Resin particles for conductive fine particles

Abstract

To provide resin particles for conductive fine particles which can achieve low resistance when being pressurized and connected at low pressure.SOLUTION: Resin particles for conductive fine particles are core-shell particles including a core and a shell coating the core, in which a compressive deformation recovery rate of the resin particles is 25% or less, a compressive elastic modulus (10% K value) when the diameter of the resin particles is displaced by 10% is 1,500 N / mm2 or less, and a coefficient (CV) of variation of the particle diameter of the resin particles is 10% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to resin particles for use as conductive fine particles. [Background technology]

[0002] Conventionally, in the assembly of electronic devices, a connection method using anisotropic conductive materials has been adopted to electrically connect a large number of opposing electrodes and wirings. Anisotropic conductive materials are materials in which conductive particles are mixed with a binder resin or the like, and examples include anisotropic conductive paste (ACP), anisotropic conductive film (ACF), anisotropic conductive ink, and anisotropic conductive sheet.

[0003] The conductive microparticles used for anisotropic conductive connections generally have a core (substrate) of resin particles with a conductive metal layer such as nickel formed on the surface of the core, because they have excellent compressive deformation properties.

[0004] In particular, in recent years, as electronic components have become smaller and more densely mounted, the electrodes that are connected, as well as the substrates and films that hold the electrodes, have tended to become thinner, and the application of excessive pressure during mounting has led to damage to the substrates, etc. Therefore, there is a demand for anisotropic conductive materials that can be used for low-pressure mounting, and various attempts have been made to obtain conductive particles that can be easily deformed without the application of excessive pressure.

[0005] For example, in Patent Document 1, the compressive elastic modulus when the diameter of the resin particles is displaced by 10% is set to 100 to 3000 N / mm 2 It is disclosed that when the post-compression recovery rate of resin particles is measured in a range where the compression rate is 10 to 60% of the diameter, there exists a compression rate where the post-compression recovery rate is 0.0%, thereby obtaining conductive particles that can achieve low resistance even when connected under pressure at low pressure.

[0006] In Patent Document 2, resin particles serving as base particles are made into core-shell particles, and the glass transition temperature (Tg core) is set to less than 40°C, and the glass transition temperature (Tg shell ) to the glass transition temperature (Tg core ) and controlling the degree of crosslinking of the shell to be equal to or higher than the degree of crosslinking of the core, it is disclosed that conductive fine particles having excellent softness and reduced variation in mechanical properties between particles can be obtained.

[0007] In Patent Document 3, the compressive elastic modulus (10% K value) when 10% of the particle diameter of the polymer microparticles is displaced is set to 10 to 250 kgf / mm 2 It is disclosed that by controlling the compressive deformation recovery rate to 30% or more and the breaking strain to 30% or more, conductive fine particles having flexibility that will not damage the substrate and its wiring can be obtained.

[0008] In Patent Document 4, the Tg of the shell portion of the fine particles changes continuously or discontinuously from the vicinity of the core portion to the outermost layer of the shell portion, the Tg near the core portion is 0°C or less, and the Tg near the outermost layer of the shell portion is 0°C or more, and the K value at 10% compression deformation is 1.47 × 10 9 N / m 2 It is disclosed that by controlling the conditions as follows, conductive fine particles that are flexible yet resistant to aggregation and coalescence can be obtained. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-96329 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-63673 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-319309 [Patent Document 4] Japanese Patent Application Laid-Open No. 2002-363205 Summary of the Invention [Problem to be solved by the invention]

[0010] However, although the softened resin particles as in Patent Documents 1 and 2 can ensure low resistance even when the pressure during pressure connection is relatively low, there are cases where the initial connection resistance cannot be kept sufficiently low when the pressure during pressure connection is low, for example, 2.5 MPa or less. Furthermore, Patent Documents 3 and 4 do not consider connection resistance at all.

[0011] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide resin particles for conductive fine particles that can achieve low resistance even when pressurized and connected at low pressure. [Means for solving the problem]

[0012] The present inventors have conducted extensive research to solve the above problems, and as a result, have discovered a method for producing core-shell particles, which have a core and a shell covering the core, and which have a compressive deformation recovery rate of 25% or less and a compressive modulus of elasticity (10% K value) of 1500 N / mm when the diameter is displaced by 10%. 2 The inventors have discovered that if the resin particles are controlled so that the coefficient of variation (CV) of particle size is 10% or less, they have excellent dispersibility and suppress aggregation, and can easily deform even at low pressure, ensuring a large contact area with the connected medium. This makes it possible to achieve low resistance even when pressure-connected at low pressure, and has led to the completion of the present invention.

[0013] That is, the resin particles according to the present invention are resin particles for conductive fine particles, and the resin particles are core-shell particles having a core and a shell covering the core, and the compressive deformation recovery rate of the resin particles is 25% or less, and the compressive elastic modulus (10% K value) when the diameter of the resin particles is displaced by 10% is 1500 N / mm 2 The resin particles are characterized in that the coefficient of variation (CV) of particle diameter is 10% or less.

[0014] In the resin particles of the present invention, the core is preferably a copolymer containing, as monomer units, a silicon-free monofunctional (meth)acrylate having a homopolymer glass transition temperature (Tg) of above 0°C and a silicon-free monofunctional (meth)acrylate having a homopolymer glass transition temperature (Tg) of 0°C or lower.

[0015] In the resin particles of the present invention, the content of the silicon-free monofunctional (meth)acrylate having a homopolymer glass transition temperature (Tg) of 0°C or less is preferably 15% by mass or more and 50% by mass or less, based on 100% by mass of the total amount of monomers forming the core.

[0016] In the resin particles of the present invention, the content of the silicon-free monofunctional (meth)acrylate having a homopolymer glass transition temperature (Tg) of more than 0°C is preferably 35% by mass or more and 70% by mass or less, based on 100% by mass of the total amount of monomers forming the core.

[0017] In the resin particles of the present invention, the glass transition temperature (Tgcore) of the core calculated based on the FOX equation is preferably 0° C. or lower.

[0018] In the resin particles of the present invention, the core preferably has a crosslinking degree represented by the following formula of 30% or less. Degree of crosslinking (%) = (mass of crosslinkable monomer / mass of total monomer) × 100

[0019] In the resin particles of the present invention, the average thickness of the shell is preferably 0.05 μm or more and 1 μm or less.

[0020] In the resin particles of the present invention, the ratio of the average shell thickness to the number-average particle size of the resin particles is preferably 0.01 or more and 0.05 or less.

[0021] In the resin particles of the present invention, the dispersion ratio calculated by the following measurement method is preferably 90% or more. (Method for measuring dispersion rate) (1) 2.5 g of resin particles and 100 g of a 1% aqueous solution of polyoxyethylene alkyl ether sulfate ester ammonium salt, which is an emulsifier, are placed in a 200 mL beaker and ultrasonically dispersed for 15 minutes, and then passed through a sieve with openings 1.6 μm times the number-average particle diameter. (2) Dry the sieve at 120°C for 2 hours. (3) The total weight (g) of the sieve and the polymer particles remaining on the sieve is measured, and the weight (g) of the sieve is subtracted to determine the weight (g) of the polymer particles remaining on the sieve. (4) The weight (g) of the polymer particles remaining on the sieve is applied to the following formula to calculate the dispersion rate (%). Dispersion rate (%) = 100 - ((weight of polymer particles remaining on the sieve (g) / 2.5 (g)) x 100) [Effects of the Invention]

[0022] According to the present invention, the resin particles are core-shell particles having a core and a shell covering the core, and have a compressive deformation recovery rate of 25% or less and a compressive elastic modulus (10% K value) of 1500 N / mm when the diameter is displaced by 10%. 2 Hereinafter, the resin particles are controlled so that the coefficient of variation (CV) of particle size is 10% or less. Therefore, by using these resin particles as a base material for conductive microparticles, it is possible to achieve low resistance even when pressure-connected at low pressure. DETAILED DESCRIPTION OF THE INVENTION

[0023] 1.Resin particles (base material) The resin particles for conductive fine particles of the present invention have a core and a shell that covers the core.

[0024] The resin particles have a compressive deformation recovery rate (hereinafter sometimes simply referred to as "recovery rate") of 25% or less. Here, the compressive deformation recovery rate is calculated by applying the maximum displacement L1 (μm) when the resin particles are compressed to the maximum load (49 mN) and the recovered displacement L2 (μm) when the load is reduced from the maximum load to the minimum load (0.49 mN) to the following formula, and the detailed measurement method will be described in the Examples. Recovery rate (%)=(L2 / L1)×100

[0025] By setting the recovery rate to 25% or less, the flexibility of the resin particles is improved, making them more easily deformable even at low pressures, such as 2.5 MPa or less. This increases the contact area with the connected medium, thereby reducing resistance even when pressure-connected at low pressures. The recovery rate of the resin particles is preferably 23% or less, more preferably 21% or less, and even more preferably 18% or less. On the other hand, if the recovery rate is too low, for example, when conductive fine particles based on resin particles are used in an anisotropic conductive material, the repulsive force in the connected state may be too small, resulting in an increase in the initial resistance value. Therefore, the recovery rate of the resin particles is preferably 1% or more, more preferably 2% or more, and even more preferably 3% or more.

[0026] The compressive elastic modulus (10% K value) of the resin particles when the diameter is displaced by 10% is 1500 N / mm 2 The 10% K value of the resin particles is 1500N / mm 2 By doing so, the softness of the resin particles is improved, making them easier to deform even at low pressure, and the contact area with the connected medium can be increased, thereby reducing resistance even when pressure-connected at low pressure.

[0027] When the number average particle diameter of the resin particles is 10.0 μm or more, the 10% K value of the resin particles is 600 N / mm 2 This makes it possible to easily deform the resin particles at a low pressure of 2.5 MPa or less. More preferably, it is 450 N / mm 2 or less, more preferably 350N / mm 2 On the other hand, if the 10% K value of the resin particles is too low, the particles become too soft and it becomes difficult to maintain their spherical shape during plating processing, etc. Therefore, the 10% K value of resin particles having a number average particle size of 10.0 μm or more is preferably 10 N / mm 2 More preferably, 50N / mm 2 More preferably, 100N / mm 2 That's all.

[0028] When the number average particle diameter of the resin particles is less than 10.0 μm, the 10% K value of the resin particles is 1350 N / mm 2 This makes it possible to easily deform the resin particles at a low pressure of 1 MPa or less. More preferably, it is 1250 N / mm 2 or less, more preferably 1000N / mm 2 On the other hand, if the 10% K value of the resin particles is too low, the particles become too soft and it becomes difficult to maintain their spherical shape during plating processing, etc. Therefore, the 10% K value of resin particles having a number average particle size of less than 10.0 μm is preferably 20 N / mm or less. 2 More preferably, 150N / mm 2 More preferably, 300N / mm 2 More than 500N / mm 2 That's all.

[0029] The 10% K value of resin particles can be measured by a compression test using a known micro-compression tester. For example, a known micro-compression tester (such as the MCT-W500 manufactured by Shimadzu Corporation) is used to apply a load toward the center of the particle at room temperature at a load application rate of 0.445 mN / sec. The compression load and compression displacement are measured when the particle is deformed until the particle diameter is displaced by 10%, and the 10% K value can be calculated based on the following formula.

[0030]

number

[0031] The number-average particle diameter of the resin particles is preferably 2 μm or more and 50 μm or less. If the number-average particle diameter of the resin particles is within the above range, the resin particles can be suitably used for, for example, electrical connection of electrodes and wiring in semiconductor packaging used for touch panels, LEDs, etc. An example of a touch panel application is the connection between a touch panel lead circuit and a flexible printed circuit board (FPC). The number-average particle diameter of the resin particles is more preferably 4 μm or more, even more preferably 6 μm or more, more preferably 35 μm or less, even more preferably 25 μm or less.

[0032] The number-based coefficient of variation (CV value) of the particle diameter of the resin particles is 10% or less. This suppresses variations in mechanical properties when the resin particles are used as conductive fine particles, thereby improving connection reliability. It is preferably 8.0% or less, more preferably 5.0% or less, even more preferably 4.0% or less, and even more preferably 3.0% or less. There is no particular restriction on the lower limit of the number-based coefficient of variation (CV value) of the particle diameter of the resin particles, but it is preferably 0.5% or more, more preferably 1% or more, and even more preferably 1.5% or more.

[0033] The number average particle size and the coefficient of variation of particle size of the resin particles referred to in the present invention are values ​​obtained by measurement using a Coulter counter method, and the measurement method will be described in detail in the Examples.

[0034] The resin particles preferably have a dispersion rate of 90% or more. A dispersion rate of 90% or more allows for the production of conductive fine particles with suppressed aggregation, making it easier to achieve low resistance. The dispersion rate of the resin particles is more preferably 93% or more, even more preferably 95% or more, even more preferably 97% or more, and most preferably 100%. The dispersion rate is measured as follows. (Method for measuring dispersion rate) (1) 2.5 g of resin particles and 100 g of a 1% aqueous solution of polyoxyethylene alkyl ether sulfate ester ammonium salt, which is an emulsifier, are placed in a 200 mL beaker and ultrasonically dispersed for 15 minutes, and then passed through a sieve with openings 1.6 μm times the number-average particle diameter. (2) Dry the sieve at 120°C for 2 hours. (3) The total weight (g) of the sieve and the polymer particles remaining on the sieve is measured, and the weight (g) of the sieve is subtracted to determine the weight (g) of the polymer particles remaining on the sieve. (4) The weight (g) of the polymer particles remaining on the sieve is applied to the following formula to calculate the dispersion rate (%). Dispersion rate (%) = 100 - ((weight of polymer particles remaining on the sieve (g) / 2.5 (g)) x 100)

[0035] When measuring the dispersion rate of resin particles, if a sieve with a mesh size 1.6 times the number-average particle size is not available, the type and mesh size of the sieve may be determined based on the following criteria: For the electroformed sieve described below, see JP-A-2001-252588. Number average particle size less than 6 μm: Electroformed sieve with 8 μm openings Number average particle size 6 μm or more but less than 9 μm: electroformed sieve with 12 μm openings Number average particle size 9 μm or more and less than 13 μm: electroformed sieve with 16 μm openings Number average particle size 13 μm or more and less than 17 μm: Stainless steel sieve with 25 μm openings Number average particle size 17 μm or more and less than 24 μm: Stainless steel sieve with 32 μm openings Number average particle size 24 μm or more and less than 40 μm: Stainless steel sieve with 45 μm openings Number average particle size 40 μm or more and less than 70 μm: Stainless steel sieve with 75 μm openings Number average particle size 70 μm or more and less than 140 μm: Stainless steel sieve with 150 μm openings Number average particle size 140 μm or more but less than 200 μm: Stainless steel sieve with 250 μm openings

[0036] The degree of crosslinking of the resin particles is preferably 50% or less, more preferably 40% or less, and even more preferably 30% or less, and is preferably 5% or more, more preferably 10% or more, and even more preferably 20% or more. When the degree of crosslinking of the resin particles is in the above range, softness and flexibility are easily exhibited. The degree of crosslinking in the resin particles can be evaluated by the following formula: In the formula, the crosslinkable monomer includes vinyl-based crosslinkable monomers and silane-based crosslinkable monomers, which will be described later. Degree of crosslinking (%) = (mass of crosslinkable monomer / mass of total monomer) × 100

[0037] The shape of the resin particles (substrate) is not particularly limited and may be, for example, spherical, spheroidal, sugar candy-like, thin plate-like, needle-like, or cocoon-like, with spherical being preferred and true sphere being particularly preferred.

[0038] 1-1. Core In the present invention, the core is preferably a copolymer containing, as monomer units, a silicon-free monofunctional (meth)acrylate having a homopolymer glass transition temperature (Tg) above 0° C. (hereinafter sometimes simply referred to as a "high Tg silicon-free monofunctional (meth)acrylate") and a silicon-free monofunctional (meth)acrylate having a homopolymer glass transition temperature (Tg) of 0° C. or lower (hereinafter sometimes simply referred to as a "low Tg silicon-free monofunctional (meth)acrylate"). A core containing these two types of monomers as constituent monomers has excellent softness and flexibility.

[0039] The glass transition temperature (Tg) of a homopolymer can be determined by differential scanning calorimetry (DSC) as shown in the Examples, for example, from the values ​​listed in POLYMER HANDBOOK FOURTH EDITION, Painting and Paints (Paint Publishing Co., Ltd., Vol. 10 (No. 358), 1982). For those not listed therein, the Tg can be determined by differential scanning calorimetry (DSC) as shown in the Examples.

[0040] Below, we will first explain general monomers that can be used as the core-constituting monomer (meaning the monomer that serves as the raw material for forming the core), and then we will explain in detail high Tg silicon-free monofunctional (meth)acrylates and low Tg silicon-free monofunctional (meth)acrylates selected from among them.

[0041] 1-1-1. Core Monomer The monomer constituting the core may be a so-called vinyl-based monomer alone, or a so-called silane-based monomer may be used in combination with the vinyl-based monomer. When a vinyl-based monomer is used, the vinyl group is polymerized to form an organic skeleton, which can exhibit excellent elastic deformation during pressure connection. On the other hand, when a silane-based monomer is used, a siloxane bond is generated by a hydrolysis and condensation reaction of the silane-based monomer to form a polysiloxane skeleton, which can exhibit high contact pressure against the connected body during pressure connection. Vinyl-based monomers are divided into vinyl-based crosslinkable monomers and vinyl-based non-crosslinkable monomers, and silane-based monomers are divided into silane-based crosslinkable monomers and silane-based non-crosslinkable monomers.

[0042] A vinyl-based crosslinkable monomer is one that has two or more crosslinkable groups, including at least a vinyl group, in the molecule. Specifically, it can be a monomer (monomer (1)) that has two or more vinyl groups in one molecule, or a monomer (monomer (2)) that has one vinyl group and a functional group other than the vinyl group (a protic hydrogen-containing group such as a carboxy group or a hydroxy group, or a terminal functional group such as an alkoxy group) in one molecule. However, in the case of monomer (2), in order to form a crosslinked structure as a vinyl-based crosslinkable monomer, it is necessary that the group that can be reacted (bonded) with, such as a carboxy group, a hydroxy group, or an alkoxy group, that monomer (2) has is present in another monomer.

[0043] In the present invention, the term "vinyl group" includes not only a carbon-carbon double bond but also a substituent having a polymerizable carbon-carbon double bond, such as a (meth)acryloyl group, an allyl group, an isopropenyl group, a vinylphenyl group, or an isopropenylphenyl group. In addition, in this specification, "(meth)acryloyl group," "(meth)acrylate," and "(meth)acrylic" respectively refer to "acryloyl group and / or methacryloyl group," "acrylate and / or methacrylate," and "acrylic and / or methacrylic."

[0044] Examples of the monomer (1) include allyl (meth)acrylates such as allyl (meth)acrylate; Alkanediol di(meth)acrylates such as 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, and 1,3-butanediol di(meth)acrylate; di(meth)acrylates such as polyalkylene glycol di(meth)acrylates such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, decaethylene glycol di(meth)acrylate, pentadecaethylene glycol di(meth)acrylate, pentacontahexaethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate; Tri(meth)acrylates such as trimethylolpropane tri(meth)acrylate; tetra(meth)acrylates such as pentaerythritol tetra(meth)acrylate; hexa(meth)acrylates such as dipentaerythritol hexa(meth)acrylate; aromatic hydrocarbon-based crosslinking agents such as divinylbenzene, divinylnaphthalene, and derivatives thereof (preferably styrene-based polyfunctional monomers such as divinylbenzene); Heteroatom-containing crosslinkers such as N,N-divinylaniline, divinyl ether, divinyl sulfide, and divinyl sulfonic acid; The monomer (1) may be used alone or in combination of two or more kinds.

[0045] Examples of the monomer (2) include monomers having a carboxy group, such as (meth)acrylic acid, carboxymethyl (meth)acrylate, carboxyethyl (meth)acrylate, carboxypropyl (meth)acrylate, carboxybutyl (meth)acrylate, and carboxypentyl (meth)acrylate; Monomers having a hydroxy group, such as hydroxy group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate, and hydroxy group-containing styrenes such as p-hydroxystyrene; Monomers having an amino group, such as aminoalkyl (meth)acrylates such as aminomethyl (meth)acrylate, aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, aminobutyl (meth)acrylate, and aminopentyl (meth)acrylate; alkylaminoalkyl (meth)acrylates such as methylaminomethyl (meth)acrylate, ethylaminomethyl (meth)acrylate, methylaminoethyl (meth)acrylate, ethylaminoethyl (meth)acrylate, methylaminopropyl (meth)acrylate, and ethylaminopropyl (meth)acrylate; and dialkylaminoalkyl (meth)acrylates such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, and diethylaminopropyl (meth)acrylate; Monomers having an alkoxy group, such as alkoxy group-containing (meth)acrylates such as 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, and 2-butoxyethyl (meth)acrylate, and alkoxystyrenes such as p-methoxystyrene; The monomer (2) may be used alone or in combination of two or more kinds.

[0046] Examples of vinyl-based non-crosslinkable monomers include a monomer (monomer (3)) having one vinyl group per molecule, or a monomer (2) in which the monomer components do not contain other monomers having a group that reacts with a functional group other than the vinyl group possessed by monomer (2).

[0047] Examples of the monomer (3) include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; cycloalkyl (meth)acrylates such as cyclopropyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cyclooctyl (meth)acrylate, cycloundecyl (meth)acrylate, cyclododecyl (meth)acrylate, isobornyl (meth)acrylate, and 4-t-butylcyclohexyl (meth)acrylate; aralkyl (meth)acrylates such as phenyl (meth)acrylate, benzyl (meth)acrylate, tolyl (meth)acrylate, and phenethyl (meth)acrylate; Alkylstyrenes such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, and pt-butylstyrene; alkylene glycol monoalkyl ether (meth)acrylates such as ethylene glycol monobutyl ether (meth)acrylate, diethylene glycol monobutyl ether (meth)acrylate, diethylene glycol monomethyl ether (meth)acrylate, diethylene glycol monoethyl ether (meth)acrylate, and triethylene glycol monomethyl ether (meth)acrylate; alkylene glycol monoaryl ether (meth)acrylates such as diethylene glycol monophenyl ether (meth)acrylate, ethylene glycol monophenyl ether (meth)acrylate, and ethylene glycol monotolyl ether (meth)acrylate; styrene-based monofunctional monomers such as halogen-containing styrenes such as o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene; The monomer (3) may be used alone or in combination of two or more kinds.

[0048] Silane-based crosslinking monomers have two or more crosslinkable groups (alkoxy groups, vinyl groups, etc.) in the molecule, and are divided into those that form a crosslinked structure (first form) between an organic polymer skeleton (e.g., a vinyl-based polymer skeleton) and an organic polymer skeleton, those that form a crosslinked structure (second form) between a polysiloxane skeleton and a polysiloxane skeleton, and those that form a crosslinked structure (third form) between an organic polymer skeleton and a polysiloxane skeleton. Among these, silane-based crosslinking monomers that can form a crosslinked structure of the third form are preferred.

[0049] Examples of silane-based crosslinkable monomers that can form the first type include dimethyldivinylsilane, methyltrivinylsilane, tetravinylsilane, etc. These silane-based crosslinkable monomers may be used alone or in combination of two or more.

[0050] Examples of silane-based crosslinkable monomers that can form the second form include tetrafunctional silane-based monomers such as tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, and tetrabutoxysilane; and trifunctional silane-based monomers such as methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, hexyltrimethoxysilane, and hexyltriethoxysilane. These silane-based crosslinkable monomers may be used alone or in combination of two or more.

[0051] Examples of silane-based crosslinkable monomers that can form the third form include those having a (meth)acryloyl group, such as 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-acryloxypropyltriethoxysilane, and 3-methacryloxyethoxypropyltrimethoxysilane; those having a vinyl group such as vinyltrimethoxysilane, vinyltriethoxysilane, and p-styryltrimethoxysilane; those having an epoxy group, such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; those having an amino group, such as 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane; The silane-based crosslinkable monomers may be used alone or in combination of two or more.

[0052] Examples of silane-based non-crosslinkable monomers include bifunctional silane-based monomers such as dialkylsilanes (e.g., dimethyldimethoxysilane, dimethyldiethoxysilane, etc.) and monofunctional silane-based monomers (e.g., trialkylsilanes (e.g., trimethylmethoxysilane, trimethylethoxysilane, etc.)) These silane-based non-crosslinkable monomers may be used alone or in combination of two or more.

[0053] 1-1-2. High Tg silicon-free monofunctional (meth)acrylate The high-Tg silicon-free monofunctional (meth)acrylate is a monomer that has a homopolymer glass transition temperature (Tg) above 0°C, does not contain silicon, and contains one (meth)acryloyl group per molecule. By including the high-Tg silicon-free monofunctional (meth)acrylate as a monomer unit in the core, the recovery rate of the resin particles can be reduced, and flexibility can be improved. The high-Tg silicon-free monofunctional (meth)acrylate preferably has a homopolymer glass transition temperature (Tg) of 5°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher, and preferably 300°C or lower, more preferably 200°C or lower, and even more preferably 150°C or lower.

[0054] The content of the high Tg silicon-free monofunctional (meth)acrylate is preferably 35% by mass or more and 70% by mass or less, based on 100% by mass of the total amount of monomers forming the core. By having the content of the high Tg silicon-free monofunctional (meth)acrylate be 35% by mass or more, the recovery rate of the resin particles can be reduced, making it easier to improve flexibility. Therefore, the content of the high Tg silicon-free monofunctional (meth)acrylate is preferably 35% by mass or more, more preferably 40% by mass or more, and even more preferably 45% by mass or more. On the other hand, if the content of the high Tg silicon-free monofunctional (meth)acrylate is too high, the content of the low Tg silicon-free monofunctional (meth)acrylate will be low, making it difficult to improve softness. Therefore, the content of the high Tg silicon-free monofunctional (meth)acrylate is preferably 70% by mass or less, more preferably 65% ​​by mass or less, and even more preferably 60% by mass or less.

[0055] Examples of high Tg silicon-free monofunctional (meth)acrylates include (meth)acrylates of the above-mentioned monomer (2) and the above-mentioned monomer (3) having a homopolymer glass transition temperature (Tg) of above 0°C.

[0056] As the monomer (2), at least one monomer selected from the group consisting of a monomer having a carboxy group and a monomer having a hydroxy group is preferred. As the monomer having a carboxy group, (meth)acrylic acid is preferred. As the monomer having a hydroxy group, hydroxyalkyl (meth)acrylate is preferred, hydroxyalkyl methacrylate is more preferred, hydroxyalkyl methacrylate having an alkyl group with 1 to 4 carbon atoms is even more preferred, and hydroxyalkyl methacrylate having an alkyl group with 2 to 3 carbon atoms is even more preferred.

[0057] As the monomer (3), at least one monomer selected from the group consisting of alkyl (meth)acrylates, cycloalkyl (meth)acrylates, and aralkyl (meth)acrylates is preferred, at least one monomer selected from the group consisting of alkyl (meth)acrylates and cycloalkyl (meth)acrylates is more preferred, and alkyl (meth)acrylates are even more preferred.

[0058] As the alkyl (meth)acrylate, at least one monomer selected from the group consisting of methyl acrylic acid and alkyl methacrylic acid having an alkyl group with 1 to 5 carbon atoms is preferred, alkyl methacrylic acid having an alkyl group with 3 to 4 carbon atoms is more preferred, and alkyl methacrylic acid having an alkyl group with 4 carbon atoms is even more preferred.

[0059] As the cycloalkyl(meth)acrylates, cycloalkyl(meth)acrylates in which the cycloalkyl group has 5 to 30 carbon atoms are preferred, cycloalkyl(meth)acrylates in which the cycloalkyl group has 5 to 10 carbon atoms are more preferred, cycloalkyl(meth)acrylates in which the cycloalkyl group has 5 to 7 carbon atoms are more preferred, and cycloalkyl(meth)acrylates in which the cycloalkyl group has 6 carbon atoms are even more preferred.

[0060] As the aralkyl(meth)acrylates, aralkyl(meth)acrylates containing an aralkyl group having 7 to 12 carbon atoms are preferred, aralkyl(meth)acrylates containing an aralkyl group having 7 to 8 carbon atoms are more preferred, and aralkyl(meth)acrylates containing an aralkyl group having 7 carbon atoms are even more preferred.

[0061] 1-1-3. Low Tg silicon-free monofunctional (meth)acrylate The low Tg silicon-free monofunctional (meth)acrylate is a monomer that has a homopolymer glass transition temperature (Tg) of 0°C or lower, does not contain silicon, and contains one (meth)acryloyl group per molecule. When the core contains the low Tg silicon-free monofunctional (meth)acrylate as a monomer unit, the 10% K value of the resin particles can be reduced, improving softness. The low Tg silicon-free monofunctional (meth)acrylate preferably has a homopolymer glass transition temperature (Tg) of -2°C or lower, more preferably -5°C or lower, and even more preferably -20°C or lower, and preferably -150°C or higher, more preferably -120°C or higher, and even more preferably -100°C or higher.

[0062] The content of the low Tg silicon-free monofunctional (meth)acrylate is preferably 15% by mass or more and 50% by mass or less, based on 100% by mass of the total amount of monomers forming the core. By ensuring that the content of the low Tg silicon-free monofunctional (meth)acrylate is 15% by mass or more, the 10% K value of the resin particles can be reduced, improving softness. Therefore, the content of the low Tg silicon-free monofunctional (meth)acrylate is preferably 15% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more. On the other hand, if the content of the low Tg silicon-free monofunctional (meth)acrylate is too high, the content of the high Tg silicon-free monofunctional acrylate will be low, making it difficult to reduce the recovery rate. Therefore, the content of the low Tg silicon-free monofunctional (meth)acrylate is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less.

[0063] The ratio of the content of the low Tg silicon-free monofunctional (meth)acrylate to the content of the high Tg silicon-free monofunctional (meth)acrylate in 100% by mass of the total amount of monomers forming the core is preferably 0.2 or more, more preferably 0.4 or more, and preferably 1.2 or less, more preferably 0.9 or less, which makes it easier to achieve both flexibility and softness.

[0064] Examples of the low Tg silicon-free monofunctional (meth)acrylate include (meth)acrylates of the above-mentioned monomer (2) and the above-mentioned monomer (3) having a homopolymer glass transition temperature (Tg) of 0° C. or lower.

[0065] As the monomer (2), a monomer having a hydroxy group is preferred. As the monomer having a hydroxy group, a hydroxyalkyl (meth)acrylate is preferred, a hydroxyalkyl acrylate is more preferred, a hydroxyalkyl acrylate in which the alkyl group has 1 to 4 carbon atoms is even more preferred, and a hydroxyalkyl acrylate in which the alkyl group has 2 to 3 carbon atoms is even more preferred.

[0066] As the monomer (3), at least one monomer selected from the group consisting of alkyl (meth)acrylates, alkylene glycol monoalkyl ether (meth)acrylates, and alkylene glycol monoaryl ether (meth)acrylates is preferred, and alkyl (meth)acrylates are more preferred.

[0067] Examples of alkyl (meth)acrylates include alkyl acrylate and alkyl methacrylate. As the alkyl acrylate, an alkyl acrylate having 2 to 10 carbon atoms in the alkyl group is preferred, and an alkyl acrylate having 2 to 6 carbon atoms is more preferred. As the alkyl methacrylate, an alkyl methacrylate having 8 to 30 carbon atoms in the alkyl group is preferred, and an alkyl methacrylate having 10 to 20 carbon atoms in the alkyl group is more preferred.

[0068] As the alkylene glycol monoalkyl ether (meth)acrylates, alkylene glycol monoalkyl ether (meth)acrylates in which the number of repeating units (n) of the alkylene glycol structure is 1 to 5 and the alkyl group has 1 to 5 carbon atoms are preferred, and alkylene glycol monoalkyl ether (meth)acrylates in which the number of repeating units (n) of the alkylene glycol structure is 1 to 3 and the alkyl group has 1 to 4 carbon atoms are more preferred.

[0069] As the alkylene glycol monoaryl ether (meth)acrylates, alkylene glycol monoaryl ether (meth)acrylates in which the number of repeating units of the alkylene glycol structure (n) is 1 to 5 are preferred, and alkylene glycol monoaryl ether (meth)acrylates in which the number of repeating units of the alkylene glycol structure (n) is 1 to 2 are more preferred.

[0070] As a combination of monomer components constituting the core as described above, a combination of a high Tg silicon-free monofunctional (meth)acrylate and a low Tg silicon-free monofunctional (meth)acrylate is preferred, and a combination of a silane-based crosslinkable monomer, a high Tg silicon-free monofunctional (meth)acrylate, a low Tg silicon-free monofunctional (meth)acrylate, and a di(meth)acrylate of monomer (1) is more preferred.

[0071] 1-1-4. Core properties The glass transition temperature (Tgcore) of the core calculated based on the FOX equation is preferably 0°C or lower. When the glass transition temperature (Tgcore) of the core is 0°C or lower, it becomes easier to reduce the 10% K value of the resin particles. The glass transition temperature (Tgcore) of the core is more preferably -3°C or lower, even more preferably -5°C or lower, and even more preferably -10°C or lower. There is no particular restriction on the lower limit of the glass transition temperature (Tgcore) of the core, but it is preferably -50°C or higher, more preferably -30°C or higher, and even more preferably -20°C or higher.

[0072] The FOX formula is a formula for calculating the glass transition temperature Tg of a copolymer based on the glass transition temperatures Tg of the homopolymers of each monomer that constitutes the copolymer, and details of the formula are described in Bulletin of the American Physical Society, Series 2, Vol. 1, No. 3, p. 123 (1956). Specifically, the glass transition temperature Tgcore calculated by the FOX formula is calculated using the following formula:

[0073]

number

[0074] [In the formula, Tgcore is the glass transition temperature (unit: absolute temperature) of a copolymer whose monomer unit is a non-crosslinkable monomer, W i is the mass fraction of non-crosslinking monomer i, Tg i represents the glass transition temperature (unit: absolute temperature) of the homopolymer formed from the non-crosslinkable monomer i. This refers to the value obtained by converting the glass transition temperature Tgcore (unit: absolute temperature) calculated by the formula (2) from absolute temperature (K) to Celsius temperature (°C).

[0075] The glass transition temperatures (Tg) of homopolymers of various monomers for calculation by the FOX equation can be, for example, those listed in POLYMER HANDBOOK FOURTH EDITION, Coatings and Paints (Paint Publishing Co., Ltd., Vol. 10 (No. 358), 1982). Glass transition temperatures not listed here can be determined by differential scanning calorimetry (DSC) as shown in the examples.

[0076] In the core of the present invention, the degree of crosslinking is preferably 30% or less, more preferably 20% or less, and even more preferably 15% or less, and is preferably 5% or more, more preferably 7% or more, and even more preferably 10% or more. When the degree of crosslinking of the core is within the above range, it is easy to exhibit appropriate softness and flexibility. The degree of crosslinking in the core can be evaluated by the following formula: In the formula, the crosslinkable monomer includes the above-mentioned vinyl-based crosslinkable monomer and the above-mentioned silane-based crosslinkable monomer. Degree of crosslinking (%) = (mass of crosslinkable monomer / mass of total monomer) × 100

[0077] The number-average particle diameter of the core is preferably 2 μm or more and 50 μm or less. If the number-average particle diameter of the core is within the above range, it can be suitably used for, for example, electrical connection of electrodes and wiring in semiconductor packaging used for touch panels, LEDs, etc. An example of use in touch panels is the connection between a touch panel lead circuit and a flexible printed circuit board (FPC). The number-average particle diameter of the core is more preferably 4 μm or more, even more preferably 6 μm or more, more preferably 40 μm or less, even more preferably 35 μm or less.

[0078] The coefficient of variation (CV value) of the core particle diameter is preferably 10% or less, more preferably 8.0% or less, even more preferably 5.0% or less, and even more preferably 4.0% or less. By reducing the coefficient of variation of the core particle diameter, it is possible to suppress variations in mechanical properties when the conductive fine particles are formed. There is no particular lower limit for the coefficient of variation of the core particle diameter, but it is preferably, for example, 0.5% or more, more preferably 1% or more, and even more preferably 1.5% or more.

[0079] 1-2.Shell The monomer component constituting the shell may be the above-mentioned vinyl-based monomer or silane-based monomer, or a combination of these may be used. The above-mentioned vinyl-based monomer is preferred as the monomer component constituting the shell, and the above-mentioned monomer (1) is preferred as the vinyl-based monomer, and di(meth)acrylates are preferred as the monomer (1). By using these monomers as the monomer component constituting the shell, the swelling resistance of the resin particles can be improved, and dispersibility can be further improved. The di(meth)acrylate is preferably polyalkylene glycol di(meth)acrylate. The polyalkylene glycol di(meth)acrylate is preferably polyalkylene glycol di(meth)acrylate having a number (n) of repeating units of the alkylene glycol structure of 2 to 8. This makes it easier for the core to exhibit flexibility. A polyalkylene glycol di(meth)acrylate having a number (n) of repeating units of the alkylene glycol structure of 3 to 5 is more preferred, and a polyalkylene glycol di(meth)acrylate having a number (n) of repeating units of the alkylene glycol structure of 3 is even more preferred.

[0080] The content of monomer (1) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, particularly preferably 97% by mass or more, and most preferably 100% by mass, based on 100% by mass of the monomer components forming the shell.

[0081] The higher the crosslinking degree of the shell, the better the swelling resistance and dispersibility of the resin particles, so the crosslinking degree of the shell is preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, even more preferably 95% or more, and most preferably 100%. The degree of crosslinking in the shell can be evaluated by the following formula: In the formula, the crosslinkable monomer includes the above vinyl-based crosslinkable monomer and the above silane-based crosslinkable monomer. Degree of crosslinking (%) = (mass of crosslinkable monomer / mass of total monomer) × 100

[0082] The average thickness of the shell is preferably 0.05 μm or more and 1 μm or less, more preferably 0.1 μm or more and 0.8 μm or less, and even more preferably 0.2 μm or more and 0.7 μm or less. This makes it easier for the shell to exhibit its functions such as swelling resistance. The average thickness of the shell referred to in the present invention can be calculated using the Coulter counter method according to the following formula. Average shell thickness (μm) = (number average particle size A of resin particles (μm) - number average particle size B of cores before shell coating (μm)) / 2

[0083] The ratio of the average shell thickness (μm) to the number-average particle size (μm) of the resin particles is preferably 0.01 to 0.05, more preferably 0.02 to 0.04, which allows the core to exhibit its flexibility and softness while the shell can easily exhibit its functions such as swelling resistance.

[0084] 2.Conductive particles The present invention also includes conductive fine particles in which at least one conductive metal layer is formed on the surface of the resin particles (substrate).The conductive fine particles will be described in detail below.

[0085] 2-1. Conductive metal layer The metal constituting the conductive metal layer is not particularly limited, and examples thereof include metals and metal compounds such as gold, silver, copper, platinum, iron, lead, aluminum, chromium, palladium, nickel, rhodium, ruthenium, antimony, bismuth, germanium, tin, cobalt, indium, nickel-phosphorus, nickel-boron, and the like, as well as alloys thereof, etc. Among these, gold, nickel, palladium, silver, copper, and tin are preferred because they form conductive fine particles with excellent conductivity. In addition, from the viewpoint of being inexpensive, nickel and nickel alloys (Ni-Au, Ni-Pd, Ni-Pd-Au, Ni-Ag, Ni-P, Ni-B, Ni-Zn, Ni-Sn, Ni-W, Ni-Co, Ni-W, Ni-Ti); copper and copper alloys (alloys of Cu and at least one metal element selected from the group consisting of Fe, Co, Ni, Zn, Sn, In, Ga, Tl, Zr, W, Mo, Rh, Ru, Ir, Ag, Au, Bi, Al, Mn, Mg, P, and B, preferably Ag, Ni, Sn, Zr) are preferred. and alloys of Ag with at least one metal element selected from the group consisting of Fe, Co, Ni, Zn, Sn, In, Ga, Tl, Zr, W, Mo, Rh, Ru, Ir, Au, Bi, Al, Mn, Mg, P, and B, preferably Ag-Ni, Ag-Sn, and Ag-Zn; and tin and tin alloys (e.g., Sn-Ag, Sn-Cu, Sn-Cu-Ag, Sn-Zn, Sn-Sb, Sn-Bi-Ag, Sn-Bi-In, Sn-Au, and Sn-Pb). Of these, nickel and nickel alloys are preferred. The conductive metal layer may be a single layer or a multilayer. In the case of a multilayer, preferred combinations include nickel-gold, nickel-palladium, nickel-palladium-gold, and nickel-silver.

[0086] The thickness of the conductive metal layer is preferably 0.010 μm or more, more preferably 0.030 μm or more, even more preferably 0.050 μm or more, and is preferably 0.30 μm or less, more preferably 0.25 μm or less, even more preferably 0.20 μm or less, and even more preferably 0.15 μm or less. If the thickness of the conductive metal layer is within the above range, stable electrical connection can be maintained when the conductive fine particles are used as an anisotropic conductive material. The thickness of the conductive metal layer can be measured, for example, by the method described later in the Examples.

[0087] The conductive metal layer may cover at least a portion of the resin particle surface, but it is preferable that the surface of the conductive metal layer does not have substantial cracks or surfaces on which the conductive metal layer is not formed. Here, "substantial cracks or surfaces on which the conductive metal layer is not formed" means that when the surfaces of any 10,000 conductive microparticles are observed using a scanning electron microscope (magnification 1000x), cracks in the conductive metal layer and exposed resin particle surfaces are not substantially visible.

[0088] 2-2.Conductive particles The number-average particle diameter of the conductive fine particles of the present invention is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 4 μm or more, and is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 25 μm or less. If the number-average particle diameter is within this range, the conductive fine particles can be suitably used for electrical connections of miniaturized and narrowed electrodes and wiring. As the number-average particle diameter of the conductive microparticles, it is preferable to use the number-based average particle diameter of 3,000 particles determined using a flow particle image analyzer (Sysmex Corporation's "FPIA (registered trademark)-3000").

[0089] The conductive fine particles of the present invention may have an insulating resin layer on at least a part of the surface. That is, an insulating resin layer may be further provided on the surface of the conductive metal layer. When an insulating resin layer is further laminated on the conductive metal layer on the surface in this manner, lateral conduction, which is likely to occur when forming a high-density circuit or connecting terminals, can be prevented.

[0090] The insulating resin layer is not particularly limited as long as it can ensure insulation between the conductive fine particles and can be easily broken down or peeled off by a certain pressure and / or heat. Examples include polyolefins such as polyethylene; (meth)acrylate polymers and copolymers such as polymethyl (meth)acrylate; polystyrene; thermoplastic resins and crosslinked products thereof; thermosetting resins such as epoxy resins, phenolic resins, and amino resins (melamine resins, etc.); water-soluble resins such as polyvinyl alcohol and mixtures thereof; etc. However, if the insulating resin layer is too hard compared to the base particles, there is a risk that the base particles themselves will break before the insulating resin layer breaks down. Therefore, it is preferable to use an uncrosslinked or relatively low-crosslinked resin for the insulating resin layer.

[0091] The insulating resin layer may be a single layer or may consist of multiple layers. For example, it may be a single or multiple film-like layer, a layer in which insulating particles of granular, spherical, lumpy, scaly, or other shapes are attached to the surface of a conductive metal layer, a layer formed by chemically modifying the surface of a conductive metal layer, or a combination of these. The thickness of the insulating resin layer is preferably 0.01 μm or more and 1 μm or less, more preferably 0.02 μm or more and 0.5 μm or less, and even more preferably 0.03 μm or more and 0.4 μm or less. If the thickness of the insulating resin layer is within the above range, good electrical insulation between particles is achieved while maintaining good conductivity due to the conductive particles.

[0092] 3. Manufacturing method First, the method for producing the resin particles will be described. The resin particles are produced by forming a core and then forming a shell so as to cover the core.

[0093] 3-1. Core manufacturing method The method for producing the core is not particularly limited as long as it polymerizes the core monomers described above, and any conventionally known method can be used, such as emulsion polymerization, suspension polymerization, dispersion polymerization, first seed polymerization, sol-gel seed polymerization, etc. In terms of ease of controlling the particle size of the core and the tendency to obtain cores with a narrow particle size distribution, for example, a method of synthesizing the core by the first seed polymerization is preferably used.

[0094] The first seed polymerization method is a method for obtaining cores through a seed particle preparation step, an absorption step in which a core monomer is absorbed into the seed particles, and a polymerization step in which the core monomer absorbed into the seed particles is polymerized. The techniques and conditions in each step are not particularly limited and may be any known seed polymerization technique, but the following techniques are preferably used, for example:

[0095] In the seed particle preparation step, when synthesizing resin particles composed only of organic materials, seed particles may be prepared using the above-mentioned vinyl-based monomers by methods such as soap-free emulsion polymerization or dispersion polymerization. In this case, it is preferable to use a styrene-based monofunctional monomer such as styrene as the vinyl-based monomer. On the other hand, when synthesizing particles composed of an organic material and a material having a polysiloxane skeleton, seed particles (polysiloxane particles) may be prepared using the above-mentioned silane-based monomers by hydrolysis and condensation polymerization in a solvent containing water (e.g., a mixed solvent of water and an organic solvent such as alcohols, ketones, esters, (cyclo)paraffins, or aromatic hydrocarbons). In this case, it is preferable to use the above-mentioned silane-based crosslinkable monomers as the silane-based monomers to form polymerizable polysiloxane particles. In the hydrolysis and condensation polymerization, a basic catalyst such as ammonia, urea, ethanolamine, tetramethylammonium hydroxide, an alkali metal hydroxide, or an alkaline earth metal hydroxide can be preferably used as a catalyst, and further, an anionic, cationic, or nonionic surfactant, or a polymer dispersant such as polyvinyl alcohol or polyvinylpyrrolidone can be used in combination as necessary.

[0096] The method for absorbing the core monomer into the seed particles in the absorption step is not particularly limited. For example, the core monomer may be added to a seed particle dispersion in which seed particles have been dispersed in a solvent, or the seed particles may be added to a solvent containing the core monomer. In the former method, the reaction solution obtained by polymerization, hydrolysis, and condensation is preferably used as the seed particle dispersion from the standpoint of process simplification and productivity. The core monomer may be added alone or as a solution dissolved in a solvent. However, for efficient absorption into the seed particles, it is preferable to emulsify and disperse the core monomer in water or an aqueous medium (e.g., a water-soluble organic solvent such as an alcohol, ketone, or ester, or a mixture of these with water) using an emulsifier before adding the emulsion. It is preferable to use at least the high-Tg silicon-free monofunctional (meth)acrylate and the low-Tg silicon-free monofunctional (meth)acrylate described above as the core monomer to be absorbed.

[0097] When the core monomer is emulsified and dispersed with an emulsifier, for example, anionic surfactants and nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxysorbitan fatty acid esters, polyoxyethylene alkylamines, glycerin fatty acid esters, and oxyethylene-oxypropylene block polymers are preferably used as the emulsifier because they can stabilize the dispersed state of the seed particles after the seed particles have absorbed the monomer. The amount of water or aqueous medium used for emulsification and dispersion is usually 0.3 to 10 times the mass of the monomer.

[0098] In the absorption step, whether the core monomer has been absorbed into the seed particles can be easily determined, for example, by observing the particles with a microscope before adding the monomer and after the absorption step is completed, and confirming that the particle size has increased due to the absorption of the monomer. In order to obtain the resin particles of the present invention, the absorption ratio represented by the following formula is not particularly limited, but is preferably 1.0 to 50 times, more preferably 2.0 to 30 times, and even more preferably 3.0 to 20 times. Absorption rate = (total mass of core monomers to be absorbed) / (mass of seed particles)

[0099] The polymerization method employed in the polymerization step is not particularly limited, and known methods such as those using radical polymerization initiators (e.g., peroxide initiators, azo initiators, etc.) can be used. The reaction temperature during radical polymerization is preferably 40°C or higher, more preferably 50°C or higher, and preferably 100°C or lower, more preferably 80°C or lower. If the reaction temperature is too low, the degree of polymerization tends to be insufficient, resulting in insufficient mechanical properties of the composite particles. On the other hand, if the reaction temperature is too high, aggregation between particles tends to occur during polymerization. The reaction time during radical polymerization can be adjusted appropriately depending on the type of polymerization initiator used, but is typically preferably 5 minutes or longer, more preferably 10 minutes or longer, and preferably 600 minutes or shorter, more preferably 300 minutes or shorter. If the reaction time is too short, the degree of polymerization may not be sufficiently increased, and if the reaction time is too long, aggregation between particles tends to occur. In such a polymerization step, when the seed particles are polymerizable polysiloxane particles, the absorbed monomer polymerizes with the radically polymerizable group of the polymerizable polysiloxane skeleton, resulting in the polysiloxane skeleton and the vinyl polymer being composited together.

[0100] 3-2. Shell formation method By forming a shell on the core so as to cover the core, resin particles that are core-shell particles are obtained.

[0101] The shell can be formed by polymerizing the above-mentioned monomers, and any conventionally known method can be used, such as emulsion polymerization, suspension polymerization, dispersion polymerization, second seed polymerization, sol-gel seed polymerization, etc. In terms of ease of controlling the shell film thickness and of easily obtaining resin particles with a uniform film thickness and a narrow particle size distribution, for example, a method of forming a shell by second seed polymerization is preferably used.

[0102] The second seed polymerization method is a method for obtaining core-shell particles through a coating step in which a shell monomer is coated on the core surface, and a polymerization step in which the shell monomer is polymerized on the core surface.

[0103] In the coating step, the method for coating the core surface with the shell monomer is not particularly limited. For example, the shell monomer may be added to a core dispersion in which the core is previously dispersed in a solvent, or the core may be added to a solvent containing the shell monomer. In particular, in the former method, it is preferable to use the reaction solution obtained by core polymerization as the core dispersion from the viewpoint of process simplification and productivity. The shell monomer may be added alone or as a solution dissolved in a solvent. However, in order to efficiently coat the core surface with the shell monomer, it is preferable to emulsify and disperse the shell monomer in water or an aqueous medium using an emulsifier beforehand to form an emulsion and then add the emulsion. The aqueous medium may be the same as the aqueous medium used in the first seed polymerization method. When the shell monomer is emulsified and dispersed with an emulsifier, the emulsifier may be the same as the emulsifier used in the first seed polymerization method.

[0104] In the coating step, whether the shell monomer has been dispersed on the core surface can be easily determined by checking that the reaction solution is an emulsion and that no precipitation occurs. To obtain the resin particles of the present invention, the coating ratio shown in the following formula is not particularly limited, but is preferably 0.01 to 1.0 times, more preferably 0.03 to 0.8 times, and even more preferably 0.05 to 0.32 times. Coverage ratio = (total mass of shell monomers to be covered) / (total mass of core)

[0105] After synthesis, the resin particles are usually dried and, in some cases, calcined. The drying temperature is not particularly limited, but is usually in the range of 40°C to 250°C.

[0106] In this manner, the resin particles are prepared so that the number average particle size, the coefficient of variation of particle size, etc., fall within the above-mentioned ranges.

[0107] 3-3. Method for forming conductive metal layer Next, a conductive metal layer is formed on the resin particles (substrate) obtained as described above, and an insulating resin layer is further formed as needed, thereby obtaining conductive fine particles.

[0108] The method for forming the conductive metal layer and the method for forming the insulating resin layer are not particularly limited, but for example, the conductive metal layer can be formed by a method of plating the surface of the substrate by electroless plating, electrolytic plating, etc., or a method of forming a conductive metal layer on the surface of the substrate by a physical vapor deposition method such as vacuum deposition, ion plating, or ion sputtering, etc. Among these, the electroless plating method is particularly preferred because it does not require large-scale equipment and can easily form a conductive metal layer.

[0109] 4. Anisotropic conductive materials The present invention also includes an anisotropic conductive material obtained by dispersing the above-mentioned conductive fine particles in a binder resin. The form of the anisotropic conductive material is not particularly limited, and various forms, such as an anisotropic conductive film, an anisotropic conductive paste, an anisotropic conductive adhesive, and anisotropic conductive ink, can be mentioned. By providing these anisotropic conductive materials between opposing substrates or between electrode terminals, good electrical connection can be achieved. Anisotropic conductive materials using the conductive fine particles of the present invention also include conductive materials for liquid crystal display elements (conductive spacers and compositions thereof). Suitable applications of the anisotropic conductive material include touch panel input and LED applications, and they are particularly suitable for use in touch panel mounting.

[0110] The binder resin is not particularly limited as long as it is an insulating resin, and examples thereof include thermoplastic resins such as acrylic resin, ethylene-vinyl acetate resin, and styrene-butadiene block copolymer; curable resin compositions that are cured by reaction with a curing agent such as a monomer or oligomer having a glycidyl group and an isocyanate; and curable resin compositions that are cured by light or heat.

[0111] The anisotropic conductive material of the present invention can be obtained by dispersing the conductive fine particles of the present invention in a binder resin and forming them into the desired form. However, for example, the binder resin and the conductive fine particles can be used separately, and the conductive fine particles can be present together with the binder resin between the substrates or electrode terminals to be connected, thereby forming the connection.

[0112] The content of the conductive fine particles in the anisotropic conductive material may be determined appropriately depending on the application, but is, for example, preferably 1% by volume or more, more preferably 2% by volume or more, and even more preferably 5% by volume or more, and preferably 50% by volume or less, more preferably 30% by volume or less, and even more preferably 20% by volume or less, based on the total amount of the anisotropic conductive material. If the content of the conductive fine particles is too low, it may be difficult to obtain sufficient electrical conductivity, while if the content of the conductive fine particles is too high, the conductive fine particles may come into contact with each other, making it difficult to function as an anisotropic conductive material.

[0113] The film thickness of the anisotropic conductive material, the coating thickness of the paste or adhesive, the printing thickness, etc. are preferably set appropriately taking into consideration the particle diameter of the conductive microparticles of the present invention used and the specifications of the electrodes to be connected, so that the conductive microparticles are sandwiched between the electrodes to be connected and the gaps between the bonded substrates on which the electrodes to be connected are formed are sufficiently filled with the binder resin layer. [Example]

[0114] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples and can be practiced with modifications within the scope of the above and below-described aims, all of which are included within the technical scope of the present invention. In the following, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass."

[0115] 1. Physical property measurement method Various physical properties were measured by the following methods.

[0116] <Number average particle size and coefficient of variation (CV value) of seed particles, cores, and resin particles> For cores and resin particles, 20 parts of a 1% aqueous solution of the emulsifier polyoxyethylene alkyl ether sulfate ester ammonium salt (Hitenol® N-08, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added to 0.1 parts of the cores or resin particles, and the resulting dispersion was ultrasonically dispersed for 10 minutes to prepare a measurement sample. For seed particles, the dispersion obtained by the hydrolysis and condensation reaction was diluted with a 1% aqueous solution of polyoxyethylene alkyl ether sulfate ester ammonium salt (Hitenol® N-08, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) to prepare a measurement sample. For each measurement sample, the particle diameter (μm) of 30,000 particles was measured using a particle size distribution analyzer (Coulter Multisizer III, manufactured by Beckman Coulter, Inc.) to determine the number-average particle diameter. For cores and resin particles, the standard deviation of the particle diameter based on the number was also determined, and the coefficient of variation (CV value) of the particle diameter was calculated according to the following formula: Coefficient of variation of particles (%) = 100 x (standard deviation of particle size / number average particle size)

[0117] <Film thickness of conductive metal layer> Using a flow particle image analyzer (Sysmex Corporation's "FPIA (registered trademark)-3000"), the number average particle diameter X (μm) of 3,000 resin particles and the number average particle diameter Y (μm) of 3,000 conductive microparticles were measured. The measurements were performed after adding 17.5 parts of a 1.4% aqueous solution of an emulsifier, polyoxyethylene oleyl ether (Kao Corporation's "Emulgen (registered trademark) 430"), to 0.25 parts of the particles and dispersing the mixture ultrasonically for 10 minutes. The film thickness of the conductive metal layer was then calculated according to the following formula: Conductive metal layer thickness (μm)=(YX) / 2

[0118] <10% K value of resin particles> Using a microcompression tester (Shimadzu Corporation, "MCT-W500"), at room temperature (25°C), a single particle was dispersed on a sample stage (made of SKS flat plate) and a 50 μm diameter circular flat indenter (made of diamond) was applied toward the center of the particle at a constant loading rate (0.445 mN / s) in the "soft surface detection" mode. The load value (mN) when the compressive displacement reached 10% of the particle diameter (10% compressive load value) and the displacement (μm) at that time were measured. Measurements were performed on 10 different particles for each sample, and the average value was used as the measured value. The obtained compressive load value (mN) was converted to compressive load (N), and the obtained displacement (μm) was converted to compressive displacement (mm). The particle radius (mm) was calculated from the number-average particle diameter (μm) of the resin particles, and these values ​​were used to calculate the particle radius according to the following formula. The above measurements were performed in a constant temperature atmosphere of 25°C.

[0119]

number

[0120] <Recovery rate of resin particles> Using a microcompression tester (Shimadzu Corporation, "MCT-W500"), at room temperature (25°C), a single particle was spread on a sample stage (made of SKS material) and compressed toward the center of the particle using a 50 μm diameter circular flat indenter (made of diamond) at a constant loading rate (2.23 mN / s) to a maximum load (49 mN). The displacement (μm) at this point was measured and designated as the maximum displacement L1. The load was then reduced to a minimum load (0.49 mN) at a constant unloading rate (2.23 mN / s). The displacement (μm) between the maximum and minimum loads was measured and designated as the recovery displacement L2. The recovery rate was calculated from the maximum and recovery displacements L1 and L2 using the following formula. Measurements were performed on 10 different particles for each sample, and the average value was used as the measured value. Recovery rate (%)=(L2 / L1)×100 The above measurements were carried out in a constant temperature atmosphere of 25°C.

[0121] <Evaluation of powder (resin particles) dispersibility in emulsified water> 2.5 g of polymer particles and 100 g of a 1% aqueous solution of emulsifier polyoxyethylene alkyl ether sulfate ester ammonium salt ("Hitenol (registered trademark) N-08" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were placed in a 200 mL beaker and ultrasonically dispersed for 15 minutes, then passed through a sieve with a mesh size 1.6 times the number-average particle size (μm) of the resin particles. After drying the sieve and the polymer particles at 120 °C for 2 hours, the total weight (g) of the sieve and the polymer particles remaining on the sieve was measured, and the weight (g) of the polymer particles remaining on the sieve was calculated by subtracting the weight (g) of the sieve. The dispersion rate (%) in emulsified water was calculated using the following formula: Dispersion rate (%) = 100 - ((weight of polymer particles remaining on the sieve (g) / 2.5 (g)) x 100)

[0122] For resin particles Nos. 1, 2, 5, 16, and 17, which have a number-average particle diameter of 19.9 to 20.8 μm (1.6-fold μm value = 31.8 to 33.2 μm), a stainless steel sieve with an opening diameter of 32 μm manufactured by AS ONE Corporation was used based on the following criteria: For resin particles Nos. 3 and 16, which have a number-average particle diameter of 9.7 to 10.7 μm (1.6-fold μm value = 15.5 to 17.1 μm), an electroformed sieve with an opening diameter of 16 μm manufactured by AS ONE Corporation was used based on the following criteria: For resin particles No. 4, which have a number-average particle diameter of 4.8 μm (1.6-fold μm value = 7.7 μm), an electroformed sieve with an opening diameter of 8 μm manufactured by AS ONE Corporation was used based on the following criteria: Number average particle size less than 6 μm: Electroformed sieve with 8 μm openings Number average particle size 6 μm or more but less than 9 μm: electroformed sieve with 12 μm openings Number average particle size 9 μm or more and less than 13 μm: electroformed sieve with 16 μm openings Number average particle size 13 μm or more and less than 17 μm: Stainless steel sieve with 25 μm openings Number average particle size 17 μm or more and less than 24 μm: Stainless steel sieve with 32 μm openings

[0123] <Homopolymer glass transition temperature (Tg)> For a monomer (isooctyl acrylate (IOA)) whose homopolymer glass transition temperature (Tg) is not listed in the Polymer Handbook Fourth Edition and Paints and Coatings (Paint Publishing, 10 (No. 358), 1982), differential scanning calorimetry (DSC) was performed as follows.

[0124] A four-neck flask equipped with a condenser, thermometer, and dropping nozzle was charged with 200 parts of a 10% aqueous solution of polyvinyl alcohol (Kuraray Co., Ltd., "Poval PVA-205") and maintained at 25°C. While stirring at 300 rpm, a solution containing 27 parts of isooctyl acrylate and 0.7 parts of 2,2'-azobis(2,4-dimethylvaleronitrile) (Wako Pure Chemical Industries, Ltd., "V-65") was added through the dropping nozzle and maintained for 2 hours to produce a suspension. The suspension was heated to 65°C under a nitrogen atmosphere with continued stirring and maintained at 65°C for 2 hours to carry out radical polymerization. The emulsion after radical polymerization was subjected to solid-liquid separation and vacuum dried at 40°C for 12 hours to obtain isooctyl acrylate homopolymer particles. Next, using a differential scanning calorimeter (BRUKER DSC3100), the obtained homopolymer particles were heated in a nitrogen atmosphere in the range of -100°C to 150°C at a heating rate of 20°C / min, and the midpoint of the peak of the obtained DSC curve was taken as the homopolymer glass transition temperature (Tg).

[0125] 2-1. Preparation of core particles Manufacturing Example 1 A four-neck flask equipped with a condenser, thermometer, and dropping nozzle was charged with 384 parts of ion-exchanged water, 1.2 parts of 25% aqueous ammonia, and 236 parts of methanol. While stirring, 100 parts of 3-methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., "KBM503") was added through the dropping nozzle to carry out a hydrolysis and condensation reaction of 3-methacryloxypropyltrimethoxysilane, producing an emulsion of polysiloxane particles (polymerizable polysiloxane particles) having methacryloyl groups. Two hours after the start of the reaction, the resulting emulsion of polysiloxane particles was sampled and the particle size was measured. The number-average particle size was 7.3 μm.

[0126] Next, a solution of 405 parts of n-butyl methacrylate, 405 parts of n-butyl acrylate, 90 parts of triethylene glycol dimethacrylate, 100 parts of 2-hydroxyethyl methacrylate, and 25 parts of 2,2′-azobis(2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd., “V-65”) was added to a solution of 25 parts of a 20% aqueous solution of polyoxyethylene styrenated phenyl ether sulfate ester ammonium salt (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., “Hitenol (registered trademark) NF-08”) as an emulsifier in 1,000 parts of ion-exchanged water, and the solution was emulsified and dispersed to prepare an emulsion of the core monomer.

[0127] In addition, 150 parts of triethylene glycol dimethacrylate was added to a solution prepared by dissolving 3.8 parts of a 20% aqueous solution of polyoxyethylene styrenated phenyl ether sulfate ester ammonium salt (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., "Hitenol (registered trademark) NF-08") as an emulsifier in 150 parts of ion-exchanged water, and the mixture was emulsified and dispersed to prepare an emulsion of the shell monomer.

[0128] The resulting emulsion of core monomer was added to the emulsion of polymerizable polysiloxane particles and further stirred. One hour after the addition of the emulsion, a sample of the mixture was taken and observed under a microscope. It was confirmed that the polymerizable polysiloxane particles had absorbed the monomer and grown in size.

[0129] Next, 1,250 parts of a 10% aqueous solution of polyvinyl alcohol ("Poval PVA-205" manufactured by Kuraray Co., Ltd.) and 1,005 parts of ion-exchanged water were added, and the reaction solution was heated to 65°C under continuous stirring in a nitrogen atmosphere to carry out radical polymerization of the core monomer.

[0130] Polymerization of the core monomer began, and the temperature inside the flask reached its peak. Immediately after reaching a maximum, the emulsion of the shell monomer was added. After the addition, the temperature was maintained at 65°C for two hours, allowing radical polymerization of the shell monomer to occur. The emulsion after radical polymerization was subjected to solid-liquid separation, and the resulting cake was washed with ion-exchanged water and methanol, then vacuum-dried at 40°C for 12 hours to obtain resin particle No. 1.

[0131] (Examples 2-12, 14-17) Resin particles Nos. 2 to 12 and 14 to 17 were obtained in the same manner as in Production Example 1, except that the amounts of ion-exchanged water, methanol, and aqueous ammonia were appropriately changed to produce polysiloxane particles having number-based average particle sizes as shown in Table 1, and the types and amounts of core monomers and shell monomers used were changed as shown in Table 1. Note that no shells were formed for resin particles Nos. 9 and 14 to 17.

[0132] (Manufacturing Example 13) A four-neck flask equipped with a condenser, thermometer, and dropping nozzle was charged with 200 parts of a 10% aqueous solution of polyvinyl alcohol ("Poval PVA-205" manufactured by Kuraray Co., Ltd.) and maintained at 25°C. While stirring at 300 rpm, a solution containing 27 parts of isooctyl acrylate, 3.0 parts of 1,6-hexanediol diacrylate, and 0.7 parts of 2,2'-azobis(2,4-dimethylvaleronitrile) ("V-65" manufactured by Wako Pure Chemical Industries, Ltd.) was added through the dropping nozzle as a core monomer and maintained for 2 hours to produce a suspension. The suspension was heated to 65°C under a nitrogen atmosphere with continued stirring to carry out radical polymerization of the core monomer.

[0133] Next, in a separate flask, 0.1 parts of a 20% aqueous solution of polyoxyethylene styrenated phenyl ether sulfate ester ammonium salt ("Hitenol (registered trademark) NF-08" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as an emulsifier was dissolved in 3.0 parts of ion-exchanged water, to which 3.0 parts of divinylbenzene as a shell monomer was added, followed by emulsification and dispersion to prepare an emulsion of the shell monomer.

[0134] Immediately after the polymerization of the core monomer began and the temperature inside the flask reached its peak, the emulsion of the shell monomer was added. After the addition, the temperature was maintained at 65°C for 2 hours to allow radical polymerization of the shell monomer. The emulsion after radical polymerization was subjected to solid-liquid separation, vacuum dried at 40°C for 12 hours, and classified to obtain resin particles No. 13. The physical properties of the obtained resin particles Nos. 1 to 17 were as shown in Table 2.

[0135] [Table 1]

[0136] [Table 2]

[0137] In Table 1, the monomers are shown by abbreviations, and the compound names corresponding to each abbreviation are as follows: For non-crosslinkable monomers, the homopolymer glass transition temperature (Tg) is also shown. nBA: n-butyl acrylate (Tg: 219K) 2EHA: 2-ethylhexyl acrylate (Tg: 223K) IOA: Isooctyl acrylate (Tg: 212K) nBMA: n-butyl methacrylate (Tg: 293K) HEMA: 2-hydroxyethyl methacrylate (Tg: 328K) St: Styrene (Tg: 380K) CHA: Cyclohexyl acrylate (Tg: 292K) MMA: Methyl methacrylate (Tg: 378K) KBM503: 3-Methacryloxypropyltrimethoxysilane 16HXA: 1,6-hexanediol diacrylate 16HX: 1,6-hexanediol dimethacrylate 3EG: Triethylene glycol dimethacrylate DVB: Divinylbenzene

[0138] 2-2. Preparation of conductive particles (formation of conductive metal layer) Example 1 Resin particles No. 1 synthesized in Production Example 1 were etched with sodium hydroxide, sensitized by contact with a tin dichloride solution, and then activated by immersion in a palladium dichloride solution (sensitization-activation method) to form palladium nuclei. Next, 2 parts of the resin particles with palladium nuclei formed were added to 400 parts of ion-exchanged water, and after ultrasonic dispersion, the resulting resin particle suspension was heated in a warm bath at 70°C. While the suspension was heated in this manner, 600 parts of an electroless plating solution ("Shumer S680" manufactured by Nippon Kangen Co., Ltd.) separately heated to 70°C was added to initiate the electroless nickel plating reaction. After confirming that hydrogen gas generation had ceased, solid-liquid separation was performed, followed by washing with ion-exchanged water and then methanol, and vacuum drying at 100°C for 2 hours to obtain nickel-plated particles. The obtained nickel-plated particles were then added to a displacement gold plating solution containing potassium gold cyanide, and the surface of the nickel layer was further plated with gold to obtain conductive fine particles No. 1. The film thickness of the conductive metal layer on the obtained conductive fine particles is shown in Table 3.

[0139] Examples 2 to 8, Comparative Examples 1 to 9 Conductive fine particles Nos. 2 to 17 were produced in the same manner as in Example 1, except that resin particles Nos. 2 to 17 synthesized in Production Examples 2 to 17 were used as the base material. The film thickness of the conductive metal layer in the obtained conductive fine particles was as shown in Table 3.

[0140] Using the obtained conductive particles Nos. 1 to 17, anisotropic conductive films were produced by the following method, and the performance thereof was evaluated by the following method. That is, for each of conductive particles No. 1 to 17, 100 parts of epoxy resin (Mitsubishi Chemical's "JER828") as a binder resin, 2 parts of curing agent (Sanshin Chemical's "Sanaide (registered trademark) SI-150"), and 100 parts of toluene were added to 1 part of the conductive particles, and 50 parts of zirconia beads with a diameter of 1 mm were further added, and the mixture was dispersed by stirring at 300 rpm for 10 minutes using two stainless steel stirring blades. The obtained paste-like composition was then applied to a release-treated PET film using a bar coater and dried to obtain an anisotropic conductive film.

[0141] The obtained anisotropic conductive films were divided into those containing resin particles with a number average particle diameter of 10.0 μm or more and those containing resin particles with a number average particle diameter of less than 10.0 μm, and the initial resistance value of each was measured under the following conditions.

[0142] (Number average particle size 10.0 μm or more) The anisotropic conductive film was sandwiched between an all-aluminum-deposited glass substrate with lines for resistance measurement and a polyimide film substrate with a copper pattern formed at a pitch of 100 μm, and then thermocompression bonded under compression conditions of 2.5 MPa and 150°C. The initial resistance between the electrodes was then measured, and connection resistance was evaluated as "Good" when the initial resistance was 5 Ω or less, and as "Poor" when it exceeded 5 Ω.

[0143] (Number average particle size less than 10.0 μm) The anisotropic conductive film was sandwiched between a fully aluminum-deposited glass substrate with resistance measurement lines and a polyimide film substrate with a copper pattern formed at a 30 μm pitch, and thermocompression bonded at 1 MPa and 150°C. The initial resistance between the electrodes was then measured, and connection resistance was evaluated as "Good" if the initial resistance was 5 Ω or less, and "Poor" if it exceeded 5 Ω. The evaluation results are shown in Table 3.

[0144] [Table 3]

[0145] As is clear from Table 3, in Examples 1 to 8 in which resin particles satisfying the requirements of the present invention were used, the initial resistance was low and the connection reliability was excellent.

[0146] On the other hand, in Comparative Examples 1 to 9, which used resin particles that did not satisfy the requirements of the present invention, the initial resistance was high and the connection reliability was poor. [Industrial Applicability]

[0147] The resin particles of the present invention are suitably used in anisotropic conductive materials such as anisotropic conductive pastes, anisotropic conductive films, anisotropic conductive adhesives, and anisotropic conductive inks.

Claims

1. Resin particles for conductive fine particles, the resin particles are core-shell particles having a core and a shell covering the core, and the ratio of the average thickness of the shell to the number-average particle diameter of the resin particles is 0.01 or more and 0.05 or less; the core is a copolymer containing, as monomer units, a silicon-free monofunctional (meth)acrylate having a homopolymer glass transition temperature (Tg) of 0°C or lower, a silicon-free monofunctional (meth)acrylate having a homopolymer glass transition temperature (Tg) of more than 0°C, and a silane-based monomer; the content of the silicon-free monofunctional (meth)acrylate having a homopolymer glass transition temperature (Tg) of 0°C or lower is 15% by mass or more and 50% by mass or less, based on 100% by mass of the total amount of monomers forming the core; the shell contains, as a monomer unit, a monomer (1) having two or more vinyl groups in one molecule, and the content of the monomer (1) is 50% by mass or more relative to 100% by mass of the monomer components forming the shell; the resin particles have a compressive deformation recovery rate of 25% or less, The compressive elastic modulus (10% K value) when the diameter of the resin particles is displaced by 10% is 1500 N / mm ２ is as follows: Resin particles for conductive fine particles, characterized in that the number-based coefficient of variation (CV) of the particle diameter of said resin particles is 10% or less.

2. 2. The resin particle for conductive microparticles according to claim 1, wherein the content of the silicon-free monofunctional (meth)acrylate having a homopolymer glass transition temperature (Tg) of more than 0°C is 35% by mass or more and 70% by mass or less, based on 100% by mass of the total amount of monomers forming the core.

3. 3. The resin particle for conductive fine particles according to claim 1, wherein the glass transition temperature (Tgcore) of the core calculated based on the FOX equation is 0° C. or lower.

4. 4. The resin particle for conductive fine particles according to claim 1, wherein the core has a degree of crosslinking represented by the following formula of 30% or less. Degree of crosslinking (%) = (mass of crosslinkable monomer / mass of total monomer) x 100

5. 5. The resin particles for conductive fine particles according to claim 1, wherein the average thickness of the shell is 0.05 μm or more and 1 μm or less.

6. 6. The resin particles for conductive fine particles according to claim 1, which have a dispersion rate of 90% or more as calculated by the following measurement method. (Method for measuring dispersion ratio) (1) 2.5 g of resin particles and 100 g of a 1% aqueous solution of polyoxyethylene alkyl ether sulfate ester ammonium salt, which is an emulsifier, are placed in a 200 mL beaker and ultrasonically dispersed for 15 minutes, and then passed through a sieve with openings 1.6 μm times the number average particle diameter. (2) Dry the sieve at 120°C for 2 hours. (3) The total weight (g) of the sieve and the polymer particles remaining on the sieve is measured, and the weight (g) of the sieve is subtracted to determine the weight (g) of the polymer particles remaining on the sieve. (4) The weight (g) of the polymer particles remaining on the sieve is applied to the following formula to calculate the dispersion rate (%). Dispersion rate (%)=100−((weight of polymer particles remaining on the sieve (g) / 2.5 (g))×100)

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