JP3654963B2 - Thin paper for high-image heat-sensitive stencil printing base paper - Google Patents

Description

【０００１】
【発明の属する技術分野】
本発明は、キセノンランプ等からの閃光照射、レーザー発振素子からの赤外線照射、または微細でかつ多数の加熱素子を有したいわゆるサーマルヘッドからなる直接または間接の接触伝熱による加熱によって、熱製版される感熱孔版印刷用原紙に用いられる、多孔性薄葉紙に関するものである。
【０００２】
【従来の技術】
従来より、ポリエステルフィルム、塩化ビニリデンフィルム等の熱可塑性樹脂フィルムと、天然繊維、化学繊維を主成分とする薄葉紙、不織布、紗などを多孔性支持体として、両者を各種の接着剤で貼り合わせた構造の感熱性孔版印刷用原紙（以下、原紙と略記する）が知られている（例えば特開昭５１−２５１３号公報、特開昭５７−１８２４９２号公報など）。しかしながら、これらの原紙は、印刷画像の鮮明度を満足させるものではなかった。また、天然繊維に化学繊維を混抄することにより、画像性が向上することが知られているが、これらの原紙は、印刷物画像濃度の均一性が十分とはいえなかった。
【０００３】
従来の原紙を用いた印刷物の画像濃度の均一性が十分でない理由は、種々考えられるが、その大きな要因の一つに孔版印刷独特のものとして、白抜け（印刷物の黒ベタ部に白い欠点が発生すること）という現象がある。これは本来原紙のフィルム部が溶融穿孔して開孔するはずであるのに原紙表面の平滑性が低く、サーマルヘッド等の接触が阻害され穿孔しない場合や、フィルムが穿孔されインキの通過が行われるはずの部分に、支持体を構成する繊維数本が凝集して結束部を形成した場合、その部分をインキが通過しにくいために発生する。また、従来の原紙の開孔面積のバラツキが大きい場合に、印刷物の画像濃度が不均一になる。
【０００４】
【発明が解決しようとする課題】
本発明の目的は、かかる従来技術の問題を解決し、印刷物の画像性、特に画像濃度の均一性を得ることが出来る感熱孔版印刷原紙用薄葉紙を提供することにある。画像濃度を均一にするためには、支持体の改良が重要であり、具体的には、（１）繊維の分散性を向上し、原紙開孔部分のばらつきを低減すること、（２）繊維径のより細い繊維を分散させることにより、原紙表面の平滑性を向上し、穿孔性をあげること、の２点が特に重要であると考えられる。しかし、天然繊維のみを用いて抄造した薄葉紙では、繊維径が太く、繊維の形状が不均一であるため、支持体繊維の結束を防止することと、繊維を均等に存在させることは満足できなかった。また、ポリエステル繊維等の合成繊維のみを用いて抄造した薄葉紙では、繊維径は小さく均一であるが繊維が数本ずつ束になりやすく分散が不均一となりやすく、製版時の熱により熱変形しやすくまた薄葉紙自体の剛性も低いため、実用上問題が多かった。
【０００５】
【課題を解決するための手段】
本発明者等は、上記課題について鋭意研究を重ねた結果、天然繊維とポリエステル繊維（以下、ＰＥＴ繊維という）とを混抄し樹脂加工した薄葉紙に於いて、２種類の繊維径の異なるＰＥＴ繊維を併用することにより、繊維の開孔面積をコントロールし、開孔面積のバラツキを少なくして、繊維の分散性を高めることにより良質な画像性を得ることを見いだし、本発明をなすに至った
すなわち、本発明は、天然繊維にＰＥＴ繊維を混抄し、ウレタン樹脂またはエポキシ樹脂加工を施した薄葉紙において、該ＰＥＴ繊維が平均繊維径３μｍ〜５．９μｍのＰＥＴ繊維と平均繊維径６μｍ〜９μｍのＰＥＴ繊維の２種類から成り、その重量比が２：８〜７：３であり、該ポリエステル繊維は薄葉紙中に２０〜８０重量％含有されていることを特徴とする高画像性感熱孔版印刷原紙用薄葉紙に関するものである。
【０００６】
以下本発明を詳細に説明する。
本発明に用いるＰＥＴ繊維としては、平均繊維径３μｍ〜５．９μｍ及び、６μｍ〜９μｍの２種類である。平均繊維径が３μｍ〜５．９μｍの繊維のみでは原紙の剛性が不足し、６μｍ〜９μｍの繊維のみでは画像性が不十分である。さらに平均繊維径が３μｍ〜５．９μｍのＰＥＴ繊維と平均繊維径が６μｍ〜９μｍのＰＥＴ繊維をそれぞれ混抄する必要がある。さらに平均繊維径が３μｍ〜５．９μｍのＰＥＴ繊維と平均繊維径が６μｍ〜９μｍのＰＥＴ繊維の重量比が１：９〜９：１である必要がある。平均繊維径が３μｍ〜５．９μｍのＰＥＴ繊維が少なくなりすぎると全体の繊維径が太くなり、画像性が低下する。また、平均繊維径が６μｍ〜９μｍのＰＥＴ繊維が少なくなりすぎると抄造後の原紙の剛度が低下し、実用上問題が発生する。好ましくは平均繊維径が３μｍ〜５．９μｍと平均繊維径が６μｍ〜９μｍのＰＥＴ繊維の重量比が３：７〜７：３であり、さらに好ましくは４：６〜６：４である。
【０００７】
また、上記２種類のＰＥＴ繊維は併せて、薄葉紙中に２０〜８０重量％含有させることが好ましい。ＰＥＴ繊維の含有量が２０重量％未満のものは、繊維の分散性に劣り、繊維結束が多くなり、画像性が低下する傾向にある。ＰＥＴ繊維の含有量が８０重量％を越えるものは、薄葉紙の剛度が小さくなり、原紙としての腰が不足し、搬送性に問題が生じやすく、また製版時の熱変形が大きくなる傾向があるので、その使用が制限される。
ＰＥＴ繊維の断面は円形、中空、異形のいずれのものを用いても良い。
本発明の薄葉紙を構成する天然繊維としては、マニラ麻、エクアドル麻、サイザル麻、ニュージーランド麻などの葉脈繊維、亜麻、黄麻、芋麻、ケナフなどの靱皮繊維、その他の天然繊維としては、エスパルト、木材パルプなどが使用できる。そのなかでも、マニラ麻、エクアドル麻、サイザル麻が好ましい。
【０００８】
本発明では、樹脂加工後の薄葉紙は、坪量５〜１５ｇ／ｍ² 、厚さ１０〜５０μｍ（ＪＩＳ Ｐ８１１８により測定）である必要がある。坪量が５ｇ／ｍ² 未満のものや、厚さが１０μｍ未満のものは、耐刷性（一枚の版で印刷可能な枚数で、本発明では、耐刷性５０００枚を最低限としている）が著しく低下する傾向があるため好ましくない。また、坪量が１５ｇ／ｍ² を越えるものや、厚さ５０μｍを越えるものは、インクの通過が著しく制限されるため好ましくない。さらに好ましくは坪量７〜１３ｇ／ｍ² 、厚さ２５〜４０μｍであり、かつ密度（坪量÷厚さ）が０．２５〜０．４０ｇ／ｃｍ³ であり、この範囲内のものは、画像性が非常に優れている。
【０００９】
【発明の実施の形態】
以下、実施例により本発明をさらに詳しく説明するが、本発明はこれらの例に限定されるものではない。
なお、薄葉紙の組成比を表１に、樹脂加工と原紙性能評価結果を表２に、使用した繊維の平均繊維径、銘柄を表３に記した。
【００１０】
平均繊維径は各繊維を任意に摘出し、顕微鏡にて１００倍にて拡大写真を撮り、繊維の径をノギスにて測定し、２０点の平均値を平均繊維径とした。
さらに、原紙の各性能の評価、測定は下記の方法に従い行った。
（１）画像性の評価
原紙を全自動デジタル孔版印刷機（理想科学工業（株）製ＲＣ−１１５) にて印刷した印刷物を肉眼判定にて評価を行った。○は黒ベタ部での白抜けがないもの、×は黒ベタ部での白抜けが目立つもの、△はその中間程度で、実用上使えるレベルのものとした。
（２）濃度均一性の評価
前述の印刷機を用いて印刷した印刷物を肉眼判定にて評価を行った。○は黒ベタ部での濃度ムラがないもの、×は黒ベタ部での濃度むらが目立つもの、△はその中間程度で、実用上使えるレベルのものとした。
（３）平滑度の測定
フィルム張り合わせ前の原紙のフィルム張り合わせ面をベック平滑度にてＪＩＳ Ｐ−８１１９により測定した。
（４）耐刷性の評価
前述の印刷機を用いて、印刷速度１３０枚／分で５０００枚以上印刷しても、印刷物の画像が乱れないものを○、５０００枚未満で画像の乱れるものを×とした。
【００１１】
【実施例１】
マニラ麻をアルカリ蒸解し、水洗後、水で濃度３％に希釈して、ビーターにて濾水度１８°ＳＲ（ＪＩＳ Ｐ−８１２１）に叩解したものを４０重量％、サイザル麻を同様にして濾水度２５°ＳＲに叩解したもの２０重量％、平均繊維径３．６μｍ、長さ３ｍｍのＰＥＴ繊維を２０重量％、平均繊維径６．０μｍ長さ３ｍｍのＰＥＴ繊維を２０重量％とを、均一に混合し、さらに、これにエポキシ化ポリアミドポリアミン樹脂を繊維に対して２％となるように水溶液にして添加し均一に混合した。これを紙料として傾斜短網抄紙機による湿式抄紙法にて、樹脂加工前の薄葉紙を得た。さらにこの薄葉紙に、グラビア塗工機を用いて、水系エマルジョンタイプのウレタン樹脂（ＨＷ３５０）を塗工量１．０ｇ／ｍ² となるように塗工し、原紙の支持体とした。
【００１２】
感熱フィルムの製造感熱層として、テレフタル酸と１、４−シクロヘキサンジメタノール３０モル％及びエチレングリコール７０％からなる混合ジオールとから得られた、ビカット軟化点８２℃、密度１．２７ｇ／ｃｍ³ 、極限粘度０．７５の実質的に非晶質の共重合ポリエステルを用い、剥離層として、エチレン−酢酸ビニル共重合体を主体とした組成物にオレイン酸エステル系の剥離剤を含有させた混合物を用い、それぞれ押し出し機で溶融し、環状多層ダイスより感熱層が剥離層の両面に形成されるように押し出した。その後、延伸倍率が縦５倍、横５倍になるように、バブル状で同時２軸延伸した後、多層フィルムを巻取った。この多層フィルムの各層厚みは感熱層／剥離層／感熱層：２／１２／２μｍであり、この感熱フィルムの結晶化度は６％で、１００℃の加熱収縮率は５９％、加熱収縮応力は２７５ｇ／ｍ² であり、この多層フィルムを原紙作成に用いた。
【００１３】
エポキシ化合物としてエチレングリコールジグリシジルエーテル（ナガセ化成工業（株）、デナコールＥＸ−８１０）、ポリアミン樹脂としてポリアミドアミン（三和化学工業（株）、サンマイド３００）を用いて、重量比をエポキシ化合物：ポリアミン樹脂＝１７：８３となるように、イソプロピルアルコールに溶解させ、接着剤溶液を調整した。
【００１４】
支持体である前述の薄葉紙にグラビアコーターを用いて、固形分塗布量が１．０ｇ／ｍ² となるように調節した接着剤溶液を塗布し、前述の多層フィルムと重ね合わせ、接合させた状態のまま、設定５０℃の乾燥炉を通過させ、溶剤を蒸発乾燥させた後巻き取った。さらに同様にして、裏面にも薄葉紙を接合し、両面に薄葉紙を形成した原紙中間体を得た。さらに、この原紙中間体を３５℃、４８時間エージングし、接着を完了させた後、原紙と剥離層を剥離した。得られた原紙を用いて、フィルム表面にシリコンオイルを０．０５ｇ／ｍ² 塗布し、熱融着防止用オーバーコート層とし、最終的な原紙を得た。
この原紙で印刷した印刷物の画像性は、黒ベタ部の白抜けも少なく評価は○であり、濃度均一性も良好であり○、平滑性耐刷性も５０００枚印刷でき、全てを満足する結果となった。
【００１５】
【実施例２】
天然繊維の比率を各重量比でマニラ麻：サイザル麻：平均繊維径３．６μｍ長さ３ｍｍＰＥＴ：平均繊維径８．０μｍ長さ５ｍｍＰＥＴ＝４０：２０：２０：２０として抄造した薄葉紙に、実施例１と同じ樹脂を０．９ｇ／ｍ² 塗布して樹脂加工し、坪量９．７ｇ／ｍ² 、厚み３０．２μｍの薄葉紙を得た。この薄葉紙と実施例１で用いたフィルムとを用いて、実施例１と同じ方法にて原紙を作成した。この原紙の性能は、実施例１と同様に非常に良好であった。
【００１６】
【実施例３】
繊維組成の比率を各重量比で、マニラ麻：サイザル麻：平均繊維径５．５μｍ長さ５ｍｍＰＥＴ：平均繊維径６．０μｍ長さ３ｍｍＰＥＴ＝４０：２０：２０：２０として抄造した薄葉紙に、実施例１と同じ樹脂を０．９ｇ／ｍ² 塗布して樹脂加工し、坪量９．５ｇ／ｍ² 、厚み２９．５μｍの薄葉紙を得た。この薄葉紙と実施例１で用いたフィルムとを用いて、実施例１と同じ方法にて原紙を作成した。この原紙の性能も良好であった。
【００１７】
【実施例４】
繊維組成の比率を各重量比で、マニラ麻：サイザル麻：平均繊維径５．５μｍ長さ５ｍｍＰＥＴ：平均繊維径８．０μｍ長さ５ｍｍＰＥＴ＝２０：４０：２０：２０として抄造した薄葉紙に、実施例１と同じ樹脂を０．８ｇ／ｍ² 塗布して樹脂加工し、坪量９．３ｇ／ｍ² 、厚み２８．５μｍの薄葉紙を得た。この薄葉紙と実施例１で用いたフィルムとを用いて、実施例１と同じ方法にて原紙を作成した。この原紙の性能も良好であった。
【００１８】
【実施例５】
繊維組成の比率を各重量比で、マニラ麻：サイザル麻：平均繊維径３．６μｍ長さ３ｍｍＰＥＴ：平均繊維径６．０μｍ長さ３ｍｍＰＥＴ＝１０：４０：１０：４０として抄造した薄葉紙に、実施例１と同じ樹脂を０．９ｇ／ｍ² 塗布して樹脂加工し、坪量１０．３ｇ／ｍ² 、厚み３１．０μｍの薄葉紙を得た。この薄葉紙と実施例１で用いたフィルムとを用いて、実施例１と同じ方法にて原紙を作成した。この原紙の性能も良好であった。
【００１９】
【比較例１】
実施例１と同じフィルムと、マニラ麻１００％の薄葉紙（坪量＝１０．５ｇ／ｍ² 、厚み＝３１．２μｍ）を用いて、実施例１と同様の方法にて、原紙を作成した。この原紙の画像性は、黒ベタ部での白点が非常に多かった。これは、天然繊維だけでは繊維の分散性が悪く、繊維の結束部が多いためである。この薄葉紙は、樹脂加工していないが、天然繊維のみのため耐刷性に問題はなかった。
【００２０】
【比較例２】
繊維組成の比率を各重量比で、マニラ麻：サイザル麻：平均繊維径６．０μｍ長さ３ｍｍＰＥＴ＝４０：２０：４０として抄造した薄葉紙に、実施例１と同じ樹脂を０．９ｇ／ｍ² 塗布して樹脂加工し、坪量１０．８ｇ／ｍ² 、厚み３１．２μｍの薄葉紙を得た。この薄葉紙と実施例１で用いたフィルムとを用いて、実施例１と同じ方法にて原紙を作成した。この原紙は実施例１の原紙に比べ、黒ベタ部での濃度にムラがみられ、均一性が劣っていた。
【００２１】
【比較例３】
繊維組成の比率を各重量比で、マニラ麻：サイザル麻：平均繊維径６．０μｍ長さ３ｍｍＰＥＴ：平均繊維径８．０μｍ長さ５ｍｍＰＥＴ＝４０：２０：２０：２０として抄造した薄葉紙に、実施例１と同じ樹脂を０．９ｇ／ｍ² 塗布して樹脂加工し、坪量１０．５ｇ／ｍ² 、厚み３１．０μｍの薄葉紙を得た。この薄葉紙と実施例１で用いたフィルムとを用いて、実施例１と同じ方法にて原紙を作成した。この原紙も実施例１の原紙に比べ、黒ベタ部での濃度にムラがみられ、均一性が劣っていた。
【００２２】
【比較例４】
繊維組成の比率を各重量比で、マニラ麻：サイザル麻：平均繊維径６．０μｍ長さ３ｍｍＰＥＴ：平均繊維径７．０μｍ長さ３ｍｍビニロン＝４０：２０：２０：２０として抄造した薄葉紙に、実施例１と同じ樹脂を０．９ｇ／ｍ² 塗布して樹脂加工し、坪量１０．８ｇ／ｍ² 、厚み３１．３μｍの薄葉紙を得た。この薄葉紙と実施例１で用いたフィルムとを用いて、実施例１と同じ方法にて原紙を作成した。この原紙も実施例１の原紙に比べ、黒ベタ部での濃度にムラがみられ、均一性が劣っていた。
【００２３】
【比較例５】
繊維組成の比率を各重量比で、マニラ麻：サイザル麻：平均繊維径３．６μｍ長さ３ｍｍＰＥＴ＝４０：２０：４０として抄造した薄葉紙に、実施例１と同じ樹脂を０．８ｇ／ｍ² 塗布して樹脂加工し、坪量９．５ｇ／ｍ² 、厚み３０．３μｍの薄葉紙を得た。この薄葉紙と実施例１で用いたフィルムとを用いて、実施例１と同じ方法にて原紙を作成した。この原紙は実施例１の原紙に比べ、強度が劣り、耐刷性が３０００枚と不良であった。
【００２４】
【表１】

【００２５】
【表２】

【００２６】
【表３】

【００２７】
【発明の効果】
本発明の薄葉紙は、繊維分散性良好な、平均繊維径が３μｍ〜５．９μｍのＰＥＴ繊維と平均繊維径が６μｍ〜９μｍのＰＥＴ繊維の構成比が２：８〜７：３であり、かつ天然繊維にＰＥＴ繊維２０〜８０重量％を抄造した混抄薄葉紙であるため、繊維径分布も安定し、かつ繊維分散性がより均一である。したがって、この薄葉紙を支持体として用いた原紙の孔版印刷で得られる印刷物は、非常に高画像性である。さらに支持体の繊維表面及び繊維交絡部に樹脂加工が施されているため、高速多数枚印刷時での原紙の伸びも抑えられ、耐刷性に優れている。[0001]
BACKGROUND OF THE INVENTION
The present invention is made by thermal engraving by flash irradiation from a xenon lamp or the like, infrared irradiation from a laser oscillation element, or heating by direct or indirect contact heat transfer comprising a so-called thermal head having fine and many heating elements. The present invention relates to a porous thin paper used for a heat-sensitive stencil paper.
[0002]
[Prior art]
Conventionally, a thermoplastic resin film such as a polyester film and vinylidene chloride film, and a thin paper, nonwoven fabric, wrinkle and the like mainly composed of natural fibers and chemical fibers have been bonded together with various adhesives. There are known heat-sensitive stencil printing base papers (hereinafter abbreviated as base papers) (for example, Japanese Patent Laid-Open Nos. 51-2513 and 57-182492). However, these base papers do not satisfy the sharpness of the printed image. In addition, it is known that image properties are improved by mixing chemical fibers with natural fibers, but these base papers cannot be said to have sufficient uniformity in printed image density.
[0003]
There are various reasons why the image density uniformity of the printed material using conventional base paper is not sufficient, but one of the major factors is that it is unique to stencil printing, with white spots (white defects in the solid black portion of the printed material). That occurs). This is because the film portion of the base paper is supposed to melt and perforate, but the surface of the base paper has low smoothness and the contact with the thermal head etc. is obstructed so that it does not perforate, or the film is perforated and ink passes therethrough. When the fibers that constitute the support are aggregated in a portion that should be formed to form a bundling portion, this occurs because the ink hardly passes through the portion. Further, when the variation in the opening area of the conventional base paper is large, the image density of the printed matter becomes non-uniform.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a thin paper for heat-sensitive stencil printing base paper that can solve the problems of the prior art and obtain image quality of printed matter, particularly uniformity of image density. In order to make the image density uniform, it is important to improve the support. Specifically, (1) improving the dispersibility of the fiber and reducing the variation in the opening portion of the base paper, (2) the fiber It is considered that the two points of improving the smoothness of the surface of the base paper and increasing the perforation property by dispersing the finer fibers are particularly important. However, thin paper made using only natural fibers has a large fiber diameter and uneven fiber shape, so it is not satisfactory to prevent binding of support fibers and to make fibers evenly present. It was. In addition, thin paper made using only synthetic fibers such as polyester fibers has a small and uniform fiber diameter, but the fibers tend to be bundled several times and disperse easily. Moreover, since the rigidity of the thin paper itself was low, there were many practical problems.
[0005]
[Means for Solving the Problems]
As a result of earnest research on the above problems, the present inventors have made two types of PET fibers having different fiber diameters in a thin paper obtained by mixing and processing natural fibers and polyester fibers (hereinafter referred to as PET fibers). By using together, it was found that the open area of the fiber is controlled, the dispersion of the open area is reduced, and the dispersibility of the fiber is improved to obtain a good image quality, that is, the present invention has been achieved. The present invention relates to a thin paper obtained by mixing PET fiber with natural fiber and processed with urethane resin or epoxy resin, and the PET fiber has PET fiber having an average fiber diameter of 3 μm to 5.9 μm and PET having an average fiber diameter of 6 μm to 9 μm. consists of two kinds of fibers, the weight ratio of 2: 8-7: 3, said polyester fibers and characterized in that it is contained 20 to 80% by weight in the thin paper That relates to tissue paper for high image thermosensitive stencil printing sheet.
[0006]
The present invention will be described in detail below.
As PET fiber used for this invention, there are two types, average fiber diameter 3 micrometers-5.9 micrometers, and 6 micrometers-9 micrometers. Only with fibers having an average fiber diameter of 3 μm to 5.9 μm, the rigidity of the base paper is insufficient, and with only fibers with 6 μm to 9 μm, image quality is insufficient. Further, it is necessary to blend PET fibers having an average fiber diameter of 3 μm to 5.9 μm and PET fibers having an average fiber diameter of 6 μm to 9 μm. Furthermore, the weight ratio of PET fibers having an average fiber diameter of 3 μm to 5.9 μm and PET fibers having an average fiber diameter of 6 μm to 9 μm needs to be 1: 9 to 9: 1. When the PET fiber having an average fiber diameter of 3 μm to 5.9 μm is too small, the entire fiber diameter is increased and image quality is deteriorated. On the other hand, if the PET fibers having an average fiber diameter of 6 μm to 9 μm are too small, the stiffness of the base paper after papermaking is lowered, which causes a practical problem. The weight ratio of PET fibers having an average fiber diameter of 3 μm to 5.9 μm and an average fiber diameter of 6 μm to 9 μm is preferably 3: 7 to 7: 3, and more preferably 4: 6 to 6: 4.
[0007]
Moreover, it is preferable to contain 20-80 weight% of said 2 types of PET fiber together in a thin paper. When the content of the PET fiber is less than 20% by weight, the dispersibility of the fiber is inferior, the fiber binding increases, and the image quality tends to be lowered. When the PET fiber content exceeds 80% by weight, the stiffness of the thin paper is reduced, the stiffness as a base paper is insufficient, the transportability is likely to be problematic, and thermal deformation during plate making tends to increase. , Its use is limited.
The cross section of the PET fiber may be circular, hollow, or irregular.
As the natural fibers constituting the thin paper of the present invention, vein fibers such as Manila hemp, Ecuador hemp, sisal hemp, New Zealand hemp, bast fibers such as flax, burlap, hemp, kenaf, and other natural fibers include esparto, wood Pulp can be used. Of these, Manila hemp, Ecuador hemp, and sisal hemp are preferred.
[0008]
In the present invention, the thin paper after resin processing needs to have a basis weight of 5 to 15 g / m ² and a thickness of 10 to 50 μm (measured according to JIS P8118). When the basis weight is less than 5 g / m ² or the thickness is less than 10 μm, the printing durability (the number of sheets that can be printed with one plate is used, and in the present invention, the printing durability is 5000 sheets at a minimum. ) Is not preferable because it tends to decrease significantly. Also, those having a basis weight exceeding 15 g / m ² or exceeding 50 μm in thickness are not preferred because the passage of ink is remarkably restricted. More preferably, the basis weight is 7 to 13 g / m ² , the thickness is 25 to 40 μm, and the density (basis weight ÷ thickness) is 0.25 to 0.40 g / cm ³ . The image quality is very good.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these examples.
The composition ratio of the thin paper is shown in Table 1, the results of resin processing and base paper performance evaluation are shown in Table 2, and the average fiber diameter and brand of the used fibers are shown in Table 3.
[0010]
For the average fiber diameter, each fiber was arbitrarily extracted, an enlarged photograph was taken at 100 times with a microscope, the fiber diameter was measured with calipers, and the average value of 20 points was defined as the average fiber diameter.
Furthermore, evaluation and measurement of each performance of the base paper were performed according to the following methods.
(1) Evaluation of image quality A printed matter obtained by printing a base paper with a fully automatic digital stencil printing machine (RC-115 manufactured by Riso Kagaku Kogyo Co., Ltd.) was evaluated by visual inspection. ○ indicates that there is no white spot in the black solid part, × indicates that the white spot in the black solid part is conspicuous, and Δ indicates a level that is practically usable.
(2) Evaluation of density uniformity The printed matter printed using the above-mentioned printing machine was evaluated by visual inspection. ○ indicates that there is no density unevenness in the black solid part, × indicates that the density unevenness in the black solid part is conspicuous, and Δ indicates a level that is practically usable.
(3) Measurement of smoothness The film lamination surface of the base paper before film lamination was measured according to JIS P-8119 with Beck smoothness.
(4) Evaluation of printing durability When the above-mentioned printing machine is used to print 5000 sheets or more at a printing speed of 130 sheets / minute, the printed image is not disturbed. X.
[0011]
[Example 1]
Manila hemp is alkali digested, washed with water, diluted to 3% with water, and beaten to a freeness of 18 ° SR (JIS P-8121) with a beater. 20% by weight of beating to a water degree of 25 ° SR, 20% by weight of PET fiber having an average fiber diameter of 3.6 μm and a length of 3 mm, and 20% by weight of PET fiber having an average fiber diameter of 6.0 μm and a length of 3 mm, The epoxidized polyamide polyamine resin was added as an aqueous solution so as to be 2% with respect to the fibers and mixed uniformly. Using this as a stock, thin paper before resin processing was obtained by a wet papermaking method using a slanted short paper machine. Further, this thin paper was coated with a water-based emulsion type urethane resin (HW350) using a gravure coating machine so that the coating amount was 1.0 g / m ^2, and used as a base paper support.
[0012]
Production of heat-sensitive film As a heat-sensitive layer, a Vicat softening point of 82 ° C., a density of 1.27 g / cm ³ , obtained from terephthalic acid and a mixed diol composed of 30 mol% of 1,4-cyclohexanedimethanol and 70% of ethylene glycol, A substantially amorphous copolymer polyester having an intrinsic viscosity of 0.75 is used, and as a release layer, a mixture containing an oleate-based release agent in a composition mainly composed of an ethylene-vinyl acetate copolymer is used. Each was melted with an extruder and extruded from an annular multilayer die so that the heat sensitive layer was formed on both sides of the release layer. Thereafter, the film was simultaneously biaxially stretched in a bubble shape so that the stretch ratio was 5 times in length and 5 times in width, and then the multilayer film was wound up. The thickness of each layer of this multilayer film is heat sensitive layer / peeling layer / heat sensitive layer: 2/12/2 μm, the crystallinity of this heat sensitive film is 6%, the heat shrinkage rate at 100 ° C. is 59%, and the heat shrinkage stress is 275 g / m ² , and this multilayer film was used for making a base paper.
[0013]
Using ethylene glycol diglycidyl ether (Nagase Kasei Kogyo Co., Ltd., Denacol EX-810) as the epoxy compound and polyamidoamine (Sanwa Chemical Industry Co., Ltd., Sanmide 300) as the polyamine resin, the weight ratio of the epoxy compound: polyamine An adhesive solution was prepared by dissolving in isopropyl alcohol so that the resin was 17:83.
[0014]
Using the gravure coater on the thin paper that is the support, the adhesive solution adjusted so that the solid content coating amount is 1.0 g / m ² is applied, superimposed on the multilayer film, and bonded. As it was, it was passed through a drying oven set at 50 ° C., and the solvent was evaporated and dried. Further, similarly, a thin paper was bonded to the back surface to obtain a base paper intermediate having thin paper formed on both sides. Further, this base paper intermediate was aged at 35 ° C. for 48 hours to complete the adhesion, and then the base paper and the release layer were peeled off. Using the obtained base paper, 0.05 g / m ² of silicon oil was applied to the film surface to form an overcoat layer for preventing heat fusion, and a final base paper was obtained.
The image quality of the printed matter printed with this base paper is evaluated as “Good” with little white solids in the black solid part, “Good”, Uniformity of density, and 5,000 smoothness and printing durability. It became.
[0015]
[Example 2]
Example 1 was applied to a thin paper made by making the ratio of natural fibers in each weight ratio: Manila hemp: sisal hemp: average fiber diameter 3.6 μm length 3 mm PET: average fiber diameter 8.0 μm length 5 mm PET = 40: 20: 20: 20 0.9 g / m ^{2 was} applied and processed to obtain a thin paper with a basis weight of 9.7 g / m ² and a thickness of 30.2 μm. Using this thin paper and the film used in Example 1, a base paper was prepared in the same manner as in Example 1. The performance of this base paper was very good as in Example 1.
[0016]
[Example 3]
Examples of thin papers made by making the ratio of the fiber composition in each weight ratio, Manila hemp: sisal hemp: average fiber diameter 5.5 μm length 5 mm PET: average fiber diameter 6.0 μm length 3 mm PET = 40: 20: 20: 20 The same resin as 1 was applied at 0.9 g / m ² and processed to obtain a thin paper having a basis weight of 9.5 g / m ² and a thickness of 29.5 μm. Using this thin paper and the film used in Example 1, a base paper was prepared in the same manner as in Example 1. The performance of this base paper was also good.
[0017]
[Example 4]
Example: To thin paper made as a ratio of fiber composition in each weight ratio, Manila hemp: sisal hemp: average fiber diameter 5.5 μm length 5 mm PET: average fiber diameter 8.0 μm length 5 mm PET = 20: 40: 20: 20 The same resin as 1 was applied at 0.8 g / m ² and processed to obtain a thin paper having a basis weight of 9.3 g / m ² and a thickness of 28.5 μm. Using this thin paper and the film used in Example 1, a base paper was prepared in the same manner as in Example 1. The performance of this base paper was also good.
[0018]
[Example 5]
Example of a thin paper made by making the ratio of the fiber composition in each weight ratio, Manila hemp: sisal hemp: average fiber diameter 3.6 μm length 3 mm PET: average fiber diameter 6.0 μm length 3 mm PET = 10: 40: 10: 40 The same resin as 1 was applied at 0.9 g / m ² and processed to obtain a thin paper having a basis weight of 10.3 g / m ² and a thickness of 31.0 μm. Using this thin paper and the film used in Example 1, a base paper was prepared in the same manner as in Example 1. The performance of this base paper was also good.
[0019]
[Comparative Example 1]
A base paper was prepared in the same manner as in Example 1, using the same film as in Example 1 and a thin paper of 100% Manila hemp (basis weight = 10.5 g / m ² , thickness = 31.2 μm). The image quality of this base paper had very many white spots in the black solid part. This is because natural fibers alone have poor fiber dispersibility, and there are many bundles of fibers. Although this thin paper was not resin-processed, there was no problem in printing durability because it was only natural fibers.
[0020]
[Comparative Example 2]
The same resin as in Example 1 was applied to 0.9 g / m ² on the thin paper made with the ratio of the fiber composition at each weight ratio, Manila hemp: sisal hemp: average fiber diameter 6.0 μm, length 3 mm PET = 40: 20: 40 Then, resin processing was performed to obtain a thin paper having a basis weight of 10.8 g / m ² and a thickness of 31.2 μm. Using this thin paper and the film used in Example 1, a base paper was prepared in the same manner as in Example 1. Compared with the base paper of Example 1, this base paper showed unevenness in density at the black solid portion and was inferior in uniformity.
[0021]
[Comparative Example 3]
Examples of thin papers made by making the ratio of the fiber composition in each weight ratio, Manila hemp: sisal hemp: average fiber diameter 6.0 μm length 3 mm PET: average fiber diameter 8.0 μm length 5 mm PET = 40: 20: 20: 20 The same resin as 1 was applied at 0.9 g / m ² and processed to obtain a thin paper having a basis weight of 10.5 g / m ² and a thickness of 31.0 μm. Using this thin paper and the film used in Example 1, a base paper was prepared in the same manner as in Example 1. Compared with the base paper of Example 1, this base paper also showed unevenness in density at the black solid portion and was inferior in uniformity.
[0022]
[Comparative Example 4]
It was carried out on a thin paper that was made with a ratio of fiber composition in each weight ratio, Manila hemp: sisal hemp: average fiber diameter 6.0 μm length 3 mm PET: average fiber diameter 7.0 μm length 3 mm vinylon = 40: 20: 20: 20 The same resin as in Example 1 was applied at 0.9 g / m ² and processed to obtain a thin paper having a basis weight of 10.8 g / m ² and a thickness of 31.3 μm. Using this thin paper and the film used in Example 1, a base paper was prepared in the same manner as in Example 1. Compared with the base paper of Example 1, this base paper also showed unevenness in density at the black solid portion and was inferior in uniformity.
[0023]
[Comparative Example 5]
0.8 g / m ^{2 of the} same resin as in Example 1 was applied to a thin paper made with a fiber composition ratio of each weight ratio and Manila hemp: sisal hemp: average fiber diameter 3.6 μm length 3 mm PET = 40: 20: 40 The resin was processed to obtain a thin paper having a basis weight of 9.5 g / m ² and a thickness of 30.3 μm. Using this thin paper and the film used in Example 1, a base paper was prepared in the same manner as in Example 1. This base paper was inferior in strength to the base paper of Example 1 and had a printing durability of 3000 sheets.
[0024]
[Table 1]

[0025]
[Table 2]

[0026]
[Table 3]

[0027]
【The invention's effect】
The thin paper of the present invention has a good fiber dispersibility, the composition ratio of PET fibers having an average fiber diameter of 3 μm to 5.9 μm and PET fibers having an average fiber diameter of 6 μm to 9 μm is 2: 8 to 7: 3 , and Since it is a mixed thin paper made of natural fiber with 20 to 80% by weight of PET fiber, the fiber diameter distribution is stable and the fiber dispersibility is more uniform. Therefore, a printed matter obtained by stencil printing of a base paper using this thin paper as a support has very high image quality. Furthermore, since the resin surface is applied to the fiber surface and fiber entangled portion of the support, the elongation of the base paper during high-speed printing of a large number of sheets can be suppressed, and the printing durability is excellent.

Claims (1)

天然繊維にポリエステル繊維を混抄し、ウレタン樹脂またはエポキシ樹脂加工を施した薄葉紙において、該ポリエステル繊維が平均繊維径３μｍ〜５．９μｍのポリエステル繊維と平均繊維径６μｍ〜９μｍのポリエステル繊維の２種類から成り、その重量比が２：８〜７：３であり、該ポリエステル繊維は薄葉紙中に２０〜８０重量％含有されていることを特徴とする高画像性感熱孔版印刷原紙用薄葉紙。In a thin paper in which natural fibers are mixed with polyester fibers and processed with urethane resin or epoxy resin, the polyester fibers are divided into two types: polyester fibers having an average fiber diameter of 3 μm to 5.9 μm and polyester fibers having an average fiber diameter of 6 μm to 9 μm. And a weight ratio of 2: 8 to 7: 3 , and the polyester fiber is contained in the thin paper in an amount of 20 to 80% by weight.