JP5567458B2 - Polymer particles, and conductive fine particles and anisotropic conductive materials using the same - Google Patents

Description

  The present invention relates to polymer particles in which one recess having a predetermined shape is formed on the particle surface.

Conventionally, as particles having unique mechanical properties and optical properties, particles having irregularities formed on the surface of spherical particles, meteorite particles, convex lens particles, flat particles, and the like have been proposed.
As a method for producing spherical particles having irregularities on the surface, for example, a first step of dispersing nonpolar solvent droplets and polymer fine particles incompatible with a polar solvent in a polar solvent, and stirring the dispersion liquid And forming a depression on the surface of the polymer fine particle (see Patent Document 1); in the absence of a crosslinking agent, the polymerizable vinyl monomer is copolymerized with the polymerizable vinyl monomer. A spherical fluorine-containing resin particle having a predetermined shape is obtained by mixing and dissolving a hydrophobic fluorine-based liquid organic compound having a predetermined viscosity and subjecting it to aqueous suspension polymerization. Production method (see Patent Document 2): In the absence of a crosslinking agent, the polymerizable vinyl monomer does not have a copolymerizability with the polymerizable vinyl monomer and has a predetermined viscosity as a hydrophobic liquid compound. A production method for obtaining spherical resin particles having a predetermined shape having a bowl-shaped depression on the particle surface by mixing and dissolving xylene or hydrocarbons and subjecting to aqueous suspension polymerization (see Patent Document 3 (Claim 6)) ; Etc. have been proposed.

  In addition, as a method for producing irregularly shaped particles such as meteorite, for example, a polymerizable monofunctional vinyl monomer and a polymerizable polyfunctional vinyl monomer are mixed with a hydrophobic liquid medium that does not copolymerize with both vinyl monomers and a phosphate ester. A method for producing irregularly shaped resin particles obtained by carrying out aqueous suspension polymerization in the presence and then removing water and a hydrophobic liquid medium to obtain irregularly shaped resin particles (see Patent Document 4); seeds comprising vinyl polymer particles A flat form in which a monomer mixture containing a (meth) acrylic acid ester monomer and a crosslinkable vinyl monomer is emulsion-polymerized in an aqueous medium using a water-soluble polymerization initiator in the presence of particles. Method for producing irregularly shaped fine particles (see Patent Document 5); making inorganic compound fine particles into a slurry having a viscosity of 10 cps or less, and spray-granulating them, followed by firing; See); and the like have been proposed.

JP 2007-217616 A JP 2002-088102 A JP 2002-003517 A JP 2004-027008 A Japanese Patent Laid-Open No. 11-181037 JP-A-62-096537

Conventionally, it is known that the outer shape of polymer particles affects the mechanical properties, optical properties, and the like of the polymer particles. However, the number of polymer particles having a specific surface shape has not been proposed, and there is still room for investigation. Then, this invention is made | formed in view of the said situation, and it aims at providing the polymer particle which has a new external shape which is not in the past.
In particular, in the present invention, by controlling the shape of the dent formed on the particle surface, it exhibits a unique deformation behavior with respect to the compressive load, and even when used as a base particle for conductive fine particles, even in a low-pressure connection. An object of the present invention is to provide polymer particles capable of achieving a low electric resistance value.

  As a result of examining the polymer particles obtained by the seed polymerization method in detail in order to provide polymer particles having a new surface shape, the present inventors have found that by performing polymerization under extremely specific conditions, it has never been achieved before. The present inventors have found that polymer particles having a new external shape can be obtained and completed the present invention.

  The polymer particle of the present invention that has solved the above problems has an outer shape in which one dent satisfying the following (a) to (d) is formed in a sphere, and its volume is half that of the original sphere. It is the above. (A) The outer peripheral shape of the dent is a polygon. (B) The ratio (L1 / D) of the major axis (L1) of the dent to the particle diameter (D) is 0.3 or more and less than 1.0. (C) The ratio (L2 / D) of the minor axis (L2) of the dent to the particle diameter (D) is 0.05 or more and less than 1.0. (D) The ratio (L2 / L1) of the major axis (L1) to the minor axis (L2) is less than 1.0.

  In all monomer components for forming polymer particles, the content of the crosslinkable monomer is preferably 5% by mass or more. The number average particle diameter of the polymer particles is preferably 0.5 μm to 50 μm, and the coefficient of variation of the particle diameter is preferably 40% or less. The ratio (H / D) between the depth (H) of the dent and the particle diameter (D) is preferably 0.5 or less. Moreover, it is preferable that the area of the dent in the polymer particle surface is 25% or less of the total surface area when it is assumed that the polymer fine particles have no dent.

  The present invention also includes conductive fine particles having a conductive metal layer on the surface of the polymer particles, and an anisotropic conductive material containing the conductive fine particles.

  Since the polymer particle of the present invention has an outer shape in which a dent having a predetermined shape is formed on the particle surface, it exhibits mechanical identification, optical characteristics, and the like that are different from those of conventional polymer particles. In particular, the polymer particles of the present invention exhibit a specific deformation behavior with respect to a compressive load, specifically, a large deformation even at a low pressure due to the formation of a dent having a predetermined shape on the particle surface. Excellent low-pressure deformability. Therefore, by using the polymer particles as base particles of conductive fine particles, conductive fine particles that can achieve a low electric resistance value even in low-pressure connection can be obtained.

It is a figure explaining the dent of a polymer particle, (a) is a top view, (b) is the arrow AA sectional view taken on the line of (a). 2 is an SEM image of polymer particles obtained in Production Example 1. 3 is an SEM image used for measuring the major axis of the dent of the polymer particles obtained in Production Example 1. 3 is an FE-SEM image of a cross section of the polymer particles obtained in Production Example 1. FIG. FIG. 3 is a diagram showing compression deformation behavior of polymer particles obtained in Production Example 1 and polymer particles obtained in Production Example 2.

1. Polymer Particles The polymer particles of the present invention are characterized in that the sphere has an outer shape in which one dent satisfying a predetermined requirement is formed, and the volume thereof is more than half of the original sphere. By having a dent of a predetermined shape in the sphere, it can be deformed with the apex portion of the polygon as a base point even with a low compressive load. Further, since the volume of the polymer particles is more than half of the original sphere, repulsive force remains as in the case of normal solid particles. Therefore, when the polymer particles of the present invention are used as the base particles of conductive fine particles, the particles can be easily deformed and electrically connected between the electrodes even at a low applied pressure during pressure connection. From the viewpoint of the repulsive force of the particles, the hemispherical portion of the polymer particles is preferably solid. That is, when the polymer particles are divided by a plane passing through the center of the original sphere, one hemisphere has one dent of a predetermined shape, and the other hemisphere does not have a dent of a predetermined shape and is solid. It is preferable. Moreover, since the polymer particles of the present invention have an unprecedented outer shape, they exhibit new light scattering performance when used as an optical member.

  In the present invention, the “dent” means that the polymer is ruptured, such as a crack formed by cracking the particle surface or a defect formed by chipping the particle surface. Are different. That is, the “dent” in the present invention is a recess formed by pulling the particle surface inward in the process of producing polymer particles, and the surface is smooth. For example, when the particle breaks, the opposing fracture surfaces have complementary shapes, and when facing each other, the concave and convex curves of the fracture surface overlap, but there is no such complementary surface in the recess of the present invention. .

  Here, with reference to FIG. 1, the major axis, minor axis, etc. of the dent will be described. 1A and 1B are diagrams for explaining a dent of polymer particles, in which FIG. 1A is a plan view and FIG. 1B is a cross-sectional view taken along line AA in FIG. The particle diameter D is the diameter of the polymer particle 1. The major axis L1 of the dent is the length of the longest part of the dent when the dent 2 is viewed from the front. The minor axis L2 of the dent is the length of the longest part of the dent in the direction orthogonal to the direction of the major axis L1 when the dent 2 is viewed from the front. The depth H of the dent is the length of the longest perpendicular when the perpendicular is drawn from the straight line B connecting the dent starting points S1 and S2 to the bottom of the dent in the cross section of the polymer particle.

  The outer peripheral shape of the dent in a front view is a polygon. If the outer peripheral shape of the dent is a polygon, when a compressive load is applied to the polymer particles, it becomes easy to deform so that the vertex of the polygon becomes the base point and the dent is folded, and it can be easily deformed even at low pressure. it can. Therefore, the conductive fine particles using the polymer particles as the base particles can be connected even at a low pressure. The polygon may be a convex polygon or a concave polygon, but is preferably a convex polygon. Each side constituting the polygon may be a straight line or a curved line.

  The ratio (L1 / D) of the major axis (L1) of the dent to the particle diameter (D) is 0.3 or more and less than 1.0. If the ratio (L1 / D) is 0.3 or more, the particles can be sufficiently deformed at a low pressure. The ratio (L1 / D) is preferably 0.4 or more, more preferably 0.5 or more, preferably 0.9 or less, more preferably 0.8 or less, and still more preferably 0.7 or less. When the ratio (L1 / D) is 0.9 or less, the dent does not become too large and the polymer particles are difficult to break.

  The ratio (L2 / D) between the minor diameter (L2) of the dent and the particle diameter (D) is 0.05 or more and less than 1.0. If the ratio (L2 / D) is 0.05 or more, the particles can be sufficiently deformed at a low pressure. The ratio (L2 / D) is preferably 0.1 or more, more preferably 0.2 or more, preferably 0.5 or less, and more preferably 0.4 or less. When the ratio (L2 / D) is 0.5 or less, the dent does not become too large, and the polymer particles are difficult to break.

  The ratio (L2 / L1) of the major axis (L1) to the minor axis (L2) of the recess is less than 1.0. When the ratio (L2 / L1) is 1.0, the shape of the recess is close to isotropic, and the polymer particles are hardly deformed at a low pressure. The ratio (L2 / L1) is preferably 0.1 or more, more preferably 0.2 or more, preferably 0.9 or less, more preferably 0.8 or less. If the ratio (L2 / L1) is 0.1 or more, the area of the dent becomes large and can be easily deformed even at a low pressure, and if it is 0.9 or less, the shape of the dent is more anisotropic. And the polymer particles can be deformed at a lower pressure.

  The ratio (H / D) of the depth (H) of the dent to the particle diameter (D) is preferably 0.05 or more, more preferably 0.07 or more, still more preferably 0.1 or more. 5 or less is preferable, more preferably 0.4 or less, and still more preferably 0.3 or less. If the ratio (H / D) is 0.05 or more, it can be easily deformed even at a low pressure. If the ratio (H / D) is 0.5 or less, the dent does not become too large and the polymer particles are difficult to break.

  The area of the dents on the surface of the polymer particles is preferably 1% or more of the total surface area of the original sphere, more preferably 3% or more, still more preferably 5% or more, preferably 25% or less, more preferably 20%. Hereinafter, it is more preferably 15% or less. If the area of the dent is 1% or more, the area of the dent becomes large and can be easily deformed even at a low pressure. If the area is 25% or less, the dent does not become too large and the polymer particles are difficult to break. Become.

  The polymer particles of the present invention are all particles each having one dent of the predetermined shape, but have the dent of the predetermined shape as long as the effect of the present invention is not impaired. There may be no particles. In this case, the number of particles having no dent of the predetermined shape is preferably 50% or less of the total number of particles, more preferably 35% or less, still more preferably 10% or less, and 5% or less (particularly Most preferably, there are no particles having no dents). Further, the polymer particles of the present invention may have dents other than the above-mentioned dents as long as the effects of the present invention are not impaired, and fine irregularities exist on the particle surface. Also good.

  The number average particle diameter of the polymer particles is preferably 0.5 μm or more, more preferably 0.6 μm or more, further preferably 1.0 μm or more, particularly preferably 1.5 μm or more, and preferably 50 μm or less, more preferably It is 30 μm or less, more preferably 20 μm or less. When the number average particle diameter is 0.6 μm or more, it is possible to further suppress the generation of particles having no predetermined shape when producing polymer particles, and when the number average particle size is 50 μm or less, the predetermined shape is used. The effect by becomes more remarkable. In particular, when polymer particles are used as the base particles of conductive fine particles, the number average particle diameter of the polymer particles is preferably 0.5 μm or more, more preferably 1.0 μm or more, and even more preferably 1.6 μm. As described above, the thickness is particularly preferably 2.0 μm or more, preferably 4.0 μm or less, more preferably 3.5 μm or less, and still more preferably 3.2 μm or less.

  The variation coefficient of the particle diameter is preferably 40% or less. If the variation coefficient of the particle diameter is 40% or less, variations in the particle diameter and the dent size of the predetermined shape are suppressed, and characteristics such as light diffusion behavior and compression deformation behavior become more uniform. The variation coefficient of the particle diameter is more preferably 20% or less, still more preferably 8% or less. In particular, when polymer particles are used as the base particles of conductive fine particles, the conductive fine particles are excellent in low-pressure deformability without variation in compression deformation behavior, and thus exhibit excellent performance as anisotropic conductive materials. .

  Examples of the material constituting the polymer particles include polyolefins such as polyethylene, polypropylene, polyvinyl chloride, polytetrafluoroethylene, polyisobutylene, and polybutadiene; vinyl heavy resins such as styrene resins, acrylic resins, and styrene-acrylic resins. Polyesters such as polyethylene terephthalate and polyethylene naphthalate; polycarbonate; polyamide; polyimide; phenol formaldehyde resin; melamine formaldehyde resin; melamine benzoguanamine formaldehyde resin; urea formaldehyde resin; Organic-inorganic composite materials obtained by compounding; The material which comprises these base particle | grains may be used independently, and 2 or more types may be used together.

  In the polymer particles of the present invention, the content of the crosslinkable monomer is preferably 5% by mass or more, more preferably 10% by mass or more, in all monomer components for forming the polymer particles. More preferably, it is 15 mass% or more, 80 mass% or less is preferable, More preferably, it is 70 mass% or less, More preferably, it is 60 mass% or less. If the content of the crosslinkable monomer is 5% by mass or more, the solvent resistance of the polymer particles can be further improved, and if it is 80% by mass or less, the polymer particles are not too hard and low. It becomes easier to deform with pressure.

Examples of the crosslinkable monomer include a crosslinkable vinyl monomer and a crosslinkable silane monomer.
The crosslinkable vinyl monomer is a crosslinkable monomer having two or more vinyl groups in one molecule. Specifically, allyl (meth) acrylates such as allyl (meth) acrylate; 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, alkanediol di (meth) acrylate such as 1,3-butylene di (meth) acrylate; diethylene glycol di (meth) acrylate , Triethylene glycol di (meth) acrylate, decaethylene glycol di (meth) acrylate, pentadecaethylene glycol di (meth) acrylate, pentacontactor ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate Di (meth) acrylates such as relate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, etc .; trimethylolpropane tri (meth) acrylate, pentaerythritol tetra Trifunctional or higher polyfunctional (meth) acrylates such as (meth) acrylate and dipentaerythritol hexa (meth) acrylate; crosslinkable styrenic monomers such as divinylbenzene, divinylnaphthalene and derivatives thereof; N, Cross-linking agents such as N-divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfonic acid; polybutadiene, polyisoprene unsaturated polyester, and the like. These crosslinkable monomers may be used alone or in combination of two or more. Among these, a crosslinkable monomer having two or more vinyl groups in one molecule is preferable, and a crosslinkable monomer having two or more (meth) acryloyl groups in one molecule is more preferable.

  The crosslinkable silane monomer has a silicon atom and can form a crosslinked structure. The cross-linked structure formed by the cross-linkable silane monomer includes one that cross-links an organic polymer skeleton (for example, a vinyl polymer skeleton) and an organic polymer skeleton (first form); One that crosslinks a polysiloxane skeleton (second form); one that crosslinks an organic polymer skeleton and a polysiloxane skeleton (third form).

  Examples of those that can form the first form include dimethyldivinylsilane, methyltrivinylsilane, and tetravinylsilane. Examples of what can form the second form include tetrafunctional silane monomers such as tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, and tetrabutoxysilane; methyltrimethoxysilane, methyltriethoxysilane And trifunctional silane monomers such as ethyltrimethoxysilane and ethyltriethoxysilane.

  Examples of those that can form the third form include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, Such as 3-methacryloxyethoxypropyltrimethoxysilane; those having a vinyl group such as vinyltrimethoxysilane, vinyltriethoxysilane, p-styryltrimethoxysilane; and the like.

  Among these, it is preferable to contain a crosslinkable silane monomer as the crosslinkable monomer, and more preferably, a crosslinkable silane monomer that can form the crosslinked structure of the second form (preferably A tetrafunctional silane monomer, more preferably tetraethoxysilane, a crosslinkable silane monomer capable of forming the crosslinked structure of the third form (preferably having a (meth) acryloyl group, more preferably Preferably contains 3-methacryloxypropyltrimethoxysilane).

  Examples of the non-crosslinkable monomer that can be used as a monomer component constituting the polymer particles include (meth) acrylic acid or a salt thereof; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) Acrylate, t-butyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2- Alkyl (preferably alkyl having 1 to 4 carbon atoms) (meth) acrylates such as ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate; cyclo Propyl (meth) acryl , Cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, cyclooctyl (meth) acrylate, cycloundecyl (meth) acrylate, cyclododecyl (meth) acrylate, isobornyl (meth) ) Acrylate, cycloalkyl (preferably alkyl having 3 to 5 carbon atoms) (meth) acrylates such as 4-t-butylcyclohexyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) Hydroxyalkyl (preferably C2-C3 alkyl) (meth) acrylates such as acrylate and 2-hydroxybutyl (meth) acrylate; phenyl (meth) acrylate, benzyl (meth) acrylate, tolyl (meth) Aromatic ring-containing (meth) acrylates such as acrylate and phenethyl (meth) acrylate; (meth) acrylic monofunctional monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene Alkyl styrenes such as p-t-butylstyrene; alkoxystyrenes such as p-methoxystyrene; aromatic ring-containing styrenes such as p-phenylstyrene; o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc. And those having one vinyl group in one molecule such as styrene monofunctional monomers such as hydroxy group-containing styrenes such as p-hydroxystyrene;

  Further, as the non-crosslinkable monomer, for example, a bifunctional silane monomer such as dialkylsilane such as dimethyldimethoxysilane or dimethyldiethoxysilane; 1 such as trialkylsilane such as trimethylmethoxysilane or trimethylethoxysilane; Functional silane monomers can also be used. These non-crosslinkable monomers may be used alone or in combination of two or more. Among these, styrene monofunctional monomers are preferable, and styrene is more preferable.

  Examples of the polymer fine particles of the present invention include the organic polymer fine particles and organic-inorganic composite particles described above. Among these, organic-inorganic composite particles are preferable. Among the organic / inorganic composite particles, organic / inorganic composite particles including a vinyl polymer skeleton and a polysiloxane skeleton are preferable. In particular, after a crosslinkable silane monomer having a polymerizable group such as a vinyl group is hydrolyzed and subjected to a condensation reaction to prepare a polymerizable polysiloxane particle, the polymerizable polysiloxane particle is made of a material other than a silane monomer. Those obtained by absorbing and polymerizing monomer components are preferred.

1-1. Production method of polymer particles Examples of the production method of the polymer particles of the present invention include, after adding alkoxysilane to a suspension of polysiloxane particles obtained by hydrolysis condensation reaction of alkoxysilane, And a method of polymerizing in the presence of a predetermined amount of a polymerization inhibitor.

  Hereinafter, as an example of the method for producing polymer particles of the present invention, after preparing polymerizable polysiloxane particles, after further adding a silane monomer, the monomer components other than the silane monomer are absorbed. A sol-gel seed polymerization method for polymerization will be described. The sol-gel seed polymerization method is an embodiment of seed polymerization, and particularly refers to a case where seed particles are synthesized by the sol-gel method. For example, the case where polysiloxane obtained by the hydrolysis condensation reaction of alkoxysilane is used as seed particles can be used.

  The sol-gel seed polymerization method preferably includes a hydrolysis-condensation step and a polymerization step, and more preferably includes an absorption step for absorbing the polymerizable monomer after the hydrolysis and condensation step and before the polymerization step. By including an absorption step, the content of the vinyl polymer skeleton component in the polymer particles can be easily adjusted.

  The hydrolysis-condensation step is a step in which a silane monomer (including a crosslinkable silane monomer having a polymerizable group) is hydrolyzed in a solvent containing water to undergo a condensation polymerization. . By the hydrolysis condensation step, particles having a polymerizable group and a polysiloxane skeleton (polymerizable polysiloxane particles) can be obtained. Hydrolysis and polycondensation can employ any method such as batch, split, and continuous. For hydrolysis and condensation polymerization, basic catalysts such as ammonia, urea, ethanolamine, tetramethylammonium hydroxide, hexadecyltrimethylammonium bromide, alkali metal hydroxide, alkaline earth metal hydroxide, etc. are used as catalysts. It can be preferably used.

  In the solvent containing water, an organic solvent can be contained in addition to water and the catalyst. Examples of the organic solvent include alcohols such as methanol, ethanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, pentanol, ethylene glycol, propylene glycol, 1,4-butanediol; acetone, Examples thereof include ketones such as methyl ethyl ketone; esters such as ethyl acetate; (cyclo) paraffins such as isooctane and cyclohexane; aromatic hydrocarbons such as benzene and toluene. These may be used alone or in combination of two or more.

  In the hydrolysis-condensation step, anionic, cationic and nonionic surfactants and polymer dispersants such as polyvinyl alcohol and polyvinylpyrrolidone can be used in combination. These may be used alone or in combination of two or more.

  Hydrolytic condensation is performed by mixing a silane monomer as a raw material and a solvent containing a catalyst, water, and an organic solvent, and then at a temperature of 0 ° C. to 100 ° C., preferably 0 ° C. to 70 ° C., for 30 minutes or more. It can carry out by stirring for 100 hours or less. Thereby, polysiloxane particles are obtained.

  Subsequently, after carrying out a hydrolytic condensation reaction to a desired degree to produce polysiloxane particles, this is used as seed particles, and a silane monomer is further added to the reaction system. The added silane monomer is considered to be absorbed into the polysiloxane particles or taken into the polysiloxane particles by reacting with the silanol groups on the surface of the polysiloxane particles. The silane monomer is preferably absorbed by the polysiloxane particles because the monomer component is easily absorbed in the next stage. Here, as the silane monomer to be further added, it is necessary to use at least one that crosslinks the polysiloxane skeleton and the polysiloxane skeleton. Examples of such silane monomers include the above-described trifunctional silane monomers and tetrafunctional silane monomers, which may be used alone or in combination of two or more. Also good. Among these, a tetrafunctional silane monomer (for example, tetraethoxysilane) having a higher degree of crosslinking is preferable. The silane monomer used here has a molecular weight of preferably 500 or less, more preferably 400 or less, and still more preferably 300 or less, from the viewpoint of penetrability into the polysiloxane particles. The lower limit of the molecular weight is not particularly limited, but is usually 150.

  Further, the amount of the silane monomer to be added is preferably 3 parts by mass or more (more preferably 5 parts by mass or more, more preferably 10 parts by mass or more) with respect to 100 parts by mass of the seed particles, and 50 parts by mass or less ( More preferably, it is 40 parts by mass or more, and more preferably 30 parts by mass or more. If the amount of the silane monomer used is within the above range, a dent having a desired size can be formed.

  After further adding a silane monomer to the reaction system, hydrolysis condensation is performed again. Hydrolytic condensation can be performed by adding a further silane monomer and then stirring at a temperature of 0 ° C. to 100 ° C., preferably 0 ° C. to 70 ° C. for 5 minutes to 300 minutes.

  The absorption process is not particularly limited as long as it proceeds in the presence of the monomer component other than the silane monomer in the presence of the polysiloxane particles. Therefore, the monomer component may be added to the solvent in which the polysiloxane particles are dispersed, or the polysiloxane particles may be added to the solvent containing the monomer component. Especially, it is preferable to add a monomer component in the solvent which disperse | distributed polysiloxane particle | grains previously like the former. In particular, the method of adding the monomer component to the reaction liquid without taking out the polysiloxane particles obtained in the hydrolysis and condensation process from the reaction liquid (polysiloxane particle dispersion) does not complicate the process. It is preferable because of its excellent properties.

  In the absorption step, the timing of adding the monomer component is not particularly limited, and 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, either the monomer component alone or the monomer component solution may be added, but the monomer component is previously added to water or an aqueous medium with an emulsifier. It is preferable to mix the emulsified and emulsified liquid into the polysiloxane particles because the polysiloxane particles can be more efficiently absorbed.

The emulsifier is not particularly limited. For example, an anionic surfactant, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxysorbitan fatty acid ester, polyoxyethylene alkyl Nonionic surfactants such as amines, glycerin fatty acid esters and oxyethylene-oxypropylene block polymers stabilize the dispersion state of the polymerizable polysiloxane particles after absorbing the polymerizable polysiloxane particles and monomer components. This is also preferable. These emulsifiers may be used alone or in combination of two or more.
Moreover, when emulsifying and dispersing the monomer component with an emulsifier, it is preferable to use water or a water-soluble organic solvent that is 0.3 to 10 times the mass of the monomer component. Examples of the water-soluble organic solvent include alcohols such as methanol, ethanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, pentanol, ethylene glycol, propylene glycol, 1,4-butanediol; acetone And ketones such as methyl ethyl ketone; esters such as ethyl acetate;

  The absorption step is preferably performed in the temperature range of 0 ° C. to 60 ° C. with stirring for 5 minutes to 720 minutes. These conditions may be set as appropriate depending on the type of polysiloxane particles and monomers to be used, and these conditions may be used alone or in combination of two or more.

  In the absorption process, for determining whether the monomer component is absorbed by the polysiloxane particles, for example, before adding the monomer component and after completion of the absorption step, observe the particles with a microscope to absorb the monomer component. Thus, it can be easily determined by confirming that the particle size is increased.

  The polymerization step is a step of obtaining particles having a vinyl polymer skeleton by polymerizing a monomer component. Specifically, the absorbed monomer component or the absorbed monomer component and the polymerizable group of the polysiloxane skeleton are polymerized to form an organic polymer skeleton (for example, a vinyl (system) polymer skeleton). Is a step of forming.

  The polymerization method is not particularly limited. For example, any of a method using a radical polymerization initiator, a method of irradiating ultraviolet rays or radiation, a method of applying heat, and the like can be adopted. Although it does not specifically limit as said radical polymerization initiator, For example, a peroxide type initiator, an azo type initiator, etc. can be used. These radical polymerization initiators may be used alone or in combination of two or more.

  The reaction temperature at the time of performing radical polymerization is preferably 40 ° C or higher, more preferably 50 ° C or higher, preferably 100 ° C or lower, more preferably 80 ° C or lower. If the reaction temperature is too low, the degree of polymerization does not increase sufficiently and the mechanical properties of the composite particles tend to be insufficient. On the other hand, if the reaction temperature is too high, aggregation between particles occurs during the polymerization. It tends to happen easily. The reaction time for performing radical polymerization may be appropriately changed according to the type of polymerization initiator to be used, but is usually preferably 5 minutes or more, more preferably 10 minutes or more, and preferably 600 minutes or less. More preferably, it is 300 minutes or less. When the reaction time is too short, the degree of polymerization may not be sufficiently increased, and when the reaction time is too long, aggregation tends to occur between particles.

  Here, when carrying out radical polymerization, a predetermined amount of a polymerization inhibitor is allowed to coexist, whereby polymer particles having a recess having a predetermined shape are obtained. The coexistence effect of the polymerization inhibitor is not clear, but the formation rate of the dent is also related to the polymerization rate, and the presence of a predetermined amount of polymerization inhibitor controls (suppresses) the radical polymerization rate. It is considered that polymer particles having dents are obtained.

  The amount of the polymerization inhibitor to be coexisted is the polymer forming component constituting the polymer particle, that is, the total amount of the monomer component other than the polysiloxane particle, the silane monomer component, and the silane monomer is 100 mass. It is preferable that it is 0.05 mass part or more with respect to a part. If it is less than 0.05 parts by mass, there is a possibility that no dent will be formed. The amount of the polymerization inhibitor used is more preferably 0.1 parts by mass or more, further preferably 0.15 parts by mass or more, and particularly preferably 0.2 parts by mass or more. The upper limit of the amount of the polymerization inhibitor used is not particularly limited, but is preferably 1% by mass or less with respect to 100 parts by mass of the polymer forming component constituting the polymer particles. If the amount of the polymerization inhibitor used exceeds 1 part by mass, the polymerization does not proceed under the temperature conditions (usually 100 ° C. or lower) possible in an aqueous medium, and polymer particles having the strength required for handling may not be obtained. is there. The amount of the polymerization inhibitor used includes a polymerization inhibitor that has been added in advance to the monomer used to produce the polymer particles.

  The polymerization inhibitor is not particularly limited as long as it inhibits radical polymerization, and a conventionally known polymerization inhibitor can be used. Examples of the polymerization inhibitor include 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-benzoyloxypiperidine-N-oxyl, 4-acetylamino-2,2,6,6-tetramethylpiperidine-N-oxyl, bis (2,2,6,6-tetramethyl-N-oxylpiperidyl) succinate, 1-oxyl-2,2,6 N-oxyl compound systems such as 1,6-tetramethyl-4- (2,3-dihydroxypropoxy) piperidine, 1-oxyl-2,2,6,6-tetramethyl-4-glycidyloxypiperidine; 4-tertiary And alkylphenols such as butylcatechol, 4-octylphenol, 4-tertiarybutylphenol, and the like. Among these, N-oxyl compound-based (from the point that polymer particles having a dent of a predetermined shape of the present invention can be obtained in an aqueous medium, and polymer particles having a relatively uniform dent shape and the like can be obtained. 4-Hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl) is preferred.

  The timing for adding the polymerization inhibitor is not particularly limited. The step of producing polysiloxane particles; the step of adding a silane monomer component; the step of adding and absorbing a monomer component other than the silane monomer; the addition of a monomer component other than the silane monomer , A stage after absorption, and may be added at any timing. Among these, the polymerization inhibitor is preferably added at a stage after adding and absorbing a monomer component other than the silane monomer. The method for adding the polymerization inhibitor is not particularly limited. You may add in the state dissolved in the monomer component for manufacturing the polymer particle of this invention, and you may add a polymerization inhibitor independently.

  According to the above-described production method, polymer particles having the predetermined shape of the recess are obtained. Since the polymer particles of the present invention have unique mechanical properties, they are useful as base particles for conductive fine particles. In addition, the polymer particles of the present invention have a crosslinked structure, are excellent in solvent resistance, and have excellent light scattering properties due to the dents, so that they are useful as optical member materials.

2. Conductive fine particles As an example of the use of polymer particles, conductive fine particles will be described.
The conductive fine particles of the present invention have a conductive metal layer that covers the surface of the polymer particles. Therefore, the conductive fine particles of the present invention have the characteristics of the polymer particles described above. The metal constituting the conductive metal layer is not particularly limited. For example, gold, silver, copper, platinum, iron, lead, aluminum, chromium, palladium, nickel, rhodium, ruthenium, antimony, bismuth, germanium, tin, Examples thereof include metals such as cobalt, indium, nickel-phosphorus, and nickel-boron, metal compounds, and alloys thereof. Among these, gold, nickel, palladium, and silver are preferable because of excellent conductivity. Moreover, nickel, nickel alloy (Ni-Au, Ni-Pd, Ni-Pd-Au, Ni-Ag) etc. are preferable at an inexpensive point. The conductive metal layer may be a single layer or multiple layers. In the case of multiple layers, for example, a combination of nickel-gold, nickel-palladium, nickel-palladium-gold, nickel-silver, etc. Is preferred.

  The thickness of the conductive metal layer is preferably 0.01 μm or more, more preferably 0.03 μm, preferably 0.20 μm or less, and more preferably 0.15 μm or less. When the thickness of the conductive metal layer is within the above range, when the conductive fine particles are used as an anisotropic conductive material, stable electrical connection can be maintained and the mechanical characteristics of the polymer particles having dents can be maintained. Can be fully utilized.

  The conductive fine particles of the present invention may further have an insulating resin layer on the surface of the conductive metal layer. The insulating resin layer is not particularly limited as long as the insulating property between the particles of the conductive fine particles can be ensured, and the insulating resin layer can be easily collapsed or peeled off by a constant pressure and / or heating. For example, polyolefins such as polyethylene; (meth) acrylate polymers and copolymers such as polymethyl (meth) acrylate; thermoplastic resins such as polystyrene; and particularly cross-linked products thereof; heat such as epoxy resins, phenol resins, and melamine resins Curable resins; water-soluble resins such as polyvinyl alcohol and mixtures thereof.

  However, when the insulating resin layer is too hard as compared with the polymer particles serving as the base material, the polymer particles themselves may be destroyed before the insulating resin layer is destroyed. Therefore, it is preferable to use uncrosslinked or relatively low degree of crosslinking resin for the insulating resin layer.

  The insulating resin layer may be a single layer or a plurality of layers. For example, single or multiple film-like layers; layers with insulating particles, spheres, lumps, scales and other shapes attached to the surface of the conductive fine particles; and the surface of the conductive fine particles is chemically modified Or a layer formed by doing so. The thickness of the resin insulating layer is preferably 0.01 μm to 1 μm, more preferably 0.1 μm to 0.5 μm. If the thickness of the resin insulating layer is within the above range, the electrical insulation between the particles becomes good while maintaining the conduction property by the conductive particles well.

2-1. Method for Producing Conductive Fine Particles The conductive fine particles of the present invention can be obtained by forming a conductive metal layer on the surface of the polymer particles. The method for coating the surface of the polymer particles with the conductive metal layer is not particularly limited. For example, a method using electroless plating, displacement plating or the like; a paste obtained by mixing metal fine powder alone or in a binder with a polymer. Methods for coating fine particles; physical vapor deposition methods such as vacuum vapor deposition, ion plating, ion sputtering and the like. Among these, the electroless plating method is preferable because a conductive metal layer can be easily formed without requiring a large-scale apparatus.

  When the conductive fine particles of the present invention have an insulating resin layer, the surface of the conductive metal layer is subjected to insulation treatment with a resin or the like after the electroless plating step. 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 treatment, interfacial polymerization, suspension polymerization, emulsion polymerization of the raw material of the insulating resin layer is performed, 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 an insulating resin is dissolved in an organic solvent and then dried; a spray drying method, by hybridization Any conventionally known method such as a method can be used.

3. Anisotropic Conductive Material The conductive fine particle of the present invention is also suitable as a constituent material of the anisotropic conductive material, and the anisotropic conductive material using the conductive fine particle of the present invention is also preferable implementation of the present invention. This is one aspect. The form of the anisotropic conductive material is not particularly limited as long as the conductive fine particles of the present invention are used. For example, an anisotropic conductive film, an anisotropic conductive paste, an anisotropic conductive adhesive is used. And various forms such as anisotropic conductive ink. That is, electrical connection can be achieved by providing these anisotropic conductive materials between opposing substrates or between electrode terminals. The anisotropic conductive material using the conductive fine particles of the present invention includes a conductive material for a liquid crystal display element (conductive spacer and composition thereof).

  The anisotropic conductive material is produced by dispersing the conductive fine particles of the present invention in an insulating binder resin to obtain a desired form. Of course, the insulating binder resin and the conductive fine particles May be used separately to connect between substrates or between electrode terminals. The binder resin is not particularly limited, and is, for example, a thermoplastic resin such as an acrylic resin, an ethylene-vinyl acetate resin, a styrene-butadiene block copolymer; a monomer or oligomer having a glycidyl group, and a curing agent such as isocyanate. Examples thereof include a curable resin composition that is cured by reaction and a curable resin composition that is cured by light and heat.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples, and may be appropriately modified and implemented within a range that can meet the purpose described above and below. All of which are within the scope of the present invention. In the following, “part” means “part by mass” and “%” means “% by mass” unless otherwise specified.

1. Evaluation method 1-1. Average particle diameter, coefficient of variation of particle diameter Using a precision particle size distribution analyzer (trade name “Coulter Multisizer III”, manufactured by Beckman Coulter, Inc.), the particle diameter of 30000 polymer particles is measured and The average particle diameter and standard deviation at the reference were measured. Further, from the measurement results obtained, the coefficient of variation of the particle diameter of the polymer particles was calculated using the following formula.
Coefficient of variation (%) = 100 × (standard deviation / average particle size)

1-2. Recess Using a scanning electron microscope (SEM, manufactured by Hitachi, Ltd .: “S-3500N”), 20 polymer particles were observed to confirm the presence or absence of a recess and the outer peripheral shape of the recess. Moreover, about the thing with a dent, the major axis (L1) and the minor axis (L2) of the dent were measured, and the average value of 20 particles was obtained.
The depth of the recess is embedded in polymer resin in an epoxy resin, a thin section (thickness 10 nm) is prepared with a microtome, and then cross-sectioned with a field emission scanning electron microscope (FE-SEM, manufactured by Hitachi High-Technologies Corporation). This was measured by observing the transmission image. Specifically, the depth of the longest part of the perpendicular line extending from the straight line connecting the two points serving as the base point of the dent to the bottom of the dent was defined as the dent depth (H).
Moreover, about the particle | grains which have a dent, ratio (L1 / D), ratio (L2 / D), ratio (L2 / L1), and ratio (H / D) were measured and the average value of 20 particle | grains was calculated | required, respectively.

1-3. Mechanical properties Using a micro compression tester (manufactured by Shimadzu Corporation, “MCT-W500”) at room temperature (25 ° C.), one particle dispersed on a sample table (material: SKS flat plate) has a diameter of 50 μm. Using a circular flat plate indenter (material: diamond), a load was applied at a constant load speed (2.2295 mN / sec) toward the center of the particle.

1-4. Solvent resistance test After adding 1.0 part of polymer particles to 10 parts of toluene and stirring for 10 minutes, the mixture was filtered through a membrane filter, and the resulting particles were dried at 120 ° C. for 2 hours to obtain a field emission scanning electron microscope (FE-). The surface of the particles was observed with SEM (manufactured by Hitachi High-Technologies Corporation, magnification 50,000 times). If the particle surface state was the same as before immersion in toluene, it was evaluated as “◯”, and if deformation or cavitation occurred, it was evaluated as “x”.

1-5. Evaluation of Anisotropic Conductive Material 0.1 mg of conductive adhesive paste is sandwiched between two glass substrates on which aluminum electrodes are formed, thermocompression bonded at 180 ° C., and a test piece (anisotropic made of conductive adhesive cured product) A connection structure having a structure in which a conductive sheet is sandwiched between electrodes was obtained. The connection resistance value (Ω) of the obtained test piece was measured by the four probe method.

2. 2. Production of polymer particles 2-1. Production Example 1
In a four-necked flask equipped with a condenser, a thermometer, and a dripping port, 804 parts of ion-exchanged water, 1.2 parts of 25% aqueous ammonia and 336.6 parts of methanol are placed under stirring and 3-methacrylic acid is added from the dripping port. A mixed solution of 50 parts of roxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., “KBM503”) and 59.4 parts of methanol was added to conduct hydrolysis and condensation reaction of 3-methacryloxypropyltrimethoxysilane, An emulsion of polysiloxane particles having methacryloyl groups (polymerizable polysiloxane particles) was prepared. Two hours after the start of the reaction, the obtained emulsion of polysiloxane particles was sampled and the particle size was measured. The number average particle size was 2.20 μm.

  Subsequently, 10.0 parts of tetraethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., “LS-2430”) is added to the emulsion of the primary polysiloxane particles, and the mixture is stirred at 25 ° C. for 30 minutes. The emulsion was adjusted.

  Next, 0.9 part of a 20% aqueous solution of ammonium polyoxyethylene styrenated phenyl ether sulfate (Daiichi Kogyo Seiyaku Co., Ltd .: “Hytenol (registered trademark) NF-08”) as an emulsifier was added to 35.0 ion-exchanged water. 35.0 parts of styrene (containing 30 ppm of 4-tertiarybutylcatechol) as a monomer, 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator (sum) A solution prepared by dissolving 0.9 part of Kojunkaku Kogyo Co., Ltd .: “V-65”) was added and emulsified and dispersed to prepare an emulsion of monomer components.

  The obtained emulsion was added to an emulsion of secondary polysiloxane particles and further stirred. One hour after the addition of the emulsified liquid, the mixed liquid was sampled and observed with a microscope. As a result, it was confirmed that the secondary polysiloxane particles absorbed the monomer and enlarged.

  Finally, 2.1 parts by mass of a 10% by mass aqueous solution of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (“Polystop 7010” manufactured by Hakutosha) and 27.9 masses of ion-exchanged water The reaction solution was heated to 65 ° C. under a nitrogen atmosphere and held at 65 ° C. for 2 hours to perform radical polymerization of the monomer composition. The reaction solution after radical polymerization was subjected to solid-liquid separation, and the resulting cake was washed with ion-exchanged water and methanol, and then dried at 120 ° C. for 2 hours to obtain polymer particles No. 1 was obtained.

2-2. Production Example 2
In Production Example 1, the same procedure as in Production Example 1 was conducted except that the tetraethoxysilane was changed to 10 parts of tetraethoxysilane tetramer (manufactured by Tama Chemical Co., Ltd., silicate 40). 2 was obtained.

2-3. Production Example 3
In Production Example 1, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl 10% by mass solution (“Polystop 7010” manufactured by Hakutosha) was not added, and Production Example 1 In the same manner, polymer particle no. 3 was obtained.

2-4. Production Example 4
In Production Example 1, polymer particles No. 1 were produced in the same manner as in Production Example 1 except that tetraethoxysilane was not added. 4 was obtained.

3. Production of Conductive Particles After polymer particles were etched with sodium hydroxide, sensitizing with a tin dichloride solution was performed. Further, activation with a palladium dichloride solution was performed to form palladium nuclei. Next, the polymer particles with palladium nuclei formed are immersed in an electroless nickel plating bath to form a nickel plating layer until the film thickness becomes 0.1 μm, and then gold substitution plating is performed to obtain a 0.02 μm gold layer. Formed. Then, after washing with ion exchange water, alcohol substitution was performed and vacuum drying was performed to obtain conductive fine particles.

4). Production of Anisotropic Conductive Material 2 g of the conductive fine particles obtained above were mixed and dispersed in 100 g of an epoxy resin (manufactured by Mitsui Chemicals: “Struct Bond (registered trademark) XN-5A”) to prepare a conductive adhesive paste.

  The evaluation results for the polymer particles obtained in Production Examples 1 to 4 are shown in Table 1, and the polymer particles No. 1 obtained in Production Example 1 were obtained. The SEM image of No. 1 is shown in FIG. An example of the SEM image used for the measurement of the dent of No. 1 is shown in FIG. The FE-SEM image of the cross section of 1 is shown in FIG. The compression deformation behavior of the polymer particles obtained in Production Example 1 and the polymer particles obtained in Production Example 2 is shown in FIG. Moreover, evaluation about the electroconductive fine particles which used the polymer particle obtained by manufacture example 1-4 as a base material particle was combined with Table 1, and was shown.

  When the polymer particles obtained in Production Examples 1 to 4 were observed, the polymer particles No. 1 had a dent of a predetermined shape. 2 to 4 did not have a predetermined shape of dent. In Production Example 2, since the tetramer of ethoxysilane was used, it was not possible to sufficiently penetrate the primary polysiloxane particles, so that it was considered that dents having a predetermined shape were not formed on the particle surfaces. In addition, in Production Example 3, a polymerization inhibitor was not added, and monomer components other than the silane monomer rapidly polymerized, and the shape in the monomer absorption process was maintained. It is considered that no dent was formed. In addition, polymer particle No. The number of particles having a predetermined shape in 1 was 71% or more of all particles.

  In addition, as shown in FIG. It can be seen that No. 1 is deformed with a low compressive load (test force) because it has dents of a predetermined shape on the particle surface. On the other hand, the polymer particle No. obtained in Production Example 2 was obtained. Since No. 2 does not have a dent of a predetermined shape on the particle surface, it can be seen that a high compressive load is required to deform the particle. These polymer particles No. In the conductive fine particles using 1-4 as the base particles, the surface of the base material particles has a dent compared to the case where the surface of the base material particles does not have a dent (Production Examples 2 to 4) (Production Example 1). It can be seen that the connection resistance value is greatly reduced.

  The polymer particles of the present invention can be used for conductive fine particles and light diffusion applications. The conductive fine particles of the present invention are suitably used for anisotropic conductive materials such as anisotropic conductive films, anisotropic conductive pastes, anisotropic conductive adhesives, anisotropic conductive inks, and the like.

1: polymer particle, 2: dent, D: particle diameter, L1: major axis, L2: minor axis, H: depth

Claims (7)

Conductive fine particles having a conductive metal layer on the surface of the polymer particles,
The polymer particles are spherical in having a contour recess is satisfied formed one below (b) ~ (d), conductivity, characterized in that its volume is equal to or more than half of the original sphere fine Particles .
( B) The ratio (L1 / D) of the major axis (L1) of the dent to the particle diameter (D) is 0.3 or more and less than 1.0.
(C) The ratio (L2 / D) of the minor axis (L2) of the dent to the particle diameter (D) is 0.05 or more and less than 1.0.
(D) The ratio (L2 / L1) of the major axis (L1) to the minor axis (L2) is less than 1.0. Total monomer component, the conductive fine particles according to claim 1, wherein the content of the crosslinkable monomer is 5% by mass or more to form a polymer particle. Conductive fine particle according to claim 1 or 2 number average particle size of the polymer particles is 0.5 to 50 .mu.m. Any conductive fine particles according to one of claims 1 to 3 variation coefficient of the particle size of the polymer particles is 40% or less. The depth of the depression in the polymer particles (H), conductive fine particles according to any one of claims 1 to 4 ratio of the particle diameter (D) (H / D) is 0.5 or less . The area of the recess in the polymer particle surface, conductive fine particles according to any one of claims 1 to 5 is 25% or less of the total surface area when it is assumed that the polymer particles do not have a recess . Anisotropic conductive material characterized by containing a conductive particle according to any one of claims 1 to 6.