JP6181368B2 - Aggregates of fibrous silver particles - Google Patents

Description

  The present invention relates to an aggregate of fibrous silver fine particles.

  Conventionally, fibrous silver fine particles have attracted attention as transparent conductive materials. Production of fibrous silver fine particles requires complicated steps such as high temperature heating at 100 ° C. or higher in ethylene glycol (Patent Document 1). There is also a problem that silver compounds such as silver nitrate used as a raw material are expensive.

US Pat. No. 7,585,349

Under such circumstances, an object of the present invention is to provide fibrous fine particles having characteristics comparable to conventional fibrous silver fine particles by a cheaper and simple method.

As a result of intensive studies, the present inventors have solved the above problem by replacing a part of copper constituting the fibrous copper fine particles with silver in the fibrous copper fine particles precipitated in an aqueous solution of 100 ° C. or less. As a result, the present invention has been reached.
That is, the gist of the present invention is, firstly, a fibrous silver fine particle aggregate in which a part of copper constituting the fibrous copper fine particles is replaced with silver, having a length of 1 μm or more and an aspect ratio of 10 or more. In the fine particle aggregate, the abundance of granular materials having a minor axis of 0.3 μm or more and an aspect ratio of 1.5 or less is 0.1 or less per fibrous silver fine particle,
A fibrous silver fine particle aggregate having a silver ratio of 50 to 80% by mass of the total, and the second includes the following steps (I) and (II): It is a manufacturing method of a body.
(I) Step of depositing fibrous copper fine particle aggregates from an aqueous solution containing a copper ion, an alkaline compound, a nitrogen-containing compound capable of forming a stable complex with copper ions and a reducing compound (II) Fibrous copper fine particle aggregates In the aqueous solution in which the copper is deposited, a part of the copper constituting the fibrous copper fine particles is replaced with silver

According to the present invention, fibrous fine particles having characteristics comparable to conventional fibrous silver fine particles can be provided by a cheaper and simpler method.
By using the fibrous silver fine particle aggregate of the present invention, a conductive coating agent, a conductive film and a conductive film having both excellent conductivity and transparency can be obtained.

Hereinafter, the present invention will be described in detail.
The fibrous silver fine particle aggregate of the present invention is a fine particle aggregate in which a part of copper constituting the fibrous copper fine particle is replaced with silver, and the length of the fibrous silver fine particle aggregate is 1 μm or more, and the aspect The ratio is 10 or more.

  As described above, the fibrous silver fine particle aggregate of the present invention is obtained by replacing a part of copper constituting the fibrous copper fine particles with silver. In addition, as long as the silver content specified in the present invention is satisfied, other noble metal elements (gold, platinum, palladium, rhodium, iridium, ruthenium, osmium, etc.) are used as metals other than silver for replacing the fibrous copper fine particles. ) Or base metal elements (iron, cobalt, tin, etc.) may be used. These may be used alone or in combination of two or more.

  The method for replacing copper in the fibrous copper fine particles with other metals such as silver is not particularly limited, but electroless plating is preferably used as a method for replacing the surface of the fibrous copper fine particles. It is done. When replacing copper in fibrous copper particles with silver by electroless plating, silver nitrate, ammonium carbonate salt or silver complex salt solution of ethylenediaminetetraacetate is used to replace and deposit silver on the surface of fibrous copper particles. Alternatively, the fibrous copper fine particles are dispersed in the chelating agent solution, the silver nitrate solution is added to the dispersion, and then the reducing agent is added to replace the silver coating on the surface of the fibrous copper particles. A method of precipitation can be used.

  In the present invention, after the step of precipitating the fibrous copper fine particle aggregate from the aqueous solution, it is preferable to continuously substitute other metals such as silver in the aqueous solution containing the fibrous copper fine particle aggregate.

  The length of the fibrous silver fine particle aggregate needs to be 1 μm or more, preferably 5 μm or more, and more preferably 10 μm or more. If the length of the fibrous silver fine particle aggregate is less than 1 μm, it is difficult to achieve both good conductivity and transparency. On the other hand, from the viewpoint of handling the coating agent when forming a conductive film or a conductive film, it may be preferable that the length of the fibrous silver fine particle aggregate does not exceed 500 μm.

  The minor axis of the fibrous silver fine particle aggregate is preferably 1 μm or less, more preferably 0.5 μm or less, further preferably 0.2 μm or less, and particularly preferably 0.1 μm or less. . When the short diameter of the fibrous silver fine particle aggregate exceeds 1 μm, the transparency may be inferior when used as a transparent conductive material.

  The aspect ratio (the length of the fibrous body / the minor axis of the fibrous body) of the fibrous silver fine particle aggregate needs to be 10 or more, preferably 100 or more, and preferably 300 or more. More preferred. When the aspect ratio of the fibrous silver fine particle aggregate is less than 10 (that is, a spherical shape), it becomes difficult to achieve both transparency and conductivity when used as a transparent conductive material. .

In the fibrous silver fine particle aggregate of the present invention, it is preferable that the entire surface is silver-substituted, but there may be a portion where copper is not exposed and silver is not substituted. As content of silver in a fibrous silver fine particle aggregate, 50-80 mass% is required with respect to the mass of the whole fibrous silver fine particle aggregate, 60-75 mass% is preferable, and 65-75 mass is preferable. % Is more preferable. If it is less than 50% by mass, good conductivity and stability due to silver may not be expressed in the fibrous silver fine particles. On the other hand, when it exceeds 80 mass%, material cost may increase or the diameter of fibrous silver fine particles may increase.
The silver content in the fibrous silver fine particle aggregate is determined by, for example, dissolving the coated fibrous copper fine particle aggregate of the present invention in a strong acid to obtain a measurement solution, and using this solution for ICP (high frequency inductively coupled plasma). ) Can be obtained by performing the measurement.

The method for calculating the short diameter and length (long diameter) of the fibrous fine particle aggregate and the granular material described later, and the method for calculating the number of granular materials per one fibrous fine particle are as follows. is there.
That is, the fibrous fine particle aggregate is observed using a transmission electron microscope (TEM), a scanning electron microscope (SEM), a digital microscope, or the like.

  Then, 100 fibrous fine particles are selected from the aggregate. The short diameter and the length of the fibrous fine particles and the granular material adhering to or in contact with the fibrous fine particles are measured, and the average value thereof can be used as the short diameter and the length. Further, the aspect ratio of the fibrous fine particles and the granular material can be calculated by dividing the length obtained as described above by the minor axis. Further, by counting the number of granular materials present and dividing the number of granular materials by the number of fibrous fine particles (100), the number of granular materials per fibrous fine particle can be calculated.

  Here, when observing the fibrous fine particle aggregate, if the fibrous fine particles overlap and are densely packed, the shapes of the fibrous fine particle aggregate and the granular material may not be accurately evaluated. Therefore, in such a case, it is possible to use an ultrasonic dispersion device or the like to solve the fibrous fine particle aggregate that is dense until adjacent fibrous fine particles are not in close contact with each other.

  In the fibrous silver fine particle aggregate of the present invention, the abundance of granules having a minor axis of 0.3 μm or more and an aspect ratio of 1.5 or less is 0.1 or less per fibrous silver fine particle. The number is preferably 0.08 or less, more preferably 0.05 or less, and most preferably none. When the above-mentioned granular material is present in excess of 0.1 per fibrous silver fine particle, the transparency may be inferior when used as a transparent conductive material.

  The minor axis of the granular material that affects the transparency is 0.3 μm or more, and the aspect ratio (the length of the granular material / the minor axis of the granular material) is 1.5 or less.

  For example, the following method is used to produce a silver-substituted fibrous copper fine particle aggregate. That is, a method of depositing fibrous copper fine particles from an aqueous solution containing a copper ion, an alkaline compound, a nitrogen-containing compound capable of forming a stable complex with copper ion, and a reducing compound is used. At this time, it is preferable to use a reducing compound that does not react with dissolved oxygen in the alkaline aqueous solution.

  When a compound that reacts with dissolved oxygen in an alkaline aqueous solution is used as the reducing compound, in the obtained fibrous silver fine particle aggregate, the proportion of the granular material exceeds 0.1 per fibrous silver fine particle. In other words, there may be cases where only an aggregate of fibrous silver fine particles having a large number of granular materials is obtained.

Here, the “reducing compound that does not react with dissolved oxygen” is defined by the following index.
First, several drops of a 10% sodium hydroxide aqueous solution are added to 500 g of pure water to prepare an alkaline aqueous solution (water temperature 25 ° C.) adjusted to pH 10.4. Let the dissolved oxygen concentration of this alkaline aqueous solution be "dissolved oxygen concentration 1". Specifically, the dissolved oxygen concentration 1 is 8.3 mg / L. For example, a dissolved oxygen meter “DO-5509” (manufactured by Lutron) is used for measuring the dissolved oxygen concentration.

  Thereafter, 100 mL of this alkaline aqueous solution is put into an open cylindrical container having a diameter of 7.0 cm, and then a reducing compound is added to the alkaline aqueous solution so as to have a concentration of 0.50 mol / L. Stir with a magnetic stirrer so that the aqueous solution does not vortex and dissolve. The dissolved oxygen concentration in the aqueous solution is measured 0.5 minutes, 5 minutes, 10 minutes, 15 minutes and 30 minutes after the addition of the reducing compound while continuing stirring after dissolution. The dissolved oxygen concentration 10 minutes after the addition of the reducing compound is defined as “dissolved oxygen concentration 2”.

And the numerical value A is calculated | required by the following formula | equation (1).
A = (Dissolved oxygen concentration 2) / (Dissolved oxygen concentration 1) (1)
In the present invention, a reducing compound having a numerical value A of 0.5 or more obtained by the formula (1) is defined as “a reducing compound that does not react with dissolved oxygen”. And the reducing compound whose numerical value A is less than 0.5 is defined as "the reducing compound which reacts with dissolved oxygen".

  Examples of the reducing compound that does not react with dissolved oxygen include ascorbic acid, erythorbic acid, glucose, or hydroxylammonium salt. The numerical value A of these reducing compounds that do not react with dissolved oxygen is 0.5 or more. Especially, it is preferable to use 1 or more types chosen from ascorbic acid, erythorbic acid, and glucose, and it is most preferable to use ascorbic acid.

  When producing a fibrous copper particulate aggregate, if a “reducing compound that reacts with dissolved oxygen” such as hydrazine is used, only a fibrous copper particulate aggregate with an increased proportion of particulates may be obtained. is there. Alternatively, the fibrous copper fine particle aggregate itself may not be deposited.

  In addition, in the hydrazine which is a reducing compound, the numerical value A obtained by the above formula (1) is about 0.05.

  The reducing compound as described above is preferably used in a proportion of 0.5 to 100 times the molar amount relative to the copper ions in the aqueous solution, and more preferably used in a proportion of 1 to 10 times the molar amount. If it is used at a ratio of less than 0.5 times the molar amount, the formation efficiency of the fibrous copper fine particles may be lowered. On the other hand, if the amount exceeds 100 times the molar amount, the formation effect of the fibrous copper fine particles is saturated, which is not preferable from the viewpoint of cost.

  Copper ions can be generated by dissolving a water-soluble copper salt in water. Examples of the water-soluble copper salt include copper sulfate, copper nitrate, copper chloride, and copper acetate. Among these, copper sulfate or copper nitrate can be preferably used from the viewpoint of easy formation of the fibrous copper fine particles of the present invention.

  The alkaline compound is not particularly limited, and sodium hydroxide, potassium hydroxide, and the like can be used.

  The concentration of the alkaline compound in the aqueous solution is preferably 10 to 50% by mass, more preferably 20 to 45% by mass, and still more preferably 20 to 40% by mass. If the concentration of the alkaline compound is less than 10% by mass, it may be difficult to form fibrous copper fine particles. On the other hand, when the concentration exceeds 50% by mass, it may be difficult to handle the aqueous solution.

  The density | concentration of the copper ion in aqueous solution is prescribed | regulated by the molar ratio of the hydroxide ion of the said alkaline compound, and a copper ion. That is, (alkali compound hydroxide ion) / (copper ion) is preferably set to have a molar ratio of 1500/1 to 6000/1, preferably 1500/1 to 5000/1. More preferably, the range is set. When the molar ratio is less than 1500/1, the formation of the granular material cannot be suppressed. As a result, in the fibrous silver fine particle aggregate after the silver substitution, the abundance of the granular material is one fibrous silver fine particle. It will exceed 0.1 per one. Alternatively, the shape of the copper fine particles may not be fibrous but spherical. On the other hand, if the molar ratio exceeds 6000/1, the formation efficiency of the fibrous copper fine particle aggregate may be deteriorated.

  Examples of the nitrogen-containing compound that forms a stable complex with divalent copper ions in an aqueous solution include ammonia, ethylenediamine, or triethylenetetramine. Among these, ethylenediamine can be preferably used from the viewpoint of easy formation of fibrous copper fine particles.

  In addition, it is preferable that said nitrogen-containing compound is used in the ratio of 1 mol or more with respect to 1 mol of copper ions from a viewpoint of the formation efficiency of a fibrous copper fine particle aggregate.

  Subsequently, the aqueous solution containing the above components is heated with an appropriate heat source, and then the desired aqueous copper fine particle aggregate is obtained by continuing the heating of the aqueous solution or lowering the liquid temperature of the aqueous solution. Precipitation can occur.

  Although the heating temperature of aqueous solution is not specifically limited, 50-100 degreeC is preferable from a viewpoint of the balance of precipitation efficiency and cost.

  The aggregate of fibrous silver fine particles after silver replacement can be recovered by solid-liquid separation by a method such as filtration, centrifugation, and pressure flotation. Furthermore, you may perform washing | cleaning, drying, etc. with respect to the collect | recovered fibrous silver fine particle aggregate as needed. In addition, when taking out the fibrous silver fine particle aggregate | assembly, it is preferable to work in inert gas atmosphere (for example, nitrogen gas atmosphere).

  The conductive coating agent of the present invention can be produced by dispersing the fibrous silver fine particle aggregate of the present invention in a liquid medium. At this time, a binder component may be further blended.

  The binder component is not particularly limited. For example, acrylic resins (acrylic silicone-modified resins, fluorine-modified acrylic resins, urethane-modified acrylic resins, epoxy-modified acrylic resins, etc.), polyester resins, polyurethane resins, olefin resins Amide resin, imide resin, epoxy resin, silicone resin, vinyl acetate resin, natural polymer starch, gelatin, agar, etc., semi-synthetic polymer carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose Cellulose derivatives such as synthetic polymers such as polyvinyl alcohol, polyacrylic acid polymers, water-soluble polymers such as polyacrylamide, polyethylene oxide, polyvinyl pyrrolidone, etc. It is possible.

  The liquid medium is not particularly limited, and examples thereof include organic solvents such as water, alcohols, glycols, cellosolves, ketones, esters, ethers, amides, and hydrocarbons. These can be used alone or in combination of two or more. Among these, it is preferable to use a solvent mainly composed of water or alcohols.

  In the conductive coating agent of the present invention, the mixing ratio of the fibrous silver fine particle aggregate and the binder is the volume ratio (A / B) of the volume (A) of the fibrous silver fine particle aggregate and the volume (B) of the binder. Therefore, it is preferably 1/100 to 5/1, and more preferably 1/20 to 1/1. When the volume ratio between the fibrous silver fine particle aggregate and the binder is less than 1/100, the conductivity may be lowered in the obtained conductive coating agent or the conductive film obtained from the coating agent. On the other hand, if the binder is so small that the volume ratio exceeds 5/1, the surface smoothness and transparency of the conductive film may be inferior, or the conductive coating agent may be used as a base material. In some cases, the adhesion with the substrate may be reduced.

  The solid content (total of the solid content of the fibrous silver fine particle aggregate of the present invention, a binder, and other additives as required) in the conductive coating agent of the present invention is excellent in the balance of conductivity and handleability. From the viewpoint, 1 to 99% by mass is preferable, and 1 to 50% by mass is more preferable.

  Moreover, the viscosity at 20 ° C. of the conductive coating agent of the present invention is preferably 0.5 to 100 mPa · s, and preferably 1 to 50 mPa · s, from the viewpoint of excellent handling properties and ease of application to a substrate. It is more preferable that

  In the conductive coating agent of the present invention, an aldehyde-based, epoxy-based, melamine-based, or isocyanate-based crosslinking agent may be used as necessary within the range not impairing the effects of the present invention.

  By forming a film of the conductive coating agent of the present invention, a conductive film can be obtained. Furthermore, a conductive film can be obtained by forming the conductive film on a substrate. The conductive film and the conductive film are excellent in both transparency and conductivity.

  As a method for forming a conductive film, the conductive coating agent of the present invention is applied on the surface of a substrate such as a plastic film, then dried, and then cured as necessary to form a film. A phase film forming method can be mentioned. Application methods include roll coating, bar coating, dip coating, spin coating, casting, die coating, blade coating, gravure coating, curtain coating, spray coating, and doctor coating. Can be used.

  The film thickness of the conductive film may be, for example, about 0.1 to 10 μm from the viewpoint of practicality.

  In addition, in order to form a conductive film or conductive film containing the fibrous silver fine particle aggregate of the present invention, only the fibrous silver fine particle aggregate of the present invention is applied on the surface of a substrate such as a plastic film. If necessary, a method of forming a coating layer for protecting the coated surface can also be used.

Hereinafter, the present invention will be described specifically by way of examples. The present invention is not limited to the examples.

The evaluation method or measurement method regarding the fibrous fine particles obtained in Examples and Comparative Examples is as follows.
1. Evaluation of Reducing Compound that Does Not React with Dissolved Oxygen Based on the above criteria (1) [that is, A = (dissolved oxygen concentration 2) / (dissolved oxygen concentration 1)], based on the judgment criteria for the reaction between the reducing compound and dissolved oxygen, The reactivity of the reducing compounds used in Examples and Comparative Examples with dissolved oxygen was evaluated.
The dissolved oxygen concentration 1 is the dissolved oxygen concentration in the alkaline aqueous solution measured as described above. The dissolved oxygen concentration 2 is the dissolved oxygen concentration in the aqueous solution 10 minutes after the addition of the reducing compound, measured as described above.

2. Dissolved oxygen concentration in alkaline aqueous solution It was measured using a dissolved oxygen meter “DO-5509” (manufactured by Lutron).

3. Short diameter and length of fibrous fine particles An aggregate of fibrous fine particles was prepared, and lightly disassembled using an ultrasonic dispersing device in order to prevent the fibrous fine particles from being in close contact with each other. Then, it observed using the digital microscope (the Keyence company make, "VHX-1000, VHX-D500 / 510"). 100 fibrous fine particles were selected from the aggregate, the short diameter and the length of each were measured, and the average values thereof were taken as the short diameter and the length.

4). 2. Aspect ratio of fibrous fine particles The aspect ratio of the fibrous fine particles was calculated by dividing the length determined in (1) by the minor axis.

5. Number of Granules per Fibrous Fine Particle An aggregate of fibrous fine particles was prepared, and lightly unraveled using an ultrasonic dispersing device in order to prevent the fibrous fine particles from being in close contact with each other. Then, it observed using the digital microscope (the Keyence company make, "VHX-1000, VHX-D500 / 510"). By selecting 100 fibrous fine particles from the aggregate, counting the number of granular materials in the fibrous fine particles, and dividing the number of granular materials by the number of fibrous fine particles (100), the fibrous shape The number of granules per fine particle was calculated.

6). Metal composition ratio (mass ratio) of fibrous fine particles
An aggregate of fibrous fine particles was collected in a glass beaker, and dissolved and diluted with nitric acid to obtain a measurement solution. The measurement solution was subjected to quantitative evaluation by ICP (manufactured by Nippon Jarrell Ash). And the metal composition ratio of the fibrous fine particles was calculated from the quantified content ratio of each metal (that is, copper and silver).

7). Volume resistance value of fibrous fine particles (unit: Ω · cm)
A collection of fibrous fine particles collected by pressure filtration with nitrogen (filter: PTFE membrane filter with a pore size of 1 μm, manufactured by Advantech), and a sample in which fibrous fine particle aggregates are laminated in a sheet form on the filter Produced. The obtained sample was dried at atmospheric pressure for 30 minutes with a drier set at 60 ° C., and then subjected to a vacuum drying treatment for 1 hour, and then the filling rate of the fibrous fine particle aggregate in the sheet was 70% by the press treatment. Adjusted as follows. The volume resistance value of the sheet-like sample was measured using a resistivity meter (Dia Instruments, Loresta AP, MCP-T400).
In addition, the value calculated from the volume of the sheet, the apparent density, and the true density was used as the filling rate of the fibrous fine particle aggregate.
Next, the sheet-like sample was heat-treated at 180 ° C. for 1 hour in an air atmosphere in a dryer, and the volume resistance value of the sample was measured in the same manner as described above.

Example 1
In a 300 mL three-necked flask, 108.0 g of sodium hydroxide (Nacalai Tesque), 0.15 g of copper nitrate trihydrate (Nacalai Tesque), 0.81 g of ethylenediamine (Nacalai Tesque) In 186 g of water (dissolved oxygen concentration at 27 ° C .: 8.7 mg / L), the mixture was stirred and mixed at 200 rpm at room temperature to prepare an aqueous solution in which each compound was dissolved. The resulting aqueous solution had a bright blue color. Here, the molar ratio of hydroxide ions to copper ions in the aqueous solution was 4500/1.

  Ascorbic acid aqueous solution (manufactured by Nacalai Tesque, the above-mentioned numerical value A: 0.88)) (4.4% by mass) 1.2 g (0.5 times molar amount with respect to copper ions) The three-necked flask was immersed in a 70 ° C. hot water bath while stirring was continued at 200 rpm. The color of the liquid gradually faded from blue and changed to almost colorless and transparent after 30 minutes.

  Further, 4.8 g of an ascorbic acid aqueous solution (4.4% by mass) (2.0 times molar amount with respect to copper ions) was added, and heating and stirring were continued in a 70 ° C. hot water bath. It was visually confirmed that the fibrous copper fine particles were precipitated to form a fibrous copper fine particle aggregate.

  A suspension (5.0 g) in which the concentration of the fine particle aggregates was adjusted to 0.2% by mass was removed from the aqueous solution in which the fibrous copper fine particle aggregates were deposited, and the suspension was stirred at 700 rpm at room temperature. Then, 2.0 g of a pre-dip solution for substitution type electroless silver plating (manufactured by Shikoku Kasei Kogyo Co., Ltd., “SSP-700P”) was added, and stirring was continued for 5 minutes after the addition. Further, while continuing stirring at 700 rpm, a solution obtained by mixing 1.2 g of a substitutional electroless silver plating solution (“SSP-700M” manufactured by Shikoku Kasei Kogyo Co., Ltd.) and 8.8 g of pure water was dropped over 5 minutes. Upon addition, the color of the suspension changed from reddish brown to gray.

  The suspension is subjected to pressure filtration with nitrogen (filter: PTFE membrane filter with a pore size of 1 μm, manufactured by Advantech), washed with pure water and dried in a dryer set at 60 ° C. On the filter, a sample in which silver-substituted fibrous fine particles gathered in a sheet form was prepared. Evaluation of said 6 and 7 was performed with respect to the obtained fibrous fine particle aggregate. The evaluation results are shown in Table 1.

(Comparative Example 1)
In Example 1, a solution obtained by mixing 1.2 g of a substitutional electroless silver plating solution (“SSP-700M” manufactured by Shikoku Kasei Kogyo Co., Ltd.) and 8.8 g of pure water was mixed with 0.4 g and 9 respectively. Except for changing to 0.6 g, silver-substituted fibrous fine particles were obtained in the same manner as in Example 1. Evaluation similar to Example 1 was performed with respect to the obtained fibrous fine particle. The evaluation results are shown in Table 1.

(Comparative Example 2)
With reference to known methods, 1.5 g of silver nitrate (Nacalai Tesque), 0.005 g of sodium chloride (Nacalai Tesque), 0.001 g of iron (III) nitrate nonahydrate (Nacalai Tesque), polyvinyl When 1.5 g of pyrrolidone (K-30, manufactured by Nacalai Tesque) was dissolved in 350 g of ethylene glycol (manufactured by Nacalai Tesque) and heated and stirred at 135 ° C. for 6 hours, fibrous silver fine particles were precipitated. Evaluation similar to Example 1 was performed with respect to the obtained fibrous silver fine particles. The evaluation results are shown in Table 1.

Example 1 is a fibrous silver fine particle obtained by replacing a part of copper constituting the fibrous copper fine particle with silver using a fibrous copper fine particle produced by a simple method, and the silver ratio is 80 In spite of the mass% or less, the volume resistance value is the same value as that of the fibrous silver fine particles consisting only of expensive silver prepared in the complicated method requiring high-temperature heating described in Comparative Example 2. That is, it had good conductivity. Further, the durability against heat treatment was equivalent to that of fibrous silver fine particles made of only silver. Furthermore, fibrous silver fine particles reflecting the good shape characteristics (fiber diameter, fiber length, granule content) of the fibrous copper fine particles to be silver-substituted were obtained.
On the other hand, Comparative Example 1 could not achieve good conductivity and durability as in Example 1 and Comparative Example 2 because the silver content constituting the fibrous fine particles was low.

Claims (5)

A fibrous silver fine particle aggregate in which a part of copper constituting the fibrous copper fine particles is replaced with silver,
A length of 1 μm or more,
The aspect ratio is 10 or more,
In the fine particle aggregate, the abundance of granular materials having a minor axis of 0.3 μm or more and an aspect ratio of 1.5 or less is 0.1 or less per one fibrous silver fine particle,
A fibrous silver fine particle aggregate having a silver ratio of 50 to 80% by mass. The method for producing an aggregate of fibrous silver fine particles according to claim 1, comprising the following steps (I) and (II).
(I) Step of depositing fibrous copper fine particle aggregates from an aqueous solution containing a copper ion, an alkaline compound, a nitrogen-containing compound capable of forming a stable complex with copper ions and a reducing compound (II) Fibrous copper fine particle aggregates In the aqueous solution in which the copper is deposited, a part of the copper constituting the fibrous copper fine particles is replaced with silver 3. The method for producing a fibrous silver fine particle aggregate according to claim 2, wherein the reducing compound contained in the aqueous solution is one that does not react with dissolved oxygen in the alkaline aqueous solution. A dispersion obtained by dispersing the fibrous silver fine particle aggregate according to claim 1 in a liquid medium. The electroconductive coating agent using the dispersion liquid of Claim 4 .