JP2015124416A - Coated copper nanoparticle, coated nanoparticle dispersion, and method for manufacturing conductive substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coated copper nanoparticle and a copper nanoparticle dispersion excellent in oxidation resistance, dispersibility, coating adaptability, and sintering property at a low temperature or in a short time, and a method for manufacturing a conductive substrate by using the above dispersion.SOLUTION: The coated copper nanoparticle comprises a copper nanoparticle coated with an alkyl amine and a polyallylamine derivative having a structural unit represented by the formula below. The copper nanoparticle dispersion comprises copper nanoparticles, an alkyl amine, a polyallylamine derivative having a structural unit of a specific structure, and a solvent. The method for manufacturing a conductive substrate includes steps of: applying a coating liquid containing a copper nanoparticle dispersion that comprises copper nanoparticles, an alkyl amine, a polyallylamine derivative having a structural unit of a specific structure, and a solvent, on a substrate to form a coating film; and firing the coating film. In the formula, Rrepresents an isolated amino group or a group represented by a specific formula, and a plurality of Rmay be the same or different from one another, however, at least one of the plurality of Ris a group represented by the specific formula.

Description

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

  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 dispersion stability and coating suitability of the metal particle dispersion and low-temperature sintering.

  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 method for producing a copper fine particle dispersion in which copper fine particles whose surfaces are coated with an aliphatic monocarboxylic acid are dispersed. According to Patent Document 2, it is described that the copper fine particle dispersion has a fine particle diameter and is excellent in sinterability at a low temperature.
However, according to the technique of Patent Document 2, since the copper fine particles are dispersed using a low molecular weight compound, the dispersibility of the copper fine particles is poor, the coating suitability is poor, and when coating on a resin substrate such as a PET film. There was a problem that unevenness occurred. Furthermore, the copper fine particles whose surface is coated with an aliphatic monocarboxylic acid have a high sintering temperature, and it is necessary to further lower the sintering temperature for use on a low heat resistant film such as a PET film.

On the other hand, Patent Document 3 describes a metal particle dispersion containing specific metal particles, a polymer dispersant having a specific polyester skeleton, and a dispersion medium. According to Patent Document 3, it is described that the specific polymer dispersant exhibits a high effect on the dispersibility of the metal particles and is easily volatilized in a subsequent sintering step.
However, according to the technique of Patent Document 3, firing of the copper nanoparticle coating film requires long-time firing with a high microwave output. In practice, as described in the examples, the firing of the copper nanoparticle coating film on the polyethylene naphthalate (PEN) film is the limit, and it is applied to a PET film or the like which is a cheaper and versatile low heat-resistant substrate. When firing under the same conditions as in Patent Document 3, there is a problem that the base material is deformed and cannot be fired before the conductivity is developed. In order to apply and fire it on a PET film or the like, it was necessary to further lower the sintering temperature.

  Patent Document 4 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. However, Patent Document 4 is a technique that focuses on improving the conductivity by firing at a high temperature of 200 ° C. or higher using a reducing atmosphere. For this reason, in order to apply and fire it on a PET film or the like, it has been necessary to further reduce the sintering temperature.

JP 2012-72418 A JP 2013-47365 A International Publication No. 2011/040189 Pamphlet International Publication No. 2013/147535 Pamphlet

As described above, conventionally, copper particle dispersions have used relatively low molecular weight dispersants such as alkylamines and aliphatic carboxylic acids in order to prevent organic components from remaining during firing. However, low molecular weight dispersants have insufficient dispersibility and coating suitability, and furthermore, have low sinterability at low temperatures or in a short time. On the other hand, 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 is coated copper nanoparticles and a copper nanoparticle dispersion excellent in oxidation resistance, dispersibility, applicability, and low temperature or short-time sinterability. And it aims at providing the manufacturing method of the electroconductive board | substrate which can obtain the electroconductive board | substrate which has the outstanding electroconductivity by baking at low temperature or a short time.

As a result of intensive studies to achieve the above object, the present inventors have coated copper nanoparticles in combination with an alkylamine and a polyallylamine derivative having a specific structure, thereby providing oxidation resistance, Knowledge that dispersibility and coating suitability are excellent and that organic components are easily decomposed or removed from the film even when baked at a low temperature or in a short time, and as a result, a film having high conductivity can be formed. Got.
The present invention has been completed based on such knowledge.

The coated copper nanoparticles according to the present invention are characterized in that the copper nanoparticles are coated with an alkylamine and a polyallylamine derivative having a structural unit represented by the following general formula (I).
Moreover, the copper nanoparticle dispersion according to the present invention comprises copper nanoparticles, an alkylamine, a polyallylamine derivative having a structural unit represented by the following general formula (I), and a solvent. To do.
Moreover, the manufacturing method of the electroconductive board | substrate of the 1st aspect which concerns on this invention is a copper nanoparticle, an alkylamine, the polyallylamine derivative which has a structural unit represented by the following general formula (I), and a solvent. It has the process of apply | coating the coating liquid containing the copper nanoparticle dispersion to contain on a base material, and forming a coating film, and the process of baking the said coating film.

In addition, the method for producing a copper nanoparticle dispersion includes a step of preparing a copper nanoparticle by heating a mixture containing a compound containing copper, a reducing compound, and an alkylamine, and the copper nanoparticle in a solvent. And a step of dispersing with a polyallylamine derivative having a structural unit represented by the following general formula (I).
Moreover, the manufacturing method of the electroconductive board | substrate of the 2nd aspect which concerns on this invention is a process which prepares a copper nanoparticle by heating the mixture containing the compound containing a copper, a reducing compound, and an alkylamine, The said copper A step of preparing a dispersion by dispersing nanoparticles in a solvent with a polyallylamine derivative having a structural unit represented by the following general formula (I), and a coating liquid containing the dispersion on a substrate It has the process of apply | coating and forming a coating film, and the process of baking the said coating film.

（一般式（Ｉ）中、Ｒ^１は遊離のアミノ基、下記一般式（ＩＩ）、又は下記一般式（ＩＩＩ）で表される基を表し、複数あるＲ^１は同一であっても異なってもよい。但し、複数あるＲ^１のうち少なくとも１個は一般式（ＩＩＩ）で示される基である。）

(In the general formula (I), R ¹ represents a free amino group, a group represented by the following general formula (II) or the following general formula (III), and a plurality of R ¹ may be the same or different. Provided that at least ^one of the plurality of R ¹ is a group represented by the general formula (III).)

（一般式（ＩＩ）、及び一般式（ＩＩＩ）中、Ｒ^２は遊離のカルボン酸を有するポリエステル、遊離のカルボン酸を有するポリアミド、及び、遊離のカルボン酸を有するポリエステルアミドのいずれかからカルボキシ基を除いた残基を表す。）

(In General Formula (II) and General Formula (III), R ² represents a carboxy group from any of a polyester having a free carboxylic acid, a polyamide having a free carboxylic acid, and a polyester amide having a free carboxylic acid. (Represents a residue excluding)

  In the method for manufacturing a conductive substrate according to the present invention, the step of baking is a step of baking by flash light irradiation, which can be performed at a low temperature or for a short time, on a low heat resistant substrate. Is preferable from the viewpoint that a conductive substrate having excellent conductivity can be obtained.

  According to the present invention, coated copper nanoparticles and a copper nanoparticle dispersion excellent in oxidation resistance, dispersibility, applicability, and sinterability at a low temperature or in a short time, and firing at a low temperature or in a short time Thus, it is possible to provide a method for manufacturing a conductive substrate, which can obtain a conductive substrate having excellent conductivity.

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

Hereinafter, the manufacturing method of the covering copper nanoparticle which concerns on this invention, a copper nanoparticle dispersion, and an electroconductive board | substrate is demonstrated.
In the present invention, (meth) acryl means either acryl or methacryl, and (meth) acrylate means either acrylate or methacrylate.

[Coated copper nanoparticles, copper nanoparticle dispersion]
The coated copper nanoparticles according to the present invention are characterized in that the copper nanoparticles are coated with an alkylamine and a polyallylamine derivative having a structural unit represented by the following general formula (I).
Moreover, the copper nanoparticle dispersion according to the present invention comprises copper nanoparticles, an alkylamine, a polyallylamine derivative having a structural unit represented by the following general formula (I), and a solvent. To do.
In the present invention, the term “coating” includes not only the form in which the entire particle surface is covered, but also the form in which it is attached to a part of the particle surface.

（一般式（Ｉ）中、Ｒ^１は遊離のアミノ基、下記一般式（ＩＩ）、又は下記一般式（ＩＩＩ）で表される基を表し、複数あるＲ^１は同一であっても異なってもよい。但し、複数あるＲ^１のうち少なくとも１個は一般式（ＩＩＩ）で示される基である。）

(In the general formula (I), R ¹ represents a free amino group, a group represented by the following general formula (II) or the following general formula (III), and a plurality of R ¹ may be the same or different. Provided that at least ^one of the plurality of R ¹ is a group represented by the general formula (III).)

（一般式（ＩＩ）、及び一般式（ＩＩＩ）中、Ｒ^２は遊離のカルボン酸を有するポリエステル、遊離のカルボン酸を有するポリアミド、及び、遊離のカルボン酸を有するポリエステルアミドのいずれかからカルボキシ基を除いた残基を表す。）

(In General Formula (II) and General Formula (III), R ² represents a carboxy group from any of a polyester having a free carboxylic acid, a polyamide having a free carboxylic acid, and a polyester amide having a free carboxylic acid. (Represents a residue excluding)

In the present invention, copper nanoparticles are coated with a combination of a relatively low molecular weight alkylamine and a polyallylamine derivative having the specific structure described above. It is estimated that a specific effect is exhibited.
In order to impart dispersibility of the copper nanoparticles, it is desirable to use a compound having a functional group that adsorbs relatively strongly on the surface of the copper nanoparticles. On the other hand, if the compound is too strongly adsorbed, It is considered that it becomes difficult to detach from the copper nanoparticles, resulting in difficulty in low-temperature sintering, and as a result, a cause of deterioration in conductivity. In that respect, in the present invention, a polyallylamine derivative having a —NH 3 ⁺ —OCO— group or a —NHCO— group that can be relatively strongly adsorbed on the surface of the copper nanoparticles, and a relatively low molecular weight that is weakly adsorbed on the surface of the copper nanoparticles. Both of the alkylamines coat the copper nanoparticles. Also in the copper nanoparticle dispersion which concerns on this invention, the alkylamine and the said polyallylamine derivative adhere to the copper nanoparticle surface, and the said copper nanoparticle is disperse | distributed in a solvent.
In the present invention, a polyallylamine derivative having a —NH 3 ⁺ —OCO— group or a —NHCO— group, which can be adsorbed relatively strongly on the surface of the copper nanoparticles, surrounds the copper nanoparticles even in a solvent and is stable due to relatively strong adsorption. It is presumed that aggregation of copper nanoparticles is less likely to occur due to steric hindrance of the polymer chain, and the dispersibility of the copper nanoparticles is excellent. Further, in the present invention, the copper nanoparticles are surrounded by the polyallylamine derivative having the above specific structure and are stably and uniformly dispersed. It is estimated that the application suitability is excellent. On the other hand, the alkylamine present together with the polyallylamine derivative having a specific structure on the surface of the copper nanoparticle is weakly adsorbed on the surface of the copper nanoparticle and has a relatively low molecular weight. But it is easy to detach. Therefore, at the time of firing, the alkylamine mixed with the polyallylamine derivative is desorbed on the surface of the copper nanoparticle, whereby the polyallylamine derivative existing on the surface of the copper nanoparticle is also easily desorbed, and the present invention. It is estimated that the copper nanoparticles are excellent in sinterability at a low temperature or in a short time.
Furthermore, since the alkylamine has a function of capturing protons, the alkylamine is presumed to suppress oxidation of copper atoms by attaching to the surface of the copper nanoparticles. Furthermore, since the polyallylamine containing an amino group covers and surrounds the copper nanoparticles, it is estimated that the effect of suppressing the oxidation of the copper nanoparticles is higher in the present invention. For this reason, sintering inhibition due to oxidation during firing hardly occurs, and it is estimated that a film having high conductivity can be formed after firing.

The coated copper nanoparticles and 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 component of the coated copper nanoparticles and the copper nanoparticle dispersion of the present invention 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 copper nanoparticles having a size of less than 1 μm, 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 of 10 nm or more and less than 1 μm from the viewpoint of achieving both dispersibility, printability of fine wiring, low-temperature firing, and conductivity. If the thickness is less than 10 nm, a large amount of polyallylamine derivative having a specific structure is required to impart dispersion stability and coating suitability, which may result in deterioration of conductivity.
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 metal 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 alkylamine, as described in detail later, alkylamine is used as an organic protective agent, and a metal compound and a reducing agent are mixed in a solvent to form copper. A method for producing 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%.
In the coated copper nanoparticles of the present invention, the content of the copper nanoparticles may be appropriately selected depending on the application, but from the viewpoint of dispersibility, the content of the copper nanoparticles is 50 to 99 with respect to the total amount of the coated copper nanoparticles. It is preferable that it is 9.9 mass%, and it is more preferable that it exists in the range of 70-99.9 mass%.

<Alkylamine>
The alkylamine used in the present invention can be appropriately selected from known alkylamines according to properties expected for the coated copper nanoparticles to be produced.
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 hydrocarbon chain may contain atoms other than carbon such as oxygen, silicon, nitrogen, sulfur, and phosphorus.

  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 Examples thereof include, but are not limited to, propylamine, 3-dibutylaminopropylamine, 3-methylaminopropylamine and the like.

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. Moreover, it is preferable that a boiling point is 300 degrees C or less, Furthermore, it is preferable that it is 200 degrees C or less. 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. 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 alkylamine may be appropriately selected according to the use, but from the viewpoint of oxidation resistance and low-temperature sinterability, the total amount of the copper nanoparticle dispersion The content is preferably 0.05 to 15% by mass, and more preferably 0.05 to 10% by mass.
Moreover, in the coated copper nanoparticles of the present invention, the content of the alkylamine may be appropriately selected depending on the use, but from the viewpoint of oxidation resistance and low-temperature sinterability, the total amount of the coated copper nanoparticles. The content is preferably 0.1 to 30% by mass, and more preferably 0.1 to 20% by mass.

<Polyallylamine derivative>
The polyallylamine derivative used in the present invention is a polymer having a structural unit represented by the following general formula (I).

（一般式（Ｉ）中、Ｒ^１は遊離のアミノ基、下記一般式（ＩＩ）、又は下記一般式（ＩＩＩ）で表される基を表し、複数あるＲ^１は同一であっても異なってもよい。但し、複数あるＲ^１のうち少なくとも１個は一般式（ＩＩＩ）で示される基である。）

(In the general formula (I), R ¹ represents a free amino group, a group represented by the following general formula (II) or the following general formula (III), and a plurality of R ¹ may be the same or different. Provided that at least ^one of the plurality of R ¹ is a group represented by the general formula (III).)

（一般式（ＩＩ）、及び一般式（ＩＩＩ）中、Ｒ^２は遊離のカルボン酸を有するポリエステル、遊離のカルボン酸を有するポリアミド、及び、遊離のカルボン酸を有するポリエステルアミドのいずれかからカルボキシ基を除いた残基を表す。）

(In General Formula (II) and General Formula (III), R ² represents a carboxy group from any of a polyester having a free carboxylic acid, a polyamide having a free carboxylic acid, and a polyester amide having a free carboxylic acid. (Represents a residue excluding)

The polyallylamine derivative having the above specific structure is relatively strongly adsorbed to the copper nanoparticles by the —NH 3 ⁺ —OCO— group or —NHCO— group, while causing steric hindrance by the polymer chain portion, It is presumed that aggregation is stably prevented. Since the polyallylamine derivative having the above specific structure is relatively strongly adsorbed with the copper nanoparticles, the dispersibility and dispersion stability are improved, so that the dispersed particle diameter of the copper nanoparticles can be reduced. Therefore, when the polyallylamine derivative is used, the smoothness and uniformity of the coating film of the coating liquid containing the copper nanoparticle dispersion are excellent. Therefore, sintering is likely to proceed uniformly. In addition, the polyallylamine derivative is easily decomposed or volatilized by firing when the conductive substrate is manufactured, and the resulting conductive substrate suppresses the remaining organic components. Furthermore, since the contained amino group has reducibility and suppresses the oxidation of the metal particles during firing, the metal film obtained after firing has few metal oxides. As a result, the obtained metal film is presumed to be excellent in conductivity.

The polyallylamine derivative represented by the general formula (I) includes, for example, allylamine polymers and polyesters having a free carboxyl group, polyamides, or co-condensates of esters and amides (polyesteramides). It is obtained by reacting with one or more selected compounds.
More specifically, the polyallylamine derivative represented by the general formula (I) is represented by the following general formula (IV) or the following general formula (V) having an allylamine polymer and a free carboxyl group. It can be obtained by reacting an amino group and a carboxyl group using polyester and at least one selected from the group consisting of polyamides represented by the following general formula (VI) or the following general formula (VII).

（一般式（ＩＶ）中、Ｒ^３は、炭素原子数２〜２０の直鎖もしくは分岐のアルキレン基を表し、ａは２〜１００の整数である。複数あるＲ^３は、互いに同一であっても異なっていてもよい。）

(In the general formula (IV), R ³ represents a linear or branched alkylene group having 2 to 20 carbon atoms, and a is an integer of 2 to 100. A plurality of R ³ are mutually identical. May be different.)

（一般式（Ｖ）中、Ｒ^４は、炭素原子数２〜２０の直鎖もしくは分岐のアルキレン基、Ｃ_６Ｈ_４、又はＣＨ＝ＣＨを表し、Ｒ^５は、炭素原子数２〜２０の直鎖もしくは分岐のアルキレン基、又はポリアルキレングリコールから２つの水酸基を除いた残基を表し、ｂは２〜１００の整数であり、前記アルキレン基は、鎖中にエーテル結合を有してもよい。複数あるＲ^４及びＲ^５は、互いに同一であっても異なっていてもよい。）

(In the general formula (V), R ⁴ represents a linear or branched alkylene group having 2 to 20 carbon atoms, C ₆ H ₄ , or CH═CH, and R ⁵ has 2 to 20 carbon atoms. A linear or branched alkylene group or a residue obtained by removing two hydroxyl groups from polyalkylene glycol, b is an integer of 2 to 100, and the alkylene group may have an ether bond in the chain. The plurality of R ⁴ and R ⁵ may be the same as or different from each other.)

（一般式（ＶＩ）中、Ｒ^６は、炭素原子数２〜２０の直鎖もしくは分岐のアルキレン基を表し、ｃは２〜１００の整数である。複数あるＲ^６は、互いに同一であっても異なっていてもよい。）

(In General Formula (VI), R ⁶ represents a linear or branched alkylene group having 2 to 20 carbon atoms, and c is an integer of 2 to 100. A plurality of R ⁶ are the same as each other. May be different.)

（一般式（ＶＩＩ）中、Ｒ^４は、上記一般式（Ｖ）におけるＲ^４と同様である。Ｒ^７は、炭素原子数２〜２０の直鎖もしくは分岐のアルキレン基を表し、ｄは２〜１００の整数である。複数あるＲ^４及びＲ^７は、互いに同一であっても異なっていてもよい。）

(In the general formula (VII), ^{R 4} is, .R ⁷ is the same as ^{R 4} in the general formula (V) is a linear or branched alkylene group having a carbon number of 2 to 20, d is 2 It is an integer of ˜100. Plural R ⁴ and R ⁷ may be the same or different from each other.

  The polyallylamine derivative used in the present invention is an allylamine polymer, a polyester in which repeating components of the general formula (IV) and the general formula (V) are randomly polymerized, a repetition of the general formula (VI) and the general formula (VII). Manufactured by reacting a polyamide in which the components are randomly polymerized, and further a polyester amide in which the repeating components of the general formulas (IV) and / or (V) and general formulas (VI) and / or (VII) are randomly polymerized. be able to.

The polyallylamine derivative preferably contains 2 to 2500 repeating units represented by the general formula (I) as the main chain allylamine polymer, more preferably 2 to 1000, and more preferably 2 to 300. More preferred. Among them, as the allylamine polymer of the main chain, it is preferable to use a polyallylamine having a polymerization degree of 2 to 2500 which is an allylamine homopolymer, more preferably a polyallylamine having a polymerization degree of 2 to 1000, and further a polymerization degree of 2 More preferably, ~ 300 polyallylamine is used.
In the present invention, a polyallylamine having a polymerization degree of 2 to 1000, a polyester having a free carboxyl group, represented by the following general formula (IV) or (V), and represented by the following general formula (VI) or (VII): A polyallylamine derivative obtained by reacting one kind of polyamide to be used alone or in combination of two or more kinds is preferred.

The polyallylamine derivative used in the present invention is preferably a residue obtained by removing a carboxyl group from a polyester in which R ² has a free carboxylic acid. The polyester preferably has a number average molecular weight in the range of 300-20000, and more preferably in the range of 500-15000.
In the formula (I), the ratio of the group represented by the general formula (III) in the n R ¹ is preferably 60 to 95 mol%.

  The weight average molecular weight of the polyallylamine derivative is preferably 3000 to 50000, and more preferably 5000 to 40000. The weight average molecular weight and number average molecular weight in the present invention can be measured by gel permeation chromatography (GPC) method (polystyrene conversion).

  Commercially available products of the polyallylamine derivatives include Azisper PB821, PB822, PB824, PB880 (manufactured by Ajinomoto Fine Techno).

In the coated copper nanoparticles and the copper nanoparticle dispersion of the present invention, the polyallylamine derivative having the specific structure may be used alone or in combination of two or more.
In the copper nanoparticle dispersion of the present invention, the content of the polyallylamine derivative having the above specific structure may be appropriately selected according to the use, but from the viewpoint of dispersibility, applicability, and low-temperature sinterability, It is preferable that it is 0.05-25 mass% with respect to the whole quantity of a copper nanoparticle dispersion, and it is still more preferable that it exists in the range of 0.5-15 mass%.
Further, in the coated copper nanoparticles of the present invention, the content of the polyallylamine derivative having the above specific structure may be appropriately selected according to the use, but from the viewpoint of dispersibility, coating suitability, and low temperature sintering properties. The content of the coated copper nanoparticles is preferably 0.1 to 50% by mass, more preferably 1 to 25% by mass.
If content of the polyallylamine derivative which has a specific structure is more than the said lower limit, the dispersibility and application | coating property 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 polyallylamine derivative which has a specific structure, 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 20 to 90 mass%. By being the said range, it can be set as the viscosity suitable for application | coating.

<Other ingredients>
In the coated copper nanoparticles and copper nanoparticle dispersion of the present invention, other components that have been used in conventional coated metal nanoparticles and metal particle dispersions may be added as necessary, as long as the effects of the present invention are not impaired. You may contain.
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.

<Method for producing coated copper nanoparticles and copper nanoparticle dispersion>
In the present invention, the method for producing the coated copper nanoparticles and the copper nanoparticle dispersion may be any method as long as the copper nanoparticles can be well dispersed, and can be appropriately selected from conventionally known methods. For example, first, copper nanoparticles having an alkylamine attached thereto are prepared, and the copper nanoparticles are dispersed with a polyallylamine derivative having a specific structure in a solvent by a conventionally known method.
As a method for preparing copper nanoparticles having an alkylamine attached thereto, copper nanoparticles produced using alkylamine as a protective agent during production may be used, or copper nanoparticles produced using other protective agents. You may substitute the alkylamine for the protective agent of particle | grains by a well-known method.

Among them, in the present invention, a method for producing a copper nanoparticle dispersion includes a step of preparing a copper nanoparticle by heating a mixture containing a compound containing copper, a reducing compound, and an alkylamine; And a step of dispersing with a polyallylamine derivative having a specific structure in a solvent.
Moreover, in the present invention, the method for producing coated copper nanoparticles comprises a step of preparing copper nanoparticles by heating a mixture containing a compound containing copper, a reducing compound, and an alkylamine, and the copper nanoparticles, It is preferable to have a step of preparing a dispersion by dispersing with a polyallylamine derivative having a specific structure in a solvent, and a step of removing the solvent in the dispersion.

(Step of preparing copper nanoparticles)
In the step of preparing the copper nanoparticles, a copper-containing compound that can form a complex compound such as a complex with the reducing compound is used as the metal source of the copper nanoparticles. Moreover, in order to reduce impurities contained in the copper nanoparticles to be produced, it is desirable to use a copper-containing compound that does not contain a metal element other than copper.

The copper-containing compound capable of forming a complex compound such as a complex with the reducing compound is not particularly limited as long as the ligand can be coordinated to the copper atom in the compound. A copper bond is preferred. In other words, when a reducing compound that generates a nitrogen-based coordination bond to a copper atom is used, if the compound is a compound in which copper is bound by an oxygen-based ligand, the strength of the coordination bond can be reduced. Reduction is likely to occur and is preferable.
As such a copper-containing compound, for example, copper oxalate, copper acetate, copper propionate, copper butyrate, copper isobutyrate, copper valerate, copper isovalerate, copper caproate, copper enanthate, copper caprylate, 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, phosphoric acid Examples include copper organic acid salts and inorganic acid salts such as copper, and complex compounds represented by acetylacetonato copper coordinated with acetylacetone. Among them, it is preferable to use fatty acid copper having 10 or less carbon atoms because copper nanoparticles can be produced at a lower temperature and low-temperature sinterability is improved. Here, the fatty acid copper is a salt compound of a fatty acid having 2 or more carbon atoms and copper, and the fatty acid may be either saturated or unsaturated.
Moreover, as fatty acid copper used as a copper-containing compound, you may use combining the raw material which fatty acid copper produces | generates, for example like the combination of copper hydroxide and a fatty acid.

First, it is preferable that a reducing compound having a reducing action is mixed with the copper-containing compound to form a composite compound such as a complex of a metal compound and a reducing compound. This is because reduction of copper ions is likely to occur, and thus liberation of copper atoms due to spontaneous pyrolysis is likely to occur compared to the copper-containing compound used.
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.

When a reducing compound is directly generated when a copper-containing compound such as fatty acid copper 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.
Moreover, the ratio of the reducing compound mixed with the copper-containing compound such as fatty acid copper for the production of a complex compound such as a complex is the molar ratio of both in the complex compound such as a complex produced from the copper-containing compound and the reducing compound. It is preferable from the viewpoint of improving the yield of the copper nanoparticles that the ratio is equal to (hereinafter referred to as “constant ratio”) or the reducing compound is 1 to 3 times the constant ratio.

In addition, when mixing a copper-containing compound such as fatty acid copper and a reducing compound, it is possible to cause a polar solvent capable of dissolving them without causing a reaction with a substance in the system and to be present as a reaction medium. It is preferable in that the formation of a complex compound is promoted and a complex compound such as a uniform complex can be rapidly formed. As such a polar solvent, it is desirable to have solubility in water (H ₂ O) at room temperature. As alcohol which shows the solubility with respect to water, it has C1-C8 methanol to C8 octanol as a linear alkyl alcohol which has one hydroxyl group, glycols which have two hydroxyl groups, and three hydroxyl groups Examples include glycerin, phenol, propylene glycol monomethyl ether, and the like in which hydrocarbon hydrogen atoms having an ether bond are substituted with a hydroxyl group, and the like can be appropriately selected and used.

In the step of preparing the copper nanoparticles in the present invention, the mixture of the copper-containing compound such as fatty acid copper and the reducing compound generated above is mixed with a sufficient amount of alkylamine and heated, and the fatty acid copper or the like is heated. It is preferable to obtain copper nanoparticles by forming and aggregating copper atoms by spontaneous decomposition reaction of the copper-containing compound. At this time, since the surface of the copper nanoparticles is coated with alkylamine, stable coated copper nanoparticles that are hardly oxidized by oxidation in the air can be obtained.
Although the reaction for generating copper atoms differs depending on the copper-containing compound used and the reducing compound, for example, a fatty acid copper having 10 or less carbon atoms such as copper nonanoate and hydrazine, a hydrazine hydrate or a derivative thereof. When used, a copper-hydrazine complex is formed, and this is mixed with an alkylamine and heated, so that a fatty acid copper having 10 or less carbon atoms such as copper nonanoate can be heated even at a low temperature of about 100 ° C. It is preferable from the point that copper nanoparticles are prepared by causing decomposition. By adjusting the molecular weight of the copper-containing compound such as fatty acid copper and the alkylamine, it is possible to adjust the particle diameter of the generated copper fine particles to a desired size.
The mixing ratio of the alkylamine to the mixture of the copper-containing compound and the reducing compound may be appropriately selected depending on the use, but from the viewpoint of oxidation resistance and low-temperature sinterability, 1 mol of the copper-containing compound. On the other hand, it is preferably 1 to 10 mol, and more preferably in the range of 2 to 6 mol.

In the embodiment of the step of preparing the copper nanoparticles, the first step of preparing a complex compound such as a complex by mixing a copper-containing compound such as fatty acid copper and a reducing compound, and the complex compound such as the complex as an alkylamine The second step of producing copper nanoparticles by heating in the presence of can be performed simultaneously or sequentially in one container. “Simultaneously” means mixing a copper-containing compound such as fatty acid copper, a reducing compound, and an alkylamine at the same time. Preferably, after adding a polar solvent to this and solubilizing it, the copper nano-particles are heated by heating. Particles can be generated. 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 dispersion is prepared by dispersing the copper nanoparticles obtained in the preparation step with a polyallylamine derivative having a specific structure in a solvent.
For example, after the polyallylamine derivative having the specific structure is mixed and stirred in the solvent to prepare a polymer solution, the polymer solution is further mixed with the copper nanoparticles obtained in the preparation step, as necessary. Coated copper nanoparticles and a copper nanoparticle dispersion can be prepared by mixing the components and dispersing them using a known stirrer or disperser.

The coated copper nanoparticles present in the dispersion can also be isolated by removing the solvent from the copper nanoparticle dispersion.
In addition, about the compound which coat | covers the copper nanoparticle surface, it can analyze by collecting the gas component which volatilizes, for example, when a coated copper nanoparticle is heated by inert gas atmosphere. The structure of the coating compound can be clarified by analyzing the gas component by, for example, various mass spectrometry, infrared absorption spectrum, NMR or the like.

The coated copper nanoparticles and copper nanoparticle dispersion obtained in the present invention are suitably used for a conductive substrate described later, and particularly preferably for conductive pattern printing. Since the coated copper nanoparticles and the copper nanoparticle dispersion of the present invention can be fired at a low temperature or in a short time, they are suitably used for low-temperature or short-time firing applications such as plasma firing and flash light firing described later.
The coated copper nanoparticles and the copper nanoparticle dispersion of the present invention are not limited to the above applications, and can be applied to various metal films. For example, they can be used for mirror surfaces for optical devices, various decoration applications, and the like.

[Method of manufacturing conductive substrate]
The manufacturing method of the electroconductive board | substrate of the 1st aspect which concerns on this invention contains a copper nanoparticle, an alkylamine, the polyallylamine derivative which has a structural unit represented by the following general formula (I), and a solvent. It has the process of apply | coating the coating liquid containing a 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 a process which prepares a copper nanoparticle by heating the mixture containing the compound containing a copper, a reducing compound, and an alkylamine, The said copper A step of preparing a dispersion by dispersing nanoparticles in a solvent with a polyallylamine derivative having a structural unit represented by the following general formula (I), and a coating liquid containing the dispersion on a substrate It has the process of apply | coating to and forming a coating film, and the process of baking the said coating film.

（一般式（Ｉ）中、Ｒ^１は遊離のアミノ基、下記一般式（ＩＩ）、又は下記一般式（ＩＩＩ）で表される基を表し、複数あるＲ^１は同一であっても異なってもよい。但し、複数あるＲ^１のうち少なくとも１個は一般式（ＩＩＩ）で示される基である。）

(In the general formula (I), R ¹ represents a free amino group, a group represented by the following general formula (II) or the following general formula (III), and a plurality of R ¹ may be the same or different. Provided that at least ^one of the plurality of R ¹ is a group represented by the general formula (III).)

（一般式（ＩＩ）、及び一般式（ＩＩＩ）中、Ｒ^２は遊離のカルボン酸を有するポリエステル、遊離のカルボン酸を有するポリアミド、及び、遊離のカルボン酸を有するポリエステルアミドのいずれかからカルボキシ基を除いた残基を表す。）

(In General Formula (II) and General Formula (III), R ² represents a carboxy group from any of a polyester having a free carboxylic acid, a polyamide having a free carboxylic acid, and a polyester amide having a free carboxylic acid. (Represents a residue excluding)

  According to the method for producing a conductive substrate of the present invention, as described above, coated copper nanoparticles and copper nanoparticles having excellent oxidation resistance, dispersibility, coating suitability, and low temperature or short-time sintering properties. Since the dispersion is used, it is possible to form a coating film with a highly uniform circuit pattern in which copper nanoparticles with suppressed oxidation are present uniformly and densely, with good pattern accuracy, and excellent conductivity after sintering. A conductive substrate having properties can be obtained.

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 a mixture containing a compound containing copper, a reducing compound, and an alkylamine, and the copper nanoparticles The step of preparing the dispersion by dispersing with a polyallylamine derivative having a specific structure in a solvent may be the same as the step of preparing the copper nanoparticles and the step of preparing the dispersion described above. The description here is omitted.
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 the coating liquid containing a copper nanoparticle dispersion | distribution on a base material, and forming a coating film>
(Coating solution containing copper nanoparticle dispersion)
The coating liquid containing the copper nanoparticle dispersion can be used as it is as the coating liquid of the copper nanoparticle dispersion according to the present invention, but if necessary, a solvent or other components may be added to form a coating liquid. It ’s good.
Examples of the solvent and other components include the solvents mentioned in the copper nanoparticle dispersion according to the present invention, surfactants, silane coupling agents, antifoaming agents, anti-repelling agents, antioxidants, and aggregation prevention agents. An agent, a viscosity modifier, etc. can be used. Furthermore, a resin binder such as an acrylic resin or a polyester resin may be added from the viewpoints of film forming properties, printability, and dispersibility within a range that does not impair the effects of the present invention.

(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, an inorganic material such as glass, alumina, or silica can be used, and a polymer material or 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 lower can be used. In addition, the glass transition temperature here is based on the differential scanning calorimetry (DSC) measurement measured according to JIS-K7121.

  Further, on the surface of the substrate, the shape of the pattern when the coating film of the coating liquid containing the copper nanoparticle dispersion is formed in a pattern is controlled, or the coating film of the coating liquid containing the copper nanoparticle dispersion You may perform the process for providing adhesiveness between. 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 the coating solution containing the copper nanoparticle dispersion is formed in a pattern on the substrate, wetting and spreading of the coating solution is suppressed and high definition is achieved. It is possible to form a simple pattern. 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)
What is necessary is just to select the method of apply | coating the said coating liquid on the said base material suitably from a conventionally well-known method. 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.

  The coating solution on the substrate may be dried by a usual method after printing. The film thickness of the printed part after drying can be controlled by appropriately changing the coating amount, the average primary particle diameter of the copper nanoparticles, etc., and can 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 baking the coating film obtained in the above step to form a metal 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 in a firing furnace (oven), infrared heating, firing in a reducing gas atmosphere, firing by laser annealing, microwave heating, and the like.
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 a step of firing with surface wave plasma generated by application of microwave energy (hereinafter sometimes referred to as plasma firing), or a step of firing by flash light irradiation. (Hereinafter, it may be called flash light baking.)
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.

  Before the microwave surface wave plasma treatment, in order to remove organic substances such as alkylamine and polyallylamine derivatives having a specific structure contained in the coating film coated with the coating liquid containing the copper nanoparticle dispersion, You may bake for about 1 minute to 2 hours at the temperature of about 50-200 degreeC in the atmosphere containing oxygen. 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, it is preferable to use a xenon flash lamp. 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 coating liquid containing the copper nanoparticle dispersion and the vicinity thereof can be heated. The influence of heat on the can be suppressed. In particular, the alkylamine and the allylamine derivative used in the present invention are easily decomposed or volatilized by irradiation with flash light and hardly remain on the metal film. Since it can be sintered, flash light firing 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 or the specific contained in the copper nanoparticle dispersion A polyallylamine derivative having a structure 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 coating liquid containing the copper nanoparticle dispersion and the vicinity thereof, and can burn the coating film at a low temperature and in a short time. Moreover, a smooth copper 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 air under atmospheric pressure, but may be performed under an inert atmosphere, a reducing atmosphere, or under 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 the production method of the present invention, a coating solution containing 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 patterned 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, Wako Pure Chemical Industries, Ltd.), 31.5 g of nonanoic acid (0.2 mol, Tokyo Chemical Industry Co., Ltd.) ), 18.5 g (20 ml, Kanto Chemical Co., Inc.) 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 (0.4 mol, Tokyo Chemical Industry Co., Ltd., boiling point 130 ° C.) of hexylamine 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, Kanto Chemical Co., Ltd.) of hydrazine monohydrate was added to 18.5 g (20 ml, Kanto Chemical Co., Inc.) in an ice bath. The solution dissolved in the company 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, Kanto Chemical Co., Inc.) was added. After centrifugation, the supernatant was removed. The precipitate was washed with hexane to obtain copper nanoparticles coated with 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 coated copper nanoparticles and copper nanoparticle dispersion Copper nanoparticles coated with hexylamine obtained above 0.75 parts by mass, poly having a structural unit represented by the general formula (I) Dispersant containing allylamine derivative (manufactured by Ajinomoto Fine-Techno Co., Ltd., Addisper PB821) 0.075 parts by mass, PGMEA 6.675 parts by mass are mixed, and pre-dispersed with a paint shaker (manufactured by Asada Tekko) for 1 hour with 2 mm zirconia beads. Further, as the main dispersion, 0.1 mm zirconia beads were dispersed for 2 hours to obtain a copper nanoparticle dispersion 1 containing coated copper nanoparticles.

(Example 2)
(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, Guangei Chemical Industry Co., Ltd., boiling point 135 ° C.) The copper nanoparticles coated with 3-ethoxypropylamine were obtained in the same manner as in Example 1 except that, instead of adding 33 g (50 ml) of hexane, 66 g (100 ml) of hexane was added.

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 coated copper nanoparticles and copper nanoparticle dispersion Copper nanoparticles coated with 3-ethoxypropylamine obtained above 0.75 part by mass, structural unit represented by general formula (I) Dispersing agent containing polyallylamine derivative (Ajinomoto Fine Techno Co., Ajisper PB821) 0.075 parts by mass and PGMEA 6.675 parts by mass are mixed, and 2 mm zirconia beads are preliminarily dispersed in a paint shaker (manufactured by Asada Tekko). The dispersion was further dispersed with 0.1 mm zirconia beads for 1 hour as a main dispersion for 2 hours to obtain a copper nanoparticle dispersion 2 containing coated copper nanoparticles.

(Example 3)
(1) Synthesis of copper nanoparticles In Example 1, instead of 40.5 g (0.4 mol) of hexylamine, 40.9 g of dimethylaminopropylamine (0.4 mol, Guangei Chemical Industry Co., Ltd., boiling point 135 ° C.) was used. Copper nanoparticles coated with dimethylaminopropylamine were obtained in the same manner as in Example 1 except that it was used.

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 coated copper nanoparticles and copper nanoparticle dispersion Copper nanoparticles coated with dimethylaminopropylamine obtained above 0.75 part by mass, the structural unit represented by the general formula (I) Dispersing agent containing polyallylamine derivative (Ajinomoto Fine Techno Co., Ajisper PB821) 0.075 parts by mass and PGMEA 6.675 parts by mass are mixed, and 1 mm with 2 mm zirconia beads as a preliminary dispersion in a paint shaker (manufactured by Asada Tekko) Dispersion was performed for 2 hours with 0.1 mm zirconia beads as the main dispersion for a time, and a copper nanoparticle dispersion 3 containing coated copper nanoparticles was obtained.

(Comparative Example 1)
In the same manner as in Example 1 (1), copper nanoparticles coated with hexylamine were obtained.
3.0 parts by mass of copper nanoparticles coated with the hexylamine and 4.5 parts by mass of PGMEA are mixed and pre-dispersed with 2 mm zirconia beads for 1 hour using a paint shaker (manufactured by Asada Tekko), and further dispersed as 0%. Although the dispersion was performed for 2 hours with 1 mm zirconia beads, the copper nanoparticles were not aggregated and dispersed, and a copper nanoparticle dispersion could not be obtained.

(Comparative Example 2)
(1) Synthesis of copper nanoparticles In Example 1, instead of hexylamine 40.5 g (0.4 mol), 1-hexanol 40.9 g (0.4 mol, Kanto Chemical Co., Inc., boiling point 157 ° C.) was used. Instead of adding 33 g (50 ml) of hexane, copper nanoparticles coated with 1-hexanol were obtained in the same manner as in Example 1 except that 66 g (100 ml) of hexane was added. When the obtained copper nanoparticles were observed with a transmission electron microscope (TEM), 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 copper nanoparticle was found to have a structure containing Cu (Cubic) and Cu ₂ O (Cubic). The peak intensity of Cu ₂ O (111) was about 85%.

(2) Preparation of comparative coated copper nanoparticles, comparative copper nanoparticle dispersion 0.75 parts by mass of the copper nanoparticles obtained above, including a polyallylamine derivative having a structural unit represented by the general formula (I) Dispersant (Ajinomoto Fine Techno Co., Ajisper PB821) 0.075 parts by mass and PGMEA 6.675 parts by mass are mixed and pre-dispersed with a paint shaker (manufactured by Asada Tekko) for 1 hour with 2 mm zirconia beads, and further as main dispersion. Dispersion was carried out with 0.1 mm zirconia beads for 2 hours to obtain a comparative copper nanoparticle dispersion 2 containing comparative coated copper nanoparticles.

Example 4 Production of Conductive Substrate by Plasma Firing
In the same manner as in Example 1 (1), copper nanoparticles coated with hexylamine were obtained.
Dispersant containing 3.0 parts by mass of copper nanoparticles coated with hexylamine obtained above and a polyallylamine derivative having a structural unit represented by the above general formula (I) (Ajinomoto Fine Techno Co., Ajisper PB821) 0.3 parts by mass and 4.2 parts by mass of PGMEA were mixed and dispersed for 1 hour with 2 mm zirconia beads as a pre-dispersion in a paint shaker (manufactured by Asada Tekko), and further with 0.1 mm zirconia beads for 2 hours as a main dispersion. A copper nanoparticle dispersion 4 was obtained.
The copper nanoparticle dispersion 4 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 1 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 Micro Electronics Co., Ltd.), firing was performed at a microwave output of 400 W for 374 seconds to obtain a conductive substrate. It was.

(Comparative Example 3 Production of Conductive Substrate by Plasma Firing)
In the same manner as (1) of Comparative Example 2, copper nanoparticles coated with 1-hexanol were obtained.
Dispersant containing 3.0 parts by mass of 1-hexanol-coated copper nanoparticles obtained above and a polyallylamine derivative having a structural unit represented by the above general formula (I) (Ajinomoto Fine Techno, Ajisper PB821 ) 0.3 parts by mass and 4.2 parts by mass of PGMEA were mixed and dispersed with a paint shaker (manufactured by Asada Tekko Co., Ltd.) as a pre-dispersion for 1 hour with 2 mm zirconia beads and further dispersed with 0.1 mm zirconia beads for 2 hours. Comparative copper nanoparticle dispersion 3 was obtained.
The comparative 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 1 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 Micro Electronics Co., Ltd.), baking was performed for 300 seconds at a microwave output of 450 W to obtain a conductive substrate. It was.

Example 5 Production of Conductive Substrate by Flash Light Baking
In the same manner as in Example 1 (1), copper nanoparticles coated with hexylamine were obtained.
Dispersant containing 3.0 parts by mass of copper nanoparticles coated with hexylamine obtained above and a polyallylamine derivative having a structural unit represented by the above general formula (I) (Ajinomoto Fine Techno Co., Ajisper PB821) 0.6 parts by mass and 3.9 parts by mass of PGMEA were mixed, and dispersed with a paint shaker (manufactured by Asada Tekko Co., Ltd.) as a pre-dispersion for 1 hour with 2 mm zirconia beads, and further dispersed with 0.1 mm zirconia beads for 2 hours, A copper nanoparticle dispersion 5 was obtained.
The copper nanoparticle dispersion 5 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 1 μm.
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 3.4 kV to obtain a conductive substrate.

Example 6 Production of Conductive Substrate by Flash Light Baking
In the same manner as in Example 1, (1), copper nanoparticles coated with 3-ethoxypropylamine were obtained.
3.0 parts by mass of copper nanoparticles coated with 3-ethoxypropylamine obtained above, a dispersant containing a polyallylamine derivative having a structural unit represented by the general formula (I) (manufactured by Ajinomoto Fine-Techno, Azisper PB821) 0.3 parts by mass and 4.2 parts by mass of PGMEA were mixed and pre-dispersed with 2 mm zirconia beads for 1 hour and further dispersed with 0.1 mm zirconia beads for 2 hours on a paint shaker (manufactured by Asada Tekko). The copper nanoparticle dispersion 6 was obtained by dispersing.
The copper nanoparticle dispersion 6 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 1 μm. 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 3.2 kV to obtain a conductive substrate.

[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. The result of the dispersion average particle diameter of the dispersion of each Example and Comparative Example is shown in Tables 1-3.

<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.

<Oxidation resistance evaluation>
The oxidation resistance was evaluated by analyzing the crystal structure of the obtained copper nanoparticles. As a measurement sample, a copper nanoparticle coating film prepared by applying a copper nanoparticle dispersion on a PET substrate and drying at room temperature was used. Using an X-ray diffractometer (manufactured by Rigaku, Smart Lab), the X-ray source was CuKα ray, tube voltage 45 kV, tube current 200 mA. Measurement was performed under the conditions of a scan rate of 4 ° per minute and a step angle of 0.05 °, and the oxidation resistance was evaluated based on the peak intensity of Cu ₂ O (111) with respect to Cu (111). Table 1 shows the results of evaluation of each example and comparative example.
A: The peak intensity of Cu ₂ O (111) with respect to Cu (111) is less than 10%. B: The peak intensity of Cu ₂ O (111) with respect to Cu (111) is 10% or more.

<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 results of evaluation are shown in Tables 2-3.

<Summary of results>
According to Examples 1 to 6, a copper nanoparticle dispersion containing an alkylamine according to the present invention, a polyallylamine derivative having a structural unit represented by the general formula (I), and a solvent, or an alkylamine and the general The coated copper nanoparticles coated with the polyallylamine derivative having the structural unit represented by the formula (I) are excellent in dispersibility and applicability while being excellent in oxidation resistance, and also at low temperature or in a short time. It has been clarified that it is excellent in sinterability and has a high conductivity with a surface resistance of 1 Ω / □ or less. When the copper nanoparticle dispersion and the coated copper nanoparticles according to the present invention are used, it is possible to form a circuit pattern with high accuracy because of excellent coating suitability.
On the other hand, the copper nanoparticle dispersion or coated copper nanoparticle of Comparative Example 1 that is coated with alkylamine and does not contain a polyallylamine derivative is excellent in oxidation resistance, but has poor dispersibility and forms a coating film. The film was repelled and only a non-uniform coating film could be formed. If the coating suitability is poor as in this example, the circuit pattern cannot be formed with high accuracy, and good conductivity cannot be obtained.
Further, the copper nanoparticle dispersion or the coated copper nanoparticle of Comparative Example 2 coated with a polyallylamine derivative having a specific structure and 1-hexanol and not coated with alkylamine is dispersible and coated with the polyallylamine derivative. Although aptitude was imparted, the oxidation resistance was poor and the dispersibility was inferior. Moreover, from the result of Comparative Example 3, when coated with a polyallylamine derivative having a specific structure and 1-hexanol and not coated with an alkylamine, low temperature sinterability can be obtained even if coating suitability is imparted. It was revealed that good conductivity could not be obtained due to the poorness.

1 Base material 2 Metal film 100 Substrate

Claims (7)

Coated copper nanoparticles, wherein the copper nanoparticles are coated with an alkylamine and a polyallylamine derivative having a structural unit represented by the following general formula (I).

(In the general formula (I), R ¹ represents a free amino group, a group represented by the following general formula (II) or the following general formula (III), and a plurality of R ¹ may be the same or different. Provided that at least ^one of the plurality of R ¹ is a group represented by the general formula (III).)

(In General Formula (II) and General Formula (III), R ² represents a carboxy group from any of a polyester having a free carboxylic acid, a polyamide having a free carboxylic acid, and a polyester amide having a free carboxylic acid. (Represents a residue excluding) A copper nanoparticle dispersion comprising copper nanoparticles, alkylamine, a polyallylamine derivative having a structural unit represented by the following general formula (I), and a solvent.

(In the general formula (I), R ¹ represents a free amino group, a group represented by the following general formula (II) or the following general formula (III), and a plurality of R ¹ may be the same or different. Provided that at least ^one of the plurality of R ¹ is a group represented by the general formula (III).)

(In General Formula (II) and General Formula (III), R ² represents a carboxy group from any of a polyester having a free carboxylic acid, a polyamide having a free carboxylic acid, and a polyester amide having a free carboxylic acid. (Represents a residue excluding) A coating solution containing a copper nanoparticle dispersion containing copper nanoparticles, alkylamine, a polyallylamine derivative having a structural unit represented by the following general formula (I), and a solvent is applied onto a substrate. A process for producing a conductive substrate, comprising: a step of forming a coating film; and a step of firing the coating film.

(In the general formula (I), R ¹ represents a free amino group, a group represented by the following general formula (II) or the following general formula (III), and a plurality of R ¹ may be the same or different. Provided that at least ^one of the plurality of R ¹ is a group represented by the general formula (III).)

(In General Formula (II) and General Formula (III), R ² represents a carboxy group from any of a polyester having a free carboxylic acid, a polyamide having a free carboxylic acid, and a polyester amide having a free carboxylic acid. (Represents a residue excluding)   The method for manufacturing a conductive substrate according to claim 3, wherein the baking step is a step of baking by irradiation with flash light. The process of preparing the copper nanoparticle by heating the mixture containing a compound containing copper, a reducing compound, and an alkylamine, and the structure represented by the following general formula (I) in the solvent in the solvent And a step of dispersing with a polyallylamine derivative having a unit.

(In the general formula (I), R ¹ represents a free amino group, a group represented by the following general formula (II) or the following general formula (III), and a plurality of R ¹ may be the same or different. Provided that at least ^one of the plurality of R ¹ is a group represented by the general formula (III).)

(In General Formula (II) and General Formula (III), R ² represents a carboxy group from any of a polyester having a free carboxylic acid, a polyamide having a free carboxylic acid, and a polyester amide having a free carboxylic acid. (Represents a residue excluding) The process of preparing the copper nanoparticle by heating the mixture containing a compound containing copper, a reducing compound, and an alkylamine, and the structure represented by the following general formula (I) in the solvent in the solvent A step of preparing a dispersion by dispersing with a polyallylamine derivative having a unit, a step of applying a coating liquid containing the dispersion on a substrate to form a coating film, and a step of baking the coating film A method for manufacturing a conductive substrate.

(In the general formula (I), R ¹ represents a free amino group, a group represented by the following general formula (II) or the following general formula (III), and a plurality of R ¹ may be the same or different. Provided that at least ^one of the plurality of R ¹ is a group represented by the general formula (III).)

(In General Formula (II) and General Formula (III), R ² represents a carboxy group from any of a polyester having a free carboxylic acid, a polyamide having a free carboxylic acid, and a polyester amide having a free carboxylic acid. (Represents a residue excluding)   The method for manufacturing a conductive substrate according to claim 6, wherein the firing step is a firing step by flash light irradiation.

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