JP2004338165A - Inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording method which can obtain an output excellent in scuff resistance and glossiness of an image and has no problem in storing stability and jetting stability of ink even when a water-based pigment ink with excellent light fastness is used. <P>SOLUTION: In the inkjet recording method by which the image is formed on an inkjet recording medium having at least one layer of a porous layer containing an inorganic fine particle on a substrate by using the water-based pigment ink, the inkjet recording method is characterized in that the water-based pigment ink comprises a water-soluble resin comprising a polymer compound with a weight-average molecular weight of 1,000-300,000, and the farthest layer from the substrate of the inkjet recording medium comprises a polymer compound having a group which can react with the ink pigment particle or a group which can make a hydrogen bonding therewith and being water-eluting. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４２】
無機微粒子として気相法により合成されたシリカを使用し、バインダーとしてポリビニルアルコールを用いた多孔質のインクジェット記録媒体が知られているが、この記録媒体は、低湿環境下でのインク吸収層の脆弱性が悪く、折り曲げた時にインク吸収層にひびが入る問題点がある。本発明では、上記構成のインクジェット記録媒体に、特に効果が大きい。その理由として、気相法により合成されたシリカは、微粒子表面の水酸基の数が約２〜３個／ｎｍ^２と少なく、分子内水素結合が起こりにくいため、孤立の水酸基の数が多くなり、他分子との水素結合性が強い。本発明においては高分子分散剤由来の水酸基と無機微粒子表面にある水酸基との水素結合により効果が大きくなるものと考えられるため、気相法により合成されたシリカで特に高い効果が得られていると考えられる。同様の理由で、無機微粒子の平均粒径がより小さい方が、無機微粒子の比表面積が大きく、水素結合をする水酸基の数が増えるため、本発明の効果が高い。
【００４３】
バインダーとしては、水酸基を含む高分子分散剤で乳化重合されたエマルジョン樹脂単独で使用しても、他の水溶性樹脂または疎水性樹脂と組み合わせて使用してもよいが、組み合わせて使用する場合は水溶性樹脂が好ましい。
【００４４】
併用する水溶性樹脂としては、ゼラチン、ポリビニルアルコール、ポリビニルピロリドン、ポリエチレンオキシド、ヒドロキシエチルセルロース、寒天、プルラン、デキストリン、アクリル酸、カルボキシメチルセルロース、カゼイン、アルギン酸等が挙げられ、２種以上を併用することもできる。これらの中で好ましい水溶性樹脂はポリビニルアルコールである。
【００４５】
併用するポリビニルアルコールには、カチオン変性したポリビニルアルコールやアニオン性基を有するアニオン変性ポリビニルアルコール、シリル基を置換したシリル変性ポリビニルアルコール等の変性ポリビニルアルコールも含まれる。
【００４６】
併用するポリビニルアルコールは、平均重合度が３００以上のものが好ましく、平均重合度が１０００〜５０００のものがより好ましく、特に好ましくは２０００〜４５００である。また、ケン化度は７０〜１００モル％のものが好ましく、８０〜９９．５モル％のものが特に好ましい。
【００４７】
他の水溶性樹脂または疎水性樹脂と組み合わせて使用する場合、バインダー中に含まれる水酸基を含む高分子分散剤で乳化重合されたエマルジョン樹脂の割合は５質量％以上であることが好ましく、１０質量％以上が特に好ましい。
【００４８】
空隙型のインク吸収層を形成するために、使用される無機微粒子とバインダーの比率は、質量比で２：１〜１０：１である。これ以上無機微粒子に対するバインダーの量が多いと空隙が形成されず、インク吸収性に劣り、逆にバインダーの量が少なすぎると、造膜性が悪く、塗布乾燥時にひび割れて膜形成が困難になる。
【００４９】
本発明において、皮膜の造膜性を改善し、また皮膜の耐水性を高めるために硬膜剤を使用することができる。硬膜剤としては、例えばジグリシジルエーテル、エチレングリコールグリシジルエーテル、ソルビトールポリグリシジルエーテル、Ｎ，Ｎ−ジグリシジル−４−グリシジルオキシアニリン等のエポキシ系硬膜剤、ホルムアルデヒド、グリオキザール等のアルデヒド系硬膜剤、２，４−ジクロロ−４−ヒドロキシ−１，３，５−ｓ−トリアジン等の活性ハロゲン系硬膜剤、ビスビニルスルホニルメチルエーテル等の活性ビニル系硬膜剤、イソシアネート系化合物、ほう酸またはその塩等が挙げられるが、ほう酸またはその塩が特に好ましい。
【００５０】
ほう酸、またはその塩としては、硼素原子を中心原子とする酸素酸及びその塩のことを示し、具体的にはオルトほう酸、メタほう酸、次ほう酸、四ほう酸、五ほう酸及びそれらの塩が含まれる。
【００５１】
硬膜剤は２種以上を併用してもよく、その使用量は塗布液中の無機微粒子やバインダーの量によって変り得るが、好ましくは記録媒体におけるインク吸収層中の使用量は１ｍ^２当たり０．１〜４ｇであり、硬膜剤としてほう酸またはその塩を使用した場合、ほう酸またはその塩の量は０．１〜２ｇが好ましい。
【００５２】
ここでインク吸収層中のほう酸またはその塩の量とは、インクジェット記録媒体１ｍ^２のインク吸収層を熱水にて抽出し、溶出されたほう酸イオンをイオンクロマトグラフィーにて測定した量を表す。
【００５３】
インク吸収層への硬膜剤の添加方法としては、インク吸収層形成用塗布液を塗布する際に該塗布液中に添加してもよく、あるいは塗布液を塗布、乾燥後に硬膜剤溶液をオーバーコートしてもよい。
【００５４】
本発明のインクジェット記録媒体のインク吸収層及び必要に応じて設けられるその他の層には、前記した以外に各種の添加剤を添加することができる。
【００５５】
例えば、印字記録後の耐水性、滲み耐性を向上させるために、カチオン性の樹脂あるいは水溶性の多価金属イオンを添加することもできる。
【００５６】
カチオン性の樹脂としては、１級〜３級アミノ基及び４級アンモニウム塩基を有するポリマー樹脂から任意に選択して使用することができるが、経時での変色や耐光性の劣化が少ないことから、好ましくは第４級アンモニウム塩基を有するポリマーであり、４級アンモニウム塩基を有するモノマーの単独重合体または他の共重合し得る１または２以上のモノマーとの共重合体または重縮合体で、平均分子量が２０００〜１０万のものが好ましい。
【００５７】
請求項６に係る発明では、水溶性多価金属塩を含有することが好ましい。
印字記録後の画像定着性を向上させるため、水溶性多価金属塩を添加することが好ましい。本発明に係る水溶性多価金属塩としては、例えば、アルミニウム、カルシウム、マグネシウム、亜鉛、鉄、ストロンチウム、バリウム、ニッケル、銅、スカンジウム、ガリウム、インジウム、チタン、ジルコニウム、スズ、鉛などの金属塩、硫酸塩、硝酸塩、ギ酸塩、コハク酸塩、マロン酸塩、クロロ酢酸塩、ｐ−トルエンスルホン酸塩といった塩として添加される。また、水溶性の多価金属イオンの塩として、ポリ塩化アルミニウムのような水溶性無機ポリマーを使用してもよい。水溶性は少なくとも０．１質量％を示すものが好ましく、より好ましくは１質量％を示すものである。中でも、アルミニウム、カルシウム、アルミニウム、マグネシウム、亜鉛からなる水溶性塩はその金属イオンが無色なため好ましい。特に好ましいのは、塩化アルミニウム、硫酸アルミニウム、硝酸アルミニウム、酢酸アルミニウム、塩化カルシウム、硫酸カルシウム、硝酸カルシウム、酢酸カルシウム、塩化マグネシウム、硫酸マグネシウム、硝酸マグネシウム、酢酸マグネシウム、塩化亜鉛、硫酸亜鉛、硝酸亜鉛、酢酸亜鉛である。
【００５８】
本発明のインクジェット記録用紙において、本発明に係る水溶性多価金属塩の含有量は５〜３００ｍｇ（金属イオンの質量に換算する）／ｍ^２が好ましく、更に好ましくは、１０〜１５０ｍｇ／ｍ^２である。
【００５９】
水溶性多価金属塩の添加方法としては、塗布液に直接添加して塗布する方法のほか、記録媒体の塗布乾燥後にカチオン性の樹脂や水溶性多価金属塩の水溶液をオーバーコートして乾燥するといった方法でも構わない。
【００６０】
上記以外に、例えば特開昭５７−７４１９３号、同５７−８７９８８号及び同６２−２６１４７６号に記載の紫外線吸収剤、特開昭５７−７４１９２号、同５７−８７９８９号、同６０−７２７８５号、同６１−１４６５９１号、特開平１−９５０９１号及び同３−１３３７６号等に記載されている褪色防止剤、特開昭５９−４２９９３号、同５９−５２６８９号、同６２−２８００６９号、同６１−２４２８７１号及び特開平４−２１９２６６号等に記載されている蛍光増白剤、硫酸、燐酸、枸櫞酸、水酸化ナトリウム、水酸化カリウム、炭酸カリウム等のｐＨ調整剤、消泡剤、防腐剤、増粘剤、帯電防止剤、マット剤等の公知の各種添加剤を含有させることもできる。
【００６１】
多孔質のインク吸収層は２層以上から構成されてもよく、この場合、それらのインク吸収層の構成は互いに同じであっても異なってもよい。
【００６２】
本発明のインクジェット記録媒体の支持体としては従来知られている公知の支持体、例えば、普通紙、アート紙、コート紙及びキャストコート紙などの紙支持体、プラスチック支持体、両面をプラスチック樹脂フィルムで被覆した紙支持体、これらを張り合わせた複合支持体等を、適宜選択して用いることができる。
本発明のインクジェット記録媒体では、支持体とインク吸収層との接着強度を高める等の目的で、インク吸収層の塗布に先立って、支持体にコロナ放電処理や下引き処理等を行うことが好ましい。更に、本発明の記録媒体は必ずしも無色である必要はなく、着色された記録用紙であってもよい。
【００６３】
本発明のインクジェット記録媒体では、紙の両面をプラスチック樹脂フィルムでラミネートした支持体を用いることが、記録画像が写真画質に近く、かつ低コストで高品質の画像が得られるため、特に好ましい。紙の両面をプラスチック樹脂フィルムで被覆した支持体として好ましいものは、紙の両面をポリオレフィン樹脂で被覆した支持体である。紙の両面を被覆するポリオレフィン樹脂としては、ポリエチレン、ポリプロピレン、ポリイソブチレン、ポリエチレンが挙げられるが、プロピレンを主体とする共重合体等のポリオレフィン類が好ましく、ポリエチレンが特に好ましい。
【００６４】
支持体の厚さは５０〜３５０μｍが好ましく、特に８０〜３００μｍのものが好ましい。
【００６５】
本発明のインクジェット記録媒体のインク吸収層及び下引き層など、必要に応じて適宜設けられる各種の親水性層を支持体上に塗布する方法は、公知の方法から適宜選択して行うことができる。好ましい方法は、各層を構成する塗布液を支持体上に塗設して乾燥して得られる。この場合、２層以上を同時に塗布することもでき、特に全ての層を１回の塗布で済ます同時塗布が好ましい。
【００６６】
塗布方式としては、ロールコーティング法、ロッドバーコーティング法、エアナイフコーティング法、スプレーコーティング法、カーテン塗布方法あるいは米国特許第２，６８１，２９４号に記載のホッパーを使用するエクストルージョンコート法が好ましく用いられる。
【００６７】
本発明のインクジェット記録媒体の記録面の膜面ｐＨは、３．５〜９が好ましい。膜面ｐＨが３．５以上の場合には、インクジェットで記録した際に染料が析出して金属状に光沢が変化する、いわゆるブロンジングを顕著に防ぐことができる。また、膜面ｐＨが９以下であれば、記録画像が滲む現象を顕著に防止することができる。
【００６８】
本発明に係る記録面の膜面ｐＨの測定は、Ｊ．ＴＡＰＰＩ紙パルプ試験方法Ｎｏ．４９に記載の方法に従って、蒸留水を用い、３０秒後に測定した。
【００６９】
本発明において記録面の膜面ｐＨは、記録面を形成した後、適当なｐＨ調整剤をオーバーコートすることにより所定の範囲にすることもできる。ｐＨ調整剤としては、適当な酸やアルカリの水溶液を用いることもでき、この場合、使用する酸やアルカリの種類、濃度は、調整するｐＨの幅によって適宜選択することができる。
【００７０】
本発明のインクジェット記録媒体を用いて画像記録する際には、水性顔料インクを用いた記録方法が用いられる。顔料としては従来公知の有機及び無機顔料を使用することができる。本発明において使用することができる顔料としては、例えば、アゾレーキ顔料、不溶性アゾ顔料、縮合アゾ顔料、キレートアゾ顔料等のアゾ顔料、フタロシアニン顔料、ペリレン及びペリレン顔料、アントラキノン顔料、キナクリドン顔料、ジオキサンジン顔料、チオインジゴ顔料、イソインドリノン顔料、キノフタロニ顔料等の多環式顔料、塩基性染料型レーキ、酸性染料型レーキ等の染料レーキ、ニトロ顔料、ニトロソ顔料、アニリンブラック、昼光蛍光顔料等の有機顔料、カーボンブラック等の無機顔料が挙げられる。また、カラーインデックスに記載されていない顔料であっても、水分散可能ならば、いずれの顔料であっても使用することが可能である。
【００７１】
本発明の水性顔料インクに含まれる水溶性樹脂は顔料分散剤として用いる。本発明に使用することのできる水溶性樹脂としては、例えば、高級脂肪酸塩、アルキル硫酸塩、アルキルエステル硫酸塩、アルキルスルホン酸塩、スルホコハク酸塩、ナフタレンスルホン酸塩、アルキルリン酸塩、ポリオキシアルキレンアルキルエーテルリン酸塩、ポリオキシアルキレンアルキルフェニルエーテル、ポリオキシエチレンポリオキシプロピレングリコール、グリセリンエステル、ソルビタンエステル、ポリオキシエチレン脂肪酸アミド、アミンオキシド等の活性剤、あるいは、スチレン、スチレン誘導体、ビニルナフタレン誘導体、アクリル酸、アクリル酸誘導体、マレイン酸、マレイン酸誘導体、イタコン酸、イタコン酸誘導体、フマル酸、フマル酸誘導体から選ばれた２種以上の単量体からなるブロック共重合体、ランダム共重合体及びこれらの塩を挙げることができる。
【００７２】
本発明の水性顔料インクの分散剤として用いる水溶性樹脂は、水素結合を受容し得る基を有することが好ましく、更に好ましくはスチレン−アクリル酸共重合系樹脂を用いる。これら水溶性樹脂の数平均分子量は１０００〜３０００００であって、１０００以下では記録媒体上での充分な定着性が得られず、３０００００以上では、粘度が高くなり、吐出安定性が不充分となる。
【００７３】
本発明に使用する顔料分散体の粒子径は、平均粒径で１０ｎｍ以上、１５０ｎｍ以下である。顔料分散体の平均粒径が１５０ｎｍを超えると光沢メディアに記録した画像において著しい光沢感の劣化が起こり、インク吐出性としても目詰まりしやすい傾向になる。顔料分散体の平均粒径が１０ｎｍ未満になると、顔料分散体の安定性が悪くなりやすく、インクの保存安定性が劣化しやすい。
【００７４】
その他の水性顔料インク添加剤としては、例えば水溶性有機溶媒（例えば、プロパノール、ヘキサノール、エチレングリコール、ジエチレングリコール、グリセリン、ヘキサンジオール、尿素等）、界面活性剤、水溶性ポリマー、防黴剤、粘度調整剤、ｐＨ調整剤を挙げることができる。
【００７５】
本発明のインクジェット記録方法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。また、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）、静電吸引方式（例えば、電解制御型、スリットジェット型等）などを具体的な例として挙げることができるが、いずれの吐出方式を用いても構わない。
【００７６】
【実施例】
以下、実施例を挙げて本発明を具体的に説明するが、本発明はこれらに限定されるものではない。尚、実施例中で「％」は、特に断りのない限り質量％を示す。
《インクジェット記録媒体の作製》
以下に示す手順に従って、インクジェット記録媒体を作製した。
【００７７】
（塗布液−１の作製）
硝酸でｐＨ２．５に調整した純水に、微粒子の気相法シリカ（トクヤマ製：レオロシールＱＳ−２０）を分散して２０％のシリカ分散液を４００ｇ調製した。これにｐＨ２．５に調整したカチオン性ポリマー（１）の２０％水溶液８０ｇ、ほう酸２．１ｇ及びホウ砂１．５ｇを溶解した水溶液６０ｍｌを添加し、高圧ホモジナイザーで分散した。得られた分散液を４０℃で攪拌しながら、表１に記載したエマルジョン（１）３ｇ、ポリビニルアルコール（クラレ製：ＰＶＡ２３５）の１０％水溶液１００ｍｌを加え、全体の液が１０００ｍｌになるように純水を加えて半透明状の塗布液−１を得た。
【００７８】
【化１】

【００７９】
（塗布液−２の作製）
硝酸でｐＨ２．５に調整した純水に、微粒子の気相法シリカ（トクヤマ製：レオロシールＱＳ−２０）を分散して２０％のシリカ分散液を４００ｇ調製した。これにｐＨ２．５に調整したカチオン性ポリマー（１）の２０％水溶液８０ｇ、ほう酸２．１ｇ及びホウ砂１．５ｇを溶解した水溶液６０ｍｌを添加し、高圧ホモジナイザーで分散した。得られた分散液を４０℃で攪拌しながら、ポリビニルアルコール（クラレ製：ＰＶＡ２３５）の１０％水溶液１６０ｍｌを加え、全体の液が１０００ｍｌになるように純水を加えて半透明状の塗布液−２を得た。
【００８０】
（記録媒体１の作製）
次に、坪量２００ｇ／ｍ^２の原紙両面をポリエチレンで被覆した支持体（厚さ２６０μｍ、記録面側のポリエチレン層中に６質量％のアナターゼ型二酸化チタン含有。）上の記録面側に、下層として上記の塗布液−２を湿潤膜厚が８０μｍになるように、上層として上記の塗布液−１を湿潤膜厚が８０μｍになるようにこの順で塗布し、８℃で１０秒間冷却した後、２０〜４０℃の風で乾燥させてインクジェット記録媒体１を得た。
【００８１】
（記録媒体２の作製）
上記記録媒体１において上層とした塗布液−１に含有するエマルジョン（１）をエマルジョン（４）に代えた以外は同様にしてインクジェット記録媒体２を作製した。
【００８２】
（記録媒体３の作製）
上記記録媒体１において上層とした塗布液−１の代わりに塗布液−２を用いた以外は同様にしてインクジェット記録媒体３を作製した。
【００８３】
《水性顔料インクの調製》
〈分散体１の調製〉

上記添加剤を混合した後、上記分散剤を０．５部添加し、６５℃で１時間の加熱攪拌と５℃で１時間の冷却を２回繰り返すことにより、分散剤を充分に吸着させたのち、遠心分離により、未分散の粗粒子を除いて、分散体１を調製した。
【００８４】
〈水性顔料インク−１〜４の調製〉
上記分散体１に、水溶性有機溶媒、イオン交換水、界面活性剤、防腐剤、ｐＨ調整剤を適宜選択して加え、孔径０．８μｍのテフロン（Ｒ）フィルターで加圧濾過を行い、顔料濃度として１．０％の水性顔料インク１を調製した。
【００８５】
得られた水性顔料インク１の顔料粒子の二次平均粒径は２８０μｍであった。尚、粒径測定はマルバーン社製ゼータサイザ１０００により行った。
【００８６】
上記水性顔料インク１の調製において、顔料をＣ．Ｉ．ピグメントレッド１２２に代えて、それぞれＣ．Ｉ．ピグメントブルー１５：３、Ｃ．Ｉ．ピグメントイエロー１２８、Ｃ．Ｉ．ピグメントブラック７を用いた以外は同様にして、二次平均粒径が２８０μｍの水性顔料インク２、３、４を調製した。
【００８７】
〈水性顔料インク５〜８の調製〉
上記水性顔料インク１〜４において、分散条件を適宜調整することによって顔料粒子の二次平均粒子径を１２０μｍに調整した以外は同様にして水性顔料インク５〜８を調製した。
【００８８】
〈水性顔料インク９〜１２の調製〉
上記水性顔料インク１〜４における分散剤の種類をスチレン−アクリル酸共重合体（重量平均分子量５２０，０００）に変更した以外は同様にして水性顔料インク９〜１２を調製した。
【００８９】
《評価用サンプルの作製》
（画像記録方法）
画像記録方法としては、ノズル孔径２０μｍ、駆動周波数１２ＫＨｚ、一色当たりのノズル数１２８、同色間のノズル密度１８０ｄｐｉ（尚、ｄｐｉは２．５４ｃｍ当たりのドット数を表す。）であるピエゾ型ヘッドを４基搭載し、最大記録密度７２０×７２０ｄｐｉのオンデマンド型のインクジェットプリンタを使用して、記録媒体上に反射濃度として１．０及び１．５を与えるイエロー、マゼンタ、シアン及びブラックの各単色画像パターンを出力画像として使用した。
【００９０】
（擦過性の評価）
上記作製した出力画像のベタ濃度１．０の部分を市販の消しゴム（ＭＯＮＯトンボ鉛筆社製）で１０往復擦った時の印字部の汚れの程度を、下記に示す基準に則り目視評価を行った。
【００９１】
○：印字部の汚れが観察されない
△：印字部の汚れが若干観察される
×：印字部の汚れが明確に観察される
（光沢性評価方法）
上記作製した出力画像のベタ濃度１．５の部分を用いて、写像性測定器ＩＣＭ−１ＤＰ（スガ試験機械社製）で反射６０度、光学くし２ｍｍで写像性（Ｃ値％）を測定し、以下の評価基準に従って光沢性を評価した。
【００９２】
○：Ｃ値％が５０％以上
△：Ｃ値％が４０％以上５０％未満
×：Ｃ値％が４０％未満
（吐出安定性、及びインク保存安定性評価方法）
上記作製した水性顔料インクを、上記画像記録方法により１０秒間連続吐出→一定時間休止→連続吐出の間欠動作を行った。この際、吐出休止後の最初で吐出方向の乱れが発生するか否かは休止時間の長さで決まるので、吐出休止時間の長さを段階的に変えることにより間欠吐出の安定性を測定し、以下の基準で評価した。尚、評価は環境温度２３℃５５％ＲＨで行った。
【００９３】
５：３１〜４５秒休止しても安定に吐出した
４：２１〜３０秒休止しても安定に吐出した
３：１１〜２０秒休止しても安定に吐出した
２：６〜１０秒休止しても安定に吐出した
１：５秒以下しか安定吐出しなかった
これと同様の評価を、密閉状態で６０℃下に１週間保存した後のインクについても行い、インクの保存安定性を評価した。
【００９４】
以上により得られた結果を表２に示す。
【００９５】
【表２】

【００９６】
表２より明らかなように本発明に係る記録媒体１、２に対し、本発明に係る水性顔料インク１〜８を用いて出力したプリントは、擦過性及び光沢性に優れ、かつ吐出安定性も優れることが分かる。これに対し、本発明に係る水溶出性高分子化合物を含有しない記録媒体３は擦過性が劣り、本発明の水溶性樹脂を含有しない水性顔料インク９〜１２を用いた場合には光沢性及び吐出安定性が劣化する。
【００９７】
【発明の効果】
本発明により、光による堅牢性に優れる水性顔料インクを用いた場合でも画像の擦過性に優れ、高い光沢性を有する出力が得られ、かつインクの保存安定性や吐出安定性に問題のないインクジェット記録方法を提供することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink-jet recording method, and particularly to an ink-jet recording method which is excellent in abrasion of an image even when an aqueous pigment ink is used, can provide an output having high gloss, and has no problem in storage stability and ejection stability of the ink. About the method.
[0002]
[Prior art]
In recent years, the image quality of ink jet recording has been rapidly improved, and the quality of photographs is approaching. In particular, regarding the final print quality, the importance of the recording medium is greatly increasing.
[0003]
As an example of such a high-quality recording medium, there is an inkjet recording medium having a swellable ink absorbing layer mainly composed of a hydrophilic binder on a support, and such a recording medium has a texture close to a photograph after recording. give. However, on the other hand, the speeding up of the ink jet recording method has progressed, and the recording medium is also required to have high ink absorbency and quick drying property, but the ink jet recording medium having a swellable ink absorbing layer has a low ink absorption speed, In the case of high-speed printing, there is a problem that unevenness in the image tends to occur due to coalescence of ink droplets.
[0004]
In order to overcome the above-mentioned problems, an ink absorbing layer comprising a porous void layer composed of a small amount of a hydrophilic binder and a crosslinking agent, and a large amount of inorganic fine particles is provided to increase the ink absorbing speed. Ink jet recording media are known.
[0005]
On the other hand, as an ink used for inkjet recording, a pigment ink having better light resistance than a dye is used for an application requiring an image that is resistant to fading due to light. However, as a problem of the pigment ink, in many cases, the fixability after being discharged onto a recording medium is not sufficient, and the water resistance of an image is often deteriorated or the rubbing property is insufficient. In order to improve these problems, a technique of increasing the size of a hole formed in the surface of a recording medium is known. However, in this case, there is a problem that the surface smoothness of the recording medium is reduced and glossiness is greatly impaired. is there. On the other hand, from the side of the aqueous pigment ink, a technique for containing a water-insoluble photocurable monomer (for example, see Patent Documents 1 and 2) and a technique for containing polyethyleneimine (for example, see Patent Document 3) are described. However, it was found that all of them had problems in the storage stability of the ink and the ejection stability such as clogging.
[0006]
[Patent Document 1]
JP-A-3-216379
[0007]
[Patent Document 2]
JP-A-8-48922
[0008]
[Patent Document 3]
JP-A-10-60352
[0009]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to solve the above problems, and particularly when using an aqueous pigment ink having excellent light fastness, the image has excellent scratch resistance, and an output having high gloss is obtained, and An object of the present invention is to provide an ink jet recording method having no problem in storage stability and ejection stability of ink.
[0010]
[Means for Solving the Problems]
The above object of the present invention is achieved by the following configurations.
[0011]
1. In an inkjet recording method for forming an image on an inkjet recording medium having a void layer containing at least one inorganic fine particle on a support by using an aqueous pigment ink, the aqueous pigment ink is a polymer compound having a weight average molecular weight of 1,000 to 300,000. And a layer farthest from the support of the ink jet recording medium having a group capable of reacting with ink pigment particles or a group capable of hydrogen bonding, and containing a water-eluting polymer compound. An ink-jet recording method, characterized in that:
[0012]
2. 2. The ink jet recording method according to claim 1, wherein the inorganic fine particles contained in the ink jet recording medium are silica or alumina.
[0013]
3. 3. The ink jet recording method according to claim 1 or 2, wherein the water-eluting polymer compound is contained as an emulsion resin obtained by emulsion polymerization with a polymer dispersant having a hydroxyl group.
[0014]
4. 4. The ink jet recording method according to the item 3, wherein the polymer dispersant is polyvinyl alcohol.
[0015]
5. 5. The ink jet recording method according to the item 3 or 4, wherein the polymer dispersant is polyvinyl alcohol having an average degree of polymerization of 1500 to 5000.
[0016]
6. 6. The ink jet recording method according to any one of items 1 to 5, wherein the ink jet recording medium contains a water-soluble polyvalent metal salt.
[0017]
7. 7. The inkjet recording method according to any one of items 1 to 6, wherein the polymer compound having a weight average molecular weight of 1,000 to 300,000 contained in the aqueous pigment ink has a group capable of accepting a hydrogen bond.
[0018]
8. 8. The ink jet recording method according to any one of items 1 to 7, wherein an average particle diameter of the pigment dispersion contained in the aqueous pigment ink is 10 nm or more and 150 nm or less.
[0019]
Hereinafter, the present invention will be described in detail.
The present invention is applied to a void-type inkjet recording medium in which at least one ink absorbing layer provided on a support contains at least inorganic fine particles and a binder and forms a porous void layer.
[0020]
Examples of the inorganic fine particles used in the present invention include light calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, hydrotalcite. Aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, magnesium hydroxide and the like.
[0021]
These inorganic fine particles may be used in a state of being uniformly dispersed in a binder as primary particles, or may be used in a state of forming secondary aggregated particles and being dispersed in a binder.
[0022]
The average particle size of the inorganic fine particles is preferably from 5 to 100 nm. If the average particle size exceeds 100 nm, it becomes difficult to maintain high gloss.
[0023]
The average particle size of the inorganic fine particles referred to here is obtained by observing the cross section and surface of the void layer with a scanning electron microscope, calculating the particle size of a plurality of arbitrary particles, and obtaining the simple average value (number average value). Can be. Here, each particle size is represented by a diameter assuming a circle having the same projected area.
[0024]
In the present invention, silica or pseudo-boehmite is preferable, particularly from the viewpoint that fine voids can be formed, and silica or pseudo-boehmite synthesized by a gas phase method having an average particle diameter of 10 to 90 nm is particularly preferable.
[0025]
The amount of the inorganic fine particles used in the ink absorbing layer depends on the type of the inorganic fine particles and the type of the binder. ² The weight is usually 5 to 30 g, preferably 10 to 25 g.
[0026]
Among the ink absorbing layers of the present invention, the layer farthest from the support has a group capable of reacting with the ink pigment particles or a group capable of hydrogen bonding and contains a water-eluting polymer compound. Ink pigment particles are generally dispersed with an anion, and the group capable of reacting with the ink pigment particles here refers to an electrostatic group such as a cationic group such as a primary to tertiary amino group or a quaternary ammonium base. Represents a group that can form a hydrogen bond such as a reactive group or a hydroxyl group. In the present invention, it preferably contains a hydroxyl group. The water-eluting polymer compound means that a part of the component is eluted when the contained recording medium is immersed in water. The ratio of the eluted components is preferably 1% to 30%. These polymer compounds are contained in the layer farthest from the support of the recording medium, and the amount added is preferably 1% to 30% of the total binder in the layer farthest from the support. If the addition amount exceeds 30%, problems such as deterioration of the transparency of the ink absorbing layer and reduction of the ink absorbing speed may occur. More preferably, it is 1% to 5%.
[0027]
The water-eluting polymer compound according to claim 3 of the present invention is an emulsion resin emulsion-polymerized with a polymer dispersant containing a hydroxyl group.
[0028]
The term “emulsion resin” as used herein refers to a resin obtained by keeping an oil-soluble monomer in an aqueous solution containing a dispersant in an emulsion state and performing emulsion polymerization using a polymerization initiator.
[0029]
As a dispersant used at the time of polymerization of the emulsion, generally, in addition to low molecular dispersants such as alkyl sulfonate, alkylbenzene sulfonate, diethylamine, ethylenediamine, and quaternary ammonium salt, polyoxyethylene Polymer dispersants such as nonylphenyl ether, polyoxyethylene laurate ether, hydroxyethylcellulose, and polyvinylpyrrolidone are exemplified.
[0030]
The emulsion resin according to the present invention is a resin in which fine (average particle diameter: 0.01 to 2 μm) resin particles are dispersed in an aqueous medium in an emulsion state, wherein an oil-soluble monomer is a polymer dispersant having a hydroxyl group. And obtained by emulsion polymerization. Although there is no fundamental difference in the polymer component of the obtained emulsion resin depending on the type of dispersant used, when emulsion polymerization is performed using a polymer dispersant having a hydroxyl group, the presence of hydroxyl groups on at least the surface of the fine fine particles is reduced. It is presumed that the emulsion has different chemical and physical properties from the emulsion resin polymerized using other dispersants.
[0031]
The hydroxyl group-containing polymer dispersant is a polymer dispersant having an average molecular weight of 10,000 or more and having a hydroxyl group substituted in a side chain or at a terminal, for example, an acrylic type dispersant such as sodium polyacrylate or polyacrylamide. And polyethers such as polyethylene glycol and polypropylene glycol, and polyvinyl alcohol. Among them, polyvinyl alcohol is particularly preferable.
[0032]
Polyvinyl alcohol used as a polymer dispersant is, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, cation-modified polyvinyl alcohol or anion-modified polyvinyl alcohol having an anionic group such as a carboxyl group And a modified polyvinyl alcohol such as a silyl-modified polyvinyl alcohol having a silyl group. Polyvinyl alcohol, the higher the average degree of polymerization, the greater the effect of suppressing the occurrence of cracks when forming the ink absorbing layer, but if the average degree of polymerization is less than 5000, the viscosity of the emulsion resin is not high, Easy to handle. Therefore, the average degree of polymerization is preferably from 300 to 5000, more preferably from 1500 to 5000, and particularly preferably from 3000 to 4500. The degree of saponification of polyvinyl alcohol is preferably from 70 to 100 mol%, more preferably from 80 to 99.5 mol%.
[0033]
Examples of the resin emulsion-polymerized with the above-mentioned polymer dispersant include homopolymers or copolymers of ethylene monomers such as acrylic acid esters, methacrylic acid esters, vinyl compounds and styrene compounds, and diene compounds such as butadiene and isoprene. Examples of the polymer include an acrylic resin, a styrene-butadiene resin, and an ethylene-vinyl acetate resin.
[0034]
These emulsion resins are those that impart flexibility at the time of forming the void layer, and those that have flexibility even at room temperature are suitable.More preferably, they are fused at room temperature to form the layer, At this time, the Tg when the emulsion resin is formed into a film is preferably 20 ° C or lower, more preferably -40 to 10 ° C.
[0035]
The average particle size of the emulsion resin emulsion-polymerized with the hydroxyl group-containing polymer dispersant according to the present invention is preferably 0.01 to 2 μm, but if the material constituting the ink absorbing layer has a large average particle size, In addition, light scattering in the ink absorbing layer lowers the transparency and lowers the print density. Therefore, a more preferred embodiment is configured to include an emulsion resin of 0.05 to 1.0 μm in which the average particle diameter of the inorganic fine particles is 5 to 100 nm and the binder is emulsion-polymerized with a polymer dispersant having a hydroxyl group. The mass ratio of the inorganic fine particles to the binder is 2: 1 to 10: 1. Further, it is particularly preferable that the emulsion resin has an average particle size of 0.05 to 0.5 μm.
[0036]
The method for producing the emulsion resin emulsion-polymerized with the hydroxyl group-containing polymer dispersant of the present invention is not particularly limited, and the emulsion resin is produced by a known emulsion polymerization method.
[0037]
Commercially available such emulsion resins include, for example, vinyl acetate emulsions such as Vinidol 480 and Vinizol 2023 manufactured by Daido Chemical Co., Ltd .; Emulsions, acrylic emulsions such as ViniBlan 2597 and ViniBlan 2561, and vinyl acetate-ethylene emulsions such as Sumikaflex S-400 and Sumikaflex S-405 manufactured by Sumitomo Chemical Co., Ltd. are exemplified.
[0038]
In the present invention, by using an emulsion resin emulsion-polymerized with a polymer dispersant having a hydroxyl group for the surface layer, the fixability of the aqueous pigment ink can be improved.
[0039]
Although the mechanism is not clear, it is considered that the fixability of the pigment ink is improved by the interaction between the emulsion resin on the surface layer and the water-soluble resin contained in the ink. That is, an emulsion resin emulsion-polymerized with a polymer dispersant having a hydroxyl group has a hydroxyl group derived from the polymer dispersant on its surface, which forms a hydrogen bond with a hydrogen bond accepting group in the water-soluble resin in the ink. By doing so, it is considered that the adhesiveness between the recording medium and the ink is improved. Furthermore, the emulsion resin that is an organic compound also forms a hydrogen bond with the surface of the inorganic fine particles contained in the recording medium. As a result, the inorganic fine particles, the emulsion resin, and the ink are firmly bonded to each other, and are excellent in scratch resistance. It is believed that an image is obtained.
[0040]
An example of emulsion resin production is shown below.
400 g of a 5% aqueous solution of polyvinyl alcohol (PVA) (degree of polymerization 1700, degree of saponification 88.5 mol%) is adjusted to pH 3.5, and while stirring, 50 g of methyl methacrylate and 50 g of butyl acrylate are added, and the temperature is raised to 60 ° C. After heating, 10 g of a 5% aqueous solution of ammonium persulfate was added to initiate polymerization. After 15 minutes, 100 g of methyl methacrylate and 100 g of butyl acrylate were gradually added over 3 hours. After 5 hours, the mixture was cooled when the conversion reached 99.9%. This was neutralized to pH 7.0 to synthesize emulsion (1). Emulsions (2) to (14) shown in Table 1 were synthesized in the same manner.
[0041]
[Table 1]

[0042]
A porous inkjet recording medium using silica synthesized by a gas phase method as inorganic fine particles and using polyvinyl alcohol as a binder is known, but this recording medium has a weak ink absorbing layer in a low humidity environment. There is a problem that the ink absorbing layer is cracked when it is bent due to poor properties. In the present invention, the effect is particularly great for the ink jet recording medium having the above configuration. The reason is that the silica synthesized by the gas phase method has a number of hydroxyl groups on the surface of the fine particles of about 2-3 / nm. ² In addition, since intramolecular hydrogen bonding hardly occurs, the number of isolated hydroxyl groups increases, and hydrogen bonding with other molecules is strong. In the present invention, since the effect is considered to be increased by the hydrogen bond between the hydroxyl group derived from the polymer dispersant and the hydroxyl group on the surface of the inorganic fine particles, particularly high effect is obtained by silica synthesized by a gas phase method. it is conceivable that. For the same reason, the smaller the average particle size of the inorganic fine particles, the greater the specific surface area of the inorganic fine particles and the number of hydroxyl groups that form hydrogen bonds.
[0043]
As the binder, the emulsion resin emulsion-polymerized with a polymer dispersant containing a hydroxyl group may be used alone, or may be used in combination with another water-soluble resin or a hydrophobic resin. Water-soluble resins are preferred.
[0044]
Examples of the water-soluble resin used in combination include gelatin, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide, hydroxyethylcellulose, agar, pullulan, dextrin, acrylic acid, carboxymethylcellulose, casein, alginic acid, and the like. it can. The preferred water-soluble resin among these is polyvinyl alcohol.
[0045]
The polyvinyl alcohol used in combination also includes modified polyvinyl alcohol such as cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol having an anionic group, and silyl-modified polyvinyl alcohol substituted with a silyl group.
[0046]
The polyvinyl alcohol used in combination preferably has an average degree of polymerization of 300 or more, more preferably has an average degree of polymerization of 1,000 to 5,000, and particularly preferably has 2,000 to 4,500. The saponification degree is preferably from 70 to 100 mol%, particularly preferably from 80 to 99.5 mol%.
[0047]
When used in combination with another water-soluble resin or hydrophobic resin, the proportion of the emulsion resin emulsion-polymerized with the polymer dispersant containing a hydroxyl group contained in the binder is preferably 5% by mass or more, and more preferably 10% by mass. % Is particularly preferable.
[0048]
The ratio of the inorganic fine particles to the binder used to form the void-type ink absorbing layer is 2: 1 to 10: 1 by mass. If the amount of the binder with respect to the inorganic fine particles is larger than this, voids are not formed, and ink absorption is inferior. Conversely, if the amount of the binder is too small, the film forming property is poor, and it is difficult to form a film due to cracking during coating and drying. .
[0049]
In the present invention, a hardener can be used to improve the film forming property of the film and to increase the water resistance of the film. Examples of the hardener include epoxy hardeners such as diglycidyl ether, ethylene glycol glycidyl ether, sorbitol polyglycidyl ether, N, N-diglycidyl-4-glycidyloxyaniline, and aldehyde hardeners such as formaldehyde and glyoxal. Active hardeners such as 2,4-dichloro-4-hydroxy-1,3,5-s-triazine, active vinyl hardeners such as bisvinylsulfonylmethyl ether, isocyanate compounds, boric acid and the like Examples thereof include salts, and boric acid or a salt thereof is particularly preferable.
[0050]
The boric acid or a salt thereof indicates an oxyacid having a boron atom as a central atom and a salt thereof, and specifically includes orthoboric acid, metaboric acid, hypoboric acid, tetraboric acid, pentaboric acid and a salt thereof. .
[0051]
Two or more hardeners may be used in combination, and the amount used may vary depending on the amount of the inorganic fine particles and the binder in the coating solution. However, the amount used in the ink absorbing layer of the recording medium is preferably 1 m. ² The amount of boric acid or a salt thereof is preferably 0.1 to 2 g when boric acid or a salt thereof is used as a hardening agent.
[0052]
Here, the amount of boric acid or a salt thereof in the ink absorbing layer is defined as 1 m of the inkjet recording medium. ² Represents the amount of boric acid ions extracted by extracting the ink absorbing layer with hot water and eluted borate ions measured by ion chromatography.
[0053]
As a method of adding a hardening agent to the ink absorbing layer, the hardening agent solution may be added to the ink absorbing layer forming coating solution when the coating solution is applied, or the hardening agent solution is applied after the coating solution is dried. You may overcoat.
[0054]
Various additives other than those described above can be added to the ink absorbing layer and other layers provided as necessary of the ink jet recording medium of the present invention.
[0055]
For example, a cationic resin or a water-soluble polyvalent metal ion can be added to improve water resistance and bleeding resistance after printing.
[0056]
As the cationic resin, a polymer resin having a primary to tertiary amino group and a quaternary ammonium group can be arbitrarily selected and used, but since there is little discoloration or deterioration of light resistance over time, It is preferably a polymer having a quaternary ammonium group, and is a homopolymer of a monomer having a quaternary ammonium group or a copolymer or polycondensate with one or more other copolymerizable monomers, and has an average molecular weight of 2,000 to 100,000 is preferred.
[0057]
In the invention according to claim 6, it is preferable to contain a water-soluble polyvalent metal salt.
In order to improve image fixability after printing and recording, it is preferable to add a water-soluble polyvalent metal salt. Examples of the water-soluble polyvalent metal salt according to the present invention include metal salts such as aluminum, calcium, magnesium, zinc, iron, strontium, barium, nickel, copper, scandium, gallium, indium, titanium, zirconium, tin, and lead. , Sulfate, nitrate, formate, succinate, malonate, chloroacetate, p-toluenesulfonate. Further, as a salt of a water-soluble polyvalent metal ion, a water-soluble inorganic polymer such as polyaluminum chloride may be used. The water solubility is preferably at least 0.1% by mass, more preferably 1% by mass. Among them, a water-soluble salt composed of aluminum, calcium, aluminum, magnesium, and zinc is preferable because its metal ion is colorless. Particularly preferred are aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum acetate, calcium chloride, calcium sulfate, calcium nitrate, calcium acetate, magnesium chloride, magnesium sulfate, magnesium nitrate, magnesium acetate, zinc chloride, zinc sulfate, zinc nitrate, It is zinc acetate.
[0058]
In the inkjet recording paper of the present invention, the content of the water-soluble polyvalent metal salt according to the present invention is 5 to 300 mg (converted to the mass of metal ions) / m. ² Is more preferable, and more preferably, 10 to 150 mg / m ² It is.
[0059]
Water-soluble polyvalent metal salts can be added by directly adding to the coating solution and applying, or by coating and drying the recording medium and then overcoating with an aqueous solution of a cationic resin or a water-soluble polyvalent metal salt. You can also do that.
[0060]
Other than the above, for example, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988 and JP-A-62-261476, JP-A-57-74192, JP-A-57-87989 and JP-A-60-72785. Anti-fading agents described in JP-A-61-14691, JP-A-1-95091 and JP-A-3-13376, JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, 61-242871, JP-A-4-219266, etc., fluorescent brightening agents, sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, pH adjusters such as potassium carbonate, defoamers, Various known additives such as a preservative, a thickener, an antistatic agent, and a matting agent can be contained.
[0061]
The porous ink absorbing layer may be composed of two or more layers. In this case, the constitutions of the ink absorbing layers may be the same or different.
[0062]
As the support of the ink jet recording medium of the present invention, a conventionally known support, for example, a paper support such as plain paper, art paper, coated paper and cast coated paper, a plastic support, and a plastic resin film on both sides And a composite support obtained by laminating the paper support and the like can be appropriately selected and used.
In the ink jet recording medium of the present invention, it is preferable to perform a corona discharge treatment, an undercoating treatment, or the like on the support prior to the application of the ink absorption layer for the purpose of increasing the adhesive strength between the support and the ink absorption layer. . Further, the recording medium of the present invention does not necessarily need to be colorless, and may be colored recording paper.
[0063]
In the ink jet recording medium of the present invention, it is particularly preferable to use a support in which both sides of the paper are laminated with a plastic resin film, since the recorded image is close to the photographic quality and a high quality image can be obtained at low cost. Preferred as a support having both sides of the paper coated with a plastic resin film is a support having both sides of the paper coated with a polyolefin resin. Examples of the polyolefin resin that coats both sides of the paper include polyethylene, polypropylene, polyisobutylene, and polyethylene. Polyolefins such as a copolymer mainly composed of propylene are preferable, and polyethylene is particularly preferable.
[0064]
The thickness of the support is preferably 50 to 350 μm, particularly preferably 80 to 300 μm.
[0065]
The method of applying various hydrophilic layers, which are appropriately provided as necessary, such as an ink absorbing layer and an undercoat layer of the inkjet recording medium of the present invention, to a support can be appropriately selected from known methods. . A preferable method is obtained by applying a coating solution constituting each layer on a support and drying the solution. In this case, two or more layers can be applied simultaneously, and in particular, simultaneous application in which all the layers only need to be applied once is preferable.
[0066]
As a coating method, a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method, or an extrusion coating method using a hopper described in US Pat. No. 2,681,294 is preferably used. .
[0067]
The recording surface pH of the recording surface of the ink jet recording medium of the present invention is preferably 3.5 to 9. When the film surface pH is 3.5 or more, so-called bronzing, which is a phenomenon in which a dye precipitates and changes in metallic luster when recording by ink jetting, can be remarkably prevented. Further, when the film surface pH is 9 or less, the phenomenon that a recorded image blurs can be significantly prevented.
[0068]
The measurement of the film surface pH of the recording surface according to the present invention is described in J. Am. TAPPI paper pulp test method No. According to the method described in No. 49, the measurement was performed after 30 seconds using distilled water.
[0069]
In the present invention, the film surface pH of the recording surface can be adjusted to a predetermined range by forming a recording surface and then overcoating with a suitable pH adjuster. As the pH adjuster, an aqueous solution of an appropriate acid or alkali can be used. In this case, the type and concentration of the acid or alkali to be used can be appropriately selected depending on the pH range to be adjusted.
[0070]
When recording an image using the inkjet recording medium of the present invention, a recording method using an aqueous pigment ink is used. Conventionally known organic and inorganic pigments can be used as the pigment. Examples of the pigments that can be used in the present invention include, for example, azo pigments, insoluble azo pigments, azo pigments such as condensation azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, Organic pigments such as thioindigo pigments, isoindolinone pigments, polycyclic pigments such as quinophthaloni pigments, dye lakes such as basic dye lakes, acid dye lakes, nitro pigments, nitroso pigments, aniline black, daylight fluorescent pigments, And inorganic pigments such as carbon black. In addition, any pigment that is not described in the color index can be used as long as it can be dispersed in water.
[0071]
The water-soluble resin contained in the aqueous pigment ink of the present invention is used as a pigment dispersant. Examples of the water-soluble resin that can be used in the present invention include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates, naphthalene sulfonates, alkyl phosphates, polyoxygens, Activator such as alkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine oxide, or styrene, styrene derivative, vinyl naphthalene Block copolymers of two or more monomers selected from derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, and fumaric acid derivatives; Copolymer and can be exemplified salts thereof.
[0072]
The water-soluble resin used as a dispersant for the aqueous pigment ink of the present invention preferably has a group capable of accepting a hydrogen bond, and more preferably a styrene-acrylic acid copolymer resin. The number-average molecular weight of these water-soluble resins is 1,000 to 300,000. If the number-average molecular weight is 1,000 or less, sufficient fixability on a recording medium cannot be obtained. If the number-average molecular weight is 300,000 or more, the viscosity increases and the ejection stability becomes insufficient. .
[0073]
The particle diameter of the pigment dispersion used in the present invention is 10 nm or more and 150 nm or less in average particle diameter. If the average particle size of the pigment dispersion exceeds 150 nm, the glossiness of the image recorded on the glossy medium is significantly deteriorated, and the ink tends to be easily clogged. When the average particle size of the pigment dispersion is less than 10 nm, the stability of the pigment dispersion is likely to deteriorate, and the storage stability of the ink is likely to deteriorate.
[0074]
Other aqueous pigment ink additives include, for example, water-soluble organic solvents (eg, propanol, hexanol, ethylene glycol, diethylene glycol, glycerin, hexanediol, urea, etc.), surfactants, water-soluble polymers, fungicides, viscosity control Agents and pH adjusters.
[0075]
The inkjet head used in the inkjet recording method of the present invention may be of an on-demand type or a continuous type. Further, as a discharge method, 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 Specific examples include an ink jet type, a bubble jet (R) type, and the like, and an electrostatic suction method (for example, an electrolysis control type, a slit jet type, and the like), and any discharge method may be used. Absent.
[0076]
【Example】
Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto. In the examples, "%" indicates% by mass unless otherwise specified.
<< Preparation of inkjet recording medium >>
An ink jet recording medium was manufactured according to the following procedure.
[0077]
(Preparation of coating liquid-1)
Fine-grain fumed silica (manufactured by Tokuyama: Reolosil QS-20) was dispersed in pure water adjusted to pH 2.5 with nitric acid to prepare 400 g of a 20% silica dispersion. To this were added 80 g of a 20% aqueous solution of the cationic polymer (1) adjusted to pH 2.5, 60 ml of an aqueous solution in which 2.1 g of boric acid and 1.5 g of borax were dissolved, and the mixture was dispersed with a high-pressure homogenizer. While stirring the obtained dispersion at 40 ° C., 3 g of the emulsion (1) shown in Table 1 and 100 ml of a 10% aqueous solution of polyvinyl alcohol (Kuraray: PVA235) were added thereto, and the mixture was purified to 1000 ml. Water was added to obtain translucent coating solution-1.
[0078]
Embedded image

[0079]
(Preparation of coating liquid-2)
Fine-grain fumed silica (manufactured by Tokuyama: Reolosil QS-20) was dispersed in pure water adjusted to pH 2.5 with nitric acid to prepare 400 g of a 20% silica dispersion. To this were added 80 g of a 20% aqueous solution of the cationic polymer (1) adjusted to pH 2.5, 60 ml of an aqueous solution in which 2.1 g of boric acid and 1.5 g of borax were dissolved, and the mixture was dispersed with a high-pressure homogenizer. While stirring the obtained dispersion at 40 ° C., 160 ml of a 10% aqueous solution of polyvinyl alcohol (manufactured by Kuraray: PVA235) was added, and pure water was added so that the total amount of the solution became 1000 ml. 2 was obtained.
[0080]
(Preparation of recording medium 1)
Next, a basis weight of 200 g / m ² The above coating solution-2 was used as a lower layer on the recording surface side on a support (thickness 260 μm, containing 6% by mass of anatase type titanium dioxide in the polyethylene layer on the recording surface side) in which both sides of the base paper were covered with polyethylene. The above coating solution-1 was applied as an upper layer so as to have a wet film thickness of 80 μm in this order so as to have a wet film thickness of 80 μm, cooled at 8 ° C. for 10 seconds, and then blown with a wind of 20 to 40 ° C. After drying, an inkjet recording medium 1 was obtained.
[0081]
(Preparation of recording medium 2)
An ink jet recording medium 2 was produced in the same manner as in the recording medium 1 except that the emulsion (1) contained in the upper coating liquid-1 was replaced with the emulsion (4).
[0082]
(Preparation of recording medium 3)
An ink jet recording medium 3 was produced in the same manner as in the recording medium 1 except that the coating liquid-2 was used instead of the coating liquid-1 as the upper layer.
[0083]
<< Preparation of aqueous pigment ink >>
<Preparation of Dispersion 1>

After mixing the above additives, 0.5 part of the above dispersant was added, and the dispersant was sufficiently adsorbed by repeating heating and stirring at 65 ° C. for 1 hour and cooling at 5 ° C. for 1 hour twice. Thereafter, Dispersion 1 was prepared by removing the undispersed coarse particles by centrifugation.
[0084]
<Preparation of aqueous pigment ink-1 to 4>
A water-soluble organic solvent, ion-exchanged water, a surfactant, a preservative, and a pH adjuster are appropriately selected and added to the dispersion 1, and the mixture is filtered under pressure through a Teflon (R) filter having a pore diameter of 0.8 μm to obtain a pigment. An aqueous pigment ink 1 having a concentration of 1.0% was prepared.
[0085]
The secondary average particle size of the pigment particles of the obtained aqueous pigment ink 1 was 280 μm. The particle size was measured with a Zetasizer 1000 manufactured by Malvern.
[0086]
In the preparation of the aqueous pigment ink 1, the pigment was C.I. I. Pigment Red 122, and C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Yellow 128, C.I. I. Pigment Black 7 was used, and aqueous pigment inks 2, 3, and 4 having a secondary average particle size of 280 μm were prepared in the same manner.
[0087]
<Preparation of aqueous pigment inks 5 to 8>
In the above aqueous pigment inks 1 to 4, aqueous pigment inks 5 to 8 were prepared in the same manner except that the secondary average particle diameter of the pigment particles was adjusted to 120 µm by appropriately adjusting the dispersion conditions.
[0088]
<Preparation of aqueous pigment inks 9 to 12>
Aqueous pigment inks 9 to 12 were prepared in the same manner except that the type of dispersant in the aqueous pigment inks 1 to 4 was changed to a styrene-acrylic acid copolymer (weight average molecular weight 520,000).
[0089]
<< Preparation of evaluation sample >>
(Image recording method)
As an image recording method, four piezo-type heads having a nozzle hole diameter of 20 μm, a driving frequency of 12 KHz, a number of nozzles of 128 per color, and a nozzle density of 180 dpi between the same colors (dpi represents the number of dots per 2.54 cm) are used. A single-color image pattern of each of yellow, magenta, cyan, and black which gives a reflection density of 1.0 and 1.5 on a recording medium by using an on-demand type ink-jet printer having a maximum recording density of 720 × 720 dpi mounted on a base. Was used as the output image.
[0090]
(Evaluation of scratch resistance)
The degree of contamination of the printed portion when the solid image having a solid density of 1.0 was rubbed 10 times with a commercially available eraser (manufactured by MONO Tombo Pencil Co., Ltd.) was visually evaluated according to the following criteria. .
[0091]
：: No stain on the printed portion observed
Δ: Slight stain on the printed area observed
×: The stain on the printed portion is clearly observed.
(Glossiness evaluation method)
Using the portion of the produced output image having a solid density of 1.5, the image clarity (C value%) was measured with an image clarity measuring device ICM-1DP (manufactured by Suga Test Machine Co.) at a reflection of 60 degrees and an optical comb of 2 mm. The gloss was evaluated according to the following evaluation criteria.
[0092]
：: C value% is 50% or more
Δ: C value% is 40% or more and less than 50%
×: C value% is less than 40%
(Ejection stability and ink storage stability evaluation method)
The above-prepared aqueous pigment ink was subjected to continuous ejection for 10 seconds → pause for a fixed time → intermittent operation for continuous ejection by the above-described image recording method. At this time, whether the disturbance of the ejection direction occurs at the beginning after the suspension of the ejection is determined by the length of the suspension time, so the stability of the intermittent ejection is measured by changing the length of the ejection suspension time stepwise. Was evaluated according to the following criteria. The evaluation was performed at an ambient temperature of 23 ° C. and 55% RH.
[0093]
5: Stable discharge even after pause for 31 to 45 seconds
4: Stable ejection even after pause for 21 to 30 seconds
3: Stable ejection even after pause for 11 to 20 seconds
2: Stable discharge even after pause for 6 to 10 seconds
1: Stable ejection for less than 5 seconds
The same evaluation as above was performed on the ink that had been stored in a sealed state at 60 ° C. for one week, and the storage stability of the ink was evaluated.
[0094]
Table 2 shows the results obtained as described above.
[0095]
[Table 2]

[0096]
As is clear from Table 2, the prints output using the aqueous pigment inks 1 to 8 according to the present invention with respect to the recording media 1 and 2 according to the present invention are excellent in abrasion and gloss, and also have excellent ejection stability. It turns out that it is excellent. On the other hand, the recording medium 3 not containing the water-eluting polymer compound according to the present invention has poor abrasion, and the aqueous pigment inks 9 to 12 containing no water-soluble resin of the present invention have gloss and gloss. Discharge stability deteriorates.
[0097]
【The invention's effect】
According to the present invention, even when an aqueous pigment ink having excellent light fastness is used, an image having excellent scratch resistance, high glossy output, and no problem in ink storage stability or ejection stability can be obtained. A recording method can be provided.

Claims (8)

In an inkjet recording method for forming an image on an inkjet recording medium having a void layer containing at least one inorganic fine particle on a support using an aqueous pigment ink, the aqueous pigment ink is a polymer compound having a weight average molecular weight of 1,000 to 300,000. And a layer farthest from the support of the ink jet recording medium having a group capable of reacting with ink pigment particles or a group capable of hydrogen bonding, and containing a water-eluting polymer compound. An ink-jet recording method, characterized in that: The ink-jet recording method according to claim 1, wherein the inorganic fine particles contained in the ink-jet recording medium are silica or alumina. The ink jet recording method according to claim 1, wherein the water-eluting polymer compound is contained as an emulsion resin emulsion-polymerized with a polymer dispersant having a hydroxyl group. The inkjet recording method according to claim 3, wherein the polymer dispersant is polyvinyl alcohol. 5. The ink jet recording method according to claim 3, wherein the polymer dispersant is polyvinyl alcohol having an average degree of polymerization of 1500 to 5000. The inkjet recording method according to claim 1, wherein the inkjet recording medium contains a water-soluble polyvalent metal salt. The inkjet recording method according to any one of claims 1 to 6, wherein the polymer compound having a weight average molecular weight of 1,000 to 300,000 contained in the aqueous pigment ink has a group capable of accepting a hydrogen bond. The ink-jet recording method according to any one of claims 1 to 7, wherein the pigment dispersion contained in the aqueous pigment ink has an average particle diameter of 10 nm or more and 150 nm or less.