JP4453239B2 - Water-based ink and image forming method using the same - Google Patents

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【００８３】
《着色微粒子分散液の調製》
（着色微粒子分散液１−１の調製：参考例）
４．６ｇのポリビニルブチラール（積水化学製ＢＬ−Ｓ、平均重合度３５０）、３．１ｇのＣ．Ｉ．Ｓｏｌｖｅｎｔ Ｙｅｌｌｏｗ ８８及び４５ｇの酢酸エチルをセパラブルフラスコに入れ、フラスコ内をＮ_２で置換した後、攪拌して上記ポリマー及び染料を完全溶解させた。次いで、ラウリル硫酸ナトリウム２．６ｇを含む水溶液９０ｇを滴下、撹拌した後、超音波分散機（ＵＨ−１５０型、株式会社エスエムテー製）を用いて、３００秒間乳化した。その後、減圧下で酢酸エチルを除去し、イエロー染料を含浸する着色微粒子分散液１−１を得た。分散液中の着色微粒子の平均粒径は９０ｎｍであった。なお、粒径測定は、大塚電子製レーザー粒径解析システムを用いて行い、体積平均粒径で表す。
【００８４】
（着色微粒子分散液１−２の調製：参考例）
上記着色微粒子分散液１−１の調製において、ラウリル硫酸ナトリウムの量を１．９ｇに変更した以外は同様にして、着色微粒子分散液１−２を得た。平均粒径は、９２ｎｍであった。
【００８５】
（着色微粒子分散液１−３の調製：比較例）
上記着色微粒子分散液１−１の調製において、ポリビニルブチラールの量を１．９ｇに変更した以外は同様にして、比較の着色微粒子分散液１−３を得た。平均粒径は、１７５ｎｍであった。
【００８６】
（着色微粒子分散液２−１の調製：参考例）
上記調製したコア型の着色微粒子分散液１−２に、０．１５ｇの過硫酸カリウムを加えて溶解し、ヒーターを付して８０℃に加温した後、更に、１．５ｇのスチレン及び１．５ｇの２−ヒドロキシエチルメタアクリレートの混合液を滴下しながら８時間反応させて、コアシェル型イエロー染料の着色微粒子分散液２−１を得た。平均粒径は、９３ｎｍであった。
【００８７】
（着色微粒子分散液２−２の調製：本発明）
上記調製したコアシェル型の着色微粒子分散液２−１に、０．１ｇの粉末活性炭（無機吸着剤）を加えて室温下で２時間撹拌した後、０．８μｍのメンブレンフィルターによって濾過して、着色微粒子分散液２−２を得た。平均粒径は、同じく９３ｎｍであった。
【００８８】
（着色微粒子分散液２−３の調製：本発明）
上記調製したコアシェル型の着色微粒子分散液２−１に、０．３ｇの粉末活性炭を加えて室温下で２時間撹拌した後、０．８μｍのメンブレンフィルターによって濾過して、着色微粒子分散液２−３を得た。平均粒径は、同じく９３ｎｍであった。
【００８９】
（着色微粒子分散液２−４の調製：比較例）
上記着色微粒子分散液２−１の調製において、コア型の着色微粒子分散液１−２の調製に用いたポリビニルブチラールの添加量を１．９ｇに変更した以外は同様にして、比較の着色微粒子分散液２−４を得た。平均粒径は、１８０ｎｍであった。
【００９０】
（着色微粒子分散液３−１の調製：参考例）
６ｇの樹脂Ｒ−１を含む酢酸エチル溶液１２ｇ、３ｇのＣ．Ｉ．Ｓｏｌｖｅｎｔ Ｙｅｌｌｏｗ ２０１、３ｇのＣ．Ｉ．Ｓｏｌｖｅｎｔ Ｙｅｌｌｏｗ １６２及び８０ｇの酢酸エチルをセパラブルフラスコに入れ、フラスコ内をＮ_２で置換した後、攪拌して染料を完全溶解させた。次いで、ラウリル硫酸ナトリウム２ｇを含む水溶液１８０ｇを滴下、攪拌した後、超音波分散機を用いて、３００秒間乳化した。その後、減圧下で酢酸エチルを除去し、着色微粒子分散液を得た。
【００９１】
次いで、フラスコ内をＮ₂で置換した後、ヒーターを付して８０℃に加温後、３ｇのスチレン、１ｇのメタクリル酸２−ヒドロキシエチル及び０．５ｇのＮ，Ｎ・ｍｅｓ−アゾビスイソバレロニトリルの混合液を滴下しながら６時間反応させてコアシェル型イエロー染料の着色微粒子分散液３−１を得た。平均粒径は、３０ｎｍであった。
【００９２】
（着色微粒子分散液３−２の調製：参考例）
上記調製した着色微粒子分散液３−１に、合成樹脂ＳＰ２０７（三菱化学株式会社製）を２０ｍｌ加え、室温下で２時間撹拌した後、１μｍの濾紙で合成樹脂を分離して、着色微粒子分散液３−２を得た。平均粒径は、３１ｎｍであった。
【００９３】
（着色微粒子分散液３−３の調製：参考例）
上記着色微粒子分散液３−１の調製において、樹脂Ｒ−１を３．５ｇのポリビニルブチラールＢＬ−Ｓに変更した以外は同様にして、コアシェル型の着色微粒子分散液を得た。次いで、この着色微粒子分散液に、合成樹脂ＳＰ２０７（三菱化学株式会社製）を２０ｍｌ加え、室温下で２時間撹拌した後、１μｍの濾紙で合成樹脂を分離して、着色微粒子分散液３−３を得た。平均粒径は、１２５ｎｍであった。
【００９４】
（着色微粒子分散液３−４の調製：参考例）
上記着色微粒子分散液３−１の調製において、樹脂Ｒ−１を２．０ｇのポリビニルブチラールＢＬ−Ｓに変更した以外は同様にして、比較の着色微粒子分散液３−４を得た。平均粒径は、１８０ｎｍであった
【００９５】
（着色微粒子分散液３−５の調製：参考例）
上記着色微粒子分散液３−２の調製において、合成樹脂ＳＰ２０７の量を５０ｍｌに変更した以外は同様にして、比較の着色微粒子分散液３−５を得た。平均粒径は１９０ｎｍであった。
【００９６】
（着色微粒子分散液４−１の調製：参考例）
３．５ｇのポリビニルブチラールＢＬ−Ｓ、４ｇのＣ．Ｉ．Ｓｏｌｖｅｎｔ Ｂｌｕｅ ７０及び４０ｇの酢酸エチルをセパラブルフラスコに入れ、フラスコ内をＮ_２で置換した後、攪拌して上記ポリマー及び染料を完全溶解させた。次いで、ラウリル硫酸ナトリウム１．６ｇを含む水溶液９０ｇを滴下、撹拌した後、超音波分散機を用いて、３００秒間乳化した。その後、減圧下で酢酸エチルを除去し、着色微粒子分散液を得た。
【００９７】
次いで、フラスコ内をＮ₂で置換した後、ヒーターを付して８０℃に加温後、１．５ｇのスチレン、０．５ｇのメタクリル酸２−ヒドロキシエチル及び０．１ｇのＮ，Ｎ・ｍｅｓ−アゾビスイソバレロニトリルの混合液を滴下しながら６時間反応させてコアシェル型シアン染料の着色微粒子分散液４−１を得た。平均粒径は、１２０ｎｍであった。
【００９８】
（着色微粒子分散液４−２の調製：参考例）
上記調製した着色微粒子分散液４−１に、合成樹脂ＳＰ２０７を２０ｍｌ加え、室温下で２時間撹拌した後、１μｍの濾紙で合成樹脂を分離して、着色微粒子分散液４−２を得た。平均粒径は、１２０ｎｍであった。
【００９９】
（着色微粒子分散液４−３の調製：参考例）
４ｇの樹脂Ｒ−２を含む酢酸エチル溶液８ｇ、４ｇのＣ．Ｉ．Ｓｏｌｖｅｎｔ Ｂｌｕｅ７０、及び４０ｇの酢酸エチルをセパラブルフラスコに入れ、フラスコ内をＮ_２で置換した後、攪拌して染料を完全溶解させた。次いで、ラウリル硫酸ナトリウム１．６ｇを含む水溶液９０ｇを滴下した後、超音波分散機を用いて、３００秒間乳化した。その後、減圧下で酢酸エチルを除去し、着色微粒子分散液を得た。この着色微粒子分散液に、合成樹脂ＳＰ２０７を１０ｍｌを加え、室温下で２時間撹拌後、１μｍの濾紙で合成樹脂を分離した。
【０１００】
次いで、フラスコ内をＮ₂で置換した後、ヒーターを付して８０℃に加温後、１．５ｇのスチレン、０．５ｇのメタクリル酸２−ヒドロキシエチル及び０．１ｇのＮ，Ｎ・ｍｅｓ−アゾビスイソバレロニトリルの混合液を滴下しながら６時間反応させてコアシェル型の着色微粒子分散液４−３を得た。平均粒径は、２２ｎｍであった。
【０１０１】
（着色微粒子分散液４−４の調製：参考例）
上記着色微粒子分散液４−３の調製において、合成樹脂ＳＰ２０７の添加量を４０ｍｌに変更した以外は同様にして着色微粒子分散液４−４を得た。平均粒径は、２０ｎｍであった。
【０１０２】
（着色微粒子分散液５−１の調製：参考例）
平均粒径として１００ｎｍに微分散されたＣ．Ｉ．Ｐｉｇｍｅｎｔ Ｒｅｄ １２２の５０ｇを含む分散液に、１．５ｇの過硫酸カリウムを加えて溶解し、ヒーターを付して８０℃に加温した後、更に２０ｇのスチレン及び２０ｇの２−ヒドロキシエチルメタアクリレートの混合液を滴下しながら７時間反応させて、顔料をシェルで被覆したマゼンタ顔料の着色微粒子分散液５−１を得た。平均粒径は、１１０ｎｍであった。
【０１０３】
（着色微粒子分散液５−２の調製：比較例）
上記着色微粒子分散液５−１の調製において、スチレンを８ｇ、２−ヒドロキシエチルメタアクリレートを８ｇに減量した以外は同様にして、比較の着色微粒子分散液５−２を調製した。平均粒径は、２１０ｎｍであった。
【０１０４】
（着色微粒子分散液６−１の調製：本発明）
６ｇの樹脂Ｒ−１を含む酢酸エチル溶液１２ｇ、３ｇのＭＳ Ｒｅｄ Ｇ（三井化学社製）、３ｇのＰｌａｓｔ Ｒｅｄ ８３７５（有本化学社製）及び８０ｇの酢酸エチルをセパラブルフラスコに入れ、攪拌して染料を完全溶解させた。次いで、ラウリル硫酸ナトリウム２ｇを含む水溶液１８０ｇを滴下した後、超音波分散機を用いて、３００秒間乳化した。その後、減圧下で酢酸エチルを除去し、着色微粒子分散液を得た。この着色微粒子分散液に、合成樹脂ＳＰ２０７を２０ｍｌ加え、室温下で２時間撹拌後、１μｍの濾紙で合成樹脂を分離した。
【０１０５】
次いで、フラスコ内をＮ₂で置換した後、ヒーターを付して８０℃に加温後、３ｇのスチレン、１ｇのメタクリル酸２−ヒドロキシエチル及び０．５ｇのＮ，Ｎ・ｍｅｓ−アゾビスイソバレロニトリルの混合液を滴下しながら６時間反応させてコアシェル型マゼンタ染料の着色微粒子分散液６−１を得た。平均粒径は、３５ｎｍであった。
【０１０６】
（着色微粒子分散液６−２の調製：比較例）
上記着色微粒子分散液６−１の調製において、樹脂Ｒ−１を樹脂Ｒ−４に変更し、かつ合成樹脂ＳＰ２０７による処理を除いた以外は同様にして、比較例の着色微粒子分散液６−２を得た。平均粒径は、１５０ｎｍであった。
【０１０７】
（着色微粒子分散液７−１の調製：本発明）
６ｇの樹脂Ｒ−３を含む酢酸エチル溶液１２ｇ、６ｇのＯｉｌ Ｂｌａｃｋ ８６０（オリエント化学社製）及び８０ｇの酢酸エチルをセパラブルフラスコに入れ、攪拌して染料を完全に溶解させた。次いで、ラウリル硫酸ナトリウム２ｇを含む水溶液１８０ｇを滴下した後、超音波分散機を用いて、３００秒間乳化した。その後、減圧下で酢酸エチルを除去し、着色微粒子分散液を得た。
【０１０８】
次いで、フラスコ内をＮ₂で置換した後、ヒーターを付して８０℃に加温後、３ｇのスチレン、１ｇのメタクリル酸２−ヒドロキシエチル及び０．５ｇのＮ，Ｎ・ｍｅｓ−アゾビスイソバレロニトリルの混合液を滴下しながら６時間反応させた。次いで、合成樹脂ＳＰ２０７を４０ｍｌ加え、室温下で２時間撹拌した後、１μｍの濾紙で合成樹脂を分離し、コアシェル型ブラック染料の着色微粒子分散液７−１を得た。平均粒径は、３３ｎｍであった。
【０１０９】
（着色微粒子分散液７−２の調製：比較例）
上記着色微粒子分散液７−１の調製において、樹脂Ｒ−３に代えて樹脂Ｒ−４を用い、かつ合成樹脂ＳＰ２０７による処理を除いた以外は同様にして、比較の着色微粒子分散液７−２を得た。平均粒径は、１６０ｎｍであった。
【０１１０】
《水性インクの調製》
上記調製した各着色微粒子分散液として、イエロー着色微粒子分散液は６０質量％、マゼンタ着色微粒子分散液は６０質量％、シアン着色微粒子分散液は６８質量％、ブラック着色微粒子分散液は６８質量％をそれぞれ秤量し、各々にエチレングリコール１５質量％、グリセリン１５質量％、サーフィノール４６５を０．５質量％、Ｐｒｏｘｅｌ ＧＸを０．１質量％を加え、残りが純水になるように添加量を調整して、各々１００ｇ水性インクを調製した。次いで、各水性インクを０．８μｍのメンブレンフィルターによって濾過し、ゴミ及び粗大粒子を除去して、水性インクを得た。
【０１１１】
《水性インクの測定及び評価》
上記調製した水性インクについて、下記の測定及び評価を行った。
【０１１２】
（各水性インクの色材の定量）
上記調製した各水性インク中の色材について、樹脂微粒子に内包されず、分散又は溶解している色材量、樹脂微粒子表面に吸着している色材量の定量を行った。
【０１１３】
染料着色微粒子については、色材溶解剤として酢酸エチルを用い、また顔料着色微粒子については、８０％硫酸を用いて、インク：色材溶解剤＝１：１９（質量比）の条件で、前述の方法に従って吸光度を測定した。吸光度は、ＭＣＰＤ−２０００（大塚電子製）を用い、３０秒毎にモニターし、吸光度の上昇が見られなくなった時点の吸光度を１とし、各時間毎に吸光度を表示し、これを規格化吸光度とした。顔料着色微粒子では、時間ごとにサンプリングし、水酸化ナトリウムで素早く中和し、超遠心分離器で固形分を分離後、０．４５μｍのメンブランフィルターで濾過したロ液の分光度を測定し、染料着色微粒子同様に規格化吸光度を求めた。得られた図１に記載の吸光度曲線より、第一段階（Ｉ）と第二段階（II）の屈曲点ａの規格吸光度をインク中に分散又は溶解している色材量とし、また、第二段階（II）と第三段階（III）の屈曲点ｂと、前記屈曲点ａとの差を着色微粒子表面に吸着している色材量とした。本発明で規定する着色微粒子に内包していない色材量は、インク中に分散又は溶解している色材量と着色微粒子表面に吸着している色材量との総量を意味する。
【０１１４】
測定は、水性インク１−１〜１−３、２−１〜２−４、５−１、５−２、６−１、６−２、７−１、７−２について行った。
【０１１５】
（水性インクの表面張力の測定）
常法に従って、市販の界面張力測定装置を用いて、表面張力（ｍＮ／ｍ）の測定を、水性インクについては、水性インク３−１〜３−５、水性インク４−１〜４−４について行い、また着色微粒子分散液については、着色微粒子分散液４−１〜４−４について行った。
【０１１６】
（水性インク中の着色微粒子の粒径分布の測定）
上記調製した水性インクについて、マルバーン製ゼータサイザー１０００を用いて着色微粒子の粒径分布を測定し、粒径が０．１〜５０ｎｍの領域に入る粒子の体積比率を算出した。なお測定は、水性インク３−１〜３−５、４−１〜４−４について行った。
【０１１７】
（水性インクの停滞安定性の評価）
上記調製した各水性インクを６０℃で１週間の強制劣化処理を行った後、大塚電子製レーザー粒径解析システムを用いて平均粒径を測定し、下式により、粒径変動率を求め、下記の基準に則り、停滞安定性の評価を行った。
【０１１８】
粒径変動率＝強制劣化後の平均粒径／強制劣化前の平均粒径×１００（％）
◎：粒径変動率が、１００〜１２０％未満である
○：粒径変動率が、１２０〜１５０％未満である
△：粒径変動率が、１５０〜２００％未満である
×：粒径変動率が、２００以上である
《インクジェット画像の印字と各画像評価》
（画像の印字）
各水性インクを、エプソン製のインクジェットプリンター（ＰＭ−８３０Ｃ）に装填し、コニカフォトジェットペーパー Ｐｈｏｔｏｌｉｋｅ ＱＰ 光沢紙（コニカ株式会社製）にベタ画像及び濃度を段階的に変化したウェッジ画像を出力し、下記の方法に従って、出射安定性及び得られた画像の光沢性、耐光性、耐水性の評価を行った。
【０１１９】
（出射安定性の評価）
上記プリンターで連続出射して１０分以上ノズル欠が出ないものを○（許容レベル）、それ未満のものを×（不可レベル）とした。
【０１２０】
（光沢性の評価）
各印字画像について、モニター１０人による目視官能評価を下記の基準に従って行い、その平均値を求めた。
【０１２１】
１：画像にざらざら感がある
２：正面から見ると光沢はあるが、斜めから見るとざらざら感がある
３：正面からみても、斜めから見ても光沢がある
平均値が高いほど、光沢性に優れていると判断した。
【０１２２】
（耐光性の評価）
濃度を段階的に変化させたウェッジ画像を、試験機として低温ＸｅウェザーメータＸＬ７５（スガ試験機製）を用いて曝射処理を行った。濃度変化はＸ−Ｒｉｔｅ９００（日本平板機材製）を用いて測定し、プリント濃度が１．０近辺での濃度変化を測定した。濃度が不足しているサンプルは最高濃度の部分の濃度変化を測定した。色材が染料の場合は１週間の連続曝射を行った後、未曝射試料の濃度から７０％以上残存しているものを◎、７０％未満から５０％残存しているものを○（許容レベル）、それ以下を×（不可レベル）とした。
【０１２３】
また、色材が顔料の場合は４０日間の連続曝射を行った後、未曝斜試料の濃度から９０％以上残存しているものを○（許容レベル）、それ以下を×（不可レベル）とした。
【０１２４】
（耐水性の評価）
各ベタ印字画像上に、マイクロピペットで水を滴下し、１分後に指で擦ってプリントに乱れが生じたか否かを目視にて判定し、○は乱れがなく許容レベル、×は乱れが発生して不可レベルとした。
【０１２５】
以上により得られた結果を、表２〜表５に示す。
【０１２６】
【表２】

【０１２７】
【表３】

【０１２８】
【表４】

【０１２９】
【表５】

【０１３０】
表２〜表５の結果より明らかなように、本発明の着色微粒子水分散液を用いた水性インクは、比較例に対して、水性インクの保存安定性、出射性が良好で、形成した画像の光沢性、耐光性及び耐水性に優れていることが分かる。
【０１３１】
実施例２
（インクセットの作製）
実施例１で調製した水性インクの中から、本発明のインクである水性インク２−３（イエロー染料インク：Ｙ）、水性インク４−４（シアン染料インク：Ｃ）、水性インク６−１（マゼンタ染料インク：Ｍ）、水性インク７−１（ブラック染料インク：Ｋ）を、各濃色インクとして用い、更に、マゼンタ及びシアン染料インクについては、染料濃度を濃色インクの１／４とし、更に溶剤としてエチレングリコール２０質量％、グリセリン２０質量％添加して、淡色インクであるライトマゼンタ染料インク（ＬＭ）、ライトシアン染料インク（ＬＣ）を調製した。また、比較インクとして、水性インク１−３（イエロー染料インク：Ｙ′）、水性インク４−１（シアン染料インク：Ｃ′）、水性インク６−２（マゼンタ染料インク：Ｍ′）、水性インク７−２（ブラック染料インク：Ｋ′）を、各濃色インクとして用い、更に、マゼンタ及びシアン染料インクについては、上記と同様にして、淡色インクであるライトマゼンタ染料インク（ＬＭ′）、ライトシアン染料インク（ＬＣ′）を調製した。
【０１３２】
上記の各染料インクを用いて、下記の組み合わせでインクセット１〜３を作製した。
【０１３３】
インクセット−１：Ｙ′、Ｍ′、Ｃ′、Ｋ′、ＬＭ′、ＬＣ′（６色の染料インクの全てが比較例）
インクセット−２：インクセット−１のうち、濃色インクのみＭ、Ｃ、ＬＭ、ＬＣを使用（濃色インクのみ本発明の染料インク）
インクセット−３：Ｙ、Ｍ、Ｃ、Ｋ、ＬＭ、ＬＣ（６色染料インクのすべてが本発明の染料インク）
（インクジェット画像の印字及び評価）
上記作製した各インクセットを、エプソン製のインクジェットプリンター（ＰＭ−８３０Ｃ）に装填し、コニカフォトジェットペーパー ＰｈｏｔｏｌｉｋｅＱＰ 光沢紙（コニカ株式会社製）に混色チャート画像を出力し、下記の方法に従って、色再現性の評価を行った。
【０１３４】
（色再現域の評価）
上記出力した混色チャートについて、明度５０における色再現域を、Ｌ^*、ａ^*、ｂ^*の面積として求め、インクセット−１を１．００としたときの各インクセットのＬ^*、ａ^*、ｂ^*の相対色再現域を求め、得られた結果を表６に示す。
【０１３５】
【表６】

【０１３６】
表６より明らかなように、本発明の水性インクを用いたインクセットにより出力した画像は、比較例に対して色再現域が拡がり、優れた色再現性を有していることが分かる。
【０１３７】
【発明の効果】
本発明により、分散安定性に優れ、吐出安定性に問題がなく、耐水性、耐光性、色再現性に優れた水性インク及びそれを用いた画像形成方法を提供することができた。
【図面の簡単な説明】
【図１】インクと色材溶解剤との溶液により得られる吸光度曲線の一例を示す模式図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aqueous ink excellent in dispersion stability, ejection stability, water resistance, light resistance, and color reproducibility, and an image forming method using the same.
[0002]
[Prior art]
In recent years, recording materials and inking materials used for printers, printing machines, markers, writing instruments, and the like have been required to be solvent-free and water-based. In particular, as water-based recording materials used for inkjet, those mainly composed of an aqueous solution of a water-soluble dye and those mainly composed of a fine pigment dispersion are widely used.
[0003]
Water-based inks that use water-soluble dyes include aqueous solutions of water-soluble dyes that are mainly classified as acid dyes, direct dyes, and some food dyes, and glycols, alkanolamines, surface tension, etc. as humectants. A surfactant for preparation, and a thickener added as necessary are used.
[0004]
Water-based inks using these water-soluble dyes are most commonly used because of their high reliability against clogging at the tip of a brush or printer. However, since the water-based ink using such a water-soluble dye is an aqueous solution of a dye, it tends to bleed on recording paper, and is inevitably limited in use and reduced in recording quality. Furthermore, water-soluble dyes that have only penetrated into the recording paper and have been dry-fixed are unlikely to be “dyed” and have a very low light fastness.
[0005]
As a method for solving the problems of water-based inks using water-soluble dyes as described above, it has long been studied to add resin fine particles such as emulsions and latexes. For example, Japanese Patent Application Laid-Open No. 55-18418 proposes an ink jet recording agent to which latex is added, which is “a kind of colloidal solution in which components such as rubber and resin are dispersed in water in the form of fine particles using an emulsifier”. is there. In order to improve the light fastness by adding latex as in the patent proposal and to have the effect of preventing bleeding, a larger amount of latex is required than the amount of dye used, and dispersion stability and ejection stability are improved. It is very difficult to secure.
[0006]
In order to solve the low water resistance and light fastness problems of water-based inks using water-soluble dyes as described above, proposals for coloring water-dispersible resins with oil-soluble dyes or hydrophobic dyes have been made as inks for inkjet recording. . For example, JP-A-55-139471, JP-A-58-45272, JP-A-3-250069, JP-A-7-258591, JP-A-8-253720, JP-A-8-92513, JP-A-8-183920, JP-A-2001-2001. In Japanese Patent No. 11347, Japanese Patent Laid-Open No. 2002-12802, etc., an ink using emulsion polymerization or dispersion polymerization particles dyed with an oil-soluble dye is proposed. In such a water-based ink using colored fine particles, the presence of a dye on the particle surface or outside the particle reduces the effect, and it is difficult to improve various properties such as dispersion stability, ejection stability, and light fastness. .
[0007]
On the other hand, in the case of pigments, attempts have been made to coat the pigment surface with a film-forming resin other than a dispersant in order to improve dispersion stability, ejection stability, and light resistance. For example, JP-A-8-269374, JP-A-9-151342, JP-A-10-88045, JP-A-10-292143, JP-A-2002-67473, JP-A-2002-69346, etc. describe examples in which a pigment is coated with a resin. Has been. However, it is not easy to completely coat the fine particle pigment, and the present situation is that a coated pigment that exceeds the performance of the conventional pigment dispersion has not yet appeared.
[0008]
As described above, colored fine particle-containing water-based inks using oil-soluble dyes and pigments can overcome the problems of conventional water-based inks using water-soluble dyes and pigment dispersions, and achieve high recording quality. Although it is a secret, it still has various problems and needs further improvements.
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and its object is to provide an aqueous ink having excellent dispersion stability, no problem in ejection stability, excellent water resistance, light resistance, and color reproducibility, and the same. It is to provide an image forming method used.
[0010]
[Means for Solving the Problems]
The above object of the present invention is achieved by the following means.
[0011]
  1. In a water-based ink in which colored fine particles made of a resin containing or coated with a color material are dispersed in water,The colored fine particles are treated with an organic adsorbent or an inorganic adsorbent and adsorbed in the ink and on the colored fine particle surface measured by the following method.A water-based ink characterized in that the color material amount is 10% or less of the total color material amount.
  Measurement method: Using a dye-dissolving agent that dissolves 30 to 100 g / L of a colorant at 20 ° C., and measuring the colorant absorbance of the mixture of aqueous ink: dye-dissolving agent = 1: 19 (mass ratio), And the amount of color material adsorbed on the surface of the colored fine particles is calculated.
[0012]
  2.SaidThe color material amount adsorbed on the surface of the colored fine particles is 5% or less of the total color material amount.As described in item 1Water based ink.
[0013]
  3. tableThe surface tension is 25-50 mN / m, andSaid80% by volume or more of the colored fine particles are distributed in a range of 1 to 50 nm as a particle diameter.Item 1 or 2Water based ink.
[0014]
  4. waterRemoves soluble organic solvents and non-reactive nonionic surfactantsThe colored fine particlesThe surface tension of the dispersion is 35 to 60 mN / m.Any one of said 1-3.Water based ink.
[0017]
  5. The above-described 1 to 3, wherein the colorant is a dye.4The water-based ink according to any one of Items.
[0018]
  6. The above-mentioned 1 to 3, wherein the color material is a pigment.4The water-based ink according to any one of Items.
[0019]
  7. The colored fine particles have a core-shell structure.6The water-based ink according to any one of Items.
[0020]
  8. The above 1 to 3, which is an inkjet ink7The water-based ink according to any one of Items.
[0021]
  9. From the above-mentioned ink jet head based on digital signals8An image forming method comprising ejecting the water-based ink according to any one of the items as droplets and attaching the droplets to an ink receiving medium.
[0022]
  As a result of diligent investigations in view of the above problems, the present inventors have found that water-based inks containing colored fine particles have various properties such as dispersion stability, ejection stability, light resistance, and the like in and out of the colored fine particles. As a result of finding the present invention, it has been found that it depends on the distribution, the completeness of the polymer film covering the surface, the interaction between the polymer and the color material, the solubility of the color material by the ink solvent, and the like. The amount of the coloring material that is not encapsulated in the colored fine particles, that is, adsorbed on the surface of the colored fine particles, or is dispersed or dissolved in the aqueous ink medium without the resin used for the colored fine particles,Treated with organic or inorganic adsorbents,Adjust to be within a specific valueAndMore excellent performances have been achieved.
[0023]
  Details of the present invention will be described below.
  In the invention according to claim 1, the amount of the color material not included in the colored fine particlesThat is, the amount of the color material adsorbed on the surface of the ink and the colored fine particles is10% or more of total colorant amountUnderIt is a feature.
[0024]
The amount of each color material existing inside and outside the colored fine particles defined in the present invention can be determined by absorbance measurement as follows.
[0025]
Specifically, the ink and the coloring material dissolving agent are mixed in a range of 1: 1 to 1:39. Preferably, the measurement is performed at 1:19 for convenience of spectral absorption measurement. The ratio of the amount of the coloring material present inside and outside the colored fine particles is measured every hour by monitoring the absorbance at regular intervals from the time of mixing, measuring the spectral absorption, and setting the concentration when all the coloring materials are eluted in the dissolving agent to 1. Plot the elution ratio of the colorant. Further, when it takes a long time to dissolve the entire amount, the same operation is performed with the concentration when the same amount of the coloring material is directly dissolved in the dissolving agent being set to 1. In the spectral absorption measurement, the measurement solution should not be vigorously stirred and shaken. When stirring is performed, the measurement solution is rotated at a rotational speed of 100 rpm or less with a magnetic stirrer.
[0026]
FIG. 1 is a schematic diagram showing an example of an absorbance curve obtained from a solution of ink and a coloring material dissolving agent.
[0027]
In FIG. 1, the elution of the color material by the color material solubilizer is rapidly dissolved as the first step (FIG. 1: I), and the color material directly dissolved or dispersed in the ink is dissolved in the second step (FIG. 1: II). ), The coloring material adsorbed on the surface of the colored fine particles elutes later than the first stage, and then, as the third stage (FIG. 1: III), the coloring material contained in the colored fine particles elutes latest. Therefore, it is possible to calculate the amount of color material present on the inside and outside of the colored fine particles and on the surface from the change in the elution rate curve.
[0028]
  In the present invention, the amount of the color material not included in the colored fine particles defined in the present invention is 10% or less of the total color material amount.To the lawAboutYesMachine or inorganic adsorbentSenseThus, desired characteristics can be achieved.
[0029]
The color material solubilizing agent as used in the present invention is a solvent that dissolves 1 to 200 g / L of the color material at 20 ° C., and various solvents from a hydrophobic solvent to a hydrophilic solvent can be used. A solvent that dissolves 30 to 100 g / L of the coloring material is preferable. Although suitable solubilizers differ depending on the color material, those having a compatibility parameter (Sp value) close to that of the color material are generally preferred. In the case of a dye, for example, ethyl acetate, dichloromethane, dichloroethane, chloroform, toluene, tetrahydrofuran, methanol, acetone and the like can be mentioned. From the Sp value of the dye used, a hydrophobic solvent is preferable, and ethyl acetate is particularly preferable. . When the coloring material is a pigment, for example, concentrated sulfuric acid, diluted sulfuric acid, Lewis acid such as trifluoroacetic acid, dimethyl sulfoxide coexisting with inorganic or organic base, N, N-dimethylformamide, etc. are preferable. . Particularly preferred is sulfuric acid. In the case of a hydrophobic solvent that is phase-separated from water, it is easy to measure the dye elution rate from the absorbance, but in the case of a water-soluble solvent, a separation operation is required, for example, filtration, salting out, aciding out, centrifugation. In addition, a general solvent and dispersed solid content separation method such as extraction can be used.
[0030]
  In the invention according to claim 4, the surface tension of the dispersion excluding the water-soluble organic solvent and the non-reactive nonionic surfactant is 35 to 60 mN / m.preferable.
[0031]
Examples of the non-reactive nonionic surfactant according to the present invention include, for example, manufactured by Kao Corporation: Emulgen 104P, 105, 106, 108, 109P, 120, 123P, 147, 130K, 210P, 220, 306P, 320P, 404 , 408, 409P, 420, 430, 705, 707, 709, LS106, LS110, LS114, MS110, A60, A90, A500, B66, etc. Rheodor SP-L10, SP-P10, SP-S10, SP-S30, SP-O10, SP-O30, TW-L120, TW-L106, TW-S120, TW-S320, MS-165 and the like. Rheodor Super SP-L10, TW-L120, TW-S120, etc. Emanon 1112, 3199, 3299, 3299R, 4110, CH-25, CH-40 and the like.
[0032]
Daiichi Kogyo Seiyaku Co., Ltd .: Neugen EA-50, EA-70, EA-80, EA-110, EA-130T, EA-140, EA-150, EA-160, EA-170, EA-190D, EA -92, EA-102, EA-112, EA-142, EA-152, EA-33, EA-73, EA-143, EA-137, EA-157, EA-167, EA-177, EA-141 ET-60E, ET-80E, ET-100E, ET-120E, ET-140E, ET-150E, ET-180E, ET-83, ET-102, ET-143, ET-160, ET-170, ET -190, ET-69, ET-89, ET-109, ET-129, ET-149, ET-159, ET-189, ET-65, ET-95, ET-115 ET-135, ET-165, ET-97, ET-107, ET-127, ET-147, ET-157, ET-167, ES-99, ES-129, ES-149, ES-169, ES- 99D, ES-129D, ES-149D, DS-601, YX-400, YX-500 and the like. Emulgit 9, 16, 25, 49, 100, 161 etc. Epan 410, 420, 450, 485, 610, 680, 710, 720, 740, 750, 785, U-103, U-105, U-108 etc. Sorgen TW-20, TW-60, TW-80, 90 etc. Lamigen ET-20, ET-70, ES-30, ES-60, ES-100 and the like.
[0033]
Sanyo Chemical Industries, Ltd .: New Pole PE-61, PE-62, PE-64, PE-68, PE-71, PE-74, PE-75, PE-78, PE-108, PE-128, and the like. Narrow Acty N-20, N-40, N-50, N-70, N-85, N-95, N-100, N-120, N-140, N-160, N-200, N-400, etc. . Nonipol 20, 40, 55, 60, 70, 85, 95, 100, 110, 120, 130, 140, 160, 200, 300, 400, etc. Emalmin 40, 50, 60, 70, NL-70, FL-80, 140, NL-110, 180, 200, 240, L-380 and the like. Sannonic SS-50, SD-50, FD-80, SS-70, DO-90, FD-140, SS-120, etc.
[0034]
Nippon Shokubai Co., Ltd .: Softanol 30, 50, 70, 90, 120, 150, 200, 300, 400, 500, EP5035, EP7025, EP7045, EP9050, etc.
[0035]
Nissin Chemical Industry Co., Ltd .: Surfynol 104E, 420, 440, 465, 485, etc. Olfin STG, E1004, E1010, etc. are mentioned.
[0036]
Examples of the water-soluble organic solvent according to the present invention include alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol), polyhydric alcohols (for example, ethylene glycol, diethylene glycol). , Triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol), polyhydric alcohol ethers (for example, ethylene glycol monomethyl ether, Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol Methyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, ethylene glycol mono Phenyl ether, propylene glycol monophenyl ether), amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine) , Tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine), amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocycles (eg, 2- Pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone), sulfoxides (for example, dimethyl sulfoxide) and the like.
[0037]
As the color material that can be used in the present invention, various color materials roughly classified into dyes and pigments can be used.
[0038]
Examples of the dye include oily dyes, disperse dyes, direct dyes, acid dyes, and basic dyes, but it is preferable to use oily dyes and disperse dyes from the viewpoint of the elution rate of the present invention. As the hue, yellow, magenta, cyan, black, blue, green, and red are preferably used, and yellow, magenta, cyan, and black dyes are particularly preferable. The oil-soluble dye includes a dye that exhibits oil-solubility by salting a water-soluble dye with a long-chain base.
[0039]
The oil-based dye is not limited to the following, and particularly preferable specific examples include, for example, Valifast Yellow 4120, Valifast Yellow 3150, Varifast Yellow 3108, Varifast Yellow 2310N, Varifast Yell 1101 manufactured by Orient Chemical Industries, Ltd. , Variast Red 3320, Variast Red 3304, Varifast Red 1306, Variast Blue 2610, Variast Blue 2606, Variast Blue 1603, Oil Yellow GG-S, Oil Yellow GG-S, Oil Yellow GG-S, Oil Yellow GG-S, Oil Yellow GG-S, Oil Yellow GG-S, Oil Yellow GG-S, Oil Yellow GG-S, Oil Yellow GG-S, Oil Yellow GG-S 105, Oil Scallet 308, Oil Red RR, Oil Red OG, Oil Red 5B, Oil Pink 312, Oil Blue BOS, Oil Blue 613, Oil Blue 2N, Oil Black BY, Oil Black BS, Oil Black 70, Oil Black 70, Oil Black BS Black 5906, Oil Black 5905,
Kayset Yellow SF-G, Kayase Yellow K-CL, Kayase Yellow GN, Kayase Yellow AG, Kayase Yellow 2G, Kayset Red SF-G, Kayset Red A-BLK , Kayset Magenta 312, Kayase Blue K-FL,
FS Yellow 1015, FS Magenta 1404, FS Cyan 1522, FS Blue 1504, C.I. I. Solvent Yellow 88, Solvent Yellow 83, Solvent Yellow 82, Solvent Yellow 79, Solvent Yellow 56, Solvent Yellow 29, Solvent Yellow 19, Solvent Yellow 16, Solvent Yellow 16, Solvent Yellow 04, Solvent Yellow 01, C.I. I. Solvent Red 84: 1, Solvent Red 84, Solvent Red 218, Solvent Red 132, Solvent Red 73, Solvent Red 72, Solvent Red 51, Solvent Red 43, Solvent Red 27, Solvent Red 24, Solvent Red 24, Solvent Red 24, Solvent Red 24, Solvent Red 24, Solvent Red 24, Solvent Red 24, Solvent Red 24, Solvent Red 24, Solvent Red 24, Solvent Red 24 . I. Solvent Blue 70, Solvent Blue 67, Solvent Blue 44, Solvent Blue 40, Solvent Blue 35, Solvent Blue 11, Solvent Blue 02, Solvent Blue 01, C.I. I. Solvent Black 43, Solvent Black 70, Solvent Black 34, Solvent Black 29, Solvent Black 27, Solvent Black 22, Solvent Black 7, Solvent Black 3, C.I. I. Solvent Violet 3, C.I. I. Solvent Green 3 and 7 etc. are mentioned.
[0040]
Further, metal complex dyes as shown in JP-A-9-277893, JP-A-10-20559, and JP-A-10-30061 are also preferably used, and a preferred structure is represented by the following general formula (1). Is.
[0041]
General formula (1)
M (Dye)_p(A)_m
In the formula, M represents a metal ion, and Dye represents a dye capable of coordinating with a metal. A represents a ligand other than a pigment, p represents an integer of 1 to 3, and m represents 0, 1, 2, or 3. When m is 0, p represents 2 or 3, in which case Dye may be the same or different. Examples of metal ions represented by M include metals belonging to Groups I to VIII of the periodic table, such as Al, Co, Cr, Cu, Fe, Mn, Mo, Ni, Sn, Ti, Pt, Pd, and Zr. And each ion of Zn. From the viewpoints of color tone and various durability, Ni, Cu, Cr, Co, Zn, and Fe ions are particularly preferable. More preferably, it is Ni ion. Various dye structures are conceivable as the dye capable of coordinating with the metal represented by Dye, but conjugated methine dyes, azomethine dyes, and those having a coordination group in the azo dye skeleton are preferred.
[0042]
The disperse dye is not limited to the following, but as a particularly preferred specific example, C.I. I. Disperse Yellow 5, 42, 54, 64, 79, 82, 83, 93, 99, 100, 119, 122, 124, 126, 160, 184: 1, 186, 198, 199, 204, 224 and 237; C . I. Disperse Orange 13, 29, 31: 1, 33, 49, 54, 55, 66, 73, 118, 119 and 163; C.I. I. Disperse Red 54, 60, 72, 73, 86, 88, 91, 92, 93, 111, 126, 127, 134, 135, 143, 145, 152, 153, 154, 159, 164, 167: 1, 177 , 181, 204, 206, 207, 221, 239, 240, 258, 277, 278, 283, 311, 323, 343, 348, 356 and 362; I. Disperse violet 33; C.I. I. Disperse Blue 56, 60, 73, 87, 113, 128, 143, 148, 154, 158, 165, 165: 1, 165: 2, 176, 183, 185, 197, 198, 201, 214, 224, 225 257, 266, 267, 287, 354, 358, 365 and 368; I. Disperse Green 6: 1 and 9 etc. are mentioned.
[0043]
The pigment is not limited to the following, but as a particularly preferred specific example, as carbon black pigment, No. manufactured by Mitsubishi Kasei Co., Ltd. can be used. 2300, no. 900, MCF-88, no. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, no. 2200B, Columbia-made Raven 700, Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Regal 400R from Cabot, Regal 330R, Regal 660R, Moul L, Monarch 700, M 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, Color Black FW1, Color Black FW2V, Color Black FW18, Color Black FW18, Color Black FW18, Color Black FW18, Color Black FW18 ck S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Printex 140V, Special Black 6, Special Black 5, Special Black 4, Special Black 4 -40, Maxsorb G-15, Maxsorb G-08, etc. can be used.
[0044]
Examples of yellow pigments include C.I. I. Pigment Yellow 1, C.I. I. Pigment Yellow 2, C.I. I. Pigment Yellow 3, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 16, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 73, C.I. I. Pigment Yellow 74, C.I. I. Pigment Yellow 75, C.I. I. Pigment Yellow 83, C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 95, C.I. I. Pigment Yellow 97, C.I. I. Pigment Yellow 98, C.I. I. Pigment Yellow 114, C.I. I. Pigment Yellow 128, C.I. I. Pigment Yellow 129, C.I. I. Pigment Yellow 151, C.I. I. Pigment Yellow 154,
Examples of magenta pigments include C.I. I. Pigment Red 5, C.I. I. Pigment Red 7, C.I. I. Pigment Red 12, C.I. I. Pigment Red 48 (Ca), C.I. I. Pigment Red 48 (Mn), C.I. I. Pigment Red 57 (Ca), C.I. I. Pigment Red 57: 1, C.I. I. Pigment Red 112, C.I. I. Pigment Red 123, C.I. I. Pigment Red 168, C.I. I. Pigment Red 184, C.I. I. Pigment Red 202,
Examples of cyan pigments include C.I. I. Pigment Blue 1, C.I. I. Pigment Blue 2, C.I. I. Pigment Blue 3, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 15:34, C.I. I. Pigment Blue 16, C.I. I. PigmentBlue 22, C.I. I. Pigment Blue 60, C.I. I. VatBlue 4, C.I. I. Vat Blue 60 etc. are mentioned.
[0045]
The colored fine particles according to the present invention can be prepared by various methods. For example, when the coloring material is a dye, an oil-soluble dye is dissolved in the monomer, emulsified in water, and then the dye is encapsulated in the polymer by polymerization. The polymer and the coloring material are dissolved in an organic solvent, Examples include a method of removing an organic solvent after emulsification in water, a method of adding porous polymer fine particles to a dye solution, and adsorbing and impregnating the dye to the fine particles. A so-called core-shell structure in which these colored fine particles are further coated with a polymer may be used.
[0046]
When the colorant is a pigment, the pigment is kneaded with the polymer, and then dispersed in an aqueous system to prepare a polymer-coated pigment core. After adding a solution in which the polymer is dissolved in an organic solvent to the pigment dispersion, the pressure is reduced. And a method of removing the solvent and coating the polymer. Furthermore, these colored fine particles can be further coated with a polymer to form a core-shell structure.
[0047]
As a method of providing a polymer shell, a method of adding a water-soluble polymer dispersant to an aqueous suspension of a core and adsorbing it, a method of gradually dropping a monomer and depositing it on the core surface simultaneously with polymerization, or a method of dissolving in an organic solvent There is a method in which a polymer is gradually dropped and adsorbed on the core surface simultaneously with precipitation. Furthermore, a method of forming a core shell in one step is also conceivable. For example, the core polymer and the coloring material are dissolved or dispersed in the shell polymer, polymerized after suspension in water, or emulsion polymerization while gradually dropping the liquid into water containing activator micelles. There are ways to go. Alternatively, there is a method in which a coloring material is dissolved or dispersed in a monomer that can become a core and a monomer that can become a shell after polymerization, and suspension polymerization or emulsion polymerization is performed.
[0048]
The colored fine particles according to the present invention may not be shelled or shelled, but those that are shelled in view of the effects of the present invention are more preferable. In that case, the amount of polymer used for the shell is preferably 5% by mass or more and 95% by mass or less of the total polymer amount. When the amount of the shell polymer is less than 5% by mass, the thickness of the shell is insufficient, and a part of the core containing a large amount of coloring material tends to appear on the particle surface. Moreover, when there are too many shell polymers, it will be easy to raise | generate the coloring material protection capability of a core. More preferably, it is 10 mass% or more and 90 mass% or less.
[0049]
The addition amount of the coloring material is preferably 20% by mass or more and 1000% by mass or less with respect to the total polymer amount. If the amount of the color material is too small compared to the polymer, the image density after ejection cannot be obtained, and if the amount of the color material is too large, the protective ability of the polymer cannot be sufficiently obtained.
[0050]
It is important to evaluate whether it is actually a core shell. In the present invention, since the individual particle diameter is as very small as 200 nm or less, the analysis method is limited from the viewpoint of resolution. As an analysis method that meets such a purpose, TEM, TOF-SIMS, or the like can be applied. When observing fine particles that have been core-shelled by TEM, the dispersion can be applied on a carbon support film, dried and observed. Since the observation image of TEM is usually monochrome, it is necessary to dye fine particles in order to evaluate whether or not the core shell is formed. Dye the fine particles of the core only, observe the TEM, and compare with the one provided with a shell. Further, the fine particles provided with the shell and the fine particles not provided are mixed and dyed, and it is confirmed whether or not the proportion of the fine particles having different dyeing degree matches the presence or absence of the shell. In TOF-SIMS, it is confirmed that by providing a shell on the particle surface, the amount of the coloring material near the surface is reduced as compared with the case of the core alone. When there is an element not contained in the polymer of the core shell in the color material, it can be confirmed whether or not a shell having a small color material content is provided using the element as a probe. In the absence of such elements, the colorant content in the shell can be compared with that without the shell using a suitable dye. The core-shell formation can be observed more clearly by embedding the core-shell particles in an epoxy resin, making an ultrathin section with a microtome, and performing staining. When there is an element that can be a probe in the polymer or the color material, the composition of the core shell and the distribution amount of the color material to the core and the shell can be estimated by TEM.
[0051]
The average particle size of the colored fine particles according to the present invention is preferably 200 nm or less from the viewpoint of stability, but more preferably 100 nm or less from the viewpoint of dispersion stability and ejection stability.
[0052]
As the use of the aqueous ink of the present invention, an inkjet ink is most preferable.
[0053]
In the present invention, in order to obtain a desired particle size, it is important to optimize each composition during preparation and to select an appropriate emulsification method. Although it varies depending on the color material and polymer used, since it is an underwater suspension type, the shell polymer generally needs to be more hydrophilic than the core polymer. Further, the coloring material contained in the shell polymer is preferably less than that in the core polymer, and the coloring material is also required to be less hydrophilic than the shell polymer. The hydrophilicity and hydrophobicity can be estimated using, for example, the solubility parameter (SP). For the solubility parameter, the value, measurement, and calculation method can be referred to the description from page 675 of POLYMER HANDBOOK 4th edition (John Wiley & Sons, Inc.).
[0054]
The polymer used for the colored fine particles preferably has a number average molecular weight of 500 to 100,000, particularly 1,000 to 30,000 from the viewpoint of film-forming properties after printing, durability and suspension formability.
[0055]
Although various kinds of Tg can be used for the polymer, it is preferable to use at least one polymer having a Tg of 10 ° C. or more.
[0056]
In the present invention, all generally known polymers can be used, but particularly preferred polymers are polymers containing an acetal group as a main functional group, a polymer containing a carbonate group, a polymer containing a hydroxyl group, And a polymer having an ester group. The above polymer may have a substituent, and the substituent may have a linear, branched, or cyclic structure. Various polymers having the above functional groups are commercially available, but can also be synthesized by a conventional method. These copolymers can also be obtained, for example, by introducing an epoxy group into one polymer molecule and then performing polycondensation with another polymer or graft polymerization using light or radiation.
[0057]
Examples of the polymer containing acetal as a main functional group include polyvinyl butyral resin. For example, # 2000-L, # 3000-1, # 3000-2, # 3000-4, # 3000-K, # 4000-1, # 4000-2, # 5000-A, # 5000 manufactured by Denki Kagaku Kogyo Co., Ltd. 6000-C, # 6000-EP, or BL-1, BL-1H, BL-2, BL-2H, BL-5, BL-10, BL-S, BL-SH, BX-10 manufactured by Sekisui Chemical Co., Ltd. , BX-L, BM-1, BM-2, BM-5, BM-S, BM-SH, BH-3, BH-6, BH-S, BX-1, BX-3, BX-5, KS -10, KS-1, KS-3, KS-5, and the like.
[0058]
The polyvinyl butyral resin is obtained as a derivative of PVA (polyvinyl alcohol), and the acetalization of the hydroxyl group of the original PVA is about 80 mol% at the maximum, and usually about 50 mol% to about 80 mol%. In addition, the acetal said here does not indicate a 1,1-diethoxyethane group in a narrow sense, but indicates a compound in general with orthoaldehyde. The hydroxyl group is not particularly specified, but it is preferably contained at 10-40 mol%. Moreover, although there is no prescription | regulation in particular in the content rate of an acetyl group, it is preferable that it is 10 mol% or less. The polymer containing acetal as a main functional group means that at least 30 mol% or more of oxygen atoms contained in the polymer forms an acetal group. In addition, Iupital series manufactured by Mitsubishi Engineering Plastics Co., Ltd. can be used as a polymer containing acetal as a main functional group. Polycarbonate resin is mentioned as a polymer which contains carbonate ester as a main functional group. For example, there are Iupilon series and Novalex series manufactured by Mitsubishi Engineering Plastics. The Iupilon series is made with bisphenol A as a raw material, and various molecular weights can be used although the values differ depending on the measurement method. In the NOVAREX series, those having a molecular weight of 20,000 to 30,000 and a glass transition point of around 150 ° C. can be used, but are not limited thereto.
[0059]
The polymer containing a carbonate group as a main functional group means that at least 30 mol% or more of oxygen atoms contained in the polymer contribute to the formation of the carbonate group.
[0060]
Examples of the polymer containing a hydroxyl group as a main functional group include PVA. Although the solubility of PVA in organic solvents is often small, the solubility in organic solvents increases with PVA having a low saponification value. PVA having high water solubility can be used by adding it to the aqueous phase and adsorbing it to the polymer suspension after removing the organic solvent.
[0061]
Commercially available PVA can be used, for example, Kuraray's Poval PVA-102, PVA-117, PVA-CSA, PVA-617, PVA-505, and other special brands of sizing agents, PVA As the PVA for molding and other functional polymers, KL-506, C-118, R-1130, M-205, MP-203, HL-12E, SK-5102, and the like can be used. The saponification degree is generally 50 mol% or more, but even when it is about 40 mol% as in LM-10HD, it can be used. In addition to PVA, those having a hydroxyl group as a main functional group can be used, but those having at least 20 mol% or more of oxygen atoms contained in the polymer can be used.
[0062]
Examples of the polymer containing an ester group as a main functional group include a methacrylic resin. Asahi Kasei Delpet series 560F, 60N, 80N, LP-1, SR8500, SR6500, etc. can be used. A polymer containing an ester group as a main functional group means that at least 30 mol% or more of oxygen atoms contained in the polymer form an ester group. These polymers may be used alone or in combination of two or more. Moreover, as long as 50% or more of these polymers are contained by mass ratio, the other polymer and the inorganic filler may be contained. Although it is also preferable to use a copolymer of these polymers, for example, as a method of copolymerizing a polymer containing a hydroxyl group and various polymers, the hydroxyl group is reacted with a monomer having an epoxy group such as glycidyl methacrylate, It can be obtained by copolymerization with a methacrylic acid ester monomer by suspension polymerization.
[0063]
In the water-based ink of the present invention, the polymer used for the colored fine particles is preferably blended in the ink in an amount of 0.5 to 50% by mass, and more preferably 0.5 to 30% by mass. If the blending amount of the polymer is less than 0.5% by mass, the color material cannot be protected sufficiently. If it exceeds 50% by mass, the storage stability of the suspension ink may be reduced, or the tip of the nozzle may The printer head may be clogged due to ink thickening or suspension aggregation caused by ink evaporation, so it is preferably within the above range.
[0064]
On the other hand, the colorant is preferably blended in the ink in an amount of 1 to 30% by mass, more preferably 1.5 to 25% by mass. If the blending amount of the coloring material is less than 1% by mass, the printing density is insufficient, and if it exceeds 30% by mass, the suspension stability with time decreases and the particle size tends to increase due to aggregation. It is preferable to be within the range.
[0065]
The water-based ink of the present invention comprises a suspension of a polymer containing water as a medium and encapsulating the coloring material. The suspension includes various conventionally known additives such as wetting agents such as polyhydric alcohols, dispersants, silicones. An antifoaming agent such as a system, an antifungal agent such as a chloromethylphenol and / or a chelating agent such as EDTA, an oxygen absorbent such as sulfite, and the like may be contained.
[0066]
Here, as the wetting agent, for example, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, glycerin, diethylene glycol diethyl ether, diethylene glycol mono n-butyl ether, ethylene glycol monomethyl ether, ethylene glycol mono Multivalents such as ethyl ether, ethylene glycol monobutyl ether, methyl carbitol, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, diethyl carbitol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether Alcohol and its ethers, acetates, - can be used methyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, triethanolamine, formamide, nitrogen-containing compounds such as dimethyl formamide, dimethyl monkey sulfoxide one or two or more kinds. Although there is no restriction | limiting in particular in the compounding quantity of these wetting agents, Preferably 0.1-50 mass% can be mix | blended in the said ink, More preferably, 0.1-30 mass% can be mix | blended.
[0067]
Further, the dispersant is not particularly limited. However, when the HLB value is 8 to 18, an effect as a dispersant is exhibited, and an increase in suspension particle diameter is suppressed. preferable.
[0068]
A commercial item can also be used as a dispersing agent. Examples of such commercially available products include dispersant Demol SNB, MS, N, SSL, ST, and P (trade names) manufactured by Kao Corporation.
[0069]
Although there is no restriction | limiting in particular in the compounding quantity of a dispersing agent, It is preferable to mix | blend 0.01-10 mass% in the water-based ink of this invention. When the compounding amount of the compound is less than 0.01% by mass, it is difficult to reduce the particle size of the suspension. When the compounding amount exceeds 10% by mass, the particle size of the suspension increases or the suspension stability decreases, and the gelation occurs. Therefore, it is preferable to be within the above range. Moreover, as said antifoamer, a commercial item can be used without a restriction | limiting in particular. Examples of such commercially available products include KF96, 66, 69, KS68, 604, 607A, 602, 603, KM73, 73A, 73E, 72, 72A, 72C, 72F, 82F, 70, 71 manufactured by Shin-Etsu Silicone. 75, 80, 83A, 85, 89, 90, 68-1F, 68-2F (trade name), and the like. Although there is no restriction | limiting in particular in the compounding quantity of these compounds, It is preferable to mix | blend 0.001-2 mass% in the colored fine particle containing aqueous ink of this invention. If the compounding amount of the compound is less than 0.001% by mass, bubbles are likely to be generated at the time of preparing the ink, and it is difficult to remove small bubbles in the ink. During printing, repellency may occur in the ink and the print quality may be deteriorated.
[0070]
Next, a method for producing the water-based ink of the present invention will be described.
The water-based ink of the present invention can be produced by various emulsification methods. Various methods can be used as the emulsification method. Examples thereof are summarized in the description on page 86 of “Advances in Functional Emulsifier / Emulsification Technology and Application Development CMC”. In the present invention, it is particularly preferable to use an emulsifying and dispersing apparatus using ultrasonic waves, high-speed rotational shearing, and high pressure.
[0071]
In the emulsification dispersion using ultrasonic waves, two types of so-called batch type and continuous type can be used. The batch method is suitable for producing a relatively small amount of sample, and the continuous method is suitable for producing a large amount of sample. In the continuous type, for example, an apparatus such as UH-600SR (manufactured by SMT Co., Ltd.) can be used. In the case of such a continuous system, the ultrasonic wave irradiation time can be obtained by the volume of the dispersion chamber / flow velocity × the number of circulations. In the case where there are a plurality of ultrasonic irradiation apparatuses, the total irradiation time is also obtained. The ultrasonic irradiation time is actually required for 3 seconds or more, and if the emulsification is completed within that time, an ultrasonic emulsification dispersion apparatus is not required. Further, if it is necessary for 10000 seconds or more, the load on the process is large, and in practice, it is necessary to shorten the emulsification dispersion time by reselecting the emulsifier. Therefore, more than 10,000 seconds are not necessary. More preferably, it is 10 seconds or more and 2000 seconds or less.
[0072]
As an emulsifying and dispersing apparatus using high-speed rotational shearing, a disperser mixer as described on pages 255 to 256 of “Functional emulsifier / emulsification technology and application development CMC”, or as described on page 251 Homomixers such as those described on page 256 can be used. These types can be properly used depending on the liquid viscosity at the time of emulsification dispersion. In the emulsification disperser using these high-speed rotary shears, the rotational speed of the stirring blade is important. Since the clearance with the stator is usually about 0.5 mm and cannot be made extremely narrow, the shearing force mainly depends on the peripheral speed of the stirring blade. If the peripheral speed is 5 m / S or more and 150 m / S or less, it can be used for emulsification and dispersion according to the present invention. This is because when the peripheral speed is low, it is often impossible to reduce the particle size even if the emulsification time is extended, and in order to achieve 150 m / S, it is necessary to extremely improve the performance of the motor. More preferably, it is 20-100 m / s.
[0073]
For emulsification and dispersion at high pressure, LAB2000 (manufactured by SMT) can be used, but the emulsification / dispersion ability depends on the pressure applied to the emulsion. Pressure is 1x10^FourkPa ~ 5 × 10^FiveA range of kPa is preferred. Moreover, it can emulsify and disperse | distribute several times as needed, and can obtain the target particle size. If the pressure is too low, the target particle size is often not achieved no matter how many times emulsification and dispersion is carried out.^FiveIn order to increase the pressure to kPa or more, a large load is applied to the apparatus, which is not practical. More preferably, 5 × 10^FourkPa ~ 2 × 10^FivekPa.
[0074]
These emulsifying / dispersing devices may be used alone or in combination as necessary. Colloid mills and flow jet mixers alone cannot achieve the object of the present invention, but by combining with the apparatus of the present invention, it is possible to enhance the effects of the present invention, such as enabling emulsification and dispersion in a single hour. is there.
[0075]
Moreover, the water-based ink of the present invention can be produced by so-called phase inversion emulsification in addition to using the above-described apparatus. Here, in the phase inversion emulsification, the polymer is dissolved in an organic solvent such as an ester or a ketone together with the dye, a neutralizing agent is added as necessary to ionize carboxyl groups in the polymer, and then the aqueous phase is After the addition, the organic solvent is distilled off and the phase is changed to an aqueous system.
[0076]
After the phase inversion is completed, the system is heated under reduced pressure to remove the ester and ketone solvents, and to remove a predetermined amount of water, thereby providing the colored fine particle-containing aqueous ink of the present invention having a desired concentration. Is obtained.
[0077]
The water-based ink of the present invention can be used as ink for writing instruments such as general fountain pens, ballpoint pens, sign pens, etc., in addition to ink for inkjet recording. The suspension of the present invention can be dried to obtain a fine powder. The obtained powder can be used for toner for electrophotography.
[0078]
【Example】
Next, the aqueous ink of the present invention will be described in more detail by way of examples, but the present invention is not limited to these.
[0079]
Example 1
<Resin synthesis>
(Synthesis of Resin R-1)
A 3 liter four-necked flask is equipped with a dropping device, a thermometer, a nitrogen gas inlet tube, a stirrer and a reflux condenser, and 1000 g of ethyl acetate is heated to reflux, 500 g of styrene, 200 g of 2-ethylhexyl acrylate, and soybean oil A mixed solution of 300 g of fatty acid-modified glycidyl methacrylate and 1 g of N, N · mes-azobisisovaleronitrile was dropped over 2 hours and reacted at the same temperature for 15 hours to obtain an ethyl acetate solution of resin R-1. .
[0080]
(Synthesis of resins R-2 to R-4)
Resins R-2 to R-4 were synthesized in the same manner except that the monomer composition was changed as shown in Table 1 in the synthesis of the resin R-1.
[0081]
In addition, the detail of the monomer of Table 1 is shown below, Moreover, the numerical value as described in Table 1 is the mass%.
ST: Styrene
MMA: Methyl acrylate
SMA: Stearyl methacrylate
EHA: 2-ethylhexyl acrylate
AAEM: 2-acetoxyethyl methacrylate
FGA: Soybean oil fatty acid modified glycidyl methacrylate
[0082]
[Table 1]

[0083]
    << Preparation of colored fine particle dispersion >>
  (Preparation of colored fine particle dispersion 1-1:Reference example)
  4.6 g of polyvinyl butyral (BL-S manufactured by Sekisui Chemical Co., Ltd., average polymerization degree 350), 3.1 g of C.I. I. Solvent Yellow 88 and 45 g of ethyl acetate were placed in a separable flask, and the flask was filled with N.₂Then, the polymer and the dye were completely dissolved by stirring. Subsequently, 90 g of an aqueous solution containing 2.6 g of sodium lauryl sulfate was dropped and stirred, and then emulsified for 300 seconds using an ultrasonic disperser (UH-150 type, manufactured by SMT Co., Ltd.). Thereafter, ethyl acetate was removed under reduced pressure to obtain a colored fine particle dispersion 1-1 impregnated with a yellow dye. The average particle diameter of the colored fine particles in the dispersion was 90 nm. The particle size is measured using a laser particle size analysis system manufactured by Otsuka Electronics, and is expressed as a volume average particle size.
[0084]
  (Preparation of colored fine particle dispersion 1-2:Reference example)
  A colored fine particle dispersion 1-2 was obtained in the same manner as in the preparation of the colored fine particle dispersion 1-1 except that the amount of sodium lauryl sulfate was changed to 1.9 g. The average particle size was 92 nm.
[0085]
(Preparation of colored fine particle dispersion 1-3: Comparative example)
Comparative colored fine particle dispersion 1-3 was obtained in the same manner except that the amount of polyvinyl butyral was changed to 1.9 g in the preparation of colored fine particle dispersion 1-1. The average particle size was 175 nm.
[0086]
  (Preparation of colored fine particle dispersion 2-1:Reference example)
  0.15 g of potassium persulfate is added to the core-type colored fine particle dispersion 1-2 prepared above and dissolved, and after heating to 80 ° C. with a heater, 1.5 g of styrene and 1 The mixture was reacted for 8 hours while dropping a mixed solution of 0.5 g of 2-hydroxyethyl methacrylate to obtain a colored fine particle dispersion 2-1 of a core-shell type yellow dye. The average particle size was 93 nm.
[0087]
  (Preparation of colored fine particle dispersion 2-2: the present invention)
  0.1 g of powdered activated carbon was added to the prepared core-shell type colored fine particle dispersion 2-1.(Inorganic adsorbent)After stirring at room temperature for 2 hours, the mixture was filtered through a 0.8 μm membrane filter to obtain a colored fine particle dispersion 2-2. The average particle size was 93 nm.
[0088]
(Preparation of colored fine particle dispersion 2-3: the present invention)
To the prepared core-shell type colored fine particle dispersion 2-1, 0.3 g of powdered activated carbon was added and stirred at room temperature for 2 hours, followed by filtration through a 0.8 μm membrane filter to obtain a colored fine particle dispersion 2- 3 was obtained. The average particle size was 93 nm.
[0089]
(Preparation of colored fine particle dispersion 2-4: comparative example)
In the preparation of the colored fine particle dispersion 2-1, a comparative colored fine particle dispersion was similarly obtained except that the addition amount of polyvinyl butyral used for the preparation of the core type colored fine particle dispersion 1-2 was changed to 1.9 g. A liquid 2-4 was obtained. The average particle size was 180 nm.
[0090]
  (Preparation of colored fine particle dispersion 3-1:Reference example)
  12 g of ethyl acetate solution containing 6 g of resin R-1 and 3 g of C.I. I. Solvent Yellow 201, 3 g C.I. I. Solvent Yellow 162 and 80 g of ethyl acetate were put into a separable flask, and the flask was filled with N.₂And the mixture was stirred to completely dissolve the dye. Next, 180 g of an aqueous solution containing 2 g of sodium lauryl sulfate was dropped and stirred, and then emulsified for 300 seconds using an ultrasonic disperser. Thereafter, ethyl acetate was removed under reduced pressure to obtain a colored fine particle dispersion.
[0091]
Next, N inside the flask₂And then heated to 80 ° C. with a heater, and dropwise added a mixed solution of 3 g styrene, 1 g 2-hydroxyethyl methacrylate and 0.5 g N, N · mes-azobisisovaleronitrile. The mixture was reacted for 6 hours to obtain a colored fine particle dispersion 3-1 of a core-shell type yellow dye. The average particle size was 30 nm.
[0092]
  (Preparation of colored fine particle dispersion 3-2:Reference example)
  20 ml of synthetic resin SP207 (manufactured by Mitsubishi Chemical Corporation) was added to the colored fine particle dispersion 3-1 prepared above and stirred at room temperature for 2 hours. Then, the synthetic resin was separated with a 1 μm filter paper, and the colored fine particle dispersion was obtained. 3-2 was obtained. The average particle size was 31 nm.
[0093]
  (Preparation of colored fine particle dispersion 3-3:Reference example)
  In the preparation of the colored fine particle dispersion 3-1, a core-shell colored fine particle dispersion was obtained in the same manner except that the resin R-1 was changed to 3.5 g of polyvinyl butyral BL-S. Next, 20 ml of synthetic resin SP207 (manufactured by Mitsubishi Chemical Corporation) was added to this colored fine particle dispersion, and the mixture was stirred at room temperature for 2 hours. Then, the synthetic resin was separated with a 1 μm filter paper, and colored fine particle dispersion 3-3 Got. The average particle size was 125 nm.
[0094]
  (Preparation of colored fine particle dispersion 3-4:Reference example)
  Comparative colored fine particle dispersion 3-4 was obtained in the same manner as in the preparation of colored fine particle dispersion 3-1, except that resin R-1 was changed to 2.0 g of polyvinyl butyral BL-S. The average particle size was 180 nm
[0095]
  (Preparation of colored fine particle dispersion 3-5:Reference example)
  A comparative colored fine particle dispersion 3-5 was obtained in the same manner as in the preparation of the colored fine particle dispersion 3-2 except that the amount of the synthetic resin SP207 was changed to 50 ml. The average particle size was 190 nm.
[0096]
  (Preparation of colored fine particle dispersion 4-1:Reference example)
  3.5 g of polyvinyl butyral BL-S, 4 g of C.I. I. Solvent Blue 70 and 40 g of ethyl acetate were placed in a separable flask, and the flask was filled with N.₂Then, the polymer and the dye were completely dissolved by stirring. Next, 90 g of an aqueous solution containing 1.6 g of sodium lauryl sulfate was dropped and stirred, and then emulsified for 300 seconds using an ultrasonic disperser. Thereafter, ethyl acetate was removed under reduced pressure to obtain a colored fine particle dispersion.
[0097]
Next, N inside the flask₂After heating to 80 ° C. with a heater, 1.5 g of styrene, 0.5 g of 2-hydroxyethyl methacrylate and 0.1 g of N, N · mes-azobisisovaleronitrile were added. The mixture was allowed to react for 6 hours while dropping the mixture to obtain a colored fine particle dispersion 4-1 of a core-shell cyan dye. The average particle size was 120 nm.
[0098]
  (Preparation of colored fine particle dispersion 4-2:Reference example)
  20 ml of the synthetic resin SP207 was added to the colored fine particle dispersion 4-1 prepared above and stirred at room temperature for 2 hours, and then the synthetic resin was separated with a 1 μm filter paper to obtain a colored fine particle dispersion 4-2. The average particle size was 120 nm.
[0099]
  (Preparation of colored fine particle dispersion 4-3:Reference example)
  8 g of ethyl acetate solution containing 4 g of resin R-2, 4 g of C.I. I. Solvent Blue 70 and 40 g of ethyl acetate were placed in a separable flask, and the flask was filled with N.₂And the mixture was stirred to completely dissolve the dye. Subsequently, 90 g of an aqueous solution containing 1.6 g of sodium lauryl sulfate was dropped, and then emulsified for 300 seconds using an ultrasonic disperser. Thereafter, ethyl acetate was removed under reduced pressure to obtain a colored fine particle dispersion. To this colored fine particle dispersion, 10 ml of synthetic resin SP207 was added and stirred at room temperature for 2 hours, and then the synthetic resin was separated with 1 μm filter paper.
[0100]
Next, N inside the flask₂After heating to 80 ° C. with a heater, 1.5 g of styrene, 0.5 g of 2-hydroxyethyl methacrylate and 0.1 g of N, N · mes-azobisisovaleronitrile were added. The mixture was allowed to react for 6 hours while dropping the liquid mixture to obtain a core-shell type colored fine particle dispersion 4-3. The average particle size was 22 nm.
[0101]
  (Preparation of colored fine particle dispersion 4-4:Reference example)
  In the preparation of the colored fine particle dispersion 4-3, a colored fine particle dispersion 4-4 was obtained in the same manner except that the addition amount of the synthetic resin SP207 was changed to 40 ml. The average particle size was 20 nm.
[0102]
  (Preparation of colored fine particle dispersion 5-1:Reference example)
  C. finely dispersed at 100 nm as an average particle size. I. 1.5 g of potassium persulfate was dissolved in a dispersion containing 50 g of Pigment Red 122, heated to 80 ° C. with a heater, and then further 20 g of styrene and 20 g of 2-hydroxyethyl methacrylate. The mixture was allowed to react for 7 hours while dropping the mixed solution to obtain a colored fine particle dispersion 5-1 of a magenta pigment coated with a pigment shell. The average particle size was 110 nm.
[0103]
(Preparation of colored fine particle dispersion 5-2: comparative example)
A comparative colored fine particle dispersion 5-2 was prepared in the same manner as in the preparation of the colored fine particle dispersion 5-1, except that styrene was reduced to 8 g and 2-hydroxyethyl methacrylate was reduced to 8 g. The average particle size was 210 nm.
[0104]
(Preparation of colored fine particle dispersion 6-1: the present invention)
12 g of ethyl acetate solution containing 6 g of resin R-1, 3 g of MS Red G (manufactured by Mitsui Chemicals), 3 g of Last Red 8375 (manufactured by Arimoto Chemical) and 80 g of ethyl acetate are placed in a separable flask and stirred. The dye was completely dissolved. Next, 180 g of an aqueous solution containing 2 g of sodium lauryl sulfate was dropped, and then emulsified for 300 seconds using an ultrasonic disperser. Thereafter, ethyl acetate was removed under reduced pressure to obtain a colored fine particle dispersion. To this colored fine particle dispersion, 20 ml of synthetic resin SP207 was added and stirred at room temperature for 2 hours, and then the synthetic resin was separated with 1 μm filter paper.
[0105]
Next, N inside the flask₂And then heated to 80 ° C. with a heater, and dropwise added a mixed solution of 3 g styrene, 1 g 2-hydroxyethyl methacrylate and 0.5 g N, N · mes-azobisisovaleronitrile. The mixture was then reacted for 6 hours to obtain a colored fine particle dispersion 6-1 of a core-shell type magenta dye. The average particle size was 35 nm.
[0106]
(Preparation of colored fine particle dispersion 6-2: comparative example)
In the preparation of the colored fine particle dispersion 6-1, the resin R-1 was changed to the resin R-4, and the treatment with the synthetic resin SP207 was omitted. Got. The average particle size was 150 nm.
[0107]
(Preparation of colored fine particle dispersion 7-1: the present invention)
12 g of an ethyl acetate solution containing 6 g of resin R-3, 6 g of Oil Black 860 (manufactured by Orient Chemical Co., Ltd.) and 80 g of ethyl acetate were placed in a separable flask and stirred to completely dissolve the dye. Next, 180 g of an aqueous solution containing 2 g of sodium lauryl sulfate was dropped, and then emulsified for 300 seconds using an ultrasonic disperser. Thereafter, ethyl acetate was removed under reduced pressure to obtain a colored fine particle dispersion.
[0108]
Next, N inside the flask₂And then heated to 80 ° C. with a heater, and dropwise added a mixed solution of 3 g styrene, 1 g 2-hydroxyethyl methacrylate and 0.5 g N, N · mes-azobisisovaleronitrile. The reaction was continued for 6 hours. Next, 40 ml of synthetic resin SP207 was added and stirred at room temperature for 2 hours, and then the synthetic resin was separated with a 1 μm filter paper to obtain a core-shell type black dye colored fine particle dispersion 7-1. The average particle size was 33 nm.
[0109]
(Preparation of colored fine particle dispersion 7-2: Comparative example)
In the preparation of the colored fine particle dispersion 7-1, a comparative colored fine particle dispersion 7-2 was used in the same manner except that the resin R-4 was used instead of the resin R-3 and the treatment with the synthetic resin SP207 was omitted. Got. The average particle size was 160 nm.
[0110]
<< Preparation of water-based ink >>
As each of the prepared colored fine particle dispersions, the yellow colored fine particle dispersion was 60% by mass, the magenta colored fine particle dispersion was 60% by mass, the cyan colored fine particle dispersion was 68% by mass, and the black colored fine particle dispersion was 68% by mass. Weigh each, add ethylene glycol 15% by mass, glycerin 15% by mass, Surfynol 465 0.5% by mass, Proxel GX 0.1% by mass, and adjust the addition amount so that the remainder is pure water Thus, 100 g of water-based ink was prepared for each. Next, each aqueous ink was filtered through a 0.8 μm membrane filter to remove dust and coarse particles, thereby obtaining an aqueous ink.
[0111]
<< Measurement and evaluation of water-based ink >>
The following measurement and evaluation were performed on the prepared water-based ink.
[0112]
(Quantification of coloring materials for each water-based ink)
With respect to the color material in each water-based ink prepared as described above, the amount of the color material that was not included in the resin fine particles but was dispersed or dissolved, and the amount of the color material adsorbed on the surface of the resin fine particles were quantified.
[0113]
For dye-colored fine particles, ethyl acetate was used as a color material solubilizer, and for pigment-colored fine particles, 80% sulfuric acid was used, and the conditions described above were ink: color material solubilizer = 1: 19 (mass ratio). Absorbance was measured according to the method. Absorbance is monitored every 30 seconds using MCPD-2000 (manufactured by Otsuka Electronics Co., Ltd.), the absorbance at the point when the increase in absorbance is no longer observed is 1, and the absorbance is displayed at each time, which is normalized absorbance. It was. For pigment-colored fine particles, sample every hour, quickly neutralize with sodium hydroxide, separate the solid content with an ultracentrifuge, measure the spectrophotometer of the filtrate filtered through a 0.45 μm membrane filter, and dye The normalized absorbance was determined in the same manner as the colored fine particles. From the obtained absorbance curve shown in FIG. 1, the standard absorbance at the bending point a in the first stage (I) and the second stage (II) is defined as the amount of the color material dispersed or dissolved in the ink. The difference between the bending point b in the second stage (II) and the third stage (III) and the bending point a was defined as the amount of color material adsorbed on the surface of the colored fine particles. The amount of the color material not encapsulated in the colored fine particles defined in the present invention means the total amount of the color material amount dispersed or dissolved in the ink and the color material amount adsorbed on the surface of the colored fine particles.
[0114]
The measurement was performed for water-based inks 1-1 to 1-3, 2-1 to 2-4, 5-1, 5-2, 6-1, 6-2, 7-1, and 7-2.
[0115]
(Measurement of surface tension of water-based ink)
According to a conventional method, the surface tension (mN / m) is measured using a commercially available interfacial tension measuring device. For water-based inks, water-based inks 3-1 to 3-5 and water-based inks 4-1 to 4-4 are used. For the colored fine particle dispersion, the colored fine particle dispersions 4-1 to 4-4 were used.
[0116]
(Measurement of particle size distribution of colored fine particles in water-based ink)
With respect to the prepared water-based ink, the particle size distribution of the colored fine particles was measured using a Malvern Zetasizer 1000, and the volume ratio of the particles entering the region having a particle size of 0.1 to 50 nm was calculated. The measurement was performed for water-based inks 3-1 to 3-5 and 4-1 to 4-4.
[0117]
(Evaluation of stagnation stability of water-based ink)
Each water-based ink prepared above was subjected to a forced deterioration treatment at 60 ° C. for 1 week, and then the average particle size was measured using a laser particle size analysis system manufactured by Otsuka Electronics, and the particle size variation rate was determined by the following equation: The stagnation stability was evaluated according to the following criteria.
[0118]
Variation rate of particle size = average particle size after forced deterioration / average particle size before forced deterioration × 100 (%)
A: Particle size variation rate is 100 to less than 120%
○: The particle size variation rate is less than 120 to 150%.
(Triangle | delta): A particle size variation rate is 150 to less than 200%
X: Particle size variation rate is 200 or more
<Inkjet image printing and image evaluation>
(Image printing)
Each water-based ink is loaded into an Epson inkjet printer (PM-830C), and a solid image and a wedge image in which the density is changed stepwise are output to Konica photo jet paper Photolike QP glossy paper (manufactured by Konica Corporation). According to the following method, the emission stability and the glossiness, light resistance, and water resistance of the obtained image were evaluated.
[0119]
(Evaluation of output stability)
A continuous emission with the printer and no nozzle missing for 10 minutes or more were marked with ○ (acceptable level), and those with less than that were marked with × (impossible level).
[0120]
(Glossiness evaluation)
For each printed image, visual sensory evaluation by 10 monitors was performed according to the following criteria, and the average value was obtained.
[0121]
1: The image has a rough feeling
2: Glossy when viewed from the front, but rough when viewed from an angle
3: Glossy when viewed from the front or obliquely
The higher the average value, the better the glossiness.
[0122]
(Evaluation of light resistance)
The wedge image with the density changed stepwise was subjected to an exposure process using a low temperature Xe weather meter XL75 (manufactured by Suga Test Instruments) as a test machine. The change in density was measured using X-Rite 900 (manufactured by Nippon Flat Plate Equipment), and the change in density when the print density was around 1.0 was measured. For samples with insufficient concentration, the change in concentration at the highest concentration portion was measured. When the coloring material is a dye, after the continuous exposure for one week, the remaining 70% or more from the concentration of the unexposed sample is ◎, and the remaining 70% to 50% is ○ ( Allowable level), and less than that is x (impossible level).
[0123]
In addition, when the colorant is a pigment, after 40 days of continuous exposure, those that remain 90% or more from the concentration of the unexposed oblique sample are ○ (acceptable level), and those that are less than × (impossible level) It was.
[0124]
(Evaluation of water resistance)
Drop water with a micropipette on each solid print image, and rub with your finger 1 minute later to visually check if the print is distorted. And it was set to the impossible level.
[0125]
The results obtained above are shown in Tables 2 to 5.
[0126]
[Table 2]

[0127]
[Table 3]

[0128]
[Table 4]

[0129]
[Table 5]

[0130]
As is clear from the results of Tables 2 to 5, the aqueous ink using the colored fine particle aqueous dispersion of the present invention is superior in the storage stability and emission of the aqueous ink to the comparative example, and the formed image. It is understood that the glossiness, light resistance, and water resistance are excellent.
[0131]
Example 2
(Preparation of ink set)
Among the water-based inks prepared in Example 1, water-based ink 2-3 (yellow dye ink: Y), water-based ink 4-4 (cyan dye ink: C), and water-based ink 6-1 (ink) of the present invention. Magenta dye ink: M) and water-based ink 7-1 (black dye ink: K) are used as dark inks. Further, for magenta and cyan dye inks, the dye concentration is 1/4 of the dark ink, Further, 20% by mass of ethylene glycol and 20% by mass of glycerin were added as solvents to prepare light magenta dye ink (LM) and light cyan dye ink (LC) as light color inks. As comparative inks, water-based ink 1-3 (yellow dye ink: Y ′), water-based ink 4-1 (cyan dye ink: C ′), water-based ink 6-2 (magenta dye ink: M ′), water-based ink 7-2 (black dye ink: K ′) is used as each dark color ink. Further, for magenta and cyan dye inks, light magenta dye ink (LM ′), which is a light color ink, and light cyan are used in the same manner as described above. A dye ink (LC ′) was prepared.
[0132]
Using the above dye inks, ink sets 1 to 3 were prepared in the following combinations.
[0133]
Ink set-1: Y ', M', C ', K', LM ', LC' (all six dye inks are comparative examples)
Ink set-2: Of ink set-1, only dark ink uses M, C, LM, LC (only dark ink is dye ink of the present invention)
Ink set-3: Y, M, C, K, LM, LC (all six color dye inks are dye inks of the present invention)
(Printing and evaluation of inkjet images)
Each ink set prepared above is loaded into an Epson inkjet printer (PM-830C), and a color chart image is output to Konica Photojet Paper Photolike QP glossy paper (manufactured by Konica Corporation), and color reproduction is performed according to the following method. Sexuality was evaluated.
[0134]
(Evaluation of color gamut)
For the output color mixture chart, the color gamut at lightness 50 is expressed as L^*, A^*, B^*L of each ink set when ink set-1 is 1.00^*, A^*, B^*The relative color reproduction range was determined, and the obtained results are shown in Table 6.
[0135]
[Table 6]

[0136]
As is apparent from Table 6, it can be seen that the image output by the ink set using the water-based ink of the present invention has a color reproduction range wider than that of the comparative example and has excellent color reproducibility.
[0137]
【The invention's effect】
According to the present invention, it is possible to provide a water-based ink excellent in dispersion stability, no problem in ejection stability, excellent in water resistance, light resistance, and color reproducibility, and an image forming method using the same.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an example of an absorbance curve obtained from a solution of ink and a coloring material dissolving agent.

Claims (9)

In an aqueous ink in which colored fine particles comprising a resin containing or coated with a color material are dispersed in water, the colored fine particles are treated with an organic adsorbent or an inorganic adsorbent, and are measured in the ink and the color measured by the following method. A water-based ink characterized in that the amount of color material adsorbed on the surface of fine particles is 10% or less of the total amount of color material.
Measurement method: Using a dye-dissolving agent that dissolves 30 to 100 g / L of a colorant at 20 ° C., and measuring the colorant absorbance of the mixture of aqueous ink: dye-dissolving agent = 1: 19 (mass ratio), And the amount of color material adsorbed on the surface of the colored fine particles is calculated. 2. The water-based ink according to claim 1, wherein the amount of the color material adsorbed on the surface of the colored fine particles is 5% or less of the total amount of the color material. 3. The water-based ink according to claim 1 , wherein a surface tension is 25 to 50 mN / m, and 80% by volume or more of the colored fine particles are distributed in a range of 1 to 50 nm as a particle diameter. . The surface tension of the colored fine particle dispersion excluding the water-soluble organic solvent and the non-reactive nonionic surfactant is 35 to 60 mN / m, according to any one of claims 1 to 3. Water based ink. The water-based ink according to any one of claims 1 to 4 , wherein the coloring material is a dye . The coloring material, an aqueous ink according to any one of claims 1 to 4, characterized in that a pigment. The colored particles, an aqueous ink according to any one of claims 1 to 6, wherein that you have have a core-shell structure. The aqueous ink according to any one of claims 1 to 7, characterized in that the ink jet ink. An image forming method, comprising: ejecting the water-based ink according to any one of claims 1 to 8 as droplets from an inkjet head based on a digital signal and attaching the droplets to an ink receiving medium .

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