JP2004353017A

JP2004353017A - Particulate-dispersing agent, particulate-dispersing method, and method for electroless plating particulate

Info

Publication number: JP2004353017A
Application number: JP2003150336A
Authority: JP
Inventors: Masao Terajima; 正雄寺島; Akira Toda; 顕戸田; Atsushi Iizuka; 淳飯塚; Naoto Hashimoto; 直人橋本
Original assignee: Meltex Inc
Current assignee: Meltex Inc
Priority date: 2003-05-28
Filing date: 2003-05-28
Publication date: 2004-12-16
Anticipated expiration: 2023-05-28
Also published as: JP3984189B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a particulate-dispersing agent capable of dispersing water-insoluble particulates in an aqueous solution; a particulate-dispersing method; and an electroless plating method for forming a plating film on the water-insoluble particulates. <P>SOLUTION: The particulate-dispersing agent for dispersing the water-insoluble particulates into the aqueous solution includes at least a glycine-based ampholytic surfactant and a benzylammonium-chloride cationic surfactant so as to control the content ratio of alkyl di(aminoethyl)glycine of the ampholytic surfactant to dimethylbenzyl alkylammonium chlorides of the cationic surfactant into a range of 3 : 5,000 to 500 : 1. The particulate-dispersing method includes adding the particulate-dispersing agent into the aqueous solution so that the concentration of alkyl di(aminoethyl)glycine of the ampholytic surfactant can be in the ranges of 0.015 to 1.5 g/L and the concentration of dimethylbenzyl alkylammonium chlorides of the cationic surfactant can be in the range of 0.003 to 2.5 g/L. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、微粒子、特に水に不溶の微粒子を水溶液に分散させるための微粒子分散剤と、このような微粒子を水溶液に分散させる微粒子分散方法、および、上記の微粒子に良好な無電解めっきを行うための無電解めっき方法に関する。
【０００２】
【従来の技術】
【特許文献１】特開２００２−８８４９７号公報
【特許文献２】特開平９−１８４０７７号公報
従来から有機質、無機質、あるいは、有機無機複合体からなる微粒子であって、水に不溶の微粒子は、一般成形品用の無電解めっき浴における分散性が悪く、表面に均一な表面処理を行うことが困難で、無めっき、不均一な析出皮膜、凝集等が生じるという問題があった。
これらを改善するために、水に不溶の微粒子を表面処理液や無電解めっき浴に分散する方法として、オリフィス収縮流、回転せん断流や超音波を用いた物理的分散方法が用いられている（特許文献１）。また、界面活性剤を使用した分散方法も提案されている（特許文献２）。
【０００３】
【発明が解決しようとする課題】
しかしながら、上述のような物理的分散方法では、分散対象となる微粒子の材質や大きさ等により、使用する装置の改良や分散条件の変更等を必要とし、工程が煩雑であったり、装置コストの増大を来たすという問題があった。また、界面活性剤を使用した従来の分散方法では、十分な分散効果が得られず、特に粒径が１μｍ以下の微粒子の分散が不十分であるという問題があった。
本発明は、上述のような実情に鑑みてなされたものであり、水に不溶の微粒子を水溶液に分散させることができる微粒子分散剤と微粒子分散方法、および、水に不溶の微粒子に良好な無電解めっきを行うための無電解めっき方法を提供することを目的とする。
【０００４】
【課題を解決するための手段】
このような目的を達成するために、本発明は、水に不溶の微粒子を水溶液に分散させるための微粒子分散剤において、少なくともグリシン系の両性界面活性剤とベンジルアンモニウム・クロライド系のカチオン界面活性剤とを含有し、両性界面活性剤のアルキルジ（アミノエチル）グリシンとカチオン界面活性剤のジメチルベンジルアルキルアンモニウムクロライドとの含有比率が、３：５０００〜５００：１の範囲内であるような構成とした。
【０００５】
本発明は、水に不溶の微粒子を水溶液に分散させる微粒子分散方法において、微粒子を分散させるための水溶液に、上記の本発明の微粒子分散剤を、両性界面活性剤のアルキルジ（アミノエチル）グリシンの濃度が０．００１５〜１．５ｇ／Ｌの範囲となり、かつ、カチオン界面活性剤のジメチルベンジルアルキルアンモニウムクロライドの濃度が０．００３〜２．５ｇ／Ｌの範囲となるように添加するような構成とした。
【０００６】
本発明は、水に不溶の微粒子を水溶液に分散させる微粒子分散方法において、微粒子を分散させるための水溶液に、両性界面活性剤のアルキルジ（アミノエチル）グリシンの濃度が０．００１５〜１．５ｇ／Ｌの範囲となり、かつ、カチオン界面活性剤のジメチルベンジルアルキルアンモニウムクロライドの濃度が０．００３〜２．５ｇ／Ｌの範囲となるようにグリシン系の両性界面活性剤とベンジルアンモニウム・クロライド系のカチオン界面活性剤とを少なくとも含有させるような構成とした。
【０００７】
本発明は、水に不溶の微粒子に表面処理を施した後、無電解めっきにより微粒子表面に皮膜を形成する無電解めっき方法において、微粒子の表面処理液、および、無電解めっき浴に、上記の本発明の微粒子分散剤を、両性界面活性剤のアルキルジ（アミノエチル）グリシンの濃度が０．００１５〜１．５ｇ／Ｌの範囲となり、かつ、カチオン界面活性剤のジメチルベンジルアルキルアンモニウムクロライドの濃度が０．００３〜２．５ｇ／Ｌの範囲となるように添加するような構成とした。
【０００８】
本発明は、水に不溶の微粒子に表面処理を施した後、無電解めっきにより微粒子表面に皮膜を形成する無電解めっき方法において、微粒子の表面処理液、および、無電解めっき浴に、両性界面活性剤のアルキルジ（アミノエチル）グリシンの濃度が０．００１５〜１．５ｇ／Ｌの範囲となり、かつ、カチオン界面活性剤のジメチルベンジルアルキルアンモニウムクロライドの濃度が０．００３〜２．５ｇ／Ｌの範囲となるようにグリシン系の両性界面活性剤とベンジルアンモニウム・クロライド系のカチオン界面活性剤とを少なくとも含有させるような構成とした。
【０００９】
【発明の実施の形態】
次に、本発明の最適な実施形態について説明する。
（微粒子分散剤）
本発明の微粒子分散剤は、少なくともグリシン系の両性界面活性剤とベンジルアンモニウム・クロライド系のカチオン界面活性剤とを含有するものであり、上記の両性界面活性剤とカチオン界面活性剤は、両性界面活性剤のアルキルジ（アミノエチル）グリシンとカチオン界面活性剤のジメチルベンジルアルキルアンモニウムクロライドとの含有比率が、３：５０００〜５００：１の範囲、好ましくは３：５００〜５０：１の範囲内となるように含有される。両性界面活性剤とカチオン界面活性剤の含有比率が上記の範囲から外れると、微粒子の攪拌分散性が不十分であったり、十分な分散状態が保持できないことになり好ましくない。
【００１０】
本発明の微粒子分散剤に含有されるグリシン系の両性界面活性剤としては、例えば、下記の一般式（１）で表されるものが好ましい。
【化１】

具体的には、アルキルジ（アミノエチル）グリシン、ナトリウムアルキルジ（アミノエチル）グリシン、塩酸アルキルジ（アミノエチル）グリシン、塩酸アルキルポリアミノエチレングリシン等を挙げることができる。
【００１１】
また、本発明の微粒子分散剤に含有されるベンジルアンモニウム・クロライド系のカチオン界面活性剤としては、例えば、下記の一般式（２）で表されるものが好ましい。
【化２】

具体的には、ジメチルベンジルアルキルアンモニウムクロライド、テトラデシルジメチルベンジルアルキルアンモニウムクロライド、オクタデシルジメチルベンジルアルキルアンモニウムクロライド等を挙げることができる。
【００１２】
上述のような本発明の微粒子分散剤は、水に不溶の微粒子を水溶液に分散させるものであり、対象となる微粒子に特に制限はなく、例えば、アクリル樹脂、スチレン樹脂、エポキシ樹脂、ポリイミド樹脂、フェノール樹脂、ポリエステル樹脂等の樹脂微粒子、活性炭、カーボンファイバー、カーボンナノチューブ、フラーレン、ダイヤモンド等の炭素原子からなる微粒子、金属微粒子、金属酸化物微粒子、金属窒化物微粒子、ケイ素系の化合物からなるセラミックス微粒子、半導体チップのような有機無機複合微粒子を挙げることができ、微粒子の平均粒径は１ｎｍ〜５ｍｍの範囲である。
尚、水に不溶の微粒子を分散させる水溶液とは、水を含む任意の水溶液であり、分散対象である微粒子に応じて適宜決まるものであり、特に制限はない。
【００１３】
（微粒子分散方法）
本発明の微粒子分散方法は、水に不溶の微粒子を水溶液に分散させる方法であり、上述の本発明の微粒子分散剤を、両性界面活性剤のアルキルジ（アミノエチル）グリシンの濃度が０．００１５〜１．５ｇ／Ｌの範囲となり、かつ、カチオン界面活性剤のジメチルベンジルアルキルアンモニウムクロライドの濃度が０．００３〜２．５ｇ／Ｌの範囲となるように、微粒子を分散させる水溶液に添加するものである。
【００１４】
また、本発明の微粒子分散方法は、水に不溶の微粒子を水溶液に分散させる方法であり、両性界面活性剤のアルキルジ（アミノエチル）グリシンの濃度が０．００１５〜１．５ｇ／Ｌの範囲となり、かつ、カチオン界面活性剤のジメチルベンジルアルキルアンモニウムクロライドの濃度が０．００３〜２．５ｇ／Ｌの範囲となるように、少なくともグリシン系の両性界面活性剤とベンジルアンモニウム・クロライド系のカチオン界面活性剤とを、微粒子を分散させる水溶液に含有させるものである。
【００１５】
本発明の微粒子分散方法では、微粒子を分散させるための水溶液に含有させる両性界面活性剤とカチオン界面活性剤の各濃度が上記の範囲から外れると、微粒子の攪拌分散性が不十分であったり、十分な分散状態が保持できないことになり好ましくない。水溶液に両性界面活性剤とカチオン界面活性剤を含有させる工程は、水溶液に微粒子を投入する工程の前後いずれであってもよい。また、微粒子の分散時に機械的攪拌、あるいは、超音波分散等を併用してもよい。
本発明の微粒子分散方法において、本発明の微粒子分散剤を使用せず、個別にグリシン系の両性界面活性剤とベンジルアンモニウム・クロライド系のカチオン界面活性剤とを水溶液に含有させる場合も、使用する両性界面活性剤、カチオン界面活性剤は、上述の本発明の微粒子分散剤に使用するものとして例示したものが好ましい。
【００１６】
本発明の微粒子分散方法において分散対象となる微粒子は、水に不溶で水溶液に分散させることが困難な微粒子であれば特に制限はなく、例えば、上述の本発明の微粒子分散剤の説明で挙げたような微粒子であり、その平均粒径は１ｎｍ〜５ｍｍの範囲である。
尚、水に不溶の微粒子を分散させる水溶液とは、水を含む任意の水溶液であり、分散対象である微粒子に応じて適宜決まるものであり、特に制限はない。
【００１７】
（微粒子への無電解めっき法）
本発明の微粒子への無電解めっき法は、両性界面活性剤のアルキルジ（アミノエチル）グリシンの濃度が０．００１５〜１．５ｇ／Ｌの範囲となり、かつ、カチオン界面活性剤のジメチルベンジルアルキルアンモニウムクロライドの濃度が０．００３〜２．５ｇ／Ｌの範囲となるように上述の本発明の微粒子分散剤を添加した表面処理液、および、無電解めっき浴を使用して、水に不溶の微粒子に表面処理を施した後、無電解めっきにより微粒子表面に皮膜を形成するものである。
【００１８】
また、本発明の微粒子への無電解めっき法は、両性界面活性剤のアルキルジ（アミノエチル）グリシンの濃度が０．００１５〜１．５ｇ／Ｌの範囲となり、かつ、カチオン界面活性剤のジメチルベンジルアルキルアンモニウムクロライドの濃度が０．００３〜２．５ｇ／Ｌの範囲となるように少なくともグリシン系の両性界面活性剤とベンジルアンモニウム・クロライド系のカチオン界面活性剤とを含有させた表面処理液、および、無電解めっき浴を使用して、水に不溶の微粒子に表面処理を施した後、無電解めっきにより微粒子表面に皮膜を形成するものである。
【００１９】
本発明における表面処理液とは、脱脂液、表面調整液、触媒付与液等である。また、本発明における無電解めっき浴とは、無電解ニッケルめっき浴、無電解銅めっき浴、、無電解錫めっき浴、無電解金めっき浴、無電解銀めっき浴、および、それらの置換型めっき浴等を挙げることができる。
【００２０】
本発明の無電解めっき方法において、表面処理液や無電解めっき浴に含有させる両性界面活性剤とカチオン界面活性剤の各濃度が上記の範囲から外れると、微粒子の攪拌分散性が不十分であったり、十分な分散状態が保持できないことになり好ましくない。尚、表面処理液や無電解めっき浴に両性界面活性剤とカチオン界面活性剤を含有させる工程は、これらの水溶液に微粒子を投入する工程の前後いずれであってもよい。また、微粒子の分散時に機械的攪拌、あるいは、超音波分散等を併用してもよい。
【００２１】
本発明の無電解めっき方法において、本発明の微粒子分散剤を使用せず、個別にグリシン系の両性界面活性剤とベンジルアンモニウム・クロライド系のカチオン界面活性剤とを表面処理液や無電解めっき浴に含有させる場合も、使用する両性界面活性剤、カチオン界面活性剤は、上述の本発明の微粒子分散剤に使用するものとして例示したものが好ましい。
本発明において無電解めっきにより皮膜を形成する対象となる微粒子は、水に不溶で、従来から無電解めっきによる皮膜形成が困難な微粒子であり、特に制限はなく、例えば、上述の本発明の微粒子分散剤の説明で挙げたような微粒子であり、その平均粒径は１ｎｍ〜５ｍｍの範囲である。
【００２２】
【実施例】
次に、実施例を示して本発明を更に詳細に説明する。
［実施例１］
グリシン系の両性界面活性剤として、日本油脂（株）製ニッサンアノンＬＧを準備し、また、ベンジルアンモニウム・クロライド系のカチオン界面活性剤として、日本油脂（株）製カチオンＦ２−５０Ｅを準備した。これらの界面活性剤を、両性界面活性剤のアルキルジ（アミノエチル）グリシンとカチオン界面活性剤のジメチルベンジルアルキルアンモニウムクロライドとの含有比率が、３：５となるように混合して、本発明の微粒子分散剤を得た。
【００２３】
次に、水に上記の微粒子分散剤を、両性界面活性剤のアルキルジ（アミノエチル）グリシンの濃度が０．１５ｇ／Ｌで、かつ、カチオン界面活性剤のジメチルベンジルアルキルアンモニウムクロライドの濃度が０．２５ｇ／Ｌとなるように添加して得た水溶液に、下記の表１に示される５種の微粒子を投入して分散状態を観察した。
比較として、同じ５種の微粒子を微粒子分散剤を添加していない水に投入して分散状態を観察した。
【００２４】
【表１】

表１に示されるように、本発明の微粒子分散剤を使用した微粒子分散方法では、５種の微粒子がいずれも均一に分散したことが確認された。
【００２５】
［実施例２］
グリシン系の両性界面活性剤として、日本油脂（株）製ニッサンアノンＬＧ（以下、本実施例では「ＬＧ」と記す）を準備し、また、ベンジルアンモニウム・クロライド系のカチオン界面活性剤として、日本油脂（株）製カチオンＦ２−５０Ｅ（以下、本実施例では「Ｆ２−５０Ｅ」と記す）を準備した。次いで、ＬＧのアルキルジ（アミノエチル）グリシンの濃度、および、Ｆ２−５０Ｅのジメチルベンジルアルキルアンモニウムクロライドの濃度が下記の表２に示される濃度となるように水に含有させて１８種の水溶液（試料１〜１８）を得た。これらの各水溶液（１０００ｍＬ）に平均粒径８μｍのアクリル樹脂微粒子（積水化学工業（株）製ＭＢＸ−８）を０．１ｇ投入して攪拌したときの分散性、および、攪拌後１時間静置した後の分散の保持性を下記の評価基準で評価して、結果を下記の表２に示した。
【００２６】
（分散性の評価基準）
◎：微粒子投入後攪拌により均一に分散する
○：微粒子投入後攪拌により均一に分散するが、液面に浮遊している微粒子が若干存在する
×：攪拌しても分散せず液面に微粒子が浮遊している
（保持性の評価基準）
◎：微粒子が均一に分散した状態が保持されている
○：微粒子の一部に沈降あるいは液面への浮遊が生じている
×：微粒子は沈降または液面への浮遊により完全に分離している
【００２７】
【表２】

【００２８】
表２に示されるように、ＬＧのアルキルジ（アミノエチル）グリシンの濃度が０．００１５〜１．５ｇ／Ｌの範囲内で、かつ、Ｆ２−５０Ｅのジメチルベンジルアルキルアンモニウムクロライドの濃度が０．００３〜２．５ｇ／Ｌの範囲内にある試料１〜１４は、アクリル樹脂微粒子の分散性および保持性が良好なことが確認された。
【００２９】
［実施例３］
無電解めっきにより皮膜を形成する対象となる微粒子として、平均粒径８μｍのアクリル樹脂微粒子（積水化学工業（株）製ＭＢＸ−８）を準備した。
また、グリシン系の両性界面活性剤として、日本油脂（株）製ニッサンアノンＬＧを準備し、また、ベンジルアンモニウム・クロライド系のカチオン界面活性剤として、日本油脂（株）製カチオンＦ２−５０Ｅを準備した。これらの界面活性剤を、ニッサンアノンＬＧのアルキルジ（アミノエチル）グリシン濃度とカチオンＦ２−５０Ｅのジメチルベンジルアルキルアンモニウムクロライド濃度が同等となるように混合して、本発明の微粒子分散剤を得た。
【００３０】
次に、市販のアルカリ脱脂液（メルテックス（株）製メルクリーナーＩＴＯ−１７０）に、上記の微粒子分散剤を、ニッサンアノンＬＧのアルキルジ（アミノエチル）グリシン濃度が０．５ｇ／Ｌで、かつ、カチオンＦ２−５０Ｅのジメチルベンジルアルキルアンモニウムクロライド濃度が０．５ｇ／Ｌとなるように添加した。このアルカリ脱脂液１０００ｍＬに上記のアクリル樹脂微粒子０．１ｇを投入し分散させて脱脂処理（３０分間）を施し、水洗した。
次いで、濃度４５ｇ／Ｌの水酸化カリウム水溶液に、上記の微粒子分散剤を、ニッサンアノンＬＧのアルキルジ（アミノエチル）グリシン濃度が０．５ｇ／Ｌで、かつ、カチオンＦ２−５０Ｅのジメチルベンジルアルキルアンモニウムクロライド濃度が０．５ｇ／Ｌとなるように添加して脱脂液を得た。この脱脂液１０００ｍＬに上記の脱脂処理後のアクリル樹脂微粒子０．１ｇを投入し分散させて再度脱脂処理（３０分間）を施し、水洗した。
【００３１】
次に、市販の表面調整剤（メルテックス（株）製メルプレートコンディショナー１１０１）に、上記の微粒子分散剤を、ニッサンアノンＬＧのアルキルジ（アミノエチル）グリシン濃度が０．５ｇ／Ｌで、かつ、カチオンＦ２−５０Ｅのジメチルベンジルアルキルアンモニウムクロライド濃度が０．５ｇ／Ｌとなるように添加した。この表面調整剤１０００ｍＬに、脱脂処理済みのアクリル樹脂微粒子０．１ｇを投入し分散させて表面調整処理（３０分間）を施し、水洗した。
次いで、市販のパラジウム触媒液（メルテックス（株）製メルプレートアクチベーター７３３１）に、上記の微粒子分散剤を、ニッサンアノンＬＧのアルキルジ（アミノエチル）グリシン濃度が０．５ｇ／Ｌで、かつ、カチオンＦ２−５０Ｅのジメチルベンジルアルキルアンモニウムクロライド濃度が０．５ｇ／Ｌとなるように添加した。このパラジウム触媒液１０００ｍＬに、上記の表面調整済みのアクリル樹脂微粒子０．１ｇを投入し分散させて触媒付与処理（３０分間）を施した。
【００３２】
その後、市販の自己触媒型の無電解ニッケルめっき液（メルテックス（株）製メルプレートＮｉ−８６７）に、上記の微粒子分散剤を、ニッサンアノンＬＧのアルキルジ（アミノエチル）グリシン濃度が０．５ｇ／Ｌで、かつ、カチオンＦ２−５０Ｅのジメチルベンジルアルキルアンモニウムクロライド濃度が０．５ｇ／Ｌとなるように添加して無電解ニッケルめっき浴とした。この無電解ニッケルめっき浴（４５℃）に、上記の触媒付与処理を施したアクリル樹脂微粒子０．１ｇを投入し分散させて無電解ニッケルめっきを行った。
【００３３】
上述のように無電解ニッケルめっきを施したアクリル樹脂微粒子の表面には、ニッケルめっき皮膜が均一に形成されていることが確認された。
また、上述の脱脂液（２種）、表面調整剤、パラジウム触媒液、および、無電解ニッケルめっき液に、本発明の微粒子分散剤を使用せず、グリシン系の両性界面活性剤である日本油脂（株）製ニッサンアノンＬＧと、ベンジルアンモニウム・クロライド系のカチオン界面活性剤である日本油脂（株）製カチオンＦ２−５０Ｅとを、ニッサンアノンＬＧのアルキルジ（アミノエチル）グリシン濃度が０．５ｇ／Ｌで、かつ、カチオンＦ２−５０Ｅのジメチルベンジルアルキルアンモニウムクロライド濃度が０．５ｇ／Ｌとなるように別個に含有させた場合も、アクリル樹脂微粒子の表面にニッケルめっき皮膜を均一に形成できることを確認した。
【００３４】
尚、上述の脱脂液（２種）、表面調整剤、パラジウム触媒液、および、無電解ニッケルめっき液のいずれも、本発明の微粒子分散剤を添加しない場合、アクリル樹脂微粒子は液面に浮遊した状態で、所望の処理を施すことができず、無めっき、不均一な析出皮膜、凝集等が生じた。
【００３５】
［比較例１］
グリシン系ではない両性界面活性剤として、日本油脂（株）製ＢＬ、日本油脂（株）製ＧＬＭ−ＲＢＬ、日本油脂（株）製ＢＤＦ−Ｒ、日本油脂（株）製ＢＦの４種を準備し、また、ベンジルアンモニウム・クロライド系ではないカチオン界面活性剤として、日本油脂（株）製ＳＡを準備した。そして、水に両性界面活性剤濃度が０．５ｇ／Ｌとなり、カチオン界面活性剤濃度が０．５ｇ／Ｌとなるように混合して、４種の水溶液を得た。この水溶液に平均粒径８μｍのアクリル樹脂微粒子（積水化学工業（株）製ＭＢＸ−８）を投入して分散状態を観察した。しかし、いずれもアクリル樹脂微粒子が水面に浮遊して、均一な分散は得られなかった。
【００３６】
［比較例２］
グリシン系ではない両性界面活性剤として、日本油脂（株）製ＢＬを準備し、また、ベンジルアンモニウム・クロライド系ではないカチオン界面活性剤として、日本油脂（株）製ＳＡ、日本油脂（株）製ＡＢの２種を準備した。そして、水に両性界面活性剤濃度が０．５ｇ／Ｌとなり、カチオン界面活性剤濃度が０．５ｇ／Ｌとなるように混合して、２種の水溶液を得た。この水溶液に平均粒径８μｍのアクリル樹脂微粒子（積水化学工業（株）製ＭＢＸ−８）を投入して分散状態を観察した。しかし、いずれもアクリル樹脂微粒子が水面に浮遊して、均一な分散は得られなかった。
【００３７】
【発明の効果】
以上詳述したように、本発明によれば微粒子分散剤が、両性界面活性剤のアルキルジ（アミノエチル）グリシンとカチオン界面活性剤のジメチルベンジルアルキルアンモニウムクロライドとが所定の比率となるようにグリシン系の両性界面活性剤とベンジルアンモニウム・クロライド系のカチオン界面活性剤とを少なくとも含有するので、この微粒子分散剤を所定の濃度で水溶液に添加することにより、あるいは、水溶液に、両性界面活性剤のアルキルジ（アミノエチル）グリシンとカチオン界面活性剤のジメチルベンジルアルキルアンモニウムクロライドとが所定の濃度となるように両性界面活性剤とカチオン界面活性剤とを少なくとも含有させることにより、水に不溶の微粒子を水溶液に分散させることができ、無電解めっき法に用いる表面処理液や無電解めっき浴においても同様に、水に不溶の微粒子を分散させることができ、このような微粒子の表面に均一なめっき皮膜を形成することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a fine particle dispersant for dispersing fine particles, particularly fine particles insoluble in water in an aqueous solution, a fine particle dispersion method for dispersing such fine particles in an aqueous solution, and performing good electroless plating on the fine particles. To an electroless plating method.
[0002]
[Prior art]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2002-88497 [Patent Document 2] Japanese Patent Application Laid-Open No. 9-184077 Conventionally, fine particles composed of an organic, inorganic, or organic-inorganic composite, and insoluble in water, Dispersibility in an electroless plating bath for general molded articles is poor, it is difficult to perform a uniform surface treatment on the surface, and there has been a problem that non-plating, non-uniform deposition film, aggregation and the like occur.
In order to improve these, as a method of dispersing water-insoluble fine particles in a surface treatment solution or an electroless plating bath, a physical dispersion method using an orifice contraction flow, a rotary shear flow, or ultrasonic waves is used ( Patent Document 1). Also, a dispersion method using a surfactant has been proposed (Patent Document 2).
[0003]
[Problems to be solved by the invention]
However, in the physical dispersion method as described above, depending on the material and size of the fine particles to be dispersed, it is necessary to improve an apparatus to be used or change dispersion conditions, and the like, and the process is complicated, and the cost of the apparatus is reduced. There was a problem of increasing. Further, the conventional dispersing method using a surfactant has a problem that a sufficient dispersing effect cannot be obtained, and in particular, dispersion of fine particles having a particle size of 1 μm or less is insufficient.
The present invention has been made in view of the above situation, and has a fine particle dispersing agent and a fine particle dispersing method capable of dispersing fine particles insoluble in water in an aqueous solution. An object of the present invention is to provide an electroless plating method for performing electrolytic plating.
[0004]
[Means for Solving the Problems]
In order to achieve such an object, the present invention provides a fine particle dispersant for dispersing water-insoluble fine particles in an aqueous solution, comprising at least a glycine-based amphoteric surfactant and a benzylammonium chloride-based cationic surfactant. And the content ratio of alkyl di (aminoethyl) glycine as the amphoteric surfactant and dimethylbenzylalkylammonium chloride as the cationic surfactant is in the range of 3: 5000 to 500: 1. .
[0005]
The present invention provides a fine particle dispersing method for dispersing fine particles insoluble in water in an aqueous solution, wherein the fine particle dispersant of the present invention is added to the aqueous solution for dispersing the fine particles by adding the amphoteric surfactant alkyldi (aminoethyl) glycine to the aqueous solution. A composition in which the concentration is in the range of 0.0015 to 1.5 g / L and the concentration of dimethylbenzylalkylammonium chloride as the cationic surfactant is added in the range of 0.003 to 2.5 g / L. And
[0006]
The present invention relates to a fine particle dispersion method for dispersing fine particles insoluble in water in an aqueous solution, wherein the aqueous solution for dispersing the fine particles has a concentration of the amphoteric surfactant alkyldi (aminoethyl) glycine of 0.0015 to 1.5 g / g. L and the concentration of the dimethylbenzylalkylammonium chloride as the cationic surfactant is in the range of 0.003 to 2.5 g / L, and the glycine amphoteric surfactant and the benzylammonium chloride cation are used. It was configured to contain at least a surfactant.
[0007]
The present invention provides an electroless plating method for forming a film on the surface of fine particles by electroless plating after subjecting the fine particles insoluble in water to surface treatment, wherein the surface treatment liquid for fine particles, and an electroless plating bath, In the fine particle dispersant of the present invention, the concentration of the amphoteric surfactant alkyldi (aminoethyl) glycine is in the range of 0.0015 to 1.5 g / L, and the concentration of the cationic surfactant dimethylbenzylalkylammonium chloride is It was configured to be added in the range of 0.003 to 2.5 g / L.
[0008]
The present invention relates to an electroless plating method for forming a film on the surface of fine particles by electroless plating after subjecting the fine particles insoluble in water to surface treatment, wherein the surface treatment liquid for fine particles, and an electroless plating bath, The concentration of the surfactant, alkyldi (aminoethyl) glycine, is in the range of 0.0015 to 1.5 g / L, and the concentration of the cationic surfactant, dimethylbenzylalkylammonium chloride, is 0.003 to 2.5 g / L. The configuration was such that at least a glycine-based amphoteric surfactant and a benzylammonium-chloride-based cationic surfactant were contained within the range.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an optimal embodiment of the present invention will be described.
(Fine particle dispersant)
The fine particle dispersant of the present invention contains at least a glycine-based amphoteric surfactant and a benzylammonium chloride-based cationic surfactant, and the amphoteric surfactant and the cationic surfactant described above are amphoteric surfactants. The content ratio of alkyldi (aminoethyl) glycine as the activator and dimethylbenzylalkylammonium chloride as the cationic surfactant is in the range of 3: 5000 to 500: 1, preferably in the range of 3: 500 to 50: 1. It is contained as follows. If the content ratio of the amphoteric surfactant and the cationic surfactant is out of the above range, the dispersibility of the fine particles under stirring is insufficient, or a sufficient dispersion state cannot be maintained, which is not preferable.
[0010]
As the glycine-based amphoteric surfactant contained in the fine particle dispersant of the present invention, for example, those represented by the following general formula (1) are preferable.
Embedded image

Specifically, alkyl di (aminoethyl) glycine, sodium alkyl di (aminoethyl) glycine, alkyl di (aminoethyl) glycine hydrochloride, alkyl polyaminoethylene glycine hydrochloride and the like can be mentioned.
[0011]
The benzylammonium chloride-based cationic surfactant contained in the fine particle dispersant of the present invention is preferably, for example, one represented by the following general formula (2).
Embedded image

Specific examples include dimethylbenzylalkylammonium chloride, tetradecyldimethylbenzylalkylammonium chloride, octadecyldimethylbenzylalkylammonium chloride and the like.
[0012]
The fine particle dispersant of the present invention as described above is for dispersing fine particles insoluble in water in an aqueous solution, and there is no particular limitation on the target fine particles, for example, an acrylic resin, a styrene resin, an epoxy resin, a polyimide resin, Fine resin particles such as phenolic resin and polyester resin, fine particles composed of carbon atoms such as activated carbon, carbon fiber, carbon nanotube, fullerene and diamond, fine metal particles, fine metal oxide particles, fine metal nitride particles, fine ceramic particles composed of silicon-based compounds And an organic-inorganic composite fine particle such as a semiconductor chip. The average particle diameter of the fine particle is in the range of 1 nm to 5 mm.
The aqueous solution in which fine particles insoluble in water are dispersed is any aqueous solution containing water, and is appropriately determined according to the fine particles to be dispersed, and is not particularly limited.
[0013]
(Particle dispersion method)
The fine particle dispersing method of the present invention is a method of dispersing fine particles insoluble in water in an aqueous solution. The fine particle dispersant of the present invention is prepared by dissolving the concentration of the amphoteric surfactant alkyldi (aminoethyl) glycine in the range of 0.0015 to 0.0015. It is added to an aqueous solution in which fine particles are dispersed such that the concentration of the surfactant is 1.5 g / L and the concentration of dimethylbenzylalkylammonium chloride as a cationic surfactant is in the range of 0.003 to 2.5 g / L. is there.
[0014]
The method of dispersing fine particles of the present invention is a method of dispersing fine particles insoluble in water in an aqueous solution, and the concentration of alkyldi (aminoethyl) glycine as an amphoteric surfactant is in the range of 0.0015 to 1.5 g / L. And at least a glycine-based amphoteric surfactant and a benzylammonium-chloride-based cationic surfactant such that the concentration of the dimethylbenzylalkylammonium chloride as the cationic surfactant is in the range of 0.003 to 2.5 g / L. The agent is contained in an aqueous solution in which fine particles are dispersed.
[0015]
In the fine particle dispersion method of the present invention, when the respective concentrations of the amphoteric surfactant and the cationic surfactant to be contained in the aqueous solution for dispersing the fine particles are out of the above ranges, the stirring and dispersibility of the fine particles is insufficient, It is not preferable because a sufficient dispersion state cannot be maintained. The step of incorporating the amphoteric surfactant and the cationic surfactant into the aqueous solution may be performed before or after the step of introducing the fine particles into the aqueous solution. Also, mechanical stirring or ultrasonic dispersion may be used in combination when dispersing the fine particles.
In the method for dispersing fine particles of the present invention, the fine particle dispersant of the present invention is not used, and a glycine-based amphoteric surfactant and a benzylammonium chloride-based cationic surfactant are separately contained in an aqueous solution. As the amphoteric surfactant and cationic surfactant, those exemplified as those used in the above-described fine particle dispersant of the present invention are preferable.
[0016]
The fine particles to be dispersed in the fine particle dispersion method of the present invention are not particularly limited as long as they are insoluble in water and difficult to disperse in an aqueous solution. For example, they are described in the description of the fine particle dispersant of the present invention described above. Such fine particles have an average particle diameter in the range of 1 nm to 5 mm.
The aqueous solution in which fine particles insoluble in water are dispersed is any aqueous solution containing water, and is appropriately determined according to the fine particles to be dispersed, and is not particularly limited.
[0017]
(Electroless plating method for fine particles)
In the electroless plating method for fine particles of the present invention, the concentration of the amphoteric surfactant alkyldi (aminoethyl) glycine is in the range of 0.0015 to 1.5 g / L, and the cationic surfactant dimethylbenzylalkylammonium is used. Fine particles insoluble in water using a surface treatment solution to which the fine particle dispersant of the present invention is added so that the chloride concentration is in the range of 0.003 to 2.5 g / L, and an electroless plating bath. After a surface treatment, a film is formed on the surface of the fine particles by electroless plating.
[0018]
In the electroless plating method for fine particles of the present invention, the concentration of the amphoteric surfactant alkyldi (aminoethyl) glycine is in the range of 0.0015 to 1.5 g / L, and the cationic surfactant dimethylbenzyl is used. A surface treatment solution containing at least a glycine-based amphoteric surfactant and a benzylammonium-chloride-based cationic surfactant such that the concentration of the alkylammonium chloride is in the range of 0.003 to 2.5 g / L; After subjecting fine particles insoluble in water to surface treatment using an electroless plating bath, a film is formed on the surfaces of the fine particles by electroless plating.
[0019]
The surface treatment liquid in the present invention is a degreasing liquid, a surface conditioning liquid, a catalyst application liquid, or the like. Further, the electroless plating bath in the present invention is an electroless nickel plating bath, an electroless copper plating bath, an electroless tin plating bath, an electroless gold plating bath, an electroless silver plating bath, and a substitution plating thereof. A bath and the like can be mentioned.
[0020]
In the electroless plating method of the present invention, when the respective concentrations of the amphoteric surfactant and the cationic surfactant to be contained in the surface treatment solution or the electroless plating bath are out of the above ranges, the stirring and dispersibility of the fine particles is insufficient. And it is not preferable because a sufficient dispersion state cannot be maintained. The step of adding the amphoteric surfactant and the cationic surfactant to the surface treatment liquid or the electroless plating bath may be before or after the step of adding the fine particles to the aqueous solution. Also, mechanical stirring or ultrasonic dispersion may be used in combination when dispersing the fine particles.
[0021]
In the electroless plating method of the present invention, without using the fine particle dispersant of the present invention, a glycine-based amphoteric surfactant and a benzylammonium chloride-based cationic surfactant are separately treated with a surface treatment solution or an electroless plating bath. Also, when used as the amphoteric surfactant and the cationic surfactant, those exemplified as those used in the fine particle dispersant of the present invention described above are preferable.
The fine particles for forming a film by electroless plating in the present invention are fine particles that are insoluble in water and difficult to form a film by electroless plating conventionally, and are not particularly limited. For example, the fine particles of the present invention described above. Fine particles as described in the description of the dispersant, and the average particle diameter is in the range of 1 nm to 5 mm.
[0022]
【Example】
Next, the present invention will be described in more detail with reference to examples.
[Example 1]
Nissan Anon LG manufactured by NOF Corporation was prepared as a glycine-based amphoteric surfactant, and Cation F2-50E manufactured by NOF Corporation was prepared as a benzylammonium chloride-based cationic surfactant. These surfactants are mixed so that the content ratio of the amphoteric surfactant alkyldi (aminoethyl) glycine to the cationic surfactant dimethylbenzylalkylammonium chloride is 3: 5, and the fine particles of the present invention are mixed. A dispersant was obtained.
[0023]
Next, the above-mentioned fine particle dispersant was added to water, the concentration of the amphoteric surfactant alkyldi (aminoethyl) glycine was 0.15 g / L, and the concentration of the cationic surfactant dimethylbenzylalkylammonium chloride was 0.1%. Five kinds of fine particles shown in the following Table 1 were charged into an aqueous solution obtained by adding the solution so as to have a concentration of 25 g / L, and a dispersion state was observed.
For comparison, the same five kinds of fine particles were put into water to which no fine particle dispersant was added, and the dispersion state was observed.
[0024]
[Table 1]

As shown in Table 1, it was confirmed that all of the five types of fine particles were uniformly dispersed in the fine particle dispersion method using the fine particle dispersant of the present invention.
[0025]
[Example 2]
As a glycine-based amphoteric surfactant, Nissan Anone LG (hereinafter, referred to as "LG" in this example) manufactured by NOF Corporation was prepared, and as a benzylammonium chloride-based cationic surfactant, A cation F2-50E (hereinafter, referred to as “F2-50E” in the present example) manufactured by Yushi Co., Ltd. was prepared. Then, the mixture was added to water so that the concentration of alkyldi (aminoethyl) glycine of LG and the concentration of dimethylbenzylalkylammonium chloride of F2-50E were as shown in Table 2 below, and 18 kinds of aqueous solution (sample 1-18) were obtained. Dispersibility when 0.1 g of acrylic resin fine particles (MBX-8 manufactured by Sekisui Chemical Co., Ltd.) having an average particle size of 8 μm was added to each of these aqueous solutions (1000 mL) and stirred, and allowed to stand for 1 hour after stirring The retention of the dispersion after the evaluation was evaluated according to the following evaluation criteria, and the results are shown in Table 2 below.
[0026]
(Dispersibility evaluation criteria)
◎: Uniformly dispersed by stirring after introduction of fine particles ○: Uniformly dispersed by stirring after introduction of fine particles, but some fine particles floating on the liquid surface were present X: Fine particles were not dispersed even by stirring and remained on the liquid surface Floating (evaluation criteria for retention)
◎: The state in which the fine particles are uniformly dispersed is maintained. ：: Part of the fine particles settles or floats on the liquid surface. X: The fine particles are completely separated by settling or floating on the liquid surface. [0027]
[Table 2]

[0028]
As shown in Table 2, the concentration of alkyldi (aminoethyl) glycine in LG was in the range of 0.0015 to 1.5 g / L, and the concentration of dimethylbenzylalkylammonium chloride in F2-50E was 0.003. It was confirmed that Samples 1 to 14 in the range of ２．５2.5 g / L had good dispersibility and retention of acrylic resin fine particles.
[0029]
[Example 3]
Acrylic resin microparticles (MBX-8, manufactured by Sekisui Chemical Co., Ltd.) having an average particle size of 8 μm were prepared as microparticles for forming a film by electroless plating.
Also, Nissan Anone LG manufactured by NOF Corporation is prepared as a glycine-based amphoteric surfactant, and Cation F2-50E manufactured by NOF Corporation is prepared as a benzylammonium chloride-based cationic surfactant. did. These surfactants were mixed so that the concentration of alkyldi (aminoethyl) glycine of Nissan Anone LG and the concentration of dimethylbenzylalkylammonium chloride of cation F2-50E became equal to obtain the fine particle dispersant of the present invention.
[0030]
Next, the above-mentioned fine particle dispersant was added to a commercially available alkaline degreasing solution (Mertex Co., Ltd., Mercleaner ITO-170) by adding Nissan Anone LG having an alkyldi (aminoethyl) glycine concentration of 0.5 g / L, and And cation F2-50E so that the concentration of dimethylbenzylalkylammonium chloride becomes 0.5 g / L. 0.1 g of the above acrylic resin fine particles were added to 1000 mL of the alkaline degreasing solution, dispersed, subjected to a degreasing treatment (30 minutes), and washed with water.
Next, the above-mentioned fine particle dispersant was added to an aqueous solution of potassium hydroxide having a concentration of 45 g / L, and the alkyldi (aminoethyl) glycine concentration of Nissan Anone LG was 0.5 g / L, and the dimethylbenzylalkyl ammonium of cation F2-50E was added. It was added so that the chloride concentration was 0.5 g / L to obtain a degreasing solution. To 1000 mL of the degreasing solution, 0.1 g of the acrylic resin fine particles after the above degreasing treatment was added and dispersed, subjected to degreasing treatment again (30 minutes), and washed with water.
[0031]
Next, the above-mentioned fine particle dispersant was added to a commercially available surface conditioner (Meltex Conditioner 1101 manufactured by Meltex Co., Ltd.), and the alkyldi (aminoethyl) glycine concentration of Nissan Anone LG was 0.5 g / L, and The cation F2-50E was added such that the dimethylbenzylalkylammonium chloride concentration of the cation F2-50E became 0.5 g / L. To 1000 mL of this surface conditioner, 0.1 g of degreased acrylic resin particles were added and dispersed, subjected to a surface condition treatment (30 minutes), and washed with water.
Then, the above-mentioned fine particle dispersant was added to a commercially available palladium catalyst solution (Meltex Co., Ltd., Melplate Activator 7331) at a concentration of 0.5 g / L for alkyldi (aminoethyl) glycine of Nissan Anone LG, and The cation F2-50E was added such that the dimethylbenzylalkylammonium chloride concentration of the cation F2-50E became 0.5 g / L. To 1000 mL of this palladium catalyst solution, 0.1 g of the above-mentioned surface-adjusted acrylic resin fine particles were charged and dispersed, and subjected to a catalyst application treatment (30 minutes).
[0032]
Thereafter, the above-mentioned fine particle dispersant was added to a commercially available autocatalytic electroless nickel plating solution (Melplate Ni-867 manufactured by Meltex Co., Ltd.), and the concentration of alkyldi (aminoethyl) glycine of Nissan Anone LG was 0.5 g. / L and the concentration of dimethylbenzylalkylammonium chloride of the cation F2-50E was adjusted to 0.5 g / L to obtain an electroless nickel plating bath. Into this electroless nickel plating bath (45 ° C.), 0.1 g of the acrylic resin fine particles subjected to the above-mentioned catalyst treatment was added and dispersed to perform electroless nickel plating.
[0033]
As described above, it was confirmed that a nickel plating film was uniformly formed on the surface of the acrylic resin fine particles subjected to the electroless nickel plating.
In addition, the above-described degreasing solution (two types), a surface conditioner, a palladium catalyst solution, and an electroless nickel plating solution do not use the fine particle dispersant of the present invention. Nissan Anone LG manufactured by Nissan Anone LG Co., Ltd. and a cation F2-50E manufactured by NOF Corporation, a benzylammonium chloride-based cationic surfactant, having a concentration of alkyl di (aminoethyl) glycine of 0.5 g / It was confirmed that a nickel plating film could be uniformly formed on the surface of the acrylic resin fine particles even when the cation F2-50E was separately contained so as to have a dimethylbenzylalkylammonium chloride concentration of 0.5 g / L. did.
[0034]
When none of the above-described degreasing solution (two types), the surface conditioner, the palladium catalyst solution, and the electroless nickel plating solution were added with the fine particle dispersant of the present invention, the acrylic resin fine particles floated on the liquid surface. In this state, the desired treatment could not be performed, and non-plating, non-uniform deposition film, aggregation and the like occurred.
[0035]
[Comparative Example 1]
Four types of amphoteric surfactants that are not glycine-based are prepared: BL manufactured by NOF Corporation, GLM-RBL manufactured by NOF Corporation, BDF-R manufactured by NOF Corporation, and BF manufactured by NOF Corporation. In addition, SA manufactured by NOF Corporation was prepared as a cationic surfactant not based on benzylammonium chloride. Then, water was mixed with the amphoteric surfactant at a concentration of 0.5 g / L and the cationic surfactant at a concentration of 0.5 g / L to obtain four kinds of aqueous solutions. Acrylic resin fine particles (MBX-8, manufactured by Sekisui Chemical Co., Ltd.) having an average particle size of 8 μm were added to this aqueous solution, and the dispersion state was observed. However, in each case, the acrylic resin particles floated on the water surface, and uniform dispersion was not obtained.
[0036]
[Comparative Example 2]
As a non-glycine-based amphoteric surfactant, BL manufactured by NOF Corporation is prepared, and as a non-benzylammonium chloride-based surfactant, SA manufactured by NOF Corporation, manufactured by NOF Corporation Two types of AB were prepared. Then, water was mixed so that the amphoteric surfactant concentration became 0.5 g / L and the cationic surfactant concentration became 0.5 g / L to obtain two kinds of aqueous solutions. Acrylic resin fine particles (MBX-8, manufactured by Sekisui Chemical Co., Ltd.) having an average particle size of 8 μm were added to this aqueous solution, and the dispersion state was observed. However, in each case, the acrylic resin particles floated on the water surface, and uniform dispersion was not obtained.
[0037]
【The invention's effect】
As described in detail above, according to the present invention, the fine particle dispersant is a glycine-based dispersant such that the amphoteric surfactant alkyldi (aminoethyl) glycine and the cationic surfactant dimethylbenzylalkylammonium chloride have a predetermined ratio. At least contains an amphoteric surfactant of benzylammonium chloride and a cationic surfactant of benzyl ammonium chloride type. By containing at least an amphoteric surfactant and a cationic surfactant so that (aminoethyl) glycine and a cationic surfactant, dimethylbenzylalkylammonium chloride, have a predetermined concentration, water-insoluble fine particles are converted into an aqueous solution. Can be dispersed and used for electroless plating Similarly in terms treatment liquid and the electroless plating bath, water can be dispersed fine particles of insoluble, it is possible to form a uniform plated film on the surface of such particles.

Claims

In a fine particle dispersant for dispersing fine particles insoluble in water in an aqueous solution,
It contains at least a glycine-based amphoteric surfactant and a benzylammonium chloride-based cationic surfactant, and the content ratio of the amphoteric surfactant alkyldi (aminoethyl) glycine to the cationic surfactant dimethylbenzylalkylammonium chloride Is in the range of 3: 5000 to 500: 1.

In a fine particle dispersion method of dispersing fine particles insoluble in water in an aqueous solution,
The fine particle dispersant according to claim 1 is added to an aqueous solution for dispersing the fine particles, and the concentration of the amphoteric surfactant alkyldi (aminoethyl) glycine is in the range of 0.0015 to 1.5 g / L, and the cation is cationic. A method for dispersing fine particles, wherein the surfactant is added so that the concentration of dimethylbenzylalkylammonium chloride is in the range of 0.003 to 2.5 g / L.

In a fine particle dispersion method of dispersing fine particles insoluble in water in an aqueous solution,
In the aqueous solution for dispersing the fine particles, the concentration of the amphoteric surfactant alkyldi (aminoethyl) glycine is in the range of 0.0015 to 1.5 g / L, and the concentration of the cationic surfactant dimethylbenzylalkylammonium chloride. A fine particle dispersion method characterized by containing at least a glycine-based amphoteric surfactant and a benzylammonium chloride-based cationic surfactant so that the content thereof is in the range of 0.003 to 2.5 g / L.

After subjecting the water-insoluble fine particles to a surface treatment, an electroless plating method of forming a film on the fine particle surface by electroless plating,
The fine particle dispersant according to claim 1 is added to the surface treatment solution for fine particles and the electroless plating bath, and the concentration of the amphoteric surfactant alkyldi (aminoethyl) glycine is in the range of 0.0015 to 1.5 g / L. And adding the dimethylbenzylalkylammonium chloride as a cationic surfactant in a concentration of 0.003 to 2.5 g / L.

After subjecting the water-insoluble fine particles to a surface treatment, an electroless plating method of forming a film on the fine particle surface by electroless plating,
The concentration of the amphoteric surfactant, alkyldi (aminoethyl) glycine, is in the range of 0.0015 to 1.5 g / L, and the cationic surfactant, dimethylbenzyl, is added to the fine particle surface treatment solution and the electroless plating bath. A glycine-based amphoteric surfactant and a benzylammonium-chloride-based cationic surfactant are contained at least so that the concentration of alkyl ammonium chloride is in the range of 0.003 to 2.5 g / L. Electroplating method.