Silicone coating film, laminated structure, and method for manufacturing a laminated structure

Abstract

The present invention provides a silicone coating film that maintains high transparency in the visible light region while ensuring resistance to ultraviolet light, a laminated structure having the silicone coating film, and a method for manufacturing the laminated structure. [Solution] The second layer 11, which is provided as a coating film on the surface of an object that is irradiated with ultraviolet light, has a silicone rubber base material 111 and contains titanium dioxide fine particles 113 with an average particle size of less than 100 nm. The laminated structure 1 has a first layer 10 having a silicone rubber base material 101, and a second layer 11 having a silicone rubber base material 111 laminated on top of the second layer 11 having a silicone rubber base material 111, and the second layer 11 contains titanium dioxide fine particles 113 with an average particle size of less than 100 nm.

Description

Technical Field

[0001] The present invention relates to a silicone coating film based on silicone rubber, and particularly to a silicone coating film provided as a surface layer of an irradiated object sterilized by ultraviolet irradiation, a laminated structure having the silicone coating film, and a method for manufacturing the laminated structure.

Background Art

[0002] Conventionally, for example, medical instruments such as medical ultrasonic probes are sterilized by ultraviolet irradiation before or after use for infection prevention. The applicant has proposed a laminated structure described in Patent Document 1 as a sheath covering a plurality of electric wires and a shield, and a coating film covering the surface of the sheath in the probe cable of the ultrasonic probe.

[0003] The laminated structure described in Patent Document 1 has a two-layer structure including a first layer and a second layer based on silicone rubber. In the first layer, compounding agents such as various crosslinking agents, crosslinking catalysts, antioxidants, plasticizers, lubricants, fillers, flame retardants, stabilizers, and colorants are added. The second layer contains silicone resin fine particles, titanium oxide fine particles, and nanosilica fine particles.

[0004] In the second layer, the silicone resin fine particles are used to impart unevenness to the surface of the second layer to enhance slipperiness, and the titanium oxide fine particles are used to absorb and / or scatter ultraviolet light to shield it and enhance the resistance to ultraviolet light. The nanosilica fine particles are used to uniformly disperse the titanium oxide fine particles in the second layer. In Patent Document 1, the average particle size of the silicone resin fine particles is 1 μm to 10 μm, the average particle size of the titanium oxide fine particles is 100 nm to 300 nm or less, and the average particle size of the nanosilica fine particles is 10 to 30 nm.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2024-51299 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] By the way, in the laminated structure described in Patent Document 1 mentioned above, there are cases where, for example, it is desirable to make the appearance of the first layer chromatic in order to consider aesthetics, but the following problems existed.

[0007] Specifically, regarding the various microparticles (silicone resin microparticles, titanium dioxide microparticles, and nanosilica microparticles) added to the second layer, which is a silicone coating film, in order to increase resistance to ultraviolet light, there was a problem in that, among these microparticles, titanium dioxide microparticles are white, so even if the first layer is made colored, the appearance when viewed through the second layer appears cloudy, which reduces the aesthetic appeal. The desired aesthetic appeal is transparency in the visible light region.

[0008] One possible solution to the aforementioned problems is to reduce the amount of titanium dioxide nanoparticles added to the second layer; however, in that case, it may become impossible to ensure resistance to ultraviolet light.

[0009] Therefore, the present invention aims to provide a silicone coating film that is transparent in the visible light region while ensuring resistance to ultraviolet light, a laminated structure having the silicone coating film, and a method for manufacturing the laminated structure. [Means for solving the problem]

[0010] The present invention aims to solve the above problems by providing a silicone coating film that is provided as a surface layer of an object that is irradiated with ultraviolet light, and which has a silicone rubber base material and contains titanium oxide fine particles with an average particle size of less than 100 nm.

[0011] Furthermore, the present invention aims to solve the above problems by providing a laminated structure in which a second layer is laminated on a first layer made of silicone rubber as a base material, wherein the second layer is the above-mentioned silicone coating film.

[0012] Furthermore, the present invention aims to solve the above problems and provides a method for manufacturing a laminated structure in which a second layer, which is made of silicone rubber and contains titanium dioxide fine particles with an average particle size of less than 100 nm, is laminated on a first layer made of silicone rubber, comprising: a preparation step of preparing a liquid mixture of a silicone rubber component, which is a component of the silicone rubber that will be the base material of the second layer, and an organic solvent; a first dispersion step of adding a silicone-based surfactant to the liquid mixture and dispersing the added silicone-based surfactant; a second dispersion step of further adding the titanium dioxide fine particles to the liquid mixture after the first dispersion step and dispersing the added titanium dioxide fine particles; a raw material attachment step of making the liquid mixture a liquid resin composition that will be the raw material for the second layer and attaching the liquid resin composition to the surface of the first layer; and a layer formation step of forming the second layer by vaporizing the organic solvent contained in the liquid resin composition attached to the surface of the first layer and curing the silicone rubber component. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a silicone coating film that is transparent in the visible light region while ensuring resistance to ultraviolet light, a laminated structure having the silicone coating film, and a method for manufacturing the laminated structure. [Brief explanation of the drawing]

[0014] [Figure 1] This is a vertical cross-sectional view of a laminated structure according to an embodiment of the present invention. [Figure 2] (a) is a plan view showing a printed medium with printed characters. (b) and (c) are plan views showing a sample with a silicone coating film formed on the surface of quartz glass. [Figure 3] This graph shows an example of the relationship between the average particle size of titanium dioxide nanoparticles dispersed in the base material and the light transmittance at each wavelength. [Figure 4] This graph shows an example of the relationship between the average particle size of titanium dioxide nanoparticles dispersed in the base material, the presence or absence of a surfactant, and the transmittance. [Figure 5] (a) is a diagram showing an example of an application configuration in which the laminated structure according to this embodiment is applied to the probe cable of a medical ultrasound probe. (b) is a cross-sectional view of (a) along line AA. [Modes for carrying out the invention]

[0015] [Embodiment] (Structure of the laminated structure) Figure 1 is a schematic diagram illustrating a vertical cross-section of a laminated structure 1 according to an embodiment of the present invention. This laminated structure 1 is a two-layer structure comprising a first layer 10 made of silicone rubber as a base material 101 and a second layer 11 laminated on the first layer 10. The second layer 11 is made of silicone rubber as a base material 111 and contains silicone resin fine particles 112, titanium oxide (TiO2) fine particles 113, and nanosilica fine particles 114. The second layer 11 is transparent in the visible light region, and the color or text of the first layer 10 can be seen through the second layer 11.

[0016] The laminated structure 1 is provided on an object that is subjected to ultraviolet irradiation. The second layer 11 is a coating film provided as the surface layer of the object that is subjected to ultraviolet irradiation, and corresponds to the silicone coating film of the present invention. The second layer 11 is directly subjected to ultraviolet irradiation. In other words, the second layer 11 is a coating film that constitutes the surface layer of the laminated structure 1 that is subjected to ultraviolet irradiation. Here, ultraviolet light in ultraviolet irradiation refers to near-ultraviolet light, including UV-A with a wavelength of 315 to 380 nm, UV-B with a wavelength of 280 to 315 nm, and UV-C with a wavelength of 200 to 280 nm.

[0017] The silicone rubbers, which are the base materials 101 and 111 of the first layer 10 and the second layer 11, are a type of silicone resin. The silicone rubber has higher resistance to ultraviolet rays compared to polyvinyl chloride, which is commonly and widely used as a material for medical cables and tubes.

[0018] The laminated structure 1 can take various forms according to its use. For example, when applied to the insulators of cables and tubes, the laminated structure 1 is formed into a tubular shape. Also, when applied to sheets for greenhouse rooms or sheets for sterilization rooms, etc., the laminated structure 1 is formed into a sheet shape. When the laminated structure 1 is applied to a sheet for a greenhouse room, it can block ultraviolet rays received from the outside and suppress the intrusion of ultraviolet rays into the greenhouse room. When the laminated structure 1 is applied to a sheet for a sterilization room, it can suppress the leakage of ultraviolet rays for sterilization from the sterilization room to the outside.

[0019] (Configuration of the second layer) The second layer 11 is a coating film that covers the surface of the first layer 10, and its raw material is a liquid resin composition (silicone rubber coating agent) containing silicone rubber as the base material 111, silicone resin fine particles 112, titanium oxide fine particles 113, and nanosilica fine particles 114. As the silicone rubber, which is 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 viewpoints of adhesion to the first layer 10 and wiping resistance, it is preferable to use an addition reaction type silicone rubber coating agent.

[0020] Here, the "wiping resistance" in this specification means, as described in paragraphs

[0108] to

[0112] of JP-A-2021-45525, 2×10 -3 MPa to 4×10 -3This refers to the characteristic where, after 20,000 repetitions of a test in which a long-fiber nonwoven fabric (50 mm in length in the wiping direction) using a cotton linter containing disinfectant alcohol to exert a shear stress of MPa, is brought into contact with the second layer 11 and the surface of the second layer 11 is wiped over a length of 150 mm in the wiping direction at a speed of 80 to 120 times / minute, the difference (absolute value) of the static friction coefficient of the second layer 11 before and after the test is 0.1 or less. Shear stress refers to the pull-out force (resistance force during pull-out) that occurs when a cable is held down with a cotton cloth impregnated with disinfectant ethanol and the cable is pulled out from the cotton cloth.

[0021] Furthermore, in order to obtain good slipperiness and wipe resistance on the surface of the laminated structure 1, the thickness T2 of the second layer 11 is preferably 3 μm or more. There is no particular upper limit to the thickness of the second layer 11, but from the viewpoint of productivity, high flexibility, and high bendability, it is preferably 100 μm or less. In addition, the second layer 11 may be laminated on both sides of the first layer 10.

[0022] The silicone resin fine particles 112 are included in the second layer 11 in order to create irregularities on the surface 11a of the second layer 11. When the surface 11a has irregularities, the contact area when the second layer 11 comes into contact with an object becomes smaller compared to when the surface 11a is flat, and the slipperiness increases.

[0023] Silicone resin has fewer reactive groups (e.g., methyl groups) than silicone rubber and is harder than silicone rubber. Therefore, silicone resin fine particles 112 can more effectively suppress deformation of the surface irregularities when the second layer 11 comes into contact with an object than silicone rubber fine particles. 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, the more effectively deformation of the surface irregularities of the second layer 11 can be suppressed. As a result, the increase in the contact area between the second layer 11 and the object can be suppressed, and the slipperiness can be maintained.

[0024] Furthermore, the interatomic bond energy in the molecular structure of silicone resin is higher than that in the molecular structure of silicone rubber. For this reason, silicone resin has higher resistance to UV-C light than silicone rubber. CH bonds, which are abundant in silicone rubber, have a bond energy (approximately 4.27 eV) that is lower than the energy of UV-C light (approximately 6.2 eV), so the bonds break when irradiated with UV-C light. However, Si-O bonds, which are abundant in silicone resin, have a bond energy (approximately 6.52 eV) that is higher than the energy of UV-C light, so the bonds do not break when irradiated with UV-C light. For this reason, silicone resin nanoparticles 112 have superior resistance to UV-C light compared to silicone rubber nanoparticles.

[0025] The average particle size of the silicone resin fine particles 112 is, for example, 1 μm or more and 10 μm or less. In this specification, "average particle size" refers to the average particle size measured by laser diffraction scattering, including that of the titanium oxide fine particles 113 and nanosilica fine particles 114 described later. The concentration of silicone resin fine particles 112 in the second layer 11 is, for example, 10% by mass or more and 60% by mass or less. Here, the concentration of silicone resin fine particles 112 is a value calculated assuming that all of the silicone rubber component of the silicone rubber coating agent (silicone rubber component + organic solvent) has hardened into silicone rubber (a value approximately equivalent to the blending mass ratio), and more specifically, it is expressed as a percentage by dividing the mass of the silicone resin fine particles 112 by the total mass of the silicone resin fine particles 112 and the silicone rubber component in the silicone rubber coating agent. On the other hand, the concentration of nanosilica fine particles 114 is expressed as a percentage by dividing the mass of nanosilica fine particles 114 by the mass of the silicone rubber component in the silicone rubber coating agent. However, similar to the calculation of the concentration of silicone resin fine particles 112, it may also be expressed as a percentage by dividing the mass of nanosilica fine particles 114 by the total mass of nanosilica fine particles 114 and the silicone rubber component in the silicone rubber coating agent. Note that the concentration of nanosilica fine particles 114 in this specification is the value calculated by the former method.

[0026] The titanium dioxide nanoparticles 113 contained in the second layer 11 can shield from ultraviolet light by absorption and / or scattering. By shielding from ultraviolet light, the titanium dioxide nanoparticles 113 can suppress degradation of the first layer 10 and the second layer 11, which have silicone rubber as the base material 101 and 111, due to ultraviolet light. In particular, degradation of the base material 101 and 111 due to UV-C light (ultraviolet light in the range of 200 to 280 nm) can be suppressed. The TiO2 constituting the titanium dioxide nanoparticles 113 may be of the anatase type, rutile type, or brookite type, or a mixture of two or more of these. Furthermore, niobium oxide may be added to the titanium dioxide to improve its stability.

[0027] Regarding the Ti concentration (titanium concentration) of the second layer 11, if the concentration is high, for example, exceeding 4.4 mass%, the surface roughness of the second layer 11 increases due to the effect of titanium oxide. As a result, dirt and bacteria not only adhere more easily, but also become difficult to remove. Furthermore, the adhesion between the silicone rubber base material 111 and the silicone resin microparticles 112 also decreases, making it easier for the silicone resin microparticles 112 to detach from the base material 111. Consequently, the irregularities on the surface 11a of the second layer 11, which were imparted by the silicone resin microparticles 112, disappear, and the slipperiness of the surface of the second layer 11 decreases.

[0028] Furthermore, if the Ti concentration in the second layer 11 is 0.5% by mass or higher, the concentration is 1404 J / cm³. 2 In a bending test of the laminated structure 1 at a tensile strength equivalent to 45-50% after irradiation with UV-C light, the occurrence of cracks that reach the first layer 10 from the surface of the laminated structure 1 can be suppressed. This bending test is performed as described in paragraphs

[0106] to

[0110] of Patent Document 1, by wrapping a test piece with the laminated structure 1 formed on one side around a cylindrical wire such that an elongation equivalent to 45-50% acts on the second layer 11, and observing the outer surface of the wrapped portion of the test piece (the surface of the second layer 11) with an optical microscope.

[0029] Based on the above, it is preferable that the Ti concentration of the second layer 11 is between 0.5% by mass and 4.4% by mass. By having a Ti concentration of 0.5% by mass and 4.4% by mass in the second layer 11, surface roughness of the second layer 11 can be suppressed, the slipperiness of the surface of the second layer 11 can be improved, and the occurrence of cracks in the second layer 11 can be suppressed.

[0030] Furthermore, all of the Ti in the second layer 11 is contained in the titanium oxide nanoparticles 113 as an oxidizable element. The Ti concentration in the second layer 11 was determined as the average value 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), and all of the Ti at this concentration is attributable to the titanium oxide nanoparticles 113.

[0031] The titanium dioxide nanoparticles 113 contained in the second layer 11 should preferably be titanium dioxide nanoparticles that have been subjected to a hydrophobic surface treatment. By using this configuration, the formation of aggregates of titanium dioxide nanoparticles 113 on the surface of the second layer 11 can be suppressed, and the titanium dioxide nanoparticles 113 can be uniformly dispersed inside the second layer 11. Similarly, the nanosilica nanoparticles 114 should also preferably be nanosilica nanoparticles that have been subjected to a hydrophobic surface treatment. By using this configuration, the formation of aggregates of nanosilica nanoparticles 114 on the surface of the second layer 11 can be suppressed, and the titanium dioxide nanoparticles 113 can be uniformly dispersed inside the second layer 11. To add to this, by using nanoparticles that have been subjected to a hydrophobic surface treatment for both the titanium dioxide nanoparticles 113 and the nanosilica nanoparticles 114, not only is the formation of aggregates between the titanium dioxide nanoparticles 113 and the nanosilica nanoparticles 114 suppressed, but the formation of aggregates between the titanium dioxide nanoparticles 113 and the silicone resin nanoparticles 112, and between the nanosilica nanoparticles 114 and the silicone resin nanoparticles 112 is also suppressed.

[0032] The nanosilica particles 114 are included in the liquid resin composition (silicone rubber coating agent), which is the raw material for the second layer 11, and impart thixotropy. At this time, the nanosilica particles 114 form a bulky network structure in the liquid. By configuring it in this way, the settling rate of the silicone resin particles 112 and titanium dioxide particles 113 can be slowed down, that is, settling can be suppressed. The average particle size of the nanosilica particles 114 is smaller than the average particle size of the titanium dioxide particles 113, and is between 10 nm and 30 nm, for example, 15 nm.

[0033] In order to effectively suppress the sedimentation of silicone resin microparticles 112 and titanium dioxide microparticles 113, the concentration of nanosilica microparticles 114 in the second layer 11 is preferably 1.0% by mass or more from the viewpoint of imparting thixotropy. However, if it exceeds 7.0% by mass, the color of the first layer 10 viewed through the second layer 11 becomes cloudy, so it is preferable that it be 7.0% by mass or less. In other words, the concentration of nanosilica microparticles 114 in the second layer 11 is preferably between 1.0% by mass and 7.0% by mass. By configuring the second layer 11 in this way, the sedimentation of silicone resin microparticles 112 and titanium dioxide microparticles 113 can be suppressed while preventing the color of the first layer 10 viewed through the second layer 11 from becoming cloudy, and the silicone resin microparticles 112 and titanium dioxide microparticles 113 can be uniformly dispersed in the liquid resin composition.

[0034] (Structure of the first layer) The first layer 10 may contain titanium dioxide nanoparticles, similar to the second layer 11, in order to suppress degradation caused by ultraviolet light transmitted through the second layer 11. Furthermore, as described above, the first layer 10 uses silicone rubber as the base material 101. However, when the laminated structure 1 is applied to a cable covering multiple wires, and the sheath of the cable is used as the first layer 10 of the laminated structure 1, silicone rubber to which various crosslinking agents, crosslinking catalysts, anti-aging agents, lubricants, plasticizers, fillers, flame retardants, stabilizers, and colorants may be added may be used as the base material 101. Additionally, the first layer 10 may contain an organic ultraviolet absorber instead of titanium dioxide nanoparticles, or it may contain both titanium dioxide nanoparticles and an organic ultraviolet absorber. The thickness T1 of the first layer 10 is set in various ways depending on the application of the object to which the laminated structure 1 is applied (cable, tube, or various sheets).

[0035] (Method of manufacturing a laminated structure) A method for manufacturing a laminated structure 1, in which a second layer 11 having a silicone rubber base material 111 and containing titanium dioxide fine particles 113 with an average particle size of less than 100 nm is laminated onto a first layer 10 having a silicone rubber base material 101, includes a raw material manufacturing step for manufacturing a liquid resin composition which is the raw material for the second layer 11; a raw material attachment step for attaching the liquid resin composition manufactured in the raw material manufacturing step to the surface of the first layer 10; and a layer formation step for forming the second layer 11 by vaporizing (vaporizing by heating) the organic solvent contained in the liquid resin composition attached in the raw material attachment step to cure the silicone rubber component.

[0036] The raw material manufacturing process described above includes: a preparation step of preparing a liquid mixture containing a silicone rubber component, which is a component of the silicone rubber that will be the base material of the second layer 11, and an organic solvent; a first dispersion step of adding a silicone-based surfactant (polyether-modified silicone oil) to the liquid mixture prepared in the preparation step and uniformly dispersing the added silicone surfactant by applying ultrasound; a second dispersion step of further adding titanium dioxide fine particles 113 to the liquid mixture after the first dispersion step and uniformly dispersing the added titanium dioxide fine particles 113 by applying ultrasound; a third dispersion step of adding nanosilica fine particles 114 having an average particle size smaller than the average particle size of the titanium dioxide fine particles 113 to the liquid mixture after the second dispersion step and uniformly dispersing the added nanosilica fine particles 114 by applying ultrasound; and a fourth dispersion step of further adding silicone resin fine particles 112 having an average particle size of 1 μm or more to the liquid mixture after the third dispersion step and uniformly dispersing the added silicone resin fine particles 112 by applying ultrasound.

[0037] Regarding the ultrasonic waves mentioned above, the application conditions were all the same: a proximity dual-frequency ultrasonic cleaner (model number: VS-D100) manufactured by AS ONE Corporation was used, and the ultrasonic cleaning mode, which rapidly switches between two frequencies of 24kHz and 31kHz, was used for 10 minutes.

[0038] However, the liquid mixture (silicone rubber component + organic solvent) obtained by the raw material manufacturing process becomes a liquid resin composition (silicone rubber coating agent) which is the raw material for the second layer 11. This liquid resin composition further contains a silicone-based surfactant in addition to silicone resin fine particles 112, titanium dioxide fine particles 113, nanosilica fine particles 114, silicone rubber, and an organic solvent. By configuring it in this way, that is, by including a silicone-based surfactant in the liquid resin composition which is the raw material for the second layer 11, the silicone-based surfactant can be attached to the titanium dioxide fine particles 113 when the titanium dioxide fine particles 113 are dispersed in the liquid mixture, thereby suppressing the aggregation of the titanium dioxide fine particles 113. As a result, the titanium dioxide fine particles 113 can be dispersed uniformly.

[0039] Furthermore, as silicone-based surfactants, those used in cosmetics are preferred. More specifically, examples include polyglycerin-modified silicone oil and polyether-modified silicone oil. In addition, the amount (g) of silicone-based surfactant added to the liquid resin composition is preferably 1 to 20% of the amount (g) of titanium dioxide fine particles 113 added.

[0040] As the organic solvent in the above-mentioned liquid mixture (silicone rubber component + 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 individually or in combination of two or more. In addition, alcohols such as ethanol and isopropyl alcohol, or acetone may also be used.

[0041] (Appearance of the laminated structure) Incidentally, depending on its application, the laminated structure 1 may be made colored in appearance when viewed from the surface 11a side of the second layer 11, or text or patterns may be added to the laminated structure 1, taking design considerations into account. For example, when the laminated structure 1 is applied as an insulator for cables, making the appearance of the laminated structure 1 various colors can not only improve the design but also have the effect of preventing miswiring. In this case, it is conceivable to incorporate a coloring agent into the first layer 10, or to print text or patterns on the surface of the first layer 10 that faces the second layer 11.

[0042] The inventors have discovered that by reducing the particle size of the primary titanium dioxide nanoparticles 113 compared to conventional methods, it is possible to achieve a silicone coating film that is transparent in the visible light region (high aesthetic appeal) while ensuring resistance to ultraviolet light. The average particle size of the titanium dioxide nanoparticles 113 that is effective in ensuring both resistance to ultraviolet light with wavelengths of 200 to 380 nm, including UV-A, UV-B, and UV-C, and transparency of the silicone coating film in the visible light region is less than 100 nm. Furthermore, the average particle size of the titanium dioxide nanoparticles 113 that is effective in ensuring both resistance to UV-C with wavelengths of 200 to 280 nm, used in sterilization treatment, and transparency of the silicone coating film in the visible light region is less than 50 nm. On the other hand, if the average particle size of the titanium dioxide nanoparticles 113 is too small, it becomes difficult to suppress aggregation of the titanium dioxide nanoparticles 113, so it is desirable that the average particle size of the titanium dioxide nanoparticles 113 be 30 nm or larger.

[0043] Figure 2(a) is a plan view showing a printing medium 20 on which characters are printed. Figures 2(b) and (c) show samples 2A and 2B, each with a silicone coating film 21 and 22 formed on the surface of quartz glass, respectively, placed on the printing medium 20 shown in Figure 2(a), and the characters printed on the printing medium 20 viewed through the silicone coating films 21 and 22. The silicone coating film 21 of sample 2A shown in Figure 2(b) is formed by dispersing titanium dioxide nanoparticles with an average particle size of 250 nm in the silicone rubber base material. The silicone coating film 22 of sample 2B shown in Figure 2(c) is formed by dispersing titanium dioxide nanoparticles with an average particle size of 35 nm in the silicone rubber base material. Synthetic quartz glass manufactured by Kenis Corporation was used as the quartz glass. The concentration of titanium dioxide nanoparticles and the thickness of the silicone coating films 21 and 22 are the same for samples 2A and 2B.

[0044] As is clear from the comparison between sample 2A shown in Figure 2(b) and sample 2B shown in Figure 2(b), reducing the particle size of titanium dioxide nanoparticles in the silicone rubber increases the transparency of the silicone coating film in the visible light region, suppressing clouding and improving the visibility of characters and patterns printed on the printing medium 20.

[0045] Figure 3 is a graph showing an example of the relationship between the average particle size of titanium dioxide nanoparticles dispersed in the base material and the transmittance of light at wavelengths of 300 nm, 325 nm, 350 nm, 375 nm, and 400 nm. As shown in this graph, by setting the average particle size of titanium dioxide nanoparticles to less than 100 nm, the transmittance in a predetermined wavelength band in the near-ultraviolet region can be made lower than the transmittance in the visible light region. In other words, it is possible to selectively lower the transmittance in a predetermined wavelength band in the near-ultraviolet region while suppressing a decrease in transparency to light in the visible light region. Furthermore, as the average particle size of titanium dioxide nanoparticles decreases, the wavelength of light at which the transmittance is minimum (the shielding rate is maximum) becomes shorter.

[0046] Figure 4 is a graph showing an example of the relationship between the average particle size of titanium dioxide nanoparticles dispersed in the base material, the presence or absence of a surfactant, and transmittance. It shows an example of the relationship between the wavelength of light and transmittance of a silicone coating film (the second layer 11 in this embodiment) containing titanium dioxide nanoparticles 113 with an average particle size of 35 nm and a silicone-based surfactant (polyether-modified silicone oil). Figure 4 also shows, for comparison, the relationship between the wavelength of light and transmittance for a silicone coating film containing titanium dioxide nanoparticles 113 with an average particle size of 35 nm but without a silicone-based surfactant, and a silicone coating film in which the average particle size of the titanium dioxide nanoparticles 113 is replaced with one with a particle size of 250 nm. The film thickness of each silicone coating film is the same, and the concentrations and average particle sizes of other additives (silicone resin nanoparticles 112 and nanosilica nanoparticles 114) and the concentration (mass%) of titanium dioxide nanoparticles are also the same in each silicone coating film.

[0047] As shown in the graph in Figure 4, by setting the average particle size of the titanium dioxide nanoparticles to 35 nm, the transmittance of ultraviolet light in the UV-A, UV-B, and UV-C bands can be significantly reduced, while the transmittance of light in the visible light region can be increased, compared to the case where the average particle size is 250 nm. Furthermore, by adding a silicone-based surfactant, the aggregation of the titanium dioxide nanoparticles 113 is suppressed and the titanium dioxide nanoparticles 113 are dispersed, further increasing the transmittance of light in the visible light region.

[0048] In Figure 4, the graph shows the transmittance when the average particle size of titanium dioxide nanoparticles containing a silicone-based surfactant is 35 nm, with the solid line representing the transmittance. However, if the average particle size of the titanium dioxide nanoparticles is less than 50 nm, the transmittance in the near-ultraviolet region can be reduced compared to conventional products where the average particle size of the titanium dioxide nanoparticles is 100 nm or more.

[0049] Figure 5(a) is a diagram showing an example of an application configuration in which the laminated structure 1 according to this embodiment is applied to the probe cable 4 of a medical ultrasound probe 3. Figure 5(b) is a cross-sectional view along line AA in Figure 5(a). The probe cable 4 is an example of an object that receives ultraviolet irradiation.

[0050] The ultrasound probe 3 is used by a clinical laboratory technician to diagnose a patient and comprises a probe cable 4, a transducer 5 attached to one end of the probe cable 4, and a probe connector 6 attached to the other end of the probe cable 4. The transducer 5 has an ultrasonic transmitting / receiving wavefront 5a that is pressed against the patient's body surface. The probe connector 6 is connected to an image forming device that performs ultrasonic image formation processing. During patient diagnosis, the clinical laboratory technician presses the ultrasonic transmitting / receiving wavefront 5a of the transducer 5 against the patient's body surface at various angles, causing the probe cable 4 to rub against the patient's body or the clinical laboratory technician's clothing. After the examination is completed, the ultrasound probe 3 is disinfected by irradiation with UV-C light.

[0051] Figure 5(b) shows a cross-section of the probe cable 4 perpendicular to its longitudinal direction. The probe cable 4 includes a cable core 40 containing multiple signal lines 41, a retaining tape 42 wrapped around the outer circumference of the cable core 40, a braided shield 43 covering the outer circumference of the retaining tape 42, a sheath 44 covering the outer circumference of the braided shield 43, and a silicone coating film 45 covering the surface 44a of the sheath 44. The sheath 44 corresponds to the first layer 10 of the laminated structure 1, and the silicone coating film 45 corresponds to the second layer 11 of the laminated structure 1. In other words, in the ultrasonic probe 3, the sheath 44 and the silicone coating film 45 correspond to the laminated structure 1.

[0052] The signal line 41 is a coaxial cable having an inner conductor and an outer conductor, with one end connected to the ultrasonic sensor inside the transducer 5 and the other end connected to the connector pin of the probe connector 6. The braided shield 43 is constructed by braiding multiple shield strands 431 in a grid pattern. The outer diameter of the probe cable 4 is, for example, 5 mm to 11 mm, and the thickness of the sheath 44 is, for example, 0.5 mm to 1.5 mm. The thickness of the silicone coating film 45 is, for example, 3 μm to 100 μm.

[0053] The silicone rubber that forms the base material of the sheath 44 has higher resistance to ultraviolet light compared to, for example, polyvinyl chloride, but it also has a characteristic stickiness sometimes referred to as tackiness. If the sheath 44 were not covered with the silicone coating film 45, the probe cable 4 would snag when rubbing against the patient's body or the clinical laboratory technician's clothing. The silicone coating film 45 covers the entire circumference of the surface 44a along the entire longitudinal direction of the sheath 44, improving the slipperiness (sliding properties) of the probe cable 4 and increasing its resistance to ultraviolet light.

[0054] (Effects of the embodiment) According to an embodiment of the present invention, the second layer 11 (silicone coating film 45 in the probe cable 4) as a silicone coating film has transparency in the visible light region while ensuring resistance to ultraviolet light. Furthermore, even when using titanium dioxide nanoparticles 113 that have a smaller particle size and are more prone to aggregation than conventional ones, the sedimentation of the titanium dioxide nanoparticles 113 is suppressed by the nanosilica nanoparticles 114, preventing loss of uniformity in the arrangement of titanium dioxide nanoparticles 113 in the base material 111. Moreover, because the particle size of the titanium dioxide nanoparticles 113 is smaller than conventional ones and the ratio of surface area to volume is larger, the same level of resistance to ultraviolet light as conventional ones can be obtained even with a smaller amount of titanium dioxide nanoparticles than conventional ones.

[0055] (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 in the following description are not limited to the components in the claims that are specifically shown in the embodiments.

[0056] [1] A coating film (second layer 11, silicone coating film 45) provided as the surface layer of an object (probe cable 4) that is irradiated with ultraviolet light, wherein the silicone coating film (11, 45) has a silicone rubber base material (111) and contains titanium oxide fine particles (113) with an average particle size of less than 100 nm.

[0057] [2] The titanium dioxide nanoparticles (113) are the silicone coating film (11, 45) described in [1] above, wherein the average particle size is less than 50 nm.

[0058] [3] Titanium oxide nanoparticles (113) are the silicone coating film (11, 45) described in [1] above, having an average particle size of 30 nm or more.

[0059] [4] The silicone coating film (11, 45) described in [1] above, further comprising a silicone-based surfactant.

[0060] [5] The silicone coating film (11, 45) according to [1] above, further comprising nanosilica nanoparticles (114) having an average particle size smaller than the average particle size of titanium oxide nanoparticles (113), and silicone resin nanoparticles (112) having an average particle size of 1 μm or more.

[0061] [6] A laminated structure (1) in which a second layer (11, 45) is laminated on a first layer (10, sheath 44) having silicone rubber as a base material (101), wherein the second layer (11, 45) is a silicone coating film (11, 45) as described in any of [1] to [5] above.

[0062] [7] A method for manufacturing a laminated structure (1) comprising a first layer (10, 44) having silicone rubber as a base material (101) and a second layer (11) having silicone rubber as a base material (111) and containing titanium oxide fine particles (113) with an average particle size of less than 100 nm, comprising: a preparation step of preparing a liquid mixture of a silicone rubber component, which is a component of the silicone rubber that will be the base material (111) of the second layer (11), and an organic solvent; a first dispersion step of adding a silicone-based surfactant to the liquid mixture and dispersing the added silicone-based surfactant; and after the first dispersion step A method for manufacturing a laminated structure, comprising: a second dispersion step of further adding the titanium dioxide fine particles (113) to the liquid mixture and dispersing the added titanium dioxide fine particles (113); a raw material attachment step of making the liquid mixture into a liquid resin composition which is the raw material for the second layer (11), and attaching the liquid resin composition to the surface of the first layer (10); and a layer formation step of forming the second layer (11) by vaporizing the organic solvent contained in the liquid resin composition attached to the surface of the first layer (10) and curing the silicone rubber component.

[0063] [8] A method for manufacturing a laminated structure according to [7], comprising: a third dispersion step of further adding nanosilica fine particles (114) having an average particle size smaller than the average particle size of the titanium oxide fine particles (113) to the liquid mixture after the second dispersion step, and dispersing the added nanosilica fine particles (114); and a fourth dispersion step of further adding silicone resin fine particles (112) having an average particle size of 1 μm or more to the liquid mixture after the third dispersion step, and dispersing the added silicone resin fine particles (112).

[0064] Although embodiments of the present invention have been described above, these embodiments do not limit the invention as defined in the claims. Furthermore, it should be noted that not all combinations of features described in the embodiments are necessarily essential for solving the problem of the invention.

[0065] Furthermore, the present invention is not limited to the embodiments described above and can be implemented with appropriate modifications. For example, in the above embodiments, the case in which the irradiated object of the present invention is embodied as a probe cable 4 was described as an example, but the present invention is not limited to this, and in addition to the above-mentioned constant temperature chamber greenhouse sheet and sterilization chamber sheet, the irradiated object can be, for example, exterior or interior materials for automobiles, outdoor products, medical devices other than probe cables, or food processing equipment that is sterilized with ultraviolet light. In other words, the present invention can be applied as an irradiated object to various products that are irradiated with ultraviolet light, not limited to ultraviolet light contained in sunlight or sterilizing ultraviolet light emitted from light-emitting elements such as deep ultraviolet LEDs, and the silicone coating film of the present invention is provided as the surface layer of the product to shield against ultraviolet light by absorbing and / or scattering ultraviolet light, thereby increasing resistance to ultraviolet light. [Explanation of Symbols]

[0066] 1…Laminated structure 10…First layer 101,111…Base material 11…Second layer 112…Silicone resin microparticles 113…Titanium dioxide microparticles 114…Nanosilica microparticles 4…Probe cable (illuminated object) 44...Sheath (first layer) 45...Silicone coating film (second layer)

Claims

1. A coating film provided as the surface layer of an object that is irradiated with ultraviolet light, A silicone rubber base material containing titanium dioxide fine particles with an average particle size of less than 100 nm. Silicone coating film.

2. The titanium oxide fine particles have an average particle size of less than 50 nm. The silicone coating film according to claim 1.

3. The titanium oxide fine particles have an average particle size of 30 nm or more. The silicone coating film according to claim 1.

4. Further containing silicone-based surfactants, The silicone coating film according to claim 1.

5. The present invention further comprises nanosilica nanoparticles having an average particle size smaller than the average particle size of the titanium oxide nanoparticles, and silicone resin nanoparticles having an average particle size of 1 μm or more. The silicone coating film according to claim 1.

6. A laminated structure in which a second layer is laminated onto a first layer made of silicone rubber, The second layer is a silicone coating film according to any one of claims 1 to 5. Laminated structure.

7. In a method for manufacturing a laminated structure in which a second layer, also made of silicone rubber and containing titanium oxide fine particles with an average particle size of less than 100 nm, is laminated onto a first layer made of silicone rubber, A preparation step of preparing a liquid mixture of a silicone rubber component, which is a component of the silicone rubber that forms the base material of the second layer, and an organic solvent, A first dispersion step involves adding a silicone-based surfactant to the liquid mixture and dispersing the added silicone-based surfactant, After the first dispersion step, a second dispersion step is performed in which the titanium dioxide fine particles are further added to the liquid mixture and the added titanium dioxide fine particles are dispersed. The liquid mixture is made into a liquid resin composition which is the raw material for the second layer, and the raw material attachment step is to attach the liquid resin composition to the surface of the first layer, The process includes a layer-forming step of forming a second layer by vaporizing the organic solvent contained in the liquid resin composition attached to the surface of the first layer to cure the silicone rubber component, A method for manufacturing a laminated structure.

8. After the second dispersion step, a third dispersion step is performed in which nanosilica particles having an average particle size smaller than the average particle size of the titanium oxide particles are further added to the liquid mixture, and the added nanosilica particles are dispersed. The method includes a fourth dispersion step in which, after the third dispersion step, silicone resin fine particles having an average particle size of 1 μm or more are further added to the liquid mixture, and the added silicone resin fine particles are dispersed. A method for manufacturing a laminated structure according to claim 7.

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