JP7848906B2 - Laminated structure, cable, tube, and method for manufacturing the laminated structure - Google Patents

Description

This invention relates to a laminated structure, a cable, a tube, and a method for manufacturing a laminated structure.

Conventionally, medical device cables are known that consist of a silicone rubber coating containing fine particles, which is applied to cover the sheath (see Patent Document 1). Silicone rubber has advantages over conventional sheath materials, such as minimal discoloration over time, but it tends to have lower surface slipperiness.

The cable sheath described in Patent Document 1 is made of silicone rubber containing fine particles, and therefore its surface has irregularities caused by these fine particles. These irregularities reduce the contact area when the sheath comes into contact with other components, thereby improving the slipperiness of the sheath surface, and thus the slipperiness of the cable.

Patent No. 6723489

In recent years, UV-C light irradiation has attracted attention as a simple, inexpensive, and reliable method for sterilizing medical device cables. However, the resistance of the cable to UV-C light is a problem for implementing UV-C light sterilization. Even cables with silicone rubber sheaths will deteriorate with repeated UV-C light irradiation, and it has been confirmed that cracks will form in the sheath when subjected to stress such as bending the cable.

The object of the present invention is to provide a laminated structure made of silicone rubber, which exhibits excellent resistance to UV-C light, as well as a cable, tube, and method for manufacturing the laminated structure, which include an insulator made from the laminated structure.

The present invention aims to solve the above problems and provides a laminated structure comprising a first layer made of silicone rubber and containing first _TiO2 fine particles, and a second layer laminated on the first layer, made of silicone rubber and containing second TiO2 _fine particles, wherein the Ti concentration of the first layer is 0.35% by mass or more and 3.0% by mass or less, and the Ti concentration of the second layer is 1.0% by mass or more and 4.4% by mass or less.
Furthermore, the present invention aims to solve the above problems and provides a method for manufacturing a laminated structure comprising: a first layer made of silicone rubber and containing first _TiO2 fine particles; and a second layer laminated on the first layer and made of silicone rubber and containing second _TiO2 fine particles, the method comprising: preparing the first layer containing the first TiO2 _fine particles having a Ti concentration of 0.35% by mass or more and 3.0% by mass or less; applying a silicone rubber coating solution containing the second fine particles onto the first layer to form a coating film; and curing the coating film to form the second layer containing the second _{TiO2 fine} particles having a Ti concentration of 1.0% by mass or more and 4.4% by mass or less.

Furthermore, the present invention aims to solve the above problems by providing a cable or tube equipped with an insulator made of the above-described laminated structure, or a method for manufacturing the laminated structure.

According to the present invention, it is possible to provide a laminated structure made of silicone rubber as a base material, which exhibits excellent resistance to UV-C light, as well as a cable, tube, and method for manufacturing the laminated structure, which include an insulator made from the laminated structure.

Figure 1 is a vertical cross-sectional view of a laminated structure according to a first embodiment of the present invention. Figure 2 is a graph showing the preferred ranges for the Ti concentration of the first layer and the Ti concentration of the second layer. Figure 3 is a schematic plan view showing the configuration of an ultrasonic probe cable according to a second embodiment of the present invention. Figure 4(a) is a radial cross-sectional view of the ultrasonic probe cable. Figure 4(b) is a radial cross-sectional view of the ultrasonic probe cable cut along the cutting line A-A shown in Figure 3. Figures 5(a) to 5(c) are radial cross-sectional views of a medical tube according to a second embodiment of the present invention, respectively. Figure 6(a) is a graph showing the results of the tensile test of sample B1. Figure 6(b) is a graph showing the results of the tensile test of sample B2. Figure 7(a) is a graph showing the results of the tensile test of sample B3. Figure 7(b) is a graph showing the results of the tensile test of sample B4. Figure 8(a) is a graph showing the relationship between UV-C light irradiation time and the stress at the time of substrate fracture for samples B1 to B4. Figure 8(b) is a graph showing the relationship between UV-C light irradiation time and the elongation at the time of substrate fracture for samples B1 to B4. Figure 9(a) is a schematic diagram showing the bending test. Figure 9(b) is a cross-sectional view of the conductor and the sheath piece wrapped around the conductor, in the radial direction of the conductor. Figures 10(a) and (b) show SEM images of the surface and cross-section of a sheath piece cut from sample C6 that was irradiated with UV-C light at an irradiation energy of 2808 J/ ^cm² . Figures 11(a) and (b) show SEM images of the surface and cross-section of a sheath piece cut from sample C7 that was irradiated with UV-C light at an irradiation energy of 2808 J/ ^cm² . Figure 12 shows typical surface images of sheath pieces cut from samples C1 to C11 after the bending test. Figures 13(a), (b), (c), and (d) are graphs showing the relationship between UV-C light irradiation energy and fracture elongation for samples D1, D3, D4, and D7, respectively. Figures 14(a), (b), (c), and (d) are graphs showing the relationship between UV-C light irradiation energy and fracture elongation for samples D8, D9, D10, and D11, respectively. Figures 15(a) and (b) are graphs plotting the relationship between the Ti concentration in the first layer and the elongation at the fracture point. Figures 16(a) and 16(b) show the surface observations of sample C11 and sample C12, respectively, before the wipe test. Figures 17(a) and 17(b) show the surface observations of sample C11 and sample C12 after the wipe test, respectively.

[First Embodiment]
(Structure of the laminated structure)
Figure 1 is a vertical cross-sectional view of a laminated structure 1 according to a first embodiment of the present invention. The laminated structure 1 comprises a first layer 10 having silicone rubber as the base material 101 and containing titanium oxide ( _TiO2 ) fine particles 102, and a second layer 11 laminated on the first layer 10, having silicone rubber as the base material 111 and containing titanium oxide ( _TiO2 ) fine particles 113.

The silicone rubber that forms the base material of the first layer 10 and the second layer 11 is a type of silicone resin. Compared to polyvinyl chloride, which is commonly used as a material for cables and tubes in medical applications, silicone rubber has higher resistance to ultraviolet light (UV-A and UV-B).

The laminated structure 1 can take various forms depending on its application. For example, when used as an insulator for cables and tubes, it is formed into a tubular shape, and when used as a sheet for applications such as high-UV-resistant constant-temperature greenhouse sheets or UV-shielding sheets (UV-shielding curtains) to block UV leakage from sterilization rooms, it is formed into a sheet shape.

(Structure of the second layer)
As the silicone rubber that forms the base material 111 of the second layer 11, for example, an addition-reaction type silicone rubber coating agent or a condensation-reaction type silicone rubber coating agent can be used. In particular, from the viewpoint of adhesion to the first layer 10, which has silicone rubber as the base material, and abrasion resistance, it is preferable to use an addition-reaction type silicone rubber coating agent.

To obtain good slipperiness and predetermined wiping resistance on the surface of the laminated structure 1 by the second layer 11, it is preferable that the thickness of the second layer 11 be 3 μm or more. Furthermore, the second layer 11 may be laminated on both sides of the first layer 10. While there is no particular upper limit to the thickness of the second layer 11, it is preferable that it be 100 μm or less from the viewpoint of productivity, high flexibility, and high bendability.

The _TiO2 fine particles 113 contained in the second layer 11 can shield against UV-C light by absorption and/or scattering. Here, UV-C light is ultraviolet light in the wavelength range of 200 to 280 nm. By shielding against UV-C light, the _TiO2 fine particles 113 can suppress the degradation of the silicone rubber matrix material 111 due to UV-C light. The _TiO2 constituting the _TiO2 fine particles 113 may be of the anatase type, rutile type, or brookite type, or a mixture of two or more types. In addition, niobium oxide may be added to the titanium dioxide to improve its stability.

Furthermore, it is preferable that the second layer 11 contains fine particles 112 to create irregularities on its surface, as shown in Figure 1. When the surface is irregular, the contact area between the second layer 11 and the object it contacts is reduced compared to a flat surface, resulting in improved slipperiness.

The fine particles 112 include, for example, at least one of silicone resin fine particles, silicone rubber fine particles, and silica fine particles. Silicone resin, which has fewer reactive groups (e.g., methyl groups) than silicone rubber, has higher hardness than silicone rubber, and silica, which has no reactive groups, has even higher hardness. Furthermore, in terms of density, silica has the highest density, followed by silicone resin, and then silicone rubber.

To suppress deformation of the surface irregularities when the second layer 11 comes into contact with an object, it is preferable that the fine particles 112 have high hardness. This is because, when pressure is applied to the surface of the second layer 11 by the object, the higher the hardness of the fine particles 112, the more effectively deformation of the surface irregularities of the second layer 11 can be suppressed. This suppresses the increase in the contact area between the second layer 11 and the object, thus maintaining its slipperiness. Therefore, from the viewpoint of suppressing deformation of the surface irregularities when the second layer 11 comes into contact with an object, silica fine particles are most preferable as the fine particles 112, followed by silicone resin fine particles.

On the other hand, because silica has a high density as described above, silica fine particles tend to settle in the silicone rubber coating agent that forms the base material during the manufacturing process of the second layer 11, making them more difficult to disperse in the silicone rubber coating agent (in the second layer 11) compared to silicone resin fine particles or silicone rubber fine particles. Therefore, from the viewpoint of improving the uniformity of dispersion in the silicone rubber coating agent (in the second layer 11), silicone rubber fine particles are most preferred as the fine particles 112, followed by silicone resin fine particles.

Therefore, in order to achieve both the maintenance of slipperiness when the second layer 11 comes into contact with the object and the uniformity of the dispersion of fine particles 112 in the silicone rubber base material 111, it is preferable to use silicone resin fine particles as the fine particles 112.

Furthermore, the interatomic bond energies in the molecular structures of silicone resin and silica are higher than those in the molecular structure of silicone rubber. Therefore, silicone resin and silica have higher resistance to UV-C light than silicone rubber.

For example, the C-H bond, which is abundant in silicone rubber, has a bond energy (approximately 4.27 eV) lower than the energy of UV-C light (approximately 6.2 eV). Therefore, the bond breaks upon irradiation with UV-C light. However, the Si-O bond, which is abundant in silicone resin, has a bond energy (approximately 6.52 eV) higher than the energy of UV-C light. Therefore, the bond does not break upon irradiation with UV-C light. For this reason, from the viewpoint of resistance to UV-C light, it is preferable to use silicone resin fine particles or silica fine particles as the fine particles 112.

The average particle size of the fine particles 112 is, for example, 1 μm to 10 μm. Furthermore, the concentration (mass%) of the fine particles 112 in the second layer 11 is, for example, 10% to 60% by mass. Here, "average particle size" in this specification refers to the particle size measured by laser diffraction scattering.

(Structure of the first layer)
The first layer 10 contains TiO2 fine particles 102 for shielding UV-C light by absorption and/or scattering, similar to the second layer 11 which contains _TiO2 fine particles 113, in order to suppress degradation caused by UV- _C light transmitted through the second layer 11.

As described above, the base material 101 is made of silicone rubber. However, when the first layer 10 is used as a sheath material, silicone rubber to which various crosslinking agents, crosslinking catalysts, anti-aging agents, plasticizers, lubricants, fillers, flame retardants, stabilizers, colorants, and other common compounding agents may be added may be used as the base material 101.

( _TiO2 fine particles)
Figure 2 is a graph showing the preferred range of Ti concentration in the first layer 10 containing _TiO2 fine particles 102 and the preferred range of Ti concentration in the second layer 11 containing _TiO2 fine particles 113.

As shown in Figure 2, the Ti concentration in the first layer 10 is preferably 0.35% by mass or more and 3.0% by mass or less. By including _TiO2 fine particles 102 in the first layer 10 at a concentration of 0.35% by mass or more, the elongation at the breaking point measured when a tensile test specified in "JIS K6251 (1994)" is performed after irradiating a cable equipped with the laminated structure 1 as an insulator (sheath and its coating) with UV-C light can be maintained at a high value. The specific method of this tensile test will be described later.

On the other hand, if the first layer 10 contains _TiO2 fine particles 102 with a Ti concentration exceeding 3.0 mass%, the first layer 10 becomes hard, reducing the flexibility of the laminated structure 1 and decreasing its tear strength. For this reason, considering the handling of cables and tubes when the first layer 10 is used as an insulator for cables and tubes, it is preferable that the Ti concentration in the first layer 10 be 3.0 mass% or less.

Furthermore, as shown in Figure 2, the Ti concentration in the second layer 11 is preferably 1.0% by mass or more and 4.4% by mass or less. By including _TiO2 fine particles 113 in the second layer 11 with a Ti concentration of 1.0% by mass or more, it is possible to suppress the occurrence of cracks on the surface of the laminated structure ¹ that reach the first layer 10, as measured by a bending test equivalent to 45-50% tensile strength after irradiation with 1404 J/cm² of UV-C light. The method of the bending test and the method of observing the presence or absence of cracks will be described later.

On the other hand, if the second layer 11 contains TiO2 _fine particles at a concentration exceeding 4.4% by mass, the surface roughness of the second layer 11 increases. Increased surface roughness makes it easier for dirt and bacteria to adhere and harder to remove. Furthermore, if the second layer 11 contains fine particles 112 such as silicone resin fine particles, and contains TiO2 _fine particles at a concentration exceeding 4.4% by mass, the adhesion between the silicone rubber base material 111 and the fine particles 112 decreases, making the fine particles 112 more likely to fall off, and reducing the slipperiness of the surface of the second layer 11. For this reason, it is preferable that the Ti concentration in the second layer 11 be 4.4% by mass or less.

Furthermore, as shown in Figure 2, it is preferable that the concentration of TiO₂ _fine particles 113 in the second layer 11 is higher than the concentration of TiO₂ _fine particles 102 in the first layer 10, that is, that the Ti concentration in the second layer 11 is higher than the Ti concentration in the first layer 10. By making the concentration of TiO₂ _fine particles 113 in the second layer 11 higher than the concentration of TiO₂ _fine particles 102 in the first layer 10, UV-C light is effectively absorbed and/or scattered in the second layer 11, thereby suppressing degradation of the first layer 10 by UV-C light and preventing a decrease in the flexibility and tear strength of the laminated structure 1.

Furthermore, the Ti in the first layer 10 is all contained in the _TiO2 fine particles 102, and the Ti in the second layer 11 is all contained in the _TiO2 fine particles 113. The Ti concentrations in the first layer 10 and the second layer 11 are determined as the average values over a measurement area of 125 μm x 95 μm using an energy-dispersive X-ray analyzer (EDS) mounted on a scanning electron microscope (SEM).

[Second Embodiment]
A second embodiment of the present invention is a cable or tube equipped with an insulator made of a laminated structure 1 according to the first embodiment. Hereinafter, as an example, a cable used in medical ultrasound probe cables will be described.

Figure 3 is a schematic plan view showing the configuration of an ultrasonic probe cable 2 according to a second embodiment of the present invention. In the ultrasonic probe cable 2, as shown in Figure 3, an ultrasonic probe 32 is attached to one end of the cable 20 via a boot 31 that protects this end. Meanwhile, a connector 33, which connects to the main body of an ultrasonic imaging device, is attached to the other end of the cable 20.

Figure 4(a) is a radial cross-sectional view of the cable 20 of the ultrasonic probe cable 2. Inside the cable 20, for example, multiple coaxial cables (electric wires 21) are housed, and a shield 22, such as a braided shield, is provided to cover these multiple electric wires 21. A sheath 23 is provided to cover the shield 22. Furthermore, a coating 24 is formed on the cable 20, covering the periphery of the sheath 23 and closely adhering to it.

Figure 4(b) is a radial cross-sectional view of the ultrasonic probe cable 2 cut along the cutting line A-A shown in Figure 3. The boot 31 is attached to the coating 24 via an adhesive layer 34, as shown in Figure 4(b), so as to cover the coating 24. The adhesive layer 34 is formed from, for example, a silicone adhesive or an epoxy adhesive. The boot 31 may also be made of, for example, PVC, silicone rubber, chloroprene rubber, etc., and preferably contains _TiO2 fine particles 102 or an organic ultraviolet absorber to shield against UV-C light, similar to the first layer 10.

The sheath 23 and coating 24 of the cable 20 consist of the first layer 10 and the second layer 11 of the laminated structure 1, respectively. In other words, the laminated structure 1 is used as the sheath 23 and coating 24 in the cable 20. Note that the _TiO2 fine particles 102 in the sheath 23 and the fine particles 112 and _TiO2 fine particles 113 in the coating 24 are not shown in the illustration.

Because the laminated structure 1, which has excellent resistance to UV-C light, is used as the insulator (sheath 23 and coating 24) of the cable 20, the cable 20 has excellent resistance to UV-C light. Furthermore, when the second layer 11 of the laminated structure 1 contains fine particles 112, the cable 20 has excellent surface slipperiness, which can suppress snagging caused by stickiness on the surface of the sheath 23. The thickness of the coating 24 is, for example, 3 μm to 100 μm.

Furthermore, if the first layer 10 contains _TiO2 fine particles 102 with a Ti concentration of 0.35% by mass or more and 3.0% by mass or less, and the second layer 11 contains TiO2 _fine particles 113 with a Ti concentration of 1.0% by mass or more and 4.4% by mass or less, the elongation at the breaking point measured by a tensile test after irradiation of the insulator (sheath 23 and coating 24) of the cable 20 with 1404 J/ ^cm² of UV-C light will be 250% or more, and the occurrence of cracks on the surface of the second layer 11 by a bending test equivalent to 45-50% tensile strength after irradiation with 1404 J/ ^cm² of UV-C light can be suppressed. In the laminated structure 1 having a second layer 11 that does not contain _TiO2 fine particles 102, the elongation at the breaking point before irradiation with UV-C light is 250% or more (see Figure 7(b)). Therefore, the goal was set to achieve an elongation at the breaking point of 250% or more even after irradiation with 1404 J/ ^cm² of UV-C light.

Furthermore, if the first layer 10 contains _TiO2 fine particles 102 with a Ti concentration of 0.35% by mass or more and 3.0% by mass or less, and the second layer 11 contains TiO2 _fine particles 113 with a Ti concentration of 1.0% by mass or more and 4.4% by mass or less, the elongation at the breaking point measured by a tensile test after irradiation of the insulator (sheath 23 and coating 24) of the cable 20 with 2808 J/ ^cm² of UV-C light will be 150% or more, and the occurrence of cracks on the surface of the second layer 11 by a bending test equivalent to 45-50% tensile strength after irradiation with 2808 J/ ^cm² of UV-C light can be suppressed. Since the elongation at the breaking point required for general rubber materials is 150% or more, a target of 150% or more elongation at the breaking point even after irradiation with 2808 J/ ^cm² of UV-C light was separately set.

If the concentration of TiO2 _fine particles in the first layer 10 increases, the flexibility and tear strength of the first layer 10 may decrease. Therefore, it is preferable to increase the concentration of _{TiO2 fine} particles in the second layer 11 to shield the second layer 11 from UV-C light. When the concentration of TiO2 _fine particles 113 in the second layer 11 is higher than the concentration of TiO2 _fine particles 102 in the first layer 10, degradation of the first layer 10 due to UV-C light can be suppressed, and the decrease in flexibility and tear strength of the insulator (sheath 23 and coating 24) of the cable 20 can be suppressed.

Next, an example of a manufacturing method for the ultrasonic probe cable 2 in this embodiment will be described. First, multiple (for example, 100 or more) electric wires 21 are bundled together. Then, a shield 22 is formed to cover the bundled multiple electric wires 21.

Next, the first layer 10 and the second layer 11 of the laminated structure 1 are formed sequentially to cover the shield 22, thereby forming the sheath 23 and the coating 24. The sheath 23 is formed, for example, by extrusion molding using an extruder. The coating 24 is formed, for example, by dipping, spray coating, or roll coating. In the dipping method, the ultrasonic probe cable 2, which has been formed up to the sheath 23, is pulled up through a liquid coating material, thereby forming the coating 24 on the surface of the sheath 23. This dipping method is superior to the spray coating and roll coating methods in terms of the uniformity of the film thickness of the formed coating 24.

The liquid coating agent used in the dipping method is a liquid silicone rubber containing fine particles 112 and TiO2 _fine particles 113, and contains an organic solvent. By adjusting the content of fine particles 112 and _TiO2 fine particles 113 contained in this liquid coating agent, the content of fine particles 112 and _TiO2 fine particles 113 contained in the coating film 24 can be controlled. As the organic solvent, for example, aromatic hydrocarbon solvents such as toluene and xylene, or aliphatic hydrocarbon solvents such as n-hexane, n-heptane, n-octane, isooctane, nonane, decane, undecane, and dodecane can be used alone or in mixtures of two or more. In addition, for example, alcohols such as ethanol and isopropyl alcohol, or acetone can be used.

Furthermore, as another example of a cable or tube equipped with an insulator made of a laminated structure 1, the configuration of a tube (hollow tube) used in medical applications such as catheters will be described below.

Figures 5(a) to 5(c) are radial cross-sectional views of medical tubes according to the second embodiment of the present invention. The medical tube 40a shown in Figure 5(a) has an outer coating 42 on the outer surface 41a of the tube body 41. The medical tube 40b shown in Figure 5(b) has an inner coating 43 on the inner surface 41b of the tube body 41. The medical tube 40c shown in Figure 5(c) has an outer coating 42 and an inner coating 43 on the outer surface 41a and inner surface 41b of the tube body 41, respectively.

As illustrated by medical tubes 40a, 40b, and 40c, the tube according to this embodiment comprises a tube body 41, an outer coating 42 covering the outer surface 41a of the tube body 41, an inner coating 43 covering the inner surface 41b of the tube body 41, or both the outer coating 42 and the inner coating 43.

The tube body 41 of the medical tubes 40a, 40b, and 40c consists of the first layer 10 of the laminated structure 1, while the outer coating 42 and inner coating 43 consist of the second layer 11 of the laminated structure 1. Therefore, the medical tubes 40a, 40b, and 40c exhibit excellent resistance to UV-C light, similar to the cable 20 of the ultrasonic probe cable 2 described above.

Furthermore, when the second layer 11 of the laminated structure 1 contains fine particles 112, the inner and outer surfaces exhibit excellent lubricity. Therefore, when using the tube in applications such as medical tubes like catheters, where instruments are inserted into the tube, smooth insertion and removal of the instruments becomes possible. In addition, the tube according to this embodiment can be used in endoscopic surgical instrument tube sets, ultrasonic surgical instrument tube sets, blood analyzer tubes, oxygen concentrator piping, hemodialysis blood circuits, cardiopulmonary bypass circuits, endotracheal tubes, and the like.

(Effects of the embodiment)
According to the first embodiment described above, a laminated structure 1 with excellent resistance to UV-C light can be provided. Furthermore, according to the second embodiment described above, by using the laminated structure 1 as an insulator, an ultrasonic probe cable 2 and medical tubes 40a, 40b, and 40c with excellent resistance to UV-C light can be provided.

(Fabrication of laminated structure 1)
Four samples (referred to as samples A1 to A4) were prepared to verify the UV-C light shielding effect of the second layer 11 of the laminated structure 1. First, 200 coaxial cables with a diameter of approximately 0.25 mm were twisted together and covered with braided wire to create a cable core. Next, using an extruder, sheath material was extruded onto the outer circumference of the cable core at a speed of 5 m/min to form a sheath 23 with a thickness of 0.8 mm as the first layer 10 of the laminated structure 1 (cable outer diameter approximately 8 mm). Here, PVC, which is commonly used, was used as the sheath material for sample A1. For samples A2 to A4, a titanium oxide-containing color batch (a mixture of "KE-color-W" and "KE-174-U" manufactured by Shin-Etsu Chemical Co., Ltd.) was used as the sheath material. The Ti concentration was analyzed using an energy-dispersive X-ray analyzer (EDS) mounted on a scanning electron microscope (SEM) (average value over a measurement area of 125 μm x 95 μm) and mixed to a value of 0.12 mass%. Through these steps, samples A1 and A2 were prepared, which do not have the coating 24 as the second layer 11 of the laminated structure 1.

Next, materials for forming the coating 24 on sample A3 were prepared. An addition-reaction type silicone rubber coating agent (product name: SILMARK-TM, manufactured by Shin-Etsu Chemical Co., Ltd.) was prepared as the rubber component for the base material 111. In addition, silicone resin microparticles with an average particle size of 5 μm (product name: X-52-1621, manufactured by Shin-Etsu Chemical Co., Ltd.) were prepared as the fine particles 112. 100 parts by mass of this rubber component were mixed with 120 parts by mass of silicone resin microparticles, 600 parts by mass of toluene as a solvent for viscosity adjustment, 8 parts by mass of a crosslinking agent (product name: CAT-TM, manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.3 parts by mass of a curing catalyst (product name: CAT-PL-2, manufactured by Shin-Etsu Chemical Co., Ltd.) to prepare a coating solution in which the ratio of fine particles 112 to the coating 24 was 55% by mass. The content of fine particles 112 in the above-mentioned coating 24 was calculated assuming that the coating agent hardens with almost no mass loss (approximately equivalent to the blending mass ratio).

Next, the surface of the sheath 23, which was mounted on the cable core, was cleaned. Then, the cable core with the sheath 23 mounted was immersed in the coating solution using a dip coating method to form a silicone rubber coating on the sheath surface. Afterward, the coating was thoroughly dried and cured at a temperature of 150°C to form a coating 24 with an uneven surface. The thickness of the coating 24 on the obtained sample A3 was 15 μm. Sample A3 was prepared through the above steps.

Next, materials for forming the coating 24 of sample A4 were prepared. For the coating 24 of sample A4, in addition to the rubber component that serves as the base material 111 and the silicone resin fine particles 112 that were used for the coating 24 of sample A3, anatase-type _TiO2 fine particles 113 with an average particle size of 250 nm were prepared. Then, 120 parts by mass of silicone resin fine particles, _TiO2 fine particles, 600 parts by mass of toluene as a solvent for viscosity adjustment, 8 parts by mass of a crosslinking agent (product name: CAT-TM, manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.3 parts by mass of a curing catalyst (product name: CAT-PL- ₂ , manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed with 100 parts by mass of the rubber component to prepare a coating solution in which the ratio of fine particles 112 to the coating 24 was 55% by mass and the ratio of _TiO2 fine particles 113 to the coating 24 was a predetermined concentration. The concentration of _{TiO2 fine} particles 113 was adjusted so that the titanium concentration in the coating 24 (average value in a measurement area of 125 μm x 95 μm) determined by an energy-dispersive X-ray analyzer (EDS) mounted on a scanning electron microscope (SEM) was 0.6 mass%. The content of fine particles 112 in the coating 24 was calculated assuming that the coating agent hardens with almost no mass loss (approximately equivalent to the blending mass ratio).

Next, similar to the coating 24 of sample A3, the surface of the sheath 23 was cleaned, a coating film was formed by the dip coating method, and the coating film was dried and cured to form a coating 24 with an uneven surface. The thickness of the coating 24 of the obtained sample A4 was 15 μm. Sample A4 was prepared through the above steps.

(Verification of resistance to UV-C light)
To verify the resistance of the laminated structure 1 to UV-C light, tensile tests were performed on samples A1 to A4 before and after UV-C light irradiation. First, a cut was made along the length of the sheath 23 (in the case of samples A3 and A4, the sheath 23 covered with coating 24) of the cable-shaped samples A1 to A4 prepared by the method described above, and the contents inside the sheath 23 were removed to open the sheath 23. Then, the opened sheath 23 was punched out with a No. 6 dumbbell to prepare dumbbell test pieces (thickness 0.8 mm). Here, the dumbbell test pieces formed from the sheath 23 (in the case of samples A3 and A4, the sheath 23 covered with coating 24) of samples A1, A2, A3, and A4 are designated as samples B1, B2, B3, and B4, respectively. Table 1 below shows the composition of samples B1 to B4.

The tensile test was conducted according to the "JIS K6251 (1994)" standard, on samples B1 to B4 under ambient temperature conditions of 15 to 35°C, ambient humidity of 28 to 65% RH, and atmospheric pressure. UV-C light irradiation was performed using a storage cabinet equipped with a germicidal lamp (Daishin Kogyo Co., Ltd. DM-5, lamp GL-10) under ambient temperature conditions of 25 to 40°C, ambient humidity of 28 to 65%, ambient pressure of 1 atmosphere (atmospheric pressure), wavelength of 253.7 nm, illuminance of 1.3 mW/ ^cm² , and irradiation times of 100 hours and 200 hours. An illuminometer, UVC-254A manufactured by MK Scientific, was used.

Figure 6(a) is a graph showing the results of the tensile test of sample B1. In Figure 6(a), "Unirradiated" shows sample B1 before UV-C light irradiation, and "After Irradiation" shows sample B1 after 200 hours of UV-C light irradiation. As shown in Figure 6(a), the strength (magnitude of stress at which the substrate breaks) and elongation were lower after UV-C light irradiation than before irradiation, confirming that sample B1 deteriorated (changed to become more prone to breakage) due to UV-C light irradiation. Furthermore, since sample B1 was gray PVC, a yellowish discoloration due to UV-C light irradiation was visually confirmed. Note that 100% elongation indicates that the length of the dumbbell test specimen doubled from its original length.

Figure 6(b) is a graph showing the results of the tensile test of sample B2. In Figure 6(b), "Unirradiated" shows sample B2 before UV-C light irradiation, and "After Irradiation" shows sample B2 after 200 hours of UV-C light irradiation. As shown in Figure 6(b), the strength and elongation were lower after UV-C light irradiation than before irradiation, confirming that sample B2 deteriorated (changed) due to UV-C light irradiation. Note that no discoloration due to UV-C light irradiation was visually observed in sample B2 (white), which is made of silicone rubber. On the other hand, compared with the graph in Figure 6(a), it can be seen that silicone rubber deteriorated more significantly due to UV-C light irradiation than PVC.

Although sample B2 contains _TiO2 nanoparticles that absorb UV-C light, the low concentration (Ti concentration in sheath 23 is 0.12 mass%) likely had little effect on its resistance to UV-C light. Furthermore, since sample B2 does not have a coating corresponding to the second layer 11, its surface slipperiness is inferior to that of samples B3 and B4.

Figure 7(a) is a graph showing the results of the tensile test of sample B3. In Figure 7(a), "Unirradiated" shows sample B3 before UV-C light irradiation, and "After Irradiation" shows sample B3 after 200 hours of UV-C light irradiation. As shown in Figure 7(a), the strength and elongation were lower after UV-C light irradiation than before irradiation, confirming that sample B3 deteriorated due to UV-C light irradiation. Furthermore, similar to sample B2, no discoloration due to UV-C light irradiation was visually observed in sample B3 (white).

As shown in Figure 7(a), cracks appear in the coating 24 corresponding to the second layer 11 when the elongation exceeds approximately 50%. The coating 24 of sample B3 contains silicone resin microparticles 112, which have excellent resistance to UV-C light. It is believed that the cracks occurred mainly in the silicone rubber in areas where these silicone resin microparticles are absent, due to degradation of the silicone rubber.

Figure 7(b) is a graph showing the results of the tensile test of sample B4. In Figure 7(b), "Unirradiated" shows sample B4 before UV-C light irradiation, and "After Irradiation" shows sample B4 after 200 hours of UV-C light irradiation. As shown in Figure 7(b), the strength and elongation were almost the same before and after UV-C light irradiation, confirming that the degradation of sample B4 due to UV-C light irradiation was effectively suppressed. Furthermore, similar to sample B2, no discoloration due to UV-C light irradiation was visually observed in sample B4 (white).

Comparing the test results of sample B4 with those of sample B3, it can be seen that the _{TiO2 fine} particles contained in the coating corresponding to the second layer 11 shielded against UV-C light, thereby suppressing degradation.

Figure 8(a) is a graph showing the relationship between UV-C light irradiation time and the stress at fracture of the substrate for samples B1 to B4. Figure 8(b) is a graph showing the relationship between UV-C light irradiation time and the elongation at fracture of the substrate for samples B1 to B4.

As shown in Figures 8(a) and 8(b), sample B3, which does not contain _TiO2 nanoparticles in the coating corresponding to the second layer 11, shows a decrease in strength and elongation with increasing UV-C light irradiation time. On the other hand, sample B4, which contains _TiO2 nanoparticles in the coating corresponding to the second layer 11, shows no change in strength and elongation even with increasing UV-C light irradiation time. Furthermore, sample B4's elongation before UV-C light irradiation is inferior to that of sample B1, but its elongation after 200 hours of UV-C light irradiation is superior to that of sample B1. These results also indicate that the _TiO2 nanoparticles contained in the coating of sample B4 can suppress the progression of degradation caused by UV-C light.

(Fabrication of laminated structure 1)
Eleven samples (referred to as samples C1 to C11) were prepared to verify the UV-C light resistance of the laminated structure 1. Each of samples C1 to C11 comprises a first layer 10 and a second layer 11, with the first layer 10 containing _TiO2 fine particles 102. Of samples C1 to C11, samples C1, C6, and C9 do not contain _TiO2 fine particles 113 in the second layer 11 and were manufactured using the same process and materials as sample A3 in Example 1. Samples C2 to C5, C7, C8, C10, and C11 contain _TiO2 fine particles 113 in the second layer 11 (Ti concentration of 1.5% by mass or 1.9% by mass) and were manufactured using the same process and materials as sample A4 in Example 1. Table 2 below shows the configuration of the sheath 23 and coating 24 of samples C1 to C11. The thickness of the first layer 10 (sheath 23) was 0.8 mm, and the thickness of the second layer 11 (coating 24) was 20 μm.

(Verification of UV-C light resistance)
To verify the UV-C light resistance of laminated structure 1 based on its bending strength, bending tests equivalent to 45-50% tensile strength were performed on samples C1-C11 after UV-C light irradiation. UV-C light irradiation was carried out using a storage cabinet equipped with a germicidal lamp (Daishin Kogyo Co., Ltd. DM-5, lamp GL-10) under the following conditions: cabinet temperature 25-40°C, cabinet humidity 28-65%, cabinet pressure 1 atm (atmospheric pressure), wavelength 253.7 nm, illuminance 1.3 mW/ ^cm² , and irradiation time 200, 300, 400, and 600 hours. An illuminometer UVC-254A manufactured by MK Scientific was used. The bending tests were also carried out on the above samples C1-C11 under the following conditions: ambient temperature 15-35°C, ambient humidity 28-65 RH%, and atmospheric pressure.

Figure 9(a) is a schematic diagram showing the bending test. The sheath pieces 50 are portions of the sheath 23 covered with the coating 24, cut from each of the samples C1 to C11. In the bending test, first, rectangular sheath pieces 50 are cut from each of the samples C1 to C11. As shown in Figure 9(a), they are wrapped around a conductor (metal wire) 51 with a radius of 0.5 mm, and the overlapping portions of the sheath pieces 50 are clamped and secured from both sides (the illustration of the fasteners is omitted). Here, the sheath pieces 50 were prepared from 1 m long cable-like samples C1 to C11, and cut at 10 equally spaced locations along the longitudinal direction of the cable, measuring 12 mm (circumferential direction of the cable) x 18 mm (longitudinal direction of the cable). Then, the sheath pieces 50 were wrapped around the conductor 51 so that the longitudinal side of the cable aligned with the circumferential direction of the conductor 51, and the second layer 11 was located on the outer circumference.

Figure 9(b) is a cross-sectional view of the conductor 51 and the sheath piece 50 wrapped around the conductor 51, in the radial direction of the conductor 51. If the radius of the conductor 51 is r and the thickness of the sheath piece 50 is t, then, as shown in Figure 9(b), the longitudinal length of the neutral surface 50a of the sheath piece 50 in any angle θ range is (r + t/2)・θ, and the longitudinal length of the outer circumferential surface 50b of the sheath piece 50 is (r + t)・θ. Therefore, the longitudinal elongation rate of the outer circumferential surface 50b of the sheath piece 50 wrapped around the conductor 51 is expressed as {(r + t)・θ - (r + t/2)・θ} / ((r + t/2)・θ) × 100 = t / (2r + t) × 100. Since the radius r of the conductor 51 is 0.5 mm and the thickness t of the sheath piece 50 is 0.82 mm, this is approximately 45%.

Bending tests were performed on sheath pieces 50 cut from samples C1 to C11. The surface of the sheath pieces 50 during the bending test (when the second layer 11 was subjected to elongation equivalent to 45-50%) was observed at 50x magnification using an optical microscope (Keyence Digital Microscope VHX-1000). As a result, for the sheath pieces 50 of samples C1, C6, and C9, which did not contain TiO2 _fine particles in the second layer 11, no cracks appeared on the surface of the samples irradiated with UV-C light at an irradiation energy of 936 J/ ^cm² (illuminance (W/ ^cm² ) × irradiation time (seconds)), but cracks appeared on the surface of the samples irradiated with UV-C light at irradiation energies of 1404 J/ ^cm² , 1872 J/ ^cm² , and 2808 J/ ^cm² .

On the other hand, for the sheath pieces 50 cut from samples C2-C5, C7, C8, C10, and C11, which contain TiO2 _fine particles in the second layer 11, no cracks were observed on any of the surfaces of the samples irradiated with UV-C light at irradiation energies of 936 J/ ^cm² , ¹⁴⁰⁴ J/ ^cm² , 1872 J/ ^cm² , and 2808 J/cm². In this bending test, a crack refers to a recess that extends from the second layer 11 (coating 24) to the first layer 10 (sheath 23).

Figures 10(a) and 10(b) show SEM images of the surface and cross-section of a sheath piece 50 cut from sample C6 irradiated with UV-C light at an irradiation energy of 2808 J/ ^cm² . Figures 11(a) and 11(b) show SEM images of the surface and cross-section of a sheath piece 50 cut from sample C7 irradiated with UV-C light at an irradiation energy of 2808 J/ ^cm² . In the SEM images of Figures 10(a) and 10(b), a crack 52 extending from the second layer 11 to the first layer 10 is observed. On the other hand, the recessed portion 53 observed in the SEM images of Figures 11(a) and 11(b) does not reach the first layer 10 and is not counted as a crack. Figures 10(a) and 11(a) are SEM images at 100x magnification, and Figures 10(b) and 11(b) are SEM images at 1000x magnification. Furthermore, the sheath piece 50 was removed from the conductor 51 after the bending test, and this is an SEM image of the removed sheath piece 50.

Furthermore, the results of this bending test were used as one of the criteria for determining whether the laminated structure 1 had resistance to UV-C light. Sheath pieces 50 were taken from 10 locations on each sample irradiated with UV-C light. The bending test described above was performed on each of these 10 sheath pieces 50, and the number of sheath pieces 50 in which cracks were observed was counted when a 1.5 mm × 4.5 mm area was observed using an optical microscope at a magnification of 50x. The laminated structure 1 was determined to have resistance to UV-C light if, when observing 10 1.5 mm × 4.5 mm areas on the surface of the sample, 3 or fewer 1.5 mm × 4.5 mm areas showed cracks.

Figure 12 shows typical surface images of sheath pieces 50 cut from samples C1 to C11 when a bending test was performed on them. The images in Figure 12 are of a 1.5 mm × 4.5 mm area on the surface of the sheath pieces 50 made from samples C1 to C11, observed at 50x magnification using an optical microscope (Keyence Digital Microscope VHX-1000 ⁾ . According to Figure 12, cracks are observed on the surface of the sheath pieces 50 of samples C1, C6, and C9, which do not contain _TiO2 fine particles in the second layer 11, when irradiated with UV-C light at irradiation energies of 1404 J/ ^cm² , 1872 J/ ^cm² , and 2808 J/cm² (illuminance (W/ ^cm² ) × irradiation time (seconds)). For the sheath pieces 50 cut from samples C2-C5, C7, C8, C10, and C11, which contain TiO2 _fine particles in the second layer 11, no cracks were observed on the surface of any of the samples irradiated with UV-C light at irradiation energies of 936 J/ ^cm² , 1404 J/ ^cm² , 1872 J/ ^cm² , and 2808 ^J /cm².

For example, in samples C10 and C11 after irradiation with an energy of 2808 J/ ^cm² , a streaky pattern is observed along the longitudinal direction of the sample. This pattern does not reach the sheath 23 and is a recess that appears only in the coating 24. That is, the thickness of the coating 24 is greater than the depth of the recess. Since such a recess does not become the starting point for fracture of the sheath 23, it is not counted as a crack, as described above. Alternatively, whether a streaky pattern is a crack can be determined by examining the cross-sectional SEM images shown in Figures 10(b) and 11(b) to see if the pattern reaches the sheath 23.

As shown in Figure 12, for samples C2-C5, C7, C8, C10, and C11, cracks were observed in 3 or fewer out of 10 1.5 mm × 4.5 mm areas (specifically, 0 areas (no cracks)), and these samples were determined to be resistant to UV-C light. On the other hand, for C1, C6, and C9, cracks were observed in 4 or more out of 10 1.5 mm × 4.5 mm areas, and these samples were determined to be resistant to UV-C light. From the above, it was found that increasing the content of _TiO2 fine particles in the second layer 11 is effective in suppressing cracks in the laminated structure 1. Specifically, it was confirmed that cracks in the laminated structure 1 can be suppressed by setting the Ti concentration in the second layer 11 to 1.0 mass% or higher.

Next, to verify the resistance of the laminated structure 1 to UV-C light from the elongation at the breaking point, tensile tests were performed on samples C1-C5 and C7-C11 after UV-C light irradiation. UV-C light irradiation was carried out using a storage cabinet equipped with a germicidal lamp (Daishin Kogyo Co., Ltd. DM-5, lamp GL-10) under the following conditions: cabinet temperature 25-40°C, cabinet humidity 28-65%, cabinet pressure 1 atm (atmospheric pressure), wavelength 253.7 nm, illuminance 1.3 mW/ ^cm² , and irradiation time of 100, 200, 300, 400, and 600 hours.

After irradiation with UV-C light, dumbbell test specimens D1-D5 and D7-D11 were formed from cable-shaped samples C1-C5 and C7-C11 using the same method as in Example 1, where samples B1-B4 were formed from samples A1-A4. Tensile tests were performed on samples D1-D5 and D7-D11 (No. 6 dumbbell test specimens) using the same method and conditions as those used for samples B1-B4, as specified in "JIS K6251 (1994)". The ambient temperature at the tensile test evaluation site was 25±3°C, the ambient humidity was 50±10%, and the pressure was atmospheric. The gauge length was 20 mm, and the tensile speed was 500 mm/min until fracture.

Figures 13(a), (b), (c), and (d) are graphs showing the relationship between UV-C light irradiation energy (illuminance (W/ ^cm² ) × irradiation time (seconds)) and fracture elongation for samples D1, D3, D4, and D7, respectively. Similarly, Figures 14(a), (b), (c), and (d) are graphs showing the relationship between UV-C light irradiation energy and fracture elongation for samples D8, D9, D10, and D11, respectively. Table 3 below shows the numerical values of the plotted points in Figures 13(a), (b), (c), and (d) and Figures 14(a), (b), (c), and (d), i.e., the fracture elongation (%) values for each UV-C light irradiation energy for each sample.

According to Figures 13(a) to (d) and 14(a) to (d), and Table 3, among the fracture elongation of samples D1, D3, D4, and D7 to D11, the fracture elongation of samples D7 to D11 is 250% or more even when the UV-C irradiation energy is 1404 J/ ^cm² , indicating that samples D7 to D11 have high resistance to UV-C light from the viewpoint of fracture elongation. Furthermore, among the fracture elongation of samples D1, D3, D4, and D7 to D11, the fracture elongation of samples D7 to D11 is 200% or more even when the UV-C irradiation energy is 1872 J/ ^cm² , indicating that samples D7 to D11 have high resistance to UV-C light from the viewpoint of fracture elongation. Furthermore, among the fracture elongation of samples D1, D3, D4, and D7-D11, the fracture elongation of samples D7-D11 was 150% or more even when the UV-C light irradiation energy was 2808 J/ ^cm² , indicating that samples D7-D11 have high resistance to UV-C light in terms of fracture elongation.

From the results in Figures 13(a) to (d) and 14(a) to (d), and Table 3, it was found that increasing the content of _TiO₂ fine particles in the first layer 10 is effective in increasing the elongation at the fracture point of the laminated structure 1. Furthermore, as shown in Figures 15(a) and (b), the relationship between the Ti concentration (content of TiO₂ _fine particles) in the first layer 10 and the elongation at the fracture point (results for D3, D7, D10 and D4, D8, D11) was plotted and polynomial approximation was performed. Figure 15(a) shows the results after irradiation with 1404 J/ ^cm² of UV-C light, and Figure 15(b) shows the results after irradiation with 2808 J/ ^cm² of UV-C light. It was found that in order to achieve a fracture elongation of 250% or more even after irradiation with 1404 J/ ^cm² of UV-C light, the Ti concentration in the first layer 10 should be 0.4 mass% or more. Furthermore, it was found that in order to achieve a fracture elongation of 150% or more even after irradiation with 2808 J/ ^cm² of UV-C light, the Ti concentration in the first layer 10 should be 0.35 mass% or more.

Next, a surface wipe test was performed on sample C11, which contains _{TiO2 fine} particles 113 with a Ti concentration of 1.9 mass% in the second layer 11, which is the coating 24, and on a sample (referred to as sample C12) prepared in the same manner as sample C11, which contains _{TiO2 fine} particles 113 with a Ti concentration of 4.4 mass% in the second layer 11. The preparation and testing of the wipe test samples were carried out in the same manner as in Patent No. 6723489. Furthermore, the preparation and measurement of samples for measuring the static friction coefficient before and after the wipe test were also carried out in the same manner as in Patent No. 6723489. The ambient temperature at the wipe test site and the static friction coefficient measurement site was 25±3℃, the ambient humidity was 50±10%, and the pressure was atmospheric pressure.

In this wiping test, a long-fiber nonwoven fabric (50 mm in length in the wiping direction) made with a cotton linter containing disinfectant alcohol was brought into contact with the surface of the coating 24 so that a shear stress of 2 × ^10⁻³ MPa to 4 × ^10⁻³ MPa was applied. The surface of the coating 24 was wiped 20,000 times (10,000 back and forth cycles) over a length of 150 mm in the wiping direction at a speed of 80 to 120 times per minute. As a result, the difference (absolute value) of the static friction coefficient of the coating 24 of samples C11 and C12 before and after the test was 0.019 and 0.047, respectively, both of which were less than 0.1. Table 4 below shows the measured values of the static friction coefficient of the coating 24 of samples C11 and C12.

On the other hand, when the surface conditions of samples C11 and C12 were observed using SEM before and after the wiping test, differences were found between the two.

Figures 16(a) and 16(b) show the surface observation images (1000x magnification) of sample C11 and sample C12 before the wipe test, respectively. Figures 17(a) and 17(b) show the surface observation images of sample C11 and sample C12 after the wipe test, respectively. The spherical particles and the white powder particles surrounding them observed in the observation images of Figures 16(a) and 17(a) and 17(b) are fine particles 112 and TiO2 _fine particles 113, respectively.

As shown in Figures 16(a) and (b), more voids were observed in the coating 24 of sample C10 than in the coating 24 of sample C11. Also, as shown in Figures 17(a) and (b), more fine particles 112 were detached from the coating 24 of sample C12 than from the coating 24 of sample C11. One of the main reasons for these results is thought to be that the concentration of TiO2 _fine particles 113 in the coating 24 (second layer 11) of sample C12 was too high. This resulted in a greater presence of TiO2 _fine particles 113 around the fine particles 112, reducing the contact area between the silicone rubber base material 111 and the fine particles 112, and consequently reducing adhesion. From the results of the wipe test and SEM observation, it was confirmed that the upper limit of the Ti concentration in the coating 24 is 4.4 mass%.

The preferred ranges for the Ti concentration of the first layer 10 containing _TiO2 fine particles 102 and the Ti concentration of the second layer 11 containing _TiO2 fine particles 113, as described with reference to Figure 2 in the first embodiment, were derived based on the test results of this embodiment.

(Summary of the embodiments)
Next, the technical concept understood from the embodiments described above will be described using the reference numerals and other symbols from the embodiments. However, the reference numerals and other symbols in the following description are not limited to the components in the claims that are specifically shown in the embodiments.

[1] A laminated structure comprising a silicone rubber matrix (101) and a first layer (10) containing first TiO2 fine particles (102), and a second layer (11) laminated on the first layer (10) and comprising a silicone rubber matrix (111) and second TiO2 fine particles (113), wherein the Ti concentration of the first layer (10) is 0.35% by mass or more and 3.0% by mass or less, the Ti concentration of the second layer (11) is 1.0% by mass or more and 4.4% by mass or less, and the Ti concentration of the second layer (11) is higher than the Ti concentration of the first layer (10), wherein the laminated structure comprises an insulator (10, 11) made of silicone rubber, and the elongation at the breaking point measured by a tensile test after irradiation with 1404 J/ ^cm² of UV-C light is 250% or more, and the 1404 J/cm² A laminated structure (1) in which, when a bending test equivalent to 45-50% tensile strength is performed after irradiation with UV-C light ( ² ), and 10 1.5 mm × 4.5 mm areas on the surface are observed at 50x magnification using an optical microscope, the number of areas where cracks are observed is 3 or less.

[2] A laminated structure comprising a silicone rubber matrix (101) and a first layer (10) containing first TiO2 fine particles (102), and a second layer (11) laminated on the first layer (10) and having a silicone rubber matrix (111) and containing second TiO2 fine particles (113), wherein the Ti concentration of the first layer (10) is 0.35% by mass or more and 3.0% by mass or less, the Ti concentration of the second layer (11) is 1.0% by mass or more and 4.4% by mass or less, and the Ti concentration of the second layer (11) is higher than the Ti concentration of the first layer (10), and comprising an insulator (10, 11) having a silicone rubber matrix, wherein the elongation at the breaking point measured by a tensile test after irradiation with 2808 J/ ^cm² of UV-C light is 150% or more, and the 2808 J/cm² A laminated structure (1) in which, when a bending test equivalent to 45-50% tensile strength is performed after irradiation with UV-C light ( ² ), and 10 1.5 mm × 4.5 mm areas on the surface are observed at 50x magnification using an optical microscope, the number of areas where cracks are observed is 3 or less.

[5] The laminated structure (1) according to [1] or [2] above, wherein the second layer (11) comprises at least one of silicone resin fine particles and silica fine particles.

[6] A cable (20) comprising insulators (23, 24) made of the laminated structure (1) described in any one of items [1] to [3] above.

[7] A tube (40a, 40b, 40c) comprising an insulator (41, 42, 43) made of the laminated structure (1) described in any one of items [1] to [3] above.

The embodiments and examples of the present invention have been described above. However, the present invention is not limited to the embodiments and examples described above, and various modifications are possible without departing from the spirit of the invention. Furthermore, the embodiments and examples described above do not limit the invention as defined in the claims. It should also be noted that not all combinations of features described in the embodiments and examples are necessarily essential for solving the problem of the invention.

1. Laminated structure 10. First layer 101. Base material 102. _TiO2 microparticles 11. Second layer 111. Base material 112. Microparticles 113. TiO2 microparticles _2. Ultrasonic probe cable 20. Cable 23. Sheath 24. Coating 40a, 40b, 40c. Medical tube 41. Tube body 42. Outer coating 43. Inner coating

Claims (6)

A silicone rubber base material, a first layer containing first TiO2 _fine particles,
Laminated on the first layer is a second layer made of silicone rubber as the base material and containing second TiO2 _fine particles,
Equipped with,
The Ti concentration of the first layer is 0.35% by mass or more and 3.0% by mass or less.
The Ti concentration of the second layer is 1.0% by mass or more and 4.4% by mass or less.
Laminated structure. The Ti concentration of the second layer is higher than the Ti concentration of the first layer.
The laminated structure according to claim 1. The second layer comprises at least one of silicone resin fine particles and silica fine particles.
The laminated structure according to claim 1 or 2. An insulator comprising a laminated structure according to any one of claims 1 to 3,
cable. An insulator comprising a laminated structure according to any one of claims 1 to 3,
tube. A method for manufacturing a laminated structure according to any one of claims 1 to 3, wherein the first layer and the second layer are formed in order,
The process includes applying a silicone rubber coating agent , the content of which is adjusted so that the Ti concentration of the second layer is 1.0% by mass or more and 4.4% by mass or less, _onto the first layer to form a coating film, and then curing the coating film to form the second layer.
A method for manufacturing a laminated structure.