JP2000198880A - Method for coating microparticle, coated microparticle, anisotropically electroconductive adhesive and electroconductive connective structural body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for coating microparticles without the need of any large-scale apparatus, highly effective because of producing no uncoated microparticles, less prone to produce multiple particles, capable of easily controlling coating layer thickness, capable of coating a large quantity of microparticles, capable of coating ill-wettable microparticles and high-specific gravity microparticles as well, and enabling coating layer thickness to be even among particles. SOLUTION: This method for coating microparticles comprises preparing a mixture of microparticles, a coating substance and a dispersion medium, and forming a coating layer of each of the microparticles through removing the dispersion medium while gradually volatilizing it; wherein it is characteristic that the microparticles are each 0.2-3,000 μm in average size, <5 in aspect ratio and <=40% in CV value, and the coating layer thickness is <=1/4 time the above average size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating fine particles, coated fine particles coated by using the method for coating fine particles, coated fine particles used for connection between fine electrodes, and anisotropic conductive adhesive. The present invention relates to an agent and a conductive connection structure.

[0002]

2. Description of the Related Art Conventionally, methods for coating fine particles include chemical methods such as interfacial polymerization, suspension polymerization in the presence of fine particles, and emulsion polymerization; spray drying, hybridization, electrostatic adhesion, spraying, and dipping. And physical and mechanical methods such as vacuum deposition. However, these coating methods require large-scale equipment, are inefficient because a large amount of uncoated particles are generated, multiple particles are generated, the coating thickness varies greatly between particles, and the film thickness is large. There are problems such as difficulty in control, unsuitability for mass production, and inability to coat particles having poor wettability or heavy particles.

Further, in electronic products such as liquid crystal displays, personal computers, and portable communication devices, small electrical components such as semiconductor elements are electrically connected to substrates, and the substrates are electrically connected to each other. What is called a conductive conductive material is used, and among the anisotropic conductive materials, an anisotropic conductive adhesive in which conductive fine particles are mixed with a binder resin is widely used.

[0004] As the conductive fine particles used in the anisotropic conductive adhesive, those obtained by plating metal particles on the surfaces of organic base particles or inorganic base particles or metal particles have been used. Such conductive fine particles are described, for example, in JP-B-6-9.
No. 6771, JP-A-4-36902, JP-A-4-269720, JP-A-3-257710 and the like.

An anisotropic conductive adhesive prepared by mixing such conductive fine particles with a binder resin to form a film or paste is disclosed in, for example, JP-A-63-23188.
9, JP-A-4-259766, JP-A-3-259766
No. 291807 and Japanese Patent Application Laid-Open No. 5-75250.

In recent years, as electronic devices and electronic components have become smaller, wirings on substrates and the like have become finer.
In order to cope with this, conductive fine particles have been made finer and the particle diameter accuracy has been improved. However, it is technically difficult to reduce the particle size beyond a certain level while maintaining high particle size accuracy. Occurs. For this reason, there is a problem that a bridge is generated by the conductive fine particles and a leak easily occurs between adjacent electrodes.

[0007]

SUMMARY OF THE INVENTION In view of the above, the present invention does not require a large-scale apparatus, does not generate uncoated fine particles, has high efficiency, is less likely to generate multiple particles, and has a simple coating layer thickness. Can be coated in large quantities, can also coat fine particles with low wettability and high specific gravity, and can coat the fine particles with a uniform thickness between the particles, and It is an object of the present invention to provide coated fine particles coated using the method for coating fine particles. Further, the present invention provides coated fine particles, anisotropic conductive adhesive, and a conductive connection structure which have a low connection resistance, a large electric capacity at the time of connection, a stable connection, and do not cause a leak phenomenon. The purpose is to:

[0008]

According to the present invention, there is provided a method of forming a coating layer on fine particles by mixing a fine particle, a coating substance and a dispersion medium to prepare a mixture, and then removing the dispersion medium while volatilizing it gradually. Wherein the fine particles have an average particle size of 0.2 to 3000 μm, an aspect ratio of less than 5, and a CV value of 40% or less, and the thickness of the coating layer is determined by the average particle size of the fine particles. Is a method of coating fine particles, wherein the method is not more than 1/4. Hereinafter, the present invention will be described in detail.

In the method for coating fine particles of the present invention, first, a mixture is prepared by mixing fine particles, a coating substance, and a dispersion medium.

The fine particles have an average particle size of 0.2 to 30.
00 μm. When the average particle diameter is less than 0.2 μm, the contact area between the particles becomes large, so that it may be difficult to form a single particle. When the average particle diameter exceeds 3000 μm, the coating layer may become uneven due to the influence of gravity. Therefore, it is limited to the above range. It is preferably 0.5 to 100 μm, more preferably 1 to 20 μm, and still more preferably 3 to 10 μm.
μm. The average particle diameter is a value obtained by observing 300 arbitrary fine particles with an electron microscope.

The fine particles have an aspect ratio of less than 5. If the aspect ratio is 5 or more, the particle diameters become uneven, so that the contact area between the particles becomes large, and it becomes difficult to form a single particle. It is preferably less than 2, more preferably less than 1.4, even more preferably less than 1.1, particularly preferably less than 1.05. The aspect ratio is a value obtained by dividing the average major axis of fine particles obtained by observing 300 arbitrary particles with an electron microscope by the average minor axis.

The fine particles have a CV value of 40% or less. When the CV value exceeds 40%, the particle diameters become uneven, so that the contact area between the particles increases, and it becomes difficult to form a single particle, so that the CV value is limited to the above range. Preferably 30%
Or less, more preferably 20% or less, still more preferably 10% or less, and particularly preferably 5% or less.

The CV value is defined by the following formula (1): CV value (%) = (σ / Dn) × 100 (1) (where σ represents the standard deviation of the particle diameter) , Dn represent the number average particle diameter). The standard deviation and the number average particle diameter are values obtained by observing 300 fine particles with an electron microscope.

The material of the fine particles is not particularly limited, and examples thereof include organic substances, resins, inorganic substances, compounds and mixtures thereof, and metals. Further, the fine particles may be conductive fine particles having a conductive layer formed on at least the surface.

The coating material is not particularly limited, but is preferably a resin-based material because the coating layer is less likely to be cracked or peeled off, and is preferably a resin soluble in a dispersion medium. Are more preferred. Examples of the resin include polyolefins such as polyethylene, ethylene / vinyl acetate copolymer, ethylene / acrylate copolymer; and polymethyl (meth) acrylate, polyethyl (meth) acrylate, and polybutyl (meth) acrylate. (Meth) acrylate polymers or copolymers; block polymers such as polystyrene, styrene / acrylate copolymers, SB-type styrene / butadiene block copolymers, SBS-type styrene / butadiene block copolymers, and water additives thereof A thermoplastic resin such as a vinyl polymer or a copolymer, an epoxy resin,
Examples include thermosetting resins such as phenolic resins and melamine resins, and mixtures thereof. When the coating layer requires resin strength, the coating layer may be formed using a resin soluble in a dispersion medium and then made insoluble by a method such as crosslinking. The components of the coating substance other than the resin include, for example, organic substances, inorganic substances, compounds and mixtures thereof, and metals.

The dispersion medium is not particularly limited as long as it is liquid at the time of preparing the mixture, and examples thereof include ordinary organic solvents, water, and inorganic solvents described in Solvent Handbook (Kodansha) and the like. And compounds and the like. The dispersion medium preferably has a boiling point of 60 to 200 ° C. at a pressure at which the dispersion medium is volatilized, in that the dispersion medium is removed while being gradually volatilized by a method described later. If the boiling point is less than 60 ° C., volatilization occurs rapidly, so that the coating substance is densely accumulated, and the fine particles are also densely agglomerated and may not be formed into single particles or the coating layer may be foamed. If it exceeds, it takes too much time to evaporate, and the productivity may be remarkably reduced or the coating layer may be deteriorated, so that the above range is preferable. The temperature is more preferably 90 to 150 ° C.

In the method of coating fine particles according to the present invention, a coating layer is formed on the fine particles by preparing a mixture having the above-described structure and then removing the dispersion medium while gradually volatilizing. The method of removing the dispersion medium while gradually volatilizing it is not particularly limited. For example, a method of volatilizing the dispersion medium at a temperature lower than the boiling point of the dispersion medium by 60 ° C. or more, 300
mmHg or less, ie, 300 mmH above atmospheric pressure
and a method of volatilizing under a condition that the pressure is not lowered not less than g.

In the above method for coating fine particles, the reason why the dispersion medium is removed while being volatilized gradually is that it is preferable to form the coating layer while generating voids between the fine particles. A suitable coating layer can be formed. In order to form a more uniform coating layer, it is preferable that at least a large part of the dispersion medium is removed by volatilization, and part of the coating material, or the interface between the fine particles and the coating material be destroyed by an external force. .

As a method of generating a void, for example,
A method of gradually evaporating the dispersion medium of the above mixture to form a thin film, a thin line, a fine lump, or the like, may be used. Among these, a method of forming a fine lump while gradually volatilizing the dispersion medium is preferable because it is easy to obtain voids at appropriate intervals.

As a method for obtaining voids at appropriate intervals, for example, when the dispersion medium is removed while being volatilized gradually, at least half or more of the fine particles whose distance between the fine particles is smaller than the average particle diameter of the fine particles are present. Method and the like.

Since the surface of the fine particles usually has irregularities, when the dispersion medium is gradually volatilized and removed, when the viscosity of the dispersion medium is high, when the surface tension of the dispersion medium is high, the coating material and If the wettability with fine particles is poor,
Air, moisture and the like may accumulate in concaves and convexes on the surface of the fine particles, and the adhesiveness between the coating substance and the fine particles may decrease.

In order to prevent a decrease in the adhesiveness between the coating substance and the fine particles, before coating the fine particles, the fine particles are preliminarily depressurized to remove air, moisture and the like existing on the surface irregularities. Further, it is preferable to return the pressure to atmospheric pressure after coating the fine particles in a reduced pressure state. The coated fine particles that have been returned to the atmospheric pressure after the pressure reduction have the coating layer and the fine particles more firmly adhere to each other due to the atmospheric pressure.

The degree of the pressure reduction is 500 mm above the atmospheric pressure.
The pressure is preferably reduced to not less than Hg, more preferably 60
Reduced pressure of 0 mmHg or more, more preferably 700 mmHg
This is the reduced pressure described above.

It is preferable that heating is performed during the pressure reduction before the coating. This is because the heating removes moisture and air from the surface of the fine particles more quickly and completely. The temperature during heating is preferably from 50 to 150 ° C, more preferably from 80 to 100 ° C.

The thickness of the coating layer formed by the method for coating fine particles of the present invention is not more than １ ／ of the average particle diameter of the fine particles. If the thickness of the coating layer is more than 1/4, the gap between the fine particles is completely filled with the coating substance. May be increased, or a lump of only the coating substance may be formed. For this reason, when forming a coating layer thicker than the above range, it is preferable to repeat the above-described step of forming the coating layer a plurality of times. The thickness of the coating layer is 1/1 of the average particle diameter of the fine particles.
It is preferably 0 or less. In addition, when the strength is too strong, when the particles are formed into single particles, the coating layer may be peeled off and bare fine particles may be formed. As in the case of producing a conductive connection structure, when it is necessary to partially remove the coating layer, if the coating strength is too strong, it may be difficult to remove the coating layer. 5 / (Molecular weight of resin forming coating layer) 1/2 of average particle diameter of fine particles
It is more preferable that: In the present specification, the molecular weight of the resin, when the resin is a cross-linked resin,
Handle as a molecular weight of 1,000,000.

The method of coating fine particles of the present invention is a fine particle having a specific gravity of 1.5 or more, which cannot form a coating layer due to sedimentation in a dispersion medium or the like by a conventional coating method such as a chemical method. The coating layer can be suitably formed. Furthermore, even if the specific gravity of the fine particles is 3 or more, or 6 or more, the coating layer can be suitably formed.

The method of coating fine particles of the present invention does not require a large-scale apparatus, and is efficient because no uncoated fine particles are generated. Thus, multiple particles are hardly generated, the thickness of the coating layer can be easily controlled, Can easily be coated, and fine particles having poor wettability and high specific gravity can be coated. Therefore, coated fine particles having a uniform coating layer thickness among particles can be produced by the above method.

The average particle diameter of the coated fine particles obtained by coating the fine particles using the above-mentioned fine particle coating method is preferably larger than 0.2 μm and smaller than 4000 μm. It is more preferably 0.5 to 100 μm, further preferably 1 to 20 μm, and particularly preferably 3 to 10 μm.
μm.

The above-mentioned coated fine particles maintain the shape of the fine particles. Therefore, when the particles having an aspect ratio of less than 5 are coated, the obtained particles have an aspect ratio of less than 5, and when the particles have an aspect ratio of less than 2, the obtained particles have an aspect ratio of less than 2. Yes, if you cover fine particles with an aspect ratio of less than 1.4,
The resulting coated fine particles have an aspect ratio of less than 1.4, and if the fine particles having an aspect ratio of less than 1.1 are coated,
The aspect ratio of the obtained coated fine particles is less than 1.1. If the fine particles having an aspect ratio of less than 1.05 are coated, the obtained coated fine particles have an aspect ratio of less than 1.05.

When the fine particles having a CV value of 40% or less are coated, the resulting coated fine particles have a CV value of 40% or less. When the fine particles having a CV value of 30% or less are coated, the obtained coated fine particles have a CV value of 30% or less. The CV value is 30% or less, and the CV value is 2
If the fine particles of 0% or less are coated, the CV value of the obtained coated fine particles is 20% or less, and if the CV value of 10% or less is coated, the CV value of the obtained coated fine particles is 10%.
Or less, if the particles have a CV value of 5% or less,
The CV value of the obtained conductive fine particles is 5% or less. The coated fine particles are also one of the present invention.

When the conductive fine particles having a conductive layer formed on at least the surface are used as fine particles when preparing the coated fine particles, the obtained coated fine particles can be used as coated conductive fine particles.

The conductive fine particles having a conductive layer formed on at least the surface thereof are not particularly limited, and may be those usually used as conductive fine particles. , Carbon particles, metal particles and the like. Among these, polymer materials with a small CV value and a small aspect ratio are used for the core of the particles, and the metal is coated on the particles, from the viewpoint of increasing the contact area with the electrode and increasing the stability. Are preferable, and those plated with gold are more preferable. Further, metal particles are also preferable in that high conductive fine particles can be obtained.

As the coating substance when the above-mentioned coated fine particles are used as the coated conductive fine particles, an insulating resin is preferable, and therefore, an insulating resin is preferable. When the coating layer is formed of an insulating material, a leak occurs between adjacent electrodes when a conductive connection structure is manufactured using the coated conductive fine particles by a process described later when the coating layer is formed of an insulating material. Without doing so, the concentration of the coated conductive fine particles can be increased. Further, in the connection direction of the electrodes, the coating layer flows by heating and pressurization, so that the coating layer is removed at the contact surface with the electrode, and conduction between the electrodes can be achieved.

Furthermore, since the coated conductive fine particles have a coating layer formed using the method for coating fine particles of the present invention, there are no particles or multiple particles having no coating layer formed thereon.
Since the thickness of the coating layer is also uniform, leakage is less likely to occur between adjacent electrodes, and there is little residue of only the coating, so that conduction between the electrodes is not hindered. The coated fine particles obtained by using the coated conductive fine particles, that is, the conductive fine particles having a conductive layer formed on at least the surface as the fine particles are also one of the present invention.

The coated conductive fine particles of the present invention mainly include
It is used when two opposing electrodes are electrically connected. As a method of electrically connecting two electrodes facing each other using the coated conductive fine particles, for example, dispersing the coated conductive fine particles in a binder resin to prepare an anisotropic conductive adhesive, 2 using anisotropic conductive adhesive
A method of bonding and connecting two electrodes, a method of separately using a binder resin and the above-mentioned coated conductive fine particles, and the like are used.

In the present specification, the anisotropic conductive adhesive includes an anisotropic conductive film, an anisotropic conductive paste, an anisotropic conductive ink and the like.

The binder resin constituting the anisotropic conductive adhesive is not particularly restricted but includes, for example, a thermoplastic resin such as an acrylate resin, an ethylene / vinyl acetate resin, a styrene / butadiene block copolymer; and a glycidyl group. A composition curable by heat or light, such as a curable resin composition obtained by reacting a monomer or oligomer with a curing agent such as isocyanate, and the like, may be mentioned. Preferably,
Among the curable resin compositions, a low-temperature curable resin that cures at a low temperature and a photocurable resin.

When an anisotropic conductive film is used as the anisotropic conductive adhesive, the coated conductive fine particles may be randomly dispersed or may be arranged at a specific position. The conductive film in which the coated conductive fine particles are randomly dispersed is usually used for general-purpose applications. In addition, the conductive film in which the coated conductive fine particles are arranged at predetermined positions can perform efficient electrical bonding. The coating thickness of the anisotropic conductive adhesive is not particularly limited, but is preferably from 10 to several hundreds of μm. Such an anisotropic conductive adhesive is also one of the present invention.

Examples of the objects to be connected by the coated conductive fine particles and the anisotropic conductive adhesive include a substrate having an electrode portion formed on a surface thereof, and electric parts such as semiconductors. The above substrate is roughly classified into a flexible substrate and a rigid substrate. Examples of the flexible substrate include a resin sheet having a thickness of 50 to 500 μm. Examples of the material of the resin sheet include polyimide, polyamide, polyester, and polysulfone.

The rigid substrate is roughly classified into a resin substrate and a ceramic substrate. Examples of the above-mentioned resin include glass fiber reinforced epoxy resin, phenol resin, cellulose fiber reinforced phenol resin and the like. Examples of the ceramic material include silicon dioxide, alumina, and glass.

The structure of the substrate is not particularly limited, and may be a single layer. In order to increase the number of electrodes per unit area, for example, a plurality of layers are formed, Accordingly, a multilayer substrate in which these layers are electrically connected to each other may be used.

The electric components are not particularly limited, and include, for example, active components such as semiconductors such as transistors, diodes, ICs, and LSIs; and passive components such as resistors, capacitors, and crystal oscillators. The shape of the electrode formed on the surface of the substrate or the electric component is not particularly limited, and examples thereof include a stripe shape, a dot shape, and an arbitrary shape.

As the material of the electrode, for example, gold,
Silver, copper, nickel, palladium, carbon, aluminum, ITO and the like can be mentioned. In order to reduce the contact resistance, it is preferable to use an electrode in which gold is further coated on copper, nickel or the like. The thickness of the electrode is 0.1 to 10
0 μm, and the width of the electrode is 1 to 5 μm.
It is preferably 00 μm.

The bonding between the coated conductive fine particles and the substrate or component may be performed, for example, by forming an anisotropic conductive film containing the coated conductive fine particles on a substrate or an electrical component having an electrode formed on the surface. Is arranged, an electrode of another substrate or an electric component is placed thereon, and heating and pressing are performed. Instead of the anisotropic conductive film, a predetermined amount of the anisotropic conductive paste containing the coated conductive fine particles can be used by printing means such as screen printing or a dispenser. For the above-mentioned heating and pressurizing, a crimping machine equipped with a heater, a bonding machine or the like is used.

A method not using the above-mentioned anisotropic conductive film and the above-mentioned anisotropic conductive paste is also possible. For example, a liquid binder is injected into a gap between two electrode portions bonded together via coated conductive fine particles. Thereafter, a method of curing or the like can be used.

The present invention also includes a conductive connection structure in which the electrodes of the substrate or the electric component are connected to each other using the coated conductive fine particles or the anisotropic conductive adhesive.

As described above, the anisotropic conductive adhesive and the conductive connection structure of the present invention comprise coated fine particles having a coating layer formed on the surface of conductive fine particles having at least a surface formed of a conductive material. It is characterized by using.
Therefore, in the anisotropic conductive adhesive and the conductive connection structure, the presence of the coating layer containing the coating fine particles does not cause a leak between adjacent electrodes, and can increase the concentration of the coating fine particles. In addition, at the contact portion between the electrode and the coated fine particles, the coating layer flows by heating and pressurization, whereby the coating layer is removed at the contact surface with the electrode. Can be contained at a high concentration, so that a large electric capacity can be secured.

[0048]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 Fine particles having an average particle diameter of 5 μm and an aspect ratio of 1.0
4. 20 g of divinylbenzene microspheres having a CV value of 4% and 1 g of a styrene-acrylic copolymer having a number average molecular weight of 30,000 soluble in xylene and a glass transition temperature (hereinafter referred to as Tg) of 80 ° C. as a coating substance. The mixture was uniformly dispersed in 20 g of xylene as a dispersion medium to obtain a mixture. Next, the obtained mixture was spread into a thin film in a vat, and while gradually evaporating xylene, the thin film mixture was cut into a mesh using a spatula to form a fine lump. Further, while the dispersion medium was volatilized to such an extent that the micro lump did not coalesce with each other, the remaining dispersion medium was volatilized while being crushed in a mortar to form single particles. When the fine particles in the mixture were observed using a scanning electron microscope, at least half of the fine particles were present at intervals equal to or less than the average particle diameter of the fine particles until the fine particles were converted into single particles. The coated fine particles thus obtained are uniformly coated with a coating thickness of about 50 nm, an average particle diameter of 5.1 μm, an aspect ratio of 1.06, and a CV value of 4%. Almost no.

Example 2 Fine particles having an average particle diameter of 2 μm and an aspect ratio of 1.0
7, 20 g of silica microspheres having a CV value of 6%, 1 g of an epoxy resin having a number average molecular weight of 10,000 soluble in xylene and Tg of 90 ° C. as a coating substance, and 1 g of titanium oxide having an average particle diameter of 50 nm in 20 g of xylene as a dispersion medium To obtain a mixture. Next, the obtained mixture was put into a ball mill, and the inside of the ball mill was stirred while reducing the pressure at -100 mmHg, and the mixture was made into a fine lump while gradually evaporating xylene. Further, the inside of the ball mill was agitated while reducing the pressure, and the remaining dispersion medium was agitated and formed into single particles. When the fine particles in the mixture were observed in the same manner as in Example 1,
At least half of the fine particles existed at intervals smaller than the average particle size of the fine particles until the fine particles were converted into single particles. The coated fine particles thus obtained have a coating thickness of about 50 n.
m, average particle diameter 2.1 μm, aspect ratio 1.09, C
It had a V value of 7%, was uniformly coated, and contained little multi-particles or residues of coating materials.

Example 3 Fine particles having an average particle diameter of 20 μm and an aspect ratio of 1.
1, 20 g of benzoguanamine-based microspheres having a CV value of 10% and a number average molecular weight of 6,000 soluble in toluene as a coating substance,
0.5 g of a curable epoxy resin having a Tg of 60 ° C., 0.5 g of a curing agent and a fine styrene-acrylic gel were uniformly dispersed in 20 g of toluene as a dispersion medium to obtain a mixture. Next, the obtained mixture was spread in a thin film in a vat, and while the toluene was gradually volatilized, the thin film mixture was cut into a network using a spatula to form a fine lump. Further, while the dispersion medium was volatilized to such an extent that the micro lumps did not coalesce with each other, the remaining dispersion medium was volatilized while being crushed by a jet mill to form single particles. When the fine particles in the mixture were observed in the same manner as in Example 1, at least half of the fine particles existed at intervals smaller than the average particle diameter of the fine particles until the fine particles were converted into single particles. The coated fine particles thus obtained have a coating thickness of about 100 nm, an average particle diameter of 20.2 μm, an aspect ratio of 1.1, and a CV value of 10%.
The coating was uniform and contained little multi-particles or residues of coating substances.

Example 4 Fine particles having an average particle diameter of 5 μm and an aspect ratio of 1.1
5, 20 g of divinylbenzene microspheres having a CV value of 12%, and a xylene-soluble number average molecular weight of 30,000 as a coating substance, Tg
1 g of a styrene-acrylic copolymer at 80 ° C. was uniformly dispersed in 20 g of xylene as a dispersion medium to obtain a mixture.
Next, the obtained mixture is spread into a thin film in a vat,
While gradually evaporating xylene, the thin film mixture was cut into a network using a spatula to form a fine lump. Further, while the dispersion medium was volatilized to such an extent that the micro lump did not coalesce with each other, the remaining dispersion medium was volatilized while being crushed in a mortar to form single particles. When the fine particles in the mixture were observed in the same manner as in Example 1, at least half of the fine particles existed at intervals smaller than the average particle diameter of the fine particles until the fine particles were converted into single particles. The coated fine particles thus obtained had a coating thickness of about 50 nm, an average particle diameter of 5.1 μm,
It was uniformly coated with an aspect ratio of 1.15 and a CV value of 12%, and contained some multi-particles and residues of the coating substance, but it was not a problem.

Example 5 Xylene-soluble number average molecular weight of 30,000 as coating material, T
Coated fine particles were obtained in the same manner as in Example 1 except that 3 g of a styrene-acrylic copolymer having a g of 80 ° C. was used. When the fine particles in the mixture were observed in the same manner as in Example 1, at least half of the fine particles existed at intervals smaller than the average particle diameter of the fine particles until the fine particles were converted into single particles. The obtained coated fine particles have a coating thickness of about 150 n.
m, average particle diameter 5.3 μm, aspect ratio 1.06, C
It had a V value of 5%, and was almost uniformly coated, contained some multi-particles and residues of the coating substance, and a very small amount of the coating layer was peeled off, but it was not a problem.

Example 6 Fine particles having an average particle diameter of 6 μm and an aspect ratio of 1.0
5. Nickel 1 in divinylbenzene microspheres with CV value 5%
20 g of fine particles having a specific gravity of 2.5 plated with 00 nm and 40 nm of gold, and 1 g of a methacrylate copolymer having a number average molecular weight of 10,000 and a Tg of 80 ° C., soluble in butyl acetate as a coating substance, and 10 g of butyl acetate as a dispersion medium The mixture was uniformly dispersed therein to obtain a mixture. Next, the obtained mixture was spread in a thin film in a vat, and while gradually evaporating butyl acetate, the thin film mixture was cut into a network using a spatula to form a fine lump. Further, while the dispersion medium was volatilized to such an extent that the fine lumps did not coalesce with each other, the remaining dispersion medium was volatilized while being crushed in a mortar to form single particles. In addition, when the fine particles in the mixture were observed in the same manner as in Example 1, at least half of the fine particles until the fine particles were converted into single particles,
The particles were present at intervals smaller than the average particle size of the fine particles. The coated conductive fine particles thus obtained have a coating thickness of about 100
nm, average particle diameter 6.2 μm, aspect ratio 1.08,
It had a CV value of 7%, was uniformly coated, and contained little multi-particles or residues of coating materials.

Further, the coated conductive fine particles were mixed and dispersed in a binder solution obtained by dissolving a thermosetting epoxy resin in toluene. Subsequently, the dispersion solution of the coated conductive fine particles was applied on a release film to a constant thickness, and toluene was evaporated to obtain an anisotropic conductive film. The thickness was 25 μm. Thereafter, 10 × 10 50 μm-square gold bumps were arranged on a glass-epoxy substrate at an electrode pitch of 70 μm, the resulting anisotropic conductive film was attached, and the same substrate was further positioned thereon and then superposed. Heated at 150 ° C for 2 minutes,
Pressure was applied to obtain a conductive connection structure. The connection resistance value of the obtained conductive connection structure was sufficiently low, and the interline insulation between adjacent electrodes was sufficiently maintained. A cooling cycle test was performed, but no change was observed.

Example 7 20 g of nickel spheres having an average particle diameter of 5 μm, an aspect ratio of 1.2 and a CV value of 15% obtained by classification as fine particles, and a number average molecular weight of 600 soluble in toluene as a coating substance were 600.
0.2 g of a curable epoxy resin having a Tg of 60 ° C. and a curing agent were uniformly dispersed in 10 g of toluene as a dispersion medium to obtain a mixture. Next, the obtained mixture was spread in a thin film in a vat, and while the toluene was gradually volatilized, the thin film mixture was cut into a network using a spatula to form a fine lump. Further, while the dispersion medium was volatilized to such an extent that the micro lump did not coalesce with each other, the remaining dispersion medium was volatilized while being crushed in a mortar to form single particles. When the fine particles in the mixture were observed in the same manner as in Example 1, at least half of the fine particles existed at intervals smaller than the average particle diameter of the fine particles until the fine particles were converted into single particles. The coated conductive fine particles thus obtained are uniformly coated with a coating thickness of about 20 nm, an average particle diameter of 5 μm, an aspect ratio of 1.2, and a CV value of 15%. Almost no.

Further, an anisotropic conductive film and a conductive connection structure were obtained in the same manner as in Example 6, except that the coated conductive fine particles were used. The connection resistance value of the obtained conductive connection structure was sufficiently low, and the interline insulation between adjacent electrodes was sufficiently maintained. A cooling cycle test was performed, but no change was observed.

Example 8 Fine particles before coating were dried under a reduced pressure of 700 mmHg from atmospheric pressure at a temperature of 80 ° C. for 5 hours.
After returning the temperature to room temperature while maintaining the reduced pressure, the pressure was returned to the atmospheric pressure, and 600 to 650 mm again from the atmospheric pressure during coating.
Coated microparticles were obtained in the same manner as in Example 1 except that the Hg pressure was reduced and the pressure was maintained for 10 minutes, and then returned to the atmospheric pressure. 1 g of the coated fine particles thus obtained was put into a high-speed stirrer (homogenizer) together with 50 g of pure water, and the mixture was stirred at 10,000 rpm for 30 minutes to forcibly peel off the coating layer. The rate of peeling of the layer was 5.5%. When the coated fine particles of Example 1 were observed in the same manner, the rate of peeling of the coated layer was 8.3%.

Example 9 Fine particles before coating were dried under a reduced pressure of 700 mmHg from atmospheric pressure and a temperature of 80 ° C. for 5 hours before use.
After returning the temperature to room temperature while maintaining the reduced pressure, the pressure was returned to the atmospheric pressure, and 600 to 650 mm again from the atmospheric pressure during coating.
Coated microparticles were obtained in the same manner as in Example 7, except that the Hg pressure was reduced and the pressure was maintained for 10 minutes, and then returned to the atmospheric pressure. Using the obtained coated fine particles, the coating layer was forcibly peeled off with a high-speed stirrer (homogenizer), and the state was observed with an electron microscope. The peeling ratio of the coating layer was 3.5%. When the coated fine particles of Example 7 were observed in the same manner, the rate of peeling of the coated layer was 15.3%.

Comparative Example 1 Titanium oxide having an average particle diameter of less than 0.2 μm as fine particles and a number average molecular weight soluble in xylene of 30,000 as a coating substance, T
g A styrene-acrylic copolymer of 80 ° C. was added so that the coating thickness became about 20 nm, and the mixture was uniformly dispersed in 20 g of xylene as a dispersion medium to obtain a mixture. Next, the obtained mixture was spread into a thin film in a vat, and while gradually evaporating xylene, the thin film mixture was cut into a network using a spatula to form a fine lump. Furthermore, while the dispersion medium was volatilized to such an extent that the fine agglomerates did not coalesce with each other, the remaining dispersion medium was volatilized while being crushed with a mortar, and the remaining dispersion medium was volatilized into single particles. Could not.

Comparative Example 2 20 g of divinylbenzene microspheres having an average particle diameter of 4000 μm, an aspect ratio of 1.04 and a CV value of 4% as fine particles.
Except for using the above, coated fine particles were obtained in the same manner as in Example 1. The obtained coated fine particles contained a large amount of resin residue at the bottom of the particles, the coating thickness was non-uniform, and a large amount of residues of the coating material.

Comparative Example 3 Fine particles having an average particle diameter of 5 μm, an aspect ratio of 5, and a CV
Except that 20 g of divinylbenzene-based short fiber having a value of 4% was used, an attempt was made to form single particles in the same manner as in Example 1, but the aggregate was hard and could not be formed into single particles. Then, when further strongly crushed, the coating layer was peeled off, a large amount of residue was generated, and some of the divinylbenzene-based short fibers were broken.

Comparative Example 4 Fine particles having an average particle diameter of 5 μm and an aspect ratio of 1.0
4. Except for using 20 g of divinylbenzene microspheres having a CV value of 50%, an attempt was made to form single particles in the same manner as in Example 1, but the aggregates were hard and could not be formed into single particles. Then, when further crushed, the coating layer was peeled off, a large amount of residue was generated, and some of the divinylbenzene microspheres were broken.

Comparative Example 5 The amount of the coating material was changed to 250 g while the amount of the coating material was changed to 50 g.
Except for changing to g, an attempt was made to form single particles in the same manner as in Example 1, but the aggregate was hard and could not be formed into single particles. Then, when further crushed, the coating layer was peeled off, a large amount of residue was generated, and some of the divinylbenzene microspheres were broken. Also, the coating thickness was non-uniform for the single particles.

Comparative Example 6 As a coating substance, a styrene-acrylic copolymer 1 soluble in diethyl ether and having a number average molecular weight of 30,000 and a Tg of 80 ° C.
g, except that the dispersion medium was changed to diethyl ether.
In the same manner as in Example 1, a mixture in which fine particles and a coating substance were dispersed was obtained. Next, the obtained mixture was spread in a thin film in a vat, and diethyl ether was evaporated. Since the evaporation rate was high, the mixture in the form of a thin film could not be cut into a mesh using a spatula. Further, the fine chunks were crushed in a mortar and tried to be formed into single particles, but the fine chunks were hard and could not be formed into single particles. Then, when further crushed, the coating layer was peeled off, a large amount of residue was generated, and some of the divinylbenzene microspheres were broken. Also, the coating thickness was non-uniform for the single particles.

Comparative Example 7 Fine particles having an average particle diameter of 5 μm and an aspect ratio of 1.0
4. Divinylbenzene microspheres having a CV value of 4%, styrene and acrylate as a coating substance, and benzoyl peroxide as a polymerization initiator were mixed, and suspension polymerization was performed in a polyvinyl alcohol dispersion medium. The polymer obtained by this polymerization reaction was a styrene-acrylic copolymer having a number average molecular weight of 30,000 and a Tg of 80 ° C., and covered divinylbenzene-based microspheres. In addition, multiple particles and many particles not containing microspheres were also generated.

Comparative Example 8 As fine particles, the average particle diameter was 5 μm and the aspect ratio was 1.0.
4, 20 g of divinylbenzene microspheres having a CV value of 4%, and a xylene-soluble number average molecular weight of 30,000 as a coating substance, Tg8
1 g of a styrene-acrylic copolymer at 0 ° C. was uniformly dispersed in 100 g of xylene as a dispersion medium to obtain a mixture. When the solvent was removed under heating and reduced pressure while spraying the obtained mixture by a spray drying method, divinylbenzene microspheres were coated, but the coating film thickness varied depending on the particles, and multiple particles and microspheres were obtained. Many particles containing no were also generated.

Comparative Example 9 An anisotropic conductive film and a conductive connection structure were obtained in the same manner as in Example 6, except that uncoated conductive fine particles were used instead of the coated conductive fine particles. Although the connection resistance value of the obtained conductive connection structure was sufficiently low, a short circuit occurred between adjacent electrodes.

Comparative Example 10 An anisotropic conductive film and a conductive connection structure were obtained in the same manner as in Example 6, except that the coated conductive fine particles obtained by suspension polymerization were used as the coated conductive fine particles. In the obtained conductive connection structure, bumps that were not connected to the counter electrode were observed, although the line insulation between adjacent electrodes was maintained. In addition, when a cooling / heating cycle test was performed, bumps that were short-circuited between adjacent electrodes were found.

[0070]

As described above, the method for coating fine particles of the present invention has the above-described structure, does not require a large-scale apparatus, does not generate uncoated fine particles, is efficient, is less likely to generate multiple particles, and can be easily coated. The thickness of the layer can be controlled, a large amount of fine particles can be coated, and fine particles having poor wettability and high specific gravity can be coated. Therefore, coated fine particles having a uniform coating layer thickness among particles can be produced by the above method. Further, the coated fine particles of the present invention are coated using the fine particle coating method of the present invention, so that the shape of the fine particles is maintained. Furthermore, when the conductive fine particles are used as the fine particles, the connection fine particles have low connection resistance,
The electric capacity at the time of connection is large, the connection is stable, and no leak phenomenon occurs. Further, the anisotropic conductive adhesive of the present invention has a low connection resistance, a large electric capacity at the time of connection, a stable connection, and does not cause a leak phenomenon. Further, the conductive connection structure of the present invention has low connection resistance, large electric capacity at the time of connection, stable connection, and does not cause a leak phenomenon.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09J 201/00 C09J 201/00

Claims (28)

[Claims] 1. A method for coating fine particles, wherein a mixture is prepared by mixing fine particles, a coating substance, and a dispersion medium, and then the dispersion medium is removed while gradually volatilizing to form a coating layer on the fine particles. The fine particles have an average particle diameter of 0.2 to
3000 μm, aspect ratio less than 5, CV value 40%
The method of coating fine particles, wherein the thickness of the coating layer is 1/4 or less of the average particle diameter of the fine particles. 2. The method for coating fine particles according to claim 1, wherein the dispersion medium is gradually volatilized while the mixture is formed into a thin film, a thin line or a fine lump. 3. The method for coating fine particles according to claim 1, wherein the coating substance is mainly composed of a resin. 4. The method for coating fine particles according to claim 1, wherein the coating substance mainly comprises a resin soluble in a dispersion medium. 5. The method according to claim 1, wherein when removing the dispersion medium while volatilizing it gradually, there are at least half or more of the fine particles having an interval between the fine particles of not more than the average particle diameter of the fine particles. A method for coating fine particles according to any one of the preceding claims. 6. The method according to claim 6, wherein after removing at least most of the dispersion medium, a part of the coating material or an interface between the fine particles and the coating material is destroyed by an external force, and the coated fine particles are converted into single particles. A method for coating fine particles according to any one of claims 1 to 5. 7. The method for coating fine particles according to claim 1, wherein the thickness of the coating layer is 1/10 or less of the average particle diameter of the fine particles. 8. The thickness of the coating layer is 5 / (the molecular weight of the resin forming the coating layer) 1/2 or less of the average particle diameter of the fine particles (however, the molecular weight of the crosslinked resin is calculated as 1,000,000). The method for coating fine particles according to any one of claims 3 to 7, characterized in that: 9. The fine particles have an average particle size of 0.5 to 100.
The method for coating fine particles according to any one of claims 1 to 8, wherein the particle size is less than 2, and the CV value is 30% or less. 10. The fine particles have an average particle diameter of 1 to 20 μm.
The method for coating fine particles according to any one of claims 1 to 9, wherein m, the aspect ratio is less than 1.4, and the CV value is 20% or less. 11. The fine particles have an average particle diameter of 3 to 10 μm.
The method for coating fine particles according to any one of claims 1 to 10, wherein m, the aspect ratio is less than 1.1, and the CV value is 10% or less. 12. The fine particles have an aspect ratio of less than 1.05 and a CV value of 5% or less.
12. The method for coating fine particles according to any one of items 11 to 11. 13. The method for coating fine particles according to claim 1, wherein the fine particles have a specific gravity of 1.5 or more. 14. The method for coating fine particles according to claim 1, wherein the fine particles have a specific gravity of 3 or more. 15. Coated fine particles coated by the method of coating fine particles according to claim 1. Description: 16. An average particle size of more than 0.2 μm
000 μm or less, aspect ratio is less than 5, CV value is 40
% Or less. 17. The coated fine particles according to claim 15, wherein the average particle diameter is 0.5 to 100 μm, the aspect ratio is less than 2, and the CV value is 30% or less. 18. The coated fine particles according to claim 15, wherein the average particle diameter is 1 to 20 μm, the aspect ratio is less than 1.4, and the CV value is 20% or less. 19. The coated fine particles according to claim 15, wherein the average particle diameter is 3 to 10 μm, the aspect ratio is less than 1.1, and the CV value is 10% or less. 20. The method for coating fine particles according to claim 1, wherein the fine particles are conductive fine particles having a conductive layer formed on at least the surface. 21. The coated fine particle according to claim 15, wherein the fine particle is a conductive fine particle having a conductive layer formed on at least a surface thereof. 22. The coated fine particle according to claim 21, wherein the material constituting the core of the conductive fine particle is a polymer. 23. The coated fine particles according to claim 21, wherein the material constituting the core of the conductive fine particles is a metal. 24. The coated fine particles according to claim 21, 22 or 23, wherein the conductive fine particles have a surface coated with a metal. 25. The coated fine particle according to claim 21, wherein the conductive fine particle has a gold-plated surface. 26. An anisotropic conductive adhesive, wherein the coated fine particles according to claim 21 are dispersed in a binder resin. 27. An electrode part constituting a substrate or an electric component is bonded via the coated fine particles according to any one of claims 21 to 25, and the coating layer of the coated fine particles is heated and heated. A conductive connection structure, wherein the conductive material of the coated fine particles comes into contact with the electrode portion by flowing under pressure, and conduction between the electrode portions is achieved. 28. A coating layer of coated fine particles in the anisotropic conductive adhesive, wherein the electrode portions constituting the substrate or the electric component are bonded together via the anisotropic conductive adhesive according to claim 26. Flows by heating and pressurizing,
A conductive connection structure, wherein the conductive material of the coated fine particles is in contact with the electrode portion, and the electrode portions are electrically connected to each other.