JP2004106327A - Inkjet recording sheet and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording sheet having an ink receiving layer which is excellent in water-based ink absorbency, sharp in ink dot shape, and excellent in ink coloring properties, gives stable high-quality printing image, and is excellent in transportability, transparency, blocking resistance, water resistance, and moisture resistance. <P>SOLUTION: In the inkjet recording sheet, at least one ink receiving layer is formed on at least one side of a substrate sheet. The ink receiving layer is formed from a hydrophilic polyurethane resin having at least a hydrophilic segments, tertiary amino groups, and polysiloxane segments and fine alumina particles. <P>COPYRIGHT: (C)2004,JPO

Description

（式中の、Ｒ_１は炭素数２０以下のアルキル基、脂環族基、芳香族基（ハロゲン、アルキル基で置換されていてもよい）であり、Ｒ_２及びＲ_３は−Ｏ−、−ＣＯ−、−ＣＯＯ−、−ＮＨＣＯ−、−Ｓ−、−ＳＯ−、−ＳＯ_２−等で連結されていてもよい低級アルキレン基であり、Ｘ及びＹは−ＯＨ、−ＣＯＯＨ、−ＮＨ_２、−ＮＨＲ_１、−ＳＨ等の反応性基であり、Ｘ及びＹは同一でも異なってもよい。又、これらの基に誘導できるエポキシ基、アルコキシ基、酸ハライド基、酸無水物基、又はカルボキシルエステル基でもよい。）
【００２６】
一般式（２）で表される化合物

（式中の、Ｒ_１、Ｒ_２、及びＲ_３は前記と同じ定義であるが、但し二つのＲ_１同士は環状構造を形成するものであってもよい。Ｒ_４は−（ＣＨ_２）_ｎ−（ｎは０〜２０の整数）である。）
【００２７】
一般式（３）で表される化合物

（式中の、Ｘ及びＹは前記の定義と同じであり、Ｗは窒素含有複素環、窒素と酸素含有複素環、又は窒素と硫黄含有複素環を表す。）
【００２８】
上記の一般式（１）、（２）又は（３）で表される化合物の具体例としては以下のものが挙げられる。
Ｎ，Ｎ−ジヒドロキシエチル−メチルアミン、
Ｎ，Ｎ−ジヒドロキシエチル−エチルアミン、
Ｎ，Ｎ−ジヒドロキシエチル−イソプロピルアミン、
Ｎ，Ｎ−ジヒドロキシエチル−ｎ−ブチルアミン、
Ｎ，Ｎ−ジヒドロキシエチル−ｔ−ブチルアミン、
メチルイミノビスプロピルアミン、
Ｎ，Ｎ−ジヒドロキシエチルアニリン、
Ｎ，Ｎ−ジヒドロキシエチル−ｍ−トルイジン、
Ｎ，Ｎ−ジヒドロキシエチル−ｐ−トルイジン、
Ｎ，Ｎ−ジヒドロキシエチル−ｍ−クロロアニリン、
Ｎ，Ｎ−ジヒドロキシエチルベンジルアミン、
Ｎ，Ｎ−ジメチル−Ｎ，Ｎ−ジヒドロキシエチル１，３−ジアミノプロパン、
Ｎ，Ｎ−ジエチル−Ｎ，Ｎ−ジヒドロキシエチル１，３−ジアミノプロパン、
【００２９】
Ｎ−ヒドロキシエチル−ピペラジン、
Ｎ，Ｎ−ジヒドロキシエチル−ピペラジン、
Ｎ−ヒドロキシエトキシエチル−ピペラジン、
１，４−ビスアミノプロピル−ピペラジン、
Ｎ−アミノプロピル−ピペラジン、
ジピコリン酸、
２，３−ジアミノピリジン、
２，５−ジアミノピリジン、
２，６−ジアミノピリジン、
２，６−ジアミノ−４−メチルピリジン、
２，６−ジヒドロキシピリジン、
２，６−ピリジン−ジメタノール、
２−（４−ピリジル）−４，６−ジヒドロキシピリミジン、
２，６−ジアミノトリアジン、
２，５−ジアミノトリアゾール、
２，５−ジアミノオキサゾール等がある。
【００３０】
又、これら第３級アミノ化合物のエチレンオキサイド付加物やプロピレンオキサイド付加物等も本発明に使用できる。その付加物としては、例えば、

（上記式中のｎは１〜６０の整数を、ｍは１〜６の整数を表す。）
【００３１】
本発明において親水性ポリウレタン系樹脂を構成する分子鎖中にポリシロキサンセグメントを導入するために使用するポリシロキサン化合物は、分子中に１個又は２個以上の活性水素を含有する反応性基（活性水素含有基）、例えば、アミノ基、エポキシ基、水酸基、メルカプト基、カルボキシル基等を有するポリシロキサン化合物である。活性水素含有基を有するポリシロキサン化合物の好ましい例としては、例えば、下記の如き化合物が挙げられる。
【００３２】
（１）アミノ変性ポリシロキサン化合物

【００３３】
（２）エポキシ変性ポリシロキサン化合物

【００３４】
（３）アルコール変性ポリシロキサン化合物

【００３５】

【００３６】
（４）メルカプト変性ポリシロキサン化合物

【００３７】
（５）カルボキシル変性ポリシロキサン化合物

【００３８】
以上列記した活性水素含有基を有するポリシロキサン化合物は、本発明において使用する好ましい化合物の例示であって、本発明はこれらの例示の化合物に限定されるものではない。従って、これらの例示の化合物のみならず、その他現在市販されており、市場から容易に入手し得る化合物は、いずれも本発明において使用することができる。
【００３９】
本発明で使用する有機ポリイソシアネートとしては、ポリウレタン系樹脂の合成に従来から使用されているものがいずれも使用でき、特に制限されない。好ましいものとして、例えば、４，４′−ジフェニルメタンジイソシアネート（ＭＤＩ）、水添ＭＤＩ、イソホロンジイソシアネート、１，３−キシリレンジイソシアネート、１，４−キシリレンジイソシアネート、２，４−トリレンジイソシアネート、２，６−トリレンジイソシアネート、１，５−ナフタレンジイソシアネート、ｍ−フェニレンジイソシアネート、ｐ−フェニレンジイソシアネート等、或いはこれらの有機ポリイソシアネートと低分子量のポリオールやポリアミンを末端イソシアネートとなる様に反応させて得られるポリウレタンプレポリマー等も使用することができる。
【００４０】
本発明で使用する高分子量親水性ポリオール又は高分子量親水性ポリアミンとしては、水酸基、アミノ基、カルボキシル基等を分子中に有する重量平均分子量が４００〜８０００の範囲のものが好ましい。
末端が水酸基で親水性を有するポリオールとしては、例えば、
ポリエチレングリコール、
ポリエチレングリコール／ポリテトラメチレングリコール共重合ポリオール、
ポリエチレングリコール／ポリプロピレングリコール共重合ポリオール、
ポリエチレングリコールアジペート、
ポリエチレングリコールサクシネート、
ポリエチレングリコール／ポリ−ε−カプロラクトン共重合ポリオール、
ポリエチレングリコール／ポリバレロラクトン共重合ポリオール、
等が挙げられる。特に好ましいのは、ポリエチレングリコールである。
【００４１】
末端がアミノ基で親水性を有するポリアミンとしては、例えば、
ポリエチレンオキサイドジアミン、
ポリエチレンオキサイドプロピレンオキサイドジアミン、
ポリエチレンオキサイドトリアミン、
ポリエチレンオキサイドプロピレンオキサイドトリアミン、
等が挙げられる。
その他、カルボキシル基やビニル基を有したエチレンオキサイド付加物等が挙げられる。
【００４２】
本発明においては、親水性ポリウレタン系樹脂に耐水性を付与するため、上記の親水性ポリオール又はポリアミンとともに、親水性鎖を有しない他のポリオール、ポリアミン、ポリカルボン酸等を適宜共重合させることも可能である。
【００４３】
本発明において必要により使用される鎖延長剤としては、例えば、低分子量ジオールやジアミン等の従来公知の鎖延長剤がいずれも使用でき、特に限定されない。例えば、エチレングリコール、１，３−プロパンジオール、１，４−ブタンジオール、１，５−ペンタンジオール、エチレンジアミン、ヘキサメチレンジアミン等が挙げられる。
【００４４】
本発明で使用するアルミナ分散親水性ポリウレタン系樹脂組成物は、上述の高分子量親水性ポリオール又はポリアミンの一部あるいは全部として、これらのそれぞれとアルミナゾルとの混合物からアルミナゾルの分散溶剤等を除去すること等により得られる微粒子アルミナが分散した高分子量親水性ポリオール又はポリアミンを用い、これらのいずれか、又は両方と有機ポリイソシアネート、少なくとも１個の活性水素含有基と少なくとも１個の第３級アミノ基とを同一分子中に有する化合物及び少なくとも１個の活性水素含有基を有するポリシロキサン化合物を、必要により鎖延長剤と、従来の公知のポリウレタン系樹脂の製造方法に準じて反応させることによって得ることができる。反応は、無溶剤でもよいし、水溶液や有機溶剤中での反応でもよい。無溶剤の場合には、得られたアルミナ分散親水性ポリウレタン系樹脂組成物は、親水性ポリウレタン系樹脂の可溶性溶剤に溶解して使用する。可溶性溶剤は特に限定されず、ジメチルホルムアミドやメチルエチルケトン等が好ましいものとして挙げられる。親水性ポリウレタン系樹脂の合成に使用される溶剤も同様である。アルミナ分散親水性ポリウレタン系樹脂組成物は、親水性ポリウレタン系樹脂溶液に微粒子アルミナが安定に分散している分散液である。親水性ポリウレタン系樹脂を無溶剤で合成した場合も、該樹脂の溶液に微粒子アルミナが安定に分散している分散液が得られる。
【００４５】
本発明で使用する親水性セグメント、第３級アミノ基及びポリシロキサンセグメントを分子鎖中に有する親水性ポリウレタン系樹脂の分子量は特に限定されず、重量平均分子量（ＧＰＣで測定した標準ポリスチレン換算）が３，０００〜８００，０００の範囲が好ましく、更に好ましくは５，０００〜５００，０００の範囲である。
【００４６】
本発明で使用するアルミナ分散親水性ポリウレタン系樹脂組成物において、微粒子アルミナの含有量は、親水性ポリウレタン系樹脂に対して５〜９５重量％が好ましく、更に好ましくは１０〜９０重量％である。微粒子アルミナの含有量が５重量％未満では、本発明の目的である耐ブロッキング性、滑性といった表面特性の発現が不十分となり、一方９５重量％を超えると皮膜の強度、基材に対する接着性等に劣るようになるので好ましくない。驚くべきことに、アルミナ微粒子の含有量が７５〜９５重量％の場合には、本発明のアルミナ分散親水性ポリウレタン系樹脂組成物を用いた塗布液を基材にコーティングすることにより、数ｍμｍ（ｎｍ）サイズの微多孔質の、透明性にも優れた皮膜が形成される。
【００４７】
本発明における親水性ポリウレタン系樹脂中の第３級アミノ基の含有量は、０．１〜５０ｅｑ（当量）／ｇの範囲が好ましく、更に好ましくは０．５〜２０ｅｑ／ｇである。第３級アミノ基の含有量が０．１ｅｑ／ｇ未満、すなわち分子量１０，０００当たり１個以下では、本発明の所期の目的である耐水性、耐ブロッキング性といった特性の発現が不十分となり、一方、第３級アミノ基の含有量が５０ｅｑ／ｇを超えると、すなわち分子量２０当たり１個を超えると樹脂中の親水性部分の減少による撥水性が強くなり、吸水性能や防曇性に劣るようになるので好ましくない。
【００４８】
本発明における親水性ポリウレタン系樹脂中のポリシロキサンセグメントは、主鎖中或いは側鎖中でも、又は両方に含有されていてもよい。親水性ポリウレタン系樹脂中の該セグメントの含有量は、０．１〜１０重量％が好ましく、更に好ましくは２〜１０重量％である。ポリシロキサンセグメントの含有量が０．１重量％未満では本発明の目的である耐水性、耐ブロッキング性、滑性といった表面特性の発現が不十分となり、一方、１０重量％を超えるとポリシロキサンセグメントによる撥水性が強くなるとともに、本発明が利用する環境応答性に乏しくなり、吸水性、防曇性や透明性に劣るようになるので好ましくない。
【００４９】
又、本発明におけるポリウレタン系樹脂中の親水性セグメントの含有量は、３０〜８０重量％の範囲が好ましく、更に好ましくは５０〜７５重量％の範囲である。親水性セグメントの含有量が３０重量％未満では、吸水性、防曇性に劣るようになり、一方、８０重量％を超えると耐水性、耐ブロッキング性に劣るようになり好ましくない。
【００５０】
本発明のインクジェット用記録シートの基材シートとしては、例えば、紙、プラスチックフィルム、ガラス、布、木材、金属等が用いられるが、特に限定されない。紙としては、例えば、上質紙、中質紙、コート紙、キャストコート紙等が挙げられる。プラスチックフィルムとしては、例えば、ポリエステル、セルローストリアセテート、ポリカーボネート、ポリ塩化ビニル、ポリプロピレン、ポリアミド、ポリスチレン、ポリエチレン、ポリメチルメタアクリレート等の厚さ５０乃至２５０μｍのシート等が挙げられる。
又、基材シートには、必要に応じてインク受容層に対する接着性を付与するプライマー層や非受容層側である基材シートの裏面にカール防止層や摩擦係数を改良する滑性層を設けることもできる。
【００５１】
本発明においてインク受容層を形成するために前記のアルミナ分散親水性ポリウレタン系樹脂組成物が使用される。
インク受容層を構成する樹脂成分としては、前記の親水性ポリウレタン系樹脂単独でもよいが、インクジェット記録用インクの組成により、親水性及び／又は吸水性を更に付与するか調整するために、前記の親水性ポリウレタン系樹脂に水溶性高分子を組み合わせて使用してもよい。
水溶性高分子としては、例えば、ポリビニルアルコール、変性ポリビニルアルコール、ヒドロキシエチルセルロース、ＣＭＣ、セルロース誘導体、ポリビニルピロリドン、ポリアクリル酸、ポリアクリル酸系重合体、澱粉、カチオン澱粉、ゼラチン、カゼイン等が挙げられる。
【００５２】
又、インク受容層や印字画像に耐水性や耐久性を更に付与するために、前記の親水性ポリウレタン系樹脂に疎水性の高分子を組み合わせて使用してもよい。疎水性高分子としては、例えば、ポリエステル樹脂、ポリ塩化ビニル樹脂、ポリスチレン樹脂、ポリメチルメタクリレート樹脂、ポリカーボネート樹脂、ポリウレタン樹脂、塩化ビニル−酢酸ビニル共重合樹脂、アクリロニトリル−スチレン共重合樹脂、ポリビニルブチラール樹脂、ポリアミド樹脂、エポキシ樹脂、尿素樹脂、メラミン樹脂等の如くインク受容層の形成に一般に使用されている合成樹脂が挙げられる。
【００５３】
又、インク受容層のインクの吸収性、定着性、発色性、更にはブロッキング性及び耐水性を向上させる目的で、アルミナ分散親水性ポリウレタン系樹脂組成物に、無機及び有機の顔料や樹脂粒子等を含有させることができる。
使用される顔料や樹脂粒子としては、例えば、カオリン、デラミカオリン、水酸化アルミニウム、シリカ、珪藻土、炭酸カルシウム、タルク、酸化チタン、硫酸カルシウム、硫酸バリウム、酸化亜鉛、珪酸カルシウム、珪酸マグネシウム、コロイダルシリカ、ゼオライト、ベンナイト、セリサイト、リトポン等の鉱物質顔料、多孔質顔料やポリスチレン樹脂、尿素樹脂、アクリル樹脂、メラミン樹脂、ベンゾグアナミン樹脂、ポリウレタン樹脂、その他有機顔料等の微粒子、多孔質微粒子及び中空粒子等の公知の顔料や樹脂粒子の中からインクジェット用記録シートの品質設計に応じて１種又は２種以上が適宜使用される。この場合、これら顔料や樹脂粒子の使用量は、インク受容層形成に使用するアルミナ分散親水性ポリウレタン系樹脂組成物の全固形分の０〜９５重量％、好ましくは１０〜９０重量％の範囲である。
【００５４】
更に、必要に応じて、アルミナ分散親水性ポリウレタン系樹脂組成物に上記以外に増粘剤、離型剤、浸透剤、湿潤剤、熱ゲル化剤、サイズ剤、消泡剤、抑泡剤、発泡剤、着色剤、蛍光増白剤、紫外線吸収剤、酸化防止剤、クエンチャー剤、防腐剤、帯電防止剤、架橋剤、分散剤、滑剤、可塑剤、ｐＨ調整剤、流動性改良剤、固化促進剤、耐水化剤等の各種助剤を適宜配合することも可能である。
【００５５】
本発明においてインク受容層を形成するために使用するアルミナ分散親水性ポリウレタン系樹脂組成物は、溶剤中で合成した前記の親水性ポリウレタン系樹脂の溶液を使用することが好ましく、無溶剤で合成した場合には前記の親水性ポリウレタン系樹脂を溶剤に溶解して使用する。必要により添加する成分が溶剤可溶性であれば、上記の親水性ポリウレタン系樹脂組成物に直接添加して溶解してもよく、又は予め溶剤に溶解して添加してもよい。更に不溶性の添加成分を加え、アルミナ分散ポリウレタン系樹脂組成物は、通常、固形分が５〜１５重量％程度の塗布液に調製される。
【００５６】
調製された塗布液は、グラビアコート、ダイレクト又はリバースロールコート、ワイヤーバーコート、エアナイフコート、カーテンコート、ブレードコート、ロッドコート、ダイコート等で基材シートに塗布される。更に、塗布後、マシンカレンダー、スーパーカレンダー、ソフトカレンダー等のカレンダーを用いて仕上げ、インクジェット記録用シートが得られる。
【００５７】
形成されるインク受容層の厚みは、上記組成物の乾燥重量で５〜１００ｇ／ｍ^２程度となる厚みが好ましく、更に好ましくは１０〜５０ｇ／ｍ^２程度である。インク受容層の厚みが５ｇ／ｍ^２未満では、インク受容層によるインクの吸収が不十分となり、厚みが１００ｇ／ｍ^２を超えると、得られる効果は飽和となり不経済であり、その上インク受容層の折れ割れやカール等の発生が起こりやすくなる。
【００５８】
【実施例】
次に実施例及び比較例を挙げて本発明を更に具体的に説明する。尚、文中の部又は％は重量基準である。
【００５９】
参考例１
ポリエチレングリコール（分子量１，０００）７００部とアルミナ水ゾル（アルミナ平均粒径１５０〜１６０ｎｍ、固形分４０重量％）７５０部を充分に混合し、得られた混合物を攪拌しながら７０℃で減圧脱水を行った。
理論量の水が留去された後、温度を１２０℃に上げ１３３．３Ｐａ以下の減圧下で水分を除去してアルミナ含有量３０％の白色固体状ポリオール（Ａ）を得た。このポリオールは、水酸基価７６ｍｇＫＯＨ／ｇ、水分率０．１５％、８０℃では透明で、粘度は３８０ｄＰａ・ｓであった。
【００６０】
参考例２
ポリエチレングリコール（分子量５９０）１００部とアルミナ水ゾル（アルミナ平均粒径１０〜２０ｎｍ、固形分２０重量％）５００部を充分に混合し、得られた混合物を攪拌しながら７０℃で減圧脱水を行った。
理論量の水が留去された後、温度を１２０℃に上げ１３３．３Ｐａ以下の減圧下で水分を除去してアルミナ含有量５０重量％の白色固体状ポリオール（Ｂ）を得た。このポリオールは、水酸基価９５ｍｇＫＯＨ／ｇ、水分率０．１２％、９０℃で軟化するものであった。
【００６１】
参考例３
ポリエチレンオキサイドジアミン（テキサコケミカル社製ジェファーミンＥＤ；分子量６００）１００部とアルミナ水ゾル（アルミナ平均粒径１５０〜１６０ｎｍ、固形分４０重量％）２２５０部を充分に混合し、得られた混合物を攪拌しながら７０℃で減圧脱水を行った。
理論量の水が留去された後、温度を１２０℃に上げ１３３．３Ｐａ以下の減圧下で水分を除去してアルミナ含有量９０重量％の白色固体状ポリアミン（Ｃ）を得た。このポリアミンは、アミン当量３０ｇ／ｍｏｌ、水分率０．２０％、１１０℃で軟化するものであった。
【００６２】
参考例４
（アルミナ分散ポリウレタン樹脂組成物の製造）

上記構造のポリジメチルシロキサンポリオール（分子量３，２００）５部と、参考例１のポリオール（Ａ）１４５部、Ｎ−メチルジエタノールアミン２０部及ジエチレングリコール３部を、２００部のメチルエチルケトンと２００部のジメチルホルムアミドとの混合溶剤中に溶解し、６０℃でよく攪拌しながら、７７部の水添ＭＤＩを１００部のメチルエチルケトンに溶解した溶液を徐々に滴下した。滴下終了後、８０℃で８時間反応させた後ジメチルホルムアミド５００部を加えて本発明のアルミナ分散ポリウレタン樹脂組成物の溶液を得た。
【００６３】
この溶液は固形分２０％で、５０ｄＰａ・ｓ（２５℃）の粘度を有し、ポリウレタン樹脂のＧＰＣで測定した（以下の例においても同様）重量平均分子量は６２，０００であり、該樹脂中の第３級アミノ基の含有量は０．７９ｅｑ／ｇ、親水性セグメントの含有量は４９．１％、ポリシロキサンセグメントの含有量は２．１％で、アルミナの含有量は１７．４％であった。
この樹脂組成物溶液から形成したフィルムは、透明で、破断強度は２８．８Ｍｐａ、破断伸度は５０％、且つ軟化点は１６３℃であった。
【００６４】
参考例５
（アルミナ分散ポリウレタン−ポリウレア樹脂組成物の製造）

上記構造のエチレンオキシド付加型ポリジメチルシロキサンポリオール（分子量４，５００）５部と参考例２のポリオール（Ｂ）１２０部及びポリエチレンオキサイドジアミン（分子量２，０００）２５部、Ｎ，Ｎ−ジメチル−Ｎ′，Ｎ′−ジヒドロキシエチル−１，３−ジアミノプロパン２５部を２００部のメチルエチルケトン及び２００部のジメチルホルムアミド混合溶剤中に溶解し、６０℃でよく攪拌しながら、６４部の水添ＭＤＩを１００部のメチルエチルケトンに溶解した溶液を徐々に滴下した。滴下終了後、８０℃で８時間反応させた後ジメチルホルムアミド４５５部を加えて本発明のアルミナ分散ポリウレタン−ポリウレア樹脂組成物の溶液を得た。
【００６５】
この溶液は固形分２０％で４０ｄＰａ・ｓ（２５℃）の粘度を有していた。ポリウレタン−ポリウレア樹脂の重量平均分子量は４１，０００であり、樹脂中の第３級アミノ基の含有量は１．４６ｅｑ／ｇ、親水性セグメントの含有量は４７．５％、ポリシロキサンセグメントの含有量は２．５％で、アルミナの含有量は２５．１％であった。
この　樹脂組成物溶液から形成したフィルムは、透明で破断強度は２１．５Ｍｐａ、破断伸度は２０％、且つ軟化点は１７６℃であった。
【００６６】
参考例６
（アルミナ分散ポリウレア樹脂組成物の製造）

上記構造のポリジメチルシロキサンジアミン（分子量３，８８０）２部、参考例３のポリアミン（Ｃ）１４８部及びメチルイミノビスプロピルアミン３部をジメチルホルムアミド２５０部に溶解し、内温を０〜−５℃に保持して充分に撹拌しながら１２部の水添ＭＤＩを１００部のジメチルホルムアミドに溶解した溶液を徐々に滴下して反応させた。
滴下終了後、次第に内温を上昇させ、５０℃に達した所でさらに５時間反応させた後ジメチルホルムアミド３１０部を加えて本発明のアルミナ分散ポリウレア樹脂組成物の溶液を得た。
【００６７】
この溶液は固形分２０％で１１０ｄＰａ・ｓ（２５℃）の粘度を有し、ポリウレア樹脂の重量平均分子量は３８，０００であり、樹脂中の第３級アミノ基の含有量は０．７２ｅｑ／ｇ、親水性セグメントの含有量は４６．５％、ポリシロキサンセグメントの含有量は６．２％で、アルミナの含有量は８０．７％であった。
この樹脂組成物溶液から形成したフィルムは、やや半透明で多孔質で、破断強度は５．０Ｍｐａ、破断伸度は５％、且つ軟化点は２１０℃であった。
【００６８】
参考例７
ポリジメチルシロキサンポリオール及びＮ−メチルジエタノールアミンを使用せず、又、参考例１のポリオール（Ａ）のアルミナを除いたポリオールを使用する他は参考例４と同じ材料と処方によりポリウレタン樹脂の溶液を得た。
この溶液は固形分２０％で、８０ｄＰａ・ｓ（２５℃）の粘度を有し、ポリウレタン樹脂の重量平均分子量は６９，０００であった。
この樹脂溶液から形成したフィルムは、破断強度４２．０Ｍｐａ、破断伸度４５０％、軟化点は１０２℃であった。
【００６９】
参考例８
ポリジメチルシロキサンポリオール及びＮ，Ｎ−ジメチル−Ｎ′，Ｎ′−ジヒドロキシエチル−１，３−ジアミノプロパンを使用せず、又、参考例２のポリオール（Ｂ）のアルミナを除いたポリオールを使用する他は参考例５と同じ材料と処方によりポリウレタン−ポリウレア樹脂の溶液を得た。
この溶液は固形分２０％で、５２ｄＰａ・ｓ（２５℃）の粘度を有し、ポリウレタン−ポリウレア樹脂の重量平均分子量は５８，０００であった。
この樹脂溶液から形成したフィルムは、破断強度３５．３ＭＰａ、破断伸度４００％、軟化点は９５℃であった。
【００７０】
参考例９
ポリジメチルシロキサンジアミン及びメチルイミノビスプロピルアミンを使用せず、又、参考例３のポリアミン（Ｃ）のアルミナを除いたポリアミンを使用する他は参考例６と同じ材料と処方によりポリウレア樹脂の溶液を得た。
この溶液は固形分２０％で、３８ｄＰａ・ｓ（２５℃）の粘度を有し、ポリウレア樹脂の重量平均分子量は４２，０００であった。
この　樹脂溶液から形成したフィルムは、破断強度２５．７ＭＰａ、破断伸度３５０％、軟化点は１１７℃であった。
【００７１】
参考例１０〜１２
参考例１〜３のそれぞれのアルミナ水ゾルを、参考例７〜９のそれぞれの樹脂溶液中に攪拌しながら添加したが、粒子が析出し溶液は不透明となった。
【００７２】
参考例１３
鹸化度９８．５％のポリビニルアルコール（重合度５５０）の５％水溶液を調製した。
【００７３】
実施例１〜３
参考例４〜６で得られたアルミナ分散親水性ポリウレタン系樹脂組成物を坪量３５ｇ／ｍ^２質紙に、エアーナイフコーターで、乾燥後の厚みが２５μｍとなるように塗工し、インク受容層を形成し、本発明のインクジェット記録用シートとした。
【００７４】
比較例１〜７
参考例７〜１３で得られた樹脂溶液を坪量３５ｇ／ｍ^２質紙に、エアーナイフコーターで、乾燥後の厚みが２５μｍとなるように塗工して、インク受容層を形成し、比較例のインクジェット記録用シートとした。
【００７５】
〔インクジェット用記録シートの評価〕
以上のようにして得られた１０種類のインクジェット用記録シートについて、水溶性染料インクで印字記録するインクジェットプリンター（セイコーエプソン社製ＰＭ−８００Ｃ）でイエロー、マゼンタ、シアン及びブラックの４色を使用して印字記録を行い、以下の項目の評価を行った。
（１）ブロッキング性
樹脂コーティング面に未処理ＰＥＴフィルムを重ね、荷重０．２９ＭＰａ、温度４０℃で一日放置後のブロッキング性の評価を行った。結果を以下のように表示する。
結果の表示は以下の通りである。
○：ブロッキング性なし　　　　△：ややブロッキング性あり
×：ブロッキング性あり
（２）透明性
樹脂コーティング面の曇りを目視にて判定した。結果を以下のように表示する。
○：完全に透明　　　　△：僅かに曇りがある　　　　×：完全に不透明
【００７６】
（３）発色鮮明性
インクジェットプリンターでカラー印字後、得られたカラー画像の発色鮮明性を目視により観察した。結果を以下のように表示する。
○：滲みがなく鮮明　　　　△：やや滲みがあり、やや不鮮明
（４）インキの乾燥性
インクジェットプリンターでカラー印字後、５０ｇ／ｍ^２の荷重で５秒間濾紙を押し付けインキが濾紙に転写しなくなるまでの時間を測定した。
（５）印字画像の耐水性
インクジェットプリンターでカラー印字後、記録シートを水中に漬け（２０℃、１時間）、その後、室温で乾燥した際の、記録画像の滲み、発色の変化を目視により観察。結果を以下のように表示する。
○：変化なし　　　　　　△：インキ及び皮膜に変化が認められる
×：インキがかなりとれるか、皮膜ごと取れる
以上の評価結果を表１に示す。
【００７７】

【００７８】
【発明の効果】
以上の本発明によれば、インクの吸収・乾燥性、発色性に優れ、安定した高品位の印字画像を形成し、印字画像に優れた耐水性、耐湿性を付与し、更にそれ自体及び印字画像の透明性に優れ、耐ブロッキング性、搬送性に優れたインク受容層を有するインクジェット用記録シートが提供される。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink jet recording sheet and a method for producing the same, and more particularly, to imparting excellent water resistance and moisture resistance to a printed image, and exhibiting excellent ink absorbency and ink color development, and stable high quality printing. The present invention relates to an ink jet recording sheet having an ink receiving layer capable of recording an image and having excellent transparency, transportability and blocking resistance, and a method for producing the same.
[0002]
[Prior art]
The ink jet recording method employs various operating principles, for example, an electrostatic suction method, a method of applying mechanical vibration or displacement to ink using a piezoelectric element, a method of heating and foaming the ink to utilize the pressure, and the like. It records images and characters by flying fine droplets and attaching them to a recording sheet such as paper. Various recording methods are available for high-speed printing, low noise generation, high-quality printing, and multicolor printing. It is rapidly spreading to applications.
[0003]
In such a recording medium used for ink jet recording, the ink adhering to the recording medium causes bleeding or flow, so that the ink is quickly absorbed so that the print quality is not impaired, and a clear ink is formed. A sheet such as paper provided with an ink receiving layer mainly composed of various pigments and resins on a support such as a paper, or a recording sheet in which a porous pigment is formed on the paper itself so that dots are formed. Proposed.
[0004]
For example, Patent Literature 1 discloses that an inorganic pigment and an organic pigment are used in combination as pigments and an ink receiving layer made of a water-soluble polymer is provided. Patent Literature 2 discloses that fine powder silica and polyvinyl having a silanol group are provided. It is disclosed that an ink receiving layer made of an alcohol copolymer is provided.
[0005]
However, with the improvement of the performance of the inkjet recording apparatus such as high-speed, high-definition or full-color of the apparatus and the expansion of applications, it is required that the inkjet recording sheet also has the following advanced characteristics. Became.
(1) Ink absorption is fast and ink absorption capacity is large;
(2) high color development of the ink;
(3) the surface strength of the ink receiving layer is high;
(4) the support has water resistance and does not cause unevenness or curl on the support by ink;
(5) The image printed on the ink receiving layer has good image storability such as water resistance and ozone resistance;
(6) The ink receiving layer does not change with time.
[0006]
Conventionally, as a component of the ink receiving layer provided on the ink jet recording sheet in order to satisfy these requirements, a porous pigment or a water-soluble polymer having excellent ink absorbency has been used, or to improve the water resistance of the ink receiving layer. It has been proposed and studied to use latex as the base material, and further to use synthetic paper or plastic having water resistance for the support itself.
[0007]
However, those using paper as a support or using only a water-soluble polymer as an ink receiving layer have poor water resistance, bleeding of a printed portion, and poor image clarity.
In the case where the porous pigment is dispersed in the ink receiving layer, the porous pigment generally reduces transparency so that it is usually used as a matting agent (matting agent). Even if the dispersion amount is small, the transparency is significantly reduced.
On the other hand, the use of synthetic paper or plastic film for the support or the use of latex for the resin of the ink receiving layer has problems in the adhesiveness between the ink receiving layer and the support, the ink absorbency and the drying property. .
[0008]
[Patent Document 1]
JP-A-57-82085 [Patent Document 2]
JP-A-62-268682 [0009]
[Problems to be solved by the invention]
The present invention is particularly excellent in water-based ink absorptivity, and the shape of the ink dots is sharp, excellent in the color developability of the ink, gives a stable high-quality printed image, further transportability, transparency, blocking resistance, It is an object of the present invention to provide an inkjet recording sheet having an ink receiving layer having excellent water resistance and moisture resistance.
[0010]
[Means for Solving the Problems]
The above object is achieved by the present invention described below.
That is, the present invention relates to an ink jet recording sheet provided with at least one ink receiving layer on at least one surface of a base sheet, wherein the ink receiving layer comprises at least an organic polyisocyanate, a high molecular weight hydrophilic polyol and / or a polyamine, A compound having one active hydrogen-containing group and at least one tertiary amino group in the same molecule, and a polysiloxane compound having at least one active hydrogen-containing group, if necessary, a chain extender An ink jet recording sheet comprising a hydrophilic polyurethane resin having a hydrophilic segment, a tertiary amino group, and a polysiloxane segment obtained by the reaction, and fine-particle alumina.
[0011]
The present invention also relates to a method for producing an ink jet recording sheet provided with at least one ink receiving layer on at least one surface of a substrate sheet, wherein the ink receiving layer comprises an organic polyisocyanate, a high molecular weight hydrophilic polyol and / or Or a polyamine, a compound having at least one active hydrogen-containing group and at least one tertiary amino group in the same molecule, and a polysiloxane compound having at least one active hydrogen-containing group, if necessary. When a hydrophilic polyurethane-based resin having a hydrophilic segment, a tertiary amino group and a polysiloxane segment is synthesized by reacting with a chain extender, a high-molecular-weight hydrophilic polyol / or at least a part of a polyamine has a high molecular weight. Using a mixture of high molecular weight hydrophilic polyol / or polyamine and fine particle alumina Is an inkjet recording sheet manufacturing method, which comprises forming with that alumina dispersion hydrophilic polyurethane resin composition.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described in more detail with reference to embodiments of the present invention.
In the ink jet recording sheet of the present invention, the ink receiving layer is composed of a hydrophilic polyurethane resin as a resin component and fine-particle alumina. The hydrophilic polyurethane resin of the present invention has an organic polyisocyanate, a high molecular weight hydrophilic polyol and / or a polyamine, and at least one active hydrogen-containing group and at least one tertiary amino group in the same molecule. Hydrophilic polyurethane having a hydrophilic segment, a tertiary amino group and a polysiloxane segment obtained by reacting a compound and a polysiloxane compound having at least one active hydrogen-containing group with a chain extender, if necessary. It is a system resin.
[0013]
On the other hand, alumina fine particles are produced by using a mixture of high molecular weight hydrophilic polyol or polyamine and fine particle alumina as at least a part of high molecular weight hydrophilic polyol or polyamine when synthesizing this hydrophilic polyurethane resin. (Dispersed) in the hydrophilic polyurethane resin (hereinafter, referred to as an alumina-dispersed hydrophilic polyurethane resin composition in the present invention). The fine-particle alumina is stably dispersed in the solution of the hydrophilic polyurethane-based resin although no dispersant is used. Using the alumina-dispersed hydrophilic polyurethane-based resin composition, an ink receiving layer of an ink jet recording sheet of the present invention is formed. In the present invention, the polyurethane-based resin is a generic term for polyurethane resin, polyurea resin, and polyurethane-polyurea resin.
[0014]
In the present invention, the mixture of high-molecular-weight hydrophilic polyol or polyamine and fine-particle alumina can be used by mechanically mixing and dispersing high-molecular-weight hydrophilic polyol or polyamine with fine-particle alumina. It is preferable to use one obtained by removing the dispersion solvent of alumina sol from the mixture with alumina sol. When the above-mentioned polyols and polyamines are used as solutions of their soluble solvents, these solvents are also removed.
The alumina sol in the present invention is usually obtained by dispersing fine-particle alumina or a fine-particle alumina compound stably in water and / or alcohol as a dispersion solvent. As the dispersing solvent, ketones, esters, and other organic solvents are also used in addition to the above. The average particle size of the fine particle alumina in the alumina sol is usually 1 μm or less, and particularly preferably 1 to 300 μm (nm).
[0015]
When the ink receiving layer of the ink jet recording paper is formed, a method using a resin solution, a dispersion, or the like is generally used.
As a method for dispersing the alumina fine particles in the solution of the polyurethane resin, the following method is exemplified. For example, a method in which alumina fine particles are dispersed in a polyurethane resin using a usual dispersion mixer, and this is dissolved in a solvent for use (1), a method in which alumina fine particles or alumina sol is added and dispersed in a polyurethane resin solution ( 2) can be considered. However, the method (1) is economically disadvantageous because a stable dispersion cannot be obtained even when a dispersant is used. The method (2) is a general method, but it is impossible to stably disperse the alumina fine particles even by using this method even if a dispersant is used. Even when alumina sol is used, the dispersion stability is low, and both are easily separated with time. The reason for this is that the compatibility (affinity) between the polyurethane resin and the fine-particle alumina and the stability of the two against changes in pH, or the difference in the surface properties between the polyurethane resin and the fine-particle alumina are different.
As another method, a method of adding alumina sol to the synthesis system at the time of the synthesis reaction of the polyurethane-based resin is also considered. However, water or alcohol-based dispersion medium of the alumina sol cannot be used because it reacts with isocyanate. Even if the solvent-based alumina sol is used, a polyurethane resin solution having dispersion stability cannot be obtained.
[0016]
However, the high molecular weight hydrophilic polyols and polyamines described below used in the present invention have extremely high compatibility (affinity) with alumina due to their hydrophilicity, and can be stably mixed with alumina sol at an arbitrary ratio. Then, by removing the dispersion medium of the alumina sol from the mixture by an arbitrary method, a high-molecular-weight hydrophilic polyol or polyamine in which fine-particle alumina is dispersed very stably is obtained, and fine particles in the high-molecular-weight hydrophilic polyol or polyamine are obtained. Even if the dispersion amount of alumina increases, the increase in the viscosity of the polyol and the polyamine is small, and by reacting this mixture with other raw material components in a solvent, the hydrophilic polyurethane resin can be used without using a dispersant. A dispersion in which the alumina fine particles are stably dispersed in the solution is obtained. When the reaction is carried out without a solvent, the same stable dispersion as described above can be obtained by dissolving the polyurethane resin in the soluble solvent. These dispersions are all very transparent, and the films formed therefrom are also transparent.
[0017]
The removal of the dispersion medium and the organic solvent of the alumina sol from the mixture of the high molecular weight hydrophilic polyol or the polyamine or the solution thereof and the alumina sol can be generally easily performed by distillation under reduced pressure or the like. In this case, the distillation is preferably performed at a low temperature under reduced pressure, and particularly preferably at 70 ° C. or lower. If the temperature is higher than this, aggregation of fine-particle alumina may occur, and the dispersion stability of alumina may be reduced, and alumina-dispersed high-molecular-weight hydrophilic polyol or polyamine having low transparency may be generated. The mixing ratio of the high molecular weight hydrophilic polyol or polyamine and the alumina sol is preferably 5 to 95% by weight, more preferably 10 to 90% by weight, based on the hydrophilic polyurethane-based resin in which the particulate alumina is formed. Amount.
[0018]
In the present invention, the hydrophilic polyurethane-based resin used as a resin constituting the ink receiving layer has at least one tertiary amino group identical to a hydrophilic segment having a high molecular weight hydrophilic polyol and / or polyamine as a structural unit. It has a tertiary amino group-containing segment having a compound in the molecule as a constitutional unit and a polysiloxane segment. When a chain extender is not used, these segments are respectively connected at random by a urethane bond, a urea bond, or a urethane-urea bond. When a chain extender is used, there is a bond in which a short chain which is a residue of the chain extender is present between these bonds together with these bonds.
[0019]
By introducing a tertiary amino group and a polysiloxane segment into the molecule, the hydrophilic polyurethane resin of the present invention has excellent adhesiveness to various materials, and excellent water absorption, antifogging properties, and transparency. , Flexibility, water-based ink writing, and excellent water resistance, blocking resistance, and lubricity.
[0020]
The reason why the water resistance is imparted is not clear, but is considered as follows. Dyeing / pigment molecules of printing inks and inkjet inks generally have an anionic carboxyl group or sulfonic acid group in the molecule, and the tertiary amino group in the hydrophilic polyurethane-based resin and the above-mentioned tertiary amino group. When the dye / pigment mixes or comes into contact with the dye / pigment, an ionic bond is formed between the dye / pigment and the tertiary amino group in the resin, and the responsiveness of the dye / pigment due to the environmental responsiveness of the polysiloxane segment described below. It is considered that the fixability and the water resistance of the recorded image are improved.
[0021]
However, in the presence of moisture, the ionic bond as described above is easily dissociated, and although water resistance cannot be expected to be improved, water resistance is improved. Although the reason for the improvement in water resistance is not clear, the polyurethane resin in the present invention is hydrophilic, but a hydrophobic portion is present in the molecule, and the hydrophilic portion and the tertiary amino acid in the resin are present. After the ionic bond is formed between the group and the dye / pigment, the hydrophobic portion is expected to surround the ionic bond portion, so that the water resistance is expected to be improved.
[0022]
Next, introduction of a hydrophobic (water-repellent) polysiloxane segment into the polyurethane resin structure should not be expected to provide good results in terms of water absorption and hydrophilicity. However, the surface of a film formed from a polyurethane resin having a low polysiloxane segment content is completely covered with a polysiloxane component in a dry state, but when immersed in water, the polysiloxane component is buried in the resin film. It is known that this phenomenon occurs, that is, there is an environmental response (Polymer Transactions, Vol. 48 [No. 4], p. 227 (1991), etc.).
[0023]
The hydrophilic polyurethane-based resin in the present invention utilizes this phenomenon, and by appropriately controlling the polysiloxane segment content in the resin, a high humidity or water-based ink is applied to the film surface using the resin. In the case of printing, etc., the surface shows hydrophilicity due to environmental responsiveness, the surface during or after drying is covered with a polysiloxane component, and excellent water resistance, blocking resistance, lubricity, etc. Is expressed. The present inventors have already applied for patent applications such as Japanese Patent Application Nos. 10-235545, 10-240811 and 10-170296 regarding the effect of introducing a polysiloxane segment into these polyurethane resins. Has revealed.
[0024]
In the present invention, the compound used to introduce a tertiary amino group into the molecular chain constituting the hydrophilic polyurethane-based resin is at least one active hydrogen-containing group (reactive group), for example, an amino group, an epoxy group, A hydroxyl group, a hydroxyl group, a mercapto group, a carboxyl group, or an alkoxy group, an acid halide group, a carboxyester group, an acid anhydride group, etc. It is a compound having three tertiary amino groups.
[0025]
Preferred examples of the tertiary amino group-containing compound having a reactive group as described above include, for example, the following compounds.
Compound represented by general formula (1)

(In the formula, R ₁ is an alkyl group having 20 or less carbon atoms, an alicyclic group, or an aromatic group (which may be substituted with a halogen or an alkyl group), and R ₂ and R ₃ represent —O—, -CO -, - COO -, - NHCO -, - S -, - SO -, - SO 2 - is a substituted lower alkylene group which may be coupled with such, X and Y are -OH, -COOH, -NH ₂ , -NHR ₁ , -SH and the like, and X and Y may be the same or different, and an epoxy group, an alkoxy group, an acid halide group, an acid anhydride group, which can be derived from these groups. Or a carboxyl ester group.)
[0026]
Compound represented by general formula (2)

(In the _formula, R 1, _{R 2,} and _{R 3} are the same definitions as described above, provided that good .R ₄ Two _{R 1} together be for forming a cyclic structure - _(CH 2) _n- (n is an integer of 0 to 20).
[0027]
Compound represented by general formula (3)

(In the formula, X and Y are the same as defined above, and W represents a nitrogen-containing heterocycle, a nitrogen- and oxygen-containing heterocycle, or a nitrogen- and sulfur-containing heterocycle.)
[0028]
Specific examples of the compound represented by the above general formula (1), (2) or (3) include the following.
N, N-dihydroxyethyl-methylamine,
N, N-dihydroxyethyl-ethylamine,
N, N-dihydroxyethyl-isopropylamine,
N, N-dihydroxyethyl-n-butylamine,
N, N-dihydroxyethyl-t-butylamine,
Methyliminobispropylamine,
N, N-dihydroxyethylaniline,
N, N-dihydroxyethyl-m-toluidine,
N, N-dihydroxyethyl-p-toluidine,
N, N-dihydroxyethyl-m-chloroaniline,
N, N-dihydroxyethylbenzylamine,
N, N-dimethyl-N, N-dihydroxyethyl 1,3-diaminopropane,
N, N-diethyl-N, N-dihydroxyethyl 1,3-diaminopropane,
[0029]
N-hydroxyethyl-piperazine,
N, N-dihydroxyethyl-piperazine,
N-hydroxyethoxyethyl-piperazine,
1,4-bisaminopropyl-piperazine,
N-aminopropyl-piperazine,
Dipicolinic acid,
2,3-diaminopyridine,
2,5-diaminopyridine,
2,6-diaminopyridine,
2,6-diamino-4-methylpyridine,
2,6-dihydroxypyridine,
2,6-pyridine-dimethanol,
2- (4-pyridyl) -4,6-dihydroxypyrimidine,
2,6-diaminotriazine,
2,5-diaminotriazole,
2,5-diaminooxazole and the like.
[0030]
Further, ethylene oxide adducts and propylene oxide adducts of these tertiary amino compounds can also be used in the present invention. As the addition, for example,

(In the above formula, n represents an integer of 1 to 60, and m represents an integer of 1 to 6.)
[0031]
In the present invention, the polysiloxane compound used for introducing the polysiloxane segment into the molecular chain constituting the hydrophilic polyurethane resin is a reactive group containing one or more active hydrogens in the molecule (active group). Hydrogen-containing group), for example, a polysiloxane compound having an amino group, an epoxy group, a hydroxyl group, a mercapto group, a carboxyl group and the like. Preferred examples of the polysiloxane compound having an active hydrogen-containing group include the following compounds.
[0032]
(1) Amino-modified polysiloxane compound

[0033]
(2) Epoxy-modified polysiloxane compound

[0034]
(3) alcohol-modified polysiloxane compound

[0035]

[0036]
(4) Mercapto-modified polysiloxane compound

[0037]
(5) Carboxyl-modified polysiloxane compound

[0038]
The polysiloxane compounds having an active hydrogen-containing group listed above are examples of preferred compounds used in the present invention, and the present invention is not limited to these exemplified compounds. Therefore, not only these exemplified compounds but also other compounds that are currently commercially available and easily available from the market can be used in the present invention.
[0039]
As the organic polyisocyanate used in the present invention, any of those conventionally used for synthesizing a polyurethane resin can be used without any particular limitation. Preferred are, for example, 4,4'-diphenylmethane diisocyanate (MDI), hydrogenated MDI, isophorone diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 2,4-tolylene diisocyanate, 2,2 Polyurethane obtained by reacting 6-tolylene diisocyanate, 1,5-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, or the like, or an organic polyisocyanate and a low molecular weight polyol or polyamine so as to be a terminal isocyanate. Prepolymers and the like can also be used.
[0040]
As the high molecular weight hydrophilic polyol or the high molecular weight hydrophilic polyamine used in the present invention, those having a hydroxyl group, an amino group, a carboxyl group and the like in the molecule and having a weight average molecular weight of 400 to 8000 are preferable.
Examples of the polyol having a terminal hydroxyl group and hydrophilicity include, for example,
Polyethylene glycol,
Polyethylene glycol / polytetramethylene glycol copolymer polyol,
Polyethylene glycol / polypropylene glycol copolymer polyol,
Polyethylene glycol adipate,
Polyethylene glycol succinate,
Polyethylene glycol / poly-ε-caprolactone copolymerized polyol,
Polyethylene glycol / polyvalerolactone copolymerized polyol,
And the like. Particularly preferred is polyethylene glycol.
[0041]
Examples of the polyamine having a terminal amino group and hydrophilicity include, for example,
Polyethylene oxide diamine,
Polyethylene oxide propylene oxide diamine,
Polyethylene oxide triamine,
Polyethylene oxide propylene oxide triamine,
And the like.
Other examples include an ethylene oxide adduct having a carboxyl group or a vinyl group.
[0042]
In the present invention, in order to impart water resistance to the hydrophilic polyurethane resin, together with the above-mentioned hydrophilic polyol or polyamine, another polyol having no hydrophilic chain, polyamine, polycarboxylic acid, or the like may be appropriately copolymerized. It is possible.
[0043]
As the chain extender used as required in the present invention, for example, any conventionally known chain extenders such as low molecular weight diols and diamines can be used and are not particularly limited. For example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, ethylenediamine, hexamethylenediamine and the like can be mentioned.
[0044]
The alumina-dispersed hydrophilic polyurethane-based resin composition used in the present invention, as a part or all of the above-mentioned high molecular weight hydrophilic polyol or polyamine, is to remove the alumina sol dispersion solvent and the like from a mixture of each of these and the alumina sol. Or the like, using a high molecular weight hydrophilic polyol or polyamine in which fine-particle alumina obtained is dispersed, and either or both of them and an organic polyisocyanate, at least one active hydrogen-containing group and at least one tertiary amino group. In the same molecule and a polysiloxane compound having at least one active hydrogen-containing group, if necessary, by reacting with a chain extender according to a conventionally known method for producing a polyurethane resin. it can. The reaction may be solventless or may be a reaction in an aqueous solution or an organic solvent. In the case of no solvent, the obtained alumina-dispersed hydrophilic polyurethane-based resin composition is used after being dissolved in a soluble solvent of the hydrophilic polyurethane-based resin. The soluble solvent is not particularly limited, and preferable examples include dimethylformamide and methyl ethyl ketone. The same applies to the solvent used for synthesizing the hydrophilic polyurethane resin. The alumina-dispersed hydrophilic polyurethane-based resin composition is a dispersion in which particulate alumina is stably dispersed in a hydrophilic polyurethane-based resin solution. When a hydrophilic polyurethane-based resin is synthesized without a solvent, a dispersion in which fine-particle alumina is stably dispersed in a solution of the resin is obtained.
[0045]
The molecular weight of the hydrophilic polyurethane-based resin having a hydrophilic segment, a tertiary amino group and a polysiloxane segment in the molecular chain used in the present invention is not particularly limited, and the weight average molecular weight (in terms of standard polystyrene measured by GPC) is not limited. The range is preferably from 3,000 to 800,000, and more preferably from 5,000 to 500,000.
[0046]
In the alumina-dispersed hydrophilic polyurethane-based resin composition used in the present invention, the content of fine-particle alumina is preferably from 5 to 95% by weight, more preferably from 10 to 90% by weight, based on the hydrophilic polyurethane-based resin. When the content of the fine-particle alumina is less than 5% by weight, the surface characteristics such as blocking resistance and lubricity, which are the objects of the present invention, become insufficient. On the other hand, when the content exceeds 95% by weight, the strength of the film and the adhesiveness to the substrate are increased. And so on, which is not preferable. Surprisingly, when the content of the alumina fine particles is 75 to 95% by weight, a coating liquid using the alumina-dispersed hydrophilic polyurethane-based resin composition of the present invention is coated on a substrate to obtain a few m μm ( nm) size, and a film having excellent transparency is formed.
[0047]
The content of the tertiary amino group in the hydrophilic polyurethane resin in the present invention is preferably in the range of 0.1 to 50 eq (equivalent) / g, more preferably 0.5 to 20 eq / g. If the content of the tertiary amino group is less than 0.1 eq / g, that is, 1 or less per 10,000 in molecular weight, the desired properties of the present invention, such as water resistance and blocking resistance, become insufficient. On the other hand, when the content of the tertiary amino group exceeds 50 eq / g, that is, when the content of the tertiary amino group exceeds 1 per 20 molecular weight, the water repellency due to the decrease in the hydrophilic portion in the resin becomes strong, and the water absorption performance and the antifogging property are deteriorated. It is not preferable because it becomes inferior.
[0048]
The polysiloxane segment in the hydrophilic polyurethane-based resin in the present invention may be contained in the main chain, in the side chain, or in both. The content of the segment in the hydrophilic polyurethane-based resin is preferably from 0.1 to 10% by weight, and more preferably from 2 to 10% by weight. When the content of the polysiloxane segment is less than 0.1% by weight, the surface properties such as water resistance, blocking resistance, and lubricity, which are objects of the present invention, become insufficient. The water repellency is increased, and the environmental responsiveness used in the present invention is poor, and the water absorbency, antifogging property, and transparency are deteriorated.
[0049]
Further, the content of the hydrophilic segment in the polyurethane resin in the present invention is preferably in the range of 30 to 80% by weight, more preferably in the range of 50 to 75% by weight. If the content of the hydrophilic segment is less than 30% by weight, water absorption and anti-fogging properties will be inferior, while if it exceeds 80% by weight, water resistance and blocking resistance will be inferior, which is not preferable.
[0050]
As the base sheet of the ink jet recording sheet of the present invention, for example, paper, plastic film, glass, cloth, wood, metal and the like are used, but are not particularly limited. Examples of the paper include high quality paper, medium quality paper, coated paper, cast coated paper, and the like. Examples of the plastic film include a sheet having a thickness of 50 to 250 μm, such as polyester, cellulose triacetate, polycarbonate, polyvinyl chloride, polypropylene, polyamide, polystyrene, polyethylene, and polymethyl methacrylate.
Further, the base sheet is provided with a primer layer for imparting adhesiveness to the ink receiving layer and a curl preventing layer and a slip layer for improving the friction coefficient on the back surface of the base sheet on the non-receiving layer side, if necessary. You can also.
[0051]
In the present invention, the above-mentioned alumina-dispersed hydrophilic polyurethane-based resin composition is used for forming an ink receiving layer.
As the resin component constituting the ink receiving layer, the above-mentioned hydrophilic polyurethane-based resin alone may be used, but depending on the composition of the ink for inkjet recording, the above-mentioned hydrophilic polyurethane-based resin is used to further impart or adjust hydrophilicity and / or water absorption. A hydrophilic polyurethane-based resin may be used in combination with a water-soluble polymer.
Examples of the water-soluble polymer include polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, CMC, cellulose derivative, polyvinyl pyrrolidone, polyacrylic acid, polyacrylic acid-based polymer, starch, cationic starch, gelatin, casein, and the like. .
[0052]
Further, in order to further impart water resistance and durability to the ink receiving layer and the printed image, the hydrophilic polyurethane resin may be used in combination with a hydrophobic polymer. As the hydrophobic polymer, for example, polyester resin, polyvinyl chloride resin, polystyrene resin, polymethyl methacrylate resin, polycarbonate resin, polyurethane resin, vinyl chloride-vinyl acetate copolymer resin, acrylonitrile-styrene copolymer resin, polyvinyl butyral resin And synthetic resins generally used for forming the ink receiving layer, such as polyamide resins, epoxy resins, urea resins, and melamine resins.
[0053]
In addition, for the purpose of improving the ink absorbency, fixing property, color developing property, further blocking property and water resistance of the ink receiving layer, the alumina-dispersed hydrophilic polyurethane resin composition may contain inorganic and organic pigments and resin particles. Can be contained.
Examples of pigments and resin particles used include kaolin, delamikaolin, aluminum hydroxide, silica, diatomaceous earth, calcium carbonate, talc, titanium oxide, calcium sulfate, barium sulfate, zinc oxide, calcium silicate, magnesium silicate, and colloidal silica. , Zeolite, benite, sericite, mineral pigments such as lithopone, porous pigments, polystyrene resin, urea resin, acrylic resin, melamine resin, benzoguanamine resin, polyurethane resin, other organic pigments and other fine particles, porous fine particles and hollow particles One or two or more of known pigments and resin particles are appropriately used according to the quality design of the ink jet recording sheet. In this case, the amount of the pigment or resin particles used is in the range of 0 to 95% by weight, preferably 10 to 90% by weight of the total solids of the alumina-dispersed hydrophilic polyurethane-based resin composition used for forming the ink receiving layer. is there.
[0054]
Further, if necessary, a thickener, a releasing agent, a penetrating agent, a wetting agent, a thermal gelling agent, a sizing agent, a defoaming agent, a defoaming agent, Foaming agents, coloring agents, fluorescent whitening agents, ultraviolet absorbers, antioxidants, quencher agents, preservatives, antistatic agents, crosslinking agents, dispersants, lubricants, plasticizers, pH adjusters, flow improvers, Various auxiliaries such as a solidification accelerator and a water-proofing agent can also be appropriately compounded.
[0055]
In the present invention, the alumina-dispersed hydrophilic polyurethane-based resin composition used to form the ink receiving layer is preferably a solution of the hydrophilic polyurethane-based resin synthesized in a solvent, and is synthesized without a solvent. In this case, the above-mentioned hydrophilic polyurethane resin is dissolved in a solvent before use. If the component to be added as necessary is soluble in a solvent, it may be directly added to the above-mentioned hydrophilic polyurethane-based resin composition and dissolved, or may be added by dissolving it in a solvent in advance. Further, an insoluble additive component is added, and the alumina-dispersed polyurethane resin composition is usually prepared as a coating solution having a solid content of about 5 to 15% by weight.
[0056]
The prepared coating liquid is applied to the substrate sheet by gravure coating, direct or reverse roll coating, wire bar coating, air knife coating, curtain coating, blade coating, rod coating, die coating, or the like. Further, after coating, finishing is performed using a calender such as a machine calender, a super calender, and a soft calender, and an ink jet recording sheet is obtained.
[0057]
The thickness of the ink-receiving layer formed has a thickness to provide a dry weight in 5 to 100 g / ^{m 2} approximately of the composition and more preferably, a 10 to 50 g / ^{m 2} approximately. When the thickness of the ink receiving layer is less than 5 g / m ² , the absorption of the ink by the ink receiving layer becomes insufficient. When the thickness exceeds 100 g / m ² , the obtained effect becomes saturated and uneconomical. The layer is likely to be broken or curled.
[0058]
【Example】
Next, the present invention will be described more specifically with reference to examples and comparative examples. The parts or percentages in the text are based on weight.
[0059]
Reference Example 1
700 parts of polyethylene glycol (molecular weight 1,000) and 750 parts of alumina water sol (average particle size of alumina 150 to 160 nm, solid content 40% by weight) are sufficiently mixed, and the resulting mixture is dehydrated under reduced pressure at 70 ° C. while stirring. Was done.
After the theoretical amount of water was distilled off, the temperature was raised to 120 ° C., and the water was removed under a reduced pressure of 133.3 Pa or less to obtain a white solid polyol (A) having an alumina content of 30%. This polyol had a hydroxyl value of 76 mgKOH / g, a water content of 0.15%, was transparent at 80 ° C., and had a viscosity of 380 dPa · s.
[0060]
Reference Example 2
100 parts of polyethylene glycol (molecular weight: 590) and 500 parts of an aqueous alumina sol (alumina average particle diameter: 10 to 20 nm, solid content: 20% by weight) are sufficiently mixed, and the resulting mixture is dehydrated under reduced pressure at 70 ° C. while stirring. Was.
After the theoretical amount of water was distilled off, the temperature was raised to 120 ° C., and the water was removed under reduced pressure of 133.3 Pa or less to obtain a white solid polyol (B) having an alumina content of 50% by weight. This polyol had a hydroxyl value of 95 mgKOH / g, a water content of 0.12%, and softened at 90 ° C.
[0061]
Reference Example 3
100 parts of polyethylene oxide diamine (Jeffamine ED, manufactured by Texaco Chemical Co., Ltd .; molecular weight: 600) and 2250 parts of an aqueous alumina sol (average particle size of alumina: 150 to 160 nm, solid content: 40% by weight) are sufficiently mixed, and the obtained mixture is stirred. Dehydration under reduced pressure was performed at 70 ° C. while heating.
After the theoretical amount of water had been distilled off, the temperature was raised to 120 ° C., and water was removed under reduced pressure of 133.3 Pa or less to obtain a white solid polyamine (C) having an alumina content of 90% by weight. The polyamine had an amine equivalent of 30 g / mol, a water content of 0.20%, and softened at 110 ° C.
[0062]
Reference example 4
(Production of alumina-dispersed polyurethane resin composition)

5 parts of polydimethylsiloxane polyol (molecular weight 3,200) having the above structure, 145 parts of polyol (A) of Reference Example 1, 20 parts of N-methyldiethanolamine and 3 parts of diethylene glycol were combined with 200 parts of methyl ethyl ketone and 200 parts of dimethylformamide. And a solution of 77 parts of hydrogenated MDI in 100 parts of methyl ethyl ketone was gradually added dropwise with good stirring at 60 ° C. After completion of the dropwise addition, the mixture was reacted at 80 ° C. for 8 hours, and 500 parts of dimethylformamide was added to obtain a solution of the alumina-dispersed polyurethane resin composition of the present invention.
[0063]
This solution had a solid content of 20% and a viscosity of 50 dPa · s (25 ° C.). The weight average molecular weight of the polyurethane resin measured by GPC (also in the following examples) was 62,000. Has a tertiary amino group content of 0.79 eq / g, a hydrophilic segment content of 49.1%, a polysiloxane segment content of 2.1%, and an alumina content of 17.4%. Met.
The film formed from this resin composition solution was transparent, had a breaking strength of 28.8 Mpa, a breaking elongation of 50%, and a softening point of 163 ° C.
[0064]
Reference example 5
(Production of alumina-dispersed polyurethane-polyurea resin composition)

5 parts of an ethylene oxide-added polydimethylsiloxane polyol (molecular weight: 4,500) having the above structure, 120 parts of the polyol (B) of Reference Example 2 and 25 parts of polyethylene oxide diamine (molecular weight: 2,000), N, N-dimethyl-N ' , N'-Dihydroxyethyl-1,3-diaminopropane (25 parts) was dissolved in 200 parts of a mixed solvent of methyl ethyl ketone and 200 parts of dimethylformamide, and while stirring well at 60 ° C., 64 parts of hydrogenated MDI were added to 100 parts. The solution dissolved in methyl ethyl ketone was gradually added dropwise. After completion of the dropwise addition, the mixture was reacted at 80 ° C. for 8 hours, and 455 parts of dimethylformamide was added to obtain a solution of the alumina-dispersed polyurethane-polyurea resin composition of the present invention.
[0065]
This solution had a viscosity of 40 dPa · s (25 ° C.) at a solid content of 20%. The weight average molecular weight of the polyurethane-polyurea resin is 41,000, the content of the tertiary amino group in the resin is 1.46 eq / g, the content of the hydrophilic segment is 47.5%, and the content of the polysiloxane segment is The amount was 2.5% and the alumina content was 25.1%.
The film formed from this resin composition solution was transparent, had a breaking strength of 21.5 Mpa, a breaking elongation of 20%, and a softening point of 176 ° C.
[0066]
Reference Example 6
(Production of alumina-dispersed polyurea resin composition)

2 parts of polydimethylsiloxanediamine (molecular weight 3,880) having the above structure, 148 parts of polyamine (C) of Reference Example 3 and 3 parts of methyliminobispropylamine are dissolved in 250 parts of dimethylformamide, and the internal temperature is adjusted to 0 to -5. A solution prepared by dissolving 12 parts of hydrogenated MDI in 100 parts of dimethylformamide was gradually added dropwise while maintaining the temperature at 0 ° C., and reacted.
After completion of the dropwise addition, the internal temperature was gradually raised, and when the temperature reached 50 ° C., the mixture was further reacted for 5 hours. Then, 310 parts of dimethylformamide was added to obtain a solution of the alumina-dispersed polyurea resin composition of the present invention.
[0067]
This solution has a viscosity of 110 dPa · s (25 ° C.) at a solid content of 20%, the weight average molecular weight of the polyurea resin is 38,000, and the content of the tertiary amino group in the resin is 0.72 eq / g, the content of the hydrophilic segment was 46.5%, the content of the polysiloxane segment was 6.2%, and the content of alumina was 80.7%.
The film formed from this resin composition solution was slightly translucent and porous, had a breaking strength of 5.0 Mpa, a breaking elongation of 5%, and a softening point of 210 ° C.
[0068]
Reference Example 7
A polyurethane resin solution was obtained by the same material and formulation as in Reference Example 4 except that the polydimethylsiloxane polyol and N-methyldiethanolamine were not used, and that the polyol (A) of Reference Example 1 except for alumina was used. Was.
This solution had a solid content of 20%, a viscosity of 80 dPa · s (25 ° C.), and the weight average molecular weight of the polyurethane resin was 69000.
The film formed from this resin solution had a breaking strength of 42.0 Mpa, a breaking elongation of 450%, and a softening point of 102 ° C.
[0069]
Reference Example 8
Polydimethylsiloxane polyol and N, N-dimethyl-N ', N'-dihydroxyethyl-1,3-diaminopropane are not used, and the polyol (B) of Reference Example 2 except for alumina is used. Otherwise, a polyurethane-polyurea resin solution was obtained using the same materials and formulation as in Reference Example 5.
This solution had a solid content of 20%, a viscosity of 52 dPa · s (25 ° C.), and the weight average molecular weight of the polyurethane-polyurea resin was 58,000.
The film formed from this resin solution had a breaking strength of 35.3 MPa, a breaking elongation of 400%, and a softening point of 95 ° C.
[0070]
Reference Example 9
A polyurea resin solution was prepared using the same material and formulation as in Reference Example 6 except that polydimethylsiloxane diamine and methyliminobispropylamine were not used, and that the polyamine (C) of Reference Example 3 except for alumina was used. Obtained.
This solution had a solid content of 20%, a viscosity of 38 dPa · s (25 ° C.), and the weight average molecular weight of the polyurea resin was 42,000.
The film formed from this resin solution had a breaking strength of 25.7 MPa, a breaking elongation of 350%, and a softening point of 117 ° C.
[0071]
Reference Examples 10 to 12
Each of the aqueous alumina sols of Reference Examples 1 to 3 was added to each of the resin solutions of Reference Examples 7 to 9 with stirring, but particles precipitated and the solution became opaque.
[0072]
Reference Example 13
A 5% aqueous solution of polyvinyl alcohol (degree of polymerization 550) having a saponification degree of 98.5% was prepared.
[0073]
Examples 1-3
The alumina-dispersed hydrophilic polyurethane-based resin composition obtained in Reference Examples 4 to 6 was applied to a base paper of 35 g / m ² with a air knife coater so that the thickness after drying became 25 μm. A layer was formed to obtain an ink jet recording sheet of the present invention.
[0074]
Comparative Examples 1 to 7
The resin solution obtained in Reference Examples 7 to 13 was applied to a base paper having a basis weight of 35 g / m ² with an air knife coater so that the thickness after drying was 25 μm to form an ink receiving layer. The ink jet recording sheet of the example was used.
[0075]
[Evaluation of inkjet recording sheet]
For the ten types of ink jet recording sheets obtained as described above, four colors of yellow, magenta, cyan and black were used with an ink jet printer (PM-800C manufactured by Seiko Epson Corporation) for printing and recording with a water-soluble dye ink. The following items were evaluated.
(1) Blocking property An untreated PET film was superimposed on the resin-coated surface, and the blocking property was evaluated after standing for one day at a load of 0.29 MPa and a temperature of 40 ° C. The results are displayed as follows.
The display of the result is as follows.
：: No blocking property Δ: Slight blocking property X: Blocking property (2) Clouding on the transparent resin coating surface was visually determined. The results are displayed as follows.
：: Completely transparent △: Slightly cloudy ×: Completely opaque
(3) Color Vividness After color printing with an inkjet printer, the color vividness of the obtained color image was visually observed. The results are displayed as follows.
：: Clear without bleeding △: Slightly bleeding and somewhat unclear (4) Drying of ink After color printing with an ink jet printer, press the filter paper with a load of 50 g / m ² for 5 seconds until the ink is no longer transferred to the filter paper. The time was measured.
(5) After printing a printed image in color with a water-resistant inkjet printer, immerse the recording sheet in water (20 ° C., 1 hour), and then visually observe the bleeding of the recorded image and changes in color development when dried at room temperature. . The results are displayed as follows.
：: No change Δ: Change in ink and film is observed X: Ink is considerably removed or the evaluation result is higher than that of the film.
[0077]

[0078]
【The invention's effect】
According to the present invention as described above, ink absorption / drying properties, excellent coloring properties, stable high-quality printed images are formed, and excellent water resistance and moisture resistance are imparted to the printed images, and further, the ink itself and printing are performed. An ink jet recording sheet having an ink receiving layer having excellent image transparency, excellent blocking resistance, and excellent transportability is provided.

Claims (10)

In an ink jet recording sheet having at least one ink receiving layer provided on at least one surface of a base sheet, the ink receiving layer contains an organic polyisocyanate, a high molecular weight hydrophilic polyol and / or a polyamine, and at least one active hydrogen. Obtained by reacting a compound having a group and at least one tertiary amino group in the same molecule with a polysiloxane compound having at least one active hydrogen-containing group, if necessary, with a chain extender. An ink jet recording sheet comprising a hydrophilic polyurethane resin having a hydrophilic segment, a tertiary amino group and a polysiloxane segment, and fine-particle alumina. 2. The ink jet recording sheet according to claim 1, wherein the content of the fine particle alumina is 5 to 95% by weight based on the hydrophilic polyurethane resin. When synthesizing the hydrophilic polyurethane resin, the fine-particle alumina is used as at least a part of the high-molecular-weight hydrophilic polyol or polyamine, by using a mixture of the high-molecular-weight hydrophilic polyol or polyamine and the fine-particle alumina. The ink jet recording sheet according to claim 1, which is contained in a conductive polyurethane resin. The inkjet recording sheet according to claim 1, wherein the fine-particle alumina has an average particle diameter of 1 to 300 nm. The content of the hydrophilic segment, the tertiary amino group and the polysiloxane segment in the hydrophilic polyurethane resin is 30 to 80% by weight, 0.1 to 50 eq / g and 0.1 to 10% by weight, respectively. The recording sheet for inkjet according to claim 1. In a method for producing an ink jet recording sheet provided with at least one or more ink receiving layers on at least one surface of a base sheet, the ink receiving layer may be formed of at least one organic polyisocyanate, high molecular weight hydrophilic polyol and / or polyamine A compound having an active hydrogen-containing group and at least one tertiary amino group in the same molecule and a polysiloxane compound having at least one active hydrogen-containing group are reacted with a chain extender, if necessary. When synthesizing a hydrophilic polyurethane-based resin having a hydrophilic segment, a tertiary amino group and a polysiloxane segment, at least a part of the high molecular weight hydrophilic polyol and / or the high molecular weight hydrophilic polyol is used as the polyamine. Alumina content using a mixture of polyamine and fine-particle alumina Ink-jet recording method of manufacturing a sheet, which comprises forming by using a hydrophilic polyurethane resin composition. The method according to claim 6, wherein the mixture is obtained by removing a dispersion solvent of alumina sol from a mixture of high molecular weight hydrophilic polyol / or polyamine and alumina sol. 7. The method for producing an ink jet recording sheet according to claim 6, wherein the content of alumina in the mixture is 5 to 95% by weight based on the hydrophilic polyurethane resin. The method for producing an ink jet recording sheet according to claim 6, wherein the fine particle alumina has an average particle diameter of 1 to 300 nm. The content of the hydrophilic segment, the tertiary amino group and the polysiloxane segment in the hydrophilic polyurethane resin is 30 to 80% by weight, 0.1 to 50 eq / g and 0.1 to 10% by weight, respectively. A method for producing an ink jet recording sheet according to claim 6.