Particle-including base material, and production method for particle-including base material

Abstract

The present disclosure provides a particle-including base material that comprises: a fiber base containing inorganic fibers; an inorganic film that is disposed on the surface of the fiber base material, and that contains an inorganic compound; and functional particles that are fixed, by the inorganic film, to the surface side of the fiber base material.

Description

Particle-attached substrate and method for manufacturing particle-attached substrate

[0001] The present disclosure relates to a particle-attached substrate and a method for manufacturing a particle-attached substrate.

[0002] BACKGROUND ART Conventionally, techniques for immobilizing functional particles on the surface of a substrate have been known in order to impart functions such as environmental purification, antibacterial, antiviral, antifungal, and self-cleaning properties to the substrate.

[0003] As a technique for fixing functional particles on the surface of a substrate, for example, there is a method using a binder. For example, Patent Documents 1 and 2 disclose photocatalytic members having a layer containing photocatalytic particles and an inorganic binder.

[0004] Furthermore, as a technique for immobilizing functional particles on the surface of a substrate, for example, a method of adsorbing functional particles onto the surface of a substrate has been proposed. For example, Patent Document 3 discloses a method of electrostatically adsorbing photocatalyst particles onto the surface of polyester fibers.

[0005] Japanese Patent Application Laid-Open No. 2008-272651 Japanese Patent Application Laid-Open No. 2018-528072 Japanese Patent Application Laid-Open No. 2007-229667

[0006] In the methods using a binder as disclosed in Patent Document 1 or Patent Document 2, functional particles can be stably fixed to the surface of a substrate. However, there is a problem in that at least a portion of the functional particles is buried in the binder, resulting in a decrease in functionality. In particular, when the layer containing the functional particles and the binder is a dense film with almost no pores, the functional particles cannot come into contact with substances in the external environment, resulting in a significant decrease in functionality.

[0007] Furthermore, the method using electrostatic adsorption as disclosed in Patent Document 3 does not use a binder, and therefore the functionality of the functional particles can be fully exhibited. Furthermore, the functional particles can be adsorbed at a high density. However, there is a problem in that the adhesion of the functional particles to the substrate is insufficient, and the functional particles tend to fall off.

[0008] The present disclosure has been made in consideration of the above-described circumstances, and aims to provide a particle-attached substrate and a method for manufacturing a particle-attached substrate, which can stably and densely fix particles to the surface of a substrate while maintaining the functionality of the particles.

[0009] One embodiment of the present disclosure provides a particle-bearing substrate having a fiber substrate containing inorganic fibers, an inorganic film disposed on the surface of the fiber substrate and containing an inorganic compound, and functional particles fixed by the inorganic film on the surface side of the fiber substrate.

[0010] Another embodiment of the present disclosure provides a method for manufacturing a particle-attached substrate, the method comprising: a functional group introduction step of introducing functional groups that become positively or negatively charged in water onto a surface of a substrate; a particle electrostatic adsorption step of electrostatically adsorbing functional particles onto the surface of the substrate onto which the functional groups have been introduced; and an inorganic film formation step of forming an inorganic film containing an inorganic compound so as to cover the surface of the substrate after the particle electrostatic adsorption step.

[0011] The present disclosure provides an effect of enabling particles to be stably and densely immobilized on a substrate surface while maintaining the functionality of the particles.

[0012] FIG. 1 is a schematic cross-sectional view illustrating a particle-attached substrate according to the present disclosure. FIG. 2 is a process chart illustrating a method for manufacturing a particle-attached substrate according to the present disclosure. FIG. 3 is a schematic cross-sectional view illustrating a particle-attached substrate according to the present disclosure. FIG. 4 is a schematic cross-sectional view illustrating a particle-attached substrate according to the present disclosure. FIG. 5 is a process chart illustrating a method for manufacturing a particle-attached substrate according to the present disclosure. FIG. 6 is an SEM image of polymethylsilsesquioxane (PMSQ) particles of Example 1. FIG. 7 is an SEM image of the particle-attached substrate of Example 1. FIG. 8 is an SEM image of the particle-attached substrate of Example 2.

[0013] Embodiments of the present disclosure will be described below with reference to the drawings and the like. However, the present disclosure can be implemented in many different forms and should not be construed as being limited to the description of the embodiments exemplified below. Furthermore, to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual form, but these are merely examples and do not limit the interpretation of the present disclosure. Furthermore, in this specification and each drawing, elements similar to those described above with reference to the previous drawings may be designated by the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0014] The particle-attached substrate and the method for producing the particle-attached substrate according to the present disclosure will be described in detail below.

[0015] A. Particle-Attached Substrate The particle-attached substrate according to the present disclosure includes a fibrous substrate containing inorganic fibers, an inorganic film that is disposed on the surface of the fibrous substrate and contains an inorganic compound, and particles that are fixed by the inorganic film on the surface side of the fibrous substrate.

[0016] 1 is a schematic cross-sectional view illustrating a particle-attached substrate according to the present disclosure. As shown in Fig. 1, the particle-attached substrate 10 includes a fiber substrate 1 containing inorganic fibers, an inorganic film 2 disposed on the surface of the fiber substrate 1 and containing an inorganic compound, and particles 3 fixed by the inorganic film 2 on the surface side of the fiber substrate 1.

[0017] In the particle-attached substrate of the present disclosure, particles are fixed to the surface side of the fibrous substrate by an inorganic film. The inorganic film is a layer for fixing the particles and contains an inorganic compound but does not contain particles. Therefore, unlike conventional methods of forming a layer using a composition containing particles and a binder, the particles can be prevented from being embedded in the binder. Furthermore, because the particles are fixed by the inorganic film and not embedded in the binder, they can come into contact with substances in the external environment that gradually diffuse and pass through the interior of the inorganic film. This allows the particles to function to a certain extent. In this case, as described below, if the inorganic film has a large number of pores large enough to allow substances in the external environment to pass through, the particles can function to their full potential. Furthermore, because the particles are fixed by the inorganic film, particle detachment can be prevented. Therefore, the particles can be stably fixed to the surface of the fibrous substrate while maintaining their function.

[0018] 2(a) to 2(d) are process diagrams illustrating a method for producing a particle-attached substrate according to the present disclosure. First, as shown in FIG. 2(a), functional groups A that are positively charged in water are introduced onto the surface of a fiber substrate 1. Next, as shown in FIGS. 2(b) and 2(c), particles 3 that are negatively charged in water are electrostatically adsorbed onto the surface of the fiber substrate 1 to which functional groups A have been introduced. Next, as shown in FIG. 2(d), an inorganic film 2 containing an inorganic compound is formed so as to cover the surface of the fiber substrate 1. This results in a particle-attached substrate 10.

[0019] As described above, the particle-attached substrate of the present disclosure can be produced by electrostatically adsorbing particles to the surface of a fibrous substrate and then forming an inorganic film to cover the surface of the fibrous substrate. By utilizing electrostatic adsorption, particles can be adsorbed at a high density on the surface of the fibrous substrate. Furthermore, as described below, the thickness of the inorganic film is preferably thin enough to allow substances in the external environment to gradually pass through by diffusion. Therefore, particles can be stably and densely fixed on the surface of the fibrous substrate while maintaining their functionality.

[0020] In the present disclosure, the fiber substrate includes inorganic fibers. The layer for immobilizing particles is an inorganic film containing an inorganic compound. Therefore, for example, when the particles are photocatalytic particles, the fiber substrate and the inorganic film are stable against radicals generated in the photocatalytic reaction. Therefore, the durability of the particle-attached substrate can be improved.

[0021] Furthermore, in the present disclosure, by using a fiber substrate, a particle-attached substrate can be produced by a roll-to-roll method, thereby improving production efficiency and reducing production costs.

[0022] Hereinafter, each configuration of the particle-attached substrate in the present disclosure will be described.

[0023] 1. Particles The particles in the present disclosure are immobilized on the surface of a fibrous substrate by an inorganic film.

[0024] The particles are preferably functional particles. Functional particles refer to particles that can affect a substance by coming into contact with the substance. Examples of functions possessed by functional particles include a photocatalytic function, an antibacterial function, an antiviral function, an antifungal function, an ion adsorption function, an ion release function, a gas adsorption function, a gas release function, a chemical substance sustained release function, a humidity control function, a catalytic function, an adhesive function, a water repellent function, a rust prevention function, a heat transfer function, a heat insulating function, a conductive function, and an insulating function.

[0025] Among these, photocatalyst particles are preferred. Photocatalyst particles can be used in a wide range of applications in the environmental field, such as environmental purification, antibacterial, antiviral, antifungal, deodorizing, antifouling, antifogging, and self-cleaning.

[0026] Examples of photocatalytic particles include titanium oxide (TiO ２ ), zinc oxide (ZnO), cadmium sulfide (CdS), niobium oxide (Nb ２ O ５ ), tantalum oxide (Ta ２ O ５ ), tungsten oxide (WO ３ ), molybdenum oxide (MoO ３ ), vanadium oxide (V ２ O ５ ) are listed.

[0027] Furthermore, the photocatalyst particles may carry a substance that improves the activity of the photocatalyst particles. The substance is not particularly limited as long as it can improve the activity of the photocatalyst particles.

[0028] Examples of functional particles include metal particles, metal oxide particles, metal carbide particles, and metal nitride particles. Metal particles may be composed of a single metal or an alloy. Examples of metal particles include silver particles, zinc particles, and copper particles.

[0029] The average particle size of the particles is not particularly limited, but is preferably 0.1 μm or more and 10 μm or less, more preferably 0.2 μm or more and 5 μm or less, and even more preferably 0.5 μm or more and 2.5 μm or less. By having a relatively large average particle size within the above range, the particles can be fixed to the surface of the fiber substrate by the inorganic film while preventing the particles from being buried in the inorganic film. On the other hand, if the average particle size of the particles is too large, the particles may easily fall off.

[0030] Here, the particle diameter of the particles can be measured by observing the cross section of the particle-attached substrate with a scanning electron microscope (SEM). The average particle diameter of the particles refers to the arithmetic mean value of the particle diameters of 20 particles measured by SEM observation. Note that if the particle shape is not spherical, the particle diameter is the major axis.

[0031] The shape of the particles is not particularly limited, and examples thereof include spherical, cubic, tabular, discoid, rod-like, and needle-like shapes.

[0032] Examples of embodiments in which particles are fixed to the surface of a fiber substrate by an inorganic film include an embodiment in which the inorganic film 2 is disposed on the surface of the fiber substrate 1 so that all of the particles 3 are covered by the inorganic film 2, as shown in Fig. 1, and an embodiment in which the inorganic film 2 is disposed on the surface of the fiber substrate 1 so that part of the particles 3 are exposed, as shown in Fig. 3. These embodiments may also be combined.

[0033] When a part of the particle is exposed, the degree of particle exposure, that is, the degree of coating of the particle with the inorganic film, is not particularly limited.

[0034] Furthermore, for example, as shown in Figure 4, the particles 3 may be fixed over the entire surface of the fiber substrate 1, or for example, as shown in Figures 1 and 3, the particles 3 may be fixed over a portion of the surface of the fiber substrate 1. For example, the particles may be fixed over only one of the two main surfaces of the fiber substrate. In particular, it is preferable that the particles are fixed over the entire surface of the fiber substrate. The function of the particles can be exerted over the entire surface of the particle-attached substrate.

[0035] The amount of particles in the particle-attached substrate is not particularly limited as long as the amount is sufficient to allow the particles to exert their functions, and is appropriately set depending on the thickness and surface area of ​​the fiber substrate, the type of particles, and the application of the particle-attached substrate. The amount of particles in the particle-attached substrate is, for example, 0.1 mg / cm ２ 10mg / cm or more ２ Preferably, 0.5 mg / cm or less ２ 5mg / cm or more ２ More preferably, 1 mg / cm or less ２ 3mg / cm or more ２ The following is even more preferred:

[0036] Here, the amount of particles in the particle-attached substrate can be measured by recovering the particles from the particle-attached substrate. For example, when the inorganic film that fixes the particles is a silica film, the particles can be recovered by dissolving the silica film in a strong alkaline aqueous solution.

[0037] 2. Inorganic Film The inorganic film in the present disclosure is disposed on the surface of the fiber substrate and contains an inorganic compound.

[0038] Examples of inorganic compounds include inorganic compounds that can form an inorganic film by a sol-gel method or a vapor deposition method. Examples of inorganic compounds include inorganic oxides, inorganic fluorides, inorganic sulfides, and inorganic nitrides. Examples of inorganic oxides include silica, titania, alumina, zirconia, zinc oxide (ZnO), indium oxide (In ２ O ３ ), tin oxide (SnO ２ ), indium tin oxide (ITO), tantalum oxide (Ta ２ O ５ Examples of inorganic fluorides include magnesium fluoride (MgF ２), aluminum fluoride (AlF ３ ), barium fluoride (BaF ２ ), calcium fluoride (CaF ２ ), cerium fluoride (CeF ３ ), yttrium fluoride (YF ３ Examples of inorganic nitrides include aluminum nitride (AlN) and silicon nitride (Si ３ N ４ ), titanium nitride (TiN).

[0039] Among these, silica is preferable because it has excellent weather resistance and durability.

[0040] The thickness of the inorganic film is not particularly limited as long as it is thick enough to fix the particles to the surface of the fiber substrate so that the particles can perform their function, and is appropriately set according to the particle diameter and shape of the particles.For example, when the particles are covered with an inorganic film, the thickness of the inorganic film is preferably thick enough that the substance can pass through or penetrate so that the particles can contact the substance.Specifically, the thickness of the inorganic film is preferably 2 nm or more and 100 nm or less, more preferably 5 nm or more and 50 nm or less, and even more preferably 10 nm or more and 30 nm or less.By making the inorganic film relatively thin within the above range, even when the particles are covered with the inorganic film, the substance can pass through or penetrate the inorganic film, and the particles can contact the substance, so that the particles can perform their function.On the other hand, if the thickness of the inorganic film is too thin, the particles may be easily dropped off.

[0041] Here, the thickness of the inorganic film means the thickness t1 of the inorganic film 2 in a region where no particles 3 are present, as shown in Fig. 5, and also means the thickness t2 of the inorganic film 2 located on the surface of the particle 3 when the entire particle 3 is covered with the inorganic film 2. The thickness of the inorganic film can be measured by observing the cross section of the particle-attached substrate with a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0042] The inorganic membrane is preferably a porous membrane, which allows substances in the external environment to pass through the inorganic membrane and come into contact with the particles, thereby allowing the particles to maximize their functionality.

[0043] A porous membrane is a membrane having a large number of pores. Preferably, the inorganic membrane has pores of a size that allows substances in the external environment to pass through. Specifically, the inorganic membrane preferably has pores with a pore diameter on the order of nanometers. Furthermore, the inorganic membrane may have any of micropores with a pore diameter of 2 nm or less, mesopores with a pore diameter of 2 nm to 50 nm, and macropores with a pore diameter of 50 nm or more. Among these, from the viewpoint of particle fixing power, i.e., the strength of the inorganic membrane, it is preferable that the inorganic membrane has micropores. That is, the inorganic membrane preferably has pores with a pore diameter of 0.3 nm to 3 nm, more preferably pores with a pore diameter of 0.4 nm to 2 nm, and even more preferably pores with a pore diameter of 0.5 nm to 1 nm.

[0044] The phrase "the inorganic membrane has pores with a pore size within a predetermined range" means that the inorganic membrane has pores, and that among the pores, there are a plurality of pores with a pore size within the predetermined range.

[0045] The pore diameter of the inorganic membrane is a value determined by observing the surface of the inorganic membrane using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). When the pores are mesopores or macropores, an SEM is used. On the other hand, when the pores are micropores, a TEM is used. As described above, it is sufficient that a plurality of pores in the inorganic membrane have a pore diameter within a predetermined range. In particular, it is preferable that 100 or more, and even 1000 or more, micropores having a pore diameter within a predetermined range are present within a 1 μm square on the surface of the inorganic membrane.

[0046] The inorganic film may be either an amorphous film or a crystalline film, but is preferably an amorphous film. Amorphous films tend to have micropores. Therefore, if the inorganic film is amorphous, substances in the external environment can pass through the inorganic film and come into contact with the particles, thereby maximizing the functionality of the particles. This also increases the fixing power of the particles.

[0047] The inorganic film is confirmed to be an amorphous film by X-ray diffraction (XRD). If no clear peak is observed in the X-ray diffraction pattern, it is considered to be an amorphous film. However, if XRD measurement is difficult, the inorganic film is confirmed to be an amorphous film by observation with a transmission electron microscope (TEM). If an image of randomly arranged black or white spots (i.e., areas where atoms are present) is observed in TEM observation, it is considered to be an amorphous film.

[0048] Examples of methods for forming an inorganic film include a sol-gel method and a vapor deposition method. Among these, the sol-gel method is preferred. The sol-gel method can form an amorphous film. That is, the inorganic film is preferably an amorphous film formed by the sol-gel method. The sol-gel method and the vapor deposition method will be described later in the section "B. Method for manufacturing a particle-attached substrate."

[0049] Here, it can be confirmed that the inorganic film is an inorganic film formed by the sol-gel method by observation with a transmission electron microscope (TEM). Inorganic films formed by the sol-gel method tend to show images in which black spots (corresponding to micropores) are randomly arranged. For example, when an inorganic film containing silica is formed by the sol-gel method using tetraethoxysilane (TEOS), an image in which black spots with a diameter of 1 nm or less are randomly arranged is often observed. In general, the density (microstructure) of an inorganic film depends greatly on the method of forming the inorganic film. For example, it is known that a silica film formed by chemical vapor deposition (CVD) is denser than a silica film formed by the sol-gel method or physical vapor deposition (PVD). By observing the density (microstructure) of the inorganic film, the method of forming the inorganic film can be estimated.

[0050] 3. Fibre Substrate The fibrous substrate in the present disclosure includes inorganic fibers.

[0051] The inorganic fibers are not particularly limited and include, for example, glass fibers, ceramic fibers, and carbon fibers. Examples of ceramic fibers include alumina-based fibers, silica fibers, zirconia fibers, silicon carbide fibers, and silicon nitride fibers. Examples of alumina-based fibers include alumina fibers, alumina-silica fibers, and mullite fibers.

[0052] In addition to the fibers made of inorganic materials as described above, the inorganic fibers may also include organic fibers made of organic materials coated with an inorganic material, an organic-inorganic hybrid material, or a metal material, and metal fibers coated with an inorganic material.

[0053] The organic fibers are not particularly limited as long as they can be coated with an inorganic material, an organic-inorganic hybrid material, or a metal material, and examples thereof include polyester fibers and polyolefin fibers. Examples of polyolefins constituting polyolefin fibers include polyethylene, polyethylene copolymers, polypropylene, and polypropylene copolymers.

[0054] The metal fibers are not particularly limited as long as they can be coated with an inorganic material.

[0055] The inorganic material is not particularly limited as long as it is an inorganic material that can coat organic fibers or metal fibers, and examples thereof include silica. The organic-inorganic hybrid material is, for example, polysiloxane. The metal material is not particularly limited as long as it is a metal material that can coat organic fibers.

[0056] The method for coating organic fibers with an inorganic material is not particularly limited, and examples thereof include the sol-gel method. Furthermore, examples of methods for coating organic fibers with an organic-inorganic hybrid material include a method in which an organosilicon compound is applied to the organic fibers and then heat-cured. Examples of organosilicon compounds that can be used include alkoxysilane, silicone resin, and polysilazane. Known methods can be used to coat organic fibers with a metal material and to coat metal fibers with an inorganic material.

[0057] Among these, inorganic fibers made of inorganic materials are preferred. When the particles are photocatalytic particles, the use of inorganic fibers made of inorganic materials can improve stability against radicals generated in the photocatalytic reaction.

[0058] Among inorganic fibers made of inorganic substances, glass fibers and ceramic fibers are preferred. Glass fibers and alumina-based fibers are particularly preferred. Glass fibers and alumina-based fibers have excellent weather resistance, heat resistance, and chemical resistance. Glass fibers are even more preferred. Glass fibers are inexpensive, allowing for reduced manufacturing costs.

[0059] The average fiber diameter of the inorganic fibers is not particularly limited, but may be, for example, 1 μm or more and 50 μm or less, and may be, for example, 5 μm or more and 20 μm or less. Furthermore, the average fiber diameter of the inorganic fibers may be, for example, 10 times or more and 20 times or less the average particle diameter of the particles described below. If the average fiber diameter of the inorganic fibers is too large, the surface area of ​​the inorganic fibers per unit area of ​​the fiber substrate tends to be small, which may reduce the amount of particles fixed to the fiber substrate. Furthermore, if the average fiber diameter of the inorganic fibers is too small, the gaps between the inorganic fibers in the fiber substrate tend to be small, which may result in particles being fixed planarly only to the surface of the fiber substrate, which may reduce the amount of particles fixed to the fiber substrate. On the other hand, if the average fiber diameter of the inorganic fibers is within the above range, the gaps between the inorganic fibers in the fiber substrate can be sufficiently large to allow particles to pass through, while the surface area of ​​the inorganic fibers per unit area of ​​the fiber substrate can be appropriately increased. Therefore, the amount of particles fixed to the fiber substrate can be increased.

[0060] Here, the fiber diameter of the inorganic fibers can be measured by observation with a scanning electron microscope (SEM). The average fiber diameter of the inorganic fibers refers to the arithmetic mean value of the fiber diameters of 50 inorganic fibers measured by SEM observation.

[0061] Examples of the fiber substrate include nonwoven fabrics, woven fabrics, and knitted fabrics, with nonwoven fabrics being preferred.

[0062] The inorganic fibers constituting the nonwoven fabric may be short fibers or long fibers. The length of the fibers is, for example, 1 mm or more and 30 mm or less. Furthermore, in the nonwoven fabric, the method of bonding between the fibers may be any of entanglement, fusion, and adhesion. When the fibers are bonded together with an adhesive (binder), the adhesive (binder) is not particularly limited, and binders generally used in nonwoven fabrics can be used. Examples of binders include acrylic resins, epoxy resins, polyvinyl alcohol, melamine resins, polyesters, and polyvinyl chloride.

[0063] The thickness of the fiber substrate is not particularly limited and is appropriately selected depending on the application of the particle-attached substrate. Specifically, the thickness of the fiber substrate is 0.1 mm or more and 2 mm or less, and may be 0.2 mm or more and 1 mm or less, or 0.3 mm or more and 0.5 mm or less. Generally, the thicker the fiber substrate, the greater the amount of particles fixed to the fiber substrate. However, in the case of photocatalytic particles, if the fiber substrate is too thick, it becomes difficult for light to reach the deep layers of the fiber substrate, and there is a possibility that the number of photocatalytic particles that do not contribute to activity will increase. If the thickness of the fiber substrate is within the above range, the photocatalytic particles can be utilized without waste.

[0064] The basis weight of the fiber substrate is not particularly limited and is appropriately selected depending on the application of the particle-attached substrate. Specifically, the basis weight of the fiber substrate is 5 g / m ２ More than 200g / m ２ less than 10 g / m ２ More than 100g / m ２ or less, and ２ 50g / m or more ２ or less. Generally, the larger the basis weight of the fiber substrate, the greater the amount of particles fixed to the fiber substrate tends to be. However, if the basis weight of the fiber substrate is too large, the fiber substrate becomes thick, and as mentioned above, in the case of photocatalytic particles, there is a possibility that the number of photocatalytic particles that do not contribute to activity will increase. Furthermore, if the basis weight of the fiber substrate is too large, the voids within the fiber substrate will become small, and as mentioned above, there is a possibility that the amount of particles fixed to the fiber substrate will decrease. On the other hand, if the basis weight of the fiber substrate is too small, the fiber substrate will become thin, and there is a possibility that the amount of particles fixed to the fiber substrate will decrease.

[0065] 4. Method for Producing Particle-Attached Substrate The particle-attached substrate of the present disclosure can be produced by the method for producing a particle-attached substrate described below.

[0066] B. Method for Producing Particle-Attached Substrate The method for producing a particle-attached substrate in the present disclosure includes a functional group introduction step of introducing functional groups that become positively or negatively charged in water onto the surface of the substrate, a particle electrostatic adsorption step of electrostatically adsorbing particles onto the surface of the substrate onto which the functional groups have been introduced, and an inorganic film formation step of forming an inorganic film containing an inorganic compound so as to cover the surface of the substrate after the particle electrostatic adsorption step.

[0067] 6(a) to 6(d) are process diagrams illustrating a method for manufacturing a particle-attached substrate according to the present disclosure. First, as shown in FIG. 6(a), functional groups A that are positively charged in water are introduced onto the surface of a substrate 11. Next, as shown in FIGS. 6(b) and 6(c), particles 3 that are negatively charged in water are electrostatically adsorbed onto the surface of the substrate 11 to which functional groups A have been introduced. Next, as shown in FIG. 6(d), an inorganic film 2 containing an inorganic compound is formed so as to cover the surface of the fiber substrate 11. This results in a particle-attached substrate 20.

[0068] In the present disclosure, particles can be adsorbed onto the surface of a substrate at high density by utilizing electrostatic adsorption.

[0069] In addition, in the present disclosure, particles are electrostatically adsorbed onto the surface of a substrate, and then a relatively thin inorganic film is formed to cover the surface of the substrate, thereby immobilizing the particles on the surface of the substrate. Therefore, unlike conventional methods in which a layer is formed using a composition containing particles and a binder, the particles can be prevented from being embedded in the binder. Furthermore, because the particles are fixed by the inorganic film and not embedded in the binder, they can come into contact with substances in the external environment that gradually diffuse and pass through the interior of the inorganic film. This allows the particles to function to a certain extent. In this case, as described above, if the inorganic film is a porous film with a large number of pores large enough to allow substances in the external environment to pass through, the particles can be maximized in function. Furthermore, because the particles can be immobilized on the surface of the substrate by the inorganic film, particle shedding can be suppressed.

[0070] Therefore, the particles can be stably and densely immobilized on the surface of the fiber substrate while maintaining the functionality of the particles.

[0071] In addition, in the present disclosure, an inorganic film containing an inorganic compound is formed as a layer for immobilizing particles. Therefore, for example, when the particles are photocatalytic particles, the inorganic film is stable against radicals generated in the photocatalytic reaction. Therefore, a substrate with particles having excellent durability can be produced.

[0072] The substrate and particles used in the method for producing a particle-attached substrate according to the present disclosure, as well as each step of the method for producing a particle-attached substrate according to the present disclosure, will be described below.

[0073] 1. Substrate The form of the substrate used in the present disclosure is not particularly limited, and examples thereof include films, sheets, plates, fiber substrates, threads, fibers, beads, porous bodies, and columns. Examples of fiber substrates include nonwoven fabrics, woven fabrics, and knitted fabrics. The form of the thread is not particularly limited. The thread may be, for example, a hollow thread or a solid thread.

[0074] Among these, the substrate is preferably a fibrous substrate, and more preferably a nonwoven fabric. When the substrate is a fibrous substrate, the particle-attached substrate can be manufactured by a roll-to-roll method. The fibrous substrate is the same as the fibrous substrate in the particle-attached substrate described above.

[0075] The material of the substrate is not particularly limited, and examples thereof include inorganic materials, organic polymers, metals, and semiconductors. Examples of inorganic materials include glass, ceramics, and carbon. Examples of ceramics include alumina, silica, zirconia, silicon carbide, and silicon nitride. Examples of alumina materials include alumina, alumina silica, and mullite. Examples of organic polymers include polyester, nylon, acrylic resin, polyethylene, polypropylene, polyvinyl chloride, phenolic resin, silicone resin, synthetic rubber, cellulose, and triacetate. Examples of metals include gold, silver, copper, and aluminum. Examples of semiconductors include silicon, gallium arsenide, and indium phosphide.

[0076] Among these, inorganic materials are preferred. For example, when the particles are photocatalytic particles, a substrate containing an inorganic material is stable against radicals generated in the photocatalytic reaction.

[0077] Furthermore, when the substrate is a fibrous substrate, the preferred materials for the substrate are the same as those described above in the section "A. Particle-attached substrate."

[0078] The method for producing the substrate is appropriately selected depending on the form and material of the substrate, and known methods can be applied. Commercially available products may also be used as the substrate.

[0079] 2. Particles The particles used in the present disclosure are the same as the particles in the particle-attached substrate described above.

[0080] Here, the particle diameter of the particles can be measured by observation with a scanning electron microscope (SEM). The average particle diameter of the particles refers to the arithmetic mean value of the particle diameters of 20 particles measured by SEM observation. Note that if the shape of the particles is not spherical, the particle diameter is the major axis.

[0081] In the inorganic film forming step described below, classified particles may be used in order to ensure that the degree of inorganic film coverage on the particles is uniform.

[0082] 3. Functional Group Introduction Step In the functional group introduction step of the present disclosure, functional groups that become positively or negatively charged in water are introduced onto the surface of the substrate. By performing the functional group introduction step, particles can be easily electrostatically adsorbed onto the surface of the substrate to which the functional groups have been introduced in the particle electrostatic adsorption step described below.

[0083] In the case of functional groups that are positively or negatively charged in water, the positive or negative charge is appropriately selected depending on the particle.

[0084] The functional group that becomes positively charged in water is not particularly limited, and examples thereof include an amino group, an ammonium group, a pyridinium group, an imidazole group, and a guanidino group.

[0085] The functional group that becomes negatively charged in water is not particularly limited, and examples thereof include a carboxy group, a sulfo group, and a phosphate group.

[0086] In the functional group introduction step, functional groups that become positively or negatively charged in water can be introduced onto the surface of the substrate by treating the substrate with a compound that contains a functional group that becomes positively or negatively charged in water and a functional group that can bond to a functional group present on the surface of the substrate.

[0087] The functional group capable of bonding to the functional group present on the surface of the substrate is appropriately selected depending on the material of the substrate and the surface activation step described below. Examples of the functional group capable of bonding to the functional group present on the surface of the substrate include an alkoxy group, a hydroxy group, an acryloyl group, an epoxy group, a urethane group, a vinyl group, and a mercapto group.

[0088] The compound containing a functional group that is positively or negatively charged in water and a functional group that can bond with a functional group present on the surface of the substrate is appropriately selected depending on these functional groups.

[0089] Examples of compounds containing a functional group that is positively charged in water and a functional group that can bond with a functional group present on the surface of a substrate include compounds containing an amino group and an alkoxy group or a hydroxy group. Examples of compounds containing an amino group and an alkoxy group or a hydroxy group include silane coupling agents containing an amino group or hydrolysates thereof. Examples of silane coupling agents containing an amino group and hydrolysates thereof include 3-aminopropyltrimethoxysilane and hydrolysates thereof, 3-aminopropyltriethoxysilane and hydrolysates thereof, 3-aminopropylmethyldimethoxysilane and hydrolysates thereof, 3-(2-aminoethylamino)propyltrimethoxysilane and hydrolysates thereof, 3-(2-aminoethylamino)propyltriethoxysilane and hydrolysates thereof, and 3-(2-aminoethylamino)propylmethyldimethoxysilane and hydrolysates thereof. The above compounds may be used alone or in combination of two or more.

[0090] Examples of compounds containing a functional group that is negatively charged in water and a functional group that can bond with a functional group present on the surface of a substrate include N-(trimethoxysilyl)ethylenediaminetriacetic acid sodium salt, 3-(trihydroxysilyl)-1-propanesulfonic acid, and 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane. One of the above compounds may be used alone, or two or more may be used in combination.

[0091] The method for treating the surface of the substrate with the compound is not particularly limited, and examples thereof include a method of applying the compound to the surface of the substrate and a vapor deposition method. Known application methods can be used, such as spray coating, spin coating, and dip coating. Vapor deposition methods include physical vapor deposition (PVD) and chemical vapor deposition (CVD). PVD methods include vacuum deposition, sputtering, and ion plating. CVD methods include thermal CVD, plasma CVD, and photo-CVD.

[0092] When applying the compound to the surface of a substrate, a composition containing the compound and an organic solvent can be used. When the compound is a silane coupling agent containing an amino group or a hydrolyzate thereof, an alcohol can be used as the organic solvent contained in the composition. Examples of alcohol include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, and n-butanol.

[0093] In addition, when using a silane coupling agent, the composition may further contain water. When the composition contains water, the hydrolysis reaction of the silane coupling agent occurs in the composition. This results in a composition containing the hydrolyzate of the silane coupling agent as the compound.

[0094] Furthermore, when the compound is a silane coupling agent containing an amino group or a hydrolysate thereof, the composition may further contain a water-soluble polymer. The inclusion of a water-soluble polymer in the composition improves the dispersibility of the silane coupling agent containing an amino group or a hydrolysate thereof. Therefore, functional groups that are positively or negatively charged in water can be uniformly introduced onto the surface of the substrate. Furthermore, as described below, when the composition is applied and then dried, removal of the silane coupling agent containing an amino group or a hydrolysate thereof during drying can be suppressed. Examples of water-soluble polymers include polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyacrylic acid, and polyethylene glycol. Among these, polyvinyl alcohol is preferred.

[0095] On the other hand, when the compound is a silane coupling agent containing an amino group or a hydrolyzate thereof, the composition does not need to contain a water-soluble polymer, which can prevent the water-soluble polymer from interfering with the introduction of functional groups that become positively or negatively charged in water onto the surface of the substrate.

[0096] The content of the water-soluble polymer in the composition is, for example, 100 parts by mass or less, or may be 10 parts by mass or less, or may be 1 part by mass or less, relative to 100 parts by mass of the compound.

[0097] When the compound is a silane coupling agent containing an amino group or a hydrolyzate thereof, the composition may be dried after application.The drying method is not particularly limited as long as it can be dried at room temperature, and examples thereof include air knife drying, spin drying, vacuum drying, and squeeze drying.The drying method may be used alone or in combination of two or more.

[0098] When the compound is a silane coupling agent containing an amino group or a hydrolysate thereof, the composition is applied, dried as necessary, and then heat-treated. This allows a condensation reaction to proceed, and the compound is immobilized on the surface of the substrate. The temperature and time of the heat treatment are appropriately selected depending on the type of silane coupling agent. When a silane coupling agent containing an amino group or a hydrolysate thereof is used, the heating temperature is, for example, 40°C or higher and 250°C or lower, or 70°C or higher and 200°C or lower, or 100°C or higher and 150°C or lower. When a silane coupling agent containing an amino group or a hydrolysate thereof is used, the heating time is, for example, 10 seconds or higher and 30 minutes or lower, or 30 seconds or higher and 10 minutes or lower, or 60 seconds or higher and 5 minutes or lower.

[0099] The thickness of the film containing the compound is usually thin, and it is sufficient if it is at least the thickness of a monolayer, for example, 2 nm to 20 nm.

[0100] 4. Particle Electrostatic Adsorption Step In the particle electrostatic adsorption step of the present disclosure, particles are electrostatically adsorbed to functional groups that are introduced onto the surface of the substrate and that become positively or negatively charged in water. In the particle electrostatic adsorption step, particles are electrostatically adsorbed onto the surface of the substrate by utilizing the electrostatic interaction that occurs between the functional groups that are introduced onto the surface of the substrate in the functional group introduction step and that become positively or negatively charged in water.

[0101] When the particle surfaces are not charged at all or are almost not charged at all, it is preferable to carry out an organic polymer adsorption step as described below.

[0102] In the particle electrostatic adsorption step, a composition containing particles, water, and an organic solvent is applied to the surface of a substrate, and the particles can be electrostatically adsorbed onto the surface of the substrate to which functional groups that become positively or negatively charged in water have been introduced. As the application method, a known application method can be applied, for example, spray coating, spin coating, or dip coating.

[0103] The organic solvent contained in the composition may be an alcohol, such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, or n-butanol.

[0104] The composition may further contain a water-soluble polymer, such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyacrylic acid, or polyethylene glycol.

[0105] After application, the composition may be dried. The drying method is not particularly limited, and examples thereof include air knife drying, heat drying, vacuum drying, spin drying, and squeeze drying. One drying method may be used alone, or two or more drying methods may be used in combination.

[0106] In particular, when the substrate is a fiber substrate and the inorganic film is formed by a sol-gel method in the inorganic film forming step described later, heat drying is preferred. By sufficiently drying the fiber substrate by heat drying, the composition containing the metal alkoxide, water, and solvent can be easily penetrated into the fiber substrate as the substrate in the inorganic film forming step. This allows the inorganic film to be formed uniformly over the entire surface of the fiber substrate as the substrate.

[0107] In the case of heat drying, the drying temperature and drying time are appropriately selected depending on, for example, the type of particles and the type and amount of solvent. The drying temperature is, for example, 40°C or higher and 250°C or lower, or may be 70°C or higher and 200°C or lower, or 100°C or higher and 150°C or lower. The drying time is, for example, 10 seconds or higher and 30 minutes or lower, or may be 30 seconds or higher and 10 minutes or lower, or may be 60 seconds or higher and 5 minutes or lower.

[0108] 5. Inorganic Film Forming Step In the inorganic film forming step according to the present disclosure, after the particle electrostatic adsorption step, an inorganic film containing an inorganic compound is formed so as to cover the surface of the substrate. By performing the inorganic film forming step, the particles electrostatically adsorbed to the surface of the substrate can be firmly fixed, and particle detachment can be suppressed.

[0109] The inorganic compound is the same as the inorganic compound used in the inorganic film of the particle-attached substrate described above.

[0110] The method for forming the inorganic film is not particularly limited as long as it is a method that can form an inorganic film so as to cover the surface of the substrate, and examples thereof include the sol-gel method and the vapor deposition method.

[0111] When the inorganic compound is silica, the inorganic film is preferably formed by treating the surface of the substrate with an organosilicon compound, such as the sol-gel method or vapor deposition method, as described above.

[0112] Examples of vapor deposition methods include physical vapor deposition (PVD) and chemical vapor deposition (CVD). Examples of PVD methods include vacuum deposition, sputtering, and ion plating. Examples of CVD methods include thermal CVD, plasma CVD, and photo CVD.

[0113] Of these, the sol-gel method is preferred.

[0114] In the sol-gel method, a composition containing a metal alkoxide, water, and an organic solvent is prepared and applied to the surface of a substrate, followed by a heat treatment. In the composition, the metal alkoxide undergoes hydrolysis and polycondensation reactions. Further, the metal alkoxide is converted into an inorganic oxide by the heat treatment.

[0115] The metal alkoxide used in the composition can be represented by the following general formula (1): １ ｎ M (OR ２ ) ｍ (1) (In the above formula (1), R １ and R ２ each independently represents an organic group having 1 to 8 carbon atoms, M represents a metal atom, n represents an integer of 0 or more, m represents an integer of 1 or more, and n+m represents the atomic valence of M.

[0116] Examples of the metal atom M include silicon, zirconium, titanium, and aluminum, with silicon being preferred.

[0117] R １ and R ２Examples of the organic group represented by the formula (I) include alkyl groups. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, and isobutyl groups. These alkyl groups may be the same or different in the same molecule.

[0118] Preferably, n is 0.

[0119] The metal alkoxide is not particularly limited. For example, a metal alkoxide in which the metal atom M is silicon and n is 0 is a tetraalkoxysilane. Examples of tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. One type of metal alkoxide may be used alone, or two or more types may be used in combination.

[0120] In the composition, the metal alkoxide may be partially hydrolyzed or partially condensed to form an oligomer, i.e., the composition may contain a hydrolysate or hydrolysis polycondensate of the metal alkoxide.

[0121] The organic solvent contained in the composition may be an alcohol, such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, or n-butanol.

[0122] The composition may further contain a water-soluble polymer. The inclusion of a water-soluble polymer in the composition improves the dispersibility of the metal alkoxide, its hydrolysate, or hydrolysis polycondensate. This allows for a uniform formation of an inorganic film on the surface of a substrate. Furthermore, as described below, when the composition is applied and then dried, removal of the metal alkoxide, its hydrolysate, or hydrolysis polycondensate during drying can be suppressed. Examples of water-soluble polymers include polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyacrylic acid, and polyethylene glycol. Among these, polyvinyl alcohol is preferred. Polyvinyl alcohol is generally obtained by saponifying polyvinyl acetate. Polyvinyl alcohol may be partially saponified polyvinyl alcohol, in which several tens of percent of acetate groups remain, or fully saponified polyvinyl alcohol, in which no acetate groups remain. However, fully saponified polyvinyl alcohol is preferred. The degree of polymerization of the polyvinyl alcohol is, for example, 1,500 or more and 2,000 or less.

[0123] The content of the water-soluble polymer in the composition is, for example, 1 part by mass or more and 100 parts by mass or less, or may be 5 parts by mass or more and 50 parts by mass or less, or may be 10 parts by mass or more and 25 parts by mass or less, relative to 100 parts by mass of the compound.

[0124] The composition may contain, as needed, for example, a catalyst that promotes the hydrolysis reaction of the metal alkoxide, or a stabilizer that controls the polycondensation reaction of the metal alkoxide. Examples of catalysts include hydrochloric acid, sulfuric acid, nitric acid, and carboxylic acid. Examples of stabilizers include acetylacetone, aminoalcohols, alkylamines, and N,N-dimethylformamide. Note that when tetraethoxysilane (TEOS) is used, the addition of a stabilizer is not necessary.

[0125] The composition can be applied by any known application method, such as spray coating, spin coating, or dip coating.

[0126] When the composition is applied, the degree of coating of the particles with the inorganic film can be controlled by adjusting the application conditions.

[0127] After application, the composition may be dried. The drying method is not particularly limited as long as it can be performed at room temperature, and examples thereof include air knife drying, spin drying, vacuum drying, and squeeze drying. One drying method may be used alone, or two or more drying methods may be used in combination.

[0128] The composition is applied, dried as necessary, and then heat-treated. The temperature and time of the heat treatment are not particularly limited as long as an inorganic oxide is obtained, and are appropriately selected depending on, for example, the type of metal alkoxide. The heating temperature is, for example, 40°C or higher and 250°C or lower, or may be 70°C or higher and 200°C or lower, or may be 100°C or higher and 150°C or lower. The heating time is, for example, 10 seconds or higher and 30 minutes or lower, or may be 30 seconds or higher and 10 minutes or lower, or may be 60 seconds or higher and 5 minutes or lower.

[0129] In the case of a method in which the surface of the substrate is treated with an organosilicon compound, the organosilicon compound is preferably tetraalkoxysilane or a hydrolyzate or hydrolysis polycondensate thereof, as described above.

[0130] The thickness of the inorganic film is the same as that of the inorganic film in the particle-attached substrate described above.

[0131] 6. Surface Activation Step The method for producing a particle-attached substrate according to the present disclosure may include a surface activation step of performing a surface activation treatment on the surface of the substrate prior to the functional group introduction step. By performing the surface activation step, it becomes easier to introduce predetermined functional groups onto the surface of the substrate in the functional group introduction step.

[0132] Surface activation treatments include physical treatments, chemical treatments, and thin film formation.

[0133] Examples of physical treatments include corona treatment, plasma treatment, ultraviolet treatment, electron beam treatment, and flame treatment.

[0134] Examples of chemical treatments include solvent treatments and chemical treatments.

[0135] In the case of forming a thin film, the thin film may be an inorganic film containing an inorganic compound. The inorganic film is the same as the inorganic film in the inorganic film forming step. The thin film forming method is the same as the inorganic film forming method in the inorganic film forming step.

[0136] 7. Organic Polymer Adsorption Step The method for producing a particle-attached substrate according to the present disclosure may include an organic polymer adsorption step, prior to the particle electrostatic adsorption step, in which an organic polymer that is positively or negatively charged in water is adsorbed onto the surface of the particles. In this case, the functional group that is positively or negatively charged in water and the organic polymer that are introduced onto the surface of the substrate have opposite charges in water. Note that when the organic polymer has both positive and negative charges in the molecule, the net charge in water is considered.

[0137] When the particle surface is not charged or is hardly charged at all, it is preferable to carry out an organic polymer adsorption step.

[0138] The organic polymer may be any organic polymer containing a functional group that is positively or negatively charged in water. The functional group contained in the organic polymer that is positively or negatively charged in water is the same as the functional group that is positively or negatively charged in water used in the functional group introduction step.

[0139] The organic polymer that is positively charged in water is not particularly limited, and examples thereof include polyethyleneimine.

[0140] The organic polymer that becomes negatively charged in water is not particularly limited, and examples thereof include polycarboxylic acids, such as polyacrylic acid and polymethacrylic acid.

[0141] The organic polymer may contain both a functional group that is positively charged in water and a functional group that is negatively charged in water. Examples of such organic polymers include gelatin and collagen.

[0142] The weight-average molecular weight of the organic polymer is, for example, from 10,000 to 1,000,000, and may be from 50,000 to 250,000. The weight-average molecular weight is a value measured by gel permeation chromatography (GPC) using polystyrene as a standard substance.

[0143] In the organic polymer adsorption step, the particles are dispersed in a composition containing an organic polymer, so that the organic polymer can be adsorbed onto the surface of the particles.

[0144] The composition may contain an organic polymer and a solvent. The solvent may be appropriately selected depending on the type of organic polymer, and may be, for example, water. That is, the composition may be an aqueous solution in which the organic polymer is dissolved.

[0145] After dispersing the particles in the composition, the particles may be washed to remove any unadsorbed organic polymers.

[0146] 8. Others The method for producing a particle-attached substrate according to the present disclosure may be carried out by a sheet-feed method or a roll-to-roll method. In the case of the roll-to-roll method, the roll-to-roll method may be applied to each step, or each step may be carried out continuously by the roll-to-roll method.

[0147] In a particle-attached substrate manufactured by the particle-attached substrate manufacturing method according to the present disclosure, the amount of particles is not particularly limited as long as the amount is an amount that allows the particles to exhibit their intended function, and is appropriately set depending on the type of particles and the intended use of the particle-attached substrate. The amount of particles in the particle-attached substrate corresponds to the increase in mass before and after the particle electrostatic adsorption process. Therefore, the particle immobilization rate is defined as in the following formula (1): Particle immobilization rate [%] = (mass of particles immobilized on substrate) / (mass of particle-attached substrate) = (mass after particle electrostatic adsorption process - mass before particle electrostatic adsorption process) / (mass of particle-attached substrate) (1) The particle immobilization rate is, for example, preferably 1% or more and 50% or less, and more preferably 5% or more and 25% or less.

[0148] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure.

[0149] The present disclosure will be further described below with reference to examples and comparative examples.

[0150] [Example 1] (1) Surface activation step Chemical solution 1 having the following composition was prepared. After stirring at room temperature for 30 minutes, chemical solution 1 became a uniform, colorless, transparent solution. Commercially available tetraethoxysilane was used as is. <Chemical solution 1> Tetraethoxysilane (Tokyo Chemical Industry Co., Ltd.) 5.5 g IPA 1.5 g Pure water 7.5 g Hydrochloric acid (0.5 M) 180 μL

[0151] Chemical solution 2 having the following composition was prepared. Chemical solution 2 became a uniform, colorless, transparent solution after stirring for 20 minutes at a liquid temperature of 80 to 90°C. Polyvinyl alcohol (polymerization degree 1500, fully saponified type) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used as is. <Chemical solution 2> Polyvinyl alcohol (polymerization degree 1500, fully saponified type) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 2.5 g Pure water 47.5 g

[0152] Paint A having the following composition was prepared. After stirring at room temperature for 1 minute, Paint A became a uniform, colorless, transparent solution. <Paint A> Chemical solution 1 12.5 g Chemical solution 2 17.5 g

[0153] A glass fiber nonwoven fabric (mass 65.9 mg, thickness 0.20 mm, basis weight 25 g / m) cut into a 5 cm square size ２ A fiber (fiber diameter: 10 μm) was immersed in paint A and immediately pulled out. Excess paint A was removed by centrifugation (centrifugal force: 500 × g, 1 minute), and then the fiber was heated at 180°C for 2 minutes. This resulted in an increase in mass of 1.6 mg. The mass was measured using an electronic balance (manufactured by Mettler Toledo, model number: AB104-S, minimum display: 0.1 mg).

[0154] (2) Functional Group Introduction Step Paint B having the following composition was prepared. Paint B became a uniform, colorless, transparent solution after stirring at room temperature for 10 minutes. Commercially available 3-aminopropyltrimethoxysilane was used as is. <Paint B> 3-aminopropyltrimethoxysilane (Tokyo Chemical Industry Co., Ltd.) 1.0 g IPA 5.0 g Pure water 45.0 g

[0155] The glass fiber nonwoven fabric after the surface activation step was immersed in paint B. After confirming that paint B had sufficiently permeated the glass fiber nonwoven fabric, the glass fiber nonwoven fabric was immediately pulled out. Excess paint B was removed by centrifugation (centrifugal force 500 × g, 1 minute), and then the fabric was heated at 180 ° C. for 2 minutes. No increase in mass was observed.

[0156] (3) Synthesis of Polymethylsilsesquioxane Particles Polymethylsilsesquioxane (PMSQ) particles were synthesized according to the following procedure. First, 10 g of methyltriethoxysilane (Tokyo Chemical Industry Co., Ltd.), 8 g of ethanol, and 1 g of hydrochloric acid (0.1 M) were stirred at room temperature for 30 minutes. 70 mL of an aqueous solution of sodium dodecyl sulfate (0.01% by mass) and 10 mL of aqueous ammonia (29% by mass) were added thereto and stirred for 30 minutes. The formed particles were precipitated by centrifugation, and the supernatant was removed.

[0157] The precipitated particles were then dispersed in 15 mL of IPA, and 15 g of a 50 mM aqueous sodium hydroxide solution was added. After 15 minutes, the particles were precipitated by centrifugation, and the supernatant was removed.

[0158] (4) Organic Polymer Adsorption Step: The PMSQ particles were dispersed in 20 g of a 0.05% aqueous gelatin solution and stirred for 60 minutes. The particles were then precipitated by centrifugation, and the supernatant was removed. The precipitated particles were dispersed in 40 mL of pure water, and again precipitated by centrifugation, and the supernatant was removed. Finally, the precipitated particles were dispersed in a 10 wt% aqueous methanol solution (solid concentration: 2.4% by mass). SEM observation revealed that the average particle size of the PMSQ particles was approximately 1 μm. Figure 7 shows an SEM photograph.

[0159] (5) Particle Electrostatic Adsorption Process After the functional group introduction process, the glass fiber nonwoven fabric was immersed in a dispersion of PMSQ particles with gelatin adsorbed on the surface. After confirming that the dispersion had sufficiently permeated the glass fiber nonwoven fabric, the glass fiber nonwoven fabric was immediately lifted out. After removing excess dispersion by centrifugation (centrifugal force 500 × g, 1 minute), the fabric was heated at 180 °C for 2 minutes. This resulted in an increase in mass of 4.4 mg.

[0160] (6) Inorganic Film Formation Step The glass fiber nonwoven fabric after the particle electrostatic adsorption step was immersed in paint A. After confirming that paint A had sufficiently permeated the glass fiber nonwoven fabric, the glass fiber nonwoven fabric was immediately lifted out. Excess paint A was removed by centrifugation (centrifugal force 500 × g, 1 minute), and then heated at 180 ° C for 2 minutes. This resulted in an increase in mass of 2.2 mg. The final mass of the particle-attached substrate was 74.7 mg, and the particle immobilization rate was 5.9%.

[0161] (7) Evaluation SEM observation of the obtained particle-attached substrate revealed that the PMSQ particles were densely immobilized in a state covered with a silica film. Figure 8(b) shows an SEM photograph of the glass fiber nonwoven fabric before particle immobilization, and Figure 8(a) shows an SEM photograph of the particle-attached substrate. Even when the particle-attached substrate was subjected to ultrasonic treatment in water, the PMSQ particles did not fall off. Furthermore, even when the particle-attached substrate was gently rubbed with a finger, the PMSQ particles did not adhere to the finger.

[0162] [Example 2] (1) Surface activation step and functional group introduction step A glass fiber nonwoven fabric (mass 66.3 mg, thickness 0.20 mm, basis weight 25 g / m) was cut into a 5 cm square size. ２ The surface activation step and the functional group introduction step were carried out in the same manner as in Example 1, except that a 1000-kJ / cm2 fiber (fiber diameter: 10 μm) was used.

[0163] (2) Particle Electrostatic Adsorption Step Titanium oxide particles (Kanto Chemical Co., Inc., particle diameter 0.1 μm to 0.3 μm) were used to prepare a titanium oxide aqueous dispersion (2 mass %). Note that the titanium oxide particles are originally negatively charged in water, so the organic polymer adsorption step is not necessary.

[0164] The glass fiber nonwoven fabric after the functional group introduction step was immersed in an aqueous titanium oxide dispersion. After confirming that the aqueous titanium oxide dispersion had sufficiently permeated the glass fiber nonwoven fabric, the glass fiber nonwoven fabric was immediately lifted out. Excess titanium oxide aqueous dispersion was removed by centrifugation (centrifugal force 500 × g, 1 minute), and then the fabric was heated at 180 °C for 2 minutes. This resulted in an increase in mass of 3.7 mg.

[0165] (3) Inorganic Film Formation Step The glass fiber nonwoven fabric after the particle electrostatic adsorption step was immersed in paint A. After confirming that the paint had sufficiently permeated the glass fiber nonwoven fabric, the glass fiber nonwoven fabric was immediately lifted out. Excess paint was removed by centrifugation (centrifugal force 500 × g, 1 minute), and then heated at 180 °C for 2 minutes. This resulted in an increase in mass of 1.7 mg. The final mass of the particle-attached substrate was 72.4 mg, and the particle immobilization rate was 5.1%.

[0166] (4) Evaluation SEM observation of the obtained particle-attached substrate revealed that the titanium oxide particles were covered with a silica film and immobilized at a high density. Figure 9 shows an SEM photograph. Even when the particle-attached substrate was subjected to ultrasonic treatment in water, the titanium oxide particles did not fall off. Furthermore, even when the particle-attached substrate was gently rubbed with a finger, the titanium oxide particles did not adhere to the finger.

[0167] Furthermore, when a portion of the silica film on the particle-attached substrate was intentionally destroyed and the cross section of the silica film was observed using an SEM, the thickness of the silica film was found to be approximately 50 nm. Furthermore, when the destroyed silica film fragment was observed using a TEM, an image of randomly arranged black spots was observed. This is an observation image characteristic of an amorphous film, and from the size of these spots, the pore size was estimated to be 1 nm or less.

[0168] [Example 3] A particle-attached substrate was prepared in the same manner as in Example 2, except that in the inorganic film-forming step, paint A was diluted two-fold with pure water. Since the mass increased by 0.3 mg in the inorganic film-forming step, the thickness of the silica film was estimated to be 10 nm. Even when the particle-attached substrate was subjected to ultrasonic treatment in water, the titanium oxide particles did not fall off. Furthermore, even when the particle-attached substrate was gently rubbed with a finger, the titanium oxide particles did not adhere to the finger.

[0169] [Example 4] A particle-attached substrate was prepared in the same manner as in Example 2, except that paint A was diluted four times with pure water in the inorganic film-forming step. Since the mass increased by 0.1 mg in the inorganic film-forming step, the thickness of the silica film was estimated to be 3 nm. Even when the particle-attached substrate was subjected to ultrasonic treatment in water, the titanium oxide particles did not fall off. Furthermore, even when the particle-attached substrate was gently rubbed with a finger, the titanium oxide particles did not adhere to the finger.

[0170] Example 5 A particle-attached substrate was prepared in the same manner as in Example 2, except that polystyrene (PS) particles (Merck, particle diameter 5 μm) were used in the particle electrostatic adsorption step. Since the mass increased by 2.7 mg in the inorganic film formation step, the thickness of the silica film was estimated to be 79 nm. Even when the particle-attached substrate was subjected to ultrasonic treatment in water, the polystyrene particles did not fall off. Furthermore, even when the particle-attached substrate was gently rubbed with a finger, the polystyrene particles did not adhere to the finger.

[0171] [Comparative Example 1] A particle-attached substrate was prepared in the same manner as in Example 1, except that the inorganic film-forming step was omitted. When the obtained particle-attached substrate was subjected to ultrasonic treatment in water, most of the PMSQ particles fell off. Furthermore, when the particle-attached substrate was gently rubbed with a finger, the PMSQ particles adhered to the finger. This indicates that the inorganic film-forming step is essential for preventing particle fall-off.

[0172] The data for the above examples and comparative examples are summarized in Table 1.

[0173]

[0174] The present disclosure provides the following items [1] to

[18] . [1] A particle-attached substrate comprising: a fibrous substrate containing inorganic fibers; an inorganic film containing an inorganic compound disposed on the surface of the fibrous substrate; and functional particles fixed to the surface side of the fibrous substrate by the inorganic film. [2] The particle-attached substrate according to [1], wherein the inorganic film has a thickness of 2 nm to 100 nm. [3] The particle-attached substrate according to [1] or [2], wherein the inorganic film is a porous film. [4] The particle-attached substrate according to any one of [1] to [3], wherein the average particle diameter of the functional particles is 0.1 μm to 10 μm. [5] The particle-attached substrate according to any one of [1] to [4], wherein the functional particles are photocatalytic particles. [6] The particle-attached substrate according to any one of [1] to [5], wherein the inorganic compound is silica. [7] The particle-attached substrate according to any one of [1] to [6], wherein the inorganic fibers are glass fibers or alumina-based fibers. [8] A method for producing a particle-attached substrate, comprising: a functional group introduction step of introducing functional groups that are positively or negatively charged in water onto the surface of the substrate; a particle electrostatic adsorption step of electrostatically adsorbing functional particles onto the surface of the substrate onto which the functional groups have been introduced; and an inorganic film formation step of forming an inorganic film containing an inorganic compound so as to cover the surface of the substrate after the particle electrostatic adsorption step. [9] A method for producing a particle-attached substrate according to [8], wherein the average particle diameter of the functional particles is from 0.1 μm to 10 μm.

[10] A method for producing a particle-attached substrate according to [8] or [9], wherein the functional particles are photocatalytic particles.

[11] A method for producing a particle-attached substrate according to any one of [8] to

[10] , wherein the inorganic compound is silica, and the surface of the substrate is treated with an organosilicon compound in the inorganic film formation step.

[12] A method for producing a particle-attached substrate according to

[11] , wherein the organosilicon compound is tetraalkoxysilane, or a hydrolysate or hydrolysis polycondensate thereof.

[13] The method for producing a particle-attached substrate according to any one of [8] to

[12] , wherein in the functional group introduction step, the surface of the substrate is treated with a silane coupling agent containing an amino group or a hydrolyzate thereof.

[14] A method for producing a particle-attached substrate according to any one of [8] to

[13] , which includes a surface activation step of performing a surface activation treatment on the surface of the substrate before the functional group introduction step.

[15] A method for producing a particle-attached substrate according to any one of [7] to

[13] , which includes an organic polymer adsorption step of adsorbing an organic polymer that is at least positively or negatively charged in water onto the surface of the functional particles before the particle electrostatic adsorption step, wherein the functional group and the organic polymer have opposite charges in water.

[16] A method for producing a particle-attached substrate according to any one of [8] to

[15] , wherein the substrate is a fibrous substrate.

[17] A method for producing a particle-attached substrate according to

[16] , wherein the fibrous substrate contains inorganic fibers.

[18] A method for producing a particle-attached substrate according to

[17] , wherein the inorganic fibers are glass fibers or alumina-based fibers.

[0175] REFERENCE SIGNS LIST 1 fiber substrate 2 inorganic film 3 particles 10 substrate with particles 11 substrate 20 substrate with particles

Claims

1. A fiber substrate containing inorganic fibers, An inorganic film disposed on the surface of the fiber substrate and containing an inorganic compound, Functional particles immobilized by the inorganic film on the surface side of the fiber substrate, A substrate with particles, which has the inorganic film with a thickness smaller than the average particle diameter of the functional particles.

2. The substrate with particles according to Claim 1, wherein the thickness of the inorganic film is 2 nm or more and 100 nm or less.

3. The substrate with particles according to Claim 1 or Claim 2, wherein the inorganic film is a porous film.

4. The substrate with particles according to Claim 1 or Claim 2, wherein the average particle diameter of the functional particles is 0.1 μm or more and 10 μm or less.

5. The substrate with particles according to Claim 1 or Claim 2, wherein the functional particles are photocatalyst particles.

6. The substrate with particles according to Claim 1 or Claim 2, wherein the inorganic compound is silica.

7. The substrate with particles according to Claim 1 or Claim 2, wherein the inorganic fibers are glass fibers or alumina-based fibers.

8. A functional group introduction step of introducing a functional group that is positively or negatively charged in water onto the surface of the substrate, A particle electrostatic adsorption step of electrostatically adsorbing functional particles onto the surface of the substrate onto which the functional group has been introduced, An inorganic film formation step of forming an inorganic film containing an inorganic compound so as to cover the surface of the substrate after the particle electrostatic adsorption step, A method for manufacturing a substrate with particles, which has these steps.

9. The method for manufacturing a substrate with particles according to Claim 8, wherein the average particle diameter of the functional particles is 0.1 μm or more and 10 μm or less.

10. The method for manufacturing a substrate with particles according to Claim 8 or Claim 9, wherein the functional particles are photocatalyst particles.

11. The inorganic compound is silica, In the inorganic film formation step, the surface of the substrate is treated with an organosilicon compound. The method for manufacturing a substrate with particles according to Claim 8 or Claim 9.

12. The method for manufacturing a substrate with particles according to Claim 11, wherein the organosilicon compound is tetraalkoxysilane or its hydrolyzate or hydrolysis polycondensate.

13. In the functional group introduction step, the surface of the substrate is treated with a silane coupling agent containing an amino group or its hydrolyzate. The method for manufacturing a substrate with particles according to Claim 8 or Claim 9.

14. The method for producing a substrate with particles according to claim 8 or claim 9, comprising a surface activation step of subjecting the surface of the substrate to a surface activation treatment before the functional group introduction step.

15. The method for producing a substrate with particles according to claim 8 or claim 9, comprising an organic polymer adsorption step of adsorbing an organic polymer that is charged positively or negatively in water onto the surface of the functional particles before the particle electrostatic adsorption step, wherein the functional group and the organic polymer have opposite charges in water.

16. The method for producing a substrate with particles according to claim 8 or claim 9, wherein the substrate is a fibrous substrate.

17. The method for producing a substrate with particles according to claim 16, wherein the fibrous substrate contains inorganic fibers.

18. The method for producing a substrate with particles according to claim 17, wherein the inorganic fibers are glass fibers or alumina-based fibers.