Patent Description:
Conventionally, a cable for medical devices made of silicone rubber including fine particles and with a layer that covers a sheath has been known (see Patent Literature <NUM>). Compared with polyvinyl chloride (PVC), which has been commonly used as a material for sheath, silicone rubber has advantages such as little discoloration over time, but it tends to have low surface slidability.

Since the layer of the cable described in Patent Literature <NUM> is made of silicone rubber including fine particles, the surface of the cable is formed with irregularities (i.e., unevenness, indentations) derived from fine particles. This uneven surface makes it possible to reduce a contact area when the layer is in contact with other parts, thereby increasing the slidability of the surface of the layer, i.e., the slidability of the cable.

In addition, patent literature <NUM> (<CIT>) discloses a composite material comprising at least two elastomer layers, the first layer having a first composition comprising from <NUM> to <NUM> percent by weight of silicone rubber, the second layer having a second composition comprising from <NUM> to <NUM> percent by weight of rubber of the ethylene-propylene copolymer and/or terpolymer type, wherein the first composition further contains from <NUM> to <NUM> percent by weight of rubber of the ethylene-propylene copolymer and/or terpolymer type, and each of the two compositions contains more than <NUM> percent, and preferably from <NUM> to <NUM> percent, by weight of silica.

Patent literature <NUM> (<CIT>) deals with the following problem to be solved: Improve tear and wear resistance of an insulated wire in which a rubber material with poor tear and wear resistance is used for an insulating layer, and also reduce the influence of external force on a conductor. The following means for solving the problem are disclosed: A plurality of insulating layers formed of rubber materials are provided, and the properties of the rubber materials are changed for each layer.

Patent literature <NUM> (<CIT>) A discloses an invention that relates to an ultraviolet radiation resistant composite insulator material added with nano particles and a preparation method thereof. According to the preparation method, silicon rubber is taken as a unit, andg is taken, <NUM>% nano SiO2 is taken, <NUM>% of hexamethyldisilazane is taken, <NUM>%-<NUM>% nano TiO2 is taken, and <NUM>% of <NUM>,<NUM>-Dimethyl-<NUM>,<NUM>-di(tert-butylperoxy)hexane is taken; a twin-roller machine is started, and after the temperature reaches <NUM> EDG C, the silicone rubber is placed in the middle of two rollers for mixing; after homogenization, nano SiO2 is added into silicone rubber evenly, and then the mixture is mixed by two rollers; at the same time, the hexamethyldisilazane is added three times; after all the additives are added, twin-roller mixing is carried out, nano TiO2 is uniformly added, and after the additives are added, twin-roll mixing is carried out to obtain a mixed material; the <NUM>,<NUM>-Dimethyl-<NUM>,<NUM>-di(tert-butylperoxy)hexane is uniformly dropped on the mixed material, twin-roller mixing is carried out, a sample is shoveled, the sample is rolled into a croissant shape, the sample is placed between the rollers for mixing again, the sample is taken down, and the sample is placed between two clean PET films; and the sample is vulcanized at high temperature by using a tablet press. The addition of the nano TiO2 does not affect the hydrophobicity of the composite insulator material.

Patent Literature <NUM> (<CIT>) discloses a flame-retardant silicone rubber composition including fine silica particles and titanium dioxide. It discloses a silicone rubber obtained by curing having excellent flame retardancy and has reduced flame retardance under long-term heating conditions.

Recently, as a method of sterilizing medical device cables, a sterilization method by UV-C light, by which the sterilization is easy, inexpensive, and reliable, is attracting attention. However, the resistance of the cable to the UV-C light is a problem in order to perform the sterilization by UV-C light. It has been confirmed that a cable equipped with a sheath made of silicone rubber will deteriorate when the UV-C light is repeatedly irradiated to the cable. Thus, the cable will have cracks in the sheath when stress such as bending the cable is applied to the sheath.

Therefore, the object of the present invention is to provide a laminate structure with silicone rubber as a base material, which is superior in resistance to UV-C light, and a cable and a tube with an insulator made of the laminate structure.

So as to achieve the above object, one aspect of the present invention provides: a laminate structure as defined in claim <NUM>.

Further, another aspect of the present invention provides: a cable or tube comprising an insulator comprising the above laminate structure.

According to the present invention, it is possible to provide a laminate structure with silicone rubber as a base material, which is superior in resistance to UV-C light, and a cable and a tube with an insulator made of the laminate structure.

<FIG> is a vertical cross-sectional view of a laminate structure <NUM> according to the first embodiment of the present invention. The laminate structure <NUM> is composed of a first layer <NUM> including silicone rubber as a base material (i.e., parent material), and a second layer <NUM> layered on the first layer <NUM>. The second layer <NUM> includes silicone rubber as a base material <NUM>, first fine particles <NUM> to give irregularities to a surface, and second fine particles <NUM> to shield UV-C light by absorption and/or scattering.

The first fine particles <NUM> are made of a material including Si such as silicone resin and silica that are more resistant to UV-C light than silicone rubber. It is also preferable that an average particle size of the second fine particles <NUM> is smaller than an average particle size of the first fine particles <NUM>. For example, the average particle size of the second fine particles <NUM> is preferably <NUM>/<NUM> or less of the average particle size of the first fine particles <NUM>, and more preferably <NUM>/<NUM> or less of the average particle size of the first fine particles <NUM>. This allows the second fine particles <NUM> to be polarized around the first fine particle <NUM> and the second fine particles <NUM> to be selectively placed in areas where the first fine particles <NUM> are not present in an in-plane direction of the second layer <NUM>. Here, UV-C light is an ultraviolet light within a wavelength range of <NUM> to <NUM>.

Silicone rubber, which is the base material for the first layer <NUM> and the second layer <NUM>, is a kind of silicone resins. The silicone rubber is more resistant to ultraviolet light (e.g., UV-A light, UV-B light) than polyvinyl chloride, which is commonly used as a material for cables and tubes to be used in medical applications.

Silicone rubber also adds the first fine particle, <NUM>, which contains Si, such as silicone resin particles (i.e., fine particles) and silica (silicon oxide) particles (i.e., fine particles), to create a surface that is uneven and irregular, thereby reducing the level of surface stickiness (i.e., tacking), and improving slidability (i.e., sliding properties). Therefore, the second layer <NUM> including the silicone rubber doped with the first fine particles <NUM> can be layered on the first layer <NUM> including the silicone rubber but free of the first fine particles <NUM> to cover the surface of the first layer <NUM>, thereby reducing the surface stickiness of the silicone rubber and improving the slidability.

On the other hand, a silicone rubber that does not include the first fine particles <NUM> should have a certain thickness to have a performance as a base material (e.g., the function to protect or accommodate other articles) compared to a silicone rubber that includes the first fine particles <NUM>. For this reason, it is preferable to use the laminate structure <NUM> as an insulator for cables and tubes, and to form the first layer <NUM> by extrusion or the like with high productivity, and then laminate the second layer <NUM> on the first layer <NUM> by coating or the like.

The laminate structure <NUM> may have various forms depending on its application. For example, when used as an insulator for cables and tubes, it is molded in a tubular form, and when used as high UV-resistant sheets for constant temperature greenhouse or UV-shield sheets (UV-shield curtains) to shield against UV leakage from sterilization rooms or the like.

The second layer <NUM> includes the first fine particles <NUM>, which create the irregularities on the surface. This results in a smaller contact area and higher slidability, when the second layer <NUM> comes into contact with a contactant, as compared to a flat surface.

For the silicone rubber which is the base material <NUM> of the second layer <NUM>, e.g., an addition reaction type silicone rubber coating agent or a condensation reaction type silicone rubber coating agent can be used. In particular, it is preferable to use the addition reaction type silicone rubber coating agent in order to ensure adhesion and wear resistance to the first layer <NUM> including the silicone rubber as the base material.

It is preferable that a thickness of the second layer <NUM> is not less than <NUM> to obtain good slidability and predetermined wipes resistance (i.e., resistance to being wiped off) of the surface of the laminate structure <NUM> by the second layer <NUM>. Also, the second layer <NUM> may be laminated on both sides of the first layer <NUM>. Although the upper limit of the thickness of the second layer <NUM> is not particularly limited, it is preferable to be not more than <NUM> from the viewpoint of productivity, high flexibility and high bending property.

The first fine particle <NUM> is, for example, a silicone resin fine particle, a silica particle, or a mixture of these two kinds of particles. The first fine particle <NUM>, preferably has a higher hardness than the base material <NUM> composed of silicone rubber (e.g., the first fine particle <NUM> has a Shore (durometer A) hardness of not lower than <NUM> times the hardness of the base material <NUM>).

Silicone resin with fewer reaction groups (e.g., methyl groups) than silicone rubber has a higher hardness than silicone rubber, and silica with no reaction group is more hardness. In terms of mass, silica is the largest, silicone resin is the second largest, and silicone rubber is the smallest.

From the viewpoint of reducing the deformation of the surface when the second layer <NUM> comes into contact with the contactant, silica with high hardness is the most preferable material for the first fine particles <NUM>, and silicone resin is the next preferable material. This is because when a contact causes pressure on the surface of the second layer <NUM>, the harder the first fine particle <NUM> can reduce the deformation of the surface of the second layer <NUM>. This will reduce the increase in contact area between the second layer <NUM> and the contactant and maintain the slidability.

On the other hand, because of the large mass of silica as described above, the first fine particle <NUM> composed of silica is easily precipitated in the silicone rubber coating agent as a base material in the manufacturing process of the second layer <NUM>. It is difficult to disperse the first fine particles <NUM> in silicone rubber (the second layer <NUM>) compared to the first fine particles <NUM> composed of the silicone resin. Therefore, from the viewpoint of improving the uniformity of dispersion in silicone rubber (the second layer <NUM>), it is preferable to use the first fine particles <NUM> composed of silicone resin.

Therefore, it is preferable to use the first fine particle <NUM> composed of silicone resin, to maintain the slidability when the second layer <NUM> comes into contact with the contactant and to achieve the uniformity of the dispersion of the first fine particles <NUM> in silicone rubber as the base material.

The average particle size of the first fine particles <NUM> is e.g., <NUM> or more and <NUM> or less. In addition, the concentration (mass%) of the first fine particles <NUM> in the second layer <NUM> is e.g., <NUM> mass% or more and <NUM> mass% or less. Here, the "average particle size" in the present application is measured by the laser diffraction scattering method.

As mentioned above, the first fine particle <NUM> is more resistant to UV-C light than the silicone rubber as the base material <NUM>. This is because the bond energy between atoms in the molecular structure of silicone resin or silica, which is the material of the first fine particle <NUM>, is higher than the bond energy between atoms in the molecular structure of silicone rubber.

For example, the binding energy of C-H bond, which is often contained in silicone rubber, is smaller (approximately <NUM> eV) than the energy of UV-C light (approximately <NUM> eV), so that the C-H bond is cut by UV-C light irradiation. Meanwhile, the binding energy of Si-O bond, which is often contained in the silicone resin, is greater (approximately <NUM> eV) than the energy of UV-C light, so that the Si-O bond does not break due to exposure of UV-C light.

The second fine particle <NUM> is composed of a material, which has the characteristics of shielding UV-C light by absorbing and/or scattering it, such as titanium oxide (TiO<NUM>), carbon (C), zinc oxide (ZnO), and iron oxide (Fe<NUM>O<NUM>). Since the second fine particles <NUM> shield UV-C light, it is possible to reduce the degradation caused by UV-C light in the base material <NUM>, which is composed of silicone rubber. Titanium oxide as a material of the second fine particle <NUM> can be either anatase, rutile, or brookite, and can be a mixture of two or more of them. In addition, titanium oxide may be supplemented with niobium oxide to provide stability.

As noted above, it is preferable that the average particle size of the second fine particles <NUM> is smaller than the average particle size of the first fine particles <NUM>. By reducing the average particle size of the second fine particles <NUM>, the second fine particle <NUM> can be present in a gap space between the first fine particles <NUM>. By reducing the average particle size of the second fine particles <NUM> to be smaller than the average particle size of the first fine particles <NUM>, the second fine particles <NUM> can be polarized around the first fine particle <NUM>, and the second fine particles <NUM> can be selectively placed in regions where the first fine particle <NUM> is not present along the in-plane direction of the second layer <NUM>. For example, if the average particle size of the second fine particles <NUM> is <NUM>/<NUM> or less, and more preferably <NUM>/<NUM> or less, of the average particle size of the first fine particles <NUM>, the second fine particles <NUM> can be more effectively polarized around the first fine particle <NUM>. The lower limit of the average particle size of the second fine particles <NUM> is not particularly limited, but from the viewpoint of availability, it is preferable that the average particle size of the second fine particles <NUM> is <NUM> or more. Here, the "average particle size" of the second fine particles <NUM> was measured by laser diffraction scattering method.

The region in which the first fine particle <NUM> is not present when the second layer <NUM> is observed from the surface (the area located between the first fine particles <NUM>) is a region that is less resistant to UV-C light, where only the base material <NUM> composed of silicone rubber is present. The inventors of the present application found that it is possible to effectively improve resistance to UV-C light by selectively placing the second fine particles <NUM> in this region and thereby shielding UV-C light.

The first layer <NUM> preferably includes a second fine particle <NUM> to absorb UV-C light, as well as the second layer <NUM> including the second fine particle <NUM>, so as reduce degradation caused by UV-C light transmitted through the second layer <NUM>. In this case, the first layer <NUM> includes a base material <NUM> composed of silicone rubber and the second fine particles <NUM> distributed in the base material <NUM>, as shown in <FIG>. For a material of the base material <NUM>, polyethylene, chlorinated polyethylene, chloroprene rubber, polyvinyl chloride (PVC), polyurethanes and the like can be used. Among them, silicone rubber and chloroprene rubber are preferable from a viewpoint of chemical resistance and heat resistance. If the first layer <NUM> is used as the sheath material, the first layer <NUM> may be composed of an insulating material with the addition of common formulations such as various crosslinkers, crosslinking catalysts, anti-aging agents, plasticizers, lubricants, fillers, flame retardants, stabilizers, colorants, and the like. It is also possible to mix organic ultraviolet absorbers instead of the second fine particles <NUM>, which is dispersed in the base material <NUM>.

The material of the second fine particle <NUM> may be the same as the material of the second fine particle <NUM>, e.g., titanium oxide, carbon. However, it is preferable that the second fine particles <NUM> are evenly distributed in the base material <NUM> so that the resistance to UV-C light in the first layer <NUM> does not vary depending on the location. For this reason, the average particle size of the second fine particles <NUM> is not particularly limited, but it is preferable to be, e.g., <NUM> or more and <NUM> or less. Here, the "average particle size" of the second fine particles <NUM> was measured by laser diffraction scattering method.

<FIG> is a graph showing preferred ranges of Ti concentration in the first layer <NUM> including TiO<NUM> fine particles <NUM> as the second fine particles and Ti concentration in the second layer <NUM> including TiO<NUM> fine particles <NUM> as the second fine particles.

As shown in <FIG>, the Ti concentration in the first layer <NUM> is preferably <NUM> mass% or more and <NUM> mass% or less. By including TiO<NUM> fine particles <NUM> at a Ti concentration of <NUM> mass% or more in the first layer <NUM>, it is possible to maintain the high elongation at break measured when the tensile test specified in "JIS K6251 (<NUM>)" is performed after UV-C light is irradiated on the cable including the laminate structure <NUM> as insulators (sheath and its layer).

The goal was set to achieve an elongation at break of <NUM>% or more after exposure of UV-C light of <NUM> J/cm<NUM> since the elongation at break is at least <NUM>% when the UV-C light was not irradiated to the laminate structure <NUM> with the second layer <NUM> that does not include the TiO<NUM> fine particles <NUM> (See <FIG>).

The goal was set to achieve an elongation at break of <NUM>% or more even after exposure to UV-C light of <NUM> J/cm<NUM>, since the elongation at break required for general rubber materials is at least <NUM>%.

The specific method of this tensile test will be described below.

On the other hand, when the first layer <NUM> includes TiO<NUM> fine particles <NUM> at a Ti concentration greater than <NUM> mass%, the first layer <NUM> will be stiffened, resulting in lower flexibility of the laminate structure <NUM> and lower tearing strength. Therefore, considering the handling of cables and tubes when the first layer <NUM> is used as the insulator for cables and tubes, the Ti concentration in the first layer <NUM> is preferably not greater than <NUM> mass%.

As shown in <FIG>, the Ti concentration in the second layer <NUM> is preferably <NUM> mass% or more and <NUM> mass% or less. By including TiO<NUM> fine particles <NUM> at a Ti concentration of <NUM> mass% or more in the second layer <NUM>, it is possible to suppress the formation of cracks, which may reach of the first layer <NUM>, on the surface of the laminate structure <NUM>, due to bending test equivalent to <NUM>% to <NUM>% tensile after exposure to UV-C light at <NUM> J/cm<NUM>. The method of the bending test and observation of the presence of cracks will be described below.

On the other hand, when the second layer <NUM> includes TiO<NUM> fine particles <NUM> at a Ti concentration greater than <NUM> mass%, the surface roughness of the second layer <NUM> will be greater. As the surface roughness increases, dirt and bacteria are easily attached and difficult to be removed. In the case where the second layer <NUM> includes the first fine particle <NUM>, such as silicone resin fine particles, when the second layer <NUM> includes TiO<NUM> fine particles <NUM> at a Ti concentration greater than <NUM> mass%, the adhesion between the base material <NUM> composed of silicone rubber and the first fine particle <NUM> is reduced, making it easier for the first fine particle <NUM> to fall off, and the sliding property of the surface of the second layer <NUM> is reduced. Therefore, the Ti concentration in the second layer <NUM> is preferably not greater than <NUM> mass%.

Also, as shown in <FIG>, the concentration of TiO<NUM> fine particle <NUM> in the second layer <NUM> is preferably higher than the concentration of TiO<NUM> fine particle <NUM> in the first layer <NUM>, i.e., the Ti concentration of the second layer <NUM> is preferably higher than the Ti concentration of the first layer <NUM>. By setting the concentration of TiO<NUM> fine particle <NUM> in the second layer <NUM> to be higher than the concentration of TiO<NUM> fine particle <NUM> in the first layer <NUM>, it is possible to effectively absorb and/or scatter UV-C light in the second layer <NUM>, thereby suppressing degradation caused by UV-C light in the first layer <NUM>, and thus suppressing the reduction in flexibility and tearing strength of the laminate structure <NUM>.

All Ti in the first layer <NUM> are contained in TiO<NUM> fine particles <NUM>, and all Ti in the second layer <NUM> are contained in TiO<NUM> fine particles <NUM>. The Ti concentration in the first layer <NUM> and the Ti concentration in the second layer <NUM> are determined as the mean values in a measuring area of <NUM> wide x <NUM> high using an energy dispersive X-ray analyzer (EDS) mounted on a scanning electron microscope (SEM).

The second embodiment of the present invention is a cable or tube with an insulator composed of the laminate structure <NUM> in the first embodiment. Next, the cable to be used as a medical ultrasonic probe cable is described below.

In recent years, it has been considered that silicone rubber, which has superior heat resistance and chemical resistance, is used as the material for sheath in cables used for medical applications. However, as mentioned above, silicone rubber has a problem of poor slidability. Therefore, when silicone rubber is used as the material for the sheath of the cable, the problems that the cable can easily be caught with other parts and that dust can easily get on the surface of the cable will occur.

In particular, if the cable is more easily caught with other parts, it will be difficult to handle the cable connected to medical devices such as ultrasonic imaging devices. This is because the examination is performed while moving the ultrasonic probe connected to the probe cable around the human body. If the probe cable is easily caught with other cables or clothing, it will not be possible to move the ultrasonic probe smoothly. Therefore, it is desired that cables used for medical applications have no stickiness and good surface slidability (static friction coefficient of <NUM> or less).

<FIG> shows a schematic diagram of the configuration of an ultrasonic probe cable <NUM> in the second embodiment of the present invention. In the ultrasonic probe cable <NUM>, an ultrasonic probe <NUM> is attached to one end of a cable <NUM> via a boot <NUM>, which protects the one end, as shown in <FIG>. Meanwhile, a connector <NUM> that connects to a main body of an ultrasonic imaging device is attached to the other end of the cable <NUM>.

<FIG> shows a radial cross-sectional view of the cable <NUM> of the ultrasonic probe cable <NUM>. The cable <NUM> includes, for example, plural electric wires <NUM>, typically coaxial cables, and a shield <NUM>, such as a braided shield, to cover the plural electric wires <NUM>. And a sheath <NUM> is provided to cover the shield <NUM>. In addition, the cable <NUM> includes a coating film (i.e., layer) <NUM> covering a circumference of the sheath <NUM> and adhering to the sheath <NUM>.

<FIG> shows a radial cross-sectional view of the ultrasonic probe cable <NUM> cut along a line A-A in <FIG>. The boot <NUM> is installed over the coating film <NUM> over an adhesive layer <NUM> covering the coating film <NUM> as shown in <FIG>. The adhesive layer <NUM> is formed from, e.g., silicone adhesive or epoxy adhesive. Also, the boot <NUM> may be formed from, e.g., PVC, silicone rubber, chloroprene rubber, etc., and the boot <NUM> preferably includes the second fine particles <NUM> or organic UV absorbers to shield UV-C light, similarly to the first layer <NUM>.

Th sheath <NUM> and the coating film <NUM> of the cable <NUM> are respectively composed of the first layer <NUM> and the second layer <NUM> of the laminate structure <NUM>. In other words, in the cable <NUM>, the laminate structure <NUM> is used as the sheath <NUM> and the coating film <NUM>. By using the coating film <NUM> composed of the second layer <NUM>, which is superior in sliding property, it is possible to suppress the ultrasonic probe cable <NUM> from being caught due the stickiness of the surface of the sheath <NUM>. For example, the thickness of the coating film <NUM> is <NUM> or more and <NUM> or less. The illustration of the second fine particles <NUM> in the sheath <NUM> and the first fine particles <NUM> and the second fine particles <NUM> in the coating film <NUM> are omitted.

The following is an example of a method for manufacturing the ultrasonic probe cable <NUM> in the present embodiment. First, plural (e.g., <NUM> or more) of electric wires <NUM> are bundled together. The shield <NUM> is then formed to cover the bundle of the electric wires <NUM>.

Then, to cover the shield <NUM>, the first layer <NUM> and the second layer <NUM> of the laminate structure <NUM> are formed in this order, then the sheath <NUM> and the coating film <NUM> are formed. The sheath <NUM> is formed by extrusion molding using e.g., an extruder. The coating film <NUM> is formed by, e.g., dipping, spraying or rolling application method. In the dipping method, the ultrasonic probe cable <NUM> formed up to the sheath <NUM> is pulled up through a liquid coating material to form the coating film <NUM> on a surface of the sheath <NUM>. This dipping method is superior to the spraying or rolling application methods in terms of uniformity of a film thickness of the coating film <NUM> to be formed.

The liquid coating agent used in the dipping method is a liquid silicone rubber including the first fine particles <NUM> and the second fine particles <NUM> and contains a solvent such as n-heptane. By adjusting the content of the first fine particles <NUM> and the second fine particles <NUM> in this liquid coating agent, the content of the first fine particles <NUM> and the second fine particles <NUM> in the coating film <NUM> can be controlled.

Next, the configuration of a tube (hollow tube) to be used for medical applications such as catheters will be described below, as another example of cables or tubes with insulators composed of the laminate structure <NUM>.

<FIG> are cross-sectional views of a medical tube in the second embodiment of the present invention. A medical tube 40a shown in <FIG> has an outer layer <NUM> on an outer surface 41a of a tube main body <NUM>. A medical tube 40b shown in <FIG> has an inner layer <NUM> on an inner surface 41b of the tube main body <NUM>. A medical tube 40c shown in <FIG> has an outer layer <NUM> and an inner layer <NUM> respectively on an outer surface 41a and an inner surface 41b of the tube main body <NUM>.

As shown in examples of the medical tubes 40a, 40b, and 40c, the tube in the present embodiment includes the tube main body <NUM>, and the outer layer <NUM> covering the outer surface 41a of the tube main body <NUM> or the inner layer <NUM> covering the inner surface 41b of the tube main body <NUM>, or alternatively, both the outer layer <NUM> and the inner layer <NUM>. The tube main body <NUM> of the medical tubes 40a, 40b, and 40c is composed of the first layer <NUM> of the laminate structure <NUM>, and the outer layer <NUM> and the inner layer <NUM> are respectively composed of the second layer <NUM> of the laminate structure <NUM>.

Because the tubes in the present embodiment have excellent slidability at the inner surface or the outer surface, for example, when devices are inserted into the tubes, such as catheters or other medical tubes, smooth insertion and removal of the devices can be achieved. Further, the tubes in the present invention may be used as tube sets for endoscopic surgical instruments, tube sets for ultrasonic surgical instruments, blood analyzer tubes, tubes within oxygen concentrators, artificial dialysis blood circuits, artificial cardiopulmonary circuits (artificial heart-lung circuits), endotracheal tubes, and so on.

According to the laminate structure <NUM> in the first embodiment, the surface has excellent slidability because the second layer <NUM> includes the first fine particles <NUM>, and the second fine particles <NUM> are polarized around the first fine particle <NUM>, which makes the laminate structure <NUM> more resistant to UV-C light. In addition, according to the ultrasonic probe cable <NUM> and the medical tubes 40a, 40b, 40c, etc., in the second embodiment, because the laminate structure <NUM> is used as an insulator, the ultrasonic probe cable <NUM> and the medical tubes 40a, 40b, 40c, etc., have excellent surface slidability and are resistant to UV-C light.

In the first embodiment, silicone rubber is used as the material for the base material <NUM> in the second layer <NUM> of the laminate structure <NUM>. However, the same effect can be achieved by using rubber components other than silicone rubber, such as chloroprene rubber, instead of silicone rubber.

Four samples (samples A1 to A4) were prepared to verify the shielding effect of UV-C light in the second layer <NUM> of the laminate structure <NUM>. First, a cable core was prepared by stranding two-hundreds coaxial cables each with a diameter of about <NUM> and covering the stranded cables with a braided wire. Then, by using an extruder, a sheath material was extruded at a speed of <NUM>/min to cover an outer periphery of the cable core, and the sheath <NUM> with a thickness of <NUM> was formed as the first layer <NUM> of the laminate structure <NUM> (an outer diameter of the cable was about <NUM>). Here, for the sheath material of the sample A1, a commonly used PVC was used. For the sheath material of the samples A2 to A4, a color batch including titanium oxide (a mixture of "KE-color-W" and "KE-<NUM>-U" made by Shin-Etsu Chemical Co. ) was used. The mixture was adjusted in such a manner that Ti concentration analyzed by an energy dispersive X-ray analyzer (EDS) mounted on a scanning electron microscope (SEM) (average value in the measuring area of <NUM> wide x <NUM> high) is <NUM> mass%. By the process so far, the samples A1 and A2, which do not have a coating film <NUM> as the second layer <NUM> of the laminate structure <NUM>, were prepared.

Next, a material for forming the coating film <NUM> of the sample A3 was prepared. An addition reaction type silicone rubber coating agent (product name: SILMARK-TM, made by Shin-Etsu Chemical Co. ) was prepared as a rubber component as the base material <NUM>. As the first fine particles <NUM>, silicone resin fine particles with an average particle size of <NUM> (product name: X-<NUM>-<NUM>, made by Shin-Etsu Chemical Co. ) were prepared. For <NUM> parts by mass of this rubber component, <NUM> parts by mass of silicone resin fine particles, <NUM> parts by mass of toluene as a solvent for viscosity adjustment, and <NUM> parts by mass of crosslinking agent (product name: CAT-TM, made by Shin-Etsu Chemical Co. ), and <NUM> parts by mass of curing catalyst (product name: CAT-PL-<NUM>, made by Shin-Etsu Chemical Co. ) were mixed, to prepare a coating solution with a ratio of <NUM> mass% of the first fine particles <NUM> to the coating film <NUM>. The content of the first fine particles <NUM> in the coating film <NUM> was calculated assuming that the coating agent cures with little or no mass reduction (approximately equivalent to the compound mass ratio).

Then, the surface of the sheath <NUM> provided on the cable core was cleaned. The sheath <NUM> was then immersed in the above coating solution using the dip coating method, and a coating composed of silicone rubber was formed on the sheath surface. After that, the coating was thoroughly dried and cured at a temperature of <NUM> to form the coating film <NUM> with uneven surface. The thickness of the coating film <NUM> of the sample A3 thus obtained was <NUM>. The sample A3 was prepared by the above process.

Next, the material for forming the coating film <NUM> of the A4 sample was prepared. For the coating film <NUM> of the A4 sample, the rubber component as the base material <NUM> and the silicone resin fine particles as the first fine particles <NUM> were prepared similarly to the materials used for the coating film <NUM> of the A3 sample. In addition, as the second fine particle <NUM>, titanium oxide (anatase-type TiO<NUM>) fine particles with an average particle size of <NUM> were prepared. For <NUM> parts by mass of the rubber component, <NUM> parts by mass of silicone resin fine particles, titanium oxide fine particles, <NUM> parts by mass of toluene as a solvent for viscosity adjustment, and <NUM> parts by mass of crosslinking agent (product name: CAT-TM, made by Shin-Etsu Chemical Co. ), and <NUM> parts by mass of curing catalyst (product name: CAT-PL-<NUM>, made by Shin-Etsu Chemical Co. ) were mixed, to prepare a coating solution with a ratio of <NUM> mass% of the first fine particles <NUM> to the coating film <NUM> and a predetermined concentration of the second fine particles <NUM> to the coating film <NUM>. The concentration of titanium oxide fine particles as the second fine particles <NUM> in the coating film <NUM> was adjusted in such a manner that Ti concentration in the coating film <NUM> analyzed by an energy dispersive X-ray analyzer (EDS) mounted on a scanning electron microscope (SEM) (mean value in the measuring area of <NUM> wide x <NUM> high) is <NUM> mass%. The content of the first fine particles <NUM> in the coating film <NUM> was calculated assuming that the coating agent cures with little or no mass reduction (approximately equivalent to the compound mass ratio).

Then, as with the coating film <NUM> of the sample A3, the surface of sheath <NUM> was cleaned, the coating film was formed by the dip coating method, and the coating film was dried and cured. The coating film <NUM> was formed with uneven surface. The thickness of the coating film <NUM> of the sample A4 thus obtained was <NUM>. The sample A4 was prepared by the above process.

To verify the UV-C light shielding effect in the second layer <NUM> of the laminate structure <NUM>, a tensile test was performed on the samples A1 to A4 before and after UV-C light exposure. First, the sheath <NUM> of each of the cable-like samples A1 to A4 (the sheath <NUM> covered with the coating film <NUM> in the samples A3 and A4) was cut along the length direction, the content in the sheath <NUM> was removed and the sheath <NUM> was opened. The opened sheath <NUM> was punched with dumbbell-shaped punch No.<NUM> to form a dumbbell test piece (thickness of <NUM>). Here, the dumbbell test pieces made from the sheaths <NUM> of the samples A1, A2, A3, and A4 (the sheath <NUM> covered with the coating film <NUM> in the samples A3 and A4) are samples B1, B2, B3, and B4, respectively. Table <NUM> below shows the compositions of the samples B1 to B4.

The tensile test is a test specified in "JIS K6251 (<NUM>)" and was performed on the above samples B1 to B4 under the condition at an ambient temperature of <NUM> to <NUM>, an ambient humidity of <NUM> to <NUM>% under an atmospheric pressure. UV-C light irradiation was performed by a storage chamber with sterilization lamps (Storage chamber DM-<NUM>, lamps GL-<NUM>, available from Daishin Kogyo Co. ,) at a chamber temperature of <NUM> to <NUM>, a chamber humidity of <NUM>% to <NUM>%, a chamber pressure of <NUM> atm (atmospheric pressure), a wavelength of <NUM>, an illuminance of <NUM> mW/cm<NUM>, and irradiation times of <NUM> hours and <NUM> hours. The illuminance meter was UVC-254A made by MK Scientific Inc.

<FIG> shows the results of the tensile test of the sample B1. In <FIG>, "unexposed" shows the sample B1 before being exposed to UV-C light, and "after" shows the sample B1 after being exposed to UV-C light irradiation for <NUM> hours. As shown in <FIG>, it was confirmed that after exposure of UV-C light, the strength (magnitude of stress when the base member is broken) and the elongation are smaller than before exposure, and that the sample B1 deteriorates (changes to break easier) with the exposure of UV-C light. Moreover, because the sample B1 was a gray PVC, it was visually confirmed that the UV-C light irradiation caused a discoloration that would appear yellow. Here, <NUM>% elongation indicates that the length of the Dumbbell test piece has doubled from the original length.

<FIG> shows the results of the tensile test of the sample B2. In <FIG>, "unexposed" shows the sample B2 before being exposed to UV-C light, and "after" shows the sample B2 after being exposed to UV-C light irradiation for <NUM> hours. As shown in <FIG>, it was confirmed that after exposure of UV-C light, the strength and the elongation are smaller than before exposure, and that the sample B2 deteriorates (alters) with the exposure of UV-C light. In addition, discoloration of the sample B2 (white) composed of silicone rubber due to exposure to UV-C light was not visually confirmed. On the other hand, compared with the graph in <FIG>, it is found that silicone rubber is more affected by UV-C light than PVC.

The sample B2 includes TiO<NUM> fine particles as the second fine particles that absorb UV-C light, but at a low level (Ti concentration in the sheath <NUM> is <NUM> mass%). It is therefore thought that the resistance to UV-C light had little effect. In addition, since the sample B2 does not have a coating film corresponding to the second layer <NUM>, it is inferior in sliding property to the samples B3 and B4.

<FIG> shows the results of the tensile test of the sample B3. In <FIG>, "unexposed" shows the sample B3 before being exposed to UV-C light, and "after" shows the sample B3 after being exposed to UV-C light irradiation for <NUM> hours. As shown in <FIG>, it was confirmed that after exposure of UV-C light, the strength and the elongation are smaller than before exposure, and that the sample B3 deteriorates with the exposure of UV-C light. In addition, discoloration of the sample B3 (white) due to exposure to UV-C light was not visually confirmed similarly to the sample B2.

According to <FIG>, cracks have occurred in the coating film <NUM> corresponding to the second layer <NUM> around the elongation of more than <NUM>%. The coating film <NUM> of the sample B3 includes silicone resin fine particles as the first fine particle <NUM>, which are resistant to UV-C light. It is therefore thought that the silicone rubber in the region where the silicone resin fine particles are not present deteriorated so that the clacks occurred.

<FIG> shows the results of the tensile test of the sample B4. In <FIG>, "unexposed" shows the sample B4 before being exposed to UV-C light, and "after" shows the sample B4 after being exposed to UV-C light irradiation for <NUM> hours. As shown in <FIG>, it was confirmed that after exposure of UV-C light, the strength and the elongation are substantially the same before and after exposure, and that deterioration of the sample B4 due to the exposure of UV-C light was effectively suppressed. In addition, discoloration of the sample B4 (white) due to exposure to UV-C light was not visually confirmed similarly to the sample B2.

When comparing the test results of the sample B4 with the test results of the sample B3, it is found that titanium oxide fine particles, which are the second fine particles in the coating film corresponding to the second layer <NUM>, have shielded UV-C light and suppressed the degradation.

<FIG> shows the relationship between the irradiation time of UV-C light and the stress at break of the substrate for the samples B1 to B4. <FIG> shows the relationship between the irradiation time of UV-C light and the elongation at break of the substrate for the samples B1 to B4.

According to <FIG>, the sample B3, which does not include titanium oxide fine particles as second fine particles in the coating film corresponding to the second layer <NUM>, has decreased in strength and elongation with increased irradiation time of UV-C light. On the other hand, the sample B4 including titanium oxide fine particles as the second fine particles in the coating film corresponding to the second layer <NUM> has no change in strength and elongation, even if the irradiation time of UV-C light increases. In addition, the sample B4 has a lower elongation before exposure of UV-C light than the sample B1, but the elongation after <NUM> hours of exposure of UV-C light is superior to the sample B1. These results also show that titanium oxide fine particles in the coating film of the sample B4 can suppress the progression of degradation caused by UV-C light.

Raman mapping analysis was performed to determine the distribution of the second fine particles <NUM> in the second layer <NUM> of the laminate structure <NUM>. In the Raman mapping analysis, Raman scattering measurements are performed while scanning the laser on the surface of the sample, and the information obtained from Raman scattering spectrum at each measurement point is mapped in two dimensions. The Raman mapping analysis was performed using the samples prior to UV-C light exposure.

Tables <NUM> and <NUM> below show the measurement and mapping conditions for the Raman scattering measurements, respectively. The Raman scattering measurements were performed using the RAMANforce Standard VIS-NIR-HS made by Nanophoton Corporation. The Raman scattering measurements were conducted at an ambient temperature of <NUM> to <NUM>, an ambient humidity of <NUM> to <NUM>% under atmospheric pressure.

The mapping analysis for this example was performed on the surface of sheet-like silicone rubber layers (samples E1 to E4) as four types of the second layer <NUM>. All samples E1 to E4 includes silicone rubber as the base material <NUM>, silicone resin fine particles with an average particle size of approximately <NUM> as the first fine particles <NUM>, titanium oxide fine particles, mainly including anatase-type TiO<NUM> fine particles with an average particle size of approximately <NUM> as the second fine particles <NUM>. The content of the silicone resin fine particles in each of the samples E1 to E4 is <NUM> mass%. The content of silicone resin fine particles in each of the samples E1 to E4 was calculated based on the assumption that silicone rubber coating agent cures with little or no mass reduction (approximately equivalent to the compound mass ratio). Specifically, the mass of silicone resin fine particles is divided by the total mass of silicone resin fine particles, titanium oxide fine particles and silicone rubber.

Table <NUM> below shows the silicone resin fine particles as the first fine particles <NUM> and the silicone resin concentration in each sample, and the average particle size of titanium oxide fine particles as the second fine particles <NUM> and the Ti concentration in each sample, in the samples E1 to E4. The Ti concentration in Table <NUM> was determined by the SEM-EDS (the average value in the measuring area of <NUM> wide by <NUM> high). The sample E1 is equivalent to the sample A4 (B4).

The samples E1 to E4 differ in the amount of titanium oxide fine particles as the second fine particles <NUM>. The Ti concentrations (as measured by SEM-EDS) of the samples E1, E2, E3, and E4 are <NUM>. <NUM> mass%, <NUM> mass%, <NUM>. <NUM> mass%, and <NUM> mass%, respectively.

<FIG> shows an example of the Raman scattering spectrum collected at a point in the sample E1. The peak at approximately <NUM>-<NUM> (e.g., <NUM> +/- <NUM>-<NUM>) (Hereinafter referred to as "the first peak") in the Raman scattering spectrum is a particularly strong peak in the scattering spectrum of titanium oxide fine particles (mainly including anatase-type TiO<NUM> fine particles), mainly derived from lattice vibration Eg of the anatase-type TiO<NUM>. The peak at <NUM> +/- <NUM>-<NUM> (Hereinafter referred to as "the second peak") is a particularly strong peak in the scattering spectrum of the silicone resin, which is derived from the CH stretch of the silicone resin. In the Raman mapping analysis for this example, the intensities of these first and second peaks were used to map the distribution of titanium oxide fine particles and silicone resin fine particles. If titanium oxide fine particles mainly include rutile type TiO<NUM> fine particles, it is preferable to use a peak at approximately <NUM>-<NUM> (e.g., <NUM> +/- <NUM>-<NUM>) derived from lattice vibration Eg as the first peak. Also, if titanium oxide fine particles mainly include brookite-type TiO<NUM> fine particles, it is preferable to use a peak at approximately <NUM>-<NUM> (e.g., <NUM> +/- <NUM>-<NUM>) as the first peak.

<FIG>, <FIG>, <FIG>, and <FIG> are respectively mapping images of the samples E1, E2, E3 and E4 obtained from the mapping analysis. The size of each mapping image (the mapping area) is <NUM>. <NUM> x <NUM>.

The mapping analysis was performed using the analysis software Raman Viewer Ver. <NUM> made by Nanophoton Corporation. The tint in the area representing the titanium oxide fine particles in <FIG>, <FIG>, <FIG>, and <FIG> was set within the range of intensity of <NUM> to <NUM> in such a manner that the tint should be darker as the intensity of the first peak increases. Further, the tint was set in such a manner that the titanium oxide fine particles should be present for the values within the range of <NUM> to <NUM>. In addition, the tint in the area representing the silicone resin fine particles was set within the range of intensity of <NUM> to <NUM> in such a manner that the tint should be darker as the intensity of the second peak increases. Further, the tint was set in such a manner that the silicone resin fine particles should be present for the values within the range of <NUM> to <NUM>. An area where neither Raman peak showing silicone resin fine particles nor Raman peak showing titanium oxide fine particles are observed, i.e., area of the silicone rubber as the base material <NUM> is observed with a different color from those areas.

According to <FIG>, <FIG>, <FIG>, and <FIG>, the titanium oxide fine particles are polarized around the silicone resin fine particle. It can be seen that the area without silicone resin fine particles (the area located between the silicone resin fine particles) is effectively filled. This is because the average particle size of the titanium oxide fine particles is smaller than the average particle size of the silicone resin fine particles (for example, <NUM>/<NUM> or less, preferably <NUM>/<NUM> or less). In addition, as the amount of titanium oxide fine particles increases, the proportion of the area occupied by titanium oxide fine particles in areas where silicone resin fine particles are not present increases, and when the Ti concentration is <NUM> mass% or more, almost all areas in the area where silicone resin fine particles are not present (areas that are less resistant to UV-C light) are occupied by titanium oxide fine particles.

Namely, the second layer <NUM> includes a region where the intensity of the first peak in the area where silicone resin fine particles are present (a circular white region: Region A in <FIG>, <FIG>, <FIG> and <FIG>) is less than the intensity of the first peak in the area where silicone resin fine particles are not present (a region located between the silicone resin fine particles: Region B), since titanium oxide fine particles are present predominantly in the area where silicone resin fine particles are not present. In this way, in the second layer <NUM>, titanium oxide fine particles are not evenly distributed, and titanium oxide fine particles are polarized around a silicone resin fine particle.

<FIG>, <FIG>, <FIG>, and <FIG>, respectively, show bivaluated analysis images of the mapping images in <FIG>, <FIG>, <FIG>, and <FIG>.

This bivaluated analysis was performed by the "area ratio analysis" function of the above analysis software, Raman Viewer Ver. In this bivalation analysis, an integral intensity of an integral range of <NUM>-<NUM> at the first peak was applied to calculation as a first peak intensity, and an integral intensity of an integral range of <NUM>-<NUM> at the second peak was applied to the calculation as a second peak intensity. In the Raman Viewer Ver. <NUM>, the intensity calculation method for the bivaluated analysis is called "area calculation".

According to the bivaluated analysis images shown in <FIG>, <FIG>, <FIG>, and <FIG>, a ratio of the area of titanium oxide fine particles to the area other than titanium oxide fine particles (i.e., total area of silicone resin fine particles and silicone rubber) is <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, and <NUM>:<NUM>, respectively.

Based on the above results, it is found that when the ratio of the area of titanium oxide fine particles to the total area of titanium oxide fine particles and silicone resin fine particles in the bivaluated analysis image conducted under the above conditions is <NUM>% or more, almost all areas in the area where silicone resin fine particles are not present are occupied by titanium oxide fine particles, and that the second layer <NUM> has excellent resistance to UV-C light. The conditions for this second layer <NUM> to have excellent resistance to UV-C light would be satisfied even if the silicone resin fine particle as the first fine particle <NUM> is changed to another fine particle such as silica fine particle, or if the titanium oxide fine particle as the second fine particle <NUM> is changed to another fine particle such as carbon particle. In order to reduce the static friction coefficient, it is necessary to have an area where some silicone resin fine particles are present. Therefore, it is preferable that the upper limit of the area of titanium oxide fine particles in the bivaluated analysis image is not less than <NUM>% relative to the total area of titanium oxide fine particles and silicone resin fine particles.

Eleven samples (samples C1 to C11) were prepared to verify the resistance of the laminate structure <NUM> to UV-C light. All the samples C1 to C11 have the first layer <NUM> and the second layer <NUM>, and the first layer <NUM> includes TiO<NUM> fine particles <NUM>. Of the samples C1 to C11, the samples C1, C6, and C9 do not include TiO<NUM> fine particles <NUM> in the second layer <NUM> and were prepared using processes and materials similar to the sample A3 in Example <NUM>. Also, the samples C2 to C5, C7, C8, C10, C11 include TiO<NUM> fine particles <NUM> in the second layer <NUM> (Ti concentration is within range from <NUM> mass % to <NUM> mass%) and were prepared using processes and materials similar to the sample A4 in Example <NUM>. Table <NUM> below shows the composition of the sheath <NUM> and the coating film <NUM> of the samples C1 to C11. The thickness of the first layer <NUM> (sheath <NUM>) was <NUM>, and the thickness of the second layer <NUM> (coating film <NUM>) was <NUM>.

In order to verify the resistance of the laminate structure <NUM> to UV-C light from the viewpoint of the strength to bending, a bending test equivalent to <NUM>% to <NUM>% tensile for the samples C1 to C11 after exposure to UV-C light was conducted. UV-C light irradiation was performed by a storage chamber with sterilization lamps (Storage chamber DM-<NUM>, lamps GL-<NUM>, available from Daishin Kogyo Co. ) at chamber temperature of <NUM> to <NUM>, chamber humidity of <NUM>% to <NUM>%, chamber pressure of <NUM> atm (atmospheric pressure), wavelength <NUM>, illuminance of <NUM> mW/cm<NUM>, and irradiation times of <NUM>, <NUM>, <NUM>, and <NUM> hours. The illuminance meter was UVC-254A made by MK Scientific Inc. The bending test was also performed on the samples C1 to C11 at an ambient temperature of <NUM> to <NUM> and an ambient humidity of <NUM> to <NUM>% under atmospheric pressure.

<FIG> shows a schematic diagram of the bending test. A sheath piece <NUM> was a part of the sheath <NUM> covered with the coating film <NUM>, cut from each of the samples C1 to C11. In the bending test, a rectangular sheath piece <NUM> is cut from each of the samples C1 to C11 and wrapped around a lead wire (metal wire) <NUM> having a radius of <NUM>, then overlapping portions of the sheath piece <NUM> are fixed by pinching them from both sides (a fixing jig is not shown). Here, cable-shape samples C1 to C11 of a length of <NUM> were prepared and cut evenly along the cable length from ten locations to provide each piece with a size of <NUM> (in a cable circumferential direction) x <NUM> (in a cable longitudinal direction). The sheath piece <NUM> was wrapped around the lead wire <NUM> in such a manner that a cable longitudinal side would be located along a circumferential direction of the lead wire <NUM> and the second layer <NUM> would be located on an outer periphery side.

<FIG> shows a cross-sectional view of the lead wire <NUM> and the sheath piece <NUM> wrapped around the lead wire <NUM>. If the radius of the lead wire <NUM> is r and the thickness of sheath piece <NUM> is t, a longitudinal length of the sheath piece <NUM> at a neutral surface 50a at any angle θ is (r+ t/<NUM>)•θ, and a longitudinal length of an outer surface 50b of the sheath piece <NUM> is (r+t)•θ, as shown in <FIG>. Therefore, a longitudinal elongation rate of the outer surface 50b of the sheath piece <NUM> wrapped around the lead wire <NUM> is expressed as {(r+t)•θ-(r+t12)•θ}/((r+t/<NUM>)•θ)x100 = t/(2r+t)x100, and the radius r of the lead wire <NUM> is <NUM> and the thickness t of the sheath piece <NUM> is <NUM>, so that the longitudinal elongation rate is approximately <NUM>%.

The bending test was performed on the sheath pieces <NUM> cut from the samples C1 to C11. The surface of the sheath piece <NUM> during the bending test (the second layer <NUM> was affected by an elongation equivalent to <NUM>% to <NUM>%) was observed with a 50X magnification ratio using an optical microscope (Digital Microscope VHX-<NUM> made by Keyence Corporation). As a result, for the sheath pieces <NUM> of the samples C1, C6, and C9 that did not include TiO<NUM> fine particles in the second layer <NUM>, no cracks occurred on the surface of the sample when being exposed to UV-C light at irradiation energy (intensity (W/cm<NUM>) x irradiation time (seconds)) of <NUM> J/cm<NUM>, but cracks occurred on the surface of the sample when being exposed to UV-C light at irradiation energy of <NUM> J/cm2, <NUM> J/cm2, and <NUM> J/cm2.

On the other hand, for the sheath pieces <NUM> cut from the samples C2 to C5, C7, C8, C10, and C11 including TiO<NUM> fine particles in the second layer <NUM>, no cracks occurred on the surface of the sample being exposed to UV-C light at irradiation energy of <NUM> J/cm<NUM>, <NUM> J/cm<NUM>, <NUM> J/cm<NUM>, and <NUM> J/cm<NUM>. In this bending test, the term "crack" refers to a recess that reaches from the second layer <NUM> (coating film <NUM>) of the first layer <NUM> (sheath <NUM>).

<FIG> show SEM observation images of a surface and a cross section of the sheath piece <NUM> cut from the sample C6 exposed to UV-C light at irradiation energy of <NUM> J/cm<NUM>. <FIG> show SEM observation images of the surface and a cross section of the sheath piece <NUM> cut from the sample C7 exposed to UV-C light with irradiation energy of <NUM> J/cm<NUM>. In the SEM observation images in <FIG>, cracks <NUM> that reach the second layer <NUM> to the first layer <NUM> were observed. On the other hand, the recess <NUM> observed in the SEM observation images in <FIG> did not reach the first layer <NUM> and was not counted as a crack. <FIG> and <FIG> are 100X SEM observation images, and <FIG> and <FIG> are 1000X SEM observation images. They are the SEM observation image of the sheath piece <NUM> which was removed from the lead wire <NUM> after the bending test.

In addition, the results of this bending test were used as one of the criteria for determining whether the laminate structure <NUM> is resistant to UV-C light. The sheath pieces <NUM> were taken from ten locations of each sample exposed to UV-C light. The bending test was conducted on each of ten sheath pieces <NUM>, the number of sheath pieces <NUM> on which the cracks were observed was counted when observing the area of <NUM> x <NUM> using an optical microscope to obtain a 50X magnification ratio. When the areas of <NUM> x <NUM> at ten locations of the sample were observed and the number of the areas of <NUM> x <NUM> in which the cracks were observed is <NUM> or less, the laminate structure <NUM> was determined to be resistant to UV-C light.

<FIG> shows a representative observation image of the surface of the sheath piece <NUM> when the bending test was performed on the sheath pieces <NUM> cut from the samples C1 to C11. The observation image in <FIG> is an image of an area of <NUM> x <NUM> on the surface of the sheath piece <NUM> prepared from the samples C1 to C1 <NUM>, which was observed with a 50X magnification using an optical microscope (Digital Microscope VHX-<NUM> made by Keyence Corporation). According to <FIG>, cracks are observed on the surface of each of the sheath pieces <NUM> of the samples C1, C6, and C9 that do not include TiO<NUM> fine particles in the second layer <NUM>, after being exposed to UV-C light at irradiation energy (intensity (W/cm<NUM>) x irradiation time (seconds)) of <NUM> J/cm<NUM>, <NUM> J/cm<NUM>, and <NUM> J/cm<NUM>. For the sheath pieces <NUM> cut from the samples C2 to C5, C7, C8, C10, and C11 including TiO<NUM> fine particles in the second layer <NUM>, no cracks occurred on any surface of the samples exposed to UV-C light with irradiation energy of <NUM> J/cm<NUM>, <NUM> J/cm<NUM>, <NUM> J/cm<NUM>, and <NUM> J/cm<NUM>.

For example, a thread-like pattern along the sample longitudinal direction was observed in the samples C10 and C11 after irradiation at <NUM> J/cm<NUM>. This pattern is a recess that did not reach the sheath <NUM> and appeared only in the coating film <NUM>. In other words, the thickness of the coating film <NUM> is greater than the depth of the recess. Such a recess is not counted as a crack, as described above, because it does not serve as the starting point for the breaking of the sheath <NUM>. It is also possible to determine whether the thread-like pattern is a crack or not by observing whether this pattern has reached the sheath <NUM> or not from the cross-sectional SEM observation images shown in <FIG> and <FIG>.

From the results in <FIG>, for the samples C2 to C5, C7, C8, C10, and C11, the number of the areas of <NUM> x <NUM> in which the cracks were observed is <NUM> or less among <NUM> locations (specifically, <NUM> (no cracks)), and these samples were found to be resistant to UV-C light. In addition, for the samples C1, C6, and C9, the number of the areas of <NUM> x <NUM> in which the cracks were observed is <NUM> or more among <NUM> locations, and these samples were found to not be resistant to UV-C light. Thus, it was found that increasing the content of the TiO<NUM> fine particles in the second layer <NUM> is effective in suppressing cracks in the laminate structure <NUM>. Specifically, it was confirmed that cracking of the laminate structure <NUM> could be suppressed by setting the Ti concentration in the second layer <NUM> to <NUM> mass% or more.

Next, to verify the resistance of the laminate structure <NUM> to UV-C light from the degree of elongation at break, a tensile test was performed on the samples C1 to C5 and C7 to C11 after UV-C light exposure. UV-C light irradiation was performed by a storage chamber with sterilization lamps (Storage chamber DM-<NUM>, lamps GL-<NUM>, available from Daishin Kogyo Co. ) at chamber temperature of <NUM> to <NUM>, chamber humidity of <NUM>% to <NUM>%, chamber pressure of <NUM> atm (atmospheric pressure), wavelength <NUM>, illuminance of <NUM> mW/cm<NUM>, and irradiation times of <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> hours.

After being exposed to UV-C light, dumbbell test pieces D1 to D5 and D7 to D11 were respectively prepared from the cable-like samples C1 to C5 and C7 to C11, in a similar way to the method used to prepare the samples B1 to B4 from the samples A1 to A4 in Example <NUM>. The tensile test for the samples D1 to D5 and D7 to D11 (Dumbbell test piece No. <NUM>) was performed in the same way and conditions as the test prescribed in "JIS K6251 (<NUM>)" for the samples B1 to B4. At the tensile test evaluation site, an ambient temperature was <NUM> +/- <NUM>, an ambient humidity was <NUM> +/- <NUM>%, and a pressure was atmospheric pressure. The distance between the marks was <NUM> and the tensile speed was <NUM>/min, leading to a break.

<FIG> are graphs showing the relationship between an irradiation energy (intensity (W/cm<NUM>) x irradiation time (seconds)) of UV-C light and the degree of elongation at break for the samples D1, D3, D4, and D7, respectively. <FIG> are graphs showing the relationship between an irradiation energy of UV-C light and the degree of elongation at break for the samples D8, D9, D10, and D11, respectively. Table <NUM> below shows the numerical values of the plotting points in <FIG>, <FIG>, i.e., the elongation at break (%) for each irradiation energy of UV-C light in each sample.

According to <FIG>, <FIG>, and Table <NUM>, the elongation at break of the samples D7 to D11 of the elongation at break of the samples D1, D3, D4 and D7 to D11 is <NUM>% or more, even when the elongation at break of the samples D7 to D11 is <NUM> J/cm<NUM>, and it is confirmed that the samples D7 to D11 have high resistance to UV-C light from the viewpoint of the elongation at break. Also, the elongation at break of the samples D7 to D <NUM><NUM> of the elongation at break of the samples D1, D3, D4 and D7 to D11 is <NUM>% or more, even when the elongation at break of the samples D7 to D11 is <NUM> J/cm<NUM>, and it is confirmed that the samples D7 to D11 have high resistance to UV-C light from the viewpoint of the elongation at break. Further, the elongation at break of the samples D7 to D <NUM><NUM> of the elongation at break of the samples D1, D3, D4 and D7 to D11 is <NUM>% or more, even when the elongation at break of the samples D7 to D11 is <NUM> J/cm<NUM>, and it is confirmed that the samples D7 to D11 have high resistance to UV-C light from the viewpoint of the elongation at break.

It is found from the results shown in <FIG>, <FIG> and Table <NUM> that it is effective to increase the amount of TiO<NUM> fine particles in the first layer <NUM> in order to increase the elongation at break of the laminate structure <NUM>. Also, as shown in <FIG>, the relationship between Ti concentration (content of TiO<NUM> fine particles) in the first layer <NUM> and the elongation at break (result of D3, D7, D10, D4, D8, and D11) is plotted, and polynomial approximations were performed. <FIG> shows the result after exposure to UV-C light at <NUM> J/cm<NUM>. <FIG> shows the result after exposure to UV-C light at <NUM> J/cm<NUM>. It is found that the Ti concentration in the first layer <NUM> should be <NUM> mass% or more to ensure that the elongation at break is at least <NUM>% even after being exposed to UV-C light of <NUM> J/cm<NUM>. In addition, it is found that the Ti concentration in the first layer <NUM> should be <NUM> mass% or more to ensure that the elongation at break is at least <NUM>% even after being exposed to UV-C light of <NUM> J/cm<NUM>.

Next, a surface wipe test was performed on a sample C11 including a TiO<NUM> fine particles <NUM> at a concentration of <NUM> mass% in the second layer <NUM> as the coating film <NUM> and a sample including TiO<NUM> fine particles <NUM> at a concentration of <NUM> mass% in the second layer <NUM> (sample C12) which was prepared similarly to the sample C11. This sample preparation and testing for the wipe test were carried out in the same way as <CIT>. Preparation of samples for measuring the static friction coefficient before and after the wipe test and measurement were performed using the same method as for <CIT>. The ambient temperature was <NUM> +/- <NUM>, the ambient humidity was <NUM> +/- <NUM>%, and the pressure was atmospheric pressure at the wiping test site and the static friction coefficient measurement site.

In this wipe test, a long fiber non-woven fabric (with a length of <NUM> in a wipe direction) including cotton linters including disinfectant alcohol was brought contiguous to the surface of the coating film <NUM> at a shearing stress of 2x10-<NUM> MPa to 4x10-<NUM> MPa, and the surface of the layer was repeatedly wiped off for approximately <NUM> length in the wipe direction at a speed between <NUM> times/min to <NUM> times/min <NUM>,<NUM> times (for <NUM>,<NUM> reciprocations). As a result, a difference (in absolute values) between the static friction coefficients of the coating film <NUM> of the samples C1 <NUM> and C12 before and after the testing was <NUM> and <NUM>, i.e., both values are not greater than <NUM>. Table <NUM> below shows the values of the static friction coefficients of the coating film <NUM> of the measured samples C11, C12.

On the other hand, the surface condition of the samples C11 and C12 before and after the wipe test was observed by SEM, and there was a difference between the two samples.

<FIG> show 1000X images of the surface before the wipe test of the samples C11 and C12, respectively. <FIG> show the surface observations after the wipe test of the samples C11 and C12, respectively. Spherical particles and white powder particles around the spherical particle observed in the observation images in <FIG>, <FIG> are the fine particles <NUM> and TiO<NUM> fine particles <NUM>, respectively.

As shown in <FIG>, the voids were more observed in the coating film <NUM> of the sample C12 than in the coating film <NUM> of the sample C11. Also, as shown in <FIG>, the drop of fine particles <NUM> in the coating film of the sample C12 was more than that in the coating film <NUM> of the sample C11. One of the major causes of these results is assumed that the concentration of TiO<NUM> fine particles <NUM> in the coating film <NUM> (second layer <NUM>) of the sample C12 was too high. The presence of more TiO<NUM> fine particles <NUM> around the fine particle <NUM> has resulted in a smaller contact area between the base material <NUM> composed of the silicone rubber and the fine particle <NUM>. This may have resulted in reduced adhesion. Based on the results of the wipe test and SEM observation, it is confirmed that the upper limit of Ti concentration in the coating film <NUM> is <NUM> mass%.

Claim 1:
A laminate structure comprising:
a first layer as a substrate; and
a second layer being provided on the first layer and comprising a rubber composition including a rubber component, first fine particles for providing a surface with irregularity, and second fine particles for shielding UV-C light,
wherein an average particle size of the second fine particles is smaller than an average particle size of the first fine particles,
wherein the average particle size of the first fine particles is <NUM> or more and <NUM> or less,
wherein the average particle size of the second fine particles is <NUM> or more and <NUM> or less,
wherein when performing Raman mapping analysis on a first peak derived from oscillation of the second fine particles in Raman scattering spectrum obtained by Raman scattering measurement of the second layer, the second layer includes a region where an intensity of the first peak is greater in an area where the first fine particles are not present than an area where the first fine particles are present, wherein
wherein the first layer comprises TiO<NUM> fine particles and said second fine particles of said second layer comprise TiO<NUM> fine particles,
wherein a Ti concentration of the first layer is <NUM> mass% or more and <NUM> mass% or less, and wherein a Ti concentration of the second layer is <NUM> mass% or more and <NUM> mass% or less,
wherein a Ti concentration of the second layer is higher than the Ti concentration of the first layer, and wherein
the the average size of the first and second particles and the Ti concentrations of the first and second layers are measured using the methods as described in the description.