JP5667555B2 - Conductive fine particles and anisotropic conductive material containing the same - Google Patents

Description

  The present invention relates to conductive fine particles, and more particularly to conductive fine particles that are less likely to deteriorate with time in conductive performance even when used for electrical connection of various electronic devices, and an anisotropic conductive material including the same. .

  Conventionally, anisotropic conductive materials have been used as a method of connecting a large number of electrodes in a liquid crystal display panel at once. Among these, anisotropic conductive adhesive compositions (anisotropic conductive paste, anisotropic conductive ink, etc.) in which conductive fine particles are dispersed in a binder resin, or anisotropic conductive films are widely used. Examples of the conductive fine particles used in these anisotropic conductive materials include those obtained by performing metal plating on the surface of organic or inorganic base particles, metal particles, and the like.

  In recent years, with the high definition of liquid crystal display panels, bumps or ITO wirings that are electrodes of driving ICs are increasingly narrowed and narrowed (fine pitch). However, when the pitch of the bump and the ITO wiring is narrowed and narrowed, there is a problem that the conductive fine particles in the anisotropic conductive adhesive come into contact between adjacent electrodes and are easily short-circuited. As a result of this narrowing, the number of conductive fine particles trapped by one bump is reduced, and there is a problem that the connection resistance between the electrodes is increased to cause connection failure.

  In order to solve such problems such as an increase in resistance value in so-called fine pitch connection, in the conductive fine particles obtained by plating a conductive metal layer on the surface of a base particle having a uniform particle diameter made of resin, Attempts have been made to reduce the connection resistance value by reducing the particle diameter, increasing the number density of conductive fine particles captured by the electrodes. However, although the initial resistance value immediately after connecting the electrodes can be reduced by reducing the particle size of the conductive fine particles, even if such small conductive fine particles are used, they are exposed to high temperature and high humidity conditions. The resistance value increases with time.

  By the way, in the conductive fine particles, a technique for setting the halogen ion content to 30 ppm or less (Patent Document 1), a halogen ion content detected by a specific measurement method is set to 30 μg / g or less, and an alkali metal ion Has been proposed (Patent Document 2). According to these techniques, it is possible to maintain electrical connection between the substrate and the semiconductor element and prevent poor conduction.

JP 2002-93240 A JP 2004-14409 A

  The present inventors have analyzed the cause of the above-mentioned problem that the resistance value increases with time when exposed to high temperature and high humidity conditions. When the thickness of the layer becomes greater than a predetermined thickness, when the conductive fine particles are subjected to compressive deformation between the electrodes, cracks that enter the conductive metal layer compared to conventional conductive fine particles having a relatively large particle diameter ( The density of the fractured part) is increased, and certain halogen ions and alkali metal ions that have hidden inside the conductive metal layer are likely to elute to the outside of the conductive fine particles. As a result, the electrodes are gradually corroded, resulting in connection resistance. I found out that the value declined.

  As described above, Patent Documents 1 and 2 also disclose techniques for solving the problems of electrode corrosion and poor conduction caused by halogen ions and alkali metal ions contained in conductive fine particles. However, according to the study by the present inventors, in the techniques disclosed in Patent Documents 1 and 2, when the particle size is reduced (for example, when the substrate particle size is about 3 μm or less), halogen ions and alkalis are used. It has been found that metal ions cannot be reduced to the desired level. Therefore, the smaller the particle size of the conductive particles so that they can be made finer and narrower, the more difficult it is to reduce the amount of halogen ions and alkali metal ions, and when the conductive particles are exposed to high temperature and high humidity conditions. It has been difficult to prevent the resistance value from increasing with time.

  The present invention has been made paying attention to the circumstances as described above, and its purpose is to stabilize the connection resistance value in a fine pitch connection, which hardly causes a significant increase in connection resistance even when exposed to high temperature and high humidity conditions. An object of the present invention is to provide conductive fine particles capable of obtaining connection reliability, and to provide an anisotropic conductive material using such conductive fine particles.

The conductive fine particles of the present invention capable of solving the above-mentioned problems are conductive fine particles comprising substrate particles made of resin and a conductive metal layer formed on the surface of the substrate particles, The number average particle size of the base particles is 1.0 to 3.0 μm, the thickness of the conductive metal layer is 0.01 to 0.10 μm, the chloride ion content is 25 μg / g or less, and It is characterized in that the content of sodium ions is 40 μg / g or less.
The chloride ion content is preferably greater than 0 μg / g, and the sodium ion content is preferably greater than 0 μg / g.
The number-based coefficient of variation (CV value) of the particle diameter of the substrate particles is preferably 10% or less, and the 10% K value of the substrate particles is desirably 1000 N / mm ² or more. The number average particle diameter of the base particles is preferably 2.5 μm or less. The conductive metal layer is preferably an electroless plating film.
The present invention also includes an anisotropic conductive material containing the conductive fine particles.

  Although the conductive fine particles of the present invention have a small particle diameter, elution of chloride ions and sodium ions is suppressed. Therefore, even when exposed to high-temperature and high-humidity conditions, it is difficult for the connection resistance value to increase. If the conductive fine particles of the present invention and the anisotropic conductive material using the same are used for fine-pitch connection, electrodes provided in various electronic devices The connection reliability between members such as the like is improved.

1. Conductive fine particles The conductive fine particles of the present invention are conductive fine particles comprising base particles made of resin and a conductive metal layer formed on the surface of the base particles, and the number average of the base particles The particle diameter is 1.0 to 3.0 μm, the thickness of the conductive metal layer is 0.01 to 0.10 μm, the chloride ion content is 25 μg / g or less, and the sodium ion content Is characterized by being 40 μg / g or less.

1-1. Chloride ion content, sodium ion content First, the content of chloride ions and sodium ions in the conductive fine particles of the present invention will be described. In the present invention, the content of chloride ions and sodium ions is limited to the above ranges in order to obtain conductive fine particles whose connection resistance value hardly increases even when exposed to high temperature and high humidity conditions. These chloride ions and sodium ions can be mixed from the environment or used in the conductive metal layer forming process (for example, a catalyzing reagent used in the electroless plating method or the electroplating method, an electroless plating solution, etc.) Or it mixes from water etc., and it is difficult to make these quantity zero. However, the present inventors have found that the above problems can be solved by setting the chloride ion content in the conductive fine particles to 25 μg / g or less and the sodium ion content to 40 μg / g or less. Completed the invention.

  The content of chloride ions in the conductive fine particles of the present invention is 25 μg / g or less, preferably 20 μg / g or less, more preferably 15 μg / g or less. When the content of chloride ions exceeds the above range, the connection resistance value increases when the conductive fine particles are exposed to high temperature and high humidity conditions.

  The content of sodium ions in the conductive fine particles of the present invention is 40 μg / g or less, preferably 35 μg / g or less, more preferably 25 μg / g or less. When the content of sodium ions exceeds the above range, the connection resistance value increases when the conductive fine particles are exposed to high temperature and high humidity conditions.

  As described above, chloride ions and sodium ions are mixed in the base particle manufacturing process and the conductive metal layer forming process, and it is difficult to reduce these amounts to zero. Further, even if the amount is reduced more than necessary, the effect of reducing the connection resistance is saturated, but the cost for reducing ions is increased. Accordingly, the content of chloride ions and sodium ions is, for example, more than 0 μg / g, preferably about 1 μg / g or more, and more preferably about 2 μg / g or more.

  The content of chloride ions and sodium ions in the present invention means that when 1 g of conductive fine particles and 10 mL of distilled water (specific resistance 18 MΩ · cm) are added to a sealed container and heated at 120 ° C. for 24 hours, Means the amount of chloride ion and sodium ion extracted. In addition, the measurement method of various ions extracted into distilled water is not particularly limited, and any of the conventionally known measurement methods such as ICP emission spectroscopy (high frequency inductively coupled plasma emission spectroscopy), ion chromatography, and the like can be used. Can be used. Detailed measurement methods will be described in the examples.

1-2. Conductive metal layer The conductive fine particle of the present invention has a base particle and a conductive metal layer formed on the surface of the base particle, and the thickness of the conductive metal layer is 0.01 μm or more, It is 0.10 μm or less. The thickness of the conductive metal layer is preferably 0.03 μm or more, more preferably 0.05 μm or more, preferably 0.09 μm or less, more preferably 0.08 μm or less. When the thickness of the conductive metal layer is smaller than 0.01 μm, the conductivity becomes insufficient and the connection resistance value increases. On the other hand, when the thickness of the conductive metal layer is larger than 0.10 μm, the conductive fine particles of the present invention have a relatively small particle size, and therefore the curvature becomes larger than that of the conductive fine particles having a large particle size. The stress tends to concentrate, and the number of cracks (breaking points) entering the conductive metal layer when the conductive fine particles are subjected to compressive deformation increases, and chloride ions and sodium ions from inside the conductive metal layer increase. There is a possibility that the amount of elution increases and the electrodes are gradually corroded to reduce the connection resistance value.

  Although it does not specifically limit as a metal which comprises the electroconductive metal layer which concerns on this invention, For example, gold, silver, copper, platinum, iron, lead, aluminum, chromium, palladium, nickel, rhodium, ruthenium, antimony, bismuth, germanium , Tin, cobalt, indium, nickel-phosphorus, nickel-boron and other metals and metal compounds, and alloys thereof. Among these, gold, nickel, palladium, silver, copper, and tin are preferable because they are conductive fine particles having excellent conductivity. From the viewpoint of cost, nickel, nickel alloys (Ni—Au, Ni—Pd, Ni—Pd—Au, Ni—Ag, Ni—P, Ni—B, Ni—Zn, Ni—Sn, Ni— W, Ni—Co, Ni—Ti); copper, copper alloy (Cu and Fe, Co, Ni, Zn, Sn, In, Ga, Tl, Zr, W, Mo, Rh, Ru, Ir, Ag, Au, Alloys with at least one metal element selected from the group consisting of Bi, Al, Mn, Mg, P, B, preferably alloys with Ag, Ni, Sn, Zn; silver, silver alloys (Ag and Fe At least one selected from the group consisting of Co, Ni, Zn, Sn, In, Ga, Tl, Zr, W, Mo, Rh, Ru, Ir, Au, Bi, Al, Mn, Mg, P, and B Alloys with other metal elements, preferably Ag-Ni, Ag-Sn, Ag-Z ); Tin, tin alloy (for example, Sn—Ag, Sn—Cu, Sn—Cu—Ag, Sn—Zn, Sn—Sb, Sn—Bi—Ag, Sn—Bi—In, Sn—Au, Sn—Pb, etc.) Etc.) are preferred. Among these, nickel and a nickel alloy are preferable because of excellent adhesion to the base particles.

  The conductive metal layer may have a single-layer structure or a multilayer structure having two or more layers made of the above-described metals. When the conductive metal layer has a multilayer structure, the nickel-based metal layer (nickel or nickel alloy) is the innermost (in other words, the surface of the base particle) from the viewpoint of adhesion between the base particle and the conductive metal layer. It is preferable to arrange it in The layer provided on the nickel-based metal layer is not particularly limited, and a layer made of the above exemplified metal can be appropriately provided depending on the purpose. In addition, from the viewpoint of reducing resistance when subjected to electrical connection, a layer made of one or more kinds of noble metals selected from the group consisting of gold, palladium, and silver is used as the outermost layer among the metals exemplified above. Is preferred.

  When the conductive metal layer has a multilayer structure, the total thickness of all the conductive metal layers may be in the range of the thickness of the conductive metal layer described above. Therefore, the thickness of each layer is not particularly limited, but from the viewpoint of ensuring the adhesion between the base particles and the conductive metal layer, for example, the thickness of the nickel-based metal layer is the thickness of the conductive metal layer. It is preferably 40% to 99% with respect to the total (100%), more preferably 50% to 95%, and still more preferably 60% to 90%. The thickness of the noble metal layer is preferably 1% to 60%, more preferably 5% to 50%, and still more preferably 10% to 40%.

  The film thickness of the conductive metal layer can be determined by, for example, the following method regardless of whether it is a single layer structure or a multilayer structure. In the following, a case where the conductive metal layer has a two-layer structure of a first conductive metal layer (for example, a nickel-based metal layer) and a second conductive metal layer (for example, a noble metal layer) will be described as an example. This will be specifically described.

First, the first and second conductive metal layers constituting the conductive fine particles are completely dissolved. The method for dissolving the conductive metal layer may be appropriately selected according to the metal species constituting each layer. For example, the first conductive metal layer is made of nickel and the second conductive metal layer is made of gold. In such a case, a method of adding 8 ml of aqua regia to 0.05 g of conductive fine particles and stirring at 80 ° C. can be employed.
Next, the concentrations of the metals and the like constituting the first and second conductive metal layers in the solution in which the conductive metal layer is dissolved (here, the concentrations of nickel, an alloy element, and a noble metal element) are set to ICP. Analysis is performed using an emission analyzer, and the thickness of the nickel-based metal layer is calculated from the following formula (1). In the formula, r is the radius of the base particle (μm), t is the thickness of the nickel-based metal layer (μm), d _Ni is the density of the nickel-based metal layer, d _base is the density of the base particle, and W is nickel. System metal layer component (nickel, alloy element contained in nickel metal layer) content (mass%), X is the content (mass%) of noble metal element.

When the conductive metal layer has a multilayer structure, that is, when X is more than 0 in the above formula (1), the thickness of the noble metal layer is calculated from the following formula (2). In the formula, a is the thickness (μm) of the noble metal layer, d _Prec is the density of the noble metal layer, and d _{(base + Ni)} is a particle in which a nickel-based metal layer is provided on the base particle (hereinafter referred to as “nickel product”). Density), X is the content (mass%) of the noble metal element. Here, the density d _{(base + Ni)} of the nickel product can be calculated using the calculation formula (3). In the formula, d _Ni is the density of the nickel-based metal layer, d _base is the density of the base particle, and W is the nickel-based metal layer component (the alloy element contained in nickel and the nickel-based metal layer) content (% by mass). It is.

  As described above, the conductive fine particles of the present invention are intended for use in electrical connection of miniaturized and narrowed electrodes and wirings. Accordingly, the average particle size of the conductive fine particles of the present invention is preferably a number average particle size of 1.1 μm or more, more preferably 1.5 μm or more, and further preferably 2.0 μm or more. It is preferably 2 μm or less, more preferably 3.0 μm or less, still more preferably 2.9 μm or less, even more preferably 2.8 μm, even more preferably 2.7 μm or less, and even more preferably 2.6 μm or less. If the number average particle diameter of the conductive fine particles is within the above range, it can be suitably used for electrical connection for miniaturized and narrowed electrodes and wirings. The number-based variation coefficient (CV value) of the conductive fine particles is preferably 20% or less, more preferably 15% or less, and further preferably 10% or less. The number average particle size and the coefficient of variation (CV value) of the conductive fine particles can be determined using, for example, a flow type particle image analyzer.

  The conductive fine particles of the present invention include conductive spacers for LCD, conductive fine particles for anisotropic conductive connection in the mounting of semiconductors and electronic circuits, anisotropic conductive films, anisotropic conductive pastes, anisotropic conductive adhesives, It can be suitably used for anisotropic conductive materials such as anisotropic conductive ink.

1-3. Base Material Particles The base material particles according to the present invention which are a base for forming the conductive metal layer are preferably resin particles containing a resin component. By using resin particles, conductive fine particles having excellent elastic deformation characteristics can be obtained. Examples of the resin particles include amino resins such as melamine formaldehyde resin, melamine-benzoguanamine-formaldehyde resin, urea formaldehyde resin; vinyl polymers such as styrene resin, acrylic resin, styrene-acrylic resin; polyethylene, polypropylene, poly Polyolefins such as vinyl chloride, polytetrafluoroethylene, polyisobutylene, and polybutadiene; polyesters such as polyethylene terephthalate and polyethylene naphthalate; polycarbonates; polyamides; polyimides; phenol formaldehyde resin; The material which comprises these resin particles may be used independently, and may use 2 or more types together. Among these, vinyl polymers are substantially free from chlorine and sodium in the production raw materials, or even if these elements are contained, those having a very low content can be used as raw materials. An amino resin and an organopolysiloxane are preferable, a vinyl polymer and an amino resin are more preferable, and a vinyl polymer is particularly 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 and / or di (meth) acrylate as a polymerization component is preferable because there is little decrease in particle strength after coating with a conductive metal.

1-3-1. Vinyl polymer particles The vinyl polymer particles are composed of a vinyl polymer. A 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 non-crosslinked monomer. It is divided into sex monomers. 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 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 (such as a carboxyl group, a protonic hydrogen-containing group such as 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-butanediol di (meth) acrylate, etc.), polyalkylene glycol di (meth) acrylate (for example, diethylene glycol di (meth) acrylate, Triethylene glycol di (meth) acrylate, decaethylene glycol Di (meth) acrylate, pentadecaethylene glycol di (meth) acrylate, pentacontactor ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) Di (meth) acrylates such as acrylate); tri (meth) acrylates such as trimethylolpropane tri (meth) acrylate; tetra (meth) acrylates such as pentaerythritol tetra (meth) acrylate; dipentaerythritol hexa Hexa (meth) acrylates such as (meth) acrylate; aromatic hydrocarbon crosslinking agents such as divinylbenzene, divinylnaphthalene, and derivatives thereof (preferably divinylbenzene Styrene 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 (meth) acrylates (polyfunctional (meth) acrylate) having two or more (meth) acryloyl groups in one molecule, (meth) acrylate having two (meth) acryloyl groups in one molecule (Di (meth) acrylate) is particularly preferred. 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 , 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, ethyl styrene (ethyl vinyl benzene), pt-butyl styrene, Examples include halogen group-containing styrenes such as o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene, and styrene is preferable. 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 including at least one selected from a styrene monofunctional monomer, a styrene polyfunctional monomer, and a polyfunctional (meth) acrylate as a constituent component is preferable. More preferably, an embodiment having a styrene polyfunctional monomer and a polyfunctional (meth) acrylate as essential constituents; an embodiment having a styrene polyfunctional monomer and a styrene monofunctional monomer as essential constituents; a polyfunctional (meth) acrylate and An embodiment having a styrene monofunctional monomer as an essential constituent. In the above embodiment, the styrene monofunctional monomer is preferably styrene, the styrene polyfunctional monomer is preferably divinylbenzene, and the polyfunctional meta (acrylate) is preferably di (meth) acrylate. Therefore, an embodiment having divinylbenzene and di (meth) acrylate as essential components; an embodiment having divinylbenzene and styrene as essential components; and an embodiment having di (meth) acrylate and styrene as essential components are particularly preferable.

The vinyl polymer particles may contain other components to the extent that the properties of the vinyl polymer are not impaired. In this case, the vinyl polymer particles preferably contain 50% by mass or more of the vinyl polymer, more preferably 60% by mass or more, and still more preferably 70% by mass or more.
Although it does not specifically limit as said other component, A polysiloxane component is preferable. By introducing a polysiloxane skeleton into the vinyl polymer particles, it is excellent in elastic deformation at the time of pressure connection.

  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. Moreover, when a silane crosslinkable monomer is used as the silane monomer, a crosslinked structure can be formed. The cross-linked structure formed by the silane cross-linkable monomer includes a cross-link between a vinyl polymer and a vinyl polymer (first form); a cross-link between a polysiloxane skeleton and a polysiloxane skeleton (second In which the vinyl polymer skeleton and the polysiloxane skeleton are cross-linked (third form).

  Examples of the silane-based crosslinkable monomer that can form the first form (crosslinking between vinyl 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 vinyl polymer and polysiloxane) include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3- (Meth) acryloyl such as acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-acryloxypropyltriethoxysilane, 3-methacryloxyethoxypropyltrimethoxysilane Di- or trialkoxysilane having a group; di- or trialkoxysilane having a vinyl group such as vinyltrimethoxysilane, vinyltriethoxysilane, p-styryltrimethoxysilane; 3-glycidoxypropyltrimethoxysilane, Di- or trialkoxysilanes having an epoxy group such as glycidoxypropyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane; 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane And di- or trialkoxysilanes having an amino group such as 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 vinyl polymer and polysiloxane) as a constituent component. More preferably, it is a polysiloxane skeleton formed by hydrolysis and condensation of 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, vinyltrimethoxysilane).

  When the polysiloxane skeleton is introduced into the vinyl polymer particles, the amount of the vinyl monomer used is preferably 100 parts by mass or more, more preferably 200 parts by mass or more with respect to 100 parts by mass of the silane monomer. More preferably, it is 300 parts by mass or more, preferably 700 parts by mass or less, more preferably 600 parts by mass or less, and still more preferably 500 parts by mass or less.

  The ratio of the crosslinkable monomer (total of vinyl-based crosslinkable monomer and silane-based crosslinkable monomer) in the total monomers constituting the vinyl polymer particles is excellent in elastic deformation and restoring force. Therefore, 20 mass% or more is preferable, More preferably, it is 30 mass% or more, More preferably, it is 50 mass% or more. When the ratio of the crosslinkable monomer is within the above range, the restoring force can be improved while maintaining excellent elastic deformation characteristics. The upper limit of the ratio of the crosslinkable monomer is not particularly limited, but depending on the type of the crosslinkable monomer used, if the ratio of the crosslinkable monomer is too large, it becomes too hard and compressively deforms during anisotropic conductive connection. Therefore, a high pressure may be required. Therefore, the proportion of the crosslinkable monomer is preferably 95% by mass or less, more preferably 90% by mass or less, and still more preferably 85% by mass or less.

  The vinyl polymer particles can be produced, for example, by polymerizing a vinyl monomer. Specifically, (i) a monomer composition containing a vinyl monomer as a polymerization component is used. A conventionally known method of aqueous suspension polymerization, dispersion polymerization, emulsion polymerization; (ii) after obtaining a vinyl group-containing polysiloxane using a silane monomer, the vinyl group-containing polysiloxane and the vinyl group Polymerization (radical polymerization) with a monomer; (iii) a so-called seed polymerization method in which a vinyl monomer is radically polymerized after the vinyl monomer is absorbed into the seed particles.

  In the said manufacturing method (i), you may use together the silane compound which has vinyl groups, such as the said silane compound which has two or more vinyl groups, and the di- or trialkoxysilane which has a vinyl group as a vinyl-type monomer. . In the production method (ii), vinyl polymer particles into which a polysiloxane skeleton is introduced can be obtained by using a silane-based crosslinkable monomer capable of forming at least the third form.

In the production method (iii), it is preferable to use non-crosslinked or low-crosslinked polystyrene particles or polysiloxane particles as seed particles. By using polysiloxane particles as seed particles, a polysiloxane skeleton can be introduced into the vinyl polymer.
Polysiloxane particles obtained by (co) hydrolytic condensation of a composition containing a silane-based crosslinkable monomer capable of forming the third form (crosslinking between vinyl polymer and polysiloxane) Particles are preferred, and vinyl group-containing polysiloxane particles are particularly preferred. When the polysiloxane particles have a vinyl group, the resulting vinyl polymer particles are particularly excellent in elastic deformation and contact pressure because the vinyl polymer and the polysiloxane skeleton are bonded via the silicon atoms constituting the polysiloxane. It will be a thing. The vinyl group-containing polysiloxane particles can be produced, for example, by (co) hydrolytic condensation of a silane monomer (mixture) containing a vinyl group-containing di- or trialkoxysilane.

  Moreover, when the said vinyl polymer particle contains polysiloxane frame | skeleton, it is also a preferable aspect to heat-process a base material particle. The heat treatment is preferably performed in an air atmosphere or an inert atmosphere, and more preferably performed in an inert atmosphere (for example, in a nitrogen atmosphere). The temperature of the heat treatment is preferably 120 ° C. (more preferably 180 ° C., more preferably 200 ° C.) or more, and preferably a thermal decomposition temperature (more preferably 350 ° C., more preferably 330 ° C.) or less. The heat treatment time is preferably 0.3 hours (more preferably 0.5 hours, more preferably 0.7 hours) or more, and preferably 10 hours (more preferably 5.0 hours, still more preferably 3.0 hours). The following are preferred.

1-3-2. Amino resin particles The amino resin particles are preferably composed of a condensate of an amino compound and formaldehyde.
Examples of the amino compounds include benzoguanamine, cyclohexanecarboguanamine, cyclohexenecarboguanamine, acetoguanamine, norbornenecarboguanamine, guanamine compounds such as spiroguanamine, and polyfunctional amino compounds such as compounds having a triazine ring structure such as melamine. . Among these, polyfunctional amino compounds are preferable, compounds having a triazine ring structure are more preferable, and melamine and guanamine compounds (particularly benzoguanamine) are particularly preferable. The amino compound may be used alone or in combination of two or more.

  The amino resin particles preferably contain 10% by mass or more of a guanamine compound in the amino compound, more preferably 20% by mass or more, and still more preferably 50% by mass or more. When the content ratio of the guanamine compound in the amino compound is within the above range, the particle size distribution is sharper and the particle size is precisely controlled. In addition, it is also preferable to use only a guanamine compound as an amino compound.

Amino resin particles can be obtained, for example, by reacting an amino compound and formaldehyde in an aqueous medium (addition condensation reaction). Usually, this reaction is performed under heating (50 to 100 ° C.). Further, the degree of crosslinking can be increased by carrying out the reaction in the presence of an acid catalyst such as dodecylbenzenesulfonic acid or sulfuric acid.
Examples of the method for producing amino resin particles include, for example, JP-A No. 2000-256432, JP-A No. 2002-293854, JP-A No. 2002-293855, JP-A No. 2002-293856, and JP-A No. 2002-293857. JP, 2003-55422, JP 2003-82049, JP 2003-138823, JP 2003-147039, JP 2003-171432, JP 2003-176330, It is preferable to apply the amino resin crosslinked particles described in JP-A-2005-97575, JP-A-2007-186716, JP-A-2008-101040, JP-A-2010-248475, and the production method thereof.

  As a specific example, the polyfunctional amino compound and formaldehyde are reacted (addition condensation reaction) in an aqueous medium (preferably a basic aqueous medium) to form a condensate oligomer, and the condensate oligomer is dissolved or dispersed. Crosslinked amino resin particles can be produced by mixing and curing an acid catalyst such as dodecylbenzenesulfonic acid or sulfuric acid in the aqueous medium. It is preferable that both the step of generating the condensate oligomer and the step of preparing the amino resin having a crosslinked structure are performed in a state of being heated at a temperature of 50 to 100 ° C. In addition, amino resin particles having a sharp particle size distribution can be obtained by performing the addition condensation reaction in the presence of a surfactant.

1-3-3. Organopolysiloxane Particles Organopolysiloxane particles (co) hydrolyze one or more silane monomers (silane crosslinkable monomers, silane noncrosslinkable monomers) that do not contain vinyl groups. It is obtained by decomposing and condensing.
Examples of the silane monomer not containing a vinyl group include trifunctional silane monomers such as methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, and phenyltrimethoxysilane. Di- or trialkoxysilanes having an epoxy group such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane; Examples thereof include di- or trialkoxysilanes having an amino group such as propyltrimethoxysilane and 3-aminopropyltriethoxysilane.

  As described above, the present invention is intended for application to fine pitch connection in various electronic devices, and is intended for conductive fine particles having a smaller particle diameter. Accordingly, the resin particles (base particles) serving as the base material for the conductive fine particles have a small particle size, and the number average particle size is 1.0 μm or more and 3.0 μm or less. The number average particle diameter is preferably 1.5 μm or more, more preferably 2.0 μm or more, preferably 2.8 μm or less, more preferably 2.7 μm or less, still more preferably 2.6 μm or less, Still more preferably, it is 2.5 μm or less. When the particle diameter of the substrate particles is smaller than 1.0 μm, it is difficult to obtain a sufficient contact area with the electrode even if the conductive fine particles are compressed and deformed, and the connection resistance value is increased. On the other hand, when the particle diameter of the substrate particles is larger than 3.0 μm, a short circuit due to contact between adjacent conductive fine particles tends to occur.

  The number-based variation coefficient (CV value) of the particle diameter of the substrate particles is preferably 20% or less, more preferably 15% or less, and further preferably 10% or less. The number average particle diameter of the base particles and the number-based variation coefficient (CV value) of the particle diameter can be determined using, for example, a particle size distribution measuring apparatus employing a Coulter counter method. It can also be determined using a flow particle image analyzer.

10% K value of the base particles is desirable is 1000 N / mm ² or more, more preferably 4000 N / mm ² or more, more preferably 5000N / mm ² or more, preferably at 70000N / mm ² or less More preferably, it is 60000 N / mm ² or less, and further preferably 50000 N / mm ² or less. If the 10% K value of the base particle is too small, the surrounding binder cannot be removed sufficiently when used as an anisotropic conductive material, or the biting into the electrode is weak, resulting in low connection resistance. There is a possibility that it cannot be obtained. On the other hand, if the 10% K value of the base particles is too large, there is a possibility that an electrically good contact state cannot be secured with respect to the connection site.

  The 10% K value of the base particle is a compression elastic modulus when the particle is compressed by 10%. For example, a known micro-compression tester (for example, “MCT-W500” manufactured by Shimadzu Corporation) is used. , Compressive load (N) and compressive displacement (mm) when a particle is deformed until a compressive displacement is 10% of the particle diameter by applying a load at a load load rate of 2.2295 mN / sec at the center of the particle at room temperature Can be determined based on the following formula.

(Where E: compression modulus (N / mm ² ), F: compression load (N), S: compression displacement (mm)
, R: radius (mm) of the particle. )

1-4. Method for producing conductive fine particles The method for forming the conductive metal layer is not particularly limited. For example, a method in which the surface of the substrate particles is plated by an electroless plating method, an electrolytic plating method, or the like; A conventionally known method such as a method of forming a conductive metal layer by a physical vapor deposition method such as plating or ion sputtering can be employed. Among these, the electroless plating method is particularly preferable because a conductive metal layer can be easily formed without requiring a large-scale apparatus. Hereinafter, the formation of the conductive metal layer by the electroless plating method will be described in detail.

  When the conductive metal layer is formed on the substrate particles by the electroless plating method, it is preferable to perform the electroless plating step after the etching treatment step and the catalyst treatment step.

Etching treatment step In the etching treatment step, for example, an oxidizing agent such as chromic acid, chromic anhydride-sulfuric acid mixture, permanganic acid; strong acid such as hydrochloric acid, sulfuric acid, hydrofluoric acid, nitric acid; strong acid such as sodium hydroxide, potassium hydroxide, etc. Using an alkaline solution; etc., hydrophilicity is imparted to the surface of the substrate particles, and the wettability to the subsequent electroless plating solution is increased. Further, minute irregularities are formed on the surface of the substrate particles, and the adhesion effect between the substrate particles and the conductive metal layer after the electroless plating process described later is aimed at by the anchor effect of the irregularities.

Catalytic Treatment Step In the catalytic treatment step, a catalyst layer (a layer of palladium catalyst or the like) that serves as a base point for plating deposition is formed on the surface of the substrate particles. The method for forming the catalyst layer is not particularly limited, and may be performed using a commercially available catalyzing reagent for electroless plating. For example, a solution containing palladium dichloride and tin dichloride is used as a catalyzing reagent, and the catalyst particles are adsorbed on the surface of the substrate particles by immersing the substrate particles in the reagent, and then an acid or water such as sulfuric acid or hydrochloric acid is used. A method of depositing palladium nuclei on the surface of the substrate particles by reducing the palladium ions with an alkali solution such as sodium oxide (catalyst-acceleration method) or a solution containing tin ions (Sn ²⁺ ) (dichloride dichloride) The base material particles are brought into contact with the base material particles by contacting the base material particles with a tin solution, etc., and then immersed in a solution containing palladium ions (Pd ²⁺ ) (such as a palladium dichloride solution). A method of depositing palladium nuclei on the particle surface (sensitizing-activating method) or the like is preferably employed.
The liquid temperature and immersion time when immersing the substrate particles in the tin ion-containing solution or palladium ion-containing solution may be adjusted as appropriate as long as each ion can be sufficiently adsorbed to the substrate particles, and is not particularly limited. For example, the liquid temperature is preferably 10 ° C to 60 ° C, and the immersion time is preferably 1 minute to 120 minutes.

Electroless Plating Step In the electroless plating step, electroless plating treatment is performed on the surface of the base material particles (hereinafter referred to as “catalyzed base material particles”) on which the catalyst layer (for example, palladium nucleus) is formed in the catalytic treatment step. To form a conductive metal layer. In the electroless plating treatment, the catalytic base material particles are immersed in a plating solution in which a reducing agent and a desired metal salt are dissolved, and the metal ions in the plating solution are reduced with the reducing agent from the catalyst. A desired metal is deposited on the surface of the material particles to form a conductive metal layer.

  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. Here, in order to develop stable conductive characteristics, it is preferable that the catalyst base material particles are sufficiently dispersed in an aqueous medium to be plated. This is because when the electroless plating treatment is performed in a state where the catalyst base material particles are aggregated, an untreated surface (a surface on which no conductive metal layer is present) is formed on the contact surface between the base material particles. 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. In addition, an ultrasonic wave or a dispersant (such as a surfactant) may be used in combination.

  Next, an aqueous slurry of the catalyzed substrate particles prepared above is added to an electroless plating solution containing a desired conductive metal salt, reducing agent, complexing agent, various additives, and the like. Causes an electroplating reaction. The electroless plating reaction starts quickly when an aqueous slurry of catalyzed substrate particles is added. 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 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 conductive metal salt contained in the electroless plating solution include metal chlorides, sulfates, acetates and the like exemplified as the metal constituting the conductive metal layer. For example, when a nickel layer is formed as the conductive metal layer, a nickel salt such as nickel chloride, nickel sulfate, or nickel acetate may be included in the electroless plating solution. Only one type of conductive metal salt may be used, or two or more types may be used. What is necessary is just to determine suitably the density | concentration of the electroconductive metal salt in an electroless plating liquid in consideration of the size (surface area) of a base particle, etc. so that the electroconductive metal layer of a desired film thickness may be formed.

  Examples of the reducing agent contained in the electroless plating solution include formaldehyde, sodium hypophosphite, dimethylamine borane, sodium borohydride, potassium borohydride, potassium tetrahydroborate, glyoxylic acid, hydrazine, and the like. . Only one reducing agent may be used, or two or more reducing agents may be used.

As the complexing agent contained in the electroless plating solution, a compound having a complexing action on ions of conductive metal can be used. For example, compounds having a complexing action on nickel include citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid, gluconic acid or carboxylic acids (salts) such as alkali metal salts and ammonium salts thereof; Amino acids; amine acids such as ethylenediamine and alkylamine; other ammonium, EDTA, pyrophosphate (salt); and the like. Only one type of complexing agent may be used, or two or more types may be used.
The pH of the electroless plating solution is not limited, but is preferably 4-14.

  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 performed on the substrate particles to obtain nickel-coated particles, the nickel-coated particles are further poured into an electroless gold plating solution to perform gold displacement plating, whereby the outermost layer is covered with a gold layer, Conductive fine particles having a nickel layer inside are obtained.

  In addition, although the said conductive metal layer should just coat | cover at least one part of the base-material particle | grain surface, the substantial crack and the conductive metal layer are not formed in the surface of a conductive metal layer. It is preferred that no surface be present. Here, “substantially cracked or a surface on which no conductive metal layer is formed” means that when the surface of any 10,000 conductive particles is observed using an electron microscope (1000 times magnification), It means that the crack of the conductive metal layer and the exposure of the surface of the base material particles are not substantially visually observed.

Deionization process The conductive fine particles obtained as described above are chloride ions and sodium ions derived from the environment and reagents (catalytic reagents used in electroless plating methods and electrolytic plating methods, electroless plating solutions, etc.). The chloride ion content is, for example, about 50 μg / g to 2000 μg / g (particularly about 50 μg / g to 500 μg / g). The content of sodium ions is, for example, about 50 μg / g to 2000 μg / g (particularly about 50 μg / g to 500 μg / g). Therefore, in the present invention, after a conductive metal layer is formed on the surface of the substrate particles, the obtained conductive fine particles are heat-treated using an alcohol / water mixed solvent (deionization process step). By heat-treating with a mixed solvent in which alcohol is added to water, the ability to remove chloride ions and sodium ions can be increased, and even if the particle size of the conductive fine particles is small, the concentration of these ions is kept below a predetermined value. It becomes possible.

  As means for reducing the amount of halogen ions and alkali metal ions such as chloride ions and sodium ions, Patent Documents 1 and 2 disclose that materials used in the manufacturing process of conductive fine particles have a low content of halogen ions and alkali metal ions. There have been proposed a method of selecting and using a method, and a method of introducing a step of washing conductive fine particles with distilled water at 100 ° C. or higher under pressure, as a production step of conductive fine particles. However, it is not realistic to completely eliminate halogen ions and alkali metal ions in the electroless plating method and the electrolytic plating method. In addition, the conductive fine particles having a small particle size that can cope with further miniaturization and narrowing cannot sufficiently reduce chloride ions and sodium ions even by the above-mentioned method, and the conductive characteristics are not good when exposed to high temperature and high humidity conditions. It became clear in the examination of the present inventors that it deteriorates with time.

  Therefore, the present inventors have further studied and heat-treating the conductive fine particles using an alcohol / water mixed solvent, so that even if the conductive fine particles have a small particle diameter, halogen such as chloride ion or sodium ion or the like. It has been found that the alkali metal ion content can be reduced. That is, when the particle size of the conductive fine particles is reduced, the dispersibility of the conductive fine particles in the aqueous medium is lowered. In particular, in the heat treatment using only water as a medium, the surface of the conductive fine particles is wetted with water (medium). Therefore, it is considered that the removal of the ion component is insufficient. Therefore, in the present invention, alcohol is used as a part of a medium (also referred to as a processing medium) for heat-treating the conductive fine particles, thereby reducing the surface tension of the processing medium and improving the wettability between the conductive fine particles and the processing medium. By increasing it, effective ion removal is realized.

  The alcohol used in the alcohol / water mixed solvent is preferably a linear or branched lower alcohol having 1 to 4 carbon atoms, specifically, methanol, ethanol, n-propanol, isopropanol, butanol, etc. Is mentioned. These alcohols may be used individually by 1 type, and 2 or more types may be mixed and used for them. Among these, methanol, ethanol, or isopropanol is preferable because wettability between the conductive fine particles and the treatment medium is improved and ions can be efficiently removed from the conductive fine particles.

  The blending amount of the alcohol in the alcohol / water mixed solvent is preferably 1.0% by volume or more, more preferably 3.0% by volume or more, further preferably 100% by volume based on the total amount of alcohol and water. Is 5.0% by volume or more, preferably 90% by volume or less, more preferably 80% by volume or less, and still more preferably 70% by volume or less. If the blending amount of the alcohol is out of the above range, a sufficient ion removal effect may not be obtained.

  In addition, the water used as the cleaning medium preferably has a low content of halogen ions or alkali metal ions. For example, the water is treated with an ultrapure water apparatus equipped with various filter media such as a filter, an ion exchange membrane, and a reverse osmosis membrane. It is recommended to use ultrapure water (specific resistance of 18 MΩ · cm or more).

  In addition, the alcohol / water mixed solvent used in the washing step may contain components other than alcohol and water. For example, organic solvents other than alcohol (aromatic hydrocarbons such as toluene, acetone, methyl ethyl ketone, etc. Ketones, esters such as ethyl acetate, aliphatic hydrocarbons such as hexane, etc.) and dispersants (polymer dispersants, surfactants, etc.) that improve the dispersibility of the conductive fine particles. In addition, it is preferable that the compounding quantity of these components shall be 0.1 part or more and 10 parts or less with respect to 100 parts of alcohol / water mixed solvents.

  The amount of the alcohol / water mixed solvent used is preferably 200 parts or more and 10,000 parts or less with respect to 100 parts of the conductive fine particles. More preferably, it is 300 parts or more, More preferably, it is 500 parts or more, More preferably, it is 9000 parts or less, More preferably, it is 8000 parts or less. If the use amount of the alcohol / water mixed solvent is too small, it is difficult to obtain a sufficient ion removal effect. On the other hand, even if it is used in a large amount, it is difficult to obtain an effect commensurate with the use amount, and a large amount of processing solution is discharged. Therefore, it is not preferable in terms of environment and economy.

  Further, the deionization treatment step is performed by heating the alcohol / water mixed solvent to 100 ° C. or higher. Preferably it is 105 degreeC or more, More preferably, it is 110 degreeC or more, More preferably, it is 120 degreeC or more, Preferably it is 200 degreeC or less, More preferably, it is 180 degreeC or less, More preferably, it is 170 degreeC or less. If the temperature of the alcohol / water mixed solvent is too low, the effect of removing ions may be insufficient. On the other hand, if the temperature is too high, the conductive metal layer may be damaged or oxidized due to the oxidation of the conductive metal layer. When used as fine particles, the resistance value may increase. Further, the deionization process may be performed under pressure. The duration of the deionization process is preferably 0.5 hours or longer, more preferably 1 hour or longer, preferably 50 hours or shorter, more preferably 20 hours or shorter. If the deionization time is outside the above range, the ion removal effect may be insufficient, or the deionization process may become inefficient.

  The deionization process is not particularly limited as long as the conductive fine particles are dispersed in an alcohol / water mixed solvent, and the deionization process may be performed either batchwise or continuously. In addition, since the deionization process according to the present invention is performed under a heating condition of 100 ° C. or more, from the viewpoint of preventing alcohol and water from vaporizing and changing the composition of the processing medium, it is a batch type. It is preferable to carry out. For the same reason, the deionization process is preferably carried out with a conventionally known sealable device such as an autoclave. You may perform a deionization process process, stirring the dispersion liquid of electroconductive fine particles.

  The deionization process is performed after the conductive metal layer is formed (for example, after the electroless plating process). When the electroless plating process is repeatedly performed, the timing and number of times of the deionization process are not particularly limited, and the deionization process may be performed each time, or the first electroless plating process may be performed. After the process, it may be carried out once or more at any stage such as after the second and subsequent electroless plating processes. From the viewpoint of efficiently reducing the amount of chloride ions and sodium ions, it is preferable to carry out a deionization treatment step after the first electroless plating step and / or after the last electroless plating step. More preferably, a deionization process is performed after the plating process.

2. Conductive fine particles having protrusions The conductive fine particles of the present invention may have a smooth surface or an uneven shape, but when used as an anisotropic conductive material, the binder resin is effectively excluded. Thus, it is preferable to have a plurality of protrusions in that the connection with the electrode can be performed. By having the protrusion, connection reliability when the conductive fine particles are used for connection between the electrodes can be improved.

  As a method of forming protrusions on the surface of the conductive fine particles, (1) after obtaining base particles having protrusions on the surface using a phase separation phenomenon of a polymer in a polymerization step in base particle synthesis A method of forming a conductive metal layer by electroless plating; (2) electroless after depositing inorganic particles such as metal particles and metal oxide particles or organic particles made of an organic polymer on the surface of the substrate particles; A method of forming a conductive metal layer by plating; (3) after performing electroless plating on the surface of the substrate particles, and attaching organic particles made of inorganic particles or organic polymers such as metal particles and metal oxide particles; (4) Utilizing the self-decomposition of the plating bath during the electroless plating reaction, depositing a metal that forms the core of the protrusion on the surface of the substrate particles, and further performing the electroless plating , Protrusion How the conductive metal layer to form a conductive metal layer which becomes continuous film comprising; and the like.

  The height of the protrusions of the conductive fine particles is preferably 20 nm to 1000 nm, more preferably 30 nm to 800 nm, still more preferably 40 nm to 600 nm, and particularly preferably 50 nm to 500 nm. When the height of the protrusion is within the above range, the connection reliability is further improved. The height of the protrusion is determined by observing 10 arbitrary conductive fine particles with an electron microscope. Specifically, for the protrusions on the periphery of the conductive fine particles to be observed, the height of any ten protrusions per conductive fine particle is measured, and the measured value is obtained by arithmetic averaging.

  The number of protrusions is not particularly limited, but it is preferable to have at least one protrusion on any orthographic projection surface when the surface of the conductive fine particles is observed with an electron microscope from the viewpoint of ensuring high connection reliability. More preferably 5 or more, and still more preferably 10 or more.

3. Insulating Coated Conductive Fine Particle The conductive fine particle of the present invention may be in an embodiment having an insulating layer on at least a part of the surface (insulating coated conductive fine particle). If an insulating layer is further laminated on the conductive metal layer on the surface in this way, it is possible to prevent lateral conduction that is likely to occur when a high-density circuit is formed or when a terminal is connected.

  The thickness of the insulating layer is preferably 0.005 μm to 1 μm, more preferably 0.01 μm to 0.8 μm. When the thickness of the insulating layer is within the above range, the electrical insulation between the particles becomes good while maintaining the conduction characteristics by the conductive fine particles.

  The insulating layer is not particularly limited as long as the insulating property between the particles of the conductive fine particles can be ensured, and the insulating layer can be easily collapsed or peeled off by a certain pressure and / or heating. Polyolefins; (meth) acrylate polymers and copolymers such as polymethyl (meth) acrylate; polystyrene; thermoplastic resins such as polystyrene; and cross-linked products thereof; thermosetting resins such as epoxy resins, phenol resins, and melamine resins; polyvinyl alcohol Water-soluble resins such as, and mixtures thereof; organic compounds such as silicone resins; or inorganic compounds such as silica and alumina.

  The insulating layer may be a single layer or a plurality of layers. For example, a single or a plurality of film-like layers may be formed, or a layer in which particles having an insulating property, spherical shape, block shape, scale shape, or other shape are attached to the surface of the conductive metal layer Further, it may be a layer formed by chemically modifying the surface of the conductive metal layer, or a combination thereof. Among these, a mode in which insulating particles (hereinafter referred to as “insulating particles”) adhere to the surface of the conductive metal layer is preferable.

  The average particle diameter of the insulating particles is appropriately selected depending on the average particle diameter of the conductive fine particles and the use of the insulating coated conductive fine particles, but the average particle diameter of the insulating particles is preferably in the range of 0.005 μm to 1 μm. More preferably, it is 0.01 micrometer-0.8 micrometer. When the average particle diameter of the insulating particles is smaller than 0.005 μm, the conductive layers between the plurality of conductive fine particles are easily brought into contact with each other. When the average particle diameter is larger than 1 μm, it is exhibited when the conductive fine particles are sandwiched between the opposing electrodes. There is a possibility that the electrical conductivity should be insufficient.

  The coefficient of variation (CV value) in the average particle diameter of the insulating particles is preferably 40% or less, more preferably 30% or less, and most preferably 20% or less. If the CV value exceeds 40%, the conductivity may be insufficient.

  The average particle diameter of the insulating particles is preferably 1/1000 or more and 1/5 or less of the average particle diameter of the conductive fine particles. When the average particle diameter of the insulating particles is within the above range, the insulating particle layer can be uniformly formed on the surface of the conductive fine particles. Two or more kinds of insulating particles having different particle diameters may be used.

  The insulating particles may have a functional group on the surface in order to improve adhesion to the conductive fine particles. Examples of the functional group include amino group, epoxy group, carboxyl group, phosphoric acid group, silanol group, ammonium group, sulfonic acid group, thiol group, nitro group, nitrile group, oxazoline group, pyrrolidone group, sulfonyl group, and hydroxyl group. Can be mentioned.

  The coverage of insulating particles on the surface of the conductive fine particles (the orthographic surface of the insulating coated conductive fine particles) is preferably 1% to 98%, more preferably 5% to 95%. When the coverage of the conductive fine particles by the insulating particles is in the above range, it is possible to reliably insulate adjacent insulating coated conductive fine particles while ensuring sufficient electrical conductivity. Note that the coverage is determined by, for example, observing the surface of any 100 insulating coated conductive fine particles using an electron microscope, and the portion of the orthographic projection surface of the insulating coated conductive fine particles coated with the insulating particles and the resin. It can be evaluated by measuring the area ratio of the uncoated part of the particles.

4). Anisotropic Conductive Material The conductive fine particles of the present invention are useful as 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 resin, styrene resin, ethylene-vinyl acetate resin, styrene-butadiene block copolymer; epoxy resin, phenol resin And thermosetting resins such as urea resin, polyester resin, urethane resin, and polyimide resin.

  For binder resin compositions, fillers, softeners, accelerators, anti-aging agents, colorants (pigments, dyes), antioxidants, various coupling agents, light stabilizers, UV absorbers, lubricants as necessary. Further, an antistatic agent, a flame retardant, a heat conduction improver, an organic solvent, and the like can be blended.

  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 separately used for connection. The conductive fine particles may be present together with the binder resin between the base materials and between the electrode terminals.

  In the anisotropic conductive material, the content of the conductive fine particles may be appropriately determined according to the use. For example, the volume is preferably 0.01% by volume or more, more preferably based on the total amount of the anisotropic conductive material. Is 0.03% by volume or more, more preferably 0.05% 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, the coating thickness of the paste or adhesive, the printed film thickness, etc., considering the particle diameter of the conductive fine particles to be used and the specifications of the electrodes to be connected. It is preferable to set appropriately so that the conductive fine particles are held between the electrodes to be connected and 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.

1. Evaluation method 1-1. Number average particle size, coefficient of variation (CV value)
<Seed particles, substrate particles>
Measure the particle size of 30000 particles with a particle size distribution measuring device (“Coulter Multisizer III type”, manufactured by Beckman Coulter, Inc.) to obtain the average particle size based on the number and the standard deviation of the particle size. The CV value (coefficient of variation) based on the number of diameters was calculated.
Particle variation coefficient (%) = 100 × (standard deviation of particle diameter / number-based average particle diameter)

  In addition, in the base particle, 20 parts of a 1% aqueous solution of a surfactant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., “Hytenol (registered trademark) N-08”) is added to 0.005 part of the base particle. A dispersion liquid dispersed for 10 minutes was used as a measurement sample. For seed particles, a dispersion obtained by hydrolysis and condensation reaction was diluted with a 1% aqueous solution of a surfactant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., “Hitenol (registered trademark) N-08”). A sample was used.

1-2. The thickness of the conductive metal layer 0.05 g of the conductive fine particles was mixed with 8 ml of aqua regia and stirred at a temperature of 80 ° C. to completely dissolve the conductive metal layer of the conductive fine particles. Next, the concentration of nickel or nickel and gold and other alloy elements in the solution in which the conductive metal layer was dissolved was analyzed with an ICP emission analyzer (CIROS120, manufactured by Rigaku Corporation). The layer thickness was calculated.

In the formula, r is the radius of the base particle (μm), t is the thickness of the nickel layer (μm), 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) content (mass%), X is the gold content (mass%).

When the conductive metal layer has a multilayer structure of two or more layers and the X is more than 0, the thickness of the gold layer was calculated from the following formula (2 ′).

In the formula, a is the thickness of the gold layer (μm), d _Au is the density of the gold layer, d _{(base + Ni)} is the density of the nickel product (nickel layer + base particle), and X is the gold content ( Mass%). Here, the density d _{(base + Ni)} of the nickel product was calculated using the above formula (3). In the formula, d _Ni is the density of the nickel layer, d _base is the density of the base particles, and W is the nickel layer component (nickel, phosphorus) content (% by mass).

1-3. Content of chloride ion and sodium ion contained in conductive fine particles Teflon (registered trademark) inner cylinder type airtight container (pressure-resistant glass industry Co., Ltd.) having a stainless steel outer cylinder and a Teflon (registered trademark) inner cylinder After the inner cylindrical container (made) was washed with distilled water, 1 g of precisely weighed conductive fine particles and 10 mL of distilled water (specific resistance 18 MΩ · cm) were added, and then the container was sealed. The container was heated in an electric oven at 120 ° C. for 24 hours, then the container was opened, and the resulting extract was filtered through a 0.1 μm membrane filter. The amount of chloride ions and sodium ions in the solution was determined by ICP. Measured with an emission spectrometer (ICS-2000, manufactured by DIONEX).
A blank test was performed in the same manner except that the conductive fine particles were not used, and the amount of eluted ions per 1 g of the conductive fine particles was calculated.

1-4. Resistance Value Evaluation 0.1 g of conductive fine particles 1 g and silica particles having a diameter corresponding to 70% of the diameter of the base particles are added to 100 g of an epoxy resin (manufactured by Mitsui Chemicals, Structbond (registered trademark) XN-5A). 5 g was added and stirred uniformly to prepare a resin paste (anisotropic conductive adhesive).
This resin paste is sandwiched between the ITO electrodes between the two glass substrates on which the ITO electrodes are formed and subjected to thermocompression bonding at 160 ° C. and a pressure of 50 kg / cm ² for 30 minutes. Was used to measure the initial resistance value (Ω). Next, the sample was placed in a constant temperature and humidity chamber at 85 ° C. and a relative humidity of 85%, and after standing for 100 hours, the resistance value (resistance value after high temperature and high humidity treatment (Ω)) was measured again. Also, based on the measured initial resistance value and the resistance value after high-temperature and high-humidity treatment, the resistance value increase rate is calculated from the following formula, and when the resistance value increase rate is 20% or less, ◎, more than 20% , 30% or less was evaluated as ○, and more than 30% as ×.
Resistance value increase rate (%) = 100 × [(resistance value after high-temperature and high-humidity treatment (Ω)) − (initial resistance value (Ω)] / (initial resistance value (Ω))

2. 2. Production of substrate particles 2-1. Synthesis example 1
In a four-necked flask equipped with a condenser, a thermometer, and a dropping port, 1800 parts of ion-exchanged water, 24 parts of 25% aqueous ammonia and 550 parts of methanol are placed, and 3-methacryloxypropyltrimethoxy is added from the dropping port with stirring. A mixed liquid of 50 parts of silane and 50 parts of methanol was added, and hydrolysis and condensation reaction of 3-methacryloxypropyltrimethoxysilane was performed to prepare an emulsion of organopolysiloxane particles.

Next, 35.0 parts of a 20% aqueous solution of polyoxyethylene styrenated phenyl ether sulfate ammonium salt ("Haitenol (registered trademark) NF-08" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as an emulsifier is added with 200 parts of ion-exchanged water. In the dissolved solution, 120 parts of styrene, 30 parts of divinylbenzene 960 (manufactured by Nippon Steel Chemical Co., Ltd., containing 96% by weight of divinylbenzene, 4% of vinyl-based non-crosslinkable monomer (such as ethyl vinylbenzene)) and 2,2 A solution in which 2.5 parts of '-azobis (2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd., “V-65”) is dissolved is added and emulsified and dispersed to prepare an emulsion of monomer components. did.
Two hours after the start of emulsification dispersion, the obtained emulsion was added to the emulsion of polysiloxane particles, and further stirred. Two hours 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, the reaction solution was heated to 65 ° C. in a nitrogen atmosphere and held at 65 ° C. for 2 hours to perform radical polymerization of the monomer component. 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 vacuum-dried at 80 ° C. for 12 hours to obtain substrate particles (1). When the particle size of the substrate particles (1) was measured with a Coulter Multisizer III type (manufactured by Beckman Coulter, Inc.), the number average particle size was 2.5 μm and the coefficient of variation (CV value) was 3.8%. .

2-2. Synthesis example 2
In preparing the emulsion of polysiloxane particles (seed particles), the base material was prepared in the same manner as in Synthesis Example 1 except that the amount of ion-exchanged water was changed to 1600 parts and the amount of methanol used was changed to 800 parts. Particles (2) were obtained. When the particle size of the substrate particles (2) was measured with a Coulter Multisizer III type (manufactured by Beckman Coulter, Inc.), the number average particle size was 3.0 μm and the coefficient of variation (CV value) was 3.5%. .

3. 3. Production of conductive fine particles 3-1. Example 1
<Preparation of conductive fine particles>
In a beaker, 50 parts of “Pink Summer (manufactured by Nippon Kanigen Co., Ltd .: tin chloride aqueous solution)” and 400 parts of ion-exchanged water were mixed. Separately, 50 parts of ion-exchanged water was prepared by ultrasonically dispersing 10 parts of base material particles (1) previously etched using a sodium hydroxide aqueous solution, and this dispersion was added to the mixture. After stirring for 10 minutes at 30 ° C. to obtain a suspension, the cake obtained by solid-liquid separation was washed with ion-exchanged water and methanol in this order, and dried in a vacuum at 100 ° C. for 2 hours in a nitrogen atmosphere. Went.

  Next, 10 parts of the dried particles are ultrasonically dispersed in 50 parts of ion-exchanged water, and 100 parts of “Red Schumer (Nihon Kanisen Co., Ltd .: palladium chloride aqueous solution)” and 350 parts of ion-exchanged water are mixed. The mixed solution was added and stirred at 30 ° C. for 10 minutes to obtain a suspension. This suspension was subjected to solid-liquid separation, and the resulting cake was washed with ion-exchanged water and methanol in that order, and vacuum-dried at 100 ° C. for 2 hours in a nitrogen atmosphere, so that palladium was deposited on the surface of the base particle (1). Adsorbed.

  The substrate particles (1) activated with palladium were mixed with 500 parts of ion-exchanged water, subjected to ultrasonic treatment for 30 minutes, and the particles were sufficiently dispersed to obtain a fine particle suspension. An electroless plating solution containing nickel sulfate hexahydrate 50 g / L, sodium hypophosphite monohydrate 40 g / L, and sodium citrate 50 g / L at a temperature of 50 ° C. while stirring the fine particle suspension. The base particles (1) were electroless nickel plated by gradually adding to the fine particle suspension. When the nickel plating layer having a thickness of 0.09 μm was formed on the surface of the substrate particles, dropping of the electroless plating solution was completed. The obtained nickel-plated base particles were separated by filtration, ultrasonically dispersed in a mixed solvent consisting of 50 ml of isopropanol / 950 ml of distilled water, and stirred (deionization treatment) at 120 ° C. for 10 hours in an autoclave equipped with a stirrer. Then, it filtered and vacuum-dried at 100 degreeC for 1 hour, and obtained electroconductive fine particles (1). The thickness of the nickel-based metal layer and the thickness of the gold layer in the obtained conductive fine particles were measured and as shown in Table 1.

3-2. Example 2
The nickel-plated substrate particles after the electroless plating step were made conductive by the same method as in Example 1 except that the deionization treatment with a mixed solvent consisting of 50 ml of isopropanol / 950 ml of distilled water was repeated twice. Fine particles (2) were obtained.

3-3. Example 3
The nickel-plated substrate particles after the electroless plating step were made conductive by the same method as in Example 1 except that the deionization treatment with a mixed solvent consisting of 50 ml of isopropanol / 950 ml of distilled water was repeated three times. Fine particles (3) were obtained.

3-4. Example 4
After performing the electroless plating step by the same method as in Example 1, 5 g / L potassium gold cyanide, 12 g / L trisodium citrate, In addition to the displacement gold plating solution containing 10 g / L ethylenediaminetetraacetic acid 4 sodium salt, displacement gold plating was performed until the gold plating thickness became 0.02 μm. The obtained nickel / gold-plated base particles were separated by filtration, ultrasonically dispersed in a mixed solvent consisting of 50 ml of isopropanol / 950 ml of distilled water, and stirred (deionization treatment) at 120 ° C. for 10 hours in an autoclave equipped with a stirrer. Then, it filtered and vacuum-dried at 100 degreeC for 1 hour, and obtained electroconductive fine particles (4).

3-5. Example 5
Conductive fine particles (5) were obtained in the same manner as in Example 1 except that the base particles (2) obtained in Synthesis Example 2 were used as the base particles.

3-6. Example 6
Except for using the nickel-plated substrate particles obtained in Example 5, nickel-gold plated conductive fine particles (6) were obtained in the same manner as in Example 4.

3-7. Example 7
Conductive fine particles (7) were obtained in the same manner as in Example 1 except that the nickel-plated substrate particles after the electroless plating step were deionized with a mixed solvent of 30 ml of isopropanol / 970 ml of distilled water. )

3-8. Example 8
Conductive fine particles were produced in the same manner as in Example 1 except that the nickel-plated substrate particles after the electroless plating step were subjected to deionization treatment with a mixed solvent consisting of 10 ml of isopropanol / 990 ml of distilled water three times. (8) was obtained.

3-9. Comparative Example 1
After completion of the electroless plating process, the nickel-plated substrate particles were filtered and vacuum dried to obtain comparative conductive fine particles (1). In Comparative Example 1, deionization treatment with an alcohol / water mixed solvent was not performed.

3-10. Comparative Example 2
Comparative conductive fine particles (2) were obtained in the same manner as in Example 1 except that 1000 ml of distilled water was used instead of the mixed solvent consisting of 50 ml of isopropanol / 950 ml of distilled water.

3-11. Comparative Example 3
Comparative electroconductive fine particles (3) were obtained in the same manner as in Example 1 except that the electroless plating solution was dropped until a nickel plating layer having a thickness of 0.11 μm was formed on the surface of the substrate particles. .

3-12. Comparative Example 4
By using the same method as in Example 4 except that the comparative conductive fine particles (3) (thickness: 0.11 μm) obtained in Comparative Example 3 were used, nickel / gold plated comparative conductive fine particles (4) were obtained. It was.

  From Tables 1 and 2, the conductive fine particles of Examples 1 to 8 in which the thickness of the conductive metal layer is within a predetermined range and the contents of chloride ions and sodium ions are reduced are compared with the comparative examples. Compared to conductive fine particles, the increase in resistance before and after high-temperature and high-humidity treatment is suppressed, and these conductive fine particles are less likely to cause corrosion or poor conduction of electrodes over time even when used in various applications. it is conceivable that. In particular, in Examples 2 and 3 in which deionization treatment with a water / alcohol mixed solvent was performed a plurality of times, the content of chloride ions and sodium ions was suppressed to a low level as compared with other examples, and resistance was reduced. The rate of increase in value was also small.

  The comparative conductive particles of Comparative Examples 3 and 4 had a small amount of chloride ions and sodium ions before the resistance value evaluation, but the resistance value increase rate was 76.9% (Comparative Example 3). 177.8% (Comparative Example 4) was a large value. This is because the conductive metal layers of the comparative conductive fine particles (3) and (4) were thick, so that cracks occurred in the conductive metal layer during the high-temperature and high-humidity treatment, and the ions existed in the deep part of the conductive fine particles. This is probably because the minute oozes out over time.

  Although the conductive fine particles of the present invention have a small particle diameter, elution of chloride ions and sodium ions is suppressed. Therefore, even when exposed to high temperature and high humidity conditions, the connection resistance value is unlikely to increase. Therefore, if the conductive fine particles of the present invention and the anisotropic conductive material including the same are used for fine pitch connection, it is considered that the connection reliability between members such as electrodes provided in various electronic devices can be improved.

Claims (2)

Conductive fine particles comprising base particles made of resin and a conductive metal layer formed on the surface of the base particles,
The number average particle diameter of the base particles is 1.0 to 3.0 μm,
The conductive metal layer has a thickness of 0.01 to 0.10 μm,
Conductive fine particles having a chloride ion content of 25 µg / g or less and a sodium ion content of 40 µg / g or less.   An anisotropic conductive material comprising the conductive fine particles according to claim 1.