JP2004115549A - Ink set, image formation method, recording unit, and ink jet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink set which can form a high-grade color image having a high density, excellent rubbing resistance, and marker resistance and reduced in bleed at the boundary among images of different colors and to provide articles related thereto. <P>SOLUTION: The ink set has a first ink and a second ink of a color different from that of the first ink and forms an image from these inks. The first ink contains a modified pigment prepared by chemically bonding organic groups to the surfaces of pigment particles. The organic groups contain a reaction product of functional groups chemically bonded to the surfaces directly or through other atomic groups with a copolymer of an ionic monomer with a hydrophobic monomer. The second ink is a water-based ink which contains a colorant and worsens the dispersion stability of the pigment in the first ink when mixed with the first ink. <P>COPYRIGHT: (C)2004,JPO

Description

（但し、上記構造式（１）中、Ｒはアルキルを表し、ｎは整数を表す。）
【００７５】

（但し、上記構造式（２）中、Ｒはアルキル基を表し、ｎは整数を表す。）
【００７６】

（但し、上記構造式（３）中、Ｒは水素原子又はアルキル基を表し、ｍ及びｎは、それぞれ整数を表す。）
【００７７】

（但し、上記構造式（４）中、ｍ及びｎは、それぞれ整数を表す。）
【００７８】
上記したような構成を有する本発明にかかるインクは、筆記具用インクや、インクジェット用インクに用いることができる。インクジェット記録方法としては、インクに力学的エネルギーを作用させ、液滴を吐出する記録方法、及びインクに熱エネルギーを加えてインクの発泡により液滴を吐出するバブルジェット（登録商標）記録方法があるが、本発明のインクは、これらの記録方法に特に好適である。
【００７９】
ところで、本発明にかかるインクを、上記したようなインクジェット記録に用いる場合には、該インクが、インクジェット記録ヘッドから良好に吐出できる特性を有することが好ましい。このため、インクジェット記録ヘッドからの吐出性という観点からは、インクの特性が、例えば、その粘度が１〜１５ｍＰａ・ｓ、表面張力が２５ｍＮ／ｍ以上、更には、粘度が１〜５ｍＰａ・ｓ、表面張力が２５〜５０ｍＮ／ｍとすることが好ましい。
【００８０】
又、インクの、記録媒体への浸透性を表わす尺度として、ブリストウ法によって求められるＫａ値がある。即ち、インクの浸透性を１ｍ^２あたりのインク量Ｖで表わすと、インク滴を吐出してから所定時間ｔが経過した後における、インクの記録媒体への浸透量Ｖ（ｍＬ／ｍ^２＝μｍ）は、下記に示すブリストウの式によって示される。
Ｖ＝Ｖｒ＋Ｋａ（ｔ−ｔｗ）^１／２
【００８１】
ここで、インク滴が記録媒体表面に付着した直後には、インクは、記録媒体表面の凹凸部分（記録媒体の表面の粗さの部分）において吸収されるのが殆どで、記録媒体内部へは殆ど浸透していない。その間の時間がコンタクトタイム（ｔｗ）であり、コンタクトタイムに記録媒体の凹凸部に吸収されたインク量がＶｒである。そして、インクが付着した後、コンタクトタイムを超えると、該コンタクトタイムを超えた時間、即ち、（ｔ−ｔｗ）の１／２乗べきに比例した分だけ記録媒体への浸透量が増加する。Ｋａは、この増加分の比例係数であり、浸透速度に応じた値を示す。そして、Ｋａ値は、ブリストウ法による液体の動的浸透性試験装置（例えば、商品名：動的浸透性試験装置Ｓ；東洋精機製作所製）等を用いて測定可能である。
【００８２】
そして、前記した本発明の各実施態様にかかるインクにおいて、このＫａ値を１．５（ｍｌ／ｍ^２／ｍｓｅｃ^１／２）未満とすることは、記録画像品質をより一層向上させる上で好ましく、更に好ましくは、０．２以上１．５（ｍｌ／ｍ^２／ｍｓｅｃ^１／２）未満とすることである。即ち、Ｋａ値が１．５（ｍｌ／ｍ^２／ｍｓｅｃ^１／２）未満である場合に、インクの記録媒体への浸透過程の早い段階で固液分離が起こり、フェザリングが極めて少ない高品質な画像を形成することができる。尚、本発明におけるブリストウ法によるＫａ値は、普通紙［例えば、キヤノン（株）製の、電子写真方式を用いた複写機やページプリンタ（レーザビームプリンタ）やインクジェット記録方式を用いたプリンタ用として用いられるＰＢ紙や、電子写真方式を用いた複写機用の紙であるＰＰＣ用紙等］を記録媒体として用いて測定した値である。又、測定環境としては、通常のオフィス環境、例えば、温度２０〜２５℃、湿度４０〜６０％を想定している。
【００８３】
［分析方法］
以下、顔料にカーボンブラックを用いた水性顔料インクを例にとって、本発明にかかるインクの特性を評価する際に用いた、分析方法及び評価方法について説明する。しかし、これによって本発明にかかるインクに使用する顔料が、特に限定されるわけではない。本発明で使用する粒子表面が改質された顔料の、表面改質状態を分析する方法としては特に限定されず、通常考えられ得る方法を用いて分析を行うことができる。好ましくは、ＥＳＣＡやＴＯＦ−ＳＩＭＳ等で、カーボンブラック等の顔料粒子表面に存在する有機基の結合状態を分析する方法が挙げられる。
【００８４】
カーボンブラック粒子の表面に結合している有機基の量等を測定する方法も特に限定されないが、例えば、下記の方法によって行なうことができる。先ず、前記表面改質したカーボンブラックを含むインクから、塩析若しくは凝析によってインク中から有機基で改質されたカーボンブラック粒子を含む固形分を分取することができる。そして、この方法によってインク中から取り出した固形分から、表面改質されたカーボンブラック（有機基が粒子表面に結合しているカーボンブラック）のみを高純度で分取するには、更に、カーボンブラック粒子表面に化学的に結合させた共重合体の良溶媒で、インク中から取り出したカーボンブラック等を洗浄、乾燥するといった方法を用いることができる。以下、更に詳細な、インク中から表面改質されたカーボンブラックを分取する方法、分取後、乾燥して得られた乾固物を測定用試料として用いることで行なう、表面改質されたカーボンブラック粒子表面に結合している有機基の量の測定、或いはフリーポリマーとしてインク中に存在していることのある該共重合体部分を含むセグメントの量を測定する分析方法について説明する。
【００８５】
先ず、分析に先だって、以下のようにして前処理を実施し、測定用試料を調製する。上記で説明した表面改質されたカーボンブラックを含むインクから、塩析若しくは凝析して沈澱物として得られる固形分を乾固させ、その後に、共重合体の良溶媒を用いて洗浄してから、該有機基が粒子表面に化学的に結合しているカーボンブラックのみの抽出処理を行う。その方法は、（１）塩析若しくは凝析、（２）沈澱物の洗浄、（３）乾固、（４）表面改質カーボンブラックのみの抽出、及び（５）乾燥、という一連の手順によって行うことができる。以下、順を追って説明する。
【００８６】
（１）インク中から、表面改質カーボンブラックを含む固形分を塩析若しくは凝析させる方法としては特に限定されず、例えば、（ａ）塩化ナトリウム、塩化カリウム等の塩で塩析させる、（ｂ）硝酸や塩酸等の酸を用いて凝析（酸析）させる、等の方法を用いることができる。この際、必要に応じて、塩析等の前工程として、例えば、限外濾過等を行ってもよい。
【００８７】
（２）上記塩析若しくは凝析等によって得られる固形分を純水で十分に洗浄する。特に、（１）に記載した（ｂ）の凝析を行う際には、洗浄後の濾液が中性になるまで十分に洗浄を行うことが好ましい。
【００８８】
（３）上記で得られる洗浄後の固形分は、オーブン等で充分に乾燥し、乾固物として取り出す。この際の乾燥条件等は特に限定されず、例えば、６０℃で２時間程度乾燥させればよい。
【００８９】
（４）上記（３）で得られる乾固物には、有機基がカーボンブラック粒子表面に化学的に結合しているカーボンブラック以外に、カーボンブラック粒子表面に化学的に結合していないフリーポリマー（顔料に物理吸着しているものも含む）が混入している可能性がある。そこで、（３）で得られた乾固物を、該共重合体の良溶媒を用いて洗浄することで、表面改質カーボンブラックを更に高純度に抽出する。上記において使用する、フリーポリマーの良溶媒は、共重合体の構造によって異なり、一概に限定できるものではないが、例えば、テトラヒドロフラン（ＴＨＦ）等は、汎用性のある良溶媒である。この場合、このような良溶媒を用いて繰り返して上記乾固物を洗浄し、固形分に混入している可能性のあるフリーポリマーの除去作業を繰り返すことが好ましい。
【００９０】
（５）上記したように共重合体部分を含むセグメントの良溶媒による洗浄によって、フリーポリマーの除去処理がなされた固形分は、最後にオーブン等で十分な乾燥処理を行って、残存水分や残存溶剤を揮発させて乾固物試料とする。乾燥の際に使用するオーブン等は特に限定されず、例えば、市販の真空乾燥機等を用いた乾燥を行えばよい。又、乾燥条件等についても、上記表面改質カーボンブラック乾固物から、十分に残存水や残存溶剤が除去できる条件であれば特に限定されない。例えば、数百Ｐａ以下の真空度で、６０℃×３時間程度で乾燥させればよい。
【００９１】
上記した（１）〜（５）の一連の方法によってインク中から取り出した表面改質カーボンブラック乾固物を測定用試料とし、該試料の重量変化を熱重量分析を用いて測定することで、カーボンブラック粒子表面に結合した有機基の結合量を定量的に測定することができる。この結果、表面改質カーボンブラック粒子の質量を基準として該カーボンブラックに化学的に結合している有機基の含有率の測定が可能となる。
【００９２】
この分別には、例えば液体クロマトグラフィーを用いることができる。又、上記（１）〜（３）までの一連の手順で得られた乾固物を測定用試料とし、該試料の重量変化を熱重量分析を用いて測定することで、カーボンブラック粒子表面に結合している有機基の他、フリーポリマー等のインク中の顔料を除く固形分の量を知ることができる。この結果、インク中に含まれている有機基とフリーポリマーとの総和に対する、有機基の割合を求めることができる。尚、インク中に、該共重合体以外の第２のポリマーが混在している場合に、インク中の、有機基とフリーポリマーとの総和に対する該有機基の割合を正確に算出するためには、該フリーポリマーのみの量を測定することが好ましい。その場合には、上記（４）の手順におけるカーボンブラックの洗浄液を、液体クロマトグラフィー等を用いて測定すれば、フリーポリマーのみの量を測定することができる。
【００９３】
上記で説明した、（１）塩析若しくは凝析、（２）沈澱物の洗浄、（３）乾固、（４）表面改質カーボンブラックのみの抽出、及び（５）乾燥という一連の手順によって得られる、表面改質カーボンブラックのみを含む乾固物試料中の、結合している有機基の含有率を測定する方法は特に限定されない。例えば、上記手順によって最終的に得られる充分に乾燥させたカーボンブラック乾固物を、熱重量分析（Ｔｈｅｒｍｏｇｒａｖｉｍｅｔｒｉｃ　Ａｎａｌｙｓｉｓ）等により測定し、その結果得られる熱重量分析重量減少率から、容易に求めることができる。以下、この際に行う熱重量分析について詳細に説明する。
【００９４】
上記方法によって測定される熱重量分析重量減少率は、表面改質カーボンブラック中におけるカーボンブラック粒子表面に導入された有機基の含有率となる。即ち、かかる熱重量分析重量減少率は下記式で与えられるが、熱重量分析前に高分子物質の良溶媒を用いて洗浄し、表面改質カーボンブラックのみを抽出した乾固物試料の重量に対する、１００〜７００℃まで昇温して行なった熱重量分析において生じる、カーボンブラック粒子表面に結合している有機基の脱着や燃焼等によって生じる重量減少量の割合である。
熱重量分析重量減少率＝Ａ／Ｂ×１００（％）
Ａ＝熱重量分析において１００〜７００℃まで昇温した際の重量減少量
Ｂ＝熱重量分析前における試料の重量
【００９５】
上記において行なう熱重量分析における分析条件等は特に限定されず、前処理や昇温速度等、通常の条件によって測定すればよい。測定装置としては、例えば、ＭＥＴＴＬＥＲ　ＴＯＬＥＤＯ社製のＴＧＡ熱重量測定装置、ＴＧＡ８５１ｅ／ＳＤＴＡ等を使用することができる。
【００９６】
更に、上記した熱重量分析重量減少率の測定方法を用いれば、本発明で用いる水性顔料インクに含まれる表面改質カーボンブラック等の顔料における、表面改質に用いた物質と顔料粒子との結合状態を知ることができる。即ち、本発明で使用する顔料である、例えば、カーボンブラック粒子表面には、有機基が化学的に結合されている。このため、カーボンブラック粒子表面の有機基は、上記高分子物質の良溶媒を用いた洗浄後も洗い流されることはなく、カーボンブラック粒子表面に安定に結合しているため、上記した抽出処理の有無にかかわらず、熱重量分析重量減少率は、ほぼ同じ値を示す。これに対して、一般的に用いられる樹脂分散型の顔料では、分散剤に用いられている水溶性樹脂がカーボンブラック（顔料）と化学的に結合しているわけではないので、分散に使用した樹脂の良溶媒によって洗浄すると、樹脂は洗い流されてしまうため、上記した抽出処理を行った場合と、処理を行わなかった場合とでは、熱重量分析重量減少率は大きく違ったものとなる。
【００９７】
このことから、本発明に好適に用いられる改質された顔料とは、該共重合体の良溶媒による洗浄の前後において、熱重量分析による重量減少率が変化しないか、或いは実質的に変化しないものとすることができる。ここで、洗浄の前後において熱重量分析による重量減少率が実質的に変化しないとは、重量減少率の洗浄前後における値の差が、例えば、７％未満、更には、５％以内であることを指す。
【００９８】
上記した熱重量分析を用いる以外にも、顔料粒子表面における、表面改質に用いた物質との結合状態を調べる方法がある。例えば、本発明で用いる表面改質したカーボンブラックを、先に述べたようにして塩析若しくは凝析した後に乾固させたカーボンブラック乾固物を測定用試料とし、かかる試料を、ＴＧ−ＧＣ−ＭＳ（熱重量分析−ガスクロマトグラフ−マススペクトル）、ＴＯＦ−ＭＳ（飛行時間型質量分析装置）、ＴＯＦ−ＳＩＭＳ（飛行時間型二次イオン質量分析）等とを組み合わせて分析する方法も好適である。これらの方法によって、カーボンブラック乾固物試料における表面改質に用いた物質の結合状態（吸着エネルギーの測定）、更には、カーボンブラック乾固物試料において、結合している有機基の、組成、分子量分布、更には結合ユニットを詳細に知ることができる。
【００９９】
＜第２のインク＞
本発明に係るインクセットは、上記で説明したような第１のインクと、該第１のインクとは色の異なる第２のインクとの組み合わせを有し、各々のインクを記録媒体に付与することによってカラー画像を記録媒体上に形成するためのものである。従って、例えば、第１のインクを、カーボンブラックを色材とする黒色インクとした場合には、第２のインクは、他のカラーインクとして構成することを要する。更に、第２のインクには、第１のインクと混合されたときに、第１のインク中の顔料の分散安定性を不安定化させる機能を有するインクを用いる。先にも述べたように、第１のインクを構成する顔料としては、カーボンブラックを用いることが好ましいため、通常、第２のインクには、カラーインクを用いる。以下、第２のインクとして使用できるインクについて、色材及び溶媒について説明し、その後、先に述べた第１のインク中の顔料の分散安定性を不安定化させる機能を有するインクとするための３つの態様について、それぞれ説明する。
【０１００】
［色材］
本発明にかかる第２のインクに用いることのできる色材としては、公知の染料や顔料を用いることができる。染料としては、例えば、酸性染料、直接染料、等を用いることができる。アニオン性染料としては、既存のものでも、新規に合成したものでも適度な色調と濃度を有するものであれば、大抵のものを用いることができる。又、これらのうち何れかを混合して用いることも可能である。
【０１０１】
本発明において、発色性等の点から特に好適に使用できるアニオン性染料としては、例えば、以下のものを挙げることができる。
【０１０２】
（イエロー用の色材）
Ｃ．Ｉ．ダイレクトイエロー　１、２、４、８、１１、１２、２６、２７、２８、３３、３４、３９、４１、４４、４８、５０、５８、８５、８６、８７、８８、８９、９８、１００、１１０、１３２、１３５、１４２、１４４
Ｃ．Ｉ．アシッドイエロー　１、３、４、７、１１、１２、１３、１４、１７、１９、２３、２５、２９、３４、３６、３８、４０、４１、４２、４４、５３、５５、６１、７６、７９、９８、９９
Ｃ．Ｉ．リィアクティブイエロー　１、２、３、４、６、７、１１、１２、１３、１４、１５、１６、１７、１８、２２、２３、２４、２５、２６、２７、３７、４２
Ｃ．Ｉ．フードイエロー　３
【０１０３】
（マゼンタ用の色材）
Ｃ．Ｉ．ダイレクトレッド　１、２、４、８、９、１１、１３、１５、２０、２３、２４、２８、３１、３３、３７、３９、４６、５１、５９、６２、６３、７３、７５、７９、８０、８１、８３、８７、８９、９０、９５、９９、１０１、１１０、１８９、１９７、２０１、２１８、２２０、２２４、２２５、２２６、２２７、２２８、２２９、２３０
Ｃ．Ｉ．アシッドレッド　１、４、６、８、９、１３、１４、１５、１８、２１、２６、２７、３２、３５、３７、４２、５１、５２、８０、８３、８７、８９、９２、１０６、１１４、１１５、１３３、１３４、１４５、１５８、１９８、２４９、２５７、２６５、２８９
Ｃ．Ｉ．リィアクティブレッド　１、２、３、４、５、６、７、８、１１、１２、１３、１５、１７、１９、２０、２１、２２、２３、２４、２８、２９、３１、３２、３３、３４、３５、３６、３７、３８、３９、４０、４１、４２、４３、４４、４５、４６、４７、４８、４９、５０、５８、５９、６３、６４、１８０
Ｃ．Ｉ．フードレッド　８７、９２、９４
【０１０４】
（シアン用の色材）
Ｃ．Ｉ．ダイレクトブルー　１、２、６、８、１５、２２、２５、３４、４１、７０、７１、７６、７７、７８、８０、８６、９０、９８、１０６、１０８、１２０、１４２、１５８、１６３、１６８、１９９、２００、２０１、２０２、２０３、２０７、２１８、２２６、２３６、２８７
Ｃ．Ｉ．アシッドブルー　１、７、９、１５、２２、２３、２５、２７、２９、４０、４３、５５、５９、６２、７４、７８、８０、８１、９０、１００、１０２、１０４、１１１、１１７、１２７、１３８、１５８、１６１、１８５、２５４
Ｃ．Ｉ．リィアクティブブルー　１、２、３、４、５、７、８、９、１３、１４、１５、１７、１８、１９、２０、２１、２５、２６、２７、２８、２９、３２、３３、３４、３７、３８、３９、４０、４１、４３、４４、４６、１００
【０１０５】
（ブラック用色材）
Ｃ．Ｉ．ダイレクトブラック　７、１９、２２、３１、３２、５１、６２、７１、７４、１１２、１１３、１５４、１６８、１９５
Ｃ．Ｉ．アシッドブラック　２、４８、５１、５２、１１０、１１５、１５６
Ｃ．Ｉ．フードブラック　１、２
【０１０６】
本発明において好適に使用できるカチオン性染料としては、例えば、以下のものを挙げることができる。
Ｃ．Ｉ．ベーシックイエロー　１、２、１１、１３、１４、１９、２１、２５、３２、３３、３６、５１
Ｃ．Ｉ．ベーシックレッド　１、２、９、１２、１３、３７、３８、３９、９２
Ｃ．Ｉ．ベーシックブルー　１、３、５、７、９、１９、２４、２５、２６、２８、２９、４５、５４、６５
Ｃ．Ｉ．ベーシックブラック　２、８
【０１０７】
第２のインクに用いることのできる有機顔料としては、下記のものが挙げられる。具体的には、トルイジンレッド、トルイジンマルーン、ハンザエロー、ベンジジンエロー、ピラゾロンレッド等の不溶性アゾ顔料、リトールレッド、ヘリオボルドー、ピグメントスカーレット、パーマネントレッド２Ｂ等の溶性アゾ顔料、アリザリン、インダントロン、チオインジゴマルーン等の建染染料からの誘導体、フタロシアニンブルー、フタロシアニングリーン等のフタロシアニン系顔料、キナクリドンレッド、キナクリドンマゼンタ等のキナクリドン系顔料、ペリレンレッド、ペリレンスカーレット等のペリレン系顔料、イソインドリノンエロー、イソインドリノンオレンジ等のイソインドリノン系顔料、ベンズイミダゾロンエロー、ベンズイミダゾロンオレンジ、ベンズイミダゾロンレッド等のイミダゾロン系顔料、ピランスロンレッド、ピランスロンオレンジ等のピランスロン系顔料、インジゴ系顔料、縮合アゾ系顔料、チオインジゴ系顔料、ジケトピロロピロール系顔料、フラバンスロンエロー、アシルアミドエロー、キノフタロンエロー、ニッケルアゾエロー、銅アゾメチンエロー、ペリノンオレンジ、アンスロンオレンジ、ジアンスラキノニルレッド、ジオキサジンバイオレット等の、その他の顔料が例示できる。
【０１０８】
又、有機顔料を、カラーインデックス（Ｃ．Ｉ．）ナンバーにて示すと、
Ｃ．Ｉ．ピグメントイエロー１、２、３、１２、１３、１４、１６、１７、２０、２４、７４、８３、８６、９３、９７、１０９、１１０、１１７、１２０、１２５、１２８、１３７、１３８、１４７、１４８、１５０、１５１、１５３、１５４、１６６、１６８、１８０、１８５、
Ｃ．Ｉ．ピグメントオレンジ１６、３６、４３、５１、５５、５９、６１、７１、
Ｃ．Ｉ．ピグメントレッド５、７、９、１２、４８、４９、５２、５３、５７、９７、１１２、１２２、１２３、１４９、１６８、１７５、１７６、１７７、１８０、１９２、２０２、２０７、２１５、２１６、２１７、２２０、２２３、２２４、２２６、２２７、２２８、２３８、２４０、２５４、２５５、２７２、
Ｃ．Ｉ．ピグメントバイオレット１９、２３、２９、３０、３７、４０、５０、
Ｃ．Ｉ．ピグメントブルー１、２、３、１５、１５：１、１５：３、１５：４、１５：６、１６、２２、６０、６４、Ｃ．Ｉ．ピグメントグリーン７、３６、
Ｃ．Ｉ．ピグメントブラウン２３、２５、２６等が例示できる。
【０１０９】
これらの顔料は、インク中に樹脂分散されていても、水溶性基をつけることにより自己分散されていても、先に述べた第１のインクと同様に、樹脂結合型自己分散をしていてもかまわない。
【０１１０】
上記した色材の含有量としては、インク全質量中の０．２〜１５質量％の範囲とするのが好ましく、より好ましくは０．５〜１０質量％の範囲とする。即ち、この範囲とすることで、例えば、発色性や、インクの吐出安定性等のインクジェット記録用インクとしての信頼性を、より一層向上させることができる。
【０１１１】
［溶媒］
上記したような色材の溶媒又は分散媒としては、例えば、水性媒体が挙げられる。水性媒体は、水、或いは水と水溶性有機溶媒との混合溶媒を用いることが好ましい。第２のインクを調製する場合に使用する水溶性有機溶媒としては、前記第１のインクにて記載したのと同様なものが挙げられる。又、第２のインクをインクジェット法（例えば、バブルジェット（登録商標）法等）で記録媒体に付着せしめる場合には、インクジェット吐出特性を有するように、前述した第１のインクにて記載したと同様に、インク所望の粘度、表面張力を有するように調製することが好ましい。
【０１１２】
ここで、第２のインク中の水溶性有機溶媒の含有量は、例えば、インクジェット記録に用いる場合には、該インクが優れたインクジェット吐出特性を備え、又、所望の色調や濃度を有するように適時選択すればよいが、目安としては、例えば、第２のインク全質量に対して３〜５０質量％の範囲が好ましい。又、インクに含有される水の量は第２のインク全質量に対して５０〜９５質量％の範囲が好ましい。
【０１１３】
［他の成分］
又、第１のインクの場合と同様に、第２のインクの成分として、インクの保湿性維持のためにの保湿性固形分や、必要に応じて、ｐＨ調整剤、防錆剤、防腐剤、防黴剤、酸化防止剤、還元防止剤、蒸発促進剤、キレート化剤等の、種々の添加剤を含有させてもよい。
【０１１４】
特に、第２のインク中には、上記で述べた成分の他に、そのインク中の色材の極性と同じか、又はノニオン性の少なくとも１種の界面活性剤を含有させることが好ましい。これらの界面活性剤を含有させることによって、インクに所望の浸透性や粘度を付与させることができ、インクジェット記録用インクに要求される性能をより一層満足させることができる。この際に使用される界面活性剤としては、下記に挙げるような、イオン性界面活性剤、非イオン性界面活性剤及び両性界面活性剤、或いは、これらの２種以上の混合物の何れでもよい。
【０１１５】
（アニオン性界面活性剤）
アニオン性界面活性剤としては、例えば、脂肪酸塩、高級アルコール酸エステル塩、アルキルベンゼンスルホン酸塩類、高級アルコールリン酸エステル塩、アルキル硫酸塩、アルキル硫酸エステル塩、ジアルキルスルホコハク酸塩、アルキルスルホ酢酸塩、スルホコハク酸ジアルキルエステル塩等が挙げられる。
【０１１６】
（カチオン性界面活性剤）
カチオン性界面活性剤としては例えば、脂肪族アミン塩、第４級アンモニウム塩、アルキルピリジニウム塩等が挙げられる。
【０１１７】
（非イオン性界面活性剤）
非イオン性界面活性剤としては、例えば、高級アルコールエチレンオキサイド付加物、アルキルフェノールエチレンオキサイド付加物、脂肪族エチレンオキサイド付加物、多価アルコール脂肪酸エステルエチレンオキサイド付加物、脂肪族アミドエチレンオキサイド付加物、高級アルキルアミンエチレンオキサイド付加物、ポリプロピレングリコールエチレンオキサイド付加物、多価アルコールの脂肪酸エステル、アルカノールアミンの脂肪酸アミド類等が挙げられる。
【０１１８】
（両性界面活性剤）
両性界面活性剤としては、例えば、アミノ酸型、ベタイン型両性界面活性剤等が挙げられる。
【０１１９】
本発明においては、これらのものは何れも好ましく使用されるが、より好ましくは、高級アルコールのエチレンオキサイド付加物、アルキルフェノールのエチレンオキサイド付加物、エチレンオキサイド−プロピレンオキサイド共重合体、アセチレングリコールのエチレンオキサイド付加物等の非イオン性界面活性剤を用いる。更に、上記エチレンオキサイド付加物の付加モル数が４〜２０の範囲のものが特に好ましい。
【０１２０】
上記のような界面活性剤の各インク中における添加量については特に制限はないが、インク全質量の０．０１〜１０質量％の範囲とするのが好ましい。０．０１質量％未満では、界面活性剤の種類にもよるが、一般に所望の浸透性が得られず、１０質量％を超える場合には、インクの初期粘度が大きくなり、好ましくない。更に好ましくは、インク全質量の０．１〜５．０質量％の範囲とするのがよい。
【０１２１】
上記した基本構成を有する第２のインクには、更に、下記に挙げる第１〜３の方法等によって、第１のインクと混合されたときに、第１のインク中の顔料の分散安定性を不安定化させる機能が付与されている。以下、これについて説明する。
【０１２２】
［第１の態様：多価金属イオン含有インク］
（多価金属塩）
第２のインクを、前記した第１のインクと混合されたときに、第１のインク中の顔料の分散安定性を不安定化させる一つの方法として、多価金属陽イオンを第２のインク中に含有させる態様がある。即ち、多価金属イオンとして、例えば、Ｍｇ^２＋、Ｃａ^２＋、Ｃｕ^２＋、Ｃｏ^２＋、Ｎｉ^２＋、Ｆｅ^２＋、Ｌａ^３＋、Ｎｄ^３＋、Ｙ^３＋及びＡｌ^３＋からなる群から選ばれる少なくとも一つが、第２のインク中に含有されるように構成する。
【０１２３】
ここで第２のインクに含有させる多価金属イオンとしては、第２のインクの全質量に対して、例えば、０．１〜１５質量％を含有させることが好ましい。上記に列挙したような多価金属陽イオンは、例えば、硝酸塩や酢酸塩等の塩でカラーインク中に添加することが好ましい。尚、第２のインクに、このような多価金属イオンを含有させる場合には、色材として、多価金属イオンと共存した場合においても、その安定性が不安定化しないものを、先に挙げたものの中から選択することが好ましいことは当然のことである。
【０１２４】
［第２の態様：ｐＨ変化に対して緩衝作用を持つインク］
第２のインクを、前記した第１のインクと混合したときに、第１のインク中の顔料の分散安定性を不安定化させる一つの方法として、第１のインクと混合されたときに、第１のインクにｐＨ変化を生じさせ、第１のインク中の顔料の分散性を不安定化させるｐＨを有し、更に、そのｐＨに対する緩衝作用を有するものとなるように、第２のインクを構成する。
【０１２５】
例えば、前記した構成の第１のインクをブラックインクとし、これと組み合わせる第２のインクをカラーインクとして、第２のインクとして、第１のインクの水素イオン濃度（ｐＨ）の変化に対して緩衝作用を持つインクを採用することで、ブラックインクで印字された画像と、カラーインクで印字された画像との境界部のブリードが有効に防止される。ここでいう「ｐＨ変化に対して緩衝作用を持つ」とは、インクが、ｐＨ変化が緩やかな特定領域を有することを意味する。具体的には、５０ｍｌのインクに対して、１規定の水酸化リチウム水溶液を１．０ｍｌ添加したインクのｐＨ値と、水酸化リチウム水溶液を添加しない状態でのインクのｐＨ値との差が、１．０以内になる領域を有することをいう。以後、上記条件を満たすことを「緩衝作用を持つ」と記す。
【０１２６】
本発明者らの検討によれば、例えば、第２のインクのカラーインクの構成を、第１のインクのブラックインクのｐＨよりも低いｐＨ領域で緩衝作用を示すようにすることによって、ブラックインクとカラーインクとの間で生じるブリードが有効に抑制されることが確認できた。特に、ブラックインクとカラーインクとの間でブリードが生じると、品位に劣る画像になる。以下、この例を用いて説明する。
【０１２７】
上記構成を有する本発明のインクセットによって、上記した効果が得られる理由としては、下記のように考えられる。ブラック画像とカラー画像とが隣接するような画像が印字され、記録媒体上で、上記構成のブラックインクとカラーインクとが隣接すると、ブラックインク中の、例えば、カーボンブラックと、カラーインク中の、例えば、アニオン性染料との間に凝集が起こる。そして、この凝集に伴って、ブラックインク中のカーボンブラックとカラーインク中の染料が、記録媒体上で移動できなくなるような状態となり、この結果、ブリードが有効に防止されたものと考えられる。
【０１２８】
つまり、記録媒体上で、ブラックインク中の、先述した樹脂結合タイプの自己分散性顔料と、カラーインク中の色材との間に電気的中和が安定して起これば、各々のインクを構成する色材等の分散状態や溶解状態が完全に破壊される。このようにして、ブラックインクやカラーインク中の色材等が移動できなくなれば、記録媒体上において、各インクで印字された領域へ、別のインクが入り込むことがなくなるので、ブリードは生じなくなる。
【０１２９】
本発明者らの検討によれば、上記した各々のインクを構成する色材等同士の電気的中和は、ブラックインクとカラーインクとが接触した際の境界部のｐＨに大きな影響を受け、境界部のｐＨにより、ブリードの効果は大きく左右されることが分かった。即ち、上記２種類のインクが接触した際のｐＨが塩基性となった場合には、色材等同士の電気的中和は、各々のインクの色材等の分散状態や溶解状態を完全に破壊するには不十分な場合があり、その場合にはブリード抑制効果が十分に達成されない可能性がある。従って、ブリードの発生をより有効に防止し、或いはより有効に抑制するためには、上記２種のインクが接触した際の境界部のｐＨが、各々のインク中の色材等の分散状態や溶解状態を完全に破壊するのに十分な色材同士の電気的中和を起こすような値で維持されるようにすることが重要となる。
【０１３０】
そこで、本発明においては、カラーインク（第２のインク）に対して、これと混合された場合にブラックインク（第１のインク）にｐＨ変化を生じさせ、且つ該ｐＨ変化に対して緩衝作用を持たせ、これにより、記録媒体上で２種のインクが接触した際のｐＨ値が、各々のインクの色材等の分散状態や溶解状態を完全に破壊するのに十分な状態に維持されるようにして、印字物のブリードの防止を図る。
【０１３１】
本発明で使用するｐＨ変化に対して緩衝作用を持つ第２のインクを調製する具体的な方法としては、先に述べたように、５０ｍｌのインクに１規定の水酸化リチウム水溶液を１．０ｍｌ添加した際のｐＨ値と、添加前のｐＨ値の差が１．０以内になるようにする。このためには、従来公知の緩衝溶液を作製するのと同様の方法を用いることができる。
【０１３２】
この際に使用する緩衝剤としては、例えば、クエン酸、コハク酸、フタル酸、フマル酸、酢酸、乳酸、酒石酸、炭酸、ジエチルバルビルツ酸等の有機酸、りん酸、ホウ酸、硫酸、塩酸、硝酸等の無機酸、クエン酸リチウム、クエン酸二水素カリウム、フタル酸水素カリウム、硫酸リチウム、硫酸ナトリウム、硫酸カリウム、硫酸アンモニウム等の硫酸塩、酢酸ナトリウム、酢酸リチウム、酢酸カリウム、酢酸アンモニウム等の酢酸塩、炭酸リチウム、炭酸ナトリウム、炭酸水素ナトリウム、炭酸カリウム、炭酸水素カリウム、炭酸アンモニウム、炭酸水素アンモニウム等の炭酸塩、乳酸ナトリウム、りん酸リチウム、りん酸一ナトリウム、りん酸二ナトリウム、りん酸三ナトリウム、りん酸カリウム、りん酸二カリウム、りん酸三カリウム、りん酸二水素カリウム、りん酸一アンモニウム、りん酸二アンモニウム、りん酸三アンモニウム等のりん酸塩、四ホウ酸ナトリウム、ジエチルバルビルツ酸ナトリウム等の有機酸のアルカリ金属塩、塩化カリウムや塩化ナトリウム、塩化カリウム、塩化リチウム等の無機アルカリ金属塩、水酸化ナトリウムや水酸化リチウム、水酸化カリウム、水酸化アンモニウム等の水酸化物、グリシン、等が挙げられる。そして、これらの緩衝剤を、単独で、若しくは適宜組み合わせて使用できる。
【０１３３】
具体的には、例えば、フタル酸水素カリウム／塩酸、フタル酸水素カリウム／水酸化ナトリウム、クエン酸カリウム／クエン酸、クエン酸二水素カリウム／塩酸、クエン酸二水素カリウム／水酸化ナトリウム、四ホウ酸ナトリウム／コハク酸、クエン酸二水素カリウム／四ホウ酸ナトリウム、乳酸ナトリウム／乳酸、酢酸ナトリウム／酢酸、りん酸水素二カリウム／クエン酸、酒石酸／酒石酸ナトリウム、ホウ酸＋クエン酸／りん酸三ナトリウム、グリシン＋塩化ナトリウム／塩酸、クエン酸＋りん酸二水素カリウム＋ホウ酸＋ジエチルバルビルツ酸／りん酸三ナトリウム、ジエチルバルビルツ酸ナトリウム＋酢酸ナトリウム／塩酸、等が挙げられる。しかし、これらの組み合わせに限定されるものではない。
【０１３４】
より具体的には、例えば、りん酸二水素ナトリウム／水酸化ナトリウム、グリシン＋塩化ナトリウム／水酸化ナトリウム、四ホウ酸ナトリウム／水酸化ナトリウム、りん酸二水素ナトリウム／四ホウ酸ナトリウム、四ホウ酸ナトリウム／炭酸ナトリウム、塩酸／炭酸ナトリウム、りん酸二水素ナトリウム／水酸化ナトリウム、塩化アンモニウム／アンモニア、ジメチルグリシンナトリウム／塩酸、ホウ酸＋塩化カリウム／炭酸ナトリウム、炭酸ナトリウム／炭酸水素ナトリウム等の緩衝剤が挙げられる。これらの塩のインクへの添加量は、好ましくは０．１〜１０質量％、更に好ましくは、１〜８質量％である。これらの範囲にすることで、インクのｐＨを一定にすることができ、且つインクの安定性を保つことができる。
【０１３５】
上記に列挙したような化合物の含有量としては、５０ｍｌの第２のインクに１規定の水酸化リチウム水溶液を１．０ｍｌ添加した際のｐＨ値と、添加前のｐＨ値との差が１．０以内という条件を、第２のインクが満たすように適宜に調製することが好ましい。但し、この際に、発色性や、インクの吐出安定性等のインクジェット記録特性が、インクジェット記録用インクとしての信頼性を損なわない範囲にする必要がある。
【０１３６】
［第３の態様：第１のインク中の顔料極性と逆の極性の色材を有するインク］
第２のインクを、前記した第１のインクと混合したときに、第１のインク中の顔料の分散安定性を不安定化させる方法として、第２のインクの構成を、前記した第１のインク中の顔料が有している極性とは逆の極性の色材を含有するものとする。
【０１３７】
本発明者らの検討によれば、例えば、第２のインクとして用いるカラーインクの色材を、第１のインクとして用いるカーボンブラックを色材とするブラックインクと逆極性とした場合に、これらのインク画像が隣接、或いは重ね打ちされた場合に、ブリードの発生が有効に抑制できることを見いだした。互いに極性の異なる色材については、先に列挙したものの中から適宜に選択して使用すればよい。
【０１３８】
例えば、先述した樹脂結合タイプのカチオン性の自己分散性顔料であるカーボンブラックを着色剤としたブラックインクと、先に挙げたアニオン性染料から選択された色材を含有するカラーインクとを用いた本発明のインクセットは、従来の自己分散性顔料であるカーボンブラックを着色剤としたブラックインクと、アニオン性染料を着色剤としたカラーインクとのインクセットと比較した場合においても、ブリードの抑制効果が格段に高いことが確認できた。本発明者らは、これは、逆極性の色材を持つカラーインクと接触したときに、従来の単なる水溶性基をつけただけの自己分散顔料の場合よりも、本発明で使用する樹脂結合タイプの自己分散顔料の場合の方が、より大きな凝集体を形成するため、紙面上でインクの移動ができなくなる結果、ブリードの発生の抑制が格段に改善できたものと考えている。
【０１３９】
（第２のインクの浸透性）
上記したような第２のインクに関して、記録媒体上に高品質なカラー画像を形成するためには、前記で説明したブリストウ法によって求められるＫａ値を、例えば、１．５（ｍｌ／ｍ^２／ｍｓｅｃ^１／２）以上のインクとすることが好ましい。即ち、このようなＫａ値を有するインクは記録媒体への浸透性が高いため、例えば、イエロー、マゼンタ及びシアンから選ばれる少なくとも２つの色の画像を隣接して記録するような場合でも、隣接する異なる色の画像間で生じる色のにじみ（ブリーディング）を抑えることができ、又、これらのインクを重ね打ちして２次色の画像を形成する場合でも、各々のインクの浸透性が高いため、異なる色の画像との間でブリードを有効に抑えることができる。第２のインクのＫａ値をこのような値に調整する方法としては、例えば、先に述べたような界面活性剤の添加、グリコールエーテル等の浸透性溶剤を添加する等の、従来公知の方法が適用できる。勿論、添加量は適宜選択すればよい。
【０１４０】
以上のような構成を有する本発明のインクセットは、インクジェット記録に用いられる際に、特に効果的である。この場合に使用するインクジェット記録方法には、インクに力学的エネルギーを作用させてインクを吐出する記録方法、及びインクに熱エネルギーを加えてインクの発泡によりインクを吐出するインクジェット記録方法がある。本発明のインクセットは、これらのインクジェット記録方法に適用した場合に、ブレードが抑制され、しかも耐擦過性や耐マーカー性に優れた画像を形成することができる。以下、これらについて説明する。
【０１４１】
［記録方法、記録ユニット、カートリッジ及び記録装置］
次に、上記した本発明にかかる第１、第２のインクを用いて記録を行うのに好適に用いることのできる、本発明にかかるインクジェット記録装置の一例について以下に説明する。先ず、熱エネルギーを利用したインクジェット記録装置の主要部であるヘッド構成の一例を図５及び図６に示す。図５は、インク流路に沿ったヘッド１３の断面図であり、図６は図５のＡ−Ｂ線での切断面図である。ヘッド１３はインクを通す流路（ノズル）１４を有するガラス、セラミック、シリコン又はプラスチック板等と発熱素子基板１５とを接着して得られる。発熱素子基板１５は、酸化シリコン、窒化シリコン、炭化シリコン等で形成される保護層１６、アルミニウム、金、アルミニウム−銅合金等で形成される電極１７−１及び１７−２、ＨｆＢ_２、ＴａＮ、ＴａＡｌ等の高融点材料から形成される発熱抵抗体層１８、熱酸化シリコン、酸化アルミニウム等で形成される蓄熱層１９、シリコン、アルミニウム、窒化アルミニウム等の放熱性のよい材料で形成される基板２０よりなっている。
【０１４２】
上記ヘッド１３の電極１７−１及び１７−２にパルス状の電気信号が印加されると、発熱素子基板１５のｎで示される領域が急速に発熱し、この表面に接しているインク２１に気泡が発生し、その圧力でメニスカス２３が突出し、インク２１がヘッドのノズル１４を通して吐出し、吐出オリフィス２２よりインク小滴２４となり、記録媒体２５に向かって飛翔する。図７には、図５に示したヘッドを多数並べたマルチヘッドの一例の外観図を示す。このマルチヘッドは、マルチノズル２６を有するガラス板２７と、図５に説明したものと同じような発熱ヘッド２８を接着して作られている。
【０１４３】
図８に、このヘッドを組み込んだインクジェット記録装置の一例を示す。図８において、６１はワイピング部材としてのブレードであり、その一端はブレード保持部材によって保持固定されており、カンチレバーの形態をなす。ブレード６１は記録ヘッド６５による記録領域に隣接した位置に配置され、又、図示した例の場合、記録ヘッド６５の移動経路中に突出した形態で保持される。
【０１４４】
６２は記録ヘッド６５の突出口面のキャップであり、ブレード６１に隣接するホームポジションに配置され、記録ヘッド６５の移動方向と垂直な方向に移動して、インク吐出口面と当接し、キャッピングを行う構成を備える。更に、６３はブレード６１に隣接して設けられるインク吸収体であり、ブレード６１と同様、記録ヘッド６５の移動経路中に突出した形態で保持される。上記ブレード６１、キャップ６２及びインク吸収体６３によって吐出回復部６４が構成され、ブレード６１及びインク吸収体６３によって吐出口面に水分、塵埃等の除去が行われる。
【０１４５】
６５は、吐出エネルギー発生手段を有し、吐出口を配した吐出口面に対向する記録媒体にインクを吐出して記録を行う記録ヘッド、６６は記録ヘッド６５を搭載して記録ヘッド６５の移動を行うためのキャリッジである。キャリッジ６６はガイド軸６７と摺動可能に係合し、キャリッジ６６の一部はモーター６８によって駆動されるベルト６９と接続（不図示）している。これによりキャリッジ６６はガイド軸６７に沿った移動が可能となり、記録ヘッド６５による記録領域及びその隣接した領域の移動が可能となる。
【０１４６】
５１は記録媒体を挿入するための紙給部、５２は不図示のモーターにより駆動される紙送りローラーである。これらの構成により記録ヘッド６５の吐出口面と対向する位置へ記録媒体が給紙され、記録の進行につれて排紙ローラー５３を配した排紙部へ排紙される。以上の構成において記録ヘッド６５が記録終了してホームポジションへ戻る際、吐出回復部６４のキャップ６２は記録ヘッド６５の移動経路から退避しているが、ブレード６１は移動経路中に突出している。その結果、記録ヘッド６５の吐出口がワイピングされる。
【０１４７】
尚、キャップ６２が記録ヘッド６５の吐出面に当接してキャッピングを行う場合、キャップ６２は記録ヘッドの移動経路中に突出するように移動する。記録ヘッド６５がホームポジションから記録開始位置へ移動する場合、キャップ６２及びブレード６１は上記したワイピングの時の位置と同一の位置にある。この結果、この移動においても記録ヘッド６５の吐出口面はワイピングされる。上述の記録ヘッドのホームポジションへの移動は、記録終了時や吐出回復時ばかりでなく、記録ヘッドが記録のために記録領域を移動する間に所定の間隔で記録領域に隣接したホームポジションへ移動し、この移動に伴って上記ワイピングが行われる。
【０１４８】
図９は、記録ヘッドにインク供給部材、例えば、チューブを介して供給されるインクを収容したインクカートリッジの一例を示す図である。ここで４０は供給用インクを収納したインク収容部、例えば、インク袋であり、その先端にはゴム製の栓４２が設けられている。この栓４２に針（不図示）を挿入することにより、インク袋４０中のインクをヘッドに供給可能にする。４４は廃インクを受容するインク吸収体である。インク収容部としてはインクとの接液面がポリオレフィン、特にポリエチレンで形成されているものが好ましい。
【０１４９】
本発明で使用されるインクジェット記録装置としては、上述のようにヘッドとインクカートリッジとが別体となったものに限らず、図１０に示すようなそれらが一体になったものにも好適に用いられる。図１０において、７０は記録ユニットであり、この中にはインクを収容したインク収容部、例えば、インク吸収体が収納されており、かかるインク吸収体中のインクが複数オリフィスを有するヘッド部７１からインク滴として吐出される構成になっている。インク吸収体の材料としてはポリウレタンを用いることが本発明にとって好ましい。又、インク吸収体を用いず、インク収容部が内部にバネ等を仕込んだインク袋であるような構造でもよい。７２はカートリッジ内部を大気に連通させるための大気連通口である。この記録ユニット７０は図８に示す記録ヘッド６５に換えて用いられるものであって、キャリッジ６６に対して着脱自在になっている。
【０１５０】
次に、力学的エネルギーを利用したインクジェット記録装置の好ましい一例としては、複数のノズルを有するノズル形成基板と、ノズルに対向して配置される圧電材料と導電材料からなる圧力発生素子と、この圧力発生素子の周囲を満たすインクを備え、印加電圧により圧力発生素子を変位させ、インクの小液滴をノズルから吐出させるオンデマンドインクジェット記録ヘッドを挙げることができる。その記録装置の主要部である記録ヘッドの構成の一例を図１１に示す。
【０１５１】
ヘッドは、インク室（不図示）に連通したインク流路８０と、所望の体積のインク滴を吐出するためのオリフィスプレート８１と、インクに直接圧力を作用させる振動板８２と、この振動板８２に接合され、電気信号により変位する圧電素子８３と、オリフィスプレート８１、振動板８２等を指示固定するための基板８４とから構成されている。
【０１５２】
図１１において、インク流路８０は、感光性樹脂等で形成され、オリフィスプレート８１は、ステンレス、ニッケル等の金属を電鋳やプレス加工による穴あけ等により吐出口８５が形成され、振動板８２はステンレス、ニッケル、チタン等の金属フィルム及び高弾性樹脂フィルム等で形成され、圧電素子８３は、チタン酸バリウム、ＰＺＴ等の誘電体材料で形成される。以上のような構成の記録ヘッドは、圧電素子８３にパルス状の電圧を与え、歪み応力を発生させ、そのエネルギーが圧電素子８３に接合された振動板を変形させ、インク流路８０内のインクを垂直に加圧しインク滴（不図示）をオリフィスプレート８１の吐出口８５より吐出して記録を行うように動作する。このような記録ヘッドは、図８に示したものと同様なインクジェット記録装置に組み込んで使用される。インクジェット記録装置の細部の動作は、先述と同様に行うもので差しつかえない。
【０１５３】
【実施例】
次に、実施例及び比較例を挙げて本発明をより具体的に説明するが、本発明はその要旨を超えない限り、下記実施例より限定されるものではない。尚、文中「部」、及び「％」とあるのは、特に断りのない限り質量基準である。
【０１５４】
［第１のインクの調製］
＜顔料分散液の調製＞
（顔料分散液１）
比表面積が２２０ｍ^２／ｇであり、ＤＢＰ吸油量が１１２ｍｌ／１００ｇであるカーボンブラックを５００ｇ、アミノフェニル−２−スルホエチル−スルフォン（ＡＰＳＥＳ）を４５ｇ、蒸留水を９００ｇ、反応器に投入し、５５℃に保温し、回転数３００ＲＰＭで２０分間攪拌した。この後、２５％濃度の亜硝酸ナトリウム４０ｇを１５分間で滴下し、更に蒸留水５０ｇを加えた。この後、６０℃に保温して、２時間反応させた。反応物を蒸留水で希釈しながら取り出し、固形分１５％の濃度に調整した。この後、遠心分離処理、及び不純物を除去する精製処理を行った。得られた分散液は、カーボンブラックに前述した（ＡＰＳＥＳ）の官能基が結合した分散液となった。この分散液をＡ１とする。
【０１５５】
ここで、この分散液Ａ１中のカーボンブラックに結合した官能基のモル数を求めるために、以下の操作を行った。分散液中のＮａイオンをプローブ式ナトリウム電極で測定し、得られた値をカーボンブラック粉末当りに換算し、カーボンブラックに結合した官能基のモル数を求めた。
【０１５６】
次いで、上記で調製した固形分１５％の分散液Ａ１を、ペンタエチレンヘキサミン（ＰＥＨＡ）溶液中に滴下した。この際、ＰＥＨＡ溶液を強力に攪拌しながら室温に保ち、１時間かけて分散液Ａ１を滴下した。このときのＰＥＨＡ濃度は、先に測定したＮａイオンのモル数の１〜１０倍量の濃度とし、溶液量は分散液Ａ１と同量で行った。更に、この混合物を１８〜４８時間攪拌し、この後、不純物を除去するための精製処理を行い、最終的に、ペンタエチレンヘキサミン（ＰＥＨＡ）が結合した固形分１０％の分散液とした。この分散液をＢ１とする。
【０１５７】
次に、共重合体セグメントとしてのスチレン−アクリル酸樹脂を以下のようにして調製した。先ず、重量平均分子量＝１５，０００、酸価＝１４０、多分散度Ｍｗ／Ｍｎ＝１．５のスチレン−アクリル酸樹脂を１９０ｇ秤り取り、これに１，８００ｇの蒸留水を加え、樹脂を中和するのに必要なＮａＯＨを加えて、攪拌して溶解して、スチレン−アクリル酸樹脂水溶液を調製した。次に、先に調製した固形分１０％の分散液Ｂ１を５００ｇ、上記スチレン−アクリル酸樹脂水溶液中に攪拌しながら滴下した。次に、分散液Ｂ１とスチレン−アクリル酸樹脂水溶液の混合物をパイレックス（登録商標）蒸発皿に移し、１５０℃で１５時間加熱し、蒸発させた後、蒸発乾燥物を室温に冷却した。
【０１５８】
次いで、この蒸発乾燥物を、ｐＨ＝９．０に調整したＮａＯＨ添加蒸留水中に分散機を用いて分散させ、更に攪拌しながら１．０ＭのＮａＯＨを添加して、ｐＨを１０〜１１に調整した。その後、脱塩、不純物を除去する精製及び粗大粒子除去を行って、顔料分散液１を得た。得られた顔料分散液１の物性値は、固形分が１０％であり、ｐＨ＝１０．１、平均粒子径１３０ｎｍであった。下記に、上記における顔料分散液１中に含まれている、カーボンブラック粒子の表面に有機基が化学的に結合してなる改質顔料の合成スキームを示す。
【０１５９】

【０１６０】
又、得られた顔料分散液１について、下記の方法で熱分析したところ重量減少率は２．５％と少なく、カーボンブラック粒子表面に共重合体セグメントが化学的に結合したものであることが確認できた。又、後述する方法で、改変された顔料の質量に対する、該顔料に化学結合している有機基の割合を測定したところ、１８％であった。
【０１６１】
先ず、顔料分散液１を、塩析若しくは凝集等を行った後のカーボンブラック沈殿物をろ過により分取し、ろ過により得られた固形分を純水で十分に洗浄し、洗浄後のカーボンブラック固形物を、６０℃のオーブンで一晩程度乾燥させた。次に、このカーボンブラック乾固物を（Ｃ）とし、このカーボンブラック乾固物を、高分子の良溶媒であるテトロヒドロフラン（ＴＨＦ）を用いてカーボンブラック乾固物の洗浄抽出作業を３回繰り返した。上記のようにして高分子を抽出除去した後のカーボンブラック乾固物から、残存水分や残存溶剤を揮発させるために、真空乾燥機を用いて数百Ｐａ以下の真空度で、６０℃×３時間程度乾燥させて、溶媒抽出後のカーボンブラックを得た。そして、この抽出後のカーボンブラックを（Ｄ）とし、顔料分散液１について、（Ｃ）及び（Ｄ）のＴＧＡ（熱重量分析）による１００℃から７００℃の範囲における重量減少率を測定した。得られたそれぞれの測定結果を用い、重量減少率の差＝（Ｃ）の重量減少率（％）−（Ｄ）の重量減少率（％）として、熱分析による重量減少率の差を求めた。
【０１６２】
（顔料分散液２の調製）
顔料分散液１を調製した場合に使用したスチレン−アクリル酸樹脂の代わりに、重量平均分子量＝１０，０００、酸価＝２４０、多分散度Ｍｗ／Ｍｎ＝１．６のスチレン−アクリル酸樹脂を用いた以外は、実施例１と同様の操作を同様に行い、顔料分散液２を得た。得られた顔料分散液２の物性値は、固形分が１０．５％、ｐＨが９．５、平均粒子径が１５５ｎｍであった。得られた顔料分散液２について、先に説明した方法で熱分析したところ、重量減少率は４．０％と少なく、カーボンブラック粒子表面に共重合体セグメントが化学的に結合したものであることが確認できた。又、後述する方法で、改変された顔料の質量に対する、該顔料に化学結合している有機基の割合を測定したところ、２０％であった。
【０１６３】
（顔料分散液Ｂｋの調製）
顔料分散液１を調製した場合に使用したスチレン−アクリル酸共重合樹脂の代わりに、重量平均分子量＝３０，０００のポリアクリル酸樹脂を用いた以外は、実施例１と同様の操作を同様に行い、樹脂結合型の顔料分散液Ｂｋを得た。得られた顔料分散液Ｂｋの物性値は、固形分が１０％、ｐＨが９．０、平均粒子径が１７５ｎｍであった。得られた顔料分散液Ｂｋについて、先に説明した方法で熱分析したところ、重量減少率は３．０％であり、カーボンブラック粒子表面に重合体セグメントが化学的に結合したものであることが確認できた。又、後述する方法で、改変された顔料の質量に対する、該顔料に化学結合している重合体の割合を測定したところ、１５％であった。
【０１６４】
［熱分析方法］
以下、表面改質された顔料中における有機基の割合の、具体的な測定方法について説明する。先ず、顔料分散液１に対してそれぞれ塩析若しくは凝析を行なった。具体的には、有機基がアニオン性基を有する場合は、塩酸又は硫酸等の酸を添加し、有機基がカチオン性基を有する場合には水酸化ナトリウム等のアルカリを添加することで顔料分散液１中の顔料及び有機基を塩析により沈殿させることができる、又、場合によってはアルコールを過剰に加える凝析を行うことにより顔料分散液１中の顔料を沈殿させることが可能である。
【０１６５】
又、顔料分散液１中の顔料を沈殿させる方法として、塩析若しくは凝析を組み合わせる、又、遠心分離を行う等とすることで、有効に顔料分散液１中の顔料を取り出すことが可能である。上記操作により得られた顔料であるカーボンブラックを含む沈澱物をろ過により分取して、ろ過した固形分を純水で十分に洗浄し、洗浄後のカーボンブラック含有固形物を、６０℃のオーブンで一晩程度乾燥させた。そして、得られたカーボンブラック含有乾固物を、該共重合体を含むセグメントの良溶媒であるテトラヒドロフラン（ＴＨＦ）で洗浄した。このカーボンブラック含有乾固物のＴＨＦによる洗浄作業を３回繰り返して行なった後、残存水分や残存溶剤を揮発させるために、真空乾燥機を用いて、数百Ｐａ以下の真空度で６０℃×３時間程度乾燥させた。以上のようにして、フリーポリマーとしての該共重合体を含むセグメントが、該共重合体の良溶媒による洗浄の結果、除去された表面改質カーボンブラックのみからなる乾固物を得た。
【０１６６】
次に、上記で得られた乾固物を測定用試料として、熱重量分析（Ｔｈｅｒｍｏｇｒａｖｉｍｅｔｒｉｃ　Ａｎａｌｙｓｉｓ）により熱重量分析重量減少率を測定した。先に述べたように、その際に得られる重量減少率の値から、顔料であるカーボンブラックに化学的に結合している有機基の結合量を求めた。尚、熱重量分析には、ＭＥＴＴＬＥＲＴＯＬＥＤＯ社製のＴＧＡ熱重量測定装置、ＴＧＡ８５１ｅ／ＳＤＴＡを使用した。
【０１６７】
図１及び２は、顔料分散液１について、上記した方法によって調製した乾固物試料に対する熱重量分析によって得られた、熱重量分析重量減少率の測定データである。図１は、凝析後の、ＴＨＦ洗浄を行なわない乾固物試料についての熱分析結果である。この図１に表われる熱重量分析重量減少率は、インク中の表面改質されてなる顔料に化学的に結合している有機基と、フリーポリマーとしての該重合体部分を含むセグメントとの総量の、該表面改質された顔料に対する割合を表している。
【０１６８】
又、図２は、上記の乾固物試料を更にＴＨＦ洗浄した後に得られる乾固物試料に対する熱重量分析の測定データである。即ち、この図２に表われている熱重量分析重量減少率は、該反応物の良溶媒であるＴＨＦによってフリーポリマーとしてのセグメントを取り除いた後の試料に対するものであるため、表面改質された顔料中の化学結合している有機基の割合を示すものである。
【０１６９】
顔料分散液１についての熱重量分析測定データでは、図１及び２に示したように、何れの場合も３５０℃近傍で著しい重量減が見られた。図２においてもこのような結果が得られたことは、熱重量分析用試料を調製する際に、乾固物を該共重合体に対する良溶媒で洗浄したにもかかわらず、該共重合体が失われなかったことを意味している。即ち、顔料分散液１中の顔料には、その表面改質によって、顔料粒子表面に有機物が化学的に結合した状態のものとなっていることを示している。更に、図１及び図２から得られる熱重量分析重量減少率から、次式によって、インク中に含まれる有機基とフリーポリマーとの総和に対する、顔料粒子表面に化学的に結合している有機基の質量割合が求められる。
【０１７０】

【０１７１】
＜インクの調製＞
ブラックンクは以下の成分を混合し、十分攪拌して溶解後、ポアサイズ３．０μｍのミクロフィルター（富士フィルム社製）にて加圧濾過し調製した。
（ブラックインク１）
・トリメチロールプロパン　　　　　　　　　５部
・グリセリン　　　　　　　　　　　　　　　７部
・１，５−ペンタンジオール　　　　　　　　６部
・顔料分散液１　　　　　　　　　　　　　５０部
・アセチレングリコールエチレンオキサイド付加物
（商品名：アセチレノールＥＨ；川研ファインケミ
カル（株）社製）　　　　　　　　　　０．１部
・水　　　　　　　　　　　　　　　　　　　残部
【０１７２】
（ブラックインク２）
・エチレングリコール　　　　　　　　　　　４部
・グリセリン　　　　　　　　　　　　　　　５部
・ジエチレングリコール　　　　　　　　　　３部
・顔料分散液２　　　　　　　　　　　　　４５部
・アセチレノールＥＨ（商品名）　　　０．１５部
・水　　　　　　　　　　　　　　　　　　　残部
【０１７３】
（ブラックインクＢｋ）
・グリセリン　　　　　　　　　　　　　　　７部
・ジエチレングリコール　　　　　　　　　　３部
・顔料分散液Ｂｋ　　　　　　　　　　　　５０部
・純水　　　　　　　　　　　　　　　　　　残部
【０１７４】
［第２のインクの調製］
カラーインクは以下の成分を混合し、十分攪拌して溶解後、ポアサイズ０．２μｍのミクロフィルター（富士フィルム社製）にて加圧濾過し調製した。
（イエローインクＹ−１）
・エチレン尿素　　　　　　　　　　　　　　６部
・グリセリン　　　　　　　　　　　　　　　６部
・２−ピロリドン　　　　　　　　　　　　　６部
・Ｃ．Ｉ．アシッドイエロー２３　　　　　　３部
・アセチレノールＥＨ（商品名）　　　　１．０部
・水　　　　　　　　　　　　　　　　　　　残部
【０１７５】
（マゼンタインクＭ−１）
・トリメチロールプロパン　　　　　　　　　６部
・１，５−ペンタンジオール　　　　　　　　６部
・２−ピロリドン　　　　　　　　　　　　　６部
・Ｃ．Ｉ．アシッドレッド５２　　　　　　　３部
・アセチレノールＥＨ（商品名）　　　　１．０部
・水　　　　　　　　　　　　　　　　　　　残部
【０１７６】
（シアンインクＣ−１）
・トリメチロールプロパン　　　　　　　　　６部
・グリセリン　　　　　　　　　　　　　　　６部
・ジエチレングリコール　　　　　　　　　　６部
・Ｃ．Ｉ．アシッドブルー９　　　　　　　　３部
・アセチレノールＥＨ（商品名）　　　　１．０部
・水　　　　　　　　　　　　　　　　　　　残部
【０１７７】
（第１の態様の第２のインク：多価金属イオン含有インク）
更に、上記の各々のカラーインクに、ブラック顔料の沈澱材として機能する２価金属塩をそれぞれ加え、多価金属イオン含有のカラーインクを調製した。
（イエローインク１）
・エチレン尿素　　　　　　　　　　　　　　６部
・グリセリン　　　　　　　　　　　　　　　６部
・２−ピロリドン　　　　　　　　　　　　　６部
・Ｃ．Ｉ．アシッドイエロー２３　　　　　　３部
・硝酸カルシウム塩　　　　　　　　　　　　２部
・アセチレノールＥＨ（商品名）　　　　１．０部
・水　　　　　　　　　　　　　　　　　　　残部
【０１７８】
（マゼンタインク１）
・トリメチロールプロパン　　　　　　　　　６部
・１，５−ペンタンジオール　　　　　　　　６部
・２−ピロリドン　　　　　　　　　　　　　６部
・Ｃ．Ｉ．アシッドレッド５２　　　　　　　３部
・硝酸マグネシウム塩　　　　　　　　　　　２部
・アセチレノールＥＨ（商品名）　　　　１．０部
・水　　　　　　　　　　　　　　　　　　　残部
【０１７９】
（シアンインク１）
・トリメチロールプロパン　　　　　　　　　６部
・グリセリン　　　　　　　　　　　　　　　６部
・ジエチレングリコール　　　　　　　　　　６部
・Ｃ．Ｉ．アシッドブルー９　　　　　　　　３部
・硝酸マグネシウム塩　　　　　　　　　　　２部
・アセチレノールＥＨ（商品名）　　　　１．０部
・水　　　　　　　　　　　　　　　　　　　残部
【０１８０】
＜実施例１〜４、比較例１〜３＞
上記で調製した第１のインクであるブラックインクと、カラーインクの各インクを下記表１のように組み合わせて、実施例１〜４、比較例１〜３のインクセットを作製した。

【０１８１】
［評価］
上記の実施例１〜４、比較例１〜３の各インクを用いて、市販コピー用紙に記録を行った。インクジェット記録装置としては、記録信号に応じた熱エネルギーをインクに付与することによりインクを吐出させるオンデマンド型マルチ記録ヘッドを有する３種類のインクジェット記録装置（商品名：ＢＪＦ−６００、ＢＪＦ−８００、ＢＪＦ−８５０；キヤノン（株）社製）を、それぞれ１／６００ｉｎｃｈ平方の領域に、ブラックインクは３０ｎｇ、カラーインクは１５ｎｇ相当のインクを付与できるように改造したものを用いた。又、印字パターンとしては、図１２のようなカラーとブラックの画像領域が隣接するものを印字し、境界部のブリードとブラック領域の白モヤの評価を目視で行った。
【０１８２】
尚、実施例２のインクセットを用いた場合では、カラーの印字領域をイエロー及びマゼンタとしたときには、記録媒体のブラックの画像が形成される領域に、シアンインクを予め打ち込んでおいた。このときのブラックインクとシアンインクとの印字デューティは、ブラックインクが１００％、シアンインクが１５％とした。実施例及び比較例のインクセットを用いて、上記のようにして画像を形成し、各画像について、下記の方法でブリードについて評価を行なった。
【０１８３】
印字パターンとしては図１２のようなカラーとブラックの画像領域が隣接するものを印字し、境界部のブリードの評価を目視で行った。実施例に用いたインクセットは何れも境界部のにじみは抑えられていたが、比較例に用いたインクセットは、何れも境界部のにじみが目立った。
【０１８４】
（第２の態様の第２のインク：ｐＨ変化に対して緩衝作用を持つインク）
先ず、下記の構成材料の混合物をベースとして、シアンインクＣ−２と、ｐＨ変化に対して緩衝作用を持つ２−１、２−２を作製した。
（シアンインクベース）
・グリセリン　　　　　　　　　　　　　　　５部
・１，５−ペンタンジオール　　　　　　　　５部
・トリメチロールプロパン　　　　　　　　　５部
・エタノール　　　　　　　　　　　　　　　２部
・アセチレノールＥＨ（商品名）　　　　１．０部
・Ｃ．Ｉ．ダイレクトブルー　１９９　　３．５部
【０１８５】
（シアンインクＣ−２）
・上記ベース　　　　　　　　　　　　２１．５部
・水　　　　　　　　　　　　　　　　７８．５部
【０１８６】
（シアンインク２−１）
・上記ベース　　　　　　　　　　　　２１．５部
・酢酸ナトリウム　　　　　　　　　　　０．５部
・酢酸　　　　　　　　　　　　　　　０．６５部
・水　　　　　　　　　　　　　　　７７．３５部
【０１８７】
（シアンインク２−２）
・上記ベース　　　　　　　　　　　　２１．５部
・コハク酸　　　　　　　　　　　　　０．３５部
・四ホウ酸ナトリウム　　　　　　　　０．６５部
・水　　　　　　　　　　　　　　　　７７．５部
【０１８８】
下記の構成材料の混合物をベースとして、シアンインクＭ−２と、ｐＨ変化に対して緩衝作用を持つ２−１、２−２を作製した。
（マゼンタインクベース）
・１，５−ペンタンジオール　　　　　　　　５部
・２−ピロリドン　　　　　　　　　　　　　５部
・エチレン尿素　　　　　　　　　　　　　　５部
・エタノール　　　　　　　　　　　　　　　２部
・アセチレノールＥＨ（商品名）　　　　１．０部
・Ｃ．Ｉ．アシッドレッド　２８９　　　　　３部
【０１８９】
（マゼンタインクＭ−２）
・上記ベース　　　　　　　　　　　　　　２１部
・水　　　　　　　　　　　　　　　　　　７９部
【０１９０】
（マゼンタインク２−１）
・上記ベース　　　　　　　　　　　　　　２１部
・クエン酸ナトリウム　　　　　　　　　　　１部
・酢酸　　　　　　　　　　　　　　　　０．９部
・水　　　　　　　　　　　　　　　　７７．１部
【０１９１】
（マゼンタインク２−２）
・上記ベース　　　　　　　　　　　　　　２１部
・クエン酸二水素カリウム　　　　　　　　　１部
・酢酸　　　　　　　　　　　　　　　　０．９部
・水　　　　　　　　　　　　　　　　７７．１部
【０１９２】
下記の構成材料の混合物をベースとして、イエローＹ−２と、ｐＨ変化に対して緩衝作用を持つ２−１、２−２を作製した。
（イエローインクベース）
・２−ピロリドン　　　　　　　　　　　　　５部
・エチレングリコール　　　　　　　　　　　５部
・トリメチロールプロパン　　　　　　　　　５部
・エタノール　　　　　　　　　　　　　　　２部
・アセチレノールＥＨ（商品名）　　　　１．０部
・Ｃ．Ｉ．アシッドイエロー　２３　　　　　３部
【０１９３】
（イエローインクＹ−２）
・上記ベース　　　　　　　　　　　　　　２１部
・水　　　　　　　　　　　　　　　　　　７９部
【０１９４】
（イエローインク２−１）
・上記ベース　　　　　　　　　　　　　　２１部
・乳酸ナトリウム　　　　　　　　　　　１．５部
・乳酸　　　　　　　　　　　　　　　１．８５部
・水　　　　　　　　　　　　　　　７５．６５部
【０１９５】
（イエローインク２−２）
・上記ベース　　　　　　　　　　　　　　２１部
・フタル酸水素カリウム　　　　　　　　　　１部
・乳酸　　　　　　　　　　　　　　　　０．９部
・水　　　　　　　　　　　　　　　　７７．１部
【０１９６】
＜実施例５〜８、比較例４〜８＞
先に調製した第１のインクであるブラックインクと、上記で得られたカラーインクを下記表１に示したように組み合わせて、実施例５〜８、比較例４〜８のインクセットを得た。
【０１９７】

【０１９８】
実施例５〜８、比較例４〜８の各インクセットを構成する第２のインクに用いたカラーインクが、ｐＨの変化に対して緩衝作用を持つか否かを、５０ｍｌのカラーインクに対して１規定の水酸化リチウム水溶液を１．０ｍｌ添加したインクのｐＨ値と、水酸化リチウム水溶液を添加しない状態でのインクのｐＨ値との差を測定することにより調べた。その結果を下記表３に示した。又、第１のインクであるブラックインクのｐＨについても表３に併せて示した。
【０１９９】

【０２００】
＜評価＞
次に、上記で得られた実施例５〜８、比較例４〜８の各インクセットを、記録信号に応じた熱エネルギーをインクに付与することによりインクを吐出させるオンデマンド型マルチ記録ヘッドを有するインクジェット記録装置であるＢＪＦ　８００（キヤノン製）の改造機に各々搭載して、印字試験を行った。そして、ブラックインクとカラーインクとの間のブリードについて評価を、下記のようにして行った。印字試験に用いた記録媒体は、キヤノン製コピー用紙：ＰＢ　ＰＡＰＥＲ（ＰＢと表示）、ゼロックス製：４０２４　ＰＡＰＥＲ（ＸＸと表示）の、普通紙２紙である。
【０２０１】
（ブラックインクと各カラーインクとの間のブリーディング）
ブラックインクとカラーインクを同一のスキャンで印字する印字方法で、上記普通紙２紙に、実施例５〜８、比較例４〜８の各インクセットを用いて、ブラックインクで形成したベタ部に、イエロー、又はマゼンタ、又はシアンインクで形成したベタ部が隣接するようなパターンを印字した。色の隣接する境界部分を目視で観察して、下記の評価基準で評価した。表４に、得られた結果を示した。
○：全ての境界とで目視でブリードが認められない。
△：目視でわずかにブリードが認められるが、あまり気にならない。
×：目視でブリードが認められる。
【０２０２】

【０２０３】
（第３の態様の第２のインク：第１のインク中の顔料極性と逆の極性の色材を有するインク）
［第１のインクの調製］
＜顔料分散液の調製＞
第１のインクとして先に調製した顔料分散液１と、下記のようにして調製した顔料分散液３〜６を用いた。
【０２０４】
（顔料分散液３）
前記した顔料分散液１と同様の作製方法で、分散液Ｂ１を調製した。そして、顔料分散液１の作製で用いた、重量平均分子量＝１５，０００、酸価＝１４０、多分散度Ｍｗ／Ｍｎ＝１．５のスチレン−アクリル酸樹脂の代わりに、重量平均分子量＝５，０００、酸価＝１４０、多分散度Ｍｗ／Ｍｎ＝１．８のスチレン−アクリル酸樹脂を用いて、その後の操作を同様に行って顔料分散液３を得た。得られた顔料分散液３の物性値は、固形分が１０．５％、ｐＨが１０、平均粒子径が１３４ｎｍであった。得られた顔料分散液３について、先に説明した方法で熱分析したところ、質量減少率は４．０％と少なく、カーボンブラック粒子表面に共重合体セグメントが化学的に結合したものであることが確認できた。
【０２０５】
（顔料分散液４）
前記した顔料分散液１と同様の作製方法で、分散液Ｂ１を調製した。そして、顔料分散液１の作製で用いた、重量平均分子量＝１５，０００、酸価＝１４０、多分散度Ｍｗ／Ｍｎ＝１．５のスチレン−アクリル酸樹脂の代わりに、重量平均分子量＝４，０００、酸価＝４８０、多分散度Ｍｗ／Ｍｎ＝２．２のスチレン−アクリル酸樹脂を用いて、その後の操作を同様に行って顔料分散液４を得た。得られた顔料分散液４の物性値は、固形分が１０％、ｐＨが９．０、平均粒子径が１４０ｎｍであった。得られた顔料分散液４について、先に説明した方法で熱分析したところ、質量減少率は６．２％と少なく、カーボンブラック粒子表面に共重合体セグメントが化学的に結合したものであることが確認できた。
【０２０６】
（顔料分散液５）
前記した顔料分散液１と同様の作製方法で、分散液Ａ１を作製した。次いで、顔料分散液１の作製の場合に使用したペンタエチレンヘキサミン（ＰＥＨＡ）の代わりに、アミン価＝２００、分子量＝１０，０００、多分散度Ｍｗ／Ｍｎ＝１．８のスチレン−Ｎ，Ｎ，−ジメチルアミノエチルメタクリレート樹脂（Ｓｔ−ＤＭ）を用い、その後の操作を同様に行って、最終的にＳｔ−ＤＭがカーボンブラックに化学的に結合した顔料分散液５を得た。得られた顔料分散液５の物性値は、固形分が１１％、ｐＨが５．５、平均粒子径が１２０ｎｍであった。得られた顔料分散液５について、先に説明した方法で熱分析したところ、質量減少率は１．８％と少なく、カーボンブラック粒子表面に共重合体セグメントが化学的に結合したものであることが確認できた。
【０２０７】
（顔料分散液６）
前記した顔料分散液１と同様の作製方法で、分散液Ａ１を作製した。次いで、顔料分散液１の作製の場合に使用したペンタエチレンヘキサミン（ＰＥＨＡ）の代わりに、アミン価＝４５０、分子量＝４，０００、多分散度Ｍｗ／Ｍｎ＝１．８のスチレン−Ｎ，Ｎ，−ジメチルアミノエチルメタクリレート樹脂（Ｓｔ−ＤＭ）を用い、その後の操作を同様に行って、最終的にＳｔ−ＤＭがカーボンブラックに化学的に結合した顔料分散液６を得た。得られた顔料分散液６の物性値は、固形分が１０％、ｐＨが４．５、平均粒子径が１４２ｎｍであった。得られた顔料分散液６について、先に説明した方法で熱分析したところ、質量減少率は３．８％と少なく、カーボンブラック粒子表面に共重合体セグメントが化学的に結合したものであることが確認できた。
【０２０８】
（インクの調製）
上記で得られた、共重合体セグメントを含む樹脂結合タイプの自己分散型カーボンブラックを用い、下記の成分を混合し、十分に攪拌して溶解或は分散した後、ポアサイズ３．０μｍのミクロフィルター（富士フィルム製）にて加圧ろ過して、第１のインクを調製した。
【０２０９】
（ブラックインク１）
・上記顔料分散液１　　　　　　　　　　　５０部
・グリセリン　　　　　　　　　　　　　　　５部
・１，５−ペンタンジオール　　　　　　　　６部
・トリメチロールプロパン　　　　　　　　　５部
・アセチレングリコールＥＯ付加物　　　０．１部
・純水　　　　　　　　　　　　　　　　　　残部
【０２１０】
（ブラックインク３）
・上記顔料分散液３　　　　　　　　　　　４５部
・グリセリン　　　　　　　　　　　　　　　５部
・１，５−ペンタンジオール　　　　　　　　５部
・トリメチロールプロパン　　　　　　　　　６部
・アセチレノールＥＨ（商品名）　　　　０．１部
・純水　　　　　　　　　　　　　　　　　　残部
【０２１１】
（ブラックインク４）
・上記顔料分散液４　　　　　　　　　　　５０部
・グリセリン　　　　　　　　　　　　　　　７部
・ジエチレングリコール　　　　　　　　　　３部
・トリメチロールプロパン　　　　　　　　　６部
・アセチレノールＥＨ（商品名）　　　　０．１部
・純水　　　　　　　　　　　　　　　　　　残部
【０２１２】
（ブラックインク５）
・上記顔料分散液５　　　　　　　　　　　５０部
・グリセリン　　　　　　　　　　　　　　　５部
・１，５−ペンタンジオール　　　　　　　　５部
・トリメチロールプロパン　　　　　　　　　５部
・アセチレノールＥＨ（商品名）　　　　０．１部
・純水　　　　　　　　　　　　　　　　　　残部
【０２１３】
（ブラックインク６）
・上記顔料分散液６　　　　　　　　　　　５０部
・グリセリン　　　　　　　　　　　　　　　５部
・１，５−ペンタンジオール　　　　　　　　５部
・トリメチロールプロパン　　　　　　　　　６部
・アセチレノールＥＨ（商品名）　　　０．１５部
・純水　　　　　　　　　　　　　　　　　　残部
【０２１４】
［第２のインクの調製］
＜カラー顔料分散液の作製＞
・スチレン−アクリル酸共重合体（分子量５０００）
５．５部
・モノエタノールアミン　　　　　　　　１．０部
・ジエチレングリコール　　　　　　　　５．０部
・純水　　　　　　　　　　　　　　　６７．５部
【０２１５】
先ず、上記成分を混合し、ウォーターバスで７０℃に加熱し、樹脂成分を完全に溶解させた。次に、この溶液にＣ．Ｉ．Ｐｉｇｍｅｎｔ　Ｙｅｌｌｏｗ　７４を２０部、イソプロピルアルコールを１．０部加え、３０分間プレミキシングを行った後、下記条件で分散処理を行い、更に、遠心分離処理を行って粗大粒子を除去することで、イエロー顔料分散液３−１を得た。
・分散機：サンドグラインダー
・粉砕メディア：ジルコニウムビーズ１ｍｍ径
・粉砕メディア充填率：５０％（体積）
・粉砕時間：３時間
【０２１６】
又、上記で用いたイエロー顔料分散液３−１のＣ．Ｉ．Ｐｉｇｍｅｎｔ　Ｙｅｌｌｏｗ　７４の代わりに、Ｃ．Ｉ．Ｐｉｇｍｅｎｔ　Ｒｅｄ　１２２を加える以外は、上記と同様にして調製し、マゼンタ顔料分散液３−１を得た。更に、イエロー顔料分散液３−１のＣ．Ｉ．Ｐｉｇｍｅｎｔ　Ｙｅｌｌｏｗ　７４の代わりに、Ｃ．Ｉ．Ｐｉｇｍｅｎｔ　Ｂｌｕｅ　１５：３を用いた以外は、上記と同様にして調製しシアン顔料分散液３−１を得た。
次に、上記で調製した各色顔料分散液３−１の作製条件において、顔料分散剤であるスチレン−アクリル酸共重合体（分子量５，０００）の代わりに、ポリオキシエチレンアミンを５．５部使用する以外は、上記したと同様にして、イエロー、マゼンタ及びシアンの各色顔料分散液３−２を作製した。
【０２１７】
＜カラーインクの作製＞
下記の成分を混合し、十分攪拌して溶解或は分散した後、ポアサイズ０．２又は３．０μｍのミクロフィルター（富士フィルム製）にて加圧ろ過し、各カラーインクを調製した。
【０２１８】
（シアンインク３−１）
・Ｃ．Ｉ．ダイレクトブルー１９９　　　　　３部
・グリセリン　　　　　　　　　　　　　　　７部
・２−ピロリドン　　　　　　　　　　　　　５部
・エチレングリコール　　　　　　　　　　　６部
・アセチレノールＥＨ（商品名）　　　　　　１部
・純水　　　　　　　　　　　　　　　　　　残部
【０２１９】
（シアンインク３−２）
・Ｃ．Ｉ．ベーシックブルー１００　　　　　３部
・グリセリン　　　　　　　　　　　　　　　７部
・２−ピロリドン　　　　　　　　　　　　　５部
・エチレングリコール　　　　　　　　　　　６部
・アセチレノールＥＨ（商品名）　　　　　　１部
・純水　　　　　　　　　　　　　　　　　　残部
【０２２０】
（シアンインク３−３）
・前記シアン顔料分散液３−１　　　　　　３０部
・グリセリン　　　　　　　　　　　　　　　８部
・ジエチレングリコール　　　　　　　　　　８部
・ポリエチレングリコール♯４００　　　　　５部
・アセチレノールＥＨ（商品名）　　　　０．８部
・純水　　　　　　　　　　　　　　　　　　残部
【０２２１】
（シアンインク３−４）
・前記シアン顔料分散液３−２　　　　　　３０部
・グリセリン　　　　　　　　　　　　　　　８部
・ジエチレングリコール　　　　　　　　　　８部
・ポリエチレングリコール♯４００　　　　　５部
・アセチレノールＥＨ（商品名）　　　　０．８部
・水　　　　　　　　　　　　　　　　　　　残部
【０２２２】
（マゼンタインク３−１）
・Ｃ．Ｉ．アシッドレッド２８９　　　　　　３部
・グリセリン　　　　　　　　　　　　　　　６部
・ジエチレングリコール　　　　　　　　　　５部
・トリエチレングリコール　　　　　　　　　７部
・アセチレノールＥＨ（商品名）　　　　　　１部
・水　　　　　　　　　　　　　　　　　　　残部
【０２２３】
（マゼンタインク３−２）
・Ｃ．Ｉ．ベーシックレッド１２　　　　　　３部
・グリセリン　　　　　　　　　　　　　　　６部
・ジエチレングリコール　　　　　　　　　　５部
・トリエチレングリコール　　　　　　　　　７部
・アセチレノールＥＨ（商品名）　　　　　　１部
・水　　　　　　　　　　　　　　　　　　　残部
【０２２４】
（マゼンタインク３−３）
・前記マゼンタ顔料分散液３−１　　　　　３０部
・グリセリン　　　　　　　　　　　　　　　８部
・ジエチレングリコール　　　　　　　　　　８部
・ポリエチレングリコール♯４００　　　　　５部
・アセチレノールＥＨ（商品名）　　　　０．８部
・純水　　　　　　　　　　　　　　　　　　残部
【０２２５】
（マゼンタインク３−４）
・前記マゼンタ顔料分散液３−２　　　　　３０部
・グリセリン　　　　　　　　　　　　　　　８部
・ジエチレングリコール　　　　　　　　　　８部
・ポリエチレングリコール♯４００　　　　　５部
・アセチレノールＥＨ（商品名）　　　　０．８部
・純水　　　　　　　　　　　　　　　　　　残部
【０２２６】
（イエローインク３−１）
・Ｃ．Ｉ．アシッドイエロー２３　　　　　　３部
・グリセリン　　　　　　　　　　　　　　　７部
・ジエチレングリコール　　　　　　　　　　７部
・尿素　　　　　　　　　　　　　　　　　　６部
・アセチレノールＥＨ（商品名）　　　　　　１部
・純水　　　　　　　　　　　　　　　　　　残部
【０２２７】
（イエローインク３−２）
・Ｃ．Ｉ．ベーシックイエロー２１　　　　　３部
・グリセリン　　　　　　　　　　　　　　　７部
・ジエチレングリコール　　　　　　　　　　７部
・尿素　　　　　　　　　　　　　　　　　　６部
・アセチレノールＥＨ（商品名）　　　　　　１部
・純水　　　　　　　　　　　　　　　　　　残部
【０２２８】
（イエローインク３−３）
・前記イエロー顔料分散液３−１　　　　　３０部
・グリセリン　　　　　　　　　　　　　　　８部
・ジエチレングリコール　　　　　　　　　　８部
・ポリエチレングリコール♯４００　　　　　５部
・アセチレノールＥＨ（商品名）　　　　０．８部
・純水　　　　　　　　　　　　　　　　　　残部
【０２２９】
（イエローインク３−４）
・前記イエロー顔料分散液３−２　　　　　３０部
・グリセリン　　　　　　　　　　　　　　　８部
・ジエチレングリコール　　　　　　　　　　８部
・ポリエチレングリコール♯４００　　　　　５部
・アセチレノールＥＨ（商品名）　　　　０．８部
・純水　　　　　　　　　　　　　　　　　　残部
【０２３０】
＜実施例９〜１７＞
上記で調製した第１のインクであるブラックインクと、上記で得られた各カラーインクを下記表５に示したように組み合わせて、第２のインク中の色材の極性が、前記第１のインク中の顔料が有している極性とは逆である、実施例９〜１７の各インクセットを得た。
【０２３１】

【０２３２】
＜比較例９＞
比表面積が２１０ｍ^２／ｇで、ＤＢＰ吸油量が７４ｍｌ／１００ｇであるカーボンブラックを７部、酸価＝２００、重量平均分子量＝１０，０００のスチレン−アクリル酸共重合体を２部、モノエタノールアミンを１部、ジエチレングリコールを１５部、グリセリンを１０部、純水６５部を混合し、サンドグラインダーを用いて１時間分散させた。その後、遠心分離処理によって粗大粒子を除去し、ポアサイズ３．０μｍのミクロフィルター（富士フィルム製）にて加圧ろ過し、ブラックインクを得た。得られたブラックインク７を、比較例９のインクセットの第１のインクに用いた。該ブラックインク７に組み合わせるカラーインクには、実施例で使用したシアンインク３−４、マゼンタインク３−４、イエローインク３−４を用いた。
【０２３３】
＜比較例１０＞
先に調製した、ポリアクリル酸樹脂がカーボンブラック表面に結合した顔料分散液３を含むブラックインク３を、比較例１０のインクセットの第１のインクに用いた。このブラックインク３に組み合わせるカラーインクには、実施例で使用した、シアンインク３−４、マゼンタインク３−４、イエローインク３−４を用いた。
【０２３４】
＜比較例１１＞
３０ｇの水にＨ_３Ｎ^＋Ｃ_６Ｈ_４Ｎ^＋（ＣＨ_３）_３Ｃｌ⁻が３．０８ｇ溶けた溶液中に、硝酸銀１．６９ｇを攪拌しながら加える。発生した沈澱物をろ過により除去し、ろ液を、水７０ｇに比表面積が２３０ｍ^２／ｇでＤＢＰＡが７０ｍｌ／１００ｇのカーボンブラック１０ｇが分散している懸濁液に攪拌しながら加えた。次に、２．２５ｇの濃塩酸を加え、それから水１０ｇに０．８３ｇの亜硝酸ナトリウムが溶けた溶液を加える。すると、ＮＮ^＋Ｃ_６Ｈ_４Ｎ^＋（ＣＨ_３）_３基を有するジアゾニウム塩がカーボンブラックと反応して、窒素ガスが発生する。窒素ガスの泡が止まったら、その分散液を２０℃のオーブンで乾燥させた。その結果、カーボンブラック粒子表面ににＣ_６Ｈ_４Ｎ^＋（ＣＨ_３）_３基がついた生成物が得られた。この生成物４部を、実施例で使用したブラックインク４の調製の際の顔料分散液４の代わりに使用して、ブラックインク８を得、これを比較例１１のインクセットの第１のインクに用いた。このブラックインク８に組み合わせるカラーインクには、実施例で使用した、シアンインク３−１、マゼンタインク３−１、イエローインク３−１を用いた。
【０２３５】
＜比較例１２＞
第１のインクとして、ブラックインク１を用い、このブラックインク１に組み合わせるカラーインクには、実施例で使用したシアンインク３−１、マゼンタインク３−１、イエローインク３−１を用いた。この組み合わせは、第２のインク中の色材の極性が、第１のインク中の顔料が有している極性と、アニオン性同士で同じである。
【０２３６】
＜比較例１３＞
第１のインクとして、ブラックインク６を用い、このブラックインク６に組み合わせるカラーインクには、実施例で使用したシアンインク３−４、マゼンタインク３−４、イエローインク３−４を用いた。この組み合わせは、第２のインク中の色材の極性が、第１のインク中の顔料が有している極性と、カチオン性同士で同じである。
【０２３７】
＜評価＞
上記上記実施例９〜１７及び比較例９〜１３の各インクを用いて、記録信号に応じて熱エネルギーをインクに付与することによりインクを吐出させる、オンデマンド型マルチ記録ヘッドを有するインクジェット記録装置ＢＪＦ−６６０（キヤノン（株）製）を改造して下記の評価を行った。そして、得られた評価結果を表６に示した。
【０２３８】
１．印字持続性
実施例及び比較例の各インクと、上記インクジェット記録装置を用い、ノズルチェックパターンが最初に入っているベタ印字を連続してＡ４用紙３枚に印字を行ない、次に、その後２時間印字を行わず、その後再びベタ印字を連続して３枚印字するサイクルを１０回繰り返した。その時の印字みだれ、及び不吐出の有無を下記の基準で評価した。
○：印字みだれ及び不吐出がみられない。
△：印字みだれが若干みられるが、不吐出はみられない。
×：印字みだれ、不吐出がみられる。
【０２３９】
２．耐マーカー性
上記各インクと上記したインクジェット記録装置とを用い、下記の５種類のコピー用普通紙Ａ〜Ｅに印字を行い、得られた画像を１日放置した後、市販の水性蛍光マーカーペン（例えば、ゼブラ製蛍光ペン　ＯＰＴＥＸ　ＯＰ−１００−Ｙ）を用いて印字部分をマーキングして、マーキング部分の汚れを観察して、以下の基準で評価した。
○：全ての紙で汚れが目立たない。
△：一部の紙で汚れが目立つ。
×：全ての紙で汚れが目立つ。
【０２４０】
上記画出し試験において、コピー用紙は以下に示すものを用いた。
Ａ：キヤノン（株）社製、ＰＰＣ用紙ＮＳＫ
Ｂ：キヤノン（株）社製、ＰＰＣ用紙ＮＤＫ
Ｃ：ゼロックス（株）社製、ＰＰＣ用紙４０２４
Ｄ：フォックスリバー（株）社製、ＰＰＣ用紙プローバーボンド
Ｅ：ノイジドラ（株）社製、キヤノン用ＰＰＣ用紙
【０２４１】
３．耐ブリード性
ブラックインクのベタ部と、イエロー又はマゼンタ、又はシアンインクのベタ部が隣接するようなパターンをＣａｎｏｎ／ＰＢ　ｐａｐｅｒに印字し、ブラックインクとカラーインクとの境界部分を目視にて観察し、ブリードの発生の有無を下記基準にて評価した。
◎：全ての境界部でブリーディングが全く認められない。
○：僅かにブリーディングが認められるが、問題ないレベルである。
△：若干のブリーディングがみられる。
×：殆どすべての境界でブリーディングが目立つ。
【０２４２】

【０２４３】
【発明の効果】
以上説明したように、本発明によれば、特に、ブラックインクに求められる印字品位、画像堅牢性等の種々の性能を満たし、このブラックインクが、他の色のインクとの間にブリードを生じることがない画像を得ることができ、優れたカラー画像の形成が可能な、記録ヘッドに対するインクの信頼性を有しつつ、且つ、印字後の擦れによる印字汚れ耐擦過性や、印字後の水性マーカーによる耐マーカー性を改善できる、インクセット、画像形成方法、記録ユニット及びインクジェット記録装置が提供される。
【図面の簡単な説明】
【図１】実施例で使用した顔料分散液の顔料を凝析した後の試料についての熱重量分析結果である。
【図２】実施例で使用した顔料分散液の顔料を凝析後、更に、ＴＨＦで洗浄処理した後の試料についての熱重量分析結果である。
【図３】比較例で使用した顔料分散液の顔料を凝析した後の試料についての熱重量分析結果である。
【図４】比較例で使用した顔料分散液の顔料を凝析後、更に、ＴＨＦで洗浄処理した後の試料についての熱重量分析結果である。
【図５】インクジェット記録装置ヘッドの縦断面図である。
【図６】インクジェット記録装置ヘッドの縦横面図である。
【図７】図５に示したヘッドをマルチ化したヘッドの外観斜視図である。
【図８】インクジェット記録装置の一例を示す斜視図である。
【図９】インクカートリッジの縦断面図である。
【図１０】記録ユニットの一例を示す斜視図である。
【図１１】記録ヘッドの構成の一例を示す図である。
【図１２】カラーとブラックの画像領域が隣接する印字パターンを示す図である。
【符号の説明】
１３：ヘッド
１４：インク溝
１５：発熱素子基板
１６：保護層
１７−１、１７−２：電極
１８：発熱抵抗体層
１９：蓄熱層
２０：基板
２１：インク
２２：吐出オリフィス（微細孔）
２３：メニスカス
２４：インク滴
２５：記録媒体
２６：マルチ溝
２７：ガラス板
２８：発熱ヘッド
４０：インク袋
４２：栓
４４：インク吸収体
４５：インクカートリッジ
５１：紙給部
５２：紙送りローラー
５３：排紙ローラー
６１：ブレード
６２：キャップ
６３：インク吸収体
６４：吐出回復部
６５：記録ヘッド
６６：キャリッジ
６７：ガイド軸
６８：モーター
６９：ベルト
７０：記録ユニット
７１：ヘッド部
７２：大気連通口
８０：インク流路
８１：オリフィスプレート
８２：振動板
８３：圧電素子
８４：基板
８５：吐出口[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink set, an image forming method, a recording unit, and an ink jet recording apparatus that are used when a color image is recorded on a recording medium by using a plurality of color inks and combining these inks. On the other hand, having a sufficient image density, a clear and high-quality image can be obtained, and furthermore, an image excellent in water resistance and light resistance of a printed matter is provided, and even when a black image and a color image are adjacent to each other. The present invention relates to an ink set that provides a color image with sufficiently reduced bleed in a boundary region thereof, an image forming method using the same, a recording unit, and an ink jet recording apparatus.
[0002]
[Prior art]
Conventionally, pigments having excellent fastness such as water resistance and light resistance have been widely used as colorants for printing inks. With respect to inks for ink jet recording, studies for adopting a pigment as a coloring material in the ink have been actively conducted in order to further improve the robustness of an ink jet recorded image. By the way, in order to use a pigment as a coloring material of an aqueous ink for inkjet, it is important to stably disperse the pigment in an aqueous medium. Generally, a dispersant, for example, a resin dispersant is used to uniformly disperse the pigment in an aqueous medium. Such a resin dispersant is generally a water-soluble resin having a hydrophilic group for stably dispersing a pigment in an aqueous medium and a hydrophobic part for physically adsorbing to a hydrophobic pigment surface. Used. An ink jet recorded image obtained with such a pigment ink has relatively good quality in terms of scratch resistance, marker resistance and the like due to the presence of the resin dispersant.
[0003]
On the other hand, in order to stably form a high-quality ink-jet recorded image, it is important that ink is ejected as stable droplets from fine nozzles of the ink-jet recording head. Specifically, for example, it is important that the ink does not solidify in the orifice of the inkjet recording head due to drying of the orifice in order to perform stable inkjet recording. However, pigment inks for inkjet, in which a pigment is dispersed in an aqueous medium by the above-described resin dispersant, have a problem in this respect. That is, it is considered that there is a considerable amount of a resin dispersant present in a dissolved state in the ink without being adsorbed on the pigment surface in the ink as described above. The nozzle may be clogged by adhering to an orifice or the like of the recording head.
[0004]
In addition, in the case of performing continuous printing such as solid printing or the like, there is a problem in that the ink ejection becomes irregular as the head temperature increases, the ejection direction bends, and the ink landing point shifts. Further, when continuous printing is continued, ink is attached to the orifice surface in the vicinity of the nozzle as the ejection is repeated while the ink overflows from the nozzle. Then, a large ink sump is formed on the orifice with the ink adhesion portion near the nozzle as a nucleus. When printing is continued in this state, the ink to be ejected is drawn into the ink summary on the orifice, and the ink cannot be ejected. There is a problem that the reliability of the ink with respect to the head is poor.
[0005]
Methods for improving the reliability of the pigment ink with respect to the above-described problems are described in, for example, Patent Documents 1 and 2. Specifically, a pigment (self-dispersible pigment) that can be stably dispersed in an aqueous ink without using a dispersant by introducing a water-soluble group into the surface of carbon black particles was used as a coloring material. And pigment inks.
[0006]
However, when printing is performed on a recording medium, particularly plain paper, using an aqueous pigment ink using such a self-dispersing pigment, even if the ink is sufficiently dried, the printing surface may be strongly rubbed. May become dirty, and the scratch resistance of the image may not be sufficient. Although not using the resin dispersant in the ink effectively functions to further improve the reliability of the ink jet recording, it may degrade some quality of the ink jet recorded matter.
[0007]
On the other hand, Patent Literature 3 discloses an inkjet ink including a self-dispersible pigment of a type in which a resin is chemically bonded to a pigment surface, and an inkjet recording method using the same. The self-dispersible pigment has a segment (A) having a reactive group capable of reacting with a functional group on the surface of the pigment, and a liquid that is substantially free of the reactive group and is more liquid than the segment (A). It is disclosed that a polymer having a segment (B) having high affinity for a medium is obtained by heating with a pigment.
[0008]
However, in the present invention, a specific functional group is required as a polymer to be reacted with the pigment surface, and a usable polymer is limited, and a functional group capable of reacting with the polymer is also essential on the pigment surface. However, there is a problem that the types of pigments that can be used are also limited. According to the study of the present inventors, it is difficult to impart ionicity to the pigment surface and the segment having no reactive group as a manufacturing problem, and the pigment has sufficient dispersibility in an aqueous medium. It is considered difficult to obtain pigments.
[0009]
Patent Document 4 discloses an ink-jet ink composition comprising a macromolecular chromophore comprising at least one water-solubilizing functional group and at least one polymer covalently attached, wherein the polymer is An ink-jet ink composition is disclosed which is attached to the macromolecular chromophore by a nucleophilic substitution or an acylation reaction. However, in the present invention, although amine or hydroxyl termination is essential in the polymer, the kind of polymer that can be used is limited, and although the scratch resistance is improved by dispersion of the terminal-modified homopolymer by the functional group, There was a problem that the marker resistance was insufficient.
[0010]
Further, Patent Document 5 discloses an inkjet ink composition containing a macromolecular chromophore, comprising at least one water-solubilizing functional group and at least one covalently attached polymer. The ink-jet ink composition of the present invention comprises modified pigment particles (macromolecule chromophores) having both functional groups attached to impart water solubility and vinyl polymer chains covalently attached. However, in producing such a composition, in the step of adding a polymer chain to the surface of the pigment by a covalent bond, the polymer is grown by radical polymerization of the pigment in the presence of a monomer and an initiator. However, according to the study of the present inventors, in this method, it is difficult to control the molecular weight of the polymer in the radical polymerization of the monomer, and it is also difficult to control the acid value or the amine value as an index of the solubility of the water-soluble polymer in water. Difficulty, and in addition, it was uncertain whether the polymers were covalently bound to the pigment surface. In other words, the terminal radicals of the growing polymer are not necessarily bound to the pigment surface and the polymerization is not always stopped, and a part is bound to the pigment surface, but the polymerization reaction is caused by the bonding between the growing polymers. In some cases, the production was stopped, and it was very difficult to efficiently attach the polymer to the pigment surface.
[0011]
Patent Document 6 describes a resin-bonded self-dispersible pigment using a plurality of molecules. This resin-bonded self-dispersible pigment can disperse an ionic aqueous pigment. However, according to the study of the present inventors, the use of these resin-bonded self-dispersible pigments can ensure the reliability of the ink for the recording head, but the image after printing has a high abrasion resistance and a high resistance. There is still room for improvement in marker properties.
[0012]
In addition to the above-mentioned problems, in recent years, in a situation where the image quality of an ink jet recording image is required to be substantially the same level as that of a silver halide photograph, not only the quality of a single color image but also Suppressing the bleeding (hereinafter, referred to as bleed) at the boundary between the images, which occurs when two images of different colors are formed adjacent to each other, is also an important technical problem to be solved.
[0013]
In order to solve these problems, conventionally, a pigment has been used for forming a black image excellent in fastness such as print density, print quality, water fastness and light fastness in ink jet recording, especially on plain paper. Black ink using, further, an ink set that does not cause bleeding at the boundary between an image printed with black ink and an image printed with color ink, and an inkjet recording method and apparatus using the same. Many reports have been made.
[0014]
For example, Patent Document 7 discloses that a bleed is performed by using a black ink composed of a colorant composed of a pigment and a dispersant that is insolubilized under a specific pH environment, and a color ink having a pH at which the dispersant is insolubilized. Describes an ink-jet printing method and an ink set that can prevent the occurrence of ink.
[0015]
Further, Patent Document 8 uses a black ink composed of a chemically modified black pigment, that is, a black pigment made water-soluble by introducing a functional group, and a color ink having a higher ionic strength than the black ink. Thus, there is described an ink set in which a sudden change in ionic strength causes aggregation of dissolved pigment to thereby reduce bleed.
[0016]
However, as described in Patent Document 7, a colorant composed of a pigment, a black ink composed of a dispersant that is insolubilized under a specific pH environment, and a color ink having a pH at which the dispersant is insolubilized, In the case of the ink set using, the occurrence of bleed is certainly suppressed considerably, but in the black ink, there is a free polymer dispersant that is not adsorbed on the pigment, and they also have a pH at which the dispersant becomes insoluble. The aggregation caused by the color inks results in the need for color inks with higher concentrations of buffer. This causes a reduction in the reliability of the inkjet recording ink, such as the ejection stability of the color ink.
[0017]
Further, as described in Patent Document 8, a black ink comprising a chemically modified black pigment, that is, a black pigment made water-soluble by introducing a functional group, and a higher ionic strength than the black ink are provided. In the case of an ink set using color ink, although it is possible to satisfy the print density, print quality, image fastness, etc. of the black ink, the effect of suppressing bleed is not sufficient, and to reduce bleeding , A high molecular weight colloid must be added to the ink, and as a result, the viscosity of the black ink may increase and the ejection performance may decrease.
[0018]
In addition, Patent Document 9 describes an ink using an acidic carbon black and an alkali-soluble polymer, and Patent Document 10 includes at least one anionic dye in a black ink. An ink jet ink set which can prevent bleeding containing at least one cationic dye and a polyvalent precipitant in a yellow ink is described. In Patent Document 11, an anionic ink and a cationic ink are used, and a polymer having the ionic property of the ink is contained in at least one of the inks. An ink set in which the occurrence of bleed is reduced by contacting an anionic ink and a cationic ink is described.
[0019]
However, in the case of an ink using an acidic carbon black and an alkali-soluble polymer as described in Patent Document 9, the carbon black is dispersed by the alkali-soluble polymer. Have many restrictions on ensuring the reliability of the head. In addition, when printing is performed on a recording medium, particularly plain paper, with these resin-dispersed or self-dispersed pigment inks, if the printed surface is strongly rubbed after the ink is sufficiently dried, the printed surface becomes dirty. There was a problem that the scratch resistance was poor, and the marker resistance was poor when the printed surface was traced with a water-based marker.
[0020]
Also, as described in Patent Document 11, at the time of multicolor printing, when bleeding is reduced by bringing an anionic ink and a cationic ink into contact with each other in the presence of a polymer, when the bleeding is reduced, Some types may adversely affect the reliability of the ink. In particular, during the printing, after the ink is ejected from a certain nozzle, if the ink is not ejected from the nozzle for a certain time (for example, about one minute), the next first ink is ejected from the nozzle. In such a case, stable ejection may not be performed, and there may be a problem that printing is disturbed. In the present specification, such a state is hereinafter referred to as “poor in oneness”.
[0021]
Further, Patent Document 12 describes an ink set using a black ink using carbon black having a cationic group on its surface as a colorant and a color ink using a colorant using an anionic dye as a colorant. . However, in this case, the black ink image formed by the black ink can satisfy the print density, the print quality, the image fastness, and the like. , The marker resistance is not sufficient, and the effect of suppressing the occurrence of bleed generated between the image and the color ink image is still insufficient.
[0022]
[Patent Document 1]
JP-A-8-3498
[Patent Document 2]
JP-A-10-195360
[Patent Document 3]
JP-A-9-272831
[Patent Document 4]
JP 2000-53902 A
[Patent Document 5]
JP 2000-95987 A
[Patent Document 6]
International Publication No. 01/51566 pamphlet
[Patent Document 7]
JP-A-7-1837
[Patent Document 8]
JP-A-10-272768
[Patent Document 9]
JP-A-3-210373
[Patent Document 10]
JP-A-6-57192
[Patent Document 11]
JP-A-7-145336
[Patent Document 12]
JP-A-10-183046
[0023]
[Problems to be solved by the invention]
Accordingly, it is an object of the present invention to provide an image having high image density (OD), excellent scratch resistance and marker resistance, and when images of different colors are adjacent to each other, the bleed at the boundary between the images is different. An object of the present invention is to provide an ink set capable of suppressing generation and achieving formation of a high-quality color image. Another object of the present invention is to provide an image forming method capable of forming a high-quality color image, a recording unit and an ink jet recording apparatus that can be used in such an image forming method.
[0024]
Further, the object of the present invention is to provide excellent color developability of an image obtained by a black ink or a color ink, and particularly to a high print quality required for a black ink image, a print stain abrasion resistance and a print stain marker resistance. While satisfying various performances such as high image fastness, image formation in which the occurrence of bleed in the boundary region between the black image and the color image formed on the recording medium can be suppressed more effectively, and An object of the present invention is to provide an ink set, an image forming method, a recording unit, and an ink jet recording apparatus in which ink has excellent ink jet recording characteristics such as ejection stability and also has high reliability for a head.
[0025]
[Means for Solving the Problems]
The above object is achieved by the present invention described below. That is, according to one embodiment of the present invention, at least a first ink and a second ink having a different color from the first ink are provided, and a color is obtained by applying each ink to a recording medium. An ink set used to form an image on a recording medium, wherein the first ink comprises a modified pigment in which an organic group is chemically bonded to the surface of pigment particles, and An aqueous medium as a dispersion medium, wherein the organic group has a functional group chemically bonded directly or via another atomic group to the pigment surface, and an ionic monomer and a hydrophobic group. The second ink contains a colorant, and when mixed with the first ink, the dispersion stability of the pigment in the first ink. It is characterized by being an aqueous ink that destabilizes the ink Is Nkusetto.
[0026]
As a preferable mode, an ink set in which the second ink contains a polyvalent metal ion in the above-described configuration is given. Further, in such a configuration, the polyvalent metal ion is Mg²⁺, Ca²⁺, Cu²⁺, Co²⁺, Ni²⁺, Fe²⁺, La³⁺, Nd³⁺, Y³⁺And Al³⁺An ink set that is at least one selected from the group consisting of: an ink set in which the polyvalent metal ion is contained in an amount of 0.1 to 15% by mass based on the total mass of the second ink; The second ink contains at least one anionic dye and has an acidic pH, and the color material in the second ink is at least one selected from an acid dye and a direct dye. Is an ink set.
[0027]
As another preferred embodiment, in the above-described configuration, the second ink causes a pH change in the first ink by mixing with the first ink, so that the dispersibility of the pigment in the first ink is improved. An ink set having a destabilizing pH and further having a buffering action on the pH (buffering action on a change in hydrogen ion concentration) is exemplified. Further, in such a configuration, the pH value of the second ink is a pH value when 1.0 ml of a 1N aqueous lithium hydroxide solution is added to 50 ml of the second ink, and the pH value of the second ink before the addition is 50%. An ink set in which the difference from the pH value of the ink is adjusted to be within 1.0; an ink set in which the pH of the first ink is lower than the pH of the second ink; An ink set in which the pH of the ink takes a value in a neutral region to an acidic region.
[0028]
As another preferable embodiment, there is provided an ink set in which the polarity of the coloring material in the second ink is opposite to the polarity of the pigment in the first ink. Further, the Ka value of the second ink having any one of the above structures and determined by the Bristow method is 1.5 (ml / m2).²/ Msec^1/2).
[0029]
As another preferred embodiment, in any one of the above-described structures, the ink set in which the pigment constituting the first ink is carbon black, and the other atomic group constituting the first ink is phenyl (2 An ink set in which the copolymer constituting the first ink has a Mw of 1,000 to 30,000 and an acid value or an amine value of 100 to 500; In addition, an ink set in which the polydispersity Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) of the copolymer constituting the first ink is 3 or less, or the above-mentioned ink set obtained by the Bristow method The Ka value of the first ink is 1.5 (ml / m²/ Msec^1/2), And the Ka value is less than 0.2 (ml / m²/ Msec^1/2The ink set described above, wherein the first ink has a ratio of the organic group in the modified pigment to the total mass of the pigment of 5 to 40% by mass, more preferably 10 to 25% by mass. And an ink set in which the first ink is a black ink and the second ink is a color ink.
[0030]
According to another embodiment of the present invention, there is provided an image forming method for forming a color image on a recording medium by an ink jet recording method using any one of the above ink sets, wherein the ink set comprises An image comprising: a step of applying the first ink to a recording medium by an inkjet method; and a step of applying the second ink constituting the ink set to a recording medium by an inkjet method. A method of forming is provided.
[0031]
According to another embodiment of the present invention, a first ink containing section that contains the first ink and a second ink that contains the second ink are included in any of the ink sets described above. A recording unit is provided which includes two ink storage units and an inkjet head group for independently discharging each ink.
[0032]
According to another embodiment of the present invention, a first ink containing section containing black ink and a second ink containing color ink constituting one of the above ink sets. And an inkjet head group for ejecting the black ink and the color ink, respectively, and means for driving the inkjet head according to recording information. Provided.
[0033]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described in more detail with reference to preferred embodiments.
An ink set according to the present invention has a combination of at least a first ink and a second ink having a different color from the first ink, and a color image is formed by applying each ink to a recording medium. An ink set used to form a pigment on a recording medium, wherein the first ink comprises a modified pigment in which an organic group is chemically bonded to the surface of pigment particles, and a dispersion of the pigment. An aqueous medium as a medium, wherein the organic group has a functional group chemically bonded directly or via another atomic group to the pigment surface, and an ionic monomer and a hydrophobic group. The second ink contains a colorant, and when mixed with the first ink, the dispersion of the pigment in the first ink is stabilized. Aqueous solution with function to destabilize And characterized in that.
[0034]
As described above, a pigment ink using a pigment as a coloring material is more advantageous than a dye ink in order to ensure high image density and complete image fastness in ink used for inkjet recording. However, in order to use a pigment as a coloring material of an ink, generally, some dispersant is added to disperse the pigment in a good state, but when such a pigment ink is used for inkjet recording, Is liable to cause various adverse effects due to the inclusion of a dispersant. For example, when a polymer type dispersant is used, there are problems that the face surface of the head portion is easily wetted, clogging occurs, and storage stability is poor. Further, when a surfactant-type dispersant is used, there are problems that the image density is low and the face of the head portion is easily wetted.
[0035]
On the other hand, in the case of a specific pigment to be contained as a coloring material of the first ink used in the present invention, the pigment itself does so-called self-dispersion without containing a dispersant, so No harm is caused by the inclusion of the dispersant. That is, the pigment used in the first ink used in the present invention is a modified pigment in which an organic group is chemically bonded to the surface of the pigment particle, and the organic group is directly or directly on the pigment surface. It includes a reaction product of a functional group chemically bonded through another atomic group and a copolymer of an ionic monomer and a hydrophobic monomer. For this reason, in the first ink used in the present invention, first, an ionic monomer unit (hydrophilic part) is contained in the copolymer constituting the reactant bonded to the pigment surface. By this function, the pigment itself can be kept in a stable dispersion state in an aqueous medium such as water, and an ink for inkjet recording can be obtained without particularly requiring a dispersant. For this reason, it is possible to effectively prevent the adverse effects caused by the inclusion of the dispersant in the ink. Further, since the copolymer constituting the reactant bonded to the pigment surface has a hydrophobic monomer unit (hydrophobic portion), it is formed by the ink despite being an aqueous pigment ink. The scratch resistance and marker resistance of the resulting image are improved. These will be described later.
[0036]
In the present invention, when forming a color image, a second ink having a color different from that of the first ink combined with the first ink is used as a second ink when mixed with the first ink. An ink having a function of destabilizing the dispersion stability of the pigment in the first ink is used. With this configuration, when ink images of different colors are adjacent to each other, it is possible to suppress bleeding that occurs at the boundary, and as a result, a high-quality color image is formed. Specific modes of the ink that, when mixed with the first ink, destabilizes the dispersion stability of the pigment in the first ink, include the following three modes. In the first embodiment, an ink containing polyvalent metal ions is used as the second ink. In the second aspect, when mixed with the first ink, the first ink has a pH that causes a change in pH and destabilizes the dispersibility of the pigment in the first ink. Further, an ink having a buffering effect on the pH is used as the second ink. Further, in the third aspect, an ink in which the polarity of the coloring material is opposite to the polarity of the pigment in the first ink is used as the second ink. Hereinafter, first, the first ink will be described, and then the second ink will be described by dividing into these three modes.
[0037]
<First ink>
The first ink constituting the ink set of the present invention is an aqueous ink containing a modified pigment in which an organic group is chemically bonded to the surface of pigment particles, and an aqueous medium as a dispersion medium of the pigment. An ink, wherein the organic group is a reaction between a functional group chemically bonded directly or via another atomic group to a pigment surface and a copolymer of an ionic monomer and a hydrophobic monomer. It is configured to include things. Hereinafter, the modified pigment constituting the first ink will be described in terms of the pigment, the functional group, and the copolymer. Further, an aqueous medium or the like that forms an ink together with the pigment will be described.
[0038]
[Pigment]
The pigment used in the first ink constituting the ink set of the present invention is not particularly limited, and the following pigments can be used. These pigments are modified and used by the methods described below. It is preferable that the content of the pigment is 0.1 to 15% by mass, more preferably 1 to 10% by mass, based on the total mass of the aqueous ink.
[0039]
As the pigment used for the black ink, carbon black is particularly preferable. For example, carbon black pigments such as furnace black, lamp black, acetylene black, and channel black. 1200, Ray-Van 1190 ULTRA-II, Ray-Van 1170, Ray-Van 1255 (all manufactured by Columbia), Black Pearls L, Regal 400R, Regal 330R, Regal 660R, Mogul L, Monarch 700, Monac 800, Monac 880, Monac 900, Monac 1000, Monac 110 , Monak 1300, Monak 1400, Monak 2000, Valcan XC-72R (all manufactured by Cabot Corporation), Color Black (Color Black) FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Printex 140V, Special Black 6, Special Black 5, Special Black 4A, Special Black 4 (above, manufactured by Degussa), No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, No. Commercially available products such as 2300, MCF-88, MA600, MA7, MA8, and MA100 (manufactured by Mitsubishi Chemical Co., Ltd.) and those newly prepared separately can also be used. However, the present invention is not limited to these, and any conventionally known carbon black can be used. In addition, not limited to carbon black, magnetic fine particles such as magnetite and ferrite, and titanium black and the like may be used as a black pigment.
[0040]
As the organic pigment, specifically, for example, insoluble azo pigments such as Toluidine Red, Toluidine Maroon, Hansa Yellow, Benzidine Yellow, Pyrazolone Red, etc., soluble azo pigments such as Litol Red, Helio Bordeaux, Pigment Scarlet, Permanent Red 2B, Alizarin, indanthrone, derivatives from vat dyes such as thioindigo maroon, phthalocyanine blue, phthalocyanine pigments such as phthalocyanine green, quinacridone red, quinacridone pigments such as quinacridone magenta, perylene red, perylene pigments such as perylene scarlet, Isoindolinone pigments such as isoindolinone yellow and isoindolinone orange, and imidants such as benzimidazolone yellow, benzimidazolone orange and benzimidazolone red Zolone pigments, pyranthrone pigments such as pyranthrone red and pyranthrone orange, indigo pigments, condensed azo pigments, thioindigo pigments, diketopyrrolopyrrole pigments, flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel azo Yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, dioxazine violet and the like. Of course, it is not limited to these, and other organic pigments may be used.
[0041]
The organic pigments that can be used in the present invention are represented by color index (CI) numbers. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 97, 109, 110, 117, 120, 125, 128, 137, 138, 147, 148, 150, 151, 153, 154, 166, 168, 180, 185, C.I. I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, 71, C.I. I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 175, 176, 177, 180, 192, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254, 255, 272, C.I. I. Pigment Violet 19, 23, 29, 30, 37, 40, 50, C.I. I. Pigment Blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64, C.I. I. Pigment Green 7, 36, C.I. I. Pigment Brown 23, 25, 26, and the like.
[0042]
[Functional group]
In the pigment in the aqueous ink according to the present invention, the functional group is chemically bonded directly to the pigment surface or via another atomic group. The functional group is for forming an organic group by a reaction with a copolymer described below, and the type of the functional group is selected in relation to the functional group carried by the copolymer. You. In consideration of the fact that the pigment is dispersed in an aqueous medium, the reaction between the functional group and the copolymer is a reaction that produces a bond that does not cause hydrolysis or the like, for example, an amide bond or the like. It is preferable that By making the functional group an amino group and making the copolymer carry a carboxyl group, the copolymer can be introduced to the pigment particle surface via an amide bond. Alternatively, the copolymer can be similarly introduced into the surface of the pigment particle via an amide bond by making the functional group a carboxyl group and carrying an amino group on the copolymer.
[0043]
Here, the functional group chemically bonded to the pigment surface may be directly bonded to the pigment surface, or may be bonded via another atomic group. However, when introducing a copolymer having a relatively large molecular weight onto the pigment surface, it is preferable to introduce a functional group onto the pigment surface via another atomic group in order to avoid steric hindrance between the copolymers. Here, other atomic groups are not particularly limited as long as they are polyvalent elements or organic groups. However, from the viewpoint of controlling the distance of the functional group from the pigment surface for the reasons described above, for example, a divalent organic residue is preferably used. Examples of the divalent organic residue include an alkylene group and an arylene group (phenylene group).
[0044]
More specifically, for example, in Examples described later, a pigment is reacted with aminophenyl (2-sulfoethyl) sulfone to introduce an aminophenyl (2-sulfoethyl) sulfone group on the pigment surface, and then pentaethylene An amino group as a functional group is introduced by reacting an amino group of hexamine with an aminophenyl (2-sulfoethyl) sulfone group. In this case, it can be said that the amino group is chemically bonded to the pigment surface via an atomic group including a phenyl (2-sulfoethyl) group. The effects of the first ink used in the present invention include the following.
[0045]
First, as a first effect, the pigment constituting the first ink used in the present invention is composed of a functional group chemically bonded directly or through another atomic group to the surface thereof, and an ionic monomer. And a copolymer of a hydrophobic monomer and a copolymer of the ionic monomer and the hydrophobic monomer. It is possible to adjust the hydrophilicity of the modified pigment appropriately. Further, since the type of the ionic monomer and the hydrophobic monomer to be used and the combination of both can be changed, various characteristics can be imparted to the pigment surface. In addition, when forming an ink, the characteristics of the ink can be controlled by selecting a solvent used in combination with such a pigment.
[0046]
Further, as a second effect, according to the study of the present inventors, when a hydrophobic monomer is used in the copolymer bonded to the pigment surface, the marker stain resistance of the ink can be improved. all right. Hereinafter, the reason for improving the marker resistance will be described.
[0047]
First, when a hydrophilic polymer is used for the surface modification of the pigment, after fixing to the recording medium, the polymer on the surface of the pigment particle is entangled with the pigment, thereby increasing the cohesive force of the pigment, As a result, the print stain resistance (rub resistance) of the ink is improved. However, when the printing surface is rubbed with a water-soluble marker pen, since what is present on the pigment surface is hydrophilic, the water in the marker pen or the aqueous organic solvent increases the hydrophilicity of the pigment particle surface. It is considered that since the molecules are re-dissolved, the pigment particles flow out so as to be melted with the rubbing of the marker pen, and as a result, it becomes difficult to develop the marker stain resistance.
[0048]
On the other hand, in the pigment constituting the first ink used in the present invention, the organic group chemically bonded to the pigment surface contains a copolymer having an ionic monomer unit (hydrophilic part). Therefore, first, after printing on the recording medium, the cohesive force of the pigment is increased due to the entanglement of the copolymer on the surface of the pigment particles on the paper surface, and the print stain resistance after ink fixing is improved. In this respect, it is the same as the case of the ink using the surface-modified pigment made of the hydrophilic polymer. However, since the organic group contains a copolymer having a hydrophobic monomer unit (hydrophobic portion) at the same time, when water and an organic solvent in the ink dry or permeate in the process of fixing the ink. It is considered that not only are the polymers on the pigment surface entangled, but also the hydrophobic portion of the copolymer bonded to the pigment surface is oriented outward on the outermost surface of the printed matter. For this reason, the hydrophobic part of the copolymer is oriented on the outermost surface of the printed matter, and the surface of the printed matter becomes hydrophobic. As a result, even when the printing surface is rubbed with a water-soluble marker pen, the pigment particles are less likely to be redissolved in water or an organic solvent in the ink of the marker pen, thereby suppressing the flow of the pigment particles due to the rubbing of the marker pen. be able to.
[0049]
[Copolymer]
As the copolymer comprising the ionic monomer and the hydrophobic monomer, for example, an anionic copolymer having an anionic property or a cationic copolymer having a cationic property is preferably used.
Examples of the anionic copolymer include a copolymer composed of a hydrophobic monomer and an anionic monomer, and salts thereof. Typical hydrophobic monomers used at this time include the following monomers, but the present invention is not limited thereto. For example, styrene, vinyl naphthalene, alkyl methacrylates such as methyl methacrylate, phenyl methacrylate, benzyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, 2-ethoxyethyl methacrylate, methacrylonitrile, 2-trimethylsiloxyethyl methacrylate, glycidyl methacrylate, Examples thereof include alkyl acrylates such as p-tolyl methacrylate, sorbyl methacrylate, and methyl acrylate, phenyl acrylate, benzyl acrylate, acrylonitrile, 2-trimethylsiloxyethyl acrylate, glycidyl acrylate, p-tolyl acrylate, and sorbyl acrylate.
[0050]
Examples of the anionic monomer used in the above include the following monomers, but the present invention is not limited thereto. For example, acrylic acid, methacrylic acid, maleic acid and the like can be mentioned.
[0051]
As one embodiment of the copolymer according to the present invention, as the anionic copolymer comprising an anionic monomer and a hydrophobic monomer, any one selected from the above-mentioned hydrophobic monomers and the above-described ones And at least one selected from anionic monomers. The copolymer includes a block copolymer, a random copolymer, a graft copolymer, a salt thereof, and the like.
[0052]
The acid value of such an anionic copolymer is preferably in the range of 100 to 500, and it is preferable to use one having a variation in acid value within 20% of the average acid value. By setting the acid value within the above range, the hydrophilicity of the pigment surface is too high, water and solvent in the ink after printing remain on the pigment surface, and after printing on a recording medium, the marker resistance of the ink. Delay in expression can be effectively suppressed. Further, it is also possible to effectively suppress that the hydrophilicity of the surface of the pigment is too low and the pigment is difficult to be stably dispersed in the ink.
[0053]
The above-mentioned salt includes, in addition to alkali metal salts such as sodium, lithium and potassium, ammonium salts, alkylamine salts, alkanolamine salts and the like, and these can be used alone or in appropriate combination of several kinds.
[0054]
The weight average molecular weight (Mw) of the above anionic copolymer segment is preferably in the range of 1,000 to 30,000, more preferably 3,000 to 20,000. It is good to use the thing of the range. Further, the polydispersity Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) of the copolymer is preferably 3 or less. The content of the anionic copolymer segment is preferably such that the content of the anionic copolymer with respect to the surface-modified pigment is 5% by mass or more and 40% by mass or less. More preferably, it is used at a ratio of 10% by mass or more and 25% by mass or less. By setting the content of the copolymer within this range, it is possible to achieve both high suppression of the viscosity increase of the ink and high dispersion stability.
[0055]
In addition, regarding the polydispersity of the copolymer, if the molecular weight distribution of the copolymer is wide, the properties based on the molecular weight of the copolymer described above are difficult to be exhibited, and the molecular weight distribution of the copolymer is uniform. Is preferred.
[0056]
Next, a cationic copolymer composed of a cationic monomer and a hydrophobic monomer will be described as another embodiment of the copolymer according to the present invention. Examples of the cationic copolymer include copolymers of the following hydrophobic monomers and cationic monomers, and salts thereof. Representative hydrophobic monomers include the following monomers, but the invention is not limited thereto. For example, styrene, vinyl naphthalene, alkyl methacrylates such as methyl methacrylate, phenyl methacrylate, benzyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, 2-ethoxyethyl methacrylate, methacrylonitrile, 2-trimethylsiloxyethyl methacrylate, glycidyl methacrylate, It is possible to use alkyl acrylates such as p-tolyl methacrylate, sorbyl methacrylate, and methyl acrylate, phenyl acrylate, benzyl acrylate, acrylonitrile, 2-trimethylsiloxyethyl acrylate, glycidyl acrylate, p-tolyl acrylate, and sorbyl acrylate. it can.
[0057]
Examples of the cationic monomer include the following monomers, but the present invention is not limited thereto. Specifically, for example, allylamine, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, tert-butylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminopropyl methacrylamide, N-vinylcarbazole, methacrylamide, acrylamide And dimethyl acrylamide.
[0058]
The cationic copolymer is a block copolymer, a random copolymer, a graft copolymer, or a block copolymer composed of at least two or more monomers including a hydrophobic monomer selected from the above monomers and a cationic monomer. And the like. In particular, the amine value of the cationic copolymer is preferably in the range of 100 to 500, and the variation of the amine value is preferably within 20% of the average amine value. The amine value is represented by the number of mg of KOH equivalent to hydrochloric acid required to neutralize 1 g of a sample.
The salts include acetic acid, hydrochloric acid, nitric acid and the like, and these can be used alone or in appropriate combination of several kinds.
[0059]
The cationic copolymer preferably has a weight average molecular weight (Mw) in the range of 1,000 to 30,000, more preferably 3,000 to 20,000. It can be used preferably. Further, it is preferable to use a cationic copolymer segment having a polydispersity Mw / Mn (weight average molecular weight Mw, number average molecular weight Mn) of 3 or less. The content of such a cationic copolymer in the ink is preferably 5% by mass or more and 40% by mass or less based on the pigment particles surface-modified by the copolymer. . More preferably, the content of the cationic copolymer is set to a ratio of 10% by mass or more and 25% by mass or less. By setting the content of the copolymer within this range, it is possible to achieve both high suppression of the viscosity increase of the ink and high dispersion stability.
[0060]
In addition, regarding the polydispersity of the copolymer, when the polydispersity is large, the molecular weight distribution of the copolymer is widened, and the above-described properties based on the molecular weight of the copolymer are difficult to develop, The molecular weight distribution of the copolymer is preferably uniform.
[0061]
Next, a method for modifying a pigment by chemically bonding an organic group to the surface of a pigment particle will be described using carbon black as an example. In the present invention, first, a functional group on the surface of a pigment particle or a functional group on a surface of a pigment particle is introduced, and a copolymer composed of an ionic monomer and a hydrophobic monomer is bonded to these functional groups. As long as the polymer is chemically bonded to the surface of the pigment particles, any method may be used, and the method is not particularly limited. As such a method, for example, the following method can be used.
[0062]
A method in which polyethyleneimine or the like is introduced on the surface of pigment particles such as carbon black, and a terminal functional group has an amino group, and a copolymer comprising an ionic monomer and a hydrophobic monomer is bonded by a diazonium reaction, A method such as a method in which a copolymer having an amino group and a carboxyl group in the molecule is bonded to the surface of pigment particles such as black by a diazonium reaction can be used. As another example, the most typical example is disclosed in WO 01/51566 A1.
[0063]
In the above-described method, for example, when the anionic copolymer is chemically bonded to the surface of the carbon black particles, the following three steps are included.
First step: a step of adding an aminophenyl (2-sulfoethyl) sulfone group (APSES) to carbon black by a diazonium reaction.
Second step: a step of adding polyethyleneimine or pentaethylenehexamine (PEHA) to the carbon black subjected to the APSES treatment.
Third step: a step of applying a copolymer of a hydrophobic monomer and an ionic monomer having a carboxyl group.
[0064]
In the second step, the phenyl (2-sulfoethyl) sulfone group chemically bonded to the carbon black surface in the first step is reacted with an amino group such as polyethyleneimine or pentaethylenehexamine (PEHA). As a result, an amino group as a functional group chemically bonded to the carbon black surface is introduced. In the third step, for example, a part of the carboxyl group of the ionic monomer portion of the copolymer is reacted with an amino group to form an amide bond, so that the copolymer is formed on the surface of carbon black by APSES. The copolymer can be introduced via an atomic group containing a phenyl (2-sulfoethyl) group, which is a residue of the above, and a residue of PEHA.
[0065]
In the above-described method, for example, when a cationic copolymer is chemically bonded to the surface of carbon black particles, the following two steps are included.
First step: a step of adding an aminophenyl (2-sulfoethyl) sulfone group (APSES) to carbon black by a diazonium reaction.
Second step: a step of applying a copolymer of a hydrophobic monomer and a cationic monomer.
Through the first step, a sulfone group is introduced as a functional group chemically bonded to the carbon black surface. Then, in the second step, for example, a part of the amino group of the ionic monomer portion of the copolymer is reacted with a sulfone group (nucleophilic substitution), and the copolymer is put on the surface of carbon black to form an APSES. The copolymer can be introduced via an atomic group containing a phenyl (2-sulfoethyl) group as a residue.
[0066]
(Presence of free polymer)
By the way, according to the present invention, a segment containing the copolymer (hereinafter, referred to as a “free polymer”, which includes a segment physically adsorbed on the pigment surface) which is not chemically bonded to the pigment surface is used as an ink. It does not exclude that it exists. However, the amount of the free polymer is preferably controlled from the viewpoint of further improving the ink jet characteristics of the aqueous ink according to the present invention. Specifically, based on the total mass of the free polymer and the organic groups bonded to the pigment surface, the proportion of the free polymer is less than 50% by mass, particularly less than 35% by mass, and even more preferably 20% by mass. It is preferred to be less than.
[0067]
When ink containing a large amount of free polymer is used for ink jet recording, free organic groups adhere to the orifices around the discharge ports of the recording head, causing uneven wetting around the discharge ports, resulting in improper ink discharge. In some cases, the ejection direction may be deviated as a rule, causing a problem that the impact point of the ink is shifted. Further, if continuous printing is continued, ink will adhere to the orifice surface near the nozzle as the ink is repeatedly ejected while overflowing from the nozzle, and the ink adhered portion near the nozzle becomes a large part with the nucleus as the nucleus. An ink puddle may form on the orifice. If printing is further continued in this state, the ink to be ejected is drawn into the ink pool on the orifice, and the ink cannot be ejected.
[0068]
The effective range of the reliability of the ink with respect to the recording head is such that the ratio of the organic group chemically bonded to the pigment particle surface to the total of the organic group and the free polymer is 50% or more. Preferably, it is more preferably at least 65%, further preferably at least 80%. This value can be determined by a thermogravimetric analysis method or the like on a dried sample taken out of the ink by a method as described below.
[0069]
[Aqueous medium]
When a modified pigment obtained by chemically bonding an organic group containing a copolymer obtained as described above to a pigment surface is used as a coloring material of an ink, an aqueous medium that is a dispersion medium of the pigment is used. Examples include water or a mixed solvent of water and a water-soluble organic solvent. As the water-soluble organic solvent, those having an effect of preventing drying of the ink are particularly preferable.
[0070]
Specifically, for example, alkyl alcohols having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, and tert-butyl alcohol; dimethylformamide; Amides such as dimethylacetamide; ketones or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol, propylene glycol, butylene glycol, tri 2 to 6 alkylene groups such as ethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol and diethylene glycol Alkylene glycols containing carbon atoms; lower alkyl ether acetates such as polyethylene glycol monomethyl ether acetate; glycerin; ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether and the like Lower alkyl ethers of polyhydric alcohols; N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. The water-soluble organic solvents as described above can be used alone or as a mixture. It is desirable to use deionized water as the water.
[0071]
The content of the above-mentioned water-soluble organic solvent contained in the ink according to the present invention is not particularly limited, but is preferably in the range of 3 to 50% by mass based on the total mass of the ink. The amount of water contained in the ink is preferably in the range of 50 to 95% by mass based on the total mass of the ink.
[0072]
In addition, in order to maintain the moisturizing property of the ink, a moisturizing solid such as urea, a urea derivative, trimethylolpropane, and trimethylolethane may be used as an ink component. In general, the content of the moisturizing solid in the ink, such as urea, a urea derivative, and trimethylolpropane, is preferably in the range of 0.1 to 20.0% by mass relative to the ink, and more preferably 3.0. -10.0% by mass.
[0073]
Further, the ink according to the present invention may further contain a surfactant, a pH adjuster, a rust inhibitor, a preservative, a fungicide, an antioxidant, an anti-reduction agent, and an evaporation promoter, if necessary, in addition to the above components. And various additives such as a chelating agent.
In particular, in the present invention, it is preferable to include any of the surfactants represented by the following structural formulas (1) to (4) in the ink.
[0074]

(However, in the structural formula (1), R represents alkyl, and n represents an integer.)
[0075]

(However, in the structural formula (2), R represents an alkyl group, and n represents an integer.)
[0076]

(However, in the structural formula (3), R represents a hydrogen atom or an alkyl group, and m and n each represent an integer.)
[0077]

(In the above structural formula (4), m and n each represent an integer.)
[0078]
The ink according to the present invention having the above-described configuration can be used for writing implement ink and inkjet ink. As the ink jet recording method, there is a recording method in which mechanical energy is applied to ink to eject droplets, and a bubble jet (registered trademark) recording method in which thermal energy is applied to ink to eject droplets by foaming of the ink. However, the ink of the present invention is particularly suitable for these recording methods.
[0079]
By the way, when the ink according to the present invention is used for the ink jet recording as described above, it is preferable that the ink has a characteristic that can be favorably ejected from the ink jet recording head. For this reason, from the viewpoint of dischargeability from the inkjet recording head, the properties of the ink are, for example, a viscosity of 1 to 15 mPa · s, a surface tension of 25 mN / m or more, and a viscosity of 1 to 5 mPa · s. It is preferable that the surface tension is 25 to 50 mN / m.
[0080]
Further, as a scale indicating the permeability of the ink into the recording medium, there is a Ka value obtained by the Bristow method. That is, the ink permeability is 1 m²In terms of the ink amount V per unit, the amount of ink permeation into the recording medium V (mL / m²= Μm) is given by Bristow's equation shown below.
V = Vr + Ka (t-tw)^1/2
[0081]
Here, immediately after the ink droplets adhere to the surface of the recording medium, the ink is mostly absorbed in the uneven portions (the surface roughness of the recording medium) on the surface of the recording medium. Almost no penetration. The time during that time is the contact time (tw), and the amount of ink absorbed by the uneven portions of the recording medium during the contact time is Vr. Then, if the contact time is exceeded after the ink has been applied, the amount of permeation into the recording medium increases by a time that exceeds the contact time, that is, by an amount proportional to a half power of (t−tw). Ka is a proportional coefficient of this increase, and shows a value corresponding to the permeation speed. The Ka value can be measured using a liquid dynamic permeability tester (for example, trade name: dynamic permeability tester S; manufactured by Toyo Seiki Seisakusho) by the Bristow method.
[0082]
In the ink according to each of the embodiments of the present invention, the Ka value is set to 1.5 (ml / m2).²/ Msec^1/2) Is preferable in order to further improve the quality of the recorded image, and more preferably 0.2 to 1.5 (ml / m²/ Msec^1/2). That is, the Ka value is 1.5 (ml / m²/ Msec^1/2When the ratio is less than (1), solid-liquid separation occurs at an early stage in the process of penetrating the ink into the recording medium, and a high-quality image with extremely little feathering can be formed. The Ka value according to the Bristow method in the present invention can be used for plain paper [for example, for a copier using an electrophotographic system, a page printer (laser beam printer), or a printer using an ink jet recording system, manufactured by Canon Inc.] PB paper used, PPC paper which is a paper for a copying machine using an electrophotographic method, etc.] as a recording medium. The measurement environment is assumed to be a normal office environment, for example, a temperature of 20 to 25 ° C. and a humidity of 40 to 60%.
[0083]
[Analysis method]
Hereinafter, taking an aqueous pigment ink using carbon black as a pigment as an example, an analysis method and an evaluation method used for evaluating the characteristics of the ink according to the present invention will be described. However, this does not limit the pigment used in the ink according to the present invention. The method for analyzing the surface-modified state of the pigment whose particle surface has been modified for use in the present invention is not particularly limited, and the analysis can be performed using a method that can be generally considered. Preferably, a method of analyzing the bonding state of an organic group present on the surface of a pigment particle such as carbon black by using ESCA or TOF-SIMS is exemplified.
[0084]
The method for measuring the amount of the organic group bonded to the surface of the carbon black particles is not particularly limited. For example, the method can be performed by the following method. First, from the ink containing the surface-modified carbon black, a solid content containing carbon black particles modified with an organic group can be collected from the ink by salting out or coagulation. In order to separate only the surface-modified carbon black (carbon black having an organic group bonded to the particle surface) with high purity from the solid content taken out from the ink by this method, the carbon black particles must be further separated. A method of washing and drying carbon black and the like taken out of the ink with a good solvent of the copolymer chemically bonded to the surface can be used. Hereinafter, a more detailed method for fractionating the surface-modified carbon black from the ink, after fractionation, drying is performed by using the obtained dried product as a measurement sample, and the surface-modified carbon black is obtained. An analysis method for measuring the amount of the organic group bonded to the surface of the carbon black particles or measuring the amount of the segment containing the copolymer portion which may be present in the ink as a free polymer will be described.
[0085]
First, prior to analysis, a pretreatment is performed as follows to prepare a measurement sample. From the ink containing the surface-modified carbon black described above, the solid content obtained as a precipitate by salting out or coagulating is dried, and then washed with a good solvent for the copolymer. Therefore, an extraction treatment is performed on only carbon black in which the organic groups are chemically bonded to the particle surface. The method consists of a series of steps of (1) salting out or coagulation, (2) washing the precipitate, (3) drying, (4) extracting only the surface-modified carbon black, and (5) drying. It can be carried out. Hereinafter, description will be made in order.
[0086]
(1) The method of salting out or coagulating a solid containing surface-modified carbon black from the ink is not particularly limited. For example, (a) salting out with a salt such as sodium chloride or potassium chloride; b) Coagulation (acid precipitation) using an acid such as nitric acid or hydrochloric acid can be used. At this time, if necessary, for example, ultrafiltration may be performed as a pre-process such as salting out.
[0087]
(2) The solid obtained by the above salting out or coagulation is sufficiently washed with pure water. In particular, when performing the coagulation of (b) described in (1), it is preferable to sufficiently wash the filtrate after washing until the filtrate becomes neutral.
[0088]
(3) The solid content after washing obtained above is sufficiently dried in an oven or the like, and is taken out as a dried product. The drying conditions and the like at this time are not particularly limited. For example, drying may be performed at 60 ° C. for about 2 hours.
[0089]
(4) The dried product obtained in the above (3) includes, in addition to carbon black having an organic group chemically bonded to the surface of the carbon black particles, a free polymer not chemically bonded to the surface of the carbon black particles. (Including those physically adsorbed to the pigment). Then, the dried product obtained in (3) is washed with a good solvent for the copolymer to extract the surface-modified carbon black with higher purity. The good solvent of the free polymer used in the above differs depending on the structure of the copolymer, and is not necessarily limited. For example, tetrahydrofuran (THF) is a versatile good solvent. In this case, it is preferable to repeat the operation of washing the dried matter using such a good solvent and removing the free polymer possibly mixed in the solid content.
[0090]
(5) The solid content from which the free polymer has been removed by washing the segment containing the copolymer portion with a good solvent as described above is finally subjected to a sufficient drying treatment in an oven or the like to obtain residual moisture and residual solids. Evaporate the solvent to obtain a dried sample. The oven or the like used for drying is not particularly limited, and for example, drying may be performed using a commercially available vacuum dryer or the like. The drying conditions and the like are not particularly limited as long as the residual water and the residual solvent can be sufficiently removed from the dried surface-modified carbon black. For example, drying may be performed at a degree of vacuum of several hundred Pa or less at 60 ° C. for about 3 hours.
[0091]
A dried sample of the surface-modified carbon black taken out of the ink by the series of methods (1) to (5) is used as a measurement sample, and the weight change of the sample is measured using thermogravimetric analysis. The amount of organic groups bonded to the surface of the carbon black particles can be quantitatively measured. As a result, the content of the organic group chemically bonded to the carbon black can be measured based on the mass of the surface-modified carbon black particles.
[0092]
For this separation, for example, liquid chromatography can be used. Further, the dried matter obtained by the series of procedures (1) to (3) is used as a measurement sample, and the weight change of the sample is measured by thermogravimetric analysis, whereby the surface of the carbon black particles is measured. In addition to the bound organic groups, the amount of solids excluding pigments in the ink such as free polymer can be known. As a result, the ratio of the organic group to the total of the organic group and the free polymer contained in the ink can be determined. In the case where the second polymer other than the copolymer is mixed in the ink, in order to accurately calculate the ratio of the organic group to the total of the organic group and the free polymer in the ink, It is preferable to measure the amount of only the free polymer. In this case, the amount of the free polymer alone can be measured by measuring the cleaning solution of carbon black in the procedure (4) using liquid chromatography or the like.
[0093]
As described above, a series of procedures (1) salting out or coagulation, (2) washing the precipitate, (3) drying, (4) extracting only the surface-modified carbon black, and (5) drying. The method for measuring the content of the bound organic group in the obtained dried product sample containing only the surface-modified carbon black is not particularly limited. For example, the fully dried carbon black finally obtained by the above procedure is measured by thermogravimetric analysis (Thermogravimetric Analysis) or the like, and easily obtained from the thermogravimetric analysis weight loss rate obtained as a result. Can be. Hereinafter, the thermogravimetric analysis performed at this time will be described in detail.
[0094]
The thermogravimetric analysis weight loss rate measured by the above method is the content of the organic group introduced into the surface of the carbon black particles in the surface-modified carbon black. That is, the thermogravimetric analysis weight loss rate is given by the following equation, but is washed with a good solvent of a polymer substance before the thermogravimetric analysis, and is based on the weight of the dried solid sample from which only the surface-modified carbon black is extracted. , A rate of weight loss caused by desorption or burning of an organic group bonded to the surface of carbon black particles, which is caused by thermogravimetric analysis performed at a temperature raised to 100 to 700 ° C.
Thermogravimetric analysis weight loss rate = A / B x 100 (%)
A = Amount of weight loss when heated to 100 to 700 ° C. in thermogravimetric analysis
B = weight of sample before thermogravimetric analysis
[0095]
The analysis conditions and the like in the thermogravimetric analysis performed above are not particularly limited, and may be measured under ordinary conditions such as a pretreatment and a heating rate. As the measuring device, for example, a TGA thermogravimetric measuring device manufactured by METTLER TOLEDO, TGA851e / SDTA or the like can be used.
[0096]
Further, by using the above-described method of measuring the weight loss rate by thermogravimetric analysis, the pigments such as the surface-modified carbon black contained in the aqueous pigment ink used in the present invention can be combined with the substance used for the surface modification and the pigment particles. You can know the status. That is, an organic group is chemically bonded to the surface of the pigment used in the present invention, for example, carbon black particles. Therefore, the organic groups on the surface of the carbon black particles are not washed out even after washing with the good solvent for the polymer substance, and are stably bonded to the surface of the carbon black particles. Regardless, the weight loss rate of thermogravimetric analysis shows almost the same value. In contrast, in the case of a commonly used resin-dispersed pigment, the water-soluble resin used as the dispersant is not chemically bonded to carbon black (pigment), and is used for dispersion. When the resin is washed with a good solvent, the resin is washed away. Therefore, the rate of weight loss by thermogravimetric analysis is significantly different between the case where the above-described extraction treatment is performed and the case where the treatment is not performed.
[0097]
From this, the modified pigment suitably used in the present invention means that the weight loss rate by thermogravimetric analysis does not change or does not substantially change before and after washing the copolymer with a good solvent. Things. Here, that the weight loss rate by thermogravimetric analysis does not substantially change before and after washing means that the difference in the weight loss rate between before and after washing is, for example, less than 7%, and further, within 5%. Point to.
[0098]
In addition to the above-described thermogravimetric analysis, there is a method of examining the bonding state of the pigment particle surface with the substance used for surface modification. For example, a carbon black dried product obtained by salting out or coagulating the surface-modified carbon black used in the present invention as described above and then drying it out is used as a measurement sample. A method in which analysis is performed in combination with -MS (thermogravimetric analysis-gas chromatograph-mass spectrum), TOF-MS (time-of-flight mass spectrometer), TOF-SIMS (time-of-flight secondary ion mass spectrometry), or the like is also preferable. is there. By these methods, the bonding state of the substance used for surface modification in the carbon black dried material sample (measurement of adsorption energy), and further, the composition of the bound organic group in the carbon black dried material sample, The molecular weight distribution and further the binding unit can be known in detail.
[0099]
<Second ink>
The ink set according to the present invention has a combination of the first ink described above and a second ink different in color from the first ink, and applies each ink to a recording medium. Thus, a color image is formed on a recording medium. Therefore, for example, when the first ink is a black ink using carbon black as a coloring material, the second ink needs to be configured as another color ink. Further, as the second ink, an ink having a function of destabilizing the dispersion stability of the pigment in the first ink when mixed with the first ink is used. As described above, since it is preferable to use carbon black as the pigment constituting the first ink, a color ink is usually used as the second ink. Hereinafter, a coloring material and a solvent will be described with respect to an ink that can be used as the second ink, and thereafter, an ink having a function of destabilizing the dispersion stability of the pigment in the first ink described above will be described. Each of the three aspects will be described.
[0100]
[Color material]
As a coloring material that can be used in the second ink according to the present invention, a known dye or pigment can be used. As the dye, for example, an acid dye, a direct dye, or the like can be used. As the anionic dye, any of existing dyes and newly synthesized dyes can be used as long as they have appropriate color tone and density. It is also possible to use a mixture of any of these.
[0101]
In the present invention, for example, the following can be mentioned as anionic dyes that can be particularly preferably used from the viewpoint of coloring properties and the like.
[0102]
(Color material for yellow)
C. I. Direct Yellow # 1, 2, 4, 8, 11, 12, 26, 27, 28, 33, 34, 39, 41, 44, 48, 50, 58, 85, 86, 87, 88, 89, 98, 100, 110, 132, 135, 142, 144
C. I. Acid Yellow # 1, 3, 4, 7, 11, 12, 13, 14, 17, 19, 23, 25, 29, 34, 36, 38, 40, 41, 42, 44, 53, 55, 61, 76, 79, 98, 99
C. I. Reactive Yellow # 1, 2, 3, 4, 6, 7, 11, 12, 13, 14, 15, 16, 17, 18, 22, 23, 24, 25, 26, 27, 37, 42
C. I. Food Yellow $ 3
[0103]
(Coloring material for magenta)
C. I. Direct Red # 1, 2, 4, 8, 9, 11, 13, 15, 20, 23, 24, 28, 31, 33, 37, 39, 46, 51, 59, 62, 63, 73, 75, 79, 80, 81, 83, 87, 89, 90, 95, 99, 101, 110, 189, 197, 201, 218, 220, 224, 225, 226, 227, 228, 229, 230
C. I. Acid Red # 1, 4, 6, 8, 9, 13, 14, 15, 18, 21, 26, 27, 32, 35, 37, 42, 51, 52, 80, 83, 87, 89, 92, 106, 114, 115, 133, 134, 145, 158, 198, 249, 257, 265, 289
C. I. Reactive Red # 1, 2, 3, 4, 5, 6, 7, 8, 11, 12, 13, 15, 17, 19, 20, 21, 22, 23, 24, 28, 29, 31, 32, 33 , 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 58, 59, 63, 64, 180
C. I. Food Red # 87, 92, 94
[0104]
(Color material for cyan)
C. I. Direct Blue # 1, 2, 6, 8, 15, 22, 25, 34, 41, 70, 71, 76, 77, 78, 80, 86, 90, 98, 106, 108, 120, 142, 158, 163, 168, 199, 200, 201, 202, 203, 207, 218, 226, 236, 287
C. I. Acid Blue # 1, 7, 9, 15, 22, 23, 25, 27, 29, 40, 43, 55, 59, 62, 74, 78, 80, 81, 90, 100, 102, 104, 111, 117, 127, 138, 158, 161, 185, 254
C. I. Reactive Blue # 1,2,3,4,5,7,8,9,13,14,15,17,18,19,20,21,25,26,27,28,29,32,33,34 , 37, 38, 39, 40, 41, 43, 44, 46, 100
[0105]
(Color material for black)
C. I. Direct Black # 7, 19, 22, 31, 32, 51, 62, 71, 74, 112, 113, 154, 168, 195
C. I. Acid Black # 2, 48, 51, 52, 110, 115, 156
C. I. Food Black 1,2
[0106]
Examples of the cationic dye that can be suitably used in the present invention include the following.
C. I. Basic Yellow # 1, 2, 11, 13, 14, 19, 21, 25, 32, 33, 36, 51
C. I. Basic Red # 1, 2, 9, 12, 13, 37, 38, 39, 92
C. I. Basic Blue # 1,3,5,7,9,19,24,25,26,28,29,45,54,65
C. I. Basic Black $ 2,8
[0107]
The following are examples of organic pigments that can be used in the second ink. Specifically, insoluble azo pigments such as Toluidine Red, Toluidine Maroon, Hansa Yellow, Benzidine Yellow, and Pyrazolone Red; soluble azo pigments such as Litol Red, Helio Bordeaux, Pigment Scarlet, and Permanent Red 2B; alizarin, indanthrone, and thioindigo. Derivatives from vat dyes such as maroon, phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green, quinacridone pigments such as quinacridone red and quinacridone magenta, perylene pigments such as perylene red and perylene scarlet, isoindolinone yellow, and isoindolin Isoindolinone pigments such as linone orange, imidazolone pigments such as benzimidazolone yellow, benzimidazolone orange and benzimidazolone red, pyranthro Red, pyranthrone pigments such as pyranthrone orange, indigo pigments, condensed azo pigments, thioindigo pigments, diketopyrrolopyrrole pigments, flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel azo yellow, copper azomethine yellow, Other pigments such as perinone orange, anthrone orange, dianthraquinonyl red, and dioxazine violet can be exemplified.
[0108]
When the organic pigment is represented by a color index (CI) number,
C. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 20, 24, 74, 83, 86, 93, 97, 109, 110, 117, 120, 125, 128, 137, 138, 147, 148, 150, 151, 153, 154, 166, 168, 180, 185,
C. I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, 71,
C. I. Pigment Red 5, 7, 9, 12, 48, 49, 52, 53, 57, 97, 112, 122, 123, 149, 168, 175, 176, 177, 180, 192, 202, 207, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254, 255, 272,
C. I. Pigment Violet 19, 23, 29, 30, 37, 40, 50,
C. I. Pigment Blue 1, 2, 3, 15, 15: 1, 15: 3, 15: 4, 15: 6, 16, 22, 60, 64, C.I. I. Pigment Green 7, 36,
C. I. Pigment Brown 23, 25, 26, and the like.
[0109]
Regardless of whether these pigments are resin-dispersed in the ink or self-dispersed by adding a water-soluble group, they are resin-bonded self-dispersed similarly to the first ink described above. It doesn't matter.
[0110]
The content of the coloring material is preferably in the range of 0.2 to 15% by mass, more preferably in the range of 0.5 to 10% by mass based on the total mass of the ink. That is, by setting the content in this range, for example, the reliability as an inkjet recording ink, such as the color developing property and the ejection stability of the ink, can be further improved.
[0111]
[solvent]
Examples of the solvent or dispersion medium for the coloring material as described above include an aqueous medium. As the aqueous medium, it is preferable to use water or a mixed solvent of water and a water-soluble organic solvent. Examples of the water-soluble organic solvent used in preparing the second ink include the same ones as described in the first ink. In the case where the second ink is applied to a recording medium by an inkjet method (for example, a bubble jet (registered trademark) method), the first ink is described as having an inkjet discharge characteristic. Similarly, it is preferable to prepare the ink so as to have desired viscosity and surface tension.
[0112]
Here, the content of the water-soluble organic solvent in the second ink is, for example, such that when the ink is used for ink-jet recording, the ink has excellent ink-jet ejection characteristics and also has a desired color tone and density. It may be selected as appropriate, but as a guide, for example, a range of 3 to 50% by mass based on the total mass of the second ink is preferable. The amount of water contained in the ink is preferably in the range of 50 to 95% by mass based on the total mass of the second ink.
[0113]
[Other components]
Further, similarly to the case of the first ink, as a component of the second ink, a moisturizing solid content for maintaining the moisturizing property of the ink, and if necessary, a pH adjuster, a rust inhibitor, a preservative, and the like. And various additives such as a fungicide, an antioxidant, a reduction inhibitor, an evaporation promoter, a chelating agent and the like.
[0114]
In particular, it is preferable that the second ink contains at least one surfactant having the same polarity as the coloring material in the ink or a nonionic surfactant, in addition to the components described above. By including these surfactants, desired permeability and viscosity can be imparted to the ink, and the performance required for the ink for inkjet recording can be further satisfied. The surfactant used at this time may be any of the following ionic surfactants, nonionic surfactants and amphoteric surfactants, or a mixture of two or more of them.
[0115]
(Anionic surfactant)
Examples of the anionic surfactant include a fatty acid salt, a higher alcohol ester salt, an alkylbenzene sulfonate, a higher alcohol phosphate ester, an alkyl sulfate, an alkyl sulfate, a dialkyl sulfosuccinate, an alkyl sulfo acetate, And dialkyl sulfosuccinates.
[0116]
(Cationic surfactant)
Examples of the cationic surfactant include an aliphatic amine salt, a quaternary ammonium salt, and an alkylpyridinium salt.
[0117]
(Nonionic surfactant)
Nonionic surfactants include, for example, higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts, aliphatic ethylene oxide adducts, polyhydric alcohol fatty acid ester ethylene oxide adducts, aliphatic amide ethylene oxide adducts, higher Examples thereof include an alkylamine ethylene oxide adduct, a polypropylene glycol ethylene oxide adduct, a fatty acid ester of a polyhydric alcohol, and a fatty acid amide of an alkanolamine.
[0118]
(Amphoteric surfactant)
Examples of the amphoteric surfactant include amino acid type and betaine type amphoteric surfactants.
[0119]
In the present invention, any of these is preferably used. A nonionic surfactant such as an adduct is used. Further, those having an addition mole number of the ethylene oxide adduct in the range of 4 to 20 are particularly preferable.
[0120]
The amount of the surfactant added in each ink is not particularly limited, but is preferably in the range of 0.01 to 10% by mass of the total mass of the ink. If the amount is less than 0.01% by mass, depending on the type of the surfactant, desired permeability cannot be generally obtained. If the amount exceeds 10% by mass, the initial viscosity of the ink increases, which is not preferable. More preferably, the content is in the range of 0.1 to 5.0% by mass of the total mass of the ink.
[0121]
The second ink having the above-described basic configuration further has a dispersion stability of the pigment in the first ink when mixed with the first ink by the following first to third methods or the like. Destabilizing function is provided. Hereinafter, this will be described.
[0122]
[First embodiment: multivalent metal ion-containing ink]
(Polyvalent metal salt)
One method for destabilizing the dispersion stability of the pigment in the first ink when the second ink is mixed with the first ink is to add a polyvalent metal cation to the second ink. There is a mode to be contained therein. That is, as a polyvalent metal ion, for example, Mg²⁺, Ca²⁺, Cu²⁺, Co²⁺, Ni²⁺, Fe²⁺, La³⁺, Nd³⁺, Y³⁺And Al³⁺At least one selected from the group consisting of: is contained in the second ink.
[0123]
Here, it is preferable that the polyvalent metal ion contained in the second ink is, for example, 0.1 to 15% by mass based on the total mass of the second ink. The polyvalent metal cations listed above are preferably added to the color ink as salts such as nitrates and acetates. When such a polyvalent metal ion is contained in the second ink, a colorant whose stability is not destabilized even when coexisting with the polyvalent metal ion is first used. Naturally, it is preferable to select from the listed ones.
[0124]
[Second embodiment: ink having a buffer action against pH change]
When the second ink is mixed with the first ink, as one method for destabilizing the dispersion stability of the pigment in the first ink, when mixed with the first ink, The second ink has a pH that causes a change in pH in the first ink, destabilizes the dispersibility of the pigment in the first ink, and has a buffering effect on the pH. Is composed.
[0125]
For example, the first ink having the above-described configuration is used as a black ink, the second ink combined with the black ink is used as a color ink, and the second ink is used as a buffer to buffer a change in the hydrogen ion concentration (pH) of the first ink. By employing an ink having an effect, bleeding at the boundary between an image printed with black ink and an image printed with color ink is effectively prevented. Here, “having a buffer action against a pH change” means that the ink has a specific region where the pH change is gentle. Specifically, the difference between the pH value of the ink in which 1.0 ml of a 1N aqueous lithium hydroxide solution was added and the pH value of the ink in the state in which the aqueous lithium hydroxide solution was not added to 50 ml of the ink was: It means having an area within 1.0. Hereinafter, satisfying the above condition is referred to as “having a buffer action”.
[0126]
According to the study of the present inventors, for example, by making the configuration of the color ink of the second ink exhibit a buffering action in a pH region lower than the pH of the black ink of the first ink, the black ink It was confirmed that bleeding generated between the ink and the color ink was effectively suppressed. In particular, when bleed occurs between the black ink and the color ink, an image of poor quality is obtained. Hereinafter, a description will be given using this example.
[0127]
The reason why the above-described effects can be obtained by the ink set of the present invention having the above configuration is considered as follows. An image in which a black image and a color image are adjacent to each other is printed, and on the recording medium, when the black ink and the color ink having the above configurations are adjacent to each other, in the black ink, for example, carbon black and in the color ink, For example, aggregation occurs with an anionic dye. Then, along with the aggregation, the carbon black in the black ink and the dye in the color ink cannot move on the recording medium, and as a result, it is considered that bleeding was effectively prevented.
[0128]
In other words, if the electrical neutralization between the resin-bonded self-dispersible pigment in the black ink and the color material in the color ink occurs stably on the recording medium, each ink is used. The dispersed state and dissolved state of the constituent color materials and the like are completely destroyed. In this way, if the color material or the like in the black ink or the color ink cannot move, another ink does not enter the area printed with each ink on the recording medium, and bleeding does not occur.
[0129]
According to the study of the present inventors, the electrical neutralization between the color materials and the like constituting each of the above-described inks is greatly affected by the pH at the boundary when the black ink and the color ink come into contact with each other, It was found that the bleeding effect was greatly affected by the pH at the boundary. That is, when the pH at the time when the two types of inks come into contact becomes basic, the electrical neutralization of the coloring materials and the like completely disperses and dissolves the coloring materials and the like of each ink. There is a case where it is not enough to break, and in that case, the bleed control effect may not be sufficiently achieved. Therefore, in order to more effectively prevent or more effectively suppress the occurrence of bleeding, the pH at the boundary when the two types of ink come into contact with each other depends on the dispersion state of the coloring material and the like in each ink. It is important that the color material is maintained at a value that causes sufficient electrical neutralization of the color materials to completely destroy the dissolved state.
[0130]
Therefore, in the present invention, when mixed with the color ink (the second ink), the black ink (the first ink) causes a pH change, and a buffer action against the pH change. Thereby, the pH value when the two types of ink come into contact with each other on the recording medium is maintained in a state sufficient to completely destroy the dispersed state or the dissolved state of the coloring material or the like of each ink. In this way, bleeding of printed matter is prevented.
[0131]
As a specific method for preparing the second ink having a buffering action against the pH change used in the present invention, as described above, 1 ml of a 1 N aqueous solution of lithium hydroxide is added to 50 ml of ink. The difference between the pH value at the time of addition and the pH value before the addition is adjusted to be within 1.0. For this purpose, the same method as that for preparing a conventionally known buffer solution can be used.
[0132]
Examples of the buffer used at this time include, for example, organic acids such as citric acid, succinic acid, phthalic acid, fumaric acid, acetic acid, lactic acid, tartaric acid, carbonic acid, diethylbarbirtic acid, phosphoric acid, boric acid, sulfuric acid, and hydrochloric acid. , Inorganic acids such as nitric acid, lithium citrate, potassium dihydrogen citrate, potassium hydrogen phthalate, lithium sulfate, sodium sulfate, potassium sulfate, ammonium sulfate and other sulfates, sodium acetate, lithium acetate, potassium acetate, ammonium acetate, etc. Acetate, lithium carbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, carbonates such as ammonium carbonate and ammonium bicarbonate, sodium lactate, lithium phosphate, monosodium phosphate, disodium phosphate, phosphoric acid Trisodium, potassium phosphate, dipotassium phosphate, tripotassium phosphate, Phosphates such as potassium dihydrogen phosphate, monoammonium phosphate, diammonium phosphate, and triammonium phosphate; alkali metal salts of organic acids such as sodium tetraborate and sodium diethylbarbilate; potassium chloride and sodium chloride And inorganic alkali metal salts such as potassium chloride and lithium chloride, hydroxides such as sodium hydroxide and lithium hydroxide, potassium hydroxide and ammonium hydroxide, and glycine. These buffers can be used alone or in appropriate combination.
[0133]
Specifically, for example, potassium hydrogen phthalate / hydrochloric acid, potassium hydrogen phthalate / sodium hydroxide, potassium citrate / citric acid, potassium dihydrogen citrate / hydrochloric acid, potassium dihydrogen citrate / sodium hydroxide, tetraborate Sodium citrate / succinic acid, potassium dihydrogen citrate / sodium tetraborate, sodium lactate / lactic acid, sodium acetate / acetic acid, dipotassium hydrogen phosphate / citric acid, tartaric acid / sodium tartrate, boric acid + citric acid / triphosphate Sodium, glycine + sodium chloride / hydrochloric acid, citric acid + potassium dihydrogen phosphate + boric acid + diethylbarbirutic acid / trisodium phosphate, sodium diethylbarbirutate + sodium acetate / hydrochloric acid, and the like. However, it is not limited to these combinations.
[0134]
More specifically, for example, sodium dihydrogen phosphate / sodium hydroxide, glycine + sodium chloride / sodium hydroxide, sodium tetraborate / sodium hydroxide, sodium dihydrogen phosphate / sodium tetraborate, tetraborate Buffering agents such as sodium / sodium carbonate, hydrochloric acid / sodium carbonate, sodium dihydrogen phosphate / sodium hydroxide, ammonium chloride / ammonia, sodium dimethylglycine / hydrochloric acid, boric acid + potassium chloride / sodium carbonate, sodium carbonate / sodium hydrogen carbonate Is mentioned. The amount of these salts added to the ink is preferably 0.1 to 10% by mass, and more preferably 1 to 8% by mass. By setting these ranges, the pH of the ink can be kept constant, and the stability of the ink can be maintained.
[0135]
As for the content of the compounds as listed above, the difference between the pH value when adding 1.0 ml of a 1N aqueous lithium hydroxide solution to 50 ml of the second ink and the pH value before addition is 1. It is preferable to appropriately adjust the condition of 0 or less so that the second ink satisfies the condition. However, at this time, it is necessary that the ink jet recording characteristics such as the color developing property and the ink ejection stability be within a range that does not impair the reliability as the ink for ink jet recording.
[0136]
[Third embodiment: an ink having a colorant having a polarity opposite to that of the pigment in the first ink]
As a method of destabilizing the dispersion stability of the pigment in the first ink when the second ink is mixed with the above-described first ink, the configuration of the second ink is the same as that of the above-mentioned first ink. It contains a coloring material having a polarity opposite to the polarity of the pigment in the ink.
[0137]
According to the study of the present inventors, for example, when the color material of the color ink used as the second ink has a polarity opposite to that of the black ink using carbon black as the color material used as the first ink, It has been found that bleeding can be effectively suppressed when ink images are adjacently or overprinted. Color materials having polarities different from each other may be appropriately selected and used from those listed above.
[0138]
For example, a black ink using carbon black, which is a resin-bonded cationic self-dispersible pigment of the above-mentioned resin as a colorant, and a color ink containing a coloring material selected from the above-mentioned anionic dyes were used. The ink set of the present invention can suppress bleeding even when compared with a conventional ink set using a black ink using carbon black as a colorant as a self-dispersible pigment and a color ink using an anionic dye as a colorant. The effect was confirmed to be extremely high. We have found that when contacted with a color ink having a colorant of the opposite polarity, the resin-bonded pigment used in the present invention is better than a conventional self-dispersed pigment merely having a water-soluble group. It is considered that the self-dispersion pigment of the type forms larger aggregates, so that the ink cannot move on the paper surface, so that the suppression of bleeding can be remarkably improved.
[0139]
(Permeability of the second ink)
With respect to the second ink as described above, in order to form a high-quality color image on a recording medium, the Ka value obtained by the Bristow method described above must be, for example, 1.5 (ml / m2).²/ Msec^1/2) It is preferable to use the above ink. That is, since the ink having such a Ka value has high permeability to the recording medium, even if images of at least two colors selected from yellow, magenta, and cyan are recorded adjacently, for example, Color bleeding (bleeding) that occurs between images of different colors can be suppressed, and even when these inks are overprinted to form a secondary color image, the permeability of each ink is high. Bleed between images of different colors can be effectively suppressed. As a method for adjusting the Ka value of the second ink to such a value, for example, a conventionally known method such as addition of a surfactant as described above, addition of a permeable solvent such as glycol ether, or the like. Can be applied. Of course, the amount of addition may be appropriately selected.
[0140]
The ink set of the present invention having the above configuration is particularly effective when used for inkjet recording. The ink jet recording method used in this case includes a recording method in which mechanical energy is applied to the ink to discharge the ink, and an ink jet recording method in which thermal energy is applied to the ink to discharge the ink by foaming of the ink. When the ink set of the present invention is applied to these ink jet recording methods, the blade can be suppressed and an image having excellent scratch resistance and marker resistance can be formed. Hereinafter, these will be described.
[0141]
[Recording method, recording unit, cartridge and recording apparatus]
Next, an example of the inkjet recording apparatus according to the present invention, which can be suitably used for performing recording using the first and second inks according to the present invention, will be described below. First, FIGS. 5 and 6 show an example of a head configuration which is a main part of an ink jet recording apparatus using thermal energy. FIG. 5 is a sectional view of the head 13 along the ink flow path, and FIG. 6 is a sectional view taken along line AB in FIG. The head 13 is obtained by bonding a heating element substrate 15 to a glass, ceramic, silicon, or plastic plate having a flow path (nozzle) 14 through which ink passes. The heating element substrate 15 includes a protective layer 16 formed of silicon oxide, silicon nitride, silicon carbide, and the like, electrodes 17-1 and 17-2 formed of aluminum, gold, an aluminum-copper alloy, and the like, and HfB.₂, TaN, TaAl, etc., a heating resistor layer 18 formed of a high melting point material, a thermal storage layer 19 formed of thermally oxidized silicon, aluminum oxide, or the like, and a material having good heat dissipation properties, such as silicon, aluminum, or aluminum nitride. Substrate 20.
[0142]
When a pulse-like electric signal is applied to the electrodes 17-1 and 17-2 of the head 13, a region indicated by n of the heating element substrate 15 rapidly generates heat, and bubbles are generated in the ink 21 in contact with the surface. Is generated, the meniscus 23 protrudes by the pressure, and the ink 21 is discharged through the nozzle 14 of the head, becomes the ink droplet 24 from the discharge orifice 22, and flies toward the recording medium 25. FIG. 7 shows an external view of an example of a multi-head in which many heads shown in FIG. 5 are arranged. This multi-head is formed by bonding a glass plate 27 having a multi-nozzle 26 and a heating head 28 similar to that described with reference to FIG.
[0143]
FIG. 8 shows an example of an ink jet recording apparatus incorporating this head. In FIG. 8, reference numeral 61 denotes a blade serving as a wiping member, one end of which is held and fixed by a blade holding member to form a cantilever. The blade 61 is arranged at a position adjacent to a recording area of the recording head 65, and is held in a form protruding into the movement path of the recording head 65 in the illustrated example.
[0144]
Reference numeral 62 denotes a cap on the protruding opening surface of the recording head 65, which is disposed at a home position adjacent to the blade 61, moves in a direction perpendicular to the moving direction of the recording head 65, abuts on the ink ejection opening surface, and performs capping. It has a configuration to perform. Further, reference numeral 63 denotes an ink absorber provided adjacent to the blade 61, and is held in a form protruding into the movement path of the recording head 65, similarly to the blade 61. The blade 61, the cap 62, and the ink absorber 63 constitute an ejection recovery unit 64, and the blade 61 and the ink absorber 63 remove moisture, dust, and the like from the ejection port surface.
[0145]
Reference numeral 65 denotes a recording head which has ejection energy generating means and performs recording by discharging ink on a recording medium facing an ejection port surface provided with ejection ports, and 66 denotes mounting of the recording head 65 and movement of the recording head 65. Is a carriage for performing the following. The carriage 66 is slidably engaged with the guide shaft 67, and a part of the carriage 66 is connected to a belt 69 driven by a motor 68 (not shown). As a result, the carriage 66 can move along the guide shaft 67, and the recording head 65 can move the recording area and the adjacent area.
[0146]
Reference numeral 51 denotes a paper feeding unit for inserting a recording medium, and reference numeral 52 denotes a paper feed roller driven by a motor (not shown). With such a configuration, the recording medium is fed to a position facing the discharge port surface of the recording head 65, and is discharged to a discharge section provided with a discharge roller 53 as recording proceeds. In the above configuration, when the recording head 65 finishes recording and returns to the home position, the cap 62 of the ejection recovery unit 64 is retracted from the moving path of the recording head 65, but the blade 61 protrudes into the moving path. As a result, the ejection openings of the recording head 65 are wiped.
[0147]
When capping is performed with the cap 62 in contact with the ejection surface of the recording head 65, the cap 62 moves so as to protrude into the movement path of the recording head. When the recording head 65 moves from the home position to the recording start position, the cap 62 and the blade 61 are at the same positions as the positions at the time of the wiping described above. As a result, the ejection port surface of the recording head 65 is also wiped during this movement. The above-described movement of the print head to the home position is performed not only at the end of printing and at the time of ejection recovery, but also at a predetermined interval while the print head moves through the printing area for printing to the home position adjacent to the printing area. Then, the wiping is performed along with this movement.
[0148]
FIG. 9 is a diagram illustrating an example of an ink cartridge that stores ink supplied to a recording head via an ink supply member, for example, a tube. Here, reference numeral 40 denotes an ink storage unit storing the supply ink, for example, an ink bag, and a rubber stopper 42 is provided at the end thereof. By inserting a needle (not shown) into the stopper 42, the ink in the ink bag 40 can be supplied to the head. An ink absorber 44 receives the waste ink. It is preferable that the ink container has a surface in contact with the ink made of polyolefin, particularly polyethylene.
[0149]
The ink jet recording apparatus used in the present invention is not limited to the one in which the head and the ink cartridge are separated as described above, and is also suitably used in an integrated one as shown in FIG. Can be In FIG. 10, reference numeral 70 denotes a recording unit, in which an ink storage unit storing ink, for example, an ink absorber is stored, and the ink in the ink absorber is transferred from a head unit 71 having a plurality of orifices. It is configured to be ejected as ink droplets. It is preferable for the present invention to use polyurethane as the material of the ink absorber. Further, a structure may be employed in which the ink storage unit is an ink bag in which a spring or the like is provided inside without using an ink absorber. Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the cartridge with the atmosphere. This recording unit 70 is used in place of the recording head 65 shown in FIG. 8, and is detachable from the carriage 66.
[0150]
Next, as a preferable example of an ink jet recording apparatus using mechanical energy, a nozzle forming substrate having a plurality of nozzles, a pressure generating element made of a piezoelectric material and a conductive material disposed to face the nozzles, An on-demand ink jet recording head which includes ink filling around the generating element, displaces the pressure generating element by an applied voltage, and discharges a small droplet of ink from a nozzle can be given. FIG. 11 shows an example of a configuration of a recording head which is a main part of the recording apparatus.
[0151]
The head includes an ink flow path 80 communicating with an ink chamber (not shown), an orifice plate 81 for discharging ink droplets of a desired volume, a vibrating plate 82 for directly applying pressure to ink, and a vibrating plate 82 And a substrate 84 for pointing and fixing an orifice plate 81, a diaphragm 82 and the like.
[0152]
In FIG. 11, an ink flow path 80 is formed of a photosensitive resin or the like, an orifice plate 81 is formed with a discharge port 85 by drilling a metal such as stainless steel or nickel by electroforming or pressing, and a diaphragm 82 is formed. The piezoelectric element 83 is formed of a metal film such as stainless steel, nickel, titanium and the like and a high elastic resin film, and the piezoelectric element 83 is formed of a dielectric material such as barium titanate and PZT. The recording head having the above-described configuration applies a pulse-like voltage to the piezoelectric element 83 to generate a strain stress, and the energy of the energy deforms the diaphragm joined to the piezoelectric element 83, causing the ink in the ink flow path 80 to move. Is pressed vertically, and an ink droplet (not shown) is ejected from the ejection port 85 of the orifice plate 81 to perform printing. Such a recording head is used by being incorporated in an ink jet recording apparatus similar to that shown in FIG. The detailed operation of the ink jet recording apparatus may be the same as that described above.
[0153]
【Example】
Next, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples unless it exceeds the gist. In the following description, “parts” and “%” are based on mass unless otherwise specified.
[0154]
[Preparation of First Ink]
<Preparation of pigment dispersion>
(Pigment dispersion liquid 1)
220m specific surface area²/ G, DBP oil absorption is 112 ml / 100 g, 500 g of carbon black, 45 g of aminophenyl-2-sulfoethyl-sulfone (APSES), 900 g of distilled water are charged into a reactor, and the temperature is kept at 55 ° C. The mixture was stirred at a rotation speed of 300 RPM for 20 minutes. Thereafter, 40 g of sodium nitrite having a concentration of 25% was added dropwise over 15 minutes, and 50 g of distilled water was further added. Thereafter, the temperature was maintained at 60 ° C., and the reaction was performed for 2 hours. The reaction product was taken out while diluting with distilled water and adjusted to a concentration of 15% solids. Thereafter, a centrifugal separation treatment and a purification treatment for removing impurities were performed. The resulting dispersion was a dispersion in which the above-mentioned (APESS) functional group was bonded to carbon black. This dispersion is designated as A1.
[0155]
Here, the following operation was performed in order to determine the number of moles of the functional group bonded to the carbon black in the dispersion A1. The Na ion in the dispersion was measured with a probe-type sodium electrode, and the obtained value was converted per carbon black powder to determine the number of moles of the functional group bonded to the carbon black.
[0156]
Next, the dispersion A1 having a solid content of 15% prepared above was dropped into a pentaethylenehexamine (PEHA) solution. At this time, the PEHA solution was kept at room temperature with vigorous stirring, and the dispersion A1 was added dropwise over 1 hour. The PEHA concentration at this time was a concentration of 1 to 10 times the number of moles of Na ions measured previously, and the solution amount was the same as that of the dispersion A1. Further, this mixture was stirred for 18 to 48 hours, and thereafter, a purification treatment for removing impurities was performed, and finally, a dispersion having a solid content of 10% to which pentaethylenehexamine (PEHA) was bound was obtained. This dispersion is designated as B1.
[0157]
Next, a styrene-acrylic acid resin as a copolymer segment was prepared as follows. First, 190 g of a styrene-acrylic acid resin having a weight average molecular weight of 15,000, an acid value of 140, and a polydispersity of Mw / Mn of 1.5 was weighed, and 1,800 g of distilled water was added thereto. NaOH necessary for neutralization was added and dissolved by stirring to prepare an aqueous styrene-acrylic acid resin solution. Next, 500 g of the previously prepared dispersion B1 having a solid content of 10% was dropped into the styrene-acrylic acid resin aqueous solution while stirring. Next, the mixture of the dispersion liquid B1 and the styrene-acrylic acid resin aqueous solution was transferred to a Pyrex (registered trademark) evaporating dish, heated at 150 ° C. for 15 hours, evaporated, and then the evaporated and dried product was cooled to room temperature.
[0158]
Next, the evaporated and dried product was dispersed in NaOH-added distilled water adjusted to pH = 9.0 using a dispersing machine, and 1.0 M NaOH was added with stirring to adjust the pH to 10 to 11. did. Thereafter, desalting, purification for removing impurities, and removal of coarse particles were performed to obtain a pigment dispersion liquid 1. Regarding the physical properties of the obtained pigment dispersion liquid 1, the solid content was 10%, the pH was 10.1, and the average particle diameter was 130 nm. The following shows a synthesis scheme of a modified pigment in which an organic group is chemically bonded to the surface of carbon black particles contained in the above-described pigment dispersion liquid 1.
[0159]

[0160]
When the obtained pigment dispersion liquid 1 was subjected to thermal analysis by the following method, the weight reduction rate was as small as 2.5%, and it was found that the copolymer dispersion was chemically bonded to the surface of the carbon black particles. It could be confirmed. Further, the ratio of the organic group chemically bonded to the pigment with respect to the mass of the modified pigment was measured by a method described later, and was found to be 18%.
[0161]
First, the pigment dispersion 1 is subjected to salting out or aggregation, etc., and then the carbon black precipitate is collected by filtration. The solid obtained by filtration is sufficiently washed with pure water, and the carbon black after washing is washed. The solid was dried in a 60 ° C. oven overnight. Next, the dried carbon black was designated as (C), and the dried carbon black was subjected to washing and extraction of the dried carbon black using tetrohydrofuran (THF), which is a good polymer solvent, in 3 hours. Repeated times. In order to volatilize residual moisture and residual solvent from the dried carbon black after extraction and removal of the polymer as described above, a vacuum dryer is used at 60 ° C. × 3 at a degree of vacuum of several hundred Pa or less. After drying for about an hour, carbon black after solvent extraction was obtained. The carbon black after the extraction was designated as (D), and the pigment dispersion 1 was measured for the weight loss rate in the range of 100 ° C. to 700 ° C. by TGA (thermogravimetric analysis) of (C) and (D). Using the obtained respective measurement results, the difference in weight loss rate by thermal analysis was determined as the difference in weight loss rate = weight loss rate (%) in (C) −weight loss rate (%) in (D). .
[0162]
(Preparation of Pigment Dispersion Liquid 2)
Instead of the styrene-acrylic acid resin used in preparing the pigment dispersion 1, a styrene-acrylic acid resin having a weight average molecular weight of 10,000, an acid value of 240, and a polydispersity Mw / Mn of 1.6 was used. A pigment dispersion 2 was obtained in the same manner as in Example 1 except that the pigment dispersion was used. Regarding the physical properties of the obtained pigment dispersion liquid 2, the solid content was 10.5%, the pH was 9.5, and the average particle diameter was 155 nm. When thermal analysis was performed on the obtained pigment dispersion liquid 2 by the method described above, the weight reduction rate was as small as 4.0%, indicating that the copolymer segment was chemically bonded to the surface of the carbon black particles. Was confirmed. Further, the ratio of the organic group chemically bonded to the modified pigment with respect to the mass of the modified pigment was measured by a method described later, and was found to be 20%.
[0163]
(Preparation of pigment dispersion Bk)
The same operation as in Example 1 was performed except that a polyacrylic acid resin having a weight average molecular weight of 30,000 was used instead of the styrene-acrylic acid copolymer resin used when preparing Pigment Dispersion Liquid 1. Thus, a resin-bound pigment dispersion Bk was obtained. Regarding the physical properties of the obtained pigment dispersion Bk, the solid content was 10%, the pH was 9.0, and the average particle diameter was 175 nm. The obtained pigment dispersion Bk was subjected to thermal analysis by the method described above. As a result, the weight loss was 3.0%, indicating that the polymer segment was chemically bonded to the surface of the carbon black particles. It could be confirmed. Further, the ratio of the polymer chemically bonded to the modified pigment with respect to the mass of the modified pigment was measured by the method described later, and it was 15%.
[0164]
[Thermal analysis method]
Hereinafter, a specific method for measuring the ratio of the organic group in the surface-modified pigment will be described. First, salting out or coagulation was performed on the pigment dispersion 1, respectively. Specifically, when the organic group has an anionic group, an acid such as hydrochloric acid or sulfuric acid is added, and when the organic group has a cationic group, an alkali such as sodium hydroxide is added to disperse the pigment. The pigment and the organic group in the liquid 1 can be precipitated by salting out, and in some cases, the pigment in the pigment dispersion 1 can be precipitated by coagulation by adding an excessive amount of alcohol.
[0165]
In addition, as a method for precipitating the pigment in the pigment dispersion 1, the pigment in the pigment dispersion 1 can be effectively taken out by combining salting out or coagulation, or by performing centrifugation. is there. The precipitate containing carbon black, which is a pigment obtained by the above operation, is collected by filtration, and the filtered solid is sufficiently washed with pure water, and the washed carbon black-containing solid is placed in an oven at 60 ° C. And dried overnight. Then, the obtained carbon black-containing dried product was washed with tetrahydrofuran (THF), which is a good solvent for the segment containing the copolymer. After the washing operation of the carbon black-containing dried product with THF was repeated three times, the remaining water and the remaining solvent were volatilized by using a vacuum dryer at a vacuum of several hundred Pa or less at 60 ° C. × It was dried for about 3 hours. As described above, a solid containing only the surface-modified carbon black whose segments containing the copolymer as a free polymer were removed by washing the copolymer with a good solvent was obtained.
[0166]
Next, the weight loss rate of thermogravimetric analysis was measured by thermogravimetric analysis using the dried product obtained above as a measurement sample. As described above, the amount of organic groups chemically bonded to carbon black as a pigment was determined from the value of the weight loss rate obtained at that time. In the thermogravimetric analysis, a TGA thermogravimetric device, TGA851e / SDTA, manufactured by METTLER TOLEDO was used.
[0167]
1 and 2 show measurement data of the thermogravimetric analysis weight loss rate obtained by thermogravimetric analysis on the dried matter sample prepared by the above method for the pigment dispersion 1. FIG. 1 shows the results of thermal analysis of a dried sample after coagulation and not subjected to THF washing. The thermogravimetric analysis weight loss rate shown in FIG. 1 is based on the total amount of the organic group chemically bonded to the surface-modified pigment in the ink and the segment containing the polymer portion as a free polymer. Is the ratio to the surface-modified pigment.
[0168]
FIG. 2 shows measurement data of thermogravimetric analysis on a dried product sample obtained after further washing the dried product sample with THF. That is, the thermogravimetric analysis weight loss rate shown in FIG. 2 is for the sample after removing the segment as a free polymer by THF which is a good solvent of the reaction product, and thus the surface modification was performed. It shows the ratio of organic groups chemically bonded in the pigment.
[0169]
According to the thermogravimetric analysis measurement data of the pigment dispersion 1, as shown in FIGS. 1 and 2, a remarkable weight loss was observed at around 350 ° C. in each case. FIG. 2 also shows that such a result was obtained even though the dried product was washed with a good solvent for the copolymer when preparing a sample for thermogravimetric analysis. It means that it was not lost. In other words, this indicates that the pigment in the pigment dispersion 1 is in a state in which an organic substance is chemically bonded to the surface of the pigment particle due to the surface modification. Further, from the thermogravimetric analysis weight loss rate obtained from FIGS. 1 and 2, the organic group chemically bonded to the pigment particle surface with respect to the sum of the organic group and the free polymer contained in the ink is calculated by the following equation. Is determined.
[0170]

[0171]
<Preparation of ink>
Black ink was prepared by mixing the following components, thoroughly stirring and dissolving, and then pressure-filtering through a 3.0 μm pore size microfilter (manufactured by Fuji Film Co., Ltd.).
(Black ink 1)
・ Trimethylolpropane 5 parts
・ Glycerin 7 parts
・ 1,5-pentanediol 6 parts
・ Pigment dispersion 1 50 parts
・ Acetylene glycol ethylene oxide adduct
(Product name: Acetyleneol EH; Kawaken Fine Chem
Cal Co.) 0.1 part
・ Water remaining
[0172]
(Black ink 2)
・ Ethylene glycol 4 parts
・ Glycerin 5 parts
・ Diethylene glycol 3 parts
・ Pigment dispersion 2 45 parts
・ Acetylenol EH (brand name) 0.15 parts
・ Water remaining
[0173]
(Black ink Bk)
・ Glycerin 7 parts
・ Diethylene glycol 3 parts
・ Pigment dispersion liquid Bk 50 parts
・ Pure water remaining
[0174]
[Preparation of second ink]
The color ink was prepared by mixing the following components, sufficiently stirring and dissolving, and then performing pressure filtration with a micro filter having a pore size of 0.2 μm (manufactured by Fuji Film Co., Ltd.).
(Yellow ink Y-1)
・ Ethylene urea 6 parts
・ Glycerin 6 parts
・ 2-pyrrolidone 6 parts
・ C. I. Acid Yellow 23 3 copies
・ Acetylenol EH (brand name) ¥ 1.0 part
・ Water remaining
[0175]
(Magenta ink M-1)
・ Trimethylolpropane 6 parts
・ 1,5-pentanediol 6 parts
・ 2-pyrrolidone 6 parts
・ C. I. Acid Red 52 3 copies
・ Acetylenol EH (brand name) ¥ 1.0 part
・ Water remaining
[0176]
(Cyan ink C-1)
・ Trimethylolpropane 6 parts
・ Glycerin 6 parts
・ Diethylene glycol 6 parts
・ C. I. Acid Blue 9 3 copies
・ Acetylenol EH (brand name) ¥ 1.0 part
・ Water remaining
[0177]
(Second ink of first embodiment: polyvalent metal ion-containing ink)
Further, to each of the above color inks, a divalent metal salt functioning as a precipitating material for a black pigment was added, respectively, to prepare a color ink containing polyvalent metal ions.
(Yellow ink 1)
・ Ethylene urea 6 parts
・ Glycerin 6 parts
・ 2-pyrrolidone 6 parts
・ C. I. Acid Yellow 23 3 copies
・ 2 parts of calcium nitrate
・ Acetylenol EH (brand name) ¥ 1.0 part
・ Water remaining
[0178]
(Magenta ink 1)
・ Trimethylolpropane 6 parts
・ 1,5-pentanediol 6 parts
・ 2-pyrrolidone 6 parts
・ C. I. Acid Red 52 3 copies
・ 2 parts magnesium nitrate
・ Acetylenol EH (brand name) ¥ 1.0 part
・ Water remaining
[0179]
(Cyan ink 1)
・ Trimethylolpropane 6 parts
・ Glycerin 6 parts
・ Diethylene glycol 6 parts
・ C. I. Acid Blue 9 3 copies
・ 2 parts magnesium nitrate
・ Acetylenol EH (brand name) ¥ 1.0 part
・ Water remaining
[0180]
<Examples 1 to 4, Comparative Examples 1 to 3>
The inks of Examples 1 to 4 and Comparative Examples 1 to 3 were prepared by combining the black ink as the first ink prepared above and the color inks as shown in Table 1 below.

[0181]
[Evaluation]
Recording was performed on commercial copy paper using the inks of Examples 1 to 4 and Comparative Examples 1 to 3 described above. As ink jet recording apparatuses, three types of ink jet recording apparatuses each having an on-demand type multi-recording head for discharging ink by applying thermal energy according to a recording signal to the ink (product names: BJF-600, BJF-800, BJF-850 (manufactured by Canon Inc.) was modified so that 30 ng of black ink and 15 ng of color ink could be applied to a 1/600 inch square area, respectively. As a print pattern, a print pattern in which color and black image areas are adjacent as shown in FIG. 12 was printed, and the bleed at the boundary and the white haze at the black area were visually evaluated.
[0182]
In the case where the ink set of Example 2 was used, when the color printing area was yellow and magenta, cyan ink was previously applied to the area of the recording medium where the black image was formed. At this time, the printing duty of the black ink and the cyan ink was 100% for the black ink and 15% for the cyan ink. Using the ink sets of Examples and Comparative Examples, images were formed as described above, and each image was evaluated for bleed by the following method.
[0183]
As a print pattern, a print pattern in which color and black image areas are adjacent to each other as shown in FIG. 12 was printed, and the evaluation of bleed at the boundary was visually performed. In each of the ink sets used in the examples, the bleeding at the boundary was suppressed, but in the ink set used in the comparative example, the bleeding at the boundary was conspicuous.
[0184]
(Second ink of second embodiment: ink having a buffering action against pH change)
First, based on a mixture of the following constituent materials, a cyan ink C-2 and 2-1 and 2-2 having a buffer action against a pH change were produced.
(Cyan ink base)
・ Glycerin 5 parts
・ 1,5-pentanediol 5 parts
・ Trimethylolpropane 5 parts
・ 2 parts ethanol
・ Acetylenol EH (brand name) ¥ 1.0 part
・ C. I. Direct Blue ¥ 199 3.5 copies
[0185]
(Cyan ink C-2)
・ Base 21.5 parts
・ Water: 78.5 parts
[0186]
(Cyan ink 2-1)
・ Base 21.5 parts
・ Sodium acetate 0.5 parts
・ Acetic acid 0.65 parts
・ Water: 77.35 parts
[0187]
(Cyan ink 2-2)
・ Base 21.5 parts
・ Succinic acid 0.35 parts
・ Sodium tetraborate 0.65 parts
・ Water: 77.5 parts
[0188]
Based on a mixture of the following constituent materials, a cyan ink M-2 and 2-1 and 2-2 having a buffer action against a pH change were prepared.
(Magenta ink base)
・ 1,5-pentanediol 5 parts
・ 2-pyrrolidone 5 parts
・ Ethylene urea 5 parts
・ 2 parts ethanol
・ Acetylenol EH (brand name) ¥ 1.0 part
・ C. I. Acid Red $ 289 3 copies
[0189]
(Magenta ink M-2)
・ The above base # 21
・ 79 yen water
[0190]
(Magenta ink 2-1)
・ The above base # 21
・ Sodium citrate 1 part
・ Acetic acid 0.9 parts
・ Water: 77.1 parts
[0191]
(Magenta Ink 2-2)
・ The above base # 21
・ Potassium dihydrogen citrate 1 part
・ Acetic acid 0.9 parts
・ Water: 77.1 parts
[0192]
Based on a mixture of the following constituent materials, Yellow Y-2 and 2-1 and 2-2 having a buffer action against a pH change were produced.
(Yellow ink base)
・ 2-pyrrolidone 5 parts
・ Ethylene glycol 5 parts
・ Trimethylolpropane 5 parts
・ 2 parts ethanol
・ Acetylenol EH (brand name) ¥ 1.0 part
・ C. I. Acid Yellow $ 23 3 copies
[0193]
(Yellow ink Y-2)
・ The above base # 21
・ 79 yen water
[0194]
(Yellow ink 2-1)
・ The above base # 21
・ Sodium lactate 1.5 parts
・ Lactic acid 1.85 parts
・ Water: 75.65 parts
[0195]
(Yellow ink 2-2)
・ The above base # 21
・ Potassium hydrogen phthalate 1 part
・ Lactic acid 0.9 parts
・ Water: 77.1 parts
[0196]
<Examples 5 to 8, Comparative Examples 4 to 8>
The black ink as the first ink prepared above and the color ink obtained above were combined as shown in Table 1 below to obtain ink sets of Examples 5 to 8 and Comparative Examples 4 to 8. .
[0197]

[0198]
Whether or not the color ink used as the second ink constituting each of the ink sets of Examples 5 to 8 and Comparative Examples 4 to 8 has a buffering action against a change in pH was determined for 50 ml of color ink. The test was conducted by measuring the difference between the pH value of the ink to which 1.0 ml of a 1N aqueous lithium hydroxide solution was added and the pH value of the ink to which no aqueous lithium hydroxide solution was added. The results are shown in Table 3 below. Table 3 also shows the pH of the black ink as the first ink.
[0199]

[0200]
<Evaluation>
Next, an on-demand type multi-recording head that ejects ink by applying heat energy according to a recording signal to each of the ink sets of Examples 5 to 8 and Comparative Examples 4 to 8 obtained above is provided. Each of them was mounted on a modified machine of BJF # 800 (manufactured by Canon Inc.), which is an ink jet recording apparatus, and a printing test was performed. Then, the bleed between the black ink and the color ink was evaluated as follows. The recording media used in the print test were two plain papers of Canon copy paper: PB @ PAPER (indicated as PB) and Xerox: 4024 @ PAPER (indicated as XX).
[0201]
(Bleeding between black ink and each color ink)
In a printing method of printing black ink and color ink by the same scan, using the ink set of Examples 5 to 8 and Comparative Examples 4 to 8 on the plain paper, , Yellow, magenta, or cyan ink, and printed a pattern in which solid portions were adjacent to each other. Adjacent color boundaries were visually observed and evaluated according to the following evaluation criteria. Table 4 shows the obtained results.
：: No bleed was visually observed at all boundaries.
Δ: Slight bleeding was observed visually, but not so much concern.
×: Bleeding is visually observed.
[0202]

[0203]
(The second ink of the third embodiment: an ink having a coloring material having a polarity opposite to that of the pigment in the first ink)
[Preparation of First Ink]
<Preparation of pigment dispersion>
As the first ink, the previously prepared pigment dispersion liquid 1 and pigment dispersion liquids 3 to 6 prepared as described below were used.
[0204]
(Pigment dispersion 3)
A dispersion B1 was prepared in the same manner as in the pigment dispersion 1 described above. Then, instead of the styrene-acrylic acid resin having a weight average molecular weight of 15,000, an acid value of 140, and a polydispersity Mw / Mn of 1.5 used in the preparation of the pigment dispersion 1, a weight average molecular weight of 5 Using a styrene-acrylic acid resin having a molecular weight of 4,000, an acid value of 140, and a polydispersity of Mw / Mn = 1.8, the subsequent operation was performed in the same manner to obtain a pigment dispersion 3. Regarding the physical properties of the obtained Pigment Dispersion 3, the solid content was 10.5%, the pH was 10, and the average particle diameter was 134 nm. The obtained pigment dispersion 3 was subjected to thermal analysis by the method described above. As a result, it was found that the mass reduction rate was as small as 4.0%, and that the copolymer segment was chemically bonded to the surface of the carbon black particles. Was confirmed.
[0205]
(Pigment dispersion liquid 4)
A dispersion B1 was prepared in the same manner as in the pigment dispersion 1 described above. Then, instead of the styrene-acrylic acid resin having a weight average molecular weight of 15,000, an acid value of 140, and a polydispersity Mw / Mn of 1.5 used in the preparation of the pigment dispersion 1, a weight average molecular weight of 4 Pigment Dispersion Liquid 4 was obtained by using a styrene-acrylic acid resin having a molecular weight of 8,000, an acid value of 480 and a polydispersity Mw / Mn of 2.2. Regarding the physical properties of the obtained Pigment Dispersion 4, the solid content was 10%, the pH was 9.0, and the average particle diameter was 140 nm. The obtained pigment dispersion 4 was subjected to thermal analysis by the method described above. As a result, the mass reduction was as low as 6.2%, indicating that the copolymer segments were chemically bonded to the carbon black particle surfaces. Was confirmed.
[0206]
(Pigment dispersion liquid 5)
Dispersion A1 was produced in the same manner as in the above-mentioned pigment dispersion 1. Then, instead of pentaethylenehexamine (PEHA) used in the preparation of the pigment dispersion 1, styrene-N, N having an amine value of 200, a molecular weight of 10,000, and a polydispersity Mw / Mn of 1.8 was used. Using-,-dimethylaminoethyl methacrylate resin (St-DM), the subsequent operation was performed in the same manner to finally obtain a pigment dispersion liquid 5 in which St-DM was chemically bonded to carbon black. Regarding the physical properties of the obtained Pigment Dispersion 5, the solid content was 11%, the pH was 5.5, and the average particle diameter was 120 nm. The obtained pigment dispersion 5 was subjected to a thermal analysis by the method described above. As a result, the mass reduction was as low as 1.8%, and the copolymer segment was chemically bonded to the surface of the carbon black particles. Was confirmed.
[0207]
(Pigment dispersion 6)
Dispersion A1 was produced in the same manner as in the above-mentioned pigment dispersion 1. Then, instead of pentaethylenehexamine (PEHA) used in the preparation of the pigment dispersion 1, styrene-N, N having an amine value of 450, a molecular weight of 4,000, and a polydispersity Mw / Mn of 1.8 were used. Using-,-dimethylaminoethyl methacrylate resin (St-DM), the subsequent operation was performed in the same manner to finally obtain a pigment dispersion 6 in which St-DM was chemically bonded to carbon black. Regarding the physical properties of the obtained pigment dispersion 6, the solid content was 10%, the pH was 4.5, and the average particle diameter was 142 nm. The obtained pigment dispersion 6 was subjected to thermal analysis by the method described above. As a result, it was found that the mass reduction rate was as small as 3.8%, and that the copolymer segment was chemically bonded to the surface of the carbon black particles. Was confirmed.
[0208]
(Preparation of ink)
Using the resin-bonded type self-dispersible carbon black containing a copolymer segment obtained above, mixing the following components, and sufficiently stirring to dissolve or disperse the mixture. Then, a microfilter having a pore size of 3.0 μm is obtained. A first ink was prepared by filtration under pressure (manufactured by Fuji Film).
[0209]
(Black ink 1)
・ 1 50 parts of the above pigment dispersion
・ Glycerin 5 parts
・ 1,5-pentanediol 6 parts
・ Trimethylolpropane 5 parts
・ Acetylene glycol EO adduct 0.1 part
・ Pure water remaining
[0210]
(Black ink 3)
・ 3 45 parts of the above pigment dispersion
・ Glycerin 5 parts
・ 1,5-pentanediol 5 parts
・ Trimethylolpropane 6 parts
・ Acetylenol EH (brand name) 0.1 part
・ Pure water remaining
[0211]
(Black ink 4)
-4 to 50 parts of the above pigment dispersion
・ Glycerin 7 parts
・ Diethylene glycol 3 parts
・ Trimethylolpropane 6 parts
・ Acetylenol EH (brand name) 0.1 part
・ Pure water remaining
[0212]
(Black ink 5)
-5 to 50 parts of the above pigment dispersion
・ Glycerin 5 parts
・ 1,5-pentanediol 5 parts
・ Trimethylolpropane 5 parts
・ Acetylenol EH (brand name) 0.1 part
・ Pure water remaining
[0213]
(Black ink 6)
6 to 50 parts of the above pigment dispersion
・ Glycerin 5 parts
・ 1,5-pentanediol 5 parts
・ Trimethylolpropane 6 parts
・ Acetylenol EH (brand name) 0.15 parts
・ Pure water remaining
[0214]
[Preparation of second ink]
<Preparation of color pigment dispersion>
・ Styrene-acrylic acid copolymer (molecular weight 5000)
5.5 parts
・ Monoethanolamine 1.0 parts
・ Diethylene glycol 5.0 parts
・ Pure water: 67.5 parts
[0215]
First, the above components were mixed and heated to 70 ° C. in a water bath to completely dissolve the resin components. Next, C.I. I. Pigment Yellow 74 and 1.0 parts of isopropyl alcohol were added, and the mixture was premixed for 30 minutes, then dispersed under the following conditions, and further subjected to centrifugation to remove coarse particles. A pigment dispersion 3-1 was obtained.
・ Dispersing machine: Sand grinder
・ Pulverizing media: zirconium beads 1mm diameter
-Filling ratio of grinding media: 50% (volume)
・ Pulverization time: 3 hours
[0216]
In addition, C.I. of the yellow pigment dispersion 3-1 used above. I. Pigment \ Yellow \ 74, C.I. I. Pigment Red 122 was added to prepare a magenta pigment dispersion 3-1. Further, C.I. of the yellow pigment dispersion 3-1. I. Pigment \ Yellow \ 74, C.I. I. Pigment Blue 15: 3, except that Pigment Blue 15: 3 was used to prepare a cyan pigment dispersion 3-1.
Next, 5.5 parts of polyoxyethylene amine was used in place of the styrene-acrylic acid copolymer (molecular weight: 5,000), which is a pigment dispersant, under the conditions for preparing each color pigment dispersion 3-1 prepared above. A yellow, magenta, and cyan color pigment dispersion liquid 3-2 was prepared in the same manner as described above, except that it was used.
[0219]
<Preparation of color ink>
After mixing and dissolving or dispersing the following components with sufficient stirring, the mixture was filtered under pressure through a micro filter (manufactured by Fuji Film) having a pore size of 0.2 or 3.0 μm to prepare each color ink.
[0218]
(Cyan ink 3-1)
・ C. I. Direct Blue 199 $ 3
・ Glycerin 7 parts
・ 2-pyrrolidone 5 parts
・ Ethylene glycol 6 parts
・ Acetylenol EH (brand name) $ 1
・ Pure water remaining
[0219]
(Cyan ink 3-2)
・ C. I. Basic Blue 100 3 copies
・ Glycerin 7 parts
・ 2-pyrrolidone 5 parts
・ Ethylene glycol 6 parts
・ Acetylenol EH (brand name) $ 1
・ Pure water remaining
[0220]
(Cyan ink 3-3)
-The cyan pigment dispersion 3-1 @ 30 parts
・ Glycerin 8 parts
・ Diethylene glycol 8 parts
・ Polyethylene glycol 400 400 parts
・ Acetylenol EH (brand name): 0.8 parts
・ Pure water remaining
[0221]
(Cyan ink 3-4)
-3 to 30 parts of the above-mentioned cyan pigment dispersion
・ Glycerin 8 parts
・ Diethylene glycol 8 parts
・ Polyethylene glycol 400 400 parts
・ Acetylenol EH (brand name): 0.8 parts
・ Water remaining
[0222]
(Magenta ink 3-1)
・ C. I. Acid Red 289 3 parts
・ Glycerin 6 parts
・ Diethylene glycol 5 parts
・ Triethylene glycol 7 parts
・ Acetylenol EH (brand name) $ 1
・ Water remaining
[0223]
(Magenta ink 3-2)
・ C. I. Basic Red 12 3 copies
・ Glycerin 6 parts
・ Diethylene glycol 5 parts
・ Triethylene glycol 7 parts
・ Acetylenol EH (brand name) $ 1
・ Water remaining
[0224]
(Magenta ink 3-3)
-The magenta pigment dispersion 3-1 @ 30 parts
・ Glycerin 8 parts
・ Diethylene glycol 8 parts
・ Polyethylene glycol 400 400 parts
・ Acetylenol EH (brand name): 0.8 parts
・ Pure water remaining
[0225]
(Magenta ink 3-4)
-3 to 30 parts of the above magenta pigment dispersion
・ Glycerin 8 parts
・ Diethylene glycol 8 parts
・ Polyethylene glycol 400 400 parts
・ Acetylenol EH (brand name): 0.8 parts
・ Pure water remaining
[0226]
(Yellow ink 3-1)
・ C. I. Acid Yellow 23 3 copies
・ Glycerin 7 parts
・ Diethylene glycol 7 parts
・ Urea 6 parts
・ Acetylenol EH (brand name) $ 1
・ Pure water remaining
[0227]
(Yellow ink 3-2)
・ C. I. Basic Yellow 21 3 copies
・ Glycerin 7 parts
・ Diethylene glycol 7 parts
・ Urea 6 parts
・ Acetylenol EH (brand name) $ 1
・ Pure water remaining
[0228]
(Yellow ink 3-3)
-The yellow pigment dispersion 3-1 @ 30 parts
・ Glycerin 8 parts
・ Diethylene glycol 8 parts
・ Polyethylene glycol 400 400 parts
・ Acetylenol EH (brand name): 0.8 parts
・ Pure water remaining
[0229]
(Yellow ink 3-4)
・ 3 to 30 parts of the above yellow pigment dispersion
・ Glycerin 8 parts
・ Diethylene glycol 8 parts
・ Polyethylene glycol 400 400 parts
・ Acetylenol EH (brand name): 0.8 parts
・ Pure water remaining
[0230]
<Examples 9 to 17>
The black ink as the first ink prepared above and the respective color inks obtained above were combined as shown in Table 5 below, and the polarity of the color material in the second ink was changed to the first ink. Each ink set of Examples 9 to 17 was obtained, which had the opposite polarity to the polarity of the pigment in the ink.
[0231]

[0232]
<Comparative Example 9>
Specific surface area is 210m²/ G, 7 parts of carbon black having a DBP oil absorption of 74 ml / 100 g, 2 parts of a styrene-acrylic acid copolymer having an acid value of 200 and a weight average molecular weight of 10,000, 1 part of monoethanolamine, 15 parts of diethylene glycol, 10 parts of glycerin, and 65 parts of pure water were mixed and dispersed using a sand grinder for 1 hour. Thereafter, coarse particles were removed by centrifugation, followed by pressure filtration with a micro filter having a pore size of 3.0 μm (manufactured by Fuji Film) to obtain a black ink. The obtained black ink 7 was used as the first ink of the ink set of Comparative Example 9. As the color ink to be combined with the black ink 7, the cyan ink 3-4, the magenta ink 3-4, and the yellow ink 3-4 used in the examples were used.
[0233]
<Comparative Example 10>
The previously prepared black ink 3 containing the pigment dispersion 3 in which the polyacrylic acid resin was bonded to the carbon black surface was used as the first ink of the ink set of Comparative Example 10. As the color ink combined with the black ink 3, the cyan ink 3-4, the magenta ink 3-4, and the yellow ink 3-4 used in the examples were used.
[0234]
<Comparative Example 11>
H in 30g of water₃N⁺C₆H₄N⁺(CH₃)₃Cl⁻1.69 g of silver nitrate is added to a solution in which 3.08 g has been dissolved while stirring. The generated precipitate was removed by filtration, and the filtrate was added to 70 g of water to have a specific surface area of 230 m.²/ G of DBPA at 70 ml / 100 g was added to a suspension in which 10 g of carbon black was dispersed with stirring. Next, 2.25 g of concentrated hydrochloric acid are added, and then a solution of 0.83 g of sodium nitrite in 10 g of water is added. Then, NN⁺C₆H₄N⁺(CH₃)₃The diazonium salt having a group reacts with carbon black to generate nitrogen gas. When the bubbling of the nitrogen gas ceased, the dispersion was dried in an oven at 20 ° C. As a result, carbon black particles₆H₄N⁺(CH₃)₃The product with the base was obtained. 4 parts of this product was used in place of the pigment dispersion 4 in the preparation of the black ink 4 used in the example, to obtain a black ink 8, which was used as the first ink in the ink set of Comparative Example 11. It was used for. As the color ink to be combined with the black ink 8, the cyan ink 3-1, the magenta ink 3-1 and the yellow ink 3-1 used in the examples were used.
[0235]
<Comparative Example 12>
The black ink 1 was used as the first ink, and the cyan ink 3-1 and the magenta ink 3-1 and the yellow ink 3-1 used in the examples were used as the color inks to be combined with the black ink 1. In this combination, the polarity of the coloring material in the second ink is the same as the polarity of the pigment in the first ink, both anionic.
[0236]
<Comparative Example 13>
The black ink 6 was used as the first ink, and the cyan ink 3-4, the magenta ink 3-4, and the yellow ink 3-4 used in the examples were used as the color inks to be combined with the black ink 6. In this combination, the polarity of the coloring material in the second ink is the same as the polarity of the pigment in the first ink, both cationic and the same.
[0237]
<Evaluation>
An ink-jet recording apparatus having an on-demand type multi-recording head for discharging ink by applying thermal energy to the ink in accordance with a recording signal using each of the inks of Examples 9 to 17 and Comparative Examples 9 to 13 described above. BJF-660 (manufactured by Canon Inc.) was modified and evaluated as follows. Table 6 shows the obtained evaluation results.
[0238]
1. Printing persistence
Using the inks of Examples and Comparative Examples and the above-described ink jet recording apparatus, solid printing in which a nozzle check pattern is first included is continuously performed on three A4 sheets, and then printing is performed for 2 hours. Thereafter, a cycle of continuously printing three sheets of solid printing was repeated 10 times. At that time, the presence or absence of print bleeding and non-ejection were evaluated according to the following criteria.
：: No print bleeding and non-discharge occurred.
Δ: Printing bleeding was slightly observed, but no ejection was not observed.
×: Printing bleeding and non-ejection were observed.
[0239]
2. Marker resistance
Using the above-mentioned inks and the above-described ink jet recording apparatus, printing is performed on the following five types of plain paper for copying A to E, and the obtained image is left for one day, and then a commercially available aqueous fluorescent marker pen (for example, The printed portion was marked with a zebra highlighter (OPTEX OP-100-Y), and the stain on the marked portion was observed and evaluated according to the following criteria.
：: Dirt is not noticeable on all papers.
Δ: Soil is noticeable on some papers.
X: Stain is conspicuous on all papers.
[0240]
In the image output test, the following copy paper was used.
A: PSK paper NSK manufactured by Canon Inc.
B: PDK paper NDK manufactured by Canon Inc.
C: PPC paper 4024, manufactured by Xerox Corporation
D: PPC paper prober bond manufactured by Fox River Co., Ltd.
E: PPC paper for Canon manufactured by Neujidora Co., Ltd.
[0241]
3. Bleed resistance
A pattern in which the solid portion of the black ink and the solid portion of the yellow, magenta, or cyan ink are adjacent to each other is printed on Canon / PB paper, and the boundary between the black ink and the color ink is visually observed. The presence or absence of occurrence was evaluated according to the following criteria.
◎: No bleeding was observed at all boundaries.
：: Slight bleeding is recognized, but at a level that does not cause any problem.
Δ: Slight bleeding is observed.
×: Bleeding is conspicuous at almost all boundaries.
[0242]

[0243]
【The invention's effect】
As described above, according to the present invention, in particular, it satisfies various performances such as print quality and image fastness required for black ink, and this black ink causes bleeding with other color inks. It is possible to obtain an image without any trouble, and it is possible to form an excellent color image.While having the reliability of the ink with respect to the recording head, and also the resistance to printing stains due to rubbing after printing, and the aqueous property after printing. Provided are an ink set, an image forming method, a recording unit, and an ink jet recording apparatus which can improve marker resistance by a marker.
[Brief description of the drawings]
FIG. 1 is a result of thermogravimetric analysis of a sample after coagulating a pigment of a pigment dispersion used in an example.
FIG. 2 shows the results of thermogravimetric analysis of a sample after coagulating the pigment of the pigment dispersion used in the example and further washing with THF.
FIG. 3 is a thermogravimetric analysis result of a sample after coagulating a pigment of a pigment dispersion used in a comparative example.
FIG. 4 is a thermogravimetric analysis result of a sample after coagulating a pigment of a pigment dispersion used in a comparative example and further washing with THF.
FIG. 5 is a longitudinal sectional view of an ink jet recording apparatus head.
FIG. 6 is a vertical and horizontal view of an ink jet recording apparatus head.
FIG. 7 is an external perspective view of a head obtained by multiplying the head shown in FIG. 5;
FIG. 8 is a perspective view illustrating an example of an ink jet recording apparatus.
FIG. 9 is a longitudinal sectional view of the ink cartridge.
FIG. 10 is a perspective view illustrating an example of a recording unit.
FIG. 11 is a diagram illustrating an example of a configuration of a recording head.
FIG. 12 is a diagram illustrating a print pattern in which color and black image areas are adjacent to each other.
[Explanation of symbols]
13: Head
14: Ink groove
15: Heating element substrate
16: protective layer
17-1, 17-2: Electrode
18: Heating resistor layer
19: Thermal storage layer
20: Substrate
21: Ink
22: Discharge orifice (micro hole)
23: Meniscus
24: ink drop
25: Recording medium
26: Multi groove
27: glass plate
28: Heating head
40: Ink bag
42: stopper
44: Ink absorber
45: Ink cartridge
51: Paper Feeding Department
52: Paper feed roller
53: Discharge roller
61: Blade
62: Cap
63: ink absorber
64: Discharge recovery unit
65: Recording head
66: Carriage
67: Guide shaft
68: Motor
69: Belt
70: Recording unit
71: Head section
72: Atmospheric communication port
80: Ink flow path
81: Orifice plate
82: diaphragm
83: Piezoelectric element
84: Substrate
85: Discharge port

Claims (24)

At least a first ink and a second ink different in color from the first ink are used to form a color image on a recording medium by applying each ink to the recording medium. Ink set,
The first ink is an aqueous ink containing a modified pigment in which an organic group is chemically bonded to the surface of pigment particles, and an aqueous medium as a dispersion medium of the pigment, The group includes a reaction product of a functional group chemically bonded directly or via another atomic group to the pigment surface, and a copolymer of an ionic monomer and a hydrophobic monomer,
The second ink is a water-based ink that contains a coloring material and that, when mixed with the first ink, destabilizes the dispersion stability of the pigment in the first ink. Ink set. The ink set according to claim 1, wherein the second ink contains a polyvalent metal ion. 3. The polyvalent metal ion is at least one selected from the group consisting of Mg ²⁺ , Ca ²⁺ , Cu ²⁺ , Co ²⁺ , Ni ²⁺ , Fe ²⁺ , La ³⁺ , Nd ³⁺ , Y ³⁺ and Al ^3+. The ink set described in the above. 4. The ink set according to claim 2, wherein the polyvalent metal ion is contained in an amount of 0.1 to 15% by mass based on the total mass of the second ink. The ink set according to claim 4, wherein the second ink contains at least one kind of anionic dye and has an acidic pH. The ink set according to any one of claims 1 to 5, wherein the coloring material in the second ink is at least one selected from an acid dye and a direct dye. The second ink has a pH that causes a pH change in the first ink by mixing with the first ink, and destabilizes the dispersibility of the pigment in the first ink. 2. The ink set according to claim 1, further comprising a buffering action for the pH. The pH value of the second ink is the difference between the pH value when 1.0 ml of a 1N aqueous lithium hydroxide solution is added to 50 ml of the second ink and the pH value of the second ink before the addition. The ink set according to claim 7, wherein the difference is adjusted to be within 1.0. 9. The ink set according to claim 7, wherein the pH of the first ink is higher than the pH of the second ink. The ink set according to any one of claims 7 to 9, wherein the pH of the second ink ranges from a neutral region to an acidic region. The ink set according to claim 1, wherein the polarity of the coloring material in the second ink is opposite to the polarity of the pigment in the first ink. Said second ink ink set according to any one of claims 1 to 11 Ka value is less than ^{1.5 (ml / m 2 / msec} 1/2) of that obtained by the Bristow method. The ink set according to any one of claims 1 to 12, wherein the pigment constituting the first ink is carbon black. The ink set according to any one of claims 1 to 13, wherein the other atomic group constituting the first ink is a phenyl (2-sulfoethyl) group. The ink according to any one of claims 1 to 14, wherein the copolymer constituting the first ink has a Mw of 1,000 to 30,000 and an acid value or an amine value of 100 to 500. set. The polydispersity Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) of the copolymer constituting the first ink is 3 or less, according to any one of claims 1 to 15. Ink set. The determined by the Bristow method first ink ink set according to any one of claims 1 to 16 Ka value is less than ^{1.5 (ml / m 2 / msec} 1/2) of. The ink set according to claim 17 wherein the Ka value is ^{0.2 (ml / m 2 / msec} 1/2) or more. The ink set according to any one of claims 1 to 18, wherein the first ink has a ratio of the organic group in the modified pigment to the total mass of the pigment of 5 to 40% by mass. . The ink set according to any one of claims 1 to 18, wherein the first ink has a ratio of the organic group in the modified pigment to the total mass of the pigment of 10 to 25% by mass. . The ink set according to claim 1, wherein the first ink is a black ink, and the second ink is a color ink. An image forming method for forming a color image on a recording medium by an ink jet recording method using the ink set according to any one of claims 1 to 21,
A step of applying the first ink constituting the ink set to the recording medium by an inkjet method, and a step of applying the second ink constituting the ink set to the recording medium by an inkjet method. An image forming method. 22. A first ink containing section containing the first ink and a second ink containing the second ink constituting the ink set according to claim 1. A recording unit, comprising: a storage section; and an inkjet head group for independently discharging each ink. A first ink containing section containing black ink, a second ink containing section containing color ink, the black ink and the color ink constituting the ink set according to claim 21. An ink jet recording apparatus, comprising: a group of ink jet heads for ejecting ink jet heads; and means for driving the ink jet heads according to recording information.

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