JPWO2019087530A1 - Manufacturing method of copper nanoparticles - Google Patents
Manufacturing method of copper nanoparticles Download PDFInfo
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Abstract
本発明の銅ナノ粒子の製造方法は、液相還元法によって平均粒子径５０ｎｍ以下の銅ナノ粒子分散液を調製する調製工程と、上記調製工程後の銅ナノ粒子分散液に凝集剤を添加する添加工程と、上記添加工程後の銅ナノ粒子分散液から液相を遠心分離する分離工程とを備える銅ナノ粒子の製造方法であって、上記銅ナノ粒子分散液に含まれる銅ナノ粒子を自然沈降させる自然沈降工程をさらに備える。The method for producing copper nanoparticles of the present invention includes a preparation step of preparing a copper nanoparticle dispersion having an average particle diameter of 50 nm or less by a liquid phase reduction method, and adding a flocculant to the copper nanoparticle dispersion after the preparation step. A method for producing copper nanoparticles, which comprises an addition step and a separation step of centrifuging the liquid phase from the copper nanoparticle dispersion liquid after the addition step, wherein the copper nanoparticles contained in the copper nanoparticle dispersion liquid are naturally produced. It further comprises a natural sedimentation step of sedimentation.
Description
本開示は、銅ナノ粒子の製造方法に関する。本出願は、２０１７年１０月３０日出願の日本出願第２０１７−２０９５１９号に基づく優先権を主張し、前記日本出願に記載された全ての記載内容を援用するものである。 The present disclosure relates to a method for producing copper nanoparticles. This application claims priority based on Japanese Application No. 2017-209519 filed on October 30, 2017, and incorporates all the contents described in the Japanese application.
金属ナノ粒子を溶液中に析出させる液相還元法が知られている。この液相還元法は、例えば錯化剤及び分散剤を含む溶液中で金属イオンを還元剤によって還元させることで金属ナノ粒子を溶液中に析出させるものである。液相還元法によって溶液中に析出した金属ナノ粒子は、溶液中の不純物を除去した後、純水等の溶媒が加えられ、濃度が調整されることで金属ナノインクとして用いられる。 A liquid phase reduction method in which metal nanoparticles are precipitated in a solution is known. In this liquid phase reduction method, for example, metal nanoparticles are precipitated in a solution by reducing metal ions with a reducing agent in a solution containing a complexing agent and a dispersant. The metal nanoparticles precipitated in the solution by the liquid phase reduction method are used as metal nanoparticles by removing impurities in the solution and then adding a solvent such as pure water to adjust the concentration.
上記溶液中から金属ナノ粒子以外の不純物を除去する方法として、例えば遠心分離機を用いて金属ナノ粒子を遠心分離する方法が発案されている（特開２００６−１８３０９２号公報参照）。 As a method for removing impurities other than metal nanoparticles from the above solution, for example, a method of centrifuging the metal nanoparticles using a centrifuge has been proposed (see JP-A-2006-183092).
本開示の一態様に係る銅ナノ粒子の製造方法は、液相還元法によって平均粒子径５０ｎｍ以下の銅ナノ粒子分散液を調製する調製工程と、上記調製工程後の銅ナノ粒子分散液に凝集剤を添加する添加工程と、上記添加工程後の銅ナノ粒子分散液から液相を遠心分離する分離工程とを備える銅ナノ粒子の製造方法であって、上記銅ナノ粒子分散液に含まれる銅ナノ粒子を自然沈降させる自然沈降工程をさらに備える。 The method for producing copper nanoparticles according to one aspect of the present disclosure includes a preparation step of preparing a copper nanoparticle dispersion having an average particle diameter of 50 nm or less by a liquid phase reduction method, and agglomeration into the copper nanoparticle dispersion after the preparation step. A method for producing copper nanoparticles comprising an addition step of adding an agent and a separation step of centrifuging the liquid phase from the copper nanoparticle dispersion liquid after the addition step, and copper contained in the copper nanoparticle dispersion liquid. Further provided is a natural sedimentation step of spontaneously precipitating nanoparticles.
［本開示が解決しようとする課題］
上記公報に記載の製造方法は、金属ナノ粒子の回収効率を高める点で課題を有する。つまり、液相還元法によって溶液中に析出した金属ナノ粒子は一定の粒子径分布を有している。そのため、この金属ナノ粒子が分散した金属ナノ粒子分散液を遠心分離すると、比較的粒子径の小さい金属ナノ粒子を液相から分離し難い。その結果、この製造方法によっては、比較的粒子径の小さい金属ナノ粒子の回収率を十分に高め難い。[Issues to be solved by this disclosure]
The production method described in the above publication has a problem in increasing the recovery efficiency of metal nanoparticles. That is, the metal nanoparticles precipitated in the solution by the liquid phase reduction method have a constant particle size distribution. Therefore, when the metal nanoparticle dispersion liquid in which the metal nanoparticles are dispersed is centrifuged, it is difficult to separate the metal nanoparticles having a relatively small particle size from the liquid phase. As a result, it is difficult to sufficiently increase the recovery rate of metal nanoparticles having a relatively small particle size depending on this production method.
本開示は、このような事情に基づいてなされたものであり、銅ナノ粒子の回収率を十分に高めることができる銅ナノ粒子の製造方法の提供を課題とする。
［本開示の効果］The present disclosure has been made based on such circumstances, and an object of the present invention is to provide a method for producing copper nanoparticles, which can sufficiently increase the recovery rate of copper nanoparticles.
[Effect of the present disclosure]
本開示の銅ナノ粒子の製造方法は、銅ナノ粒子の回収率を十分に高めることができる。 The method for producing copper nanoparticles of the present disclosure can sufficiently increase the recovery rate of copper nanoparticles.
［本開示の実施形態の説明］
最初に本開示の実施態様を列記して説明する。[Explanation of Embodiments of the present disclosure]
First, embodiments of the present disclosure will be listed and described.
本開示の一態様に係る銅ナノ粒子の製造方法は、液相還元法によって平均粒子径５０ｎｍ以下の銅ナノ粒子分散液を調製する調製工程と、上記調製工程後の銅ナノ粒子分散液に凝集剤を添加する添加工程と、上記添加工程後の銅ナノ粒子分散液から液相を遠心分離する分離工程とを備える銅ナノ粒子の製造方法であって、上記銅ナノ粒子分散液に含まれる銅ナノ粒子を自然沈降させる自然沈降工程をさらに備える。 The method for producing copper nanoparticles according to one aspect of the present disclosure includes a preparation step of preparing a copper nanoparticle dispersion having an average particle diameter of 50 nm or less by a liquid phase reduction method, and agglomeration into the copper nanoparticle dispersion after the preparation step. A method for producing copper nanoparticles comprising an addition step of adding an agent and a separation step of centrifuging the liquid phase from the copper nanoparticle dispersion liquid after the addition step, and copper contained in the copper nanoparticle dispersion liquid. Further provided is a natural sedimentation step of spontaneously precipitating nanoparticles.
当該銅ナノ粒子の製造方法は、銅ナノ粒子分散液に含まれる銅ナノ粒子を自然沈降させる自然沈降工程を備えるので、比較的粒子径の大きい銅ナノ粒子を沈降させることができる。また、当該銅ナノ粒子の製造方法は、調製工程後の銅ナノ粒子分散液に凝集剤を添加する添加工程を備えるので、比較的粒子径の小さい銅ナノ粒子を凝集させることができ、この銅ナノ粒子の２次粒子径を十分に大きくすることができる。そのため、当該銅ナノ粒子の製造方法は、上記分離工程で比較的粒子径の大きい銅ナノ粒子を遠心分離すればよいので、銅ナノ粒子の回収率を十分に高めることができる。 Since the method for producing copper nanoparticles includes a natural sedimentation step of spontaneously precipitating copper nanoparticles contained in a copper nanoparticle dispersion liquid, copper nanoparticles having a relatively large particle size can be precipitated. Further, since the method for producing the copper nanoparticles includes an addition step of adding a coagulant to the copper nanoparticle dispersion liquid after the preparation step, copper nanoparticles having a relatively small particle size can be agglomerated, and the copper can be agglomerated. The secondary particle size of the nanoparticles can be made sufficiently large. Therefore, in the method for producing the copper nanoparticles, the copper nanoparticles having a relatively large particle size may be centrifuged in the separation step, so that the recovery rate of the copper nanoparticles can be sufficiently increased.
当該銅ナノ粒子の製造方法は、上記自然沈降工程を上記調製工程直後に行うとよい。このように、上記自然沈降工程を上記調製工程直後に行うことで、自然沈降後の上澄み液に含まれる比較的１次粒子径の小さい銅ナノ粒子を上記添加工程によって効率的に凝集させることができる。 As for the method for producing the copper nanoparticles, the natural sedimentation step may be performed immediately after the preparation step. In this way, by performing the natural sedimentation step immediately after the preparation step, copper nanoparticles having a relatively small primary particle size contained in the supernatant after the natural sedimentation can be efficiently aggregated by the addition step. it can.
当該銅ナノ粒子の製造方法は、上記自然沈降工程後に、上記銅ナノ粒子分散液の上澄み液を回収する上澄み液回収工程をさらに備え、上記上澄み液回収工程後に、上記添加工程で上記上澄み液に上記凝集剤を添加するとよい。このように、上記自然沈降工程後に、上記銅ナノ粒子分散液の上澄み液を回収する上澄み液回収工程をさらに備え、上記上澄み液回収工程後に、上記添加工程で上記上澄み液に上記凝集剤を添加することによって、従来では廃棄等されていた上澄み液に含まれる比較的１次粒子径の小さい銅ナノ粒子を他の銅ナノ粒子と分離して効率的に遠心分離することができる。従って、銅ナノ粒子の回収率をさらに高めることができる。また、遠心分離後に再分散される銅ナノ粒子の粒子径の均一化を図ることができる。 The method for producing the copper nanoparticles further includes a supernatant liquid recovery step of recovering the supernatant liquid of the copper nanoparticles dispersion liquid after the natural sedimentation step, and after the supernatant liquid recovery step, the supernatant liquid is added by the addition step. The above flocculant may be added. As described above, after the natural sedimentation step, the supernatant recovery step for recovering the supernatant liquid of the copper nanoparticle dispersion liquid is further provided, and after the supernatant recovery step, the flocculant is added to the supernatant liquid in the addition step. By doing so, copper nanoparticles having a relatively small primary particle diameter contained in the supernatant liquid, which has been conventionally discarded, can be separated from other copper nanoparticles and efficiently centrifuged. Therefore, the recovery rate of copper nanoparticles can be further increased. Further, it is possible to make the particle size of the copper nanoparticles redispersed after centrifugation uniform.
上記凝集剤としては有機酸塩が好ましい。上記凝集剤が有機酸塩であることによって、上記銅ナノ粒子を容易かつ確実に凝集させることができる。 The organic acid salt is preferable as the flocculant. When the flocculant is an organic acid salt, the copper nanoparticles can be easily and surely aggregated.
上記自然沈降工程における自然沈降時間としては、１０時間以上が好ましい。このように、上記自然沈降工程における自然沈降時間が上記下限以上であることによって、比較的粒子径の大きい銅ナノ粒子を十分に沈降させることができる。 The natural sedimentation time in the natural sedimentation step is preferably 10 hours or more. As described above, when the natural sedimentation time in the natural sedimentation step is equal to or longer than the above lower limit, copper nanoparticles having a relatively large particle size can be sufficiently precipitated.
上記添加工程における凝集剤の添加量としては、１．０質量％以上７．５質量％以下が好ましい。このように、上記添加工程における凝集剤の添加量が上記範囲内であることによって、銅ナノ粒子を適切に凝集させることができる。 The amount of the flocculant added in the addition step is preferably 1.0% by mass or more and 7.5% by mass or less. As described above, when the amount of the flocculant added in the addition step is within the above range, the copper nanoparticles can be appropriately aggregated.
なお、本開示において、銅ナノ粒子分散液における銅ナノ粒子の「平均粒子径」とは、レーザ回折法で測定した体積基準の累積分布から算出されるメディアン径をいう。 In the present disclosure, the "average particle size" of copper nanoparticles in the copper nanoparticle dispersion liquid means the median diameter calculated from the volume-based cumulative distribution measured by the laser diffraction method.
［本開示の実施形態の詳細］
以下、本開示に係る銅ナノ粒子の製造方法の各実施形態について図面を参照しつつ詳説する。[Details of Embodiments of the present disclosure]
Hereinafter, each embodiment of the method for producing copper nanoparticles according to the present disclosure will be described in detail with reference to the drawings.
［第一実施形態］
図１に示すように、当該銅ナノ粒子の製造方法は、液相還元法によって平均粒子径５０ｎｍ以下の銅ナノ粒子分散液を調製する調製工程（Ｓ０１）と、上記銅ナノ粒子分散液に含まれる銅ナノ粒子を自然沈降させる自然沈降工程（Ｓ０２）と、調製工程（Ｓ０１）後の銅ナノ粒子分散液に凝集剤を添加する添加工程（Ｓ０４）と、添加工程（Ｓ０４）後の銅ナノ粒子分散液から液相を遠心分離する分離工程（Ｓ０５）とを備える。なお、当該銅ナノ粒子の製造方法によって得られる銅ナノ粒子は、例えばプリント配線板のベースフィルム上に銅ナノ粒子の焼結体層を形成するのに用いられる。[First Embodiment]
As shown in FIG. 1, the method for producing the copper nanoparticles includes a preparation step (S01) for preparing a copper nanoparticle dispersion having an average particle diameter of 50 nm or less by a liquid phase reduction method, and the copper nanoparticle dispersion. A natural sedimentation step (S02) for spontaneously precipitating copper nanoparticles, an addition step (S04) for adding a flocculant to the copper nanoparticle dispersion after the preparation step (S01), and a copper nano after the addition step (S04). A separation step (S05) for centrifuging the liquid phase from the particle dispersion is provided. The copper nanoparticles obtained by the method for producing copper nanoparticles are used, for example, to form a sintered body layer of copper nanoparticles on a base film of a printed wiring board.
当該銅ナノ粒子の製造方法は、銅ナノ粒子分散液に含まれる銅ナノ粒子を自然沈降させる自然沈降工程（Ｓ０２）を備えるので、比較的粒子径の大きい銅ナノ粒子を沈降させることができる。また、当該銅ナノ粒子の製造方法は、調製工程（Ｓ０１）後の銅ナノ粒子分散液に凝集剤を添加する添加工程（Ｓ０４）を備えるので、比較的粒子径の小さい銅ナノ粒子を凝集させることができ、この銅ナノ粒子の２次粒子径を十分に大きくすることができる。そのため、当該銅ナノ粒子の製造方法は、分離工程（Ｓ０５）で比較的粒子径の大きい銅ナノ粒子を遠心分離すればよいので、銅ナノ粒子の回収率を十分に高めることができる。 Since the method for producing copper nanoparticles includes a natural sedimentation step (S02) for spontaneously precipitating copper nanoparticles contained in a copper nanoparticles dispersion, copper nanoparticles having a relatively large particle size can be precipitated. Further, since the method for producing the copper nanoparticles includes an addition step (S04) of adding a flocculant to the copper nanoparticle dispersion liquid after the preparation step (S01), the copper nanoparticles having a relatively small particle size are aggregated. The secondary particle size of the copper nanoparticles can be made sufficiently large. Therefore, in the method for producing the copper nanoparticles, the copper nanoparticles having a relatively large particle size may be centrifuged in the separation step (S05), so that the recovery rate of the copper nanoparticles can be sufficiently increased.
当該銅ナノ粒子の製造方法は、自然沈降工程（Ｓ０２）を調製工程（Ｓ０１）直後に行うことが好ましい。当該銅ナノ粒子の製造方法は、自然沈降工程（Ｓ０２）後に、上記銅ナノ粒子分散液の上澄み液を回収する上澄み液回収工程（Ｓ０３）を備える。当該銅ナノ粒子の製造方法は、上澄み液回収工程（Ｓ０３）後に、添加工程（Ｓ０４）で上記上澄み液に上記凝集剤を添加する。 As for the method for producing the copper nanoparticles, it is preferable to carry out the natural sedimentation step (S02) immediately after the preparation step (S01). The method for producing the copper nanoparticles includes a supernatant recovery step (S03) for recovering the supernatant of the copper nanoparticles dispersion after the natural sedimentation step (S02). In the method for producing the copper nanoparticles, the flocculant is added to the supernatant in the addition step (S04) after the supernatant recovery step (S03).
つまり、当該銅ナノ粒子の製造方法は、まず調製工程（Ｓ０１）で調製された銅ナノ粒子分散液に含まれる比較的粒子径の大きい銅ナノ粒子を自然沈降工程（Ｓ０２）で自然沈降させた後、この自然沈降工程（Ｓ０２）によって沈降しなかった比較的粒子径の小さい銅ナノ粒子を含む上澄み液を上澄み液回収工程（Ｓ０３）で回収する。続いて、当該銅ナノ粒子の製造方法は、添加工程（Ｓ０４）によって、上澄み液回収工程（Ｓ０３）で回収された上澄み液に凝集剤を添加したうえ、この凝集剤添加後の上澄み液を分離工程（Ｓ０５）で遠心分離する。 That is, in the method for producing the copper nanoparticles, first, the copper nanoparticles having a relatively large particle size contained in the copper nanoparticles dispersion prepared in the preparation step (S01) were naturally precipitated in the natural sedimentation step (S02). After that, the supernatant liquid containing copper nanoparticles having a relatively small particle size that did not settle in the natural sedimentation step (S02) is recovered in the supernatant liquid recovery step (S03). Subsequently, in the method for producing the copper nanoparticles, a flocculant is added to the supernatant recovered in the supernatant recovery step (S03) by the addition step (S04), and the supernatant after the addition of the flocculant is separated. Centrifuge in step (S05).
当該銅ナノ粒子の製造方法は、自然沈降工程（Ｓ０２）を調製工程（Ｓ０１）直後に行うことで、自然沈降後の上澄み液に含まれる比較的１次粒子径の小さい銅ナノ粒子を添加工程（Ｓ０４）で効率的に凝集させることができる。また、添加工程（Ｓ０４）で比較的１次粒子径の小さい銅ナノ粒子を選択的に凝集させることで、後述する分離工程（Ｓ０５）による遠心分離後の銅ナノ粒子の再分散性を高めることができる。 The method for producing the copper nanoparticles is a step of adding copper nanoparticles having a relatively small primary particle size contained in the supernatant after the natural sedimentation by performing the natural sedimentation step (S02) immediately after the preparation step (S01). It can be efficiently aggregated in (S04). Further, by selectively aggregating copper nanoparticles having a relatively small primary particle size in the addition step (S04), the redispersibility of the copper nanoparticles after centrifugation by the separation step (S05) described later is enhanced. Can be done.
当該銅ナノ粒子の製造方法は、自然沈降工程（Ｓ０２）後に、上記銅ナノ粒子分散液の上澄み液を回収する上澄み液回収工程（Ｓ０３）を備え、上澄み液回収工程（Ｓ０３）後に、添加工程（Ｓ０４）で上記上澄み液に上記凝集剤を添加するので、従来では廃棄等されていた上澄み液に含まれる比較的１次粒子径の小さい銅ナノ粒子を他の銅ナノ粒子と分離して効率的に遠心分離することができる。つまり、上記上澄み液に含まれる銅ナノ粒子は粒子径が小さいため、遠心分離し難く、従来では廃棄されることが多かった。これに対し、当該銅ナノ粒子の製造方法は、上記上澄み液に含まれる銅ナノ粒子を選択的に凝集させることで、この銅ナノ粒子の２次粒子径を遠心分離しやすい程度まで大きくすることができる。従って、当該銅ナノ粒子の製造方法は、銅ナノ粒子の回収率をさらに高めることができる。当該銅ナノ粒子の製造方法は、分離工程（Ｓ０５）によって比較的１次粒子径の小さい銅ナノ粒子を選択的に遠心分離することができるので、遠心分離後に再分散される銅ナノ粒子の粒子径の均一化を図ることができる。また、比較的粒子径の小さい銅ナノ粒子を用いて上記焼結体層を形成する場合、焼結体層の緻密化を図ることができるので、この焼結体層を有するプリント配線板の品質を高めることができる。 The method for producing the copper nanoparticles includes a supernatant recovery step (S03) for recovering the supernatant of the copper nanoparticles dispersion after the natural sedimentation step (S02), and an addition step after the supernatant recovery step (S03). Since the coagulant is added to the supernatant in (S04), copper nanoparticles having a relatively small primary particle size contained in the supernatant, which has been conventionally discarded, can be separated from other copper nanoparticles for efficiency. Can be centrifuged. That is, since the copper nanoparticles contained in the supernatant have a small particle size, they are difficult to centrifuge and have been often discarded in the past. On the other hand, the method for producing the copper nanoparticles is to selectively agglomerate the copper nanoparticles contained in the supernatant to increase the secondary particle size of the copper nanoparticles to a degree that facilitates centrifugation. Can be done. Therefore, the method for producing copper nanoparticles can further increase the recovery rate of copper nanoparticles. In the method for producing copper nanoparticles, copper nanoparticles having a relatively small primary particle size can be selectively centrifuged by the separation step (S05), so that the particles of the copper nanoparticles are redispersed after centrifugation. The diameter can be made uniform. Further, when the sintered body layer is formed by using copper nanoparticles having a relatively small particle diameter, the sintered body layer can be densified, so that the quality of the printed wiring board having the sintered body layer can be improved. Can be enhanced.
以下、図２を参照しつつ、当該銅ナノ粒子の製造方法における各工程の詳細について説明する。 Hereinafter, details of each step in the method for producing the copper nanoparticles will be described with reference to FIG.
（調製工程）
Ｓ０１では、例えば水に銅ナノ粒子を形成する銅イオンのもとになる水溶性の銅化合物と、分散剤及び錯化剤とを溶解させると共に、還元剤を加えて一定時間銅イオンを還元反応させる。この液相還元法で製造される銅ナノ粒子は、形状が球状又は粒状で揃っており、しかも平均粒子径が５０ｎｍ以下の微細な粒子とすることができる。上記銅イオンのもとになる水溶性の銅化合物としては、硝酸銅三水和物（ＩＩ）（Ｃｕ（ＮＯ３）２・３Ｈ２Ｏ）、硫酸銅（ＩＩ）五水和物（ＣｕＳＯ４・５Ｈ２Ｏ）等が挙げられる。(Preparation process)
In S01, for example, a water-soluble copper compound that is a source of copper ions forming copper nanoparticles in water, a dispersant and a complexing agent are dissolved, and a reducing agent is added to reduce the copper ions for a certain period of time. Let me. The copper nanoparticles produced by this liquid phase reduction method can be made into fine particles having a spherical or granular shape and an average particle diameter of 50 nm or less. Examples of the water-soluble copper compound underlying the copper ions, copper nitrate trihydrate (II) (Cu (NO 3 ) 2 · 3H 2 O), copper (II) sulfate pentahydrate (CuSO 4・ 5H 2 O) and the like.
上記還元剤としては、液相（水溶液）の反応系において、銅イオンを還元及び析出させることができる種々の還元剤を用いることができる。この還元剤としては、例えば水素化ホウ素ナトリウム、次亜リン酸ナトリウム、ヒドラジン、３価のチタンイオンや２価のコバルトイオン等の遷移金属のイオン、アスコルビン酸、グルコースやフルクトース等の還元性糖類、エチレングリコールやグリセリン等の多価アルコールなどが挙げられる。中でも、還元剤としては３価のチタンイオンが好ましい。なお、３価のチタンイオンを還元剤とする液相還元法は、チタンレドックス法という。チタンレドックス法では、３価のチタンイオンが４価に酸化される際の酸化還元作用によって銅イオンを還元し、銅ナノ粒子を析出させる。このチタンレドックス法によると、微細かつ均一な粒子径を有する銅ナノ粒子を形成しやすい。 As the reducing agent, various reducing agents capable of reducing and precipitating copper ions in the reaction system of the liquid phase (aqueous solution) can be used. Examples of this reducing agent include transition metal ions such as sodium borohydride, sodium hypophosphate, hydrazine, trivalent titanium ion and divalent cobalt ion, ascorbic acid, reducing saccharides such as glucose and fructose, and the like. Examples thereof include polyhydric alcohols such as ethylene glycol and glycerin. Of these, trivalent titanium ions are preferable as the reducing agent. The liquid phase reduction method using trivalent titanium ions as a reducing agent is called a titanium redox method. In the titanium redox method, copper ions are reduced by a redox action when trivalent titanium ions are oxidized to tetravalent, and copper nanoparticles are precipitated. According to this titanium redox method, it is easy to form copper nanoparticles having a fine and uniform particle size.
上記分散剤は、周辺部材の劣化防止の観点より、硫黄、リン、ホウ素、ハロゲン及びアルカリを含まないものが好ましい。好ましい分散剤としては、ポリエチレンイミン、ポリビニルピロリドン等の窒素含有高分子分散剤、ポリアクリル酸、カルボキシメチルセルロース等の分子中にカルボキシ基を有する炭化水素系の高分子分散剤、ポバール（ポリビニルアルコール）、スチレン−マレイン酸共重合体、オレフィン−マレイン酸共重合体、１分子中にポリエチレンイミン部分とポリエチレンオキサイド部分とを有する共重合体等の極性基を有する高分子分散剤などを挙げることができる。 The dispersant preferably does not contain sulfur, phosphorus, boron, halogen and alkali from the viewpoint of preventing deterioration of peripheral members. Preferred dispersants include nitrogen-containing polymer dispersants such as polyethyleneimine and polyvinylpyrrolidone, hydrocarbon-based polymer dispersants having a carboxy group in the molecule such as polyacrylic acid and carboxymethyl cellulose, and Poval (polyvinyl alcohol). Examples thereof include a styrene-maleic acid copolymer, an olefin-maleic acid copolymer, and a polymer dispersant having a polar group such as a copolymer having a polyethyleneimine moiety and a polyethylene oxide moiety in one molecule.
上記錯化剤としては、例えばクエン酸ナトリウム、酒石酸ナトリウム、酢酸ナトリウム、グルコン酸、チオ硫酸ナトリウム、アンモニア、エチレンジアミン四酢酸等が挙げられ、これらの１種又は２種以上を用いることができる。中でも、上記錯化剤としてはクエン酸ナトリウムが好ましい。 Examples of the complexing agent include sodium citrate, sodium tartrate, sodium acetate, gluconic acid, sodium thiosulfate, ammonia, ethylenediaminetetraacetic acid and the like, and one or more of these can be used. Of these, sodium citrate is preferable as the complexing agent.
銅ナノ粒子の粒子径を調整するには、銅化合物、分散剤及び還元剤の種類並びに配合割合を調整すると共に、銅化合物を還元反応させる際に、攪拌速度、温度、時間、ｐＨ等を調整すればよい。反応系のｐＨの下限としては７が好ましく、反応系のｐＨの上限としては１３が好ましい。反応系のｐＨを上記範囲とすることで、微小な粒子径の銅ナノ粒子を得ることができる。このときｐＨ調整剤を用いることで、反応系のｐＨを上記範囲に容易に調整することができる。このｐＨ調整剤としては、塩酸、硫酸、硝酸、水酸化ナトリウム、炭酸ナトリウム、アンモニア等の一般的な酸又はアルカリが使用できるが、特に周辺部材の劣化を防止するために、アルカリ金属、アルカリ土類金属、ハロゲン元素、硫黄、リン、ホウ素等の不純物を含まない硝酸及び炭酸ナトリウムが好ましい。 In order to adjust the particle size of the copper nanoparticles, the types and blending ratios of the copper compound, dispersant and reducing agent are adjusted, and the stirring speed, temperature, time, pH, etc. are adjusted when the copper compound is reduced. do it. The lower limit of the pH of the reaction system is preferably 7, and the upper limit of the pH of the reaction system is preferably 13. By setting the pH of the reaction system in the above range, copper nanoparticles having a fine particle size can be obtained. At this time, by using a pH adjuster, the pH of the reaction system can be easily adjusted within the above range. As this pH adjuster, general acids or alkalis such as hydrochloric acid, sulfuric acid, nitric acid, sodium hydroxide, sodium carbonate and ammonia can be used, but in order to prevent deterioration of peripheral members in particular, alkali metals and alkaline soils can be used. Nitric acid and sodium carbonate that do not contain impurities such as metals, halogen elements, sulfur, phosphorus, and boron are preferable.
銅ナノ粒子分散液における銅ナノ粒子の含有割合としては、例えば０．１質量％以上５．０質量％以下が好ましい。 The content ratio of the copper nanoparticles in the copper nanoparticles dispersion is preferably, for example, 0.1% by mass or more and 5.0% by mass or less.
銅ナノ粒子分散液における銅ナノ粒子の平均粒子径は、上述のように５０ｎｍ以下である。銅ナノ粒子分散液における銅ナノ粒子は、例えば５ｎｍ以上３５ｎｍ以下の範囲に粒子径分布のピークを有する。この銅ナノ粒子の粒子径分布のピークは１つであってもよく２以上であってもよい。 The average particle size of the copper nanoparticles in the copper nanoparticle dispersion is 50 nm or less as described above. The copper nanoparticles in the copper nanoparticles dispersion have a peak of particle size distribution in the range of, for example, 5 nm or more and 35 nm or less. The particle size distribution of the copper nanoparticles may have one peak or two or more peaks.
（自然沈降工程）
Ｓ０２では、Ｓ０１で調製された銅ナノ粒子分散液を容器中で所定時間放置することによりこの銅ナノ粒子分散液に含まれる銅ナノ粒子の一部を自然沈降させる。Ｓ０２は、例えば空気雰囲気下において室温（２５℃）で行うことができる。Ｓ０２により、比較的粒子径の大きい銅ナノ粒子が容器の底部に沈降する。これにより、図２に示すように、容器の底部には沈殿液（以下、「第１沈殿液Ｐ１」という）が滞留する。一方、Ｓ０２では、粒子径が２０ｎｍ以下程度の比較的粒子径の小さい銅ナノ粒子は沈降せず上澄み液（以下、「第１上澄み液Ｌ１」という）中に分散される。(Natural sedimentation process)
In S02, a part of the copper nanoparticles contained in the copper nanoparticle dispersion liquid is naturally precipitated by leaving the copper nanoparticle dispersion liquid prepared in S01 in a container for a predetermined time. S02 can be carried out at room temperature (25 ° C.), for example, in an air atmosphere. By S02, copper nanoparticles having a relatively large particle size settle on the bottom of the container. As a result, as shown in FIG. 2, the precipitate liquid (hereinafter, referred to as “first precipitate liquid P1”) stays at the bottom of the container. On the other hand, in S02, copper nanoparticles having a relatively small particle diameter of about 20 nm or less do not settle and are dispersed in the supernatant liquid (hereinafter, referred to as “first supernatant liquid L1”).
Ｓ０２における自然沈降後の第１上澄み液Ｌ１には、例えばＳ０１で調製された銅ナノ粒子の全量に対する５０質量％以上８０質量％以下程度の銅ナノ粒子が含有される。つまり、Ｓ０１で調製された全銅ナノ粒子に対するＳ０２における沈降割合としては、例えば２０質量％以上５０質量％以下とすることができる。また、Ｓ０１で調製された銅ナノ粒子分散液の全量に対する第１上澄み液Ｌ１の体積割合は８５体積％以上９７体積％以下程度である。 The first supernatant L1 after natural sedimentation in S02 contains, for example, about 50% by mass or more and 80% by mass or less of copper nanoparticles with respect to the total amount of copper nanoparticles prepared in S01. That is, the sedimentation ratio in S02 with respect to the total copper nanoparticles prepared in S01 can be, for example, 20% by mass or more and 50% by mass or less. The volume ratio of the first supernatant L1 to the total amount of the copper nanoparticle dispersion liquid prepared in S01 is about 85% by volume or more and 97% by volume or less.
Ｓ０２における自然沈降時間の下限としては、１０時間が好ましく、１２時間がより好ましく、１８時間がさらに好ましい。上記自然沈降時間が上記下限に満たないと、比較的粒子径の大きい銅ナノ粒子を十分に沈降させることができないおそれがある。これに対し、上記自然沈降時間が上記下限以上であることで、比較的粒子径の大きい銅ナノ粒子を十分に沈降させることができ、第１上澄み液Ｌ１中に比較的粒子径の小さい銅ナノ粒子を集中的に分散させやすい。なお、上記自然沈降時間の上限としては、自然沈降時間が不要に長くなることを防止する点から、例えば７２時間とすることができる。 The lower limit of the natural settling time in S02 is preferably 10 hours, more preferably 12 hours, and even more preferably 18 hours. If the natural sedimentation time does not reach the lower limit, copper nanoparticles having a relatively large particle size may not be sufficiently precipitated. On the other hand, when the natural settling time is equal to or longer than the above lower limit, copper nanoparticles having a relatively large particle size can be sufficiently settled, and copper nanoparticles having a relatively small particle size can be sufficiently settled in the first supernatant L1. It is easy to disperse particles intensively. The upper limit of the natural sedimentation time can be, for example, 72 hours from the viewpoint of preventing the natural sedimentation time from becoming unnecessarily long.
（上澄み液回収工程）
Ｓ０３では、Ｓ０２後の第１上澄み液Ｌ１を別の容器に回収する。(Supernatant liquid recovery process)
In S03, the first supernatant liquid L1 after S02 is collected in another container.
（添加工程）
Ｓ０４では、Ｓ０３で回収した第１上澄み液Ｌ１に凝集剤Ｆを添加する。Ｓ０４で添加する凝集剤Ｆとしては、例えば有機酸塩、アルカリ金属塩、多価金属塩等が挙げられ、有機酸塩が好ましい。中でも、クエン酸塩が好ましく、クエン酸ナトリウムが特に好ましい。凝集剤Ｆが有機酸塩であることによって、銅ナノ粒子を容易かつ確実に凝集させることができる。有機酸塩、中でもクエン酸塩が好ましい理由は、必ずしも明らかではないが、銅ナノ粒子分散液のイオン濃度が上昇することで銅ナノ粒子表面のゼータ電位が低下すためと考えられる。つまり、上記有機酸塩は、例えば酸化還元電位を調整することで銅ナノ粒子の凝集を促進するものではない。なお、凝集剤Ｆは、遠心分離後の銅ナノ粒子に付着することでこの銅ナノ粒子の焼結性等に悪影響を与える場合がある。一方、クエン酸ナトリウムは、液相還元法としてチタンレドックス法を用いた場合に通常錯化剤として使用されるものである。そのため、このクエン酸ナトリウムを凝集剤Ｆとして用いることで、凝集剤Ｆの添加量を抑制することができると共に、遠心分離後に得られる銅ナノ粒子のコンタミネーションのおそれを抑制することができる。また、凝集剤Ｆとしてクエン酸ナトリウムを用いることで、分離工程（Ｓ０５）による遠心分離後の銅ナノ粒子の再分散性を向上することができ、これにより緻密な焼結体層を形成しやすい。(Addition process)
In S04, the flocculant F is added to the first supernatant L1 recovered in S03. Examples of the flocculant F added in S04 include organic acid salts, alkali metal salts, polyvalent metal salts and the like, and organic acid salts are preferable. Of these, citrate is preferable, and sodium citrate is particularly preferable. Since the flocculant F is an organic acid salt, copper nanoparticles can be easily and surely aggregated. The reason why organic acid salts, especially citrate salts, are preferable is not necessarily clear, but it is considered that the zeta potential on the surface of copper nanoparticles decreases as the ion concentration of the copper nanoparticle dispersion liquid increases. That is, the organic acid salt does not promote the aggregation of copper nanoparticles, for example, by adjusting the redox potential. The flocculant F may adhere to the copper nanoparticles after centrifugation, which may adversely affect the sinterability of the copper nanoparticles. On the other hand, sodium citrate is usually used as a complexing agent when the titanium redox method is used as the liquid phase reduction method. Therefore, by using this sodium citrate as the flocculant F, the amount of the flocculant F added can be suppressed, and the risk of contamination of the copper nanoparticles obtained after centrifugation can be suppressed. Further, by using sodium citrate as the flocculant F, the redispersibility of the copper nanoparticles after centrifugation in the separation step (S05) can be improved, which makes it easy to form a dense sintered body layer. ..
Ｓ０４における凝集剤Ｆの添加量（凝集剤Ｆ添加前の第１上澄み液Ｌ１の全量を１００質量％とした場合の添加量）の下限としては、１．０質量％が好ましく、３．０質量％がより好ましい。一方、Ｓ０４における凝集剤Ｆの添加量の上限としては、７．５質量％が好ましく、５．０質量％がより好ましい。凝集剤Ｆの添加量が上記下限に満たないと、銅ナノ粒子を十分に凝集させることができないおそれがある。逆に、凝集剤Ｆの添加量が上記上限を超えると、銅ナノ粒子が凝集しすぎることで、分離工程（Ｓ０５）による遠心分離後の銅ナノ粒子の再分散性が不十分となるおそれがある。 The lower limit of the amount of the coagulant F added in S04 (the amount added when the total amount of the first supernatant L1 before the addition of the coagulant F is 100% by mass) is preferably 1.0% by mass, preferably 3.0% by mass. % Is more preferable. On the other hand, the upper limit of the amount of the flocculant F added in S04 is preferably 7.5% by mass, more preferably 5.0% by mass. If the amount of the flocculant F added is less than the above lower limit, the copper nanoparticles may not be sufficiently aggregated. On the contrary, if the amount of the flocculant F added exceeds the above upper limit, the copper nanoparticles may be excessively aggregated, resulting in insufficient redispersibility of the copper nanoparticles after centrifugation in the separation step (S05). is there.
（分離工程）
図３に示すように、Ｓ０５は、上澄み液除去工程（Ｓ１１）と、遠心分離工程（Ｓ１２）とを有する。(Separation process)
As shown in FIG. 3, S05 includes a supernatant liquid removing step (S11) and a centrifugation step (S12).
〈上澄み液除去工程〉
Ｓ１１では、まずＳ０４による凝集剤Ｆ添加後の第１上澄み液Ｌ１を所定時間放置することでこの第１上澄み液Ｌ１に含まれる銅ナノ粒子を自然沈降させる。これにより、図２に示すように、第１上澄み液Ｌ１は、銅ナノ粒子が沈殿した沈殿液（以下、「第２沈殿液Ｐ２」という）と、この第２沈殿液Ｐ２上の上澄み液（以下、「第２上澄み液Ｌ２」という）とに分離される。Ｓ１１では、銅ナノ粒子が自然沈降した後の第２上澄み液Ｌ２を除去する。<Supernatant liquid removal process>
In S11, first, the copper nanoparticles contained in the first supernatant L1 are naturally precipitated by leaving the first supernatant L1 after the addition of the flocculant F by S04 for a predetermined time. As a result, as shown in FIG. 2, the first supernatant L1 is a precipitate in which copper nanoparticles are precipitated (hereinafter referred to as "second precipitate P2") and a supernatant on the second precipitate P2 (hereinafter referred to as "second precipitate P2"). Hereinafter, it is separated into "second supernatant liquid L2"). In S11, the second supernatant liquid L2 after the copper nanoparticles have naturally settled is removed.
Ｓ１１における自然沈降は、例えば空気雰囲気下において室温（２５℃）で行うことができる。また、Ｓ１１における自然沈降時間の下限としては、３時間が好ましく、１５時間がより好ましい。上記自然沈降時間が上記下限に満たないと、銅ナノ粒子を十分に沈降させることができないおそれがある。なお、上記自然沈降時間の上限としては、自然沈降時間が不要に長くなることを防止する点から、例えば７２時間とすることができる。 The natural sedimentation in S11 can be performed at room temperature (25 ° C.), for example, in an air atmosphere. The lower limit of the natural sedimentation time in S11 is preferably 3 hours, more preferably 15 hours. If the natural sedimentation time does not reach the lower limit, the copper nanoparticles may not be sufficiently precipitated. The upper limit of the natural sedimentation time can be, for example, 72 hours from the viewpoint of preventing the natural sedimentation time from becoming unnecessarily long.
〈遠心分離工程〉
Ｓ１２では、Ｓ１１で第２上澄み液Ｌ２を除去した後の第２沈殿液Ｐ２から液相を遠心分離する。具体的には、Ｓ１２では、第２沈殿液Ｐ２を銅ナノ粒子を含む銅ナノ粒子濃縮液（以下、「第１銅ナノ粒子濃縮液Ｃ１」という）と液相（以下、「第１液相Ｄ１という）とに遠心分離する。Ｓ１２は、公知の遠心分離機を用いて行うことができる。当該銅ナノ粒子の製造方法は、Ｓ１２によって比較的１次粒子径の小さい銅ナノ粒子を効率的に回収することができる。<Centrifugation process>
In S12, the liquid phase is centrifuged from the second precipitate liquid P2 after removing the second supernatant liquid L2 in S11. Specifically, in S12, the second precipitate P2 is a copper nanoparticle concentrate containing copper nanoparticles (hereinafter referred to as “first copper nanoparticle concentrate C1”) and a liquid phase (hereinafter, “first liquid phase”). Centrifuge to (D1). S12 can be carried out using a known centrifuge. The method for producing the copper nanoparticles is such that copper nanoparticles having a relatively small primary particle diameter are efficiently produced by S12. Can be collected in.
Ｓ１２における遠心加速度の下限としては、２００００Ｇが好ましく、５００００Ｇがより好ましい。上記遠心加速度が上記下限に満たないと、銅ナノ粒子を十分に遠心分離することができないおそれがある。なお、上記遠心加速度の上限としては、特に限定されないが、例えば１２００００Ｇとすることができる。上記遠心加速度が上記上限を超えると、遠心分離後の第１銅ナノ粒子濃縮液Ｃ１の濃度が高くなり過ぎて、この第１銅ナノ粒子濃縮液Ｃ１が容器等に固着し歩留まりが低下するおそれがある。 As the lower limit of the centrifugal acceleration in S12, 20000G is preferable, and 50,000G is more preferable. If the centrifugal acceleration does not reach the lower limit, the copper nanoparticles may not be sufficiently centrifuged. The upper limit of the centrifugal acceleration is not particularly limited, but may be, for example, 120,000 G. If the centrifugal acceleration exceeds the upper limit, the concentration of the first copper nanoparticle concentrate C1 after centrifugation becomes too high, and the first copper nanoparticle concentrate C1 may stick to a container or the like to reduce the yield. There is.
Ｓ１２における遠心分離後の第１銅ナノ粒子濃縮液Ｃ１の固形分濃度の下限としては、８０質量％が好ましく、８５質量％がより好ましい。上記固形分濃度が上記下限に満たないと、この第１銅ナノ粒子濃縮液Ｃ１を用いて得られる銅ナノインク中における不純物を十分に除去できないおそれがある。一方、上記固形分濃度の上限としては、特に限定されないが、例えば９５質量％とすることができる。 The lower limit of the solid content concentration of the first copper nanoparticle concentrate C1 after centrifugation in S12 is preferably 80% by mass, more preferably 85% by mass. If the solid content concentration does not reach the above lower limit, impurities in the copper nanoink obtained by using the first copper nanoparticle concentrate C1 may not be sufficiently removed. On the other hand, the upper limit of the solid content concentration is not particularly limited, but may be, for example, 95% by mass.
図４に示すように、当該銅ナノ粒子の製造方法は、Ｓ１２の後に、再遠心分離工程（Ｓ０６）、水添工程（Ｓ０７）及び攪拌工程（Ｓ０８）をさらに備えていてもよい。Ｓ０６〜Ｓ０８は、当該銅ナノ粒子の製造方法の銅ナノ粒子洗浄工程を構成する。また、当該銅ナノ粒子の製造方法は、Ｓ０６〜Ｓ０８のうちの一部の工程のみを備えていてもよく、例えばＳ０７等、特定の工程を複数回行ってもよい。Ｓ０６では、Ｓ１２で分離された第１銅ナノ粒子濃縮液Ｃ１を超遠心分離機によって超遠心分離する。Ｓ０７では、Ｓ０６で分離された銅ナノ粒子濃縮液に水、典型的には純水を添加する。当該銅ナノ粒子の製造方法はＳ０７を複数回行う場合、一旦添加された水を除去した後に、再度水を添加する。Ｓ０８では、Ｓ０７で水が添加された銅ナノ粒子濃縮液に超音波を照射したり、この銅ナノ粒子濃縮液を高圧ホモジナイザー、ミキサー等の公知の装置で処理することで、Ｓ０４による凝集剤Ｆの添加によって凝集した銅ナノ粒子を液中に再分散させる。Ｓ０８による再分散後の銅ナノ粒子の平均粒子径の上限としては、２５ｎｍが好ましく、２０ｎｍがより好ましい。上記平均粒子径が上記上限より大きいと、銅ナノ粒子が径の大きな粒子を起点に凝集し、分散性のない凝集物が発生するおそれがある。一方、Ｓ０８による再分散後の銅ナノ粒子の平均粒子径の下限としては、製造容易性の観点から、例えば５ｎｍが好ましく、１０ｎｍがより好ましい。なお、当該銅ナノ粒子の製造方法は、Ｓ０８によって液中に銅ナノ粒子が再分散した分散液を粒子濃度を調整したうえ銅ナノインクとして用いてもよく、Ｓ０８後の分散液をさらに１又は複数回遠心分離し、この遠心分離後の分散液を粒子濃度を調整したうえ銅ナノインクとして用いてもよい。 As shown in FIG. 4, the method for producing the copper nanoparticles may further include a recentrifugation step (S06), a hydrogenation step (S07), and a stirring step (S08) after S12. S06 to S08 constitute a copper nanoparticle cleaning step of the method for producing the copper nanoparticles. Further, the method for producing the copper nanoparticles may include only a part of the steps of S06 to S08, and a specific step such as S07 may be performed a plurality of times. In S06, the first copper nanoparticle concentrate C1 separated in S12 is ultracentrifuged by an ultracentrifuge. In S07, water, typically pure water, is added to the copper nanoparticle concentrate separated in S06. In the method for producing copper nanoparticles, when S07 is performed a plurality of times, water once added is removed, and then water is added again. In S08, the copper nanoparticle concentrate to which water was added in S07 is irradiated with ultrasonic waves, or the copper nanoparticle concentrate is treated with a known device such as a high-pressure homogenizer or a mixer to obtain a flocculant F according to S04. The copper nanoparticles aggregated by the addition of the above are redispersed in the liquid. The upper limit of the average particle size of the copper nanoparticles after redispersion by S08 is preferably 25 nm, more preferably 20 nm. If the average particle size is larger than the upper limit, copper nanoparticles may aggregate starting from particles having a large diameter, and non-dispersible aggregates may be generated. On the other hand, as the lower limit of the average particle size of the copper nanoparticles after redispersion by S08, for example, 5 nm is preferable and 10 nm is more preferable from the viewpoint of ease of production. In the method for producing the copper nanoparticles, a dispersion liquid in which the copper nanoparticles are redistributed in the liquid by S08 may be used as the copper nanoink after adjusting the particle concentration, and one or more dispersion liquids after S08 may be used. Centrifugation may be performed, and the dispersion after centrifugation may be used as copper nanoink after adjusting the particle concentration.
また、当該銅ナノ粒子の製造方法は、図２に示すように、Ｓ０３で第１上澄み液Ｌ１を回収した後に残った第１沈殿液Ｐ１についても、第２銅ナノ粒子濃縮液Ｃ２と第２液相Ｄ２とに遠心分離してもよい。また、この遠心分離後の銅ナノ粒子濃縮液について、上述の銅ナノ粒子洗浄工程を行い、銅ナノインクを製造してもよい。 Further, as shown in FIG. 2, as shown in FIG. 2, the method for producing the copper nanoparticles also includes the second copper nanoparticles concentrate C2 and the second copper nanoparticles concentrate C2 for the first precipitate solution P1 remaining after the first supernatant liquid L1 is recovered in S03. It may be centrifuged to the liquid phase D2. Further, the copper nanoparticle concentrating solution after centrifugation may be subjected to the above-mentioned copper nanoparticle cleaning step to produce copper nanoinks.
［第二実施形態］
図５の銅ナノ粒子の製造方法は、液相還元法によって平均粒子径５０ｎｍ以下の銅ナノ粒子分散液を調製する調製工程（Ｓ２１）と、Ｓ２１で調製された銅ナノ粒子分散液に含まれる銅ナノ粒子を自然沈降させる自然沈降工程（Ｓ２２）と、自然沈降工程（Ｓ２２）後の銅ナノ粒子分散液に凝集剤を添加する添加工程（Ｓ２３）と、添加工程（Ｓ２３）後の銅ナノ粒子分散液から液相を遠心分離する分離工程（Ｓ２４）とを備える。[Second Embodiment]
The method for producing copper nanoparticles in FIG. 5 is included in the preparation step (S21) for preparing a copper nanoparticle dispersion having an average particle diameter of 50 nm or less by a liquid phase reduction method, and the copper nanoparticle dispersion prepared in S21. A natural sedimentation step (S22) for spontaneously precipitating copper nanoparticles, an addition step (S23) for adding a flocculant to the copper nanoparticle dispersion liquid after the natural sedimentation step (S22), and a copper nano after the addition step (S23). A separation step (S24) for centrifuging the liquid phase from the particle dispersion is provided.
当該銅ナノ粒子の製造方法は、自然沈降工程（Ｓ２２）後の銅ナノ粒子分散液から上澄み液を回収することなくこの銅ナノ粒子分散液にそのまま凝集剤を添加する以外、図１の銅ナノ粒子の製造方法と同様の方法で実施することができる。 The method for producing the copper nanoparticles is that the coagulant is added to the copper nanoparticles dispersion as it is without recovering the supernatant from the copper nanoparticles dispersion after the natural precipitation step (S22), but the copper nanoparticles in FIG. 1 are produced. It can be carried out in the same manner as the method for producing particles.
当該銅ナノ粒子の製造方法は、Ｓ２１で調製された銅ナノ粒子分散液が容器中で上澄み液と沈殿液とに分離された状態で凝集剤を添加する。当該銅ナノ粒子の製造方法は、この構成によっても、比較的粒子径の小さい銅ナノ粒子を凝集させたうえで遠心分離することができるので、銅ナノ粒子の回収率を十分に高めることができる。 In the method for producing copper nanoparticles, a flocculant is added in a state where the copper nanoparticle dispersion liquid prepared in S21 is separated into a supernatant liquid and a precipitate liquid in a container. In the method for producing copper nanoparticles, even with this configuration, copper nanoparticles having a relatively small particle size can be aggregated and then centrifuged, so that the recovery rate of the copper nanoparticles can be sufficiently increased. ..
［その他の実施形態］
今回開示された実施の形態は全ての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は、上記実施形態の構成に限定されるものではなく、請求の範囲によって示され、請求の範囲と均等の意味及び範囲内での全ての変更が含まれることが意図される。[Other Embodiments]
It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is not limited to the configuration of the above-described embodiment, but is indicated by the claims and is intended to include all modifications within the meaning and scope equivalent to the claims.
例えば上記自然沈降工程は、必ずしも上記添加工程の前に行う必要はない。つまり、当該銅ナノ粒子の製造方法は、銅ナノ粒子分散液に凝集剤を添加した後に、銅ナノ粒子分散液に含まれる銅ナノ粒子を自然沈降させてもよい。但し、凝集後の銅ナノ粒子の再分散性を高める点からは、銅ナノ粒子を自然沈降させた後に銅ナノ粒子分散液に凝集剤を添加することが好ましい。 For example, the natural sedimentation step does not necessarily have to be performed before the addition step. That is, in the method for producing the copper nanoparticles, the copper nanoparticles contained in the copper nanoparticles dispersion may be naturally precipitated after the flocculant is added to the copper nanoparticles dispersion. However, from the viewpoint of enhancing the redispersibility of the copper nanoparticles after aggregation, it is preferable to add the aggregating agent to the copper nanoparticles dispersion liquid after the copper nanoparticles are naturally precipitated.
以下、実施例によって本開示をさらに詳細に説明するが、本発明はこれらの実施例に限定されるものではない。 Hereinafter, the present disclosure will be described in more detail by way of examples, but the present invention is not limited to these examples.
［Ｎｏ．１］
（調製工程）
反応タンクに還元剤としての三塩化チタン溶液８００ｇ（０．１Ｍ）、ｐＨ調整剤としての炭酸ナトリウム５００ｇ、錯化剤としてのクエン酸ナトリウム９００ｇ、及び分散剤としてのポリビニルピロリドン（分子量３００００）１０ｇを純水１０Ｌに溶解し、この水溶液を３５℃に保温した。この水溶液に同温度で保温した硝酸銅三水和物１００ｇ（０．０４Ｍ）の水溶液を撹拌しながら２秒で投入して、銅粒子２５ｇを析出させ銅ナノ粒子分散液を調製した。[No. 1]
(Preparation process)
In the reaction tank, 800 g (0.1 M) of titanium trichloride solution as a reducing agent, 500 g of sodium carbonate as a pH adjuster, 900 g of sodium citrate as a complexing agent, and 10 g of polyvinylpyrrolidone (molecular weight 30,000) as a dispersant. It was dissolved in 10 L of pure water, and the aqueous solution was kept warm at 35 ° C. An aqueous solution of 100 g (0.04 M) of copper nitrate trihydrate kept warm at the same temperature was added to this aqueous solution in 2 seconds with stirring to precipitate 25 g of copper particles to prepare a copper nanoparticle dispersion.
（自然沈降工程）
この銅ナノ粒子分散液を室温（２５℃）で１８時間静置し、比較的粒子径の大きな粒子を自然沈降させた。この自然沈降した銅ナノ粒子（以下「自然沈降粒子」ともいう）の平均粒子径及び粒子径分布をマイクロトラック・ベル社製の「ＮａｎｏＴｒａｃ Ｗａｖｅ」を用いて測定したところ、平均粒子径は２５ｎｍ、粒子径分布は１０ｎｍ以上３５ｎｍ以下であった。また、銅ナノ粒子分散液に含まれる銅ナノ粒子全量に対する上澄み液に含まれる銅ナノ粒子の割合（以下「分離割合」ともいう）は６０質量％であった。(Natural sedimentation process)
The copper nanoparticle dispersion was allowed to stand at room temperature (25 ° C.) for 18 hours to allow particles having a relatively large particle size to spontaneously settle. The average particle size and particle size distribution of the naturally precipitated copper nanoparticles (hereinafter, also referred to as "naturally precipitated particles") were measured using "NanoTrac Wave" manufactured by Microtrac Bell, and the average particle size was 25 nm. The particle size distribution was 10 nm or more and 35 nm or less. The ratio of copper nanoparticles contained in the supernatant to the total amount of copper nanoparticles contained in the copper nanoparticle dispersion (hereinafter, also referred to as “separation ratio”) was 60% by mass.
（上澄み液回収工程）
上記自然沈降工程後の銅ナノ粒子分散液の上澄み液を分離回収した。上記調製工程で調製された銅ナノ粒子分散液の全量に対する上澄み液の体積割合は８５体積％以上９５体積％以下であった。(Supernatant liquid recovery process)
The supernatant of the copper nanoparticle dispersion liquid after the natural sedimentation step was separated and recovered. The volume ratio of the supernatant liquid to the total amount of the copper nanoparticle dispersion liquid prepared in the above preparation step was 85% by volume or more and 95% by volume or less.
（添加工程）
上記上澄み液回収工程で回収した上澄み液に凝集剤としてクエン酸ナトリウムを上澄み液１００質量％に対して４．０質量％の割合で添加した。(Addition process)
Sodium citrate was added as a flocculant to the supernatant recovered in the above supernatant recovery step at a ratio of 4.0% by mass with respect to 100% by mass of the supernatant.
（分離工程）
まず、上記凝集剤添加後の上澄み液を室温（２５℃）で１５時間静置し、この上澄み液中の銅ナノ粒子を自然沈降させた。この上澄み液中の銅ナノ粒子の全量に対する自然沈降しなかった銅ナノ粒子の割合（未回収率）は１０質量％であった。次に、この自然沈降後の上澄み液を分離し廃棄した。さらに、自然沈降した銅ナノ粒子を含む沈殿液を、遠心分離機を用い、銅ナノ粒子を含む銅ナノ粒子濃縮液と液相とに遠心加速度５００００Ｇで遠心分離した。(Separation process)
First, the supernatant after adding the flocculant was allowed to stand at room temperature (25 ° C.) for 15 hours, and the copper nanoparticles in the supernatant were naturally precipitated. The ratio (unrecovered rate) of the copper nanoparticles that did not spontaneously settle to the total amount of the copper nanoparticles in the supernatant was 10% by mass. Next, the supernatant liquid after this natural sedimentation was separated and discarded. Further, the precipitate containing the naturally precipitated copper nanoparticles was centrifuged into the concentrated copper nanoparticles containing the copper nanoparticles and the liquid phase at a centrifugal acceleration of 50,000 G using a centrifuge.
（銅ナノ粒子洗浄工程）
続いて、上記遠心分離された銅ナノ粒子濃縮液を日立工機株式会社製のロータ「Ｐ７０ＡＴ」を用い、５００００ｒｐｍの超遠心で１時間、最大遠心加速度７００００Ｇで、銅ナノ粒子濃縮液及び液相に超遠心分離した。さらに、超遠心分離後の銅ナノ粒子濃縮液を純水８０ｇで２回水洗し銅粉末を得た。(Copper nanoparticle cleaning process)
Subsequently, the centrifugally separated copper nanoparticle concentrate was used in a rotor "P70AT" manufactured by Hitachi Koki Co., Ltd., and the copper nanoparticle concentrate and liquid phase were subjected to ultracentrifugation at 50,000 rpm for 1 hour and a maximum centrifugal acceleration of 70,000 G. Ultracentrifuged. Further, the copper nanoparticle concentrate after ultracentrifugation was washed twice with 80 g of pure water to obtain a copper powder.
（銅ナノインクの製造）
上記銅ナノ粒子洗浄工程後の銅粉末に純水を加えた後、濃度を３０質量％に調整して銅ナノインクを製造した。(Manufacturing of copper nano ink)
After adding pure water to the copper powder after the copper nanoparticle washing step, the concentration was adjusted to 30% by mass to produce copper nanoinks.
［Ｎｏ．２〜Ｎｏ．２４］
上記自然沈降工程における自然沈降時間と、上記添加工程における凝集剤の種類及び添加量と、上記分離工程における自然沈降時間及び遠心加速度を表１の通りとした以外、Ｎｏ．１と同様の手順によって銅ナノインクを製造した。Ｎｏ．２〜Ｎｏ．２４における自然沈降粒子の平均粒子径及び粒子径分布、分離割合、並びに未回収率を表１に示す。[No. 2-No. 24]
No. 1 except that the natural sedimentation time in the natural sedimentation step, the type and amount of the flocculant in the addition step, and the natural sedimentation time and the centrifugal acceleration in the separation step are as shown in Table 1. Copper nanoink was produced by the same procedure as in 1. No. 2-No. Table 1 shows the average particle size and particle size distribution, separation ratio, and unrecovered rate of the naturally settled particles in No. 24.
［Ｎｏ．２５］
Ｎｏ．１と同様の調製工程を行い、自然沈降工程の自然沈降時間を２４時間とし、この自然沈降工程後の上澄み液回収工程によって上澄み液と分離された沈殿液について遠心分離を行い、この遠心分離後の銅ナノ粒子を洗浄して得られた銅粉末に純水を加え、濃度を３０質量％に調整して銅ナノインクを製造した。Ｎｏ．２５における自然沈降粒子の平均粒子径及び粒子径分布、並びに分離割合を表１に示す。[No. 25]
No. The same preparation step as in 1 was performed, the natural sedimentation time of the natural sedimentation step was set to 24 hours, and the precipitate liquid separated from the supernatant liquid by the supernatant liquid recovery step after this natural sedimentation step was centrifuged, and after this centrifugation. Pure water was added to the copper powder obtained by washing the copper nanoparticles of the above, and the concentration was adjusted to 30% by mass to produce copper nanoinks. No. Table 1 shows the average particle size and particle size distribution of the naturally settled particles in No. 25, and the separation ratio.
［Ｎｏ．２６〜Ｎｏ．２８］
Ｎｏ．１と同様の調製工程を行い、自然沈降工程の自然沈降時間を２４時間とし、この自然沈降工程後の上澄み液回収工程で分離回収された上澄み液の全量をＮｏ．１と同様の遠心分離機を用い、銅ナノ粒子を含む銅ナノ粒子濃縮液と液相とに表１の遠心加速度で遠心分離した。続いて、上記遠心分離された銅ナノ粒子濃縮液をＮｏ．１と同様に洗浄し、洗浄後の銅粉末に純水を加えた後、濃度を３０質量％に調整して銅ナノインクを製造した。Ｎｏ．２６〜Ｎｏ．２８における自然沈降粒子の平均粒子径及び粒子径分布、分離割合、並びに未回収率を表１に示す。[No. 26-No. 28]
No. The same preparation step as in No. 1 was performed, the natural sedimentation time of the natural sedimentation step was set to 24 hours, and the total amount of the supernatant liquid separated and recovered in the supernatant liquid recovery step after this natural sedimentation step was No. Using the same centrifuge as in No. 1, the copper nanoparticle concentrate containing copper nanoparticles and the liquid phase were centrifuged at the centrifugal acceleration shown in Table 1. Subsequently, the centrifuged copper nanoparticle concentrate was added to No. After washing in the same manner as in No. 1 and adding pure water to the washed copper powder, the concentration was adjusted to 30% by mass to produce copper nanoink. No. 26-No. Table 1 shows the average particle size and particle size distribution, separation ratio, and unrecovered rate of the naturally settled particles in No. 28.
［Ｎｏ．２９〜Ｎｏ．３９］
上記自然沈降工程における自然沈降時間と、上記添加工程における凝集剤の種類及び添加量と、上記分離工程における自然沈降時間とを表１の通りとした以外、Ｎｏ．１と同様の手順によって銅ナノインクを製造した。Ｎｏ．２９〜Ｎｏ．３９における自然沈降粒子の平均粒子径及び粒子径分布、分離割合、並びに未回収率を表１に示す。[No. 29-No. 39]
No. 1 except that the natural sedimentation time in the natural sedimentation step, the type and amount of the flocculant in the addition step, and the natural sedimentation time in the separation step are as shown in Table 1. Copper nanoink was produced by the same procedure as in 1. No. 29-No. Table 1 shows the average particle size and particle size distribution, separation ratio, and unrecovered rate of the naturally precipitated particles in 39.
＜銅ナノ粒子の回収率＞
上澄み液回収工程で回収した上澄み液に含まれる銅ナノ粒子の全量に対するこの上澄み液を用いて得られた銅ナノインクに含まれる銅ナノ粒子の回収率を表２に示す。なお、Ｎｏ．２５では上澄み液回収工程で分離回収された上澄み液は廃棄しているため、調製工程によって得られた銅ナノ粒子の全量に対する沈殿液を遠心分離することで得られた銅ナノインクに含まれる銅ナノ粒子の割合を回収率とした。<Recovery rate of copper nanoparticles>
Table 2 shows the recovery rate of copper nanoparticles contained in the copper nanoparticles obtained by using this supernatant with respect to the total amount of copper nanoparticles contained in the supernatant recovered in the supernatant recovery step. In addition, No. In No. 25, since the supernatant liquid separated and recovered in the supernatant liquid recovery step is discarded, the copper nanoparticles contained in the copper nanoink obtained by centrifuging the precipitate liquid with respect to the total amount of the copper nanoparticles obtained in the preparation step. The proportion of particles was taken as the recovery rate.
＜銅ナノ粒子の品質＞
上記超遠心分離後の銅ナノ粒子濃縮液に純水を添加した状態で、銅ナノ粒子の品質を目視によって以下の基準で評価した。この評価結果を表２に示す。
Ａ：銅ナノ粒子の凝集物が視認されなかった。
Ｂ：銅ナノ粒子の凝集物が視認された。
Ｃ：銅ナノ粒子の変質が確認された。<Quality of copper nanoparticles>
With pure water added to the concentrated copper nanoparticles after ultracentrifugation, the quality of the copper nanoparticles was visually evaluated according to the following criteria. The evaluation results are shown in Table 2.
A: No agglomerates of copper nanoparticles were visible.
B: Aggregates of copper nanoparticles were visually recognized.
C: Deterioration of copper nanoparticles was confirmed.
＜不純物＞
Ｎｏ．１〜Ｎｏ．３９によって得られた銅ナノインクについて凝集剤に由来する不純物の有無をサーモフィッシャーサイエンティフィック社製のイオンクロマトグラフィーシステム「ＩＣＳ−２１００」及び同社のＩＣＰ発光分析装置「ｉＣＡＰ６３００」を用いて測定し、以下の基準で評価した。この評価結果を表２に示す。
Ａ：不純物が検出されなかった。
Ｂ：不純物が僅かに検出された。
Ｃ：不純物が大量に検出された。
なお、Ｎｏ．３４及びＮｏ．３８については、銅ナノ粒子が変質したため不純物の測定ができなかった。<Impurities>
No. 1-No. The presence or absence of impurities derived from the flocculant was measured for the copper nanoink obtained by 39 using the ion chromatography system "ICS-2100" manufactured by Thermo Fisher Scientific Co., Ltd. and the ICP emission spectrometer "iCAP6300" manufactured by Thermo Fisher Scientific Co., Ltd. It was evaluated according to the following criteria. The evaluation results are shown in Table 2.
A: No impurities were detected.
B: A small amount of impurities were detected.
C: A large amount of impurities were detected.
In addition, No. 34 and No. For 38, impurities could not be measured because the copper nanoparticles were altered.
＜平均粒子径＞
マイクロトラック・ベル社製の「ＮａｎｏＴｒａｃ Ｗａｖｅ」を用い、Ｎｏ．１〜Ｎｏ．３９によって得られた銅ナノインクに含まれる銅ナノ粒子の平均粒子径（Ｄ５０）を測定した。この測定結果を表２に示す。なお、Ｎｏ．３４及びＮｏ．３８については、銅ナノ粒子が変質したため銅ナノ粒子の平均粒子径の測定ができなかった。<Average particle size>
Using "NanoTrac Wave" manufactured by Microtrack Bell, No. 1-No. The average particle size (D50) of the copper nanoparticles contained in the copper nanoinks obtained by 39 was measured. The measurement results are shown in Table 2. In addition, No. 34 and No. For 38, the average particle size of the copper nanoparticles could not be measured because the copper nanoparticles were altered.
＜粒子径分布＞
マイクロトラック・ベル社製の「ＮａｎｏＴｒａｃ Ｗａｖｅ」を用い、Ｎｏ．１〜Ｎｏ．３９によって得られた銅ナノインクに含まれる銅ナノ粒子の粒子径分布を測定した。
この測定結果を表２に示す。なお、Ｎｏ．３４及びＮｏ．３８については、銅ナノ粒子が変質したため銅ナノ粒子の粒子径分布の測定ができなかった。<Particle size distribution>
Using "NanoTrac Wave" manufactured by Microtrack Bell, No. 1-No. The particle size distribution of the copper nanoparticles contained in the copper nanoinks obtained by 39 was measured.
The measurement results are shown in Table 2. In addition, No. 34 and No. For 38, the particle size distribution of the copper nanoparticles could not be measured because the copper nanoparticles were altered.
［評価結果］
表１及び表２から分かるように、Ｎｏ．１、Ｎｏ．５〜Ｎｏ．１０、Ｎｏ．１３、Ｎｏ．１４、Ｎｏ．１６〜Ｎｏ．１８、Ｎｏ．２０、Ｎｏ．２１については、凝集剤がクエン酸塩であり、凝集剤の添加量が４質量％以上であり、分離工程における自然沈降時間が３時間超であることから、銅ナノ粒子の回収率が９０％以上となっている。中でも、凝集剤の添加量が１０．０質量％未満であるＮｏ．１、Ｎｏ．５、Ｎｏ．６、Ｎｏ．８〜Ｎｏ．１０、Ｎｏ．１３、Ｎｏ．１４、Ｎｏ．１６〜Ｎｏ．１８、Ｎｏ．２０、Ｎｏ．２１については、銅ナノインク中に不純物が検出されておらず、コンタミネーションが防止されている。このうち、Ｎｏ．８については、部分的に凝集物が発生しているが、これは自然沈降工程における自然沈降時間が不十分であることで再分散性のない凝集物が発生したためと考えられる。なお、Ｎｏ．１５は、凝集剤がクエン酸塩であり、凝集剤の添加量が４質量％以上であり、分離工程における自然沈降時間が３時間超であるが、遠心分離加速度が不十分であるため、粒子径の小さい銅ナノ粒子を十分に回収することができず、回収率が９０％未満となっている。[Evaluation results]
As can be seen from Tables 1 and 2, No. 1, No. 5-No. 10, No. 13, No. 14, No. 16-No. 18, No. 20, No. Regarding 21, the coagulant is citrate, the amount of the coagulant added is 4% by mass or more, and the natural sedimentation time in the separation step is more than 3 hours, so that the recovery rate of copper nanoparticles is 90%. That is all. Among them, No. 1 in which the amount of the flocculant added was less than 10.0% by mass. 1, No. 5, No. 6, No. 8 to No. 10, No. 13, No. 14, No. 16-No. 18, No. 20, No. With respect to 21, no impurities were detected in the copper nanoink, and contamination was prevented. Of these, No. Regarding No. 8, agglomerates were partially generated, which is considered to be due to insufficient natural settling time in the natural settling step, which caused non-redispersible agglomerates. In addition, No. In No. 15, the flocculant is citrate, the amount of the flocculant added is 4% by mass or more, and the natural sedimentation time in the separation step is more than 3 hours, but the centrifugation acceleration is insufficient, so that the particles Copper nanoparticles with a small diameter could not be sufficiently recovered, and the recovery rate was less than 90%.
これに対し、Ｎｏ．２５に示すように、凝集剤添加工程を有さず、上澄み液回収工程で分離回収された上澄み液を廃棄する従来の方法を用いた場合、粒子径の小さい銅ナノ粒子を十分に回収し難いため、回収率が低くなると共に、銅ナノインクに含まれる銅ナノ粒子の平均粒子径が比較的大きくなっている。 On the other hand, No. As shown in FIG. 25, when a conventional method of discarding the supernatant liquid separated and recovered in the supernatant liquid recovery step without the coagulant addition step is used, it is difficult to sufficiently recover copper nanoparticles having a small particle size. Therefore, the recovery rate is low, and the average particle size of the copper nanoparticles contained in the copper nanoink is relatively large.
また、上澄み液回収工程で分離回収された上澄み液の全量について凝集剤を添加することなく遠心分離を行ったＮｏ．２６〜Ｎｏ．２８は、粒子径の小さい銅ナノ粒子を十分に遠心分離することが困難で回収率が低くなっている。なお、Ｎｏ．２７及びＮｏ．２８では、遠心分離加速度を大きくすることで比較的粒子径の小さい銅ナノ粒子も回収できているが、遠心分離処理時間が長くなり処理効率を十分に高めることができなかった。 In addition, the total amount of the supernatant liquid separated and recovered in the supernatant liquid recovery step was centrifuged without adding a coagulant. 26-No. In No. 28, it is difficult to sufficiently centrifuge copper nanoparticles having a small particle size, and the recovery rate is low. In addition, No. 27 and No. In No. 28, copper nanoparticles having a relatively small particle size could be recovered by increasing the centrifugation acceleration, but the centrifugation treatment time became long and the treatment efficiency could not be sufficiently improved.
Ｃ１ 第１銅ナノ粒子濃縮液
Ｃ２ 第２銅ナノ粒子濃縮液
Ｄ１ 第１液相
Ｄ２ 第２液相
Ｆ 凝集剤
Ｌ１ 第１上澄み液
Ｌ２ 第２上澄み液
Ｐ１ 第１沈殿液
Ｐ２ 第２沈殿液C1 1st copper nanoparticle concentrate C2 2nd copper nanoparticle concentrate D1 1st liquid phase D2 2nd liquid phase F flocculant L1 1st supernatant L2 2nd supernatant P1 1st precipitate P2 2nd precipitate
Claims (6)
上記調製工程後の銅ナノ粒子分散液に凝集剤を添加する添加工程と、
上記添加工程後の銅ナノ粒子分散液から液相を遠心分離する分離工程と
を備える銅ナノ粒子の製造方法であって、
上記銅ナノ粒子分散液に含まれる銅ナノ粒子を自然沈降させる自然沈降工程をさらに備える銅ナノ粒子の製造方法。A preparation step for preparing a copper nanoparticle dispersion having an average particle diameter of 50 nm or less by a liquid phase reduction method, and
An addition step of adding a flocculant to the copper nanoparticle dispersion liquid after the above preparation step, and
A method for producing copper nanoparticles, which comprises a separation step of centrifuging the liquid phase from the copper nanoparticle dispersion liquid after the addition step.
A method for producing copper nanoparticles further comprising a natural sedimentation step of spontaneously precipitating copper nanoparticles contained in the copper nanoparticles dispersion liquid.
上記上澄み液回収工程後に、上記添加工程で上記上澄み液に上記凝集剤を添加する請求項２に記載の銅ナノ粒子の製造方法。After the natural sedimentation step, a supernatant recovery step for recovering the supernatant of the copper nanoparticle dispersion is further provided.
The method for producing copper nanoparticles according to claim 2, wherein the flocculant is added to the supernatant in the addition step after the supernatant recovery step.
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