JP5619675B2 - Conductive fine particles and anisotropic conductive materials - Google Patents

Description

  The present invention relates to conductive fine particles that can exhibit high connection reliability even by electrical connection at a low temperature, and an anisotropic conductive material using the same.

  Conventionally, connection of a TCP (tape carrier package) or COF (chip on film) package with a driver IC for sending a signal for driving a liquid crystal display (LCD) panel or a plasma display (PDP) panel to the panel, or TCP or COF Connection to the printed wiring board, and further, anisotropy such as anisotropic conductive film (ACF) and anisotropic conductive paste (ACP) on COG (chip-on-glass) where the driver IC is mounted on the panel as it is Conductive material is used. For example, an anisotropic conductive film is a film-like adhesive in which conductive fine particles having a particle diameter of about several μm are uniformly dispersed in an adhesive, and is sandwiched between upper and lower electrodes to be connected, usually 150 to 180 ° C. By heating and pressurizing at a temperature of 5 to 10 seconds, the conductive fine particles are brought into contact with the electrode in a deformed state, and a large number of electrodes can be connected together. As the conductive fine particles used for such an anisotropic conductive material, those obtained by coating the surfaces of polymer fine particles used as metal particles or base particles with a conductive metal layer are used.

  By the way, in recent years, in electrical connection using such an anisotropic conductive material, it has been a problem that the printed wiring board or the glass substrate is bent (deformed) due to heat at the time of connection. There is a need for an anisotropic conductive material that can be connected. However, in general, when the heating temperature at the time of electrical connection is lowered, the conductive fine particles contained in the anisotropic conductive material are not easily deformed, and the contact area with the connection site becomes insufficient. As a result, the connection resistance value is increased, which hinders electrical connection.

  Therefore, attempts have been made to improve the conductive fine particles contained in the anisotropic conductive material and the anisotropic conductive material itself so as to enable electrical connection at a low temperature. For example, 20% compressive modulus (20% K value) and 30% compressive modulus (30% K value) of base material particles are set to specific ranges as conductive fine particles that can be connected at low temperature, and fracture strain is specified. Conductive fine particles set in a range have been proposed (Patent Document 1). An anisotropic conductive film using a polymerizable acrylic compound that can be cured at a relatively lower temperature than a thermosetting epoxy resin together with a film-forming resin has also been proposed (Patent Document 2).

JP 2004-165123 A JP 2010-37539 A

  However, the conductive fine particles disclosed in Patent Document 1 and Patent Document 2 are not sufficiently satisfactory in terms of connection reliability. Here, specifically, the connection reliability is a characteristic that the resistance value does not increase over time as well as the low resistance in the initial stage.

  Therefore, the present invention provides conductive fine particles that can exhibit high connection reliability even when used for electrical connection at low temperatures, and an anisotropic conductive material using the same. With the goal.

  The present inventor has intensively studied to solve the above problems. As a result, when performing electrical connection at a low temperature, the conductive fine particles are not easily deformed, and the contact area with the connection site tends to be insufficient. The idea was to construct the base particles with a polymer having a relatively low glass transition temperature. And while advancing the study according to this idea, if the glass transition temperature of the polymer constituting the base particle is set low, the resistance value increases with time, and there arises a problem that connection reliability is impaired. I found it. Therefore, as a result of further studies to solve this problem, it was found that there is an appropriate lower limit for lowering the glass transition temperature of the polymer constituting the base particle, and in addition, the resistance value over time. It was found that in order to suppress the increase in the temperature, the glass transition temperature should be optimized and the thickness of the conductive metal layer covering the base particles should be set to be thinner than a specific range. The present invention has been completed based on these findings.

  That is, the conductive fine particles according to the present invention are conductive fine particles comprising base particles and a conductive metal layer covering the surface of the base particles, and the base particles have a glass transition temperature (Tg). Is polymer particles having a temperature of 50 ° C. or more and 100 ° C. or less, and the conductive metal layer has a thickness of 0.01 to 0.15 μm.

  In the conductive fine particles of the present invention, the conductive metal layer preferably has a thickness of less than 0.10 μm. The substrate particles preferably have a number average particle diameter of 0.5 to 10.0 μm, and are obtained by polymerizing a polymerizable composition containing 5% by mass or more of a vinyl group-containing monomer and / or polymerizable polysiloxane. Preferably there is. The conductive fine particles of the present invention preferably have an insulating resin layer on at least a part of the surface.

  The anisotropic conductive material according to the present invention contains the conductive fine particles of the present invention.

  According to the present invention, high connection reliability can be exhibited even when electrical connection is performed at a low temperature. Specifically, the conductive fine particles of the present invention can be obtained by controlling both the glass transition temperature of the polymer constituting the base particle and the film thickness of the conductive metal layer within a predetermined range, thereby reducing the initial connection resistance value. Is sufficiently low, and it is possible to suppress an increase in resistance value over time, and the effect of exhibiting excellent connection reliability is achieved. Such conductive fine particles of the present invention are suitably used for anisotropic conductive materials such as anisotropic conductive films, anisotropic conductive pastes, anisotropic conductive adhesives, anisotropic conductive inks, and the like.

FIG. 1 is a graph showing the K value for each compression rate when the base particles in Examples 1, 2, 17, 18 and Comparative Examples 1 and 9 are compressed at 25 ° C. FIG. 2 is a graph showing the K value for each compression ratio when the base particles in Examples 1, 2, 17, 18 and Comparative Examples 1 and 9 are compressed at 150 ° C.

(Conductive fine particles)
The conductive fine particles of the present invention include base particles and a conductive metal layer that covers the surface of the base particles.

  It is important that the base particles constituting the conductive fine particles of the present invention are polymer particles having a glass transition temperature (Tg) of 50 ° C. or higher and 100 ° C. or lower. When the glass transition temperature of the substrate particles exceeds 100 ° C., when connecting at low temperature, the deformability of the conductive fine particles becomes insufficient, and the contact area between the connection site and the conductive fine particles tends to be small. The initial resistance value becomes high. On the other hand, when the glass transition temperature of the substrate particles is less than 50 ° C., the resistance value increases with time when the connection is performed at a low temperature. This is presumably because the base particles soften and deform each time a thermal history is received after connection, and the initial connection state cannot be maintained and a gap is formed between the conductive fine particles and the connection site. The The glass transition temperature of the polymer particles constituting the substrate particles is preferably 51.5 ° C. or higher, more preferably 52.5 ° C. or higher, still more preferably 65 ° C. or higher, more preferably 75 ° C. or higher. The temperature should preferably be 98.5 ° C. or lower, more preferably 97 ° C. or lower, more preferably 90 ° C. or lower.

  In the present invention, the glass transition temperature (Tg) of the base particles can be measured, for example, by the method described in the examples described later.

  In order to set the glass transition temperature (Tg) of the polymer particles used as the base particles within the above range, for example, the composition (type and amount) of the polymerizable composition used for the polymerization when the polymer particles are obtained. Can be adjusted. Specifically, a polymerizable compound that lowers the glass transition temperature of the polymer forming the polymer particles is used, or a crosslinkable compound contained in the polymerizable composition (that is, a polymerizable group is contained in one molecule). If the ratio of the polymerizable compound having two or more is reduced to lower the cross-linking degree of the polymer, the Tg of the base particles tends to decrease. Of course, the means for controlling the glass transition temperature of the substrate particles is not limited to this, and a known Tg control means can be appropriately employed.

  The polymerizable composition constituting the polymer particles used as the substrate particles preferably contains a vinyl group-containing monomer and / or polymerizable polysiloxane as the polymerizable compound. For example, in the case of a polymerizable composition containing a vinyl group-containing monomer, the base particle has an organic skeleton formed by polymerizing the vinyl group of the vinyl group-containing monomer, and has good deformability when connected. It becomes the particle | grains provided with the softness required in order to express. On the other hand, in the case of a polymerizable composition containing a polymerizable polysiloxane, the substrate particles have a polysiloxane skeleton derived from the polymerizable polysiloxane, and ensure a sufficient contact pressure with respect to the connection site at the time of connection. It becomes the particle | grains provided with required hardness. Most preferably, the polymerizable composition should contain both a vinyl group-containing monomer and a polymerizable polysiloxane, in which case the substrate particles will have both an organic skeleton and a polysiloxane skeleton. As a base particle of conductive fine particles that can give excellent connection reliability, the particles have both hardness and softness that are optimum. In the present invention, the “vinyl group” includes a substituent having a polymerizable carbon-carbon double bond such as a (meth) acryloxy group, an allyl group, an isopropenyl group, a vinylphenyl group, and an isopropenylphenyl group. Meaning.

  Examples of the vinyl group-containing monomer include (meth) acrylic acid or a salt thereof; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, t-butyl (meth) acrylate, n-butyl (meth) ) Acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) ) Acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, etc. (preferably alkyl having 1 to 4 carbon atoms) (meth) acrylates; cyclopropyl (meth) acrylate, cyclopentyl (meth) acrylate Rate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, cyclooctyl (meth) acrylate, cycloundecyl (meth) acrylate, cyclododecyl (meth) acrylate, isobornyl (meth) acrylate, 4-t- Cycloalkyl (preferably C3-C5 alkyl) (meth) acrylates such as butylcyclohexyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl ( Hydroxyalkyl such as (meth) acrylate (preferably alkyl having 2 to 3 carbon atoms) (meth) acrylates; phenyl (meth) acrylate, benzyl (meth) acrylate, tolyl (meth) acrylate, phenethyl (meth) (Meth) acrylic monofunctional monomers such as aromatic ring-containing (meth) acrylates such as acrylate; styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, pt-butyl Alkyl styrenes such as styrene; Alkoxy styrenes such as p-methoxystyrene; Aromatic ring-containing styrenes such as p-phenylstyrene; Halogen group-containing styrenes such as o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene A hydroxy group-containing styrene such as p-hydroxystyrene; a styrenic monofunctional monomer such as p-hydroxystyrene; and the like having one vinyl group in one molecule.

  In the present invention, “(meth) acrylate” and “(meth) acryl” indicate “acrylate and / or methacrylate” and “acryl and / or methacryl”.

  As the vinyl group-containing monomer, in addition to the above, a crosslinkable vinyl group-containing monomer having one or more polymerizable groups together with a vinyl group in one molecule (hereinafter referred to as “crosslinkable vinyl group-containing monomer”). ) Can also be used. Here, the “polymerizable group” may be any group that can form a bond with another monomer. For example, in addition to a radical polymerizable group such as a vinyl group, an ester such as a carboxylic acid group, a hydroxy group, or an alkoxy group. Also included are condensable reactive groups capable of forming a bond.

  Examples of the crosslinkable vinyl group-containing monomer include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1, Alkanediol di (meth) acrylates such as 10-decanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, 1,3-butylene di (meth) acrylate; diethylene glycol di (meth) acrylate, triethylene glycol di ( Glycol-based di (meth) acrylates such as (meth) acrylate, decaethylene glycol di (meth) acrylate, pentadecaethylene glycol di (meth) acrylate, pentacontactor ethylene glycol di (meth) acrylate; trimethylol group Multifunctional (meth) acrylates such as pantri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate; unsaturated groups such as allyl (meth) acrylate Containing mono (meth) acrylates; (meth) acrylic monomers such as; aromatic hydrocarbon crosslinking agents such as divinylbenzene, divinylnaphthalene, and derivatives thereof (preferably styrenic polyfunctional monomers such as divinylbenzene); And heteroatom-containing crosslinking agents such as N, N-divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfonic acid, and the like. Among these, in order to further improve the connection reliability, a monomer having a small number of carbons interposed between two polymerizable groups (such as vinyl groups) (for example, two polymerizable groups (such as vinyl groups)) The number of intervening carbon atoms is 10 or less, preferably 9 or less), and 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, and divinylbenzene are suitable.

  When the crosslinkable vinyl group-containing monomer is used as the vinyl group-containing monomer, the content thereof is preferably 50% by mass or less, more preferably 40% by mass or less, further preferably, based on the total amount of the vinyl group-containing monomer. Is preferably 20% by mass or less. When the amount of the crosslinkable vinyl group-containing monomer is increased, the Tg of the polymer particles obtained by increasing the degree of crosslinking is likely to increase, so that it may be difficult to control the Tg of the polymer particles within the above range.

The polymerizable polysiloxane is a hydrolytic condensate of a silane monomer and has a siloxane bond. Here, “polymerizable” means having a carbon-carbon double bond capable of radical polymerization. That is, the polymerizable polysiloxane is at least a silane monomer having at least one radical polymerizable group such as a vinyl group and at least one condensable reactive group in the molecule (hereinafter also referred to as “crosslinkable silane compound”). Is obtained by hydrolysis and condensation. Examples of the crosslinkable silane compound include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 1-hexenyltrimethoxysilane, and 1-hexenyltriethoxysilane. And silane monomers such as vinyl alkoxysilane monomers (particularly vinyl C _1-2 alkoxysilane monomers). Among these, 3-methacryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane are preferable.

  The polymerizable polysiloxane, together with the crosslinkable silane compound, is a silane monomer having at least one condensable reactive group in the molecule but no radical polymerizable group such as a vinyl group (hereinafter referred to as “non-crosslinkable silane compound”). May be obtained by hydrolysis and condensation. Non-crosslinkable silane compounds include, for example, tetraalkoxysilane monomers such as tetramethoxysilane and tetraethoxysilane; trialkoxysilane monomers such as methyltrimethoxysilane and methyltriethoxysilane; dimethyldimethoxysilane and dimethyldiethoxysilane Dialkoxysilane monomers such as trialkoxysilane, monoalkoxysilane monomers such as trimethylmethoxysilane, and hydrolytic condensates thereof.

  The polymerizable polysiloxane preferably has a weight average molecular weight of 300 to 5,000, more preferably a weight average molecular weight of 500 to 2,000. When the weight average molecular weight is in the above range, polymer particles having excellent compatibility with the vinyl group-containing monomer and uniform particle size distribution can be easily obtained.

  In the polymerizable composition constituting the base particle, the vinyl group-containing monomer (the total of the crosslinkable vinyl group-containing monomer and the vinyl group-containing monomer other than the crosslinkable vinyl group-containing monomer) and / or the polymerizable property. The content of polysiloxane (the total content when both are included) is preferably 5% by mass or more, more preferably 50% by mass or more, and more preferably 80% by mass or more based on the total amount of the polymerizable composition. More preferably, it is more preferably 90% by mass or more, particularly preferably 95% by mass or more. It is preferable that the total content of the vinyl group-containing monomer and the polymerizable polysiloxane is in the above range because the Tg of the polymer particles can be easily controlled in the above range.

  When the polymerizable composition contains both the vinyl group-containing monomer and the polymerizable polysiloxane, the ratio of both is a mass ratio, and the value of the vinyl group-containing monomer / polymerizable polysiloxane is 0.1 to 50. It is preferable that it is the range which becomes, More preferably, it is 0.3-20, More preferably, it is the range used as 0.5-8.

  In addition to the vinyl group-containing monomer and the polymerizable polysiloxane, the polymerizable composition constituting the base particle is copolymerized with another monomer having a substituent capable of reacting with at least one of them. It may be. Examples of the other monomer include the above-described crosslinkable silane compound or non-crosslinkable silane compound.

  The base particles are obtained by polymerizing the polymerizable composition. The polymerization method is not particularly limited, and conventionally known methods such as an emulsion polymerization method, a suspension polymerization method, a seed polymerization method, and a sol-gel method can be appropriately employed. In particular, a seed polymerization method is preferably employed. Hereinafter, the seed polymerization method will be described.

  In the seed polymerization method, a seed particle manufacturing process in which a part of the polymerizable composition is used to manufacture seed particles, an absorption process in which the obtained seed particles absorb the remainder of the polymerizable composition, and a polymerization composition is polymerized. Through the polymerization step, polymer particles are obtained.

  In the seed particle manufacturing process, as a seed particle, a polymerization reaction is performed using a polymerizable polysiloxane or a silane monomer (hereinafter sometimes referred to as a “silane compound”) as a raw material for the polymerizable polysiloxane. It is preferable to form polysiloxane particles. Specifically, the silane compound may be hydrolyzed and subjected to a condensation reaction in a solvent containing water. In hydrolyzing and condensing, a basic catalyst such as ammonia, urea, ethanolamine, tetramethylammonium hydroxide, alkali metal hydroxide, or alkaline earth metal hydroxide can be preferably used as a catalyst. The solvent containing water may contain an organic solvent in addition to water and the catalyst. Moreover, when performing a hydrolysis and condensation, a conventionally well-known emulsifier can also be used together. The heating temperature at the time of hydrolysis and condensation is usually 0 ° C. or higher and 100 ° C. or lower, preferably 0 ° C. or higher and 70 ° C. or lower, more preferably 5 ° C. or higher and 50 ° C. or lower. Minutes to 100 hours, preferably 5 minutes to 50 hours, more preferably 10 minutes to 20 hours.

  In the absorption step, the method of causing the seed particles to absorb the polymerizable composition may be any method that allows the absorption to proceed by allowing the polymerizable composition to exist in the presence of the seed particles. For example, the polymerizable composition may be added in a solvent in which seed particles are dispersed, or the seed particles may be added in a solvent containing the polymerizable composition. Preferably, the method of adding the polymerizable composition to the reaction solution without removing the polysiloxane particles obtained by hydrolysis and condensation reaction from the reaction solution (polysiloxane particle dispersion) does not complicate the process. Excellent in productivity. In this case, the timing of addition of the polymerizable composition is not particularly limited, and the polymerizable composition may be added all at once, may be added in several times, or may be fed at an arbitrary rate. Good. In addition, when adding the polymerizable composition, the polymerizable composition may be added alone or a solution of the polymerizable composition may be added, but the polymerizable composition is previously added with water or aqueous solution with a conventionally known emulsifier. It is preferable to add a monomer emulsion emulsified and dispersed in a medium because absorption into the seed particles is performed more efficiently. Absorption of the polymerizable composition into the seed particles is preferably performed, for example, in a temperature range of 0 ° C. or more and 60 ° C. or less with stirring for 5 minutes or more and 720 minutes or less. In addition, in the absorption step, for determining whether the polymerizable composition is absorbed by the seed particles, for example, before adding the polymerizable composition and after the absorption step, the particles are observed with a microscope, It can be easily determined by confirming that the particle size is increased by absorption.

  In the polymerization step, for example, any of a polymerization method using a polymerization initiator, a polymerization method of irradiating ultraviolet rays or radiation, a polymerization method of applying heat, etc. can be adopted.

  As a polymerization initiator, the well-known thing conventionally used for superposition | polymerization, such as a peroxide type initiator and an azo type initiator, can be used, for example. The amount of the polymerization initiator used is preferably 0.001 part by mass or more, more preferably 0.01 part by mass or more, further preferably 0.1 part by mass with respect to 100 parts by mass of the total mass of the polymerizable composition. It is preferably no less than 20 parts by mass, more preferably no more than 10 parts by mass, and even more preferably no more than 5 parts by mass. The polymerization temperature is preferably 40 ° C. or higher, more preferably 50 ° C. or higher, preferably 100 ° C. or lower, more preferably 80 ° C. or lower. The polymerization time may be appropriately changed according to the type of polymerization initiator to be used, but it is usually preferably 5 minutes or longer, more preferably 10 minutes or longer, 600 minutes or shorter, more preferably 300 minutes or shorter.

  The particle diameter of the substrate particles is preferably 0.5 to 10.0 μm in number average particle diameter. If the number average particle size is too small, the particles are likely to aggregate and it may be difficult to form a uniform conductive metal layer. On the other hand, if the number average particle size is too large, the application as conductive fine particles is limited. Therefore, the industrial application field tends to be reduced. The number average particle diameter of the base particles is more preferably 1.0 μm or more and 5.0 μm or less, further preferably 1.2 μm or more and 3.0 μm or less, and further preferably 1.5 μm or more. 7 μm or less. Further, according to the present invention, even when electrical connection is performed at a low temperature, the conductive fine particles can be sufficiently deformed to ensure a large contact area with respect to the connected body. In general, the effect of the present invention described above is more meaningful in the small particle diameter region in view of the fact that the smaller the particle diameter, the more difficult it is to secure the contact area with the connected body. From this point of view, the number average particle diameter of the base particles is most preferably 2.5 μm or less.

  The number average particle diameter is specifically a number-based value measured by a precision particle size distribution measuring apparatus using the Coulter principle (for example, “Coulter Multisizer III type” manufactured by Beckman Coulter, Inc.). .

The coefficient of variation (CV value) in the particle diameter of the substrate particles is preferably 10% or less, more preferably 7% or less, still more preferably 5% or less, and most preferably 4% or less. The coefficient of variation of the particle diameter is a value obtained by applying the following equation to the average particle diameter of the particles measured by a precision particle size distribution measuring apparatus using the Coulter principle and the standard deviation of the particle diameter of the particles. .
Variation coefficient of particles (%) = 100 × (standard deviation of particle diameter / number average particle diameter)

10% K value of the base material particles, 1000 N / mm ² or more, preferably 30000 N / mm ² or less. If the 10% K value of the substrate particles is too small, the connection resistance is low due to the fact that the surrounding binder cannot be removed sufficiently when used as an anisotropic conductive material, and the biting into the electrode is weak. There is a possibility that the value 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. 10% K value of the substrate particles is 2000N / mm ² or more, more preferably 25000N / mm ² or less.

  The 10% K value of the base particle is a compression elastic modulus when the particle is compressed by 10% (when the diameter of the particle is displaced by 10%). For example, a known micro compression tester (manufactured by Shimadzu Corporation) MCT-W500 "etc.), the load when the particles are deformed until the compression displacement becomes 10% of the particle diameter by applying a load at a load load rate of 2.22 mN / sec toward the center of the particles at room temperature. The load (N) and the amount of displacement (compression displacement: mm) can be measured and determined based on the following formula.

（ここで、Ｅ：圧縮弾性率（Ｎ／ｍｍ²）、Ｆ：圧縮荷重（Ｎ）、Ｓ：圧縮変位（ｍｍ）、Ｒ：粒子の半径（ｍｍ）である。）

(Here, E: compression elastic modulus (N / mm ² ), F: compression load (N), S: compression displacement (mm), R: radius of particle (mm))

  By the way, generally, when the temperature at which particles are compressed increases, the compression modulus (K value) tends to decrease. Here, focusing on the compression modulus (50% K value) when the particles are compressed by 50% (when the diameter of the particles is displaced by 50%), the temperature of the base particles is reduced from 25 ° C. The 50% K value reduction rate (hereinafter referred to as “50% K value reduction rate”) when the temperature is raised to 150 ° C. is preferably 40% or more, more preferably 45% or more, and still more preferably 50%. That's it. When the 50% K value reduction rate is in the above range, when subjected to heat connection as an anisotropic conductive material, it is greatly deformed at a low pressure, and a larger contact area can be secured. The upper limit of the 50% K value reduction rate is not particularly limited, but is preferably 90% or less, more preferably 80% or less, from the viewpoint of satisfying good indentation to the electrode.

The 50% K value reduction rate is the same as the 10% K value described above except that the temperature during compression (loading) is changed and the particles are deformed until the compression displacement becomes 50% of the particle diameter. The 50% K value at 25 ° C. and the 50% K value at 150 ° C. can be obtained and calculated based on the following formula. More specifically, for example, it can be determined by the method described in the examples described later.
50% K value reduction rate (%) = 100 − [(50% K value at 150 ° C./50% K value at 25 ° C.) × 100]

  The shape of the substrate 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., but a spherical shape is preferable, and a true spherical shape is particularly preferable. preferable.

  The conductive metal layer constituting the conductive fine particles of the present invention has a thickness of 0.01 to 0.15 μm. If the conductive metal layer exceeds 0.15 μm, even if the Tg of the substrate particles is set in the above range, the resistance value increases with time when the connection is made at a low temperature. On the other hand, when the conductive metal layer is less than 0.01 μm, the initial resistance value is high and the conductivity is insufficient. The film thickness of the conductive metal layer is preferably 0.12 μm or less, more preferably 0.10 μm or less, most preferably less than 0.10 μm, preferably 0.04 μm or more, more preferably 0.06 μm or more. .

In the present invention, the thickness of the conductive metal layer is expressed by the following formula by dissolving the conductive metal layer with an acidic solution such as nitric acid or sulfuric acid and measuring the particle diameter before and after dissolution of the conductive metal layer with a particle size distribution meter. Can be obtained.
Conductive metal layer thickness (μm) = (particle diameter before dissolution of conductive metal layer−particle diameter after dissolution of conductive metal layer) / 2

  In order to set the film thickness of the conductive metal layer within the above range, specifically, the base particle concentration (the amount of base particles per treatment liquid) at the time of performing the electroless plating treatment or the electroless plating described later. The concentration and pH of the electroless plating solution used in the treatment, or the reaction temperature of the electroless plating treatment may be adjusted. For example, when the amount of base particles per treatment solution for electroless plating treatment is reduced or the concentration of the electroless plating solution used in the electroless plating treatment is reduced, the thickness of the conductive metal layer is reduced.

  The metal constituting the conductive metal layer is not particularly limited as long as it is a compound having conductivity. Examples thereof include nickel, palladium, gold, silver, copper, platinum, iron, tin, lead, cobalt, titanium, bismuth, zinc, aluminum, indium, and alloys thereof. Among these, gold, nickel, palladium, silver, and copper are preferable because of excellent conductivity. In addition, the conductive metal layer may be a single layer or multiple layers. In the case of multiple layers, for example, a combination of nickel-gold, nickel-palladium, nickel-palladium-gold, nickel-silver, etc. Is preferred.

  The method for forming the conductive metal layer on the surface of the substrate particles is not particularly limited, and a conventionally known method, for example, a method of plating such as an electroless plating method or an electrolytic plating method; a metal fine powder alone or a binder A method of coating the base particles with a paste mixed with the above; a physical vapor deposition method such as vacuum deposition, ion plating, ion sputtering, etc. may be employed. Among these, the electroless plating method is particularly preferable in that a conductive metal layer can be easily formed without requiring a large-scale apparatus.

  The formation of the conductive metal layer by the electroless plating method is recommended to be performed through (i) a catalyst step and (ii) an electroless plating step. Hereinafter, each process of (i) and (ii) is demonstrated in detail.

(I) Catalyzing step In the catalyzing step, a catalyst layer serving as a base point of electroless plating performed in the next step 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 catalytic reagent commercially available 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. Reduction of the palladium ions with an alkaline solution such as sodium oxide to precipitate palladium on the surface of the substrate particles (catalyst-acceleration method), or contact of the substrate particles with tin dichloride for tin ions Examples include a method of causing palladium to be deposited on the surface of the base particle by immersing the base material on the surface of the base particle, and then immersing it in a palladium dichloride solution (sensitizing-activation method).

  In addition, in order to improve the adhesion between the base material particles and the conductive metal layer, the base particles used in the catalyzing step are subjected to a degreasing process in advance, and then fine irregularities are formed on the surface of the base material particles. Etching treatment may be performed.

(Ii) Electroless plating step In the electroless plating step, the surface of the substrate particles on which the catalyst layer has been formed in the catalyzing step is subjected to an electroless plating treatment to form a conductive metal layer. The electroless plating treatment reduces the metal ions in the plating solution with the reducing agent, starting from the catalyst, by immersing the substrate particles with the catalyst layer in the plating solution in which the reducing agent and the desired metal salt are dissolved. Then, a desired metal is deposited on the surface of the substrate particles to form a conductive metal layer.

  In the electroless plating step, first, the base particles subjected to the catalyst treatment are sufficiently dispersed in water to prepare an aqueous slurry of the base particles. Here, in order to develop stable conductive characteristics, it is preferable that the base particles are sufficiently dispersed in an aqueous medium for plating. This is because if the electroless plating treatment is performed in a state where the base particles are aggregated, an untreated surface (a surface on which no conductive metal layer is present) is generated on the contact surface between the base particles. As a means for dispersing the base 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. A sound wave or a dispersant (such as a surfactant) may be used in combination.

  Next, electroless plating is performed by adding the aqueous slurry of the base particles prepared above to an electroless plating solution containing a desired conductive metal salt, reducing agent, complexing agent and various additives. Cause a reaction. The electroless plating reaction starts quickly when an aqueous slurry of 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 completely recognized. After completion of the electroless plating reaction, the conductive 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 chlorides, sulfates, acetates, and the like of the metals exemplified above 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 contained 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 sodium hypophosphite, dimethylamine borane, sodium borohydride, potassium borohydride, hydrazine, and the like. Only one reducing agent may be used, or two or more reducing agents may be used.

  As the complexing agent to be contained in the electroless plating solution, a compound having a complexing action on the conductive metal ions 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 metals. Specifically, after nickel plating is performed on the substrate particles to obtain nickel-coated particles, the outermost layer is a gold layer by adding the nickel-coated particles to an electroless gold plating solution and performing gold displacement plating. Thus, conductive fine particles having a nickel layer on the inside can be obtained.

The conductive fine particles may have a smooth surface or an uneven shape, but preferably have a plurality of protrusions from the viewpoint that the binder resin can be effectively removed to connect to the electrode. By having the protrusion, connection reliability when the conductive fine particles are used for connection between the electrodes can be improved.
The method of forming protrusions on the surface of the conductive fine particles is as follows: 1) After attaching inorganic particles such as metal particles and metal oxide particles or organic particles made of an organic polymer to the surface of the substrate particles, electroless plating 2) After electroless plating is performed on the surface of the base material particles, inorganic particles such as metal particles and metal oxide particles, or organic particles made of an organic polymer are attached, and Method of performing electroless plating, 3) By using the self-decomposition of the plating bath at the time of electroless plating reaction, depositing a metal that becomes the core of the projection on the base particle, and further performing electroless plating, the projection portion And a method of forming a conductive metal layer in which a conductive metal layer containing a continuous film is formed.

  The conductive fine particles of the present invention preferably have an insulating resin layer on at least a part of the surface. When the insulating resin layer is further laminated on the conductive metal layer on the surface as described above, 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 resin constituting the insulating resin layer may be any resin as long as the insulating property between the particles of the conductive fine particles can be ensured, and the insulating resin layer can be easily collapsed or peeled off by a certain pressure and / or heating. It is not limited. For example, in addition to the polymers and copolymers composed of the above-mentioned vinyl group-containing monomers, polyolefins such as polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer; polystyrene, styrene-acrylic acid ester copolymer Block polymers such as polymers, SB type styrene-butadiene block copolymers, SBS type styrene-butadiene block copolymers and their hydrogenated compounds; thermoplastic resins such as vinyl polymers and copolymers, and in particular their crosslinking A thermosetting resin such as an epoxy resin, a phenol resin, and a melamine resin; a water-soluble resin such as polyvinyl alcohol, polyacrylic acid, polyacrylamide, polyvinyl pyrrolidone, polyethylene oxide, and methyl cellulose; and a mixture thereof.

  The insulating resin 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 particles having insulating particles, spheres, lumps, scales, or other shapes attached to the surface of the conductive metal layer. Further, it may be formed by chemically modifying the surface of the conductive metal layer, or may be a combination thereof.

  The thickness of the insulating resin layer is preferably 0.01 to 1 μm. More preferably, it is 0.1 μm or more and 0.5 μm or less. If the thickness of the insulating resin layer is too thin, the electrical insulation is insufficient. On the other hand, if the thickness is too thick, the conduction characteristics may be deteriorated.

  The method for forming the insulating resin layer is not particularly limited. For example, in the presence of conductive fine particles after the electroless plating step, the monomer of the resin material constituting the insulating resin layer is interfacially polymerized and suspended. Polymerization or emulsion polymerization, a method of microencapsulating conductive fine particles with an insulating resin; a dipping method in which conductive fine particles are dispersed in an insulating resin solution in which the insulating resin is dissolved in an organic solvent, and then dried; spray Conventionally known methods such as a dry method and a method by hybridization can be employed.

(Anisotropic conductive material)
The anisotropic conductive material of the present invention contains the conductive fine particles of the present invention. The form of the anisotropic conductive material is not particularly limited. For example, the anisotropic conductive film, the anisotropic conductive paste, the anisotropic conductive adhesive, the anisotropic conductive ink, or the like between the opposing substrates or The thing which enables an electrical connection by providing between electrode terminals is mentioned. The anisotropic conductive material of the present invention also includes a conductive material for liquid crystal display elements such as a conductive spacer and its composition.

  For example, the anisotropic conductive film is made into a liquid by adding a solvent to the film-forming composition containing the conductive fine particles of the present invention and a binder resin, and this liquid is applied onto a film made of polyethylene terephthalate, and then the solvent. Can be obtained by evaporation. The obtained anisotropic conductive film is disposed on electrodes, for example, and is used for connection between the electrodes by superposing a counter electrode on the anisotropic conductive film and heating and compressing it.

  The anisotropic conductive paste is obtained, for example, by making a resin composition containing the conductive fine particles of the present invention and a binder resin into a paste. The obtained anisotropic conductive paste is placed in, for example, a suitable dispenser, applied on the electrode to be connected with a desired thickness, and the counter electrode is superimposed on the coated anisotropic conductive paste. It is used for connection between electrodes by curing the resin by applying pressure while heating.

  The anisotropic conductive adhesive can be obtained, for example, by adjusting a resin composition containing the conductive fine particles of the present invention and a binder resin to a desired viscosity. The obtained anisotropic conductive adhesive is used to connect between electrodes by coating the electrodes with a desired thickness, then overlaying the counter electrodes and bonding them together, as with the anisotropic conductive paste. Is done.

  The anisotropic conductive ink can be obtained, for example, by adjusting a viscosity suitable for printing by adding a solvent to the resin composition containing the conductive fine particles of the present invention and a binder resin. The obtained anisotropic conductive ink is obtained by, for example, screen-printing on the electrode to be bonded, evaporating the solvent, superimposing the counter electrode on the printing surface with the anisotropic conductive ink, and heating and compressing the electrode. Used for connection between.

  Such an anisotropic conductive material is usually manufactured by dispersing the conductive fine particles of the present invention in an insulating binder resin to obtain a desired form. However, the insulating binder resin, the conductive fine particles, May be used separately to connect between substrates or between electrode terminals.

  The binder resin is not particularly limited. For example, a thermoplastic resin such as an acrylic resin, an ethylene-vinyl acetate resin, a styrene-butadiene block copolymer; a reaction with a curing agent such as a monomer or oligomer having a glycidyl group or isocyanate. Curable resin composition cured by light, curable resin composition cured by light or heat, and the like.

  In the anisotropic conductive material of the present invention, the content of the conductive fine particles of the present invention may be appropriately determined according to the application, but for example, 2 to 70% by volume with respect to the total amount of the anisotropic conductive material. Is preferred. More preferably, it is 5 volume% or more, More preferably, it is 10 volume% or more, More preferably, it is 50 volume% or less, More preferably, it is 40 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.

  About the film thickness in the anisotropic conductive material of the present invention, the coating thickness of the paste or adhesive, the printed film thickness, etc., the particle diameter of the conductive fine particles of the present invention to be used and the specifications of the electrode to be connected In consideration of the above, it is preferable to appropriately set so that the conductive fine particles are sandwiched 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. .

  The anisotropic conductive material according to the present invention is capable of sufficiently reducing the initial connection resistance value even when subjected to electrical connection at a low temperature, and can suppress an increase in resistance value over time. Demonstrate reliability. Therefore, the connection method for electrically connecting the connection parts using the anisotropic conductive material of the present invention is not particularly limited, but the effect of the present invention is significantly exhibited when performed at a temperature lower than usual. This is desirable. Specifically, the temperature at the time of connection is preferably 190 ° C. or lower, more preferably 170 ° C. or lower, and further preferably 150 ° C. or lower. However, if the temperature at the time of connection is too low, the connection may be incomplete. Therefore, the temperature at the time of connection is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, more preferably 120 ° C. It is good to be the above. Even when connected at such a low temperature, the connection structure connected by the anisotropic conductive material of the present invention is excellent in connection reliability.

  When electrical connection is performed using the anisotropic conductive material of the present invention, the pressure at the time of connection is not particularly limited, but is usually 1 to 100 MPa. Further, the connection time (time for applying heat and pressure) may be appropriately set according to the temperature and pressure, but is usually 10 seconds to 3600 seconds.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

  In the following, “part” means “part by mass” and “%” means “mass%” unless otherwise specified.

  In the following examples and comparative examples, various physical properties of the particles were measured by the following methods.

<Number average particle diameter, 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.) to obtain the number average particle size and the standard deviation of the particle size. CV value (coefficient of variation) was calculated.
Variation coefficient of particles (%) = 100 × (standard deviation of particle diameter / number average particle diameter)

<Glass transition temperature>
Using a differential scanning calorimeter (“EXSTAR6000” manufactured by Seiko Instruments Inc.), a sample amount of 10 mg to 20 mg under a nitrogen stream (flow rate: 50 mL / min), a temperature increase rate from 30 ° C. to 200 ° C. is 10 ° C. / The sample (base material particles) was heated under the conditions of minutes and measured. Specifically, first, a sample (base particle) is weighed on a specified aluminum pan, and set together with a reference aluminum pan (without a sample) at a predetermined position on the differential scanning calorimeter, and nitrogen is specified. The flow rate (50 mL / min) was adjusted to flow, and after the apparatus was stabilized, the first temperature increase was started. After raising the temperature from 30 ° C. to 200 ° C., it was once cooled, and then the second temperature was raised under the same conditions as the first. Based on the baseline shift of the DSC curve obtained at this time, the glass transition temperature of the substrate particles was calculated.

<Conductive metal layer thickness>
First, the particle diameter Y (μm) of 1000 particles of the obtained conductive fine particles was measured with a flow type particle image analyzer (“FPIA-3000” manufactured by Sysmex Corporation). Next, 10 g of 20% saline is added to 1 g of the obtained conductive fine particles, and after ultrasonic dispersion, 1 g of 69% nitric acid is added and stirred at 80 ° C. to dissolve the conductive metal layer. Thereafter, the base particle was taken out by filtration and dried to obtain a base particle powder. About the base particle obtained by dissolving this electroconductive metal layer, the particle diameter X (micrometer) of 1000 particle | grains was measured with the same flow type particle image analyzer as the above. And the film thickness of the electroconductive metal layer was computed according to the following formula.
Conductive metal layer thickness (μm) = (Y−X) / 2

<50% K value reduction rate>
Using a microhardness tester (“HM2000LT” manufactured by H. FISHHER) at a temperature of 25 ° C., each particle spread on a microslide glass (precrine water polishing: thickness 1.3 mm) has a square plane of 50 μm. Using an indenter (material: diamond), in the load increase (dSQRT (F) / dt = constant) mode, a load was applied toward the center of the particle so that the maximum load of 50 mN was reached in 25 seconds. Then, the load value (mN) when the particle diameter is displaced by 50% and the displacement amount (μm) at that time are measured, and the obtained load value (mN) is converted into the compression load (N). The amount of displacement (μm) was converted to compression displacement (mm), and the particle radius (mm) was calculated from the average particle diameter (μm) of the particles. Using these, the compression modulus at 25 ° C. ( K value) was calculated. In addition, the measurement was performed on 10 different particles for each sample, and the average value was used as the measurement value.

（ここで、Ｅ：圧縮弾性率（Ｎ／ｍｍ²）、Ｆ：圧縮荷重（Ｎ）、Ｓ：圧縮変位（ｍｍ）、Ｒ：粒子の半径（ｍｍ）である。）

(Here, E: compression elastic modulus (N / mm ² ), F: compression load (N), S: compression displacement (mm), R: radius of particle (mm))

Next, the particles on the micro slide glass are heated to 150 ° C. by the heating stage of the micro hardness tester, and in this state, the 50% K value at 150 ° C. is the same as the 50% K value at 25 ° C. described above. The value was determined.
Then, a 50% K value reduction rate (%) was calculated from the 50% K value at 25 ° C. and the 50% K value at 150 ° C. based on the following formula.
50% K value decrease rate (%) = 100 − [(50% K value at 150 ° C.) / (50% K value at 25 ° C.) × 100]

  As a reference, when obtaining the 50% K value at the predetermined temperature (25 ° C. and 150 ° C.) as described above, when the particle diameter is displaced 10%, displaced 20%, or displaced 30% Each load value (mN) at 40% displacement and 60% displacement and the amount of displacement (μm) at that time are also measured, and 10% at 25 ° C. and 150 ° C. is measured in the same manner as the 50% K value. The% K value, 20% K value, 30% K value, 40% K value, and 60% K value were also determined.

[Example 1]
(Preparation of substrate particles)
A four-necked flask equipped with a condenser, a thermometer, and a dripping port is charged with 1625 parts of ion-exchanged water, 25 parts of 25% aqueous ammonia and 564 parts of methanol, and under stirring, 3-methacryloxypropyltrimethoxylane from the dripping port. A mixed liquid of 145 parts and 240 parts of methanol was added and stirred at 30 ° C. for 2 hours to hydrolyze and condense 3-methacryloxypropyltrimethoxysilane to obtain an emulsion of polysiloxane particles.

  On the other hand, 21.5 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 diluted with 850 parts of ion-exchanged water. In the solution, a polymerizable composition comprising 737 parts of styrene and 130 parts of butyl acrylate, and 2,2′-azobis (2,4-dimethylvaleronitrile) (“W— 65 ") 10 parts of a dissolved solution was added and emulsified and dispersed to prepare an emulsion of the polymerizable composition.

  The emulsion of the polymerizable composition obtained above was subsequently added to the emulsion of the polysiloxane particles obtained above, and further stirred. Two hours after the addition of the emulsion, the mixed solution was sampled and observed with a microscope, and it was confirmed that the polysiloxane particles absorbed the polymerizable composition and were enlarged.

  Next, 100 parts of a 20% aqueous solution of polyoxyethylene styrenated phenyl ether sulfate ammonium salt ("Hitenol (registered trademark) NF-08" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 2000 parts of ion-exchanged water are added to the mixed solution, The temperature was raised to 65 ° C. under a nitrogen atmosphere and kept at 65 ° C. for 2 hours to carry out radical polymerization of the polymerizable composition. Thereafter, the reaction solution (emulsion) 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). The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

(Preparation of conductive fine particles)
After the base particle (1) is etched with sodium hydroxide, it is sensitized by bringing it into contact with a tin dichloride solution, and then activated by being immersed in a palladium dichloride solution. Palladium nuclei were formed by the ging-activation method.

  After 10 parts of the base particles having palladium nuclei formed in this manner were added to 400 parts of ion-exchanged water and subjected to ultrasonic dispersion treatment, the base particle suspension was heated in a 70 ° C. warm bath. While this suspension was heated, 600 parts of an electroless plating solution (“Schumar S680” manufactured by Nippon Kanisen Co., Ltd.) separately heated to 70 ° C. was added to cause an electroless nickel plating reaction. After confirming that the generation of hydrogen gas was completed, solid-liquid separation was performed, followed by gold displacement plating treatment to deposit gold on the surface. Next, after solid-liquid separation and washing in order of ion-exchanged water and methanol, vacuum drying was performed at 100 ° C. for 2 hours to obtain nickel-gold plated conductive fine particles (1). The film thickness of the conductive metal layer in the obtained conductive fine particles was 0.09 μm.

[Example 2]
In Example 1, except that the polymerizable composition was changed to 607 parts of styrene and 260 parts of butyl acrylate, base material particles (2) were obtained in the same manner as in Example 1 (Preparation of base material particles). It was. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, in place of the base particle (1), the base particle (2) is used, and the amount of electroless plating solution used and the use of ion exchange water so that the conductive metal layer has a thickness of 0.08 μm. Except for adjusting the amount, conductive fine particles (2) were obtained in the same manner as in Example 1 (Preparation of conductive fine particles).

Example 3
In Example 1, the charging composition into the four-necked flask when obtaining an emulsion of polysiloxane particles was changed to 1625 parts of ion-exchanged water, 25 parts of 25% ammonia water, and 704 parts of methanol, and dropped with stirring. Example 1 (Preparation of substrate particles) except that the amount of 3-methacryloxypropyltrimethoxysilane and methanol added from the mouth was changed to 145 parts of 3-methacryloxypropyltrimethoxysilane and 100 parts of methanol. In the same manner as above, substrate particles (3) were obtained. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, in place of the base particle (1), the base particle (3) is used, and the amount of electroless plating solution used and the use of ion-exchanged water so that the thickness of the conductive metal layer is 0.08 μm. Except that the amount was adjusted, conductive fine particles (3) were obtained in the same manner as in Example 1 (Preparation of conductive fine particles).

Example 4
In Example 1, the blending into the four-necked flask when obtaining an emulsion of polysiloxane particles was changed to 1625 parts of ion-exchanged water, 25 parts of 25% aqueous ammonia and 724 parts of methanol, and dropped with stirring. Example 1 (Preparation of substrate particles) except that the amount of 3-methacryloxypropyltrimethoxysilane and methanol added from the mouth was changed to 145 parts of 3-methacryloxypropyltrimethoxysilane and 80 parts of methanol. In the same manner as above, substrate particles (4) were obtained. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, conductive fine particles (4) were obtained in the same manner as in Example 1 (Preparation of conductive fine particles) except that the base particle (4) was used instead of the base particle (1). .

Example 5
In Example 4, base material particles (5) were obtained in the same manner as in Example 4 except that the polymerizable composition was changed to 806 parts of styrene and 61 parts of butyl acrylate. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, in place of the base particle (1), the base particle (5) is used, and the amount of electroless plating solution used and the use of ion exchange water so that the conductive metal layer has a thickness of 0.08 μm. Except for adjusting the amount, conductive fine particles (5) were obtained in the same manner as in Example 1 (Preparation of conductive fine particles).

Example 6
In Example 4, base material particles (6) were obtained in the same manner as in Example 4 except that the polymerizable composition was changed to 607 parts of styrene and 260 parts of butyl acrylate. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, conductive fine particles (6) were obtained in the same manner as in Example 1 (Preparation of conductive fine particles) except that the base particle (6) was used instead of the base particle (1). .

Example 7
In Example 4, base material particles (7) were obtained in the same manner as in Example 4 except that the polymerizable composition was changed to 572 parts of styrene and 295 parts of butyl acrylate. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, conductive fine particles (7) were obtained in the same manner as in Example 1 (Preparation of conductive fine particles) except that the base particle (7) was used instead of the base particle (1). .

Example 8
In Example 1, the charging composition into the four-necked flask when obtaining an emulsion of polysiloxane particles was changed to 1625 parts of ion-exchanged water, 25 parts of 25% aqueous ammonia and 794 parts of methanol, and dropped with stirring. Example 1 (Preparation of substrate particles) except that the amount of 3-methacryloxypropyltrimethoxysilane and methanol added from the mouth was changed to 145 parts of 3-methacryloxypropyltrimethoxysilane and 10 parts of methanol. In the same manner as above, substrate particles (8) were obtained. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, in place of the base particle (1), the base particle (8) is used, and the amount of electroless plating solution used and the use of ion exchange water so that the film thickness of the conductive metal layer is 0.07 μm. Except for adjusting the amount, conductive fine particles (8) were obtained in the same manner as in Example 1 (Preparation of conductive fine particles).

Example 9
In Example 8, substrate particles (9) were obtained in the same manner as in Example 8, except that the polymerizable composition was changed to 806 parts of styrene and 61 parts of butyl acrylate. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, in place of the base particle (1), the base particle (9) is used, and the amount of electroless plating solution used and the use of ion exchange water so that the film thickness of the conductive metal layer is 0.07 μm. Except that the amount was adjusted, conductive fine particles (9) were obtained in the same manner as in Example 1 (Preparation of conductive fine particles).

Example 10
In Example 8, substrate particles (10) were obtained in the same manner as in Example 8, except that the polymerizable composition was changed to 607 parts of styrene and 260 parts of butyl acrylate. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, in place of the base particle (1), the base particle (10) is used, and the amount of electroless plating solution used and the use of ion exchange water so that the film thickness of the conductive metal layer is 0.07 μm. Except having adjusted the quantity, it carried out similarly to (Preparation of electroconductive fine particles) of Example 1, and obtained electroconductive fine particles (10).

Example 11
In Example 8, substrate particles (11) were obtained in the same manner as in Example 8, except that the polymerizable composition was changed to 572 parts of styrene and 295 parts of butyl acrylate. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, in place of the base particle (1), the base particle (11) is used, and the amount of electroless plating solution used and the use of ion exchange water so that the film thickness of the conductive metal layer is 0.07 μm. Except for adjusting the amount, conductive fine particles (11) were obtained in the same manner as in Example 1 (Preparation of conductive fine particles).

Example 12
In Example 1, the blending of the four-necked flask when obtaining an emulsion of polysiloxane particles was changed to 1625 parts of ion-exchanged water, 25 parts of 25% aqueous ammonia, and 564 parts of methanol, and dropped with stirring. Example 1 (Preparation of substrate particles) except that the amount of 3-methacryloxypropyltrimethoxysilane and methanol added from the mouth was changed to 145 parts of 3-methacryloxypropyltrimethoxysilane and 240 parts of methanol. In the same manner as above, substrate particles (12) were obtained. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, in place of the base particle (1), the base particle (12) is used, and the amount of electroless plating solution used and the use of ion-exchange water so that the film thickness of the conductive metal layer is 0.06 μm. Except that the amount was adjusted, conductive fine particles (12) were obtained in the same manner as in Example 1 (Preparation of conductive fine particles).

Example 13
(Preparation of substrate particles)
In a four-necked flask equipped with a condenser, a thermometer, and a dropping port, 90 parts of ion-exchanged water, 10 parts of styrene as a part of the polymerizable composition, 0.5 part of n-decyl mercaptan, 0.1 part of sodium chloride Then, the reaction vessel was purged with nitrogen by flowing nitrogen into the reaction vessel for 1 hour. Thereafter, the temperature of the mixed solution in the reaction vessel was raised to 70 ° C., 0.1 part of potassium persulfate dissolved in a small amount of ion-exchanged water was added to the mixed solution, and then the reaction was performed at 70 ° C. for 24 hours. . Thereafter, the reaction solution (emulsion) was subjected to solid-liquid separation, and the resulting cake was washed with ion-exchanged water and methanol to obtain polymer seed particles. When the particle size of the obtained polymer seed particles was measured, the number average particle size was 0.7 μm, and the coefficient of variation (CV value) was 3.0%.

  Next, to a four-necked flask equipped with a condenser, a thermometer, and a dropping port, 0.5 parts of the obtained polymer seed particles, 50 parts of ion-exchanged water, 0.05 parts of sodium lauryl sulfate as an emulsifier are added, A polymer seed particle dispersion was prepared by uniformly dispersing, and 20 parts of a 3% aqueous solution of polyvinyl alcohol was added thereto. On the other hand, in a solution obtained by dissolving 0.1 part of sodium lauryl sulfate in 50 parts of ion-exchanged water, 4.25 parts of styrene and 0.75 part of butyl acrylate as the remainder of the polymerizable composition, and peroxide as a polymerization initiator A monomer emulsion was prepared by mixing with 0.10 parts of benzoyl and stirring with a homogenizer. Next, the obtained monomer emulsion was added to the polymer seed particle dispersion and stirred. After the temperature was raised to 70 ° C. in a nitrogen atmosphere, the temperature was maintained at 70 ° C. for 24 hours to radical polymerization of the polymerizable composition. Went. Thereafter, the reaction liquid (emulsion) 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 base particles (13). The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

(Preparation of conductive fine particles)
Conductive fine particles (13) were obtained in the same manner as in Example 1 (Preparation of conductive fine particles) except that the base particle (13) was used instead of the base particle (1).

Example 14
In Example 13, except that the remainder of the polymerizable composition was changed to 3.5 parts of styrene and 1.5 parts of butyl acrylate, in the same manner as in (Production of base material particles) of Example 13, Particles (14) were obtained. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, in place of the base particle (1), the base particle (14) is used, and the amount of electroless plating solution used and the use of ion-exchanged water so that the film thickness of the conductive metal layer is 0.08 μm. Except that the amount was adjusted, conductive fine particles (14) were obtained in the same manner as in Example 1 (Preparation of conductive fine particles).

Example 15
In Example 4, except that the amount of electroless plating solution and the amount of ion-exchanged water were adjusted so that the thickness of the conductive metal layer was 0.12 μm, the same as in Example 4, Conductive fine particles (15) were obtained.

Example 16
In Example 4, except that the amount of electroless plating solution and the amount of ion-exchanged water were adjusted so that the film thickness of the conductive metal layer was 0.15 μm, Conductive fine particles (16) were obtained.

Example 17
In Example 1, except that the blending of the four-necked flask when obtaining an emulsion of polysiloxane particles was changed to 3250 parts of ion-exchanged water, 50 parts of 25% aqueous ammonia and 1128 parts of methanol. In the same manner as in Example 1 (Preparation of substrate particles), substrate particles (17) were obtained. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, in place of the base particle (1), the base particle (17) is used, and the amount of electroless plating solution used and the use of ion exchange water so that the conductive metal layer has a thickness of 0.07 μm. Except that the amount was adjusted, conductive fine particles (17) were obtained in the same manner as in Example 1 (Preparation of conductive fine particles).

Example 18
In Example 17, base material particles (18) were obtained in the same manner as in Example 17, except that the polymerizable composition was changed to 607 parts of styrene and 260 parts of butyl acrylate. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, in place of the base particle (1), the base particle (18) is used, and the amount of electroless plating solution used and the use of ion-exchange water so that the film thickness of the conductive metal layer is 0.07 μm. Except that the amount was adjusted, conductive fine particles (18) were obtained in the same manner as in Example 1 (Preparation of conductive fine particles).

[Comparative Example 1]
In Example 1, except that the polymerizable composition was changed to 867 parts of styrene, a base material particle (C1) for comparison was obtained in the same manner as in Example 1 (Preparation of base material particle). The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, conductive fine particles (C1) for comparison were used in the same manner as in (Preparation of conductive fine particles) of Example 1 except that the substrate particles (C1) were used instead of the substrate particles (1). Got.

[Comparative Example 2]
In Example 1, except that the polymerizable composition was changed to 538 parts of styrene and 329 parts of butyl acrylate, in the same manner as in Example 1 (Preparation of base material particles), comparative base material particles (C2 ) The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, conductive fine particles (C2) for comparison were used in the same manner as in (Preparation of conductive fine particles) of Example 1 except that the substrate particles (C2) were used instead of the substrate particles (1). Got.

[Comparative Example 3]
Comparative Example Particles (C3) were obtained in the same manner as in Example 4 except that the polymerizable composition was changed to 867 parts of styrene in Example 4. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, in place of the base particle (1), the base particle (C3) is used, and the amount of electroless plating solution used and the use of ion-exchange water so that the film thickness of the conductive metal layer is 0.08 μm. Except having adjusted the quantity, it carried out similarly to (preparation of electroconductive fine particles) of Example 1, and obtained the electroconductive fine particles (C3) for a comparison.

[Comparative Example 4]
Comparative Example Particles (C4) were obtained in the same manner as in Example 4 except that the polymerizable composition was changed to 538 parts of styrene and 329 parts of butyl acrylate in Example 4. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, in place of the base particle (1), the base particle (C4) is used, and the amount of electroless plating solution used and the use of ion-exchange water so that the film thickness of the conductive metal layer is 0.08 μm. Except having adjusted the quantity, it carried out similarly to (preparation of electroconductive fine particles) of Example 1, and obtained the electroconductive fine particles (C4) for a comparison.

[Comparative Example 5]
In Example 13, the base material particle (C5) for a comparison was obtained like Example 13 except having changed the remainder of the polymeric composition into 5 parts of styrene. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, in place of the base particle (1), the base particle (C5) is used, and the amount of electroless plating solution used and the use of ion-exchange water so that the film thickness of the conductive metal layer is 0.08 μm. Except having adjusted the quantity, it carried out similarly to (Preparation of electroconductive fine particles) of Example 1, and obtained the electroconductive fine particles (C5) for a comparison.

[Comparative Example 6]
In Example 13, except that the remainder of the polymerizable composition was changed to 3.1 parts of styrene and 1.9 parts of butyl acrylate, the base material particles for comparison (C6) were prepared in the same manner as in Example 13. Obtained. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, in place of the base particle (1), the base particle (C6) is used, and the amount of electroless plating solution used and the use of ion exchange water so that the film thickness of the conductive metal layer is 0.08 μm. Except that the amount was adjusted, the same conductive fine particles (C6) for comparison were obtained as in Example 1 (Preparation of conductive fine particles).

[Comparative Example 7]
In Example 4, except that the amount of electroless plating solution and the amount of ion-exchanged water were adjusted so that the film thickness of the conductive metal layer was 0.18 μm, Conductive fine particles (C7) for comparison were obtained.

[Comparative Example 8]
In Example 4, except that the amount of electroless plating solution and the amount of ion-exchanged water were adjusted so that the thickness of the conductive metal layer was 0.008 μm, Conductive fine particles (C8) for comparison were obtained.

[Comparative Example 9]
In Example 17, a comparative base particle (C9) was obtained in the same manner as in Example 17 except that the polymerizable composition was changed to 867 parts of styrene. The number average particle size, coefficient of variation (CV value) and glass transition temperature of the obtained base particles were as shown in Table 1.

  Next, conductive fine particles for comparison (C9) were used in the same manner as in (Preparation of conductive fine particles) of Example 1 except that the substrate particles (C9) were used instead of the substrate particles (1). Got.

  Of the base particles obtained in the above Examples and Comparative Examples, the base particles (1), the base particles (2), the base particles (C1), the base particles (17), and the base particles For (18) and substrate particles (C9), the 50% K value at 25 ° C. and 150 ° C. was measured to determine the 50% K value reduction rate (%). The measurement results are shown in Table 2. For reference, 10% K value, 20% K value, 30% K value, 40% K value, and 60% K value at 25 ° C. and 150 ° C. are shown in Table 2, and the K value for each compression rate at 25 ° C. FIG. 1 shows the K value for each compression rate at 150 ° C., and FIG.

  Next, an anisotropic conductive material (conductive adhesive paste) was prepared using the conductive fine particles obtained in Examples 1 to 18 and Comparative Examples 1 to 9, and after the initial resistance value and the temperature cycle test Connection reliability was evaluated by measuring resistance values.

That is, 2 g of conductive fine particles were mixed and dispersed in 100 g of an epoxy resin (“Stractbond (registered trademark) XN-5A” manufactured by Mitsui Chemicals) to prepare a conductive adhesive paste. This conductive adhesive paste 0.1 mg was sandwiched between two PET substrates with an ITO transparent electrode film formed on the inner surface, and subjected to thermocompression bonding at 130 ° C. for 30 minutes while applying a pressure of 13.7 MPa with a press. A piece was made. And first, about the obtained test piece, the resistance value ((ohm)) immediately after preparation was measured by the four probe method, and this was made into the initial stage resistance value. Next, the test piece is subjected to a temperature cycle test, specifically, a test in which the sample is placed in an atmosphere of −40 ° C. for 30 minutes and then in an atmosphere of 100 ° C. for 30 minutes, and this test is repeated 1000 cycles. The resistance value (Ω) after the test was measured by the four probe method, and this was set as the resistance value after the temperature cycle test. The rate of change (%) was calculated from the obtained initial resistance value and the resistance value after the temperature cycle test based on the following formula. The lower the change rate, the better the connection reliability, and specifically, the case where the change rate was less than 10% was regarded as acceptable.
Rate of change (%) = [(resistance value after temperature cycle test−initial resistance value) / initial resistance value] × 100
The obtained initial resistance value, resistance value after temperature cycle test, and rate of change are summarized in Table 1.

  From Table 1, the conductive fine particles of Examples 1 to 18 in which the glass transition temperature of the base particles is 50 to 100 ° C. are both low in initial resistance value and resistance value after temperature cycle test, and also in a small change rate. It was found that it can exhibit excellent connection reliability. In addition, when Examples 4, 15, and 16 were compared, the tendency for the rate of change to increase somewhat as the thickness of the metal layer increased was observed.

  On the other hand, the conductive fine particles of Comparative Examples 2, 4, and 6 in which the glass transition temperature of the base material particles is around 46 ° C. have the initial resistance value equivalent to that of the example, but the resistance value greatly increases after the temperature cycle test. The rate of change was 20% or more, and it was clear that the connection reliability was inferior. Further, the conductive fine particles of Comparative Examples 1, 3, 5, and 9 having a glass transition temperature of around 105 ° C. were found to have a tendency to increase the initial resistance value. Further, the conductive fine particles of Comparative Example 7 having a metal layer thickness of 0.18 μm which is too thick, although the initial resistance value is equivalent to that of the example, the resistance value after the temperature cycle test is increased, resulting in a large change rate. On the contrary, it was clear that the initial resistance value was high in the conductive fine particles of Comparative Example 8 in which the metal layer was too thin as 0.008 μm.

Claims (5)

A conductive fine particle comprising substrate particles and a conductive metal layer covering the surface of the substrate particles, wherein the substrate particles have a glass transition temperature (Tg) of 50 ° C. or higher and 100 ° C. or lower. Conductive fine particles, wherein the conductive metal layer has a thickness of 0.01 μm or more and less than 0.10 μm . The conductive fine particles according to claim 1, wherein the number average particle diameter of the base material particles is 0.5 to 10.0 μm. The conductive fine particles according to claim 1 or 2 , wherein the substrate particles are obtained by polymerizing a polymerizable composition containing 5% by mass or more of a vinyl group-containing monomer and / or polymerizable polysiloxane. At least a portion of the surface with an insulating resin layer, conductive fine particles according to any one of claims 1-3. Anisotropic conductive material comprising conductive fine particles according to any one of claims 1-4.

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