WO2013146389A1

WO2013146389A1 - Method for producing conductor film

Info

Publication number: WO2013146389A1
Application number: PCT/JP2013/057534
Authority: WO
Inventors: 智柏原; 米田　貴重; 平社　英之; 亮太村上
Original assignee: 旭硝子株式会社
Priority date: 2012-03-28
Filing date: 2013-03-15
Publication date: 2013-10-03
Also published as: JP2015111492A; TW201344712A

Abstract

Provided is a method by which a conductor film having a low volume resistivity is produced without thermally affecting the base even in cases where a base having a low heat resistance, such as PET and PEN, is used. A method for producing a conductor film, which comprises: a step of preparing a base; a step of forming a coating film of a conductive ink on the base, said conductive ink containing fine copper hydride particles or fine copper particles; a step of forming a fired film by heating the coating film at 100-200°C; and a step of heating the fired film at 300-500°C by irradiation of laser light.

Description

Method for producing conductive film

The present invention relates to a method for producing a conductor film.

For example, as a method for producing a substrate with a conductor having a circuit pattern such as a printed wiring, a conductive ink made of a dispersion in which metal fine particles such as silver and copper are dispersed is printed on the substrate by an inkjet printing method, A method of forming a conductor by heating is known. In particular, conductive ink containing copper as a main component is more advantageous than silver fine particles in terms of cost and is widely used.

In the method of forming the conductor, it is necessary to heat at a high temperature in order to promote the sintering of the metal particles and to obtain a conductor having sufficient chemical resistance and weather resistance and having a small volume resistivity. On the other hand, a conductor is also formed by printing using a polymer film such as PET (polyethylene terephthalate) or PEN (polyethylene naphthalate) as a substrate. In this case, the heat resistance of the substrate From this point, it is necessary to perform heating at a low temperature of 200 ° C. or lower.

As a heating method for promoting such sintering, Patent Document 1 discloses a method of heating by light irradiation using a pulse light source. Patent Document 2 discloses a method of heating the surface using a laser or the like.

Japanese National Table 2008-522369 Japanese Unexamined Patent Publication No. 2011-252202

However, in the methods of Patent Documents 1 and 2, the characteristics of nanoparticles, such as silver, copper, iron, zinc, and titanium, and the conditions of pulse irradiation and laser irradiation and the combination thereof are not optimized. When heating the conductive ink containing copper hydride fine particles or copper fine particles by the method, it is difficult to control the heating temperature, and sufficient fusion between the copper fine particles does not proceed, and the volume of the obtained conductor There was a problem that the resistivity was not sufficiently reduced.

The present invention has been made to solve such problems. Even when a base material having low heat resistance such as PET or PEN is used, the conductor film does not affect the base material and has a small volume resistivity. A method of manufacturing the same is provided.

The present invention provides the following method for producing a conductor film.
(1) preparing a substrate;
Forming a conductive ink coating film containing copper hydride fine particles or copper fine particles having an average primary particle diameter of 5 to 100 nm on the substrate;
Heating the coating film at 100 to 200 ° C. to form a fired film;
And a step of heating the fired film at 300 to 500 ° C. by laser light irradiation.
(2) The method for producing a conductor film according to (1), wherein the light absorption rate of the fired film is 40 to 100% at a wavelength of 300 to 1000 nm.
(3) The method for producing a conductor film according to (1) or (2), wherein the conductor film includes copper fine particles connected to each other.
(4) The conductor film manufacturing method according to any one of (1) to (3), wherein the conductor film includes boron, sodium, and carbon.
(5) The conductive ink is
A conductive ink in which an alkylamine having an alkyl group having a boiling point of 250 ° C. or lower and a carbon number of 7 or more and copper hydride fine particles or copper fine particles having a primary particle diameter of 5 to 80 nm are dispersed in a water-insoluble organic solvent, The method for producing a conductor film according to any one of (1) to (4), wherein the surface tension is 25 to 40 dyn / cm and the viscosity at 20 ° C. is 8 to 40 mPa · s.

According to the method for producing a conductor film of the present invention, a coating film formed of conductive hydride containing copper hydride fine particles or copper fine particles having an average primary particle diameter of 5 to 100 nm or less is heated at 100 to 200 ° C. Since the conductive film can be formed by heating only the fired film portion at a high temperature by laser irradiation, even when using a base material with low heat resistance such as PET or PEN, the volume resistance is not affected. A conductor film having a low rate can be obtained.

It is a graph which shows the relationship between the light absorption rate by the fired film in Examples 1, 2, and a wavelength. 10 is a graph showing the relationship between the light absorption rate and the wavelength by a fired film in Example 3.

<Method for producing conductor film>
The present invention relates to a method for producing a conductor film, comprising a step of preparing a base material, a step of forming a conductive ink coating film on the base material, and heating the coating film at 100 to 200 ° C. A step of forming a fired film, and a step of heating the fired film at 300 to 500 ° C. by laser irradiation. Each step in the production method of the present invention will be described.

In the present embodiment, a process of forming a conductive ink coating film (hereinafter also referred to as a coating process) will be described.
In the coating process of the present embodiment, the method of applying the conductor ink includes methods such as inkjet printing, screen printing, roll coating, air knife coating, blade coating, bar coating, gravure coating, die coating, spray coating, and slide coating. It is done. Of these, inkjet printing is particularly preferred.

The coating pattern at this time can be applied to the entire surface of the substrate, or can be applied in a pattern or pattern. Depending on the application method, purpose of use, and application, the particle size of the copper hydride fine particles or copper fine particles, the dispersant, the solvent, and other types of blends can be appropriately selected. Similarly, the viscosity of the dispersion and the concentration of the copper hydride fine particles or the solid content of the copper fine particles can be appropriately selected.

When inkjet printing is used, a desired pattern can be drawn on the substrate by changing the relative position between the nozzle, which is a discharge port for the conductive ink, and the substrate. The thickness and width of the coating can be adjusted.

In the case of inkjet printing, from the viewpoint of easy formation of a conductor film having a desired pattern, the diameter of the ink discharge hole is set to 0.5 to 100 μm, and the diameter of the conductive ink adhered on the substrate is set to 1 to 100 μm. It is preferable to do.

(Base material)
As the base material, glass such as alkali-free glass, quartz glass, crystallized transparent glass, Pyrex (registered trademark) glass, sapphire glass, Al ₂ O ₃ , MgO, BeO, ZrO ₂ , Y ₂ O ₃ , CaO, Inorganic materials such as GGG (Gadolinium Gallium Garnet), acrylic resins such as PET (polyethylene terephthalate), PEN (polyethylene naphthalate), polypropylene, polycarbonate, polymethyl methacrylate, chlorides such as polyvinyl chloride, vinyl chloride copolymers Organic materials such as vinyl resin, epoxy resin, polyarylate, polysulfone, polyethersulfone, polyimide, fluororesin, phenoxy resin, polyolefin resin, nylon, styrene resin, ABS resin, etc. Inorganic particles A substrate, a silicon wafer, a metal plate, or the like formed of a composite material in which is dispersed can be used. These materials can be appropriately selected depending on the application. For electronic member applications, PET and PEN are particularly preferred because they are easy to mold and have excellent chemical properties such as chemical resistance. The size is not limited, and the shape may be any shape such as a disk shape, a card shape, or a sheet shape, and the surface of the base material does not need to be a flat surface, and may have an unevenness or a curved surface. .

An underlayer may be provided on the base material for the purpose of improving the flatness of the surface of the base material, improving the adhesive force, and preventing alteration of the metallic copper-containing film. Examples of the underlayer include an underlayer formed of a surface modifier such as a polymer material, thermosetting or light / electron beam curable resin, or a coupling material. The base layer is preferably one that improves the adhesion between the base material and the conductor film, or one having lyophilicity or liquid repellency, specifically, thermosetting or photo / electron beam curable resin, A layer formed using a surface modifier such as a coupling agent, colloidal silica, or the like is preferable if necessary.

(Conductive ink)
The conductive ink used in the present invention contains copper hydride fine particles or copper fine particles, and a conductive ink produced using a copper hydride fine particle dispersion or a copper fine particle dispersion obtained by a production method described later can be used.

<Method for producing copper hydride fine particle dispersion>
The dispersion containing the copper hydride fine particles of the embodiment is preferably obtained by a method of reducing a copper (II) salt with a hydride-based reducing agent in the presence of an alkylamine (B) in a solvent (A).

The solvent (A) is preferably a solvent having an SP value of 8 to 12. When the SP value is 8 to 12, the compatibility between the solvent (A) and water is low, and the mixing of water into the reaction system can be suppressed. Thereby, it can suppress that the hydride type | system | group reducing agent melt | dissolved in the solvent (A) reacts with water and inactivates.
The SP value of the solvent (A) is more preferably 8.5 to 9.5.

Examples of the solvent (A) include cyclohexane (SP value 8.2), isobutyl acetate (SP value 8.3), isopropyl acetate (SP value 8.4), butyl acetate (SP value 8.5), and tetrachloride. Carbon (SP value 8.6), ethylbenzene (SP value 8.8), xylene (SP value 8.8), toluene (SP value 8.9), ethyl acetate (SP value 9.1), tetrahydrofuran (SP value) 9.1), benzene (SP value 9.2), chloroform (SP value 9.3), methylene chloride (SP value 9.7), carbon disulfide (SP value 10.0), acetic acid (SP value 10. 1), pyridine (SP value 10.7), dimethylformamide (SP value 12.0) and the like.

The alkylamine (B) is preferably an alkylamine having an alkyl group having 7 or more carbon atoms and a boiling point of 250 ° C. or less.
If the carbon number of the alkyl group in the alkylamine (B) is 7 or more, the dispersibility of the produced copper hydride fine particles will be good. In the present invention, since the reaction field is an organic phase, it is not necessary to use an alkylamine having a large carbon number for the purpose of protection from water. The number of carbon atoms of the alkyl group in the alkylamine (B) is preferably 11 or less from the viewpoint of suppressing the boiling point from becoming too high.

When the boiling point of the alkylamine (B) is 250 ° C. or less, the conductor film having a low volume resistivity is released when the alkylamine (B) is desorbed from the surface of the fine particles and volatilized when the conductor film is formed using the conductive ink. Can be formed. The boiling point of the alkylamine (B) is preferably 250 ° C. or less, and more preferably 200 ° C. or less, from the viewpoint of desorption and volatility during heating. Moreover, the boiling point of the alkylamine (B) is usually preferably 150 ° C. or higher from the viewpoint that the alkyl group has 7 or more carbon atoms.
The alkyl group of the alkylamine (B) is preferably a linear alkyl group from the viewpoint of dispersion stability of the obtained copper hydride fine particles. However, the alkyl group of the alkylamine (B) may be a branched alkyl group.

Examples of the alkylamine (B) include n-heptylamine (alkyl group having 7 carbon atoms and a boiling point of 157 ° C.), n-octylamine (alkyl group having 8 carbon atoms and a boiling point of 176 ° C.), n-nonylamine (carbon of the alkyl group). (9, boiling point: 201 ° C.), 1-aminodecane (alkyl group having 10 carbon atoms, boiling point: 220 ° C.), 1-aminoundecane (alkyl group having 11 carbon atoms, boiling point: 242 ° C.), n-heptylamine, n- Octylamine is more preferred.
An alkylamine (B) may be used individually by 1 type, and may use 2 or more types together.

The addition amount of the alkylamine (B) is 0.2 × 10 ^{− with} respect to 1 g of the solvent (A) because the dispersibility of the copper hydride fine particles in the obtained copper hydride fine particle dispersion becomes good. ³ mol or more is preferable, 0.25 × 10 ⁻³ mol or more is more preferable, and 0.3 × 10 ⁻³ mol or more is particularly preferable. Moreover, when the addition amount of the alkylamine (B) is excessive, the alkylamine (B) that cannot be coordinated to the copper (II) salt remains at the time of forming the conductor film, and increases the volume resistivity of the conductor film. There is a fear. Therefore, the amount of the alkylamine (B) is preferably 0.75 × 10 ⁻³ mol or less, more preferably 0.7 × 10 ⁻³ mol or less, and 0.6 ×× 1 g of the solvent (A). ^10-3 mol or less is particularly preferred.

In this way, hydrogenated copper hydride fine particles (primary particles) having an average primary particle diameter of 5 to 100 nm, preferably 5 to 80 nm, more preferably 5 to 70 nm, and particularly preferably 5 to 35 nm are dispersed in the solvent (A). A copper fine particle dispersion is obtained. The average primary particle diameter of the copper hydride fine particles can be adjusted by the addition amount of the alkylamine (B) and the addition amount of the hydride reducing agent. By increasing the addition amount of the alkylamine (B), the average primary particle diameter of the copper hydride fine particles tends to decrease. Moreover, there exists a tendency for the average primary particle diameter of a copper hydride microparticle to become small by reducing the addition amount of a hydride type | system | group reducing agent.
In this specification, an average primary particle diameter can be calculated | required as follows. The particle size of 100 randomly extracted fine particles was measured using a transmission electron microscope (for example, Hitachi, Ltd., device name: H-9000) or a scanning electron microscope (for example, Hitachi, Ltd., device name: S). -800) and average the values to determine the average particle size.

The concentration of the copper hydride fine particles as a solid content in the obtained copper hydride fine particle dispersion is preferably 1 to 6% by mass, more preferably 2.5 to 4.5% by mass, based on 100% by mass of the entire dispersion. . If the solid content concentration of the copper hydride fine particle dispersion is less than 1% by mass, the concentration process takes time, and the productivity may be reduced. If the solid content concentration of the copper hydride fine particle dispersion exceeds 6% by mass, the dispersion stability of the copper hydride fine particles in the dispersion may be deteriorated.

<Method for producing copper fine particle dispersion>
The copper fine particle dispersion can be produced by heat-treating the copper hydride fine particle dispersion obtained by the copper hydride fine particle dispersion production method at a temperature of 60 ° C. or higher in an inert atmosphere.
The heating temperature is preferably from 80 to 100 ° C. from the viewpoint of the heat treatment time (it takes time when the temperature is low) and the dispersed particle diameter of the obtained copper fine particles (aggregates when the temperature is too high).

Thus, copper fine particles (primary particles) having an average primary particle diameter of 5 to 100 nm, preferably 5 to 80 nm, more preferably 5 to 70 nm, and particularly preferably 5 to 35 nm are dispersed in the solvent (A). A fine particle dispersion is obtained. The average primary particle diameter of the copper fine particles can be adjusted in the same manner as in the case of producing the above-described copper hydride fine particle dispersion.

The concentration of the copper fine particles as a solid content in the obtained copper fine particle dispersion is preferably 1 to 6% by mass, more preferably 2.5 to 4.5% by mass, based on 100% by mass of the entire dispersion. If the solid content concentration of the copper fine particle dispersion is less than 1% by mass, the concentration process takes time, and the productivity may be reduced. When the solid content concentration of the copper hydride fine particle dispersion exceeds 6% by mass, the dispersion stability of the copper fine particles in the dispersion may be deteriorated.

In the conductive ink used in the present invention, the copper hydride fine particle dispersion obtained by the production method described above or the solvent (A) of the copper fine particle dispersion is replaced with the solvent (C), and the solid content concentration and viscosity are adjusted. Is obtained.

As the solvent (C), a water-insoluble organic solvent is used. Water-insoluble means that the amount dissolved in 100 g of water at room temperature (20 ° C.) is 0.5 g or less. The solvent (C) is preferably an organic solvent having a small polarity from the viewpoint of affinity with the alkylamine (B). Further, the solvent (C) is preferably one that does not cause thermal decomposition by heating when forming the conductor film.
Examples of the solvent (C) include decane (insoluble in water), dodecane (insoluble in water), tetradecane (insoluble in water), decene (insoluble in water), dodecene (insoluble in water), tetradecene. (Insoluble in water), dipentene (dissolved in 100 g of water 0.001 g (20 ° C.)), α-terpineol (dissolved in 100 g of water 0.5 g (20 ° C.)), mesitylene (insoluble in water) Etc.). Of these, α-terpineol, decane, dodecane, and tetradecane are preferable because the drying property of the ink and the coating property are easily controlled.
A solvent (C) may be used individually by 1 type, and may use 2 or more types together.

As a method for substituting the solvent (A) of the copper hydride fine particle dispersion or the copper fine particle dispersion with the solvent (C), a known solvent substitution method can be employed. For example, while concentrating the solvent (A) under reduced pressure, The method of adding (C) is mentioned.

The conductive ink used in the present invention may contain a silane coupling agent and other additives in addition to the above-described copper hydride fine particles or copper fine particles, alkylamine and solvent. Examples of other additives include antifoaming agents, wetting and dispersing agents, leveling agents, anti-drying agents, rheology control agents, and adhesion imparting agents.

The solid content concentration of the conductive ink (100% by mass) used in the present invention varies depending on the required viscosity, but is preferably 15 to 70% by mass, more preferably 20 to 60% by mass. When the solid content concentration of the conductive ink is 15% by mass or more within the above range, a conductor film having a sufficient thickness can be easily formed. When the solid content concentration of the conductive ink is 70% by mass or less of the above range, the ink characteristics such as viscosity and surface tension can be easily controlled, and the formation of the conductor film is facilitated.

Note that the copper hydride fine particle dispersion or the conductive ink obtained from the copper fine particle dispersion contains a reducing agent and an alkylamine because of its production method, but these components remain in the produced conductor film. However, there is no problem because there is little residue. If the component derived from the reducing agent and the carbon derived from the alkylamine are present in the conductor film, a material for producing the conductor film can be estimated. For example, when NaBH ₄ is used as the reducing agent, boron, sodium, and carbon are contained in the conductor film.

The viscosity of the conductive ink used in the present invention at 20 ° C. is preferably 5 to 60 mPa · s, more preferably 8 to 40 mPa · s. If the viscosity of the conductive ink is 5 mPa · s or more, the ink can be accurately discharged even when ink jet printing is used. If the viscosity of the conductive ink is 60 mPa · s or less, it can be applied to almost all available inkjet heads.

The surface tension of the conductive ink used in the present invention is preferably 20 to 45 dyn / cm, and more preferably 25 to 40 dyn / cm. If the surface tension of the conductive ink is 20 dyn / cm or more, the ink can be ejected with high accuracy. If the surface tension of the conductive ink is 45 dyn / cm or less in the above range, it can be applied to almost all available inkjet heads.
In the present specification, the viscosity of the conductive ink is a value measured with a B-type viscometer (manufactured by Toki Sangyo Co., Ltd., apparatus name: TVB35L). The surface tension is a value measured by a surface tension meter (manufactured by Kyowa Interface Science Co., Ltd., device name: DY-500).

The conductive ink used in the present invention includes a water-insoluble organic solvent, an alkylamine having a boiling point of 250 ° C. or lower and an alkyl group having 7 or more carbon atoms, copper hydride fine particles having a primary particle diameter of 5 to 80 nm, or copper It is particularly preferable that the conductive ink has fine particles dispersed therein, the viscosity at 20 ° C. is 8 to 40 mPa · s, and the surface tension is 25 to 40 dyn / cm.

After the coating process, the coating film is heated at 100 to 200 ° C. to form a fired film. Here, the fired film means a film obtained by decomposing and / or vaporizing a compound contained in a coating film such as a protective agent or a solvent by the heating. Examples of the heating method include a method using oven, hot plate heating, IR heating, flash lamp heating, laser heating, μ-wave plasma heating and the like. The heating is preferably performed in an inert atmosphere such as a nitrogen atmosphere from the viewpoint of easily suppressing the oxidation of the conductor film to be formed.

The heating temperature can be appropriately set according to the type of the substrate, but is preferably 100 to 200 ° C. which does not affect the plastic substrate such as PET or PEN. Further, using the above-described copper hydride fine particles or conductive ink containing copper fine particles, heating is performed in a nitrogen atmosphere or in vacuum in order to set the light absorption rate of the fired film to 40% or more at a wavelength of 300 to 1000 nm. It is preferable.

The light absorption rate of the laser light irradiated in the laser irradiation process by the fired film is preferably 40% or more. The light absorption rate of the fired film is more preferably 40% or more at a wavelength of 300 to 1000 nm. This is because laser irradiation energy, which will be described later, is absorbed by the fired film and can be heated to a temperature of 300 ° C. or higher in a short time. If the light absorptance is less than 40%, most of the laser irradiation energy is reflected, so the temperature cannot be raised in a short time. If the light absorptance is 5% or less, it is difficult to raise the temperature by laser irradiation. .
In the present specification, the light absorption rate of the fired film can be determined as follows. Using a UV-visible spectrophotometer (for example, Hitachi High-Technologies Corporation, device name: U-4100 type), the light transmittance and light reflectance at a wavelength of 300 to 1000 nm of the fired film are measured, and the light absorption rate is calculated. .

The heating time can be appropriately set according to the heating temperature. When using the above-described copper hydride fine particles or conductive ink containing copper fine particles, the solvent (C), the acid liberated from the copper (II) salt, the alkylamine (B) desorbed from the fine particle surface, etc. are volatilized to absorb light. What is necessary is just a time during which a fired film having a rate within the above-mentioned range can be formed, and about 10 minutes to 48 hours is appropriate.

(Laser heating process)
The entire region or a partial region of the fired film formed by the heating is irradiated with laser light to be heated to 300 to 500 ° C. (hereinafter also referred to as a laser heating step). The laser light oscillated by a laser oscillator is collected by a lens, and the pattern is drawn on the base material by moving the laser mounting portion or the base material while irradiating the fired film with the laser light by appropriately setting the irradiation diameter. The laser light is absorbed by the fired film, and the generated heat decomposes and / or vaporizes the organic compound such as the dispersant, while reducing the copper hydride fine particles and fusing adjacent copper fine particles. The volume resistivity of the irradiated part can be reduced. Moreover, by this, the obtained conductor film contains copper fine particles connected to each other. It is considered that the copper fine particles adhere to each other even at the interface with the base material due to physical and chemical effects. The heating method by laser light irradiation has an advantage that only the fired film can be heated, and a conductor film can be formed without causing thermal damage to the substrate. That is, with local and short-time heating by laser irradiation, the temperature rise of the copper fine particles is extremely fast, so the temperature rise around the copper fine particles due to heat transfer is slight, and the substrate is relatively heat resistant. Even if the polymer film is not formed, the conductive film can be formed without melting the entire polymer film.

The wavelength of the laser beam can be arbitrarily selected within the range where the light absorption rate by the fired film is 40% or more depending on the type and blending amount of the dispersant, additive and solvent to be used. In view of the ease of the above, 350 to 900 nm is preferable. Typical lasers include semiconductor lasers such as GaN, GaAsAl, and InGaAsP, excimer lasers such as ArF, KrF, and XeCl, dye lasers such as rhodamine, gases such as He—Ne, He—Cd, CO ₂ , and Ar ions. Examples thereof include solid lasers such as lasers, free electron lasers, ruby lasers, and Nd: YAG lasers. Further, higher harmonics such as second harmonic and third harmonic of these lasers may be used, and laser light having any wavelength in the ultraviolet region, visible light region, or infrared region can be used. Further, continuous wave irradiation or pulse wave irradiation may be used. In general, a semiconductor laser is preferable because it is suitable for irradiation with a continuous laser beam having an infrared wavelength.

Each condition relating to the applied energy such as the laser beam irradiation diameter, scanning speed, and output can be set as appropriate within a range where oxidation of the formed conductor film, ablation of the fired film, and peening do not occur. The laser irradiation diameter (beam diameter) can be appropriately set according to the pattern or pattern to be drawn, but is preferably 10 μm to 10 mm. The scanning speed can be appropriately set according to other parameters, required accuracy, manufacturing capability, and the like.

The atmosphere for laser irradiation is preferably an inert gas atmosphere in order to suppress oxidation of the formed conductor film. Specifically, it is preferable to irradiate a continuous wave laser beam having an infrared wavelength in an atmosphere containing nitrogen gas at a scanning speed of 1 to 500 mm / second in an output range of 1 to 140 W. At this time, in order to sufficiently sinter the copper fine particles and sufficiently reduce the volume resistivity, the laser irradiation conditions are set so that the temperature of the portion irradiated with the laser light is 300 to 500 ° C., more preferably 300 to 400 ° C. adjust.

The heating time may be set according to the heating temperature so that the copper fine particles are densely sintered and the volume resistivity is sufficiently reduced to form the conductor film.
In order to heat the fired film at the above-described temperature, the laser beam output is more preferably 5 to 100 W, and further preferably 5 to 50 W. The scanning speed is more preferably 0.3 to 20 mm / second. Since the fired film is heated at a high temperature of 300 to 500 ° C. by such a laser heating process, a conductor film having a volume resistivity of 10 Ω · cm or less can be formed.
In this specification, the volume resistivity can be determined as follows. The surface resistance value of the conductor film is measured using a four-point probe resistance meter (for example, Mitsubishi Oil Chemical Co., Ltd., apparatus name: Loresta GP MCP-T610). The volume resistivity is obtained by multiplying the measured surface resistance value by the thickness of the conductor film.

The laser heating process described above minimizes the thermal effect on the base material, and even when a plastic such as PET, PEN or the like, which is a low heat resistant base material, is used, only the fired film can be heated at a high temperature. Moreover, since it heats at 300 degreeC or more by laser irradiation, the conductor film which reduced the volume resistivity sufficiently can be formed.

In the present embodiment, the thickness of the conductor film to be manufactured is preferably 0.3 to 2.0 μm.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples. Examples 1 and 2 are examples, and example 3 is a comparative example. Each method of identification of fine particles, measurement of the average particle diameter of fine particles, measurement of the thickness of the conductor film, and measurement of the volume resistivity of the conductor film in Examples and Comparative Examples is shown below.

[Identification of fine particles]
The identification of the fine particles was performed using an X-ray diffraction apparatus (manufactured by Rigaku Instruments Co., Ltd., apparatus name: RINT2500).

[Average particle size of fine particles]
Using a transmission electron microscope (manufactured by Hitachi, Ltd., device name: H-9000) or a scanning electron microscope (manufactured by Hitachi, Ltd., device name: S-800) The average particle size was determined by averaging the values.
[Thickness of conductor film]
It measured using the contact-type film thickness measuring apparatus (the product made by Veeco, apparatus name: DEKTAK150).
[Volume resistivity of conductor film]
Using a four-probe resistance meter (Mitsubishi Yuka Co., Ltd., apparatus name: Loresta GP MCP-T610), the surface resistance value of the conductor film was measured. The volume resistivity was obtained by multiplying the measured surface resistance value by the thickness of the conductor film.
[Measurement of light absorption rate]
Using a UV-visible spectrophotometer (manufactured by Hitachi High-Technologies Corporation, apparatus name: U-4100 type), the light transmittance and light reflectance at a wavelength of 300 to 1000 nm of the fired film were measured, and the light absorption rate was calculated.

(Manufacture of conductive ink)
To a glass container, 300 g of toluene, 30 g of copper (II) formate tetrahydrate as a copper (II) salt, and 15 g of n-heptylamine (boiling point 157 ° C.) as an alkylamine were added and stirred. Next, 4.5 g of NaBH ₄ which is a hydride reducing agent was added and stirred to obtain a black dispersion liquid in which fine particles were dispersed in toluene.
The fine particles in the obtained dispersion were collected and identified by X-ray diffraction. As a result, it was confirmed to be copper hydride fine particles. The average primary particle diameter of the copper hydride fine particles (primary particles) was 10 nm. Further, the solid content concentration of the obtained copper hydride fine particle dispersion was 4% by mass.

Next, the obtained copper hydride fine particle dispersion was concentrated under reduced pressure, and α-terpineol was added to adjust the viscosity to obtain a conductive ink. The obtained conductive ink had a solid content of copper hydride fine particles of 30% by mass.

[Example 1]
A PET film was used as the substrate. Using the above conductive ink, a wiring pattern was printed on a PET substrate so as to have a length of 5 cm and a width of 5 mm by an industrial ink jet printer (manufactured by Fuji Film Graphic System Co., Ltd., device name: DMP2813). The PET substrate after printing was heated at 150 ° C. for 1 hour in a nitrogen atmosphere to obtain a PET substrate on which a fired film was formed. The obtained fired film had a thickness of 0.5 μm and a volume resistivity of 20 μΩ · cm.
The light absorption rate of the obtained fired film is shown in FIG. As can be seen from FIG. 1, the light absorptance at wavelengths of 300 nm to 1000 nm is 40% or more.
In order to heat the above-obtained fired film at 300 ° C. or higher, a semiconductor laser (manufactured by Hamamatsu Photonics, apparatus name: L10402-72, wavelength: 808 nm, beam diameter: 1.75 × 5) is heated in a nitrogen atmosphere. .58 mm, irradiation output: 5 W), and laser irradiation was performed at a scanning speed of 1 mm / second. The volume resistivity of the conductor film after laser irradiation was 7 μΩ · cm.

[Example 2]
Using the above conductive ink, a wiring pattern was printed on a PET substrate so as to have a length of 5 cm and a width of 5 mm by an industrial ink jet printer (manufactured by Fuji Film Graphic System Co., Ltd., device name: DMP2813). The printed PET substrate was heated in vacuum at 100 ° C. for 1 hour to obtain a PET substrate on which a fired film was formed. The obtained fired film had a thickness of 0.6 μm and a volume resistivity of 55 μΩ · cm.
The light absorption rate of the obtained fired film was the same as in FIG. From FIG. 1, the light absorptance at a wavelength of 300 to 1000 nm was 40% or more. In order to heat the fired film obtained above at 300 ° C. or higher, in a nitrogen atmosphere, a semiconductor laser (manufactured by Hamamatsu Photonics, apparatus name: L10402-72, wavelength: 808 nm, beam diameter: 1.75 × 5. 58 mm, irradiation output: 5 W), and laser irradiation was performed at a scanning speed of 1 mm / second. The volume resistivity of the conductor film after laser irradiation was 5 μΩ · cm.

[Example 3]
Using the above conductive ink, a wiring pattern was printed on a PET substrate so as to have a length of 5 cm and a width of 5 mm by an industrial ink jet printer (manufactured by Fuji Film Graphic System Co., Ltd., device name: DMP2813). The PET substrate after printing was heated at 120 ° C. for 1 hour in an atmosphere in which 3% by volume of hydrogen was mixed with nitrogen to obtain a PET substrate on which a fired film was formed. The obtained fired film had a thickness of 0.5 μm and a volume resistivity of 15 μΩ · cm.
The light absorption rate of the obtained fired film is shown in FIG. The light absorption rate at a wavelength of 600 to 1000 nm was 40% or less. The fired film obtained above was used in a nitrogen atmosphere using a semiconductor laser (manufactured by Hamamatsu Photonics, apparatus name: L10402-72, wavelength: 808 nm, beam diameter: 1.75 × 5.58 mm, irradiation output: 5 W). Laser irradiation was performed at a scanning speed of 1 mm / second. The volume resistivity of the conductor film after laser irradiation was 15 μΩ · cm.

In Examples 1 and 2, the light absorption rate at a wavelength of 300 to 1000 nm of the fired film is 40% or more. By heating the fired film with a laser beam having a wavelength of 808 nm, the temperature becomes 300 ° C. or more. It can be seen that the volume resistivity could be reduced. On the other hand, in Example 3, the light absorption rate at a wavelength of 600 to 1000 nm of the fired film is 40% or less, and the fired film is not heated even when irradiated with laser light having a wavelength of 808 nm, and the volume resistivity cannot be sufficiently reduced. I understand that.

Although the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2012-074697 filed on Mar. 28, 2012, the contents of which are incorporated herein by reference.

Moreover, according to the manufacturing method of the base material with a conductor of this invention, even when using base materials with low heat resistance, such as PET and PEN, a conductive film with a small volume resistivity can be manufactured, and this conductive film was formed. The base material is suitably used as a highly reliable wiring board.

Claims

Preparing a substrate;
Forming a conductive ink coating film containing copper hydride fine particles or copper fine particles having an average primary particle diameter of 5 to 100 nm on the substrate;
Heating the coating film at 100 to 200 ° C. to form a fired film;
And a step of heating the fired film at 300 to 500 ° C. by laser light irradiation.
The method for producing a conductor film according to claim 1, wherein the light absorption rate of the fired film is 40 to 100% at a wavelength of 300 to 1000 nm.
3. The method of manufacturing a conductor film according to claim 1, wherein the conductor film includes copper fine particles connected to each other.
The method of manufacturing a conductor film according to any one of claims 1 to 3, wherein the conductor film contains boron, sodium, and carbon.
The conductive ink is
A conductive ink in which an alkylamine having an alkyl group having a boiling point of 250 ° C. or lower and a carbon number of 7 or more and copper hydride fine particles or copper fine particles having a primary particle diameter of 5 to 80 nm are dispersed in a water-insoluble organic solvent, 5. The method for producing a conductor film according to claim 1, wherein the surface tension is 25 to 40 dyn / cm and the viscosity at 20 ° C. is 8 to 40 mPa · s.