JP4863418B2 - Ink jet recording ink, color ink set, and image forming method - Google Patents

Description

Ｚ ：窒素又はリン
Ｒ_１〜Ｒ_４ ：水素、炭素数１〜４のアルキル基、ヒドロキシル基又は
ハロゲン化アルキル基
【００１９】
［３］含有される湿潤剤が、グリセロール及びジエチレングリコールの混合物であって、かつインク全量の１０〜３０重量％含有されることを特徴とする前記［１］又は［２］に記載のインクジェット記録用インク。
【００２２】
［８］前記［１］〜［３］のいずれかに記載のインクジェット記録用インクを搭載したインクジェット記録装置。
【００２３】
［９］前記［１］〜［３］のいずれかに記載のインクジェット記録用インクを用いた画像の形成方法において、ステキヒトサイズ度が３秒以上の紙に、複数のインク吐出口を有するヘッドを用いて印字する際、複数回のスキャンで全てのインク吐出口に対応する印字ドットを印字することを特徴とするカラー画像の形成方法。
【００２４】
以下具体例を挙げて、本発明の詳細な説明を行う。
本発明は、水、水に溶解する着色剤、浸透剤、湿潤剤、界面活性剤を含むインクジェット記録用インクにおいて、浸透剤として不純物量がある特定の範囲内にあるＥＨＤを使用することにより、高速印字時も画像濃度が高く滲みの少ない高品位な画像を得ることができることを見いだしたものである。また不純物量を抑えることにより、より長期放置後の信頼性も向上し、また臭気の問題も改善されることとなった。
【００２５】
このような不純物の少ないＥＨＤは原材料であるアルデヒドの段階から純度の高いものを使用することで製造されるが、このようにして製造されたＥＨＤとしては、例えば具体的には協和発酵社製の「オクタンジオール」として入手することができる。
【００２６】
本発明では、浸透剤として不純物量がある特定範囲内にあるＥＨＤを添加することで、インクの浸透性を上げると同時に着色剤を表面にとどめることで、境界滲みがなく、画像濃度が高くかつ裏写りの少ない印字画像を得ることが可能となった。ＥＨＤの添加量としてはインク全量の０．１〜４重量％が好ましく、更に好ましくは０．５〜３重量％である。０．１重量％未満では効果が少なく、４重量％を越えるとではこれ自体の溶解性が低いために、信頼性が悪くなる。
【００２７】
また本発明では、ＥＨＤ以外にも、特性に影響を及ぼさない範囲内で、以下に示すような浸透剤を併用しても良い。併用できる浸透剤としては、グリコールエーテル類が望ましく、中でもジエチレングリコールモノブチルエーテル、トリエチレングリコールモノブチルエーテル、プロピレングリコールモノブチルエーテル、及びジプロピレングリコールモノブチルエーテル等が好ましい。
【００２８】
また本発明で使用される界面活性剤としては、下記一般式（１）で表される界面活性剤を使用することで、乾燥性が速く、かつ境界滲み、文字滲みのない鮮明なカラー画像の提供が可能となった。
ＲＯ（ＣＨ₂ＣＨ₂Ｏ）_nＣＨ₂ＣＯＯＭ （１）
Ｒ：炭素数１３又は１４の直鎖あるいは分岐したアルキル基
ｎ：３〜１２の整数
Ｍ：アルカリ金属、第４級アンモニウム、第４級ホスホニウム又は
アルカノールアミン
【００２９】
市販の界面活性剤で本化合物を主成分として含有するものとしては、日光ケミカルズ（株）より入手可能なＥＣＴＤ−３ＮＥＸ（一般式（１）において、Ｒ：トリデシル基、ｎ：３、Ｍ：Ｎａ）、ＥＣＴＤ−６ＮＥＸ（一般式（１）において、Ｒ：トリデシル、ｍ：６、Ｍ：Ｎａ）等の界面活性剤が挙げられる。
【００３０】
本発明では、上記界面活性剤の他に、インク特性に影響を及ぼさない範囲内で、下記に示すような界面活性剤を併用してもよい。併用できる界面活性剤としては、ポリオキシエチレンアルキルエーテル、ポリオキシエチレンアルキルフェニルエーテル、ポリオキシエチレングリコールエステル、あるいはアセチレン系界面活性剤やシリコン系界面活性剤等のノニオン系界面活性剤や、ポリオキシエチレンアルキルエーテル酢酸塩、ジアルキルスルホコハク酸塩等のアニオン系界面活性剤が挙げられる。
【００３１】
具体的には、ノニオン系界面活性剤としては、ＢＴシリーズ（日光ケミカルズ）ノニポールシリーズ（三洋化成）、サーフィノールシリーズ（エアープロダクツ）シリコーン（東レダウコーニング等）として、入手できる。またアニオン系界面活性剤としては、具体的にはニッコールＥＣＴシリーズ（商品名、日本サーファクタント工業化学社製）等として、入手できる。
【００３２】
これらの界面活性剤はインクの表面張力を下げ、インクの紙への浸透性を上げることによって、印字画像の乾燥性を速めるために添加されるものであり、その添加量は、インクの表面張力が、通常、５０ｍＮ／ｍ以下、好ましくは４０ｍＮ／ｍ以下になるように調整され、水性インク組成物全量に対して、０.５〜３重量％が好ましい。前記界面活性剤の添加量は、０．５重量％よりも少ないと、動的表面張力が高いため乾燥性が悪く、逆に３重量％よりも多いと保存時に界面活性剤の析出などが生じる。
【００３３】
また着色剤の対イオン及び界面活性剤の対イオンはナトリウム、リチウム及び／又は下記一般式（２）で示される第４級アンモニウム、第４級ホスホニウム、アルカノールアミンイオンである場合に優れた溶解安定性及び良好な印字画像が得られる。
【００３４】
【化３】

Ｚ ：窒素又はリン
Ｒ_１〜Ｒ_４ ：水素、炭素数１〜４のアルキル基、ヒドロキシル基又は
ハロゲン化アルキル基
【００３５】
対イオンをこのようなアルカリイオンにするには、インク調整時にこれらを水に溶解する際、所望のアルカリイオンを含んだアルカリ水酸化物を添加することにより容易に行える。例えばリチウム塩の場合は水酸化リチウムを添加することにより行える。
【００３６】
また本発明で使用される湿潤剤としては、ジエチレングリコール及びグリセロールの混合物を使用することで、インクの保存安定性及び吐出安定性が、格段に向上することが明らかとなった。
【００３７】
本発明では、上記湿潤剤の他に、特性に影響を及ぼさない範囲内で、下記に示すような湿潤剤を併用してもよい。併用できる湿潤剤としては、エチレングリコール、トリエチレングリコール、ポリエチレングリコール、ポリプロピレングリコール、１，５−ペンタンジオール、１，６−ヘキサンジオール、１，２，６−ヘキサントリオール、１，２，４−ブタントリオール、１，２，３−ブタントリオール、ペトリオール等の多価アルコール類、 エチレングリコールモノエチルエーテル、エチレングリコールモノブチルエーテル、ジエチレングリコールモノメチルエーテル、ジエチレングリコールモノエチルエーテル、ジエチレングリコールモノブチルエーテル、テトラエチレングリコールモノメチルエーテル、プロピレングリコールモノエチルエーテル等の多価アルコールアルキルエーテル類、エチレングリコールモノフェニルエーテル、エチレングリコールモノベンジルエーテル等の多価アルコールアリールエーテル類、２−ピロリドン、Ｎ−メチル−２−ピロリドン、Ｎ−ヒドロキシエチル−２−ピロリドン、１，３−ジメチルイミイダゾリジノン、ε−カプロラクタム等の含窒素複素環化合物などが挙げられるが、本発明はこれらに限定されるものではない。
【００３８】
湿潤剤の含有量としては１０〜３０重量％の範囲で使用されるが、より好ましくは１２〜２０重量％である。湿潤剤量が１０重量％より少ないと、染料の溶解安定性が不十分でノズル部での染料析出が起こりやすく、また湿潤剤量が３０重量％を越えると環境温度変化に伴うインクの増粘が問題となる。
【００３９】
また、特定の着色剤を組み合わせたインクを使用することで、色調が良好で、耐水耐光性、色再現性に優れ、コントラストが高く裏写りの少ない画像が得られ、かつ保存安定性、吐出安定性の高い、全てにバランスのとれたインクセット及びカラー画像の提供が可能となる。
【００４０】
さらに詳細には、水、水に溶解する着色剤、湿潤剤、界面活性剤およびＥＨＤを含む、イエロー、マゼンタ、シアン、ブラックの４色のインクで構成されたインクジェット記録用インクセットにおいて、前記イエローインクが少なくともPro-jet Fast Yellow ２（ゼネカ社製）及びC.I.Direct Yellow １４２を染料として含有し、前記マゼンタインクが少なくともC.I.Acid Red ５２及びＭＪＲ６１１（三菱化学社製）を染料として含有し、前記シアンインクが少なくともPro-jet Fast Cyan ２（ゼネカ社製）を染料として含有し、前記ブラックインクのが少なくともC.I.Direct Black １６８を染料として含有するインクを用いることにより、色調が良好で、耐水耐光性、色再現性に優れ、保存安定性、吐出安定性の高い、全てにバランスのとれたインクセット及びカラー画像の提供が可能となった。
【００４１】
本発明で使用されるインク中に含有される着色剤としては、上記染料以外の染料でも、色調その他の特性に悪影響を及ぼさない範囲であれば、添加しても構わない。併用可能な染料の具体例を以下に示すが、本発明はこれらに限定されるものではない。
【００４２】
酸性染料、食用染料としては
Ｃ．Ｉ．アシッドイエロー １７，２３，４２，４４，７９，１４２
Ｃ．Ｉ．アシッドレッド １，８，１３，１４，１８，２６，２７，３５，
３７，４２，８７，８９，９２，９７，１０６，
１１１，１１４，１１５，１３４，１８６，
２４９，２５４，２８９
Ｃ．Ｉ．アシッドブルー ９，２９，４５，９２，２４９
Ｃ．Ｉ．アシッドブラック １，２，７，２４，２６，９４
Ｃ．Ｉ．フードイエロー ３，４
Ｃ．Ｉ．フードレッド ７，９，１４
Ｃ．Ｉ．フードブラック １，２
【００４３】
直接性染料としては
Ｃ．Ｉ．ダイレクトイエロー １，１２，２４，２６，３３，４４，５０，
８６，１２０，１３２，１４２，１４４
Ｃ．Ｉ．ダイレクトレッド １，４，９，１３，１７，２０，２８，３１，
３９，８０，８１，８３，８９，２２５，
２２７
Ｃ．Ｉ．ダイレクトオレンジ ２６，２９，６２，１０２
Ｃ．Ｉ．ダイレクトブルー １，２，６，１５，２２，２５，７１，７６，
７９，８６，８７，９０，９８，１６３，
１６５，１９９，２０２
Ｃ．Ｉ．ダイレクトブラック １９，２２，３２，３８，５１，５６，７１，
７４，７５，７７，１５４，１７１
等が、挙げられる。
【００４４】
また本発明においては、上記添加剤の他に、防腐防かび剤を添加しても良い。良好な防腐防かび剤としては、１，２−ベンズイソチアゾリン−３−オンが使用でき、これにより保存安定性及び吐出安定性等の信頼性を確保しつつ、防腐防かび効果に優れるインク及びカラー画像が提供できる。防腐防かび剤の添加量としては、０.２〜１.０重量％が好ましい。添加量が０.２重量％より少ないと、防腐防かび効果が不十分となり、また添加量が１.０重量％を越えると、防腐防かび剤自体の析出が問題となる場合がある。１，２−ベンズイソチアゾリン−３−オンを含有する、市販される防腐防かび剤としては、サンアイバックＡＰ（三愛石油社製）や、プロキセルＸＬ（Ｉ．Ｃ．Ｉ．製）などが挙げられる。
【００４５】
本発明のインクは、染料の溶解安定性を保ち、またノズルプレートに使用される金属への影響を考慮し、ｐＨを９〜１１に調整することで、より信頼性の高いインクとして提供できることとなった。
【００４６】
また、本発明においては、その他目的に応じて、浸透剤、金属腐食抑制剤、水溶性紫外線吸収剤、水溶性赤外線吸収剤等を添加することもできる。
【００４７】
本発明のインクセットを、ステキヒトサイズ度が３秒以上の紙に、複数のインク吐出口を有するヘッドを用いて印字する際、複数回のスキャンで全てのインク吐出口に対応する印字ドットを印字することのできるカラー画像の形成方法に用いることにより、より鮮明で高品位なカラー画像を得ることができる。
【００４８】
【発明の実施の形態】
以下に本発明の実施例および比較例を示す。
実施例１
協和発酵社製のＥＨＤ「オクタンジオール」の純度を、ガスクロマトグラフィーにて分析し、不純物量が０．０１重量以上で１重量％未満であることを確認した。
【００４９】
このＥＨＤを使用して、下記の組成でインクを作製したが、インク作製時の臭気は全く気にならなかった。
〈ブラックインクの組成〉
C.I.Direct Black １６８（ゼネカ社製） ４重量％
ＥＨＤ（「オクタンジオール」協和発酵社製） ２重量％
ジエチレングリコール １５重量％
グリセロール ５重量％
ＥＣＴＤ−３ＮＥＸ（日光ケミカルズ） １重量％
プロキセルＸＬ（Ｉ．Ｃ．Ｉ．製） ０.４重量％
イオン交換水 残量
【００５０】
比較例１
市販の特級試薬のＥＨＤの純度を、実施例１同様にガスクロマトグラフィーにて分析し、不純物量が３重量％以上あることを確認した。
【００５１】
このＥＨＤを使用して、下記の組成でインクを作製したが、インク作製時の臭気が気になった。
〈ブラックインクの組成〉
C.I.Direct Black １６８（ゼネカ社製） ４重量％
ＥＨＤ（市販の特級試薬） ２重量％
ジエチレングリコール １５重量％
グリセロール ５重量％
ＥＣＴＤ−３ＮＥＸ（日光ケミカルズ） １重量％
プロキセルＸＬ（Ｉ．Ｃ．Ｉ．製） ０.４重量％
イオン交換水 残量
【００５２】
上記組成で処方した実施例１及び比較例１のインク組成物を、それぞれ室温中で撹拌溶解し、水酸化リチウムにてｐＨを１０．５に調整した後、０．２２μｍのテフロンフィルターにて濾過し、更に３０分程度の脱気を行って各インクを作製した。
【００５３】
次にこれらのインクについて、長期放置後の信頼性評価、及びインク作製時の臭気のありなしを評価した。結果は表１に示す。
【００５４】
評価１：長期放置後の信頼性評価
ノズルプレートがニッケルで形成された積層ＰＺＴを液室流路の加圧に使用した３００dpiのノズルを有するインクジェットプリンターに実施例１インク、及び比較例１インクを充填し、キャップをした状態で室温中に３ヶ月間放置後、ワイピング、吸引等のクリーニング操作を０回及び１回行って印字させ、放置前後の画素径、ドット位置精度の比較を行った。
クリーニング操作０回で、画素径、ドット位置精度ともに問題がない場合を○、クリーニング操作１回で回復する場合に△、それ以外を×とした。
【００５５】
【表１】

【００５６】
比較例２
実施例１インクのＥＨＤの量を２重量％から５重量％に変えた他は、実施例１と同様にしてインクを作製した。
【００５７】
比較例３
実施例１インクのＥＨＤの量を２重量％から０.０５重量％に変えた他は、実施例１と同様にしてインクを作製した。
【００５８】
上記比較例２インク及び比較例３インクについて、下記に示す画像の鮮明性の評価及び上記に示した長期放置後の信頼性評価を行い、実施例１インクと比較した。結果は表２に示す。
【００５９】
評価２：画像鮮明性の評価
試験２−１：画像濃度の評価
各インクにて印字した１００％黒のベタ部を、反射型カラー分光測色濃度計Ｘ−Ｒite９３８（Ｘ−Ｒite社製）を用いてその画像濃度を測定をした。
試験２−２：裏抜けの評価
各インクにて印字した１００％黒のベタ部を、紙の裏側から反射型カラー分光測色濃度計Ｘ−Ｒite９３８（Ｘ−Ｒite社製）を用いてその画像濃度（裏抜け）を測定した。
試験２−３：．滲みの評価
各インクにて、印字したサンプルの滲みを目視によりそれぞれ評価した。印字用紙としては、市販の再生紙、コピー用紙、インクジェット専用紙の３紙に印字し、評価は、３紙とも良好なものを○、それ以外を×とした。
【００６０】
【表２】

【００６１】
実施例２
下記組成にて、インクを作製し、実施例１インクの黒インクと合わせて、実施例２インクセットとした。
〈イエローインクの組成〉
Pro-jet Fast Yellow ２（ゼネカ社製） １.５重量％
C.I.Direct Yellow １４２（ダイワ化成社製） ０.５重量％
ＥＨＤ（「オクタンジオール」協和発酵社製） ２重量％
ジエチレングリコール １５重量％
グリセロール ５重量％
ＥＣＴＤ−３ＮＥＸ（日光ケミカルズ） １重量％
サンアイバックＡＰ（三愛石油社製） ０.４重量％
イオン交換水 残量
【００６２】
〈マゼンタインクの組成〉
C.I.Acid Red ５２（ダイワ化成社製） ０.７重量％
ＭＪＲ６１１（三菱化学社製） １.３重量％
ＥＨＤ（「オクタンジオール」協和発酵社製） １重量％
ジエチレングリコール １５重量％
グリセロール ５重量％
ＥＣＴＤ−３ＮＥＸ（日光ケミカルズ） １重量％
プロキセルＸＬ（Ｉ．Ｃ．Ｉ．製） ０.４重量％
イオン交換水 残量
【００６３】
〈シアンインクの組成〉
Pro-jet Fast Cyan ２（ゼネカ社製） ３重量％
ＥＨＤ（「オクタンジオール」協和発酵社製） １重量％
ジエチレングリコール １５重量％
グリセロール ５重量％
ＥＣＴＤ−３ＮＥＸ（日光ケミカルズ） １重量％
サンアイバックＡＰ（三愛石油社製） ０.４重量％
イオン交換水 残量
【００６４】
上記組成で処方した各インク組成物を、室温中で撹拌溶解し、水酸化リチウムにてｐＨを１０．５に調整した後、０．２２μｍのテフロンフィルターにて濾過し、更に３０分程度の脱気を行ってインクを作製した。
【００６５】
比較例４
下記組成でインクを作製し、比較例４インクセットとした。
〈イエローインクの組成〉
Pro-jet Fast Yellow ２（ゼネカ社製） ２重量％
１，５−ペンタンジオール １０重量％
グリセロール ２重量％
ＥＣＴＤ−３ＮＥＸ（日光ケミカルズ） １重量％
サンアイバックＡＰ（三愛石油社製） ０.４重量％
イオン交換水 残量
【００６６】
〈マゼンタインクの組成〉
C.I.Acid Red ５２（ダイワ化成社製） １.８重量％
１，５−ペンタンジオール １０重量％
ＥＣＴＤ−３ＮＥＸ（日光ケミカルズ） １重量％
サンアイバックＡＰ（三愛石油社製） ０.４重量％
イオン交換水 残量
【００６７】
〈シアンインクの組成〉
Pro-jet Fast Cyan ２（ゼネカ社製） ３重量％
ジエチレングリコール ５重量％
グリセロール ２重量％
ＥＣＴＤ−３ＮＥＸ（日光ケミカルズ） １重量％
サンアイバックＡＰ （三愛石油社製） ０.４重量％
イオン交換水 残量
【００６８】
〈ブラックインクの組成〉
C.I.Direct Black １６８（ゼネカ社製） ４重量％
ジエチレングリコール ２３重量％
グリセロール １０重量％
ＥＣＴＤ−３ＮＥＸ（日光ケミカルズ） １重量％
サンアイバックＡＰ（三愛石油社製） ０.４重量％
イオン交換水 残量
【００６９】
上記組成で処方した各インク組成物を、室温中で撹拌溶解し、水酸化リチウムにてｐＨを１０．５に調整した後、０．２２μｍのテフロンフィルターにて濾過し、更に３０分程度の脱気を行ってインクを作製した。
【００７０】
比較例５
下記組成にて、インクを作製し、比較例５インクセットとした。
〈イエローインクの組成〉
C.I.Acid Yellow ２３ １.５重量％
ＥＨＤ（市販の特級試薬） １重量％
ジエチレングリコール １５重量％
グリセロール ５重量％
ＥＣＴＤ−３ＮＥＸ（日光ケミカルズ） １重量％
サンアイバックＡＰ（三愛石油社製） ０.４重量％
イオン交換水 残量
【００７１】
〈マゼンタインクの組成〉
C.I.Direct Red ２２７ ３重量％
ＥＨＤ（市販の特級試薬） １重量％
ジエチレングリコール １５重量％
グリセロール ５重量％
ＥＣＴＤ−３ＮＥＸ（日光ケミカルズ） １重量％
サンアイバックＡＰ（三愛石油社製） ０.４重量％
イオン交換水 残量
【００７２】
〈シアンインクの組成〉
C.I.Direct Blue １９９ ３重量％
ＥＨＤ（市販の特級試薬） １重量％
ジエチレングリコール １５重量％
グリセロール ５重量％
ＥＣＴＤ−３ＮＥＸ（日光ケミカルズ） １重量％
サンアイバックＡＰ（三愛石油社製） ０.４重量％
イオン交換水 残量
【００７３】
〈ブラックインクの組成〉
C.I.Direct Black １５４ ３重量％
ＥＨＤ（市販の特級試薬） １重量％
ジエチレングリコール １５重量％
グリセロール ５重量％
ＥＣＴＤ−３ＮＥＸ（日光ケミカルズ） １重量％
プロキセルＸＬ（Ｉ．Ｃ．Ｉ．製） ０.４重量％
イオン交換水 残量
【００７４】
上記組成で処方した各インク組成物を、室温中で撹拌溶解し、水酸化リチウムにてｐＨを１０．５に調整した後、０．２２μｍのテフロンフィルターにて濾過し、更に３０分程度の脱気を行ってインクを作製した。
【００７５】
実施例２インクセット、比較例４インクセット、比較例５インクセットについて、長期保存後の信頼性評価、及び下記に示す、耐水性評価、色調、色境界滲みの評価、保存性評価を行った。評価結果は表３に示す。
【００７６】
評価３：印字画像の耐水性評価
各インクにて印字した画像サンプルを３０℃の水に１分間浸漬し、浸漬前後の画像濃度の変化をマクベス濃度計で測定し、下記の式にて耐水性（退色率％）を求め、退色率が３０％未満の場合に○、３０％以上の場合に×とした。
【００７７】
【数１】

【００７８】
評価４：色調、色境界滲みの評価
各インクセットにて、カラー画像の印字を行い、色調、色境界滲みを目視によりそれぞれ評価した。印字用紙としては、市販の再生紙、コピー用紙、インクジェット専用紙の３紙に印字し、評価は、３紙とも良好なものを○、それ以外を×とした。
【００７９】
評価５：保存安定性の評価
各インクをポリエチレン容器に入れ、−２０℃、２０℃、５０℃のそれぞれの条件下で２カ月保存し、保存後の表面張力、粘度、及び沈澱物析出の有無を調べた。どの条件で保存しても、物性等の変化がなく、沈殿がみられないものを○とし、それ以外を×とした。
【００８０】
【表３】

【００８１】
比較例６
実施例２インクセットの各インク組成において、界面活性剤をノニオン系界面活性剤ＢＴ−７（日光ケミカルズ）に変えた他は、同様の組成として、比較例６インクセットを作製した。
【００８２】
このインクについて、評価２を行ったところ印字画像の滲みが×となった。また下記に示す評価６を実施例２インクセット及び比較例６インクセットについて行った。結果は表４に示す。
【００８３】
評価６：印字方法による画像の鮮明性
リコー社製のプリンター ＩＰＳｉＯ ＪＥＴ ３００を用い、１スキャンによる印字画像と２スキャンによる印字画像との境界滲み及び文字の滲みを評価した。印字用紙は、市販の再生紙、コピー用紙、インクジェット専用紙の３紙を用い、目視により総合的に判断した。
【００８４】
【表４】

【００８５】
表４に示す通り、２スキャンで印字を行う方が、２色重ね部での境界滲み及び文字の滲みが、１スキャンでの印字に比べ格段に向上することが、確認された。
【００８６】
比較例７
実施例２インクセットにおいて、ｐＨ調整を行わないで、比較例７インクセットとした。
【００８７】
次に実施例２インクセット及び比較例７インクセットに対し、評価１及び下記に示す評価７を行った。結果は表５に示す。
【００８８】
評価７：金属腐食性評価
各インク２０ｍｌに対し、オリフィスを形成させたニッケルプレート(表面積２ｃｍ²)を、浸漬させ、６０℃の環境中に２週間放置し、試験の前後でインク中のニッケルイオン量が、変化するかどうかを、ＩＣＰ（inductively coupled plasma）発光分析にて測定した。試験の前後で、ニッケルイオンの増加量が、２ｐｐｍ以下の場合を○とし、２ｐｐｍを越える場合に×とした。
【００８９】
【表５】

【００９０】
【発明の効果】
請求項１の効果：本発明によれば、浸透剤として純度の高いＥＨＤを添加することで、印字したときの画像濃度が高く、かつ裏抜けの少ない、滲みのない画像が得られるインクを提供することが可能となった。
【００９１】
請求項２の効果：本発明によれば、ＥＨＤの添加量を特定の範囲にすることで、信頼性が高く、高品質な画像が得られるインクの提供が可能となった。
【００９２】
請求項３の効果：本発明によれば、特定の界面活性剤を含有させることで、速乾性で、かつ文字滲み、境界滲みのない、鮮明なカラー画像の提供が可能となった。
【００９３】
請求項４の効果：本発明によれば、特定のカウンターイオンを用いることで、より信頼性の高いインク及びカラー画像の提供が可能となった。
【００９４】
請求項５の効果：本発明によれば、特定の湿潤剤を含有させることで、より保存安定性及び吐出安定性に優れたインク及びカラー画像の提供が可能となった。
【００９５】
請求項６の効果：滲みのない特定の染料を組み合わせたインクを使用することで、耐水耐光性に優れ、画像濃度も高く、色調も良好で、かつ色再現性に優れた高品位なカラー画像の提供が可能となった。
【００９６】
請求項７の効果：本発明によれば、ｐＨを特定の領域に調整することで、金属腐食を抑え、目詰まりのない、保存安定性及び吐出安定性に優れたインク及びカラー画像の提供が可能となった。
【００９７】
請求項８の効果：本発明によれば、従来の欠点を解消したカラー画像を得られる記録装置の提供が可能となった。
【００９８】
請求項９の効果： 本発明によれば、従来のような１スキャンで全印字ドットを印字する方法に比較して、２色の境界滲みだけでなく、文字の滲みも少ない高品位なカラー画像を提供できる。[0001]
BACKGROUND OF THE INVENTION
The present invention can provide a high-quality image with high image density and little blurring, and can be used for double-sided printing. The present invention relates to a color ink set having excellent color tone and color reproducibility and a method for forming a color image.
[0002]
[Prior art]
The inkjet recording method is capable of high-speed recording, non-contact with the recording medium, so that various types of recording media such as plain paper can be used, and color images can be obtained at low cost. Due to certain advantages, there is a remarkable spread in recent years. In ink jet recording, in order to perform good print recording over a long period of time, the ink used is required to satisfy the following conditions.
[0003]
1. Excellent ejection characteristics such as ink ejection direction stability and ejection stability.
2. Ink storage stability is excellent. That is, precipitation occurs due to chemical changes during long-term storage, continuous use, or recording pause, and the nozzles are not clogged or the ink physical properties do not change.
3. The printed image has a sufficiently high contrast and is a clear image without blur.
4). The recorded image dries quickly.
5. The printed image has excellent water resistance, light resistance, etc., that is, storage stability.
6). As color ink for full-color printers, it must have high purity color tone and image formation with excellent color reproducibility.
[0004]
In order to satisfy the above requirements, many proposals have been made as inks used for ink jet recording and the like, but no ink that sufficiently satisfies all the above conditions has yet been obtained. It is.
[0005]
Further, in the case of a color printer, even if a high-quality image can be ensured in the magenta, yellow, and cyan single color printing portions, image quality such as bleeding is likely to occur in the two-color overlapping portion of red, green, and blue. In the case of drying without using the ink, if the drying speed of the ink is low, the image quality such as boundary bleeding is significantly deteriorated.
[0006]
Furthermore, considering that the printing speed will be further increased in the future and that the color boundary in the color image and the image quality of the two-color overlapping portion will be improved, it is an important issue to accelerate the drying of the ink. It is no exaggeration to say that the choice of penetrant that controls penetrability affects the image quality.
[0007]
The surfactant is added for the purpose of lowering the surface tension of the ink and increasing the permeability to paper. For example, in the formulation described in JP-A-55-29546, although the apparent drying property is increased, this surfactant is increased. The formulation had the disadvantage that it oozed significantly with paper. Japanese Patent Publication No. 58-6752 discloses a quick-drying ink with improved permeability and less bleeding by using an ethylene oxide adduct pair having an acetylene bond as a surfactant. However, there is a problem in that the drying rate does not improve due to the interaction depending on the dye used at the same time. According to Japanese Examined Patent Publication No. 60-23793, dialkylsulfosuccinic acid as a surfactant improves drying properties and reduces image quality degradation. However, conventionally known sodium dioctylsulfosuccinate and di (2 -Ethylhexyl) sodium sulfosuccinate and the like have a problem that the pixel diameter varies greatly depending on the paper. JP-A-6-157959 discloses that 2-ethyl-1,3-hexanediol (EHD) should be added. However, EHD alone has poor solubility, and there is a balance between ink drying properties and image quality. It was insufficient. In addition, depending on the degree of purification of EHD, there may remain a problem in storage stability, clogging is likely to occur, and odor due to impurities may be a problem.
[0008]
Regarding the light resistance, water resistance, color tone, and color reproduction region of an image, it is mainly caused by a dye which is a colorant in the composition constituting the ink. For example, when the dye concentration is high, a clear printed image with high contrast can be obtained, but in order to increase the concentration, it is necessary that the dissolution stability of the dye is high. However, when the dissolution stability of the dye is increased, the storage stability and ejection stability of the ink are increased, but conversely, the water resistance of the printed image is deteriorated. In color image formation, the color tone of each dye for good color tone reproduction is also an important problem.
[0009]
As a balanced ink set for forming a color image having excellent water resistance, light resistance, sharpness, and mutual color rendering, for example, in JP-A-8-310116, yellow, magenta, cyan, In addition, it is recommended to combine black dyes with these dyes, but these dyes are not sufficient in water resistance, and color tone and color reproducibility are not satisfactory. According to US Pat. No. 5,143,547, the combination of Acid Yellow 23, Direct Red 227, and Acid Blue 9 as a combination of three colors of yellow, magenta, and cyan has good color reproducibility. No. 23 has poor water resistance, and Direct Red 227 is not sufficiently satisfactory in terms of water resistance and color tone. According to US Pat. No. 5,145,519, the combination of direct yellow 86, acid red 52, and acid blue 9 is excellent in color reproducibility, but direct yellow 86 has problems such as insufficient color tone. However, the present situation is that an ink set based on a combination of dyes balanced in all is not obtained.
[0010]
Further, as a role of the wetting agent, clogging due to dye precipitation or the like accompanying water evaporation in the vicinity of the nozzle or the like can be prevented by stably dissolving the colorant in water. If the amount of the wetting agent is large, the storage stability of the ink is increased. However, if the amount is too large, the viscosity becomes high, and problems such as difficulty in discharging from the nozzle occur.
[0011]
[Problems to be solved by the invention]
An object of the present invention is to provide a color ink set for ink-jet recording and a color image forming method which have solved all the conventional drawbacks. Specifically, it is possible to provide a high-quality image with particularly high image density and little bleeding, and there are few back-throughs that enable double-sided printing. An object of the present invention is to provide a color ink set and a color image that are excellent in water resistance, light resistance, color reproducibility, storage stability, and ejection stability and are well balanced.
[0012]
In more detail, firstly, presenting a kind of penetrant for obtaining high image quality and improving both the reliability and safety of the ink, and presenting an allowable range with respect to the amount of impurities. Secondly, presenting an appropriate amount of penetrating agent for maintaining a high reliability and obtaining a clear image with high image density, and third, a surfactant for providing a clearer image. Presenting the structure and addition amount; fourth, presenting the structure of a counter ion to ensure higher reliability; and fifth, the wetting agent for providing an ink with higher storage stability. Present the type and amount of addition, sixth, present a combination of dyes with good color tone, excellent water resistance, light resistance and color reproducibility, and seventh, suppress corrosion of metal parts and clogging Excellent storage stability and discharge stability Presenting an appropriate pH range for providing the ink, eighthly providing a recording apparatus equipped with a color ink set for ink-jet recording that has solved all the conventional drawbacks, and ninth, clearer and higher An object is to present a printing method for providing a high-quality color image.
[0013]
[Means for Solving the Problems]
The present invention can provide a high-quality image with high image density and little blurring, and can be used for double-sided printing. The present invention relates to a color ink set and a color image forming method excellent in color tone and color reproducibility, and the constitution is as follows.
[0014]
[1] In an ink containing water, a colorant that dissolves in water, a surfactant, a wetting agent, and 2-ethyl-1,3-hexanediol (hereinafter abbreviated as EHD), the amount of impurities contained in the EHD is 0 In the range of 0.01 to 2% by weight.The amount of EHD contained is in the range of 0.1 to 4% by weight of the total amount of ink.The surfactant isA surfactant represented by the following general formula (1), the content of which is 0.5 to 3% by weight of the total amount of the ink, and the pH of the ink is adjusted to 9 to 11.Ink for ink jet recording characterized by the above-mentioned.
    RO (CH ₂ CH ₂ O) _n CH ₂ COOM (1)
      R: linear or branched alkyl group having 13 or 14 carbon atoms n: an integer of 3 to 12
      M: alkali metal, quaternary ammonium, quaternary phosphonium or
          Alkanolamine
[0017]
[2] The counter ion of the colorant and / or the surfactant contained in the ink is sodium, lithium and / or quaternary ammonium, quaternary phosphonium represented by the following general formula (2), The ink for inkjet recording according to the above [1], which is an alkanolamine ion.
[0018]
[Chemical 2]

Z: Nitrogen or phosphorus
R₁~ R₄ : Hydrogen, alkyl group having 1 to 4 carbon atoms, hydroxyl group or
Halogenated alkyl group
[0019]
[3The above-mentioned [1], wherein the contained wetting agent is a mixture of glycerol and diethylene glycol and is contained in an amount of 10 to 30% by weight based on the total amount of the ink.Or [2]2. Ink for ink jet recording described in 1.
[0022]
[8] saidAny one of [1] to [3]For inkjet recording as describedinkInkjet recording device equipped with
[0023]
[9] saidAny one of [1] to [3]For inkjet recording as describedinkIn a method of forming an image using, when printing using a head having a plurality of ink outlets on a paper having a Steecht sizing degree of 3 seconds or more, printing corresponding to all the ink outlets in a plurality of scans A method of forming a color image, comprising printing dots.
[0024]
Hereinafter, the present invention will be described in detail with specific examples.
In the ink for inkjet recording containing water, a colorant that dissolves in water, a penetrating agent, a wetting agent, and a surfactant, the present invention uses EHD that has a certain amount of impurities as a penetrating agent. It has been found that a high-quality image with high image density and little blur can be obtained even during high-speed printing. Further, by suppressing the amount of impurities, the reliability after being left for a longer period of time is improved, and the problem of odor is also improved.
[0025]
Such an EHD with less impurities is produced by using a high-purity material from the aldehyde stage as a raw material. As the EHD produced in this way, for example, specifically, Kyowa Hakko Co., Ltd. Available as “octanediol”.
[0026]
In the present invention, by adding EHD having a certain amount of impurities as a penetrating agent, the penetrability of the ink is increased, and at the same time, the colorant is kept on the surface, so that there is no boundary bleeding, the image density is high, and It became possible to obtain printed images with little show-through. The amount of EHD added is preferably 0.1 to 4% by weight, more preferably 0.5 to 3% by weight, based on the total amount of ink. If the amount is less than 0.1% by weight, the effect is small, and if it exceeds 4% by weight, the solubility is low and the reliability is deteriorated.
[0027]
In the present invention, in addition to EHD, a penetrant as shown below may be used in combination as long as the properties are not affected. As penetrants that can be used in combination, glycol ethers are desirable, and among them, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, and the like are preferable.
[0028]
In addition, as the surfactant used in the present invention, a surfactant represented by the following general formula (1) is used, so that the drying property is fast, and a clear color image having no boundary bleeding and character bleeding is obtained. Offering became possible.
RO (CH₂CH₂O)_nCH₂COOM (1)
R: linear or branched alkyl group having 13 or 14 carbon atoms
n: an integer from 3 to 12
M: alkali metal, quaternary ammonium, quaternary phosphonium or
Alkanolamine
[0029]
Commercially available surfactants containing this compound as a main component include ECTD-3NEX available from Nikko Chemicals (in general formula (1), R: tridecyl group, n: 3, M: Na ), ECTD-6NEX (in the general formula (1), R: tridecyl, m: 6, M: Na) and the like.
[0030]
In the present invention, in addition to the above surfactants, the following surfactants may be used in combination as long as the ink characteristics are not affected. Surfactants that can be used in combination include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene glycol esters, nonionic surfactants such as acetylene surfactants and silicon surfactants, and polyoxyethylene alkyl ethers. Anionic surfactants such as ethylene alkyl ether acetates and dialkyl sulfosuccinates can be mentioned.
[0031]
Specifically, nonionic surfactants can be obtained as BT series (Nikko Chemicals) Nonipol series (Sanyo Kasei), Surfynol series (Air Products) silicone (Toray Dow Corning, etc.). As an anionic surfactant, specifically, Nikkor ECT series (trade name, manufactured by Nippon Surfactant Chemical Co., Ltd.) can be obtained.
[0032]
These surfactants are added to reduce the surface tension of the ink and increase the permeability of the ink to the paper, thereby increasing the dryness of the printed image. The amount of the surfactant added is the surface tension of the ink. Is usually adjusted to 50 mN / m or less, preferably 40 mN / m or less, and is preferably 0.5 to 3% by weight based on the total amount of the water-based ink composition. If the amount of the surfactant added is less than 0.5% by weight, the dynamic surface tension is high and the drying property is poor, and conversely if it exceeds 3% by weight, precipitation of the surfactant occurs during storage. .
[0033]
In addition, when the counter ion of the colorant and the counter ion of the surfactant are sodium, lithium and / or quaternary ammonium, quaternary phosphonium or alkanolamine ion represented by the following general formula (2), excellent dissolution stability And a good printed image can be obtained.
[0034]
[Chemical Formula 3]

Z: Nitrogen or phosphorus
R₁~ R₄ : Hydrogen, alkyl group having 1 to 4 carbon atoms, hydroxyl group or
Halogenated alkyl group
[0035]
The counter ion can be easily converted to such an alkali ion by adding an alkali hydroxide containing a desired alkali ion when dissolving them in water during ink preparation. For example, in the case of a lithium salt, it can be performed by adding lithium hydroxide.
[0036]
In addition, as a wetting agent used in the present invention, it was revealed that the storage stability and ejection stability of ink are remarkably improved by using a mixture of diethylene glycol and glycerol.
[0037]
In the present invention, in addition to the above-described wetting agents, wetting agents as shown below may be used in combination within a range that does not affect the properties. Wetting agents that can be used in combination include ethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,5-pentanediol, 1,6-hexanediol, 1,2,6-hexanetriol, 1,2,4-butane. Polyols such as triol, 1,2,3-butanetriol, petriol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, Polyhydric alcohol alkyl ethers such as propylene glycol monoethyl ether, ethylene glycol monophenyl ether, ethylene glycol Including polyhydric alcohol aryl ethers such as coal monobenzyl ether, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, etc. Examples thereof include nitrogen heterocyclic compounds, but the present invention is not limited thereto.
[0038]
The content of the wetting agent is 10 to 30% by weight, and more preferably 12 to 20% by weight. When the amount of the wetting agent is less than 10% by weight, the dye has insufficient dissolution stability and the dye tends to precipitate at the nozzle portion. When the amount of the wetting agent exceeds 30% by weight, the viscosity of the ink increases with changes in the environmental temperature. Is a problem.
[0039]
In addition, by using inks that combine specific colorants, it is possible to obtain images with good color tone, excellent water and light resistance and color reproducibility, high contrast and low show-through, storage stability and ejection stability. It is possible to provide an ink set and a color image that are highly balanced and well balanced.
[0040]
More specifically, in the ink set for ink jet recording composed of four colors of yellow, magenta, cyan, and black, including water, a colorant that dissolves in water, a wetting agent, a surfactant, and EHD, the yellow The ink contains at least Pro-jet Fast Yellow 2 (manufactured by Zeneca) and CIDirect Yellow 142 as dyes, and the magenta ink contains at least CI Acid Red 52 and MJR611 (manufactured by Mitsubishi Chemical Corporation) as dyes. The ink contains at least Pro-jet Fast Cyan 2 (manufactured by Zeneca) as a dye, and the black ink uses an ink containing at least CIDirect Black 168 as a dye. Excellent color reproducibility, storage stability, high ejection stability, balanced ink set and color The provision of image has become possible.
[0041]
As the colorant contained in the ink used in the present invention, a dye other than the above dyes may be added as long as it does not adversely affect the color tone and other characteristics. Although the specific example of the dye which can be used together is shown below, this invention is not limited to these.
[0042]
As acid dyes and food dyes
C. I. Acid Yellow 17, 23, 42, 44, 79, 142
C. I. Acid Red 1,8,13,14,18,26,27,35,
37, 42, 87, 89, 92, 97, 106,
111, 114, 115, 134, 186
249,254,289
C. I. Acid Blue 9, 29, 45, 92, 249
C. I. Acid Black 1, 2, 7, 24, 26, 94
C. I. Food yellow 3, 4
C. I. Food Red 7, 9, 14
C. I. Food black 1, 2
[0043]
As a direct dye
C. I. Direct yellow 1,12,24,26,33,44,50,
86, 120, 132, 142, 144
C. I. Direct Red 1, 4, 9, 13, 17, 20, 28, 31,
39, 80, 81, 83, 89, 225
227
C. I. Direct orange 26, 29, 62, 102
C. I. Direct blue 1, 2, 6, 15, 22, 25, 71, 76,
79, 86, 87, 90, 98, 163
165, 199, 202
C. I. Direct black 19, 22, 32, 38, 51, 56, 71,
74, 75, 77, 154, 171
Etc. are mentioned.
[0044]
In the present invention, an antiseptic and fungicidal agent may be added in addition to the above additives. As a good antiseptic and fungicidal agent, 1,2-benzisothiazolin-3-one can be used, and thus ink and color excellent in antiseptic and antifungal effects while ensuring reliability such as storage stability and ejection stability. Images can be provided. The addition amount of the antiseptic and fungicide is preferably 0.2 to 1.0% by weight. When the addition amount is less than 0.2% by weight, the antiseptic and fungicidal effect becomes insufficient, and when the addition amount exceeds 1.0% by weight, precipitation of the antiseptic and fungicidal agent itself may be a problem. Examples of the commercially available antiseptic and fungicides containing 1,2-benzisothiazolin-3-one include Sun Ibakku AP (manufactured by Sanai Oil Co., Ltd.) and Proxel XL (manufactured by IC). .
[0045]
The ink of the present invention can be provided as a more reliable ink by maintaining the dissolution stability of the dye and adjusting the pH to 9 to 11 in consideration of the influence on the metal used in the nozzle plate. became.
[0046]
In the present invention, penetrants, metal corrosion inhibitors, water-soluble ultraviolet absorbers, water-soluble infrared absorbers, and the like can be added according to other purposes.
[0047]
When printing the ink set of the present invention on a paper having a sizing degree of 3 seconds or more using a head having a plurality of ink ejection openings, printing dots corresponding to all the ink ejection openings are obtained by a plurality of scans. By using the method for forming a color image that can be printed, a clearer and higher-quality color image can be obtained.
[0048]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the present invention and comparative examples are shown below.
Example 1
The purity of EHD “octanediol” manufactured by Kyowa Hakko was analyzed by gas chromatography, and it was confirmed that the amount of impurities was 0.01 wt% or more and less than 1 wt%.
[0049]
Using this EHD, an ink was prepared with the following composition, but the odor at the time of ink preparation was not noticed at all.
<Black ink composition>
C.I.Direct Black 168 (Zeneca) 4% by weight
EHD (“Octanediol” manufactured by Kyowa Hakko) 2% by weight
Diethylene glycol 15% by weight
Glycerol 5% by weight
ECTD-3NEX (Nikko Chemicals) 1% by weight
Proxel XL (manufactured by IC) 0.4% by weight
Ion exchange water
[0050]
Comparative Example 1
The purity of the commercially available special grade reagent, EHD, was analyzed by gas chromatography in the same manner as in Example 1 to confirm that the amount of impurities was 3% by weight or more.
[0051]
Using this EHD, an ink was prepared with the following composition, but I was worried about the odor when preparing the ink.
<Black ink composition>
C.I.Direct Black 168 (Zeneca) 4% by weight
EHD (commercial grade reagent) 2% by weight
Diethylene glycol 15% by weight
Glycerol 5% by weight
ECTD-3NEX (Nikko Chemicals) 1% by weight
Proxel XL (manufactured by IC) 0.4% by weight
Ion exchange water
[0052]
The ink compositions of Example 1 and Comparative Example 1 formulated with the above composition were stirred and dissolved at room temperature, adjusted to pH 10.5 with lithium hydroxide, and then filtered through a 0.22 μm Teflon filter. Further, each ink was prepared by deaeration for about 30 minutes.
[0053]
Next, these inks were evaluated for reliability after being left for a long time, and for the presence or absence of odor during ink preparation. The results are shown in Table 1.
[0054]
Evaluation 1: Reliability evaluation after prolonged standing
Example 1 ink and Comparative Example 1 ink were filled in an ink jet printer having a 300 dpi nozzle using a laminated PZT having a nozzle plate made of nickel for pressurizing the liquid chamber flow path, and the cap was capped at room temperature. After being left for 3 months, cleaning operations such as wiping and suction were performed 0 times and once to perform printing, and the pixel diameter and dot position accuracy before and after being left were compared.
The case where there was no problem in the pixel diameter and the dot position accuracy after 0 cleaning operations was indicated by ◯, the case where the cleaning operation was recovered once, Δ, and the other cases were indicated by ×.
[0055]
[Table 1]

[0056]
Comparative Example 2
Example 1 An ink was prepared in the same manner as in Example 1 except that the amount of EHD in the ink was changed from 2 wt% to 5 wt%.
[0057]
Comparative Example 3
Example 1 An ink was prepared in the same manner as in Example 1 except that the amount of EHD in the ink was changed from 2% by weight to 0.05% by weight.
[0058]
The comparative example 2 ink and comparative example 3 ink were subjected to the following evaluation of image sharpness and the reliability evaluation after standing for a long time as described above, and compared with the ink of Example 1. The results are shown in Table 2.
[0059]
Evaluation 2: Evaluation of image clarity
Test 2-1: Evaluation of image density
The image density of a 100% black solid portion printed with each ink was measured using a reflective color spectrocolorimetric densitometer X-Rite 938 (manufactured by X-Rite).
Test 2-2: Evaluation of strike-through
The image density (back-through) of a 100% black solid portion printed with each ink was measured from the back side of the paper using a reflective color spectrophotometric densitometer X-Rite 938 (manufactured by X-Rite).
Test 2-3:. Bleeding assessment
Each ink was visually evaluated for bleeding of the printed sample. As printing paper, printing was performed on three sheets of commercially available recycled paper, copy paper, and inkjet exclusive paper. Evaluation was good for all three papers, and x for the other.
[0060]
[Table 2]

[0061]
Example 2
An ink was prepared with the following composition, and combined with the black ink of Example 1 to make an ink set of Example 2.
<Composition of yellow ink>
Pro-jet Fast Yellow 2 (Zeneca) 1.5% by weight
C.I.Direct Yellow 142 (Daiwa Kasei Co., Ltd.) 0.5% by weight
EHD (“Octanediol” manufactured by Kyowa Hakko) 2% by weight
Diethylene glycol 15% by weight
Glycerol 5% by weight
ECTD-3NEX (Nikko Chemicals) 1% by weight
Sun Eye Back AP (manufactured by Sanai Oil Co., Ltd.) 0.4% by weight
Ion exchange water
[0062]
<Magenta ink composition>
C.I. Acid Red 52 (Daiwa Kasei Co., Ltd.) 0.7% by weight
MJR611 (Mitsubishi Chemical Corporation) 1.3% by weight
EHD (“Octanediol” manufactured by Kyowa Hakko) 1% by weight
Diethylene glycol 15% by weight
Glycerol 5% by weight
ECTD-3NEX (Nikko Chemicals) 1% by weight
Proxel XL (manufactured by IC) 0.4% by weight
Ion exchange water
[0063]
<Composition of cyan ink>
Pro-jet Fast Cyan 2 (manufactured by Zeneca) 3% by weight
EHD (“Octanediol” manufactured by Kyowa Hakko) 1% by weight
Diethylene glycol 15% by weight
Glycerol 5% by weight
ECTD-3NEX (Nikko Chemicals) 1% by weight
Sun Eye Back AP (manufactured by Sanai Oil Co., Ltd.) 0.4% by weight
Ion exchange water
[0064]
Each ink composition formulated with the above composition is stirred and dissolved at room temperature, adjusted to pH 10.5 with lithium hydroxide, filtered through a 0.22 μm Teflon filter, and further removed for about 30 minutes. Care was taken to make an ink.
[0065]
Comparative Example 4
An ink was prepared with the following composition to prepare an ink set for Comparative Example 4.
<Composition of yellow ink>
Pro-jet Fast Yellow 2 (Zeneca) 2% by weight
1,5-pentanediol 10% by weight
Glycerol 2% by weight
ECTD-3NEX (Nikko Chemicals) 1% by weight
Sun Eye Back AP (manufactured by Sanai Oil Co., Ltd.) 0.4% by weight
Ion exchange water
[0066]
<Magenta ink composition>
C.I. Acid Red 52 (Daiwa Kasei) 1.8% by weight
1,5-pentanediol 10% by weight
ECTD-3NEX (Nikko Chemicals) 1% by weight
Sun Eye Back AP (manufactured by Sanai Oil Co., Ltd.) 0.4% by weight
Ion exchange water
[0067]
<Composition of cyan ink>
Pro-jet Fast Cyan 2 (manufactured by Zeneca) 3% by weight
Diethylene glycol 5% by weight
Glycerol 2% by weight
ECTD-3NEX (Nikko Chemicals) 1% by weight
Sun Eye Back AP (manufactured by Sanai Oil Co., Ltd.) 0.4% by weight
Ion exchange water
[0068]
<Black ink composition>
C.I.Direct Black 168 (Zeneca) 4% by weight
Diethylene glycol 23% by weight
Glycerol 10% by weight
ECTD-3NEX (Nikko Chemicals) 1% by weight
Sun Eye Back AP (manufactured by Sanai Oil Co., Ltd.) 0.4% by weight
Ion exchange water
[0069]
Each ink composition formulated with the above composition is stirred and dissolved at room temperature, adjusted to pH 10.5 with lithium hydroxide, filtered through a 0.22 μm Teflon filter, and further removed for about 30 minutes. Care was taken to make an ink.
[0070]
Comparative Example 5
An ink was prepared with the following composition, and a comparative example 5 ink set was prepared.
<Composition of yellow ink>
C.I. Acid Yellow 23 1.5% by weight
EHD (commercial special grade reagent) 1% by weight
Diethylene glycol 15% by weight
Glycerol 5% by weight
ECTD-3NEX (Nikko Chemicals) 1% by weight
Sun Eye Back AP (manufactured by Sanai Oil Co., Ltd.) 0.4% by weight
Ion exchange water
[0071]
<Magenta ink composition>
C.I.Direct Red 227 3% by weight
EHD (commercial special grade reagent) 1% by weight
Diethylene glycol 15% by weight
Glycerol 5% by weight
ECTD-3NEX (Nikko Chemicals) 1% by weight
Sun Eye Back AP (manufactured by Sanai Oil Co., Ltd.) 0.4% by weight
Ion exchange water
[0072]
<Composition of cyan ink>
C.I.Direct Blue 199 3% by weight
EHD (commercial special grade reagent) 1% by weight
Diethylene glycol 15% by weight
Glycerol 5% by weight
ECTD-3NEX (Nikko Chemicals) 1% by weight
Sun Eye Back AP (manufactured by Sanai Oil Co., Ltd.) 0.4% by weight
Ion exchange water
[0073]
<Black ink composition>
C.I.Direct Black 154 3% by weight
EHD (commercial special grade reagent) 1% by weight
Diethylene glycol 15% by weight
Glycerol 5% by weight
ECTD-3NEX (Nikko Chemicals) 1% by weight
Proxel XL (manufactured by IC) 0.4% by weight
Ion exchange water
[0074]
Each ink composition formulated with the above composition is stirred and dissolved at room temperature, adjusted to pH 10.5 with lithium hydroxide, filtered through a 0.22 μm Teflon filter, and further removed for about 30 minutes. Care was taken to make an ink.
[0075]
Example 2 Ink set, Comparative example 4 Ink set, Comparative example 5 Ink set was subjected to reliability evaluation after long-term storage, water resistance evaluation, color tone, evaluation of color boundary bleeding, and storage stability evaluation shown below. . The evaluation results are shown in Table 3.
[0076]
Evaluation 3: Evaluation of water resistance of printed image
An image sample printed with each ink is immersed in water at 30 ° C. for 1 minute, a change in image density before and after immersion is measured with a Macbeth densitometer, water resistance (fading rate%) is obtained by the following formula, and fading is observed. When the rate was less than 30%, it was marked as ◯, and when it was 30% or more, it was marked as x.
[0077]
[Expression 1]

[0078]
Evaluation 4: Evaluation of color tone and color boundary bleeding
A color image was printed with each ink set, and color tone and color boundary bleeding were visually evaluated. As printing paper, printing was performed on three sheets of commercially available recycled paper, copy paper, and inkjet exclusive paper. Evaluation was good for all three papers, and x for the other.
[0079]
Evaluation 5: Evaluation of storage stability
Each ink was put in a polyethylene container and stored for 2 months under the conditions of −20 ° C., 20 ° C., and 50 ° C., and the surface tension, viscosity, and presence of precipitates after storage were examined. Even if it preserve | saves on what conditions, the thing which does not change a physical property etc. and precipitation is not seen was set as (circle), and other than that was set as x.
[0080]
[Table 3]

[0081]
Comparative Example 6
Example 2 An ink set of Comparative Example 6 was prepared with the same composition except that the surfactant was changed to nonionic surfactant BT-7 (Nikko Chemicals) in each ink composition of the ink set.
[0082]
When this ink was evaluated, bleeding of the printed image was x. Evaluation 6 shown below was performed on the ink set of Example 2 and the ink set of Comparative Example 6. The results are shown in Table 4.
[0083]
Evaluation 6: Image clarity by printing method
Using a printer IPSiO JET 300 manufactured by Ricoh Co., Ltd., the blurring of the boundary between the printed image by one scan and the printed image by two scans and the bleeding of characters were evaluated. Three types of printing paper, commercially available recycled paper, copy paper, and ink jet exclusive paper, were used, and comprehensive judgment was made visually.
[0084]
[Table 4]

[0085]
As shown in Table 4, it was confirmed that printing with two scans markedly improved boundary bleeding and character bleeding at the two-color overlapping portion compared to printing with one scan.
[0086]
Comparative Example 7
In Example 2, the ink set was made as Comparative Example 7 without adjusting pH.
[0087]
Next, Evaluation 1 and Evaluation 7 shown below were performed on the ink set of Example 2 and Comparative Example 7. The results are shown in Table 5.
[0088]
Evaluation 7: Metal corrosion evaluation
A nickel plate (surface area 2 cm) with orifices formed for 20 ml of each ink²Was immersed in an environment of 60 ° C. for 2 weeks, and whether or not the amount of nickel ions in the ink changed before and after the test was measured by ICP (inductively coupled plasma) emission analysis. Before and after the test, the case where the increase amount of nickel ions was 2 ppm or less was evaluated as ◯, and the case where it exceeded 2 ppm was evaluated as x.
[0089]
[Table 5]

[0090]
【The invention's effect】
Effect of Claim 1 According to the present invention, by adding high-purity EHD as a penetrating agent, there is provided an ink with a high image density when printed and with little blurring and without blurring. It became possible to do.
[0091]
Effect of Claim 2 According to the present invention, it is possible to provide an ink with high reliability and high quality image by setting the addition amount of EHD within a specific range.
[0092]
Effect of Claim 3 According to the present invention, by including a specific surfactant, it is possible to provide a clear color image which is quick-drying and free from character bleeding and boundary bleeding.
[0093]
According to the present invention, it is possible to provide a more reliable ink and color image by using a specific counter ion.
[0094]
Effect of Claim 5: According to the present invention, by including a specific wetting agent, it is possible to provide an ink and a color image that are more excellent in storage stability and ejection stability.
[0095]
Effect of Claim 6: By using an ink combined with a specific dye without bleeding, a high-quality color image having excellent water resistance and light resistance, high image density, good color tone and excellent color reproducibility Is now available.
[0096]
Effect of Claim 7: According to the present invention, by adjusting the pH to a specific region, it is possible to provide an ink and a color image excellent in storage stability and ejection stability that are free from clogging and that are free from clogging. It has become possible.
[0097]
Advantage of Claim 8: According to the present invention, it is possible to provide a recording apparatus capable of obtaining a color image that eliminates the conventional drawbacks.
[0098]
[Effect of Claim 9] According to the present invention, compared to the conventional method of printing all print dots in one scan, not only the boundary blur of two colors but also a high-quality color image with less blur of characters. Can provide.

Claims (5)

In an ink containing water, a colorant that dissolves in water, a surfactant, a wetting agent, and 2-ethyl-1,3-hexanediol (hereinafter abbreviated as EHD), the amount of impurities contained in the EHD is 0.01 to in the range of 2 wt%, the amount of EHD contained in the ink is, Ri range der of 0.1 to 4 percent by weight of the total ink, the surfactant is represented by the following general formula (1) An ink for ink jet recording , which is a surfactant, the content of which is 0.5 to 3% by weight of the total amount of ink, and the pH of the ink is adjusted to 9 to 11 .
RO (CH ₂ CH ₂ O) _n CH ₂ COOM (1)
R: linear or branched alkyl group having 13 or 14 carbon atoms
n: an integer from 3 to 12
M: alkali metal, quaternary ammonium, quaternary phosphonium or
Alkanolamine The counter ion of the colorant and / or surfactant contained in the ink is sodium, lithium and / or quaternary ammonium, quaternary phosphonium or alkanolamine ion represented by the following general formula (2) The ink for inkjet recording according to claim 1, wherein

Z: nitrogen or phosphorus R ₁ to R _4: hydrogen, an alkyl group having 1 to 4 carbon atoms, hydroxyl group, or
Halogenated alkyl group The ink for inkjet recording according to claim 1 or 2 , wherein the wetting agent is a mixture of glycerol and diethylene glycol and is contained in an amount of 10 to 30% by weight based on the total amount of the ink. An ink jet recording apparatus comprising the ink for ink jet recording according to claim 1. The method for forming an image using the ink for ink jet recording according to any one of claims 1 to 3, wherein printing is performed using a head having a plurality of ink discharge ports on a paper having a Steecht sizing degree of 3 seconds or more. A method for forming an image, wherein printing dots corresponding to all ink ejection openings are printed by a plurality of scans.