JP6350475B2 - Method for producing copper powder and method for producing conductive paste using the same - Google Patents

Description

  The present invention relates to a method for producing copper powder used as a material for conductive paste and the like, and more specifically, a method for producing copper powder having a novel shape capable of improving conductivity and the same. The present invention relates to a method for producing a conductive paste.

  For the formation of wiring layers, electrodes, and the like in electronic devices, many pastes using metal fillers such as silver powder and copper powder, such as resin paste and fired paste, are used. A metal filler paste made of silver powder, copper powder, or the like is applied or printed on various substrates of an electronic device, and is subjected to heat curing or heat baking to form a conductive film that becomes a wiring layer, an electrode, or the like.

  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.

  As a metal filler used in these resin-type conductive pastes and fired-type conductive pastes, silver powder has been conventionally used in many cases. However, in recent years, the price of precious metals has risen, and the use of copper powder that is cheaper than silver powder has been favored for cost reduction.

  Here, as powders, such as copper used as a metal filler, since particle | grains connected and electrically conductive as above-mentioned, shapes, such as a granular form, dendritic shape, and flat form, have been used. In particular, when evaluating particles from the size in the three directions of length, width, and thickness, a flat plate shape with a small thickness contributes to a reduction in the thickness of the wiring material due to a decrease in thickness, and a certain thickness. There is an advantage that a larger area where the grains come into contact with each other than a certain cubic or spherical particle can be ensured, and that low resistance, that is, high conductivity can be achieved. For this reason, tabular copper powder is particularly suitable for conductive paints and conductive pastes for which electrical conductivity is desired to be maintained. In addition, when using a thin conductive paste, it is preferable to consider the influence of impurities contained in the copper powder.

  In order to produce such a flat copper powder, for example, Patent Document 1 discloses a method for obtaining a flaky copper powder suitable for a metal filler of a conductive paste. Specifically, a spherical copper powder having an average particle size of 0.5 μm to 10 μm is used as a raw material, and mechanically processed into a flat plate shape by a mechanical energy of a medium loaded in the mill using a ball mill or a vibration mill. is there.

  Further, for example, Patent Document 2 discloses a technique relating to a copper powder for conductive paste, more specifically, a disk-shaped copper powder capable of obtaining high performance as a copper paste for through holes and external electrodes, and a method for manufacturing the same. Specifically, the granular atomized copper powder is put into a medium stirring mill, a steel ball having a diameter of 1/8 inch to 1/4 inch is used as a grinding medium, and the fatty acid is added to the copper powder by 0.5 by weight. % To 1%, and processed into a flat plate shape by pulverization in air or in an inert atmosphere.

  Furthermore, for example, Patent Document 3 discloses a method for obtaining electrolytic copper powder that can be molded with high strength, with improved formability than conventional electrolytic copper powder, without unnecessarily developing the branches of electrolytic copper powder. Yes. Specifically, in order to increase the strength of the electrolytic copper powder itself and precipitate the electrolytic copper powder that can be molded to a high strength, the electrolytic solution is used for the purpose of reducing the size of the crystallites constituting the electrolytic copper powder. One or two or more selected from tungstate, molybdate, and sulfur-containing organic compounds are added to a certain aqueous copper sulfate solution to deposit electrolytic copper powder.

  In any of the methods disclosed in these patent documents, the obtained granular copper powder is formed into a flat plate shape by mechanically deforming (processing) using a medium such as a ball. Therefore, the size of the processed flat copper powder is, for example, 1 μm to 30 μm in the average particle size in the technique of Patent Document 1 and 7 μm to 12 μm in the technique of Patent Document 3.

  On the other hand, electrolytic copper powder deposited in a dendritic shape called dendritic shape is known, and since the shape is dendritic, it has a large surface area, excellent formability and sinterability, and is used for powder metallurgy applications Used as a raw material for oil-impregnated bearings and machine parts. In particular, oil-impregnated bearings and the like have been reduced in size, and along with this, are becoming porous and thin, and complex shapes are required. In order to satisfy these requirements, for example, Patent Document 4 discloses a copper powder for metal powder injection molding having a complicated three-dimensional shape and high dimensional accuracy, and a method for manufacturing an injection molded product using the same. Specifically, it has been shown that by further developing the dendritic shape, the dendrites of the electrolytic copper powder adjacent to each other at the time of compression molding are intertwined and firmly connected to each other, so that it can be molded with high strength. Furthermore, when used as a conductive paste or a metal filler for electromagnetic wave shielding, since it has a dendritic shape, it can be used that it can have more contacts than a spherical one.

  However, when the dendritic copper powder as described above is used as a metal filler such as a conductive paste or a resin for electromagnetic wave shielding, the dendritic copper powder has a shape in which the metal filler in the resin has developed into a dendritic shape. They are entangled with each other and agglomerate occurs, which causes a problem that they are not uniformly dispersed in the resin, and the viscosity of the paste increases due to agglomeration, resulting in problems in wiring formation by printing. Such a problem is pointed out in Patent Document 3, for example.

  As described above, it is not easy to use dendritic copper powder as a metal filler such as a conductive paste, and it has been a cause of difficulty in improving the conductivity of the paste. In addition, in order to ensure electroconductivity, a dendritic shape is easy to ensure a contact rather than granular, and can ensure high electroconductivity as a conductive paste or an electromagnetic wave shield.

Japanese Patent Laid-Open No. 2005-200734 JP 2002-15622 A JP 2011-58027 A Japanese Patent Laid-Open No. 9-3510

  The present invention has been proposed in view of the above-described circumstances, and is preferably used as an application such as a conductive paste or an electromagnetic wave shield while ensuring excellent conductivity by increasing the number of contacts between copper powders. It aims at providing the method of manufacturing the copper powder which can do.

  The inventors of the present invention have made extensive studies for solving the above-described problems. As a result, it is a shape having a main trunk that grows in a dendritic shape and a plurality of branches separated from the main trunk, and is a copper powder constituted by aggregating flat copper particles having a cross-sectional average thickness within a specific range. In addition, the average particle diameter (D50) of the copper powder is in a specific range, so that excellent conductivity can be ensured and, for example, it can be uniformly mixed with a resin, which is suitable for applications such as a conductive paste. The present invention has been completed by finding that it can be used. That is, the present invention provides the following.

  (1) A first invention of the present invention is a method for producing copper powder by depositing from an electrolytic solution on an anode by an electrolysis method, wherein the copper powder comprises a main trunk and a plurality of branches separated from the main trunk. The main trunk and the branches are composed of tabular copper particles having an average cross-sectional thickness of 0.02 μm to 5.0 μm and an average particle diameter (D50) of 1.0 μm to 100 μm. It is a manufacturing method of the copper powder characterized by being.

(2) the second invention of the present invention, in the first aspect, the bulk density of the copper powder ^is in the range of ^{0.5g / cm 3 ~5.0g / cm 3} , in the manufacturing method of the copper powder is there.

(3) A third invention of the present invention, in the first or second invention, BET specific surface area of the copper powder ^is 0.2m ² /g~5.0m 2 / g, the production of copper powder Is the method.

  (4) According to a fourth aspect of the present invention, in any one of the first to third aspects, the crystallite diameter in the Miller index of the (111) plane by X-ray diffraction of the copper powder is in the range of 80 nm to 300 nm. Is a method for producing copper powder.

［式（１）中、Ｒ_１，Ｒ_２，Ｒ_３，Ｒ_４，Ｒ_６，Ｒ_７，Ｒ_８，Ｒ_９は、それぞれ別個に、水素、ハロゲン、アミノ、ＯＨ、−Ｏ、ＣＮ、ＳＣＮ、ＳＨ、ＣＯＯＨ、ＣＯＯ塩、ＣＯＯエステル、ＳＯ_３Ｈ、ＳＯ_３塩、ＳＯ_３エステル、ベンゼンスルホン酸、及びＣ１〜Ｃ８アルキルからなる群から選択される基であり、Ｒ_５は、水素、ハロゲン、アミノ、ＯＨ、−Ｏ、ＣＮ、ＳＣＮ、ＳＨ、ＣＯＯＨ、ＣＯＯ塩、ＣＯＯエステル、ＳＯ_３Ｈ、ＳＯ_３塩、ＳＯ_３エステル、ベンゼンスルホン酸、低級アルキル、及びアリールからなる群から選択される基であり、Ａ⁻がハライドアニオンである。］

［式（２）中、Ｒ_１，Ｒ_２，Ｒ_３，Ｒ_４，Ｒ_５，Ｒ_６，Ｒ_７，Ｒ_８，Ｒ_９，Ｒ_１０は、それぞれ別個に、水素、ハロゲン、アミノ、ＯＨ、−Ｏ、ＣＮ、ＳＣＮ、ＳＨ、ＣＯＯＨ、ＣＯＯ塩、ＣＯＯエステル、ＳＯ_３Ｈ、ＳＯ_３塩、ＳＯ_３エステル、ベンゼンスルホン酸、低級アルキル、及びアリールからなる群から選択される基である。］

［式（３）中、Ｒ_１，Ｒ_２，Ｒ_４，Ｒ_６，Ｒ_７，Ｒ_８，Ｒ_９，Ｒ_１０，Ｒ_１１，Ｒ_１２，Ｒ_１３は、それぞれ別個に、水素、ハロゲン、アミノ、ＯＨ、−Ｏ、ＣＮ、ＳＣＮ、ＳＨ、ＣＯＯＨ、ＣＯＯ塩、ＣＯＯエステル、ＳＯ_３Ｈ、ＳＯ_３塩、ＳＯ_３エステル、ベンゼンスルホン酸、及びＣ１〜Ｃ８アルキルからなる群から選択される基であり、Ｒ_３は、水素、ハロゲン、アミノ、ＯＨ、−Ｏ、ＣＮ、ＳＣＮ、ＳＨ、ＣＯＯＨ、ＣＯＯ塩、ＣＯＯエステル、ＳＯ_３Ｈ、ＳＯ_３塩、ＳＯ_３エステル、ベンゼンスルホン酸、低級アルキル、及びアリールからなる群から選択される基であり、Ａ⁻がハライドアニオンである。］ (5) According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the electrolytic solution is a sulfuric acid copper electrolytic solution containing copper ions, and the electrolytic solution contains 1 mg / L. A compound having a phenazine structure represented by the following formula (1), a compound having an azobenzene structure represented by the following formula (2), and a phenazine represented by the following formula (3) with a content of 10,000 mg / L It is a manufacturing method of copper powder which contains 1 type, or 2 or more types chosen from the group which consists of a compound which has a structure and an azobenzene structure.

[In the formula (1), R ₁ , R ₂ , R ₃ , R ₄ , R ₆ , R ₇ , R ₈ , R ₉ are each independently hydrogen, halogen, amino, OH, —O, CN, SCN. , SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl, R ₅ is hydrogen, halogen , Amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, and aryl. And A ⁻ is a halide anion. ]

[In formula (2), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ are each independently hydrogen, halogen, amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, a group selected from the group consisting of benzenesulfonic acid, lower alkyl, and aryl. ]

[In the formula (3), R ₁ , R ₂ , R ₄ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ are each independently hydrogen, halogen, amino , OH, -O, CN, SCN , SH, COOH, COO salt, COO _ester, SO 3 H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and a radical selected from the group consisting of C1~C8 alkyl R ₃ is hydrogen, halogen, amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, and a group selected from the group consisting of aryl, a ^- is a halide anion. ]

  (6) The sixth invention of the present invention is the method for producing copper powder according to the fifth invention, wherein the electrolytic solution contains chloride ions at a content of 500 mg / L or less.

  (7) 7th invention of this invention is a manufacturing method of copper powder whose copper ion concentration in the said electrolyte solution is 1g / L-20g / L in 5th or 6th invention.

  (8) According to an eighth aspect of the present invention, the copper powder obtained by the copper powder manufacturing method according to any one of the first to seventh aspects of the present invention is contained in a proportion of 20% by mass or more in the entire metal filler. This is a method for producing a metal filler.

  (9) A ninth invention of the present invention is a method for producing a conductive paste, characterized in that a metal filler obtained by the method for producing a metal filler according to the eighth invention is mixed with a resin.

  According to the present invention, it is possible to secure a large number of contacts and a large contact area, to ensure excellent conductivity, and to prevent agglomeration, which is suitable for applications such as a conductive paste and an electromagnetic wave shield. The copper powder which can be utilized can be manufactured.

It is a figure showing the relationship between the safranine density | concentration in electrolyte solution, and the specific surface area of copper powder. It is a figure showing the relationship between the safranine density | concentration in electrolyte solution, and the cross-sectional average thickness of the copper particle which comprises copper powder. It is a figure showing the relationship between the methyl orange density | concentration in electrolyte solution and the specific surface area of copper powder. It is a figure showing the relationship between the methyl orange density | concentration in electrolyte solution, and the bulk density of copper powder. It is a figure showing the relationship between the Janus green B density | concentration in electrolyte solution, and the specific surface area of copper powder. It is a figure showing the relationship between the Janus green B density | concentration in electrolyte solution, and the crystallite diameter of copper powder.

  Hereinafter, specific embodiments of the present invention (hereinafter referred to as “present embodiments”) will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments, and Various modifications can be made without departing from the scope of the invention. In this specification, “X to Y” (X and Y are arbitrary numerical values) means “X or more and Y or less”.

<< 1. Dendritic copper powder and its shape >>
The method for producing copper powder according to the present embodiment produces copper powder by depositing it from an electrolytic solution on a cathode by an electrolysis method. First, the copper powder obtained by this manufacturing method and its shape will be described.

  When observed using a scanning electron microscope (SEM), the copper powder according to the present embodiment has a dendritic shape having a main trunk that grows linearly and a plurality of branches separated from the main trunk. The main trunk and branches are composed of tabular copper particles having a cross-sectional average thickness of 0.02 μm to 5.0 μm. Thus, the copper powder which concerns on this Embodiment is comprised from a flat copper particle, and the average particle diameter (D50) is 1.0 micrometer-100 micrometers.

  The copper powder composed of the flat copper particles and having a dendritic shape is not limited to one composed of only one layer, and may be composed of a plurality of laminated structures. Below, the copper powder which concerns on this Embodiment is also called "dendritic copper powder."

  Note that, as described above, the dendritic copper powder according to the present embodiment is produced by, for example, an electrolytic method in which an anode and a cathode are immersed in a sulfuric acid electrolytic solution containing copper ions, and electrolysis is performed by flowing a direct current. It can be produced by depositing on the plate, the cross-sectional average thickness of the flat copper particles, the average particle diameter of the dendritic copper powder, the bulk density, the BET specific surface area, the crystallite diameter, etc. It can be controlled by doing. Details will be described later.

  Here, the flat copper particles constituting the main trunk and the branches have a cross-sectional average thickness of 0.02 μm to 5.0 μm. The thinner the cross-sectional average thickness of the flat copper particles, the more the flat plate effect is exhibited. That is, the main trunk and the branches are constituted by flat copper particles having a cross-sectional average thickness of 5.0 μm or less, thereby ensuring a large contact area between the copper particles or dendritic copper powders constituted thereby. can do. And since the contact area becomes large, low resistance, that is, high conductivity can be realized. By this, it is more excellent in electroconductivity, can maintain the electroconductivity favorably, and can use it suitably for the use of an electroconductive coating material or an electroconductive paste. Moreover, it can contribute to thickness reduction of wiring materials etc. because dendritic copper powder is comprised with the fine flat copper particle.

  In addition, even if the cross-sectional average thickness of the flat copper particles is as thin as 5.0 μm or less, if the size of the flat plate is too small, unevenness will be reduced, so when the copper powders come into contact with each other The number of contacts will be reduced. Accordingly, the lower limit value of the cross-sectional average thickness of the copper particles is preferably 0.02 μm or more as described above. Thus, since the cross-sectional average thickness of a flat copper particle is 0.02 micrometer-5.0 micrometers, the number of contacts can be increased effectively.

  Moreover, in the dendritic copper powder which concerns on this Embodiment, the average particle diameter (D50) is 1.0 micrometer-100 micrometers. The average particle diameter can be controlled by changing the electrolysis conditions described later. Further, if necessary, it can be further adjusted to a desired size by adding mechanical pulverization such as a jet mill, a sample mill, a cyclone mill, and a bead mill. In addition, an average particle diameter (D50) can be measured by the laser diffraction scattering type particle size distribution measuring method, for example.

  Thus, when the average particle diameter of the dendritic copper powder is 1.0 μm to 100 μm, the surface area is increased, and good moldability and sinterability can be ensured. And the dendritic copper powder which concerns on this Embodiment is dendritic since the main trunk and the branch are comprised from the flat copper particle in addition to being dendritic shape as mentioned above. Due to this three-dimensional effect and the effect that the copper particles constituting the dendritic shape are flat, it is possible to secure more contacts between the copper powders.

  Here, as described in Patent Document 1 and Patent Document 2, for example, when spherical copper powder is formed into a flat plate shape by a mechanical method, it is necessary to prevent copper oxidation during mechanical processing. It is processed into a flat plate shape by adding a fatty acid and pulverizing it in air or in an inert atmosphere. However, it cannot be completely prevented from oxidation, and the fatty acid added at the time of processing may affect the dispersibility when it is made into a paste. The fatty acid may be firmly fixed to the copper surface due to the pressure during machining, which causes a problem that it cannot be completely removed.

  In this respect, the dendritic copper powder according to the present embodiment can be produced by forming flat copper particles by direct electrolysis without growing into a dendritic shape without performing mechanical processing. Therefore, there is no generation of oxidation which is a problem, and it is not necessary to remove fatty acids, so that the electrical conductivity characteristics can be made extremely good.

Further, the dendritic copper powder according to the present embodiment is not particularly limited, it is preferable that the bulk density is in the range of ^{0.5g / cm 3 ~5.0g / cm 3} . If the bulk density is less than 0.5 g / cm ³ , there is a possibility that sufficient contact between the copper powders cannot be ensured. On the other hand, if the bulk density exceeds 5.0 g / cm ³ , the average particle diameter of the copper powder also increases, the surface area decreases, and the moldability and sinterability may deteriorate.

Further, the dendritic copper powder according to the present embodiment is not particularly limited, it is preferable the value of the BET specific surface is 0.2m ² /g~5.0m ² / g. If the BET specific surface area is less than 0.2 m ² / g, the copper particles constituting the dendritic copper powder may not have the desired flat shape as described above, and high conductivity cannot be obtained. Sometimes. On the other hand, when the BET specific surface area exceeds 5.0 m ² / g, aggregation tends to occur and it becomes difficult to uniformly disperse the resin in the paste. The BET specific surface area can be measured in accordance with JIS Z8830: 2013.

  Moreover, although the dendritic copper powder which concerns on this Embodiment is not specifically limited, It is preferable that the crystallite diameter belongs to the range of 80 nm-300 nm. If the crystallite diameter is less than 80 nm, the copper particles constituting the main trunk and branches tend to be in the shape of a sphere rather than a flat plate, making it difficult to ensure a sufficiently large contact area and lowering the conductivity. there's a possibility that. On the other hand, when the crystallite diameter exceeds 300 nm, the average particle diameter of the copper powder also increases, the surface area decreases, and the moldability and sinterability may deteriorate.

The crystallite diameter here is obtained from a diffraction pattern obtained by an X-ray diffractometer, based on Scherrer's formula expressed by the following formula, and in the Miller index of the (111) plane by X-ray diffraction. The crystallite size.
D = 0.9λ / βcos θ
(D: crystallite diameter (nm), β: diffraction peak spread (rad) depending on crystallite size, λ: X-ray wavelength [CuKα] (nm), θ: diffraction angle (°). .)

  In addition, when the dendritic copper powder having the shape as described above is occupied at a predetermined ratio in the obtained copper powder when observed with an electron microscope, copper powder having other shapes is mixed. However, the effect similar to the copper powder which consists only of the dendritic copper powder can be acquired. Specifically, when observed with an electron microscope (for example, 500 times to 20,000 times), the dendritic copper powder having the shape described above is 50% by number or more, preferably 80% by number or more of the total copper powder, More preferably, as long as it occupies a ratio of 90% by number or more, copper powder of other shapes may be included.

≪2. Method for producing dendritic copper powder >>
Next, the method for producing the dendritic copper powder as described above will be described in detail. The dendritic copper powder according to the present embodiment can be produced, for example, by a predetermined electrolytic method using a sulfuric acid acidic solution containing copper ions as an electrolytic solution.

  In electrolysis, for example, the above-described sulfuric acid-containing electrolytic solution containing copper ions 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 solution is subjected to electrolytic treatment by applying a direct current at a predetermined current density. Thereby, a dendritic copper powder can be deposited (electrodeposition) on a cathode with electricity supply. In particular, in the present embodiment, flat copper particles are gathered only by electrolysis without mechanically deforming the granular copper powder obtained by electrolysis using a medium such as a ball. Thus, the dendritic copper powder having a dendritic shape can be deposited on the cathode surface.

  In the method for producing copper powder according to the present embodiment, the sulfuric acid electrolyte solution includes a copper ion, a compound having a phenazine structure, a compound having an azobenzene structure, and a compound having a phenazine structure and an azobenzene structure. More preferably, the dendritic copper powder with controlled cross-sectional average thickness, BET specific surface area, bulk density, and crystallite diameter can be precipitated by adding one or more selected from the group consisting of .

  More specifically, as an electrolytic solution, for example, a solution having a water-soluble copper salt, sulfuric acid, and an additive composed of a specific compound can be preferably used.

[Water-soluble copper salt]
The water-soluble copper salt is a copper ion source that supplies copper ions, and examples thereof include copper sulfate such as copper sulfate pentahydrate, copper nitrate, and the like, but are not particularly limited. Alternatively, copper oxide may be dissolved in a sulfuric acid solution to make a sulfuric acid acidic solution.

  Although it does not specifically limit as a copper ion density | concentration in electrolyte solution, About 1 g / L-20 g / L, Preferably it can be set as about 5 g / L-10 g / L.

[Sulfuric acid]
Sulfuric acid is for making a sulfuric acid electrolyte. The sulfuric acid concentration in the electrolytic solution can be about 20 g / L to 300 g / L, preferably about 50 g / L to 150 g / L, as the free sulfuric acid concentration. Since the sulfuric acid concentration affects the conductivity of the electrolyte, it affects the uniformity of the copper powder obtained on the cathode.

[Additive]
As an additive, a compound selected from the group consisting of a compound having a phenazine structure, a compound having an azobenzene structure, and a compound having a phenazine structure and an azobenzene structure is added to a sulfuric acid acidic solution containing copper ions.

  Each type of the compound having a phenazine structure, the compound having an azobenzene structure, and the compound having a phenazine structure and an azobenzene structure will be described later, but one or more kinds selected from compounds having different molecular structures are used. It can be contained in the electrolytic solution.

  An additive composed of such a compound precipitates dendritic copper powder having different average particle diameter and shape depending on the amount of the additive. Therefore, it is preferable to change the addition amount according to the specific surface area, crystallite diameter, etc. of the dendritic copper powder desired.

  Specifically, the concentration in the electrolyte of an additive selected from the group consisting of a compound having a phenazine structure, a compound having an azobenzene structure, and a compound having a phenazine structure and an azobenzene structure is, for example, the total of compounds to be added Therefore, it is preferably about 1 mg / L to 10,000 mg / L, more preferably 10 mg / L to 5,000 mg / L, and still more preferably 20 mg / L to 2,000 mg / L.

(Compound having phenazine structure)
A compound having a phenazine structure can be represented by the following formula (1). In the method for producing a dendritic copper powder according to the present embodiment, one or more compounds having a phenazine structure represented by the following formula (1) can be contained in the electrolyte as an additive. .

Here, in the formula (1), R ₁ , R ₂ , R ₃ , R ₄ , R ₆ , R ₇ , R ₈ and R ₉ are each independently hydrogen, halogen, amino, OH, —O, CN, SCN, a group SH, COOH, COO salt, COO _ester, SO 3 H, SO ₃ salt, is selected SO ₃ ester, benzenesulfonic acid, and from the group consisting of C1~C8 alkyl. R ₅ is hydrogen, halogen, amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, And a group selected from the group consisting of aryl. A ⁻ is a halide anion.

  Specific examples of the compound having a phenazine structure include 5-methylphenazine-5-ium, eruginosine B, aeruginosine A, 5-ethylphenazine-5-ium, 3,7-diamino-5-phenylphenazine-5-ium. 5-ethylphenazine-5-ium, 5-methylphenazine-5-ium, 3-amino-5-phenyl-7- (diethylamino) phenazine-5-ium, 2,8-dimethyl-3,7-diamino- 5-phenylphenazine-5-ium, 1-methoxy-5-methylphenazine-5-ium, 3-amino-7- (dimethylamino) -1,2-dimethyl-5- (3-sulfonatophenyl) phenazine- 5-ium, 1,3-diamino-5-methylphenazine-5-ium, 1,3-diamino-5-phenylphenazine -Ium, 3-amino-7- (diethylamino) -2-methyl-5-phenylphenazine-5-ium, 3,7-bis (diethylamino) -5-phenylphenazine-5-ium, 2,8-dimethyl- 3,7-diamino-5- (4-methylphenyl) phenazine-5-ium, 3- (methylamino) -5-methylphenazine-5-ium, 3-hydroxy-7- (diethylamino) -5-phenylphenazine -5-ium, 5-azoniaphenazine, 1-hydroxy-5-methylphenazine-5-ium, 4H, 6H-5-phenyl-3,7-dioxophenazine-5-ium, anilinoaposafranine, pheno Safranin, neutral red, etc. are mentioned.

(Compound having azobenzene structure)
The compound having an azobenzene structure can be represented by the following formula (2). In the method for producing a dendritic copper powder according to the present embodiment, one or more compounds having an azobenzene structure represented by the following formula (2) can be contained in the electrolyte as an additive. .

Here, in the formula (2), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ and R ₁₀ are each independently hydrogen, halogen, amino A group selected from the group consisting of OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, and aryl. is there.

  Specifically, examples of the compound having an azobenzene structure include azobenzene, 4-aminoazobenzene-4'-sulfonic acid, 4- (dimethylamino) -4 '-(trifluoromethyl) azobenzene, C.I. I. Acid Red 13, Mercury Orange, 2 ′, 4′-Diamino-5′-methylazobenzene-4-sulfonic acid sodium salt, methyl red, methyl yellow, methyl orange, azobenzene-2,4-diamine, alizarin yellow GG, 4- Dimethylaminoazobenzene, orange I, salazosulfapyridine, 4- (diethylamino) azobenzene, orange OT, 3-methoxy-4-aminoazobenzene, 4-aminoazobenzene, N, N, 2-trimethylazobenzene-4-amine, 4 -Hydroxyazobenzene, Sudan I, 4-amino-3,5-dimethylazobenzene, N, N-dimethyl-4-[(quinolin-6-yl) azo] benzenamine, o-aminoazotoluene, Alizarin Yellow R, 4 '-(Aminosulfonyl) 4-hydroxy-azobenzene-3-carboxylic acid, Congo red, vital red, Metanil Yellow, Orange II, Disperse Orange 3, C. I. Direct orange 39, 2,2'-dihydroxyazobenzene, azobenzene-4,4'-diol, naphthyl red, 5-phenylazobenzene-2-ol, 2,2'-dimethylazobenzene, C.I. I. Examples include Mordant Yellow 12, Mordant Yellow 10, Acid Yellow, Disperse Blue, New Yellow RMF, Vistramine Brown G, and the like.

(Compound having phenazine structure and azobenzene structure)
A compound having a phenazine structure and an azobenzene structure can be represented by the following formula (3). In the method for producing a dendritic copper powder according to the present embodiment, one or more compounds having a phenazine structure and an azobenzene structure represented by the following formula (3) are used as an additive in the electrolytic solution. It can be included.

Here, in formula (3), R ₁ , R ₂ , R ₄ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ are each independently hydrogen, halogen, amino, OH, -O, CN, SCN , SH, COOH, COO salt, COO _ester, SO 3 H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and is selected from the group consisting of C1~C8 alkyl It is a group. R ₃ is hydrogen, halogen, amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, And a group selected from the group consisting of aryl. A ⁻ is a halide anion.

  Specifically, as a compound having a phenazine structure and an azobenzene structure, 3- (diethylamino) -7-[(4-hydroxyphenyl) azo] -2,8-dimethyl-5-phenylphenazine-5-ium, 3 -[[4- (Dimethylamino) phenyl] azo] -7- (diethylamino) -5-phenylphenazine-5-ium, Janus Green B, 3-amino-7-[(2,4-diaminophenyl) azo] -2,8-dimethyl-5-phenylphenazine-5-ium, 2,8-dimethyl-3-amino-5-phenyl-7- (2-hydroxy-1-naphthylazo) phenazine-5-ium, 3- [ [4- (Dimethylamino) phenyl] azo] -7- (dimethylamino) -5-phenylphenazine-5-ium, 3-amino-7-[[4- (dimethyl) Ruamino) phenyl] azo] -5-phenylphenazine-5-ium, 2- (diethylamino) -7- [4- (methylpropargylamino) phenylazo] -9-phenyl-9-azonia-10-azaanthracene, 2- (Diethylamino) -7- [4- (methyl 4-pentynylamino) phenylazo] -9-phenyl-9-azonia-10-azaanthracene, 2- (diethylamino) -7- [4- (methyl 2,3- Dihydroxypropylamino) phenylazo] -9-phenyl-9-azonia-10-azaanthracene and the like.

[Chloride ion]
Further, the electrolyte solution can contain chloride ions. Thus, dendritic copper powder having different cross-sectional average thickness, BET specific surface area, bulk density, and crystallite diameter can be precipitated by containing chloride ions in the electrolyte and controlling the concentration thereof. it can.

  As a chloride ion, it can be made to contain by adding the compound (chloride ion source) which supplies chloride ions, such as hydrochloric acid and sodium chloride, in electrolyte solution, for example.

  The concentration of chloride ions in the electrolytic solution is not particularly limited, but is preferably 500 mg / L or less, more preferably 1 mg / L to 500 mg / L, and 10 mg / L to 300 mg / L. More preferably.

In the method for producing a dendritic copper powder according to the present embodiment, for example, the copper powder is deposited and produced on the cathode by electrolysis using the electrolytic solution having the composition as described above. As the electrolysis method, a known method can be used. For example, the current density is preferably in the range of 5 A / dm ^{2 to} 40 A / dm ² when electrolyzing using a sulfuric acid electrolyte, and the electrolyte is energized while stirring. Moreover, as a liquid temperature (bath temperature) of electrolyte solution, it can be set as about 20 to 60 degreeC, for example.

≪3. Applications of conductive paste, conductive paint, etc. >>
The dendritic copper powder produced by the above-described production method is a dendritic copper powder having a dendritic shape having a main trunk and a plurality of branches branched from the main trunk, and an average cross-sectional thickness of 0.02 μm to 5 A plate-like copper particle of 0.0 μm is assembled. And the average particle diameter (D50) of the said dendritic copper powder is 1.0 micrometer-100 micrometers. Also preferably, the BET specific surface area of 0.2m ² /g~5.0m ² / g.

  In such a dendritic copper powder, a dendritic shape has a large surface area, an excellent moldability and sinterability, and a dendritic flat plate having a predetermined cross-sectional average thickness. By being comprised from the shape-like copper particle, many contact numbers can be ensured and the outstanding electroconductivity is exhibited.

  Further, according to the dendritic copper powder having such a predetermined structure, even when it is a conductive paste (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 paste viscosity. Moreover, the electroconductivity excellent as an electrically conductive paste can be exhibited by being dendritic copper powder which consists of an aggregate | assembly of a flat copper particle. Therefore, the dendritic copper powder can be suitably used for applications such as conductive paste and conductive paint.

  For example, as a conductive paste, the dendritic copper powder according to the present embodiment is contained as a metal filler, and by kneading a binder resin, a solvent, and further additives such as an antioxidant and a coupling agent as necessary. Can be produced.

  In this Embodiment, it comprises so that the dendritic copper powder mentioned above may become a ratio of the quantity of 20 mass% or more, Preferably it is 30 mass% or more, More preferably, it is 50 mass% or more in a metal filler. Furthermore, the above-mentioned dendritic copper powder can be used alone or in combination of two or more different specific surface areas. When the proportion of the dendritic copper powder in the metal filler is 20% by mass or more, 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 It can prevent that it raises too much and printability defect arises.

  In addition, as a metal filler, as long as it contains the dendritic copper powder so that it may become the ratio of the quantity of 20 mass% or more as mentioned above, for example, the spherical copper powder of about 1 micrometer-20 micrometers is mixed. May be.

  Specifically, the binder resin is not particularly limited, but an epoxy resin, a phenol resin, or the like 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 is adjusted in consideration of the particle size of the dendritic copper powder so that the viscosity is suitable for a conductive film forming method such as screen printing or a dispenser. be able to.

  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.

  Further, as an additive, an antioxidant or the like can be added in order to improve the conductivity after firing. 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 wave 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, the resin used for forming the electromagnetic wave shielding layer of the electromagnetic wave shielding conductive sheet is not particularly limited, and conventionally used vinyl chloride resin, vinyl acetate resin, vinylidene chloride resin, Thermoplastic resin, thermosetting resin, radiation curable type made of various polymers and copolymers such as acrylic resin, polyurethane resin, polyester resin, olefin resin, chlorinated olefin resin, polyvinyl alcohol resin, alkyd resin, phenol resin, etc. Resin etc. can be used suitably.

  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.

  Moreover, even when using the metal filler according to the present embodiment as a conductive paint for electromagnetic wave shielding, it is not limited to use under particularly limited conditions, but a general method such as a metal filler is used. It can be used as a conductive paint by mixing with a resin and a solvent, and further mixing and kneading an antioxidant, a thickener, an anti-settling agent and the like as necessary.

  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, phenol resin, and the like that have been used in the past are used. Can be used. As the solvent, conventionally used alcohols such as isopropanol, aromatic hydrocarbons such as toluene, esters such as methyl acetate, ketones such as methyl ethyl ketone, and the like can be used. Also, as the antioxidant as an additive, conventionally used fatty acid amides, higher fatty acid amines, phenylenediamine derivatives, titanate coupling agents and the like can be used.

  Examples of the present invention will be described below in more detail with reference to comparative examples, but the present invention is not limited to the following examples.

<Evaluation method>
The copper powder obtained in the following Examples and Comparative Examples was subjected to shape observation, average particle diameter measurement, and crystallite diameter measurement by the following methods.

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

(Measurement of average particle size)
The average particle diameter (D50) of the obtained copper powder was measured using a laser diffraction / scattering particle size distribution measuring instrument (manufactured by Nikkiso Co., Ltd., HRA9320 X-100).

(Measurement of crystallite diameter)
The crystallite diameter was calculated from a diffraction pattern obtained by an X-ray diffractometer (manufactured by PAN analytical, X'Pert PRO) using a known method generally known as Scherrer's equation.

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

(Specific resistance measurement)
About the specific resistance value of a film, a sheet resistance value is measured by a four-terminal method using a low resistivity meter (manufactured by Mitsubishi Chemical Corporation, Loresta-GP MCP-T600). The film thickness of the coating film was measured by SURFCOM130A, manufactured by Tokyo Seimitsu Co., Ltd., and the sheet resistance value was determined by dividing the film thickness by the film thickness.

(Electromagnetic wave shielding characteristics)
The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate of the samples obtained in the examples and comparative examples using an electromagnetic wave having a frequency of 1 GHz. Specifically, the level in the case of Comparative Example 3 not using the dendritic copper powder is set as “△”, and the level worse than the level of Comparative Example 3 is set as “X”. Was evaluated as “◯”, and when it was excellent, “◎”.

  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.

<Examples and comparative examples>
[Example 1]
In an electrolytic cell having a capacity of 100 L, an electrode plate made of titanium having an electrode area of 200 mm × 200 mm is used as a cathode, and a copper electrode plate having an electrode area of 200 mm × 200 mm is used as an anode, and an electrolytic solution is loaded in the electrolytic cell. Then, a direct current was applied thereto to deposit copper powder on the cathode plate.

  At this time, an electrolytic solution having a copper ion concentration of 12 g / L and a sulfuric acid concentration of 120 g / L was used. Further, a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added to this electrolytic solution so that the chloride ion concentration was 80 mg / L. In addition, safranin (manufactured by Kanto Chemical Co., Ltd.), which is a compound having a phenazine structure as an additive, is used as an additive in this electrolytic solution at a concentration of 20, 50, 100, 200, 500, 1,000, 2, 000, 5,000, and 10,000 mg / L were added.

Then, while circulating the electrolytic solution adjusted to the concentration as described above at a flow rate of 15 L / min using a pump, the temperature is maintained at 25 ° C. and the current density of the cathode is set to 16 A / dm ^2. Then, copper powder was deposited on the cathode plate.

  The electrolytic copper powder deposited on the cathode plate was recovered by mechanically scraping it off the bottom of the electrolytic cell using a scraper, and the recovered copper powder was washed with pure water and then put in a vacuum dryer and dried. .

  As a result of observing the shape of the obtained electrolytic copper powder in a 10,000 × field of view by the method using the scanning electron microscope (SEM) described above, at least 90% or more of the copper powder is two-dimensional or three-dimensional. It was confirmed that the copper powder had a dendritic shape, and the main trunk and a plurality of branches branched from the main trunk were dendritic copper powder composed of flat copper particles.

  Moreover, the result of having measured the BET specific surface area in FIG. 1 is shown.

  Moreover, the result of having calculated | required the cross-sectional average thickness of the flat copper particle which observes with the method by SEM mentioned above in FIG. 2, and comprises dendritic copper powder is shown.

  As shown in the results of FIGS. 1 and 2, depending on the amount of the compound having a phenazine structure to be added, the BET specific surface area of the precipitated dendritic copper powder and the average cross-sectional thickness of the copper particles constituting the dendritic copper powder It turned out that thinner flat dendritic copper powder can be produced.

[Example 2]
A hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) is added to the electrolyte so that the chloride ion concentration becomes 200 mg / L, and methyl orange (Kanto Chemical Industries, Ltd.), which is a compound having an azobenzene structure as an additive, is added. Manufactured) was added in a concentration of 20, 50, 100, 200, 500, 1,000, 2,000, 5,000, 10,000 mg / L in the electrolytic solution. Otherwise, electrolytic treatment was performed under the same conditions as in Example 1 to produce electrolytic copper powder.

  As a result of observing the shape of the obtained electrolytic copper powder in the field of view with a magnification of 10,000 times by the above-described SEM method, at least 90% by number or more of the copper powder is a two-dimensional or three-dimensional dendritic copper. It was a powder, and it was confirmed that the main trunk and a plurality of branches branched from the main trunk were dendritic copper powder composed of flat copper particles.

  Moreover, the result of having measured the BET specific surface area about dendritic copper powder like Example 1 at FIG. 3 is shown. Moreover, the result of having measured the bulk density of the dendritic copper powder in FIG. 4 is shown.

[Example 3]
To the electrolyte solution, a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added so that the chloride ion concentration was 100 mg / L, and Janus Green B (a compound having a phenazine structure and an azobenzene structure as an additive) Manufactured by Kanto Chemical Co., Inc.) and added to the cathode in a concentration of 50, 100, 200, 500, 1,000, 2,000, 5,000, 10,000 mg / L in the electrolyte. The current was supplied so that the current density was 10 A / dm ² . Otherwise, electrolytic treatment was performed under the same conditions as in Example 1 to produce electrolytic copper powder.

  As a result of observing the shape of the obtained electrolytic copper powder in the field of view with a magnification of 10,000 times by the above-described SEM method, at least 90% by number or more of the copper powder is a two-dimensional or three-dimensional dendritic copper. It was a powder, and it was confirmed that the main trunk and a plurality of branches branched from the main trunk were dendritic copper powder composed of flat copper particles.

  Moreover, the result of having measured the BET specific surface area about dendritic copper powder like FIG.

[Example 4]
A hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) is added to the electrolyte so that the chloride ion concentration is 100 mg / L, and methyl orange (Kanto Chemical Industries, Ltd.), which is a compound having an azobenzene structure as an additive, is added. Product) and Janus Green B (manufactured by Kanto Chemical Co., Ltd.), which is a compound having a phenazine structure and an azobenzene structure, at a concentration of 20 in the electrolytic solution. , 50, 100, 200, 500, 1,000, 2,000, 5,000, 10,000 mg / L, and added so that the current density of the cathode is 10 A / dm ^2. I let you. Otherwise, electrolytic treatment was performed under the same conditions as in Example 1 to produce electrolytic copper powder.

  As a result of observing the shape of the obtained electrolytic copper powder in the field of view with a magnification of 10,000 times by the above-described SEM method, at least 90% by number or more of the copper powder is a two-dimensional or three-dimensional dendritic copper. It was a powder, and it was confirmed that the main trunk and a plurality of branches branched from the main trunk were dendritic copper powder composed of flat copper particles.

  FIG. 6 shows the result of calculating the crystallite diameter of the obtained dendritic copper powder from the diffraction pattern obtained by the above-mentioned X-ray diffraction measurement apparatus (manufactured by PAN analytical, X′Pert PRO).

[Example 5]
In Example 1, a specific surface area of 1.28 m was obtained from an electrolyte obtained by adding safranin (manufactured by Kanto Chemical Co., Ltd.), which is a compound having a phenazine structure, to a concentration of 200 mg / L in the electrolyte. ² / g of dendritic copper powder 55 parts by mass, 15 parts by mass of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211), 10 parts by mass of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed, Using a kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. The obtained conductive paste was printed on a glass with a metal squeegee and cured in air at 150 ° C. and 200 ° C. for 30 minutes.

  Table 1 summarizes the measurement results of the specific resistance values of the coatings obtained by curing.

[Example 6]
In Example 2, the specific surface area obtained by an electrolytic solution obtained by adding methyl orange (manufactured by Kanto Chemical Co., Ltd.), which is a compound having an azobenzene structure, to a concentration of 200 mg / L in the electrolytic solution was 1. 11 parts by mass of 11 m ² / g dendritic copper powder, 15 parts by mass of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 parts by mass of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) Using a small kneader (manufactured by Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), it was made into a paste 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 in air at 150 ° C. and 200 ° C. for 30 minutes.

  Table 1 summarizes the measurement results of the specific resistance values of the coatings obtained by curing.

[Example 7]
In Example 1, a specific surface area of 2.56 m was obtained from an electrolytic solution obtained by adding safranin (manufactured by Kanto Chemical Industry Co., Ltd.), which is a compound having a phenazine structure, to a concentration of 1000 mg / L in the electrolytic solution. ² / g of dendritic copper powder 55 parts by mass, 15 parts by mass of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211), 10 parts by mass of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed, Using a kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. The obtained conductive paste was printed on a glass with a metal squeegee and cured in air at 150 ° C. and 200 ° C. for 30 minutes.

  Table 1 summarizes the measurement results of the specific resistance values of the coatings obtained by curing.

[Example 8]
In Example 1, the specific surface area obtained by the electrolytic solution in which safranin (manufactured by Kanto Chemical Co., Ltd.), which is a compound having a phenazine structure, was added so that the concentration in the electrolytic solution was 100 mg / L was 0.81 m ² / g of dendritic copper powder and methyl orange which is a compound having an azobenzene structure in Example 2 (manufactured by Kanto Chemical Industry Co., Ltd.) was added to an electrolyte so that the concentration in the electrolyte was 2000 mg / L. ² parts different from the dendritic copper powder having a specific surface area of 2.56 m ² / g were mixed at a ratio of 50:50 to 55 parts by mass (total value) of the dendritic copper powder, Co., Ltd., PL-2211) 15 parts by mass and butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) 10 parts by mass are mixed, and a small kneader (manufactured by Nippon Seiki Seisakusho, Non-Bubbling Ni A paste was formed by repeating kneading at 1200 rpm for 3 minutes three times using a feeder NBK-1). The obtained conductive paste was printed on a glass with a metal squeegee and cured in air at 150 ° C. and 200 ° C. for 30 minutes.

  Table 1 summarizes the measurement results of the specific resistance values of the coatings obtained by curing.

[Example 9]
In Example 1, a specific surface area of 1.98 m obtained from an electrolytic solution in which safranin (manufactured by Kanto Chemical Co., Ltd.), which is a compound having a phenazine structure, was added so that the concentration in the electrolytic solution was 500 mg / L. ² / g dendritic copper powder 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.

[Example 10]
In Example 1, a specific surface area of 2.56 m was obtained from an electrolytic solution obtained by adding safranin (manufactured by Kanto Chemical Industry Co., Ltd.), which is a compound having a phenazine structure, to a concentration of 1000 mg / L in the electrolytic solution. ² / g dendritic copper powder 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.

[Example 11]
In Example 1, a specific surface area of 0.81 m was obtained from an electrolytic solution obtained by adding safranin (manufactured by Kanto Chemical Industry Co., Ltd.), which is a compound having a phenazine structure, to a concentration of 100 mg / L in the electrolytic solution. ² / g dendritic copper powder 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.

[Comparative Example 1]
Copper powder was deposited on the cathode plate under the same conditions as in Example 1 except that only chloride ions were added and no compound having a phenazine structure or the like was added as an additive.

  As a result of observing the shape of the obtained electrolytic copper powder in a 10,000 × field of view by the SEM method described above, it was a copper powder having a two-dimensional or three-dimensional dendritic shape. The plurality of branches branched from the plate were not composed of flat copper particles.

Moreover, it was 0.16 m < ² > / g as a result of measuring the BET specific surface area of the obtained copper powder like Example 1. FIG.

[Comparative Example 2]
To 55 parts by mass of dendritic copper powder having a BET specific surface area of 0.16 m ² / g obtained in Comparative Example 1, 15 parts by mass of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211), butyl cellosolve (Kanto Chemical) It was made into a paste by mixing 10 parts by mass (manufactured by Deka Special Grade Co., Ltd.) and 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 in air at 150 ° C. and 200 ° C. for 30 minutes.

  Table 1 summarizes the measurement results of the specific resistance values of the coatings obtained by curing.

[Comparative Example 3]
Dendritic copper powder having a BET specific surface area of 0.16 m ² / g obtained in Comparative 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 are respectively mixed with 40 g of the dendritic copper powder prepared in Comparative Example 1, and kneading at 1200 rpm for 3 minutes is 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.

  As described above, in the electrolyte solution, safranin having a phenazine structure (Example 1), methyl orange having an azobenzene structure (Example 2), Janus Green B having a phenazine structure and an azobenzene structure (Example 3), and By changing the concentration of these additives from Examples 1 to 4 to which two kinds (Example 4) of methyl orange having an azobenzene structure and Janus Green B having a phenazine structure and an azobenzene structure were added, respectively. It can be seen that the BET specific surface area, bulk density, crystallite diameter, and average cross-sectional thickness of the copper particles constituting the copper powder can be controlled. Moreover, from the results of Examples 5 to 11, a dendritic copper powder in which the BET specific surface area, bulk density, crystallite diameter, and cross-sectional average thickness of copper particles were controlled was used as a metal filler, and the metal filler was used. It was found that the conductive paste, the conductive paint for electromagnetic wave shield, and the conductive sheet for electromagnetic wave shield exhibit good characteristics.

  On the other hand, Comparative Example 1 in which only a chloride ion was added to the electrolytic solution as an additive without adding a compound having a phenazine structure, a compound having an azobenzene structure, and a compound having a phenazine structure and an azobenzene structure. Then, it turned out that only a copper powder whose BET specific surface area is smaller than the copper powder obtained in Examples 1-4 is obtained. Further, from the results of Comparative Examples 2 and 3, using the copper powder having a small BET specific surface area obtained in Comparative Example 1, a conductive paste, a conductive paint for electromagnetic shielding, and a conductive sheet for electromagnetic shielding. However, it has been found that it does not have sufficient characteristics.

Claims (9)

It is a method for producing copper powder by depositing on an anode from an electrolyte by an electrolytic method ,
The electrolytic solution is a sulfuric acid copper electrolytic solution containing copper ions,
In the electrolyte,
A compound having a phenazine structure represented by the following formula (1), a compound having an azobenzene structure represented by the following formula (2), and a following formula (3) at a content of 1 mg / L to 10,000 mg / L. One or more selected from the group consisting of compounds having a phenazine structure and an azobenzene structure are contained .

[In the formula (1), R ₁ , R ₂ , R ₃ , R ₄ , R ₆ , R ₇ , R ₈ , R ₉ are each independently hydrogen, halogen, amino, OH, —O, CN, SCN. , SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl, R ₅ is hydrogen, halogen , Amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, and aryl. And A ⁻ is a halide anion. ]

[In formula (2), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ are each independently hydrogen, halogen, amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, a group selected from the group consisting of benzenesulfonic acid, lower alkyl, and aryl. ]

[In the formula (3), R ₁ , R ₂ , R ₄ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ are each independently hydrogen, halogen, amino , OH, -O, CN, SCN , SH, COOH, COO salt, COO _ester, SO 3 H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and a radical selected from the group consisting of C1~C8 alkyl R ₃ is hydrogen, halogen, amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, and a group selected from the group consisting of aryl, a ^- is a halide anion. ] The copper powder is
It has a dendritic shape having a main trunk and a plurality of branches separated from the main trunk, and the main trunk and the branches are composed of tabular copper particles having a cross-sectional average thickness of 0.02 μm to 5.0 μm,
The average particle diameter (D50) is 1.0 μm to 100 μm
The manufacturing method of the copper powder of Claim 1. The bulk density of the copper ^powder, method for producing a copper powder according to claim 1 or 2 in the range of ^{0.5g / cm 3 ~5.0g / cm 3} . The BET specific surface area of the copper ^powder, method for producing a copper powder according to any one of claims 1 to 3 is 0.2m ² /g~5.0m 2 / g. The manufacturing method of the copper powder of any one of Claims 1 thru | or 4 with which the crystallite diameter in the Miller index | exponent of the (111) plane by the X-ray diffraction of the said copper powder belongs to the range of 80 nm-300 nm. The manufacturing method of the copper powder of any one of Claims 1 thru | or 5 which makes the said electrolyte solution contain a chloride ion with content of 500 mg / L or less. The copper ion concentration in the electrolytic solution is 1 g / L to 20 g / L. The method for producing copper powder according to any one of claims 1 to 6. A method for producing a metal filler, comprising:
The copper powder obtained by the manufacturing method of the copper powder of any one of Claims 1 thru | or 7 is contained in the ratio of 20 mass% or more in the said whole metal filler. The manufacturing method of the metal filler characterized by the above-mentioned. A method for producing a conductive paste, comprising mixing a metal filler obtained by the method for producing a metal filler according to claim 8 in a resin.

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