JP6893399B2 - Insulation coated particles, methods for producing insulating coated particles, particle-containing compositions, and anisotropic conductive adhesives. - Google Patents

Description

The present invention relates to insulating coated particles, a method for producing insulating coated particles, a particle-containing composition, and an anisotropic conductive adhesive.

Conventionally, an anisotropic conductive adhesive in which conductive particles are dispersed in a binder such as a curable resin is used to electrically connect circuit boards having a plurality of terminals via the respective terminals. The connection method used is adopted. This anisotropic conductive adhesive is placed between circuit boards facing each other and thermocompression bonded with a heater or the like to provide conductivity between the facing terminals via conductive particles. , Has a function of maintaining insulation between adjacent terminals on each substrate.

Here, in recent years, there is a demand for miniaturization and high performance of devices such as mobile devices. In order to meet such demands, in recent circuit boards used in the apparatus, the connection surface of each terminal has been reduced in area, and the number of terminals per unit area of the circuit board has increased. That is, the circuit board described above tends to have a short distance between adjacent terminals.

In order to join such circuit members with a short distance between adjacent terminals with an anisotropic conductive adhesive and to secure conductivity by interposing a sufficient amount of conductive particles, the binder is used. It is necessary to increase the density of conductive particles. However, if the density of the conductive particles in the binder is increased, a short circuit is likely to occur between the adjacent terminals.

As a countermeasure against such a situation, for example, in Patent Document 1, by coating the surface of conductive particles with an insulating resin, short-circuiting between adjacent terminals can be prevented, and between facing terminals during crimping. It is disclosed that the insulating resin on the surface of the conductive particles is removed by the pressure, and the conductivity can be ensured. Then, it is known that the conductive particles coated with such an insulating resin can be produced by a dry method using a hybridizer or the like, as disclosed in Patent Documents 1 and 2.

Japanese Patent No. 2794009 Japanese Unexamined Patent Publication No. 2007-258141

However, when a film-like or paste-like anisotropic conductive adhesive is produced using the conductive particles coated with the insulating resin as described above, the insulating property covering the conductive particles may be produced. There is a problem that the resin layer causes swelling, dissolution, or deformation with the solvent used in the production. In such a case, at least one of the conductivity and the insulating property of the anisotropic conductive adhesive is adversely affected.

Further, in the above-mentioned conventional dry method, it is difficult to form a film having sufficient adhesiveness on the particle surface. Therefore, the coverage of the film on the particle surface reaches a plateau, and the insulating property itself can be sufficiently enhanced. could not.

In addition, the above-mentioned conventional dry method has a problem that the yield is not sufficient and there is a limit in increasing the processing amount per batch.

The present invention has been made in view of such circumstances, and when circuit boards having a plurality of terminals are electrically connected to each other, sufficient insulation between adjacent terminals on each board is sufficiently ensured. Provided are insulating coating particles capable of obtaining an anisotropic conductive adhesive that provides conductivity between opposing terminals, and a particle-containing composition and an anisotropic conductive adhesive containing the insulating coating particles. The purpose is to do. Another object of the present invention is to provide a method for producing insulating coated particles capable of efficiently producing the above-mentioned insulating coated particles.

The present inventors have conducted extensive research in order to solve the above problems. As a result, the particles in which the insulating substance is firmly adhered to the surface of the conductive particles can provide excellent insulating properties and anisotropic conductivity to the anisotropic conductive adhesive, and such We have found that particles can be obtained by using a new method instead of the dry method, and have completed the present invention.

The present invention is based on the above-mentioned findings by the present inventors, and the means for solving the above-mentioned problems are as follows.
[1] Insulating coated particles, characterized in that an insulating polymer containing a structural unit derived from a polymerizable monomer is fixed to at least a part of the surface of the conductive particles.
With the above configuration, it is possible to obtain an anisotropic conductive adhesive that provides conductivity while sufficiently ensuring insulating properties.
[2] The insulating coated particles according to the above [1], wherein the insulating polymer has a coverage of more than 40%.
[3] The insulating coating particles according to the above [1] or [2], wherein the polymerizable monomer contains a monomer having two or more polymerizable functional groups.
[4] The insulating coated particles according to the above [3], wherein the monomer having two or more polymerizable functional groups is divinylbenzene.
[5] The insulating coating particles according to the above [3], wherein the monomer having two or more polymerizable functional groups is a (meth) acrylate compound.
[6] The insulating coating particles according to any one of [1] to [5], wherein the average coating thickness of the insulating polymer is 50 nm or more.
[7] A step of preparing a mixture of a polymerizable monomer, conductive particles, and a reaction initiator and a solvent.
By applying energy to the mixture while stirring the mixture, an insulating polymer obtained by polymerizing the polymerizable monomer is produced, and at least a part of the surface of the conductive particles is insulated. The process of fixing the sex polymer and
A method for producing insulating coated particles, which comprises.
With the above configuration, the above-mentioned insulating coating particles can be efficiently produced.
[8] The method for producing an insulating coated particle according to the above [7], wherein the solvent is a solvent that dissolves the polymerizable monomer but does not dissolve the insulating polymer.
[9] The method for producing insulating coated particles according to the above [7] or [8], wherein the energy is thermal energy.
[10] A particle-containing composition comprising the insulating coating particles according to any one of the above [1] to [6].
[11] An anisotropic conductive adhesive comprising the particle-containing composition according to the above [10].

According to the present invention, when circuit boards having a plurality of terminals are electrically connected to each other, while sufficiently ensuring the insulation between adjacent terminals on each board, the conductivity between the opposing terminals is maintained. It is possible to provide an insulating coating particle capable of obtaining an anisotropic conductive adhesive to be brought about, and a particle-containing composition and an anisotropic conductive adhesive containing the insulating coating particle. Further, according to the present invention, it is possible to provide a method for producing insulating coated particles capable of efficiently producing the above-mentioned insulating coated particles.

It is a figure which explains each step of the manufacturing method of the insulating coating particle which concerns on one Embodiment of this invention. It is a figure which shows typically the mechanism which the polymer adheres to the surface of the conductive particle by carrying out the manufacturing method of the insulating coating particle which concerns on one Embodiment of this invention. It is a medium-magnification image of the insulating coated particles according to one embodiment of the present invention by a scanning electron microscope (SEM). It is a high-magnification image of the insulating coating particle according to one embodiment of the present invention by a scanning electron microscope (SEM). It is a medium-magnification image of a coating particle according to a conventional embodiment by a scanning electron microscope (SEM). It is a high-magnification image of the coated particles according to a conventional embodiment by a scanning electron microscope (SEM).

Hereinafter, the present invention will be specifically described based on the embodiments.

<Insulation coated particles>
The insulating coated particles according to an embodiment of the present invention include at least conductive particles and an insulating polymer containing a structural unit derived from a polymerizable monomer, and are formed on at least a part of the surface of the conductive particles. , The above-mentioned insulating polymer is fixed.
The insulating polymer that can be fixed to the surface of the conductive particles has low solubility in the solvent, and the polymer that is fixed to the surface of the conductive particles (that is, firmly adhered) comes into contact with the solvent. Even if it does, it is difficult to peel off. Therefore, the insulating coating particles according to the embodiment of the present invention have the polymer peeled off from the surface of the conductive particles and the weight of the surface of the conductive particles due to the solvent used at the time of producing the anisotropic conductive adhesive. The erosion to the coalescence is suppressed, and the insulating property of the anisotropic conductive adhesive (hereinafter, this may be simply referred to as “insulating property”) can be maintained high.
Further, when the insulating coating particles according to the embodiment of the present invention are dispersed in an anisotropic conductive adhesive, and the anisotropic conductive adhesive is placed between circuit boards with facing terminals and crimped. In addition, the polymer was excellent between the opposing terminals via a surface that was not originally coated (the surface of the conductive particles) and / or a surface where the adhered polymer was removed by the pressure during crimping. It can provide conductivity (hereinafter, this may be simply referred to as "conductivity").
Then, the insulating coating particles according to the embodiment of the present invention can be produced, for example, by the method for producing the insulating coating particles according to the embodiment of the present invention, which will be described later.

In the present specification, the term "polymer is fixed" to the surface of particles means that 10 g of particles whose surface is coated with the polymer is dispersed in 50 ml of distilled water, shaken, and allowed to stand. Later, when the supernatant of this liquid is visually confirmed, it means that the polymer is firmly adhered to the surface of the particles to the extent that it is not confirmed to be turbid. The term "sticking" for the surface of a particle is also used herein as a subordinate concept of "coating".

(Conductive particles)
The conductive particles included in the insulating coating particles according to the embodiment of the present invention are not particularly limited, and for example, any known conductive particles used in the anisotropic conductive adhesive can be used. Specifically, the conductive particles include particles of various metals or metal alloys such as nickel, iron, copper, aluminum, tin, lead, chromium, cobalt, silver and gold; metal oxides, carbon, graphite and glass. A metal-coated surface of particles such as ceramic, plastic, and resin; and the like. Here, when the surface of the resin particles is coated with a metal, the resin particles include, for example, epoxy resin, phenol resin, acrylic resin, acrylonitrile-styrene (AS) resin, benzoguanamine resin, divinylbenzene resin, and styrene. Examples include particles such as styrene resins. The conductive particles may be one kind alone or a combination of two or more kinds.
The shape and size of the conductive particles are not particularly limited and can be appropriately selected depending on the intended purpose.

(Insulating polymer)
The insulating polymer (hereinafter, may be simply referred to as “polymer”) included in the insulating coated particles according to the embodiment of the present invention contains a structural unit derived from a polymerizable monomer and is a conductive particle. It is fixed to at least a part of the surface of the.
In the present specification, the "polymerizable monomer" refers to a compound having a property of polymerizing when energy such as thermal energy or ultraviolet energy is applied, and is usually a compound having a double bond. .. Further, the polymerizable monomer may be a single type or a combination of two or more types.

In the insulating coating particles according to the embodiment of the present invention, the polymerizable monomer preferably contains a monomer having two or more polymerizable functional groups. As a result, the obtained polymer has a so-called three-dimensional network structure, and has lower solubility in solvents (including low boiling point solvents such as methyl ethyl ketone and ethyl acetate, and high boiling point solvents such as toluene). Therefore, a sufficiently high insulating property can be maintained.
In addition, in this specification, a "polymerizable functional group" refers to a group used for a polymerization reaction and / or a crosslinking reaction at the time of curing. Further, the polymerizable functional group contained in the polymerizable monomer may be one kind alone or a combination of two or more kinds.

Specific examples of the polymerizable functional group include a vinyl group, an allyl group, a (meth) acryloyl group, and the like. Further, as the monomer having two or more polymerizable functional groups, specifically, a vinyl compound such as a divinyl compound, an allyl compound such as a diallyl compound, and a (meth) acrylate compound such as a di (meth) acrylate compound, And so on. In the insulating coated particles according to the embodiment of the present invention, the monomer having two or more polymerizable functional groups is a vinyl compound, particularly divinylbenzene, from the viewpoint of obtaining better insulating properties. It is preferable, and it is also preferable that it is a (meth) acrylate compound.
In the present specification, the "(meth) acryloyl group" refers to at least one of an acryloyl group and a meta-acryloyl group, and the "(meth) acrylate" refers to at least one of an acrylate and a methacrylate. Point to.

Examples of the (meth) acrylate compound which is a monomer having two or more polymerizable functional groups include ethylene glycol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, and propylene glycol di (meth). Acrylate, (poly) propylene glycol di (meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropanthry (meth) acrylate, dipentaerythritol hexa. (Meta) acrylate, dipentaerythritol penta (meth) acrylate, glycerol tri (meth) acrylate, glycerol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, tetra Examples thereof include methylol methanetri (meth) acrylate, tetramethylol propanetetra (meth) acrylate, tricyclodecanedimethanol di (meth) acrylate, and (poly) ethoxylated bisphenol A di (meth) acrylate.

The polymer may contain structural units other than the structural units derived from the above-mentioned polymerizable monomer. However, from the viewpoint of ensuring excellent insulating properties, the proportion of the structural unit derived from the polymerizable monomer is preferably 50% by mass or more, and more preferably 90% by mass or more.

It is preferable that the polymer is hardly dissolved in the solvent used for preparing the anisotropic conductive adhesive at the drying temperature at the time of preparing the anisotropic conductive adhesive. For example, the amount of the polymer dissolved in 100 g of methyl ethyl ketone at 50 ° C. is preferably 0.1 g or less, and the amount of the polymer dissolved in 100 g of ethyl acetate at 50 ° C. is preferably 0.1 g or less, and 70. The amount dissolved in 100 g of toluene at ° C. is preferably 0.1 g or less. By satisfying at least one of these characteristics, erosion of the polymer by the solvent used in the preparation of the anisotropic conductive adhesive can be more reliably avoided. In addition, these characteristics can be achieved, for example, by polymerizing using the above-mentioned monomer having two or more polymerizable functional groups.

(Structure of insulating coated particles)
The insulating coated particles according to the embodiment of the present invention preferably have a polymer coverage of more than 40%. When the coverage of the polymer is more than 40%, a sufficiently high insulating property can be ensured.
Further, the insulating coating particles according to the embodiment of the present invention are not particularly limited, and it is preferable that the coverage of the polymer is 75% or less from the viewpoint of effectively suppressing deterioration of conductivity.
In addition, in this specification, the "covering ratio" of a polymer refers to the ratio of the area of the part covered with a polymer to the total surface area of conductive particles, and is described in the Examples of this specification. It can be obtained by the method.

The insulating coating particles according to the embodiment of the present invention preferably have an average coating thickness of a polymer of 50 nm or more. When the average coating thickness of the adhered polymer is 50 nm or more, the insulating property can be sufficiently enhanced.
Further, from the viewpoint of ensuring conductivity, the insulating coating particles according to the embodiment of the present invention preferably have an average coating thickness of a polymer of 500 nm or less, more preferably 350 nm or less, and 250 nm or less. Is more preferable.
In the present specification, the "average coating thickness" of the polymer refers to the average value of the thickness of the polymer coating the surface, and can be measured by the method described in the examples of the present specification. ..

<Manufacturing method of insulating coated particles>
The method for producing an insulating coating particle of the present invention includes at least a mixing step and an energy applying step, and if necessary, a degassing step, an inerting step, a slow cooling step, a settling step, a supernatant removing step, and a cleaning step. Includes steps, solid-liquid separation steps, and drying steps. Here, the method for producing insulating coated particles of the present invention is classified into a so-called wet method, and can sufficiently increase the yield and the amount of processing per batch as compared with the conventional dry method. , An efficient method.
Hereinafter, a method for producing insulating coated particles according to an embodiment of the present invention will be described.

(Mixing process)
The mixing step is a step of preparing a mixture (slurry liquid) of the polymerizable monomer, the conductive particles, the reaction initiator and the solvent (FIG. 1 (a)).
Further, in the mixing step, any material other than the polymerizable monomer, the conductive particles, the reaction initiator and the solvent may be blended depending on the purpose.
The polymerizable monomer and the conductive particles can be appropriately selected depending on the intended purpose, and the details thereof are as described above in the description of the insulating coated particles. In particular, as the polymerizable monomer, it is preferable to select one such that the polymer obtained by the polymerization has an insulating property.

The reaction initiator is not particularly limited as long as it can be dissolved in the solvent and initiate the polymerization reaction of the polymerizable monomer, and a known reaction initiator can be appropriately used. Specific examples of the reaction initiator include thermal polymerization initiators such as azo compounds and organic peroxides; ultraviolet polymerization initiators such as alkylphenone type and acylphosphine oxide type; among these. As the reaction initiator, it is preferable to use an azo compound or an organic peroxide.
The reaction initiator may be used alone or in combination of two or more.

The solvent is not particularly limited as long as it can dissolve the above-mentioned polymerizable monomer and reaction initiator, and a known solvent can be appropriately used. Here, specific examples of the solvent include hexane, cyclohexane, diethyl ether, polyether (glyme), γ-butyrolactone, N-methylpyrrolidone, acetonitrile, tetrahydrofuran, ethyl acetate, xylene, toluene, benzene, dimethyl sulfoxide, acetone, and the like. Examples thereof include methyl ethyl ketone, ethanol, methanol and water. The solvent may be used alone or in combination of two or more.

However, from the viewpoint of accelerating the polymerization reaction and enhancing the performance of the insulating polymer obtained by the polymerization, the solvent is such that the solubility of the polymerizable monomer in the above-mentioned mixture is such that the polymerizable monomer is polymerized. It is preferable that the solubility of the polymer is higher than that of the polymer. Then, from the same viewpoint, the solvent dissolves the polymerizable monomer in the above-mentioned mixture, but it is more preferable that the solvent does not dissolve the polymer obtained by polymerizing the polymerizable monomer. When the solvent is a good solvent with respect to the polymerizable monomer, the polymerization reaction is promoted, and the solvent is poor with respect to the polymer obtained by polymerizing the polymerizable monomer. This is because the redissolution of the polymer to be obtained can be suppressed and the polymer can be satisfactorily fixed to the conductive particles.
It should be noted that the above-mentioned solubility or whether or not it dissolves is measured or determined by the temperature of the mixture during the energy application step described later.

Specifically, when divinylbenzene is used as the polymerizable monomer, it is preferable to use ethanol or a mixture of ethanol and isopropyl alcohol as the solvent. When a (meth) acrylate compound is used as the polymerizable monomer, it is preferable to use ethanol or a mixture of ethanol and toluene as the solvent.

(Degassing process)
The degassing step is an arbitrary step in the method for producing insulating coated particles of the present invention, and is a step of degassing the mixture prepared in the mixing step (FIG. 1 (b)). By carrying out the degassing step, the surface wettability of the conductive particles can be promoted. Examples of the degassing method include a method using decompression and / or ultrasonic waves.

(Inertization process)
The inerting step is an arbitrary step in the method for producing insulating coated particles of the present invention, and is a step of inerting the mixture after the mixing step or before or after the arbitrary degassing step (FIG. 1 (FIG. 1). c)). By carrying out the inerting step, it is possible to suppress the inhibition of the polymerization reaction in the energy applying step described later. The method of inertation is not particularly limited, and examples thereof include a method of supplying an inert gas such as nitrogen by bubbling while stirring the mixture.

(Energy application process)
The energy applying step is a step of applying energy to the mixture while stirring the mixture after the mixing step or any degassing step or inertification step. By applying energy to the mixture, the polymerization reaction is started, the polymerizable monomer is polymerized, and an insulating polymer is produced. At the same time, the insulating polymer adheres to at least a part of the surface of the conductive particles in the mixture to generate insulating coated particles.
In the method for producing insulating coated particles according to an embodiment of the present invention, the polymerizable monomer, the conductive particles, and the reaction initiator are mixed with the solvent in the mixing step, and the mixture is mixed in the energy applying step. By applying energy to the conductive particles, aggregation of the conductive particles can be suppressed and an insulating polymer having a desired thickness can be formed on the conductive particles. As a result of forming a coating having better insulating properties than the conventional one, the finally obtained insulating coated particles are greatly improved in insulating properties while maintaining high conductivity.

Examples of the energy given to the mixture include thermal energy and light energy such as ultraviolet rays, and the type of the above-mentioned reaction initiator can be appropriately selected depending on the type of energy. However, in the method for producing insulating coated particles according to an embodiment of the present invention, it is preferable to apply thermal energy to the mixture (that is, to heat the mixture) as shown in FIG. 1 (d). By using thermal energy, it is possible to easily and surely produce an insulating polymer. Examples of the method of heating the mixture include, as shown in FIG. 1D, a method of immersing a container containing the mixture in a temperature-controlled constant temperature bath.

Here, when heat energy is applied to the mixture (that is, the mixture is heated), the heating temperature of the mixture is preferably 0 ° C. or higher and 200 ° C. or lower. When the heating temperature of the mixture is 0 ° C. or higher and 200 ° C. or lower, a polymer having high insulating properties can be produced more reliably. From the same viewpoint, the heating temperature of the mixture is more preferably 25 ° C. or higher and 150 ° C. or lower.

(Slow cooling process)
The slow cooling step is an arbitrary step in the method for producing insulating coated particles of the present invention, and is a step of slowly cooling the mixture containing the conductive particles to which the insulating polymer is adhered after the energy applying step to room temperature. (Fig. 1 (e)). By carrying out the slow cooling step, it is possible to precipitate an insulating polymer dissolved in a small amount in the solvent and increase the thickness of the insulating polymer adhered to the insulating coating particles. The method of slow cooling is not particularly limited, and examples thereof include a method of immersing a container containing a mixture in a cooling tank while controlling the temperature, as shown in FIG. 1 (e).

Here, the mechanism by which the insulating polymer adheres to the surface of the conductive particles by the above-mentioned energy application step and any slow cooling step will be considered below with reference to the drawings.
First, before the energy application step, that is, before the polymerization reaction starts, the conductive particles and the polymerizable monomer are present in the mixture in a state of being dispersed or dissolved in a solvent (FIG. 2A). Then, when energy is applied to the mixture in the energy application step, the polymerizable monomer is polymerized in the mixture, polymerized to the precipitation critical chain length in the solvent, and then the conductive particles are used as a trigger (nucleus) for precipitation. , An insulating polymer is deposited on the surface of the conductive particles (FIG. 2 (b)). Here, the generated insulating polymer is insoluble in a solvent, or even if it is dissolved, it is very small when taken as a whole. When the polymerizable functional group remains in the precipitated insulating polymer, the polymerizable monomer reacts with the insulating polymer, further precipitation occurs, and the chemistry of the conductive particles on the surface of the conductive particles occurs. Lamination of physical and chemical insulating polymers is expected. After that, when a slow cooling step is carried out, the solubility of the insulating polymer in the solvent decreases, and as a result, the insulating polymer dissolved in a small amount in the solvent has the thickness of the insulating polymer on the surface of the conductive particles. Contribution to the increase and gradual contribution can reduce the concern of coalescence (Fig. 2 (c)). In the method for producing insulating coated particles according to an embodiment of the present invention, the selectivity of the conductive particles to the surface is higher than that of emulsion polymerization in which the insulating coated particles are embedded by random phase separation, and the insulating polymer is uniform. Can be coated (fixed). The generated insulating coating particles have higher insulating properties than the conventional ones.
The method for producing insulating coated particles according to an embodiment of the present invention includes a reaction of precipitating an insulating polymer on the surface of conductive particles, and this reaction is similar to precipitation polymerization. However, this reaction differs from ordinary precipitation polymerization in that it is not a mechanism mainly due to electrostatic attraction / adsorption, absorption of monomers and reaction initiator components, bonding by surface functional groups, and the like. ..
Further, in FIG. 2, it is shown that the entire surface of the conductive particles is coated with the insulating polymer, but this figure is merely a schematic view, and is actually one of the surfaces of the conductive particles. The part can also be coated with an insulating polymer.

The coating thickness of the insulating polymer on the surface of the conductive particles was higher when divinylbenzene was used as the polymerizable monomer than when a (meth) acrylate compound was used as the polymerizable monomer. Can be made larger.

(Settlement process)
The settling step is an arbitrary step in the method for producing insulating coated particles of the present invention, and is a step of settling the obtained insulating coated particles after an energy application step or an arbitrary slow cooling step (FIG. 1 (f)). ). By carrying out the settling step, the insulating coating particles and the solvent can be easily separated. The method of sedimentation is not particularly limited, and examples thereof include a method of allowing the container to stand for a certain period of time.

(Supernatant removal process)
The supernatant removing step is an arbitrary step in the method for producing insulating coated particles of the present invention, and is a step of removing the supernatant after an arbitrary sedimentation step (not shown). The method for removing the supernatant is not particularly limited, and examples thereof include decantation.

(Solid-liquid separation process)
The solid-liquid separation step is an arbitrary step in the method for producing insulating coated particles of the present invention, and is a solid content containing insulating coated particles after an energy applying step, an arbitrary slow cooling step, or a cleaning step described later. This is a step of separating the liquid from the liquid (not shown). The solid-liquid separation method is not particularly limited, and examples thereof include suction filtration and the like.

(Washing process)
The cleaning step is an arbitrary step in the method for producing insulating coated particles of the present invention, and is a step of cleaning solids after an arbitrary supernatant removing step or solid-liquid separation step (not shown). The cleaning method is not particularly limited, and examples thereof include a method of adding an arbitrary solvent and stirring.

(Drying process)
The drying step is an arbitrary step in the method for producing insulating coated particles of the present invention, and is a step of drying after an arbitrary supernatant removing step or a solid-liquid separation step (not shown).

Here, in the method for producing insulating coated particles according to an embodiment of the present invention, for the coverage of the polymer in the obtained insulated coated particles, for example, an appropriate solvent for adjusting the control temperature during the reaction is selected. It can be adjusted by controlling the precipitation rate of the polymer. Specifically, when the precipitation rate of the polymer is increased, the homogeneity is lowered and the coverage is lowered.
Further, in the method for producing an insulating coating particle according to an embodiment of the present invention, the average coating thickness of the polymer in the obtained insulating coating particle is, for example, a blending of a polymerizable monomer, a reaction initiator and a solvent in the mixing step. Adjust the ratio, adjust the amount of energy applied in the energy application process (for example, heating temperature), select an appropriate solvent by focusing on the solubility of the insulating polymer produced by polymerization, and focus on the polymerization reaction rate. It can be adjusted by selecting an appropriate polymerizable monomer.

<Particle-containing composition>
The particle-containing composition of the present invention is characterized by containing the above-mentioned insulating coating particles of the present invention. Since the particle-containing composition of the present invention contains the above-mentioned insulating coating particles of the present invention, it provides high conductivity and is also excellent in insulating properties.
The components other than the insulating coating particles contained in the particle-containing composition of the present invention are not particularly limited and may be appropriately selected depending on the intended purpose.

<Animate conductive adhesive>
The anisotropic conductive adhesive of the present invention is characterized by containing the above-mentioned particle-containing composition of the present invention. The anisotropic conductive adhesive of the present invention may contain the above-mentioned particle-containing composition of the present invention itself, or may further contain any component other than the above-mentioned particle-containing composition of the present invention. For example, a curable resin such as an epoxy resin, a curing agent, an organic solvent, and the like can be further contained.
Further, the anisotropic conductive adhesive of the present invention can be in the form of a film (may be an anisotropic conductive adhesive film). The anisotropic conductive adhesive film is, for example, mixed with at least the insulating coating particles of the present invention, a curable resin such as an epoxy resin, a curing agent and an organic solvent, and the obtained mixture is applied in layers, and then the obtained coating film is obtained. It can be produced by volatilizing an organic solvent from.

Since the anisotropic conductive adhesive of the present invention contains the above-mentioned particle-containing composition of the present invention, that is, contains at least the above-mentioned insulating coating particles of the present invention, it provides high conductivity and is also excellent in insulating properties. .. Specifically, the anisotropic conductive adhesive of the present invention comprises insulating coated particles that are not originally coated with an insulating polymer when they are placed between circuit boards with terminals facing each other and crimped. Excellent conductivity can be provided between the opposing terminals through the surface (the surface of the conductive particles) and / or the surface where the adhered insulating polymer is removed by the pressure during crimping. Such an effect is exhibited when the distance between adjacent terminals on the circuit board is short, and when a solvent, particularly a solvent having a low boiling point such as methyl ethyl ketone and ethyl acetate, is used for preparing the anisotropic conductive adhesive. Even so, it is brought.

Next, the present invention will be specifically described based on examples. However, the present invention is not limited to the following examples.

(Examples 1 to 7)
After putting the amount of conductive particles (manufactured by Sekisui Chemical Co., Ltd., “AUL704”) shown in Table 1 and ethanol as a solvent in an amount of 95% of the amount shown in Table 1 into a glass container, the stirring blade is placed. To prepare a slurry solution. Nitrogen was added to this slurry liquid at a flow rate of 160 mL / min for inertation, and the polymerizable monomers shown in Table 1 were added in the amounts shown in Table 1.
Ten minutes after the addition of the polymerizable monomer, the amount of the reaction initiator (oil-soluble azo compound) shown in Table 1 previously dissolved in 5% of the amount shown in Table 1 was added to the slurry solution. In this way, a mixture of the polymerizable monomer, the conductive particles, and the reaction initiator and the solvent was prepared. After adding the reaction initiator and stirring for 5 minutes, the inertation with nitrogen was stopped.
Then, the mixture was heated to 70 ° C. with stirring (that is, heat energy was applied to the mixture) and held for 3 hours, and then slowly cooled to 40 ° C. As a result, in the mixture, the polymerizable monomer was polymerized to form a polymer, and a solid content in which the surface of the conductive particles was coated with the polymer was generated. After slow cooling, the mixture was allowed to stand for 15 minutes to allow the solid content dispersed in the mixture to settle. After sedimentation, the supernatant was removed by decantation, 750 g of a solvent was added, and the mixture was stirred for 15 minutes to wash the solid content.
Then, the solid content was recovered by suction filtration, and the recovered solid content was dried at 70 ° C. for 12 hours to obtain insulating coated particles.
Here, for reference, FIG. 3 shows an image of the insulating coated particles according to Example 1 by a scanning electron microscope (SEM). FIG. 3A is a medium-magnification image and FIG. 3B is a high-magnification image.
The obtained insulating coated particles were evaluated for the average coating thickness, coating ratio and adhesiveness of the polymer according to the following methods (1) to (3).

Next, 30 parts by mass of the obtained insulating coating particles, 60 parts by mass of phenoxy resin (manufactured by Nippon Steel Chemical Co., Ltd., "YP-50"), and 40 parts by mass of liquid epoxy resin (manufactured by Mitsubishi Chemical Co., Ltd., "EP828"). 3 parts by mass of a curing agent for epoxy resin (manufactured by Sanshin Chemical Industry Co., Ltd., "SI-60L") and 1 part by mass of a silane coupling agent (manufactured by Shinetsu Chemical Industry Co., Ltd., "KBM403") in toluene. Mixed in. This mixture is applied on a PET film that has been peeled off with a bar coater, and then dried at 70 ° C. to volatilize toluene to produce an "anisometric conductive adhesive film (using toluene)" with a thickness of 20 μm. did.
Further, in the above, except that methyl ethyl ketone (MEK) was used instead of toluene and the drying temperature was changed from 70 ° C. to 50 ° C., the “anisometric conductive adhesive film” having a thickness of 20 μm was used in the same manner as above. MEK used) ”was manufactured.
Using the obtained anisotropic conductive adhesive film, the insulating property and the conductivity were evaluated according to the following methods (4) and (5).

(Comparative Example 1)
Conductive particles (manufactured by Sekisui Chemical Co., Ltd., "AUL704") were prepared. Then, various evaluations were carried out in the same manner as in Examples 1 to 7 except that the conductive particles were used instead of the insulating coating particles in Examples 1 to 7.

(Comparative Examples 2 and 3)
A crosslinked acrylic resin (manufactured by Soken Kagaku Co., Ltd., trade name: MP series) was prepared as a polymer for coating the surface of conductive particles. 4 g of this crosslinked acrylic resin and 20 g of conductive particles (manufactured by Sekisui Chemical Co., Ltd., "AUL704") were introduced into a polymerizer (manufactured by Nara Machinery Co., Ltd., trade name: NHS series), and the dry method was used. The conductive particles were coated with a polymer to obtain coated particles. The processing conditions for the hybridizer were a rotation speed of 16000 / min and a reaction vessel temperature of 60 ° C., and the hybridizer was operated until a desired coating thickness was obtained.
Here, for reference, FIG. 4 shows an image of the coated particles according to Comparative Example 2 by a scanning electron microscope (SEM). FIG. 4A is a medium-magnification image and FIG. 4B is a high-magnification image.
Then, various evaluations were carried out in the same manner as in Examples 1 to 7 except that the coated particles were used instead of the insulating coated particles in Examples 1 to 7.

(Evaluation)
The following evaluations were performed on each of the obtained coated particles.

(1) Average coating thickness of polymer After cutting each coated particle using a focused ion beam (FIB), the average thickness of the coated polymer is observed by observing the cross section with a transmission electron microscope (TEM). (Average coating thickness of polymer) (nm) was measured. The results are shown in Table 1. Specifically, among the surfaces of the conductive particles in the coated particles observed by TEM, the portion coated with the polymer is averaged so as to include the portion having the maximum coating thickness and the portion having the minimum coating thickness. The coating thickness was measured. Then, the one obtained by averaging the average coating thickness from the two coating particle samples was adopted.

(2) Polymer coverage After cutting each coated particle using a focused ion beam (FIB), the cross section is observed with a transmission electron microscope (TEM), and the weight of the total surface area of each coated particle is heavy. The ratio (%) of the surface area covered with the coalescence was determined as the coverage of the polymer. Then, it was evaluated according to the following criteria. The results are shown in Table 1.
Polymer coverage is over 40% ... A
The coverage of the polymer is 25% or more and 40% or less ... B
Polymer coverage is more than 0% and less than 25% ... C
The coverage of the polymer is 0% ... D

(3) Adhesion of Polymer 10 g of each coated particle was dispersed in 50 ml of distilled water, shaken, and then allowed to stand. Then, the supernatant liquid of this liquid was visually confirmed, and when it was not turbid, it was evaluated as ◯, and when it was turbid, it was evaluated as x. The results are shown in Table 1. If the supernatant is not turbid, it indicates that the polymer coating the surface of the conductive particles is adhered to the surface.

(4) Conductivity For evaluation of continuity, an IC substrate having a width of 1.8 mm, a length of 20 mm, and a thickness of 0.5 mm was provided, and a plurality of gold-plated bumps were formed in a single row straight arrangement along one side edge. I prepared an IC. Each bump was 30 μm × 85 μm and had a thickness of 15 μm.
Further, as a glass substrate for conductivity evaluation, an ITO pattern glass having a thickness of 0.7 mm and an electrode pattern having the same size and pitch as the bump of the IC was prepared.
Then, after the anisotropic conductive adhesive film was temporarily attached to the glass substrate, a connector sample was prepared from the bumps on the IC and the electrodes on the glass substrate. Here, the conditions for thermocompression bonding were 170 ° C., 60 MPa, 5 sec / Teflon (registered trademark) 50 μm.
For each of the prepared connection samples, the conduction resistance was measured when a current of 1 mA was passed for 500 hours under the conditions of 85 ° C. and 85% RH. When the measured value is less than 1.8Ω, it is ◎ (best), when it is 1.8Ω or more and less than 3Ω, it is ○ (good), when it is 3Ω or more and less than 5Ω, it is △ (normal), and when it is 5Ω or more. It was marked as × (defective). The results are shown in Table 1.

(5) Insulation For evaluation of insulation, an IC substrate having a width of 1.5 mm, a length of 130 mm, and a thickness of 0.5 mm was provided, and a plurality of gold-plated bumps were formed in a single row straight arrangement along one side edge. I prepared an IC. In this IC, the thickness of each bump is 15 μm, and the space between bumps is 10 μm.
Further, as a glass substrate for insulating property evaluation, an ITO pattern glass having a thickness of 0.5 mm and a comb-teeth-like electrode pattern having the same size and pitch as the bump of the IC was prepared.
Then, after the anisotropic conductive adhesive film is temporarily attached to the glass substrate, the IC is mounted while aligning the bumps on the IC with the electrode patterns on the glass substrate, and the IC is thermocompression bonded by a thermocompression bonding head to form a connector. A sample was prepared. Here, the conditions for thermocompression bonding were 170 ° C., 60 MPa, 5 sec / Teflon (registered trademark) 50 μm.
For each of the prepared connection samples, the resistance value between adjacent bumps was measured by the two-terminal method. The IC was formed with eight electrode patterns composed of 10 sets of bumps, and the number of electrode patterns in which one or more sets of short circuits occurred out of 10 sets was counted. When the measured resistance value is 108Ω or less, a short circuit occurs. When the number of electrode patterns in which a short circuit occurs is 0 (best), and when there is one electrode pattern in which a short circuit occurs, ○ (good). ), The case where the electrode pattern where the short circuit occurred was 2 places was evaluated as Δ (normal), and the case where the electrode pattern where the short circuit occurred was 3 places or more was evaluated as × (defective). The results are shown in Table 1.

* 1 Conductive particles: "AUL704" manufactured by Sekisui Chemical Co., Ltd.
* 2 Divinylbenzene: Wako Pure Chemical Industries, Ltd. * 3 (Meta) Acrylate compound A: 1.6-Hexanediol dimethacrylate, Kyoeisha Chemical Co., Ltd., "Light ester 1.6HX"
* 4 (Meta) acrylate compound B: Ethylene glycol dimethacrylate, manufactured by Kyoeisha Chemical Co., Ltd., "Light ester EG"
* 5 Reaction initiator: 2,2'-azobis (2,4-dimethylvaleronitrile), manufactured by Wako Pure Chemical Industries, Ltd., "V-65"

From Table 1, it can be seen that Examples 1 to 7 using the insulating coated particles in which the insulating polymer is fixed to at least a part of the surface of the conductive particles are excellent in both conductivity and insulating property. From FIG. 3, it can be seen that the insulating coated particles according to the examples have the insulating polymer firmly adhered to at least a part of the surface of the conductive particles.
On the other hand, in Comparative Example 1 using particles not coated with the insulating polymer, it can be seen that the insulating property is at least inferior.
Further, it can be seen that in Comparative Examples 2 and 3 using the coated particles obtained by coating the surface of the conductive particles with the polymer by the conventional dry method, at least the insulating property is inferior. This is because, as is clear from FIG. 4, especially FIG. 4A, the polymer cannot be firmly adhered to the surface of the conductive particles, and the coated polymer is an anisotropic conductive adhesive film. It is considered that this was due to erosion by the solvent used for the preparation.

According to the present invention, when circuit boards having a plurality of terminals are electrically connected to each other, while sufficiently ensuring the insulation between adjacent terminals on each board, the conductivity between the opposing terminals is maintained. It is possible to provide an insulating coating particle capable of obtaining an anisotropic conductive adhesive to be brought about, and a particle-containing composition and an anisotropic conductive adhesive containing the insulating coating particle. Further, according to the present invention, it is possible to provide a method for producing insulating coated particles capable of efficiently producing the above-mentioned insulating coated particles.

Claims (17)

An insulating polymer containing a structural unit derived from a polymerizable monomer is precipitated and fixed on at least a part of the surface of the conductive particles to form a uniform film .
The polymerizable monomer contains a monomer having two or more polymerizable functional groups.
The insulating coated particles are characterized in that the proportion of structural units derived from the monomer having two or more polymerizable functional groups is 50% by mass or more. An insulating polymer containing a structural unit derived from a polymerizable monomer is fixed to at least a part of the surface of the conductive particles.
Insulating coated particles, characterized in that the insulating polymer is a precipitate. The insulating coated particles according to claim 1 or 2, wherein the insulating polymer has a coverage of more than 40%. The polymerizable monomer contains a monomer having two or more polymerizable functional groups.
The insulating coating particles according to any one of claims 1 to 3, wherein the monomer having two or more polymerizable functional groups is divinylbenzene. The polymerizable monomer contains a monomer having two or more polymerizable functional groups.
The insulating coating particles according to any one of claims 1 to 3, wherein the monomer having two or more polymerizable functional groups is a (meth) acrylate compound. The insulating polymer according to claim 1 to 5, wherein the amount of the insulating polymer dissolved in 100 g of methyl ethyl ketone at 50 ° C. is 0.1 g or less, and the amount of the insulating polymer dissolved in 100 g of toluene at 70 ° C. is 0.1 g or less. Insulation coated particles. The insulating coating particles according to claim 1 to 6, wherein the insulating polymer has a dissolution amount of 0.1 g or less in 100 g of ethyl acetate at 50 ° C. The insulating coating particles according to any one of claims 1 to 7, wherein the insulating polymer has an average coating thickness of 50 nm or more. A mixing step of preparing a mixture of a polymerizable monomer, conductive particles, and a reaction initiator and a solvent.
After the mixing step, an inerting step of inertating the mixture and
After the inerting step, by applying energy to the mixture while stirring the mixture, an insulating polymer obtained by polymerizing the polymerizable monomer is produced, and the surface of the conductive particles is surfaced. An energy applying step of fixing the insulating polymer to at least a part of the polymer to generate insulating coated particles.
A method for producing insulating coated particles, which comprises. The method for producing an insulating coated particle according to claim 9, wherein the solvent is a solvent that dissolves the polymerizable monomer but does not dissolve the insulating polymer. The method for producing insulating coated particles according to claim 9 or 10, wherein the energy is thermal energy. The method for producing insulating coated particles according to any one of claims 9 to 11, wherein the polymerizable monomer contains a monomer having two or more polymerizable functional groups. The method for producing insulating coated particles according to claim 12, wherein the monomer having two or more polymerizable functional groups is divinylbenzene. The method for producing insulating coated particles according to claim 12, wherein the monomer having two or more polymerizable functional groups is a (meth) acrylate compound. The method for producing insulating coated particles according to any one of claims 9 to 14, wherein the insulating polymer has a ratio of structural units derived from a polymerizable monomer of 50% by mass or more. A particle-containing composition comprising the insulating coating particles according to any one of claims 1 to 8. An anisotropic conductive adhesive comprising the particle-containing composition according to claim 16.

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