JP7623896B2 - Metal wiring manufacturing apparatus and method for manufacturing metal wiring - Google Patents

Description

The present invention relates to a metal wiring manufacturing apparatus and a metal wiring manufacturing method.

A circuit board has a structure in which conductive metal wiring is applied onto a substrate. The manufacturing method for a circuit board is generally as follows. First, a photoresist is applied onto a substrate to which metal foil has been attached. Next, the photoresist is exposed and developed to obtain a negative shape of the desired circuit pattern. Next, the metal foil not covered by the photoresist is removed by chemical etching to form a pattern. This allows a high-performance conductive substrate to be manufactured.

However, conventional methods have drawbacks, such as the large number of steps, the complexity, and the need for photoresist materials.

In response to this, direct metal wiring printing technology has been attracting attention, in which a desired metal wiring pattern is directly printed on a substrate using a dispersion (hereinafter also referred to as a "paste material") in which particles selected from the group consisting of metal particles and metal oxide particles are dispersed. This technology has extremely high productivity, as it requires a small number of steps and does not require the use of photoresist materials.

One example of a direct printing metal wiring technology is a method in which a paste material is applied to the entire surface of a substrate, and the paste material is selectively thermally fired by irradiating it with laser light in a pattern to obtain a desired metal wiring pattern (see, for example, Patent Documents 1 and 2).

Patent document 2 describes that when drawing is performed by irradiating GaAlAs laser light with a wavelength of 830 nm, the beam diameter on the copper oxide thin film is 5 μm, and the copper oxide is reduced in the area irradiated with the laser light due to local heating, forming a reduced metal area made of reduced copper with a width of approximately 5 μm.

International Publication No. 2010/024385 Japanese Patent Application Publication No. 5-37126

Generally, for example, a galvanometer scanner is used for scanning the laser light, which irradiates a single point of laser light and moves it in a single stroke to irradiate an area of the desired size and shape on the coating surface containing metal particles and/or metal oxide particles.

In circuit boards, it is required that the resistance value of the metal wiring is uniform (i.e., there is little variation from one location to another). When a laser beam is scanned over a coating film, any variation in the heating conditions of the laser beam will cause variation in the resistance value of the metal wiring. In particular, when the shape of the metal wiring is not a simple shape (such as a line or a rectangle), variation in the resistance value is likely to occur.

In addition, since paste materials usually contain organic components such as solvents and dispersants, heating with laser light can cause the paste material to emit smoke. If this smoke gets into the irradiation path of the laser light and blocks the laser light, it can cause variations in the heating conditions of the coating film and lead to variations in the resistance value of the metal wiring.

Furthermore, the width of the metal wiring formed by drawing with laser light irradiation is narrow and approximately equal to the beam diameter, so when forming larger metal wiring, it is necessary to repeatedly scan the laser light over the coating film containing metal particles and/or metal oxide particles to widen the area irradiated with the laser light. In this case, if the laser light irradiation area is wide, the amount of smoke generated also increases, causing variation in the resistance value of the metal wiring.

The present invention was made in consideration of these points, and aims to provide a metal wiring manufacturing device and a metal wiring manufacturing method that can easily obtain metal wiring with a uniform resistance value.

That is, the present invention includes the following aspects.
[1] A metal wiring manufacturing apparatus for manufacturing a metal wiring by irradiating a laser beam onto a coating film of a structure having the coating film containing metal particles and/or metal oxide particles, comprising:
a laser light irradiation unit that irradiates the coating film with laser light;
a gas flow generating unit that generates a gas flow on the coating film;
A metal wiring manufacturing apparatus comprising:
[2] The metal wiring manufacturing apparatus according to the above aspect 1, wherein the gas flow generating unit is a blower and/or a gas suction device.
[3] Further comprising a box for covering the structure,
The blower is disposed inside or outside the box,
3. The metal wiring manufacturing apparatus according to claim 2, further comprising a pipe for introducing gas from the blower into the box when the blower is disposed outside the box.
[4] The metal wiring manufacturing apparatus according to any one of the above aspects 1 to 3, wherein the gas is at least one selected from the group consisting of air, nitrogen, helium, and argon.
[5] The metal wiring manufacturing apparatus according to any one of the above aspects 1 to 4, wherein the laser light has a central wavelength in the range of 350 nm or more and 600 nm or less.
[6] The laser light irradiation unit,
a laser oscillator that emits laser light;
a galvano scanner that irradiates the coating film with an oscillated laser beam;
The metal wiring manufacturing apparatus according to any one of the above aspects 1 to 5,
[7] A laser light irradiation step of irradiating a coating film of a structure having a coating film containing metal particles and/or metal oxide particles with a laser light to form a metal wiring,
The method for producing metal wiring, wherein in the laser light irradiation step, a gas flow is generated on the coating film simultaneously with the irradiation of the laser light.
[8] The method for producing a metal wiring according to the above-mentioned aspect 7, further comprising generating a gas flow on the coating film by a blower and/or a gas suction device.
[9] The method for producing a metal wiring according to aspect 7 or 8, wherein the structure is covered with a box, and the coating film is irradiated with laser light while a gas is flowing inside the box.
[10] The method for producing a metal wiring according to any one of the above aspects 7 to 9, wherein the coating film is irradiated with laser light while flowing a gas in a direction opposite to a moving direction of the laser light on the coating film.
[11] The method for producing a metal wiring according to any one of the above aspects 7 to 10, wherein the irradiation output of the laser light is 100 mW or more and 1500 mW or less.
[12] Repeatedly scanning the laser light on the coating film while overlapping the laser light in a line width direction of the scanning line of the laser light,
12. The method for producing a metal wiring according to any one of the above aspects 7 to 11, wherein the overlap is 5% or more and 99.5% or less of the line width.
[13] The method for producing a metal wiring according to any one of aspects 7 to 12, wherein in the laser light irradiation step, laser light irradiation for 10 seconds or more and 60 seconds or less and no laser light irradiation for 1 second or more and 10 seconds or less are alternately repeated.
[14] The method for producing a metal wiring according to any one of Aspects 7 to 13, wherein in the laser light irradiation step, a formation rate per area of the continuous metal wiring formed by the laser light is 0.01 sec/mm2 or ^more and 500 sec/mm2 or ^less .
[15] The method for producing metal wiring according to any one of aspects 7 to 14, wherein in the laser light irradiation step, a time period of 0.01 seconds or more and 100 seconds or less during which the laser light is not irradiated onto the coating film is provided between the formation of a certain continuous metal wiring pattern and the formation of another continuous metal wiring pattern.
[16] The method for producing a metal wiring according to any one of the above aspects 7 to 15, wherein the gas is at least one selected from the group consisting of air, nitrogen, helium, and argon.

According to one aspect of the present invention, it is possible to provide a metal wiring manufacturing apparatus and a metal wiring manufacturing method that can easily obtain metal wiring with a uniform resistance value.

1 is a schematic diagram of a metal wiring manufacturing apparatus according to one embodiment of the present invention. 1 is a schematic diagram of a metal wiring manufacturing apparatus according to one embodiment of the present invention. 1 is a schematic diagram of a metal wiring manufacturing apparatus according to one embodiment of the present invention. 1 is a schematic diagram of a metal wiring manufacturing apparatus according to one embodiment of the present invention. 1A to 1C are schematic diagrams illustrating overlapping irradiation of laser light in a method for manufacturing a metal wiring according to one embodiment of the present invention. 1A to 1C are schematic diagrams illustrating a continuous metal wiring pattern formed in a method for producing metal wiring according to one embodiment of the present invention.

One embodiment of the present invention (hereinafter abbreviated as "this embodiment") will be described in detail below.

The inventors focused on the problem of smoke generated by laser irradiation blocking the optical path of the laser light, resulting in uneven irradiation of the laser light onto the coating film, and discovered that this problem can be solved by using a gas flow to move the smoke out of the laser optical path.

<Metal wiring manufacturing equipment>
One aspect of the present invention provides a metal wiring production apparatus for producing metal wiring by irradiating a coating film of a structure having the coating film containing metal particles and/or metal oxide particles with laser light. 1A to 1C and 2 are schematic diagrams of a metal wiring manufacturing apparatus according to one embodiment of the present invention.

Referring to FIG. 1A, the metal wiring manufacturing apparatus 10 includes a laser light irradiation unit 101 that irradiates laser light L onto the coating film 12 of the structure 1 including a substrate 11 and a coating film 12 containing metal particles and/or metal oxide particles arranged on the substrate 11, and a blower 102a as a gas flow generating unit that generates a flow of gas G on the coating film 12. By generating a flow of gas G on the coating film 12 by the blower 102a, the smoke generated by the laser light irradiation unit 101 can be made to flow outside the laser light path. This allows the laser light to be irradiated onto the coating film under uniform conditions without being blocked by the smoke.

Referring to FIG. 1B, in the metal wiring manufacturing apparatus 20, a gas suction device 102b is used as the gas flow generating unit instead of the blower 102a shown in FIG. 1A, so that a flow of gas G is generated on the coating film, and the smoke generated by the laser light irradiation can be made to flow outside the laser light path.

Furthermore, referring to FIG. 1C, in the metal wiring manufacturing apparatus 30, a blower 102a and a gas suction device 102b are combined to generate a flow of gas G on the coating film, and the smoke generated by the laser light irradiation can be made to flow outside the laser light path.

[Laser light irradiation unit]
The laser light irradiation unit 101 includes a laser light oscillator. When using laser light, a coating film containing metal particles and/or metal oxide particles formed on a substrate can be heated to a high temperature in a short time and baked by irradiating the coating film with high-intensity light for a short time. Laser light can reduce the baking time, so that it causes less damage to the substrate, and can be applied even when the substrate is, for example, a resin film substrate with low heat resistance. In addition, when using laser light, there is a large degree of freedom in wavelength selection, and the wavelength can be selected taking into consideration the light absorption wavelength of the coating film or the light absorption wavelength of the substrate. Furthermore, with laser light, exposure by beam scanning is possible, so that it is easy to adjust the exposure range, and it is possible to selectively irradiate (draw) light to the target area of the coating film without using a mask.

Laser light sources can include YAG (yttrium aluminum garnet), YVO (yttrium vanadate), Yb (ytterbium), semiconductors (GaAs, GaAlAs, GaInAs), and carbon dioxide gas. As for the laser light, not only the fundamental wave but also higher harmonics can be extracted and used as necessary.

The laser light irradiated to the coating preferably has a central wavelength in the range of 350 nm to 600 nm. For example, when cuprous oxide (described below) is used as the metal oxide, the above wavelength is absorbed by cuprous oxide, so that reduction of cuprous oxide occurs uniformly, and low-resistance metal wiring can be formed.

The laser light irradiation unit preferably has a galvanometer scanner. By scanning the laser light through the galvanometer scanner, metal wiring of any shape can be easily formed.

[Gas flow generating section]
The gas flow generating unit is not particularly limited as long as it can generate a gas flow on the coating film. Examples of the gas flow generating unit include a blower 102a and a gas suction device 102b. In one embodiment, the gas flow generating unit is a blower and/or a gas suction device.

(Blower)
The type of the blower 102a is not particularly limited as long as it can blow gas onto the coating film. The blower may be a type that blows air by being driven by a motor, may be a type that is configured to blow gas directly from a high-pressure gas cylinder through a pipe, or may be a device that blows gas compressed by a compressor or the like.

In addition, the gas flow does not need to occur at the same flow rate over the entire coating film, but only needs to occur at the point on the coating film where the laser light is irradiated. From the viewpoint of obtaining the effect of the present invention, it is preferable that the gas flow occurs in an area with a radius of 10 mm from the point on the coating film where the laser light is irradiated. In this case, it is not necessary for the gas flow to occur at the same level over the entire area, but it is preferable that the gas flow occurs over the area at a flow rate of 0.01 m/s or more, or 0.05 m/s or more, or 0.1 m/s or more, and/or 20 m/s or less, or 10 m/s or less, or 1.0 m/s or less, or 0.8 m/s or less, or 0.6 m/s or less. When the flow rate is 0.01 m/s or more, the effect of removing smoke is good, and when it is 20 m/s or less, the gas blown in the device is less likely to cause turbulence, so that the intrusion of smoke into the optical path of the laser light can be prevented. In this disclosure, the flow velocity of the gas on the coating film is determined by measuring the flow velocity of the gas on the coating film by placing the measuring part of the anemometer at a position 10 mm away from the laser light irradiation point on the coating film surface in the perpendicular direction to the coating film.

The metal wiring manufacturing apparatus of this embodiment is used to form metal wiring by irradiating a coating film containing metal particles and/or metal oxide particles with laser light. Since the coating film contains organic components such as solvents and dispersants, smoke may be generated from the coating film when heated by the laser light. If this smoke enters the irradiation optical path of the laser light and blocks the laser light, the heating conditions of the coating film by the laser light will vary, causing variation in the resistance value of the formed metal wiring. By providing the metal wiring manufacturing apparatus with a blower and/or a gas suction device, gas can be made to flow onto the coating film when irradiating the laser light, and the smoke can be removed from the optical path of the laser light.

The type of gas supplied by the blower onto the coating film is not particularly limited as long as it can remove smoke generated from the coating film from the optical path of the laser light, but from the viewpoint of preventing deterioration of the coating film, it is preferable that the gas be at least one selected from the group consisting of air, nitrogen, helium, and argon.

(Gas suction device)
The metal wiring manufacturing apparatus preferably includes a gas suction device 102b (FIGS. 1B and 1C) for suctioning gas and/or decomposition gas. The gas suction device 102b stabilizes the direction of gas flow by suctioning gas G (i.e., gas and/or decomposition gas on the coating film), and can better prevent smoke from entering the laser light irradiation path. The decomposition gas is decomposition gas (smoke) generated by decomposition of the coating film when the coating film is irradiated with laser light. The gas suction device is not particularly limited, but may be an exhaust fan, a pump such as a diaphragm pump, or an intake device using a compressor.

[stage]
1A to 1C and 2, the metal wiring manufacturing apparatus 10, 20, 30, 40 preferably has a stage 103 on which the structure 1 having the coating film 12 containing metal particles and/or metal oxide particles is placed when the structure 1 is irradiated with laser light. The shape, material, and structure of the stage are not particularly limited as long as it can hold the structure. The stage may be flat and plate-like, or may have a three-dimensional shape. A stage that is configured to be drivable is preferable because it can irradiate laser light to any position. The stage may also have a form that directly holds the structure, like a robot arm.

[box]
2, from the viewpoint of efficiently flowing gas onto the coating film, the metal wiring manufacturing apparatus 40 preferably further includes a box 104 that covers the structure 1 having the coating film 12. A blower 102a may be disposed inside the box 104, or as shown in FIG. 2, a gas flow G may be generated above the coating film 12 in the box 104 by introducing gas into the box 104 through a pipe from the blower 102a disposed outside the box 104. By using the box 104, the gas flow can be limited within the box and the gas can be more efficiently flowed above the coating film, so that a metal wiring having a more uniform resistance value can be obtained.

The shape and material of the box are not particularly limited, and the box may be large enough to completely accommodate the structure. As shown in FIG. 2, the box 104 may have a window W for allowing the laser light to enter the coating film inside the box from outside the box. The window W is preferably made of a material that allows the laser light to pass through, such as glass.

In one embodiment, the laser light is moved in a second direction different from the first direction (e.g., perpendicular to the first direction) while scanning the coating surface in a first direction. The direction of movement of the laser light is preferably opposite to the direction of smoke flow (i.e., the direction of gas flow by the blower). This makes it possible to better suppress the effect of smoke on the laser light irradiation conditions. The aforementioned galvano scanner is also advantageous in that it can easily control the direction of movement of the laser light.

<Structure>
The structure has a coating film containing metal particles and/or metal oxide particles. In one embodiment, the structure has a substrate and the coating film disposed on the substrate. The substrate is preferably made of an insulating material in order to ensure electrical insulation between metal wiring patterns formed by laser light. However, it is not necessary that the entire substrate is made of an insulating material. It is sufficient that the portion constituting the surface on which the metal wiring is disposed is made of an insulating material.

[Substrate]
The material of the substrate is preferably a material having a heat resistance of 60° C. or higher in order to prevent the substrate from being burned by the laser light and generating smoke when irradiated with the laser light. The substrate does not need to be made of a single material, and for example, glass fiber may be added to the resin in order to increase the heat resistance temperature.

The surface of the substrate on which the coating film is disposed may be flat or curved, or may be a surface including steps or the like. More specifically, the substrate may be a substrate (e.g., a plate, film, or sheet) or a three-dimensional object (e.g., a housing, etc.). A plate is, for example, a support used in a circuit board such as a printed circuit board. A film or sheet is, for example, a base film that is a thin-film insulator used in a flexible printed circuit board.

Examples of three-dimensional objects include the housings of electrical devices such as mobile phone terminals, smartphones, smart glasses, televisions, and personal computers. Other examples of three-dimensional objects include dashboards, instrument panels, steering wheels, and chassis in the automotive field.

Specific examples of the substrate include a substrate made of an inorganic material (hereinafter referred to as an "inorganic substrate"), and a substrate made of a resin (hereinafter referred to as a "resin substrate").

The inorganic substrate is composed of, for example, glass, silicon, mica, sapphire, quartz, a clay film, a ceramic material, etc. The ceramic material is selected from, for example, alumina, silicon nitride, silicon carbide, zirconia, yttria, aluminum nitride, and a mixture of at least two of these. In addition, as the inorganic substrate, a substrate composed of glass, sapphire, quartz, etc., which have particularly high optical transparency, can be used.

Resin substrates include, for example, polypropylene (PP), polyimide (PI), polyester (polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), etc.), polyethersulfone (PES), polycarbonate (PC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyacetal (POM), polyarylate (PAR), polyamide (PA) (PA6, PA66, etc.), polyamideimide (PAI), polyetherimide (PEI), polyphenylene ether (PPE), modified polyphenylene ether (m-PPE), polyphenylene sulfide (PPS), polyetherketone (PEK), polyetheretherketone (PEEK), polyphthalamide (PPA), polyethernitrile (PENt), polybenzimidazole (PBI), polycarbodiimide, polymethacrylamide, nitrile rubber, acrylic rubber, polyethylene tetrafluoride, epoxy resin It is composed of oil, phenolic resin, melamine resin, urea resin, polymethylmethacrylate resin (PMMA), polybutene, polypentene, ethylene-propylene copolymer, ethylene-butene-diene copolymer, polybutadiene, polyisoprene, ethylene-propylene-diene copolymer, butyl rubber, polymethylpentene (PMP), polystyrene (PS), styrene-butadiene copolymer, polyethylene (PE), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), phenol novolac, benzocyclobutene, polyvinylphenol, polychloropyrene, polyoxymethylene, polysulfone (PSF), polyphenylsulfone resin (PPSU), cycloolefin polymer (COP), acrylonitrile-butadiene-styrene resin (ABS), acrylonitrile-styrene resin (AS), polytetrafluoroethylene resin (PTFE), polychlorotrifluoroethylene (PCTFE), and silicone resin (polysiloxane).

In addition to the above, a resin sheet containing cellulose nanofibers can also be used as the substrate.

In particular, at least one selected from the group consisting of PI, PET, and PEN has excellent adhesion to metal wiring, is readily available in the market, and is available at low cost, making it advantageous and preferable from a business perspective.

Furthermore, at least one selected from the group consisting of PP, PA, ABS, PE, PC, POM, PBT, m-PPE, and PPS has excellent adhesion to metal wiring, and is also excellent in formability and mechanical strength after molding, especially when used for a housing. Furthermore, these materials are preferable because they have sufficient heat resistance to withstand heat from laser light, etc., that is irradiated when forming the metal wiring.

The material of the three-dimensional object is preferably at least one selected from the group consisting of polypropylene resin, polyamide resin, acrylonitrile butadiene styrene resin, polyethylene resin, polycarbonate resin, polyacetal resin, polybutylene terephthalate resin, modified polyphenylene ether resin, and polyphenylene sulfide resin.

The deflection temperature under load of the resin substrate is preferably 400°C or less, more preferably 280°C or less, and even more preferably 250°C or less. Substrates with a deflection temperature under load of 400°C or less are preferred because they are available at low cost and are advantageous from a business perspective. From the viewpoint of the handleability of the resin substrate, the deflection temperature under load is preferably 70°C or more, or 80°C or more, or 90°C or more, or 100°C or more. The deflection temperature under load is a value measured in accordance with JIS K7191.

When the substrate is, for example, a plate, film or sheet, the thickness is preferably 1 μm to 100 mm, or 25 μm to 10 mm, or 25 μm to 250 μm. When the substrate has a thickness of 250 μm or less, the electronic device produced can be made lighter, more space-saving and more flexible, which is preferable.

When the substrate is a three-dimensional object, its maximum dimension (i.e., the maximum length of one side) is preferably 1 μm to 1000 mm, or 200 μm to 100 mm, or 200 μm to 5 mm. When a substrate having a thickness within the above range is used, the mechanical strength and heat resistance after molding are good.

[Metal particles and/or metal oxide particles]
The metal contained in the metal particles and/or metal oxide particles is aluminum, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, ruthenium, rhodium, palladium, silver, indium, tin, antimony, iridium, platinum, gold, thallium, lead, bismuth, etc., and may be an alloy or mixture containing two or more of these. In addition, the metal oxide may be an oxide of the metal exemplified above. Among them, silver or copper metal oxide particles are preferred because they are easily reduced when irradiated with laser light and can form uniform metal wiring. In particular, copper metal oxide particles are preferred because they have relatively high stability in air and can be obtained at low cost, which is advantageous from the viewpoint of business. Copper oxide includes, for example, cuprous oxide and cupric oxide. Cuprous oxide is particularly preferred because it has high absorbance to laser light, can be sintered at low temperature, and can form low-resistance metal wiring. Cuprous oxide and cupric oxide may be used alone or in combination.

(Copper oxide particles)
In one embodiment, the coating comprises copper oxide particles, which may have a core/shell structure, and either the core or the shell may be cuprous oxide or may comprise cupric oxide.

The coating film containing copper oxide particles may further contain copper particles. That is, the dispersion described below may contain copper. In this case, it is preferable from the viewpoint of electrical conductivity and crack prevention that the mass ratio of copper particles to copper oxide particles in the coating film (hereinafter referred to as "copper particles/copper oxide particles") is 1.0 or more and 7.0 or less.

The average secondary particle diameter of the copper oxide particles is not particularly limited, but is preferably 500 nm or less, more preferably 200 nm or less, and even more preferably 80 nm or less. The average secondary particle diameter of the particles is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 15 nm or more.

The average secondary particle diameter is the average particle diameter of an aggregate (secondary particle) formed by gathering multiple primary particles. If this average secondary particle diameter is 500 nm or less, fine metal wiring can be formed on the substrate, which is preferable. If the average secondary particle diameter is 5 nm or more, it is preferable because the long-term storage stability of the dispersion is improved. The average secondary particle diameter of the particles is measured from an image observed with a scanning electron microscope. From the image, the particle diameter ((major axis + minor axis) / 2) is measured, and the number average value of 10 particles is taken as the secondary particle diameter.

The average primary particle diameter of the primary particles constituting the secondary particles is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 20 nm or less. The average primary particle diameter is preferably 1 nm or more, more preferably 2 nm or more, and even more preferably 5 nm or more.

When the average primary particle size is 100 nm or less, the baking temperature of the coating film by laser light irradiation tends to be lower. The reason why such low-temperature baking is possible is thought to be that the smaller the particle size of the particles, the higher the surface energy and the lower the melting point. By lowering the baking temperature, the amount of smoke generated can be reduced.

In addition, an average primary particle diameter of 1 nm or more is preferable because good dispersibility of the particles in the dispersion can be obtained. When forming a metal wiring pattern on a substrate, the average primary particle diameter is preferably 2 nm or more and 100 nm or less, more preferably 5 nm or more and 50 nm or less, from the viewpoint of adhesion between the substrate and the coating film and low resistance. This tendency is remarkable when the substrate is a resin. The average primary particle diameter of the particles is measured from an image observed with a transmission electron microscope. The diameter ((major axis + minor axis)/2) of a single particle is measured from the image, and the number average value of 10 particles is calculated as the primary particle diameter.

The content of copper oxide particles in the coating film is preferably 40% by mass or more, more preferably 55% by mass or more, and even more preferably 70% by mass or more, based on 100% by mass of the coating film. The content is preferably 98% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less.

The content of copper oxide particles in the coating film is preferably 10% by volume or more, more preferably 15% by volume or more, and even more preferably 25% by volume or more, based on 100% by volume of the coating film. The content is preferably 90% by volume or less, more preferably 76% by volume or less, and even more preferably 60% by volume or less.

If the content of copper oxide particles in the coating film is 40% by mass or more or 10% by volume or more, the particles are fused together by firing to exhibit good electrical conductivity, which is preferable. The higher the concentration of copper oxide particles, the better in terms of electrical conductivity. However, if the content is 98% by mass or less or 90% by volume or less, the coating film can be firmly attached to the substrate, and in particular, if the content is 95% by mass or less or 76% by volume or less, the coating film is more firmly attached to the substrate, which is preferable. In addition, if the content is 90% by mass or less or 60% by volume or less, the coating film is highly flexible, cracks are less likely to occur when folded, and reliability is improved. In one embodiment, the area of the coating film that is not irradiated with laser light may remain as an insulating area that insulates between metal wirings, and from the viewpoint of imparting excellent electrical insulation to the insulating area in this case, the content of copper oxide particles in the coating film may be 90% by volume or more.

As the copper oxide, a commercially available product or a synthetic product may be used. An example of a commercially available product is cuprous oxide particles having an average primary particle diameter of 18 nm, sold by EM Japan.

The particles containing cuprous oxide can be synthesized, for example, by the following method.
(1) A method in which water and a copper acetylacetonate complex (hereinafter referred to as an organocopper compound) are added to a polyol solvent, the organocopper compound is heated to dissolve, and then an amount of water required for the reaction is further added and the organocopper is reduced by heating to the reduction temperature.
(2) A method in which an organic copper compound (copper-N-nitrosophenylhydroxylamine complex) is heated at a high temperature of about 300° C. in the presence of a protective agent such as hexadecylamine in an inert atmosphere.
(3) A method in which copper salt dissolved in an aqueous solution is reduced with hydrazine.

The above method (1) can be carried out, for example, under the conditions described in Angewandte Chemistry International Edition, No. 40, Vol. 2, p. 359, 2001.

The above method (2) can be carried out, for example, under the conditions described in Journal of the American Chemical Society, 1999, Vol. 121, p. 11595.

In the above method (3), a divalent copper salt can be suitably used as the copper salt, and examples of such a salt include copper(II) acetate, copper(II) nitrate, copper(II) carbonate, copper(II) chloride, and copper(II) sulfate. The amount of hydrazine used is preferably 0.2 to 2 moles, and more preferably 0.25 to 1.5 moles, per mole of copper salt.

A water-soluble organic substance may be added to the aqueous solution in which the copper salt is dissolved. By adding a water-soluble organic substance to the aqueous solution, the melting point of the aqueous solution is lowered, making it possible to carry out reduction at a lower temperature. Examples of water-soluble organic substances that can be used include alcohols and water-soluble polymers.

As the alcohol, for example, methanol, ethanol, 1-propanol, 1-butanol, 1-hexanol, 1-octanol, 1-decanol, ethylene glycol, propylene glycol, glycerin, etc. can be used. As the water-soluble polymer, for example, polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol copolymer, etc. can be used.

The temperature during reduction in the above method (3) can be, for example, -20°C to 60°C, and is preferably -10°C to 30°C. This reduction temperature may be constant during the reaction, or may be increased or decreased during the reaction. In the early stages of the reaction when hydrazine activity is high, reduction is preferably performed at 10°C or lower, and more preferably at 0°C or lower. The reduction time is preferably 30 to 300 minutes, and more preferably 90 to 200 minutes. The reduction atmosphere is preferably an inert atmosphere such as nitrogen or argon.

Among the above methods (1) to (3), method (3) is preferred because it is easy to operate and produces particles with a small particle size.

Thus, in this embodiment, the coating film may contain hydrazine and/or hydrazine hydrate. When the coating film contains hydrazine and/or hydrazine hydrate, copper oxide is easily reduced to copper when irradiated with laser light, and the resistance of copper after reduction can be reduced. Hydrazine and/or hydrazine hydrate remain in the area of the coating film that is not irradiated with laser light. It is preferable that the total content of hydrazine and/or hydrazine hydrate (based on the amount of hydrazine) and the content of copper oxide in the coating film satisfy the following relationship.
0.0001≦(hydrazine mass/copper oxide mass)≦0.10

<Metal wiring>
The metal wiring is formed by irradiating a coating film containing metal particles and/or metal oxide particles with laser light. The metal particles and/or metal oxide particles may be fused to each other by laser light irradiation. In the metal wiring, the particle shape of the metal and/or metal oxide may disappear and all of them may be fused, or a part of the metal and/or metal oxide may retain the particle shape and the other part may be fused. When metal oxide particles are used, it is preferable that the metal oxide is reduced to metal by laser light. This can increase the conductivity of the metal wiring. By firing the metal particles and/or metal oxide particles by laser light irradiation, a metal wiring pattern of any shape can be easily formed.

From the viewpoint of obtaining high electrical conductivity, the content of metal elements relative to 100% by volume of the metal wiring is preferably 50% by volume or more, 60% by volume or more, or 70% by volume or more, and may be 100% by volume.

The metal wiring may contain the organic material. The content of the organic material in the metal wiring is preferably 0.5 volume % or more and 20 volume % or less, relative to 100 volume % of the metal wiring. When the content is 0.5 volume % or more, the bending resistance of the metal wiring is high, and when it is 20 volume % or less, the metal wiring has low resistance and is suitable for practical use.

The surface of the substrate with which the metal wiring comes into contact may have a predetermined roughness. The arithmetic mean surface roughness Ra of the substrate surface on which the metal wiring is formed is preferably 20 nm or more and 500 nm or less, or 50 nm or more and 300 nm or less, or 50 nm or more and 200 nm or less, in order to improve the adhesion between the metal wiring and the substrate by allowing part of the metal wiring to penetrate into the unevenness of the substrate surface.

<Metal Wiring Manufacturing Method>
One aspect of the present invention provides a method for producing a metal wiring, the method comprising: irradiating a coating film of a structure having a coating film containing metal particles and/or metal oxide particles with a laser beam to form a metal wiring. In one aspect, a gas flow is generated on the coating film simultaneously with the irradiation of the laser beam.

[Formation of structure]
First, a structure having a coating film containing metal particles and/or metal oxide particles is formed. In one embodiment, a dispersion containing metal particles and/or metal oxide particles is applied onto a substrate, followed by drying to form a structure having a coating film disposed on the substrate.

(Preparation of Dispersion)
In the following, an example will be described in which copper oxide is used as the metal particles and/or metal oxide particles, but the metal particles and/or metal oxide particles are not limited to copper oxide.

First, a copper oxide dispersion is prepared by dispersing copper oxide particles in a dispersion medium. The dispersion may further contain a dispersant (e.g., a phosphorus-containing organic compound). In one embodiment, after synthesizing cuprous oxide by the above-mentioned method (3), the copper oxide particles are separated from the reaction solution by a known method such as centrifugation. The dispersion medium and dispersant are added to the obtained copper oxide particles, and the mixture is stirred by a known method such as a homogenizer to disperse the copper oxide particles in the dispersion medium.

Depending on the dispersion medium, copper oxide particles may not disperse easily and may not be dispersed sufficiently. In such cases, for example, an alcohol in which copper oxide particles disperse easily, such as butanol, may be used to disperse the copper oxide, after which the dispersion medium is replaced with the desired one and concentrated to the desired concentration. One example is concentration using an ultrafiltration (UF) membrane, and a method of repeatedly diluting and concentrating with the desired dispersion medium.

(Application of Dispersion onto Substrate)
A coating film of the above-mentioned dispersion is formed on the surface of the substrate as described above. More specifically, for example, the dispersion is applied onto the substrate, and the dispersion medium is removed by drying as necessary to form a coating film. The coating method is not particularly limited, and coating methods such as die coating, spin coating, slit coating, bar coating, knife coating, spray coating, and dip coating can be used. It is desirable to apply the dispersion to a uniform thickness on the substrate using these methods.
In this manner, a structure can be formed.

[Laser light irradiation]
The coating film of the structure formed above is irradiated with laser light to reduce the copper oxide in the coating film to generate copper particles, and the coating film is heated under conditions in which the generated copper particles are fused together to form an integrated body, thereby forming metal wiring. In other words, the coating film is fired by laser light irradiation.

In this embodiment, the coating film is irradiated with laser light while gas is flowing over the coating film to form metal wiring. Because the coating film contains organic components such as solvents and dispersants, smoke may be generated from the coating film when heated by the laser light. If this smoke enters the irradiation optical path of the laser light and blocks the laser light, the heating conditions by the laser light will vary, causing variations in the resistance value of the metal wiring. It is effective to blow gas to prevent smoke from entering the irradiation optical path of the laser light.

In this process, the flow velocity of the gas blown onto the coating is preferably 0.01 m/s or more, or 0.05 m/s or more, or 0.1 m/s or more, and 20 m/s or less, or 10 m/s or less, or 1.0 m/s or less, or 0.8 m/s or less, or 0.6 m/s or less. When the flow velocity of the gas is 0.01 m/s or more, the smoke removal effect is good, and when it is 20 m/s or less, the gas blown inside the device is less likely to cause turbulence, so that the intrusion of smoke into the optical path of the laser light can be prevented.

It is also preferable to blow gas onto the coating film and simultaneously suck the gas while irradiating the film with laser light. By simultaneously sucking the gas while blowing, the direction of the gas flow can be stabilized and smoke can be prevented from entering the irradiation path of the laser light.

It is also preferable to place the structure including the coating film in a box and irradiate the laser light while flowing gas inside the box. In this case, the flow of gas can be limited to within the box, so that the gas can be more efficiently flowed over the coating film, and the effect of removing smoke from the optical path of the laser light is more excellent.

In this embodiment, it is preferable to flow the gas so that the laser light travels in the opposite direction to the gas flow. This prevents the gas from flowing ahead of the laser light travel direction, thereby preventing the irradiation path of the laser light from being obstructed.

In this embodiment, the irradiation output of the laser light is preferably 100 mW or more and 1500 mW or less, or 200 mW or more and 1250 mW or less, or 300 mW or more and 1000 mW or less. When the irradiation output of the laser light is 100 mW or more, the reduction of cuprous oxide can be performed efficiently. Furthermore, when the irradiation output is 1500 mW or less, the output of the laser light can be suppressed, the destruction of the metal wiring due to ablation can be suppressed, low-resistance metal wiring can be obtained, damage to the substrate can be suppressed, excess smoke is not generated from the substrate, and the laser light can be irradiated uniformly.

In this embodiment, the laser light is preferably irradiated through a galvanometer scanner. By scanning through the galvanometer scanner, metal wiring of any shape can be easily formed. In particular, the galvanometer scanner makes it easy to control the irradiation position so that the laser light moves in the opposite direction to the direction in which the smoke generated from the coating flows, thereby suppressing the effects of the smoke.

In this embodiment, the laser light may be repeatedly irradiated at a desired position on the coating film. FIG. 3 is a schematic diagram illustrating overlapping irradiation of laser light in a method for manufacturing metal wiring according to one aspect of the present invention. Referring to FIG. 3, after irradiating the laser light as a first scanning line R1 having a scanning line width S1, the laser light is irradiated as a second scanning line R2 so as to overlap the first scanning line R1 in the scanning line width direction. This increases the amount of heat stored in the overlapping area, thereby increasing the degree of sintering of the metal particles, and as a result, the resistance value of the metal wiring can be reduced. Furthermore, when the overlapping area is large, that is, when the area of the part of the coating film where the laser light is irradiated for the first time in the second irradiation is small, the amount of smoke generated in the second irradiation is reduced, so that the effect of removing the smoke by the gas flow is increased, and the influence of the smoke can be suppressed well.

The ratio S2/S1 of the overlap width S2 to the scanning line width S1 of the first scanning line R1 (also referred to as the overlap rate S in this disclosure) is preferably 5% or more and 99.5% or less, or 10% or more and 99.5% or less, or 15% or more and 99.5% or less. By having an overlap rate of 5% or more, the degree of sintering of the metal particles can be increased and the amount of smoke generated can be suppressed. By increasing the overlap rate, the degree of sintering can be increased and a hard metal wiring can be manufactured. Such metal wiring is advantageous in that it can follow the flexible substrate without cracking, for example, even when formed on a flexible substrate and bent. In addition, by having a ratio of 99.5% or less, the coating film can be sintered while moving the laser light in the scanning line width direction at an industrially practical speed. The scanning direction of the second scanning line may be the same as or different from that of the first scanning line.

When irradiating the laser light, it is preferable to alternate between 10 to 60 seconds of laser light irradiation and 1 to 10 seconds of no laser light irradiation (rest time). For example, when placing a structure inside a box, if a large amount of smoke is generated from the coating film by irradiating the laser light, the box will be filled with smoke and will obstruct the optical path of the laser light. By providing a rest time, it is possible to eliminate the large amount of smoke that may enter the optical path of the laser light.

When irradiating the laser light, the formation speed per area of the continuous metal wiring formed by the laser light is preferably 0.01 sec/mm2 or ^more , or 0.1 sec/mm2 ^or more, or 1 sec/ ^mm2 or more, and preferably 500 sec/mm2 or ^less , or 100 sec/mm2 or ^less , or ²⁰ sec/mm2 or less.

The forming speed per area of metal wiring is a value expressed by T A /S A , where S _A is the area of a certain continuous metal wiring pattern and T _A is the time required to produce a certain continuous metal wiring pattern, as shown in Figure _4. By setting the forming speed to 0.01 _seconds /mm ² or more, it is possible to irradiate a laser beam sufficient to sinter the coating film, thereby increasing the degree of sintering of the metal wiring and obtaining metal wiring with a low resistance value. In addition, by setting the forming speed to 500 seconds/mm ² or less, it is possible to prevent ablation due to excessive laser beam irradiation, prevent the generation of excess decomposition gas from the substrate, and increase the production efficiency of the metal wiring.

In the laser light irradiation process, when a certain continuous metal wiring pattern and another continuous metal wiring pattern are formed as shown in FIG. 4, it is preferable to provide a time during which the laser light is not irradiated onto the coating film between the formation of these metal wiring patterns. The time during which the laser light is not irradiated onto the coating film is preferably 0.01 seconds or more, or 0.1 seconds or more, or 1 second or more, and preferably 100 seconds or less, or 50 seconds or less, or 10 seconds or less. By having a time during which the laser light is not irradiated onto the coating film of 0.01 seconds or more, the smoke generated by the laser light irradiation onto the coating film can be sufficiently removed from the coating film, and the influence of the smoke can be effectively suppressed when the next continuous metal wiring pattern is formed. In addition, by having a time during which the laser light is not irradiated onto the coating film of 100 seconds or less, the production efficiency of the metal wiring can be improved.

As described above, according to the metal wiring manufacturing method and metal wiring manufacturing apparatus of this embodiment, by using a blower to generate a gas flow on a coating film containing metal particles and/or metal oxide particles, laser light can be irradiated onto the coating film under uniform conditions, making it easy to obtain metal wiring with a uniform resistance value.

<Application Examples>
The metal wiring manufactured by the metal wiring manufacturing apparatus and metal wiring manufacturing method according to the present embodiment can be formed on substrates of various shapes, and can be suitably applied to, for example, metal wiring materials for electronic circuit boards and the like (printed circuit boards, RFID, replacement for wire harnesses in automobiles, etc.), antennas formed on the housings of portable information devices (smartphones, etc.), mesh electrodes (electrode films for capacitive touch panels), electromagnetic wave shielding materials, and heat dissipation materials.

The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these examples and comparative examples.

<Evaluation method>
[Resistance measurement]
A tester was applied to both ends of the metal wiring, and the resistance value was measured as an index of conductivity. For each example, the resistance value was measured three times, the average value was designated as X, the standard deviation was designated as σ, and the index of variation A was calculated according to the following formula.
A=(σ/X)×100
If the value of A was less than 20%, the electrical conductivity was determined to be good.

<Production of Metal Wiring>
[Example 1]
(Preparation of Dispersion)
80 g of copper(II) acetate monohydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in a mixed solvent consisting of 800 g of ion-exchanged water and 400 g of 1,2-propylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.), 20 g of hydrazine hydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the mixture was stirred under a nitrogen atmosphere, and then separated into a supernatant and a precipitate by centrifugation.

0.4 g of DISPERBYK-145 (trade name, manufactured by BYK-Chemie) (BYK-145) as a phosphorus-containing organic compound and 6.6 g of ethanol (manufactured by Wako Pure Chemical Industries) as a dispersion medium were added to 2.8 g of the obtained precipitate, and the mixture was dispersed under a nitrogen atmosphere using a homogenizer, and then centrifuged to recover the precipitate. The precipitate was diluted with ethanol and dispersed using a homogenizer. By repeating the above-mentioned centrifugation (concentration) and dispersion (dilution), a dispersion containing cuprous oxide particles containing cuprous oxide (copper(I) oxide) was obtained. At this time, the solid residue (cuprous oxide particles) when the dispersion was heated at normal pressure and 60°C for 4.5 hours was 34.7 mass%.

(Formation of coating film)
The surface of a polyimide substrate having dimensions of 70 mm x 70 mm x 0.1 mm in width x depth x thickness was subjected to UV ozone treatment for 3 minutes, and then 1 ml of the dispersion was dropped onto the substrate and spin-coated (500 rpm x 30 seconds), dried at room temperature for 10 minutes, and then dried at 90°C for 2 hours, to obtain a structure in which a coating film having a thickness of 3.5 μm was formed on the substrate.

(Laser light irradiation)
A box with a size of 200 mm x 150 mm x 41 mm, the upper surface of which was made of quartz glass, was prepared. The box had a hole connected to a blower on the side, and the gas was blown through the hole in parallel to the surface direction of the coating film in the box. The above structure was placed at the bottom of the box, with the coating film on the upper side. A compressor was used as a blower, and compressed air was separated into nitrogen and oxygen by a separation membrane, and the separated nitrogen gas was blown onto the coating film. At this time, a gas suction machine was not installed, and the gas was discharged from the gap between the quartz glass on the upper surface of the box and the side surface of the box. Next, the coating film was repeatedly irradiated with a laser light (center wavelength 532 nm, frequency 300 kHz, pulse, output 337 mW) while scanning it, while moving the focal position at a speed of 5 mm/sec using a galvano scanner, and a copper metal wiring with the desired dimensions of length 5 mm x width 1 mm was formed over 50 seconds (formation speed per area of metal wiring 10 seconds/ ^mm2 ). At this time, the laser light was repeatedly irradiated while moving in the scanning line width direction so that the overlap rate was 93.2%. During the laser light irradiation, nitrogen gas was flowed from the hole in the side of the box toward the coating surface in parallel with the coating surface and in parallel with the moving direction of the laser light. Two more copper wirings were produced under the same conditions, resulting in a total of three copper wirings. At this time, between the formation of each successive copper wiring pattern, a time of 10 seconds was provided during which the laser light was not irradiated.

(Resistance value)
The resistance value of each metal wiring was evaluated, and the results were 0.18Ω, 0.19Ω, and 0.19Ω after three repeated evaluations, and the value of the variation index A was 3.1%.

[Example 2]
(Preparation of Dispersion)
3,224 g of copper acetate (II) monohydrate (manufactured by Nippon Kagaku Sangyo Co., Ltd.) was dissolved in a mixed solvent consisting of 30,240 g of ion-exchanged water and 13,976 g of 1,2-propylene glycol (manufactured by Asahi Glass Co., Ltd.), 940 g of hydrazine hydrate (manufactured by Nippon Finechem Co., Ltd.) was added, and the mixture was stirred. Then, the mixture was separated into a supernatant and a precipitate by centrifugation.

75 g of DISPERBYK-145 (trade name, manufactured by BYK-Chemie) (BYK-145) as a phosphorus-containing organic compound and 455 g of Mixed Ethanol NP (manufactured by Yamaichi Chemical Industry Co., Ltd.) as a dispersion medium were added to 1,136 g of the obtained precipitate, and the mixture was dispersed using a homogenizer under a nitrogen atmosphere. Furthermore, 214 g of the obtained liquid was weighed, and 11 g of DISPERBYK-145 and 25 g of Mixed Ethanol NP were added, and the mixture was dispersed using a homogenizer under a nitrogen atmosphere to obtain a dispersion containing cuprous oxide particles containing cuprous oxide (copper (I) oxide). At this time, the solid residue (cuprous oxide particles) when the dispersion was heated at normal pressure and 60°C for 4.5 hours was 44.6 mass%.

(Formation of coating film)
A polycarbonate substrate having a width x depth x thickness of 70 mm x 70 mm x 2 mm was washed with 50 ml of ethanol and dried. After that, the substrate surface was subjected to UV ozone treatment for 3 minutes, and then 2 ml of the dispersion was dropped onto the substrate and spin-coated (400 rpm x 300 seconds), dried at room temperature for 10 minutes, and then dried at 90°C for 2 hours to obtain a structure in which a coating film having a thickness of 4.8 μm was formed on the substrate.

(Laser light irradiation)
A box with a size of 200 mm x 150 mm x 41 mm, the upper surface of which was made of quartz glass, was prepared. The box had a hole connected to a blower on the side, and the gas was blown through the hole in parallel to the surface direction of the coating film in the box. The above structure was placed at the bottom of the box with the coating film on the upper side. A compressor was used as a blower, and compressed air was separated into nitrogen and oxygen by a separation membrane, and the separated nitrogen gas was blown onto the coating film. At this time, gas was discharged from the gap between the quartz glass on the upper surface of the box and the side surface of the box. Next, the coating film was repeatedly irradiated with a laser light (center wavelength 355 nm, frequency 300 kHz, pulse, output 207 mW) while scanning it, while moving the focal position at a speed of 25 mm/sec using a galvano scanner, and a copper metal wiring with the desired dimensions of length 5 mm x width 5 mm was formed over 50 seconds (formation speed per area of metal wiring 10 seconds/ ^mm2 ). At this time, the laser light was repeatedly irradiated while moving in the scanning line width direction so that the overlap rate was 86.7%. During the laser light irradiation, nitrogen gas was flowed from the hole in the side of the box toward the coating surface in parallel with the coating surface and in parallel with the moving direction of the laser light. Two more copper wirings were produced under the same conditions, resulting in a total of three copper wirings. At this time, between the formation of each successive copper wiring pattern, a time of 10 seconds was provided during which the laser light was not irradiated. Through the above procedure, a structure with copper wiring was obtained.

After that, the copper-wiring structure was plated. The plating method was as follows. 60 g of ALC-009 (Uemura Kogyo Co., Ltd.) was added to 1,140 g of industrially purified water as a cleaning agent for the copper wiring surface to prepare a pretreatment solution. 700 g of the pretreatment solution was weighed out and placed in a glass beaker, and heated to 48°C in a water bath while stirring with a stirrer. Next, the copper-wiring structure was immersed in the solution for 5 minutes to perform pretreatment. Next, 30 ml of OPC Copper NCA-1 (Okuno Chemical Industries Co., Ltd.), 4.8 ml of OPC Copper NCA-4 (Okuno Chemical Industries Co., Ltd.), 300 ml of OPC Copper NCA-2 (Okuno Chemical Industries Co., Ltd.), and 4.8 ml of OPC Copper NCA-3 (Okuno Chemical Industries Co., Ltd.) were added to 424.8 g of industrially purified water. 700 g of the liquid was weighed out and placed in a glass beaker, and heated to 59°C in a water bath while stirring with a stirrer. Next, 6.3 ml of electroless copper R-H (manufactured by Okuno Chemical Industries Co., Ltd.) was added to prepare a plating solution. The structure was immersed in the plating solution for 30 minutes while air bubbling was performed in the plating solution. After immersion, the structure was removed and immersed in 700 ml of industrial purified water, and then washed with running water using 50 ml of industrial purified water to obtain a plated structure.

(Resistance value)
After the above plating process, the resistance value of each metal wiring was evaluated. When the evaluation was repeated three times, the values were 0.013Ω, 0.012Ω, and 0.012Ω, and the value of the variation index A was 4.7%.

[Example 3]
Metal wiring was manufactured in the same manner as in Example 2, except that when irradiating the laser light, the polycarbonate substrate coated with the dispersion was not placed in a box, and furthermore, a blower was not used. Instead, a gas suction machine with a rectangular opening of 120 mm x 70 mm connected to an exhaust fan was installed at a position 130 mm horizontally and 100 mm vertically away from the center position of the structure.

The resistance value of each metal wiring was evaluated, and after three repeated evaluations, the results were 0.020Ω, 0.022Ω, and 0.020Ω, with the variation index A being 5.6%.

[Example 4]
(Preparation of Dispersion)
3,224 g of copper acetate (II) monohydrate (manufactured by Nippon Kagaku Sangyo Co., Ltd.) was dissolved in a mixed solvent consisting of 30,240 g of ion-exchanged water and 13,976 g of 1,2-propylene glycol (manufactured by Asahi Glass Co., Ltd.), 940 g of hydrazine hydrate (manufactured by Nippon Finechem Co., Ltd.) was added, and the mixture was stirred. Then, the mixture was separated into a supernatant and a precipitate by centrifugation.

76 g of DISPERBYK-145 (trade name, manufactured by BYK-Chemie) (BYK-145) as a phosphorus-containing organic compound and 615 g of 1-butanol (manufactured by Sankyo Chemical) as a dispersion medium were added to 575 g of the obtained precipitate, and the mixture was dispersed using a homogenizer under a nitrogen atmosphere. Furthermore, 1222 g of the obtained liquid was weighed, and 11 g of DISPERBYK-145 and 167 g of 1-butanol were added, and the mixture was dispersed using a homogenizer under a nitrogen atmosphere to obtain a dispersion containing cuprous oxide particles containing cuprous oxide (copper (I) oxide). At this time, the solid residue (cuprous oxide particles) when the dispersion was heated at normal pressure and 60°C for 4.5 hours was 30.1 mass%.

(Formation of coating film)
A PI substrate having dimensions of 70 mm x 70 mm x 1 mm in width x depth x thickness was subjected to UV ozone treatment for 3 minutes, and then 1 ml of the dispersion was dropped onto the substrate and spin-coated (300 rpm x 300 seconds), dried at room temperature for 10 minutes, and then dried at 60°C for 1 hour, to obtain a structure in which a coating film having a thickness of 0.8 μm was formed on the substrate.

(Laser light irradiation)
When irradiating the laser light, the PI substrate coated with the dispersion was not placed in a box, and a blower was not used. Instead, a gas suction machine with an opening surface of 120 mm x 70 mm and a rectangular shape connected to an exhaust fan was installed at a position 130 mm horizontally and 100 mm vertically away from the center of the structure. At this time, the wind speed at a position 10 mm vertically away from the center of the coating film surface was measured to be 0.03 m/s. Next, the coating film was repeatedly irradiated with a laser light (center wavelength 355 nm, frequency 300 kHz, pulse, output 387 mW) while scanning it, while moving the focal position at a speed of 25 mm/sec using a galvano scanner, to form a copper metal wiring with the desired dimensions of length 5 mm x width 1 mm over 34 seconds (formation speed per area of metal wiring 7 seconds/ ^mm2 ). At this time, the laser light was repeatedly irradiated while moving it so that the overlap rate was 80% in the scanning line width direction. Two more copper wirings were fabricated under the same conditions, giving a total of three copper wirings, with a 10-second period during which no laser light was irradiated between each successive copper wiring pattern.

(Resistance value)
The resistance value of each metal wiring was evaluated, and the results were 2.4Ω, 2.6Ω, and 3.3Ω after three repeated evaluations, and the value of the variation index A was 17%.

[Comparative Example 1]
Metal wiring was produced in the same manner as in Example 1, except that the polyimide substrate coated with the dispersion was not placed in a box and a blower was not used during laser light irradiation, so that laser light was irradiated without generating a gas flow above the coating film.

A tester was placed on both ends of the metal wiring in the longitudinal direction to evaluate the conductivity. After repeating the evaluation three times, the values were 0.7Ω, 1.2Ω, and 0.9Ω, and the value of the variation index A was 27%.

According to the present invention, it is possible to provide metal wiring that can greatly simplify the manufacturing process, has excellent electrical insulation between metal wiring, and is highly reliable. Furthermore, according to the present invention, it is possible to provide a metal wiring manufacturing apparatus and a metal wiring manufacturing method that can reduce the manufacturing costs of metal wiring by eliminating the need for equipment for a vacuum atmosphere or an inert gas atmosphere when irradiating laser light.

As a result, the metal wiring obtained by the present invention can be suitably used as metal wiring material for electronic circuit boards, mesh electrodes, electromagnetic shielding materials, heat dissipation materials, etc.

REFERENCE SIGNS LIST 1 Structure 10, 20, 30, 40 Metal wiring manufacturing apparatus 11 Substrate 12 Coating film 101 Laser light irradiation section 102a Blower 102b Gas suction device 103 Stage 104 Box G Gas L Laser light R1 First scanning line R2 Second scanning line S1 Scanning line width S2 Overlap width

Claims (17)

A metal wiring manufacturing apparatus for manufacturing a metal wiring by irradiating a laser beam onto a coating film of a structure having a coating film containing metal particles and/or metal oxide particles, the apparatus comprising:
a laser light irradiation unit that irradiates the coating film with laser light;
a gas flow generating unit that generates a gas flow on the coating film in a direction opposite to a moving direction of the laser light ;
A metal wiring manufacturing apparatus comprising: The metal wiring manufacturing apparatus according to claim 1, wherein the gas flow generating unit is a blower and/or a gas suction device. Further comprising a box for enclosing the structure,
The blower is disposed inside or outside the box,
3. The metal wiring manufacturing apparatus according to claim 2, further comprising a pipe for introducing gas from the blower into the box when the blower is disposed outside the box. The metal wiring manufacturing apparatus according to any one of claims 1 to 3, wherein the gas is at least one selected from the group consisting of air, nitrogen, helium, and argon. The metal wiring manufacturing device according to any one of claims 1 to 4, wherein the laser light has a central wavelength in the range of 350 nm to 600 nm. The laser light irradiation unit is
a laser oscillator that emits laser light;
a galvano scanner that irradiates the coating film with an oscillated laser beam;
The metal wiring manufacturing apparatus according to any one of claims 1 to 5, further comprising: A laser light irradiation step of irradiating a coating film of a structure having a coating film containing metal particles and/or metal oxide particles with a laser light to form metal wiring,
In the laser light irradiation step, a gas flow is generated on the coating film simultaneously with the irradiation of the laser light ,
The method for manufacturing metal wiring further comprises irradiating the coating film with laser light while flowing the gas in a direction opposite to a moving direction of the laser light on the coating film . A laser light irradiation step of irradiating a coating film of a structure having a coating film containing metal particles and/or metal oxide particles with a laser light to form metal wiring,
In the laser light irradiation step, a gas flow is generated on the coating film simultaneously with the laser light irradiation,
A method for manufacturing a metal wiring, wherein in the laser light irradiation step, laser light irradiation for 10 seconds or more and 60 seconds or less and no laser light irradiation for 1 second or more and 10 seconds or less are alternately repeated . A laser light irradiation step of irradiating a coating film of a structure having a coating film containing metal particles and/or metal oxide particles with a laser light to form metal wiring,
In the laser light irradiation step, a gas flow is generated on the coating film simultaneously with the laser light irradiation,
In the laser light irradiation step, a period of time during which the laser light is not irradiated onto the coating film is set to 0.01 seconds or more and 100 seconds or less between the formation of a certain continuous metal wiring pattern and the formation of another continuous metal wiring pattern . 10. The method for producing a metal wiring according to claim 7, wherein in the laser light irradiation step, laser light irradiation for 10 seconds or more and 60 seconds or less and no laser light irradiation for 1 second or more and 10 seconds or less are alternately repeated. 9. The method for producing metal wiring according to claim 7 or 8, wherein in the laser light irradiation step, a time period of 0.01 seconds or more and 100 seconds or less is provided between the formation of a certain continuous metal wiring pattern and the formation of another continuous metal wiring pattern during which the coating film is not irradiated with laser light. The method for producing a metal wiring according to any one of claims 7 to 11 , further comprising generating a gas flow on the coating film by a blower and/or a gas suction device. The method for producing a metal wiring according to any one of claims 7 to 12, wherein the structure is covered with a box, and the coating film is irradiated with laser light while a gas is flowing inside the box. 14. The method for producing a metal wiring according to claim 7, wherein the irradiation output of the laser light is 100 mW or more and 1500 mW or less. the laser light is repeatedly scanned onto the coating film while overlapping in a line width direction of the scanning line of the laser light;
The method for manufacturing a metal wiring according to any one of claims 7 to 14 , wherein the overlap is from 5% to 99.5% of the line width. 16. The method for producing metal wiring according to claim 7, wherein in the laser light irradiation step, a formation speed per area of the continuous metal wiring formed by the laser light is 0.01 sec/mm2 or ^more and 500 sec/mm2 or ^less . 17. The method for producing a metal wiring according to claim 7, wherein the gas is at least one selected from the group consisting of air, nitrogen, helium, and argon.

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