JP2004195779A - Recording medium for ink jet and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording medium for ink jet which has a high glossiness and few cracks and which enables attainment of an ink absorption capacity (ink overflow tolerance) and is excellent in the maximum density of an image, and a manufacturing method of the recording medium for ink jet which enables inexpensive manufacture of the recording medium with excellent productivity. <P>SOLUTION: The recording medium for ink jet has an ink receiving layer which is obtained by applying a coating solution containing a silica particulate dispersion on a substrate, and the coating solution containing the silica particulate dispersion contains at least an at least one sort of vapor phase process silica particulate and an at least one sort of wet type process silica particulate which are pulverized and dispersed. The average particle diameters of these particulates are 100 to 350 nm. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００４４】
【化２】

【００４５】
上記第４級アンモニウム塩基と共重合し得るモノマーはエチレン性不飽和基を有する化合物であり、例えば以下の具体例を挙げることが出来る。
【００４６】
【化３】

【００４７】
特に第４級アンモニウム塩基を有するカチオン性ポリマーが共重合体である場合、カチオン性モノマーの比率は１０モル％以上が好ましく、より好ましくは２０モル％以上、特に好ましくは３０モル％以上である。
【００４８】
第４級アンモニウム塩基を有するモノマーは単一でも２種類以上であっても良い。
【００４９】
以下に本発明に用いることができるカチオン性ポリマーの具体例を挙げるが、これらに限定されるものではない。
【００５０】
【化４】

【００５１】
【化５】

【００５２】
【化６】

【００５３】
【化７】

【００５４】
上記第４級アンモニウム塩基を有するカチオン性ポリマーは第４級アンモニウム塩基のために水溶性が一般に高い。共重合する第４級アンモニウム塩基を含まないモノマーの組成や比率によっては水に充分に溶解しないことはあるが、水混和性有機溶媒と水との混合溶媒に溶解させることにより溶解し得るもので有れば本発明に使用できる。
【００５５】
ここで水混和性有機溶媒とは、メタノール、エタノール、イソプロパノール、ｎ−プロパノールなどのアルコール類、エチレングリコール、ジエチレングリコール、グリセリンなどのグリコール類、酢酸エチル、酢酸プロピル等のエステル類、アセトン、メチルエチルケトン等のケトン類、Ｎ，Ｎ−ジメチルホルムアミド等のアミド類など、水に対して通常１０％以上溶解し得る有機溶媒を言う。この場合、有機溶媒の使用量は水の使用量以下であることが好ましい。
【００５６】
本発明に用いるカチオン性ポリマーは数平均分子量が１０万以下であることが好ましい。ここで数平均分子量は、ゲルパーミエーションクロマトグラフィーから求められたポリエチレングリコール値に換算した値である。
【００５７】
数平均分子量が１０万を越える場合には、カチオン性ポリマーの溶液を表面がアニオン性であるシリカ微粒子を含有する分散液に添加した際に凝集物の発生が激しく、またその後分散処理を施しても均一な分散液に成りにくく粗大粒子が多数存在して均一な分散液に成りにくい。このようなカチオン性ポリマーとシリカ微粒子を含有する複合微粒子分散液を使用してインクジェット用記録媒体を作製した場合、高い光沢性が得られにくい。特に好ましい数平均分子量は５万以下である。また数平均分子量の下限はインクの耐水性の点から通常２０００以上である。
【００５８】
上記シリカ微粒子とカチオン性ポリマーの比率は、シリカ微粒子の種類や粒径、あるいはカチオン性ポリマーの種類や数平均分子量で変わり得る。
【００５９】
本発明において、上記比率はシリカ微粒子の表面がカチオン性に置き換わって安定化させる必要があることから、１：０．０１〜１：１であることが好ましい。
【００６０】
上記の分散液を調製する際には、各種の添加剤を添加することが出来る。
例えば、ノニオン性またはカチオン性の各種の界面活性剤（アニオン性界面活性剤は凝集物を形成するために好ましくない）、消泡剤、ノニオン性の親水性ポリマー（ポリビニルアルコール、ポリビニルピロリドン、ポリエチレンオキサイド、ポリアクリルアミド、各種の糖類、ゼラチン、プルラン等）、ノニオン性またはカチオン性のラテックス分散液、水混和性有機溶媒（酢酸エチル、メタノール、エタノール、イソプロパノール、ｎ−プロパノール、アセトンなど）、無機塩類、ｐＨ調整剤など、必要に応じて適宜使用することが出来る。
【００６１】
特に水混和性有機溶媒は、シリカ微粒子とカチオン性ポリマーを混合した際の微小なダマの形成を抑制するので好ましい。そのような水混和性有機溶媒は分散液中に好ましくは０．１〜２０質量％、特に好ましくは０．５〜１０質量％使用される。
【００６２】
シリカ微粒子とカチオン性ポリマーの分散液を調製する際のｐＨはシリカ微粒子の種類やカチオン性ポリマーの種類、各種の添加剤等により広範に変化し得るが、一般的にはｐＨが１〜８であり、特に２〜７が好ましい。
【００６３】
本発明に用いるバインダーとしては、水溶性ポリマーが好ましく、例えばゼラチン（酸処理ゼラチンが好ましい）、ポリビニルピロリドン（平均分子量が約２０万以上が好ましい）、プルラン、ポリビニルアルコールまたはその誘導体、カチオン変性ポリビニルアルコール、ポリエチレングリコール（平均分子量が１０万以上が好ましい）、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を挙げることができ、これらの水溶性ポリマーはインク受容層の親水性バインダーとして機能し、単独で使用しても良く、２種以上を併用しても良い。
【００６４】
特に好ましい親水性バインダーは、ポリビニルアルコールまたはカチオン変性ポリビニルアルコールである。
【００６５】
本発明に好ましく用いられるポリビニルアルコールは平均重合度が３００〜４０００のもので、特に平均分子量が１０００以上のものが得られる皮膜の脆弱性が良好であることから好ましい。
【００６６】
また、ポリビニルアルコールのケン化度は７０〜１００％のものが好ましく、８０〜１００％のものが特に好ましい。
【００６７】
また、カチオン変性ポリビニルアルコールは、カチオン性基を有するエチレン性不飽和単量体と酢酸ビニルとの共重合体をケン化することにより得られる。
【００６８】
カチオン性基を有するエチレン性不飽和単量体としては、例えばトリメチル−（２−アクリルアミド−２，２−ジメチルエチル）アンモニウムクロライド、トリメチル−（３−アクリルアミド−３，３−ジメチルプロピル）アンモニウムクロライド、Ｎ−ビニルイミダゾール、Ｎ−ビニル−２−メチルイミダゾール、Ｎ−（３−ジメチルアミノプロピル）メタクリルアミド、ヒドロキシルエチルジメチル（３−メタクリルアミド）アンモニウムクロライド、トリメチル−（３−メタクリルアミドプロピル）アンモニウムクロライド、Ｎ−（１，１−ジメチル−３−ジメチルアミノプロピル）アクリルアミド等が挙げられる。
【００６９】
カチオン変性ポリビニルアルコールのカチオン変性基含有単量体の比率は、酢酸ビニルに対して０．１〜１０モル％が好ましく、より好ましくは０．２〜５モル％である。またカチオン変性ポリビニルアルコールの重合度は通常５００〜４０００、好ましくは１０００〜４０００が好ましい。更に、カチオン変性ポリビニルアルコールのケン化度は通常６０〜１００モル％、好ましくは７０〜９９モル％である。
【００７０】
本発明のインクジェト用記録媒体において、高光沢性で高い空隙率を皮膜の脆弱性を劣化させずに得るために、前記水溶性ポリマーが硬膜剤により硬膜されていることが好ましい。
【００７１】
硬膜剤は、一般的には前記水溶性ポリマーと反応し得る基を有する化合物あるいは水溶性ポリマーが有する異なる基同士の反応を促進するような化合物であり、水溶性ポリマーの種類に応じて適宜選択して用いられる。
【００７２】
硬膜剤の具体例としては、例えば、エポキシ系硬膜剤（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）、アルデヒド系硬膜剤（ホルムアルデヒド、グリオキザール等）、活性ハロゲン系硬膜剤（２，４−ジクロロ−４−ヒドロキシ−１，３，５−ｓ−トリアジン等）、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）、ほう酸、その塩、ほう砂、アルミ明礬等が挙げられる。
【００７３】
水溶性ポリマーとしてポリビニルアルコールまたはカチオン変成ポリビニルアルコールを使用する場合には、ほう酸、その塩またはエポキシ系硬膜剤から選ばれる硬膜剤を使用するのが好ましい。
【００７４】
最も好ましいのはほう酸またはその塩から選ばれる硬膜剤である。
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およびその塩のことを示し、具体的にはオルトほう酸、二ほう酸、メタほう酸、四ほう酸、五ほう酸、八ほう酸またはそれらの塩が挙げられる。
【００７５】
上記硬膜剤の使用量は水溶性ポリマーの種類、硬膜剤の種類、シリカ微粒子、水溶性ポリマーに対する比率等により変化するが、通常水溶性ポリマー１ｇ当たり５〜５００ｍｇ、好ましくは１０〜３００ｍｇである。
【００７６】
上記硬膜剤は、空隙層を形成する塗布液を塗布する際に、空隙層を形成する塗布液中及び／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く、あるいは予め硬膜剤を含有する塗布液を塗布してある支持体上に、該空隙層を形成する塗布液を塗布する。さらには空隙層を形成する硬膜剤非含有の塗布液を塗布乾燥後に硬膜剤溶液をオーバーコートするなどして空隙層に硬膜剤を供給することもできる。好ましくは製造上の効率の観点から、空隙層を形成する塗布液またはこれに隣接する層を形成する塗布液中に硬膜剤を添加して、空隙層を形成するのと同時に硬膜剤を供給するのが好ましい。
【００７７】
本発明で特に好ましいのはシリカ微粒子を１次粒子として使用し、親水性バインダーとしてポリビニルアルコールまたは変性ポリビニルアルコールを用いる場合である。この場合、シリカ微粒子表面のシラノール基とビニルアルコールの水酸基が弱い水素結合を行い、軟凝集体が形成されて空隙率が高く成りやすい。
【００７８】
上記水溶性ポリマーとシリカ微粒子の比率は、通常１：１０〜１：３であり、特に好ましくは１：８〜１：５である。
【００７９】
水溶性ポリマーを前記分散液に添加混合する方法は、水溶性ポリマーの水溶液を分散液に攪拌しながらバッチ内で添加する方法や、前記分散液と水溶性ポリマーを連続的にスタチックミキサー等の混合機で混合する方法が挙げられる。本発明に好ましく用いられる水溶性ポリマー、特にポリビニールアルコールは、重合度が高い為、溶解性が悪く、ダマが出来やすい、更に溶解時間がかかるため、生産効率上、品質上問題がある。
【００８０】
溶解温度を１００℃以上にすることで、溶解時間が短縮できてダマがなくなる。溶解温度は、１００℃以上１５０℃以下が好ましく、更に好ましくは１１０℃以上１３０℃以下である。あまり温度を上げると、構造が破壊され、強いては、空隙率をダウンさせる。１００℃以上での溶解は、熱源として、電気、オイル、加圧蒸気等を用いることが出来る。生産効率上、連続的に溶解するのが好ましく、例えばノリタケ製溶解システムを用いることが出来る。溶解温度が低いと、ダマが完全に溶解しきれず、ひび割れの原因になる。
【００８１】
本発明のインクジェット用記録媒体の支持体としては、従来インクジェット用記録用紙として公知の紙支持体、プラスチック支持体（透明支持体）、複合支持体など適宜使用できるが、より高い濃度で鮮明な画像を得るためには支持体中にインク液が浸透しない疎水性支持体を用いるのが好ましい。
【００８２】
透明支持体としては、例えば、ポリエステル系樹脂、ジアセテート系樹脂、トリアセテート系樹脂、アクリル系樹脂、ポリカーボネート系樹脂、ポリ塩化ビニル系樹脂、ポリイミド系樹脂、セロハン、セルロイド等の材料からなるフィルム等が挙げられ、中でもＯＨＰとして使用されたときの輻射熱に耐える性質のものが好ましく、ポリエチレンテレフタレートが特に好ましい。このような透明な支持体の厚さとしては、１０〜２００μｍが好ましい。透明支持体のインク受容層側およびバッキング層側には公知の下引き層を設けることが、インク受容層やバック層と支持体の接着性の観点から好ましい。
【００８３】
また、透明である必要のない場合に用いる支持体としては、例えば、基紙の少なくとも一方に白色顔料等を添加したポリオレフィン樹脂被覆層を有する樹脂被覆紙（いわゆるＲＣペーパー）、ポリエチレンテレフタレートに白色顔料を添加してなるいわゆるホワイトペットが好ましい。
【００８４】
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出来る。好ましい方法は、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、特に全ての親水性バインダー層を１回の塗布で済ます同時塗布が好ましい。
【００８５】
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。
【００８６】
【実施例】
以下に実施例を挙げて本発明を具体的に説明するが、本発明の実施態様はこれらに限定されるものではない。なお、実施例中で「％」は特に断りのない限り絶乾（水分無しの状態）質量％を示す。
【００８７】
実施例１
［シリカ微粒子分散液の調製］
（シリカ微粒子予備分散液１（シリカ微粒子：湿式法シリカ微粒子）の調製）
市販湿式シリカ微粒子（トクヤマ社製、商品名：Ｔ−３２、比表面積２０２／ｇ、平均２次粒径１．５μｍ沈降法シリカ微粒子）を容器に投入された水性媒体中に高速回転式攪拌分散機を周速２０ｍ／ｓｅｃで回転させながら、徐々に投入し、粉砕分散した。水性媒体には、ホウ酸とＰ−９を含有させた。ホウ酸はシリカ質量に対して２．７％、Ｐ−９は４％になるようにした。尚、シリカ微粒子予備分散液１中のシリカ濃度は３０％にした。
【００８８】
（シリカ微粒子予備分散液２（シリカ微粒子：気相法シリカ微粒子）の調製）
上記市販湿式シリカ微粒子の代わりに市販気相法シリカ微粒子（日本アエロジル社製、商品名：Ａ−３００、比表面積３００ｇ／ｍ²、平均１次粒径７ｎｍ、気相法シリカ微粒子）を用いて、シリカ微粒予備分散液１と同様にしてシリカ微粒子予備分散液２を調製した。但し、水性媒体にはホウ酸、ホウ砂とＰ−９を含有させ、ホウ酸、ホウ砂はシリカ質量に対して各１．４％、Ｐ−９は１１％になるようにした。尚、シリカ微粒子予備分散液２中のシリカ濃度は２０％にした。２０％以上の濃度についても行ってみたが、増粘が激しく、ハンドリング、装置負荷を考慮すると２０％が限界であった）。
【００８９】
（シリカ微粒子予備分散液３（シリカ微粒子：湿式シリカ微粒子）の調製）
上記市販湿式シリカ微粒子をシリカ微粒子（日本シリカ社製、商品名：ＡＺ−２０４、比表面積３００ｇ／ｍ²、平均２次粒径１．３μｍ、ゲル法シリカ微粒子）に変えた以外は、シリカ微粒子予備分散液１と同様にしてシリカ微粒子予備分散液３作製した。
【００９０】
（シリカ微粒子本分散液１−１の調製）
前記シリカ微粒子予備分散液１をサンドミル分散機（アシザワ社製、ＲＬ−１２５、以下ＳＭと称す）で分散し、その後、フィルター処理を行った。ＳＭの周速は、１０ｍ／ｓｅｃで滞留時間５ｍｉｎで２ｐａｓｓ行った。フィルターは日本ポール社製のプロファイルを用いた。平均粒径と粗大粒子を測定し式（１）の値を求めた所、４００であった。このときの平均粒径は２２０ｎｍであった。
【００９１】
（シリカ微粒子本分散液１−２の調製）
ＳＭのｐａｓｓ回数を５ｐａｓｓにした以外は、シリカ微粒子本分散液１−１と同様に作製した。式（１）の値は、１８０で、平均粒径は１２０ｎｍであった。
【００９２】
（シリカ微粒子本分散液１−３の調製）
ＳＭの周速を７ｍ／ｓｅｃにした以外は、シリカ微粒子本分散液１−１と同様に作製した。式（１）の値は、４９０で、平均粒径は３３０ｎｍであった。
【００９３】
（シリカ微粒子本分散液１−４の調製）
フィルター処理を行わなかった以外は、シリカ微粒子本分散液１−１と同様に作製した。式（１）の値は、５５０で平均粒径は２３０ｎｍであった
（シリカ微粒子本分散液１−５の調製）
ＳＭの周速を１５ｍ／ｓｅｃにした以外はシリカ微粒子本分散液１−２と同様に作製した。式（１）の値は、１４０で平均粒径は８０ｎｍであった
（シリカ微粒子本分散液１−６の調製）
ＳＭを高圧ホモジナイザーにかえ、圧力を３５０ｋｇ／ｃｍ²で１回分散し、フィルター処理を行わなかった以外はシリカ微粒子本分散液１−１と同様に作製した。式（１）の値は８００で平均粒径は４００ｎｍであった。
【００９４】
（シリカ微粒子本分散液２−１の調製）
前記シリカ微粒子予備分散液２を用い、ＳＭのｐａｓｓ回数を１ｐａｓｓにした以外はシリカ微粒子本分散液１−１と同様に作製した。式（１）の値は３００で平均粒径は２００ｎｍであった。
【００９５】
（シリカ微粒子本分散液３−１の調製）
前記シリカ微粒子予備分散液３を用いた以外はシリカ微粒子本分散液１−１と同様に作製した。式（１）の値は４９０で平均粒径は３００ｎｍであった。
【００９６】
［記録媒体１の作製］
シリカ微粒子本分散液２−１（シリカ微粒子：気相法シリカ微粒子）と本分散液１−１（シリカ微粒子：湿式シリカ微粒子）をシリカ質量比で５０：５０になるように混合した液に、ポリビニールアルコール溶液（１０％、クラレ社製：ＰＶＡ２３５、）を混合し、両面をポリエチレンで被覆した紙支持体（厚みが２２０μｍでインク吸収層面のポリエチレン中にはポリエチレンに対して１３質量％のアナターゼ型酸化チタンを含有）に、シリカ付量が１６ｇ／ｍ²になるように塗布し、記録媒体１を得た。シリカとポリビニールアルコールの質量比は６．５：１で行った。なお塗布は塗布液を４０℃でカーテンコーターを用いて行い、塗布直後に０℃に保たれた冷却ゾーンで２０秒間冷却した後、２５℃の風（相対湿度が１５％）で６０秒間、４５℃の風（相対湿度が２５％）で６０秒間、５０℃の風（相対湿度が２５％）で６０秒間順次乾燥し、２０〜２５℃、相対湿度が４０〜６０％の雰囲気下で、２分間調湿した。塗布速度は３００ｍ／ｍｉｎで行った。
【００９７】
［記録媒体２〜１５の作製］
シリカ微粒子本分散液２−１（シリカ微粒子：気相法シリカ微粒子）と本分散液１−１（シリカ微粒子：湿式シリカ微粒子）の代わりに、表１記載のようにシリカ微粒子本分散液２−１（気相法シリカ）とシリカ微粒子本分散液１−１〜１−６、３−１（湿式シリカ）を用い、かつ、混合シリカ質量比を変えた他は記録媒体１と同様にして記録媒体２〜１５を得た。
【００９８】
得られた記録媒体１〜１５について、以下の項目を評価した。
（１）ひび割れ
塗布面の０．３ｍ²当たりのひび割れ箇所数を目視でカウントした。ひび割れ箇所数は、通常１０箇所以下であれば実用上問題ないと考えられる。
【００９９】
（２）インク溢れ耐性
セイコーエプソン社製のインクジェットプリンター、ＰＭ７５０Ｃを使用して、マゼンタのベタ印字を行い、目視にてインク溢れの状態を観察し、下記基準にて評価した。この評価は、インク吸収量（空隙量）の評価となる。
【０１００】
○：溢れ無し
△：若干溢れはあるが実用上問題ないし
×：実用上問題有り
（３）光沢度
日本電色工業株式会社製変角光度計（ＶＧＳ−１００１ＤＰ）を用いて、７５度光沢度を測定した。この値が４５％以上であればフォトライクな記録媒体として有効である。
【０１０１】
（４）最大濃度
セイコーエプソン社製のインクジェットプリンター、ＰＭ７５０Ｃを使用して、マゼンタのベタ印字を行い、その最大濃度（最大反射濃度）を測定した。
【０１０２】
結果を表１に示す。
【０１０３】
【表１】

【０１０４】
表１から明らかなように、本発明のインクジェット用記録媒体は比較のものに比べてひび割れ、インク溢れ耐性、光沢度、最大濃度で総合的に優れていることがわかる。
【０１０５】
【発明の効果】
本発明により、光沢度が大きく、ひび割れが少ない、かつインク吸収容量（インク溢れ耐性）が充分に得られ画像の最大濃度が優れたインクジェット用記録媒体、および該インクジェット用記録媒体を優れた生産性で安価に製造できるインクジェット用記録媒体の製造方法を提供できた。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an inkjet recording medium (hereinafter, also simply referred to as a recording medium). More specifically, the present invention has a high glossiness, a small number of cracks, a sufficient ink absorption capacity (ink overflow resistance), and a maximum image density. The present invention relates to an excellent ink jet recording medium and a method for manufacturing the ink jet recording medium capable of producing the ink jet recording medium at low cost with excellent productivity.
[0002]
[Prior art]
Ink-jet recording is the recording of images and characters by flying fine droplets of ink by various operating principles and attaching them to a recording sheet such as paper. It has advantages such as ease of use, and has been rapidly spreading in recent years. On the other hand, it is also used for high-quality printing of photographs and the like, so-called photo-like recording sheets. The recording sheets have high gloss, have a large amount of ink absorption, and have no failures such as foreign substances and cracks on the sheets. Is required. Photo-like recording sheets are expensive, and lower prices are increasingly required in the future.
[0003]
Many techniques have been proposed to solve these problems.
For example, Japanese Patent Publication No. 3-56552, Japanese Patent Laid-Open No. 2-188287, Japanese Patent Laid-Open No. 10-81064, Japanese Patent Laid-Open No. 10-119423, Japanese Patent Laid-Open No. 10-175365, Japanese Patent Laid-Open No. 10-193776, and Japanese Patent Laid-Open No. 10-203006. JP-A-10-217601, JP-A-11-20300, JP-A-11-20306, JP-A-11-34481 (Patent Document 1), and the like disclose the use of fumed silica. . This fumed silica is ultrafine particles having primary particles having an average particle size of several nm to several tens of nm, has high gloss, and has a high ink absorbency (high voids) because the fine particles have a three-dimensional network structure. ). However, due to the high porosity, the strength of the film is weak, and cracks (cracks) are likely to occur. In addition, when fumed silica is dispersed in an aqueous medium, the viscosity is rapidly increased, and it cannot be dispersed at a high concentration, and productivity is reduced. It is disadvantageous in that it is low and, furthermore, fumed silica itself is expensive.
[0004]
Gel silica, sedimentation silica, and the like (hereinafter referred to as wet silica) produced by a wet method with respect to fumed silica are inexpensive and have a cost merit, but have a disadvantage that gloss is hardly produced. On the other hand, JP-A-11-91240 (Patent Document 2), JP-A-2002-211113, and the like propose that a glossy layer is provided, and that a heating mirror surface treatment and a calendering treatment are further performed. The manufacturing process is complicated and, on the contrary, expensive. In addition, the ink absorbability is deteriorated.
[0005]
JP-A-9-286165, JP-A-10-71764, JP-A-10-86509, JP-A-10-175367, JP-A-10-181190 (Patent Document 3), JP-A-10-181191, and the like include silica. However, a technique in which the average particle size is specified is disclosed, but the average particle size alone is not sufficient to obtain high gloss.
[0006]
Japanese Patent Application Laid-Open No. 2002-274221 (Patent Document 4) discloses a technique of mixing fumed silica and colloidal silica. However, the gloss is increased, but the ink absorption and cracking are not satisfactory.
[0007]
At present, an ink jet recording medium that satisfies gloss, ink absorbency, and cracks, has high productivity, and is cost-effective has not been obtained.
[0008]
[Patent Document 1]
JP-A-11-34481 (paragraph number [0076])
[0009]
[Patent Document 2]
JP-A-11-91240 (Claims 2 and 3, and paragraph numbers [0016], [0030], [0034])
[0010]
[Patent Document 3]
JP-A-10-181190 (Claim 1)
[0011]
[Patent Document 4]
Japanese Patent Application Laid-Open No. 2002-270421 (Claim 1)
[0012]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a large glossiness, a small number of cracks, a sufficient ink absorption capacity (ink overflow resistance), and an excellent maximum density of an image. An object of the present invention is to provide an ink jet recording medium and a method of manufacturing the ink jet recording medium capable of manufacturing the ink jet recording medium at low cost with excellent productivity.
[0013]
[Means for Solving the Problems]
The above object of the present invention has been achieved by the following constitutions.
[0014]
1. In an inkjet recording medium having an ink receiving layer obtained by applying a coating liquid containing a silica fine particle dispersion on a support, at least one kind of the coating liquid containing the silica fine particle dispersion is at least pulverized and dispersed. An ink jet recording medium containing fumed silica fine particles and at least one kind of wet-process silica fine particles, wherein the fumed silica fine particles and the wet-process silica fine particles have an average particle diameter of 100 nm to 350 nm. .
[0015]
2. 2. The ink jet recording medium according to item 1, wherein the wet-process silica fine particles are wet-process silica fine particles produced from a wet-process silica of a precipitation method or a gel method.
[0016]
3. 3. The ink jet recording medium according to 1 or 2, wherein the mass ratio of the fumed silica fine particles to the wet method silica fine particles is 50:50 to 10:90.
[0017]
4. The relationship between the average particle size (y (nm)) of the silica fine particles and the number (x) of the silica fine particles having a particle size of 10 μm or more in 1 g of the silica fine particles is determined for each of the fumed silica fine particles and the wet-process silica fine particles. 4. The ink jet recording medium according to any one of the above items 1 to 3, wherein the following formula (1) is satisfied.
[0018]
Equation (1)
150 <y + 17 · ln (x) <500
5. The inkjet recording medium according to any one of the above items 1 to 4, wherein the surface glossiness of the inkjet recording medium is 45% or more as measured at 75 °.
[0019]
6. A method for producing an ink jet recording medium having an ink receiving layer containing at least one kind of fumed silica fine particles and at least one kind of wet method silica fine particles on a support, comprising: An ink receiving layer is provided by applying a coating solution containing a mixture of a fumed silica fine particle dispersion and a wet silica fine particle dispersion prepared by separately pulverizing and dispersing in an aqueous medium and providing an ink receiving layer. Manufacturing method of recording medium.
[0020]
7. A method for producing an ink jet recording medium having an ink receiving layer containing at least one kind of fumed silica fine particles and at least one kind of wet method silica fine particles on a support, comprising: a fumed method silica fine particle and a wet method silica. After pulverizing and dispersing the fine particles, through a centrifugal separation or filter treatment step, a step of coating and drying the vapor-phase silica fine particles and the wet-process silica fine particles in which the coarse particle components are controlled together with at least a binder on a support. A method for producing an ink jet recording medium, comprising applying an ink receiving layer by using an ink.
[0021]
Hereinafter, the present invention will be described in detail.
The ink jet recording medium of the present invention is an ink jet recording medium having an ink receiving layer obtained by applying a coating liquid containing a silica fine particle dispersion on a support, wherein the coating liquid containing the silica fine particle dispersion is It contains at least one kind of fumed silica fine particles and at least one kind of wet-processed silica fine particles which are pulverized and dispersed, and the average particle diameter of the fumed silica fine particles and the wet-processed silica fine particles is 100 nm to 350 nm. It is characterized by the following. The average particle diameter of the fumed silica fine particles may be 350 nm or less, but is preferably 100 nm to 350 nm. If it is smaller than 100 nm, the ink absorbency may deteriorate. If it is larger than 350 nm, the gloss may deteriorate. The average particle diameter of the wet method silica fine particles is 100 nm to 350 nm, and if it is smaller than 100 nm, the ink absorbency may be deteriorated. If it is larger than 350 nm, the gloss may deteriorate.
[0022]
The inkjet recording medium of the present invention comprises a wet-process silica fine particle dispersion obtained by pulverizing and dispersing silica fine particles (hereinafter, also referred to as wet-process silica fine particles) on a support in an aqueous medium, and a gas phase method. A coating liquid containing, at a specific ratio, a fumed silica fine particle dispersion obtained by pulverizing and dispersing silica fine particles (hereinafter also referred to as fumed silica fine particles) in an aqueous medium, and further containing at least a binder. Having an ink receiving layer formed by applying The average particle size and the number of coarse particles of the wet method silica fine particles and the gas phase method silica fine particles according to the present invention are controlled by reducing and removing the number of coarse particles after pulverization and dispersion. By using such wet-process silica fine particles and vapor-phase process silica fine particles, the ink receiving layer having a gloss of 45% or more as measured at a surface gloss of 75 ° and having excellent ink absorbability can be formed with cracks. And can be obtained by a method with excellent productivity and cost. The gloss is preferably 45% or more. It is more preferably from 45 to 80%, particularly preferably from 50 to 70%. If it is less than 45%, a rough feeling is conspicuous and a photo-like image may be deteriorated. On the other hand, if it exceeds 80%, the gloss is too high, and the difference between the printed portion and the non-printed portion becomes large, which may be undesirable.
[0023]
The fumed silica fine particles and the wet-process silica fine particles used in the present invention will be described.
[0024]
Silica fine particles can be roughly classified into vapor-phase silica fine particles and wet-process silica fine particles according to the manufacturing method. Further, wet-process silica fine particles are distinguished from silica fine particles manufactured by a gel method (hereinafter, also referred to as gel silica fine particles) by a sedimentation method. It is subdivided into manufactured silica fine particles (hereinafter, also referred to as precipitated silica fine particles). The fumed silica fine particles are spherical anhydrous silica fine particles having an average primary particle diameter of 5 to 50 nm and produced by burning silicon tetrachloride with oxygen and hydrogen. The fumed silica fine particles have a small apparent specific gravity and a high specific surface area, but since spherical particles are easily aggregated in a network form, it is difficult to disperse in water at a high concentration, and in addition to the stability of the dispersion over time. It is low in properties and easily cracks when formed into a coating film, but is advantageous for obtaining gloss and color density.
[0025]
The fumed silica fine particles used in the present invention preferably have an average primary particle diameter of 4 to 30 nm. For example, Aerosil manufactured by Nippon Aerosil Co., Ltd. is commercially available.
[0026]
On the other hand, the silica gel fine particles form a silica sol by mixing, for example, sodium silicate and sulfuric acid using high-purity silica sand as raw materials. Silicic acid sol gradually polymerizes to form primary particles, and further forms aggregates three-dimensionally and gels. This gel-like silica is pulverized by a general method such as drying and air-flow pulverization and pulverized into fine particles. That is, in the gel method, reaction polymerization is carried out on the acidic side, the solution is allowed to stand until it becomes a gel, washed with water, dried and pulverized to obtain gel method silica fine particles. Precipitated silica fine particles can be obtained by reacting and polymerizing on the alkali side, and then directly sedimenting and drying. Since these wet process silica fine particles have internal pores in the primary particles, they are more advantageous in terms of ink absorption capacity than gas phase silica fine particles having no internal pores. Further, since the fine particles contain more water than the fumed silica fine particles, the fine particles are easily dispersed in an aqueous medium, and there is an advantage that a high-concentration dispersion can be obtained.
[0027]
In terms of color density and absorption capacity, the specific surface area has a great influence, and wet method silica fine particles having a specific surface area of 150 m ² / g or more are preferable.
[0028]
Further, since the wet-processed silica fine particles can be dispersed at a high concentration, the water content in the coating liquid at the time of coating can be reduced, which is advantageous for drying, and as a result, there is an advantage that the coating speed can be increased. Furthermore, the shrinkage of the film during drying is small, the stress applied to the film is small, and coating failures such as cracks (cracks) can be reduced.
[0029]
Since the wet-processed silica fine particles used in the present invention are pulverized and dispersed and used as fine particles, the average particle diameter before the pulverization and dispersion is preferably 1.0 to 10 μm. Fine silica and Tokuseal manufactured by Tokuyama Corporation and NIPGEL and NIPSIL manufactured by Nippon Silica Industry Co., Ltd. are commercially available.
[0030]
Conventionally, when wet-processed silica fine particles are pulverized and dispersed, a large amount of time and energy have to be applied to reduce the average particle size in order to obtain a gloss of 45% or more by measuring a photo-like level at 75 ° at present. Although there is gloss due to this, the ink absorptivity deteriorates conversely, and a satisfactory recording medium has not been obtained.
[0031]
Therefore, as a result of diligent studies, we found the idea of using unprecedented coarse particles, and furthermore, by using a mixture of fumed silica fine particles and wet-process silica fine particles, we have achieved the advantage of luster, which is the advantage of fumed silica fine particles. We have succeeded in obtaining a recording medium that satisfies all of the properties of gloss, absorption, color density, cracking, and productivity, which combine the advantages of cracks, productivity, cost, and absorbency, which are the advantages of wet silica fine particles, and color density and wet silica particles. . Specifically, it is preferable that the mixing mass ratio of the fumed silica fine particles and the wet silica fine particles is 50:50 to 10:90. When the ratio of the fumed silica fine particles is high, cracks are deteriorated, and when the ratio is small, it is difficult to obtain glossiness.
[0032]
Further, in the present invention, it is preferable that the relationship between the average particle size and the coarse particles satisfies the expression (1). As coarse particles, the number of particles of 10 μm or more is important. When the value of the expression (1) is 150 or less, the ink absorbency deteriorates, and when the value is 500 or more, the gloss deteriorates.
[0033]
In the present invention, the average particle diameter of the wet silica fine particles is from 100 nm to 350 nm. If the average particle diameter is smaller than 100 nm, the ink absorbency is deteriorated. The average particle diameter of the vapor-phase method fine particles is not particularly limited as long as it is 350 nm or less, but is preferably 100 nm to 350 nm. If it is smaller than 100 nm, the ink absorbency deteriorates, and if it is larger than 350 nm, the gloss deteriorates. .
[0034]
Here, the average particle size is a value measured by a photon correlation method Zetasizer 1000HS manufactured by Malvern. The number of coarse particles is a value measured by HIAC / ROYCO Model 8000A Particle Counter manufactured by Pacific Scientific. The number of coarse particles was measured by diluting the silica fine particle dispersion to prepare a 0.25% solution by mass of the silica fine particles, measuring the coarse particles in 10 ml of the 0.25% liquid using the measuring instrument, This is a value converted into the number of coarse particles per gram of fine particles. The measurement range was measured in the range of 2 to 100 μm, and the number of particles of 10 μm or more was defined as the number of coarse particles.
[0035]
As a pulverization dispersion method for pulverizing and dispersing silica fine particles in an aqueous medium, it is preferable to have a preliminary dispersion step and a main dispersion step, and as a pulverization dispersion method that can be used, a high-speed stirring disperser, an ultrasonic disperser, A roller mill type, a kneader type, a pin mixer type, a high-pressure homogenizer, a wet media type pulverizer (sand mill, ball mill) and the like can be used.
[0036]
The silica concentration at the time of pulverizing and dispersing is preferably 20% or more and 50% or less, more preferably 25% or more and 40% or less in consideration of production efficiency and handleability.
[0037]
The crushed and dispersed silica fine particles go through a step of controlling the number of coarse particles. As a method, a method using centrifugation, a method using a filter, or the like can be used. As a method for centrifugation, Microcut, manufactured by Cletech, Inc. can be used. Examples of the filter include a profile manufactured by Nippon Pall Co., Ltd., and a TCPD manufactured by Advantech Toyo Co., Ltd.
[0038]
After the above-described processing steps, the ink-receiving layer is mixed with a binder, applied to a support, and dried to form an ink receiving layer.
[0039]
After mixing the silica fine particles with a binder, it is preferable to perform treatment again with a filter.
[0040]
The aqueous medium preferably contains at least a cationic polymer. More preferably, a hardener is also contained.
[0041]
The cationic polymer is preferably a polymer having a quaternary ammonium base, and particularly preferably a homopolymer of a monomer having a quaternary ammonium base or a copolymer with one or more other copolymerizable monomers. It is united.
[0042]
Examples of the monomer having a quaternary ammonium base include the following examples.
[0043]
Embedded image

[0044]
Embedded image

[0045]
The monomer copolymerizable with the quaternary ammonium base is a compound having an ethylenically unsaturated group, and examples thereof include the following specific examples.
[0046]
Embedded image

[0047]
Particularly when the cationic polymer having a quaternary ammonium base is a copolymer, the proportion of the cationic monomer is preferably at least 10 mol%, more preferably at least 20 mol%, particularly preferably at least 30 mol%.
[0048]
The monomer having a quaternary ammonium base may be a single monomer or two or more monomers.
[0049]
Hereinafter, specific examples of the cationic polymer that can be used in the present invention will be described, but the invention is not limited thereto.
[0050]
Embedded image

[0051]
Embedded image

[0052]
Embedded image

[0053]
Embedded image

[0054]
The cationic polymer having a quaternary ammonium base is generally highly water-soluble because of the quaternary ammonium base. Depending on the composition and ratio of the monomer containing no quaternary ammonium base to be copolymerized, it may not be sufficiently dissolved in water, but can be dissolved by being dissolved in a mixed solvent of a water-miscible organic solvent and water. If present, it can be used in the present invention.
[0055]
Here, the water-miscible organic solvent includes alcohols such as methanol, ethanol, isopropanol and n-propanol, glycols such as ethylene glycol, diethylene glycol and glycerin, esters such as ethyl acetate and propyl acetate, acetone, methyl ethyl ketone and the like. It refers to an organic solvent such as ketones, amides such as N, N-dimethylformamide, etc., which is generally soluble in water by 10% or more. In this case, the amount of the organic solvent used is preferably equal to or less than the amount of water used.
[0056]
The cationic polymer used in the present invention preferably has a number average molecular weight of 100,000 or less. Here, the number average molecular weight is a value converted into a polyethylene glycol value determined by gel permeation chromatography.
[0057]
When the number average molecular weight exceeds 100,000, the generation of agglomerates is severe when the solution of the cationic polymer is added to the dispersion containing the fine silica particles whose surface is anionic. Also, it is difficult to form a uniform dispersion because a large number of coarse particles are present. When an inkjet recording medium is manufactured using such a composite fine particle dispersion containing a cationic polymer and silica fine particles, it is difficult to obtain high gloss. A particularly preferred number average molecular weight is 50,000 or less. The lower limit of the number average molecular weight is usually 2,000 or more from the viewpoint of the water resistance of the ink.
[0058]
The ratio of the silica fine particles to the cationic polymer can vary depending on the type and particle size of the silica fine particles, or the type and number average molecular weight of the cationic polymer.
[0059]
In the present invention, the ratio is preferably 1: 0.01 to 1: 1 because the surface of the silica fine particles needs to be stabilized by replacing the surface with cationic.
[0060]
When preparing the above dispersion, various additives can be added.
For example, various nonionic or cationic surfactants (anionic surfactants are not preferable because they form aggregates), antifoaming agents, nonionic hydrophilic polymers (polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide) , Polyacrylamide, various sugars, gelatin, pullulan, etc.), nonionic or cationic latex dispersion, water-miscible organic solvents (ethyl acetate, methanol, ethanol, isopropanol, n-propanol, acetone, etc.), inorganic salts, A pH adjuster or the like can be appropriately used as needed.
[0061]
In particular, a water-miscible organic solvent is preferable because it suppresses the formation of fine lumps when the silica fine particles and the cationic polymer are mixed. Such a water-miscible organic solvent is preferably used in the dispersion in an amount of 0.1 to 20% by mass, particularly preferably 0.5 to 10% by mass.
[0062]
The pH at the time of preparing a dispersion of silica fine particles and a cationic polymer can vary widely depending on the type of silica fine particles, the type of cationic polymer, and various additives, but generally the pH is 1 to 8. Yes, particularly preferably 2 to 7.
[0063]
The binder used in the present invention is preferably a water-soluble polymer, such as gelatin (preferably acid-treated gelatin), polyvinylpyrrolidone (preferably having an average molecular weight of about 200,000 or more), pullulan, polyvinyl alcohol or a derivative thereof, and cation-modified polyvinyl alcohol. And polyethylene glycol (preferably having an average molecular weight of 100,000 or more), hydroxyethylcellulose, dextran, dextrin, and water-soluble polyvinyl butyral. These water-soluble polymers function as a hydrophilic binder for the ink receiving layer, and may be used alone. They may be used or two or more of them may be used in combination.
[0064]
Particularly preferred hydrophilic binders are polyvinyl alcohol or cation-modified polyvinyl alcohol.
[0065]
The polyvinyl alcohol preferably used in the present invention has an average degree of polymerization of 300 to 4,000, and is particularly preferable because the film having an average molecular weight of 1,000 or more has good brittleness.
[0066]
Further, the degree of saponification of polyvinyl alcohol is preferably from 70 to 100%, particularly preferably from 80 to 100%.
[0067]
Further, the cation-modified polyvinyl alcohol is obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.
[0068]
Examples of the ethylenically unsaturated monomer having a cationic group include trimethyl- (2-acrylamido-2,2-dimethylethyl) ammonium chloride, trimethyl- (3-acrylamido-3,3-dimethylpropyl) ammonium chloride, N-vinylimidazole, N-vinyl-2-methylimidazole, N- (3-dimethylaminopropyl) methacrylamide, hydroxylethyldimethyl (3-methacrylamido) ammonium chloride, trimethyl- (3-methacrylamidopropyl) ammonium chloride, N- (1,1-dimethyl-3-dimethylaminopropyl) acrylamide and the like.
[0069]
The ratio of the cation-modified group-containing monomer in the cation-modified polyvinyl alcohol is preferably from 0.1 to 10 mol%, more preferably from 0.2 to 5 mol%, based on vinyl acetate. Further, the polymerization degree of the cation-modified polyvinyl alcohol is usually 500 to 4000, preferably 1000 to 4000. Further, the degree of saponification of the cation-modified polyvinyl alcohol is usually 60 to 100 mol%, preferably 70 to 99 mol%.
[0070]
In the inkjet recording medium of the present invention, the water-soluble polymer is preferably hardened with a hardener in order to obtain high gloss and high porosity without deteriorating the brittleness of the film.
[0071]
The hardener is generally a compound having a group that can react with the water-soluble polymer or a compound that promotes the reaction between different groups of the water-soluble polymer, and is appropriately selected depending on the type of the water-soluble polymer. Used selectively.
[0072]
Specific examples of the hardener include, for example, epoxy hardeners (diglycidylethyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidylcyclohexane, N, N- Diglycidyl-4-glycidyloxyaniline, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, etc., aldehyde hardener (formaldehyde, glyoxal, etc.), active halogen hardener (2,4-dichloro-4-hydroxy-1) , 3,5-s-triazine, etc.), active vinyl compounds (1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonylmethyl ether, etc.), boric acid, salts thereof, borax, aluminum alum, etc. Is mentioned.
[0073]
When polyvinyl alcohol or cationically modified polyvinyl alcohol is used as the water-soluble polymer, it is preferable to use a hardener selected from boric acid, a salt thereof, or an epoxy hardener.
[0074]
Most preferred are hardeners selected from boric acid or salts thereof.
As boric acid or a salt thereof, it refers to an oxyacid having a boron atom as a central atom and a salt thereof.Specifically, orthoboric acid, diboric acid, metaboric acid, tetraboric acid, pentaboric acid, octanoic acid or a salt thereof is used. No.
[0075]
The amount of the hardener used varies depending on the type of the water-soluble polymer, the type of the hardener, the type of the silica particles, the ratio to the water-soluble polymer, and the like, but is usually 5 to 500 mg, preferably 10 to 300 mg per gram of the water-soluble polymer. is there.
[0076]
When applying the coating liquid for forming the void layer, the hardener may be added to the coating liquid for forming the void layer and / or to the coating liquid for forming another layer adjacent to the void layer. Alternatively, a coating solution for forming the void layer is applied on a support on which a coating solution containing a hardener is applied in advance. Further, the hardener can be supplied to the void layer by, for example, overcoating the hardener solution after applying and drying the hardener-free coating solution for forming the void layer. Preferably, from the viewpoint of manufacturing efficiency, a hardening agent is added to the coating solution for forming the void layer or the coating solution for forming a layer adjacent thereto, and the hardening agent is simultaneously formed with the void layer. Preferably it is supplied.
[0077]
Particularly preferred in the present invention is a case where silica fine particles are used as primary particles and polyvinyl alcohol or modified polyvinyl alcohol is used as a hydrophilic binder. In this case, the silanol group on the surface of the silica fine particles and the hydroxyl group of vinyl alcohol form a weak hydrogen bond, so that a soft aggregate is formed and the porosity tends to increase.
[0078]
The ratio of the water-soluble polymer to the silica fine particles is usually from 1:10 to 1: 3, particularly preferably from 1: 8 to 1: 5.
[0079]
The method of adding and mixing the water-soluble polymer to the dispersion is, for example, a method of adding the aqueous solution of the water-soluble polymer to the dispersion in a batch while stirring the dispersion, or the method of continuously adding the dispersion and the water-soluble polymer to a static mixer or the like. The method of mixing with a mixer is mentioned. The water-soluble polymer preferably used in the present invention, particularly polyvinyl alcohol, has a high degree of polymerization and therefore has poor solubility, easily forms lumps, and requires a long dissolution time, and therefore has problems in production efficiency and quality.
[0080]
By setting the dissolution temperature to 100 ° C. or higher, the dissolution time can be shortened and lumps are eliminated. The melting temperature is preferably from 100 ° C to 150 ° C, more preferably from 110 ° C to 130 ° C. Raising the temperature too much destroys the structure and, at best, lowers the porosity. For melting at 100 ° C. or more, electricity, oil, pressurized steam, or the like can be used as a heat source. From the viewpoint of production efficiency, it is preferable to dissolve continuously, and for example, a dissolution system manufactured by Noritake can be used. If the melting temperature is low, the lumps cannot be completely dissolved, causing cracks.
[0081]
As the support of the ink jet recording medium of the present invention, a paper support, a plastic support (transparent support), a composite support, etc., which are conventionally known as ink jet recording paper, can be used as appropriate, but a clear image with higher density can be used. It is preferable to use a hydrophobic support in which the ink liquid does not penetrate into the support in order to obtain the ink.
[0082]
Examples of the transparent support include, for example, a film made of a material such as a polyester resin, a diacetate resin, a triacetate resin, an acrylic resin, a polycarbonate resin, a polyvinyl chloride resin, a polyimide resin, cellophane, and celluloid. Among them, those having the property of resisting radiant heat when used as OHP are preferable, and polyethylene terephthalate is particularly preferable. The thickness of such a transparent support is preferably from 10 to 200 μm. It is preferable to provide a known undercoat layer on the ink receiving layer side and the backing layer side of the transparent support from the viewpoint of the adhesion between the ink receiving layer or the back layer and the support.
[0083]
Examples of the support used when it is not necessary to be transparent include resin-coated paper (so-called RC paper) having a polyolefin resin-coated layer obtained by adding a white pigment or the like to at least one of the base paper, and white pigment in polyethylene terephthalate. Is preferred.
[0084]
The method of coating on the support can be appropriately selected from known methods. A preferred method is obtained by applying a coating solution on a support and drying. In this case, two or more layers can be applied simultaneously, and in particular, simultaneous application in which all the hydrophilic binder layers need only be applied once is preferable.
[0085]
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.
[0086]
【Example】
Hereinafter, the present invention will be described specifically with reference to Examples, but embodiments of the present invention are not limited thereto. In the examples, "%" indicates absolutely dry (without moisture) mass% unless otherwise specified.
[0087]
Example 1
[Preparation of silica fine particle dispersion]
(Preparation of silica fine particle pre-dispersion liquid 1 (silica fine particles: wet method silica fine particles))
High-speed rotary stirring and dispersion of commercially available wet silica fine particles (manufactured by Tokuyama Corporation, trade name: T-32, specific surface area 202 / g, average secondary particle size 1.5 μm, precipitated silica fine particles) in an aqueous medium charged into a container. While rotating the machine at a peripheral speed of 20 m / sec, it was gradually charged and pulverized and dispersed. The aqueous medium contained boric acid and P-9. Boric acid was adjusted to 2.7% and P-9 to 4% based on the mass of silica. The silica concentration in the silica fine particle pre-dispersion liquid 1 was 30%.
[0088]
(Preparation of silica fine particle pre-dispersion liquid 2 (silica fine particles: vapor-phase method silica fine particles))
Instead of the above-mentioned commercially available wet silica fine particles, commercially available fumed silica fine particles (manufactured by Nippon Aerosil Co., Ltd., trade name: A-300, specific surface area 300 g / m ² , average primary particle diameter 7 nm, fumed silica fine particles) are used. In the same manner as the silica fine particle preliminary dispersion 1, a silica fine particle preliminary dispersion 2 was prepared. However, boric acid, borax and P-9 were contained in the aqueous medium, so that the content of boric acid and borax was 1.4% and the content of P-9 was 11% based on the mass of silica. The silica concentration in the silica fine particle pre-dispersion liquid 2 was 20%. A concentration of 20% or more was also tested, but the viscosity increased sharply, and the limit was 20% in consideration of handling and equipment load.)
[0089]
(Preparation of silica fine particle pre-dispersion liquid 3 (silica fine particles: wet silica fine particles))
Silica fine particles except that the above commercially available wet silica fine particles were changed to silica fine particles (manufactured by Nippon Silica Co., trade name: AZ-204, specific surface area 300 g / m ² , average secondary particle size 1.3 μm, gel method silica fine particles). In the same manner as the preliminary dispersion 1, a silica fine particle preliminary dispersion 3 was prepared.
[0090]
(Preparation of silica fine particle dispersion liquid 1-1)
The silica fine particle pre-dispersion liquid 1 was dispersed with a sand mill disperser (RL-125, manufactured by Ashizawa Corporation, hereinafter referred to as SM), and then subjected to a filter treatment. The peripheral speed of the SM was 10 m / sec and the residence time was 5 min, and 2 passes were performed. The filter used was a profile manufactured by Pall Corporation. When the average particle size and the coarse particles were measured and the value of the formula (1) was determined, it was 400. The average particle size at this time was 220 nm.
[0091]
(Preparation of silica fine particle dispersion liquid 1-2)
The dispersion was prepared in the same manner as the silica fine particle dispersion liquid 1-1, except that the pass number of the SM was changed to 5 pass. The value of the expression (1) was 180, and the average particle size was 120 nm.
[0092]
(Preparation of silica fine particle dispersion liquid 1-3)
Except that the peripheral speed of the SM was 7 m / sec, the dispersion was prepared in the same manner as the silica fine particle dispersion liquid 1-1. The value of equation (1) was 490, and the average particle size was 330 nm.
[0093]
(Preparation of silica fine particle dispersion liquid 1-4)
Except that the filter treatment was not performed, it was prepared in the same manner as the silica fine particle dispersion liquid 1-1. The value of the formula (1) was 550 and the average particle size was 230 nm (Preparation of silica fine particle dispersion liquid 1-5).
The dispersion was prepared in the same manner as the silica fine particle dispersion 1-2 except that the peripheral speed of the SM was changed to 15 m / sec. The value of formula (1) was 140 and the average particle size was 80 nm (Preparation of silica fine particle dispersion liquid 1-6).
The SM was replaced with a high-pressure homogenizer, dispersed once at a pressure of 350 kg / cm ² , and prepared in the same manner as in the silica fine particle dispersion 1-1 except that the filter treatment was not performed. The value of equation (1) was 800 and the average particle size was 400 nm.
[0094]
(Preparation of silica fine particle dispersion 2-1)
It was prepared in the same manner as the silica fine particle dispersion liquid 1-1, except that the pass number of SM was set to 1 pass using the silica fine particle preliminary dispersion liquid 2. The value of equation (1) was 300 and the average particle size was 200 nm.
[0095]
(Preparation of silica fine particle dispersion 3-1)
Except for using the silica fine particle preliminary dispersion 3, a dispersion was prepared in the same manner as the silica fine particle dispersion 1-1. The value of equation (1) was 490 and the average particle size was 300 nm.
[0096]
[Preparation of Recording Medium 1]
A liquid obtained by mixing the silica fine particle main dispersion 2-1 (silica fine particles: vapor-phase method silica fine particles) and the present dispersion 1-1 (silica fine particles: wet silica fine particles) in a silica mass ratio of 50:50, Polyvinyl alcohol solution (10%, manufactured by Kuraray Co., Ltd .: PVA235) was mixed and coated on both sides with polyethylene. Paper support (thickness of 220 μm, 13% by mass of polyethylene relative to polyethylene in polyethylene on the ink absorbing layer side) (Containing titanium oxide) so as to give a silica coating amount of 16 g / m ² , to thereby obtain a recording medium 1. The mass ratio of silica to polyvinyl alcohol was 6.5: 1. The coating solution was applied at 40 ° C. using a curtain coater. Immediately after coating, the coating solution was cooled in a cooling zone maintained at 0 ° C. for 20 seconds, and then blown for 45 seconds in a wind at 25 ° C. (relative humidity: 15%) for 45 seconds. C. wind (relative humidity: 25%) for 60 seconds, 50 ° C. wind (relative humidity: 25%) for 60 seconds, and dry at 20 to 25 ° C. and 40 to 60% relative humidity. Conditioned for minutes. The coating speed was 300 m / min.
[0097]
[Preparation of Recording Media 2 to 15]
Instead of the silica fine particle main dispersion 2-1 (silica fine particles: vapor-phase method silica fine particles) and the main dispersion 1-1 (silica fine particles: wet silica fine particles), as shown in Table 1, the silica fine particle main dispersion 2- 1 (gas phase method silica) and silica fine particle dispersions 1-1 to 1-6 and 3-1 (wet silica), and recording was performed in the same manner as recording medium 1 except that the mixed silica mass ratio was changed. Mediums 2 to 15 were obtained.
[0098]
The following items were evaluated for the obtained recording media 1 to 15.
(1) The number of cracks per 0.3 m ^{2 of the} crack application surface was visually counted. If the number of cracks is usually 10 or less, it is considered that there is no practical problem.
[0099]
(2) Ink overflow resistance Magenta solid printing was performed using an inkjet printer PM750C manufactured by Seiko Epson Corporation, and the state of ink overflow was visually observed, and evaluated according to the following criteria. This evaluation is an evaluation of the ink absorption amount (void amount).
[0100]
○: No overflow △: There is some overflow but there is no problem in practical use ×: There is a problem in practical use (3) Gloss 75 degree gloss using a variable angle photometer (VGS-1001DP) manufactured by Nippon Denshoku Industries Co., Ltd. Was measured. If this value is 45% or more, it is effective as a photo-like recording medium.
[0101]
(4) Maximum density Magenta solid printing was performed using an inkjet printer PM750C manufactured by Seiko Epson Corporation, and the maximum density (maximum reflection density) was measured.
[0102]
Table 1 shows the results.
[0103]
[Table 1]

[0104]
As is clear from Table 1, it can be seen that the ink jet recording medium of the present invention is generally superior in cracking, ink overflow resistance, glossiness and maximum density as compared with the comparative recording medium.
[0105]
【The invention's effect】
INDUSTRIAL APPLICABILITY According to the present invention, an ink jet recording medium having a high gloss, a small number of cracks, a sufficient ink absorption capacity (ink overflow resistance), and an excellent maximum image density, and an excellent productivity of the ink jet recording medium And a method for manufacturing an ink jet recording medium which can be manufactured at low cost.

Claims (7)

In an ink jet recording medium having an ink receiving layer obtained by applying a coating liquid containing a silica fine particle dispersion on a support, at least one kind of the coating liquid containing the silica fine particle dispersion is at least pulverized and dispersed. An ink jet recording medium containing fumed silica fine particles and at least one kind of wet-process silica fine particles, wherein the fumed silica fine particles and the wet-process silica fine particles have an average particle diameter of 100 nm to 350 nm. . 2. The ink jet recording medium according to claim 1, wherein the wet-processed silica fine particles are wet-processed silica fine particles produced from a wet-process silica of a precipitation method or a gel method. 3. The ink jet recording medium according to claim 1, wherein the mass ratio of the fumed silica fine particles and the wet method silica fine particles is 50:50 to 10:90. The relationship between the average particle size (y (nm)) of the silica fine particles and the number (x) of the silica fine particles having a particle size of 10 μm or more in 1 g of the silica fine particles is determined for each of the fumed silica fine particles and the wet-process silica fine particles. The inkjet recording medium according to any one of claims 1 to 3, wherein the following expression (1) is satisfied.
Equation (1)
150 <y + 17 · ln (x) <500 The inkjet recording medium according to any one of claims 1 to 4, wherein the surface glossiness of the inkjet recording medium is 45% or more as measured at 75 °. A method for producing an ink jet recording medium having an ink receiving layer containing at least one kind of fumed silica fine particles and at least one kind of wet method silica fine particles on a support, comprising: An ink receiving layer is provided by applying a coating solution containing a mixture of a fumed silica fine particle dispersion and a wet silica fine particle dispersion prepared by separately pulverizing and dispersing in an aqueous medium and providing an ink receiving layer. Manufacturing method of recording medium. A method for producing an ink jet recording medium having an ink receiving layer containing at least one kind of fumed silica fine particles and at least one kind of wet method silica fine particles on a support, comprising: a fumed method silica fine particle and a wet method silica. After pulverizing and dispersing the fine particles, through a centrifugal separation or filter treatment step, a step of coating and drying the vapor-phase silica fine particles and the wet-process silica fine particles in which the coarse particle components are controlled together with at least a binder on a support. A method for producing an ink jet recording medium, comprising applying an ink receiving layer by using an ink.