wire (Reference Example 6) used in the core wire of a guidewire with a different configuration were measured. The measurement was performed using an autograph with a pivot distance of 25.4 mm and an R2 mm indentation tool. The obtained three-point bending stiffness results are shown in Table 7. The bending stiffness of the wire can be considered an indicator of the pushability when advancing the guidewire into a stenotic lesion and the supportability of the catheter. The higher the bending stiffness, the better the pushability and supportability of the guidewire. From Table 7, it was confirmed that Examples 18 and 19 showed higher bending stiffness compared to Reference Example 6.

[0106]

[0107] As described above, the guide wire 10 according to this embodiment is a guide wire 10 having a long core wire 20, the core wire 20 having a base core 40, an intermediate core 50 joined to the tip of the base core 40 and having an intermediate core first constant outer diameter portion (second constant outer diameter portion 53), and a tip core 60 joined to the tip of the intermediate core 50 and having a tip core constant outer diameter portion (fourth constant outer diameter portion 63) made of a material that has a smaller outer diameter than the intermediate core first constant outer diameter portion and lower rigidity than the intermediate core 50, and the intermediate core 50 and tip The tip joint portion 30 that joins the end core 60 has an intermediate core second constant outer diameter portion (third constant outer diameter portion 55) having an outer diameter approximately equal to that of the tip core constant outer diameter portion, a base end side reduced diameter portion (fourth reduced diameter portion 56) that decreases in diameter from the tip of the intermediate core second constant outer diameter portion toward the tip, an enlarged diameter portion (third enlarged diameter portion 57 and fourth enlarged diameter portion 61) that expands in diameter from the tip of the base end side reduced diameter portion so that its outer diameter is larger than that of the tip core constant outer diameter portion, and a tip side reduced diameter portion (fifth reduced diameter portion 62) that decreases in diameter from the tip of the enlarged diameter portion toward the base end of the tip core constant outer diameter portion. As a result, the guide wire 10 has a smaller outer diameter for the intermediate core 50 than for the tip core 60 at the tip joint 30, and a second constant outer diameter section for the intermediate core is provided on the base end side of the tip joint 30. Compared to the case where the outer diameter is continuously increased from the base end of the tip joint 30 toward the tip of the first constant outer diameter section for the intermediate core without the second constant outer diameter section for the intermediate core, the length of the low-rigidity section near the base end of the tip joint 30 is shortened, while suppressing abrupt changes in the rigidity of the core wire 20 along the long axis direction caused by the difference in rigidity between the tip core 60 and the intermediate core 50. Therefore, the guide wire 10 has improved kink resistance and can suppress the occurrence of prolapse near the tip joint 30. Furthermore, by providing the guide wire 10 with an enlarged diameter section at the tip joint section 30 that expands its outer diameter to be larger than the constant outer diameter section of the tip core, the area of ​​the joint surface (tip joint surface 31) between the tip core 60 and the intermediate core 50 can be secured, thereby achieving high joint strength between the intermediate core 50 and the tip core 60.

[0108] The tip joint surface 31 between the intermediate core 50 and the tip core 60 is located closer to the base end than the portion of the tip joint 30 having the maximum outer diameter. This suppresses stress concentration on the tip joint surface 31 when the guide wire 10 is rotated while the tip joint 30 is curved, thereby improving its kink resistance.

[0109] The base-side reduced-diameter section (fourth reduced-diameter section 56) and the enlarged-diameter section (third enlarged-diameter section 57) are connected by a curved surface 58 that forms a smooth concave shape in the longitudinal section passing through the central axis X of the core wire 20. As a result, stress concentration at the tip joint surface 31 of the guide wire 10 is suppressed, thereby improving its kink resistance.

[0110] The intermediate core 50 is made of SUS301 series stainless steel. This allows the guide wire 10 to have high rigidity in the intermediate section, improving its pushability, torque transmission, and support for treatment devices such as catheters.

[0111] The tip core 60 is formed from a nickel-titanium alloy. This allows the guidewire 10 to have the appropriate flexibility and resilience to bend necessary when passing through sharply curved blood vessels.

[0112] The proximal joint 21, which joins the proximal core 40 and the intermediate core 50, includes a proximal projection 23 (a first enlarged diameter portion 43 and a second reduced diameter portion 51) that protrudes radially outward between the proximal end and the tip, which have substantially equal outer diameters. As a result, the guidewire 10 has a larger surface area at the joint surface (proximal joint surface 22) between the proximal core 40 and the intermediate core 50 of the proximal joint 21, thereby improving the joint strength between the proximal core 40 and the intermediate core 50. Therefore, it is possible to easily obtain a long guidewire 10 for use in procedures to treat lesions in the blood vessels of the lower limbs from the blood vessels of the wrist by joining multiple cores.

[0113] The proximal core 40 is made of the same metal as the intermediate core 50. This makes it easy to obtain a long guidewire 10 that has vascular selectivity, stenosis passage, pushability, and torque transmission properties suitable for procedures in which the wire is inserted into a blood vessel from the radial artery to treat vascular lesions in the lower limb region.

[0114] Furthermore, the guide wire 10 according to this embodiment includes a core wire 20 formed by solid-state bonding a first core (base core 40) and a second core (intermediate core 50), wherein the first core and the second core are made of stainless steel, and the joint portion (base joint portion 21) between the first core and the second core has a protruding portion (base protruding portion 23) that protrudes radially outward, and the protruding portion (base protruding portion 23) has a low-hardness portion 26 that has a lower Vickers hardness than the first core on the base end side of the joint and the second core on the tip side. As a result, the area of ​​the joint surface (base joint surface 22) between the first core and the second core is increased at the joint portion where hardness tends to decrease due to bonding, thereby improving the bonding strength between the first core and the second core.

[0115] The protruding portion (base protruding portion 23) may have a constant hardness portion 28 at the joint portion (base joint portion 21) where the Vickers hardness is lowest and substantially constant along the longitudinal axis. As a result, the constant hardness portion 28, which includes the part with the lowest hardness at the joint portion, has a predetermined length in the longitudinal axis direction of the core wire 20, thereby suppressing localized stress concentration at the joint portion when the guide wire 10 is bent. Therefore, the guide wire 10 does not break at the joint portion, and its kink resistance is improved.

[0116] The decrease in Vickers hardness of the base joint surface 22 relative to the Vickers hardness of the first core (first constant outer diameter portion 41) adjacent to the base end of the joint (base joint portion 21) and / or the second core (second constant outer diameter portion 53) adjacent to the tip end of the joint is 50% or less. As a result, the guide wire 10 is solid-state bonded with the first core and the second core by sufficient diffusion of atoms to each other without unnecessarily reducing the hardness of the core wire 20 near the joint, thus improving kink resistance. If the hardness reduction rate exceeds 50%, the joint may become too flexible, potentially resulting in insufficient kink resistance.

[0117] The length of the constant hardness section 28 along the long axis is 0.5 mm to 0.6 mm. This effectively suppresses localized stress concentration at the joint (base joint 21) when the guide wire 10 is bent, thereby improving the tensile strength and kink resistance at the joint. If the length of the constant hardness section 28 along the long axis is shorter than the lower limit, localized stress concentration may occur in the constant hardness section 28, potentially reducing the tensile strength and kink resistance. If the length of the constant hardness section 28 along the long axis is longer than the upper limit, the length of the low-hardness portion increases, potentially making it more susceptible to plastic deformation.

[0118] The length of the low-hardness portion 26 along its long axis is 0.7 mm to 0.8 mm. As a result, if the length of the low-hardness portion 26 along its long axis is shorter than the lower limit, localized stress concentration may occur in the constant-hardness portion 28, potentially reducing tensile strength and kink resistance. If the length of the low-hardness portion 26 along its long axis is longer than the upper limit, the length of the low-hardness portion increases, making it more susceptible to plastic deformation and potentially reducing kink resistance.

[0119] The joint (base joint 21) has recesses (base recess 24 and tip recess 25) on the base side and tip side of the protrusion, respectively. As a result, the guide wire 10 can gradually decrease in rigidity towards the protrusion, which has lower hardness than the first and second cores, by reducing its outer diameter with the recesses. This makes it possible to smooth the change in rigidity along the long axis near the joint. Therefore, the guide wire 10 can suppress stress concentration at the joint when bending, improving its kink resistance.

[0120] The Vickers hardness of the recessed portion is approximately constant along the longitudinal axis. As a result, the guide wire 10 can gradually decrease in rigidity towards the protruding portion, which has lower hardness than the first and second cores, by reducing its outer diameter in the recessed portion, thus making it easy to adjust the rigidity along the longitudinal axis around the joint.

[0121] The joint (proximal joint 21) has approximately equal outer diameters at the proximal and tip. This allows for the easy manufacture of long guidewires 10 used in procedures to treat vascular lesions in the lower limb region, by inserting them into the blood vessels from the radial artery, while gradually reducing the change in rigidity along the longitudinal axis around the joint.

[0122] The first and second cores are made of SUS301 series stainless steel. This allows the guidewire 10 to have high rigidity, improving its pushability, torque transmission, and support for treatment devices such as catheters.

[0123] Furthermore, the guidewire 10 according to the embodiment is a guidewire 10 equipped with a long core wire 20, the core wire 20 containing 6.0 wt% to 8.0 wt% nickel and stainless steel having a processing-induced martensite phase of 84 vol% or more. As a result, by using stainless steel with a low nickel content in the core wire 20, the guidewire 10 can contain a large amount of processing-induced martensite phase through processing, making it less susceptible to plastic deformation. Therefore, the guidewire 10 has excellent torque transmission and rotational operability while possessing pushability and catheter support.

[0124] Stainless steel contains at least 0.15 wt% of solid solution elements. As a result, the solid solution elements accumulate around dislocations in the lattice strain of the metal crystal core wire 20, effectively suppressing dislocation movement and making plastic deformation less likely. Consequently, the guide wire 10 is less prone to bending even in curved blood vessels, resulting in high torque transmission performance.

[0125] The solid solution elements consist of C in the range of 0.08 wt% to 0.11 wt% and N in the range of 0.04 wt% to 0.07 wt%. This allows the guide wire 10 to possess both appropriate strength and corrosion resistance.

[0126] Stainless steel has a shear modulus of 82 GPa or higher. As a result, the guide wire 10 containing this stainless steel has improved torsional rigidity, thus providing high torque transmission performance.

[0127] The stainless steel is selected from the SUS301 series. By using SUS301 series stainless steel, which has a composition with a low nickel content and a high content of carbon (C), a solid solution element, a core wire 20 suitable for the guide wire 10 can be easily obtained.

[0128] The core wire 20 comprises a second wire (tip core 60) made of a superelastic alloy, which is joined to the tip of a first wire (intermediate core 50) made of stainless steel. This allows the guide wire 10 to have appropriate flexibility and resilience against bending at its tip, which is necessary when selecting blood vessels or passing through sharply curved blood vessels, and high rigidity at its proximal end, which is necessary for improving pushability, torque transmission, and support for treatment devices such as catheters.

[0129] Furthermore, the method for manufacturing the guidewire 10 according to this embodiment is a method for manufacturing a guidewire 10 comprising a long core wire 20, wherein the core wire 20 contains stainless steel with a work-induced martensite phase of 84 vol% or more, formed by heat treatment of stainless steel containing 6.0 to 8.0 wt% nickel and at least 0.15 wt% or more solid solution elements. The method for manufacturing the guidewire 10 allows for the inclusion of a large amount of work-induced martensite phase by drawing stainless steel with a low nickel content, thus enabling the production of a guidewire 10 with high pushability, high torque transmission, and high catheter support.

[0130] In the manufacturing method of the guide wire 10, the heat treatment is performed at a temperature of 300°C to 500°C for 1 to 60 minutes. As a result, the manufacturing method of the guide wire 10 makes it possible to produce a guide wire 10 that is resistant to plastic deformation because the stainless steel undergoes a strain aging effect.

[0131] In the method for manufacturing the guide wire 10, the solid solution elements consist of C in the range of 0.08 wt% to 0.11 wt% and N in the range of 0.04 wt% to 0.07 wt%. As a result, the method for manufacturing the guide wire 10 makes it possible to produce a guide wire 10 that possesses both appropriate strength and corrosion resistance.

[0132] Furthermore, the guide wire 10 according to the embodiment is a guide wire 10 equipped with a long core wire 20, wherein at least a portion of the core wire 20 is made of stainless steel having a fibrous structure in which the crystal grains of the metallic structure in a longitudinal cross-section including the long axis of the guide wire 10 extend in the direction of the long axis and are arranged in layers, and an irregular structure in which the crystal grains of the metallic structure in a cross-section perpendicular to the long axis are arranged irregularly. As a result, the shear modulus of the core wire 20 is improved because the crystal grains in the longitudinal cross-section extend in the direction of the long axis and are aligned in orientation. On the other hand, since the orientation of the crystal grains in the cross-section of the core wire 20 is irregular and not aligned in one direction, rotational forces are less likely to be suppressed. As a result, the torque transmission performance of the guide wire 10 is improved.

[0133] In the longitudinal section, the guidewire 10 has a fibrous structure, with at least 50% of the layers consisting of crystal grains less than 50 nm thick. As a result, the guidewire 10 is less susceptible to plastic deformation because the movement of dislocations is hindered by the fine crystal grains in the metal structure of the core wire 20.

[0134] The guide wire 10 has an average thickness of 60 nm for the layer of crystal grains forming the fibrous structure in its longitudinal section, with a standard deviation of 41 nm or less. As a result, the guide wire 10 has less variation in the size of the crystal grains in the metal structure of the core wire 20, so that the crystal grains in the longitudinal section extend in the longitudinal axis direction and are more aligned in one direction, improving the shear modulus and further improving torque transmission.

[0135] It should be noted that the present invention is not limited to the embodiments described above, and various modifications can be made by those skilled in the art within the technical framework of the present invention. For example, the guide wire may be in a form without a coil.

[0136] This application is based on Japanese Patent Application No. 2025-056113, filed on March 28, 2025, and its disclosures are referenced and incorporated as a whole.

[0137] 10 Guide wire 20 Core wire 21 Base end joint 22 Base end joint surface 23 Base end projection 24 Base end recess 25 Tip side recess 26 Low hardness section 27 Base end transition section 28 Constant hardness section 29 Tip transition section 30 Tip joint 31 Tip joint surface 32 Tip projection 40 Base end core 41 First constant outer diameter section 42 First reduced diameter section 50 Intermediate core 52 Second enlarged diameter section 53 Second constant outer diameter section 55 Third constant outer diameter section 56 Fourth reduced diameter section 57 Third enlarged diameter section 58 Curved surface 60 Tip core 61 Fourth enlarged diameter section 62 Fifth reduced diameter section 63 Fourth constant outer diameter section

Claims

1. A guide wire having a long core wire, wherein the core wire contains stainless steel containing 6.0 wt% to 8.0 wt% nickel and 84 vol% or more of the work-induced martensite phase.

2. The guide wire according to claim 1, characterized in that the stainless steel contains at least 0.15 wt% or more of a solid solution element.

3. The guide wire according to claim 2, characterized in that the solid solution element consists of C in the range of 0.08 wt% to 0.11 wt% and N in the range of 0.04 wt% to 0.07 wt%.

4. The guide wire according to any one of claims 1 to 3, characterized in that the stainless steel has a shear modulus of 82 GPa or more.

5. The guide wire according to any one of claims 1 to 3, characterized in that the stainless steel is selected from the SUS301 series.

6. The guide wire according to any one of claims 1 to 3, characterized in that the core wire comprises a second wire made of a superelastic alloy joined to the tip of a first wire made of stainless steel.

7. A method for manufacturing a guide wire having a long core wire, wherein the core wire contains stainless steel having a work-induced martensite phase of 84 vol% or more, formed by heat-treating stainless steel containing 6.0 to 8.0 wt% nickel and at least 0.15 wt% or more solid solution elements.

8. The method for manufacturing a guide wire according to claim 7, characterized in that the heat treatment is performed at a temperature of 300°C to 500°C for 1 to 60 minutes.

9. The method for manufacturing a guide wire according to claim 7 or 8, characterized in that the solid solution element consists of C in the range of 0.08 to 0.11 wt% and N in the range of 0.04 to 0.07 wt%.

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