JP6151017B2 - Nickel ultrafine powder, conductive paste, and method for producing nickel ultrafine powder - Google Patents
Nickel ultrafine powder, conductive paste, and method for producing nickel ultrafine powder Download PDFInfo
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- 229910052759 nickel Inorganic materials 0.000 title claims description 109
- 239000000843 powder Substances 0.000 title claims description 105
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- 239000001301 oxygen Substances 0.000 claims description 35
- 229910052760 oxygen Inorganic materials 0.000 claims description 35
- 239000012298 atmosphere Substances 0.000 claims description 24
- 239000002245 particle Substances 0.000 claims description 20
- 229910001453 nickel ion Inorganic materials 0.000 claims description 17
- 238000006243 chemical reaction Methods 0.000 claims description 14
- 238000010828 elution Methods 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 14
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- 238000002156 mixing Methods 0.000 claims description 11
- 229910000480 nickel oxide Inorganic materials 0.000 claims description 11
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 claims description 11
- 238000003756 stirring Methods 0.000 claims description 11
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- 239000001856 Ethyl cellulose Substances 0.000 claims description 4
- ZZSNKZQZMQGXPY-UHFFFAOYSA-N Ethyl cellulose Chemical compound CCOCC1OC(OC)C(OCC)C(OCC)C1OC1C(O)C(O)C(OC)C(CO)O1 ZZSNKZQZMQGXPY-UHFFFAOYSA-N 0.000 claims description 4
- 239000002270 dispersing agent Substances 0.000 claims description 4
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- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 6
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- VEQPNABPJHWNSG-UHFFFAOYSA-N Nickel(2+) Chemical compound [Ni+2] VEQPNABPJHWNSG-UHFFFAOYSA-N 0.000 description 3
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- 239000002184 metal Substances 0.000 description 3
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- BFDHFSHZJLFAMC-UHFFFAOYSA-L nickel(ii) hydroxide Chemical compound [OH-].[OH-].[Ni+2] BFDHFSHZJLFAMC-UHFFFAOYSA-L 0.000 description 3
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- UODXCYZDMHPIJE-UHFFFAOYSA-N menthanol Chemical compound CC1CCC(C(C)(C)O)CC1 UODXCYZDMHPIJE-UHFFFAOYSA-N 0.000 description 2
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- IGODOXYLBBXFDW-UHFFFAOYSA-N alpha-Terpinyl acetate Chemical compound CC(=O)OC(C)(C)C1CCC(C)=CC1 IGODOXYLBBXFDW-UHFFFAOYSA-N 0.000 description 1
- WUOACPNHFRMFPN-UHFFFAOYSA-N alpha-terpineol Chemical compound CC1=CCC(C(C)(C)O)CC1 WUOACPNHFRMFPN-UHFFFAOYSA-N 0.000 description 1
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- SQIFACVGCPWBQZ-UHFFFAOYSA-N delta-terpineol Natural products CC(C)(O)C1CCC(=C)CC1 SQIFACVGCPWBQZ-UHFFFAOYSA-N 0.000 description 1
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- GCLGEJMYGQKIIW-UHFFFAOYSA-H sodium hexametaphosphate Chemical compound [Na]OP1(=O)OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])O1 GCLGEJMYGQKIIW-UHFFFAOYSA-H 0.000 description 1
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Description
本発明は、ニッケル超微粉、導電ペーストおよびニッケル超微粉の製造方法に関する。 The present invention relates to a nickel ultrafine powder, a conductive paste, and a method for producing a nickel ultrafine powder.
積層セラミックコンデンサ内部電極に用いられるニッケル超微粉は、有機樹脂等のバインダーを加えて、ペースト化して使用されることが一般的である。ペーストはスクリーン印刷等により、セラミックグリーンシート上に薄層に塗布される。そのようなセラミックグリーンシートと内部電極層とを数百にも積層した積層体について、脱脂工程、焼結工程、焼成工程を行うことで、積層セラミックコンデンサを製造する。 The nickel ultrafine powder used for the multilayer ceramic capacitor internal electrode is generally used in the form of a paste by adding a binder such as an organic resin. The paste is applied in a thin layer on the ceramic green sheet by screen printing or the like. A multilayer ceramic capacitor is manufactured by performing a degreasing step, a sintering step, and a firing step on a laminate in which hundreds of such ceramic green sheets and internal electrode layers are laminated.
近年、電子機器の小型化への進展は止まるところがなく、電子機器の構成部品である積層セラミックコンデンサについても、より一層の小型化が求められている。それに伴って、積層チップ部品をさらに小型化することを目的として、内部電極層をより薄層化し、積層数を増加させる技術の開発が行われている。上記技術の一つとして、内部電極材料であるニッケル微粉末の小径化が挙げられる。 In recent years, the progress toward miniaturization of electronic devices has not been stopped, and further miniaturization is required for multilayer ceramic capacitors which are components of electronic devices. Along with this, for the purpose of further reducing the size of the multilayer chip component, the development of a technique for making the internal electrode layer thinner and increasing the number of layers has been performed. One of the above-mentioned techniques is to reduce the diameter of nickel fine powder that is an internal electrode material.
しかしながら、上記ニッケル微粉末は、上述した焼成工程の温度よりも大幅に低い温度で、熱収縮を突如引き起こす傾向があり、この傾向はニッケル微粉末が細粒化するほど顕著になる。
ニッケル微粉末が熱収縮を起こすと、内部電極の製造時、セラミック基材と金属ニッケル微粉末との熱収縮特性の相違に起因し、焼成の際にニッケル微粉末のデラミネーション（剥離）やクラック（割れ）等の欠陥が発生する。
However, the nickel fine powder tends to suddenly cause thermal shrinkage at a temperature significantly lower than the temperature of the above-described firing step, and this tendency becomes more prominent as the nickel fine powder becomes finer.
When the nickel fine powder undergoes heat shrinkage, due to the difference in heat shrinkage characteristics between the ceramic substrate and the metal nickel fine powder during the production of the internal electrode, delamination (cracking) and cracking of the nickel fine powder during firing Defects such as (cracking) occur.
また、薄層化された電極には、膜表面粗さが小さく、膜密度の高い乾燥膜が得られ、かつ粘度が安定した導電ペーストが求められているが、ニッケル超微粉の細粒化が進むにつれて、導電ペーストの分散が困難となり、ペースト粘度が安定しない問題が発生する。
ペースト粘度が経時変化を起こして増粘すると、製造現場での取り扱いが困難となり、導電ペーストに加工して以降の長期保管が困難となり、電子部品の製造等に用いる導電ペーストとしての品質管理、品質維持に費やす管理が煩雑となる。すなわち、導電ペーストとしての品質である分散性のほか、粘度を適正に維持できる性質を具備していることが求められる。
In addition, for thin electrodes, there is a demand for a conductive paste having a low film surface roughness, a high film density, and a stable viscosity. As the process proceeds, it becomes difficult to disperse the conductive paste, and the paste viscosity is not stable.
If the paste viscosity changes over time, it becomes difficult to handle at the manufacturing site, and it becomes difficult to store for a long time after processing into a conductive paste. Quality control and quality as a conductive paste used in the manufacture of electronic components, etc. The management spent on maintenance becomes complicated. That is, in addition to dispersibility, which is a quality as a conductive paste, it is required to have the property of maintaining a proper viscosity.
ニッケル超微粉の耐熱収縮性とペースト粘度安定化とを両立させるためには、ニッケル超微粉の表面に適度な酸化層を設ければよいことが、本発明者等の研究から分かってきた。ニッケル超微粉の表面に酸化層を形成しようとすれば、最も単純には、大気中で加熱することにより、容易に酸化被膜を形成できる。
また、従来のニッケル超微粉の表面酸化方法としては、例えば、特許文献１や特許文献２に記載された方法がある。
It has been found from studies by the present inventors that an appropriate oxide layer should be provided on the surface of the nickel ultrafine powder in order to achieve both heat shrinkage resistance of the nickel ultrafine powder and stabilization of the paste viscosity. If an oxide layer is to be formed on the surface of nickel ultrafine powder, the oxide film can be easily formed by heating in the air most simply.
Moreover, as a conventional surface oxidation method of nickel ultrafine powder, for example, there are methods described in Patent Document 1 and
しかしながら、従来の方法により得られたニッケル超微粉においては、熱収縮性の改善ならびに導電ペーストにおける分散性および粘度安定性が不十分であることが分かった。
本発明は、以上の点を鑑みてなされたものであり、耐熱収縮性が良好で、かつ、ペースト化したときの分散性および経時的な粘度安定性に優れるニッケル超微粉を提供することを目的とする。
However, it has been found that the nickel ultrafine powder obtained by the conventional method has insufficient heat shrinkability and insufficient dispersibility and viscosity stability in the conductive paste.
The present invention has been made in view of the above points, and an object of the present invention is to provide an ultrafine nickel powder that has good heat shrinkage resistance and is excellent in dispersibility when formed into a paste and viscosity stability over time. And
本発明者らが、上記目的を達成するために鋭意検討した結果、所定の方法により粒子表面に酸化ニッケル層を形成したニッケル超微粉においては、耐熱収縮性が良好で、かつ、ペースト化したときの分散性および経時的な粘度安定性に優れることを見出し、本発明を完成させた。 As a result of intensive studies by the present inventors to achieve the above object, the nickel ultrafine powder in which the nickel oxide layer is formed on the particle surface by a predetermined method has good heat shrinkage resistance and is made into a paste. Was found to be excellent in dispersibility and viscosity stability over time, and the present invention was completed.
すなわち、本発明は、以下の（１）〜（５）を提供する。
（１）酸素含有量が０．２質量％以上であり、ペースト化したときのニッケルイオン溶出率が０．０５質量％以下である、ニッケル超微粉。
（２）カールフィッシャー法により測定される３００℃と１５０℃との水分量差で規定される水酸化物水分量が０．２質量％未満である、上記（１）に記載のニッケル超微粉。
（３）上記（１）または（２）に記載のニッケル超微粉を用いて作製した導電ペーストであって、１０μｍの厚さに塗布し、乾燥して得られる乾燥膜を倍率４０倍の光学顕微鏡で観察した際の１視野面積２８．３ｍｍ２あたりの最小径５μｍ以上である凝集体の個数が１０個以下であり、かつ、２２℃で保管した場合におけるペースト作製２０日後の粘度上昇率が２０％以下である、導電ペースト。
（４）ニッケル超微粉を、大気雰囲気または酸化雰囲気である反応雰囲気中で、周速５ｍ／ｓ以上で混合攪拌し、品温が１００〜２５０℃となるようにメカノケミカル処理を施すことにより、上記（１）または（２）に記載のニッケル超微粉を得る、ニッケル超微粉の製造方法。
（５）上記反応雰囲気中の酸素濃度および／または上記反応雰囲気の雰囲気ガス流量を調整することにより、得られるニッケル超微粉の酸素含有量を制御する、上記（４）に記載のニッケル超微粉の製造方法。
That is, the present invention provides the following (1) to (5).
(1) Nickel ultrafine powder having an oxygen content of 0.2% by mass or more and a nickel ion elution rate of 0.05% by mass or less when formed into a paste.
(2) The nickel ultrafine powder according to (1) above, wherein the hydroxide moisture content defined by the moisture content difference between 300 ° C. and 150 ° C. measured by the Karl Fischer method is less than 0.2 mass%.
(3) A conductive paste produced using the ultrafine nickel powder described in (1) or (2) above, applied to a thickness of 10 μm and dried to obtain a dried film obtained by an optical microscope with a magnification of 40 times When the number of aggregates having a minimum diameter of 5 μm or more per visual field area of 28.3 mm 2 is 10 or less, and when stored at 22 ° C., the rate of increase in viscosity after 20 days of paste preparation is 20 % Is a conductive paste.
(4) By mixing and stirring nickel ultrafine powder at a peripheral speed of 5 m / s or more in a reaction atmosphere that is an air atmosphere or an oxidizing atmosphere, and performing mechanochemical treatment so that the product temperature becomes 100 to 250 ° C., The manufacturing method of the nickel ultrafine powder which obtains the nickel ultrafine powder as described in said (1) or (2).
(5) The oxygen content of the nickel ultrafine powder obtained is controlled by adjusting the oxygen concentration in the reaction atmosphere and / or the atmospheric gas flow rate in the reaction atmosphere. Production method.
本発明によれば、耐熱収縮性が良好で、かつ、ペースト化したときの分散性および経時的な粘度安定性に優れるニッケル超微粉を提供することができる。 According to the present invention, it is possible to provide an ultrafine nickel powder that has good heat shrinkage resistance and is excellent in dispersibility when formed into a paste and viscosity stability over time.
［ニッケル超微粉およびその製造方法］
以下では、まず、本発明のニッケル超微粉について説明しつつ、本発明のニッケル超微粉の製造方法についても併せて説明する。
[Nickel ultrafine powder and its production method]
Below, first, the manufacturing method of the nickel ultrafine powder of this invention is also demonstrated, describing the nickel ultrafine powder of this invention.
本発明のニッケル超微粉は、酸素含有量が０．２質量％以上であり、ペースト化したときのニッケルイオン溶出率が０．０５質量％以下である、ニッケル超微粉である。
本発明のニッケル超微粉の製造方法（以下、単に「本発明の製造方法」ともいう）は、ニッケル超微粉を、大気雰囲気または酸化雰囲気である反応雰囲気中で、周速５ｍ／ｓ以上で混合攪拌し、品温が１００〜２５０℃となるようにメカノケミカル処理を施すことにより、上述した本発明のニッケル超微粉を得る、ニッケル超微粉の製造方法である。
The nickel ultrafine powder of the present invention is a nickel ultrafine powder having an oxygen content of 0.2% by mass or more and a nickel ion elution rate of 0.05% by mass or less when formed into a paste.
The nickel ultrafine powder production method of the present invention (hereinafter also simply referred to as “the production method of the present invention”) comprises mixing nickel ultrafine powder at a peripheral speed of 5 m / s or more in a reaction atmosphere that is an air atmosphere or an oxidizing atmosphere. It is the manufacturing method of the nickel ultrafine powder which stirs and performs the mechanochemical process so that product temperature may be 100-250 degreeC, and obtains the nickel ultrafine powder of this invention mentioned above.
以下では、本発明の製造方法において、原料として用いられるニッケル超微粉を、便宜的に「原料ニッケル超微粉」と呼ぶ場合がある。
原料ニッケル超微粉の平均粒子径は、特に限定されないが、得られる本発明のニッケル超微粉が積層セラミックコンデンサの電極に用いられるという理由から、０．０５〜２μｍが好ましく、０．１〜１μｍがより好ましい。
なお、本発明において、平均粒子径は、レーザー回折・散乱式粒度分布計により粒度分布の累積度数が体積百分率で５０％となる粒子径（Ｄ５０）である。
Below, in the manufacturing method of this invention, the nickel ultrafine powder used as a raw material may be called "raw material nickel ultrafine powder" for convenience.
The average particle diameter of the raw material nickel ultrafine powder is not particularly limited, but 0.05 to 2 μm is preferable and 0.1 to 1 μm is preferable because the obtained nickel ultrafine powder of the present invention is used for an electrode of a multilayer ceramic capacitor. More preferred.
In the present invention, the average particle size is a particle size (D50) at which the cumulative frequency of the particle size distribution is 50% by volume by a laser diffraction / scattering particle size distribution analyzer.
原料ニッケル超微粉として用いられる通常のニッケル超微粉の粒子表面は、必ず酸素が酸化ニッケルまたは水酸化ニッケルの形態で存在する被膜によって覆われているが、その被膜は薄いまたは不均一である。
そのため、原料ニッケル超微粉をそのまま導電ペーストに用いると（後述する比較例１を参照）、ペースト作製時の分散工程において、ニッケル金属表面が露出してニッケルイオンが溶出し、溶出したニッケルイオンによってエチルセルロース等の樹脂が絡まりあって増粘する。また、このような被膜では、十分な耐熱収縮性が得られない。
The surface of particles of normal nickel ultrafine powder used as raw material nickel ultrafine powder is always covered with a film in which oxygen is present in the form of nickel oxide or nickel hydroxide, but the film is thin or non-uniform.
Therefore, when the raw material nickel ultrafine powder is used as it is for the conductive paste (see Comparative Example 1 described later), the nickel metal surface is exposed and nickel ions are eluted in the dispersion process during paste preparation, and ethyl cellulose is eluted by the eluted nickel ions. The resin such as In addition, such a film cannot provide sufficient heat shrinkage.
また、原料ニッケル超微粉を、混合攪拌を伴わないバッチ式焼成炉などを用いて、酸化雰囲気中等で焼成して得られるニッケル超微粉（後述する比較例２を参照）においては、ある程度の膜厚を有する酸化ニッケルの被膜が形成されると考えられる。しかし、この場合、凝集した状態の原料ニッケル超微粉の表面に被膜が形成されるため、被膜が不均一であるほか、凝集がさらに強固となり分散しにくくなるうえ、ペースト作製時の分散工程において、ニッケル金属表面が露出し、やはり、多くのニッケルイオンが溶出する。 In addition, in nickel ultrafine powder (see Comparative Example 2 described later) obtained by firing raw material nickel ultrafine powder in an oxidizing atmosphere or the like using a batch-type firing furnace that does not involve mixing and stirring, a certain film thickness is obtained. It is considered that a nickel oxide film having the following is formed. However, in this case, since a coating is formed on the surface of the raw material nickel ultrafine powder in an agglomerated state, the coating is not uniform, and the aggregation is further strengthened and difficult to disperse. The nickel metal surface is exposed, and again many nickel ions are eluted.
これに対して、本発明においては、原料ニッケル超微粉を、上記反応雰囲気中で、周速５ｍ／ｓ以上で混合攪拌し、品温が１００〜２５０℃となるようにメカノケミカル処理を施すことにより、原料ニッケル超微粉を分散させながら、発生した攪拌熱や摩擦熱によって、分散された一つ一つの粒子表面に緻密な酸化ニッケル層が十分に形成される。すなわち、本発明の製造方法では、分散処理と酸化処理とを同時に行っているため、ニッケル超微粉の一つ一つの粒子表面に均一な酸化ニッケル層を形成できる。こうして、酸素含有量が０．２質量％以上であって、ペースト化したときのニッケルイオン溶出率が０．０５質量％以下と極めて低い、本発明のニッケル超微粉が得られる。
このような本発明のニッケル超微粉においては、耐熱収縮性にも優れ、かつ、ペースト化の際の分散性が良好であり、また、増粘を防止ができる。
On the other hand, in the present invention, raw material nickel ultrafine powder is mixed and stirred in the reaction atmosphere at a peripheral speed of 5 m / s or more, and subjected to mechanochemical treatment so that the product temperature becomes 100 to 250 ° C. Thus, a dense nickel oxide layer is sufficiently formed on the surface of each dispersed particle by the generated stirring heat and frictional heat while dispersing the raw nickel ultrafine powder. That is, in the production method of the present invention, since the dispersion treatment and the oxidation treatment are performed simultaneously, a uniform nickel oxide layer can be formed on the surface of each particle of the nickel ultrafine powder. Thus, the nickel ultrafine powder of the present invention having an oxygen content of 0.2% by mass or more and an extremely low nickel ion elution rate of 0.05% by mass or less when formed into a paste can be obtained.
Such an ultrafine nickel powder of the present invention is excellent in heat shrinkage resistance, has good dispersibility during paste formation, and can prevent thickening.
なお、本発明において、「ニッケルイオン溶出率」とは、ニッケル超微粉を、後述［実施例］の＜導電ペーストの作製＞に記載した条件で、ペースト化（導電ペーストを作製）したときの「ニッケルイオン溶出率」である。
このとき、ニッケルイオン溶出率は、作製した導電ペーストにトルエンを加えて超音波洗浄機を用いて分散させた後、溶媒のみを分離し、誘導結合プラズマ発光分光分析装置（ＩＣＰ−ＡＥＳ）定量値からニッケルイオン溶出量を算出して、導電ペースト中のニッケル超微粉の量に対する百分率として求められるが、詳細については、後述［実施例］に記載する。
このようなニッケルイオン溶出率は、粘度安定性がより優れ、分散性もより良好になるという理由から、０．０４質量％以下が好ましく、０．０３質量％以下がより好ましい。
In the present invention, the “nickel ion elution rate” means “when nickel ultrafine powder is pasted (prepared conductive paste) under the conditions described in <Preparation of conductive paste> in [Example] described later. Nickel ion elution rate ".
At this time, the nickel ion elution rate was determined by adding toluene to the produced conductive paste and dispersing it using an ultrasonic cleaner, separating only the solvent, and determining the inductively coupled plasma emission spectrometer (ICP-AES) quantitative value. The nickel ion elution amount is calculated from the above, and is obtained as a percentage of the amount of the ultrafine nickel powder in the conductive paste. Details will be described later in [Examples].
Such a nickel ion elution rate is preferably 0.04% by mass or less, and more preferably 0.03% by mass or less, because the viscosity stability is more excellent and the dispersibility is also better.
本発明のニッケル超微粉において、酸素含有量は０．２質量％以上であれば特に限定されないが、耐熱収縮性がより良好になり、耐酸化性も優れるという理由から、０．２５質量％以上が好ましく、０．３質量％以上がより好ましい。
なお、本発明のニッケル超微粉における酸素含有量の上限値は、特に限定されないが、５．０質量％以下が好ましく、３．０質量％以下がより好ましい。
In the nickel ultrafine powder of the present invention, the oxygen content is not particularly limited as long as it is 0.2% by mass or more, but is 0.25% by mass or more because it has better heat shrinkage resistance and excellent oxidation resistance. Is preferable, and 0.3 mass% or more is more preferable.
In addition, although the upper limit of the oxygen content in the nickel ultrafine powder of the present invention is not particularly limited, it is preferably 5.0% by mass or less, and more preferably 3.0% by mass or less.
本発明のニッケル超微粉において、カールフィッシャー法により測定される３００℃と１５０℃との水分量差で規定される水酸化物水分量は、導電ペーストの溶剤との親和性が高くなるという理由から、０．２質量％未満が好ましく、０．１５質量％未満がより好ましく、０．１質量％未満がさらに好ましい。
なお、ニッケル超微粉の粒子表面に付着した水分は約１５０℃までに蒸発除去され、水酸化ニッケルに代表される水酸化物の分解により発生する水分は約１５０℃から３００℃で分離生成する。このため、３００℃で測定される水分量と１５０℃で測定される水分量との差によって、付着水分を除く水酸化物のみに由来する水分の量が規定される。
このような水酸化物水分量の下限値としては、特に限定されないが、０．００１質量％以上が好ましい。
In the ultrafine nickel powder of the present invention, the hydroxide water content defined by the water content difference between 300 ° C. and 150 ° C. measured by the Karl Fischer method is because the affinity with the solvent of the conductive paste is increased. , Less than 0.2% by mass, more preferably less than 0.15% by mass, and even more preferably less than 0.1% by mass.
The water adhering to the particle surface of the nickel ultrafine powder is evaporated and removed by about 150 ° C., and the water generated by the decomposition of the hydroxide represented by nickel hydroxide is separated and generated at about 150 ° C. to 300 ° C. For this reason, the amount of moisture derived only from the hydroxide excluding attached moisture is defined by the difference between the moisture content measured at 300 ° C. and the moisture content measured at 150 ° C.
The lower limit of the hydroxide water content is not particularly limited, but is preferably 0.001% by mass or more.
本発明のニッケル超微粉の平均粒子径は、特に限定されないが、積層セラミックコンデンサの電極に用いられるという理由から、０．０５〜２μｍが好ましく、０．１〜１μｍがより好ましい。 The average particle diameter of the nickel ultrafine powder of the present invention is not particularly limited, but is preferably 0.05 to 2 μm and more preferably 0.1 to 1 μm because it is used for an electrode of a multilayer ceramic capacitor.
本発明において、メカノケミカル処理とは、原料ニッケル超微粉に対して分散力とせん断力とを同時にかける処理をいう。
本発明の製造方法に用いられる装置としては、混合攪拌によって原料ニッケル超微粉にメカノケミカル処理を施すことができる装置であれば、装置構造は特に限定されず、粉体を分散しながらシェアをかけることが可能である混合機であればよく、例えば、ヘンシェルミキサー、ハイスピードミキサー、ユニバーサルミキサー等が好適に挙げられる。
In the present invention, the mechanochemical treatment refers to a treatment in which a dispersion force and a shearing force are simultaneously applied to the raw material nickel ultrafine powder.
The apparatus used in the production method of the present invention is not particularly limited as long as it is an apparatus capable of performing mechanochemical treatment on the raw material nickel ultrafine powder by mixing and stirring. For example, a Henschel mixer, a high-speed mixer, a universal mixer, and the like are preferable.
本発明の製造方法における反応雰囲気は、大気雰囲気または酸化雰囲気であれば特に限定されない。
ここで、酸化雰囲気とは、例えば、窒素と酸素との混合気体の雰囲気であり、その混合比は、体積比（窒素／酸素）で、７５／２５〜９９．５／０．５が好ましく８０／２０〜９９／１がより好ましい。
本発明においては、導入される雰囲気ガス中の酸素の９０％以上が反応して酸化ニッケルの生成に使用されるため、目標とする酸素含有量のニッケル超微粉を得ることが可能となる。すなわち、反応雰囲気中の酸素濃度および／または反応雰囲気の雰囲気ガス流量を調整することにより、得られるニッケル超微粉の酸素含有量を制御できる。
これに対して、例えば後述比較例２のようにバッチ式焼成炉を用いた場合には、導入酸素の２５％程度しか反応せず、得られるニッケル超微粉の酸素含有量を制御することが困難である。
このため、目標とする酸素含有量のニッケル超微粉が得られるという本発明の製造方法が奏する効果は、従来の方法と比較した格別な効果であるといえる。
The reaction atmosphere in the production method of the present invention is not particularly limited as long as it is an air atmosphere or an oxidizing atmosphere.
Here, the oxidizing atmosphere is, for example, an atmosphere of a mixed gas of nitrogen and oxygen, and the mixing ratio is preferably 75/25 to 99.5 / 0.5 in volume ratio (nitrogen / oxygen). / 20 to 99/1 is more preferable.
In the present invention, since 90% or more of oxygen in the introduced atmospheric gas reacts and is used to generate nickel oxide, it is possible to obtain nickel ultrafine powder having a target oxygen content. That is, the oxygen content of the obtained nickel ultrafine powder can be controlled by adjusting the oxygen concentration in the reaction atmosphere and / or the atmospheric gas flow rate in the reaction atmosphere.
On the other hand, for example, when a batch-type firing furnace is used as in Comparative Example 2 described later, only about 25% of the introduced oxygen reacts, and it is difficult to control the oxygen content of the obtained nickel ultrafine powder. It is.
For this reason, it can be said that the effect which the manufacturing method of this invention that the nickel ultrafine powder of the target oxygen content is obtained is a special effect compared with the conventional method.
本発明の製造方法において、混合攪拌の周速は、５ｍ／ｓ以上であり、メカノケミカル反応を起こしやすく、粒子表面により均一な酸化ニッケル層を形成できるという理由から、１０ｍ／ｓ以上が好ましく、１５ｍ／ｓ以上がより好ましい。 In the production method of the present invention, the peripheral speed of mixing and stirring is 5 m / s or more, and a mechanochemical reaction is likely to occur, and a uniform nickel oxide layer can be formed on the particle surface. 15 m / s or more is more preferable.
本発明の製造方法においては、原料ニッケル超微粉の粒子表面で酸化反応を行う観点から、混合攪拌により品温が１００〜２５０℃となるようにメカノケミカル処理を施すが、酸化をより効率的に行うと同時にニッケル超微粉の焼結を抑制するという観点から、品温が１５０〜２４０℃となるようにするのが好ましく、１７０〜２３０℃がより好ましい。 In the production method of the present invention, from the viewpoint of performing an oxidation reaction on the surface of the raw material nickel ultrafine particles, a mechanochemical treatment is performed so that the product temperature becomes 100 to 250 ° C. by mixing and stirring, but the oxidation is more efficiently performed. From the viewpoint of suppressing the sintering of the nickel ultrafine powder at the same time, the product temperature is preferably 150 to 240 ° C, more preferably 170 to 230 ° C.
［導電ペースト］
本発明の導電ペーストは、概略的には、上述した本発明のニッケル超微粉を用いて作製した導電ペーストであり、例えば、本発明のニッケル超微粉と、樹脂と、溶剤と、任意の添加剤とを含有する組成物を、三本ロールミル等の分散装置を用いて分散させることにより得られる。
[Conductive paste]
The conductive paste of the present invention is roughly a conductive paste prepared using the above-described nickel ultrafine powder of the present invention. For example, the nickel ultrafine powder of the present invention, a resin, a solvent, and any additive Is dispersed using a dispersing device such as a three-roll mill.
本発明の導電ペーストにおいて、本発明のニッケル超微粉の含有量は、ペースト全体に対して、４０〜６０質量％が好ましく、４５〜５０質量％がより好ましい。
また、樹脂としては、例えば、エチルセルロース、アクリル樹脂、ポリビニルブチラール等が好適に用いられ、その含有量は、分子量にもよるが、ペースト全体に対して、０．５〜１０質量％が好ましく、１〜７質量％がより好ましい。
また、溶剤としては、例えば、ターピネオールＣ、ジヒドロターピネオール、ターピネオールアセテート等が好適に用いられる。
なお、本発明の導電ペーストには、任意の添加剤を添加することができ、例えば、分散剤、共材等が挙げられ、その含有量は、適宜選択されるが、例えばペースト全体に対して、分散剤は０．０５〜５質量％、共材は１０〜２５質量％が好ましい。
このとき、分散条件は、特に限定されず、従来公知の条件を用いることができる。
In the conductive paste of the present invention, the content of the ultrafine nickel powder of the present invention is preferably 40 to 60% by mass and more preferably 45 to 50% by mass with respect to the entire paste.
As the resin, for example, ethyl cellulose, acrylic resin, polyvinyl butyral and the like are preferably used, and the content thereof is preferably 0.5 to 10% by mass with respect to the whole paste, although it depends on the molecular weight. -7 mass% is more preferable.
As the solvent, for example, terpineol C, dihydroterpineol, terpineol acetate and the like are preferably used.
In addition, arbitrary additives can be added to the electrically conductive paste of this invention, For example, a dispersing agent, a co-material, etc. are mentioned, Although the content is selected suitably, For example, with respect to the whole paste The dispersant is preferably 0.05 to 5% by mass, and the common material is preferably 10 to 25% by mass.
At this time, the dispersion conditions are not particularly limited, and conventionally known conditions can be used.
このような本発明の導電ペーストは、本発明のニッケル超微粉を含有することにより、分散性および経時的な粘度安定性に優れる。
すなわち、本発明の導電ペーストは、１０μｍの厚さに塗布し、乾燥して得られる乾燥膜を倍率４０倍の光学顕微鏡で観察した際の１視野面積２８．３ｍｍ２あたりの最小径５μｍ以上である凝集体の個数が１０個以下であり、９個以下であるのが好ましい。
また、本発明の導電ペーストは、２２℃で保管した場合におけるペースト作製２０日後の粘度上昇率が２０％以下であり、１５％以下であるのが好ましい。
Such a conductive paste of the present invention is excellent in dispersibility and viscosity stability over time by containing the nickel ultrafine powder of the present invention.
That is, the conductive paste of the present invention is applied to a thickness of 10 μm and dried, and the dried film obtained by observation with an optical microscope with a magnification of 40 times has a minimum diameter of 5 μm or more per 28.3 mm 2 visual field area. The number of aggregates is 10 or less, and preferably 9 or less.
The conductive paste of the present invention has a viscosity increase rate of 20% or less, preferably 15% or less after 20 days from the preparation of the paste when stored at 22 ° C.
以上説明したように、本発明のニッケル超微粉は、導電ペーストにしたときの分散性および経時的な粘度安定性が良好であって、かつ、積層セラミックコンデンサの電極を製造する際に求められる低温での耐熱収縮性にも優れる。このため、本発明のニッケル超微粉は、積層セラミックコンデンサの製造において、導電ペーストとしての品質維持に費やす管理が容易となり、また、デラミネーション（剥離）やクラック（割れ）の発生を防止できるため、内部電極の形成用途に極めて好適である。
また、例えばバッチ式焼成炉を用いる従来の製造方法では、目標とする酸素含有量のニッケル超微粉を得ること非常に困難であったが、本発明の製造方法においては、例えば導入酸素濃度を調整することで酸素含有量の制御を容易に行うことができるため、目標とする酸素含有量のニッケル超微粉を低コストで大量に製造できる。
As described above, the nickel ultrafine powder of the present invention has good dispersibility when used as a conductive paste and stable viscosity over time, and low temperature required when manufacturing an electrode of a multilayer ceramic capacitor. Excellent heat shrinkage resistance. For this reason, the nickel ultrafine powder of the present invention can be easily managed to maintain the quality as a conductive paste in the production of a multilayer ceramic capacitor, and can prevent the occurrence of delamination and cracks. It is extremely suitable for use in forming internal electrodes.
In addition, in the conventional manufacturing method using, for example, a batch-type firing furnace, it was very difficult to obtain ultrafine nickel powder having a target oxygen content, but in the manufacturing method of the present invention, for example, the introduced oxygen concentration is adjusted. By doing so, the oxygen content can be easily controlled, so that a nickel ultrafine powder having a target oxygen content can be produced in large quantities at a low cost.
以下に、実施例を挙げて本発明を具体的に説明する。ただし、本発明はこれらに限定されるものではない。 Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these.
＜ニッケル超微粉の製造＞
（実施例１）
窒素９９体積％と酸素１体積％との混合気体を２０Ｌ／ｍｉｎ導入したヘンシェルミキサー（日本コークス工業社製ＦＭ−１０Ｃ）に、化学的気相反応によって製造された、平均粒子径０．２μｍで粒子表面がほぼ水酸化ニッケルで覆われている原料ニッケル超微粉を３．５ｋｇ投入し、品温が２１０℃となるようにして、周速２１ｍ／ｓで４０分間混合攪拌して、メカノケミカル処理を施すことにより、実施例１のニッケル超微粉を得た。
<Manufacture of nickel ultrafine powder>
Example 1
A Henschel mixer (FM-10C manufactured by Nippon Coke Kogyo Co., Ltd.) into which a mixed gas of 99% by volume of nitrogen and 1% by volume of oxygen was introduced at a rate of 20 L / min. Raw material nickel ultrafine powder whose particle surface is almost covered with nickel hydroxide is charged in 3.5 kg, mixed and stirred at a peripheral speed of 21 m / s for 40 minutes with a product temperature of 210 ° C., and mechanochemical treatment The nickel ultrafine powder of Example 1 was obtained.
（実施例２）
窒素９８体積％と酸素２体積％との混合気体を１０Ｌ／ｍｉｎ導入したヘンシェルミキサー（日本コークス工業社製ＦＭ−１０Ｃ）に、実施例１と同じ原料ニッケル超微粉を３．５ｋｇ投入し、品温が２１０℃となるようにして、周速２１ｍ／ｓで８０分間混合攪拌して、メカノケミカル処理を施すことにより、実施例２のニッケル超微粉を得た。
(Example 2)
3.5 kg of the same raw material nickel ultrafine powder as in Example 1 was introduced into a Henschel mixer (FM-10C manufactured by Nippon Coke Kogyo Co., Ltd.) into which a mixed gas of 98% by volume of nitrogen and 2% by volume of oxygen was introduced at 10 L / min. Nickel ultrafine powder of Example 2 was obtained by mixing and stirring for 80 minutes at a peripheral speed of 21 m / s and applying a mechanochemical treatment so that the temperature was 210 ° C.
（実施例３）
窒素９５体積％と酸素５体積％との混合気体を２０Ｌ／ｍｉｎ導入したヘンシェルミキサー（日本コークス工業社製ＦＭ−１０Ｃ）に、実施例１と同じ原料ニッケル超微粉を３．５ｋｇ投入し、品温が２１０℃となるようにして、周速２１ｍ／ｓで８０分間混合攪拌して、メカノケミカル処理を施すことにより、実施例３のニッケル超微粉を得た。
(Example 3)
3.5 kg of the same raw material nickel ultrafine powder as in Example 1 was introduced into a Henschel mixer (FM-10C manufactured by Nihon Coke Kogyo Co., Ltd.) into which a mixed gas of 95% by volume of nitrogen and 5% by volume of oxygen was introduced at 20 L / min. Nickel ultrafine powder of Example 3 was obtained by mixing and stirring for 80 minutes at a peripheral speed of 21 m / s and applying a mechanochemical treatment at a temperature of 210 ° C.
（実施例４）
乾燥空気を７５Ｌ／ｍｉｎ導入したヘンシェルミキサー（日本コークス工業社製ＦＭ−５００Ｊ）に、実施例１と同じ原料ニッケル超微粉を２００ｋｇ投入し、品温が２１０℃となるようにして、周速３０ｍ／ｓで４０分間混合攪拌して、メカノケミカル処理を施すことにより、実施例４のニッケル超微粉を得た。
Example 4
200 kg of the same raw material nickel ultrafine powder as in Example 1 was introduced into a Henschel mixer (FM-500J, manufactured by Nippon Coke Kogyo Co., Ltd.) into which dry air was introduced at 75 L / min, the product temperature was 210 ° C., and the peripheral speed was 30 m. The nickel ultrafine powder of Example 4 was obtained by mixing and stirring at / s for 40 minutes and performing a mechanochemical treatment.
（比較例１）
実施例１と同じ原料ニッケル超微粉を、未処理で、比較例１のニッケル超微粉とした。
(Comparative Example 1)
The same raw material nickel ultrafine powder as in Example 1 was untreated and made the nickel ultrafine powder of Comparative Example 1.
（比較例２）
窒素９９体積％と酸素１体積％との混合気体を２Ｌ／ｍｉｎ導入したバッチ式焼成炉に、実施例１と同じ原料ニッケル超微粉を５０ｇを投入し、２１０℃で３０分間焼成して、比較例２のニッケル超微粉を得た。
(Comparative Example 2)
50 g of the same raw material nickel ultrafine powder as in Example 1 was introduced into a batch-type firing furnace into which a mixed gas of 99 vol% nitrogen and 1 vol% oxygen was introduced at 2 L / min, and calcined at 210 ° C. for 30 minutes. The nickel ultrafine powder of Example 2 was obtained.
＜導電ペーストの作製＞
次に、得られた実施例１〜４および比較例１〜２のニッケル超微粉を用いて、下記条件で導電ペーストを作製した。
・ペースト全体に対するニッケル超微粉の量：５０質量％
・樹脂：エチルセルロース（ペースト全体に対して２．５質量％）
・溶剤：ターピネオールＣ（ヤスハラケミカル社製）
・分散剤：ＫＤ−１２（クローダジャパン社製、ペースト全体に対して０．９質量％）
・分散装置：三本ロールミル（ビューラー社製ＳＤＹ−３００）
・分散条件：８ｂａｒ、１０ｂａｒ、１２ｂａｒ、１４ｂａｒの圧力でそれぞれ１パスずつ、計４パスで分散
<Preparation of conductive paste>
Next, using the obtained nickel ultrafine powders of Examples 1 to 4 and Comparative Examples 1 to 2, conductive pastes were produced under the following conditions.
-Amount of ultrafine nickel powder with respect to the entire paste: 50% by mass
・ Resin: Ethylcellulose (2.5% by mass with respect to the whole paste)
・ Solvent: Turpineol C (manufactured by Yasuhara Chemical)
-Dispersant: KD-12 (manufactured by Croda Japan, 0.9% by mass with respect to the entire paste)
-Dispersing device: Three roll mill (Bueller SDY-300)
・ Dispersion condition: Dispersed in 4 passes in total, 1 pass for each pressure of 8 bar, 10 bar, 12 bar, 14 bar
＜評価＞
次に、実施例１〜４および比較例１〜２のニッケル超微粉および導電ペーストについて、以下に説明する各種評価を行った。結果を下記第１表ならびに図１および図２に示す。
<Evaluation>
Next, various evaluations described below were performed on the nickel ultrafine powder and the conductive paste of Examples 1 to 4 and Comparative Examples 1 and 2. The results are shown in Table 1 below and FIGS. 1 and 2.
（酸素含有量）
上記ニッケル超微粉について、酸素含有量（単位：質量％）を、酸素窒素同時分析装置（ＬＥＣＯジャパン社製ＴＣ−６００）を用いて測定した。
(Oxygen content)
About the said nickel ultrafine powder, oxygen content (unit: mass%) was measured using the oxygen-nitrogen simultaneous analyzer (TC-600 by LECO Japan).
（水酸化物水分量）
上記ニッケル超微粉について、水酸化物水分量を測定した。具体的には、カールフィッシャー法により測定される３００℃での水分量と、同法により測定される１５０℃での水分量との差（水分量差）を、水酸化物水分量（単位：質量％）として求めた。
なお、カールフィッシャー法による水分量の測定には、平沼産業社製の微量水分測定装置（ＡＱ−２１００、気化装置 ＥＶ−２０００）を用いた。
(Hydroxide moisture content)
About the said nickel ultrafine powder, the hydroxide water content was measured. Specifically, the difference between the water content at 300 ° C. measured by the Karl Fischer method and the water content at 150 ° C. measured by the same method (water content difference) is determined by the hydroxide water content (unit: Mass%).
In addition, the trace amount moisture measuring apparatus (AQ-2100, vaporizer EV-2000) made from Hiranuma Sangyo Co., Ltd. was used for the measurement of the moisture content by the Karl Fischer method.
（レーザー回折・散乱式粒度分布）
上記ニッケル超微粉について、レーザー回折・散乱式粒度分布（単位：μｍ）の測定を、下記条件で行った。
・装置機種：日機装社製マイクロトラックＨＲＡ（９３２０−Ｘ１００）
・予備分散：０．２質量％Ｎｉ−０．４質量％ヘキサメタリン酸ナトリウム溶液１００ｍＬを日本精機製作所社製の超音波ホモジナイザーＵＴ−３００（チップ径φ１２ｍｍ）を用いて出力３００Ｗで２分間分散した。水で１００倍に希釈後、さらに測定機種内にて出力４０Ｗで１分間分散した。
(Laser diffraction / scattering particle size distribution)
The above-mentioned nickel ultrafine powder was measured for laser diffraction / scattering particle size distribution (unit: μm) under the following conditions.
-Device model: Nikkiso Microtrac HRA (9320-X100)
Preliminary dispersion: 100 mL of 0.2 mass% Ni-0.4 mass% sodium hexametaphosphate solution was dispersed at an output of 300 W for 2 minutes using an ultrasonic homogenizer UT-300 (chip diameter φ12 mm) manufactured by Nippon Seiki Seisakusho. After being diluted 100 times with water, it was further dispersed for 1 minute at an output of 40 W in the measurement model.
（表面粗さ）
上記導電ペーストをスライドガラスにアプリケータを用いて１０μｍの厚さに塗布し、１００℃で１分間乾燥して得られたペースト乾燥膜について、表面粗さ測定機（東京精密社製ＳＵＲＦＣＯＭ ４８０Ａ）を用いて、表面粗さ（算術平均粗さＲａ）を測定した。
(Surface roughness)
About the paste dry film | membrane obtained by apply | coating the said electrically conductive paste to the thickness of 10 micrometers on a slide glass using an applicator, and drying for 1 minute at 100 degreeC, surface roughness measuring machine (SURFCOM 480A by Tokyo Seimitsu Co., Ltd.) is used. Used to measure the surface roughness (arithmetic mean roughness Ra).
（密度）
上記導電ペーストをＰＥＴフィルムにアプリケータを用いて３００μｍの厚さに塗布し、１００℃で１５分間乾燥して得られたペースト乾燥膜について、治具を使用して一定面積にくり貫き、その高さおよび質量から、密度を測定した。
(density)
The paste paste film obtained by applying the conductive paste to a PET film with a thickness of 300 μm using an applicator and drying at 100 ° C. for 15 minutes is cut into a certain area using a jig, The density was measured from the thickness and mass.
（凝集体数）
上記導電ペーストをスライドガラスにアプリケータを用いて１０μｍの厚さに塗布し、１００℃で１分間乾燥して得られたペースト乾燥膜を、光学顕微鏡（倍率：４０倍）で観察し、１視野（視野面積：２８．３ｍｍ２）あたりの凝集体の個数をカウントした。このとき、凝集体としては、その視野における最小径が５μｍ以上である凝集体のみをカウントした。
(Number of aggregates)
The paste paste film obtained by applying the conductive paste to a slide glass to a thickness of 10 μm using an applicator and drying at 100 ° C. for 1 minute was observed with an optical microscope (magnification: 40 ×). The number of aggregates per (viewing area: 28.3 mm 2 ) was counted. At this time, only aggregates having a minimum diameter in the visual field of 5 μm or more were counted as aggregates.
（ニッケルイオン溶出率）
上記ニッケル超微粉のニッケルイオン溶出率（単位：質量％）を求めた。具体的には、上記導電ペースト２５ｇにトルエン６５ｇを加えて超音波洗浄機（出力：３００Ｗ）を用いて１０分間分散させた後、溶媒のみを分離し、誘導結合プラズマ発光分光分析装置（ＩＣＰ−ＡＥＳ）定量値からニッケルイオン溶出量を算出して、導電ペースト中のニッケル超微粉の量に対する百分率として求めた。
(Nickel ion elution rate)
The nickel ion elution rate (unit: mass%) of the nickel ultrafine powder was determined. Specifically, 65 g of toluene was added to 25 g of the above conductive paste and dispersed for 10 minutes using an ultrasonic cleaner (output: 300 W), then only the solvent was separated, and an inductively coupled plasma emission spectrometer (ICP- AES) The nickel ion elution amount was calculated from the quantitative value, and obtained as a percentage with respect to the amount of ultrafine nickel powder in the conductive paste.
（粘度経時変化）
上記導電ペーストの粘度経時変化を評価した。具体的には、まず、導電ペーストについて、作製直後の粘度を測定した後、２２℃で各日保管し、各日の粘度を測定して、作製直後の粘度との差（粘度増加量）を求めた。粘度増加量を作製直後の粘度に対する百分率として求めたものを粘度上昇率（単位：％）とした。なお、粘度は、粘度計（ＢＲＯＯＫＦＩＥＬＤ社製ＤＶ−ＩＩ＋Ｐｒｏ）を用いて測定された１０ｒｐｍのときの粘度である。
図１は、導電ペーストの粘度経時変化を示すグラフである。図１のグラフにおいて、横軸は、導電ペースト作製後の経過日数（単位：日）を示し、縦軸は導電ペーストの粘度上昇率（単位：％）を示す。
(Viscosity change with time)
The viscosity change with time of the conductive paste was evaluated. Specifically, first, after measuring the viscosity immediately after production of the conductive paste, each day is stored at 22 ° C., the viscosity of each day is measured, and the difference (viscosity increase amount) from the viscosity immediately after production is determined. Asked. The viscosity increase rate (unit:%) was determined as the percentage increase in viscosity immediately after production. The viscosity is a viscosity at 10 rpm measured using a viscometer (BROOKFIELD DV-II + Pro).
FIG. 1 is a graph showing changes in viscosity of a conductive paste with time. In the graph of FIG. 1, the horizontal axis indicates the number of days elapsed (unit: day) after the production of the conductive paste, and the vertical axis indicates the rate of increase in viscosity (unit:%) of the conductive paste.
（熱収縮特性）
上記ニッケル超微粉について、熱収縮特性を評価した。具体的には、まず、ニッケル超微粉１０ｇと１０％ポリビニルアルコール０．５ｍＬとを乳鉢で混練後、解砕して、サンプルを得た。次に、得られたサンプル０．５７ｇを直径７ｍｍの圧縮金型に入れ、直径７ｍｍ、厚さ３ｍｍの円柱状に成形した。この成形サンプルの厚さの変化を、下記の条件で測定した。
・測定機種 ：セイコーインスツル株式会社製ＥＸＳＴＡＲ ＴＭＡ ＳＳ６０００
・昇温速度：５℃／ｍｉｎ
・温度範囲：室温〜１３００℃
・荷重：９８．１ｍＮ
・雰囲気：Ｎ２＋Ｈ２（１２００ｐｐｍ），２００ｍＬ／ｍｉｎ
図２は、ニッケル超微粉の熱収縮特性を示すグラフである。図２のグラフにおいて、横軸は温度（単位：℃）を示し、縦軸は成形サンプルの厚さの変化率（単位：％）を示す。
(Heat shrinkage characteristics)
About the said nickel ultrafine powder, the heat contraction characteristic was evaluated. Specifically, first, 10 g of nickel ultrafine powder and 0.5 mL of 10% polyvinyl alcohol were kneaded in a mortar and then crushed to obtain a sample. Next, 0.57 g of the obtained sample was put into a compression mold having a diameter of 7 mm and formed into a cylindrical shape having a diameter of 7 mm and a thickness of 3 mm. The change in the thickness of the molded sample was measured under the following conditions.
Measurement model: EXSTAR TMA SS6000 manufactured by Seiko Instruments Inc.
・ Raising rate: 5 ° C / min
-Temperature range: room temperature to 1300 ° C
・ Load: 98.1mN
Atmosphere: N 2 + H 2 (1200 ppm), 200 mL / min
FIG. 2 is a graph showing the heat shrinkage characteristics of nickel ultrafine powder. In the graph of FIG. 2, the horizontal axis represents temperature (unit: ° C.), and the vertical axis represents the rate of change in thickness of the molded sample (unit:%).
上記第１表（その１）に示す結果から明らかなように、実施例１のニッケル超微粉は、比較例１のニッケル超微粉（未処理の原料ニッケル超微粉）と比べて、酸素含有量および水酸化物水分量が低い。これは、１５０℃以上で処理されたことによって、ニッケル超微粉の粒子表面でＮｉ(ＯＨ)２→ＮｉＯ＋Ｈ２Ｏの反応が起こり、水酸化物が分解したためと考えられる。
実施例２〜４のニッケル超微粉は、比較例１のニッケル超微粉に比べて酸素含有量が高い。これは、２Ｎｉ(Ｍｅ)＋Ｏ２→２ＮｉＯの反応が起こっているためと考えられる。
As is clear from the results shown in Table 1 (Part 1) above, the nickel ultrafine powder of Example 1 was compared with the nickel ultrafine powder of Comparative Example 1 (untreated raw material nickel ultrafine powder) and the oxygen content and Low hydroxide moisture content. This is presumably because the reaction of Ni (OH) 2 → NiO + H 2 O occurred on the surface of the nickel ultrafine particles due to the treatment at 150 ° C. or higher, and the hydroxide was decomposed.
The nickel ultrafine powders of Examples 2 to 4 have a higher oxygen content than the nickel ultrafine powder of Comparative Example 1. This is considered to be due to the reaction of 2Ni (Me) + O 2 → 2NiO.
なお、上記第１表（その１）に示す実施例１〜４の対比から、例えば反応雰囲気中の酸素濃度を調整することにより、得られるニッケル超微粉の酸素含有量の制御を容易に行えることが分かった。 In addition, from the comparison of Examples 1 to 4 shown in Table 1 (Part 1) above, the oxygen content of the obtained nickel ultrafine powder can be easily controlled by adjusting the oxygen concentration in the reaction atmosphere, for example. I understood.
上記第１表（その１）に示す粒度分布の結果から、実施例１〜４のニッケル超微粉は、比較例２のニッケル超微粉に比べて、分散性が非常に良好であることが分かった。これは、実施例１〜４では、一つ一つの粒子表面に均一な酸化ニッケル層が形成されているためと考えられる。
一方、バッチ式焼成炉を用いた比較例２では、凝集が強固になり、分散しにくくなったものと考えられる。
From the results of the particle size distribution shown in Table 1 (Part 1), it was found that the nickel ultrafine powders of Examples 1 to 4 had very good dispersibility compared to the nickel ultrafine powder of Comparative Example 2. . This is presumably because in Examples 1 to 4, a uniform nickel oxide layer was formed on each particle surface.
On the other hand, in Comparative Example 2 using a batch-type firing furnace, it is considered that the aggregation became strong and difficult to disperse.
上記第１表（その２）に示す結果を見ると、実施例１〜４のペースト乾燥膜の表面粗さがいずれも比較例１〜２を下回っていること、および、実施例１〜４のペースト乾燥膜における凝集体の個数が比較例２に比べて著しく少ないことから、実施例１〜４のニッケル超微粉のペースト分散性が良好であることが分かった。 When the result shown in the said 1st table | surface (the 2) is seen, all the surface roughness of the paste dry film | membrane of Examples 1-4 is lower than Comparative Examples 1-2, and of Examples 1-4 Since the number of aggregates in the paste dry film was significantly smaller than that in Comparative Example 2, it was found that the paste dispersibility of the nickel ultrafine powders of Examples 1 to 4 was good.
なお、上記第１表（その２）に示すように、実施例１〜４においては、ニッケルイオン溶出率が０．０５質量％以下であり、一つ一つの粒子表面に均一な酸化ニッケル層が形成されているといえる。 In addition, as shown in the said Table 1 (the 2), in Examples 1-4, nickel ion elution rate is 0.05 mass% or less, and the uniform nickel oxide layer is on each particle surface. It can be said that it is formed.
次に、図１に示すグラフにおいて、２２℃で保管した場合におけるペースト作製２０日後の粘度上昇率を見ると、比較例１では２２０％、比較例２では６０％の粘度上昇が認められた。
これに対して、実施例１〜４の導電ペーストでは、粘度経時変化は低く、経時的な粘度安定性が著しく高いことが分かった。
Next, in the graph shown in FIG. 1, when the rate of increase in
On the other hand, in the conductive pastes of Examples 1 to 4, it was found that the viscosity change with time was low and the viscosity stability with time was extremely high.
また、図２に示すグラフから、実施例１〜４および比較例２のニッケル超微粉は、未処理である比較例１のニッケル超微粉と比較して、熱収縮開始温度が高温側にシフトしていることが分かった。なかでも、酸素含有量が多い実施例３および実施例４では、耐熱収縮性がより優れており、熱収縮開始温度が比較例１と比べて約１００℃以上高くなることが分かった。 Further, from the graph shown in FIG. 2, the nickel ultrafine powders of Examples 1 to 4 and Comparative Example 2 have the heat shrinkage start temperature shifted to the high temperature side as compared with the untreated nickel ultrafine powder of Comparative Example 1. I found out. Especially, in Example 3 and Example 4 with much oxygen content, it turned out that heat-shrink property is more excellent and heat shrink start temperature becomes higher about 100 degreeC or more compared with the comparative example 1. FIG.
Claims (2)
（ニッケル超微粉Ａ）
粒子表面に酸化ニッケル層が形成され、酸素含有量が０．２質量％以上であり、下記条件でペースト化したときのニッケルイオン溶出率が０．０５質量％以下であるニッケル超微粉。
（ニッケル超微粉Ｂ）
粒子表面に酸化ニッケル層が形成され、酸素含有量が０．２質量％以上であり、下記条件でペースト化したときのニッケルイオン溶出率が０．０５質量％以下であり、カールフィッシャー法により測定される３００℃と１５０℃との水分量差で規定される水酸化物水分量が０．２質量％未満である、ニッケル超微粉。
（ペースト化条件）
・ペースト全体に対するニッケル超微粉の量：５０質量％
・樹脂：エチルセルロース（ペースト全体に対して２．５質量％）
・溶剤：ターピネオールＣ（ヤスハラケミカル社製）
・分散剤：ＫＤ−１２（クローダジャパン社製、ペースト全体に対して０．９質量％）
・分散装置：三本ロールミル（ビューラー社製ＳＤＹ−３００）
・分散条件：８ｂａｒ、１０ｂａｒ、１２ｂａｒ、１４ｂａｒの圧力でそれぞれ１パスずつ、計４パスで分散 The ultrafine nickel powder, in a reaction atmosphere is air atmosphere or an oxidizing atmosphere, followed by stirring and mixing at a peripheral speed 5 m / s or higher, by performing a mechanochemical treatment such product temperature is 100 to 250 ° C., the following nickel than The manufacturing method of the nickel ultrafine powder which obtains the fine powder A or the following nickel ultrafine powder B.
(Nickel super fine powder A)
Nickel ultrafine powder having a nickel oxide layer formed on the particle surface, an oxygen content of 0.2% by mass or more, and a nickel ion elution rate of 0.05% by mass or less when pasted under the following conditions.
(Nickel super fine powder B)
A nickel oxide layer is formed on the particle surface, the oxygen content is 0.2% by mass or more, and the nickel ion elution rate is 0.05% by mass or less when pasted under the following conditions, measured by the Karl Fischer method The nickel ultrafine powder whose hydroxide moisture content prescribed | regulated by the moisture content difference of 300 degreeC and 150 degreeC is less than 0.2 mass%.
(Paste condition)
-Amount of ultrafine nickel powder with respect to the entire paste: 50% by mass
・ Resin: Ethylcellulose (2.5% by mass with respect to the whole paste)
・ Solvent: Turpineol C (manufactured by Yasuhara Chemical)
-Dispersant: KD-12 (manufactured by Croda Japan, 0.9% by mass with respect to the entire paste)
-Dispersing device: Three roll mill (Bueller SDY-300)
・ Dispersion condition: Dispersed in 4 passes in total, 1 pass for each pressure of 8 bar, 10 bar, 12 bar, 14 bar
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