Photocatalyst coating film

Abstract

To provide a photocatalyst coating film that utilizes a photocatalytic material to impart high antibacterial-antiviral capability to a product surface.SOLUTION: A photocatalyst coating film contains a photocatalytic material and has a surface zeta potential of +5 mV or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a photocatalytic coating comprising a photocatalytic material. [Background technology]

[0002] There are currently studies being conducted on imparting antibacterial and / or antiviral properties to the surfaces of various products, such as home appliances and vehicle interior components.

[0003] For example, Patent Document 1 describes a laminated film having a resin layer containing 20% ​​by weight or more and 90% by weight or less of cerium oxide particles on at least one side of a thermoplastic film, in which the surface zeta potential of the resin layer is adjusted to a range of -10 mV or more and +70 mV or less, and cerium oxide particles are used as an antibacterial and antiviral material.

[0004] Patent Document 2 describes a method for producing an antibacterial and antiviral fiber in which an antibacterial and antiviral compound having a cationic group on the surface of a quaternary ammonium salt, which is said to have antibacterial and antiviral properties, is applied to the fiber surface, and the zeta potential of the fiber surface is described to be in the range of -100 mV or more and -0.1 mV or less.

[0005] Patent Document 3 describes a technology for manufacturing an antibacterial and antiviral adhesive tape (film) that includes an adhesive layer, an antibacterial and antiviral layer comprising a mixture of copper compound particles that act as an antibacterial and antiviral agent, a cationic surfactant that acts as a surface potential control agent, and a resin, and a contact inhibition layer that contains resin, is disposed between the adhesive layer and the antibacterial and antiviral layer, and inhibits contact between the copper compound particles and the adhesive layer, and it is described that the surface potential control agent is used to change the electric potential of the resin on the surface of the antibacterial and antiviral layer in a positive direction.

[0006] Patent Document 1 uses cerium oxide particles as an antibacterial and antiviral material, and is characterized by a surface zeta potential of -10 mV or more and +70 mV or less, but explains that the expected mechanism of action of the antiviral properties is different from the photocatalytic effect. Furthermore, Patent Document 1 only confirms the antiviral effect by observing the change in the oxidizing power of the sample, and does not conduct a virus inactivation test, and does not show any improvement in antiviral performance.

[0007] In Patent Document 2, an antibacterial and antiviral agent using a quaternary ammonium salt is used, and is characterized by negatively charging the zeta potential of the fiber surface.

[0008] In Patent Document 3, a copper compound is used as an antibacterial and antiviral agent, and a cationic surfactant is used to adjust the electric potential of the resin on the surface of the antibacterial and antiviral layer. However, because this is a technology that uses an organic surfactant, it is not applicable to material systems that use photocatalysts with excellent oxidizing capabilities, as the surfactant is decomposed. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent Publication No. 2022-079832 [Patent Document 2] Patent Publication No. 2022-076352 [Patent Document 3] JP 2016-088916 A Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide a photocatalytic coating film that utilizes a photocatalytic material to impart high antibacterial and antiviral properties to a product surface. [Means for solving the problem]

[0011] The present invention is a photocatalytic coating film that contains a photocatalytic material and has a surface zeta potential of +5 mV or more.

[0012] In the photocatalytic coating film, the photocatalytic material is preferably a visible light responsive photocatalytic material that responds to visible light.

[0013] In the photocatalytic coating film, the visible light responsive photocatalytic material is preferably nitrogen-doped titanium oxide.

[0014] In the photocatalytic coating film, the primary particle size of the nitrogen-doped titanium oxide is preferably 100 nm or less.

[0015] The photocatalytic coating film preferably contains a surface potential adjusting material for adjusting the surface potential.

[0016] In the photocatalytic coating film, the surface potential adjusting material is preferably particles of an inorganic oxide having an isoelectric point of 7 or more.

[0017] In the photocatalytic coating film, the inorganic oxide particles are preferably at least one of aluminum oxide particles, zirconium oxide particles, magnesium oxide particles, zinc oxide particles, and surface-modified silica particles.

[0018] In the photocatalytic coating film, the inorganic oxide particles preferably have a primary particle size of 100 nm or less.

[0019] In the photocatalytic coating film, the surface zeta potential is preferably in the range of +6 to +20 mV. Effect of the Invention

[0020] The present invention provides a photocatalytic coating film that utilizes a photocatalytic material and can impart high antibacterial and antiviral properties to the surface of a product. [Brief description of the drawings]

[0021] [Figure 1] 1 is a graph showing the results of antibacterial and antiviral performance tests in Example 1 and Comparative Example 1. [Diagram 2] 1 is a graph showing the surface ζ potential (mV) of each sample in Examples 2 to 4 and Comparative Examples 1 and 2. [Diagram 3] 1 is a graph showing antibacterial and antiviral activity values ​​versus surface ζ potential (mV) for each sample in Examples 2 to 4 and Comparative Examples 1 and 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of the present invention. The embodiment is merely an example of implementing the present invention, and the present invention is not limited to the embodiment.

[0023] The photocatalytic coating film according to this embodiment is a photocatalytic coating film that contains a photocatalytic material and has a surface potential of +5 mV or more.

[0024] The photocatalytic coating film according to this embodiment can impart high antibacterial and antiviral properties to the product surface by utilizing a photocatalytic material. Even under low illumination conditions (e.g., 500 Lx or less), it can achieve antibacterial and antiviral properties of, for example, JIS-compliant activity value 2 or more, and can impart antibacterial and antiviral properties to various products such as home appliances and vehicle interior components.

[0025] For example, by adding a material with an isoelectric point of 7 or higher to the photocatalytic coating, the surface potential of the coating can be adjusted to a positive potential, promoting the adsorption of bacteria and viruses and increasing the frequency of contact between the photocatalytic surface and bacteria and viruses. This effect is believed to make it possible to improve the inactivation performance of bacteria and viruses by the photocatalyst, which is a surface reaction.

[0026] Conventional antibacterial and antiviral materials include photocatalytic materials, metals such as copper (Cu) and silver (Ag), inorganic materials such as their oxides, and organic materials such as quaternary ammonium salts. All of these inactivate bacteria and viruses by interacting with reactive species generated on the surface of the material. In particular, reactive oxygen species, which are considered to be the main cause of inactivation, are unstable and have a short lifespan, so it is important to increase the frequency of contact between the material surface and the target object such as bacteria or viruses. Here, the surfaces of general bacteria and viruses are negatively charged in a neutral wet area due to the composition of the shell and membrane that they are made of, and it is thought that bacteria and viruses are electrostatically repelled by negatively charged surfaces and adsorption is suppressed. Photocatalytic materials such as titanium oxide have an isoelectric point of the surface around 5, so they are negatively charged in neutral water, which suppresses adsorption of bacteria and viruses, and it is an issue that their antibacterial and antiviral performance is not fully demonstrated on smooth surfaces, for example. The present inventors have found that, for example, by mixing a surface potential adjusting material such as an inorganic oxide, which has an isoelectric point of 7 or more and has almost no effect on the photocatalytic reaction, into a photocatalytic coating film containing a photocatalytic material to positively charge the coating film and promote the adsorption of bacteria and viruses by setting the surface potential at +5 mV or more, it is possible to increase the frequency of contact with bacteria and viruses on the photocatalytic surface and impart high antibacterial and antiviral performance. It is believed that this effect makes it possible to improve the inactivation performance of bacteria and viruses by the photocatalyst, which is a surface reaction.

[0027] For the above reasons, the photocatalytic coating film according to this embodiment has the ability to overcome the above problems, and is an excellent technology, particularly for antibacterial and antiviral materials with excellent oxidizing power that utilize photocatalysts.

[0028] The photocatalyst material is not particularly limited as long as it responds to light and exhibits antibacterial and antiviral properties. Examples of the photocatalyst material include visible light responsive photocatalyst materials such as nitrogen-doped titanium oxide, tungsten oxide, and metal-doped titanium oxide, and ultraviolet light responsive photocatalyst materials such as titanium oxide and zinc oxide. From the viewpoint of indoor use, the photocatalyst material is preferably a visible light responsive photocatalyst material that responds to visible light.

[0029] As the visible light responsive photocatalyst material, nitrogen-doped titanium oxide is preferred from the viewpoint of fine particle formation for forming a transparent film.

[0030] The primary particle size of the nitrogen-doped titanium oxide is preferably 100 nm or less, more preferably 30 nm or less. If the primary particle size of the nitrogen-doped titanium oxide exceeds 100 nm, the transparency of the film may decrease. The lower limit of the primary particle size of the nitrogen-doped titanium oxide is not particularly limited, but is, for example, 5 nm.

[0031] The photocatalytic coating film preferably contains a surface potential adjusting material for adjusting the surface potential. Examples of the surface potential adjusting material include materials having an isoelectric point of 7 or more, preferably materials having an isoelectric point of 8 to 14. Examples of materials having an isoelectric point of 7 or more include particles of aluminum oxides such as boehmite and alumina, zirconium oxides, zinc oxides, magnesium oxides, cadmium oxides, lead oxides, nickel oxides, and copper oxides, surface-modified silica particles, hydroxides of various metals, and organic substances such as quaternary ammonium salts.

[0032] Of these, the surface potential adjusting material is preferably at least one of aluminum oxide particles, zirconium oxide particles, magnesium oxide particles, zinc oxide particles, and surface-modified silica particles, because they are low in toxicity, colorless, and do not become oxidized by the photocatalyst, reducing their activity.

[0033] The primary particle size of the inorganic oxide particles is preferably 100 nm or less. If the primary particle size of the inorganic oxide particles exceeds 100 nm, the transparency of the film may decrease. The lower limit of the primary particle size of the inorganic oxide particles is not particularly limited, but is, for example, 5 nm.

[0034] In the photocatalytic coating film, the surface zeta potential is +5 mV or more, and preferably in the range of +6 to +20 mV. If the surface zeta potential is less than +5 mV, the antibacterial and antiviral performance may not be fully exhibited, and if it exceeds +20 mV, the dispersibility of the coating liquid may decrease, and the photocatalytic particles may aggregate, resulting in a decrease in the transparency of the film.

[0035] The content of the photocatalytic material in the photocatalytic coating film is, for example, in the range of 20% by mass to 90% by mass, and preferably in the range of 60% by mass to 85% by mass, based on the mass of the solid content of the photocatalytic coating film. If the content of the photocatalytic material in the photocatalytic coating film is less than 20% by mass based on the mass of the solid content of the photocatalytic coating film, the antibacterial and antiviral performance may be insufficient, and if it exceeds 90% by mass, the film strength may decrease.

[0036] The content of the surface potential adjusting material in the photocatalytic coating film is not particularly limited as long as it is an amount that can make the surface potential +5 mV or more. The content of the surface potential adjusting material in the photocatalytic coating film is, for example, in the range of 5 mass % to 50 mass % relative to the mass of the solid content of the photocatalytic coating film, and preferably in the range of 10 mass % to 25 mass %. If the content of the surface potential adjusting material in the photocatalytic coating film is less than 5 mass % relative to the mass of the solid content of the photocatalytic coating film, the surface potential may not be made +5 mV or more, and if it exceeds 50 mass %, the amount of photocatalyst is relatively small, and the photocatalytic activity and antibacterial and antiviral performance may be reduced.

[0037] The photocatalytic coating film may contain, in addition to the photocatalytic material and the surface potential adjusting material, other materials such as a binder, a color tone adjusting material, and a film surface hardening material.

[0038] When other components are contained, the content of the other components in the photocatalytic coating film is, for example, in the range of 5 mass % to 80 mass % relative to the mass of the solid content of the photocatalytic coating film.

[0039] The photocatalytic coating film according to this embodiment can be applied to products such as home appliances, components for vehicle interiors, indoor products for use indoors such as hospitals and public facilities, and outdoor products for use in the shade where there is little ultraviolet light. Since this material is responsive even in the absence of ultraviolet light, it is particularly suitable for use in components for vehicle interiors and indoor products. The photocatalytic coating film according to this embodiment can impart high antibacterial and antiviral performance to the surfaces of these various products.

[0040] The photocatalytic coating film according to this embodiment may be formed on the surface of a target product, etc., by a known film formation method such as spin coating, spraying, immersion, etc., using a photocatalyst-containing liquid in which a photocatalytic material and, if necessary, a surface potential adjusting material, etc. are dissolved or dispersed in a solvent.

[0041] Examples of the solvent include water and organic solvents such as alcohol.

[0042] The solid content concentration of the photocatalyst-containing liquid may be appropriately selected depending on the film formation method, and is not particularly limited.

[0043] This specification includes the following embodiments. (1) A photocatalytic coating film containing a photocatalytic material and having a surface potential of +5 mV or more.

[0044] (2) The photocatalytic coating film according to (1), The photocatalytic coating film, wherein the photocatalytic material is a visible light responsive photocatalytic material that responds to visible light.

[0045] (3) The photocatalytic coating film according to (2), A photocatalytic coating film, wherein the visible light responsive photocatalytic material is nitrogen-doped titanium oxide.

[0046] (4) The photocatalytic coating film according to (3), A photocatalytic coating film, wherein the primary particle size of the nitrogen-doped titanium oxide is 100 nm or less.

[0047] (5) A photocatalytic coating film according to any one of (1) to (4), A photocatalytic coating film comprising a surface potential adjusting material for adjusting the surface potential.

[0048] (6) The photocatalytic coating film according to (5), The photocatalytic coating film, wherein the surface potential adjusting material is particles of an inorganic oxide having an isoelectric point of 7 or more.

[0049] (7) The photocatalytic coating film according to (6), The photocatalytic coating film, wherein the inorganic oxide particles are at least one of aluminum oxide particles, zirconium oxide particles, magnesium oxide particles, zinc oxide particles, and surface-modified silica particles.

[0050] (8) A photocatalytic coating film according to (6) or (7), A photocatalytic coating film, wherein the primary particle size of the inorganic oxide particles is 100 nm or less.

[0051] (9) A photocatalytic coating film according to any one of (1) to (8), The photocatalytic coating film, wherein the surface potential is in the range of +6 to +20 mV. EXAMPLES

[0052] EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0053] [How to make photocatalytic coating film] A 5 cm × 5 cm glass plate was spin-coated with 1 mL of photocatalytic coating solution containing nitrogen-doped titanium oxide (visible light responsive photocatalytic material) carrying copper as a photocatalytic material, with the amount of photocatalytic material being 0.5 g / m 2 The coated sample was heat treated at 200°C for 30 minutes, and then the irradiance was adjusted to 1.0 mW / cm 2The sample was irradiated with ultraviolet light of an intensity of 100 nm for 24 hours. When adding a surface potential adjusting material, a surface potential adjusting liquid in which boehmite (γ-AlOOH) was dispersed in ethanol, or a surface potential adjusting liquid in which alumina (Al2O3) sol was dispersed in water was added to the photocatalytic coating liquid in a predetermined amount, and a coating sample was similarly prepared. The primary particle size of the nitrogen-doped titanium oxide identified by X-ray diffraction was approximately 20 nm, the primary particle size of the boehmite was approximately 50 nm, and the primary particle size of the alumina was approximately 20 nm.

[0054] <Example 1> A photocatalytic coating film to which boehmite (γ-AlOOH) was added as a surface potential adjusting material at 10 mass % based on the total solid content of the photocatalytic coating film was used as Example 1.

[0055] <Example 2> A photocatalytic coating film in which alumina (Al2O3) sol was added as a surface potential adjusting material at 10 mass % based on the total solid content of the photocatalytic coating film was used as Example 2.

[0056] <Example 3> A photocatalytic coating film in which Al2O3 sol was added as a surface potential adjusting material at 25 mass % based on the total solid content of the photocatalytic coating film was used as Example 3.

[0057] <Example 4> A photocatalytic coating film in which a surface-modified silica (SiO2) sol was added as a surface potential adjusting material at 10 mass % based on the total solid content of the photocatalytic coating film was used as Example 4.

[0058] <Comparative Example 1> A photocatalytic coating film using only the photocatalytic material without adding the surface potential adjusting material was used as Comparative Example 1.

[0059] <Comparative Example 2> A photocatalytic coating film in which only Al2O3 sol was used as the surface potential adjusting material without adding any photocatalytic material was used as Comparative Example 2.

[0060] [Antibacterial and antiviral tests] The antibacterial test was conducted based on the film adhesion method in Chapter 9 of JIS R 1752:2020 "Fine ceramics - Antibacterial test methods and antibacterial effects of visible light responsive photocatalytic antibacterial products."

[0061] In addition, the antiviral test was conducted based on JIS R 1756:2020 "Fine ceramics - Antiviral test method for visible light responsive photocatalytic materials - Method using bacteriophage Qβ".

[0062] The light illuminance during the test was 500Lx, and visible light was irradiated with a filter that cuts off ultraviolet light below 380nm.The antibacterial and antiviral performance is shown by the activity value calculated in (a) below. Antibacterial and antiviral activity value in light = log(B L / A)-log(C L / A)=log(B L / C L ) (a) A: Mean viable cell count or infectious titer immediately after inoculation of unprocessed specimens B L : Average number of viable bacteria or infectious value after irradiation for a specified time on unprocessed specimens C L : Average number of viable bacteria or infectious value after irradiation for a specified time on processed specimens

[0063] FIG. 1 shows the results of the antibacterial and antiviral performance tests in Example 1 and Comparative Example 1.

[0064] A double-digit reduction in infectivity is considered to indicate antibacterial and antiviral performance. Example 1 demonstrated high antibacterial and antiviral performance.

[0065] [Zeta potential measurement of dispersion liquid] The zeta potential of the dispersed particles of the photocatalyst coating liquid and the surface potential adjusting liquid was measured using a Zetasizer Nano ZSP (Malvern Panaltical). The zeta potential of the dispersed particles of the photocatalyst coating liquid and the surface potential adjusting liquid is shown in Table 1.

[0066] [Surface potential measurement] The zeta potential of the sample surface was measured using a flat plate cell unit in a zeta potential measurement system ELS2000ZS (Otsuka Electronics Co., Ltd.).

[0067] [Table 1]

[0068] Fig. 2 shows the surface ζ potential of each sample in Examples 2 to 4 and Comparative Examples 1 and 2. Fig. 3 shows the antibacterial and antiviral activity value versus the surface ζ potential of each sample in Examples 2 to 4 and Comparative Examples 1 and 2.

[0069] In this manner, in the examples, a photocatalytic coating film capable of imparting high antibacterial and antiviral properties to the product surface was obtained by utilizing a photocatalytic material.

Claims

1. A photocatalytic coating film comprising a photocatalytic material and having a surface zeta potential of +5 mV or more.

2. The photocatalytic coating film according to claim 1, A photocatalytic coating film, characterized in that the photocatalytic material is a visible light responsive photocatalytic material that responds to visible light.

3. The photocatalytic coating film according to claim 2, A photocatalytic coating film, characterized in that the visible light responsive photocatalytic material is nitrogen-doped titanium oxide.

4. The photocatalytic coating film according to claim 3, A photocatalytic coating film, characterized in that the primary particle size of the nitrogen-doped titanium oxide is 100 nm or less.

5. The photocatalytic coating film according to claim 1, A photocatalytic coating film comprising a surface potential adjusting material for adjusting the surface potential.

6. The photocatalytic coating film according to claim 5, A photocatalytic coating film, wherein the surface potential adjusting material is particles of an inorganic oxide having an isoelectric point of 7 or more.

7. The photocatalytic coating film according to claim 6, The photocatalytic coating film is characterized in that the inorganic oxide particles are at least one of aluminum oxide particles, zirconium oxide particles, magnesium oxide particles, zinc oxide particles, and surface-modified silica particles.

8. The photocatalytic coating film according to claim 6 or 7, A photocatalytic coating film, characterized in that the primary particle size of the inorganic oxide particles is 100 nm or less.

9. The photocatalytic coating film according to claim 1, A photocatalytic coating film characterized in that the surface zeta potential is in the range of +6 to +20 mV.

Images