TWI790326B - Method of manufacturing conductive film and conductive film - Google Patents

Abstract

The present invention provides a method for producing a conductive film and a conductive film. The method for producing a conductive film comprises: a coating step, wherein copper particles are selected from the group consisting of reducing ketones and having two or more carboxyl groups and one or more carboxyl groups in the molecule. The conductive film-forming composition of at least one reducing agent in the group of hydroxy carboxylic acids of the hydroxyl group and the dispersion medium is applied to the surface of the substrate to form a coating film; in the drying step, the coating film is placed in an oxidizing environment at a temperature below 150°C Drying at a temperature to obtain a dry film comprising a lower layer of oxide that does not actually contain copper and an upper layer of oxide containing copper disposed on the lower layer on the substrate; and a stripping step of removing the upper layer from the dry film to obtain a conductive film.

Description

Method for producing conductive film and conductive film

The invention relates to a method for manufacturing a conductive film and the conductive film.

Copper fine particles are a material that is excellent in electrical conductivity and is inexpensive compared to metals such as silver, and thus is widely used as a raw material for, for example, conductive coating agents. Such conductive coating agents are widely used as materials for forming circuits in printed wiring boards and the like using various printing methods, various electrical contact members, and the like.

Furthermore, in recent years, in order to meet the demands for miniaturization and higher functionality of electronic equipment, wiring in printed wiring boards and the like has been further miniaturized and highly integrated. Accordingly, it is necessary to be able to form a conductive film exhibiting excellent conductivity on a substrate.

For example, Patent Document 1 describes a fibrous copper microparticle composition characterized by containing fibrous copper microparticles, a dispersion medium, and a reducing compound without an amine group (Claim 1). [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2014-118586

In addition, from the viewpoint of reducing the production cost of the conductive film, it is necessary to exhibit excellent conductivity even when the film is formed in an oxidizing environment such as the air.

As a result of research conducted by the present inventors, it was found that the conductivity of a conductive film formed in the air by applying the composition described in Patent Document 1 on a substrate was not up to the level, and a conductive film showing excellent conductivity could not be obtained. .

Therefore, an object of the present invention is to provide a method for producing a conductive film and a conductive film capable of forming a conductive film exhibiting excellent conductivity even when the film is formed in an oxidizing environment such as the air.

As a result of intensive studies by the present inventors in order to solve the above-mentioned problems, a conductive film capable of forming a conductive film exhibiting excellent conductivity even when formed in an oxidizing environment such as the atmosphere was obtained by a method for producing a conductive film. , The manufacturing method of the conductive film comprises: a coating step, at least one of copper particles selected from the group consisting of reducing ketones and hydroxycarboxylic acids having two or more carboxyl groups and one or more hydroxyl groups in the molecule The conductive film-forming composition of the reducing agent and the dispersion medium is applied to the surface of the substrate to form a coating film; in the drying step, the coating film is dried in an oxidizing environment at a temperature below 150°C to obtain a dry film including the upper layer and the lower layer. film, the upper layer contains copper oxide and is located on the opposite side of the substrate, the lower layer does not actually contain copper oxide and is located on the substrate side; and a lift-off step, removing the upper layer from the dried film to obtain a conductive film, thereby completing the present invention . That is, the present invention provides the following [1] to [12].

[1] A method for producing a conductive film comprising: a coating step of coating copper particles selected from the group consisting of reductones and hydroxycarboxylic acids having two or more carboxyl groups and one or more hydroxyl groups in the molecule. The conductive film-forming composition of at least one reducing agent and dispersion medium is applied to the surface of the substrate to form a coating film; the drying step is to dry the above-mentioned coating film in an oxidizing environment at a temperature below 150°C, and the coating film is dried on the substrate obtaining a dry film comprising an oxide lower layer substantially not containing copper and an oxide upper layer containing copper disposed on the lower layer; and a lift-off step of removing the upper layer from the dried film to obtain a conductive film. [2] The method for producing a conductive film according to [1], wherein the (111) peak of Cu ₂ O by X-ray diffraction is detected in the upper layer but not detected in the lower layer. [3] The method for producing a conductive film according to [1] or [2], wherein the reducing agent is at least one selected from the group consisting of ascorbic acid, ascorbic acid derivatives, and citric acid. [4] The method for producing a conductive film according to any one of [1] to [3], wherein the copper particles have an average particle diameter within a range of 25 to 1500 nm. [5] The method for producing a conductive film according to any one of [1] to [4], further comprising: heating the conductive film at a temperature of more than 150°C to 190°C after the peeling step. The heating step. [6] The method for producing a conductive film according to any one of [1] to [5], wherein the temperature in the drying step is 125° C. or lower. [7] The method for producing a conductive film according to any one of [1] to [6], wherein the composition for forming a conductive film does not contain a binder. [8] The method for producing a conductive film according to any one of [1] to [7], wherein the ratio of the mass of the copper particles to the mass of the reducing agent is 90 to 99% by mass. [9] A conductive film comprising copper, at least one reducing agent selected from the group consisting of reducing ketones and hydroxycarboxylic acids having two or more carboxyl groups and one or more hydroxyl groups in the molecule, wherein the conductive film , The content of the above-mentioned copper is 90% by mass or more with respect to the total mass of the above-mentioned conductive film. [10] The conductive film according to [9], wherein the reducing agent is at least one selected from the group consisting of ascorbic acid, ascorbic acid derivatives, and citric acid. [11] The conductive film according to [9] or [10], which does not contain a binder. [12] The conductive film according to any one of [9] to [11], wherein the (111) peak of Cu ₂ O by X-ray diffraction method is not detected. [Invention effect]

According to the present invention, it is possible to provide a production method capable of forming a conductive film exhibiting excellent conductivity even when the film is formed in an oxidizing environment such as the air, and a conductive film.

Hereinafter, the electroconductive film and the manufacturing method of an electroconductive film of this invention are demonstrated in detail. In addition, the range shown using "-" in this specification means the range which includes the both ends described before and after "-" within the range.

[Manufacturing method of conductive film] The method for producing a conductive film of the present invention includes: a coating step of applying at least copper particles selected from the group consisting of reducing ketones and hydroxycarboxylic acids having two or more carboxyl groups and one or more hydroxyl groups in the molecule. A conductive film-forming composition composed of a reducing agent and a dispersion medium is applied to the surface of a substrate to form a coating film; in the drying step, the coating film is dried in an oxidizing environment at a temperature below 150°C, and the substrate is obtained on the substrate. a dried film of a lower layer not including copper oxide and an upper layer including copper oxide disposed on the lower layer; and a lift-off step of removing the upper layer from the dried film to obtain a conductive film.

The outline of the method for producing the conductive film of the present invention will be described with reference to FIGS. 1A to 1D . A substrate 11 is prepared ( FIG. 1A ), and a composition for forming a conductive film is applied on the surface of the substrate 11 to form a coating film 12 ( FIG. 1B ). Next, the coating film 12 formed on the surface of the substrate 11 is dried in an oxidizing environment at a temperature of 150° C. or lower to form a dry film 13 ( FIG. 1C ). The dry film 13 is divided into a lower layer (conductive film) 14 on the surface side of the substrate 11 and an upper layer 15 on the opposite side to the substrate 11 at the interface 16 ( FIG. 1C ). This is because, by drying in an oxidizing environment, the copper particles close to the surface of the coating film 12 opposite to the substrate 11 side are oxidized, and the copper particles are fused on the substrate 11 side of the coating film 12 to form a metal conductor. . In the drying process, the concentration of the reducing agent is unbalanced in the thickness direction in the coating film 12, the oxygen concentration is high and the reducing agent concentration is low in the upper layer 15 of the dry film 13, so the oxidation of copper proceeds, and the lower layer of the dry film 13 In 14, the oxygen concentration was low and the reducing agent concentration was high, so the oxidation of copper was suppressed. An interface 16 is formed between the upper layer 15 and the lower layer 14 . By removing the upper layer 15 , a conductive film excellent in conductivity can be obtained as the lower layer (conductive film) 14 including a metal conductor ( FIG. 1D ). Each step will be described in detail below.

＜Coating procedure＞ In the coating step, the composition for forming a conductive film is applied to the surface of the substrate to form a coating film.

"Conductive Film Formation Composition" The composition for forming a conductive film used in the method for producing a conductive film of the present invention contains copper particles, and is selected from the group consisting of reducing ketones and hydroxycarboxylic acids having two or more carboxyl groups and one or more hydroxyl groups in the molecule. at least one reducing agent and dispersion medium.

The mass ratio of the above-mentioned copper particles and the above-mentioned reducing agent in the above-mentioned composition for forming a conductive film is not particularly limited, and the ratio of the mass of the copper particles to the mass of the reducing agent is preferably 90% by mass to 99% by mass, and 90% by mass is preferred. The mass % - 97 mass % is more preferable, 91 mass % - 95 mass % is still more preferable, and 93 mass % - 95 mass % is still more preferable. If the mass ratio of the said copper particle and the said reducing agent exists in this range, the electroconductivity of the electroconductive film obtained will become more favorable.

The content of the dispersion medium in the conductive film forming composition is not particularly limited, but is preferably 1 to 10,000 parts by mass, more preferably 10 to 500 parts by mass, based on 100 parts by mass of the copper particles. 20 mass parts - 200 mass parts are still more preferable. If the content of the above-mentioned dispersion medium is within this range, the conductivity of the obtained conductive film will become better.

(copper particles) The above-mentioned copper particles serve as metal conductors in the conductive film. By drying the composition for forming a conductive film applied to the substrate, the copper particles are fused together to form a metal conductor in the conductive film. As said copper particle, the conventionally well-known copper particle normally used for the composition for conductive film formation can be used. The above-mentioned copper particles may be primary particles or secondary particles. Moreover, the shape of the said copper particle is not specifically limited, Spherical shape may be sufficient, and plate shape may be sufficient. The average particle diameter of the above-mentioned copper particles is not particularly limited, in the case of the primary particle, it is the average particle diameter of the primary particle, in the case of the secondary particle, it is the average particle diameter of the secondary particle, preferably 25nm to 1500nm, and 200nm It is more preferably from 1500 nm to 500 nm to 1500 nm, and still more preferably from 500 nm to 1500 nm. In addition, the average particle diameter of copper particles (A) is measured by measuring the particle diameters of 100 particles randomly selected from an image of a scanning electron microscope (hereinafter sometimes referred to as "SEM") and arithmetically averaging the measured values. And the one who calculates.

(reducing agent) The reducing agent is at least one selected from the group consisting of reductones and hydroxycarboxylic acids having two or more carboxyl groups and one or more hydroxyl groups in the molecule.

((Reductone)) Reductone refers to a structure represented by the following formula (I) or the following formula (II), which has a form in which a carbonyl group and an enediol structure are adjacently bonded (hereinafter referred to as "reductone"). Ketone structure".) Organic compounds. Reductones are reducing and highly acidic organic acids. [chemical formula 1]

Representative examples of the above-mentioned reducing ketones are acrylic acid represented by the following formula (Ia), reductive acid represented by the following formula (Ib), and ascorbic acid and ascorbic acid derivatives described below, but are not limited to these . [chemical formula 2]

The above reducing agent is preferably at least one selected from the group consisting of ascorbic acid, ascorbic acid derivatives and citric acid, at least one selected from the group consisting of ascorbic acid and ascorbic acid derivatives is more preferred, ascorbic acid is further preferred .

(((Ascorbic acid))) The above-mentioned ascorbic acid is selected from the group consisting of (2R)-2-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxy-2H-furan-5-one (formed by A compound represented by the following formula (A-1); sometimes this compound is called "ascorbic acid in the narrow sense" or "L-ascorbic acid".), (2S)-2-[(1R)-1,2-dihydroxy Ethyl]-3,4-dihydroxy-2H-furan-5-one (a compound represented by the following formula (A-2); this compound is sometimes called "D-ascorbic acid".), (2S) -2-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxy-2H-furan-5-one (a compound represented by the following formula (A-3); sometimes this The compound is called "L-erythorbic acid".) and (2R)-2-[(1R)-1,2-dihydroxyethyl]-2,3-dihydroxy-2H-furan-5-one (from the following The compound represented by the above-mentioned formula (A-4); sometimes this compound is called "erythorbic acid" or "D-erythorbic acid".) At least one compound in the group. [chemical formula 3]

(((Ascorbic Acid Derivatives))) The aforementioned ascorbic acid derivatives are compounds represented by the following general formula (B-1) (sometimes referred to as "ascorbic acid derivatives (B-1)") or compounds represented by the following general formula (B-2) ( Sometimes called "Ascorbic Acid Derivatives (B-1)".) is preferred. The reducing power to copper oxide originates from the enediol structure in the ascorbic acid derivative. Therefore, derivatives of ascorbic acid can also be synthesized in a form leaving its structure, and can be used after appropriately adjusting solubility and polarity.

通式（B-1）中，R¹ 及R² 分別獨立地表示氫原子或可以具有取代基之醯基。其中，R¹ 及R² 不同時表示氫原子。• Ascorbic acid derivative represented by general formula (B-1) [chemical formula 4]

In the general formula (B-1), R ¹ and R ² each independently represent a hydrogen atom or an acyl group which may have a substituent. Wherein, R ¹ and R ² do not represent a hydrogen atom at the same time.

The acyl group in R ¹ and R ² in the above general formula (B-1) is not particularly limited, and the aliphatic bond of a straight chain, branched chain, monocyclic or condensed polycyclic aliphatic bond with 1 to 18 carbons The bonded carbonyl group or the bonded carbonyl group of a monocyclic or condensed polycyclic aryl group having 6 to 10 carbon atoms is preferred.

Specific examples of the above-mentioned acyl group are selected from the group consisting of formyl, acetyl, propionyl, butyryl, isobutyryl, pentyl, isopentyl, trimethylacetyl, lauryl, myristyl palmityl, stearyl, cyclopentylcarbonyl, cyclohexylcarbonyl, acryl, methacryl, crotonyl, isocrotonyl, oleyl, benzoyl, 1- Any one of the group of naphthoyl and 2-naphthoyl, but not limited thereto.

The above-mentioned acyl groups can be substituted by substituents for the hydrogen atoms in the acyl groups, whereby the solubility and polarity can be further adjusted. Specific examples of the above-mentioned substituent include at least one substituent selected from the group including a hydroxyl group and a halogen atom, but are not limited thereto.

其中，上述式（B-1-X）中，X表示選自包括以下所示之化學結構之群組中之任一個。另外，各化學結構中的“*”表示X鍵結於抗壞血酸的五員環部位之位置。 [化學式6]

[化學式7]

A representative example of the aforementioned ascorbic acid derivative (B-1) is represented by the following formula (B-1-X). However, the ascorbic acid derivative (B-1) in the present invention is not limited to these representative examples. [chemical formula 5]

Wherein, in the above-mentioned formula (B-1-X), X represents any one selected from the group including the chemical structures shown below. In addition, "*" in each chemical structure represents the position where X is bonded to the five-membered ring site of ascorbic acid. [chemical formula 6]

[chemical formula 7]

通式（B-2）中，R³ 及R⁴ 分別獨立地表示氫原子或可以具有取代基之烷基。• General formula (B-2) [Chemical formula 8]

In the general formula (B-2), R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group which may have a substituent.

The compound represented by the general formula (B-2) is an ascorbic acid derivative that forms an acetal structure or a ketal structure by reacting two hydroxyl groups present on the side chain of ascorbic acid with an aldehyde or a ketone.

The alkyl groups in ^R3 and ^R4 in the above general formula (B-2) are not particularly limited, and linear, branched, monocyclic or condensed polycyclic alkyl groups with 1 to 18 carbons are preferred. good.

Specific examples of the above-mentioned alkyl groups are selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, octadecyl, iso Propyl, isobutyl, isopentyl, second butyl, third butyl, second pentyl, third pentyl, third octyl, neopentyl, cyclopropyl, cyclobutyl, cyclopentyl Any one of the group of radical, cyclohexyl, adamantyl, norbornyl and 4-decylcyclohexyl, but not limited thereto.

Each of the above-mentioned alkyl groups may be substituted with a substituent for a hydrogen atom in the alkyl group, whereby solubility and polarity can be further adjusted. Specific examples of the above-mentioned substituents are one or more substituents selected from the group including hydroxyl groups and halogen atoms, but are not limited thereto.

The aforementioned R ³ and the aforementioned R ⁴ may be integrated to form a ring structure.

其中，上述式（B-2-Y）中，Y表示選自包括以下所示之化學結構之群組中之任一個。另外，各化學結構中的“*”表示Y鍵結於抗壞血酸的五員環部位之位置。A representative example of the aforementioned ascorbic acid derivative (B-2) is represented by the following formula (B-2-Y). However, the ascorbic acid derivative (B-2) in the present invention is not limited to these representative examples. [chemical formula 9]

However, in the above-mentioned formula (B-2-Y), Y represents any one selected from the group including the chemical structures shown below. In addition, "*" in each chemical structure indicates the position where Y is bonded to the five-membered ring site of ascorbic acid.

[chemical formula 10]

((Hydroxycarboxylic acid having two or more carboxyl groups and one or more hydroxyl groups in the molecule)) The above-mentioned hydroxycarboxylic acid having two or more carboxyl groups and one or more hydroxyl groups in the molecule is not particularly limited, but a hydroxycarboxylic acid having three or more carboxyl groups and one or more hydroxyl groups in the molecule is preferred. Examples of the hydroxycarboxylic acid having two or more carboxyl groups and one or more hydroxyl groups in the molecule include citric acid and isocitric acid, but are not limited thereto. In the conductive film of the present invention, it is preferable that the hydroxycarboxylic acid having two or more carboxyl groups and one or more hydroxyl groups in the molecule is at least one hydroxycarboxylic acid selected from the group including citric acid and isocitric acid , citric acid is better.

(dispersion medium) The above-mentioned dispersion medium is not particularly limited as long as it can dissolve or disperse the above-mentioned reducing agent. Specific examples of the above-mentioned dispersion medium are selected from water, methanol, ethanol, propanol, 2-propanol, cyclohexanone, cyclohexanol, terpineol (terpineol), ethylene glycol, ethylene glycol monoethyl ether, ethyl alcohol, Glycol monobutyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether At least one of the group of diethyl ether acetate and diethylene glycol monobutyl ether acetate, preferably at least one selected from the group including water, methanol, ethanol, propanol and 2-propanol, At least one selected from the group consisting of water, methanol and ethanol is more preferred, and water is further preferred. As the above-mentioned water, ion-exchanged water, RO (Reverse Osmosis: reverse osmosis) water, distilled water or other pure water, or ASTM D 1193-06 Type 1 grade other ultrapure water is preferable.

(Method for producing conductive film-forming composition) The method for producing the composition for forming a conductive film used in the method for producing a conductive film of the present invention is not particularly limited, and can be as follows, for example.

((mixture of copper particles, reducing agent and dispersion medium)) The method of mixing copper particles, a reducing agent, and a dispersion medium is not particularly limited, and conventionally known methods can be employed. For example, after adding copper particles and a reducing agent to the dispersion medium, the components are dispersed by known methods such as ultrasonic method (for example, treatment using an ultrasonic homogenizer), mixing method, three-roll method and ball milling method, thereby composition can be obtained.

((reduction of copper oxide)) It is preferable to perform reduction treatment of copper oxide after mixing copper particles, a reducing agent, and a dispersion medium. Specifically, for example, the mixture of the copper particles, the reducing agent and the dispersion medium is put into an airtight container, and the air is blocked, and it is preferably left to stand in an oxygen-free state for more than 48 hours. In addition, the temperature at the time of standing still is preferably 1°C to 30°C. By performing the reduction treatment of copper oxide, the conductivity of the obtained conductive film becomes better.

(adhesive) It is preferable that the above-mentioned composition for forming a conductive film does not contain a binder. The binder generally has the effect of improving the adhesiveness of the conductive film to the substrate, but in the conductive film of the present invention, since the conductive film may lower the conductivity, it is not preferable. Among them, examples of the binder include resins and organic compounds with a molecular weight of 200 or more.

As said resin, a thermosetting resin and a thermoplastic resin are mentioned. Specific examples of the above-mentioned thermosetting resins include phenol resins, epoxy resins, unsaturated polyester resins, vinyl ester resins, diallyl phthalate resins, low polyester acrylate resins, xylene resins, bis Maleimide trimethoprene resin, furan resin, urea resin, polyurethane, melamine resin, silicone resin, acrylic resin, oxetane resin, oxalane resin, etc. Specific examples of the above-mentioned thermoplastic resin include polyamide resin , polyimide resins, acrylic resins, ketone resins, polystyrene resins, and thermoplastic polyester resins, but are not limited thereto.

The above-mentioned organic compound with a molecular weight of 200 or more is not particularly limited, and examples include organic acids with a molecular weight of 200 or more, polyalkylene glycols with a molecular weight of 200 or more, sugar alcohols with a molecular weight of 200 or more, oligosaccharides, and polysaccharides.

"Substrate" As the above-mentioned substrate, conventionally known ones can be used. In addition, specific examples of the material used for the substrate include resin, paper, glass, silicon-based semiconductor, compound semiconductor, metal, metal oxide, metal nitride, wood, or their composites, but are not limited thereto.

Specific examples of the above-mentioned resins are low-density polyethylene resins, high-density polyethylene resins, ABS (Acrylonitrile Butadiene Styrene: acrylonitrile-butadiene-styrene) resins, acrylic resins, styrene resins, vinyl chloride resins, and polyester resins. (polyethylene terephthalate (PET)), polyacetal resin, polyresin, polyetherimide resin, polyetherketone resin, polyimide resin and cellulose derivatives, but not limited to Wait. Specific examples of the above-mentioned paper are coated printing paper, finely coated printing paper, coated printing paper (art paper, coat paper), special printing paper, copy paper (PPC paper), uncoated Bleached packaging paper (unbleached kraft paper for heavy bags, unbleached kraft paper), bleached packaging paper (bleached kraft paper, pure white roll paper), coated cardboard, chipboard, corrugated cardboard, etc., but not limited to these. Specific examples of the above glass are soda glass, borosilicate glass, silica glass, and quartz glass, but are not limited thereto. Specific examples of the aforementioned silicon-based semiconductors are amorphous silicon and polysilicon, but are not limited thereto. Specific examples of the aforementioned compound semiconductors are CdS, CdTe, and GaAs, but are not limited thereto. Specific examples of the aforementioned metals are copper, iron, and aluminum, but are not limited thereto. Specific examples of the above-mentioned metal oxides are alumina, sapphire, zirconia, titanium oxide, yttrium oxide, indium oxide, ITO (indium tin oxide), IZO (indium zinc oxide), NESA (tin oxide) , ATO (antimony-doped tin oxide), fluorine-doped tin oxide, zinc oxide, AZO (aluminum-doped zinc oxide), and gallium-doped zinc oxide, but are not limited to these. A specific example of the above-mentioned metal nitride is aluminum nitride, but it is not limited thereto. Also, specific examples of the above-mentioned composites are paper-resin composites such as paper-phenol resin, paper-epoxy resin, and paper-polyester resin, glass cloth-epoxy resin (glass epoxy resin), glass cloth-polyamide Imide-based resins, and glass cloth-fluororesins, but are not limited to these. The substrate for forming the conductive film of the present invention is not particularly limited, and a glass substrate, a polyimide substrate or a polyethylene terephthalate (PET) substrate is preferred.

"Method of Imparting a Composition for Forming a Conductive Film on a Substrate" There is no particular limitation on the method of applying the above-mentioned conductive film-forming composition to the substrate, and known methods can be employed. For example, coating methods such as a screen printing method, a dip coating method, a spray coating method, a spin coating method, and an inkjet method are mentioned. The shape of the coating is not particularly limited, and may be a planar shape covering the entire surface of the substrate, or a pattern shape (for example, wiring shape, dot shape).

The coating amount of the composition for forming a conductive film on the substrate can be adjusted appropriately according to the film thickness of the desired conductive film. Usually, the film thickness (thickness) of the coating film is preferably 2 μm to 600 μm, preferably 10 μm It is more preferably ˜300 μm, and is still more preferably 10 μm to 200 μm.

＜Drying procedure＞ In the drying step, the coating film is dried in an oxidizing environment at a temperature below 150°C, and a dried film including an oxide lower layer that does not actually contain copper and an upper layer of oxide that is disposed on the lower layer and includes copper oxide is obtained on the substrate . Moreover, the said dry film has a lower layer and an upper layer in this order from a board|substrate side.

In the drying step, the formed coating film is dried in an oxidizing environment and the dispersion medium is removed. By removing the dispersion medium remaining in the coating film, and forming a metal conductor by fusion of copper particles on the side of the substrate close to the coating film and forming copper oxide on the surface side of the coating film, the separation from the interface is obtained. It is the dry film of the upper layer and the lower layer.

An example of an oxidizing environment is an environment including oxygen in the atmosphere or air, but is not limited thereto.

As a method of drying, a method of drying with a hot air dryer or the like can be used.

The temperature during drying (hereinafter sometimes referred to as "drying temperature") is not particularly limited as long as it is 150°C or less, preferably 0°C to 150°C, more preferably 0°C to 125°C, and 4°C to 100°C for further improvement. In addition, when the temperature during drying exceeds 150° C., the oxidation rate of copper oxide is increased by the reducing agent, and a conductive film exhibiting desired conductivity cannot be obtained.

The drying time (hereinafter sometimes referred to as "drying time") is not particularly limited, but is preferably from 1 second to 96 hours, more preferably from 5 seconds to 72 hours, and still more preferably from 10 seconds to 48 hours. Here, the drying time can be appropriately set in accordance with the drying temperature as long as substantially all of the dispersion medium can be removed from the coating film.

<Peeling Step> In the peeling step, the upper layer is removed from the dry film to obtain a conductive film. The method of removing the upper layer is not particularly limited, and examples thereof include a method of scraping off the upper layer with a scraper or the like on the surface of the dry film, and a method of wiping the upper layer with a rag such as wiping paper. In addition, in this step, the entire upper layer is removed. The conductive film obtained by the method for producing a conductive film of the present invention suppresses the oxidation of copper by the reducing agent that coexists with copper, and therefore does not substantially contain copper oxide. Here, oxides that do not actually contain copper mean that (111) derived from copper (I) oxide [Cu ₂ O] was not detected by X-ray diffraction (XRD: X-ray diffraction) method. The peak, including oxide of copper, refers to measurement by X-ray diffractometry, and a (111) peak derived from copper (I) oxide [Cu ₂ O] was detected.

In addition, among them, the measurement conditions of X-ray diffraction are as follows. X-ray diffraction device RINT Ultima III X-Ray Diffractometer (manufactured by Rigaku Corporation) 2θ/ω 30～45 degrees Sampling step 0.01 degree Scanning speed 10 degrees/min Attenuator (ATT: Attenuator) open Divergence slit (DS: Dvergence slit) 1.00mm Scattering slit (SS: Scattering slit) open Receiving slit (RS: Receiving slit) open Optical System Parallel Slit PB Incidence Longitudinal Limiting Soller Slit V5 Longitudinal limiting slit 10×10 Parallel Slit Analyzer PSA

In addition, the (111) peak _of copper (I) oxide [Cu ₂ O] "not detected" by the X-ray diffraction method refers to the ( The ratio of 111) peak intensity to Cu (111) peak intensity Z [Z={Cu ₂ O (111) peak intensity/Cu (111) peak intensity}×100 (%)] is less than 0.1%, by X The "detection" of the (111) peak of copper(I) oxide [ _Cu2O ] by X-ray diffraction means that the above-mentioned Z is 0.1% or more.

＜Heating step＞ The manufacturing method of the conductive film of the present invention may include a heating step of heating the obtained conductive film at a temperature higher than 150° C. and lower than 190° C. after the peeling step. By performing the heating step, the conductivity of the conductive film becomes better.

The heating mechanism is not particularly limited, and known heating mechanisms such as an oven and a hot plate can be used.

The temperature during heating is preferably 155°C to 190°C, more preferably 160°C to 190°C, and still more preferably 160°C to 180°C from the viewpoint of being able to form a conductive film with better conductivity.

The heating time is not particularly limited, and from the viewpoint of forming a more excellent conductive film due to conductivity, the heating time is preferably 1 minute to 120 minutes, more preferably 5 minutes to 60 minutes, and 5 minutes ~30 points are further preferred.

The environment during heating is not particularly limited, and may be either a non-oxidizing environment or an oxidizing environment. Examples of the non-oxidizing atmosphere include inert gas atmospheres such as nitrogen and argon, reducing gas atmospheres such as hydrogen, and the like. Moreover, as said oxidizing atmosphere, an air atmosphere and an oxygen atmosphere are mentioned.

[conductive film] The conductive film of the present invention comprises copper and at least one reducing agent selected from the group consisting of reducing ketones and hydroxycarboxylic acids having two or more carboxyl groups and one or more hydroxyl groups in the molecule, and the content of copper is relative to that of the conductive film. The total mass is 90% by mass or more.

＜Copper・reducing agent＞ The above-mentioned copper is metallic copper. The content of copper in the conductive film is not particularly limited as long as it is at least 90% by mass of the total mass of the conductive film, preferably at least 93% by mass and less than 100% by mass, and preferably at least 95% by mass and less than 100% by mass. More preferably, it is more preferably 97 mass % or more and less than 100 mass %. The copper content in the conductive film can be measured by dissolving the obtained conductive film in nitric acid and analyzing the copper concentration in the solution by X-ray Fluorescence (XRF: X-ray Fluorescence) analysis.

XRF measurement was performed under the following measurement conditions using a fluorescent X-ray analyzer (Axios, manufactured by PANalytical). Line: Kα rays Crystallization: LIF200 Collimator: 150um Detector: Duplex Tube filter: no Voltage: 60kV Current: 60mA Measuring time: 40 seconds Irradiation area: 20φ

The copper contained in the conductive film of the present invention is a state in which a plurality of copper particles are fused to form a conductor. In addition, the said copper particle is the same as what was described in the manufacturing method of the electroconductive film of this invention.

The reducing agent contained in the conductive film of the present invention is the same as that described in the method for producing the conductive film of the present invention.

In the conductive film of the present invention, since copper and a reducing agent coexist in the conductive film, generation of copper oxides due to the reaction between metallic copper and oxygen in the air is suppressed, and excellent conductivity can be maintained over a long period of time. Since the reducing agent is present in the conductive film of the present invention, it is considered that copper oxides other than copper (I) oxide such as copper (II) oxide do not exist as long as copper (I) oxide does not exist in the conductive film. Therefore, it is possible to measure the surface of the most easily oxidized conductive film by contacting the conductive film with air and using the X-ray diffraction (XRD: X-ray diffraction) method, and no peaks from copper (I) oxide are detected, thereby It can be judged that the conductive film of the present invention does not contain copper oxide. Therefore, it is preferable that the conductive film of the present invention does not detect the (111) peak of copper (I) oxide [Cu ₂ O] by the X-ray diffraction method.

However, the measurement conditions of X-ray diffraction are as follows. X-ray diffraction device RINT Ultima III X-Ray Diffractometer (manufactured by Rigaku Corporation) 2θ/ω 30～45 degrees Sampling step 0.01 degree Scanning speed 10 degrees/min Attenuator (ATT: Attenuator) open Divergence slit (DS: Dvergence slit) 1.00mm Scattering slit (SS: Scattering slit) open Receiving slit (RS: Receiving slit) open Optical System Parallel Slit PB Incidence Longitudinal Limiting Soller Slit V5 Longitudinal limiting slit 10×10 Parallel Slit Analyzer PSA

In addition, "not detected" the (111) peak of copper (I) oxide [Cu ₂ O] by the X-ray diffraction method refers to the (111) peak of Cu ₂ O measured under the above-mentioned X-ray diffraction conditions. The ratio Z of the intensity to the (111) peak intensity of Cu [Z={(111) peak intensity of Cu ₂ O/(111) peak intensity of Cu}×100 (%)] is less than 0.1%, by X-ray diffraction method "Detecting" the (111) peak of copper(I) oxide [Cu ₂ O] means that the above Z is 0.1% or more.

＜Adhesive＞ It is preferable that the conductive film of the present invention does not contain a binder. In addition, the said binder is the same as what was described in the manufacturing method of the electroconductive film of this invention.

<Thickness of conductive film> The thickness of the conductive film of the present invention is not particularly limited, but is preferably 1 μm to 100 μm, more preferably 1 μm to 50 μm, and still more preferably 1 μm to 30 μm. If the thickness of the conductive film of the present invention is within the above range, it is possible to obtain a conductive film having sufficient film strength in the step of peeling off the lower layer substantially not containing copper oxide and the upper layer containing copper oxide.

＜Substrate＞ The conductive film of the present invention is preferably formed on a substrate. In addition, the said board|substrate is the same as what was described in the manufacturing method of the electroconductive film of this invention. [Example]

Hereinafter, the present invention will be described in further detail according to the examples, but the present invention is not limited to these examples.

[Example 1] <Preparation of conductive film-forming composition> 10 parts by mass of copper particles (average particle diameter 750 nm; manufactured by MITSUI MINING & SMELTING CO., LTD.) and 1.8 parts by mass of L-ascorbic acid (manufactured by Wako Pure Chemical, Ltd.) were mixed with 18.2 parts by mass of ion-exchanged water, and The mixed solution was obtained by stirring well at 2000 rpm for 5 minutes using a mixer. After stirring, the mixture was transferred to an airtight container, and kept at 25°C for 48 hours with the air blocked to obtain a composition for forming a conductive film (hereinafter sometimes referred to as "composition 1 for forming a conductive film"). ).

＜Manufacture of conductive film＞ "Coating" A glass substrate (76 mm in length×26 mm in width×0.9 mm in thickness; manufactured by Matsunami Glass Ind., Ltd.) was prepared. The composition 1 for forming a conductive film was coated on the glass substrate with a wire bar in a size of 61 mm in length×26 mm in width×40 μm in wet thickness to form a coating film on the surface of the glass substrate.

"dry" The coating film formed on the glass substrate was dried under the drying conditions shown in Table 1, and a dried film was formed on the glass substrate.

"Peel Off" The surface of the dry film was wiped with a wiping paper to peel off the upper layer of the dry film to obtain a conductive film.

"heating" The glass substrate on which the conductive film was formed was heated at 150° C. for 1 hour in the atmosphere.

＜Measurement＞ (1) Film thickness measurement The film thickness before peeling was determined by measuring the thickness of the dried film obtained in the drying step. In addition, the film thickness after peeling was obtained by measuring the thickness of the conductive film obtained in the peeling step. Regarding the film thickness, a part of the coating film was scraped off with a metal spatula, and the level difference between the substrate surface and the coating film surface was measured using a surface profile measuring device (Dektak 150 Surface Profiler, manufactured by Veeco Instruments, Inc.). The film thickness before peeling and the film thickness after peeling are shown in the column of "before peeling" and "after peeling" of "thickness [μm]" in Table 1, respectively.

(2) XRD measurement The XRD measurement before peeling was performed on the surface of the dried film obtained in the drying step. In addition, XRD measurement after peeling was performed on the surface of the conductive film obtained in the peeling step. The XRD measurement was performed using an X-ray diffraction apparatus (RINT Ultima III X-Ray Diffractometer, manufactured by Rigaku Corporation) under the following measurement conditions. 2θ/ω 30～45 degrees Sampling step 0.01 degree Scanning speed 10 degrees/min Attenuator (ATT: Attenuator) open Divergence slit (DS: Dvergence slit) 1.00mm Scattering slit (SS: Scattering slit) open Receiving slit (RS: Receiving slit) open Optical System Parallel Slit PB Incidence Longitudinal Limiting Soller Slit V5 Longitudinal limiting slit 10×10 Parallel Slit Analyzer PSA

The XRD measurement results were evaluated as follows. A...The (111) peak from Cu ₂ O was not detected B...The (111) peak from Cu ₂ O was detected Wherein, "not detected" (111) peak from Cu ₂ O means The ratio Z of the (111) peak intensity from Cu ₂ O to the (111) peak intensity from Cu based on XRD measurements [Z={(111) peak intensity from Cu ₂ O/(111) from Cu ) peak intensity}×100 (%)] is less than 0.1%, and "detected" means that the above-mentioned Z is more than 0.1%. The XRD measurement results before peeling and the XRD measurement results after peeling are shown in the columns of "before peeling" and "after peeling" of "XRD" in Table 1, respectively.

(3) Conductivity The measurement of the volume resistance value after peeling was performed on the conductive film obtained in the peeling step. In addition, the measurement of the volume resistance value after heating was performed on the conductive film obtained in the heating step. The volume resistance value of the film was measured by the four-terminal method. The measurement results of the volume resistance value after peeling and the measurement results of the volume resistance value after heating are shown in the columns "after peeling" and "after heating" of "volume resistance value [Ω･m]" in Table 1, respectively.

[Embodiments 2-4] <Example 2> A conductive film was formed in the same manner as in Example 1, except that the drying conditions of the coating film formed on the glass substrate were performed under the conditions shown in the "drying conditions" column of Table 1. The thickness of the dried film before peeling and the thickness of the conductive film obtained by peeling the upper layer of the dried film are shown in the "before peeling" column and the "after peeling" column of the "thickness" column in Table 1, respectively. The XRD measurement results of the dried film before peeling and the XRD measurement results of the conductive film obtained by peeling off the upper layer of the dried film are shown in the "before peeling" column and the "after peeling" column of the "XRD" column in Table 1. The volume resistance value of the conductive film obtained by peeling off the upper layer of the dry film and the volume resistance value after heating the conductive film are shown in the column "after peeling" and "after heating" in the column "volume resistance value" of Table 1, respectively. . In addition, a graph showing the XRD measurement results of the conductive film of Example 2 is shown in FIG. 2 .

(4) Analysis of metal copper and reducing agent in the conductive film XRF measurement of metallic copper in the conductive film was performed under the following measurement conditions using a fluorescent X-ray analyzer (Axios, manufactured by PANalytical). Line: Kα rays Crystallization: LIF200 Collimator: 150um Detector: Duplex Tube filter: no Voltage: 60kV Current: 60mA Measuring time: 40 seconds Irradiation area: 20φ

Also, regarding the measurement of the content of ascorbic acid in the conductive film, using a high-performance liquid chromatography (Prominence-comprehensive HPLC series, manufactured by Shimadzu Corporation), the scraped conductive film was added to the ion exchange by the following measurement conditions. solution in water and irradiated with ultrasonic waves for 10 minutes. Column: Shiseido CAPCELL PAK C18 AQ 5um Protection column: no Flow rate: 0.8ml/min Column temperature: 40°C Detection wavelength: 254nm Eluent: A: 25mM potassium dihydrogen phosphate-phosphoric acid aqueous solution (pH=2.5) B: Methanol (no buffer) Flushing solution: water: methanol = 1:1 (vol%) Time program: 0～8.0min: B.conc=0% 8.01～13.0min: B.conc=80% 13.1～35.0min: B.conc=0%

As a result of the measurement performed above, the content of metallic copper in the conductive film was 92.2% by mass, and the content of ascorbic acid as a reducing agent was 7.8% by mass.

<Example 3> A conductive film was formed in the same manner as in Example 1, except that the drying conditions of the coating film formed on the glass substrate were performed under the conditions shown in the "drying conditions" column of Table 1. The thickness of the dried film before peeling and the thickness of the conductive film obtained by peeling the upper layer of the dried film are shown in the "before peeling" column and the "after peeling" column of the "thickness" column in Table 1, respectively. The XRD measurement results of the dry film before peeling and the XRD measurement results of the conductive film obtained by peeling the upper layer of the dry film are shown in the "before peeling" column and the "after peeling" column of the "XRD" column in Table 1. The volume resistance value of the conductive film obtained by peeling off the upper layer of the dry film is shown in the "after peeling" column of the "volume resistance value" column of Table 1.

<Example 4> A conductive film was formed in the same manner as in Example 2 except for using citric acid instead of L-ascorbic acid. The thickness of the dried film before peeling and the thickness of the conductive film obtained by peeling the upper layer of the dried film are shown in the "before peeling" column and the "after peeling" column of the "thickness" column in Table 1, respectively. The XRD measurement results of the dry film before peeling and the XRD measurement results of the conductive film obtained by peeling the upper layer of the dry film are shown in the "before peeling" column and the "after peeling" column of the "XRD" column in Table 1. The volume resistance value of the conductive film obtained by peeling off the upper layer of the dry film is shown in the "after peeling" column of the "volume resistance value" column of Table 1.

[Comparative examples 1 to 7] ＜Comparative example 1＞ A dry film was formed on a glass substrate in the same manner as in Example 2, except that the conductive film-forming composition was prepared in the formulation shown in Table 2. When the surface of the dry film formed on the glass substrate was lightly wiped with a wiping paper, all the dry film was wiped off as a powder and completely peeled off. The thickness of the dry film before peeling is shown in the "before peeling" column of the "thickness" column in Table 1, and the XRD measurement results before peeling are shown in the "before peeling" column of the "XRD" column in Table 1. The volume resistance value after peeling off the dry film could not be measured. Moreover, the graph which shows the XRD measurement result of the dry film before peeling of the comparative example 1 is shown in FIG.

＜Comparative example 2＞ In the same manner as in Example 2, a dry film was formed on the glass substrate, but the upper layer was not peeled off. The thickness of the dry film is shown in the "before peeling" column of the "thickness" column in Table 1, the XRD measurement results are shown in the "before peeling" column of the "XRD" column in Table 1, and the measurement results of the volume resistance value are shown in The "before peeling" column of the "volume resistance value" column of Table 1.

＜Comparative example 3＞ In the same manner as in Example 2, a dry film was formed on a glass substrate, but only a part of the upper layer was peeled in the thickness direction. The thicknesses of the dry film before peeling and after a part of peeling are shown in the "before peeling" column and the "after peeling" column of the "thickness" column in Table 1, respectively. The XRD measurement results before peeling of the dry film are shown in the "before peeling" column of the "XRD" column in Table 1. The volume resistance values of the dry film before peeling and after a part of peeling are shown in the column of "before peeling" and "after peeling" in the column of "volume resistance value" in Table 1, respectively.

＜Comparative example 4＞ A composition for forming a conductive film was prepared in the same manner as in Example 4 except that the reducing agent was changed to formic acid, and a dry film and a conductive film were formed on a glass substrate. The thickness of the dried film before peeling and the thickness of the conductive film obtained by peeling the upper layer of the dried film are shown in the "before peeling" column and the "after peeling" column of the "thickness" column in Table 1, respectively. The XRD measurement results of the dried film before peeling and the XRD measurement results of the conductive film obtained by peeling off the upper layer of the dried film are shown in the "before peeling" column and the "after peeling" column of the "XRD" column in Table 1. The volume resistance value of the conductive film obtained by peeling off the upper layer of the dry film is shown in the "after peeling" column of the "volume resistance value" column of Table 1.

＜Comparative example 5＞ A composition for forming a conductive film was prepared in the same manner as in Comparative Example 1 except that the reducing agent was changed to oxalic acid, and a dry film was formed on a glass substrate. When the surface of the dry film formed on the glass substrate was lightly wiped with a wiping paper, all the dry film was wiped off as a powder and completely peeled off. The thickness of the dry film before peeling is shown in the "before peeling" column of the "thickness" column in Table 1, and the XRD measurement results before peeling are shown in the "before peeling" column of the "XRD" column in Table 1. The volume resistance value after peeling off the dry film could not be measured.

＜Comparative example 6＞ A composition for forming a conductive film was prepared in the same manner as in Comparative Example 1 except that the reducing agent was changed to acetic acid, and a dry film was formed on a glass substrate. When the surface of the dry film formed on the glass substrate was lightly wiped with a wiping paper, all the dry film was wiped off as a powder and completely peeled off. The thickness of the dry film before peeling is shown in the "before peeling" column of the "thickness" column in Table 1, and the XRD measurement results before peeling are shown in the "before peeling" column of the "XRD" column in Table 1. The volume resistance value after peeling off the dry film could not be measured.

＜Comparative example 7＞ A composition for forming a conductive film was prepared in the same manner as in Example 4 except that the reducing agent was changed to L-cysteine, and a dry film and a conductive film were formed on a glass substrate. The thickness of the dried film before peeling and the thickness of the conductive film obtained by peeling the upper layer of the dried film are shown in the "before peeling" column and the "after peeling" column of the "thickness" column in Table 1, respectively. The XRD measurement results of the dry film before peeling and the XRD measurement results of the conductive film obtained by peeling the upper layer of the dry film are shown in the "before peeling" column and the "after peeling" column of the "XRD" column in Table 1. The volume resistance value of the conductive film obtained by peeling off the upper layer of the dried film is shown in the "after peeling" column of the "volume resistance value" column of Table 1.

[Table 1]

[Table 2]

In Table 2, "Total Peeling" in the "Thickness" column indicates that there is no peeling into upper and lower layers, the dry film is completely wiped off as a powder and all peeled off, and "N.A." in the "Volume Resistance Value" column indicates that the dry film As a result of total peeling, the volume resistance value could not be measured. Also, in Table 2, "O.L." in the column of "volume resistance value" indicates that the volume resistance value was high and exceeded the measurement limit. In addition, "after peeling" in Comparative Example 3 represents the volume resistance value measured after removing a part of the upper layer of the dry film in the thickness direction.

In Examples 1 to 4, after the dry film was peeled off, a conductive film excellent in conductivity was obtained. On the other hand, in Comparative Examples 1-7, the electroconductive film excellent in electroconductivity could not be obtained.

Comparative Example 1 is an example in which the composition for forming a conductive film does not contain a reducing agent. In Comparative Example 1, the copper oxide was not reduced to metallic copper, and the upper layer containing copper oxide and the lower layer containing metallic copper were not formed even when the coating film was dried. Things are wiped off. Therefore, a conductive film excellent in conductivity cannot be obtained.

Comparative Examples 2 and 3 are the same as in Example 2 until the dry film is formed on the substrate, but only the upper layer of the dry film is not peeled off (Comparative Example 2), or only part of the upper layer of the dry film is peeled off in the thickness direction (Comparative Example 3 ). In Comparative Examples 2 and 3, since the upper layer was not completely removed, a conductive film having excellent conductivity could not be obtained.

Comparative Examples 4 to 7 are examples in which formic acid (Comparative Example 4), oxalic acid (Comparative Example 5), acetic acid (Comparative Example 6), or L-cysteine (Comparative Example 7) was used as a reducing agent.

In Comparative Example 4, the reducibility was insufficient, but the fusion state of the particles of the conductive film was insufficient, and a conductive film excellent in conductivity could not be obtained. This is presumed to be because formic acid has a low boiling point, so that unevenness of the reducing agent cannot be effectively performed in the drying process of the coating film.

In Comparative Examples 5 and 6, since the reducing power was insufficient, a conductive film excellent in conductivity could not be obtained.

In Comparative Example 7, the reducibility was sufficient and the unevenness of the reducing agent in the coating was also progressing, but the L-cysteine consumed in the reduction became insoluble crystals and precipitated in the coating, so copper The particles could not contact effectively, the welded state of the conductive film was insufficient, and a coating film excellent in conductivity could not be obtained.

11‧‧‧substrate 12‧‧‧coating film 13‧‧‧Dry film 14‧‧‧Lower layer (conductive film) 15‧‧‧upper floor 16‧‧‧Interface 17‧‧‧Conductive film surface

FIG. 1A is a schematic diagram showing a substrate before forming a coating film. FIG. 1B is a schematic diagram showing a state in which a coating film is formed on the surface of a substrate. FIG. 1C is a schematic view showing a state where a dry film in which the lower layer (conductive film) and the upper layer are in contact with each other at the interface is formed on the surface of the substrate. FIG. 1D is a schematic diagram showing a state where a lower layer (conductive film) is formed on the surface of the substrate after the upper layer is removed. FIG. 2 is a graph showing the XRD measurement results of Example 2 and Comparative Example 1. FIG. In addition, the comparative example 1 and cuprous oxide (reference) respectively increase the count amount which shows the reference line in parentheses.

Claims (8)

A method for producing a conductive film comprising: a coating step of coating copper particles with at least one selected from the group consisting of reducing ketones and hydroxycarboxylic acids having two or more carboxyl groups and one or more hydroxyl groups in the molecule. A conductive film-forming composition of a reducing agent and a dispersion medium is applied to the surface of a substrate to form a coating film; in the drying step, the coating film is dried in an oxidizing environment at a temperature below 150°C, and the substrate is obtained including a dry film of a lower layer substantially not containing copper oxide and an upper layer of copper oxide disposed on the lower layer; and a lift-off step of removing the upper layer from the dry film to obtain a conductive film. The method for manufacturing a conductive film according to Claim 1, wherein the (111) peak of Cu ₂ O based on X-ray diffraction is detected in the upper layer but not in the lower layer. The method for manufacturing a conductive film as described in claim 1 of the patent application, wherein the reducing agent is at least one selected from the group consisting of ascorbic acid, ascorbic acid derivatives, and citric acid. The method for manufacturing a conductive film as described in item 1 of the scope of the patent application, wherein the average particle size of the copper particles is within the range of 25~1500nm. The method for producing a conductive film as described in claim 1, further comprising a heating step of heating the conductive film at a temperature greater than 150°C and lower than 190°C after the peeling step. The method for manufacturing a conductive film as described in claim 1, wherein the temperature of the drying step is below 125°C. The method for producing a conductive film as described in claim 1, wherein the composition for forming a conductive film does not contain a binder. The method for manufacturing a conductive film according to any one of the first to seventh claims of the patent application, wherein the ratio of the mass of the copper particles to the mass of the reducing agent is 90-99% by mass.

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