JP3941864B2 - Method for producing inkjet recording sheet - Google Patents

Description

（式中の、Ｒ₁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、Ｒ₂及びＲ₃は−Ｏ−、
−ＣＯ−、−ＣＯＯ−、−ＮＨＣＯ−、−Ｓ−、−ＳＯ−、−ＳＯ₂−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、
−ＮＨ₂、−ＮＨＲ₁−、−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。）
【００２３】
一般式（２）で表される化合物

（式中の、Ｒ₁、Ｒ₂、及びＲ₃は前記と同じ定義であるが、但し二つのＲ₁同士は環状構造を形成するものであってもよい。Ｒ₄は−（ＣＨ₂）_n−（ｎは０〜２０の整数）である。）
【００２４】
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。）
【００２５】
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、
【００２６】
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。
【００２７】
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。）
【００２８】
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。
【００２９】
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。
【００３０】
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。
【００３１】
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及び／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。
【００３２】
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。
【００３３】
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及び／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及び／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、及び少なくとも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。
【００３４】
本発明で使用する親水性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。
【００３５】
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。
【００３６】
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、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。
【００３７】
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。
【００３８】
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。
【００３９】
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。
【００４０】
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。
【００４１】
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。
【００４２】
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。
【００４３】
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。
【００４４】
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。
【００４５】
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／ｍ²程度となる厚みが好ましく、更に好ましくは１０〜５０ｇ／ｍ²程度である。インク受容層の厚みが５ｇ／ｍ²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／ｍ²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。
【００４６】
【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。
【００４７】
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。
【００４８】
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。
【００４９】
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。
【００５０】
参考例４
（アルミナ分散ポリウレタン樹脂組成物の製造）
ポリエチレングリコール（分子量２，０４０）５０部、参考例１のポリオール（Ａ）１００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５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、８０部の水添ＭＤＩを２００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４２０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。
【００５１】
この溶液は固形分２０％で、２２ｄＰａ・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５２，０００であり、アルミナの含有量は１１．７％であった。この樹脂組成物溶液から形成したフィルムは、透明で、破断強度は２３．７Ｍｐａ、破断伸度は５５％、且つ軟化点は１５５℃であった。
【００５２】
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）
ポリエチレンオキサイドジアミン（ジェファーミンＥＤ；分子量２，０００）３０部、参考例２のポリオール（Ｂ）１２０部、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２５部を１００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、６５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５６０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。
【００５３】
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５１，０００であり、アルミナの含有量は２４％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１８．５Ｍｐａ、破断伸度は２０％、且つ軟化点は１６５℃であった。
【００５４】
参考例６
（アルミナ分散ポリウレア樹脂組成物の製造）
ポリエチレンオキサイドジアミン（ジェファーミンＥＤ；分子量２，０００）５部、参考例３のポリアミン（Ｃ）１４５部、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部中に溶解し、内温を０〜−５℃に保ってよく攪拌しながら、７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℃に達したところでさらに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。
【００５５】
この溶液は固形分２０％で、８０ｄＰａ・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、アルミナの含有量は７９％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４．２Ｍｐａ、破断伸度は３％、且つ軟化点は２１０℃であった。
【００５６】
参考例７
参考例４のＮ−メチルジエタノールアミンを使用せず、又、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１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、５０ｄＰａ・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６８，０００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３５．０Ｍｐａ、破断伸度４５０％、軟化点は１０３℃であった。
【００５７】
参考例８
参考例５の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、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２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、４０ｄＰａ・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５５，０００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２５．３ＭＰａ、破断伸度４００％、軟化点は９５℃であった。
【００５８】
参考例９
参考例６のメチルイミノビスプロピルアミンを使用せず、又、ポリオール（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３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、２５ｄＰａ・ｓ（２５℃）の粘度を有し、ポリウレア樹脂の重量平均分子量は３２，０００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２２．７ＭＰａ、破断伸度３５０％、軟化点は１１５℃であった。
【００５９】
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。
【００６０】
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。
【００６１】
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／ｍ² の上質紙に、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。
【００６２】
比較例１〜７
参考例７〜１３で得られた樹脂溶液を坪量３５ｇ／ｍ² の上質紙に、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。
【００６３】
〔インクジェット記録用シートの評価〕
以上のようにして得られた１０種類のインクジェット記録用シートについて、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
【００６４】
（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／ｍ²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。
【００６５】

【００６６】
【発明の効果】
以上の本発明によれば、耐水性、耐ブロッキング性、滑性に優れたインクジェット記録用シートが提供される。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an ink jet recording sheet, more particularly, excellent water resistance to the printing image, and impart moisture resistance, and ink absorbency, excellent color forming property of the ink, a stable and high quality printing It can record image further transparency, transportability, a method of manufacturing the inkjet recording sheet having an ink-receiving layer having excellent blocking resistance.
[0002]
[Prior art]
An ink jet recording method, various working principles, for example, an electrostatic attraction method, a method to provide mechanical vibration or displacement of the ink using a piezoelectric element, ink by methods such as utilizing the pressure is foamed by heating the ink This is a recording method that allows high-quality printing and multi-color printing with high-speed printing, low noise generation, and recording of images, characters, etc. It is rapidly spreading to various applications.
[0003]
In such a recording medium used for ink-jet recording, the ink adhering to the recording medium is blotted and flowed, so that the ink is quickly absorbed and the clear ink is not lost. In order to form dots, there are paper sheets and other supports that are provided with an ink-receiving layer mainly composed of various pigments and resins, or recording sheets in which porous pigments are embedded in the paper itself. Proposed.
[0004]
For example, JP-A-57-82085 discloses that an inorganic pigment and an organic pigment are used in combination as the pigment and an ink receiving layer made of a water-soluble polymer is provided. JP-A-62-268682 discloses And providing an ink-receiving layer made of a finely divided silica and a polyvinyl alcohol copolymer having a silanol group.
[0005]
However, as the performance of inkjet recording devices such as higher speed, higher definition, or full color is improved and applications are expanded, it is required that inkjet recording sheets also have the following advanced characteristics. Became.
(1) fast ink absorption and large ink absorption capacity;
(2) High color developability of the ink,
(3) the surface strength of the ink receiving layer is high;
(4) The support has water resistance, and the ink does not cause irregularities or curls on the support.
(5) The image printed on the ink receiving layer has good image preservation such as water resistance and ozone resistance,
(6) The ink receiving layer does not change with time.
[0006]
Conventionally, a porous pigment or a water-soluble polymer having excellent ink absorbability is used as a component of an ink receiving layer provided on an ink jet recording sheet to satisfy these requirements, or water resistance of the ink receiving layer is improved. It has been proposed and studied to use latex for the substrate, 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 printed portions, and poor image clarity.
In addition, in the case where the porous pigment is dispersed in the ink receiving layer, the porous pigment generally decreases transparency so that it is usually used as a matting agent (matting agent). Even if the dispersion amount is small, the transparency is remarkably lowered. On the other hand, when using synthetic paper or plastic film for the support or using latex for the resin of the ink receiving layer, there are problems with the adhesion between the ink receiving layer and the support, the ink absorbability and the drying property. .
[0008]
[Problems to be solved by the invention]
The present invention is particularly excellent in water-absorbing ink absorbency, the shape of the ink dots is sharp, the ink coloring property is excellent, and a stable and high-quality printed image is provided, and further, transportability, transparency, blocking resistance, An object of the present invention is to provide an ink jet recording sheet having an ink receiving layer excellent in water resistance and moisture resistance.
[0009]
[Means for Solving the Problems]
The above object is achieved by the present invention described below. That is, the present invention is, on at least one side of the substrate sheet, a method for producing an ink jet recording sheet provided with at least one layer of the ink receiving layer, an ink-receiving layer, and an organic polyisocyanate, a high molecular weight hydrophilic polyol and / with or polyamine and a compound having at least one active hydrogen-containing group and at least one tertiary amino group in the same molecule, by reacting, a hydrophilic segment and a tertiary amino group in synthesizing the hydrophilic polyurethane resin, as at least part of the high molecular weight hydrophilic polyol and / or polyamine, obtained by using a mixture of a high molecular weight hydrophilic polyol and / or polyamine and particulate alumina, alumina dispersed hydrophilic It is formed using a polyurethane-based resin composition, and for inkjet It is a manufacturing method of the recording sheet.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in more detail with reference to embodiments of the 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 comprises an organic polyisocyanate , a high molecular weight hydrophilic polyol and / or polyamine, at least one active hydrogen-containing group and at least one tertiary amino group in the same molecule. It is a hydrophilic polyurethane-based resin having a hydrophilic segment and a tertiary amino group obtained by reacting a compound having the compound with a chain extender as necessary.
[0011]
On the other hand, alumina fine particles, when synthesizing the hydrophilic polyurethane resin, as at least part of the high molecular weight hydrophilic polyol and / or polyamine, using a mixture of high molecular weight hydrophilic polyol and / or polyamine and particulate alumina Thus, it is contained (dispersed) in the generated hydrophilic polyurethane resin (this is 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 resin, although no dispersant is used. The ink receiving layer of the ink jet recording sheet of the present invention is formed using this alumina-dispersed hydrophilic polyurethane resin composition. In the present invention, the polyurethane-based resin is a generic term for polyurethane resin, polyurea resin, and polyurethane-polyurea resin.
[0012]
In the present invention, a mixture of high molecular weight hydrophilic polyol and / or polyamine and particulate alumina, mechanically mixing the particulate alumina high molecular weight hydrophilic polyol and / or polyamine, can be used are dispersed, the It is preferable to use a product obtained by removing the dispersion solvent of alumina sol from a mixture of polyol and / or polyamine and alumina sol. If the polyol and / or polyamine is used as a solution of their soluble solvent, this solvent is also removed.
[0013]
The alumina sol in the present invention is a dispersion in which fine particle alumina or fine particle alumina compound is usually stably dispersed in water and / or alcohol as a dispersion solvent. In addition to the above, ketones, esters, and other organic solvents are also used as the dispersion solvent. The average particle diameter of the fine particle alumina in the alumina sol is usually 1 μm or less, particularly preferably 1 to 300 mμm (nm).
[0014]
When forming an ink receiving layer of an inkjet recording sheet , a method using a resin solution, a dispersion, or the like is common.
Examples of the method for dispersing the alumina fine particles in the polyurethane resin solution include the following methods. For example, a method in which alumina fine particles are dispersed in a polyurethane resin using an ordinary dispersion mixer and dissolved in a solvent (1), and a method in which alumina fine particles or alumina sol are added to and dispersed in a polyurethane resin solution ( 2) is considered. However, method (1) is economically disadvantageous because a stable dispersion cannot be obtained even if a dispersant is used. Although the method (2) is a general method, the alumina fine particles cannot be stably dispersed even if this method or a dispersant is used. Even when an alumina sol is used, the dispersion stability is low, and both are easily separated with time. This is because the compatibility (affinity) between the polyurethane-based resin and the particulate alumina, the stability of both of them against changes in pH, or the surface properties of the polyurethane-based resin and the particulate 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 resin can be considered. A polyurethane-based resin solution having a dispersion stability cannot be obtained even if the solvent-based alumina sol is used.
[0015]
However, the high molecular weight hydrophilic polyol and / or polyamine described later used in the present invention has extremely high compatibility (affinity) with alumina due to its hydrophilicity, and can be stably mixed with alumina sol at an arbitrary ratio. . Then, by removing the dispersion medium of the alumina sol from this mixture by an arbitrary method, a high molecular weight hydrophilic polyol and / or polyamine in which fine particle alumina is dispersed in an extremely stable manner can be obtained, and the high molecular weight hydrophilic polyol and / or Even if the dispersion amount of fine particle alumina in the polyamine is increased, the viscosity of the polyol and / or the polyamine is little increased, and a dispersant can be used by reacting this mixture with other raw material components in a solvent. In addition, a dispersion in which alumina fine particles are stably dispersed in a hydrophilic polyurethane resin 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. All of these dispersions are extremely transparent, and the film formed therefrom is also transparent.
[0016]
The removal of the dispersion medium and organic solvent of the alumina sol from the mixture of the high molecular weight hydrophilic polyol and / or polyamine or a solution thereof and the alumina sol can generally be easily distilled off under reduced pressure. In this case, the distillation is preferably carried out at a low temperature under reduced pressure, and particularly preferably distilled off at 70 ° C. or lower. When the temperature is higher than this, the fine particle alumina may be aggregated, the dispersion stability of the alumina may be lowered, and an alumina-dispersed high molecular weight hydrophilic polyol and / or polyamine having low transparency may be generated. The mixing ratio of the high molecular weight hydrophilic polyol and / or polyamine and alumina sol, particulate alumina, preferably the amount to be 5 to 95 wt% with respect to the hydrophilic polyurethane resin produced, more preferably from 10 to 90 It is the amount which becomes weight%.
[0017]
In the present invention, the hydrophilic polyurethane resin used as the resin constituting the ink receiving layer has the same hydrophilic segment having a high molecular weight hydrophilic polyol and / or polyamine as the constituent unit and at least one tertiary amino group. And a tertiary amino group-containing segment whose constituent unit is a compound contained in the molecule. When no chain extender is used, these segments are bonded at random by urethane bonds, urea bonds, or urethane-urea bonds. When a chain extender is used, there is a bond in which a short chain that is a residue of the chain extender exists between these bonds together with these bonds.
[0018]
By introducing a tertiary amino group into the molecule, the hydrophilic polyurethane resin in the present invention has excellent adhesiveness to various materials, and excellent water absorption, antifogging properties, transparency, and flexibility. In addition, the writing property of water-based ink and excellent water resistance, blocking resistance, and lubricity are imparted.
[0019]
The reason why water resistance is imparted is not clear, but is considered as follows. Dyed & Pigments used in the printing inks and inkjet inks is generally have anionic carboxyl group or sulfonic acid group in the molecule, a hydrophilic polyurethane was introduced tertiary amino group When the resin and the above-mentioned dye / pigment are mixed or contacted, an ionic bond is formed between the dye / pigment and the tertiary amino group in the resin, thereby fixing the dye / pigment and the recorded image. It is thought that water resistance is improved.
[0020]
However, in the presence of moisture, the ionic bonds as described above are easily dissociated, and improvement in water resistance should not be expected, but water resistance is improved. The reason for improving the water resistance is not clear, but the polyurethane resin in the present invention is hydrophilic, but there is also a hydrophobic part in the molecule, and the hydrophilic part and tertiary amino in the resin are present. After the ionic bond is formed between the group and the dye / pigment, the hydrophobic portion is surrounded by the ionic bond portion, so that the water resistance is considered to be improved.
[0021]
In the present invention, the compound used to introduce a tertiary amino group into the molecular chain constituting the hydrophilic polyurethane-based resin has at least one active hydrogen-containing group (reactive group), for example, an amino group, It is a compound having an epoxy group, a hydroxyl group, a mercapto group, a carboxyl group, an alkoxy group, an acid halide group, a carboxyester group, an acid anhydride group, etc., and having at least one tertiary amino group in the molecular chain. .
[0022]
Preferable examples of the tertiary amino group-containing compound having a reactive group as described above include 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 are —O—,
A lower alkylene group which may be linked by —CO—, —COO—, —NHCO—, —S—, —SO—, —SO ₂ — and the like, and X and Y are —OH, —COOH,
It is a reactive group such as —NH ₂ , —NHR ₁ — or —SH, and X and Y may be the same or different. In addition, an epoxy group, an alkoxy group, an acid halide group, an acid anhydride group, or a carboxyl ester group that can be derived from these groups may be used. )
[0023]
Compound represented by general formula (2)

(In the formula, R ₁ , R ₂ , and R ₃ have the same definitions as described above, but two R _{1 s} may form a cyclic structure. R ₄ represents — (CH ₂ ). _n - _(n is 0 to 20 integer) is).
[0024]
Compound represented by general formula (3)

(In the formula, X and Y are as defined above, and W represents a nitrogen-containing heterocycle, nitrogen and oxygen-containing heterocycle, or nitrogen and sulfur-containing heterocycle.)
[0025]
Specific examples of the compound represented by the 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,
[0026]
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,
There are 2,5-diaminooxazole and the like.
[0027]
Also, ethylene oxide adducts and propylene oxide adducts of these tertiary amino compounds can be used in the present invention. As the adduct, for example,

(In the above formula, n represents an integer of 1 to 60, and m represents an integer of 1 to 6.)
[0028]
As the organic polyisocyanate used in the present invention, any of those conventionally used for the synthesis of polyurethane resins can be used and is not particularly limited. Preferred examples include 4,4′-diphenylmethane diisocyanate (MDI), hydrogenated MDI, isophorone diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 2,4-tolylene diisocyanate, 2, 6-tolylene diisocyanate, 1,5-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, etc., or polyurethane obtained by reacting these organic polyisocyanates with low molecular weight polyols or polyamines to form terminal isocyanates A prepolymer or the like can also be used.
[0029]
As the high molecular weight hydrophilic polyol or high molecular weight hydrophilic polyamine used in the present invention,
Those having a hydroxyl group, amino group, carboxyl group, etc. in the molecule and having a weight average molecular weight in the range of 400 to 8000 are preferred.
Examples of the polyol having a hydroxyl group at the end and hydrophilicity include:
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 copolymer polyol,
And polyethylene glycol / polyvalerolactone copolymer polyol. Particularly preferred is polyethylene glycol.
[0030]
Examples of the polyamine having a terminal amino group and hydrophilicity include:
Polyethylene oxide diamine,
Polyethylene oxide, propylene oxide diamine,
Polyethylene oxide triamine,
Polyethylene oxide propylene oxide triamine, etc.
Is mentioned.
Other examples include ethylene oxide adducts having a carboxyl group or a vinyl group.
[0031]
In the present invention, in order to impart water resistance to the hydrophilic polyurethane-based resin, other polyols, polyamines, polycarboxylic acids, etc. that do not have a hydrophilic chain are appropriately copolymerized together with the above-described hydrophilic polyol and / or polyamine. It is also possible.
[0032]
As the chain extender used as necessary in the present invention, for example, any conventionally known chain extender such as low molecular weight diol and diamine can be used, and it is not particularly limited. For example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, ethylenediamine, hexamethylenediamine and the like can be mentioned.
[0033]
The alumina-dispersed hydrophilic polyurethane resin composition used in the present invention removes a dispersion solvent of alumina sol from a mixture of each of these high molecular weight hydrophilic polyols and / or polyamines and alumina sol as a part or all of them. A high molecular weight hydrophilic polyol and / or polyamine in which fine particle alumina obtained by dispersing is used, and either or both of them, an organic polyisocyanate, and at least one active hydrogen-containing group and at least one first group are used. It can be obtained by reacting a compound having a tertiary amino group in the same molecule with a chain extender, if necessary, according to a conventional method for producing a conventional polyurethane resin. The reaction may be solventless or a reaction in an aqueous solution or an organic solvent. In the case of no solvent, the obtained alumina-dispersed hydrophilic polyurethane resin composition is used after being dissolved in a soluble solvent of the hydrophilic polyurethane resin. The soluble solvent is not particularly limited, and preferred examples include dimethylformamide and methyl ethyl ketone. The same applies to the solvent used for the synthesis of the hydrophilic polyurethane resin. The alumina-dispersed hydrophilic polyurethane resin composition is a dispersion in which fine particle alumina is stably dispersed in a hydrophilic polyurethane resin solution. Even when the hydrophilic polyurethane-based resin is synthesized without a solvent, a dispersion in which fine particle alumina is stably dispersed in the resin solution can be obtained.
[0034]
The molecular weight of the hydrophilic polyurethane resin having a hydrophilic segment for use in the present invention in the molecular chain is not particularly limited, the range weight average molecular weight (standard polystyrene measured by GPC) is 3,000～800,000 Is more preferable, and the range of 5,000 to 500,000 is more preferable.
[0035]
In the alumina-dispersed hydrophilic polyurethane resin composition used in the present invention, the content of fine particle alumina is preferably 5 to 95% by weight, more preferably 10 to 90% by weight, based on the hydrophilic polyurethane resin. If 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, are insufficient. On the other hand , if the content exceeds 95% by weight, the strength of the film and the adhesion to the substrate are insufficient. Since it becomes inferior to property etc., it is not preferable. Surprisingly, when the content of the alumina fine particles is 75 to 95% by weight, by coating the base material with a coating solution using the alumina-dispersed hydrophilic polyurethane resin composition of the present invention, nm) size microporous film with excellent transparency is formed.
[0036]
When the content of the tertiary amino group in the hydrophilic polyurethane-based resin in the present invention is 1 or less per 10,000 molecular weight, characteristics such as water resistance and blocking resistance, which are the intended purposes of the present invention, are exhibited. On the other hand, if the content of the tertiary amino group exceeds 1 per 20 molecular weights, the water repellency increases due to the decrease in the hydrophilic portion in the resin, and the water absorption performance and antifogging properties become poor. It is not preferable.
[0037]
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, the water absorption and antifogging properties are inferior. On the other hand, if it exceeds 80% by weight, the water resistance and blocking resistance are inferior.
[0038]
As the base material 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 sheets having a thickness of 50 to 250 μm, such as polyester, cellulose triacetate, polycarbonate, polyvinyl chloride, polypropylene, polyamide, polystyrene, polyethylene, polymethyl methacrylate, and the like. In addition, the base sheet is provided with a primer layer for providing adhesion to the ink receiving layer and a slipping layer for improving the friction coefficient on the back surface of the base sheet on the non-receptive layer side as necessary. You can also
[0039]
In the present invention, the above-mentioned alumina-dispersed hydrophilic polyurethane resin composition is used to form an ink receiving layer. The resin component constituting the ink receiving layer may be the above-mentioned hydrophilic polyurethane resin alone. However, in order to further adjust the hydrophilicity and / or water absorption depending on the composition of the ink for inkjet recording, A water-soluble polymer may be used in combination with the water-soluble polyurethane resin. Examples of the water-soluble polymer include polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, CMC, cellulose derivatives, polyvinyl pyrrolidone, polyacrylic acid, polyacrylic acid polymer, starch, cationic starch, gelatin, and casein. .
[0040]
In order to further impart water resistance and durability to the ink receiving layer and the printed image, a hydrophobic polymer may be used in combination with the hydrophilic polyurethane resin. Examples of the hydrophobic polymer include 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 resin, epoxy resin, urea resin, melamine resin and the like.
[0041]
In addition, for the purpose of improving the ink absorbability, fixing property, color development property, and blocking property and water resistance of the ink receiving layer, inorganic and organic pigments, resin particles, etc. are added to the alumina-dispersed hydrophilic polyurethane resin composition. Can be contained. Examples of pigments and resin particles used include kaolin, delaminated kaolin, aluminum hydroxide, silica, diatomaceous earth, calcium carbonate, talc, titanium oxide, calcium sulfate, barium sulfate, zinc oxide, calcium silicate, magnesium silicate, and colloidal silica. Mineral pigments such as zeolite, bennite, sericite, lithopone, porous pigments, polystyrene resins, urea resins, acrylic resins, melamine resins, benzoguanamine resins, polyurethane resins, other organic pigments, porous fine particles and hollow particles Among the known pigments and resin particles such as the above, one or more kinds are appropriately used according to the quality design of the recording sheet for inkjet. In this case, the amount of these pigments and resin particles used is in the range of 0 to 95% by weight, preferably 10 to 90% by weight, based on the total solid content of the alumina-dispersed hydrophilic polyurethane resin composition used for forming the ink receiving layer. is there.
[0042]
Further, if necessary, the alumina-dispersed hydrophilic polyurethane-based resin composition may include a thickener, a release agent, a penetrating agent, a wetting agent, a thermal gelling agent, a sizing agent, an antifoaming agent, an antifoaming agent, Foaming agent, colorant, fluorescent whitening agent, ultraviolet absorber, antioxidant, quencher agent, preservative, antistatic agent, crosslinking agent, dispersant, lubricant, plasticizer, pH adjuster, fluidity improver, Various auxiliary agents such as a solidification accelerator and a water-proofing agent can be appropriately blended.
[0043]
In the present invention, the alumina-dispersed hydrophilic polyurethane resin composition used for forming the ink receiving layer is preferably a solution of the hydrophilic polyurethane resin synthesized in a solvent, and synthesized without a solvent. In such a case, the above-mentioned hydrophilic polyurethane resin is used by dissolving in a solvent. If the component added as necessary is solvent-soluble, it may be directly added to the hydrophilic polyurethane resin composition and dissolved, or may be added in advance in a solvent. 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.
[0044]
The prepared coating solution 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 and the like. Further, after application, the sheet is finished by using a calendar such as a machine calendar, a super calendar, or a soft calendar to obtain an ink jet recording sheet.
[0045]
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. If the thickness of the ink receiving layer is less than 5 g / m ² , the ink absorption by the ink receiving layer is insufficient, and if the thickness exceeds 100 g / m ² , the obtained effect becomes saturated and uneconomical, and the ink receiving Layer breakage, curling, etc. are likely to occur.
[0046]
【Example】
Next, the present invention will be described more specifically with reference to examples and comparative examples. In addition, the part or% in a sentence is a weight reference | standard.
[0047]
Reference example 1
700 parts of polyethylene glycol (molecular weight: 1,000) and 750 parts of alumina water sol (alumina average particle size: 150 to 160 nm, solid content: 40% by weight) are thoroughly mixed, and the resulting mixture is stirred at 70 ° C. under reduced pressure. Went. After the theoretical amount of water was distilled off, the temperature was raised to 120 ° C. and 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 moisture content of 0.15%, was transparent at 80 ° C., and had a viscosity of 380 dPa · s.
[0048]
Reference example 2
100 parts of polyethylene glycol (molecular weight 590) and 500 parts of alumina water sol (alumina average particle size 10-20 nm, solid content 20% by weight) are thoroughly mixed, and the resulting mixture is subjected to vacuum dehydration at 70 ° C. with stirring. It was. After the theoretical amount of water was 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 polyol (B) having an alumina content of 50% by weight. This polyol had a hydroxyl value of 95 mgKOH / g, a moisture content of 0.12%, and softened at 90 ° C.
[0049]
Reference example 3
100 parts of polyethylene oxide diamine (Jefamine ED manufactured by Texaco Chemical Co., Ltd .; molecular weight 600) and 2250 parts of alumina water sol (alumina average particle size 150 to 160 nm, solid content 40% by weight) are sufficiently mixed, and the resulting mixture is stirred. Under reduced pressure, dehydration was performed at 70 ° C. 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 polyamine (C) having an alumina content of 90% by weight. This polyamine was softened at an amine equivalent of 30 g / mol, a moisture content of 0.20%, and 110 ° C.
[0050]
Reference example 4
(Production of alumina-dispersed polyurethane resin composition)
50 parts of polyethylene glycol (molecular weight 2,040), 100 parts of polyol (A) of Reference Example 1, 20 parts of N-methyldiethanolamine and 5 parts of diethylene glycol are mixed in a mixed solvent of 200 parts of methyl ethyl ketone and 200 parts of dimethylformamide. Dissolve and add 60 parts of hydrogenated MDI in 200 parts of methyl ethyl ketone gradually while stirring well at 60 ° C. After completion of the addition, react at 80 ° C for 8 hours, and then add 420 parts of dimethylformamide. In addition, a solution of the alumina-dispersed polyurethane resin composition of the present invention was obtained.
[0051]
This solution has a solid content of 20%, a viscosity of 22 dPa · s (25 ° C.), a weight average molecular weight of 52,000 as measured by GPC of a polyurethane resin (the same applies to the following examples), and contains alumina. The amount was 11.7%. The film formed from this resin composition solution was transparent, had a breaking strength of 23.7 Mpa, a breaking elongation of 55%, and a softening point of 155 ° C.
[0052]
Reference Example 5
(Production of alumina-dispersed polyurethane-polyurea resin composition)
30 parts of polyethylene oxide diamine (Jefamine ED; molecular weight 2,000), 120 parts of polyol (B) of Reference Example 2, and N, N-dimethyl-N ′, N′-dihydroxyethyl-1,3-diaminopropane 25 A solution of 65 parts of hydrogenated MDI dissolved in 100 parts of methyl ethyl ketone was gradually added dropwise to 100 parts of methyl ethyl ketone and 200 parts of dimethylformamide mixed solvent. After completion of dropping, the mixture was reacted at 80 ° C. for 8 hours, and then 560 parts of dimethylformamide was added to obtain a solution of the alumina-dispersed polyurethane-polyurea resin composition of the present invention.
[0053]
This solution had a solid content of 20% and a viscosity of 40 dPa · s (25 ° C.). The polyurethane-polyurea resin had a weight average molecular weight of 51,000 and an alumina content of 24%. The film formed from this resin composition solution was transparent, had a breaking strength of 18.5 Mpa, a breaking elongation of 20%, and a softening point of 165 ° C.
[0054]
Reference Example 6
(Production of alumina-dispersed polyurea resin composition)
Polyethylene oxide diamine (Jephamine ED; molecular weight 2,000) 5 parts, polyamine (C) 145 parts of Reference Example 3 and 3 parts of methyliminobispropylamine are dissolved in 250 parts of dimethylformamide, and the internal temperature is adjusted to 0- A solution prepared by dissolving 7 parts of hydrogenated MDI in 100 parts of dimethylformamide was gradually added dropwise and reacted while stirring at 5 ° C. After completion of the dropwise addition, to raise the internal temperature gradually to obtain a solution of alumina dispersed polyurea resin composition of dimethylformamide 310 parts of the present invention beside After further 5 hours was reached 50 ° C..
[0055]
This solution had a solid content of 20%, a viscosity of 80 dPa · s (25 ° C.), the polyurea resin had a weight average molecular weight of 38,000, and an alumina content of 79%. The film formed from this resin composition solution was slightly translucent and porous, had a breaking strength of 4.2 Mpa, a breaking elongation of 3%, and a softening point of 210 ° C.
[0056]
Reference Example 7
A polyurethane resin solution was obtained by the same material and formulation as in Reference Example 1 except that N-methyldiethanolamine of Reference Example 4 was not used and polyol of polyol (A) except for alumina was used. This solution had a solid content of 20%, a viscosity of 50 dPa · s (25 ° C.), and the weight-average molecular weight of the polyurethane resin was 68,000. The film formed from this resin solution had a breaking strength of 35.0 Mpa, a breaking elongation of 450%, and a softening point of 103 ° C.
[0057]
Reference Example 8
N Reference Example 5, N-dimethyl -N ', N'-dihydroxyethyl-1,3-diaminopropane without using, also addition to using a polyol except the alumina polyol (B) Reference Example 2 A polyurethane-polyurea resin solution was obtained using the same materials and formulation. This solution had a solid content of 20%, a viscosity of 40 dPa · s (25 ° C.), and the weight-average molecular weight of the polyurethane-polyurea resin was 55,000. The film formed from this resin solution had a breaking strength of 25.3 MPa, a breaking elongation of 400%, and a softening point of 95 ° C.
[0058]
Reference Example 9
Without the use of methyl iminobispropylamine in Reference Example 6, also, in addition to using a polyamine other than alumina polyol (C) is to obtain a solution of polyurea resin according to the formulation the same material as in Reference Example 3. This solution had a solid content of 20%, a viscosity of 25 dPa · s (25 ° C.), and the polyurea resin had a weight average molecular weight of 32,000. The film formed from this resin solution had a breaking strength of 22.7 MPa, a breaking elongation of 350%, and a softening point of 115 ° C.
[0059]
Reference Examples 10-12
Each alumina water sol of Reference Examples 1 to 3 was added to each of the resin solutions of Reference Examples 7 to 9 with stirring, but the particles precipitated and the solution became opaque.
[0060]
Reference Example 13
A 5% aqueous solution of polyvinyl alcohol (polymerization degree 550) having a saponification degree of 98.5% was prepared.
[0061]
Examples 1-3
The alumina dispersion hydrophilic polyurethane resin composition obtained in Reference Example 4-6 on quality paper having a basis weight of 35 g / m ^2, an air knife coater, was coated to a thickness after drying of 25 [mu] m, An ink receiving layer was formed to obtain an ink jet recording sheet of the present invention.
[0062]
Comparative Examples 1-7
The resin solution obtained in Reference Example 7-13 on quality paper having a basis weight of 35 g / m ^2, an air knife coater, a thickness after drying was coated so that the 25 [mu] m, to form an ink-receiving layer The ink jet recording sheet of Comparative Example was used.
[0063]
[Evaluation of inkjet recording sheet]
For the 10 types of ink jet recording sheets obtained as described above, four colors of yellow, magenta, cyan and black are used in an ink jet printer (PM-800C manufactured by Seiko Epson Corporation) for recording with water-soluble dye ink. The following items were evaluated.
(1) Blocking property An untreated PET film was stacked on the resin coating 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 results are displayed as follows.
○: No blocking property Δ: Some blocking property ×: Blocking property (2) Transparency The cloudiness of the resin coating surface was visually determined. The results are displayed as follows:
○: completely transparent Δ: slightly cloudy ×: completely opaque
(3) Colored sharpness After color printing with an inkjet printer, the color sharpness of the obtained color image was visually observed. The results are displayed as follows:
○: Clear and clear △: Slightly blurred and slightly unclear (4) Ink drying characteristics After color printing with an inkjet printer, press the filter paper for 5 seconds at a load of 50 g / m ² until the ink does not transfer to the filter paper. Time was measured.
(5) Water resistance of printed image After color printing with an ink jet printer, the recording sheet is immersed in water (20 ° C, 1 hour), and then visually observed for bleeding and color change of the recorded image when dried at room temperature. . The results are displayed as follows:
○: No change Δ: Change is observed in ink and film ×: Ink can be considerably removed or the entire film can be taken Table 1 shows the above evaluation results.
[0065]

[0066]
【The invention's effect】
According to the above present invention, resistance to aqueous, blocking resistance, excellent ink jet recording sheet in lubricity is provided.

Claims (5)

In a method for producing an ink jet recording sheet in which at least one ink receiving layer is provided on at least one side of a substrate sheet, the ink receiving layer comprises an organic polyisocyanate , a high molecular weight hydrophilic polyol and / or a polyamine , and at least one. A hydrophilic polyurethane-based resin having a hydrophilic segment and a tertiary amino group is obtained by reacting a compound having one active hydrogen-containing group and at least one tertiary amino group in the same molecule. when synthesizing, as at least a part of the high molecular weight hydrophilic polyol and / or polyamine, obtained by using a mixture of a high molecular weight hydrophilic polyol and / or polyamine and particulate alumina, the alumina dispersion hydrophilic polyurethane resin composition Production of an ink jet recording sheet characterized by using Law. 2. The method for producing an ink jet recording sheet according to claim 1 , wherein the mixture is obtained by removing a dispersion solvent of alumina sol from a mixture of high molecular weight hydrophilic polyol and / or polyamine and alumina sol.   2. The method for producing an ink jet recording sheet according to claim 1, wherein the content of alumina in the mixture is 5 to 95% by weight with respect to the hydrophilic polyurethane resin. The method for producing an ink jet recording sheet according to claim 1, wherein the fine particle alumina has an average particle diameter of 1 to 300 nm. The method for producing an inkjet recording sheet according to claim 1 , wherein the content of the hydrophilic segment in the hydrophilic polyurethane-based resin is 30 to 80% by weight.