JP3898974B2

JP3898974B2 - Electrophotographic transfer paper

Info

Publication number: JP3898974B2
Application number: JP2002118037A
Authority: JP
Inventors: 司松田; 邦夫桜井; 克明大西; 建和林
Original assignee: Fuji Xerox Co Ltd; Oji Holdings Corp; Oji Paper Co Ltd; Fujifilm Business Innovation Corp
Current assignee: New Oji Paper Co Ltd; Oji Holdings Corp; Fujifilm Business Innovation Corp
Priority date: 2002-04-19
Filing date: 2002-04-19
Publication date: 2007-03-28
Anticipated expiration: 2022-03-28
Also published as: JP2003005421A

Description

【０００１】
【発明の属する技術分野】
本発明は、間接乾式電子写真方式のフルカラー、若しくは、モノクローム複写機、プリンター等に用いられて、高画質な画像が得られ、かつ、カールの小さい転写紙に関する。
【０００２】
【従来の技術】
近年、電子写真方式の複写機、プリンターのカラー化、デジタル化等に伴い、電子写真方式の複写機やプリンター等の高画質化が検討されてきている。特に、電子写真方式のフルカラー複写機やプリンターにおいては、高画質画像を得るために、画像の入出力のデジタル化が進み、画像入力方法及び入力した画像の処理方法や、現像法、転写法、定着法等が大きく改善されている。また、現像剤や感光体の画像形成材料についても、デジタル高精細、高発色カラー記録に対応して改善されている。
【０００３】
しかしながら、電子写真方式のモノクローム複写機やプリンターに使用されている従来の電子写真用紙を、上記の改善された電子写真方式のフルカラー複写機やプリンターに使用すると、写真画像等に多く存在する中間調領域での粒状性（画像のざらつき感）が悪く、高画像密度領域では濃度のむらが目立ち、また、彩度が低くカラー発色性に劣るという問題があった。また、フルカラー複写、プリントの場合には、写真画像等の画像面積率の大きな画像が紙上に形成されることが多く、画像面積率の小さな画像と比較して、熱加圧定着後に比べものにならないほど大きなカールが生じるという問題があった。このような定着工程後の大きなカールは、ドキュメントとしての取扱性が悪いばかりでなく、排紙トレイやソーターへの収容性不良が生じ、この収容性不良に起因する種々のトラブルの原因になっていた。
【０００４】
ところで、特開昭62-198,876号公報や特開昭62-198,877号公報には、特別な塗工紙を使用することにより画像欠陥を改善する提案がされている。しかしながら、これらの提案においては、中間調領域での粒状性の改善や、発色性の向上についての改善手段の提示はなされておらず、また、塗工紙であるために鉛筆での筆記性に劣り、コストも高く、しかも、上質紙とは異なる風合があるという欠点があった。
【０００５】
また、特開平1-292,354号公報には、記録後にカールを低減する方法が開示されているが、上記と同様に塗工紙であるために、風合、鉛筆筆記性、コスト等の点で問題があった。更に、特開平2-217,862号公報、特開平3-243,953号公報、特開平3-236,062号公報及び特開平3-180,599号公報には、電子写真用上質紙のカールや寸法安定性の改善に関する方法が開示されているが、何れもフルカラー高画像面積記録の定着後カールに対しては問題があり、その改善手段の提示はなされておらず、また、フルカラー画像の粒状性、濃度むら、発色性等の画質改善に対する改善手段の提示もされていない。
【０００６】
【発明が解決しようとする課題】
本発明は、このような従来の電子写真用転写紙が有している問題を克服したものであり、間接乾式電子写真方式のデジタルフルカラー複写機やプリンターで記録された場合においても、中間調領域の粒状性、高画像密度領域の濃度むら、発色性が何れも良好で、なおかつ、トナーの定着性を損なうことがなく、高画像面積の記録を行う場合においても、定着後カールが小さい電子写真用上質転写紙を提供することを目的とするものである。
【０００７】
【課題を解決するための手段】
本発明は、JIS-P-8124による坪量が７５〜９５g/m²でJIS-P-8119によるベック平滑度が表裏共に６５〜１２０秒であり、かつ、JIS-P-8118による密度が０．８０g/cm³以上である上質紙において、温度２０℃及び湿度６５%RHから温度２０℃及び湿度２５%RHに変化したときのＣＤ（抄紙機の進行方向に対して直角方向）の伸縮率が０．４５%以下であり、JIS-P-8118で前処理された用紙のＣＤの引張弾性率Ｅ（kgf/mm²）と紙の厚さｔ（mm）とがＥｔ³≧０．２６（式１）の関係を満たすことを特徴とするものである。更に好ましい態様としては、JIS-P-8123によるハンター白色度が８２%以上であり、超音波伝播法によるＭＤ（抄紙機の進行方向）とＣＤとの間の繊維配向比が１．１０〜１．３０である電子写真用転写紙である。
【０００８】
本発明における「紙の伸縮率」とは、温度２０℃、“湿度６５%RH→２５%RH→６５%RH→９０%RH”で３サイクル吸脱湿処理を繰り返し、最後に６５%RH→２５%RHと変化させた時の寸法変化率を意味する。
【０００９】
また、本発明において、超音波伝播法によるＭＤとＣＤとの繊維配向比は次式で示される値を意味する。
超音波伝播法による繊維配向比＝ＭＤの超音波伝播速度／ＣＤの超音波伝播速度また、本発明における上記超音波伝播法による繊維配向比は、図１に示す測定方法によっても求めることができる。すなわち、厚さ１０mmの気泡入りゴム板１上に試料２を載置し、１５０mmの間隔をおいて送波振動子３と受波振動子４とを接触させ、送波部５から超音波パルスの縦波を送り出し、これを受波部６で受け、この縦波が送波振動子３を通過して試料２を通り受波振動子４を通過するまでの時間を測定し、これを伝播速度に変換する。試料について、それぞれＭＤ及びＣＤ両方向の伝播速度を測定し、その伝播速度比を求める。なお、図中、符号７は演算素子であり、符号８は表示素子である。
【００１０】
本発明においては、紙表面をベック平滑度で表裏共に６５〜１２０秒に平滑化し、更に、密度を０．８０g/cm³以上に高密度化するものであり、これによって、熱加圧定着時に溶融したトナーが紙表面で繊維に沿って流れ出したり、紙内部空隙に浸透する現象を抑制することができる。この時、ベック平滑度が１２０秒を越える処理を施しても、粒状性等の画質がそれ以上改善されないばかりか、塗工紙のような風合が生じて好ましくない。
【００１１】
また、本発明で使用する紙はその秤量が７５〜９５g/m²である。７５g/m²を下回る坪量の紙に対して、ベック平滑度が６５秒以上で密度が０．８０g/cm³以上となる処理を施すと、紙厚が薄くなり、また、紙層内の空気層が少なくなるために、光の屈折率が低下し画像の裏写りを生じたり、紙の腰が弱くなるために走行不良を生じたり、トレイやソーターへの収容性不良を生ずる。また、９５g/m²を越える坪量では、紙の熱容量が大きくなるために、定着時にトナーを十分溶融することができなくなり、定着性の不良やトナー発色の低下を引き起こすことがある。
【００１２】
電子写真方式のフルカラー複写機やプリンターでは、一般に、黒、イエロー、マゼンタ及びシアンからなる各色のトナーを紙上に転写し、定着工程で溶融し、その後固化したトナーの減法混色により発色させている。このため、トナーについては、溶融定着時に透明性の高いものが使われ、紙上のカラー画像の発色性はその紙の色の影響を受けやすい。そこで、色の濁りが少なく、彩度の高い高発色画像を得るためには、この紙の色についてのハンター白色度が８２%以上であることが好ましく、これによってフルカラー発色の特に優れた記録を得ることができる。
【００１３】
ところで、フルカラー画質を向上させるために、坪量が７５〜９５g/m²の電子写真用転写紙をベック平滑度で６５〜１２０秒とし、密度を０．８０g/cm³以上と高密度処理すると、定着後のカールが極端に大きくなるという現象が生じる。そこで、本発明者らがこのカール発生のメカニズムについて検討した結果、低画像密度時の定着後のカールは、熱加圧定着時の紙の脱湿収縮によるカールが支配的であり、また、高画像密度時の定着後カールは、トナー層と紙層とのバイメタルの様な構造により生じており、吸脱湿による伸縮の小さいトナー層に対して紙層の吸脱湿による伸縮が大きい時に生じる場合と、定着時に溶融したトナー層が室温に冷却固化する際に収縮し、紙層に対して曲げ応力を与え、カールを生じる場合とがあることを知見した。そして、前者に対しては、ＣＤの２０℃、６５%RHから２０℃、２５%RHへの伸縮率を０．４５%以下とすることで解決でき、また、後者に対しては、ＣＤの弾性率Ｅ（kgf/mm²）と紙の厚さｔ（mm）で示される紙の曲げ剛度Ｅｔ³を０．２６以上、好ましくは０．２８以上とすることによって解決できることを見出した。従って、本発明においては、ＣＤの伸縮率を０．４５%以下とし、また、紙の曲げ剛度Ｅｔ³を０．２６以上とすることが必要である。
【００１４】
また、坪量７５〜９５g/m²、ベック平滑度で６５〜１２０秒、密度を０．８０g/cm³以上の上質紙を使用し、上記ＣＤの伸縮率とＥｔ³とを満たすためには、好ましくは、ＣＤの繊維の配向を増加させ、超音波伝播法によるＭＤとＣＤの繊維配向比を１．１０〜１．３０にするのがよい。この超音波伝播法によるＭＤとＣＤの繊維配向比が１．１０を下回ると、ねじれカールが大きくなり好ましくない。
【００１５】
以下、本発明で要求される条件を満足する電子写真用転写紙について詳細に説明する。本発明の電子写真用転写紙に使用するパルプは、ＬＢＫＰ（広葉樹晒クラフトパルプ）、ＮＢＫＰ（針葉樹晒クラフトパルプ）、ＬＢＳＰ（広葉樹晒亜硫酸パルプ）、ＮＢＳＰ（針葉樹晒亜硫酸パルプ）等、従来から知られているケミカルパルプの何れも使用できるが、ＣＤの伸縮率を小さくし、かつ、Ｅｔ³を大きくする観点から、ＬＢＫＰを全パルプ中８０%以上配合することが好ましい。また、ＬＢＫＰ等の乾燥パルプを全パルプ中３０%以上配合することにより、繊維間結合面積を減少させることが可能であり、ＣＤの伸縮やＥｔ³の観点から、更に望ましい。更に、このようなケミカルパルプには、綿パルプ等の非木材パルプ、古紙パルプ、ＧＰ（グランドパルプ）、ＴＭＰ（サーモメカニカルパルプ）等の高収率パルプをハンター白色度が８２%を下回らない範囲で混合してもよい。このハンター白色度を８２%以上にするためには、前記パルプを選択して使用してもよいが、パルプの漂白工程を強化したパルプを利用したり、パルプスラリー中へ蛍光染料を混合してもよい。また、抄紙の前にパルプスラリーの濾水度調整のため、調整工程で叩解度の調整が行われる。叩解度は、高密度に処理した紙においても、繊維間結合面積を低く抑え、ＣＤ伸縮量を小さくするため、４００mlC.S.F.以上、好ましくは、４５０mlC.S.F.以上となるように調整するのがよい。
【００１６】
本発明の電子写真用転写紙には、不透明度、白さ、表面平滑性等の調整のため、填料を使用する。使用できる填料としては、重質炭酸カルシウム、軽質炭酸カルシウム、チョーク等の炭酸カルシウム、カオリン、焼成クレー、パイオロフィライト、セリサイト、タルク等のケイ酸類や、二酸化チタン等の無機填料、及び、尿素樹脂、スチレン等の有機顔料があるが、これらに限られるものではない。電子写真方式における画質維持性及び白色度向上の観点から炭酸カルシウムの配合が好ましい。また、ベック平滑度が６５秒以上の高平滑処理を助けるためや、紙層内部の繊維間結合をある程度切断しＣＤ伸縮率を低下させるために、填料の配合量については、５〜１５重量%、好ましくは７〜１３重量%とする。填料の配合量が５重量%を下回ると、カレンダー処理等による平滑化処理がかかり難くなったり、填料による光の屈折が低下し、不透明度が低下したり、ＣＤ伸縮率が大きくなりすぎたり、更には、紙の腰が強くなりすぎて走行性が低下するという弊害が生じる。また、この填料の配合量が１５重量%を上回ると、紙粉の発生が多くなり、複写機やプリンター内を汚染したり、紙の摩擦係数が上がりすぎるために走行性が低下する。
【００１７】
本発明において使用する内添サイズ剤としては、ロジン系サイズ剤、合成サイズ剤、石油樹脂系サイズ剤、中性サイズ剤等のサイズ剤が使用でき、硫酸バンド、カチオン化澱粉等、適当なサイズ剤と繊維との定着剤を組み合せて使用する。望ましくは、電子写真方式の複写機、プリンター等における走行性及びコピー後の用紙保存性の観点から、中性サイズ剤、特にアルケニル無水コハク酸系サイズ剤を使用するのがよい。このほかに、紙力増強剤、染料、ｐＨ調整剤等を添加してもかまわない。
【００１８】
本発明の電子写真用転写紙の製造条件のコントロールとしては、前述した紙料を用いて、坪量が７５〜９５g/m²となるように抄紙する。前述したように坪量が７５g/m²を下回ると、裏写りを生じたり、走行性、収容性不良を生じ、９５g/m²を上回ると、定着不良や、トナーの発色性不良を生じる。また、ＣＤ伸縮率を０．４５%以下にし、Ｅｔ³を０．２６以上にするためには、繊維配向比を制御することが好ましく、超音波伝播法によるＭＤとＣＤの繊維配向比を１．１０〜１．３０とするために、JET／WIRE比（原料噴出速度／抄紙機ワイヤー速度比）を調整する方法が有効である。これ以外にも、プレス時の紙のマシン方向の張力及びドライヤー乾燥時のマシン方向の張力を小さくすることにより制御することもできる。更に、ベック平滑度を６５〜１２０秒とし、密度を０．８０g/cm³以上とするために、プレスを強化したり、マシンカレンダーを強化するのがよい。また、スーパーカレンダーによる処理も可能であるが、これらに限られるものではない。
【００１９】
また本発明では、電子写真方式における画像の乱れを防止し、適当なコピー画像濃度を維持するため、塩化ナトリウム、塩化カリウム、スチレン−マレイン酸コポリマー、第４級アンモニウム塩等の導電剤を抄紙機のサイズプレスで表面塗布して、転写紙の表面電気抵抗（JIS-K-6911）を１０９〜１０１１Ωにする。また、開封直後の製品水分は波打ちや、コピー後カールの発生を抑えるために適正水分の４．０〜６．５%になるよう抄紙機のドライヤー、キャレンダー工程や、断裁工程等で調整する。また、保管時に吸脱湿が発生しないように、ポリエチレンラミネート紙等の防湿包装紙や、ポリプロピレンフィルム等で包装する。
【００２０】
【実施例】
以下、実施例及び比較例に基づいて本発明をより具体的に説明するが、本発明はこれにより限定されるものではない。
【００２１】
実施例１
酸素晒等で多段漂白し高白色化したＬＢＫＰをろ水度４７０mlC.S.F.まで叩解したパルプを原料とし、軽質炭酸カルシウム（TP121：奥多摩工業社製）を１０重量%となるよう添加し、内添サイズ剤としてアルケニル無水コハク酸（ファイブラン81：王子ナショナル社製）を対パルプ当り０．０８重量%配合し、カチオン化澱粉（Cate 15：王子ナショナル社製）を対パルプ当り０．５重量%配合した。この紙料に抄紙後のハンター白色度が８４%となるように少量の蛍光染料を配合し、坪量７５g/m²で、かつ、超音波伝播法による繊維配向比が１．２０前後となるように、JET／WIRE比とWIRE速度とを調整して長網多筒式抄紙機で抄紙し、抄紙後水分が５重量%となるようにドライヤー条件を調整した。また、サイズプレス工程で酸化でんぷんを０．９g/m²、ＮａＣｌを０．１g/m²塗工した。更に、プレス工程、及び、マシンカレンダーを強化して平滑性及び密度を高くした。この電子写真用転写紙の各特性は、坪量７５g/m²、密度０．８２g/cm³、ＦＳ（フェルトサイド）の平滑度８５秒、ＷＳ（ワイヤーサイド）の平滑度７２秒、超音波伝播法による繊維配向比１．１８、ＣＤ伸縮率０．３２、Ｅｔ³０．２６、ハンター白色度８４%であった。この電子写真用紙をデジタルフルカラー複写機Ａ color630（富士ゼロックス社製）を用いて、Black、Yellow、Magenta、Cyan、Red、Green、Blue、及び、Yellow、Magenta、Cyanの混色Blackの、各画像面積率１０、２０、３０、４０、５０、６０、７０、８０、９０、１００%の２cm×２cmのパッチを平滑度の低い用紙面に転写、定着し、中間調領域の粒状性としては、各色の画像面積率２０、３０、４０%のパッチを目視で評価した。高画像密度領域の濃度むらは、各色の画像面積率７０、８０、９０、１００%のパッチを目視で評価した。また、発色性の良否を各色の画像面積率１０〜１００%のパッチを目視で評価した。また、この画像の裏写りの評価を目視で行った。トナーの定着度は、Yellow、Magenta、Cyanの混色Blackの画像面積率１００%のパッチを中央から画像が内側になるよう折り曲げ、その折り曲げ部に２ｋｇのロールを転がした後、画像面を開き、軽く布でふきとった時の折り曲げ部のトナーの剥離程度を目視により評価した。定着後のカールの評価は、Magentaトナー、Cyanトナーの２色からなるBlueのベタ画像を用紙全面に記録し、定着５分後のカールの大きさを評価した。この時の実験環境は、２２℃ ５５%RH．とした。その他、得られた電子写真用紙の普通紙感等の風合は、男性１５名、女性１５名のパネラーにより官能評価して問題点を抽出した。以上の結果、特に粒状性、濃度むら、トナー定着性に優れた転写紙が得られた。なお、これらデジタルフルカラー複写機での画質、トナー定着性、カールの評価尺度を次に示す。
〔中間調領域粒状性〕
○：問題とならない、□：わずかにざらつき感があるが許容できる、△：ざらつき感が少しある、×：ざらつき感がめだつ。
〔高画像密度領域の濃度むら〕
○：問題とならない、□：わずかに濃度むらがあるが許容できる、△：濃度むらが少しある、×：濃度むらがめだつ。
〔発色性〕
○：濁りのない鮮やかな発色、□：わずかに濁りがあるが許容できる、△：濁りが少しある、×：暗く濁りがある。
〔トナーの定着度〕
○：トナーがほとんど剥離しない、□：わずかに剥離するが許容できる、△：かなり剥離する、×：剥離領域が大きい。
〔定着後カール〕
○：ほとんどカールしない、□：少しカールするが許容できる、△：かなりカールする、×：カールが大きく場合によっては、円筒となる。
【００２２】
実施例２、３、４
実施例１と同様の紙料を用いて、マシンカレンダーを実施例１より若干弱くかけて、密度を０．８０g/cm³とし、その他の抄紙条件は、実施例１と同様にして実施例２の転写紙を得た。実施例１と同様の紙料を用いて、実施例２の抄紙条件のうち、JET／WIRE比を変更し、超音波伝播法による繊維配向比が１．１６になるよう調整し、実施例３の転写紙を得た。また、同様に実施例２に対し、超音波伝播法による繊維配向比が１．３０となるよう調整し、実施例４の転写紙を得た。実施例２、３、４の転写紙の坪量、密度、平滑度、超音波伝播法による繊維配向比、ＣＤ伸縮率、Ｅｔ³、ハンター白色度は、所定の値となった。これらの転写紙を実施例１と同様の方法により、画質、トナー定着性、定着後カール、風合等を評価した。実施例２、３は、特に定着後カールにすぐれた転写紙が得られた。実施例４では、実用上満足できる転写紙が得られた。
【００２３】
実施例５、６、７、８
実施例１と同様の紙料を用いて、坪量を８１g/m²にした以外は、実施例１と同様の抄紙条件で、実施例５の転写紙を得た。また、実施例５に使用したパルプ原料を変更し、乾燥パルプを３０%含むＬＢＫＰを使用した他は、実施例５と同様の紙料、同様の抄紙条件で実施例６の転写紙を得た。実施例７の転写紙は、実施例５と同様の紙料を用い、マシンカレンダーを実施例５より強くかけて、密度を０．８５g/cm³とし、その他の抄紙条件は、実施例５と同様にして得た。この時の平滑度は、ＦＳで１２０秒であった。実施例８の転写紙は、実施例５と同様の紙料を用いて、超音波伝播法による繊維配向比が１．３０となるよう調整したほかは、実施例５と同様の抄紙条件により得た。実施例５、６、７、８の転写紙の坪量、密度、平滑度、超音波伝播法による繊維配向比、ＣＤ伸縮率、Ｅｔ³、ハンター白色度は、所定の値となった。これらの転写紙を実施例１と同様の方法により、画質、トナー定着性、定着後カール、風合等を評価した。実施例５は、画質、トナー定着性、定着後カール全てに優れた転写紙が得られた。実施例６は、実施例５よりもＣＤ伸縮率が更に小さく定着後カールにより一層すぐれる転写紙が得られた。実施例７は、高平滑なため少し普通紙らしくない風合を与えるが、許容範囲内であり、画質、トナー定着性、定着後カールに優れた転写紙が得られた。実施例８は、特に画質、トナー定着性に優れた転写紙が得られた。
【００２４】
実施例９、１０、１１
実施例１と同様の紙料を用いて、坪量を９０g/m²にした以外は、実施例１と同様の抄紙条件で、実施例９の転写紙を得た。また、実施例１と同様の紙料を用いて、坪量を９５g/m²にした以外は、実施例１と同様の抄紙条件で、実施例１０の転写紙を得た。実施例１１の転写紙は、実施例１０と同様の紙料を用いて、超音波伝播法による繊維配向比が１．３０となるよう調整したほかは、実施例１０と同様の抄紙条件により得た。実施例９、１０、１１の転写紙の坪量、密度、平滑度、超音波伝播法による繊維配向比、ＣＤ伸縮率、Ｅｔ³、ハンター白色度は、所定の値となった。これらの転写紙を実施例１と同様の方法により、画質、トナー定着性、定着後カール、風合等を評価した。実施例９は、画質、トナー定着性、定着後カール全てに優れた転写紙が得られた。実施例１０は、特に画質、定着後カールに優れた転写紙が得られた。実施例１１は、特に中間調領域の粒状性、高画像密度領域の濃度むらに優れた転写紙が得られた。
【００２５】
実施例１２
実施例５の紙料から、蛍光染料を除去し、実施例５と同様の抄紙条件で、実施例１２の転写紙を得た。ハンター白色度は、８２%であった。本転写紙の坪量、密度、平滑度、超音波伝播法による繊維配向比、ＣＤ伸縮率、Ｅｔ³は、所定の値となった。本転写紙を実施例１と同様の方法により、画質、トナー定着性、定着後カール、風合等を評価した。実施例１２は、わずかに濁った発色を示すが許容レベルであり、その他画質、トナー定着性、定着後カール共に優れた転写紙が得られた。
【００２６】
比較例１、２
坪量を７０g/m²とした以外は、実施例１と同様の紙料、抄紙方法により比較例１の転写紙を得た。同様に坪量を１００g/m²とした以外は、実施例１と同様の紙料、抄紙方法により比較例２の転写紙を得た。これらの転写紙の密度、平滑度、超音波伝播法による繊維配向比、ＣＤ伸縮率、Ｅｔ³、ハンター白色度は、所定の値となった。これらの転写紙の坪量の影響を確認するために実施例１と同様の方法により、画質、トナー定着性、定着後カール、風合等を評価した。比較例１は、カールが非常に大きくなり、比較例２の転写紙は、トナーの定着が悪く発色も濁ったものとなった。何れの転写紙も実用に供さないものであった。
【００２７】
比較例３、４、５
密度を０．７８g/cm³とした以外は、実施例５と同様の紙料、抄紙方法により比較例３の転写紙を得た。この転写紙の平滑度は、平滑度の低い面で、５９秒であった。比較例３に対し密度を０．７６g/cm³と更に低くした以外は同様の方法で比較例４を得た。密度を０．９０g/cm³とした以外は、実施例５と同様の紙料、抄紙方法により比較例５の転写紙を得た。この転写紙の平滑度は、平滑度の高い面で、２０７秒であった。これらの転写紙の坪量、密度、平滑度、超音波伝播法による繊維配向比、ＣＤ伸縮率、Ｅｔ³、ハンター白色度は、所定の値となった。これらの転写紙の平滑度、密度の影響を確認するために実施例１と同様の方法により、画質、トナー定着性、定着後カール、風合等を評価した。比較例３は中間調領域のざらつきが悪く、高画像密度領域の濃度むらも発生した。比較例４は更に中間調領域のざらつきが悪く、高画像密度領域の濃度むらも更に顕著となった。比較例５の転写紙は高平滑となり過ぎたために普通紙の風合を失い、鉛筆での筆記性も十分ではなく、Ｅｔ³も小さい値となったため、大きなカールを生じた。何れの転写紙も実用に供さないものであった。
【００２８】
比較例６、７、８
実施例３と同様の紙料を用いて、超音波伝播法による繊維配向比が１．３５となるよう調整したほかは、実施例３と同様の抄紙条件により比較例６の転写紙を得た。この転写紙のＣＤ伸縮率は、０．４６%であった。また、実施例５と同様の紙料を用いて、超音波伝播法による繊維配向比が１．３５となるよう調整したほかは、実施例５と同様の抄紙条件により比較例７の転写紙を得た。この転写紙のＣＤ伸縮率は、０．４９%であった。更に、実施例１０と同様の紙料を用いて、超音波伝播法による繊維配向比が１．４５となるよう調整したほかは、実施例１０と同様の抄紙条件により比較例８の転写紙を得た。この転写紙のＣＤ伸縮率は、０．５５%であった。これらの転写紙の坪量、密度、平滑度、超音波伝播法による繊維配向比、ＣＤ伸縮率、Ｅｔ³、ハンター白色度は、所定の値となった。これらの転写紙の主にＣＤ伸縮率の影響を確認するために実施例１と同様の方法により、画質、トナー定着性、定着後カール、風合等を評価した。比較例６はＣＤ伸縮率が大きくＥｔ³も小さい値となったため、大きなカールを発生した。比較例７の転写紙はＣＤ伸縮率が比較例５よりも大きいため、非常に大きなカールを生じた。比較例８の転写紙はＣＤ伸縮率が大きいため、非常に大きなカールを生じた。何れの転写紙も実用に供さないものであった。
【００２９】
比較例９、１０
実施例７と同様の紙料を用いて、超音波伝播法による繊維配向比が１．２８となるよう調整したほかは、実施例７と同様の抄紙条件により比較例９の転写紙を得た。この転写紙のＥｔ³は、０．２４であった。また、実施例１と同様の紙料を用いて、超音波伝播法による繊維配向比が１．３０となるよう調整したほかは、実施例１と同様の抄紙条件により比較例１０の転写紙を得た。この転写紙のＥｔ³は、０．２２であった。これらの転写紙の坪量、密度、平滑度、超音波伝播法による繊維配向比、ＣＤ伸縮率、Ｅｔ³、ハンター白色度は、所定の値となった。これらの転写紙の主にＥｔ³の影響を確認するために実施例１と同様の方法により、画質、トナー定着性、定着後カール、風合等を評価した。比較例９は、Ｅｔ³も小さい値となったため、大きなカールを発生した。比較例１０の転写紙は、Ｅｔ³が比較例９よりも更に小さいため、非常に大きなカールを生じた。何れの転写紙も実用に供さないものであった。
【００３０】
比較例１１
漂白程度を落としたＬＢＫＰを使用した以外は、実施例５と同様の紙料、抄紙方法により比較例１１の転写紙を得た。本転写紙の密度、平滑度、超音波伝播法による繊維配向比、ＣＤ伸縮率、Ｅｔ³、ハンター白色度は、所定の値となった。本転写紙のハンター白色度の影響を確認するために実施例１と同様の方法により、画質、トナー定着性、定着後カール、風合等を評価した。比較例１１は、発色が濁ったものとなり実用に供さないものであった。
【００３１】
比較例１２
坪量が７８ g/m²の市販の電子写真用転写紙を実施例１と同様の方法により、画質、トナー定着性、定着後カール、風合等を評価した。本転写紙の坪量、密度、平滑度、超音波伝播法による繊維配向比、ＣＤ伸縮率、Ｅｔ³、ハンター白色度は、所定の値であった。比較例１２は、画質、定着後カール共に悪く、実用に供さないものであった。
【００３２】
【発明の効果】
本発明は、上記のような構成、特徴を持ってなるため、間接電子写真方式のフルカラー及びモノクローム記録における中間調領域の粒状性に優れ、高画像密度領域の濃度むらの発生もなく、更に、フルカラー画像の発色性にも優れ、トナーの定着性も良好な画像を提供でき、フルカラー高画像面積記録の定着後カールも小さい電子写真用転写紙を提供できるものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transfer paper that is used in an indirect dry electrophotographic full color or monochrome copying machine, a printer, and the like to obtain a high-quality image and has small curl.
[0002]
[Prior art]
In recent years, along with the colorization and digitization of electrophotographic copying machines and printers, improvement in image quality of electrophotographic copying machines and printers has been studied. Especially in electrophotographic full-color copiers and printers, in order to obtain high-quality images, digitization of image input / output has progressed, and image input methods and input image processing methods, development methods, transfer methods, The fixing method has been greatly improved. Further, image forming materials for developers and photoreceptors have also been improved in response to digital high definition and high color development color recording.
[0003]
However, when conventional electrophotographic paper used in electrophotographic monochrome copiers and printers is used in the above-described improved electrophotographic full-color copiers and printers, halftones that are often present in photographic images, etc. There is a problem that the graininess (roughness of the image) in the area is poor, the density unevenness is conspicuous in the high image density area, and the color saturation is low and the color developability is inferior. In the case of full-color copying and printing, an image with a large image area ratio such as a photographic image is often formed on paper, which is not comparable after heat and pressure fixing as compared with an image with a small image area ratio. There was a problem that a large curl was generated. Such a large curl after the fixing process causes not only poor handling as a document but also a poor storage capacity in a paper discharge tray or a sorter, causing various troubles due to the poor storage capacity. It was.
[0004]
By the way, Japanese Patent Laid-Open Nos. 62-198,876 and 62-198,877 propose to improve image defects by using special coated paper. However, in these proposals, no improvement means for improving the graininess in the halftone region and the improvement of the color developability has been presented, and since it is a coated paper, the writing property with a pencil is improved. Inferiority, high cost, and a different texture from fine paper.
[0005]
Japanese Patent Laid-Open No. 1-292,354 discloses a method for reducing curl after recording, but because it is a coated paper as described above, in terms of texture, pencil writing property, cost, etc. There was a problem. Further, JP-A-2-217,862, JP-A-3-243,953, JP-A-3-236,062 and JP-A-3-180,599 relate to the improvement of curl and dimensional stability of high quality electrophotographic paper. Although methods have been disclosed, there are problems with post-fix curling of full color high image area recording, no improvement means has been presented, and granularity, density unevenness, color development of full color images have not been presented. There is no suggestion for improving the image quality such as sex.
[0006]
[Problems to be solved by the invention]
The present invention overcomes the problems associated with such conventional electrophotographic transfer paper, and even when recorded by an indirect dry electrophotographic digital full-color copier or printer, An electrophotographic image having good graininess, density unevenness in a high image density region, color developability, and having a low post-fixing curl even when recording a high image area without impairing toner fixing properties. It is an object to provide a high-quality transfer paper for use.
[0007]
[Means for Solving the Problems]
In the present invention, the basis weight according to JIS-P-8124 is 75 to 95 g / m. ² The Beck smoothness according to JIS-P-8119 is 65 to 120 seconds on both sides, and the density according to JIS-P-8118 is 0.80 g / cm. ^Three In the above-mentioned high-quality paper, when the temperature is changed from 20 ° C. and humidity 65% RH to temperature 20 ° C. and humidity 25% RH, the expansion ratio of CD (perpendicular to the machine direction) is 0.45%. The following is the tensile modulus E (kgf / mm) of CD of paper pretreated with JIS-P-8118 ² ) And paper thickness t (mm) are Et ^Three It satisfies the relationship of ≧ 0.26 (Formula 1). As a more preferred embodiment, the Hunter whiteness according to JIS-P-8123 is 82% or more, and the fiber orientation ratio between MD (paper machine traveling direction) and CD by the ultrasonic wave propagation method is 1.10 to 1 .30 is an electrophotographic transfer paper.
[0008]
In the present invention, the “paper expansion / contraction ratio” means that the temperature is 20 ° C., “humidity 65% RH → 25% RH → 65% RH → 90% RH” is repeated three cycles of moisture absorption and desorption, and finally 65% RH → It means the dimensional change rate when changed to 25% RH.
[0009]
Moreover, in this invention, the fiber orientation ratio of MD and CD by an ultrasonic wave propagation method means the value shown by following Formula.
Fiber orientation ratio by ultrasonic propagation method = Ultrasonic propagation speed of MD / Ultrasonic propagation speed of CD Further, the fiber orientation ratio by the ultrasonic propagation method in the present invention can also be obtained by the measuring method shown in FIG. . That is, a sample 2 is placed on a foamed rubber plate 1 having a thickness of 10 mm, the transmitting transducer 3 and the receiving transducer 4 are brought into contact with each other at an interval of 150 mm, and an ultrasonic pulse is transmitted from the transmitting unit 5. The longitudinal wave is sent out and received by the receiving unit 6. The longitudinal wave passes through the transmitting vibrator 3, passes through the sample 2 and passes through the receiving vibrator 4, and propagates it. Convert to speed. The propagation velocity in both the MD and CD directions is measured for each sample, and the propagation velocity ratio is obtained. In the figure, reference numeral 7 is an arithmetic element, and reference numeral 8 is a display element.
[0010]
In the present invention, the surface of the paper is smoothed with Beck smoothness on both sides in 65 to 120 seconds, and the density is 0.80 g / cm. ^Three As a result, the density of the toner is increased. As a result, it is possible to suppress the phenomenon that the toner melted at the time of heat and pressure fixing flows out along the fiber on the paper surface or penetrates into the voids in the paper. At this time, even if the Beck smoothness exceeds 120 seconds, the image quality such as the graininess is not improved any more, and a texture like coated paper is generated.
[0011]
The paper used in the present invention has a weight of 75 to 95 g / m. ² It is. 75g / m ² The paper has a basis weight of less than 1, the Beck smoothness is 65 seconds or more and the density is 0.80 g / cm ^Three When the above processing is performed, the paper thickness is reduced, and the air layer in the paper layer is reduced, so that the refractive index of light is lowered to cause image show-through and the paper is weakened. In this case, a poor running occurs, and a poor storage capacity in a tray or a sorter occurs. 95g / m ² If the basis weight exceeds 1, the heat capacity of the paper increases, so that the toner cannot be sufficiently melted at the time of fixing, which may cause a poor fixing property and a decrease in toner coloring.
[0012]
In electrophotographic full-color copying machines and printers, generally, toner of each color consisting of black, yellow, magenta and cyan is transferred onto paper, melted in a fixing process, and then colored by subtractive color mixing of solidified toner. For this reason, toner having high transparency at the time of melting and fixing is used, and the color developability of the color image on the paper is easily influenced by the color of the paper. Therefore, in order to obtain a highly colored image with little color turbidity and high saturation, the hunter whiteness of this paper color is preferably 82% or more, and this enables particularly excellent recording of full color development. Obtainable.
[0013]
By the way, in order to improve full color image quality, the basis weight is 75 to 95 g / m. ² The electrophotographic transfer paper with a Beck smoothness of 65 to 120 seconds and a density of 0.80 g / cm ^Three When the high density processing is performed as described above, a phenomenon that the curl after fixing becomes extremely large occurs. Thus, as a result of the study of the mechanism of the curling by the present inventors, the curling after fixing at low image density is dominated by curling due to dehumidification and shrinkage of the paper at the time of heat and pressure fixing. Curling after fixing at the image density is caused by a bimetal-like structure of the toner layer and the paper layer, and occurs when the expansion and contraction due to moisture absorption / desorption of the paper layer is large compared to the toner layer whose expansion / contraction due to moisture absorption / desorption is small. In some cases, it was found that the toner layer melted at the time of fixing shrinks when cooled and solidified to room temperature, gives a bending stress to the paper layer, and may curl. For the former, it can be solved by reducing the expansion / contraction ratio of CD from 20 ° C. and 65% RH to 20 ° C. and 25% RH to 0.45% or less. Elastic modulus E (kgf / mm ² ) And paper thickness t (mm) ^Three It has been found that this can be solved by setting the ratio to 0.26 or more, preferably 0.28 or more. Therefore, in the present invention, the expansion / contraction ratio of the CD is set to 0.45% or less, and the bending stiffness Et of the paper is Et. ^Three Needs to be 0.26 or more.
[0014]
Also, basis weight 75-95g / m ² , Beck smoothness 65-120 seconds, density 0.80 g / cm ^Three Using the above-mentioned high-quality paper, the above-mentioned CD stretch rate and Et ^Three In order to satisfy the above, preferably, the fiber orientation of CD is increased, and the fiber orientation ratio of MD and CD by the ultrasonic wave propagation method is 1.10 to 1.30. If the fiber orientation ratio of MD and CD by this ultrasonic wave propagation method is less than 1.10, the twist curl becomes large, which is not preferable.
[0015]
Hereinafter, the electrophotographic transfer paper that satisfies the conditions required in the present invention will be described in detail. The pulp used for the electrophotographic transfer paper of the present invention is conventionally known, such as LBKP (hardwood bleached kraft pulp), NBKP (softwood bleached kraft pulp), LBSP (hardwood bleached sulfite pulp), NBSP (softwood bleached sulfite pulp). Any of the chemical pulps that are used can be used, but the shrinkage ratio of CD is reduced, and Et ^Three From the viewpoint of increasing the size, it is preferable to blend 80% or more of LBKP in the total pulp. Further, by blending 30% or more of dry pulp such as LBKP in the total pulp, it is possible to reduce the bonding area between fibers, and the expansion and contraction of CD and Et. ^Three From the viewpoint of, it is further desirable. Furthermore, for such chemical pulp, high-yield pulp such as non-wood pulp such as cotton pulp, waste paper pulp, GP (grand pulp), TMP (thermomechanical pulp) and the like, the hunter whiteness does not fall below 82%. May be mixed. In order to increase the Hunter whiteness to 82% or more, the above-mentioned pulp may be selected and used. However, it is possible to use a pulp with enhanced pulp bleaching process or to mix a fluorescent dye into the pulp slurry. Also good. In addition, in order to adjust the freeness of the pulp slurry before papermaking, the beating degree is adjusted in the adjusting step. The beating degree should be adjusted to 400 mlC.SF or more, preferably 450 mlC.SF or more in order to suppress the bonding area between fibers and reduce the amount of CD expansion and contraction, even in paper processed at high density. .
[0016]
In the electrophotographic transfer paper of the present invention, a filler is used for adjusting the opacity, whiteness, surface smoothness and the like. As fillers that can be used, heavy calcium carbonate, light calcium carbonate, calcium carbonate such as chalk, kaolin, calcined clay, silicic acid such as pyrophyllite, sericite, talc, inorganic fillers such as titanium dioxide, and There are organic pigments such as urea resin and styrene, but are not limited thereto. From the viewpoint of image quality maintenance and whiteness improvement in the electrophotographic system, calcium carbonate is preferred. Further, in order to help high smoothing processing with a Beck smoothness of 65 seconds or more, or to cut the interfiber bond in the paper layer to some extent and to reduce the CD expansion / contraction rate, the blending amount of the filler is 5 to 15% by weight Preferably, the content is 7 to 13% by weight. When the blending amount of the filler is less than 5% by weight, it becomes difficult to perform a smoothing process such as a calendar process, the refraction of light by the filler is lowered, the opacity is lowered, the CD expansion / contraction rate is too large, Furthermore, there is a problem that the paper becomes too stiff and the running performance is lowered. On the other hand, when the blending amount of the filler exceeds 15% by weight, the generation of paper dust is increased, the inside of the copying machine or printer is contaminated, and the running coefficient is lowered because the friction coefficient of the paper is excessively increased.
[0017]
As the internally added sizing agent used in the present invention, sizing agents such as rosin-based sizing agents, synthetic sizing agents, petroleum resin-based sizing agents, and neutral sizing agents can be used. A combination of a fixing agent of fiber and fiber is used. Desirably, a neutral sizing agent, particularly an alkenyl succinic anhydride-based sizing agent, may be used from the viewpoints of runnability in an electrophotographic copying machine, printer, and the like and storage stability after copying. In addition, a paper strength enhancer, a dye, a pH adjuster, etc. may be added.
[0018]
As a control for the production conditions of the electrophotographic transfer paper of the present invention, the basis weight is 75 to 95 g / m using the above-mentioned stock. ² Make paper so that As described above, the basis weight is 75 g / m. ² If it is less than 95g / m, show-through, runnability and poor storage will occur. ² Above this, fixing failure and toner color developability will occur. Also, the CD expansion / contraction rate is 0.45% or less, Et ^Three In order to make the fiber orientation ratio 0.26 or more, it is preferable to control the fiber orientation ratio, and in order to set the fiber orientation ratio of MD and CD by the ultrasonic wave propagation method to 1.10 to 1.30, the JET / WIRE ratio A method of adjusting (raw material ejection speed / paper machine wire speed ratio) is effective. In addition to this, it is also possible to control by reducing the tension in the machine direction of the paper during pressing and the tension in the machine direction during drying of the dryer. Furthermore, the Beck smoothness is 65 to 120 seconds, and the density is 0.80 g / cm. ^Three In order to achieve the above, it is better to strengthen the press or the machine calendar. Moreover, although processing by a super calendar is also possible, it is not restricted to these.
[0019]
Further, in the present invention, a conductive agent such as sodium chloride, potassium chloride, styrene-maleic acid copolymer, quaternary ammonium salt, or the like is used to prevent image disturbance in the electrophotographic system and maintain an appropriate copy image density. The surface electrical resistance (JIS-K-6911) of the transfer paper is set to 109 to 1011 Ω by surface coating with a size press. In addition, the product moisture immediately after opening is adjusted in the paper machine dryer, calendar process, cutting process, etc. so that the moisture content is 4.0 to 6.5% of the appropriate moisture in order to prevent the occurrence of curling after copying. . Moreover, it is packed with moisture-proof wrapping paper such as polyethylene laminated paper or polypropylene film so that moisture absorption and desorption does not occur during storage.
[0020]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited by this.
[0021]
Example 1
Using LBKP, which has been whitened by multistage bleaching by oxygen bleaching, etc., as a raw material, beaten to a freeness of 470 ml C.SF, and added light calcium carbonate (TP121: manufactured by Okutama Kogyo Co., Ltd.) to 10% by weight. As a sizing agent, alkenyl succinic anhydride (Fibran 81: manufactured by Oji National) was added at 0.08% by weight per pulp, and cationized starch (Cate 15: manufactured by Oji National) was added at 0.5% by weight per pulp. Blended. A small amount of fluorescent dye is added to this stock so that the Hunter whiteness after paper making is 84%, and the basis weight is 75 g / m. ² In addition, the JET / WIRE ratio and the WIRE speed were adjusted so that the fiber orientation ratio by the ultrasonic wave propagation method was around 1.20, and the paper was made with a long-mesh multi-cylinder paper machine. The dryer conditions were adjusted to be wt%. Also, 0.9g / m of oxidized starch in the size press process ² , NaCl 0.1g / m ² Coated. Furthermore, the smoothness and density were increased by strengthening the press process and machine calendar. Each characteristic of this electrophotographic transfer paper has a basis weight of 75 g / m. ² , Density 0.82g / cm ^Three , Smoothness of FS (felt side) 85 seconds, smoothness of WS (wire side) 72 seconds, fiber orientation ratio 1.18 by ultrasonic wave propagation method, CD expansion ratio 0.32, Et ^Three It was 0.26 and Hunter whiteness was 84%. Using this digital photographic paper A color630 (manufactured by Fuji Xerox), each image area of Black, Yellow, Magenta, Cyan, Red, Green, Blue, and Yellow, Magenta, Cyan mixed color Black A 2 cm × 2 cm patch with a rate of 10, 20, 30, 40, 50, 60, 70, 80, 90, 100% is transferred and fixed on a paper surface with low smoothness. The patches having an image area ratio of 20, 30, and 40% were visually evaluated. Density unevenness in the high image density region was visually evaluated for patches having an image area ratio of 70, 80, 90, and 100% for each color. In addition, patches having an image area ratio of 10 to 100% for each color were visually evaluated for the color development. In addition, the show-through of this image was evaluated visually. The fixing degree of the toner is such that the patch of Yellow, Magenta, and Cyan mixed black with an image area ratio of 100% is folded from the center so that the image is inward, a 2 kg roll is rolled on the folded part, and then the image surface is opened. The degree of toner peeling at the bent portion when lightly wiped with a cloth was visually evaluated. For evaluation of curling after fixing, a blue solid image composed of two colors of Magenta toner and Cyan toner was recorded on the entire surface of the paper, and the curl size after 5 minutes of fixing was evaluated. The experimental environment at this time was 22 ° C. and 55% RH. It was. In addition, the texture of the obtained electrophotographic paper such as plain paper was subjected to sensory evaluation by 15 panelists and 15 panelists to extract problems. As a result, a transfer paper excellent in graininess, density unevenness, and toner fixing property was obtained. The evaluation scales for image quality, toner fixability, and curl in these digital full-color copying machines are shown below.
[Grade of halftone area]
○: No problem, □: Slightly rough, but acceptable, Δ: Slightly rough, x: Rough.
[Uneven density in high image density area]
○: No problem, □: Slight density unevenness, but acceptable, Δ: Slight density unevenness, x: Concentration unevenness.
[Color development]
○: Vivid color without turbidity, □: Slightly turbid but acceptable, Δ: Slightly turbid, ×: Dark and turbid.
[Toner fixing degree]
○: toner hardly peels, □: slightly peeled but acceptable, Δ: considerably peeled, ×: peeled area is large.
[Curl after fixing]
◯: hardly curled, □: slightly curled but acceptable, Δ: considerably curled, x: large curl in some cases, a cylinder.
[0022]
Examples 2, 3, 4
Using the same material as in Example 1, apply a machine calendar slightly weaker than Example 1, and a density of 0.80 g / cm. ^Three The transfer paper of Example 2 was obtained in the same manner as in Example 1 except for the other papermaking conditions. Using the same material as in Example 1, among the papermaking conditions in Example 2, the JET / WIRE ratio was changed and adjusted so that the fiber orientation ratio by the ultrasonic wave propagation method was 1.16. No transfer paper was obtained. Similarly, the transfer paper of Example 4 was obtained by adjusting the fiber orientation ratio obtained by the ultrasonic wave propagation method to 1.30 with respect to Example 2. Basis weight, density, smoothness, fiber orientation ratio by ultrasonic wave propagation method, CD stretch ratio, Et ^Three The Hunter whiteness was a predetermined value. These transfer papers were evaluated in the same manner as in Example 1 for image quality, toner fixability, post-fix curl, texture, and the like. In Examples 2 and 3, a transfer paper excellent in curling after fixing was obtained. In Example 4, a transfer paper that was practically satisfactory was obtained.
[0023]
Examples 5, 6, 7, 8
Using the same material as in Example 1, the basis weight was 81 g / m. ² A transfer paper of Example 5 was obtained under the same papermaking conditions as in Example 1 except that. Moreover, except that the pulp raw material used in Example 5 was changed and LBKP containing 30% of dry pulp was used, the transfer paper of Example 6 was obtained with the same stock and paper making conditions as in Example 5. . The transfer paper of Example 7 uses the same material as that of Example 5, applies a machine calendar stronger than Example 5, and has a density of 0.85 g / cm. ^Three The other papermaking conditions were obtained in the same manner as in Example 5. The smoothness at this time was 120 seconds in FS. The transfer paper of Example 8 was obtained under the same papermaking conditions as in Example 5 except that the same paper material as in Example 5 was used and the fiber orientation ratio by the ultrasonic wave propagation method was adjusted to 1.30. It was. Basis weight, density, smoothness, fiber orientation ratio by ultrasonic wave propagation method, CD stretch ratio, Et of transfer papers of Examples 5, 6, 7, and 8 ^Three The Hunter whiteness was a predetermined value. These transfer papers were evaluated in the same manner as in Example 1 for image quality, toner fixability, post-fix curl, texture, and the like. In Example 5, a transfer paper excellent in image quality, toner fixability, and curling after fixing was obtained. In Example 6, a transfer paper having a smaller CD expansion / contraction ratio than Example 5 and better curling after fixing was obtained. In Example 7, although it was highly smooth, it gave a texture that did not look like plain paper, but it was within the allowable range, and a transfer paper excellent in image quality, toner fixability, and curling after fixing was obtained. In Example 8, a transfer paper particularly excellent in image quality and toner fixability was obtained.
[0024]
Examples 9, 10, 11
Using the same material as in Example 1, the basis weight was 90 g / m. ² A transfer paper of Example 9 was obtained under the same papermaking conditions as in Example 1 except that. Further, using the same material as in Example 1, the basis weight was 95 g / m. ² A transfer paper of Example 10 was obtained under the same papermaking conditions as in Example 1 except that. The transfer paper of Example 11 was obtained under the same papermaking conditions as in Example 10, except that the same material as in Example 10 was used and the fiber orientation ratio by the ultrasonic wave propagation method was adjusted to 1.30. It was. Basis weight, density, smoothness, fiber orientation ratio by ultrasonic wave propagation method, CD expansion / contraction rate, Et of transfer papers of Examples 9, 10, and 11 ^Three The Hunter whiteness was a predetermined value. These transfer papers were evaluated in the same manner as in Example 1 for image quality, toner fixability, post-fix curl, texture, and the like. In Example 9, a transfer paper excellent in all of image quality, toner fixability, and curling after fixing was obtained. In Example 10, a transfer paper excellent in image quality and curling after fixing was obtained. In Example 11, a transfer paper having excellent graininess in the halftone area and density unevenness in the high image density area was obtained.
[0025]
Example 12
The fluorescent dye was removed from the stock of Example 5, and the transfer paper of Example 12 was obtained under the same papermaking conditions as in Example 5. Hunter whiteness was 82%. Basis weight, density, smoothness of this transfer paper, fiber orientation ratio by ultrasonic wave propagation method, CD stretch ratio, Et ^Three Became a predetermined value. The transfer paper was evaluated for image quality, toner fixability, post-fix curl, texture, and the like in the same manner as in Example 1. In Example 12, a slightly turbid color was developed but at an acceptable level, and a transfer paper excellent in other image quality, toner fixability, and curling after fixing was obtained.
[0026]
Comparative Examples 1 and 2
Basis weight is 70g / m ² A transfer paper of Comparative Example 1 was obtained by the same paper and paper making method as in Example 1 except that. Similarly, basis weight is 100g / m ² A transfer paper of Comparative Example 2 was obtained by the same paper and paper making method as in Example 1 except that. The density of these transfer papers, smoothness, fiber orientation ratio by ultrasonic wave propagation method, CD stretch ratio, Et ^Three The Hunter whiteness was a predetermined value. In order to confirm the influence of the basis weight of these transfer papers, image quality, toner fixability, post-fixing curl, texture and the like were evaluated by the same method as in Example 1. In Comparative Example 1, the curl was very large, and the transfer paper of Comparative Example 2 had poor toner fixing and color development became cloudy. None of the transfer papers were put to practical use.
[0027]
Comparative Examples 3, 4, 5
Density 0.78g / cm ^Three A transfer paper of Comparative Example 3 was obtained by the same paper material and paper making method as in Example 5 except that. The smoothness of this transfer paper was 59 seconds on the low smoothness surface. Compared to Comparative Example 3, the density is 0.76 g / cm. ^Three Comparative Example 4 was obtained in the same manner except that it was further lowered. Density 0.90g / cm ^Three A transfer paper of Comparative Example 5 was obtained by the same stock and paper making methods as in Example 5 except that. The smoothness of this transfer paper was 207 seconds in terms of high smoothness. Basis weight, density, smoothness of these transfer papers, fiber orientation ratio by ultrasonic wave propagation method, CD stretch ratio, Et ^Three The Hunter whiteness was a predetermined value. In order to confirm the influence of the smoothness and density of these transfer papers, the image quality, toner fixability, post-fixing curl, texture and the like were evaluated by the same method as in Example 1. In Comparative Example 3, the roughness of the halftone area was poor, and the density unevenness in the high image density area also occurred. In Comparative Example 4, the roughness of the halftone area was further deteriorated, and the density unevenness in the high image density area was further remarkable. Since the transfer paper of Comparative Example 5 was too smooth, it lost the texture of plain paper, the writing performance with a pencil was not sufficient, and Et. ^Three Was also a small value, resulting in a large curl. None of the transfer papers were put to practical use.
[0028]
Comparative Examples 6, 7, and 8
A transfer paper of Comparative Example 6 was obtained under the same papermaking conditions as in Example 3 except that the fiber orientation ratio by the ultrasonic wave propagation method was adjusted to 1.35 using the same material as in Example 3. . The CD stretch ratio of this transfer paper was 0.46%. Further, the transfer paper of Comparative Example 7 was prepared under the same papermaking conditions as in Example 5 except that the fiber orientation ratio by the ultrasonic wave propagation method was adjusted to 1.35 using the same material as in Example 5. Obtained. The CD stretch ratio of this transfer paper was 0.49%. Furthermore, the transfer material of Comparative Example 8 was prepared under the same papermaking conditions as in Example 10 except that the fiber orientation ratio by the ultrasonic wave propagation method was adjusted to 1.45 using the same material as in Example 10. Obtained. The CD stretch ratio of this transfer paper was 0.55%. Basis weight, density, smoothness of these transfer papers, fiber orientation ratio by ultrasonic wave propagation method, CD stretch ratio, Et ^Three The Hunter whiteness was a predetermined value. In order to confirm mainly the influence of the CD expansion / contraction ratio of these transfer papers, the image quality, toner fixing property, post-fixing curl, texture and the like were evaluated by the same method as in Example 1. Comparative Example 6 has a large CD expansion / contraction ratio and Et ^Three Since the value was also small, a large curl was generated. Since the transfer paper of Comparative Example 7 had a CD expansion / contraction ratio larger than that of Comparative Example 5, very large curling occurred. Since the transfer paper of Comparative Example 8 had a large CD expansion / contraction rate, very large curling occurred. None of the transfer papers were put to practical use.
[0029]
Comparative Examples 9 and 10
A transfer paper of Comparative Example 9 was obtained under the same papermaking conditions as in Example 7, except that the fiber orientation ratio by the ultrasonic wave propagation method was adjusted to 1.28 using the same material as in Example 7. . Et of this transfer paper ^Three Was 0.24. The transfer paper of Comparative Example 10 was prepared under the same papermaking conditions as in Example 1 except that the fiber orientation ratio by the ultrasonic wave propagation method was adjusted to 1.30 using the same material as in Example 1. Obtained. Et of this transfer paper ^Three Was 0.22. Basis weight, density, smoothness of these transfer papers, fiber orientation ratio by ultrasonic wave propagation method, CD stretch ratio, Et ^Three The Hunter whiteness was a predetermined value. Most of these transfer papers are Et. ^Three In order to confirm the influence, the image quality, toner fixability, post-fixing curl, texture and the like were evaluated by the same method as in Example 1. Comparative Example 9 is Et ^Three Since the value was also small, a large curl was generated. The transfer paper of Comparative Example 10 is Et. ^Three Is much smaller than that of Comparative Example 9, resulting in a very large curl. None of the transfer papers were put to practical use.
[0030]
Comparative Example 11
A transfer paper of Comparative Example 11 was obtained by the same paper material and papermaking method as Example 5 except that LBKP having a reduced bleaching degree was used. Density, smoothness of this transfer paper, fiber orientation ratio by ultrasonic wave propagation method, CD stretch ratio, Et ^Three The Hunter whiteness was a predetermined value. In order to confirm the influence of the Hunter whiteness of the transfer paper, the image quality, toner fixability, post-fixing curl, texture, and the like were evaluated by the same method as in Example 1. In Comparative Example 11, the color development was turbid and not practical.
[0031]
Comparative Example 12
Basis weight is 78 g / m ² In the same manner as in Example 1, the commercially available electrophotographic transfer paper was evaluated for image quality, toner fixability, post-fixing curl, texture, and the like. Basis weight, density, smoothness of this transfer paper, fiber orientation ratio by ultrasonic wave propagation method, CD stretch ratio, Et ^Three The Hunter whiteness was a predetermined value. In Comparative Example 12, both the image quality and the curl after fixing were poor and were not put to practical use.
[0032]
【The invention's effect】
Since the present invention has the above-described configuration and characteristics, it is excellent in the graininess of the halftone area in full-color and monochrome recording of the indirect electrophotographic method, there is no occurrence of density unevenness in the high image density area, and It is possible to provide an electrophotographic transfer paper that is excellent in color development of a full-color image, can provide an image with good toner fixability, and has a small post-fixing curl in full-color high image area recording.

Claims

In a high-quality paper having a basis weight of 75 to 95 g / m ² , Beck smoothness of 65 to 120 seconds on both sides and a density of 0.80 g / cm ³ or more, the CD expansion and contraction rate is 0.00. 45% or less, and the following formula 1
Et ³ ≧ 0.26 (1)
An electrophotographic transfer paper satisfying [wherein E represents the tensile modulus of elasticity (kgf / mm ² ) of CD and t represents the thickness (mm) of the paper].

2. The electrophotographic transfer paper according to claim 1, wherein the Hunter whiteness is 82% or more.

The electrophotographic transfer paper according to claim 1 or 2, wherein a fiber orientation ratio by an ultrasonic wave propagation method is 1.10 to 1.30.

2. The electrophotographic transfer paper according to claim 1, wherein a pulp having a beating degree of 400 mlC.S.F. or more is used as a raw material.