JP3994508B2 - Double-sided coated paper for printing - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は印刷用塗被紙に関し、特に白紙光沢、印刷光沢および平滑性に優れ、かつ剛度（紙腰）が高く、印刷作業性に優れる印刷用両面塗被紙に関する。
【０００２】
【従来の技術】
一般的に、印刷用塗被紙に対しては高光沢と高平滑性および優れた印刷適性が要求される。近年、印刷技術の向上と相まって高速印刷のニーズが高まるに伴い、印刷作業性や印刷適性の観点から、前記したような紙質特性は勿論、強い紙腰（所謂、剛度）を具備した印刷用塗被紙が求められている。通常、紙腰が弱い（剛度が低い）と高速印刷等に際して、紙折れ等が発生し、満足な印刷作業ができず、作業能率の低下を招き、ユーザークレームの起因となることが多い。他方、紙腰が強い（高い）と、高速印刷に際し円滑な紙送りが可能となるのみならず、剛度が高いことで、製品に嵩高（重厚）さが生まれ、結果的に印刷物に高級感が醸成される。さらに、付言すると、剛度の高い印刷物（塗被紙）を本文用紙に用いて雑誌やカタログに製本して仕上げると、自然と豪華さや重量感が醸成され、それだけ印刷用紙としての商品価値が高められることになる。
【０００３】
ところで、紙の剛度はその米坪（重量）や密度と密接な関係にあり、一般的には米坪が大きくなる程、剛度が高くなり、他方紙の密度が高くなると、剛度は低下する傾向にある。したがって、製品の坪量を増すと、自然と剛度は高くなる。
一方、紙の坪量が増すと、重量感等は得られるものの、紙の重量が必要以上に重くなり、量が制限されるカタログや郵便物等として利用するに際し、枚数の制限や重量制限等の問題が派生し、種々の不都合がある。そのために、製品重量はできるだけ軽く、他方では剛度の高い塗被紙製品が要望されている。
【０００４】
なお、印刷用塗被紙については、通常剛度以外に優れた印刷仕上りが求められるために、結果的に製品に対し一層優れた光沢や平滑性が要請される。そして、所望とされる高光沢や高平滑性を塗被紙に付与するには、ある程度、紙の密度を高めることが必要となる。
即ち、塗被紙に高光沢や高平滑性を付加するにはキャレンダー掛けが不可欠であり、キャレンダー処理を行えば、必然的に密度が高まり、剛度は反対に低下するようになる。このように、高光沢や高平滑性を高める手段と剛度を高めることとは相反する関係にあり、両方を上手くバランスさせることは極めて難しいのが現状である。また、塗被層中に接着剤を多く配合して密度高く仕上げると印刷適性、特にインキセットやインキ着肉性が悪化し問題となり易い。
【０００５】
ところで、従来より印刷用塗被紙の剛度の改善技術については種々の提案がなされている。例えば、原紙を構成するパルプとして針葉樹パルプ（ＮＫＰ）の高率配合、塗料配合の観点からは、澱粉の高率配合、さらには特開平６−２８７５０３号公報に提案されているようにガラス転移温度（以下、Ｔｇと称す）の高い共重合体ラテックスを高率配合する等の方法が提案され、所期の目的を達成しようとするのが現状である。
【０００６】
しかしながら、原紙に針葉樹パルプを高率配合したり、顔料と接着剤を主成分とする水性組成物（以後、塗料と称す）中に澱粉を高率配合すると、紙腰（剛度）は高くなるものの、一方で塗被紙面の平滑性や光沢が低下するといった難点が付随する。そこで、そのような欠点を回避するために、塗料中にＴｇの高い共重合体ラテックスを接着剤として高率配合することで剛度改善（紙腰を強める）の手段とすることが多かった。なお、Ｔｇの高い共重合体ラテックスを接着剤として使用した場合には、その特性上、より優れた光沢を発現させるために、例えば特開昭５３−７９６４号公報に開示されているように、グロスキャレンダーあるいはソフトキャレンダーと呼ばれる１００℃以上の高温キャレンダーに当該塗被紙を通紙し、加圧処理して仕上げられる。
【０００７】
他方、Ｔｇの高い共重合体ラテックスを使用すると、接着強度が低下する傾向にあり、その結果、塗被層の一部剥離といった不具合が生じる。そこで、そのような不具合を改善するために、例えば特開昭５６−６８１８８号公報には、Ｔｇが３８℃以上の共重合体ラテックスとＴｇが５〜２５℃の共重合体ラテックスとを併用使用することが提案されている。しかしながら、このような提案による方法であっても、高いＴｇの共重合体ラテックスに十分な接着強度を発現させるためには、高温キャレンダーの処理条件を強くする必要がある。その結果、得られる塗被紙の印刷適性やキャレンダー操業性が低下するといった難点がある。
【０００８】
ここで、高温キャレンダーの操業について付記すると、このキャレンダー処理は前記した共重合体ラテックス等の熱可塑性物質を含有する塗被層を設けた紙匹を高温金属ロールと弾性ロールからなるキャレンダーニップ部を通過させて処理するものである。即ち、紙匹に付加される高温、高圧によって前記共重合体ラテックスを可塑化させて塗被層中の顔料を効果的に配向させたり、あるいは金属ロール表面を写し取ることで、高光沢を有する塗被紙を得ようとする作業である。
一方、このような高温と加圧手段を取ると、高温の金属ロールや弾性ロールの表面に塗被層が貼り付いたり、塗被層の一部がロール表面に剥ぎ取られて、製品価値を低下させたり、ロール汚れを誘発させるなど操業性を低下させることが多かった。
【０００９】
なお、前記の如きロール汚れやロール表面への貼り付きを防止する方法として、塗料中にワックス類、脂肪酸類、脂肪酸塩類、シリコーン樹脂などの離型剤を添加したり、あるいは前記離型剤を上記ロール表面に直接塗布することも行われている。しかし、このような手段を取ると、過剰の離型剤がロール表面に蓄積し、汚れの原因となったり、塗被紙の光沢を低下させるといった難点が付随する。
上記の如き理由より、一般に市販されている、所謂スーパーアート紙やアート紙と呼ばれる高光沢印刷用塗被紙は、光沢や平滑性の点では優れるものの、一方で本発明が所望とする高い剛度を有する製品は未だに得られていない。
【００１０】
次いで、剛度について補足すると、紙の剛度を示す指標の１つとして、ＪＩＳＰ８１４３のＡ法が規定されている。この方法はクラーク法とも呼ばれ、紙を手（指）で持ち上げた場合の手触り感（重厚さ）に合う評価法として知られているものである。そして、このクラーク法は紙を測定したときの突き出し長さＬ（単位：ｃｍ）を３乗して１００で割った値を剛度（剛度＝Ｌ3 ／１００）と規定している。因みに、本発明では、製品の縦、横目における突き出し長さＬの平均値（単位：ｍｍ表示）をもって剛度と定義するものである。
【００１１】
また、光沢度はＪＩＳ Ｐ８１４２に準拠して測定される数値で表すのが普通であり、本発明ではこの光沢度が７５％以上である高光沢度を呈する製品を対象とするものである。即ち、このような光沢度を呈する両面塗被紙は通常は相当に加圧処理されて光沢が付加されているものである。他方、このような両面塗被紙の剛度は感覚的に低く、手肉感（重厚さ）の貧弱なものが多いのが実状である。
例えば、一般に市販されている、所謂スーパーアート紙、あるいはアート紙と呼ばれている製品について、本発明者らは前記した如く本発明で特定する剛度Ｌを測定した結果、米坪が１００〜１１０ｇ／ｍ2 程度のものの剛度Ｌ（ｍｍ）は概略１５０〜１７２ｍｍ、１２５〜１３５ｇ／ｍ2 程度のもので、１６２〜２００ｍｍ、さらに１５５〜１６５ｇ／ｍ2 程度のものでは、２１０〜２３８ｍｍといった値（注：値が大きい程、剛度が高い）を示す。勿論、これら製品の光沢度はいずれもＪＩＳ Ｐ８１４２に準拠して測定した値で７５％を越えるものばかりである。そして、いずれの製品も高光沢、高平滑を呈する割りには、手肉感（重厚さ）に乏しいものが多い。
【００１２】
【発明が解決しようとする課題】
上記の如く、従来の高光沢印刷用両面塗被紙については、強い条件（高温、高圧）でのキャレンダー処理等が施される関係もあり、その紙面光沢や平滑性には優れるものの、一方で重厚感に欠けるきらいがある。紙面の光沢や平滑性を改善することと、塗被紙のもつ重厚感、所謂剛度（紙腰）との間には相反する傾向が強く、両者をバランスさせて共に改善する方法が未だに見つかっていないのが実状である。
本発明者らは、このような高光沢印刷用塗被紙の抱える難点を解決するべく、鋭意検討を重ねてきた。その結果、本発明は印刷用両面塗被紙に関し、特に特定の剛度を有し、かつその塗被層面を水銀ポロシメーターで測定したときに、特定の空隙（微細孔）の規定範囲における、それら空隙容積の容量を特定することによって、高剛度と優れた光沢および平滑性、さらに優れた印刷適性（吸水着肉性、インキ乾燥性等）を具備する塗被紙を提供するものである。
【００１３】
【課題を解決するための手段】
本発明は、原紙上に顔料と接着剤を主成分とする塗被層を設けてなる印刷用両面塗被紙において、該両面塗被紙が原紙上に顔料と接着剤を主成分とする下塗り用水性組成物および上塗り用水性組成物を塗被、乾燥して複層塗被層を設けた後、１００℃以上の熱キャレンダーに通紙して加圧処理されてなる両面塗被紙であって、該下塗り用水性組成物が接着剤として、ガラス転移温度が３０℃以上の共重合体ラテックスを下塗り用水性組成物の全顔料に対して、固形分対比で１５重量％以上含有し、さらに上塗り用水性組成物が顔料として、サチンホワイトを上塗り用水性組成物の全顔料に対し、５〜２０重量％含有し、かつ接着剤として、ガラス転移温度が２５〜６０℃の酢酸ビニル系共重合体を上塗り用水性組成物の全顔料に対し、８〜２０重量％含有し、該両面塗被紙のＪＩＳ Ｐ８１４３のＡ法に準拠して測定したクラーク突出し長さの縦目および横目における平均値Ｌが下記（１）式を満足し、かつ該両面塗被紙を水銀ポロシメーターで測定したときの微細孔０．０３〜０．３μｍにおける空隙容積が９．００ｃｃ／ｍ2 〜１１．５０ｃｃ／ｍ2 であることを特徴とする印刷用両面塗被紙である。
Ｌ ＞ １．２８Ｘ ＋ ４０ （１）
〔ここに、Ｌ＝両面塗被紙の縦目および横目におけるクラーク突出し長さの平均値（単位：ｍｍ）、Ｘ＝製品米坪（ｇ／ｍ2 ）である〕
【００１５】
【発明の実施の形態】
本発明は、原紙上に顔料と接着剤を主成分とする塗被層を設けてなる塗被紙を高温キャレンダーで加圧処理することによって、極めて優れた光沢、平滑性を示し、かつ紙腰が強く、印刷適性（特に、吸水着肉性やインキ乾燥性）に優れる印刷用両面塗被紙を提供するものである。
而して、本発明は、原紙上に顔料と接着剤を主成分とする塗被層を設けてなる印刷用両面塗被紙であって、特に、該両面塗被紙のＪＩＳ Ｐ８１４３のＡ法に準拠して測定したクラーク突出し長さの縦目および横目における平均値Ｌが下記（１）式を満足し、かつ該両面塗被紙を水銀ポロシメーターで測定したときの微細孔０．０３〜０．３μｍにおける空隙容積が９．００ｃｃ／ｍ2 〜１１．５０ｃｃ／ｍ2 の範囲にあることを特徴とする印刷用両面塗被紙である。
Ｌ ＞ １．２８Ｘ ＋ ４０ （１）
〔ここに、Ｌ＝両面塗被紙の縦目および横目におけるクラーク突出し長さの平均値（単位：ｍｍ）、Ｘ＝製品米坪（ｇ／ｍ2 ）である〕
【００１６】
なお、本発明では、塗被紙製品の縦目、横目における突き出し長さＬを測定し、その平均値を塗被紙の剛度Ｌ（単位：ｍｍ）とした場合に、紙腰の強さ（剛度）と手触り感（重厚さ）との相関関係が十分に得られることを確認でき、上記したように塗被紙の縦目、横目における突き出し長さの平均値（Ｌ：ｍｍ）を剛度と定義するものである。
【００１７】
上記したように、本発明の特徴である特定の剛度（Ｌ）と空隙容積を満足し、かつ優れた印刷適性を有する塗被紙は、原紙上に顔料と接着剤を主成分とする下塗り用水性組成物および上塗り用水性組成物を塗被、乾燥して複層塗被層を設けた後、１００℃以上の熱キャレンダーに通紙して加圧処理されてなる印刷用両面塗被紙において、該下塗り用水性組成物の接着剤として、Ｔｇが３０℃以上の共重合体ラテックスが下塗り用水性組成物の全顔料に対して固形分対比で１５重量％以上含有せしめられ、さらに上塗り用水性組成物の顔料として、サチンホワイトが上塗り用水性組成物の全顔料に対し、５〜２０重量％含有せしめられ、かつ接着剤として、Ｔｇが２５〜６０℃の酢酸ビニル系共重合体が上塗り用水性組成物の全顔料に対し、８〜２０重量％含有せしめられたことを特徴とする印刷用両面塗被紙である。
【００１８】
本発明は、前記したように、特定の材料構成になる下塗り、および上塗り用水性組成物（以後、単に塗料と称す）の複層塗工になる塗被層を設けた後、１００℃以上の熱キャレンダーに通紙し、加圧仕上げすることによって、特に効果的に所望とする印刷用両面塗被紙を得るものである。
そして、高品質の印刷用両面塗被紙を得るためには、下塗り用塗料の接着剤として、Ｔｇが３０℃以上の共重合体ラテックスが下塗り用塗料中の顔料に対し、固形分対比で１５重量％以上含有せしめられ、さらに上塗り用塗料中に顔料としてサチンホワイトが上塗り用塗料の全顔料に対し固形分対比で５〜２０重量％含有せしめられ、かつ接着剤として、Ｔｇが２５〜６０℃の酢酸ビニル系共重合体が上塗り用塗料の全顔料に対し、固形分対比で８〜２０重量％含有せしめられていることが重要である。
なお、本発明において、高温キャレンダーに通紙して仕上げた後の両面塗被紙の物性値、即ち、ＪＩＳ Ｐ８１１８に準拠して測定した密度が１．１５〜１．３５ｇ／ｃｍ3 、塗被層面のＪＩＳ Ｐ８１４２に準拠して測定した光沢度が７５％以上、およびＪ．ＴＡＰＰＩ紙パルプ試験方法Ｎｏ．５Ａ法のスムースター平滑度計による測定値で１５ｍｍＨｇ以下であるような物性値を示すように仕上げると、特に所望とする高品質の印刷用両面塗被紙が得られ易い。
【００１９】
本発明は前記したクラーク法により測定した塗被紙の縦目、横目における突き出し長さの平均値（Ｌ）が（１）式を満たし、かつ塗被層面の水銀ポロシメーターで測定した微細孔０．０３〜０．３μｍにおける空隙容積が９．００ｃｃ／ｍ2 〜１１．５０ｃｃ／ｍ2 を満足するように仕上げることで、高平滑、高光沢を呈し、さらに高剛度、所謂重量感（高級感）を呈するのは勿論、印刷適性（吸水着肉性、インキ乾燥性）に優れる両面塗被紙が得られることを初めて見出し、本発明を完成するに至った。
【００２０】
上記（１）式で定義される剛度（Ｌ値）は製品米坪が大きくなる程、当然高くなるが、特に本発明に係る塗被紙の場合、従来品（同等米坪品）に比較し、大きい値を示し、極めて重厚感のある製品となる。なお、このような高いＬ値を有する製品を得るための好ましい実施態様の１つが、前記した複層塗被層、即ち下塗り塗被層および上塗り塗被層に配合した特定の高Ｔｇ共重合体ラテックスの作用効果にある。
【００２１】
即ち、下塗り用塗料に配合される接着剤としてＴｇが３０℃以上、好ましくは３０℃以上、４５℃以下の共重合体ラテックスを塗料中の顔料に対し、固形分対比で１５重量％以上、好ましくは１５〜３０重量％で配合される。因みに、Ｔｇが３０℃未満、あるいは配合量が１５重量％未満の場合は、所望の剛度が得られない虞れがあり、一方、配合量が３０重量％を越えるか、あるいはＴｇが４５℃を越えるような共重合体ラテックスを配合すると、塗被層の空隙容積が小さくなる傾向にあり、インキ乾燥性や吸水着肉性が悪化し、印刷適性を低下させる虞れがある。
なお、高Ｔｇ共重合体ラテックスはそれ自体が硬い性質を有しており、高熱により可塑性を示すものの、冷却後は被膜形状を維持すると同時に塗被層を固くする結果、剛度が高められるものである。
【００２２】
また、本発明では、上塗り用塗料中にもＴｇが２５〜６０℃の酢酸ビニル系共重合体を顔料に対し、８〜２０重量％配合することによって、剛度をより一層高めるものである。要するに、下塗りおよび上塗り塗被層の接着剤として、いずれも高Ｔｇ共重合体ラテックスを配合することで、従来の製品では得られていない極めて高い剛度を得るものである。
上塗り用塗料へ配合する上記高Ｔｇの酢酸ビニル系共重合体の目的は剛度を高くする以外に、印刷適性（特に、吸水着肉性）の改善を図ることにある。因みに、酢酸ビニル系共重合体のＴｇが２５℃未満の場合には、剛度を高める効果が少なくなり、一方６０℃を越えるようなものはオフセット印刷時の吸水性不良や接着強度の低下を招く虞れがあり好ましくない。なお、共重合体ラテックスのＴｇの調整は、共重合体ラテックスを構成するモノマー成分の種類や配合比率を適宜操作することで行うことができる。
上述したように、本発明では２層構成になる塗被層の各塗被層に高Ｔｇ共重合体ラテックスを配合することで、剛度を高め、かつ上塗り塗被層中に高Ｔｇの酢酸ビニル系共重合体を配合することで剛度の向上は勿論、印刷適性の改善がより効果的に図られるものである。
【００２３】
次に、本発明におけるもう１つの重要な要素としては、水銀ポロシメーターで測定した塗被層面における微細孔０．０３〜０．３μｍにおける空隙容積が９．００ｃｃ／ｍ2 〜１１．５０ｃｃ／ｍ2 を満足することにある。
即ち、一般に印刷用塗被紙はパルプ繊維を主体とする原紙上に顔料と接着剤を主成分とする塗被層を設けて仕上げられている。その場合、原紙層はパルプ繊維の網目構造を取り、顔料塗被層は原紙の網目構造を被覆して緻密な層構成をとることで、最終製品としての白紙外観や印刷適性の改善効果を出すための働きをしている。しかも、通常の印刷用塗被紙は最終仕上げ段階でスーパーキャレンダーやソフトキャレンダー等の加圧処理機でその表面を高平滑化したり、高光沢を付加して仕上げられる。
そして、これら繊維の網目構造や塗被層をミクロ的に観察すると、繊維層には微細孔（例えば、大きいものでは数１０μｍ、場合によっては数１００μｍも存在する）が存在し、他方顔料塗被層は極めて小さい粒子径の顔料および接着剤を主成分とする水性組成物で繊維の網目層を被覆し、かつ繊維の凹凸を補正する役目をしているので、塗被層表面における微細孔は繊維の網目構造における微細孔に比較し、極めて小さいものであり、その大きさは最も大きいものでも０．５μｍ以下である。そして、印刷仕上がり、所謂印刷効果に影響を及ぼすものは、この塗被層を構成する顔料や接着剤そのものの他に、塗被層表面に存在する微細孔である。
【００２４】
塗被層表面に存在する微細孔は印刷インクを適宜吸収することで多色印刷が施される。ところで、仮に塗被層面に全く微細孔が存在せずにフィルム状の層だとすると、インキの層内への浸透に時間がかかり過ぎて、満足な印刷が出来なくなる。したがって、適宜微細な孔が存在することで効果的に印刷インキが塗被層内へ浸透することでバランスされているものである。他方、微細な孔であっても多すぎると、インキの浸透が進みすぎて、印刷時間等には問題はないが、インキが層内部へ浸透し過ぎるために、経時により印刷光沢が低下し、印刷効果が下がり好ましくない。
上記の観点から、種々検討を重ねた結果、本発明では、水銀ポロシメーターで測定した塗被層面における微細孔０．０３〜０．３μｍの空隙容積が９．００ｃｃ／ｍ2 〜１１．５０ｃｃ／ｍ2 となるように塗被層を仕上げると、極めて優れた印刷効果および印刷適性を呈する製品が得られることを見出したのである。
【００２５】
因みに、微細孔０．０３μｍ未満といった極めて小さい空隙については、印刷時のインキ浸透には余り影響がなく、他方０．３μｍを越えるような空隙は通常に仕上げた塗被層中には殆ど存在せず、それ以上の大きな空隙については原紙に存在する微細孔であり、印刷効果に強い影響をもつ塗被層とは関係の少ないものである。
さらに、付記すると、塗被層に存在する微細孔の殆どは０．３μｍ以下であるといえる。また、本発明では、前記したように微細孔０．０３μｍ〜０．３μｍの空隙容積が９．００ｃｃ／ｍ2 〜１１．５０ｃｃ／ｍ2 となるように設定すると極めて優れた印刷効果を呈するものである。因みに、９．００ｃｃ／ｍ2 未満の場合にはインキ吸収性が低下し、結果としてインキ乾燥性が悪化し、他方、１１．５０ｃｃ／ｍ2 を越えると、インキが浸透し易くなり、結果としてインキ光沢が無くなり、いずれにしても印刷適性が低下するので好ましくない。したがって、上記した如き特定の空隙容積となるように塗被層面を調整することにより、本発明が所望とする優れた効果が得られる。
【００２６】
なお、塗被層の特定微細孔の空隙容積を上記の如き範囲に調整する方法については特に限定するものではないが、例えば塗被層を構成する塗料中にサチンホワイトを配合し、キャレンダー条件（操作）等を組み合わせることで、所要の値を得ることができる。
サチンホワイトの配合量は上塗り塗被層中に顔料として、上塗り塗被層の全顔料に対し５〜２０重量％で調節される。因みに、５重量％未満では所望の空隙容積が得られ難く、他方２０重量％を越えると、インキ光沢の低下や、熱キャレンダーロールへの貼り付き、さらには塗料調製等に難点を生じ易く好ましくない。さらに、顔料や接着剤の種類、顔料と接着剤との組合わせ、あるいは加熱キャレンダー条件等によっても空隙容積は変わるので、品質バランスとの調整を図りながら、適宜調整して所望の空隙容積を得ることになる。
【００２７】
本発明では、さらに得られる製品の物性値、即ち、ＪＩＳ Ｐ８１１８に準拠して測定した密度が１．１５〜１．３５ｇ／ｃｍ3 、ＪＩＳ Ｐ８１４２に準拠して測定した光沢度が７５％以上、およびＪ．ＴＡＰＰＩ紙パルプ試験法Ｎｏ．５Ａに準拠して測定した平滑度（スムースター平滑度）が１５ｍｍＨｇ以下に仕上げることで、本発明が目的とする、高剛度、高光沢、高平滑性および極めて優れた印刷適性および印刷作業性を有する印刷用両面塗被紙を効率良く得ることができる。
なお、上記特定の密度や平滑度、さらに光沢度を得る方法は、高温キャレンダーの設定条件、あるいは下、上塗り塗被層を構成する材料の選択や配合量を適宜調整することでもバランスさせることができ、特に限定されるものではない。
【００２８】
本発明において、下塗り用塗料の顔料としては特に限定されるものではないが、例えばカオリン、焼成クレー、水酸化アルミニウム、炭酸カルシウム、タルク等の無機顔料およびプラスチックピグメント等の有機顔料の１種および２種以上が適宜併用して使用される。特にカオリン、焼成クレー、水酸化アルミニウム等が塗被層に空隙を付与する上で有効である。
また、接着剤としては、前記したＴｇが３０℃以上の共重合体ラテックスとして、例えばスチレン−ブタジエン共重合体ラテックス、メチルメタクリレート−ブタジエン共重合体ラテックス、あるいはアクリル系共重合体等が例示される。さらに、上記共重合体ラテックスでＴｇが３０℃未満のもの、カゼイン、合成蛋白等の蛋白類、ポリビニルアルコール、オレフィン−無水マレイン酸樹脂、メラミン樹脂等の合成樹脂系接着剤、酸化澱粉、熱化学変成澱粉等の澱粉類、カルボキシメチルセルロース、ヒドロキシエチルセルロース等のセルロース誘導体等の如き一般に公知公用の接着剤も適宜併用できる。
【００２９】
次いで、上塗り用塗料の顔料としては前記したサチンホワイトの他に、例えばカオリン、炭酸カルシウム、タルク、水酸化アルミニウム等の無機顔料、ポリスチレン、エポキシ樹脂、スチレン−アクリル共重合体樹脂等の有機顔料等通常の塗被紙製造分野で使用される顔料の１種以上を選択して使用できる。
また、上塗り塗被層の接着剤としては、前記した如く特定の酢酸ビニル系共重合体以外に、本発明の効果を損なわない程度に従来から使用されている共重合体ラテックス、例えばスチレン−ブタジエン共重合体ラテックス、メチルメタクリレート−ブタジエン共重合体ラテックス等の共役ジエン系共重合体ラテックス、さらにはカゼイン、大豆蛋白等の蛋白類、ポリビニルアルコール、メラミン樹脂等の合成樹脂系接着剤、酸化澱粉、熱化学変性澱粉等の澱粉類等の如き通常の接着剤が適宜選択使用される。
【００３０】
なお、下、上塗り用塗料へ配合される全接着剤量は、下塗り用塗料では、顔料に対し、固形分対比１５〜２５重量％で調整される。一方、上塗り用塗料では、顔料に対し、固形分対比８〜２５重量％で調整される。また、下塗り用塗料、および上塗り用塗料を形成する塗料中には、必要に応じて消泡剤、着色剤、離型剤、流動変性剤、防腐剤等の各種助剤を適宜添加することもできる。
【００３１】
上記の如き条件で調製された下、上塗り塗被層用塗料の原紙への塗工方法については特に限定されるものではなく、例えばブレードコーター、エアナイフコーター、ロールコーター、バーコーター等の塗工装置を設けたオンマシン、あるいはオフマシンコーターによって塗被される。
【００３２】
原紙としては一般の印刷用塗被紙に使用される米坪３０〜３００ｇ／ｍ2 程度の原紙が用いられるが、本発明の場合、特に原紙米坪が１４０ｇ／ｍ2 以下、好ましくは１１０ｇ／ｍ2 〜３０ｇ／ｍ2 の原紙を使用した場合に本発明が所望とする極めて優れた作用効果が得られる。なお、３０ｇ／ｍ2 未満の薄物原紙では、必然的に原紙の紙力が弱くなり、満足な生産ができない虞れがある。一方、１４０ｇ／ｍ2 を越えるような厚物原紙の場合は当初から紙腰の強い状態であり、それ以上剛度を高める必要性がない。
【００３３】
原紙への下塗り用塗料の塗被量は、製品の空隙容積、紙腰（剛度）あるいは白紙品質、印刷品質、塗工適性等を考慮すると５ｇ／ｍ2 〜２０ｇ／ｍ2 程度で調節することが望ましい。次いで、上塗り用塗料の塗被量は、製品の印刷適性（吸水着肉性やインキ乾燥性）および品質（インキグロスと平滑性）等を考慮すると、１２ｇ／ｍ2 〜２５ｇ／ｍ2 程度で調節される。
なお、塗工後の塗被層の乾燥については、蒸気乾燥、熱風乾燥、ガスヒーター加熱、電気ヒーター加熱、赤外線ヒーター加熱等、塗被紙製造分野で従来使用されている各種の乾燥方法が適宜使用される。
【００３４】
本発明では、上記の如く下、上塗り用塗料を塗被、乾燥して得られる塗被紙を１００℃以上の高温キャレンダーを使用して通紙処理を行い、高品質の両面塗被紙に仕上げるものである。この場合のキャレンダーについては特に限定するものではないが、例えばスーパーキャレンダー、グロスキャレンダー、ソフトキャレンダー等の金属ロールまたはドラムと弾性ロールからなる各種キャレンダーがオンラインやインラインまた、オフラインの状態で適宜使用される。その場合、金属ロールの表面温度としては１００〜３００℃、製品品質、キャレンダー操業性等を考慮すると、１００〜２００℃での温度範囲がより望ましい。
また、弾性ロールについては高温、高圧下での耐久性、および耐熱性に耐え得るものであって、かつ高光沢、高平滑性を付与できることが重要であり、ショアーＤ硬度で８５〜９５度、またその表面粗さとしてＲｍａｘが５μｍ以下、好ましくは３μｍ以下、より好ましくは１μｍ以下にまで研磨した樹脂ロールが使用される。
【００３５】
本発明の所望とする製品をより効率良く得るために、仕上げ後の両面塗被紙の密度が１．１５〜１．３５ｇ／ｃｍ3 となるように、高温キャレンダー処理が施される。因みに、密度が１．１５ｇ／ｃｍ3 未満の場合、所望とする光沢や平滑性が得られず、さらには塗被層の接着強度が低下する虞れがある。一方、１．３５ｇ／ｃｍ3 を越えると、塗被層が緻密化し過ぎて顔料間の空隙が大幅に減少し、所望とするポロシティーが得られず、吸水着肉性の悪化やインキ乾燥性不良等印刷適性や印刷作業性への悪影響が懸念される。
【００３６】
【実施例】
以下に実施例を挙げて本発明を具体的に説明する。勿論、本発明はそれらの範囲に限定されるものではない。また、例中の「部」および「％」は特に断らない限り、それぞれ「重量部」および「重量％」を示す。
なお、各評価項目および評価基準は下記の通りである。そして、得られた結果を表１に示した。
【００３７】
〔共重合体ラテックスのガラス転移点〕
共重合体ラテックスを室温で乾燥してフィルムを作成し、示差熱走査熱量計（ＤＳＣ−８２３０Ｄ／リガク：昇温速度１０℃／分）を用いて測定した。
【００３８】
〔密度〕
ＪＩＳ Ｐ８１１８に準拠して測定した。
【００３９】
〔白紙光沢〕
ＪＩＳ Ｐ８１４２に準拠して測定した。
【００４０】
〔平滑度〕
ＪＡＰＡＮ ＴＡＰＰＩ紙パルプ試験法Ｎｏ．５Ａに準拠して測定した。
【００４１】
〔剛度〕
ＪＩＳ Ｐ８１４３のＡ法に準拠して、サンプルの縦目および横目の突き出し長さを測定し、その平均値を突出し長さＬ（剛度：ｍｍ）で示した。
【００４２】
〔空隙容積〕
ＰＭＩ（ＰＯＲＯＵＳ ＭＡＴＥＲＩＡＬＳ ＩＮＣ．）社製の水銀ポロシメーター（西華産業）を使用して、紙片１グラムを採集し、測定を行った後、微細孔０．０３〜０．３μｍにおける空隙容積を積算し、製品１ｍ2 当たりの空隙容積に換算した値で示した。
【００４３】
〔インキ乾燥性〕
ＲＩ印刷適性評価機（明製作所）を用い、オフセット枚葉印刷用墨インキ０．５ｃｃを展色して印刷し、印刷６０秒後に上質紙を印刷面に一定圧力で接着して上質紙へのインキ転移（セットオフ）状況を以下の基準（５点法）で評価した。
５ ； セットが非常に速く、オフセット枚葉印刷の高速印刷にも対応でき、スプレーパウダーの量を多くする必要がなく、裏移りの問題がないレベル。
４ ； セットが速く通常印刷ではスプレーパウダーの量を多くする必要がなく、裏移りの問題がないレベル。
３ ； 標準レベル。
２ ； セットがやや遅く、スプレーパウダーを多くする必要があるが印刷条件の調整により、印刷可能なレベル。
１ ； セットが遅く、オフセット印刷としては使用不可能なレベル。
【００４４】
〔吸水着肉性〕
ＲＩ印刷適性評価機（明製作所）を用い、オフセット枚葉印刷用墨インキ０．５ｃｃを展色して印刷し、印刷６０秒後に上質紙を印刷面に一定圧力で接着して上質紙へのインキ転移（セットオフ）状況を以下の基準で評価した。
５ ； オフセット枚葉印刷にては高速印刷および高精細印刷にまで耐えれ、かつ湿し水が増えても吸水着肉性は極めて良好なレベル。
４ ； オフセット枚葉印刷にては高速印刷に対応でき、吸水着肉性も良好なレベル。
３ ； 標準レベル。
２ ； 吸水着肉性がやや劣るが、オフセット印刷にて湿し水の量、印刷スピードを制限すれば印刷可能なレベル。
１ ； 吸水着肉性が劣り、オフセット印刷としては使用困難なレベル。
【００４５】
実施例１
〔下塗り工程〕
（下塗り用塗料の調製）
顔料としてカオリン（商品名：ＵＷ−９０／エンゲルハード社）９０部とカルシウム（商品名：ＦＭＴ−９０／ファイマテック社）１０部使用し、分散剤として顔料に対してポリアクリル酸ソーダを０．２部添加し、コーレス分散機を用いて固形分濃度が７０％の顔料スラリーを調製した。
かくして得られたスラリーに高Ｔｇラテックスとして、Ｔｇが３５℃のスチレン−ブタジエン共重合体ラテックス（商品名：Ｐ−５９８０／住化Ａ＆Ｌ社）を固形分概算で１８部、リン酸エステル化澱粉（商品名：エースＰ２６０／王子コーンスターチ社）の濃度３０％にて調製したものを固形分概算で（商品名：エースＰ２６０／王子コーンスターチ社）を１．５部、さらに水を加えて固形分濃度６０％の塗料を調製した。
【００４６】
（塗工）
次いで、上記で調製した塗料を中性抄紙で抄造された米坪７６ｇ／ｍ2 の上質原紙上に、乾燥後の塗被量が片面当たり１０ｇ／ｍ2 となるように、熱風温度が１５０℃の熱風乾燥機を備えたブレードコーターを用いて両面に塗被、乾燥して米坪９６ｇ／ｍ2 の下塗り塗被紙を得た。
【００４７】
〔上塗り工程〕
（上塗り用塗料の調製）
顔料としてサチンホワイト（商品名：ＳＷ−ＢＬ／白石工業社）１０部、カオリン（商品名：ミラクリプスＰＧ／エンゲルハード社）６０部、アラゴナイト系軽質炭酸カルシウム（商品名：ＴＰ−１２３ＣＳ／奥多摩工業社）２５部、および有機顔料（商品名：ローペイクＨＰ−９１／ローム＆ハース社）５部を使用し、分散剤としてポリアクリル酸ソーダを顔料に対し、固形分対比で０．２部、水酸化ナトリウム０．２部を添加し、コーレス分散機を用いて固形分濃度が６５％の顔料スラリーを調製した。
【００４８】
かくして得られた顔料スラリーに、Ｔｇが３０℃の酢酸ビニル系共重合体ラテックス（商品名：レジン２２５ー５０９９／日本エヌエスシー社）を１２部、Ｔｇが０℃のスチレン−ブタジエン共重合体ラテックス（商品名：０６３２／日本合成ゴム社）７部、およびリン酸エステル化澱粉（商品名：エースＰ２６０／王子コーンスターチ社）１．５部（各々、固形分換算）、さらに水を加えて固形分濃度５３％の塗料を調製した。
【００４９】
（塗工）
次いで、上記で得られた塗料を、前述の下塗り塗被紙（９６ｇ／ｍ2 ）に、乾燥後の塗被量が片面当たり１６ｇ／ｍ2 となるように、熱風温度が１７０℃の熱風乾燥機を備えたブレードコーターを用いて両面に塗被、乾燥した。
【００５０】
〔ソフトキャレンダー仕上げ〕
かくして得られた、片面２度塗りの両面塗被紙を、表面温度が１３０℃のクロムメッキ仕上げした金属ロールとショアーＤ硬度が９１°の樹脂製弾性ロールの構成になるニップ部に、表、裏それぞれの面が２回ずつ金属面に接触するように通紙（線圧２５０ＫＮ／ｍ，速度５００ｍ／分）して高光沢印刷用両面塗被紙を得た。得られた両面塗被紙の品質評価を行い、その結果を表１に示す。
【００５１】
実施例２
実施例１において、サチンホワイトの配合率を５部にし、カオリン（商品名；ミラクリプスＰＧ／エンゲルハード社）を６５部に変更した以外は実施例１と同様にして両面塗被紙を得た。かくして得られた両面塗被紙の品質評価結果を表１に示す。
【００５２】
実施例３
実施例１の上塗り用塗料調製において、酢酸ビニル系共重合体の配合率を１８部に変更した以外は実施例１と同様にして両面塗被紙を得た。かくして得られた両面塗被紙の品質評価結果を表１に示す。
【００５３】
実施例４
実施例１の上塗り塗料の調製において、使用した酢酸ビニル系共重合体に代えて、Ｔｇが４４℃の酢酸ビニル系共重合体（商品名；プライマルＰ−３１０／ロームアンドハース社）に変更した以外は実施例１と同様にして両面塗被紙を得た。かくして得られた両面塗被紙の品質評価結果を表１に示す。
【００５４】
実施例５
実施例１のソフトキャレンダー仕上げにおいて、加熱ロール温度を１３０℃から１５０℃に変更した以外は実施例１と同様にして両面塗被紙を得た。かくして得られた両面塗被紙の品質評価結果を表１に示す。
【００５５】
比較例１
実施例１の下塗り塗料の調製において、Ｔｇが３５℃のスチレン−ブタジエン共重合体ラテックス（商品名：Ｐ−５９８０／住化Ａ＆Ｌ社）をＴｇが０℃のスチレン−ブタジエン共重合体ラテックス（商品名：０６３２／日本合成ゴム社）に変更した以外は実施例１と同様にして両面塗被紙を得た。かくして得られた両面塗被紙の品質評価結果を表１に示す。
【００５６】
比較例２
実施例１の上塗り塗料の調製において、サチンホワイト（顔料）１０部を全量カオリン（ミラクリプスＰＧ）に移行し、ミラクリプスＰＧを７５部とした以外は実施例１と同様にして両面塗被紙を得た。かくして得られた両面塗被紙の品質評価結果を表１に示す。
【００５７】
比較例３
実施例１の上塗り塗料の調製において、酢酸ビニル系共重合体をスチレン−ブタジエン共重合体ラテックス（商品名：０６３２／日本合成ゴム社）に全量変更した以外は実施例１と同様にして両面塗被紙を得た。かくして得られた両面塗被紙の品質評価結果を表１に示す。
【００５８】
比較例４
実施例１の上塗り塗料の調製において、使用した酢酸ビニル系共重合体をガラス転移点が２０℃の酢酸ビニル系共重合体（商品名；モビニール６３０／ヘキスト合成社）に変更した以外は実施例１と同様にして両面塗被紙を得た。かくして得られた両面塗被紙の品質評価結果を表１に示す。
【００５９】
比較例５
実施例１において下塗り層を設けず、上塗り塗被層を片面当たり２８ｇ／ｍ2 にした以外は実施例１と同様に両面塗被紙を得た。かくして得られた両面塗被紙の品質評価結果を表１に示す。
【００６０】
比較例６
実施例１において、ソフトキャレンダーによる通紙仕上げに際し、金属ロール温度を５０℃とした以外は実施例１と同様にして両面塗被紙を得た。かくして得られた両面塗被紙の品質評価結果を表１に示す。
【００６１】
【表１】
【発明の効果】
表１より明らかなように、本発明の実施例に係る塗被紙は、高光沢、高平滑性の塗被層面を有し、かつ剛度が極めて高く（重厚感に優れる）、インキ乾燥性や吸水着肉性等の印刷適性に優れる印刷用両面塗被紙であった。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coated paper for printing, and more particularly to a double-sided coated paper for printing that is excellent in blank gloss, printing gloss and smoothness, has high rigidity (paper stiffness), and has excellent printing workability.
[0002]
[Prior art]
Generally, high gloss, high smoothness, and excellent printability are required for coated paper for printing. In recent years, as the need for high-speed printing has increased in conjunction with improvements in printing technology, from the viewpoints of printing workability and printing suitability, of course, the above-mentioned paper quality characteristics as well as printing coatings with strong paper stiffness (so-called stiffness) are provided. Paper is required. Usually, if the paper is weak (low rigidity), paper breakage or the like occurs during high-speed printing and the like, and a satisfactory printing operation cannot be performed, resulting in a decrease in work efficiency and often causing user complaints. On the other hand, if the paper is strong (high), not only smooth paper feeding is possible during high-speed printing, but also the high rigidity makes the product Bulky (Heaviness) is born, and as a result, a sense of quality is nurtured in the printed matter. In addition, if a high-stiffness printed material (coated paper) is used as a text sheet and bound into a magazine or catalog, it will naturally create a sense of luxury and weight, and that will increase the commercial value of the printed paper. It will be.
[0003]
By the way, the stiffness of paper is closely related to its weight (weight) and density. Generally, the larger the weight of rice, the higher the stiffness, while the higher the density of paper, the lower the stiffness. It is in. Therefore, increasing the basis weight of the product naturally increases the stiffness.
On the other hand, when the basis weight of the paper increases, a feeling of weight is obtained, but the weight of the paper becomes heavier than necessary, and when using it as a catalog or mail, etc. where the amount is limited, the number of sheets and the weight limit, etc. This problem is derived and has various disadvantages. For this purpose, there is a need for coated paper products that are as light as possible and on the other hand highly rigid.
[0004]
Note that the coated paper for printing usually requires an excellent printing finish other than the stiffness, and as a result, more excellent gloss and smoothness are required for the product. In order to impart the desired high gloss and high smoothness to the coated paper, it is necessary to increase the density of the paper to some extent.
That is, calendering is indispensable for adding high gloss and high smoothness to the coated paper. If the calendering process is performed, the density inevitably increases and the stiffness decreases. As described above, there is a contradictory relationship between means for increasing high gloss and high smoothness and increasing rigidity, and it is extremely difficult to achieve a good balance between the two. Also, if a large amount of adhesive is blended in the coating layer and finished with a high density, the printability, particularly the ink set and ink fillability, are likely to be problematic.
[0005]
By the way, various proposals have conventionally been made for techniques for improving the stiffness of coated paper for printing. For example, from the viewpoint of blending soft wood pulp (NKP) as a pulp constituting the base paper, paint blending, and glass transition temperature as proposed in JP-A-6-287503. A method of blending a copolymer latex having a high rate (hereinafter referred to as Tg) at a high rate has been proposed, and the present situation is to achieve the intended purpose.
[0006]
However, if a high percentage of softwood pulp is blended into the base paper, or a high percentage of starch is blended in an aqueous composition mainly composed of pigment and adhesive (hereinafter referred to as paint), the stiffness of the paper increases. On the other hand, there is a problem that the smoothness and gloss of the coated paper surface are lowered. Therefore, in order to avoid such drawbacks, it has often been a means for improving the rigidity (strengthening the paper) by blending high-g copolymer latex in the paint as a bonding agent at a high rate. In addition, when a copolymer latex having a high Tg is used as an adhesive, in order to develop a more excellent gloss on its properties, for example, as disclosed in JP-A-53-7964, The coated paper is passed through a high temperature calendar of 100 ° C. or higher called a gloss calendar or a soft calendar, and finished by pressing.
[0007]
On the other hand, when a copolymer latex having a high Tg is used, the adhesive strength tends to decrease, and as a result, a problem such as partial peeling of the coating layer occurs. Therefore, in order to improve such problems, for example, JP-A-56-68188 uses a copolymer latex having a Tg of 38 ° C. or higher and a copolymer latex having a Tg of 5 to 25 ° C. It has been proposed to do. However, even with such a proposed method, it is necessary to increase the processing conditions of the high-temperature calendar in order to develop sufficient adhesive strength in the high Tg copolymer latex. As a result, there is a problem that the printability and calendar operability of the coated paper obtained are lowered.
[0008]
Here, the operation of the high temperature calender is described. This calender treatment is a calender consisting of a high temperature metal roll and an elastic roll. The calender is provided with a coating layer containing a thermoplastic substance such as copolymer latex. Processing is performed through the nip portion. That is, the copolymer latex is plasticized by high temperature and high pressure applied to the paper web to effectively orient the pigment in the coating layer, or by copying the surface of the metal roll, the coating having a high glossiness. This is an operation to obtain the paper.
On the other hand, when such high temperature and pressure are applied, the coating layer is stuck on the surface of the high-temperature metal roll or elastic roll, or a part of the coating layer is peeled off on the roll surface. In many cases, the operability was lowered, such as lowering or inducing roll dirt.
[0009]
In addition, as a method for preventing the above-described roll dirt and sticking to the roll surface, a release agent such as waxes, fatty acids, fatty acid salts, silicone resins, or the like is added to the paint, or the release agent is added. Direct application to the roll surface is also performed. However, when such measures are taken, excessive release agent accumulates on the roll surface, which causes problems such as contamination and a decrease in gloss of the coated paper.
For the reasons described above, a commercially available high gloss printing paper called so-called super art paper or art paper is excellent in terms of gloss and smoothness, but on the other hand, high rigidity desired by the present invention. The product which has is not yet obtained.
[0010]
Next, supplementing the stiffness, the A method of JISP8143 is defined as one of the indices indicating the stiffness of paper. This method is also called the Clark method, and is known as an evaluation method that matches the feel (heavyness) when the paper is lifted by hand (finger). In this Clark method, the value obtained by dividing the protrusion length L (unit: cm) when measuring the paper to the third power and dividing by 100 is the stiffness (rigidity = L Three / 100). Incidentally, in the present invention, the average value (unit: mm display) of the protruding length L in the vertical and horizontal directions of the product is defined as the rigidity.
[0011]
Further, the glossiness is usually expressed by a numerical value measured according to JIS P8142, and the present invention is intended for a product exhibiting a high glossiness having a glossiness of 75% or more. That is, a double-sided coated paper exhibiting such glossiness is usually subjected to a considerable pressure treatment to add gloss. On the other hand, the rigidity of such double-sided coated paper is sensually low, and many of them have poor hand feeling (heavyness).
For example, as a result of measuring the rigidity L specified in the present invention as described above for the so-called super art paper or a product called art paper, which is generally marketed, the present inventors measured 100 to 110 g of rice tsubo. / M 2 Roughness L (mm) of the one of about 150 to 172 mm, 125 to 135 g / m 2 About 162 to 200 mm, and further 155 to 165 g / m 2 A value of about 210 to 238 mm (note: the larger the value, the higher the stiffness) is shown. Of course, the glossiness of these products is only over 75% as measured according to JIS P8142. Each product has high gloss and high smoothness, but many of them have poor hand feeling (heavyness).
[0012]
[Problems to be solved by the invention]
As described above, the conventional double-sided coated paper for high-gloss printing may be subjected to a calendering process under strong conditions (high temperature, high pressure), and the paper surface gloss and smoothness are excellent. And lacks profound feeling. There is a strong contradiction between improving the gloss and smoothness of the paper and the heavy feeling of the coated paper, the so-called stiffness (paper stiffness), and there is still a way to improve both by balancing the two. There is no actual situation.
The present inventors have intensively studied in order to solve the difficulty of such coated paper for high gloss printing. As a result, the present invention relates to a double-sided coated paper for printing, and has a specific rigidity, and when the surface of the coated layer is measured with a mercury porosimeter, the voids in a specific range of specific voids (micropores). By specifying the capacity of the volume, a coated paper having high rigidity, excellent gloss and smoothness, and excellent printability (water absorption property, ink drying property, etc.) is provided.
[0013]
[Means for Solving the Problems]
The present invention relates to a double-sided coated paper for printing in which a coating layer mainly composed of a pigment and an adhesive is provided on a base paper. After coating a base paper with an aqueous composition for undercoating and an aqueous composition for overcoating mainly comprising a pigment and an adhesive and drying to provide a multi-layer coating layer, it is passed through a heat calender at 100 ° C. or higher. A double-sided coated paper obtained by applying pressure to a paper, wherein the undercoat aqueous composition is used as an adhesive, and a copolymer latex having a glass transition temperature of 30 ° C. or higher is used as the total pigment in the undercoat aqueous composition. On the other hand, it is contained in an amount of 15% by weight or more in terms of solid content, the aqueous composition for top coating is further contained as a pigment, and satin white is contained in an amount of 5 to 20% by weight based on the total pigment of the aqueous composition for top coating, and as an adhesive. , Containing a vinyl acetate copolymer having a glass transition temperature of 25 to 60 ° C. in an amount of 8 to 20% by weight based on the total pigment of the aqueous composition for top coating, When the average value L of the length and width of the Clark protrusion measured in accordance with method A of JIS P8143 satisfies the following formula (1), and the double-sided coated paper is measured with a mercury porosimeter Micropore The void volume at 0.03 to 0.3 μm is 9.00 cc / m 2 ~ 11.50cc / m 2 A double-sided coated paper for printing, characterized in that
L> 1.28X + 40 (1)
[Where, L = average value of clerk protrusion length (unit: mm) in the vertical and horizontal directions of the double-sided coated paper, X = product tsubo (g / m 2 )
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The present invention shows extremely excellent gloss and smoothness by pressurizing a coated paper comprising a coating layer mainly composed of a pigment and an adhesive on a base paper with a high-temperature calendar. The present invention provides a double-sided coated paper for printing that is firm and has excellent printability (particularly water absorption and ink drying properties).
Thus, the present invention is a double-sided coated paper for printing in which a coating layer mainly composed of a pigment and an adhesive is provided on a base paper, and in particular, method A of JIS P8143 for the double-sided coated paper. When the average value L of the length and width of the clerk protrusion measured in accordance with the above equation satisfies the following formula (1), and the double-side coated paper is measured with a mercury porosimeter Micropore The void volume at 0.03 to 0.3 μm is 9.00 cc / m 2 ~ 11.50cc / m 2 It is the double-sided coated paper for printing characterized by being in the range.
L> 1.28X + 40 (1)
[Where, L = average value of clerk protrusion length (unit: mm) in the vertical and horizontal directions of the double-sided coated paper, X = product tsubo (g / m 2 )
[0016]
In the present invention, the protrusion length L of the coated paper product in the vertical and horizontal eyes is measured, and when the average value is the stiffness L (unit: mm) of the coated paper, It can be confirmed that there is a sufficient correlation between the stiffness (rigidity) and the feeling of touch (heavyness). As described above, the average value (L: mm) of the protruding length of the coated paper in the vertical and horizontal eyes is determined as the stiffness. To define.
[0017]
As described above, it satisfies the specific rigidity (L) and the void volume, which are the characteristics of the present invention, and has excellent printability. The coated paper is on the base paper Apply an aqueous composition for undercoating and an aqueous composition for topcoating mainly composed of pigment and adhesive, and dry to form a multilayer coating layer. After providing In a double-sided coated paper for printing formed by passing through a heat calendar at 100 ° C. or higher and subjected to pressure treatment, a copolymer latex having a Tg of 30 ° C. or higher is used as an adhesive for the undercoat aqueous composition. Aqueous composition for undercoat 15% by weight or more based on the solid content with respect to all the pigments of the above, and as a pigment of the aqueous composition for top coating, satin white is contained at 5 to 20% by weight based on the total pigment of the aqueous composition for top coating. And a double-sided coating for printing, characterized in that a vinyl acetate copolymer having a Tg of 25 to 60 ° C. is contained as an adhesive in an amount of 8 to 20% by weight based on the total pigment of the aqueous coating composition. Paper.
[0018]
As described above, the present invention provides an undercoat having a specific material structure and a coating layer that is a multi-layer coating of an aqueous composition for topcoat (hereinafter simply referred to as a paint), and then has a temperature of 100 ° C. or higher. By passing the paper through a heat calendar and pressurizing it, the desired double-sided coated paper for printing is obtained particularly effectively.
In order to obtain a high-quality double-sided coated paper for printing, a copolymer latex having a Tg of 30 ° C. or more as an adhesive for the undercoat paint is 15% by solids relative to the pigment in the undercoat paint. In addition, 5% to 20% by weight of satin white as a pigment in the top coat paint is contained in the top coat paint with respect to the solid content, and Tg is 25 to 60 ° C. as an adhesive. It is important that the vinyl acetate copolymer is contained in an amount of 8 to 20% by weight based on the solid content with respect to all pigments of the overcoating paint.
In the present invention, the physical properties of double-sided coated paper after finishing by passing through a high temperature calendar, that is, the density measured according to JIS P8118 is 1.15 to 1.35 g / cm. Three , Glossiness measured in accordance with JIS P8142 of the coated layer surface is 75% or more, and J.P. TAPPI paper pulp test method no. When finished so as to exhibit a physical property value of 15 mmHg or less as measured by the smoother smoothness meter of the 5A method, a desired high-quality double-sided coated paper for printing is easily obtained.
[0019]
In the present invention, the average length (L) of the protruding length of the coated paper measured by the Clark method described above satisfies the formula (1) and measured with a mercury porosimeter on the coated layer surface. Micropore The void volume at 0.03 to 0.3 μm is 9.00 cc / m 2 ~ 11.50cc / m 2 Finishing so as to satisfy the requirements, it exhibits high smoothness, high gloss, high rigidity, so-called heavy feeling (high-class feeling), as well as excellent printability (water absorption and ink drying properties). It was discovered for the first time that a paper was obtained, and the present invention was completed.
[0020]
The stiffness (L value) defined by the above formula (1) naturally increases as the product weight of the product increases, but in the case of the coated paper according to the present invention, compared to the conventional product (equivalent product of the same weight). , Show a large value and become a very profound product. One of the preferred embodiments for obtaining a product having such a high L value is a specific high Tg copolymer blended in the above-mentioned multilayer coating layer, that is, the undercoat coating layer and the top coating layer. It is in the effect of latex.
[0021]
That is, a copolymer latex having a Tg of 30 ° C. or higher, preferably 30 ° C. or higher and 45 ° C. or lower as an adhesive compounded in the undercoat coating is preferably 15% by weight or more based on the solid content of the pigment in the coating. Is blended at 15 to 30% by weight. Incidentally, if the Tg is less than 30 ° C. or the blending amount is less than 15% by weight, the desired rigidity may not be obtained, while the blending amount exceeds 30% by weight or the Tg exceeds 45 ° C. When a copolymer latex exceeding the above is blended, the void volume of the coating layer tends to be small, the ink drying property and the water absorption property are deteriorated, and the printability may be lowered.
The high Tg copolymer latex itself has a hard property and exhibits plasticity due to high heat. However, after cooling, the coating shape is maintained and at the same time the coating layer is hardened, resulting in increased rigidity. is there.
[0022]
In the present invention, the rigidity is further increased by blending 8 to 20% by weight of a vinyl acetate copolymer having a Tg of 25 to 60 ° C. with respect to the pigment in the overcoating paint. In short, by adding a high Tg copolymer latex as an adhesive for the undercoat and topcoat coating layers, extremely high rigidity not obtained with conventional products can be obtained.
The purpose of the high Tg vinyl acetate copolymer to be blended into the top coating is to improve the printability (particularly, the water absorbability) in addition to increasing the rigidity. Incidentally, when the Tg of the vinyl acetate copolymer is less than 25 ° C., the effect of increasing the rigidity is reduced, while those exceeding 60 ° C. cause poor water absorption at the time of offset printing and decrease in adhesive strength. There is a fear and it is not preferable. In addition, adjustment of Tg of copolymer latex can be performed by manipulating the kind and compounding ratio of the monomer component which comprises copolymer latex suitably.
As described above, in the present invention, by adding a high Tg copolymer latex to each coating layer of the two-layer coating layer, the rigidity is increased, and a high Tg vinyl acetate in the top coating layer. By blending the copolymer, not only the rigidity can be improved, but also the printability can be improved more effectively.
[0023]
Next, another important factor in the present invention is that the void volume at the fine pores of 0.03 to 0.3 μm on the coated layer surface measured with a mercury porosimeter is 9.00 cc / m. 2 ~ 11.50cc / m 2 Is to satisfy.
That is, in general, a coated paper for printing is finished by providing a coated layer mainly composed of a pigment and an adhesive on a base paper mainly composed of pulp fibers. In that case, the base paper layer takes the mesh structure of the pulp fiber, and the pigment coating layer covers the base paper network structure to form a dense layer structure, thereby improving the white paper appearance and printability as the final product. I work for you. In addition, ordinary coated paper for printing is finished in a final finishing stage with a high-smooth surface or a high glossiness by a pressure processing machine such as a super calender or soft calender.
When the network structure and the coating layer of these fibers are observed microscopically, the fiber layer has micropores (for example, several tens of μm for large ones and several hundreds μm in some cases), while the pigment coating is applied. The layer covers the fiber network layer with an aqueous composition mainly composed of a pigment and an adhesive having a very small particle diameter, and serves to correct the unevenness of the fiber. Compared to the fine pores in the fiber network structure, it is extremely small, and even the largest is 0.5 μm or less. In addition to the pigment and the adhesive constituting the coating layer, the fine pores existing on the surface of the coating layer are those that affect the printing finish, the so-called printing effect.
[0024]
The micropores present on the surface of the coating layer are subjected to multicolor printing by appropriately absorbing the printing ink. By the way, if it is a film-like layer without any micropores on the coating layer surface, it takes too much time for the ink to penetrate into the layer, and satisfactory printing cannot be performed. Therefore, the printing ink is effectively infiltrated into the coating layer due to the presence of appropriately fine pores, which is balanced. On the other hand, if there are too many fine holes, the penetration of the ink proceeds too much, and there is no problem in printing time etc., but since the ink penetrates too much into the layer, the printing gloss decreases with time, The printing effect is lowered, which is not preferable.
From the above viewpoint, as a result of various studies, in the present invention, the void volume of the fine pores 0.03 to 0.3 μm on the coating layer surface measured with a mercury porosimeter is 9.00 cc / m. 2 ~ 11.50cc / m 2 It was found that a product exhibiting an extremely excellent printing effect and printability can be obtained by finishing the coating layer so that
[0025]
By the way, for very small voids such as fine pores of less than 0.03 μm, there is not much influence on ink penetration during printing, while voids exceeding 0.3 μm are hardly present in the normally finished coating layer. On the other hand, the larger voids are fine holes existing in the base paper and have little relation to the coating layer having a strong influence on the printing effect.
In addition, it can be said that most of the micropores present in the coating layer are 0.3 μm or less. In the present invention, as described above, the void volume of the micropores 0.03 μm to 0.3 μm is 9.00 cc / m. 2 ~ 11.50cc / m 2 If the setting is made, the printing effect is extremely excellent. By the way, 9.00cc / m 2 If it is less than 1, the ink absorptivity is lowered, and as a result, the ink drying property is deteriorated. On the other hand, 11.50 cc / m 2 Exceeding this range is not preferable because the ink easily permeates, and as a result, the ink gloss is lost. Therefore, by adjusting the coating layer surface so as to have the specific void volume as described above, the excellent effect desired by the present invention can be obtained.
[0026]
The method for adjusting the void volume of the specific fine pores of the coating layer to the above range is not particularly limited, but for example, satin white is blended in the coating material constituting the coating layer, and the calendar conditions A desired value can be obtained by combining (operation) and the like.
The blending amount of satin white is adjusted to 5 to 20% by weight with respect to the total pigment of the top coat layer as a pigment in the top coat layer. Incidentally, if it is less than 5% by weight, it is difficult to obtain a desired void volume. On the other hand, if it exceeds 20% by weight, ink gloss is lowered, sticking to a heat calender roll, and further, it is preferable to cause difficulties in preparing a paint. Absent. Furthermore, since the void volume varies depending on the type of pigment or adhesive, the combination of pigment and adhesive, or the heating calender conditions, etc., the desired void volume can be adjusted by adjusting the quality balance as appropriate. Will get.
[0027]
In the present invention, the physical properties of the obtained product, that is, the density measured according to JIS P8118 is 1.15 to 1.35 g / cm. Three , Glossiness measured in accordance with JIS P8142 is 75% or more; TAPPI Paper Pulp Test Method No. By finishing the smoothness (smooster smoothness) measured in accordance with 5A to 15 mmHg or less, the object of the present invention is to achieve high rigidity, high gloss, high smoothness and extremely excellent printability and printing workability. The double-sided coated paper for printing can be obtained efficiently.
In addition, the method for obtaining the specific density, smoothness, and glossiness described above can be balanced by appropriately adjusting the setting conditions of the high temperature calendar, or the selection and blending amount of the material constituting the undercoat coating layer. There is no particular limitation.
[0028]
In the present invention, the pigment for the undercoat paint is not particularly limited. For example, inorganic pigments such as kaolin, calcined clay, aluminum hydroxide, calcium carbonate, and talc, and organic pigments such as plastic pigments 1 and 2 More than one species are used in combination as appropriate. In particular, kaolin, calcined clay, aluminum hydroxide and the like are effective for imparting voids to the coating layer.
Examples of the adhesive include copolymer latexes having a Tg of 30 ° C. or higher, such as styrene-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, and acrylic copolymer. . Furthermore, the above-mentioned copolymer latex having a Tg of less than 30 ° C., proteins such as casein and synthetic proteins, synthetic resin adhesives such as polyvinyl alcohol, olefin-maleic anhydride resin and melamine resin, oxidized starch, thermochemistry Generally known and publicly used adhesives such as starches such as modified starches and cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose can be used as appropriate.
[0029]
Next, as the pigment for the top coating, in addition to the above-described satin white, for example, inorganic pigments such as kaolin, calcium carbonate, talc, aluminum hydroxide, organic pigments such as polystyrene, epoxy resin, styrene-acrylic copolymer resin, etc. One or more pigments used in the ordinary coated paper manufacturing field can be selected and used.
In addition to the specific vinyl acetate copolymer as described above, the copolymer latex conventionally used to the extent that the effects of the present invention are not impaired, such as styrene-butadiene, is used as the adhesive for the top coat layer. Copolymer latex, conjugated diene copolymer latex such as methylmethacrylate-butadiene copolymer latex, protein such as casein and soybean protein, synthetic resin adhesive such as polyvinyl alcohol and melamine resin, oxidized starch, Ordinary adhesives such as starches such as thermochemically modified starch are appropriately selected and used.
[0030]
Note that the total amount of adhesive blended into the undercoat paint is adjusted to 15 to 25% by weight relative to the pigment in the undercoat paint. On the other hand, in the paint for top coating, the solid content is adjusted to 8 to 25% by weight with respect to the pigment. In addition, various auxiliary agents such as antifoaming agents, colorants, mold release agents, flow modifiers, preservatives, etc. may be appropriately added to the paint for forming the undercoat paint and the topcoat paint as necessary. it can.
[0031]
The method for coating the base paper of the undercoat coating material prepared under the above conditions is not particularly limited. For example, a coating apparatus such as a blade coater, air knife coater, roll coater, bar coater, etc. It is applied by an on-machine or an off-machine coater provided with
[0032]
As a base paper, 30 to 300 g / m of rice basis weight used for general printing coated paper 2 However, in the case of the present invention, the base paper weight is 140 g / m. 2 Or less, preferably 110 g / m 2 ~ 30g / m 2 When this base paper is used, the extremely excellent action and effect desired by the present invention can be obtained. 30g / m 2 If it is less than 10%, the paper strength of the base paper is inevitably weakened, and there is a possibility that satisfactory production cannot be performed. Meanwhile, 140 g / m 2 In the case of a thick base paper that exceeds 50%, the paper is stiff from the beginning, and there is no need to further increase the rigidity.
[0033]
The coating amount of the undercoat paint on the base paper is 5 g / m considering the void volume of the product, paper stiffness (rigidity) or blank paper quality, print quality, coating suitability, etc. 2 ~ 20g / m 2 It is desirable to adjust the degree. Next, the coating amount of the top coating is 12 g / m in consideration of the printability (water absorption and ink drying properties) and quality (ink gloss and smoothness) of the product. 2 ~ 25g / m 2 Adjusted by degree.
As for the drying of the coating layer after coating, various drying methods conventionally used in the coated paper manufacturing field such as steam drying, hot air drying, gas heater heating, electric heater heating, infrared heater heating, etc. are appropriately used. used.
[0034]
In the present invention, the coated paper obtained by coating and drying the undercoat as described above is subjected to a paper passing process using a high-temperature calendar at 100 ° C. or higher to obtain a high-quality double-sided coated paper. It is something to finish. The calendar in this case is not particularly limited. For example, a metal roll such as a super calender, a gloss calender, a soft calender, etc., or various calendars composed of a drum and an elastic roll are in an online, in-line, or offline state. Is used as appropriate. In this case, the surface temperature of the metal roll is preferably 100 to 300 ° C., and the temperature range of 100 to 200 ° C. is more preferable in consideration of product quality, calendar operability, and the like.
Further, it is important that the elastic roll can withstand durability at high temperature and high pressure, and heat resistance, and can give high gloss and high smoothness, and has a Shore D hardness of 85 to 95 degrees, Further, a resin roll having a surface roughness Rmax of 5 μm or less, preferably 3 μm or less, more preferably 1 μm or less is used.
[0035]
In order to obtain the desired product of the present invention more efficiently, the density of the double-sided coated paper after finishing is 1.15 to 1.35 g / cm. Three A high temperature calendar process is applied so that Incidentally, the density is 1.15 g / cm. Three If it is less than the range, the desired gloss and smoothness cannot be obtained, and the adhesive strength of the coating layer may be lowered. Meanwhile, 1.35 g / cm Three If it exceeds, the coating layer becomes too dense and the gaps between the pigments are greatly reduced, the desired porosity cannot be obtained, the printability and printing workability such as poor water absorption and poor ink drying properties, etc. There are concerns about adverse effects on
[0036]
【Example】
The present invention will be specifically described below with reference to examples. Of course, the present invention is not limited to these ranges. In the examples, “parts” and “%” represent “parts by weight” and “% by weight”, respectively, unless otherwise specified.
Each evaluation item and evaluation criteria are as follows. The obtained results are shown in Table 1.
[0037]
[Glass transition point of copolymer latex]
The copolymer latex was dried at room temperature to prepare a film, and the film was measured using a differential thermal scanning calorimeter (DSC-8230D / Rigaku: temperature rising rate 10 ° C./min).
[0038]
〔density〕
It measured based on JISP8118.
[0039]
[Blank gloss]
It measured based on JISP8142.
[0040]
[Smoothness]
JAPAN TAPPI Paper Pulp Test Method No. Measured according to 5A.
[0041]
[Stiffness]
Based on the method A of JIS P8143, the protrusion lengths of the vertical and horizontal eyes of the sample were measured, and the average value was expressed as a protrusion length L (rigidity: mm).
[0042]
[Void volume]
Using a mercury porosimeter manufactured by PMI (POROUS MATERIALS INC.) (Seika Sangyo), 1 gram of paper was collected and measured, Micropore Accumulate the void volume from 0.03 to 0.3 μm, product 1m 2 It was shown as a value converted to a permeation void volume.
[0043]
[Ink drying properties]
Using an RI printing aptitude evaluation machine (Ming Seisakusho), 0.5cc of ink for offset sheet-fed printing was developed and printed, and after 60 seconds printing, the high quality paper was bonded to the printing surface with a certain pressure and applied to the high quality paper. The ink transfer (set-off) situation was evaluated according to the following criteria (5-point method).
5; Very fast setting, high speed printing of offset sheet-fed printing, no need to increase the amount of spray powder, and no leveling problem.
4; Fast setting, normal printing does not require a large amount of spray powder, and there is no problem of set-off.
3; standard level.
2; Setting is a little slow and it is necessary to increase the amount of spray powder, but it is possible to print by adjusting the printing conditions.
1; Level that is slow to set and cannot be used for offset printing.
[0044]
[Water absorption meat characteristics]
Using an RI printing aptitude evaluation machine (Ming Seisakusho), 0.5cc of ink for offset sheet-fed printing was developed and printed, and after 60 seconds printing, the high quality paper was bonded to the printing surface with a certain pressure and applied to the high quality paper. The ink transfer (set-off) situation was evaluated according to the following criteria.
5; In offset sheet-fed printing, it can withstand high-speed printing and high-definition printing, and even if the amount of dampening water increases, the level of water absorption is extremely good.
4; Offset sheet-fed printing can handle high-speed printing and has a good level of water absorption.
3; standard level.
2; Although the water absorption property is slightly inferior, it is possible to print if the amount of dampening water and the printing speed are limited by offset printing.
1; Level of water absorption is inferior and difficult to use for offset printing.
[0045]
Example 1
[Undercoating process]
(Preparation of undercoat paint)
As a pigment, 90 parts of kaolin (trade name: UW-90 / Engelhard) and 10 parts of calcium (trade name: FMT-90 / Fimatec) are used, and as a dispersant, sodium polyacrylate is added to the pigment. Two parts were added, and a pigment slurry having a solid content concentration of 70% was prepared using a coreless disperser.
As a high Tg latex, a styrene-butadiene copolymer latex (trade name: P-5980 / Suika A & L Co.) having a Tg of 35 ° C. was added to the slurry thus obtained. Product name: Ace P260 / Oji Corn Starch Co., Ltd.) 30% concentration, solid content estimated (Product Name: Ace P260 / Oji Corn Starch Co., Ltd.) 1.5 parts, further water added, solid content 60 % Paint was prepared.
[0046]
(Coating)
Next, 76 g / m2 of rice tsubo made from the above-prepared paint with neutral papermaking 2 On high-quality base paper, the coating amount after drying is 10 g / m per side 2 As shown in the figure, 96 g / m of rice basis weight is coated and dried on both sides using a blade coater equipped with a hot air dryer having a hot air temperature of 150 ° C. 2 Undercoated paper was obtained.
[0047]
[Overcoating process]
(Preparation of top coat)
10 parts of satin white (trade name: SW-BL / Shiraishi Kogyo Co., Ltd.), 60 parts of kaolin (trade name: Miracrips PG / Engelhard Co., Ltd.), Aragonite light calcium carbonate (trade name: TP-123CS / Okutama Kogyo Co., Ltd.) ) 25 parts and 5 parts of organic pigment (trade name: Ropeke HP-91 / Rohm & Haas), 0.2 parts by weight of solid content of sodium polyacrylate as a dispersing agent relative to the pigment 0.2 parts of sodium was added, and a pigment slurry having a solid content concentration of 65% was prepared using a coreless disperser.
[0048]
A styrene-butadiene copolymer latex having a Tg of 30 ° C. and a vinyl acetate copolymer latex (trade name: Resin 225-5099 / Nihon NSC) with a Tg of 30 ° C. and a Tg of 0 ° C. (Product name: 0632 / Nippon Synthetic Rubber Co., Ltd.) 7 parts and phosphate esterified starch (Product name: Ace P260 / Oji Cornstarch Co., Ltd.) 1.5 parts (each in terms of solid content) A paint with a concentration of 53% was prepared.
[0049]
(Coating)
Next, the paint obtained above was applied to the above-mentioned undercoated paper (96 g / m 2 ) And the coating amount after drying is 16 g / m per side 2 Then, both sides were coated and dried using a blade coater equipped with a hot air dryer having a hot air temperature of 170 ° C.
[0050]
[Soft calendar finish]
The thus obtained double-sided coated paper with a single-sided coating was applied to a nip portion comprising a chromium-plated metal roll having a surface temperature of 130 ° C. and a resin elastic roll having a Shore D hardness of 91 °. Paper was passed (line pressure 250 KN / m, speed 500 m / min) so that each side of the back surface was in contact with the metal surface twice to obtain a double-coated paper for high gloss printing. The quality of the obtained double-sided coated paper was evaluated, and the results are shown in Table 1.
[0051]
Example 2
A double-sided coated paper was obtained in the same manner as in Example 1, except that the blending ratio of satin white was changed to 5 parts and kaolin (trade name; Miracrips PG / Engelhard) was changed to 65 parts. Table 1 shows the quality evaluation results of the double-sided coated paper thus obtained.
[0052]
Example 3
A double-sided coated paper was obtained in the same manner as in Example 1 except that in the preparation of the topcoat paint of Example 1, the blending ratio of the vinyl acetate copolymer was changed to 18 parts. Table 1 shows the quality evaluation results of the double-sided coated paper thus obtained.
[0053]
Example 4
In the preparation of the top coat of Example 1, instead of the vinyl acetate copolymer used, it was changed to a vinyl acetate copolymer having a Tg of 44 ° C. (trade name: Primal P-310 / Rohm and Haas). Except for the above, a double-sided coated paper was obtained in the same manner as in Example 1. Table 1 shows the quality evaluation results of the double-sided coated paper thus obtained.
[0054]
Example 5
In the soft calendar finishing of Example 1, double-sided coated paper was obtained in the same manner as in Example 1 except that the heating roll temperature was changed from 130 ° C to 150 ° C. Table 1 shows the quality evaluation results of the double-sided coated paper thus obtained.
[0055]
Comparative Example 1
In the preparation of the undercoat paint of Example 1, a styrene-butadiene copolymer latex (trade name: P-5980 / Suika A & L Co.) having a Tg of 35 ° C. and a styrene-butadiene copolymer latex (product) having a Tg of 0 ° C. Name: 0632 / Nippon Synthetic Rubber Co.) A double-sided coated paper was obtained in the same manner as in Example 1 except that Table 1 shows the quality evaluation results of the double-sided coated paper thus obtained.
[0056]
Comparative Example 2
A double-sided coated paper was obtained in the same manner as in Example 1 except that 10 parts of satin white (pigment) were transferred to kaolin (Miracrips PG) and 75 parts of Miracrips PG were used in the preparation of the top coat of Example 1. It was. Table 1 shows the quality evaluation results of the double-sided coated paper thus obtained.
[0057]
Comparative Example 3
In the preparation of the top coat of Example 1, both surfaces of the vinyl acetate copolymer were changed to styrene-butadiene copolymer latex (trade name: 0632 / Nippon Synthetic Rubber) in the same manner as in Example 1 except that the total amount was changed. A paper was obtained. Table 1 shows the quality evaluation results of the double-sided coated paper thus obtained.
[0058]
Comparative Example 4
Example 1 In the preparation of the top coat of Example 1, the vinyl acetate copolymer used was changed to a vinyl acetate copolymer having a glass transition point of 20 ° C. (trade name; Movinyl 630 / Hoechst Synthesis Co., Ltd.). In the same manner as in Example 1, a double-sided coated paper was obtained. Table 1 shows the quality evaluation results of the double-sided coated paper thus obtained.
[0059]
Comparative Example 5
In Example 1, no undercoat layer was provided, and the topcoat layer was 28 g / m per side. 2 A double-sided coated paper was obtained in the same manner as in Example 1 except that. Table 1 shows the quality evaluation results of the double-sided coated paper thus obtained.
[0060]
Comparative Example 6
In Example 1, double-sided coated paper was obtained in the same manner as in Example 1 except that the metal roll temperature was set to 50 ° C. during paper passing finishing with a soft calendar. Table 1 shows the quality evaluation results of the double-sided coated paper thus obtained.
[0061]
[Table 1]
【The invention's effect】
As is clear from Table 1, the coated paper according to the examples of the present invention has a highly glossy and highly smooth coated layer surface, and has extremely high rigidity (excellent feeling of solidness), ink drying properties and It was a double-sided coated paper for printing that was excellent in printability such as water absorbability.
Claims (2)
Ｌ ＞ １．２８Ｘ ＋ ４０ （１）
〔ここに、Ｌ＝両面塗被紙の縦目および横目におけるクラーク突出し長さの平均値（単位：ｍｍ）、Ｘ＝製品米坪（ｇ／ｍ2 ）である〕A double-sided coated paper for printing in which a coating layer mainly comprising a pigment and an adhesive is provided on a base paper, wherein the double-sided coated paper is an aqueous composition for undercoating mainly comprising a pigment and an adhesive on the base paper. And a double-sided coated paper that is coated with an aqueous composition for overcoating, dried to provide a multilayer coating layer, and then passed through a thermal calendar at 100 ° C. or higher and subjected to pressure treatment, The undercoat aqueous composition is used as an adhesive, and a copolymer latex having a glass transition temperature of 30 ° C. or higher is contained in an amount of 15% by weight or more with respect to the total pigment of the undercoat aqueous composition. The composition contains 5 to 20% by weight of satin white based on the total pigment of the aqueous composition for overcoating as a pigment, and is overcoated with a vinyl acetate copolymer having a glass transition temperature of 25 to 60 ° C. as an adhesive. 8 to 20% by weight based on the total pigment of the aqueous composition And the average value L of the wales and courses of the double-sided Clark protruding length was measured in accordance with coated A method of paper JIS P8143 satisfies the following equation (1), and a double-sided coated paper mercury A double-sided coated paper for printing, wherein the void volume in a fine pore of 0.03 to 0.3 μm as measured with a porosimeter is 9.00 cc / m 2 to 11.50 cc / m 2 .
L> 1.28X + 40 (1)
[Here, L = average value of the protruding length of the clerks in the vertical and horizontal directions of the double-sided coated paper (unit: mm), X = product weight per square meter (g / m 2 ))
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP04717298A JP3994508B2 (en) | 1998-02-27 | 1998-02-27 | Double-sided coated paper for printing |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP04717298A JP3994508B2 (en) | 1998-02-27 | 1998-02-27 | Double-sided coated paper for printing |
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| Publication Number | Publication Date |
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| JP3994508B2 true JP3994508B2 (en) | 2007-10-24 |
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| ATE374113T1 (en) * | 2002-10-01 | 2007-10-15 | Sappi Netherlands Services Bv | COATED PRINTING SHEET AND ITS PRODUCTION PROCESS |
| US7160608B2 (en) * | 2003-06-30 | 2007-01-09 | Oji Paper Co., Ltd. | Coated paper |
| JP4996820B2 (en) * | 2004-11-02 | 2012-08-08 | 大王製紙株式会社 | Coated paper manufacturing method and manufacturing equipment |
| KR20180067526A (en) | 2015-09-03 | 2018-06-20 | 니뽄 세이시 가부시끼가이샤 | Evaluation method of coated paper, coated substrate, and ink drying property |
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