JP5620678B2 - Metal film forming method and conductive particles - Google Patents
Metal film forming method and conductive particles Download PDFInfo
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- JP5620678B2 JP5620678B2 JP2009538214A JP2009538214A JP5620678B2 JP 5620678 B2 JP5620678 B2 JP 5620678B2 JP 2009538214 A JP2009538214 A JP 2009538214A JP 2009538214 A JP2009538214 A JP 2009538214A JP 5620678 B2 JP5620678 B2 JP 5620678B2
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/31—Coating with metals
- C23C18/42—Coating with noble metals
- C23C18/44—Coating with noble metals using reducing agents
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/1601—Process or apparatus
- C23C18/1633—Process of electroless plating
- C23C18/1635—Composition of the substrate
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/18—Pretreatment of the material to be coated
- C23C18/1851—Pretreatment of the material to be coated of surfaces of non-metallic or semiconducting in organic material
- C23C18/1872—Pretreatment of the material to be coated of surfaces of non-metallic or semiconducting in organic material by chemical pretreatment
- C23C18/1875—Pretreatment of the material to be coated of surfaces of non-metallic or semiconducting in organic material by chemical pretreatment only one step pretreatment
- C23C18/1879—Use of metal, e.g. activation, sensitisation with noble metals
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/18—Pretreatment of the material to be coated
- C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
- C23C18/28—Sensitising or activating
- C23C18/30—Activating or accelerating or sensitising with palladium or other noble metal
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
- H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
- H05K3/321—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by conductive adhesives
- H05K3/323—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by conductive adhesives by applying an anisotropic conductive adhesive layer over an array of pads
Description
本発明は、例えば導電材、電磁波シールド材等に利用可能な導電性粒子、及び非導電性粒子に金属皮膜を形成する方法に関する。 The present invention relates to a conductive particle usable for, for example, a conductive material, an electromagnetic wave shielding material, and the like, and a method for forming a metal film on non-conductive particles.
非導電性粒子に金属皮膜を形成する技術として無電解めっきが知られている。無電解めっきの反応を促進するため、非導電性粒子の表面には、無電解めっきを開始する触媒を付着させるために前処理が施される。この前処理では、例えば、非導電性粒子を塩化第一スズの水溶液に接触させた後、塩化パラジウムの水溶液に接触させる。すると、非導電性粒子の表面に吸着したスズイオンの還元作用により、パラジウムコロイドが非導電性粒子の表面に吸着される。パラジウムコロイドは、無電解めっきを開始させる触媒として作用する。また、無電解めっき浴には、金属塩、金属錯化剤、ｐＨ調整剤、還元剤等が含まれている。ところで、上述した前処理をして行う無電解めっきにおいては、金属皮膜の厚さが極めて不均一で、連続した皮膜を形成できないという問題がある。 Electroless plating is known as a technique for forming a metal film on non-conductive particles. In order to accelerate the electroless plating reaction, a pretreatment is performed on the surface of the nonconductive particles in order to adhere a catalyst for starting the electroless plating. In this pretreatment, for example, non-conductive particles are brought into contact with an aqueous solution of stannous chloride and then brought into contact with an aqueous solution of palladium chloride. Then, the colloid of palladium is adsorbed on the surface of the nonconductive particles by the reducing action of the tin ions adsorbed on the surface of the nonconductive particles. The palladium colloid acts as a catalyst for initiating electroless plating. The electroless plating bath contains a metal salt, a metal complexing agent, a pH adjusting agent, a reducing agent, and the like. By the way, in the electroless plating performed by performing the pretreatment described above, there is a problem that the thickness of the metal film is extremely nonuniform and a continuous film cannot be formed.
例えば、特許文献１では、均質で、かつ強固な被覆力を有する金属めっき粉末が提案されている。この文献に開示の金属めっき粉末は、貴金属イオンを芯材表面に担持する触媒化工程と、その後、芯材に無電解めっきを行う無電解めっき処理とを経て得られる。触媒化工程では、有機質又は無機質の芯材に貴金属イオンを捕捉させた後、その貴金属イオンを還元して芯材に貴金属を担持させる。無電解めっき処理では、無電解めっき液を少なくとも２液から構成し、それらを個別に、かつ同時に添加して無電解めっきを行う。 For example, Patent Document 1 proposes a metal plating powder that is homogeneous and has a strong covering power. The metal plating powder disclosed in this document is obtained through a catalyzing step for supporting noble metal ions on the surface of the core material, and then an electroless plating process for performing electroless plating on the core material. In the catalyzing step, after the noble metal ions are captured by the organic or inorganic core material, the noble metal ions are reduced and the noble metal is supported on the core material. In the electroless plating treatment, an electroless plating solution is composed of at least two solutions, which are added individually and simultaneously to perform electroless plating.
また、特許文献２又は特許文献３には、非導電性粒子に貴金属皮膜を形成する技術として置換めっきが開示されている。置換めっきとしては、無電解ニッケルめっきにより下地層を形成し、ニッケルを貴金属と置換する方法が一般的である。無電解ニッケルめっきにおいて、通常は、めっき液のｐＨを適正に調整するため、次亜リン酸ナトリウム１水和物、クエン酸等が添加される。一方、置換めっきにおいて、通常は、貴金属皮膜の結晶構造を制御するため、コバルトの濃度が数百ｐｐｍになるようめっき液にコバルトが添加される。置換めっきにより作製した金属皮膜には、銀及び金よりも電気抵抗値が高いニッケルや、不純物であるリン、コバルト等が含まれている。 Patent Document 2 or Patent Document 3 discloses displacement plating as a technique for forming a noble metal film on non-conductive particles. As displacement plating, a method of forming a base layer by electroless nickel plating and replacing nickel with a noble metal is common. In electroless nickel plating, sodium hypophosphite monohydrate, citric acid, and the like are usually added to appropriately adjust the pH of the plating solution. On the other hand, in displacement plating, usually, cobalt is added to the plating solution so that the concentration of cobalt is several hundred ppm in order to control the crystal structure of the noble metal film. The metal film produced by displacement plating contains nickel having a higher electrical resistance than silver and gold, impurities such as phosphorus and cobalt.
金及び銀は、導電率の高い貴金属として知られている。銀は、金よりも高い導電率を有することに加えて、安価でもある。このため、非導電性粒子とその表面に銀からなる金属皮膜とを備えた導電性粒子の利用価値は高い。ところが、銀からなる金属皮膜を置換めっきにより形成する場合、下地層であるニッケル層、及び銀層の少なくとも二つの層を含む金属被膜が形成される。このように複数の層からなる金属皮膜はコスト的に不利である。非導電性粒子に対し、例えばカップリング剤を用いた前処理を施してから無電解めっきを行うことにより、銀からなる金属皮膜を形成することも考えられる。ところが、ミクロンオーダーの非導電性粒子に前処理を施しても、非導電性粒子に銀からなる金属皮膜を形成できないか、又は不連続な金属皮膜しか形成されない。このように、ミクロンサイズの非導電性粒子に対して、銀からなる金属皮膜を単層として形成する技術の実用性は、未だ得られていない。
本発明者は、ミクロンサイズの非導電性粒子に対して、銀からなる金属皮膜を単層で、かつ連続して形成できる技術を見出した。本発明の目的は、銀からなる金属皮膜を単層で形成することの容易な金属皮膜形成方法を提供することにある。また、本発明の目的は、導電性に優れ、かつ低コストである導電性粒子を提供することにある。 The present inventor has found a technique capable of continuously forming a metal film made of silver as a single layer on micron-sized non-conductive particles. An object of the present invention is to provide a method for forming a metal film which can easily form a metal film made of silver as a single layer. Moreover, the objective of this invention is providing the electroconductive particle which is excellent in electroconductivity and is low-cost.
上記の課題を解決するため、本発明の第一の態様によれば、粒径が０．５μｍ〜５０μｍの範囲の非導電性粒子に、金属皮膜を無電解めっきにより形成する金属皮膜形成方法が提供される。無電解めっきは、非導電性粒子に金属核を付着させる前処理の後に実施されるとともに、チオール基を有するシラン化合物の存在下において銀からなる金属皮膜を形成する。 In order to solve the above problems, according to the first aspect of the present invention, there is provided a metal film forming method for forming a metal film by electroless plating on non-conductive particles having a particle size in a range of 0.5 μm to 50 μm. Provided. The electroless plating is performed after a pretreatment for attaching metal nuclei to nonconductive particles, and forms a metal film made of silver in the presence of a silane compound having a thiol group.
上記の金属皮膜形成方法において、チオール基を有するシラン化合物と水との混合液を非導電性粒子に接触した後、無電解めっきを開始することが好ましい。
上記の金属皮膜形成方法において、チオール基を有するシラン化合物が３−メルカプトプロピルトリエトキシシランであることが好ましい。In the above metal film forming method, it is preferable to start electroless plating after contacting a mixed liquid of a silane compound having a thiol group and water with non-conductive particles.
In the above metal film formation method, the silane compound having a thiol group is preferably 3-mercaptopropyltriethoxysilane.
上記の金属皮膜形成方法において、無電解めっきが、銀鏡反応により実施されることが好ましい。
上記の金属皮膜形成方法において、前処理が、シランカップリング剤、加水分解触媒及び金属塩を含む処理液を、非導電性粒子に接触させた後に、還元剤により金属塩の金属を析出させることにより金属核を付着させる処理であり、シランカップリング剤は、金属塩の金属に対してキレートを形成する官能基を有することが好ましい。In the metal film forming method, the electroless plating is preferably performed by a silver mirror reaction.
In the method for forming a metal film, the pretreatment includes bringing the metal salt of the metal salt with a reducing agent after bringing the treatment liquid containing the silane coupling agent, the hydrolysis catalyst, and the metal salt into contact with the non-conductive particles. The silane coupling agent preferably has a functional group that forms a chelate with respect to the metal of the metal salt.
上記の金属皮膜形成方法において、金属核の金属が金又は銀であることが好ましい。
上記の課題を解決するため、本発明の第二の態様によれば、非導電性粒子の表面全体に形成された金属皮膜により導電性が付与された導電性粒子が提供される。非導電性粒子の粒径は、０．５μｍ〜５０μｍの範囲である。また、金属皮膜は、銀の単層から構成される。In the above metal film forming method, the metal of the metal core is preferably gold or silver.
In order to solve the above problems, according to the second aspect of the present invention, there are provided conductive particles imparted with conductivity by a metal film formed on the entire surface of the non-conductive particles. The particle size of the non-conductive particles is in the range of 0.5 μm to 50 μm. The metal film is composed of a single layer of silver.
上記の導電性粒子において、導電性粒子の蛍光Ｘ線分析において非導電性粒子に含まれる元素以外の元素として金、銀及び硫黄のみが検出される。
上記の導電性粒子において、液晶表示素子のシール剤として用いられることが好ましい。
In the above conductive particles, as the fluorescent X-ray elements other than elements included in the non-conductive particles in the analysis of conductive particles of gold, only silver and sulfur is discovered.
The conductive particles are preferably used as a sealing agent for liquid crystal display elements.
上記の導電性粒子において、異方導電性材料として用いられることが好ましい。 In the above conductive particles, it is preferable to be used as an anisotropic conductive material.
以下、本発明を具体化した実施形態について詳細に説明する。
＜金属皮膜形成方法＞
本実施形態の金属皮膜形成方法は、粒径が０．５μｍ〜５０μｍの非導電性粒子に金属皮膜を無電解めっきにより形成する方法である。無電解めっきは、非導電性粒子に金属核を付着させる前処理の後に実施されるとともに、チオール基を有するシラン化合物の存在下で銀からなる金属皮膜を形成する。DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments embodying the present invention will be described in detail.
<Metal film forming method>
The metal film forming method of this embodiment is a method for forming a metal film on non-conductive particles having a particle diameter of 0.5 μm to 50 μm by electroless plating. The electroless plating is performed after a pretreatment for attaching metal nuclei to nonconductive particles, and forms a metal film made of silver in the presence of a silane compound having a thiol group.
非導電性粒子は、金属皮膜が形成される基材として構成される。非導電性粒子の材質として、例えば、シリカ、セラミックス、ガラス、樹脂類から選ばれる少なくとも一種が挙げられる。シリカとして、例えば、完全結晶化した乾式シリカ（クリストバライト）、水分散型シリカ（コロイダルシリカ）等が挙げられる。セラミックスとして、例えば、アルミナ、サファイア、ムライト、チタニア、炭化ケイ素、窒化ケイ素、窒化アルミニウム、ジルコニア等が挙げられる。ガラスとして、例えば、ＢＫ７、ＳＦ１１、ＬａＳＦＮ９等の各種ショットガラス、光学クラウンガラス、ソーダガラス、低膨張ボロシリケートガラス等が挙げられる。樹脂類として、例えば、シリコーン樹脂、フェノール樹脂、天然変性フェノール樹脂、エポキシ樹脂、ポリビニルアルコール系樹脂、セルロース系樹脂等や、ポリオレフィン系樹脂、スチレン系樹脂、アクリル系樹脂等の変性物又はコロナ放電等による表面処理物が挙げられる。非導電性粒子として、例えば、粒径のばらつきが小さいという観点から、好ましくは、シリカ、セラミックス、及びガラスから選ばれる少なくとも一種が挙げられ、より好ましくは、シリカが挙げられる。非導電性粒子の形状として、例えば、球状、棒状、板状、針状、中空状等が挙げられる。非導電性粒子の分散性又は得られる導電性粒子の分散性等を考慮すると、非導電性粒子の形状は球状であることが好ましい。 Non-conductive particles are configured as a substrate on which a metal film is formed. Examples of the material of the non-conductive particles include at least one selected from silica, ceramics, glass, and resins. Examples of silica include completely crystallized dry silica (cristobalite), water-dispersed silica (colloidal silica), and the like. Examples of the ceramic include alumina, sapphire, mullite, titania, silicon carbide, silicon nitride, aluminum nitride, and zirconia. Examples of the glass include various shot glasses such as BK7, SF11, and LaSFN9, optical crown glass, soda glass, low expansion borosilicate glass, and the like. Examples of resins include silicone resins, phenol resins, naturally-modified phenol resins, epoxy resins, polyvinyl alcohol resins, cellulose resins, polyolefin resins, styrene resins, acrylic resins, and other modified products, corona discharge, etc. And surface treated products. As the non-conductive particles, for example, at least one selected from silica, ceramics, and glass is preferable from the viewpoint of small variation in particle diameter, and silica is more preferable. Examples of the shape of the non-conductive particles include a spherical shape, a rod shape, a plate shape, a needle shape, and a hollow shape. Considering the dispersibility of the non-conductive particles or the dispersibility of the obtained conductive particles, the shape of the non-conductive particles is preferably spherical.
非導電性粒子の粒径は、０．５μｍ〜１００μｍの範囲である。非導電性粒子の粒径は、走査型電子顕微鏡の写真を用いて測定される。金属皮膜形成方法に供される非導電性粒子の平均粒径は、好ましくは、１μｍ〜５０μｍ、より好ましくは、１μｍ〜２０μｍである。 The particle size of the non-conductive particles is in the range of 0.5 μm to 100 μm. The particle size of the nonconductive particles is measured using a photograph of a scanning electron microscope. The average particle diameter of the nonconductive particles subjected to the metal film forming method is preferably 1 μm to 50 μm, more preferably 1 μm to 20 μm.
特に、液晶表示素子用部材等に用いる場合、予め非導電性粒子の粒径を揃えておく必要がある。この場合、非導電性粒子の粒径分布は、以下に示す式で求められるＣＶ値が１０％以下であることが好ましく、５％以下であることがより好ましい。 In particular, when used for a liquid crystal display element member or the like, it is necessary to make the particle diameters of the non-conductive particles in advance. In this case, as for the particle size distribution of the non-conductive particles, the CV value obtained by the following formula is preferably 10% or less, and more preferably 5% or less.
ＣＶ値（％）＝｛［粒子径の標準偏差（μｍ）］／［平均粒径（μｍ）］｝×１００
無電解めっきは、非導電性粒子に金属核を付着させる前処理の後に実施される。前処理により付着する金属核の金属としては、金属皮膜となる銀の導電性に悪影響を与え難く、金属皮膜が安定的に形成されるという観点から、金又は銀が好ましい。前処理として、例えば、シランカップリング剤、加水分解触媒及び金属塩を含む処理液を、非導電性粒子に接触させ、その後、還元剤により金属塩の金属を析出させることにより、非導電性粒子に金属核を付着させることが好ましい。これにより、無電解めっきによる金属皮膜の形成を、均一に進行させることができる。このとき、シランカップリング剤として、金属塩の金属に対してキレートを形成する官能基を有するシランカップリング剤が用いられる。CV value (%) = {[standard deviation of particle diameter (μm)] / [average particle diameter (μm)]} × 100
Electroless plating is performed after pretreatment for attaching metal nuclei to non-conductive particles. As the metal of the metal nucleus attached by the pretreatment, gold or silver is preferable from the viewpoint that the conductivity of silver to be the metal film is not adversely affected and the metal film is stably formed. As pretreatment, for example, a non-conductive particle is obtained by bringing a treatment liquid containing a silane coupling agent, a hydrolysis catalyst, and a metal salt into contact with non-conductive particles, and then depositing metal of the metal salt with a reducing agent. It is preferable to attach a metal nucleus to the substrate. Thereby, formation of the metal film by electroless plating can be advanced uniformly. At this time, a silane coupling agent having a functional group that forms a chelate with respect to the metal of the metal salt is used as the silane coupling agent.
金属塩の金属に対しキレートを形成する官能基として、極性基又は親水性基が挙げられる。具体的には、窒素原子、硫黄原子及び酸素原子の原子から選ばれる少なくとも１種以上の原子を有する官能基であることが好ましい。そのような官能基として、−ＳＨ、−ＣＮ、−ＮＨ２、−ＳＯ２ＯＨ、−ＳＯＯＨ、−ＯＰＯ（ＯＨ）２、−ＣＯＯＨからなる群から選ばれる少なくとも１種以上の官能基が挙げられる。これらの官能基は、塩を形成していてもよい。官能基が−ＯＨ、−ＳＨ、−ＳＯ２ＯＨ、−ＳＯＯＨ、−ＯＰＯ（ＯＨ）２、−ＣＯＯＨなどの酸性基である場合、その塩として、ナトリウム、カリウム、リチウム等のアルカリ金属塩、又はアンモニウム塩等が挙げられる。一方、−ＮＨ２等の塩基性基である場合、その塩として、塩酸、硫酸、硝酸等の無機酸塩、ギ酸、酢酸、プロピオン酸、トリフルオロ酢酸等の有機酸塩が挙げられる。Examples of the functional group that forms a chelate with respect to the metal of the metal salt include a polar group and a hydrophilic group. Specifically, a functional group having at least one atom selected from nitrogen atom, sulfur atom and oxygen atom is preferable. Examples of such a functional group include at least one functional group selected from the group consisting of —SH, —CN, —NH 2 , —SO 2 OH, —SOOH, —OPO (OH) 2 , and —COOH. . These functional groups may form a salt. When the functional group is an acidic group such as —OH, —SH, —SO 2 OH, —SOOH, —OPO (OH) 2 , —COOH, etc., as its salt, an alkali metal salt such as sodium, potassium, lithium, or the like An ammonium salt etc. are mentioned. On the other hand, when it is a basic group such as —NH 2 , examples of the salt include inorganic acid salts such as hydrochloric acid, sulfuric acid and nitric acid, and organic acid salts such as formic acid, acetic acid, propionic acid and trifluoroacetic acid.
シランカップリング剤は、加水分解によりシラノール基を生成する加水分解性官能基を有している化合物である。加水分解性官能基として、Ｓｉ原子に直接結合したアルコキシ（−ＯＲ）基等が挙げられ、上記アルコキシ基を構成するＲとして、炭素数が１〜６である直鎖状、分岐状、環状いずれかのアルキル基が好ましく、具体的には、メチル基、エチル基、ｎ−プロピル基、イソプロピル基、ｎ−ブチル基、イソブチル基、ｓｅｃ−ブチル基、ｔｅｒｔ−ブチル基、ペンチル基、ヘキシル基、シクロペンチル基、シクロヘキシル基等を挙げることができる。 The silane coupling agent is a compound having a hydrolyzable functional group that generates a silanol group by hydrolysis. Examples of the hydrolyzable functional group include an alkoxy (—OR) group directly bonded to an Si atom, and the R constituting the alkoxy group is any of linear, branched or cyclic having 1 to 6 carbon atoms. These alkyl groups are preferred, and specifically, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, A cyclopentyl group, a cyclohexyl group, etc. can be mentioned.
シランカップリング剤の具体例として、３−アミノプロピルトリメトキシシラン、３−アミノプロピルトリエトキシシラン、Ｎ−２−（アミノエチル）−３−アミノプロピルトリメトキシシラン、Ｎ−２−（アミノエチル）−３−アミノプロピルトリエトキシシラン等が挙げられる。シランカップリング剤として、コスト及び取り扱いの容易さという観点から、３−アミノプロピルトリメトキシシランが、特に好ましい。 Specific examples of the silane coupling agent include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, and N-2- (aminoethyl). -3-aminopropyltriethoxysilane and the like. As the silane coupling agent, 3-aminopropyltrimethoxysilane is particularly preferable from the viewpoint of cost and ease of handling.
加水分解触媒は、上述した加水分解性官能基の加水分解を促進する。加水分解触媒として、例えば、無水酢酸、氷酢酸、プロピオン酸、クエン酸、ギ酸、シュウ酸等の有機酸、アルミニウムアルキルアセテート等のアルミニウムキレート化合物、アンモニア水等の無機アルカリ性化合物等が挙げられる。これらの中、好ましいシランカップリング剤である３−アミノプロピルトリメトキシシランとの反応性、コストを考慮すると、アンモニア水が好ましい。 The hydrolysis catalyst promotes hydrolysis of the hydrolyzable functional group described above. Examples of the hydrolysis catalyst include organic acids such as acetic anhydride, glacial acetic acid, propionic acid, citric acid, formic acid, and oxalic acid, aluminum chelate compounds such as aluminum alkyl acetate, and inorganic alkaline compounds such as aqueous ammonia. Among these, ammonia water is preferable in consideration of reactivity with 3-aminopropyltrimethoxysilane, which is a preferred silane coupling agent, and cost.
シランカップリング剤１モルに対する加水分解触媒の使用量は、０．５〜５．０モルであることが好ましく、１．５〜２．５モルであることがより好ましい。また、シランカップリング剤１モルに対する金属塩の使用量は、０．００５〜０．０５モルであることが好ましく、０．０１５〜０．０２５モルであることがより好ましい。さらに、金属塩１モルに対する還元剤の使用量は、０．０２５〜０．２５モルであることが好ましく、０．０７５〜０．１２５モルであることがより好ましい。 The amount of the hydrolysis catalyst used relative to 1 mol of the silane coupling agent is preferably 0.5 to 5.0 mol, and more preferably 1.5 to 2.5 mol. Moreover, it is preferable that it is 0.005-0.05 mol, and, as for the usage-amount of the metal salt with respect to 1 mol of silane coupling agents, it is more preferable that it is 0.015-0.025 mol. Furthermore, it is preferable that it is 0.025-0.25 mol, and, as for the usage-amount of the reducing agent with respect to 1 mol of metal salts, it is more preferable that it is 0.075-0.125 mol.
前処理の処理液として、水又は水性溶媒が挙げられる。水性溶媒は、水と有機溶媒との混合溶媒である。有機溶媒として、例えば、メタノール、エタノール、プロパノール、ブタノールなどの低級アルコール類、アセトンなどのケトン類等が挙げられる。これらの有機溶媒は、単独で用いてもよく、複数種を組み合わせて用いてもよい。 Examples of the pretreatment liquid include water and an aqueous solvent. The aqueous solvent is a mixed solvent of water and an organic solvent. Examples of the organic solvent include lower alcohols such as methanol, ethanol, propanol and butanol, and ketones such as acetone. These organic solvents may be used independently and may be used in combination of multiple types.
無電解めっきは、チオール基を有するシラン化合物の存在下で、銀からなる金属皮膜を形成する。チオール基を有するシラン化合物は、下記一般式（１）に示される。
Ｘｍ（Ｙ）３−ｍＳｉ（ＣＨ２）ｎＳＨ ・・・（１）
（一般式（１）において、Ｘは炭素数が１〜６であるアルキル基、Ｙは炭素数が１〜６のアルコキシ基であり、ｍは０又は１、ｎは１〜５の整数である）
Ｘで示されるアルキル基は、直鎖状、分岐状及び環状のいずれかのアルキル基であって、例えば、メチル基、エチル基、ｎ−プロピル基、イソプロピル基、ｎ−ブチル基、イソブチル基、ｓｅｃ−ブチル基、ｔｅｒｔ−ブチル基、ペンチル基、ヘキシル基、シクロペンチル基、シクロヘキシル基等が挙げられる。Ｙで示されるアルコキシ基は、−ＯＲで示され、そのアルコキシ基を構成するＲとしては、直鎖状、分岐状及び環状のいずれかのアルキル基であって、例えば、メチル基、エチル基、ｎ−プロピル基、イソプロピル基、ｎ−ブチル基、イソブチル基、ｓｅｃ−ブチル基、ｔｅｒｔ−ブチル基、ペンチル基、ヘキシル基、シクロペンチル基、シクロヘキシル基等が挙げられる。一般式（１）で示されるメルカプト化合物として、金属皮膜が安定的に形成されるという観点から、３−メルカプトプロピルトリエトキシシランが好ましい。In electroless plating, a metal film made of silver is formed in the presence of a silane compound having a thiol group. The silane compound having a thiol group is represented by the following general formula (1).
X m (Y) 3-m Si (CH 2) n SH ··· (1)
(In General Formula (1), X is an alkyl group having 1 to 6 carbon atoms, Y is an alkoxy group having 1 to 6 carbon atoms, m is 0 or 1, and n is an integer of 1 to 5. )
The alkyl group represented by X is a linear, branched or cyclic alkyl group such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, Examples include sec-butyl group, tert-butyl group, pentyl group, hexyl group, cyclopentyl group, cyclohexyl group and the like. The alkoxy group represented by Y is represented by -OR, and R constituting the alkoxy group is a linear, branched or cyclic alkyl group, for example, a methyl group, an ethyl group, Examples include n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, cyclopentyl group, cyclohexyl group and the like. As the mercapto compound represented by the general formula (1), 3-mercaptopropyltriethoxysilane is preferable from the viewpoint that a metal film is stably formed.
銀は、金よりも高い導電率を有することに加えて、安価でもある。このため、非導電性粒子とその表面に銀からなる金属皮膜とを備えた導電性粒子の利用価値は高い。無電解めっきとして、金属塩、還元剤等を用いる周知の無電解めっき法を適用できる。還元剤として、例えば、テトラヒドロホウ酸ナトリウム等の水素化ホウ素酸塩（水素化ホウ素ナトリウム等のアルカリ金属水素化ホウ酸塩類、アンモニウム水素化ホウ酸塩類等）、ヒドラジン系化合物類、次亜塩素酸塩などの無機系還元剤、ホルムアルデヒド、アセトアルデヒド、クエン酸、クエン酸ナトリウムなどの有機系還元剤が用いられる。これらの還元剤は、単独で用いてもよく、二種以上を組み合わせて用いてもよい。無電解めっきとして、反応の安定性に優れるとともに、不純物を可能な限り低減できるという観点から、銀鏡反応を用いるのが好ましい。銀鏡反応は、銀のアンミン錯体を還元剤で還元して銀を析出する反応である。具体的には、硝酸銀のアンモニア水溶液中にホルマリン等の還元剤を添加することにより、非導電性粒子の表面に銀を析出させる。 In addition to having a higher conductivity than gold, silver is also inexpensive. For this reason, the utility value of the electroconductive particle provided with the nonelectroconductive particle and the metal membrane | film | coat which consists of silver on the surface is high. As electroless plating, a known electroless plating method using a metal salt, a reducing agent, or the like can be applied. Examples of the reducing agent include borohydrides such as sodium tetrahydroborate (alkali metal borohydrides such as sodium borohydride, ammonium borohydrides), hydrazine compounds, hypochlorous acid, and the like. Inorganic reducing agents such as salts, and organic reducing agents such as formaldehyde, acetaldehyde, citric acid and sodium citrate are used. These reducing agents may be used alone or in combination of two or more. As electroless plating, it is preferable to use a silver mirror reaction from the viewpoints of excellent reaction stability and reducing impurities as much as possible. The silver mirror reaction is a reaction in which silver ammine complex is reduced with a reducing agent to precipitate silver. Specifically, silver is deposited on the surface of the non-conductive particles by adding a reducing agent such as formalin into an aqueous ammonia solution of silver nitrate.
チオール基を有するシラン化合物と水との混合液を非導電性粒子に接触させた後に、無電解めっきを開始することが好ましい。これにより、シラン化合物が安定的に作用するようになる。また、シラン化合物の溶解性を考慮して、水と相溶する有機溶媒を水に混合してもよい。こうした混合液を用いた無電解めっきの温度条件、反応時間等は、無電解めっきの常法に応じて設定される。 It is preferable to start electroless plating after bringing a mixed liquid of a silane compound having a thiol group and water into contact with non-conductive particles. Thereby, a silane compound comes to act stably. In consideration of the solubility of the silane compound, an organic solvent compatible with water may be mixed with water. The temperature conditions, reaction time, etc. of electroless plating using such a mixed solution are set according to the conventional method of electroless plating.
チオール基を有するシラン化合物１モルに対する金属塩の使用量は、０．００５〜０．０５モルであることが好ましく、０．０１５〜０．０２５モルであることがより好ましい。さらに、金属塩１モルに対する還元剤の使用量は、０．０２５〜０．２５モルであることが好ましく、０．０７５〜０．１２５モルであることがより好ましい。 The amount of the metal salt used relative to 1 mole of the silane compound having a thiol group is preferably 0.005 to 0.05 mole, and more preferably 0.015 to 0.025 mole. Furthermore, it is preferable that it is 0.025-0.25 mol, and, as for the usage-amount of the reducing agent with respect to 1 mol of metal salts, it is more preferable that it is 0.075-0.125 mol.
本発明の金属皮膜形成方法により得られる金属皮膜は、金属のバルク材や従来の無電解めっき法により形成された金属皮膜よりも低い密度を有している。詳しくは、金属のバルク材に対する本発明の金属皮膜の密度比（本発明の金属皮膜の密度／金属のバルク材の密度（１０．５ｇ／ｃｍ３）×１００）は、多少のばらつきはあるものの、概ね、５０％〜８５％の範囲であり、より具体的には、５０％〜７０％である。このため、例えば、対向する電極間に金属被覆を含む基材を配置し、両電極を接近させて基材を圧縮した場合、金属皮膜は密度が低いために容易に変形する。その結果、電極と金属皮膜との接地面積が増大し、金属皮膜を介した両電極間の導通に関する信頼性が向上する。
＜導電性粒子＞
非導電性粒子の表面全体には、金属皮膜が形成されている。導電性粒子には、その金属被膜により導電性が付与されている。非導電性粒子の粒径は、０．５μｍ〜５０μｍの範囲である。金属皮膜は、銀の単層からなる。The metal film obtained by the metal film forming method of the present invention has a lower density than a metal bulk material or a metal film formed by a conventional electroless plating method. Specifically, the density ratio of the metal film of the present invention to the metal bulk material (the density of the metal film of the present invention / the density of the metal bulk material (10.5 g / cm 3 ) × 100) varies slightly. In general, the range is from 50% to 85%, and more specifically, from 50% to 70%. For this reason, for example, when a base material including a metal coating is disposed between opposing electrodes and the base material is compressed by bringing both electrodes close to each other, the metal film is easily deformed because of its low density. As a result, the ground contact area between the electrode and the metal film is increased, and the reliability of conduction between the two electrodes via the metal film is improved.
<Conductive particles>
A metal film is formed on the entire surface of the non-conductive particles. Conductivity is imparted to the conductive particles by the metal coating. The particle size of the non-conductive particles is in the range of 0.5 μm to 50 μm. The metal film consists of a single layer of silver.
金属皮膜は、連続した銀微粒子の集合体からなる。つまり、金属皮膜は、緻密に配列された銀微粒子からなり、連続した皮膜である。連続した銀微粒子の集合体とは、走査型顕微鏡により金属皮膜を５０００倍〜１００００倍の倍率で観察した場合に、不連続となる金属皮膜を確認できないレベルにまで緻密に配列されている集合体を指す。金属皮膜の厚さは、安定した導電性が得られるとの観点から、５０ｎｍ以上であることが好ましい。 The metal film is composed of an aggregate of continuous silver fine particles. That is, the metal film is a continuous film composed of finely arranged silver fine particles. An aggregate of continuous silver fine particles is an aggregate that is densely arranged to a level at which a discontinuous metal film cannot be confirmed when the metal film is observed at a magnification of 5000 to 10,000 times with a scanning microscope. Point to. The thickness of the metal film is preferably 50 nm or more from the viewpoint that stable conductivity is obtained.
本実施形態の金属皮膜では、その蛍光Ｘ線分析において、非導電性粒子に含まれる元素以外の元素として、金、銀及び硫黄のみが検出されることが好ましい。これにより、金属皮膜の純度が高められ、安定した電気特性が得られる。導電性粒子の平均粒径は、液晶表示素子用部材や異方性導電材料として適しているとの観点から、好ましくは、０．５μｍ〜１００μｍ、より好ましくは、１μｍ〜２０μｍである。こうして得られた導電性粒子は、例えば、液晶表示素子のシール剤の他に、各種の異方導電性材料に適している。 In the metal film of this embodiment, it is preferable that only gold, silver, and sulfur are detected as elements other than the elements contained in the non-conductive particles in the fluorescent X-ray analysis. Thereby, the purity of the metal film is increased, and stable electrical characteristics can be obtained. The average particle diameter of the conductive particles is preferably 0.5 μm to 100 μm, more preferably 1 μm to 20 μm, from the viewpoint of being suitable as a liquid crystal display element member or an anisotropic conductive material. The conductive particles thus obtained are suitable for various anisotropic conductive materials in addition to, for example, a sealing agent for liquid crystal display elements.
以上、詳述した本実施形態によれば、次のような効果が得られる。
（１）金属皮膜形成方法としての無電解めっきは、非導電性粒子に金属核を付着させる前処理の後に実施されるとともに、チオール基を有するシラン化合物の存在下で銀からなる金属皮膜を形成する。このため、ミクロンサイズの非導電性粒子に金属皮膜を形成する場合であっても、銀の単層を容易に構成することができる。As mentioned above, according to this embodiment explained in full detail, the following effects are acquired.
(1) Electroless plating as a method for forming a metal film is performed after a pretreatment for attaching metal nuclei to non-conductive particles, and forms a metal film made of silver in the presence of a silane compound having a thiol group. To do. For this reason, even if it is a case where a metal membrane | film | coat is formed in the nonelectroconductive particle of micron size, a silver single layer can be comprised easily.
（２）チオール基を有するシラン化合物と水との混合液を非導電性粒子に接触した後、無電解めっきが開始される。これにより、シラン化合物の作用がより高められるため、金属皮膜を安定的に形成することができる。 (2) After contacting a non-conductive particle with a mixed liquid of a silane compound having a thiol group and water, electroless plating is started. Thereby, since the effect | action of a silane compound is improved more, a metal membrane | film | coat can be formed stably.
（３）例えば、チオール基を有するシラン化合物として３−メルカプトプロピルトリエトキシシランを用いたり、無電解めっきを銀鏡反応により実施したりすることにより、金属皮膜の表面の均一性を高めることができる。 (3) For example, the uniformity of the surface of the metal film can be enhanced by using 3-mercaptopropyltriethoxysilane as a silane compound having a thiol group or by performing electroless plating by a silver mirror reaction.
（４）無電解めっきの前処理は、シランカップリング剤、加水分解触媒及び金属塩を含む処理液を、非導電性粒子に接触させ、その後、還元剤により金属塩の金属を析出させることにより、非導電性粒子に金属核を付着させる処理であることが好ましい。これにより、非導電性粒子に対し金属核をより均一に付着させることができ、金属皮膜の表面の均一性を更に高めることができる。 (4) The pretreatment of electroless plating is performed by bringing a treatment liquid containing a silane coupling agent, a hydrolysis catalyst and a metal salt into contact with non-conductive particles, and then depositing a metal of the metal salt with a reducing agent. The treatment is preferably a treatment for attaching metal nuclei to non-conductive particles. Thereby, a metal nucleus can be made to adhere more uniformly with respect to a nonelectroconductive particle, and the uniformity of the surface of a metal film can further be improved.
（５）金属核の金属は金又は銀である。これにより、金属皮膜を形成する銀の導電性に悪影響を与え難くすることができ、金属皮膜を安定的に形成することができる。
（６）導電性粒子を構成する金属皮膜は、銀の単層からなる。このため、導電性に優れ、かつ低コストである導電性粒子を提供することができる。このような導電性粒子は、安定的な導電性及び優れた電気的特性により、例えば、液晶表示素子のシール剤用、異方導電性材料に適している。(5) The metal of the metal core is gold or silver. Thereby, it can be made hard to give a bad influence on the electroconductivity of silver which forms a metal film, and a metal film can be formed stably.
(6) The metal film constituting the conductive particles is composed of a single layer of silver. For this reason, the electroconductive particle which is excellent in electroconductivity and is low-cost can be provided. Such conductive particles are suitable for, for example, an anisotropic conductive material for a sealant of a liquid crystal display element due to stable conductivity and excellent electrical characteristics.
（７）導電性粒子の蛍光Ｘ線分析において、非導電性粒子に含まれる元素以外の元素として、金、銀及び硫黄のみが検出されることが好ましい。この場合、導電性粒子の電気特性が確実に発揮される。 (7) In the fluorescent X-ray analysis of the conductive particles, it is preferable that only gold, silver and sulfur are detected as elements other than the elements contained in the nonconductive particles. In this case, the electrical characteristics of the conductive particles are reliably exhibited.
（８）非導電性粒子に貴金属皮膜を形成する技術の一つである置換めっきは、無電解ニッケルめっきを下地層として形成し、ニッケルを貴金属と置換する方法である。しかし、高温、高湿下条件で、ニッケルの耐腐食性は不安定である。また、シリカ、セラミックス、ガラスは、樹脂類よりも熱、湿度に対して非常に安定である。このため、本発明の導電性粒子を構成する非導電性粒子としてシリカ、セラミックス、ガラスを使用することにより、熱、湿度に対する安定性が向上する、よって、熱安定性が必要な用途に適した導電性粒子を提供することができる。 (8) Displacement plating, which is one of the techniques for forming a noble metal film on non-conductive particles, is a method in which electroless nickel plating is formed as an underlayer and nickel is replaced with a noble metal. However, the corrosion resistance of nickel is unstable under high temperature and high humidity conditions. Silica, ceramics, and glass are much more stable against heat and humidity than resins. For this reason, by using silica, ceramics, and glass as the non-conductive particles constituting the conductive particles of the present invention, the stability to heat and humidity is improved, and thus suitable for applications that require thermal stability. Conductive particles can be provided.
なお、上記実施形態は以下のように変更してもよい。
・本実施形態において、銀からなる金属皮膜は単層から構成されていたが、複数の層により構成されてもよい。また、銀からなる金属皮膜は、１回の無電解めっきにより形成してもよく、複数回の無電解めっきにより形成してもよい。In addition, you may change the said embodiment as follows.
In the present embodiment, the metal film made of silver is composed of a single layer, but may be composed of a plurality of layers. Further, the metal film made of silver may be formed by one time of electroless plating or may be formed by a plurality of times of electroless plating.
次に、実施例及び比較例を挙げて前記実施形態をさらに具体的に説明する。
（実施例１）
（Ａ）前処理
５００ｍＬの三角フラスコにシリカ粒子（平均粒径：６．４０μｍ、ＣＶ値：０．９６％、走査型電子顕微鏡写真より粒子７０個の粒径を測定）１０ｇを入れ、イソプロピルアルコール（ＩＰＡ）６３ｇを加え、１０分間超音波処理した。更にメタノール６３ｇを加えてマグネチックスターラーで１０分間攪拌し、２５％アンモニア水溶液５０ｇを加え、３０℃のオイルバス中で１０分間攪拌することにより、Ａ液を調整した。Next, the embodiment will be described more specifically with reference to examples and comparative examples.
Example 1
(A) Pretreatment 10 g of silica particles (average particle size: 6.40 μm, CV value: 0.96%, particle size of 70 particles measured from scanning electron micrograph) is placed in a 500 mL Erlenmeyer flask, and isopropyl alcohol (IPA) 63 g was added and sonicated for 10 minutes. Further, 63 g of methanol was added and stirred with a magnetic stirrer for 10 minutes, 50 g of 25% aqueous ammonia solution was added, and the mixture was stirred for 10 minutes in an oil bath at 30 ° C. to prepare solution A.
塩化金酸（ＨＡｕＣｌ４・４Ｈ２Ｏ）０．２３ｇにメタノール５０ｍＬを加えてマグネチックスターラーで１０分間攪拌後、３−アミノプロピルトリメトキシシラン４．５ｍＬを加えて更に１０分間攪拌することにより、Ｂ液を調整した。By adding 50 mL of methanol to 0.23 g of chloroauric acid (HAuCl 4 · 4H 2 O) and stirring for 10 minutes with a magnetic stirrer, adding 4.5 mL of 3-aminopropyltrimethoxysilane and further stirring for 10 minutes, B liquid was adjusted.
テトラヒドロホウ酸ナトリウム（ＮａＢＨ４）０．１０７ｇにメタノール５０ｍＬを加えてマグネチックスターラーで１０分間攪拌することにより、Ｃ液を調整した。
Ａ液にＢ液を加えて３０℃で５分間攪拌した後、Ｃ液をゆっくり滴下したところ、反応系は赤色へと変化した。Ｃ液滴下後、オイルバスを６５℃に加熱して３時間攪拌した。攪拌を止めて、メタノール分級を３回行った。その後、吸引ろ過して金属核が形成されたシリカ粒子を採取し、オーブンで７０℃、３時間乾燥させた。得られた粒子は赤色を呈していた。Solution C was prepared by adding 50 mL of methanol to 0.107 g of sodium tetrahydroborate (NaBH 4 ) and stirring with a magnetic stirrer for 10 minutes.
After adding B liquid to A liquid and stirring at 30 degreeC for 5 minute (s), when C liquid was dripped slowly, the reaction system changed to red. After dropping C droplets, the oil bath was heated to 65 ° C. and stirred for 3 hours. Stirring was stopped and methanol classification was performed three times. Thereafter, silica particles with metal nuclei formed by suction filtration were collected and dried in an oven at 70 ° C. for 3 hours. The obtained particles were red.
図１は、シリカ粒子の走査型電子顕微鏡写真を示す。また、図２は、金属核が形成されたシリカ粒子の走査型電子顕微鏡写真を示す。図２を参照すると、シリカ粒子の全表面に金の超微粒子が均一に付着していた。走査型電子顕微鏡写真より粒子７０個の平均粒径を測定するとともに、粒径の分布の広がりの程度を示すＣＶ値を求めた。その結果を表１に示す。 FIG. 1 shows a scanning electron micrograph of silica particles. Moreover, FIG. 2 shows the scanning electron micrograph of the silica particle in which the metal nucleus was formed. Referring to FIG. 2, the ultrafine gold particles were uniformly attached to the entire surface of the silica particles. While measuring the average particle diameter of 70 particles from a scanning electron micrograph, a CV value indicating the extent of the distribution of the particle diameter was determined. The results are shown in Table 1.
（Ｂ）金属皮膜の形成
上記「（Ａ）前処理」で得られた粒子１ｇに水２００ｍＬを加えて１０分間超音波処理した後、３−メルカプトトリエトキシシラン０．０１５ｍｌを加え、マグネチックスターラーで５分間攪拌した。その後、硝酸銀０．６５ｇを加えて更に１０分間攪拌した。次に、２５％アンモニア水溶液１３ｍＬを加えた後、０．２４ｍｍｏｌ／Ｌホルマリン水溶液を２０ｍＬ添加して５分間攪拌した。沈殿した銀層被覆シリカ粒子を吸引ろ過で採取し、メタノールで洗浄した後、オーブン７０℃で３時間乾燥した。(B) Formation of metal film After adding 200 mL of water to 1 g of the particles obtained in the above “(A) pretreatment” and ultrasonically treating for 10 minutes, 0.015 ml of 3-mercaptotriethoxysilane was added, and a magnetic stirrer was added. For 5 minutes. Thereafter, 0.65 g of silver nitrate was added and the mixture was further stirred for 10 minutes. Next, after adding 13 mL of 25% aqueous ammonia solution, 20 mL of 0.24 mmol / L formalin aqueous solution was added and stirred for 5 minutes. The precipitated silver layer-coated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 ° C. for 3 hours.
図３は、金属皮膜が形成された導電性粒子の走査型電子顕微鏡写真を示す。図３を参照すると、シリカ粒子の全表面に金属皮膜が形成されていた。
走査型電子顕微鏡写真より粒子７０個の平均粒径を測定し、ＣＶ値を求めた。その結果を表２に示す。FIG. 3 shows a scanning electron micrograph of conductive particles on which a metal film is formed. Referring to FIG. 3, a metal film was formed on the entire surface of the silica particles.
The average particle diameter of 70 particles was measured from a scanning electron micrograph and the CV value was determined. The results are shown in Table 2.
金属皮膜の厚みは０．１１μｍであった。
＜樹脂中での分散性評価＞
樹脂（商品名：ＳＴＲＵＣＴ ＢＯＮＤ）１０ｇを混練機で１分間攪拌した。この樹脂に実施例１の導電性粒子０．２ｇを加え、１分間攪拌した。導電性粒子が配合された樹脂を、スライドガラスに押し付け、カバーガラスを被せて光学顕微鏡で観察した。光学顕微鏡写真を図４に示す。The thickness of the metal film was 0.11 μm.
<Dispersibility evaluation in resin>
10 g of resin (trade name: STRUCT BOND) was stirred with a kneader for 1 minute. To this resin, 0.2 g of the conductive particles of Example 1 was added and stirred for 1 minute. The resin containing the conductive particles was pressed against a slide glass, covered with a cover glass, and observed with an optical microscope. An optical micrograph is shown in FIG.
光学顕微鏡観察より、粒子３０２個中、２個以上の合着粒子数は４個（１．３２％）だけであり、樹脂中での分散性は非常に良好であった。
＜蛍光Ｘ線分析＞
実施例１で得られた導電性粒子を全自動蛍光Ｘ線分析装置（スペクトリス社製、ＰＷ２４００型、管球：Ｒｈ、測定元素：Ｎａ〜Ｕ、照射面積：２５ｍｍφ）を使用して、定性分析を行った。まず、導電性粒子を約２ｇ採取し、ポリプロピレン製６μｍフィルム上へ均一にマウントした。次に、そのフィルムを全自動蛍光Ｘ線分析装置にセットして、測定部をヘリウムで置換した。Ｎａ〜Ｕの元素の蛍光Ｘ線を検出できる波長範囲を走査することにより、元素を特定した。その結果、検出された元素は硫黄、銀及び金の三種のみであった。それら三種の元素以外の元素は検出されなかった。蛍光Ｘ線分析のチャートを図５〜図７に示す。なお、図５は銀の検出を示す蛍光Ｘ線分析のチャートであり、図６は金の検出を示す蛍光Ｘ線分析のチャートであり、図７は硫黄の検出を示す蛍光Ｘ線分析のチャートである。From observation with an optical microscope, among 302 particles, the number of coalesced particles of 2 or more was only 4 (1.32%), and the dispersibility in the resin was very good.
<Fluorescence X-ray analysis>
Qualitative analysis of the conductive particles obtained in Example 1 using a fully automatic X-ray fluorescence analyzer (Spectris PW2400, tube: Rh, measurement element: Na to U, irradiation area: 25 mmφ) Went. First, about 2 g of conductive particles were collected and mounted uniformly on a 6 μm film made of polypropylene. Next, the film was set in a fully automatic fluorescent X-ray analyzer, and the measurement part was replaced with helium. Elements were identified by scanning a wavelength range in which fluorescent X-rays of Na to U elements could be detected. As a result, only three elements, sulfur, silver and gold, were detected. No elements other than these three elements were detected. The fluorescent X-ray analysis charts are shown in FIGS. 5 is a chart of fluorescent X-ray analysis showing detection of silver, FIG. 6 is a chart of fluorescent X-ray analysis showing detection of gold, and FIG. 7 is a chart of fluorescent X-ray analysis showing detection of sulfur. It is.
＜電気抵抗値の測定＞
微小圧縮試験機（島津製作所製）を用いて、実施例１の導電性粒子２０個の電気抵抗値を測定して、平均値を求めた。得られた結果を標準偏差とともに表３に示す。<Measurement of electrical resistance value>
Using a micro compression tester (manufactured by Shimadzu Corporation), the electrical resistance value of 20 conductive particles of Example 1 was measured, and the average value was obtained. The results obtained are shown in Table 3 together with the standard deviation.
（実施例２）
シリカ粒子（平均粒径：４．２２μｍ、ＣＶ：１．１３％）を使用した以外は、実施例１と同様にして銀層被覆シリカ粒子を作製した。
＜耐湿熱評価＞
得られた導電性粒子について、恒湿恒温器（エスペック製）を用いて、６０℃、９０％ＲＨ、２４０ｈの条件で、湿熱試験を行った。図８は、湿熱試験前における導電性粒子の走査型電子顕微鏡写真を示し、図９は、湿熱試験後における導電性粒子の走査型電子顕微鏡の写真を示す。図８及び図９を比較した結果、湿熱試験の前後で銀層の状態に変化は見られなかった。(Example 2)
Silver layer-coated silica particles were produced in the same manner as in Example 1 except that silica particles (average particle size: 4.22 μm, CV: 1.13%) were used.
<Heat and heat resistance evaluation>
The obtained conductive particles were subjected to a moist heat test under the conditions of 60 ° C., 90% RH, and 240 h using a thermo-hygrostat (manufactured by ESPEC). FIG. 8 shows a scanning electron micrograph of the conductive particles before the wet heat test, and FIG. 9 shows a scanning electron micrograph of the conductive particles after the wet heat test. As a result of comparing FIG. 8 and FIG. 9, there was no change in the state of the silver layer before and after the wet heat test.
湿熱試験の前後で導電性粒子５０個の電気抵抗値を測定し、電気抵抗値が観測された導電性粒子の個数と、電気抵抗値の平均値とをそれぞれ求めた。得られた結果を表４に示す。 The electric resistance value of 50 conductive particles was measured before and after the wet heat test, and the number of conductive particles in which the electric resistance value was observed and the average value of the electric resistance value were obtained. Table 4 shows the obtained results.
表４の結果から、湿熱試験前後で電気抵抗値が観測されなかった粒子の個数差は４個のみであった。
（実施例３）
実施例１「（Ａ）前処理」で得られた粒子１ｇに水２００ｍＬを加えて１０分間超音波処理した後、３-メルカプトプロピルメチルジメトキシシラン０．０１５ｍｌを加え、マグネチックスターラーで５分間攪拌した。その後、硝酸銀０．６５ｇを加えて更に１０分間攪拌した。次に、２５％アンモニア水溶液１３ｍＬを加えた後、０．２４ｍｍｏｌ／Ｌホルマリン水溶液を２０ｍＬ添加して５分間攪拌した。沈殿した銀層被覆シリカ粒子を吸引ろ過で採取し、メタノールで洗浄した後、オーブン７０℃で３時間乾燥した。From the results in Table 4, the difference in the number of particles in which no electrical resistance value was observed before and after the wet heat test was only 4.
Example 3
200 g of water was added to 1 g of the particles obtained in Example 1 “(A) pretreatment” and subjected to ultrasonic treatment for 10 minutes, 0.015 ml of 3-mercaptopropylmethyldimethoxysilane was added, and the mixture was stirred with a magnetic stirrer for 5 minutes. did. Thereafter, 0.65 g of silver nitrate was added and the mixture was further stirred for 10 minutes. Next, after adding 13 mL of 25% aqueous ammonia solution, 20 mL of 0.24 mmol / L formalin aqueous solution was added and stirred for 5 minutes. The precipitated silver layer-coated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 ° C. for 3 hours.
図１０は、金属皮膜が形成された導電性粒子の走査型電子顕微鏡写真を示す。図１０を参照すると、シリカ粒子のほぼ全表面に金属皮膜が形成されていた。
（実施例４）
実施例１「（Ａ）前処理」で得られた粒子１ｇに水２００ｍＬを加えて１０分間超音波処理した後、３-メルカプトプロピルトリメトキシシラン０．０１５ｍｌを加え、マグネチックスターラーで５分間攪拌した。その後、硝酸銀０．６５ｇを加えて更に１０分間攪拌した。次に、２５％アンモニア水溶液１３ｍＬを加えた後、０．２４ｍｍｏｌ／Ｌホルマリン水溶液を２０ｍＬ添加して５分間攪拌した。沈殿した銀層被覆シリカ粒子を吸引ろ過で採取し、メタノールで洗浄した後、オーブン７０℃で３時間乾燥した。FIG. 10 shows a scanning electron micrograph of conductive particles on which a metal film is formed. Referring to FIG. 10, a metal film was formed on almost the entire surface of the silica particles.
Example 4
200 g of water was added to 1 g of the particles obtained in Example 1 “(A) pretreatment” and subjected to ultrasonic treatment for 10 minutes, 0.015 ml of 3-mercaptopropyltrimethoxysilane was added, and the mixture was stirred for 5 minutes with a magnetic stirrer. did. Thereafter, 0.65 g of silver nitrate was added and the mixture was further stirred for 10 minutes. Next, after adding 13 mL of 25% aqueous ammonia solution, 20 mL of 0.24 mmol / L formalin aqueous solution was added and stirred for 5 minutes. The precipitated silver layer-coated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 ° C. for 3 hours.
図１１は、金属皮膜が形成された導電性粒子の走査型電子顕微鏡写真を示す。図１１を参照すると、シリカ粒子のほぼ全表面に金属皮膜が形成されていた。
（比較例１）
実施例１「（Ａ）前処理」と同様にして得られた粒子１ｇに水２００ｍＬを加えて１０分間超音波処理した後、硝酸銀０．６５ｇを加えてマグネチックスターラーで１０分間攪拌した。次に、２５％アンモニア水溶液１３ｍＬを加えた後、０．２４ｍｍｏｌ／Ｌホルマリン水溶液を２０ｍＬ添加して５分間攪拌した。沈殿した銀層被覆シリカ粒子を吸引ろ過で採取し、メタノールで洗浄した後、オーブン７０℃で３時間乾燥した。FIG. 11 shows a scanning electron micrograph of conductive particles on which a metal film is formed. Referring to FIG. 11, a metal film was formed on almost the entire surface of the silica particles.
(Comparative Example 1)
200 g of water was added to 1 g of the particles obtained in the same manner as in Example 1 “(A) pretreatment” and subjected to ultrasonic treatment for 10 minutes, then 0.65 g of silver nitrate was added, and the mixture was stirred with a magnetic stirrer for 10 minutes. Next, after adding 13 mL of 25% aqueous ammonia solution, 20 mL of 0.24 mmol / L formalin aqueous solution was added and stirred for 5 minutes. The precipitated silver layer-coated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 ° C. for 3 hours.
図１２は、金属皮膜が形成された導電性粒子の走査型電子顕微鏡写真を示す。図１２を参照すると、比較例１の導電性粒子では、非導電性粒子の表面の一部に金属皮膜が形成されていなかった。
（比較例２）
（Ａ）表面処理
５００ｍＬの三角フラスコに非導電性粒子としてのシリカ粒子（平均粒径６．４０μｍ、ＣＯＵＬＴＥＲ社製ＭＵＬＴＩＳＩＺＥＲＩＩで測定）１０ｇを入れ、イソプロピルアルコール（ＩＰＡ）６３ｇを加え、１０分間超音波処理した。更にメタノール６３ｇを加えてマグネチックスターラーで１０分間攪拌し、２５％アンモニア水溶液５０ｇを加え、３０℃のオイルバス中で１０分間攪拌することにより、Ａ液を調整した。FIG. 12 shows a scanning electron micrograph of conductive particles on which a metal film is formed. Referring to FIG. 12, in the conductive particles of Comparative Example 1, a metal film was not formed on a part of the surface of the nonconductive particles.
(Comparative Example 2)
(A) Surface treatment Into a 500 mL Erlenmeyer flask, 10 g of silica particles (non-conductive particle size: 6.40 μm, measured with MULTISIZER II manufactured by COULTER) was added, 63 g of isopropyl alcohol (IPA) was added, and ultrasonication was performed for 10 minutes Processed. Further, 63 g of methanol was added and stirred with a magnetic stirrer for 10 minutes, 50 g of 25% aqueous ammonia solution was added, and the mixture was stirred for 10 minutes in an oil bath at 30 ° C. to prepare solution A.
３−メルカプトプロピルトリエトキシシラン４．５ｍＬをＡ液に加えてオイルバスを６５℃に過熱して３時間攪拌した。攪拌を止め、メタノール分級を３回行った後、吸引ろ過してチオールで表面処理されたシリカ粒子を採取し、オーブンで７０℃、３時間乾燥させた。 4.5 mL of 3-mercaptopropyltriethoxysilane was added to the liquid A, and the oil bath was heated to 65 ° C. and stirred for 3 hours. Stirring was stopped, and methanol classification was performed three times. Then, silica particles surface-treated with thiol by suction filtration were collected, and dried in an oven at 70 ° C. for 3 hours.
（Ｂ）金属皮膜の形成
（Ａ）表面処理で得られた粒子１ｇに水２００ｍＬを加えて１０分間超音波処理した後、硝酸銀０．６５ｇを加えて１０分間攪拌した。次に、２５％アンモニア水溶液１３ｍＬを加えた後、０．２４ｍｍｏｌ／Ｌホルマリン水溶液を２０ｍＬ添加して５分間攪拌した。沈殿したシリカ粒子を吸引ろ過で採取し、メタノールで洗浄した後、オーブン７０℃で３時間乾燥した。(B) Formation of metal film (A) After adding 200 mL of water to 1 g of the particles obtained by the surface treatment and ultrasonicating for 10 minutes, 0.65 g of silver nitrate was added and stirred for 10 minutes. Next, after adding 13 mL of 25% aqueous ammonia solution, 20 mL of 0.24 mmol / L formalin aqueous solution was added and stirred for 5 minutes. The precipitated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 ° C. for 3 hours.
図１３は、得られたシリカ粒子の走査型電子顕微鏡写真を示す。図１３を参照すると、シリカ粒子に銀が被覆されていなかった。
（比較例３）
樹脂粒子に無電解ニッケルめっきにより下地層を形成し、ニッケルを金と置換する置換金めっきにより得られた導電性粒子（平均粒径：３．５５μm、ＣＶ値：４．５０％）について、上記と同じ条件で耐湿熱評価を行った。図１４は、湿熱試験前における走査型電子顕微鏡写真を示し、図１５は、湿熱試験後における走査型電子顕微鏡写真を示す。図１４及び図１５を参照すると、湿熱試験後の金属層の状態は、湿熱試験前のものと比べて大きく変化し、荒れている。これは、ニッケルが酸化して腐食したことによるものと考えられる。FIG. 13 shows a scanning electron micrograph of the obtained silica particles. Referring to FIG. 13, the silica particles were not coated with silver.
(Comparative Example 3)
About conductive particles (average particle diameter: 3.55 μm, CV value: 4.50%) obtained by substitution gold plating in which a base layer is formed on resin particles by electroless nickel plating and nickel is replaced with gold. The moisture and heat resistance evaluation was performed under the same conditions. FIG. 14 shows a scanning electron micrograph before the wet heat test, and FIG. 15 shows a scanning electron micrograph after the wet heat test. Referring to FIGS. 14 and 15, the state of the metal layer after the wet heat test is greatly changed and rough as compared with that before the wet heat test. This is considered to be because nickel was oxidized and corroded.
湿熱試験の前後で導電性粒子５０個の電気抵抗値を測定して、電気抵抗値が観測された導電性粒子の個数と、電気抵抗値の平均値とをそれぞれ求めた。得られた結果を表５に示す。 The electric resistance value of 50 conductive particles was measured before and after the wet heat test, and the number of conductive particles in which the electric resistance value was observed and the average value of the electric resistance value were obtained. The results obtained are shown in Table 5.
表５の結果から、湿熱試験前後で電気抵抗値が観測されなかった粒子の個数差は３９個であり、試験後の発現率はわずか１０％（５／５０個）であった。
（比較例４）
シリカ粒子（平均粒径：６．４２μm、ＣＶ値：０．７０％）に無電解ニッケルめっきにより下地層を形成し、ニッケルを金と置換する置換金めっきにより得られた導電性粒子（平均粒径：６．７５μm、ＣＶ値：０．７７％）について、上記と同じ条件で耐湿熱評価を行った。図１６は、湿熱試験前における走査型電子顕微鏡写真を示し、図１７は、湿熱試験後における走査型電子顕微鏡写真を示す。図１６及び図１７を参照すると、湿熱試験後の金属層の状態は大きく変化し、荒れている。これは、ニッケルが酸化して腐食したことによるものと考えられる。From the results of Table 5, the difference in the number of particles in which no electrical resistance value was observed before and after the wet heat test was 39, and the expression rate after the test was only 10% (5/50).
(Comparative Example 4)
Conductive particles (average particle size) obtained by displacement gold plating in which a base layer is formed by electroless nickel plating on silica particles (average particle size: 6.42 μm, CV value: 0.70%). (Diameter: 6.75 μm, CV value: 0.77%), the wet heat resistance was evaluated under the same conditions as described above. FIG. 16 shows a scanning electron micrograph before the wet heat test, and FIG. 17 shows a scanning electron micrograph after the wet heat test. Referring to FIGS. 16 and 17, the state of the metal layer after the wet heat test is greatly changed and roughened. This is considered to be because nickel was oxidized and corroded.
湿熱試験の前後で導電性粒子５０個の電気抵抗値を測定し、電気抵抗値が観測された導電性粒子の個数と、電気抵抗値の平均値とをそれぞれ求めた。得られた結果を表６に示す。 The electric resistance value of 50 conductive particles was measured before and after the wet heat test, and the number of conductive particles in which the electric resistance value was observed and the average value of the electric resistance value were obtained. The results obtained are shown in Table 6.
表６の結果から、湿熱試験の前後で電気抵抗値が観測されなかった粒子の個数差は４０個であり、試験後の発現率はわずか１２％（６／５０個）であった。
（比較例５）
実施例１の「（Ａ）前処理」で得られた粒子１ｇに水２００ｍＬを加えて１０分間超音波処理した後、２−メルカプトエタノール０．０２０ｍｌを加え、マグネチックスターラーで５分間攪拌した。その後、硝酸銀０．６５ｇを加えて更に１０分間攪拌した。次に、２５％アンモニア水溶液１３ｍＬを加えた後、０．２４ｍｍｏｌ／Ｌホルマリン水溶液を２０ｍＬ添加して５分間攪拌した。沈殿した銀層被覆シリカ粒子を吸引ろ過で採取し、メタノールで洗浄した後、オーブン７０℃で３時間乾燥した。From the results in Table 6, the difference in the number of particles in which no electrical resistance value was observed before and after the wet heat test was 40, and the expression rate after the test was only 12% (6/50 particles).
(Comparative Example 5)
200 g of water was added to 1 g of the particles obtained in “(A) pretreatment” in Example 1 and subjected to ultrasonic treatment for 10 minutes, 0.020 ml of 2-mercaptoethanol was added, and the mixture was stirred with a magnetic stirrer for 5 minutes. Thereafter, 0.65 g of silver nitrate was added and the mixture was further stirred for 10 minutes. Next, after adding 13 mL of 25% aqueous ammonia solution, 20 mL of 0.24 mmol / L formalin aqueous solution was added and stirred for 5 minutes. The precipitated silver layer-coated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 ° C. for 3 hours.
図１８は、金属皮膜が形成された導電性粒子の走査型電子顕微鏡写真を示す。図１８を参照すると、シリカ粒子の表面に銀が被覆されていなかった。
（比較例６）
実施例１「（Ａ）前処理」で得られた粒子１ｇに水２００ｍＬを加えて１０分間超音波処理した後、オクタン酸２−メルカプトエチル０．０１５ｍｌを加え、マグネチックスターラーで５分間攪拌した。その後、硝酸銀０．６５ｇを加えて更に１０分間攪拌した。次に、２５％アンモニア水溶液１３ｍＬを加えた後、０．２４ｍｍｏｌ／Ｌホルマリン水溶液を２０ｍＬ添加して５分間攪拌した。沈殿した銀層被覆シリカ粒子を吸引ろ過で採取し、メタノールで洗浄した後、オーブン７０℃で３時間乾燥した。FIG. 18 shows a scanning electron micrograph of conductive particles on which a metal film is formed. Referring to FIG. 18, the surface of the silica particles was not coated with silver.
(Comparative Example 6)
200 g of water was added to 1 g of the particles obtained in Example 1 “(A) pretreatment” and subjected to ultrasonic treatment for 10 minutes, then 0.015 ml of 2-mercaptoethyl octoate was added, and the mixture was stirred for 5 minutes with a magnetic stirrer. . Thereafter, 0.65 g of silver nitrate was added and the mixture was further stirred for 10 minutes. Next, after adding 13 mL of 25% aqueous ammonia solution, 20 mL of 0.24 mmol / L formalin aqueous solution was added and stirred for 5 minutes. The precipitated silver layer-coated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 ° C. for 3 hours.
図１９は、金属皮膜が形成された導電性粒子の走査型電子顕微鏡写真を示す。図１９を参照すると、シリカ粒子の表面に銀被が覆されていなかった。
（比較例７）
実施例１「（Ａ）前処理」で得られた粒子１ｇに水２００ｍＬを加えて１０分間超音波処理した後、メルカプト酢酸カルシウム三水和物０．０１３ｇを加え、マグネチックスターラーで５分間攪拌した。その後、硝酸銀０．６５ｇを加えて更に１０分間攪拌した。次に、２５％アンモニア水溶液１３ｍＬを加えた後、０．２４ｍｍｏｌ／Ｌホルマリン水溶液を２０ｍＬ添加して５分間攪拌した。沈殿した銀層被覆シリカ粒子を吸引ろ過で採取し、メタノールで洗浄した後、オーブン７０℃で３時間乾燥した。FIG. 19 shows a scanning electron micrograph of conductive particles on which a metal film is formed. Referring to FIG. 19, the silver coat was not covered on the surface of the silica particles.
(Comparative Example 7)
200 g of water was added to 1 g of the particles obtained in Example 1 “(A) pretreatment” and subjected to ultrasonic treatment for 10 minutes, 0.013 g of calcium mercaptoacetate trihydrate was added, and the mixture was stirred with a magnetic stirrer for 5 minutes. did. Thereafter, 0.65 g of silver nitrate was added and the mixture was further stirred for 10 minutes. Next, after adding 13 mL of 25% aqueous ammonia solution, 20 mL of 0.24 mmol / L formalin aqueous solution was added and stirred for 5 minutes. The precipitated silver layer-coated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 ° C. for 3 hours.
図２０は、金属皮膜が形成された導電性粒子の走査型電子顕微鏡写真を示す。図２０を参照すると、シリカ粒子の表面に銀が被覆されていなかった。
（比較例８）
実施例１「（Ａ）前処理」で得られた粒子１ｇに水２００ｍＬを加えて１０分間超音波処理した後、３−アミノプロピルトリメトキシシラン０．０１５ｍｌを加え、マグネチックスターラーで５分間攪拌した。その後、硝酸銀０．６５ｇを加えて更に１０分間攪拌した。次に、２５％アンモニア水溶液１３ｍＬを加えた後、０．２４ｍｍｏｌ／Ｌホルマリン水溶液を２０ｍＬ添加して５分間攪拌した。沈殿した銀層被覆シリカ粒子を吸引ろ過で採取し、メタノールで洗浄した後、オーブン７０℃で３時間乾燥した。FIG. 20 shows a scanning electron micrograph of conductive particles on which a metal film is formed. Referring to FIG. 20, the surface of the silica particles was not coated with silver.
(Comparative Example 8)
200 g of water was added to 1 g of the particles obtained in Example 1 “(A) pretreatment” and subjected to ultrasonic treatment for 10 minutes, 0.015 ml of 3-aminopropyltrimethoxysilane was added, and the mixture was stirred with a magnetic stirrer for 5 minutes. did. Thereafter, 0.65 g of silver nitrate was added and the mixture was further stirred for 10 minutes. Next, after adding 13 mL of 25% aqueous ammonia solution, 20 mL of 0.24 mmol / L formalin aqueous solution was added and stirred for 5 minutes. The precipitated silver layer-coated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 ° C. for 3 hours.
図２１は、金属皮膜が形成された導電性粒子の走査型電子顕微鏡写真を示す。図２１を参照すると、非導電性粒子の表面の一部には金属皮膜が形成されていなかった。
得られた導電性粒子について、樹脂中での分散性評価を行った。図２２は、分散性評価に使用した光学顕微鏡写真を示す。図２２を参照すると、導電性粒子が凝集している様子が観察された。このことは、液晶表示素子のシール剤として用いられる単分散の導電性粒子の収率が低いことを示唆している。FIG. 21 shows a scanning electron micrograph of conductive particles on which a metal film has been formed. Referring to FIG. 21, a metal film was not formed on part of the surface of the non-conductive particles.
About the obtained electroconductive particle, the dispersibility evaluation in resin was performed. FIG. 22 shows an optical micrograph used for evaluation of dispersibility. Referring to FIG. 22, it was observed that the conductive particles were aggregated. This has suggested that the yield of the monodispersed electroconductive particle used as a sealing agent of a liquid crystal display element is low.
Claims (9)
前記無電解めっきは、前記非導電性粒子に金属核を付着させる前処理の後に実施されるとともに、チオール基を有するシラン化合物の存在下で銀からなる前記金属皮膜を形成することを特徴とする金属皮膜形成方法。 A metal film forming method for forming a metal film by electroless plating on non-conductive particles having a particle size in a range of 0.5 μm to 100 μm,
The electroless plating is performed after a pretreatment for attaching a metal nucleus to the nonconductive particles, and forms the metal film made of silver in the presence of a silane compound having a thiol group. Metal film formation method.
前記シランカップリング剤は、前記金属塩の金属に対してキレートを形成する官能基を有することを特徴とする請求項１から請求項４のいずれか一項に記載の金属皮膜形成方法。 In the pretreatment, after a treatment liquid containing a silane coupling agent, a hydrolysis catalyst and a metal salt is brought into contact with the non-conductive particles, a metal nucleus is attached by depositing a metal of the metal salt with a reducing agent. Process
The said silane coupling agent has a functional group which forms a chelate with respect to the metal of the said metal salt, The metal film formation method as described in any one of Claims 1-4 characterized by the above-mentioned.
前記非導電性粒子の粒径は、０．５μｍ〜１００μｍの範囲であり、
前記金属皮膜は、銀の単層から構成され、
前記導電性粒子の蛍光Ｘ線分析において前記非導電性粒子に含まれる元素以外の元素として金、銀及び硫黄のみが検出されることを特徴とする導電性粒子。 Conductive particles provided with conductivity by a metal film formed on the entire surface of the non-conductive particles,
The particle size of the non-conductive particles is in the range of 0.5 μm to 100 μm,
The metal film is composed of a single layer of silver ,
Conductive particles characterized in that only gold, silver and sulfur are detected as elements other than the elements contained in the non-conductive particles in the fluorescent X-ray analysis of the conductive particles.
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