JP2005048005A - Aqueous pigment dispersion for inkjet ink, aqueous ink composition for inkjet ink and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous pigment dispersion for red or magenta inkjet ink which has excellent dispersibility and dispersion stability, hardly causes increase in its particle size or its viscosity even when kept at a high temperature for a long term and exhibits excellent printing stability, and an aqueous ink composition for inkjet recording using the same. <P>SOLUTION: The aqueous pigment dispersion for the inkjet ink comprises a quinacridone pigment (a), a styrene resin (b), an alkali metal hydroxide (c) and an auxiliary dispersant (d), where the styrene resin (b) is one obtained by copolymerizing (i) at least 60 mass%, based on the whole monomer component, of a styrene monomer with (ii) a monomer containing an unsaturated aliphatic carboxylic acid bearing a radically polymerizable double bond and has a weight-average molecular weight of 7,500-40,000. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

｛式中、Ｒ_１〜Ｒ_１０は各々独立的に水素原子、フッ素原子、塩素原子、臭素原子、ヨウ素原子、メチル基若しくは炭素数２〜８個のアルキル基、又は式ＩＩ
【００２９】
【式２】

（式中、Ｒ_１１はメチレン基又は炭素数２〜８個のアルキレン基若しくはアルケニレン基、Ｒ_１２〜Ｒ_１５は各々独立的に水素原子、フッ素原子、塩素原子、臭素原子、ヨウ素原子、メチル基若しくは炭素数２〜８個のアルキル基、又はフェニル基を表す。）で表される基であり、Ｒ_１〜Ｒ_１０の少なくとも一つは前記式ＩＩで表される基である。｝
【００３０】
式Ｉで表される化合物（ｅ）の中で好ましい化合物の具体例としては、下記式ＩＩＩで表される基を有する下記式ＩＶで表される化合物である。
【００３１】
【式２】

【００３２】
【式２】

（式中、ｍ及びｎはそれぞれ独立的に０、１、２又は３を表す。但し、ｍとｎが共に０となることはない。）
【００３３】
また、本発明で使用する化合物（ｅ）としては、式ＩＶで表される化合物の中でも式ＩＩＩで表される基を１分子あたり１個あるいは複数個有する化合物であることが好ましく、１分子あたり平均１〜２個有する化合物であることが好ましい。特に、１分子あたり平均１〜１．５個有する化合物であることが特に好ましい。式ＩＩＩで表される基が１分子あたり平均１個未満であると分散安定性に対する効果が現れにくく、１分子あたり平均２個を越えると、滲みなど、インクジェットインク用水性インク組成物としての特性を低下させる可能性がある。
【００３４】
式Ｉで表される化合物（ｅ）が、例えば、上記式ＩＩＩで表される基を有する化合物である場合は、無置換キナクリドン、ジメチルキナクリドン、ジクロロキナクリドン等とフタルイミド及びホルムアルデヒドあるいはパラホルムアルデヒドとを濃硫酸中で反応させることにより合成することができる。
【００３５】
本発明では分散助剤（ｄ）として、キナクリドンスルホン酸系化合物（ｆ）を使用することもできる。キナクリドンスルホン酸系化合物（ｆ）としては、公知慣用のものが使用できる。例えば無置換キナクリドン、ジメチルキナクリドン、ジクロロキナクリドン等を公知の方法により濃硫酸等と反応させることで合成できるキナクリドンスルホン酸類、及びそのナトリウム、アルミニウム、カルシウム等の金属塩類、ならびにそのアンモニウム、オクタデシルアンモニウム、ジドデシルアンモニウム、ジメチルオクタデシルアンモニウム、ジメチルジオクタデシルアンモニウム、ベンジルジメチルオクタデシルアンモニウム等のアンモニウム塩類が挙げられる。これらの中でも、アルカリ金属塩であることが好ましい。より具体的には、本発明で使用するキナクリドンスルホン酸系化合物（ｆ）としては、３，１０−ジクロロキナクリドンスルホン酸ナトリウム塩が好ましい。
【００３６】
本発明で使用する分散助剤（ｄ）としては、式Ｉで表される化合物（ｅ）とキナクリドンスルホン酸系化合物（ｆ）を使用することが好ましい。
【００３７】
本発明においては、キナクリドン系顔料（ａ）１００質量部に対する式Ｉで表される化合物（ｅ）とキナクリドンスルホン酸系化合物（ｆ）の使用量は、それぞれ２質量部以上であって、且つ式Ｉで表される化合物（ｅ）とキナクリドンスルホン酸系化合物（ｆ）の総量は４〜２０質量部であり、４〜１５質量部であることがより好ましい。使用量が上記の範囲であると分散液及びインク組成物の保存安定性が良好である。また、特にサーマルジェット方式のプリンターで印字した際のインク吐出状態が良好である。
【００３８】
本発明の水性顔料分散液、インク組成物において、キナクリドン系顔料（ａ）と式Ｉで表される化合物（ｅ）とキナクリドンスルホン酸系化合物（ｆ）との合計１００質量部に対するスチレン系樹脂（ｂ）の使用量は１０〜５０質量部であることが好ましく、１０〜４０質量部であることがより好ましい。スチレン系樹脂（ｂ）の使用量が１０質量部未満であると、水性顔料分散液の分散安定性が低下するとともに水性顔料分散液を用いてインク組成物を調製したとき、耐摩擦性が低下する傾向にあり、５０質量部を超えた場合は、インク組成物の粘度が高くなりすぎる傾向がある。
【００３９】
本発明の水性顔料分散液には、水性顔料分散液の乾燥防止及びインク組成物の乾燥防止のために湿潤剤（ｈ）を使用するのが好ましい。湿潤剤（ｈ）としては、公知慣用のものが使用できる。そのような湿潤剤（ｈ）としては、例えばグリセリン、エチレングリコール、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、プロピレングリコール、ジプロピレングリコール、ポリプロピレングリコール、１，３−プロパンジオール、１，４−ブタンジオール、１，５−ペンタンジオール、１，６−ヘキサンジオール、１，２，６−ヘキサントリオール、トリメチロールプロパン、ペンタエリスリトール等のポリオール類、２−ピロリドン、Ｎ−メチル−２−ピロリドン、ε−カプロラクタム等のラクタム類、１，３−ジメチルイミダゾリジノン等が挙げられる。
【００４０】
本発明の水性顔料分散液において、分散助剤（ｄ）として式Ｉの化合物（ｅ）とキナクリドンスルホン酸系化合物（ｆ）を使用する場合、下記の方法によりインクジェットインク用水性顔料分散液を製造するのが好ましい。その方法とは、（Ｉ）キナクリドン系顔料（ａ）、（ｉ）全モノマー成分に対して６０質量％以上のスチレン系モノマーと（ｉｉ）ラジカル重合性の二重結合を有する不飽和脂肪族カルボン酸を含有するモノマーを共重合させた樹脂であり、且つ重量平均分子量が７，５００〜４０，０００の範囲内であるスチレン系樹脂（ｂ）、アルカリ金属水酸化物（ｃ）の水溶液又は有機溶剤溶液、及び前記式Ｉで表される化合物（ｅ）を共に混練することによりインクジェットインク用着色混練物（ｇ）を製造する第１工程を行い、次いで、（ＩＩ）前記混練物（ｇ）に前記キナクリドンスルホン酸系化合物（ｆ）と水性媒体を添加することにより前記混練物（ｇ）を前記水性媒体中に分散させ第２Ａ工程を行うか、又は、第１工程に続いて、（ＩＩＩ）前記混練物（ｇ）に水性媒体を添加することにより前記混練物（ｇ）を前記水性媒体中に分散させ、その後、前記キナクリドンスルホン酸系化合物（ｆ）を添加する第２Ｂ工程を順次行うことにより水性顔料分散液を製造する方法である。
【００４１】
スチレン系樹脂（ｂ）をキナクリドン系顔料（ａ）、アルカリ金属水酸化物（ｃ）、及び式Ｉで表される化合物（ｅ）と共に混練する場合、高剪断力下で混練することが好ましい。高剪断力下で混練することにより、キナクリドン系顔料（ａ）が微粉砕され、更にその粒子表面にスチレン系樹脂（ｂ）の吸着が進行し、均一なインクジェットインク用着色混練物が得られる。
【００４２】
アルカリ金属水酸化物（ｃ）は、アルカリ金属水酸化物（ｃ）の水溶液、又は有機溶剤溶液として添加する。この場合、アルカリ金属水酸化物（ｃ）の水溶液又は有機溶剤溶液の濃度は、２０質量％〜５０質量％であることが好ましい。また、アルカリ金属水酸化物（ｃ）を溶解する有機溶剤としては、メタノール、エタノール、イソプロパノール、等のアルコール系溶剤を用いることが好ましい。中でも、本発明では、アルカリ金属水酸化物（ｃ）の水溶液を用いることが好ましい。
【００４３】
前記各原料を混練する際の着色混練物（ｇ）中の固形分濃度は５０〜８０質量％であることが好ましい。固形分濃度が５０質量％以下であると充分な剪断力をかけることができず、キナクリドン系顔料（ａ）の粉砕が不充分となると同時に、均一な着色混練物（ｇ）が得られない。また固形分濃度が８０質量％を超えると、たとえ加温して樹脂を充分に軟化させたとしても混練が困難になる。また、混練終了後に混練物を水性媒体中に分散させることが困難となるおそれがある。
【００４４】
混練時には湿潤剤（ｈ）を添加することが好ましい。その際の湿潤剤（ｈ）の添加量は、キナクリドン系顔料（ａ）１００質量部に対して、４０〜８０質量部の範囲内である。湿潤剤を含有させることにより、固形分比を混練装置に適した値に調整することが容易になるとともに、前記顔料表面が湿潤剤によって濡れやすいため、湿潤剤がスチレン系樹脂（ｂ）に置き換わることで顔料表面の被覆が速やかに進行する。
【００４５】
着色混練物（ｇ）を製造する際には、二本ロール等の撹拌槽を有しない開放型の混練機を用いるよりは、撹拌槽を有する混練機を用いることが好ましい。この様な混練機を使用すると、混練後の着色混練物（ｇ）を、キナクリドンスルホン酸系化合物（ｆ）を含む水性媒体で直接希釈して水性顔料分散液を製造することも可能である。撹拌槽を有する混練機の具体例としてはプラネタリーミキサーが好ましい。プラネタリーミキサーは二本ロール等と比較すると、広い範囲の粘度領域で混練処理が可能であり、更に水性媒体の添加及び減圧溜去も可能であるため、混練時の粘度及び負荷剪断力の調整が容易である。
【００４６】
混練後の着色混練物（ｇ）をキナクリドンスルホン酸系化合物（ｆ）を含む水性媒体で希釈して得た水性顔料分散液は、更に分散機により分散処理することが好ましい。分散処理を行うことによって、水性顔料分散液中の粗大分散粒子が更に粉砕され、より分散粒子の粒径が小さくなることによって、インク組成物の吐出安定性、印字濃度などのインクジェット特性がより改善されるためである。
【００４７】
分散処理を行う際の分散機としては、公知慣用の機器が使用でき、例えば、超音波ホモジナイザー、高圧ホモジナイザー、ペイントシェーカー、ボールミル、ロールミル、サンドミル、サンドグラインダー、ダイノーミル、ディスパーマット、ナノミル、ＳＣミル、ナノマイザー等を挙げることができ、これらのうちの１つを単独で用いても良く、２種類以上装置を組み合わせて用いても良い。
【００４８】
着色混練物（ｇ）を希釈する際のキナクリドンスルホン酸系化合物（ｆ）を含む水性媒体は水性顔料分散液の乾燥防止、及び分散処理実施時の粘度調整の必要性から湿潤剤（ｈ）を含んでいても良く、その量は着色混練物（ｇ）中の湿潤剤（ｈ）と合わせて、水性顔料分散液中に３〜５０質量％であることが好ましく、５〜４０質量％であることがより好ましい。この下限未満では、乾燥防止効果が不充分となる傾向にあり、上記上限を超えると分散液の分散安定性が低下する傾向にある。着色混練物（ｇ）製造時と、これを希釈する際のキナクリドンスルホン酸系化合物（ｆ）を含む水性媒体に使用される湿潤剤（ｈ）は、同一でも良く、異なっていても良い。
【００４９】
本発明のインク組成物は、水性顔料分散液を用いて、常法により調製することができる。本発明の水性顔料分散液を用いてインク組成物を調製する場合は、粗大粒子が、ノズル詰まり、その他の画像特性を劣化させる原因になるため、インク調製後に、遠心分離、あるいは濾過処理等により粗大粒子を除去しても良い。
【００５０】
本発明の水性顔料分散液を用いてインク組成物を調製する場合、インクの乾燥防止を目的として、先に例示した湿潤剤（ｈ）を同様に添加することができる。乾燥防止を目的とする湿潤剤（ｈ）のインク中の含有量は３〜５０質量％であることが好ましい。また、本発明の水性顔料分散液を用いてインク組成物を調製する場合、被記録媒体への浸透性改良や記録媒体上でのドット径調整を目的として浸透剤を添加することができる。
【００５１】
浸透剤としては、例えばエタノール、イソプロピルアルコール等の低級アルコール、エチレングリコールヘキシルエーテルやジエチレングリコールブチルエーテル等のアルキルアルコールのエチレンオキシド付加物やプロピレングリコールプロピルエーテル等のアルキルアルコールのプロピレンオキシド付加物等が挙げられる。インク中の浸透剤の含有量は０．０１〜１０質量％であることが好ましい。
【００５２】
本発明の水性顔料分散液を用いてインク組成物を調製する場合、表面張力等のインク特性を調整するために、界面活性剤を添加することができる。このために添加することのできる界面活性剤は特に限定されるものではなく、各種のアニオン性界面活性剤、ノニオン性界面活性剤、カチオン性界面活性剤、両性界面活性剤などが挙げられ、これらの中では、アニオン性界面活性剤、ノニオン性界面活性剤が好ましい。
【００５３】
アニオン性界面活性剤としては、例えば、アルキルベンゼンスルホン酸塩、アルキルフェニルスルホン酸塩、アルキルナフタレンスルホン酸塩、高級脂肪酸塩、高級脂肪酸エステルの硫酸エステル塩、高級脂肪酸エステルのスルホン酸塩、高級アルコールエーテルの硫酸エステル塩及びスルホン酸塩、高級アルキルスルホコハク酸塩、ポリオキシエチレンアルキルエーテルカルボン酸塩、ポリオキシエチレンアルキルエーテル硫酸塩、アルキルリン酸塩、ポリオキシエチレンアルキルエーテルリン酸塩等が挙げられ、これらの具体例として、ドデシルベンゼンスルホン酸塩、イソプロピルナフタレンスルホン酸塩、モノブチルフェニルフェノールモノスルホン酸塩、モノブチルビフェニルスルホン酸塩、ジブチルフェニルフェノールジスルホン酸塩などを挙げることができる。
【００５４】
ノニオン性界面活性剤としては、例えば、ポリオキシエチレンアルキルエーテル、ポリオキシエチレンアルキルフェニルエーテル、ポリオキシエチレン脂肪酸エステル、ソルビタン脂肪酸エステル、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、グリセリン脂肪酸エステル、ポリオキシエチレングリセリン脂肪酸エステル、ポリグリセリン脂肪酸エステル、ショ糖脂肪酸エステル、ポリオキシエチレンアルキルアミン、ポリオキシエチレン脂肪酸アミド、脂肪酸アルキロールアミド、アルキルアルカノールアミド、アセチレングリコール、アセチレングリコールのオキシエチレン付加物、ポリエチレングリコールポリプロピレングリコールブロックコポリマー、等を挙げることができ、これらの中では、ポリオキシエチレンノニルフェニルエーテル、ポリオキシエチレンオクチルフェニルエーテル、ポリオキシエチレンドデシルフェニルエーテル、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脂肪酸エステル、ソルビタン脂肪酸エステル、ポリオキシエチレンソルビタン脂肪酸エステル、脂肪酸アルキロールアミド、アセチレングリコール、アセチレングリコールのオキシエチレン付加物、ポリエチレングリコールポリプロピレングリコールブロックコポリマーが好ましい。
【００５５】
その他の界面活性剤として、ポリシロキサンオキシエチレン付加物のようなシリコーン系界面活性剤；パーフルオロアルキルカルボン酸塩、パーフルオロアルキルスルホン酸塩、オキシエチレンパーフルオロアルキルエーテルのようなフッ素系界面活性剤；スピクリスポール酸、ラムノリピド、リゾレシチンのようなバイオサーファクタント等も使用することができる。これらの界面活性剤は、単独で用いることもでき、また、２種類以上を混合して用いることもできる。また、界面活性剤の溶解安定性等を考慮すると、そのＨＬＢは、７〜２０の範囲であることが好ましい。
【００５６】
界面活性剤を添加する場合は、その添加量はインクの全質量に対し、０．００１〜１質量％の範囲が好ましく、０．００１〜０．５質量％であることがより好ましく、０．０１〜０．２質量％の範囲であることが更に好ましい。界面活性剤の添加量が０．００１質量％未満の場合は、界面活性剤添加の効果が得られない傾向にあり、１質量％を超えて用いると、画像が滲むなどの問題を生じやすくなる。
【００５７】
本発明の水性顔料分散液を用いてインク組成物を調製する場合は、必要に応じて防腐剤、粘度調整剤、ｐＨ調整剤、キレート化剤、可塑剤、酸化防止剤、紫外線吸収剤等をも添加することができる。
【００５８】
本発明の水性顔料分散液に占める、キナクリドン系顔料（ａ）の量は５〜２５質量％であることが好ましく、５〜２０質量％であることがより好ましい。キナクリドン系顔料（ａ）の量が５質量％より少ない場合は、本発明の水性顔料分散液から調製したインク組成物の着色が不充分であり、充分な画像濃度が得られない傾向にある。また、逆に２５質量％よりも多い場合は、水性顔料分散液において顔料の分散安定性が低下する傾向がある。本発明の水性顔料分散液から調製するインク組成物に占める、キナクリドン系顔料（ａ）の量は、充分な画像濃度を得る必要性と、インク中での分散粒子の分散安定性を確保するために、２〜１０質量％であることが好ましい。
【００５９】
このインク組成物は、インクジェット記録用のインクとして好適に用いることができる。適用するインクジェットの方式は特に限定するものではないが、連続噴射型（荷電制御型、スプレー型など）、ドロップオンデマンド型（ピエゾ方式、サーマル方式、静電吸引方式など）などの公知のものを例示することができる。中でも、サーマルインクジェット記録方式のプリンターに使用することが好ましい。
【００６０】
【実施例】
以下、実施例により本発明を具体的に説明する。
尚、特に断りがない限り「部」は「質量部」、「％」は「質量％」を表すものとする。
【００６１】
本実施例において使用する樹脂は以下のＡ〜Ｆである。
樹脂Ａ：モノマー組成比において、スチレン／アクリル酸／メタクリル酸＝７７／１０／１３（質量比）であり、重量平均分子量１１０００、酸価１５２ｍｇＫＯＨ／ｇ、ガラス転移点１１８℃である樹脂。
樹脂Ｂ：モノマー組成比において、スチレン／アクリル酸／メタクリル酸＝７７／１０／１３（質量比）であり、重量平均分子量２００００、酸価１５１ｍｇＫＯＨ／ｇ、ガラス転移点１２１℃である樹脂。
樹脂Ｃ：モノマー組成比においてスチレン／メタクリル酸＝７７／２３（質量比）であり、重量平均分子量１０７００、酸価１４６ｍｇＫＯＨ／ｇ、ガラス転移点１２６℃である樹脂。
樹脂Ｄ：モノマー組成比において、スチレン／アクリル酸／メタクリル酸＝７７／１０／１３（質量比）であり、重量平均分子量５０００、酸価１５０ｍｇＫＯＨ／ｇ、ガラス転移点１０５℃である樹脂。
樹脂Ｅ：モノマー組成比において、スチレン／アクリル酸／メタクリル酸＝７７／１０／１３（質量比）であり、重量平均分子量４５０００、酸価１５３ｍｇＫＯＨ／ｇ、ガラス転移点１２８℃である樹脂。
樹脂Ｆ：モノマー組成比において、スチレン／メタクリル酸メチル／アクリル酸／メタクリル酸＝５０／２２／１０／１３（質量比）であり、重量平均分子量１２０００、酸価１４９ｍｇＫＯＨ／ｇ、ガラス転移点１１８℃である樹脂。
【００６２】
ここで重量平均分子量とはＧＰＣ（ゲル浸透クロマトグラフィー）法で測定される値であり、標準物質として使用するポリスチレンの分子量に換算した値である。
尚、測定は以下の装置及び条件により実施した。
送液ポンプ：ＬＣ−９Ａ
システムコントローラー：ＳＣＬ−６Ｂ
オートインジェクター：ＳＩＬ−６Ｂ
検出器：ＲＩＤ−６Ａ
以上島津製作所社製。
データ処理ソフト：Ｓｉｃ４８０ＩＩデータステーション（システムインスツルメンツ社製）。
カラム：ＧＬ−Ｒ４００（ガードカラム）＋ＧＬ−Ｒ４４０＋ＧＬ−Ｒ４５０＋ＧＬ−Ｒ４００Ｍ（日立化成工業社製）
溶出溶媒：ＴＨＦ
溶出流量：２ｍｌ／ｍｉｎ
カラム温度：３５℃
【００６３】
（実施例１）
・混練条件
下記組成の混合物を、容量５０ＬのプラネタリーミキサーＰＬＭ−Ｖ−５０Ｖ（株式会社井上製作所製）に仕込み、ジャケットを加温し、内容物の温度が６０℃になるまで低速（自転回転数：２１回転／分，公転回転数：１４回転／分）で混練を行い、内容物の温度が６０℃に達した後、高速（自転回転数：３５回転／分，公転回転数：２４回転／分）に切り替え、混練を継続した。
樹脂Ａ ７５０ｇ
キナクリドン系顔料 ４７５０ｇ
（ファストゲンスーパーマゼンタＲＴＳ、大日本インキ化学工業（株）製）
式ＩＶの化合物 ２５０ｇ
（１分子あたりの平均フタルイミドメチル基数１．４）
ジエチレングリコール ３０００ｇ
３４％水酸化カリウム水溶液 ３３５ｇ
【００６４】
高速への切り替え時のプラネタリーミキサー電流値は５Ａであった。その後、混練を継続し、プラネタリーミキサーの最大電流値が１２Ａを示した。最大電流値を示してから１．５時間、混練を継続した後、プラネタリーミキサーの電流値は１０Ａであった。この様にして得た撹拌槽内の混練物に、６０℃に加温したイオン交換水を２００ｇ徐々に加えて混練を継続した。
【００６５】
最大電流値を観測してから４時間経過した時点まで混練を継続し着色混練物を得た。得られた着色混練物にプラネタリーミキサーによる撹拌を継続しながら、２時間で総量６８００ｇの６０℃に加温したイオン交換水を加えた。その後、プラネタリーミキサーから水希釈後の着色混練物を取り出した。水希釈後の着色混練物の固形分濃度は３９．４質量％であった。更に、水希釈後の着色混練物１２ｋｇに、ジエチレングリコール１．６１ｋｇ、イオン交換水１０．０２ｋｇを分散撹拌機で撹拌しながら少量ずつ添加し、水性顔料分散液前駆体Ａ−１を得た。
【００６６】
この水性顔料分散液前駆体Ａ−１、１８ｋｇを、ビーズミル（浅田鉄工製ナノミルＮＭ−Ｇ２Ｌ）にて下記条件で分散処理を実施し水性顔料分散液前駆体Ａ−２を得た。
・分散条件（１）
分散機 ナノミルＮＭ−Ｇ２Ｌ（浅田鉄工製）
ビーズ φ０．３ｍｍジルコニアビーズ
ビーズ充填量 ８５％
冷却水温度 １０℃
回転数 ２６６０回転／分
（ディスク周速：１２．５ｍ／ｓｅｃ）
送液量 ２００ｇ／１０秒
尚、分散は上記条件で、１時間循環しながら分散処理を行った。水性顔料分散液前駆体Ａ−２のキナクリドン系顔料濃度は１６．２質量％であった。
【００６７】
水性顔料分散液前駆体Ａ−２に対して下記の条件にて分散処理を行い、水性顔料分散液Ａ−３を得た。
・分散条件（２）
２５０ｍｌのポリエチレン製瓶にφ１．２ｍｍのジルコニアビーズ２００ｇを入れ、更に下記配合を行いペイントコンディショナー（東洋精機製）で３０分間処理し、水性顔料分散液Ａ−３を得た。得られた水性顔料分散液Ａ−３中のキナクリドン系顔料濃度は１２．８％であった。

【００６８】
（実施例２）
実施例１で作製した水性顔料分散液前駆体Ａ−２を使用して、以下の方法により水性顔料分散液を作製した。
下記の配合物を用いて、実施例１の分散条件（２）に記載された操作と同様な操作を行い、水性顔料分散液Ｂ−３を得た。得られた水性顔料分散液Ｂ−３中のキナクリドン系顔料濃度は１３．５％であった。

【００６９】
（実施例３）
実施例１で作製した水性顔料分散液前駆体Ａ−２を使用して、以下の方法により水性顔料分散液を作製した。
下記の配合物を用いて、実施例１の分散条件（２）に記載された操作と同様な操作を行い、水性顔料分散液Ｃ−３を得た。得られた水性顔料分散液Ｃ−３中のキナクリドン系顔料濃度は１３．９％であった。

【００７０】
（実施例４）
実施例１と同様な混練条件下で下記組成の混合物を混練した。
樹脂Ａ ７５０ｇ
キナクリドン系顔料 ４６３０ｇ
（ファストゲンスーパーマゼンタＲＴＳ、大日本インキ化学工業（株）製）
式ＩＶの化合物 ３８０ｇ
（１分子あたりの平均フタルイミドメチル基数１．４）
ジエチレングリコール ２９００ｇ
３４質量％水酸化カリウム水溶液 ３３５ｇ
【００７１】
高速への切り替え時のプラネタリーミキサー電流値は５Ａであった。その後、混練を継続し、プラネタリーミキサーの最大電流値が１５Ａを示した。最大電流値を示してから３０分ごとに６０℃に加温したイオン交換水を１００ｇ追加しながら混練を４時間継続し着色混練物を得た。この間のプラネタリーミキサーの電流値は１２Ａであった。この様にして得た撹拌槽内の着色混練物に、混練を継続しながら、２時間で総量６２００ｇの６０℃に加温したイオン交換水を加えた。
【００７２】
イオン交換水の添加が終了した後、プラネタリーミキサーから水希釈後の着色混練物を取り出した。この水希釈後の着色混練物の固形分濃度は３９．９質量％であった。更に取り出した水希釈後の着色混練物１２ｋｇに、ジエチレングリコール５．８１ｋｇ、イオン交換水６．１５ｋｇを分散撹拌機で撹拌しながら少量ずつ添加し、水性顔料分散液前駆体Ｄ−１を得た。
【００７３】
この水性顔料分散液前駆体Ｄ−１、１８ｋｇを用いて、送液量を１８５ｇ／１０秒とする以外は、実施例１の分散条件（１）と同様な条件で分散処理を実施し水性顔料分散液前駆体Ｄ−２を得た。水性顔料分散液前駆体Ｄ−２のキナクリドン系顔料濃度は１５．８質量％であった。
【００７４】
次いで、下記の配合物を用いて、実施例１の分散条件（２）に記載された操作と同様な操作を行い、水性顔料分散液Ｄ−３を得た。得られた水性顔料分散液Ｄ−３中のキナクリドン系顔料濃度は１２．８％であった。

【００７５】
（実施例５）
実施例４で作製した水性顔料分散液前駆体Ｄ−２を使用して、以下の方法により水性顔料分散液を作製した。
下記の配合物を用いて、実施例１の分散条件（２）に記載された操作と同様な操作を行い、水性顔料分散液Ｅ−３を得た。得られた水性顔料分散液Ｅ−３中のキナクリドン系顔料濃度は１３．５％であった。

【００７６】
（実施例６）
実施例１と同様な混練条件下で下記組成の混合物を混練した。
樹脂Ｂ １０００ｇ
キナクリドン系顔料 ４７５０ｇ
（ファストゲンスーパーマゼンタＲＴＳ、大日本インキ化学工業（株）製）
式ＩＶの化合物 ２５０ｇ
（１分子あたりの平均フタルイミドメチル基数１．４）
ジエチレングリコール ３０００ｇ
３４質量％水酸化カリウム水溶液 ４４４ｇ
【００７７】
高速への切り替え時のプラネタリーミキサー電流値は５Ａであった。その後、混練を継続し、プラネタリーミキサーの最大電流値が１２Ａを示した。最大電流値を示してから１時間、混練を継続した後、プラネタリーミキサーの電流値は１０Ａであった。この様にして得た撹拌槽内の混練物に、ジエチレングリコール２００ｇ徐々に加えて混練を継続した。
【００７８】
最大電流値を観測してから４時間経過した時点まで混練を継続し着色混練物を得た。得られた着色混練物にプラネタリーミキサーによる撹拌を継続しながら、２時間で総量７０００ｇの６０℃に加温したイオン交換水を加えた。イオン交換水の添加が終了した後、プラネタリーミキサーから水希釈後の着色混練物を取り出した。水希釈後の着色混練物の固形分濃度は３９．０質量％であった。更に、水希釈後の着色混練物１２ｋｇに、ジエチレングリコール１．３７ｋｇ、イオン交換水１０．０５ｋｇ、３，１０−ジクロロキナクリドンスルホン酸ナトリウム塩（平均スルホン基数１．３）の固形分濃度１０．０％の含水スラリー３．２６ｋｇを分散撹拌機で撹拌しながら少量ずつ添加し、水性顔料分散液前駆体Ｆ−１を得た。
【００７９】
この水性顔料分散液前駆体Ｆ−１、１８ｋｇを用いて、実施例１の分散条件（１）と同様な条件で分散処理を実施し水性顔料分散液Ｆ−３を得た。水性顔料分散液Ｆ−３のキナクリドン系顔料濃度は１３．６質量％であった。
【００８０】
（実施例７）
実施例１と同様な混練条件下で下記組成の混合物を混練した。
樹脂Ｃ ７５０ｇ
キナクリドン系顔料 ４６３０ｇ
（ファストゲンスーパーマゼンタＲＴＳ、大日本インキ化学工業（株）製）
式ＩＶの化合物 ３８０ｇ
（１分子あたりの平均フタルイミドメチル基数１．４）
ジエチレングリコール ３１００ｇ
３４質量％水酸化カリウム水溶液 ３２２ｇ
【００８１】
高速への切り替え時のプラネタリーミキサー電流値は５Ａであった。その後、混練を継続し、プラネタリーミキサーの最大電流値が１５Ａを示した。最大電流値を示してから２時間、混練を継続した後、プラネタリーミキサーの電流値は１２Ａであった。この様にして得た撹拌槽内の混練物に、６０℃に加温したイオン交換水を３００ｇ徐々に加えて混練を継続した。
【００８２】
最大電流値を観測してから４時間経過した時点まで混練を継続し着色混練物を得た。得られた着色混練物にプラネタリーミキサーによる撹拌を継続しながら、２時間で総量６７００ｇの６０℃に加温したイオン交換水を加えた。イオン交換水の添加が終了した後、プラネタリーミキサーから水希釈後の着色混練物を取り出した。水希釈後の着色混練物の固形分濃度は３８．１質量％であった。更に、水希釈後の着色混練物１２ｋｇに、ジエチレングリコール１．４９ｋｇ、イオン交換水９．３４ｋｇを分散撹拌機で撹拌しながら少量ずつ添加し、水性顔料分散液前駆体Ｇ−１を得た。
【００８３】
この水性顔料分散液前駆体Ｇ−１、１８ｋｇを用いて、送液量を１９５ｇ／１０秒とする以外は、実施例１の分散条件（１）と同様な条件で分散処理を実施し水性顔料分散液前駆体Ｇ−２を得た。水性顔料分散液前駆体Ｇ−２のキナクリドン系顔料濃度は１５．８質量％であった。
【００８４】
下記の配合物を用いて、実施例１の分散条件（２）に記載された操作と同様な操作を行い、水性顔料分散液Ｇ−３を得た。得られた水性顔料分散液Ｇ−３中のキナクリドン系顔料濃度は１３．１％であった。

【００８５】
（比較例１）
実施例１と同様な混練条件下で下記組成の混合物を混練した。
樹脂Ａ １０００ｇ
キナクリドン系顔料 ５０００ｇ
（ファストゲンスーパーマゼンタＲＴＳ、大日本インキ化学工業（株）製）
ジエチレングリコール ３２００ｇ
３４質量％水酸化カリウム水溶液 ４４７ｇ
【００８６】
高速への切り替え時のプラネタリーミキサー電流値は５Ａであった。その後、混練を継続し、プラネタリーミキサーの最大電流値が１０Ａを示した。最大電流値を示してから２時間、混練を継続した後、プラネタリーミキサーの電流値は８Ａであった。この様にして得た撹拌槽内の混練物に、６０℃に加温したイオン交換水を２００ｇ徐々に加えて混練を継続した。
【００８７】
最大電流値を観測してから４時間経過した時点まで混練を継続し着色混練物を得た。得られた着色混練物にプラネタリーミキサーによる撹拌を継続しながら、２時間で総量６０００ｇの６０℃に加温したイオン交換水を加えた。イオン交換水の添加が終了した後、プラネタリーミキサーから水希釈後の着色混練物を取り出した。水希釈後の着色混練物の固形分濃度は４０．４質量％であった。更に、水希釈後の着色混練物１２ｋｇに、ジエチレングリコール１．４２ｋｇ、イオン交換水１１．２５ｋｇを分散撹拌機で撹拌しながら少量ずつ添加し、水性顔料分散液前駆体Ｈ−１を得た。
【００８８】
この水性顔料分散液前駆体Ｈ−１、１８ｋｇを用いて、実施例１の分散条件（１）と同様な条件で分散処理を実施し水性顔料分散液Ｈ−３を得た。顔料分散液Ｈ−３のキナクリドン系顔料濃度は１６．０質量％であった。
【００８９】
（比較例２）
実施例１と同様な混練条件下で下記組成の混合物を混練した。
樹脂Ａ ７５０ｇ
キナクリドン系顔料 ４２５０ｇ
（ファストゲンスーパーマゼンタＲＴＳ、大日本インキ化学工業（株）製）
式ＩＶの化合物 ７５０ｇ
（１分子あたりの平均フタルイミドメチル基数１．４）
ジエチレングリコール ２６００ｇ
３４質量％水酸化カリウム水溶液 ３３５ｇ
【００９０】
高速への切り替え時のプラネタリーミキサー電流値は５Ａであった。その後、混練を継続し、プラネタリーミキサーの最大電流値が１５Ａを示した。最大電流値を示してから４時間、混練を継続した後、プラネタリーミキサーの電流値は１０Ａであった。
【００９１】
最大電流値を観測してから４時間経過した時点まで混練を継続し着色混練物を得た。得られた着色混練物にプラネタリーミキサーによる撹拌を継続しながら、２時間で総量６０００ｇの６０℃に加温したイオン交換水を加えた。
【００９２】
イオン交換水の添加が終了した後、プラネタリーミキサーから水希釈後の着色混練物を取り出した。水希釈後の着色混練物の固形分濃度は４２．５質量％であった。更に、水希釈後の着色混練物１２ｋｇに、ジエチレングリコール２．０９ｋｇ、イオン交換水１１．４１ｋｇを分散撹拌機で撹拌しながら少量ずつ添加し、水性顔料分散液前駆体Ｉ−１を得た
【００９３】
この水性顔料分散液前駆体Ｉ−１、１８ｋｇを用いて、実施例１の分散条件（１）と同様な条件で分散処理を実施し水性顔料分散液Ｉ−３を得た。顔料分散液Ｉ−３のキナクリドン系顔料濃度は１４．５質量％であった。
【００９４】
（比較例３）
実施例１と同様な混練条件下で下記組成の混合物を混練した。
樹脂Ｄ ７５０ｇ
キナクリドン系顔料 ４６３０ｇ
（ファストゲンスーパーマゼンタＲＴＳ、大日本インキ化学工業（株）製）
式ＩＶの化合物 ３８０ｇ
（１分子あたりの平均フタルイミドメチル基数１．４）
ジエチレングリコール ２５００ｇ
３４質量％水酸化カリウム水溶液 ３３１ｇ
【００９５】
高速への切り替え時のプラネタリーミキサー電流値は５Ａであった。その後、混練を継続し、プラネタリーミキサーの最大電流値が１２Ａを示した。最大電流値を示してから２時間、混練を継続した後、プラネタリーミキサーの電流値は１０Ａであった。この様にして得た撹拌槽内の混練物に、６０℃に加温したイオン交換水を２００ｇ徐々に加えて混練を継続した。
【００９６】
最大電流値を観測してから４時間経過した時点まで混練を継続し着色混練物を得た。得られた着色混練物にプラネタリーミキサーによる撹拌を継続しながら、２時間で総量６８００ｇの６０℃に加温したイオン交換水を加えた。この水希釈後の着色混練物の固形分濃度は３９．０質量％であった。イオン交換水の添加が終了した後、プラネタリーミキサーから水希釈後の着色混練物を取り出した。更に取り出した水希釈後の着色混練物１２ｋｇに、ジエチレングリコール２．００ｋｇ、イオン交換水９．４０ｋｇを分散撹拌機で撹拌しながら少量ずつ添加し、水性顔料分散液前駆体Ｊ−１を得た。
【００９７】
この水性顔料分散液前駆体Ｊ−１、１８ｋｇを用いて、実施例１の分散条件（１）と同様な条件で分散処理を実施し水性顔料分散液前駆体Ｊ−２を得た。水性顔料分散液前駆体Ｊ−２のキナクリドン系顔料濃度は１５．８質量％であった。
【００９８】
下記の配合物を用いて、実施例１の分散条件（２）に記載された操作と同様な操作を行い、水性顔料分散液Ｊ−３を得た。得られた水性顔料分散液Ｊ−３中のキナクリドン系顔料濃度は１３．１％であった。

【００９９】
（比較例４）
実施例１と同様な混練条件下で下記組成の混合物を混練した。
樹脂Ｅ ７５０ｇ
キナクリドン系顔料 ４６３０ｇ
（ファストゲンスーパーマゼンタＲＴＳ、大日本インキ化学工業（株）製）
式ＩＶの化合物 ３８０ｇ
（１分子あたりの平均フタルイミドメチル基数１．４）
ジエチレングリコール ３３００ｇ
３４質量％水酸化カリウム水溶液 ３３８ｇ
イオン交換水 ２００ｇ
【０１００】
高速への切り替え時のプラネタリーミキサー電流値は５Ａであった。その後、混練を継続し、プラネタリーミキサーの最大電流値が１５Ａを示した。最大電流値を示してから１時間、混練を継続した後、プラネタリーミキサーの電流値は１３Ａであった。この様にして得た撹拌槽内の混練物に、６０℃に加温したイオン交換水を２００ｇ加えて混練を継続し、均一に混合されたことを確認して、更に１時間経過後２００ｇの６０℃に加温したイオン交換水を加え、同様に均一になるまで混合し、混練を継続した。
最大電流値を観測してから４時間経過した時点まで混練を継続し着色混練物を得た。得られた着色混練物にプラネタリーミキサーによる撹拌を継続しながら、２時間で総量６４００ｇの６０℃に加温したイオン交換水を加えた。
【０１０１】
イオン交換水の添加が終了した後、プラネタリーミキサーから水希釈後の着色混練物を取り出した。この水希釈後の着色混練物の固形分濃度は３８．４質量％であった。更に取り出した水希釈後の着色混練物１２ｋｇに、ジエチレングリコール１．３４ｋｇ、イオン交換水９．７０ｋｇを分散撹拌機で撹拌しながら少量ずつ添加し、水性顔料分散液前駆体Ｋ−１を得た。
【０１０２】
この水性顔料分散液前駆体Ｋ−１、１８ｋｇを用いて、送液量を１９５ｇ／１０秒とする以外は、実施例１の分散条件（１）と同様な条件で分散処理を実施し水性顔料分散液前駆体Ｋ−２を得た。水性顔料分散液前駆体Ｋ−２のキナクリドン系顔料濃度は１５．８質量％であった。
【０１０３】
下記の配合物を用いて、実施例１の分散条件（２）に記載された操作と同様な操作を行い、水性顔料分散液Ｋ−３を得た。得られた水性顔料分散液Ｋ−３中のキナクリドン系顔料濃度は１３．５％であった。

【０１０４】
（比較例５）
実施例１と同様な混練条件下で下記組成の混合物を混練した。
樹脂Ｆ ７５０ｇ
キナクリドン系顔料 ４６３０ｇ
（ファストゲンスーパーマゼンタＲＴＳ、大日本インキ化学工業（株）製）
式ＩＶの化合物 ３８０ｇ
（１分子あたりの平均フタルイミドメチル基数１．４）
ジエチレングリコール ３０００ｇ
３４質量％水酸化カリウム水溶液 ３２９ｇ
【０１０５】
高速への切り替え時のプラネタリーミキサー電流値は５Ａであった。その後、混練を継続し、プラネタリーミキサーの最大電流値が１５Ａを示した。最大電流値を示してから１時間、混練を継続した後、プラネタリーミキサーの電流値は１３Ａであった。この様にして得た撹拌槽内の混練物に、６０℃に加温したイオン交換水を３００ｇ加えて混練を継続し、均一に混合されたことを確認して、更に１時間経過後２００ｇの６０℃に加温したイオン交換水を加え、同様に均一になるまで混合し、混練を継続した。
最大電流値を観測してから４時間経過した時点まで混練を継続し着色混練物を得た。得られた着色混練物にプラネタリーミキサーによる撹拌を継続しながら、２時間で総量６５００ｇの６０℃に加温したイオン交換水を加えた。
【０１０６】
イオン交換水の添加が終了した後、プラネタリーミキサーから水希釈後の着色混練物を取り出した。この水希釈後の着色混練物の固形分濃度は３９．２質量％であった。更に取り出した水希釈後の着色混練物１２ｋｇに、ジエチレングリコール１．６１ｋｇ、イオン交換水９．９１ｋｇを分散撹拌機で撹拌しながら少量ずつ添加し、水性顔料分散液前駆体Ｌ−１を得た。
【０１０７】
この水性顔料分散液前駆体Ｌ−１、１８ｋｇを用いて、実施例１の分散条件（１）と同様な条件で分散処理を実施し水性顔料分散液前駆体Ｌ−２を得た。水性顔料分散液前駆体Ｌ−２のキナクリドン系顔料濃度は１５．８質量％であった。
【０１０８】
下記の配合物を用いて、実施例１の分散条件（２）に記載された操作と同様な操作を行い、水性顔料分散液Ｌ−３を得た。得られた水性顔料分散液Ｌ−３中のキナクリドン系顔料濃度は１３．１％であった。

【０１０９】
（水性顔料分散液の評価）
上述の様にして得られた実施例、比較例の水性顔料分散液について、マイクロトラックＵＰＡ粒度分析計（Ｌｅｅｄｓ＆Ｎｏｒｔｈｒｕｐ社製）でセル温度２５℃にて粒径測定を実施した。その際、粒径測定サンプルは、各サンプルともにイオン交換水でキナクリドン系顔料濃度を１２．５％に希釈して調製し、更にイオン交換水で５００倍に希釈した。結果を表１に示す。
【０１１０】
（分散安定性の評価）
実施例、比較例の水性顔料分散液について、分散液の評価と同様に、それぞれキナクリドン系顔料濃度が１２．５質量％になるようにイオン交換水を加えて調整を行った。顔料濃度の調整を行った分散液について、スクリュー管等のガラス容器に密栓し、６０℃の恒温器で１週間の加熱試験を行い、加熱試験前後の粒径変化を観察することにより、分散安定性の評価を実施した。結果を表１に示す。
【０１１１】
【表１】
表１

【０１１２】
表１から明らかなように、本発明によって得られる水性顔料分散液は、加熱試験後の粒径変化率が小さいことが分かる。つまり、本発明によって分散安定性に優れた水性顔料分散液が得られる。
【０１１３】
（インク組成物の調製）
各実施例及び各比較例で得られた水性顔料分散液Ａ−３、Ｂ−３、Ｃ−３、Ｄ−３、Ｅ−３、Ｆ−３、Ｇ−３、Ｈ−３、Ｉ−３、Ｊ−３、Ｋ−３、Ｌ−３にイオン交換水を加えて、キナクリドン系顔料濃度１０質量％の水性顔料希釈液５０．０ｇを調製した。この水性顔料希釈液を用い下記配合にてキナクリドン系顔料濃度５質量％のインク組成物を調製した。
水性顔料希釈液 ５０．０ｇ
２−ピロリジノン ８．０ｇ
トリエチレングリコールモノブチルエーテル ８．０ｇ
グリセリン ３．０ｇ
サーフィノール４４０（エアープロダクツ社製） ０．５ｇ
イオン交換水 ３０．５ｇ
【０１１４】
（インク組成物の安定性試験）
得られたインク組成物について、スクリュー管等のガラス容器に密栓し、７０℃の恒温器で１週間の加熱試験を行い、加熱試験前後の粒径及び粘度変化を観察することにより、インク組成物の安定性の評価を実施した。結果を表２に示す。尚、粒径測定はインク組成物をイオン交換水で１００倍に希釈した以外は、水性顔料分散液の評価と同様に行った。また、粘度はＥ型粘度計（東京計器（株）社製ＶＩＳＣＯＭＥＴＥＲ ＴＶ−２０）を用いて２５℃にて測定した。
【０１１５】
（インクジェット記録適性評価）
得られた加熱試験前のインク組成物をヒューレットパッカード社製ＤｅｓｋＪｅｔ９５７Ｃのブラックペンに搭載し、印字試験を実施した。具体的には、Ａ４の用紙にベタ印字と細線印字を行い、インクの吐出状態を観察した。結果を表２に示す。
【０１１６】
【表２】
表２

【０１１７】
上記表２のインクジェット記録適性評価欄におけるランク付けの基準は以下の通りである。
◎：すべての印字サンプルにおいて、均一なベタ印字で細線部でも吐出不良が無い
○：ベタ印字でやや均一性に欠けるが、細線部では吐出不良がない
△：ベタ印字で均一性が劣り、細線部では吐出不良は無いが、印字位置ずれが見られる。
×：ベタ印字で吐出不良による印字ムラが見られ、細線部でも吐出不良による印字欠けが一部見られる。
××：吐出不良が多発する。
【０１１８】
表２から明らかなように、本発明によって得られるインク組成物は良好な保存安定性を示すと同時に、良好なインクジェット記録適性を有することが分かる。同様に、得られた加熱試験前のインク組成物をピエゾジェット方式のエプソン社製ＥＭ−９００Ｃのブラックペンに搭載し、印字試験を実施した。具体的には、Ａ４の用紙にベタ印字と細線印字を行い、インクの吐出状態を観察したが、実施例、比較例ともに特に問題は認められなかった。
【０１１９】
【発明の効果】
本発明のインクジェットインク用水性顔料分散液を用いることによって、顔料の微分散化が達成できると同時に、分散性及び分散安定性に優れ、高温で長期間放置しても粒径の増大が少なく、且つ粘度上昇も少なく印字安定性の優れた赤色ないしマゼンタ色のインクジェットインク用水性インク組成物を得ることができる。本発明のインクジェットインク用水性顔料分散液を用いたインクジェットインク用水性インク組成物は、特にサーマルインクジェットインク用水性インク組成物として好適に使用できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aqueous pigment dispersion for red or magenta inkjet ink, an aqueous ink composition for inkjet ink, and a method for producing the same, and particularly an ink composition suitable for a thermal jet recording method and a method for producing the same. About.
[0002]
[Prior art]
Inks using pigments have been developed as water-based inks for inkjet recording. Although inks using pigments can be expected to have excellent water resistance and light resistance, nozzle clogging due to pigment aggregation and sedimentation has become a new problem. In order to solve this, a method of dispersing a pigment in an aqueous medium using a polymer-based dispersant has been studied, but it is possible to stably disperse a pigment over a long period of time only with a polymer-based dispersant. It has been difficult to provide a water-based ink composition for pigment-dispersed water-based inkjet inks that is excellent in long-term storage stability.
[0003]
As a method of dispersing a pigment in an aqueous medium using a polymer-based dispersant, for example, an aqueous solution in which a water-soluble polymer dispersant is dissolved in water in the presence of a basic component is prepared, and the pigment is added thereto. In addition, a method using a high-speed sand mill or the like having higher dispersion efficiency after sufficiently stirring has been proposed. However, this method has a problem that the dispersion time is long and the production efficiency is low. Also, the aqueous pigment dispersion thus obtained still has insufficient dispersion stability. The step of producing an aqueous pigment dispersion using a sand mill is usually performed using a low-viscosity dispersion such as a pigment having a small solid content ratio. Therefore, it is difficult to apply a strong share to the pigment, and it takes a lot of time to grind the coarse particles of the pigment. The aqueous pigment dispersion thus obtained contains a considerable amount of coarse particles having a particle diameter of 1 μm or more even after dispersion. Therefore, since the ejection stability of the ink jet cannot be ensured as it is, a step of removing coarse particles by further centrifugation, filtration, etc. is necessary, which further reduces the production efficiency and the yield. It was.
[0004]
By the way, in order to keep the dispersion state of the pigment stable for a long time, for example, a method using a pigment and a sulfonic acid group-containing pigment derivative and utilizing electrostatic repulsion of the sulfonic acid group-containing pigment derivative adsorbed on the pigment surface has been proposed. (See Patent Document 1). According to this method, the dispersion stability of the coloring material is improved. However, the printed matter using the ink using this coloring material has a high affinity with water due to the presence of the polar functional group on the coloring material surface, and the pigment itself is colored. There is a problem that the water resistance is inferior to the ink used as the material.
[0005]
Furthermore, in order to achieve the dispersibility and dispersion stability of an aqueous pigment dispersion or recording ink using a quinacridone pigment as a color material, a microencapsulated pigment dispersion using a quinacridone pigment and a dimethylaminomethylated quinacridone compound in combination The body contains a quinacridone pigment, a phthalimidomethylated quinacridone compound, a quinacridone sulfonic acid compound, and an anionic group-containing organic polymer compound having a glass transition point of -20 to 60 ° C. An aqueous pigment dispersion has been proposed (see Patent Document 3). However, the magenta water-based pigment dispersions described in these publications are not sufficiently satisfactory in terms of dispersion level and dispersion stability. In particular, the thermal stability was insufficient when applied to thermal jet ink jet recording.
[0006]
On the other hand, an example of an aqueous pigment dispersion for inkjet ink using a styrene acrylic resin (styrene / acrylic acid / methacrylic acid = 77/10/30, molecular weight 50,000) as a resin for dispersing a quinacridone pigment is known. (See Patent Document 4). However, the magenta aqueous pigment dispersion described in this publication is not fully satisfactory in terms of dispersion level and dispersion stability. In particular, when applied to thermal jet ink jet recording, it was not possible to ensure sufficient ejection stability.
[0007]
In addition, an example of an aqueous pigment dispersion for inkjet ink using a styrene acrylic resin (styrene / acrylic acid / methacrylic acid = 77/10/30, molecular weight 7200, and 8300) as a resin for dispersing carbon black is known. (See Patent Document 5 and Patent Document 6). However, even in these publications, a magenta aqueous pigment dispersion using a quinacridone pigment having excellent dispersion stability has not been obtained.
[0008]
Thus, there are no known documents that provide meaningful suggestions for improving the dispersion stability of the water-based ink composition for ink jet recording, particularly for performing good thermal jet ink jet recording.
[0009]
[Patent Document 1]
JP 2002-241638 A
[Patent Document 2]
Japanese Patent Laid-Open No. 9-151342
[Patent Document 3]
JP 2000-191974 A
[Patent Document 4]
JP 2000-186244 A (Example 5)
[Patent Document 5]
JP 2001-164165 A (Example)
[Patent Document 6]
JP 2003-41178 A (Example)
[0010]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a red or magenta inkjet ink that is excellent in dispersibility and dispersion stability, has a small increase in particle size even when left for a long period of time at a high temperature, has little increase in viscosity, and has excellent printing stability. Water-based pigment dispersion and water-based ink composition for ink-jet recording using the same.
[0011]
Another object of the present invention is to provide an aqueous pigment dispersion for inkjet ink and an aqueous ink composition for inkjet recording suitable for the thermal inkjet recording method.
[0012]
[Means for Solving the Problems]
As a result of intensive studies on this problem, the present inventors have solved the problem by using the following means. That is, the present invention is an aqueous pigment dispersion for inkjet ink containing a quinacridone pigment (a), a styrene resin (b), an alkali metal hydroxide (c), and a dispersion aid (d), The styrenic resin (b) is a mixture of (i) a monomer containing 60% by mass or more of a styrenic monomer and (ii) an unsaturated aliphatic carboxylic acid having a radical polymerizable double bond with respect to all monomer components. A water-based pigment dispersion for inkjet ink, characterized in that it is a polymerized resin and the weight average molecular weight of the styrene resin (b) is in the range of 7,500 to 40,000. .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The aqueous pigment dispersion for inkjet ink of the present invention will be specifically described. In the following description, “aqueous pigment dispersion for inkjet ink” is “aqueous pigment dispersion”, “aqueous ink composition for inkjet ink” is “ink composition”, and aqueous pigment dispersion for inkjet ink is manufactured. The “colored kneaded product for inkjet ink” for this purpose is abbreviated as “colored kneaded product”.
[0014]
As the quinacridone-based pigment (a) used in the present invention, any known and conventional ones can be used. I. Dimethylquinacridone pigments such as CI Pigment Red 122; I. Pigment red 202, C.I. I. Dichloroquinacridone pigments such as CI Pigment Red Red 209; I. Examples thereof include unsubstituted quinacridone such as CI Pigment Violet 19, and a mixture or solid solution of at least two pigments selected from these pigments. The pigment may be a dry pigment in the form of powder, granules or lumps, or may be a wet cake or a slurry. Among the quinacridone pigments (a), C.I. I. Pigment Red 122 is preferable.
[0015]
The styrenic resin (b) used in the present invention comprises (i) 60 mass% or more of a styrenic monomer and (ii) an unsaturated aliphatic carboxylic acid having a radical polymerizable double bond with respect to all monomer components. It is a resin obtained by copolymerizing the monomer to be contained, and the styrene resin (b) has a weight average molecular weight in the range of 7,500 to 40,000.
A known compound can be used as the styrene monomer. For example, alkylstyrene such as styrene, α-methylstyrene, β-methylstyrene, 2,4-dimethylstyrene, α-ethylstyrene, α-butylstyrene, α-hexylstyrene, 4-chlorostyrene, 3-chlorostyrene, There are halogenated styrenes such as 3-bromostyrene, 3-nitrostyrene, 4-methoxystyrene, vinyltoluene and the like.
[0016]
The use ratio of the styrene monomer, which is the raw material of the styrene resin (b), with respect to all monomer components is more preferably 60 to 90% by mass, and particularly preferably 70 to 90% by mass. If the ratio of the styrene monomer used is less than 60% by mass, the affinity of the styrene resin (b) to the quinacridone pigment (a) tends to be insufficient, and the dispersion stability of the aqueous pigment dispersion tends to decrease. is there. Further, the plain paper recording characteristics of the ink composition obtained from the aqueous pigment dispersion tend to deteriorate, the image recording density tends to decrease, and the water resistance tends to decrease. When the amount of the styrene monomer is within the above range, the solubility of the styrene resin (b) in the aqueous medium can be improved, and the dispersibility and dispersion stability of the pigment in the aqueous pigment dispersion for inkjet ink are improved. Can be made. Furthermore, the printing stability when used as an ink composition is improved.
[0017]
As the unsaturated aliphatic carboxylic acid having a radical polymerizable double bond to be copolymerized with a styrene monomer, a known compound can be used. For example, acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, α-methylcrotonic acid, α-ethylcrotonic acid, isocrotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid , Etc. Among them, it is preferable to use acrylic acid and methacrylic acid, and it is particularly preferable to use both in combination. By using acrylic acid and methacrylic acid together, the copolymerization at the time of resin synthesis is improved and the uniformity of the resin is improved. As a result, it is possible to obtain a pigment dispersion having good storage stability and more fine particles.
[0018]
As the monomer of the styrenic resin (b) used in the present invention, it is particularly preferable to use three kinds of monomers of styrenic monomer, acrylic acid, and methacrylic acid, and the total content ratio thereof is the total monomer component. On the other hand, it is preferably 95% by mass or more from the viewpoint of further improving dispersibility and achieving a high Tg.
[0019]
A known monomer other than the styrene monomer and the unsaturated aliphatic carboxylic acid having a radical polymerizable double bond can be used for the styrene resin (b). Examples of such monomers include methyl acrylate, methyl methacrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, tert-butyl acrylate, 2-ethylbutyl acrylate, 1,3-dimethylbutyl Acrylic esters such as acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, ethyl methacrylate, n-butyl methacrylate, 2-methylbutyl methacrylate, pentyl methacrylate, heptyl methacrylate, nonyl methacrylate or methacrylic Acid esters; 3-ethoxypropyl acrylate, 3-ethoxybutyl acrylate, dimethylaminoethyl acrylate Acrylic acid ester derivatives or methacrylic acid ester derivatives such as 2-hydroxyethyl acrylate, hydroxybutyl acrylate, ethyl-α- (hydroxymethyl) acrylate, dimethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate; Acrylic acid aryl esters or acrylic acid aralkyl esters such as phenyl acrylate, benzyl acrylate, phenyl ethyl acrylate, phenyl ethyl methacrylate; monohydric alcohols such as diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, bisphenol A Acrylic acid esters or monomethacrylic acid esters; Dimethyl maleate And maleic acid dialkyl esters such as diethyl maleate, vinyl acetate and the like. One or more of these monomers can be added as monomer components.
[0020]
As a method for producing the styrene-based resin (b), a usual polymerization method can be employed, and examples thereof include a method in which a polymerization reaction is performed in the presence of a polymerization catalyst, such as solution polymerization, suspension polymerization, and bulk polymerization. Examples of the polymerization catalyst include 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile), Examples thereof include benzoyl peroxide, dibutyl peroxide, butyl peroxybenzoate, and the amount used is preferably 0.1 to 10.0% by mass of the vinyl monomer component.
[0021]
The weight average molecular weight of the styrene resin (b) used in the present invention is in the range of 7,500 to 40,000. In particular, it is preferably in the range of 7,500 to 30,000, and more preferably in the range of 10,000 to 25,000. If the weight average molecular weight is less than 7,500, the initial dispersion and particle size of the quinacridone pigment (a) can be easily reduced, but the long-term storage stability of the aqueous pigment dispersion for inkjet ink tends to deteriorate. In some cases, sedimentation may occur due to pigment aggregation. When the weight average molecular weight of the styrene resin (b) exceeds 40,000, the viscosity of the ink composition prepared from the aqueous pigment dispersion for inkjet ink using the styrene resin (b) becomes high, and the ejection stability of the ink is unstable. Tend to be.
[0022]
The glass transition point of the styrenic resin (b) is preferably 90 ° C. or higher, more preferably 90 to 150 ° C., and particularly preferably 95 to 120 ° C. When the glass transition point is 90 ° C. or higher, the thermal stability of the ink composition is improved. For this reason, even if the water-based ink composition for ink-jet recording prepared from the water-based pigment dispersion is used for thermal jet type ink-jet recording, it does not cause characteristic changes that cause defective discharge due to repeated heating.
The glass transition point of the styrenic resin (b) used in the present invention is a value obtained by DSC (differential scanning calorimetry) measurement.
[0023]
The styrenic resin (b) used in the present invention preferably forms a stable pigment surface coating in an aqueous medium, and has a stable water dispersibility by neutralizing acid groups with a basic compound. It is preferable to have. For this purpose, it is preferable to use one having an acid value of 50 to 300. When the acid value is less than 50, the hydrophilicity becomes small and the dispersion stability of the pigment may be lowered. On the other hand, if the acid value is greater than 300, the pigments tend to aggregate, and the water resistance of the printed product using the ink composition may be reduced. As a value of an acid value, 60-250 are more preferable, and it is still more preferable that it is 70-200.
[0024]
The styrenic resin (b) used in the present invention may be a random copolymer or a graft copolymer. As the graft copolymer, a copolymer of polystyrene or a nonionic monomer copolymerizable with styrene and styrene is used as a trunk or branch, and a copolymer of acrylic acid, methacrylic acid and other monomers including styrene is branched. Or the graft copolymer used as a trunk can be shown as the example. The styrene resin (b) may be a mixture of the graft copolymer and the random copolymer.
[0025]
As the alkali metal hydroxide (c) used in the present invention, for example, sodium hydroxide, potassium hydroxide, lithium hydroxide and the like can be used, and potassium hydroxide is particularly preferably used. The addition amount of the alkali metal hydroxide (c) is an amount corresponding to 0.8 to 1.2 times the amount necessary for neutralizing all the carboxyl groups of the styrene resin (b). It is preferable.
[0026]
As the dispersion aid (d) used in the present invention, a known compound can be used. For example, a so-called pigment derivative in which a dialkylaminomethyl group, an arylamidomethyl group, a sulfonic acid amide group, a sulfonic acid group and a salt thereof, a phthalimide group, or the like is introduced into the pigment skeleton can be given.
[0027]
Among these, the dispersion aid (d) used in the present invention is preferably a compound (e) represented by the following formula I.
[0028]
[Formula 1]

{Where R is ₁ ~ R ₁₀ Each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a methyl group or an alkyl group having 2 to 8 carbon atoms, or a compound of formula II
[0029]
[Formula 2]

(Wherein R ₁₁ Is a methylene group or an alkylene or alkenylene group having 2 to 8 carbon atoms, R ₁₂ ~ R ₁₅ Each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a methyl group, an alkyl group having 2 to 8 carbon atoms, or a phenyl group. ) And R ₁ ~ R ₁₀ At least one of is a group represented by the formula II. }
[0030]
A specific example of a preferable compound among the compounds (e) represented by the formula I is a compound represented by the following formula IV having a group represented by the following formula III.
[0031]
[Formula 2]

[0032]
[Formula 2]

(In the formula, m and n each independently represent 0, 1, 2, or 3, provided that m and n are not 0.)
[0033]
The compound (e) used in the present invention is preferably a compound having one or more groups represented by the formula III per molecule among the compounds represented by the formula IV. A compound having an average of 1 to 2 is preferred. Particularly preferred is a compound having an average of 1 to 1.5 molecules per molecule. When the number of groups represented by Formula III is less than 1 per molecule on average, the effect on dispersion stability is difficult to appear, and when the average exceeds 2 groups per molecule, bleeding and other characteristics as an aqueous ink composition for inkjet ink May be reduced.
[0034]
When the compound (e) represented by the formula I is, for example, a compound having a group represented by the above formula III, an unsubstituted quinacridone, dimethylquinacridone, dichloroquinacridone, etc. and phthalimide and formaldehyde or paraformaldehyde are concentrated. It can be synthesized by reacting in sulfuric acid.
[0035]
In the present invention, the quinacridone sulfonic acid compound (f) can also be used as the dispersion aid (d). As the quinacridone sulfonic acid compound (f), known and conventional compounds can be used. For example, quinacridone sulfonic acids that can be synthesized by reacting unsubstituted quinacridone, dimethylquinacridone, dichloroquinacridone, and the like with concentrated sulfuric acid by a known method, and metal salts thereof such as sodium, aluminum, and calcium, and ammonium, octadecylammonium, di Ammonium salts such as dodecylammonium, dimethyloctadecylammonium, dimethyldioctadecylammonium, and benzyldimethyloctadecylammonium are listed. Among these, an alkali metal salt is preferable. More specifically, 3,10-dichloroquinacridonesulfonic acid sodium salt is preferable as the quinacridonesulfonic acid compound (f) used in the present invention.
[0036]
As the dispersion aid (d) used in the present invention, it is preferable to use the compound (e) represented by the formula I and the quinacridone sulfonic acid compound (f).
[0037]
In the present invention, the amount of the compound (e) represented by the formula I and the quinacridone sulfonic acid compound (f) used per 100 parts by mass of the quinacridone pigment (a) is 2 parts by mass or more, and The total amount of the compound (e) represented by I and the quinacridone sulfonic acid compound (f) is 4 to 20 parts by mass, and more preferably 4 to 15 parts by mass. When the amount used is in the above range, the storage stability of the dispersion and the ink composition is good. In addition, the ink discharge state is particularly good when printing is performed with a thermal jet printer.
[0038]
In the aqueous pigment dispersion and ink composition of the present invention, a styrene resin (100 parts by mass in total of the quinacridone pigment (a), the compound (e) represented by the formula I, and the quinacridone sulfonic acid compound (f)) ( The amount of b) used is preferably 10 to 50 parts by mass, and more preferably 10 to 40 parts by mass. When the amount of the styrene resin (b) used is less than 10 parts by mass, the dispersion stability of the aqueous pigment dispersion decreases, and when the ink composition is prepared using the aqueous pigment dispersion, the friction resistance decreases. When the amount exceeds 50 parts by mass, the viscosity of the ink composition tends to be too high.
[0039]
In the aqueous pigment dispersion of the present invention, it is preferable to use a wetting agent (h) for preventing drying of the aqueous pigment dispersion and preventing drying of the ink composition. As the wetting agent (h), known and commonly used ones can be used. Examples of the wetting agent (h) include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,3-propanediol, 1,4 -Butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2,6-hexanetriol, polyols such as trimethylolpropane, pentaerythritol, 2-pyrrolidone, N-methyl-2-pyrrolidone, Examples include lactams such as ε-caprolactam, 1,3-dimethylimidazolidinone, and the like.
[0040]
When the compound (e) of formula I and the quinacridone sulfonic acid compound (f) are used as the dispersion aid (d) in the aqueous pigment dispersion of the present invention, an aqueous pigment dispersion for inkjet ink is produced by the following method. It is preferable to do this. The method includes (I) quinacridone pigment (a), (i) 60% by mass or more of a styrene monomer and (ii) an unsaturated aliphatic carboxyl having a radical polymerizable double bond based on all monomer components. A styrene resin (b), an aqueous solution of an alkali metal hydroxide (c) or an organic resin which is a resin copolymerized with an acid-containing monomer and has a weight average molecular weight in the range of 7,500 to 40,000 A first step of producing a colored kneaded product (g) for inkjet inks by kneading the solvent solution and the compound (e) represented by the formula I together is performed, and then (II) the kneaded product (g) The kneaded product (g) is dispersed in the aqueous medium by adding the quinacridone sulfonic acid compound (f) and the aqueous medium to Step 2A, or, following the Step 1, (II ) Step 2B of sequentially adding the aqueous medium to the kneaded product (g) to disperse the kneaded product (g) in the aqueous medium and then adding the quinacridone sulfonic acid compound (f). This is a method for producing an aqueous pigment dispersion.
[0041]
When the styrene resin (b) is kneaded with the quinacridone pigment (a), the alkali metal hydroxide (c), and the compound (e) represented by the formula I, it is preferably kneaded under a high shear force. By kneading under a high shearing force, the quinacridone pigment (a) is finely pulverized, and further, the styrene resin (b) is adsorbed on the surface of the particles to obtain a uniform colored kneaded product for inkjet ink.
[0042]
The alkali metal hydroxide (c) is added as an aqueous solution of an alkali metal hydroxide (c) or an organic solvent solution. In this case, the concentration of the aqueous solution or the organic solvent solution of the alkali metal hydroxide (c) is preferably 20% by mass to 50% by mass. Moreover, as an organic solvent which melt | dissolves an alkali metal hydroxide (c), it is preferable to use alcoholic solvents, such as methanol, ethanol, isopropanol. Especially, in this invention, it is preferable to use the aqueous solution of an alkali metal hydroxide (c).
[0043]
It is preferable that the solid content concentration in the colored kneaded product (g) when kneading the raw materials is 50 to 80% by mass. When the solid content concentration is 50% by mass or less, a sufficient shearing force cannot be applied, and the quinacridone pigment (a) is not sufficiently pulverized, and at the same time, a uniform colored kneaded product (g) cannot be obtained. If the solid content exceeds 80% by mass, kneading becomes difficult even if the resin is sufficiently softened by heating. Further, it may be difficult to disperse the kneaded material in the aqueous medium after the kneading is completed.
[0044]
It is preferable to add a wetting agent (h) during kneading. The addition amount of the wetting agent (h) in that case is in the range of 40 to 80 parts by mass with respect to 100 parts by mass of the quinacridone pigment (a). By including the wetting agent, it becomes easy to adjust the solid content ratio to a value suitable for the kneading apparatus, and the wetting agent is replaced with the styrenic resin (b) because the pigment surface is easily wetted by the wetting agent. As a result, the coating of the pigment surface proceeds promptly.
[0045]
In producing the colored kneaded product (g), it is preferable to use a kneader having a stirring tank rather than using an open kneader having no stirring tank such as a two-roll. When such a kneader is used, the colored kneaded product (g) after kneading can be directly diluted with an aqueous medium containing the quinacridone sulfonic acid compound (f) to produce an aqueous pigment dispersion. A planetary mixer is preferable as a specific example of a kneader having a stirring tank. Planetary mixers can be kneaded in a wider range of viscosity than a two-roller, etc., and can also be added with an aqueous medium and distilled under reduced pressure, so the viscosity and load shear force during kneading can be adjusted. Is easy.
[0046]
The aqueous pigment dispersion obtained by diluting the colored kneaded product (g) after kneading with an aqueous medium containing the quinacridone sulfonic acid compound (f) is preferably further subjected to a dispersion treatment by a disperser. By carrying out the dispersion treatment, the coarsely dispersed particles in the aqueous pigment dispersion are further pulverized, and the particle size of the dispersed particles is further reduced, thereby further improving ink jet characteristics such as ejection stability and print density of the ink composition. It is to be done.
[0047]
As the disperser for carrying out the dispersion treatment, known and commonly used equipment can be used, for example, an ultrasonic homogenizer, a high-pressure homogenizer, a paint shaker, a ball mill, a roll mill, a sand mill, a sand grinder, a dyno mill, a dispar mat, a nano mill, an SC mill, Nanomizer etc. can be mentioned, One of these may be used independently and may be used in combination of 2 or more types of apparatuses.
[0048]
The aqueous medium containing the quinacridone sulfonic acid compound (f) when diluting the colored kneaded product (g) is used to prevent the drying of the aqueous pigment dispersion and to adjust the viscosity when carrying out the dispersion treatment. The amount thereof may be 3 to 50% by mass in the aqueous pigment dispersion together with the wetting agent (h) in the colored kneaded product (g), and preferably 5 to 40% by mass. It is more preferable. If it is less than this lower limit, the anti-drying effect tends to be insufficient, and if it exceeds the above upper limit, the dispersion stability of the dispersion tends to decrease. The wetting agent (h) used in the aqueous medium containing the quinacridone sulfonic acid compound (f) when the colored kneaded product (g) is produced and when it is diluted may be the same or different.
[0049]
The ink composition of the present invention can be prepared by a conventional method using an aqueous pigment dispersion. When an ink composition is prepared using the aqueous pigment dispersion of the present invention, coarse particles cause nozzle clogging and other image characteristics to be deteriorated. Therefore, after ink preparation, centrifugation or filtration treatment is performed. Coarse particles may be removed.
[0050]
When preparing an ink composition using the aqueous pigment dispersion of the present invention, the wetting agent (h) exemplified above can be added in the same manner for the purpose of preventing the ink from drying. The content of the wetting agent (h) in the ink for the purpose of preventing drying is preferably 3 to 50% by mass. Further, when preparing an ink composition using the aqueous pigment dispersion of the present invention, a penetrant can be added for the purpose of improving the permeability to a recording medium and adjusting the dot diameter on the recording medium.
[0051]
Examples of the penetrant include lower alcohols such as ethanol and isopropyl alcohol, ethylene oxide adducts of alkyl alcohols such as ethylene glycol hexyl ether and diethylene glycol butyl ether, and propylene oxide adducts of alkyl alcohols such as propylene glycol propyl ether. The penetrant content in the ink is preferably 0.01 to 10% by mass.
[0052]
When an ink composition is prepared using the aqueous pigment dispersion of the present invention, a surfactant can be added in order to adjust ink characteristics such as surface tension. The surfactant that can be added for this purpose is not particularly limited, and examples include various anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Of these, anionic surfactants and nonionic surfactants are preferred.
[0053]
Examples of the anionic surfactant include alkylbenzene sulfonate, alkylphenyl sulfonate, alkylnaphthalene sulfonate, higher fatty acid salt, sulfate of higher fatty acid ester, sulfonate of higher fatty acid ester, higher alcohol ether. Sulfate salts and sulfonates of the above, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, etc. Specific examples include dodecylbenzene sulfonate, isopropyl naphthalene sulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenyl sulfonate, dibutylphenylphenol disulfate. , And the like salts.
[0054]
Nonionic surfactants include, for example, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester , Polyoxyethylene glycerin fatty acid ester, polyglycerin fatty acid ester, sucrose fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene fatty acid amide, fatty acid alkylolamide, alkyl alkanolamide, acetylene glycol, oxyethylene adduct of acetylene glycol, Polyethylene glycol polypropylene glycol block copolymer, etc. Among them, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, fatty acid Preference is given to alkylolamide, acetylene glycol, oxyethylene adducts of acetylene glycol and polyethylene glycol polypropylene glycol block copolymers.
[0055]
Other surfactants include silicone surfactants such as polysiloxane oxyethylene adducts; fluorine surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and oxyethylene perfluoroalkyl ethers. Biosurfactants such as spicrispolic acid, rhamnolipid, lysolecithin and the like can also be used. These surfactants can be used alone or in combination of two or more. In consideration of the dissolution stability of the surfactant, the HLB is preferably in the range of 7-20.
[0056]
When the surfactant is added, the addition amount is preferably in the range of 0.001 to 1% by mass, more preferably 0.001 to 0.5% by mass, based on the total mass of the ink. More preferably, it is in the range of 01 to 0.2% by mass. When the addition amount of the surfactant is less than 0.001% by mass, the effect of adding the surfactant tends to be not obtained, and when it exceeds 1% by mass, problems such as blurring of the image are likely to occur. .
[0057]
When preparing an ink composition using the aqueous pigment dispersion of the present invention, a preservative, a viscosity modifier, a pH adjuster, a chelating agent, a plasticizer, an antioxidant, an ultraviolet absorber, etc. are added as necessary. Can also be added.
[0058]
The amount of the quinacridone pigment (a) in the aqueous pigment dispersion of the present invention is preferably 5 to 25% by mass, and more preferably 5 to 20% by mass. When the amount of the quinacridone pigment (a) is less than 5% by mass, the ink composition prepared from the aqueous pigment dispersion of the present invention is insufficiently colored, and a sufficient image density tends not to be obtained. On the other hand, when the amount is more than 25% by mass, the dispersion stability of the pigment tends to decrease in the aqueous pigment dispersion. The amount of the quinacridone pigment (a) in the ink composition prepared from the aqueous pigment dispersion of the present invention is sufficient to ensure the necessity of obtaining a sufficient image density and the dispersion stability of the dispersed particles in the ink. It is preferable that it is 2-10 mass%.
[0059]
This ink composition can be suitably used as an ink for inkjet recording. The ink jet method to be applied is not particularly limited, but known ones such as a continuous jet type (charge control type, spray type, etc.) and a drop-on-demand type (piezo type, thermal type, electrostatic suction type, etc.) It can be illustrated. Among these, it is preferable to use the printer for a thermal ink jet recording system.
[0060]
【Example】
Hereinafter, the present invention will be described specifically by way of examples.
Unless otherwise specified, “part” represents “part by mass” and “%” represents “% by mass”.
[0061]
Resins used in this example are A to F below.
Resin A: Resin having a monomer composition ratio of styrene / acrylic acid / methacrylic acid = 77/10/13 (mass ratio), a weight average molecular weight of 11,000, an acid value of 152 mgKOH / g, and a glass transition point of 118 ° C.
Resin B: Resin having a monomer composition ratio of styrene / acrylic acid / methacrylic acid = 77/10/13 (mass ratio), a weight average molecular weight of 20000, an acid value of 151 mgKOH / g, and a glass transition point of 121 ° C.
Resin C: A resin having a monomer composition ratio of styrene / methacrylic acid = 77/23 (mass ratio), a weight average molecular weight of 10700, an acid value of 146 mgKOH / g, and a glass transition point of 126 ° C.
Resin D: Resin having a monomer composition ratio of styrene / acrylic acid / methacrylic acid = 77/10/13 (mass ratio), a weight average molecular weight of 5000, an acid value of 150 mgKOH / g, and a glass transition point of 105 ° C.
Resin E: A resin having a monomer composition ratio of styrene / acrylic acid / methacrylic acid = 77/10/13 (mass ratio), a weight average molecular weight of 45,000, an acid value of 153 mgKOH / g, and a glass transition point of 128 ° C.
Resin F: Monomer composition ratio: styrene / methyl methacrylate / acrylic acid / methacrylic acid = 50/22/10/13 (mass ratio), weight average molecular weight 12000, acid value 149 mgKOH / g, glass transition point 118 ° C. Resin.
[0062]
Here, the weight average molecular weight is a value measured by a GPC (gel permeation chromatography) method, and is a value converted to a molecular weight of polystyrene used as a standard substance.
In addition, the measurement was implemented with the following apparatuses and conditions.
Liquid feed pump: LC-9A
System controller: SCL-6B
Autoinjector: SIL-6B
Detector: RID-6A
Made by Shimadzu Corporation.
Data processing software: Sic480II data station (manufactured by System Instruments).
Column: GL-R400 (guard column) + GL-R440 + GL-R450 + GL-R400M (manufactured by Hitachi Chemical Co., Ltd.)
Elution solvent: THF
Elution flow rate: 2 ml / min
Column temperature: 35 ° C
[0063]
(Example 1)
・ Kneading conditions
A mixture having the following composition was charged into a planetary mixer PLM-V-50V (manufactured by Inoue Mfg. Co., Ltd.) having a capacity of 50 L, the jacket was heated, and the speed of the contents was reduced until the temperature of the contents reached 60 ° C. (rotation speed: 21 Kneading at a rotation / min, revolution speed: 14 revolutions / minute), and after the temperature of the contents reaches 60 ° C., high speed (autorotation speed: 35 revolutions / minute, revolution speed: 24 revolutions / minute) The kneading was continued.
Resin A 750g
Quinacridone pigment 4750g
(Fastgen Super Magenta RTS, manufactured by Dainippon Ink & Chemicals, Inc.)
250 g of the compound of formula IV
(Average number of phthalimidomethyl groups per molecule 1.4)
3000 g of diethylene glycol
335 g of 34% potassium hydroxide aqueous solution
[0064]
The planetary mixer current value at the time of switching to high speed was 5A. Thereafter, the kneading was continued, and the maximum current value of the planetary mixer was 12A. After continuing the kneading for 1.5 hours after showing the maximum current value, the current value of the planetary mixer was 10A. 200 g of ion-exchanged water heated to 60 ° C. was gradually added to the kneaded material in the stirring tank thus obtained, and the kneading was continued.
[0065]
The kneading was continued until 4 hours after the maximum current value was observed to obtain a colored kneaded product. While continuing stirring with a planetary mixer, the total amount of 6800 g of ion-exchanged water heated to 60 ° C. was added to the colored kneaded product obtained in 2 hours. Then, the colored kneaded material after water dilution was taken out from the planetary mixer. The solid content concentration of the colored kneaded material after dilution with water was 39.4% by mass. Furthermore, 1.61 kg of diethylene glycol and 10.02 kg of ion-exchanged water were added little by little to 12 kg of the colored kneaded material after dilution with water to obtain an aqueous pigment dispersion precursor A-1.
[0066]
This aqueous pigment dispersion precursor A-1 (18 kg) was subjected to a dispersion treatment with a bead mill (Nanomill NM-G2L manufactured by Asada Tekko Co., Ltd.) under the following conditions to obtain an aqueous pigment dispersion precursor A-2.
・ Dispersion condition (1)
Disperser Nanomill NM-G2L (manufactured by Asada Tekko)
Beads φ0.3mm zirconia beads
Bead filling 85%
Cooling water temperature 10 ℃
Number of revolutions 2660 revolutions / minute
(Disk peripheral speed: 12.5 m / sec)
Liquid feed amount 200g / 10 seconds
Dispersion was performed while circulating for 1 hour under the above conditions. The concentration of the quinacridone pigment in the aqueous pigment dispersion precursor A-2 was 16.2% by mass.
[0067]
The aqueous pigment dispersion precursor A-2 was subjected to a dispersion treatment under the following conditions to obtain an aqueous pigment dispersion A-3.
・ Dispersion condition (2)
In a 250 ml polyethylene bottle, 200 g of φ1.2 mm zirconia beads were added, and the following blending was carried out, followed by treatment with a paint conditioner (manufactured by Toyo Seiki) for 30 minutes to obtain an aqueous pigment dispersion A-3. The concentration of the quinacridone pigment in the obtained aqueous pigment dispersion A-3 was 12.8%.

[0068]
(Example 2)
Using the aqueous pigment dispersion precursor A-2 prepared in Example 1, an aqueous pigment dispersion was prepared by the following method.
Using the following formulation, the same operation as described in the dispersion condition (2) of Example 1 was performed to obtain an aqueous pigment dispersion B-3. The concentration of the quinacridone pigment in the obtained aqueous pigment dispersion B-3 was 13.5%.

[0069]
(Example 3)
Using the aqueous pigment dispersion precursor A-2 prepared in Example 1, an aqueous pigment dispersion was prepared by the following method.
Using the following formulation, the same operation as described in the dispersion condition (2) of Example 1 was performed to obtain an aqueous pigment dispersion C-3. The concentration of the quinacridone pigment in the obtained aqueous pigment dispersion C-3 was 13.9%.

[0070]
(Example 4)
A mixture having the following composition was kneaded under the same kneading conditions as in Example 1.
Resin A 750g
Quinacridone pigment 4630g
(Fastgen Super Magenta RTS, manufactured by Dainippon Ink & Chemicals, Inc.)
380 g of the compound of formula IV
(Average number of phthalimidomethyl groups per molecule 1.4)
Diethylene glycol 2900g
335 g of 34 mass% potassium hydroxide aqueous solution
[0071]
The planetary mixer current value at the time of switching to high speed was 5A. Thereafter, the kneading was continued, and the maximum current value of the planetary mixer was 15A. Kneading was continued for 4 hours while adding 100 g of ion-exchanged water heated to 60 ° C. every 30 minutes after showing the maximum current value to obtain a colored kneaded product. During this period, the current value of the planetary mixer was 12A. To the colored kneaded material in the stirring tank thus obtained, ion-exchanged water heated to 60 ° C. in a total amount of 6200 g was added over 2 hours while continuing kneading.
[0072]
After the addition of ion-exchanged water was completed, the colored kneaded material after dilution with water was taken out from the planetary mixer. The solid content concentration of the colored kneaded material after dilution with water was 39.9% by mass. Further, 5.81 kg of diethylene glycol and 6.15 kg of ion-exchanged water were added little by little while stirring with a dispersion stirrer to 12 kg of the colored kneaded material after dilution with water to obtain an aqueous pigment dispersion precursor D-1.
[0073]
A dispersion treatment was carried out under the same conditions as the dispersion condition (1) in Example 1 except that 18 kg of this aqueous pigment dispersion precursor D-1 was used and the amount of liquid fed was 185 g / 10 seconds. A dispersion precursor D-2 was obtained. The concentration of the quinacridone pigment in the aqueous pigment dispersion precursor D-2 was 15.8% by mass.
[0074]
Next, using the following formulation, the same operation as described in the dispersion condition (2) of Example 1 was performed to obtain an aqueous pigment dispersion D-3. The concentration of the quinacridone pigment in the obtained aqueous pigment dispersion D-3 was 12.8%.

[0075]
(Example 5)
Using the aqueous pigment dispersion precursor D-2 prepared in Example 4, an aqueous pigment dispersion was prepared by the following method.
Using the following formulation, the same operation as described in the dispersion condition (2) of Example 1 was performed to obtain an aqueous pigment dispersion E-3. The concentration of the quinacridone pigment in the obtained aqueous pigment dispersion E-3 was 13.5%.

[0076]
(Example 6)
A mixture having the following composition was kneaded under the same kneading conditions as in Example 1.
Resin B 1000g
Quinacridone pigment 4750g
(Fastgen Super Magenta RTS, manufactured by Dainippon Ink & Chemicals, Inc.)
250 g of the compound of formula IV
(Average number of phthalimidomethyl groups per molecule 1.4)
3000 g of diethylene glycol
444 g of 34 mass% potassium hydroxide aqueous solution
[0077]
The planetary mixer current value at the time of switching to high speed was 5A. Thereafter, the kneading was continued, and the maximum current value of the planetary mixer was 12A. After continuing the kneading for 1 hour after showing the maximum current value, the current value of the planetary mixer was 10A. 200 g of diethylene glycol was gradually added to the kneaded material in the stirring tank thus obtained and the kneading was continued.
[0078]
The kneading was continued until 4 hours after the maximum current value was observed to obtain a colored kneaded product. While continuing stirring by the planetary mixer to the obtained colored kneaded product, ion exchanged water heated to 60 ° C. in a total amount of 7000 g was added in 2 hours. After the addition of ion-exchanged water was completed, the colored kneaded material after dilution with water was taken out from the planetary mixer. The solid content concentration of the colored kneaded product after water dilution was 39.0% by mass. Furthermore, the solid content concentration of diethylene glycol 1.37 kg, ion-exchanged water 10.05 kg, 3,10-dichloroquinacridonesulfonic acid sodium salt (average sulfone group number 1.3) 10.0% to 12 kg of the colored kneaded material after water dilution 3.26 kg of the hydrous slurry was added little by little while stirring with a dispersion stirrer to obtain an aqueous pigment dispersion precursor F-1.
[0079]
Using this aqueous pigment dispersion precursor F-1, 18 kg, a dispersion treatment was carried out under the same conditions as the dispersion condition (1) of Example 1 to obtain an aqueous pigment dispersion F-3. The concentration of the quinacridone pigment in the aqueous pigment dispersion F-3 was 13.6% by mass.
[0080]
(Example 7)
A mixture having the following composition was kneaded under the same kneading conditions as in Example 1.
Resin C 750g
Quinacridone pigment 4630g
(Fastgen Super Magenta RTS, manufactured by Dainippon Ink & Chemicals, Inc.)
380 g of the compound of formula IV
(Average number of phthalimidomethyl groups per molecule 1.4)
Diethylene glycol 3100g
34% by mass potassium hydroxide aqueous solution 322g
[0081]
The planetary mixer current value at the time of switching to high speed was 5A. Thereafter, the kneading was continued, and the maximum current value of the planetary mixer was 15A. After continuing the kneading for 2 hours after showing the maximum current value, the current value of the planetary mixer was 12A. Kneading was continued by gradually adding 300 g of ion-exchanged water heated to 60 ° C. to the kneaded material in the stirring tank thus obtained.
[0082]
The kneading was continued until 4 hours after the maximum current value was observed to obtain a colored kneaded product. While continuing stirring by the planetary mixer to the obtained colored kneaded product, ion-exchanged water heated to 60 ° C. in a total amount of 6700 g was added over 2 hours. After the addition of ion-exchanged water was completed, the colored kneaded material after dilution with water was taken out from the planetary mixer. The solid content concentration of the colored kneaded product after water dilution was 38.1% by mass. Furthermore, 1.49 kg of diethylene glycol and 9.34 kg of ion-exchanged water were added little by little to 12 kg of the colored kneaded material after dilution with water to obtain an aqueous pigment dispersion precursor G-1.
[0083]
Using this aqueous pigment dispersion precursor G-1, 18 kg, the dispersion treatment was carried out under the same conditions as the dispersion condition (1) in Example 1 except that the liquid feed amount was 195 g / 10 seconds. A dispersion precursor G-2 was obtained. The concentration of the quinacridone pigment in the aqueous pigment dispersion precursor G-2 was 15.8% by mass.
[0084]
Using the following formulation, the same operation as described in the dispersion condition (2) of Example 1 was performed to obtain an aqueous pigment dispersion G-3. The concentration of the quinacridone pigment in the obtained aqueous pigment dispersion G-3 was 13.1%.

[0085]
(Comparative Example 1)
A mixture having the following composition was kneaded under the same kneading conditions as in Example 1.
Resin A 1000g
Quinacridone pigment 5000g
(Fastgen Super Magenta RTS, manufactured by Dainippon Ink & Chemicals, Inc.)
Diethylene glycol 3200g
34 mass% potassium hydroxide aqueous solution 447 g
[0086]
The planetary mixer current value at the time of switching to high speed was 5A. Then, kneading | mixing was continued and the maximum electric current value of the planetary mixer showed 10A. After continuing the kneading for 2 hours after showing the maximum current value, the current value of the planetary mixer was 8A. 200 g of ion-exchanged water heated to 60 ° C. was gradually added to the kneaded material in the stirring tank thus obtained, and the kneading was continued.
[0087]
The kneading was continued until 4 hours after the maximum current value was observed to obtain a colored kneaded product. While continuing stirring with a planetary mixer, the ion-exchanged water heated to 60 ° C. in a total amount of 6000 g was added to the obtained colored kneaded product for 2 hours. After the addition of ion-exchanged water was completed, the colored kneaded material after dilution with water was taken out from the planetary mixer. The solid content concentration of the colored kneaded product after water dilution was 40.4% by mass. Further, 1.42 kg of diethylene glycol and 11.25 kg of ion-exchanged water were added little by little to 12 kg of the colored kneaded material after dilution with water to obtain an aqueous pigment dispersion precursor H-1.
[0088]
Using this aqueous pigment dispersion precursor H-1, 18 kg, a dispersion treatment was carried out under the same conditions as the dispersion condition (1) of Example 1 to obtain an aqueous pigment dispersion H-3. The quinacridone pigment concentration of Pigment Dispersion Liquid H-3 was 16.0% by mass.
[0089]
(Comparative Example 2)
A mixture having the following composition was kneaded under the same kneading conditions as in Example 1.
Resin A 750g
Quinacridone pigment 4250g
(Fastgen Super Magenta RTS, manufactured by Dainippon Ink & Chemicals, Inc.)
750 g of the compound of formula IV
(Average number of phthalimidomethyl groups per molecule 1.4)
Diethylene glycol 2600g
335 g of 34 mass% potassium hydroxide aqueous solution
[0090]
The planetary mixer current value at the time of switching to high speed was 5A. Thereafter, the kneading was continued, and the maximum current value of the planetary mixer was 15A. After continuing the kneading for 4 hours after showing the maximum current value, the current value of the planetary mixer was 10A.
[0091]
The kneading was continued until 4 hours after the maximum current value was observed to obtain a colored kneaded product. While continuing stirring with a planetary mixer, the ion-exchanged water heated to 60 ° C. in a total amount of 6000 g was added to the obtained colored kneaded product for 2 hours.
[0092]
After the addition of ion-exchanged water was completed, the colored kneaded material after dilution with water was taken out from the planetary mixer. The solid content concentration of the colored kneaded product after water dilution was 42.5% by mass. Further, 2.09 kg of diethylene glycol and 11.41 kg of ion-exchanged water were added little by little while stirring with a dispersion stirrer to 12 kg of the colored kneaded material after dilution with water to obtain an aqueous pigment dispersion precursor I-1.
[0093]
Using this aqueous pigment dispersion precursor I-1, 18 kg, a dispersion treatment was carried out under the same conditions as the dispersion condition (1) of Example 1 to obtain an aqueous pigment dispersion I-3. The concentration of the quinacridone pigment in the pigment dispersion I-3 was 14.5% by mass.
[0094]
(Comparative Example 3)
A mixture having the following composition was kneaded under the same kneading conditions as in Example 1.
Resin D 750g
Quinacridone pigment 4630g
(Fastgen Super Magenta RTS, manufactured by Dainippon Ink & Chemicals, Inc.)
380 g of the compound of formula IV
(Average number of phthalimidomethyl groups per molecule 1.4)
Diethylene glycol 2500g
34 mass% potassium hydroxide aqueous solution 331 g
[0095]
The planetary mixer current value at the time of switching to high speed was 5A. Thereafter, the kneading was continued, and the maximum current value of the planetary mixer was 12A. After continuing the kneading for 2 hours after showing the maximum current value, the current value of the planetary mixer was 10A. 200 g of ion-exchanged water heated to 60 ° C. was gradually added to the kneaded material in the stirring tank thus obtained, and the kneading was continued.
[0096]
The kneading was continued until 4 hours after the maximum current value was observed to obtain a colored kneaded product. While continuing stirring with a planetary mixer, the total amount of 6800 g of ion-exchanged water heated to 60 ° C. was added to the colored kneaded product obtained in 2 hours. The solid content concentration of the colored kneaded material after dilution with water was 39.0% by mass. After the addition of ion-exchanged water was completed, the colored kneaded material after dilution with water was taken out from the planetary mixer. Further, 2.00 kg of diethylene glycol and 9.40 kg of ion-exchanged water were added little by little while stirring with a dispersion stirrer to 12 kg of the colored kneaded material after dilution with water to obtain an aqueous pigment dispersion precursor J-1.
[0097]
Using this aqueous pigment dispersion precursor J-1, 18 kg, a dispersion treatment was carried out under the same conditions as the dispersion condition (1) of Example 1 to obtain an aqueous pigment dispersion precursor J-2. The concentration of the quinacridone pigment in the aqueous pigment dispersion precursor J-2 was 15.8% by mass.
[0098]
Using the following formulation, the same operation as described in the dispersion condition (2) of Example 1 was performed to obtain an aqueous pigment dispersion J-3. The concentration of the quinacridone pigment in the obtained aqueous pigment dispersion J-3 was 13.1%.

[0099]
(Comparative Example 4)
A mixture having the following composition was kneaded under the same kneading conditions as in Example 1.
Resin E 750g
Quinacridone pigment 4630g
(Fastgen Super Magenta RTS, manufactured by Dainippon Ink & Chemicals, Inc.)
380 g of the compound of formula IV
(Average number of phthalimidomethyl groups per molecule 1.4)
Diethylene glycol 3300g
34 mass% potassium hydroxide aqueous solution 338 g
200g of ion exchange water
[0100]
The planetary mixer current value at the time of switching to high speed was 5A. Thereafter, the kneading was continued, and the maximum current value of the planetary mixer was 15A. After continuing the kneading for 1 hour after showing the maximum current value, the current value of the planetary mixer was 13A. 200 g of ion-exchanged water heated to 60 ° C. was added to the kneaded product in the stirring tank thus obtained, and kneading was continued. After confirming that the mixture was uniformly mixed, 200 g Ion exchange water heated to 60 ° C. was added, and the mixture was similarly mixed until uniform, and kneading was continued.
The kneading was continued until 4 hours after the maximum current value was observed to obtain a colored kneaded product. While continuing the stirring by the planetary mixer, the ion-exchanged water heated to 60 ° C. in a total amount of 6400 g was added to the colored kneaded product obtained in 2 hours.
[0101]
After the addition of ion-exchanged water was completed, the colored kneaded material after dilution with water was taken out from the planetary mixer. The solid content concentration of the colored kneaded material after dilution with water was 38.4% by mass. Further, 1.34 kg of diethylene glycol and 9.70 kg of ion-exchanged water were added little by little while stirring with a dispersion stirrer to 12 kg of the colored kneaded material after dilution with water to obtain an aqueous pigment dispersion precursor K-1.
[0102]
A dispersion treatment was carried out under the same conditions as the dispersion condition (1) of Example 1 except that 18 kg of this aqueous pigment dispersion precursor K-1 was used and the liquid feed amount was 195 g / 10 seconds. A dispersion precursor K-2 was obtained. The concentration of the quinacridone pigment in the aqueous pigment dispersion precursor K-2 was 15.8% by mass.
[0103]
Using the following formulation, the same operation as described in the dispersion condition (2) of Example 1 was performed to obtain an aqueous pigment dispersion K-3. The concentration of the quinacridone pigment in the obtained aqueous pigment dispersion K-3 was 13.5%.

[0104]
(Comparative Example 5)
A mixture having the following composition was kneaded under the same kneading conditions as in Example 1.
Resin F 750g
Quinacridone pigment 4630g
(Fastgen Super Magenta RTS, manufactured by Dainippon Ink & Chemicals, Inc.)
380 g of the compound of formula IV
(Average number of phthalimidomethyl groups per molecule 1.4)
3000 g of diethylene glycol
34 mass% potassium hydroxide aqueous solution 329 g
[0105]
The planetary mixer current value at the time of switching to high speed was 5A. Thereafter, the kneading was continued, and the maximum current value of the planetary mixer was 15A. After continuing the kneading for 1 hour after showing the maximum current value, the current value of the planetary mixer was 13A. 300 g of ion-exchanged water heated to 60 ° C. was added to the kneaded material in the stirring tank thus obtained, and kneading was continued to confirm that the mixture was uniformly mixed. Ion exchange water heated to 60 ° C. was added, and the mixture was similarly mixed until uniform, and kneading was continued.
The kneading was continued until 4 hours after the maximum current value was observed to obtain a colored kneaded product. While continuing stirring by the planetary mixer, the ion-exchanged water heated to 60 ° C. in a total amount of 6500 g was added to the resulting colored kneaded product for 2 hours.
[0106]
After the addition of ion-exchanged water was completed, the colored kneaded material after dilution with water was taken out from the planetary mixer. The solid content concentration of the colored kneaded material after dilution with water was 39.2% by mass. Furthermore, 1.61 kg of diethylene glycol and 9.91 kg of ion-exchanged water were added little by little while stirring with a dispersion stirrer to 12 kg of the colored kneaded material after dilution with water to obtain an aqueous pigment dispersion precursor L-1.
[0107]
Using this aqueous pigment dispersion precursor L-1, 18 kg, a dispersion treatment was carried out under the same conditions as the dispersion condition (1) of Example 1 to obtain an aqueous pigment dispersion precursor L-2. The concentration of the quinacridone pigment in the aqueous pigment dispersion precursor L-2 was 15.8% by mass.
[0108]
Using the following formulation, the same operation as described in the dispersion condition (2) of Example 1 was performed to obtain an aqueous pigment dispersion L-3. The concentration of the quinacridone pigment in the obtained aqueous pigment dispersion L-3 was 13.1%.

[0109]
(Evaluation of aqueous pigment dispersion)
With respect to the aqueous pigment dispersions of Examples and Comparative Examples obtained as described above, the particle size was measured with a Microtrac UPA particle size analyzer (manufactured by Leeds & Northrup) at a cell temperature of 25 ° C. At that time, each particle size measurement sample was prepared by diluting the quinacridone pigment concentration to 12.5% with ion-exchanged water and further diluted 500 times with ion-exchanged water. The results are shown in Table 1.
[0110]
(Evaluation of dispersion stability)
The aqueous pigment dispersions of Examples and Comparative Examples were adjusted by adding ion-exchanged water so that the quinacridone pigment concentration was 12.5% by mass in the same manner as the evaluation of the dispersion. Dispersion stability of the dispersion whose pigment concentration has been adjusted is sealed by sealing it in a glass container such as a screw tube and conducting a one-week heating test with a 60 ° C. thermostat and observing the particle size change before and after the heating test. A sex assessment was performed. The results are shown in Table 1.
[0111]
[Table 1]
Table 1

[0112]
As is apparent from Table 1, the aqueous pigment dispersion obtained by the present invention has a small particle size change rate after the heating test. That is, an aqueous pigment dispersion excellent in dispersion stability can be obtained by the present invention.
[0113]
(Preparation of ink composition)
Aqueous pigment dispersions A-3, B-3, C-3, D-3, E-3, F-3, G-3, H-3, I-3 obtained in each Example and each Comparative Example , J-3, K-3, and L-3 were added with ion-exchanged water to prepare 50.0 g of an aqueous pigment diluent having a quinacridone pigment concentration of 10% by mass. Using this aqueous pigment diluent, an ink composition having a quinacridone pigment concentration of 5% by mass was prepared by the following composition.
Aqueous pigment diluent 50.0g
2-Pyrrolidinone 8.0g
Triethylene glycol monobutyl ether 8.0g
Glycerin 3.0g
Surfynol 440 (Air Products) 0.5g
Ion exchange water 30.5g
[0114]
(Ink composition stability test)
The obtained ink composition is sealed in a glass container such as a screw tube, subjected to a heating test for one week with a thermostat at 70 ° C., and the change in particle diameter and viscosity before and after the heating test is observed. Evaluation of stability was conducted. The results are shown in Table 2. The particle size was measured in the same manner as the evaluation of the aqueous pigment dispersion, except that the ink composition was diluted 100 times with ion-exchanged water. The viscosity was measured at 25 ° C. using an E-type viscometer (VISCOMETER TV-20 manufactured by Tokyo Keiki Co., Ltd.).
[0115]
(Inkjet recording suitability evaluation)
The obtained ink composition before the heating test was mounted on a black pen of Desk Jet 957C manufactured by Hewlett-Packard Company, and a printing test was performed. Specifically, solid printing and fine line printing were performed on A4 paper, and the ink ejection state was observed. The results are shown in Table 2.
[0116]
[Table 2]
Table 2

[0117]
The criteria for ranking in the ink jet recording suitability evaluation column of Table 2 are as follows.
A: All print samples have uniform solid prints and no discharge defects even at fine lines.
○: Slightly lacking uniformity in solid printing, but there is no ejection failure in the thin line area
Δ: Uniformity is poor in solid printing, and there is no ejection failure in the thin line portion, but printing position deviation is observed.
X: Printing unevenness due to ejection failure is observed in solid printing, and some printing defects due to ejection failure are partially observed even in the thin line portion.
XX: Discharge defects frequently occur.
[0118]
As can be seen from Table 2, it can be seen that the ink composition obtained by the present invention exhibits good storage stability and at the same time has good ink jet recording suitability. Similarly, the obtained ink composition before the heating test was mounted on a piezo jet type EM-900C black pen manufactured by Epson Corporation, and a printing test was performed. Specifically, solid printing and fine line printing were performed on A4 paper, and the ink ejection state was observed, but no particular problem was observed in both the examples and comparative examples.
[0119]
【The invention's effect】
By using the aqueous pigment dispersion for inkjet ink of the present invention, fine dispersion of the pigment can be achieved, and at the same time, the dispersibility and dispersion stability are excellent, and the particle size does not increase even when left at high temperature for a long period of time. In addition, it is possible to obtain a red or magenta ink-jet aqueous ink composition with little increase in viscosity and excellent printing stability. The aqueous ink composition for inkjet inks using the aqueous pigment dispersion for inkjet inks of the present invention can be suitably used particularly as an aqueous ink composition for thermal inkjet inks.

Claims (9)

An aqueous pigment dispersion for inkjet ink containing a quinacridone pigment (a), a styrene resin (b), an alkali metal hydroxide (c), and a dispersion aid (d), wherein the styrene resin (b ) Is a resin obtained by copolymerizing a monomer containing (i) 60% by mass or more of a styrene monomer and (ii) an unsaturated aliphatic carboxylic acid having a radical polymerizable double bond with respect to all monomer components. An aqueous pigment dispersion for inkjet ink, wherein the styrene-based resin (b) has a weight average molecular weight in the range of 7,500 to 40,000. The styrene resin (b) is a resin obtained by copolymerizing (i) a monomer containing 60% by mass or more of a styrene monomer and (iii) acrylic acid and methacrylic acid with respect to all monomer components. The aqueous pigment dispersion for inkjet ink as described. The aqueous pigment dispersion for inkjet ink according to claim 2, wherein the total content ratio of the styrene monomer, acrylic acid, and methacrylic acid is 95% by mass or more based on the total monomer components. The aqueous pigment dispersion for inkjet ink according to any one of claims 1, 2, and 3, wherein the glass transition point of the styrenic resin (b) is 90 ° C or higher. Said dispersing aid (d) is of formula I
[Formula 1]

{Wherein R _{1 to} R ₁₀ are each independently a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a methyl group or an alkyl group having 2 to 8 carbon atoms, or a compound of formula II
[Formula 2]

(In the formula, R ₁₁ represents a methylene group, an alkylene group having 2 to 8 carbon atoms or an alkenylene group, and R _{12 to} R ₁₅ each independently represent a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, or a methyl group. Or an alkyl group having 2 to 8 carbon atoms or a phenyl group), and at least one of R _{1 to} R ₁₀ is a group represented by the formula II. }
The aqueous pigment dispersion for inkjet inks according to any one of claims 1, 2, 3 and 4, comprising a compound (e) represented by formula (1) and a quinacridone sulfonic acid compound (f). An aqueous ink composition for ink-jet inks using the aqueous pigment dispersion for ink-jet inks according to any one of claims 1, 2, 3, 4 and 5. The aqueous ink composition for inkjet ink according to claim 6, which is used in a thermal inkjet recording system. Quinacridone pigments (a), (i) copolymerization of 60% by mass or more of styrenic monomer and (ii) a monomer containing an unsaturated aliphatic carboxylic acid having a radical polymerizable double bond with respect to all monomer components A styrene resin (b) having a weight average molecular weight in the range of 7,500 to 40,000, an aqueous solution or an organic solvent solution of an alkali metal hydroxide (c), and Formula I
[Formula 1]

{Wherein R _{1 to} R ₁₀ are each independently a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a methyl group or an alkyl group having 2 to 8 carbon atoms, or a compound of formula II
[Formula 2]

(In the formula, R ₁₁ represents a methylene group, an alkylene group having 2 to 8 carbon atoms or an alkenylene group, and R _{12 to} R ₁₅ each independently represent a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, or a methyl group. Or an alkyl group having 2 to 8 carbon atoms or a phenyl group), and at least one of R _{1 to} R ₁₀ is a group represented by the formula II. }
The first step of producing a colored kneaded product (g) for inkjet inks by kneading together the compound (e) represented by the formula (1), and then the quinacridone sulfonic acid compound (f) and the kneaded product (g) A method for producing an aqueous pigment dispersion for ink-jet ink, comprising sequentially performing step 2A of dispersing the kneaded product (g) in the aqueous medium by adding an aqueous medium. Instead of the step 2A, an aqueous medium is added to the kneaded product (g) to disperse the kneaded product (g) in the aqueous medium, and then the quinacridone sulfonic acid compound (f) is added. The method for producing an aqueous pigment dispersion for inkjet ink according to claim 8, wherein the second step B is performed.