JP2017066463A - Ni-COATED COPPER POWDER, AND CONDUCTIVE PASTE, CONDUCTIVE PAINT AND CONDUCTIVE SHEET USING THE SAME, AND METHOD FOR PRODUCING Ni-COATED COPPER POWDER - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dendritic Ni-coated copper powder capable of preventing agglomeration, thereby being suitably used for conductive pastes, electromagnetic shields or the like, while increasing the number of contact points when Ni-coated dendritic copper powders contact with one another to ensure excellent conductivity.SOLUTION: An Ni-coated copper powder is formed in a dendritic shape having a plurality of branches, by agglomerating copper particles 2, the surfaces of which are coated with Ni or Ni alloy, wherein the copper particles 2, the surface of which are coated with Ni or Ni alloy, are in ellipsoids having an average minor axis diameter of 0.2 to 0.5 μm and an average major axis diameter of 0.5 to 2.0 μm. The copper powder formed by agglomerating the copper particles 2 in ellipsoids, the surface of the copper powder being coated with Ni or Ni alloy, has an average particle diameter (D50) of 5.0 to 20 μm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to copper powder (nickel-coated copper powder) whose surface is coated with nickel (Ni), and more specifically, a new material that can improve conductivity by using as a material such as a conductive paste. The present invention relates to a dendritic nickel-coated copper powder.

  For the formation of wiring layers and electrodes in electronic devices, pastes and paints using metal fillers such as copper powder and silver powder, such as resin pastes, fired pastes, and electromagnetic wave shielding paints, are often used. Metal filler pastes such as copper powder and silver powder are applied or printed on various base materials, and are subjected to heat curing or heat baking treatment to form a conductive film to be a wiring layer or an electrode.

  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.

  On the other hand, electromagnetic wave shields are used to prevent the generation of electromagnetic noise from electronic equipment. Especially in recent years, personal computers and mobile phone cases have been made of resin, so that the case is made conductive. In order to secure the properties, there are a method of forming a thin metal film by a vapor deposition method or a sputtering method, a method of applying a conductive paint, a method of attaching a conductive sheet to a necessary place and shielding an electromagnetic wave, etc. Proposed. Among them, special methods are required in the processing process for the method of applying the metal filler dispersed in the resin and the method of dispersing the metal filler in the resin and processing it into a sheet and attaching it to the housing. It has excellent flexibility and is widely used.

  However, in the case where such a metal filler is dispersed in a resin and applied or processed into a sheet shape, the dispersion state of the metal filler in the resin is not uniform. A method such as increasing the filling rate of the metal filler is required. However, in such a case, the addition of a large amount of metal filler causes problems such as an increase in sheet weight and a loss of flexibility of the resin sheet. Therefore, for example, in Patent Document 1, a method of using a flat metal filler has been proposed in order to solve these problems, and as a result, a thin sheet having excellent electromagnetic shielding effect and good flexibility. Can be formed.

Copper powder as a metal powder material used as a metal filler for such conductive paste and electromagnetic wave shielding material is covered with copper oxide when oxidized, causing adverse effects on sinterability, corrosion resistance, or conductivity Become. For this reason, in order to prevent oxidation of the copper powder, the surface of the copper particles is coated with a noble metal such as Pt, Pd, Ag, Au, etc., coated with a SiO ₂ oxide, or coated with Ni. Those with improved oxidation resistance are known. For example, Patent Document 2 discloses a nickel-coated copper powder having a copper powder surface coated with nickel (Ni).

  As a method for coating the surface of the copper powder with nickel, a method by electroless nickel plating may be mentioned. The coating method by electroless nickel plating is to perform nickel coating on the copper powder surface by reducing nickel ions in the plating solution with a reducing agent. The types of reducing agents are hypophosphites and borohydrides. And hydrazine compounds. Specifically, in nickel coating treatment using hypophosphite as a reducing agent, a Ni—P alloy coating is formed because phosphorus is contained in the coating during the reduction reaction. Further, in the nickel coating treatment using a borohydride compound as the reducing agent, since the boron is contained in the coating during the reduction reaction, a Ni-B alloy coating is formed. Further, in the nickel coating process using a hydrazine compound as a reducing agent, a high-purity Ni coating with few impurities is formed.

  As the copper powder, electrolytic copper powder deposited in a dendritic shape called a dendritic shape is known. Since the shape is a dendritic shape, it is characterized by a large surface area. Due to the dendritic shape as described above, when this is used for a conductive film or the like, the dendritic branches are overlapped with each other, conduction is easy, and the number of contact points between particles is larger than that of spherical particles. Therefore, there is an advantage that the amount of conductive filler such as conductive paste can be reduced. For example, Patent Documents 3 and 4 propose silver-coated copper powder in which the surface of a copper powder having a dendritic shape is coated with silver.

  Specifically, Patent Documents 3 and 4 disclose a dendrite characterized by a long branch branched from the main axis as further grown in a dendrite shape, and the silver-coated copper powder is more granular than the conventional dendrite. By increasing the number of contact points, the conductivity is improved, and when used in a conductive paste or the like, the conductivity can be increased even if the amount of conductive powder is reduced. Further, in Patent Document 5, an Ni alloy layer is formed on a copper surface and Ag coating is performed thereon to ensure oxidation resistance, and the electrolytic copper powder in a dendritic form is used as the copper powder used here. It is described that it is appropriate from the viewpoint of mutual entanglement.

  On the other hand, when developing a branch of electrolytic copper powder, when used in conductive paste, etc., the electrolytic copper powder is entangled more than necessary and agglomeration occurs, so that it does not disperse uniformly in the resin, and the fluidity is It is pointed out in Patent Document 6 that it decreases and becomes very difficult to handle, causing problems in wiring formation by printing or the like and reducing productivity. In addition, in patent document 6, in order to raise the intensity | strength of electrolytic copper powder itself, the intensity | strength of electrolytic copper powder itself is improved by adding tungstate in 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 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 order to ensure conductivity, a dendritic shape having a three-dimensional shape is easier to secure a contact than a granular one, and high conductivity can be expected as a conductive paste or electromagnetic wave shield. . However, the conventional nickel-coated copper powder having a dendrite-like shape is a dendrite characterized by a long branch branched from the main shaft, and has a long and narrow branch-like shape. The structure is simple, and it is not an ideal shape for effectively securing a contact using less nickel-coated copper powder.

JP 2003-258490 A JP-A-5-342908 JP 2013-89576 A JP 2013-100592 A JP 2002-075057 A JP 2011-58027 A

  The present invention has been proposed in view of such circumstances, and prevents aggregation while increasing the number of contacts when the dendritic copper powders coated with nickel are in contact with each other to ensure excellent conductivity. An object of the present invention is to provide a dendritic nickel-coated copper powder that can be suitably used for applications such as conductive pastes and electromagnetic wave shields.

  This inventor repeated earnest examination in order to solve the subject mentioned above. As a result, the dendritic copper powder has a dendritic shape having a main axis and a plurality of branches separated from the main axis, and has a fine protruding dendritic shape on the main axis and branched branches. Ni-coated copper powder with Ni or Ni alloy coated on the surface of the powder is excellent in electrical conductivity, and it is possible to secure a sufficient contact when copper powder contacts each other, and it is also necessary for pasting. The present invention has been completed by finding that it has excellent dispersibility and can be suitably used for applications such as conductive paste. That is, the present invention provides the following.

  (1) A first invention of the present invention is a Ni-coated copper powder in which copper particles coated with nickel (Ni) or a Ni alloy are aggregated to form a dendritic shape having a plurality of branches. The copper particles whose surfaces are coated with Ni or Ni alloy have a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter of 0.5 μm to 2.0 μm. The Ni-coated copper powder characterized in that the average particle diameter (D50) of the copper powder which is an ellipsoid and the ellipsoidal copper particles are aggregated and whose surface is coated with Ni or Ni alloy is 5.0 μm to 20 μm It is.

  (2) 2nd invention of this invention is Ni coat | court copper powder whose average thickness of the said branch part which comprises dendritic shape is 0.5 micrometer-2.0 micrometers in 1st invention.

  (3) According to a third aspect of the present invention, in the first or second aspect, the Ni content coated as Ni or Ni alloy is the mass of the entire Ni-coated copper powder coated with Ni or Ni alloy. It is Ni coat copper powder which is 1 mass%-50 mass% to%.

  (4) According to a fourth aspect of the present invention, in any one of the first to third aspects, the surface is coated with a Ni alloy, and cobalt, zinc, tungsten, molybdenum, palladium, platinum, tin, phosphorus And Ni-coated copper coated with a Ni alloy containing at least one selected from the group consisting of boron at a content of 0.1% by mass to 20% by mass with respect to 100% by mass of the Ni alloy It is powder.

(5) Fifth invention of the present invention, in the first to fourth invention of any one of, BET specific surface area of ^a 0.2m ² /g~5.0m 2 / g, Ni-coated copper powder It is.

(6) Sixth aspect of the present invention, in any of the first to fifth bulk density ⁱⁿ the range of ^{0.5g / cm 3 ~5.0g / cm 3} , Ni -coated copper powder It is.

  (7) A seventh aspect of the present invention is a metal filler characterized in that the Ni-coated copper powder according to any one of the first to sixth aspects of the invention is contained in a proportion of 20% by mass or more of the whole. It is.

  (8) The eighth invention of the present invention is a conductive paste characterized by mixing a metal filler according to the seventh invention with a resin.

  (9) A ninth invention of the present invention is a conductive paint for electromagnetic wave shielding, characterized by using the metal filler according to the seventh invention.

  (10) A tenth invention of the present invention is an electromagnetic wave shielding conductive sheet characterized by using the metal filler according to the seventh invention.

  (11) An eleventh aspect of the present invention is a method for producing a Ni-coated copper powder according to any one of the first to sixth aspects, wherein the copper powder is deposited on the cathode from the electrolytic solution by an electrolytic method. And a step of coating the copper powder with nickel (Ni) or a Ni alloy, wherein the electrolytic solution contains copper ions and a polyether compound to perform electrolysis. It is a manufacturing method of Ni coat copper powder.

  According to the Ni-coated copper powder according to the present invention, by being constituted by a copper powder having a dendritic shape, it is possible to effectively ensure a contact point when the Ni-coated copper powder contacts each other, Moreover, since Ni or Ni alloy is coat | covered on the surface, it has high electroconductivity. Moreover, it has the excellent dispersibility required for paste formation, and can suppress aggregation. Such Ni-coated copper powder can be suitably used for a conductive paste, a conductive paint for electromagnetic wave shielding, a conductive sheet, and the like.

It is the figure which showed typically the specific shape of the dendritic copper powder before coat | covering nickel or a nickel alloy. It is a photograph figure which shows an example of an observation image when the dendritic copper powder before coat | covering nickel or a nickel alloy is observed with a scanning electron microscope at a magnification of 5,000 times. It is a photograph figure which shows an example of an observation image when dendritic nickel coat copper powder is observed with a scanning electron microscope at a magnification of 5,000 times. It is a photograph figure which shows an example of an observation image when dendritic nickel coat copper powder is observed with a scanning electron microscope at a magnification of 10,000 times.

  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 nickel (Ni) coated copper powder >>
The nickel-coated copper powder according to the present embodiment is a copper powder in which copper particles are aggregated to form a dendritic shape having a plurality of branches, and the surface is coated with Ni or a Ni alloy. In this specification, nickel-coated copper powder is referred to as “Ni-coated copper powder”. Further, nickel or nickel alloy to be coated is expressed as “Ni” and “Ni alloy”, respectively, and when Ni is coated on the surface of copper powder or Ni alloy is coated on the surface of copper powder, “Ni coating” is generally used. ".

  Specifically, in the Ni-coated copper powder according to the present embodiment, the copper powder having a dendritic shape having a plurality of branches has a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average. It is an ellipsoid having a diameter in the range of 0.5 μm to 2.0 μm, and is composed of copper particles whose surfaces are coated with Ni or a Ni alloy. And the average particle diameter (D50) of the dendritic copper powder comprised by the copper particle by which the surface of Ni or Ni alloy was coat | covered is 5.0 micrometers-20 micrometers.

  More specifically, the shape of the copper powder constituting the Ni-coated copper powder will be described below.

≪2. Dendritic copper powder shape >>
FIG. 1 is a diagram schematically showing a specific shape of the dendritic copper powder before the Ni or Ni alloy is coated, which constitutes the Ni-coated copper powder according to the present embodiment. As shown in the schematic diagram of FIG. 1, the dendritic copper powder 1 constituting the Ni-coated copper powder has a dendritic shape having a plurality of branches, and is an assembly of fine copper particles 2 having an ellipsoidal shape. It consists of a body. The Ni-coated copper powder (hereinafter also referred to as “dendritic Ni-coated copper powder”) is obtained by coating the surface of the dendritic copper powder 1 with Ni or a Ni alloy.

  More specifically, the copper particles 2 are ellipsoidal copper particles having a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter of 0.5 μm to 2.0 μm. And the dendritic copper powder 1 which is an aggregate | assembly of the ellipsoidal copper particle 2 has the average particle diameter (D50) of 5.0 micrometers-20 micrometers. Even after the surface of the dendritic copper powder 1 is coated with Ni or a Ni alloy, the minor axis average diameter and the major axis average diameter of the Ni-coated copper particles constituting the Ni-coated copper powder, and its The average particle diameter of the Ni-coated copper powder is almost the same.

  Although the dendritic copper powder 1 will be described in detail later, for example, the dendritic copper powder 1 is obtained by immersing the anode and the cathode in a sulfuric acid electrolytic solution containing copper ions, and depositing on the cathode by flowing a direct current and performing electrolysis. Can do. That is, the dendritic copper powder 1 having a small shape as described above can be deposited and formed by electrolysis without performing physical treatment such as pulverization and crushing. In addition, since the conventional dendritic copper powder has a very large shape and cannot be used as it is, it was used as a small shape by performing a pulverization process. Therefore, the shape of the conventional dendritic copper powder is considered to be a dendritic copper powder in which shapes of 10 μm or less are assembled.

  FIG. 2 is a photograph showing an example of an observation image of a copper powder before being coated with Ni or Ni alloy by a scanning electron microscope (SEM). Moreover, FIG.3 and FIG.4 is a photograph figure which shows an example of the SEM observation image of the dendritic Ni coat | court copper powder which concerns on this Embodiment. 2 shows the dendritic copper powder observed at a magnification of 5,000 times, FIG. 3 shows the Ni coated copper powder observed at a magnification of 5,000 times, and FIG. 4 shows the dendritic Ni coated copper. The powder was observed at a magnification of 10,000 times.

  As observed in FIG. 2, the copper powder before coating with Ni exhibits a dendritic precipitation state. And this dendritic copper powder 1 forms the dendritic shape which has a some branch because the fine copper particle 2 which has an elliptical shape aggregates. Here, the size of the copper particles 2 is an ellipsoidal shape having a minor axis average diameter of 0.5 μm or less and a major axis average diameter of 2.0 μm or less.

  Increasing the number of contacts when dendritic Ni-coated copper powders are in contact with each other by having a long axis average diameter of the shape of the copper particles 2 constituting the dendritic copper powder 1 is 2.0 μm or less. Can do. That is, by being an aggregate of copper particles 2 having a major axis average diameter of 2.0 μm or less, the branch portion of the dendritic Ni-coated copper powder can be confirmed by the observation results shown in FIGS. Fine protrusions are formed, which can secure many contacts between the dendritic Ni-coated copper powders.

  However, when the long axis average diameter is longer than 2.0 μm, the distance between the branches of the dendritic copper powder becomes narrower and becomes a dense shape on the whole, so that the contacts between the dendritic copper powders tend to decrease. Become. Conversely, when the major axis average diameter of the copper particles becomes too short, formation of protrusions cannot be obtained. Therefore, the long axis average diameter of the copper particles 2 is preferably 0.5 μm to 2.0 μm.

  Further, the minor axis average diameter of the copper particles 2 is 0.5 μm or less. When the minor axis average diameter of the copper particles 2 is thicker than 0.5 μm, when the copper particles are assembled to form a dendritic copper powder, the thickness of the branch portion of the dendritic copper powder (for example, in FIG. 1) “D1”) in the schematic diagram increases. When the thickness of the branch portion is increased, the interval between the branches of the dendritic Ni-coated copper powder in which the surface of the dendritic copper powder is coated with Ni or Ni alloy is narrowed, resulting in a dense shape as a whole. No dendritic effect. Conversely, if the diameter of the branch part of the dendritic copper powder composed of copper particles is too thin, it becomes a fine whisker-like state, ensuring sufficient conductivity when the dendritic Ni-coated copper powders are in contact with each other become unable. For this reason, it is preferable that the minor axis average diameter of the copper particles 2 is 0.2 μm to 0.5 μm, thereby providing sufficient conductivity while exhibiting a three-dimensional dendritic effect. Can be secured.

  Furthermore, the average thickness (D1) of the branch portion of the dendritic copper powder 1 constituted by the aggregation of the copper particles 2 is preferably 2.0 μm or less. When the average thickness of the branch portion exceeds 2.0 μm, the interval between the branches of the dendritic copper powder is narrowed and the shape becomes dense as a whole. On the other hand, if the thickness of the branch portion is too small, the strength of the dendritic Ni-coated copper powder in which the surface of the dendritic copper powder is coated with Ni or Ni alloy will be insufficient, especially when molded into a conductive sheet In consideration of the flexibility, since the strength of the dendritic Ni-coated copper powder is low, there is a possibility that it breaks at the branch portion of the copper powder and loses conductivity. Therefore, the thickness of the branch portion of the dendritic copper powder 1 is preferably 0.5 μm to 2.0 μm.

  Next, the size (average particle diameter (D50)) of the dendritic copper powder 1 is 5.0 μm to 20 μm. 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 crushing or crushing such as a jet mill, a sample mill, a cyclone mill, or 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.

  Here, as pointed out in Patent Document 6, as a problem of dendritic copper powder, when used as a metal filler such as a conductive paste or a resin for electromagnetic wave shielding, the metal filler in the resin is dendritic. Due to the developed shape, the dendritic copper powders are entangled with each other, causing aggregation and not being uniformly dispersed in the resin. In addition, the agglomeration increases the viscosity of the paste and causes problems in wiring formation by printing. These occur due to the large shape of the dendritic copper powder, and in order to solve this problem while effectively utilizing the dendritic shape, it is necessary to appropriately reduce the size of the dendritic copper powder. There is. However, if the size of the dendritic copper powder is too small, the dendritic shape cannot be secured. Therefore, in order to ensure the effect of having a dendritic shape, that is, the effect of ensuring a large number of contact points between copper powders, the size of the dendritic copper powder (average particle diameter) is larger than a predetermined size. Is required.

  In this regard, in the Ni-coated copper powder according to the present embodiment, the size of the dendritic copper powder 1 before coating with Ni or Ni alloy, that is, the average particle diameter (D50) is 5.0 μm to 20 μm. Yes, by comprising the dendritic copper powder 1 of such a size, it is possible to secure a large number of contact points between the copper powders by the effect of the three-dimensional dendritic shape, and to suppress aggregation in the resin. Can be dispersed well, and an increase in paste viscosity can be suppressed.

≪3. Ni coating amount >>
In the dendritic Ni-coated copper powder according to the present embodiment, the surface of the dendritic copper powder 1 described above is coated with Ni or a Ni alloy. The coating amount of Ni or Ni alloy on the surface of the Ni-coated copper powder will be described below.

  The dendritic Ni-coated copper powder according to the present embodiment contains Ni with respect to 100% of the total mass of the Ni-coated copper powder coated with Ni on the dendritic copper powder 1 before being coated with Ni or Ni alloy. Ni or Ni alloy is coated at a ratio of 1% by mass to 50% by mass, and the thickness of Ni or Ni alloy (coating thickness) is 0.1 μm or less, preferably 0.02 μm or less. It is an extremely thin film. From this, the resinous Ni-coated copper powder has a shape that retains the shape of the dendritic copper powder 1 before being coated with Ni or Ni alloy. Therefore, both the shape of the copper powder before coating Ni or Ni alloy and the shape of the Ni-coated copper powder after coating the copper powder with Ni or Ni alloy are both dendritic shapes.

  As described above, the content of Ni coated as Ni or Ni alloy in the dendritic Ni-coated copper powder is 1% by mass to 50% by mass with respect to 100% by mass of the Ni-coated copper powder as a whole. A range is preferable. The content of Ni coated as Ni or Ni alloy is preferably as low as possible because the conductivity of Ni itself is lower than copper, but if it is too small, a uniform Ni or Ni alloy film cannot be secured on the copper powder surface. As a result, copper is oxidized to cause a decrease in conductivity. Therefore, the content of Ni coated as Ni or Ni alloy is preferably 1% by mass or more with respect to 100% by mass of the entire Ni-coated copper powder 1 coated with Ni, and is 2% by mass or more. It is more preferable that the content is 5% by mass or more.

  On the other hand, if the content of Ni coated as Ni or Ni alloy increases, the electrical conductivity decreases, which is not preferable. Accordingly, the coating amount of Ni or Ni alloy is preferably 50% by mass or less, more preferably 30% by mass or less, with respect to 100% by mass of the entire Ni-coated copper powder 1 coated with Ni. More preferably, it is 20 mass% or less.

  In the dendritic Ni-coated copper powder according to the present embodiment, the average thickness of Ni or Ni alloy coated on the surface of the copper particles is about 0.0003 μm to 0.1 μm, and 0.005 μm to 0.02 μm. It is preferable that If the coating thickness of Ni or Ni alloy is less than 0.0003 μm on average, a uniform Ni or Ni alloy coating cannot be secured on the surface of the copper powder, and copper conductivity cannot be suppressed, resulting in a decrease in conductivity. Cause. On the other hand, when the coating thickness of Ni or Ni alloy exceeds 0.1 μm on average, it is not preferable from the viewpoint of decreasing the electrical conductivity.

  Thus, the average thickness of Ni or Ni alloy coated on the surface of the dendritic Ni-coated copper powder is about 0.0003 μm to 0.1 μm, and constitutes the dendritic copper powder 1 before coating with Ni or Ni alloy. It is smaller than the size of the copper particles 2 (the ellipsoid having a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter of 0.5 μm to 2.0 μm). Therefore, the form of the copper powder does not substantially change before and after the surface of the dendritic copper powder 1 is coated with Ni or Ni alloy.

  Further, as will be described later, Ni coated on the dendritic copper powder 1 may be a Ni alloy. The element added as the Ni alloy is preferably an element from Group 6 to Group 14 of the periodic table, and particularly preferably at least one selected from zinc, cobalt, tungsten, molybdenum, palladium, platinum, and tin. Further, as will be described later, when using electroless plating in the step of coating Ni on the dendritic copper powder 1 and further using hypophosphite or borohydride as the reducing agent, the Ni coating obtained Are a Ni-P alloy and a Ni-B alloy, respectively.

Further, the dendritic Ni-coated copper powder according to the present embodiment is not particularly limited, it is preferable the value of the BET specific surface area of 0.2m ² /g~5.0m ² / g. When the BET specific surface area value is less than 0.2 m ² / g, the copper particles 2 coated with Ni or Ni alloy may not have the desired size and shape as described above, and high conductivity is obtained. It may not be possible. On the other hand, if the BET specific surface area value exceeds 5.0 m ² / g, the Ni or Ni alloy coating on the surface of the dendritic Ni-coated copper powder becomes non-uniform and high conductivity may not be obtained. In addition, the copper particles 2 constituting the Ni-coated copper powder become too fine, and the Ni-coated copper powder may be in a fine whisker-like state, resulting in a decrease in conductivity. The BET specific surface area can be measured in accordance with JIS Z8830: 2013.

As the bulk density of the dendritic Ni-coated copper powder according to the present embodiment is not particularly ^limited, is preferably 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 dendritic Ni-coated 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 dendritic Ni-coated copper powder also increases, and the surface area may decrease, and the formability and sinterability may deteriorate. .

  If the dendritic Ni-coated copper powder having the above-mentioned shape is occupied at a predetermined ratio in the obtained Ni-coated copper powder when observed with an electron microscope, Ni of other shapes Even if the coated copper powder is mixed, the same effect as that of the copper powder composed only of the dendritic Ni-coated copper powder can be obtained. Specifically, when observed with an electron microscope (for example, 500 to 20,000 times), the dendritic Ni-coated copper powder having the shape described above is 80% by number or more, preferably 90% of the total Ni-coated copper powder. As long as it occupies a ratio of several percent or more, Ni-coated copper powder of other shapes may be included.

<< 4. Method for producing dendritic Ni-coated copper powder >>
Next, the manufacturing method of the dendritic Ni coat | court copper powder 1 which has the above characteristics is demonstrated. Below, first, the manufacturing method of the dendritic copper powder which comprises the Ni coat copper powder 1 is demonstrated, Then, Ni or Ni alloy is coat | covered with respect to the dendritic copper powder, and the method of obtaining Ni coat copper powder Will be described.

<4-1. Method for producing dendritic copper powder>
The dendritic copper powder 1 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, the dendritic copper powder 1 can be deposited (electrodeposited) on the cathode with energization. In particular, in this embodiment, the ellipsoidal copper particles 2 are gathered only by the electrolysis without mechanically deforming the granular copper powder obtained by the electrolysis using a medium such as a ball. Thus, dendritic copper powder 1 having a dendritic shape can be deposited on the cathode surface.

  More specifically, for example, an electrolytic solution containing a water-soluble copper salt, sulfuric acid, an additive such as a polyether compound, and chloride ions can be used.

  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. The copper ion concentration in the electrolytic solution can be about 1 g / L to 20 g / L, preferably about 5 g / L to 10 g / L.

  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.

  As the additive, for example, a polyether compound can be used. This polyether compound, together with chloride ions described later, contributes to shape control of the deposited copper powder, and the copper powder deposited on the cathode is an ellipsoidal copper having a predetermined minor axis average diameter and major axis average diameter. It can be set as the dendritic copper powder 1 which the particle | grains 2 aggregated and made the dendritic shape.

  The polyether compound is not particularly limited. For example, polyethylene glycol, polypropylene glycol, polyethyleneimine, pluronic surfactant, tetronic surfactant, polyoxyethylene glycol / glycerin ether, polyoxyethylene glycol / dialkyl ether And polymer compounds such as polyoxyethylene polyoxypropylene glycol / alkyl ether and aromatic alcohol alkoxylate.

Further, the number average molecular weight of the polyether compound is not particularly limited, but is preferably 100 to 200,000, more preferably 200 to 15,000, and 1,000 to 10,000. Is more preferable. 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 0.6 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.

  In addition, as a polyether compound, you may add individually by 1 type and may add it in combination of 2 or more types. The amount of the polyether compound added is preferably such that the concentration in the electrolytic solution is in the range of about 0.1 mg / L to 5,000 mg / L.

  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. By containing chloride ions in the electrolytic solution, the shape of the deposited copper powder can be controlled more effectively. The chloride ion concentration in the electrolytic solution can be about 1 mg / L to 1000 mg / L, preferably about 10 mg / L to 800 mg / L, more preferably about 20 mg / L to 500 mg / L.

In the method for producing the dendritic copper powder according to the present embodiment, for example, the dendritic copper powder is produced by depositing on the cathode by electrolysis using the electrolytic solution having the composition 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} 30 A / dm ² when electrolyzing using a sulfuric acid electrolytic solution, 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.

  <4-2. Ni Coating Method (Production of Ni Coated Copper Powder)>

  The dendritic Ni-coated copper powder according to the present embodiment is produced by coating the surface of the dendritic copper powder prepared by the above-described electrolytic method with Ni or Ni alloy using, for example, an electroless plating method. Can do.

  In order to coat Ni or Ni alloy with a uniform thickness on the surface of the dendritic copper powder, it is preferable to wash before the Ni plating, and the dendritic copper powder is dispersed in the cleaning liquid and washed while stirring. It can be carried out. This washing treatment is preferably carried out in an acidic solution, and after washing, filtration, separation and washing of the dendritic copper powder 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 Ni coating is performed by the electroless plating method, the electroless Ni plating solution is added to the copper slurry obtained after washing the dendritic copper powder, or the copper slurry is added to the electroless Ni plating solution. By uniformly stirring, the surface of the dendritic copper powder can be coated more uniformly with Ni or Ni alloy.

  The electroless Ni plating solution is not particularly limited. The electroless Ni plating solution performs Ni coating by reducing Ni ions in the plating solution with a reducing agent. Examples of the reducing agent include hypophosphites, borohydrides, and hydrazine compounds. It is done.

  Specifically, examples of hypophosphites include hypophosphites such as potassium hypophosphite and sodium hypophosphite, and phosphites such as potassium phosphite and sodium phosphite. Can be mentioned.

  Examples of the borohydride compound include dimethylhexaborane, dimethylamineborane (DMAB), diethylamineborane, morpholineborane, pyridineamineborane, piperidineborane, ethylenediamineborane, ethylenediaminebisborane, t-butylamineborane, imidazoleborane, methoxy Examples include ethylamine borane and sodium borohydride.

  As the hydrazine compound, hydrazine and hydrates thereof, hydrazine salts such as hydrazine sulfate and hydrazine hydrochloride, hydrazine derivatives such as pyrazoles, triazoles, and hydrazides can be used. Among these hydrazine derivatives, pyrazoles such as 3,5-dimethylpyrazole and 3-methyl-5-pyrazolone can be used as pyrazoles in addition to pyrazole. As triazoles, 4-amino-1,2,4-triazole, 1,2,3-triazole, and the like can be used. As hydrazides, adipic hydrazide, maleic hydrazide, carbohydrazide, and the like can be used. As hydrazines, hydrazine sulfate, hydrazine hydrochloride, adipic hydrazide, maleic hydrazide, carbohydrazide, and the like can be used.

  Examples of the nickel source include nickel salts such as nickel sulfate, nickel chloride, nickel acetate, and nickel sulfamate.

  Further, the plating solution can contain a complexing agent, a pH buffering agent, and a pH adjusting agent.

  Specifically, a known complexing agent can be used as the complexing agent. For example, amino acids such as glycine, citrates such as sodium citrate and ammonium citrate, lactic acid, oxalic acid, malonic acid, malic acid, tartaric acid, aspartic acid, glutamic acid, gluconic acid, sodium salts or ammonium salts, ammonia, etc. Is mentioned.

  A known complexing agent can be used as the pH buffering agent. For example, ammonium chloride, ammonium sulfate, boric acid, sodium acetate and the like can be mentioned.

  A known complexing agent can be used as the pH adjuster. For example, an acid or alkali compound can be used, and examples thereof include alkali metal hydroxides such as ammonia and sodium hydroxide, nickel carbonate, sulfuric acid, and hydrochloric acid. In addition, when using ammonia, it can supply as ammonia water.

  Moreover, you may use an antifoamer and a dispersing agent as needed.

  Furthermore, in order to improve the permeability of the plating solution, a surfactant can be contained. As the surfactant, any of nonionic, cationic, anionic and amphoteric surfactants can be used, and one kind can be used alone, or two or more kinds can be used in combination.

  Here, in Ni coating by electroless plating, the Ni coating deposited differs depending on the hypophosphorous acid bath salt, the borohydride compound, and the hydrazine compound which are reducing agents in the electroless Ni plating solution. Specifically, when hypophosphorous acid bath salt is used as the reducing agent, since the phosphorus is contained in the coating during the reduction reaction, a Ni-P alloy coating is formed. Further, when a borohydride compound is used as the reducing agent, since a boron is contained in the coating during the reduction reaction, a Ni-B alloy coating is formed. Further, when a hydrazine compound is used as the reducing agent, a high-purity Ni film with few impurities is formed.

  Furthermore, by making the Ni film to be formed contain other elements, that is, by forming a Ni alloy film on the surface of the copper powder, using the Ni-coated copper powder, heat resistance and corrosion resistance In addition, an excellent conductive paste or the like can be realized.

  Specifically, as an element to be included in the Ni film, that is, as an element other than Ni constituting the Ni alloy, elements of Groups 6 to 14 of the periodic table can be mentioned, and among them, zinc, palladium, Examples include cobalt, rhodium, iron, platinum, iridium, tungsten, molybdenum, chromium, and tin. In particular, one or more elements selected from zinc, cobalt, tungsten, molybdenum, palladium, platinum, and tin are preferable, and a Ni alloy film having excellent conductivity is formed by using an Ni alloy containing these elements. be able to.

  The content of these elements constituting the Ni alloy is preferably 0.1% by mass to 20% by mass with respect to 100% by mass of the Ni alloy, from the viewpoint of conductivity and dispersibility, and preferably 1% by mass to 15%. More preferably, it is more preferably 2% by mass to 10% by mass. In addition, also about the Ni-P alloy and Ni-B alloy which are each formed with the kind of reducing agent mentioned above, the content of phosphorus or boron is 0.1 mass% with respect to 100 mass of Ni alloy film similarly. It is preferably ˜20% by mass, more preferably 1% by mass to 15% by mass, and further preferably 2% by mass to 10% by mass.

  When the Ni alloy is used, if the content of elements other than Ni is excessively increased, the conductivity is lowered, so that the content is preferably 20% by mass or less. On the other hand, if the content is less than 0.1% by mass, the effect of improving the heat resistance and corrosion resistance cannot be sufficiently obtained even if these elements are contained together with Ni to form a Ni alloy. In addition, content of the element in Ni alloy can be measured by converting content of each element which comprises Ni coat | court copper powder, for example by a high frequency inductively coupled plasma (ICP) emission spectroscopy analysis method. In addition, each element in the Ni alloy coating can be quantitatively analyzed from the cross section of the Ni-coated copper powder or the like by energy dispersive X-ray spectroscopy (EDX) method or Auger electron spectroscopy (AES) method.

  As a method for forming a Ni alloy coating, ions such as cobalt, zinc, tungsten, molybdenum, palladium, platinum, and tin are added to the above-described electroless Ni plating solution, and electroless plating using the plating solution is performed. Can be formed. The ion source such as cobalt, zinc, tungsten, molybdenum, palladium, platinum, and tin is not particularly limited as long as it is a soluble metal salt.

  Specifically, the cobalt ion source is not particularly limited as long as it is soluble in the plating solution as a cobalt compound and can obtain an aqueous solution having a predetermined concentration. Examples thereof include cobalt sulfate, cobalt chloride, and cobalt sulfamate. These cobalt compounds can be used individually by 1 type or in mixture of 2 or more types.

  The zinc ion source is not particularly limited as long as it is soluble in the plating solution as a zinc compound and can obtain an aqueous solution having a predetermined concentration. For example, zinc chloride, zinc sulfamate, zinc sulfate, zinc acetate and the like can be mentioned. These zinc compounds can be used singly or in combination of two or more.

  The tungsten ion source is not particularly limited as long as it is soluble in a plating solution as a tungsten compound and can obtain an aqueous solution having a predetermined concentration. Examples thereof include sodium tungstate, potassium tungstate, and ammonium tungstate. These tungsten compounds can be used singly or in combination of two or more.

  The molybdenum ion source is not particularly limited as long as it is soluble in a plating solution as a molybdenum compound and can obtain an aqueous solution having a predetermined concentration. Examples thereof include molybdenum trioxide, sodium molybdate, diammonium molybdate, calcium molybdate, molybdic acid, phosphomolybdic acid, and molybdate gluconic acid complex. These molybdenum compounds can be used singly or in combination of two or more.

  The palladium ion source is not particularly limited as long as it is soluble in the plating solution as a palladium compound and can obtain an aqueous solution having a predetermined concentration. For example, water-soluble palladium compounds such as palladium sulfate, palladium chloride, palladium acetate, dichlorodiethine rediamine palladium, and tetraammine palladium dichloride can be used. Further, as the palladium compound, a so-called palladium solution in which palladium is made into a solution can also be used. As the palladium solution, for example, a dichlorodiethylenediamine palladium solution or a tetraammine palladium dichloride solution can be used. These palladium compounds can be used individually by 1 type or in mixture of 2 or more types.

  The platinum ion source is not particularly limited as long as it is soluble in a plating solution as a platinum compound and can obtain an aqueous solution having a predetermined concentration. For example, platinum chloride, chloroplatinic acid, chloroplatinic acid salt, platinum hydroxide acid, platinum hydroxide salt, dinitrodiammine platinum complex salt, dinitrosulfitoplatinum complex salt, tetraammine platinum complex salt, hexaammine platinum complex salt can be mentioned. A platinum compound can be used individually by 1 type or in mixture of 2 or more types.

  The tin ion source is not particularly limited as long as it is soluble in the plating solution as a tin compound and can obtain an aqueous solution having a predetermined concentration. For example, stannous chloride, stannic chloride, stannous sulfate, stannic sulfate, stannous pyrophosphate, and other inorganic acid salts of tin, stannous citrate, stannous citrate, stannous oxalate Of tin carboxylates such as stannic oxalate, tin methanesulfonate, tin 1-ethanesulfonate, tin 2-ethanesulfonate, tin 1-propanesulfonate, tin 3-propanesulfonate Alkane sulfonate, tin methanol sulfonate, tin hydroxyethane-1-sulfonate, tin 1-hydroxypropane-1-sulfonate, tin tin hydroxyethane-2-sulfonate, tin 1-hydroxypropane-3-sulfonate, etc. Alkanol sulfonates, tin hydroxides such as stannous hydroxide and stannic hydroxide, and metastannic acid.

  The method for forming the Ni alloy film is not limited to the above-described electroless plating method. For example, an element other than Ni constituting the Ni alloy is included in the dendritic copper powder before coating with Ni, and after forming a film made only of Ni (Ni film), it is added to the copper powder in advance. A Ni alloy film can also be formed by diffusing the elements previously deposited into the Ni film.

≪5. Use of conductive paste, conductive paint for electromagnetic wave shield, conductive sheet >>
As described above, the Ni-coated copper powder according to the present embodiment has a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter of 0.5 μm to 2.0 μm. The ellipsoidal copper particles 2 are aggregated, and the surface of the dendritic copper powder 1 is coated with Ni or a Ni alloy. In such a Ni-coated copper powder, fine protrusions are formed on the branches constituting the dendritic shape, and the size (average particle diameter (D50)) of the Ni-coated copper powder is 5.0 μm to 20 μm. It is.

  As described above, the dendritic Ni-coated copper powder according to the present embodiment has fine protrusions formed on the branches, and the average particle diameter (D50) is 5.0 μm to 20 μm. According to such Ni-coated copper powder, it is possible to secure more contacts between the copper powders than the conventional dendrite-like shape, that is, the shape of the dendrite-like copper powders shown in Patent Documents 3 and 4. The above conductivity can be ensured. In addition, when the Ni-coated copper powder is used as a metal filler, it is possible to prevent entanglement and aggregation from occurring, and to prevent the resin from being uniformly dispersed in the resin. It can use suitably for uses, such as a conductive paint for conductive materials and a conductive sheet. Furthermore, since this dendritic Ni-coated copper powder provides the strength of the branch portion, it is excellent in flexibility when formed into a conductive sheet, for example.

  When the dendritic Ni-coated copper powder according to the present embodiment is used as a metal filler, it can be used by mixing with copper powder of other shapes. At this time, the proportion of the dendritic Ni-coated copper powder in the total amount of copper powder is preferably 20% by mass or more, more preferably 60% by mass or more, and further preferably 75% by mass or more. preferable. Thus, when used as a metal filler, by mixing with copper powder of other shapes such as particles or flakes, the gap between the dendritic Ni-coated copper powder is filled with copper powder of other shapes. As a result, more contacts for ensuring conductivity can be ensured. The metal powder to be mixed with the dendritic Ni-coated copper powder is not limited to copper powder having other shapes, and for example, spherical silver powder may be mixed.

  When the dendritic Ni-coated copper powder is less than 20% by mass of the total amount of copper powder used as the metal filler, the contacts between the dendritic Ni-coated copper powders are reduced and other shapes of copper powder are mixed. Even if the increase in the contact due to is taken into account, the conductivity of the metal filler is lowered.

  When using a metal filler to make a conductive paste, it is not limited to use under particularly limited conditions, but a general method, for example, mixing the metal filler with a binder resin and a solvent, and further required Accordingly, a conductive paste can be obtained by mixing and kneading with a curing agent, a coupling agent, a corrosion inhibitor or the like.

  The binder resin used at this time is not particularly limited, and those conventionally used can be used. For example, an epoxy resin, a phenol resin, an unsaturated polyester resin, or the like can be used. As the solvent, conventionally used terpineol, ethyl carbitol, carbitol acetate, butyl cellosolve, and the like can be used. Moreover, conventionally used 2-ethyl 4-methylimidazole etc. can be used also about a hardening | curing agent. Furthermore, conventionally used benzothiazole, benzimidazole, and the like can also be used for the corrosion inhibitor.

  Furthermore, other resin components can be added for viscosity adjustment. For example, a cellulose-based resin typified by ethyl cellulose can be used, and it 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.

  Various electrical circuits can be formed using a conductive paste produced using a metal filler. Even in this case, the circuit pattern forming method or the like conventionally used can be used without being limited to use under particularly limited conditions. For example, a conductive paste produced using the metal filler is applied or printed on a fired substrate or an unfired substrate, heated, and then pressed and cured as needed to cure and print. An electric circuit of an electronic component, an external electrode, or the like can be formed.

  Moreover, even when using the above-mentioned metal filler as an electromagnetic shielding material, it is not limited to use under particularly limited conditions, but a general method, for example, using the metal filler mixed with a resin can do.

  For example, even when a metal filler is used as a conductive paint for electromagnetic wave shielding, a general method, for example, the metal filler is mixed with a resin and a solvent, and an antioxidant, a thickener, It can be used as a conductive coating by mixing with an anti-settling agent and kneading. The binder resin and solvent used at this time are not particularly limited, and those conventionally used can be used.

  Specifically, vinyl chloride resin, vinyl acetate resin, acrylic resin, polyester resin, fluorine resin, silicon resin, phenol resin, or the like can be used as the binder resin. 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. As for the antioxidant, conventionally used fatty acid amides, higher fatty acid amines, phenylenediamine derivatives, titanate coupling agents and the like can be used.

  Further, even when a conductive sheet for electromagnetic wave shielding is made using a metal filler, the resin for forming the electromagnetic wave shielding layer of the conductive sheet for electromagnetic wave shielding is not particularly limited and conventionally used. You can use what you have. For example, various polymers and copolymers such as vinyl chloride resin, vinyl acetate resin, vinylidene chloride resin, acrylic resin, polyurethane resin, polyester resin, olefin resin, chlorinated olefin resin, polyvinyl alcohol resin, alkyd resin, phenol resin, etc. A thermoplastic resin, a thermosetting resin, a radiation curable resin, and the like can be appropriately used.

  The method for producing the electromagnetic shielding material is not particularly limited. For example, an electromagnetic shielding layer is formed by applying or printing a coating material in which a metal filler and a resin are dispersed or dissolved in a solvent on a substrate, and the surface is solidified. It can manufacture by drying to such an extent. In the conductive adhesive layer of the conductive sheet, a metal filler containing Ni-coated copper powder according to the present embodiment can also 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≫
With respect to the Ni-coated copper powders obtained in the following examples and comparative examples, the shape was observed, the average particle diameter was measured, and the like 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 the appearance of the copper powder contained in the visual field was observed.

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

(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 of Comparative Example 3 in which no dendritic Ni-coated copper powder is used is “△”, and the level worse than that of Comparative Example 3 is “×”. The case where it was better than the level 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, comparative example≫
[Example 1]
<Preparation of electrolytic copper powder>
An electrolytic cell with a capacity of 100 L is used with a titanium electrode plate having 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, and an electrolytic solution is charged into 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 composition with a copper ion concentration of 10 g / L and a sulfuric acid concentration of 100 g / L was used. Further, polyethylene glycol (PEG) having a molecular weight of 400 (manufactured by Wako Pure Chemical Industries, Ltd.) as an additive was added to this electrolytic solution so that the concentration in the electrolytic solution was 500 mg / L, and a hydrochloric acid solution (Wako Pure Chemical Industries, Ltd.) was further added. Yakuhin Kogyo Co., Ltd.) was added at a chloride ion (chlorine ion) concentration of 50 mg / L.

Then, the current density of the cathode is 20 A / dm ² under the condition that the temperature is maintained at 30 ° C. while circulating the electrolytic solution whose concentration is adjusted as described above at a flow rate of 10 L / min using a metering pump. In this way, copper powder was deposited on the cathode plate.

  The electrolytic copper powder deposited on the cathode plate was mechanically scraped and collected on the bottom of the electrolytic cell, and the collected 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 copper powder thus obtained in the field of view with a magnification of 5,000 times by the method using the scanning electron microscope (SEM) described above, the deposited copper powder has a minor axis average diameter of 0.2 μm to 0 μm. It was a dendritic copper powder having a dendritic shape composed of ellipsoidal copper particles having a major axis average diameter of 0.5 μm to 2.0 μm. Moreover, the average particle diameter (D50) of the dendritic copper powder formed by aggregation of the copper particles was 5.0 μm to 20 μm. Moreover, it was confirmed that the copper particles gathered to form a dendritic copper powder in which the average thickness of the branches was 0.5 μm to 2.0 μm.

<Preparation of dendritic Ni-coated copper powder (reducing agent: borohydride)>
Using 100 g of the obtained dendritic copper powder, Ni was coated on the surface of the copper powder by electroless plating to prepare a Ni-coated copper powder. In addition, the electroless Ni plating solution whose reducing agent is a borohydride compound was used.

  Specifically, as an electroless Ni plating solution, nickel sulfate 30 g / L, sodium succinate 50 g / L, boric acid 30 g / L, ammonium chloride 30 g / L, dimethylamine borane 4 g / L were added at each concentration, 500 mL of a plating solution adjusted to pH 6.0 by adding sodium hydroxide was prepared.

  In this electroless Ni plating solution, a slurry in which 100 g of the dendritic copper powder prepared by the above method is dispersed in 100 mL of water is stirred for 10 minutes at 25 ° C., and then the bath temperature is heated to 60 ° C. to 60 ° C. Stir for minutes.

  After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder in which Ni was coated on the surface of the dendritic copper powder was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 18.6% by mass with respect to 100% by mass of the entire Ni-coated copper powder. Further, the content of boron (B) contained in the Ni alloy was 6.1% by mass with respect to 100% by mass of the Ni alloy.

  Moreover, as a result of observing the obtained Ni-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of the Ni-coated copper powder has a dendritic shape in which copper particles are aggregated, It was dendritic Ni-coated copper powder in which the Ni alloy was uniformly coated on the surface of the copper particles. Further, the copper particles constituting the Ni-coated copper powder and coated with the Ni alloy on the surface have a minor axis average diameter of 0.2 μm to 0.5 μm and an average of 0.39 μm, and a major axis average It was an ellipsoid having a diameter of 0.5 μm to 2.0 μm and an average size of 1.6 μm.

  The average particle diameter (D50) of the dendritic Ni-coated copper powder formed by aggregating ellipsoidal copper particles coated with these Ni alloys is 21.2 μm, and the average thickness of the branch portion is 1 It was 5 μm.

Furthermore, the bulk density of the obtained Ni-coated copper powder was 1.25 g / cm ³ . The BET specific surface area was 1.7 m ² / g.

[Example 2]
<Manufacture of electrolytic copper powder>
As the electrolytic solution, a composition having a copper ion concentration of 10 g / L and a sulfuric acid concentration of 125 g / L is used, and polyethylene glycol (PEG) as an additive is 150 mg / L as an additive in the electrolytic solution. Copper powder (dendritic copper powder) on the cathode plate under the same conditions as in Example 1 except that the hydrochloric acid solution was added to a concentration of 100 mg / L as the chloride ion concentration in the electrolytic solution. Precipitated.

<Production of dendritic Ni-coated copper powder (reducing agent: hypophosphite)>
Next, using the electrolytic copper powder produced by the method described above, Ni-coated copper powder was produced by electroless plating. In addition, an electroless Ni plating solution whose reducing agent is hypophosphite was used.

  Specifically, as an electroless Ni plating solution, nickel sulfate 20 g / L, sodium hypophosphite 25 g / L, sodium acetate 10 g / L, sodium citrate 10 g / L were added at each concentration, and sodium hydroxide was further added. 500 mL of a plating solution adjusted to pH 5.0 by addition was prepared.

  In this electroless Ni plating solution, a slurry in which 100 g of electrolytic copper powder prepared by the above-described method is dispersed in 100 mL of water is stirred for 10 minutes at 25 ° C., and then the bath temperature is heated to 90 ° C. for 60 minutes. Stir.

  After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder in which Ni alloy containing phosphorus (P) was coated on the surface of dendritic copper powder was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 13.1% by mass with respect to 100% by mass of the entire Ni-coated copper powder. Moreover, content of P contained in Ni alloy was 8.1 mass% with respect to 100 mass of Ni alloy.

  Moreover, as a result of observing the obtained Ni-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of the Ni-coated copper powder has a dendritic shape in which copper particles are aggregated, It was Ni coat copper powder by which Ni alloy was uniformly coat | covered on the surface of the copper particle. Further, the copper particles constituting the Ni-coated copper powder and coated with the Ni alloy on the surface have a minor axis average diameter of 0.2 μm to 0.5 μm and an average of 0.27 μm, and a major axis average It was an ellipsoid having a diameter of 0.5 μm to 2.0 μm and an average size of 1.2 μm.

  The average particle diameter (D50) of dendritic Ni-coated copper powder formed by agglomeration of ellipsoidal copper particles coated with these Ni alloys is 8.3 μm, and the average thickness of the branch portion is 1 .1 μm.

Furthermore, the bulk density of the obtained Ni-coated copper powder was 2.77 g / cm ³ . The BET specific surface area was 1.2 m ² / g.

[Example 3]
<Preparation of dendritic Ni-coated copper powder (reducing agent: hydrazine compound)>
Using 100 g of the dendritic copper powder obtained in Example 2, Ni was coated on the surface of the copper powder by electroless plating to produce a Ni-coated copper powder. Electroless Ni plating using a hydrazine compound as a reducing agent was performed.

  Specifically, nickel acetate was added to a slurry in which 100 g of the dendritic copper powder obtained in Example 2 was dispersed in 500 mL of water to a concentration of 12.4 g / L, and an 80% by mass aqueous solution of hydrazine monohydrate. 6 g was added dropwise into the bath with slow stirring over 60 minutes. At this time, the bath temperature was controlled to 60 ° C.

  After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder in which Ni was coated on the surface of the dendritic copper powder was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 7.7% by mass with respect to 100% by mass of the entire Ni-coated copper powder.

  Moreover, as a result of observing the obtained Ni-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of the Ni-coated copper powder has a dendritic shape in which copper particles are aggregated, It was Ni coat copper powder by which Ni was uniformly coat | covered on the surface of the copper particle. Further, the copper particles constituting the Ni-coated copper powder and coated with Ni on the surface have a minor axis average diameter of 0.2 μm to 0.5 μm and an average of 0.24 μm, and a major axis average diameter. Was an ellipsoid having a size of 0.5 μm to 2.0 μm and an average size of 1.1 μm.

  The average particle diameter (D50) of the dendritic Ni-coated copper powder formed by agglomeration of ellipsoidal copper particles coated with Ni is 9.6 μm, and the average thickness of the branch portion is 1.3 μm. Met.

Furthermore, the bulk density of the obtained Ni-coated copper powder was 2.92 g / cm ³ . Further, the BET specific surface area was 1.6 m ² / g.

[Examples 4 to 10]
<Preparation of dendritic Ni-coated copper powder (Ni alloy)>
Using 100 g of the dendritic copper powder obtained in Example 2, the surface of the copper powder was coated with a Ni alloy by electroless plating.

  As an electroless Ni plating solution for an alloy, nickel acetate was added to a slurry in which 100 g of the dendritic copper powder obtained in Example 2 was dispersed in 500 mL of water to a concentration of 12.4 g / L, and hydrazine 3. 2 g was added dropwise into the bath over 60 minutes with slow stirring. The bath temperature was controlled to 60 ° C.

  At this time, each metal compound was added to a bath containing copper powder slurry and nickel acetate, and hydrazine was gradually added so that each desired Ni alloy film was formed. As a metal compound, in Example 4, 1.5 g of sodium tungstate was added to form a Ni—W alloy film. In Example 5, 2 g of cobalt sulfate was added to form a Ni—Co alloy film. In Example 6, 4 g each of zinc sulfate heptahydrate and sodium citrate were added to form a Ni—Zn alloy film. In Example 7, 2 g of palladium chloride was added to form a Ni—Pd alloy film. In Example 8, 2 g of potassium tetrachloroplatinate and 1 g of glycine were added to form a Ni—Pt alloy film. In Example 9, 1 g of each of sodium molybdate and trisodium citrate was added to form a Ni-Mo alloy coating. In Example 10, 1 g of sodium stannate was added to form a Ni—Sn alloy film.

  After each reaction was completed, the powder was filtered, washed with water, and dried through ethanol to obtain Ni-coated copper powder in which the surface of the dendritic copper powder was coated with Ni alloy. The Ni-coated copper powder was recovered and the Ni alloy coating amount was measured. Table 1 shows the results of measuring the content of Ni with respect to 100% by mass of the entire Ni-coated copper powder and the content of elements that become Ni alloys with respect to 100% by mass of the Ni alloy.

  In addition, as a result of observing each of the obtained Ni-coated copper powders with a field of view of 5,000 times by SEM, at least 90% by number or more of Ni-coated copper powders are aggregated with copper particles in a dendritic shape. It was a Ni-coated copper powder that had a shape and was uniformly coated with a Ni alloy on the surface of the copper particles. Further, the copper particles constituting the Ni-coated copper powder and coated with Ni on the surface have a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter of 0.5 μm to 2.0 μm. It was an ellipsoid of the size.

  Moreover, the average particle diameter (D50), the bulk density, and the BET specific surface area were measured about the dendritic Ni coat | court copper powder formed by gathering the ellipsoidal copper particle coat | covered with these Ni alloys. Table 1 summarizes these measurement results.

[Example 11]
<Preparation of dendritic Ni-coated copper powder (hypophosphite + tungsten compound)>
In Example 11, 100 g of the dendritic copper powder produced in Example 1 was used, and the copper powder surface was coated with a Ni alloy by electroless plating.

  As the electroless Ni plating solution, a plating solution containing hypophosphite as the same reducing agent as in Example 1 was used, and a metal other than Ni was added to the plating solution to produce a Ni alloy.

  Specifically, as an electroless Ni plating solution, a plating solution in which nickel sulfate 20 g / L, sodium hypophosphite 25 g / L, sodium acetate 10 g / L, and sodium citrate 10 g / L are added at each concentration, 500 g of a plating solution prepared by adding 1.5 g of sodium tungstate and adjusting the pH to 5.0 by adding sodium hydroxide was prepared. The bath temperature was controlled to 60 ° C.

  In this electroless Ni plating solution, a slurry in which 100 g of the dendritic copper powder prepared in Example 1 was dispersed in 100 mL of water was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 90 ° C. Stir for 60 minutes.

  After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder coated with a Ni-WP alloy was obtained. When the obtained Ni-coated copper powder was recovered and the content of Ni was measured, it was 12.3% by mass with respect to 100% by mass of the entire Ni-coated copper powder. The content of P contained in the Ni alloy was 7.1% by mass with respect to 100% by mass of the Ni alloy. Moreover, content of W contained in Ni alloy was 5.5 mass% with respect to 100 mass of Ni alloy.

  Moreover, as a result of observing the obtained Ni-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of the Ni-coated copper powder has a dendritic shape in which copper particles are aggregated, It was Ni coat copper powder by which Ni alloy was uniformly coat | covered on the surface of the copper particle. Further, the copper particles constituting the Ni-coated copper powder and coated with a Ni alloy on the surface have a minor axis average diameter of 0.2 μm to 0.5 μm and an average of 0.34 μm, and a major axis average It was an ellipsoid having a diameter of 0.5 μm to 2.0 μm and an average size of 1.6 μm.

  The average particle diameter (D50) of the dendritic Ni-coated copper powder formed by aggregating ellipsoidal copper particles coated with these Ni alloys is 21.2 μm, and the average thickness of the branch portion is 1 It was 5 μm.

Furthermore, the bulk density of the obtained Ni-coated copper powder was 1.25 g / cm ³ . The BET specific surface area was 1.7 m ² / g.

[Example 12]
30 g of the dendritic Ni-coated copper powder obtained in Example 1 is mixed with 15 g of phenol resin (PL-2211, manufactured by Gunei Chemical Co., Ltd.) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Using a 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 glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 9.0 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited. Table 1 shows these results.

[Example 13]
30 g of the dendritic Ni-coated copper powder obtained in Example 2 is mixed with 20 g of a phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). 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 glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 9.2 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited. Table 1 shows these results.

[Example 14]
The dendritic Ni-coated copper powder obtained in Example 1 was dispersed in a resin to obtain an electromagnetic wave shielding material.

  That is, 30 g of dendritic Ni-coated copper powder obtained in Example 1 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 using a Mayer bar on a substrate made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm 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 these results.

[Comparative Example 1]
Copper powder was deposited on the cathode plate in the same manner as in Example 1 except that PEG as an additive and chlorine ions were not added to the electrolytic solution. Subsequently, in the same manner as in Example 1, the surface of the obtained copper powder was coated with a Ni alloy to obtain a Ni-coated copper powder.

  In addition, content of Ni of the Ni coat copper powder was 18.3 mass% with respect to 100 weight of the whole Ni coat copper powder which coat | covered Ni alloy. Moreover, content of B contained in Ni alloy was 6.0 mass% with respect to 100 mass of Ni alloy.

  As a result of observing the shape of the obtained Ni-coated copper powder with a field of view of 10,000 times by SEM, the obtained Ni-coated copper powder had a dendritic shape, but the thickness of the branch portion was 10 μm. It was confirmed that this was a very large dendritic Ni-coated copper powder. Moreover, the average particle diameter (D50) of the Ni-coated copper powder was 22.3 μm.

  Next, with respect to 60 g of the dendritic Ni-coated copper powder produced by the above-described method, 15 g of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) The mixture was mixed with a small kneader (Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), and kneaded at 1200 rpm for 3 minutes three times to form a paste. During pasting, the viscosity increased every time kneading was repeated. This is considered to be caused by a part of the copper powder being aggregated, and uniform dispersion was difficult. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing is 6.7 × 10 ⁻⁴ Ω · cm, and the specific resistance value is extremely high and inferior in conductivity compared to the conductive paste obtained in the examples. Met.

[Comparative Example 2]
The characteristic of the conductive paste by spherical Ni coat copper powder was evaluated, and it compared with the characteristic of the conductive paste produced using the dendritic Ni coat copper powder in an Example. The spherical Ni-coated copper powder used was obtained by pulverizing electrolytic copper powder into a granular form.

That is, an electrolytic copper powder having an average particle size of 30.5 μm (manufactured by Nexel Japan, trade name: electrolytic copper powder Cu-300), a high-pressure jet airflow swirl vortex jet mill (manufactured by Tokusu Kogakusha Co., Ltd., NJ Nanogrine) Using a Ding mill NJ-30), spherical copper powder was prepared by grinding and pulverizing by performing 8 passes at an air flow rate of 200 liters / minute, a grinding pressure of 10 kg / cm ² and about 400 g / hour. The obtained spherical copper powder was observed by SEM with a field of view of 5,000 times magnification and confirmed to be granular. Moreover, the average particle diameter (D50) of the spherical copper powder was 5.6 μm.

  The obtained spherical copper powder was coated with Ni on the surface of the copper powder by electroless plating in the same manner as that shown in Example 3. And when spherical Ni coat copper powder after electroless plating was collect | recovered and content of Ni was measured, it was 7.4 mass% with respect to the weight 100 of the said Ni coat copper powder whole.

The obtained spherical Ni-coated copper powder had an average particle size (D50) of 5.8 μm and a bulk density of 3.83 g / cm ³ . Further, the BET specific surface area was 0.16 m ² / g.

  Next, 60 g of this spherical Ni-coated copper powder is mixed with 15 g of a phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) to produce a small kneader. Using a non-bubbling kneader NBK-1 (manufactured by Nippon Seiki Seisakusho Co., Ltd.), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing is 8.2 × 10 ⁻⁴ Ω · cm, and the specific resistance value is extremely high and inferior in conductivity compared to the conductive paste obtained in the examples. Met.

[Comparative Example 3]
The characteristic of the electromagnetic shielding material by spherical Ni coat copper powder was evaluated, and it compared with the characteristic of the electromagnetic shielding material produced using the dendritic Ni coat copper powder in Example 1. The spherical Ni-coated copper powder used in Comparative Example 2 was used as the spherical Ni-coated copper powder.

  Specifically, 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone are mixed with 50 g of spherical Ni-coated copper powder, and the mixture is made into a paste by repeating kneading at 1200 rpm for 3 minutes three times using a small kneader. did. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. This was applied and dried on a substrate 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 30 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.

1 Copper powder (dendritic copper powder)
2 Copper particles (fine copper particles)
D1 Branch thickness

Claims (11)

Copper particles coated with nickel (Ni) or Ni alloy on the surface are assembled to form a dendritic shape having a plurality of branches, Ni-coated copper powder,
The copper particles coated with Ni or Ni alloy on the surface have an ellipsoid with a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter of 0.5 μm to 2.0 μm. The average particle diameter (D50) of the copper powder in which the ellipsoidal copper particles are aggregated and whose surface is coated with Ni or Ni alloy is 5.0 μm to 20 μm. The Ni-coated copper powder according to claim 1, wherein an average thickness of the branch portions constituting the dendritic shape is 0.5 μm to 2.0 μm. The content of Ni coated as Ni or Ni alloy is 1% by mass to 50% by mass with respect to 100% by mass of the entire Ni-coated copper powder coated with Ni or Ni alloy. Ni-coated copper powder. Ni alloy is coated on the surface,
At least one selected from the group consisting of cobalt, zinc, tungsten, molybdenum, palladium, platinum, tin, phosphorus, and boron is 0.1% by mass to 20% by mass with respect to 100% by mass of the Ni alloy. The Ni-coated copper powder according to any one of claims 1 to 3, wherein the Ni-coated copper powder is coated with a Ni alloy containing the content. BET specific surface area ^of, Ni-coated copper powder according to any one of claims 1 to 4 is 0.2m ² /g~5.0m 2 / g. Bulk ^density, Ni-coated copper powder according to any one of claims 1 to 5 in the range of ^{0.5g / cm 3 ~5.0g / cm 3} .   A metal filler comprising the Ni-coated copper powder according to any one of claims 1 to 6 in a proportion of 20% by mass or more of the whole.   A conductive paste comprising the metal filler according to claim 7 mixed with a resin.   A conductive paint for electromagnetic wave shielding, comprising the metal filler according to claim 7.   An electroconductive sheet for electromagnetic wave shielding, comprising the metal filler according to claim 7. A method for producing the Ni-coated copper powder according to any one of claims 1 to 6,
A step of depositing copper powder on the cathode from the electrolyte by an electrolytic method;
Coating the copper powder with nickel (Ni) or Ni alloy,
In the electrolyte,
A method for producing a Ni-coated copper powder, comprising electrolyzing copper ions and a polyether compound.