Medical balloon and catheter

Abstract

Provided is a medical balloon (1) having a longitudinal direction (x), a radial direction (y), and a circumferential direction (p), the medical balloon (1) having an outer layer (2) that is formed from a first polymer material and an inner layer (3) that is disposed inside the outer layer (2) and is formed from a second polymer material, wherein the birefringence of the inner layer (3) in a cross section perpendicular to the longitudinal direction (x) is higher than the birefringence of the outer layer (2) in a cross section perpendicular to the longitudinal direction (x). Here, the birefringence of the inner layer (3) is the absolute value of a difference between the refractive index in the circumferential direction and the refractive index in the radial direction (y) of an inner part of the inner layer (3) when divided into two equal parts in the radial direction (y), and the birefringence of the outer layer (2) is the absolute value of a difference between the refractive index in the circumferential direction and the refractive index in the radial direction (y) of an inner part of the outer layer (2) when divided into two equal parts in the radial direction (y).

Description

Medical Balloons and Catheters

[0001] The present invention relates to a medical balloon and a catheter equipped with the balloon.

[0002] Angioplasty, which uses a medical balloon and a catheter equipped with the balloon to dilate the narrowed area, is one treatment for conditions such as angina pectoris and myocardial infarction caused by narrowing of blood vessels. Various balloon catheters have also been proposed for the purpose of dilating narrowed areas in body cavities, such as the trachea and digestive tract. Treatment using balloon catheters is widely used because it is a minimally invasive therapy that does not require open chest surgery, such as bypass surgery.

[0003] Patent Documents 1 to 5 disclose balloons in which the balloon membrane is constructed with multiple layers in order to design the balloon to have desired performance.

[0004] International Publication No. 2013 / 47449 Special Publication No. 2009-519810 Special Publication No. 2016-502436 Special Publication No. 2010-527700 Special Publication No. 2009-534094

[0005] The basic performance characteristics of a medical balloon include pressure resistance, which directly affects its ability to dilate the lesion, and compliance, which allows the balloon's shape to fit the shape of the body cavity and change its diameter in response to the balloon's load pressure. Pressure resistance can be expressed, for example, in terms of tensile strength or burst pressure. Pressure resistance and compliance are essentially in a trade-off relationship; the harder the balloon membrane, the higher the pressure resistance, but the lower the compliance, which limits the types of lesions that can be treated. Therefore, an object of the present invention is to provide a medical balloon and a catheter equipped with such a balloon that have both high pressure resistance and high compliance.

[0006] The medical balloon according to the embodiment of the present invention that has solved the above problems is as follows: [1] A medical balloon having a longitudinal direction, a radial direction, and a circumferential direction, comprising: an outer layer made of a first polymer material; and an inner layer made of a second polymer material, disposed inside the outer layer, wherein the birefringence of the inner layer in a cross section perpendicular to the longitudinal direction is higher than the birefringence of the outer layer in a cross section perpendicular to the longitudinal direction. Here, the birefringence of the inner layer in the cross section perpendicular to the longitudinal direction is the absolute value of the difference between the circumferential refractive index of the inner portion of the inner layer and the radial refractive index of the inner portion of the inner layer, when the inner layer is divided into two equal parts in the radial direction into an inner portion and an outer portion. The birefringence of the outer layer in the cross section perpendicular to the longitudinal direction is the absolute value of the difference between the circumferential refractive index of the inner portion of the outer layer and the radial refractive index of the inner portion of the outer layer, when the outer layer is divided into two equal parts in the radial direction into an inner portion and an outer portion.

[0007] Furthermore, the medical balloon according to the embodiment is preferably any one of the following [2] to [8]. [2] The medical balloon according to [1], wherein the birefringence of the inner layer in a cross section perpendicular to the longitudinal direction is 0.001 or more higher than the birefringence of the outer layer in a cross section perpendicular to the longitudinal direction. [3] The medical balloon according to [1] or [2], wherein the first polymer material is polyamide, and the second polymer material is polyamide elastomer. [4] The medical balloon according to any one of [1] to [3], wherein the compliance of the medical balloon is higher than the compliance of a hypothetical single-layer balloon having the same outer diameter and thickness as the medical balloon. [5] The medical balloon according to any one of [1] to [4], wherein the tensile strength of the medical balloon is higher than the tensile strength of a hypothetical single-layer balloon having the same outer diameter and thickness as the medical balloon. [6] The medical balloon according to any one of [1] to [5], wherein the cross-sectional area of ​​the inner layer in a cross section perpendicular to the longitudinal direction is 20% or more of the cross-sectional area of ​​the outer layer in a cross section perpendicular to the longitudinal direction. [7] The medical balloon according to any one of [1] to [6], wherein a coating layer is disposed outside the outer layer, and the coating layer contains a physiologically active agent. [8] The medical balloon according to [7], wherein the physiologically active agent has a crystalline structure.

[0008] The catheter according to the embodiment of the present invention that can solve the above problems is as follows: [9] A catheter equipped with the medical balloon according to any one of [1] to [8].

[0009] The medical balloon and catheter equipped with it have both high pressure resistance and compliance, allowing them to be used for a variety of treatments, eliminating the need to use different balloons and catheters depending on the type of lesion or body part.

[0010] 1 is a longitudinal cross-sectional view of a medical balloon according to an embodiment of the present invention; FIG. 2 is an end view of a cut portion of the balloon taken along line II-II in FIG. 1; FIG. 3 is an end view of a cut portion showing a modification of the cut portion of the balloon shown in FIG. 2; FIG. 4 is an explanatory diagram showing a sample for measuring birefringence; FIG. 5 is a longitudinal cross-sectional view of a hypothetical single-layer balloon; FIG. 6 is an end view of a cut portion of a hypothetical single-layer balloon taken along line VI-VI in FIG. 5; FIG. 7 is an end view of a cut portion showing another modification of the cut portion of the balloon shown in FIG. 2; FIG. 8 is a schematic diagram of a catheter equipped with the balloon shown in FIG. 1; FIG. 10 is an optical microscope photograph showing the cutting position of a sample from the balloon in Example 1; FIG. 11 is an optical microscope photograph showing the cutting position of a sample from the balloon in Example 2; FIG. 12 is an optical microscope photograph showing the cutting position of a sample from the balloon in Example 3; FIG. 13 is an explanatory diagram showing the retardation measurement position in the examples; FIG. 14 is an optical microscope photograph showing the retardation measurement position in the cross section of the sample in Example 1; FIG. 15 is an optical microscope photograph showing the retardation measurement position in the cross section of the sample in Example 2; FIG. 16 is an optical microscope photograph showing the retardation measurement position in the cross section of the sample in Example 3.

[0011] The present invention will be described in more detail below based on the following embodiments. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the above and below-described purposes, and all such modifications are included within the technical scope of the present invention. For convenience, hatching and component symbols may be omitted in the drawings. In such cases, reference should be made to the specification and other drawings. The dimensions of various components in the drawings may differ from their actual dimensions, as priority is given to helping understand the features of the present invention.

[0012] A medical balloon according to one embodiment of the present invention is a medical balloon having longitudinal, radial, and circumferential directions, comprising an outer layer made of a first polymer material and an inner layer disposed inside the outer layer and made of a second polymer material, wherein the birefringence of the inner layer in a cross section perpendicular to the longitudinal direction is higher than the birefringence of the outer layer in a cross section perpendicular to the longitudinal direction, where the birefringence of the inner layer in the cross section perpendicular to the longitudinal direction is the absolute value of the difference between the circumferential refractive index of the inner portion of the inner layer and the radial refractive index of the inner portion of the inner layer when the inner layer is divided into two equal parts radially into an inner portion and an outer portion, and the birefringence of the outer layer in the cross section perpendicular to the longitudinal direction is the absolute value of the difference between the circumferential refractive index of the inner portion of the outer layer and the radial refractive index of the inner portion of the outer layer when the outer layer is divided into two equal parts radially into an inner portion and an outer portion. The medical balloons described above have both high pressure resistance and compliance, allowing them to be used for a variety of treatments, eliminating the need to select different balloons depending on the type of lesion or body part.

[0013] A medical balloon and catheter according to one embodiment of the present invention will be described with reference to Figures 1 to 8. Hereinafter, the medical balloon may be simply referred to as a balloon. Figure 1 is a longitudinal cross-sectional view of a medical balloon according to one embodiment of the present invention. Figure 2 is a cross-sectional end view of the balloon taken along line II-II in Figure 1. Figure 3 is a cross-sectional end view showing a modified cross-section of the balloon shown in Figure 2. Figure 4 is an explanatory diagram showing a sample for measuring the circumferential refractive index. Figure 5 is a longitudinal cross-sectional view of a hypothetical single-layer balloon. Figure 6 is a cross-sectional end view of a hypothetical single-layer balloon taken along line VI-VI in Figure 5. Figure 7 is a cross-sectional end view showing another modified cross-section of the balloon shown in Figure 2. Figure 8 is a schematic diagram of a catheter equipped with the balloon shown in Figure 1.

[0014] As shown in FIG. 1 , the balloon 1 has a longitudinal direction x, a radial direction y, and a circumferential direction p. As shown in FIG. 1 , the balloon 1 preferably has a distal end 5A and a proximal end 5B in the longitudinal direction x. The proximal side of the balloon 1 refers to the direction toward the user or surgeon with respect to the longitudinal direction x of the balloon 1, and the distal side refers to the opposite direction from the proximal side, i.e., the direction toward the treatment target. Note that in FIG. 1 , the right side of the figure is the proximal side, and the left side of the figure is the distal side. The radial direction y of the balloon 1 refers to the radial direction of the balloon 1. In the radial direction y of the balloon 1, the inward direction refers to the direction toward the center of the longitudinal axis of the balloon 1, and the outward direction in the radial direction y refers to the direction extending radially from the center of the longitudinal axis opposite to the inward direction. The circumferential direction p of the balloon 1 refers to the direction around the longitudinal axis. The balloon 1 preferably has an outer surface 6A and an inner surface 6B.

[0015] As shown in FIGS. 1 and 2 , the balloon 1 has an outer layer 2 made of a first polymer material and an inner layer 3 made of a second polymer material and disposed inside the outer layer 2. The inner layer 3 is disposed inside the outer layer 2 in the radial direction y. The outer layer 2 may be disposed on the outermost side in the radial direction y. The inner layer 3 may be disposed on the innermost side in the radial direction y. As shown in FIG. 2 , the outer layer 2 and the inner layer 3 may be in contact with each other in the radial direction y. One or more layers may be disposed between the outer layer 2 and the inner layer 3 in the radial direction y. For example, in FIG. 3 , an intermediate layer 4 is disposed between the outer layer 2 and the inner layer 3.

[0016] As shown in FIG. 2, the balloon 1 has a birefringence Δn ｉ (ring) is the birefringence Δn of the outer layer 2 in a cross section perpendicular to the longitudinal direction x ｏ Here, the birefringence Δn of the inner layer 3 in a cross section perpendicular to the longitudinal direction x is ｉ The (ring) is the refractive index n of the inner portion 3A of the inner layer 3 in the circumferential direction p when the inner layer 3 is divided into two equal parts, an inner portion 3A and an outer portion 3B, in the radial direction y. ｒｉ and the refractive index n of the inner portion 3A of the inner layer 3 in the radial direction y ｄｉ and the birefringence Δn of the outer layer 2 in a cross section perpendicular to the longitudinal direction x. ｏThe (ring) is the refractive index n of the inner portion 2A of the outer layer 2 in the circumferential direction p when the outer layer 2 is divided into two equal parts, an inner portion 2A and an outer portion 2B, in the radial direction y. ｒо and the refractive index n in the radial direction y of the inner portion 2A of the outer layer 2 ｄｏ This is the absolute value of the difference between the birefringence of the outer layer 2 and the inner layer 3. By setting the magnitude relationship between the birefringence of the outer layer 2 and the inner layer 3 in this way, the balloon 1 has both high pressure resistance and high compliance. This allows the balloon to be used for a variety of treatments, eliminating the need to select different balloons depending on the type of lesion or body part.

[0017] In this specification, the refractive index refers to the relative refractive index. The birefringence Δn of the outer layer 2 in a cross section perpendicular to the longitudinal direction x ｏ (ring) and birefringence Δn of inner layer 3 ｉ The ring can be measured by the following method. As shown in FIG. 4 , a balloon piece obtained by cutting the balloon 1 along the longitudinal direction x and the radial direction y is used as the measurement sample 15. The sample 15 is obtained by cutting the membrane of the balloon 1 using a blade such as a knife or a laser irradiation device. The size and shape of the sample 15 are arbitrary. Hereinafter, a cross section of the sample 15 perpendicular to the longitudinal direction x of the balloon 1 may be referred to as a ring cut surface 16, and a cross section of the sample 15 along the longitudinal direction x of the balloon 1 may be referred to as a long-axis cross section 17. The ring cut surface 16 of the sample 15 is observed with a polarizing microscope, and (i) the retardation R at the ring cut surface 16 of the sample 15 in the inner portion 2A of the outer layer 2 is measured using a compensator. ｏ (ii) the retardation R at the ring section 16 of the sample 15 in the inner portion 3A of the inner layer 3 ｉ (circle). Also, the thickness t of the sample 15 １ The thickness t １ is the length of the sample 15 in the direction perpendicular to the cross-section 16 of the sample 15. The unit of retardation is nm, and the thickness t １ As shown in FIG. 4, the retardation R ｏ (ring) is the thickness t in equation (1) １ Substituting these values ​​and calculating the formulas (1) to (3), the birefringence Δn of the outer layer 2 at the cross section 16 is ｏ(ring) can be calculated. In addition, the retardation R ｉ (ring) is the thickness t in equation (1) １ Substituting these values ​​and calculating the formulas (1) to (3), the birefringence Δn of the inner layer 3 at the cross section 16 is ｉ In the following equations, C is a constant (unitless) that depends on the thickness of the crystal attached to the compensator, and i is the correction angle (rad) of the compensator. Δn = R / t (1) R = C × f(i) (2) f(i) = sin ２ i(1+0.2041×sin ２ i+0.0627×sin ４ i) ... (3)

[0018] The birefringence Δn of the outer layer 2 in the major axis cross section 17 is calculated by the following method. ｏ (long) and the birefringence Δn of the inner layer 3 ｉ First, the longitudinal cross section 17 of the sample 15 is observed with a polarizing microscope, and (iii) the retardation R ｏ (Long), and (iv) retardation R at the long axis cross section 17 of the sample 15 in the inner portion 3A of the inner layer 3 ｉ At this time, the thickness t of the sample 15 is measured. ２ The thickness t ２ is the length of the sample 15 in the direction perpendicular to the long-axis cross section 17 of the sample 15. The sample used to measure the retardation at the cross section 16 and the sample used to measure the retardation at the long-axis cross section 17 may be the same, or may be cut out separately from the balloon. The unit of retardation is nm, and the unit of thickness t ２ The unit of is μm. The retardation R ｏ (length) is the thickness t in equation (1) ２ Substituting these values ​​and calculating the formulas (1) to (3), the birefringence Δn of the outer layer 2 in the major axis cross section 17 is ｏ (length) can be calculated. In addition, the retardation R ｉ (length) is the thickness t in equation (1) ２Substituting these values ​​and calculating the formulas (1) to (3), the birefringence Δn of the inner layer 3 in the major axis cross section 17 is ｉ (Long) can be obtained.

[0019] Birefringence Δn of the outer layer 2 at the cross section 16 ｏ (ring) and the birefringence Δn of the outer layer 2 in the major axis cross section 17 ｏ (Long) is expressed by the following formulas (4) to (6). In the following formulas, n ｒｏ : refractive index (unitless) of the outer layer 2 in the circumferential direction p of the balloon 1, n ｄｏ : refractive index (unitless) of the outer layer 2 in the thickness direction (radial direction y) of the balloon 1, n Ｌｏ : refractive index (unitless) of the outer layer 2 in the longitudinal direction x of the balloon 1, n ｏ : average refractive index of the outer layer 2 (unitless). ｏ (ring)=|n ｒｏ -n ｄｏ | ... (4) Δn ｏ (long)=|n Ｌｏ -n ｄｏ |・・・(5) n ｏ = (n ｒｏ ２ +n Ｌｏ ２ +n ｄｏ ２ ) / 3 ... (6)

[0020] Birefringence Δn of the inner layer 3 at the cross section 16 ｏ (ring) and the birefringence Δn of the inner layer 3 in the major axis cross section 17 ｏ (Long) is expressed by the following formulas (7) to (9). In the following formulas, n ｒｉ : refractive index of the inner layer 3 in the circumferential direction p of the balloon 1 (unitless), n ｄｉ : refractive index (unitless) of the inner layer 3 in the thickness direction (radial direction y) of the balloon 1, n Ｌｉ : refractive index of the inner layer 3 in the longitudinal direction x of the balloon 1 (unitless), n ｉ : Average refractive index of the inner layer 3 (unitless). ｉ (ring)=|n ｒｉ -n ｄｉ | ... (7) Δn ｉ (long)=|n Ｌｉ -n ｄｉ |・・・(8) nｉ = (n ｒｉ ２ +n Ｌｉ ２ +n ｄｉ ２ ) / 3 ... (9)

[0021] If the above equations (4) to (9) are solved as in the following equations (10) to (14), the refractive index n in the circumferential direction p of the balloon 1 is obtained. ｒ can be obtained.

[0022]

[0023] n Ｌ = n ｄ +Δn (long)...(11) n ｄ = n ｒ -Δn (ring)...(12) b=2Δn(length)-4Δn(ring)...(13) c=2(Δn(ring)) ２ +Δn (long)) ２ -2Δn (ring) x Δn (length) -3n ２ ...(14)

[0024] The retardation value at each cross section of the sample in the inner portion 2A of the outer layer 2 is preferably the retardation at the inner position in the radial direction y of the inner portion 2A, more preferably the retardation in the innermost region in the radial direction y when the inner portion 2A is divided into two equal parts in the radial direction y of the balloon 1, even more preferably the retardation in the innermost region in the radial direction y when the inner portion 2A is divided into three equal parts in the radial direction y of the balloon 1, and even more preferably the retardation in the innermost region in the radial direction y when the inner portion 2A is divided into four equal parts in the radial direction y of the balloon 1.

[0025] The retardation value at each cross section of the sample in the inner portion 3A of the inner layer 3 is preferably the retardation at the inner position in the radial direction y of the inner portion 3A, more preferably the retardation in the innermost region in the radial direction y when the inner portion 3A is divided into two equal parts in the radial direction y of the balloon 1, even more preferably the retardation in the innermost region in the radial direction y when the inner portion 3A is divided into three equal parts in the radial direction y of the balloon 1, and even more preferably the retardation in the innermost region in the radial direction y when the inner portion 3A is divided into four equal parts in the radial direction y of the balloon 1.

[0026] The refractive indexes of the inner portion 2A of the outer layer 2 (n ｒｏ , n ｄｏ , n Ｌｏ ) is preferably the refractive index at the inner position in the radial direction y of the inner portion 2A, more preferably the refractive index at the innermost region in the radial direction y when the inner portion 2A is divided into two equal parts in the radial direction y of the balloon 1, even more preferably the refractive index at the innermost region in the radial direction y when the inner portion 2A is divided into three equal parts in the radial direction y of the balloon 1, and even more preferably the refractive index at the innermost region in the radial direction y when the inner portion 2A is divided into four equal parts in the radial direction y of the balloon 1.

[0027] The refractive indexes of the inner portion 3A of the inner layer 3 (n ｒｉ , n ｄｉ , n Ｌｉ ) is preferably the refractive index at the inner position in the radial direction y of the inner portion 3A, more preferably the refractive index at the innermost region in the radial direction y when the inner portion 3A is divided into two equal parts in the radial direction y of the balloon 1, even more preferably the refractive index at the innermost region in the radial direction y when the inner portion 3A is divided into three equal parts in the radial direction y of the balloon 1, and even more preferably the refractive index at the innermost region in the radial direction y when the inner portion 3A is divided into four equal parts in the radial direction y of the balloon 1.

[0028] In this specification, the retardation R may be measured at any position in the longitudinal direction x of the balloon 1, but is preferably measured in the straight pipe portion 11A of the balloon 1, and more preferably in a portion of the straight pipe portion of the balloon 1 that includes the central position in the longitudinal direction x. That is, it is preferable that the measurement sample 15 is cut out from the straight pipe portion 11A of the balloon 1. The straight pipe portion 11A will be described later.

[0029] Birefringence Δn of the inner layer 3 in a cross section (circular cross section 16) perpendicular to the longitudinal direction x ｉ (ring) is the birefringence Δn of the outer layer 2 in a cross section (ring cross section 16) perpendicular to the longitudinal direction x о It is preferable that the birefringence is at least 0.001 higher than that of the ring. By setting the magnitude relationship of the birefringence in this way, it becomes easier to obtain a balloon 1 that has both high pressure resistance and high compliance.

[0030] Birefringence Δn of the inner layer 3 at the cross section 16 ｉ (ring) is the birefringence Δn of the outer layer 2 at the ring cross section 16 о The birefringence may be higher than the ring by 0.002 or more, 0.003 or more, 0.006 or more, 0.008 or more, 0.010 or more, or 0.030 or less, 0.025 or less, 0.020 or less, 0.018 or less, or 0.014 or less. By setting the magnitude relationship of the birefringence in this way, it becomes easier to obtain a balloon 1 that has both high pressure resistance and high compliance performance.

[0031] Examples of polymer materials constituting the balloon 1 include polyolefin-based resins such as polyethylene, polypropylene, and ethylene-propylene copolymer; polyester-based resins such as polyethylene terephthalate and polyester elastomer; polyurethane-based resins such as polyurethane and polyurethane elastomer; polyphenylene sulfide-based resins; polyamide-based resins such as polyamide and polyamide elastomer; fluorine-based resins; silicone-based resins; and natural rubbers such as latex rubber. These materials may be used alone or in combination. Among these, polyamide-based resins, polyester-based resins, and polyurethane-based resins are preferred. Elastomer resins are particularly preferred in terms of thinning and flexibility of the balloon 1. For example, among polyamide-based resins, nylon 12 and nylon 11 are preferred as resins constituting the balloon 1, with nylon 12 being more preferred due to its relatively easy moldability during blow molding. Furthermore, polyamide elastomers such as polyetheresteramide elastomers and polyamideether elastomers are preferred in terms of thinning and flexibility of the balloon 1. Among these, polyether ester amide elastomers are preferably used because they have high yield strength and provide good dimensional stability to the balloon 1 .

[0032] The first polymer material constituting the outer layer 2 and the second polymer material constituting the inner layer 3 may be the same type, but preferably are different types. Among the above-mentioned polymer materials, it is preferable that both the first polymer material and the second polymer material are polyamide-based resins. It is also preferable that the first polymer material is polyamide and the second polymer material is polyamide elastomer. By selecting the materials for the outer layer 2 and the inner layer 3 in this manner, it is possible to obtain a balloon 1 that has both high pressure resistance and high compliance.

[0033] As shown in Figure 3, when the balloon 1 has an intermediate layer 4 between the outer layer 2 and the inner layer 3, the intermediate layer 4 can also be made of the above-mentioned polymer material. The third polymer material constituting the intermediate layer 4 may be the same type as the first polymer material constituting the outer layer 2, but preferably they are different types. The third polymer material constituting the intermediate layer 4 may be the same type as the second polymer material constituting the inner layer 3, but preferably they are different types.

[0034] The balloon 1 can be manufactured by molding a polymer material. For example, the balloon 1 can be manufactured by placing a tube extruded by extrusion molding in a mold and biaxially stretching blow molding the tube. The balloon 1 can be formed into any shape depending on the shape of the mold. In addition to biaxial stretching blow molding, the balloon 1 can also be manufactured by other molding methods such as dip molding, injection molding, and compression molding.

[0035] The thickness of the balloon 1 can be, for example, 10 μm or more, 30 μm or more, or 50 μm or more, and can also be 150 μm or less, 120 μm or less, or 100 μm or less. The numerical ranges described here may be the thickness after expansion, but are preferably the thickness before expansion. The thickness of the balloon 1 can be measured using a known displacement meter.

[0036] The compliance (unit: mm / atm) of the balloon 1 is preferably higher than that of a hypothetical monolayer balloon 50 having the same outer diameter and membrane thickness as the balloon 1. This allows a single product to cover a wider range of blood vessel diameters than conventional monolayer balloons. Furthermore, because it is more flexible than conventional monolayer balloons, it prevents damage to blood vessels and provides good followability to proximal manipulations when inserting the balloon 1 into the body. Figures 5 and 6 show the configuration of the hypothetical monolayer balloon 50. The material of the balloon membrane of the hypothetical monolayer balloon 50 is not particularly limited, but it can be made of the same material as the outer layer 2, inner layer 3, or middle layer 4 of the balloon 1. Figures 5 and 6 show a monolayer balloon 50 made of a polyamide layer 51.

[0037] The compliance of the balloon 1 is preferably 1.03 times or more, preferably 1.05 times or more, preferably 1.07 times or more, preferably 1.10 times or more, preferably 1.30 times or more, or even 1.50 times or more of the compliance of a hypothetical single-layer balloon 50 having the same outer diameter and thickness as the balloon 1. The compliance of the balloon 1 may also be 5.00 times or less, 4.00 times or less, 3.00 times or less, or 2.70 times or less of the compliance of a hypothetical single-layer balloon 50 having the same outer diameter and thickness as the balloon 1.

[0038] The compliance of the balloon 1 is expressed as the slope (mm / atm) of the compliance curve that shows the relationship between the increase in the outer diameter of the balloon 1 and the inflation pressure (atm) applied to the inside of the balloon 1 within a predetermined operating range, for example, from 1 atm to the burst diameter. The outer diameter of the balloon 1 can be measured using a known measuring device such as a vernier caliper.

[0039] The tensile strength (unit: MPa) of the balloon 1 is preferably higher than the tensile strength of a hypothetical single-layer balloon 50 having the same outer diameter and film thickness as the balloon 1. This allows the balloon 1 to be used even when high pressure is applied to its interior, resulting in a high expansion force and making it suitable for expanding hard lesions such as calcified areas. Furthermore, because the balloon 1 has good pushability, it is easy to push the balloon 1 through a stricture when inserted into the body.

[0040] The tensile strength of balloon 1 is expressed as the balloon's burst pressure x balloon outer diameter just before bursting / balloon membrane thickness. The burst pressure (unit: MPa) is the pressure measured when the balloon bursts, measured by measuring the pressure of the fluid supplied into the balloon while expanding the balloon's diameter. The balloon membrane thickness is the membrane thickness when no load other than gravity is applied to the balloon, and is the membrane thickness before fluid is supplied into the balloon.

[0041] The tensile strength of balloon 1 is preferably 1.02 times or more, more preferably 1.05 times or more, even more preferably 1.10 times or more, and even more preferably 1.15 times or more, of the tensile strength of a hypothetical single-layer balloon 50 having the same outer diameter and film thickness as balloon 1, and is also acceptable to be 3.00 times or less, 2.50 times or less, 2.00 times or less, or 1.80 times or less.

[0042] The burst pressure of the balloon 1 is preferably higher than the burst pressure of a hypothetical single-layer balloon 50 having the same outer diameter and film thickness as the balloon 1. This allows the balloon 1 to be used even when high pressure is applied to its interior, resulting in a high expansion force of the balloon 1, making it suitable for use in expanding hard lesions such as calcified areas. In addition, because the balloon 1 has good pushability, it is easy to push the balloon 1 through a stricture when inserted into the body.

[0043] The burst pressure of balloon 1 is preferably 1.1 times or more, more preferably 1.2 times or more, and even more preferably 1.3 times or more, of the burst pressure of a hypothetical single-layer balloon 50 having the same outer diameter and film thickness as balloon 1, and is also acceptable to be 5.0 times or less, 4.0 times or less, 3.0 times or less, 2.8 times or less, or 2.5 times or less.

[0044] As can be seen from Figure 2, the cross-sectional area of ​​the inner layer 3 in a cross section perpendicular to the longitudinal direction x is preferably at least 20% of the cross-sectional area of ​​the outer layer 2 in a cross section perpendicular to the longitudinal direction x. By setting the cross-sectional area ratio between the outer layer 2 and the inner layer 3 in this manner, it becomes easier to obtain a balloon 1 that has both high pressure resistance and high compliance performance. Here, the cross section perpendicular to the longitudinal direction x for comparing the cross-sectional area ratio refers to a cross section at any position in the longitudinal direction x of the balloon 1, but may also be, for example, a cross section at the center of the balloon 1 in the longitudinal direction x. The same applies to the following explanation.

[0045] As can be seen from Figure 2, the cross-sectional area of ​​the inner layer 3 in a cross section perpendicular to the longitudinal direction x is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more of the cross-sectional area of ​​the outer layer 2 in a cross section perpendicular to the longitudinal direction x. Furthermore, the cross-sectional area of ​​the inner layer 3 in a cross section perpendicular to the longitudinal direction x is preferably 90% or less, more preferably 80% or less, and even more preferably 70% or less of the cross-sectional area of ​​the outer layer 2 in a cross section perpendicular to the longitudinal direction x. Setting the cross-sectional area ratio between the outer layer 2 and the inner layer 3 in this manner facilitates the production of a balloon 1 that exhibits both high pressure resistance and high compliance.

[0046] 1, the balloon 1 may have an expansion section 11, a distal sleeve section 12A located distal to the expansion section 11, and a proximal sleeve section 12B located proximal to the expansion section 11. The distal sleeve section 12A and / or the proximal sleeve section 12B are preferably fixed to a shaft 30, which will be described later.

[0047] 1 , throughout the entire longitudinal direction x of the expansion section 11 of the balloon 1, the cross-sectional area of ​​the inner layer 3 in a cross section perpendicular to the longitudinal direction x is preferably 20% or more, more preferably 30% or more, even more preferably 40% or more, and even more preferably 50% or more of the cross-sectional area of ​​the outer layer 2. Furthermore, throughout the entire longitudinal direction x of the expansion section 11 of the balloon 1, the cross-sectional area of ​​the inner layer 3 in a cross section perpendicular to the longitudinal direction x is preferably 90% or less, more preferably 80% or less, and even more preferably 70% or less of the cross-sectional area of ​​the outer layer 2. Setting the cross-sectional area ratio of the outer layer 2 to the inner layer 3 in the expansion section 11 in this manner facilitates the production of a balloon 1 that exhibits both high pressure resistance and high compliance.

[0048] The thickness ratio of the outer layer 2 to the inner layer 3 of the balloon 1 (thickness of the outer layer 2 / thickness of the inner layer 3) may be 1 / 9 or more, 2 / 8 or more, 3 / 7 or more, or 4 / 6 or more, or may be 9 / 1 or less, 8 / 2 or less, 7 / 3 or less, or 6 / 4 or less.

[0049] The thickness of the balloon 1, i.e., the thickness of the entire balloon including the outer layer 2 and the inner layer 3, can be, for example, 10 μm or more, 30 μm or more, or 50 μm or more, and can also be 150 μm or less, 120 μm or less, or 100 μm or less. The numerical ranges described here may be the thickness after expansion, but are preferably the thickness before expansion. Furthermore, the thickness described here is preferably the minimum thickness of the balloon 1. The thickness of the balloon 1 can be measured using a known displacement meter.

[0050] As shown in Figure 7, the balloon 1 may have a coating layer 20 disposed outside the outer layer 2. The presence of the coating layer 20 increases the slipperiness of the outer surface of the balloon 1, thereby improving the insertability of the balloon 1 when it is inserted into a body cavity.

[0051] The material forming the coating layer 20 may be hydrophilic or hydrophobic, but is preferably hydrophilic. Examples of hydrophilic coating agents include hydrophilic polymers such as polyvinyl alcohol, polyethylene glycol, polyacrylamide, polyvinylpyrrolidone, and methyl vinyl ether maleic anhydride copolymer, as well as hydrophilic coating agents made from any combination thereof. Examples of hydrophobic coating agents include polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), silicone oil, hydrophobic urethane resin, carbon coating, diamond coating, diamond-like carbon (dLC) coating, ceramic coating, and substances with low surface free energy terminated with alkyl or perfluoroalkyl groups.

[0052] The coating layer 20 preferably contains a physiologically active agent. When the coating layer 20 of the balloon 1 contains a physiologically active agent, the efficiency of treatment can be improved.

[0053] Examples of physiologically active substances used in the physiologically active drug include paclitaxel, docetaxel, sirolimus, temsirolimus, everolimus, zotarolimus, biolimus A9, cilostazol, cyclosporine, and NF-κB decoy oligonucleotides. The physiologically active substances used in the physiologically active drug may be used alone or in combination. Furthermore, the balloon 1 may be coated with a physiologically active substance alone, or an appropriate additive may be used in combination.

[0054] It is preferable that the physiologically active agent has a crystalline structure. When the agent has a crystalline structure, the agent is more likely to be retained on the surface of the balloon 1 during delivery. In addition, the position of the agent molecules is fixed within the crystalline structure, which also stabilizes the agent against changes in the environment and temperature. Furthermore, when the physiologically active agent has a crystalline structure, the agent becomes more brittle, making it more likely to peel off from the outer surface of the balloon 1 when the balloon 1 is inflated.

[0055] When a physiologically active drug having a crystalline structure is used, it is preferable that the physiologically active substance is crystalline. Examples of crystalline physiologically active substances include paclitaxel, sirolimus, everolimus, zotarolimus, etc. It is also preferable that the additive contained together with the physiologically active substance is crystalline. Examples of crystalline additives include sugar, urea, salts such as potassium iodide, ascorbic acid, polylactic acid, polyglycolic acid, etc.

[0056] Although not shown, the balloon 1 may have a balloon body and a protruding portion protruding outward in the radial direction y of the balloon body. The protruding portion of the balloon 1 is a portion that protrudes outward in the radial direction y beyond the outer surface of the balloon body when the balloon 1 is in an inflated state. The protruding portion makes it easier to make an incision of an appropriate depth in the narrowed area, facilitating incision. It also improves the strength of the balloon 1 and prevents over-expansion of the balloon 1 when pressurized. When the balloon 1 has a balloon body and a protruding portion, it is preferable that the balloon body has the outer layer 2 and inner layer 3 described above. The protruding portion may be made of the same material as the balloon body or a different material.

[0057] 1, the expansion section 11 of the balloon 1 may have a straight tube section 11A, a distal tapered section 11B located distal to the straight tube section 11A, and a proximal tapered section 11C located proximal to the straight tube section 11A. It is preferable that the outer diameters of the distal tapered section 11B and the proximal tapered section 11C decrease with increasing distance from the straight tube section 11A.

[0058] The shape of the expansion portion 11 of the balloon 1 is not particularly limited, but may be a sphere, an oval sphere, a cylinder, a cone, a frustum, or a combination of these shapes.

[0059] As shown in Figure 8, a catheter 40 according to one embodiment of the present invention includes the above-described balloon 1. Because the catheter 40 including the balloon 1 has high pressure resistance and compliance, it can be used to treat a variety of lesions, eliminating the need to use different balloons 1 depending on the type of lesion or body part.

[0060] As shown in Figure 8, the catheter 40 preferably includes a shaft 30 and a balloon 1 disposed on the outside of the shaft 30. The catheter 40 has a distal side and a proximal side, and the balloon 1 is preferably disposed on the distal side of the shaft 30. The catheter 40 is configured so that a fluid is supplied to the inside of the balloon 1 through the shaft 30, and the expansion and contraction of the balloon 1 can be controlled using an indeflator (balloon pressurizer). The fluid may be pressurized fluid pressurized by a pump or the like.

[0061] The shaft 30 may have an internal passage for a fluid used to inflate the balloon as well as a passage for a guidewire. For example, as can be seen from FIG. 8 , the shaft 30 may have an outer tube 31 and an inner tube 32 disposed within the lumen of the outer tube 31. In this case, the lumen of the inner tube 32 functions as a passage for a guidewire, and the space between the inner tube 32 and the outer tube 31 functions as a fluid passage. When the shaft 30 has the outer tube 31 and the inner tube 32, it is preferable that the inner tube 32 extends from the distal end of the outer tube 31 and penetrates distally of the balloon 1, the distal side of the balloon 1 being joined to the inner tube 32, and the proximal side of the balloon 1 being joined to the outer tube 31.

[0062] Examples of materials that can be used to form the shaft 30 include polyamide resins, polyester resins, polyurethane resins, polyolefin resins, fluorine-based resins, vinyl chloride resins, silicone resins, and natural rubber. These materials may be used alone or in combination. Among these, it is preferable that the material that forms the shaft 30 be at least one of polyamide resins, polyolefin resins, and fluorine-based resins. This can increase the slipperiness of the surface of the shaft 30 and improve the ease of insertion of the catheter 40 into a body cavity.

[0063] The balloon 1 and the shaft 30 can be joined by bonding with an adhesive, welding, or by attaching a ring-shaped member to the overlapping portion of the end of the balloon 1 and the shaft 30 and crimping the member.

[0064] As shown in FIG. 8 , a catheter 40 may be provided with a hub 35 on the proximal side of the shaft 30. The hub 35 may be provided with a fluid injection section 37 that communicates with a flow path for fluid supplied to the interior of the balloon 1. The hub 35 preferably has a guidewire insertion section 36 that communicates with a guidewire insertion passage. This facilitates operations such as supplying fluid to the interior of the balloon 1 to expand or contract the balloon 1 and delivering the catheter 40 to a treatment site along the guidewire. While FIG. 8 shows an example in which the balloon 1 is applied to a so-called over-the-wire catheter 40 in which a guidewire is inserted from the distal side to the proximal side of the shaft 30, the balloon 1 can also be applied to a so-called rapid exchange catheter in which a guidewire is inserted partway from the distal side to the proximal side of the shaft.

[0065] This application claims the benefit of priority based on Japanese Patent Application No. 2024-53838, filed on March 28, 2024. The entire contents of the specification of Japanese Patent Application No. 2024-53838, filed on March 28, 2024, are incorporated herein by reference.

[0066] Examples and comparative examples of the present invention will be described below. Note that the medical balloon according to one embodiment of the present invention is not limited to the descriptions of the examples and comparative examples.

[0067] (Preparation of Balloons) Example 1 A two-layer tube was molded using a polyamide outer layer (Rilsamid AESNO MED manufactured by Arkema) and a polyamide elastomer inner layer (PEBAX 6333 manufactured by Arkema). Dry nitrogen was blown into the resulting tube at 120°C under a pressure of 5.0 MPa for 60 seconds to perform blow molding. This resulted in a balloon with an outer diameter of 4.00 mm and a membrane thickness of 40.0 μm. The outer diameter shown here refers to the mold diameter, and this also applies to Examples 2 and 3 and Comparative Examples 12 to 14.

[0068] Example 2 A two-layer tube was produced using the same materials and molding conditions as in Example 1, and a two-layer balloon having an outer diameter of 6.00 mm and a film thickness of 40.0 μm was produced using the same blow molding conditions as in Example 1.

[0069] Example 3 A two-layer tube was produced using the same materials and molding conditions as in Example 1, and a two-layer balloon having an outer diameter of 8.00 mm and a film thickness of 40.0 μm was produced using the same blow molding conditions as in Example 1.

[0070] Comparative Examples 12 to 14 A single-layer balloon made of polyamide, Rilsamid AESNO MED (outer diameter 6.00 mm, film thickness 30 μm) manufactured by Arkema (Comparative Example 12), a single-layer balloon made of polyamide, SHIDEN HP (outer diameter 5.00 mm, film thickness 40 μm) manufactured by Kaneka Corporation (Comparative Example 13), and a single-layer balloon made of polyamide elastomer, PEBAX 6333 (outer diameter 3.50 mm, film thickness 30 μm) manufactured by Arkema (Comparative Example 14) were prepared.

[0071] The physical properties of the balloons of Examples 1 to 3 and Comparative Examples 12 to 14 (dimensions of the tube used to manufacture the balloon, thickness ratio of each layer to the total thickness in the radial direction of the balloon, expansion ratio (mold diameter / tube dimension), membrane thickness, burst pressure, outer diameter of the balloon at 0.1 MPa, outer diameter of the balloon at RBP, outer diameter of the balloon at rupture, tensile strength, compliance, elongation, birefringence of the outer layer in a cross section perpendicular to the longitudinal direction, and birefringence of the inner layer in a cross section perpendicular to the longitudinal direction) were measured and calculated using the following methods. The physical properties of the balloons of Comparative Examples 1 to 11 were determined by transcribing and converting the data described in Examples 1 to 9 and Comparative Examples 1 and 2 of Patent Document 1 (WO 2013 / 47449) or by calculating the necessary physical properties based on this data. The results are shown in Tables 2 and 3.

[0072] (Tube Dimensions) For Examples 1 to 3 and Comparative Examples 12 to 14, the inner and outer diameters of the tubes used to manufacture balloons were measured using an optical microscope, Axis Pro, manufactured by Micro Support Co., Ltd. For Comparative Examples 1 to 11, the dimensions of the tubes described in Examples 1 to 9 and Comparative Examples 1 and 2 of Patent Document 1 (for example, φ0.37 × 0.47 × 0.82 × 0.88 mm in Example 1 of Patent Document 1) were transcribed.

[0073] (Thickness ratio of each layer to the total thickness in the balloon's radial direction) For Examples 1 to 3 and Comparative Examples 12 to 14, the thickness of the entire balloon was measured using a Mitutoyo Digimatic Micrometer K330721A. For Examples 1 to 3 and Comparative Examples 12 to 14, the thickness of each layer of the balloon was measured using an Axis Pro optical microscope manufactured by Micro Support. The thickness ratio (%) of each layer to the total thickness in the balloon's radial direction was then calculated. For Comparative Examples 1 to 11, the thickness ratio of each layer to the total thickness in the balloon's radial direction was calculated from the dimensions of the tube described in Examples 1 to 9 and Comparative Examples 1 and 2 of Patent Document 1 (e.g., φ0.37 × 0.47 × 0.82 × 0.88 mm in Example 1 of Patent Document 1).

[0074] (Expansion Ratio Ratio (Mold Diameter / Tube Dimensions)) For Examples 1 to 3 and Comparative Examples 1 to 14, the expansion ratio was calculated from the mold diameter and tube dimension. Table 2 also lists the mold diameter. The mold diameters for Examples 1 to 3 and Comparative Examples 12 to 14 were measured using a Mitutoyo Digimatic Micrometer K330721A. The mold diameters for Comparative Examples 1 to 11 were calculated using the formula "tube innermost diameter x inner diameter expansion ratio." For example, in Comparative Example 1 (Example 1 of Patent Document 1), the tube innermost diameter was 0.37 mm and the inner diameter expansion ratio was 8.2 times, so the mold diameter was 3.03 mm.

[0075] (Film Thickness) For Examples 1 to 3 and Comparative Examples 12 to 14, the film thickness of the entire balloon was measured using a Digimatic Micrometer K330721A manufactured by Mitutoyo Corporation. For Comparative Examples 1 to 11, the film thickness was calculated from the dimensions of the tube described in Examples 1 to 9 and Comparative Examples 1 and 2 of Patent Document 1 (for example, φ0.37 × 0.47 × 0.82 × 0.88 mm in Example 1 of Patent Document 1).

[0076] (Burst Pressure) The pressure of the fluid supplied into the balloon was measured while the balloon was being expanded in diameter in Examples 1 to 3 and Comparative Examples 12 to 14, and the pressure applied to the balloon immediately before it burst was taken as the burst pressure (MPa). The burst pressures in Examples 1 to 3 and Comparative Examples 12 to 14 were measured using a Leak Tester 1000 manufactured by Crescent Design. The burst pressures in Comparative Examples 1 to 11 were calculated by converting the pressure resistance (burst pressure of the balloon) values ​​described in the examples of Patent Document 1 from atm to MPa.

[0077] (Outer diameter of balloon at 0.1 MPa applied, outer diameter of balloon at RBP, and outer diameter of balloon at rupture) For Examples 1 to 3 and Comparative Examples 12 to 14, the outer diameter of the balloon at 0.1 MPa applied and at rupture were measured. Measurements were performed using a Crescent Design Leak Tester 1000 and a Keyence High-Precision Dimension Measuring Instrument LS-3100. For Comparative Examples 1 to 11, the outer diameter at 22 atm pressurization, the maximum value that can be calculated from Patent Document 1 (outer diameter at 12 atm + outer diameter when expanded according to the compliance described up to RBP (22 atm)), was calculated and used as the outer diameter of the balloon at RBP. For example, in the case of Comparative Example 1 (Example 1 of Patent Document 1), this is 3.00 + 0.01 × 10 = 3.1 mm. Here, RBP (Rated Burst Pressure) is the lower limit pressure at which 99.9% or more of the balloons burst within a 95% confidence interval.

[0078] (Tensile Strength) The tensile strength (MPa) of the balloons in Examples 1 to 3 and Comparative Examples 12 to 14 was calculated using the formula "Tensile Strength = Burst Pressure × {(Outer Diameter of Balloon at Burst - Film Thickness × 2) / 2} / Film Thickness." For Comparative Examples 1 to 11, since Patent Document 1 does not disclose the inner diameter of the balloon at burst, the outer diameter at a pressure of 22 atm, which is the maximum value that can be calculated from Patent Document 1, was used as the outer diameter of the balloon at burst, and the tensile strength was calculated using the formula above.

[0079] (Compliance) The compliance of Examples 1 to 3 and Comparative Examples 12 to 14 was calculated from "(outer diameter of balloon at collapse (mm) - outer diameter of balloon at 0.1 MPa (mm)) / collapse pressure (MPa)". The compliance of Comparative Examples 1 to 11 was calculated from "(outer diameter of balloon at RBP (mm) - mold diameter (mm)) / pressure at RBP (MPa)". Generally, compliance is calculated by calculating the amount of change per unit pressure from nominal pressure (12 atm in the Example of Patent Document 1) to RBP pressure (22 atm in the Example of Patent Document 1), as described in Patent Document 1. The nominal pressure is the pressure when the balloon is inflated to its nominal outer diameter. However, (1) the balloons in the Examples and Comparative Examples of Patent Document 1 differ in outer diameter and pressure resistance characteristics. Furthermore, (2) the operating range of inflation pressure for calculating the above-mentioned general compliance value can be freely set by a person skilled in the art to a certain extent. Furthermore, (3) because the balloon outer diameter changes nonlinearly up to the time of rupture, there is a risk that convenient interpretations may be made depending on the numerical setting of the operating range of the balloon inflation pressure. Because of the above (1) to (3), we believe that it is not desirable to compare using general compliance (nominal pressure to RBP pressure). In this paper, we calculated the range from the minimum outer diameter to the maximum outer diameter that can be experimentally measured or calculated as the amount of change per unit pressure. The same applies to the degree of elongation, which will be described later.

[0080] (Elongation) The elongation (%) is the ratio of the outer diameter of the balloon to the inner diameter of the mold. For Examples 1 to 3 and Comparative Examples 12 to 14, the outer diameter of the balloon at rupture and at a pressure of 0.1 MPa was measured using a Leak Tester 1000 manufactured by Crescent Design Co., Ltd. and a High-Precision Dimension Measuring Instrument LS-3100 manufactured by Keyence Corporation, and the elongation was calculated using the formula "(outer diameter of the balloon at rupture - diameter of the balloon at a pressure of 0.1 MPa) / outer diameter of the balloon at a pressure of 0.1 MPa." The elongation of Comparative Examples 1 to 11 was calculated using the formula "(outer diameter of the balloon at RBP - diameter of the mold) / diameter of the mold." Here, the reason for this calculation in Comparative Examples 1 to 11 is that Patent Document 1 only describes the average elongation rate from the nominal pressure to the RBP, so the outer diameter at the RBP, which is the maximum value that can be calculated and grasped (in Comparative Example 1, the outer diameter was 3.1 mm at 2.2 MPa (22 atm)), was used as the maximum diameter, and the die diameter was used as the minimum value, and the elongation was calculated.

[0081] (The birefringence Δn of the outer layer in the cross section perpendicular to the longitudinal direction ｏ (ring), birefringence Δn of the inner layer in a cross section perpendicular to the longitudinal direction (ring cross section) ｉ (Ring)) Examples 1 to 3 As shown in sample 15 in Figure 4, rectangular parallelepiped balloon pieces were cut in the longitudinal and circumferential directions from the center of the straight tube part of the balloon produced in Examples 1 to 3, and used as measurement samples. Here, the sample used to measure the retardation at the ring cross section 16 and the sample used to measure the retardation at the major axis cross section 17 were not the same, but were cut out separately from the balloon. Figures 9, 10, and 11 show the cutting positions of the samples from the balloons used in Examples 1, 2, and 3, respectively. The ring cross section of the sample (ring cross section 16 in Figure 4) was observed with a Nikon polarizing microscope, Nikon OPTIPHOT-POL, and a compensator was used to measure (i) the retardation R at the ring cross section of the sample at the inner part of the outer layer. ｏ (ring), and (ii) retardation R at the ring cross section of the sample at the inner part of the inner layer. ｉ The retardation of the outer layer R ｏ (Ring) is measured at a position radially outwardly away from the inner surface of the outer layer by a distance of one-third of the thickness of the outer layer, and the retardation Rｉ The (ring) was measured at a position radially outwardly spaced a distance of one-third of the thickness of the inner layer from the inner surface of the inner layer. In Fig. 12, the measurement position of the retardation of the outer layer is indicated by P1, and the measurement position of the retardation of the inner layer is indicated by P2. Figs. 13, 14, and 15 show the measurement positions of the retardation on the ring cross section and the long axis cross section of the samples of Example 1, Example 2, and Example 3, respectively. The thickness t of the sample was measured using a laser microscope LEXT OLS4100 manufactured by Olympus Corporation. １ The thickness t １ is the length of the sample in the direction perpendicular to the cross-section of the sample. Table 1 shows the sizes of the samples used in Examples 1 to 3. C (a constant that depends on the thickness of the crystal attached to the compensator) is 0.713822 × 10 ４ From the above formulas (1) to (3), the birefringence Δn of the outer layer in the cross section (circular cross section) perpendicular to the longitudinal direction is ｏ (ring), birefringence Δn of the inner layer in a cross section perpendicular to the longitudinal direction (ring cross section) ｉ (ring) was measured.

[0082]

[0083] (The birefringence Δn of the outer layer in the cross section perpendicular to the longitudinal direction ｏ (ring), birefringence Δn of the inner layer in a cross section perpendicular to the longitudinal direction (ring cross section) ｉ (Ring)) Comparative Examples 1 to 11 The refractive index n in the circumferential direction of the inner surface (measurement point 1) of the polyamide layer of the middle layer described in Examples 1 to 9 and Comparative Examples 1 and 2 of Patent Document 1 ｒｏ , the refractive index n in the circumferential direction of the inner surface (measurement point 0) of the polyamide elastomer layer of the inner layer ｒｉ , and the average refractive index n: 1.51 are substituted into the above-mentioned formulas (4) to (9), and the birefringence Δn of the outer layer in the cross section perpendicular to the longitudinal direction is calculated. ｏ (ring) and the birefringence Δn of the inner layer in a cross section perpendicular to the longitudinal direction (ring cross section) ｉ (circles) was calculated.

[0084]

[0085]

[0086] (Summary) As in Examples 1 to 3, the birefringence Δn of the inner layer in the cross section perpendicular to the longitudinal direction ｉ (ring) is the birefringence Δn of the outer layer in a cross section perpendicular to the longitudinal direction ｏ It was found that balloons with a refractive index higher than that of the inner layer (annulus) had both high pressure resistance (burst pressure, tensile strength) and high compliance. On the other hand, balloons in which the circumferential refractive index of the inner portion of the outer layer was higher than the circumferential refractive index of the inner portion of the inner layer, such as those in Comparative Examples 1 to 11, and single-layer balloons, such as those in Comparative Examples 12 to 14, exhibited reduced pressure resistance (burst pressure, tensile strength) and / or compliance.

[0087] 1: Balloon 2: Outer layer 2A: Inner portion 2B: Outer portion 3: Inner layer 3A: Inner portion 3B: Outer portion 4: Middle layer 5A: Distal end 5B: Proximal end 6A: Outer surface 6B: Inner surface 11: Expanded portion 11A: Straight tube portion 11B: Distal tapered portion 11C: Proximal tapered portion 12A: Distal sleeve portion 12B: Proximal sleeve portion 15: Sample 16: Ring section 17: Longitudinal cross section 20: Coating layer 30: Shaft 35: Hub 40: Catheter 50: Virtual single-layer balloon 51: Polyamide layer x: Longitudinal direction y: Radial direction p: Circumferential direction

Claims

1. A medical balloon having a longitudinal direction, a radial direction, and a circumferential direction, comprising: an outer layer made of a first polymer material; and an inner layer made of a second polymer material disposed inside the outer layer, wherein the birefringence of the inner layer in a cross section perpendicular to the longitudinal direction is higher than the birefringence of the outer layer in a cross section perpendicular to the longitudinal direction, wherein the birefringence of the inner layer in the cross section perpendicular to the longitudinal direction is the absolute value of the difference between the circumferential refractive index of the inner portion of the inner layer and the radial refractive index of the inner portion of the inner layer when the inner layer is divided into two equal parts in the radial direction, and the birefringence of the outer layer in the cross section perpendicular to the longitudinal direction is the absolute value of the difference between the circumferential refractive index of the inner portion of the outer layer and the radial refractive index of the inner portion of the outer layer when the outer layer is divided into two equal parts in the radial direction.

2. The medical balloon according to claim 1, wherein the birefringence of the inner layer in a cross section perpendicular to the longitudinal direction is 0.001 or more higher than the birefringence of the outer layer in a cross section perpendicular to the longitudinal direction.

3. The medical balloon according to claim 1 or 2, wherein the first polymer material is polyamide, and the second polymer material is polyamide elastomer.

4. A medical balloon according to claim 1 or 2, wherein the compliance of said medical balloon is higher than the compliance of a hypothetical single-layer balloon having the same outer diameter and membrane thickness as said medical balloon.

5. A medical balloon according to claim 1 or 2, wherein the tensile strength of the medical balloon is higher than the tensile strength of a hypothetical single-layer balloon having the same outer diameter and film thickness as the medical balloon.

6. A medical balloon according to claim 1 or 2, wherein the cross-sectional area of ​​the inner layer in a cross section perpendicular to the longitudinal direction is 20% or more of the cross-sectional area of ​​the outer layer in a cross section perpendicular to the longitudinal direction.

7. A medical balloon according to claim 1 or 2, further comprising a coating layer disposed outside the outer layer, the coating layer containing a physiologically active agent.

8. The medical balloon according to claim 7, wherein the physiologically active agent has a crystalline structure.

9. A catheter comprising the medical balloon according to claim 1 or 2.

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