JP2004204029A - Colored microparticle dispersion, water-based ink, and method of image formation using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a colored microparticle dispersion excellent in dispersibility, storage stability and jet stability affording small-sized colored microparticles, to provide a water-based ink, and to provide a method of image formation affording high-quality images. <P>SOLUTION: The colored microparticle dispersion is obtained by dispersing colored microparticles prepared by mixing a coloring material with polymers in water. In this dispersion, at least one of the polymers is obtained by polymerizing a polymerizable monomer of the general formula(a) in the presence of a surfactant. Formula (a): CH<SB>2</SB>=C(X)-Y-(AO)<SB>n</SB>-Z( wherein, X is hydrogen atom or methyl; Y is a ≤9C linkage group; Z is an anionic group; AO is an alkylene oxide group; and n is an integer of 1-30 ). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００５１】
上記一般式（１）において、Ｒ¹は炭素原子数７〜２０の直鎖アルキル基、分岐アルキル基、または置換もしくは無置換の芳香族基を表し、例えば、上記Ａ項に記載のヘプチル基、オクチル基、ノニル基、デシル基、ドデシル基などの直鎖アルキル基、２−エチルヘキシル基などの分岐アルキル基、フェニル基、ノニルフェニル基、ナフチル基などの芳香族置換基などが挙げられる。
【００５２】
Ｒ²はラジカル重合可能な重合性基を有する置換基を表し、例えば、上記Ｃ項に記載のエチレン性不飽和基であるアクリレート基、メタクリレート基、マレイミド基等が挙げられる。Ｙ¹はスルホン酸、カルボン酸、またはそれらの塩を表す。
【００５３】
一般式（１）で表される化合物は、当業者が公知の方法で合成して得ることができる。また、市販品より容易に入手することができ、例えば、花王社製の「ラテムル Ｓ−１２０」、「ラテムル Ｓ−１２０Ａ」、「ラテムル Ｓ−１８０」、「ラテムル Ｓ−１８０Ａ」や、三洋化成工業社製の「エレミノール ＪＳ−２」等を挙げることができる。
【００５４】
また、本発明に係る反応性乳化剤として、下記一般式（２）で表される化合物が好ましい。
【００５５】
【化２】

【００５６】
上記一般式（２）において、Ｒ³、Ｒ⁴は、上記一般式（１）のＲ¹、Ｒ²のそれぞれと同義である。Ｙ²は水素原子、スルホン酸もしくはそれらの塩、またはカルボン酸もしくはそれらの塩を表す。ＡＯはアルキレンオキサイドを表す。
【００５７】
本発明に係る一般式（２）で表される化合物は、当業者が公知の方法で合成して得ることができる。また、市販品より容易に入手することができ、例えば、旭電化工業社製の「アデカリアソープ ＮＥ−１０」、「アデカリアソープ ＮＥ−２０」、「アデカリアソープ ＮＥ−３０」等のＮＥシリーズ、「アデカリアソープ ＳＥ−１０Ｎ」、「アデカリアソープ ＳＥ−２０Ｎ」、「アデカリアソープ ＳＥ−３０Ｎ」等のＳＥシリーズ、第一工業製薬社製の「アクアロン ＲＮ−１０」、「アクアロン ＲＮ−２０」、「アクアロン ＲＮ−３０」、「アクアロン ＲＮ−５０」等のＲＮシリーズ、「アクアロン ＨＳ−０５」、「アクアロン ＨＳ−１０」、「アクアロン ＨＳ−２０」、「アクアロン ＨＳ−３０」等のＨＳシリーズ、あるいはアクアロン ＢＣシリーズ等を挙げることができる。
【００５８】
また、本発明に係る反応性乳化剤として、下記一般式（３）で表される化合物が好ましい。
【００５９】
【化３】

【００６０】
上記一般式（３）において、Ｒ⁵、Ｒ⁶、Ｙ³及びＡＯは、前記一般式（１）のＲ¹、Ｒ²、Ｙ¹及び前記一般式（２）のＡＯのそれぞれと同義である。
【００６１】
一般式（３）で表される化合物は、当業者が公知の方法で合成して得ることができる。また、市販品より容易に入手することができ、例えば、第一工業製薬社製の「アクアロン ＫＨ−０５」、「アクアロン ＫＨ−１０」、「アクアロンＫＨ−２０」等を挙げることができる。
【００６２】
上記一般式（２）及び（３）において、アルキレンオキサイド鎖（ＡＯ）の平均重合度ｎが、１〜１０であることが好ましく、例えば、上記の第一工業製薬社製の「アクアロン ＫＨ−０５」、「アクアロン ＫＨ−１０」、「アクアロンＨＳ−０５」、「アクアロン ＨＳ−１０」等を挙げることができる。
【００６３】
また、本発明においては、反応性乳化剤が、アニオン性であることが好ましく、例えば、上述の「アデカリアソープ ＳＥシリーズ」（旭電化工業社製）、「アクアロン ＨＳシリーズ」（第一工業製薬社製）、「ラテムル Ｓシリーズ」（花王社製）、「エレミノール ＪＳシリーズ」（三洋化成工業社製）等を挙げることができる。
【００６４】
本発明において、これら反応性乳化剤の使用量は、本発明に用いられる重合性モノマー合計１００質量部当たり、一般に０．１〜８０質量部用いられ、好ましくは１〜７０質量部、特に好ましくは１０〜６０質量部用いられる。
【００６５】
本発明の着色微粒子分散体調製時の乳化共重合に際しては、得られる共重合体水分散物の性能に悪影響を及ぼさない範囲において、以上述べた反応性乳化剤とともに必要に応じて、通常のアニオン系及び／又はノニオン系乳化剤（界面活性剤）を併用することができる。
【００６６】
上記通常のノニオン系乳化剤類として、例えば、ポリオキシエチレンラウリルエーテル、ポリオキシエチレンステアリルエーテル等のポリオキシエチレンオクアルキルエーテル類；例えば、ポリオキシエチレンノニルフェニルエーテル等のポリオキシエチレンアルキルフェニルエーテル類；例えば、ソルビタンモノラウレート、ソルビタンモノステアレート、ソルビタントリオレエート等のソルビタン高級脂肪酸エステル類；例えば、ポリオキシエチレンソルビタンモノラウレート等のポリオキシエチレンソルビタン高級脂肪酸エステル類；例えば、ポリオキシエチレンモノラウレート、ポリオキシエチレンモノステアレート等のポリオキシエチレン高級脂肪酸エステル類；例えばオイレン酸モノグリセライド、ステアリン酸モノグリセライド等のグリセリン高級脂肪酸エステル類；例えば、ポリオキシエチレン−ポリオキシプロピレン−ブロックコポリマー；等を挙げることができる。
【００６７】
また上記通常のアニオン系乳化剤としては、例えば、オレイン酸ナトリウム等の高級脂肪酸塩類；例えば、ドデシルベンゼンスルホン酸ナトリウム等のアルキルアリールスルホン酸塩類；例えば、ラウリル硫酸ナトリウム等のアルキル硫酸エステル塩類；例えば、ポリエキシエチレンラウリルエーテル硫酸ナトリウム等のポリオキシエチレンアルキルエーテル硫酸エステル塩類；例えば、ポリオキシエチレンノニルフェニルエーテル硫酸ナトリウム等のポリオキシエチレンアルキルアリールエーテル硫酸エステル塩類；モノオクチルスルホコハク酸ナトリウム、ジオクチルスルホコハク酸ナトリウム、ポリオキシエチレンラウリルスルホコハク酸ナトリウム等のアルキルスルホコハク酸エステル塩及びその誘導体類；等を挙げることができ、更には、本発明においては、界面活性剤の少なくとも１種が、構造中にポリアルキレンオキサイド硫酸エステル基を含まない界面活性剤であることが好ましい。
【００６８】
本発明においては、着色微粒子が、前記一般式（ａ）で表される重合性モノマー、少なくとも１種の前記一般式（ａ）で表される重合性モノマー（ａ）を除く重合性モノマー及び色材からなる混合物を、界面活性剤により乳化した後、重合反応を行うことにより得られることが好ましい。
【００６９】
本発明で用いることのできる前記一般式（ａ）で表される重合性モノマー（ａ）を除く重合性モノマーとしては、スチレン−アクリル酸エステルが挙げられ、具体的なモノマーとしては、酢酸ビニル、アクリル酸メチル、アクリル酸エチル、アクリル酸ｎ−ブチル、アクリル酸ｔ−ブチル、アクリル酸２−エチルヘキシル、アクリル酸イソノニル、アクリル酸ドデシル、アクリル酸オクタデシル、２−フェノキシエチルアクリレート、メタクリル酸メチル、メタクリル酸エチル、メタクリル酸ｎ−ブチル、メタクリル酸イソブチル、メタクリル酸２−エチルヘキシル、メタクリル酸２−ヒドロキシエチル、メタクリル酸ドデシル、メタクリル酸オクタデシル、メタクリル酸シクロヘキシル、メタクリル酸ステアリル、メタクリル酸ベンジル、メタクリル酸グリシジル、メタクリル酸フェニル、スチレン、α−メチルスチレン、アクリロニトリル等、アセトアセトキシエチルメタクリレート、メタクリル酸グリシジルの大豆油脂肪酸変性品（ブレンマーＧ−ＦＡ：日本油脂社製）等が挙げられる。
【００７０】
より好ましい組み合わせとしては、スチレン、またはメタクリル酸メチルを主成分としてアセトアセトキシエチルメタクリレート、メタクリル酸グリシジルの大豆油脂肪酸変性品（ブレンマーＧ−ＦＡ：日本油脂社製）、及びアクリル酸ｎ−ブチル、メタクリル酸ステアリル、アクリル酸２−エチルヘキシル等の長鎖（メタ）アクリル酸エステルから選ばれるもの少なくとも一種を加え、更に物性改良のために必要に応じてアクリロニトリル、ジビニルベンゼン、ジエチレングリコールジメタクリレート等を加えて作られる共重合体を挙げることができる。
【００７１】
上記のポリマーは、置換基を有していてもよく、その置換基は直鎖状、分岐、あるいは環状構造をとっていてもよい。また、上記の官能基を有するポリマーは、各種のものが市販されているが、常法によって合成することもできる。また、これらの共重合体は、例えば１つのポリマー分子中にエポキシ基を導入しておき、後に他のポリマーと縮重合させたり、光や放射線を用いてグラフト重合を行っても得られる。
【００７２】
本発明に係る着色微粒子としては、ポリマーと色材の相溶物とを界面活性剤により乳化した後、少なくとも１種の前記一般式（ａ）で表される重合性モノマー（ａ）を添加して乳化重合を行うことにより調製する方法も好ましい。上記ポリマーとしては、アクリル重合体またはスチレン−アクリル重合体が好ましく、例えば、アクリル酸エステル、スチレン−アクリル酸エステル等の共重合体等が好ましい。上記のポリマーを与える具体的なモノマーとしては、上記のスチレン−アクリル酸エステルとして列挙した各モノマーを挙げることができる。
【００７３】
また、本発明に係る着色微粒子の調製方法として、自己乳化性の着色微粒子分散体に、前記一般式（ａ）で表される重合性モノマーと、少なくとも１種の前記一般式（ａ）で表される重合性モノマー（ａ）を除く他の重合性モノマーとを添加して、乳化重合を行うことにより調製することが、特徴である。
【００７４】
本発明でいう自己乳化性の着色微粒子分散体とは、着色微粒子を調製する際のポリマーとして、水分散（自己乳化）型のポリマーを用いて調製した着色微粒子であり、水分散型のポリマーとしては、イオン性ポリマー、非イオン性分散性基含有型ポリマー、これらの混合型ポリマー、のいずれであってもよい。イオン性ポリマーとしては、三級アミノ基等のカチオン性基を有するポリマーや、カルボン酸、スルホン酸等のアニオン性の解離性基を含有するポリマーが挙げられる。また、非イオン性分散性基含有型ポリマーとしては、ポリエチレンオキシ基等の非イオン性分散性基を含有するポリマーが挙げられる。これらの中でも、着色微粒子の分散安定性の点で、アニオン性の解離性基を含有するイオン性ポリマー、非イオン性分散性基含有型ポリマー、これらの混合型ポリマーが好ましい。
【００７５】
本発明の着色微粒子分散体においては、着色微粒子がポリアルキレンオキサイド硫酸エステル基を表面に有し、かつ該界面活性剤の少なくとも１種が、該ポリアルキレンオキサイド硫酸エステル基とは異なる構造のポリアルキレンオキサイド硫酸エステル基を有することが好ましい。
【００７６】
すなわち、表面にポリアルキレンオキサイド硫酸エステル基が付加している着色微粒子と、ポリアルキレンオキサイド硫酸エステル基を有する界面活性剤が、インク中に共存しているときに、両者のポリアルキレンオキサイド硫酸エステル基が、異なる構造であることが、着色微粒子の分散安定性あるいは保存安定性を実現する上で好ましいことを見出したものである。
【００７７】
本発明の着色微粒子分散体の乳化重合に際しては、得られる共重合体水分散物の性能に悪影響を及ぼさない範囲において、上述した一般式（ａ）で表される重合性モノマー、反応性乳化剤及び通常のアニオン系及び／又はノニオン系乳化剤とともに水溶性保護コロイドを併用することもできる。
【００７８】
水溶性保護コロイドとしては、例えば、部分ケン化ポリビニルアルコール、完全ケン化ポリビニルアルコール、変性ポリビニルアルコール等のポリビニルアルコール類；例えば、ヒドロキシエチルセルロース、ヒドロキシプロピルセルロース、カルボキシメチルセルロース塩等のセルロース誘導体；及びグアガムなどの天然多糖類；等が挙げられ、これらは、単独でも複数種併用でも利用できる。水溶性保護コロイドの使用量は、前記単量体の合計１００質量部当たり０〜１０質量部であるのが好ましい。
【００７９】
更に、乳化重合に際しては、通常、例えば、過硫酸ナトリウム、過硫酸カリウム、過硫酸アンモニウムなどの過硫酸塩類；ｔ−ブチルヒドロパーオキシド、クメンヒドロパーオキシド、ｐ−メンタンヒドロパーオキシドなどの有機過酸化物類；過酸化水素；などの重合開始剤が使用される。これら重合開始剤も一種もしくは複数種併用のいずれの態様でも利用できる。これらの重合開始剤は、前記単量体の合計１００質量部に対して、０．１〜１質量部用いるのが好ましい。
【００８０】
また乳化重合に際して、所望により、重合開始剤とともに還元剤を併用することができる。このような還元剤としては、例えば、アスコルビン酸、酒石酸、クエン酸、ブドウ糖、ホルムアルデヒドスルホキシラート金属塩等の還元性有機化合物；チオ硫酸ナトリウム、亜硫酸ナトリウム、重亜硫酸ナトリウム、メタ重亜硫酸ナトリウム等の還元性無機化合物；等を挙げることができる。これら還元剤は、前記単量体の合計１００質量部に対して、０．１〜１質量部用いるのが好ましい。
【００８１】
更にまた、乳化重合に際しては連鎖移動剤を使用することができる。このような連鎖移動剤としては、例えば、ドデシルメルカプタン、ｔ−ドデシルメルカプタン、ブチルメルカプタン、２−エチルヘキシルチオグリコレート、２−メルカプトエタノール、トリクロロブロモメタン等を挙げることができる。これら連鎖移動剤は、前記単量体の合計１００質量部に対して、０〜１質量部用いるのが好ましい。
【００８２】
また乳化共重合に際して、好適に採用される共重合温度は、４０〜１００℃が好ましく、６０〜９０℃が特に好ましい。
【００８３】
次いで、本発明に係る色材について説明する。
本発明に用いられる色材の色相としては、イエロー、マゼンタ、シアン、ブラック、ブルー、グリーン、レッドが好ましく用いられ、特に好ましくはイエロー、マゼンタ、シアン、ブラックの各色材である。
【００８４】
本発明においては、色材が油溶性染料であることが好ましい。油溶性染料は、通常、カルボン酸やスルホン酸等の水溶性基を有さない有機溶剤に可溶で水に不溶な染料であるが、水溶性染料を長鎖の塩基と造塩することにより油溶性を示す染料も含まれる。例えば、酸性染料、直接染料、反応性染料と長鎖アミンとの造塩染料が知られている。油溶性染料としては、以下に限定されるものではないが、特に好ましい具体例としては、例えば、オリエント化学工業株式会社製Ｖａｌｉｆａｓｔ Ｙｅｌｌｏｗ ４１２０、Ｖａｌｉｆａｓｔ Ｙｅｌｌｏｗ ３１５０、Ｖａｌｉｆａｓｔ Ｙｅｌｌｏｗ ３１０８、Ｖａｌｉｆａｓｔ Ｙｅｌｌｏｗ ２３１０Ｎ、Ｖａｌｉｆａｓｔ Ｙｅｌｌｏｗ １１０１、Ｖａｌｉｆａｓｔ Ｒｅｄ ３３２０、Ｖａｌｉｆａｓｔ Ｒｅｄ ３３０４、Ｖａｌｉｆａｓｔ Ｒｅｄ １３０６、Ｖａｌｉｆａｓｔ Ｂｌｕｅ ２６１０、Ｖａｌｉｆａｓｔ Ｂｌｕｅ ２６０６、Ｖａｌｉｆａｓｔ Ｂｌｕｅ １６０３、Ｏｉｌ Ｙｅｌｌｏｗ ＧＧ−Ｓ、Ｏｉｌ Ｙｅｌｌｏｗ ３Ｇ、Ｏｉｌ Ｙｅｌｌｏｗ １２９、Ｏｉｌ Ｙｅｌｌｏｗ １０７、Ｏｉｌ Ｙｅｌｌｏｗ １０５、Ｏｉｌ Ｓｃａｒｌｅｔ 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 ８６０、ＯｉｌＢｌａｃｋ ５９７０、Ｏｉｌ Ｂｌａｃｋ ５９０６、Ｏｉｌ Ｂｌａｃｋ５９０５、日本化薬株式会社製Ｋａｙａｓｅｔ Ｙｅｌｌｏｗ ＳＦ−Ｇ、Ｋａｙａｓｅｔ Ｙｅｌｌｏｗ Ｋ−ＣＬ、Ｋａｙａｓｅｔ Ｙｅｌｌｏｗ ＧＮ、Ｋａｙａｓｅｔ Ｙｅｌｌｏｗ Ａ−Ｇ、Ｋａｙａｓｅｔ Ｙｅｌｌｏｗ ２Ｇ、Ｋａｙａｓｅｔ Ｒｅｄ ＳＦ−４Ｇ、Ｋａｙａｓｅｔ Ｒｅｄ Ｋ−ＢＬ、Ｋａｙａｓｅｔ Ｒｅｄ Ａ−ＢＲ、Ｋａｙａｓｅｔ Ｍａｇｅｎｔａ３１２、Ｋａｙａｓｅｔ Ｂｌｕｅ Ｋ−ＦＬ、有本化学工業株式会社製ＦＳ Ｙｅｌｌｏｗ １０１５、ＦＳ Ｍａｇｅｎｔａ １４０４、ＦＳ Ｃｙａｎ １５２２、ＦＳ Ｂｌｕｅ １５０４ 、Ｃ．Ｉ．Ｓｏｌｖｅｎｔ Ｙｅｌｌｏｗ ８８、８３、８２、７９、５６、２９、１９、１６、１４、０４、０３、０２、０１、Ｃ．Ｉ．Ｓｏｌｖｅｎｔ Ｒｅｄ ８４：１、Ｃ．Ｉ．Ｓｏｌｖｅｎｔ Ｒｅｄ ８４、２１８、１３２、７３、７２、５１、４３、２７、２４、１８、０１、Ｃ．Ｉ．Ｓｏｌｖｅｎｔ Ｂｌｕｅ ７０、６７、４４、４０、３５、１１、０２、０１、Ｃ．Ｉ．Ｓｏｌｖｅｎｔ Ｂｌａｃｋ ４３、７０、３４、２９、２７、２２、７、３、Ｃ．Ｉ．Ｓｏｌｖｅｎｔ Ｖｉｏｌｅｔ ３、Ｃ．Ｉ．Ｓｏｌｖｅｎｔ Ｇｒｅｅｎ ３及び７、Ｐｌａｓｔ Ｙｅｌｌｏｗ ＤＹ３５２、Ｐｌａｓｔ Ｒｅｄ ８３７５、三井化学社製ＭＳ Ｙｅｌｌｏｗ ＨＤ−１８０、ＭＳ Ｒｅｄ Ｇ、ＭＳ Ｍａｇｅｎｔａ ＨＭ−１４５０Ｈ、ＭＳ Ｂｌｕｅ ＨＭ−１３８４、住友化学社製ＥＳ Ｒｅｄ ３００１、ＥＳ Ｒｅｄ ３００２、ＥＳ Ｒｅｄ ３００３、ＴＳ Ｒｅｄ ３０５、ＥＳ Ｙｅｌｌｏｗ １００１、ＥＳ Ｙｅｌｌｏｗ １００２、ＴＳ Ｙｅｌｌｏｗ １１８、ＥＳ Ｏｒａｎｇｅ ２００１、ＥＳ Ｂｌｕｅ ６００１、ＴＳ Ｔｕｒｑ Ｂｌｕｅ ６１８、Ｂａｙｅｒ社製ＭＡＣＲＯＬＥＸ Ｙｅｌｌｏｗ ６Ｇ、Ｃｅｒｅｓ Ｂｌｕｅ ＧＮＮＥＯＰＡＮ Ｙｅｌｌｏｗ Ｏ７５、Ｃｅｒｅｓ Ｂｌｕｅ ＧＮ、ＭＡＣＲＯＬＥＸ Ｒｅｄ Ｖｉｏｌｅｔ Ｒ等が挙げられる。
【００８５】
また、特開平９−２７７６９３号、同１０−２０５５９号、同１０−３００６１号に示されるような、金属錯体色素も好ましく用いられ、好ましい構造としては下記一般式（４）で表されるものである。
【００８６】
一般式（４）
Ｍ（Ｄｙｅ）_p（Ａ）_m
式中、Ｍは金属イオンを表し、Ｄｙｅは金属と配位結合可能な色素を表す。Ａは色素以外の配位子を表し、ｐは１ないし３、ｍは０、１、２、３を表す。ｍが０の時、ｐは２または３を表し、その場合Ｄｙｅは同種でも異なってもよい。
【００８７】
Ｍで表される金属イオンとしては、周期表の第１〜１７族に属する金属を挙げることができる。Ｄｙｅで表される金属と配位結合可能な色素としては種々の色素構造が考えられるが、共役メチン色素、アゾメチン色素、アゾ色素骨格に配位基を有するものが好ましい。
【００８８】
油溶性染料として分散染料を用いることができ、分散染料としては、以下に限定されるものではないが、特に好ましい具体例としては、Ｃ．Ｉ．ディスパーズイエロー５、４２、５４、６４、７９、８２、８３、９３、９９、１００、１１９、１２２、１２４、１２６、１６０、１８４：１、１８６、１９８、１９９、２０４、２２４及び２３７；Ｃ．Ｉ．ディスパーズオレンジ１３、２９、３１：１、３３、４９、５４、５５、６６、７３、１１８、１１９及び１６３；Ｃ．Ｉ．ディスパーズレッド５４、６０、７２、７３、８６、８８、９１、９２、９３、１１１、１２６、１２７、１３４、１３５、１４３、１４５、１５２、１５３、１５４、１５９、１６４、１６７：１、１７７、１８１、２０４、２０６、２０７、２２１、２３９、２４０、２５８、２７７、２７８、２８３、３１１、３２３、３４３、３４８、３５６及び３６２；Ｃ．Ｉ．ディスパーズバイオレット３３；Ｃ．Ｉ．ディスパーズブルー５６、６０、７３、８７、１１３、１２８、１４３、１４８、１５４、１５８、１６５、１６５：１、１６５：２、１７６、１８３、１８５、１９７、１９８、２０１、２１４、２２４、２２５、２５７、２６６、２６７、２８７、３５４、３５８、３６５及び３６８並びにＣ．Ｉ．ディスパーズグリーン６：１及び９等が挙げられる。
【００８９】
その他、油溶性染料として、フェノール、ナフトール類、又、ピラゾロン、ピラゾロトリアゾール等の環状メチレン化合物、或いは、開鎖メチレン化合物等のいわゆるカプラーに、ｐ−フェニレンジアミン類或いはｐ−ジアミノピリジン類等、アミノ化合物を酸化カップリングさせ得られるアゾメチン色素、インドアニリン色素等も好ましい。特にマゼンタ染料として、ピラゾロトリアゾール環を有するアゾメチン色素は好ましい。
【００９０】
次いで、本発明に係る着色微粒子の調製方法について説明する。
本発明の着色微粒子分散体は、上記油溶性染料を有機溶剤中に溶解し、これに反応性乳化剤等の界面活性剤の存在下で、一般式（ａ）で表される重合性モノマーと必要に応じてその他の重合性モノマーと共重合させることにより得られる。
【００９１】
この様な着色微粒子分散体は、これを用いてインクジェットインクを形成することができるが、更に長期に亘って該着色微粒子分散体の凝集を防止し、微粒子のインクサスペンションとしての安定性を向上させ、メディアに印画したときの画像の色調や光沢、更に耐光性等、画像に堅牢性を付与するために、本発明では、該着色微粒子をコアとして、更に有機ポリマーからなるシェルを形成したコアシェル型着色微粒子であることが好ましい。
【００９２】
シェルを形成する方法としては、有機溶剤に溶解したポリマーを徐々に滴下し、析出と同時に該着色微粒子コア表面に吸着させる方法などもあるが、本発明においては、色材と樹脂を含有したコアとなる着色微粒子を形成した後、重合性不飽和二重結合を有するモノマーを添加し、活性剤の存在下、乳化重合を行い、重合と同時にコア表面に沈着させシェルを形成する方法が好ましい。この方法で形成した場合においても、例えば、色材として染料を用いた場合等にみられるが、コア／シェル界面での幾分かの相の混合がありシェルにおける色材含有率は必ずしも零とはならないが、混合は少ない方が好ましく、シェルにおける色材含有率（濃度）は、コア／シェル化を行っていないコアにおける色材含有率（濃度）の０．８以下であることが好ましく、更に好ましくは０．５以下である。
【００９３】
色材粒子をシェルとして被覆するポリマーを形成する重合性不飽和二重結合を有するモノマーとしては、本発明に係る一般式（ａ）で表される重合性モノマーの他、エチレン、プロピレン、ブタジエン、塩化ビニル、塩化ビニリデン、酢酸ビニル、スチレン、（メタ）アクリル酸エステル類、（メタ）アクリル酸等、アクリルアミド類等から選ばれる化合物、特スチレンや（メタ）アクリル酸エチル、（メタ）アクリル酸ブチル、（メタ）アクリル酸エチルヘキシル等の（メタ）アクリル酸エステル類等が好ましいが、これらのモノマーに加えて、分子内にヒドロキシル基を含有する重合性不飽和モノマー、例えば、ヒドロキシエチル（メタ）アクリレート等の様なヒドロキシアルキル（メタ）アクリレート等のエステルを、その他のエチレン性不飽和二重結合を有するモノマーと混合して用いてもよい。
【００９４】
実際にコアシェル化されているかを評価することは重要である。本発明においては、個々の粒子径が２００ｎｍ以下と非常に微小であるため、分析手法は分解能の観点から限られる。このような目的に沿う分析手法としては、ＴＥＭやＴＯＦ−ＳＩＭＳなどが適用できる。ＴＥＭによりコアシェル化した微粒子を観察する場合、カーボン支持膜上に分散液を塗布、乾燥させ観察することができる。ＴＥＭの観察像は、有機物であるポリマーの種類のみではコントラスト差が小さい場合があるため、コアシェル化されているかどうかを評価するために、微粒子を、４酸化オスミウム、４酸化ルテニウム、クロロスルホン酸／酢酸ウラニル、硫化銀等を用いて染色することが好ましい。コアだけの微粒子を染色しそのＴＥＭ観察を行い、シェルを設けたものと比較する。さらに、シェルを設けた微粒子と設けていない微粒子を混合後、染色し、染色度合いの異なる微粒子の割合がシェルの有無に一致しているかの確認を行う。
【００９５】
ＴＯＦ−ＳＩＭＳような質量分析装置では、粒子表面にシェルを設けることで表面近傍の色材量がコアだけの時よりも減少していることを確認する。色材にコアシェルのポリマーに含有されていない元素がある場合、その元素をプローブとして色材含有量の少ないシェルが設けられたかを確認することができる。
【００９６】
そのような元素がない場合、適当な染色剤を用いてシェル中の色材含有量をシェルを設けていないものと比較することができる。例えば、コアシェル粒子をエポキシ樹脂内に埋胞し、ミクロトームで超薄い切片を作製、染色を行うことでコアシェル化をより明瞭に観察できる。上記のように、ポリマーや、色材にプローブとなりうる元素がある場合、ＴＯＦ−ＳＩＭＳやＴＥＭによってコアシェルの組成、色材のコアとシェルへの分布量を見積もることもできる。
【００９７】
本発明の着色微粒子分散体において、適切な粒子径を得るには、処方の最適化と、適当な乳化法の選定が重要である。処方とは用いる色材、ポリマーによって異なるが、水中のサスペンションであるので、コアを構成するポリマーよりシェルを構成するポリマーの方が一般的に親水性が高いことが必要である。また、シェルを構成するポリマーに含有される色材は、前記のようにコアを構成するポリマー中より少ないことが好ましく、色材もシェルを構成するポリマーよりも親水性の低いことが必要である。親水性、疎水性は、例えば前記の溶解性パラメーター（ＳＰ）を用いて見積もることができる。
【００９８】
本発明の着色微粒子分散体、また、更に好ましいコア／シェルの形態を有する着色微粒子は、色材とポリマーの比率として１：０．１〜１：５の範囲とすることが好ましく、またポリマー量として本発明の水性インク中に０．５〜５０質量％配合されることが好ましく、０．５〜３０質量％配合されることが更に好ましい。上記ポリマーの配合量が０．５質量％に満たないと、色材の保護能が十分でなく、５０質量％を超えると、サスペンションの水性インクとしての保存安定性が低下したり、ノズル先端部でのインク蒸発に伴うインクの増粘やサスペンションの凝集が起こることによってプリンタヘッドの目詰りが起こる場合があるので、上記範囲内とすることが好ましい。
【００９９】
一方、上記色材は、該インク中に１〜３０質量％配合されることが好ましく、１．５〜２５質量％配合されることが更に好ましい。上記色材の配合量が１質量％に満たないと印字濃度が不十分であり、３０質量％を超えるとサスペンションの経時安定性が低下し、凝集等による粒径増大の傾向があるので、上記範囲内とすることが好ましい。
【０１００】
次に、本発明の着色微粒子分散体の製造に用いられる乳化方法について説明する。本発明の着色微粒子分散体は、例えば、コアとなる色材粒子の製造において、各種の乳化法を用いることができる。それらの乳化法は、例えば、「機能性乳化剤・乳化技術の進歩と応用展開 シー エム シー」の８６ページの記載にまとめられている。本発明においては、特に、染料コアの形成には超音波、高速回転せん断、高圧による乳化分散装置を使用することが好ましい。
【０１０１】
超音波による乳化分散では、いわゆるバッチ式と連続式の２通りが使用可能である。バッチ式は、比較的少量のサンプル作製に適し、連続式は大量のサンプル作製に適する。連続式では、たとえば、ＵＨ−６００ＳＲ（株式会社エスエムテー製）のような装置を用いることが可能である。このような連続式の場合、超音波の照射時間は、分散室容積／流速×循環回数で求めることができる。超音波照射装置が複数ある場合は、それぞれの照射時間の合計としてもとめられる。超音波の照射時間は実際上は１００００秒以下である。また、１００００秒以上必要であると、工程の負荷が大きく、実際上は乳化剤の再選択などにより乳化分散時間を短くする必要がある。そのため１００００秒以上は必要でない。さらに好ましくは、１０秒以上、２０００秒以内である。
【０１０２】
高速回転せん断による乳化分散装置としては、「機能性乳化剤・乳化技術の進歩と応用展開 シー エム シー」の２５５〜２５６ページに記載されているような、ディスパーミキサーや、２５１ページに記載されているようなホモミキサー、２５６ページに記載されているようなウルトラミキサーなどが使用できる。これらの型式は、乳化分散時の液粘度によって使い分けることができる。これらの高速回転せん断による乳化分散機では、攪拌翼の回転数が重要である。ステーターを有する装置の場合、攪拌翼とステーターとのクリアランスは通常０．５ｍｍ程度で、極端に狭くはできないので、せん断力は主として攪拌翼の周速に依存する。周速が５ｍ／Ｓ以上１５０ｍ／Ｓ以内であれば本発明の乳化・分散に使用できる。周速が遅い場合、乳化時間を延ばしても小粒径化が達成できない場合が多く、１５０ｍ／Ｓにするにはモーターの性能を極端に上げる必要があるからである。さらに好ましくは、２０〜１００ｍ／Ｓである。
【０１０３】
高圧による乳化分散では、ＬＡＢ２０００（エスエムテー社製）などが使用できるが、その乳化・分散能力は、試料にかけられる圧力に依存する。圧力は１０⁴ｋＰａ〜５×１０⁵ｋＰａの範囲が好ましい。また、必要に応じて数回乳化・分散を行い、目的の粒径を得ることができる。圧力が低すぎる場合、何度乳化分散を行っても目的の粒径は達成できない場合が多く、また、圧力を５×１０⁵ｋＰａにするためには、装置に大きな負荷がかかり実用的ではない。さらに好ましくは５×１０⁴ｋＰａ〜２×１０⁵ｋＰａの範囲である。
【０１０４】
これらの乳化・分散装置は単独で用いてもよいが、必要に応じて組み合わせて使用することが可能である。コロイドミルや、フロージェットミキサなども単独では本発明の目的を達成できないが、本発明の装置との組み合わせにより、短時間で乳化・分散を可能にするなど本発明の効果を高めることが可能である。
【０１０５】
本発明の着色微粒子分散体に含まれる着色微粒子は、体積平均粒子径が５ｎｍ以下になると単位体積あたりの表面積が非常に大きくなるため、色材をコアシェルポリマー中に封入する効果が小さくなる。一方、２００ｎｍを越えるほど大きな粒子では、ヘッドに詰まりやすく、またインク中での沈降が起き易く、停滞安定性が劣化する。従って着色微粒子の体積平均粒子径は５ｎｍ〜１００ｎｍが好ましい。
【０１０６】
本発明に係る着色微粒子の体積平均粒子径は、透過型電子顕微鏡（ＴＥＭ）写真の投影面積（少なくとも１００粒子以上に対して求める）の平均値から得られた円換算平均粒径を、球形換算して求められる。体積平均粒子径とその標準偏差を求め、標準偏差を体積平均粒子径で割ることで変動係数を求められる。或いは、動的光散乱法を利用して変動係数を求めることも出来る。例えば、大塚電子製レーザー粒径解析システムや、マルバーン（Ｍａｌｖｅｒｎ）社製ゼータサイザー（Ｚｅｔａｓｉｚｅｒ）１０００ＨＳを用いて求める事ができる。
【０１０７】
また、本発明に記載の効果を好ましく奏する着色微粒子分散体を得る観点から、着色微粒子の体積平均粒径は小さいことが好ましいが、５ｎｍ〜１００ｎｍの範囲のような、微粒子になるにつれ、体積平均粒径は少量の大粒子（例えば、６０ｎｍ〜１００ｎｍ程度）により数値変動を受けやすいので、画質評価の観点からは、下記に示すピーク粒径で評価することが好ましい。
【０１０８】
本発明に係るピーク粒径について説明する。
本発明の着色微粒子分散体を、本発明の水性インクに適用する場合には、着色微粒子のピーク粒径が５０ｎｍ以下であることが好ましく、更に好ましくは、３０ｎｍ〜５０ｎｍの範囲であり、特に好ましくは、５ｎｍ〜３０ｎｍの範囲である。
【０１０９】
ここで、着色微粒子のピーク粒径は、Ｍａｌｖｅｒｎ社製のＺｅｔａｓｉｚｅｒ １０００ＨＳで体積平均粒径分布を求め、その分布曲線の頂点に対応する粒径のことであり、粒径分布をもとに算出することが出来る。
【０１１０】
次いで、着色微粒子の変動係数について説明する。
粒子径の変動係数は、粒子径の標準偏差を粒子径で割った値であるが、この値が大きいほど粒子径の分布が広いことを意味する。体積平均粒子径の変動係数が８０％以上であると、粒径分布が非常に広くなり、コアシェルの厚みが不均一となり易く、粒子間の表面物性にばらつきが生じ易くなる。表面物性のばらつきは粒子の凝集を招きやすく、インクジェットヘッドの詰まりを起こし易い。また、粒子の凝集はメディア上で、色材の光散乱を招き易く、画質の低下も招き易くする。変動係数は５０％以下が好ましい。
【０１１１】
本発明においては、シェルに用いられるポリマー量が総ポリマー量の５質量％以上、９５質量％以下であることが好ましい。５質量％より少ないとシェルの厚みが不十分で、色材を多く含有するコアの一部が粒子表面に現れ易くなる。また、シェルのポリマーが多すぎると、コアの色材保護能低下を起こし易い。さらに好ましくは１０質量％以上９０質量％以下である。
【０１１２】
次いで、本発明の水性インクについて説明する。
本発明の水性インクは、水を媒体とし、上記色材を封入したポリマーのサスペンジョンからなり、該サスペンションには従来公知の各種添加剤、例えば、多価アルコール類のような湿潤剤、無機塩、界面活性剤、防腐剤、防黴剤、ｐＨ調整剤、シリコーン系等の消泡剤、粘度調整剤又はＥＤＴＡ等のキレート剤、又、亜硫酸塩等の酸素吸収剤等を必要に応じて添加してもよい。
【０１１３】
本発明で用いることのできる湿潤剤としては、例えば、エチレングリコール、プロピレングリコール、ジエチレングリコール、トリエチレングリコール、テトラエチレングリコール、ポリエチレングリコール、グリセリン、ジエチレングリコールジエチルエーテル、ジエチレングリコールモノｎ−ブチルエーテル、エチレングリコールモノメチルエーテル、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、メチルカルビトール、エチルカルビトール、ブチルカルビトール、エチルカルビトールアセテート、ジエチルカルビトール、トリエチレングリコールモノメチルエーテル、トリエチレングリコールモノエチルエーテル、プロピレングリコールモノメチルエーテル等の多価アルコール及びそのエーテル、アセテート類、Ｎ−メチル−２−ピロリドン、１，３−ジメチルイミダゾリジノン、トリエタノールアミン、ホルムアミド、ジメチルホルムアミド等の含窒素化合物類、ジメチルサルフォキサイドの一種又は二種以上を使用することができる。これらの湿潤剤の配合量に特に制限はないが、上記水性インク中に好ましくは０．１〜５０質量％配合することができ、更に好ましくは０．１〜３０質量％配合することができる。
【０１１４】
又、インクの粘度を安定に保つため、発色をよくするために、インク中に無機塩を添加してもかまわない。無機塩としてはたとえば塩化ナトリウム、硫酸ナトリウム、塩化マグネシウム、硫化マグネシウム等が挙げられる。本発明を実施する場合、これらに限定されるものではない。
【０１１５】
また、乳化剤、分散剤としては特に制限されるものではないが、そのＨＬＢ値が８〜１８であることが、効果の発現の点からみて或いはサスペンションの粒子径の増大抑制効果がある点から好ましい。
【０１１６】
界面活性剤としては、陽イオン性、陰イオン性、両性、非イオン性のいずれも用いることが出来る。
【０１１７】
乳化剤或いは分散剤として、好ましくは陰イオン性界面活性剤又は高分子界面活性剤であり、陰イオン性界面活性剤が特によい。
【０１１８】
又、インクの表面張力調整用の活性剤としては好ましくはノニオン性界面活性剤である。
【０１１９】
陽イオン性界面活性剤としては、脂肪族アミン塩、脂肪族４級アンモニウム塩、ベンザルコニウム塩、塩化ベンゼトニウム、ピリジニウム塩、イミダゾリニウム塩等が挙げられる。また、陰イオン性界面活性剤としては、脂肪酸石鹸、Ｎ−アシル−Ｎ−メチルグリシン塩、Ｎ−アシル−Ｎ−メチル−β−アラニン塩、Ｎ−アシルグルタミン酸塩、アルキルエーテルカルボン酸塩、アシル化ペプチド、アルキルスルホン酸塩、アルキルベンゼンスルホン酸塩、アルキルナフタレンスルホン酸塩、ジアルキルスルホ琥珀酸エステル塩、アルキルスルホ酢酸塩、α−オレフィンスルホン酸塩、Ｎ−アシルメチルタウリン、硫酸化油、高級アルコール硫酸エステル塩、第２級高級アルコール硫酸エステル塩、アルキルエーテル硫酸塩、第２級高級アルコールエトキシサルフェート、ポリオキシエチレンアルキルフェニルエーテル硫酸塩、モノグリサルフェート、脂肪酸アルキロールアミド硫酸エステル塩、アルキルエーテルリン酸エステル塩、アルキルリン酸エステル塩等が挙げられる。また、両性界面活性剤としては、カルボキシベタイン型、スルホベタイン型、アミノカルボン酸塩、イミダゾリニウムベタイン等が挙げられる。また、非イオン性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２級アルコールエーテル、ポリオキシエチレンアルキルフェニルエーテル（例えば、エマルゲン９１１）、ポリオキシエチレンステロールエーテル、ポリオキシエチレンラノリン誘導体、ポリオキシエチレンポリオキシプロピレンアルキルエーテル（例えば、ニューポールＰＥ−６２）、ポリオキシエチレングリセリン脂肪酸エステル、ポリオキシエチレンヒマシ油、硬化ヒマシ油、ポリオキシエチレンソルビタン脂肪酸エステル、ポリオキシエチレンソルビトール脂肪酸エステル、ポリエチレングリコール脂肪酸エステル、脂肪酸モノグリセリド、ポリグリセリン脂肪酸エステル、ソルビタン脂肪酸エステル、プロピレングリコール脂肪酸エステル、ショ糖脂肪酸エステル、脂肪酸アルカノールアミド、 ポリオキシエチレン脂肪酸アミド、ポリオキシエチレンアルキルアミン、アルキルアミンオキサイド、アセチレングリコール、アセチレンアルコール等が挙げられる。その他に、界面活性剤としては、例えば、花王（株）製の分散剤デモールＳＮＢ、ＭＳ、Ｎ、ＳＳＬ、ＳＴ、Ｐ（商品名）もあげられる。
【０１２０】
これらの界面活性剤を使用する場合、単独又は２種類以上を混合して用いることが出来、インク全量に対して、０．００１〜１．０質量％の範囲で添加することにより、インクの表面張力を任意に調整することが出来る。本発明を実施する場合、これらに限定されるものではない。インクの長期保存安定性を保つため、防腐剤、防黴剤をインク中に添加してもかまわない。
【０１２１】
又、高分子界面活性剤として、以下の水溶性樹脂を用いることができ、吐出安定性の観点から好ましい。水溶性樹脂として好ましく用いられるのは、スチレン−アクリル酸−アクリル酸アルキルエステル共重合体、スチレン−アクリル酸共重合体、スチレン−マレイン酸−アクリル酸アルキルエステル共重合体、スチレン−マレイン酸共重合体、スチレン−メタクリル酸−アクリル酸アルキルエステル共重合体、スチレン−メタクリル酸共重合体、スチレン−マレイン酸ハーフエステル共重合体、ビニルナフタレン−アクリル酸共重合体、ビニルナフタレン−マレイン酸共重合体等を挙げることができる。高分子界面活性剤の例として、その他に、アクリル−スチレン系樹脂であるジョンクリル等（ジョンソン社）が挙げられる。これらの高分子界面活性剤は、２種以上併用することも可能である。
【０１２２】
上記の各高分子界面活性剤の分散インク全量に対する添加量としては、０．１〜１０質量％が好ましく、より好ましくは０．３〜５質量％である。配合量が０．０１質量％に満たないとサスペンションの小粒径化が困難であり、１０質量％を超えるとサスペンションの粒径が増大したりサスペンション安定性が低下し、ゲル化するおそれがある。
【０１２３】
防腐剤・防黴剤としては、芳香族ハロゲン化合物（例えば、Ｐｒｅｖｅｎｔｏｌ ＣＭＫ、クロロメチルフェノール等）、メチレンジチオシアナート、含ハロゲン窒素硫黄化合物、１，２−ベンズイソチアゾリン−３−オン（例えば、ＰＲＯＸＥＬ ＧＸＬ）などが挙げられるが、本発明を実施する場合、これらに限定されるものではない。
【０１２４】
インク中を安定に保つために、インク中にｐＨ調整剤を添加してもかまわない。ｐＨ調整剤としては、塩酸や酢酸、クエン酸、水酸化ナトリウム、水酸化カリウム等を水など薄めたりそのまま使用したりできる。
【０１２５】
また、上記消泡剤としては、特に制限なく、市販品を使用することができる。そのような市販品としては、例えば、信越シリコーン社製のＫＦ９６、６６、６９、ＫＳ６８、６０４、６０７Ａ、６０２、６０３、ＫＭ７３、７３Ａ、７３Ｅ、７２、７２Ａ、７２Ｃ、７２Ｆ、８２Ｆ、７０、７１、７５、８０、８３Ａ、８５、８９、９０、６８−１Ｆ、６８−２Ｆ（商品名）等が挙げられる。これら化合物の配合量に特に制限はないが、本発明に係るインク中に、０．００１〜２質量％配合されることが好ましい。該化合物の配合量が０．００１質量％に満たないとインク調製時に泡が発生し易く、又、インク内での小泡の除去が難しく、２質量％を超えると泡の発生は抑えられるものの、印字の際、インク内でハジキが発生し印字品質の低下が起こる場合があるので、上記範囲内とすることが好ましい。
【０１２６】
本発明において、インクセットを吐出して画像形成を行う際に、使用するインクジェットヘッドは、オンデマンド方式でもコンティニュアス方式でも構わない。又吐出方式としては、電気−機械変換方式（例えば、シングルキャビティー型、ダブルキャビティー型、ベンダー型、ピストン型、シェアーモード型、シェアードウォール型等）、電気−熱変換方式（例えば、サーマルインクジェット型、バブルジェット（Ｒ）型等）等など何れの吐出方式を用いてもよい。
【０１２７】
（画像形成方法）
本発明の画像形成方法について説明する。
【０１２８】
本発明の画像形成方法においては、本発明のインクセットを装填したプリンター等により、デジタル信号に基づきインクジェットヘッドよりインクを液滴として吐出させ、インクジェット記録媒体上に付着させることが好ましい。
【０１２９】
インクジェット記録媒体としては、例えば、普通紙、コート紙、キャストコート紙、光沢紙、光沢フィルム、ＯＨＰフィルムのいずれも使用することができ、中でも、例えば、支持体上に多孔質層が形成されている、いわゆる空隙層を有するインク吸収層を有する記録媒体が好ましい。上述した支持体の素材或いは形状に特に限定されるものではなく、例えば、シート状に形成されたもの以外に立体的な構造を有するものであってもよい。
【０１３０】
【実施例】
以下、合成例、実施例を挙げて本発明を更に詳細に説明するが、本発明は、これら実施例に限定されるものではない。
【０１３１】
《ポリマーの合成》
〔ポリマーＰ−１〜Ｐ−３の合成〕
３リットルの四つ口フラスコに、滴下装置、温度計、窒素ガス導入管、撹拌装置及び還流冷却管を付し、酢酸エチル１０００ｇを加熱して、温度を８０℃に調整し、窒素ガスを導入しながら、これに下記に記載の組成割合からなるモノマーを総量が１０００ｇとなるように秤量し、更にＮ，Ｎ′−アゾビスイソバレロニトリル２０ｇを前記モノマーに加えた混合液を、２時間かけて滴下し、同温度にて５時間反応させた後、溶剤を減圧留去して、ポリマーＰ−１〜Ｐ−３を合成した。
【０１３２】
Ｐ−１のモノマー組成（質量％）：メタクリル酸メチル／メタクリル酸ステアリル／メタクリル酸２−アセトアセトキシエチル（日本合成化学製）＝５０／２０／３０
Ｐ−２のモノマー組成（質量％）：メタクリル酸メチル／アクリル酸ブチル／アクリル酸２−エチルヘキシル＝８０／１０／１０
Ｐ−３のモノマー組成（質量％）：メタクリル酸メチル／アクリル酸２−エチルヘキシル＝８０／２０
（ポリマーＰ−４の合成）
上記ポリマーＰ−１〜Ｐ−３の合成において、下記のモノマーを用いてポリマーを合成した後、酸性基をアンモニア水により中和した以外は同様にして、ポリマーＰ−４を合成した。
【０１３３】
Ｐ−４のモノマー組成（質量％）：アクリル酸／スチレン／メタクリル酸メチル＝２０／３０／５０
《着色微粒子分散体の調製》
〔着色微粒子分散体ＣＰ−１の調製〕
クレアミックスＣＬＭ−０．８Ｓ（エムテクニク（株）社製）のポットに、ＦＳ Ｂｌｕｅ １５０４（有本化学製）１２ｇ（Ａ：染料）、固形分換算１２ｇのポリマーＰ−２（Ｂ：ポリマー）、及び１２０ｇの酢酸エチルを入れ、攪拌して染料を完全溶解させた。純水にドデシル硫酸ナトリウム（ＳＤＳ）０．５ｇ（Ｃ：乳化剤、界面活性剤）を加えて総量を２７０ｇとし、これを上記染料溶液に添加後、回転数２００００ｒｐｍで５分間乳化した。その後、減圧下で酢酸エチルを除去し、コア着色微粒子分散体を得た。
【０１３４】
このコア着色微粒子を三頭のセパラブルフラスコに移し、フラスコ内を窒素ガスで置換した後、ヒーターを付して８０℃に加温した。これに、３ｇのエレミノールＲＳ−３０（三洋化成工業（株）製）（Ｄ：解離性基導入モノマー）、４．８ｇのスチレン（Ｅ：その他のモノマー）及び０．３ｇのＮ，Ｎ′−アゾビスイソバレロニトリル（ＡＩＶＮ Ｆ：重合開始剤）の混合液を１時間で滴下し、更に６時間反応させて、コアシェル型着色微粒子分散体ＣＰ−１を調製した。
【０１３５】
〔着色微粒子分散体ＣＰ−２〜ＣＰ−５の調製〕
上記着色微粒子ＣＰ−１の調製において、Ａ：染料、Ｂ：ポリマー、Ｃ：乳化剤、界面活性剤、Ｄ：解離性基導入モノマー、Ｅ：その他のモノマー、Ｆ：重合開始剤を、表１に記載のように変更した以外は同様にして、着色微粒子分散体ＣＰ−２〜ＣＰ−５を調製した。
【０１３６】
〔着色微粒子分散体ＣＰ−６の調製〕
クレアミックスＣＬＭ−０．８Ｓ（エムテクニク（株）社製）のポットに、ＦＳ Ｂｌｕｅ １５０４（有本化学製）１２ｇ（Ａ：染料）に、１４ｇのメタクリル酸メチル、３ｇのアクリル酸ブチル、３ｇのアクリル酸２−エチルヘキシル（Ｅ：その他のモノマー）を加えて溶解させて染料溶液を調製した。純水に、ドデシル硫酸ナトリウム（ＳＤＳ）６ｇ（Ｃ：乳化剤）を加えて総量を２７０ｇとし、これを上記染料溶液に添加した後、回転数２００００ｒｐｍで５分間乳化した。
【０１３７】
次いで、上記乳化液を３頭のセパラブルフラスコに移し、フラスコ内を窒素ガスで置換した後、ヒーターを付して８０℃に加温した。４ｇのエレミノールＲＳ−３０（三洋化成工業（株）製）（Ｄ：解離性基導入モノマー）及び１ｇのＮ，Ｎ′−アゾビスイソバレロニトリル（Ｆ：重合開始剤）の混合液を、１時間かけて滴下し、更に６時間反応させて表１の着色微粒子分散液ＣＰ−６を得た。
【０１３８】
〔着色微粒子分散体ＣＰ−７の調製〕
クレアミックスＣＬＭ−０．８Ｓ（エムテクニク（株）社製）のポットに、特開２００１−１３１４５４号に記載のＮｏ．１のＹ染料を１２ｇ（Ａ：染料）、固形分換算８０ｇのポリマーＰ−４（Ｂ：ポリマー）、及び１２０ｇの酢酸エチルを入れ、攪拌して染料を完全溶解させて染料溶液を調製した。この染料溶液に、純水を２７０ｇ添加した後、回転数２００００ｒｐｍで５分間乳化した。その後、減圧下で酢酸エチルを除去し、コア着色微粒子分散体を得た。
【０１３９】
このコア着色微粒子分散体を３頭のセパラブルフラスコに移し、フラスコ内を窒素ガスで置換した後、ヒーターを付して８０℃に加温した。次いで、１ｇのエレミノールＲＳ−３０（三洋化成工業（株）製）（Ｄ：解離性基導入モノマー）、３ｇのアクリル酸メチル（Ｅ：その他のモノマー）及び０．３ｇのＮ，Ｎ′−アゾビスイソバレロニトリル（Ｆ：重合開始剤）の混合液を１時間かけて滴下し、更に６時間反応させて着色微粒子分散体ＣＰ−７を得た。
【０１４０】
〔着色微粒子分散体ＣＰ−８の調製：比較例〕
クレアミックスＣＬＭ−０．８Ｓ（エムテクニク（株）社製）のポットに、ＦＳ Ｂｌｕｅ １５０４（有本化学製）１２ｇ（Ａ：染料）に、固形分換算１２ｇのポリマーＰ−２（Ｂ：ポリマー）、及び１２０ｇの酢酸エチルを加え、攪拌して染料を完全溶解させて染料溶液を調製した。純水にエレミノールＲＳ−３０（三洋化成工業（株）製）１０ｇ（Ｃ：乳化剤、界面活性剤）を加えて総量を２７０ｇとし、これを上記染料溶液に添加した後、回転数２００００ｒｐｍで５分間乳化した。
【０１４１】
この乳化液を３頭のセパラブルフラスコに移し、フラスコ内を窒素ガスで置換した後、ヒーターを付して８０℃に加温した。次いで、４．８ｇのアクリル酸メチル（Ｅ：その他のモノマー）及び０．３ｇのＮ，Ｎ′−アゾビスイソバレロニトリル（Ｆ：重合開始剤）の混合液を１時間かけて滴下し、更に６時間反応させて着色微粒子ＣＰ−８を得た。
【０１４２】
〔着色微粒子分散体ＣＰ−９、１０の調製：比較例〕
前記着色微粒子分散体ＣＰ−１、２の調製において、Ｄ：解離性基導入モノマーを、エレミノールＲＳ−３０に代えてアクリル酸またはメタクリル酸を使用し、更に、各添加剤を表１に記載のように変更した以外は同様にして、着色微粒子分散体ＣＰ−９、１０の調製を調製した。また、各着色微粒子分散体を調製した後、酸と当量モルの０．１モル／ＬのＮａＯＨ水溶液により中和した。
【０１４３】
以上により調製した着色微粒子分散体ＣＰ−１〜ＣＰ−１０の詳細を、表１に示す。
【０１４４】
【表１】

【０１４５】
なお、表１に略称で記載した各添加剤の詳細を、以下に列挙する。
Ｃ：シアン着色微粒子分散体
Ｙ：イエロー着色微粒子分散体
ＦＳＢ１５０４：ＦＳ Ｂｌｕｅ １５０４（有本化学製）
Ｙ染料：特開２００１−１３１４５４号に記載のＮｏ．１のＹ染料
ＳＤＳ：ラウリル硫酸スルホン酸ナトリウム塩
Ｓ−１８０：ラテムルＳ−１８０ 花王（株）製
ＫＨ−０５：アクアロンＫＨ−５（第一工業製薬社製）
ＨＳ−１０：アクアロンＨＳ−１０（第一工業製薬社製）
ＡＡ：アクリル酸
ＭＡ：メタクリル酸
ＳＴ：スチレン
ＭＭＡ：メタクリル酸メチル
ＢＡ：アクリル酸ブチル
ＥＨＡ：アクリル酸−２−エチルヘキシル
〔着色微粒子分散体の評価〕
上記調製した着色微粒子分散体ＣＰ−１〜ＣＰ−１０について、下記の評価を行った。
【０１４６】
（着色微粒子分散体の分散性の評価）
各着色微粒子分散体を、調製直後に０．８μｍのメンブランフィルター（ＡＤＶＡＮＴＥＣ製、φ２５ｍｍ）で濾過し、フィルター１個あたりの濾過量（ｍｌ）を測定し、これを分散性の尺度とした。
【０１４７】
（着色微粒子分散体の保存安定性の評価）
上記の濾過液をガラス瓶に入れ密封して６０℃で一ヶ月間保管した後、上記と同様の方法でフィルター１個あたりの濾過量を測定し、これを保存安定性の尺度とした。
【０１４８】
《水性インクの調製》
前記調製した着色微粒子分散体（ＣＰ−１〜ＣＰ−１０）５０．０質量％、エチレングリコール１５．０質量％、グリセリン２０．０質量％、オルフィンＥ１０１０（日信化学製）０．５質量％、及び防腐剤Ｐｒｏｘｅｌ ＧＸ（Ａｖｅｃｉａ社製）０．１質量％を混合し、イオン交換水１４．４質量％を加えて水性インクを調製した。次いで、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インクジェット用の水性インクＩ−１〜１０を得た。
【０１４９】
（ピーク粒径の測定）
上記調製した各水性インク中の着色微粒子のピーク粒径を下記の方法に従って測定した。
【０１５０】
Ｍａｌｖｅｒｎ社製のＺｅｔａｓｉｚｅｒ １０００ＨＳを用いて、着色微粒子の体積平均粒径分布を求め、それをもとにピーク粒径を算出した。また、同時に透過型電子顕微鏡（ＴＥＭ）でも粒径測定を行い、相違がないことを確認した。
【０１５１】
（吐出安定性の評価）
各水性インクを純正カラーインクカートリッジに詰めて、インクジェットプリンターＣＬ−７５０（セイコーエプソン社製）に装填し、インクジェットペーパーフォトライクＱＰ（コニカ社製）に、プリンタドライバーをオフにして、１０ｃｍ×２０ｃｍのベタ画像を連続５枚プリントし、５枚目のベタ画像の状態を目視観察し、下記の基準に則り吐出安定性の評価を行った。
【０１５２】
Ａ：スジやムラが全く見られない（良好）
Ｂ：若干のスジが見られる（許容）
Ｃ：多数のスジ、ムラが見られる
Ｄ：ほとんど印字されていない
以上により得られた結果を、表２に示す。
【０１５３】
【表２】

【０１５４】
表２より明らかなように、本発明に係る着色微粒子は、比較例に対し、ピーク粒径が小さく、濾過性（分散性）も優れており、粗大粒子が少ないことが分かる。また、強制劣化条件で保存した後でも濾過性が良好であり、保存安定性に優れ、更に水性インクとしたときの吐出安定性に優れていることが分かる。これは、解離性基を効果的に導入したモノマーを用いることによって、着色微粒子間の凝集が抑えられているためであると考えられる。
【０１５５】
一方、エレミノールＲＳ−３０を乳化剤として用いた比較の着色微粒子分散体ＣＰ−８は、濾過性が悪く、また、水性インクとして調製した後のピーク粒径も大きかった。また、解離性基導入モノマーとしてアクリル酸、メタクリル酸を用いた比較の着色微粒子分散体ＣＰ−９、１０は、同様に着色微粒子の粒径が大きくなる傾向にあった。それぞれ、エレミノールＲＳ−３０の乳化力不足、酸モノマーによる粒子の凝集が原因であるものと思われる。更に、これらの着色微粒子分散体は、強制劣化後の分散体の保存も悪く、また、水性インクとしたときの吐出安定性に劣っていることがわかる。
【０１５６】
また、本発明の水性インクを用いて形成した画像は、比較例に対し、透明感があり、高い明度、彩度の高品位画像が得られることを確認することができた。
【０１５７】
【発明の効果】
本発明により、小粒径の着色微粒子を得ることができ、分散性、保存安定性及び吐出安定性に優れた着色微粒子分散体、水性インクと、それを用いて高画質の画像が得られる画像形成方法を提供することができた。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a novel colored fine particle dispersion, an aqueous ink, 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 desolvated and made aqueous. In particular, as an aqueous recording material used for ink jet recording, those mainly composed of an aqueous solution of a water-soluble dye and those mainly composed of a fine dispersion of a pigment are widely used.
[0003]
Aqueous inks using water-soluble dyes include aqueous dyes mainly classified as acid dyes, direct dyes, and some food dyes, and glycols, alkanolamines as humectants, and surface tension adjusters. To which a surfactant and, if necessary, a thickener and the like are added. Water-based inks using these water-soluble dyes are most commonly used because of their high reliability against clogging at the brush tip or printer, but they easily bleed on the recording paper, limiting their use and reducing the quality of recording. Have to be forced. That is, a water-soluble dye which merely permeates into a recording paper and is dried and fixed is hardly said to be "dyed" and has a very low light fastness.
[0004]
Further, in order to solve the problems of low water fastness and light fastness of an aqueous ink using a water-soluble dye, there has been proposed a method of coloring a water-dispersible resin with an oil-soluble dye or a hydrophobic dye, for example, as disclosed in JP-A-139471, JP-A-58-45272, JP-A-3-250069, JP-A-8-253720, JP-A-8-92513, JP-A-8-183920, JP-A-2001-11347 and the like.
[0005]
In addition to coloring the water-dispersible resin with an oil-soluble dye or a hydrophobic dye, it is also possible to form a coloring material and colored fine particles composed of a resin coated with the coloring material, or a coloring material particle composed of a coloring material and a resin to further form a film. Attempts have been made to use colored fine particles coated with a resin.
[0006]
However, when producing particles obtained by coloring a water-dispersible resin with these oil-soluble dyes or hydrophobic dyes, or colored fine particles obtained by further coating these particles with a resin, the solubility or affinity of the dye or resin with respect to an organic solvent, etc. In many cases, a fine particle dispersion containing a high concentration of a coloring material cannot be stably produced due to insufficient dyeing, and the dye is easily precipitated even when dissolved or dispersed, or the dye is present on the particle surface (resin Etc.), the dispersion stability of the colored fine particles themselves is impaired, and it is difficult to enhance various properties such as dispersion stability and ejection stability required for ink-jet inks, and to improve light resistance. However, there has been a problem that the effects of the above-mentioned methods are reduced.
[0007]
Several techniques have been proposed in which a coloring material and a resin are mixed and dispersed in water to form a colored fine particle dispersion, and this is used as an inkjet ink.
[0008]
Among these, as a characteristic of the resin, Japanese Patent Application Laid-Open No. 2001-98194 discloses a resin using a copolymer resin composed of a hydrophilic polymerized chain portion and a hydrophobic polymerized chain portion. Japanese Patent Application Laid-Open No. 9-157508 discloses a polymer using a polymerizable unsaturated acid monomer, a hydroxyl group-containing monomer, a styrene macromer and the like, and a polyester resin containing a cyclohexene dicarboxylic acid.
[0009]
However, the above-mentioned colored fine particles are still insufficient, such as a particle size of about 100 nm being large, dispersion stability, ink storage stability, ejection stability, and insufficient transparency of the print. Has not been obtained.
[0010]
Japanese Patent Application Laid-Open No. 9-157508 discloses a method of dissolving and emulsifying a polyester resin and an oily dye, and further polymerizing an ethylenically unsaturated monomer to obtain water of composite colored fine particles having a core-shell structure. Dispersions are also described.
[0011]
However, the above-mentioned colored fine particles having a core-shell structure have a large particle size, have a problem in dispersion stability, and are not practical.
[0012]
JP-A-2002-47440, JP-A-2002-88294, and JP-A-2002-97395 describe fine particles having a small particle diameter of 50 nm or less. However, the dispersion stability is insufficient, the storage stability is low, and the secondary Aggregation reduces the transparency of the image, and the effect of the fine particles is insufficient. JP-A-2002-80746 and JP-A-2002-80772 disclose compositions in which an oil-soluble dye dissolved in an organic solvent having a high boiling point is dispersed in an aqueous medium. However, these compositions cannot be used without a medium such as gelatin. It is stable and does not have stable ink ejection.
[0013]
Various methods have been proposed to impart the dispersion stability of the colored fine particles to the above problem. For example, a method of adding an acid monomer such as acrylic acid or methacrylic acid when preparing colored fine particles by polymerization of a monomer for the purpose of improving the storage stability of the colored fine particles is disclosed (for example, Patent Document 1). reference.). However, when these acids are used during monomer polymerization, the particle size of the colored fine particles may be increased. Furthermore, in order to further improve the storage stability, a neutralization reaction may be performed after the polymerization, if necessary.However, this causes aggregation of the colored fine particles, resulting in an increase in the particle size, which in turn impairs the storage stability. was there. In addition, there is also a problem that an undesirable water-soluble polymer is generated by self-polymerization of acid monomers.
[0014]
Further, a method of using an anionic reactive emulsifier having an alkylene oxide group, for example, Eleminol RS-30 manufactured by Sanyo Chemical Industry Co., Ltd. to improve the stability of the colored fine particles is known (for example, Patent References 2 to 4). Since the reactive emulsifier has already been neutralized for acidic groups, it is possible to avoid aggregation of particles due to neutralization after polymerization. In addition, since it has high copolymerizability with other monomers and poor self-polymerizability, almost no unnecessary water-soluble polymer is produced. As described above, the reactive emulsifier has excellent properties as a monomer, but has poor emulsifying properties. Therefore, in a system of colored fine particles requiring finer dispersion, it is not suitable to be used alone as a reactive emulsifier for emulsion polymerization.
[0015]
[Patent Document 1]
JP-A-10-251567 (Claims)
[0016]
[Patent Document 2]
JP 2001-247797 A
[0017]
[Patent Document 3]
Japanese Patent Publication No. 2002-127585
[0018]
[Patent Document 4]
Japanese Patent Publication No. 2002-127586
[0019]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and an object thereof is to obtain colored fine particles having a small particle diameter, and have excellent dispersibility, storage stability, and ejection stability. Another object of the present invention is to provide an image forming method capable of obtaining a high quality image.
[0020]
[Means for Solving the Problems]
The above object of the present invention is achieved by the following configurations.
[0021]
1. In a colored fine particle dispersion obtained by dispersing colored fine particles prepared by mixing a coloring material and a polymer in water, at least one kind of the polymer is represented by the general formula (a) in the presence of a surfactant. A colored fine particle dispersion obtained by polymerizing the polymerizable monomer represented.
[0022]
2. 2. The colored fine particle dispersion according to the item 1, wherein the mass ratio of the compound represented by the general formula (a) to the surfactant is from 5: 1 to 0.1: 1.
[0023]
3. 3. The colored fine particle dispersion according to the above 1 or 2, wherein Y in the general formula (a) is a carbonyl group, and Z is a sulfonate.
[0024]
4. The colored fine particle dispersion according to any one of Items 1 to 3, wherein the average degree of polymerization (n) of the alkylene oxide group in the general formula (a) is 3 to 15.
[0025]
5. The colored fine particle dispersion according to any one of Items 1 to 4, wherein the surfactant is a reactive emulsifier.
[0026]
6. A mixture in which the colored fine particles are composed of a polymerizable monomer represented by the general formula (a), at least one polymerizable monomer other than the polymerizable monomer (a) represented by the general formula (a), and a coloring material The colored fine particle dispersion according to any one of the above items 1 to 5, which is obtained by emulsifying the above with a surfactant and then performing a polymerization reaction.
[0027]
7. After the colored fine particles emulsify a polymer and a compatible material of a coloring material with a surfactant, at least one polymerizable monomer (a) represented by the general formula (a) is added to carry out emulsion polymerization. The colored fine particle dispersion according to any one of the above items 1 to 5, which is obtained by performing the method.
[0028]
8. In a colored fine particle dispersion obtained by dispersing colored fine particles prepared by mixing a coloring material and a polymer in water, the colored fine particles are converted into a self-emulsifiable colored fine particle dispersion by the general formula (a). And a polymerizable monomer other than the polymerizable monomer (a) represented by the general formula (a) represented by the general formula (a) is added, and emulsion polymerization is performed. Characterized colored fine particle dispersion.
[0029]
9. A colored fine particle dispersion obtained by dispersing colored fine particles prepared by mixing a colorant and a polymer in water and a surfactant, wherein the colored fine particles have a polyalkylene oxide sulfate group on the surface thereof, and A colored fine particle dispersion, wherein at least one of the activators has a polyalkylene oxide sulfate group having a structure different from that of the polyalkylene oxide sulfate group.
[0030]
10. 10. The colored fine particle dispersion according to any one of items 1 to 9, wherein at least one of the surfactants does not include a polyalkylene oxide sulfate group in the structure.
[0031]
11. The colored material dispersion according to any one of Items 1 to 10, wherein the coloring material is an oil-soluble dye.
[0032]
12. The colored fine particle dispersion according to any one of Items 1 to 11, wherein the colored fine particles have a core-shell structure.
[0033]
13. 13. An aqueous ink comprising the colored fine particle dispersion according to any one of the above items 1 to 12.
[0034]
14． 14. The aqueous ink according to the item 13, wherein the colored fine particles have a peak particle size of 50 nm or less.
[0035]
15. 15. The aqueous ink according to the above item 13 or 14, which is an ink jet ink.
[0036]
16. 16. An image forming method, comprising: ejecting the aqueous ink according to the above item 15 by an ink jet recording apparatus to form an image.
[0037]
The present inventors have conducted intensive studies in view of the above problems, and as a result, at least one type of the polymer was obtained in a colored fine particle dispersion obtained by dispersing colored fine particles prepared by mixing a coloring material and a polymer in water. Can be prepared by polymerizing the polymerizable monomer represented by the general formula (a) in the presence of a surfactant to prepare colored microparticles, or by converting the colored microparticles into a self-emulsifying colored microparticle dispersion, A polymerizable monomer represented by the general formula (a) and at least one polymerizable monomer other than the polymerizable monomer (a) represented by the general formula (a) are added to carry out emulsion polymerization. Or the colored fine particles have a polyalkylene oxide sulfate group on the surface, and at least one of the surfactants is different from the polyalkylene oxide sulfate group. By preparing colored fine particles by a method having a structure having a polyalkylene oxide sulfate ester group, colored fine particles of fine particles can be obtained, and the colored fine particles having excellent dispersion stability, storage stability and ejection stability can be obtained. It has been found that the present invention can realize a body, an aqueous ink and an image forming method capable of obtaining a high-quality image, and has reached the present invention.
[0038]
Further, the mass ratio of the compound represented by the general formula (a) to the surfactant is in the range of 5: 1 to 0.1: 1, and in the general formula (a), Y is a carbonyl group. Yes, Z is a sulfonate, or the average degree of polymerization (n) of the alkylene oxide group is 3 to 15, a reactive emulsifier is used as a surfactant, and the colored fine particles have the general formula ( After emulsifying a mixture comprising a polymerizable monomer represented by a), at least one polymerizable monomer other than the polymerizable monomer (a) represented by the general formula (a), and a coloring material with a surfactant, Performing a polymerization reaction, after the colored fine particles emulsify the polymerizable polymer and the compatible material of the coloring material with a surfactant, and then form at least one polymerizable monomer (a) represented by the general formula (a). ) To perform emulsion polymerization The above effect can be further improved because at least one of the surfactants does not contain a polyalkylene oxide sulfate group in the structure, the coloring material is an oil-soluble dye, and the coloring fine particles have a core-shell structure. It is even better.
[0039]
Hereinafter, details of the present invention will be described.
The colored fine particle dispersion of the present invention is characterized in that, when preparing colored fine particles, a polymerizable monomer represented by the general formula (a) is used as one of the monomers.
[0040]
First, a polymerizable monomer having a dissociable group represented by the general formula (a) (hereinafter, also referred to as a monomer (a)) will be described.
[0041]
The polymerizable monomer represented by the general formula (a) according to the present invention is a polymerization monomer for forming resin fine particles together with a coloring material by a polymerization reaction, and substantially functions as a surfactant. Absent. Specifically, the present invention relates to a method for preparing colored fine particles, for example, in which a monomer (a) is added to a colorant particle emulsified by a surfactant or a self-emulsifying colorant particle to perform a polymerization reaction. Is included. In addition, when emulsifying the colored fine particles, even when the monomer (a) is present in the emulsification system, when another emulsifier or surfactant is used in combination at a certain ratio, and then the polymerization reaction is performed, The monomer (a) can be interpreted as playing a role as a monomer for polymerization. At this time, the mass ratio of the monomer (a) to the surfactant is preferably in the range of 5: 1 to 0.1: 1.
[0042]
In the general formula (a), X represents a hydrogen atom or a methyl group. The linking group Y represents a group linking the olefin moiety and the alkylene oxide group in the general formula (a), and the total number of carbon atoms is preferably 9 or less. If the total number of carbon atoms exceeds 9, the emulsifiability will be improved but the copolymerization rate will be reduced, making it unsuitable for use as a monomer. The linking group Y having 9 or less total carbon atoms is particularly preferably a carbonyl group. AO represents an alkylene oxide group such as ethylene oxide and propylene oxide, and the degree of polymerization is preferably in the range of 3 or more and 15 or less. Z represents an anionic group, and specific examples thereof include salts of sulfonic acid, carboxylic acid, phosphoric acid and the like. Of these, salts of sulfonic acids are most preferred.
[0043]
The polymerizable monomer having a dissociable group represented by the general formula (a) according to the present invention can be obtained by synthesis by a method known to those skilled in the art, and can be easily obtained as a commercial product. For example, Sanyo Kasei Kogyo Co., Ltd. Eleminor RS-30 is mentioned.
[0044]
The present invention is characterized in that colored particles are prepared by polymerizing the polymerizable monomer represented by the general formula (a) in the presence of a surfactant. It is preferable to use an acidic emulsifier.
[0045]
The reactive emulsifier preferably used in the present invention is not particularly limited, whether it is an anionic or nonionic reactive emulsifier, but is preferably a compound having the following substituents A, B or C.
[0046]
A: a linear alkyl group, a branched alkyl group, or a substituted or unsubstituted aromatic group having a total carbon atom number of 7 or more
B: Nonionic or anionic substituent that exhibits surface activity
C: radically polymerizable polymerizable group
Examples of the substituent described in section A include a heptyl group, an octyl group, a nonyl group, a decyl group, a linear alkyl group such as a dodecyl group, a branched alkyl group such as a 2-ethylhexyl group, a phenyl group, a nonylphenyl group, Examples include an aromatic substituent such as a naphthyl group.
[0047]
Examples of the nonionic substituent or anionic substituent that expresses the surface activity described in Section B include, for example, nonionic substituents include polyalkylene oxides such as polyethylene oxide, polypropylene oxide, and copolymers thereof. . Specific examples of the anionic substituent include carboxylic acid, phosphoric acid, sulfonic acid, and salts thereof. In addition, one in which the terminal of the alkylene oxide is substituted by the above-described anionic group is also one of the specific examples of the anionic group. As the substituent represented by the item B, an anionic group is preferable, and the terminal is more preferably a salt.
[0048]
The radically polymerizable group described in the section C is a group that undergoes polymerization and crosslinking reaction by a radical active species, and is a vinyl group, an allyl group, a 1-propenyl group, or an isopropenyl group that is an ethylenically unsaturated group. An acrylate group, a methacrylate group, a maleimide group, and the like.More specifically, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, unsaturated carboxylic acid groups such as maleic acid and salts thereof, a urethane group, Examples include amide groups, anhydrides, acrylonitrile groups, styryl groups, and radically polymerizable groups such as various unsaturated polyester groups, unsaturated polyether groups, unsaturated polyamide groups, and unsaturated urethane groups.
[0049]
As the reactive emulsifier according to the present invention, a compound represented by the following general formula (1) is preferable.
[0050]
Embedded image

[0051]
In the general formula (1), R¹Represents a linear alkyl group having 7 to 20 carbon atoms, a branched alkyl group, or a substituted or unsubstituted aromatic group, for example, a heptyl group, an octyl group, a nonyl group, a decyl group, a dodecyl described in the above section A. And a branched alkyl group such as a 2-ethylhexyl group, an aromatic substituent such as a phenyl group, a nonylphenyl group, and a naphthyl group.
[0052]
R^TwoRepresents a substituent having a polymerizable group capable of radical polymerization, and examples thereof include an acrylate group, a methacrylate group, and a maleimide group, which are the ethylenically unsaturated groups described in the above section C. Y¹Represents a sulfonic acid, a carboxylic acid, or a salt thereof.
[0053]
The compound represented by the general formula (1) can be obtained by a person skilled in the art by a known method. In addition, it can be easily obtained from commercial products. For example, “Latemul S-120”, “Latemul S-120A”, “Latemul S-180”, “Latemul S-180A”, and Sanyo Chemical "Eleminol JS-2" manufactured by Kogyo Co., Ltd. can be mentioned.
[0054]
Further, as the reactive emulsifier according to the present invention, a compound represented by the following general formula (2) is preferable.
[0055]
Embedded image

[0056]
In the above general formula (2), R^Three, R^FourIs R in the above general formula (1)¹, R^TwoIs synonymous with each of Y^TwoRepresents a hydrogen atom, a sulfonic acid or a salt thereof, or a carboxylic acid or a salt thereof. AO represents an alkylene oxide.
[0057]
The compound represented by the general formula (2) according to the present invention can be obtained by a person skilled in the art by synthesizing by a known method. Further, it can be easily obtained from commercial products. For example, NE such as "Adekaria Soap NE-20", "Adekaria Soap NE-20", and "Adekaria Soap NE-30" manufactured by Asahi Denka Kogyo Co., Ltd. SE series such as "Adekaria Soap SE-10N", "Adekaria Soap SE-20N", "Adekaria Soap SE-30N", "AQUALON RN-10" and "AQUALON RN" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. -20 "," AQUARON RN-30 ", RN series such as" AQUALON RN-50 "," AQUALON HS-05 "," AQUALON HS-10 "," AQUALON HS-20 "," AQUALON HS-30 ", etc. HS series or Aqualon BC series.
[0058]
Further, as the reactive emulsifier according to the present invention, a compound represented by the following general formula (3) is preferable.
[0059]
Embedded image

[0060]
In the general formula (3), R^Five, R⁶, Y^ThreeAnd AO represent the R of the general formula (1)¹, R^Two, Y¹And the same as each of AO in the general formula (2).
[0061]
The compound represented by the general formula (3) can be obtained by a person skilled in the art by synthesizing by a known method. In addition, it can be easily obtained from commercial products, and examples thereof include "AQUALON KH-05", "AQUALON KH-10", and "AQUALON KH-20" manufactured by Daiichi Kogyo Seiyaku.
[0062]
In the general formulas (2) and (3), the average degree of polymerization n of the alkylene oxide chain (AO) is preferably 1 to 10, and for example, “AQUALON KH-05” manufactured by Daiichi Kogyo Seiyaku Co., Ltd. , "AQUALON KH-10", "AQUALON HS-05", "AQUALON HS-10", and the like.
[0063]
Further, in the present invention, the reactive emulsifier is preferably anionic. For example, the above-mentioned "Adecaria Soap SE Series" (manufactured by Asahi Denka Kogyo), "Aqualon HS Series" (Daiichi Kogyo Seiyaku) ), "Latemul S Series" (manufactured by Kao Corporation), "Eleminol JS Series" (manufactured by Sanyo Chemical Industries) and the like.
[0064]
In the present invention, the use amount of these reactive emulsifiers is generally 0.1 to 80 parts by mass, preferably 1 to 70 parts by mass, particularly preferably 10 to 70 parts by mass, per 100 parts by mass of the total of the polymerizable monomers used in the present invention. ６０60 parts by mass.
[0065]
In the emulsion copolymerization at the time of preparing the colored fine particle dispersion of the present invention, as long as it does not adversely affect the performance of the obtained aqueous copolymer dispersion, if necessary, together with the reactive emulsifier described above, a usual anionic system And / or a nonionic emulsifier (surfactant) can be used in combination.
[0066]
Examples of the usual nonionic emulsifiers include, for example, polyoxyethylene ocalkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; for example, polyoxyethylene alkyl phenyl ethers such as polyoxyethylene nonyl phenyl ether; For example, sorbitan higher fatty acid esters such as sorbitan monolaurate, sorbitan monostearate and sorbitan trioleate; for example, polyoxyethylene sorbitan higher fatty acid esters such as polyoxyethylene sorbitan monolaurate; for example, polyoxyethylene monolau Higher fatty acid esters such as polyoxyethylene monostearate and the like; for example, monoglyceride oleate and monoglyceride stearate Glycerine higher fatty acid esters and the like; for example, polyoxyethylene - polyoxypropylene - block copolymers; and the like can be given.
[0067]
Examples of the above-mentioned ordinary anionic emulsifiers include, for example, higher fatty acid salts such as sodium oleate; alkylaryl sulfonates such as sodium dodecylbenzenesulfonate; alkyl sulfate salts such as sodium lauryl sulfate; Polyoxyethylene alkyl ether sulfates such as sodium polyethoxyethylene lauryl ether sulfate; polyoxyethylene alkyl aryl ether sulfates such as sodium polyoxyethylene nonylphenyl ether sulfate; sodium monooctyl sulfosuccinate, sodium dioctyl sulfosuccinate Alkylsulfosuccinates such as sodium polyoxyethylene laurylsulfosuccinate and derivatives thereof; and the like. The, in the present invention, at least one surfactant, preferably a surfactant containing no polyalkylene oxide sulfate group in its structure.
[0068]
In the present invention, the colored fine particles may be a polymerizable monomer represented by the general formula (a), at least one polymerizable monomer other than the polymerizable monomer (a) represented by the general formula (a), and a colorant. Preferably, the mixture is obtained by emulsifying a mixture of materials with a surfactant and then performing a polymerization reaction.
[0069]
Examples of the polymerizable monomer other than the polymerizable monomer (a) represented by the general formula (a) that can be used in the present invention include styrene-acrylate, and specific monomers include vinyl acetate and Methyl acrylate, ethyl acrylate, n-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, dodecyl acrylate, octadecyl acrylate, 2-phenoxyethyl acrylate, methyl methacrylate, methacrylic acid Ethyl, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, stearyl methacrylate, benzyl methacrylate, Methacrylic acid glycidyl, phenyl methacrylate, styrene, alpha-methyl styrene, acrylonitrile, acetoacetoxyethyl methacrylate, glycidyl methacrylate of soybean oil fatty acid modified products: include (Blenmer G-FA manufactured by NOF Corporation) and the like.
[0070]
As a more preferable combination, styrene or methyl methacrylate as a main component, acetoacetoxyethyl methacrylate, soybean oil fatty acid-modified glycidyl methacrylate (Blemmer G-FA: manufactured by NOF CORPORATION), and n-butyl acrylate, methacrylic acid At least one selected from long-chain (meth) acrylates such as stearyl acrylate and 2-ethylhexyl acrylate is added, and acrylonitrile, divinylbenzene, diethylene glycol dimethacrylate, etc. are added as needed to improve physical properties. Can be mentioned.
[0071]
The above-mentioned polymer may have a substituent, and the substituent may have a linear, branched, or cyclic structure. Various polymers having the above functional group are commercially available, but can also be synthesized by a conventional method. Further, these copolymers can also be obtained, for example, by introducing an epoxy group into one polymer molecule and subsequently condensing with another polymer, or performing graft polymerization using light or radiation.
[0072]
As the colored fine particles according to the present invention, at least one polymerizable monomer (a) represented by the general formula (a) is added after emulsifying a polymer and a compatible material of a coloring material with a surfactant. Also, a method of preparing by carrying out emulsion polymerization is preferable. As the polymer, an acrylic polymer or a styrene-acrylic polymer is preferable, and for example, a copolymer of an acrylate, a styrene-acrylate, or the like is preferable. Specific monomers that give the above polymer include the monomers listed as styrene-acrylates above.
[0073]
Further, as a method for preparing colored fine particles according to the present invention, a polymerizable monomer represented by the general formula (a) and at least one kind represented by the general formula (a) are added to a self-emulsifying colored fine particle dispersion. It is characterized in that it is prepared by adding an other polymerizable monomer other than the polymerizable monomer (a) to be subjected to emulsion polymerization.
[0074]
The self-emulsifying colored fine particle dispersion in the present invention is a colored fine particle prepared by using an aqueous dispersion (self-emulsifying) type polymer as a polymer for preparing the colored fine particles. May be any of an ionic polymer, a nonionic dispersible group-containing polymer, and a mixed polymer thereof. Examples of the ionic polymer include a polymer having a cationic group such as a tertiary amino group and a polymer having an anionic dissociable group such as a carboxylic acid and a sulfonic acid. Examples of the nonionic dispersible group-containing polymer include polymers containing a nonionic dispersible group such as a polyethyleneoxy group. Among these, from the viewpoint of dispersion stability of the colored fine particles, an ionic polymer containing an anionic dissociable group, a nonionic dispersible group-containing polymer, and a mixed polymer thereof are preferable.
[0075]
In the colored fine particle dispersion of the present invention, the colored fine particles have a polyalkylene oxide sulfate group on the surface, and at least one of the surfactants has a polyalkylene oxide structure different from the polyalkylene oxide sulfate group. It preferably has an oxide sulfate group.
[0076]
That is, when the coloring fine particles having a polyalkylene oxide sulfate group added to the surface thereof and a surfactant having a polyalkylene oxide sulfate group coexist in the ink, when both of the polyalkylene oxide sulfate group are present in the ink, However, it has been found that different structures are preferable for achieving the dispersion stability or the storage stability of the colored fine particles.
[0077]
In the emulsion polymerization of the colored fine particle dispersion of the present invention, the polymerizable monomer represented by the above general formula (a), the reactive emulsifier, and the like, as long as the performance of the obtained aqueous dispersion of the copolymer is not adversely affected. A water-soluble protective colloid can be used in combination with a usual anionic and / or nonionic emulsifier.
[0078]
Examples of the water-soluble protective colloid include polyvinyl alcohols such as partially saponified polyvinyl alcohol, completely saponified polyvinyl alcohol, and modified polyvinyl alcohol; cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose, and carboxymethyl cellulose salts; and guar gum. And natural polysaccharides; and these can be used alone or in combination of two or more. The amount of the water-soluble protective colloid used is preferably 0 to 10 parts by mass per 100 parts by mass of the total of the monomers.
[0079]
Further, in the emulsion polymerization, usually, for example, persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate; and organic peroxides such as t-butyl hydroperoxide, cumene hydroperoxide and p-menthane hydroperoxide. Polymerization initiator such as hydrogen peroxide. These polymerization initiators can be used in either one kind or a combination of plural kinds. These polymerization initiators are preferably used in an amount of 0.1 to 1 part by mass based on 100 parts by mass of the total of the monomers.
[0080]
In the emulsion polymerization, a reducing agent can be used together with the polymerization initiator, if desired. Examples of such a reducing agent include reducing organic compounds such as ascorbic acid, tartaric acid, citric acid, glucose, and formaldehyde sulfoxylate metal salt; sodium thiosulfate, sodium sulfite, sodium bisulfite, sodium metabisulfite, and the like. Reducing inorganic compounds; and the like. It is preferable to use these reducing agents in an amount of 0.1 to 1 part by mass based on 100 parts by mass of the total of the monomers.
[0081]
Furthermore, a chain transfer agent can be used in the emulsion polymerization. Examples of such a chain transfer agent include dodecyl mercaptan, t-dodecyl mercaptan, butyl mercaptan, 2-ethylhexyl thioglycolate, 2-mercaptoethanol, and trichlorobromomethane. These chain transfer agents are preferably used in an amount of 0 to 1 part by mass based on a total of 100 parts by mass of the monomers.
[0082]
In the emulsion copolymerization, the copolymerization temperature suitably employed is preferably from 40 to 100 ° C, particularly preferably from 60 to 90 ° C.
[0083]
Next, the coloring material according to the present invention will be described.
As the hue of the color material used in the present invention, yellow, magenta, cyan, black, blue, green and red are preferably used, and particularly preferably yellow, magenta, cyan and black color materials.
[0084]
In the present invention, the coloring material is preferably an oil-soluble dye. Oil-soluble dyes are usually dyes that are soluble in organic solvents that do not have a water-soluble group such as carboxylic acid or sulfonic acid and are insoluble in water, but by forming a water-soluble dye with a long-chain base to form a salt. Oil-soluble dyes are also included. For example, acid dyes, direct dyes, and salt-forming dyes comprising a reactive dye and a long-chain amine are known. The oil-soluble dye is not limited to the following, but particularly preferred specific examples include, for example, Validif Yellow 4120, Validif Yellow 3150, Validif Yellow 3108, Validif Yellow 2310N, and 1101 Valif, manufactured by Orient Chemical Industries, Ltd. , Valifast Red 3320, Valifast Red 3304, Valifast Red 1306, Valifast Blue 2610, Valifast Blue 2606, Valifast Blue 1603, Oil Yellow 3Wl, Oil Yellow 3W, Oil Yellow GG-S w 105, Oil Scarlet 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 70, Oil Black 70, Oil Black 70, Oil Black 70 Oil Black 5906, Oil Black 5905, Nippon Kayaku Co., Ltd. Kayaset Yellow SF-G, Kayaset Yellow K-CL, Kayaset Yellow GN, Kayaset Yellow AG-K, Kayaset Yellow R-Ked, 2K-Ketset, 2K-Kayset, 2K, 2K, 2K, 2K-K , Kayaset Red A-BR, Ka aset Magenta312, Kayaset Blue K-FL, Arimoto Chemical Industry Co., Ltd. FS Yellow 1015, FS Magenta 1404, FS Cyan 1522, FS Blue 1504, C. I. Solvent Yellow 88, 83, 82, 79, 56, 29, 19, 16, 14, 04, 03, 02, 01, C.I. I. Solvent Red 84: 1, C.I. I. Solvent Red 84, 218, 132, 73, 72, 51, 43, 27, 24, 18, 01, C.I. I. Solvent Blue 70, 67, 44, 40, 35, 11, 02, 01, C.I. I. Solvent Black 43, 70, 34, 29, 27, 22, 7, 3, C.I. I. Solvent Violet 3, C.I. I. Solvent Green 3 and 7, Plast Yellow DY352, Plast Red 8375, MS Yellow HD-180 manufactured by Mitsui Chemicals, MS Red G, MS Magenta HM-1450H, MS Blue HM-1384, ES Red 3001 manufactured by Sumitomo Chemical, ES Red 3001 3002, ES Red 3003, TS Red 305, ES Yellow 1001, ES Yellow 1002, TS Yellow 118, ES Orange 2001, ES Blue 6001, TS Turq Blue OS 618, MACROX Yellow Glass by Bayer, Inc. GN, MACROLEX Red V olet R, and the like.
[0085]
Further, metal complex dyes as shown in JP-A-9-277693, JP-A-10-20559, and JP-A-10-30061 are also preferably used, and a preferred structure is represented by the following general formula (4). is there.
[0086]
General formula (4)
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 dye, p represents 1 to 3, and m represents 0, 1, 2, and 3. When m is 0, p represents 2 or 3, in which case Dye may be the same or different.
[0087]
Examples of the metal ion represented by M include metals belonging to Groups 1 to 17 of the periodic table. Various dye structures can be considered as the dye capable of coordinating with the metal represented by Dye, but conjugated methine dyes, azomethine dyes, and dyes having a coordinating group in the azo dye skeleton are preferable.
[0088]
Disperse dyes can be used as the oil-soluble dyes. The disperse dyes are not limited to the following, but particularly preferred specific examples include C.I. I. Disperse Yellow 5, 42, 54, 64, 79, 82, 83, 93, 99, 100, 119, 122, 124, 126, 160, 184: 1, 186, 198, 199, 204, 224 and 237; . I. Disperse Orange 13, 29, 31: 1, 33, 49, 54, 55, 66, 73, 118, 119 and 163; I. Disperse Red 54, 60, 72, 73, 86, 88, 91, 92, 93, 111, 126, 127, 134, 135, 143, 145, 152, 153, 154, 159, 164, 167: 1, 177 , 181, 204, 206, 207, 221, 239, 240, 258, 277, 278, 283, 311, 323, 343, 348, 356 and 362; I. Disperse Violet 33; 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 and C.I. I. Disperse Green 6: 1 and 9 and the like.
[0089]
Other oil-soluble dyes include phenols, naphthols, cyclic methylene compounds such as pyrazolone and pyrazolotriazole, and so-called couplers such as open-chain methylene compounds, and p-phenylenediamines or p-diaminopyridines. Azomethine dyes and indoaniline dyes obtained by oxidative coupling of compounds are also preferred. In particular, an azomethine dye having a pyrazolotriazole ring is preferable as the magenta dye.
[0090]
Next, a method for preparing the colored fine particles according to the present invention will be described.
The colored fine particle dispersion of the present invention is obtained by dissolving the oil-soluble dye in an organic solvent, and dissolving the oil-soluble dye with the polymerizable monomer represented by the general formula (a) in the presence of a surfactant such as a reactive emulsifier. And by copolymerizing with other polymerizable monomers.
[0091]
Such a colored fine particle dispersion can be used to form an ink-jet ink, but further prevents aggregation of the colored fine particle dispersion over a long period of time and improves the stability of the fine particle as an ink suspension. In order to impart robustness to an image, such as color tone and gloss of an image printed on a medium, and light fastness, the present invention provides a core-shell type in which the colored fine particles are used as a core and a shell made of an organic polymer is further formed. It is preferably colored fine particles.
[0092]
As a method for forming the shell, there is a method in which a polymer dissolved in an organic solvent is gradually dropped, and the polymer is adsorbed on the surface of the colored fine particle core simultaneously with precipitation. In the present invention, a core containing a coloring material and a resin is used. After forming colored fine particles, a monomer having a polymerizable unsaturated double bond is added, emulsion polymerization is performed in the presence of an activator, and the emulsion is deposited on the core surface simultaneously with polymerization to form a shell. Even in the case of forming by this method, for example, when a dye is used as a coloring material, there is some mixing of phases at the core / shell interface, and the coloring material content in the shell is not necessarily zero. Although it is not necessary, the mixing is preferably smaller, and the color material content (concentration) in the shell is preferably 0.8 or less of the color material content (concentration) in the core not subjected to the core / shell formation. More preferably, it is 0.5 or less.
[0093]
Examples of the monomer having a polymerizable unsaturated double bond forming a polymer that coats the colorant particles as a shell include, in addition to the polymerizable monomer represented by the general formula (a) according to the present invention, ethylene, propylene, butadiene, Compounds selected from vinyl chloride, vinylidene chloride, vinyl acetate, styrene, (meth) acrylates, (meth) acrylic acid, acrylamides, etc., styrene, ethyl (meth) acrylate, butyl (meth) acrylate And (meth) acrylic esters such as ethylhexyl (meth) acrylate. In addition to these monomers, a polymerizable unsaturated monomer having a hydroxyl group in the molecule, for example, hydroxyethyl (meth) acrylate Ester such as hydroxyalkyl (meth) acrylate, etc. It may be mixed with a monomer having a sexual unsaturated double bond.
[0094]
It is important to evaluate whether it is actually core-shelled. In the present invention, the analysis method is limited from the viewpoint of the resolution because the individual particle diameter is very small, 200 nm or less. TEM, TOF-SIMS, and the like can be applied as an analysis method that meets such a purpose. When observing the core-shelled fine particles by TEM, the dispersion can be applied on a carbon support film, dried, and observed. In the TEM observation image, the contrast difference may be small only with the kind of polymer which is an organic substance. Therefore, in order to evaluate whether or not core-shell is formed, the fine particles are osmium tetroxide, ruthenium tetroxide, chlorosulfonic acid / It is preferable to dye using uranyl acetate, silver sulfide, or the like. The fine particles of only the core are stained and observed by TEM, and compared with those provided with a shell. Further, after mixing the fine particles provided with the shell and the fine particles not provided with the shell, dyeing is performed, and it is confirmed whether or not the ratio of the fine particles having different dyeing degrees matches the presence or absence of the shell.
[0095]
In a mass spectrometer such as TOF-SIMS, it is confirmed that by providing a shell on the particle surface, the amount of coloring material near the surface is smaller than when only the core is used. When there is an element not contained in the core shell polymer in the coloring material, it is possible to confirm whether a shell having a small coloring material content is provided by using the element as a probe.
[0096]
In the absence of such an element, the colorant content in the shell can be compared to that without the shell using a suitable dye. For example, core-shell formation can be more clearly observed by burying core-shell particles in an epoxy resin, producing an ultrathin section with a microtome, and performing staining. As described above, when a polymer or a coloring material includes an element that can serve as a probe, the composition of the core-shell and the distribution amount of the coloring material to the core and the shell can be estimated by TOF-SIMS or TEM.
[0097]
In the colored fine particle dispersion of the present invention, optimization of the formulation and selection of an appropriate emulsification method are important for obtaining an appropriate particle size. The formulation differs depending on the coloring material and polymer used, but since it is a suspension in water, it is generally necessary that the polymer constituting the shell has higher hydrophilicity than the polymer constituting the core. Further, the coloring material contained in the polymer constituting the shell is preferably smaller than that of the polymer constituting the core as described above, and the coloring material also needs to be less hydrophilic than the polymer constituting the shell. . The hydrophilicity and hydrophobicity can be estimated using, for example, the solubility parameter (SP) described above.
[0098]
The colored fine particle dispersion of the present invention, and the colored fine particles having a more preferable core / shell form, preferably have a ratio of the coloring material to the polymer of 1: 0.1 to 1: 5, and have a polymer amount of Is preferably incorporated in the aqueous ink of the present invention in an amount of 0.5 to 50% by mass, more preferably 0.5 to 30% by mass. When the amount of the polymer is less than 0.5% by mass, the ability to protect the coloring material is not sufficient, and when the amount exceeds 50% by mass, the storage stability of the suspension as an aqueous ink is reduced, In some cases, the ink may thicken and the suspension may aggregate due to evaporation of the ink, which may cause clogging of the printer head.
[0099]
On the other hand, the coloring material is preferably contained in the ink in an amount of 1 to 30% by mass, more preferably 1.5 to 25% by mass. When the amount of the coloring material is less than 1% by mass, the print density is insufficient, and when the amount is more than 30% by mass, the stability with time of the suspension is reduced, and the particle size tends to increase due to aggregation or the like. It is preferable to be within the range.
[0100]
Next, the emulsification method used for producing the colored fine particle dispersion of the present invention will be described. For the colored fine particle dispersion of the present invention, for example, various emulsification methods can be used in the production of the core color material particles. These emulsification methods are summarized in, for example, page 86 of “Progress of Functional Emulsifiers / Emulsification Technology and Application Development”. 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 for forming the dye core.
[0101]
In emulsification and dispersion by ultrasonic waves, two types, a so-called batch type and a continuous type, can be used. The batch method is suitable for producing a relatively small amount of sample, and the continuous method is suitable for producing a large amount of sample. In the continuous method, for example, an apparatus such as UH-600SR (manufactured by SMT Co., Ltd.) can be used. In the case of such a continuous system, the irradiation time of the ultrasonic wave can be obtained by (dispersion chamber volume / flow rate × circulation number). In the case where there are a plurality of ultrasonic irradiation devices, it is determined as the sum of the respective irradiation times. The irradiation time of the ultrasonic wave is practically 10,000 seconds or less. In addition, if it is required to be 10,000 seconds or more, the load on the process is large, and in practice, it is necessary to shorten the emulsification dispersion time by reselecting an emulsifier or the like. Therefore, 10,000 seconds or more are not necessary. More preferably, it is 10 seconds or more and 2000 seconds or less.
[0102]
Examples of the emulsifying and dispersing apparatus using high-speed rotational shear include disperser mixers as described on pages 255 to 256 of "Progress of Functional Emulsifiers / Emulsification Technology and Application Development CMC", and pages 251. Such a homomixer, an ultramixer described on page 256, and the like can be used. These types can be properly used depending on the liquid viscosity at the time of emulsification and dispersion. In these high-speed shearing emulsifying and dispersing machines, the rotation speed of the stirring blade is important. In the case of an apparatus having a stator, the clearance between the stirring blade and the stator is usually about 0.5 mm and cannot be extremely narrow, so that the 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 of the present invention. If the peripheral speed is low, it is often impossible to achieve a small particle size even if the emulsification time is extended, and it is necessary to increase the performance of the motor extremely to achieve 150 m / S. More preferably, it is 20 to 100 m / S.
[0103]
In emulsification and dispersion by high pressure, LAB2000 (manufactured by SMT Corporation) and the like can be used, but the emulsification / dispersion ability depends on the pressure applied to the sample. Pressure is 10^FourkPa-5 × 10^FiveThe range of kPa is preferable. Further, emulsification / dispersion may be performed several times as necessary to obtain a target particle size. If the pressure is too low, the target particle size cannot be achieved in many cases even if emulsification and dispersion are performed many times.^FiveIn order to make the pressure kPa, a large load is applied to the apparatus, which is not practical. More preferably, 5 × 10^FourkPa ~ 2 × 10^FiveThe range is kPa.
[0104]
These emulsifying / dispersing devices may be used alone, but may be used in combination as needed. A colloid mill, a flow jet mixer, etc. alone cannot achieve the object of the present invention, but in combination with the apparatus of the present invention, it is possible to enhance the effects of the present invention such as enabling emulsification and dispersion in a short time. is there.
[0105]
The colored fine particles contained in the colored fine particle dispersion of the present invention have a very large surface area per unit volume when the volume average particle diameter is 5 nm or less, so that the effect of enclosing the coloring material in the core-shell polymer is reduced. On the other hand, particles larger than 200 nm tend to clog the head, easily settle in the ink, and degrade stagnation stability. Therefore, the volume average particle diameter of the colored fine particles is preferably 5 nm to 100 nm.
[0106]
The volume average particle diameter of the colored fine particles according to the present invention is obtained by converting the circular average particle diameter obtained from the average value of the projected area (determined for at least 100 particles) of a transmission electron microscope (TEM) photograph into a spherical equivalent. Is required. The coefficient of variation can be obtained by obtaining the volume average particle diameter and its standard deviation, and dividing the standard deviation by the volume average particle diameter. Alternatively, the coefficient of variation can be determined using the dynamic light scattering method. For example, it can be determined by using a laser particle size analysis system manufactured by Otsuka Electronics Co., Ltd., or a Zetasizer 1000HS manufactured by Malvern.
[0107]
In addition, from the viewpoint of obtaining a colored fine particle dispersion that preferably exhibits the effects described in the present invention, it is preferable that the volume average particle diameter of the colored fine particles is small, but as the fine particles become in the range of 5 nm to 100 nm, the volume average Since the particle size is susceptible to numerical fluctuations due to a small amount of large particles (for example, about 60 nm to 100 nm), it is preferable to evaluate the particle size with the following peak particle size from the viewpoint of image quality evaluation.
[0108]
The peak particle size according to the present invention will be described.
When the colored fine particle dispersion of the present invention is applied to the aqueous ink of the present invention, the colored fine particles preferably have a peak particle size of 50 nm or less, more preferably 30 nm to 50 nm, and particularly preferably. Is in the range of 5 nm to 30 nm.
[0109]
Here, the peak particle size of the colored fine particles is a particle size corresponding to the top of a distribution curve obtained by obtaining a volume average particle size distribution using Zetasizer 1000HS manufactured by Malvern, and is calculated based on the particle size distribution. I can do it.
[0110]
Next, the variation coefficient of the colored fine particles will be described.
The coefficient of variation of the particle diameter is a value obtained by dividing the standard deviation of the particle diameter by the particle diameter. The larger the value, the wider the distribution of the particle diameter. If the coefficient of variation of the volume average particle diameter is 80% or more, the particle size distribution becomes very wide, the thickness of the core shell tends to be nonuniform, and the surface properties between particles tend to vary. Variations in the surface properties tend to cause aggregation of the particles and clog the inkjet head. In addition, the aggregation of the particles easily causes light scattering of the coloring material on the medium, and also tends to cause deterioration in image quality. The coefficient of variation is preferably 50% or less.
[0111]
In the present invention, the amount of the polymer used in the shell is preferably 5% by mass or more and 95% by mass or less of the total polymer amount. If the amount is less than 5% by mass, the thickness of the shell is insufficient, and a part of the core containing a large amount of the coloring material tends to appear on the particle surface. On the other hand, if the amount of the polymer in the shell is too large, the ability of the core to protect the coloring material tends to be reduced. More preferably, the content is 10% by mass or more and 90% by mass or less.
[0112]
Next, the aqueous ink of the present invention will be described.
The aqueous ink of the present invention comprises a suspension of a polymer in which water is used as a medium and the coloring material is encapsulated, and the suspension includes various conventionally known additives, for example, a wetting agent such as a polyhydric alcohol, an inorganic salt, Surfactants, preservatives, fungicides, pH adjusters, defoamers such as silicones, viscosity adjusters or chelating agents such as EDTA, and oxygen absorbers such as sulfites are added as necessary. You may.
[0113]
Examples of the wetting agent that can be used in the present invention include, 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 monoethyl 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, etc. A polyhydric alcohol and its ether, Use of one or more of nitrogen-containing compounds such as acetates, N-methyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, triethanolamine, formamide, and dimethylformamide, and dimethyl sulfoxide Can be. The amount of these wetting agents is not particularly limited, but may be preferably 0.1 to 50% by mass, more preferably 0.1 to 30% by mass, in the aqueous ink.
[0114]
In addition, an inorganic salt may be added to the ink in order to keep the viscosity of the ink stable and improve the color development. Examples of the inorganic salt include sodium chloride, sodium sulfate, magnesium chloride, magnesium sulfide and the like. The present invention is not limited to these embodiments.
[0115]
The emulsifier and dispersant are not particularly limited, but preferably have an HLB value of 8 to 18 from the standpoint of exhibiting the effect or having the effect of suppressing an increase in the particle diameter of the suspension. .
[0116]
As the surfactant, any of cationic, anionic, amphoteric and nonionic can be used.
[0117]
The emulsifier or dispersant is preferably an anionic surfactant or a polymeric surfactant, and an anionic surfactant is particularly preferred.
[0118]
The activator for adjusting the surface tension of the ink is preferably a nonionic surfactant.
[0119]
Examples of the cationic surfactant include an aliphatic amine salt, an aliphatic quaternary ammonium salt, a benzalkonium salt, a benzethonium chloride, a pyridinium salt, an imidazolinium salt and the like. Examples of the anionic surfactant include fatty acid soap, N-acyl-N-methylglycine salt, N-acyl-N-methyl-β-alanine salt, N-acylglutamate, alkyl ether carboxylate, and acyl. Peptide, alkyl sulfonate, alkyl benzene sulfonate, alkyl naphthalene sulfonate, dialkyl sulfosuccinate, alkyl sulfo acetate, α-olefin sulfonate, N-acylmethyltaurine, sulfated oil, higher alcohol Sulfate, secondary higher alcohol sulfate, alkyl ether sulfate, secondary higher alcohol ethoxy sulfate, polyoxyethylene alkyl phenyl ether sulfate, monoglyculfate, fatty acid alkylolamide sulfate, alkyl ether phosphorus Acid acid Examples thereof include steal salts and alkyl phosphate esters. Examples of the amphoteric surfactant include a carboxybetaine type, a sulfobetaine type, an aminocarboxylate, and imidazolinium betaine. Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether (for example, Emulgen 911), polyoxyethylene sterol ether, polyoxyethylene lanolin derivative, Polyoxyethylene polyoxypropylene alkyl ether (for example, Newpol PE-62), polyoxyethylene glycerin fatty acid ester, polyoxyethylene castor oil, hydrogenated castor oil, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyethylene Glycol fatty acid ester, fatty acid monoglyceride, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid Ester, sucrose fatty acid esters, fatty acid alkanolamides, polyoxyethylene fatty acid amides, polyoxyethylene alkyl amines, alkyl amine oxides, acetylene glycol, acetylene alcohol, and the like. In addition, examples of the surfactant include, for example, Kao Corporation's dispersant Demol SNB, MS, N, SSL, ST, and P (trade name).
[0120]
When these surfactants are used, they can be used alone or as a mixture of two or more kinds. By adding them in the range of 0.001 to 1.0% by mass based on the total amount of the ink, the surface of the ink The tension can be adjusted arbitrarily. The present invention is not limited to these embodiments. In order to maintain the long-term storage stability of the ink, a preservative and a fungicide may be added to the ink.
[0121]
In addition, the following water-soluble resins can be used as the polymer surfactant, which is preferable from the viewpoint of ejection stability. Preferred examples of the water-soluble resin include styrene-acrylic acid-alkyl acrylate copolymer, styrene-acrylic acid copolymer, styrene-maleic acid-alkyl acrylate copolymer, and styrene-maleic acid copolymer. Copolymer, styrene-methacrylic acid-alkyl acrylate copolymer, styrene-methacrylic acid copolymer, styrene-maleic acid half ester copolymer, vinylnaphthalene-acrylic acid copolymer, vinylnaphthalene-maleic acid copolymer And the like. Other examples of the polymer surfactant include acryl-styrene-based resin such as john krill (Johnson). Two or more of these polymeric surfactants can be used in combination.
[0122]
The amount of each of the above-mentioned polymer surfactants added to the total amount of the dispersed ink is preferably 0.1 to 10% by mass, and more preferably 0.3 to 5% by mass. If the amount is less than 0.01% by mass, it is difficult to reduce the particle size of the suspension. If the amount exceeds 10% by mass, the particle size of the suspension increases, the suspension stability decreases, and gelation may occur. .
[0123]
Examples of preservatives and fungicides include aromatic halogen compounds (eg, Preventol CMK, chloromethylphenol, etc.), methylene dithiocyanate, halogen-containing sulfur compounds, 1,2-benzisothiazolin-3-one (eg, PROXEL) GXL) and the like, but the present invention is not limited to these when practicing the present invention.
[0124]
To keep the ink stable, a pH adjuster may be added to the ink. As the pH adjuster, hydrochloric acid, acetic acid, citric acid, sodium hydroxide, potassium hydroxide or the like can be diluted with water or used as it is.
[0125]
The defoaming agent is not particularly limited, and a commercially available product can be used. Examples of such commercially available products include, for example, KF96, 66, 69, KS68, 604, 607A, 602, 603, KM73, 73A, 73E, 72, 72A, 72C, 72F, 82F, 70, 71 manufactured by Shin-Etsu Silicone Co., Ltd. , 75, 80, 83A, 85, 89, 90, 68-1F, 68-2F (trade name) and the like. The amount of these compounds is not particularly limited, but is preferably 0.001 to 2% by mass in the ink according to the present invention. If the compounding amount of the compound is less than 0.001% by mass, bubbles are easily generated at the time of ink preparation, and it is difficult to remove small bubbles in the ink. If it exceeds 2% by mass, the generation of bubbles is suppressed. During printing, repelling may occur in the ink and the printing quality may be degraded.
[0126]
In the present invention, when an image is formed by discharging an ink set, an ink jet head used may be an on-demand type or a continuous type. Examples of the discharge method include an electro-mechanical conversion method (for example, a single-cavity type, a double-cavity type, a bender type, a piston type, a shared mode type, a shared wall type, etc.) and an electro-thermal conversion method (for example, thermal ink jet. And any other ejection method such as a bubble jet (R) type or the like.
[0127]
(Image forming method)
The image forming method of the present invention will be described.
[0128]
In the image forming method of the present invention, it is preferable that ink is ejected as droplets from an inkjet head based on a digital signal by a printer or the like loaded with the ink set of the present invention, and adhered to an inkjet recording medium.
[0129]
As the inkjet recording medium, for example, any of plain paper, coated paper, cast-coated paper, glossy paper, glossy film, and OHP film can be used. Among them, for example, a porous layer is formed on a support. That is, a recording medium having an ink absorbing layer having a so-called void layer is preferable. There is no particular limitation on the material or shape of the support described above, and for example, a material having a three-dimensional structure other than a sheet-like material may be used.
[0130]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Synthesis Examples and Examples, but the present invention is not limited to these Examples.
[0131]
《Synthesis of polymer》
[Synthesis of Polymers P-1 to P-3]
A 3-liter four-necked flask was equipped with a dropping device, a thermometer, a nitrogen gas inlet tube, a stirrer, and a reflux condenser, heated 1000 g of ethyl acetate, adjusted the temperature to 80 ° C., and introduced nitrogen gas. Meanwhile, a monomer having the composition ratio described below was weighed so that the total amount became 1000 g, and a mixed liquid obtained by further adding 20 g of N, N'-azobisisovaleronitrile to the monomer was added for 2 hours. After the reaction was carried out at the same temperature for 5 hours, the solvent was distilled off under reduced pressure to synthesize polymers P-1 to P-3.
[0132]
P-1 monomer composition (% by mass): methyl methacrylate / stearyl methacrylate / 2-acetoacetoxyethyl methacrylate (Nippon Synthetic Chemical) = 50/20/30
P-2 monomer composition (% by mass): methyl methacrylate / butyl acrylate / 2-ethylhexyl acrylate = 80/10/10
P-3 monomer composition (% by mass): methyl methacrylate / 2-ethylhexyl acrylate = 80/20
(Synthesis of Polymer P-4)
In the synthesis of the polymers P-1 to P-3, a polymer P-4 was synthesized in the same manner as described above except that a polymer was synthesized using the following monomers, and then the acidic groups were neutralized with aqueous ammonia.
[0133]
P-4 monomer composition (% by mass): acrylic acid / styrene / methyl methacrylate = 20/30/50
<< Preparation of colored fine particle dispersion >>
[Preparation of Colored Fine Particle Dispersion CP-1]
In a pot of CLEARMIX CLM-0.8S (manufactured by M-Technik Co.), 12 g (A: dye) of FS Blue 1504 (manufactured by Arimoto Chemical), polymer P-2 (B: polymer) having a solid content of 12 g, And 120 g of ethyl acetate were added thereto and stirred to completely dissolve the dye. 0.5 g of sodium dodecyl sulfate (SDS) (C: emulsifier, surfactant) was added to pure water to make the total amount 270 g, and after adding to the above dye solution, the mixture was emulsified at 20,000 rpm for 5 minutes. Thereafter, ethyl acetate was removed under reduced pressure to obtain a core colored fine particle dispersion.
[0134]
The core-colored fine particles were transferred to a three-head separable flask, the inside of which was replaced with nitrogen gas, and heated to 80 ° C. with a heater. 3 g of Eleminol RS-30 (manufactured by Sanyo Chemical Industries, Ltd.) (D: dissociative group-introduced monomer), 4.8 g of styrene (E: other monomer) and 0.3 g of N, N'- A mixed solution of azobisisovaleronitrile (AIVNF: polymerization initiator) was added dropwise over 1 hour, and the mixture was further reacted for 6 hours to prepare a core-shell type colored fine particle dispersion CP-1.
[0135]
[Preparation of Colored Fine Particle Dispersions CP-2 to CP-5]
In the preparation of the colored fine particles CP-1, A: dye, B: polymer, C: emulsifier, surfactant, D: dissociative group-introduced monomer, E: other monomer, and F: polymerization initiator are shown in Table 1. Colored fine particle dispersions CP-2 to CP-5 were prepared in the same manner, except that the modification was carried out as described.
[0136]
[Preparation of colored fine particle dispersion CP-6]
In a pot of CLEARMIX CLM-0.8S (manufactured by M-Technik Co., Ltd.), 12 g (A: dye) of FS Blue 1504 (manufactured by Arimoto Chemical), 14 g of methyl methacrylate, 3 g of butyl acrylate, and 3 g of 2-Ethylhexyl acrylate (E: other monomer) was added and dissolved to prepare a dye solution. To pure water, 6 g of sodium dodecyl sulfate (SDS) (C: emulsifier) was added to make a total amount of 270 g, which was added to the above-mentioned dye solution, followed by emulsification at 20,000 rpm for 5 minutes.
[0137]
Next, the above-mentioned emulsion was transferred to a three-head separable flask, the inside of the flask was replaced with nitrogen gas, and the flask was heated to 80 ° C. with a heater. A mixed solution of 4 g of Eleminol RS-30 (manufactured by Sanyo Chemical Industry Co., Ltd.) (D: dissociative group-introduced monomer) and 1 g of N, N'-azobisisovaleronitrile (F: polymerization initiator) was mixed with 1 The mixture was added dropwise over a period of time, and the mixture was further reacted for 6 hours to obtain a colored fine particle dispersion CP-6 shown in Table 1.
[0138]
[Preparation of Colored Fine Particle Dispersion CP-7]
No. 4 described in JP-A-2001-131454 was added to a pot of CLEARMIX CLM-0.8S (manufactured by M-Technik Co., Ltd.). 12 g (A: dye) of 1 Y dye, 80 g of polymer P-4 (B: polymer) in terms of solid content, and 120 g of ethyl acetate were added thereto, and the dye was completely dissolved by stirring to prepare a dye solution. After 270 g of pure water was added to this dye solution, the mixture was emulsified at 20,000 rpm for 5 minutes. Thereafter, ethyl acetate was removed under reduced pressure to obtain a core colored fine particle dispersion.
[0139]
The core-colored fine particle dispersion was transferred to a three-head separable flask, the inside of which was replaced with nitrogen gas, and heated to 80 ° C. with a heater. Then, 1 g of Eleminol RS-30 (manufactured by Sanyo Kasei Kogyo Co., Ltd.) (D: dissociative group-introduced monomer), 3 g of methyl acrylate (E: other monomer) and 0.3 g of N, N'-azo A mixed solution of bisisovaleronitrile (F: polymerization initiator) was added dropwise over 1 hour, and the mixture was further reacted for 6 hours to obtain colored fine particle dispersion CP-7.
[0140]
[Preparation of Colored Fine Particle Dispersion CP-8: Comparative Example]
In a pot of CLEARMIX CLM-0.8S (manufactured by M-Technik Co., Ltd.), 12 g of FS Blue 1504 (manufactured by Arimoto Chemical) (A: dye) and 12 g of solid content equivalent polymer P-2 (B: polymer) , And 120 g of ethyl acetate were added, and the mixture was stirred to completely dissolve the dye, thereby preparing a dye solution. 10 g (C: emulsifier, surfactant) of Eleminol RS-30 (manufactured by Sanyo Chemical Industry Co., Ltd.) was added to pure water to make a total amount of 270 g, which was added to the above dye solution, and then rotated at 20,000 rpm for 5 minutes. Emulsified.
[0141]
This emulsion was transferred to a three-head separable flask, the inside of the flask was replaced with nitrogen gas, and then heated to 80 ° C. with a heater. Next, a mixed solution of 4.8 g of methyl acrylate (E: other monomer) and 0.3 g of N, N'-azobisisovaleronitrile (F: polymerization initiator) was added dropwise over 1 hour, and further, The mixture was reacted for 6 hours to obtain colored fine particles CP-8.
[0142]
[Preparation of Colored Fine Particle Dispersions CP-9 and 10: Comparative Example]
In the preparation of the colored fine particle dispersions CP-1 and CP-2, acrylic acid or methacrylic acid was used in place of D: dissociable group-introducing monomer in place of Eleminol RS-30, and further, each additive was described in Table 1. Except having been changed as described above, preparation of colored fine particle dispersions CP-9 and 10 was similarly prepared. Further, after each colored fine particle dispersion was prepared, the dispersion was neutralized with a 0.1 mol / L aqueous solution of NaOH equivalent to an acid.
[0143]
Table 1 shows the details of the colored fine particle dispersions CP-1 to CP-10 prepared as described above.
[0144]
[Table 1]

[0145]
The details of each additive described in Table 1 by abbreviations are listed below.
C: Cyan colored fine particle dispersion
Y: Yellow colored fine particle dispersion
FSB1504: FS Blue 1504 (manufactured by Arimoto Chemical)
Y dye: No. 1 described in JP-A-2001-131454. 1 Y dye
SDS: lauryl sulfate sulfonic acid sodium salt
S-180: Latemul S-180 manufactured by Kao Corporation
KH-05: Aqualon KH-5 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
HS-10: Aqualon HS-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
AA: Acrylic acid
MA: methacrylic acid
ST: Styrene
MMA: Methyl methacrylate
BA: butyl acrylate
EHA: 2-ethylhexyl acrylate
(Evaluation of colored fine particle dispersion)
The following evaluation was performed about the prepared coloring fine particle dispersions CP-1 to CP-10.
[0146]
(Evaluation of dispersibility of colored fine particle dispersion)
Immediately after the preparation, each colored fine particle dispersion was filtered through a 0.8 μm membrane filter (ADVANTEC, φ25 mm), and the amount of filtration (ml) per filter was measured, and this was used as a measure of dispersibility.
[0147]
(Evaluation of storage stability of colored fine particle dispersion)
After the above filtrate was sealed in a glass bottle and stored at 60 ° C. for one month, the amount of filtration per filter was measured in the same manner as above, and this was used as a measure of storage stability.
[0148]
<< Preparation of water-based ink >>
50.0% by mass of the prepared colored fine particle dispersion (CP-1 to CP-10), 15.0% by mass of ethylene glycol, 20.0% by mass of glycerin, 0.5% by mass of Olfin E1010 (manufactured by Nissin Chemical) And 0.1% by mass of a preservative Proxel GX (manufactured by Avecia) were mixed, and 14.4% by mass of ion-exchanged water was added to prepare an aqueous ink. Subsequently, the mixture was filtered through a 0.8 μm membrane filter to remove dust and coarse particles, thereby obtaining aqueous inks I-1 to I-10 for inkjet.
[0149]
(Measurement of peak particle size)
The peak particle size of the colored fine particles in each of the aqueous inks prepared above was measured according to the following method.
[0150]
The volume average particle size distribution of the colored fine particles was determined using Zetasizer 1000HS manufactured by Malvern, and the peak particle size was calculated based on the distribution. At the same time, the particle size was measured with a transmission electron microscope (TEM), and it was confirmed that there was no difference.
[0151]
(Evaluation of discharge stability)
Each water-based ink was packed in a genuine color ink cartridge, loaded into an ink jet printer CL-750 (manufactured by Seiko Epson Corporation), and turned off for a 10 cm × 20 cm ink jet paper photo-like QP (manufactured by Konica) with the printer driver turned off. Five continuous solid images were printed, the state of the fifth solid image was visually observed, and the ejection stability was evaluated according to the following criteria.
[0152]
A: No streaks or unevenness is observed (good)
B: Some streaks are observed (acceptable)
C: Many streaks and unevenness are observed
D: Almost no printing
Table 2 shows the results obtained as described above.
[0153]
[Table 2]

[0154]
As is clear from Table 2, the colored fine particles according to the present invention have smaller peak particle diameters, better filterability (dispersibility), and less coarse particles than the comparative examples. Further, it can be seen that even after storage under forced deterioration conditions, the filterability is good, the storage stability is excellent, and the ejection stability when used as an aqueous ink is also excellent. This is considered to be because aggregation of the colored fine particles was suppressed by using a monomer into which a dissociative group was effectively introduced.
[0155]
On the other hand, the comparative colored fine particle dispersion CP-8 using Eleminol RS-30 as an emulsifier had poor filterability, and also had a large peak particle size after being prepared as an aqueous ink. Similarly, the comparative colored fine particle dispersions CP-9 and CP-9 using acrylic acid and methacrylic acid as the dissociative group-introducing monomers tended to have a large particle diameter of the colored fine particles. It is considered that this is caused by insufficient emulsifying power of Eleminol RS-30 and aggregation of particles by acid monomer, respectively. Further, it can be seen that these colored fine particle dispersions are poor in storage of the dispersion after forced deterioration, and are inferior in ejection stability when used as an aqueous ink.
[0156]
Further, it was confirmed that the image formed by using the aqueous ink of the present invention had a sense of transparency compared to the comparative example, and that a high-quality image with high brightness and saturation was obtained.
[0157]
【The invention's effect】
According to the present invention, colored fine particles having a small particle diameter can be obtained, and a colored fine particle dispersion excellent in dispersibility, storage stability and ejection stability, an aqueous ink, and an image using the same to obtain a high-quality image A forming method could be provided.

Claims (16)

In a colored fine particle dispersion obtained by dispersing colored fine particles prepared by mixing a coloring material and a polymer in water, at least one kind of the polymer is represented by the following general formula (a) in the presence of a surfactant. A colored fine particle dispersion obtained by polymerizing the polymerizable monomer represented.
General formula (a)
_{CH 2 = C (X) -Y-} (AO) n -Z
[In the formula, X represents a hydrogen atom or a methyl group, Y represents a linking group having 9 or less total carbon atoms, Z represents an anionic group, and AO represents an alkylene oxide group. n represents an integer of 1 to 30. ] The colored fine particle dispersion according to claim 1, wherein the mass ratio of the compound represented by the general formula (a) to the surfactant is 5: 1 to 0.1: 1. 3. The colored fine particle dispersion according to claim 1, wherein Y in the general formula (a) is a carbonyl group, and Z is a sulfonate. The colored fine particle dispersion according to any one of claims 1 to 3, wherein the average degree of polymerization (n) of the alkylene oxide group in the general formula (a) is 3 to 15. The colored surfactant according to any one of claims 1 to 4, wherein the surfactant is a reactive emulsifier. A mixture in which the colored fine particles are composed of a polymerizable monomer represented by the general formula (a), at least one polymerizable monomer other than the polymerizable monomer (a) represented by the general formula (a), and a coloring material The colored fine particle dispersion according to any one of claims 1 to 5, wherein the colored fine particle dispersion is obtained by performing a polymerization reaction after emulsifying with a surfactant. After the colored fine particles emulsify a polymer and a compatible material of a coloring material with a surfactant, at least one polymerizable monomer (a) represented by the general formula (a) is added to carry out emulsion polymerization. The colored fine particle dispersion according to any one of claims 1 to 5, which is obtained by performing the method. In a colored fine particle dispersion obtained by dispersing colored fine particles prepared by mixing a coloring material and a polymer in water, the colored fine particles are converted into a self-emulsifiable colored fine particle dispersion by the general formula (a). And a polymerizable monomer other than the polymerizable monomer (a) represented by the general formula (a) represented by the general formula (a) is added, and emulsion polymerization is performed. Characterized colored fine particle dispersion. A colored fine particle dispersion obtained by dispersing colored fine particles prepared by mixing a colorant and a polymer in water and a surfactant, wherein the colored fine particles have a polyalkylene oxide sulfate group on the surface thereof, and A colored fine particle dispersion, wherein at least one of the activators has a polyalkylene oxide sulfate group having a structure different from that of the polyalkylene oxide sulfate group. The colored fine particle dispersion according to any one of claims 1 to 9, wherein at least one of the surfactants does not include a polyalkylene oxide sulfate group in the structure. The colored fine particle dispersion according to any one of claims 1 to 10, wherein the coloring material is an oil-soluble dye. The colored fine particle dispersion according to any one of claims 1 to 11, wherein the colored fine particles have a core-shell structure. An aqueous ink comprising the colored fine particle dispersion according to claim 1. 14. The aqueous ink according to claim 13, wherein the colored fine particles have a peak particle size of 50 nm or less. The aqueous ink according to claim 13, which is an inkjet ink. An image forming method, comprising: ejecting the aqueous ink according to claim 15 by an ink jet recording apparatus to form an image.