JP2004117460A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method with which the degradation in electrostatic chargeability with lapse of time can be suppressed without being affected by environmental conditions and without the degradation in the aggregation properties of recycled toners, and images of good graininess can be obtained. <P>SOLUTION: The toners used in the developing step of the image forming method contains at least a binder resin, a coloring agent, wax, and a charge controlling agent. When the calorific value ratio of the peak of the wax in a DSC curve measured by a differential scanning calorimeter is defined as Pw, the calorific value ratio of the peak of the binder resin as Pb, and the calorific value ratio Pw/Pb of Pw and Pb as R, the ratio R2/R1 of the calorific value ratio R1 of the fresh toners and the calorific value ratio R2 of the recycled toners ranges from 1.0 to 1.2. <P>COPYRIGHT: (C)2004,JPO

Description

（式中、Ｘは水素原子、低級アルキル基、ニトロ基、ハロゲン原子等を示し、それぞれが同一または異なっていても良く、Ａ＋は水素イオン、ナトリウムイオン、カリウムイオン、アンモニウムイオン、脂肪族アンモニウムイオンを示す。）
【００１３】
請求項４に記載の本発明は、前記荷電制御剤は、ジルコニウムと芳香族オキシカルボン酸又はその塩とからなるジルコニウム化合物から成り、該荷電制御剤のＣｕＫα特性Ｘ線回析に対するブラッグ角２θの主要ピークＡは５．５度±０．３度であり、該Ｘ線回析強度はスキャンスピード０．５〜４度／分で２０００〜１５０００ｃｐｓの範囲にあることを特徴とする請求項３に記載の画像形成方法である。
請求項５に記載の本発明は、前記荷電制御剤は、ジルコニウムと芳香族オキシカルボン酸又はその塩とからなるジルコニウム化合物から成り、該荷電制御剤のＣｕＫα特性Ｘ線回析に対するブラッグ角２θの主要ピークは、メインピークＡが５．５度±０．３度、サブピークＢが３１．６度±０．３度であり、ピークＡ及びＢの強度比Ａ／Ｂが３〜２５の範囲にあることを特徴とする請求項３または４に記載の画像形成方法である。
【００１４】
請求項６に記載の本発明は、前記荷電制御剤は、前記一般式（１）で示されるクロム錯体化合物から成り、該荷電制御剤のＣｕＫα特性Ｘ線回析に対するブラッグ角２θの主要ピークＣは８．６度±０．３度であり、該Ｘ線回析強度はスキャンスピード０．５〜４度／分で８０００〜１５０００ｃｐｓの範囲にあることを特徴とする請求項３に記載の画像形成方法である。
請求項７に記載の本発明は、前記荷電制御剤は、前記一般式（１）で示されるクロム錯体化合物から成り、該荷電制御剤のＣｕＫα特性Ｘ線回析に対するブラッグ角２θの主要ピークは、少なくとも、メインピークＣが８．６度±０．３度、メインピークＣの半値幅が０．３０度以下であることを特徴とする請求項３または６に記載の画像形成方法である。
請求項８に記載の本発明は、前記荷電制御剤は、前記一般式（１）で示されるクロム錯体化合物から成り、該荷電制御剤のＣｕＫα特性Ｘ線回析に対するブラッグ角２θの主要ピークは、少なくとも、メインピークＣが８．６度±０．３度、サブピークＤが７．９度±０．３度にあり、この強度比がピークＣの強度を１００としたときにピークＤの強度が３０〜６０の範囲にあることを特徴とする請求項３、６、７のいずれかに記載の画像形成方法である。
【００１５】
請求項９に記載の本発明は、前記トナーは、ＴＨＦ可溶分により求められたＧＰＣ（ゲルパーミエーションクロマトグラフィ）による分子量分布でのピークトップ分子量が、３８００〜４５００の範囲にあることを特徴とする請求項１ないし８のいずれかに記載の画像形成方法である。
請求項１０に記載の本発明は、前記帯電工程は、帯電部材を像担持体に接触させ、外部より帯電部材に電圧を印加して、像担持体を帯電することを特徴とする請求１ないし９のいずれかに記載の画像形成方法である。
請求項１１に記載の本発明は、前記転写工程は、像担持体と転写手段とが転写部材を介して当接して、転写部材に転写することを特徴とする請求項１ないし１０のいずれかに記載の画像形成方法である。
【００１６】
【発明の実施の形態】
以下より、本発明の実施の形態について図に基づき説明する。
本発明の画像形成方法は、像担持体に帯電を行う帯電工程と、帯電している像担持体に静電荷像を形成する静電潜像形成工程と、静電荷像をトナーによって現像してトナー画像を形成する現像工程と、トナー画像を転写体上に転写する転写工程と、転写体上のトナー画像を加熱定着する定着工程と、転写後の像担持体表面をクリーニングして像担持体表面上のトナーを回収し、回収したトナーを現像工程に供給して使用するリサイクル工程からなる画像形成方法である。
【００１７】
図１は、本発明の画像形成方法が適用される画像形成装置の主要部を示す概略構成図である。ドラム状の像担持体（１）の周囲に、帯電工程を行うための帯電部材（２）と、静電潜像形成工程を行うための露光手段（３）と、現像工程を行うための現像手段（４）と、転写工程を行うための転写手段（５）と、転写体を分離させるための分離チャージャー（６）と、像担持体（１）をクリーニングしやすくするためのクリーニング前チャージャー（７）と、像担持体（１）をクリーニングするためのクリーニング手段（８）と、像担持体（１）を除電するための除電ランプ（９）とが配置されており、以下の動作で画像形成を行う。なお、図１の例においては画像形成の一連のプロセスはネガポジプロセスで行う。
【００１８】
有機光導電層を有する感光体（ＯＰＣ）である像担持体（１）は、除電ランプ（９）で除電され、帯電部材（２）により一様に負に帯電（−７００Ｖ）され、レーザー光学系の露光手段（３）により照射されるレーザー光で潜像形成（露光部電位は−１００Ｖ）が行われる。レーザー光は、半導体レーザーから発せられて高速で回転する六角柱の多面鏡（ポリゴンミラー）によって像担持体（１）表面を像担持体（１）の回転方向に走査する。像担持体（１）はレーザー光の走査速度に比較して極めて低速で回転するため、レーザー光は像担持体（１）の表面全体を走査することができる。そのようにして形成された潜像が現像手段（４）の磁気ブラシにより現像（現像バイアスは−５５０Ｖ）され、トナー像が形成される。用いられる現像剤は非磁性トナーと磁性キャリアからなる二成分現像剤である。
【００１９】
一方、転写体が図示していない給紙機構から給送され、図示していない上下一体のレジストローラーで画像先端と同期をとって、像担持体（１）と転写手段（５）との間に給送されてトナー像が転写される。このとき、転写手段（５）に印加される転写バイアスは＋９５０Ｖである。その後、転写体（例えば転写紙）（１０）は像担持体（１）より分離された後、定着手段（１１）を経てコピーとして排出される。現像手段（４）で現像されたトナーはほぼ全てマイナス極性に帯電されているが、転写手段（５）ではプラス電荷が供給されるため転写残りトナーの一部には転写手段（５）から電荷が注入されてプラス極性のトナーになる。これらのトナーに対してクリーニング前チャージャー（７）がマイナスコロナを供給しトナーはマイナスに再帯電する。このようにトナーにおける電荷は外部の電位差、チャージによりすばやくその帯電挙動の応答速度がプロセス全体の速度向上や画像の安定性に必要である。
【００２０】
以上のような動作で画像が形成される。１枚分の画像が形成されるとクリーニング手段（８）は回転方向及び速度の少なくとも一方が切り替わり、同時に負極性のバイアスが印加され回収したトナーが像担持体（１）に排出される。排出されたトナーは像担持体（１）の回転に伴って現像領域に搬送される。なお、現像手段（４）には正極性のバイアスが印加される。現像領域では磁気ブラシが像担持体（１）上のトナーに衝撃力を与えバイアスによりトナーを回収する。以上の動作によりトナーのリサイクルが実現される。
【００２１】
帯電工程は、帯電部材（２）を像担持体（１）に接触させ、外部より帯電部材（２）に電圧を印加して像担持体（１）を帯電する、接触帯電方式が好ましい。これにより画像の粒状度が向上する。
また、転写工程は、像担持体（１）上の静電潜像を現像されたトナー像を、転写手段（５）を介して転写材（Ｐ）へ静電転写する、接触転写方式が好ましい。これによりさらに画像の粒状度が向上する。
【００２２】
次に、定着手段（１１）について詳細に説明する。
図２は、熱ローラ方式の定着手段（１１）の一例を示す概略図である。基本構成としては、ハロゲンランプ等の加熱ヒータ（１４）を有する加熱ローラ（１１ａ）と、芯金（１６）上に発泡シリコーンゴム等の弾性層（１７）を有し、加熱ローラ（１１ａ）に圧接される加圧ローラ（１１ｂ）とを備えている。
弾性層は、均一な定着ニップ部Ｎを得るために、少なくとも一方のローラに設けられていることが必要であり、好ましくは両方に設ける。定着工程において１本または２本のローラが弾性を有することにより、画像の粒状度が向上する。これはローラのもつ弾性により、トナー像の表面及び転写紙との接点がより密着され定着性が向上し、画像濃度のばらつきや光沢の不均一性が少なくなるためである。
【００２３】
加圧ローラ（１１ｂ）の弾性層（１７）上には導電性のＰＦＡチューブ等からなる離型層（１８）が設けられている。弾性層（１７）の軸上のゴム硬度は４２ＨＳ（アスカＣ）であり、離型層（１８）は外径φ３０、肉厚６ｍｍで構成される。
定着ローラ（１１ａ）は、肉厚０．４ｍｍのアルミの芯金（１２）の上にシリコーンゴム等の弾性層（１５）を設け、更にトナーの粘性による付着を防止する目的で、フッ素樹脂等の離型性の良い樹脂表層（１３）が形成されている。弾性層（１５）の層厚は画像品質と定着時の熱伝達効率を考慮して通常は１００〜５００μｍ程度の厚さが好ましい。また樹脂表層（１３）は、加圧ローラ（１１ｂ）と同様にＰＦＡチューブ等で構成され、その厚みは機械的劣化を考慮して１０〜５０μｍ程度の厚みが好ましい。
本構成において定着ニップ部Ｎを得るために、ローラの両端に片側８８Ｎの圧力がかけられており、その時の面圧は９．３Ｎ／ｃｍ^２になっている。
【００２４】
定着ローラ（１１ａ）の外周面には、温度検知手段（１９）が設けられ、定着ローラ（１１ａ）の表面温度を検知することで、その温度をほぼ一定に保つように加熱ヒータ（１４）を制御している。
このような構成の定着手段（１１）において、定着ローラ（１１ａ）と加圧ローラ（１１ｂ）とが、所定の加圧力で圧接されて定着ニップ部Ｎを構成し、駆動手段（図示せず）により駆動を受けてそれぞれ矢印Ｒ１方向、矢印Ｒ５方向に回転することによって、上述の定着ニップ部Ｎにて転写材Ｐを挟持搬送する。この際、定着ローラ（１１ａ）は加熱ヒータ（１４）によって所定の温度に制御されており、転写材Ｐ上のトナー像Ｔは、両ローラ間を通過するときに、圧力を受けながら熱溶融し、両ローラ間を出て冷却されることによって永久像として転写材Ｐに定着される。
【００２５】
現像手段（４）内でトナーが磨耗されいわゆるトナー微粉を生じると、トナー微粉はトナー転写工程において像担持体（１）に対する物理的付着力が大きいために通常の粒径のトナーに比べ転写しにくい。このためトナー微粉が選択的にリサイクルされ現像手段（４）内のトナー微粉が増加する。
このリサイクルトナーの構成成分を分析した結果、示差走査熱量計により測定されるＤＳＣ曲線において、ワックスとバインダー樹脂のピークの熱量比を比較したときに、新トナーに比べ、リサイクルトナーのワックス強度比が増加していることが判明した。ＤＳＣ曲線におけるピークの熱量は、各構成材料を同一のものを使用した場合、含有量に比例する。つまり、新トナーに比べ、リサイクルトナーのワックス含有量が増加していることが判明した。
【００２６】
トナーは組成の不均一などによる界面からわれやすく微粉化が発生しやすい。ワックスはバインダーレジンと相溶せずに分散されているため、この界面から微粉化が発生していると考える。このワックス量の増加がリサイクルトナーの凝集性悪化を引き起こす大きな要因となっていることが判明した。特に前述のようにリサイクルトナーは新トナーに比べ微粉化しているため、補給トナーよりも比表面積が大きい。さらに含有量が補給トナーよりも増加するとワックスが表面に析出する量は増大し、凝集性が悪化する。さらにワックスはバインダー樹脂と比較し軟質であるため、外添剤が容易に埋め込まれやすい。そのため、ワックスが表面に析出する量が増大すると外添剤の埋め込みが促進し、さらに凝集性が悪化し、このようなリサイクルトナーが現像機内に供給されると、現像剤の帯電量分布のブロード化や逆帯電量トナーの発生を引き起こし劣悪な画像となる。
【００２７】
従ってリサイクルトナーの凝集性悪化を抑制するためには、示差走査熱量計により測定されるＤＳＣ曲線において、ワックスとバインダー樹脂のピークの熱量比を各々Ｐｗ、Ｐｂとし、ＰｗとＰｂの熱量比をＲとしたときに、新トナーの熱量比Ｒ１とリサイクルトナーの熱量比Ｒ２との比Ｒ２／Ｒ１が１．０〜１．２の範囲にあることが必要である。
Ｒ＝Ｐｗ（ワックス）／Ｐｂ（バインダー樹脂）
Ｒ１：新トナーのＤＳＣにおける熱量比Ｐｗ_１／Ｐｂ_１
Ｒ２：リサイクルトナーのＤＳＣにおける熱量比Ｐｗ_２／Ｐｂ_２
Ｒ２／Ｒ１＝１．０〜１．２　　　　…式３
Ｒ２／Ｒ１が１．０未満になるとリサイクルトナーの凝集性悪化は抑制できるが、ワックス含有量が低下するために定着性が悪化する。Ｒ２／Ｒ１が１．２を超えるとリサイクルトナーの凝集性が極端に悪化する。Ｒ２／Ｒ１＝１．０〜１．２の範囲であることにより、リサイクルシステムにおいても粒状度の良好な画像を得ることができる。
【００２８】
Ｒ２／Ｒ１＝１．０〜１．２の範囲を得るためには、トナー中の各構成材料、とりわけワックスが均一に分散されていることが必要である。そのためには、まず原材料としてのワックス粒径が所望の大きさで均一に分布していることが望ましい。例えば、平均粒径が３００±５０μｍで７００μｍ以上の成分量が５重量％以下、５０μｍ以下の成分量が１０重量％以下の分布であることが好ましい。その他にも樹脂の粒度分布をたとえば２００±５０μｍで４００μｍ以上の成分量が５重量％以下、３０μｍ以下の成分量が５重量％以下の分布に整粒することが必要である。
【００２９】
本発明に用いるトナーの製造方法としては、少なくともバインダー樹脂、荷電制御剤および顔料を含むトナー成分を機械的に混合する工程と、溶融混練する工程と、混練物を冷却水により冷却しながら圧延する工程と、粉砕する工程と、分級する工程とを有するトナーの製造方法が適用できる。また機械的に混合する工程や溶融混練する工程において、粉砕または分級する工程で得られる製品となる粒子以外の粉末を戻して再利用する製造方法も含まれる。
ここで言う製品となる粒子以外の粉末（副製品）とは、溶融混練する工程後、粉砕工程で得られる所望の粒径の製品となる成分以外の微粒子や粗粒子や引き続いて行われる分級工程で発生する所望の粒径の製品となる成分以外の微粒子や粗粒子を意味する。このような副製品を混合工程や溶融混練する工程で原料と好ましくは副製品１に対しその他原材料９９から副製品５０に対し、その他原材料５０の重量比率で混合するのが好ましい。
【００３０】
少なくともバインダー樹脂、荷電制御剤および顔料、副製品を含むトナー成分を機械的に混合する混合工程は、回転させる羽による通常の混合機などを用いて通常の条件で行えばよく、特に制限はない。
以上の混合工程が終了したら、次いで混合物を混練機に仕込んで溶融混練する。溶融混練機としては、一軸、二軸の連続混練機や、ロールミルによるバッチ式混練機を用いることができる。
この溶融混練は、バインダー樹脂の分子鎖の切断を招来しないような適正な条件で行うことが重要である。具体的には、溶融混練温度は、結着剤樹脂の軟化点を参考に行うべきであり、軟化点より低温過ぎると切断が激しく、高温過ぎると分散が進まない。
【００３１】
以上の溶融混練工程が終了したら、次いで混練物を冷却水により冷却しながら圧延する。このときの冷却速度が実は、ワックスや他顔料の分散性に大きく寄与する。除冷するとワックスや他顔料が再凝集するため、溶融混練工程で得られた分散性を維持するためには可能な限り急冷することが望ましい。次の粉砕工程においては、まず粗粉砕し、次いで微粉砕することが好ましい。この際　ジェット気流中で衝突板に衝突させて粉砕したり、機械的に回転するローターとステーターの狭いギャップで粉砕する方式が好ましく用いられる。
この粉砕工程が終了した後に、粉砕物を遠心力などで気流中で分級し、もって所定の粒径例えば平均粒径が５〜１０μｍのトナーを製造する。
【００３２】
また、トナーを調製する際には、トナーの流動性や保存性、現像性、転写性を高めるために、以上のようにして製造されたトナーにさらに先に挙げた疎水性シリカ微粉末等の無機微粒子を添加混合してもよい。　外添剤の混合は一般の粉体の混合機が用いられるが、ジャケット等を装備して、内部の温度を調節できることが好ましい。外添剤に与える負荷の履歴を変えるには、途中または漸次外添剤を加えていけばよい。もちろん混合機の回転数、転動速度、時間、温度などを変化させてもよい。はじめに強い負荷を、次に比較的弱い負荷を与えても良いし、その逆でも良い。
使用できる混合設備の例としては、Ｖ型混合機、ロッキングミキサー、レーディゲミキサー、ナウターミキサー、ヘンシェルミキサーなどが挙げられる。
【００３３】
さらに、リサイクルシステムでは、トナーが高い帯電性を有することはもちろんのことであるが、同時にシャープな帯電量分布及び高温高湿及び低温低湿での環境変動に対する帯電量の安定性が必要である。さらに、１日数十枚程度の印字枚数の使用においては、さらに早い帯電の立ち上がり性と高い帯電性が必要となる。
そのためには、荷電制御剤がジルコニウムと芳香族オキシカルボン酸又はその塩からなるジルコニウム化合物、または下記一般式（１）で示されるクロム錯体化合物のうちの１つから成ることが良い。
【化３】

（式中、Ｘは水素原子、低級アルキル基、ニトロ基、ハロゲン原子等を示し、それぞれが同一または異なっていても良く、Ａ＋は水素イオン、ナトリウムイオン、カリウムイオン、アンモニウムイオン、脂肪族アンモニウムイオンを示す。）
さらに、その結晶面が同一面で成長していることにより高い帯電性付与がえられる。
【００３４】
ジルコニウムと芳香族オキシカルボン酸又はその塩からなるジルコニウム化合物は、結晶面が、ＣｕＫα特性Ｘ線回析に対するブラッグ角２θの主要ピークＡが５．５度±０．３度であり、このＸ線回析強度がスキャンスピード０．５〜４度／分において２０００〜１５０００ｃｐｓの範囲にあることがよい。
一般的にＸ線回折測定では、結晶性物質はブラッグの回折条件により結晶面間隔に応じて固有の回折ピークが表れ、回折強度は結晶の状態、結晶化度に依存しており、結晶化による硬度もある範囲においては結晶化度に依存している。２θピークＡ：５．５度±０．３度は、ジルコニウムと芳香族オキシカルボン酸又はその塩からなるジルコニウム化合物の主成分に起因するピークである。
【００３５】
この強度が２０００ｃｐｓ未満であると結晶性が低いため、生産時の混練の熱やせん断のエネルギーにより、ジルコニア化合物内の結合の切断がおこりやすくなり、帯電性が低くなってしまう。特に高温高湿環境において顕著に帯電量の低下が発生するとリサイクルトナーが増量するとともに凝集性が悪化する。
また、１５０００ｃｐｓを超えると負極性が増大し、凝集力が増大するため、他材料との分散性が不十分となりシャープな帯電量分布が得られなくなる。
すなわちＣｕＫα特性Ｘ線回析に対するブラッグ角２θの主要ピークがピークＡ：５．５度±０．３度にあり、このＸ線回析強度がスキャンスピード０．５〜４度／分において２０００〜１５０００ｃｐｓの範囲にあることで、リサイクルトナーにおいても高い帯電性とシャープな帯電量分布を得ることが可能となる。
【００３６】
さらに、該荷電制御剤のＣｕＫα特性Ｘ線回析に対するブラッグ角２θの主要ピークが少なくともメインピークＡ：５．５度±０．３度、サブピークＢ：３１．６度±０．３度にあり、この強度比ピークＡ／Ｂが３〜２５の範囲にあることにより、高温高湿及び低温低湿での環境変動に対する帯電量の安定性がさらに良好となる。
サブピークＢ：３１．６度±０．３度は、面間隔：２．８５５３〜２．８９１４Åに相当し、電子密度が大きいため、水分子と水素結合しにくく、高温高湿環境における帯電量の低下を抑制できると考えられる。このときの比率はピークＡ／Ｂが３〜２５の範囲が良い。３未満であると高温高湿環境における帯電量安定性に十分な効果がなく、２５を超えるとメインピークに由来する単結晶性の性質が不十分となり多結晶性となるため、帯電量分布がブロードになりやすく、転写残トナーの増加をまねく。
【００３７】
前述の一般式（１）で示されるクロム錯体化合物は、結晶面が、ＣｕＫα特性Ｘ線回析での測定角２θが５〜３０度の範囲に、ブラッグ角２θの主要ピークが、ピークＡ：８．６度±０．３度にあり、このＸ線強度がスキャンスピード０．５〜４度／分において８０００〜１５０００ｃｐｓの範囲にあることが必要であることが判明した。２θピークＣ：８．６度±０．３度はクロム錯体の主成分に起因するピークである。
この強度が８０００ｃｐｓ未満であると結晶性が低いため、生産時の混練の熱やせん断のエネルギーにより、クロム化合物内のキレート結合の切断がおこりやすくなり、帯電性が低くなってしまい、特に高温高湿環境において顕著に帯電量の低下が発生してしまう。また１５０００ｃｐｓを超えると負極性が増大し、凝集力が増大するため、他材料との分散性が不十分となりシャープな帯電量分布が得られなくなる。
【００３８】
すなわちＣｕＫα特性Ｘ線回析に対するブラッグ角２θの主要ピークがピークＣ：８．６度±０．３度にあり、このＸ線強度がスキャンスピード０．５〜４度／分において８０００〜１５０００ｃｐｓの範囲にあることで、帯電の立ち上がりが早く、且つ高い帯電性とシャープな帯電量分布、良好な分散性を得ることが可能となる。さらに、このピークＣの半値幅が０．３０度以下にあることにより、さらに帯電性がシャープになり、環境変動に対して安定化する。ピークの半値幅は結晶状態の均一性に関与するため、０．３０度以下であることにより結晶性の均一性が高まるためと考えられる。
【００３９】
さらに該荷電制御剤のＣｕＫα特性Ｘ線回析に対するブラッグ角２θの主要ピークが、少なくともメインピークＣ：８．６度±０．３度、サブピークＤ：７．９度±０．３度にあり、この強度比がピークＣの強度を１００としたときにピークＤの強度が３０〜６０の範囲にあることにより、さらに帯電の立ち上がりの早いシャープな帯電量分布が得られる。
一つの単結晶面には等価な面が存在し、ある面形に属する等価な格子面の数を面の多重度と呼び、これらの格子面群は等しい面間隔をもっているが、これが本発明におけるクロム化合物の結晶中においては、サブピークＣとＤに対応し、サブピークＣ：８．６度±０．３度は面間隔９．９２７〜１０．６３４Å、サブピークＤ：７．９度±０．３度は面間隔１０．７７３〜１１．６２２Åに相当する。この面間隔で結晶性が成長しているものが極めて良好な帯電特性を示すことが判明した。
サブピークＣとＤとの強度比は、ピークＣの強度を１００としたときにピークＤの強度が３０〜６０の範囲にある構造のものが、最も帯電の立ち上がりの早いシャープな帯電量分布が得られる。
【００４０】
また、これらの荷電制御剤を含有するトナーは、トナーのＴＨＦ可溶分により求められたＧＰＣ（ゲルパーミエーションクロマトグラフィ）による分子量分布において、ピークトップ分子量が３８００〜４５００であることがよい。３８００未満では現像手段（４）内の微粉化が発生し、４５００を超えると定着性が悪化することで画質を劣化させる。
【００４１】
本発明による荷電制御剤としてジルコニウムと芳香族オキシカルボン酸又はその塩からなるジルコニウム化合物を使用する場合、オキシカルボン酸としては公知のものが使用可能であるが、下記の一般式（２）であらわされる化合物が帯電付与能力の点から好ましい。
【化４】

【００４２】
さらに帯電付与の点から以下の具体例のものが好ましい。
【化５】

【００４３】
上記トナーに用いられるバインダー樹脂としては、従来より公知の樹脂が全て使用される。例えば、スチレン、ポリ−α−スチルスチレン、スチレン−クロロスチレン共重合体、スチレン−プロピレン共重合体、スチレン−ブタジェン共重合体、スチレン−塩化ビニル共重合体、スチレン−酢酸ビニル共重合体、スチレン−マレイン酸共重合体、スチレン−アクリル酸エステル共重合体、スチレン−メタクリル酸エステル共重合体、スチレン−α−クロルアクリル酸メチル共重合体、スチレン−アクリロニトリル−アクリル酸エステル共重合体等のスチレン系樹脂（スチレンまたはスチレン置換体を含む単重合体または共重合体）、ポリエステル樹脂、エポキシ樹脂、塩化ビニル樹脂、ロジン変性マレイン酸樹脂、フェノール樹脂、ポリエチレン樹脂、ポリプロピレン樹脂、石油樹脂、ポリウレタン樹脂、ケトン樹脂、エチレン−エチルアクリレート共重合体、キシレン樹脂、ポリビニルブチラート樹脂などが挙げられるが、特にポリエステル樹脂を用いる事が好ましい。
【００４４】
ポリエステル樹脂は、アルコールとカルボン酸との縮重合によって得られる。使用されるアルコールとしては、例えばエチレングリコール、ジエングリコール、トリエチレングリコール、プロピレングリコール等のグリコール類、１、４−ビス（ヒドロキシメタ）シクロヘキサン、及びビスフェノールＡ等のエーテル化ビスフェノール類、その他二価のアルコール単量体、三価以上の多価アルコール単量体を挙げることができる。また、カルボン酸としては、例えばマレイン酸、フマール酸、フタル酸、イソフタル酸、テレフタル酸、コハク酸、マロン酸等の二価の有機酸単量体、１、２、４−ベンゼントリカルボン酸、１、２、５−ベンゼントリカルボン酸、１、２、４−シクロヘキサントリカルボン酸、１、２、４−ナフタレントリカルボン酸、１、２、５−ヘキサントリカルボン酸、１、３−ジカルボキシル−２−メチレンカルボキシプロパン、１、２、７、８−オクタンテトラカルボン酸等の三価以上の多価カルボン酸単量体を挙げることができる。ポリエステル樹脂のＴｇは５８〜７５℃が好ましい。また、以上の樹脂は単独使用も可能であるが二種類以上併用しても良い。
また、これら樹脂の製造方法も特に限定されるものではなく、塊状重合、溶液重合、乳化重合、懸濁重合いずれも使用できる。
【００４５】
また、上記トナーでは、用いる着色剤としては、従来からトナー用着色剤として使用されてきた顔料及び染料の全てが適用される。具体的には、カーボンブラック、ランプブラック、鉄黒、群青、ニグロシン染料、アニリンブルー、カルコオイルブルー、オイルブラック、アゾオイルブラックなど特に限定されない。
着色剤の使用量は１〜１０重量部、好ましくは３〜７重量部である。
ワックスとしては、例えば、ポリプロピレンワックス、ポリエチレンワックス等のようなポリオレフィンワックスや、キャンデリラワックス、ライスワックス、カルナウバワックス等の天然ワックスが使用可能である。ワックス成分の添加量は０．５〜１０重量部が好ましい。
【００４６】
上記トナーには、前述したように、必要に応じてその他、添加剤を添加する事も可能である。添加剤としては、シリカ、酸化アルミニウム類、酸化チタン類を例示することができる。高流動性を付与する事を主目的する場合には、疎水化処理シリカあるいはルチル型微粒子酸化チタンとして、平均一次粒径が０．００１〜１μｍ、好ましくは０．００５〜０．１μｍの範囲ものから適宜選択でき、特に有機シラン表面処理シリカあるいはチタニアが好ましく、通常０．１〜５重量％、好ましくは０．２〜２重量％の割合で使用される。
【００４７】
また、例えば上記トナーを二成分系乾式トナーとして使用する場合に混合して使用するキャリアとしては、ガラス、鉄、フェライト、ニッケル、ジルコン、シリカ等を主成分とする、粒径３０〜１０００μｍ程度の粉末、または、該粉末を芯材としてスチレン−アクリル系樹脂、シリコン系樹脂、ポリアミド系樹脂、ポリフッ化ビニリデン系樹脂等をコーティングしたものから適宜選択して使用可能である。
【００４８】
以下に各測定方法について記載する。
本発明のＸ線回折の測定には、例えば日立製作所製ＲＩＮＴ１１００を用いることができる。ＣｕＫα線を用い、Ｘ線管球：Ｃｕ、管電圧：５０ＫＶ、管電流：３０Ｍａ、スキャンスピード：２度／分の条件により測定する。
【００４９】
本発明におけるＧＰＣによる分子量分布測定方法を以下に示す。４０℃のヒートチャンバーの中でカラムを安定させ、この温度におけるカラムに溶媒としてＴＨＦ（テトラヒドロフラン）を毎分１ｍｌの流速で流し、ＴＨＦ試料溶液を約１００Μｌ注入して測定する。試料の分子量測定にあたっては、試料の有する分子量分布を数種の単分散ポリスチレン標準試料により作成された検量線の対数値とカウント数との関係から算出した。検量線作成の標準ポリスチレン試料としては、例えばＰｒｅｓｓｕｒｅ　Ｃｈｅｍｉｃａｌ　Ｃｏ．製あるいは東洋ソーダ社製、昭和電工社製の、分子量１００〜８０００万程度のものを用い、少なくとも１０点程度の標準ポリスチレン試料を用いるのが適当である。検出器は屈折率検出器を用いる。カラムは市販のポリスチレンゲルカラムを複数本くみあわせるのがよく、例えば昭和電工社製Ｓｈｏｄｅｘ　ＧＰＣ　ＫＦ−８０１、８０２、８０３、８０４、８０５、８０６、８００ｐの組み合わせ等があげられる。
【００５０】
本発明において、示差走査熱量計ＤＳＣにより測定されるワックスとバインダー樹脂のピークの熱量比の測定方法としては、具体的には、ＴＧＡ−７、ＰＥ７７００（パーキンエルマー社製）を使用し、トナー３〜８ｍｇを精秤し、窒素気流下で３０〜２００℃まで昇温速度１０℃／分で加熱したときの、バインダーレジンとワックスのピーク面積を算出し、その比率から熱量比を算出する。
【００５１】
【実施例】
以下具体的実施例によって本発明を説明するが、本発明はこれにより限定されるものではない。
トナー処方
（実施例１〜１２）
ポリエステル樹脂（ガラス転移点６５℃、ＴＨＦ不溶解分３０％含有）　７０重量部
スチレン−ｎブチルアクリレート共重合体　　３０重量部
カーボンブラック（三菱化成　＃４４）　　１０重量部
カルナウバワックス（融点８２℃）　　４重量部
後述の処方により得られる荷電制御剤　　１重量部
【００５２】
以上の処方で２軸エクストルーダーを用いて混練後、冷却急冷しながら圧延し、次いで粉砕、分級し、表１に記載した７μｍの重量平均粒径とした。その後ヘンシェルミキサーを用い、シリカ微粉末（Ｒ−９７２：クライアントジャパン製）１．０重量部とを混合しトナーを得た。
本トナーと平均粒径５０μｍのフェライト粒子にシリコーン樹脂コートしたキャリアで４．０％トナー濃度で混合し、二成分現像剤を作成した。
【００５３】
（実施例１３〜２０）
ポリエステル樹脂（ガラス転移点６５℃、ＴＨＦ不溶解分３０％含有）　８０重量部
スチレン−ｎブチルアクリレート共重合体　　２０重量部
カーボンブラック（三菱化成　＃４４）　　１０重量部
カルナウバワックス（融点８２℃）　　４重量部
後述の処方により得られる荷電制御剤　　１重量部
以上のトナー材料を実施例１〜１２同様の添加剤処方によりトナーを得て、同様に二成分現像剤を得た。
【００５４】
（比較例１〜５）
ポリエステル樹脂（ガラス転移点６５℃、ＴＨＦ不溶解分３０％含有）　８０重量部
スチレン−ｎブチルアクリレート共重合体　　２０重量部
カーボンブラック（三菱化成　＃４４）　　１０重量部
カルナウバワックス（融点８２℃）　　４重量部
後述の処方により得られる荷電制御剤　　１重量部
以上のトナー材料を実施例１〜１２同様の添加剤処方によりトナーを得て、同様に二成分現像剤を得た。
【００５５】
荷電制御剤処方
実施例１〜３に使用する荷電制御剤を得る方法としては、５−メトキシサリチル酸７〜４０部と２５％苛性ソーダ５〜３５部を水２００〜６００部に溶解して５０℃に昇温し、攪拌しながらオキシ塩化ジルコニウム５〜２０部を水８０〜１５０部に溶解した溶液を滴下した。同温度で０．５〜２．５時間攪拌後室温１〜１０℃／分の速度で冷却し２５％苛性ソーダ約１０部を加えＰＨ７．５〜８．０に調整した。析出した結晶をろ過、水洗、乾燥して２０〜３０部の白色結晶を得た。
【００５６】
実施例４〜１２、比較例１〜５において使用される荷電制御剤としては、３，５−ジ−タ−シャリ−ブチルサリチル酸２５〜４５部と２５％苛性ソーダ１０〜４０部を水５００〜８００部に溶解し、５０℃、５〜１５℃／分の速度で昇温し攪拌しながらオキシ塩化ジルコニウム２０〜４０部を水１００〜３００部に溶解した溶液を滴下した。同温度で０．５〜３時間攪拌後室温５〜１５℃／分の速度で冷却し２５％苛性ソーダ３〜２０部を加えＰＨ７．５〜８．０に調整した。析出した結晶をろ過、水洗、乾燥して２０〜５０部の白色結晶をえた。
【００５７】
実施例１３〜２０に使用する荷電制御剤を得る方法としては、エチルセロソルブ８００ｇ及びエチレングリコール４２０ｇに蟻酸クロム（３価）１１０ｇ（０．５９ｍｏｌ）を加えたものを８５度で１時間攪拌した。これにモノアゾ化合物を４４５ｇ加え１２５度に昇温させて４時間攪拌した。この反応溶液を３％塩酸水溶液５０００ｍｌに分散させ、６０度で１時間攪拌後ろ過し、ろ取物を温水洗浄し乾燥させることにより紫粉末４３０ｇをえた。
【００５８】
リサイクルトナー凝集度測定方法
まず上から７５μｍメッシュの篩、４５μｍメッシュの篩、２２μｍメッシュの篩を重ね、試料２ｇを最上設置の篩に投入する。これを細川ミクロン製パウダーテスターで３０秒振動させる。篩内のトナー残量を計量し凝集度を下式にて算出する。
凝集度（％）＝｛（７５μｍふるい上のトナー残量）＋０．６×（４５μｍふるい上のトナー残量）＋０．２（２２μｍふるい上のトナー残量）｝　／２．０×１００
【００５９】
各環境におけるトナーの帯電量の測定方法
高温高湿（３０℃、９０％）、常温常湿（２５℃、６５％）にて平均粒径５０μのフェライト粒子にシリコーン樹脂コートしたキャリアで４．０％トナー濃度で混合し、現像剤を作成し、東芝ケミカル（株）製のブローオフ粉体帯電量測定装置ＴＢ−２００にて帯電量を測定した。
【００６０】
定着性および画像評価方法
トナーリサイクル機構を搭載している、リコー製ｉｍａｇｉｏ　Ｎｅｏ７００機または一部改造し、以下の条件で使用した。
実施例１、２：該マシンの定着ローラをシリコンローラとし、転写チャージャーを装着した
実施例３〜９：転写チャージャーを装着した
実施例１０：該マシンをそのまま使用した
実施例１１〜２０、比較例１〜５：該マシンに帯電ローラを装着した
【００６１】
定着性の評価方法
上記記載マシンにて、ヒーター温度を振ってコピーを行い、定着画像を得た。定着後の画像にメンデイングテープ（３Ｍ社製）を貼り、一定の圧力を掛けた後、ゆっくり引き剥がす。その前後の画像濃度をマクベス濃度計により測定し、次式にて定着率を算出する。定着ローラの温度を段階的に下げて、下記式で示す定着率が８０％以下となるときの温度を定着温度とする。
定着率（％）＝テープ付着画像濃度／画像濃度×１００
◎優れている　○普通　△やや劣る
【００６２】
画像評価方法粒状度の測定方法
上記記載マシンにて、常温湿にて５００００枚複写後、リコー標準プリンタテストチャートをプリントしたサンプルを得た。次にプリント画像のドットで作られたグレークケール（ハーフトーン部）を、大日本スクリーン社のＧｅｎａＳｃａｎ５０００スキャナで１０００ｄｐｉにて読み込み、画像データを得た。画像データから、濃度分布に変換し、式３にて粒状度を評価し、５００００枚後の画像評価とした。引き続き、３０℃９０％環境室内にて単位時間あたり３００枚にて１日３０００枚の複写枚数で５日間複写後、同様にリコー標準プリンタテストチャートをプリントしたサンプルを得、粒状度を評価し、高温湿での１５０００枚後の画像評価とした。
【００６３】
以上の処方条件および評価結果を以下の表に示す。
【表１】

【００６４】
【表２】

【００６５】
【表３】

表１、２、３から分かるように、本発明の条件を満たすことで、リサイクルトナー凝集度が低く、定着性、帯電性に優れ、環境条件に左右されずに経時良好な画像を得ることが可能な画像形成方法を得ることができた。
【００６６】
【発明の効果】
以上説明したように、本発明はリサイクルシステムを搭載した画像形成方法において、補給トナーとリサイクルトナーのＤＳＣ測定により得られる熱量比を特定することにより、リサイクルトナーの凝集性が悪化せず、粒状度が良好な画像品質を得るという優れた効果を発揮する画像形成方法を提供し得る。
さらに高温湿下にて１日数十枚程度の使用においても帯電の立ち上がり性がはやく帯電量の低下が無く、粒状度が良好な画像品質を得るという優れた効果を発揮する画像形成方法を提供し得る。
【図面の簡単な説明】
【図１】本発明の画像形成方法を実施するための画像形成装置の概略構成図である。
【図２】定着手段を示す図である。
【符号の説明】
１　像担持体
２　帯電部材
３　露光手段
４　現像手段
５　転写手段
７　クリーニング前チャージャー
８　クリーニング手段
９　除電ランプ
１１　定着手段
１１ａ　加熱ローラ
１１ｂ　加圧ローラ
１２　芯金
１４　加熱ヒータ
１５　弾性層
１６　芯金
１７　弾性層
１８　離型層
１９　温度検知手段
Ｎ　定着ニップ部
Ｐ　転写材
Ｔ　トナー像[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming method using an electrophotographic method, and more particularly to an image forming method including a toner recycling step and providing an image having high transfer efficiency and no fogging using a toner having excellent charging characteristics. Things.
[0002]
[Prior art]
Conventionally, in an electrophotographic process, which is the most common electrostatic image developing method, an electrostatic latent image is formed on the surface of an image carrier by charging and exposure, and then toner is electrostatically adhered on the latent image to perform development. Do. The obtained toner image is again electrostatically transferred to a transfer medium such as paper, and finally fixed to the transfer medium by a heat roll. Further, the toner remaining on the image carrier in the toner transfer step is removed from the photoconductor by the cleaning blade after the image carrier is neutralized, and is collected. In recent years, from the viewpoint of environmental protection, a toner recycling mechanism has been adopted in which the untransferred toner is directly supplied to a toner supply box and reused for image formation. In an image forming apparatus having a toner recycling mechanism, various studies have been made on the requirement that the charge amount of the toner as a developer does not change and that the cohesiveness does not deteriorate.
[0003]
For example, Patent Literature 1 discloses a technique in which the amount of change in dynamic friction coefficient before and after the addition of an external additive, the melting point of wax, and the specific surface area of the external additive are disclosed, whereby the amount of waste toner generated can be reduced. It is said that it is possible to prevent a reduction in the charge amount of the recycled toner.
Further, Patent Document 2 discloses a technique in which the wax is desolvated and the DSC endothermic peak and the heat loss are defined, whereby a decrease in fluidity can be suppressed even in a waste toner recycling step.
[0004]
However, especially when stored or used for a long period of time under high humidity, or when used with several copies per day, the charge amount decreases, the cohesiveness of the recycled toner deteriorates, and the image deteriorates. Resulting in. In addition, when used in a recycling system, the charging characteristics are significantly degraded due to electric stress, particularly from a charger, and this leads to a problem that background contamination and toner scattering occur due to deterioration of the charging startability.
In order to solve this, Patent Document 3 discloses a technique containing a quaternary ammonium salt group-containing copolymer and defining the molecular weight and the viscosity thereof. Although the charging characteristics are improved by this, the problem that heat-resistant storage stability and filming deteriorate due to the inclusion of the low molecular weight component of the quaternary ammonium salt group-containing copolymer occurs.
Patent Document 4 discloses a technique that regulates the particle size distribution of a toner, and provides a toner suitable for recycling. Although this does not include the coarse particles or extremely small particles generated by the recycling system, the charging characteristics of the recycled toner are not always good. The occurrence cannot be resolved.
[0005]
Patent Document 5 discusses the molecular weight distribution of the binder resin and the amide wax. However, although the blocking property is improved by this, the cohesion of the recycled toner cannot be sufficiently suppressed. In Patent Document 6, it is possible to obtain a toner effective for hot offset resistance by obtaining a specific molecular weight distribution while securing the low-temperature fixing property by lowering the viscosity of the binder resin with a non-crosslinked polymer and obtaining a low molecular weight distribution. This also cannot suppress the deterioration of the cohesiveness of the recycled toner.
[0006]
In addition, various studies have been made especially on charge control agents as a study for suppressing the decrease in the charge amount particularly under high humidity. For example, in Patent Documents 7 and 8, etc. The ratio is examined, and Patent Document 9 examines a constituent unit of a zirconium atom and an aromatic carboxylic acid. As a result, a high triboelectric charge can be maintained even under high humidity, but the problem that when the charge of the carrier is low, the charge distribution of the developer becomes broad and fogging is not solved.
Further, in Patent Document 10, although retransfer is improved by defining X-ray diffraction of a metal salt of an amorphous or low-crystalline aromatic compound, a non-crystalline or low-crystalline charge control agent is produced. The structure changes due to heat and shear energy from the kneading process at the time, and the production conditions are considerably limited in order to achieve the desired quality, and the carrier is contaminated in durability, leading to deterioration of the developer. At present, there is no one that satisfies everything, such as having drawbacks.
[0007]
In recent years, from the viewpoint of environmental protection, not only recycling of waste toner by a recycling system, but also attempts to reuse fine powder generated during fine powder classification in a toner manufacturing process have been made. If it is reused, the kneadability decreases, and the image quality deteriorates due to the deterioration of dispersibility.
Under such circumstances, the image quality has been further improved, and the particle size of the toner has tended to be smaller. When the toner particle size is small, even if pressure is applied between the fixing rollers, it is difficult to apply pressure to the toner particles, so that it becomes difficult to uniformly fix the toner image. In particular, in the case of a fixing device having a low surface pressure, this tendency is remarkable. Further, when thin paper is used as the transfer paper, the surface pressure is further reduced, the surface properties of the toner image are deteriorated, and the image quality is deteriorated. Further, when thick paper is used, the surface pressure becomes high, so that the toner is crushed and unevenness is emphasized, and image quality is deteriorated. This phenomenon is particularly remarkable in the case of digital development, and the reproducibility of independent dots is greatly affected.
[0008]
Halftone densities should be uniform, but micro-density irregularities can give a rough impression to the naked eye.
The physical evaluation value of the roughness is the granularity.
The noise can be measured by a Wiener spectrum which is a frequency characteristic of the density fluctuation.
Assuming that the density fluctuation component whose average value is 0 is f (x),
F (u) = {f (x) exp (-2πiux) dx} Equation 1
WS (u) = F (u)²… Equation 2
Where u is the spatial frequency.
The granularity (GS) is a value obtained by integrating the product of WS and visual frequency characteristics (Visual / Transfer / Function: VTF), and is expressed by the following equation.
GS = exp (−1.8 <D>) ∫WS (u)^1/2VTF (u) du Equation 3
Exp (-1.8 <D>) is a coefficient for correcting the difference between the density and the brightness perceived by a person. <D> represents the average value of the density.
The granularity has a high correlation with the subjective evaluation of the smoothness of the image. The smaller the value of the granularity, the smoother the image quality becomes, and the larger the value of the granularity, the rougher the image quality becomes.
[0009]
[Patent Document 1]
JP-A-11-95477
[Patent Document 2]
JP-A-11-84711
[Patent Document 3]
JP 2001-13732 A
[Patent Document 4]
JP-A-6-59501
[Patent Document 5]
JP-A-7-77834
[Patent Document 6]
Patent No. 2681859
[Patent Document 7]
Patent No. 3135507
[Patent Document 8]
Patent No. 3154088
[Patent Document 9]
JP-A-2001-66830
[Patent Document 10]
JP 2000-147828 A
[0010]
[Problems to be solved by the invention]
In view of the above problems, it is an object of the present invention to provide a recycling system in which the cohesiveness of the recycled toner does not deteriorate, and that the chargeability can be suppressed even under high humidity, and that an image with good granularity can be obtained. An image forming method is provided. In addition, an image forming method that has an excellent effect of rapidly charging up the toner even when it is used for several tens of sheets per day under high temperature and humidity, without reducing the charge amount, and obtaining good image quality with good granularity. To provide.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, the present invention according to claim 1 includes a charging step of charging an image carrier by a charging member, a step of forming an electrostatic image on the charged image carrier, and A developing step of developing the image with toner to form a toner image, a transfer step of applying a voltage to a transfer member by a transfer unit to transfer the toner image onto the transfer member, and a plurality of toner images transferred on the transfer member. And a recycling step of cleaning the surface of the image carrier after transfer with a cleaning member to collect toner on the surface of the image carrier, and supplying the collected toner to the developing process for use. In the image forming method, the toner used in the developing step is a toner containing at least a binder resin, a colorant, a wax, and a charge control agent. When the calorific ratio of the peak of the wax is Pw, the calorific ratio of the peak of the binder resin is Pb, and the calorific ratio of Pw and Pb, Pw / Pb, is R in the DSC curve measured by the meter, the calorific value of the new toner An image forming method, wherein the ratio R2 / R1 of the ratio R1 and the calorific value ratio R2 of the recycled toner is in the range of 1.0 to 1.2.
According to a second aspect of the present invention, in the image forming method according to the first aspect, in the fixing step, at least one roller has an elastic layer.
[0012]
According to a third aspect of the present invention, the charge control agent comprises a zirconium compound comprising zirconium and an aromatic oxycarboxylic acid or a salt thereof, or a chromium complex compound represented by the following general formula (1). The image forming method according to claim 1, wherein:
Embedded image

(Wherein, X represents a hydrogen atom, a lower alkyl group, a nitro group, a halogen atom, etc., which may be the same or different, and A + represents a hydrogen ion, sodium ion, potassium ion, ammonium ion, aliphatic ammonium ion Is shown.)
[0013]
The present invention according to claim 4, wherein the charge control agent comprises a zirconium compound comprising zirconium and an aromatic oxycarboxylic acid or a salt thereof, and the charge control agent has a Bragg angle 2θ with respect to CuKα characteristic X-ray diffraction. The main peak A is 5.5 degrees ± 0.3 degrees, and the X-ray diffraction intensity is in the range of 2000 to 15000 cps at a scan speed of 0.5 to 4 degrees / minute. It is an image forming method described in the above.
The present invention according to claim 5, wherein the charge control agent comprises a zirconium compound composed of zirconium and an aromatic oxycarboxylic acid or a salt thereof, and the charge control agent has a Bragg angle 2θ with respect to CuKα characteristic X-ray diffraction. The main peak has a main peak A of 5.5 degrees ± 0.3 degrees, a sub-peak B of 31.6 degrees ± 0.3 degrees, and an intensity ratio A / B of the peaks A and B within a range of 3 to 25. 5. The image forming method according to claim 3, wherein:
[0014]
The present invention according to claim 6, wherein the charge control agent comprises a chromium complex compound represented by the general formula (1), and the charge control agent has a main peak C of a Bragg angle 2θ with respect to CuKα characteristic X-ray diffraction. 4. The image according to claim 3, wherein the X-ray diffraction intensity is 8.6 ° ± 0.3 °, and the X-ray diffraction intensity is in a range of 8000 to 15000 cps at a scan speed of 0.5 to 4 ° / min. It is a forming method.
According to a seventh aspect of the present invention, the charge control agent comprises a chromium complex compound represented by the general formula (1), and the charge control agent has a main peak of a Bragg angle 2θ with respect to CuKα characteristic X-ray diffraction. 7. The image forming method according to claim 3, wherein at least the main peak C is 8.6 degrees ± 0.3 degrees, and the half width of the main peak C is 0.30 degrees or less.
In the present invention according to claim 8, the charge control agent comprises a chromium complex compound represented by the general formula (1), and the charge control agent has a main peak of a Bragg angle 2θ with respect to CuKα characteristic X-ray diffraction. At least, the main peak C is at 8.6 degrees ± 0.3 degrees, the sub-peak D is at 7.9 degrees ± 0.3 degrees, and the intensity ratio of the peak D is 100 when the intensity ratio of the peak C is 100. The image forming method according to any one of claims 3, 6, and 7, wherein is in the range of 30 to 60.
[0015]
According to a ninth aspect of the present invention, in the toner, a peak top molecular weight in a molecular weight distribution determined by GPC (gel permeation chromatography) determined by a THF soluble component is in a range of 3800 to 4500. An image forming method according to any one of claims 1 to 8.
According to a tenth aspect of the present invention, in the charging step, the image bearing member is charged by bringing the charging member into contact with the image carrier and applying a voltage to the charging member from outside. 9. The image forming method according to any one of 9 above.
According to a still further aspect of the present invention, in the transfer step, the image carrier and the transfer unit are in contact with each other via a transfer member to transfer the image to the transfer member. 2. The image forming method described in 1. above.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The image forming method of the present invention includes a charging step of charging an image carrier, an electrostatic latent image forming step of forming an electrostatic image on a charged image carrier, and developing the electrostatic image with toner. A developing step of forming a toner image, a transfer step of transferring the toner image onto a transfer body, a fixing step of heating and fixing the toner image on the transfer body, and an image carrier by cleaning the surface of the image carrier after transfer This is an image forming method including a recycling process in which the toner on the surface is collected, and the collected toner is supplied to a developing process and used.
[0017]
FIG. 1 is a schematic configuration diagram showing a main part of an image forming apparatus to which the image forming method of the present invention is applied. A charging member (2) for performing a charging process, an exposure unit (3) for performing an electrostatic latent image forming process, and a developing device for performing a developing process are provided around a drum-shaped image carrier (1). Means (4), a transfer means (5) for performing a transfer step, a separation charger (6) for separating a transfer body, and a pre-cleaning charger () for facilitating cleaning of the image carrier (1). 7), a cleaning means (8) for cleaning the image carrier (1), and a discharge lamp (9) for discharging the image carrier (1) are arranged. Perform formation. In the example of FIG. 1, a series of image forming processes is performed by a negative-positive process.
[0018]
The image carrier (1), which is a photoconductor (OPC) having an organic photoconductive layer, is neutralized by a neutralization lamp (9), is uniformly negatively charged (−700 V) by a charging member (2), and has a laser beam. A latent image is formed (exposure portion potential is -100 V) by laser light irradiated by the exposure means (3) of the system. The laser light scans the surface of the image carrier (1) in the rotating direction of the image carrier (1) by a hexagonal prism (polygon mirror) emitted from a semiconductor laser and rotating at a high speed. Since the image carrier (1) rotates at an extremely low speed as compared with the scanning speed of the laser beam, the laser beam can scan the entire surface of the image carrier (1). The latent image thus formed is developed by the magnetic brush of the developing means (4) (developing bias is -550 V), and a toner image is formed. The developer used is a two-component developer comprising a non-magnetic toner and a magnetic carrier.
[0019]
On the other hand, the transfer body is fed from a paper feed mechanism (not shown), and is synchronized with the leading edge of the image by an upper and lower integrated registration roller (not shown) to transfer the image between the image carrier (1) and the transfer means (5). And the toner image is transferred. At this time, the transfer bias applied to the transfer means (5) is + 950V. Thereafter, the transfer body (for example, transfer paper) (10) is separated from the image carrier (1), and is discharged as a copy via a fixing unit (11). Almost all of the toner developed by the developing means (4) is negatively charged, but a positive charge is supplied to the transfer means (5). Is injected into a positive polarity toner. The pre-cleaning charger (7) supplies a minus corona to the toner, and the toner is recharged to a negative value. As described above, the response speed of the charge behavior of the toner due to the external potential difference and charge is required for the improvement of the speed of the entire process and the stability of the image.
[0020]
An image is formed by the above operation. When one sheet of image is formed, at least one of the rotation direction and the speed of the cleaning means (8) is switched, and at the same time, a negative bias is applied and the collected toner is discharged to the image carrier (1). The discharged toner is conveyed to the developing area as the image carrier (1) rotates. Incidentally, a positive bias is applied to the developing means (4). In the developing area, the magnetic brush applies an impact force to the toner on the image carrier (1) and collects the toner by a bias. By the above operation, toner recycling is realized.
[0021]
The charging step is preferably a contact charging method in which the charging member (2) is brought into contact with the image carrier (1), and a voltage is externally applied to the charging member (2) to charge the image carrier (1). This improves the granularity of the image.
The transfer step is preferably a contact transfer method in which a toner image obtained by developing the electrostatic latent image on the image carrier (1) is electrostatically transferred to a transfer material (P) via a transfer unit (5). . This further improves the granularity of the image.
[0022]
Next, the fixing means (11) will be described in detail.
FIG. 2 is a schematic diagram showing an example of the fixing means (11) of the heat roller type. As a basic configuration, a heating roller (11a) having a heater (14) such as a halogen lamp and an elastic layer (17) such as foamed silicone rubber on a cored bar (16) are provided. And a pressure roller (11b) to be pressed against.
The elastic layer needs to be provided on at least one of the rollers in order to obtain a uniform fixing nip N, and is preferably provided on both. Since one or two rollers have elasticity in the fixing step, the granularity of the image is improved. This is because, due to the elasticity of the roller, the surface of the toner image and the contact point with the transfer paper are more closely contacted with each other, so that the fixing property is improved, and the unevenness of image density and the unevenness of gloss are reduced.
[0023]
A release layer (18) made of a conductive PFA tube or the like is provided on the elastic layer (17) of the pressure roller (11b). The rubber hardness on the axis of the elastic layer (17) is 42 HS (Asuka C), and the release layer (18) has an outer diameter of φ30 and a thickness of 6 mm.
The fixing roller (11a) is provided with an elastic layer (15) made of silicone rubber or the like on an aluminum core (12) having a thickness of 0.4 mm, and further, for the purpose of preventing adhesion due to viscosity of the toner, a fluorine resin or the like. The resin surface layer (13) having good releasability is formed. The thickness of the elastic layer (15) is usually preferably about 100 to 500 μm in consideration of image quality and heat transfer efficiency during fixing. The resin surface layer (13) is formed of a PFA tube or the like similarly to the pressure roller (11b), and its thickness is preferably about 10 to 50 μm in consideration of mechanical deterioration.
In this configuration, in order to obtain the fixing nip portion N, a pressure of 88 N on one side is applied to both ends of the roller, and the surface pressure at that time is 9.3 N / cm.²It has become.
[0024]
Temperature detecting means (19) is provided on the outer peripheral surface of the fixing roller (11a), and by detecting the surface temperature of the fixing roller (11a), a heater (14) is provided so as to keep the temperature substantially constant. Controlling.
In the fixing unit (11) having such a configuration, the fixing roller (11a) and the pressure roller (11b) are pressed against each other with a predetermined pressure to form a fixing nip portion N, and a driving unit (not shown) , And is rotated in the directions of the arrows R1 and R5, respectively, so that the transfer material P is nipped and conveyed in the above-described fixing nip portion N. At this time, the fixing roller (11a) is controlled at a predetermined temperature by the heater (14), and the toner image T on the transfer material P is thermally fused while receiving pressure when passing between the two rollers. After being cooled between the rollers, the image is fixed on the transfer material P as a permanent image.
[0025]
When the toner is abraded in the developing means (4) to produce so-called toner fine powder, the toner fine powder is transferred compared with toner having a normal particle diameter due to a large physical adhesion to the image carrier (1) in a toner transfer step. Hateful. For this reason, the toner fine powder is selectively recycled, and the toner fine powder in the developing means (4) increases.
As a result of analyzing the constituent components of the recycled toner, the DSC curve measured by a differential scanning calorimeter shows that when the calorific ratio of the peak of the wax and the binder resin is compared, the wax strength ratio of the recycled toner is higher than that of the new toner. It was found to be increasing. The calorific value of the peak in the DSC curve is proportional to the content when the same constituent material is used. That is, it was found that the wax content of the recycled toner was increased as compared with the new toner.
[0026]
The toner is apt to be separated from the interface due to non-uniform composition or the like, and is likely to be pulverized. Since the wax is dispersed without being compatible with the binder resin, it is considered that pulverization occurs from this interface. It has been found that this increase in the amount of wax is a major factor causing deterioration of the cohesiveness of the recycled toner. In particular, as described above, the recycled toner is finer than the new toner, and therefore has a larger specific surface area than the replenished toner. Further, when the content is larger than that of the replenishment toner, the amount of wax precipitated on the surface increases, and the cohesiveness deteriorates. Further, since the wax is softer than the binder resin, the external additive is easily embedded. Therefore, when the amount of the wax deposited on the surface increases, the embedding of the external additive is promoted, and the cohesiveness further deteriorates. When such recycled toner is supplied into the developing machine, the broadening of the charge amount distribution of the developer is caused. And the generation of toner having the opposite charge amount causes a poor image.
[0027]
Therefore, in order to suppress the deterioration of the cohesiveness of the recycled toner, in the DSC curve measured by the differential scanning calorimeter, the calorific ratios of the peaks of the wax and the binder resin are Pw and Pb, respectively, and the calorific ratio of Pw and Pb is R In this case, the ratio R2 / R1 of the calorific value ratio R1 of the new toner and the calorific value ratio R2 of the recycled toner needs to be in the range of 1.0 to 1.2.
R = Pw (wax) / Pb (binder resin)
R1: Calorific value ratio Pw of new toner in DSC₁/ Pb₁
R2: Heat value ratio Pw of DSC of recycled toner₂/ Pb₂
R2 / R1 = 1.0-1.2 Equation 3
When R2 / R1 is less than 1.0, the deterioration of the cohesiveness of the recycled toner can be suppressed, but the fixability deteriorates due to the decrease in the wax content. When R2 / R1 exceeds 1.2, the cohesiveness of the recycled toner is extremely deteriorated. When R2 / R1 is in the range of 1.0 to 1.2, an image having good granularity can be obtained even in a recycling system.
[0028]
In order to obtain a range of R2 / R1 = 1.0 to 1.2, it is necessary that each constituent material in the toner, especially wax, is uniformly dispersed. To this end, it is desirable that the wax particle size as a raw material is uniformly distributed in a desired size. For example, the distribution is preferably such that the average particle size is 300 ± 50 μm, the component amount of 700 μm or more is 5% by weight or less, and the component amount of 50 μm or less is 10% by weight or less. In addition, it is necessary to adjust the particle size distribution of the resin to a distribution of, for example, 200 ± 50 μm, the component amount of 400 μm or more is 5% by weight or less, and the component amount of 30 μm or less is 5% by weight or less.
[0029]
As a method for producing a toner used in the present invention, a step of mechanically mixing a toner component containing at least a binder resin, a charge control agent and a pigment, a step of melt-kneading, and rolling while cooling the kneaded material with cooling water. A toner manufacturing method including a step, a pulverizing step, and a classifying step can be applied. Further, in the step of mechanically mixing and the step of melt-kneading, a production method in which powder other than the particles serving as a product obtained in the step of pulverization or classification is returned and reused is also included.
The powder (by-product) other than the particles that become the product referred to here is the fine-grained or coarse particles other than the components that become the product having the desired particle size obtained in the pulverization step after the step of melt-kneading, and the subsequent classification step Means fine particles and coarse particles other than the components that result in the desired particle size. In the mixing step or the melt-kneading step of such a by-product, it is preferable to mix the raw materials and preferably the by-product 1 at a weight ratio of the other raw material 50 to the by-product 50 from the other raw material 99.
[0030]
The mixing step of mechanically mixing the toner components including at least the binder resin, the charge control agent and the pigment, and by-products may be performed under normal conditions using a normal mixer or the like with a rotating wing, and is not particularly limited. .
After the completion of the above mixing step, the mixture is then charged into a kneader and melt-kneaded. As the melt kneader, a uniaxial or biaxial continuous kneader or a batch kneader using a roll mill can be used.
It is important that the melt-kneading is performed under appropriate conditions so as not to cause the molecular chains of the binder resin to be cut. Specifically, the melt-kneading temperature should be determined with reference to the softening point of the binder resin. If the temperature is lower than the softening point, cutting is severe, and if the temperature is too high, dispersion does not proceed.
[0031]
When the above-described melt-kneading step is completed, the kneaded material is then rolled while being cooled by cooling water. Actually, the cooling rate at this time greatly contributes to the dispersibility of wax and other pigments. After cooling, wax and other pigments re-aggregate, so it is desirable to cool as quickly as possible in order to maintain the dispersibility obtained in the melt-kneading step. In the next pulverization step, it is preferable to first perform coarse pulverization and then finely pulverize. At this time, a method of pulverizing by colliding with a collision plate in a jet stream or pulverizing with a narrow gap between a mechanically rotating rotor and a stator is preferably used.
After the completion of the pulverizing step, the pulverized product is classified in a gas stream by centrifugal force or the like, thereby producing a toner having a predetermined particle size, for example, an average particle size of 5 to 10 μm.
[0032]
Further, when preparing the toner, in order to enhance the fluidity and storability of the toner, developability, transferability, the toner produced as described above, such as the hydrophobic silica fine powder further mentioned above in the toner produced above Inorganic fine particles may be added and mixed. (4) A general powder mixer is used for mixing the external additive, but it is preferable that the internal temperature can be adjusted by providing a jacket or the like. In order to change the history of the load applied to the external additive, the external additive may be added during or gradually. Of course, the rotation speed, rolling speed, time, temperature, etc. of the mixer may be changed. A strong load may be applied first, followed by a relatively weak load, or vice versa.
Examples of the mixing equipment that can be used include a V-type mixer, a rocking mixer, a Lodige mixer, a Nauter mixer, and a Henschel mixer.
[0033]
Further, in the recycling system, it is needless to say that the toner has high chargeability, but at the same time, a sharp charge amount distribution and stability of the charge amount with respect to environmental fluctuations at high temperature, high humidity, and low temperature and low humidity are required. Further, in the case of using several tens of printed sheets per day, a faster charging rise property and a higher charging property are required.
For this purpose, the charge control agent is preferably composed of a zirconium compound composed of zirconium and an aromatic oxycarboxylic acid or a salt thereof, or one of chromium complex compounds represented by the following general formula (1).
Embedded image

(Wherein, X represents a hydrogen atom, a lower alkyl group, a nitro group, a halogen atom, etc., which may be the same or different, and A + represents a hydrogen ion, sodium ion, potassium ion, ammonium ion, aliphatic ammonium ion Is shown.)
Further, since the crystal planes are grown on the same plane, high chargeability can be imparted.
[0034]
The zirconium compound composed of zirconium and an aromatic oxycarboxylic acid or a salt thereof has a crystal plane whose main peak A of Bragg angle 2θ with respect to CuKα characteristic X-ray diffraction is 5.5 ° ± 0.3 °, and this X-ray The diffraction intensity is preferably in the range of 2000 to 15000 cps at a scan speed of 0.5 to 4 degrees / minute.
In general, in X-ray diffraction measurement, a crystalline substance shows a unique diffraction peak according to the crystal plane spacing according to Bragg's diffraction condition, and the diffraction intensity depends on the crystal state and the degree of crystallinity. The hardness also depends on the crystallinity in a certain range. 2θ peak A: 5.5 ° ± 0.3 ° is a peak derived from a main component of a zirconium compound composed of zirconium and an aromatic oxycarboxylic acid or a salt thereof.
[0035]
If the strength is less than 2000 cps, the crystallinity is low, so that the bond in the zirconia compound is likely to be broken due to heat or shearing energy during kneading during production, and the chargeability is reduced. In particular, when the charge amount significantly decreases in a high-temperature and high-humidity environment, the amount of the recycled toner increases and the cohesion deteriorates.
If it exceeds 15000 cps, the negative polarity increases and the cohesive force increases, so that the dispersibility with other materials becomes insufficient and a sharp charge amount distribution cannot be obtained.
That is, the main peak of the Bragg angle 2θ for the CuKα characteristic X-ray diffraction is at peak A: 5.5 ° ± 0.3 °, and this X-ray diffraction intensity is 2000 to 2000 at a scan speed of 0.5 to 4 ° / min. When it is in the range of 15000 cps, it is possible to obtain high chargeability and a sharp charge amount distribution even in the recycled toner.
[0036]
Further, the main peak A at a Bragg angle 2θ of the charge control agent with respect to the CuKα characteristic X-ray diffraction is at least main peak A: 5.5 ° ± 0.3 ° and subpeak B: 31.6 ° ± 0.3 °. When the intensity ratio peak A / B is in the range of 3 to 25, the stability of the charge amount with respect to environmental changes at high temperature and high humidity and low temperature and low humidity is further improved.
Subpeak B: 31.6 degrees ± 0.3 degrees corresponds to a plane spacing of 2.8553 to 2.8914 degrees, and has a large electron density, so it is difficult to form a hydrogen bond with water molecules, and the charge amount in a high temperature and high humidity environment is low. It is considered that the decrease can be suppressed. The ratio at this time is preferably such that the peak A / B is in the range of 3 to 25. If it is less than 3, there is no sufficient effect on the charge stability in a high-temperature and high-humidity environment, and if it exceeds 25, the single-crystalline property derived from the main peak becomes insufficient and becomes polycrystalline. It is easy to be broadened, resulting in an increase in transfer residual toner.
[0037]
The chromium complex compound represented by the above-mentioned general formula (1) has a crystal plane in which the measurement angle 2θ in CuKα characteristic X-ray diffraction is in the range of 5 to 30 degrees and the main peak of the Bragg angle 2θ is peak A: It is 8.6 degrees ± 0.3 degrees, which indicates that the X-ray intensity needs to be in the range of 8000 to 15000 cps at a scan speed of 0.5 to 4 degrees / minute. 2θ peak C: 8.6 degrees ± 0.3 degrees is a peak derived from the main component of the chromium complex.
If the strength is less than 8000 cps, the crystallinity is low, so that the heat of the kneading or the energy of shear during the production tends to cause breakage of the chelate bond in the chromium compound, resulting in low chargeability, and particularly high temperature and high temperature. In a humid environment, the charge amount is significantly reduced. On the other hand, if it exceeds 15000 cps, the negative polarity increases and the cohesive force increases, so that the dispersibility with other materials becomes insufficient and a sharp charge amount distribution cannot be obtained.
[0038]
That is, the main peak of the Bragg angle 2θ for the CuKα characteristic X-ray diffraction is at peak C: 8.6 ° ± 0.3 °, and this X-ray intensity is 8000 to 15000 cps at a scan speed of 0.5 to 4 ° / min. When the content is within the range, it is possible to obtain a quick charge rise, high chargeability, a sharp charge amount distribution, and good dispersibility. Further, when the half width of the peak C is 0.30 degrees or less, the charging property becomes sharper, and the peak C is stabilized against environmental fluctuation. It is considered that the half width of the peak is related to the uniformity of the crystalline state, and the uniformity of the crystallinity is improved by setting the half value width to 0.30 degrees or less.
[0039]
Further, the main peak of the Bragg angle 2θ with respect to the CuKα characteristic X-ray diffraction of the charge control agent is at least the main peak C: 8.6 degrees ± 0.3 degrees and the sub-peak D: 7.9 degrees ± 0.3 degrees. When the intensity ratio is such that the intensity of the peak C is 100 and the intensity of the peak D is in the range of 30 to 60, a sharp charge amount distribution with a further rapid rise of charging can be obtained.
Equivalent planes exist in one single crystal plane, and the number of equivalent lattice planes belonging to a certain plane shape is called multiplicity of planes, and these lattice plane groups have equal plane spacing, which is the present invention. In the crystal of the chromium compound, the peaks correspond to subpeaks C and D, and the subpeak C: 8.6 degrees ± 0.3 degrees is 9.927 to 10.634 °, and the subpeak D is 7.9 degrees ± 0.3 degrees. The degree corresponds to a surface spacing of 10.773 to 11.622 °. It has been found that those having crystallinity growing at this plane spacing exhibit extremely good charging characteristics.
Regarding the intensity ratio between the sub-peaks C and D, the structure having the peak D intensity in the range of 30 to 60 when the intensity of the peak C is set to 100 has the sharpest charge amount distribution with the fastest rise of charging. Can be
[0040]
In addition, the toner containing these charge control agents preferably has a peak top molecular weight of 3800 to 4500 in a molecular weight distribution determined by GPC (gel permeation chromatography) determined from a THF-soluble component of the toner. If it is less than 3800, pulverization in the developing means (4) occurs, and if it exceeds 4500, the fixability deteriorates and the image quality deteriorates.
[0041]
When a zirconium compound consisting of zirconium and an aromatic oxycarboxylic acid or a salt thereof is used as the charge control agent according to the present invention, known oxycarboxylic acids can be used, and the oxycarboxylic acid is represented by the following general formula (2). Are preferred from the viewpoint of charge-imparting ability.
Embedded image

[0042]
Further, the following specific examples are preferable from the viewpoint of charging.
Embedded image

[0043]
As the binder resin used for the toner, all conventionally known resins are used. For example, styrene, poly-α-stillstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene Styrene such as maleic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-methyl methacrylate copolymer, styrene-acrylonitrile-acrylic acid ester copolymer Resin (mono- or copolymer containing styrene or styrene substituent), polyester resin, epoxy resin, vinyl chloride resin, rosin-modified maleic resin, phenol resin, polyethylene resin, polypropylene resin, petroleum resin, polyurethane resin, Ketone resin, ethylene-ethylene Examples thereof include a acrylate copolymer, a xylene resin, and a polyvinyl butyrate resin, and it is particularly preferable to use a polyester resin.
[0044]
The polyester resin is obtained by condensation polymerization of an alcohol and a carboxylic acid. Examples of the alcohol used include glycols such as ethylene glycol, diene glycol, triethylene glycol, and propylene glycol, 1,4-bis (hydroxymeth) cyclohexane, and etherified bisphenols such as bisphenol A, and other divalent alcohols. Alcohol monomers and trihydric or higher polyhydric alcohol monomers can be exemplified. Examples of the carboxylic acid include divalent organic acid monomers such as maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, and malonic acid; 1,2,4-benzenetricarboxylic acid; 2,2,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methylenecarboxy Examples thereof include trivalent or higher polyvalent carboxylic acid monomers such as propane, 1, 2, 7, 8-octanetetracarboxylic acid. The Tg of the polyester resin is preferably from 58 to 75C. The above resins may be used alone or in combination of two or more.
Also, the method for producing these resins is not particularly limited, and any of bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization can be used.
[0045]
Further, in the above-mentioned toner, as a coloring agent to be used, all of pigments and dyes which have been conventionally used as coloring agents for toner are applied. Specifically, carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, calco oil blue, oil black, azo oil black and the like are not particularly limited.
The amount of the colorant used is 1 to 10 parts by weight, preferably 3 to 7 parts by weight.
As the wax, for example, polyolefin wax such as polypropylene wax, polyethylene wax and the like, and natural wax such as candelilla wax, rice wax and carnauba wax can be used. The addition amount of the wax component is preferably 0.5 to 10 parts by weight.
[0046]
As described above, other additives can be added to the toner as needed. Examples of the additive include silica, aluminum oxides, and titanium oxides. When the primary purpose is to impart high fluidity, the average primary particle size is preferably from 0.001 to 1 μm, and more preferably from 0.005 to 0.1 μm, as hydrophobized silica or rutile type particulate titanium oxide. The organic silane surface-treated silica or titania is particularly preferred, and is usually used at a ratio of 0.1 to 5% by weight, preferably 0.2 to 2% by weight.
[0047]
Further, for example, when the above toner is used as a two-component dry toner, the carrier used as a mixture is a glass, iron, ferrite, nickel, zircon, silica, or the like as a main component, having a particle size of about 30 to 1000 μm. It can be used by appropriately selecting from powders or those coated with styrene-acrylic resin, silicon-based resin, polyamide-based resin, polyvinylidene fluoride-based resin or the like using the powder as a core material.
[0048]
The following describes each measurement method.
For the measurement of X-ray diffraction of the present invention, for example, RINT1100 manufactured by Hitachi, Ltd. can be used. The measurement is performed using CuKα rays under the following conditions: X-ray tube: Cu, tube voltage: 50 KV, tube current: 30 Ma, scan speed: 2 ° / min.
[0049]
The method of measuring the molecular weight distribution by GPC in the present invention is described below. The column is stabilized in a heat chamber at 40 ° C., and THF (tetrahydrofuran) is flown as a solvent at a flow rate of 1 ml per minute into the column at this temperature, and about 100 μl of a THF sample solution is injected to measure. In measuring the molecular weight of the sample, the molecular weight distribution of the sample was calculated from the relationship between the logarithmic value of a calibration curve prepared from several types of monodisperse polystyrene standard samples and the count number. Examples of the standard polystyrene sample for preparing the calibration curve include, for example, Pressure Chemical Co. It is suitable to use those having a molecular weight of about 100 to 80,000,000 manufactured by Toyo Soda Co., Ltd. and Showa Denko KK, and to use at least about 10 standard polystyrene samples. The detector uses a refractive index detector. As the column, a plurality of commercially available polystyrene gel columns are preferably combined, and examples thereof include a combination of Showex DPC Corporation Shodex GPC KF-801, 802, 803, 804, 805, 806, and 800p.
[0050]
In the present invention, as a method of measuring the calorific ratio of the peak of the wax and the binder resin measured by the differential scanning calorimeter DSC, specifically, TGA-7 and PE7700 (manufactured by PerkinElmer) are used. ８8 mg is precisely weighed, and the peak area of the binder resin and the wax when heated to a temperature of 30 to 200 ° C. at a rate of 10 ° C./min under a nitrogen stream is calculated, and the calorific ratio is calculated from the ratio.
[0051]
【Example】
Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited thereto.
Toner prescription
(Examples 1 to 12)
Polyester resin (glass transition point 65 ° C, containing 30% of THF insoluble matter) 70 parts by weight
Styrene-n-butyl acrylate copolymer 30 parts by weight
Carbon black (Mitsubishi Kasei # 44) 10 parts by weight
Carnauba wax (melting point 82 ° C) 4 parts by weight
Charge control agent obtained by the following formulation: 1 part by weight
[0052]
After kneading using the twin-screw extruder with the above formulation, rolling was performed while cooling and quenching, followed by pulverization and classification to obtain a weight average particle size of 7 μm shown in Table 1. Then, using a Henschel mixer, 1.0 part by weight of silica fine powder (R-972: manufactured by Client Japan) was mixed to obtain a toner.
This toner was mixed with ferrite particles having an average particle size of 50 μm and a carrier coated with a silicone resin at a toner concentration of 4.0% to prepare a two-component developer.
[0053]
(Examples 13 to 20)
Polyester resin (glass transition point 65 ° C, containing 30% of THF insoluble matter) 80 parts by weight
Styrene-n-butyl acrylate copolymer 20 parts by weight
Carbon black (Mitsubishi Kasei # 44) 10 parts by weight
Carnauba wax (melting point 82 ° C) 4 parts by weight
Charge control agent obtained by the following formulation: 1 part by weight
Toners were obtained from the above toner materials by the same additive formulation as in Examples 1 to 12, and two-component developers were obtained in the same manner.
[0054]
(Comparative Examples 1 to 5)
Polyester resin (glass transition point 65 ° C, containing 30% of THF insoluble matter) 80 parts by weight
Styrene-n-butyl acrylate copolymer 20 parts by weight
Carbon black (Mitsubishi Kasei # 44) 10 parts by weight
Carnauba wax (melting point 82 ° C) 4 parts by weight
Charge control agent obtained by the following formulation: 1 part by weight
Toners were obtained from the above toner materials by the same additive formulation as in Examples 1 to 12, and two-component developers were obtained in the same manner.
[0055]
Charge control agent formulation
As a method for obtaining the charge control agent used in Examples 1 to 3, 7 to 40 parts of 5-methoxysalicylic acid and 5-35 parts of 25% caustic soda were dissolved in 200 to 600 parts of water, and the temperature was raised to 50 ° C. While stirring, a solution of 5 to 20 parts of zirconium oxychloride dissolved in 80 to 150 parts of water was added dropwise. After stirring at the same temperature for 0.5 to 2.5 hours, the mixture was cooled at a room temperature of 1 to 10 ° C./min, and adjusted to pH 7.5 to 8.0 by adding about 10 parts of 25% caustic soda. The precipitated crystals were filtered, washed with water and dried to obtain 20 to 30 parts of white crystals.
[0056]
Examples of the charge control agents used in Examples 4 to 12 and Comparative Examples 1 to 5 include 25 to 45 parts of 3,5-di-tert-butylsalicylic acid and 10 to 40 parts of 25% caustic soda in 500 to 800 parts of water. Then, a solution prepared by dissolving 20 to 40 parts of zirconium oxychloride in 100 to 300 parts of water was added dropwise while stirring at 50 ° C. at a rate of 5 to 15 ° C./min. After stirring at the same temperature for 0.5 to 3 hours, the mixture was cooled at a room temperature of 5 to 15 ° C./min, and adjusted to pH 7.5 to 8.0 by adding 3 to 20 parts of 25% caustic soda. The precipitated crystals were filtered, washed with water and dried to obtain 20 to 50 parts of white crystals.
[0057]
As a method for obtaining the charge control agent used in Examples 13 to 20, a mixture obtained by adding 110 g (0.59 mol) of chromium formate (trivalent) to 800 g of ethyl cellosolve and 420 g of ethylene glycol was stirred at 85 ° C. for 1 hour. To this was added 445 g of the monoazo compound, and the mixture was heated to 125 ° C. and stirred for 4 hours. This reaction solution was dispersed in 5000 ml of a 3% hydrochloric acid aqueous solution, stirred at 60 ° C. for 1 hour, and filtered. The collected matter was washed with warm water and dried to obtain 430 g of a purple powder.
[0058]
Recycled toner aggregation degree measurement method
First, a 75-μm mesh sieve, a 45-μm mesh sieve, and a 22-μm mesh sieve are stacked on top of each other, and 2 g of the sample is put into the uppermost sieve. This is vibrated for 30 seconds with a powder tester made by Hosokawa Micron. The remaining amount of toner in the sieve is measured, and the degree of aggregation is calculated by the following equation.
Cohesion degree (%) = {(remaining toner on 75 μm sieve) + 0.6 × (remaining toner on 45 μm sieve) +0.2 (remaining toner on 22 μm sieve)} / 2.0 × 100
[0059]
Measuring method of toner charge amount in each environment
At high temperature and high humidity (30 ° C., 90%) and normal temperature and normal humidity (25 ° C., 65%), a ferrite particle having an average particle diameter of 50 μm is mixed with a carrier coated with a silicone resin at a toner concentration of 4.0%, and the developer is mixed. The charge was measured using a blow-off powder charge meter TB-200 manufactured by Toshiba Chemical Corporation.
[0060]
Fixability and image evaluation method
Ricoh's imageio @ Neo700 machine equipped with a toner recycling mechanism or partially modified was used under the following conditions.
Examples 1 and 2: The fixing roller of the machine was a silicon roller, and a transfer charger was mounted.
Examples 3 to 9: A transfer charger was mounted.
Example 10: The machine was used as it was
Examples 11 to 20, Comparative Examples 1 to 5: A charging roller was mounted on the machine.
[0061]
Evaluation method of fixability
Using the machine described above, copying was performed while varying the heater temperature to obtain a fixed image. A fixing tape (manufactured by 3M) is applied to the image after fixing, and after applying a certain pressure, the film is slowly peeled off. The image density before and after that is measured by a Macbeth densitometer, and the fixing rate is calculated by the following equation. The temperature of the fixing roller is gradually lowered, and the temperature at which the fixing rate represented by the following equation becomes 80% or less is defined as the fixing temperature.
Fixing rate (%) = image density on tape / image density × 100
◎ Excellent ○ Normal △ Slightly inferior
[0062]
Image evaluation method Measurement method of granularity
After printing 50,000 sheets at normal temperature and humidity using the above-described machine, a sample was printed on which a Ricoh standard printer test chart was printed. Next, the grayscale (halftone portion) formed by the dots of the print image was read at 1,000 dpi with a GenaScan 5000 scanner manufactured by Dainippon Screen to obtain image data. The image data was converted into a density distribution, and the granularity was evaluated by Expression 3, and the image evaluation was performed after 50,000 sheets. Subsequently, a sample of the Ricoh standard printer test chart was printed in the same manner after copying for 5 days at 30 ° C., 90% in an environment room at 300 sheets per unit time and 3000 sheets per day, and the granularity was evaluated. The image was evaluated after 15,000 sheets in hot and humid conditions.
[0063]
The following prescription conditions and evaluation results are shown in the following table.
[Table 1]

[0064]
[Table 2]

[0065]
[Table 3]

As can be seen from Tables 1, 2 and 3, by satisfying the conditions of the present invention, it is possible to obtain an image having a low degree of agglomeration of recycled toner, excellent fixability and chargeability, and a good image over time without being affected by environmental conditions. A possible image forming method was obtained.
[0066]
【The invention's effect】
As described above, according to the present invention, in the image forming method equipped with the recycling system, by specifying the calorific ratio obtained by the DSC measurement of the replenishment toner and the recycled toner, the cohesiveness of the recycled toner is not deteriorated, and the granularity is reduced. Can provide an image forming method exhibiting an excellent effect of obtaining good image quality.
Further, the present invention provides an image forming method exhibiting an excellent effect of obtaining a good image quality with a quick start-up property of the charge, no decrease in the charge amount, and a good granularity even when using several tens of sheets per day under high temperature and humidity. I can do it.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus for performing an image forming method of the present invention.
FIG. 2 is a diagram illustrating a fixing unit.
[Explanation of symbols]
1 Image carrier
2) Charging member
3) Exposure means
4 Developing means
5 Transfer means
7 Charger before cleaning
8 Cleaning means
9 Static elimination lamp
11 Fixing means
11a Heating roller
11b pressure roller
12mm core
14 heater
15 elastic layer
16 metal core
17 ° elastic layer
18 ° release layer
19 Temperature detection means
N fixing nip
P transfer material
T toner image

Claims (11)

A charging step of charging the image carrier with a charging member, a step of forming an electrostatic image on the charged image carrier, a developing step of developing the electrostatic image with toner to form a toner image, and a transfer member Transferring a toner image onto a transfer member by applying a voltage to the transfer member, fixing the toner image transferred onto the transfer member by heating with a plurality of rollers, and cleaning the surface of the image carrier after the transfer. An image forming method comprising a recycling step of cleaning with a cleaning member to collect toner on the surface of the image bearing member and supplying the collected toner to the developing step for use.
The toner used in the developing step is a toner containing at least a binder resin, a colorant, a wax, and a charge control agent,
In the DSC curve measured by the differential scanning calorimeter, when the calorific ratio of the peak of the wax is Pw, the calorific ratio of the peak of the binder resin is Pb, and the calorific ratio Pw / Pb of Pw and Pb is R,
An image forming method, wherein the ratio R2 / R1 of the calorific value ratio R1 of the new toner and the calorific value ratio R2 of the recycled toner is in the range of 1.0 to 1.2. 2. The image forming method according to claim 1, wherein in the fixing step, at least one roller has an elastic layer. The said charge control agent consists of a zirconium compound which consists of zirconium and an aromatic oxycarboxylic acid or its salt, or a chromium complex compound shown by the following general formula (1), The characterized by the above-mentioned. Image forming method.

(Wherein, X represents a hydrogen atom, a lower alkyl group, a nitro group, a halogen atom, etc., which may be the same or different, and A + represents a hydrogen ion, sodium ion, potassium ion, ammonium ion, aliphatic ammonium ion Is shown.) The charge control agent comprises a zirconium compound consisting of zirconium and an aromatic oxycarboxylic acid or a salt thereof,
The main peak A of the Bragg angle 2θ for the CuKα characteristic X-ray diffraction of the charge control agent is 5.5 ± 0.3 °, and the X-ray diffraction intensity is 0.5 to 4 ° / min at a scan speed. 4. The image forming method according to claim 3, wherein the value is in a range of 2000 to 15000 cps. The charge control agent comprises a zirconium compound consisting of zirconium and an aromatic oxycarboxylic acid or a salt thereof,
The main peak of the Bragg angle 2θ with respect to CuKα characteristic X-ray diffraction of the charge control agent is 5.5 ° ± 0.3 ° for main peak A, 31.6 ° ± 0.3 ° for sub-peak B, and 5. The image forming method according to claim 3, wherein the intensity ratio A / B of A and B is in a range of 3 to 25. The charge control agent comprises a chromium complex compound represented by the general formula (1),
The main peak C of the Bragg angle 2θ for the CuKα characteristic X-ray diffraction of the charge control agent is 8.6 ± 0.3 °, and the X-ray diffraction intensity is at a scan speed of 0.5 to 4 ° / min. 4. The image forming method according to claim 3, wherein the value is in a range of 8000 to 15000 cps. The charge control agent comprises a chromium complex compound represented by the general formula (1),
At least the main peak of the Bragg angle 2θ of the charge control agent with respect to CuKα characteristic X-ray diffraction has a main peak C of 8.6 ° ± 0.3 ° and a half width of the main peak C of 0.30 ° or less. The image forming method according to claim 3, wherein: The charge control agent comprises a chromium complex compound represented by the general formula (1),
The main peak of the Bragg angle 2θ for the CuKα characteristic X-ray diffraction of the charge control agent has at least a main peak C of 8.6 degrees ± 0.3 degrees and a subpeak D of 7.9 degrees ± 0.3 degrees. 8. The image forming method according to claim 3, wherein the intensity ratio of the peak D is in a range of 30 to 60 when the intensity ratio of the peak C is 100. The toner according to any one of claims 1 to 8, wherein a peak top molecular weight in a molecular weight distribution determined by GPC (gel permeation chromatography) determined by a THF soluble component is in a range of 3800 to 4500. The image forming method as described in the above. 10. The image forming method according to claim 1, wherein in the charging step, the charging member is brought into contact with the image carrier, and a voltage is externally applied to the charging member to charge the image carrier. . 11. The image forming method according to claim 1, wherein in the transfer step, the image carrier and the transfer unit are in contact with each other via a transfer member to transfer the image to the transfer member.

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