Antiviral composition and member having same on surface

Abstract

Provided is an antiviral composition having a photocatalytic function and exhibiting high antiviral properties against viruses that have not been enveloped and that have been difficult to inactivate with a silver compound so far in a dark place where illumination is not possible. The antiviral composition contains the following two kinds of particles: photocatalyst particles; and silver nanoparticles having a dispersion particle diameter of 1000 nm or less and a primary particle diameter of 500 nm or less, the silver nanoparticles having a protective agent adsorbed on the surface thereof. The antiviral activity value in the dark in accordance with JIS R1756: 2020 is greater than 0.3, and the antiviral activity value due to light irradiation in accordance with JIS R1756: 2020 is 0.3 or more.

Description

Technical Field

[0001] The present invention relates to an antiviral composition containing photocatalyst particles and silver nanoparticles as active ingredients and a member having the composition on the surface. More specifically, it relates to a highly transparent antiviral composition that exhibits antiviral properties in the dark and whose antiviral properties are further improved by irradiation with light and a member having the composition on the surface. Background Art

[0002] In recent years, consumers have been increasingly pursuing a hygienic living environment, and interest in daily necessities that have been processed to maintain cleanliness, such as antiviral properties, has been growing.

[0003] If a composition having antiviral properties can be formed on the surfaces of various members, it can be widely used, and therefore a technology for imparting antiviral properties to members is required.

[0004] When the object to be imparted with antiviral properties is a member requiring visibility such as an operation touch panel or a member having design characteristics, it is desirable that the composition having antiviral properties formed on the surface thereof has excellent transparency.

[0005] It is known that copper oxide compounds such as cuprous oxide have antiviral properties (Patent Document 1). However, monovalent copper is easily oxidized to divalent copper by air or water, and there is a problem that the high antiviral properties of monovalent copper cannot be maintained.

[0006] There are many reports that silver shows a wide antibacterial spectrum, for example, Patent Document 2 discloses an antibacterial agent that utilizes the antibacterial effect of silver ions. On the other hand, the current situation is that there are fewer reports on the antiviral properties of silver than on the antibacterial properties. In addition, silver is considered to have low antiviral properties against viruses without an envelope (Non-Patent Document 1).

[0007] Patent Document 3 reports the antiviral activity of silver particles against influenza viruses. However, there is no mention of the antiviral activity against viruses that do not have an envelope, nor is there any description of the effect of light irradiation.

[0008] Patent Document 4 reports that metal particles containing silver particles and platinum particles exhibit antiviral properties against non-enveloped viruses. However, it is recorded that silver particles alone cannot inactivate viruses such as adenovirus. In addition, Patent Document 4 evaluates the antiviral properties of antiviral agent dispersions, but does not mention imparting antiviral properties to components.

[0009] The antiviral properties of molybdenum oxide and zinc oxide have been reported (Patent Documents 5 and 6). However, these metal oxides are easily aggregated, and it is difficult to obtain a composition having the required transparency for practical use.

[0010] Photocatalytic materials have attracted attention due to their photocatalytic reactions when exposed to light such as sunlight and artificial lighting, which have a wide range of effects on cleaning the surface of substrates, such as antibacterial, antifungal, antiviral, and deodorizing.

[0011] The so-called photocatalytic reaction refers to the reaction caused by excited electrons and holes generated by photocatalysts represented by titanium oxide absorbing light. The excited electrons and holes generated on the surface of titanium oxide by the photocatalytic reaction undergo redox reactions with oxygen or water adsorbed on the surface of titanium oxide to generate active species. It is believed that microorganisms, viruses, odors and dirt composed of organic matter are decomposed by the active species, so the above-mentioned cleaning effect of the substrate surface can be obtained. However, the photocatalytic reaction caused by titanium oxide, which is a representative photocatalyst, is caused by irradiation with light in the ultraviolet region (wavelength 10 to 420nm), so in principle, such an effect cannot be obtained in dark places where natural light and artificial lighting cannot reach, and under white LED lighting and fluorescent lighting that almost do not contain light with a wavelength of less than 420nm. In addition, although research is being conducted on the visible light response of titanium oxide and tungsten oxide with a wide wavelength range of available light, light irradiation is indispensable for the generation of excited electrons.

[0012] On the other hand, it is known that viruses attached to the surface of objects maintain their infection levels for several hours to several days. For products such as antiviral products that require sustained performance, materials that exhibit antiviral properties even in a dark place without light exposure are required.

[0013] In order to cope with the above-mentioned problems, research on photocatalytic materials that supplement the photocatalyst function by using a photocatalyst and an antiviral agent other than the photocatalyst has been conducted (Patent Document 7, Patent Document 8). Since the photocatalyst decomposes organic matter, it is appropriate to use an inorganic antiviral agent. For example, Patent Document 7 and Patent Document 8 disclose adding an antiviral agent such as a silver compound or a copper compound to a photocatalyst to obtain antiviral properties in the dark. Generally, a photocatalyst is used by dispersing photocatalyst particles in a solvent, mixing film-forming components to form a coating, and applying it on a substrate. As mentioned above, if metal components such as silver, copper, and zinc are added, practical problems are often generated. That is, as a method for loading metals such as silver, copper, and zinc or their compounds, when a metal raw material is reacted with a photocatalyst particle powder to load it, it is necessary to disperse it in a solvent later, and a large amount of labor is required, so it is not preferred. When a metal raw material is added to a dispersion liquid in which the photocatalyst particles are pre-dispersed, the dispersion stability of the photocatalyst particles is hindered, which becomes a cause of agglomeration, and there is a concern that the reduction in the reaction surface area leads to a reduction in the photocatalytic function and the occurrence of poor appearance of the construction part.

[0014] As described above, there is no photocatalyst thin film that has both sufficient antiviral properties and practicality.

[0015] Prior art literature

[0016] Patent Literature

[0017] Patent Document 1: Japanese Patent Application Publication No. 2014-231525

[0018] Patent Document 2: Japanese Patent Application Publication No. 2010-202561

[0019] Patent Document 3: International Publication No. 2008 / 147427

[0020] Patent Document 4: International Publication No. 2020 / 162485

[0021] Patent Document 5: Japanese Patent Application Publication No. 2019-182846

[0022] Patent Document 6: International Publication No. 2013 / 073555

[0023] Patent Document 7: International Publication No. 2016 / 042913

[0024] Patent Document 8: Japanese Patent Application Publication No. 2018-111063

[0025] Non-patent literature

[0026] Non-patent document 1: Y.Mori et al.; Nanoscale Research Letters 8, 93, (2013) Summary of the invention

[0027] Problems to be solved by the invention

[0028] Therefore, an object of the present invention is to provide an antiviral composition having a photocatalytic function and exhibiting high antiviral activity against non-enveloped viruses that have been difficult to be inactivated by silver compounds in dark places where light cannot reach, and a member having the composition on its surface.

[0029] Means for solving problems

[0030] The present inventors have conducted intensive studies to achieve the above-mentioned object, and as a result, have found that the following antiviral composition can achieve the above-mentioned object, thereby completing the present invention.

[0031] Therefore, the present invention provides the antiviral composition described below and a member having the composition on the surface.

[0032] [1] An antiviral composition comprising the following two particles: i) photocatalyst particles; and ii) silver nanoparticles having a dispersed particle size of 1000 nm or less and a primary particle size of 500 nm or less and a protective agent adsorbed on the surface, wherein the antiviral activity value of the antiviral composition in a dark place based on JIS R1756:2020 is greater than 0.3, and the antiviral activity value is further increased by 0.3 or more by light irradiation.

[0033] [2] The antiviral composition according to [1], further comprising a binder.

[0034] [3] The antiviral composition according to [1] or [2], wherein the amount of the protective agent relative to the amount of the metal component in the silver nanoparticles (ii) is in the range of 0.001 to 10 in terms of mass ratio.

[0035] [4] A member having the antiviral composition according to [3] on its surface.

[0036] [5] The antiviral composition according to [1] or [2], further comprising an aqueous dispersion medium.

[0037] Effects of the Invention

[0038] According to the present invention, it is possible to provide an antiviral composition having the characteristics of showing high antiviral activity in a dark place and further improving the antiviral activity by light irradiation. DETAILED DESCRIPTION

[0039] The antiviral composition of the present invention which exhibits high antiviral activity in a dark place and whose antiviral activity is further improved by light irradiation is described in detail below.

[0040] In this specification, the term "antiviral property" is used as a term that includes the meaning of making viruses inactive (reducing or inactivating the infectivity of viruses). The antiviral property is evaluated using the "antiviral activity value" calculated in accordance with JIS R1756:2020 "Fine ceramics-Test method for antiviral property of visible light responsive photocatalytic materials-Method using bacteriophage Qβ", using the standards described in the examples.

[0041] Viruses can be roughly divided into viruses with an envelope (lipid double membrane) and viruses without an envelope based on their structure, and bacteriophage Qβ is a virus without an envelope. Generally speaking, viruses without an envelope have higher tolerance to disinfectants and the like than viruses with an envelope, and the test method has been established with high accuracy and reproducibility, so bacteriophage Qβ was used in the evaluation of the antiviral activity of the present invention.

[0042] The virus that the antiviral composition of the present invention exhibits antiviral properties may or may not have an envelope. As enveloped viruses, phage φ6, human influenza virus, influenza virus type 3, rubella virus, herpes simplex virus, HIV, dengue virus, mimi virus, rabies virus, Ebola virus, Lassa virus, monkeypox virus, SARS coronavirus, MERS coronavirus, Ebola virus, spindle virus, West Nile virus, Zika virus, etc. can be cited. As non-enveloped viruses, phage Qβ, adenovirus, norovirus, feline calicivirus, rotavirus, sapovirus, poliovirus, astrovirus, enterovirus, human papillomavirus, hepatitis E virus, tobacco mosaic virus, etc. can be cited.

[0043] [Antiviral composition]

[0044] The antiviral composition of the present invention contains two types of particles: i) photocatalyst particles; and ii) silver nanoparticles having a dispersed particle size of 1000 nm or less and a primary particle size of 500 nm or less and having a protective agent adsorbed on the surface.

[0045] <Photocatalyst particles>

[0046] As the photocatalyst particles contained in the antiviral composition of the present invention, it is possible to use the currently available titanium oxide system, tungsten oxide system, zinc oxide system and niobium oxide system particles and the like as crystal particles of metal oxides of n-type semiconductors. For example, anatase titanium dioxide (TiO2), rutile titanium dioxide (TiO2), tungsten trioxide (WO3), zinc oxide (ZnO), Ga-doped zinc oxide (GZO), niobium oxide (Nb2O5), etc. can be used. Among them, it is preferred to use easily available anatase titanium dioxide (TiO2), rutile titanium dioxide (TiO2), tungsten trioxide (WO3). In addition, photocatalyst particles with high visible light activity can be used, such as rutile titanium oxide loaded with platinum, rutile titanium oxide loaded with iron, rutile titanium oxide loaded with copper, rutile titanium oxide loaded with copper hydroxide, anatase titanium oxide loaded with gold, tungsten trioxide loaded with platinum, etc.

[0047] In addition, with regard to the photocatalyst particles, it is preferred to use particles with a fine primary particle size, that is, particles with a primary particle size of 500 nm or less, more preferably particles in the range of 1 to 100 nm, and further preferably particles in the range of 1 to 50 nm. If the primary particle size is larger than 100 nm, the transparency of the composition is sometimes reduced, and when a dispersion is prepared, the dispersion stability in the dispersion is sometimes reduced. Furthermore, in the present invention, "primary particle size" refers to the arithmetic mean of the projected area circle equivalent diameter (Heywood diameter) of about 1,000 particles that do not overlap with each other, randomly selected from multiple particle images taken using a transmission electron microscope (e.g., H-9500 manufactured by Hitachi High-Technologies Co., Ltd.).

[0048] <Silver Nanoparticles>

[0049] The silver nanoparticles contained in the antiviral composition of the present invention contain at least silver and may contain other components. As components other than silver, there is no particular limitation, for example, copper, zinc, platinum, palladium, nickel, aluminum, titanium, cobalt, zirconium, molybdenum, tungsten, gold, antimony, tin, sodium, magnesium, silicon, phosphorus, sulfur, potassium, calcium, scandium, vanadium, chromium, manganese, iron, gallium, germanium, arsenic, selenium, yttrium, niobium, ruthenium, rhodium, indium, tellurium, barium, hafnium, tantalum, rhenium, osmium, iridium, mercury, thallium, lead, bismuth, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, thorium, etc., or a mixture or alloy of two or more thereof. Among these, as components other than silver contained in the silver nanoparticles, metal components other than silver are preferred, and iron, palladium, gold, platinum, copper, zinc, tin, molybdenum, titanium, and tungsten are more preferred.

[0050] When the silver nanoparticles contain metal components other than silver, the content thereof is preferably 0.01 to 49% by mass, more preferably 0.1 to 40% by mass, and further preferably 1 to 30% by mass relative to the mass of the metal components in the silver nanoparticles. This is because, when the content of the metal components other than silver exceeds 50% by mass relative to the mass of the metal components in the silver nanoparticles, the antiviral property is sometimes not fully exerted. In addition, this is because, when the content of the metal components other than silver is less than 0.01% by mass, the characteristics of the silver nanoparticles such as antiviral property and dispersion stability are hardly affected.

[0051] The silver nanoparticles contained in the antiviral composition of the present invention have a protective agent adsorbed on the surface. In the present invention, the so-called protective agent refers to a surfactant having the property of aggregating at the interface of two phases, a compound having a low molecular weight metal ligand such as an alkylthiol, an amine group, a silane group, a phosphine group, etc. that interacts strongly with metal particles, a polymer having a large number of adsorption segments and easily adsorbed on the particle surface, etc., and refers to the fact that these substances are adsorbed and coordinated on the surface of silver nanoparticles, thereby generating electrostatic repulsion or steric repulsion between silver nanoparticles, inhibiting the combination and aggregation of silver nanoparticles, and maintaining a dispersed state. Examples of the protective agent include surfactants such as anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants; water-soluble polymer compounds such as polyvinyl pyrrolidone, polyvinyl alcohol, polyethyleneimine, polyethylene oxide, polyacrylic acid, and methylcellulose; amino acids such as cysteine, arginine, asparagine, and asparagine; aliphatic amine compounds such as ethanolamine, diethanolamine, triethanolamine, and propanolamine; polyphenols such as tannic acid, gallic acid, gallic acid, pyrogallol, 4-benzylpyrogallol (2,3,4-trihydroxydiphenylmethane), and ellagitannin; primary amine compounds such as butylamine, dibutylamine, hexylamine, cyclohexylamine, heptylamine, 3-butoxypropylamine, octylamine, nonylamine, decylamine, dodecylamine, hexadecylamine, oleylamine, and octadecylamine; diamine compounds such as N,N-dimethylethylenediamine and N,N-diethylethylenediamine; carboxylic acid compounds such as oleic acid and citric acid, and salts thereof; and the like. The protective agent may be one of the above compounds or a combination of two or more.

[0052] The protective agent adsorbed on the surface of the silver nanoparticles is preferably in the range of 0.001 to 10, more preferably in the range of 0.005 to 5, and even more preferably in the range of 0.01 to 1, in terms of mass ratio relative to the metal component in the silver nanoparticles.

[0053] As for the dispersed particle size of silver nanoparticles, the 50% cumulative distribution diameter (D50) based on the number measured by the dynamic light scattering method using laser is less than 1000nm, preferably 1 to 1000nm, more preferably 1 to 200nm, and further preferably 1 to 70nm. For the lower limit of the dispersed particle size, theoretically, silver nanoparticles with the minimum particle size that can have antiviral properties can be used, and practically, it is preferably 1nm or more. In addition, when the dispersed particle size exceeds 1000nm, not only the haze value deteriorates when the antiviral composition is made, but also the antiviral property is sometimes reduced, so it is not preferred. In addition, as a device for measuring the dispersed particle size, for example, ELSZ-2000ZS (manufactured by Otsuka Electronics Co., Ltd., Japan), Nanotrac UPA-EX150 (manufactured by Nikkiso Co., Ltd., Japan), LA-910 (manufactured by Horiba, Ltd., Japan) and the like can be used.

[0054] The primary particle size of the silver nanoparticles is 500 nm or less, preferably 1 to 500 nm, more preferably 1 to 100 nm, and further preferably 1 to 50 nm. As for the lower limit of the primary particle size, theoretically, silver nanoparticles with the smallest particle size that can have antiviral properties can be used, but in practice, it is preferably 1 nm or more. In addition, when the primary particle size exceeds 500 nm, not only the haze value deteriorates when the antiviral composition is prepared, but also the antiviral property is sometimes reduced, so it is not preferred.

[0055] The ratio of the photocatalyst particles to the silver nanoparticles in the antiviral composition is preferably 1:0.0001 to 1:0.1, and more preferably 1:0.0005 to 1:0.05, based on the mass. In addition to the photocatalyst particles and the silver nanoparticles, the antiviral composition may contain additives such as a binder and a surfactant within the range that does not impair the effects of the present invention.

[0056] <Adhesive>

[0057] The antiviral composition of the present invention may further contain an adhesive. The antiviral composition of the present invention further improves the antiviral effect produced by light irradiation by containing an adhesive. As adhesives, for example, metal compound-based adhesives containing silicon, aluminum, titanium, zirconium, etc. and organic resin-based adhesives containing fluorine-based resins, acrylic resins, polyurethane resins, etc. can be listed. Among them, in order to obtain an excellent composition with high antiviral properties, it is preferred to use a silicon compound-based adhesive. The so-called silicon compound-based adhesive is a colloidal dispersion, solution, or emulsion of a silicon compound formed by containing a solid or liquid silicon compound in an aqueous dispersion medium. Specifically, colloidal silicon dioxide (preferably with a particle size of 1 to 150 nm) can be listed; silicate solutions such as silicates; silane, siloxane hydrolyzate emulsions; silicone resin emulsions; silicone-acrylic resin copolymers, silicone-polyurethane resin copolymers, etc., emulsions of copolymers of silicone resins and other resins, etc.

[0058] The content of the photocatalyst particles in the antiviral composition is preferably 20 to 99.99% by mass, more preferably 30 to 99.95% by mass. In addition, the content of the silver nanoparticles in the antiviral composition is preferably 0.01 to 20% by mass, more preferably 0.05 to 10% by mass. In addition, the content of the binder in the antiviral composition is preferably 0 to 79.99% by mass, more preferably 10 to 69.99% by mass. In addition to the photocatalyst particles, silver nanoparticles and binders, the antiviral composition may also contain additives such as surfactants within the range that does not impair the effects of the present invention.

[0059] As one embodiment of the antiviral composition of the present invention, an antiviral composition (dispersion liquid) further containing an aqueous dispersion medium can also be mentioned.

[0060] For the aqueous dispersion medium, an aqueous solvent is usually used, preferably water, a water-soluble organic solvent that can be mixed with water, or a mixed solvent of water and a water-soluble organic solvent. As water, for example, deionized water, distilled water, pure water, etc. are preferred. In addition, as a water-soluble organic solvent, for example, alcohols such as methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, tert-butanol, ethylene glycol, diethylene glycol, polyethylene glycol, etc. can be listed; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether; diol ethers such as diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol n-propyl ether; ketones such as acetone, methyl ethyl ketone, 2-pyrrolidone, N-methylpyrrolidone, etc., water-soluble nitrogen-containing compounds; ethyl acetate, etc., one of these can be used or two or more can be used in combination.

[0061] The concentration of the silver nanoparticles in the dispersion is not particularly limited. Generally, the lower the concentration, the better the dispersion stability. Therefore, the silver component is preferably 0.0001 to 10 mass %, more preferably 0.0005 to 5 mass %, and further preferably 0.001 to 1 mass %. If the concentration of the silver nanoparticles is 0.0001 mass % or more, the antiviral property in dark places is exerted, so it is preferred.

[0062] The concentration of the photocatalyst particles in the dispersion is not particularly limited. Generally, the lower the concentration, the better the dispersion stability. Therefore, the photocatalyst component is preferably 0.0001 to 80 mass %, more preferably 0.001 to 50 mass %, and further preferably 0.01 to 20 mass %. If the concentration of the photocatalyst particles is 0.0001 mass % or more, the effect of inactivating the virus produced by the photocatalyst particles is obtained, so it is preferred.

[0063] The concentration of the binder in the dispersion is not particularly limited, but generally, the lower the concentration, the better the dispersion stability, so it is preferably 0.0001 to 90% by mass, more preferably 0.001 to 50% by mass, and even more preferably 0.01 to 20% by mass. If the concentration of the binder is 0.0001% by mass or more, the effect of light irradiation is further improved, and it is easy to apply to the surface of various components, so it is preferred.

[0064] The antiviral composition of the present invention has the following characteristics: it has high antiviral activity in the dark, and the antiviral activity is further improved by light irradiation, characterized in that the antiviral activity value in the dark specified in JIS R1756:2020 is greater than 0.3, and the antiviral activity value generated by light irradiation specified in JIS R1756:2020 is greater than 0.3.

[0065] In particular, the antiviral activity value of the antiviral composition containing the adhesive is greatly improved by light irradiation, and the antiviral activity value by light irradiation specified in JIS R1756:2020 is preferably increased by 0.5 or more, more preferably by 1.0 or more, and further preferably by 1.5 or more.

[0066] As light for improving antiviral properties, it is sufficient to include light of a wavelength absorbed by photocatalyst particles and silver nanoparticles, and its wavelength is 200 to 800 nm, and more preferably 300 to 700 nm. In the case of less than 200 nm, sometimes the light itself shows antiviral properties, so it is not practical. In the case of more than 800 nm, sometimes it is difficult to improve the antiviral properties through light irradiation and it is not preferred. As a light source, it is sufficient to include light of these wavelengths, for example, fluorescent lamps, LEDs, incandescent lamps, low-pressure sodium lamps, high-pressure sodium lamps, metal halide lamps, mercury lamps, xenon lamps, organic ELs, krypton bulbs, halogen bulbs, sunlight, etc., and one of these can be used or two or more can be used in combination. The light irradiation illuminance is 5 to 500,000 lx, and more preferably 10 to 200,000 lx. If it is less than 5 lx, the effect of light irradiation cannot be confirmed sometimes, and conditions exceeding 500,000 lx are difficult to imagine in actual environments. Furthermore, as an apparatus for measuring illumination, for example, LX-105 (manufactured by CUSTOM Corporation), CHF-LT1 (manufactured by SANWA SUPPLY INC.), T-10A (manufactured by Konica Minolta Japan Co., Ltd.), etc. can be used. There is no particular regulation on the irradiation time, but in terms of the nature of the antiviral measurement test, the irradiation time is preferably about 1 minute to 48 hours.

[0067] [Manufacturing method]

[0068] The method for producing the antiviral composition of the present invention, particularly the dispersion, includes, for example, a method comprising the following steps (1) to (6).

[0069] (1) Step of dispersing photocatalyst particles in an aqueous dispersion medium to obtain a photocatalyst particle dispersion liquid

[0070] (2) Step of producing a solution containing a raw material silver compound and a reducing agent and a protective agent dissolved in an aqueous dispersion medium

[0071] (3) A step of mixing the solution containing the raw silver compound produced in the step (2) above with a solution containing a reducing agent and a protective agent to produce a silver nanoparticle dispersion

[0072] (4) A step of washing the silver nanoparticle dispersion prepared in the step (3) with an aqueous dispersion medium by membrane filtration

[0073] (5) A step of mixing the photocatalyst particle dispersion obtained in step (1) with the silver nanoparticle dispersion obtained in step (4)

[0074] (6) A step of mixing a binder with the dispersion obtained in (5)

[0075] The details of each step are described below.

[0076] <Preparation of photocatalyst particle dispersion>

[0077] Process (1):

[0078] In step (1), the photocatalyst particles are dispersed with an aqueous dispersion medium to prepare a photocatalyst particle dispersion. The photocatalyst particles can use particles of titanium oxide, tungsten oxide, zinc oxide, niobium oxide, etc., as well as crystal particles of metal oxides as n-type semiconductors, and specifically, the various photocatalyst particles mentioned above can be listed. Only one type of photocatalyst particles can be used, or two or more types can be used in combination. There is no particular limitation on the method for manufacturing photocatalyst particles, and gas phase methods (CVD method, PVD method, etc.), liquid phase methods (hydrothermal method, sol-gel method, etc.), solid phase methods (high temperature sintering method, etc.), etc. can be listed. A pulverizer or a classifier can be used to form small particles and classify the photocatalyst particle size.

[0079] As an aqueous dispersion medium for dispersing the photocatalyst particles, water is preferably used, and a mixed solvent of a hydrophilic organic solvent and water mixed with water in an arbitrary ratio can be used. As water, for example, purified water such as filtered water, deionized water, distilled water, and pure water is preferred. In addition, as a hydrophilic organic solvent, for example, alcohols such as methanol, ethanol, and isopropanol are preferred; diols such as ethylene glycol; diol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and propylene glycol n-propyl ether are preferred. When a mixed solvent is used, the proportion of the hydrophilic organic solvent in the mixed solvent is greater than 0% by mass, preferably less than 50% by mass, more preferably less than 20% by mass, and further preferably less than 10% by mass.

[0080] There is no particular limitation on the method of dispersing the photocatalyst particles in the aqueous dispersion medium. It can be a method of stirring with a stirrer or a method of dispersing with an ultrasonic disperser. The temperature during mixing is 20 to 100°C, preferably 20 to 80°C, more preferably 20 to 40°C, and the time is preferably 1 minute to 3 hours. There is no particular limitation on the concentration of the photocatalyst in the photocatalyst particle dispersion. Generally, the lower the concentration, the better the dispersion stability. Therefore, it is preferably 0.0001 to 80% by mass, and more preferably 0.001 to 50% by mass.

[0081] The obtained photocatalyst particle dispersion may contain alkaline substances or acidic substances for pH adjustment, etc. As alkaline substances, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate; alkali metal bicarbonates such as sodium bicarbonate and potassium bicarbonate; alkali metal alcoholates such as tert-butoxypotassium, sodium methoxide and sodium ethoxide; alkali metal salts of aliphatic hydrocarbons such as butyl lithium; amines such as triethylamine, diethylaminoethanol and diethylamine, etc. As acidic substances, inorganic acids such as aqua regia, hydrochloric acid, nitric acid and sulfuric acid; organic acids such as formic acid, acetic acid, chloroacetic acid, dichloroacetic acid, oxalic acid, trifluoroacetic acid and trichloroacetic acid, etc., can be listed. In addition, ion exchange treatment or filtration and washing treatment can be performed to adjust the concentration of ion components, and solvent replacement treatment can also be performed to change the solvent components.

[0082] The pH of the photocatalyst particle dispersion is preferably 3 to 13, more preferably 4 to 12. The mass of the photocatalyst particles contained in the photocatalyst particle dispersion can be calculated from the mass and concentration of the photocatalyst particle dispersion. Furthermore, as for the method for determining the concentration of the photocatalyst particle dispersion, a portion of the photocatalyst particle dispersion is sampled, and the mass of the non-volatile component (photocatalyst particles) after heating at 105°C for 1 hour to volatilize the solvent and the mass of the sampled photocatalyst particle dispersion can be calculated according to the following formula.

[0083] Concentration of photocatalyst particle dispersion (%) = [mass of non-volatile component (g) / mass of photocatalyst particle dispersion (g)] × 100

[0084] <Preparation of silver nanoparticle dispersion>

[0085] Step (2):

[0086] In step (2), two solutions are prepared: (2-1) a solution in which a raw silver compound is dissolved in an aqueous dispersion medium; and (2-2) a solution in which a reducing agent and a protective agent are dissolved in an aqueous dispersion medium. The reducing agent in solution (2-2) has a function of reducing the raw silver compound in solution (2-1). In addition, when solution (2-1) and solution (2-2) are mixed in the subsequent step (3) to reduce the silver compound, the protective agent in solution (2-2) has a function of adsorbing on the surface of the silver compound to improve the dispersion stability in the aqueous dispersion medium.

[0087] The preparation method of these solutions can be a method in which the raw silver compound, the reducing agent and the protective agent are added, stirred and dissolved in an aqueous dispersion medium. The stirring method is not particularly limited as long as it is a method that can be uniformly dissolved in an aqueous dispersion medium, and a generally available stirrer can be used.

[0088] As the raw silver compound, various silver compounds can be used, for example, inorganic acid salts such as chloride, nitrate, and sulfate of silver; organic acid salts such as formic acid, citric acid, oxalic acid, lactic acid, and glycolic acid; complex salts such as amino complexes, cyano complexes, halogen complexes, and hydroxy complexes, and these can be used alone or in combination of two or more. Among them, inorganic acid salts such as chloride, nitrate, and sulfate of silver are preferably used.

[0089] The content of the raw silver compound is an amount such that the concentration of Ag in the solution (2-1) containing the raw silver compound becomes 0.5 to 200 mmol / L, preferably 5 to 100 mmol / L.

[0090] When the silver nanoparticles contain a metal component other than silver, it is preferred that a raw material compound of the metal component other than silver is further added to the solution (2-1) containing the raw material silver compound and dissolved.

[0091] Examples of raw material compounds of metal components other than silver include inorganic acid salts such as chlorides, nitrates, and sulfates of zinc, platinum, palladium, nickel, aluminum, titanium, cobalt, zirconium, molybdenum, tungsten, gold, antimony, tin, sodium, magnesium, silicon, phosphorus, sulfur, potassium, calcium, scandium, vanadium, chromium, manganese, iron, gallium, germanium, arsenic, selenium, yttrium, niobium, ruthenium, rhodium, indium, tellurium, barium, hafnium, tantalum, rhenium, osmium, iridium, mercury, thallium, lead, bismuth, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, and thorium; organic acid salts of formic acid, citric acid, oxalic acid, lactic acid, and glycolic acid; and complex salts such as amino complexes, cyano complexes, halogen complexes, and hydroxy complexes.

[0092] The content of the raw material compound of the metal component other than silver is an amount such that the concentration of the element of the component becomes 0.01 to 40 mmol / L, preferably 0.1 to 20 mmol / L.

[0093] As the aqueous dispersion medium of the solution (2-1) containing the raw silver compound, an aqueous solvent is usually used, preferably water, a water-soluble organic solvent miscible with water, or a mixed solvent of water and a water-soluble organic solvent. As water, for example, deionized water, distilled water, pure water, etc. are preferred. In addition, as the water-soluble organic solvent, for example, alcohols such as methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, tert-butanol, ethylene glycol, diethylene glycol, polyethylene glycol, etc.; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol n-propyl ether, etc.; ketones such as acetone and methyl ethyl ketone; water-soluble nitrogen-containing compounds such as 2-pyrrolidone and N-methylpyrrolidone; ethyl acetate, etc., and one of these can be used or two or more can be used in combination. The amount of the aqueous dispersion medium in the solution (2-1) containing the raw material silver compound is the balance of the content of the raw material silver compound and the raw material compounds of components other than silver.

[0094] The reducing agent is not particularly limited, and any reducing agent that can reduce the silver ions constituting the raw silver compound can be used. Examples thereof include hydrazine, hydrazine monohydrate, phenylhydrazine, sulfuric acid, Hydrazines; amines such as dimethylaminoethanol, triethylamine, octylamine, dimethylaminoborane, benzotriazole; organic acids such as oxalic acid, citric acid, ascorbic acid, tartaric acid, malic acid, malonic acid, formic acid; polyphenols such as gallic acid, chlorogenic acid, catechins, anthocyanins, epigallocatechin, delphinidin, tannic acid, saponins; aldehydes such as formaldehyde, acetaldehyde, ethanolaldehyde; hydrides such as sodium borohydride, lithium borohydride, lithium triethylborohydride, lithium aluminum hydride, diisobutylaluminum hydride, tributyltin hydride, lithium tri(sec-butyl)borohydride, potassium tri(sec-butyl)borohydride, zinc borohydride, sodium acetoxyborohydride ; pyrrolidones such as polyvinylpyrrolidone (PVP), 1-vinylpyrrolidone, N-vinylpyrrolidone, and methylpyrrolidone; reducing sugars such as glucose, galactose, mannose, fructose, sucrose, maltose, raffinose, and stachyose; divalent irons such as ferrous sulfate (II), ferrous oxide (II), ammonium iron (II), iron (II) chloride, iron (II) perchlorate, iron (II) oxalate, iron (II) fumarate, and potassium hexacyanoferrate (II); sugar alcohols such as sorbitol, and their salts, etc., and one of these can be used or two or more can be used in combination. Among them, hydrazines such as hydrazine monohydrate, organic acid salts such as sodium citrate, polyphenols such as gallic acid and tannic acid, hydrides such as sodium borohydride, and aldehydes such as formaldehyde or ethanolaldehyde are particularly preferred, which have excellent silver ion reducing ability and small molecular weight and can be easily filtered and separated in the washing process of the aqueous solvent of the silver nanoparticles. As the aqueous dispersion medium for dissolving the reducing agent, the same aqueous dispersion medium as that used for the above-mentioned aqueous dispersion medium of the metal compound can be used.

[0095] The content of the reducing agent can be set to 0.001 to 50% by mass, preferably 0.01 to 40% by mass, relative to the total mass of the solution (2-2) containing the reducing agent and the protective agent. This is because, when the content of the reducing agent exceeds 50% by mass, the contents of the protective agent and the aqueous solvent are relatively reduced, and a sufficient amount of the protective agent cannot be adsorbed on the surface of the silver nanoparticles, and sometimes silver nanoparticles with high dispersion stability are not formed. In addition, when the content of the reducing agent is less than 0.001% by mass, a large amount of the solution containing the reducing agent and the protective agent must be added to the solution containing the raw silver compound, which is not practical.

[0096] There are no particular limitations on the protective agent, and any protective agent that can be adsorbed on the surface of the reduced raw silver compound to improve the dispersion stability in the aqueous dispersion medium can be used. For example, surfactants such as anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants; water-soluble polymer compounds such as PVP, polyethylene glycol, polyvinyl alcohol, polyethyleneimine, polyethylene oxide, polyacrylic acid, methylcellulose, and gelatin; amino acids such as cysteine, arginine, asparagine, and asparagine; aliphatic amine compounds such as ethanolamine, diethanolamine, triethanolamine, and propanolamine; tannic acid, gallic acid, pyrogallol, 4- Benzylpyrogallol (2,3,4-trihydroxydiphenylmethane), ellagitannin and other polyphenols; butylamine, dibutylamine, hexylamine, cyclohexylamine, heptylamine, 3-butoxypropylamine, octylamine, nonylamine, decylamine, dodecylamine, hexadecylamine, oleylamine, octadecylamine and other primary amine compounds; N,N-dimethylethylenediamine, N,N-diethylethylenediamine and other diamine compounds; sodium silicate, water-soluble silicate, colloidal silica and other silicon oxide compounds; oleic acid, citric acid and other carboxylic acid compounds and their salts, hindered amine and other light stabilizers, etc. Among them, organic acid salts such as sodium citrate, gallic acid, tannic acid and other polyphenols, and carboxylic acid compounds such as sodium oleate are more preferred, which have excellent stability of silver nanoparticles and small molecular weight and can be easily filtered and separated in the washing process of the silver nanoparticles in an aqueous solvent. In addition, one of these can be used or two or more can be used in combination. There is no particular limitation on the combination. For example, when sodium silicate, gelatin, aliphatic amine compounds, hindered amines, etc. are used as protective agents in addition to PVP and sodium citrate, which are excellent in the dispersion stability of silver nanoparticles, durability is sometimes improved, so it is preferred. In addition, it is more preferred to use surfactants or polyphenols as protective agents, so that the antiviral property is improved.

[0097] The content of the protective agent is preferably 0.001 to 60% by mass, more preferably 0.01 to 50% by mass, relative to the total mass of the solution (2-2) containing the reducing agent and the protective agent. This is because, when the content of the protective agent exceeds 60% by mass, the contents of the reducing agent and the aqueous solvent are relatively reduced, and the yield of the silver nanoparticles may be poor. At the same time, a large amount of aqueous solvent is required in the subsequent step of washing the silver nanoparticle dispersion with an aqueous solvent, which is not practical. In addition, when the content of the protective agent is less than 0.001% by mass, a sufficient amount of the protective agent cannot be adsorbed on the surface of the silver nanoparticles, and silver nanoparticles with high dispersion stability may not be formed.

[0098] As the aqueous dispersion medium (aqueous solvent) of the solution (2-2) containing the reducing agent and the protective agent, water, a water-soluble organic solvent that can be mixed with water, or a mixed solvent of water and a water-soluble organic solvent is preferably used. As water, for example, deionized water, distilled water, pure water, etc. are preferred. In addition, as the water-soluble organic solvent, for example, alcohols such as methanol, ethanol, isopropanol, n-propanol, 2-propanol, n-butanol, 2-butanol, tert-butanol, ethylene glycol, diethylene glycol, etc.; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol n-propyl ether, etc.; ketones such as acetone and methyl ethyl ketone, water-soluble nitrogen-containing compounds such as 2-pyrrolidone and N-methylpyrrolidone, ethyl acetate, etc., and the water-soluble organic solvent can be used alone or in combination of two or more.

[0099] The content of the aqueous solvent is 0.1 to 99.99% by mass, preferably 1.0 to 99.9% by mass, relative to the total mass of the solution (2-2) containing the reducing agent and the protective agent. This is because, when the content of the aqueous solvent exceeds 99.99% by mass, a large amount of the solution containing the reducing agent and the protective agent needs to be added to the solution containing the raw silver compound, which is not practical. In addition, when the content of the aqueous solvent is less than 0.1% by mass, the effect of improving the fluidity in the solution containing the reducing agent and the protective agent is small.

[0100] The above-mentioned alkaline substance or acidic substance can be added to the solution (2-2) containing the reducing agent and the protective agent. As the alkaline substance that can be added to the solution (2-2), the same alkaline substances as those exemplified above as the alkaline substances that can be added to the photocatalyst particle dispersion can be listed, and as the acidic substance that can be added to the solution (2-2), the same acidic substances as those exemplified above as the acidic substances that can be added to the photocatalyst particle dispersion can be listed.

[0101] The content of the alkaline substance or acidic substance when mixed can be set to 0.0001 to 30% by mass, preferably 0.001 to 20% by mass relative to the total mass of the solution (2-2) containing the reducing agent and the protective agent. This is because, when the content of the alkaline substance or acidic substance exceeds 30% by mass, the content of the reducing agent and the protective agent becomes relatively small, and silver nanoparticles with high dispersion stability may not be formed. In addition, when the content of the alkaline substance or acidic substance is less than 0.0001% by mass, the influence on the pH of the solution containing the reducing agent and the protective agent is small.

[0102] The concentrations of these two solutions are not particularly limited. Generally, the lower the concentration, the smaller the primary particle size of each silver nanoparticle formed. Therefore, it is preferred to set a preferred concentration range according to the target primary particle size range.

[0103] The pH when the two solutions are mixed can be any condition that reduces silver. Depending on the reducing agent used, the appropriate pH range varies. For example, when using a divalent iron or the like that undergoes a reduction reaction in an acidic aqueous solution as a reducing agent, it is preferably adjusted so that the pH when the two solutions are mixed is in the range of 0 to 7. When the pH exceeds 7, the reduction reaction of silver may not proceed. When it is less than 0, a large amount of labor is spent in the subsequent filtration process, and productivity is reduced, so it is not preferred. In addition, when using hydrazines or polyphenols that undergo a reduction reaction in an alkaline aqueous solution as a reducing agent, it is preferably adjusted so that the pH when the two solutions are mixed is in the range of 7 to 16. When the pH is less than 7, the reduction reaction of silver may not proceed. When it exceeds 15, a large amount of labor is spent in the subsequent filtration process, and productivity is reduced, so it is not preferred.

[0104] Step (3):

[0105] In step (3), the solution prepared in step (2) by dissolving the raw material silver compound in an aqueous dispersion medium is mixed with a solution prepared by dissolving a reducing agent and a protective agent in an aqueous dispersion medium to prepare a silver nanoparticle dispersion.

[0106] The method for mixing the two solutions is not particularly limited as long as it is a method that can uniformly mix the two solutions. Examples thereof include a method of placing a silver compound solution and a solution of a reducing agent and a protecting agent in a reaction container and stirring and mixing them; a method of dropping a solution of a reducing agent and a protecting agent into a reaction container while stirring the silver compound solution; a method of dropping a solution of a reducing agent and a protecting agent into a reaction container while stirring the silver compound solution; a method of continuously and quantitatively supplying a silver compound solution and a solution of a reducing agent and a protecting agent and mixing them using a reaction container or a microreactor, etc.

[0107] The temperature during mixing is not particularly limited, and is preferably adjusted to an appropriate temperature depending on the molar ratio of silver to the metal component other than silver in the target silver nanoparticles, the primary particle size, the reaction time, and the like.

[0108] Step (4):

[0109] In step (4), the silver nanoparticle dispersion produced in step (3) is washed with an aqueous dispersion medium by membrane filtration.

[0110] As the aqueous dispersion medium, water, a water-soluble organic solvent that can be mixed with water, and a mixed solvent of water and a water-soluble organic solvent are preferably used. As water, for example, deionized water, distilled water, pure water, etc. are preferred. In addition, as the water-soluble organic solvent, for example, alcohols such as methanol, ethanol, isopropanol, n-propanol, 2-propanol, n-butanol, 2-butanol, tert-butanol, ethylene glycol, diethylene glycol, etc.; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol n-propyl ether, etc.; ketones such as acetone, methyl ethyl ketone, water-soluble nitrogen-containing compounds such as 2-pyrrolidone and N-methylpyrrolidone, ethyl acetate, etc., and the water-soluble organic solvent can use one of these or a combination of two or more.

[0111] The non-volatile impurities other than the silver nanoparticles, such as components other than silver in the raw silver compound, reducing agents, protective agents not adsorbed on the silver nanoparticles, etc. are washed and separated from the silver nanoparticle dispersion by a membrane filtration method. The amount of the protective agent adsorbed on the surface of the silver nanoparticles is preferably washed to 0.001 to 10, more preferably washed to 0.001 to 5, and further preferably washed to 0.001 to 1, relative to the total amount of the metal components in the silver nanoparticles in the silver nanoparticle dispersion. When the mass ratio is less than 0.001, the dispersion stability of the silver nanoparticles may be reduced. When it exceeds 10, the amount of protective agent adsorbed on the surface of the silver nanoparticles is large, and the antiviral property may not be fully exerted.

[0112] Quantification of metal component concentration in silver nanoparticle dispersion (ICP-OES)

[0113] The concentration of the metal component in the silver nanoparticle dispersion can be measured by appropriately diluting the silver nanoparticle dispersion with pure water and introducing the diluted solution into an inductively coupled plasma optical emission spectrometer (trade name: "Agilent 5110ICP-OES", Agilent Technologies Inc.).

[0114] Quantification of protective agent adsorbed on the surface of silver nanoparticles in silver nanoparticle dispersion

[0115] Among them, by sampling a portion of the silver nanoparticle dispersion, heating it at 105°C for 3 hours, and subtracting the metal component concentration quantified in the above-mentioned ICP-OES from the non-volatile component concentration calculated from the mass of the non-volatile component (metal component + protective agent adsorbed on the surface of the silver nanoparticles) after volatilization of the solvent and the mass of the sampled silver nanoparticle dispersion, the concentration of the protective agent adsorbed on the surface of the silver nanoparticles in the silver nanoparticle dispersion can be calculated.

[0116] Concentration of protective agent adsorbed on the surface of silver nanoparticles (ppm) = [mass of non-volatile components (g) / mass of silver nanoparticle dispersion (g)] × 100 × 10000 - concentration of metal components in silver nanoparticle dispersion (ppm)

[0117] From the obtained concentration of the protective agent adsorbed on the surface of the silver nanoparticles, the mass ratio of the protective agent adsorbed on the surface of the silver nanoparticles to silver can be calculated.

[0118] The mass ratio of the protective agent adsorbed on the surface of the silver nanoparticles to the metal component = the concentration of the protective agent adsorbed on the surface of the silver nanoparticles (ppm) / the concentration of the metal component in the silver nanoparticles (ppm)

[0119] The membrane used in the membrane filtration method is not particularly limited as long as it can separate the silver nanoparticles from the silver nanoparticle dispersion and non-volatile impurities other than the silver nanoparticles. Examples thereof include precision filtration membranes, ultrafiltration membranes, and nanofiltration membranes. Among these, a membrane having an appropriate pore size can be used for implementation.

[0120] As the filtering method, any method such as centrifugal filtration, pressure filtration, cross-flow filtration, etc. can be adopted.

[0121] As the shape of the filtration membrane, a filtration membrane in an appropriate form such as a hollow fiber type, a spiral type, a tubular type, or a flat membrane type can be used.

[0122] The material of the filter membrane is not particularly limited as long as it is durable against the silver nanoparticle dispersion, and can be appropriately selected from organic membranes such as polyethylene, tetrafluoroethylene, polypropylene, cellulose acetate, polyacrylonitrile, polyimide, polysulfone, polyethersulfone, and inorganic membranes such as silica, alumina, zirconium oxide, and titanium dioxide.

[0123] Specific examples of the above-mentioned filtration membrane include Microza (manufactured by Asahi Kasei Chemicals Co., Ltd.), Amicon Ultra (manufactured by Merck Millipore Corporation), MOLSEP (Daicen Membrane-Systems Ltd.), ULTRA FILTER (Advantec Toyo Kaisha, Ltd.), and MEMBRALOX (manufactured by Pall Corporation).

[0124] <Preparation of Photocatalyst-Silver Nanoparticle Dispersion Liquid>

[0125] Step (5):

[0126] In step (5), the photocatalyst particle dispersion prepared in step (1) is mixed with the silver nanoparticle dispersion prepared in step (4) to obtain a photocatalyst-silver nanoparticle dispersion. The mixing method is not particularly limited as long as it is a method for uniformly mixing the two dispersions, and the mixing can be performed by stirring using a generally available stirrer, for example.

[0127] The mixing ratio of the photocatalyst particle dispersion and the silver nanoparticle dispersion is 1 to 100,000, preferably 10 to 10,000, and more preferably 20 to 1000, in terms of the mass ratio of the particles in each dispersion of the photocatalyst particles and the silver nanoparticles (photocatalyst particles / silver nanoparticles). If the mass ratio is less than 1, the photocatalytic performance is not fully exerted, which is not preferred, and if it exceeds 100,000, the antiviral property in the dark is not fully exerted, which is not preferred.

[0128] <Preparation of photocatalyst-silver nanoparticle-binder dispersion>

[0129] Step (6):

[0130] In step (6), in order to further enhance the antiviral effect of light irradiation and facilitate coating of the photocatalyst-silver nanoparticle dispersion on the surface of various components as described later, and to facilitate bonding of the particles, a binder can be mixed with the photocatalyst-silver nanoparticle dispersion produced in step (5) to obtain a photocatalyst-silver nanoparticle-binder dispersion. The mixing method is not particularly limited as long as it is a method for uniformly mixing them, and for example, mixing can be performed by stirring using a generally available stirrer.

[0131] When a binder is mixed, the mixing ratio of the binder preferably satisfies both the mass ratio of the photocatalyst particles to the binder component and the mass ratio of the silver nanoparticles to the binder component shown below.

[0132] The mixing ratio of the photocatalyst particle dispersion and the binder is 0.01 to 50, preferably 0.05 to 30, and more preferably 0.1 to 10, in terms of the mass ratio of the photocatalyst particles to the binder component (photocatalyst / binder). When the ratio is less than 0.01, the photocatalytic function may not be fully exerted and is not preferred. When the ratio exceeds 50, the effect of improving the antiviral property by light irradiation may not be confirmed and is not preferred.

[0133] The mixing ratio of the silver nanoparticle dispersion and the binder is 0.00001 to 10, preferably 0.0001 to 1, and more preferably 0.001 to 0.5, as measured by the mass ratio of the silver nanoparticles to the binder component (silver nanoparticles / binder). When it is less than 0.00001, the antiviral effect in the dark is sometimes reduced and is not preferred, and when it exceeds 10, the effect of improving the antiviral property by light irradiation is sometimes not confirmed, which is not preferred.

[0134] <Components>

[0135] The photocatalyst-silver nanoparticle dispersion can be used to form an antiviral composition on the surface of various components. There are no particular restrictions on the various components, and the materials of the components include, for example, organic materials and inorganic materials. They can have various shapes that are consistent with their respective purposes and uses.

[0136] Examples of organic materials include synthetic resin materials such as vinyl chloride resin (PVC), polyethylene (PE), polypropylene (PP), polycarbonate (PC), acrylic resin, polyacetal, fluororesin, silicone resin, ethylene-vinyl acetate copolymer (EVA), acrylonitrile-butadiene rubber (NBR), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyvinyl butyral (PVB), ethylene-vinyl alcohol copolymer (EVOH), polyimide resin, polyphenylene sulfide (PPS), polyetherimide (PEI), polyetheretherimide (PEEI), polyetheretherketone (PEEK), melamine resin, phenolic resin, acrylonitrile-butadiene-styrene (ABS) resin, natural materials such as natural rubber, or semi-synthetic materials of the above synthetic resin materials and natural materials. These products can be made into the desired shapes and structures such as films, sheets, fiber materials, fiber products, other molded products, and laminates.

[0137] As inorganic materials, for example, non-metallic inorganic materials and metallic inorganic materials are included. As non-metallic inorganic materials, for example, glass, ceramics, stone materials, etc. can be listed. These products can be made into various shapes such as tiles, glass, mirrors, walls, design materials, etc. As metallic inorganic materials, for example, cast iron, steel, iron, iron alloy, aluminum, aluminum alloy, nickel, nickel alloy, zinc die casting, etc. can be listed. For these, the above-mentioned metallic inorganic material can be plated, the above-mentioned organic material can be coated, or the plating can be implemented on the surface of the above-mentioned organic material or non-metallic inorganic material.

[0138] As a method for forming a photocatalyst-silver nanoparticle composition on the surface of various components, the photocatalyst-silver nanoparticle dispersion is applied to the surface of the component by a known coating method such as spraying or dipping, and then dried by a known drying method such as far infrared drying, IH drying, or hot air drying. The thickness of the dried photocatalyst-silver nanoparticle composition can be selected in various ways, and is generally preferably in the range of 10 nm to 10 μm. Thus, the above-mentioned photocatalyst-silver nanoparticle composition is formed on the surface of the component.

[0139] The photocatalyst-silver nanoparticle composition formed on the component in this way exerts antiviral activity in the dark, and further, obtains high antiviral activity through light irradiation, and various components having the photocatalyst-silver nanoparticle composition thereon can exert surface antiviral effects.

[0140] Example

[0141] The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[0142] The antiviral activity in the present invention was measured as follows. Measurements other than the antiviral activity were performed by the above-mentioned methods unless otherwise specified.

[0143] The antiviral activity value was calculated according to JIS R1756:2020 "Fine ceramics - Test method for antiviral activity of visible light responsive photocatalytic materials - Method using bacteriophage Qβ", and the antiviral activity of the composition was evaluated using the following standards. As a member on which the composition is formed, a 50 mm × 50 mm × 2 mm glass piece (hereinafter referred to as a test piece) was used.

[0144] <Measurement of antiviral properties based on JIS R1756:2020>

[0145] Place a glass rod in a moisturizing vessel, and set a test piece on the glass rod. Place 200 μL of phage liquid on the test piece, cover the phage liquid with a covering film, and cover the vessel with a moisturizing glass. Let the prepared vessel stand for 4 hours in a dark place (0 lx) or a bright place (shielding visible light obtained by a white fluorescent lamp with a wavelength below 380nm: 500 lx). A digital illuminometer LX-105 (manufactured by CUSTOM corporation) was used in the measurement of illumination. After standing, the test piece and the covering film were transferred to a sterilized strip bag, rinsed with 5 mL of physiological saline containing a surfactant, and the phage liquid was recovered. Dilute the recovered phage liquid, mix the liquid with 100 μL of Escherichia coli liquid each, and then mix it with soft agar medium and sow it in the medium. Cultivate overnight at 37°C, count the dead Escherichia coli groups (plaques), and thus calculate the infection value of the virus.

[0146] The antiviral activity value based on JIS R1756:2020 is a value obtained by performing the above-mentioned operation using a test piece subjected to antiviral treatment and a test piece without treatment, and determining the value as the difference between the average values ​​of the common logarithms of the infection values ​​of the two.

[0147] The antiviral activity value of the dark space of the test piece subjected to antiviral treatment (-) = log 10 (Viral infection value after the antiviral treated test piece was left in the dark for 4 hours (-))-log 10 (Virus infection value after the unprocessed test piece was left in the dark for 4 hours (-))

[0148] The antiviral activity value of the bright spot of the test piece subjected to antiviral treatment (-) = log 10 (Viral infection value after the antiviral treated test piece was left in a bright place for 4 hours (-))-log 10 (Viral infection value after the unprocessed test piece was left in a bright place for 4 hours (-))

[0149] In addition, the effect of light irradiation was calculated from the antiviral activity value in the dark and the antiviral activity value in the bright, and evaluated according to the following criteria.

[0150] Effect of light irradiation (antiviral activity value by light irradiation) = antiviral activity value of the bright area of ​​the test piece subjected to antiviral treatment - antiviral activity value of the dark area of ​​the test piece subjected to antiviral treatment

[0151] ·High antiviral activity in dark places (indicated by ◎)···Antiviral activity value in dark places is 2.0 or more

[0152] ·Has antiviral activity in dark places (indicated by ○)···Antiviral activity value in dark places is 1.0 or more and less than 2.0

[0153] ·The antiviral activity in the dark is low (indicated by ×)···The antiviral activity value in the dark is less than 1.0

[0154] ·High photocatalytic function (indicated by ◎)···The effect of light irradiation is 0.6 or more

[0155] ·Has photocatalytic function (indicated by ○)···The effect of light irradiation is 0.3 or more and less than 0.6

[0156] · Low photocatalytic function (indicated by △)··· The effect of light irradiation is more than 0 and less than 0.3

[0157] ·No photocatalytic function (indicated by ×)···The effect of light irradiation is 0 or less

[0158] [Preparation Example 1-1]

[0159] <Preparation of rutile titanium oxide dispersion>

[0160] As a photocatalyst material, commercially available MPT-623 (rutile titanium oxide, manufactured by Ishihara Sangyo Co., Ltd.) was dispersed in pure water and used as a photocatalyst dispersion liquid (1A) (titanium oxide concentration: 1.2% by mass).

[0161] The photocatalyst particles in the obtained photocatalyst dispersion were observed by the above method using a transmission electron microscope, and the primary particle size was confirmed to be 18 nm. The photocatalyst dispersions obtained in Preparation Examples 1-1 to 1-3 are summarized in Table 1 below.

[0162] [Preparation Example 1-2]

[0163] <Preparation of anatase-type titanium oxide dispersion: Synthesis of titanium oxide by liquid phase method>

[0164] After a 36% by mass titanium (IV) chloride aqueous solution was diluted 10 times with pure water, 10% by mass ammonia water was slowly added for neutralization and hydrolysis, thereby obtaining a titanium hydroxide precipitate. The pH at this time was 8.5. The obtained precipitate was repeatedly deionized by adding pure water and decantation. 35% by mass hydrogen peroxide water was added to the titanium hydroxide precipitate after the deionization treatment so that the H2O2 / Ti (molar ratio) became 8, and then stirred at 60°C for 2 hours to fully react to obtain an orange transparent peroxy titanic acid solution (2a).

[0165] 400 mL of peroxytitanic acid solution (2a) was placed in a 500 mL autoclave and hydrothermally treated at 130°C for 90 minutes. Then, pure water was added to adjust the concentration to obtain a dispersion of titanium oxide particles (2A) (titanium oxide concentration: 1.2 mass %).

[0166] [Preparation Example 1-3]

[0167] <Preparation of tungsten oxide dispersion>

[0168] Commercially available tungsten trioxide nanoparticles (99.95%, orthorhombic (manufactured by EM Japan Co., LTD.)) as a photocatalytic material were dispersed in pure water and used as a photocatalyst dispersion (3A) (tungsten oxide concentration: 1.2 mass %).

[0169] [Preparation Example 2-1]

[0170] <Preparation of silver nanoparticle dispersion protected with sodium citrate>

[0171] Silver nitrate was dissolved in pure water as a solvent so that the concentration in terms of Ag became 65.0 mmol / L, thereby obtaining a solution (I) containing a raw material silver compound.

[0172] A solution (i) containing a reducing agent and a protective agent was obtained by mixing 98.5 mass % of pure water as a solvent, 0.5 mass % of ferrous sulfate as a reducing agent, and 1.0 mass % of trisodium citrate dihydrate as a reducing agent / protecting agent.

[0173] In a reactor, 1500 mL of a solution (i) containing a reducing agent and a protective agent at 25° C. was mixed with 300 mL of a solution (I) containing a raw silver compound at 25° C. to obtain a liquid (pH=4.6), which was concentrated using an ultrafiltration membrane with a molecular weight cutoff of 50,000 (MOLSEP, DAICEN MEMBRANE-SYSTEMS Ltd.) and washed with pure water to obtain a silver nanoparticle dispersion (α). For the measurement of pH, a tabletop pH meter F-71 (manufactured by HORIBA Advanced Techno, Co., Ltd.) was used.

[0174] For the obtained silver nanoparticle dispersion, the metal concentration was measured by ICP-OES (Agilent Technologies, Inc.), and the mass ratio of the protective agent and the metal component was calculated from the non-volatile component concentration and the metal concentration. Furthermore, the silver nanoparticle dispersion was diluted to a specified concentration, and the dispersed particle size was measured by ELSZ-2000ZS (manufactured by Otsuka Electronics Co., Ltd., Japan). In addition, as with the above-mentioned photocatalyst particles, the obtained silver nanoparticle dispersion was photographed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Co., Ltd., Japan), and the projected area circle equivalent diameter (Heywood diameter) of 1000 particles randomly selected from multiple particle images that do not overlap with each other was measured, and the primary particle size of the silver nanoparticles was calculated from the arithmetic mean. The composition and physical properties of the silver nanoparticle dispersions obtained in Preparation Examples 2-1 to 2-6 are summarized in Table 2.

[0175] [Preparation Example 2-2]

[0176] <Preparation of silver nanoparticle dispersion protected with tannic acid>

[0177] Silver nitrate was dissolved in pure water as a solvent so that the concentration of Ag became 6.0 mmol / L, thereby obtaining a solution (II) containing a raw material silver compound.

[0178] A solution (ii) containing a reducing agent and a protecting agent was obtained by mixing 94.3% by mass of pure water, 1.9% by mass of tannic acid as a reducing agent / protecting agent, and 3.8% by mass of potassium hydroxide as an alkaline substance.

[0179] In a reactor, 1000 mL of a solution (II) containing a raw silver compound at 90°C and 100 mL of a solution (ii) containing a reducing agent and a protective agent at 60°C were mixed to obtain a liquid (pH = 12.6). The liquid was concentrated and washed with pure water in the same manner as in Preparation Example 2-1 to obtain a silver nanoparticle dispersion (β).

[0180] [Preparation Example 2-3]

[0181] <Preparation of silver-iron nanoparticle dispersion protected by tannic acid and sodium oleate>

[0182] Silver nitrate and iron (II) nitrate nonahydrate were dissolved in pure water so that the concentration of Ag became 6.0 mmol / L and the concentration of Fe became 1.1 mmol / L, thereby obtaining a solution (III) containing a raw material silver compound.

[0183] 92.4 mass % of pure water as a solvent, 1.9 mass % of tannic acid as a reducing agent / protecting agent, 1.9 mass % of sodium oleate as a protecting agent, and 3.8 mass % of potassium hydroxide as an alkaline substance were mixed to prepare a solution (iii) containing a reducing agent and a protecting agent.

[0184] A silver-iron nanoparticle dispersion (γ) was obtained in the same manner as in Preparation Example 2-2, except that a solution (III) containing a raw silver compound was used instead of a solution (II) containing a raw silver compound, and a solution (iii) containing a reducing agent and a protective agent was used instead of a solution (ii) containing a reducing agent and a protective agent. The pH of the liquid before concentration using an ultrafiltration membrane and washing with pure water was 12.7. In addition, relative to the mass of the metal component of the silver-iron nanoparticles in the silver-iron nanoparticle dispersion (γ), the content of the silver component was 90% by mass, and the content of the iron component was 10% by mass.

[0185] [Preparation Example 2-4]

[0186] <Preparation of silver palladium nanoparticle dispersion protected by polyvinyl pyrrolidone>

[0187] Silver nitrate and palladium nitrate dihydrate were dissolved in pure water so that the concentration of Ag became 6.0 mmol / L and the concentration of Pd became 0.1 mmol / L, thereby obtaining a solution (IV) containing a raw material silver compound.

[0188] A solution (iv) containing a reducing agent and a protective agent was obtained by mixing 55% by mass of ethylene glycol and 8% by mass of pure water as a solvent, 2% by mass of potassium hydroxide as an alkaline substance, 20% by mass of hydrazine monohydrate as a reducing agent, 5% by mass of dimethylaminoethanol, and 10% by mass of polyvinylpyrrolidone K30 (PVP, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a reducing agent and a protective agent.

[0189] A silver palladium nanoparticle dispersion (δ) was obtained in the same manner as in Preparation Example 2-2, except that a solution (IV) containing a raw silver compound was used instead of a solution (II) containing a raw silver compound, and a solution (iv) containing a reducing agent and a protective agent was used instead of a solution (ii) containing a reducing agent and a protective agent. The pH of the liquid before concentration using an ultrafiltration membrane and washing with pure water was 13.2. In addition, relative to the mass of the metal component of the silver palladium nanoparticles in the silver palladium nanoparticle dispersion (δ), the content of the silver component was 98% by mass, and the content of the palladium component was 2% by mass.

[0190] [Preparation Example 2-5]

[0191] A silver palladium nanoparticle dispersion (ε) was obtained in the same manner as in Preparation Example 2-4 except that the temperature of the solution containing the raw silver compound was set to 25° C. and the temperature of the solution containing the reducing agent and the protective agent was set to 25° C. The pH of the liquid before concentration using an ultrafiltration membrane and washing with pure water was 13.2.

[0192] [Preparation Example 2-6]

[0193] <Preparation of coarse silver particle dispersion>

[0194] A solution (v) containing a reducing agent was obtained by mixing 55% by mass of ethylene glycol and 18% by mass of pure water as a solvent, 2% by mass of potassium hydroxide as an alkaline substance, 20% by mass of hydrazine monohydrate as a reducing agent, and 5% by mass of dimethylaminoethanol.

[0195] A silver particle dispersion (ζ) was obtained in the same manner as in Preparation Example 2-2 except that a solution (v) containing a reducing agent was used instead of a solution (ii) containing a reducing agent and a protective agent. The pH of the liquid before concentration by an ultrafiltration membrane and washing with pure water was 13.2.

[0196] The compositions of the dispersions of the following Examples and Comparative Examples are summarized in Table 3, and the results of the antiviral evaluation of the compositions of the Examples and Comparative Examples are summarized in Table 4.

[0197] [Example 1]

[0198] The photocatalyst particle dispersion (1A) and the silver nanoparticle dispersion (α) were mixed so that the photocatalyst component was 4200 ppm and the silver component was 33 ppm on a mass basis, thereby obtaining a photocatalyst-silver nanoparticle dispersion (a).

[0199] The photocatalyst-silver nanoparticle dispersion was applied to a glass substrate to a concentration of 10 g / m 2 , dried to form a photocatalyst-silver nanoparticle composition (A) on a glass substrate, and the antiviral activity was measured.

[0200] [Example 2]

[0201] The photocatalyst particle dispersion (2A) and the silver nanoparticle dispersion (β) were mixed so that the photocatalyst component became 2400 ppm and the silver component became 33 ppm, thereby obtaining a photocatalyst-silver nanoparticle dispersion (b). Otherwise, a photocatalyst-silver nanoparticle composition (B) was prepared in the same manner as in Example 1, and the antiviral properties were measured.

[0202] [Example 3]

[0203] The photocatalyst particle dispersion (3A) and the silver nanoparticle dispersion (γ) were mixed so that the photocatalyst component became 4200 ppm and the silver component became 13 ppm, thereby obtaining a photocatalyst-silver nanoparticle dispersion (c). Otherwise, a photocatalyst-silver nanoparticle composition (C) was prepared in the same manner as in Example 1, and the antiviral properties were measured.

[0204] [Example 4]

[0205] The photocatalyst particle dispersion (1A) and the silver nanoparticle dispersion (δ) were mixed so that the photocatalyst component became 4200 ppm and the silver component became 33 ppm, thereby obtaining a photocatalyst-silver nanoparticle dispersion (d). In addition, a photocatalyst-silver nanoparticle composition (D) was prepared in the same manner as in Example 1, and the antiviral property was measured.

[0206] [Example 5]

[0207] The photocatalyst particle dispersion (1A) and the silver nanoparticle dispersion (ε) were mixed so that the photocatalyst component became 7000 ppm, the silver component became 33 ppm, and the binder concentration became 4200 ppm, thereby obtaining a photocatalyst-silver nanoparticle dispersion (e). Otherwise, a photocatalyst-silver nanoparticle composition (E) was prepared in the same manner as in Example 1, and its antiviral properties were measured.

[0208] [Example 6]

[0209] A photocatalyst particle dispersion (1A) was mixed with a silver nanoparticle dispersion (α) and colloidal silica (trade name: SNOWTEX 20, manufactured by Nissan Chemical Industries, Ltd.) so that the photocatalyst component was 4200 ppm, the silver component was 33 ppm, and the adhesive concentration was 4200 ppm, thereby obtaining a photocatalyst-silver nanoparticle-adhesive dispersion (f). Otherwise, a photocatalyst-silver nanoparticle-adhesive composition (F) was prepared in the same manner as in Example 1, and its antiviral properties were measured.

[0210] [Example 7]

[0211] A photocatalyst particle dispersion (1A) was mixed with a silver nanoparticle dispersion (α) and a silicate aqueous solution (trade name: Scutum S, manufactured by Shin-Etsu Chemical Co., Ltd.) so that the photocatalyst component was 4200 ppm, the silver component was 33 ppm, and the binder concentration was 6200 ppm, thereby obtaining a photocatalyst-silver nanoparticle-binder dispersion (g). Otherwise, a photocatalyst-silver nanoparticle-binder composition (G) was prepared in the same manner as in Example 1, and its antiviral properties were measured.

[0212] [Example 8]

[0213] A photocatalyst particle dispersion (1A) and a silver nanoparticle dispersion (α) were mixed with a product of JIS No. 3 sodium silicate (manufactured by Fuji Chemical Co., Ltd., Japan) adjusted to pH 4.0 using a cation exchange resin (trade name: Amberlite HPR1024H, manufactured by Organo Corporation) so that the photocatalyst component became 4200 ppm, the silver component became 33 ppm, and the binder concentration became 2200 ppm to obtain a photocatalyst-silver nanoparticle-binder dispersion (h). Otherwise, a photocatalyst-silver nanoparticle-binder composition (H) was prepared in the same manner as in Example 1, and the antiviral property was measured.

[0214] [Comparative Example 1]

[0215] The photocatalyst particle dispersion (1A) and the silver particle dispersion (ζ) were mixed so that the photocatalyst component became 4200 ppm and the silver component became 33 ppm, thereby obtaining a photocatalyst-silver particle dispersion (i). In addition, a photocatalyst-silver nanoparticle composition (I) was prepared in the same manner as in Example 1, and the antiviral property was measured.

[0216] [Comparative Example 2]

[0217] A photocatalyst particle dispersion (1A) was mixed with a silver particle dispersion (ζ) and colloidal silica (trade name: SNOWTEX20, manufactured by Nissan Chemical Industries, Ltd.) so that the photocatalyst component was 4200 ppm, the silver component was 33 ppm, and the adhesive concentration was 4200 ppm, thereby obtaining a photocatalyst-silver particle-adhesive dispersion (j). In addition, a photocatalyst-silver particle-adhesive composition (J) was prepared in the same manner as in Example 1, and its antiviral properties were measured.

[0218] [Comparative Example 3]

[0219] A photocatalyst composition (K) was prepared in the same manner as in Example 1, and its antiviral property was measured, except that the photocatalyst particle dispersion (1A) was diluted with pure water so that the photocatalyst component became 4200 ppm to obtain a photocatalyst dispersion (k).

[0220] [Comparative Example 4]

[0221] A photocatalyst particle dispersion (1A) and a silicate aqueous solution (trade name: Scutum S, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed so that the photocatalyst component concentration was 4200 ppm and the adhesive concentration was 4200 ppm to obtain a photocatalyst-adhesive dispersion (l). Otherwise, a photocatalyst-adhesive composition (L) was prepared in the same manner as in Example 1, and its antiviral properties were measured.

[0222] [Comparative Example 5]

[0223] The silver nanoparticle dispersion (α) was mixed to obtain a silver nanoparticle dispersion (m). A silver nanoparticle composition (M) was prepared in the same manner as in Example 1 except that the silver content was 33 ppm, and the antiviral activity was measured.

[0224] [Table 1]

[0225]

[0226] [Table 2]

[0227]

[0228] [Table 3]

[0229]

[0230]

Table 4

[0231]

[0232] As can be seen from Examples 1 to 8, the antiviral activity value of the antiviral composition of the present invention comprising silver nanoparticles having a dispersed particle size of 1000 nm or less and a primary particle size of 500 nm or less and photocatalyst particles in the dark is 1.0 (making about 90% of viruses inactive) or more, and the effect of light irradiation exceeds 0.3, confirming the antiviral activity of the composition and the improvement of the antiviral activity by light irradiation. In particular, in Examples 6 to 8, the antiviral activity value in the dark is 2.0 (making about 99% of viruses inactive) or more, confirming the high antiviral activity of the composition in the dark.

[0233] From Examples 6 to 8, it is found that if the composition further contains a binder component, the effect of light irradiation is improved while maintaining high antiviral properties in dark places, and this is a feature that was unexpected for conventional photocatalyst compositions.

[0234] From Comparative Examples 1 and 2, it can be seen that the composition containing coarse silver particles exhibits antiviral properties in the dark, but in terms of the effect of light irradiation, Comparative Examples 3 and 4 using a photocatalyst alone are superior, confirming that coarse silver particles hinder the photocatalytic function. In addition, the antiviral properties in the dark and the effects of light irradiation are reduced due to the addition of a binder.

[0235] Comparative Examples 3 to 5 show that the antiviral property in the dark is low when the photocatalyst is used alone, and the effect of light irradiation is low when the silver nanoparticles are used alone. In addition, the antiviral property in the dark and the effect of light irradiation are both reduced due to the addition of a binder.

Claims

1. An antiviral composition comprising the following two particles: i) photocatalyst particles; and ii) silver nanoparticles having a dispersed particle size of 1000 nm or less and a primary particle size of 500 nm or less and having a protective agent adsorbed on the surface; The antiviral activity value of the antiviral composition in a dark place based on JIS R1756:2020 is greater than 0.3, and the antiviral activity value of the composition by light irradiation based on JIS R1756:2020 is 0.3 or more.

2. The antiviral composition according to claim 1, further comprising a binder.

3. The antiviral composition according to claim 1 or claim 2, wherein: The amount of the protective agent is in the range of 0.001 to 10 in terms of mass ratio relative to the amount of the metal component in the silver nanoparticles (ii).

4. A member having the antiviral composition according to claim 3 on its surface.

5. The antiviral composition according to claim 1 or claim 2, further comprising an aqueous dispersion medium.

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