JP2012036335A - Polymer fine particle and conductive fine particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide polymer fine particles, which enables electric connection with excellent connection reliability.SOLUTION: In a compression test of compressing the polymer fine particles at loading speed of 0.2275 gf/sec, the polymer fine particles exhibit a preliminary breaking behavior in which a part of the polymer fine particles preliminarily breaks, before exhibiting a breaking behavior in which the whole of polymer fine particles breaks.

Description

  The present invention relates to polymer fine particles useful for anisotropic conductive materials and the like, and conductive fine particles using the same.

  Electronic devices are becoming smaller and more sophisticated year by year. For example, connection between ITO electrodes of a liquid crystal display panel and a driving LSI, connection between an LSI chip and a circuit board, and connection between fine pattern electrode terminals, etc. In electrical connection between minute parts of electronic devices, application of a connection method using an anisotropic conductive material containing conductive fine particles is expanding instead of a conventional connection method using solder or a connector. At this time, the conductive fine particles in the anisotropic conductive material may be expected to serve as a spacer that electrically connects the connection parts and keeps the distance between the connection parts constant.

  As the conductive fine particles, conductive fine particles in which a metal plating layer is provided on the surface of a base particle serving as a nucleus are used. Here, the substrate particles are required to have both hardness and softness. That is, the conductive fine particles are brought into surface contact with the connection site in a thermocompression-bonded state. At that time, the larger the contact area, the lower the contact resistance and the stable connection becomes possible. For this reason, the base material particles serving as the core of the conductive fine particles are required to have flexibility enough to facilitate deformation. On the other hand, it is possible to reduce the contact resistance by increasing the contact pressure of the conductive fine particles with respect to the connection site. From this point of view, highly recoverable base particles having a certain degree of hardness are desired. In addition, as described above, when the conductive fine particles function as a spacer after connection, the substrate particles need to have high hardness.

  Therefore, polymer particles having a so-called core / shell structure in which the core particles are covered with a shell layer are used as the base particles, and the hardness (softness) of the core particles and the shell layer is changed by relatively changing the hardness and softness. Various techniques have been proposed for obtaining conductive fine particles that have both softness and low contact resistance and excellent connection reliability. For example, Patent Documents 1 to 3 describe conductive fine particles having core particles that are hard core particles and soft shell layers as cores, and Patent Documents 4 to 6 include fine particles that have soft core particles and hard shell layers. A conductive fine particle as a nucleus is described.

JP 2001-11503 A Japanese Patent Laid-Open No. 08-193186 JP 2003-318502 A JP 2006-156068 A JP 2002-33022 A JP 2001-35248 A

  By the way, in recent years, as the performance of electronic devices has further improved, the demand for connection reliability with respect to conductive fine particles is increasing. However, the conductive fine particles described in Patent Documents 1 to 6 may not fully meet the demand.

  Therefore, the present invention intends to provide polymer fine particles that enable electrical connection with excellent connection reliability, and conductive fine particles and anisotropic conductive materials using the same.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, it was found that excellent connection reliability can be obtained if the polymer fine particles exhibit fracture behavior in two stages when subjected to a specific compression test. In other words, in the case of polymer fine particles that show two-stage fracture behaviors, the preliminary fracture behavior and the main fracture behavior, if the connection is made in a state between immediately after the start of the preliminary fracture behavior and until this fracture behavior occurs. Part of the particles crushed by the preliminary fracture behavior (substantially equivalent to the shear layer in the case of the core / shell structure) improves the contact area with the connection site and remains without being crushed. Part of the particles (substantially corresponding to the core particles in the case of the core / shell structure) maintains a high contact pressure with respect to the connection site. Therefore, if the polymer fine particles exhibit a two-stage fracture behavior of the preliminary fracture behavior and the main fracture behavior, the connection reliability can be improved from the viewpoint of both the contact area and the contact pressure with respect to the connection site. In addition, as described above, when some of the particles that remain without being crushed are present, sufficient hardness required for the spacer can be exhibited. Therefore, such polymer fine particles are themselves used as spacers for liquid crystal display elements, and conductive fine particles having the polymer fine particles as a core are used as conductive materials for liquid crystal display elements (conductive spacers) and anisotropic conductive materials. It becomes possible to use as a fine particle. The present invention has been completed based on these findings.

  That is, the polymer fine particles according to the present invention are preliminarily formed in the compression test in which the polymer fine particles are compressed at a load loading rate of 0.2275 gf / sec. It is characterized by exhibiting a preliminary fracture behavior in which a part is destroyed.

  The polymer fine particles of the present invention preferably have core particles and a shell layer provided on the surface of the core particles.

  In a preferred embodiment of the polymer fine particles of the present invention, the core particles are observed to be broken after the shell layer is broken in the compression test. Preferably, the particle size in the compression direction of the polymer fine particles at the start point of the preliminary fracture behavior in the compression test is A, and the particle size in the compression direction of the polymer fine particles at the start point of the present fracture behavior is B, When the particle diameter in the compression direction of the polymer fine particles before being subjected to the compression test is C, the connection area ratio determined by the connection area ratio (%) = [(A−B) / C] × 100 is 1 to 1. It should be 50%.

Both the core particles and the shell layer are preferably polymers of vinyl group-containing monomers. Each of the vinyl group-containing monomers constituting the core particles and the shell layer contains at least a crosslinkable monomer having two or more polymerizable groups including vinyl groups in one molecule, and vinyl constituting the core particles. When the content of the crosslinkable monomer in the group-containing monomer is Xc (mass%) and the content of the crosslinkable monomer in the vinyl group-containing monomer constituting the shell layer is Xs (mass%), Xc ≧ 25, It is preferable that Xs ≧ 20. Furthermore, it is preferable that Xc> Xs. When the 10% K value of the core particles is Yc (kgf / mm ² ) and the 10% K value of the shell layer is Ys (kgf / mm ² ), Yc ≧ 800, Ys ≧ 600, and Yc It is preferable that> Ys. The thickness of the shell layer is preferably 0.05 μm or more.

  The conductive fine particles according to the present invention include the polymer fine particles of the present invention and a conductive metal layer.

  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, the polymer fine particles suitable as the core of the conductive fine particles and the spacer for the liquid crystal display element, the conductive fine particles capable of reliably performing electrical connection with excellent connection reliability, and the fine particles are contained. An anisotropic conductive material can be provided.

  More specifically, the polymer fine particles of the present invention are preliminarily broken in order to show a pre-breaking behavior in which a part of the polymer fine particles are broken before the entire fine polymer particles show this breaking behavior. When a pressure necessary to cause the failure is applied, a large contact area can be secured based on a part of the plastic deformation that is broken, and a contact pressure based on the restoring force exhibited by the part that is not broken is obtained. Therefore, conductive fine particles having such polymer fine particles as the core are used as materials for electrical connection by pressurization such as anisotropic conductive materials, and the pressure is higher than the pressure at the point where the preliminary fracture behavior starts. A connection structure with excellent connection reliability that maintains a large contact area and high contact pressure between the conductive fine particles and the connected medium such as an electrode by connecting at a pressure less than the pressure at which the fracture behavior starts. Obtainable.

  Further, when the polymer fine particle of the present invention has a structure having a core particle and a shell layer provided on the surface thereof, the above-described effect is exhibited even by low-pressure connection by controlling the compressive fracture strength of the shell layer. It becomes. For example, in order to realize a large display panel and a thin film of a material (such as a glass substrate) constituting the display panel, a reliable electrical connection at a low pressure is required. It is particularly useful as conductive fine particles for anisotropic conductive materials used in such cases.

It is a graph which shows the compression displacement curve obtained by using the polymer fine particle of Example 1 for the compression test which concerns on this invention. It is a graph which shows the compression displacement curve obtained by using the polymer fine particle of the comparative example 1 for the compression test which concerns on this invention.

(Polymer fine particles)
In the compression test in which the polymer fine particles are compressed at a load load rate of 0.2275 gf / sec, before the polymer fine particles show the fracture behavior in which the entire polymer fine particles are broken, It shows the preliminary fracture behavior to be destroyed. Preferably, the polymer fine particles of the present invention are core-shell structured particles having core particles and a shell layer provided on the surface of the core particles.

  Hereinafter, the fracture behavior when polymer fine particles are subjected to the compression test will be described with reference to a graph showing a compression displacement curve. FIG. 1 shows a compression displacement curve of the polymer fine particles of the present invention, and FIG. 2 shows a compression displacement curve of conventional polymer fine particles. The compression displacement curve is the load when a particle is loaded and compressed at a constant speed (ie, the cumulative load from the start of particle compression to the point in time) and the amount of displacement of the particle (ie, the original The relationship between the diameter of the particle in the compression direction and the value obtained by subtracting the diameter of the particle in the compression direction at that time) is plotted, and the fracture behavior of the particle can be determined from the compression displacement curve.

  In other words, from FIG. 1, when the polymer fine particles of the present invention are compressed, the graph reaches the first elastic limit point indicated by a in FIG. 1 (starting point of preliminary fracture behavior; hereinafter referred to as “a point”). It can be seen that the inclination of is moderate and almost constant, and the particle diameter gradually shrinks at a constant speed under load (in other words, elastically deforms). Then, when the point a is exceeded, the graph changes to be almost flat, and until the second elastic deformation start point (hereinafter referred to as “b point”) shown by b in FIG. It can be seen that the displacement increases at a stretch. The state from point a to point b corresponds to the preliminary fracture behavior (also referred to as first plastic deformation). A part of the polymer fine particles is destroyed by this preliminary fracture behavior (first plastic deformation). For example, in the case of a core-shell structure, the shell layer is usually destroyed in the preliminary fracture behavior, and this mode is preferable.

  Then, when the compression continues, the graph rises immediately after exceeding the point b as shown in FIG. 1, and the second elastic limit point indicated by c in FIG. 1 (the starting point of this fracture behavior; hereinafter referred to as “point c”). Until this value is reached, a substantially constant inclination is maintained (in other words, it is newly elastically deformed). From this, it can be said that the particles are hardly deformed from the point b to the point c even when a load is applied. This is because part of the particles crushed by the preliminary fracture behavior (the shell layer in the case of the core-shell structure) makes it difficult for deformation to proceed, and at the same time, part of the particles that remain without being crushed (core -If it is a shell structure, it is thought that it is because a core particle) maintains the particle diameter reliably.

  When electrical connection is made with conductive fine particles obtained using the polymer fine particles of the present invention as base particles, it is preferably between the above-mentioned point a (first elastic limit point) to point c (second elastic limit point). If the connection is made between the point b (second elastic deformation start point) and the point c (second elastic limit point), the contact area with respect to the connection site is based on the fact that some of the particles are crushed. As a result, the contact pressure to the connection site is maintained high based on the fact that some of the particles remain without being crushed. As a result, the connection reliability is improved in terms of both the contact area and the contact pressure with respect to the connection site. Can be improved. In other words, the polymer fine particles of the present invention exhibit the first elastic deformation and then the plastic deformation, and by compressing the particles into the first plastic deformation area and the subsequent elastic deformation area, It can be said that high contact pressure can be achieved.

  Next, when the compression continues, the graph in FIG. 1 is almost leveled beyond the point c, and the load is almost applied until the fracture completion point indicated by d in FIG. 1 (hereinafter referred to as “d point”) is reached. Even if it is not, the amount of particle displacement increases at a stretch. The state from the point c (second elastic limit point) to the point d (failure completion point) corresponds to the fracture behavior (also referred to as second plastic deformation). All of the polymer fine particles are destroyed by this breaking behavior. For example, in the case of a core / shell structure, the core particles remaining in the preliminary fracture behavior are destroyed in the main fracture behavior. When the point d is reached, the particles are completely destroyed, and the graph of FIG.

  On the other hand, when the conventional polymer fine particles are compressed, as shown in FIG. 2, the slope of the graph is gentle and almost constant until the elastic limit point indicated by e in FIG. 2 (hereinafter referred to as “e point”). Yes, the particle size is gradually reduced at a constant speed under load (in other words, elastically deformed), and when the point e is exceeded, the graph is almost flat and the fracture is completed as indicated by f in FIG. Even when a load is hardly applied until reaching a point (hereinafter referred to as “point f”), the amount of displacement of the particles increases at a stretch. That is, the main fracture behavior occurs between the point e (elastic limit point) and the point f (destruction completion point), and the polymer fine particles are completely destroyed. After the complete destruction, the graph of FIG. Thus, when it is used as a base particle of conductive fine particles, the electrical connection by the obtained conductive fine particles is such that the particles are completely destroyed by one destruction behavior until the destruction behavior occurs (FIG. 2). Must be performed in a state where the amount of displacement is small (between the start point and point e). On the other hand, particles having a two-stage fracture behavior such as the polymer fine particles of the present invention, as described above, immediately after the start of the preliminary fracture behavior until this fracture behavior occurs (point a in FIG. 1). If the electrical connection is made in the state between the point and the point c), the contact area with respect to the connection site is improved based on the fact that some of the particles are crushed, and some of the particles remain without being crushed. As a result, the contact pressure with respect to the connection site is maintained high, and as a result, the connection reliability can be improved from the viewpoint of both the contact area and the contact pressure with respect to the connection site.

  When the polymer fine particles of the present invention have a core / shell structure, as described above, the shell layer is normally broken in the preliminary fracture behavior in the present invention, and the remaining core particles are usually broken in the fracture behavior. Therefore, in a preferred embodiment of the polymer fine particles of the present invention, the destruction of the core particles is observed after the destruction of the shell layer in the compression test.

  In the present invention, the compression test may be performed at room temperature (25 ° C.) using, for example, a micro compression tester equipped with a flat plate indenter made of diamond.

In the present invention, the particle diameter in the compression direction of the polymer fine particles at the starting point of the preliminary fracture behavior in the compression test (point a in FIG. 1) is A (μm), and the starting point of the fracture behavior (FIG. When the particle size in the compression direction of the polymer fine particles at point c in 1) is B (μm) and the particle size in the compression direction of the polymer fine particles before being subjected to the compression test is C (μm), It is preferable that the connection area ratio calculated | required by a following formula is 1 to 50%.
Connection area ratio (%) = [(A−B) / C] × 100

  Here, the connection region means a region that can be connected with a good contact area and contact pressure when conducting electrical connection with the conductive fine particles obtained using the polymer fine particles of the present invention as base particles. The connection area ratio is the ratio of the connection area to the particle diameter of the original polymer fine particles. If the connection area ratio is lower than the above range, the connection area is too narrow, and it tends to be difficult to connect in a state where the connection area is just in the electrical connection. On the other hand, if the connection area ratio is higher than the above range, the diameter of the portion remaining at the time of electrical connection (core particle in the case of a core / shell structure) is relatively small, which is not preferable. The lower limit of the connection area ratio is more preferably 3% or more, still more preferably 5% or more, and the upper limit is more preferably 40% or less, still more preferably 35% or less.

In the present invention, the particle diameter in the compression direction of the polymer fine particles at the starting point of the preliminary fracture behavior in the compression test (point a in FIG. 1) is A (μm), and before being subjected to the compression test. When the particle diameter in the compression direction of the polymer fine particles is C (μm), the first elastic limit ratio obtained by the following formula is preferably 45 to 90%.
First elastic limit ratio (%) = (A / C) × 100

  Here, the first elastic limit ratio is a percentage of the particle diameter of the polymer fine particles at the start of the preliminary fracture behavior with respect to the particle diameter of the original polymer fine particles. When the first elastic limit ratio of the particles is in the above range, a good connection state can be achieved in ACF mounting.

  The particles exhibiting the two-stage fracture behavior as described above can be obtained, for example, by appropriately setting the monomer composition of the polymer constituting the core-shell structure particles. Hereinafter, the monomer composition capable of exhibiting the above-described two-stage fracture behavior will be described in detail. The polymer fine particles of the present invention showing a two-stage fracture behavior are not limited to those having the following monomer composition, and means for developing the two-stage fracture behavior is not limited to the setting of the monomer composition.

  In the present invention, the monomer composition of the polymer constituting the core particle and the shell layer may be an embodiment containing at least a vinyl group-containing monomer. In other words, both the core particle and the shell layer are preferably a polymer of a vinyl group-containing monomer. More preferably, each of the vinyl group-containing monomers constituting the core particle and the shell layer is a crosslinkable monomer having two or more polymerizable groups including a vinyl group in one molecule (hereinafter referred to as “crosslinkable vinyl group-containing monomer”). May be referred to as at least). When the core particle is composed of a monomer component containing a crosslinkable vinyl group-containing monomer, the conductive fine particles obtained using the polymer fine particles of the present invention as base material particles exhibit a high contact pressure. Moreover, when the shell layer is composed of a monomer component containing a crosslinkable vinyl group-containing monomer, conductive fine particles capable of maintaining a large contact area with the connection site can be obtained by plastic deformation based on the preliminary fracture behavior. Of course, the monomer component constituting the core particle and the shell layer is a monomer having one vinyl group in one molecule as the vinyl group-containing monomer (hereinafter also referred to as “non-crosslinkable vinyl group-containing monomer”). It may contain, and may contain the other monomer which does not contain a vinyl group.

  In the present invention, the term “vinyl group” includes a substituent having a polymerizable carbon-carbon double bond such as (meth) acryloxy group, allyl group, isopropenyl group, vinylphenyl group, isopropenylphenyl group. It is.

  In the present invention, the “polymerizable group” may be any group that can form a bond with another monomer. In addition to a radical polymerizable group such as a vinyl group, a carboxylic acid group, a hydroxy group, an alkoxy group, etc. Also included are condensable reactive groups capable of forming an ester bond or a siloxane bond. Here, the condensable reactive group may be bonded to either a carbon atom or a silicon atom, but is preferably bonded to a silicon atom. Preferable polymerizable groups include a vinyl group, an alkoxy group bonded to a silicon atom, or a hydroxy group.

Among the vinyl group-containing monomers, the crosslinkable vinyl group-containing monomer includes a monomer having two or more vinyl groups in the molecule, or a monomer having one vinyl group and one or more condensable reactive groups in the molecule. Can be mentioned. Examples of the former include, for example, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, and 1,10-decanediol. Alkanediol di (meth) acrylates such as di (meth) acrylate, ethylene glycol di (meth) acrylate, 1,3-butylene di (meth) acrylate; diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, Glycol-based di (meth) acrylates such as decaethylene glycol di (meth) acrylate, pentadecaethylene glycol di (meth) acrylate, and pentacontahector ethylene glycol di (meth) acrylate; trimethylolpropane tri (meth) acrylate Polyfunctional (meth) acrylates such as acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate; unsaturated group-containing mono (meta) such as allyl (meth) acrylate ) Acrylates; aromatic hydrocarbon crosslinking agents such as divinylbenzene, divinylnaphthalene, and derivatives thereof (preferably styrenic polyfunctional monomers such as divinylbenzene); N, N-divinylaniline, divinyl ether, divinyl sulfide, A heteroatom-containing crosslinking agent such as divinylsulfonic acid; and the like. Among these, (meth) acrylic polyfunctional monomers and styrenic polyfunctional monomers are preferable, and in order to obtain particles having a large displacement in the preliminary fracture behavior, like ethylene glycol di (meth) acrylate and divinylbenzene. Monomers having a small number of carbons interposed between vinyl groups are preferred. Examples of the latter include, for example, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 1-hexenyltrimethoxysilane, 1-hexenyltriethoxysilane, etc. Silane monomers such as vinyl alkoxysilane monomers (particularly vinyl C _1-2 alkoxysilane monomers) and their hydrolysis condensates. Among these, 3-methacryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane are preferable.

  In the present invention, (meth) acrylate refers to acrylate, methacrylate, and a mixture thereof.

  Among the vinyl group-containing monomers, examples of the non-crosslinkable 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, nonyl (meth) acrylate, decyl ( Alkyl (meth) acrylates such as (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate; 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 (meth) acrylates such as butylcyclohexyl (meth) acrylate; Hydroxy group-containing (meth) such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate Acrylates: (Meth) acrylics such as phenyl (meth) acrylate, benzyl (meth) acrylate, tolyl (meth) acrylate, phenethyl (meth) acrylate and other aromatic ring-containing (meth) acrylates Monofunctional monomers; alkyl styrenes such as styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, α-methyl styrene, p-tert-butyl styrene; alkoxy styrenes such as p-methoxy styrene; p- Styrene monofunctional monomers such as aromatic ring-containing styrenes such as phenylstyrene; halogen group-containing styrenes such as o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene; hydroxy group-containing styrenes such as p-hydroxystyrene And the like.

  When the monomer composition of the polymer constituting the core particle and the shell layer contains a monomer that does not contain a vinyl group, a condensable reactive group selected according to the type of the vinyl group-containing monomer to be used together is preferably in the molecule. It is preferable to use a compound having one, more preferably two or more. For example, when a vinyl alkoxysilane monomer is used as the vinyl group-containing monomer, a tetraalkoxysilane monomer such as tetramethoxysilane or tetraethoxysilane, a trialkoxysilane monomer such as methyltrimethoxysilane or methyltriethoxysilane, or dimethyldimethoxy Dialkoxysilane monomers such as silane and dimethyldiethoxysilane, monoalkoxysilane monomers such as trimethylmethoxysilane and trimethylethoxysilane, and silane monomers such as hydrolysis condensates thereof can be used.

  The monomer composition (monomer type and content) of each monomer component constituting the core particle and the shell layer preferably has the following mutual relationship in order to develop a two-stage fracture behavior. That is, the content of the crosslinkable monomer (crosslinkable vinyl group-containing monomer) in the vinyl group-containing monomer constituting the core particle is Xc (mass%), and the crosslinkable monomer (crosslink in the vinyl group-containing monomer constituting the shell layer). Xc ≧ 25 and Xs ≧ 20 are preferable when the content of the functional vinyl group-containing monomer is Xs (mass%). Furthermore, it is preferable that Xc> Xs. More preferably, Xc ≧ 35 and Xs ≧ 30, and further preferably Xc ≧ 55 and Xs ≧ 50. When Xc> Xs, the core particles exhibit a higher crosslink density than the shell layer, which facilitates the two-stage fracture behavior described above. However, in order to show the above-described two-stage fracture behavior, it may not be sufficient if the crosslinking density of the core particles and the shell layer relatively satisfy a predetermined relationship, and Xc and Xs each fall within the above range. It is preferable that both the core particle and the shell layer have a predetermined crosslinking density.

  In addition, when the monomer component which comprises a core particle contains the monomer which does not contain a vinyl group, a vinyl group containing monomer (crosslinkable vinyl group containing monomer + non-crosslinkable vinyl group containing monomer) with respect to the monomer component whole quantity of a core particle. The content ratio is preferably 20% by mass or more, more preferably 40% by mass or more, and still more preferably 60% by mass or more. On the other hand, when the monomer component constituting the shell layer includes a monomer that does not contain a vinyl group, the vinyl group-containing monomer (crosslinkable vinyl group-containing monomer + non-crosslinkable vinyl group-containing monomer) with respect to the total monomer component of the shell layer The content ratio is preferably 20% by mass or more, more preferably 40% by mass or more, and still more preferably 60% by mass or more.

  When the polymer fine particles of the present invention are obtained, the monomer amount, the degree of crosslinking and the like are adjusted in order to control the fracture behavior. As the polymerization method, conventionally known production can be used as appropriate. When the polymer fine particle of the present invention is a particle having a core-shell structure, for example, first, as a monomer component constituting the core particle, a monomer component containing a monomer having a reactive substituent that does not participate in a polymerization reaction is used. Various reactive substituents (for example, alkoxysilyl group, silanol group, vinyl group, methacryloyl group, acryloyl group, etc.) can be obtained by polymerizing monomer components by emulsion polymerization, suspension polymerization, seed polymerization, sol-gel method, etc. The core particle which has is produced. Next, the monomer component constituting the shell layer in the presence of the obtained core particle is polymerized by an emulsion polymerization method, a suspension polymerization method, a seed polymerization method, a sol-gel method, etc. What is necessary is just to chemically react with the monomer component which comprises.

  When obtaining the polymer fine particles of the present invention, it is preferable to perform polymerization of the monomer components constituting the core particles and the shell layer by a seed polymerization method. Specifically, the seed production process for producing seed particles using a part of the monomer component, the absorption process for absorbing the remainder of the monomer component in the obtained seed particle, and the polymerization process for polymerizing the monomer component, the particles Get. In the case of the shell layer, in the seed manufacturing step, the shell layer seed portion may be manufactured using a part of the monomer component that constitutes the shell layer in the presence of the core particles prepared earlier. Thus, according to the method in which seed particles (seed portions) are first formed with a part of the monomer component, and then the monomer component is polymerized after absorbing the remainder of the monomer component, the hardness of the core particles and the shell layer is reduced. Core-shell particles that are easy to control and that exhibit two-stage fracture behavior can be easily obtained.

  Hereafter, each process at the time of obtaining the polymer fine particle of this invention which has a core shell structure by a seed polymerization method is demonstrated in detail.

  First, a core particle is formed using the monomer component which comprises a core particle.

  As a part of the monomer component used in the seed production process, it is preferable to use a silane-based monomer that is a crosslinkable vinyl group-containing monomer among the monomer components constituting the core particle. It is preferable to obtain polysiloxane particles by hydrolysis and condensation reaction in a solvent. 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.

  The method for absorbing the monomer component in the absorption step may be any method that allows the monomer component to be present in the presence of the seed particles (the seed part of the core particle) and allows the absorption to proceed. For example, the monomer component may be added to a solvent in which seed particles (the seed part of the core particle) are dispersed, or the seed particles may be added to a solvent containing the monomer component. Preferably, the method of adding the monomer component to the reaction liquid without removing the seed particles (the seed part of the core particle) from the reaction liquid does not complicate the process and is excellent in productivity. In this case, the timing of addition of the monomer component is not particularly limited, and the monomer component may be added all at once, may be added in several times, or may be fed at an arbitrary rate. In addition, when adding the monomer component, the monomer component may be added alone or a solution of the monomer component may be added. However, the monomer emulsion in which the monomer component is previously emulsified and dispersed in water or an aqueous medium with a conventionally known emulsifier. Is preferable because absorption is more efficiently performed. The absorption of the monomer component is preferably performed, for example, in the temperature range of 0 ° C. to 60 ° C. with stirring for 5 minutes to 720 minutes. In addition, for determining whether the monomer component is absorbed in the seed particles (the seed part of the core particle) in the absorption process, for example, before adding the monomer composition and after the absorption process, observe the particles with a microscope, It can be easily determined by confirming that the particle size is increased by absorption of the monomer component.

  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, and further preferably 0.1 part by mass with respect to 100 parts by mass of the total mass of the monomer components. It is above, and it is preferable that it is 20 mass parts or less, More preferably, it is 10 mass parts or less, More preferably, it is 5 mass parts or less. 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.

  By performing the seed production process, the absorption process and the polymerization process using the monomer components constituting the core particles, a dispersion liquid in which the core particles are dispersed is obtained. Next, in order to form the shell layer, the seed production process, the absorption process and the polymerization process are performed using the monomer components constituting the shell layer, in the same manner as the core particle formation method, except that the core particles are present. Just do it.

  For example, by adding a silane-based monomer that is a crosslinkable vinyl group-containing monomer as a part of the monomer component for forming a shell layer to the dispersion in which the core particles are dispersed, the core particles are subjected to hydrolysis and condensation reaction. A shell layer seed portion made of polysiloxane is formed on the surface. Suitable aspects such as the catalyst and temperature conditions used for hydrolysis and condensation are the same as in the case of forming the core particle seed portion. Next, the monomer component was absorbed into the shell layer seed portion by adding and mixing the monomer component to the dispersion liquid in which the particles having the shell layer seed portion made of polysiloxane formed on the core particle surface were dispersed. Thereafter, a shell layer can be formed on the surface of the core particle by polymerization. The preferred embodiment for absorbing the monomer and the preferred embodiment for polymerizing are the same as in the case of forming the core particles.

When the polymer fine particles of the present invention are particles having a core / shell structure, the 10% K value of the core particles is Yc (kgf / mm ² ), and the 10% K value of the shell layer is Ys (kgf / mm ² ). It is preferable that Yc ≧ 800, Ys ≧ 600, and Yc> Ys. Preferably, Yc ≧ 900 and Ys ≧ 700. When Yc> Ys, the core particles have a higher hardness than the shell layer, and this facilitates the development of the two-stage fracture behavior as described above. However, in order to show the two-stage fracture behavior described above, there are cases where it is not sufficient that the hardness of the core particles and the shell layer relatively satisfy a predetermined relationship. High hardness is preferable, and the values of Yc and Ys are preferably within the above-mentioned range. The 10% K value of the core particle and the 10% K value of the shell layer are respectively 10% for each sample particle obtained by preparing sample particles having the same composition as the monomer component constituting the core particle and the shell layer. It can be determined by measuring the% K value.

10% K value of the polymer fine particles of the present invention, 700 kgf / mm ² or more, preferably 2,000 kgf / mm ² or less. When the 10% K value of the polymer fine particles is less than 700 kgf / mm ² , the surrounding binder cannot be sufficiently removed when used as conductive fine particles in the anisotropic conductive material, and the degree of biting into the electrode However, if it exceeds 2000 kgf / mm ² , a good contact state with the electrode may not be obtained. The 10% K value of the polymer fine particles is more preferably 750 kgf / mm ² or more and 1500 kgf / mm ² or less.

  In the present invention, the 10% K value is obtained by applying a load at a load load rate of 0.2275 gf / sec in the center direction of the particle, for example, using the same compression tester as that for performing the compression test. The load and the amount of displacement (mm) when the particles are deformed to 10% can be measured and determined based on the following formula. In the present invention, the 10% K value of 10 different particles is obtained, and the average value thereof is taken as the 10% K value of the polymer fine particles. In addition, when the polymer fine particles of the present invention are particles having a core / shell structure, the 10% K value of the shell layer is determined by the same method as the preparation of the core particles using the monomer component constituting the shell layer. Test particles for 10% K value measurement were prepared and measured using the obtained test particles.

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

  When the polymer fine particles of the present invention are particles having a core-shell structure, the diameter of the core particles is not particularly limited, but if used as an anisotropic conductive material, the number average particle diameter is 0.4. Is preferably 10 μm or less, more preferably 3 μm or less, still more preferably 2.5 μm or less, and most preferably 2.0 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.). .

  When the polymer fine particles of the present invention are particles having a core / shell structure, the thickness of the shell layer is preferably 0.05 μm or more, more preferably, in order to develop a preliminary fracture behavior with a large displacement. Is preferably 0.1 μm or more. The upper limit of the thickness of the shell layer is not particularly limited, but is usually 1 μm or less.

  The particle diameter of the polymer fine particles of the present invention is preferably 0.5 to 12 μm in number average particle diameter. When the number average particle diameter is smaller than 0.5 μm, the particles are likely to aggregate when the surface is coated with a conductive metal layer to form conductive fine particles, and it may be difficult to form a uniform conductive metal layer. On the other hand, when the particle diameter exceeds 12 μm, the application application when conductive fine particles are used is limited, and there is a tendency that the industrial application fields are reduced. In particular, when used as a base particle of conductive fine particles used for an anisotropic conductive material, the number average particle diameter is more preferably 4.0 μm or less, further preferably 3.5 μm or less. Most preferably, it is 2 μm or less, while the lower limit is more preferably 1 μm or more. With the fine pitch and low gap of the connected medium, the conductive fine particles in the anisotropic conductive material will be required to have a small particle size. However, the polymer fine particles of the present invention achieve a large contact area and a high contact pressure with respect to the connection site even if the polymer fine particles of the present invention have a small particle size as described above. It is particularly useful because it can.

  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 polymer fine particles of the present invention is preferably 20% or less, more preferably 10% or less, and even more preferably 7% or less. The variation coefficient of the particle diameter is obtained by applying the following formula to the average particle diameter of the polymer fine particles measured by a precision particle size distribution measuring apparatus using the Coulter principle and the standard deviation of the particle diameter of the polymer fine particles. Value.
Coefficient of variation (%) of polymer fine particles = 100 × standard deviation of particle diameter / average particle diameter

  The shape of the polymer fine particle of the present invention is not particularly limited, and may be any of, for example, a spherical shape, a spheroid shape, a confetti shape, a thin plate shape, a needle shape, an eyebrow shape, etc. A spherical shape is preferred.

(Conductive fine particles)
In the conductive fine particles of the present invention, a conductive metal layer is formed on the surface with the polymer fine particles of the present invention (hereinafter also referred to as substrate particles) as nuclei.

  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, and indium. Among these, gold, nickel, palladium, and silver are preferable because of excellent conductivity. Further, the conductive metal layer may be a single layer or multiple layers. In the case of multiple layers, for example, nickel-gold, nickel-palladium, nickel-palladium-gold, nickel-silver and the like are preferable. Can be mentioned.

  The thickness of the conductive metal layer is preferably 0.005 to 1.0 μm, more preferably 0.05 μm or more and 0.3 μm or less. If the conductive metal layer is too thin, it tends to be difficult to maintain a stable electrical connection when the conductive fine particles are used as an anisotropic conductive material. On the other hand, if the conductive metal layer is too thick, the surface hardness of the conductive fine particles becomes too high, and the above-described effects based on the two-stage fracture behavior characteristic of the polymer fine particles of the present invention may not be fully utilized. is there.

  The particle diameter of the conductive fine particles is preferably 0.7 to 12 μm in number average particle diameter. In particular, when used for an anisotropic conductive material, the number average particle diameter is more preferably 4.2 μm or less, further preferably 3.7 μm or less, and most preferably 3.4 μm or less. On the other hand, the lower limit is more preferably 1.2 μm or more. If the number average particle diameter of the conductive fine particles is too small, the particles are likely to aggregate and it may be difficult to form a uniform conductive metal layer. Tend to be less.

  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; metal fine powder alone or in a binder A method of coating polymer fine particles in a mixed paste form; 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 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; polymethyl (meth) acrylate, polyethyl ( (Meth) acrylate polymers and copolymers such as (meth) acrylate and polybutyl (meth) acrylate; polystyrene, styrene-acrylate copolymer, SB type styrene-butadiene block copolymer, SBS type styrene-butadiene block copolymer Polymers and block polymers such as hydrogenated compounds thereof; thermoplastic resins such as vinyl polymers and copolymers and particularly cross-linked products thereof; thermosetting resins such as epoxy resins, phenol resins and melamine resins; polyvinyl alcohol; Polyacrylic acid Polyacrylamide, polyvinyl pyrrolidone, polyethylene oxide, water-soluble resins and mixtures thereof, such as methyl cellulose; and the like. However, if the insulating resin layer is too hard compared to the base particles (polymer fine particles), the base particles themselves may be destroyed before the insulating resin layer is destroyed. When using a polymer and a copolymer made of a vinyl group-containing monomer for the resin layer, it is preferable to use an uncrosslinked or (co) polymer having a relatively low degree of crosslinking.

  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. When the thickness of the insulating resin layer is too thin, the electrical insulation becomes insufficient, while when it 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. Specific examples of anisotropic conductive materials include anisotropic conductive films, anisotropic conductive pastes, anisotropic conductive adhesives, anisotropic conductive inks, and the like between adjacent substrates and electrode terminals. The thing which enables electrical connection by providing is mentioned. The anisotropic conductive material using the conductive fine particles of the present invention also includes a conductive material for a liquid crystal display element such as a conductive spacer and a composition thereof.

  An anisotropic conductive material is usually produced by dispersing the conductive fine particles of the present invention in an insulating binder resin to obtain a desired form, but the insulating binder resin and the conductive fine particles are separately provided. It may be used 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.

  The connection method for electrically connecting the connection sites using the anisotropic conductive material of the present invention is not particularly limited, but the pressure applied at the time of connection is the polymer of the present invention contained in the anisotropic conductive material. More than the pressure at the point at which the preliminary fracture behavior starts when the microparticles are subjected to the compression test described above, and less than the pressure at the point at which this fracture behavior starts (ie, the first in the compression displacement curve obtained in the compression test) It is preferable to set the load to be between the elastic limit point and less than the second elastic limit point, and more preferably at the point at which this fracture behavior starts above the pressure at which the preliminary fracture behavior has ended. It is preferable to set the pressure less than the pressure (that is, the load between the second elastic deformation start point and the second elastic limit point in the compression displacement curve obtained in the compression test). Accordingly, the contact area between the conductive fine particles and the connected medium such as the electrode can be increased, and the contact pressure between the conductive fine particles and the connected medium can be kept high. Therefore, the connection structure that uses the anisotropic conductive material of the present invention and is connected by applying the pressure in the specific range has excellent connection reliability.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited by the following Example, As long as it changes and implements in the range which does not deviate from the meaning of this invention, it is contained in the scope of the present invention. In the following, “part” means “part by mass” and “%” means “% by mass” unless otherwise specified.

[Example 1]
(Preparation of polymer fine particles)
In a four-necked flask equipped with a condenser, a thermometer, and a dripping port, 840.0 parts of ion-exchanged water, 12.0 parts of 25% aqueous ammonia and 360.0 parts of methanol were added, and 3 g -70.0 parts of methacryloxypropyltrimethoxysilane ("KBM503" manufactured by Shin-Etsu Chemical Co., Ltd.) was added to hydrolyze and condense 3-methacryloxypropyltrimethoxysilane to produce polysiloxane particle milk. A suspension was prepared.

  Next, in a solution obtained by dissolving 0.3 part of sodium dodecyl sulfate as an emulsifier in 49 parts of ion-exchanged water, 49 parts of divinylbenzene (“DVB960” manufactured by Nippon Steel Chemical Co., Ltd.) and 2,2′- Add 1.2 parts of azobis (4-methoxy-2,4-dimethylvaleronitrile) (“V-70” manufactured by Wako Pure Chemical Industries, Ltd.), and emulsify and disperse the monomer component by stirring for 2 hours. A liquid was prepared. The obtained emulsion was added to an emulsion of polysiloxane particles and further stirred. One hour after the addition of the emulsified liquid, the mixed liquid was sampled and observed with a microscope, and it was confirmed that the polysiloxane particles were enlarged by absorbing the monomer component.

  Next, 6.0 parts of a 20% aqueous solution of polyoxyethylene styrenated ammonium sulfate ester ammonium salt (“Hytenol (registered trademark) NF-08” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was added as an emulsifier, and 65% under a nitrogen atmosphere. The temperature was raised to 0 ° C. and held at 65 ° C. for 2 hours to radically polymerize the monomer component. After radical polymerization, the obtained emulsion was subjected to solid-liquid separation, and the resulting cake was washed with ion-exchanged water and then with methanol, and then calcined at 280 ° C. for 1 hour in a nitrogen atmosphere to obtain core particles (1). Got. When the particle size of the core particles (1) was measured with a particle size distribution measuring apparatus (“Coulter Multisizer III type” manufactured by Beckman Coulter, Inc.), the number average particle size was 1.97 μm, and the coefficient of variation (CV value) was 3. 0%. The content Xc of the crosslinkable monomer in the vinyl group-containing monomer constituting the core particle (1) is 100% by mass.

  Next, in a four-necked flask equipped with a cooling tube, a thermometer, and a dropping port, 65.0 parts of core particles (1), 650 parts of methanol, 1.3 parts of 25% aqueous ammonia, 1300 parts of ion-exchanged water, an emulsifier As a solution, 3.3 parts of 20% aqueous solution of polyoxyethylene styrenated phenyl ether sulfate ammonium salt (“HITENOL (registered trademark) NF-08” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was added, and 3-methacryloxypropyltrimethoxysilane was added. (Shin-Etsu Chemical Co., Ltd. "KBM503") 16.3 parts was dripped. After completion of dropping, the mixture was stirred for 2 hours, and the particle size of the polysiloxane-coated particles obtained with a particle size distribution measuring device (“Coulter Multisizer III type” manufactured by Beckman Coulter, Inc.) was measured. Met.

  Next, 4.0 parts of 20% aqueous solution of polyoxyethylene styrenated phenyl ether sulfate ammonium salt (“HITENOL (registered trademark) NF-08” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as an emulsifier is dissolved in 163 parts of ion-exchanged water. In this solution, 48.8 parts of styrene, 113.8 parts of divinylbenzene (“DVB960” manufactured by Nippon Steel Chemical Co., Ltd.), 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator (Wako Pure Chemical Industries, Ltd.) 1.8 parts of "V-65" manufactured by Kogyo Co., Ltd.) was added and the mixture was stirred for 1 hour to be emulsified and dispersed to prepare an emulsion of monomer components. The obtained emulsion was added to the emulsion of polysiloxane-coated particles and further stirred. One hour after the addition of the emulsified liquid, the mixed liquid was sampled and observed with a microscope. As a result, it was confirmed that the polysiloxane-coated particles were enlarged by absorbing the monomer component.

  Next, the temperature of the reaction solution was raised to 65 ° C. in a nitrogen atmosphere and held at 65 ° C. for 2 hours to perform radical polymerization of the monomer component, thereby terminating the reaction. The obtained emulsion is subjected to solid-liquid separation, and the resulting cake is washed with ion-exchanged water and then with methanol, and then dried in a vacuum at 120 ° C. for 2 hours under a nitrogen atmosphere to obtain a heavy layer having a shell layer on the surface of the core particles. Combined fine particles (1) were obtained. The content Xs of the crosslinkable monomer in the vinyl group-containing monomer constituting the shell layer of the polymer fine particles (1) is 72.7% by mass.

  When the particle diameter of the obtained polymer fine particles (1) was measured with a particle size distribution analyzer (“Coulter Multinizer III type” manufactured by Beckman Coulter, Inc.), the number average particle diameter was 3.04 μm. The thickness of the shell layer was 0.54 μm when calculated from the core-shell structured polymer fine particles (1) and the number average particle diameter of the core particles.

Further, the 10% K value (Yc) of the core particles constituting the polymer fine particles (1) and the 10% K value (Ys) of the shell layer were examined by the following method. That is, particles having the same composition as the core particles and the shell layer constituting the polymer fine particles (1) and a particle size of 3.0 μm were prepared, and these were used as sample particles. -W500 "), one sample particle dispersed on a sample stage (material: SKS flat plate) at room temperature (25 ° C) using a circular plate indenter (material: diamond) with a diameter of 50 μm, constant toward the center of the particle A load was applied at a load speed of 0.2275 gf / second, and the displacement (μm), load value (gf), and 10% displacement load value at the time of particle breakage were measured. As a result, Yc = 1148 kgf / mm ² and Ys = 882 kgf / mm ² .

  When subjected to a compression test in which the polymer fine particles (1) are compressed at a load load rate of 0.2275 gf / sec, as shown in FIG. 1, the preliminary fracture behavior and the two-stage fracture behavior are shown. I was able to confirm. In FIG. 1, a is the starting point of the preliminary fracture behavior, and the displacement at this time was 0.89 μm and the load was 0.30 gf. From this, the particle diameter A in the compression direction of the polymer fine particles at the starting point of the preliminary fracture behavior is the displacement from the number average particle diameter (3.04 μm) of the polymer fine particles (1) before being subjected to the compression test. The value (2.15 μm) is obtained by subtracting the amount (0.89 μm). In FIG. 1, c is the starting point of the fracture behavior, and the displacement at this time was 1.74 μm and the load was 0.79 gf. From this, the particle diameter B in the compression direction of the polymer fine particles at the starting point of the fracture behavior is the amount of displacement from the number average particle diameter (3.04 μm) of the polymer fine particles (1) before being subjected to the compression test. A value obtained by subtracting (1.74 μm) (1.30 μm). Since the particle diameter C in the compression direction of the polymer fine particles before being subjected to the compression test is 3.04 μm, the connection area ratio of the obtained polymer fine particles (1) is 28%.

(Preparation of conductive fine particles)
The polymer fine particles (1) were etched with sodium hydroxide, then sensitized with a tin dichloride solution, and then activated with a palladium dichloride solution to form palladium nuclei. Polymer fine particles (1) having palladium nuclei formed in this manner are immersed in an electroless nickel plating bath to form a nickel plating layer, followed by gold displacement plating, and then washing with ion exchange water, methanol. Substitution was performed and vacuum drying was performed to obtain conductive fine particles (1).

  An anisotropic conductive material was produced using the obtained conductive fine particles (1), and the initial resistance value was evaluated. That is, 2.0 parts of the conductive fine particles (1) were mixed and dispersed in 100.0 parts of an epoxy resin (“Stractbond (registered trademark) XN-5A” manufactured by Mitsui Chemicals) to prepare a conductive adhesive paste. A test piece was prepared by sandwiching 0.01 part of this conductive adhesive paste between two glass substrates on which aluminum electrodes were formed and thermocompression bonding at 180 ° C. for 20 seconds. When the connection resistance value (Ω) of the obtained test piece was measured by the four-terminal method, it was 7.8Ω.

[Comparative Example 1]
The core particles (1) obtained in Example 1 were used as polymer fine particles (C1) for comparison as they were.

  When the polymer fine particles (C1) were subjected to a compression test in which the polymer fine particles (C1) were compressed at a load load rate of 0.2275 gf / sec, the entire polymer fine particles were broken by a single breaking behavior as shown in FIG. In FIG. 2, e is the starting point of the fracture behavior, the displacement amount at this time was 0.856 μm, and the load was 0.50 gf.

  Conductive fine particles were produced in the same manner as in Example 1 except that the polymer fine particles (C1) were used, and the conductive adhesive paste produced in the same manner as in Example 1 using the conductive fine particles (C1). The initial resistance value was evaluated in the same manner as in Example 1. As a result, the connection resistance value (Ω) of the obtained test piece was 20.2Ω.

Claims (11)

  In a compression test in which polymer fine particles are compressed at a load load rate of 0.2275 gf / sec, a preliminary fracture behavior in which a part of the polymer fine particles is broken in advance is shown before the main fracture behavior in which the whole polymer fine particles are broken. Polymer fine particles characterized in that shown.   The polymer fine particles according to claim 1, comprising core particles and a shell layer provided on the surface of the core particles.   The polymer fine particles according to claim 2, wherein destruction of the core particles is observed after the destruction of the shell layer in the compression test. In the compression test, the particle size in the compression direction of the polymer fine particles at the starting point of the preliminary fracture behavior is A, and the particle size in the compression direction of the polymer fine particles at the start point of the present fracture behavior is B. The polymer fine particles according to any one of claims 1 to 3, wherein a connection area ratio obtained by the following formula is 1 to 50%, where C is the particle size in the compression direction of the polymer fine particles before being subjected to the treatment. .
Connection area ratio (%) = [(A−B) / C] × 100   Polymer fine particles according to any one of claims 2 to 4, wherein both the core particle and the shell layer are polymers of vinyl group-containing monomers.   Each of the vinyl group-containing monomers constituting the core particle and the shell layer contains at least a crosslinkable monomer having two or more polymerizable groups including vinyl groups in one molecule, and contains vinyl groups constituting the core particles. When the content of the crosslinkable monomer in the monomer is Xc (mass%) and the content of the crosslinkable monomer in the vinyl group-containing monomer constituting the shell layer is Xs (mass%), Xc ≧ 25, Xs ≧ Polymer fine particles according to any one of claims 2 to 5, wherein 20 and Xc> Xs. When the 10% K value of the core particles is Yc (kgf / mm ² ) and the 10% K value of the shell layer is Ys (kgf / mm ² ), Yc ≧ 800, Ys ≧ 600, and Yc> Ys The polymer fine particles according to claim 2, wherein   The polymer fine particle according to any one of claims 2 to 7, wherein the shell layer has a thickness of 0.05 µm or more.   Conductive fine particles comprising the polymer fine particles according to claim 1 and a conductive metal layer.   The conductive fine particles according to claim 9, which have an insulating resin layer on at least a part of the surface.   An anisotropic conductive material comprising the conductive fine particles according to claim 9 or 10.