JP2015176824A - Conductive fine particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive fine particle capable of achieving excellent conductivity.SOLUTION: A conductive fine particle has a base particle and a conductive metal layer to cover a surface of the base particle. The conductive metal layer contains nickel and boron. When a surface of the conductive metal layer is observed by a scanning electron microscopic image at 100,000x magnification, less than 20 granular structures having a long diameter of not less than 5 nm nor more than 100 nm exist in a 200 nm square.

Description

  The present invention particularly relates to conductive fine particles having excellent conductivity.

  2. Description of the Related Art Conventionally, in assembling electronic devices, a connection method using an anisotropic conductive material has been adopted to make electrical connection between a large number of opposing electrodes and wirings. An anisotropic conductive material is a material in which conductive fine particles are mixed with a binder resin, for example, anisotropic conductive paste (ACP), anisotropic conductive film (ACF), anisotropic conductive ink, anisotropic conductive. There are sheets. As the conductive fine particles used for this anisotropic conductive material, in addition to metal particles, those obtained by coating the surface of resin particles serving as a substrate with a conductive metal layer are used. Conductive fine particles composed of resin particles and a metal layer are electrically connected between electrodes and wirings by a conductive metal layer formed on the surface.

  In electronic devices, it is important to reduce power loss. In order to reduce electrical resistance between electrodes and wiring, conductive fine particles that can achieve a lower connection resistance value are desired. Since the conductivity of the conductive fine particles depends on the conductivity of the metal layer, some efforts have been made to increase the conductivity of the metal layer. Among others, it is known that a metal layer formed by nickel-boron plating has higher conductivity than a metal layer formed by nickel-phosphorus plating.

  As an example of forming a metal layer of conductive fine particles by nickel-boron plating, for example, Patent Documents 1 and 2 form a metal coating layer containing nickel as a main component and containing boron and phosphorus on the surface of resin fine particles. Conductive fine particles are described. Further, Patent Documents 3 and 4 have a nickel-boron conductive layer containing nickel and boron on the surface of the base particles, and the nickel content is 97% in the total 100 wt% of the nickel-boron conductive layer. Conductive particles that are greater than or equal to weight percent are described. Patent Document 5 discloses a conductive particle having a nickel conductive layer containing nickel and boron on the surface of a base particle, and a coating containing nickel oxide or nickel hydroxide on the outer surface of the nickel conductive layer. Have been described.

Japanese Patent No. 4052832 Japanese Patent No. 4714719 JP 2011-243455 A JP 2011-243456 A JP 2012-4034 A

  However, these conductive fine particles subjected to nickel-boron plating may not have sufficient conductivity. This invention is made | formed in view of such a situation, The objective has the electroconductive metal layer which contains the nickel and boron on the surface of a base particle, and can achieve the outstanding electroconductivity. It is to provide fine particles.

  As a result of intensive studies in order to solve the above problems, the present inventors have found that, in addition to the material of the conductive metal layer, the structure is also important for improving the conductivity of the conductive fine particles. I got the knowledge. Then, when a granular structure of a specific size exists on the surface of the conductive metal layer, it is found that the conductivity of the conductive fine particles tends to be lowered, and it is found that if the granular structure of a specific size is reduced, the conductivity can be improved. Was completed.

  That is, the conductive fine particle according to the present invention is a conductive fine particle having a base particle and a conductive metal layer covering the surface of the base particle, and the conductive metal layer contains nickel and boron. When the surface of the conductive metal layer is observed with a scanning electron microscope image (SEM image) at a magnification of 100,000 times, the number of granular structures having a major axis of 5 nm to 100 nm per 200 nm square Is less than 20. The major axis of the granular structure is preferably 5 nm or more and 30 nm or less.

The conductive fine particles of the present invention preferably have a number average particle size of 1 μm or more and 30 μm or less, the number-based particle size variation coefficient (CV value) is preferably 10% or less, and the diameter is 10%. compression modulus when the displacement (10% K value) is 1000 N / mm ² or more, preferably 30,000 N / mm ² or less.

  The conductive fine particles of the present invention preferably have a boron content of 0.1% by mass or more and less than 1.5% by mass in 100% by mass of the conductive metal layer. The conductive fine particles of the present invention have a highly conductive and uniform (no plating unevenness) conductive metal layer even when the phosphorus content is less than 5% by mass in 100% by mass of the conductive metal layer.

  Since the surface coating layer of the conductive fine particles of the present invention is a conductive metal layer containing nickel and boron, and the number of granular structures having a specific size is reduced, excellent conductivity can be exhibited. As a result, even when used as an anisotropic conductive material, a lower connection resistance value can be achieved.

FIG. 1 is a scanning electron microscope image of the surface of the conductive fine particles obtained in Example 1 at a magnification of 9,000 times. FIG. 2 is a scanning electron microscope image at a magnification of 100,000 times of the fracture surface of the conductive metal layer of the conductive fine particles obtained in Example 1. FIG. 3 is a scanning electron microscope image of the surface of the conductive fine particles obtained in Example 2 at a magnification of 9,000 times. FIG. 4 is a scanning electron microscope image at a magnification of 100,000 times of the fracture surface of the conductive metal layer of the conductive fine particles obtained in Example 2. FIG. 5 is a scanning electron microscope image of the surface of the conductive fine particles obtained in Comparative Example 1 at a magnification of 9,000 times. FIG. 6 is a scanning electron microscope image with a magnification of 100,000 times of the fracture surface of the conductive metal layer of the conductive fine particles obtained in Comparative Example 1. FIG. 7 is a scanning electron microscope image of the surface of the conductive fine particles obtained in Comparative Example 2 at a magnification of 9,000 times. FIG. 8 is a scanning electron microscope image at a magnification of 100,000 times of the fracture surface of the conductive metal layer of the conductive fine particles obtained in Comparative Example 2.

TECHNICAL FIELD The present invention is directed to conductive fine particles having substrate particles and a nickel-boron conductive metal layer (hereinafter sometimes referred to as “metal layer”) covering the surface thereof, When the surface of the conductive metal layer is observed with a scanning electron microscope image having a magnification of 100,000, the number of granular structures having a major axis of 5 nm to 100 nm is less than 20 per 200 nm square. To do. In the conductive fine particles of the present invention, the ratio of the granular structure having the specific size is reduced, so that the inhibition of current occurring at the boundary between the grain units (hereinafter sometimes referred to as “grain boundaries”) is prevented. As a result, the conductive fine particles as a whole can exhibit good conductivity. The number of the granular structures having the specific size is preferably 15 or less, more preferably 12 or less per 200 nm square when observed with a scanning electron microscope image with a magnification of 100,000. preferable.

  Further, when a granular structure is present in the conductive metal layer of the conductive fine particles, the major axis of the granular structure present in the conductive metal layer may be 5 nm or more and 30 nm or less from the viewpoint of improving conductivity. preferable. That is, when the surface of the conductive metal layer is observed with an SEM image at a magnification of 100,000, the number of granular structures having a major axis of 5 nm or more and 30 nm or less is preferably less than 20 per 200 nm square. . Also regarding the granular structure having a major axis of 5 nm or more and 30 nm or less, the number of existing particles is more preferably 15 or less, and further preferably 12 or less.

  The major axis of the granular structure referred to in the present invention means the major axis of the granular structure observed when the surface of the conductive metal layer is observed with a scanning electron microscope image with a magnification of 100,000. The major axis of the granular structure is obtained by, for example, using a scanning electron microscope (SEM) (“S-4800” manufactured by Hitachi, Ltd.), an image of the surface of the metal layer observed at a magnification of 100,000 times, and image processing software (Media Introduced into “Image-Pro Plus” manufactured by Cybernetics), the granular structure is extracted, and the maximum diameter of each granular structure can be measured as the major axis.

  In addition, the said granular structure means the structure where each grain unit exists as an independent grain | grain, and does not include the structure where a grain boundary interrupts and a grain unit and a grain unit partially unite. In addition, unevenness may be observed on the surface of the conductive metal layer even if it does not have a granular structure, but if each unevenness unit is not independent and partially united, the current at the grain boundary Since the influence of the inhibition is sufficiently reduced, the conductive fine particles as a whole can exhibit good conductivity. When unevenness is observed on the surface of the conductive metal layer, and it is not clear from the surface observation alone whether the granular structure exists, the surface layer region in the fracture surface of the conductive metal layer is observed, and this corresponds to the granular structure. Can be determined. Since the conductive metal layer breaks along the grain boundary, if there is a grain structure on the surface of the conductive metal layer, it is derived from the granular structure in the surface layer region (surface side) in the fracture surface of the conductive metal layer. The unevenness to be observed is observed. Therefore, if irregularities derived from the granular structure are observed in the surface layer region, it is determined that there is a granular structure on the surface of the conductive metal layer. On the other hand, if only normal fracture traces (not correlated with the major axis of the grain unit) are observed in the surface layer region of the metal layer fracture surface, it is determined that there is no granular structure on the surface of the conductive metal layer can do.

  Further, when reading the number of granular structures, it is preferable to read the central region of conductive fine particles (hereinafter simply referred to as “conductive fine particles” in this paragraph) on a scanning electron microscope image. The central region refers to a central 25% (area basis) region of conductive fine particles. The central region can be specified as a region inside the concentric circle when a concentric circle having a half diameter of the conductive fine particle is drawn in a certain conductive fine particle. When the number of granular structures is read, if they are read in the central region, the granular structures per 200 nm square can be read without being affected by the depth of the scanning electron microscope image.

In the conductive fine particles of the present invention, the surface of the conductive metal layer is observed with a scanning electron microscope at an accelerating voltage of 20.0 kV and an enlargement magnification of 9000 times, and the maximum circle including only a portion where no irregularities are observed is observed with the scanning electron microscope. When drawn on an image, the area of the maximum circle is preferably 3 μm ² or more. When the area of the maximum circle is 3 μm ² or more, the proportion of the granular structure is reduced, which is preferable because good conductivity is exhibited. The area of the maximum circle is more preferably 4 μm ² or more, and further preferably 5 μm ² or more. Further, the preferable range of the area of the maximum circle varies depending on the particle diameter of the conductive fine particles. The area of the maximum circle is preferably 0.15 or more, more preferably 0.2 or more, with respect to the square of the radius of the conductive fine particles (when the square of the radius of the conductive fine particles is 1). Yes, more preferably 0.25 or more.

Further, the conductive fine particles of the present invention are obtained by observing the surface of the conductive metal layer with a scanning electron microscope at an acceleration voltage of 20.0 kV and an enlargement magnification of 9000 times, and scanning the maximum circle including only the portion where no irregularities are observed. It is also preferable that the area of the maximum circle is less than 3 μm ² when drawn on an electron microscope image. Even if the area of the maximum circle is less than 3 μm ² , it is preferable that the number of granular structures is not more than a predetermined value because good conductivity is exhibited. The area of the maximum circle is more preferably 2 μm ² or less, and further preferably 1.5 μm ² or less. Further, the preferable range of the area of the maximum circle varies depending on the particle diameter of the conductive fine particles. The area of the maximum circle is preferably less than 0.15, more preferably 0.1 or less, with respect to the square of the radius of the conductive fine particles (when the square of the radius of the conductive fine particles is 1). Yes, more preferably 0.07 or less.

The number average particle size of the conductive fine particles means an average particle size obtained from a number-based particle size distribution, preferably 1.0 μm or more, more preferably 1.1 μm or more, and still more preferably 1.2 μm or more. More preferably, it is 1.3 μm or more, particularly preferably 1.4 μm or more, preferably 50 μm or less, more preferably 30 μm or less, still more preferably 25 μm or less, and still more preferably 20 μm or less. The coefficient of variation (CV value) of the particle diameter of the conductive fine particles is a value determined from the number-based particle size distribution, preferably 10.0% or less, more preferably 8.0% or less, and still more preferably. It is 5.0% or less, more preferably 4.5% or less, and particularly preferably 4.0% or less. The “number average particle size” and the “particle size variation coefficient” in the present invention are precision particle size distribution measuring devices using the Coulter principle (for example, trade name “Coulter Multisizer III type”, manufactured by Beckman Coulter, Inc.). The value measured by The coefficient of variation of the particle diameter is a value calculated according to the following formula.
Variation coefficient of particle diameter (%) = 100 × (standard deviation of particle diameter / number-based average particle diameter)
Specifically, the number average particle diameter and coefficient of variation of the conductive fine particles can be measured by the method described later in Examples.

  In general, when the conductive fine particles become fine (specifically, the number average particle diameter is less than 10.0 μm), the connection resistance value of the conductive fine particles is more likely to increase, but the conductive fine particles of the present invention have high conductivity. Therefore, even if it is fine, an increase in connection resistance value can be suppressed. Therefore, from the viewpoint that the high conductivity effect of the conductive fine particles of the present invention becomes more prominent, the number average particle diameter of the conductive fine particles is preferably less than 10.0 μm, more preferably 3.5 μm or less, More preferably, it is 3.2 μm or less, more preferably 3.0 μm or less, even more preferably 2.8 μm or less, still more preferably 2.7 μm or less, particularly preferably 2.6 μm or less, while 1.1 μm. The above is preferable, and 1.6 μm or more is more preferable.

  On the other hand, when the substrate particles are soft, the contact area with the electrode increases, and therefore the conductivity of the metal layer (nickel surface metal layer) significantly affects the connection resistance value. The soft base particles are particularly useful when the number average particle diameter of the conductive fine particles is, for example, 6.3 μm or more, more preferably 7.3 μm or more, and further preferably 8.3 μm or more. In this case, the upper limit is, for example, 25 μm or less, more preferably 23 μm or less, and still more preferably 20 μm or less.

The conductive fine particles of the present invention preferably have a compressive modulus (10% K value) of 1,000 N / mm ² or more and 30,000 N / mm ² or less when the particle diameter is displaced by 10%. When the 10% K value is in the above range, the conductive fine particles have an appropriate deformation rate and restoration property, and a contact area with the electrode can be ensured. 10% K value is more preferably 5,000 N / mm ² or more, further preferably 6,000N / mm ² or more. When the 10% K value is in the above range, the conductive fine particles are reasonably hard, so that they are not easily deformed when dispersed in a binder resin or the like, and it is easy to ensure a connection with an electrode or the like. Moreover, 10% K value is more preferably 28,000N / mm ^2, more preferably not more than 25,000N / mm ^2. As the 10% K value is smaller, the deformation is appropriately performed according to the compressive stress, and a sufficient contact area between the electrode and the conductive fine particles is ensured, so that an increase in the connection resistance value can be further suppressed.

  Specifically, the 10% K value is constant in the direction of the center of the particle using a circular plate indenter (material: diamond) having a diameter of 50 μm for one sample particle spread on the sample table (material: SKS flat plate). And a load speed of 2.65 mN / sec (0.27 gf / sec). Then, the compression load (N) and the amount of compression variation (mm) when the particle is deformed until the particle diameter is displaced by 10% are measured, and the 10% K value is calculated based on the following formula. The 10% K value is preferably measured, for example, by measuring about 10 points for the same type of conductive fine particles. The ambient temperature at the time of measurement is 25 ° C.

(In the formula, E is the compressive elastic modulus (N / mm ² ), F is the compressive load (N), S is the amount of compressive displacement (mm), and R is the radius (mm) of the sample particles)

  The compressive fracture deformation (displacement of the particle diameter at the time of fracture) of the conductive fine particles of the present invention is not particularly limited, but is generally 30% or more. In view of the remarkable influence, it is preferably 40% or more, more preferably 50% or more, further preferably 53% or more, and particularly preferably 55% or more. Further, the upper limit of the compression fracture deformation is not particularly limited, but is generally 80% or less, and more preferably 75% or less.

Conductive metal layer The conductive metal layer in the present invention contains nickel and boron as essential constituent elements. Specifically, it is preferable to have a metal layer mainly composed of nickel, and it is preferable that the metal layer contains a nickel-boron alloy. Elements can be included. The conductive metal layer of the present invention may have another metal layer (preferably a gold layer) in addition to the metal layer mainly composed of nickel. Nickel is inexpensive and easily available and can be easily plated. Therefore, using this as the main component makes it possible to provide the conductive fine particles of the present invention at low cost. When nickel is contained in an appropriate amount, the conductivity of the metal layer can be improved.

  The content of nickel constituting the metal layer mainly composed of nickel is, for example, 50% by mass or more, preferably 90% by mass or more, more preferably 95% in 100% by mass of the metal layer mainly composed of nickel. It is at least 9 mass%, more preferably at least 98.5 mass%. The higher the nickel content, the better the conductivity from the material perspective. The nickel content is preferably 99.9% by mass or less, more preferably 99.8% by mass or less, and still more preferably 99.7% by mass or less. The smaller the nickel content, the more the formation of the granular structure of the specific size can be suppressed, and the conductivity of the metal layer mainly composed of nickel can be improved from the viewpoint of the structure.

  The boron content constituting the nickel-based metal layer is preferably less than 1.5% by mass in 100% by mass of the nickel-based metal layer. The smaller the boron content, the more the formation of the granular structure with the specific size can be suppressed, and the conductivity can be improved from the viewpoint of the structure. Therefore, it is more preferably 1.3% by mass or less, and still more preferably 1.2% by mass or less. Moreover, it is preferable that content of a boron is 0.1 mass% or more. If the content of boron in the metal layer containing nickel as a main component is too small, the flexibility of the metal layer is impaired and cracking or peeling tends to occur. The boron content is more preferably 0.2% by mass or more, and still more preferably 0.3% by mass or more.

  The other elements that can be contained in the nickel-based metal layer are not particularly limited. For example, gold, silver, copper, platinum, iron, lead, aluminum, chromium, palladium, rhodium, ruthenium. , Metal elements such as antimony, bismuth, germanium, tin, cobalt, indium, and phosphorus. These contents are preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, and still more preferably 10% by mass or less, in 100% by mass of the metal layer mainly composed of nickel. Especially preferably, it is 5 mass% or less. These other metal elements are plated with gold on the surface of a metal layer (layer formed of a nickel-boron alloy) containing nickel as a main component (for example, the surface of the nickel-boron alloy layer). It can also be used as an element constituting the applied embodiment.

  The metal layer mainly composed of nickel in the conductive metal layer of the conductive fine particles of the present invention contains nickel and boron, and the phosphorus content is less than 5% by mass in 100% by mass of the metal layer. However, it is highly conductive and homogeneous (no plating unevenness). The phosphorus content is more preferably 3% by mass or less, still more preferably 1% by mass or less, and particularly preferably even if it does not contain any phosphorus, it is highly conductive and uniform (no plating unevenness or the like). In addition, in the metal layer containing nickel as a main component, as the phosphorus content decreases, the solderability, slipperiness, and the like improve. In addition, content of each element contained in the said metal layer can be measured by ICP emission analysis, for example.

The thickness of the metal layer containing nickel as a main component is preferably 0.01 μm or more, more preferably 0.03 μm or more, still more preferably 0.05 μm or more, and preferably 0.20 μm or less, more preferably 0.00. It is 18 μm or less, more preferably 0.15 μm or less. When the thickness of the metal layer containing nickel as the main component is within the above range, stable electrical connection can be maintained when the conductive fine particles are used as the anisotropic conductive material.
The ratio of the thickness of the metal layer mainly composed of nickel and the thickness of the conductive metal layer (metal layer mainly composed of nickel / conductive metal layer) is preferably 0.5 or more, for example. Preferably it is 0.7 or more, more preferably 0.8 or more, particularly preferably 1. As the ratio (metal layer containing nickel as a main component / conductive metal layer) is larger, the conductive fine particles can be made inexpensive and excellent in conductivity. The upper limit of the ratio (metal layer containing nickel as a main component / conductive metal layer) is 1.
Furthermore, the thickness of the conductive metal layer when the conductive metal layer is composed of a metal layer mainly composed of nickel and another metal layer (for example, when the surface of the nickel-boron alloy layer is plated with gold) Is the total thickness of the nickel-boron alloy layer and the gold layer) is preferably 0.01 μm or more, more preferably 0.03 μm or more, still more preferably 0.05 μm or more, and preferably 0.20 μm or less. Preferably it is 0.18 micrometer or less, More preferably, it is 0.15 micrometer or less. When the thickness of the metal layer is within the above range, stable electrical connection can be maintained when the conductive fine particles are used as the anisotropic conductive material.

  The measuring method of the thickness of the metal layer which has nickel as a main component, and the thickness of an electroconductive metal layer is not specifically limited, Various well-known methods are employable. For example, the value obtained by dividing the difference between the number average particle diameter of the conductive fine particles and the number average particle diameter of the base particles by 2 may be the thickness of the conductive metal layer, or the conductive fine particles are cut along the diameter. And it can measure by observing the cross section with an electron microscope etc., and can also obtain | require by analyzing the metal concentration which melt | dissolved the metal layer and dissolved with the ICP emission spectrometer. In the latter method, for example, when the surface of a metal layer (nickel-boron alloy layer) containing nickel as a main component is subjected to gold plating, the thickness of each layer can be obtained individually. Hereinafter, the latter method will be described by taking as an example the case of conductive fine particles obtained by performing gold plating on the surface of a nickel-boron alloy layer.

  That is, first, the metal layer contained in the conductive fine particles is completely dissolved in the liquid. Here, the method for dissolving the metal layer may be appropriately selected according to the metal species. For example, a method of adding aqua regia to the conductive fine particles and stirring under heating can be employed. Next, the concentrations of the metals (nickel, boron) and gold constituting the nickel-boron alloy layer in the dissolved liquid are analyzed using an ICP emission analyzer, and nickel-boron is calculated from the following equation (1). The thickness of the alloy layer is calculated, and the thickness of the gold layer can be calculated from the following equation (2).

In the formula (1), r is the radius of the base particle (μm), t is the thickness of the nickel-boron alloy layer (μm), d _Ni is the density of the nickel-boron alloy layer, d _base is the density of the base particle, W is the content (mass%) of the component (nickel, boron) of the nickel-boron alloy layer, and X is the content (mass%) of gold.

In formula (2), a is the thickness of the gold layer (μm), d _Au is the density of the gold layer, d _{(base + Ni)} is a particle in which a nickel-boron alloy layer is provided on the base particle (hereinafter “nickel product”) X) is the gold content (mass%). Here, the density d _{(base + Ni)} of the nickel product can be calculated using the calculation formula (3). In Formula (3), d _Ni is the density of the nickel-boron alloy layer, d _base is the density of the base particle, and W is the content (mass%) of the constituent components (nickel, boron) of the nickel-boron alloy layer. It is.

Base Particles The base particles in the present invention are preferably particles containing a resin component (hereinafter referred to as resin particles). By using particles (resin particles) containing a resin component, conductive fine particles having excellent elastic deformation characteristics can be obtained. The resin particles are not limited to resin particles composed only of organic materials, but may be resin particles composed of organic-inorganic composite materials.

  Examples of the organic material constituting the resin particles include polyolefins such as polyethylene, polypropylene, polyvinyl chloride, polytetrafluoroethylene, polyisobutylene, and polybutadiene; vinyl heavy resins such as styrene resins, acrylic resins, and styrene-acrylic resins. Polyesters such as polyethylene terephthalate and polyethylene naphthalate; polycarbonates; polyamides; polyimides; phenol formaldehyde resins; melamine formaldehyde resins; melamine benzoguanamine formaldehyde resins; Examples of the organic / inorganic composite material include a silicone resin and a material containing the organic material and a polysiloxane skeleton (for example, a material in which a polysiloxane skeleton and a vinyl polymer are combined). The material which comprises these resin particles may be used independently, and 2 or more types may be used together.

  Among the materials constituting the resin particles, those containing a vinyl polymer and / or a polysiloxane skeleton are preferable. A material containing a vinyl polymer has an organic skeleton formed by polymerizing vinyl groups, and is excellent in elastic deformation during pressure connection. In particular, a vinyl polymer containing divinylbenzene as a polymerization component has little decrease in particle strength after coating with a conductive metal. In addition, the material containing the polysiloxane skeleton has excellent contact pressure with respect to the connected body during pressure connection. In particular, a material in which a polysiloxane skeleton and a vinyl polymer are combined is preferable because it is excellent in elastic deformability and contact pressure, and the connection reliability of the obtained conductive fine particles becomes more excellent.

  The vinyl polymer can be formed by polymerizing a vinyl monomer (vinyl group-containing monomer) (radical polymerization). This vinyl monomer is composed of a vinyl crosslinkable monomer and a vinyl noncrosslinkable. Divided into monomers. The polysiloxane skeleton can be formed by using a silane monomer, and the silane monomer is divided into a silane crosslinkable monomer and a silane noncrosslinkable monomer.

  The “vinyl group” includes not only a carbon-carbon double bond but also a functional group such as (meth) acryloxy group, allyl group, isopropenyl group, vinylphenyl group, isopropenylphenyl group, and polymerizable carbon- Substituents composed of carbon double bonds are also included. In this specification, “(meth) acryloxy group”, “(meth) acrylate” and “(meth) acryl” are “acryloxy group and / or methacryloxy group”, “acrylate and / or methacrylate” and “acryl and / Or methacryl ".

  The ratio of the crosslinkable monomer (for example, the total of the vinyl-based crosslinkable monomer and the silane-based crosslinkable monomer) in the total monomers constituting the resin particles is preferably 1% by mass or more, more preferably. Is 5% by mass or more, more preferably 10% by mass or more. When the ratio of the crosslinkable monomer is within the above range, solvent resistance can be imparted to the obtained conductive fine particles, and for example, when used for ACF formation, swelling and deformation of particles due to the influence of the solvent can be prevented. it can. On the other hand, the upper limit of the ratio of the crosslinkable monomer is not particularly limited, but is preferably 90% by mass or less, more preferably 80% by mass or less, and further preferably 70% by mass or less.

  When the resin particles are made of an organic-inorganic composite material containing a vinyl polymer and a polysiloxane skeleton, the amount of the vinyl monomer used is preferably 1 part by mass or more with respect to 100 parts by mass of the silane monomer, More preferably, it is 5 mass parts or more, More preferably, it is 10 mass parts or more, 5000 mass parts or less are preferable, More preferably, it is 4000 mass parts or less, More preferably, it is 3000 mass parts or less.

  The vinyl-based crosslinkable monomer has a vinyl group and can form a crosslinked structure, and specifically, a monomer (monomer having two or more vinyl groups in one molecule). (1)), or having one vinyl group and a binding functional group other than a vinyl group in one molecule (a protic hydrogen-containing group such as a carboxyl group or a hydroxy group, or a terminal functional group such as an alkoxy group). A monomer (monomer (2)) is mentioned. However, in order to form a crosslinked structure with the monomer (2), it is necessary to have a counterpart monomer capable of reacting (binding) with the binding functional group of the monomer (2).

  Examples of the monomer (1) (monomer having two or more vinyl groups in one molecule) among the vinyl-based crosslinkable monomers include, for example, allyl (meth) acrylate such as allyl (meth) acrylate. ) Acrylates; alkanediol di (meth) acrylate (for example, ethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9- Nonanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, 1,3-butylene di (meth) acrylate, etc.), polyalkylene glycol di (meth) acrylate (for example, diethylene glycol di (meth) acrylate, Triethylene glycol di (meth) acrylate, decaethylene glycol di ( ) Acrylate, pentadecaethylene glycol di (meth) acrylate, pentacontahector ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate Di (meth) acrylates such as trimethylolpropane tri (meth) acrylate; tetra (meth) acrylates such as pentaerythritol tetra (meth) acrylate; dipentaerythritol hexa (meth) ) Hexa (meth) acrylates such as acrylates; aromatic hydrocarbon-based crosslinking agents such as divinylbenzene, divinylnaphthalene, and derivatives thereof (preferably divinylbenzene Ren-based polyfunctional monomer); N, N-divinyl aniline, divinyl ether, divinyl sulfide, hetero atom-containing crosslinking agents such as divinyl sulfonic acid; and the like. Among these, (meth) acrylates (polyfunctional (meth) acrylate) having two or more (meth) acryloyl groups in one molecule and aromatic hydrocarbon crosslinking agents (especially styrene polyfunctional monomers) are included. preferable. Among the (meth) acrylates having two or more (meth) acryloyl groups in one molecule, (meth) acrylates having three or more (meth) acryloyl groups in one molecule are particularly preferable. Among these, acrylates having 3 or more acryloyl groups in one molecule are preferable. Among the styrenic polyfunctional monomers, monomers having two vinyl groups in one molecule such as divinylbenzene are preferable. A monomer (1) may be used independently and may use 2 or more types together.

  Among the vinyl-based crosslinkable monomers, the monomer (2) (monomer having one vinyl group and a binding functional group other than vinyl group in one molecule) is, for example, (meth) Monomers having a carboxyl group such as acrylic acid; hydroxy group-containing (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate and 2-hydroxybutyl (meth) acrylate, p -Monomers having hydroxy groups such as hydroxy group-containing styrenes such as hydroxystyrene; alkoxy groups such as 2-methoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, 2-butoxyethyl (meth) acrylate Contains (meth) acrylates and alkoxy groups such as alkoxystyrenes such as p-methoxystyrene That monomer; and the like. A monomer (2) may be used independently and may use 2 or more types together.

  The vinyl-based non-crosslinkable monomer is a monomer having one vinyl group in one molecule (monomer (3)) or the monomer in the case where there is no counterpart monomer (2) (monomer having one vinyl group and a binding functional group other than vinyl group in one molecule).

  Among the vinyl non-crosslinkable monomers, the monomer (3) (monomer having one vinyl group in one molecule) includes (meth) acrylate monofunctional monomers and styrene monofunctional monomers. Monomers are included. Examples of the (meth) acrylate monofunctional monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, and pentyl (meth) acrylate. , Hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, 2-ethylhexyl (meth) acrylate Alkyl (meth) acrylates such as: cyclopropyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cyclooctyl (meth) acrylate, cyclo Cycloalkyl (meth) acrylates such as ndecyl (meth) acrylate, cyclododecyl (meth) acrylate, isobornyl (meth) acrylate, 4-t-butylcyclohexyl (meth) acrylate; phenyl (meth) acrylate, benzyl (meth) acrylate And aromatic ring-containing (meth) acrylates such as tolyl (meth) acrylate and phenethyl (meth) acrylate, and alkyl (meth) acrylates such as methyl (meth) acrylate are preferred. Styrene monofunctional monomers include styrene; alkyl styrenes such as o-methyl styrene, m-methyl styrene, p-methyl styrene, α-methyl styrene, pt-butyl styrene, o-chlorostyrene, m-chloro. Examples include halogen group-containing styrenes such as styrene and p-chlorostyrene, and styrene is preferred. A monomer (3) may be used independently and may use 2 or more types together.

  The vinyl monomer preferably includes at least the vinyl crosslinkable monomer (1). Among them, the vinyl crosslinkable monomer (1) and the vinyl noncrosslinkable monomer ( 3) (in particular, a copolymer of the monomer (1) and the monomer (3)) is preferable. Specifically, an embodiment containing a styrene monofunctional monomer as a constituent component, an embodiment containing a styrene monofunctional monomer and a monomer having two or more (meth) acryloyl groups in one molecule, a styrene monofunctional An embodiment containing a monomer and a styrenic polyfunctional monomer is preferred. Among these, an embodiment including a styrene monofunctional monomer and a styrene polyfunctional monomer is preferable.

  The polysiloxane skeleton is formed by hydrolyzing a silane monomer and generating a siloxane bond by a condensation reaction. In particular, when a silane crosslinkable monomer is used as a silane monomer, a crosslinked structure is formed. Can do. Examples of the crosslinked structure formed by the silane-based crosslinking monomer include those that crosslink an organic polymer skeleton (for example, a vinyl polymer skeleton) and an organic polymer skeleton (first form); a polysiloxane skeleton; One that crosslinks a polysiloxane skeleton (second form); one that crosslinks an organic polymer skeleton and a polysiloxane skeleton (third form).

  Examples of the silane-based crosslinkable monomer that can form the first form (crosslinking between organic polymers) include silane compounds having two or more vinyl groups such as dimethyldivinylsilane, methyltrivinylsilane, and tetravinylsilane. Can be mentioned. Examples of the silane crosslinkable monomer that can form the second form (crosslink between polysiloxanes) include tetrafunctional silane single monomers such as tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, and tetrabutoxysilane. Examples of the polymer include trifunctional silane monomers such as methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, and ethyltriethoxysilane. Examples of the silane-based crosslinkable monomer that can form the third form (crosslinking between organic polymer and polysiloxane) include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3- (Meth) acryloyl such as acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-acryloxypropyltriethoxysilane, 3-methacryloxyethoxypropyltrimethoxysilane Di- or trialkoxysilanes having a group; di- or trialkoxysilanes having a vinyl group such as vinyltrimethoxysilane, vinyltriethoxysilane, p-styryltrimethoxysilane; 3-glycidoxypropyltrimethoxysilane, 3 Di- or trialkoxysilanes having an epoxy group such as glycidoxypropyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane; 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, etc. Or a di- or trialkoxysilane having an amino group. These silane crosslinking monomers may be used alone or in combination of two or more.

  Examples of the silane-based non-crosslinkable monomer include bifunctional silane-based monomers such as dimethyldimethoxysilane and dialkylsilane such as dimethyldiethoxysilane; and trialkylsilanes such as trimethylmethoxysilane and trimethylethoxysilane. And monofunctional silane-based monomers. These silane non-crosslinkable monomers may be used alone or in combination of two or more.

  In particular, the polysiloxane skeleton is preferably a skeleton derived from a polymerizable polysiloxane having a radical-polymerizable carbon-carbon double bond (for example, a vinyl group such as a (meth) acryloyl group). That is, the polysiloxane skeleton is a silane crosslinkable monomer (preferably having a (meth) acryloyl group) capable of forming at least the third form (crosslinking between the organic polymer and the polysiloxane) as a constituent component. More preferably, it is a polysiloxane skeleton formed by hydrolysis and condensation of 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, vinyltrimethoxysilane).

  In addition, the composition ratio of each monomer constituting the resin particle is not particularly limited, and depends on characteristics (for example, hardness, recovery rate during compression, heat resistance, etc.) required for the base particle, What is necessary is just to set suitably.

  The base particle of the present invention may be a particle having a thermal decomposition start temperature exceeding 280 ° C. (for example, a particle having a thermal decomposition start temperature of about 280 to 400 ° C.). Even particles having a temperature of, for example, 280 ° C. or lower, preferably 270 ° C. or lower (for example, about 200 to 265 ° C.) can be used. The thermal decomposition start temperature of the base particles can be measured by performing thermogravimetric analysis under a nitrogen atmosphere.

  As the method for producing the resin particles, emulsion polymerization, suspension polymerization, dispersion polymerization, seed polymerization, sol-gel seed polymerization method and the like can be adopted, but seed polymerization and sol-gel seed polymerization method are preferable because the particle size distribution can be reduced. . The sol-gel seed polymerization method is an embodiment of seed polymerization, and particularly means that the seed particles are synthesized by the sol-gel method. For example, the case where polysiloxane obtained by the hydrolysis condensation reaction of alkoxysilane is used as seed particles can be used. Therefore, the seed polymerization includes a case where the seed particles are made of an organic material and a case where the seed particles are made of a material in which an organic material and an inorganic material are combined (in the case of a sol-gel seed polymerization method). For example, in the case where the resin particles have a vinyl polymer skeleton and a polysiloxane skeleton, the production method thereof is to polymerize a crosslinkable silane monomer having a radical polymerizable group by hydrolysis and condensation reaction. After preparing the polysiloxane particles, a method of polymerizing the polymerizable polysiloxane particles by absorbing the vinyl monomer and the like is preferably employed.

The substrate particles preferably have a hydrophilic surface. If the surface is hydrophilic, the wettability to the electroless plating solution described later is high, and a conductive metal layer can be uniformly formed on the surface of the substrate particles. Moreover, when the micro unevenness | corrugation is formed in the resin particle surface by the hydrophilization process, the effect that the adhesiveness of a base particle and an electroconductive metal layer improves further by the anchor effect of the unevenness | corrugation is also acquired.
The substrate particles having a hydrophilic surface can be obtained by subjecting the above-described resin particles to a hydrophilic treatment. The method of the hydrophilization treatment is not particularly limited, and a conventionally known method can be adopted. For example, oxidizer such as chromic acid, chromic anhydride-sulfuric acid mixed solution, permanganic acid; hydrochloric acid, sulfuric acid, hydrofluoric acid, nitric acid, etc. A strong alkaline solution such as sodium hydroxide or potassium hydroxide; a method using various other commercially available hydrophilizing agents (etching agents), and gas phase treatment such as ozone gas treatment.

The base particles preferably have a compression modulus (10% K value) of 1,000 N / mm ² or more and 30,000 N / mm ² or less when the diameter is displaced by 10%. When the 10% K value is in the above range, it is easy to control to the same 10% K value conductive fine particles, and as a result, a good contact area with the electrode can be obtained. The 10% K value of the base particles is more preferably 5,000 N / mm ² or more, and further preferably 6,000 N / mm ² or more. When the 10% K value of the base particles is within the above range, the conductive fine particles are likely to be reasonably hard, and as a result, they are not easily deformed when dispersed in a binder resin or the like, and it is easy to ensure a connection with an electrode or the like. Become. Further, more preferably 28,000N / mm ^2, more preferably not more than 25,000N / mm ^2. The smaller the 10% K value, the more moderately deforms according to the compressive stress, and the sufficient contact area between the electrode and the conductive fine particles can be secured, so that the increase in connection resistance value can be further suppressed.

  The number average particle size of the substrate particles (resin particles) means an average particle size determined from a number-based particle size distribution, preferably 1.0 μm or more, more preferably 1.1 μm or more, and even more preferably 1. .2 μm or more, more preferably 1.3 μm or more, preferably 50 μm or less, more preferably 30 μm or less, still more preferably 25 μm or less, and even more preferably 20 μm or less. The coefficient of variation (CV value) of the particle size of the substrate particles is a value determined from the number-based particle size distribution, preferably 10.0% or less, more preferably 8.0% or less, and even more preferably 5 0.0% or less, more preferably 4.5% or less, and particularly preferably 4.0% or less. The number average particle diameter and the coefficient of variation of the particle diameter of the substrate particles can be measured by the same method as the number average particle diameter and the coefficient of variation of the conductive fine particles, and specifically, a method described later in Examples. Can be measured.

  If the substrate particles are fine (specifically, the number average particle diameter is less than 10.0 μm), the conductive fine particles become fine accordingly, and the connection resistance value is more likely to rise. The effect of high conductivity of the conductive fine particles becomes more remarkable. Therefore, the number average particle diameter of the base particles is preferably less than 10.0 μm, more preferably 3.3 μm or less, still more preferably 3.0 μm or less, still more preferably 2.8 μm or less, and even more preferably 2. It is less than 8 μm, still more preferably 2.6 μm or less, particularly preferably 2.5 μm or less, while 1.0 μm or more is preferable and 1.5 μm or more is more preferable.

  On the other hand, as described above, there is an aspect in which the base particles are soft as an aspect in which the conductive effect of the conductive fine particles of the present invention is more remarkable, and the preferred number average particle diameter of the conductive fine particles in that case Is 6.3 μm or more and 25 μm or less. In view of this point, the number average particle diameter of the base particles is preferably 6 μm or more, more preferably 7 μm or more, and further preferably 8 μm or more. In this case, the upper limit is preferably 25 μm or less, more preferably 23 μm or less, and still more preferably 20 μm or less.

  The shape of the substrate particles (resin particles) is not particularly limited, and may be any of a spherical shape, a spheroid shape, a confetti shape, a thin plate shape, a needle shape, an eyebrow shape, etc., and a spherical shape is preferable. In particular, a true spherical shape is preferable.

Production Method of Conductive Fine Particles The conductive fine particles of the present invention can be produced by forming a metal layer on the surface of the substrate particles by an electroless plating method. When the electroless plating method is used, a conductive metal layer containing nickel and boron can be easily formed without requiring a large apparatus, and the conductive fine particles of the present invention can be obtained efficiently.
Hereinafter, the electroless plating method will be described.

Catalytic Step First, the base material particles subjected to electroless plating are subjected to a catalytic treatment. In this catalyzing treatment, after precious metal ions are captured on the surface of the base material particles, they are reduced and supported on the surface of the base material particles. As the noble metal ion, a divalent palladium ion is preferable. In addition, as the base particles to be subjected to the catalyst treatment, the above-described base particles having a hydrophilic surface are preferable. When the substrate particles themselves do not have the ability to capture noble metal ions, it is also preferable to perform a surface modification treatment before the catalytic conversion. The surface modification treatment can be performed by bringing the substrate particles into contact with water or an organic solvent in which the surface treatment agent is dissolved. As the surface treatment agent, for example, cationic surfactants such as amine salts and quaternary ammonium salts are preferably used.

As the catalytic treatment method, for example, a solution containing palladium chloride and tin chloride is used as a catalytic reagent, and the base metal particles are immersed in the catalytic reagent to adsorb the catalytic metal on the surface of the base particles, A method (catalyst-accelerator method) in which palladium is deposited on the surface of the substrate particles by reducing the palladium ions with an alkali solution such as sulfuric acid or hydrochloric acid, or an alkali solution such as sodium hydroxide, or tin ions (Sn ²⁺ ) The solution containing the substrate is brought into contact with the substrate particles to adsorb tin ions on the surface of the substrate particles, and then immersed in a solution containing palladium ions (Pd ²⁺ ) to deposit palladium on the surface of the substrate particles. Method (sensitizing-activating method) and the like. Among these, the catalyst-accelerator method is preferable from the viewpoint of suppressing the generation of the specific granular structure.

Electroless Plating Step In the electroless plating step, a conductive metal layer is formed on the surface of the catalyst base material particles on which the palladium catalyst is adsorbed by the catalyst treatment. Specifically, the nickel-boron alloy layer can be formed by performing an electroless plating reaction using an electroless plating solution containing a nickel salt and a boron-based reducing agent.

  In this electroless plating step, first, the catalyst base material particles are sufficiently dispersed in water to prepare an aqueous slurry of the catalyst base material particles. At this time, in order to form a uniform conductive metal layer, it is preferable to sufficiently disperse the catalyzed base material particles in an aqueous medium to be plated. In order to improve the dispersibility of the base particles, it is preferable to add a dispersant such as a surfactant. As this dispersant, perfluoroalkyltrimethylammonium salt, perfluoroalkylsulfonate, perfluoroalkyl phosphate ester. It is preferable to use a fluorosurfactant such as perfluoroalkyl carboxylate, perfluoroalkyl ammonium iodide, and perfluoroalkylamine oxide. In addition, conventionally known dispersing means such as a shearing dispersing device such as a normal stirring device, a high speed stirring device, a colloid mill, or a homogenizer may be employed as the dispersing means for the catalyzed base particles. Ultrasound may be used in combination.

  Next, an electroless plating solution containing a nickel salt and a boron-based reducing agent is added to the aqueous slurry of the catalyzed substrate particles prepared above.

  Examples of the nickel salt contained in the electroless plating solution include nickel chloride, nickel sulfate, and nickel acetate. There may be only one kind of nickel salt, or two or more kinds. The concentration of the nickel salt in the electroless plating solution may be appropriately determined in consideration of the size (surface area) of the base particles so that a conductive metal layer having a desired thickness is formed.

  The boron reducing agent contained in the electroless plating solution is not particularly limited as long as it contains boron, but it is preferable to use a boron hydride reducing agent such as sodium borohydride or lithium borohydride, Sodium borohydride is particularly preferred. The amount of the boron-based reducing agent used is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and still more preferably 1 part by mass or more with respect to 100 parts by mass of the nickel salt. It is preferably no greater than 5 parts by mass, more preferably no greater than 5 parts by mass and even more preferably no greater than 3 parts by mass. When the content of the boron-based reducing agent is in the above range, the activity of the plating reaction is appropriate.

Surface granular structure control In the present invention, the electroless plating solution preferably contains an amine compound. When the electroless plating solution contains an amine compound, the granular structure on the surface of the conductive metal layer can be reduced. As the amine compound, an ethyleneamine compound can be preferably used. The ethyleneamine compound is a compound in which an amino group which may have a substituent is bonded to both ends of ethylene. For example, an ethyleneamine compound may have n ethylene groups and n + 1 substituents. And a compound in which these ethylene groups and amino groups are alternately arranged. However, n represents an integer of 1 or more, preferably 5 or less. Examples of the substituent include an alkyl group (particularly a C _1-4 alkyl group), a hydroxycarbonylalkyl group (such as a hydroxycarbonyl C _1-4 alkyl group such as a hydroxycarbonylmethyl group), and the like.

  Among the ethyleneamine compounds, the compound in which n is 1 (hereinafter sometimes referred to as “monoethyleneamine compound”) includes ethylenediamine, N, N-dimethylethylenediamine, N, N, N ′, N′—. Ethylenediamines such as tetramethylethylenediamine and ethylenediaminetetraacetic acid; examples of the compound wherein n is 2 (diethyleneamine compound) include diethylenetriamines such as diethylenetriamine and diethylenetriaminepentaacetic acid; Examples of the ethyleneamine compound) include triethylenetetramines such as triethylenetetramine; examples of the compound in which n is 4 (tetraethyleneamine compound) include tetraethylenepentamines; compound in which n is 5 (Pentaethylene amino Examples of the compound) include pentaethylenehexamines, and the ethyleneamine compound may be used alone or in combination of two or more, among which n is 1 as the amine compound. As mentioned above, the ethyleneamine compound which is 3 or less is preferable, the ethyleneamine compound whose n is 1 is more preferable, and ethylenediamine is especially preferable.

  The amount of the amine compound used in the electroless plating solution is preferably 100 parts by mass or more, more preferably 110 parts by mass or more, and still more preferably 120 parts by mass or more with respect to 100 parts by mass of the nickel salt. Moreover, 300 mass parts or less are preferable, More preferably, it is 250 mass parts or less, More preferably, it is 200 mass parts or less. When the amount of the amine compound used is within the above range, the plating reaction can be easily controlled, and the granular structure on the surface of the conductive metal layer can be further reduced. Although the mechanism of action of the amine compound is not clear, it is presumed that it may act as a complexing agent having N of the amino group as a coordination site.

  The electroless plating solution may contain a conventionally known complexing agent as necessary. The complexing agent is preferably a dicarboxylic acid compound. Examples of the dicarboxylic acid compounds include dicarboxylic acids and salts thereof. Examples of the dicarboxylic acids include dicarboxylic acids having 3 carbon atoms such as malonic acid; dicarboxylic acids having 4 carbon atoms such as tartaric acid, malic acid, and succinic acid; C5 dicarboxylic acid such as glutaric acid; C6 dicarboxylic acid such as adipic acid. Moreover, as a salt of these dicarboxylic acids, an alkali metal (lithium, sodium, potassium) salt or an ammonium salt can be used. As the dicarboxylic acid compound, it is preferable to use one kind alone. Among these, as the dicarboxylic acid compound, a C4 dicarboxylic acid and its alkali metal salt are preferable.

  The ratio of the amine compound is preferably 80 parts by mass or more, more preferably 90 parts by mass or more, and still more preferably 95 parts by mass or more with respect to 100 parts by mass in total of the amine compound and the dicarboxylic acid compound. Yes, particularly preferably 100 parts by mass. The higher the ratio of the amine compound relative to the total of the amine compound and the dicarboxylic acid compound, the easier the control of the plating reaction and the further reduction of the granular structure on the surface of the conductive metal layer.

  The electroless plating solution preferably contains a base. By including a base, it is easy to adjust the activity of the plating reaction, and the generation of a specific granular structure is further suppressed. Examples of the base include alkali metals such as sodium hydroxide and potassium hydroxide, and sodium hydroxide is particularly preferable. When the electroless plating solution contains a base, the amount used is preferably 80 parts by mass or more, more preferably 90 parts by mass or more, and still more preferably 95 parts by mass or more with respect to 100 parts by mass of the nickel salt. Moreover, 120 mass parts or less are preferable, More preferably, it is 110 mass parts or less, More preferably, it is 105 mass parts or less.

  In addition, the electroless plating solution may contain various additives. Examples of the additive include a buffer and a stabilizer. The buffering agent stabilizes the pH of the electroless plating solution, thereby suppressing the increase in pH due to the oxidizing reaction of the reducing agent, and stabilizes the electroless plating reaction. Further, the stabilizer has an action of suppressing the self-decomposition reaction of the electroless plating solution, and stabilizes the electroless plating reaction. When various additives are included, the total content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and still more preferably 3 parts by mass or less with respect to 100 parts by mass of the nickel salt. is there. Moreover, although a minimum is not specifically limited, For example, it is 0.1 mass part or more, Preferably it may be 1 mass part or more.

  The electroless plating solution is preferably added (dropped) gradually to the aqueous slurry. The dropping rate of the electroless plating solution may be adjusted as appropriate, but the addition amount of the nickel salt is preferably 5 parts by mass / min or more, more preferably 10 parts by mass / min with respect to 100 parts by mass of the base particles. It is min or more, more preferably 15 parts by mass / min or more, preferably 35 parts by mass / min or less, more preferably 30 parts by mass / min or less, and further preferably 25 parts by mass / min or less.

  The liquid temperature when the electroless plating solution is dropped into the aqueous slurry may be appropriately adjusted, but the liquid temperature is preferably 50 ° C. or higher and lower than 100 ° C. The pH of the electroless plating solution is not limited, but is preferably 4 or more and 14 or less. The pH of the electroless plating solution can be adjusted by appropriately adding an alkaline aqueous solution such as sodium hydroxide, sodium carbonate, sodium hydrogen carbonate, or aqueous ammonia, or an acidic aqueous solution such as sulfuric acid or hydrochloric acid.

  When the electroless plating solution is added to the aqueous slurry of the catalyst base material particles, the electroless plating reaction starts immediately. Since the electroless plating reaction is accompanied by the generation of hydrogen gas, the electroless plating reaction may be terminated when the generation of hydrogen gas is not completely recognized. After the electroless plating reaction is completed, the conductive fine particles can be obtained by taking out the substrate particles on which the conductive metal layer is formed from the reaction system and washing and drying as necessary.

  The electroless plating process may be repeated as necessary. For example, by repeating the electroless plating process using electroless plating solutions having different metal types, the surface of the substrate particles can be coated with several layers of different kinds of metals. For example, after nickel plating is applied to the base particles, the obtained nickel-coated particles are further poured into an electroless gold plating solution to perform gold displacement plating, so that the outermost layer is covered with a gold layer, and the nickel layer is covered with nickel. -Conductive fine particles having a boron layer are obtained.

The conductive fine particles of the present invention can be provided with an insulating resin layer on at least a part of the surface. That is, the aspect which further formed the insulating resin layer on the surface of the said electroconductive metal layer may be sufficient. When the insulating resin layer is further laminated on the conductive metal layer on the surface in this way, it is possible to prevent the lateral conduction that is likely to occur when a high-density circuit is formed or when a terminal is connected.
Further, the conductive fine particles of the present invention can be subjected to a surface treatment with a silane coupling agent, an organic compound or the like as necessary within a range not impairing the effects of the present invention.

  The conductive fine particles of the present invention can be preferably used for anisotropic conductive materials. Examples of the anisotropic conductive material include those in which the conductive fine particles are dispersed in a binder resin. The form of the anisotropic conductive material is not particularly limited, and examples thereof include various forms such as an anisotropic conductive film, an anisotropic conductive paste, an anisotropic conductive adhesive, and an anisotropic conductive ink. By providing these anisotropic conductive materials between opposing substrates or between electrode terminals, good electrical connection can be achieved. The anisotropic conductive material using the conductive fine particles of the present invention includes a conductive material for a liquid crystal display element (conductive spacer and composition thereof).

  The binder resin is not particularly limited as long as it is an insulating resin. For example, thermoplastic resins such as acrylic resins, ethylene-vinyl acetate resins, styrene-butadiene block copolymers; monomers and oligomers having a glycidyl group; Examples thereof include a curable resin composition that is cured by a reaction with a curing agent such as isocyanate; a curable resin composition that is cured by light or heat; The anisotropic conductive material can be obtained by dispersing conductive fine particles in the binder resin to obtain a desired form. For example, the binder resin and the conductive fine particles are used separately to try to connect them. You may connect by making electroconductive fine particles exist with binder resin between the base material to perform or between electrode terminals.

  In the anisotropic conductive material containing the conductive fine particles of the present invention, the content of the conductive fine particles may be appropriately determined depending on the application, but for example, with respect to the total amount (100% by volume) of the anisotropic conductive material. Is preferably 1% by volume or more, more preferably 2% by volume or more, further preferably 5% by volume or more, preferably 50% by volume or less, more preferably 30% by volume or less, and still more preferably 20% by volume or less. . If the content of the conductive fine particles is too small, it may be difficult to obtain sufficient electrical continuity. On the other hand, if the content of the conductive fine particles is too large, the conductive fine particles are in contact with each other, and anisotropy is caused. The function as a conductive material may be difficult to be exhibited.

  Regarding the film thickness in the anisotropic conductive material referred to in the present invention, the coating thickness of the paste or adhesive, the print thickness, etc., consider the particle size of the conductive fine particles to be used and the specifications of the electrode to be connected. In addition, it is preferable that the conductive fine particles are sandwiched between the electrodes to be connected and that the gap between the bonding substrates on which the electrodes to be connected are formed is sufficiently filled with the binder resin layer.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention. In the following, “part” means “part by mass” and “%” means “mass%” unless otherwise specified.
In addition, various analyzes and conductivity evaluation in Examples and Comparative Examples were performed by the following methods.

<Number average particle diameter and variation coefficient (CV value) of seed particles, base particles and conductive fine particles>
Measure the particle size of 30000 particles with a particle size distribution measuring device (“Coulter Multisizer III type” manufactured by Beckman Coulter, Inc.), obtain the average particle size based on the number and the standard deviation of the particle size, and determine the particle size according to the following formula: The number-based CV value (coefficient of variation) was calculated.
Particle variation coefficient (%) = 100 × (standard deviation of particle diameter / number-based average particle diameter)
In the measurement of base particles and conductive fine particles, 0.005 part by weight of the base particles or conductive fine particles is a surfactant ("Hitenol (registered trademark) N-08" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). A dispersion obtained by adding 20 parts by mass of a mass% aqueous solution and subjecting it to ultrasonic dispersion for 10 minutes was used as a measurement sample. In the measurement of seed particles, the seed particle dispersion obtained by hydrolysis and condensation reaction is diluted with a 1% by mass aqueous solution of a surfactant ("Haitenol (registered trademark) N-08" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). This was used as a measurement sample.

<Surface shape observation (evaluation of granular structure density)>
The surface of the conductive metal layer of the conductive fine particles was observed with a scanning electron microscope (magnification of 100,000 times). The number of granular structures having a major axis of 5 nm or more and 100 nm or less existing in a 200 nm square range in the central region of the conductive fine particle image was read. The above evaluation was performed on 10 conductive fine particles, and the average value was defined as the density of the granular structure.
The major axis of the granular structure was measured as follows.
An image in a 200 nm square area in the central region of the conductive fine particle image is introduced into image processing software (“Image-Pro Plus” manufactured by Media Cybernetics) to extract the granular structure, and the maximum diameter of each granular structure is determined. Measured as the major axis.

<Measurement of 10% K value of substrate particles and conductive fine particles>
Using a micro-compression tester (“MCT-W500” manufactured by Shimadzu Corporation) at room temperature (25 ° C.), one sample particle dispersed on the sample table was used as a “standard surface” using a circular flat plate indenter with a diameter of 50 μm. A load was applied at a constant loading rate (2.65 mN / sec (0.27 gf / sec)) toward the center of the particles in the “detection” mode. Then, the load (mN) when the compression displacement became 10% of the particle diameter was measured, and a 10% K value was calculated from the obtained compression load, particle compression displacement, and particle diameter. In addition, the measurement was performed on 10 different particles for each sample, and the average value was used as the measurement value.

<Thermal decomposition start temperature of the base particles>
Using a thermal analyzer (“TG-DTA2000-SA” manufactured by Burker), the thermogravimetric (TG) measurement of the substrate particles was performed under a nitrogen atmosphere, and the weight reduction start temperature was defined as the thermal decomposition start temperature.

<Conductivity evaluation of conductive fine particles: resistance value ρ>
Using conductive fine particles as sample particles, a resistance value (Ω) was measured at room temperature (25 ° C.) using a Shimadzu micro-compression tester (“MCT-W200” manufactured by Shimadzu Corporation; attached to a resistance measurement kit). Specifically, with respect to one sample particle spread on the sample stage, a constant loading speed (2.65 mN / sec (0.27 gf / sec)) toward the center of the particle using a circular plate indenter with a diameter of 50 μm. The measurement was performed with a load applied. The measurement was performed 10 times, the average value of the resistance values at the time of 50% compression deformation of the particle diameter was determined, and this was set as the resistance value ρ of the conductive fine particles.

(Manufacture of substrate particles)
(Production Example 1)
Into a four-necked flask equipped with a condenser, a thermometer, and a dropping port, 1800 parts by mass of ion-exchanged water and 24 parts by mass of 25% by mass ammonia water are added, and then, 3-methacryloxypropyltrimethoxy is added from the dropping port with stirring. A mixed liquid of 100 parts by mass of silane and 600 parts by mass of methanol is added to perform hydrolysis and condensation reaction of 3-methacryloxypropyltrimethoxysilane to form polysiloxane particles (polymerizable polysiloxane) having methacryloyl groups as seed particles. Particle) emulsion. The number average particle diameter of the polysiloxane particles was 4.71 μm.

  Subsequently, 10 parts by mass of a 20% by mass aqueous solution of polyoxyethylene styrenated phenyl ether sulfate ammonium salt (“HITENOL (registered trademark) NF-08” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as an emulsifier is added to 400 parts by mass of ion-exchange water. In a solution diluted with styrene, 470 parts by mass of styrene and 30 parts by mass of divinylbenzene (“DVB960” manufactured by Nippon Steel Chemical Co., Ltd .; 96% by mass of divinylbenzene) as monomer components, 2,2′-azobis (2, 4-Dimethylvaleronitrile) (“V-65” manufactured by Wako Pure Chemical Industries, Ltd.) (4.8 parts by mass) was added and emulsified and dispersed to prepare an emulsion of monomer components. After stirring this emulsion for 2 hours, it was added to the emulsion of the polysiloxane particles and further stirred. One hour after the addition of the emulsified liquid, the mixed liquid was sampled and observed with a microscope. As a result, it was confirmed that the polysiloxane particles, which are seed particles, absorbed the monomer and enlarged.

Next, 96 parts by mass of a 20% by mass aqueous solution of the same polyoxyethylene styrenated phenyl ether sulfate ammonium salt and 500 parts by mass of ion-exchanged water are added to the obtained mixed liquid, and 65 ° C. in a nitrogen atmosphere. After the temperature was raised to 65 ° C., the monomer component was radically polymerized by holding at 65 ° C. for 2 hours. Then, the emulsion after radical polymerization was subjected to solid-liquid separation, and the obtained cake was washed with ion-exchanged water and methanol, and then dried at 80 ° C. for 4 hours in a nitrogen atmosphere to obtain polymer particles. The polymer particles were subjected to an etching treatment with sodium hydroxide or the like for hydrophilization, and the obtained particles were used as substrate particles (1). The number average particle size of the substrate particles (1) was 9.02 μm, the coefficient of variation (CV value) of the number-based particle size was 3.6%, and the thermal decomposition starting temperature was 263 ° C. The 10% K value of the substrate particles (1) was 3362 N / mm ² .

Example 1
The base particles (1) produced in Production Example 1 were directly subjected to electroless plating to produce conductive fine particles. Specifically, 0.5 g of the base particle (1) was treated with 100 ml of an aqueous solution containing 1 g / L of the nonionic surfactant PEG1000 to modify the surface of the base particle. Next, after washing with water, the obtained particles were immersed in an aqueous solution consisting of 100 mg / L of palladium chloride, 10 g / L of tin chloride and 100 mL / L of concentrated hydrochloric acid, filtered and washed with water, and then treated with 10% by mass hydrochloric acid. Then, the palladium catalyst was supported on the surface of the base material particles.

  Next, the obtained base particles were washed with water, and then added to pure water containing a fluorosurfactant (perfluoroalkyltrimethylammonium salt) to prepare a slurry. The slurry was put into 2000 mL of pure water heated to 70 ° C. and stirred to prepare a base particle dispersion. Next, while stirring the obtained base particle dispersion, 2000 mL of an electroless nickel plating solution prepared with the following composition was dropped into the base particle dispersion at a dropping rate of 160 mL / min.

  The electroless nickel plating solution was prepared to be nickel sulfate hexahydrate 30 g / L, ethylenediamine 50 g / L, sodium hydroxide 30 g / L, and sodium borohydride 0.6 g / L. The electroless nickel plating solution used for the dropping was adjusted to pH 6 and heated to 70 ° C.

After completion of dropping of the electroless nickel plating solution, stirring was continued for 60 minutes to complete the reaction. Thereafter, the generated electroless plating particles were filtered, washed with water, and dried to obtain conductive fine particles (1). The number average particle diameter of the conductive fine particles (1) was 9.32 μm, the coefficient of variation (CV value) was 3.9%, and the thickness of the conductive metal layer (Ni—B layer) was 150 nm.
Table 1 shows the composition conditions of the electroless plating solution used for the production of the conductive fine particles (1), and the analysis and evaluation results of the conductive fine particles (1).

Example 2 and Comparative Examples 1 and 2
In the same manner as in Example 1, except that the electroless plating solution composition was changed as shown in Table 1, conductive fine particles (2) (Example 2), conductive fine particles (c1) (Comparative Example 1) and conductive Fine particles (c2) (Comparative Example 2) were produced. Table 1 shows the composition conditions, analysis results, and evaluation results of the electroless plating solution used for production for each conductive fine particle.

  From Table 1 above, the number of granular structures having a major axis of 5 nm or more and 100 nm or less present in a 200 nm square region in a substantially central region of the conductive fine particle image observed with a scanning electron microscope (magnification magnification 100,000 times) Is within the predetermined range, it can be seen that the resistance value of the conductive fine particles is low and the conductivity is excellent.

  In the conductive fine particles of the present invention, the conductive metal layer covering the surface of the base particle is a conductive metal layer containing nickel and boron, and the granular structure of a specific size is reduced in this conductive metal layer. Therefore, excellent conductivity can be expressed. As a result, even when used as an anisotropic conductive material, a lower connection resistance value can be achieved. For this reason, it is extremely useful for anisotropic conductive materials such as anisotropic conductive films, anisotropic conductive pastes, anisotropic conductive adhesives, and anisotropic conductive inks.

Claims (5)

Conductive fine particles having substrate particles and a conductive metal layer covering the surface of the substrate particles,
The conductive metal layer includes nickel and boron;
When the surface of the conductive metal layer is observed with a scanning electron microscope image having a magnification of 100,000 times, the number of granular structures having a major axis of 5 nm to 100 nm is less than 20 per 200 nm square. Characteristic conductive fine particles.   The conductive fine particles according to claim 1, wherein a major axis of the granular structure is 5 nm or more and 30 nm or less. The number average particle size is 1 μm or more and 30 μm or less, the number-based particle size variation coefficient (CV value) is 10% or less, and the compression elastic modulus (10% K value) when the diameter is displaced by 10%. 1000 N / mm ² or more, 30,000 N / mm ² or less conductive fine particles according to claim 1 or 2.   The conductive fine particles according to any one of claims 1 to 3, wherein the content of boron is 0.1% by mass or more and less than 1.5% by mass in 100% by mass of the conductive metal layer.   The conductive fine particles according to claim 1, wherein the content of phosphorus is less than 5% by mass in 100% by mass of the conductive metal layer.