JP2004285215A - Colored fine particle dispersion and water-based ink containing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preparing a colored fine particle dispersion capable of giving inkjet printing ink by using a water-soluble colored fine particle dispersion, free of particle coagulation due to solvent shock and excellent in stability with the elapse of time. <P>SOLUTION: In this method for preparing a colored fine particle dispersion, a coloring material and a resin are dissolved into a water-insoluble organic solvent, and the solution is emulsified by using an emulsifier into a mixture of water and a water-soluble organic solvent and then the water-insoluble organic solvent is removed. The colored fine particle dispersion is free of particle coagulation due to solvent shock in the inkjet printing ink preparing process, and this enables the formation of inkjet printing ink high in stability. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４９】
ここで、Ｒ′はイソシアネート基が結合するポリマーの残基を表し、Ｒ″は同じくアミン残基を表す（以下同様である）。
【００５０】
また、アミン類のなかでも、イソシアネート基との反応点を二つ以上有するジアミン類（例えば、ヘキサメチレンジアミン、ジエチレントリアミン等）、更にヒドロキシル基含有アミン類、例えばアミノプロパノール等を架橋剤として用いるのが好ましい。ヒドロキシル基含有アミン類はその中でも好ましく、例えば、アミノプロパノールの場合、ポリマー中のイソシアネート基とアミノ基が反応してウレイド結合（カルバモイルアミノ基）を、また、ヒドロキシ基が反応してウレタン結合（カルバモイルオキシ基）をそれぞれ形成する。
【００５１】
このようなイソシアネート基を有する重合体を用いる場合に好ましい架橋剤としては、前記一級アミン類のほか、３−アミノプロパノール、またヒドロキシエチルアミノプロピルアミン等の化合物も使用可能である。
【００５２】
【化２】

【００５３】
また、逆にポリマーが、例えばヒドロキシル基を側鎖に有する場合には、これに対して多官能性の例えば複数のイソシアネート基を有する化合物を架橋性化合物（架橋剤）として反応させてもよい。これらの組み合わせとしては、例えばヒドロキシ基のような活性な水素を有するヒドロキシエチルアクリレート（ＨＥＭＡ）を構成成分とするアクリル系樹脂に、多官能のイソシアネート類例えば、日本ポリウレタン社製：コロネートシリーズ、住友バイエル社製：デスモジュールシリーズ等の架橋剤を反応させることで、ポリマーから見て結合の様式は反対になるものの、同様のウレタン結合（カルバモイルオキシ結合）を形成することができる。
【００５４】
これらのウレイド結合あるいはウレタン結合を便宜的にここでは総称してウレタン結合として一括に呼ぶこととする。
【００５５】
このように、イソシアネート基のような官能基に対して活性な水素を複数有する化合物を架橋剤として用いてもよく、また、逆に活性水素を有する重合体を用いた場合には、多官能の化合物を架橋性化合物として用いてもよい。
【００５６】
架橋を形成する基（あるいは反応）としては、前記ウレタン結合のほかにも、代表的には、以下の様な基あるいは反応があげられる。架橋反応は、活性な水素とこれと反応する官能基との反応によるもので官能基を有する重合体に対しては活性な水素を複数有する化合物が架橋剤となり、また、逆に活性水素を有する重合体を用いた場合には、多官能性化合物が架橋性剤となる。
【００５７】
例えば、官能基としてエポキシ基を含有するポリマー（例えば、グリシジルアクリレート等を構成成分とする重合体など）をもちい、架橋剤としてアミン類用いると反応してイミノ基が生成し架橋を形成する。
【００５８】
【化３】

【００５９】
ここで、Ｒ′はやはりポリマー残基を表し、Ｒ″はアミン残基を表す。
これらの架橋剤として、は前記イソシアネート基を有する重合体の場合に用いることのできるアミンが架橋剤が好ましく用いられる。
【００６０】
架橋反応としては更に、カルボキシル基とオキサゾリン基の反応によるアミドエステル形成がある。
【００６１】
カルボキシル基含有ポリマー（例えば、アクリル酸、メタアクリル酸等を共重合成分とするアクリル樹脂）を用いる場合、ポリマーの重合度をあげるために、例えば、オキサゾリン基含有水溶性ポリマーであるエポクロスＷＳシリーズ（日本触媒製）を用い架橋反応させることができる。以下のように架橋構造としてはアミドエステル結合を形成する。これにより分子量が増大し耐溶剤性が増す。
【００６２】
【化４】

【００６３】
ここで、Ｒ′はやはりポリマー残基を表し、Ｒ″は反応性のオキサゾリン基に連結した架橋剤残基を表す。
【００６４】
また、ヒドラジド形成によって架橋してもよい。活性な水素を有するヒドラジド架橋剤、
Ｈ_２ＮＨＮＣＯ−Ｒ″−ＣＯＮＨＮＨ_２（ここでＲ″はアルキレン等の２価の基を表す）、例えば、アジピン酸ヒドラジド（ＡＤＨ；協和発酵製）等を用い、一方、ポリマーとして、このような活性な水素と反応することのできる、カルボニル基の様な官能基を有するモノマー成分（例えばダイアセトンアクリルアマイド；協和発酵製）を共重合成分として有するアクリル系重合体を着色微粒子分散体の樹脂として用いることで、ヒドラゾン結合による架橋を形成できる。
【００６５】
【化５】

【００６６】
架橋反応は、例えば活性な水素とこれと反応する官能基との反応によるもので、活性水素あるいは官能基が樹脂中あるいは架橋剤中のどちらにあってもよい。上記に典型的に用いられる架橋反応を示したが、上記以外の架橋反応を用いても勿論かまわない。例えば、前記グリシジルメタクリレート等のほか、Ｎ−メチロール基を有するＮ−メチロールアクリルアミド等も官能基を有するモノマーと考えられる。
【００６７】
また、上記以外にも、架橋反応を行えるような、反応成分或いは基を、それぞれポリマー中および架橋剤中に用いてもよい。
【００６８】
架橋構造を形成する基と架橋剤の組み合わせとして、本発明においては上記の基を例に挙げたが、これに限定されるものでなく、架橋により分子量の増加をもたらし、樹脂のＴｇ等、耐溶剤性や膨潤性に影響を与えるものであれば、好ましく用いることができる。
【００６９】
前記のイソシアネート基或いはエポキシ基の様な官能基、また水酸基やカルボキシル基等の活性水素を有するモノマーが入手可能であることから、本発明においては、これらのモノマーと前記重合性ビニルモノマーとのラジカル重合法による共重合ポリマーが好ましい。
【００７０】
活性水素或いは、官能基を有するモノマー成分は、それぞれ、形成する架橋構造によって（即ち、官能基の種類また架橋剤によって異なるが）０．１〜３０質量％、好ましくは０．３〜１５質量％の範囲で含有される。あまり少ないと架橋結合の形成が少ないために、本発明の効果がなく、また、多すぎると、樹脂の染料との相互作用や溶剤に対する親和性が大きく変化してしまう。
【００７１】
これら重合性ビニルモノマーを公知の手法を用い、前記官能基あるいは活性水素を有するビニルモノマーとラジカル共重合させることによって、本発明に係わる、未架橋のポリマーが得られ、該未架橋のポリマーを用い、乳化後に、これを架橋構造を形成する基とそれぞれ反応して架橋を形成する各架橋性化合物（架橋剤）で処理して、具体的には、分散体に混合して、反応させ、架橋結合を形成させる。
【００７２】
また、本発明に係わる未架橋の樹脂（ポリマー）には、立体障害性を有する基を有する成分を導入して、乳化時に粒子間架橋を抑制することが好ましい。立体障害性を有する基としては、粒子の安定性からも親水性、かつ長鎖のポリエチレンオキサイド或いはポリプロピレンオキサイド等の基が好ましく、例えば、下記一般式（１）で表される構造を同時に含有している成分を有する樹脂が好ましい。
【００７３】
一般式（１）
−（ＥＯ）_ｍ−（ＰＯ）_ｎ−（ＴＯ）_ｐ−Ｒ
ここにおいて、ＥＯはエチレンオキサイド基、ＰＯはプロピレンオキサイド基、ＴＯはテトラメチレンオキサイド基を表し、それぞれランダム或いはブロック共重合している。ＥＯ、ＰＯまたはＴＯで表されるこれらのエチレンオキサイド基、プロピレンオキサイド基、更にテトラメチレンオキサイド基は更に置換されていてもよい。ｍ、ｎ、ｐはそれぞれ０〜５００までの整数であり、２≦ｍ＋ｎ＋ｐ≦５００、Ｒは水素原子、ヒドロキシル基またはアルキル基、アリール基またはヘテロ環基等の置換基を表すが、Ｒは活性な水素をもたない基であることが好ましい。好ましいアルキル基としては、メチル、エチル、ブチル等炭素数１〜２２までの直鎖、或いは分岐のアルキル基、またやはり炭素数１〜２２までのシクロプロピル基、シクロペンチル基等の脂環式基であってもよい。これらはさらに他の置換基で置換されていてもよいが、置換基は活性な水素をもたない基であることが好ましい。アリール基としては、フェニル基、ナフチル基等の基であり、やはり、活性な水素をもたない置換基で置換されていてもよい。また、ヘテロ環基としては、アジリジン、ピロリジン、フラン、チオフェン、ピロール、ピラゾール、イミダゾール、オキサゾール、チアゾール、ピリジン、ピリダジン等のヘテロ環基があげられ、これらに限定されないが、これらのヘテロ環基は、活性水素をもたないものが好ましく、さらに、置換基を有していてもよく、また、置換基も活性な水素をもたないものが好ましい。
【００７４】
一般式（１）で表される、親水性かつ立体障害性を有するポリエチレンオキサイド或いはポリプロピレンオキサイド等の基を有する樹脂は、架橋構造を形成するために用いられる官能基あるいは活性な水素を有する樹脂と混合し用いてもよい。但し、好ましいのは、前記親水性かつ立体障害性を有するポリエチレンオキサイド或いはポリプロピレンオキサイド等の基を有する樹脂が、同時に架橋構造を形成するための官能基あるいは活性水素を有する樹脂であって、同一ポリマー中にこれらの基を同時に有する均一な構造を有していることが好ましい。
【００７５】
ポリエチレンオキサイド基、ポリプロピレンオキサイド基は、親水性の基であるが、前記調製された着色微粒子の表面を立体的に保護すると考えられ、粒子間の架橋を抑え、凝集を抑え、それにより微粒子で安定な分散体を得ることができる。あまり疎水性の高い基では、粒子表面を覆う効果が小さくなるためと考えられるが、本発明の効果が小さくなる。
【００７６】
前記親水性のポリエチレンオキサイド鎖やポリプロピレンオキサイド鎖をポリマー中に導入するには、前記一般式（１）で表される基を含有するビニルモノマーを用いて前記のビニルモノマーと共重合するのが好ましく、これらビニルモノマーの具体的な例としては日本油脂製ブレンマーシリーズ、代表的には、ブレンマーＡＭＥシリーズ（ブレンマーＡＭＥ−４００等）、ブレンマーＰＭＥシリーズ、（ブレンマーＰＭＥ−１０００、ブレンマーＰＭＥ−４０００等）、ブレンマー５０ＰＯＥＰ−８００Ｂ、ブレンマー５５ＰＥＴシリーズ（ブレンマー５５ＰＥＴ８００等）、ブレンマーＰＰシリーズ（ブレンマーＰＰ８００等）がある。
【００７７】
また、これらのポリエチレンオキサイド基、ポリプロピレンオキサイド基の末端となる前記一般式（１）においてＲで表される基は、活性な水素を含有しないものが好ましい。活性水素を有する場合、官能基を有する架橋剤によって粒子間架橋が起こる可能性がある。
【００７８】
前記一般式（１）で表されるポリエチレンオキサイド基、ポリプロピレンオキサイド基を有する重合性ビニルモノマーを他の共重合成分とラジカル共重合させることで、これらの構成成分を有する樹脂（ポリマー）を得ることができるが、ポリマー成分中にポリエチレンオキサイド基、ポリプロピレンオキサイド基を有するモノマー成分は１〜６０質量％、好ましくは３〜３０質量％の割合で含有しているものが好ましい。少ない場合には当然、架橋剤による架橋反応が粒子間で起こるため凝集が避けられない。また、多すぎる場合にはやはりポリマー全体が親水性となるため、色材との親和性が低下し、相分離等を起こすためやはり安定な微粒子分散体を形成しない或いは凝集が大きくなる等好ましくない。
【００７９】
本発明において、好ましい樹脂（ポリマー）の例について、実施例中にいくつかの組成例を示した。
【００８０】
次に、上記樹脂（ポリマー）とともに種粒子中に封入される色材について説明する。
【００８１】
該色材としては、上記ポリマーに溶解或いは分散可能な色材であれば特に制限無く用いることができ、例えば、油性染料、分散染料、直接染料、酸性染料及び塩基性染料等を挙げることができるが、良好な封入性の観点から油性染料及び分散染料を用いることが好ましい。上記分散染料として、特に好ましい具体例を以下に示すが、これのみに限定されるものではない。特に好ましい具体例としては、Ｃ．Ｉ．ディスパーズイエロー５、４２、５４、６４、７９、８２、８３、９３、９９、１００、１１９、１２２、１２４、１２６、１６０、１８４：１、１８６、１９８、１９９、２０４、２２４及び２３７；Ｃ．Ｉ．ディスパーズオレンジ１３、２９、３１：１、３３、４９、５４、５５、６６、７３、１１８、１１９及び１６３；Ｃ．Ｉ．ディスパーズレッド５４、６０、７２、７３、８６、８８、９１、９２、９３、１１１、１２６、１２７、１３４、１３５、１４３、１４５、１５２、１５３、１５４、１５９、１６４、１６７：１、１７７、１８１、２０４、２０６、２０７、２２１、２３９、２４０、２５８、２７７、２７８、２８３、３１１、３２３、３４３、３４８、３５６及び３６２；Ｃ．Ｉ．ディスパーズバイオレッド３３；Ｃ．Ｉ．ディスパーズブルー５６、６０、７３、８７、１１３、１２８、１４３、１４８、１５４、１５８、１６５、１６５：１、１６５：２、１７６、１８３、１８５、１９７、１９８、２０１、２１４、２２４、２２５、２５７、２６６、２６７、２８７、３５４、３５８、３６５及び３６８；並びにＣ．Ｉ．ディスパーズグリーン６：１及び９等が挙げられる。一方、上記油性染料としては、以下に限定されるものではないが、特に好ましい具体例としては、例えば、Ｃ．Ｉ．ソルベント・ブラック３、７、２７、２９及び３４；Ｃ．Ｉ．ソルベント・イエロー１４、１６、１９、２９、５６及び８２；Ｃ．Ｉ．ソルベント・レッド１、３、８、１８、２４、２７、４３、５１、７２、７３、１３２及び２１８；Ｃ．Ｉ．ソルベント・バイオレット３；Ｃ．Ｉ．ソルベント・ブルー２、１１及び７０；Ｃ．Ｉ．ソルベント・グリーン３及び７；並びにＣ．Ｉ．ソルベント・オレンジ２等が挙げられる。
【００８２】
また、水や各種有機溶剤に不溶な顔料をポリマー媒体中に分散して用いることも可能である。
【００８３】
本発明に使用できる顔料としては、従来公知の有機及び無機顔料が使用できる。例えばアゾレーキ、不溶性アゾ顔料、縮合アゾ顔料、キレートアゾ顔料等のアゾ顔料や、フタロシアニン顔料、ペリレン及びペリレン顔料、アントラキノン顔料、キナクリドン顔料、ジオキサンジン顔料、チオインジゴ顔料、イソインドリノン顔料、キノフタロニ顔料等の多環式顔料や、塩基性染料型レーキ、酸性染料型レーキ等の染料レーキや、ニトロ顔料、ニトロソ顔料、アニリンブラック、昼光蛍光顔料等の有機顔料、カーボンブラック等の無機顔料が挙げられる。
【００８４】
具体的な有機顔料を以下に例示する。
マゼンタまたはレッド用の顔料としては、Ｃ．Ｉ．ピグメントレッド２、Ｃ．Ｉ．ピグメントレッド３、Ｃ．Ｉ．ピグメントレッド５、Ｃ．Ｉ．ピグメントレッド６、Ｃ．Ｉ．ピグメントレッド７、Ｃ．Ｉ．ピグメントレッド１５、Ｃ．Ｉ．ピグメントレッド１６、Ｃ．Ｉ．ピグメントレッド４８：１、Ｃ．Ｉ．ピグメントレッド５３：１、Ｃ．Ｉ．ピグメントレッド５７：１、Ｃ．Ｉ．ピグメントレッド１２２、Ｃ．Ｉ．ピグメントレッド１２３、Ｃ．Ｉ．ピグメントレッド１３９、Ｃ．Ｉ．ピグメントレッド１４４、Ｃ．Ｉ．ピグメントレッド１４９、Ｃ．Ｉ．ピグメントレッド１６６、Ｃ．Ｉ．ピグメントレッド１７７、Ｃ．Ｉ．ピグメントレッド１７８、Ｃ．Ｉ．ピグメントレッド２２２等が挙げられる。
【００８５】
オレンジまたはイエロー用の顔料としては、Ｃ．Ｉ．ピグメントオレンジ３１、Ｃ．Ｉ．ピグメントオレンジ４３、Ｃ．Ｉ．ピグメントイエロー１２、Ｃ．Ｉ．ピグメントイエロー１３、Ｃ．Ｉ．ピグメントイエロー１４、Ｃ．Ｉ．ピグメントイエロー１５、Ｃ．Ｉ．ピグメントイエロー１７、Ｃ．Ｉ．ピグメントイエロー９３、Ｃ．Ｉ．ピグメントイエロー９４、Ｃ．Ｉ．ピグメントイエロー１３８等が挙げられる。
【００８６】
グリーンまたはシアン用の顔料としては、Ｃ．Ｉ．ピグメントブルー１５、Ｃ．Ｉ．ピグメントブルー１５：２、Ｃ．Ｉ．ピグメントブルー１５：３、Ｃ．Ｉ．ピグメントブルー１６、Ｃ．Ｉ．ピグメントブルー６０、Ｃ．Ｉ．ピグメントグリーン７等が挙げられる。
【００８７】
本発明のインクに使用する顔料分散体の平均粒径は１０〜２００ｎｍであることが好ましく、１０〜１５０ｎｍがより好ましく、１０〜１００ｎｍがさらに好ましい。顔料分散体の平均粒径が１５０ｎｍを越えると光沢メディアに記録した画像では光沢感の劣化が起こり、トランスペアレンシーメディアに記録した画像では著しい透明感の劣化が起こる。また、顔料分散体の平均粒径が１０ｎｍ未満になると顔料分散体の安定性が悪くなり易く、インクの保存安定性が劣化し易くなる。
【００８８】
顔料分散体の粒径測定は、光散乱法、電気泳動法、レーザードップラー法等を用いた市販の粒径測定機器により求めることができる。また、透過型電子顕微鏡による粒子像撮影を少なくとも１００粒子以上に対して行い、この像をＩｍａｇｅ−Ｐｒｏ（メディアサイバネティクス製）等の画像解析ソフトを用いて統計的処理を行うことによっても求めることが可能である。
【００８９】
色材として、あるいは、特開平９−２７７６９３号、特開平１０−２０５５９号、特開平１０−３００６１号に示されるような、金属錯体色素も使用可能である。たとえば、特開平１０−２０５５９号に記載の一般式（Ｉ）及び一般式（ＩＩ）で表される色素が使用可能である。
【００９０】
【化６】

【００９１】
一般式（Ｉ）において、Ｘ^１は、金属イオンと少なくとも２座の配位結合を形成可能な構造を有する原子の集まりを表し、Ｙ^１は芳香族炭化水素環、５員或いは６員の複素環又は−Ｌ^４＝Ｙ^２を表し、Ｙ^２は含窒素の５員或いは６員の複素環を表す。Ｌ^１、Ｌ^４は置換又は非置換のメチン基並びに窒素原子を表し、Ｌ^２、Ｌ^３は置換又は非置換のメチン基を表す。Ｍは金属イオンを表し、Ｘ^１で形成される原子の集まりと少なくとも２座の配位結合を形成している。ｍは０、１、２又は３の整数を表し、ｎ１は１、２又は３の整数を表す。又、一般式（ＩＩ）において、Ｘ^３、Ｙ^３、Ｍ及びｎ２はそれぞれ上記Ｘ^１、Ｙ^１、Ｍ及びｎ１と同義である。
【００９２】
さらにこれらの具体例として以下の色素が挙げられる。
【００９３】
【化７】

【００９４】
【化８】

【００９５】
【化９】

【００９６】
【化１０】

【００９７】
【化１１】

【００９８】
【化１２】

【００９９】
【化１３】

【０１００】
【化１４】

【０１０１】
【化１５】

【０１０２】
【化１６】

【０１０３】
【化１７】

【０１０４】
【化１８】

【０１０５】
【化１９】

【０１０６】
【化２０】

【０１０７】
本発明においては、これらの色材を前記ポリマーおよび前記非水溶性有機溶剤と共に混合、溶解し、水および前記水溶性有機溶剤を含有する水性媒体中おいて、乳化剤を用いて、乳化・分散し、その後、有機溶剤等を留去することで、架橋前の着色微粒子分散体が得られる。
【０１０８】
乳化の際にもちいることのできる乳化剤としては、通常のノニオン系乳化剤として、例えば、ポリオキシエチレンラウリルエーテル等のポリオキシエチレンオクアルキルエーテル類；例えば、ポリオキシエチレンノニルフェニルエーテル等のポリオキシエチレンアルキルフェニルエーテル類；ソルビタンモノラウレート等のソルビタン高級脂肪酸エステル類等、
またアニオン系乳化剤として、例えば、オレイン酸ナトリウム等の高級脂肪酸塩類；例えば、ドデシルベンゼンスルホン酸ナトリウム等のアルキルアリールスルホン酸塩類；例えば、ラウリル硫酸ナトリウム等のアルキル硫酸エステル塩類；例えば、ポリオキシエチレンラウリルエーテル硫酸ナトリウム等のポリオキシエチレンアルキルエーテル硫酸エステル塩類；ジオクチルスルホコハク酸ナトリウム、等のアルキルスルホコハク酸エステル塩及びその誘導体類等を用いることができる。
【０１０９】
また、前記の乳化剤に代え、或いはそれに加え、重合可能な乳化剤（反応性乳化剤）を用いるのが好ましい。
【０１１０】
反応性乳化剤としては、アニオン系及びノニオン系のいづれの乳化剤でも特に限定されず、例えば、（メタ）アリル基、（メタ）アクリル基、スチリル基などのラジカル重合性不飽和基を有する乳化剤が単独で又は２種類以上組み合わせて使用できる。
【０１１１】
反応性乳化剤としては、アニオン系及びノニオン系のいづれの乳化剤でも特に限定されず、例えば、（メタ）アリル基、（メタ）アクリル基、スチリル基などのラジカル重合性不飽和基を有する乳化剤が単独で又は２種類以上組み合わせて使用できる。
【０１１２】
このようなアニオン系反応性乳化剤としては、例えば、下記一般式（２）〜（５）で表される反応性乳化剤を挙げることができる。
【０１１３】
【化２１】

【０１１４】
式中、Ｒ^２は水素、メチル基、Ｒ^３は炭素数６〜１８のアルキル基、アルケニル基、アリール基又はアラルキル基、Ｒ^４は水素又はメチル基、Ｒ^５は炭素数６〜１８のアルキル基、アルケニル基、アリール基又はアラルキル基、Ｘは単結合またはメチレン基、Ｍはアルカリ金属、ｍは１〜５０の自然数、ｎは１〜５０の自然数、ｑは０又は１である。
【０１１５】
上記一般式（２）で表されるアニオン系反応性乳化剤の具体例としては、例えば、「アデカリアソープ ＳＥ−１０Ｎ」、「アデカリアソープ ＳＥ−２０Ｎ」、「アデカリアソープ ＳＥ−３０Ｎ」（以上、旭電化工業（株）製）が、上記一般式（３）で表されるアニオン系反応性乳化剤の具体例としては、例えば、「アクアロン ＨＳ−０５」、「アクアロン ＨＳ−１０」、「アクアロン ＨＳ−２０」、「アクアロン ＨＳ−３０」（以上、第一工業製薬（株）製）等が、また、上記一般式（４）のアニオン系反応性乳化剤の具体例としては、例えば「ラテムル Ｓ−１２０」、「ラテムル Ｓ−１２０Ａ」、「ラテムル Ｓ−１８０」、「ラテムル Ｓ−１８０Ａ」（以上、花王（株）製）、「エレミノールＪＳ−２１」（以上、三洋化成工業（株）製）等が、一般式（５）のアニオン系反応性乳化剤の具体例としては、例えば「アントックス ＭＳ−６０」（日本乳化剤（株）製）を挙げることができる。
【０１１６】
その他、アニオン系反応性乳化剤としては、例えば「ラテムル ＡＳＫ」（花王（株）製）等のアルキルアルケニルコハク酸エステル塩系反応性乳化剤；例えば「エレミノール ＲＳ−３０」（三洋化成工業（株）製）等のポリオキシアルキレン（メタ）アクリレート硫酸エステル塩系反応性乳化剤；例えば「ＲＡ−１１２０」、「ＲＡ−２６１４」（以上、日本乳化剤（株）製）等のポリオキシアルキレンアルキルエーテル脂肪族不飽和ジカルボン酸エステル塩系反応性乳化剤；例えば「アントックス ＭＳ−２Ｎ」（日本乳化剤（株）製）等の（メタ）アクリル酸スルホアルキルエステル塩系反応性乳化剤；フタル酸ジヒドロキシアルキル（メタ）アクリレート硫酸エステル塩系反応性乳化剤；例えば「Ｈ−３３３０ＰＬ」（第一工業製薬（株）製）等のモノもしくはジ（グリセロール−１−アルキルフェニル−３−アリル−２−ポリオキシアルキレンエーテル）リン酸エステル塩系反応性乳化剤等が、また、ノニオン系反応乳化剤としては、例えば、下記一般式（６）及び（７）で示される反応性乳化剤を挙げることができる。
【０１１７】
【化２２】

【０１１８】
式中、Ｒ^２は水素、メチル基、Ｒ^３は炭素数６〜１８のアルキル基、ｍは１〜５０の自然数、アルケニル基、アリール基又はアラルキル基、Ｒ^４は水素又はメチル基、Ｘは単結合またはメチレン基、Ｍはアルカリ金属である。
【０１１９】
上記一般式（６）で表されるノニオン系反応性乳化剤の具体例としては、例えば「アデカリアソープＮＥ−１０」、「アデカリアソープＮＥ−２０」、「アデカリアソープＮＥ−３０」（以上、旭電化工業（株）製）等が、一般式（６）で表されるノニオン系反応性乳化剤の具体例としては、例えば「アクアロン ＲＮ−１０」、「アクアロン ＲＮ−２０」、「アクアロン ＲＮ−３０」、「アクアロン ＲＮ−５０」（以上、第一工業製薬（株）製）等が、またその他、例えば「ＲＭＡ−５６４」、「ＲＭＡ−５６８」（以上、日本乳化剤（株）製）等のポリオキシアルキレンアルキルフェニルエーテル（メタ）アクリレート系反応性乳化剤；例えば「ＲＭＡ−１１１４」（日本乳化剤（株）製）等のポリオキシアルキレンアルキルフェニルエーテル（メタ）アクリレート系反応性乳化剤等も挙げることができる。
【０１２０】
これら反応性乳化剤の使用量は、ポリマーの合計１００質量部当たり、一般に０．１〜３０質量部、好ましくは２〜２５質量部、特に好ましくは３〜２０質量部の範囲で用いるのがよい。
【０１２１】
これらの乳化剤は、粒子近傍に安定な電気二重層を形成すると同時に、樹脂との反応性を有するために、乳化時或いは乳化後に、樹脂中にポリエチレンオキサイド鎖、ポリプロピレンオキサイド鎖と共に架橋を導入でき好ましい。
【０１２２】
これらの色材および前記樹脂からなる着色微粒子については、各種の乳化法で製造することができる。乳化法としては、各種の方法を用いることができる。それらの例は、例えば、「機能性乳化剤・乳化技術の進歩と応用展開 シー エムシー」の８６ページの記載にまとめられている。本発明においては、特に、超音波、高速回転せん断、高圧による乳化分散装置を使用することが好ましい。
【０１２３】
超音波による乳化分散では、いわゆるバッチ式と連続式の２通りが使用可能である。バッチ式は、比較的少量のサンプル作製に適し、連続式は大量のサンプル作製に適する。連続式では、たとえば、ＵＨ−６００ＳＲ（株式会社エスエムテー製）のような装置を用いることが可能である。このような連続式の場合、超音波の照射時間は、分散室容積／流速×循環回数で求めることができる。超音波照射装置が複数ある場合は、それぞれの照射時間の合計としてもとめられる。超音波の照射時間は実際上は１００００秒以下である。また、１００００秒以上必要であると、工程の負荷が大きく、実際上は乳化剤の再選択などにより乳化分散時間を短くする必要がある。そのため１００００秒以上は必要でない。さらに好ましくは、１０秒以上、２０００秒以内である。
【０１２４】
高速回転せん断による乳化分散装置としては、「機能性乳化剤・乳化技術の進歩と応用展開 シー エム シー」の２５５〜２５６ページに記載されているような、ディスパーミキサーや、２５１ページに記載されているようなホモミキサー、２５６ページに記載されているようなウルトラミキサーなどが使用できる。これらの型式は、乳化分散時の液粘度によって使い分けることができる。これらの高速回転せん断による乳化分散機では、攪拌翼の回転数が重要である。ステーターを有する装置の場合、攪拌翼とステーターとのクリアランスは通常０．５ｍｍ程度で、極端に狭くはできないので、せん断力は主として攪拌翼の周速に依存する。周速が５ｍ／Ｓ以上１５０ｍ／Ｓ以内であれば本発明の乳化・分散に使用できる。周速が遅い場合、乳化時間を延ばしても小粒径化が達成できない場合が多く、１５０ｍ／Ｓにするにはモーターの性能を極端に上げる必要があるからである。さらに好ましくは、２０〜１００ｍ／ｓである。
【０１２５】
高圧による乳化分散では、ＬＡＢ２０００（エスエムテー社製）などが使用できるが、その乳化・分散能力は、試料にかけられる圧力に依存する。圧力は１０^４ｋＰａ〜５×１０^５ｋＰａの範囲が好ましい。また、必要に応じて数回乳化・分散を行い、目的の粒径を得ることができる。圧力が低すぎる場合、何度乳化分散を行っても目的の粒径は達成できない場合が多く、また、圧力を５×１０^５ｋＰａにするためには、装置に大きな負荷がかかり実用的ではない。さらに好ましくは５×１０^４ｋＰａ〜２×１０^５ｋＰａの範囲である。
【０１２６】
これらの乳化・分散装置は単独で用いてもよいが、必要に応じて組み合わせて使用することが可能である。コロイドミルや、フロージェットミキサなども単独では本発明の目的を達成できないが、本発明の装置との組み合わせにより、短時間で乳化・分散を可能にするなど本発明の効果を高めることが可能である。
【０１２７】
本発明においては、前記油溶性染料を、前記ポリエチレンオキサイド基またはポリプロピレンオキサイド基、およびイソシアネート基等の架橋構造を形成する基を有する共重合ポリマー樹脂と共に、酢酸エチル等の有機溶剤に溶解・混合した後、前記分散装置により、水および前記水溶性有機溶剤を含有する水性媒体中おいて、乳化・分散し、溶剤を除去して前記水溶性有機溶剤を含有する水性の分散体を形成した後、架橋剤として、前記架橋構造を形成する基とそれぞれ反応する、例えば前記ジエチレントリアミン、３−アミノプロパノール等のアミン化合物を、乳化、分散した水性分散体に混合して架橋させる。反応を促進するために、例えば、必要な場合には水性分散体を４０〜９０℃の範囲で加温し、十分な時間（形成される架橋結合によって異なるが、例えば、数分から必要な場合には数時間をかけて）反応させ、微粒子内部での架橋反応を十分行わせることも好ましい。
【０１２８】
また、反応が比較的ゆっくりである場合には、これら架橋剤は、ポリマー、染料と共に混合溶解して、その後乳化、分散するという方法でもよい。
【０１２９】
ここにおいて水性分散体とは水を主体とする前記水溶性有機溶媒が混合された媒体中に前記着色微粒子が分散しているものをいい、媒体中での水の割合が５０％以上のものをいい、水性インクの水性も同じ意味である。
【０１３０】
本発明に係わる着色微粒子分散体は、前記色材および樹脂（ポリマー）を含有する着色微粒子散体を種粒子として、これに重合可能な素材を添加、重合させ、更にシード重合させ、コアシェル構造とすることが好ましい。
【０１３１】
重合可能な素材を添加して、種粒子上でシード重合させる方法としては、色材と樹脂を含有する着色微粒子の前記分散体を形成した後、重合可能な素材として重合性不飽和二重結合を有するモノマーを添加し活性剤の存在下、乳化重合を行って、重合と同時に種粒子となる着色微粒子表面に沈着させる方法が本発明においては好ましい。この方法で形成した場合、好ましい場合には、後添加した重合性不飽和二重結合を有するモノマーは、前記種粒子上で重合してポリマーシェルを形成する。
【０１３２】
色材と樹脂からなる着色微粒子を種粒子として、これに後添加して、種粒子上で重合させる重合性不飽和二重結合を有するモノマーとしては、エチレン、プロピレン、ブタジエン、塩化ビニル、塩化ビニリデン、酢酸ビニル、スチレン、（メタ）アクリル酸エステル類、（メタ）アクリル酸等、アクリルアミド類等から選ばれる化合物、特スチレンや（メタ）アクリル酸エチル、（メタ）アクリル酸ブチル、（メタ）アクリル酸エチルヘキシル等の（メタ）アクリル酸エステル類等が好ましいが、これらのモノマーに加えて、分子内にヒドロキシル基を含有する重合性不飽和二重結合を有するモノマー、例えば、ヒドロキシエチル（メタ）アクリレート等のヒドロキシアルキル（メタ）アクリレート、或いはヒドロキシル基を有する重合性不飽和二重結合を有するモノマーを、後添加する原料モノマー全体の中で、最大５０％、その他のエチレン性不飽和二重結合を有するモノマーと混合して用い共重合させることが粒子の安定性を得る上で好ましい。
【０１３３】
このような共重合体として、例えば、スチレン／メタクリル酸２−ヒドロキシエチル、スチレン／アクリル酸２−ヒドロキシエチル等が好ましい例としてあげられる。
【０１３４】
また、シェルの安定性を増す等の理由から、アクリル酸、メタクリル酸等のカルボン酸を含有するモノマー或いはスルホン酸を含有するモノマー等、ｐＫａ値で３〜７の解離性基を含有するエチレン性不飽和モノマーを共重合成分の１０％以下用いてもよい。これらのモノマー成分をシェル形成に用いることによって、当該コア／シェル着色微粒子の水分散体の安定性が向上する。
【０１３５】
また、前記架橋剤と反応する、官能基を有する重合性不飽和二重結合を有するモノマーを最大５０％含有させて、シェル形成後に架橋を行うことが好ましい。例えば、イソシアネート基、エポキシ基等を含有する前記ビニルモノマー、オキサゾリン基と反応するカルボキシル基を含有するビニルモノマー、また、活性な水素を有するヒドラジド架橋剤、例えば、前記アジピン酸ヒドラジド（ＡＤＨ；協和発酵製）等と架橋反応する基を有するビニルモノマー等を用いて、シェル形成する。それによりシェル形成後に架橋剤により架橋反応をさせることができる。
【０１３６】
また、シェルにおいて架橋を導入する場合、前記酢酸ビニル、スチレン、（メタ）アクリル酸エステル類等の重合性不飽和二重結合を有するモノマーと共に、多官能性ビニルモノマー例えば、エチレングリコールジメタクリレート、エチレングリコールジアクリレートまたはジビニルベンゼン等を共重合成分として用いて、シェル形成してもよく、シェル形成と同時に、或いはシェル形成後にシェル内で３次元架橋反応をさせることができる。
【０１３７】
本発明においては、シェルに用いられるポリマー量は総ポリマー量の５質量％以上９５質量％以下である。５質量％より少ないとシェルの厚みが不十分で、色材を多く含有するコアの一部が粒子表面に現れ易くなる。また、シェルのポリマーが多すぎると、コアの色材保護能低下を起こし易い。さらに好ましくは１０質量％以上９０質量％以下である。
【０１３８】
シェル形成のためのシード重合は前記着色微粒子分散体からの連続した反応であり、分散媒体中には、前記水溶性有機溶剤が含有されているが、シード重合時にさらに、水溶性有機溶剤を前記の範囲内で添加してもよい。
【０１３９】
色材の総量は総ポリマー量に対して２０質量％以上１０００質量％以下であることが好ましい。色材量がポリマーに比して少なすぎると吐出後の画像濃度が上がらず、また、色材質量が多すぎるとポリマーの保護能が十分に得られない。
【０１４０】
このようにして形成された本発明に係わる着色微粒子分散体の着色微粒子の体積換算平均粒径は１０〜１００ｎｍ、好ましくは２０〜８０ｎｍであり、この粒径範囲において安定であるため、鮮やかな色を有すると同時に、インクとしたときの安定性に優れる。
【０１４１】
前記架橋反応により、染料含有コアについては、あまり架橋を導入して、色材との相分離を起こさない範囲で、また、シェルについては、好ましくは最表面であるが、後述するように、架橋の導入により粒子間架橋が起こらないような適度な範囲で架橋を導入する必要がある。
【０１４２】
また、シェルについて、粒子間架橋を抑えるために、シェル形成するモノマー成分として、多官能性ビニルモノマーのような架橋を形成する基、或いは架橋剤と反応して共に架橋結合を形成する基を含有するモノマー成分に加えて、前記のように、ポリエチレンオキサイド或いはポリプロピレンオキサイド等の立体障害性を有する基を有する成分を導入して、粒子間架橋を抑制することも好ましい。
【０１４３】
個々の粒子径が１００ｎｍ以下と非常に微小であるため、形成された着色微粒子分散体が、実際にコアシェル化されているかは、分解能の観点から分析手法が限られる。この目的に沿う分析手法としては、ＴＥＭやＴＯＦ−ＳＩＭＳなどが適用できる。ＴＥＭによりコアシェル化した微粒子を観察する場合、カーボン支持膜上に分散液を塗布、乾燥させ観察することができる。ＴＥＭの観察像は、有機物であるポリマーの種類のみではコントラスト差が小さいため、コアシェル化されているかどうかを評価するために、微粒子を、４酸化オスミウム、４酸化ルテニウム、クロロスルホン酸／酢酸ウラニル、硫化銀等を用いて染色する必要がある。コアだけの微粒子を染色しそのＴＥＭ観察を行い、シェルを設けたものと比較する。さらに、シェルを設けた微粒子と設けていない微粒子を混合後、染色し、染色度合いの異なる微粒子の割合がシェルの有無に一致しているかの確認を行う。
【０１４４】
ＴＯＦ−ＳＩＭＳような質量分析装置では、粒子表面にシェルを設けることで表面近傍の色材量がコアだけの時よりも減少していることを確認する。色材にコアシェルのポリマーに含有されていない元素がある場合、その元素をプローブとして色材含有量の少ないシェルが設けられたかを確認することができる。
【０１４５】
即ち、色材含有率（濃度）は、ＴＯＦ−ＳＩＭＳによって、個々の微粒子表面について、先ず質量数１〜１０００のイオンの総量を測定し、その中で染料に含有されるコアシェルのポリマーに含有されていない元素に由来するイオンの総量との比から求めることができる。この方法によりシェルとコア／シェル化を行っていないコア、それぞれの色材含有率を比較することによりそれぞれの色素含有率（濃度）を測定できる。ＴＯＦ−ＳＩＭＳでは、表面から深さ方向に数ｎｍの元素分析ができるため本発明の様なコア／シェル微粒子の分析が可能である。
【０１４６】
そのような元素がない場合、適当な染色剤を用いてシェル中の色材含有量がシェルを設けていないものと比較することができる。
【０１４７】
又、コアシェル粒子をエポキシ樹脂内に埋胞し、ミクロトームで超薄い切片を作成、染色を行うことでコアシェル化はより明瞭に観察できる。上記のように、ポリマーや、色材にプローブとなりうる元素がある場合、ＴＯＦ−ＳＩＭＳやＴＥＭによってコアシェルの組成、色材のコアとシェルへの分布量を見積もることもできる。
【０１４８】
本発明においては、シェルにおける色材含有率（濃度）が、コア／シェル化を行っていないコアにおける色材含有率（濃度）の０．８以下である。好ましくは０．５以下であり、更に好ましくは０．２以下である（勿論０或いは限りなく０に近い値であってもよい）。これにより、ポリマーコアが、色材の主たる部分を包含することで、その堅牢性や色調を保持するのに寄与し、一方ポリマーシェルは色材を包含したこれら微粒子のインクサスペンションとしての安定性を増す事に寄与すると共にメディア上での色材の定着促進、凝集の防止、画質の向上や色材の堅牢性、色調の保持にも貢献する。
【０１４９】
必要な粒径を得るには、処方の最適化と、適当な乳化法の選定が重要である。処方は用いる色材、ポリマーによって異なるが、水中の分散体であるので、コアを構成するポリマーよりシェルを構成するポリマーの方が一般的に親水性が高いことが必要である。また、シェルを構成するポリマーに含有される色材は、前記のようにコアを構成するポリマー中より少ないことが好ましく、色材もシェルを構成するポリマーよりも親水性の低いことが必要である。親水性、疎水性は、例えば溶解性パラメータ（ＳＰ）を用いて見積もることができる。溶解性パラメータは、その値や、測定、計算法がＰＯＬＹＭＥＲ ＨＡＮＤＢＯＯＫ 第４版（ＪＯＨＮ ＷＩＬＥＹ ＆ ＳＯＮＳ，ＩＮＣ．）６７５ページからの記載が参考になる。
【０１５０】
また、コア／シェルで用いられるポリマーは、その数平均分子量が５００〜１０００００、特に１０００〜３００００であることが、印刷後の製膜性、その耐久性及びサスペンションの形成性の点から好ましい。
【０１５１】
また、体積平均粒径の変動係数が８０％以下である分散体が好ましく経時での粒径変動も少ない。変動係数は５０％以下がさらに好ましい。
【０１５２】
体積平均粒子径は、透過型電子顕微鏡（ＴＥＭ）写真の投影面積（少なくとも１００粒子以上に対して求める）の平均値から得られた円換算平均粒径を、球形換算して求めた。また、体積平均粒径とその標準偏差を求め、標準偏差を体積平均粒径で割ることで変動係数を求めた。或いは、動的光散乱法を利用して変動係数を求めることも出来る。例えば、大塚電子製レーザー粒径解析システムや、マルバーン社製、ゼータサイザーを用いて求める事が出来る。
【０１５３】
粒径の変動係数は、粒径の標準偏差を粒径で割った値であるが、この値が大きいほど粒径の分布が広い事を意味する。体積平均粒径の変動係数が８０％以上であると、粒径分布が非常に広くなり、粒子間の表面物性にばらつきが生じ、これにより粒子の凝集を招きやすい。また、粒子の凝集はメディア上で、色材の光散乱を招き易く、画質の低下も招き易くする。
【０１５４】
この様にして形成された、本発明にかわる着色微粒子分散体は、トータルのポリマー量として本発明のポリマーエマルジョン型水性インク中にポリマーが０．５〜５０質量％配合されることが好ましく、０．５〜３０質量％配合されることが更に好ましい。上記ポリマーの配合量が０．５質量％に満たないと、色材の保護能が十分でなく、５０質量％を超えると、サスペンションのインクとしての保存安定性が低下したり、ノズル先端部でのインク蒸発に伴うインクの増粘やサスペンションの凝集が起こることによってプリンタヘッドの目詰りが起こる場合があるので、上記範囲内とすることが好ましい。
【０１５５】
一方、上記色材は、該インク中に１〜３０質量％配合されることが好ましく、１．５〜２５質量％配合されることが更に好ましい。上記色材の配合量が１質量％に満たないと印字濃度が不十分であり、３０質量％を超えるとエマルジョンの経時安定性が低下し、凝集等による粒径増大の傾向があるので、上記範囲内とすることが好ましい。
【０１５６】
本発明の水性インクは、水を主体とする水性媒体とし、上記色材を封入した前記着色微粒子分散体に、従来公知の各種添加剤、例えば多価アルコール類のような湿潤剤、分散剤、シリコーン系等の消泡剤、クロロメチルフェノール系等の防黴剤及び／又はＥＤＴＡ等のキレート剤、又、亜硫酸塩等の酸素吸収剤等を含有させ調製する。
【０１５７】
本発明に係わる着色微粒子分散体は、乳化時に、水溶性有機溶剤の存在下において、乳化され、水溶性有機溶剤を含有していることから、上記多価アルコール等の湿潤剤等を混合する際、浸透圧の急激な、また局所的な変化（いわゆる溶剤ショック）が少なく、分散体微粒子の、凝集や、沈降を引き起こしにくいので、経時での安定性に優れる。
【０１５８】
本発明に係わる着色微粒子分散体は、また樹脂が架橋されており、耐溶剤性が高いため前記多価アルコール類のような湿潤剤（低表面張力を実現する効果がある）との共存下での安定性が特に高く凝集を起こしにくい。
【０１５９】
湿潤剤としては、前記の着色微粒子分散体の乳化、調製時に共存させる、例えば、エチレングリコール、プロピレングリコール等の水溶性有機溶剤と同じものであり、それらの一種又は二種以上を湿潤剤として使用することができる。これらの水溶性有機溶剤は湿潤剤として、上記インク中に好ましくは０．１〜５０質量％配合することができ、更に好ましくは０．１〜３０質量％配合することができる。
【０１６０】
また、上記分散剤としては、特に制限されるものではないが、そのＨＬＢ値が８〜１８であることが、分散剤としての効果が発現し、分散体の粒径の増大抑制効果がある点から好ましい。
【０１６１】
分散剤として市販品も使用することができる。そのような市販品としては、例えば花王（株）製の分散剤デモールＳＮＢ，ＭＳ，Ｎ，ＳＳＬ，ＳＴ，Ｐ（商品名）が挙げられる。
【０１６２】
分散剤の配合量に特に制限はないが、本発明のインク中に、０．０１〜１０質量％配合されることが好ましい。該化合物の配合量が０．０１質量％に満たないとサスペンションの小粒径化が困難であり、１０質量％を超えるとエマルジョンの粒径が増大したりエマルジョン安定性が低下し、ゲル化するおそれがあり、上記範囲内とすることが好ましい。
【０１６３】
また、上記消泡剤としては、特に制限なく、市販品を使用することができる。そのような市販品としては、例えば信越シリコーン社製のＫＦ９６、６６、６９、ＫＳ６８、６０４、６０７Ａ、６０２、６０３、ＫＭ７３、７３Ａ、７３Ｅ、７２、７２Ａ、７２Ｃ、７２Ｆ、８２Ｆ、７０、７１、７５、８０、８３Ａ、８５、８９、９０、６８−１Ｆ、６８−２Ｆ（商品名）等が挙げられる。これら化合物の配合量に特に制限はないが、本発明のポリマーエマルジョン型水系インク中に、０．００１〜２質量％配合されることが好ましい。該化合物の配合量が０．００１質量％に満たないとインク調製時に泡が発生し易く、又、インク内での小泡の除去が難しく、２質量％を超えると泡の発生は抑えられるものの、印字の際、インク内でハジキが発生し印字品質の低下が起こる場合があるので、上記範囲内とすることが好ましい。
【０１６４】
本発明のインクジェット記録用水性インクを使用するインクジェットヘッドはオンデマンド方式でもコンティニュアス方式でも構わない。又吐出方式としては、電気−機械変換方式（例えば、シングルキャビティー型、ダブルキャビティー型、ベンダー型、ピストン型、シェアーモード型、シェアードウォール型等）、電気−熱変換方式（例えば、サーマルインクジェット型、バブルジェット（Ｒ）型等）等など何れの吐出方式を用いても構わない。
【０１６５】
本発明のインクジェット記録用水性インクを用いた画像形成においては、例えば、インクジェット記録用水性インクを装填したプリンター等により、デジタル信号に基づきインクジェットヘッドよりインクを液滴として吐出させインク受容体に付着させることで、例えばインクジェット画像記録媒体上にインクジェット記録画像が形成されたインクジェットプリントが得られる。
【０１６６】
インクジェット画像記録媒体としては、例えば、普通紙、コート紙、キャストコート紙、光沢紙、光沢フィルム、ＯＨＰフィルムのいずれも使用することができ、なかでも例えば多孔質層が形成されている所謂空隙層を有する被記録媒体であれば好ましい。上述した支持体の素材或いは形状に特に限定されるものではなく、例えばシート状に形成されたもの以外に立体的な構造を有するものであってもよい。
【０１６７】
本発明の製造方法により得られた、着色微粒子分散体をもちいた水性インクは、インクジェット記録用のインクとして以外に、例えば、一般の万年筆、ボールペン、サインペン等の筆記具用のインクとしても使用可能である。本発明の着色微粒子分散体を乾燥し、微粒の粉体を得ることもできる。得られた粉体は、電子写真のトナーなどにも使用可能である。
【０１６８】
【実施例】
以下に、合成例、実施例を挙げて本発明を更に詳細に説明するが、本発明は、これら実施例の範囲に限定されるものではない。
【０１６９】
《樹脂合成１》
０．３リットルの四つ口セパラブルフラスコに滴下装置、温度計、窒素ガス導入管、撹拌装置及び還流冷却管を付し、脱水したメチルエチルケトン２０ｇをしこみ、８０℃に加熱した。表１の組成割合のモノマーを総量が１００ｇとなるように秤量し、更にＮ，Ｎ′−アゾビスイソバレロニトリル２ｇを前記モノマーに加えた混合液を、フラスコ中に２時間かけて滴下し、同温度にて５時間反応させた。その後メチルエチルケトン８０ｇを添加し冷却、ポリマー５０質量％のポリマー溶液を得た。
【０１７０】
【表１】

【０１７１】
ブレンマーＰＭＥ−１０００：
−（ＥＯ）_ｍ−ＣＨ_３ （ｍ≒２３）を有するメタアクリレート
ブレンマーＰＭＥ−４０００：
−（ＥＯ）_ｍ−ＣＨ_３ （ｍ≒９０）を有するメタアクリレート
ここにおいて、ＥＯは−ＣＨ_２ＣＨ_２Ｏ−を表す。
ブレンマーＧ：
グリシジルメタクリレート
以上日本油脂製。
ＨＥＭＡ：メタクリル酸２−ヒドロキシエチル、ＳＴ：スチレン、ＭＭＡ：メタクリル酸メチル、ＳＭＡ：ステアリルメタクリレート、カレンズＭＯＩ：２−メタクリロイルオキシエチルイソシアネート（昭和電工製）。
《着色微粒子の製造》
実施例１（水溶性有機溶剤として、エチレングリコールで膨潤した着色微粒子の製造）
表１の樹脂Ｒ１を１２ｇを含む液２４ｇに、２ｇのイソホロンジイソシアネートと０．１ｇのジブチルチンジラウレートを加え４０℃で３０分反応させた（▲２▼樹脂）後、クレアミックスＣＬＭ−０．８Ｓ（エムテクニック（株）社製）のポットに１２ｇのＣ． Ｉ． Ｓｏｌｖｅｎｔ Ｙｅｌｌｏｗ １６２（▲１▼染料）、及び１２０ｇの酢酸エチルと共に入れ、攪拌して染料を完全溶解させた。さらに、ＫＨ−０５（第一工業製）（▲３▼乳化剤）を２質量％含む水溶液２４０ｇ、エチレングリコール３０ｇを添加後、４０℃に温度を保ちながら回転数１２０００ｒｐｍで５分間乳化した。酢酸エチルを４０℃で減圧除去した後、２−ヒドロキシエチルアミノプロピルアミンを添加し、６０℃で１２０分架橋反応させ、着色微粒子分散体１を製造した。
【０１７２】
比較例１
実施例１で、エチレングリコールを入れずに架橋反応までを行い、比較の着色微粒子分散体１を製造した。
【０１７３】
実施例２（水溶性有機溶剤として、トリエチレングリコールモノ−ｎ−ブチルエーテルで膨潤した着色微粒子の製造）
実施例１の着色微粒子１の製法で、樹脂Ｒ１を１２ｇを含む液２４ｇに、２ｇのイソホロンジイソシアネートと０．１ｇのジブチルチンジラウレートを加え４０℃で３０分反応させたものを用いる代わりに、樹脂Ｒ２を用い、エチレングリコール３０ｇの代わりにトリエチレングリコールモノ−ｎ−ブチルエーテル１０ｇを用いた。また架橋剤として、エポメートＱＸ２（ジャパンエポキシレジン製）を２ｇをあらかじめ乳化油相に添加しておき、乳化後に８０℃で１２０分架橋反応させることで着色微粒子分散体２を作成した。
【０１７４】
比較例２
実施例２でトリエチレングリコールモノ−ｎ−ブチルエーテルを加えずに架橋反応まで行い、比較の着色微粒子分散体２を製造した。
【０１７５】
実施例３（水溶性有機溶剤として、グリセリンで膨潤した着色微粒子の製造）
実施例２の着色微粒子２の製法で、染料として、１２ｇのシアン染料ＦＳＢ１５０４を用い、樹脂Ｒ２を用いる代わりに、樹脂Ｒ３を用い、トリエチレングリコールモノ−ｎ−ブチルエーテル１０ｇの代わりにグリセリン３０ｇを用いた以外は同様にして、着色微粒子分散体３を作成した。
【０１７６】
また、着色微粒子３を６５℃に保温して、ＭＭＡ３ｇと、過硫酸カリウム０．１ｇを含む水溶液３ｇをそれぞれ１時間かけて添加し、そのまま５時間反応させて、コアシェル構造を有する着色微粒子分散体３Ｂを得た。
【０１７７】
比較例３
実施例３で、グリセリンを添加せずに着色微粒子を作成し、比較の着色微粒子分散体３を製造した。
【０１７８】
《耐溶剤性評価》
比較例の着色微粒子分散体各４ｇに対し、各々実施例と同じ水溶性有機溶剤を用い、濃度が同じになるよう、それぞれ各溶剤をゆっくり加え、良く攪拌した後、６０度で１日静置し、各分散体粒径（体積平均粒径）の変化率を計算した。また各実施例の着色微粒子分散体を同じ条件で静置したものについて同じデータをとった。
なお、粒径変化率は
６０℃１日後の粒径／元の粒径×１００（％）
で計算し、各粒径は、体積平均粒径であり、大塚電子製レーザー粒径解析システムを用いて測定した（ｎｍ）。
【０１７９】
また、ＴＥＭ写真の投影面積の平均値から得られた円換算平均粒径を、球形換算して体積平均粒径とその標準偏差を求め体積平均粒径で割ることで変動係数を求めた。
【０１８０】
【表２】

【０１８１】
本発明の製造方法により得られた着色微粒子は、粒径の分布を表す変動係数が小さく、また粒径の変化率が小さく分散液の安定性がよい。
【０１８２】
【発明の効果】
インクジェット用インクを調製する際に溶剤ショックによる粒子の凝集がなく、安定性がよいインクを形成出来る着色微粒子分散体の製造方法が提供できた。[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a colored fine particle dispersion useful as an aqueous ink, particularly an ink jet ink, and a method for producing the same.
[0002]
[Prior art]
`` Ink using colored polymer fine particles as recording material '' in which a water-dispersible resin is colored with an oil-soluble dye or a hydrophobic dye, for example, an oil-in-water dispersion of a mixture of a hydrophobic dye solution and vinyl polymer fine particles Inks and inks using emulsion polymerization or dispersion polymerization particles dyed with a dye are known. These are aqueous inks in which water is used as a continuous phase and colored vinyl polymer particles are used as a dispersed phase.
[0003]
These aqueous inks are prepared by preparing a colored fine particle dispersion in which colored fine particles are dispersed in an oil-in-water type, and mixing various components necessary as an ink based on the dispersion.
[0004]
In the inkjet ink, a water-soluble organic solvent is mixed at a predetermined ratio as one of these components for the purpose of preventing decapping, controlling viscosity and surface tension, and the like.
[0005]
Hitherto, in order to enhance the stability of the finely divided colored fine particles in an aqueous ink containing a water-soluble organic solvent, studies have been made from various aspects such as the composition of the dye and the polymer and the configuration of the dispersed particles.
[0006]
For example, Patent Document 1 discloses core-shell particles which are surface-crosslinked to improve solvent resistance, and Patent Document 2 describes polymer fine particles which are emulsifying and are crosslinked by urethane bonds. Have been. These increase the molecular weight of the resin by crosslinking, and improve the solvent resistance of the aqueous dispersion.
[0007]
However, on the other hand, when an aqueous dispersion resin (emulsion) is used for inks, paints and the like as one of the solvent resistances, in the case of mixing and contacting with a solvent (wetting agent) used for preventing decapping and the like, so-called It is described that solvent shock may occur and the dispersion system may be destroyed (Patent Document 3). Even if the molecular weight is increased by crosslinking as described above, the effect on this phenomenon is limited, and solvent resistance from this viewpoint is necessary and important.
[0008]
[Patent Document 1]
JP 2002-121417 A
[0009]
[Patent Document 2]
JP-A-8-218015
[0010]
[Patent Document 3]
JP-A-7-90218
[0011]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide an inkjet ink using an aqueous colored fine particle dispersion, which does not cause aggregation of particles due to solvent shock and can provide an inkjet ink having good stability over time. An object of the present invention is to provide a method for producing a dispersion.
[0012]
[Means for Solving the Problems]
The above object of the present invention is achieved by the following configurations.
[0013]
1. A step of dissolving the coloring material and the resin in the water-insoluble organic solvent, dispersing the coloring material and the resin in a mixture of water and a water-soluble organic solvent using an emulsifier, and then removing the water-insoluble organic solvent. A method for producing a colored fine particle dispersion, characterized by being formed through the following steps.
[0014]
2. 2. The method for producing a colored fine particle dispersion according to the above item 1, wherein the resin has a crosslinked structure.
[0015]
3. 3. The method for producing a colored fine particle dispersion according to the above item 2, wherein the crosslinked structure is introduced after the emulsification.
[0016]
4. 4. The method for producing a colored fine particle dispersion according to any one of the above items 1 to 3, wherein a polymerizable emulsifier is used.
[0017]
5. 5. A colored fine particle dispersion produced by the method for producing a colored fine particle dispersion according to any one of 1 to 4 above.
[0018]
6. 6. The colored fine particle dispersion according to the item 5, having a core-shell structure.
[0019]
7. 7. The colored fine particle dispersion according to the above item 5 or 6, wherein the volume average particle diameter of the colored fine particles is 10 to 100 nm.
[0020]
8. An aqueous ink comprising the colored fine particle dispersion according to any one of the above items 5 to 7.
[0021]
9. 9. The aqueous ink according to the item 8, which is an ink jet ink.
[0022]
10. An image forming method, wherein the aqueous ink described in the above item 9 is ejected as droplets from an inkjet head based on a digital signal and adheres to an ink receiver.
[0023]
The present invention relates to a method for producing a colored fine particle dispersion composed of a resin and a coloring material, which is useful as an aqueous ink, particularly an inkjet ink, in which an aqueous emulsion (dispersion) has reduced so-called solvent shock.
[0024]
In the case of producing an aqueous dispersion of colored fine particles composed of a resin and a coloring material, a method of dissolving the resin and the coloring material in an organic solvent, emulsifying and dispersing the dispersion in water as a dispersion medium, and further removing the organic solvent is known. I have.
[0025]
The colored fine particle dispersion thus obtained is a water-based aqueous dispersion of the resin encapsulating the coloring material, and various additives to the colored fine particle dispersion, such as polyhydric alcohols. It contains a wetting agent, a dispersant, an antifoaming agent such as a silicone type, a fungicide such as a chloromethylphenol type and / or a chelating agent such as EDTA, and an oxygen absorbent such as a sulfite. can get.
[0026]
Examples of the wetting agent include polyhydric alcohols such as ethylene glycol, propylene glycol, and diethylene glycol, and water-soluble organic solvents described below such as ethers and acetates thereof. It is blended in the ink in the range of 0.1 to 50% by mass for adjusting the tension.
[0027]
When mixing the water-soluble organic solvent as the wetting agent with the colored fine particle dispersion, an osmotic pressure is generated at the interface between the fine particles and the dispersion medium (water), which adversely affects the dispersion state of the particles. There are many. One of them is the so-called solvent shock, and the amount of the water-soluble organic solvent actually added and the mixing procedure are very careful. If this solvent shock is large, it affects the dispersion system, causing partial aggregation, which affects the dispersion stability of the aqueous ink.
[0028]
In the present invention, a water-soluble organic solvent is previously added to water when preparing an aqueous dispersion of colored fine particles in order to reduce the solvent shock. When this is emulsified, an emulsified state is obtained while a part of the water-soluble organic solvent is taken in the emulsified oil droplets.
[0029]
Since the water-soluble organic solvent is contained in the emulsified oil droplets in advance in the colored fine particle dispersion thus obtained, the rapid generation of osmotic pressure when the water-soluble organic solvent is added is suppressed, and the dispersion is stable. Deterioration can be prevented.
[0030]
However, since the water-soluble organic solvent is contained in the oil droplets, the emulsified oil droplets are soft, and thus the emulsified particles are easily fused together. In the present invention, it is preferable to introduce a crosslinked structure into the resin.
[0031]
The cross-linking is preferably introduced after emulsification, so that the resin can be penetrated into the resin of the water-soluble organic solvent in an amount sufficient to relieve the solvent shock.
[0032]
If cross-linking is introduced into the resin in advance, the solvent resistance of the resin (polymer) is improved, but the compatibility with the coloring material is impaired (phase separation occurs with the dye), or a water-insoluble organic solvent or a mixed aqueous solution is used. It also causes the compatibility (affinity) to be impaired with respect to the organic solvent. Therefore, the amount of the solvent that actually permeates and swells into the fine particles is limited.
[0033]
Further, in an ink using a dispersion of colored fine particles composed of a resin and a coloring material, the volume average particle diameter of the colored fine particles is preferably 5 nm or more and 200 nm or less, and most preferably 10 nm or more and 50 nm or less. If the molecular weight of the polymer is increased from the beginning, the viscosity of the polymer (solution) is increased, so that the emulsified particle size of the fine particle dispersion does not decrease. Crosslinking after emulsification is also effective for atomizing this.
[0034]
Accordingly, the colored fine particle dispersion according to the present invention is obtained by mixing a coloring material and a resin, dissolving the same in a water-insoluble organic solvent, and then emulsifying and dispersing in a mixed solution containing water and a water-soluble organic solvent using an emulsifier. Further, it is formed through a step of removing a water-insoluble organic solvent.
[0035]
Here, the water-insoluble organic solvent that dissolves the coloring material and the resin is a non-water-soluble organic solvent having a low boiling point (preferably 150 ° C. or less at atmospheric pressure, more preferably 100 ° C. or less) because it is easily removed later. Water-soluble organic solvents are preferred. The water-insoluble organic solvent is an organic solvent in which the solubility of the water-insoluble organic solvent in an aqueous solution at 25 ° C is at least 25%, preferably 15% or less. There is no particular limitation as long as it has these properties, but examples include ethyl acetate, methyl acetate, butyl acetate, diethyl ether, methyl ethyl ketone, toluene, xylene, cyclohexanone, n-butanol, n-amyl alcohol, methylene chloride, Chloroform and the like.
[0036]
Since these water-insoluble organic solvents are removed later, the amount used is not particularly strict, but is preferably 0.5 to 20 parts with respect to the amount of the resin or the coloring material.
[0037]
Further, a low-boiling water-soluble organic solvent, for example, acetone, methanol, alcohol, or the like may be appropriately mixed with these water-insoluble organic solvents to have a role of assisting the dissolution of the resin or coloring material.
[0038]
Further, as the water-soluble organic solvent to be mixed in the medium for mixing and emulsifying the coloring material and the resin, a high-boiling water-soluble organic solvent to be mixed at the time of preparing the ink described below is preferable, and In the step of removing the solvent, without removing, when the aqueous ink, the decap prevention, viscosity, can be used as a so-called wetting agent that can control the surface tension and the like, ethylene glycol, In addition to propylene glycol and diethylene glycol, for example, triethylene glycol, tetraethylene glycol, polyethylene glycol, glycerin, diethylene glycol diethyl ether, diethylene glycol mono n-butyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene Glycol monobutyl ether, methyl carbitol, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, diethyl carbitol, polyhydric alcohols such as triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether and the like. Ethers, acetates, N-methyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, triethanolamine, formamide, nitrogen-containing compounds such as dimethylformamide, and one or more dimethyl sulfoxides; Can be mentioned. The mixing amount of these water-soluble organic solvents with water at the time of the emulsification is in the range of 0.1 to 50% by mass, and more preferably 0.1 to 30% by mass.
[0039]
The resin (polymer) used in the present invention will be described.
The resin (polymer) used in the present invention has a number average molecular weight of from 500 to 100,000, particularly from 1,000 to 30,000, so that the film forming property after printing the ink, its durability and It is preferable from the viewpoint of suspension formability.
[0040]
As the Tg of the polymer, various types can be used, but it is preferable to use at least one polymer having a Tg of 10 ° C. or higher.
[0041]
In the present invention, generally known resins (polymers) can be used. For example, a polymer containing an acetal group as a main functional group, a polymer containing a carbonate group, a polymer containing a hydroxyl group, a polymer having an ester group, and the like, and particularly a polymer containing an acetal group, among which polyvinyl butyral and the like are preferable. .
[0042]
The above-mentioned polymer may have a substituent, and the substituent may have a linear, branched, or cyclic structure.
[0043]
Further, a polymer obtained by radical polymerization of a vinyl monomer having a polymerizable ethylenically unsaturated double bond is also preferably used. Ethylene, propylene, butadiene, vinyl chloride, vinylidene chloride, vinyl acetate, styrene, (meth) acrylates (for example, ethyl acrylate, n-butyl acrylate, t-butyl acrylate, hydroxyethyl acrylate, methyl methacrylate) , Isobutyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, stearyl methacrylate, benzyl methacrylate, phenyl methacrylate), radical polymerization of (meth) acrylic acid, etc., and acrylamides Styrene / ethyl acrylate or butyl acrylate, or copolymers such as styrene / ethyl hexyl methacrylate, and the like. There are a copolymer such as styrene / methacrylic acid ethylhexyl / hydroxyethyl acrylate. In these copolymers, a monomer component containing an active group such as [2-acetoacetoxyethyl methacrylate], triethylene glycol methacrylate, ethoxytriethylene glycol methacrylate, or glycidyl methacrylate was used in an amount of 10% by mass of the copolymer component. The following may be used, and a monomer having a hydrophilic group such as a sulfonic acid group, a phosphoric acid group, or a quaternary ammonium group, a monomer such as 2-acrylamido-2-methylpropanesulfonic acid, or diethylaminoethyl methacrylate may be used in an amount of 20% by mass. The following ratio may be used. Further, a plurality of resins may be mixed and used.
[0044]
The aqueous dispersion of the colored fine particles of the present invention is obtained by dissolving (or dispersing) the above-described resin and a coloring material (a pigment may be used, but a dye is preferred) in an organic solvent, and containing the water-soluble organic solvent. It is obtained by emulsifying and dispersing in water and then forming by a method of removing an organic solvent.For example, an aqueous dispersion of resin fine particles is previously formed by emulsion polymerization in water containing the water-soluble organic solvent, and this resin is formed. A method in which an organic solvent solution in which a dye is dissolved is mixed with the aqueous fine particle dispersion, and the dye is subsequently impregnated into the resin fine particles may be used.
[0045]
In the present invention, it is preferable that the colored fine particle dispersion formed in the presence of a water-soluble organic solvent has a crosslinked structure introduced into a resin. The crosslinking is preferably introduced after emulsification and after formation of the colored fine particle dispersion.
[0046]
In the present invention, in order to introduce a crosslinked structure into a resin after emulsification, a group that forms a crosslinked structure is introduced into a resin (polymer) molecule. For example, a resin (polymer) into which a group that forms a cross-linking structure is introduced in advance as the polymer, and after emulsification, reacts with a group that forms the cross-linking structure to form a cross-linkable compound (cross-linking agent). Contact and allow crosslinks to form. The group that forms a crosslinked structure may be a group that forms a crosslinked structure as a pendant group after the production of the copolymer resin, but a group that forms a crosslinked structure during polymerization of the copolymer may be introduced. The monomers can be previously mixed and copolymerized.
[0047]
For example, there is an isocyanate group as a group which forms a crosslinked structure. In order to introduce an isocyanate group into a polymer, a monomer having an isocyanate group in a molecule, for example, a monomer such as Karenz MOI (manufactured by Showa Denko) is used as an acrylate ester. And isocyanate groups are introduced into the polymer. The polymer having an isocyanate group formed in this manner is dissolved together with a dye in a solvent such as ethyl acetate to form an aqueous dispersion by dispersing in an aqueous medium. By treating with an amine, preferably a primary amine, the isocyanate groups in the polymer react with the amine to form ureido linkages and form three-dimensional crosslinks between the polymers.
[0048]
Embedded image

[0049]
Here, R 'represents a polymer residue to which an isocyanate group is bonded, and R "represents an amine residue (the same applies hereinafter).
[0050]
Among amines, diamines having two or more reaction points with isocyanate groups (for example, hexamethylenediamine, diethylenetriamine, etc.), and hydroxyl-containing amines, for example, aminopropanol, are preferably used as crosslinking agents. preferable. Among them, hydroxyl group-containing amines are preferable. For example, in the case of aminopropanol, an isocyanate group and an amino group in the polymer react with each other to form a ureido bond (carbamoylamino group), and a hydroxy group reacts with a urethane bond (carbamoyl group). Oxy group).
[0051]
When a polymer having such an isocyanate group is used, a compound such as 3-aminopropanol or hydroxyethylaminopropylamine can be used as a preferable crosslinking agent in addition to the primary amines.
[0052]
Embedded image

[0053]
Conversely, when the polymer has, for example, a hydroxyl group in a side chain, a multifunctional compound having, for example, a plurality of isocyanate groups may be reacted as a crosslinkable compound (crosslinking agent). Examples of such a combination include an acrylic resin containing hydroxyethyl acrylate (HEMA) having an active hydrogen such as a hydroxy group as a component, and a polyfunctional isocyanate such as Nippon Polyurethane Co., Ltd .: Coronate series, Sumitomo A similar urethane bond (carbamoyloxy bond) can be formed by reacting a cross-linking agent such as Desmodur series manufactured by Bayer AG, although the bonding mode is reversed from the viewpoint of the polymer.
[0054]
For convenience, these ureido bonds or urethane bonds are collectively referred to herein as urethane bonds.
[0055]
As described above, a compound having a plurality of active hydrogens for a functional group such as an isocyanate group may be used as a crosslinking agent, and when a polymer having an active hydrogen is used, a polyfunctional compound may be used. The compound may be used as a crosslinkable compound.
[0056]
Examples of the group (or reaction) for forming a cross-link include the following groups and reactions in addition to the urethane bond. The cross-linking reaction is a reaction between active hydrogen and a functional group that reacts with the compound.For a polymer having a functional group, a compound having a plurality of active hydrogens becomes a cross-linking agent, and conversely, has a active hydrogen. When a polymer is used, the polyfunctional compound serves as a crosslinking agent.
[0057]
For example, a polymer containing an epoxy group as a functional group (for example, a polymer containing glycidyl acrylate or the like) is used, and when an amine is used as a cross-linking agent, an imino group is formed to form a cross-link.
[0058]
Embedded image

[0059]
Here, R 'also represents a polymer residue, and R "represents an amine residue.
As these crosslinking agents, amines which can be used in the case of the polymer having the isocyanate group are preferably used.
[0060]
The cross-linking reaction further includes amide ester formation by a reaction between a carboxyl group and an oxazoline group.
[0061]
In the case of using a carboxyl group-containing polymer (for example, an acrylic resin having acrylic acid, methacrylic acid, or the like as a copolymer component), for example, Epocross WS series (an oxazoline group-containing water-soluble polymer) in order to increase the degree of polymerization of the polymer. (Nippon Shokubai)). An amide ester bond is formed as a crosslinked structure as described below. This increases the molecular weight and increases the solvent resistance.
[0062]
Embedded image

[0063]
Here, R 'also represents a polymer residue, and R "represents a crosslinking agent residue linked to a reactive oxazoline group.
[0064]
Alternatively, crosslinking may be performed by hydrazide formation. A hydrazide crosslinking agent having active hydrogen,
H ₂ NHNCO-R ″ -CONHNH ₂ (Here, R ″ represents a divalent group such as alkylene), for example, adipic hydrazide (ADH; manufactured by Kyowa Hakko) and the like, while it can react with such active hydrogen as a polymer. By using an acrylic polymer having a monomer component having a functional group such as a carbonyl group (eg, diacetone acrylamide; manufactured by Kyowa Hakko Co., Ltd.) as a resin for the colored fine particle dispersion, crosslinking by hydrazone bond can be prevented. Can be formed.
[0065]
Embedded image

[0066]
The crosslinking reaction is, for example, a reaction between active hydrogen and a functional group that reacts with the active hydrogen. The active hydrogen or the functional group may be present in either the resin or the crosslinking agent. Although the cross-linking reaction typically used is shown above, a cross-linking reaction other than the above may be used. For example, in addition to glycidyl methacrylate and the like, N-methylol acrylamide having an N-methylol group and the like are also considered to be monomers having a functional group.
[0067]
In addition to the above, a reaction component or a group that can perform a crosslinking reaction may be used in the polymer and the crosslinking agent, respectively.
[0068]
In the present invention, as a combination of a group forming a cross-linked structure and a cross-linking agent, the above-described groups are exemplified. However, the present invention is not limited thereto. Any substance that affects the solvent properties and swelling properties can be preferably used.
[0069]
Since a monomer having an active hydrogen such as a functional group such as the isocyanate group or the epoxy group, or a hydroxyl group or a carboxyl group is available, in the present invention, a radical between these monomers and the polymerizable vinyl monomer is used. A copolymer obtained by a polymerization method is preferred.
[0070]
The active hydrogen or the monomer component having a functional group is 0.1 to 30% by mass, preferably 0.3 to 15% by mass, respectively, depending on the cross-linking structure to be formed (that is, it differs depending on the type of the functional group and the cross-linking agent). It is contained in the range. If the amount is too small, the effect of the present invention is not obtained because the formation of cross-linking is small, and if the amount is too large, the interaction of the resin with the dye and the affinity for the solvent are greatly changed.
[0071]
Using a known method, these polymerizable vinyl monomers are radically copolymerized with the vinyl monomer having the functional group or active hydrogen to obtain an uncrosslinked polymer according to the present invention. After emulsification, this is treated with each crosslinkable compound (crosslinking agent) which reacts with a group which forms a crosslinked structure to form a crosslink, specifically, mixed with a dispersion, reacted, and crosslinked. Form a bond.
[0072]
In addition, it is preferable to introduce a component having a group having steric hindrance into the uncrosslinked resin (polymer) according to the present invention to suppress interparticle crosslinking during emulsification. The group having steric hindrance is preferably a group having hydrophilic and long-chain polyethylene oxide or polypropylene oxide in view of the stability of the particles, and for example, simultaneously contains a structure represented by the following general formula (1). Are preferred.
[0073]
General formula (1)
-(EO) _m -(PO) _n -(TO) _p -R
Here, EO represents an ethylene oxide group, PO represents a propylene oxide group, and TO represents a tetramethylene oxide group, each of which is randomly or block copolymerized. These ethylene oxide groups, propylene oxide groups, and further tetramethylene oxide groups represented by EO, PO, or TO may be further substituted. m, n, and p are each an integer from 0 to 500, 2 ≦ m + n + p ≦ 500, and R represents a hydrogen atom, a hydroxyl group or a substituent such as an alkyl group, an aryl group, or a heterocyclic group; Preferably, the group does not have any hydrogen. Preferred alkyl groups include straight-chain or branched alkyl groups having 1 to 22 carbon atoms such as methyl, ethyl and butyl, and also alicyclic groups such as cyclopropyl groups and cyclopentyl groups having 1 to 22 carbon atoms. There may be. These may be further substituted with another substituent, but the substituent is preferably a group having no active hydrogen. The aryl group is a group such as a phenyl group and a naphthyl group, and may be substituted with a substituent having no active hydrogen. Examples of the heterocyclic group include heterocyclic groups such as aziridine, pyrrolidine, furan, thiophene, pyrrole, pyrazole, imidazole, oxazole, thiazole, pyridine and pyridazine, but are not limited thereto. It is preferable that the compound does not have active hydrogen. Further, the compound may have a substituent, and the compound preferably does not have active hydrogen.
[0074]
The resin having a hydrophilic and sterically hindered group such as polyethylene oxide or polypropylene oxide represented by the general formula (1) is a resin having a functional group used for forming a crosslinked structure or a resin having active hydrogen. You may mix and use. However, it is preferable that the resin having a group such as polyethylene oxide or polypropylene oxide having hydrophilicity and steric hindrance is a resin having a functional group for forming a crosslinked structure or a resin having active hydrogen at the same time. It is preferable to have a uniform structure having these groups at the same time.
[0075]
The polyethylene oxide group and the polypropylene oxide group are hydrophilic groups, but are considered to three-dimensionally protect the surface of the prepared colored fine particles, thereby suppressing cross-linking between particles and suppressing aggregation, thereby stabilizing the fine particles. And a suitable dispersion can be obtained. It is thought that the effect of covering the particle surface is reduced with a group having too high hydrophobicity, but the effect of the present invention is reduced.
[0076]
In order to introduce the hydrophilic polyethylene oxide chain or polypropylene oxide chain into the polymer, it is preferable to copolymerize with the vinyl monomer using a vinyl monomer having a group represented by the general formula (1). Specific examples of these vinyl monomers include Blemmer series manufactured by NOF Corporation, typically Blemmer AME series (Blemmer AME-400, etc.), Blemmer PME series, (Blemmer PME-1000, Blemmer PME-4000, etc.). , Blemmer 50POEP-800B, Blemmer 55 PET series (such as Blemmer 55PET800), and Blemmer PP series (such as Blemmer PP800).
[0077]
Further, the group represented by R in the above-mentioned general formula (1), which is the terminal of these polyethylene oxide groups and polypropylene oxide groups, preferably does not contain active hydrogen. When it has active hydrogen, cross-linking between particles may occur due to a cross-linking agent having a functional group.
[0078]
Obtaining a resin (polymer) having these constituent components by radically copolymerizing a polymerizable vinyl monomer having a polyethylene oxide group or a polypropylene oxide group represented by the general formula (1) with another copolymerization component. However, it is preferable that a monomer component having a polyethylene oxide group or a polypropylene oxide group in the polymer component is contained in a proportion of 1 to 60% by mass, preferably 3 to 30% by mass. When the amount is small, the cross-linking reaction by the cross-linking agent occurs between the particles, so that aggregation is inevitable. In addition, when the amount is too large, the whole polymer becomes hydrophilic, so that the affinity with the coloring material is lowered, and phase separation or the like is caused, so that a stable fine particle dispersion is not formed or aggregation is unfavorably increased. .
[0079]
In the present invention, some examples of preferred resins (polymers) are shown in the examples.
[0080]
Next, the coloring material enclosed in the seed particles together with the resin (polymer) will be described.
[0081]
As the coloring material, any coloring material that can be dissolved or dispersed in the polymer can be used without particular limitation, and examples thereof include an oil dye, a disperse dye, a direct dye, an acid dye, and a basic dye. However, it is preferable to use an oil dye and a disperse dye from the viewpoint of good encapsulation. Particularly preferred specific examples of the disperse dye are shown below, but are not limited thereto. Particularly preferred specific examples include C.I. I. Disperse Yellow 5, 42, 54, 64, 79, 82, 83, 93, 99, 100, 119, 122, 124, 126, 160, 184: 1, 186, 198, 199, 204, 224 and 237; . I. Disperse Orange 13, 29, 31: 1, 33, 49, 54, 55, 66, 73, 118, 119 and 163; I. Disperse Red 54, 60, 72, 73, 86, 88, 91, 92, 93, 111, 126, 127, 134, 135, 143, 145, 152, 153, 154, 159, 164, 167: 1, 177 , 181, 204, 206, 207, 221, 239, 240, 258, 277, 278, 283, 311, 323, 343, 348, 356 and 362; I. Disperse Bio Red 33; C.I. I. Disperse Blue 56, 60, 73, 87, 113, 128, 143, 148, 154, 158, 165, 165: 1, 165: 2, 176, 183, 185, 197, 198, 201, 214, 224, 225 C., 257, 266, 267, 287, 354, 358, 365 and 368; I. Disperse Green 6: 1 and 9 and the like. On the other hand, the oily dye is not limited to the following, but particularly preferred specific examples include, for example, C.I. I. Solvent Black 3, 7, 27, 29 and 34; C.I. I. Solvent Yellow 14, 16, 19, 29, 56 and 82; C.I. I. Solvent Red 1, 3, 8, 18, 24, 27, 43, 51, 72, 73, 132 and 218; I. Solvent Violet 3; I. Solvent Blue 2, 11, and 70; I. Solvent Green 3 and 7; and C.I. I. Solvent Orange 2 and the like.
[0082]
It is also possible to use a pigment insoluble in water or various organic solvents dispersed in a polymer medium.
[0083]
As the pigment that can be used in the present invention, conventionally known organic and inorganic pigments can be used. For example, azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, and chelated azo pigments; and phthalocyanine pigments, perylene and perylene pigments; Dye lakes such as cyclic pigments, basic dye lakes, and acid dye lakes; organic pigments such as nitro pigments, nitroso pigments, aniline black and daylight fluorescent pigments; and inorganic pigments such as carbon black.
[0084]
Specific organic pigments are exemplified below.
Pigments for magenta or red include C.I. I. Pigment Red 2, C.I. I. Pigment Red 3, C.I. I. Pigment Red 5, C.I. I. Pigment Red 6, C.I. I. Pigment Red 7, C.I. I. Pigment Red 15, C.I. I. Pigment Red 16, C.I. I. Pigment Red 48: 1, C.I. I. Pigment Red 53: 1, C.I. I. Pigment Red 57: 1, C.I. I. Pigment Red 122, C.I. I. Pigment Red 123, C.I. I. Pigment Red 139, C.I. I. Pigment Red 144, C.I. I. Pigment Red 149, C.I. I. Pigment Red 166, C.I. I. Pigment Red 177, C.I. I. Pigment Red 178, C.I. I. Pigment Red 222 and the like.
[0085]
Examples of orange or yellow pigments include C.I. I. Pigment Orange 31, C.I. I. Pigment Orange 43, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 15, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 94, C.I. I. Pigment Yellow 138 and the like.
[0086]
Examples of green or cyan pigments include C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 2, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 16, C.I. I. Pigment Blue 60, C.I. I. Pigment Green 7 and the like.
[0087]
The average particle size of the pigment dispersion used in the ink of the invention is preferably from 10 to 200 nm, more preferably from 10 to 150 nm, even more preferably from 10 to 100 nm. If the average particle diameter of the pigment dispersion exceeds 150 nm, the glossiness of an image recorded on a glossy medium is deteriorated, and the transparency of an image recorded on a transparency medium is significantly deteriorated. Further, when the average particle size of the pigment dispersion is less than 10 nm, the stability of the pigment dispersion tends to deteriorate, and the storage stability of the ink tends to deteriorate.
[0088]
The particle size of the pigment dispersion can be measured by a commercially available particle size measuring device using a light scattering method, an electrophoresis method, a laser Doppler method, or the like. In addition, it is also possible to obtain a particle image using a transmission electron microscope for at least 100 particles or more and to perform a statistical process on the image using image analysis software such as Image-Pro (manufactured by Media Cybernetics). It is possible.
[0089]
Metal complex dyes such as those disclosed in JP-A-9-277693, JP-A-10-20559, and JP-A-10-30061 can also be used as coloring materials. For example, dyes represented by formulas (I) and (II) described in JP-A-10-20559 can be used.
[0090]
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[0091]
In the general formula (I), X ¹ Represents a group of atoms having a structure capable of forming at least a bidentate coordination bond with a metal ion; ¹ Is an aromatic hydrocarbon ring, a 5- or 6-membered heterocyclic ring, or -L ⁴ = Y ² And Y ² Represents a 5- or 6-membered nitrogen-containing heterocyclic ring. L ¹ , L ⁴ Represents a substituted or unsubstituted methine group and a nitrogen atom; ² , L ³ Represents a substituted or unsubstituted methine group. M represents a metal ion, X ¹ And at least a bidentate coordination bond with the group of atoms formed by m represents an integer of 0, 1, 2 or 3, and n1 represents an integer of 1, 2 or 3. In the general formula (II), X ³ , Y ³ , M and n2 are each X ¹ , Y ¹ , M and n1.
[0092]
Further, specific examples thereof include the following dyes.
[0093]
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[0094]
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[0095]
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[0096]
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[0097]
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[0098]
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[0099]
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[0100]
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[0101]
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[0102]
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[0103]
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[0104]
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[0105]
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[0106]
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[0107]
In the present invention, these coloring materials are mixed and dissolved together with the polymer and the water-insoluble organic solvent, and in an aqueous medium containing water and the water-soluble organic solvent, emulsified and dispersed using an emulsifier. Thereafter, the organic solvent and the like are distilled off to obtain a colored fine particle dispersion before crosslinking.
[0108]
Examples of the emulsifier that can be used for emulsification include ordinary nonionic emulsifiers, for example, polyoxyethylene ocalkyl ethers such as polyoxyethylene lauryl ether; for example, polyoxyethylene such as polyoxyethylene nonylphenyl ether. Alkyl phenyl ethers; sorbitan higher fatty acid esters such as sorbitan monolaurate;
Examples of anionic emulsifiers include higher fatty acid salts such as sodium oleate; alkyl aryl sulfonates such as sodium dodecylbenzenesulfonate; alkyl sulfate salts such as sodium lauryl sulfate; and polyoxyethylene lauryl Polyoxyethylene alkyl ether sulfates such as sodium ether sulfate; alkyl sulfosuccinates such as sodium dioctyl sulfosuccinate and derivatives thereof can be used.
[0109]
Further, it is preferable to use a polymerizable emulsifier (reactive emulsifier) instead of or in addition to the emulsifier.
[0110]
The reactive emulsifier is not particularly limited as an anionic emulsifier or a nonionic emulsifier. For example, an emulsifier having a radical polymerizable unsaturated group such as a (meth) allyl group, a (meth) acryl group, and a styryl group may be used alone. Or in combination of two or more.
[0111]
The reactive emulsifier is not particularly limited as an anionic emulsifier or a nonionic emulsifier. For example, an emulsifier having a radical polymerizable unsaturated group such as a (meth) allyl group, a (meth) acryl group, and a styryl group may be used alone. Or in combination of two or more.
[0112]
Examples of such an anionic reactive emulsifier include reactive emulsifiers represented by the following general formulas (2) to (5).
[0113]
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[0114]
Where R ² Is hydrogen, methyl, R ³ Is an alkyl, alkenyl, aryl or aralkyl group having 6 to 18 carbon atoms, R ⁴ Is hydrogen or a methyl group, R ⁵ Is an alkyl group, alkenyl group, aryl group or aralkyl group having 6 to 18 carbon atoms, X is a single bond or a methylene group, M is an alkali metal, m is a natural number of 1 to 50, n is a natural number of 1 to 50, and q is It is 0 or 1.
[0115]
Specific examples of the anionic reactive emulsifier represented by the general formula (2) include, for example, “Adecaria Soap SE-10N”, “Adecaria Soap SE-20N”, and “Adecaria Soap SE-30N” ( As described above, as specific examples of the anionic reactive emulsifier represented by the general formula (3), "Aqualon HS-05", "Aqualon HS-10", and "Aqualon HS-10" Aqualon HS-20 "and" Aqualon HS-30 "(all manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.). Specific examples of the anionic reactive emulsifier of the general formula (4) include, for example," Latemul ". S-120 "," Latemul S-120A "," Latemul S-180 "," Latemul S-180A "(all manufactured by Kao Corporation)," Eleminor JS-21 "(all manufactured by Sanyo Chemical Industries ( ) Ltd.). Examples of the specific examples of the anionic reactive emulsifier of the general formula (5) include, for example, "Ann Krytox MS-60" (manufactured by Nippon Emulsifier Co.).
[0116]
Other anionic reactive emulsifiers include, for example, alkyl alkenyl succinate salt-based reactive emulsifiers such as "Latemul ASK" (manufactured by Kao Corporation); and "Eleminor RS-30" (manufactured by Sanyo Chemical Industries, Ltd.). ) And other polyoxyalkylene (meth) acrylate sulfate ester-based reactive emulsifiers; for example, polyoxyalkylene alkyl ether aliphatic esters such as "RA-1120" and "RA-2614" (all manufactured by Nippon Emulsifier Co., Ltd.). Saturated dicarboxylic ester salt-based reactive emulsifier; for example, (meth) acrylic acid sulfoalkyl ester salt-based reactive emulsifier such as "ANTOX MS-2N" (manufactured by Nippon Emulsifier Co., Ltd.); dihydroxyalkyl (meth) acrylate phthalate Sulfate-based reactive emulsifier; for example, “H-3330PL” (Daiichi Kogyo Seiyaku ( )), And mono- or di (glycerol-1-alkylphenyl-3-allyl-2-polyoxyalkylene ether) phosphate ester-based reactive emulsifiers. Reactive emulsifiers represented by the general formulas (6) and (7) can be mentioned.
[0117]
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[0118]
Where R ² Is hydrogen, methyl, R ³ Is an alkyl group having 6 to 18 carbon atoms, m is a natural number of 1 to 50, alkenyl group, aryl group or aralkyl group, R ⁴ Is hydrogen or a methyl group, X is a single bond or a methylene group, and M is an alkali metal.
[0119]
Specific examples of the nonionic reactive emulsifier represented by the general formula (6) include, for example, “Adecaria Soap NE-10”, “Adecaria Soap NE-20”, and “Adecaria Soap NE-30” (the above) Examples of the nonionic reactive emulsifier represented by the general formula (6) include “AQUALON RN-10”, “AQUALON RN-20”, and “AQUALON RN”. -30 "and" AQUALON RN-50 "(both manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and others, for example," RMA-564 "and" RMA-568 "(both manufactured by Nippon Emulsifier Co., Ltd.) Polyoxyalkylene alkyl phenyl ether (meth) acrylate-based reactive emulsifiers; for example, polyoxyalkylene alkyl phenyl ethers such as "RMA-1114" (manufactured by Nippon Emulsifier Co., Ltd.) Examples thereof include a ter (meth) acrylate-based reactive emulsifier.
[0120]
The amount of the reactive emulsifier to be used is generally 0.1 to 30 parts by mass, preferably 2 to 25 parts by mass, particularly preferably 3 to 20 parts by mass, per 100 parts by mass of the total polymer.
[0121]
These emulsifiers form a stable electric double layer in the vicinity of the particles and, at the same time, have a reactivity with the resin. .
[0122]
These coloring materials and colored fine particles made of the resin can be produced by various emulsification methods. Various methods can be used as the emulsification method. Examples of these are summarized in, for example, page 86 of "Progress and Application Development of Functional Emulsifiers / Emulsification Technology". In the present invention, it is particularly preferable to use an emulsifying and dispersing apparatus using ultrasonic waves, high-speed rotational shearing, and high pressure.
[0123]
In emulsification and dispersion by ultrasonic waves, two types, a so-called batch type and a continuous type, can be used. The batch method is suitable for producing a relatively small amount of sample, and the continuous method is suitable for producing a large amount of sample. In the continuous method, for example, an apparatus such as UH-600SR (manufactured by SMT Co., Ltd.) can be used. In the case of such a continuous system, the irradiation time of the ultrasonic wave can be obtained by (dispersion chamber volume / flow rate × circulation number). In the case where there are a plurality of ultrasonic irradiation devices, it is determined as the sum of the respective irradiation times. The ultrasonic irradiation time is practically 10,000 seconds or less. In addition, if it is required to be 10,000 seconds or more, the load of the process is large, and in practice, it is necessary to shorten the emulsification dispersion time by reselection of the emulsifier. Therefore, 10,000 seconds or more are not necessary. More preferably, it is 10 seconds or more and 2000 seconds or less.
[0124]
Examples of the emulsifying and dispersing apparatus using high-speed rotational shear include disperser mixers as described on pages 255 to 256 of "Progress of functional emulsifiers and emulsifying technology and application development CMC", and pages 251 Such a homomixer, an ultramixer described on page 256, and the like can be used. These types can be properly used depending on the liquid viscosity at the time of emulsification and dispersion. In these high-speed shearing emulsifying and dispersing machines, the rotation speed of the stirring blade is important. In the case of a device having a stator, the clearance between the stirring blade and the stator is usually about 0.5 mm and cannot be extremely narrow, so that the shear force mainly depends on the peripheral speed of the stirring blade. If the peripheral speed is 5 m / S or more and 150 m / S or less, it can be used for emulsification / dispersion of the present invention. If the peripheral speed is low, it is often impossible to achieve a small particle size even if the emulsification time is extended, and it is necessary to increase the performance of the motor extremely to achieve 150 m / S. More preferably, it is 20 to 100 m / s.
[0125]
In emulsification and dispersion by high pressure, LAB2000 (manufactured by SMT Co., Ltd.) can be used, but the emulsification / dispersion ability depends on the pressure applied to the sample. Pressure is 10 ⁴ kPa-5 × 10 ⁵ The range of kPa is preferable. Further, emulsification / dispersion may be performed several times as needed to obtain a target particle size. If the pressure is too low, the target particle size cannot be achieved in many cases even if emulsification and dispersion are performed many times. ⁵ In order to make the pressure kPa, a large load is applied to the apparatus, which is not practical. More preferably, 5 × 10 ⁴ kPa ~ 2 × 10 ⁵ The range is kPa.
[0126]
These emulsifying / dispersing devices may be used alone, but may be used in combination as needed. A colloid mill, a flow jet mixer, etc. alone cannot achieve the object of the present invention, but in combination with the apparatus of the present invention, it is possible to enhance the effects of the present invention such as enabling emulsification and dispersion in a short time. is there.
[0127]
In the present invention, the oil-soluble dye was dissolved and mixed in an organic solvent such as ethyl acetate together with the polyethylene oxide group or the polypropylene oxide group, and a copolymer resin having a group forming a crosslinked structure such as an isocyanate group. Thereafter, by the dispersing device, in an aqueous medium containing water and the water-soluble organic solvent, emulsified and dispersed, after removing the solvent to form an aqueous dispersion containing the water-soluble organic solvent, As a cross-linking agent, an amine compound which reacts with the group forming the cross-linked structure, such as diethylene triamine or 3-aminopropanol, is mixed with an emulsified and dispersed aqueous dispersion to cross-link. To promote the reaction, for example, if necessary, the aqueous dispersion is warmed in the range of 40-90 ° C. and left for a sufficient amount of time (depending on the crosslinks formed, It is also preferable to allow the reaction to take place over several hours) to allow the crosslinking reaction inside the fine particles to be sufficiently performed.
[0128]
When the reaction is relatively slow, these crosslinking agents may be mixed and dissolved together with a polymer and a dye, and then emulsified and dispersed.
[0129]
Here, the aqueous dispersion refers to a dispersion in which the coloring fine particles are dispersed in a medium in which the water-soluble organic solvent mainly containing water is mixed, and a dispersion in which the proportion of water in the medium is 50% or more. Good, water-based ink has the same meaning.
[0130]
The colored fine particle dispersion according to the present invention is characterized in that the colored fine particle dispersion containing the coloring material and the resin (polymer) is used as seed particles, and a polymerizable material is added thereto, polymerized, and further subjected to seed polymerization to obtain a core-shell structure. Is preferred.
[0131]
As a method of adding a polymerizable material and performing seed polymerization on the seed particles, after forming the dispersion of colored fine particles containing a coloring material and a resin, a polymerizable unsaturated double bond is used as the polymerizable material. In the present invention, a method is preferred in which a monomer having the formula (1) is added, emulsion polymerization is carried out in the presence of an activator, and the emulsion is simultaneously deposited on the surface of the colored fine particles serving as seed particles. When formed in this manner, if preferred, the post-added monomer having a polymerizable unsaturated double bond is polymerized on the seed particles to form a polymer shell.
[0132]
Colored fine particles composed of a colorant and a resin are used as seed particles, and monomers having a polymerizable unsaturated double bond to be subsequently added thereto and polymerized on the seed particles include ethylene, propylene, butadiene, vinyl chloride, and vinylidene chloride. , Vinyl acetate, styrene, (meth) acrylic esters, (meth) acrylic acid, etc., compounds selected from acrylamides, etc., styrene, ethyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylic (Meth) acrylic esters such as ethylhexyl acid are preferred, and in addition to these monomers, monomers having a polymerizable unsaturated double bond containing a hydroxyl group in the molecule, for example, hydroxyethyl (meth) acrylate Such as hydroxyalkyl (meth) acrylate or polymerizable polymer having hydroxyl group The monomer having a double bond can be copolymerized with a monomer having a maximum of 50% of the other monomers having an ethylenically unsaturated double bond in the post-addition of the raw material monomer, and the copolymerization can improve the stability of the particles. It is preferable for obtaining.
[0133]
Preferred examples of such a copolymer include styrene / 2-hydroxyethyl methacrylate and styrene / 2-hydroxyethyl acrylate.
[0134]
Further, for reasons such as increasing the stability of the shell, ethylenic acid containing a dissociable group having a pKa value of 3 to 7 such as a monomer containing a carboxylic acid such as acrylic acid or methacrylic acid or a monomer containing a sulfonic acid. Unsaturated monomers may be used up to 10% of the copolymerization component. By using these monomer components for shell formation, the stability of the aqueous dispersion of the core / shell colored fine particles is improved.
[0135]
In addition, it is preferable to include a monomer having a polymerizable unsaturated double bond having a functional group at a maximum of 50% and react with the cross-linking agent, and to perform cross-linking after shell formation. For example, the vinyl monomer containing an isocyanate group, an epoxy group, or the like, the vinyl monomer containing a carboxyl group that reacts with an oxazoline group, or a hydrazide crosslinking agent having an active hydrogen, for example, the adipic acid hydrazide (ADH; Kyowa Hakko) Is formed by using a vinyl monomer having a group capable of undergoing a cross-linking reaction. Thereby, a crosslinking reaction can be caused by the crosslinking agent after the shell is formed.
[0136]
When cross-linking is introduced into the shell, a polyfunctional vinyl monomer such as ethylene glycol dimethacrylate, ethylene glycol, and a monomer having a polymerizable unsaturated double bond such as the above-mentioned vinyl acetate, styrene, and (meth) acrylates. A shell may be formed using glycol diacrylate, divinylbenzene, or the like as a copolymerization component, and a three-dimensional crosslinking reaction can be caused in the shell at the same time as or after the shell is formed.
[0137]
In the present invention, the amount of the polymer used in the shell is 5% by mass or more and 95% by mass or less of the total amount of the polymer. If the amount is less than 5% by mass, the thickness of the shell is insufficient, and a part of the core containing a large amount of the coloring material tends to appear on the particle surface. On the other hand, if the amount of the polymer in the shell is too large, the ability of the core to protect the coloring material tends to be reduced. More preferably, the content is 10% by mass or more and 90% by mass or less.
[0138]
Seed polymerization for shell formation is a continuous reaction from the colored fine particle dispersion, and the dispersion medium contains the water-soluble organic solvent. May be added within the range.
[0139]
The total amount of the coloring material is preferably 20% by mass or more and 1000% by mass or less based on the total amount of the polymer. If the amount of the coloring material is too small as compared with the polymer, the image density after ejection will not increase, and if the amount of the coloring material is too large, sufficient protection of the polymer will not be obtained.
[0140]
The colored fine particles of the colored fine particle dispersion according to the present invention thus formed have an average particle size in terms of volume of 10 to 100 nm, preferably 20 to 80 nm, and are stable in this particle size range. And at the same time, have excellent stability when used as an ink.
[0141]
Due to the cross-linking reaction, the dye-containing core introduces too much cross-linking within a range that does not cause phase separation with the colorant, and the shell is preferably the outermost surface. It is necessary to introduce crosslinks within an appropriate range such that interparticle crosslinking does not occur by the introduction of.
[0142]
In addition, the shell contains, as a monomer component for forming a shell, a group that forms a crosslink such as a polyfunctional vinyl monomer or a group that forms a crosslink bond together with a crosslinker in order to suppress crosslinkage between particles. As described above, it is also preferable to introduce a component having a group having steric hindrance, such as polyethylene oxide or polypropylene oxide, in addition to the monomer component to suppress interparticle crosslinking.
[0143]
Since the individual particle diameter is very small, 100 nm or less, the method of analysis is limited from the viewpoint of resolution as to whether the formed colored fine particle dispersion is actually core-shelled. TEM, TOF-SIMS, or the like can be applied as an analysis method for this purpose. When observing the core-shelled fine particles by TEM, the dispersion can be applied onto a carbon support film, dried, and observed. The observation image of the TEM shows that the contrast difference is small only with the kind of polymer which is an organic substance. Therefore, in order to evaluate whether or not the polymer is core-shell, fine particles were osmium tetroxide, ruthenium tetroxide, chlorosulfonic acid / uranyl acetate, It is necessary to dye using silver sulfide or the like. The fine particles of only the core are stained and observed with a TEM, and compared with those provided with a shell. Further, after mixing the fine particles provided with the shell and the fine particles not provided with the shell, dyeing is performed, and it is confirmed whether or not the ratio of the fine particles having different dyeing degrees matches the presence or absence of the shell.
[0144]
In a mass spectrometer such as TOF-SIMS, it is confirmed that by providing a shell on the particle surface, the amount of coloring material near the surface is smaller than when only the core is used. When there is an element not contained in the core shell polymer in the coloring material, it is possible to confirm whether a shell having a small coloring material content is provided by using the element as a probe.
[0145]
That is, the coloring material content (concentration) is determined by first measuring the total amount of ions having a mass number of 1 to 1000 on the surface of each fine particle by TOF-SIMS, and is contained in the core-shell polymer contained in the dye. It can be determined from the ratio to the total amount of ions derived from the elements not included. By this method, the content (density) of each dye can be measured by comparing the content of the coloring material with the content of the shell and the core that has not been subjected to core / shell formation. In TOF-SIMS, elemental analysis of several nm in the depth direction from the surface can be performed, so that core / shell fine particles as in the present invention can be analyzed.
[0146]
In the absence of such an element, the colorant content in the shell can be compared to that without the shell using a suitable dye.
[0147]
The core-shell formation can be more clearly observed by burying the core-shell particles in an epoxy resin, forming an ultrathin section with a microtome, and performing staining. As described above, when a polymer or a coloring material includes an element that can serve as a probe, the composition of the core-shell and the distribution amount of the coloring material to the core and the shell can be estimated by TOF-SIMS or TEM.
[0148]
In the present invention, the color material content (concentration) in the shell is 0.8 or less of the color material content (concentration) in the core that is not cored / shelled. It is preferably 0.5 or less, more preferably 0.2 or less (of course, it may be 0 or a value infinitely close to 0). As a result, the polymer core contains the main part of the coloring material, thereby contributing to maintaining its robustness and color tone, while the polymer shell reduces the stability of these fine particles containing the coloring material as an ink suspension. It also contributes to the increase of the color material on the media, the prevention of aggregation, the improvement of image quality, the robustness of the color material, and the preservation of color tone.
[0149]
In order to obtain the required particle size, it is important to optimize the formulation and select an appropriate emulsification method. The formulation differs depending on the coloring material and polymer used, but since it is a dispersion in water, it is generally necessary that the polymer constituting the shell has higher hydrophilicity than the polymer constituting the core. In addition, the coloring material contained in the polymer constituting the shell is preferably less than the polymer constituting the core as described above, and the coloring material also needs to be lower in hydrophilicity than the polymer constituting the shell. . The hydrophilicity and the hydrophobicity can be estimated using, for example, a solubility parameter (SP). As for the solubility parameter, its value, measurement and calculation method can be referred to from POLYMER HANDBOOK 4th edition (John Wiley & Sons, Inc.), page 675.
[0150]
The number average molecular weight of the polymer used in the core / shell is preferably from 500 to 100,000, particularly preferably from 1,000 to 30,000, from the viewpoint of film forming properties after printing, its durability and formability of the suspension.
[0151]
Further, a dispersion having a variation coefficient of the volume average particle diameter of 80% or less is preferable, and the fluctuation of the particle diameter with time is small. The coefficient of variation is more preferably 50% or less.
[0152]
The volume average particle diameter was determined by converting the average particle diameter in a circle, which was obtained from the average value of the projected area (determined for at least 100 particles) of a transmission electron microscope (TEM) photograph, into a spherical form. In addition, the volume average particle diameter and its standard deviation were determined, and the standard deviation was divided by the volume average particle diameter to obtain a coefficient of variation. Alternatively, the coefficient of variation can be determined using the dynamic light scattering method. For example, it can be determined using a laser particle size analysis system manufactured by Otsuka Electronics Co., Ltd., or a Zetasizer manufactured by Malvern.
[0153]
The coefficient of variation of the particle size is a value obtained by dividing the standard deviation of the particle size by the particle size. The larger the value, the wider the distribution of the particle size. When the coefficient of variation of the volume average particle size is 80% or more, the particle size distribution becomes very wide, and the surface properties between the particles vary, thereby easily causing aggregation of the particles. In addition, the aggregation of the particles easily causes light scattering of the coloring material on the medium, and also tends to cause deterioration in image quality.
[0154]
The thus-formed colored fine particle dispersion according to the present invention is preferably such that the polymer is incorporated in the polymer emulsion type aqueous ink of the present invention in an amount of 0.5 to 50% by mass as a total polymer amount. More preferably, it is blended in an amount of 0.5 to 30% by mass. When the amount of the polymer is less than 0.5% by mass, the ability to protect the coloring material is not sufficient, and when the amount exceeds 50% by mass, the storage stability of the suspension as ink deteriorates, Since the thickening of the ink and the aggregation of the suspension caused by the evaporation of the ink may cause the clogging of the printer head, it is preferable that the amount is within the above range.
[0155]
On the other hand, the coloring material is preferably contained in the ink in an amount of 1 to 30% by mass, more preferably 1.5 to 25% by mass. When the amount of the coloring material is less than 1% by mass, the print density is insufficient, and when the amount is more than 30% by mass, the temporal stability of the emulsion is reduced and the particle size tends to increase due to aggregation or the like. It is preferable to be within the range.
[0156]
The aqueous ink of the present invention is an aqueous medium mainly composed of water, and in the colored fine particle dispersion encapsulating the coloring material, conventionally known various additives, for example, wetting agents such as polyhydric alcohols, dispersants, It is prepared by adding a defoaming agent such as a silicone type, a fungicide such as a chloromethylphenol type and / or a chelating agent such as EDTA, and an oxygen absorbent such as a sulfite.
[0157]
The colored fine particle dispersion according to the present invention is emulsified in the presence of a water-soluble organic solvent at the time of emulsification, and contains a water-soluble organic solvent. Since the osmotic pressure does not cause a sudden or local change (so-called solvent shock) and the dispersion particles hardly cause aggregation or sedimentation, the stability over time is excellent.
[0158]
The colored fine particle dispersion according to the present invention is also crosslinked with a resin and has high solvent resistance, so that it can be used in the presence of a wetting agent such as the polyhydric alcohol (which has an effect of realizing a low surface tension). Is particularly high in stability and hardly causes aggregation.
[0159]
The wetting agent is the same as a water-soluble organic solvent such as ethylene glycol and propylene glycol, which coexists during the emulsification and preparation of the above-mentioned colored fine particle dispersion, and one or more of them are used as the wetting agent. can do. These water-soluble organic solvents can be used as a wetting agent in the ink, preferably in an amount of 0.1 to 50% by mass, and more preferably in an amount of 0.1 to 30% by mass.
[0160]
Further, the dispersant is not particularly limited, but the HLB value of 8 to 18 exhibits the effect as the dispersant and has the effect of suppressing the increase in the particle size of the dispersion. Is preferred.
[0161]
Commercial products can also be used as dispersants. Examples of such commercially available products include, for example, Kao Corporation's dispersant Demol SNB, MS, N, SSL, ST, P (trade name).
[0162]
The amount of the dispersant is not particularly limited, but is preferably 0.01 to 10% by mass in the ink of the present invention. If the compounding amount of the compound is less than 0.01% by mass, it is difficult to reduce the particle size of the suspension, and if it exceeds 10% by mass, the emulsion particle size increases, the emulsion stability decreases, and gelation occurs. There is a possibility that there is a possibility that it is within the above range.
[0163]
Moreover, there is no restriction | limiting in particular as said defoaming agent, A commercial item can be used. Examples of such commercially available products include KF96, 66, 69, KS68, 604, 607A, 602, 603, KM73, 73A, 73E, 72, 72A, 72C, 72F, 82F, 70, 71 manufactured by Shin-Etsu Silicone Co., Ltd. 75, 80, 83A, 85, 89, 90, 68-1F, 68-2F (trade name) and the like. The amount of these compounds is not particularly limited, but is preferably 0.001 to 2% by mass in the polymer emulsion type water-based ink of the present invention. If the compounding amount of the compound is less than 0.001% by mass, bubbles are easily generated at the time of ink preparation, and it is difficult to remove small bubbles in the ink. If it exceeds 2% by mass, the generation of bubbles is suppressed. In printing, repelling may occur in the ink and the printing quality may be degraded.
[0164]
The inkjet head using the aqueous ink for inkjet recording of the present invention may be of an on-demand type or a continuous type. Examples of the discharge method include an electro-mechanical conversion method (for example, a single-cavity type, a double-cavity type, a bender type, a piston type, a shared mode type, a shared wall type, etc.) and an electro-thermal conversion method (for example, thermal ink jet. , Or a bubble jet (R) type).
[0165]
In the image formation using the aqueous ink for inkjet recording of the present invention, for example, a printer or the like loaded with the aqueous ink for inkjet recording discharges the ink as droplets from an inkjet head based on a digital signal and attaches the ink to an ink receptor. Thus, for example, an ink jet print in which an ink jet recorded image is formed on an ink jet image recording medium is obtained.
[0166]
As the inkjet image recording medium, for example, any of plain paper, coated paper, cast-coated paper, glossy paper, glossy film, and OHP film can be used. Among them, for example, a so-called void layer having a porous layer formed thereon It is preferable that the recording medium has the following. The material or shape of the above-described support is not particularly limited. For example, the support may have a three-dimensional structure in addition to a sheet-like material.
[0167]
The aqueous ink obtained using the colored fine particle dispersion obtained by the production method of the present invention can be used not only as an ink for ink-jet recording, but also as an ink for writing implements such as a general fountain pen, a ball-point pen, and a felt-tip pen. is there. The colored fine particle dispersion of the present invention can be dried to obtain fine powder. The obtained powder can also be used for an electrophotographic toner.
[0168]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Synthesis Examples and Examples, but the present invention is not limited to the scope of these Examples.
[0169]
<< Resin synthesis 1 >>
A 0.3-liter four-neck separable flask was equipped with a dropping device, a thermometer, a nitrogen gas inlet tube, a stirrer, and a reflux condenser, and 20 g of dehydrated methyl ethyl ketone was poured into the flask and heated to 80 ° C. A monomer having a composition ratio shown in Table 1 was weighed so that the total amount was 100 g, and a mixed solution obtained by further adding 2 g of N, N'-azobisisovaleronitrile to the monomer was dropped into the flask over 2 hours. The reaction was performed at the same temperature for 5 hours. Thereafter, 80 g of methyl ethyl ketone was added thereto, followed by cooling to obtain a polymer solution of 50% by mass of the polymer.
[0170]
[Table 1]

[0171]
Blemmer PME-1000:
-(EO) _m -CH ₃ Methacrylate having (m ≒ 23)
Blemmer PME-4000:
-(EO) _m -CH ₃ Methacrylate having (m ≒ 90)
Here, EO is -CH ₂ CH ₂ Represents O-.
Blemmer G:
Glycidyl methacrylate
Made by Nippon Yushi.
HEMA: 2-hydroxyethyl methacrylate, ST: styrene, MMA: methyl methacrylate, SMA: stearyl methacrylate, Karenz MOI: 2-methacryloyloxyethyl isocyanate (manufactured by Showa Denko).
《Manufacture of colored fine particles》
Example 1 (Production of colored fine particles swollen with ethylene glycol as a water-soluble organic solvent)
2 g of isophorone diisocyanate and 0.1 g of dibutyltin dilaurate were added to 24 g of a liquid containing 12 g of the resin R1 shown in Table 1 and reacted at 40 ° C. for 30 minutes ((2) resin), followed by Clearmix CLM-0.8S (Made by M Technique Co., Ltd.) in a pot of 12 g of C.I. I. Solvent Yellow 162 ((1) dye) and 120 g of ethyl acetate were added and stirred to completely dissolve the dye. Further, 240 g of an aqueous solution containing 2% by mass of KH-05 (manufactured by Daiichi Kogyo) (3) emulsifier, and 30 g of ethylene glycol were added, and the mixture was emulsified at 12,000 rpm for 5 minutes while maintaining the temperature at 40 ° C. After removing ethyl acetate under reduced pressure at 40 ° C., 2-hydroxyethylaminopropylamine was added, and a crosslinking reaction was performed at 60 ° C. for 120 minutes to produce a colored fine particle dispersion 1.
[0172]
Comparative Example 1
In Example 1, the cross-linking reaction was carried out without adding ethylene glycol, and Comparative Colored Fine Particle Dispersion 1 was produced.
[0173]
Example 2 (Production of colored fine particles swollen with triethylene glycol mono-n-butyl ether as a water-soluble organic solvent)
In the method for producing the colored fine particles 1 of Example 1, instead of using 24 g of the liquid containing 12 g of the resin R1, 2 g of isophorone diisocyanate and 0.1 g of dibutyltin dilaurate and reacting at 40 ° C. for 30 minutes, Using R2, 10 g of triethylene glycol mono-n-butyl ether was used instead of 30 g of ethylene glycol. In addition, as a crosslinking agent, 2 g of epomate QX2 (manufactured by Japan Epoxy Resin) was added to the emulsified oil phase in advance, and after emulsification, a crosslinking reaction was performed at 80 ° C. for 120 minutes to prepare a colored fine particle dispersion 2.
[0174]
Comparative Example 2
The procedure of Example 2 was repeated up to the crosslinking reaction without adding triethylene glycol mono-n-butyl ether to prepare a comparative colored fine particle dispersion 2.
[0175]
Example 3 (Production of colored fine particles swollen with glycerin as a water-soluble organic solvent)
In the method for producing the colored fine particles 2 of Example 2, 12 g of the cyan dye FSB1504 was used as the dye, 30 g of glycerin was used instead of 10 g of triethylene glycol mono-n-butyl ether instead of using the resin R2. A colored fine particle dispersion 3 was prepared in the same manner except for the above.
[0176]
In addition, while keeping the colored fine particles 3 at 65 ° C., 3 g of MMA and 3 g of an aqueous solution containing 0.1 g of potassium persulfate are added over 1 hour, and the mixture is reacted for 5 hours to obtain a colored fine particle dispersion having a core-shell structure. 3B was obtained.
[0177]
Comparative Example 3
In Example 3, colored fine particles were prepared without adding glycerin, and a comparative colored fine particle dispersion 3 was produced.
[0178]
<< Solvent resistance evaluation >>
For each 4 g of the colored fine particle dispersion of the comparative example, the same water-soluble organic solvent as in the example was used, and each solvent was slowly added so that the concentration became the same, and after stirring well, the mixture was allowed to stand at 60 ° C. for 1 day. Then, the change rate of each dispersion particle size (volume average particle size) was calculated. In addition, the same data was obtained for the dispersions of the colored fine particles of each example which were allowed to stand under the same conditions.
The particle size change rate is
Particle size after 1 day at 60 ° C./Original particle size × 100 (%)
Each particle size is a volume average particle size, and was measured using a laser particle size analysis system manufactured by Otsuka Electronics (nm).
[0179]
Further, the average particle diameter in terms of circle obtained from the average value of the projected area of the TEM photograph was converted into a sphere, and the volume average particle diameter and its standard deviation were obtained.
[0180]
[Table 2]

[0181]
The colored fine particles obtained by the production method of the present invention have a small coefficient of variation representing the particle size distribution, a small change rate of the particle size, and good dispersion stability.
[0182]
【The invention's effect】
The present invention provides a method for producing a colored fine particle dispersion capable of forming an ink with good stability without aggregation of particles due to a solvent shock when preparing an ink for inkjet.

Claims (10)

A step of dissolving the coloring material and the resin in a water-insoluble organic solvent, then emulsifying and dispersing the mixture in water and a water-soluble organic solvent using an emulsifier, and then removing the water-insoluble organic solvent. A method for producing a colored fine particle dispersion, characterized by being formed through the following steps. The method according to claim 1, wherein the resin has a crosslinked structure. The method for producing a colored fine particle dispersion according to claim 2, wherein the crosslinked structure is introduced after emulsification. The method for producing a colored fine particle dispersion according to any one of claims 1 to 3, wherein a polymerizable emulsifier is used. A colored fine particle dispersion produced by the method for producing a colored fine particle dispersion according to claim 1. The colored fine particle dispersion according to claim 5, having a core-shell structure. The colored fine particle dispersion according to claim 5, wherein the volume average particle diameter of the colored fine particles is 10 to 100 nm. An aqueous ink comprising the colored fine particle dispersion according to any one of claims 5 to 7. The aqueous ink according to claim 8, which is an ink jet ink. An image forming method, comprising discharging the aqueous ink according to claim 9 from an inkjet head as droplets based on a digital signal and attaching the droplets to an ink receiver.