JP2015050112A - Conductive fine particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive fine particle which has a nickel-containing conductive metal layer on the surface of a base particle and can exert excellent oxidation resistance, essentially without a heat treatment process.SOLUTION: A conductive fine particle consists of a base particle and a conductive metal layer covering the surface of the base particle, and the conductive metal layer contains nickel and phosphorus. Taking the peak area of peaks corresponding to nickel in the metallic state, among peaks obtained by observing the conductive metal layer by the X-ray photoelectron spectroscopy, as Sand the peak area of peaks corresponding to the oxidation state of nickel as S, the content ratio(%) of metallic nickel in the conductive metal layer, determined by [S/(S+S)]×100, is higher than 20% for the conductive fine particle after a 2-h treatment at the temperature of 200°C in an oxidizing atmosphere.

Description

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

  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.

  By the way, an electronic device may generate heat during operation. In this case, the electronic circuit is exposed to a high temperature atmosphere, and the conductive fine particles are also exposed to a high temperature. In addition, air is present in the electronic device, which is an oxidizing atmosphere. Therefore, when the electronic device is operated, the conductive fine particles are exposed to a high-temperature oxidizing atmosphere. As a result, there is a problem that the metal layer is oxidized and the resistance value between the electrodes is increased. Therefore, the conductive fine particles are required to have high temperature oxidation resistance. In particular, in recent years, the amount of heat generation tends to increase as the computing performance of electronic devices increases. In small-sized integrated electronic devices such as smartphones and tablet terminals, heat generation is concentrated and heat is easily accumulated. The temperature rise inside the device becomes more remarkable. Also, in applications such as in-vehicle electronic devices (such as car navigation systems) and solar cells (tab wire connection) that are exposed to a high-temperature atmosphere during use, the temperature rise inside the electronic devices is also significant due to the influence of external heat. become. Therefore, the conductive fine particles used for such applications are required to have particularly excellent high temperature oxidation resistance.

  The increase in resistance value due to oxidation is particularly remarkable when the conductive metal layer is made of nickel, which is an easily oxidizable metal element. However, nickel is a metal element that is inexpensive and readily available, is easily plated, and has a relatively low resistance. Therefore, it is desired to use nickel as a surface metal layer of conductive fine particles.

  Therefore, after the nickel particles are subjected to hydrogen reduction treatment and / or etching treatment as conductive fine particles exhibiting excellent oxidation resistance even when having an easily oxidizable metal element such as nickel on the outermost surface, Has been proposed for conducting fine particles that have been oxidized for 10 to 60 minutes at 200 to 500 ° C. (Patent Document 1).

JP 2010-15756 A

  However, since the technique described in Patent Document 1 requires a heat treatment process for oxidation treatment, when applied to conductive fine particles composed of resin particles and a conductive metal layer, the base particles are heat resistant. If the resin is formed of a low resin, there is a concern about deterioration of the base particles during the heat treatment process. For this reason, there is a limitation that substantially only heat-resistant particles can be used as the base particles. In addition, the method described in Patent Document 1 requires a heat treatment process and further a hydrogen reduction treatment and / or an etching treatment, and is disadvantageous in terms of production time and production cost. The conductive fine particles obtained by the method described in Patent Document 1 have improved oxidation resistance by covering the particle surface with an oxide film, and no metallic nickel is present on the particle surface (paragraph 0036). etc).

The present invention has been made paying attention to the circumstances as described above, and its purpose is to have a conductive metal layer containing nickel on the surface of the base particles, and even if a heat treatment process is not essential, An object of the present invention is to provide conductive fine particles capable of exhibiting excellent oxidation resistance.
Another object of the present invention is a conductive fine particle having a conductive metal layer containing nickel on the surface of the base particle, and not only the base particle having excellent heat resistance but also the base particle having poor heat resistance. An object of the present invention is to provide conductive fine particles that can exhibit excellent oxidation resistance even when used.

The conductive fine particles of the present invention capable of achieving the above object are conductive fine particles having base particles and a conductive metal layer covering the surface of the base particles, wherein the conductive metal layer is Among observation peaks obtained by X-ray photoelectron spectroscopy analysis of the conductive metal layer containing nickel and phosphorus, the peak area of the peak corresponding to the metal state of nickel corresponds to S _metal and the oxidation state of nickel. When the peak area of the peak is S _oxide , the following formula:
Metal nickel content ratio (%) = [S _metal / (S _metal + S _oxide )] × 100
The content ratio (%) of metallic nickel in the conductive metal layer required in (1) is more than 20% in the conductive fine particles after being treated at 200 ° C. for 2 hours in an oxidizing atmosphere. is there.

In this invention, it is preferable that phosphorus content is 5 mass% or more in 100 mass% of said electroconductive metal layers. Further, in the present invention, the content ratio of metallic nickel after treatment at a temperature of 200 ° C. for 2 hours in the oxidizing atmosphere is Ni _after (%), and the content ratio of metallic nickel before the treatment is Ni _before (%). The following formula: change rate of metallic nickel (%) = [(Ni _before −Ni _after ) / Ni _before ] × 100
It is preferable that the change rate of the metallic nickel calculated | required by is 70% or less.

  In the conductive fine particles of the present invention, the conductive metal layer covering the surface of the substrate particles contains phosphorus together with nickel, and the content ratio of the metal nickel in the conductive metal layer is not limited even after heat treatment under predetermined conditions. Since it exceeds 20%, even though the conductive metal layer contains nickel, it can exhibit excellent oxidation resistance without requiring a heat treatment process, and as a result, oxidized as an anisotropic conductive material. Even when used in a neutral atmosphere, an increase in resistance value is suppressed and excellent conductivity is exhibited. According to the present invention, in order to improve oxidation resistance, base particles can be selected without being restricted by heat resistance, and the metal layer should be made of nickel that is inexpensive and easily available and can be easily plated. Therefore, it is possible to provide conductive fine particles having excellent oxidation resistance at low cost. Further, since the oxidation resistance expressed in the present invention is extremely excellent, for example, small integrated electronic devices such as smartphones and tablet terminals, in-vehicle electronic devices such as car navigation systems, particularly high acid resistance such as solar cells. The present invention can be preferably applied even in applications that require a changeability.

1. Conductive fine particles The conductive fine particles of the present invention have base material particles and a conductive metal layer (hereinafter also referred to as “metal layer”) covering the surface of the base material particles. Contains nickel and phosphorus, and the content ratio of metallic nickel in the metal layer is more than 20% in the conductive fine particles after being treated at 200 ° C. for 2 hours in an oxidizing atmosphere. Since such conductive fine particles have excellent oxidation resistance, even when exposed to high temperatures in an oxidizing atmosphere, good conductivity can be maintained without causing an increase in resistance value.

In the present invention, the content ratio of metallic nickel in the metal layer refers to the peak area of the peak corresponding to the metallic state of nickel among the observation peaks obtained by X-ray photoelectron spectroscopic analysis of the metal layer of conductive fine particles. _When the peak area of the peak corresponding to the oxidation state of _metal and nickel is S _oxide , the following formula:
Metal nickel content ratio (%) = [S _metal / (S _metal + S _oxide )] × 100
Is required. Therefore, in the present invention, the content ratio of metallic nickel in the metal layer means the ratio of nickel element in the metal state among the nickel elements contained in the metal layer.

Specifically, for example, if the X-ray source of X-ray photoelectron spectroscopy is MgKα ray, the peak attributed to the 2P2 / 3 orbit of Ni detected from the spectrum obtained by X-ray photoelectron spectroscopy is a nickel metal. The peak corresponding to the state (binding energy 852 to 854 eV) and the peak corresponding to the oxidation state of nickel (binding energy 854 to 857 eV) are separated into peaks, and for each separated peak, the formula: peak area = peak intensity × half width , Peak areas (S _metal , S _oxide ) may be calculated. Here, the peak intensity means the peak height. When there are a plurality of peaks derived from nickel existing as an oxidation state (NiO, Ni ₂ O _3, etc.), the sum of these peak areas is defined as the peak area (S _oxide ) of the peak corresponding to the oxidation state. Good.

The content ratio of metallic nickel in the metal layer after the treatment for 2 hours at 200 ° C. in an oxidizing atmosphere (hereinafter sometimes referred to as “oxidative heat treatment”) is preferably 25% or more, More preferably, it is 40% or more, more preferably 50% or more, and most preferably 100%. The higher the content ratio of metallic nickel, the more excellent oxidation resistance can be expressed.
In the present invention, the oxidizing atmosphere usually means an air atmosphere (usually air at 1 atm). Therefore, the oxidizing heat treatment is usually performed in an air atmosphere, but can also be performed in an atmosphere having the same or almost the same concentration of oxygen and nitrogen as air.

  As will be described in detail later, in order to increase the content ratio of metallic nickel in the metal layer to more than 20%, for example, a plating solution containing at least three kinds of dicarboxylic acids (salts) as a complexing agent is used. In this case, the electroless plating reaction may be performed in the presence of a fluorosurfactant, while the sulfur-based stabilizer is not used in the electroless plating reaction.

In the present invention, when the content ratio of metallic nickel after the oxidizing heat treatment described above is Ni _after (%) and the content ratio of metallic nickel before the oxidizing heat treatment is Ni _before (%), The following formula:
Change rate of nickel metal (%)
= [(Ni _before -Ni _after ) / Ni _before ] × 100
It is preferable that the change rate of metallic nickel calculated | required by is 80% or less. More preferably, it is 70% or less, more preferably 50% or less, particularly preferably 30% or less, and most preferably 20% or less. In the conventional conductive fine particles, even though the metal nickel content ratio before the oxidative heat treatment was high, the amount of metal nickel tended to decrease significantly when the oxidative heat treatment was performed (see Comparative Example 1). The conductive fine particles of the present invention have a feature that the change rate of the amount of metallic nickel before and after the oxidative heat treatment is small, in addition to the metal nickel content ratio after the oxidative heat treatment being a certain level or more. Therefore, in the present invention, in consideration of the reduction of metallic nickel when exposed to high temperature in an oxidizing atmosphere, the amount after metallic heat treatment can be reduced even if the amount of metallic nickel is not set excessively in advance. It becomes possible to make the metal nickel content ratio more than 20%.

  The content ratio of metallic nickel in the metal layer before the oxidizing heat treatment is not particularly limited, but is preferably 40% or more, more preferably 50% or more, still more preferably 60% or more, and further preferably 80%. Above, most preferably 100%.

  The number average particle diameter of the conductive fine particles is preferably 1.0 μm or more, more preferably 1.1 μm or more, further preferably 1.2 μm or more, still more preferably 1.3 μm or more, and particularly preferably 1.4 μm or more. It is 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 number-based variation coefficient (CV value) of the conductive fine particles is preferably 10.0% or less, more preferably 8.0% or less, still more preferably 5.0% or less, and still more preferably 4%. .5% or less, particularly preferably 4.0% or less. In addition, the number average particle diameter and variation coefficient of the conductive fine particles can be measured, for example, by a method described later in Examples.

  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 generally tends to increase, but the conductive fine particles of the present invention are fine. Even if it exists, the connection resistance value raise under high temperature oxidizing conditions can be suppressed effectively. Therefore, the number average particle diameter of the conductive fine particles is preferably less than 10.0 μm, more preferably 3.2 μm or less, still more preferably 3.0 μm or less, and still more preferably, in that the effect of the present invention becomes more remarkable. Is 2.8 μm or less, more preferably 2.7 μm or less, and even more preferably 2.6 μm or less, while 1.1 μm or more is preferable and 1.6 μm or more is more preferable.

  On the other hand, if the substrate particles are soft, the contact area with the electrode is increased, so that the oxidation state of the metal layer (nickel surface metal layer) significantly affects the increase in the connection resistance value. According to the conductive fine particles of the present invention, even if the substrate particles are soft, an increase in connection resistance value can be more effectively suppressed even under high-temperature oxidizing conditions. 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.

1-1. Conductive Metal Layer The metal layer in the present invention contains nickel and phosphorus as essential constituent elements. Specifically, a nickel-phosphorus alloy containing nickel as a main component is preferable, and other elements can be contained as needed within a range not impairing the effects of the present invention. Nickel is inexpensive and easily available, and is easily plated. Therefore, using this as a main component makes it possible to provide the conductive fine particles of the present invention at low cost. When the nickel is contained in an appropriate amount, the metal layer can be prevented from being oxidized.

  The content of nickel constituting the metal layer is preferably 80% by mass or more, more preferably 85% by mass or more, and preferably 95% by mass or less, more preferably 92% by mass or less, in 100% by mass of the metal layer. More preferably, it is 88 mass% or less. When the nickel content is within the above range, conductive fine particles can be produced at low cost while exhibiting excellent oxidation resistance.

  The content of phosphorus constituting the metal layer is preferably 5% by mass or more, more preferably 8% by mass or more, still more preferably 12% by mass or more, and preferably 20% by mass or less, in 100% by mass of the metal layer. More preferably, it is 15 mass% or less. When the phosphorus content is in the above range, excellent oxidation resistance can be exhibited.

  Other elements that can be contained in the metal layer are not particularly limited. For example, gold, silver, copper, platinum, iron, lead, aluminum, chromium, palladium, nickel, rhodium, ruthenium, antimony, bismuth. , Metal elements such as germanium, tin, cobalt, and indium. These contents are preferably 50% by mass or less, more preferably 40% by mass or less, and still more preferably 30% by mass or less, in 100% by mass of the metal layer. These other metal elements may form one layer together with nickel and phosphorus, or may form another layer on the surface of a layer formed of a nickel-phosphorus alloy (for example, nickel- An embodiment in which the surface of the phosphorus alloy layer is plated with gold may be used.

  However, it is important that the metal layer in the present invention does not substantially contain elemental sulfur. Usually, the sulfur content in 100% by mass of the metal layer is less than 0.1% by mass, preferably 0.8%. It is 05 mass% or less, More preferably, it is 0.01 mass% or less. When there is more sulfur element than the said range, as a result that oxidation resistance becomes inadequate, electroconductivity will fall.

  In addition, content of each element contained in the said metal layer can be measured by the method mentioned later in an Example, for example.

  The thickness of the conductive metal layer (for example, when the surface of the nickel-phosphorus alloy layer is gold-plated, the total thickness of the nickel-phosphorus alloy layer and the gold layer) is preferably 0.01 μm or more, more preferably Is 0.03 μm or more, more preferably 0.05 μm or more, preferably 0.20 μm or less, more preferably 0.18 μm or less, still more preferably 0.15 μm 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 method for measuring the thickness of the conductive metal layer is not particularly limited, and various known methods can be employed. For example, it can be measured by cutting conductive fine particles along the diameter and observing the cross section with an electron microscope or the like, or by dissolving the metal layer and analyzing the dissolved metal concentration with an ICP emission analyzer. You can ask for it. In the latter method, for example, when the surface of the nickel-phosphorus alloy layer is plated with gold, 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 in which the surface of the nickel-phosphorus alloy layer is plated with gold.
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 metals (nickel, phosphorus) and gold constituting the nickel-phosphorus alloy layer in the dissolved liquid were analyzed using an ICP emission analyzer, and the nickel-phosphorus was calculated from the following formula (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-phosphorus alloy layer (μm), d _Ni is the density of the nickel-phosphorus alloy layer, d _base is the density of the base particle, W is the content (mass%) of the constituent components (nickel, phosphorus) of the nickel-phosphorus alloy layer, and X is the gold content (mass%).

In formula (2), a is the thickness (μm) of the gold layer, d _Au is the density of the gold layer, d _{(base + Ni)} is a particle in which a nickel-phosphorus 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-phosphorus alloy layer, d _base is the density of the base particle, and W is the content (mass%) of the constituent components (nickel, phosphorus) of the nickel-phosphorus alloy layer. It is.

1-2. Base Material Particles In the present invention, it is not necessary to perform heat treatment after forming the metal layer as in Patent Document 1, and therefore the base material particles in the present invention are a base material having high heat resistance without being restricted by the heat resistance. A wide selection can be made from particles to base particles having relatively low heat resistance.
Specifically, the base particles of the present invention may be particles having a thermal decomposition starting temperature exceeding 280 ° C. (for example, particles having a thermal decomposition starting temperature of about 280 to 400 ° C.). Then, even particles having a thermal decomposition start 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.

  The substrate particles in the present invention are preferably resin particles containing a resin component. By using resin particles, 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.

  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 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 number average particle diameter of the substrate particles (resin particles) is preferably 1.0 μm or more, more preferably 1.1 μm or more, still more preferably 1.2 μm or more, still more preferably 1.3 μm or more, and 50 μm or less. More preferably, it is 30 micrometers or less, More preferably, it is 25 micrometers or less, More preferably, it is 20 micrometers or less. The number-based variation coefficient (CV value) of the particle diameter of the substrate particles is preferably 10.0% or less, more preferably 8.0% or less, still more preferably 5.0% or less, and still more preferably 4. 5% or less, particularly preferably 4.0% or less. In addition, the number average particle diameter and variation coefficient of the base particles can be measured by the method described later in Examples.

  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, so that the effect of the present invention becomes more remarkable as described above. . Therefore, the number average particle diameter of the base particles is preferably less than 10.0 μm, more preferably 3.0 μm or less, even more preferably 2.8 μm or less, still more preferably less than 2.8 μm, and even more preferably 2. 7 μm or less, 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, as an aspect in which the effect of the present invention becomes more prominent, there is an aspect in which the base particles are soft, and the preferable number average particle diameter of the conductive fine particles in that case is 6.3 μm or more and 25 μm or less. is there. 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.

1-3. 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. According to the electroless plating method, it is easy to obtain the conductive fine particles of the present invention having a conductive metal layer excellent in oxidation resistance by controlling the content ratio of metallic nickel in the metal layer to the above-mentioned range, and it is not large. A metal layer can be easily formed without requiring an apparatus.
In the present invention, when the electroless plating is performed, (i) at least three kinds of dicarboxylic acids (salts) are used as a complexing agent, and (ii) the electroless plating reaction is performed in the presence of a fluorosurfactant. And (iii) performing the electroless plating reaction without using a sulfur-based stabilizer. If electroless plating is performed under conditions satisfying all of (i) to (iii), the content ratio of metallic nickel in the metal layer after the oxidative heat treatment can be made to exceed 20%. 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 the catalyzing treatment, noble metal ions are captured on the surface of the substrate particles, and then reduced to support the noble metal on the surface of the substrate particles. As the base particles to be subjected to the catalyst treatment, the above-described base particles having a hydrophilic surface are preferable. In the case where 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. Here, as the surface treatment agent, for example, in addition to cationic surfactants such as amine salts and quaternary ammonium salts, fluorine surfactants described later are preferably used.

As the catalyst treatment method, for example, a solution containing palladium chloride and tin chloride is used as a catalyst reagent, and the catalyst particles are adsorbed on the surface of the substrate particles by immersing the substrate particles in the solution. By reducing the palladium ions with an acid solution such as hydrochloric acid or an alkali solution such as sodium hydroxide, palladium is deposited on the surface of the substrate particles (catalyst-accelerator method), or the substrate particles are treated with tin ions (Sn ^2+). ) Is caused to be deposited on the surface of the substrate particles by allowing the tin ions to be adsorbed on the surface of the substrate particles and then immersed in a solution containing palladium ions (Pd ²⁺ ). (Sensitizing-activating method) and the like.

Electroless plating step In electroless plating, 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-phosphorus alloy layer can be formed by performing an electroless plating reaction using an electroless plating solution containing a complexing agent, a phosphorus-based reducing agent, and a nickel salt.

  In the electroless plating step, it is important that the above condition (i), that is, the electroless plating solution contains at least three kinds of dicarboxylic acids (salts) as a complexing agent. Examples of the dicarboxylic acid include dicarboxylic acids such as tartaric acid, malic acid, and succinic acid. Moreover, as these salts, alkali metal (lithium, sodium, potassium) salt, ammonium salt etc. are mentioned, for example. As a combination of three or more kinds of dicarboxylic acids (salts), a combination containing tartaric acid, malic acid and succinic acid is preferable. As the complexing agent, together with three or more kinds of dicarboxylic acids (salts), for example, monocarboxylic acids such as hydroxyacetic acid, lactic acid and gluconic acid; tricarboxylic acids such as citric acid; or salts thereof (alkali metal (lithium, Sodium, potassium) salt, ammonium salt, etc.) may be used in combination.

  The amount of the complexing agent used is preferably 100 parts by mass or more, more preferably 150 parts by mass or more, still more preferably 200 parts by mass or more, and preferably 500 parts by mass or less with respect to 100 parts by mass of the nickel salt. More preferably, it is 450 mass parts or less, More preferably, it is 400 mass parts or less.

In the electroless plating step, it is important to perform the above condition (ii), that is, the electroless plating reaction in the presence of a fluorosurfactant.
Examples of the fluorosurfactant include perfluoroalkyl trimethyl ammonium salt, perfluoroalkyl sulfonate, perfluoroalkyl phosphate, perfluoroalkyl carboxylate, perfluoroalkyl ammonium iodide, perfluoroalkylamine oxide. Etc. Only 1 type may be used for a fluorochemical surfactant and it may use 2 or more types together.
As a method of adding a fluorosurfactant into the reaction system, a method of adding as a surface treatment agent for base particles; a method of adding to disperse base particles when preparing an aqueous slurry; The method of mix | blending with plating solution is mentioned.

  Although the usage-amount in each method of the said fluorosurfactant is not specifically limited, 1 mass part or more is preferable with respect to 100 mass parts of base material particles, More preferably, it is 2.5 mass parts or more, More preferably, 5 It is at least 20 parts by mass, more preferably at most 18 parts by mass, even more preferably at most 14 parts by mass.

  In the electroless plating step, it is important to perform the above condition (iii), that is, the electroless plating reaction without using a sulfur-based stabilizer. In general, the electroless plating solution is not discarded after a single use, but is usually reused for multiple electroless plating reactions, but the electroless plating solution gradually deteriorates as the number of uses increases. To do. Therefore, a sulfur-based stabilizer is usually added to the electroless plating solution so that it can withstand multiple reuses. However, according to the study by the present inventors, when using three types of dicarboxylic acid (salt) and a fluorine-based surfactant, even when using a sulfur-based stabilizer, the oxidation resistance of the plating layer is sufficient. It turned out not to improve. Therefore, in the present invention, this sulfur stabilizer is not used.

  In the 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 nickel layer, it is preferable that the catalyzed base material particles are sufficiently dispersed in an aqueous medium to be plated. In order to improve the dispersibility of the substrate particles, it is preferable to add a dispersant such as a surfactant, and it is preferable to use the above-mentioned fluorosurfactant as the dispersant. In addition, as a means for dispersing the catalyzed substrate particles in the aqueous medium, for example, a conventionally known dispersing means such as a normal stirring device, a high-speed stirring device, a shearing dispersion device such as a colloid mill or a homogenizer may be employed. If necessary, ultrasonic waves may be used in combination.

  Next, an electroless plating reaction containing an electroless plating solution containing a nickel salt, a phosphorus-based reducing agent, a complexing agent and various additives is added to the aqueous slurry of the catalyzed base particles prepared above, thereby Give rise to In addition, at least one of the electroless plating solution or the aqueous slurry of the catalyzed base particles contains a fluorosurfactant. The electroless plating reaction starts rapidly when the electroless plating solution is added to the aqueous slurry of the catalyzed substrate particles. Moreover, since this 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.

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 reducing agent is preferably a phosphorus source. For example, hypophosphites such as sodium hypophosphite are preferably used. Only one reducing agent may be used, or two or more reducing agents may be used.

  The electroless plating is preferably gradually added (dropped) 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 4-14. 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.

  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 phosphorus 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.

2. Anisotropic Conductive Material The conductive fine particles of the present invention can be preferably used for an anisotropic conductive material. Examples of the anisotropic conductive material include those obtained by dispersing the conductive fine particles 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 according to the application, for example, 1% by volume or more based on the total amount of the anisotropic conductive material. More preferably, it is 2 volume% or more, More preferably, it is 5 volume% or more, 50 volume% or less is preferable, More preferably, it is 30 volume% or less, More preferably, it is 20 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 addition, various analyzes and conductivity evaluation in Examples and Comparative Examples were performed by the following methods.

<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.

<Number average particle diameter of base particles and seed particles, coefficient of variation (CV value)>
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 the base particles, 20 parts by weight of a 1% by weight aqueous solution of a surfactant (“Hitenol (registered trademark) N-08” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was added to 0.005 parts by weight of the base particles. A dispersion obtained by applying a dispersion treatment with ultrasonic waves 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.

<Number average particle diameter of conductive fine particles, coefficient of variation (CV value)>
Using a flow-type particle image analyzer ("FPIA (registered trademark) -3000" manufactured by Sysmex Corporation), the particle diameter (μm) of 3000 conductive fine particles is measured, and the number-based average particle diameter and particle diameter standard While calculating | requiring a deviation, according to the same formula as the case of the said base material particle | grains, the CV value (coefficient of variation) of the particle | grain number basis was computed.

<Thickness of conductive metal layer>
20 mL of aqua regia was added to 0.02 g of conductive fine particles, and the metal layer was dissolved by heating, followed by filtration. The metal layer component in the obtained filtrate was analyzed using an ICP emission analyzer, and the thickness of the metal layer (nickel layer) was calculated from the following formula. In the formula, r is the radius (μm) of the base particle, t is the thickness of the nickel layer, d _Ni is the density of the nickel layer, d _base is the density of the base particle, and W is the nickel layer component (nickel, phosphorus). It is a content rate (mass%).

<Composition of conductive metal layer (Ni, P, S content)>
20 mL of aqua regia was added to 0.02 g of conductive fine particles, and the metal layer was dissolved by heating, followed by filtration. The obtained filtrate was analyzed using an ICP emission analyzer (using an ultrasonic nebulizer), and the contents of nickel, phosphorus and sulfur were measured. And the ratio (mass%) of each element amount (Ni, P, S) with respect to the total content of nickel, phosphorus, and sulfur was calculated | required as content.

<Metal nickel content ratio>
About the obtained electroconductive fine particles, the metal nickel content ratio of the electroconductive metal layer before and after the process of heating for 2 hours in an air atmosphere at 200 ° C. was measured using an X-ray photoelectron spectrometer (ESCA) (“JPS” manufactured by JEOL Ltd.). -9000MC ")). The measurement was performed using MgKα rays as an X-ray source, tube voltage: 10.0 kV, tube current: 10.0 mA, and scan count 40.
Specifically, for the obtained spectrum, a peak attributed to the Ni 2p3 / 2 orbital is detected, and a peak corresponding to the metallic state nickel (binding energy 852 to 854 eV) and nickel bonded to an oxygen atom (NiO, Ni Peak separation was performed on the peak corresponding to ₂ O ₃ ) (binding energy: 854 to 857 eV). For each peak after separation, the peak area (S _metal ) of the peak corresponding to nickel in the metallic state and the peak area (S _oxide ) corresponding to nickel bonded to the oxygen atom are obtained based on the following formula, and the obtained values From the following equation, the peak area ratio (%) corresponding to the metallic nickel was calculated.

<Electrical conductivity evaluation when using anisotropic conductive paste (ACP): resistance value ρ (f)>
10 parts by mass of conductive fine particles, 100 parts by mass of an epoxy resin (“JER828” manufactured by Mitsubishi Chemical Corporation) as a binder resin, 2 parts by mass of a curing agent (“Sun Aid (registered trademark) SI-150” manufactured by Sanshin Chemical Co., Ltd.) and 100 parts by mass of toluene was added. This mixture was stirred and dispersed at 300 rpm for 10 minutes using two stainless steel stirring blades to prepare an anisotropic conductive paste.
The obtained anisotropic conductive paste was applied to a glass substrate having an ITO wiring for resistance measurement with a bar coater, and sandwiched between the same substrates, followed by thermocompression bonding under a pressure bonding condition of 5 MPa and 150 ° C., and then between the electrodes. The resistance value (Ω) was measured and used as the resistance value ρ (f) in the anisotropic conductive paste (ACP).

<Conductivity evaluation of conductive fine particles: resistance value ρ (p)>
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 (2.6 mN / second (0.27 gf / second)) 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 (p) of the conductive fine particles.

  The conductive fine particles used for the above-described conductivity evaluation (resistance value ρ (f) and resistivity ρ (p)) are manufactured under an air atmosphere at a relative humidity of 65% ± 10% and a room temperature of 20 ° C. ± 5 ° C. Stored in.

(Manufacture of substrate particles)
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 were enlarged by absorbing the monomer.

  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 hydrophilic treatment, and the obtained particles were used as base particles. The number average particle diameter of the substrate particles was 9.02 μm, the coefficient of variation (CV value) was 3.6%, and the thermal decomposition starting temperature was 263 ° C.

(Example 1)
23 g of the substrate particles obtained above were treated with 3 g of a fluorosurfactant (perfluoroalkyltrimethylammonium salt) to modify the surface of the substrate particles. 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 1.5 g of a fluorosurfactant (perfluoroalkyltrimethylammonium salt) to prepare a slurry. The slurry was put into 2000 mL of pure water heated to 95 ° 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 have concentrations of nickel sulfate 30 g / L, malic acid 30 g / L, tartaric acid 30 g / L, succinic acid 30 g / L, and sodium hypophosphite 30 g / L. In addition, the electroless nickel plating solution used for dripping was adjusted to pH 4.5 and heated to 95 ° 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 3.8%, and the thickness of the conductive metal layer (Ni—P layer) was 150 nm.
Table 1 shows the analysis and evaluation results of the conductive fine particles (1).

(Comparative Example 1)
In Example 1, in preparing the electroless nickel plating solution, conductive fine particles (c1) were obtained in the same manner as in Example 1, except that 30 ppm of the sulfur-based additive was contained on a mass basis. The number average particle diameter of the conductive fine particles (c1) was 9.32 μm, the coefficient of variation (CV value) was 3.9%, and the thickness of the conductive metal layer (Ni—P layer) was 150 nm.
Table 1 shows the analysis and evaluation results of the conductive fine particles (c1).

  From Table 1 above, even if three types of dicarboxylic acids (salts) are used as complexing agents and the electroless reaction is performed in the presence of a fluorosurfactant, if a sulfur stabilizer is used, The content ratio of metallic nickel after the oxidation treatment does not exceed 20%, and it can be seen that the resistance value increases significantly with such conductive fine particles.

Claims (3)

Conductive fine particles having substrate particles and a conductive metal layer covering the surface of the substrate particles,
The conductive metal layer comprises nickel and phosphorus; and
Of the observation peaks obtained by X-ray photoelectron spectroscopy analysis of the conductive metal layer, the peak area of the peak corresponding to the nickel metal state is S _metal , and the peak area of the peak corresponding to the nickel oxidation state is S _oxide . When the following formula:
Metal nickel content ratio (%) = [S _metal / (S _metal + S _oxide )] × 100
The content ratio (%) of metallic nickel in the conductive metal layer required in (1) is more than 20% in the conductive fine particles after being treated at 200 ° C. for 2 hours in an oxidizing atmosphere. Fine particles.   2. The conductive fine particle according to claim 1, wherein a phosphorus content is 5% by mass or more in 100% by mass of the conductive metal layer. When the content ratio of metallic nickel after treatment for 2 hours at a temperature of 200 ° C. in the oxidizing atmosphere is Ni _after (%) and the content ratio of metallic nickel before the treatment is Ni _before (%), the following formula:
Change rate of nickel metal (%)
= [(Ni _before -Ni _after ) / Ni _before ] × 100
The electroconductive fine particles according to claim 1 or 2, wherein the rate of change of metallic nickel obtained by (1) is 70% or less.