JPWO2019167365A1 - Composition for forming a conductive film and a method for producing a conductive film - Google Patents

Abstract

A composition for forming a conductive film containing copper particles, a fusion accelerator for copper particles, and a solvent, which is the total number of atoms in the fusion accelerator that act on copper and destabilize its crystal structure. A composition for forming a conductive film having a value of the ratio of the mass MReact to the total mass MCu of copper particles MCu of 0.020 to 0.25, and the composition for forming the conductive film are applied onto the substrate. Provided is a method for producing a conductive film, comprising a coating film forming step of forming a coating film and a conductive film forming step of drying the coating film at a temperature of 150 ° C. or lower to form a conductive film.

Description

The present invention relates to a composition for forming a conductive film and a method for producing a conductive film.

As a method of forming a conductive film on a substrate, a composition for forming a conductive film containing copper particles is applied to the substrate by a printing method and then fired by heating or light irradiation to conduct electrical conduction of wiring or the like on the conductive film or circuit board. Techniques for forming sites are known.

As such a composition for forming a conductive film, for example, Patent Document 1 describes copper fine particles having an average particle size of 1 to 100 nm coated with an azole compound, and coarse copper particles having an average particle size of 0.3 to 20 μm. A conductive paste comprising a resin, a chlorine compound, and a glycol-based solvent is described (claim 1). Then, a conductive film can be formed on the substrate by applying this conductive paste to the substrate, pre-baking it, and then irradiating it with light to fire it (claim 9).

Japanese Unexamined Patent Publication No. 2016-13107

However, in recent years, there has been a demand for a composition for forming a conductive film and a method for producing a conductive film, which can form a conductive film by fusing copper particles in the atmosphere at a lower temperature.
As a result of examination by the present inventor, in order to form a conductive film using the conductive paste described in Patent Document 1, it is indispensable to bake at a high temperature by means such as light irradiation, and it may be fired at a low temperature. , It was not possible to form a conductive film having excellent conductivity.

Therefore, the present invention provides a conductive film forming composition and a method for producing a conductive film, which can form a conductive film having excellent conductivity by drying at a low temperature even in an oxidizing atmosphere. That is the issue.

As a result of diligent studies to solve the above problems, the present inventor has found that a composition for forming a conductive film containing copper particles, a fusion accelerator for copper particles, and a solvent is contained in the fusion accelerator. The value of the ratio of _{the total mass M React of the} atom and the total mass M _Cu of the copper particles that act on the copper to destabilize the crystal structure of the _{copper M React} / M _Cu is 0.020 to 0.25, which is a conductive film. It was found that the forming composition can form a conductive film having excellent conductivity by drying at a low temperature even in an oxidizing atmosphere, and completed the present invention.

That is, the present invention provides the following [1] to [15].
[1] A composition for forming a conductive film, which comprises copper particles, a fusion accelerator for the copper particles, and a solvent.
In the fusion promoter, a total mass _{M React} atoms destabilizing the crystal structure acts on the copper, the value _M React _{/ M Cu} ratio of total mass _{M Cu} of the copper particles 0.020 A composition for forming a conductive film, which is ~ 0.25.
[2] The composition for forming a conductive film according to the above [1], wherein the fusion accelerator is at least one selected from the group consisting of a halogen compound, a sulfur-containing compound, and phosphoric acid and a salt thereof.
[3] The fusion accelerator is a halogen compound.
Of the conductive film forming composition, the total mass _{M Halogen} halogen in the halogen compound, the value _{M Halogen} / _{M Cu} ratio of total mass _{M Cu} of the copper particles is from 0.020 to 0.25 , The composition for forming a conductive film according to the above [1] or [2].
[4] The composition for forming a conductive film according to the above [3], wherein the fusion accelerator is at least one selected from the group consisting of an ionic compound containing a halide ion and hydrogen halide.
[5] The composition for forming a conductive film according to the above [4], wherein the fusion accelerator is an ionic compound containing a halide ion.
[6] The conductive film forming according to the above [5], wherein the ionic compound containing the halide ion is at least one selected from the group consisting of a halide of an alkali metal and a halide of an alkaline earth metal. Composition for.
[7] The composition for forming a conductive film according to any one of the above [1] to [6], which does not contain a binder.
[8] The composition for forming a conductive film according to any one of the above [1] to [6], which further contains a binder.
[9] The value of the ratio of _{the total mass M Binder of the} binder to the total mass M _Cu of the copper particles in the composition for forming a conductive film _{M Binder} / M _Cu is 0.010 to 0.20. 8] The composition for forming a conductive film.
[10] The content of the copper particles in the conductive film forming composition is more than 90% by mass and less than 100% by mass with respect to the total mass of the solid content in the conductive film forming composition. 1] The composition for forming a conductive film according to any one of [9].
[11] The contents of the copper particles in the conductive film forming composition are 40% by mass or more and less than 100% by mass with respect to the total mass of the conductive film forming composition. 10] The composition for forming a conductive film according to any one of.
[12] The composition for forming a conductive film according to any one of the above [1] to [11], wherein the average particle diameter of the copper particles is in the range of 25 nm to 1500 nm.
[13] A coating film forming step of applying the conductive film forming composition according to any one of the above [1] to [12] onto a substrate to form a coating film.
A method for producing a conductive film, comprising a conductive film forming step of drying the coating film at a temperature of 150 ° C. or lower to form a conductive film.
[14] The method for producing a conductive film according to the above [13], wherein the coating film is dried in an oxidizing atmosphere in the conductive film forming step.
[15] After the conductive film forming step,
The method for producing a conductive film according to the above [13] or [14], further comprising a heating step of heating the conductive film at a temperature higher than the drying temperature of the coating film in the conductive film forming step and at a temperature of 150 ° C. or lower. ..

According to the present invention, there is provided a conductive film forming composition and a method for producing a conductive film, which can form a conductive film having excellent conductivity by drying at a low temperature even in an oxidizing atmosphere. be able to.

Hereinafter, the composition for forming a conductive film of the present invention and the method for producing the conductive film will be described in detail.
In the present invention, the range represented by using "~" means a range including both ends described before and after "~" in the range.

[Composition for forming a conductive film]
The composition for forming a conductive film of the present invention is a composition for forming a conductive film containing copper particles, a fusion accelerator for copper particles, and a solvent, and acts on copper in the fusion accelerator. the value _M React _{/ M Cu} ratio of total mass _{M Cu} of the total weight _{M React} copper atomic particles destabilizing the crystal structure is 0.020 to 0.25, a conductive film forming composition.

<Copper particles>
The copper particles serve as a metal conductor in the conductive film. By drying the composition for forming a conductive film, the copper particles are fused to each other to form a metal conductor in the conductive film.
As the copper particles, conventionally known copper particles generally used in a composition for forming a conductive film can be used. The copper particles may be primary particles or secondary particles. The shape of the copper particles is not particularly limited, and may be spherical or plate-shaped.

(Average particle size of copper particles)
The average particle size of the copper particles is not particularly limited, and in the case of primary particles, it is the average particle size of primary particles, and in the case of secondary particles, it is the average particle size of secondary particles, which is 25 nm to 1500 nm. The range of 30 nm to 1000 nm is more preferable, and the range of 50 nm to 500 nm is further preferable.
The average particle size of the copper particles (A) is the particle size (median size, 50% particle size, D50) at the point where the distribution curve of the integrated% of the particle size distribution measured by the particle size distribution measuring device intersects the 50% axis. ).

(Copper particle content-in solid content)
The content of the copper particles in the conductive film forming composition of the present invention is not particularly limited, but is more than 90% by mass and 100 mass with respect to the total mass of the solid content in the conductive film forming composition of the present invention. % Is preferable, 95% by mass or more and less than 100% by mass is more preferable, and 99% by mass or more and less than 100% by mass is further preferable.
When the content of the copper particles in the conductive film forming composition of the present invention is within the above range, the conductivity of the conductive film obtained by drying the conductive film forming composition of the present invention is more excellent. It becomes a thing.
It is considered that this is because the content of copper, which is a conductor, in the conductive film obtained by drying the conductive film forming composition of the present invention increases.

(Copper particle content-in all compositions)
The content of the copper particles in the conductive film forming composition of the present invention is not particularly limited, but is 40% by mass or more and less than 100% by mass with respect to the total mass of the conductive film forming composition of the present invention. Is more preferable, 40% by mass to 90% by mass is more preferable, 40% by mass to 70% by mass is further preferable, and 40% by mass or more and less than 50% by mass is even more preferable.
When the content of the copper particles in the conductive film forming composition of the present invention is within the above range, the conductivity of the conductive film obtained by drying the conductive film forming composition of the present invention is more excellent. It becomes a thing.
It is considered that this is because the content of copper, which is a conductor, in the conductive film obtained by drying the conductive film forming composition of the present invention increases.

<Fusion accelerator>
The fusion accelerator promotes fusion / fusion of the copper particles.
The details of the mechanism by which the fusion accelerator promotes fusion and fusion between the copper particles in the present invention have not been clarified, but the surface energy of the copper particles is significantly increased in the copper particles. Therefore, it is considered that they aggregate with each other and are easily fused and fused between the particles. In the present invention, atoms that act on copper and destabilize its crystal structure act on the surface of copper particles to increase destabilizing energy, and as a result, fusion and fusion of copper particles are promoted. It is considered to be. Then, the copper particles are fused and fused to form a conductor.

(Content of fusion accelerator)
In the composition for forming a conductive film of the present invention, the content of the fusion accelerator is the total mass M _{React of} atoms in the fusion accelerator that acts on copper to destabilize its crystal structure. The value of the ratio of the total mass M _{Cu of the copper particles M React} / M _Cu is an amount of 0.020 to 0.25, preferably 0.020 to 0.20, and 0.020 to 0. An amount of .10 is more preferable, and an amount of 0.020 to 0.050 is even more preferable.
When M _React / M _Cu is within this range, the effect of the fusion accelerator to promote the fusion and fusion of copper particles is well exhibited, and the conductive film obtained by drying the conductive film forming composition. The residual amount of the fusion accelerator in the film is small, and the adverse effect on the conductivity of the conductive film is small.

The fusion accelerator is preferably at least one selected from the group consisting of halogen compounds, sulfur-containing compounds and phosphoric acid and salts thereof.

《Halogen compound》
The halogen compound is not particularly limited as long as it is a compound containing a halogen, but at least one selected from the group consisting of an ionic compound containing a halide ion and a hydrogen halide is preferable, and an ionic compound containing a halide ion is more preferable. preferable.

In the present invention, halogen refers to fluorine (element symbol: F), chlorine (element symbol: Cl), and bromine (element symbol) among the Group 17 elements in the IUPAC (International Union of Pure and Applied Chemistry) periodic table. : Br) and iodine (element symbol: I), preferably chlorine, bromine and iodine, more preferably chlorine and bromine, and even more preferably chlorine. Further, in the present invention, astatine (element symbol: At) and tennessine (element symbol: Ts) are not included in the halogen.

(Ionic compounds containing halide ions)
The ionic compound containing the halide ion is at least one selected from the group consisting of, for example, a halide of an alkali metal, a halide of an alkaline earth metal, a hydrogen halide of an organic amine, and ammonium halide. , At least one selected from the group consisting of alkali metal halides and alkaline earth metal halides is preferred, and alkali metal halides are more preferred.

(Alkali metal halide)
Examples of the alkali metal halides include chlorides such as lithium chloride, sodium chloride and potassium chloride, bromides such as lithium bromide, sodium bromide and potassium bromide, lithium iodide, sodium iodide and potassium iodide. Iodide, and fluorides such as lithium fluoride, sodium fluoride and potassium fluoride.
The alkali metal halide is at least one selected from the group consisting of sodium chloride, sodium bromide, sodium iodide, potassium chloride, potassium bromide, potassium iodide, lithium chloride, lithium bromide and lithium iodide. Preferably, at least one selected from the group consisting of sodium chloride, sodium bromide, sodium iodide, potassium chloride, potassium bromide and potassium iodide is more preferred, from the group consisting of sodium chloride, sodium iodide and sodium iodide. At least one selected is more preferred, and sodium chloride is even more preferred.

In the present invention, the alkali metal refers to lithium (element symbol: Li), sodium (element symbol: Na), potassium (element symbol: K), rubidium (element symbol: element symbol) among the Group 1 elements in the IUPAC periodic table. : Rb) and cesium (element symbol: Cs), preferably lithium, sodium, potassium and rubidium, more preferably lithium, sodium and potassium, and even more preferably sodium and potassium. In the present invention, francium (element symbol: Fr) is not included in the alkali metal.

(Halogen of alkaline earth metal)
Examples of the above-mentioned halides of alkaline earth metals include chlorides such as calcium chloride, strontium chloride, barium chloride, beryllium chloride and magnesium chloride, calcium bromide, strontium bromide, barium bromide, beryllium bromide and magnesium bromide. And the like, as well as iodides such as calcium iodide, strontium iodide, barium iodide, beryllium iodide and magnesium iodide.
The halide of the alkaline earth metal is at least selected from the group consisting of calcium chloride, strontium chloride, barium chloride, calcium bromide, strontium bromide, strontium bromide, calcium iodide, strontium iodide and barium iodide. One is preferred, and at least one selected from the group consisting of calcium chloride, strontium chloride, barium chloride, calcium bromide, strontium bromide and barium bromide is more preferably selected from the group consisting of calcium chloride, strontium chloride and barium chloride. At least one is more preferred, and calcium chloride is even more preferred.

In the present invention, the alkaline earth metal refers to barium (element symbol: Be), magnesium (element symbol: Mg), calcium (element symbol: Ca), and strontium (element symbol: Ca) among the Group 2 elements in the IUPAC periodic table. It refers to element symbol: Sr) and barium (element symbol: Ba), preferably calcium, strontium and barium, and more preferably calcium. In the present invention, radium (element symbol: Ra) is not included in alkaline earth metals.

(Halogenated hydrogen salt of organic amine)
Examples of the above-mentioned hydrogen halide salts of organic amines include triethylamine hydrochloride, triethylamine hydrobromide, triethylamine hydroiodide, triethylamine hydrofluorate, pyridine hydrochloride, pyridine hydrobromide, and pyridine iodide. Hydrochloride, pyridine hydrofluorate, betaine hydrochloride, betaine hydrobromide, betaine hydroiodide, betaine hydrofluorate and the like.
As the hydrogen halide salt of the organic amine, N, N, N-trimethylglycine hydrochloride is preferable.

(Ammonium halide)
Examples of the above ammonium halides are ammonium chloride, ammonium bromide, ammonium iodide, ammonium fluoride and the like.
As the ammonium halide, ammonium chloride is preferable.

(Hydrogen halide)
Examples of the above hydrogen halide are hydrogen chloride, hydrogen bromide, hydrogen iodide, hydrogen fluoride and the like.
The hydrogen halide is preferably at least one selected from the group consisting of hydrogen chloride, hydrogen bromide and hydrogen iodide, more preferably at least one selected from the group consisting of hydrogen chloride and hydrogen bromide, and hydrogen chloride is more preferable. More preferred.

(Content of halogen compound)
In the conductive film forming composition of the present invention, the content of the halogen compound, in the halogen compound, and the total mass _{M Halogen} halogen, the values of the ratio of the total mass _{M Cu} of the copper particles _{M Halogen} / _{M Cu} However, the amount is 0.020 to 0.25, preferably 0.020 to 0.20, more preferably 0.020 to 0.10, and 0.020 to 0.050. Is more preferred.
When M _Halogen / M _Cu is within this range, the effect of the fusion accelerator to promote the fusion and fusion of copper particles is well exhibited, and the conductive film obtained by drying the conductive film forming composition. The residual amount of the fusion accelerator in the film is small, and the adverse effect on the conductivity of the conductive film is small.

<< Sulfur-containing compounds >>
The sulfur-containing compound is not particularly limited as long as it is a compound having a sulfur atom, and examples thereof include methanethiol, ethanethiol, 1-propanethiol, 2-propanethiol, 1-butanethiol, 2-butanethiol, and 2-. Methyl-1-propanethiol, 2-methyl-2-propanethiol, thiophenol, cysteine, glutathione, thioglycolic acid, pentaerythritol tetrakis (3-mercaptobutyrate), 1,4-bis (3-mercaptobutyryloxy) ) Butane, 1,3,5-tris (3-mercaptobutyryloxyethyl) -1,3,5-triazine-2,4,6- (1H, 3H, 5H) -trione, hydrogen sulfide, sulfuric acid, sulfuric acid Examples thereof include sodium hydrogen hydrogen, sodium sulfate, sulfite, sodium hydrogen sulfite, sodium sulfite, magnesium sulfate and the like.

The sulfur-containing compounds include ethanethiol, 1-propanethiol, 2-propanethiol, 1-butanethiol, 2-butanethiol, 2-methyl-1-propanethiol, 2-methyl-2-propanethiol, and thioglycolic acid. , Sulfate, sodium hydrogensulfate, sodium sulfate, sulfite, sodium hydrogensulfate, sodium sulfite, and magnesium sulfate, preferably at least one selected from the group consisting of 1-propanethiol, 2-propanethiol, 1-butanethiol, 2 More preferably, at least one selected from the group consisting of -butanethiol, 2-methyl-1-propanethiol, 2-methyl-2-propanethiol, sulfuric acid, sodium hydrogensulfate, sodium sulfate, and magnesium sulfate, 1-butane. More preferably, at least one selected from the group consisting of thiol, 2-butanethiol, 2-methyl-1-propanethiol, 2-methyl-2-propanethiol, sulfuric acid, sodium hydrogensulfate, sodium sulfate, and magnesium sulfate. Sulfuric acid is more preferred.

(Content of sulfur-containing compound)
In the composition for forming a conductive film of the present invention, the content of the sulfur-containing compound is the value of the ratio of _{the total mass M S} of the sulfur atom to the total mass M _{Cu of the copper particles in the sulfur-containing compound M S.} / M _Cu is an amount of 0.020 to 0.25, preferably 0.020 to 0.20, more preferably 0.020 to 0.10, and 0.020 to 0. An amount of .050 is even more preferred.
When M _S / M _Cu is within this range, the effect of the fusion accelerator to promote the fusion / fusion of copper particles is well exhibited, and the conductive film obtained by drying the conductive film forming composition is exhibited. The residual amount of the fusion accelerator in the film is small, and the adverse effect on the conductivity of the conductive film is small.

《Phosphoric acid and its salts》
The phosphoric acid and its salt are not particularly limited, and examples thereof include phosphoric acid and alkali metal salts of phosphoric acid. Here, the alkali metal is as described above.
Examples of alkali metal salts of phosphate are trilithium phosphate (Li ₃ PO ₄ ), dilithium hydrogen phosphate (Li ₂ HPO ₄ ), lithium dihydrogen phosphate (LiH ₂ PO ₄ ), disodium phosphate (trisodium phosphate). Na ₃ PO ₄ ), disodium hydrogen phosphate (Na ₂ HPO ₄ ), sodium dihydrogen phosphate (NaH ₂ PO ₄ ), tripotassium phosphate (K ₃ PO ₄ ), dipotassium hydrogen phosphate (K ₂ HPO) ₄ ) and potassium dihydrogen phosphate (KH ₂ PO ₄ ).
The alkali metal salt of phosphoric acid is selected from the group consisting of phosphoric acid, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, tripotassium phosphate, dipotassium hydrogen phosphate and potassium dihydrogen phosphate. At least one selected from the group consisting of phosphoric acid, trisodium phosphate, disodium hydrogen phosphate and sodium dihydrogen phosphate is more preferable, and phosphoric acid is even more preferable.

(Contents of phosphoric acid and its salts)
In the composition for forming a conductive film of the present invention, the content of the phosphoric acid and its salt constitutes phosphoric acid, phosphoric acid ion, hydrogen phosphate ion or dihydrogen phosphate ion in the phosphoric acid and its salt. a total mass _{M P} of the phosphorus atom, the value _M P _{/ M Cu} ratio of total mass _{M Cu} of the copper particles is an amount that is at 0.020 to 0.25, and 0.020 to 0.20 The amount is preferably 0.020 to 0.10, more preferably 0.020 to 0.050.
When _MP / M _Cu is within this range, the effect of the fusion accelerator to promote the fusion / fusion of copper particles is well exhibited, and the conductive film obtained by drying the conductive film forming composition is exhibited. The residual amount of the fusion accelerator in the film is small, and the adverse effect on the conductivity of the conductive film is small.

<solvent>
The solvent is not particularly limited as long as it can disperse the copper particles and dissolve or disperse the fusion accelerator.
Specific examples of the above solvent include water, methanol, ethanol, propanol, 2-propanol, cyclohexanone, cyclohexanol, terpineol, ethylene glycol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, and ethylene glycol mono. At least one selected from the group consisting of butyl ether acetate, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether acetate and diethylene glycol monobutyl ether acetate, and the group consisting of water, methanol, ethanol, propanol and 2 propanol. At least one selected from is preferred, at least one selected from the group consisting of water, methanol and ethanol is more preferred, and water is even more preferred. As the water, ion-exchanged water, RO (reverse osmosis) water, distilled water or other pure water, or ASTM D 1193-06 type 1 grade or other ultrapure water is preferable.

<binder>
The composition for forming a conductive film of the present invention may or may not contain a binder.
Here, examples of the binder include resins and organic compounds having a molecular weight of 1000 or more.

Examples of the resin include thermosetting resins and thermoplastic resins.
Specific examples of the above-mentioned thermoplastic resin include phenol resin, epoxy resin, unsaturated polyester resin, vinyl ester resin, diallyl phthalate resin, oligo ester acrylate resin, xylene resin, bismalade triazine resin, furan resin, urea resin, polyurethane, and the like. Examples of the thermoplastic resin include melamine resin, silicon resin, acrylic resin, oxetane resin, and oxazine resin, and specific examples of the thermoplastic resin include polyamide resin, polyimide resin, acrylic resin, ketone resin, polystyrene resin, and thermoplastic polyester resin. However, it is not limited to these.

The organic compound having a molecular weight of 1000 or more is not particularly limited, and examples thereof include an organic acid having a molecular weight of 1000 or more, a polyalkylene glycol having a molecular weight of 1000 or more, a sugar alcohol having a molecular weight of 1000 or more, an oligosaccharide, and a polysaccharide.

The binder has the effect of improving the adhesion of the conductive film to the substrate, but at the same time, it may reduce the conductivity. Therefore, the content of the binder when the composition for forming a conductive film of the present invention contains a binder is a value of the ratio of _{the total mass M Binder} of the binder in the composition for forming a conductive film to the total mass M _{Cu of the copper particles.} The amount of M _Binder / M _Cu is preferably 0.010 to 0.20, more preferably 0.010 to 0.15, and even more preferably 0.010 to 0.10.
In the conductive film forming composition of the present invention, when the above M _Binder / M _Cu is within this range, the effect of improving the adhesion of the conductive film due to the inclusion of the binder can be exhibited, and the adverse effect on the conductivity is minimized. It can be suppressed to the limit.

<Method for preparing a composition for forming a conductive film>
The method for preparing the composition for forming a conductive film of the present invention is not particularly limited, but can be described below, for example.

(Mixing of copper particles, fusion accelerator and solvent)
The method for mixing the copper particles, the fusion accelerator and the solvent is not particularly limited, and a conventionally known method can be adopted.
For example, known means such as an ultrasonic method (for example, treatment with an ultrasonic homogenizer), a mixer method, a three-roll method, and a ball mill method after adding copper particles and a fusion accelerator to a solvent. The composition can be obtained by dispersing the components with.
If the fusion accelerator is a solid, it may be added after being dissolved or dispersed in a solvent. When the fusion accelerator is a gas, it may be added after being dissolved in a solvent.
For example, when hydrogen chloride is added, it may be added as hydrochloric acid, which is an aqueous solution. However, in this case, water, which is a solvent for hydrogen chloride, is treated as a solvent contained in the composition for forming a conductive film.

[Manufacturing method of conductive film]
The method for producing a conductive film of the present invention includes a coating film forming step of applying the conductive film forming composition onto a substrate to form a coating film, and drying the coating film at a temperature of 150 ° C. or lower to form a conductive film. This is a method for producing a conductive film, which comprises a conductive film forming step for forming the film.

<substrate>
As the substrate, a conventionally known substrate can be used.
Specific examples of the material used for the substrate are resin, paper, glass, silicon-based semiconductor, compound semiconductor, metal, metal oxide, metal nitride, wood, or a composite thereof. It is not limited.

Specific examples of the above resins include low-density polyethylene resin, high-density polyethylene resin, ABS (Acrylonitrile Butadiene Styrene) resin, acrylic resin, styrene resin, vinyl chloride resin, polyester resin (polyethylene terephthalate (PET)), polyacetal resin, and polysulfone resin. , Polyetherimide resin, polyetherketone resin, polyimide resin, and cellulose derivative, but are not limited thereto.
Specific examples of the above papers include coating printing paper, fine coating printing paper, coating printing paper (art paper, coated paper), special printing paper, copy paper (PPC paper), and unbleached wrapping paper (both for heavy bags). Sarah kraft paper, Ryosara kraft paper), bleached wrapping paper (bleached kraft paper, pure white roll paper), coated balls, chip balls, and cardboard, but are not limited to these.
Specific examples of the above glass are, but are not limited to, soda glass, borosilicate glass, silica glass, and quartz glass.
Specific examples of the silicon-based semiconductor are amorphous silicon and polysilicon, but the present invention is not limited thereto.
Specific examples of the compound semiconductor are, but are not limited to, CdS, CdTe and GaAs.
Specific examples of the above metals are, but are not limited to, copper, iron, and aluminum.
Specific examples of the above metal oxides include alumina, sapphire, zirconia, titania, ittrium oxide, indium oxide, ITO (indium tin oxide), IZO (indium zinc oxide), nesa (tin oxide), and ATO (antimony-doped oxidation). Tin), fluorine-doped zinc oxide, zinc oxide, AZO (aluminum-doped zinc oxide), and gallium-doped zinc oxide, but are not limited thereto.
Specific examples of the metal nitride are, but are not limited to, aluminum nitride.
Specific examples of the above-mentioned composites include paper-resin composites such as paper-phenol resin, paper-epoxy resin, and paper-polyester resin, glass cloth-epoxy resin (glass epoxy resin), and glass cloth-polygonic resin. And glass cloth-fluororesin, but not limited to these.
The substrate on which the conductive film of the present invention is formed is not particularly limited, but a glass substrate, a polyimide substrate, or a polyethylene terephthalate (PET) substrate is preferable.

<Method of applying the composition for forming a conductive film on a substrate>
The method of applying the conductive film forming composition onto the substrate is not particularly limited, and a known method can be adopted. For example, a coating method such as a screen printing method, a dip coating method, a spray coating method, a spin coating method, and an inkjet method can be 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, a wiring shape or a dot shape).

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

<Conducting film forming process>
In the conductive film forming step, the coating film is dried at a temperature of 150 ° C. or lower to obtain a conductive film on the substrate.
In the method for producing a conductive film of the present invention, a conductive film having excellent conductivity can be produced by drying the coating film at a low temperature of 150 ° C. or lower.

(Drying method)
As a drying method in the conductive film forming step, a method of drying using a warm air dryer or the like can be used.

(Temperature during drying)
In the conductive film forming step, the drying of the coating film is not particularly limited as long as it is carried out at a temperature of 150 ° C. or lower, but is preferably 0 ° C. to 120 ° C., more preferably 0 ° C. to 100 ° C., and preferably 15 ° C. to 100 ° C. More preferred.

(Atmosphere when drying)
In the conductive film forming step, the contact between the insulating coating film and the fusion accelerator may be carried out in an oxidizing atmosphere, an inert atmosphere or a reducing atmosphere. It is good, but one of the effects of the present invention is that a conductive film having excellent conductivity can be formed even in an oxidizing atmosphere.
The oxidative atmosphere is, for example, air or air, a mixed gas of air or air and an inert gas, or a mixed gas of air or air and a gaseous state or a vaporized fusion accelerator, and oxygen is 5.0. Those containing% (v / v) or more are preferable, and those containing 5.0% (v / v) or more and less than 21.0% (v / v) are preferable.
Examples of the inert atmosphere or reducing atmosphere include an inert gas, preferably having an oxygen content of 0.005% (v / v) or less, and more preferably having an unavoidably trace amount. Examples of the inert gas include nitrogen gas, argon gas, neon gas, xenon gas and the like. Examples of the reducing gas include hydrogen gas and formic acid gas.

(Drying time)
The time for drying (hereinafter, may be referred to as “drying time”) is not particularly limited, but is preferably 1 second to 96 hours, more preferably 5 seconds to 72 hours, and even more preferably 10 seconds to 48 hours. However, the drying time only needs to be able to remove substantially all of the solvent from the coating film, and can be appropriately set depending on the temperature at the time of drying.

<Heating process>
The method for producing a conductive film of the present invention includes, after the conductive film forming step, a heating step of heating the conductive film at a temperature higher than the drying temperature of the coating film in the conductive film forming step and at a temperature of 150 ° C. or lower. You may.
By heating the conductive film obtained in the conductive film forming step at a temperature higher than the drying temperature of the coating film in the conductive film forming step and at a temperature of 150 ° C. or lower, the conductivity of the conductive film is further improved. can do.

(Heating method)
The heating method in the heating step is not particularly limited, and may be performed in the same manner as the drying method, or may be heated using a heating device such as a hot plate.

(Temperature during heating)
In the heating step, the heating of the conductive film is not particularly limited as long as it is performed at a temperature higher than the drying temperature of the coating film in the conductive film forming step and at a temperature of 150 ° C. or lower.

(Atmosphere during heating)
In the heating step, the heating of the conductive film may be performed in an oxidizing atmosphere or a reducing atmosphere. The oxidative atmosphere and the reducing atmosphere are the same as those in the conductive film forming step.

(Heating time)
The time during heating (hereinafter, may be referred to as “heating time”) is not particularly limited, but is preferably 1 second to 96 hours, more preferably 5 seconds to 72 hours, and even more preferably 10 seconds to 48 hours. However, the heating time can be appropriately set depending on the temperature at the time of heating.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

[Centrifugation]
In the following examples and comparative examples, the centrifuge was performed using an ultracentrifuge (CS150GXL, manufactured by Himac) under the condition of 50,000 rpm × 10 minutes.

[Average particle size]
In the following examples and comparative examples, the average particle diameter is the median diameter (D50) measured using a nanoparticle analyzer (nanoPartica SZ-100, manufactured by HORIBA, Ltd.).

[Example 1]
<Preparation of composition for forming a conductive film>
To 20 parts by mass of copper particle ink (copper particle-containing ethylene glycol ink having an average particle diameter of 80 nm and a solid content concentration of 50% by mass; manufactured by Promethean Particles), 2.45 parts by mass of a 20% aqueous solution of sodium chloride (Wako Pure Chemical Industries, Ltd.) was added. Addition was made to prepare a copper ink (hereinafter referred to as "composition for forming a conductive film 1").

<Manufacturing of conductive film>
A glass substrate (length 76 mm × width 26 mm × thickness 0.9 mm; manufactured by Matsunami Glass Co., Ltd.) was subjected to UV-ozone treatment in the atmosphere for 1 minute to prepare a hydrophilized glass substrate.
On this glass substrate, the conductive film forming composition 1 was applied with a coil bar to a length of 61 mm, a width of 26 mm, and a wet thickness of 40 μm to form a coating film on the surface of the glass substrate.
The coating film formed on the glass substrate was dried in the air at 100 ° C. for 1 minute to form a conductive film on the glass substrate.

<Evaluation of conductivity>
The volume resistance value of the obtained conductive film was measured to evaluate the conductivity.
The volume resistance value of the conductive film was measured by the four-terminal method.
The measured volume resistance values are shown in the corresponding columns of Table 1.

[Example 2]
<Preparation of composition for forming a conductive film>
In a glove box with an oxygen concentration controlled to 70 ppm, 0.67 parts by mass of polyacrylic acid (molecular weight: 5000; manufactured by Wako Pure Chemical Industries, Ltd.), 2972 parts by mass of ion-exchanged water, sodium hydroxide (Wako Pure) in a three-necked flask. (Manufactured by Yakusha) 0.37 parts by mass was dissolved. Then, a solution consisting of 10 parts by mass of copper nitrate and 90 parts by mass of ion-exchanged water was added, and the mixture was stirred at 260 rpm for 30 minutes. The stirring speed was changed to 500 rpm, an aqueous solution consisting of 13.1 parts by mass of hydrazine monohydrate (manufactured by Wako Pure Chemical Industries, Ltd.) and 87.1 parts by mass of ion-exchanged water was added at room temperature, and the mixture was stirred for 1 hour. The obtained aqueous solution was packed in a centrifuge tube and centrifuged under the above conditions. The obtained sediment was suspended in ion-exchanged water and centrifuged again. When the average particle size was measured under the above conditions, it was 80 nm. It was confirmed that it was pure copper by X-ray diffraction analysis under the conditions described later.
The obtained sediment was suspended in ion-exchanged water to prepare a copper particle dispersion having a solid content concentration of 50%. A copper ink (hereinafter referred to as "composition for forming a conductive film 2") was prepared by adding 2.45 parts by mass of a 20% aqueous solution of sodium chloride to 20 parts by mass of a copper particle dispersion.

<Manufacturing of conductive film / evaluation of conductivity>
Using the prepared conductive film forming composition 2, a conductive film was produced in the same procedure as in Example 1, and the conductivity of the obtained conductive film was evaluated. The measured volume resistance values are shown in the corresponding columns of Table 1.

<X-ray diffraction analysis>
The above X-ray diffraction analysis was performed using an X-ray diffractometer (RINT Ultima III X-Ray Diffractometer, manufactured by Rigaku Co., Ltd.) under the following measurement conditions.
2Θ / ω 30-45 degrees Sampling step 0.01 degrees Scan speed 10 degrees / minute Attenuator (ATT: Attenuator) Open divergence slit (DS: Divergence slit) 1.00 mm
Scattering slit (SS: Scattering slit) Open light receiving slit (RS: Receiving slit) Open optical system Parallel slit PB
Incident vertical restriction solar slit V5
Vertical restriction slit 10 x 10
Parallel Slit Analyzer PSA

As a result of X-ray diffraction analysis, it was confirmed that the copper particles were pure copper because the (111) peak derived from _{Cu 2 O was not detected.}
Here, "the (111) peak derived from _{Cu 2 O is" not detected "means the (111) peak intensity derived from Cu 2} O and the (111) peak intensity derived from Cu by X-ray diffraction analysis. The ratio Z [Z = { _{(111) peak intensity derived from Cu 2} O / (111) peak intensity derived from Cu} × 100 (%)] is less than 0.1%, and is “detected”. "" Means that the above Z is 0.1% or more.

[Example 3]
<Preparation of composition for forming a conductive film>
Copper ink (hereinafter referred to as "conductive film formation") is carried out in the same manner as in Example 1 except that 2.45 parts by mass of a 20% aqueous solution of sodium chloride is changed to 2.65 parts by mass of a 20% aqueous solution of ammonium chloride (Wako Pure Chemical Industries, Ltd.). Composition 3 ”) was prepared.

<Manufacturing of conductive film / evaluation of conductivity>
Using the prepared conductive film forming composition 3, a conductive film was produced in the same procedure as in Example 1, and the conductivity of the obtained conductive film was evaluated. The measured volume resistance values are shown in the corresponding columns of Table 1.

[Example 4]
<Preparation of composition for forming a conductive film>
Copper ink (hereinafter referred to as "conductive film formation") is carried out in the same manner as in Example 2 except that 2.45 parts by mass of a 20% aqueous solution of sodium chloride is changed to 2.65 parts by mass of a 20% aqueous solution of ammonium chloride (Wako Pure Chemical Substances). Composition 4 ”) was prepared.

<Manufacturing of conductive film / evaluation of conductivity>
Using the prepared conductive film forming composition 4, a conductive film was produced in the same procedure as in Example 1, and the conductivity of the obtained conductive film was evaluated. The measured volume resistance values are shown in the corresponding columns of Table 1.

[Comparative Example 1]
<Preparation of composition for forming a conductive film>
A copper ink (hereinafter referred to as “conductive film forming composition 5”) was prepared in the same manner as in Example 1 except that a 20% aqueous solution of sodium chloride was not used.

<Manufacturing of film / evaluation of conductivity>
Using the prepared composition 5 for forming a conductive film, a film was produced in the same procedure as in Example 1, and the conductivity of the obtained film was evaluated. The measured volume resistance values are shown in the corresponding columns of Table 1.

[Comparative Example 2]
<Preparation of composition for forming a conductive film>
To the solution prepared in Example 2, 22.05 parts by mass of an aqueous sodium chloride solution and 3.2 parts by mass of a 50% by mass aqueous solution of sodium polyacrylate were additionally added to make a copper ink (hereinafter, "composition for forming a conductive film 6"). ”) Was prepared.

<Manufacturing of film / evaluation of conductivity>
Using the prepared conductive film forming composition 6, a film was produced in the same procedure as in Example 1, and the conductivity of the obtained film was evaluated. The measured volume resistance values are shown in the corresponding columns of Table 1.

[Comparative Example 3]
<Preparation of composition for forming a conductive film>
Copper ink (hereinafter, "composition for forming a conductive film 7") was obtained in the same manner as in Example 1 except that 2.45 parts by mass of a 20% aqueous solution of sodium chloride was changed to 1.50 parts by mass of a 20% aqueous solution of sodium chloride. ”) Was prepared.

<Manufacturing of film / evaluation of conductivity>
A film was produced using the prepared composition for forming a conductive film in the same procedure as in Example 1, and the conductivity of the obtained film was evaluated. The measured volume resistance values are shown in the corresponding columns of Table 1.

[Comparative Example 4]
<Preparation of composition for forming a conductive film>
Copper ink (hereinafter, "composition for forming a conductive film 8") was obtained in the same manner as in Example 1 except that 2.45 parts by mass of a 20% aqueous solution of sodium chloride was changed to 22.5 parts by mass of a 20% aqueous solution of sodium chloride. ”) Was prepared.

<Manufacturing of film / evaluation of conductivity>
Using the prepared composition 8 for forming a conductive film, a film was produced in the same procedure as in Example 1, and the conductivity of the obtained film was evaluated. The measured volume resistance values are shown in the corresponding columns of Table 1.

[Comparative Example 5]
<Preparation of composition for forming a conductive film>
20 parts by mass of copper particle ink (ethylene glycol ink containing copper particles with an average particle diameter of 80 nm and a solid content concentration of 50% by mass; manufactured by Promethean Particles), 1.25 parts by mass of a 20% aqueous solution of sodium chloride (Wako Pure Chemical Industries, Ltd.), A copper ink (hereinafter referred to as "composition for forming a conductive film 9") was prepared by adding 4.50 parts by mass of a 20% aqueous solution of polyvinylpyrrolidone (K-30; manufactured by Nippon Catalyst Co., Ltd.).

<Manufacturing of film / evaluation of conductivity>
Using the prepared composition for forming a conductive film 9, a film was produced in the same procedure as in Example 1, and the conductivity of the obtained film was evaluated. The measured volume resistance values are shown in the corresponding columns of Table 1.

In Table 1, "chlorine / copper" represents the ratio of the total mass of chlorine atoms, which are atoms that act on copper to destabilize its crystal structure, with the total mass of copper particles.
"Binder / copper" represents the ratio of the mass of the binder to the mass of copper.

In Examples 1 to 4 in which a conductive film was produced using the conductive film forming composition of the present invention, the conductive film forming composition was dried in the air at a low temperature of 100 ° C. to have excellent conductivity. A conductive film having the above was obtained.
On the other hand, Comparative Example 1 in which the composition for forming a conductive film does not contain a fusion accelerator, Comparative Examples 3 and 5 in which the fusion accelerator is less than the scope of the present invention, and the fusion accelerator is the scope of the present invention. In Comparative Examples 2 and 4, which were more than the above, the conductivity of the film obtained by drying the composition for forming a conductive film was poor.

Claims (15)

A composition for forming a conductive film containing copper particles, a fusion accelerator for the copper particles, and a solvent.
Wherein in the fusing promoter, the total mass _{M React} atoms destabilizing the crystal structure acts on the copper, the value _M React _{/ M Cu} ratio of total mass _{M Cu} of the copper particles is 0.020 A composition for forming a conductive film, which is ~ 0.25. The composition for forming a conductive film according to claim 1, wherein the fusion accelerator is at least one selected from the group consisting of a halogen compound, a sulfur-containing compound, and phosphoric acid and a salt thereof. The fusion accelerator is a halogen compound,
Of the conductive film forming composition, the total mass _{M Halogen} halogen in the halogen compound, the value _{M Halogen} / _{M Cu} ratio of total mass _{M Cu} of the copper particles is 0.020 to 0.25 , The composition for forming a conductive film according to claim 1 or 2. The composition for forming a conductive film according to claim 3, wherein the fusion accelerator is at least one selected from the group consisting of an ionic compound containing a halide ion and hydrogen halide. The composition for forming a conductive film according to claim 4, wherein the fusion accelerator is an ionic compound containing a halide ion. The composition for forming a conductive film according to claim 5, wherein the ionic compound containing a halide ion is at least one selected from the group consisting of a halide of an alkali metal and a halide of an alkaline earth metal. The composition for forming a conductive film according to any one of claims 1 to 6, which does not contain a binder. The composition for forming a conductive film according to any one of claims 1 to 6, further comprising a binder. The value of the ratio of _{the total mass M Binder of the} binder to the total mass M _Cu of the copper particles in the composition for forming a conductive film _{M Binder} / M _Cu is 0.010 to 0.20, according to claim 8. Composition for forming a conductive film. Claims 1 to 9 in which the content of the copper particles in the conductive film forming composition is more than 90% by mass and less than 100% by mass with respect to the total mass of the solid content in the conductive film forming composition. The composition for forming a conductive film according to any one of the above items. Any one of claims 1 to 10, wherein the content of the copper particles in the conductive film-forming composition is 40% by mass or more and less than 100% by mass with respect to the total mass of the conductive film-forming composition. The composition for forming a conductive film according to the above item. The composition for forming a conductive film according to any one of claims 1 to 11, wherein the average particle diameter of the copper particles is in the range of 25 nm to 1500 nm. A coating film forming step of applying the conductive film forming composition according to any one of claims 1 to 12 onto a substrate to form a coating film.
A method for producing a conductive film, comprising a conductive film forming step of drying the coating film at a temperature of 150 ° C. or lower to form a conductive film. The method for producing a conductive film according to claim 13, wherein in the conductive film forming step, the coating film is dried in an oxidizing atmosphere. After the conductive film forming step,
The method for producing a conductive film according to claim 13 or 14, further comprising a heating step of heating the conductive film at a temperature higher than the drying temperature of the coating film in the conductive film forming step and at a temperature of 150 ° C. or lower.