JP2008066298A - Conductive hollow object and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive hollow object having small hardness and true specific gravity, and improved dispersibility to resin, and to provide a manufacturing method of the conductive hollow object. <P>SOLUTION: The conductive hollow object comprises: a hollow object body comprising an outer shell section made of a thermoplastic resin, and a hollow section surrounded by the outer shell section; and a conductive particle adhering to the outer surface of the outer shell section, or a conductive metal layer for covering the outer surface of the outer shell section. The true specific gravity is 0.01-0.65 g/cc. The manufacturing method of the conductive hollow object includes a process for covering the outer surface of the hollow object body that comprises the outer shell section made of a thermoplastic resin and the hollow section surrounded by the outer shell section and has a true specific gravity of 0.005-0.30 g/cc with a conductive metal layer by an electroless plating method. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a conductive hollow body and a method for producing the same. More specifically, the present invention relates to a conductive hollow body having excellent elasticity and a small true specific gravity, and a method for producing the same.

Main constituent materials of anisotropic conductive materials such as anisotropic conductive films, conductive pastes, conductive adhesives, conductive adhesives, and the like can be obtained by mixing conductive particles with a binder resin or the like, for example.
An important characteristic required for conductive particles is high conductivity when used in anisotropic conductive materials, and metal particles (especially ultrafine metal particles) are preferred as conductive particles. Widely used because of its excellent oxidation resistance. However, since silver ultrafine particles have a high hardness, damage to the substrate becomes a problem. Further, silver ultrafine particles have a high specific gravity, so that the problem is that they are inferior in dispersibility in resins.

Conventionally, as conductive particles having a small hardness and specific gravity, those having a metal layer on the surface of acrylic fine particles are known (see Patent Document 1). However, the acrylic fine particles have a drawback that they are not satisfactory in terms of damage to the substrate and dispersibility in the resin.
As a resin material with excellent damage to the substrate and dispersibility in the resin, the outer shell is usually a thermoplastic resin such as vinylidene chloride copolymer, acrylonitrile copolymer, and acrylic copolymer. Hollow particles obtained by expanding thermally expandable microspheres (generally called thermally expandable microcapsules) having a structure in which a hydrocarbon-based blowing agent such as isobutane or isopentane is enclosed are known. (See Patent Document 2).
Japanese Patent Publication No. 7-97717 US Pat. No. 3,615,972

  An object of the present invention is to provide a conductive hollow body having small hardness and true specific gravity and excellent dispersibility in a resin, and a method for producing the same.

As a result of diligent studies to solve the above problems, the present inventors have found that the conductive particles have a structure in which conductive particles are attached to a hollow body body composed of an outer shell portion made of a thermoplastic resin and a hollow portion surrounded by the outer shell portion. A hollow hollow body, a hollow hollow body made of a thermoplastic resin, and a hollow hollow body composed of a hollow portion surrounded by the hollow hollow body and covered with a conductive metal layer, and its true specific gravity falls within a specific range. If it exists, the knowledge that the said subject will be solved at once will be acquired, and this invention will be reached | attained.
That is, the conductive hollow body according to the present invention includes a hollow body body composed of an outer shell part made of a thermoplastic resin and a hollow part surrounded by the outer shell part, and conductive particles attached to the outer surface of the outer shell part or It consists of a conductive metal layer covering the outer surface of the outer shell, and has a true specific gravity of 0.01 to 0.65 g / cc.

The average particle diameter of the conductive hollow body is preferably 0.1 to 1000 μm. The coefficient of variation CV value of the particle size distribution of the conductive hollow body is preferably 30% or less.
It is preferable that the deformation rate during compression is 70% or more and the restoration rate after decompression is 40% or less.
The conductive particles are preferably particles containing at least one selected from the group consisting of silver, gold, platinum, nickel, copper, carbon black, zinc oxide and titanium oxide. On the other hand, it is preferable that the conductive metal layer contains at least one metal selected from the group consisting of silver, gold, platinum, nickel and copper.

The method for producing a conductive hollow body according to the present invention comprises an outer shell portion made of a thermoplastic resin and a hollow portion surrounded by the outer shell portion, and has a true specific gravity of 0.005 to 0.30 g / cc. It is a manufacturing method including the process of coat | covering an outer surface with an electroconductive metal layer by the electroless-plating method.
Another method for producing a conductive hollow body according to the present invention includes a thermally expandable microsphere that is comprised of a foaming agent encapsulated in an outer shell made of a thermoplastic resin and having a boiling point equal to or lower than the softening point of the thermoplastic resin. And the step of mixing the conductive particles, the mixture obtained in the mixing step is heated to a temperature above the softening point to expand the thermally expandable microspheres, and the outside of the obtained hollow body main body It is a manufacturing method including the process of attaching the said electroconductive particle to the surface.

The conductive hollow body of the present invention has low hardness and true specific gravity, and is excellent in dispersibility in a resin.
All of the methods for producing a conductive hollow body of the present invention can efficiently produce a conductive hollow body having low hardness and true specific gravity and excellent dispersibility in a resin.

[Conductive hollow body]
The conductive hollow body of the present invention comprises a hollow body body and conductive particles or a conductive metal layer. Since the hollow body is made of a thermoplastic resin as will be described later, the hardness and the true specific gravity are small and the dispersibility in the resin is excellent. The conductivity of the conductive hollow body is exhibited by the conductive particles or the conductive metal layer.
The true specific gravity of the conductive hollow body is 0.01 to 0.65 g / cc, preferably 0.02 to 0.55 g / cc, more preferably 0.03 to 0.45 g / cc, and particularly preferably 0. 0.04 to 0.40 g / cc, most preferably 0.05 to 0.35 g / cc. When the true specific gravity is smaller than 0.01 g / cc, the uniform dispersibility may be lowered when used as a conductive material, which is not preferable. On the other hand, when the true specific gravity is larger than 0.65 g / cc, the effect of lowering the specific gravity is lowered when used as a conductive material, so that the amount of the conductive hollow body added becomes large, which is uneconomical.

The average particle size (volume average particle size) of the conductive hollow body is not particularly limited because it can be freely designed according to the use, but is usually 0.1 to 1000 μm, preferably 0.3 to 500 μm, More preferably, it is 0.5-300 micrometers, Most preferably, it is 0.8-200 micrometers.
The coefficient of variation CV of the particle size distribution of the conductive hollow body is not particularly limited, but is preferably 30% or less, more preferably 25% or less, and particularly preferably 20% or less. The variation coefficient CV is calculated by the following calculation formulas (1) and (2).

（式中、sは粒子径の標準偏差、＜ｘ＞は平均粒子径、ｘ_i
はｉ番目の粒子径、ｎは粒子の数である。）

(In the formula, s is the standard deviation of the particle diameter, <x> is the average particle diameter, x _i
Is the i-th particle diameter, and n is the number of particles. )

In the conductive hollow body of the present invention, when the compression deformation rate and the decompression restoration rate are within a specific range, the hardness is small and the elasticity is high.
Although it will not specifically limit if the deformation rate at the time of compression of an electroconductive hollow body is 70% or more, Preferably it is 70 to 99.6%, More preferably, it is 72 to 95%, Most preferably, it is 75 to 90%. When the deformation rate during compression is less than 70%, the conductive hollow body may not be elastic, that is, the hardness may be increased, which may be undesirable. On the other hand, when the deformation rate at the time of compression exceeds 99.6%, the thermoplastic resin in the outer shell portion of the hollow body may be broken.
The restoration rate after decompression of the conductive hollow body is not particularly limited as long as it is 40% or less, but is preferably 0.01 to 40%, more preferably 0.01 to 35%, and particularly preferably 0.01 to 35%. 30%. When the restoration rate after decompression is more than 40%, the conductive hollow body does not have elasticity, that is, becomes brittle, which is not preferable. On the other hand, the restoration rate after decompression of less than 0.01% is synonymous with the fact that the shape is almost restored to the shape before compression after decompression.

Hereinafter, the hollow body main body, the conductive particles, and the conductive metal layer will be described in detail.
(Hollow body)
The hollow body main body constituting the conductive hollow body of the present invention includes an outer shell portion and a hollow portion surrounded by the outer shell portion. The hollow body is (substantially) spherical and has a hollow portion corresponding to a large cavity inside. If the shape of the hollow body is compared with familiar articles, for example, a soft tennis ball can be mentioned. Since the hollow body has a small hardness and true specific gravity, it imparts the same physical properties to the conductive hollow body of the present invention.

The average particle size of the hollow body is not particularly limited, but is preferably 0.1 to 1000 μm, more preferably 0.3 to 500 μm, particularly preferably 0.5 to 300 μm, and most preferably 0.8 to 200 μm.
The true specific gravity of the hollow body is not particularly limited, but is usually 0.005 to 0.30 g / cc, preferably 0.010 to 0.25 g / cc, more preferably 0.015 to 0. 20 g / cc. When the true specific gravity of the hollow body is less than 0.005 g / cc, the durability may be lowered. On the other hand, when the true specific gravity of the hollow body is larger than 0.30 g / cc, the effect of lowering the specific gravity is lowered, so that the amount of the conductive hollow body is increased, which may be uneconomical.

The outer shell portion constituting the hollow body is made of a thermoplastic resin constituting the outer shell of the thermally expandable microsphere described in detail below. The outer shell portion is surrounded by the outer surface and the inner surface, has no end portion, and has a continuous shape. The thickness of the outer shell, that is, the distance between the outer surface and the inner surface is preferably uniform, but may be non-uniform.
The average thickness of the outer shell portion is not particularly limited, but is preferably 0.01 to 10 μm, more preferably 0.1 to 5 μm, and particularly preferably 0.2 to 1 μm. When the average thickness of the outer shell is smaller than 0.01 μm, the durability may be lowered. On the other hand, when the average thickness of the outer shell is larger than 10 μm, the elasticity may be lowered. The average thickness of the outer shell is an average thickness of the outer shell calculated from the average particle diameter of the entire thermally expandable microsphere, and is calculated by the calculation formula shown in the examples.

The ratio of the average thickness of the outer shell part to the average particle diameter of the hollow body body (average thickness of the outer shell part / average particle diameter of the hollow body body) is not particularly limited, but is preferably 0.0005 to 0.1. More preferably, it is 0.0010 to 0.7, and particularly preferably 0.0015 to 0.5. If the average thickness of the outer shell / the average particle diameter of the hollow body is outside the range of 0.0005 to 0.1, the hollow body may not exhibit elasticity.
The hollow part constituting the hollow body is (substantially) spherical and is in contact with the inner surface of the outer shell part. The hollow portion is basically filled with a gas obtained by vaporizing the foaming agent described in detail below, and the foaming agent may be in a liquefied state. All or part of the blowing agent may be replaced with another gas such as air.

There may be a plurality of hollow portions in the hollow body, but usually there is often one large hollow portion.
(Conductive particles)
The conductive particles are attached to the outer surface of the outer shell. The adhesion referred to here may be simply a state in which conductive particles are adsorbed on the outer surface of the hollow body, and the thermoplastic resin near the outer surface of the hollow body is melted by heating, This means that the conductive particles may sink into the outer surface and be fixed.

The particle shape of the conductive particles may be indefinite or spherical, but it is preferable to contain 50% or more of spherical particles from the viewpoint of powder fluidity at room temperature. Here, the spherical shape means that the ratio of the major axis / minor axis of the particles is in the range of 1.0 to 1.5.
Examples of the material constituting the conductive particles include chromium, iron, copper, cobalt, nickel, titanium, palladium, zinc, tin, gold, platinum, silver, aluminum, indium, and the like; zinc oxide, titanium oxide, and oxide. Examples thereof include metal oxides such as indium and tin oxide; carbon black and the like. The conductive particles may be particles made of an alloy of these metals, and may be composed of one or more of particles made of the metal, particles made of the metal oxide, and particles made of carbon black. Good.

The conductive particles are preferably particles containing at least one selected from the group consisting of silver, gold, platinum, nickel, copper, carbon black, zinc oxide and titanium oxide, because the conductivity is good, and oxidation is preferable. From the viewpoint of properties, it is more preferable that the particles contain silver.
The average particle diameter of the conductive particles is appropriately selected depending on the hollow body body to be used, and is not particularly limited. However, from the viewpoint of conductivity, it is preferably 0.001 to 10 μm, more preferably 0.005 to 5 μm, particularly Preferably it is 0.01-3 micrometers.

The ratio of the average particle diameter of the conductive particles to the average particle diameter of the hollow body main body (average particle diameter of the conductive particles / average particle diameter of the hollow body main body) is preferably 0 from the viewpoint of adhesion to the hollow body surface. .20 or less, more preferably 0.15 or less, and particularly preferably 0.01 or less.
The weight ratio of the conductive particles and the hollow body (conductive particles / hollow body) is not particularly limited, but is preferably 99.5 / 0.5 to 50/50, more preferably 99/1. 55/45, particularly preferably 97/3 to 60/40. When the conductive particles / hollow body main body (weight ratio) is larger than 99.5 / 0.5, the true specific gravity of the conductive hollow body may increase and the effect of reducing the specific gravity may not be exhibited. On the other hand, when the conductive particle / hollow body main body (weight ratio) is smaller than 50/50, the surface coating of the conductive particles may be insufficient, resulting in deterioration of conductivity or generation of a fused body during production. .
(Conductive metal layer)

The conductive metal layer covers the outer surface of the outer shell portion.
Examples of the conductive metal layer may include the metals described in the description of the conductive particles, and may be made of an alloy of these metals.

When the conductive metal layer contains at least one metal selected from the group consisting of silver, gold, platinum, nickel and copper, it is preferable because the conductivity is good, and from the viewpoint of oxidizing properties, it contains silver. More preferably, it is a particle.
The average thickness of the conductive metal layer is not particularly limited, but is preferably 0.01 μm to 10 μm, more preferably 0.05 to 2 μm, and particularly preferably 0.1 from the viewpoint of the specific gravity of the conductive hollow body. ˜1 μm. When the average thickness of the conductive metal layer is smaller than 0.01 μm, the conductivity may be lowered. On the other hand, when the average thickness of the conductive metal layer is larger than 10 μm, the true specific gravity of the conductive hollow body is increased, and the effect of lowering the specific gravity may be reduced.
(Method for producing conductive hollow body)

The method for producing the conductive hollow body is not particularly limited. For example, the outer surface of the hollow body is covered with a conductive metal layer by electroless plating, electroplating, vacuum deposition, ion plating, ion sputtering, or the like. The method of manufacturing; It manufactures by the method etc. which adhere electroconductive particle to the outer surface of a hollow body main body. Among these production methods, the method using electroless plating described later and the method of attaching conductive particles are preferable in that the load on the hollow body main body is small in load such as pressure change and temperature change.
[Method for producing conductive hollow body (1)]
The manufacturing method of the electroconductive hollow body of this invention is a manufacturing method including the process of coat | covering the outer surface of a hollow body main body with an electroconductive metal layer by the electroless-plating method.

The hollow body main body is composed of an outer shell portion made of a thermoplastic resin and a hollow portion surrounded by the outer shell portion, and has a true specific gravity of 0.005 to 0.30 g / cc. The hollow body main body is as described above.
The electroless plating method for coating the outer surface of the hollow body with a conductive metal layer is generally divided into an etching process, an activation process, and an electroless plating process in order.

An etching process is a process of forming the unevenness | corrugation in the outer surface of a hollow body main body using etching liquid, and improving the adhesiveness of the electroconductive metal layer which coat | covers an outer surface. The etching solution is not particularly limited, and examples thereof include an alkaline aqueous solution such as a caustic soda aqueous solution and an acid aqueous solution such as a chromic anhydride aqueous solution. These etching liquids may be used independently and 2 or more types may be used together. Note that the etching step is not necessarily required, and may be omitted when a highly adhesive conductive metal layer is formed.
Next, the activation step is a step of activating the catalyst layer while forming a layer (catalyst layer) made of the catalyst on the outer surface of the hollow body main body (after the etching step). The activation of the catalyst layer promotes metal deposition in the next electroless plating step. Although there is no limitation in particular as a catalyst used at an activation process, For example, alkali catalysts (alkali catalyst), such as an amine complex type catalyst, etc. are mentioned. These catalysts may be used independently and 2 or more types may be used together.

Finally, the electroless plating step is a step of coating the outer surface of the hollow body main body on which the catalyst layer is formed with a conductive metal layer. In the electroless plating step, a conductive metal layer is formed on the outer surface of the hollow body by immersing the hollow body in which the catalyst layer is formed in an electroless metal plating solution. When a silver plating layer is formed on the outer surface of the hollow body, the catalyst layer of the hollow body is reduced with a reducing agent such as dimethylaminoborane and then immersed in an electroless silver plating solution or a catalyst layer is formed. A silver plating layer can be formed on the outer surface of the hollow body main body by immersing the hollow body main body in an electroless silver plating solution and then adding a reducing agent for reduction.
[Method for producing conductive hollow body (2)]
Another method for producing a conductive hollow body according to the present invention includes a step of mixing thermally expandable microspheres and conductive particles (mixing step), and the mixture obtained in the mixing step is brought to a temperature above the softening point. It is a manufacturing method including a step (attachment step) of heating and expanding the thermally expandable microspheres and attaching the conductive particles to the outer surface of the obtained hollow body main body.
(Mixing process)

The mixing step is a step of mixing thermally expandable microspheres and conductive particles.
The conductive particles used in the mixing step are as described above. The heat-expandable microspheres are composed of a foaming agent that is encapsulated in an outer shell made of a thermoplastic resin and has a boiling point equal to or lower than the softening point of the thermoplastic resin. The thermally expandable microspheres expand by heating at a temperature above the softening point of the thermoplastic resin, and the hollow body body is obtained.

The weight ratio of the heat-expandable microspheres and the conductive particles (conductive particles / heat-expandable microspheres) in the mixing step is not particularly limited, but is preferably 99.5 / 0.5 to 50/50, More preferably, it is 99 / 1-55 / 45, Most preferably, it is 97 / 3-60 / 40. When the conductive particle / thermally expandable microsphere (weight ratio) is larger than 99.5 / 0.5, the true specific gravity of the conductive hollow body is increased, and the effect of reducing the specific gravity is decreased. On the other hand, when the conductive particles / heat-expandable microspheres (weight ratio) is smaller than 50/50, the surface coating becomes insufficient, resulting in deterioration of conductivity and occurrence of a fused product during production.
The thermally expandable microsphere is composed of an outer shell made of a thermoplastic resin and a foaming agent encapsulated therein and having a boiling point equal to or lower than the softening point of the thermoplastic resin. It exhibits thermal expansibility (property that the entire microsphere expands by heating). In the following description, the inclusion substance and the foaming agent may be used synonymously.

The foaming agent is not particularly limited as long as it has a boiling point equal to or lower than the softening point of the thermoplastic resin. For example, hydrocarbons having 1 to 12 carbon atoms and their halides; fluorine-containing compounds; tetraalkylsilanes; Examples thereof include a compound that thermally decomposes by heating amide or the like to generate a gas. These foaming agents may be used alone or in combination of two or more.
Examples of the hydrocarbon having 1 to 12 carbon atoms include propane, cyclopropane, propylene, butane, normal butane, isobutane, cyclobutane, normal pentane, cyclopentane, isopentane, neopentane, normal hexane, isohexane, cyclohexane, heptane, and cycloheptane. , Hydrocarbons such as octane, isooctane, cyclooctane, 2-methylpentane, 2,2-dimethylbutane, and petroleum ether. These hydrocarbons may be linear, branched or alicyclic, and are preferably aliphatic.
Examples of the hydrocarbon halide having 1 to 12 carbon atoms include methyl chloride, methylene chloride, chloroform and carbon tetrachloride. These halides are preferably the above-described hydrocarbon halides (fluoride, chloride, bromide, iodide, etc.).

The fluorine-containing compound is not particularly limited, and for example, a compound having an ether structure, not containing a chlorine atom and a bromine atom, and having 2 to 10 carbon atoms is preferable. Specifically, C ₃ H ₂ F ₇ OCF ₂ H, C ₃ HF ₆ OCH ₃ , C ₂ HF ₄ OC ₂ H ₂ F ₃ , C ₂ H ₂ F ₃ OC ₂ H ₂ F ₃ , C ₄ HF ₈ OCH ₃ , C ₃ H ₂ F ₅ OC ₂ H ₃ F ₂ , C ₃ HF ₆ OC ₂ H ₂ F ₃ , C ₃ H ₃ F ₄ OCHF ₂ , C ₃ HF ₆ OC ₃ H ₂ F ₅ , C ₄ H _{3 F 6 OCHF 2, C 3} H 3 F 4 OC 2 HF 4, C 3 HF 6 OC 3 H 3 F 4, C 3 F 7 OCH 3, C 4 F 9 OCH 3, C 4 F 9 OC 2 H 5 And hydrofluoroethers such as C ₇ F ₁₅ OC ₂ H ₅ . The (fluoro) alkyl group of the hydrofluoroether may be linear or branched.
The heat-expandable microsphere is composed of, for example, a thermoplastic resin obtained by polymerizing a monomer mixture containing a radical polymerizable monomer, and by appropriately blending and polymerizing a polymerization initiator in the monomer mixture. The outer shell of the thermally expandable microsphere can be formed.

The radical polymerizable monomer is not particularly limited. For example, nitrile monomers such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, fumaronitrile; acrylic acid, methacrylic acid, itaconic acid Carboxyl group-containing monomers such as maleic acid, fumaric acid and citraconic acid; vinylidene chloride; vinyl acetate; methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, (Meth) acrylate monomers such as t-butyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, β-carboxyethyl acrylate; styrene, α-methylstyrene , Chlorostyrene etc. Tylene monomers; acrylamide monomers such as acrylamide, substituted acrylamide, methacrylamide, substituted methacrylamide; N-phenylmaleimide, N- (2-chlorophenyl) maleimide, N-cyclohexylmaleimide, N-laurylmaleimide, etc. And maleimide monomers. As for the carboxyl group-containing monomer, some or all of the carboxyl groups may be neutralized during polymerization.
These radically polymerizable monomers may be used alone or in combination of two or more. Among these, the monomer mixture was selected from a nitrile monomer, a (meth) acrylic acid ester monomer, a carboxyl group-containing monomer, a styrene monomer, vinyl acetate, and vinylidene chloride. A monomer mixture containing at least one radically polymerizable monomer is preferred. In particular, the monomer mixture is preferably a monomer mixture containing a nitrile monomer as an essential component because heat resistance can be imparted. The weight ratio of the nitrile monomer is preferably 80% by weight or more, more preferably 90% by weight or more, particularly preferably 95% by weight or more, considering heat resistance with respect to the monomer mixture. It is.

  In addition, when the monomer mixture is a monomer mixture containing a nitrile monomer and a carboxyl group-containing monomer as an essential component, heat resistance can be imparted, and the thermally expandable microspheres can be expanded. The resulting thermally expanded microspheres can be manufactured to have a re-expandable capacity, and re-expansion is initiated at a temperature of 90 ° C. or higher (preferably 100 ° C. or higher, more preferably 120 ° C. or higher). Therefore, it is more preferable. The weight ratio of the nitrile monomer is based on the monomer mixture considering the retention rate and foamability of the encapsulated foaming agent, as well as adjusting the re-expansion start temperature of the thermally expanded microspheres. And preferably 20 to 95% by weight, more preferably 20 to 80% by weight, still more preferably 20 to 60% by weight, particularly preferably 20 to 50% by weight, most preferably 20 to 40% by weight. In addition, the weight ratio of the carboxyl group-containing monomer is determined by adjusting the re-expansion start temperature of the thermally expanded microspheres, and further considering the inclusion retention rate and foamability of the encapsulated foaming agent. Preferably it is 5 to 80 weight% with respect to a mixture, More preferably, it is 20 to 80 weight%, More preferably, it is 40 to 80 weight%, Most preferably, it is 50 to 80 weight%, Most preferably Is 60 to 80% by weight.

When the monomer mixture contains a carboxyl group-containing monomer as an essential component, it reacts with the carboxyl group of the carboxyl group-containing monomer as a monomer other than the carboxyl group-containing monomer contained in the monomer component A monomer may be contained. Examples of the monomer that reacts with the carboxyl group of the carboxyl group-containing monomer include, for example, N-methylol (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth). Acrylate, magnesium mono (meth) acrylate, zinc mono (meth) acrylate, vinyl glycidyl ether, propenyl glycidyl ether, glycidyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy Examples thereof include butyl (meth) acrylate and 2-hydroxy-3-phenoxypropyl (meth) acrylate. The weight ratio of the monomer that reacts with the carboxyl group of the carboxyl group-containing monomer is preferably 0.1 to 10% by weight, more preferably 1 to 8% by weight, based on the monomer mixture. Most preferably, it is 3 to 5% by weight.
The monomer mixture may contain a polymerizable monomer (crosslinking agent) having two or more polymerizable double bonds in addition to the radical polymerizable monomer. By polymerizing using a crosslinking agent, the content of aggregated microspheres contained in the thermally expanded microspheres obtained by this production method is reduced, and the retention rate of the encapsulated foaming agent after thermal expansion (encapsulation retention) Rate) is suppressed, and effective thermal expansion can be achieved.

The weight ratio of the crosslinking agent is not particularly limited, but it is preferable for the monomer mixture in consideration of the degree of crosslinking, the retention rate of the foaming agent encapsulated in the outer shell, heat resistance and thermal expansion. Is 0.01 to 5% by weight, more preferably 0.05 to 3% by weight.
There is no limitation in particular about a polymerization initiator, A well-known polymerization initiator can be used. The polymerization initiator is preferably an oil-soluble polymerization initiator that is soluble in the radical polymerizable monomer.

Thermally expansible microspheres can be manufactured using various methods used in a conventionally known method for manufacturing thermally expandable microcapsules.
That is, a monomer mixture containing a radically polymerizable monomer and optionally containing a crosslinking agent, a polymerization initiator, and a foaming agent are mixed, and the resulting mixture is mixed with an aqueous suspension containing an appropriate dispersion stabilizer and the like. For example, suspension polymerization in a suspension.

Although superposition | polymerization temperature is freely set by the kind of polymerization initiator, Preferably it is 40-100 degreeC, More preferably, it is 45-90 degreeC, Most preferably, it controls in the range of 50-85 degreeC. The initial polymerization pressure is 0 to 5.0 MPa, more preferably 0.1 to 3.0 MPa, and particularly preferably 0.2 to 2.0 MPa in terms of gauge pressure.
The average particle diameter of the heat-expandable microsphere is not particularly limited because it can be designed freely according to the use, and is preferably 1 to 100 μm, more preferably 2 to 80 μm, and particularly preferably 5 to 60 μm. is there.

Further, the coefficient of variation CV of the particle size distribution of the thermally expandable microspheres is not particularly limited, but is preferably 30% or less, more preferably 25% or less, and particularly preferably 20% or less.
In the mixing step, the apparatus used for mixing the thermally expandable microspheres and the conductive particles is not particularly limited, and can be performed using an apparatus having a very simple mechanism such as a container and a stirring blade. . Moreover, you may use the powder mixer which can perform a general rocking | swiveling or stirring. Examples of the powder mixer include a powder mixer that can perform rocking stirring or stirring, such as a ribbon mixer and a vertical screw mixer. In recent years, super mixers (manufactured by Kawata Co., Ltd.), high-speed mixers (manufactured by Fukae Co., Ltd.), and Newgram Machines (Seishin Co., Ltd.), which are efficient and multifunctional powder mixers by combining stirring devices Product), SV mixer (manufactured by Shinko Environmental Solution Co., Ltd.), and the like.
(Adhesion process)

In the attaching step, the mixture containing the heat-expandable microspheres and the conductive particles obtained in the mixing step is heated to a temperature above the softening point of the thermoplastic resin constituting the outer shell of the heat-expandable microsphere. It is a process. In the attaching step, the thermally expandable microspheres are expanded, and the conductive particles are attached to the outer surface of the obtained hollow body. The term “adhesion” as used herein may be a state in which conductive particles are simply adsorbed on the outer surface of the hollow body main body, and the thermoplastic resin near the outer surface of the hollow body main body is melted by heating, and the hollow body main body. The conductive particles may sink into the outer surface of the substrate and be fixed.
Heating may be performed using a general contact heat transfer type or direct heating type mixed drying apparatus. The function of the mixing type drying apparatus is not particularly limited, but it is preferable to be able to adjust the temperature and disperse and mix the raw materials, and optionally equipped with a decompression device and a cooling device for speeding up drying. Although there is no limitation in particular as an apparatus used for a heating, For example, a Ladige mixer (made by Matsubo Co., Ltd.), solid air (Hosokawa Micron Co., Ltd.), etc. can be mentioned.

The heating temperature condition depends on the type of thermally expandable microspheres, but it is preferable to set the optimum expansion temperature, preferably about 60 to 250 ° C, more preferably 70 to 230 ° C, and still more preferably 80 to 220 ° C. It is.
[Use of conductive hollow bodies]
The conductive hollow body of the present invention can be applied in various ways. For example, a conductive composition can be obtained by dispersing the conductive hollow body of the present invention in a resin.

As the resin, known rubbers, thermosetting resins and thermoplastic resins can be used.
Examples of rubbers include natural rubber, butyl rubber, and silicon rubber.

Examples of the thermosetting resin include an epoxy resin, a phenol resin, and a melamine resin.
Examples of the thermoplastic resin include polyolefin resins such as polyethylene, ethylene-vinyl acetate copolymer and ethylene- (meth) acrylic acid ester copolymer; polymethyl (meth) acrylate, polyethyl (meth) acrylate and polybutyl (meta ) Acrylate resins such as acrylates; polystyrene resins such as polystyrene, styrene-acrylic acid ester copolymers, SB type styrene-butadiene block copolymers, styrene-isoprene block copolymers and their water additives Is mentioned.

Examples of the present invention will be specifically described below. The present invention is not limited to these examples.
About the thermally expansible microsphere manufactured by the Example and the comparative example, the physical property was measured in the way shown below, and also the performance was evaluated.

[Measurement of average particle size and particle size distribution]
A laser diffraction particle size distribution analyzer (HEROS & RODOS manufactured by SYMPATEC) was used. The dispersion pressure of the dry dispersion unit was 5.0 bar and the degree of vacuum was 5.0 mbar, measured by a dry measurement method, and the D50 value was taken as the average particle size.
[Measurement of true specific gravity]
The true specific gravity was measured by a liquid displacement method (Archimedes method) using isopropyl alcohol at a temperature of 25 ° C.

(Measurement of true specific gravity of thermally expandable microspheres)
True specific gravity d _c is the ambient temperature 25 ° C., as measured by 50% relative humidity immersion method using isopropyl alcohol in an atmosphere of (Archimedes method).
Specifically, the volumetric flask having a capacity of 100 cc was emptied and dried, and the weight of the volumetric flask (WB ₁ ) was weighed. After the weighed volumetric flask was accurately filled with isopropyl alcohol to the meniscus, the weight (WB ₂ ) of the volumetric flask filled with 100 cc of isopropyl alcohol was weighed.
Further, the volumetric flask with a capacity of 100 cc was emptied and dried, and the weight of the volumetric flask (WS ₁ ) was weighed. The weighed volumetric flask was filled with about 50 cc of thermally expandable microspheres, and the weight (WS ₂ ) of the volumetric flask filled with thermally expandable microspheres was weighed. Then, the weight (WS ₃ ) after accurately filling the meniscus with isopropyl alcohol so that bubbles do not enter the volumetric flask filled with thermally expandable microspheres was weighed. Then, the _{WB 1, WB 2, WS 1} , WS 2 and WS ₃ obtained by introducing the following formula was calculated the true specific gravity _{d c} of the heat-expandable microspheres.
True specific gravity d _c = {(WS ₂ −WS ₁ ) × (WB ₂ −WB ₁ ) / 100} / {(WB ₂ −WB ₁ ) − (WS ₃ −WS ₂ )}
The true specific gravity of the thermally expanded microsphere was also calculated in the same manner as described above.

[Measurement of true specific gravity of outer shell resin of microsphere]
The true specific gravity d _p of the outer shell resin (thermoplastic resin constituting the outer shell) was measured by dispersing 30 g of thermally expandable microspheres in 900 ml of acetonitrile and then treating with ultrasonic disperser for 30 minutes, and at room temperature for 3 hours. After leaving it to stand, it was dried by heating at 120 ° C. for 5 hours. The obtained dried microspheres were further dried under reduced pressure with a vacuum pump for 2 hours, and it was confirmed that there was no mass change, and the true specific gravity of the outer shell resin was measured in the same manner as in the true specific gravity measurement method.

[Measurement of moisture content of thermally expandable microspheres]
As a measuring apparatus, a Karl Fischer moisture meter (MKA-510N type, manufactured by Kyoto Electronics Industry Co., Ltd.) was used for measurement.
[Measurement of encapsulation rate of foaming agent enclosed in thermally expandable microspheres]
1.0 g of thermally expandable microspheres were placed in a stainless steel evaporation dish having a diameter of 80 mm and a depth of 15 mm, and the weight (W ₁ ) was measured. 30 ml of acetonitrile was added and dispersed uniformly, left at room temperature for 3 hours, then heated at 120 ° C. for 2 hours, and the weight (W ₂ ) after drying was measured. The encapsulation rate of the foaming agent is calculated by the following formula.
Inclusion rate (% by weight) = (W ₁ −W ₂ ) (g) /1.0 (g) × 100− (water content) (% by weight)
(In the formula, the moisture content is measured by the above method.)

(Calculation of outer shell average thickness)
The outer shell average thickness is calculated according to the following formula.
Outer shell average thickness = <x> / 2 _{[1- {1-d c (1} -G / 100) / d p} 1/3 ]
<X>: Average particle diameter (μm) of the whole thermally expandable microsphere
d _c : average true specific gravity of microsphere (g / cc)
d _p : Average true specific gravity (g / cc) of the thermoplastic resin constituting the outer shell
G: Inclusion rate (% by weight)

[Measurement of deformation rate during compression and restoration rate after decompression]
The conductive hollow body is put in an aluminum cup having a diameter of 6 mm (inner diameter 5.65 mm) and a depth of 4.8 mm to a height of about 4 mm, and an aluminum lid having a diameter of 5.6 mm and a thickness of 0.1 mm is formed on the upper part of the conductive hollow body layer. A sample was placed as a sample. Then, using a DMA (DMAQ800 type, manufactured by TA instruments), a conductive hollow body layer in a state where a force of 0.01 N was applied to the sample from the top of the aluminum lid with a pressurizer under an environment of 25 ° C. to measure the height _{L 1.} Thereafter, it was measured the height _{L 2} of the conductive hollow body layer of an electrically conductive hollow body layer from 0.01N to 18N at a rate of 10 N / min after pressing. The height _{L 3} of the conductive hollow body layer after depressurized at a rate of 10 N / min from 18N to 0.01N were measured. Then, as shown in the following equation, the deformation rate during compression is defined from the ratio of the measured height L ₁ and L ₂ of the conductive hollow body layer. Further, the restoration rate after decompression is defined from the ratio of the measured height L ₁ and L _{3 of} the conductive hollow body layer.
Deformation rate during compression (%) = (1−L ₂ / L ₁ ) × 100
Restoration rate after decompression (%) = (1−L ₃ / L ₁ ) × 100

[Measurement of average coating thickness of metal layer]
About 0.5 g of conductive hollow body is precisely weighed and dissolved in 10 ml of 30% nitric acid aqueous solution. Then, the solution is accurately measured to 200 ml while being filtered through a filter paper. About silver content WA _Ag and nickel content W _Ni Is Cu-PAN (metal indicator, manufactured by Dojin Chemical Co., Ltd.) under weak acidity, and copper content W _Cu is a 0.01M EDTA standard solution using Cu-PAN (metal indicator, manufactured by Dojin Chemical Co., Ltd.) as an indicator under weak basicity. Each was measured by chelate titration. The thickness of each metal plating layer is calculated by the following formula.
Silver plating layer thickness (μm) = (ρ _P × W _Ag × D) / {6 × ρ _Ag × (100−W _Ag )}
Nickel plating layer thickness (μm) = (ρ _P × W _Ni × D) / {6 × ρ _Ni × (100−W _Ni )}
Copper plating layer thickness (μm) = (ρ _P × W _Cu × D) / {6 × ρ _Cu × (100−W _Cu )}
ρ _P : Specific gravity of the hollow body ρ _Ag : Specific gravity of silver ρ _Ni : Specific gravity of nickel ρ _Cu : Specific gravity of copper W _Ag : Silver content (%)
W _Ni : Nickel content (%)
W _Cu : copper content (%)
D: Average particle diameter of the hollow body (μm)

[Evaluation of Dispersibility of Conductive Hollow Body]
2.5 parts by weight of a conductive hollow body was dispersed in 100 parts by weight of an epoxy resin (epoxy adhesive: Araldai Rapid, manufactured by Huntsman Advanced Materials) and cured at 20 to 25 ° C. for 24 hours. . Thereafter, the resulting cured product was sliced with a microtome (Leica, RM2235). Next, the sliced cross section was observed with an electron microscope (50 times magnification), and the dispersibility of the conductive hollow body was visually determined.

[Example 1]
Matsumoto Microsphere F-80ED (manufactured by Matsumoto Yushi Seiyaku Co., Ltd., average particle size: 100.0 μm, true specific gravity: 0.022 g / cc, outer shell average thickness: 0.30 μm, CV: 29%) as a hollow body 1g was weighed, dispersed in a pre-dip solution for powder plating (Okuno Pharmaceutical Co., Ltd.), and etched by stirring at 30 ° C. for 30 minutes. The etched hollow body was washed with water, added to 100 ml of a Pd-catalyzed solution containing 1% by weight of palladium sulfate, and stirred at 30 ° C. for 30 hours to adsorb palladium ions to the particles. The particles were collected by filtration and washed with water, and then added to a 0.5% by weight dimethylamine borane solution (adjusted to pH 6.0) to obtain a hollow body main body in which Pd was activated.
A suspension was obtained by adding 500 ml of distilled water to the obtained Pd-activated hollow body main body and sufficiently dispersing using an ultrasonic treatment machine. While stirring this suspension at 50 ° C., an electroless plating solution (adjusted to pH 7.5) composed of 50 g / L silver sulfate, 40 g / L sodium hypophosphite, and 50 g / L citric acid was gradually added. Electroless silver plating was performed. When the metal coating layer became approximately 0.10 μm, the addition of the electroless plating solution was stopped, and after substitution with alcohol, vacuum drying was performed to obtain a conductive hollow body coated with silver (Ag plating layer thickness: 0.15 μm, true specific gravity: 0.138 g / cc, average particle size: 100.4 μm, deformation rate during compression 81%, restoration rate after decompression 30%). The obtained conductive hollow body showed conductivity. The evaluation of dispersibility by SEM was good.

[Comparative Example 1]
<Preparation of hollow body>
To 340 g of ion-exchanged water, 25 g of a 20% by weight aqueous solution of colloidal silica and 10 g of a 10% by weight aqueous solution of polystyrene sulfonic acid were uniformly mixed to obtain an aqueous phase. Next, 80 g of acrylonitrile, 10 g of methacrylic acid, 0.8 g of hydroxyethyl methacrylate, 1.5 g of ethylene glycol dimethacrylate, 10 g of methyl methacrylate, 0.5 g of azobisisobutyronitrile and 62 g of n-hexane were mixed uniformly. This was dissolved to obtain an oil phase. The aqueous phase and oil phase prepared above were mixed and stirred for 1 minute at 16000 rpm with a homomixer to obtain an oil phase / water phase suspension. This suspension was charged into an autoclave and polymerized at 60 ° C. for 20 hours. The obtained dispersion was filtered through filter paper and dried with a circulating dryer at 40 ° C. to obtain thermally expandable microspheres (average particle size: 2.1 μm).

100 g of the heat-expandable microspheres obtained above were spread on a release paper to an area of about 100 cm ² , expanded by heat treatment for 15 minutes in a circulating air dryer at 180 ° C. (average particle diameter) : 5.1 μm, true specific gravity: 0.34 g / cc, outer shell average thickness: 0.30 μm, CV: 36%).
<Production of silver-coated conductive hollow body>
A silver-coated conductive hollow body was obtained by the same operation as in Example 1 except that the hollow body body obtained in <Preparation of hollow body body> was used (Ag plating layer thickness: 0.18 μm, true Specific gravity: 0.69 g / cc, average particle size: 5.5 μm, deformation rate at compression 54%, restoration rate after decompression 42%). In order to obtain the same conductivity as the conductive hollow body of Example 1 using this conductive hollow body, 2.5 times the amount (weight ratio) was necessary. The evaluation of dispersibility by SEM was not uniform, and a bias was observed.

[Example 2]
Passet CK (conductive zinc oxide manufactured by Hakusui Tech Co., Ltd., average particle size: 2.5 μm) 9 kg and Matsumoto Microsphere F-100D (Matsumoto Yushi Seiyaku Co., Ltd., average particle size: 25 μm, true specific gravity: 1.02 g) / Cc) 1 kg was charged into an SV mixer (manufactured by Shinko Environmental Solution Co., Ltd., internal volume: 30 L) and mixed for 10 minutes. Thereafter, the obtained mixture is put into a Laedige mixer (manufactured by Matsubo Co., Ltd.), heated at a jacket temperature of 230 ° C. for 10 minutes, cooled when the temperature of the mixture reaches 170 ° C., and the conductive hollow body is removed. Obtained (average particle size: 87 μm, true specific gravity: 0.28 g / cc, deformation rate during compression 83%, restoration rate after decompression 24%). The obtained conductive hollow body showed conductivity. The evaluation of dispersibility by SEM was good.

Example 3
In order to perform nickel plating, the electroless plating solution in Example 1 was replaced with Nimden NPR-4 (manufactured by Uemura Kogyo Co., Ltd.), and stirred and added at 80 ° C. in the same manner as in Example 1, A nickel-coated conductive hollow body was obtained (Ni plating layer thickness: 0.13 μm, true specific gravity: 0.120 g / cc, average particle size: 100.3 μm, deformation rate during compression 78%, restoration rate after decompression 34 %). The obtained conductive hollow body showed conductivity. The evaluation of dispersibility by SEM was good.

Example 4
In order to carry out copper plating, the electroless plating solution in Example 1 was replaced with Sulcup PEA (manufactured by Uemura Kogyo Co., Ltd.), and the same procedure as in Example 1 was followed except for stirring and adding at 35 ° C. (Cu plating layer thickness: 0.14 μm, true specific gravity: 0.121 g / cc, average particle diameter: 100.3 μm, deformation rate during compression 79%, restoration rate after decompression 31%) . The obtained conductive hollow body showed conductivity. The evaluation of dispersibility by SEM was good.

Claims (8)

  A hollow body body composed of an outer shell portion made of a thermoplastic resin and a hollow portion surrounded by the outer shell portion, and conductive particles adhering to the outer surface of the outer shell portion or the conductivity covering the outer surface of the outer shell portion A conductive hollow body comprising a metal layer and having a true specific gravity of 0.01 to 0.65 g / cc.   The conductive hollow body according to claim 1, wherein the average particle diameter is 0.1 to 1000 μm.   The conductive hollow body according to claim 1 or 2, wherein the coefficient of variation CV value of the particle size distribution is 30% or less.   The conductive hollow body according to any one of claims 1 to 3, wherein a deformation rate during compression is 70% or more and a restoration rate after decompression is 40% or less.   The said electroconductive particle is a particle | grain containing at least 1 sort (s) chosen from the group which consists of silver, gold | metal | money, platinum, nickel, copper, carbon black, zinc oxide, and titanium oxide in any one of Claims 1-4. Conductive hollow body.   The conductive hollow body according to any one of claims 1 to 4, wherein the conductive metal layer contains at least one metal selected from the group consisting of silver, gold, platinum, nickel, and copper.   A conductive metal layer is formed by electroless plating on the outer surface of the hollow body body which is composed of an outer shell portion made of a thermoplastic resin and a hollow portion surrounded by the outer shell portion and whose true specific gravity is 0.005 to 0.30 g / cc. The manufacturing method of an electroconductive hollow body including the process coat | covered with. Mixing thermally expandable microspheres composed of a foaming agent encapsulated in an outer shell made of a thermoplastic resin and having a boiling point not higher than the softening point of the thermoplastic resin, and conductive particles;
Heating the mixture obtained in the mixing step at a temperature above the softening point to expand the thermally expandable microspheres, and attaching the conductive particles to the outer surface of the hollow body body from which the conductive particles can be obtained. The manufacturing method of a conductive hollow body.