JP2016139597A - Manufacturing method of dendritic silver coated copper powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a dendritic silver coated copper powder capable of controlling specific surface area value in an appropriate range in an industrially efficient manner at low cost.SOLUTION: The manufacturing method of a dendritic silver coated copper powder includes a process of depositing a dendritic copper powder on a cathode from a sulfuric acid acidic solution by an electrolysis and a process of coating the resulting dendritic copper powder with silver, where the sulfuric acid acidic solution contains copper ions, a nonionic surfactant of 1 mg/L to 10000 mg/L and chloride ions of 0.1 mg/L to 500 mg/L.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a dendritic silver-coated copper powder, and more specifically, a method for producing a dendritic silver-coated copper powder in which the surface of a fine dendritic copper powder having a controlled specific surface area is coated with silver, and the obtained The present invention relates to a conductive copper paste, a conductive paint, and a conductive sheet in which one or two or more dendritic silver-coated copper powders are mixed.

  For the formation of wiring layers, electrodes, and the like in electronic devices, pastes using metal fillers such as silver powder and copper powder, such as resin pastes and fired pastes, are frequently used. That is, a conductive film to be a wiring layer, an electrode, or the like can be formed by applying or printing a paste containing a metal filler of silver or copper on various substrates and then heat-curing or baking.

  For example, a resin-type conductive paste is made of a metal filler, a resin, a curing agent, a solvent, etc., printed on a conductor circuit pattern or terminal, and cured by heating at 100 ° C. to 200 ° C. An electrode is formed. In the resin-type conductive paste, since the thermosetting resin is cured and contracted by heat, when the metal filler is pressed and brought into contact, the metal filler overlaps and an electrically connected current path is formed. Since this resin-type conductive paste is processed at a curing temperature of 200 ° C. or less, it is used for a substrate using a heat-sensitive material such as a printed wiring board.

  Firing-type conductive paste is made of a metal filler, glass, solvent, etc., printed on a conductor circuit pattern or terminal, and heated and fired at 600 ° C. to 800 ° C. to form wiring and electrodes as a conductive film. To do. The fired conductive paste is processed at a high temperature to sinter the metal filler and ensure conductivity. Although this firing-type conductive paste has a high firing temperature, it cannot be used for printed wiring boards that use resin materials, but it can realize low resistance because the metal filler is sintered by high-temperature treatment. Become. Therefore, the fired conductive paste is used for an external electrode of a multilayer ceramic capacitor.

  Silver powder is often used as the metal filler used in such resin-type conductive pastes and fired-type conductive pastes, but due to the demand for lower costs, copper powder that is cheaper than silver powder tends to be used. It is in.

  Regarding copper powder, electrolytic copper powder deposited in a dendritic shape called dendritic shape is known, and since the shape is dendritic, the surface area is large, and formability and sinterability are excellent. It is used as a raw material for oil-impregnated bearings and machine parts for powder metallurgy.

  In particular, oil-impregnated bearings and the like have been reduced in size, and accordingly, the copper powder used as a raw material is required to have a porous shape and a reduced thickness, and a more complicated shape. In order to satisfy such a demand, in Patent Document 1, by developing a dendritic shape, the adjacent branches of copper powder are intertwined and firmly connected at the time of compression molding, resulting in high strength. It has been shown that it can be molded.

  Moreover, when using as a conductive paste or a metal filler for electromagnetic wave shielding, since it is dendritic shape, it can utilize that a contact can be increased compared with spherical copper powder. However, when using dendritic copper powder for applications such as conductive paste, the particle size of ordinary dendritic copper powder is very large. Therefore, in patent document 2, it is supposed that after making the oil for antioxidants adhere to dendritic copper powder, it grind | pulverizes with a jet mill and refines | miniaturizes.

  Moreover, in patent document 3, it is a rod shape obtained by pulverizing the dendritic copper powder of particle shape as copper powder for conductive paint having good solderability and solderable, and having a maximum grain size The dendritic copper powder having a diameter of 44 μm or less is crushed by a pulverizer to obtain a rod-like copper powder having an average particle diameter of 10 μm or less, and the copper powder is treated with a pickling solution comprising an inorganic acid or an organic acid to A method is disclosed in which an oxide film is dissolved and removed, washed with water, sprayed with a quick-drying organic solvent, and dried with hot air to produce a solderable conductive coating copper powder.

  Also in Patent Document 4, since the dendritic electrolytic copper powder cannot be used as it is in order to use it as a metal filler such as a conductive paste, a high-pressure jet stream swirl vortex method is used in an air atmosphere or an inert atmosphere. It is said that spherical or granular fine copper powder having an average particle diameter of 1 to 6 μm is obtained by pulverization and densification using a jet mill.

  On the other hand, silver powder is often used as the metal filler used for these conductive pastes and electromagnetic wave shields. However, as described above, due to the trend toward cost reduction, silver is applied to the surface of copper powder that is cheaper than silver powder. There is also a tendency to use silver-coated copper powder in which the amount of silver used is reduced by coating.

  Here, as a method of coating the surface of the copper powder with silver, there are a method of coating silver by a substitution reaction and a method of coating silver using an electroless plating solution containing a reducing agent.

  In the method of coating silver on the surface of copper powder by a substitution reaction, a silver film is formed on the surface of the copper powder by reducing silver ions by electrons generated when copper is eluted in the solution. For example, Patent Document 5 discloses a production method in which a silver film is formed on the surface of a copper powder by a substitution reaction between copper and silver ions by introducing the copper powder into a solution containing silver ions. . However, in the method based on this substitution reaction, when a silver film is formed on the surface of the copper powder, there is a problem that the amount of silver coating cannot be controlled because the further dissolution of copper does not proceed.

  In order to solve such a problem, there is a method of coating silver with an electroless plating solution containing a reducing agent. For example, Patent Document 6 proposes a method for producing copper powder coated with silver by a reaction between copper powder and silver nitrate in a solution in which a reducing agent is dissolved.

  As the copper powder constituting the silver-coated copper powder, the electrolytic copper powder deposited in a dendritic shape called dendritic shape is known as described above, and the shape is dendritic. When used for a film or the like, the number of contact points between particles is larger than that of spherical particles, and there is an advantage that the amount of conductive filler in a conductive paste or the like can be reduced. For example, Patent Documents 7 and 8 propose silver-coated copper powder in which silver is coated on the surface of a dendritic copper powder.

  Specifically, Patent Documents 7 and 8 disclose a dendrite characterized by having a long branch branched from the main axis as a further grown dendritic shape, and the silver-coated copper powder is a conventional dendrite. It is said that the conductivity is improved by increasing the number of contact points between the particles, and that the conductivity can be increased even if the amount of the conductive powder is reduced when used in a conductive paste or the like.

  On the other hand, when using a silver-coated dendritic copper powder (dendritic silver-coated copper powder) as a metal filler such as a conductive paste or an electromagnetic shielding resin, the metal filler has a dendritic shape. And dendritic copper powders are entangled with each other and agglomerate occurs, and the resin does not disperse uniformly in the resin. It has been pointed out in Patent Document 9 that the productivity is lowered due to the occurrence of the above. In addition, in patent document 9, in order to raise the intensity | strength of electrolytic copper powder itself, the intensity | strength of electrolytic copper powder itself is improved by adding a tungstate to the copper sulfate aqueous solution of the electrolyte solution for depositing electrolytic copper powder. It is said that it is difficult to break the branches and can be molded with high strength.

  As described above, it is not easy to use the dendritic copper powder coated with silver as a metal filler such as a conductive paste, which is a cause of difficulty in improving the conductivity of the paste.

Japanese Patent No. 46976643 Japanese Patent No. 4230017 JP-A-6-158103 Japanese Patent No. 5181434 JP 2000-248303 A JP 2006-161081 A JP 2013-89576 A JP 2013-100592 A JP 2011-58027 A

  As described above, in order to ensure conductivity, a dendritic shape having a three-dimensional shape is easier to secure a contact than a granular one, and ensures high conductivity as a conductive paste or electromagnetic wave shield. can do. However, the conventional silver-coated copper powder having a dendritic shape cannot be easily controlled, and thus is not an ideal shape for effectively securing a contact.

  Therefore, if the shape can be controlled while ensuring high conductivity and the dendritic silver-coated copper powder is not aggregated, a more effective metal filler such as a conductive paste or an electromagnetic shielding resin can be used. It can be used as When the dendritic shape is represented by another index, it is considered effective to use the specific surface area as an index. The higher the specific surface area value, the finer and denser the dendritic shape is.

  The present invention has been proposed in view of the above situation, and in a dendritic silver-coated copper powder, it is industrially efficient and can control the specific surface area value within an appropriate range at low cost. It aims at providing the manufacturing method of dendritic silver coat copper powder which can be performed.

  The inventors of the present invention have made extensive studies in order to solve the above-described problems. As a result, a dendritic copper powder having a controlled specific surface area is obtained by an electrolytic method using a sulfuric acid acidic copper bath containing a nonionic surfactant and chloride ions, and the surface of the dendritic copper powder is coated with silver. As a result, it was found that a fine dendritic silver-coated copper powder was obtained, and the present invention was completed. That is, the present invention provides the following.

(1) A first invention of the present invention is a dendritic silver coat comprising a step of depositing dendritic copper powder on a cathode from a sulfuric acid acidic solution by an electrolytic method, and a step of coating silver on the dendritic copper powder. A method for producing copper powder, wherein the sulfuric acid acidic solution contains copper ions, 1 mg / L to 10000 mg / L nonionic surfactant, and 0.1 mg / L to 500 mg / L chloride ions. A method for producing a dendritic silver-coated copper powder characterized by comprising:

（但し、式中、Ｒ_１は、炭素数５〜３０の高級アルコールの残基、炭素数１〜３０のアルキル基を有するアルキルフェノールの残基、炭素数１〜３０のアルキル基を有するアルキルナフトールの残基、炭素数３〜２５の脂肪酸アミドの残基、炭素数２〜５のアルキルアミンの残基、又は水酸基を示し、Ｒ_２及びＲ_３は、水素原子又はメチル基を示し、ｍ及びｎは、１〜１００の整数を示す。） (2) According to a second aspect of the present invention, in the first aspect, the nonionic surfactant is polyethylene glycol, polypropylene glycol, polyethyleneimine, pluronic surfactant, tetronic surfactant, polyoxyethylene. 1 selected from the group consisting of glycol glycerin ether, polyoxyethylene glycol dialkyl ether, polyoxyethylene polyoxypropylene glycol alkyl ether, aromatic alcohol alkoxylate, and a polymer compound represented by the following formula (x) It is a method for producing a dendritic silver-coated copper powder characterized by being a seed or more.

(In the formula, R ₁ represents a residue of a higher alcohol having 5 to 30 carbon atoms, a residue of an alkylphenol having an alkyl group having 1 to 30 carbon atoms, or an alkylnaphthol having an alkyl group having 1 to 30 carbon atoms. A residue, a residue of a fatty acid amide having 3 to 25 carbon atoms, a residue of an alkylamine having 2 to 5 carbon atoms, or a hydroxyl group, R ₂ and R ₃ represent a hydrogen atom or a methyl group, m and n Represents an integer of 1 to 100.)

  (3) A third invention of the present invention is the method for producing a dendritic copper powder according to the first or second invention, wherein the chloride ion is hydrochloric acid or sodium chloride.

  (4) A fourth invention of the present invention is the method for producing a dendritic copper powder according to the first to third inventions, wherein the copper ion concentration is 1 g / L to 20 g / L. is there.

  (5) According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the silver coating amount is 1% by mass with respect to 100% by mass of the entire dendritic silver-coated copper powder coated with silver. It is a manufacturing method of dendritic silver coat copper powder characterized by being -50 mass%.

(6) Sixth aspect of the present invention, in any one of the first to fifth specific surface ^area, dendritic, which is a 0.3m ² /g~3.0m 2 / g It is a manufacturing method of silver coat copper powder.

  According to the method for producing a dendritic silver-coated copper powder according to the present invention, a specific surface area of the dendritic copper powder according to its use by an electrolytic method using a sulfuric acid copper bath containing a nonionic surfactant and chloride ions. Is controlled, and the dendritic copper powder is coated with silver, whereby a dendritic silver-coated copper powder having a fine and optimum shape can be produced.

  Moreover, the dendritic silver coat copper powder obtained by this manufacturing method is 1 type, or by mixing 2 or more types from which a specific surface area differs, it is suitable as a use of an electrically conductive paste or an electromagnetic wave shield by mixing it. Can be used.

3 is a graph showing the relationship of the BET specific surface area to the concentration of polyethylene glycol having a molecular weight of 600 in Example 1. FIG. 6 is a graph showing the relationship of the BET specific surface area to the chloride ion concentration in Example 2. FIG. 6 is a graph showing the relationship of the BET specific surface area with respect to the concentration of polyoxyethylene polyoxypropylene butyl ether having a molecular weight of 1,000 in Example 3. FIG. 6 is a graph showing the relationship of the BET specific surface area with respect to the concentration of polyoxyethylene polyoxypropylene butyl ether having a molecular weight of 3,000 in Example 4. FIG.

  Hereinafter, a specific embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention.

<< 1. Dendritic silver coated copper powder shape >>
When observed using a scanning electron microscope (SEM), the copper powder according to the present embodiment has a dendritic shape, and the dendritic silver coated copper powder (hereinafter, “dendritic silver coat”). the specific surface area of also called copper powder ") is 0.3m ² /g~3.0m ² / g, more preferably 1.0m ² /g~2.5m ² / g. The specific surface area value becomes an index representing the dendritic shape, and the higher the specific surface area value, the finer and denser the dendritic shape becomes.

Regarding the specific surface area value, if the specific surface area value of the dendritic silver-coated copper powder is less than 0.3 m ² / g, the average particle size is large, and the dendritic development of each particle is insufficient and the shape becomes rough. Therefore, when it is used as a metal filler such as a conductive paste, the contact between the dendritic silver-coated copper powders is reduced, and the conductivity may be lowered. On the other hand, when the specific surface area value of the dendritic silver-coated copper powder exceeds 3.0 m ² / g, the average particle diameter is small, and the dendrites of each particle are developed and densely formed. When used as a metal filler, dendritic silver-coated copper powders may be entangled and aggregated to reduce dispersibility, and the paste may thicken and printability may decrease.

  In addition, a specific surface area value can be measured based on JISZ8830: 2013 as a BET specific surface area.

  Here, as described later, the silver coating amount of the dendritic silver-coated copper powder according to the present embodiment is 1% by mass to 50% by mass with respect to 100% by mass of the silver-coated dendritic silver-coated copper powder as a whole. %, But the thickness of silver (coating thickness) is an extremely thin film of 0.1 μm or less. Therefore, the dendritic silver-coated copper powder has a shape that retains the shape of the dendritic copper powder before coating with silver.

≪2. Silver coverage of dendritic silver coated copper powder >>
Dendritic silver-coated copper powder according to the present embodiment, as described above, the specific surface area of 0.3m ² /g~3.0m ² / g, more preferably 1.0 m ² / g to 2 0.5 m ² / g. The silver coating on the surface of the dendritic silver-coated copper powder will be described below.

The dendritic silver-coated copper powder according to the present embodiment is preferably 1% by mass to 50% with respect to 100% by mass of the entire dendritic silver-coated copper powder coated with silver on the dendritic copper powder before silver coating. Silver is coated at a rate of mass%, and the silver thickness (coating thickness) is an extremely thin film of 0.1 μm or less. From this, this dendritic silver coat copper powder becomes the shape which retained the shape of the dendritic copper powder before silver coating. Moreover, the change of the specific surface area value by coat | covering silver is less than 0.1 m < ² > / g, and a specific surface area does not change a lot by coat | covering silver.

  As described above, the silver coating amount in the dendritic silver-coated copper powder is preferably in the range of 1% by mass to 50% by mass with respect to 100% by mass of the silver-coated dendritic silver-coated copper powder as a whole. . The silver coating amount is preferably as small as possible from the viewpoint of cost. However, if the amount is too small, a uniform silver film cannot be secured on the copper surface, causing a decrease in conductivity. Therefore, the coating amount of silver is preferably 1% by mass or more, more preferably 2% by mass or more, and further preferably 5% by mass or more with respect to 100% by mass of copper.

  On the other hand, an increase in the amount of silver coating is not preferable from the viewpoint of cost. From this, the silver coating amount is preferably 50% by mass or less, more preferably 30% by mass or less, with respect to 100% by mass of the silver-coated dendritic silver-coated copper powder as a whole. More preferably, it is 20 mass% or less.

  Moreover, in the dendritic silver coat copper powder which concerns on this Embodiment, as average thickness of the silver coat | covered on the surface of dendritic copper powder, it is about 0.0003 micrometer-0.1 micrometer, and 0.01 micrometer-0.05 micrometer. It is more preferable that If the silver coating thickness is less than 0.0003 μm on average, a uniform silver coating cannot be ensured, and this causes a decrease in conductivity. On the other hand, when the silver coating thickness exceeds 0.1 μm on average, it is not preferable from the viewpoint of cost.

≪3. Method for producing dendritic silver-coated copper powder >>
The dendritic silver-coated copper powder according to the present embodiment has a step of depositing the dendritic copper powder on the cathode from the sulfuric acid acidic solution by an electrolytic method, and a step of coating the deposited dendritic copper powder with silver. . Below, about the dendritic copper powder before coat | covering silver on the surface first, the manufacturing method of the dendritic copper powder with which the specific surface area was controlled is demonstrated, and silver is subsequently added with respect to the dendritic copper powder. A method for coating to obtain silver-coated copper powder will be described.

<3-1. Method for producing dendritic copper powder with controlled specific surface area>
The dendritic copper powder constituting the dendritic silver-coated copper powder according to the present embodiment is, for example, using a sulfuric acid acidic solution containing copper ions, a nonionic surfactant, and chloride ions as an electrolytic solution, It can be manufactured by a predetermined electrolytic method.

  In electrolysis (electrolysis), for example, the above-described sulfuric acid acidic electrolyte solution is accommodated in an electrolytic cell in which metallic copper is used as an anode (anode) and a stainless steel plate or a titanium plate is used as a cathode (cathode). The electrolytic treatment is performed by applying a direct current to the electrolytic solution at a predetermined current density. Thereby, a fine dendritic copper powder can be deposited (electrodeposited) on the cathode with the energization. In particular, in this embodiment, by adding a nonionic surfactant and chloride ions to a sulfuric acid copper sulfate solution, fine dendritic copper powder with a controlled specific surface area may be precipitated. it can.

[Copper ion]
Copper ions can be supplied using a water-soluble copper salt. Examples of the water-soluble copper salt include, but are not limited to, copper sulfate such as copper sulfate pentahydrate, copper nitrate, and the like. Alternatively, copper oxide may be used as the water-soluble copper salt, and it may be dissolved in a sulfuric acid solution described later to form a sulfuric acid acidic solution containing copper ions.

  The copper ion concentration in the electrolytic solution is not particularly limited, but is preferably 1 g / L to 20 g / L, more preferably 5 g / L to 15 g / L, and more preferably 5 g / L to 10 g / L. More preferably. If the copper ion concentration is too high, it becomes difficult to form dendritic copper powder on the cathode during electrolysis, and a film-like electrolytic copper may be formed, but a copper ion concentration of 20 g / L or less. Therefore, dendritic copper powder can be deposited without any problem. On the other hand, the lower limit of the copper ion concentration is preferably a concentration of 1 g / L or more, considering that dendritic copper powder can be efficiently deposited from the cathode during electrolysis.

[Sulfuric acid (sulfuric acid electrolyte)]
In the present embodiment, the electrolytic solution is sulfuric acid. It contains sulfuric acid to make a sulfuric acid electrolyte.

  The sulfuric acid concentration in the electrolytic solution is preferably 20 g / L to 300 g / L, more preferably 50 g / L to 150 g / L, as the free sulfuric acid concentration. Since the concentration of sulfuric acid affects the conductivity of the electrolyte, it is related to the uniformity of the copper powder obtained on the cathode. The concentration of sulfuric acid also affects the solubility of copper ions. Whether the sulfuric acid concentration is too low or too high, the solubility of copper ions becomes low, and copper sulfate crystals may be deposited in the electrolyte.

[Additive]
In the present embodiment, a nonionic surfactant and chloride ions are included as additives in the sulfuric acid acidic electrolyte. Depending on the amount of these additives to be added to the electrolyte, dendritic copper powder with different specific surface area values will be deposited, so it is necessary to change the addition amount according to the desired specific surface area, By adding the nonionic surfactant to a concentration of 1 mg / L to 10,000 mg / L and the chloride ion to a concentration of 0.1 mg / L to 500 mg / L, the specific surface area is 0.3 m ² / A dendritic copper powder of g to 3.0 m ² / g can be obtained.

(Nonionic surfactant)
As the nonionic surfactant, surfactants having different molecular structures and molecular weights can be used singly or in combination of two or more.

The number average molecular weight of the nonionic surfactant is not particularly limited, but is preferably 100 to 200,000, more preferably 200 to 15,000, and 1,000 to 10,000. Further preferred. If the number average molecular weight is less than 100, fine electrolytic copper powder that does not have a dendritic shape may be deposited. On the other hand, when the number average molecular weight exceeds 200,000, electrolytic copper powder having a large average particle size is precipitated, and only dendritic copper powder having a specific surface area of less than 0.3 m ² / g may be obtained. . In the present embodiment, the number average molecular weight is a molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

  The type of nonionic surfactant is not particularly limited, but is preferably a nonionic surfactant having an ether group, such as polyethylene glycol, polypropylene glycol, polyethyleneimine, pluronic surfactant, tetronic surfactant. Agents, polyoxyethylene glycol / glycerin ether, polyoxyethylene glycol / dialkyl ether, polyoxyethylene polyoxypropylene glycol / alkyl ether, aromatic alcohol alkoxylate, polymer compound represented by the following formula (x), and the like. These nonionic surfactants can be used alone or in combination of two or more.

（式（ｉ）中、ｎ１は、１〜１２０の整数を示す。） More specifically, as polyethylene glycol, what is represented, for example by following formula (i) can be used.

(In formula (i), n1 represents an integer of 1 to 120.)

（式（ｉｉ）中、ｎ１は、１〜９０の整数を示す。） Moreover, as polypropylene glycol, what is represented, for example by following formula (ii) can be used.

(In formula (ii), n1 represents an integer of 1 to 90.)

（式（ｉｉｉ）中、ｎ１は、１〜１２０の整数を示す。） Moreover, as polyethyleneimine, what is represented, for example by following formula (iii) can be used.

(In formula (iii), n1 represents an integer of 1 to 120.)

（式（ｉｖ）中、ｎ２及びｌ２は１〜３０の整数を、ｍ２は１０〜１００の整数を示す。） Moreover, as a pluronic-type surfactant, what is represented, for example by following formula (iv) can be used.

(In formula (iv), n2 and l2 represent an integer of 1 to 30, and m2 represents an integer of 10 to 100.)

（式（ｖ）中、ｎ３は１〜２００の整数を、ｍ３は１〜４０の整数を示す。） Moreover, as a tetronic type surfactant, what is represented, for example by following formula (v) can be used.

(In formula (v), n3 represents an integer of 1 to 200, and m3 represents an integer of 1 to 40.)

（式（ｖｉ）中、ｎ４、ｍ４、及びｌ４はそれぞれ１〜２００の整数を示す。） Moreover, as polyoxyethylene glycol glyceryl ether, what is represented, for example by a following formula (vi) can be used.

(In formula (vi), n4, m4, and l4 each represent an integer of 1 to 200.)

（式（ｖｉｉ）中、Ｒ_１及びＲ_２は水素原子又は炭素数１〜５の低級アルキル基を示し、ｎ５は２〜２００の整数を示す。） Moreover, as polyoxyethylene glycol dialkyl ether, what is represented, for example by a following formula (vii) can be used.

(In formula (vii), R ₁ and R ₂ represent a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms, and n5 represents an integer of 2 to 200.)

（式（ｖｉｉｉ）中、Ｒ_３は水素原子又は炭素数１〜５の低級アルキル基を示し、ｍ６又はｎ６は２〜１００の整数を示す。） Moreover, as polyoxyethylene polyoxypropylene glycol alkyl ether, what is represented, for example by a following formula (viii) can be used.

(In the formula (viii), R ₃ represents a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms, and m6 or n6 represents an integer of 2 to 100.)

（式（ｉｘ）中、ｍ７は１〜５の整数、ｎ７は１〜１２０の整数を示す。） Moreover, as an aromatic alcohol alkoxylate, what is represented, for example by a following formula (ix) can be used.

(In formula (ix), m7 represents an integer of 1 to 5, and n7 represents an integer of 1 to 120.)

（式（ｘ）中、Ｒ_１は、炭素数５〜３０の高級アルコールの残基、炭素数１〜３０のアルキル基を有するアルキルフェノールの残基、炭素数１〜３０のアルキル基を有するアルキルナフトールの残基、炭素数３〜２５の脂肪酸アミドの残基、炭素数２〜５のアルキルアミンの残基、又は水酸基を示し、Ｒ_２及びＲ_３は、水素原子又はメチル基を示し、ｍ及びｎは、１〜１００の整数を示す。） Also, a polymer compound represented by the following formula (x) can be used.

(In Formula (x), R ₁ is a residue of a higher alcohol having 5 to 30 carbon atoms, a residue of an alkylphenol having an alkyl group having 1 to 30 carbon atoms, or an alkyl naphthol having an alkyl group having 1 to 30 carbon atoms. A residue of a fatty acid amide having 3 to 25 carbon atoms, a residue of an alkylamine having 2 to 5 carbon atoms, or a hydroxyl group, R ₂ and R ₃ represent a hydrogen atom or a methyl group, m and n represents an integer of 1 to 100.)

(Chloride ion)
As a chloride ion, it can be made to contain by adding the compound (chloride ion source) which supplies a chloride ion in electrolyte solution. Although it does not specifically limit as a chloride ion source, Hydrochloric acid, sodium chloride, etc. can be mentioned.

[Electrolytic treatment]
In the method for producing a dendritic copper powder according to the present embodiment, for example, the electrolytic treatment is performed using the electrolytic solution having the composition as described above, so that the copper powder is deposited and produced on the cathode.

As the electrolysis method, a known method can be used. For example, the current density is preferably 5 A / dm ^{2 to} 40 A / dm ² and more preferably 10 A / dm ^{2 to} 30 A / dm ² when electrolysis is performed using a sulfuric acid electrolytic solution. . In order to deposit fine dendritic copper powder, it is necessary to perform electrolysis under conditions where hydrogen is generated at the cathode, and it is necessary to select conditions of current density, copper concentration, and electrolysis temperature. If the current density is less than 5 A / dm ² , production efficiency may be significantly reduced. On the other hand, the higher the current density, the faster the production speed. However, when the current density exceeds 40 A / dm ² , hydrogen generation is increased more than necessary, which may lower the production efficiency.

  In order to deposit uniform dendritic copper powder, it is preferable to energize the electrolyte while stirring.

  The liquid temperature (bath temperature) of the electrolytic solution is preferably 20 ° C. to 60 ° C., and more preferably 25 ° C. to 50 ° C. When the liquid temperature of the electrolytic solution is less than 20 ° C., the current efficiency is remarkably lowered and the production efficiency may be lowered. On the other hand, when the liquid temperature exceeds 60 ° C., decomposition of the added nonionic surfactant may proceed faster.

<3-2. Silver coating method (production of silver-coated copper powder)>
The dendritic silver-coated copper powder according to the present embodiment is coated on the surface of the dendritic copper powder prepared by the above-described electrolytic method using, for example, a reduction electroless plating method or a substitutional electroless plating method. Can be manufactured.

  In order to coat the surface of the dendritic copper powder with a uniform thickness, it is preferable to wash before silver plating, and the dendritic copper powder is dispersed in a cleaning solution and washed while stirring. it can. This washing treatment is preferably carried out in an acidic solution, more preferably a polyvalent carboxylic acid that is also used for a reducing agent described later. After washing, filtration and separation of the dendritic copper powder and washing with water are repeated as appropriate to obtain a water slurry in which the dendritic copper powder is dispersed in water. In addition, what is necessary is just to use a well-known method about filtration, isolation | separation, and water washing.

  Specifically, when silver coating is performed by a reduction type electroless plating method, the surface of the dendritic copper powder is obtained by adding a reducing agent and a silver ion solution to the water slurry obtained after washing the dendritic copper powder. Can be coated with silver. Here, after adding a reducing agent to the water slurry in advance and dispersing it, the silver ion solution is continuously added to the water slurry containing the reducing agent and the dendritic copper powder, thereby adding to the surface of the dendritic copper powder. Silver can be coated more uniformly.

  Various reducing agents can be used as the reducing agent, but a reducing agent having a weak reducing power that cannot reduce the complex ion of copper is preferable. As the weak reducing agent, a reducing organic compound can be used. For example, carbohydrates, polyvalent carboxylic acids and salts thereof, aldehydes, and the like can be used. More specifically, glucose (glucose), lactic acid, oxalic acid, tartaric acid, malic acid, malonic acid, glycolic acid, sodium potassium tartrate, formalin and the like can be mentioned.

  After adding the reducing agent to the water slurry containing the dendritic copper powder, it is preferable to perform stirring or the like in order to sufficiently disperse the reducing agent. Moreover, in order to adjust a water slurry to desired pH, an acid or an alkali can be added suitably. Further, the dispersion of the reducing organic compound as the reducing agent may be promoted by adding a water-soluble organic solvent such as alcohol.

  As the silver ion solution to be continuously added, known silver plating solutions can be used, and among them, a silver nitrate solution is preferably used. The silver nitrate solution is more preferably added as an ammoniacal silver nitrate solution because complex formation is easy. The ammonia used in the ammoniacal silver nitrate solution is added to the silver nitrate solution, previously added to the water slurry together with the reducing agent, or added to the water slurry at the same time as an ammonia solution separate from the silver nitrate solution. Any method including these combinations may be used.

  For example, when the silver ion solution is added to the water slurry containing the dendritic copper powder and the reducing agent, it is preferable to gradually add the silver ion solution at a relatively slow rate. It can be formed on the surface of copper powder. Moreover, in order to improve the uniformity of the thickness of the coating, it is more preferable to keep the addition rate constant. Further, a reducing agent or the like previously added to the water slurry may be adjusted with another solution and gradually added together with the silver ion solution.

  Thus, the water slurry to which the silver ion solution or the like is added is filtered, separated, washed with water, and then dried to obtain a dendritic silver-coated copper powder. The processing means after the filtration is not particularly limited, and a known method may be used.

  On the other hand, the silver coating method using the substitutional electroless plating method utilizes the difference in ionization tendency between copper and silver, and the silver ions in the solution are converted by the electrons generated when copper is dissolved in the solution. It is reduced and deposited on the copper surface. Therefore, the substitutional electroless silver plating solution can be coated with silver as a silver ion source, a complexing agent, and a conductive salt as main components. In order to do so, surfactants, brighteners, crystal modifiers, pH adjusters, precipitation inhibitors, stabilizers and the like can be added as necessary. Even in the production of the silver-coated copper powder according to the present embodiment, the plating solution is not particularly limited.

  More specifically, as the silver salt, silver nitrate, silver iodide, silver sulfate, silver formate, silver acetate, silver lactate or the like can be used, and can be reacted with the dendritic copper powder dispersed in the water slurry. . The silver ion concentration in the plating solution can be about 1 g / L to 100 g / L.

  The complexing agent forms a complex with silver ions, and typical examples include citric acid, tartaric acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid, ethylenediamine, glycine, hydantoin, pyrrolidone, succinimide, and the like. N-containing compounds, hydroxyethylidene diphosphonic acid, aminotrimethylenephosphonic acid, mercaptopropionic acid, thioglycol, thiosemicarbazide and the like can be used. The concentration of the complexing agent in the plating solution can be about 10 g / L to 100 g / L.

  Further, as the conductive salt, inorganic acids such as nitric acid, boric acid and phosphoric acid, organic acids such as citric acid, maleic acid, tartaric acid and phthalic acid, or sodium, potassium and ammonium salts thereof can be used. The concentration of the conductive salt in the plating solution can be about 5 g / L to 50 g / L.

  Control of the coating amount when the surface of the dendritic copper powder is coated with silver can be controlled, for example, by changing the input amount of silver in the substitutional electroless plating solution. Moreover, in order to improve the uniformity of the thickness of the coating, it is preferable to keep the addition rate constant.

  In this way, the slurry after the reaction is filtered, separated, washed with water, and then dried to obtain dendritic silver-coated copper powder. The processing means after the filtration is not particularly limited, and a known method may be used.

<< 4. Applications of conductive paste, conductive paint, etc. >>
Dendritic silver-coated copper powder obtained by the production method described above, the specific surface area of 0.3m ² /g~3.0m ² / g. According to such a dendritic silver-coated copper powder, a larger number of contacts can be ensured than a spherical one, and excellent conductivity is exhibited. In addition, according to the fine dendritic silver-coated copper powder having such a specific surface area, even when it is a copper paste or the like, aggregation can be suppressed and the resin can be uniformly dispersed in the resin. In addition, it is possible to suppress the occurrence of poor printability due to an increase in the viscosity of the paste. Therefore, such dendritic silver-coated copper powder can be suitably used for applications such as conductive pastes and conductive paints.

  Specifically, as the metal filler, the above-described dendritic silver-coated copper powder can be used alone or in combination of two or more having different specific surface areas. By using a metal filler having such a configuration, for example, when the metal filler is used in a conductive paste, it can be uniformly dispersed in the resin, and the viscosity of the paste is excessively increased, resulting in poor printability. Etc. can be prevented. Moreover, the electroconductivity excellent as an electrically conductive paste can be exhibited because it is a silver coat copper powder having a dendritic shape.

  For example, as a conductive paste (copper paste), the dendritic silver-coated copper powder according to the present embodiment is included as a metal filler, such as a binder resin, a solvent, and an antioxidant or a coupling agent as necessary. It can be prepared by kneading the additive.

  Although it does not specifically limit as binder resin, An epoxy resin, a phenol resin, etc. can be used.

  Moreover, as a solvent, organic solvents, such as ethylene glycol, diethylene glycol, triethylene glycol, glycerol, and terpineol, can be used. Further, the amount of the organic solvent added is not particularly limited, but the amount added in consideration of the particle size of the dendritic silver-coated copper powder so as to have a viscosity suitable for a conductive film forming method such as screen printing or a dispenser. It is preferable to adjust.

  Furthermore, other resin components can be added for viscosity adjustment. For example, as the resin component, a cellulose resin typified by ethyl cellulose and the like can be mentioned, and the resin component can be added as an organic vehicle dissolved in an organic solvent such as terpineol. In addition, it is necessary to suppress the addition amount of the resin component to an extent that does not impair the sinterability, and is preferably 5% by mass or less of the whole.

  Moreover, as an additive, in order to improve the electroconductivity after baking, antioxidant etc. can be added. Although it does not specifically limit as antioxidant, For example, a hydroxycarboxylic acid etc. can be mentioned. More specifically, hydroxycarboxylic acids such as citric acid, malic acid, tartaric acid, and lactic acid are preferable, and citric acid or malic acid having a high adsorptive power to copper is particularly preferable. The addition amount of the antioxidant can be, for example, about 1% by mass to 15% by mass in consideration of the antioxidant effect, the viscosity of the paste, and the like.

  Next, even when the metal filler according to the present embodiment is used as an electromagnetic shielding material, it is not limited to use under particularly limited conditions, but a general method, for example, using a metal filler as a resin Can be used as a mixture.

  For example, when forming the electromagnetic wave shielding layer of the conductive sheet for electromagnetic wave shielding, the resin to be used is not particularly limited, and vinyl chloride resin, vinyl acetate resin, vinylidene chloride, which are conventionally used, are not limited. Resin, acrylic resin, polyurethane resin, polyester resin, olefin resin, chlorinated olefin resin, polyvinyl alcohol resin, alkyd resin, thermoplastic resin made of various polymers and copolymers, thermosetting resin, radiation A curable resin or the like can be used as appropriate.

  As a method for producing an electromagnetic shielding material, for example, the above-described metal filler and resin are dispersed or dissolved in a solvent to form a coating material, and the coating material is applied or printed on the substrate to form the electromagnetic shielding layer. It can be manufactured by forming and drying to such an extent that the surface solidifies. Moreover, a metal filler can also be utilized for the conductive adhesive layer of a conductive sheet.

  Further, even when the metal filler according to the present embodiment is used as the material for the conductive coating for electromagnetic wave shielding, it is not limited to use under particularly limited conditions, but a general method such as a metal filler Can be mixed with a resin and a solvent, and further mixed with an antioxidant, a thickener, an anti-settling agent, etc., if necessary, and kneaded to obtain a conductive paint.

  The binder resin and solvent used at this time are not particularly limited, and vinyl chloride resin, vinyl acetate resin, acrylic resin, polyester resin, fluororesin, silicon resin, and phenol resin as conventionally used are used. Etc. can be used. As for the solvent, alcohols such as isopropanol, aromatic hydrocarbons such as toluene, esters such as methyl acetate, ketones such as methyl ethyl ketone, and the like, which have been conventionally used, can be used. In addition, as an antioxidant as an additive, a fatty acid amide, a higher fatty acid amine, a phenylenediamine derivative, a titanate coupling agent, and the like that are conventionally used can be used.

  Examples of the present invention will be specifically described below together with comparative examples. The present invention is not limited to the following examples.

≪Evaluation method≫
With respect to the copper powder obtained in the following examples and comparative examples, the following methods were used to observe the shape, measure the BET specific surface area, measure the specific resistance value, and evaluate the electromagnetic shielding characteristics.

(Observation of shape)
20 visual fields were arbitrarily observed with a scanning electron microscope (manufactured by JEOL Ltd., JSM-7100F) at a predetermined magnification, and copper powder and silver-coated copper powder contained in the visual field were observed.

(BET specific surface area)
The BET specific surface area was measured using a specific surface area / pore distribution measuring device (manufactured by Cantachrome, QUADRASORB SI).

(Specific resistance value)
The specific resistance value of the film was measured by measuring the sheet resistance value by a four-terminal method using a low resistivity meter (Loresta-GP MCP-T600, manufactured by Mitsubishi Chemical Corporation), and a surface roughness shape measuring instrument (Tokyo Seimitsu Co., Ltd.). The film thickness of the coating film was measured by SURFCO M130A), and the sheet resistance value was obtained by dividing by the film thickness.

(Electromagnetic wave shielding characteristics)
The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate of the samples obtained in each example and comparative example using an electromagnetic wave having a frequency of 1 GHz. Specifically, the shield characteristic level of the electromagnetic wave shield produced in Comparative Example 2 is set as “Δ”, and the case where it is worse than the level of Comparative Example 3 is set as “X”, which is better than the level of Comparative Example 3 The case was evaluated as “◯”, and the case where it was superior was evaluated as “◎”.

  Moreover, in order to evaluate also about the flexibility of an electromagnetic wave shield, the produced electromagnetic wave shield was bent and it was confirmed whether the electromagnetic wave shielding characteristic changed.

<Example>
<Preparation of electrolytic copper powder>
[Example 1]
Using a titanium electrode plate with an electrode area of 200 mm × 200 mm as a cathode and a copper electrode plate with an electrode area of 200 mm × 200 mm as an anode in an electrolytic cell having a capacity of 100 L, a direct current was passed through the copper plate Powder was deposited on the cathode plate.

  At this time, as the electrolytic solution, a sulfuric acid electrolytic solution having a copper ion concentration of 10 g / L and a sulfuric acid concentration of 100 g / L was used. Further, a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added to the electrolyte so that the chloride ion (chlorine ion) concentration was 100 mg / L, and polyethylene glycol (PEG) having a molecular weight of 600 as a nonionic surfactant was used. ) (Manufactured by Wako Pure Chemical Industries, Ltd.) so that the concentration in the electrolyte solution is 1, 50, 100, 200, 500, 1,000, 2,000, 5,000, 10,000 mg / L, respectively. Changed and added.

The current density of the cathode was 20 A / dm ^{2 under} the condition that the temperature (electrolyte temperature) was maintained at 30 ° C. while circulating each electrolyte adjusted to the above concentration at a flow rate of 10 L / min. It energized so that copper powder might be deposited on the cathode plate. The electrolytic copper powder deposited on the cathode plate was mechanically scraped and recovered, washed with pure water, and then dried in a vacuum dryer.

  As a result of observing the electrolytic copper powder thus obtained in a field of view with a magnification of 10,000 times by the method using the scanning electron microscope (SEM) described above, a copper powder having a dendritic shape (dendritic copper powder) It was confirmed that.

  Moreover, the result of having measured the BET specific surface area about the obtained dendritic copper powder in FIG. 1 is shown. As shown in the results of FIG. 1, it was found that the specific surface area of the precipitated dendritic copper powder changes depending on the concentration of PEG added to the electrolytic solution, and a finer dendritic copper powder can be produced.

  Next, 100 g of the obtained dendritic copper powder was stirred for about 1 hour in a 3% aqueous tartaric acid solution, filtered, washed with water, and dispersed in 2 liters of ion-exchanged water. Then, 6 g of tartaric acid, 6 g of glucose, and 60 ml of ethanol are added, and further 60 ml of 28% ammonia water is added and stirred. Thereafter, an aqueous solution in which 70 g of silver nitrate is dissolved in 4.5 liters of ion-exchanged water, 30 g of glucose, 30 g of an aqueous solution obtained by dissolving 300 ml of ethanol in 900 ml of ion-exchanged water and 300 ml of 28% ammonia water were gradually added over 60 minutes. The bath temperature at this time was 25 ° C.

  After the addition of each aqueous solution was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, a silver-coated copper powder in which the surface of the dendritic copper powder was coated with silver was obtained.

  As a result of observing the obtained dendritic silver-coated copper powder with a field of view of 5,000 times by SEM, the surface of the dendritic copper powder before silver coating was uniformly coated with silver and exhibited a dendritic shape. It was dendritic silver coated copper powder. Moreover, when the dendritic silver coat copper powder was collect | recovered and the silver coating amount was measured, it was 30.3 mass%-30.8 mass% with respect to 100 mass of the whole dendritic silver coat copper powder coated with silver. there were.

[Example 2]
To the electrolytic solution, PEG having a molecular weight of 600 (manufactured by Wako Pure Chemical Industries, Ltd.) as a nonionic surfactant was added to a concentration of 1,000 mg / L in the electrolytic solution, and added with a hydrochloric acid solution (Wako Pure Chemical Industries, Ltd.). Co., Ltd.) was added in such a manner that the chloride ion concentration in the electrolytic solution was 0.1, 10, 20, 50, 100, 200, 300, 400, and 500 mg / L, respectively. In addition, copper powder was deposited on the same conditions as Example 1 except it.

  As a result of observing the electrolytic copper powder thus obtained in a field of view with a magnification of 10,000 times by the method using the scanning electron microscope (SEM) described above, a copper powder having a dendritic shape (dendritic copper powder) It was confirmed that.

  Moreover, the result of having measured the BET specific surface area about the obtained dendritic copper powder in FIG. 2 is shown. As shown in FIG. 2, it was found that the specific surface area of the deposited dendritic electrolyte powder changes depending on the concentration of chloride ions added and contained in the electrolytic solution, and a finer dendritic copper powder can be produced.

  Next, when the surface of the obtained dendritic copper powder was coated with silver in the same procedure as in Example 1, a silver-coated copper powder in which the surface of the dendritic copper powder was coated with silver was obtained. .

  As a result of observing the obtained silver-coated copper powder with a SEM field of view at a magnification of 5,000 times, the surface of the dendritic copper powder before silver coating was uniformly coated with silver, and the dendritic shape having a dendritic shape It was silver coated copper powder. Moreover, when the dendritic silver coat copper powder was collect | recovered and the silver coating amount was measured, it was 30.2 mass%-30.9 mass% with respect to 100 mass of the whole dendritic silver coat copper powder coated with silver. there were.

[Example 3]
Polyoxyethylene polyoxypropylene butyl ether having a molecular weight of 1,000 as a nonionic surfactant (manufactured by NOF Corporation, trade name: UNILOVE 50MB-11) is used as the nonionic surfactant, and the concentration in the electrolytic solution is 1, 50, 100, respectively. , 200, 500, 1,000, 2,000, 5,000, 10,000 mg / L, and added, and a hydrochloric acid solution (Wako Pure Chemical Industries, Ltd.) was added to the chloride ion concentration. To 50 mg / L. In addition, copper powder was deposited on the same conditions as Example 1 except it.

  As a result of observing the electrolytic copper powder thus obtained in a field of view with a magnification of 10,000 times by the method using the scanning electron microscope (SEM) described above, a copper powder having a dendritic shape (dendritic copper powder) It was confirmed that.

  Moreover, the result of having measured the BET specific surface area about the obtained dendritic copper powder in FIG. 3 is shown. As shown in FIG. 3, it was found that the specific surface area of the precipitated dendritic copper powder changes depending on the concentration of polyoxyethylene polyoxypropylene butyl ether to be added, and a finer dendritic copper powder can be produced.

  Next, 100 g of the obtained dendritic copper powder was used to cover the surface of the copper powder with a substitutional electroless plating solution. As a substitutional electroless plating solution, a solution having a composition in which 25 g of silver nitrate, 20 g of citric acid, and 10 g of ethylenediamine are dissolved in 1 liter of ion-exchanged water is used, and 100 g of dendritic copper powder is put into the solution and stirred for 45 minutes. And reacted. In addition, the bath temperature at this time was 30 degreeC.

  After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, a silver-coated copper powder in which the surface of the dendritic copper powder was coated with silver was obtained.

  As a result of observing the obtained silver-coated copper powder with a SEM field of view at a magnification of 5,000 times, the surface of the dendritic copper powder before silver coating was uniformly coated with silver, and the dendritic shape having a dendritic shape It was silver coated copper powder. Moreover, when the dendritic silver coat copper powder was collect | recovered and the silver coating amount was measured, it is 10.0 mass%-10.4 mass% with respect to 100 mass of the mass of the whole silver coated dendritic silver coat copper powder. there were.

[Example 4]
Polyethylene glycol (PEG) having a molecular weight of 600 (manufactured by Wako Pure Chemical Industries, Ltd.) as a nonionic surfactant is added to the electrolytic solution so that the concentration in the electrolytic solution is 1,000 mg / L, and the molecular weight is 3,000. Oxyethylene polyoxypropylene butyl ether (manufactured by NOF Corporation, trade name: UNILOVE 50MB-72), the concentration in the electrolyte is 1, 50, 100, 200, 500, 1,000, 2,000, 5, respectively. In addition, a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added so that the chloride ion concentration was 100 mg / L. In addition, copper powder was deposited on the same conditions as Example 1 except it.

  As a result of observing the electrolytic copper powder thus obtained in a field of view with a magnification of 10,000 times by the method using the scanning electron microscope (SEM) described above, a copper powder having a dendritic shape (dendritic copper powder) It was confirmed that.

  Moreover, the result of having measured the BET specific surface area about the obtained dendritic copper powder in FIG. 4 is shown. As shown in FIG. 4, it was found that the specific surface area of the precipitated dendritic copper powder changes depending on the concentration of the two types of nonionic surfactants to be added, and a finer dendritic copper powder can be produced.

  Next, when the surface of the obtained dendritic copper powder was coated with silver in the same procedure as in Example 1, a silver-coated copper powder in which the surface of the dendritic copper powder was coated with silver was obtained. .

  As a result of observing the obtained silver-coated copper powder with a SEM field of view at a magnification of 5,000 times, the surface of the dendritic copper powder before silver coating was uniformly coated with silver, and the dendritic shape having a dendritic shape It was silver coated copper powder. Moreover, when the dendritic silver coat copper powder was collect | recovered and the silver coating amount was measured, it was 30.0 mass%-30.7 mass% with respect to 100 mass of the whole dendritic silver coat copper powder coated with silver. there were.

<Preparation of conductive paste>
[Reference Example 1]
A phenol resin (Gunei Chemical Co., Ltd.) was added to 55 parts by mass of dendritic copper powder having a specific surface area of 1.2 m ² / g, which was obtained using the electrolytic solution in which the concentration of PEG having a molecular weight of 600 was 500 mg / L in Example 1. Company, PL-2211) 15 parts by mass, butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) 10 parts by mass, 1200 rpm using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), A paste was made by repeating the kneading for 3 minutes three times.

  The obtained conductive paste was printed on a glass with a metal squeegee and cured at 150 ° C. and 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance values of the films obtained by curing were 21 × 10 ⁻⁶ Ω · cm (curing temperature 150 ° C.) and 3.6 × 10 ⁻⁶ Ω · cm (curing temperature 200 ° C.), respectively. Table 1 summarizes these results.

[Reference Example 2]
In 55 parts by weight of the dendritic copper powder having a specific surface area of 2.5 m ² / g obtained from the electrolytic solution in which the concentration of PEG having a molecular weight of 600 was 5,000 mg / L in Example 1, phenol resin (group Chemical Co., Ltd., PL-2211) 15 parts by mass, butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) 10 parts by mass, and using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), The paste was made by repeating kneading at 1200 rpm for 3 minutes three times.

  The obtained conductive paste was printed on a glass with a metal squeegee and cured at 150 ° C. and 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance values of the coatings obtained by curing were 16 × 10 ⁻⁶ Ω · cm (curing temperature 150 ° C.) and 3.1 × 10 ⁻⁶ Ω · cm (curing temperature 200 ° C.), respectively. Table 1 summarizes these results.

[Reference Example 3]
A dendritic copper powder having a specific surface area of 1.2 m ² / g obtained from the electrolytic solution in which the concentration of PEG having a molecular weight of 600 was 500 mg / L in Example 1 (in Table 1, the dendritic copper powder [1] and Notation) and a dendritic copper powder having a specific surface area of 2.5 m ² / g obtained from an electrolyte solution having a chloride ion concentration of 300 mg / L in Example 2 (dendritic copper powder [2 in Table 1] ] In a total amount of 55 parts by mass with two different types of dendritic copper powder in a mass ratio of 60% and 40%, respectively, and phenol resin (PL-2211 manufactured by Gunei Chemical Co., Ltd.) 15 Mass part and 10 parts by mass of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed, and kneading at 1200 rpm for 3 minutes 3 times using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1). It was made into a paste by repeating.

  The obtained conductive paste was printed on a glass with a metal squeegee and cured at 150 ° C. and 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance values of the coatings obtained by curing were 17 × 10 ⁻⁶ Ω · cm (curing temperature 150 ° C.) and 3.1 × 10 ⁻⁶ Ω · cm (curing temperature 200 ° C.), respectively. Table 1 summarizes these results.

[Reference Example 4]
The phenol resin (Gunei Chemical Co., Ltd.) was added to 55 parts by mass of the dendritic copper powder having a specific surface area of 0.6 m ² / g obtained from the electrolytic solution in which the concentration of PEG having a molecular weight of 600 was 50 mg / L in Example 1. Company, PL-2211) 15 parts by mass, butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) 10 parts by mass, 1200 rpm using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), A paste was made by repeating the kneading for 3 minutes three times.

  The obtained conductive paste was printed on a glass with a metal squeegee and cured at 150 ° C. and 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance values of the coatings obtained by curing were 34 × 10 ⁻⁶ Ω · cm (curing temperature 150 ° C.) and 5.1 × 10 ⁻⁶ Ω · cm (curing temperature 200 ° C.), respectively. Table 1 summarizes these results.

<Preparation of electromagnetic shielding layer>
[Reference Example 5]
Dendritic copper powder having a specific surface area of 1.2 m ² / g obtained in Example 1 was dispersed in a resin to prepare an electromagnetic wave shielding material.

  That is, 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone were mixed with 40 g of the dendritic copper powder obtained in Example 1, and kneading at 1200 rpm for 3 minutes was repeated three times using a small kneader. To make a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. This was coated and dried on a base material made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm using a Mayer bar to form an electromagnetic wave shielding layer having a thickness of 25 μm.

  The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate using an electromagnetic wave having a frequency of 1 GHz. Table 1 shows the results of the characteristic evaluation.

[Reference Example 6]
Dendritic copper powder having a specific surface area of 2.5 m ² / g obtained in Example 2 was dispersed in a resin to prepare an electromagnetic wave shielding material.

  That is, 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone were mixed with 40 g of the dendritic copper powder obtained in Example 2, and kneading at 1200 rpm for 3 minutes was repeated three times using a small kneader. To make a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. This was coated and dried on a base material made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm using a Mayer bar to form an electromagnetic wave shielding layer having a thickness of 25 μm.

  The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate using an electromagnetic wave having a frequency of 1 GHz. Table 1 shows the results of the characteristic evaluation.

[Reference Example 7]
Dendritic copper powder having the same specific surface area as used in Reference Example 4 having a specific surface area of 0.6 m ² / g was dispersed in a resin to prepare an electromagnetic shielding material.

  That is, 40 g of the same dendritic copper powder as used in Reference Example 4 was mixed with 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone, and kneaded at 1200 rpm for 3 minutes using a small kneader. The paste was made by repeating the process once. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. This was coated and dried on a base material made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm using a Mayer bar to form an electromagnetic wave shielding layer having a thickness of 25 μm.

  The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate using an electromagnetic wave having a frequency of 1 GHz. Table 1 shows the results of the characteristic evaluation.

≪Comparative example≫
<Production of electrolytic copper powder, production of conductive paste>
[Comparative Example 1]
An electrolytic copper powder was produced under the same conditions as in Example 1 except that the nonionic surfactant was not added to the electrolytic solution. As a result, the specific surface area of the obtained electrolytic copper powder was 0.2 m ² / g. In addition, as a result of observing the obtained electrolytic copper powder by the method by SEM, it was confirmed that it is a copper powder (dendritic copper powder) having a dendritic shape.

  Next, when the surface of the obtained dendritic copper powder was coated with silver in the same procedure as in Example 1, a dendritic silver-coated copper powder in which the surface of the dendritic copper powder was coated with silver was obtained. It was. Moreover, when the dendritic silver coat copper powder was collect | recovered and the silver coating amount was measured, it was 30.4 mass% with respect to 100 mass of the whole dendritic silver coat copper powder coated with silver.

And the obtained specific surface area is 0.2 m ² / g dendritic silver coat copper powder 55 parts by mass, phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) 15 parts by mass, butyl cellosolve (Kanto Chemical Co., Ltd.) 10 parts by mass (manufactured by Shika Special Grade) were mixed and paste-formed by repeating kneading at 1200 rpm for 3 minutes three times using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1).

  The obtained conductive paste was printed on a glass with a metal squeegee and cured at 150 ° C. and 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance values of the coatings obtained by curing were 52 × 10 ⁻⁶ Ω · cm (curing temperature 150 ° C.) and 6.6 × 10 ⁻⁶ Ω · cm (curing temperature 200 ° C.), respectively. Table 1 summarizes these results.

[Comparative Example 2]
An electrolytic copper powder was produced under the same conditions as in Example 2 except that the hydrochloric acid solution was not added to the electrolytic solution. As a result, the specific surface area of the obtained electrolytic copper powder was 0.2 m ² / g. In addition, as a result of observing the obtained electrolytic copper powder by the method by SEM, it was confirmed that it is a copper powder (dendritic copper powder) having a dendritic shape.

  Next, when the surface of the obtained dendritic copper powder was coated with silver in the same procedure as in Example 1, a dendritic silver-coated copper powder in which the surface of the dendritic copper powder was coated with silver was obtained. It was. Moreover, when the dendritic silver coat copper powder was collect | recovered and the silver coating amount was measured, it was 30.6 mass% with respect to 100 mass of the whole dendritic silver coat copper powder coated with silver.

And the obtained specific surface area is 0.2 m ² / g dendritic silver coat copper powder 55 parts by mass, phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) 15 parts by mass, butyl cellosolve (Kanto Chemical Co., Ltd.) 10 parts by mass (manufactured by Shika Special Grade) were mixed and paste-formed by repeating kneading at 1200 rpm for 3 minutes three times using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1).

  The obtained conductive paste was printed on a glass with a metal squeegee and cured at 150 ° C. and 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance values of the coatings obtained by curing were 61 × 10 ⁻⁶ Ω · cm (curing temperature 150 ° C.) and 7.3 × 10 ⁻⁶ Ω · cm (curing temperature 200 ° C.), respectively. Table 1 summarizes these results.

<Preparation of electromagnetic shielding layer>
[Reference Example 8]
The dendritic silver-coated copper powder having a specific surface area of 0.2 m ² / g prepared in Comparative Example 1 was dispersed in a resin to obtain an electromagnetic wave shielding material.

That is, 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone are used with respect to 40 g of dendritic silver-coated copper powder having a specific surface area of 0.2 m ² / g prepared under the condition where no nonionic surfactant is added (others are the same as in Example 1). And kneading at 1200 rpm for 3 minutes three times using a small kneader to make a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. This was coated and dried on a base material made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm using a Mayer bar to form an electromagnetic wave shielding layer having a thickness of 25 μm.

  The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate using an electromagnetic wave having a frequency of 1 GHz. Table 1 shows the results of the characteristic evaluation.

≪Summary of evaluation results≫
Table 1 below collectively shows the property evaluation results of the conductive pastes of Reference Examples 1 to 4 and Comparative Examples 1 and 2, and the property evaluation results of the electromagnetic wave shields of Reference Examples 5 to 7 and Reference Example 8.

Claims (6)

A method for producing a dendritic silver-coated copper powder comprising a step of depositing a dendritic copper powder on a cathode from a sulfuric acid acidic solution by an electrolytic method, and a step of coating silver on the dendritic copper powder,
The sulfuric acid acidic solution contains copper ions, 1 mg / L to 10000 mg / L nonionic surfactant, and 0.1 mg / L to 500 mg / L chloride ions. Method for producing coated copper powder. The nonionic surfactant is polyethylene glycol, polypropylene glycol, polyethyleneimine, pluronic surfactant, tetronic surfactant, polyoxyethylene glycol / glycerin ether, polyoxyethylene glycol / dialkyl ether, polyoxyethylene polyoxy The dendritic silver according to claim 1, wherein the dendritic silver is one or more selected from the group consisting of propylene glycol / alkyl ether, aromatic alcohol alkoxylate, and a polymer compound represented by the following formula (x). Method for producing coated copper powder.

(In the formula, R ₁ represents a residue of a higher alcohol having 5 to 30 carbon atoms, a residue of an alkylphenol having an alkyl group having 1 to 30 carbon atoms, or an alkylnaphthol having an alkyl group having 1 to 30 carbon atoms. A residue, a residue of a fatty acid amide having 3 to 25 carbon atoms, a residue of an alkylamine having 2 to 5 carbon atoms, or a hydroxyl group, R ₂ and R ₃ represent a hydrogen atom or a methyl group, m and n Represents an integer of 1 to 100.) The said chloride ion uses hydrochloric acid or sodium chloride. The manufacturing method of the dendritic silver coat copper powder of Claim 1 or 2 characterized by the above-mentioned. The density | concentration of the said copper ion is 1g / L-20g / L. The manufacturing method of the dendritic silver coat copper powder of any one of Claims 1-3 characterized by the above-mentioned. The silver coating amount is 1% by mass to 50% by mass with respect to 100% by mass of the entire dendritic silver-coated copper powder coated with silver. A method for producing dendritic silver-coated copper powder. Specific surface ^area, 0.3m ^{2 /g~3.0m} 2 / method for producing dendritic silver-coated copper powder according to any one of claims 1 to 5, characterized in that g is.

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