JP2017022125A - Copper nanoparticle dispersion and method of manufacturing conductive substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a conductive substrate capable of providing the conductive substrate having excellent conductivity by burning at low temperature or for short time.SOLUTION: There is provided a method of manufacturing a conductive substrate having a copper nanoparticle coated by carboxylic acid, and alkyl amine containing a primary or secondary amino group but containing no hydroxy group, the copper nanoparticles dispersed in a polymer dispersant and a solvent, where the polymer dispersant has an acid value of 30 to 160 mgKOH/g and an amine value of 0 to 160 mgKOH/g, the method including a step of applying a copper nanoparticle dispersant having a volume average particle diameter based on a dynamic light scattering of 500 nm or less on a substrate to form a coating film and a step of burning the coating film.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a copper nanoparticle dispersion and a method for producing a conductive substrate using the dispersion.

  A method of forming a circuit pattern by printing a pattern directly on a base material by a printing process such as screen printing or ink jet printing using a metal particle dispersion in which metal particles are dispersed, and sintering the metal particles. Attention has been paid. According to the technique of printing a pattern directly on a substrate, productivity is dramatically improved as compared with a conventional photoresist method or the like.

  It is known that the melting point of the metal particles dramatically decreases as the metal particles are refined. This is because the specific surface area of the particles increases and the surface energy increases as the particle size of the metal particles decreases. If this effect is utilized, the sintering of metal particles can proceed at a lower temperature than in the past, and circuit formation by printing is possible even for resin substrates with low heat resistance that have been difficult to use conventionally. Is expected to be possible. However, as the particle size of the metal particles is reduced, aggregation tends to occur, dispersibility and dispersion stability cannot be ensured, and a problem arises in coating suitability. If there is a problem in coating suitability and a highly uniform coating film cannot be formed, the accuracy of the circuit pattern will deteriorate, the metal particles will not be present uniformly and densely, and the conductivity after sintering will deteriorate. Thus, it has been difficult in the past to achieve both the dispersion stability and coating suitability of the metal particle dispersion and the low-temperature firing property.

  Further, a metal particle dispersion using silver particles is difficult to oxidize and is excellent in conductivity, but silver itself is expensive or has problems of ion migration. Therefore, development of a metal particle dispersion using copper as an inexpensive metal with excellent migration resistance is required. However, since copper particles are generally more easily oxidized than silver particles, there is a problem that conductivity is difficult to be expressed.

In Patent Document 1, a compound containing copper and a reducing compound are mixed, and a step of producing a composite compound that can be thermally decomposed in an alkylamine to form copper, and the composite compound is heated in an alkylamine. And a process for producing copper fine particles coated with an alkylamine. According to Patent Document 1, it is described that the coated copper fine particles have a narrow and fine particle size distribution, excellent storage stability and can be sintered at a low temperature.
However, according to the technique of Patent Document 1, the dispersibility of copper fine particles is poor, the coating suitability is poor, and unevenness occurs when coating on a resin substrate such as a PET film, as in the comparative example described later. was there. Furthermore, when trying to improve dispersibility, it is necessary to use a large amount of alkylamine, and there is a problem that the sinterability deteriorates.

Patent Document 2 describes a specific metal fine particle, a polymer dispersant having a specific polyester skeleton, a metal fine particle dispersion containing a dispersion medium, and a method for producing a conductive substrate using the dispersion. Has been. According to Patent Document 2, it is described that the specific polymer dispersant exhibits a high effect on the dispersibility of the metal fine particles and is easily volatilized in a subsequent sintering step.
However, since the technique of Patent Document 2 retains dispersibility only with a dispersant, organic substances are likely to remain during sintering, and firing of a metal fine particle coating film requires long firing with high microwave output. It has become. Actually, as described in the examples of the document, firing of metal fine particle coating film on polyethylene naphthalate (PEN) film is the limit, and PET film, which is a cheaper and versatile low heat resistant substrate, etc. When it was applied and fired under the same conditions as in Patent Document 2, there was a problem that the base material was deformed and could not be fired before conductivity was developed. In order to coat and fire a PET film or the like, it was necessary to further lower the sintering temperature. Further, in the technique of Patent Document 2, since organic substances are likely to remain at the time of sintering, it is difficult to perform chemical etching after sintering because the degree of sintering tends to be inclined between the coating film surface and inside.

  Patent Document 3 describes a method for producing a conductive metal thin film using metal nanoparticles synthesized from a solution containing a metal precursor, an acid, an amine, and a reducing agent. It is also stated that it is good. However, Patent Document 3 is a technique that focuses on improving the conductivity by firing at a high temperature of 200 ° C. or higher using a reducing atmosphere. Although the technique specifically disclosed in Patent Document 3 has poor dispersibility of metal nanoparticles as in the comparative example described later, a certain degree of conductivity can be obtained by high-temperature firing. . Therefore, in order to coat and sinter on a PET film or the like, it is necessary to study further lowering the sintering temperature.

JP 2012-72418 A International Publication No. 2011/040189 Pamphlet International Publication No. 2013/147535 Pamphlet

As described above, conventionally, in the copper particle dispersion, a relatively low molecular weight dispersant has been used in order to prevent the organic component from remaining during firing. However, the dispersant having a low molecular weight has insufficient dispersibility and applicability, and attempts to improve dispersibility and applicability have resulted in insufficient sinterability at low temperatures or in a short time. Alternatively, in order to improve the dispersibility and dispersion stability of the copper particles, if the copper particles are dispersed using a polymer dispersant as a dispersant, the substrate that can be used is limited because high temperature firing is required, In the firing, the volume resistivity of the substrate obtained by leaving the polymer dispersant in the metal film is increased, and there are cases where sufficient performance as a conductive substrate cannot be obtained. On the other hand, there is a problem that copper particles are easily oxidized. Therefore, it is a very difficult problem to obtain a dispersion that is excellent in dispersibility and coating suitability while suppressing copper oxidation, and that can form a film having high conductivity after firing at a low temperature or in a short time. there were.
The present invention has been made under such circumstances, and a copper nanoparticle dispersion excellent in oxidation resistance, dispersibility, applicability, and sinterability at low temperature or in a short time, and low temperature or short It aims at providing the manufacturing method of an electroconductive board | substrate which can obtain the electroconductive board | substrate which has the outstanding electroconductivity by baking by time.

As a result of intensive studies to achieve the above object, the present inventors have combined copper nanoparticles with a carboxylic acid, an alkylamine, and a polymer dispersant having a specific amine value or acid value. By making a copper nanoparticle dispersion having a volume average particle size of 500 nm or less, it is excellent in oxidation resistance, dispersibility, and coating suitability, and is organic from the film even when baked at a low temperature or in a short time. Since the components are easily decomposed or removed, and the nanoparticles are uniformly and densely arranged in the coating film, it has been found that a film having high conductivity can be formed.
The present invention has been completed based on such knowledge.

  In the method for producing a conductive substrate according to the first aspect of the present invention, copper nanoparticles coated with a carboxylic acid and an alkylamine having a primary or secondary amino group and not containing a hydroxy group are polymer dispersing agents. And the polymer dispersant has an acid value of 30 to 160 mgKOH / g, an amine value of 0 to 160 mgKOH / g, and a volume average particle size by dynamic light scattering of 500 nm or less. It has the process of apply | coating a certain copper nanoparticle dispersion on a base material, and forming a coating film, and the process of baking the said coating film.

Moreover, the manufacturing method of the electroconductive board | substrate of the 2nd aspect which concerns on this invention is 1 or more types of reducing compounds selected from the compound containing copper, the hydrazine and the hydrate of hydrazine, carboxylic acid, and primary or 2 A mixture containing an alkylamine having a primary amino group and no hydroxy group, or one or more reducing compounds selected from carboxylic acid copper, hydrazine and hydrazine hydrate, and a primary or secondary amino group Preparing copper nanoparticles by heating any of the mixtures comprising alkylamines having no hydroxy groups, and
By dispersing the copper nanoparticles in a solvent with a polymer dispersant having an acid value of 30 to 160 mgKOH / g and an amine value of 0 to 160 mgKOH / g, the volume average particle diameter by a dynamic light scattering method is increased. Preparing a copper nanoparticle dispersion that is 500 nm or less;
Applying the copper nanoparticle dispersion on a substrate to form a coating film;
And a step of firing the coating film.

  In addition, the copper nanoparticle dispersion according to the present invention includes a carboxylic acid and a copper nanoparticle coated with an alkylamine having a primary or secondary amino group and not containing a hydroxy group, as a polymer dispersant and a solvent. The polymer dispersant is characterized by having an acid value of 30 to 160 mgKOH / g, an amine value of 0 to 160 mgKOH / g, and a volume average particle size by dynamic light scattering method of 500 nm or less. And

  In the method for producing a conductive substrate and the copper nanoparticle dispersion according to the present invention, the polymer dispersant has a low 90% thermal weight loss temperature of 420 ° C. or less, low temperature sinterability and after sintering. It is preferable from the point which the electroconductivity of a coating film is excellent.

  In the method for producing a conductive substrate and the copper nanoparticle dispersion according to the present invention, the carboxylic acid has 10 or less carbon atoms, and the low-temperature firing property and the conductivity of the coated film after sintering are excellent. It is preferable from the point.

  Further, in the method for manufacturing a conductive substrate according to the present invention, the baking step is a step of baking by plasma or a step of baking by irradiation with flash light, which can be performed at a low temperature or for a short time. It is preferable because a conductive substrate having excellent conductivity can be obtained even on a low heat-resistant substrate.

  Moreover, in the manufacturing method of the electroconductive board | substrate which concerns on this invention, the method which has the process of carrying out the chemical etching of the obtained sintered film after the said baking process is also used suitably. Since the sintered film formed in the present invention is imparted with smoothness and adhesion, a chemical etching method can be used to form a fine conductive pattern.

  According to the present invention, the copper nanoparticle dispersion excellent in oxidation resistance, dispersibility, applicability, and sinterability at a low temperature or in a short time, and excellent conductivity by firing at a low temperature or in a short time. It is possible to provide a method for manufacturing a conductive substrate capable of obtaining a conductive substrate having a property.

FIG. 1 is a schematic view showing an example of a conductive substrate obtained by the production method of the present invention. FIG. 2 is a schematic view showing another example of a conductive substrate obtained by the production method of the present invention.

Hereinafter, the copper nanoparticle dispersion according to the present invention and the method for producing a conductive substrate will be described.
In the present invention, (meth) acryl represents each of acryl and methacryl, and (meth) acrylate represents each of acrylate and methacrylate.

[Copper nanoparticle dispersion]
The copper nanoparticle dispersion according to the present invention contains copper nanoparticles, a carboxylic acid, an alkylamine, a polymer dispersant, and a solvent, and the polymer dispersant has one of an amine value and an acid value. 30 to 160 mgKOH / g, the other of the amine value and the acid value is 0 to 160 mgKOH / g, and the volume average particle size by dynamic light scattering is 500 nm or less.

In the present invention, the copper nanoparticles have a relatively low molecular weight carboxylic acid and an alkylamine, one of an amine value and an acid value of 30 to 160 mgKOH / g, and the other of an amine value and an acid value of 0 to 160 mgKOH / In combination with the polymer dispersant that is g, the volume average particle size is dispersed so as to be 500 nm or less. Therefore, it is estimated that the following specific effects are exhibited by their synergistic action. The
In order to impart dispersibility of the copper nanoparticles, it is desirable to use a compound having a functional group that strongly adsorbs to the surface of the copper nanoparticles. It is considered that it becomes difficult to detach from the particles, and as a result, it becomes a factor of deterioration of conductivity. In that respect, in the present invention, both a relatively low molecular weight carboxylic acid that can be strongly adsorbed on the surface of the copper nanoparticles and a relatively low molecular weight alkylamine that is weakly adsorbed on the surface of the copper nanoparticles, And a polymer dispersant having a specific amine value and acid value having at least one kind of acidic functional group is attached to the copper nanoparticles, and the copper nanoparticles are dispersed in the solvent. In the present invention, the polymer dispersant having a specific amine value and acid value has at least one kind of basic and acidic functional groups, and acid-base interaction with carboxylic acid or alkylamine on the surface of the copper nanoparticles. It can be considered that there is something attached due to the above.
In the present invention, the carboxylic acid that can be strongly adsorbed on the surface of the copper nanoparticles is present stably surrounding the copper nanoparticles in the solvent due to the strong adsorption. And, since the alkylamine has a charge different from that of the carboxylic acid at the adsorption site and further adheres to the copper nanoparticles, the low molecular weight dispersants of carboxylic acid and alkylamine can adhere more closely to the copper nanoparticles. It is estimated to be. Furthermore, since the polymer dispersant is selected so as to have a specific amine value and acid value, the polymer dispersant can be stably attached to the copper nanoparticles to which both the carboxylic acid and the alkylamine are attached. It is presumed that due to the steric hindrance of the polymer chain, aggregation of copper nanoparticles is less likely to occur, and excellent dispersibility of the copper nanoparticles can be achieved. As shown in the comparative example described later, for the copper nanoparticles to which both carboxylic acid and alkylamine are attached, the amine value and acid value of the polymer dispersant are too low or too high. In either case, the polymer dispersant cannot be stably attached, but rather the dispersibility deteriorates.
In the present invention, since the copper nanoparticles are surrounded by a polymer dispersant having a specific amine value and acid value and are stably dispersed uniformly in a fine particle size, film formation of a polymer chain Depending on the properties, it is estimated that the coating suitability of the copper nanoparticle dispersion is excellent and the smoothness of the coating film is increased.
Moreover, by setting the volume average particle diameter of the dispersion to 500 nm or less, the copper nanoparticles are uniformly arranged in the coating film, and a high-density film can be formed. Since the relatively low molecular weight alkylamine is weakly adsorbed on the surface of the copper nanoparticles, it is easily detached during drying when forming a coating film. On the other hand, it is considered that the polymer dispersing agent remains to prevent non-uniform aggregation of the copper nanoparticles, and the copper nanoparticles are arranged at a higher density during drying. It is presumed that carboxylic acid is easily desorbed even during drying, low temperature or short time baking because it is mixed with easily desorbed alkylamine. In addition, since the polymer dispersant has the specific amine value and acid value, the adsorption is not too strong, and the polymer dispersant is uniformly disposed around the copper nanoparticles, so that the low temperature is low in the subsequent firing step. It is presumed that a metal thin film having excellent electrical conductivity can be obtained by fusion of copper nanoparticles arranged at high density, which is easily desorbed or decomposed even after baking for a short time. When the volume average particle size of the dispersion exceeds 500 nm in the system as in the present application, the copper nanoparticles cannot be arranged at high density, so that they are non-uniformly baked and can adhere stably to the copper nanoparticles. It is presumed that an unsatisfactory polymer dispersant is present in the coating film, which inhibits sintering at a low temperature or a short time and prevents excellent conductivity.
Copper nanoparticles are particularly easily oxidized when synthesized in the atmosphere. Therefore, oxidation can be suppressed by suppressing oxidation at the time of nanoparticle production and immediately dispersing in a solvent to make it difficult to touch oxygen. In the present invention, the alkylamine has a function of scavenging protons in the amino group, and therefore adheres to the surface of the copper nanoparticles during production, thereby suppressing oxidation of copper atoms during production and in the dispersion. It is estimated that In addition, the present invention has an effect of suppressing the oxidation of copper nanoparticles in the present invention because the copper nanoparticles are closely surrounded with a carboxylic acid that can be strongly adsorbed on the surface of the copper nanoparticles, and further a polymer dispersant is attached. Is estimated to be high. From these, it is presumed that sintering inhibition due to oxidation during firing hardly occurs, and a film having high conductivity can be formed after firing.

The copper nanoparticle dispersion of the present invention may contain other components in addition to the above essential components as long as the effects of the present invention are not impaired.
Hereinafter, each configuration of the copper nanoparticle dispersion will be described in detail in order.

<Copper nanoparticles>
In the present invention, the copper nanoparticles are typically metallic copper particles. However, since copper is a metal that is very easily oxidized, the surface of the metallic copper nanoparticles is partially oxidized into an oxide. It may be included.

The copper nanoparticles mean particles having a diameter of the order of nm (nanometer), that is, less than 1 μm. In the present invention, by using such copper nanoparticles, sintering at a low temperature is easy to proceed, and the printability of fine wiring is improved. The copper nanoparticles used in the present invention are preferably particles having an average primary particle size of 1 nm to 100 nm, and more preferably 10 nm to 100 nm, from the viewpoint of achieving both dispersibility, applicability, low temperature firing, and conductivity. Of these particles, it is preferable. This is because if it is less than the lower limit, a large amount of a polymeric dispersant is required to impart dispersion stability and coating suitability, and as a result, there is a risk of deteriorating conductivity. If the upper limit is exceeded, the dispersed particle size becomes large, and as a result, there is a possibility that the conductivity is deteriorated.
In addition, the average primary particle diameter of the said copper nanoparticle can be calculated | required by the method of measuring the magnitude | size of a primary particle directly from an electron micrograph. Specifically, a particle image was measured with a transmission electron micrograph (TEM) (for example, H-7650 manufactured by Hitachi High-Tech), and the average value of the length of the longest part of 100 randomly selected primary particles was calculated. The average primary particle size can be obtained.

  What is necessary is just to select the preparation method of the said copper nanoparticle suitably from a conventionally well-known method. For example, a physical method of pulverizing metal powder by mechanochemical method, etc .; chemical dry method such as chemical vapor deposition method (CVD method), vapor deposition method, sputtering method, thermal plasma method, laser method; thermal decomposition method The copper nanoparticles can be obtained using a chemical wet method such as a chemical reduction method, an electrolysis method, an ultrasonic method, a laser ablation method, a supercritical fluid method, or a microwave synthesis method.

For example, in the vapor deposition method, fine particles are produced by bringing a vapor of a metal heated and brought into contact with a low vapor pressure liquid containing a dispersant under a high vacuum.
Further, as one type of chemical reduction method, there is a method in which a copper-containing compound and a reducing agent are mixed in a solvent in the presence of a complexing agent and an organic protective agent.
In addition to the above method, commercially available copper nanoparticles can be used as appropriate.
In the present invention, since copper nanoparticles are coated with carboxylic acid and alkylamine, among them, as will be described in detail later, using carboxylic acid and alkylamine as an organic protective agent, a copper-containing compound and a reducing agent, A method of mixing copper in a solvent to produce copper nanoparticles is preferably used.

  In the copper nanoparticle dispersion of the present invention, the content of the copper nanoparticles may be appropriately selected according to the use, but from the viewpoint of dispersibility, 0.01% with respect to the total amount of the copper nanoparticle dispersion. It is preferable that it is -90 mass%, and it is still more preferable that it exists in the range of 0.1-85 mass%.

<Carboxylic acid>
The carboxylic acid used in the present invention is a compound that can be bonded to copper by an oxygen atom as a ligand. Therefore, in the copper nanoparticle dispersion, the carboxylic acid contributing to the dispersion usually exists in a state of being bonded to copper by at least one oxygen atom.
Examples of the carboxylic acid include saturated aliphatic monocarboxylic acids such as acetic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, and hexadecanoic acid; oleic acid, Unsaturated aliphatic monocarboxylic acids such as linoleic acid; Aliphatic polycarboxylic acids such as oxalic acid, malonic acid, and succinic acid; Aliphatic unsaturated polycarboxylic acids such as maleic acid; Aromatic monocarboxylic acids such as benzoic acid Examples thereof include, but are not limited to, acids; aromatic polycarboxylic acids such as phthalic acid; and hydroxycarboxylic acids such as citric acid.
Among these, a carboxylic acid having 10 or less carbon atoms is preferable from the viewpoint that the low-temperature baking property is improved and the conductivity is improved. Also, carboxylic acids having 2 or more carbon atoms are used from the viewpoint of dispersibility. In particular, an aliphatic carboxylic acid having 10 or less carbon atoms is preferable from the viewpoint of improving dispersibility and low-temperature calcination properties and improving conductivity. The aliphatic carboxylic acid may be either saturated or unsaturated.

As the carboxylic acid used in the present invention, one carboxylic acid may be used, or two or more carboxylic acids may be mixed and used.
The carboxylic acid used in the present invention is preferably a carboxylic acid having one or two carboxyl groups in the molecule, since the polarity is relatively weak and easily desorbed at the time of firing. It is preferable to use a carboxylic acid having a group.

  In addition, the carboxylic acid used in the present invention is preferably not too high in molecular weight, and preferably has a molecular weight of 300 or less, and more preferably 200 or less, from the viewpoint of easy desorption during firing. Moreover, it is preferable that a boiling point is 400 degrees C or less, Furthermore, it is preferable that it is 300 degrees C or less. On the other hand, the molecular weight of the carboxylic acid is preferably 50 or more from the viewpoint of desorption during storage of nanoparticles and storage and prevention of volatilization. Moreover, it is preferable that a boiling point is 50 degreeC or more.

In the copper nanoparticle dispersion of the present invention, the content of the carboxylic acid may be appropriately selected according to the use, but from the viewpoint of low-temperature calcinability, 0.1 to 30 mass with respect to 100 mass parts of copper. Part, and more preferably within the range of 0.1 to 20 parts by mass.
In the copper nanoparticle dispersion of the present invention, the content of the carboxylic acid may be appropriately selected according to the use, but from the viewpoint of low-temperature calcinability, 0.05% with respect to the total amount of the copper nanoparticle dispersion. It is preferably ˜15% by mass, and more preferably in the range of 0.05 to 10% by mass.

<Alkylamine>
The alkylamine used in the present invention can be appropriately selected from known alkylamines according to properties expected for the produced copper nanoparticle dispersion.
It is presumed that the alkylamine has a function of capturing protons, thereby preventing the copper atom from being oxidized.
Alkylamine has a structure in which an amino group is bonded to a part of an alkyl group. In order to form a coordination bond to a copper atom, RNH ₂ (R is a hydrocarbon chain) in which at least one of the amino groups contained in the alkylamine used is a primary amino group or R ₁ is a secondary amino group R ₂ NH (R ₁ and R ₂ may be the same or different in the hydrocarbon chain) is desirable. The alkyl chain may be linear, branched or cyclic. The hydrocarbon chain may contain atoms other than carbon such as oxygen, silicon, nitrogen, sulfur, and phosphorus. For example, specifically, it may be an alkylamine having a substituent such as an alkoxy group, an alkoxysilyl group, or an alkylthio group, or may have two amino groups in the molecule.

  Examples of the alkylamine (monoamine) having one amino group in the molecule include 2-ethoxyethylamine, dipropylamine, dibutylamine, hexylamine, cyclohexylamine, heptylamine, 3-methoxypropylamine, and 3-ethoxypropyl. Alkylamines such as amine, 3-butoxypropylamine, octylamine, nonylamine, decylamine, 3-aminopropyltriethoxysilane, dodecylamine, hexadecylamine, octadecylamine and oleylamine are industrially produced and easily available. It is practical.

  On the other hand, examples of the alkyldiamine having two amino groups in the molecule include ethylenediamine, N, N-dimethylethylenediamine, N, N′-dimethylethylenediamine, N, N-diethylethylenediamine, N, N′-diethylethylenediamine, 1 , 3-propanediamine, 2,2-dimethyl-1,3-propanediamine, N, N-dimethyl-1,3-diaminopropane, N, N′-dimethyl-1,3-diaminopropane, N, N— Diethyl-1,3-diaminopropane, 1,4-diaminobutane, 1,5-diamino-2-methylpentane, 1,6-diaminohexane, N, N′-dimethyl-1,6-diaminohexane, 1, 7-diaminoheptane, 1,8-diaminooctane, 3-dimethylaminopropylamine, 3-diethylamino Ropiruamin, 3-dibutylaminopropylamine, 3 but methylaminopropylamine and the like, but is not limited thereto.

As the alkylamine used in the present invention, one type of alkylamine may be used, or two or more types of alkylamine may be mixed and used.
The alkylamine used in the present invention is preferably an alkylamine having one or two amino groups in the molecule from the viewpoint that the polarity is relatively weak and that it is easily eliminated during firing.

In addition, the alkylamine used in the present invention is preferably not too high in molecular weight, and preferably has a molecular weight of 300 or less, more preferably 200 or less, from the viewpoint of easy desorption during firing. In addition, the alkylamine used in the present invention preferably has 8 or less carbon atoms, and more preferably 6 or less, from the viewpoint that it is easily detached during firing.
In addition, the alkylamine used in the present invention preferably has a boiling point of 300 ° C. or lower, more preferably 200 ° C. or lower, from the viewpoint of easy desorption during firing. On the other hand, the molecular weight of the alkylamine is preferably 50 or more from the viewpoints of desorption during storage and storage and prevention of volatilization. The boiling point is preferably 23 ° C. or higher, and more preferably 50 ° C. or higher.

In the copper nanoparticle dispersion of the present invention, the content of the alkylamine may be appropriately selected according to the use, but from the viewpoint of low-temperature calcinability, 0.1 to 30 masses with respect to 100 mass parts of copper. Part, and more preferably within the range of 0.1 to 20 parts by mass.
In the copper nanoparticle dispersion of the present invention, the content of the alkylamine may be appropriately selected according to the use, but from the viewpoint of oxidation resistance and low-temperature sinterability, it is based on the total amount of the copper nanoparticle dispersion. , 0.05 to 15% by mass, and more preferably 0.05 to 10% by mass.

<Polymer dispersant>
The polymer dispersant used in the present invention is a polymer dispersant in which one of the amine value and the acid value is 30 to 160 mgKOH / g, and the other one of the amine value and the acid value is 0 to 160 mgKOH / g, Having at least one of a functional functional group and an acidic functional group.
Examples of basic functional groups include primary, secondary, or tertiary amino groups, nitrogen-containing heterocycles such as pyridine, pyrimidine, and pyrazine. Examples of acidic functional groups include carboxylic acid groups, phosphoric acid groups, and sulfonic acid groups.
The amine value indicates the total amount of free base and base, and is expressed in mg of potassium hydroxide equivalent to the hydrochloric acid required to neutralize 1 g of the sample. The acid value represents the total amount of free acid and acid, and is expressed in mg of potassium hydroxide required to neutralize 1 g of the sample. The amine value can be measured by a method according to JIS-K7237, and the acid value can be measured by a method according to JIS-K0070.

The polymer dispersant used in the present invention has the above-mentioned specific amine value and acid value with respect to copper nanoparticles to which both carboxylic acid and alkylamine are attached, and an appropriate amount of basic functional group or acidity. Since it has a functional group, it is presumed that it adsorbs stably to the copper nanoparticles, while causing a steric hindrance by the polymer chain portion and stably preventing aggregation of the copper nanoparticles.
As shown in the examples and comparative examples described later, for the copper nanoparticles to which both carboxylic acid and alkylamine are attached, the amine value and acid value of the polymer dispersant are too low or too high. In either case, the polymer dispersant cannot be stably attached, but rather the dispersibility deteriorates. In particular, when combined with a carboxylic acid having a low dispersibility but excellent low-temperature calcinability and having a small number of carbon atoms, it is clear that the polymer dispersant cannot be dispersed if the amine value and acid value are too low or too high. It was made.

  In the present invention, the polymer dispersant having the specific amine value and acid value is stably adsorbed to the copper nanoparticles, whereby dispersibility and dispersion stability are improved. The diameter can be reduced. Therefore, when the above polymer dispersant is used, the smoothness and uniformity of the coating film of the copper nanoparticle dispersion are excellent, and the copper nanoparticles in the coating film are arranged at high density. Therefore, sintering is easy to proceed uniformly, and the copper nanoparticles are easily fused. In addition, the polymer dispersant is easily decomposed or volatilized by baking due to a synergistic effect with the alkylamine, and the resulting conductive substrate suppresses the remaining organic components. As a result, the obtained metal film is presumed to be excellent in conductivity.

  The polymer dispersant used in the present invention has one of an amine value and an acid value of 30 to 160 mgKOH / g and the other of an amine value and an acid value of 0 to 160 mgKOH / g for the reasons described above. One of the amine value and the acid value is 40 to 140 mgKOH / g, and the other one of the amine value and the acid value is preferably 0 to 140 mgKOH / g.

  The polymer dispersant used in the present invention preferably has a weight average molecular weight of 800 or more, more preferably 900 or more, particularly 1000 or more, from the viewpoint of excellent dispersibility and coating suitability. Is preferred. On the other hand, from the viewpoint of excellent low-temperature calcinability, it is preferably 30000 or less, more preferably 20000 or less, and particularly preferably 10,000 or less. In addition, the weight average molecular weight in this invention can be measured by the gel permeation chromatography (GPC) method (polystyrene conversion).

  Further, the polymer dispersant used in the present invention has a 90% thermogravimetric decrease temperature of 450 ° C. or lower, and further 420 ° C. or lower, so that the low-temperature firing property and the conductivity of the coated film after sintering are reduced. It is preferable from an excellent point. Here, the 90% thermogravimetric decrease temperature is a value measured by thermogravimetry (TG) as follows. Using a thermogravimetry apparatus (for example, DTG-60A manufactured by Shimadzu Corporation), about 5 mg of a sample is measured under a nitrogen atmosphere. The heating rate is 10 ° C./min, and the temperature is measured from room temperature (23 ° C.) to 600 ° C. In the present invention, the temperature at which 90% is reduced based on the sample weight at room temperature is defined as the 90% thermogravimetric decrease temperature.

The polymer dispersant having one of an amine value and an acid value of 30 to 160 mg KOH / g and the other one of an amine value and an acid value used in the present invention is usually 0 to 160 mg KOH / g. It can be appropriately selected from polymer dispersants used for dispersing colorants.
Examples of the polymer dispersant include (co) polymers of unsaturated carboxylic acid esters such as polyacrylic acid esters; (partial) amine salts of (co) polymers of unsaturated carboxylic acid such as polyacrylic acid , (Partial) ammonium salts and (partial) alkylamine salts; hydroxyl group-containing unsaturated carboxylic acid ester (co) polymers such as hydroxyl group-containing polyacrylates and their modified products; polyurethanes; unsaturated polyamides; Long chain polyaminoamide phosphates; Polyethyleneimine derivatives (amides and their bases obtained by reaction of poly (lower alkyleneimines) with free carboxyl group-containing polyesters); Polyallylamine derivatives (polyallylamine and free radicals) Polyester, polyamide or ester and amide having carboxyl group Compound reaction product obtained by the reaction of one or more compounds selected from the three compounds of (polyester amide)), and the like.

  The polymer dispersant used in the present invention preferably has a polyester skeleton or a polyether skeleton in at least one of the main chain and the side chain. Such a polymer dispersant is excellent in conductivity of the fired film because it is easily decomposed by baking at a low temperature due to its skeletal structure, and organic matter hardly remains.

In the copper nanoparticle dispersion of the present invention, one type of polymer dispersant may be used, or two or more types may be used in combination, and the content depends on the type of copper nanoparticles used. Although it sets suitably according to it, it is usually in the range of 0.1-100 mass parts with respect to 100 mass parts of copper nanoparticles, and is preferably 1-50 mass parts, and is 2-30 mass parts. It is more preferable.
In the copper nanoparticle dispersion of the present invention, the content of the polymer dispersant may be appropriately selected according to the use, but from the viewpoint of dispersibility, coating suitability, and low-temperature firing properties, the copper nanoparticle dispersion It is preferable that it is 0.05-25 mass% with respect to the whole quantity of, and it is still more preferable that it exists in the range of 0.5-15 mass%.
If content of the said polymer dispersing agent is more than the said lower limit, the dispersibility and dispersion stability of a copper nanoparticle dispersion can be made excellent. Moreover, if it is below the said upper limit, it is excellent in the electroconductivity of the film | membrane after baking.

<Solvent>
In the copper nanoparticle dispersion of the present invention, the solvent is not particularly limited as long as it is an organic solvent that does not react with each component in the copper nanoparticle dispersion and can dissolve or disperse them. An organic solvent conventionally used for the copper nanoparticle dispersion may be appropriately selected and used. Among them, as the solvent used in the present invention, MBA (3-methoxybutyl acetate), PGMEA (propylene glycol monomethyl ether acetate), DMDG (diethylene glycol dimethyl ether), diethylene glycol methyl ethyl ether, PGME (propylene glycol monomethyl ether) or these can be used. What mixed is preferable from the point of the solubility of the said polymer dispersing agent, and the applicability | paintability.

  The content of the solvent in the copper nanoparticle dispersion of the present invention is not particularly limited as long as each component of the copper nanoparticle dispersion can be uniformly dissolved or dispersed. In the present invention, the solid content in the copper nanoparticle dispersion is preferably in the range of 5 to 95 mass%, more preferably in the range of 10 to 90 mass%. By being the said range, it can be set as the viscosity suitable for application | coating.

<Other ingredients>
The copper nanoparticle dispersion of the present invention may appropriately contain other known components conventionally used in copper nanoparticle dispersions as needed, as long as the effects of the present invention are not impaired.
Other components include, for example, complexing agents, organic protective agents, reducing agents, surfactants for improving wettability, silane coupling agents for improving adhesion, antifoaming agents, repellency inhibitors, and antioxidants. Agents, anti-aggregation agents, viscosity modifiers, and the like. Moreover, as long as the effect of this invention is not impaired, the other dispersing agent may be contained. Furthermore, a resin binder such as an acrylic resin, a polyester resin, a cellulose resin, and an olefin resin may be added from the viewpoints of film forming property, printability, and dispersibility within a range that does not impair the effects of the present invention.

<Volume average particle diameter of copper nanoparticle dispersion>
The copper nanoparticle dispersion of the present invention has a volume average particle size of 500 nm or less by dynamic light scattering method, and preferably 450 nm or less. Since the copper nanoparticle dispersion of the present invention has such a small dispersed particle size, excellent smoothness and uniformity of the coating film and high density arrangement of the copper nanoparticles in the coating film are realized. To do.
The volume average particle diameter by the dynamic light scattering method in the copper nanoparticle dispersion is a dispersion average particle diameter of copper nanoparticles dispersed in a dispersion medium containing at least a solvent, and is a laser light scattering particle size distribution analyzer. It is measured by. As the measurement of the particle size with a laser light scattering particle size distribution meter, the copper nano particle dispersion is appropriately diluted to a concentration that can be measured with a laser light scattering particle size distribution meter with a solvent used in the copper nano particle dispersion (for example, 1000 times, etc.) and can be measured at 23 ° C. by a dynamic light scattering method using a laser light scattering particle size distribution meter (for example, Nikkiso Nanotrack particle size distribution measuring device UPA-EX150).

<Method for producing copper nanoparticle dispersion>
In this invention, the manufacturing method of a copper nanoparticle dispersion should just be a method in which a copper nanoparticle can disperse | distribute favorably, and can be suitably selected and used from a conventionally well-known method. For example, first, copper nanoparticles to which carboxylic acid and alkylamine are attached are prepared, and the copper nanoparticles are dispersed in the solvent with the above-described polymer dispersant by a conventionally known method.
As a method for preparing copper nanoparticles having carboxylic acid and alkylamine attached thereto, copper nanoparticles produced using carboxylic acid and alkylamine as a protective agent during production may be used, or other protective agents may be used. The copper nanoparticle protective agent produced in this manner may be substituted with a carboxylic acid or an alkylamine by a known method.

Among them, in the present invention, the method for producing a copper nanoparticle dispersion includes a compound containing copper, a reducing compound, a mixture containing a carboxylic acid and an alkylamine, or a copper carboxylate, a reducing compound and an alkylamine. The step of preparing copper nanoparticles by heating any one of the mixtures, and the copper nanoparticles having one of an amine value and an acid value of 30 to 160 mgKOH / g, and the other of the amine value and the acid value of 0 to 0 It is preferable to have the process of preparing the copper nanoparticle dispersion whose volume average particle diameter by a dynamic light-scattering method is 500 nm or less by disperse | distributing in a solvent by the polymer dispersing agent which is 160 mgKOH / g.
In addition, if the compound containing copper, a reducing compound, a carboxylic acid, and a mixture containing an alkylamine or a mixture containing copper carboxylate, a reducing compound, and an alkylamine is the mixture at the time of heating. good.

(Step of preparing copper nanoparticles)
In the step of preparing the copper nanoparticles, a compound containing copper (hereinafter sometimes referred to as a copper-containing compound) is a copper-containing compound capable of forming a complex compound such as a complex with a reducing compound. Used as a metal source for particles. Examples of the copper-containing compound include copper hydroxide, copper oxalate, copper acetate, copper propionate, copper butyrate, copper isobutyrate, copper valerate, copper isovalerate, copper caproate, copper enanthate, and caprylic acid. Copper, copper nonanoate, copper caprate, copper pivalate, copper malonate, copper succinate, copper maleate, copper benzoate, copper citrate, copper tartrate, copper nitrate, copper nitrite, copper sulfite, copper sulfate, Examples include organic acid salts and inorganic acid salts of copper such as copper phosphate, and complex compounds represented by acetylacetonato copper coordinated with acetylacetone.

  When copper carboxylate is not used as the copper-containing compound used as the metal source, it is preferable to use a carboxylate copper such as fatty acid copper by the copper-containing compound other than copper carboxylate and the carboxylic acid. This is because copper carboxylate serves as a carboxylic acid source to be coated on the copper nanoparticles and easily forms a complex compound such as a complex with the reducing compound.

Next, it is preferable that a reducing compound having a reducing action is mixed with the copper carboxylate to produce a composite compound such as a complex of copper and the reducing compound. When copper carboxylate is not used as the copper-containing compound used as the metal source, the composite compound may be generated using a mixture of the copper-containing compound other than copper carboxylate, the reducing compound, and the carboxylic acid. .
As the reducing compound used in this case, for example, the reducing compound described in JP 2012-72418 A can be appropriately selected and used.
Among these, reducing compounds having an amino group such as hydrazine, hydrazine hydrate, hydroxylamine, and derivatives thereof are preferably used.

In addition, when a reduction reaction occurs directly when copper carboxylate and a reducing compound are mixed, it is desirable to suppress the reduction reaction by mixing in a cooled environment. For example, a compound containing copper such as fatty acid copper and a reducing compound are preferably mixed by cooling to 30 ° C. or lower, more preferably 25 ° C. or lower, and most preferably 20 ° C. or lower.
In addition, with respect to copper carboxylate, a reducing compound having a reducing action is mixed to form a complex compound such as a complex of copper and a reducing compound, for example, refer to JP 2012-72418 A It can be selected appropriately.

In the step of preparing the copper nanoparticles in the present invention, the mixture of the copper carboxylate and the reducing compound produced above is mixed with a sufficient amount of alkylamine and heated to spontaneously decompose the copper carboxylate. It is preferable to obtain copper nanoparticles by forming and aggregating copper atoms. At this time, since the surface of the copper nanoparticles is coated with a carboxylic acid and an alkylamine, stable coated copper nanoparticles that are hardly oxidized by oxidation in the air can be obtained. By adjusting the molecular weight of carboxylic acid or alkylamine, it is possible to adjust the primary particle size of the produced copper nanoparticles to a desired size.
The mixing ratio of the alkylamine to the mixture of the copper carboxylate and the reducing compound may be appropriately selected according to the use, but from the viewpoint of oxidation resistance and low-temperature calcination, it is based on 1 mol of the copper carboxylate. It is preferably 1 to 10 mol, and more preferably in the range of 2 to 6 mol.

A step of preparing copper nanoparticles by heating either a compound containing copper, a reducing compound, a carboxylic acid, and a mixture containing an alkylamine, or a mixture containing copper carboxylate, a reducing compound, and an alkylamine. In the embodiment, a first step of preparing a complex compound such as a complex by mixing a compound containing copper, a reducing compound and a carboxylic acid, or mixing a copper carboxylate and a reducing compound, and the complex The second step of heating a complex compound such as alkylamine in the presence of an alkylamine to produce copper nanoparticles can be performed simultaneously or sequentially in one container. Preferably, after adding a polar solvent thereto and solubilizing it, copper nanoparticles can be produced by heating. The heating temperature in the presence of alkylamine is preferably 60 ° C to 150 ° C.
When preparing copper nanoparticles, it is preferable to sequentially perform the first step and the second step, the first step is performed by cooling to about 30 ° C. or less, and the second step It is preferable that the process is performed by heating to 60 ° C to 150 ° C.

(Process for preparing a dispersion)
A copper nanoparticle dispersion having a volume average particle size of 500 nm or less by dynamic light scattering method is prepared by dispersing the copper nanoparticles obtained in the preparation step with the specific polymer dispersant in a solvent. To do.
For example, after the specific polymer dispersant is mixed and stirred in the solvent to prepare a polymer dispersant solution, the polymer dispersant solution is mixed with the copper nanoparticles obtained in the preparation step, as necessary. Accordingly, a copper nanoparticle dispersion can be prepared by mixing other components and dispersing them using a known stirrer or disperser.

The copper nanoparticle dispersion obtained in the present invention is preferably used for a conductive substrate described later, and particularly preferably for conductive pattern printing. Since the copper nanoparticle dispersion of the present invention can be fired at a low temperature and in a short time, it is suitably used for low-temperature or short-time firing applications such as plasma firing and flash light firing described later.
The copper nanoparticle dispersion obtained in the present invention can be further applied to a seed layer for plating and various metal films, and can be used, for example, for mirror surfaces for optical devices and various decoration applications.

[Method of manufacturing conductive substrate]
The method for producing a conductive substrate according to the first aspect of the present invention includes a copper nanoparticle, a carboxylic acid, an alkylamine, and one of an amine value and an acid value of 30 to 160 mgKOH / g, an amine value and an acid value. A copper nanoparticle dispersion containing a polymer dispersant, the other of which is 0 to 160 mg KOH / g, and a solvent and having a volume average particle diameter of 500 nm or less by dynamic light scattering method is applied onto a substrate. And a step of forming a coating film and a step of baking the coating film.
Moreover, the manufacturing method of the electroconductive board | substrate of the 2nd aspect which concerns on this invention is a compound containing copper, a reducing compound, carboxylic acid, and the mixture containing an alkylamine, or copper carboxylate, a reducing compound, and alkyl. A step of preparing copper nanoparticles by heating any one of a mixture containing an amine; and the copper nanoparticles having an amine value and an acid value of 30 to 160 mgKOH / g, an amine value and an acid value in a solvent. A step of preparing a copper nanoparticle dispersion having a volume average particle diameter of 500 nm or less by a dynamic light scattering method by dispersing with a polymer dispersant in which the other is 0 to 160 mgKOH / g; It has the process of apply | coating a particle dispersion on a base material, forming a coating film, and the process of baking the said coating film.

  According to the method for producing a conductive substrate of the present invention, as described above, copper nanoparticles having a small dispersed particle diameter, excellent in oxidation resistance, dispersibility, applicability, and sintering property at low temperature or in a short time. Since the dispersion is used, it is possible to form a smooth and highly uniform coating film in which copper nanoparticles whose oxidation is suppressed are present uniformly and at a high density. As a result, a conductive substrate having good pattern accuracy and excellent conductivity after sintering can be obtained.

FIG. 1 is a schematic view showing an example of a conductive substrate obtained by the production method of the present invention. A conductive substrate 100 shown in FIG. 1 includes a metal film 2 formed on one surface of a base material 1 by baking a coating film of a copper nanoparticle dispersion.
FIG. 2 is a schematic view showing another example of a conductive substrate obtained by the production method of the present invention. A conductive substrate 101 shown in FIG. 2 is provided with a patterned metal film 3 on both surfaces of a base material 1 by baking a coating film of a copper nanoparticle dispersion.
As described above, the conductive substrate obtained by the production method of the present invention may be provided with a metal film obtained by firing a coating film of a copper nanoparticle dispersion only on one surface of a base material. Further, a metal film obtained by firing a coating film of a copper nanoparticle dispersion on both surfaces of a base material may be used. In addition, the metal film provided on only one surface of the base material and the metal film provided on both surfaces of the base material are each a solid metal film having no pattern even if it is a patterned metal film. There may be. Furthermore, the metal film provided on both surfaces of the base material may be a metal film having one surface that is a patterned metal film and the other surface that is a solid film. Moreover, when the metal film provided on both surfaces of the substrate is a patterned metal film on both surfaces, the patterns on both surfaces may be the same or different. Further, when the patterned metal films provided on both surfaces of the substrate have the same pattern, the patterns on both surfaces may be at the same position or at different positions on both surfaces.

In the method for producing a conductive substrate according to the first aspect of the present invention, a step of preparing a copper nanoparticle dispersion, and a compound containing copper in the method for producing a conductive substrate according to the second aspect of the present invention, A step of preparing copper nanoparticles by heating either a mixture containing a reducing compound, a carboxylic acid and an alkylamine, or a mixture containing copper carboxylate, a reducing compound and an alkylamine; A step of preparing a copper nanoparticle dispersion having a volume average particle diameter of 500 nm or less by a dynamic light scattering method by dispersing particles in a solvent with a polymer dispersant having the specific amine value and acid value. Since it may be the same as the step of preparing the copper nanoparticles and the step of preparing the copper nanoparticle dispersion described above, the description thereof is omitted here.
Hereafter, each process of the process of forming a coating film and the process of baking the said coating film which are common to a 1st aspect and a 2nd aspect is demonstrated in order.
In addition, the manufacturing method of the said electroconductive board | substrate which concerns on this invention may have another process as needed, unless the effect of this invention is impaired.

<The process of apply | coating a copper nanoparticle dispersion | distribution on a base material, and forming a coating film>
(Base material)
What is necessary is just to select the base material used for this invention suitably from the base materials used for an electroconductive board | substrate according to a use. For example, inorganic materials such as glass, alumina, silica, and SUS foil can be used, and polymer materials and paper can also be used. Since the metal fine particle dispersion for conductive substrate according to the present invention can obtain a metal film having excellent conductivity even when fired at a lower temperature than before, soda lime glass, which has been difficult to apply conventionally, Even molecular materials can be suitably used, and are particularly useful in that a resin film can be used.

  Examples of the resin film include polyimide, polyamide, polyamideimide, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyphenylene sulfide, polyether ether ketone, polyether sulfone, polycarbonate, polyether imide, epoxy resin, and phenol resin. , Glass-epoxy resins, polyphenylene ethers, acrylic resins, polyolefins such as polyethylene and polypropylene, polycycloolefins such as polynorbornene, and liquid crystalline polymer compounds. In particular, in the present invention, a resin film having a glass transition temperature of 100 ° C. or less, such as PET, can be used. In addition, the glass transition temperature here is based on the differential scanning calorimetry (DSC) measurement measured according to JIS-K7121.

  In addition, on the surface of the base material, when the coating film of the copper nanoparticle dispersion is formed in a pattern, the shape of the pattern is controlled, or adhesion between the coating film of the copper nanoparticle dispersion is given. You may perform the process for doing. The treatment method for the substrate surface can be appropriately selected from conventionally known methods. Specifically, for example, corona treatment, UV treatment, vacuum ultraviolet lamp treatment, dry treatment such as plasma treatment, amine silane coupling agent, imidazole silane coupling agent, titanium coupling agent, aluminum coupling agent treatment, etc. Chemical layer treatment, porous silica, porous membrane formation treatment such as cellulose-based receiving layer, active energy ray curable resin layer, thermosetting resin layer, thermoplastic resin layer and other resin layer formation treatment . By providing the substrate surface with liquid repellency by this treatment, when the coating film of copper nanoparticle dispersion is formed in a pattern on the substrate, wetting spread of the coating solution is suppressed and a high-definition pattern is formed Is possible. In addition, by forming an ink receiving layer such as a porous film on the surface of the substrate, it is possible to penetrate the solvent component and form a high-definition pattern. On the contrary, the applicability | paintability with respect to a base material can be improved by giving lyophilic property to the base-material surface. These treatments on the surface of the substrate can be used properly according to the purpose and purpose.

  What is necessary is just to select the shape of the said base material suitably according to a use, and although it may be flat form or may have a curved surface, it is usually flat form. In the case of using a flat substrate, the thickness of the substrate may be appropriately set according to the application, and may be, for example, about 10 μm to 1 mm.

(Application method)
The method for applying the copper nanoparticle dispersion onto the substrate may be appropriately selected from conventionally known application or printing methods. Among these, gravure printing, gravure offset printing, reverse offset printing, flexographic printing, screen printing, and ink jet printing are preferable because fine patterning can be performed when printing a conductive pattern. Alternatively, the coating method includes a case where the entire surface is coated. In the case of whole surface application, a pattern can be formed by a chemical etching method as described later on a copper nanoparticle sintered film obtained by baking the coating film.

  The copper nanoparticle dispersion on the substrate may be dried by a usual method after coating. The film thickness of the coated film after drying can be controlled by appropriately changing the coating amount, the average primary particle diameter of the copper nanoparticles, etc., and may be appropriately adjusted according to the application, but is usually 0. The range is 0.01 to 50 μm, and preferably 0.1 to 20 μm.

<Step of baking the coating film>
This step is a step of forming a metal film by baking the coating film obtained in the above step to form a sintered film.
The firing method can be appropriately selected from conventionally known firing methods. Specific examples of the firing method include, for example, methods such as heating by a firing furnace (oven), infrared heating, various laser annealing, ultraviolet light, visible light, light irradiation firing with flash light, microwave heating, and the like. In addition, it is preferably performed in an inert gas atmosphere or a reducing gas atmosphere. In the case of an air atmosphere, it is preferable that heating is performed instantaneously in order to prevent oxidation during firing.
Since the copper nanoparticle dispersion of the present invention can be fired at a low temperature or in a short time, it can be fired at a lower temperature than the conventional method.

In the present invention, in particular, the firing step is plasma firing, in particular, firing by surface wave plasma generated by application of microwave energy, or firing by flash light irradiation (hereinafter referred to as flash light firing). It is preferable that any one of the above.
When these methods are used, thermal damage to the substrate can be reduced, and oxidation of the metal during firing can be suppressed. Moreover, since it is baking for a short time, there also exists a merit that productivity is high.

(Plasma firing)
Firing using microwave surface wave plasma is preferably performed in an inert gas atmosphere or a reducing gas atmosphere from the viewpoint of the conductivity of the obtained sintered film.
In particular, in the present invention, the microwave surface wave plasma is preferably generated in a reducing gas atmosphere, and more preferably generated in a hydrogen gas atmosphere. Thereby, the insulating oxide which exists in the copper nanoparticle surface is reduced and removed, and the conductive pattern with favorable conductive performance is formed.

  Prior to microwave surface wave plasma treatment, in order to remove organic substances such as alkylamines, carboxylic acids, polymer dispersants, etc. contained in the coating film coated with copper nanoparticle dispersion, in the atmosphere or in an atmosphere containing oxygen Further, it may be fired for about 1 minute to 2 hours at a temperature of about 50 to 200 ° C. This treatment may be performed under reduced pressure. By this firing, organic substances are oxidatively decomposed and removed, and the sintering of the copper nanoparticles is promoted in the microwave surface wave plasma treatment.

  The generation method of the microwave surface wave plasma may be appropriately selected from conventionally known methods. For example, the method described in International Publication No. 2011/040189 pamphlet can be used.

(Flash light firing)
Flash light firing is a method of firing in an extremely short time by irradiation with flash light. Here, in the present invention, flash light refers to light having a relatively short lighting time, and the lighting time is referred to as a pulse width. The light source of the flash light is not particularly limited, and examples thereof include a flash lamp and a laser in which a rare gas such as xenon is sealed. Among them, it is preferable to irradiate light having a continuous wavelength spectrum from ultraviolet to infrared, and specifically, a xenon flash lamp is preferably used. When such a light source is used, the same effect as when UV irradiation is performed simultaneously with heating can be obtained, and baking can be performed in an extremely short time. In addition, when such a light source is used, by controlling the pulse width and irradiation energy, only the coating film of the copper nanoparticle dispersion and its vicinity can be heated, and the influence of heat on the substrate Can be suppressed. In particular, the polymer dispersant used in the present invention is uniformly present around the copper nanoparticles due to a synergistic effect with the alkylamine and carboxylic acid, and therefore easily decomposes or volatilizes by irradiation with flash light. Since it is easy and hardly remains on the metal film, it can be easily sintered even by irradiation with flash light for a very short time. Therefore, flash light baking is preferably used in the present invention.

In the present invention, the pulse width of the flash light may be appropriately adjusted, but is preferably set between 1 μs and 10,000 μs, and more preferably within the range of 10 μs to 5000 μs. The irradiation energy per one flash light is ^{preferably 0.1J / cm 2 ~100J / cm 2} , 0.5J / cm 2 ~50J / cm 2 is more preferable.
In flash light firing, the number of times of flash light irradiation may be appropriately adjusted according to the composition, film thickness, area, etc. of the coating film, and the number of times of irradiation may be only once or may be repeated two or more times. Good. Especially, it is preferable to set the frequency | count of irradiation to 1-100 times, and it is preferable to set it as 1-50 times. When the flash light is irradiated a plurality of times, the irradiation interval of the flash light may be adjusted as appropriate. In particular, the irradiation interval is preferably set within a range of 10 μsec to 2 seconds, and more preferably set within a range of 100 μsec to 1 second.
By setting the flash light as described above, it is possible to suppress the influence on the base material and to suppress the oxidation of the copper nanoparticles, and the alkylamine and carboxylic acid contained in the copper nanoparticle dispersion The above-described polymer dispersant can be easily detached or decomposed to obtain a conductive substrate having excellent conductivity.

Such flash light baking can heat only the coating film of the copper nanoparticle dispersion and its vicinity, and can burn the coating film at a low temperature and in a short time. A nanoparticle sintered film can be formed. In the flash light firing, the heating temperature and the processing depth can be controlled by appropriately adjusting the pulse width and irradiation energy of the flash light. As a result, a non-uniform film is rarely formed and grain growth can be prevented, so that a very dense and smooth film can be obtained. Moreover, since baking is possible in a very short time, the oxidation of copper nanoparticles can be suppressed, and a sintered film having excellent conductivity can be obtained.
The flash light baking can be performed in the atmosphere at atmospheric pressure, but may be performed in an inert gas atmosphere, a reducing gas atmosphere, or a reduced pressure. Moreover, you may perform flash light baking, heating a coating film.

The thickness of the metal film of the conductive substrate thus obtained may be appropriately adjusted according to the use, but the thickness is usually about 0.01 to 50 μm, and 0.05 to 30 μm. It is preferable that the thickness is 0.1 to 20 μm.
The volume resistivity of the metal film is preferably 1.0 × 10 ⁻⁴ Ω · cm or less.

  In addition, the sintered film obtained using the copper nanoparticle dispersion of the present invention has a smooth surface and low resistance, and is less likely to generate voids at the interface with the substrate, and has good adhesion. And it has a moderate space | gap. Conventionally, it has been difficult to obtain a sintered film having a smooth surface, low resistance, and appropriate voids, and it has been difficult to form a pattern by chemical etching. However, the sintered film obtained by using the copper nanoparticle dispersion of the present invention can also form fine wiring by further chemically etching after forming the sintered film by the entire surface coating as described above. Is suitable.

  Pattern formation by chemical etching is performed by applying a photoresist or laminating a dry film resist to a sintered film formed on the entire surface to form a photoresist layer, and then exposing and developing by a photolithography method using a photomask. After the pattern is formed, etching with ferric chloride, cupric chloride, phosphorous nitric acid or the like is performed, and the remaining resist is peeled off to form a patterned metal film.

Moreover, the manufacturing method of the present invention is a pattern in which a copper nanoparticle dispersion is applied in a pattern on a substrate to form a coating film, and the coating film is baked to form a patterned metal film. It may be a method for manufacturing a conductive substrate.
The conductive substrate obtained by the method for producing a conductive substrate of the present invention has good pattern accuracy and excellent conductivity. An electronic member using such a conductive substrate can be effectively used for an electromagnetic wave shielding film having a low surface resistance, a conductive film, a flexible printed wiring board, and the like.

Hereinafter, the present invention will be specifically described with reference to examples. These descriptions do not limit the present invention.
Example 1
(1) Synthesis of copper nanoparticles In a 200 ml three-necked flask, 10.0 g of copper hydroxide (0.1 mol, manufactured by Wako Pure Chemical Industries), 31.5 g of nonanoic acid (0.2 mol, manufactured by Tokyo Chemical Industry, boiling point) 254 ° C.) and 18.5 g (20 ml, manufactured by Kanto Chemical) of propylene glycol monomethyl ether (PGME). The mixture was heated to 100 ° C. with stirring and the temperature was maintained for 20 minutes. Thereafter, 40.5 g of hexylamine (0.4 mol, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point: 130 ° C.) was added, and the mixture was heated and stirred at 100 ° C. for 10 minutes. After cooling this mixed solution to 10 ° C. using an ice bath, 10.0 g (0.2 mol, manufactured by Kanto Chemical Co., Ltd.) of hydrazine monohydrate and 18.5 g of PGME (20 ml, manufactured by Kanto Chemical Co., Ltd.) were used in the ice bath. The solution dissolved in was added and stirred for 10 minutes. Thereafter, the reaction solution was heated to 100 ° C., and the temperature was maintained for 10 minutes. After cooling to 30 ° C., 33 g of hexane (50 ml, manufactured by Kanto Chemical Co., Inc.) was added. After centrifugation, the supernatant was removed. The precipitate was washed with hexane to obtain copper nanoparticles coated with nonanoic acid and hexylamine.

When the obtained copper nanoparticles were observed with a transmission electron microscope (TEM), the average primary particle size was 39 nm. Specifically, the obtained copper nanoparticles were dispersed in toluene, and this was dropped onto a TEM substrate (manufactured by Hitachi High-Tech Fielding Co., Ltd., Cu grid with elastic carbon support film) and dried to prepare a sample for observation. The particle image was measured with TEM (H-7650 manufactured by Hitachi High-Tech), and the average value of the length of the longest part of 100 randomly selected primary particles was defined as the average primary particle size.
Moreover, when the crystal structure of the copper nanoparticle obtained by the X-ray diffractometer was measured, the main structure of the copper nanoparticle was Cu (Cubic), and a part of Cu ₂ O (Cubic) structure was observed, and Cu (111) The peak intensity of Cu ₂ O (111) relative to was about 3%.

(2) Preparation of copper nanoparticle dispersion 3.0 parts by mass of copper nanoparticles coated with nonanoic acid and hexylamine obtained above, Solsperse 41000 (manufactured by Nippon Lubrizol, acid value 50 mgKOH / g, amine value 0 mgKOH / G, weight average molecular weight 3500, 90% thermogravimetric reduction temperature is 370.4 ° C.) 0.3 parts by mass and 4.2 parts by mass of PGME are mixed, and 2 mm zirconia is preliminarily dispersed in a paint shaker (manufactured by Asada Tekko). Dispersion was carried out for 1 hour with beads and further for 2 hours with 0.1 mm zirconia beads as the main dispersion to obtain a copper nanoparticle dispersion 1.

(3) Production of conductive substrate by plasma firing The copper nanoparticle dispersion 1 is applied to a PET film (Cosmo Shine A4100) having a thickness of 100 μm with a wire bar and dried to form a coating film having a thickness of 0.5 μm. It was.
Then, while introducing hydrogen gas at an introduction pressure of 20 Pa, using a microwave surface wave plasma processing apparatus (MSP-1500, manufactured by Microelectronics), firing was performed at a microwave output of 450 W for 300 seconds to obtain a conductive substrate.

(4) Production of conductive substrate by flash light baking The copper nanoparticle dispersion 1 is applied to a PET film (Cosmo Shine A4100) having a thickness of 100 μm with a wire bar and dried to obtain a coating having a thickness of 0.5 μm. A membrane was obtained.
Thereafter, using a pulsed xenon lamp device (SINTERON 2000 (manufactured by Xenon Corporation)), irradiation was performed once with a pulse width of 500 μsec and an applied voltage of 3.7 kV to obtain a conductive substrate.

(Example 2)
In Example 1, (2), instead of Solsperse 41000, Solsperse 53095 (manufactured by Nippon Lubrizol, acid value 47 mgKOH / g, amine value 0 mgKOH / g, weight average molecular weight 3900, 90% thermogravimetric decrease temperature is 360.7. C.) was used in the same manner as (2) of Example 1 except that the copper nanoparticle dispersion 2 was obtained.
Using the obtained copper nanoparticle dispersion 2, a conductive substrate was produced by plasma firing in the same manner as (3) of Example 1.
Using the obtained copper nanoparticle dispersion 2, a conductive substrate was produced by flash light baking in the same manner as in (4) of Example 1.

(Reference Example 3)
In Example 1 (2), instead of Solsperse 41000, Solsperse 71000 (manufactured by Nippon Lubrizol, acid value 0 mgKOH / g, amine value 77.4 mgKOH / g, weight average molecular weight 4700, 90% thermogravimetric reduction temperature is 405. .9 ° C) was used in the same manner as (2) of Example 1 to obtain a copper nanoparticle dispersion 3.
Using the obtained copper nanoparticle dispersion 3, a conductive substrate was produced by plasma firing in the same manner as (3) of Example 1.
Using the obtained copper nanoparticle dispersion 3, a conductive substrate was produced by flash light baking in the same manner as in (4) of Example 1.

Example 4
In Example 1, (2), instead of Solsperse 41000, Disper byk-111 (manufactured by Big Chemie Japan, acid value 129 mgKOH / g, amine value 0 mgKOH / g, weight average molecular weight 1700, 90% thermogravimetric decrease temperature is 320. .4 ° C.) was used in the same manner as (2) of Example 1 to obtain a copper nanoparticle dispersion 4.
Using the obtained copper nanoparticle dispersion 4, a conductive substrate was produced by plasma firing in the same manner as (3) of Example 1.
Using the obtained copper nanoparticle dispersion 4, a conductive substrate was produced by flash light baking in the same manner as in Example 1 (4).

(Example 5)
In Example 1 (2), instead of Solsperse 41000, Disper byk-145 (manufactured by Big Chemie Japan, acid value 76 mgKOH / g, amine value 71 mgKOH / g, weight average molecular weight 1800, 90% thermogravimetric decrease temperature is 378 .2 ° C.) was used in the same manner as (2) of Example 1 to obtain a copper nanoparticle dispersion 5.
Using the obtained copper nanoparticle dispersion 5, a conductive substrate was produced by plasma firing in the same manner as in (1) of Example 1.
Using the obtained copper nanoparticle dispersion 5, a conductive substrate was produced by flash light baking in the same manner as in Example 1 (4).

(Example 6)
In Example 1 (2), instead of Solsperse 41000, Disper byk-180 (manufactured by BYK Japan, acid value 94 mgKOH / g, amine value 94 mgKOH / g, THF-soluble matter weight average molecular weight 1000, 90% heat A copper nanoparticle dispersion 6 was obtained in the same manner as (2) of Example 1 except that the weight reduction temperature was 350.2 ° C.
Using the obtained copper nanoparticle dispersion 6, a conductive substrate was produced by plasma firing in the same manner as in (1) of Example 1.
Using the obtained copper nanoparticle dispersion 6, a conductive substrate was produced by flash light baking in the same manner as in Example 1 (4).

(Example 7)
(1) Synthesis of copper nanoparticles In Example 1, instead of 40.5 g (0.4 mol) of hexylamine, 35.7 g of 3-methoxypropylamine (0.4 mol, manufactured by Guangei Chemical Industry Co., Ltd., boiling point 116 ° C.) was used. Except having used, it carried out similarly to Example 1, and obtained the copper nanoparticle coat | covered with nonanoic acid and 3-methoxypropylamine.

When the obtained copper nanoparticles were observed with a transmission electron microscope (TEM) in the same manner as in Example 1, the average primary particle size was 65 nm.
Moreover, when the crystal structure of the copper nanoparticle obtained by the X-ray diffractometer was measured, the main structure of the copper nanoparticle was Cu (Cubic), and a part of Cu ₂ O (Cubic) structure was observed, and Cu (111) The peak intensity of Cu ₂ O (111) relative to was about 1%.

(2) Preparation of copper nanoparticle dispersion Copper nanoparticle was prepared in the same manner as in (2) of Example 1 except that the copper nanoparticle coated with nonanoic acid and 3-methoxypropylamine obtained above was used. A particle dispersion 7 was obtained.

(3) Production of conductive substrate by plasma firing Using the obtained copper nanoparticle dispersion 7, a conductive substrate was produced by plasma firing in the same manner as in (1) of Example 1.
(4) Production of conductive substrate by flash light firing Using the obtained copper nanoparticle dispersion 7, a conductive substrate was produced by flash light firing in the same manner as in (4) of Example 1.

(Reference Example 8)
(1) Synthesis of copper nanoparticles In Example 1, instead of 40.5 g (0.4 mol) of hexylamine, 41.3 g of 3-ethoxypropylamine (0.4 mol, manufactured by Guangei Chemical Industry Co., Ltd., boiling point 135 ° C.) was used. In the same manner as in Example 1 except that 63.0 g (100 ml) of hexane was added instead of adding 33.0 g (50 ml) of hexane, copper nano-particles coated with nonanoic acid and 3-ethoxypropylamine were used. Particles were obtained.

When the obtained copper nanoparticles were observed with a transmission electron microscope (TEM) in the same manner as in Example 1, the average primary particle size was 65 nm.
Moreover, when the crystal structure of the copper nanoparticle obtained by the X-ray diffractometer was measured, the main structure of the copper nanoparticle was Cu (Cubic), and a part of Cu ₂ O (Cubic) structure was observed, and Cu (111) The peak intensity of Cu ₂ O (111) relative to was about 5%.

(2) Preparation of copper nanoparticle dispersion In (2) of Example 1, the copper nanoparticles coated with nonanoic acid and 3-ethoxypropylamine obtained above were used as the copper nanoparticles, and instead of Solsperse 41000 In addition, Solsperse 71000 (manufactured by Nippon Lubrizol, acid value 0 mgKOH / g, amine value 77.4 mgKOH / g, weight average molecular weight 4700, 90% thermogravimetric decrease temperature is 405.9 ° C.) is used. In the same manner as (2), a copper nanoparticle dispersion 8 was obtained.

(3) Production of conductive substrate by plasma firing Using the obtained copper nanoparticle dispersion 8, a conductive substrate was produced by plasma firing in the same manner as (3) of Example 1.
(4) Production of conductive substrate by flash light firing Using the obtained copper nanoparticle dispersion 8, a conductive substrate was produced by flash light firing in the same manner as in (4) of Example 1.

Example 9
(1) Synthesis of copper nanoparticles In Reference Example 8, instead of 31.5 g (0.2 mol) of nonanoic acid, 34.5 g of decanoic acid (0.2 mol, Kao Lunak 10-98, boiling point 268 ° C.) was used. Except for the above, copper nanoparticles coated with decanoic acid and 3-ethoxypropylamine were obtained in the same manner as in Reference Example 8.

When the obtained copper nanoparticles were observed with a transmission electron microscope (TEM) in the same manner as in Example 1, the average primary particle size was 48 nm.
Moreover, when the crystal structure of the copper nanoparticle obtained by the X-ray diffractometer was measured, the main structure of the copper nanoparticle was Cu (Cubic), and a part of Cu ₂ O (Cubic) structure was observed, and Cu (111) The peak intensity of Cu ₂ O (111) relative to was about 7%.

(2) Preparation of copper nanoparticle dispersion Copper nanoparticle was prepared in the same manner as (2) of Example 1 except that the copper nanoparticles coated with decanoic acid and 3-ethoxypropylamine obtained above were used. A particle dispersion 9 was obtained.

(3) Production of conductive substrate by plasma firing Using the obtained copper nanoparticle dispersion 9, a conductive substrate was produced by plasma firing in the same manner as in (1) of Example 1.
(4) Production of conductive substrate by flash light firing Using the obtained copper nanoparticle dispersion 9, a conductive substrate was produced by flash light firing in the same manner as in (4) of Example 1.

(Reference Example 10)
In Example 1 (2), copper nanoparticles coated with decanoic acid and 3-ethoxypropylamine obtained in the same manner as in Example 9 (1) were used as copper nanoparticles, instead of Solsperse 41000. In addition, Solsperse 71000 (manufactured by Nippon Lubrizol, acid value 0 mgKOH / g, amine value 77.4 mgKOH / g, weight average molecular weight 4700, 90% thermogravimetric decrease temperature is 405.9 ° C.) is used. In the same manner as (2), a copper nanoparticle dispersion 10 was obtained.
Using the obtained copper nanoparticle dispersion 10, a conductive substrate was produced by plasma firing in the same manner as (3) of Example 1.
Using the obtained copper nanoparticle dispersion 10, a conductive substrate was produced by flash light baking in the same manner as in (4) of Example 1.

(Example 11)
In Example 1 (2), copper nanoparticles coated with decanoic acid and 3-ethoxypropylamine obtained in the same manner as in Example 9 (1) were used as copper nanoparticles, instead of Solsperse 41000. In addition, Disper byk-102 (manufactured by Big Chemie Japan, acid value 101 mgKOH / g, amine value 0 mgKOH / g, weight average molecular weight 1400, 90% thermogravimetric decrease temperature is 327.5 ° C.) In the same manner as (2), a copper nanoparticle dispersion 11 was obtained.
Using the obtained copper nanoparticle dispersion 11, a conductive substrate was produced by plasma firing in the same manner as in (1) of Example 1.
Using the obtained copper nanoparticle dispersion 11, a conductive substrate was produced by flash light baking in the same manner as in Example 1 (4).

(Example 12)
In Example 1 (2), copper nanoparticles coated with decanoic acid and 3-ethoxypropylamine obtained in the same manner as in Example 9 (1) were used as copper nanoparticles, instead of Solsperse 41000. Example 1 except that Disper byk-106 (manufactured by Big Chemie Japan, acid value 132 mgKOH / g, amine value 74 mgKOH / g, weight average molecular weight 1400, 90% thermogravimetric decrease temperature is 405.3 ° C.) was used. In the same manner as (2), a copper nanoparticle dispersion 12 was obtained.
Using the obtained copper nanoparticle dispersion 12, a conductive substrate was produced by plasma firing in the same manner as in (1) of Example 1.
Using the obtained copper nanoparticle dispersion 12, a conductive substrate was produced by flash light baking in the same manner as in (4) of Example 1.

(Example 13)
In Example 1 (2), copper nanoparticles coated with decanoic acid and 3-ethoxypropylamine obtained in the same manner as in Example 9 (1) were used as copper nanoparticles, instead of Solsperse 41000. In addition, Disper byk-111 (manufactured by Big Chemie Japan, acid value 129 mg KOH / g, amine value 0 mg KOH / g, weight average molecular weight 1700, 90% thermogravimetric decrease temperature is 320.4 ° C.) In the same manner as (2), a copper nanoparticle dispersion 13 was obtained.
Using the obtained copper nanoparticle dispersion 13, a conductive substrate was produced by plasma firing in the same manner as (3) of Example 1.
Using the obtained copper nanoparticle dispersion 13, a conductive substrate was produced by flash light baking in the same manner as in Example 1 (4).

(Reference Example 14)
(1) Synthesis of copper nanoparticles In Example 1, instead of hexylamine 40.5 g (0.4 mol), 40.9 g of dimethylaminopropylamine (0.4 mol, manufactured by Guangei Chemical Industry Co., Ltd., boiling point 135 ° C.) was used. Except for the above, copper nanoparticles coated with nonanoic acid and dimethylaminopropylamine were obtained in the same manner as in Example 1.

When the obtained copper nanoparticles were observed with a transmission electron microscope (TEM) in the same manner as in Example 1, the average primary particle size was 64 nm.
Moreover, when the crystal structure of the copper nanoparticle obtained by the X-ray diffractometer was measured, the main structure of the copper nanoparticle was Cu (Cubic), and a part of Cu ₂ O (Cubic) structure was observed, and Cu (111) The peak intensity of Cu ₂ O (111) relative to was about 1%.

(2) Preparation of Copper Nanoparticle Dispersion Using the copper nanoparticle coated with nonanoic acid and dimethylaminopropylamine obtained above, Solsperse 71000 (manufactured by Nippon Lubrizol, acid value 0 mgKOH / g, amine value 77.4 mgKOH / g, weight average molecular weight 4700, 90% thermogravimetric reduction temperature is 405.9 ° C.) 14 was obtained.

(3) Production of conductive substrate by plasma firing Using the obtained copper nanoparticle dispersion 14, a conductive substrate was produced by plasma firing in the same manner as (3) of Example 1.
(4) Production of conductive substrate by flash light firing Using the obtained copper nanoparticle dispersion 14, a conductive substrate was produced by flash light firing in the same manner as in (4) of Example 1.

(Reference Example 15)
(1) Synthesis of copper nanoparticles In Example 1, instead of 31.5 g (0.2 mol) of nonanoic acid, 28.2 g of oleic acid (0.1 mol, manufactured by Kanto Chemical Co., Ltd., boiling point: 360 ° C.) was used, and hexylamine was used. Instead of 40.5 g (0.4 mol), oleic acid and octylamine were obtained in the same manner as in Example 1 except that 51.7 g (0.4 mol, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point: 176 ° C.) was used. Copper nanoparticles coated with were obtained.

When the obtained copper nanoparticles were observed with a transmission electron microscope (TEM) in the same manner as in Example 1, the average primary particle size was 28 nm.
Moreover, when the crystal structure of the copper nanoparticle obtained by the X-ray diffractometer was measured, the main structure of the copper nanoparticle was Cu (Cubic), and a part of Cu ₂ O (Cubic) structure was observed, and Cu (111) The peak intensity of Cu ₂ O (111) relative to was about 12%.

(2) Preparation of Copper Nanoparticle Dispersion Using the copper nanoparticles coated with oleic acid and octylamine obtained above, instead of Solsperse 41000, Solsperse 71000 (manufactured by Nippon Lubrizol, acid value 0 mgKOH / g, The copper nanoparticle dispersion 15 was prepared in the same manner as (2) of Example 1 except that an amine value of 77.4 mgKOH / g, a weight average molecular weight of 4700, and a 90% thermogravimetric decrease temperature of 405.9 ° C. were used. Obtained.

(3) Production of conductive substrate by plasma firing Using the obtained copper nanoparticle dispersion 15, a conductive substrate was produced by plasma firing in the same manner as (3) of Example 1.
(4) Production of conductive substrate by flash light firing Using the obtained copper nanoparticle dispersion 15, a conductive substrate was produced by flash light firing in the same manner as in (4) of Example 1.

(Comparative Example 1)
The nonanoic acid obtained in the same manner as in Example 1 (1) and copper nanoparticles coated with hexylamine (3.0 parts by mass) and PGME (4.5 parts by mass) were mixed, and a paint shaker (manufactured by Asada Tekko) was mixed. Then, 2 mm zirconia beads were preliminarily dispersed for 1 hour, and 0.1 mm zirconia beads were further dispersed for 2 hours as the main dispersion. However, the copper nanoparticles were not aggregated and dispersed, and a copper nanoparticle dispersion could not be obtained.

(Comparative Example 2)
In the same manner as in Example 1 (1), copper nanoparticles coated with nonanoic acid and hexylamine were obtained.
The copper nanoparticles in Example 2 (2), instead of Solsperse 41000, Solsperse 16000 (manufactured by Nippon Lubrizol, acid value 20 mgKOH / g, amine value 0 mgKOH / g, weight average molecular weight 4200, 90% thermogravimetric weight) Dispersion was carried out in the same manner as in (2) of Example 1 except that the reduction temperature was 405.5 ° C. However, the copper nanoparticles were not aggregated and dispersed, and a copper nanoparticle dispersion could not be obtained.

(Comparative Example 3)
In the same manner as in Example 1 (1), copper nanoparticles coated with nonanoic acid and hexylamine were obtained.
In Example 1 (2), instead of Solsperse 41000, the copper nanoparticles were Solsperse 76500 (manufactured by Nippon Lubrizol, acid value 0 mgKOH / g, amine value 15.2 mgKOH / g, 90% thermogravimetric decrease temperature) Dispersion was carried out in the same manner as (2) of Example 1 except that over 600 ° C. (32% remaining even at 600 ° C.) was used. However, the copper nanoparticles were not aggregated and dispersed, and a copper nanoparticle dispersion could not be obtained.

(Comparative Example 4)
In the same manner as in Example 9, (1), copper nanoparticles coated with decanoic acid and 3-ethoxypropylamine were obtained.
In Example 1 (2), instead of Solsperse 41000, the copper nanoparticles were disper byk-130 (manufactured by BYK Japan, acid value of less than 3 mgKOH / g, amine value of 190 mgKOH / g, 90% thermogravimetric decrease temperature) Was 474.8 ° C.) in the same manner as in Example 1 (2). However, the copper nanoparticles were not aggregated and dispersed, and a copper nanoparticle dispersion could not be obtained.

(Comparative Example 5)
In the same manner as in Reference Example 15 (1), copper nanoparticles coated with oleic acid and octylamine were obtained.
In Example 1 (2), instead of Solsperse 41000, the copper nanoparticles were disper byk-130 (manufactured by BYK Japan, acid value of less than 3 mgKOH / g, amine value of 190 mgKOH / g, 90% thermogravimetric decrease temperature) Was used in the same manner as in (2) of Example 1 except that 474.8 ° C. was used to obtain Comparative Copper Nanoparticle Dispersion 5.
Using the obtained comparative copper nanoparticle dispersion 5, a conductive substrate was produced by plasma firing in the same manner as (3) of Example 1.
Using the obtained comparative copper nanoparticle dispersion 5, a conductive substrate was produced by flash light baking in the same manner as in (4) of Example 1.

(Comparative Example 6)
(1) Synthesis of copper nanoparticles In Example 1, instead of 31.5 g (0.2 mol) of nonanoic acid, 28.2 g of oleic acid (0.1 mol, manufactured by Kanto Chemical Co., Ltd., boiling point: 360 ° C.) was used. In the same manner as in Example 1, copper nanoparticles coated with oleic acid and hexylamine were obtained.

When the obtained copper nanoparticles were observed with a transmission electron microscope (TEM) in the same manner as in Example 1, the average primary particle size was 24 nm.
Moreover, when the crystal structure of the copper nanoparticle obtained by the X-ray diffractometer was measured, the main structure of the copper nanoparticle was Cu (Cubic), and a part of Cu ₂ O (Cubic) structure was observed, and Cu (111) The peak intensity of Cu ₂ O (111) relative to was about 17%.

(2) Preparation of copper nanoparticle dispersion Using the copper nanoparticles coated with oleic acid and hexylamine obtained above, Solsperse 16000 (manufactured by Nippon Lubrizol, acid value 20 mgKOH / g, instead of Solsperse 41000, Comparative Copper Nanoparticle Dispersion 6 was obtained in the same manner as (2) of Example 1 except that the amine value was 0 mg KOH / g, the weight average molecular weight was 4200, and the 90% thermogravimetric decrease temperature was 405.5 ° C. It was.

(3) Production of Conductive Substrate by Plasma Firing Using the obtained comparative copper nanoparticle dispersion 6, a conductive substrate was produced by plasma firing in the same manner as (3) of Example 1.
(4) Production of conductive substrate by flash light firing Using the obtained comparative copper nanoparticle dispersion 6, a conductive substrate was produced by flash light firing in the same manner as in (4) of Example 1.

(Comparative Example 7)
In the same manner as in Comparative Example 6 (1), copper nanoparticles coated with oleic acid and hexylamine were obtained.
In Example 1 (2), instead of Solsperse 41000, the copper nanoparticles were Solsperse 76500 (manufactured by Nippon Lubrizol, acid value 0 mgKOH / g, amine value 15.2 mgKOH / g, 90% thermogravimetric decrease temperature) A comparative copper nanoparticle dispersion 7 was obtained by dispersing in the same manner as in (2) of Example 1 except that over 600 ° C (32% remaining even at 600 ° C) was used.
Using the obtained comparative copper nanoparticle dispersion 7, a conductive substrate was produced by plasma firing in the same manner as in Example 1 (3).
Using the obtained comparative copper nanoparticle dispersion 7, a conductive substrate was produced by flash light baking in the same manner as in Example 1 (4).

[Evaluation]
<Dispersibility evaluation>
As an evaluation of the dispersibility of the copper nanoparticles, the dispersion average particle diameter of the copper nanoparticles in the copper nanoparticle dispersion obtained in each of the examples and the comparative examples was measured. For measurement of the dispersion average particle size, Nikkiso “Microtrac particle size distribution analyzer UPA-EX150” was used. The value of the volume average particle diameter was used as the value of the dispersion average particle diameter, and the dispersion that settled after standing for 12 hours was not dispersible. Table 1 shows the results of dispersion average particle diameters of the dispersions of Examples and Comparative Examples.

<Applicability evaluation>
After forming the coating film of the copper nanoparticle dispersion obtained in each Example and Comparative Example, the coating suitability was evaluated by visually observing the film quality of the coating film of the metal fine particle dispersion before firing. Table 1 shows the results of the applicability evaluation of the dispersions of Examples and Comparative Examples.
[Applicability evaluation criteria]
A: There is no repellency and the coating film is uniform.
B: There is repellency and the coating film is non-uniform.

<Electrical conductivity evaluation>
Conductivity evaluation was performed on the conductive substrate. Using a surface resistance meter ("Loresta GP" manufactured by Dia Instruments, PSP probe type), 4 probes are brought into contact with the metal film of the conductive substrate of each example and comparative example, and the sheet resistance value is determined by the 4 probe method. It was measured. The evaluation results are shown in Table 1. The lower the sheet resistance value, the better the conductivity. The upper limit of sheet resistance measured by this measurement method was 10 ⁸ Ω / □. In the table, O.D. L. Represents Over Load.

<Summary of results>
According to the examples, the copper nanoparticle dispersion containing a carboxylic acid, an alkylamine, a polymer dispersant having a specific amine value and an acid value, and a solvent according to the present invention is excellent in dispersibility and applicability, Furthermore, it has been clarified that excellent sinterability at a low temperature or in a short time and high conductivity with a surface resistance of 1 Ω / □ or less can be obtained. In particular, it was found that the use of a carboxylic acid having 10 or less carbon atoms improves the conductivity. Moreover, when the copper nanoparticle dispersion which concerns on this invention is used, since it is excellent in application | coating suitability in this way, it is possible to form a circuit pattern accurately. In addition, the copper nanoparticles obtained in the examples have good oxidation resistance at the time of production. Above all, when a carboxylic acid having 10 or less carbon atoms is used, the copper nanoparticles are also excellent in oxidation resistance at the time of production. I understood that.
On the other hand, the copper nanoparticle dispersion of Comparative Example 1 containing a carboxylic acid and an alkylamine but not containing a polymer dispersant has poor dispersibility, and even if a coating film is formed, it has repelling and is not uniform. Only a thin film could be formed. Moreover, from the results of Comparative Examples 2, 3 and 4, when a carboxylic acid having a small carbon number such as decanoic acid or nonanoic acid and an alkylamine are included, the amine value or acid value is smaller or larger than the value specified in the present application. It was revealed that the polymer dispersant cannot be dispersed.
Since the comparative example 5 corresponding to the Example of patent document 3 coat | covers oleic acid with a large carbon number as carboxylic acid, even if it uses the polymer dispersing agent which has an amine value larger than the value specified by this application. Although dispersible, the dispersibility was poor and a uniform coating film could not be formed. Further, it has been clarified that excellent conductivity cannot be obtained by low-temperature or short-time firing.
Similarly, when oleic acid having a large number of carbon atoms is used as the carboxylic acid, even a polymer dispersant having an amine value or acid value smaller than the value specified in the present application can be dispersed, but the dispersibility is poor. It has been clarified that excellent conductivity cannot be obtained by low-temperature or short-time firing.
On the other hand, even when oleic acid having a large number of carbon atoms is used as the carboxylic acid, the polymer dispersant having the amine value or acid value specified in the present application can provide excellent dispersibility, so that it can be fired at low temperature or in a short time. High conductivity with a surface resistance of 1 Ω / □ or less is obtained (Reference Example 15).

(Reference Example 16)
In the same manner as in Reference Example 3, a copper nanoparticle dispersion 3 was obtained.
The obtained copper nanoparticle dispersion 3 was applied to a PET film (Cosmo Shine A4100) having a thickness of 100 μm with a wire bar and dried to form a coating film having a thickness of 0.5 μm.
Thereafter, while introducing hydrogen gas at an introduction pressure of 20 Pa, using a microwave surface wave plasma processing apparatus (MSP-1500, manufactured by Microelectronics), firing was performed at a microwave output of 450 W for 300 seconds, and the copper nanoparticle dispersion was fired. The resulting sintered film (copper film) was used as a PET film with a copper thin film.
A UV curable ink was applied to a cleaned glass substrate with a spin coater, and the PET film with a copper thin film obtained above was affixed to prevent bubbles from entering, and the glass and the film were fixed by UV irradiation from the back side. . Next, a commercially available naphthoquinone-based positive resist was spin-coated on the surface of the PET film with a copper thin film and hot-plate dried at 100 ° C. for 3 minutes to form a dry film thickness of about 1 μm. Further, a photomask was brought into contact with the positive resist film surface, exposed at 40 mJ / cm ² , then paddle developed for 20 seconds with NMD-3 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), and rinsed with pure water to obtain a resist pattern. Further, the substrate was rinsed with pure water for 80 seconds while being positively moved with a phosphoric acid-acetic acid-based etching solution at 23 ° C., and then etched with pure water. Thereafter, the entire surface is exposed at 100 mJ / cm ² , then paddle developed for 60 seconds with NMD-3 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), and rinsed with pure water to form a 3.8 μm copper wiring pattern on the PET film. I was able to.

<Smoothness evaluation>
The cross section of the obtained copper wiring pattern was measured with a scanning electron microscope (SEM, scanning electron microscope “S-4800” manufactured by Hitachi High-Technology) to obtain a 100,000 times cross-sectional observation image. An uneven line (length 2 μm) at the interface between the substrate and the sintered film is extracted, and from the uneven line, the maximum height (Rz, the difference between the most peak and the most valley, according to the definition of JIS B0601 (2001)) Asked. Uneven lines were extracted from any 10 locations in the surface, and the average value of the maximum heights was defined as the average roughness.
In addition, the uneven | corrugated line converted the image obtained by SEM observation into black-and-white, and extracted the line along the metal sintered film side by making a white part into the metal sintered film side. Parts with obvious irregularities such as foreign matter and filler contained in the film were not used.
As a result, the unevenness of the interface between the base material and the metal sintered film was 12.4 nm, and it was confirmed that the above-mentioned interface was smooth.
<Adhesion evaluation>
The obtained copper wiring pattern was subjected to a peel test using an adhesive tape (trade name: Scotch Mending Tape, manufactured by Sumitomo 3M). As a result, it was confirmed that the wiring did not peel off, and it was confirmed that the adhesion was good even after etching.

DESCRIPTION OF SYMBOLS 1 Base material 2 Metal film 3 Patterned metal film 100 Conductive substrate 101 Conductive substrate

Claims (13)

Copper nanoparticles coated with a carboxylic acid and an alkylamine having a primary or secondary amino group and not containing a hydroxy group are dispersed in a polymer dispersant and a solvent. A copper nanoparticle dispersion having a value of 30 to 160 mgKOH / g, an amine value of 0 to 160 mgKOH / g, and a volume average particle size of 500 nm or less by a dynamic light scattering method is applied onto a substrate and coated Forming a step;
A method for producing a conductive substrate, comprising a step of firing the coating film.   The method for producing a conductive substrate according to claim 1, wherein the polymer dispersant has a 90% thermal weight loss temperature of 420 ° C. or less.   The method for producing a conductive substrate according to claim 1, wherein the carboxylic acid has 10 or less carbon atoms.   The method for manufacturing a conductive substrate according to any one of claims 1 to 3, wherein the baking step is a step of baking by plasma or a step of baking by irradiation with flash light.   The method for producing a conductive substrate according to any one of claims 1 to 4, further comprising a step of chemically etching the obtained sintered film after the firing step. A compound containing copper, one or more reducing compounds selected from hydrazine and hydrazine hydrate, a carboxylic acid, and a mixture containing a primary or secondary amino group and an alkylamine containing no hydroxy group, or Heating one or more reducing compounds selected from copper carboxylates, hydrazines and hydrazine hydrates, and mixtures containing alkylamines having primary or secondary amino groups and no hydroxy groups. A step of preparing copper nanoparticles by:
By dispersing the copper nanoparticles in a solvent with a polymer dispersant having an acid value of 30 to 160 mgKOH / g and an amine value of 0 to 160 mgKOH / g, the volume average particle diameter by a dynamic light scattering method is increased. Preparing a copper nanoparticle dispersion that is 500 nm or less;
Applying the copper nanoparticle dispersion on a substrate to form a coating film;
A method for producing a conductive substrate, comprising a step of firing the coating film.   The method for producing a conductive substrate according to claim 6, wherein the polymer dispersant has a 90% thermal weight loss temperature of 420 ° C. or less.   The method for producing a conductive substrate according to claim 6 or 7, wherein the carboxylic acid has 10 or less carbon atoms.   The method for manufacturing a conductive substrate according to claim 6, wherein the baking step is a step of baking by plasma or a step of baking by irradiation with flash light.   The method for manufacturing a conductive substrate according to any one of claims 6 to 9, further comprising a step of chemically etching the obtained sintered film after the baking step.   Copper nanoparticles coated with a carboxylic acid and an alkylamine having a primary or secondary amino group and not containing a hydroxy group are dispersed in a polymer dispersant and a solvent. A copper nanoparticle dispersion having a value of 30 to 160 mgKOH / g, an amine value of 0 to 160 mgKOH / g, and a volume average particle size by dynamic light scattering of 500 nm or less.   The copper nanoparticle dispersion according to claim 11, wherein the polymer dispersant has a 90% thermal weight loss temperature of 420 ° C. or less.   The copper nanoparticle dispersion according to claim 11 or 12, wherein the carboxylic acid has 10 or less carbon atoms.