JP2005028747A - Ink jet recording paper and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly glossy ink jet recording paper, having a porous ink absorbing layer, which shows outstanding smoothness, gloss, resistance to cracking and ink absorptivity, and a method for manufacturing the ink jet recording paper. <P>SOLUTION: In the ink jet recording paper having the porous layer, containing a hydrophilic polymer compound which is crosslinkable by ionizing radiation and an inorganic fine particle, formed on a support, the hydrophilic polymer compound which is crosslinkable by the ionizing radiation, is further crosslinked by a crosslinking agent. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００３５】
で表される２−アジド−５−ニトロフェニルカルボニルオキシエチレン構造、又は、
【００３６】
【化３】

【００３７】
で表される４−アジド−３−ニトロフェニルカルボニルオキシエチレン構造を有する樹脂組成物である。
【００３８】
感光性樹脂の具体例は、該公報中の実施例１、２に、また感光性樹脂の構成成分及びその使用割合は該公報第２頁に記載されている。
【００３９】
また、特開昭６０−１２９７４２号公報には、感光性樹脂としてポリビニルアルコール構造体中に
【００４０】
【化４】

【００４１】
の構造を有する樹脂組成物が挙げられている。
本発明においては、電離放射線により架橋する親水性高分子化合物の中でも、光重合型の変性基としては、例えば、特開２０００−１８１０６２号公報に開示されている前記一般式（１）で示される構成単位を有するポリ酢酸ビニルケン化物が、反応性との観点から好ましい。
【００４２】
本発明に係る親水性の高分子化合物において、重合度や架橋密度は皮膜形成時の強度や柔軟性に影響し、重合度が低かったり架橋変性基が多すぎたりすると塗布乾燥時のひび割れや乾燥塗膜の折れ割れといった故障が生じてしまう。したがって、前記一般式（１）で示される構成単位を有するポリ酢酸ビニルケン化物を含む親水性の高分子化合物においては、重合度は４００〜５０００であることが好ましく、１０００〜４０００であることがより好ましい。また、セグメントに対する電離放射線反応架橋基の変性率が４ｍｏｌ％以下であることが好ましく、より好ましくは０．０１〜１ｍｏｌ％である。
【００４３】
なお、本発明においては、本発明の目的効果を損なわない範囲で、従来公知の親水性樹脂を併用しても良い。公知の親水性樹脂としては、例えば、ゼラチン、ポリビニルピロリドン、プルラン、ポリビニルアルコールまたはその誘導体、ポリエチレングリコール、ヒドロキシエチルセルロース、デキストラン、デキストリン、水溶性ポリビニルブチラール等を挙げることができる。
【００４４】
本発明においては、光重合開始剤や増感剤を添加するのも好ましい。これらの化合物は溶媒に溶解、または分散した状態か、もしくは感光性樹脂に対して化学的に結合されていてもよい。
【００４５】
適用される光重合開始剤、光増感剤について特に制限はなく、従来公知の物を用いることができ、例えば、ベンゾフェノン、ヒドロキシベンゾフェノン、ビス−Ｎ，Ｎ−ジメチルアミノベンゾフェノン、ビス−Ｎ，Ｎ−ジエチルアミノベンゾフェノン、４−メトキシ−４’−ジメチルアミノベンゾフェノン等のベンゾフェノン類。チオキサトン、２、４−ジエチルチオキサントン、イソプロピルチオキサントン、クロロチオキサントン、イソプロポキシクロロチオキサントン等のチオキサントン類。エチルアントラキノン、ベンズアントラキノン、アミノアントラキノン、クロロアントラキノン等のアントラキノン類。アセトフェノン類。ベンゾインメチルエーテル等のベンゾインエーテル類。２，４，６−トリハロメチルトリアジン類、１−ヒドロキシシクロヘキシルフェニルケトン、２−（ｏ−クロロフェニル）−４，５−ジフェニルイミダゾール２量体、２−（ｏ−クロロフェニル）−４，５−ジ（ｍ−メトキシフェニル）イミダゾール２量体、２−（ｏ−フルオロフェニル）−４，５−フェニルイミダゾール２量体、２−（ｏ−メトキシフェニル）−４，５−フェニルイミダゾール２量体、２−（ｐ−メトキシフェニル）−４，５−ジフェニルイミダゾール２量体、２，−ジ（ｐ−メトキシフェニル）−５−フェニルイミダゾール２量体、２−（２，４−ジメトキシフェニル）−４，５−ジフェニルイミダゾール２量体の２，４，５−トリアリールイミダゾール２量体、ベンジルジメチルケタール、２−ベンジル−２−ジメチルアミノ−１−（４−モルホリノフェニル）−ブタン−１−オン、２−メチル−１−［４−（メチルチオ）フェニル］−２−モルホリノ−１−プロパノン、２−ヒドロキシ−２−メチル−１−フェニル−プロパン−１−オン、１−［４−（２−ヒドロキシエトキシ）−フェニル］−２−ヒドロキシ−２−メチル−１−プロパン−１−オン、フェナントレンキノン、９，１０−フェナンスレンキノン、メチルベンゾイン、エチルベンゾイン等ベンゾイン類、９−フェニルアクリジン、１，７−ビス（９，９’−アクリジニル）ヘプタン等のアクリジン誘導体、ビスアシルフォスフィンオキサイド、及びこれらの混合物等が挙げられ、上記は単独で使用しても混合して使用してもかまわない。
【００４６】
本発明のインクジェット記録用紙においては、特に、混合性等に優れ架橋効率の観点からも水溶性光重合開始剤を用いることが好ましく、例えば、水溶性の１−［４−（２−ヒドロキシエトキシ）−フェニル］−２−ヒドロキシ−２−メチル−１−プロパン−１−オン、４−（２−ヒドロキシエトキシ）−フェニル・（２・ヒドロキシ−２−プロピル）ケトン、チオキサントンアンモニウム塩、ベンゾフェノンアンモニウム塩等の水溶性光重合開始剤を挙げることができる。
【００４７】
これらの光重合開始剤に加え、重合促進剤等を添加することもできる。これらの例として、ｐ−ジメチルアミノ安息香酸エチル、ｐ−ジメチルアミノ安息香酸イソアミル、エタノールアミン、ジエタノールアミン、トリエタノールアミン等があげられる。
【００４８】
次に、本発明に使用される架橋剤について説明する。
多孔質の空隙構造を有するインク吸収層を有する記録用紙においては、インク吸収層を架橋させればさせるほどインク吸収性（速乾性）が速くなる傾向がある。この理由としては、空隙構造からなるインク吸収層を有する記録用紙においては、空隙構造を形成している親水性樹脂の膨潤性がより押さえられることにより、インク吸収層の上部（即ち、より表面に近い側）で親水性樹脂の膨潤によるインクの浸透阻害が抑制されるためであると考えられる。
【００４９】
従って、空隙構造からなるインク吸収層を有するインクジェット記録用紙においては、インク吸収層の架橋がされればされるだけインク吸収性が増大し、しかも皮膜の耐水性を向上することができる。
【００５０】
しかしながら、本発明の電離放射線により架橋する親水性高分子化合物と無機微粒子を含有する多孔質層を有するインクジェット記録用紙においては、電離放射線により架橋する親水性高分子化合物は、塗布液が湿潤した状態で電離放射線により架橋し、三次元ネットワークを形成してゲル化し、乾燥後にはこの三次元ネットワークが折りたたまれた状態となって、無機微粒子との相互作用により空隙構造が形成されていると思われる。この状態のままではプリント時にインクがインク吸収層の上部（即ち、より表面に近い側）に到達したとき、折りたたまれていた三次元ネットワークが再び広がって膨潤し、空隙構造が親水性高分子化合物により埋まってしまい、更なるインクの浸透が阻害されるため、電離放射線による架橋を増やすことは、インク吸収性に対してあまり効果的であるとはいえない。
【００５１】
そこで電離放射線により架橋する親水性高分子化合物と無機微粒子を含有する多孔質層を有するインクジェット記録用紙に、さらに架橋剤による架橋を加えることによって、高温乾燥による生産性の向上と共に、高いインク吸収性を両立することができることを見出した。
【００５２】
本発明において使用される架橋剤は、従来公知の架橋剤を併用して良く、架橋剤の種類は親水性高分子化合物の種類に応じて適宜選択して用いられるが、乾燥して濃縮された状態で架橋反応が進行するものが好ましく、更に好ましくは、ほう酸もしくはその塩、エポキシ系化合物、イソシアネート系化合物、アルデヒド系化合物、活性ハロゲン系化合物及び活性ビニル系化合物から選ばれる少なくとも１種である。
【００５３】
架橋剤の具体例としては、例えば、エポキシ系化合物（ジグリシジルエチルエーテル、エチレングリコールジグリシジルエーテル、１，４−ブタンジオールジグリシジルエーテル、１，６−ジグリシジルシクロヘキサン、Ｎ，Ｎ−ジグリシジル−４−グリシジルオキシアニリン、ソルビトールポリグリシジルエーテル、グリセロールポリグリシジルエーテル等）、イソシアネート系化合物（ヘキサメチレンジイソシアネート、芳香族ポリイソシアネート、トリレンジイソシアネート、トリメチロールプロパン−トリレンジイソシアネートの付加物、メチレンビス−４−フェニルメタントリイソシアネートやメチレンビスイソホロンジイソシアネートのケトオキシムブロック物等）アルデヒド系化合物（ホルムアルデヒド、グリオキザール等）、活性ハロゲン系化合物（２，４−ジクロロ−４−ヒドロキシ−１，３，５−ｓ−トリアジン等）、活性ビニル系化合物（１，３，５−トリスアクリロイル−ヘキサヒドロ−ｓ−トリアジン、ビスビニルスルホニルメチルエーテル等）、ホウ酸およびその塩があげられる。
【００５４】
上記架橋剤の好ましい使用量は、親水性高分子化合物の種類、架橋剤の種類、無機微粒子の種類や親水性高分子化合物に対する比率等により変化するが、概ね親水性高分子化合物１ｇ当たり５〜５００ｍｇ、より好ましくは１０〜４００ｍｇである。
【００５５】
上記架橋剤の供給方法としては、空隙層を構成する塗布液を塗布する際に、空隙層形成の塗布液中及びまたは空隙層に隣接するその他の層を形成する塗布液中に添加してもよい。あるいは予め架橋剤を含有する塗布液を塗布してある支持体上に、前記空隙層を形成する塗布液を塗布したり、更には空隙層を形成する架橋剤非含有の塗布液の塗布と同時、または塗布後で乾燥を開始する前、あるいは乾燥中に、直接、または架橋剤の水溶液やアルコールなどの有機溶媒に溶解させた溶液をオーバーコートし、乾燥することによって供給してもよい。さらに別の架橋剤の付与の方法として、インク吸収層を形成する塗布液を塗布、乾燥終了後に、直接、または架橋剤の水溶液やアルコールなどの有機溶媒に溶解させた溶液をインク吸収層上にオーバーコートし、乾燥することによって供給してもよい。オーバーコートの方法としては、架橋剤または架橋剤溶液を塗布しても、スプレーによる供給でも、架橋剤または架橋剤溶液に浸漬してもよい。
【００５６】
本発明に係る空隙構造を有するインク吸収層は、無機微粒子を含有する。
インク吸収層に使用される無機微粒子の例として、軽質炭酸カルシウム、炭酸マグネシウム、カオリン、クレー、タルク、硫酸カルシウム、硫酸バリウム、二酸化チタン、酸化亜鉛、水酸化亜鉛、硫化亜鉛、炭酸亜鉛、ハイドロタルサイト、珪酸アルミニウム、ケイソウ土、珪酸カルシウム、珪酸マグネシウム、合成非晶質シリカ、コロイダルシリカ、アルミナ、コロイダルアルミナ、ベーマイト、擬ベーマイト、水酸化アルミニウム、リトポン、ゼオライト、水酸化マグネシウム等が挙げられる。
【００５７】
これら無機微粒子は、１次粒子のまま均一に分散された状態で用いられていても、また２次凝集粒子を形成して分散された状態で用いられていても良い。
【００５８】
無機微粒子の平均粒子径は０．００５〜０．４μｍのものがインク吸収層の光沢の点で好ましい。ここでいう無機微粒子の平均粒子径は、空隙層の断面や表面を走査型電子顕微鏡で観察し、複数個の任意の粒子の粒径を求めてその単純平均値（個数平均値）として求めることができる。ここにおいて、個々の粒径はその投影面積に等しい円を想定した時の直径で表したものである。
【００５９】
本発明においては、特に微細な空隙を形成できる観点から、平均粒子径が０．００５〜０．４μｍのシリカ、アルミナまたはアルミナ水和物が好ましく、特にインクジェット記録用紙のインク吸収層の光沢の点で平均粒子径が０．０１〜０．４μｍの気相法により合成されたシリカまたはアルミナ、およびアルミナ水和物である擬ベーマイトが好ましい。
【００６０】
インク吸収層に用いられる無機微粒子の使用量は、無機微粒子の種類に依存するが、インクジェット記録用紙１ｍ^２あたり、通常５〜３０ｇ、好ましくは１０〜２５ｇである。
【００６１】
本発明に係る多孔質層において、親水性高分子化合物（Ｂ）に対する無機微粒子（Ｐ）の比率（Ｐ／Ｂ）は、質量比で３〜５０倍であることが好ましい。質量比が３倍以上であれば、多孔質層の空隙率は良好であり、充分な空隙容量が得やすい。一方、この比率が５０倍以下であれば、多孔質層を厚膜で塗布した際に、ひび割れが生じにくく好ましい。特に好ましい親水性高分子化合物に対する無機微粒子の比率（Ｐ／Ｂ）は５〜２０倍である。
【００６２】
本発明に係る空隙層は、塗膜の単位面積あたり１５〜４０ｍｌ／ｍ^２の容量を持つことが好ましい。ここでいう容量とは、単位体積の塗膜を水につけたときに発生した気泡の体積、塗膜が吸収しうる水の体積、または最終的に得られる記録用紙を、Ｊ．ＴＡＰＰＩ ５１に規定される紙および板紙の液体吸収性試験方法（ブリストー法）で測定したときの、接触時間が２秒における液体転移量などで定義される。
【００６３】
本発明に係るインク吸収層やインク吸収層を形成する水溶性塗布液中には、各種の添加剤を添加することもできる。そのような添加剤としては、例えば、媒染剤としてカチオン性媒染剤や多価金属化合物、界面活性剤（例えば、カチオン、ノニオン、アニオン、両性界面活性剤）、白地色調調整剤、蛍光増白剤、防黴剤、粘度調整剤、低沸点有機溶媒、高沸点有機溶媒、ラテックスエマルジョン、退色防止剤、紫外線吸収剤、マット剤、シリコンオイル等が挙げられる。
【００６４】
カチオン媒染剤としては、第１級〜第３級アミノ基および第４級アンモニウム塩基を有するポリマー媒染剤が用いられるが、長期保存での変色や耐光性の劣化が少ないこと、染料の媒染能が充分高いことなどから、第４級アンモニウム塩基を有するポリマー媒染剤が好ましい。好ましいポリマー媒染剤は、上記第４級アンモニウム塩基を有するモノマーの単独重合体やその他のモノマーとの共重合体または縮重合体として得られる。
【００６５】
また、多価金属化合物としてはアルミニウム、カルシウム、マグネシウム、亜鉛、鉄、ジルコニウム、スズ、鉛などの金属塩があげられる。中でもマグネシウム、アルミニウム、ジルコニウム、カルシウム、亜鉛からなる化合物は無色の為好ましい。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良い。
【００６６】
カチオン性ポリマー、あるいは水溶性の多価金属化合物の使用量は、無機微粒子に対する質量比で１０質量％以下、より好ましくは８質量％以下であることがインク吸収性の劣化を抑制する為に好ましい。
【００６７】
カチオン性ポリマー、あるいは水溶性の多価金属化合物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の多価金属化合物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かまわない。
【００６８】
本発明のインクジェット記録用紙に用いられる支持体としては、より高品位なプリントが得られる観点から、非吸水性支持体であることが好ましい。
【００６９】
好ましく用いられる非吸水性支持体としては、例えば、ポリエステル系フィルム、ジアセテート系フィルム、トリアテセート系フィルム、ポリオレフィン系フィルム、アクリル系フィルム、ポリカーボネート系フィルム、ポリ塩化ビニル系フィルム、ポリイミド系フィルム、セロハン、セルロイド等の材料からなる透明または不透明のフィルム、あるいは基紙の両面をポリオレフィン樹脂等で被覆した樹脂被覆紙、いわゆるＲＣペーパー等が挙げられる。
【００７０】
上記支持体上に、前記の水溶性塗布液を塗布するに当たっては、表面と塗布層との間の接着強度を大きくする等の目的で、支持体表面にコロナ放電処理や下引処理等を行うことが好ましい。更に、本発明のインクジェット記録用紙では着色された支持体であってもよい。
【００７１】
本発明で好ましく用いられ支持体は、透明ポリエステルフィルム、不透明ポリエステルフィルム、不透明ポリオレフィン樹脂フィルムおよび紙の両面をポリオレフィン樹脂でラミネートした紙支持体である。
【００７２】
以下、最も好ましいポリオレフィン樹脂の代表であるポリエチレンでラミネートした非吸水性の紙支持体について説明する。
【００７３】
紙支持体に用いられる原紙は、木材パルプを主原料とし、必要に応じて木材パルプにポリプロピレンなどの合成パルプあるいはナイロンやポリエステルなどの合成繊維を加えて抄紙される。木材パルプとしては、例えば、ＬＢＫＰ、ＬＢＳＰ、ＮＢＫＰ、ＮＢＳＰ、ＬＤＰ、ＮＤＰ、ＬＵＫＰ、ＮＵＫＰのいずれも用いることができるが、短繊維分の多いＬＢＫＰ、ＮＢＳＰ、ＬＢＳＰ、ＮＤＰ、ＬＤＰをより多く用いることが好ましい。但し、ＬＢＳＰまたはＬＤＰの比率は１０質量％以上、７０質量％以下であることが好ましい。
【００７４】
上記パルプは、不純物の少ない化学パルプ（硫酸塩パルプや亜硫酸塩パルプ）が好ましく用いられ、又、漂白処理を行って白色度を向上させたパルプも有用である。
【００７５】
原紙中には、高級脂肪酸、アルキルケテンダイマー等のサイズ剤、炭酸カルシウム、タルク、酸化チタンなどの白色顔料、スターチ、ポリアクリルアミド、ポリビニルアルコール等の紙力増強剤、蛍光増白剤、ポリエチレングリコール類等の水分保持剤、分散剤、４級アンモニウム等の柔軟化剤などを適宜添加することができる。
【００７６】
抄紙に使用するパルプの濾水度は、ＣＳＦの規定で２００〜５００ｍｌであることが好ましく、また、叩解後の繊維長がＪＩＳ−Ｐ−８２０７に規定される２４メッシュ残分質量％と、４２メッシュ残分の質量％との和が３０〜７０質量％が好ましい。なお、４メッシュ残分の質量％は、２０質量％以下であることが好ましい。
【００７７】
原紙の坪量は３０〜２５０ｇが好ましく、特に５０〜２００ｇが好ましい。原紙の厚さは４０〜２５０μｍが好ましい。原紙は、抄紙段階または抄紙後にカレンダー処理を施して、高平滑性を与えることもできる。原紙密度は０．７〜１．２ｇ／ｃｍ^３（ＪＩＳ−Ｐ−８１１８に規定の方法に準ずる）が一般的である。更に、原紙剛度はＪＩＳ−Ｐ−８１４３に規定される条件で２０〜２００ｇが好ましい。原紙表面には表面サイズ剤を塗布しても良く、表面サイズ剤としては、前述の原紙中に添加できるサイズ剤と同様のものを使用することができる。原紙のｐＨは、ＪＩＳ−Ｐ−８１１３で規定された熱水抽出法ににより測定した場合、５〜９であることが好ましい。
【００７８】
原紙表面および裏面を被覆するポリエチレンは、主として低密度のポリエチレン（ＬＤＰＥ）または高密度のポリエチレン（ＨＤＰＥ）であるが、他のＬＬＤＰＥやポリプロピレン等も一部使用することができる。
【００７９】
また、インク吸収層を塗布する面側のポリエチレン層は、写真用印画紙で広く行われているようにルチルまたはアナターゼ型の酸化チタンをポリエチレン中に添加し、不透明度および白色度を改良したものが好ましい。酸化チタン含有量は、ポリエチレンに対して１〜２０質量％、好ましくは２〜１５質量％である。
【００８０】
ポリエチレン被覆紙は光沢紙として用いることも、また、ポリエチレンを原紙表面上に溶融押し出してコーティングする際に、いわゆる型付け処理を行って通常の写真印画紙で得られるようなマット面や絹目等の微細面を形成したものも本発明で使用することができる。
【００８１】
原紙の表裏のポリエチレンの使用量は、水系塗布組成物の膜厚やバック層を設けた後での低湿、あるいは高湿下でのカールを最適化するように選択されるが、本発明においては、水系塗布組成物を塗布する面側のポリエチレン層としては２０〜４０μｍ、バック層塗設面側が１０〜３０μｍの範囲であることが好ましい。
【００８２】
更に、上記ポリエチレン被覆紙支持体は、以下の特性を有していることが好ましい。
【００８３】
１）引っ張り強さ：ＪＩＳ−Ｐ−８１１３で規定される強度で、縦方向が２０〜３００Ｎ、横方向が１０〜２００Ｎであることが好ましい
２）引き裂き強度：ＪＩＳ−Ｐ−８１１６による規定方法で、縦方向が０．１〜２Ｎ、横方向が０．２〜２Ｎが好ましい
３）圧縮弾性率：≧１０３０Ｎ／ｃｍ^２
４）表面ベック平滑度：ＪＩＳ−Ｐ−８１１９に規定される条件で、５００秒以上が光沢面としては好ましいが、いわゆる型付け品ではこれ以下であっても良い
５）裏面ベック平滑度：ＪＩＳ−Ｐ−８１１９に規定される条件で、１００〜８００秒が好ましい
６）不透明度：直線光入射／拡散光透過条件の測定条件で、可視域の光線での透過率が２０％以下、特に１５％以下が好ましい
７）白さ：ＪＩＳ−Ｐ−８１２３に規定されるハンター白色度で、９０％以上が好ましい。また、ＪＩＳ−Ｚ−８７２２（非蛍光）、ＪＩＳ−Ｚ−８７１７（蛍光剤含有）により測定し、ＪＩＳ−Ｚ−８７３０に規定された色の表示方法で表示したときの、Ｌ^＊＝９０〜９８、ａ^＊＝−５〜＋５、ｂ^＊＝−１０〜＋５が好ましい。
【００８４】
上記支持体のインク吸収層面側には、インク吸収層との接着性を改良する目的で、下引き層を設けることができる。下引き層のバインダーとしては、ゼラチンやポリビニルアルコール等の親水性ポリマーやＴｇが−３０〜６０℃のラテックスポリマーなどが好ましい。これらバインダーは、記録用紙１ｍ^２当たり０．００１〜２ｇの範囲で用いられる。下引き層中には、帯電防止の目的で、従来公知のカチオン性ポリマーなどの帯電防止剤を少量含有させることができる。
【００８５】
上記支持体のインク吸収層面側とは反対側の面には、滑り性や帯電特性を改善する目的でバック層を設けることもできる。バック層のバインダーとしては、ゼラチンやポリビニルアルコール等の親水性ポリマーやＴｇが−３０〜６０℃のラテックスポリマーなどが好ましく、またカチオン性ポリマーなどの帯電防止剤や各種の界面活性剤、更には平均粒径が０．５〜２０μｍ程度のマット剤を添加することもできる。バック層の厚みは、概ね０．１〜１μｍであるが、バック層がカール防止のために設けられる場合には、概ね１〜２０μｍの範囲である。また、バック層は２層以上から構成されていても良い。
【００８６】
本発明のインクジェット記録用紙の製造において、支持体上にインク吸収層塗布液を塗設する際に用いる塗布方法としては、公知の方法から適宜選択して行うことができ、例えば、グラビアコーティング法、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、押し出し塗布方法、カーテン塗布方法あるいは米国特許第２，６８１，２９４号明細書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。
【００８７】
本発明の記録用紙に係る多孔質層は、単層であっても２層以上で構成されていても良く、２層以上で構成されている場合、それらのインク吸収層の構成はお互いに同じであっても異なっていても良い。また２層以上で構成する場合には、全ての構成層を同時に塗布する方法であることが、生産性向上の観点から好ましい。
【００８８】
本発明のインクジェット記録用紙の製造方法においては、電離放射線により高分子化合物と無機微粒子とが架橋形成されうる構造を含む塗布液を塗布し、該塗布層の総固形分濃度が５〜９０％の時に電離放射線を照射して塗布層をゲル化させ、その後乾燥することを特徴とする。本発明でいう電離放射線とは、例えば、電子線、紫外線、α線、β線、γ線、エックス線等が挙げられるが、人体への危険性や取り扱いが容易で、かつ工業的にもその利用が普及している点で電子線または紫外線が好ましい。
【００８９】
電子線の照射方法としては、例えば、スキャニング方式、カーテンビーム方式、ブロードビーム方式などがあるが、処理能力の観点からカーテンビーム方式が好ましい。電子線の加速電圧は、塗膜の比重と膜厚により適時変化させることができるが、２０〜３００ｋＶが適当である。電子線の照射量は０．１〜２０Ｍｒａｄの範囲が好ましい。
【００９０】
紫外線の光源としては、例えば、数１００Ｐａ〜約１ＭＰａまでの動作圧力を有する低圧、中圧、高圧水銀ランプ、メタルハライドランプ等が用いられるが、光源の波長分布という観点で高圧水銀灯、メタルハライドランプが好ましく、メタルハライドランプがより好ましい。
【００９１】
特に光源の波長に３００ｎｍ以下の紫外線を含まない場合や、照射エネルギーとして１Ｊ／ｃｍ^２以下の場合には、電離放射線架橋性樹脂の母核、または共存させる各種添加剤の電離放射線による分解が生じず、分解物に由来する臭気などの問題が起こりにくくなるため好ましい。また、照射エネルギーが１ｍＪ／ｃｍ^２以上の場合に、高い架橋効率による本発明の効果が十分に発揮されるため好ましい。したがって、光源としては３００ｎｍ以下の波長光をカットするフィルターを設けることが好ましい。本発明では照射エネルギーとしては１ｍＪ／ｃｍ^２〜１Ｊ／ｃｍ^２であることが好ましく、５０ｍＪ／ｃｍ^２〜１００ｍＪ／ｃｍ^２であることがより好ましい。
【００９２】
照度としては１ｍＷ／ｃｍ^２〜１Ｗ／ｃｍ^２が好ましい。照度が１Ｗ／ｃｍ^２以下であれば塗膜の表面硬化性は向上し、深部まで均一に架橋され硬化した膜が得られ、膜の深度方向の硬さのバランスが均質となり、カール等も起こりにくくなるため好ましい。また、照度が１ｍＷ／ｃｍ^２以上であれば膜中の散乱等による架橋の不均一化が避けられ、本発明の効果が得られるため好ましい。
【００９３】
同一積算光量（ｍＪ／ｃｍ^２）を与える場合、照度に好ましい範囲があることは、その光の透過率が変化することに起因する。紫外線の透過性により、発生した架橋反応種の濃度分布が異なり、仮に紫外線照度が高すぎる場合、表層に高濃度の架橋反応種が発生する恐れがあり、塗膜表層に堅い緻密な膜が形成されてしまうこともある。照度が好ましい範囲にある場合には、表層の架橋度合いも低く、深部方向への光透過性が高いため緩やかな架橋が深部方向へ均一に形成される。また仮に照度が低すぎる場合には、必要積算照度を与える場合に照射時間がかかってしまい、設備導入等の面で不利であるばかりでなく、塗膜による紫外線の散乱による絶対光線量が不足することもある。
【００９４】
本発明のインクジェット記録用紙を用いて画像記録する際には、水性インクを用いた記録方法が好ましく用いられる。
【００９５】
上記水性インクとは、下記着色剤及び液媒体、その他の添加剤を有する記録液体である。着色剤としては、インクジェットで公知の直接染料、酸性染料、塩基性染料、反応性染料あるいは食品用色素等の水溶性染料あるいは水分散性顔料が使用できる。
【００９６】
水性インクの溶媒としては、水及び水溶性の各種有機溶剤、例えば、メチルアルコール、イソプロピルアルコール、ブチルアルコール、ｔｅｒｔ−ブチルアルコール、イソブチルアルコール等のアルコール類；ジメチルホルムアミド、ジメチルアセトアミド等のアミド類；アセトン、ジアセトンアルコール等のケトンまたはケトンアルコール類；テトラヒドロフラン、ジオキサン等のエーテル類；ポリエチレングリコール、ポリプロピレングリコール等のポリアルキレングリコール類；エチレングリコール、プロピレングリコール、ブチレングリコール、トリエチレングリコール、１，２，６−ヘキサントリオール、チオジグリコール、ヘキシレングリコール、ジエチレングリコール、グリセリン、トリエタノールアミン等の多価アルコール類；エチレングリコールメチルエーテル、ジエチレングリコールメチル（又はエチル）エーテル、トリエチレングリコールモノブチルエーテル等の多価アルコールの低級アルキルエーテル類等が挙げられる。中でも、ジエチレングリコール、トリエタノールアミンやグリセリン等の多価アルコール類、トリエチレングリコールモノブチルエーテルの多価アルコールの低級アルキルエーテル等は好ましいものである。
【００９７】
その他の水性インクの添加剤としては、例えば、ｐＨ調節剤、金属封鎖剤、防カビ剤、粘度調整剤、表面張力調整剤、湿潤剤、界面活性剤及び防錆剤、等が挙げられる。
【００９８】
水性インク液は記録用紙に対する濡れ性を良好にするために、２０℃において、通常、２５〜６０ｍＮ／ｍ、好ましくは３０〜５０ｍＮ／ｍの範囲内の表面張力を有するのが好ましい。上記インクのｐＨは、好ましくは５〜１０であり、特に好ましくは６〜９である。
【００９９】
【実施例】
以下、本発明の効果について実施例を挙げて説明するが、本発明はこれらの例に限定されるものではない。なお、実施例中に記載の「％」は、特に断りのない限り質量％を表す。
【０１００】
《電離放射線により架橋される親水性高分子化合物の調製》
特開２０００−１８１０６２号公報の実施例に記載の方法に従って、重合度２５００、ケン化度８８％のポリビニルアルコールにｐ−（３−メタクリロキシ−２−ヒドロキシプロピルオキシ）ベンズアルデヒドを反応させ、下記式（６）の構造を有する紫外線重合型ポリビニルアルコール誘導体１（架橋基変性率１ｍｏｌ％、固形分濃度１０％）の水溶液を調製した。
【０１０１】
【化５】

【０１０２】
同様にして、重合度が３００、１０００の樹脂溶液を調製した。また、前記式（４）で示されるスチリルピリジニウム基を導入した紫外線重合型ポリビニルアルコール誘導体２（架橋基変性率１ｍｏｌ％、固形分濃度１０％）の水溶液も同様にして調製した。
【０１０３】
《記録用紙の作製》
〔記録用紙１の作製〕
高速攪拌分散機を用いて、硝酸でｐＨを４．０に調整した１％エタノール水溶液７００ｍｌ中に、平均一次粒子径が１２ｎｍでＢＥＴ法により測定した比表面積が２００ｍ^２／ｇの気相法シリカを２００ｇ徐々に加えて分散した。ここへ５質量％硼酸水溶液を７０ｇ、及び上記調製した紫外線重合型ポリビニルアルコール誘導体２の１０％水溶液３３０ｇを撹拌しながら徐々に添加した。次いで、サンドミルで分散液中のシリカ微粒子の平均二次粒子径が０．４μｍ以下になるまで分散し、最後に純水で１８００ｇに仕上げ塗布液を得た。なお、分散液中での無機微粒子の平均粒子径は、分散液を５０倍に希釈し動的光散乱方式粒子径測定装置ゼータサイザー１０００ＨＢ（マルバーン社製）を用いて測定した値である。
【０１０４】
上記調製した塗布液を、厚さ１７０ｇ／ｍ^２の原紙の両面をポリエチレンで被覆したポリエチレンコート紙（インク吸収層側のポリエチレン中の８質量％のアナターゼ型酸化チタン含有；インク吸収層面側に０．０５ｇ／ｍ^２のゼラチン下引き層、反対側にＴｇが約８０℃のラテックス性ポリマーをバック層０．２ｇ／ｍ^２として有する）に、４０℃にてバーコーターにより湿潤膜厚１６０μｍで塗布し、その後３６５ｎｍに主波長を持つメタルハライドランプで、エネルギー量７０ｍＪ／ｃｍ^２の紫外線を照射し、その後８０℃の熱風型オーブンで乾燥させてインクジェット記録紙１を得た。なお、記録用紙の表面を電子顕微鏡で観察して求めた平均粒子径と、電離放射線により架橋する親水性高分子化合物に対する無機微粒子の質量比（無機微粒子／電離放射線により架橋する親水性高分子化合物）をＰ／Ｂとして表１に示す。
【０１０５】
〔記録用紙２の作製〕
高速攪拌分散機を用いて、硝酸でｐＨを４．０に調整した１％エタノール水溶液６００ｍｌ中に、平均一次粒子径が１２ｎｍでＢＥＴ法により測定した比表面積が２００ｍ^２／ｇの気相法シリカを２００ｇ徐々に加えて分散した。次いで、この液に５質量％硼酸水溶液を７０ｇ、および下記カチオン性ポリマー（１）の２５％水溶液８５ｇを加え、更にサンドミルで分散液中の無機微粒子の平均粒子径が０．４μｍ未満になるように分散し、最後に純水を加えて１０００ｇに仕上げた。
【０１０６】
【化６】

【０１０７】
この分散液を、４０℃で攪拌しながら上記調製した紫外線重合型ポリビニルアルコール誘導体１の１０％水溶液３３０ｇと光重合開始剤（日本化薬製 カヤキュアＱＴＸ）０．５ｇとを攪拌しながら徐々に添加し、純水で１８００ｇに仕上げて塗布液を調製した。この塗布液を記録用紙１と同様にして塗布、乾燥して記録用紙２を作製した。
【０１０８】
〔記録用紙３〜６の作製〕
記録用紙２の作製において、紫外線重合型ポリビニルアルコール誘導体１の重合度、Ｐ／Ｂを表１に記載の様に変更した以外は同様にして、記録用紙３〜６を作製した。
【０１０９】
〔記録用紙７の作製〕
高速攪拌分散機を用いて、硝酸でｐＨを４．０に調整した１％エタノール水溶液６５０ｍｌ中に、平均一次粒子径が１２ｎｍでＢＥＴ法により測定した比表面積が２００ｍ^２／ｇの気相法シリカを２００ｇ徐々に加えて分散した。次いで、この液にカチオン性ポリマー（１）の２５％水溶液８５ｇを加え、更にサンドミルで分散液中の無機微粒子の平均粒子径が０．４μｍ未満になるように分散し、最後に純水を加えて１０００ｇに仕上げた。
【０１１０】
この分散液を４０℃で攪拌しながら紫外線重合型ポリビニルアルコール誘導体１の１０％水溶液３３０ｇと光重合開始剤（日本化薬製 カヤキュアＱＴＸ）０．５ｇ、および架橋剤としてエチレングリコールジグリシジルエーテル１．５ｇとを攪拌しながら徐々に添加し、純水で１８００ｇに仕上げて塗布液を調製した。この塗布液を記録用紙１と同様にして塗布、乾燥して、記録用紙７を作製した。
【０１１１】
〔記録用紙８の作製〕
上記記録用紙７の作製において、エチレングリコールジグリシジルエーテル１．５ｇを、グリオキザール１．０ｇに変更した以外は同様にして、記録用紙８を作製した。
【０１１２】
〔記録用紙９の作製〕
前記記録用紙７の作製において、エチレングリコールジグリシジルエーテル１．５ｇを、５％の２，４−ジクロロ−４−ヒドロキシ−１，３，５−ｓ−トリアジン４０ｇに変更した以外は同様にして、記録用紙９を作製した。
【０１１３】
〔記録用紙１０の作製〕
前記記録用紙７の作製において、エチレングリコールジグリシジルエーテル１．５ｇを、５％のビスビニルスルホニルメチルエーテル３５ｇに変更した以外は同様にして、記録用紙１０を作製した。
【０１１４】
〔記録用紙１１の作製〕
高速攪拌分散機を用いて、硝酸でｐＨを４．０に調整した１％エタノール水溶液６５０ｍｌ中に、気相法アルミナ（平均一次粒子径１３ｎｍ、ＢＥＴ法により測定した比表面積１００ｍ^２／ｇ）２００ｇを徐々に加え、次いでこの液に５質量％硼酸水溶液を５０ｇ加えて分散した。その後、更にサンドミルで分散液中の無機微粒子の平均粒子径が０．４μｍ未満になるように分散し、最後に純水を加えて１０００ｇに仕上げた。
【０１１５】
この分散液を４０℃で攪拌しながら紫外線重合型ポリビニルアルコール誘導体１の１０％水溶液２５０ｇと光重合開始剤（日本化薬製 カヤキュアＱＴＸ）０．４ｇとを攪拌しながら徐々に添加し、純水で１８００ｇに仕上げて塗布液を調製した。この塗布液を記録用紙１と同様にして塗布、乾燥して、記録用紙１１を作製した。
【０１１６】
〔記録用紙１２の作製〕
高速攪拌分散機を用いて、硝酸でｐＨを４．０に調整した１％エタノール水溶液７００ｍｌ中に、気相法アルミナ（平均一次粒子径１３ｎｍ、ＢＥＴ法により測定した比表面積１００ｍ^２／ｇ）２００ｇを徐々に加えて分散した。その後、更にサンドミルで分散液中の無機微粒子の平均粒子径が０．４μｍ未満になるように分散し、最後に純水を加えて１０００ｇに仕上げた。
【０１１７】
この分散液を４０℃で攪拌しながら紫外線重合型ポリビニルアルコール誘導体１の１０％水溶液３３０ｇと光重合開始剤（日本化薬製 カヤキュアＱＴＸ）０．４ｇ、及びエチレングリコールジグリシジルエーテル１．５ｇとを攪拌しながら徐々に添加し、純水で１８００ｇに仕上げて塗布液を調製した。この塗布液を記録用紙１と同様にして塗布、乾燥して、記録用紙１２を作製した。
【０１１８】
〔記録用紙１３、１４の作製〕
記録用紙１１及び１２の作製において、気相法アルミナに代えてアルミナ水和物である疑ベーマイト（０．０１×０．１μｍの針状の一次粒子、ＢＥＴ法により測定した比表面積２５０ｍ^２／ｇ）を用いた以外は同様にして、記録用紙１３及び１４を作製した。
【０１１９】
〔記録用紙１５の作製〕
前記記録用紙２の作製において、気相法シリカを同質量のゲル法湿式シリカ（平均一次粒子径１０ｎｍ、比表面積２００ｍ^２／ｇ）に変更した以外は同様にして記録用紙１５を作製した。
【０１２０】
〔記録用紙１６の作製〕
前記記録用紙１５の作製において、分散液中の無機微粒子の平均粒子径を０．４μｍ以上になるようにサンドミルの分散条件を適宜変更した以外は同様にして記録用紙１６を作製した。
【０１２１】
〔記録用紙１７の作製〕
高速攪拌分散機を用いて、硝酸でｐＨを４．０に調整した１％エタノール水溶液６５０ｍｌ中に、平均一次粒子径が１２ｎｍでＢＥＴ法により測定した比表面積が２００ｍ^２／ｇの気相法シリカ２００ｇを徐々に加えて分散した。次いで、この液にカチオン性ポリマー（１）の２５％水溶液８５ｇを加え、更にサンドミルで分散液中の無機微粒子の平均粒子径が０．４μｍ未満になるように分散し、最後に純水を加えて１０００ｇに仕上げた。
【０１２２】
この分散液を４０℃で攪拌しながら、紫外線重合型ポリビニルアルコール誘導体１の１０％水溶液３３０ｇと光重合開始剤（日本化薬製 カヤキュアＱＴＸ）０．５ｇを攪拌しながら徐々に添加し、純水で１８００ｇに仕上げて塗布液を調製した。この塗布液を記録用紙１と同様にして塗布、乾燥した。この記録用紙の１ｍ^２あたりの吸水量は２０ｍｌであった。
【０１２３】
次いで、この記録用紙に、２％の硼酸水溶液を、常法に従ってオーバーコート及び乾燥して、記録用紙１７を作製した。
【０１２４】
〔記録用紙１８の作製〕
上記記録用紙１７の作製において、２％の硼酸水溶液に代えて、ヘキサメチレンジイソシアネートの５％酢酸エチル溶液を用いてオーバーコートした以外は同様にして、記録用紙１８を作製した。
【０１２５】
〔記録用紙１９の作製〕
上記記録用紙１７の作製において、２％の硼酸水溶液に代えて、エチレングリコールジグリシジルエーテルの１．２％水溶液を用いてオーバーコートした以外は同様にして、記録用紙１９を作製した。
【０１２６】
（記録用紙−２０の作成）
高速攪拌分散機を用いて、硝酸でｐＨを４．０に調整した１％エタノール水溶液６５０ｍｌ中に、平均一次粒子径が１２ｎｍでＢＥＴ法により測定した比表面積が２００ｍ^２／ｇの気相法シリカを２００ｇ徐々に加えて分散した。次いで、この液にカチオン性ポリマー（１）の２５％水溶液８５ｇを加え、更にサンドミルで分散液中の無機微粒子の平均粒子径が０．４μｍ未満になるように分散し、最後に純水を加えて１０００ｇに仕上げた。
【０１２７】
この分散液を４０℃で攪拌しながら、紫外線重合型ポリビニルアルコール誘導体１の１０％水溶液３３０ｇと光重合開始剤（日本化薬製 カヤキュアＱＴＸ）０．５ｇを攪拌しながら徐々に添加し、純水で１８００ｇに仕上げて塗布液を調製した。この塗布液を記録用紙１と同様に塗布、乾燥して記録用紙２０を作製した。
【０１２８】
〔記録用紙２１の作製〕
前記記録用紙２の作製において、紫外線重合型ポリビニルアルコール誘導体１に代えて、未変性のポリビニルアルコール（重合度２５００、ケン化度８８％）を用いた以外は同様にして、記録用紙２１を作製した。
【０１２９】
以上の様にして作製した記録用紙１〜２１の詳細を以下に示す。
なお、表１に記載の架橋剤の略称の詳細は、以下の通りである。
【０１３０】
＊Ａ：エチレングリコールジグリシジルエーテル
＊Ｂ：グリオキザール
＊Ｃ：２，４−ジクロロ−４−ヒドロキシ−１，３，５−ｓ−トリアジン
＊Ｄ：ビスビニルスルホニルメチルエーテル
＊Ｅ：ヘキサメチレンジイソシアネート
【０１３１】
【表１】

【０１３２】
《記録用紙の各特性の評価》
以上により作製した各記録用紙について、以下に記載の方法により各評価を行った。
【０１３３】
〔平滑性の評価〕
上記作製した各記録用紙のインク吸収層面を、ＪＩＳ Ｂ ０６０１に規定される方法に準じて、中心線表面粗さ（いずれも基準長２．５ｍｍ、カットオフ値０．８ｍｍで測定した）を求め、下記の基準に則り平滑性の評価を行った。
【０１３４】
◎：中心線表面粗さＲａが１．０μｍ未満であり、美観を損なわない
○：中心線表面粗さＲａが１．０〜１．５μｍ未満であり、美観を損なうことはない
△：中心線表面粗さＲａが１．５μｍ以上で、やや美観を損なっている
×：目視評価で塗膜全面にひび割れ多発し、実用上使用に耐えない
〔光沢度の評価〕
日本電色工業株式会社製の変角光沢度計（ＶＧＳ−１００１ＤＰ）を用いて７５度光沢を測定した。
【０１３５】
◎：光沢度が５５％以上
○：光沢度が５０％以上５５％未満
△：光沢度が４５％以上５０％未満
×：光沢度が４５％未満
〔ひび割れ耐性の評価〕
上記作製した各記録用紙のインク吸収層表面をルーペ観察し、１００ｃｍ^２中に発生している膜面のひび割れ個数をカウントして、これをひび割れ耐性の尺度とし、下記に記載の基準に則り評価を行った。
【０１３６】
◎：ひび割れの発生個数が０〜３個
○：ひび割れの発生個数が４〜１０個
△：ひび割れの発生個数が１１〜２０個
×：ひび割れの発生個数が２１個以上
〔インク吸収性の評価〕
セイコーエプソン社製インクジェットプリンター・ＰＭ３０００Ｃで緑色のベタ印字を行い、画像部分のマダラの発生を目視観察し、下記の評価基準に則りインク吸収性の評価を行った。インク吸収速度が遅い場合、マダラの発生が大きくなる。
【０１３７】
◎：マダラの発生が全くなし
○：画像面を注視すると、わずかにマダラが認められる
△：画像面から２０ｃｍ離れて観察してもマダラが認められる
×：画像面から４０ｃｍ離れて観察してもマダラが認められる
以上により得られた結果を、表２に示す。
【０１３８】
【表２】

【０１３９】
表２より明らかなように、本発明の記録用紙は、平滑性、インク吸収性及び光沢性を同時に満足し、加えて、塗布乾燥時にひび割れが発生しにくいことがわかる。一方比較例の記録用紙は、インク吸収性に劣っていたり、あるいは乾燥時にひび割れてしまい生産適性に劣っているなどいずれかの性能を欠くものであった。
【０１４０】
【発明の効果】
本発明により、平滑性、光沢、ひび割れ耐性及びインク吸収性に優れた多孔質インク吸収層を有する高光沢なインクジェット記録用紙とその製造方法を提供することができた。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet recording paper (hereinafter also simply referred to as a recording paper) and a method for producing the same, and more particularly to an ink jet recording paper having good ink absorbability and excellent gloss, smoothness and crack resistance, and a method for producing the same. Is.
[0002]
[Prior art]
In recent years, in the ink jet recording system, image quality has been improved rapidly, and the image quality is approaching that of silver halide photography. As a means for achieving such a silver salt photographic image quality by the ink jet recording method, rapid technical improvement is also being made on the ink jet recording paper to be used.
[0003]
In general, as an ink absorbing layer used in ink jet recording paper, for example, ink jet recording in which a hydrophilic resin such as gelatin or polyvinyl alcohol is applied as an ink absorbing layer on a support having high smoothness to form an ink absorbing layer. The paper is known. This type of recording paper is a method of absorbing ink by utilizing the swelling property of resin, and is called a swelling type ink jet recording paper.
[0004]
This swelling type ink absorbing layer has a water-soluble resin as a constituent resin, so that it is difficult to dry the ink after printing, the image and film are weak against moisture and poor in water resistance, and the resin swells. Ink absorbs slowly, and the printing surface does not dry for a while after printing, which makes it unsuitable for high-speed printing.
[0005]
For swelling type ink jet recording paper that absorbs ink by utilizing the swelling property of the water-based resin, inorganic fine particles and a relatively small amount of hydrophilic resin (also called hydrophilic binder) are used, and voids are formed between the inorganic fine particles. There is an ink jet recording paper having an ink absorption layer made of a porous layer having a high porosity with the formation of. A void-type inkjet recording paper provided with such a porous layer having a minute void as an ink absorbing layer has a relatively high ink absorbability and quick-drying property, and is the closest to the silver salt photographic image quality. One of the obtained methods.
[0006]
In particular, when a non-absorbent support is used as the support, there is no cockling (wrinkle) after printing as seen in a water-absorbing support, and there is an advantage that a highly smooth surface can be maintained. Can be obtained.
[0007]
In the case of recording paper using such a non-absorbing support, since it is necessary to absorb all of the ink ejected from the printer with the ink absorbing layer, a large amount of coating is required for the ink absorbing layer. In many cases, the coating film was relatively thick.
[0008]
In general, as a method of applying and drying a coating solution on a support, there are methods of drying by applying hot air to the surface of the coated coating solution, or heating and drying with infrared rays or the like. However, when a thick film is applied as described above, convection due to the wind pressure of the hot air or the heat of the coating liquid occurs, and the coating liquid flows and the coating layer becomes non-uniform, or the coating layer is applied due to drying shrinkage stress. Cracks, so-called cracks, sometimes occurred in the layer.
[0009]
As one of the methods for solving the above problem, there is a method in which the coating layer is thickened and gelled before the drying step and then dried, for example, a coating solution mainly composed of gelatin is applied to the upper layer, A method of drying after cooling to gel is disclosed (for example, see Patent Document 1). Further, a method is disclosed in which a coating liquid composed of polyvinyl alcohol, inorganic fine particles, and boric acid is applied, cooled and gelled, and then dried (see, for example, Patent Document 2). However, these gelation methods are thermoreversible gelation, and when the coating solution becomes high temperature, the gelation is relaxed and fluidized, so it cannot be dried at a high temperature, and can be dried only at a temperature below 60 ° C. at most. There wasn't. Therefore, the drying process at the time of production takes time, and has the subject that cost increases.
[0010]
Furthermore, crosslinking agents such as those generally used for hydrophilic resins used in inkjet recording paper other than boric acid, such as epoxy compounds, aldehyde compounds, active halogen compounds, active vinyl compounds, etc. Since the crosslinking resin is poor, the concentration of the hydrophilic resin is low in the coating liquid state, so that the crosslinking reaction hardly proceeds and the crosslinking is not performed until the hydrophilic resin is concentrated and close in the process of drying the coating liquid. The reaction often proceeds. Therefore, many of these compounds did not lead to crosslinking or gelation even when applied before the drying step.
[0011]
On the other hand, as a method for gelling the coating layer before drying, a step of applying a coating liquid mainly composed of an inorganic sol and an ionizing radiation curable monomer / oligomer and then curing the compound by irradiating with ionizing radiation. After that, a method of drying the coating film to form an ink absorption layer has been proposed (see, for example, Patent Document 3).
[0012]
Certainly, gelation by this method is not thermoreversible and can be dried at high temperatures. However, in general, ionizing radiation curable monomers / oligomers have a relatively low molecular weight and are strongly irritating to the skin, and there are concerns about adverse effects on the quality of printed images due to unreacted components and safety. There were many drawbacks. Furthermore, most of the compounds on the market have low hydrophilicity and are unsuitable for many of the aqueous coating solutions used for forming the ink jet receiving layer, and the selection range of the compounds is naturally extremely narrow. There was also.
[0013]
Also, recent ink jet printers have increased in speed and definition, and depending on printing conditions and printed images, ink absorption does not follow the ink discharge amount and speed even on gap-type ink jet recording paper. There are also problems such as overflow and mottled factors, and further improvement in ink absorbency is demanded.
[0014]
[Patent Document 1]
JP-A-9-156202 (Claims)
[0015]
[Patent Document 2]
JP-A-10-175364 (Example)
[0016]
[Patent Document 3]
JP-A-9-263038 (Claims)
[0017]
[Problems to be solved by the invention]
An object of the present invention is to provide a highly glossy ink jet recording paper having a porous ink absorbing layer excellent in smoothness, gloss, crack resistance and ink absorbability, and a method for producing the same.
[0018]
[Means for Solving the Problems]
As a result of intensive studies on the above problems, the present inventors have made use of a hydrophilic polymer compound and inorganic fine particles that are cross-linked by ionizing radiation, and enable high-temperature and high-speed drying by gelling before the drying step. The present inventors have found that a high gloss inkjet recording paper having a porous ink absorbing layer with improved smoothness, gloss, crack resistance and ink absorbability and a method for producing the same can be realized by using an agent together.
[0019]
That is, the said subject is achieved by the following structure.
1. In an inkjet recording paper having a porous layer containing a hydrophilic polymer compound that is crosslinked by ionizing radiation and inorganic fine particles on a support, the hydrophilic polymer compound that is crosslinked by ionizing radiation is further crosslinked by a crosslinking agent. An ink jet recording paper characterized by being made.
[0020]
2. 2. The crosslinking agent according to item 1, wherein the crosslinking agent is at least one selected from boric acid or a salt thereof, an epoxy compound, an isocyanate compound, an aldehyde compound, an active halogen compound, and an active vinyl compound. Inkjet recording paper.
[0021]
3. 3. The inkjet according to 1 or 2, wherein a mass ratio (P / B) of the inorganic fine particles (P) to the hydrophilic polymer compound (B) crosslinked by the ionizing radiation is 3 to 50. 4. Recording sheet.
[0022]
4). 4. The inkjet recording paper according to any one of 1 to 3, wherein the inorganic fine particles are silica, alumina, or alumina hydrate having an average particle diameter of 0.005 to 0.4 μm.
[0023]
5. The inkjet recording paper according to any one of 1 to 4, wherein the hydrophilic polymer compound that is cross-linked by the ionizing radiation is a nonionic compound.
[0024]
6). 6. The hydrophilic polymer compound that is cross-linked by ionizing radiation is a polyvinyl acetate saponified product having a structural unit represented by the general formula (1), according to any one of 1 to 5 above. Inkjet recording paper.
[0025]
7). 7. The inkjet recording paper as described in 6 above, wherein the polymerization degree of the polyvinyl acetate saponified product is 400 to 5000.
[0026]
8). 8. The inkjet recording paper according to any one of 1 to 7 above, which contains at least one water-soluble photopolymerization initiator.
[0027]
9. 9. The ink jet recording paper according to any one of 1 to 8, wherein the support is a non-absorbent support.
[0028]
10. 10. A method for producing the ink jet recording paper according to any one of 1 to 9, wherein a hydrophilic polymer compound, an inorganic fine particle, and a cross-linking agent having a structure in which cross-linking is formed by ionizing radiation on a support. A method for producing an ink jet recording paper, comprising: applying a coating liquid containing the composition, and then drying to produce.
[0029]
11. 10. A method for producing an ink jet recording paper according to any one of items 1 to 9, wherein the coating comprises a hydrophilic polymer compound having a structure that is crosslinked by ionizing radiation and inorganic fine particles on a support. An ink jet recording paper characterized by forming a porous layer by coating a liquid, supplying a coating liquid containing a cross-linking agent onto the porous layer simultaneously with or after the coating, and then drying to produce Manufacturing method.
[0030]
Hereinafter, the present invention will be described in detail.
The polymer compound that is cross-linked by water-soluble ionizing radiation used in the porous layer (hereinafter also referred to as ink absorbing layer) according to the present invention is crosslinked by irradiation with ionizing radiation such as ultraviolet rays and electron beams. A water-soluble polymer compound that reacts and is water-soluble before the cross-linking reaction but becomes substantially water-insoluble after the cross-linking reaction. This polymer compound remains hydrophilic after the cross-linking reaction. And maintains a sufficient affinity for ink.
[0031]
Such polymer compounds include saponified polyvinyl acetate, polyvinyl acetal, polyethylene oxide, polyalkylene oxide, polyvinyl pyrrolidone, polyacrylamide, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose and other hydrophilic resins, or derivatives thereof. , As well as at least one selected from the group consisting of these copolymers, or a hydrophilic resin such as a photodimerization type, a photodecomposition type, a photopolymerization type, a photomodification type, or a photodepolymerization type It is modified by a group. Among these, a resin modified with a photodimerization type or photopolymerization type modification group is preferable from the viewpoint of sensitivity or stability of the resin itself.
[0032]
As the photodimerization-type modifying group, those having a diazo group, a cinnamoyl group, a styrylpyridinium group, or a stilquinolium group introduced are preferable, and a resin that is dyed with a water-soluble dye such as an anionic dye after photodimerization is preferable. Examples of such a resin include resins having a cationic group such as a primary amino group or a quaternary ammonium group, such as JP-A-62-283339, JP-A-1-198615, and JP-A-60-252341. No., JP-A 56-67309, JP-A 60-129742, etc., photosensitive resins (compositions), and after curing, become cationic after curing such as an azide group that becomes an amino group Resins, for example, photosensitive resins (compositions) described in JP-A-56-67309 and the like, and specific examples thereof include the following compounds.
[0033]
The photosensitive resin described in JP-A-56-67309 contains a polyvinyl alcohol structure,
[0034]
[Chemical formula 2]

[0035]
2-azido-5-nitrophenylcarbonyloxyethylene structure represented by:
[0036]
[Chemical Formula 3]

[0037]
It is a resin composition which has 4-azido-3-nitrophenyl carbonyloxyethylene structure represented by these.
[0038]
Specific examples of the photosensitive resin are described in Examples 1 and 2 in the official gazette, and the constituent components and usage ratio of the photosensitive resin are described on page 2 of the official gazette.
[0039]
JP-A-60-129742 discloses a polyvinyl alcohol structure as a photosensitive resin.
[0040]
[Formula 4]

[0041]
The resin composition which has the following structure is mentioned.
In the present invention, among the hydrophilic polymer compounds that are cross-linked by ionizing radiation, the photopolymerizable modifying group is represented by, for example, the general formula (1) disclosed in JP-A No. 2000-181062. A saponified polyvinyl acetate having a structural unit is preferred from the viewpoint of reactivity.
[0042]
In the hydrophilic polymer compound according to the present invention, the degree of polymerization and the crosslink density affect the strength and flexibility at the time of film formation. If the degree of polymerization is too low or there are too many crosslinkable groups, cracking and drying during coating and drying will occur. Failure such as breakage of the paint film will occur. Therefore, in the hydrophilic polymer compound containing the polyvinyl saponified product having the structural unit represented by the general formula (1), the degree of polymerization is preferably 400 to 5000, more preferably 1000 to 4000. preferable. Moreover, it is preferable that the modification | denaturation rate of the ionizing radiation reaction crosslinking group with respect to a segment is 4 mol% or less, More preferably, it is 0.01-1 mol%.
[0043]
In addition, in this invention, you may use together a conventionally well-known hydrophilic resin in the range which does not impair the objective effect of this invention. Examples of known hydrophilic resins include gelatin, polyvinyl pyrrolidone, pullulan, polyvinyl alcohol or derivatives thereof, polyethylene glycol, hydroxyethyl cellulose, dextran, dextrin, water-soluble polyvinyl butyral, and the like.
[0044]
In the present invention, it is also preferable to add a photopolymerization initiator or a sensitizer. These compounds may be dissolved or dispersed in a solvent, or may be chemically bonded to the photosensitive resin.
[0045]
There is no restriction | limiting in particular about the photoinitiator applied and a photosensitizer, A conventionally well-known thing can be used, For example, a benzophenone, a hydroxybenzophenone, bis-N, N- dimethylamino benzophenone, bis-N, N -Benzophenones such as diethylaminobenzophenone and 4-methoxy-4'-dimethylaminobenzophenone. Thioxanthones such as thioxatone, 2,4-diethylthioxanthone, isopropylthioxanthone, chlorothioxanthone, and isopropoxychlorothioxanthone. Anthraquinones such as ethyl anthraquinone, benzanthraquinone, aminoanthraquinone and chloroanthraquinone. Acetophenones. Benzoin ethers such as benzoin methyl ether. 2,4,6-trihalomethyltriazines, 1-hydroxycyclohexyl phenyl ketone, 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 2- (o-chlorophenyl) -4,5-di ( m-methoxyphenyl) imidazole dimer, 2- (o-fluorophenyl) -4,5-phenylimidazole dimer, 2- (o-methoxyphenyl) -4,5-phenylimidazole dimer, 2- (P-methoxyphenyl) -4,5-diphenylimidazole dimer, 2, -di (p-methoxyphenyl) -5-phenylimidazole dimer, 2- (2,4-dimethoxyphenyl) -4,5 -2,4,5-triarylimidazole dimer of diphenylimidazole dimer, benzyldimethyl ketal, 2-benzyl-2-dimethyl Amino-1- (4-morpholinophenyl) -butan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-1-propanone, 2-hydroxy-2-methyl-1- Phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, phenanthrenequinone, 9,10-phenanthrenequinone Benzoins such as methylbenzoin and ethylbenzoin, 9-phenylacridine, acridine derivatives such as 1,7-bis (9,9′-acridinyl) heptane, bisacylphosphine oxide, and mixtures thereof, etc. May be used alone or in combination.
[0046]
In the ink jet recording paper of the present invention, it is particularly preferable to use a water-soluble photopolymerization initiator from the viewpoint of excellent mixing property and crosslinking efficiency, for example, water-soluble 1- [4- (2-hydroxyethoxy). -Phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 4- (2-hydroxyethoxy) -phenyl. (2.hydroxy-2-propyl) ketone, thioxanthone ammonium salt, benzophenone ammonium salt, etc. And water-soluble photopolymerization initiators.
[0047]
In addition to these photopolymerization initiators, polymerization accelerators and the like can also be added. Examples of these include ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, ethanolamine, diethanolamine, triethanolamine and the like.
[0048]
Next, the crosslinking agent used in the present invention will be described.
In a recording sheet having an ink absorption layer having a porous void structure, the ink absorption (fast drying) tends to be faster as the ink absorption layer is cross-linked. This is because, in a recording paper having an ink absorbing layer having a void structure, the swelling property of the hydrophilic resin forming the void structure is further suppressed, so that the upper part of the ink absorbing layer (that is, more on the surface). This is probably because the ink penetration inhibition due to the swelling of the hydrophilic resin is suppressed on the near side.
[0049]
Therefore, in an ink jet recording sheet having an ink absorbing layer having a void structure, the ink absorbability increases as the ink absorbing layer is cross-linked, and the water resistance of the film can be improved.
[0050]
However, in the inkjet recording paper having a hydrophilic polymer compound that is crosslinked by ionizing radiation and a porous layer containing inorganic fine particles of the present invention, the hydrophilic polymer compound that is crosslinked by ionizing radiation is in a state where the coating liquid is wet. Crosslinks with ionizing radiation to form a three-dimensional network that gels, and after drying, the three-dimensional network is folded and appears to have a void structure due to interaction with inorganic fine particles. . In this state, when the ink reaches the upper part of the ink absorption layer (that is, the side closer to the surface) during printing, the folded three-dimensional network expands again and swells, and the void structure becomes a hydrophilic polymer compound. Therefore, increasing the number of crosslinks by ionizing radiation is not very effective for ink absorption.
[0051]
Therefore, by adding crosslinking with a crosslinking agent to inkjet recording paper having a porous layer containing a hydrophilic polymer compound and inorganic fine particles that are crosslinked by ionizing radiation, productivity is improved by high-temperature drying and high ink absorbency. It was found that both can be achieved.
[0052]
The cross-linking agent used in the present invention may be used in combination with a conventionally known cross-linking agent, and the type of the cross-linking agent is appropriately selected according to the type of the hydrophilic polymer compound, but is dried and concentrated. Those in which the crosslinking reaction proceeds in a state are preferred, and more preferred is at least one selected from boric acid or a salt thereof, an epoxy compound, an isocyanate compound, an aldehyde compound, an active halogen compound, and an active vinyl compound.
[0053]
Specific examples of the crosslinking agent include, for example, epoxy compounds (diglycidyl ethyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidyl cyclohexane, N, N-diglycidyl-4 -Glycidyloxyaniline, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, etc.), isocyanate compounds (hexamethylene diisocyanate, aromatic polyisocyanate, tolylene diisocyanate, trimethylolpropane-tolylene diisocyanate adduct, methylene bis-4-phenyl Methane triisocyanate and methylenebisisophorone diisocyanate ketoxime block products) Aldehyde compounds (formaldehyde, glyoxal, etc.) Active halogen compounds (2,4-dichloro-4-hydroxy-1,3,5-s-triazine, etc.), active vinyl compounds (1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonyl) Methyl ether, etc.), boric acid and its salts.
[0054]
The preferred amount of the crosslinking agent varies depending on the type of hydrophilic polymer compound, the type of crosslinking agent, the type of inorganic fine particles, the ratio to the hydrophilic polymer compound, etc., but is generally 5 to 5 g per 1 g of the hydrophilic polymer compound. 500 mg, more preferably 10 to 400 mg.
[0055]
As a method for supplying the crosslinking agent, when the coating liquid constituting the void layer is applied, it may be added in the coating liquid for forming the void layer and / or in the coating liquid for forming another layer adjacent to the void layer. Good. Alternatively, on the support on which a coating solution containing a crosslinking agent has been applied in advance, the coating solution for forming the void layer is coated, or further, simultaneously with the coating of the coating solution not containing the crosslinking agent for forming the void layer. Alternatively, it may be supplied by overcoating a solution dissolved in an organic solvent such as an aqueous solution of a cross-linking agent or an alcohol, and drying, before starting drying after coating or during drying. As another method for applying a cross-linking agent, a coating solution for forming an ink absorbing layer is applied, and after completion of drying, a solution obtained by dissolving an aqueous solution of the cross-linking agent or an organic solvent such as alcohol on the ink absorbing layer. You may supply by overcoating and drying. As the overcoat method, a crosslinking agent or a crosslinking agent solution may be applied, sprayed, or immersed in the crosslinking agent or the crosslinking agent solution.
[0056]
The ink absorption layer having a void structure according to the present invention contains inorganic fine particles.
Examples of inorganic fine particles used in the ink absorbing layer include light calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, hydrotal Site, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, boehmite, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, magnesium hydroxide and the like.
[0057]
These inorganic fine particles may be used in a state of being uniformly dispersed as primary particles, or may be used in a state of being dispersed by forming secondary agglomerated particles.
[0058]
The average particle size of the inorganic fine particles is preferably 0.005 to 0.4 μm from the viewpoint of gloss of the ink absorbing layer. The average particle size of the inorganic fine particles referred to here is obtained as a simple average value (number average value) by observing the cross section and surface of the void layer with a scanning electron microscope and determining the particle size of a plurality of arbitrary particles. Can do. Here, each particle size is represented by a diameter assuming a circle equal to the projected area.
[0059]
In the present invention, silica, alumina or alumina hydrate having an average particle diameter of 0.005 to 0.4 μm is preferable from the viewpoint of forming fine voids in particular, and particularly the glossiness of the ink absorbing layer of ink jet recording paper. Silica or alumina synthesized by a gas phase method having an average particle diameter of 0.01 to 0.4 μm and pseudoboehmite which is an alumina hydrate are preferable.
[0060]
The amount of inorganic fine particles used in the ink absorption layer depends on the type of inorganic fine particles, but it is 1 m of inkjet recording paper.²Usually, it is 5-30 g, preferably 10-25 g.
[0061]
In the porous layer according to the present invention, the ratio (P / B) of the inorganic fine particles (P) to the hydrophilic polymer compound (B) is preferably 3 to 50 times in mass ratio. When the mass ratio is 3 times or more, the porosity of the porous layer is good, and a sufficient void volume is easily obtained. On the other hand, if this ratio is 50 times or less, it is preferable that cracking hardly occurs when the porous layer is applied as a thick film. The ratio (P / B) of the inorganic fine particles to the particularly preferred hydrophilic polymer compound is 5 to 20 times.
[0062]
The void layer according to the present invention is 15 to 40 ml / m per unit area of the coating film.²It is preferable to have a capacity of The term “capacity” as used herein refers to the volume of bubbles generated when a unit volume of the coating film is put on water, the volume of water that can be absorbed by the coating film, or the recording paper finally obtained. It is defined as the amount of liquid transfer when the contact time is 2 seconds as measured by the liquid absorbency test method (Bristow method) for paper and paperboard specified in TAPPI 51.
[0063]
Various additives may be added to the ink-absorbing layer and the water-soluble coating liquid for forming the ink-absorbing layer according to the present invention. Such additives include, for example, cationic mordants, polyvalent metal compounds, surfactants (for example, cations, nonions, anions, amphoteric surfactants), white background tone adjusters, fluorescent whitening agents, anti-foaming agents as mordants. Examples thereof include glazes, viscosity modifiers, low-boiling organic solvents, high-boiling organic solvents, latex emulsions, anti-fading agents, ultraviolet absorbers, matting agents, and silicone oil.
[0064]
As the cationic mordant, a polymer mordant having a primary to tertiary amino group and a quaternary ammonium base is used, but there is little discoloration or deterioration of light resistance during long-term storage, and the mordant ability of the dye is sufficiently high. Therefore, a polymer mordant having a quaternary ammonium base is preferable. A preferred polymer mordant is obtained as a homopolymer of a monomer having the quaternary ammonium base, a copolymer with another monomer, or a condensation polymer.
[0065]
Examples of the polyvalent metal compound include metal salts such as aluminum, calcium, magnesium, zinc, iron, zirconium, tin, and lead. Of these, compounds composed of magnesium, aluminum, zirconium, calcium and zinc are preferred because they are colorless. Further, a water-soluble inorganic polymer such as polyaluminum chloride may be used as a salt of water-soluble polyvalent metal ions.
[0066]
The use amount of the cationic polymer or the water-soluble polyvalent metal compound is preferably 10% by mass or less, more preferably 8% by mass or less in terms of the mass ratio with respect to the inorganic fine particles, in order to suppress deterioration of ink absorbability. .
[0067]
As a method for adding a cationic polymer or a water-soluble polyvalent metal compound, in addition to a method of directly adding to a coating liquid and coating, a cationic resin or a water-soluble polyvalent metal compound can be added after coating and drying of a recording medium. A method of overcoating with an aqueous solution and drying may also be used.
[0068]
The support used for the ink jet recording paper of the present invention is preferably a non-water-absorbing support from the viewpoint of obtaining a higher quality print.
[0069]
Examples of the non-water-absorbing support preferably used include, for example, polyester film, diacetate film, triatesate film, polyolefin film, acrylic film, polycarbonate film, polyvinyl chloride film, polyimide film, cellophane, Examples thereof include a transparent or opaque film made of a material such as celluloid, or a resin-coated paper in which both surfaces of a base paper are coated with a polyolefin resin or the like, so-called RC paper.
[0070]
In applying the water-soluble coating solution on the support, the surface of the support is subjected to corona discharge treatment, subbing treatment, or the like for the purpose of increasing the adhesive strength between the surface and the coating layer. It is preferable. Further, the inkjet recording paper of the present invention may be a colored support.
[0071]
The support preferably used in the present invention is a transparent polyester film, an opaque polyester film, an opaque polyolefin resin film, and a paper support in which both sides of paper are laminated with a polyolefin resin.
[0072]
Hereinafter, a non-water-absorbing paper support laminated with polyethylene, which is the most preferred polyolefin resin, will be described.
[0073]
The base paper used for the paper support is made from wood pulp as the main raw material, and if necessary, synthetic pulp such as polypropylene or synthetic fibers such as nylon or polyester is added to the wood pulp. As wood pulp, for example, any of LBKP, LBSP, NBKP, NBSP, LDP, NDP, LUKP, NUKP can be used, but more LBKP, NBSP, LBSP, NDP, LDP with more short fibers are used. Is preferred. However, the ratio of LBSP or LDP is preferably 10% by mass or more and 70% by mass or less.
[0074]
The pulp is preferably a chemical pulp (sulfate pulp or sulfite pulp) with few impurities, and a pulp having a whiteness improved by bleaching is also useful.
[0075]
In the base paper, sizing agents such as higher fatty acids and alkyl ketene dimers, white pigments such as calcium carbonate, talc and titanium oxide, paper strength enhancing agents such as starch, polyacrylamide and polyvinyl alcohol, fluorescent whitening agents, polyethylene glycols A water retaining agent such as a dispersant, a softening agent such as a quaternary ammonium, and the like can be appropriately added.
[0076]
The freeness of the pulp used for papermaking is preferably 200 to 500 ml as defined by CSF, and the fiber length after beating is a 24 mesh residual mass% defined by JIS-P-8207, and 42 30-70 mass% of sum with the mass% of a mesh remainder is preferable. In addition, it is preferable that the mass% of 4 mesh remainder is 20 mass% or less.
[0077]
The basis weight of the base paper is preferably 30 to 250 g, particularly preferably 50 to 200 g. The thickness of the base paper is preferably 40 to 250 μm. The base paper can be given a high smoothness by subjecting it to a calendar process at the paper making stage or after paper making. Base paper density is 0.7-1.2g / cm³(In accordance with the method prescribed in JIS-P-8118) is common. Furthermore, the base paper stiffness is preferably 20 to 200 g under the conditions specified in JIS-P-8143. A surface sizing agent may be applied to the surface of the base paper. As the surface sizing agent, the same sizing agents that can be added to the base paper can be used. The pH of the base paper is preferably 5 to 9 when measured by a hot water extraction method defined in JIS-P-8113.
[0078]
The polyethylene covering the front and back surfaces of the base paper is mainly low-density polyethylene (LDPE) or high-density polyethylene (HDPE), but some other LLDPE, polypropylene, etc. can also be used.
[0079]
In addition, the polyethylene layer on the side where the ink absorbing layer is applied is obtained by adding rutile or anatase type titanium oxide to polyethylene and improving opacity and whiteness, as is widely done in photographic paper. Is preferred. The titanium oxide content is 1 to 20% by mass, preferably 2 to 15% by mass, based on polyethylene.
[0080]
Polyethylene-coated paper can be used as glossy paper. Also, when polyethylene is melt-extruded onto the surface of the base paper and coated, so-called typing treatment is used to produce matte surfaces, silks, etc. What formed the fine surface can also be used by this invention.
[0081]
The amount of polyethylene used on the front and back of the base paper is selected so as to optimize the film thickness of the aqueous coating composition, the low humidity after providing the back layer, or the curl under high humidity. The polyethylene layer on the surface side to which the aqueous coating composition is applied is preferably in the range of 20 to 40 μm, and the back layer coating surface side is in the range of 10 to 30 μm.
[0082]
Furthermore, the polyethylene-coated paper support preferably has the following characteristics.
[0083]
1) Tensile strength: strength specified in JIS-P-8113, preferably 20 to 300N in the vertical direction and 10 to 200N in the horizontal direction.
2) Tear strength: 0.1 to 2N in the vertical direction and 0.2 to 2N in the horizontal direction are preferred according to a method defined by JIS-P-8116.
3) Compression modulus: ≧ 1030 N / cm²
4) Surface Beck smoothness: 500 seconds or more is preferable as a glossy surface under the conditions specified in JIS-P-8119, but it may be less than this for so-called molded products.
5) Back surface Beck smoothness: 100 to 800 seconds are preferable under the conditions specified in JIS-P-8119.
6) Opacity: Under the measurement conditions of linear light incidence / diffuse light transmission conditions, the transmittance for light in the visible region is 20% or less, particularly preferably 15% or less.
7) Whiteness: Hunter whiteness specified in JIS-P-8123, preferably 90% or more. In addition, when measured according to JIS-Z-8722 (non-fluorescent) and JIS-Z-8717 (containing fluorescent agent) and displayed by the color display method defined in JIS-Z-8730, L^*= 90-98, a^*= -5 to +5, b^*= -10 to +5 is preferable.
[0084]
An undercoat layer can be provided on the ink absorbing layer surface side of the support for the purpose of improving adhesiveness with the ink absorbing layer. The binder for the undercoat layer is preferably a hydrophilic polymer such as gelatin or polyvinyl alcohol, or a latex polymer having a Tg of −30 to 60 ° C. These binders are 1m of recording paper.²It is used in the range of 0.001 to 2 g per unit. In the undercoat layer, a small amount of a conventionally known antistatic agent such as a cationic polymer can be contained for the purpose of antistatic.
[0085]
A back layer may be provided on the surface of the support opposite to the ink absorbing layer surface for the purpose of improving slipperiness and charging characteristics. The binder for the back layer is preferably a hydrophilic polymer such as gelatin or polyvinyl alcohol, a latex polymer having a Tg of −30 to 60 ° C., an antistatic agent such as a cationic polymer, various surfactants, and an average. A matting agent having a particle size of about 0.5 to 20 μm can also be added. The thickness of the back layer is generally 0.1 to 1 μm, but in the case where the back layer is provided for preventing curling, it is generally in the range of 1 to 20 μm. Further, the back layer may be composed of two or more layers.
[0086]
In the production of the ink jet recording paper of the present invention, the coating method used when coating the ink absorbing layer coating liquid on the support can be appropriately selected from known methods, for example, a gravure coating method, Roll coating method, rod bar coating method, air knife coating method, spray coating method, extrusion coating method, curtain coating method or extrusion coating method using a hopper described in US Pat. No. 2,681,294 is preferably used. It is done.
[0087]
The porous layer according to the recording paper of the present invention may be a single layer or may be composed of two or more layers. When the porous layer is composed of two or more layers, the structures of the ink absorbing layers are the same as each other. Or different. Moreover, when it comprises by two or more layers, it is preferable from a viewpoint of productivity improvement that it is the method of apply | coating all the structural layers simultaneously.
[0088]
In the method for producing an ink jet recording paper of the present invention, a coating solution containing a structure capable of crosslinking a polymer compound and inorganic fine particles by ionizing radiation is applied, and the total solid concentration of the coating layer is 5 to 90%. The coating layer is sometimes gelled by irradiating with ionizing radiation, and then dried. Examples of the ionizing radiation in the present invention include electron beams, ultraviolet rays, α rays, β rays, γ rays, and X-rays. In view of the widespread use of electron beam, ultraviolet rays or ultraviolet rays are preferable.
[0089]
Examples of the electron beam irradiation method include a scanning method, a curtain beam method, and a broad beam method. The curtain beam method is preferable from the viewpoint of processing capability. The acceleration voltage of the electron beam can be changed as appropriate depending on the specific gravity and film thickness of the coating film, but 20 to 300 kV is appropriate. The irradiation amount of the electron beam is preferably in the range of 0.1 to 20 Mrad.
[0090]
As the ultraviolet light source, for example, a low pressure, medium pressure, high pressure mercury lamp, metal halide lamp or the like having an operating pressure of several hundred Pa to about 1 MPa is used, but a high pressure mercury lamp and a metal halide lamp are preferable from the viewpoint of wavelength distribution of the light source. A metal halide lamp is more preferable.
[0091]
Especially when the wavelength of the light source does not include ultraviolet rays of 300 nm or less, or the irradiation energy is 1 J / cm²In the following cases, it is preferable that the base of the ionizing radiation crosslinkable resin or the coexisting additives are not decomposed by the ionizing radiation, and problems such as odor derived from the decomposition product are less likely to occur. The irradiation energy is 1 mJ / cm²The above case is preferable because the effects of the present invention due to high crosslinking efficiency are sufficiently exhibited. Therefore, it is preferable to provide a filter that cuts light having a wavelength of 300 nm or less as the light source. In the present invention, the irradiation energy is 1 mJ / cm.²~ 1J / cm²Preferably, 50 mJ / cm²~ 100mJ / cm²It is more preferable that
[0092]
Illuminance is 1mW / cm²~ 1W / cm²Is preferred. Illuminance is 1 W / cm²If it is the following, the surface curability of the coating film is improved, and a film that is uniformly cross-linked and cured to the deep part can be obtained. Also, the illuminance is 1mW / cm²The above is preferable because non-uniform cross-linking due to scattering in the film can be avoided and the effects of the present invention can be obtained.
[0093]
Same integrated light intensity (mJ / cm²), The preferable range of illuminance is due to the change in the light transmittance. Concentration distribution of the generated cross-linked reactive species varies depending on the UV transmittance, and if the UV illuminance is too high, a high concentration of cross-linked reactive species may be generated on the surface layer, forming a tight and dense film on the coating surface It may be done. When the illuminance is in a preferable range, the degree of cross-linking of the surface layer is low and light permeability in the deep direction is high, so that gentle cross-linking is uniformly formed in the deep direction. In addition, if the illuminance is too low, it takes an irradiation time to give the necessary integrated illuminance, which is not only disadvantageous in terms of equipment introduction, but also the amount of absolute light due to scattering of ultraviolet rays by the coating film is insufficient. Sometimes.
[0094]
When recording an image using the ink jet recording paper of the present invention, a recording method using water-based ink is preferably used.
[0095]
The water-based ink is a recording liquid having the following colorant, liquid medium, and other additives. As the colorant, water-soluble dyes or water-dispersible pigments such as direct dyes, acid dyes, basic dyes, reactive dyes or food dyes known for inkjet can be used.
[0096]
Examples of water-based ink solvents include water and various water-soluble organic solvents, for example, alcohols such as methyl alcohol, isopropyl alcohol, butyl alcohol, tert-butyl alcohol, and isobutyl alcohol; amides such as dimethylformamide and dimethylacetamide; acetone , Ketones such as diacetone alcohol or ketone alcohols; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6 -Polyhydric alcohols such as hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol, glycerin, triethanolamine , Ethylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether, lower alkyl ethers of polyhydric alcohols such as triethylene glycol monobutyl ether. Of these, polyhydric alcohols such as diethylene glycol, triethanolamine and glycerin, and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monobutyl ether are preferable.
[0097]
Examples of other water-based ink additives include pH adjusters, metal sequestering agents, fungicides, viscosity modifiers, surface tension adjusters, wetting agents, surfactants and rust inhibitors.
[0098]
In order to improve the wettability with respect to the recording paper, the aqueous ink liquid preferably has a surface tension usually within a range of 25 to 60 mN / m, preferably 30 to 50 mN / m at 20 ° C. The pH of the ink is preferably 5 to 10, particularly preferably 6 to 9.
[0099]
【Example】
Hereinafter, although an example is given and the effect of the present invention is explained, the present invention is not limited to these examples. In the examples, “%” represents mass% unless otherwise specified.
[0100]
<< Preparation of hydrophilic polymer compound crosslinked by ionizing radiation >>
According to the method described in Examples of JP-A No. 2000-181062, p- (3-methacryloxy-2-hydroxypropyloxy) benzaldehyde is reacted with polyvinyl alcohol having a polymerization degree of 2500 and a saponification degree of 88%, and the following formula ( An aqueous solution of UV-polymerizable polyvinyl alcohol derivative 1 having a structure of 6) (crosslinking group modification rate 1 mol%, solid content concentration 10%) was prepared.
[0101]
[Chemical formula 5]

[0102]
Similarly, resin solutions having polymerization degrees of 300 and 1000 were prepared. In addition, an aqueous solution of an ultraviolet-polymerizable polyvinyl alcohol derivative 2 (crosslinking group modification rate 1 mol%, solid content concentration 10%) into which a styrylpyridinium group represented by the above formula (4) was introduced was prepared in the same manner.
[0103]
<Production of recording paper>
[Preparation of recording paper 1]
Using a high-speed stirring disperser, in 700 ml of 1% ethanol aqueous solution adjusted to pH 4.0 with nitric acid, the average primary particle diameter was 12 nm and the specific surface area measured by the BET method was 200 m.²200 g of gas phase method silica / g was gradually added and dispersed. 70 g of a 5% by mass boric acid aqueous solution and 330 g of a 10% aqueous solution of the UV-polymerized polyvinyl alcohol derivative 2 prepared above were gradually added thereto with stirring. Subsequently, it was dispersed with a sand mill until the average secondary particle size of the silica fine particles in the dispersion became 0.4 μm or less, and finally a final coating solution was obtained to 1800 g with pure water. In addition, the average particle diameter of the inorganic fine particles in the dispersion is a value measured by diluting the dispersion 50 times and using a dynamic light scattering particle diameter measuring apparatus Zetasizer 1000HB (Malvern).
[0104]
The coating solution prepared above has a thickness of 170 g / m.²Polyethylene coated paper coated with polyethylene on both sides (containing 8% by mass of anatase-type titanium oxide in polyethylene on the ink absorbing layer side; 0.05 g / m on the ink absorbing layer side)²Of gelatin undercoat layer, latex polymer having Tg of about 80 ° C. on the opposite side, 0.2 g / m of back layer²And a wet coating thickness of 160 μm by a bar coater at 40 ° C., and then a metal halide lamp having a dominant wavelength at 365 nm with an energy amount of 70 mJ / cm²Were then dried in a hot air oven at 80 ° C. to obtain inkjet recording paper 1. The average particle diameter obtained by observing the surface of the recording paper with an electron microscope and the mass ratio of the inorganic fine particles to the hydrophilic polymer compound cross-linked by ionizing radiation (inorganic fine particles / hydrophilic polymer compound cross-linked by ionizing radiation) ) Is shown in Table 1 as P / B.
[0105]
[Preparation of recording paper 2]
Using a high-speed stirring disperser, in 600 ml of 1% ethanol aqueous solution adjusted to pH 4.0 with nitric acid, the average primary particle diameter was 12 nm and the specific surface area measured by the BET method was 200 m.²200 g of gas phase method silica / g was gradually added and dispersed. Next, 70 g of a 5% by weight aqueous solution of boric acid and 85 g of a 25% aqueous solution of the following cationic polymer (1) are added to this liquid, and the average particle size of the inorganic fine particles in the dispersion is further reduced to less than 0.4 μm by a sand mill. Finally, pure water was added to finish 1000 g.
[0106]
[Chemical 6]

[0107]
While stirring this dispersion at 40 ° C., 330 g of the 10% aqueous solution of the UV-polymerized polyvinyl alcohol derivative 1 prepared above and 0.5 g of a photopolymerization initiator (Nippon Kayaku Kayacure QTX) were gradually added with stirring. And finished with 1800 g of pure water to prepare a coating solution. This coating solution was applied and dried in the same manner as recording paper 1 to prepare recording paper 2.
[0108]
[Preparation of recording sheets 3 to 6]
Recording papers 3 to 6 were prepared in the same manner except that the polymerization degree and P / B of the ultraviolet polymerization polyvinyl alcohol derivative 1 were changed as shown in Table 1 in the production of the recording paper 2.
[0109]
[Preparation of recording paper 7]
Using a high-speed stirring disperser, in 650 ml of 1% aqueous ethanol solution adjusted to pH 4.0 with nitric acid, the average primary particle size was 12 nm and the specific surface area measured by the BET method was 200 m.²200 g of gas phase method silica / g was gradually added and dispersed. Next, 85 g of a 25% aqueous solution of the cationic polymer (1) is added to this solution, and further dispersed with a sand mill so that the average particle size of the inorganic fine particles in the dispersion is less than 0.4 μm. Finally, pure water is added. To 1000 g.
[0110]
While stirring this dispersion at 40 ° C., 330 g of a 10% aqueous solution of UV-polymerizable polyvinyl alcohol derivative 1 and 0.5 g of a photopolymerization initiator (Kayacure QTX, manufactured by Nippon Kayaku Co., Ltd.), and ethylene glycol diglycidyl ether 1. 5 g was gradually added while stirring, and finished to 1800 g with pure water to prepare a coating solution. This coating liquid was applied and dried in the same manner as recording paper 1 to prepare recording paper 7.
[0111]
[Preparation of recording paper 8]
A recording paper 8 was produced in the same manner as in the production of the recording paper 7 except that 1.5 g of ethylene glycol diglycidyl ether was changed to 1.0 g of glyoxal.
[0112]
[Preparation of recording paper 9]
In the production of the recording paper 7, in the same manner except that 1.5 g of ethylene glycol diglycidyl ether was changed to 40 g of 5% 2,4-dichloro-4-hydroxy-1,3,5-s-triazine, Recording paper 9 was produced.
[0113]
[Preparation of recording paper 10]
A recording paper 10 was produced in the same manner as in the production of the recording paper 7, except that 1.5 g of ethylene glycol diglycidyl ether was changed to 35 g of 5% bisvinylsulfonylmethyl ether.
[0114]
[Preparation of recording paper 11]
In a 650 ml of 1% ethanol aqueous solution adjusted to pH 4.0 with nitric acid using a high-speed stirring disperser, vapor phase method alumina (average primary particle size 13 nm, specific surface area 100 m measured by BET method)²/ G) 200 g was gradually added, and then 50 g of a 5 mass% boric acid aqueous solution was added and dispersed in this solution. Then, it further disperse | distributed so that the average particle diameter of the inorganic fine particle in a dispersion liquid might be less than 0.4 micrometer with a sand mill, and finally it added pure water and finished it to 1000g.
[0115]
While stirring this dispersion at 40 ° C., 250 g of a 10% aqueous solution of UV-polymerizable polyvinyl alcohol derivative 1 and 0.4 g of a photopolymerization initiator (Nippon Kayaku Co., Ltd. Kayacure QTX) were gradually added with stirring. To 1800 g to prepare a coating solution. This coating liquid was applied and dried in the same manner as recording paper 1 to produce recording paper 11.
[0116]
[Preparation of recording paper 12]
Gas phase method alumina (average primary particle size 13 nm, specific surface area 100 m measured by BET method) in 700 ml of 1% ethanol aqueous solution adjusted to pH 4.0 with nitric acid using a high speed stirring disperser²/ G) 200 g was gradually added and dispersed. Then, it further disperse | distributed so that the average particle diameter of the inorganic fine particle in a dispersion liquid might be less than 0.4 micrometer with a sand mill, and finally it added pure water and finished it to 1000g.
[0117]
While stirring this dispersion at 40 ° C., 330 g of a 10% aqueous solution of UV-polymerizable polyvinyl alcohol derivative 1, 0.4 g of a photopolymerization initiator (Kayacure QTX manufactured by Nippon Kayaku), and 1.5 g of ethylene glycol diglycidyl ether were added. The mixture was gradually added while stirring and finished to 1800 g with pure water to prepare a coating solution. This coating liquid was applied and dried in the same manner as recording paper 1 to produce recording paper 12.
[0118]
[Preparation of recording sheets 13 and 14]
In preparation of the recording papers 11 and 12, suspect boehmite (0.01 × 0.1 μm needle-shaped primary particles, specific surface area 250 m measured by the BET method) instead of vapor phase method alumina is used.²/ G), recording sheets 13 and 14 were produced in the same manner.
[0119]
[Preparation of recording paper 15]
In the production of the recording paper 2, the vapor phase method silica is the same mass gel method wet silica (average primary particle diameter 10 nm, specific surface area 200 m).²/ G) A recording paper 15 was produced in the same manner except that the recording paper 15 was changed.
[0120]
[Preparation of recording paper 16]
In the production of the recording paper 15, the recording paper 16 was produced in the same manner except that the dispersion condition of the sand mill was appropriately changed so that the average particle diameter of the inorganic fine particles in the dispersion liquid was 0.4 μm or more.
[0121]
[Preparation of recording paper 17]
Using a high-speed stirring disperser, in 650 ml of 1% aqueous ethanol solution adjusted to pH 4.0 with nitric acid, the average primary particle size was 12 nm and the specific surface area measured by the BET method was 200 m.²200 g of gas phase method silica / g was gradually added and dispersed. Next, 85 g of a 25% aqueous solution of the cationic polymer (1) is added to this solution, and further dispersed with a sand mill so that the average particle size of the inorganic fine particles in the dispersion is less than 0.4 μm. Finally, pure water is added. To 1000 g.
[0122]
While stirring this dispersion at 40 ° C., 330 g of a 10% aqueous solution of UV-polymerizable polyvinyl alcohol derivative 1 and 0.5 g of a photopolymerization initiator (Nippon Kayaku Kayacure QTX) were gradually added with stirring. To 1800 g to prepare a coating solution. This coating solution was applied and dried in the same manner as recording paper 1. 1m of this recording paper²The water absorption amount per unit was 20 ml.
[0123]
Next, a recording paper 17 was prepared by overcoating and drying a 2% boric acid aqueous solution on the recording paper according to a conventional method.
[0124]
[Preparation of recording paper 18]
A recording paper 18 was prepared in the same manner as in the preparation of the recording paper 17 except that the recording paper 17 was overcoated with a 5% ethyl acetate solution of hexamethylene diisocyanate instead of the 2% boric acid aqueous solution.
[0125]
[Preparation of recording paper 19]
A recording paper 19 was prepared in the same manner as in the preparation of the recording paper 17 except that the recording paper 17 was overcoated with a 1.2% aqueous solution of ethylene glycol diglycidyl ether instead of the 2% boric acid aqueous solution.
[0126]
(Preparation of recording paper-20)
Using a high-speed stirring disperser, in 650 ml of 1% aqueous ethanol solution adjusted to pH 4.0 with nitric acid, the average primary particle size was 12 nm and the specific surface area measured by the BET method was 200 m.²200 g of gas phase method silica / g was gradually added and dispersed. Next, 85 g of a 25% aqueous solution of the cationic polymer (1) is added to this solution, and further dispersed with a sand mill so that the average particle size of the inorganic fine particles in the dispersion is less than 0.4 μm. Finally, pure water is added. To 1000 g.
[0127]
While stirring this dispersion at 40 ° C., 330 g of a 10% aqueous solution of UV-polymerizable polyvinyl alcohol derivative 1 and 0.5 g of a photopolymerization initiator (Nippon Kayaku Kayacure QTX) were gradually added with stirring. To 1800 g to prepare a coating solution. This coating solution was applied and dried in the same manner as recording paper 1 to prepare recording paper 20.
[0128]
[Preparation of recording paper 21]
In the production of the recording paper 2, a recording paper 21 was produced in the same manner except that unmodified polyvinyl alcohol (polymerization degree 2500, saponification degree 88%) was used instead of the UV-polymerizable polyvinyl alcohol derivative 1. .
[0129]
Details of the recording sheets 1 to 21 produced as described above are shown below.
In addition, the detail of the abbreviation of the crosslinking agent of Table 1 is as follows.
[0130]
* A: Ethylene glycol diglycidyl ether
* B: Glyoxal
* C: 2,4-dichloro-4-hydroxy-1,3,5-s-triazine
* D: Bisvinylsulfonylmethyl ether
* E: Hexamethylene diisocyanate
[0131]
[Table 1]

[0132]
<Evaluation of characteristics of recording paper>
Each recording paper produced as described above was evaluated by the methods described below.
[0133]
[Evaluation of smoothness]
The center line surface roughness (measured with a reference length of 2.5 mm and a cut-off value of 0.8 mm) was determined for the ink absorbing layer surface of each recording paper produced in accordance with the method defined in JIS B 0601. The smoothness was evaluated according to the following criteria.
[0134]
A: The center line surface roughness Ra is less than 1.0 μm, and the aesthetic appearance is not impaired.
○: The center line surface roughness Ra is less than 1.0 to 1.5 μm, and the aesthetic appearance is not impaired.
Δ: Centerline surface roughness Ra is 1.5 μm or more, and the appearance is slightly impaired.
×: Cracks occur frequently on the entire surface of the coating film by visual evaluation, and cannot be used practically.
[Glossiness evaluation]
The 75 degree gloss was measured using a variable angle gloss meter (VGS-1001DP) manufactured by Nippon Denshoku Industries Co., Ltd.
[0135]
A: Glossiness is 55% or more
○: Glossiness is 50% or more and less than 55%
Δ: Glossiness is 45% or more and less than 50%
X: Glossiness is less than 45%
[Evaluation of crack resistance]
Observe the surface of the ink absorbing layer of each recording paper produced above with a magnifying glass.²The number of cracks in the film surface generated inside was counted, and this was used as a measure of crack resistance, and evaluation was performed according to the criteria described below.
[0136]
A: 0 to 3 cracks generated
○: Number of cracks generated is 4-10
Δ: Number of cracks generated is 11-20
×: Number of cracks generated is 21 or more
[Evaluation of ink absorbency]
Green solid printing was performed with an Seiko Epson inkjet printer, PM3000C, and the occurrence of madras in the image portion was visually observed, and ink absorbency was evaluated according to the following evaluation criteria. When the ink absorption speed is low, the occurrence of spotting becomes large.
[0137]
A: No madara
○: Slight madara is observed when looking at the image surface
Δ: Spotted even when observed 20 cm away from the image surface
×: Spotted even when observed 40 cm away from the image plane
The results obtained as described above are shown in Table 2.
[0138]
[Table 2]

[0139]
As can be seen from Table 2, the recording paper of the present invention satisfies the smoothness, ink absorbability and glossiness at the same time, and in addition, it is difficult to generate cracks during coating and drying. On the other hand, the recording paper of the comparative example lacked any performance such as inferior ink absorbability, or cracked when dried and poor productivity.
[0140]
【The invention's effect】
According to the present invention, it is possible to provide a high gloss inkjet recording paper having a porous ink absorbing layer excellent in smoothness, gloss, crack resistance and ink absorbability, and a method for producing the same.

Claims (11)

In an inkjet recording paper having a porous layer containing a hydrophilic polymer compound that is crosslinked by ionizing radiation and inorganic fine particles on a support, the hydrophilic polymer compound that is crosslinked by ionizing radiation is further crosslinked by a crosslinking agent. An ink jet recording paper characterized by being made. The said crosslinking agent is at least 1 sort (s) chosen from a boric acid or its salt, an epoxy-type compound, an isocyanate type compound, an aldehyde type compound, an active halogen type compound, and an active vinyl type compound, It is characterized by the above-mentioned. Inkjet recording paper. 3. The inkjet according to claim 1, wherein a mass ratio (P / B) of the inorganic fine particles (P) to the hydrophilic polymer compound (B) crosslinked by the ionizing radiation is 3 to 50. 4. Recording sheet. The inkjet recording paper according to any one of claims 1 to 3, wherein the inorganic fine particles are silica, alumina, or alumina hydrate having an average particle diameter of 0.005 to 0.4 µm. The inkjet recording paper according to claim 1, wherein the hydrophilic polymer compound that is cross-linked by ionizing radiation is a nonionic compound. The hydrophilic polymer compound that is cross-linked by the ionizing radiation is a polyvinyl acetate saponified product having a structural unit represented by the following general formula (1), according to any one of claims 1 to 5. Inkjet recording paper.

[Wherein, R ₁ represents a hydrogen atom or a methyl group, Y represents an aromatic ring or a simple bond, and X represents — (CH ₂ ) _m —COO—, —O—CH ₂ —COO— or — O- represents, m represents an integer of 0 to 6, and n represents 1 or 2. ] The ink-jet recording paper according to claim 6, wherein the polymerization degree of the polyvinyl acetate saponified product is 400 to 5,000. The inkjet recording paper according to claim 1, comprising at least one water-soluble photopolymerization initiator. The inkjet recording paper according to claim 1, wherein the support is a non-absorbent support. A method for producing an ink jet recording paper according to any one of claims 1 to 9, wherein a hydrophilic polymer compound, an inorganic fine particle, and a cross-linking agent having a structure in which cross-linking is formed by ionizing radiation on a support. A method for producing an ink jet recording paper, comprising: applying a coating liquid containing the composition; A method for producing an ink jet recording paper according to any one of claims 1 to 9, wherein the coating comprises a hydrophilic polymer compound having a structure that is crosslinked by ionizing radiation and inorganic fine particles on a support. An ink jet recording paper characterized by forming a porous layer by coating a liquid, supplying a coating liquid containing a cross-linking agent onto the porous layer simultaneously with or after the coating, and then drying to produce Manufacturing method.