JP2004115546A - Ink, inkjet recording method, ink cartridge, recording unit, and inkjet recording apparatus - Google Patents

Abstract

[PROBLEMS] To solve the problem of ejection bend and non-ejection, to suppress the stain due to rubbing after printing while maintaining the reliability of ink for a recording head, and to apply a water-based marker to an image after printing. The present invention provides a water-based ink containing a resin-bonded self-dispersible pigment having improved marker resistance against print stains, and in particular, having a small variation in ejection amount, and an ink jet recording method and apparatus using the same.
An aqueous ink comprising a modified pigment in which an organic group is chemically bonded to the surface of a pigment particle and an aqueous medium as a dispersion medium of the pigment, wherein the organic group is directly or directly on the surface of the pigment. An aqueous ink containing a reaction product of a functional group chemically bonded via another atomic group and a copolymer of a nonionic monomer containing an ionic monomer, a hydrophobic monomer, and at least one hydroxyl group; Inkjet equipment.
[Selection diagram] None

Description

（但し、上記構造式（１）中、Ｒはアルキル基を表し、ｎは整数を表す。）
【００５８】

（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。）
【００５９】

（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、夫々整数を表す。）
【００６０】

（但し、上記構造式（４）中、ｍ及びｎは、夫々整数を表す。）
【００６１】
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。
【００６２】
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。
【００６３】
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
【００６４】
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。
【００６５】
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（ｍｌ／ｍ^２／ｍｓｅｃ^１／２）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。
【００６６】
［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。
【００６７】
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。
【００６８】
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。
【００６９】
（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。
【００７０】
（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。
【００７１】
（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。
【００７２】
（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。
【００７３】
（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。
【００７４】
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。
【００７５】
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。
【００７６】
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。
【００７７】
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
【００７８】
上記において行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。
【００７９】
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、本発明の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。
【００８０】
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。
【００８１】
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。このような分析に使用することのできる具体的な装置の一例を以下に示す。
【００８２】
・ＴＧ−ＤＴＡ：サーモプラス（Ｔｈｅｒｍｏ　Ｐｌｕｓ）ＴＧ８１２０（理化学電気社製）
・ＧＣ：ＨＰ６８９０（ヒューレット・パッカード社製）
・ＭＳ：ＪＭＳ−ＡＭ　ＩＩ（日本電子製）
・ＴＯＦ−ＭＳ：島津ＭＡＬＤＩ−ＴＯＦＭＳ　ＡＸＩＭＡ−ＣＦＲ（島津製作所社製）
・ＴＯＦ−ＳＩＭＳ：ＰＨＩ　ＴＲＦＴ　ＩＩ（アルバックファイ社製）
【００８３】
以上のような構成を有する本発明の水性顔料インクは、先にも述べたように、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。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が、それらのインクジェット記録方法に、本発明の水性顔料インクは特に好適である。以下、これらについて説明する。
【００８４】
［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水性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を以下に説明する。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１及び図２に示す。図１は、インク流路に沿ったヘッド１３の断面図であり、図２は図１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。
【００８５】
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、被記録材２５に向かって飛翔する。図３には、図１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１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。
【００８６】
図４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４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、本例の場合、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。
【００８７】
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。
【００８８】
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被記録材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。
【００８９】
５１は被記録材を挿入するための給紙部、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被記録材が給紙され、記録が進行する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。
【００９０】
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。
【００９１】
図５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。
【００９２】
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６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６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４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。
【００９３】
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７に示す。
【００９４】
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。
【００９５】
図７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４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。
【００９６】
【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、下記実施例よって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。
【００９７】
［顔料分散液１−１の調製］
比表面積２２０ｍ^２／ｇでＤＢＰ吸油量１１２ｍｌ／１００ｇのカーボンブラック５００ｇ、アミノフェニル（２−スルホエチル）スルフォン（ＡＰＳＥＳ）４５ｇ、蒸留水９００ｇを反応器に投入し、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分間滴下し、更に蒸留水５０ｇを加えた。この後、６０℃に保温しながら、２時間反応させた。そして、得られた反応物を蒸留水で希釈しながら取り出し、固形分が１５％となる濃度に調整した。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。この作成した分散液は、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。
【００９８】
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。次いで、先に調製した固形分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％の分散液となった。この分散液をＢ１とする。
【００９９】
次に、先に調製した固形分が１０％濃度の分散液Ｂ１を５００ｇ、スチレン−アクリル酸−ヒドロキシエチルアクリレート（モノマー比１５％）共重合樹脂を溶解した樹脂水溶液に攪拌しながら滴下した。ここで使用した樹脂水溶液は、重量平均分子量＝１５，０００、酸価＝１６０、多分散度Ｍｗ／Ｍｎ＝１．６の、スチレン−アクリル酸−ヒドロキシエチルアクリレート共重合樹脂１９０ｇを秤り採り、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、攪拌して溶解して調製したもである。次に、上記滴下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、更に、蒸発乾燥物を室温に冷却する。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する。更に攪拌しながら１．０ＭのＮａＯＨを添加して、ｐＨを１０〜１１に調整する。この後、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１−１を得た。得られた顔料分散液１−１の物性値は、固形分が１０．５％、ｐＨ＝９．０、平均粒子径が１００ｎｍであった。
【０１００】
［顔料分散液１−２の調製］
顔料分散液１−１を調製した場合に使用したスチレン−アクリル酸−ヒドロキシエチルアクリレート共重合樹脂の代わりに、重量平均分子量＝１０，０００、酸価＝３００、多分散度Ｍｗ／Ｍｎ＝１．７のスチレン−アクリル酸−ヒドロキシプロピルメタクリレート（モル比５％）共重合樹脂を用いた以外は、顔料分散液１−１の調製の際と同様の操作を行い、顔料分散液１−２を得た。得られた顔料分散液１−２の物性値は、固形分が１０．１％、ｐＨが９．０、平均粒子径が１３０ｎｍであった。
【０１０１】
［顔料分散液１−３の調製］
顔料分散液１−１を調製した場合と同様の作成方法で、分散液Ａ１を作製した。次いで、顔料分散液１−１の調製の際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＝１３，０００、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−ヒドロキシブチルメタクリレート（モル比２０％）共重合樹脂（Ｓｔ−ＤＭ−ＨＢＭＡ）を用いた以外は、顔料分散液１−１の調製の場合と同様の処理を行い、最終的に、カーボンブラック粒子表面に、Ｓｔ−ＤＭ−ＨＢＭＡが結合した顔料分散液１−３を得た。得られた顔料分散液１−３の物性値は、固形分が１０．２％、ｐＨ＝４．５、平均粒子径が１２５ｎｍであった。
【０１０２】
＜実施例１−１〜１−３＞
上記で得られた顔料分散液１−１〜１−３を含む、表１に記載した成分を混合し、十分攪拌して溶解或いは分散した後、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、実施例１−１〜１−３のインクを調製した。各インクの組成を表１に示した。
【０１０３】
又、表１中に、実施例１−１〜１−３の各インクについて、先に説明した方法で得たブリストウ法によって求めたＫａ値の測定値を併せて記載した。更に、後述する方法で測定した熱重量分析によって得た、実施例１−１〜１−３の各インクについての、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（％）を有効数字２桁で求めて、表１中に併せて示した。
【０１０４】

【０１０５】
以下、表１中に示した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、実施例１−１〜１−３の各インクに対して夫々塩析若しくは凝析、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インク中の顔料及び有機基を塩析により沈澱させた。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インク中の顔料を沈澱させることも可能である。
【０１０６】
又、インク中の顔料を沈澱させる方法としては、塩析若しくは凝析を組み合わせる、或いは、遠心分離を行う、等することで、有効にインク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。
【０１０７】
次に、上記で得られたＴＨＦによる洗浄前後の乾固物を夫々測定用試料として、熱重量分析（Ｔｈｅｒｍｏｇｒａｖｉｍｅｔｒｉｃ　Ａｎａｌｙｓｉｓ）を行い、熱重量分析重量減少率を測定した。そして、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、ＭＥＴＴＬＥＲ　ＴＯＬＥＤＯ社製のＴＧＡ熱重量測定装置、ＴＧＡ８５１ｅ／ＳＤＴＡを使用した。常温から７００℃まで昇温して熱重量分析を行った。
【０１０８】
上記した方法によって調製した凝析後のＴＨＦ洗浄を行わない乾固物試料についての熱分析によって得ら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。更に、上記の乾固物試料を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に表われる熱重量分析重量減少率は、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り、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。
【０１０９】
実施例１−１〜１−３のインクについての熱重量分析測定データでは、何れの場合も３５０℃近傍で著しい重量減が見られた。このことは、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、実施例１−１〜１−３のインク中の顔料には、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、上記した各試料に対す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。表１中に、この値を示した。
【０１１０】

【０１１１】
［顔料分散液２−１の調製］
比表面積２２０ｍ^２／ｇでＤＢＰ吸油量１１２ｍｌ／１００ｇのカーボンブラック５００ｇ、アミノフェニル（２−スルホエチル）スルフォン（ＡＰＳＥＳ）４５ｇ、蒸留水９００ｇを反応器に投入し、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分間滴下し、更に蒸留水５０ｇを加えた。この後、６０℃に保温しながら、２時間反応させた。そして、得られた反応物を蒸留水で希釈しながら取り出し、固形分が１５％となる濃度に調整した。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。この作成した分散液は、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。
【０１１２】
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。次いで、先に調製した固形分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％の分散液となった。この分散液をＢ１とする。
【０１１３】
次に、先に調製した固形分が１０％濃度の分散液Ｂ１を５００ｇ、スチレン−アクリル酸−メトキシポリエチレングリコールモノアクリレート（エチレンオキシド２３モル付加物、及びモノマー比１０％）共重合樹脂を溶解した水溶液に攪拌しながら滴下した。ここで使用した樹脂水溶液は、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−メトキシポリエチレングリコールモノアクリレート（エチレンオキシド２３モル付加物、及びモノマー比１０％）共重合樹脂を１９０ｇ秤り採り、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、攪拌して溶解して調製したものである。次に、上記滴下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、更に、蒸発乾燥物を室温に冷却する。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する。更に攪拌しながら、１．０ＭのＮａＯＨを添加してｐＨを１０〜１１に調整する。この後、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２−１を得た。得られた顔料分散液２−１の物性値は、固形分が１０％、ｐＨ＝９．６、平均粒子径が１１５ｎｍであった。
【０１１４】
［顔料分散液２−２］
顔料分散液２−１の調製の場合に使用したスチレン−アクリル酸−メトキシポリエチレングリコールモノアクリレート（エチレンオキシド２３モル付加物、及びモノマー比１０％）共重合樹脂の代わりに、重量平均分子量＝１０，０００、酸価３８０、多分散度Ｍｗ／Ｍｎ＝１．６の、スチレン−アクリル酸−フェノキシポリエチレングリコールモノアクリレート（エチレンオキシド６モル付加物、モノマー比５％）共重合樹脂を用いた以外は、顔料分散液２−１の調製の際と同様の操作を行い、顔料分散液２−２を得た。得られた顔料分散液２−２の物性値は、固形分が１０．３％、ｐＨ＝９．９、平均粒子径が１３０ｎｍであった。
【０１１５】
［顔料分散液２−３］
顔料分散液２−１を調製した場合と同様の作成方法で、分散液Ａ１を作成した。次いで、顔料分散液２−１の調製の際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−メトキシポリエチレングリコールモノアクリレート樹脂（Ｓｔ−ＤＭ−ＭＰＥＡ）を用いた以外は、顔料分散液２−１の調製の場合と同様の処理を行い、最終的に、カーボンブラック粒子表面に、Ｓｔ−ＤＭ−ＭＰＥＡが結合した顔料分散液２−３を得た。得られた顔料分散液２−３の物性値は、固形分が１０％、ｐＨ＝５．０、平均粒子径が１２５ｎｍであった。
【０１１６】
＜実施例２−１〜２−３＞
上記で得られた顔料分散液２−１〜２−３を含む、表２に記載した成分を混合し、十分攪拌して溶解或いは分散した後、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、実施例２−１〜２−３のインクを調製した。各インクの組成を表２に示した。
【０１１７】
又、表２中に、実施例２−１〜２−３の各インクについて、先に説明した方法で得たブリストウ法によって求めたＫａ値の測定値を併せて記載した。更に、先の実施例１−１〜１−３の場合に行ったと同様の熱重量分析によって得た、実施例２−１〜２−３の各インクについての、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（％）を有効数字２桁で求めて、表２中に併せて示した。
【０１１８】

【０１１９】
＜比較例１＞
比表面積２１０ｍ^２／ｇで、ＤＢＰ吸油量７４ｍｌ／１００ｇのカーボンブラック７部、酸価１８０、重量平均分子量１０，０００のスチレン−アクリル酸共重合体２部、モノエタノールアミン１部、ジエチレングリコール１５部、グリセリン１０部、純水６５部とを混合し、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、比較例１のインクを得た。得られた顔料分散液の物性値は、固形分が１０％、ｐＨ＝９．０、平均粒子径が１４０ｎｍであった。
【０１２０】
以下に記載した成分を混合し、十分攪拌して溶解或いは分散した後、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、比較例１のインクを調整した。
・顔料分散液　　　　　　　　　　　　　　５０部
・グリセリン　　　　　　　　　　　　　　　７部
・ジエチレングリコール　　　　　　　　　　３部
・純水　　　　　　　　　　　　　　　　　４０部
【０１２１】
上記で得られた比較例１のインクについて、実施例の場合と同様に測定した、ブリストウ法によって求められるＫａ値は０．７であった。又、実施例の場合と同様に測定した、熱重量分析によって得た熱重量分析重量減少率の割合（％）は、２．０％であった。
【０１２２】
（評価）
上記で得られた実施例１−１〜１−３、２−１〜２−３及び比較例１の各インクについて、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（キヤノン製）の改造機を用いて画出し試験をし、下記の評価を行った。評価結果は、表３に示す。
【０１２３】
１．印字持続性
各インクと、上記したインクジェット記録装置を用い、先ず、ノズルチェックパターンが最初に入っているべた印字を連続してＡ４用紙３枚に印字した。その後２時間印字を行わず、次に再びべた印字を、連続してＡ４用紙３枚に印字するサイクルを５０回繰り返した。その時に生じた印字の乱れ、及び不吐出の有無を下記の基準で評価した。
○：印字の乱れ及び不吐出がみられない。
△：印字の乱れが若干みられるが、不吐出はみられない。
×：印字の乱れ、及び不吐出がみられる。
【０１２４】
２．文字品位
各インクと、上記したインクジェット記録装置を用い、下記の５種類のコピー用の普通紙Ａ、Ｂ、Ｃ、Ｄ及びＥに文字印字を行い、その時に発生した文字の滲みを下記の基準で評価した。
○：５紙とも滲みが殆どない。
△：多少滲む紙がみられる。
×：５紙とも滲む。
【０１２５】
尚、コピー用紙は以下に示すものを用いた。
Ａ：キヤノン（株）製、ＰＰＣ用紙ＮＳＫ
Ｂ：キヤノン（株）製、ＰＰＣ用紙ＮＤＫ
Ｃ：ゼロックス（株）製、ＰＰＣ用紙４０２４
Ｄ：フォックスリバー（株）製　ＰＰＣ用紙プローパーボンド
Ｅ：ノイジドラ（株）製、キヤノン用ＰＰＣ用紙
【０１２６】
３．耐マーカー性
各インクと、上記したインクジェット記録装置を用い、先に使用した５種類のコピー用普通紙Ａ、Ｂ、Ｃ、Ｄ及びＥに印字を行い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、マーキング部分のよご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。
【０１２７】
４．吐出量安定性
各インクと、上記したインクジェット記録装置を用い、吐出量の測定を行った。印字ドット数は、既知のパターンを５枚印字し、インク量の減少量を印字ドット数で割ったものを平均吐出量とし、吐出量の測定に用いた。先ず、ノズルチェックパターンが最初に入っているべた印字を連続してＡ４用紙１０枚に行い、その後、２時間印字を行わず、その後に上記した方法で吐出量測定を行った。次に、再びべた印字を連続して３枚印字し、その後に吐出量の測定を行った。このサイクルを１０回繰り返して、吐出量の変化をみた。得られた吐出量を用いて、以下の基準で吐出量の安定性を判断した。
○：吐出量のばらつきが±１０％の範囲内であった。
△：吐出量のばらつきが±１５％の範囲内であった。
×：吐出量のばらつきが±２０％を超えていた。
【０１２８】

【０１２９】
【発明の効果】
以上説明したように、本発明によれば、水性インクの顔料として、顔料粒子の表面に有機基が化学的に結合している改質された顔料を用いることで、とりわけ、インクジェット用インクとして用いた場合に、吐出曲がりや、ヌレ不吐が解消され、特に吐出性が安定し、インクの吐出量の変動の少ない、記録ヘッドに対するインクの高い信頼性を有し、しかも、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印字汚れ耐マーカー性をも改善された水性インク、かかるインクを使用したインクジェット記録方法、インクカートリッジ、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】インクジェット記録装置ヘッドの縦断面図である。
【図２】インクジェット記録装置ヘッドの縦横面図である。
【図３】図１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４】インクジェット記録装置の一例を示す斜視図である。
【図５】インクカートリッジの縦断面図である。
【図６】記録ユニットの一例を示す斜視図である。
【図７】記録ヘッドの構成の一例を示す図である。
【符号の説明】
１３：ヘッド
１４：インクノズル
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：被記録材
２６：マルチノズル
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：給紙部
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 aqueous ink, an ink jet recording method using the ink, and further relates to an ink cartridge, 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. It can be said that 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 due to drying of the orifice of the inkjet recording head 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.
However, when printing is performed on a recording medium, particularly plain paper, with an aqueous ink using such a self-dispersible pigment, even after the ink is sufficiently dried, the printed surface becomes dirty when the printed surface is strongly rubbed. As a result, 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.
[0006]
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.
[0007]
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.
[0008]
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.
[0009]
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.
[0010]
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.
[0011]
[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
[0012]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to solve the problem of ejection bend and non-discharge, as well as the self-dispersing pigment described above, and in particular, the ejection property is stable, the fluctuation of the ejection amount is small, and the ink for the recording head is high. Abrasion resistance (hereinafter referred to as "print dirt rub resistance") that can suppress print stains due to rubbing after printing while improving reliability, and when an aqueous marker is added to the printed image The present invention provides an aqueous ink containing a self-dispersible pigment of a resin-bonded type having improved marker resistance to print stains (hereinafter referred to as print stain marker resistance), and further records by applying such an ink. An object of the present invention is to provide an ink jet recording method, an ink cartridge using the ink, a recording unit, and an ink jet recording apparatus.
[0013]
[Means for Solving the Problems]
The above object is achieved by the present invention described below. That is, a first aspect of the present invention is an aqueous ink including 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 organic group comprises a functional group chemically bonded directly or via another atomic group to the pigment surface, an ionic monomer, a hydrophobic monomer, and a nonionic monomer containing at least one hydroxyl group. The present invention relates to an aqueous ink comprising a reaction product of a copolymer and a copolymer.
[0014]
A second aspect of the present invention is an aqueous ink including 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 organic group is a nonionic monomer containing a functional group chemically bonded directly or via another atomic group to the pigment surface, an ionic monomer, a hydrophobic monomer, and at least one alkylene oxide group. A water-based ink containing a reaction product of a copolymer consisting of:
[0015]
Preferred embodiments of the present invention include the following. In the constitutions of the aqueous inks of the first and second embodiments, the other atomic group is a phenyl (2-sulfoethyl) group, and the polydispersity Mw / Mn (Mw: weight) of the copolymer (Average molecular weight, Mn: number average molecular weight) is 2 or less, aqueous ink in which the proportion of nonionic monomer units in the copolymer is 3 to 50% by mole, and the pigment is carbon black An aqueous ink having an Mw of 1,000 to 20,000 and an acid value or an amine value of 100 to 500, and a Ka value of the ink determined by the Bristow method of 1 .5 (ml / m²/ Msec^1/2), The Ka value of which is less than 0.2 (ml / m²/ Msec^1/2A) the aqueous ink described above, wherein the ratio of the organic groups in the modified pigment to the total mass of the modified pigment is 5 to 40% by mass; Aqueous ink wherein the ratio of the organic group to the total mass of the modified pigment is 10 to 25 mass%, and the ratio of the modified pigment to the total mass of the aqueous ink is 0.1 to 15 mass%. %, And a ratio of the modified pigment to the total mass of the aqueous ink is 1 to 10% by mass. Further, there may be mentioned those aqueous inks which are aqueous inks for inkjet.
[0016]
Further, another embodiment of the present invention relates to an ink jet recording method including a step of discharging the aqueous ink of the first and second embodiments of the present invention by an ink jet method. In addition, an ink cartridge comprising the above-described ink storage portion storing the aqueous ink, an ink storage portion storing the above-described aqueous ink for inkjet, and a device for discharging the ink An ink jet head, and a recording unit, comprising: an ink container that stores the above-described aqueous ink for ink jet; and an ink jet head for discharging the ink. To an ink jet recording apparatus.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described in more detail with reference to preferred embodiments. An aqueous ink according to a first embodiment of the present invention is an aqueous pigment comprising 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 for the pigment. The ink is a nonionic monomer having the above organic group, a functional group on the surface of the pigment particles or a functional group introduced therein, an ionic monomer, a hydrophobic monomer, and a hydroxyl group further bonded to the functional group. And a copolymer segment comprising:
[0018]
Further, an aqueous ink according to the second embodiment 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. Wherein the organic group contains a functional group on the surface of the pigment particles or a functional group that is introduced, and an ionic monomer, a hydrophobic monomer, and an alkylene oxide group bonded to the functional group. And a copolymer segment comprising a monomer. Hereinafter, each material constituting these pigment inks will be described.
[0019]
[Pigment]
The pigment that can be used in the aqueous pigment ink of the present invention is not particularly limited, and the following pigments can be used. These pigments are modified and used by a method described later. In the present invention, the ratio of the modified pigment to the total mass of the aqueous ink is 0.1 to 15% by mass, and further 1 to 10% by mass. %.
[0020]
As the pigment used for the black ink, carbon black is preferable. For example, any of carbon blacks such as furnace black, lamp black, acetylene black, and channel black can be used. Specifically, for example, Ray-Van (Raven) 7000, Ray-Van 5750, Ray-Van 5250, Ray-Van 5000ULTRA, Ray-Van 3500, Ray-Van 2000, Ray-Van 1500, Ray-Van 1250, Ray-Van 1200, Ray-Van 1190ULTRA-II, Ray-Van 1170, Ray-Van 1255 (or more, Colombia), Black Pearls L, Regal 400R, Regal 330R, Regal 660R, Mogul L, Monarch 700, Monac 800, Monac 880, Monac 900, Monac 1000, Monac 1100, Monak 1300, Monak 1400, Monak 2000, Valcan XC-72R (or more, Color Black (FW), Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, Printtex 35, Printtex U, Printex V, Printex 140U, Printex 140V, Special Black 6, Special Black 5, Special Black 4A, Special Black 4 (all made by Degussa), No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, No. Commercial products such as 2300, MCF-88, MA600, MA7, MA8, and MA100 (all manufactured by Mitsubishi Chemical Corporation) can be used. In addition, carbon black separately newly prepared for the present invention 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.
[0021]
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 Zilone pigments, pyranthrone pigments such as pyranthrone red and pyranthrone orange, thioindigo 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, the present invention is not limited to this, and other organic pigments may be used.
[0022]
The organic pigments that can be used in the present invention can be represented by, for example, C.I. 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.
[0023]
[Functional group]
The functional group in the pigment in the aqueous ink according to the present invention 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. Then, the reaction between the functional group and the copolymer, taking into account that the pigment is dispersed in an aqueous medium, a bond that does not cause hydrolysis or the like, for example, an amide bond or the like is generated. Preferably, it is a reaction. 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.
[0024]
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).
[0025]
More specifically, for example, in the examples described below, the pigment is reacted with aminophenyl (2-sulfoethyl) sulfone to introduce an aminophenyl (2-sulfoethyl) sulfone group on the pigment surface, and then the pentane is added. An amino group as a functional group is introduced by reacting an amino group of ethylenehexamine 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.
By the way, the effects of the aqueous ink according to the present invention include the following.
[0026]
First, as a first effect, the surface-modified pigment used in the present invention is characterized in that a functional group chemically bonded to the surface directly or via another atomic group, and an ionic monomer. A reaction product (aqueous pigment ink of the first embodiment) of a copolymer of a hydrophobic monomer and a nonionic monomer having a hydroxyl group, or the above functional group, an ionic monomer, a hydrophobic monomer, and an alkylene (Aqueous pigment ink of the second embodiment), which is a reaction product of a copolymer composed of a nonionic monomer having an oxide group, and a copolymerization ratio of each monomer which is a material forming these copolymers Can be appropriately changed, whereby the hydrophilicity of the pigment can be appropriately adjusted. In addition, since the types of ionic monomers, hydrophobic monomers, nonionic monomers having a hydroxyl group, and nonionic monomers having an alkylene oxide group, and combinations thereof can be appropriately changed, various characteristics can be applied to the pigment surface. Can be given. 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.
[0027]
As a second effect, since the hydrophobic monomer is used in the copolymer constituting the reactant bonded to the surface of the pigment, the marker stain resistance of the ink is improved. Hereinafter, the reason why the marker resistance is improved will be described.
[0028]
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.
[0029]
On the other hand, in the pigment used in the present invention, the organic group chemically bonded to the pigment surface contains a copolymer having an ionic monomer unit (hydrophilic part). After printing, the cohesive force of the pigment is increased by the entanglement of the copolymer on the surface of the pigment particles on the paper surface, and the print stain resistance after fixing the ink 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.
[0030]
Furthermore, in the water-based ink of the first embodiment according to the present invention, the above-mentioned copolymer has a nonionic monomer unit containing a hydroxyl group using a third monomer as a material for forming the copolymer. According to the study by the inventors, such a configuration makes it possible to stabilize the ink jet ejection property and to minimize fluctuations in the ink ejection amount from the ink jet head, particularly when the ink is used for ink jet recording. I understood.
[0031]
Further, in the aqueous ink of the second embodiment according to the present invention, the above-described copolymer has a nonionic monomer unit containing an alkylene oxide group using a third monomer as a material for forming the copolymer. According to the study of the present inventors, with such a configuration, particularly when the ink is used for ink jet recording, the ink jet discharge property is stabilized, and the fluctuation of the ink discharge amount from the ink jet head can be suppressed as much as possible. It turned out to be.
[0032]
[Copolymer]
Examples of the hydrophobic monomer constituting the copolymer include the following monomers, but the present invention is not limited thereto. For example, styrene, vinylnaphthalene, alkyl methacrylates such as methyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethoxyethyl methacrylate, methacrylonitrile, ethyl methacrylate, 2-trimethylsiloxyethyl methacrylate, glycidyl methacrylate, p-tolyl methacrylate, Examples include acrylate alkyl esters such as sorbyl methacrylate and methyl acrylate, phenyl acrylate, benzyl acrylate, acrylonitrile, 2-trimethylsiloxyethyl acrylate, glycidyl acrylate, p-tolyl acrylate, and sorbyl acrylate.
[0033]
As the ionic monomer constituting the copolymer, an anionic monomer or a cationic monomer as described below can be used. Examples of the anionic monomer include acrylic acid, methacrylic acid, and maleic acid, but the present invention is not limited to these.
[0034]
Examples of the cationic monomer include, for example, allylamine, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, tert-butylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminopropyl methacrylamide, N-vinylcarbazole, methacrylamide, Examples include acrylamide and dimethylacrylamide, but the present invention is not limited to these.
[0035]
Further, the nonionic monomer having a hydroxyl group used in the aqueous ink of the first embodiment according to the present invention includes, for example, carbon number of acrylic acid such as 2-hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate. Examples include 2 to 8 hydroxyalkyl esters, N-methylolacrylamide, allyl alcohol, and the like, but the invention is not limited thereto. These may be used alone or in combination of two or more.
[0036]
Further, the nonionic monomer containing an alkylene oxide group used in the aqueous ink of the second embodiment according to the present invention includes, for example, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, polyethylene propylene glycol ( Examples include (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, and propoxypolypropylene (meth) acrylate, but the present invention is not limited to these. These may be used alone or in combination of two or more.
[0037]
Among the above-mentioned alkylene oxide groups, ethylene oxide, propylene oxide and the like are preferably used. Further, it is preferable to use one having a mole number of the alkylene oxide group contained in the unit monomer of 1 to 50.
[0038]
In addition, it is possible to use a copolymer in which the proportion of each of the nonionic monomer units in the copolymer according to the present invention occupies 3 to 50% by mole ratio. It is preferable in obtaining.
[0039]
Incidentally, the copolymer composed of the above-mentioned materials includes a block copolymer, a random copolymer, a graft copolymer, a salt thereof, and the like.
[0040]
In the case of an anionic copolymer using an anionic monomer as the ionic monomer, the acid value is preferably in the range of 100 to 500, and the variation of the acid value is kept within 10% of the average acid value. Is preferred. The salt includes, for example, alkali metal salts such as sodium, lithium, and potassium, as well as ammonium salts, alkylamine salts, and alkanolamine salts. These can be used alone or in appropriate combination of several kinds.
[0041]
The anionic copolymer preferably has a weight average molecular weight in the range of 1,000 to 20,000, and more preferably 3,000 to 20,000. Further, the polydispersity Mw / Mn (weight average molecular weight Mw, number average molecular weight Mn) of the copolymer is preferably 2 or less. Further, the content of the anionic copolymer is such that the ratio of the organic group to the total mass of the modified pigment is 5 to 40% by mass, more preferably 10 to 25% by mass. Those are preferred.
[0042]
By using an acid value within the above range, the hydrophilicity of the pigment surface is too high, water and solvent in the ink after printing remains on the pigment surface, after printing on the recording medium, the ink Can be effectively suppressed from delaying the expression of marker resistance. 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.
[0043]
In the case of a cationic copolymer using a cationic monomer as the ionic monomer, it is preferable that the amine value is in the range of 100 to 500, and the variation of the amine value is 10% of the average amine value. It is preferable to keep within. The amine value is a value expressed in mg of KOH equivalent to hydrochloric acid required to neutralize 1 g of a sample. The salt includes acetic acid, hydrochloric acid, nitric acid and the like, and these can be used alone or in appropriate combination of several kinds.
[0044]
The above-mentioned cationic copolymer preferably has a weight average molecular weight in the range of 1,000 to 20,000, and more preferably has a weight average molecular weight in the range of 3,000 to 20,000. preferable. Further, the polydispersity Mw / Mn (weight average molecular weight Mw, number average molecular weight Mn) of the copolymer is preferably 2 or less. The content of the cationic copolymer is such that the ratio of the organic group to the total mass of the modified pigment is 5 to 40% by mass, and more preferably 10 to 25% by mass. Those are preferred.
[0045]
By controlling the content of the anionic or cationic copolymer in the modified pigment within the above range, it is possible to achieve both high suppression of ink viscosity and dispersion stability at a high level. it can. 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.
[0046]
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 the pigment particles or a functional group is introduced into the surface of the pigment particles. And any method can be used as long as it is a method of chemically bonding the copolymer to the surface of the pigment particles, and is not particularly limited. As such a method, for example, the following method can be used.
[0047]
A method in which polyethyleneimine or the like is introduced on the surface of pigment particles such as carbon black, and a copolymer having an amino group is bonded to the terminal functional group by a diazonium reaction. A method such as a method of bonding a copolymer having an amino group and a carboxyl group by a diazonium reaction can be used. As another example, the most typical example is disclosed in WO 01/51566 A1.
[0048]
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, an ionic monomer having a carboxyl group, and a specific nonionic monomer.
[0049]
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.
[0050]
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, a cationic monomer, and a specific nonionic monomer.
[0051]
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.
[0052]
[Aqueous medium]
When a pigment obtained by chemically bonding an organic group containing a copolymer obtained as described above to the pigment surface is used as a coloring material of an ink, an aqueous medium that is a dispersion medium of the pigment is described below. Will be described. Examples of the aqueous medium that can be used in the present invention include, for example, 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.
[0053]
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. As the water, it is desirable to use deionized water.
[0054]
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.
[0055]
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.
[0056]
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.
[0057]

(However, in the structural formula (1), R represents an alkyl group, and n represents an integer.)
[0058]

(However, in the structural formula (2), R represents an alkyl group, and n represents an integer.)
[0059]

(However, in the structural formula (3), R represents a hydrogen atom or an alkyl group, and m and n each represent an integer.)
[0060]

(In the above structural formula (4), m and n each represent an integer.)
[0061]
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.
[0062]
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.
[0063]
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
[0064]
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.
[0065]
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 a recorded image, and more preferably 0.2 (ml / m2).²/ Msec^1/2) More than 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%.
[0066]
[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.
[0067]
The method for measuring the amount of the organic group bonded to the surface of the carbon black particles and the like are 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, more detailed, a method of fractionating the surface-modified carbon black from the ink, after fractionation, performed by using a dried product obtained by drying as a measurement sample, the surface-modified 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.
[0068]
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.
[0069]
(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.
[0070]
(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.
[0071]
(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.
[0072]
(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.
[0073]
(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.
[0074]
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.
[0075]
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.
[0076]
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.
[0077]
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 the 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
[0078]
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.
[0079]
Furthermore, if the thermogravimetric analysis method for measuring the weight loss rate described above is used, in the pigment such as the surface-modified carbon black contained in the aqueous pigment ink of the present invention, the bonding state between the substance used for the surface modification and the pigment particles You can know. 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.
[0080]
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.
[0081]
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. An example of a specific device that can be used for such an analysis is shown below.
[0082]
-TG-DTA: Thermo Plus TG8120 (manufactured by RIKEN ELECTRIC)
・ GC: HP6890 (Hewlett-Packard)
・ MS: JMS-AM II (manufactured by JEOL)
・ TOF-MS: Shimadzu MALDI-TOFMS @ AXIMA-CFR (manufactured by Shimadzu Corporation)
・ TOF-SIMS: PHI TRFT II (manufactured by ULVAC-PHI)
[0083]
As described above, the aqueous pigment ink of the present invention having the above-described configuration is particularly effective when used for ink jet recording. Ink jet recording methods include 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. Particularly, the aqueous pigment ink of the present invention is particularly suitable. Hereinafter, these will be described.
[0084]
[Recording method, recording unit, cartridge and recording apparatus]
Next, an example of the ink jet recording apparatus according to the present invention, which can be suitably used for performing recording using the above-described aqueous ink according to the present invention, will be described below. First, an example of a head configuration which is a main part of an ink jet recording apparatus using thermal energy is shown in FIGS. FIG. 1 is a cross-sectional view of the head 13 along the ink flow path, and FIG. 2 is a cross-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.
[0085]
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 ejected through the nozzle 14 of the head, becomes an ink droplet 24 from the ejection orifice 22, and flies toward the recording material 25. FIG. 3 shows an external view of an example of a multi-head in which many heads shown in FIG. 1 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 in FIG.
[0086]
FIG. 4 shows an example of an ink jet recording apparatus incorporating this head. In FIG. 4, reference numeral 61 denotes a blade as a wiping member, one end of which is held and fixed by a blade holding member, and forms a cantilever. The blade 61 is disposed at a position adjacent to a recording area of the recording head 65, and in this embodiment, is held in a form protruding into the movement path of the recording head 65.
[0087]
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.
[0088]
Reference numeral 65 denotes a recording head which has ejection energy generating means and performs recording by discharging ink on a recording material opposed to a discharge port surface provided with discharge ports, and 66 denotes a recording head 65 on which the recording head 65 is mounted. This is a carriage for performing movement. 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.
[0089]
Reference numeral 51 denotes a paper feed unit for inserting a recording material, and 52 denotes a paper feed roller driven by a motor (not shown). With such a configuration, the recording material is fed to a position facing the ejection opening 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.
[0090]
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.
[0091]
FIG. 5 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.
[0092]
The ink jet recording device 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. 6, 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. 4, and is detachable from the carriage 66.
[0093]
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. 7 shows an example of a configuration of a recording head which is a main part of the recording apparatus.
[0094]
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.
[0095]
In FIG. 7, an ink channel 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.
[0096]
【Example】
Next, the present invention will be described more specifically with reference to examples and comparative examples. However, 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.
[0097]
[Preparation of Pigment Dispersion 1-1]
Specific surface area 220m²/ G of DBP oil absorption at 500 g / g, 500 g of carbon black, 45 g of aminophenyl (2-sulfoethyl) sulfone (APSES), and 900 g of distilled water were charged into a reactor, kept at 55 ° C., and stirred at 300 rpm for 20 minutes. did. Thereafter, 40 g of sodium nitrite having a concentration of 25% was added dropwise for 15 minutes, and 50 g of distilled water was further added. Thereafter, the reaction was carried out for 2 hours while keeping the temperature at 60 ° C. Then, the obtained reaction product was taken out while diluting with distilled water, and adjusted to a concentration at which the solid content became 15%. After that, a centrifugation treatment and a purification treatment for removing impurities were performed. The dispersion thus prepared was a dispersion in which the above-mentioned (APSES) functional group was bonded to carbon black. This dispersion is designated as A1.
[0098]
The following operation was performed to determine the number of moles of the functional group bonded to 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. Next, the previously prepared dispersion A1 having a solid content of 15% 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, the mixture was stirred for 18 to 48 hours, and thereafter, a purification treatment for removing impurities was carried out, and finally, a dispersion having a solid content of 10% to which pentaethylenehexamine (PEHA) was bound was obtained. This dispersion is designated as B1.
[0099]
Next, 500 g of the previously prepared dispersion B1 having a solid content of 10% was dropped into a resin aqueous solution in which a styrene-acrylic acid-hydroxyethyl acrylate (monomer ratio: 15%) copolymer resin was dissolved while stirring. The resin aqueous solution used here weighed 190 g of a styrene-acrylic acid-hydroxyethyl acrylate copolymer resin having a weight average molecular weight of 15,000, an acid value of 160, and a polydispersity Mw / Mn of 1.6, This was prepared by adding 1,800 g of distilled water, adding NaOH necessary for neutralizing the resin, and stirring to dissolve. Next, the dropped mixture is transferred to a Pyrex (registered trademark) evaporating dish, heated at 150 ° C. for 15 hours, evaporated, and the evaporated and dried product is cooled to room temperature. Next, the evaporatively dried product is dispersed in NaOH-added distilled water adjusted to pH = 9.0 using a disperser. The pH is adjusted to 10-11 by further adding 1.0 M NaOH with stirring. Thereafter, desalting, purification for removing impurities, and coarse particle removal were performed to obtain a pigment dispersion liquid 1-1. Regarding the physical properties of the obtained pigment dispersion liquid 1-1, the solid content was 10.5%, the pH was 9.0, and the average particle diameter was 100 nm.
[0100]
[Preparation of Pigment Dispersion Liquid 1-2]
Instead of the styrene-acrylic acid-hydroxyethyl acrylate copolymer resin used in preparing the pigment dispersion liquid 1-1, the weight average molecular weight was 10,000, the acid value was 300, and the polydispersity Mw / Mn was 1. Pigment dispersion liquid 1-2 was obtained in the same manner as in the preparation of the pigment dispersion liquid 1-1, except that the styrene-acrylic acid-hydroxypropyl methacrylate (molar ratio 5%) copolymer resin of No. 7 was used. Was. Regarding the physical properties of the obtained pigment dispersion 1-2, the solid content was 10.1%, the pH was 9.0, and the average particle diameter was 130 nm.
[0101]
[Preparation of pigment dispersion liquid 1-3]
Dispersion A1 was prepared in the same manner as in the preparation of Pigment Dispersion 1-1. Then, instead of pentaethylenehexamine (PEHA) used in the preparation of the pigment dispersion 1-1, a styrene resin having an amine value of 200, a molecular weight of 13,000 and a polydispersity Mw / Mn of 1.8 was used. Except for using N, N, -dimethylaminoethyl methacrylate-hydroxybutyl methacrylate (molar ratio 20%) copolymer resin (St-DM-HBMA), the same treatment as in the preparation of the pigment dispersion liquid 1-1 was performed. This was performed to finally obtain a pigment dispersion liquid 1-3 in which St-DM-HBMA was bonded to the surface of the carbon black particles. Regarding the physical properties of the obtained pigment dispersion liquid 1-3, the solid content was 10.2%, the pH was 4.5, and the average particle diameter was 125 nm.
[0102]
<Examples 1-1 to 1-3>
After mixing the components shown in Table 1, including the pigment dispersions 1-1 to 1-3 obtained above, and dissolving or dispersing them with sufficient stirring, a microfilter having a pore size of 3.0 μm (manufactured by Fuji Film) , To prepare inks of Examples 1-1 to 1-3. Table 1 shows the composition of each ink.
[0103]
Table 1 also shows the measured values of the Ka values obtained by the Bristow method obtained by the method described above for each of the inks of Examples 1-1 to 1-3. Further, for each of the inks of Examples 1-1 to 1-3 obtained by thermogravimetric analysis measured by the method described below, the ratio (%) of the organic group chemically bonded in the surface-modified pigment. Was calculated using two significant figures, and is also shown in Table 1.
[0104]

[0105]
Hereinafter, a specific method for measuring the ratio of the organic group in the surface-modified pigment shown in Table 1 will be described. First, salting out or coagulation for each of the inks of Examples 1-1 to 1-3, specifically, when the organic group has an anionic group, an acid such as hydrochloric acid or sulfuric acid is added, When the organic group had a cationic group, the pigment and the organic group in the ink were precipitated by salting out by adding an alkali such as sodium hydroxide. Further, in some cases, it is possible to precipitate the pigment in the ink by performing coagulation by adding an excessive amount of alcohol.
[0106]
As a method for precipitating the pigment in the ink, the pigment in the ink can be effectively taken out by combining salting out or coagulation, or by performing centrifugation. 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 dried product consisting of only the surface-modified carbon black was obtained in which the segment containing the copolymer as a free polymer was removed as a result of washing the copolymer with a good solvent.
[0107]
Next, thermogravimetric analysis (Thermogravimetric Analysis) was performed using the dried matter obtained before and after washing with THF as a measurement sample, and the weight loss rate of thermogravimetric analysis was measured. Then, from the value of the weight loss rate obtained at that time, the amount of organic groups chemically bonded to carbon black as the pigment was determined. In the thermogravimetric analysis, a TGA851e / SDTA TGA thermogravimetric device manufactured by METTLER TOLEDO was used. The temperature was raised from room temperature to 700 ° C., and thermogravimetric analysis was performed.
[0108]
The thermogravimetric analysis weight loss obtained by thermal analysis of the dried solid sample not subjected to THF washing after coagulation prepared by the above method is chemically bonded to the surface-modified pigment in the ink. The ratio of the total amount of the organic group and the segment containing the polymer portion as a free polymer to the surface-modified pigment is shown. In addition, the thermogravimetric analysis weight loss rate in the thermogravimetric analysis of the dried product sample obtained after washing the dried product sample with THF is obtained by removing the segment as a free polymer by THF which is a good solvent of the reactant. And shows the ratio of organic groups chemically bonded to the surface-modified pigment.
[0109]
In the thermogravimetric analysis measurement data of the inks of Examples 1-1 to 1-3, a remarkable weight loss was observed at around 350 ° C. in each case. This means that the copolymer was not lost when the dried product was washed with a good solvent for the copolymer when preparing the sample for thermogravimetric analysis. That is, it is shown that the pigment in the inks of Examples 1-1 to 1-3 is in a state in which an organic substance is chemically bonded to the surface of the pigment particles due to the surface modification. Further, from the thermogravimetric analysis weight loss rate for each sample described above, the mass ratio of 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 required. This value is shown in Table 1.
[0110]

[0111]
[Preparation of Pigment Dispersion 2-1]
Specific surface area 220m²/ G of DBP oil absorption at 500 g / g, 500 g of carbon black, 45 g of aminophenyl (2-sulfoethyl) sulfone (APSES), and 900 g of distilled water were charged into a reactor, kept at 55 ° C., and stirred at 300 rpm for 20 minutes. did. Thereafter, 40 g of sodium nitrite having a concentration of 25% was added dropwise for 15 minutes, and 50 g of distilled water was further added. Thereafter, the reaction was carried out for 2 hours while keeping the temperature at 60 ° C. Then, the obtained reaction product was taken out while diluting with distilled water, and adjusted to a concentration at which the solid content became 15%. Thereafter, a centrifugal separation treatment and a purification treatment for removing impurities were performed. The dispersion thus prepared was a dispersion in which the above-mentioned (APSES) functional group was bonded to carbon black. This dispersion is designated as A1.
[0112]
The following operation was performed to determine the number of moles of the functional group bonded to 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. Next, the previously prepared dispersion A1 having a solid content of 15% 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, the mixture was stirred for 18 to 48 hours, and thereafter, a purification treatment for removing impurities was carried out, and finally, a dispersion having a solid content of 10% to which pentaethylenehexamine (PEHA) was bound was obtained. This dispersion is designated as B1.
[0113]
Next, an aqueous solution in which 500 g of the previously prepared dispersion B1 having a solid content of 10% and a copolymer resin of styrene-acrylic acid-methoxypolyethylene glycol monoacrylate (addition product of 23 mol of ethylene oxide and a monomer ratio of 10%) was dissolved. While stirring. The aqueous resin solution used here was a styrene-acrylic acid-methoxypolyethylene glycol monoacrylate (23 mol ethylene oxide adduct, weight average molecular weight = 15,000, acid value = 140, polydispersity Mw / Mn = 1.5). And a monomer ratio of 10%) was prepared by weighing 190 g of the copolymer resin, adding 1,800 g of distilled water, adding NaOH necessary for neutralizing the resin, and stirring to dissolve. is there. Next, the dropped mixture is transferred to a Pyrex (registered trademark) evaporating dish, heated at 150 ° C. for 15 hours, evaporated, and the evaporated and dried product is cooled to room temperature. Next, the evaporatively dried product is dispersed in NaOH-added distilled water adjusted to pH = 9.0 using a disperser. With further stirring, the pH is adjusted to 10-11 by adding 1.0 M NaOH. Thereafter, desalting, purification for removing impurities and removal of coarse particles were performed to obtain a pigment dispersion liquid 2-1. Regarding the physical properties of the obtained pigment dispersion liquid 2-1, the solid content was 10%, the pH was 9.6, and the average particle diameter was 115 nm.
[0114]
[Pigment dispersion liquid 2-2]
Instead of the styrene-acrylic acid-methoxypolyethylene glycol monoacrylate (ethylene oxide 23 mol adduct and monomer ratio 10%) copolymer resin used in the preparation of the pigment dispersion liquid 2-1, the weight average molecular weight is 10,000. Pigment dispersion except that a styrene-acrylic acid-phenoxy polyethylene glycol monoacrylate (ethylene oxide 6 mol adduct, monomer ratio 5%) copolymer resin having an acid value of 380 and a polydispersity Mw / Mn of 1.6 was used. The same operation as in the preparation of the liquid 2-1 was performed to obtain a pigment dispersion 2-2. Regarding the physical properties of the obtained pigment dispersion liquid 2-2, the solid content was 10.3%, the pH was 9.9, and the average particle diameter was 130 nm.
[0115]
[Pigment dispersion liquid 2-3]
A dispersion A1 was prepared in the same manner as in the case of preparing the pigment dispersion 2-1. Then, instead of pentaethylenehexamine (PEHA) used in the preparation of the pigment dispersion liquid 2-1, a styrene resin having an amine value of 200, a molecular weight of 10,000 and a polydispersity Mw / Mn of 1.8 was used. Except for using N, N, -dimethylaminoethyl methacrylate-methoxypolyethylene glycol monoacrylate resin (St-DM-MPEA), the same treatment as in the preparation of the pigment dispersion liquid 2-1 was performed. Pigment dispersion liquid 2-3 in which St-DM-MPEA was bonded to the surface of carbon black particles was obtained. Regarding the physical properties of the obtained pigment dispersion liquid 2-3, the solid content was 10%, the pH was 5.0, and the average particle diameter was 125 nm.
[0116]
<Examples 2-1 to 2-3>
After mixing the components shown in Table 2 including the pigment dispersions 2-1 to 2-3 obtained above and dissolving or dispersing them with sufficient stirring, a microfilter having a pore size of 3.0 μm (manufactured by Fuji Film) To obtain inks of Examples 2-1 to 2-3. Table 2 shows the composition of each ink.
[0117]
Table 2 also shows the measured values of the Ka values obtained by the Bristow method obtained by the method described above for each of the inks of Examples 2-1 to 2-3. Furthermore, in each of the inks of Examples 2-1 to 2-3 obtained by the same thermogravimetric analysis as performed in the case of the above Examples 1-1 to 1-3, the surface-modified pigment was used. The ratio (%) of the organic group chemically bonded was determined using two significant figures, and is shown in Table 2.
[0118]

[0119]
<Comparative Example 1>
Specific surface area 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 180 and a weight average molecular weight of 10,000, 1 part of monoethanolamine, 15 parts of diethylene glycol, and 10 parts of glycerin And 65 parts of pure water, and the mixture was dispersed for 1 hour using a sand grinder. Then, coarse particles were removed by centrifugation, and the mixture was filtered under pressure with a micro filter (manufactured by Fuji Film) having a pore size of 3.0 μm. Thus, an ink of Comparative Example 1 was obtained. Regarding the physical properties of the obtained pigment dispersion, the solid content was 10%, the pH was 9.0, and the average particle size was 140 nm.
[0120]
After mixing and dissolving or dispersing the components described below sufficiently with stirring, the mixture was subjected to pressure filtration with a micro filter (manufactured by Fuji Film) having a pore size of 3.0 μm to prepare the ink of Comparative Example 1.
・ Pigment dispersion: 50 parts
・ Glycerin 7 parts
・ Diethylene glycol 3 parts
・ Pure water 40 parts
[0121]
For the ink of Comparative Example 1 obtained above, the Ka value determined by the Bristow method, which was measured in the same manner as in the example, was 0.7. The thermogravimetric analysis weight loss rate (%) obtained by thermogravimetric analysis, which was measured in the same manner as in the example, was 2.0%.
[0122]
(Evaluation)
For each of the inks of Examples 1-1 to 1-3, 2-1 to 2-3, and Comparative Example 1 obtained above, the ink is ejected by applying thermal energy to the ink in accordance with the recording signal. An image output test was performed using a modified machine of an inkjet recording apparatus BJF-660 (manufactured by Canon) having an on-demand type multi-recording head, and the following evaluation was performed. Table 3 shows the evaluation results.
[0123]
1. Printing persistence
Using each ink and the above-described ink jet recording apparatus, first, solid printing in which a nozzle check pattern was first included was continuously printed on three A4 sheets. After that, no printing was performed for 2 hours, and then a solid printing was continuously repeated 50 times on three A4 sheets 50 times. The disturbance of printing and the presence or absence of non-ejection at that time were evaluated according to the following criteria.
：: Disturbed printing and non-discharge were not observed.
Δ: Disturbance of printing is slightly observed, but no ejection is not observed.
X: Disturbance of printing and non-ejection are observed.
[0124]
2. Character quality
The following five types of plain paper for copying A, B, C, D, and E are used to perform character printing using each ink and the above-described ink jet recording apparatus, and the bleeding of characters generated at that time is evaluated based on the following criteria. did.
：: Almost no bleeding on all five papers.
Δ: Some bleeding paper is observed.
×: Bleed on all five papers.
[0125]
The following copy paper was used.
A: PSK paper NSK manufactured by Canon Inc.
B: NDK PPC paper NDK
C: PPC paper 4024, manufactured by Xerox Corporation
D: Fox River Co., Ltd. PPC Paper Proper Bond
E: PPC paper for Canon manufactured by Neujidora Co., Ltd.
[0126]
3. Marker resistance
Using each of the inks and the above-described ink jet recording apparatus, printing was performed on the five types of plain paper for copying A, B, C, D and E previously used and left for one day, and then a commercially available aqueous fluorescent marker pen (for example, And a zebra highlighter, OPTEX (OP-100-Y), and marking was performed on the printed portion.
：: Dirt is not noticeable on all papers.
Δ: Soil is noticeable on some papers.
X: Stain is conspicuous on all papers.
[0127]
4. Discharge volume stability
The ejection amount was measured using each ink and the above-described ink jet recording apparatus. The number of print dots was determined by printing a known pattern on five sheets, dividing the amount of decrease in ink amount by the number of print dots, and determining the average discharge amount. First, solid printing including the nozzle check pattern at the beginning was continuously performed on 10 sheets of A4 paper. Thereafter, printing was not performed for 2 hours, and thereafter, the discharge amount was measured by the above-described method. Next, three solid printings were continuously performed again, and thereafter, the ejection amount was measured. This cycle was repeated 10 times, and the change in the discharge amount was observed. Using the obtained discharge amount, the stability of the discharge amount was determined based on the following criteria.
：: The variation of the ejection amount was within the range of ± 10%.
Δ: The variation in the ejection amount was within the range of ± 15%.
X: The variation of the discharge amount exceeded ± 20%.
[0128]

[0129]
【The invention's effect】
As described above, according to the present invention, as a pigment of an aqueous ink, by using a modified pigment in which an organic group is chemically bonded to the surface of a pigment particle, the pigment is particularly used as an inkjet ink. In this case, the ejection bend and non-discharge are eliminated, especially the ejection property is stable, the variation in the ejection amount of the ink is small, and the ink has high reliability with respect to the recording head. A water-based ink having improved print stain rub resistance and print stain marker resistance using a water-based marker after printing, an inkjet recording method using such an ink, an ink cartridge, a recording unit, and an inkjet recording apparatus are provided.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an ink jet recording apparatus head.
FIG. 2 is a vertical and horizontal view of an ink jet recording apparatus head.
FIG. 3 is an external perspective view of a head obtained by multiplying the head shown in FIG. 1;
FIG. 4 is a perspective view illustrating an example of an ink jet recording apparatus.
FIG. 5 is a vertical sectional view of the ink cartridge.
FIG. 6 is a perspective view illustrating an example of a recording unit.
FIG. 7 is a diagram illustrating an example of a configuration of a recording head.
[Explanation of symbols]
13: Head
14: Ink nozzle
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 material
26: Multi nozzle
27: glass plate
28: Heating head
40: Ink bag
42: stopper
44: Ink absorber
45: Ink cartridge
51: Paper feed unit
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 (20)

An aqueous ink comprising a modified pigment in which an organic group is chemically bonded to the surface of the pigment particles, and an aqueous medium as a dispersion medium for the pigment,
The organic group includes a functional group chemically bonded directly or via another atomic group to the pigment surface, a ionic monomer, a hydrophobic monomer, and a nonionic monomer containing at least one hydroxyl group. A water-based ink comprising a reaction product of a coalescence with a coalescence. An aqueous ink comprising a modified pigment in which an organic group is chemically bonded to the surface of the pigment particles, and an aqueous medium as a dispersion medium for the pigment,
The organic group comprises a functional group chemically bonded directly or via another atomic group to the pigment surface, an ionic monomer, a hydrophobic monomer, and a nonionic monomer containing at least one alkylene oxide group. An aqueous ink comprising a reaction product of a copolymer and a copolymer. 3. The aqueous ink according to claim 1, wherein the other atomic group is a phenyl (2-sulfoethyl) group. The aqueous ink according to any one of claims 1 to 3, wherein the polydispersity Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) of the copolymer is 2 or less. The aqueous ink according to any one of claims 1 to 4, wherein the proportion of the nonionic monomer unit in the copolymer is 3 to 50% by molar ratio. The aqueous ink according to any one of claims 1 to 5, wherein the pigment is carbon black. The aqueous ink according to any one of claims 1 to 6, wherein the copolymer has Mw of 1,000 to 20,000 and an acid value or an amine value of 100 to 500. Ka value of the ink determined by the Bristow method ^{is, 1.5 (ml / m 2 /} msec 1/2) than an aqueous ink according to any one of claims 1 to 7. Ka ^{value, 0.2 (ml / m 2 /} msec 1/2) or more in an aqueous ink according to claim 8. The aqueous ink according to any one of claims 1 to 9, wherein a ratio of an organic group in the modified pigment to a total mass of the modified pigment is 5 to 40% by mass. The aqueous ink according to claim 10, wherein a ratio of an organic group in the modified pigment to a total mass of the modified pigment is 10 to 25% by mass. The aqueous ink according to any one of claims 1 to 11, wherein a ratio of the modified pigment to the total mass of the aqueous ink is 0.1 to 15% by mass. The aqueous ink according to claim 12, wherein a ratio of the modified pigment to the total mass of the aqueous ink is 1 to 10% by mass. The aqueous ink according to any one of claims 1 to 13, wherein the aqueous ink is an aqueous ink for inkjet. An inkjet recording method, comprising: discharging the aqueous ink according to claim 14 by an inkjet method. 16. The ink jet recording method according to claim 15, wherein the ink jet method is a method in which thermal energy is applied to the ink to discharge droplets by foaming of the ink. The inkjet recording method according to claim 15, wherein the inkjet method includes a step of applying mechanical energy to the ink to eject the ink. An ink cartridge, comprising: an ink storage unit that stores the aqueous ink according to claim 1. A recording unit comprising: an ink storage unit that stores the aqueous ink according to claim 14; and an inkjet head that discharges the ink. An ink jet recording apparatus, comprising: an ink container that stores the aqueous ink according to claim 14; and an ink jet head for discharging the ink.

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