Coated film and method for forming coated film

Abstract

A coating film satisfying conditions necessary for an optical irradiation device and a method for forming the same are provided. A coating film 36, which is a coating film 36 for coating the surface of a substrate, wherein the coating film 36 contains a thermoplastic elastomer and a pigment, the mass ratio of the thermoplastic elastomer to the pigment is less than 1:2.0, in a tensile test in which a test piece obtained by coating the coating film 36 on a substrate having a width of 10 mm and a length of 40 mm is set in a tensile testing machine with a grip distance of 25 mm and measured at a tensile speed of 25 mm / minute, the elongation at break of the test piece (A) composed of the substrate and the coating film 36 is less than the elongation at break of a test piece (B) composed of the substrate, and the elongation of the test piece (A) is 40% or more of the elongation of the test piece (B).

Description

Technical Field

[0001] This invention relates to a coating film for application to the surface of a substrate and a method thereof for forming the same, for use in medical light irradiation devices. Background Technology

[0002] Various medical devices, such as catheters, are known for insertion into living organisms for treatment. In some medical devices, a coating applied to the surface of a substrate is required as a marker for visual identification of locations within the organism, or as a light shield to prevent light from reaching areas outside a specified range in light-irradiation devices.

[0003] As an example of a light irradiation device, there are known devices for irradiating lesions with light in photodynamic therapy (PDT) and photoimmunotherapy (PIT), which use photoreactive substances selective for tumor cells. The light irradiation medical device includes at least: a light-emitting part; and an elongated component with the light-emitting part at its front end. This light irradiation device has a balloon at the front end of the elongated component, and a light irradiator with the light irradiation part is disposed inside the balloon, allowing light to be irradiated from a light-transmitting window disposed in the balloon. In this light irradiation device, by expanding the balloon, the distance between the lesion and the light irradiation part can be maintained constant, and the position of the light irradiation part can be fixed relative to the lesion, thus enabling stable irradiation of the lesion with light.

[0004] In order to form a light-transmitting window in the balloon, a light-shielding body made of a coating with low light transmittance is formed on the surface of the balloon, which serves as the substrate, in the area outside the light-transmitting window. The coating is formed, for example, by vapor deposition of metal onto the substrate. As a light irradiation device having such a coating, the device described in Patent Document 1 is an example.

[0005] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2005-46640 Summary of the Invention

[0006] The problem that the invention aims to solve For coatings used in light irradiation devices, in addition to requiring sufficiently low light transmittance, several other conditions must be met. Since the light irradiation device is inserted into a living organism, the coating must exhibit low cytotoxicity. Furthermore, the coating must be water-resistant to prevent peeling due to water. Additionally, the coating must be formed at a temperature that does not deform the substrate. Moreover, to maintain the substrate's flexibility when the coating is applied, the coating must follow the substrate's elongation to a certain extent. This requires coatings that meet these conditions and methods for their formation.

[0007] The present invention was made to solve the above-mentioned problems, and its purpose is to provide a coating and a method thereof that meet the necessary conditions for use in light irradiation devices.

[0008] Methods for solving problems The present invention, which achieves the above-mentioned objective, relates to (1) a coating film for coating on the surface of a substrate, wherein the coating film comprises a thermoplastic elastomer and a pigment, the mass ratio of the thermoplastic elastomer to the pigment being less than 1:2.0, and in a tensile test in which a test piece obtained by coating the aforementioned substrate with the aforementioned coating film with a width of 10 mm and a length of 40 mm is placed in a tensile testing machine with a clamping distance of 25 mm and the test piece is measured at a tensile speed of 25 mm / min, the elongation at break of the test piece (A) composed of the aforementioned substrate and the aforementioned coating film is less than the elongation at break of the test piece (B) composed of the aforementioned substrate, and the elongation of the aforementioned test piece (A) is more than 40% of the elongation of the aforementioned test piece (B).

[0009] In the method for forming a coating film according to the present invention (10) to achieve the above-mentioned objective, a first solution is prepared by dissolving the aforementioned pigment in a solvent in such a way that the mass ratio of thermoplastic elastomer to pigment is less than 1:2.0; a second solution is prepared by dissolving the aforementioned thermoplastic elastomer in the aforementioned first solution; the aforementioned second solution is applied to a substrate and dried to obtain a coating film; in a tensile test in which a test piece obtained by applying the aforementioned coating film to the aforementioned substrate with a width of 10 mm and a length of 40 mm is placed in a tensile testing machine with a clamping distance of 25 mm and the test piece is measured at a tensile speed of 25 mm / min, the elongation at break of the test piece (A) composed of the aforementioned substrate and the aforementioned coating film is less than the elongation at break of the test piece (B) composed of the aforementioned substrate, and the aforementioned elongation of the aforementioned test piece (A) is more than 40% of the elongation of the aforementioned test piece (B).

[0010] Invention Effects The coating film constructed as described above is water-resistant and can be formed at a temperature that does not deform the substrate. Furthermore, the coating film follows the deformation of the substrate as it elongates to a certain extent, thus suppressing peeling or cracking from the substrate. Therefore, the coating film possesses the mechanical and optical properties necessary for realizing the function of a light irradiation device, and meets the characteristics required for use in a light irradiation device.

[0011] (2) In the coating described in (1) above, the elongation of the aforementioned test piece (A) may be more than 90% of the elongation of the aforementioned test piece (B). As a result, the coating can better follow the elongation of the substrate, and thus can reliably recover to its original shape when the substrate elongates or shrinks.

[0012] (3) In the coating of (1) or (2) above, the cytotoxicity intensity (IC50) can be, when the coating is evaluated in accordance with ISO 10993, be measured. 50 The cytotoxicity of the coating is weaker than that of the polyurethane membrane containing 0.25% zinc dibutyldithiocarbamate (ZDBC), which served as the positive control material B. Therefore, the cytotoxicity of the coating can be reduced to a level necessary for use in light-irradiated devices.

[0013] (4) In any of the coatings in (1) to (3) above, the film thickness of the aforementioned coating is 60 μm or less. As a result, the outer diameter of the light irradiation device can be suppressed.

[0014] (5) In any of the coatings in (1) to (4) above, the light transmittance of the aforementioned coating is 31% or less. Thus, the optical performance of the coating can be satisfied.

[0015] (6) In any of the coatings described in (1) to (5) above, the aforementioned thermoplastic elastomer may be a polyurethane elastomer. This improves the coating's ability to follow the deformation of the substrate.

[0016] (7) In any of the coatings described in (1) to (6) above, the aforementioned pigment may be titanium dioxide, carbon black, or a mixture of the aforementioned titanium dioxide and the aforementioned carbon black. Thus, it is possible to produce white, black, or gray coatings that meet the requirements for cytotoxicity strength.

[0017] (8) In any of the coatings in (1) to (7) above, the substrate may be a balloon made of a light-transmitting material and the thickness of the balloon is 30 μm. Thus, in a light irradiation device having a light irradiator inside the balloon (which has a coating formed in a way that allows light to be irradiated in a certain direction), the biological safety, mechanical and optical properties of the balloon can be satisfied.

[0018] (9) In any of the above (1) to (8), the mass ratio of the aforementioned thermoplastic elastomer to the aforementioned pigment is 1:0.5 or less, the thickness of the aforementioned coating is 30 μm or less, the light transmittance of the aforementioned coating is 0%, and the aforementioned pigment is carbon black. Thus, the coating has high biological safety and can also reduce the film thickness.

[0019] The coating film formation method described above can form a coating film with water resistance and the ability to be formed at a temperature that does not deform the substrate, thus meeting the characteristics required by light irradiation devices. Attached Figure Description

[0020] [ Figure 1[This is an overall view of the light irradiation device and the endoscope device having the coating of this embodiment.]

[0021] [ Figure 2 [This is a three-dimensional diagram of the balloon.]

[0022] [ Figure 3 [This is an enlarged cross-sectional view of the area near the front end of the light-illuminating instrument inserted into the endoscope.] Detailed Implementation

[0023] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that, for ease of explanation, the dimensions in the drawings are sometimes exaggerated and differ from the actual dimensions. Furthermore, in this specification and the accompanying drawings, constituent elements having substantially the same functional configuration are omitted from repeated description by assigning the same reference numerals. In this specification, the side of the device inserted into the organism is referred to as the "front end side," and the side where the operation is performed is referred to as the "base end side."

[0024] The light irradiation device 10 of this embodiment can be configured to be suitable for approaching and treating tumor cells via an endoscope system using an endoscope device 100. For example... Figure 1As shown, the light irradiation device 10 is used, for example, by being inserted into the endoscope device 100. The type of tumor is not particularly limited, but when used as an endoscope system by being inserted into the endoscope 100, it can be applied to tumors occurring in luminal organs such as the esophagus, stomach, small intestine, large intestine, urinary tract, blood vessels, external auditory canal, Eustachian tube, and nasal cavity. In this embodiment, the light irradiation device 10 is used, for example, in the following photoimmunotherapy: irradiating a drug adsorbed onto target cells disclosed in Japanese Patent No. 6127045 with light, thereby destroying the target cells. The target cells are tumor cells such as cancer cells or precancerous lesion cells. In this treatment method, a photosensitizing substance is used as the drug, which adsorbs an antibody that specifically binds only to antigens specific to the surface of tumor cells, and a photosensitizing substance paired with that antibody. Antibodies are not specifically limited, but examples include panitumumab, trastuzumab, HuJ591, pertuzumab, lapatinib, palbociclib, and olaparib. Photosensitizing substances are, for example, substances that react with near-infrared light at approximately 700 nm wavelength (IR700), i.e., hydrophilic phthalocyanines, but are not limited to these. When IR700 receives near-infrared light at approximately 660–740 nm wavelength, the ligands of the water-soluble functional groups break, resulting in a structural change from water-soluble to hydrophobic. Through this structural change, membrane proteins are pulled out, creating openings in the cell membrane, allowing water to enter the cell, thereby causing tumor cells to rupture and be destroyed. Additionally, IR700, when excited by near-infrared light, emits fluorescence at a wavelength different from the excitation wavelength. For example, when excited by near-infrared light with a wavelength around 690 nm, IR700 emits fluorescence with a wavelength around 700 nm. IR700 emits fluorescence through a photoreaction, while simultaneously changing its structure. After exerting its effect as a drug by destroying tumor cells, it ceases to emit fluorescence.

[0025] The endoscopic instrument 100 has an endoscope body 120 connected to a control display unit 110. The operator inserts the endoscope body 120 into a living organism and performs various procedures. The endoscope body 120 has: an elongated insertion portion 121 for insertion into the living organism; and a handle portion 122 provided at the base of the elongated insertion portion 121. The handle portion 122 has a forceps jaw 122b communicating with the cavity 125 of the elongated insertion portion 121. A light irradiation device 10 is inserted into the endoscopic instrument 100 through the forceps jaw 122b of the handle portion 122.

[0026] The light irradiation device 10 includes: a shaft portion 20 that extends through an endoscope 100; and a balloon 30 disposed at the front end of the shaft portion 20 and exposed at the front end of the strip insertion portion 121. Furthermore, the light irradiation device 10 has a base hub 70 disposed at its base end. An expansion device 80 for injecting fluid to inflate the balloon 30 is connected to the base hub 70. For example, an indeflator can be used as the expansion device 80.

[0027] In the light irradiation device 10, a light irradiator 90 is inserted into the bulb 30. The light irradiator 90 is exposed further from the base end of the light irradiation device 10 than the base end hub 70, and is connected to the light source section 95 that outputs light. The light irradiator 90 has: a light irradiation section 92 provided at the front end of the light irradiator 90 in the long axis direction; and an optical fiber connected to the light irradiation section 92 and extending towards the base end of the light irradiation device 90 in the long axis direction. For example, the light irradiator 90 is composed of a side-emitting optical fiber that can irradiate light radially outward around its entire circumference at its front end. It should be noted that the light irradiation section 92 and the optical fiber can be configured such that the diameter of the light irradiation section 92 is larger than the diameter of the optical fiber in the long axis direction of the light irradiator 90.

[0028] like Figure 2 As shown, the balloon 30 is capable of radial expansion between its foremost point 31 and its base 32. The central portion of the balloon 30 along its long axis is a straight cylindrical portion 33 with the same diameter along the long axis, while the two ends of the balloon 30 along its long axis are tapered portions 34 that taper towards both ends. Figure 2 As shown, the conical portion 34 can be configured as a hemispherical shape. It should be noted that the conical portion 34 can also be conical. The balloon 30 is formed of a light-transmitting material such as nylon or urethane. The thickness of the balloon 30 is, for example, 30 μm.

[0029] The aforementioned light irradiator 90 is disposed inside the balloon 30. The balloon 30 has a light-transmitting window 37 that allows light from the light irradiation section 92 of the light irradiator 90 to pass through; and a coating 36 whose light transmittance from the light irradiation section 92 is lower than that of the light-transmitting window 37. The coating 36 is formed by coating the balloon 30 onto its outer surface. In other words, the balloon 30 has a film formed by the coating 36 coated on its outer surface as a light-shielding body. As for the light-transmitting window 37, since the surface of the balloon 30, which is the substrate, is not covered by the coating 36, light from the light irradiation section 92 can pass through. That is, the portion not covered by the light-shielding body is defined as the light-transmitting window 37. The light-transmitting window 37 can be provided throughout the circumference (360 degrees) or provided on a portion of the circumference (e.g., 180 degrees).

[0030] like Figure 3As shown, the balloon 30 can protrude and expand from the front opening 125a of the lumen 125 of the endoscope 100 towards the front end. The endoscope 100 has an endoscope body 123 at its front end, which allows for visual identification of the balloon 30's state. The base end of the balloon 30 engages with the front end of the shaft portion 20 inserted into the lumen 125 of the endoscope 100. A tip 35 is provided at the front end of the balloon 30.

[0031] A tubular body 40 having an inner cavity 41 along its long axis is disposed inside the balloon 30. The tubular body 40 extends along its long axis inside the shaft portion 20. An expansion cavity 21 for fluid to flow through, allowing the balloon 30 to expand, is located inside the shaft portion 20 and outside the tubular body 40.

[0032] The light irradiator 90 is inserted into the inner cavity 41 of the tubular body 40. As a side-emitting optical fiber capable of irradiating light radially outward around its entire circumference, the light irradiator 90 has a light irradiation section 92 at its front end capable of irradiating light radially. The tubular body 40 is formed of a light-transmitting material so that light from the light irradiation section 92 can pass through.

[0033] Light from the light irradiation unit 92 passes through the light transmission window 37 of the balloon 30 and irradiates the outside. The portion of the balloon 30 outside the light transmission window 37 is covered by the coating 36, resulting in low light transmittance from the light irradiation unit 92. To selectively irradiate only the lesion and its surrounding area, the coating 36 requires sufficiently low light transmittance as an optical property. Furthermore, the coating 36 requires mechanical properties including the ability to deform with the expansion and contraction of the balloon 30, and water resistance and abrasion resistance when the balloon 30 is inserted into the body. In addition, since the coating 36 is used in the light irradiation device 10 inserted into the body, it also needs to be biologically safe.

[0034] The coating 36 formed on the balloon 30, which serves as the substrate, will be described in detail. The coating 36 comprises a thermoplastic elastomer and a pigment. In this embodiment, a polyurethane elastomer is used as the thermoplastic elastomer. However, polystyrene elastomers, polyamide elastomers, and other materials can also be used as the thermoplastic elastomer, and are not limited to polyurethane elastomers.

[0035] There are no particular limitations on the pigments used, as long as they are substances capable of coloring the coating 36. However, in this embodiment, titanium dioxide is used as the pigment for white coloring, and carbon black is used as the pigment for black coloring. Alternatively, the coating 36 can be colored gray by mixing titanium dioxide and carbon black. Other pigments can also be used, such as phthalocyanine blue or phthalocyanine green.

[0036] As an example of coating 36, coating 36 is formed on a substrate using the formulations and thicknesses listed in Table 1. It should be noted that the markings... The transmittance is the transmittance estimated from the measured reflectance.

[0037] [Table 1] The method for forming coating 36 is as follows. First, a thermoplastic elastomer and pigment, which are the materials for coating 36, and a solvent for dissolving them are prepared. In step 1, the pigment is dissolved in the solvent to prepare a first solution. Next, the thermoplastic elastomer is dissolved in the solution obtained by dissolving the pigment in the solvent (the first solution) to prepare a second solution. Thus, by dissolving the pigment in the solvent in step 1 and then dissolving the thermoplastic elastomer, the pigment can be easily diffused in the solvent. THF (tetrahydrofuran) can be used as the solvent. The mass ratio of thermoplastic elastomer to pigment is shown in Table 1, ranging from 1:1.0 to 1:2.0 when the pigment is titanium oxide, and from 1:0.4 to 1:0.5 when the pigment is carbon black. Furthermore, when titanium oxide and carbon black are mixed, the mass ratio of thermoplastic elastomer to pigment is set to 1:1.0. The mixing ratio of titanium oxide to carbon black is 100:1. These thermoplastic elastomers and pigments are dissolved in the solvent to prepare the solutions. Regarding the formulation of the solution, when the mass ratio of thermoplastic elastomer to pigment is 1:1.0, the thermoplastic elastomer is 10% by mass, the pigment is 10% by mass, and the solvent is 80% by mass.

[0038] After preparing the solution, it is applied to the substrate. The substrate for coating 36 in Table 1 is a PET film. The solution is applied by immersion. The film thickness of coating 36 can be adjusted by the immersion pull-up speed and the number of immersions. For example, the immersion pull-up speed is 0.5 mm / s, and the number of immersions is once.

[0039] After applying the solution to the substrate, the coating film 36 is dried. THF, used as a solvent, has a boiling point of 66°C, allowing the coating film 36 to dry at room temperature. The solvent used to form the coating film 36 can be any solvent other than THF, as long as it can dry the coating film 36 at a low temperature between room temperature and 60°C. This allows the coating film 36 to be formed without deforming the substrate. Specifically, in addition to THF, solvents such as methanol and hexane can also be used.

[0040] When the coating film 36 is formed under the conditions in Table 1, if the mass ratio of thermoplastic elastomer to pigment is 1:2.0, powder is generated on the surface and the coating film 36 is not fully formed. Therefore, the mass ratio of thermoplastic elastomer to pigment for forming the coating film 36 needs to be set to less than 1:2.0.

[0041] To suppress the outer diameter of the light irradiation device 10, the thickness of the coating 36 is preferably as small as possible while satisfying certain optical properties. Under the conditions in Table 1, when the pigment is carbon black, the coating 36 can achieve a sufficiently low transmittance with a thickness of 30 μm or less. Furthermore, when the pigment is titanium oxide, and the mass ratio of thermoplastic elastomer to pigment is 1:1.2 with a coating thickness of 60 μm, the light transmittance is 9%; when the mass ratio of thermoplastic elastomer to pigment is 1:1.0 with a coating thickness of 15 μm, the light transmittance is 31%; and when the mass ratio of thermoplastic elastomer to pigment is 1:1.5 with a coating thickness of 14 μm, the light transmittance is 27%. Additionally, when the pigment is a mixture of titanium oxide and carbon black, and the mass ratio of thermoplastic elastomer to pigment is 1:1.0 with a coating thickness of 12 μm, the light transmittance is 8%. These results show that by setting the thickness of the coating 36 to 60 μm or less, the light transmittance can be set to at least 31% or less, thus sufficiently ensuring the optical properties of the coating 36. Furthermore, by setting the thickness of the coating 36 to 30 μm or less (more preferably 22 μm or less), it can deform in accordance with the expansion and contraction of the balloon 30, which serves as the substrate, and the mechanical properties of the balloon 30, such as water resistance, abrasion resistance, and ease of insertion and removal, can be sufficiently ensured when the balloon 30 is inserted into the forceps channel of the endoscope or into a biological body.

[0042] To ensure the aforementioned biological safety, coating 36 needs to have low cytotoxicity. The intensity of cytotoxicity can be measured using IC50. 50 The value is evaluated. IC 50 The value is the concentration (%) of the test solution that inhibits colony formation rate (with the average number of colonies in the control group or solvent control group set as 100%) to 50%. In this embodiment, the evaluation was performed according to ISO 10993-5 (2009); Biological evaluation of medical devices - Part 5: Tests for in vitro cytotoxicity. Table 1 shows the IC50 of titanium dioxide used in coating 36. 50 The value is 78-100%. Furthermore, carbon black is non-cytotoxic, therefore its IC50 value is... 50 The value is above 100%. In contrast, in this embodiment, the positive control material B (a polyurethane membrane containing 0.25% zinc dibutyldithiocarbamate (ZDBC)) has an IC50 value of over 100%. 50 The value was 60%. Table 1 shows that coating 36 had a cytotoxicity intensity (IC50). 50The values ​​were all above 60%, thus confirming that the cytotoxicity was weaker than that of the polyurethane membrane containing 0.25% zinc dibutyldithiocarbamate (ZDBC) used as positive control material B.

[0043] The coating 36 of this embodiment contains a thermoplastic elastomer, thus exhibiting flexibility and the ability to expand and contract in accordance with the expansion and contraction of the balloon 30. In other words, the coating 36 follows the deformation of the balloon 30, which serves as the substrate. Furthermore, the coating 36 has high adhesion to the substrate, improving its abrasion resistance within the body. Additionally, the coating 36, containing a thermoplastic elastomer, is water-resistant. Therefore, the coating 36 satisfies the aforementioned mechanical properties.

[0044] Tensile tests were performed on substrates with and without coating 36. First, test pieces (A) were prepared by coating a substrate with a width of 10 mm and a length of 40 mm with coating 36, and test pieces (B) were prepared solely from a substrate with a width of 10 mm and a length of 40 mm. These test pieces were placed in a tensile testing machine with a clamping distance of 25 mm, and the tensile test was performed at a tensile speed of 25 mm / min.

[0045] The results of tensile tests on 3 specimens (A) and 3 specimens (B) are shown in Table 2.

[0046] [Table 2] The tensile test results were as follows: the average elongation at fracture of test piece (A) composed of the substrate and coating 36 was 28.099 mm, while the average elongation at fracture of test piece (B) composed only of the substrate was 28.904 mm. That is, the elongation at fracture of test piece (A) composed of the substrate and coating 36 was smaller than that of test piece (B). Here, elongation refers to the elongation rate of the balloon under various pressures, expressed as a percentage. Furthermore, elongation at fracture refers to the elongation rate of the test piece at fracture, expressed as a percentage. That is, elongation is obtained by subtracting the clamping distance of the test piece before tension from the clamping distance of the test piece at fracture, dividing by the clamping distance of the test piece before tension, and then multiplying by 100.

[0047] The minimum elongation at break of test piece (A), 27.664 mm / 25.000 mm × 100, is 93.98% (approximately 94%) of the maximum elongation at break of test piece (B), 29.437 mm / 25.000 mm × 100. Therefore, the elongation at break of test piece (A) relative to the clamping distance before stretching is more than 90% of the elongation at break of test piece (B). If such a coating 36 is formed using a balloon as a substrate, when the balloon is expanded and contracted within a living organism, the coating 36 elongates along with the balloon's expansion, and when the balloon is contracted and removed from the living organism, it also contracts along with the balloon, without hindering the balloon's folding action.

[0048] To confirm the mechanical properties of the substrate, the following tests were performed. A balloon made of nylon 12 was prepared as the substrate. Specifically, balloon D with an outer diameter of 20 mm and a length of 45 mm, and balloon E with an outer diameter of 15 mm and a length of 45 mm, were prepared from nylon 12. Both balloons D and E were uncoated balloons without the coating 36. For balloons D and E, a pressure device was used to inflate the balloons at pressures of 0.5 atm, and elongation was measured. Here, elongation refers to the rate of elongation of the balloon at each pressure, expressed as a percentage. Furthermore, elongation at break refers to the rate of elongation at the point of breakage (rupture), expressed as a percentage. That is, the outer diameter of the balloon at atmospheric pressure (1.0 atm) (the balloon before stretching) was set as 0% as a baseline, representing the degree of elongation until rupture. Here, balloons D and E are designed to be approximately 20 mm and approximately 15 mm in rated diameter (outer diameter) at 2.0 atm, respectively.

[0049] For example, in one example of balloon D, the diameter is 18.467 mm at atmospheric pressure (1.0 atm) and 19.787 mm at normal operating pressure (2.0 atm). Balloon D inflates to a diameter of 21.567 mm at 5.0 atm but ruptures at 5.5 atm. Therefore, the maximum inflated diameter of balloon D is 21.567 mm, representing an elongation of 16.79% relative to its diameter at atmospheric pressure. Additionally, balloon D elongates by 7.15% relative to its diameter at atmospheric pressure at normal operating pressure. Therefore, the elongation of balloon D at normal operating pressure relative to its maximum inflated diameter is approximately 42.58%. In one example of balloon E, the diameter is 14.696 mm at atmospheric pressure (1.0 atm) and 15.533 mm at normal operating pressure (2.0 atm). Balloon E expands to a diameter of 17.475 mm at 8.0 atm, but ruptures at 8.5 atm. Therefore, the maximum expansion diameter of balloon E is 17.475 mm, and balloon E elongates by 18.91% based on its diameter at atmospheric pressure. Furthermore, balloon E elongates by 5.70% based on its diameter at atmospheric pressure under normal operating pressure. Therefore, the ratio of the elongation of balloon E under normal operating pressure to the elongation at its maximum expansion diameter is approximately 30.14%. From the above, it can be seen that the balloon without coating 36 elongates by more than 30% of its maximum expansion diameter under normal operating pressure. Coating 36 is required to follow the deformation of the balloon as a substrate and not peel off or crack from the balloon. Therefore, the substrate with coating 36 is required to follow the elongation of more than 30%. On the other hand, due to the coating 36, the elongation at fracture of the substrate with coating 36 is smaller compared to the substrate without coating 36. Therefore, it can be assumed that, compared to a substrate without coating 36, the elongation at break of the substrate with coating 36 relative to the original outer diameter of the balloon (the diameter of the balloon at atmospheric pressure) is smaller. The elongation of the substrate with coating 36 relative to the original outer diameter of the balloon only needs to be at least 30% greater than the elongation at break of the substrate without coating 36 relative to the outer diameter of the balloon before stretching. In fact, in a balloon F with coating 36, formed of nylon 12, with an outer diameter of 15 mm and a length of 45 mm, the elongation at normal operating pressure is at least 40% greater than the elongation at the maximum expansion diameter of balloon E. More specifically, balloon F has a diameter of 13.679 mm at atmospheric pressure (1.0 atm) and a diameter of 14.737 mm at normal operating pressure (2.0 atm). Balloon F expands to a diameter of 17.152 mm at 7.0 atm but ruptures at 7.5 atm. The balloon F elongated by 7.73% based on its diameter at atmospheric pressure under normal operating pressure.Therefore, it can be seen that the elongation of balloon F under normal operating pressure is approximately 40.90% relative to the elongation of balloon E at its maximum expansion diameter. Thus, it can be considered that the elongation at break of the substrate with coating 36 relative to the original outer diameter of the balloon is at least 40% of the elongation at break of the substrate without coating 36 relative to the original outer diameter of the balloon. Based on this configuration, in the light irradiation device 10 with balloon 30, when balloon 30 is placed inside a living organism and expands, coating 36 can effectively function as a light-shielding element.

[0050] As explained above, (1) the coating 36 involved in this embodiment is a coating 36 for coating the surface of a substrate. The coating 36 includes a thermoplastic elastomer and a pigment, and the mass ratio of the thermoplastic elastomer to the pigment is less than 1:2.0. Regarding the coating 36, in a tensile test in which a test piece obtained by coating a substrate with a width of 10 mm and a length of 40 mm with the coating 36 is placed in a tensile testing machine with a clamping distance of 25 mm and the test piece is measured at a tensile speed of 25 mm / min, the elongation at break of the test piece (A) composed of the substrate and the coating 36 is less than the elongation at break of the test piece (B) composed of the substrate, and the elongation of the test piece (A) is more than 40% of the elongation of the test piece (B). The coating 36 thus formed has water resistance and can be formed at a temperature at which the substrate does not deform. In addition, the coating follows the deformation when the substrate elongates to a certain extent, which can suppress peeling or cracking from the substrate. Thus, the coating 36 is able to have mechanical and optical properties for realizing the function of the light irradiation device 10, and meets the characteristics necessary for use in the light irradiation device 10.

[0051] (2) In the coating 36 of (1) above, the elongation at the time of fracture of the test piece (A) may be more than 93.5% of the elongation at the time of fracture of the test piece (B). As a result, the coating 36 can better follow the elongation of the substrate, and thus can reliably recover to its original shape when the substrate elongates or shrinks.

[0052] (3) In the coating 36 of (1) or (2) above, the cytotoxicity intensity (IC50) can be, when the coating 36 is evaluated in accordance with ISO 10993, be measured. 50 The cytotoxicity of the coating 36 is weaker than that of the polyurethane membrane containing 0.25% zinc dibutyldithiocarbamate (ZDBC), which is used as the positive control material B. Therefore, the cytotoxicity of the coating 36 can be reduced to the level necessary for its use in the light irradiation device 10.

[0053] (4) In any of the coatings 36 in (1) to (3) above, the coating thickness of the coating 36 may be 60 μm or less. As a result, the outer diameter of the light irradiation device can be suppressed.

[0054] (5) In any of the coatings 36 described in (1) to (4) above, the light transmittance of the coating 36 may be 31% or less. Thus, the optical performance of the coating 36 can be satisfied.

[0055] (6) In any of the coatings 36 described in (1) to (5) above, the thermoplastic elastomer may be a polyurethane elastomer. This improves the ability of the coating 36 to follow the deformation of the substrate.

[0056] (7) In any of (1) to (6) above, the coating 36 may be made of titanium dioxide, carbon black, or a mixture of titanium dioxide and carbon black. Thus, white, black or gray coatings 36 can be made, and coatings 36 that meet the requirements of cytotoxicity strength can be made.

[0057] (8) In any of the coatings in (1) to (7) above, the substrate may be a balloon 30 made of a light-transmitting material, and the thickness of the balloon 30 is 30 μm. Thus, in the light irradiation device 10 having a light irradiator 90 inside the balloon 30 (which has a coating 36 formed in a manner that enables light to be irradiated in a certain direction), the biological safety, as well as the mechanical and optical properties of the balloon 30, can be satisfied.

[0058] (9) In any of the above (1) to (8), the coating 36 may have a mass ratio of thermoplastic elastomer to pigment of 1:0.5 or less, a film thickness of 30 μm or less, a light transmittance of 0%, and the pigment is carbon black. Thus, the coating 36 has high biological safety and can also reduce the film thickness.

[0059] (10) In the method for forming the coating 36 of this embodiment, a first solution is prepared by dissolving the pigment in a solvent such that the mass ratio of thermoplastic elastomer to pigment is less than 1:2.0. A second solution is prepared by dissolving the thermoplastic elastomer in the first solution. The second solution is applied to a substrate and dried to obtain a coating. In a tensile test, a test piece obtained by applying the coating 36 to a substrate with a width of 10 mm and a length of 40 mm is placed in a tensile testing machine with a clamping distance of 25 mm and a tensile speed of 25 mm / min. The elongation at break of the test piece (A) composed of the substrate and the coating is less than the elongation at break of the test piece (B) composed of the substrate, and the elongation of the test piece (A) is more than 40% of the elongation of the test piece (B). The method for forming the coating 36 in this way can form a coating 36 that has water resistance and can be formed at a temperature at which the substrate does not deform, thus meeting the characteristics required by the light irradiation device.

[0060] It should be noted that the present invention is not limited to the above-described embodiments, and those skilled in the art can make various modifications within the scope of the technical concept of the present invention.

[0061] It should be noted that this application is based on Japanese Patent Application No. 2023-187768, filed on November 1, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0062] Explanation of reference numerals in the attached figures 10. Light irradiation equipment 20 Shaft section 21. Expand the internal cavity 30 balloons 36 light shield 37. Light shines through the window. 40 tubular body 41. Inner cavity 100 endoscopic instruments 122 Handheld Part 125 Inner cavity

Claims

1. A coating film, which is a coating film applied to the surface of a substrate, wherein, The coating film comprises a thermoplastic elastomer and a pigment. The mass ratio of the thermoplastic elastomer to the pigment is less than 1:2.

0. Regarding the coating, in a tensile test in which a test piece obtained by coating the substrate with the coating with a width of 10 mm and a length of 40 mm is placed in a tensile testing machine with a clamping distance of 25 mm and the test piece is measured at a tensile speed of 25 mm / min, the elongation at break of the test piece (A) composed of the substrate and the coating is less than the elongation at break of the test piece (B) composed of the substrate, and the elongation of the test piece (A) is more than 40% of the elongation of the test piece (B).

2. The coating as described in claim 1, wherein, The elongation of the test piece (A) is more than 90% of the elongation of the test piece (B).

3. The coating as described in claim 1 or 2, wherein, When the coating is evaluated according to ISO 10993, the cytotoxicity intensity (IC50) is... 50 The value was weaker than that of the polyurethane film containing 0.25% zinc dibutyldithiocarbamate (ZDBC), which was used as positive control material B.

4. The coating as described in claim 1 or 2, wherein, The coating thickness is less than 60 μm.

5. The coating as described in claim 1 or 2, wherein, The light transmittance of the coating is less than 31%.

6. The coating as described in claim 1 or 2, wherein, The thermoplastic elastomer is a polyurethane elastomer.

7. The coating as described in claim 1 or 2, wherein, The pigment is titanium dioxide, carbon black, or a mixture of titanium dioxide and carbon black.

8. The coating as described in claim 1 or 2, wherein, The substrate is a balloon made of a light-transmitting material, and the thickness of the balloon is 30 μm.

9. The coating as described in claim 1 or 2, wherein, The mass ratio of the thermoplastic elastomer to the pigment is less than 1:0.5, the film thickness is less than 30 μm, the light transmittance of the coating is 0%, and the pigment is carbon black.

10. A method for forming a coating film, wherein, A first solution is prepared by dissolving the pigment in a solvent in such a manner that the mass ratio of thermoplastic elastomer to pigment is less than 1:2.

0. A second solution is prepared by dissolving the thermoplastic elastomer in the first solution. The second solution is applied to a substrate and dried to obtain the coating film. In a tensile test, in which a test piece obtained by coating a substrate with a width of 10 mm and a length of 40 mm is placed in a tensile testing machine with a clamping distance of 25 mm and the test piece is measured at a tensile speed of 25 mm / min, the elongation at break of the test piece (A) composed of the substrate and the coating is less than the elongation at break of the test piece (B) composed of the substrate, and the elongation of the test piece (A) is more than 40% of the elongation of the test piece (B).

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