JP2014186831A - Method of producing conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a conductive film which enables easy production of a conductive film excellent in conduction characteristics by using a metallic coper particle.SOLUTION: A method of producing a conductive film includes a step of forming a precursor film containing a metallic copper particle, a thermoplastic resin and an alcohol of a boiling point of 100-230°C on a substrate and a step of reducing the pressure and carrying out a thermal sintering treatment of the precursor film, while keeping a reduced-pressure condition leading to an alcohol atmosphere of an alcohol concentration of 5 vol.% or higher, to form a conductive film containing metallic copper.

Description

  The present invention relates to a method for manufacturing a conductive film, and more particularly to a method for manufacturing a conductive film having a step of performing a thermal sintering process while maintaining a predetermined alcohol concentration in a reduced pressure process.

As a method of forming a metal film on a base material, a metal film or a circuit board is formed by applying a dispersion of metal particles or metal oxide particles to the base material by a printing method and then sintering by heat treatment or light irradiation treatment. A technique for forming an electrically conductive portion such as a wiring in is known.
Since the above method is simpler, energy-saving, and resource-saving than conventional high-heat / vacuum processes (sputtering) and plating processes, it is highly anticipated in the development of next-generation electronics.

  For example, Patent Document 1 discloses a conductive metal paste containing a metal fine powder. In the example column of Patent Document 1, a conductive film is formed by thermal sintering using fine silver powder.

JP 2012-119132 A

On the other hand, copper is stable in an oxidized state at room temperature (25 ° C.). Therefore, an oxidized copper atom is usually included on the copper surface, and a copper atom in an oxidized state is necessary to develop a conductor and heat conductivity as metallic copper. Needs to be reduced to a metal copper continuum.
As described in Patent Document 1, the present inventors conducted production of a conductive film only by thermal sintering using metallic copper particles. As a result, the conductive characteristics of the obtained conductive film were at the level required today. It was not satisfied and further improvement was necessary.

  An object of this invention is to provide the manufacturing method of the electrically conductive film which can manufacture the electrically conductive film which is simply excellent in an electroconductive characteristic using a metal copper particle in view of the said situation.

As a result of intensive studies, the present inventors have found that the above problem can be solved by performing thermal sintering in an alcohol atmosphere in which an alcohol concentration having a predetermined boiling point is a predetermined value or more.
That is, it has been found that the above object can be achieved by the following configuration.

(1) forming a precursor film containing at least metal copper particles, a thermoplastic resin, and an alcohol having a boiling point of 100 ° C to 230 ° C on the substrate;
A process of forming a conductive film containing metallic copper by performing a pressure reduction treatment and performing a heat sintering process on the precursor film while maintaining a reduced pressure state in which an alcohol atmosphere has an alcohol concentration of 5% by volume or more. The manufacturing method of the electrically conductive film which has these.
(2) The manufacturing method of the electrically conductive film as described in (1) in which a copper oxide particle is further contained in a precursor film | membrane.
(3) The thermoplastic resin is a thermoplastic resin having a thermogravimetric reduction rate of 80% or more when the temperature is increased from 25 ° C. to 400 ° C. at a temperature increase rate of 10 ° C./min. (1) or (2 The manufacturing method of the electrically conductive film as described in).
(4) The method for producing a conductive film according to any one of (1) to (3), wherein the thermoplastic resin is selected from the group consisting of polyethyleneimine, polyethylene oxide, polypropylene oxide, and polyacetal.
(5) The manufacturing method of the electrically conductive film as described in any one of (1)-(4) whose boiling point of alcohol is 150-230 degreeC.
(6) The ratio (A / B) between the mass A of the copper metal particles and the mass B of the copper oxide particles in the precursor film is 4 or more, according to any one of (2) to (5). Manufacturing method of electrically conductive film.
(7) The manufacturing method of the electrically conductive film as described in any one of (1)-(5) with which a pressure reduction process is implemented at 1-100 mmHg.
(8) The manufacturing method of the electrically conductive film as described in any one of (1)-(6) with which a pressure reduction process is implemented at 1-50 mmHg.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the electrically conductive film which can manufacture the electrically conductive film which is easily excellent in an electroconductive characteristic using a metal copper particle can be provided.

It is sectional drawing which shows each process in the suitable aspect of the manufacturing method of the electrically conductive film of this invention in order of a process. It is sectional drawing which shows the other embodiment of a precursor film | membrane.

Below, the suitable aspect of the manufacturing method of the electrically conductive film of this invention is explained in full detail.
First, the feature point compared with the prior art of this invention is explained in full detail.
As described above, the feature of the present invention is that a precursor film containing an alcohol having a predetermined boiling point is produced, subjected to a decompression process, the alcohol is vaporized, and a reduced pressure state is obtained so that an atmosphere of a predetermined alcohol concentration is obtained. The point which heat-sinters is mentioned, maintaining this. According to this method, the alcohol in the atmosphere contributes to the reduction of the copper oxide on the surface of the metallic copper during the thermal sintering, and the reduction of the surface that is easy to oxidize becomes possible. The ratio of the metallic copper in the inside increases, and a conductive film having excellent conductive properties can be produced. Moreover, in this method, since the alcohol that contributes to the reduction is supplied from the precursor film, it is not necessary to prepare a device for introducing an alcohol gas separately, which is an industrially excellent method.

The suitable aspect of the manufacturing method of the electrically conductive film of this invention is maintaining the atmosphere of predetermined alcohol concentration, after performing the process (precursor film formation process) of forming a precursor film | membrane on a base material, and a pressure reduction process. A step of performing thermal sintering (sintering step).
Hereinafter, the procedure of each process will be described in detail with reference to the drawings.

<Precursor film forming step>
The precursor film forming step is a step of forming a precursor film containing at least metal copper particles, a thermoplastic resin, and an alcohol having a boiling point of 100 ° C. to 230 ° C. on the substrate. As shown in FIG. 1A, a precursor film 12 is formed on the base material 10. By performing this step, a precursor film to be processed by a sintering step described later is formed.
Below, the material used at this process is explained in full detail first.

(Base material)
The base material used at this process supports a precursor film | membrane and an electrically conductive film, A well-known thing can be used. Examples of the material used for the substrate include resin, paper, glass, silicon-based semiconductor, compound semiconductor, metal oxide, metal nitride, wood, or a composite thereof. Especially, a resin base material has versatility and is preferable.
More specifically, low density polyethylene resin, high density polyethylene resin, ABS resin, acrylic resin, styrene resin, vinyl chloride resin, polyester resin (polyethylene terephthalate), polyacetal resin, polysulfone resin, polyetherimide resin, polyether ketone Resin base materials such as resin and cellulose derivatives; uncoated printing paper, fine coated printing paper, coated printing paper (art paper, coated paper), special printing paper, copy paper (PPC paper), unbleached wrapping paper ( Paper substrates such as double kraft paper for heavy bags, double kraft paper), bleached wrapping paper (bleached kraft paper, pure white roll paper), coated balls, chip balls, corrugated cardboard; soda glass, borosilicate glass, silica glass, Glass substrates such as quartz glass; silicon-based semiconductor substrates such as amorphous silicon and polysilicon; Compound semiconductor substrates such as dS, CdTe, GaAs; metal substrates such as copper plate, iron plate, aluminum plate; alumina, sapphire, zirconia, titania, yttrium oxide, indium oxide, ITO (indium tin oxide), IZO (indium zinc) Oxides), Nesa (tin oxide), ATO (antimony-doped tin oxide), fluorine-doped tin oxide, zinc oxide, AZO (aluminum-doped zinc oxide), gallium-doped zinc oxide, aluminum nitride substrate, silicon carbide, and other inorganic materials Base materials: Paper-resin composites such as paper-phenolic resin, paper-epoxy resin, paper-polyester resin, glass cloth-epoxy resin, glass cloth-polyimide resin, glass cloth-fluorine resin, etc. And the like, and the like. Among these, a glass epoxy base material, a polyester base material, a polyimide base material, a polyetherimide base material, a paper base material, and a glass base material are preferably used.

(Metal copper particles)
The metallic copper particles constitute metallic copper in the conductive film by a sintering process described later.
The average particle diameter of the metal copper particles is not particularly limited, but is preferably 1 nm to 10 μm, and more preferably 10 nm to 5 μm.
An average particle diameter of 1 nm or more is preferable because the activity on the particle surface does not become too high and the handleability is excellent. Moreover, if it is 10 micrometers or less, the composition used when manufacturing a precursor film | membrane can be used as an inkjet ink composition or a paste composition for screen printing, and pattern formations, such as wiring, can be performed by various printing methods. It becomes easy, and when making a composition into a conductor, since the electroconductivity of the electrically conductive film obtained is favorable, it is preferable.
In addition, the average particle diameter in this invention points out an average primary particle diameter. The average particle diameter is obtained by measuring the particle diameter (diameter) of at least 50 metal copper particles by observation with a transmission electron microscope (TEM) or scanning electron microscope (SEM) and arithmetically averaging them. In addition, when the shape of the metal copper particles is not a perfect circle in the observation drawing, the major axis is measured as the diameter.
As the metal copper particles, for example, Copper, powder particle size 3 microm 99.7% (manufactured by Aldrich) can be preferably used.

(Thermoplastic resin)
The thermoplastic resin serves as a binder in the precursor film, and is preferably thermally decomposed and removed in a sintering process described later.
The kind in particular of a thermoplastic resin is not restrict | limited, A well-known resin can be used. For example, vinyl resin, acrylic resin, styrene resin, polyolefin resin, polyamide resin, and the like can be given. These resins may be used alone or in combination of two or more.
Among them, the thermoplastic resin is preferably selected from the group consisting of polyvinylpyrrolidone, polyvinyl alcohol, polyethyleneimine, polyethylene oxide, polypropylene oxide, and polyacetal, and polyethyleneimine, polyethylene oxide, polypropylene oxide, or polyacetal. Is more preferable. If it is the said thermoplastic resin (polymer), the electroconductivity of the electrically conductive film obtained will be more excellent.

One preferred embodiment of the thermoplastic resin is a thermoplastic resin having a thermogravimetric reduction rate of 80% or more when the temperature is increased from 25 ° C. to 400 ° C. at a temperature increase rate of 10 ° C./min. If it is this thermoplastic resin, it will be easy to decompose | disassemble and vaporize in the sintering process mentioned later, and since a residue does not remain in a conductive film easily, as a result, the electroconductivity of a conductive film is more excellent.
In addition, the range of the preferable thermal weight reduction rate is 80% or more, and 90% or more is more preferable. The upper limit is not particularly limited, but is 95%.
The thermal weight loss rate is measured in nitrogen using EXSTAR TG / DTA6000 (manufactured by SII).

(alcohol)
Alcohol is contained in the precursor film and is vaporized in a sintering process described later to become a supply source of the alcohol atmosphere. The vaporized alcohol functions as a reducing agent that reduces the surface copper oxide of the metal copper particles during the thermal sintering.
The alcohol used has a boiling point of 100 to 230 ° C, preferably 150 to 230 ° C, and more preferably 170 to 220 ° C. When the temperature is lower than 100 ° C., vaporization is rapid and disappears when the pressure is reduced, and the reducing ability with respect to copper oxide is low, resulting in poor conductive properties of the obtained conductive film. If it exceeds 230 ° C., it is difficult to volatilize, it is difficult to adjust to an atmosphere of a predetermined alcohol concentration, and the conductive properties of the obtained conductive film are also inferior.
In the present specification, “boiling point” means a boiling point under a pressure of 1 atm.

If the kind of alcohol used is an alcohol which shows the said boiling point, the kind in particular will not be restrict | limited. Among these, primary alcohols are preferable in that the conductive properties of the conductive film obtained with high reducibility are more excellent.
Specific examples of the alcohol [boiling point] include, for example, butanol [117 ° C.], propylene glycol [188 ° C.], dipropylene glycol [230 ° C.], 1,2-butanediol [194 ° C.], 1,2-pentanediol. [210 ° C], 1,2-hexanediol [224 ° C], 1,2-heptanediol [227 ° C], 3-methyl-1,3-butanediol [203 ° C], 2-ethyl-2-methyl- 1,3-propanediol [226 ° C.], 2-methyl-1,3-propanediol [214 ° C.], 2-methyl-2-propyl-1,3-propanediol [230 ° C.], 2,2-dimethyl -1,3-propanediol [210 ° C.], 2-methylpentane-2,4-diol [197 ° C.], ethylene glycol [197 ° C.], 1-octanol 194 ° C], cyclohexanol [161 ° C], 1-nonanol [boiling point 213.5 ° C], isodecyl alcohol [boiling point 220 ° C], 2-decanol [boiling point 211 ° C], 2,5-hexanediol [boiling point 216 ° C] ], 3-methyl-1,3-butanediol [boiling point 203 [deg.] C.], 1,2-pentanediol [boiling point 206 [deg.] C.], 1,2-hexanediol [boiling point 223 [deg.] C.], ethylene glycol monohexyl ether [boiling point 208] ° C], ethylene glycol monooctyl ether [boiling point 229 ° C.], dipropylene glycol monopropyl ether [boiling point 212 ° C.], dipropylene glycol monobutyl ether [boiling point 229 ° C.] and the like.

(Other optional materials)
The precursor film contains the metal copper particles, the thermoplastic resin, and the alcohol, but may contain other components.
For example, copper oxide particles may be included. By including the copper oxide particles, the conductive properties of the conductive film are further improved. In addition, the copper oxide particles are reduced during the sintering step described later, and are converted into metallic copper contained in the conductive film.
The “copper oxide” in the present invention is a compound that does not substantially contain copper that has not been oxidized. Specifically, in crystal analysis by X-ray diffraction, a peak derived from copper oxide is detected, and It refers to a compound in which no metal-derived peak is detected. Although not containing copper substantially, it means that content of copper is 1 mass% or less with respect to copper oxide particles.

As the copper oxide, copper (I) oxide or copper (II) oxide is preferable, and copper (II) oxide is more preferable because it is available at low cost and has high stability.
The average particle size of the copper oxide particles is not particularly limited, but is preferably 500 nm or less, and more preferably 100 nm or less. Although a minimum in particular is not restrict | limited, 1 nm or more is preferable and 50 nm or more is more preferable.
An average particle diameter of 1 nm or more is preferable because the activity on the particle surface does not become too high and the handleability is excellent. Moreover, if it is 500 nm or less, it becomes easy to form a pattern such as wiring by a printing method using a composition containing copper oxide particles as an ink-jet ink composition, and reduction to metallic copper is sufficient and obtained. It is preferable because the conductive film has good conductivity.
In addition, the average particle diameter in this invention points out an average primary particle diameter. The average particle diameter is determined by measuring the particle diameter (diameter) of at least 50 or more copper oxide particles by observation with a transmission electron microscope (TEM) or scanning electron microscope (SEM) and arithmetically averaging them. In the observation diagram, when the shape of the copper oxide particles is not a perfect circle, the major axis is measured as the diameter.
As the copper oxide particles, for example, CuO nanoparticles made by Kanto Chemical Co., CuO nanoparticles made by Sigma-Aldrich, etc. can be preferably used.

  Note that the precursor film may contain a solvent other than alcohol as long as the effects of the present invention are not impaired.

(Precursor film)
The precursor film contains the metal copper particles, the thermoplastic resin, and the alcohol.
Although content in particular of a metallic copper particle in a precursor film | membrane is not restrict | limited, 5-60 mass% is preferable with respect to precursor film | membrane total mass, and 9.5-50 mass% is more preferable. If it is the said range, the electroconductivity of the electrically conductive film obtained will be more excellent.
In addition, the content of the thermoplastic resin in the precursor film is not particularly limited, but is preferably 0.05 to 10% by mass, and more preferably 0.5 to 5% by mass with respect to the total mass of the precursor film. If it is the said range, the electroconductivity of the electrically conductive film obtained will be more excellent.
Moreover, content of alcohol in a precursor film | membrane is not restrict | limited in particular, However, 50-90 mass% is preferable with respect to precursor film | membrane total mass, and 70-90 mass% is more preferable. If it is the said range, the electroconductivity of the electrically conductive film obtained will be more excellent.
When the precursor film contains copper oxide particles, the ratio (A / B) of the mass A of the metal copper particles to the mass B of the copper oxide particles in the precursor film is preferably 4 or more, more preferably 8 or more. preferable. If it is the said range, the electroconductivity of the electrically conductive film obtained will be more excellent.

Although the thickness of a precursor film | membrane is not restrict | limited in particular, 1-50 micrometers is preferable and 10-30 micrometers is more preferable at the point which the electroconductivity of the electrically conductive film obtained is more excellent.
In addition, the precursor film | membrane 12 may be arrange | positioned over the whole surface of the base material 10, as shown to FIG. 1 (A), and is arrange | positioned in pattern form on the base material 10, as shown in FIG. May be.

(Precursor film production method)
The manufacturing method of a precursor film | membrane is not specifically limited, A well-known method is employ | adopted.
Among them, at least the metal copper particles, the thermoplastic resin, and the alcohol are contained because the thickness of the precursor film can be easily adjusted and the alcohol concentration in the precursor film can be easily adjusted. A method (coating method) in which the precursor film-forming composition is applied onto a substrate to form a precursor film is preferable. In addition, you may implement a drying process after application | coating as needed.
As another method, a method of producing the above precursor film on a temporary support and transferring it onto a substrate can also be mentioned.
Hereinafter, the coating method will be described in detail.

The definitions of the components (metal copper particles, thermoplastic resin, alcohol, optional components, etc.) contained in the precursor film forming composition are as described above.
The content of alcohol in the precursor film-forming composition is not particularly limited, but is preferably 50 to 90% by mass and more preferably 70 to 90% by mass in terms of excellent coatability.
The content of the metallic copper particles in the precursor film-forming composition is not particularly limited, but is preferably 80 to 99% by mass with respect to the total solid content in terms of excellent coating properties, and is preferably 85 to 85%. It is more preferable that it is 99 mass%.
The content of the thermoplastic resin in the precursor film forming composition is not particularly limited, but is preferably 0.05 to 20% by mass with respect to the total solid content in terms of excellent coating properties. More preferably, it is 1-10 mass%.
The composition for forming a precursor film may contain copper oxide particles. When copper oxide particles are contained, the ratio of the mass A of the metal copper particles to the mass B of the copper oxide particles (A / B) is preferably in the above-mentioned range.
The total solid content means a component that forms a precursor film excluding a solvent such as alcohol.

  The method for preparing the precursor film-forming composition is not particularly limited, and a known method can be adopted. For example, after adding metallic copper particles and thermoplastic resin to alcohol, the components are dispersed by known means such as ultrasonic method (for example, treatment with ultrasonic homogenizer), mixer method, three-roll method, ball mill method, etc. By making it, a composition can be obtained.

The method for applying the precursor film-forming composition onto the substrate is not particularly limited, and a known method 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 ink jet method can be used.
The shape of application is not particularly limited, and may be a surface covering the entire surface of the substrate or a pattern (for example, a wiring or a dot).
The coating amount of the precursor film-forming composition on the substrate may be appropriately adjusted according to the desired film thickness of the conductive film, but usually the coating film thickness is preferably 0.01 to 5000 μm. 0.1 to 1000 μm is more preferable.

In this step, if necessary, the precursor film-forming composition may be applied to the substrate and then dried to remove excess alcohol. By removing the excess alcohol, it is possible to suppress the generation of minute cracks and voids due to the vaporization and expansion of excess alcohol in the sintering process described later. From the viewpoint of adhesiveness.
As a method for the drying treatment, a hot air dryer or the like can be used, and the temperature is preferably 40 to 200 ° C., more preferably 50 to 150 ° C. More preferably, the heat treatment is performed at 70 ° C. to 120 ° C.
In addition, the conditions which suppress the oxidation of a metal copper particle are preferable, for example, it is more preferable in inert gas atmosphere, such as nitrogen and argon, and it is still more preferable to dry in reducing gas atmosphere, such as hydrogen.

<Sintering process>
A sintering process performs a pressure reduction process, heat-sinters with respect to a precursor film | membrane, maintaining the pressure-reduced state used as the alcohol atmosphere whose alcohol concentration is 5 volume% or more, and forms the electrically conductive film which has metallic copper. It is a process of forming. In this step, first, a decompression process is performed to create an alcohol atmosphere having a predetermined alcohol concentration, and a thermal sintering process is performed without introducing gas from the outside while maintaining the state of the alcohol atmosphere. By carrying out this step, a conductive film 14 is formed on the substrate 10 as shown in FIG.
Hereinafter, the procedure of this step will be described in detail.

The method for the decompression treatment is not particularly limited, and a known method is employed. For example, the method of putting a base material with a precursor film in a reduced pressure processing apparatus and carrying out a reduced pressure process is mentioned.
The conditions for the decompression treatment are not particularly selected as long as the environment in which the substrate with the precursor film is allowed to stand (for example, the environment in the decompression treatment apparatus) is an alcohol atmosphere having a predetermined concentration. Optimum conditions are appropriately selected depending on the boiling point of.
For example, when the boiling point of the alcohol is 100 ° C. or higher and lower than 150 ° C., the degree of reduced pressure in the reduced pressure treatment is preferably 50 to 100 mmHg, and more preferably 70 to 100 mmHg. If the degree of vacuum is within the above range, the alcohol concentration is easy to adjust.
Moreover, when the boiling point of alcohol is 150 degreeC or more and less than 200 degreeC, 10-50 mmHg is preferable as a pressure reduction degree of a pressure reduction process, and 20-50 mmHg is more preferable. If the degree of vacuum is within the above range, the alcohol concentration is easy to adjust.
Moreover, when the boiling point of alcohol is 200 degreeC or more and 230 degrees C or less, as a pressure reduction degree of a pressure reduction process, 1-10 mmHg is preferable and 5-10 mmHg is more preferable. If the degree of vacuum is within the above range, the alcohol concentration is easy to adjust.

  The time for the decompression treatment is not particularly limited as long as a predetermined alcohol concentration is achieved, but 5 minutes to 1 hour is preferable and 5 to 10 minutes is more preferable from the viewpoint of productivity.

By performing the decompression process, the alcohol in the precursor film is vaporized and an alcohol atmosphere is formed. The alcohol atmosphere means an atmosphere containing alcohol, and may contain other gases. Examples of other gas components include argon, nitrogen, hydrogen, oxygen, and the like.
The alcohol concentration in the alcohol atmosphere is 5% by volume or more, and above all, 6% by volume or more is preferable and 7% by volume or more is more preferable because the conductive properties of the obtained conductive film are more excellent. The upper limit is not particularly limited, but is often 50% by volume or less, preferably 40% by volume or less, from the relationship between the boiling point of the alcohol and the degree of vacuum.
When the alcohol concentration is less than 5% by volume, the reduction of the metal surface does not proceed sufficiently and the conductive properties of the resulting conductive film are inferior.
As a method for measuring the alcohol concentration in an alcohol atmosphere, a predetermined amount of gas under a reduced pressure environment is sampled, nitrogen is injected to return to normal pressure, and the gas is subjected to component analysis by gas chromatography. More specifically, for example, the base material with the precursor film is allowed to stand in a vacuum processing apparatus (for example, a glow box) having a predetermined volume space inside, and the vacuum processing is performed under predetermined conditions. After that, the decompression process is stopped, nitrogen is injected to return the inside of the apparatus to normal pressure, the gas in the apparatus is collected, the gas is subjected to component analysis by gas chromatography, and the volume ratio of alcohol is calculated. . The volume ratio of alcohol is calculated from the ratio (B / A) of the volume A inside the decompression apparatus and the calculated volume B of alcohol.

In this step, the heat-sintering process is performed after the decompression process is performed and the alcohol atmosphere having the alcohol concentration in the above range is achieved. Note that the decompression process is controlled so that the alcohol concentration is within the above range even during the thermal sintering process.
Usually, when the decompression process is being performed, it is preferable that no other gas is introduced from the outside.

By carrying out the thermal sintering treatment, the metallic copper particles are fused together to form grains, and the grains are bonded and fused together to form a thin film. At that time, the copper oxide film on the surface of the metal copper particles is reduced by the alcohol floating as a gas, and as a result, a conductive film with a small content of copper oxide is formed.
In addition, when a copper oxide particle is contained in a precursor film | membrane, a copper oxide particle is reduce | restored to a metal copper particle by this process, and comprises a part of electrically conductive film.

The optimum conditions for the thermal sintering treatment are appropriately selected depending on the type of thermoplastic resin and alcohol used. Among them, the heating temperature is preferably 50 to 500 ° C., more preferably 100 to 500 ° C., and the heating time is 1 to 60 minutes in that a conductive film that is superior in conductivity can be formed in a short time. Preferably, 1 to 20 minutes is more preferable.
The heating means is not particularly limited, and known heating means such as an oven and a hot plate can be used.
In the present invention, the conductive film can be formed by heat treatment at a relatively low temperature, and therefore, the process cost is low.

(Conductive film)
By carrying out the above steps, a conductive film (metal copper film) containing metal copper is obtained.
The film thickness of the conductive film is not particularly limited, and an optimum film thickness is appropriately adjusted according to the intended use. Especially, from the point of a printed wiring board use, 0.01-1000 micrometers is preferable and 0.1-100 micrometers is more preferable.
The film thickness is a value (average value) obtained by measuring three or more thicknesses at arbitrary points on the conductive film and arithmetically averaging the values.
The volume resistance value of the conductive film is preferably 5.0 × 10 ⁻³ Ωcm or less, more preferably 1 × 10 ⁻⁴ Ωcm or less, and even more preferably 5 × 10 ⁻⁴ Ωcm or less from the viewpoint of conductive characteristics.
The volume resistance value can be calculated by multiplying the obtained surface resistance value by the film thickness after measuring the surface resistance value of the conductive film by the four-probe method.

The conductive film may be provided on the entire surface of the base material or in a pattern. The patterned conductive film is useful as a conductor wiring (wiring) such as a printed wiring board.
As a method for obtaining a patterned conductive film, the above precursor film-forming composition is applied to a substrate in a pattern and subjected to thermal sintering treatment, or a conductive film provided on the entire surface of the substrate is patterned. And a method of etching into a shape.
The etching method is not particularly limited, and a known subtractive method, semi-additive method, or the like can be employed.

When a patterned conductive film is configured as a multilayer wiring board, an insulating layer (insulating resin layer, interlayer insulating film, solder resist) is further laminated on the surface of the patterned conductive film, and further wiring (metal) is formed on the surface. Pattern) may be formed.
The base material (base material with a conductive film) having the conductive film obtained above can be used for various applications. For example, a printed wiring board, TFT, FPC, RFID, etc. are mentioned.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.

<Example 1>
The following composition for forming a conductive film was applied (spin coated) on a glass substrate to produce a precursor film on the glass substrate. The substrate with the precursor film was placed in a glow box in a nitrogen atmosphere, and the inside of the glow box was evacuated to 10 mmHg. After reducing the pressure for 10 minutes, it was confirmed that the alcohol concentration in the glow box was 7% by volume by the alcohol concentration measurement method described later. After the confirmation, while maintaining the alcohol concentration, the substrate with the precursor film was subjected to a heat sintering process at 400 ° C. for 20 minutes to produce a conductive film (copper thin film).

(Composition for forming conductive film)
・ Copper particles (Mitsui Metals) (average particle size: 1.1 μm) 1 g
-Copper oxide particles (manufactured by CIK Nanotech) (average particle size: 50 nm) 0.1 g
・ Polyethylene glycol (molecular weight 2000, Wako Pure Chemical Industries) 0.1g
・ Ethylene glycol (boiling point 195 ° C) 5g

(Alcohol concentration measurement method)
0.2 L of gas in a glow box under a reduced pressure environment was sampled. After injecting nitrogen into the gas to return to normal pressure, ethylene glycol was quantified using gas chromatography (GC-2014, manufactured by Shimadzu Corporation).
As a sampling method, an openable / closable container having a volume of 0.2 L was placed in the glove box in an open state, and after a predetermined pressure reduction condition, the container was sealed and taken out from the glove box. Then, nitrogen was put into the container, the pressure was returned to normal pressure, and measurement was performed by gas chromatography.
In Example 1, the amount of ethylene glycol was 1.7 × 10 ⁻¹ mL. Since this corresponds to 0.012 L under 10 mmHg, the alcohol concentration is calculated to be 7% by volume.

<Example 2>
A conductive film was produced according to the same procedure as in Example 1 except that butanol (boiling point: 117 ° C.) was used instead of ethylene glycol.

<Example 3>
A conductive film was produced according to the same procedure as in Example 1 except that the content of the copper oxide particles was changed from 0.1 g to 0.2 g.

<Example 4>
A conductive film was produced according to the same procedure as in Example 1 except that the content of the copper oxide particles was changed from 0.1 g to 0.3 g.

<Example 5>
A conductive film was produced according to the same procedure as in Example 1 except that polyvinylpyrrolidone K60 (molecular weight 220,000, manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of polyethylene glycol.

<Example 6>
A conductive film was produced according to the same procedure as in Example 1 except that the degree of vacuum was changed from 10 mmHg to 50 mmHg.

<Example 7>
A conductive film was produced according to the same procedure as in Example 1 except that the degree of vacuum was changed from 10 mmHg to 1 mmHg.

<Example 8>
A conductive film was produced according to the same procedure as in Example 1 except that the degree of vacuum was changed from 10 mmHg to 100 mmHg.

<Example 9>
A conductive film was produced according to the same procedure as in Example 1 except that the amount of ethylene glycol used was changed from 5 g to 3 g.

<Comparative Example 1>
A conductive film was produced according to the same procedure as in Example 1 except that the thermal sintering treatment was carried out without carrying out the above-mentioned decompression treatment.

<Comparative example 2>
A conductive film was produced according to the same procedure as in Example 1 except that cyclohexanone (boiling point 156 ° C.) was used instead of ethylene glycol.

<Comparative Example 3>
A conductive film was produced according to the same procedure as in Example 2 except that the thermal sintering treatment was carried out without carrying out the above-described decompression treatment.

<Comparative example 4>
The same procedure as in Example 1 except that a 3: 1 mixture of epoxy resin (thermosetting resin, Epicoat 802 manufactured by Mitsubishi Chemical) and novolak resin (curing agent: PHENOLITE TD-2131) was used instead of ethylene glycol. In accordance with the above, a conductive film was manufactured.

<Comparative Example 5>
A conductive film was produced according to the same procedure as in Example 1 except that the amount of ethylene glycol used was changed from 5 g to 2 g and the temperature of the thermal sintering treatment was changed from 400 ° C. to 500 ° C.

(Conductivity evaluation)
The volume resistivity was measured with respect to the obtained electrically conductive film using the four-probe method resistivity meter.
In addition, the volume resistivity in Table 1 is a value obtained by measuring the volume resistivity at any four locations of the conductive film and arithmetically averaging them. The results are summarized in Table 1.

  In Table 1, “PEO” means polyethylene glycol and “PVP” means polyvinylpyrrolidone. PEO has a thermal weight reduction rate of 80% or more when the temperature is raised from 25 ° C. to 400 ° C. at a rate of temperature increase of 10 ° C./min, but PVP is less than 80%.

As shown in Table 1 above, the conductive film obtained from the production method of the present invention showed excellent conductivity.
In particular, as can be seen from the comparison between Examples 1 and 2, when the boiling point of the alcohol is 150 to 230 ° C., it was confirmed that the conductive properties of the conductive film were more excellent.
Further, as can be seen from the comparison between Examples 3 and 4, when the ratio (A / B) of the mass A of the metal copper particles to the mass B of the copper oxide particles in the precursor film is 4 or more, the conductive film It was confirmed that the conductive properties of the were superior.
Further, as can be seen from a comparison between Examples 1 and 5, it was confirmed that the conductive properties of the conductive film were more excellent when a thermoplastic resin having a thermal weight reduction of 80% or more was used.
On the other hand, in Comparative Examples 1 and 3 in which no decompression treatment was performed, in Comparative Example 2 in which no alcohol was used, and in Comparative Example 4 in which a thermosetting resin was used, the conductive characteristics of the conductive film were compared with those of the Examples. It was inferior. Furthermore, also in the comparative example 5 whose alcohol concentration is below a predetermined value, the conductive properties of the conductive film were inferior.

10 Substrate 12 Precursor film 14 Conductive film

Claims (8)

Forming a precursor film containing at least metal copper particles, a thermoplastic resin, and an alcohol having a boiling point of 100 ° C. to 230 ° C. on a substrate;
A pressure reduction treatment is performed, and while maintaining a reduced pressure state in which the alcohol concentration is 5% by volume or more, a thermal sintering treatment is performed on the precursor film to form a conductive film containing metallic copper. A process for producing a conductive film.   The manufacturing method of the electrically conductive film of Claim 1 with which a copper oxide particle is further contained in the said precursor film | membrane.   3. The thermoplastic resin according to claim 1, wherein the thermoplastic resin is a thermoplastic resin having a thermal weight reduction rate of 80% or more when the temperature is increased from 25 ° C. to 400 ° C. at a temperature increase rate of 10 ° C./min. Manufacturing method of electrically conductive film.   The method for producing a conductive film according to claim 1, wherein the thermoplastic resin is selected from the group consisting of polyethyleneimine, polyethylene oxide, polypropylene oxide, and polyacetal.   The manufacturing method of the electrically conductive film of any one of Claims 1-4 whose boiling point of the said alcohol is 150-230 degreeC.   The electrically conductive film according to any one of claims 2 to 5, wherein a ratio (A / B) of a mass A of the metal copper particles to a mass B of the copper oxide particles in the precursor film is 4 or more. Manufacturing method.   The manufacturing method of the electrically conductive film of any one of Claims 1-5 by which the said pressure reduction process is implemented at 1-100 mmHg.   The manufacturing method of the electrically conductive film of any one of Claims 1-6 by which the said pressure reduction process is implemented at 1-50 mmHg.

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