TWI501260B - Conductive paste and substrate with conductive film - Google Patents

Description

Conductive paste and substrate with conductive film

The present invention relates to a conductive paste and a substrate using the same with a conductive film.

Conventionally, a method of forming a conductive paste for forming a wiring conductor such as an electronic component or a printed wiring board has been known. Among them, the production of the printed wiring board is performed by applying a conductive paste to a desired pattern shape on an insulating substrate and curing it to form a wiring pattern.

As a conductive paste, from the viewpoint of improving the reliability of an electronic device or a wiring board, a technique of using a copper paste instead of a silver paste containing silver as a main component has been proposed. Since the copper paste is difficult to cause migration, the connection reliability of the circuit can be improved.

The printed wiring board and the like require various characteristics, and the adhesion to the base material of the wiring pattern is one of the most important characteristics because it has an important influence on reliability.

As a base material used for a printed wiring board, glass, polyethylene terephthalate (PET), polyimine (PI, Polyimide), etc. are used previously, but in recent years, a touch panel etc. are used. The use is centered on a substrate coated with an ITO film of a tin-doped indium tin oxide (ITO) film as a transparent conductive film on an insulating substrate such as glass or PET. Further, a structure in which a conductive film is formed on an ITO film has been proposed (for example, see Patent Document 1).

In such a structure, as a method of improving the adhesion of the conductive film to the ITO film, a solution obtained by dissolving a transition metal compound in an organic solvent is applied to the surface of the ITO film, and heat treatment is performed to form a substrate. The method of the layer (for example, refer to Patent Document 2).

However, in this method, since it is necessary to form a base layer and to apply a conductive paste after the base layer is formed, there is a problem that the number of steps is increased and workability is poor.

In addition, in order to improve durability such as heat resistance, moisture resistance, and fastness of a wiring pattern (conductive film) of a printed wiring board, it is proposed to include a thermosetting resin such as copper powder or a phenol resin, and lauric acid a conductive paste or conductive powder containing an amine group-containing carboxylic acid such as an acid and a polyamine (for example, a polyethyleneimine) having a weight average molecular weight of 80 to 30,000 in one molecule and having 3 or more nitrogen atoms; A conductive paste of a thermosetting resin such as a phenol resin or an amine salt of p-toluenesulfonic acid (see, for example, Patent Document 3 and Patent Document 4). However, in the case of using the conductive paste shown in Patent Document 3, as described in Comparative Example 6 and Comparative Example 7 in the following examples, the ITO film did not exhibit good adhesion. Further, in the case of using the conductive paste shown in Patent Document 4, as described in Comparative Example 8 and Comparative Example 9 in the following examples, the ITO film did not exhibit good adhesion.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open Publication No. 2009-116452

Patent Document 2: Japanese Patent Laid-Open Publication No. 2005-293937

Patent Document 3: Japanese Patent Laid-Open No. Hei 4-253773

Patent Document 4: Japanese Patent Laid-Open No. Hei 9-293413

The present invention has been made to solve the above problems, and an object thereof is to provide a conductive film which is excellent in adhesion and can be formed by directly coating and hardening a base layer without forming an underlayer on an ITO film. The conductive paste and the substrate with the conductive film formed using the conductive paste.

The present invention provides the following conductive paste and a substrate with a conductive film.

[1] A conductive paste characterized by comprising:

(A) copper particles having an average particle diameter of 10 nm to 20 μm,

(B) a carboxylate of a polymer compound having at least one primary amino group in the molecule (the number of carbons including a carbon of a carbonyl group is 10 or less), and

(C) a resin containing an acidic functional group capable of reacting with the above primary amine group.

[2] The conductive paste according to [1], wherein the (A) copper particles are copper particles having a surface oxygen content of 0.5 or less.

[3] The conductive paste according to [1] or [2], wherein the polymer compound containing the primary amino group has a mass average molecular weight (Mw) of 300 to 20,000.

[4] The conductive paste according to any one of [1] to [3] wherein the polymer compound containing the above-described primary amine group has an amine value of from 700 to 1500 mgKOH/g according to the specification of JIS K7237.

[5] The conductive paste according to any one of [1] to [4] wherein the polymer compound containing the above primary amine group is polyethyleneimine or polyallylamine.

[6] The conductive paste according to any one of [1] to [5] wherein the carboxylate of the component (B) is a formate.

[7] The conductive paste according to any one of [1] to [6] wherein the (C) acid functional group-containing resin is a phenol resin.

[8] The conductive paste according to any one of [1] to [7] wherein the content of the carboxylate of the polymer compound containing the primary amine group (B) is 100 parts by mass relative to the copper particle of the above (A). It is 0.05 to 5 parts by mass.

[9] of [1] to [8] in the conductive paste according to any one of the, further comprising at 25 deg.] C and ionic strength of the case when a copper ion-stabilization degree constant of 0.1 logK _Cu chelate is from 5 to 15 of Compound.

[10] A substrate with a conductive film, comprising: a substrate having a tin-doped indium oxide (ITO) film, and coating on the ITO film as in [1] to [9] A conductive paste that hardens and forms a conductive film.

According to the present invention, it is possible to obtain a conductive paste which can form a conductive film having good adhesion to an ITO film and having high conductivity without forming a base layer on an ITO film having a substrate having an ITO film. Further, the conductive paste is excellent in storage stability, and can form a conductive film which does not deteriorate in adhesion to the ITO film or conductivity after storage for a long period of time.

Further, according to the present invention, by using such a conductive paste, a substrate having a conductive film having a conductive film having good adhesion to an ITO film and having high conductivity can be obtained.

Hereinafter, embodiments of the present invention will be described. Furthermore, the invention is not limited by the following description.

<conductive paste>

The conductive paste according to the embodiment of the present invention contains (A) a copper particle having an average particle diameter of 10 nm to 20 μm and (B) a polymer compound having at least one primary amine group in the molecule (hereinafter, sometimes referred to as The carboxylate of the polymer compound containing an amine group and (C) a resin containing an acidic functional group capable of reacting with a primary amine group of the above-mentioned amine group-containing polymer compound. Hereinafter, each component constituting the conductive paste will be described in detail.

(A) copper particles

(A) The copper particles are conductive components of the conductive paste, and copper particles having an average particle diameter of 10 nm to 20 μm are used. Moreover, it is preferable that the (A) copper particles have a surface oxygen amount of 0.5 or less.

The "surface oxygen amount" in the present invention is expressed by the ratio of the surface oxygen concentration (unit: atom%) to the surface copper concentration (unit: atom%) of the copper particles. The surface oxygen amount is preferably 0.3 or less. Further, the surface copper concentration and the surface oxygen concentration of the copper particles were determined by X-ray photoelectron spectroscopy. The measurement is performed on a range from the surface of the particle toward the center up to a depth of about 3 nm. When the range is measured, the state of the particle surface can be sufficiently grasped.

Further, the (A) copper particles preferably have an oxygen concentration of 700 ppm or less as a whole. This oxygen concentration can be measured using an oxygen concentration meter.

In the present invention, by using such (A) copper particles, the contact resistance between the copper particles becomes smaller, and the conductivity of the obtained conductive film is improved.

As the copper particles (A), various particles can be used as long as they are copper particles having the above surface oxygen amount. As described below, the copper particles may be the first particles or the second particles, and further may be formed by combining the first particles and the second particles (particles attached to or bonded to the surface of the first particles) Wait).

The average particle diameter of the (A) copper particles is preferably in the range of 10 nm to 20 μm, and may be appropriately adjusted within the range depending on the shape of the copper particles. The average particle diameter (average primary particle diameter) of the case where the copper particles contain the first particles is more preferably 0.3 to 20 μm. Further, the average particle diameter (average aggregated particle diameter) when the copper particles are composed only of the second particles is preferably 0.01 to 1 μm, particularly preferably 0.02 to 0.4 μm. When the average particle diameter of the copper particles is at least the above lower limit value, the flow characteristics of the conductive paste containing the copper particles are good. In addition, when the average particle diameter of the copper particles is at most the above upper limit value, it becomes easy to produce fine wiring.

As the (A) copper particles, for example, copper particles (A1) to (A5) shown below are preferably used.

(A1) Copper particles which are first particles and have an average primary particle diameter of 0.3 to 20 μm.

(A2) a copper composite particle which is attached to a surface of a copper particle which is a first particle having an average primary particle diameter of 0.3 to 20 μm, and a copper hydride particle which is a second particle having an average agglomerated particle diameter of 20 to 400 nm. .

(A3) Copper hydride fine particles which are second particles and have an average aggregated particle diameter of 10 nm to 1 μm.

(A4) copper composite particles which are attached to the surface of copper particles as the first particles and having an average primary particle diameter of 1 to 20 μm or more, and having copper as an average particle diameter of 20 to 400 nm Microparticles.

(A5) Copper microparticles which are second particles and have an average agglomerated particle diameter of 10 nm to 1 μm.

The copper hydride fine particles are converted into metallic copper by heating to become copper fine particles. That is, the copper particles (A2) are heated to become copper particles (A4). Further, the copper particles (A3) are heated to form copper particles (A5).

The average particle diameter in the present specification can be determined in the following manner depending on the shape of the copper particles. The average primary particle diameter of the primary particles is calculated by measuring the Feret diameter of 100 particles randomly selected from a scanning electron microscope (hereinafter referred to as "SEM", Scanning Electron Microscope) image, and Calculate the average of these. The secondary particle system is calculated by measuring the Feret diameter of 100 particles randomly selected from the image of a transmission electron microscope (hereinafter referred to as "TEM", Transmission Electron Microscope), and calculating the same. average value.

Further, when the copper particles (A2) contain copper particles as the first particles and copper hydride fine particles as the second particles attached to the copper particles, all the particles are observed by SEM, and the measurement also includes The Feret diameter of the second particle.

As the copper particles having a surface oxygen amount of 0.5 or less, "surface-modified copper particles" obtained by subjecting the surface of copper particles to reduction treatment or "composite of copper particles attached to at least a part of the surface of copper particles" can be preferably used. Metallic copper particles."

In the present invention, the "surface-modified copper particles" obtained by subjecting the surface of the copper particles to a reduction medium having a pH of 3 or less can be produced, for example, by the following wet reduction method: (1) Copper particles are used. After dispersing in a dispersion medium to form a "copper dispersion", (2) adjusting the pH of the copper dispersion to a specific value or less, and (3) adding a reducing agent to the copper dispersion. The steps of (1) to (3) will be described below.

(1) Production of copper dispersion

As the copper particles dispersed in the copper dispersion, copper particles which are usually used as a conductive paste can be used, and the particle shape can be spherical or plate-shaped.

The average particle diameter of the copper particles dispersed in the copper dispersion is preferably from 0.3 to 20 μm, more preferably from 1 to 10 μm. If the average particle diameter of the copper particles is less than 0.3 μm, the fluidity of the conductive paste is lowered. On the other hand, when the average particle diameter of the copper particles exceeds 20 μm, it is difficult to produce fine wiring by using the obtained conductive paste.

The copper dispersion can be obtained by introducing the above copper particles into a dispersion medium. The concentration of the copper particles in the copper dispersion is preferably from 0.1 to 50% by mass. When the concentration of the copper particles is less than 0.1% by mass, the amount of the dispersion medium contained in the copper dispersion liquid is too large, and the production efficiency cannot be maintained at a sufficient level. On the other hand, when the concentration of the copper particles exceeds 50% by mass, the influence of aggregation of the particles becomes excessive, and the yield of the surface-modified copper particles is lowered.

The dispersion medium of the copper dispersion liquid is not particularly limited as long as it can disperse the copper particles, and those having high polarity can be preferably used. As the highly polar dispersion medium, for example, water; alcohols such as methanol, ethanol, and 2-propanol; glycols such as ethylene glycol; and media in which these are mixed, in particular, water can be preferably used. .

The copper particles dispersed in the dispersion medium may be subjected to surface treatment of the surface of the particles by a surface treatment agent from the viewpoint of preventing oxidation of the surface of the particles. As the surface treatment agent, a long-chain carboxylic acid such as stearic acid, palmitic acid or myristic acid can be used.

Further, in the case where a long-chain carboxylic acid is used as the surface treatment agent, the copper particles may be directly supplied to the reduction treatment, but in order to smoothly carry out the reduction reaction described below, it is preferred to use a long-chain carboxylic acid (surface treatment agent). After being removed from the particle surface, it is dispersed in the dispersion medium. The removal of the long-chain carboxylic acid can be carried out by a method such as washing with an acid.

Further, from the viewpoint of improving the dispersibility of the copper particles to the dispersion medium, it is preferred to carry out pretreatment. Since the surface of the particles is made hydrophilic by pretreatment, the dispersibility of the highly polar dispersion medium such as water can be improved.

As the pretreatment agent, for example, an aliphatic monocarboxylic acid having an aliphatic carbon number of 6 or less, an aliphatic monocarboxylic acid such as an aliphatic hydroxymonocarboxylic acid or an aliphatic amino acid, and an aliphatic polycarboxylic acid can be preferably used (for example). An aliphatic polycarboxylic acid or an aliphatic hydroxy polycarboxylic acid having a carbon number of 10 or less. More preferably, it is an aliphatic polycarboxylic acid having a carbon number of 8 or less, and specifically, glycine acid, alanine, citric acid, malic acid, maleic acid, malonic acid or the like can be preferably used.

It is preferred to add a dispersing agent to the copper dispersion obtained in the above manner. As the dispersing agent, various compounds which are water-soluble to the copper particles can be used. As the dispersing agent, specifically, for example, a water-soluble polymer compound such as polyvinyl alcohol, polyacrylic acid, polyvinylpyrrolidone, hydroxypropylcellulose, propylcellulose or ethylcellulose, or ethylenediaminetetraacetic acid can be used. a chelate compound such as iminodiacetic acid or the like.

The amount of the surface treatment agent, the pretreatment agent, and the dispersant present on the copper particles after the above treatment is preferably 0.1 to 10% by mass based on the copper particles.

The treatment of the copper particles by the pretreatment agent or the dispersing agent can be carried out by adding a pretreatment agent or the like to a solution obtained by using a solvent such as water, adding copper particles and stirring the mixture on the surface of the copper particles. Treatment agent, etc.

From the viewpoint of increasing the processing speed, it is preferred to carry out the pretreatment, preferably while heating the solution. The heating temperature is preferably carried out at a temperature of 50 ° C or more and a boiling point of a solvent (water or the like) or less. When a surface treatment agent such as a carboxylic acid or a dispersant is added to the solvent, the heating temperature is preferably set to be equal to or lower than the boiling point of the compounds. The heat treatment time is preferably 5 minutes or longer and 180 minutes or shorter. If the heating time is less than 5 minutes, the effect of increasing the processing speed cannot be sufficiently obtained. On the other hand, if the heat treatment is performed for more than 3 hours, the cost becomes too high, which is not economically preferable.

Further, in the pretreatment or the like, from the viewpoint of preventing oxidation of the surface of the copper particles, it is preferred to carry out the replacement of the inside of the processing container with an inert gas such as nitrogen or argon. After the pretreatment, the solvent is removed, and if necessary, washed with water or the like, whereby copper particles dispersed in the dispersion can be obtained.

(2) Adjustment of pH of copper dispersion

The adjustment of the pH can be carried out by adding a pH adjuster to the copper dispersion. As the pH adjuster, an acid can be used, and for example, a carboxylic acid such as formic acid, citric acid, maleic acid, malonic acid, acetic acid or propionic acid; or an inorganic acid such as sulfuric acid, nitric acid or hydrochloric acid can be preferably used. As the carboxylic acid, the same compound as the carboxylic acid used as the pretreatment agent can be used.

Among these, the carboxylic acid is preferably used as a pH adjuster by adhering to the surface of the copper particles and remaining on the surface of the surface-modified copper particles after the reduction treatment to protect the surface of the particles, thereby suppressing the oxidation reaction of copper. Use. In particular, since formic acid contains a reducing aldehyde group (-CHO), it is possible to suppress the progress of oxidation of the surface of the particles by remaining on the surface of the surface-modified copper particles. By using a conductive paste in which such copper particles are blended, it is difficult to form an oxide film, and a conductive film in which an increase in volume resistivity is suppressed can be formed. Further, the pH adjuster is not limited to the acid component. For example, when the pH of the dispersion is low, a base may be used as the pH adjuster.

The oxide film on the surface of the particle is smoothly removed by the subsequent reduction treatment step, and from the viewpoint of lowering the surface oxygen concentration of the surface-modified copper particles obtained, the pH of the copper dispersion is preferably 3 or less. . When the pH of the dispersion exceeds 3, the effect of removing the oxide film formed on the surface of the copper particles cannot be sufficiently obtained, and the oxygen concentration on the surface of the copper particles cannot be sufficiently reduced. On the other hand, it is preferred to set the pH of the dispersion to 0.5 or more. When the pH of the dispersion is less than 0.5, the copper ions are excessively eluted, and the surface modification of the copper particles becomes difficult to proceed smoothly. The pH of the dispersion is more preferably 0.5 or more and 2 or less. Further, when the pH of the dispersion is 3 or less, the pH adjustment may be carried out without adding a pH adjuster, and the dispersion may be directly subjected to reduction treatment.

(3) Reduction treatment of copper dispersion

The reducing agent is added to the copper dispersion whose pH is adjusted to carry out a reduction treatment. As the reducing agent to be added, at least one selected from the group consisting of hypophosphites such as metal hydrides, hypophosphite, and sodium hypophosphite, amine borane such as dimethylamine borane, and formic acid can be used. Examples of the metal hydride include lithium aluminum hydride, lithium borohydride, sodium borohydride, aluminum hydride, potassium hydride, and calcium hydride. Among these, hypophosphorous acid and sodium hypophosphite can be preferably used. Further, as described above, since formic acid is also used as a pH adjuster, when formic acid is added to a dispersion medium, it functions as a reducing agent and also functions as a pH adjuster.

The reducing agent to be added to the copper dispersion is preferably added in a large excess amount with respect to the amount of copper atoms on the surface of the particles. Specifically, it is preferable to add a reducing agent in an amount of 1 time or more in terms of a molar ratio with respect to the total number of moles of copper particles contained in the dispersion liquid, particularly preferably all copper atoms with respect to the copper particles. Moir number, using a reducing agent in an amount of 1.2 to 10 times in terms of molar ratio. If a reducing agent is added in an amount of 10 times or more with respect to the total number of moles of copper, it is disadvantageous in terms of cost, and the production cost becomes too high. Further, the amount of decomposition products derived from the reducing agent becomes excessive, and the removal thereof becomes complicated.

The reduction reaction is preferably carried out by setting the temperature of the dispersion medium to 5 to 60 ° C, more preferably 35 to 50 ° C. By setting the temperature of the dispersion liquid to 60 ° C or lower, the influence of the concentration change of the entire dispersion liquid when the dispersion medium is evaporated and removed from the copper dispersion liquid can be reduced.

The reduction of the copper particles can be carried out by adding a reducing agent to the copper dispersion as described above or by dispersing copper particles in a dispersion medium to which a reducing agent is added.

In addition, from the viewpoint of smoothly removing the oxide film on the surface of the copper particles, the pH of the copper dispersion liquid after the addition of the reducing agent is preferably maintained at a state of 3 or less from the start of the reaction to the end of the reaction.

The oxidation-reduction potential of the copper dispersion can be appropriately adjusted by the amount or type of the reducing agent added. From the viewpoint of smoothly performing the reduction reaction of copper ions, the potential of the redox potential of the copper dispersion is preferably 100 to 300 mV with respect to a standard hydrogen electrode (SHE, Standard Hydrogen Elect), particularly preferably 100 to 220 mV. . Further, the oxidation-reduction potential can be obtained as a potential difference from the standard electrode. In the present specification, the oxidation-reduction potential is labeled with a potential difference measured using a standard hydrogen electrode as a standard electrode.

After the decomposition of the reducing agent is substantially completed, the surface-modified copper particles are separated from the dispersion, washed with water or the like as needed, and surface-modified copper particles having a surface oxygen content of 0.5 or less can be obtained. Copper particles of the component (A). (A) The surface oxygen concentration of the copper particles can be adjusted to be required by the adjustment of the pH of the copper dispersion or the adjustment of the redox potential of the copper dispersion in the steps (1) to (3) above. range.

In addition, by performing the surface treatment of the above (1) to (3), copper oxide (Cu ₂ O, CuO) existing on the surface of the copper particles as a starting material can be reduced to copper atoms, so that it can be reduced as a hindrance. The amount of copper oxide present, which is the main cause of electrical conductivity.

Further, since by-products such as a reducing agent decomposition product are usually soluble in the component of the dispersion medium, they can be separated from the surface-modified copper particles by filtration or centrifugation.

Further, on the surface of the copper particles after the surface treatment of the above (1) to (3), a part of the copper atoms is reduced by the reducing agent to form copper hydride. Therefore, after the surface-treated copper particles are separated from the dispersion, the copper hydride can be changed to copper by heat treatment at 40 to 120 °C.

In the present invention, the "composite metal copper particles" are obtained by adhering metallic copper fine particles to at least a part of the surface of the metallic copper particles, and heating the "copper composite particles" obtained by adhering the copper hydride fine particles to the surface of the metallic copper particles. And the copper hydride microparticles are converted into metal copper microparticles. Further, whether or not fine particles were adhered to the surface of the metallic copper particles was observed by observing the SEM image. Further, the identification of the copper hydride fine particles adhering to the surface of the metal copper particles can be carried out using an X-ray diffraction apparatus (manufactured by Rigaku Corporation, TTR-111).

As the metal copper particles in the copper composite particles, known copper particles which are generally used in the conductive paste can be used, and the particle shape can be spherical or plate-like. Further, the average particle diameter of the metallic copper particles is preferably from 0.3 to 20 μm, more preferably from 1 to 10 μm. When the average particle diameter of the metallic copper particles is less than 0.3 μm, sufficient flow characteristics cannot be obtained when the conductive paste is formed. On the other hand, when the average particle diameter of the metallic copper particles exceeds 20 μm, it is difficult to produce fine wiring by using the obtained conductive paste. In addition, as described above, the average particle diameter of the metallic copper particles is measured by measuring the Feret diameter of 100 metal copper particles randomly selected from the TEM image or the SEM image, and calculating the average value of the measured values.

The copper hydride fine particles in the copper composite particles are mainly present as secondary particles in which primary particles of about 1 to 20 nm are aggregated, and the particle shape may be spherical or plate-shaped. The average particle diameter of the copper hydride fine particles is preferably from 20 to 400 nm, more preferably from 30 to 300 nm, and still more preferably from 50 to 200 nm. Particularly good is 80~150 nm. When the average particle diameter of the copper hydride fine particles is less than 20 nm, the copper hydride fine particles are likely to be welded and grown, and when the conductive film is formed, defects such as cracks accompanying volume shrinkage may occur. On the other hand, when the average particle diameter of the copper hydride fine particles exceeds 400 nm, the surface area of the particles is insufficient, and it is difficult to cause surface melting, and it is difficult to form a dense conductive film. The average particle diameter of the copper hydride fine particles is measured by measuring the particle diameters of 100 hydrogenated copper fine particles randomly selected from the TEM image or the SEM image, and calculating the average value of the measured values.

The amount of the copper hydride fine particles adhering to the surface of the metal copper particles is preferably from 5 to 50% by mass, more preferably from 10 to 35% by mass, based on the amount of the metal copper particles. When the amount of the copper hydride fine particles is less than 5% by mass of the amount of the metal copper particles, the conductive channels are not sufficiently formed between the metal copper particles, and the effect of lowering the volume resistivity of the conductive film cannot be sufficiently obtained. On the other hand, when the amount of the copper hydride fine particles exceeds 50% by mass of the amount of the metal copper particles, it is difficult to ensure sufficient fluidity as the conductive paste. Further, the amount of the copper hydride fine particles adhering to the surface of the metal copper particles can be, for example, the copper ion concentration in the water-soluble copper compound solution before the addition of the reducing agent, and the copper remaining in the reaction liquid after the formation of the copper hydride fine particles is completed. Calculated by the difference in ion concentration.

The copper composite particles can be produced, for example, by the following wet reduction method: (i) after the copper hydride fine particles are formed in the reaction system R; (ii) the metal copper particles are introduced into the reaction system R, and the copper hydride fine particles are attached to the metal copper particles. "Copper composite particles" are formed on the surface; (iii) "Copper composite particles" are separated from the reaction system R. Further, by heating the copper composite particles, the copper hydride fine particles can be converted into metal copper fine particles to obtain "composite metal copper particles".

In the present specification, the term "reaction system R" means a system for producing copper hydride fine particles. The reaction system R contains not only (I) a system in which an unreacted state of a water-soluble copper compound solution is added with a reducing agent, but also (II) a copper hydride microparticle is being formed by a reaction of a water-soluble copper compound and a reducing agent. In the state of the system, (III) the reaction in which the copper hydride microparticles are formed is completed, and the hydrogen hydride copper particles after the formation is dispersed; in the solvent such as water, in addition to the water-soluble copper compound, copper ions, and various anions, After the copper hydride fine particles are formed, various ions, other residues, a reducing agent, or a decomposition product thereof remaining in the solvent are present. Therefore, the resulting copper hydride microparticles are separately separated from the solution and redispersed in the dispersion medium to obtain a dispersion which does not conform to the reaction system R in the present specification. The steps of (i) to (iii) are further described below.

(i) Formation of copper hydride microparticles

The reaction system R can be formed by adding at least a reducing agent to a water-soluble copper compound solution formed by adding a water-soluble copper compound to a solvent.

As the water-soluble copper compound forming the reaction system R, a copper salt is preferred. As the copper salt, a salt of a copper (II) ion and an inorganic acid or a carboxylic acid is preferred. The carboxylic acid preferably includes a carboxylic acid having a carbon atom of a carboxyl group of 1 to 4, particularly preferably formic acid, acetic acid or propionic acid. The water-soluble copper compound is preferably copper sulfate, copper nitrate, copper formate, copper acetate, copper chloride, copper bromide or copper iodide.

Further, the solvent of the water-soluble copper compound solution is not limited to those capable of dissolving a water-soluble copper compound, and in particular, water can be preferably used.

The concentration of the water-soluble copper compound contained in the water-soluble copper compound solution is preferably from 0.1 to 30% by mass. When the concentration of the water-soluble copper compound is less than 0.1% by mass, the amount of water in the solution becomes excessive, and the production efficiency of the copper hydride fine particles is lowered. On the other hand, when the concentration of the water-soluble copper compound exceeds 30% by mass, the yield of the copper hydride fine particles is rather lowered.

The water-soluble copper compound solution to which the reducing agent is added is preferably adjusted to have a pH value below a specific value. The pH adjuster for the water-soluble copper compound solution can be used in the production step of the surface-modified copper particles in the same manner as the acid component exemplified as the pH adjuster for the copper dispersion. Specifically, for example, formic acid, citric acid, maleic acid, malonic acid, acetic acid, propionic acid, sulfuric acid, nitric acid, hydrochloric acid or the like can be used.

Among these, formic acid can be particularly preferably used as the pH adjuster of the water-soluble copper compound solution. Since formic acid contains a reducing aldehyde group (-CHO), it can suppress oxidation of copper fine particles by remaining on the surface of the particle.

The pH of the water-soluble copper compound solution is preferably set to 3 or less. By setting the pH of the water-soluble copper compound solution to 3 or less, the production efficiency of the copper hydride fine particles can be improved. The reason is presumed to be that the reduction treatment can be carried out in a state where copper ions and hydrogen ions are mixed in the solution. When the pH of the water-soluble copper compound solution exceeds 3, the metal copper fine particles are likely to be formed, and the formation ratio of the copper hydride fine particles is lowered. The pH of the water-soluble copper compound solution is more preferably set to 0.5 to 2 from the viewpoint of increasing the production rate of the copper hydride fine particles.

As the reducing agent, at least one selected from the group consisting of a hypophosphite such as a metal hydride, hypophosphorous acid, and sodium hypophosphite, an amine borane such as dimethylamine borane, and formic acid can be used. Examples of the metal hydride include lithium aluminum hydride, lithium borohydride, sodium borohydride, aluminum hydride, potassium hydride, and calcium hydride. Among these, hypophosphorous acid and sodium hypophosphite can be preferably used. In addition, since formic acid is also used as a pH adjuster as described above, when formic acid is added to the dispersion medium, it functions as a reducing agent and functions as a pH adjuster.

The reducing agent of the water-soluble copper compound solution is preferably added in an amount of 1.2 to 10 times the equivalent amount of the copper ion in the solution. If the amount of the reducing agent added to the water-soluble copper compound solution is less than 1.2 times the equivalent amount of the copper ion, it is difficult to obtain a sufficient reduction effect. On the other hand, when the amount of the reducing agent added exceeds 10 times the equivalent amount of the copper ion, the content of impurities such as sodium, boron, and phosphorus in the copper hydride fine particles may increase.

The reaction system R may be formed by mixing a reducing agent solution obtained by mixing a solvent such as the reducing agent and water with a water-soluble copper compound solution, or may be formed by adding a reducing agent in a solid state to a water-soluble copper compound solution. In the reaction system R thus formed, under acidic conditions, copper ions are reduced by a reducing agent to form copper hydride fine particles, and the crystal grains are grown.

(ii) Formation of copper composite particles

The metal copper particles are introduced into the reaction system R formed in the above (i), and the copper hydride fine particles are attached to the surface of the metal copper particles to form "copper composite particles". Further, the shape and particle diameter of the metal copper particles charged in the reaction system R are as described above.

The metal copper particles are preferably added to the reaction system R in the stage in which copper ions are present or the water-soluble copper compound solution. By adding metallic copper particles to the reaction system R in which copper ions are present, since the reduction reaction of copper ions occurs in the environment in which the metallic copper particles and the copper hydride fine particles coexist, the copper copper particles and the copper hydride fine particles can be formed. A firm combination. Further, whether or not copper ions are present in the reaction system R can be confirmed by measurement using a copper ion electrode or a concentration of copper ions in a visible light absorption spectrum, or can be confirmed by measurement of an oxidation-reduction potential of an aqueous solution.

That is, the metal copper particles are preferably added to the reaction system R in the process of producing the copper hydride fine particles, or the metal copper particles are added to the water-soluble copper compound solution before the addition of the reducing agent, and then a reducing agent is added thereto. Reaction system R. It is preferred to add metal copper particles to the reaction system R in the process of producing copper hydride fine particles.

Further, the reaction system R to which the metal copper particles are added is not limited to the above state. For example, the amount of copper ions or the amount of reduction in the reaction system R may be reduced by the progress of the reduction reaction, or may be formed by the copper hydride fine particles or Metal copper particles are added to the reaction system R in a state in which the growth of the hydrogenated copper microparticles after the formation is stopped. In other words, the metal copper particles may be introduced into the reaction system R before the formation of the copper hydride fine particles, or may be introduced into the reaction system R in the process of generating the copper hydride fine particles, or may be introduced into the reaction system R after the formation of the copper hydride fine particles. .

By adding metallic copper particles to the reaction system R, hydrogenated copper fine particles can be attached to the surface of the metallic copper particles, and "copper composite particles" can be formed in the reaction system R. The amount of the copper ion contained in the reaction system R to which the metal copper particles are added is preferably from 1 to 100% by mass, more preferably from 5 to 100% by mass based on the amount of the copper ion of the water-soluble copper compound solution before the addition of the reducing agent. ~100% by mass. Further, the copper in the water-soluble copper compound solution is all ionized.

The temperature of the reaction system R is preferably 60 ° C or lower. By setting the temperature of the reaction system R to 60 ° C or lower, the decomposition of the copper hydride fine particles in the reaction system R can be suppressed.

The metal copper particles are preferably added in a state where the redox charge of the reaction system R is in the range of 100 to 300 mVSHE. Further, as described above, "SHE" means a standard hydrogen electrode, and "mVSHE" means an oxidation-reduction potential measured based on a standard hydrogen electrode. In the present specification, the measured value of the oxidation-reduction potential is measured based on a standard hydrogen electrode.

(iii) Separation of copper composite particles

The copper composite particles formed in the reaction system R are separated from the reaction system R. The method of separating the copper composite particles from the reaction system R is not particularly limited. For example, the powdery copper composite particles can be separated from the reaction system R by a method such as centrifugation or filtration.

After the separation from the reaction system, the soluble impurities adhering to the surface of the particles are washed and purified by removing the washing liquid such as water, and the powdery copper composite particles can be obtained. Further, the solvent of the reaction system R may be replaced before the separation of the copper composite particles, and the impurities (decomposed products of the reducing agent, etc.) may be removed together with the solvent.

By heat-treating the copper composite particles separated from the reaction system R, the copper hydride fine particles are converted into metal copper fine particles, and "composite metal copper particles" having a surface oxygen amount of 0.5 or less can be obtained.

Since the composite metal copper particles can form a conductive path reliably by using the metal copper fine particles existing between the metal copper particles, the volume resistivity at the time of forming the conductive film can be reduced. Further, when the metallic copper fine particles are free from the conductive paste, the viscosity of the conductive paste is increased. As described above, since the copper hydride fine particles are converted into the metallic copper fine particles, the metallic copper fine particles are difficult to be made from the metal. Since the copper particles are peeled off, it is possible to obtain a conductive paste in which the increase in viscosity is suppressed.

The heat treatment of the copper composite particles is preferably carried out at a temperature of from 60 to 120 °C. When the heating temperature exceeds 120 ° C, the metal copper fine particles are likely to be welded to each other, and the volume resistivity when the conductive film is formed becomes high. On the other hand, if the heating temperature is less than 60 ° C, the time required for the heat treatment becomes long, which is not preferable in terms of manufacturing cost. The heat treatment of the copper composite particles is more preferably carried out at 60 to 100 ° C, and more preferably at 60 to 90 ° C. In addition, the residual moisture content of the composite metal copper particles obtained after the heat treatment is preferably 3% by mass or less, and more preferably 1.5% by mass or less.

The heat treatment of the copper composite particles is preferably carried out under a reduced pressure of -101 to -50 kPa. If the heat treatment is carried out at a pressure of more than -50 kPa, the time required for drying becomes long, which is not preferable in terms of production cost. On the other hand, when the pressure at the time of heat treatment is less than -101 kPa, it is necessary to use a large-sized apparatus for removal and drying of an excess solvent (for example, water), and the manufacturing cost becomes high.

The surface oxygen concentration of the "composite metal copper particles" can be adjusted by adjusting the pH of the water-soluble copper compound solution, the oxidation-reduction potential of the reaction system R, or the temperature of the reaction system R by the steps (i) to (iii) above. Or adjusting the partial pressure of oxygen during the heat treatment of the copper composite particles, and adjusting to the desired range.

As the other (A) copper particles, it is also preferred to use hydrogenated copper fine particles having an average agglomerated particle diameter of 10 nm to 1 μm as the copper particles (A3). The particles can be obtained by adding a reducing agent to a solution of the water-soluble copper compound at a pH of 3 or less and an oxidation-reduction potential of 100 to 300 mVSHE (preferably 100 to 220 mVSHE). The reducing agent may be the same as the reducing agent described above, and preferably the same. Further, the average agglomerated particle diameter of the copper hydride fine particles can be adjusted by controlling the reaction temperature or the reaction time and adding a dispersing agent.

Moreover, the method of obtaining the copper particles (A) having a surface oxygen amount of 0.5 or less is not limited to the method of wet reduction as described above, and for example, it may be carried out by using hydrochloric acid, sulfuric acid, nitric acid, or the like. The acid is washed with an oxide film formed on the surface of the copper particles to dissolve and remove the oxide film.

Further, as a method of obtaining the copper particles (A) having a surface oxygen amount of 0.5 or less, in addition to the above method, for example, a reducing gas may be introduced into the surface of the copper particles, and the copper particles may be heated in the gas. Implemented by processing, etc. Specifically, for example, by introducing a reducing gas such as hydrogen, carbon monoxide, natural gas, or ammonia decomposition gas, or by making the inside a vacuum, the inside of the reduction furnace is brought into a reducing atmosphere, and copper particles are placed in the reduction furnace. The copper particles are reduced in a temperature range of 120 to 400 ° C, thereby removing oxides on the surface of the particles.

Further, as another method using a reducing gas, the surface of the copper particles may be subjected to a reduction treatment by a plasma treatment of the surface of the copper particles by generating a plasma in a mixed gas of an inert gas and a reducing gas.

(B) a carboxylate of a polymer compound containing an amine group

The amine group-containing polymer compound constituting the component (B) of the present invention is a high molecular weight amine having at least one, preferably a plurality of primary amine groups in the molecule and having a mass average molecular weight Mw of from 300 to 20,000. The mass average molecular weight (Mw) of the amine group-containing polymer compound is preferably in the range of 600 to 10,000, more preferably 600 to 2,000, and particularly preferably 600 to 1600.

The amine group-containing polymer compound preferably contains at least one, preferably a plurality of primary amine groups, and contains a secondary amine group and/or a tertiary amine group; the amine value (according to JIS K7237) is preferably 700. ~1500 mgKOH/g, especially preferably 850~1200 mgKOH/g. The polymer compound containing an amine group may be a compound having a linear main chain or a compound having a branched structure. Among them, a polymer amine having a branched structure is preferred. Specific examples of the polymer compound containing an amine group include a polyethyleneimine or a polyallylamine having a mass average molecular weight (Mw) in the above range. Particularly preferred is polyethyleneimine.

In the component (B), the amine group-containing polymer compound is formed by reacting an amine group (a primary amine group, a secondary amine group, and/or a tertiary amine group) with a carboxylic acid to form a salt. contain. Examples of the acid which forms a salt with the amine group of the polymer compound containing an amine group include hydrochloric acid, sulfuric acid, nitric acid, a carboxylic acid, a sulfonic acid, etc., and since the bonding strength with the amine group is suitable, it is preferably a carboxyl group. acid. In the present invention, a carboxylic acid having a carbon number of 10 or less including a carbon atom of a carbonyl group is used for the carboxylic acid. When a carboxylic acid having a carbon number of more than 10 is used, the volume of a portion other than the carboxyl group becomes large, so that the interaction between the amine group and the resin or ITO is inhibited, and the adhesion is deteriorated. In the present invention, a carboxylic acid having 4 or less carbon atoms including a carbon atom of a carbonyl group is preferably used, and particularly preferably formic acid.

(B) The amount of the carboxylate of the polymer compound containing an amine group is preferably 0.05 to 5 parts by mass, particularly preferably 0.1 to 2 parts by mass, per 100 parts by mass of the copper particles. That is, the blending ratio of the (B) amino group-containing polymer compound carboxylate to the copper particles is preferably 0.05 to 5% by mass, particularly preferably 0.1 to 2% by mass. When the amount of the (B) amine group-containing polymer compound carboxylate is 0.05 parts by mass or more based on 100 parts by mass of the copper particles, the adhesion between the obtained conductive film and the surface of the ITO film is good. When the amount is 5 parts by mass or less, the conductivity is inhibited and the volume resistivity of the conductive film is deteriorated, and a conductive film having good conductivity can be formed.

(C) Resins containing acidic functional groups

The resin containing an acidic functional group as the component (C) contains a resin capable of reacting with an amine group of the above-described amine group-containing polymer compound to form an acidic group of a bond. A resin containing an acidic functional group capable of reacting with an amine group can be selected from known thermosetting resins used as a binder resin for a conductive paste. Specific examples thereof include a phenol resin or a carboxyl group-modified acrylic resin, and particularly preferably a phenol resin.

The content of the (C) resin having an acidic functional group (hereinafter sometimes referred to as a binder resin) in the conductive paste is appropriately selected from the ratio of the volume of the copper particles (A) to the volume of the void portion existing between the copper particles. The selection is usually carried out, and is usually 5 to 40 parts by mass, more preferably 5 to 20 parts by mass, per 100 parts by mass of the copper particles. When it is 5 parts by mass or more, the flow characteristics of the conductive paste become good. If it is 40 parts by mass or less, the volume resistivity of the obtained conductive film can be controlled to be low.

In addition to the components (A) to (C), the conductive paste of the present invention may contain a chelate compound shown below as long as it does not impair the effects of the present invention.

(D) Chelating compounds

The chelating compound is a compound which can coordinate with copper ions and form a complex compound with copper ions by a reaction represented by the following formula (1). By blending such a chelating compound, the amount of copper ions which react with dissolved oxygen in the atmosphere can be reduced in the (A) copper particles, and the formation of copper oxide can be suppressed.

[Number 1]

The symbols in the formula indicate the following meanings.

M: copper ion

Z: Chelating compound

MZ: wrong salt

X: number of chelating compounds bonded to one copper ion

(D) A compound having a chelating compound and a copper ion having a stability constant log K _Cu of 5 to 15 at an ionic strength of 0.1 at 25 ° C. The stability constant logKC _u is an index indicating the strength of the bonding force between the chelate compound and the metal, and can be obtained as a logarithmic value of the equilibrium constant K _Cu of the reaction formula shown in the above formula (1). Specifically, K _Cu can be obtained by the following formula (2).

[Number 2]

The "stability constant log K _Cu " in the present invention is described in, for example, a chemical handbook (Maruzen), Stability Constants of Metal-Ion Complexes (PERGAMON PRESS), and Journal of Chemical Engineering Data (ACS Publications). Etc. in the literature.

It is considered that a compound having a stability constant logK _Cu of copper ions of 5 or more is formulated as a chelate compound, and at least a part of copper ions formed in the conductive paste (copper paste) form a complex with the chelate compound. . Therefore, the amount of copper ions which react with moisture or oxygen in the atmosphere (for example, O ₂ , H ₂ O, etc.) can be reduced, and the formation of copper oxide in the copper paste can be suppressed. Further, since the chelating compound is difficult to dissociate from the copper ions, the state of the complex compound can be maintained for a long period of time even when placed in an environment of high humidity. Therefore, it is difficult to form an oxide film, and it is possible to form a conductive paste which can form a conductive film in which the increase in volume resistivity is suppressed.

Because if the stability constant of the chelate compound logK _Cu less than 5, the bonding force is insufficient to copper ions, it can not sufficiently reduce the amount of copper ions in the atmosphere of the reaction of moisture or oxygen and the like occur, copper oxide, The suppression of generation becomes difficult. Further, since when the chelating agent (B) of the stabilizer is greater than 15 degrees logK _Cu, the bonding strength of the copper ions is too strong, so hinder the copper particles contact each other, there is fear that the deterioration of conductivity. The reason is presumed to be that it acts not only on copper ions existing on the surface of the particles but also on copper (metal copper). Further, the stability constant log K _{Cu is more} preferably 7 to 14.

As the chelating compound, specifically, a compound selected from the group consisting of salicyl hydroxamic acid, salicylaldoxime, ortho-aminophenol, salicylic acid and the like can be used.

When the (D) chelate compound is added to the conductive paste, the content thereof is preferably 0.01 to 1 part by mass based on 100 parts by mass of the copper particles (A). When the content of the chelating compound in the conductive paste is less than 0.01 parts by mass, the effect of suppressing the increase in volume resistivity is small. On the other hand, when the content of the chelating compound exceeds 1 part by mass, the copper particles are prevented from coming into contact with each other to lower the conductivity.

(E) Other ingredients

In addition to the components of the above (A) to (C) and (D), the conductive paste of the present invention may contain a solvent or various additives (leveling agent, coupling agent) as needed within a range not impairing the effects of the present invention. , viscosity modifiers, antioxidants, etc.). In particular, in order to obtain a paste having moderate fluidity, it is preferred to contain a solvent which can dissolve the thermosetting resin.

As the solvent, for example, cyclohexanone, cyclohexanol, rosinol, ethylene glycol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether can be used. Acetate, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate. The amount of the solvent contained in the conductive paste is preferably from 1 to 10% by mass based on the copper particles from the viewpoint of a moderate viscosity range.

The conductive paste can be obtained by mixing the components of the above (A) to (D) and, if necessary, the solvent or the like. When the components (A) to (C) are mixed, the heating can be carried out while heating at a temperature which does not cause curing of the thermosetting resin or volatilization of the solvent.

The temperature during mixing and stirring is preferably set to 10 to 40 °C. More preferably, it is set to 20 to 30 °C. By heating to a temperature of 10 ° C or higher when the conductive paste is prepared, the viscosity of the paste can be sufficiently lowered, and the stirring can be smoothly and sufficiently performed. On the other hand, when the temperature at which the conductive paste is prepared exceeds 40 ° C, there is a possibility that the resin is hardened in the paste or that the particles are welded to each other. Further, in order to prevent oxidation of the copper particles during mixing, it is preferred to carry out the mixing in a vessel substituted with an inert gas.

The conductive paste of the present invention described above contains (A) a copper particle having a specific average particle diameter, and (B) a carboxylate containing a polymer compound of an amine group, and (C) containing The resin (binder resin) of the acidic functional group which reacts with the amine group of the above-mentioned amine group-containing polymer compound is excellent in adhesion between the conductive film formed of the conductive paste and the ITO film. The reason for this is that an amine group such as a primary amine group contained in the amine group-containing polymer compound reacts with an acid gene acid base contained in the binder resin to form a bond, and also interacts with the surface of the ITO film. Therefore, the conductive film obtained from the conductive paste of the present invention has good adhesion to the surface of the ITO film.

Further, in the conductive paste of the present invention, since the amine group in the amine group-containing polymer compound exists in the form of a carboxylate salt, the amine group-containing polymer compound and the binder are stored in a paste state. The acid-base reaction of the resin is very slow, but if the paste is cured to be high temperature, the reaction between the amine group of the amine group-containing polymer compound and the acidic group of the binder resin is rapidly performed to form an adhesion to the ITO film. Excellent conductive film. As described above, the conductive paste of the present invention is excellent in storage stability in a paste state, and there is no possibility that the conductivity of the formed conductive film or the adhesion to the ITO film is lowered due to long-term storage.

<Substrate with conductive film>

A substrate having a conductive film according to an embodiment of the present invention includes a substrate having an ITO film, and a conductive film formed by applying and curing the conductive paste of the present invention onto the ITO film of the substrate.

Examples of the substrate main body include a glass substrate, a plastic substrate (for example, a polyimide substrate, a polyester substrate, and the like), and a substrate including a fiber-reinforced composite material (for example, a glass fiber-reinforced resin substrate). An ITO film is formed on the surface of the substrate body to form a substrate with an ITO film.

Examples of the coating method of the conductive paste include a screen printing method, a roll coating method, an air knife coating method, a knife coating method, a bar coating method, a gravure coating method, a die coating method, and a swash plate coating method. And other known methods. Among these, a screen printing method is preferred.

The curing of the coating layer is performed by heating by a method such as warm air heating or heat radiant heating to cure the resin (thermosetting resin) in the conductive paste.

The heating temperature and the heating time may be appropriately determined depending on the characteristics required for the conductive film. The heating temperature is preferably from 80 to 200 °C. When the heating temperature is 80° C. or more, the curing of the binder resin proceeds smoothly, the contact between the copper particles is good, and the conductivity is improved, and the amine group and the binder resin of the amine compound-containing carboxylate are contained. The reaction of the acidic functional group proceeds smoothly, and the adhesion between the conductive film and the ITO film is improved. When the heating temperature is 200 ° C or lower, a plastic substrate can be used as the substrate body, so that the degree of freedom in substrate selection is improved.

The thickness of the conductive film formed on the ITO film is preferably in the range of 1 to 200 μm, more preferably 5 to 100 μm from the viewpoint of ensuring stable conductivity and maintenance of the wiring shape.

The volume resistivity (also referred to as specific resistance) of the conductive film is preferably 1.0 × 10 ^-4 Ωcm or less. When the volume resistivity of the conductive film exceeds 1.0 × 10 ^-4 Ωcm, it is difficult to use it as an electric conductor for an electronic device.

Further, the adhesion between the conductive film and the surface of the ITO film is preferably 80/100 or more in terms of a value measured by a cross-cut method. When the adhesion to the ITO film is less than 80/100, it is difficult to use it as an electric conductor for an electronic device. Further, the measurement of the adhesion by the cross-cut method is performed by cross-cutting the conductive film into a grid shape by the method prescribed in JIS K 5600-5-6-1999, using Cellophane tape ( Product name: Saiyan Fan #405 Nichiban Co., Ltd.) The conductive film is peeled off. Further, the number of meshes remaining without being peeled off was set to X, and X/100 was set as the measured value of the adhesion.

Example

Hereinafter, the present invention will be described in more detail by way of examples, but the invention is not limited to the examples. Further, the average particle diameter of the copper particles, the thickness of the conductive film, and the volume resistivity (specific resistance) were measured using the apparatus shown below.

(The average particle size)

The average particle diameter of the copper particles is measured by the Feret diameter of 100 particles randomly selected from SEM images obtained by SEM (manufactured by JEOL Ltd., S-4300), and the average value (quantity average) is calculated. And find it.

(thickness of conductive film)

The thickness of the conductive film was measured using DEKTAK3 (manufactured by Veeco Metrology Group Co., Ltd.).

(volume resistivity of conductive film)

The volume resistivity of the conductive film was measured using a four-probe volume resistivity meter (manufactured by Mitsubishi Petrochemical Co., Ltd., model: Loresta IP MCP-T250).

Example 1

A glass beaker was placed in a water bath in which the water temperature was set to 50 ° C, and polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., trade name: SP012, Mw: 1200, amine value: 1064 mgKOH) was placed in the beaker. /g) 50 g, 43 g of formic acid was slowly added dropwise while stirring vigorously. The above-mentioned polyethyleneimine, which is pale yellow, reacts violently while being smoked, and turns into a brownish-brown liquid. After the completion of the dropwise addition, the mixture was stirred in this state for 30 minutes, and then the product was recovered into a glass vessel. The weight was the sum of polyethyleneimine and formic acid, and the product was observed by FT-IR (manufactured by Nicolet Co., Avatar 370), and the peak of the carbonyl group derived from the carboxylic acid which appeared at around 1700 cm ^-1 disappeared. Thereby, it was confirmed that a salt of polyethyleneimine and formic acid was formed.

After placing 3.0 g of formic acid and 9.0 g of a 50% by mass aqueous solution of hypophosphite in another glass beaker, the beaker was placed in a water bath and kept at 40 °C. Copper particles (manufactured by Mitsui Mining & Mining Co., Ltd., trade name: 1400YP, average primary particle diameter: 7 μm) 5.0 g were gradually added to the beaker, and stirred for 30 minutes to obtain a copper dispersion.

The precipitate was collected from the obtained copper dispersion by centrifugal separation using a centrifugal separator at a number of revolutions of 3000 rpm for 10 minutes. The precipitate was dispersed in 30 g of distilled water, and the aggregate was again precipitated by centrifugation, and the precipitate was separated. Thereafter, the obtained precipitate was heated under a reduced pressure of -35 kPa and heated at 80 ° C for 60 minutes to volatilize residual moisture and gradually removed, thereby obtaining surface-modified copper particles (A-1). .

The surface oxygen amount of the obtained copper particles (A-1) was 0.16. This value was calculated by X-ray photoelectron spectroscopy (manufactured by ULVAC Fire Co., Ltd., ESCA 5500) to determine the surface oxygen concentration [atomic %] and the surface copper concentration [atomic %], and the surface copper concentration was divided by the surface oxygen concentration. Further, the amount of oxygen in the copper particles (A-1) was 460 ppm using an oxygen meter (manufactured by LECO Co., Ltd., product number: "ROH-600").

Then, the obtained surface-modified copper particles (A-1) 12 g were added to a phenol resin (manufactured by QunRong Chemical Co., Ltd., trade name: Resitop PL6220, the same in the following examples) 7.4 g dissolved in ethylene glycol single The ether ether acetate was made into a resin solution of 4.3 g. Further, 0.05 g of the formate of polyethyleneimine obtained above was placed in a mortar together with the mixture, and mixed at room temperature to obtain a copper paste. Further, the amount of the formate of polyethyleneimine was 0.4% by mass based on the copper particles.

Example 2

A glass beaker was placed in a water bath set to a water temperature of 50 ° C, and polyallylamine was placed in the beaker (manufactured by Nitto Spin Co., Ltd., trade name: PAA-01, Mw: 1600, amine value: 1120 mgKOH/g) 50 g of a 15% by mass aqueous solution, and 6.5 g of formic acid was slowly added dropwise while stirring vigorously. The above-mentioned polyallylamine, which is pale yellow, reacts violently while being smoked, and turns into a brownish-brown liquid. After the completion of the dropwise addition, after stirring for 30 minutes in this state, the product was recovered in an eggplant-shaped flask. The product was dried at 50 ° C for 24 hours in an eggplant-shaped flask to obtain a dried polyallylamine formate.

Then, 12 g of the surface-modified copper particles (A-1) obtained in the same manner as in Example 1 was added to a resin obtained by dissolving 7.4 g of a phenol resin in 4.3 g of ethylene glycol monobutyl ether acetate. In the solution, 0.05 g of the polyallylamine formate obtained above was placed in a mortar together with the mixture, and mixed at room temperature to obtain a copper paste. Further, the amount of the polyallylamine formate was 0.4% by mass based on the copper particles.

Example 3

A copper paste was obtained in the same manner as in Example 1 except that a polyethyleneimine formate was prepared in the same manner as in Example 1 except that the amount of the polyethyleneimine formate was changed to 0.07 g. Further, the blending amount of the polyethyleneimine formate was 0.6% by mass based on the copper particles.

Example 4

A copper paste was obtained in the same manner as in Example 1 except that a polyethyleneimine formate was prepared in the same manner as in Example 1 except that the amount of the polyethyleneimine formate was changed to 0.24 g. Further, the blending amount of the polyethyleneimine formate was 2% by mass based on the copper particles.

Example 5

A copper paste was obtained in the same manner as in Example 1 except that a polyethyleneimine formate was prepared in the same manner as in Example 1 except that the amount of the polyethyleneimine formate was changed to 0.024 g. Further, the blending amount of the polyethyleneimine formate was 0.2% by mass based on the copper particles.

Example 6

A glass beaker was placed in a water bath set to a water temperature of 50 ° C, and polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., trade name: SP006, Mw: 600, amine value: 1120 mgKOH/g) was placed in the beaker. g, 45 g of formic acid was slowly added dropwise while stirring vigorously. The above-mentioned polyethyleneimine, which is pale yellow, reacts violently while being smoked, and turns into a brownish-brown liquid. After completion of the dropwise addition, the mixture was stirred in this state for 30 minutes, and then the formate of polyethyleneimine as a product was recovered in a glass container.

Then, 12 g of the surface-modified copper particles (A-1) obtained in the same manner as in Example 1 was added to a resin obtained by dissolving 7.4 g of a phenol resin in 4.3 g of ethylene glycol monobutyl ether acetate. In the solution, 0.05 g of the polyethyleneimine formate obtained above was placed in a mortar together with the mixture, and mixed at room temperature to obtain a copper paste. Further, the blending amount of the polyethyleneimine formate was 0.4% by mass based on the copper particles.

Example 7

A glass beaker was placed in a water bath set to a water temperature of 50 ° C, and polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., trade name: SP018, Mw: 1800, amine value: 1064 mgKOH/g) was placed in a beaker. g, 43 g of formic acid was slowly added dropwise while stirring vigorously. The above-mentioned polyethyleneimine, which is pale yellow, reacts violently while being smoked, and turns into a brownish-brown liquid. After completion of the dropwise addition, the mixture was stirred in this state for 30 minutes, and then the formate of polyethyleneimine as a product was recovered in a glass container.

Then, 12 g of the surface-modified copper particles (A-1) obtained in the same manner as in Example 1 was added to a resin obtained by dissolving 7.4 g of a phenol resin in 4.3 g of ethylene glycol monobutyl ether acetate. In the solution, 0.05 g of the polyethyleneimine formate obtained above was placed in a mortar together with the mixture, and mixed at room temperature to obtain a copper paste. Further, the blending amount of the polyethyleneimine formate was 0.4% by mass based on the copper particles.

Example 8

A glass beaker was placed in a water bath set to a water temperature of 50 ° C, and polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., trade name: SP020, Mw: 10000, amine value: 1008 mgKOH/g) was placed in the beaker. g, 41 g of formic acid was slowly added dropwise while stirring vigorously. The above-mentioned polyethyleneimine, which is pale yellow, reacts violently while being smoked, and turns into a brownish-brown liquid. After completion of the dropwise addition, the mixture was stirred in this state for 30 minutes, and then the formate of polyethyleneimine as a product was recovered in a glass container.

Then, 12 g of the surface-modified copper particles (A-1) obtained in the same manner as in Example 1 was added to a resin obtained by dissolving 7.4 g of a phenol resin in 4.3 g of ethylene glycol monobutyl ether acetate. In the solution, 0.05 g of the polyethyleneimine formate obtained above was placed in a mortar together with the mixture, and mixed at room temperature to obtain a copper paste. Further, the blending amount of the polyethyleneimine formate was 0.4% by mass based on the copper particles.

Example 9

A copper paste was obtained in the same manner as in Example 1 except that a polyethyleneimine formate was prepared in the same manner as in Example 1 except that the amount of the polyethyleneimine formate was changed to 0.63 g. Further, the blending amount of the polyethyleneimine formate was 5% by mass based on the copper particles.

Example 10

A polyethyleneimine acetate was prepared in the same manner as in Example 1 except that 56 g of acetic acid was added instead of 43 g of formic acid, and a copper paste was obtained in the same manner as in Example 1. The blending amount of the polyethyleneimine acetate was 0.46% by mass.

Example 11

A polyethyleneimine propionate was prepared in the same manner as in Example 1 except that 69 g of propionic acid was added instead of 43 g of formic acid, and a copper paste was obtained in the same manner as in Example 1. The blending amount of the propionate of polyethyleneimine was 0.51% by mass.

Comparative example 1

12 g of surface-modified copper particles (A-1) obtained in the same manner as in Example 1 was added to a resin solution obtained by dissolving 7.4 g of a phenol resin in 4.3 g of ethylene glycol monobutyl ether acetate. . Further, the mixture was placed in a mortar and mixed at room temperature to obtain a copper paste.

Comparative example 2

12 g of surface-modified copper particles (A-1) obtained in the same manner as in Example 1 was added to a resin solution obtained by dissolving 7.4 g of a phenol resin in 4.3 g of ethylene glycol monobutyl ether acetate. Further, together with the mixture, polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., trade name: SP012, Mw: 1200, amine value: 1064 mmol/g) 0.05 g was placed in a mortar and mixed at room temperature to obtain Copper paste. Further, the amount of the polyethyleneimine blended was 0.4% by mass based on the copper particles.

Comparative example 3

In 12 g of the surface-modified copper particles (A-1) obtained in the same manner as in Example 1, and a resin solution obtained by dissolving 7.4 g of a phenol resin in 4.3 g of ethylene glycol monobutyl ether acetate. 0.05 g of 1,10-diaminodecane was added together. The same operation as in Example 1 was carried out to obtain a copper paste. The amount of 1,10-diaminodecane was 0.4% by mass based on the copper particles.

Comparative example 4

In 12 g of the surface-modified copper particles (A-1) obtained in the same manner as in Example 1, together with a resin solution obtained by dissolving 7.4 g of a phenol resin in 4.3 g of ethylene glycol monobutyl ether acetate. Polyvinylpyrrolidone (manufactured by Junsei Chemical Co., Ltd., trade name: PVP-K15) 0.05 g was added. The same operation as in Example 1 was carried out to obtain a copper paste. The blending amount of polyvinylpyrrolidone was 0.4% by mass based on the copper particles.

Comparative Example 5

In 12 g of the surface-modified copper particles (A-1) obtained in the same manner as in Example 1, together with a resin solution obtained by dissolving 7.4 g of a phenol resin in 4.3 g of ethylene glycol monobutyl ether acetate. A melamine resin (manufactured by Mitsui Chemicals, Inc., trade name: UVAN122) of 0.083 g was added. The same operation as in Example 1 was carried out to obtain a copper paste. The blending amount of the melamine resin was 0.4% by mass based on the copper particles.

Comparative Example 6

A glass beaker was placed in a water bath set to a water temperature of 50 ° C, and polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., trade name: SP012, Mw: 1200, amine value: 1064 mmol/g) was placed in the beaker. g and stir. While vigorously stirring, slowly add 25 g of lauric acid to the creatinine. The above polyethyleneimine which is pale yellow turns into a pale yellow turbid liquid. After the completion of the dropwise addition, the mixture was stirred in this state for 30 minutes, and then the product was recovered in a glass vessel. Thus, a product of Laurel Creatine, which is considered to be a polyethyleneimine, was obtained. Further, in the following description and the table, the product thus obtained is represented by the polyimidate of Laurel Creatine.

Then, 12 g of the surface-modified copper particles (A-1) obtained in the same manner as in Example 1 was added to a resin obtained by dissolving 7.4 g of a phenol resin in 4.3 g of ethylene glycol monobutyl ether acetate. In solution. Further, 0.05 g of the polyethylenimine lauric acid creatinine obtained above was placed in a mortar together with the mixture, and mixed at room temperature to obtain a copper paste. Further, the blending amount of the lauric acid creatine of the polyethyleneimine was 0.4% by mass based on the copper particles.

Comparative Example 7

A copper paste was obtained in the same manner as in Comparative Example 6, except that the polyethylenimine lauric acid mytamine obtained in the same manner as in Comparative Example 6 was set to 0.18 g. Further, the blending amount of the lauric acid creatine of the polyethyleneimine was 1.4% by mass based on the copper particles.

Comparative Example 8

12 g of surface-modified copper particles (A-1) obtained in the same manner as in Example 1 was added to a resin solution obtained by dissolving 7.4 g of a phenol resin in 4.3 g of ethylene glycol monobutyl ether acetate. Further, 0.07 g of an amine salt of p-toluenesulfonic acid (manufactured by KING INDUSTRY Co., Ltd., trade name: NACURE 2500) was placed in a mortar together with the mixture, and mixed at room temperature to obtain a copper paste. Further, the amount of the above-mentioned amine salt of p-toluenesulfonic acid was 0.6% by mass based on the copper particles.

Comparative Example 9

12 g of surface-modified copper particles (A-1) obtained in the same manner as in Example 1 was added to a resin solution obtained by dissolving 7.4 g of a phenol resin in 4.3 g of ethylene glycol monobutyl ether acetate. Further, 0.72 g of an amine salt of p-toluenesulfonic acid (manufactured by KING INDUSTRY Co., Ltd., trade name: NACURE 2500) was placed in a mortar together with the mixture, and mixed at room temperature to obtain a copper paste. Further, the amount of the above-mentioned amine salt of p-toluenesulfonic acid was 6.0% by mass based on the copper particles.

Then, the copper pastes obtained in Examples 1 to 11 and Comparative Examples 1 to 9 were respectively applied onto an ITO film (thickness: 100 nm) of a glass substrate with an ITO film formed by sputtering, and The phenol resin was hardened by heating at 150 ° C for 30 minutes to form a conductive film having a thickness of 20 μm. Further, the resistance value of the obtained conductive film was measured using a resistance meter (manufactured by Keithley Co., Ltd., trade name: Milliohm High-Tester), and the volume resistivity (specific resistance; unit μΩcm) was measured. Further, the adhesion of the conductive film was evaluated by a cross-cut method.

Further, the copper pastes obtained in Examples 1 to 11 and Comparative Example 2 were used for storage for 30 days at 3 ° C, and were applied to an ITO film in the same manner as described above to form a conductive film. Further, the volume resistivity of the obtained conductive film was measured and the adhesion was evaluated. The measurement and evaluation results are shown in Table 1.

As is known from Table 1, a formate of polyethyleneimine, an acetate of polyethyleneimine, a propionate of polyethyleneimine or a polyallylamine is formulated together with surface-modified copper particles. The conductive film formed of the copper pastes of Examples 1 to 11 having a formate was excellent in adhesion to the ITO film, and had a low volume resistivity and a sufficiently high conductivity. Further, these copper pastes are also excellent in storage stability, and the adhesion and conductivity of the conductive film and the ITO film are not lowered even after long-term storage.

The present invention has been described in detail with reference to the specific embodiments thereof. It is understood that various changes and modifications may be made without departing from the spirit and scope of the invention.

The present application is based on Japanese Patent Application No. 2010-255652 filed on Jan.

Industrial availability

The conductive paste of the present invention can be used for various applications, for example, for formation and repair of wiring patterns in printed wiring boards and the like, interlayer wiring in a semiconductor package, and bonding of printed wiring boards and electronic parts.

Claims (10)

A conductive paste comprising: (A) a copper particle having an average particle diameter of 10 nm to 20 μm, and (B) a carboxylate of a polymer compound having at least one primary amine group in the molecule (the carboxylic acid includes a carbonyl group) The carbon number of the carbon is 10 or less, and (C) a resin containing an acidic functional group capable of reacting with the above primary amine group. The conductive paste according to claim 1, wherein the (A) copper particles are copper particles having a surface oxygen content of 0.5 or less. The conductive paste according to claim 1 or 2, wherein the polymer compound containing the primary amine group has a mass average molecular weight (Mw) of from 300 to 20,000. The conductive paste of claim 1 or 2, wherein the polymer compound containing the above primary amine group has an amine value of from 700 to 1500 mgKOH/g according to the provisions of JIS K7237-1995. The conductive paste according to claim 1 or 2, wherein the polymer compound containing the above primary amine group is polyethyleneimine or polyallylamine. The conductive paste of claim 1 or 2, wherein the carboxylate of the component (B) is a formate. The conductive paste of claim 1 or 2, wherein the (C) acid functional group-containing resin is a phenol resin. The conductive paste according to claim 1 or 2, wherein the content of the carboxylate of the polymer compound containing the primary amine group (B) is 0.05 to 5 parts by mass based on 100 parts by mass of the copper particles (A). The conductive paste according to claim 1 or 2, which further contains a chelate compound having a stability constant logK _Cu of 5 to 15 in the case where the ionic strength is 0.1 at 25 ° C. A substrate with a conductive film, comprising: a substrate having a tin-doped indium oxide (ITO) film, and coating the conductive layer of any one of claims 1 to 9 on the ITO film A conductive film that is cured and hardened.