Novel composite material and method for manufacturing composite material

Abstract

A composite material comprising a core material made of cellulose nanofibers, and a coating layer made of copper that coats the core material.

Description

Technical Field

[0001] The present disclosure relates to a novel composite material, a method for producing the composite material, and a spray, sanitary material, filter, and coating agent containing the composite material.

Background Art

[0002] Copper has various functions such as conductivity, heat conductivity, and antibacterial properties. However, copper is easily oxidized, and once oxidized, it cannot exhibit the above functions. Therefore, in the use of copper, improvement of oxidation resistance is desired. For example, Patent Document 1 discloses surface-coated copper fine particles having copper fine particles and a specific organic film formed on the surface of the copper fine particles. The surface-coated copper fine particles are said to be excellent in the oxidation resistance of the copper fine particles and excellent in the conductivity of the obtained sintered body. Further, Patent Document 2 describes metal-containing oxidized cellulose nanofibers containing a metal other than sodium in the form of a salt, and the metal-containing oxidized cellulose nanofibers are said to have a high antibacterial effect. [[ID=**********]]

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

[0004] The composite material of the present disclosure has a core material made of cellulose nanofibers and a coating layer made of copper that coats the core material.

Modes for Carrying Out the Invention

[0005] Although the surface-coated copper fine particles described in Patent Document 1 are excellent in conductivity during sintering, since the resistance increases due to the organic film on the surface unless sintered, the desired conductivity cannot be obtained. The metal-containing oxidized cellulose nanofiber described in Patent Document 2 has a low concentration of metal ions, resulting in low antiviral and antibacterial effects. Furthermore, its deodorizing effect makes long-term use difficult, indicating room for improvement.

[0006] This disclosure is made in view of the above circumstances and aims to provide a novel composite material that can reduce copper oxidation and exhibit copper's functions such as antibacterial properties and conductivity, as well as a method for manufacturing the composite material.

[0007] The present disclosure will be described in detail below with reference to one embodiment.

[0008] [Composite material] The composite material of this disclosure comprises a core material made of cellulose nanofibers and a coating layer made of copper that covers the core material. The composite material of this disclosure reduces copper oxidation by coating a core material made of cellulose nanofibers with a coating layer made of copper, thereby enabling it to exhibit functions of copper such as antibacterial properties and conductivity.

[0009] The core material that makes up the composite material is made of cellulose nanofibers. Cellulose nanofibers refer to fibrous materials with a fiber diameter of 500 nm or less, produced by defibrating plant fibers at the nanoscale. The average fiber diameter of cellulose nanofibers is not particularly limited, but from the viewpoint of maintaining transparency, it may be 3 nm to 100 nm, 3 nm to 80 nm, 4 nm to 60 nm, or 4 nm to 40 nm. Furthermore, the average fiber length of the cellulose nanofibers is not particularly limited, but from the viewpoint of handling, it may be 0.5 μm to 100 μm, 0.5 μm to 50 μm, or 0.5 μm to 5 μm. The average fiber diameter and average fiber length of cellulose nanofibers are determined by averaging the fiber diameter and fiber length obtained from observing each fiber using an atomic force microscope (AFM).

[0010] The average aspect ratio of cellulose nanofibers may be 10 or greater, or 50 or greater. There is no particular upper limit to the average aspect ratio, but it is usually 1000 or less. The average aspect ratio can be calculated using the following formula (1). Aspect ratio = average fiber length / average fiber diameter (1)

[0011] The raw materials for cellulose nanofibers are not particularly limited, but examples include wood; bamboo; hemp; jute; kenaf; agricultural waste; cloth; unbleached softwood kraft pulp (NUKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), bleached hardwood kraft pulp (LBKP), unbleached softwood sulfite pulp (NUSP), bleached softwood sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, and waste paper pulp. One type of cellulose raw material may be used, or two or more types may be used in combination.

[0012] Cellulose nanofibers may be subjected to modification treatments. Specific examples of modification treatments include esterification such as acetylation, phosphorylation, urethaneization, carbamideization, etherification, carboxymethylation, TEMPO(2,2,6,6-tetramethylpiperidine-1-oxyl radical) oxidation, and periodic acid oxidation. Cellulose nanofibers may be subjected to only one of these modification treatments, or to two or more.

[0013] Commercially available cellulose nanofibers may be used. Examples of commercially available cellulose nanofibers include ELLEX-☆ (manufactured by Daio Paper Corporation), ELLEX-S (manufactured by Daio Paper Corporation), and Selenpia (registered trademark) (manufactured by Nippon Paper Industries Ltd.).

[0014] The coating layer covering the core material is made of copper. The copper forming the coating layer may be derived from copper compounds such as copper halides, copper carboxylates, or cuprous oxide. Examples of copper halides include copper iodide, copper bromide, and copper chloride. Examples of copper carboxylates include copper oxalate and copper acetate. From the viewpoint of manufacturability, the copper compound may be a copper halide or a copper chloride.

[0015] The thickness of the coating layer may be between 1 nm and 150 nm, between 2 nm and 120 nm, or between 3 nm and 100 nm. A coating layer thickness of 1 nm or more allows copper to exhibit its antibacterial properties, conductivity, and other functions more effectively, while a thickness of 150 nm or less reduces copper oxidation. The thickness of the coating layer can be calculated by cutting the composite material with a focused ion beam (FIB) to prepare cross-sectional sections, photographing these sections with a transmission electron microscope (TEM), and taking the average value of 100,000 to 500,000 measurements. Specifically, it can be measured by the method described in the examples. Furthermore, if the composite material of this disclosure has a plating layer as described later, the range of thickness of the coating layer includes the total thickness of the copper coating layer and the plating layer.

[0016] The covering layer may cover the entire surface of the core material, or it may cover only a portion of it. The coverage rate of the coating layer on the core material may be 0.5% to 99%, 1% to 99%, 5% to 99%, or 10% to 99%. When the coverage rate of the coating layer is 0.5% or higher, the functions of copper, such as antibacterial properties and conductivity, can be exhibited more effectively, and when it is 99% or lower, the oxidation of copper can be reduced. The coverage rate of the coating layer can be measured by a pyrolysis method using an electric furnace or a differential thermogravimetric / thermogravimetric analysis device (TG / DTA). Specifically, it can be measured by the method described in the examples.

[0017] From the perspective of further exerting the functions of copper such as antibacterial properties and conductivity, the composite material of the present disclosure may have a plating layer covering the coating layer. Examples of the metal constituting the plating layer include copper, nickel, chromium, cobalt, tin, and the like.

[0018] The thickness of the plating layer may be 0.01 μm or more and 0.50 μm or less, may be 0.01 μm or more and 0.20 μm or less, or may be 0.01 μm or more and 0.10 μm or less. When the thickness of the plating layer is 0.01 μm or more, the functions of copper such as antibacterial properties and conductivity can be more exerted, and when it is 0.50 μm or less, transparency can be maintained. The thickness of the plating layer can be measured by a fluorescent X-ray analyzer or a FIB-TEM (Focused Ion Beam-Transmission Electron Microscope).

[0019] [Manufacturing method of composite material] The manufacturing method of the composite material of the present disclosure is a method of immersing cellulose nanofibers in a copper particle dispersion liquid. The copper particle dispersion liquid is obtained by mixing a copper compound, a reducing compound, a water-soluble chloride, and a reducing saccharide in a dispersion medium. The copper compound is not particularly limited as long as it contains copper atoms. Examples of the copper compound include copper halides, copper carboxylates, copper oxides, and the like. Examples of the copper halide include copper iodide, copper bromide, copper chloride, and the like. Examples of the copper carboxylate include copper oxalate, copper acetate, and the like. From the perspective of manufacturability, the copper compound may be a copper halide or copper chloride. The copper compound may be used alone or in combination of two or more.

[0020] The reducing compound is not particularly limited as long as it has a reducing power to reduce the copper compound and liberate metallic copper. Examples of the reducing compound include sodium compounds such as sodium borohydride, sodium sulfite, sodium bisulfite, sodium thiosulfate, and sodium hypophosphite; hydrazine compounds such as hydrazine, hydrazine derivatives, hydrazine hydrochloride, and hydrazine sulfate; and organic acids such as oxalic acid and formic acid. From the viewpoint of adjusting the thickness of the coating layer to a desired thickness, the reducing compound may be a sodium compound or sodium borohydride. The reducing compound may be used alone or in combination of two or more kinds.

[0021] From the viewpoint of adjusting the thickness of the coating layer to a desired thickness, the blending amount of the reducing compound may be 1 mol or more and 50 mol or less, 2 mol or more and 40 mol or less, or 2 mol or more and 30 mol or less with respect to 1 mol of the copper compound.

[0022] The water-soluble chloride is used as a colloid stabilizer. Examples of the water-soluble chloride include sodium chloride, potassium chloride, and magnesium chloride. The water-soluble chloride may be sodium chloride. The water-soluble chloride may be used alone or in combination of two or more kinds.

[0023] From the viewpoint of the stability of the copper particle dispersion liquid, the blending amount of the water-soluble chloride may be 2 mol or more and 80 mol or less, 2 mol or more and 60 mol or less, or 2 mol or more and 40 mol or less with respect to 1 mol of the copper compound.

[0024] The reducing saccharide is used as a reduction aid. Examples of the reducing saccharide include sucrose, galactose, and fructose. The reducing saccharide may be sucrose. The reducing saccharide may be used alone or in combination of two or more kinds.

[0025] The amount of reducing sugars added may be 0.5 mol to 10 mol, 1 mol to 5 mol, or 1 mol to 2 mol per mol of copper compound, from the viewpoint of the reducing properties of the copper compound.

[0026] Examples of dispersion media include water and alcohol. Examples of alcohols include methanol, ethanol, propanol, and butanol. The dispersion medium should be in an amount sufficient to disperse the copper particles.

[0027] A copper particle dispersion can be prepared by adding a copper compound, a reducing compound, a water-soluble chloride, and a reducing sugar to a dispersion medium and stirring thoroughly by hand or with a stirrer. The order in which the above compounds are mixed is not particularly limited, but the reducing compound may be added while stirring after adding the copper compound, water-soluble chloride, and reducing sugar to the dispersion medium. The rate at which the reducing compound is added may be 0.1 g / min to 5.0 g / min, 0.1 g / min to 3.0 g / min, or 0.1 g / min to 2.0 g / min, from the viewpoint of adjusting the thickness of the coating layer to the desired thickness.

[0028] The solid content concentration of the copper particle dispersion may be 1% by mass or more and 80% by mass or less, 5% by mass or more and 50% by mass or less, or 10% by mass or more and 40% by mass or less, based on the total volume (100% by mass) of the dispersion. If the solid content concentration is 1% by mass or more, the coverage rate of the coating layer can be adjusted to a desired range, and if it is 80% by mass or less, the dispersibility of the copper particles is ensured. In this disclosure, "solid content concentration" refers to the content (concentration) of components other than the dispersion medium.

[0029] Various known agitators can be used in the dispersion process to obtain a copper particle dispersion. Examples include high-speed stirring and mixing devices such as dispersers and homomixers; kneaders such as roll mills, kneaders and extruders; high-pressure dispersers such as high-pressure homogenizers; media-type dispersers such as paint shakers and bead mills; and mixing and stirring devices such as anchor blades. Multiple of these devices can also be used in combination.

[0030] The copper particles contained in the copper particle dispersion may have an average particle diameter of 1 nm to 150 nm, 2 nm to 130 nm, or 3 nm to 120 nm. When the average particle diameter of the copper particles is 1 nm or more, antibacterial properties can be exhibited, and when it is 150 nm or less, the resulting composite material can exhibit more of the functions of copper, such as antibacterial properties and conductivity. The average particle size of copper particles can be measured using a field emission scanning electron microscope (FE-SEM). Specifically, it can be measured by the method described in the examples.

[0031] The shape of the copper particles is not particularly limited and may include spherical, plate-shaped, flake-shaped, flaky, dendritic, rod-shaped, wire-shaped, etc.

[0032] Next, the cellulose nanofibers are immersed in a copper particle dispersion. This yields a composite material having a core made of cellulose nanofibers and a coating layer made of copper that covers the core. The conditions for immersing cellulose nanofibers in a copper particle dispersion are not particularly limited, but may be 5°C to 60°C for 0.1 to 6 hours, 5°C to 40°C for 0.1 to 3 hours, or 10°C to 40°C for 0.5 to 2 hours. By immersing cellulose nanofibers in a copper particle dispersion under the above conditions, the coverage of the coating layer can be adjusted to a desired range. Furthermore, by appropriately adjusting the amount of cellulose nanofibers immersed in the copper particle dispersion, the coverage of the coating layer can be adjusted to a desired range.

[0033] From the viewpoint of adsorption of copper particles, cellulose nanofibers may be immersed in an aqueous solution of a cationic surfactant having a quaternary amine group before immersing them in a copper particle dispersion. Examples of cationic surfactants having a quaternary amine group include trimethylstearylammonium chloride and dicocoyldimethylammonium chloride. The cationic surfactant having a quaternary amine group may also be trimethylstearylammonium chloride.

[0034] The composite material obtained in this way may be washed with water or alcohol. Examples of alcohols used for washing include methanol, ethanol, and propanol.

[0035] A plating treatment may be applied to the coating layer of the composite material to form a plating layer on the surface of the coating layer. Electroless plating is used for the plating treatment. Electroless plating is a method of forming a plating layer consisting of a metal film by, for example, bringing an electroless plating solution into contact with the coating layer of the composite material, thereby depositing the metal contained in the electroless plating solution. The electroless plating solution used for the electroless plating treatment can be a known electroless plating solution, and there are no particular restrictions. Alternatively, after applying electroless plating to the coating layer, electroplating may be performed to form a plating layer. The electroplating treatment can be carried out by known methods and is not particularly limited.

[0036] [Dispersion] The composite material of this disclosure may also be in the form of a dispersion in which the composite material is dispersed. Examples of dispersion media for dispersing the composite material include water, organic solvents, and resins. Examples of organic solvents used as dispersion media include ethanol, terpineol, and carbitol acetate. Organic solvents may be used individually or in combination of two or more.

[0037] Examples of resins used as dispersion media include siloxane resins, epoxy resins, and acrylic resins. Resins may be used individually or in combination of two or more types.

[0038] The dispersion can be prepared by adding the composite material to the dispersion medium and stirring thoroughly by hand or with a stirrer.

[0039] The solid content concentration of the dispersion may be 0.1% by mass or more and 50% by mass or more and 40% by mass or more and 20% by mass or more, based on the total volume (100% by mass) of the dispersion. An antibacterial effect can be achieved when the solid content concentration is 0.1% by mass or more, and dispersibility in the dispersion medium can be ensured when it is 50% by mass or less.

[0040] [Application] The composite material of this disclosure exhibits reduced copper oxidation and can demonstrate the functions of copper, such as antibacterial properties and conductivity. Therefore, the composite material of this disclosure and dispersions thereof are suitable for use in sprays; sanitary materials such as masks, diapers, and sanitary products; transparent conductive materials used in liquid crystal displays, touch panels, and solar cells; filters for air conditioners and air purifiers; and coating agents for anti-fouling and anti-scratch applications. [Examples]

[0041] The present disclosure will now be specifically illustrated by examples, but the present disclosure is not limited in any way by these examples.

[0042] (Manufacturing Example 1) To a reactor containing 1 L of an aqueous solution containing 20 mmol of copper chloride (CuCl2) and 0.1 mol of sodium chloride (NaCl), 10 g of sucrose was added, and while stirring, sodium borohydride (NaBH4) was added dropwise at a rate of 1 g / min to obtain a copper nanocolloid solution containing copper particles with an average particle size of 5 nm and a solid content concentration of 1% by mass. Cellulose nanofibers (product name: ELLEX-☆, manufactured by Daio Paper Corporation, average fiber diameter 5 nm, average fiber length 1 μm) that had been pre-washed with a 1 M sodium hydroxide (NaOH) aqueous solution were immersed in a 1% trimethylstearylammonium chloride aqueous solution, and then immersed in the above copper nanocolloid solution at a temperature of 25°C for 1 hour. After washing with ethanol, composite material 1 was obtained. When the cross-section of the obtained composite material 1 was observed with a field emission scanning electron microscope (FE-SEM) (JSM-7401F, manufactured by JEOL Ltd.), it was confirmed that a copper layer (coating layer) of almost uniform thickness was formed over the entire surface of the cellulose nanofibers in composite material 1. Composite material 1 had a coating layer coverage rate of 99% and a coating layer thickness of 5 nm.

[0043] (Manufacturing example 2) To a reactor containing 1 L of an aqueous solution with 30 mmol of copper chloride (CuCl2) and 0.1 mol of sodium chloride (NaCl), 10 g of sucrose was added, and sodium borohydride (NaBH4) was added dropwise at a rate of 2 g / min while stirring to obtain a copper nanocolloid solution containing copper particles with an average particle size of 20 nm. The obtained copper nanocolloid solution was diluted with 1 L of water to obtain a copper nanocolloid solution with a solid content concentration of 2% by mass. Cellulose nanofibers (product name: ELLEX-☆, manufactured by Daio Paper Corporation, average fiber diameter 5 nm, average fiber length 1 μm) that had been pre-washed with a 1 M sodium hydroxide (NaOH) aqueous solution were immersed in a 1% trimethylstearylammonium chloride aqueous solution, and then immersed in the above copper nanocolloid solution at a temperature of 25°C for 1 hour, after which they were washed with ethanol to obtain a composite material 2 in which a copper layer (coating layer) was formed on the surface of the cellulose nanofibers. Furthermore, composite material 2 had a coating layer coverage rate of 50% and a coating layer thickness of 20 nm.

[0044] (Manufacturing Example 3) To a reactor containing 1 L of an aqueous solution with 50 mmol of copper chloride (CuCl2) and 0.1 mol of sodium chloride (NaCl), 10 g of sucrose was added, and sodium borohydride (NaBH4) was added dropwise at a rate of 2.5 g / min while stirring to obtain a copper nanocolloid solution containing copper particles with an average particle size of 50 nm. The obtained copper nanocolloid solution was diluted with 4 L of water to obtain a copper nanocolloid solution with a solid content concentration of 5% by mass. Cellulose nanofibers (product name: ELLEX-☆, manufactured by Daio Paper Corporation, average fiber diameter 5 nm, average fiber length 1 μm) that had been pre-washed with a 1 M sodium hydroxide (NaOH) aqueous solution were immersed in a 1% trimethylstearylammonium chloride aqueous solution, and then immersed in the above copper nanocolloid solution at a temperature of 25°C for 1 hour. After washing with ethanol, a composite material 3 was obtained in which a copper layer (coating layer) was formed on the surface of the cellulose nanofibers. Furthermore, composite material 3 had a coating layer coverage rate of 20% and a coating layer thickness of 50 nm.

[0045] (Manufacturing example 4) A composite material 4' was obtained in which a copper layer (coating layer) was formed on the surface of cellulose nanofibers, in the same manner as in Manufacturing Example 1, except that cellulose nanofibers with product name: ELLEX-S, manufactured by Daio Paper Corporation, with an average fiber diameter of 20 nm and an average fiber length of 1 μm were used. The obtained composite material 4' was immersed in an electroless plating solution (OPC-700 Electroless Copper MK, manufactured by Okuno Pharmaceutical Co., Ltd.) and subjected to electroless copper plating treatment to obtain a composite material 4 in which a copper plating layer was formed on the surface of the coating layer. Furthermore, composite material 4 had a coating layer coverage rate of 99%, and the total thickness of the copper layer (5 nm) and the copper plating layer (75 nm) was 80 nm.

[0046] (Manufacturing example 5) To a reactor containing 1 L of an aqueous solution with 20 mmol of copper chloride (CuCl2) and 0.1 mol of sodium chloride (NaCl), 10 g of sucrose was added, and sodium borohydride (NaBH4) was added dropwise at a rate of 1 g / min while stirring to obtain a copper nanocolloid solution containing copper particles with an average particle size of 5 nm. The obtained copper nanocolloid solution was diluted with 9 L of water to obtain a copper nanocolloid solution with a solid content concentration of 0.1% by mass. Cellulose nanofibers (product name: ELLEX-☆, manufactured by Daio Paper Corporation, average fiber diameter 5 nm, average fiber length 1 μm) that had been pre-washed with a 1 M sodium hydroxide (NaOH) aqueous solution were immersed in a 1% trimethylstearylammonium chloride aqueous solution, and then immersed in the above copper nanocolloid solution at a temperature of 25°C for 0.5 hours, after which they were washed with ethanol to obtain a composite material 5 in which a copper layer (coating layer) was formed on the surface of the cellulose nanofibers. Furthermore, composite material 5 had a coating layer coverage rate of 10% and a coating layer thickness of 5 nm.

[0047] (Manufacturing example 6) In a reaction flask, 2 L of 15 M sodium hydroxide (NaOH), 100 mL of 0.2 M copper(II) nitrate (Cu(NO3)2), 30 mL of ethylenediamine (EDA), and 2.5 mL of 35% by mass aqueous hydrazine solution were added and stirred for 20 seconds. This solution was heated to 80°C and stirred at 200 rpm for 60 minutes. After the reaction, the reaction solution was washed with 3% by mass aqueous hydrazine solution to obtain copper nanowires.

[0048] [Evaluation items] (Average particle size of copper particles) Copper particles were obtained by evaporating the dispersion medium from the copper nanocolloidal liquids obtained in Production Examples 1-5. The average particle size of the copper particles was calculated as the average value of 100 copper particles from images of the copper particles taken using a field emission scanning electron microscope (FE-SEM) (JSM-7401F, manufactured by JEOL Ltd.).

[0049] (Shape of copper particles) Copper particles were obtained by evaporating the dispersion medium from the copper nanocolloidal liquids obtained in Production Examples 1-5. The shape of the copper (particles) was confirmed from images taken of the copper particles or the copper nanowires obtained in Manufacturing Example 6 using a field emission scanning electron microscope (FE-SEM) (JSM-7401F, manufactured by JEOL Ltd.).

[0050] (Coverage rate of the coating layer, or the percentage of copper contained in the copper nanowire) The obtained composite material or copper nanowire was subjected to a differential thermogravimetric / thermogravimetric analysis (TG / DTA) (TG209F1Libra, NETZSCH). A 10 mg sample was heated in an argon atmosphere at a heating rate of 10°C / min from 25°C to 600°C, and the mass of the sample was measured after 60 minutes. The coverage rate of the coating layer in the composite material was calculated as the ratio of the mass of the sample after measurement to the mass of the sample before measurement. The proportion of copper in the copper nanowire was calculated from the ratio of the mass of the sample after measurement to the mass of the sample before measurement.

[0051] (Thickness of the coating layer, or diameter of the copper nanowire) The thickness of the coating layer of the composite material and the diameter of the copper nanowires were calculated by preparing cross-sectional sections by cutting the obtained composite material or copper nanowires with a focused ion beam (FIB), and then photographing these sections with a transmission electron microscope (TEM) at a magnification of 500,000x, and taking the average value of 500,000 measurements. In Table 1, the thickness of the coating layer of composite material 4 obtained in manufacturing example 4 is the total thickness of the copper layer and the copper plating layer.

[0052] [Table 1]

[0053] (Examples 1-5, Comparative Examples 1 and 2) A dispersion was prepared by mixing the components listed in Table 2 according to their type and proportion.

[0054] The details of each component listed in Table 2 used in the preparation of the dispersion are as follows: • Composite material 1: Composite material manufactured in manufacturing example 1 • Composite material 2: Composite material manufactured in manufacturing example 2 • Composite material 3: Composite material manufactured in manufacturing example 3 • Composite material 4: Composite material manufactured in manufacturing example 4 • Composite material 5: Composite material manufactured in manufacturing example 5 • Copper nanowires: Copper nanowires manufactured in Manufacturing Example 6 • Cellulose nanofiber (CNF): ELLEX-☆ (Elex-Star), manufactured by Daio Paper Corporation, average fiber diameter 5 nm, average fiber length 1 μm. • Ethanol (dispersion medium): Manufactured by Tokyo Chemical Industry Co., Ltd.

[0055] [Evaluation items] (Degree of oxidation) For composite materials or copper nanowires, the content of each component, Cu, CuO, and Cu2O, was quantified using the RIR (reference intensity ratio) method based on the integrated intensity ratio of the strongest line peaks of each component by X-ray diffraction (XRD). The degree of oxidation was calculated using the following formula (1) and evaluated according to the following evaluation criteria.

[0056]

number

[0057] In formula (1), [Cu] represents the copper (Cu) content (mass%) in the composite material or copper nanowire, [CuO] represents the copper(II) oxide content (mass%) in the composite material or copper nanowire, and [Cu2O] represents the copper(I) oxide content (mass%) in the composite material or copper nanowire.

[0058] [Evaluation Criteria] A: Oxidation level less than 1% B: Oxidation level between 1% and less than 3% C: Oxidation level of 3% or higher

[0059] (Antiviral) The antiviral effect of an antiviral product (antiviral-treated glass) obtained by coating a dispersion onto glass and drying it was evaluated. On the surface of the antiviral-treated glass measuring 5cm x 5cm, a viral infectivity titer of 2 x 10⁶ was evaluated. 4 100 mL of influenza A virus solution at PFU / mL was added and allowed to stand at 25°C for 2 hours. The virus solution was then collected from the antiviral treated glass surface, and the number of plaques in the collected solution was measured to determine the viral infectivity titer. The viral infectivity titer was also measured for the influenza A virus solution before the 2-hour standing period. The antiviral effect was determined by these viral infectivity titers. A "++" rating indicated that the viral infectivity titer after 2 hours was below the detection limit. A "+" rating indicated that the antiviral activity value calculated using the following formula had decreased by 1 or more after 2 hours. A "-" rating indicated that the viral infectivity titer after 2 hours was anything other than "++" and the antiviral activity value was anything other than "+". Antiviral activity value = log(Vb) - log(Vc) In the formula, log(Vb) is the common logarithm of the viral infectivity titer of the influenza A virus solution before standing for 2 hours, and log(Vc) is the common logarithm of the viral infectivity titer of the influenza A virus solution after standing for 2 hours on an antiviral treated glass surface.

[0060] (Antibacterial and deodorizing effect) The dispersion was applied to a sterile standard cotton cloth, and its antibacterial and deodorizing effects were evaluated. The meaning of each evaluation index in Table 2 is as follows. (Antibacterial testing) The antibacterial test was conducted in accordance with JIS L-1902:2008 quantitative test (bacterial suspension absorption method). 0.9 mL of the dispersion was added to 0.4 g of sterile standard cotton cloth to prepare the test sample. Escherichia coli or Staphylococcus aureus was used as the test bacterial strain. After incubation at room temperature (25°C) for 24 hours, an antibacterial activity value of 2.2 or higher (bacterial reduction rate = 99.4% or higher) was used as the evaluation value for effectiveness. (Deodorization test) A test cotton cloth containing 3L of test gas (ammonia gas) and 1mL of dispersion was placed in a 5L Tedlar bag, and the result was determined when the gas concentration decreased by more than 90% from the initial concentration (=100ppm) after 2 hours. [Judgment criteria] Based on the above measurement results, the following criteria were used for evaluation. A: In the antibacterial test, the antibacterial activity value was 2.4 or higher, and in the deodorizing test, the gas concentration decreased by 96% or more, confirming a high antibacterial and deodorizing effect. B: In the antibacterial test, the antibacterial activity value was between 2.2 and less than 2.4, and in the deodorizing test, the gas concentration decreased by 90% or more and less than 96%, confirming the antibacterial and deodorizing effect. C: In the antibacterial test, the antibacterial activity value was less than 2.2, or in the deodorizing test, the reduction in gas concentration was less than 90%, so no antibacterial or deodorizing effect could be confirmed.

[0061] (Conductivity (surface resistivity)) The surface resistivity of composite materials, copper nanowires, or CNF was measured using the four-terminal method with the "Loresta HP MCP-T410" manufactured by Mitsubishi Chemical Analytech Co., Ltd., and evaluated according to the following evaluation criteria. [Evaluation Criteria] A: Surface resistivity is less than 50 Ω / sq. B: Surface resistivity of 50 Ω / sq. or more and less than 100 Ω / sq. C: Surface resistivity of 100 Ω / sq. or higher

[0062] (transmittance) A dispersion was applied to a glass substrate, and the total light transmittance of the dispersion was measured. A haze meter "NDH 2000" manufactured by Nippon Denshoku Industries Co., Ltd. was used to measure the total light transmittance. Additionally, an uncoated glass substrate was used as a reference sample for optical property measurement, and the optical properties of the coated film alone were measured.

[0063] [Table 2]

[0064] Examples 1 to 5, which used dispersions containing the composite material of this disclosure, show low copper oxidation and good evaluation of antiviral properties, antibacterial and deodorizing effects, conductivity, and transmittance.

Claims

1. A core material made of cellulose nanofibers, A conductive composite material having a coating layer made of copper covering the core material, The average thickness of the coating layer is 150 nm or less. Here, the average thickness of the coating layer is the average value of the thickness of the coating layer measured at 500,000 points by cutting the conductive composite material with a focused ion beam to prepare a cross-sectional section, and then photographing the cross-section with a transmission electron microscope. Conductive composite material.

2. The conductive composite material according to claim 1, wherein the average thickness of the coating layer is 1 nm or more and 150 nm or less.

3. The conductive composite material according to claim 1, wherein the coverage rate of the coating layer on the core material is 10% or more and 99% or less.

4. The conductive composite material according to claim 1, wherein the average fiber diameter of the cellulose nanofibers is 3 nm or more and 100 nm or less.

5. The average aspect ratio of the cellulose nanofibers is 10 or more and 1000 or less. The conductive composite material according to claim 1, wherein the average aspect ratio of the cellulose nanofibers is the ratio of the average fiber length of the cellulose nanofibers to the average fiber diameter of the cellulose nanofibers.

6. The conductive composite material according to claim 1, having a plating layer covering the aforementioned coating layer.

7. The conductive composite material according to claim 1, wherein the surface resistivity is less than 100 Ω / sq.

8. The conductive composite material according to claim 1, wherein the surface resistivity is less than 50 Ω / sq.

9. A method for producing a conductive composite material according to any one of claims 1 to 8, wherein cellulose nanofibers are immersed in a copper particle dispersion.

10. The method for producing a conductive composite material according to claim 9, wherein the average particle size of the copper particles contained in the copper particle dispersion is 1 nm or more and 150 nm or less.

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