JP3907387B2 - Toner and image forming method - Google Patents

Description

（式中、Ｌ₀は、粒子像と同じ投影面積をもつ円の周囲長を示し、Ｌは、粒子の投影像の周囲長を示す。）
により求められる円形度から計算される該トナーの平均円形度を０．９７０以上とすることが、トナーの帯電性の均一化および安定化に極めて有効であることを見出し、本発明に到達したものである。
【００５６】
また、上記の如きトナーを用いることにより、トナーの回収不良に伴うゴースト画像の発生しやすいクリーナレス構成や接触帯電を組み合わせた画像形成方法や、接触帯電工程と一成分非接触現像工程と接触転写工程とを含む画像形成方法においても、感光体の削れ、帯電不良や転写不良が著しく抑制され、長期間の使用においてもカブリその他の画像欠陥の無い高精細な画像が安定して得られることを見出し、本発明に到達したものである。
【００５７】
これは、従来より一般に用いられる磁性酸化鉄を用いた磁性トナーでは達成が困難であったものである。
【００５８】
その理由は、用いる磁性酸化鉄を十分且つ均―に疎水化できていなかったことに起因する。
【００５９】
磁性トナーを製造するときには、表面が疎水化処理された磁性酸化鉄を用いることにより、トナー結着樹脂中への磁性酸化鉄粒子の分散性を向上することができる、また、トナー粒子表面に磁性酸化鉄が多く露出している場合にも、磁性酸化鉄の表面が均一に疎水化処理されていればどのような環境下においてもトナーの帯電性能を損ないにくくなる。
【００６０】
そこで以前より、磁性酸化鉄粒子の表面を疎水化する方法が種々提案されている。しかしながらこれまでの方法では、十分に且つ均一に疎水化された磁性酸化鉄はなかなか得られにくかった。また、処理剤等を多量に使用したり、高粘性の処理剤等を使用した場合、疎水化度は確かに上がるものの、粒子同士の合一等が生じ、疎水性と分散性の両立は必ずしも達成されていなかった。
【００６１】
一般に、未処理の酸化鉄表面は親水性を有しているので、疎水性の酸化鉄を得るには、親水性の酸化鉄を疎水化する必要があるが、これまでの表面処理法では疎水化の均一性が不十分であり、そのような酸化鉄を用いた従来のトナーは湿度などに応じて帯電性が変動してしまい、安定性に欠けるものであった。
【００６２】
これに対し、本発明のトナーにおいて磁性体として使用される酸化鉄は、非常に高いレベルでの疎水化の均一性が図られているものであり、例えば、疎水化する際、水系媒体中で、酸化鉄を一次粒径となるよう分散しながらカップリング剤を加水分解しながら表面処理することによって得られる酸化鉄である。水系媒体中での疎水化処理方法は、気相中での処理に比べ、酸化鉄粒子同士の合一が生じにくく、また疎水化処理による酸化鉄粒子間の帯電反発作用が働き、酸化鉄はほぼ一次粒子の状態で表面処理されるようになるため、高い均一性の疎水化が達成される。
【００６３】
カップリング剤を水系媒体中で加水分解しながら酸化鉄表面を処理する方法は、クロロシラン類やシラザン類のようにガスを発生するようなカップリング剤を使用する必要もなく、さらに、これまで気相中では酸化鉄粒子同士が合一しやすくて、良好な処理が困難であった高粘性のカップリング剤も使用できるようになり、疎水化の効果は絶大である。
【００６４】
本発明に使用できるカップリング剤としては、例えば、シランカップリング剤、チタンカップリング剤が挙げられる。より好ましく用いられるのはシランカップリング剤であり、一般式
Ｒ_mＳｉＹ_n
［式中、Ｒはアルコキシ基を示し、ｍは１〜３の整数を示し、Ｙはアルキル基、ビニル基、グリシドキシ基、メタクリル基の如き炭化水素基を示し、ｎは１〜３の整数を示す。］で示されるものである。例えばビニルトリメトキシシラン、ビニルトリエトキシシラン、γ−メタクリルオキシプロピルトリメトキシシラン、ビニルトリアセトキシシラン、メチルトリメトキシシラン、メチルトリエトキシシラン、イソブチルトリメトキシシラン、ジメチルジメトキシシラン、ジメチルジエトキシシラン、トリメチルメトキシシラン、ヒドロキシプロピルトリメトキシシラン、フェニルトリメトキシシラン、ｎ−ヘキサデシルトリメトキシシラン、ｎ−オクタデシルトリメトキシシランを挙げることができる。
【００６５】
特に、式
Ｃ_pＨ_2p+1−Ｓｉ−（ＯＣ_qＨ_2q+1）₃
［式中、ｐは２〜２０の整数を示し、ｑは１〜３の整数を示す］で示されるアルキルトリアルコキシシランカップリング剤を使用して水系媒体中で酸化鉄を疎水化処理するのが良い。
【００６６】
上記式におけるｐが２より小さいと、疎水化処理は容易となるが、疎水性を十分に付与することが困難であり、またｐが２０より大きいと、疎水性は十分になるが、酸化鉄粒子同士の合一が多くなり、トナー中へ酸化鉄粒子を十分に分散させることが困難になる。
【００６７】
また、ｑが３より大きいと、シランカップリング剤の反応性が低下して疎水化が十分に行われにくくなる。
【００６８】
特に、式中のｐが２〜２０の整数（より好ましくは、３〜１５の整数）を示し、ｑが１〜３の整数（より好ましくは、１又は２の整数）を示すアルキルトリアルコキシシランカップリング剤を使用するのが良い。
【００６９】
その処理量は酸化鉄１００質量部に対して、０．０５〜２０質量部、好ましくは０．１〜１０質量部とするのが良い。
【００７０】
本発明において、水系媒体とは、水を主要成分としている媒体である。具体的には、水系媒体として水そのもの、水に少量の界面活性剤を添加したもの、水にｐＨ調整剤を添加したもの、水に有機溶剤を添加したものが挙げられる。界面活性剤としては、ポリビニルアルコールの如きノンイオン系界面活性剤が好ましい。界面活性剤は、水に対して０．１〜５質量％添加するのが良い。ｐＨ調整剤としては、塩酸の如き無機酸が挙げられる。
【００７１】
撹拌は、例えば撹拌羽根を有する混合機（具体的には、アトライター、ＴＫホモミキサーの如き高剪断力混合装置）で、酸化鉄微粒子が水系媒体中で、一次粒子になるように充分におこなうのが良い。
【００７２】
こうして得られる酸化鉄粒子は表面が均一に疎水化処理されているため、トナー材料として用いた場合、トナー中への分散性が非常に良好であり、しかもトナー表面からの露出が無い。従って、こういった酸化鉄を用いることにより、Ｘ線光電子分光分析により測定されるトナーの表面に存在する炭素元素の含有量（Ａ）に対する鉄元素の含有量（Ｂ）の比（Ｂ／Ａ）が０．００１未満という本発明のトナーを得ることが可能となり、トナーの帯電の均一性及び安定化が達成でき、このトナーを用いることによって、高画質及び高耐久安定性が達成できる。さらには、（Ｂ／Ａ）を０．０００５未満とすることで、帯電性及び安定性がより一層向上する。
【００７３】
本発明のトナーに用いられる酸化鉄は、例えば下記方法で製造される。
【００７４】
硫酸第一鉄水溶液に、鉄成分に対して当量または当量以上の水酸化ナトリウムの如きアルカリを加え、水酸化第一鉄を含む水溶液を調製する。調製した水溶液のｐＨをｐＨ７以上（好ましくはｐＨ８〜１０）に維持しながら空気を吹き込み、水溶液を７０℃以上に加温しながら水酸化第一鉄の酸化反応をおこない、磁性酸化鉄粒子の芯となる種晶をまず生成する。
【００７５】
次に、種晶を含むスラリー状の液に、前に加えたアルカリの添加量を基準として約１当量の硫酸第一鉄を含む水溶液を加える。液のｐＨを６〜１０に維持しながら空気を吹込みながら水酸化第一鉄の反応をすすめ種晶を芯にして磁性酸化鉄粒子を成長させる。酸化反応がすすむにつれて液のｐＨは酸性側に移行していくが、液のｐＨは６未満にしない方が好ましい。酸化反応の終期に液のｐＨを調整し、磁性酸化鉄が一次粒子になるよう十分に撹拌し、カップリング剤を添加して十分に混合撹拌し、撹拌後に濾過し、乾燥し、軽く解砕することで疎水性処理磁性酸化鉄粒子が得られる。あるいは、酸化反応終了後、洗浄、濾過して得られた酸化鉄粒子を、乾操せずに別の水系媒体中に再分散させた後、再分散液のｐＨを調整し、十分撹拌しながらシランカップリング剤を添加し、カップリング処理を行っても良い。
【００７６】
いずれにせよ、水溶液中で生成した未処理の酸化鉄粒子を、乾燥工程を経る前の含水スラリーの状態で疎水化することが肝要である。これは、未処理の酸化鉄粒子をそのまま乾燥してしまうと粒子同士の凝集による合一が避けられず、こういった凝集状態の粉末にたとえ湿式疎水化処理を行なっても均一な疎水化処理が難しいためであり、このような表面処理酸化鉄を用いたトナーでは、本発明に係るトナーの如く、Ｂ／Ａ＜０．００１を達成することは困難だからである。
【００７７】
第一鉄塩としては、一般的に硫酸法チタン製造に副生する硫酸鉄、鋼板の表面洗浄に伴って副生する硫酸鉄の利用が可能であり、更に塩化鉄等が可能である。
【００７８】
水溶液法による磁性酸化鉄の製造方法は一般に反応時の粘度の上昇を防ぐこと、及び、硫酸鉄の溶解度から鉄濃度０．５〜２ｍｏｌ／リットルが用いられる。硫酸鉄の濃度は一般に薄いほど製品の粒度が細かくなる傾向を有する。また、反応に際しては、空気量が多い程、そして反応温度が低いほど微粒化しやすい。
【００７９】
このようにして製造された疎水性酸化鉄粒子をトナーに使用することにより、画像特性及び安定性に優れた本発明のトナーを得ることが可能となる。
【００８０】
なお、特公昭６０−３１８１号公報においても、表面をシランカップリング剤で湿式処理した磁性体微粒子を含有する磁性重合トナーの製造方法が開示されている。
【００８１】
しかしながら、特公昭６０−３１８１号公報は、乾燥粉末状の未処理磁性体をシランカップリング剤で湿式表面処理することに関して記載しているものである。
【００８２】
こういった未処理の乾燥磁性体粉末は、乾燥時の一次凝集による粒子同士の合一が避けられないため、湿式表面処理を行なっても個々の磁性体粒子の均一な疎水化は困難である。従ってこのような表面処理磁性体を用いて重合トナーを製造しても、本発明に係るトナーの特徴であるＢ／Ａ＜０．００１を達成することは困難である。
【００８３】
トナーの投影面積相当径をＣとし透過型電子顕微鏡（ＴＥＭ）を用いた該トナーの断面観察における酸化鉄とトナー表面との距離の最小値をＤとしたとき、Ｄ／Ｃ≦０．０２の関係を満たすトナーの個数が５０％以上であることもまた、本発明のトナーに必要な態様の一つである。
【００８４】
本発明においては、Ｄ／Ｃ≦０．０２の関係を満たすトナー数が５０％以上であることが必要であり、６５％以上が好ましく、７５％以上がさらに好ましい。
【００８５】
Ｄ／Ｃ≦０．０２の関係を満たすトナー数が５０％未満の場合には、過半数のトナーにおいて少なくともＤ／Ｃ＝０．０２境界線よりも外側には磁性粒子が全く存在しないことになる。仮にこのような粒子を球形として想定すると、１つのトナーを全空間とした場合に酸化鉄の存在しない空間は、トナーの表面に少なくとも１１．５％は存在することになる。実際には、最近接位置に酸化鉄が均一に整列してトナー内部に内壁を作るように存在するわけではないので１２％以上になることは明らかである。この様な粒子から構成されるトナーにおいては、前述の如き様々な弊害が生じやすい。
【００８６】
本発明において、ＴＥＭによる具体的なＤ／Ｃの測定方法としては、常温硬化性のエポキシ樹脂中へ観察すべき粒子を十分に分散させた後に温度４０℃の雰囲気中で２日間硬化させ得られた硬化物を、そのまま、あるいは凍結してダイヤモンド歯を備えたミクロトームにより薄片状のサンプルとして観察する方法が好ましい。
【００８７】
該当する粒子数の割合の具体的な決定方法については、以下のとおりである。ＴＥＭにてＤ／Ｃを決定するための粒子は、顕微鏡写真での断面積から円相当径を求め、その値がコールターカウンターを用いる後述の方法により求めた数平均粒径の±１０％の幅に含まれるものを該当粒子とし、その該当粒子１００個について、磁性粒子表面との距離の最小値（Ｄ）を計測し、Ｄ／Ｃを求め、Ｄ／Ｃ値が０．０２以下の粒子の割合を計算する。このときの顕微鏡写真は精度の高い測定を行うために、１万〜２万倍の倍率が好適である。本発明では、透過型電子顕微鏡（日立製Ｈ−６００型）を装置として用い、加速電圧１００ｋＶで観察し、拡大倍率が１万倍の顕微鏡写真を用いて観察、測定した。
【００８８】
Ｂ／Ａ＜０．００１を満足し、Ｄ／Ｃ≦０．０２の関係を満足するトナー数が５０％以上であるようなトナーとは、磁性体がトナー表面に局在していたり、また逆に極端に内包化されてトナー内部に偏在していたりしているようなトナーではなく、磁性体がトナー中に、実質的に均一に分散されつつ、トナー表面への磁性体の露出が抑制されているトナーであります。磁性体の分散状態が不均一であるような場合には、本願発明にかかる規定を満足することは困難であります。
【００８９】
また、酸化鉄がトナー粒子表面にほとんど露出していない磁性現像剤を用いれば、帯電部材や転写部材等によりトナーが静電荷像担持体表面に圧接される様な画像形成方法においても、静電荷像担持体表面を削ることはほとんど無く、長期にわたり静電荷像担持体の削れやトナー融着を著しく低減させることが可能となる。
【００９０】
本発明のトナーに用られる酸化鉄は、結着樹脂１００質量部に対して、１０〜２００質量部用いることが好ましく、２０〜１８０質量部用いることが更に好ましい。酸化鉄の配合量が１０質量部未満では現像剤の着色力が乏しく、カブリの抑制も困難であり、一方、２００質量部を越えると、現像剤担持体への磁力による保磁力が強まり現像性が低下したり、個々のトナー粒子への酸化鉄の均一な分散が難しくなるだけでなく、定着性が低下してしまう。
【００９１】
次に、本発明のもう一つの特徴であるトナーの円形度について説明する。静電荷像担持体上の非画像部へのトナー付着や転写残余トナー量を低減するには、トナー粒子の帯電性が十分で且つ均一であることが必要である。さらに、高画質化の観点から微小粒径のトナーを用いる場合は、トナー粒子の付着力が増大するため、トナー粒子の形状も静電荷像担持体上の非画像部へのトナー付着に大きな影響を及ぼす。すなわち、トナー粒子が球形に近く、形状が揃っているほど粒子の付着面積が減少し、静電荷像担持体上の非画像部へのトナー付着や転写残余トナー量が低減され、高画質及び耐久安定性が達成される。
【００９２】
加えて、本発明に係るトナー粒子は帯電性が十分であり、且つ上述した如く、トナー粒子の付着力が低減されていることにより、静電荷像担持体から紙等の転写材へのトナーの転写効率も大きく改善される。これは、微小ドット画像の再現性と共に高解像性を達成するための重要なトナー性能と言える。
【００９３】
従って、本発明のトナーにおいては、トナーの平均円形度が０．９７０以上である必要があり、これによって高画質や高安定性が達成される。
【００９４】
従って、このような現像剤を用いれば転写残トナーが非常に低減されるため、帯電部材と感光体との圧接部におけるトナーの存在量が非常に少なく、接触帯電工程を有する画像形成方法においても、感光体の削れ及びトナー融着が防止され、画像欠陥が著しく抑制されるものと考えられる。さらに、平均円形度が０．９７０以上のトナーは表面のエッジ部がほとんど無いため、帯電部材と感光体との圧接部において感光体表面を引っ掻くことが無いことから、感光体表面の削れが抑制されることも挙げられる。
【００９５】
これらの効果は、転写中抜けの発生しやすい接触転写工程を含む画像形成方法においても、顕著となって現れる。
【００９６】
本発明のトナーにおいては、重量平均粒径が２〜１０μｍであることが好ましい。
【００９７】
トナーの重量平均粒径が１０μｍを超えるような場合、微小ドット画像の再現性が低下するため、本発明により得られる過酷環境下でのトナーの帯電安定性が十分発揮し得ない。一方、トナーの重量平均粒径が２μｍより小さい場合には、本発明の特殊な酸化鉄を用いてもトナーの流動性は著しく低くなり、帯電不良によるカブリ、濃度うす等の問題が発生しやすくなる。
【００９８】
つまり、本発明のトナーにおいて帯電安定性や流動性の改善等、従来例と比較して顕著な効果が画像上に現れるのは、重量平均粒径が２〜１０μｍ（より好ましくは、３〜１０μｍ）であり、さらに、より一層の高画質化という点では３．５〜８．０μｍが好ましい。
【００９９】
次に本発明におけるトナーの製造方法を説明する。
【０１００】
本発明のトナーは、粉砕法によって製造することも可能であるが、粉砕法ではトナーの平均円形度を０．９７０以上とするために機械的、熱的あるいは何らかの特殊な処理を行うことが必要となることから、懸濁重合法により製造することが好ましい。通常の磁性体を用いて懸濁重合によりトナーを製造したとしても、磁性体が分散性に劣るために磁性体がトナー表面に偏在してしまったり、水系媒体中における造粒時に磁性体が乱雑に動き、それに引きずられて粒子形状がゆがんだりするために、平均円形度が０．９７０以上のトナーは得られがたいものであったが、本発明において用いられる酸化鉄は、高いレベルでの均一な疎水化が行われているため、平均円形度が０．９７０以上のトナーを容易に得ることができる。
【０１０１】
本発明に使用される重合性単量体系を構成する重合性単量体としては以下のものが挙げられる。
【０１０２】
重合性単量体としては、スチレン、ｏ−メチルスチレン、ｍ−メチルスチレン、ｐ−メチルスチレン、ｐ−メトキシスチレン、ｐ−エチルスチレンの如きスチレン系単量体；アクリル酸メチル、アクリル酸エチル、アクリル酸ｎ−ブチル、アクリル酸イソブチル、アクリル酸ｎ−プロピル、アクリル酸ｎ−オクチル、アクリル酸ドデシル、アクリル酸２−エチルヘキシル、アクリル酸ステアリル、アクリル酸２−クロルエチル、アクリル酸フェニルの如きアクリル酸エステル類；メタクリル酸メチル、メタクリル酸エチル、メタクリル酸ｎ−プロピル、メタクリル酸ｎ−ブチル、メタクリル酸イソブチル、メタクリル酸ｎ−オクチル、メタクリル酸ドデシル、メタクリル酸２−エチルヘキシル、メタクリル酸ステアリル、メタクリル酸フェニル、メタクリル酸ジメチルアミノエチル、メタクリル酸ジエチルアミノエチルの如きメタクリル酸エステル類；アクリロニトリル、メタクリロニトリル、アクリルアミドが挙げられる。
【０１０３】
これらの単量体は単独または混合して使用し得る。上述の単量体の中でも、スチレンまたはスチレン誘導体を単独で、あるいはほかの単量体と混合して使用することがトナーの現像特性及び耐久性の点から好ましい。
【０１０４】
また、本発明のトナーは、結着樹脂に対して０．５〜５０質量％の離型剤を含有することも好ましい使用形態の一つである。通常、トナー像は、転写工程で転写材上に転写され、そして、このトナー像はその後、熱・圧力等のエネルギーにより転写材上に定着され、半永久的な画像が得られる。この際の定着方法としては、熱ロール式定着が一般に良く用いられるが、上記のように、重量平均粒径が１０μｍ以下のトナーを用いれば非常に高精細な画像を得ることができるが、粒径の細かいトナー粒子は紙等の転写材を使用した場合に紙の繊維の隙間に入り込み、熱定着用ローラーからの熱の受け取りが不十分となり、低温オフセットが発生しやすい。しかしながら、本発明のトナーにおいて、離型剤として適正量のワックスを含有させることにより、高解像性と耐オフセット性を両立させつつ感光体の削れを防止することが可能となる。
【０１０５】
本発明のトナーに使用可能なワックスとしては、パラフィンワックス、マイクロクリスタリンワックス、ペトロラクタムの如き石油系ワックス及びその誘導体、モンタンワックスびその誘導体、フィッシャートロプシュ法による炭化水素ワックス及びその誘導体、ポリエチレンに代表されるポリオレフィンワックス及びその誘導体、カルナバワックス、キャンデリラワックスの如き天然ワックス及びその誘導体などが含まれる。ここでの誘導体には酸化物や、ビニル系モノマーとのブロック共重合物、グラフト変性物が含まれる。さらに、高級脂肪族アルコール、ステアリン酸、パルミチン酸の如き脂肪酸またはその化合物、酸アミドワックス、エステルワックス、ケトン、硬化ヒマシ油及びその誘導体、植物系ワックス、動物性ワックスも使用できる。
【０１０６】
これらのワックス成分の内では、示差走査熱量計により測定されるＤＳＣ曲線において、昇温時に４０〜１１０℃の領域に最大吸熱ピークを有するものが好ましく、４５〜９０℃の領域に最大吸熱ピークを有するものが更に好ましい。上記の温度領域に最大吸熱ピークを有することにより、低温定着に大きく貢献しつつ、離型性をも効果的に発現することができる。この最大吸熱ピークが４０℃未満であるとワックス成分の自己凝集力が弱くなり、結果として耐高温オフセット性が悪化する。一方、この最大吸熱ピークが１１０℃を越えると定着温度が高くなり低温オフセットが発生しやすくなり好ましくない。さらに、水系媒体中で造粒／重合を行い重合方法により直接トナーを得る場合、この最大吸熱ピーク温度が高いと、主に造粒中にワックス成分が析出する等の問題が生じるため好ましくない。
【０１０７】
ワックス成分の最大吸熱ピーク温度の測定は、「ＡＳＴＭ Ｄ ３４１８−８」に準じて行う。測定には、例えばパーキンエルマー社製ＤＳＣ−７を用いる。装置検出部の温度補正はインジウムと亜鉛の融点を用い、熱量の補正についてはインジウムの融解熱を用いる。測定サンプルにはアルミニウム製のパンを用い、対照用に空パンをセットし、昇温速度１０℃／ｍｉｎで測定を行う。
【０１０８】
本発明のトナーにおいて、上記のワックス成分の含有量は、結着樹脂に対して０．５〜５０質量％の範囲であるのが好ましい。ワックス成分の含有量が０．５質量％未満では低温オフセット抑制効果に乏しく、５０質量％を超えてしまうと長期間の保存性が低下すると共に、他のトナー材料の分散性が悪くなり、トナーの流動性の劣化や画像特性の低下につながる。
【０１０９】
本発明では、単量体系に樹脂を添加して重合しても良い。例えば、単量体では水溶性のため水性懸濁液中では溶解して乳化重合を起こすため使用できないアミノ基、カルボン酸基、水酸基、スルフォン酸基、グリシジル基、ニトリル基の如き親水性官能基含有の単量体成分をトナー中に導入したい時には、これらとスチレンあるいはエチレン等ビニル化合物とのランダム共重合体、ブロック共重合体、あるいはグラフト共重合体の如き共重合体の形にして、あるいはポリエステル、ポリアミドの如き重縮合体、ポリエーテル、ポリイミンの如き重付加重合体の形で使用が可能となる。こうした極性官能基を含む高分子重合体をトナー中に共存させると、前述のワックス成分を相分離させ、より内包化が強力となり、耐オフセット性、耐ブロッキング性、低温定着性の良好なトナーを得ることができる。その使用量としては、重合性単量体１００質量部に対して１〜２０質量部が好ましい。使用量が１質量部未満では添加効果が小さく、一方２０質量部を超えて使用された場合には、重合トナーの種々の物性設計が難しくなってしまう。またこれら極性官能基を含む高分子重合体の平均分子量は３０００以上が好ましく用いられる。分子量３０００未満、特に２０００以下では、本重合体が表面付近に集中し易いことから、現像性、耐ブロッキング性等に悪い影響が起こり易くなり好ましくない。また、単量体を重合して得られるトナーの分子量範囲とは異なる分子量の重合体を単量体中に溶解して重合すれば、分子量分布の広い、耐オフセット性の高いトナーを得ることができる。
【０１１０】
本発明のトナーには、荷電特性を安定化するために荷電制御剤を配合しても良い。荷電制御剤としては、公知のものが利用できるが、特に帯電スピードが速く、且つ、一定の帯電量を安定して維持できる荷電制御剤が好ましい。
【０１１１】
さらに、トナーを直接重合法を用いて製造する場合には、重合阻害性が低く、水系分散媒体への可溶化物が実質的にない荷電制御剤が特に好ましい。具体的な化合物としては、ネガ系荷電制御剤としてサリチル酸、アルキルサリチル酸、ジアルキルサリチル酸、ナフトエ酸、ダイカルボン酸の如き芳香族カルボン酸の金属化合物、アゾ染料もしくはアゾ顔料の金属塩または金属錯体、スルホン酸又はカルボン酸基を側鎖に持つ高分子型化合物、ホウ素化合物、尿素化合物、ケイ素化合物、カリックスアレーンが挙げられる。ポジ系荷電制御剤として四級アンモニウム塩、その四級アンモニウム塩を側鎖に有する高分子型化合物、グアニジン化合物、ニグロシン系化合物、イミダゾール化合物が挙げられる。これらの荷電制御剤は、重合性単量体１００質量部に対して０．５〜１０質量部使用することが好ましい。しかしながら、本発明の画像形成方法に関わる現像剤は、荷電制御剤の添加は必須ではなく、現像剤の層圧規制部材や現像剤担持体との摩擦帯電を積極的に利用することでトナー中に必ずしも荷電制御剤を含む必要はない。
【０１１２】
また、本発明のトナーにおいて磁性体として用いられる酸化鉄は、リン、コバルト、ニッケル、銅、マグネシウム、マンガン、アルミニウム、ケイ素の如き元素を含んでもよく、四三酸化鉄、γ−酸化鉄を主成分とするものであり、これらを１種または２種以上を併用して用いられる。これら酸化鉄は、窒素吸着法によるＢＥＴ比表面積が好ましくは２〜３０ｍ²／ｇ、特に３〜２８ｍ²／ｇであり、更にモース硬度が５〜７のものが好ましい。
【０１１３】
また、酸化鉄の形状としては、８面体、６面体、球状、針状、鱗片状などがあるが、８面体、６面体、球状、不定形の如き異方性の少ないものが画像濃度を高める上で好ましい。こういった形状は、ＳＥＭなどによって確認することができる。酸化鉄の粒度としては、０．０３μｍ以上の粒径を有する粒子を対象とした粒度の測定において、体積平均粒径が、０．１〜０．３μｍであり、かつ０．０３〜０．１μｍの粒子が４０個数％以下であることが好ましい。
【０１１４】
平均粒径が０．１μｍ未満の酸化鉄を用いた磁性トナーから画像を得ると、画像の色味が赤味にシフトし、画像の黒色度が不足したり、ハーフトーン画像ではより赤味が強く感じられる傾向が強くなるなど、一般的に好ましいものではない。また、酸化鉄の表面積が増大するために分散性が低下し、製造時に要するエネルギーが増大し、効率的ではない。また、酸化鉄の着色剤としての効果が弱くなり、画像の濃度が不足することもあり、好ましいものではない。
【０１１５】
一方、酸化鉄の平均粒径が０．３μｍを超えると、一粒子あたりの質量が大きくなるため、製造時にバインダーとの比重差の影響でトナー表面に露出する確率が高まったり、製造装置の摩耗などが著しくなる可能性が高まったり、分散物の沈降安定性などが低下するため好ましくない。
【０１１６】
また、トナー中において、該酸化鉄の０．１μｍ以下の粒子が４０個数％を超えると、酸化鉄の表面積が増大して分散性が低下し、トナー中にて凝集塊を生じやすくなりトナーの帯電性を損なったり、着色力が低下したりする可能性が高まるため４０個数％以下であることが好ましい。さらに、３０個数％以下とすると、その傾向はより小さくなるため、より好ましい。
【０１１７】
尚、０．０３μｍ未満の酸化鉄は、粒子径が小さいことに起因してトナー製造時に受ける応力が小さいため、トナー粒子の表面へ出る確率が低くなる。さらに、仮に粒子表面に露出してもリークサイトとして作用することはほとんど無く実質上問題とならない。そのため、本発明では、０．０３〜０．１μｍの粒子に注目し、その個数％を定義するものである。
【０１１８】
また、酸化鉄中の０．３μｍ以上の粒子が１０個数％を超えると、着色力が低下し、画像濃度が低下する傾向になることに加え、同じ使用量であっても個数的に少ないためにトナー粒子表面の近傍まで存在させること及び各トナー粒子に均一個数を含有させることが確率的に難しくなり、好ましくない。より好ましくは５個数％以下とするのが良い。
【０１１９】
本発明においては、前述の粒度分布の条件を満たすよう、酸化鉄製造条件を設定したり、予め粉砕及び分級の如き粒度分布の調整を行ったものを使用することが好ましい。分級方法としては、例えば、遠心分離やシックナーといった沈降分離を利用したものや、例えばサイクロンを利用した湿式分級装置などの手段が好適である。
【０１２０】
酸化鉄の体積平均粒径及び粒度分布の決定は、以下の測定方法によって行う。粒子を十分に分散させた状態で、透過型電子顕微鏡（ＴＥＭ）において３万倍の拡大倍率の写真で視野中の１００個の酸化鉄粒子のそれぞれ投影面積を測定し、測定された各粒子の投影面積に等しい円の相当径を各粒子径として求めた。さらに、その結果を基に、体積平均粒径の算出ならび０．０３〜０．１μｍの粒子と、０．３μｍ以上の粒子の個数％を計算した。尚、粒度の測定は、０．０３μｍ以上の粒径を有する粒子を対象とした。また、画像解析装置により粒子径を測定することも可能である。
【０１２１】
トナー粒子中の酸化鉄の体積平均粒径及び粒度分布を決定する場合には、以下の測定方法により行う。
【０１２２】
エポキシ樹脂中へ観察すべきトナー粒子を十分に分散させた後、温度４０℃の雰囲気中で２日間硬化させ得られた硬化物を、ミクロトームにより薄片状のサンプルとして、透過型電子顕微鏡（ＴＥＭ）において１万〜４万倍の拡大倍率の写真で視野中の１００個の酸化鉄の粒子径のそれぞれ投影面積を測定し、測定された各粒子の投影面積に等しい円の相当径を酸化鉄の粒子径として求めた。さらに、その結果を基に、０．０３〜０．１μｍの粒子と、０．３μｍ以上の粒子の個数％を計算した。また、画像解析装置により粒子径を測定することも可能である。
【０１２３】
さらにまた、酸化鉄以外に他の着色剤を併用しても良い。併用し得る着色材料としては、磁性あるいは非磁性無機化合物、公知の染料及び顔料が挙げられる。具体的には、例えば、コバルト、ニッケルの如き強磁性金属粒子、またはこれらにクロム、マンガン、銅、亜鉛、アルミニウム、希土類元素を加えた合金、ヘマタイト、チタンブラック、ニグロシン染料／顔料、カーボンブラック、フタロシアニンが挙げられる。これらもまた、表面を処理して用いても良い。
【０１２４】
本発明に使用する重合開始剤としては重合反応時に半減期０．５〜３０時間であるものを、重合性単量体の０．５〜２０質量％の添加量で重合反応を行なうと、分子量１万〜１０万の間に極大を有する重合体を得、トナーに望ましい強度と適当な溶融特性を与えることができる。重合開始剤の例としては、２，２’−アゾビス−（２，４−ジメチルバレロニトリル）、２，２’−アゾビスイソブチロニトリル、１，１’−アゾビス（シクロヘキサン−１−カルボニトリル）、２，２’−アゾビス−４−メトキシ−２，４−ジメチルバレロニトリル、アゾビスイソブチロニトリルの如きアゾ系またはジアゾ系重合開始剤；ベンゾイルパーオキサイド、メチルエチルケトンパーオキサイド、ジイソプロピルパーオキシカーボネート、クメンヒドロパーオキサイド、２，４−ジクロロベンゾイルパーオキサイド、ラウロイルパーオキサイドの如き過酸化物系重合開始剤が挙げられる。
【０１２５】
本発明では、架橋剤を添加しても良く、好ましい添加量としては、重合性単量体の０．００１〜１５質量％である。
【０１２６】
懸濁重合法によるトナーの製造では、一般に上述のトナー組成物、すなわち重合性単量体中に、酸化鉄、着色剤、離型剤、可塑剤、結着剤、荷電制御剤、架橋剤等トナーとして必要な成分及びその他の添加剤、例えば重合反応で生成する重合体の粘度を低下させるために入れる有機溶媒、分散剤等を適宜加えて、ホモジナイザー、ボールミル、コロイドミル、超音波分散機等の分散機に依って均一に溶解または分散せしめた単量体系を、分散安定剤を含有する水系媒体中に懸濁する。この時、高速撹拌機もしくは超音波分散機のような高速分散機を使用して一気に所望のトナー粒子のサイズとするほうが、得られるトナー粒子の粒径がシャープになる。重合開始剤添加の時期としては、重合性単量体中に他の添加剤を添加する時同時に加えても良いし、水系媒体中に懸濁する直前に混合しても良い。また、造粒直後、重合反応を開始する前に重合性単量体あるいは溶媒に溶解した重合開始剤を加えることもできる。
【０１２７】
造粒後は、通常の撹拌機を用いて、粒子状態が維持され且つ粒子の浮遊・沈降が防止される程度の撹拌を行なえば良い。
【０１２８】
本発明の懸濁重合法においては、分散安定剤として公知の界面活性剤や有機・無機分散剤が使用でき、中でも無機分散剤が有害な超微粉を生じ難く、その立体障害性により分散安定性を得ているので反応温度を変化させても安定性が崩れ難く、洗浄も容易でトナーに悪影響を与え難いので、好ましく使用できる。こうした無機分散剤の例としては、燐酸カルシウム、燐酸マグネシウム、燐酸アルミニウム、燐酸亜鉛の如き燐酸多価金属塩；炭酸カルシウム、炭酸マグネシウムの如き炭酸塩；メタ硅酸カルシウム、硫酸カルシウム、硫酸バリウムの如き無機塩；水酸化カルシウム、水酸化マグネシウム、水酸化アルミニウム、シリカ、ベントナイト、アルミナの如き無機酸化物が挙げられる。
【０１２９】
これらの無機分散剤は、重合性単量体１００質量部に対して、０．２〜２０質量部を単独でまたは２種類以上組み合わせて使用することが好ましい。平均粒径が５μｍ以下である様な、より微粒化されたトナーを目的とする場合には、０．００１〜０．１質量部の界面活性剤を併用しても良い。
【０１３０】
界面活性剤としては、例えばドデシルベンゼン硫酸ナトリウム、テトラデシル硫酸ナトリウム、ペンタデシル硫酸ナトリウム、オクチル硫酸ナトリウム、オレイン酸ナトリウム、ラウリル酸ナトリウム、ステアリン酸ナトリウム、ステアリン酸カリウムが挙げられる。
【０１３１】
これら無機分散剤を用いる場合には、そのまま使用しても良いが、より細かい粒子を得るため、水系媒体中にて該無機分散剤粒子を生成させることができる。例えば、燐酸カルシウムの場合、高速撹拌下、燐酸ナトリウム水溶液と塩化カルシウム水溶液とを混合して、水不溶性の燐酸カルシウムを生成させることができ、より均一で細かな分散が可能となる。この時、同時に水溶性の塩化ナトリウム塩が副生するが、水系媒体中に水溶性塩が存在すると、重合性単量体の水への溶解が抑制されて、乳化重合に依る超微粒トナーが発生し難くなるので、より好都合である。重合反応終期に残存重合性単量体を除去する時には障害となることから、水系媒体を交換するか、イオン交換樹脂で脱塩したほうが良い。無機分散剤は、重合終了後酸あるいはアルカリで溶解して、ほぼ完全に取り除くことができる。
【０１３２】
前記重合工程においては、重合温度は４０℃以上、一般には５０〜９０℃の温度に設定して重合を行なう。この温度範囲で重合を行なうと、内部に封じられるべき離型剤やワックスの類が、相分離により析出して内包化がより完全となる。残存する重合性単量体を消費するために、重合反応終期ならば、反応温度を９０〜１５０℃にまで上げることは可能である。
【０１３３】
また、本発明のトナーには、流動性向上剤として、無機微粉体または疎水性無機微粉体が混合されることが好ましい。例えば、酸化チタン微粉末、シリカ微粉末、アルミナ微粉末を添加して用いることが好ましく、特にシリカ微粉末を用いることが好ましい。
【０１３４】
現像剤に用いられる無機微粉体は、ＢＥＴ法で測定した窒素吸着による比表面積が３０ｍ²／ｇ以上のもの、特に５０〜４００ｍ²／ｇの範囲のものが良好な結果を与えることができるため好ましい。
【０１３５】
本発明に用いられるシリカ微粉体はケイ素ハロゲン化合物の蒸気相酸化により生成されたいわゆる乾式法またはヒュームドシリカと称される乾式シリカ及び水ガラス等から製造されるいわゆる湿式シリカの両方が使用可能であるが、表面及び内部にあるシラノール基が少なく、製造残渣のない乾式シリカが好ましく用いられる。
【０１３６】
さらに本発明に用いるシリカ微粉体は疎水化処理されているものが好ましい。疎水化処理するには、シリカ微粉体と反応あるいは物理吸着する有機ケイ素化合物などで化学的に処理することによって付与される。好ましい方法としては、ケイ素ハロゲン化合物の蒸気相酸化により生成された乾式シリカ微粉体をシランカップリング剤で処理した後、あるいはシランカップリング剤で処理すると同時にシリコーンオイルの如き有機ケイ素化合物で処理する方法が挙げられる。
【０１３７】
疎水化処理に使用されるシランカップリング剤としては、例えばヘキサメチルジシラザン、トリメチルシラン、トリメチルクロルシラン、トリメチルエトキシシラン、ジメチルジクロルシラン、メチルトリクロルシラン、アリルジメチルクロルシラン、アリルフェニルジクロルシラン、ベンジルジメチルクロルシラン、ブロムメチルジメチルクロルシラン、α−クロルエチルトリクロルシラン、β−クロルエチルトリクロルシラン、クロルメチルジメチルクロルシラン、トリオルガノシランメルカプタン、トリメチルシリルメルカプタン、トリオルガノシリルアクリレート、ビニルジメチルアセトキシシラン、ジメチルエトキシシラン、ジメチルジメトキシシラン、ジフェニルジエトキシシラン、ヘキサメチルジシロキサン、１，３−ジビニルテトラメチルジシロキサン、１，３−ジフェニルテトラメチルジシロキサンが挙げられる。
【０１３８】
有機ケイ素化合物としては、シリコーンオイルが挙げられる。好ましいシリコーンオイルとしては、２５℃における粘度がおよそ３０〜１，０００ｍｍ²／ｓ（ｃＳｔ）のものが用いられ、例えばジメチルシリコーンオイル、メチルフェニルシリコーンオイル、α−メチルスチレン変性シリコーンオイル、クロルフェニルシリコーンオイル、フッ素変性シリコーンオイルが好ましい。
【０１３９】
シリコーンオイル処理の方法は、例えばシランカップリング剤で処理されたシリカ微粉体とシリコーンオイルとをヘンシェルミキサー等の混合機を用いて直接混合しても良いし、ベースとなるシリカへシリコーンオイルを噴射する方法によっても良い。あるいは適当な溶剤にシリコーンオイルを溶解あるいは分散せしめた後、ベースのシリカ微粉体とを混合し、溶剤を除去して作製しても良い。
【０１４０】
本発明中のトナーには、必要に応じて流動性向上剤以外の外部添加剤を添加してもよい。
【０１４１】
例えば、クリーニング性を向上させる等の目的で、一次粒径が３０ｎｍを超える（好ましくは比表面積が５０ｍ²／ｇ未満）微粒子、より好ましくは一次粒径が５０ｎｍ以上（好ましくは比表面積が３０ｍ²／ｇ未満）で球状に近い無機微粒子または有機微粒子をさらに添加することも好ましい形態の一つである。例えば球状のシリカ粒子、球状のポリメチルシルセスキオキサン粒子、球状の樹脂粒子を用いるのが好ましい。
【０１４２】
更に他の添加剤、例えばテフロン粉末、ステアリン酸亜鉛粉末、ポリフッ化ビニリデン粉末の如き滑剤粉末；または酸化セリウム粉末、炭化硅素粉末、チタン酸ストロンチウム粉末の如き研磨剤；ケーキング防止剤；または例えばカーボンブラック粉末、酸化亜鉛粉末、酸化スズ粉末の如き導電性付与剤；また、逆極性の有機微粒子、及び無機微粒子を現像性向上剤として少量加えることもできる。これらの添加剤も、その表面を疎水化処理して用いることも可能である。
【０１４３】
上述の如き、外添剤は、トナー１００質量部に対して０．１〜５質量部（好ましくは０．１〜３質量部）使用するのが良い。
【０１４４】
本発明のトナーを粉砕法により製造する場合は、公知の方法が用いることができる。公知の方法としては、例えば、結着樹脂、磁性体、離型剤、荷電制御剤、場合によっては着色剤等のトナーとして必要な成分及びその他の添加剤等をヘンシェルミキサー、ボールミル等の混合器中で十分混合した後、加熱ロール、ニーダー、エクストルーダーのような熱混練機を用いて熔融混練して、樹脂類をお互いに相熔させた中に磁性体等の他のトナー材料を分散又は溶解させ、冷却固化、粉砕後に、分級、必要に応じて表面処理を行なってトナー粒子を得、必要に応じて微粉体等を添加して混合することによって現像剤を得ることが出来る。分級及び表面処理の順序はどちらが先でもよい。分級工程においては生産効率の点からは、多分割分級機を用いることが好ましい。
【０１４５】
粉砕工程は、機械衝撃式、ジェット式等の公知の粉砕装置を用いて行うことができる。本発明に係わる特定の円形度を有する現像剤を得るためには、さらに熱をかけて粉砕したり、または補助的に機械的衝撃を加える処理をすることが好ましい。また、微粉砕（必要に応じて分級）されたトナー粒子を熱水中に分散させる湯浴法，熱気流中を通過させる方法などを用いてもよい。
【０１４６】
機械的衝撃力を加える方法としては、例えば川崎重工社製のクリプトロンシステムやターボ工業社製のターボミル等の機械衝撃式粉砕機を用いる方法がある。また、ホソカワミクロン社製のメカノフージョンシステムや奈良機械製作所製のハイブリダイゼーションシステム等の装置のように、高速回転する羽根によりトナーをケーシングの内側に遠心力により押しつけ、圧縮力、摩擦力等の力によりトナーに機械的衝撃力を加える方法を用いてもよい。
【０１４７】
機械的衝撃を加える処理をする場合には、処理時の雰囲気温度をトナーのガラス転移点Ｔｇ付近の温度（すなわち、ガラス転移点Ｔｇの±３０℃の範囲の温度）とすることが、凝集防止と生産性の観点から好ましい。さらに好ましくは、トナーのガラス転移点Ｔｇの±２０℃の範囲の温度で処理を行うことが、転写効率を向上させるのに特に有効である。
【０１４８】
さらにまた、本発明のトナーは、特公昭５６−１３９４５号公報等に記載のディスク又は多流体ノズルを用いて溶融混合物を空気中に霧化し球状トナーを得る方法や、単量体には可溶で得られる重合体が不溶な水系有機溶剤を用いて直接トナーを生成する分散重合方法、又は水溶性の極性重合開始剤の存在下で直接重合させてトナーを生成するソープフリー重合方法に代表される乳化重合方法等を用いてトナーを製造する方法でも製造が可能である。
【０１４９】
本発明のトナーを粉砕法により製造する場合の結着樹脂としては、ポリスチレン、ポリビニルトルエンの如きスチレン及びその置換体の単重合体；スチレン−プロピレン共重合体、スチレン−ビニルトルエン共重合体、スチレン−ビニルナフタリン共重合体、スチレン−アクリル酸メチル共重合体、スチレン−アクリル酸エチル共重合体、スチレン−アクリル酸ブチル共重合体、スチレン−アクリル酸オクチル共重合体、スチレン−アクリル酸ジメチルアミノエチル共重合体、スチレン−メタアクリル酸メチル共重合体、スチレン−メタアクリル酸エチル共重合体、スチレン−メタアクリル酸ブチル共重合体、スチレン−メタクリル酸ジメチルアミノエチル共重合体、スチレン−ビニルメチルエーテル共重合体、スチレン−ビニルエチルエーテル共重合体、スチレン−ビニルメチルケトン共重合体、スチレン−ブタジエン共重合体、スチレン−イソプレン共重合体、スチレン−マレイン酸共重合体、スチレン−マレイン酸エステル共重合体の如きスチレン系共重合体；ポリメチルメタクリレート、ポリブチルメタクリレート、ポリ酢酸ビニル、ポリエチレン、ポリプロピレン、ポリビニルブチラール、シリコン樹脂、ポリエステル樹脂、ポリアミド樹脂、エポキシ樹脂、ポリアクリル酸樹脂、ロジン、変性ロジン、テンペル樹脂、フェノール樹脂、脂肪族または脂環族炭化水素樹脂、芳香族系石油樹脂、パラフィンワックス、カルナバワックスを単独または混合して使用できる。特に、スチレン系共重合体及びポリエステル樹脂が現像特性、定着性等の点で好ましい。
【０１５０】
次に本発明のトナーを使用した現像方法について説明する。
【０１５１】
先ず、トナー担持体と静電荷像担持体とが非接触である系について説明する。
【０１５２】
非接触の現像方法においては、トナー担持体上にトナー担持体−感光体（静電荷像担持体）の最近接距離（Ｓ−Ｄ間）よりも小さい層厚で、磁性トナーを塗布し、交番電界を印加して現像を行う。すなわち、トナー担持体上の磁性トナーを規制する層厚規制部材によってトナー担持体上のトナー層厚よりも感光体とトナー担持体の最近接間隙が広くなるように設定して用いる。この際に、トナー担持体上の磁性トナーを規制する層厚規制部材が、弾性部材であり、トナーを介してトナー担持体に当接されていることが磁性トナーを均一帯電させる観点から特に好ましい。
【０１５３】
また、トナー担持体は感光体に対して１００〜５００μｍの離間距離を有して対向して設置されることが好ましく、１２０〜５００μｍの離間距離を有して対向して設置されることが更に好ましい。トナー担持体の感光体に対する離間距離が１００μｍよりも小さいと、離間距離の振れに対するトナーの現像特性の変化が大きくなるため、安定した画像性を満足する画像形成装置を量産することが困難となる。トナー担持体の感光体に対する離間距離が５００μｍよりも大きいと、現像装置への転写残トナーの回収性が低下し、回収不良によるカブリを生じ易くなる。また、感光体上の潜像に対するトナーの追従性が低下するために、解像性の低下、画像濃度の低下等の画質低下を招いてしまう。
【０１５４】
本発明においては、トナー担持体上に５〜３０ｇ／ｍ²のトナー層を形成するよう積層させることが好ましい。トナー担持体上のトナー量が５ｇ／ｍ²よりも小さいと、十分な画像濃度が得られにくく、トナーの帯電が過剰になることによるトナー層のムラを生じる。トナー担持体上のトナー量が３０ｇ／ｍ²よりも多くなると、トナー飛散を生じ易くなる。
【０１５５】
また、本発明に使用されるトナー坦持体の表面粗度Ｒａ（ＪＩＳ中心線平均粗さ）は、０．２〜３．５μｍの範囲にあることが好ましい。Ｒａが０．２μｍ未満ではトナー担持体上の帯電量が高くなり、現像性が不充分となる。また、Ｒａが３．５μｍを超えると、トナー担持体上のトナーの積層にむらが生じ、画像上で濃度のむらとなる。表面粗度Ｒａは、０．５〜３．０μｍの範囲にあることが更に好ましい。
【０１５６】
本発明において、トナー担持体の表面粗度Ｒａは、ＪＩＳ表面粗さ「ＪＩＳ Ｂ ０６０１」に基づき、表面粗さ測定器（サーフコーダＳＥ−３０Ｈ、株式会社小坂研究所社製）を用いて測定される中心線平均粗さに相当する。具体的には、粗さ曲線からその中心線の方向に測定長さａとして２．５ｍｍの部分を抜き取り、この抜き取り部分の中心線をＸ軸、縦倍率の方向をＹ軸、粗さ曲線をｙ＝ｆ（ｘ）で表したとき、次式によって求められる値をマイクロメートル（μｍ）で表したものである。
【０１５７】
【外２】

【０１５８】
さらに、本発明に係わる磁性トナーは高い帯電能力を有するために、現像に際してはトナーの総帯電量をコントロールすることが好ましい。また、本発明に係わるトナー担持体の表面は導電性微粒子及び／又は滑剤を分散した樹脂層で被覆されていることが好ましい。
【０１５９】
トナー担持体表面を被覆する樹脂層に含有される導電性微粒子としては、カーボンブラック、グラファイト、導電性酸化亜鉛の如き導電性金属酸化物及び金属複酸化物を単独でもしくは２種類以上組み合わせて用いるのが好ましい。この導電性微粒子及び／又は滑剤が分散される樹脂としては、フェノール系樹脂、エポキシ系樹脂、ポリアミド系樹脂、ポリエステル系樹脂、ポリカーボネート系樹脂、ポリオレフィン系樹脂、シリコーン系樹脂、フッ素系樹脂、スチレン系樹脂、アクリル系樹脂の如き公知の樹脂が用いられる。特に熱硬化性樹脂または光硬化性の樹脂が好ましい。
【０１６０】
また、非接触の現像方法においては、現像工程でトナーを担持して現像部に搬送するトナー担持体の移動速度を、感光体の移動速度に対して速度差をもたせることが好ましい。このような速度差を設けることにより、トナー担持体側から感光体側へトナー粒子および導電性微粉末を十分に供給することができ、良好な画像を得ることができるためである。
【０１６１】
トナーを担持するトナー担持体表面は、感光体表面の移動方向と同方向に移動していてもよいし、逆方向に移動していてもよい。その際の速度としては、トナー担持体表面と感光体表面の移動速度が等速であるより、一方が他方に対して１．０２〜３．０倍の速度で移動していることが好ましい。
【０１６２】
現像部においては、該磁性トナーを静電潜像に転移させて現像するために交流バイアスが印加されているが、この際の交流バイアスは、少なくともピークトゥーピークの電界強度が３×１０⁶〜１×１０⁷Ｖ／ｍであり、周波数１００〜５０００Ｈｚであることが好ましい。また、更に直流バイアスを重畳することも好ましい形態である。
【０１６３】
一方、トナー担持体と静電荷像担持体とを接触させて現像を行う系について説明する。
【０１６４】
接触現像方法においては、反転現像を用いることが好ましい。
【０１６５】
さらに、クリーナレスプロセスを併用することも好ましい形態であり、装置の大幅な小型化が可能となる。このとき、現像時あるいは現像前後の空白時には、直流あるいは交流成分のバイアスを印加し、現像と感光体上の残余のトナーを回収できるような電位に制御され、このとき直流成分は、明部電位と暗部電位の間に位置する。
【０１６６】
トナー担持体としては、弾性ローラを用いることが好ましく、表面にトナーをコーティングし、これを感光体表面と接触させる。この場合、トナーを介して感光体と感光体表面に対向する弾性ローラ間に働く電界によって現像されるので、弾性ローラ表面あるいは、表面近傍が電位をもち、感光体表面とトナー担持体表面の狭い間隙で電界を有する必要性がある。このため、弾性ローラの弾性ゴムが中抵抗領域に抵抗制御されて感光体表面との導通を防ぎつつ電界を保つか、または導電性ローラの表面層に薄層の絶縁層を設ける方法も利用できる。さらには、導電性ローラ上に感光体表面に対向する側を絶縁性物質により被覆した導電性樹脂スリーブあるいは、絶縁性スリーブで感光体に対向しない側に導電層を設けた構成も可能である。また、トナー担持体として剛体ローラを用い、感光体をベルトの如きフレキシブルな物とした構成も可能である。トナー担持体としての弾性ローラの抵抗としては１０²〜１０⁹Ω・ｃｍの範囲が好ましい。
【０１６７】
トナー担持体の表面形状としては、その表面粗度Ｒａ（μｍ）を０．２〜３．０となるように設定すると、高画質及び高耐久性を両立できる。該表面粗度Ｒａはトナー搬送能力及びトナー帯電能力と相関する。該トナー担持体の表面粗度Ｒａが３．０を超えると、該トナー担持体上のトナー層の薄層化が困難となるばかりか、トナーの帯電性が改善されないので画質の向上は望めない。３．０以下にすることでトナー担持体表面のトナーの搬送能力を抑制し、該トナー担持体上のトナー層を薄層化すると共に、該トナー担持体とトナーの接触回数が多くなるため、該トナーの帯電性も改善されるので相乗的に画質が向上する。一方、表面粗度Ｒａが０．２よりも小さくなると、トナーコート量の制御が難しくなる。
【０１６８】
接触現像方法においては、トナー担持体は感光体の周速同方向に回転していてもよいし、逆方向に回転していてもよい。その回転が同方向である場合、トナー担持体の周速を感光体の周速に対し１．０５〜３．０倍となるように設定することが好ましい。
【０１６９】
トナー担持体の周速が、感光体の周速に対し１．０５倍未満であると、感光体上のトナーの受ける撹拌効果が不十分となり、良好な画像品質が望めない。また、ベタ黒画像等、広い面積にわたって多くのトナー量を必要とする画像を現像する場合、静電潜像へのトナー供給量が不足し画像濃度が薄くなる。周速比が高まれば高まるほど、現像部位に供給されるトナーの量は多く、潜像に対しトナーの脱着頻度が多くなり、不要な部分は回収され必要な部分には付与されるという繰り返しにより、潜像に忠実な画像が得られる。但し、逆に周速比が３．０を超える場合には、上記の如きトナーの過剰な帯電によって引き起こされる種々の問題（トナーの過度なチャージアップによる画像濃度低下等）の他に、機械的ストレスによるトナーの劣化やトナー担持体へのトナー固着が発生、促進され、好ましくない。
【０１７０】
次に帯電工程について説明する。
【０１７１】
本発明においては、コロナ放電を用いた帯電装置を使用する帯電工程の如き非接触の帯電工程でも構わないが、帯電部材を感光体に当接させる接触帯電法が好ましい帯電法である。この場合、接触帯電部材としては、帯電ローラを用いることが好ましい。
【０１７２】
帯電ローラーを用いたときの好ましいプロセス条件としては、ローラーの当接圧が４．９〜４９０Ｎ／ｍ（５〜５００ｇ／ｃｍ）で、直流電圧または直流電圧に交流電圧を重畳したものが用いられる。直流電圧に交流電圧を重畳したものを用いる場合は、交流電圧＝０．５〜５ｋＶｐｐ、交流周波数＝５０〜５ｋＨｚ、直流電圧＝±０．２〜±５ｋＶが好ましい。
【０１７３】
この他の帯電手段としては、帯電ブレードを用いる方法や、導電性ブラシを用いる方法がある。これらの接触帯電手段を使用する場合にも、高電圧が不要になったり、オゾンの発生が低減するといった効果がある。
【０１７４】
接触帯電手段としての帯電ローラ及び帯電ブレードの材質としては、導電性ゴムが好ましく、その表面に離型性被膜を設けてもよい。離型性被膜としては、ナイロン系樹脂、ＰＶｄＦ（ポリフッ化ビニリデン）、ＰＶｄＣ（ポリ塩化ビニリデン）、フッ素アクリル樹脂が適用可能である。
【０１７５】
次に転写工程について説明する。
【０１７６】
本発明においては、コロナ放電を用いた転写装置を使用する転写工程の如き非接触の転写工程でも構わないが、好ましくは転写手段を転写材を介して感光体に当接させて転写を行う接触転写方法である。
【０１７７】
転写手段の当接圧力としては線圧２．９Ｎ／ｍ（３ｇ／ｃｍ）以上であることが好ましく、より好ましくは１９．６Ｎ／ｍ（２０ｇ／ｃｍ）以上である。当接圧力としての線圧が２．９Ｎ／ｍ（３ｇ／ｃｍ）未満であると、転写材の搬送ずれや転写不良の発生が起こりやすくなるため好ましくない。
【０１７８】
また、接触転写工程における転写手段としては、転写ローラあるいは転写ベルトを有する装置が使用される。図５に転写ローラの構成の一例を示す。転写ローラ３４は少なくとも芯金３４ａと導電性弾性層３４ｂからなり、導電性弾性層はカーボン等の導電材を分散させたウレタンやＥＰＤＭ等の、体積抵抗１０⁶〜１０¹⁰Ωｃｍ程度の弾性体で作られており、転写バイアス電源３５により転写バイアスが印加されている。
【０１７９】
次に、本発明において用いられる感光体について以下に説明する。
【０１８０】
感光体としては、ａ−Ｓｅ、ＣｄＳ、ＺｎＯ₂、ＯＰＣ（有機感光体）、ａ−Ｓｉの如き光導電絶縁物質層を持つ感光ドラムもしくは感光ベルトが好適に使用される。
【０１８１】
特に、本発明においては感光体表面が高分子結着剤を主体として構成されている感光体を用いることが好ましい。例えば、セレン、アモルファスシリコンなどの無機感光体の上に、樹脂を主体とした保護膜（保護層）を設ける場合、または機能分離型の有機感光体の電荷輸送層として電荷輸送材と樹脂からなる表面層を設ける場合、またその表面層の上に樹脂を主体とした保護層を設ける場合等がある。これらの表面層（または保護層）は離型性を有していることが好ましく、実際に離型性を付与する手段としては、
▲１▼膜を構成する樹脂自体に表面エネルギーの低いものを用いる、
▲２▼撥水、親油性を付与するような添加剤を加える、
▲３▼高い離型性を有する材料を粉体状にして分散させる、
手段などが挙げられる。▲１▼の例としては、樹脂の構成単位の構造中にフッ素含有基、シリコーン含有基の如き官能基を導入することが挙げられる。▲２▼の撥水、親油性を付与するような添加剤としては、例えば、界面活性剤が挙げられる。▲３▼の高い離型性を有する材料としては、フッ素原子を含む化合物、すなわちポリ４フッ化エチレン、ポリフッ化ビニリデン、フッ化カーボンが挙げられる。
【０１８２】
これらの手段によって、感光体表面の水に対する接触角を８５度以上とすることができ、トナーの転写性及び感光体の耐久性を一層向上させることができる。感光体表面の水に対する接触角は、９０度以上であることが好ましい。本発明においては、上記▲１▼〜▲３▼の手段の中では、▲３▼のように含フッ素樹脂の離型性粉体の最表面層へ分散させることが好適であり、離型性粉体としてはポリ４フッ化エチレンを使用するのが特に好ましい。
【０１８３】
これらの粉体を表面に含有させるためには、バインダー樹脂中に離型性粉体を分散させた層を感光体最表面に設けるか、または、感光体自体が樹脂を主体として構成されている有機感光体であれば、新たに表面層を設けなくても、最上層に離型性粉体を分散させればよい。離型性粉体の添加量は、表面層総量に対して、１〜６０質量％が好ましく、２〜５０質量％が更に好ましい。離型性粉体の添加量が１質量％より少ないとトナーの転写性及び感光体の耐久性改善の効果が不十分であり、６０質量％を越えると保護膜の強度が低下したり、感光体への入射光量が著しく低下したりするため好ましくない。
【０１８４】
本発明においては、帯電手段が帯電部材を感光体に当接させる接触帯電法が好ましい帯電方法であるが、帯電手段が感光体に接することのないコロナ放電等による方法にくらべて感光体表面に対する負荷が大きいので、感光体の表面に保護層（保護膜）を設けることが耐久性に関する改善効果が顕著であり、好ましい適用形態の一つである。
【０１８５】
また、本発明においては、接触帯電方法、接触転写方法を適用することが好ましいため、直径が５０ｍｍ以下の径が小さい感光体を有する画像形成装置に対し特に有効に用いられる。即ち、画像形成において使用する感光体の径が小さい場合には、同一の線圧に対する曲率が大きく、当接部における圧力の集中が起こりやすいためである。ベルト感光体でも同一の現象があると考えられるが、本発明は転写部での曲率半径が２５ｍｍ以下の画像形成装置に対しても有効である。
【０１８６】
本発明に用いられる感光体の好ましい様態の一つを以下に説明する。
【０１８７】
導電性基体としては、アルミニウム・ステンレスの如き金属、アルミニウム合金、酸化インジウム−酸化錫合金による被膜層を有するプラスチック、導電性粒子を含侵させた紙、プラスチック、導電性ポリマーを有するプラスチックの円筒状シリンダー及びフィルムが用いられる。
【０１８８】
これら導電性基体上には、感光層の接着性の向上、塗工性の改良、基体の保護、基体上の欠陥の被覆、基体からの電荷注入性の改良、感光層の電気的破壊に対する保護等を目的として下引き層を設けても良い。下引き層は、ポリビニルアルコール、ポリ−Ｎ−ビニルイミダゾール、ポリエチレンオキシド、エチルセルロース、メチルセルロース、ニトロセルロース、エチレン−アクリル酸コポリマー、ポリビニルブチラール、フェノール樹脂、カゼイン、ポリアミド、共重合ナイロン、ニカワ、ゼラチン、ポリウレタン、酸化アルミニウムの如き材料によって形成される。下引き層の膜厚は通常、０．１〜１０μｍであり、好ましくは０．１〜３μｍ程度である。
【０１８９】
電荷発生層は、アゾ系顔料、フタロシアニン系顔料、インジゴ系顔料、ペリレン系顔料、多環キノン系顔料、スクワリリウム色素、ピリリウム塩類、チオピリリウム塩類、トリフェニルメタン系色素、セレン、非晶質シリコンの如き無機物質の様な電荷発生物質を適当な結着剤に分散し塗工するか、または蒸着により形成される。結着剤としては、例えば、ポリカーボネート樹脂、ポリエステル樹脂、ポリビニルブチラール樹脂、ポリスチレン樹脂、アクリル樹脂、メタクリル樹脂、フェノール樹脂、シリコン樹脂、エポキシ樹脂、酢酸ビニル樹脂が挙げられ、このような広範囲な樹脂から任意に結着剤を選択できる。電荷発生層中に含有される結着剤の量は、電荷発生層全体に対して８０質量％以下が好ましく、０〜６０質量％が更に好ましい。また、電荷発生層の膜厚は５μｍ以下が好ましく、特には０．０５〜２μｍが好ましい。
【０１９０】
電荷輸送層は、電界の存在下で電荷発生層から電荷キャリアを受け取り、これを輸送する機能を有している。電荷輸送層は電荷輸送物質を必要に応じて結着樹脂と共に溶剤中に溶解させ、塗工することによって形成される。電荷発生層の膜厚は一般的には５〜４０μｍである。電荷輸送物質としては、主鎖または側鎖にビフェニレン、アントラセン、ピレン、フェナントレンの如き構造を有する多環芳香族化合物、インドール、カルバゾール、オキサジアゾール、ピラゾリンの如き含窒素環式化合物、ヒドラゾン化合物、スチリル化合物、セレン、セレン−テルル、非晶質シリコン、硫化カドニウムが挙げられる。
【０１９１】
また、これら電荷輸送物質を分散させる結着樹脂としては、ポリカーボネート樹脂、ポリエステル樹脂、ポリメタクリル酸エステル、ポリスチレン樹脂、アクリル樹脂、ポリアミド樹脂の如き樹脂、ポリ−Ｎ−ビニルカルバゾール、ポリビニルアントラセンの如き有機光導電性ポリマーが挙げられる。
【０１９２】
更に、表面層として、更に別途保護層を設けてもよい。保護層の樹脂としては、ポリエステル、ポリカーボネート、アクリル樹脂、エポキシ樹脂、フェノール樹脂、またはこれらの樹脂の硬化剤を単独または２種以上組み合わせて用いることができる。
【０１９３】
また、保護層の樹脂中に導電性微粒子を分散してもよい。導電性微粒子の例としては、金属、金属酸化物が挙げられ、好ましくは、酸化亜鉛、酸化チタン、酸化スズ、酸化アンチモン、酸化インジウム、酸化ビスマス、酸化スズ被膜酸化チタン、スズ被膜酸化インジウム、アンチモン被膜酸化スズ、酸化ジルコニウムの超微粒子が挙げられる。これらの導電性微粒子は単独で用いてもよいし、２種以上を混合して用いてもよい。一般的に保護層に粒子を分散させる場合、分散粒子による入射光の散乱を防ぐために入射光の波長よりも粒子の粒径の方が小さいことが必要であり、本発明における保護層に分散される導電性微粒子の粒径は０．３μｍ以下であることが好ましい。また、保護層中での導電性微粒子の含有量は、保護層総重量に対して２〜９０質量％が好ましく、５〜８０質量％がより好ましい。保護層の膜厚は、０．１〜１０μｍが好ましく、１〜７μｍがより好ましい。
【０１９４】
表面層の塗工は、樹脂分散液をスプレーコーティング、ビームコーティングまたは浸透（ディッピング）コーティングすることによって行うことができる。
【０１９５】
次に、本発明の画像形成方法を図に沿って具体的に説明する。
【０１９６】
図１の画像形成装置において、１００は感光ドラムで、その周囲に一次帯電ローラー１１７、現像器１４０、転写帯電ローラー１１４、クリーナ１１６、レジスタローラー１２４等が設けられている。そして感光体１００は一次帯電ローラー１１７によって、例えば−７００Ｖに帯電される。（印加電圧は交流電圧−２．０ ｋ Ｖｐｐ、直流電圧−７００ Ｖｄｃ）そして、レーザー発生装置１２１によりレーザー光１２３を感光体１００に照射することによって露光される。感光体１００上の静電潜像は現像器１４０によって一成分磁性現像剤で現像され、転写材を介して感光体に当接された転写ローラー１１４により転写材上へ転写される。トナー画像をのせた転写材は搬送ベルト１２５等により定着器１２６へ運ばれ転写材上に定着される。また、一部感光体上に残されたトナーはクリーニング手段１１６によりクリーニングされる。現像器１４０は図２に示すように感光体１００に近接してアルミニウム、ステンレスの如き非磁性金属で作られた円筒状のトナー担持体１０２（以下現像スリーブと称す）が配設され、感光体１００と現像スリーブ１０２との間隙は図示されないスリーブ／感光体間隙保持部材等により約３００μｍに維持されている。現像スリーブ内にはマグネットローラー１０４が現像スリーブ１０２と同心的に固定、配設されている。但し現像スリーブ１０２は回転可能である。マグネットローラー１０４には図示のように複数の磁極が具備されており、Ｓ１は現像、Ｎ１はトナーコート量規制、Ｓ２はトナーの取り込み／搬送、Ｎ２はトナーの吹き出し防止に影響している。トナーは、トナー塗布ローラ１４１によって、現像スリーブ１０２に塗布され、付着して搬送される。搬送されるトナー量を規制する部材として、弾性ブレード１０３が配設され弾性ブレード１０３の現像スリーブ１０２に対する当接圧により現像領域に搬送されるトナー量が制御される。現像領域では、感光体１００と現像スリーブ１０２との間に直流及び交流の現像バイアスが印加され、現像スリーブ上現像剤は静電潜像に応じて感光体１００上に飛翔し可視像となる。
【０１９７】
次に本発明の画像形成方法を図３及び図４を参照しながら以下に説明する。
【０１９８】
図３は、クリーナレスプロセスを用いた画像形成装置の概略を示しており、４０は現像装置、１は感光体、２７は紙などの被転写体（転写材）、１４は転写部材、２６は定着用加圧ローラー、２８は定着用加熱ローラー、１７は感光体１に接触して直接帯電を行う一次帯電部材を示す。一次帯電部材１７には、感光体１表面を一様に帯電するようにバイアス電源３１が接続されている。
【０１９９】
現像装置４０はトナー４２を収容しており、感光体１と接触して矢印方向に回転するトナー担持体４を具備する。さらに、トナー量規制及び帯電付与のための現像ブレード４３，トナー４２をトナー担持体４に付着させ、かつトナー担持体４との摩擦でトナーヘの帯電付与を行うため矢印方向に回転する塗布ローラ４１も備えている。トナー担持体４には現像バイアス電源３３が接続されている。塗布ローラ４１にもバイアス電源３２が接続されており、負帯電性トナーを使用する場合は現像バイアスよりも負側に、正帯電性トナーを使用する場合は現像バイアスよりも正側に電圧が設定される。
【０２００】
転写部材１４には感光体１と反対極性の転写バイアス電源３４が接続されている。
【０２０１】
ここで、感光体１とトナー担持体４の接触部分における回転方向の長さ、いわゆる現像ニップ幅は０．２〜８．０ｍｍが好ましい。０．２ｍｍ未満では現像量が不足して満足な画像濃度が得られず、転写残トナーの回収も不十分となる。８．０ｍｍを超えてしまうと、トナーの供給量が過剰となり、カブリ抑制が悪化しやすく、また、感光体１の摩耗にも悪影響を及ぼす。
【０２０２】
トナー担持体４としては、表面に弾性層を有する、いわゆる弾性ローラが好ましく用いられる。
【０２０３】
使用される弾性層の材料の硬度としては、２０〜６５度（ＪＩＳ Ａ）のものが好適に使用される。
【０２０４】
また、トナー担持体４の抵抗としては、体積抵抗値で１０²〜１０⁹Ω・ｃｍ程度の範囲が好ましい。１０²Ω・ｃｍよりも低い場合、例えば感光体１の表面にピンホール等がある場合、過電流が流れる恐れがある。反対に１０⁹Ω・ｃｍよりも高い場合は、摩擦帯電によるトナーのチャージアップが起こりやすく、画像濃度の低下を招きやすい。
【０２０５】
トナー担持体４上のトナーコート量は、０．ｌ２．０ｍｇ／ｃｍ²が好ましい。０．ｌｍｇ／ｃｍ²よりも少ないと十分な画像濃度が得にくく、２．０ｍｇ／ｃｍ²よりも多くなると個々のトナー粒子全てを均一に摩擦帯電することが難しくなり、カブリ抑制の悪化の要因となる。さらに、０．２〜１．２ｍｇ／ｃｍ²がより好ましい。
【０２０６】
トナーコート量は現像ブレード１４３により制御されるが、この現像ブレード１４３はトナー層を介してトナー担持体１０４に接触している。この時の接触圧は、５〜５０ｇ／ｃｍが好ましい範囲である。５ｇ／ｃｍよりも小さいとトナーコート量の制御に加え均一な摩擦帯電も難しくなり、カブリ抑制の悪化等の原因となる。一方、５０ｇ／ｃｍよりも大きくなるとトナー粒子が過剰な負荷を受けるため、粒子の変形や現像ブレード１４３あるいはトナー担持体１０４へのトナーの融着等が発生しやすくなり、好ましくない。
【０２０７】
トナーコート量の規制部材としては、トナーを圧接塗布するための弾性ブレード以外にも、金属ブレードあるいはローラを用いても良い。
【０２０８】
弾性の規制部材には、所望の極性にトナーを帯電させるのに適した摩擦帯電系列の材質を選択することが好ましく、シリコーンゴム、ウレタンゴム、ＮＢＲの如きゴム弾性体、ポリエチレンテレフタレートの如き合成樹脂弾性体、ステンレス、銅、リン青銅の如き金属弾性体が使用できる。また、それらの複合体であっても良い。
【０２０９】
また、弾性の規制部材とトナー担持体に耐久性が要求される場合には、金属弾性体に樹脂やゴムをスリーブ当接部に当たるように貼り合わせたり、コーティング塗布したものが好ましい。
【０２１０】
更に、弾性の規制部材中に有機物や無機物を添加してもよく、溶融混合させても良いし、分散させても良い。例えば、金属酸化物、金属粉、セラミックス、炭素同素体、ウィスカー、無機繊維、染料、顔料、界面活性剤を添加することにより、トナーの帯電性をコントロールできる。特に、弾性体がゴムや樹脂等の成型体の場合には、シリカ、アルミナ、チタニア、酸化錫、ジルコニア、酸化亜鉛の如き金属酸化物微粉末、カーボンブラック、一般にトナーに用いられる荷電制御剤を含有させることも好ましい。
【０２１１】
またさらに、規制部材に直流電場及び／または交流電場を印加することによっても、トナーヘのほぐし作用のため、均一薄層塗布性、均一帯電性がより向上し、充分な画像濃度の達成及び良質の画像を得ることができる。
【０２１２】
図３において、一次帯電部材１７は矢印方向に回転する感光体１を一様に帯電する。
【０２１３】
ここで用いている一次帯電部材は、中心の芯金１７ｂとその外周を形成した導電性弾性層１７ａとを基本構成とする帯電ローラである。帯電ローラ１７は、静電潜像担持体一面に押圧力を持って当接され、感光体１の回転に伴い従動回転する。
【０２１４】
帯電ローラ１１７を用いたときの好ましいプロセス条件としては、ローラの当接圧が５〜５００ｇ／ｃｍであり、印加電圧としては直流電圧あるいは直流電圧に交流電圧を重畳したもの等が用いられ、特に限定されないが、本発明においては直流電圧のみの印加電圧が好適に用いられ、この場合の電圧値としては±０．２〜±５ｋＶの範囲で使用される。
【０２１５】
この他の帯電手段としては、帯電ブレードを用いる方法や、導電性ブラシを用いる方法がある。これらの接触帯電手段は、非接触のコロナ帯電に比べて、高電圧が不必要になったり、オゾンの発生が低減するといった効果がある。接触帯電手段としての帯電ローラおよび帯電ブレードの材質としては、導電性ゴムが好ましく、その表面に離型性被膜を設けても良い。離型性被膜としては、ナイロン系樹脂、ＰＶＤＦ（ポリフッ化ビニリデン）、ＰＶＤＣ（ポリ塩化ビニリデン）が適用可能である。
【０２１６】
一次帯電工程に次いで、発光素子２１からの露光２３によって感光体１上に情報信号に応じた静電潜像を形成し、トナー担持体４と当接する位置においてトナーにより静電潜像を現像し可視像化する。さらに、本発明の画像形成方法において、特に感光体上にデジタル潜像を形成した現像システムと組み合わせることで、潜像を乱さないためにドット潜像に対して忠実に現像することが可能となる。次に、該可視像を芯金１４ａとその外周を形成した導電性弾性層１４ｂとを基本構成とする転写部材１４により被転写体２７上に転写し、更に転写トナー２９は被転写体２７と共に、搬送ローラ２５によって定着用加圧ローラー２６と定着用加圧ローラー２８とを有する定着装置に搬送して定着され、永久画像を得る。なお、加熱加圧定着手段としては、ここに示したハロゲンヒーターの如き発熱体を内蔵した加熱ローラーとこれと押圧力をもって圧接された弾性体の加圧ローラーを基本構成とする熱ローラー方式以外に、フィルムを介してヒーターにより加熱定着する方式も用いられる。
【０２１７】
一方、転写されずに感光体１上に残った転写残トナーは、感光体１と一次帯電部材１７の間を通過して、再び現像ニップ部に到達し、トナー担持体４によって現像器４０内に回収される。
【０２１８】
本発明における各種物性データの測定法を以下に詳述する。
【０２１９】
（１）トナー表面に存在する炭素元素の含有量（Ａ）に対する鉄元素の含有量（Ｂ）の比（Ｂ／Ａ）
本発明におけるトナー表面に存在する炭素元素の含有量（Ａ）に対する鉄元素の含有量（Ｂ）の比（Ｂ／Ａ）は、ＥＳＣＡ（Ｘ線光電子分光分析）により表面組成分析を行い算出した。
【０２２０】
本発明では、ＥＳＣＡの装置および測定条件は、下記の通りである。
使用装置：ＰＨＩ社（Ｐｈｙｓｉｃａｌ Ｅｌｅｃｔｒｏｎｉｃｓ Ｉｎｄｕｓｔｒｉｅｓ，Ｉｎｃ．）製 １６００Ｓ型 Ｘ線光電子分光装置

【０２２１】
本発明では、測定された各元素のピーク強度から、ＰＨＩ社提供の相対感度因子を用いて表面原子濃度（原子％）を算出した。
【０２２２】
測定試料としては、トナーを用いるが、トナーに外添剤が添加されている場合には、イソプロパノールの如きトナーを溶解しない溶媒を用いて、トナーを洗浄し、外添剤を取り除いた後に測定を行う。
【０２２３】
（２）トナーの平均円形度
本発明における円形度は、粒子の形状を定量的に表現する簡便な方法として用いたものであり、本発明では東亜医用電子社製フロー式粒子像分析装置ＦＰＩＡ−１０００を用いて粒子形状の測定を行い、円形度を下記式により求める。更に下式で示すように、測定された全粒子の円形度の総和を全粒子数で除した値を平均円形度と定義する。
【０２２４】
【外３】

【０２２５】
なお、本発明で用いている測定装置である「ＦＰＩＡ−１０００」は、各粒子の円形度を算出後、平均円形度の算出に当たって、粒子を得られた円形度によって、円形度０．４００〜１．０００を０．０１０間隔で、０．４００以上０．４１０未満、０．４１０以上０．４２０未満・・・０．９９０以上１．０００未満及び１．０００の如くに６１分割した分割範囲に分け、分割点の中心値と頻度を用いて平均円形度の算出を行う算出法を用いている。
【０２２６】
この算出法で算出される平均円形度の各値と、上述した各粒子の円形度を直接用いる算出式によって算出される平均円形度の各値との誤差は、非常に少なく、実質的には無視できる程度であるため、本発明においては、算出時間の短縮化や算出演算式の簡略化の如きデータの取り扱い上の理由で、上述した各粒子の円形度を直接用いる算出式の概念を利用し、一部変更したこの様な算出法を用いている。
【０２２７】
本発明における円形度は、粒子の凹凸の度合いを示す指標であり、粒子が完全な球形の場合に１．０００を示し、表面形状が複雑になる程、円形度は小さな値となる。
【０２２８】
円形度の具体的な測定方法としては、ノニオン型界面活性剤約０．１ｍｇを溶解している水１０ｍｌにトナー約５ｍｇを分散させ分散液を調整し、超音波（２０ｋＨｚ、５０Ｗ）を分散液に５分間照射し、分散液濃度を５０００〜２００００個／μｌとして、上記フロー式粒子像測定装置を用い、３μｍ以上の円相当径を有する粒子の円形度分布を測定する。
【０２２９】
測定の概略は、東亜医用電子社（株）発行のＦＰＩＡ−１０００のカタログ（１９９５年６月版）、測定装置の操作マニュアル及び特開平８−１３６４３９号公報に記載されているが、以下の通りである。
【０２３０】
試料分散液は、フラットで扁平な透明フローセル（厚み約２００μｍ）の流路（流れ方向に沿って広がっている）を通過させる。フローセルの厚みに対して交差して通過する光路を形成するように、ストロボとＣＣＤカメラが、フローセルに対して、相互に反対側に位置するように装着される。試料分散液が流れている間に、ストロボ光がフローセルを流れている粒子の画像を得るために１／３０秒間隔で照射され、その結果、それぞれの粒子はフローセルに平行な一定範囲を有する２次元画像として撮影される。それぞれの粒子の２次元画像の面積から、同一の面積を有する円の直径を円相当径として算出する。それぞれの粒子の２次元画像の投影面積及び投影像の周囲長から上記の円形度算出式を用いて各粒子の円形度を算出する。
【０２３１】
（３）トナーの粒度分布
測定装置としてはコールターカウンターＴＡ−ＩＩ型（コールター社製）を用い、個数分布、体積分布を出力するインターフェイス（日科機製）及びＣＸ−１パーソナルコンピュータ（キヤノン製）を接続し、電解液は１級塩化ナトリウムを用いて１％ＮａＣｌ水溶液を調製する。例えば、ＩＳＯＴＯＮ Ｒ−ＩＩ（コールターサイエンティフィックジャパン社製）を使用できる。測定法としては前記電解水溶液１００〜１５０ｍｌ中に分散剤として界面活性剤（好ましくはアルキルベンゼンスルホン酸塩）を０．１〜５ｍｌ加え、さらに測定試料を２〜２０ｍｇ加える。試料を懸濁した電解液は超音波分散器で約１〜３分間分散処理を行い、前記コールターカウンターＴＡ−ＩＩ型により、アパチャーとして１００μｍアパチャーを用いて、トナーの体積、個数を測定して２〜４０μｍの粒子の体積分布と個数分布とを算出する。それから数平均粒径（Ｄ１）体積分布から求めた重量基準の重量平均径Ｄ４（各チャンネルの中央値をチャンネルごとの代表値とする）、体積分布から求めた重量基準の１２．７μｍ以上の重量分布を求める。
【０２３２】
【実施例】
以下、本発明を製造例および実施例により具体的に説明するが、これは本発明をなんら限定するものではない。実施例に記載されている部数または％は、質量部または質量％を示す。
【０２３３】
（疎水性酸化鉄の製造例１）
硫酸第一鉄水溶液中に、鉄イオンに対して１．０〜１．１当量の苛性ソーダ溶液を混合し、水酸化第一鉄を含む水溶液を調製した。
【０２３４】
水溶液をｐＨ９に維持しながら、空気を吹き込み、８０〜９０℃で酸化反応を行い、種晶を生成させるスラリー液を調製した。
【０２３５】
次いで、このスラリー液に当初のアルカリ量（苛性ソーダのナトリウム成分）に対し０．９〜１．２当量となるよう硫酸第一鉄水溶液を加えた後、スラリー液をｐＨ８に維持して、空気を吹込みながら酸化反応をすすめ、酸化反応の終期にｐＨを約６に調整し、シランカップリング剤［ｎ−Ｃ₄Ｈ₉Ｓｉ（ＯＣＨ₃）₃］を磁性酸化鉄１００部に対し０．５部添加し、十分撹拌した。生成した疎水性酸化鉄粒子を常法により洗浄、濾過、乾燥し、次いで凝集している粒子を解砕処理し、疎水性酸化鉄１を得た。疎水性酸化鉄１の物性を表１に示す。
【０２３６】
（疎水性酸化鉄の製造例２）
製造例１と同様に酸化反応を進め、酸化反応後に生成した磁性酸化鉄粒子を洗浄、濾過して一旦取り出し、乾燥せずに別の水中に再分散させた後、再分散液のｐＨを調整し、十分撹拌しながらシランカップリング剤［ｎ−Ｃ₆Ｈ₁₃Ｓｉ（ＯＣＨ₃）₃］を０．５部添加し、カップリング処理を行った。生成した疎水性酸化鉄粒子を常法により洗浄、濾過、乾燥し、次いで凝集している粒子を軽く解砕処理し、疎水性酸化鉄２を得た。
【０２３７】
（疎水性酸化鉄の製造例３）
シランカップリング剤としてｎ−Ｃ₁₀Ｈ₂₁Ｓｉ（ＯＣＨ₃）₃を使用することを除いて、製造例２と同様にして疎水性酸化鉄３を得た。
【０２３８】
（疎水性酸化鉄の製造例４）
シランカップリング剤としてγ−グリシジルトリメトキシシランを使用することを除いて、製造例２と同様にして疎水性酸化鉄４を得た。
【０２３９】
（疎水性酸化鉄の製造例５）
硫酸第一鉄水溶液中に、鉄イオンに対して１．０〜１．１当量の苛性ソーダ溶液を混合し、水酸化第一鉄を含む水溶液を調製した。
【０２４０】
水溶液をｐＨ９に維持しながら、空気を吹き込み、８０〜９０℃で酸化反応を行い、種晶を生成させるスラリー液を調製した。
【０２４１】
次いで、このスラリー液に当初のアルカリ量（苛性ソーダのナトリウム成分）に対し０．９〜１．２当量となるよう硫酸第一鉄水溶液を加えた後、スラリー液をｐＨ８に維持して、空気を吹込みながら酸化反応をすすめ、酸化反応の終期にｐＨを調整し、酸化反応を終了した。生成した粒子を常法により洗浄、濾過、乾燥し、次いで凝集している粒子を解砕処理し酸化鉄粒子ａを得た。得られた酸化鉄粒子ａを気相中にてメタノールで１０倍希釈したシランカップリング剤［ｎ−Ｃ₆Ｈ₁₃Ｓｉ（ＯＣＨ₃）₃］（酸化鉄１００部に対して、カップリング剤が０．５部となる様に調整）で疎水化することにより疎水性酸化鉄５を得た。
【０２４２】
（疎水性酸化鉄の製造例６）
疎水性酸化鉄の製造例５で得られた酸化鉄粒子ａを、水中に分散し、酸化鉄分散水溶液のｐＨを調整して、シランカップリング剤［ｎ−Ｃ₆Ｈ₁₃Ｓｉ（ＯＣＨ₃）₃］０．５部を添加し、十分に混合撹拌を行った。生成した疎水性酸化鉄粒子を常法により洗浄、濾過、乾燥し、次いで凝集している粒子を解砕処理し、疎水性酸化鉄６を得た。
【０２４３】
上記の疎水性酸化鉄２〜６の物性を表１に示す。
【０２４４】
【表１】

【０２４５】
次に、下記実施例１〜６および比較例１〜４において用いた画像形成装置について説明する。
【０２４６】
非接触の現像方法によって現像を行う市販のレーザービームプリンターＬＢＰ−ＳＸ（キヤノン製）を以下に示す如く改造して用いた。すなわち、プロセスカートリッジ部分のトナー層厚規制部材をウレタンゴム製の弾性ブレードに変え、トナー塗布ローラーおよびクリーニング用マグネットローラを設置し、トナー担持体（現像スリーブ）１５に内包されている磁石を取り除いたＬＢＰプリンターを用いた。
【０２４７】
画出し条件を下記に示す。
【０２４８】
図６は、使用される交番電圧を説明したものである。Ｖ_dcは直流電源電圧を示し、Ｖ_dは静電潜像担持体上の暗部電位、Ｖ_Lは明部電位をそれぞれ表す。ｆは交番電圧の周波数、Ｖ_ppは交番電圧のピーク間の電圧を示す。
【０２４９】
Ｖ_dを−６００Ｖとして静電潜像を形成し、感光ドラム３と現像スリーブ１５上の現像剤層を非接触に間隙（３００μｍ）を設定し、現像スリーブ１５にはバイアス印加手段１２により、交流バイアス（ｆ＝３２００Ｈｚ Ｖ_pp＝１８００Ｖ）及び直流バイアス（Ｖ_dc＝−４００Ｖ）とを印加し、Ｖ_Lを−１５０Ｖに設定し画出しを行った。
【０２５０】
また、感光ドラムに対する現像スリーブの周速比を２００％に設定した。
【０２５１】
＜実施例１＞
イオン交換水７０９質量部に０．１ｍｏｌ／リットル−Ｎａ₃ＰＯ₄水溶液４５１質量部を投入し６０℃に加温した後、１．０ｍｏｌ／リットル−ＣａＣｌ₂水溶液６７．７質量部を徐々に添加してＣａ₃（ＰＯ₄）₂を含む水系媒体を得た。
【０２５２】
一方、
・スチレン ８２部
・ｎ−ブチルアクリレート １８部
・ポリエステル樹脂 ５部
・負荷電性制御剤（モノアゾ染料系のＦｅ化合物） ２部
・疎水性酸化鉄１ １００部
上記処方をアトライター（三井三池化工機（株））を用いて均一に分散混合した。
【０２５３】
この単量体組成物を６０℃に加温し、そこにエステルワックス（ｍｐ．７０℃）２０部を混合溶解し、これに重合開始剤２，２’−アゾビス（２，４−ジメチルバレロニトリル［ｔ_1/2＝１４０分，６０℃条件下］８質量部及びジメチル−２，２’−アゾビスイソブチレート［ｔ_1/2＝２７０分，６０℃条件下；ｔ_1/2＝８０分，８０℃条件下］２質量部を溶解した。
【０２５４】
前記水系媒体中に上記重合性単量体系を投入し、６０℃，Ｎ₂雰囲気下においてＴＫ式ホモミキサー（特殊機化工業（株））にて１０，０００ｒｐｍで１５分間撹拌し、造粒した。その後パドル撹拌翼で撹拌しつつ、６０℃で１時間反応させた。その後液温を８０℃とし更に１０時間撹拌を続けた。反応終了後、懸濁液を冷却し、塩酸を加えてＣａ₃（ＰＯ₄）₂を溶解し、濾過，水洗，乾燥してトナー粒子を得た。
【０２５５】
このトナー粒子１００部と、ヘキサメチルジシラザン処理した後シリコーンオイルで処理し、処理後のＢＥＴ比表面積が１２０ｍ²／ｇの疎水性シリカ微粉体１．４部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＡ（重量平均粒径６．２μｍ）を調製した。
【０２５６】
ここで、透過型電子顕微鏡（ＴＥＭ）を用いたトナー粒子の断層面観察により、トナーＡの粒子内部での疎水性酸化鉄の分散状態を評価した。
【０２５７】
ＴＥＭによる具体的な評価方法としては、上述したトナー粒子中の酸化鉄の体積平均粒径及び粒度分布を決定する場合と同様の方法で行った。
【０２５８】
トナー粒子内部での疎水性酸化鉄の分散状態の具体的評価は以下のように行った。トナーの数平均粒径の±１０％の径を有する粒子断層面を抽出し、その断層面と中心を同じにして径が半分の相似図形を書く（相似図形の面積は粒子断層面面積の１／４となる）。
【０２５９】
次に、粒子断層面内（相似図形内も含む）に存在する０．０３μｍ以上の疎水性酸化鉄粉末の個数を数え、その個数をａとする。同様に相似図形内に存在する０．０３μｍ以上の疎水性酸化鉄粉末の個数を数え、その個数をｂとする。こうして得られたａ、ｂについてその比ｂ／ａを計算する。
【０２６０】
比ｂ／ａの値がそれぞれの面の面積比である １／４に近いほど、疎水性酸化鉄粉末がトナー粒子の中心から表層付近まで同じ存在量であること、即ち、トナー粒子内での疎水性酸化鉄の分散状態が均一であることを意味し、ｂ／ａの値が３／８〜１／５の範囲にあれば、ほぼ良好な分散がなされているといえる。
【０２６１】
トナーＡについてｂ／ａを求めたところ、ほぼ１／４であり、トナー粒子内での疎水性酸化鉄の分散状態が非常に均一であることが分かった。
【０２６２】
トナーＡを用いて、常温常湿環境下（２３℃，６５％ＲＨ）５０００枚の画出し試験を行なった。その結果、連続５０００枚プリント後においても飛び散りの無い良好な画像が得られた。また、スリーブ上のトナーをエアで除去した後、目視観察をしたが、スリーブ上は現像剤固着も全くなかった。後述の評価方法による画像濃度、カブリ量及びドット再現性の評価結果を表３に示す。
【０２６３】
同様にして、高温高湿環境下（３２．５℃，８５％ＲＨ）及び低温低湿環境下（１０℃，１５％ＲＨ）において画出し試験をおこなった。結果を表２に示す。
【０２６４】
＜実施例２＞
実施例１の疎水性酸化鉄１を１００部の疎水性酸化鉄２に変え、造粒時の撹拌速度を変えた以外は同様にして磁性トナー粒子を得た。得られたトナー粒子１００部に実施例１と同様にして疎水性コロイダルシリカ１．７部を外添しトナーＢ（重量平均粒径４．９μｍ）を調製した。
【０２６５】
得られたトナーＢを用いて、実施例１と同様にして画出し試験を行なった。
【０２６６】
＜実施例３＞
実施例１の疎水性酸化鉄１を１５０部の疎水性酸化鉄３に変えた以外は同様にしてトナー粒子を得た。得られたトナー粒子１００部に実施例１と同様にして疎水性コロイダルシリカ０．７部を外添しトナーＣ（重量平均粒径９．７μｍ）を調製した。
【０２６７】
得られたトナーＣを用いて、実施例１と同様にして画出し試験を行なった。
【０２６８】
＜実施例４＞
実施例１の疎水性酸化鉄１を１９０部の疎水性酸化鉄４に変えた以外は同様にしてトナー粒子を得た。得られたトナー粒子１００部に実施例１と同様にして疎水性コロイダルシリカ２．０部を外添しトナーＤ（重量平均粒径３．５μｍ）を調製した。
【０２６９】
得られたトナーＤを用いて、実施例１と同様にして画出し試験を行なった。
【０２７０】
＜実施例５、６＞
疎水性酸化鉄３の使用量を４０部又は２００部に変更し、Ｎａ₃ＰＯ₄水溶液とＣａＣｌ₂水溶液の投入量を変更した以外は、実施例３と同様にして、トナー粒子を得た。得られたそれぞれのトナー粒子１００部に実施例１と同様にして疎水性コロイダルシリカ１．０部、３．０部を外添しトナーＥ（重量平均粒径１０．５μｍ）、Ｆ（重量平均粒径１．９μｍ）を調製した。
【０２７１】
得られたトナーＥ、Ｆを用いて、実施例１と同様にして画出し試験を行なった。
【０２７２】
＜比較例１＞
イオン交換水７０９質量部に０．１ｍｏｌ／リットル−Ｎａ₃ＰＯ₄水溶液４５１質量部を投入し６０℃に加温した後、１．０ｍｏｌ／リットル−ＣａＣｌ₂水溶液６７．７質量部を徐々に添加してＣａ₃（ＰＯ₄）₂を含む水系媒体を得た。
【０２７３】
一方、
・スチレン ８２部
・ｎ−ブチルアクリレート １８部
・ポリエステル樹脂 ５部
・疎水性酸化鉄１ １００部
上記処方をアトライター（三井三池化工機（株））を用いて均一に分散混合した。
【０２７４】
この単量体組成物を６０℃に加温し、これに重合開始剤２，２’−アゾビス（２，４−ジメチルバレロニトリル［ｔ_1/2＝１４０分，６０℃下］８質量部及びジメチル−２，２’−アゾビスイソブチレート［ｔ_1/2＝２７０分，６０℃下；ｔ_1/2＝８０分，８０℃下］２質量部を溶解した。
【０２７５】
前記水系媒体中に上記重合性単量体系を投入し、６０℃，Ｎ₂雰囲気下においてＴＫ式ホモミキサー（特殊機化工業（株））にて１０，０００ｒｐｍで１５分間撹拌し、造粒した。その後パドル撹拌翼で撹拌しつつ、６０℃で１時間反応させた。その後液温を８０℃とし更に１０時間撹拌を続けた。反応終了後、懸濁液を冷却し、塩酸を加えてＣａ₃（ＰＯ₄）₂を溶解し、濾過，水洗，乾燥して重量平均粒径１０．０μｍの酸化鉄含有樹脂粉を得た。
【０２７６】
つぎに、
・上記酸化鉄含有樹脂粉 ２０５部
・負荷電性制御剤（モノアゾ染料系のＦｅ化合物） ０．８部
・エチレン−プロピレン共重合体（Ｍｗ＝６０００） ３部
を混合し、１４０℃に加熱された二軸エクストルーダーで溶融混練し、混練物を冷却した後ハンマーミルで粗粉砕し、粗粉砕物をジェットミルで微粉砕し得られた微粉砕物を風力分級してトナー粒子ａを得た。このトナー粒子ａ１００部に対して、実施例１で使用した疎水性コロイダルシリカ１．２部を加えた混合物をヘンシェルミキサーで混合しトナーＧ（重量平均粒径７．４μｍ）を調製した。
【０２７７】
得られたトナーＧを用いて、実施例１と同様にして画出し試験を行なった。
【０２７８】
＜比較例２＞
比較例１で得られたトナー粒子ａを機械的衝撃力により表面処理しトナー粒子ｂを得た。このトナー粒子ｂ１００部に対して実施例１で使用した疎水性コロイダルシリカ１．２部を加えた混合物をヘンシェルミキサーで混合しトナーＨを調製した。
【０２７９】
得られたトナーＨを用いて、実施例１と同様にして画出し試験を行なった。
【０２８０】
＜比較例３＞
実施例１の疎水性酸化鉄１を１００部の疎水性酸化鉄５に変えた以外は同様にしてトナー粒子を得た。得られたトナー粒子１００部に実施例１と同様にして疎水性コロイダルシリカ１．２部を外添しトナーＩ（重量平均粒径６．９μｍ）を調製した。
【０２８１】
このトナーＩについて、トナーＡの場合と同様にＴＥＭ観察により粒子内部での酸化鉄の分散状態を評価したところ、ｂ／ａが約１／６であり、トナー粒子内での酸化鉄の分散状態が不均一であって、特にトナー粒子表面に多く存在していることが分かった。これは、酸化鉄の疎水性が不均一なため、疎水性の低い酸化鉄粉末が懸濁重合時にトナー粒子表面に多く集まってしまったためと思われる。
【０２８２】
得られたトナーＩを用いて、実施例１と同様にして画出し試験を行なった。
【０２８３】
＜比較例４＞
実施例１の疎水性酸化鉄１を１５０部の疎水性酸化鉄６に変えた以外は同様にしてトナー粒子を得た。得られたトナー粒子１００部に実施例１と同様にして疎水性コロイダルシリカ１．７部を外添しトナーＪ（重量平均粒径４．８μｍ）を調製した。
【０２８４】
得られたトナーＪを用いて、実施例１と同様にして画出し試験を行なった。
【０２８５】
得られた各トナーの物性は表２に示した。また、各トナーの画出し試験結果は表３に示した。なお、評価方法は次の通りである。
【０２８６】
ａ）画像濃度の測定はマクベス濃度計ＲＤ９１８（マクベス社製）で測定した。
【０２８７】
ｂ）カブリの測定は、東京電色社製のＲＥＦＬＥＣＴＭＥＴＥＲ ＭＯＤＥＬＴＣ−６ＤＳを使用して測定した。フィルターは、グリーンフィルターを用い、下記の式より算出した。
【０２８８】
カブリ（反射率）（％）＝標準紙上の反射率（％）−サンプル非画像部の反射率（％）
【０２８９】
カブリは、２．０％以下であれば良好な画像である。
【０２９０】
ｃ）ドット再現性は、図７に示す８０μｍ×５０μｍのチェッカー模様を用いて画出し試験をおこない、顕微鏡により黒色部の欠損の有無を観察し、評価した。
Ａ：１００個中欠損が２個以下
Ｂ：１００個中欠損が３〜５個
Ｃ：１００個中欠損が６〜１０個
Ｄ：１００個中欠損が１１個以上
【０２９１】
ｄ）耐久初期（１００枚時）の転写効率は、ベタ黒画像転写後の感光体上の転写残トナーをマイラーテープによりテーピングしてはぎ取り、紙上に貼ったもののマクベス濃度の値をＣ、転写後定着前のトナーの載った紙上にマイラーテープを貼ったもののマクベス濃度をＥ、未使用の紙上に貼ったマイラーテープのマクベス濃度をＤとした時、近似的に以下の式で計算した。
【０２９２】
【外４】

【０２９３】
転写効率は９０％以上であれば問題のない画像である。
【０２９４】
【表２】

【０２９５】
【表３】

【０２９６】
（トナーの製造例１）
イオン交換水７０９質量部に０．１ｍｏｌ／リットル−Ｎａ₃ＰＯ₄水溶液４５１質量部を投入し６０℃に加温した後、１．０ｍｏｌ／リットル−ＣａＣｌ₂水溶液６７．７質量部を徐々に添加してＣａ₃（ＰＯ₄）₂を含む水系媒体を得た。
【０２９７】
一方、
・スチレン ８２部
・ｎ−ブチルアクリレート １８部
・ポリエステル樹脂 ５部
・負荷電性制御剤（モノアゾ染料系のＦｅ化合物） ２部
・疎水性酸化鉄１ １００部
上記処方をアトライター（三井三池化工機（株））を用いて均一に分散混合した。
【０２９８】
この単量体組成物を６０℃に加温し、そこにエステルワックス（ｍｐ．７０℃）２０部を混合溶解し、これに重合開始剤２，２’−アゾビス（２，４−ジメチルバレロニトリル［ｔ_1/2＝１４０分，６０℃条件下］８質量部及びジメチル−２，２’−アゾビスイソブチレート［ｔ_1/2＝２７０分，６０℃条件下；ｔ_1/2＝８０分，８０℃条件下］２質量部を溶解した。
【０２９９】
前記水系媒体中に上記重合性単量体系を投入し、６０℃，Ｎ₂雰囲気下においてＴＫ式ホモミキサー（特殊機化工業（株））にて１０，０００ｒｐｍで１５分間撹拌し、造粒した。その後パドル撹拌翼で撹拌しつつ、６０℃で１時間反応させた。その後液温を８０℃とし更に１０時間撹拌を続けた。反応終了後、懸濁液を冷却し、塩酸を加えてＣａ₃（ＰＯ₄）₂を溶解し、濾過，水洗，乾燥してトナー粒子を得た。
【０３００】
このトナー粒子１００部と、ヘキサメチルジシラザン処理した後シリコーンオイルで処理し、処理後のＢＥＴ値が１２０ｍ²／ｇの疎水性シリカ微粉体１．４部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＫ（重量平均粒径６．１μｍ）を調製した。
【０３０１】
（トナーの製造例２）
製造例１の疎水性酸化鉄１を１００部の疎水性酸化鉄２に変えた以外は同様にして磁性トナー粒子を得た。得られたトナー粒子１００部に製造例１と同様にして疎水性コロイダルシリカ１．７部を外添しトナーＬ（重量平均粒径５．０μｍ）を調製した。
【０３０２】
（トナーの製造例３）
製造例１の疎水性酸化鉄１を１５０部の疎水性酸化鉄３に変えた以外は同様にしてトナー粒子を得た。得られたトナー粒子１００部に製造例１と同様にして疎水性コロイダルシリカ０．７部を外添しトナーＭ（重量平均粒径９．８μｍ）を調製した。
【０３０３】
（トナーの製造例４）
製造例１の疎水性酸化鉄１を１９０部の疎水性酸化鉄４に変えた以外は同様にしてトナー粒子を得た。得られたトナー粒子１００部に製造例１と同様にして疎水性コロイダルシリカ２．０部を外添しトナーＮ（重量平均粒径３．６μｍ）を調製した。
【０３０４】
（トナーの製造例５、６）
疎水性酸化鉄３の使用量を１０部又は２００部に変更し、Ｎａ₃ＰＯ₄水溶液とＣａＣｌ₂水溶液の投入量を変更した以外は、製造例３と同様にして、トナー粒子を得た。得られたそれぞれのトナー粒子１００部に製造例１と同様にして疎水性コロイダルシリカ１．０部、３．０部を外添しトナーＯ（重量平均粒径１０．９μｍ）、Ｐ（重量平均粒径２．４μｍ）を調製した。
【０３０５】
（トナーの比較製造例１）
イオン交換水７０９質量部に０．１ｍｏｌ／リットル−Ｎａ₃ＰＯ₄水溶液４５１質量部を投入し６０℃に加温した後、１．０ｍｏｌ／リットル−ＣａＣｌ₂水溶液６７．７質量部を徐々に添加してＣａ₃（ＰＯ₄）₂を含む水系媒体を得た。
【０３０６】
一方、
・スチレン ８２部
・ｎ−ブチルアクリレート １８部
・ポリエステル樹脂 ５部
・疎水性酸化鉄１ １００部
上記処方をアトライター（三井三池化工機（株））を用いて均一に分散混合した。
【０３０７】
この単量体組成物を６０℃に加温し、これに重合開始剤２，２’−アゾビス（２，４−ジメチルバレロニトリル［ｔ_1/2＝１４０分，６０℃下］８質量部及びジメチル−２，２’−アゾビスイソブチレート［ｔ_1/2＝２７０分，６０℃下；ｔ_1/2＝８０分，８０℃下］２質量部を溶解した。
【０３０８】
前記水系媒体中に上記重合性単量体系を投入し、６０℃，Ｎ₂雰囲気下においてＴＫ式ホモミキサー（特殊機化工業（株））にて１０，０００ｒｐｍで１５分間撹拌し、造粒した。その後パドル撹拌翼で撹拌しつつ、６０℃で１時間反応させた。その後液温を８０℃とし更に１０時間撹拌を続けた。反応終了後、懸濁液を冷却し、塩酸を加えてＣａ₃（ＰＯ₄）₂を溶解し、濾過，水洗，乾燥して重量平均粒径１０．０μｍの酸化鉄含有樹脂粉を得た。
【０３０９】
つぎに、
・上記酸化鉄含有樹脂粉 ２０５部
・負荷電性制御剤（モノアゾ染料系のＦｅ化合物） ０．８部
・エチレン−プロピレン共重合体（Ｍｗ＝６０００） ３部
を混合し、１４０℃に加熱された二軸エクストルーダーで溶融混練し、混練物を冷却した後ハンマーミルで粗粉砕し、粗粉砕物をジェットミルで微粉砕し得られた微粉砕物を風力分級してトナー粒子ｃを得た。このトナー粒子ｃ１００部に対して、製造例１で使用した疎水性コロイダルシリカ１．２部を加えた混合物をヘンシェルミキサーで混合しトナーＱ（重量平均粒径７．２μｍ）を調製した。
【０３１０】
（トナーの比較製造例２）
比較製造例１で得られたトナー粒子ｃを機械的衝撃力により表面処理しトナー粒子ｄを得た。このトナー粒子ｄ１００部に対して、製造例１で使用した疎水性コロイダルシリカ１．２部を加えた混合物をヘンシェルミキサーで混合しトナーＲを調製した。
【０３１１】
（トナーの比較製造例３）
製造例１の疎水性酸化鉄１を１００部の疎水性酸化鉄５に変えた以外は同様にしてトナー粒子を得た。得られたトナー粒子１００部に製造例１と同様にして疎水性コロイダルシリカ１．２部を外添しトナーＳ（重量平均粒径７．０μｍ）を調製した。
【０３１２】
（トナーの比較製造例４）
製造例１の疎水性酸化鉄１を１５０部の疎水性酸化鉄６に変えた以外は同様にしてトナー粒子を得た。得られたトナー粒子１００部に製造例１と同様にして疎水性コロイダルシリカ１．７部を外添しトナーＴ（重量平均粒径４．６μｍ）を調製した。
【０３１３】
得られた各トナーの物性は表４に示した。
【０３１４】
【表４】

【０３１５】
［実施例７〜１２及び比較例５〜８］
図３および４のような構成を有する電子写真装置として６００ｄｐｉレーザービームプリンター（キヤノン製：ＬＢＰ−８６０）を用意した。プロセススピードは、６０ｍｍ／ｓに改造してある。
【０３１６】
このプロセスカートリッジにおけるクリーニングブレードを取りはずし、装置の帯電方式をゴムローラを当接して行う直接帯電とし、印加電圧を直流成分のみ（−１２００Ｖ）とした。
【０３１７】
次に、プロセスカートリッジにおける現像部分を改造した。トナー担持体であるステンレススリーブの代わりに、カーボンブラックを分散したシリコーンゴムからなる中抵抗ゴムローラ（直径１６ｍｍ、硬度ＡＳＫＥＲ Ｃ４５度、抵抗１０⁵Ω・ｃｍ）を用いて、感光体に当接させた。この時の現像当接幅は約３ｍｍとなるようにした。該トナー担持体の回転周速は、感光体との接触部分において同方向であり、該感光体回転周速に対し１４０％となるように駆動する。
【０３１８】
ここで用いる感光体としては、直径３０ｍｍ，長さ２５４ｍｍのＡｌシリンダーを基体としたもので、これに、以下に示すような構成の層を順次浸漬塗布により積層して、感光体を作製した。
（１）導電性被覆層：酸化錫及び酸化チタンの粉末をフェノール樹脂に分散したものを主体とする。膜厚１５μｍ。
（２）下引き層：変性ナイロン、及び共重合ナイロンを主体とする。膜厚０．６μｍ。
（３）電荷発生層：長波長域に吸収を持つチタニルフタロシアニン顔料をブチラール樹脂に分散したものを主体とする。膜厚０．６μｍ。
（４）電荷輸送層：ホール搬送性トリフェニルアミン化合物をポリカーボネート樹脂（オストワルド粘度法による分子量２万）に８：１０の質量比で溶解したものを主体とする。膜厚２０μｍ。
【０３１９】
トナー担持体にトナーを塗布する手段として、現像器内に発泡ウレタンゴムからなる塗布ローラを設け、該トナー担持体に当接させた。塗布ローラには、約−５５０Ｖの電圧を印加する。さらに、該トナー担持体上トナーのコート層制御のために樹脂をコートしたステンレス製ブレードを、トナー担持体との接触圧が線圧約２０ｇ／ｃｍとなるように取付けた。概略を図５に示す。また、現像時の印加電圧を直流成分（−４５０Ｖ）のみとした。
【０３２０】
これらのプロセスカートリッジの改造に適合するよう電子写真装置に以下のように改造及びプロセス条件設定を行った。
【０３２１】
改造された装置はローラ帯電器（直流のみを印加）を用い感光体を一様に帯電する。帯電に次いで、レーザー光で画像部分を露光することにより静電潜像を形成し、トナーで現像するにより可視画像とした後に、電圧を＋７００Ｖ印加したローラによりトナー像を転写材に転写するプロセスを持つ。
【０３２２】
また、感光体帯電電位は、暗部電位を−５８０Ｖとし、明部電位を−１５０Ｖとした。転写材としては、７５ｇ／ｍ²の紙を用いた。
【０３２３】
トナーＫ〜Ｔを用いて、上記画像形成装置により常温常湿環境下（２３℃，６５％ＲＨ）において画出し試験を行った。なお、耐久性評価は以下のように評価した。
【０３２４】
ａ）現像剤の帯電部材汚染は、帯電不良による画像不良が現れやすいハーフトーン画像上及びベタ白画像上に帯電部材汚染による帯電ムラが発生した耐久枚数で判断した。発生した枚数が多い程、現像剤の耐久性が良好なことを意味する。
【０３２５】
ｂ）耐久初期の転写効率の測定方法は、上記表３に示した場合と同様である。
【０３２６】
ｃ）現像工程でのトナーの回収性は、得られた画像サンプル上において、非印刷部での画像（いわゆるゴースト画像）が発生するか否かで判断した。即ち、転写されずに感光体上に残ったトナーが現像工程で回収されれば、非印刷部に画像は発生しないが、トナーの回収性が良くない場合、未回収のトナーは再度転写工程を通過し、紙上に転写され、ゴースト画像が発生することになる。
【０３２７】
Ａ：ゴースト全く発生せず
Ｂ：良好（画像を凝視しなければ確認できないレベル）
Ｃ：ゴーストは発生するが、実用可能レベル
【０３２８】
ゴースト、帯電ムラが発生しない場合は５０００枚（５Ｋ）までプリントアウトを続けた。
【０３２９】
ｄ）耐久初期（１００枚時）の解像力は、潜像電界によって電界が閉じやすく、再現しにくい６００ｄｐｉにおける小径孤立１ドット（直径６０μｍ）の再現性によって評価した。
【０３３０】
Ａ：１００個中の欠損が５個以下
Ｂ：１００個中の欠損が６〜１０個
Ｃ：１００個中の欠損が１１〜２０個
Ｄ：１００個中の欠損が２１個以上
【０３３１】
ｅ）カブリの測定は、上記表３に示した場合と同様である。
【０３３２】
同様にして、高温高湿環境下（３２．５℃，８５％ＲＨ）及び低温低湿環境下（１０℃，１５％ＲＨ）において画出し試験をおこなった。結果を表５に示す。
【０３３３】
【表５】

【０３３４】
（疎水性酸化鉄の製造例７）
硫酸第一鉄水溶液中に、鉄イオンに対してｌ．０〜１．１当量の苛性ソーダ溶液を混合し、水酸化第一鉄を含む水溶液を調製した。
【０３３５】
水溶液のｐＨを９前後に維持しながら、空気を吹き込み、８０〜９０℃で酸化反応を行い、種晶を生成させるスラリー液を調製した。
【０３３６】
次いで、このスラリー液に当初のアルカリ量（苛性ソーダのナトリウム成分）に対し０．９〜１．２当量となるよう硫酸第一鉄水溶液を加えた後、スラリー液をｐＨ８に維持して、空気を吹込みながら酸化反応をすすめ、酸化反応後に生成した磁性酸化鉄粒子を洗浄、濾過して一旦取り出した。この時、含水サンプルを少量採取し、含水量を測定した。次に、この含水サンプルを乾燥せずに別の水系媒体中に再分散させた後、再分散液のｐＨを約６に調整し、十分攪拌しながらシランカップリング剤（ｎ−Ｃ₁₀Ｈ₂₁Ｓｉ（ＯＣＨ₃）₃）を磁性酸化鉄１００部に対し０．５部（磁性酸化鉄の量は含水サンプルから含水量を引いた値として計算した）添加し、カップリング処理を行った。生成した疎水性酸化鉄粒子を常法により洗浄、濾過、乾燥し、次いで若干凝集している粒子を解砕処理して、疎水性酸化鉄７を得た。
【０３３７】
（磁性体の製造例１）
磁性酸化鉄の製造例７と同様に酸化反応を進め、酸化反応後に生成した磁性酸化鉄粒子を洗浄、濾過後乾燥し、凝集している粒子を解砕処理し磁性体１を得た。
【０３３８】
（疎水性酸化鉄の製造例８）
磁性体の製造例１で得られた磁性体１を、別の水系媒体中に再分散させた後、再分散液のｐＨを約６に調整し、十分攪拌しながらシランカップリング剤（ｎ−Ｃ₁₀Ｈ₂₁Ｓｉ（ＯＣＨ₃）₃）を磁性酸化鉄に対し０．５部添加し、カップリング処理を行った。生成した疎水性の酸化鉄粒子を常法により洗浄、濾過、乾燥し、次いで凝集している粒子を解砕処理して、疎水性酸化鉄８を得た。
【０３３９】
（疎水性酸化鉄の製造例９）
疎水性酸化鉄の製造例７において、磁性酸化鉄粒子の合成時の硫酸第一鉄水溶液を減らし、空気の吹き込み量を増加させて、疎水性酸化鉄９を得た。
【０３４０】
（疎水性酸化鉄の製造例１０）
疎水性酸化鉄の製造例７において、磁性酸化鉄粒子の合成時の硫酸第一鉄水溶液を増やし、空気の吹き込み量を減少させる以外は同様にして疎水性酸化鉄１０を得た。
【０３４１】
（疎水性酸化鉄の製造例１１）
疎水性酸化鉄７の製造例１において、磁性酸化鉄粒子の合成時の空気の吹き込み量を増やして疎水性酸化鉄１１を得た。
【０３４２】
上記の述くして得られた疎水性酸化鉄７〜１１及び磁性体１の物性を表６に示す。
【０３４３】
【表６】

【０３４４】
＜トナーの製造例７＞
イオン交換水７０９質量部に０．１ｍｏｌ／リットル−Ｎａ₃ＰＯ₄水溶液４５１質量部を投入し６０℃に加温した後、１．０ｍｏｌ／リットル−ＣａＣｌ₂水溶液６７．７質量部を徐々に添加してＣａ₃ （ＰＯ₄）₂を含む水系媒体を得た。
【０３４５】
スチレン ８０部
ｎ−ブチルアクリレート ２０部
ビスフェノールＡのプロピレンオキサイド付加物及びエチレンオキサイド付加物とフマル酸の縮合反応により得られる不飽和ポリエステル樹脂 ２部
負荷電性制御剤（下記の式に示すモノアゾ染料系のＦｅ化合物） ４部
疎水性酸化鉄１ ８０部
上記処方をアトライター（三井三池化工機（株））を用いて均一に分散混合した。
【０３４６】
【外５】

【０３４７】
この単量体組成物を６０℃に加温し、そこにＤＳＣにおける吸熱ピーク温度が７５℃のエステルワックス１０部を添加混合し、これに重合開始剤２，２’−アゾビス（２，４−ジメチルバレロニトリル）［ｔ_1/2＝１４０分，６０℃条件下］８質量部及びジメチル−２，２’−アゾビスイソブチレート［ｔ_1/2＝２７０分，６０℃条件下；ｔ_1/2＝８０分，８０℃条件下］２質量部を溶解させた。
【０３４８】
前記水系媒体中に上記重合性単量体系を投入し、６０℃、Ｎ₂雰囲気下においてＴＫ式ホモミキサー（特殊機化工業（株））にて１０，０００ｒｐｍで１５分間撹拌し、造粒した。その後パドル撹拌翼で撹拌しつつ、６０℃で１時間反応させた。その後液温を８０℃とし更に１０時間撹拌を続けた。反応終了後、懸濁液を冷却し、塩酸を加えてＣａ₃（ＰＯ₄）₂を溶解し、濾過，水洗，乾燥して重量平均粒径７．０μｍの磁性トナー粒子を得た。
【０３４９】
この磁性トナー粒子１００部と、ヘキサメチルジシラザンで表面を処理し処理後のＢＥＴ比表面積が２００ｍ²／ｇの疎水性シリカ微粉体１．２部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＵを調製した。トナーＵの物性を表７に示す。
【０３５０】
このトナーＵについて、トナーＡの場合と同様にＴＥＭ観察により粒子内部での酸化鉄の分散状態を評価したところ、ｂ／ａがほぼ１／４であり、トナー粒子内での酸化鉄の分散状態が非常に均一であることが分かった。
【０３５１】
＜トナーの製造例８＞
トナーの製造例７と同様の方法により重量平均粒径６．９μｍの磁性トナー粒子を得た。
【０３５２】
この磁性トナー粒子１００部と、ヘキサメチルジシラザン処理した後シリコーンオイルで処理し、処理後のＢＥＴ比表面積が１８０ｍ²／ｇの疎水性シリカ微粉体１．２部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＶを調製した。トナーＶの物性を表７に示す。
【０３５３】
＜トナーの製造例９＞
トナーの製造例７において、Ｎａ₃ＰＯ₄水溶液とＣａＣｌ₂水溶液の投入量を変更し、さらにドデシルベンゼンスルホン酸ナトリウムを用いて、重量平均粒径３．８μｍの磁性トナー粒子を得た。この磁性トナー粒子１００部と、トナーの製造例８で使用した疎水性シリカ微粉体２．５部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＷを調製した。トナーＷの物性を表７に示す。
【０３５４】
＜トナーの製造例１０＞
トナーの製造例７において、Ｎａ₃ＰＯ₄水溶液とＣａＣｌ₂水溶液の投入量を変更し、重量平均粒径１０．４μｍの磁性トナー粒子を得た。この磁性トナー粒子１００部と、トナーの製造例８で使用した疎水性シリカ微粉体０．８部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＸを調製した。トナーＸの物性を表７に示す。
【０３５５】
＜トナーの製造例１１＞
トナーの製造例７において、エステルワックスの使用量を５１部とする以外は同様の方法により、重量平均粒径８．２μｍの磁性トナー粒子を得た。この磁性トナー粒子１００部と、トナーの製造例８で使用した疎水性シリカ微粉体１．１部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＹを調製した。トナーＹの物性を表７に示す。
【０３５６】
＜トナーの製造例１２＞
トナーの製造例７において、エステルワックスの使用量を０．４部とする以外は同様の方法により、重量平均粒径６．８μｍの磁性トナー粒子を得た。この磁性トナー粒子１００部と、トナーの製造例８で使用した疎水性シリカ微粉体１．２部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＺを調製した。トナーＺの物性を表７に示す。
【０３５７】
＜トナーの製造例１３＞
トナーの製造例７において、エステルワックスに代えてＤＳＣにおける吸熱ピーク温度が１１５℃の低分子量ポリエチレンワックスを１０部用いる以外は同様の方法により、重量平均粒径８．４μｍの磁性トナー粒子を得た。この磁性トナー粒子１００部と、トナーの製造例８で使用した疎水性シリカ微粉体１．１部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＡＡを調製した。トナーＡＡの物性を表７に示す。
【０３５８】
＜トナーの製造例１４＞
トナーの製造例７において、疎水性酸化鉄７の使用量を３０部とする以外は同様の方法により、重量平均粒径６．９μｍの磁性トナー粒子を得た。この磁性トナー粒子１００部と、トナーの製造例８で使用した疎水性シリカ微粉体１．２部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＢＢを調製した。トナーＢＢの物性を表７に示す。
【０３５９】
＜トナーの製造例１５＞
トナーの製造例７において、疎水性酸化鉄７を２０５部使用する以外は同様の方法により、重量平均粒径７．９μｍの磁性トナー粒子を得た。この磁性トナー粒子１００部と、トナーの製造例８で使用した疎水性シリカ微粉体１．１部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＣＣを調製した。トナーＣＣの物性を表７に示す。
【０３６０】
＜トナーの製造例１６〜１８＞
トナーの製造例７において、疎水性酸化鉄７に代えて疎水性酸化鉄９〜１１を使用する以外は同様の方法により、磁性トナーを得た。これれの磁性トナー粒子１００部と、トナーの製造例８で使用した疎水性シリカ微粉体１．２部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＤＤ〜ＦＦを調製した。トナーＤＤ〜ＦＦの物性を表７に示す。
【０３６１】
＜トナーの比較製造例５＞
トナーの製造例７において、疎水性酸化鉄７に代えて磁性体１を８０部使用する以外は同様の方法により、重量平均粒径８．８μｍの磁性トナー粒子を得た。この磁性トナー粒子１００部と、トナーの製造例８で使用した疎水性シリカ微粉体１．０部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＧＧを調製したトナーＧＧの物性を表７に示す。
【０３６２】
このトナーＧＧについて、トナーＡの場合と同様にＴＥＭ観察により粒子内部での酸化鉄の分散状態を評価したところ、ｂ／ａが約１／８であり、トナー粒子内での酸化鉄の分散状態が不均一であって、特にトナー粒子表面に非常に多く存在していることが分かった。
【０３６３】
＜トナーの比較製造例６＞
トナーの製造例７において、疎水性酸化鉄７に代えて疎水性酸化鉄８を８０部使用する以外は同様の方法により、重量平均粒径８．１μｍの磁性トナー粒子を得た。この磁性トナー粒子１００部と、トナーの製造例８で使用した疎水性シリカ微粉体１．１部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＨＨを調製した。トナーＨＨの物性を表７に示す。
【０３６４】
このトナーＨＨについて、トナーＡの場合と同様にＴＥＭ観察により粒子内部での酸化鉄の分散状態を評価したところ、ｂ／ａが約１／６であり、トナー粒子内での酸化鉄の分散状態が不均一であって、特にトナー粒子表面に非常に多く存在していることが分かった。
【０３６５】
＜トナーの比較製造例７＞

上記材料をブレンダーにて混合し、１１０℃に加熱した２軸エクストルーダーで溶融混練し、冷却した混練物をハンマーミルで粗粉砕し、粗粉砕物をジェットミルで微粉砕後、得られた微粉砕物を風力分級して重量平均粒径１０．４μｍの磁性トナー粒子を得た。この磁性トナー粒子１００部に対してトナーの製造例８で使用した疎水性シリカ微粉体０．８部を加えた混合物をヘンシェルミキサーで混合しトナーＩＩを調製した。トナーＩＩの物性を表７に示す。
【０３６６】
＜トナーの比較製造例８＞
トナーの比較製造例７において、粗粉砕物をターボミル（ターボ工業社製）で微粉砕する以外は同様の方法により、磁性トナー粒子を得た。その後衝撃式表面処理装置（処理温度５０℃、回転式処理ブレード周速９０ｍ／ｓｅｃ．）を用いて重量平均粒径１０．３μｍの球形化トナーを得た。
【０３６７】
次に、得られた球形化トナー１００部に対してトナーの製造例８で使用した疎水性シリカ微粉体０．８部を加えた混合物をヘンシェルミキサーで混合しトナーＪＪを調製した。トナーＪＪの物性を表７に示す。
【０３６８】
＜トナーの比較製造例９＞
イオン交換水７０９質量部に０．１ｍｏｌ／リットル−Ｎａ₃ＰＯ₄水溶液４５１質量部を投入し６０℃に加温した後、１．０ｍｏｌ／リットル−ＣａＣｌ₂水溶液６７．７質量部を徐々に添加してＣａ₃ （ＰＯ₄）₂を含む水系媒体を得た。
【０３６９】

上記処方をアトライター（三井三池化工機（株））を用いて均一に分散混合した。
【０３７０】
この単量体組成物を６０℃に加温し、そこにトナーの製造例７で使用したエステルワックス１２部を添加混合し、これに重合開始剤２，２’−アゾビス（２，４−ジメチルバレロニトリル）［ｔ_1/2＝１４０分，６０℃条件下］８質量部及びジメチル−２，２’−アゾビスイソブチレート［ｔ_1/2＝２７０分，６０℃条件下；ｔ_1/2＝８０分，８０℃条件下］２質量部を溶解した。
【０３７１】
前記水系媒体中に上記重合性単量体系を投入し、６０℃、Ｎ₂雰囲気下においてＴＫ式ホモミキサー（特殊機化工業（株））にて１０，０００ｒｐｍで１５分間撹拌し、造粒した。その後パドル撹拌翼で撹拌しつつ、６０℃で１時間反応させた。その後液温を８０℃とし更に１０時間撹拌を続けた。
【０３７２】
次に、この水系懸濁液中に
スチレン １６部
ｎ−ブチルアクリレート ４部
２，２’−アゾビス（２，４−ジメチルバレロニトリル） ０．４部
ベヘニン酸ナトリウム ０．１部
水 ２０部
の混合物を添加し、再度、液温を８０℃として１０時間撹拌を続けた。
反応終了後、懸濁液を冷却し、塩酸を加えてＣａ₃（ＰＯ₄）₂を溶解し、濾過、水洗、乾燥して重量平均粒径８．５μｍのトナー粒子を得た。
【０３７３】
このトナー粒子１００部と、トナーの製造例８で使用した疎水性シリカ微粉体１．０部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＫＫを調製した。トナーＫＫの物性を表７に示す。
【０３７４】
＜トナーの比較製造例１０＞
トナーの製造例９において、疎水性酸化鉄７に代えて磁性体１を９６部使用する以外は同様の手法により、重量平均粒径８．３μｍの磁性トナー粒子を得た。この磁性トナー粒子１００部と、トナーの製造例８で使用した疎水性シリカ微粉体１．０部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＬＬを調製したトナーＬＬの物性を表７に示す。
【０３７５】
【表７】

【０３７６】
（感光体製造例１）
感光体としては直径３０のＡｌシリンダーを基体とした。これに、図８に示すような構成の層を順次浸漬塗布により積層して、感光体を作成した。
（１）導電性被覆層：酸化錫及び酸化チタンの粉末をフェノール樹脂に分散したものを主体とする。膜厚１５μｍ。
（２）下引き層：変性ナイロン、及び共重合ナイロンを主体とする。膜厚０．６μｍ。
（３）電荷発生層：長波長域に吸収を持つアゾ顔料をブチラール樹脂に分散したものを主体とする。膜厚０．６μｍ。
（４）電荷輸送層：ホール搬送性トリフェニルアミン化合物をポリカーボネート樹脂（オストワルド粘度法による分子量２万）に８：１０の質量比で溶解したものを主体とし、さらにポリ４フッ化エチレン粉体（粒径０．２μｍ）を総固形分に対して１０質量％添加し、均一に分散した。膜厚は２５μｍであり、水に対する接触角は９５度であった。
【０３７７】
なお、接触角は、純水を用い、協和界面科学（株）製の接触角計ＣＡ−Ｘ型装置を用いて測定した。
【０３７８】
（実施例１）
画像形成装置として、概ね図１に示されるものを用いた。
【０３７９】
静電荷像坦持体としては（感光体製造例１）の有機感光体（ＯＰＣ）ドラムを用いた。この感光体に、一次帯電部材として導電性カーボンを分散しナイロン樹脂で被覆されたゴムローラー帯電器を当接させ（当接圧６０ｇ／ｃｍ）、直流電圧−７００Ｖｄｃに交流電圧２．０ｋＶｐｐを重畳したバイアスを印加して感光体上を一様に帯電する。一次帯電に次いで、レーザー光で画像部分を露光することにより静電潜像を形成する。この時、暗部電位Ｖｄ＝−７００Ｖ、明部電位ＶＬ＝−２００Ｖとした。
【０３８０】
感光ドラムと現像スリーブとの間隙は２８０μｍとし、トナー担持体として下記の構成の層厚約７μｍ、ＪＩＳ中心線平均粗さ（Ｒａ）１．３μｍの樹脂層を、表面が鏡面である直径２０のアルミニウム円筒上に形成した現像スリーブを使用し、現像磁極９５ｍＴ（９５０ガウス）、トナー規制部材として厚み１．０ｍｍ、自由長１０ｍｍのウレタンゴム製ブレードを１４．７Ｎ／ｍ（１５ｋｇ／ｍ）の線圧で当接させた。
【０３８１】
フェノール樹脂 １００部
グラファイト（粒径約７μｍ） ９０部
カーボンブラック １０部
【０３８２】
次いで、現像バイアスとして直流バイアス成分Ｖｄｃ＝−４００Ｖ、重畳する交流バイアス成分Ｖ_pp＝１６００Ｖ、ｆ＝２０００Ｈｚを用いた。また、現像スリーブの周速は感光体周速（８０ｍｍ／ｓｅｃ）に対して順方向に１１０％のスピード（８８ｍｍ／ｓｅｃ）とした。
【０３８３】
また、図５のような転写ローラー（導電性カーボンを分散したエチレン−プロピレンゴム製、導電性弾性層の体積抵抗値１０⁸Ωｃｍ、表面ゴム硬度２４゜、直径２０ｍｍ、当接圧５９ Ｎ／ｍ（６ｋｇ／ｍ））を図５中Ａ方向の感光体周速（８０ｍｍ／ｓｅｃ）に対して等速とし、転写バイアスは直流１．５ｋＶとした。
【０３８４】
定着方法としては熱ローラー定着装置を用いた。
【０３８５】
まず、トナーとしてトナーＵを使用し、１５℃１０％ＲＨ環境下において画出し試験を行った。転写材としては９０ｇ／ｍ²の紙を使用した。その結果、初期において高い転写性を示し、文字やラインの転写中抜け及び定着オフセットによる裏汚れもなく、非画像部へのカブリもない良好な画像が得られた。
【０３８６】
次に、印字面積比率５％の縦ラインのみからなる画像パターンで耐久性の評価を行った。
【０３８７】
画像評価は以下のように行った。
【０３８８】
感光体の削れ及びトナー融着の評価は、画像不良が現れやすいハーフトーン画像上に、削れあるいはトナー融着による画像不良、即ち黒点あるいは白抜けが発生した耐久枚数で判断した。発生するまでの耐久枚数が多い程、画像形成方法の耐久性が良好なことを意味する。加えて、転写残トナーによる一次帯電不良に起因する画像不良、即ち帯電ムラもハーフトーン画像上で評価した。これらの画像不良が発生しない場合は印字枚数５０００枚まで耐久試験を続けた。
ａ）転写効率の測定方法は上記表３に示した場合と同様である。
ｂ）耐久初期の解像力の評価方法は上記表５に示した場合と同様である。
ｃ）画像濃度の測定方法は上記表３に示した場合と同様である。
ｄ）カブリの評価は上記表３に示した場合と同様である。
ｅ）定着オフセット性は、初期から耐久１００枚までの画像サンプルの裏側に発生する汚れを観察し、発生枚数を数えた。
【０３８９】
得られた結果を表８に示す。
【０３９０】
（実施例１４）
トナーとしてトナーＶを使用し、実施例１３と同様の画像形成方法で画出し試験を行ったところ、印字枚数５０００枚まで、表８に示した様に非常に良好な結果が得られた。
【０３９１】
（実施例１５〜２４）
トナーとしてトナーＷ〜ＦＦを使用し、実施例１３と同様の画像形成方法で画出し試験を行った。その結果、表８に示した様に、実用的には問題の無い結果が得られた。
【０３９２】
（比較例９）
トナーとしてトナーＧＧを使用し、実施例１３と同様の画像形成方法で画出し試験を行った。その結果、印字枚数２５００枚目からハーフトーン画像上に感光体の削れに起因する黒点が発生し、３０００枚目からはトナー融着に起因する白抜けが発生しだした。未処理の磁性体を使用したため、トナー表面からの酸化鉄の露出が多く、転写残トナーが帯電ローラーによる摺擦時に感光体を削ってしまったためと思われる。
【０３９３】
（比較例１０）
トナーとしてトナーＨＨを使用し、実施例１３と同様の画像形成方法で画出し試験を行った。その結果、印字枚数３５００枚目からハーフトーン画像上に感光体の削れに起因する黒点が発生し、４０００枚目からはトナー融着に起因する白抜けが発生しだした。使用した疎水性酸化鉄の疎水化処理が不均一なため、トナー表面からの酸化鉄の露出が防ぎきれず、転写残トナーが帯電ローラーによる摺擦時に感光体を削ってしまったためと思われる。
【０３９４】
（比較例１１）
トナーとしてトナーＩＩを使用し、実施例１３と同様の画像形成方法で画出し試験を行った。その結果、印字枚数１０００枚目からハーフトーン画像上に感光体の削れに起因する黒点が発生し、１５００枚目からはトナー融着に起因する白抜けが発生し、２０００枚目からは転写残トナーによる帯電ムラも発生しだした。表面が均一に疎水化処理された酸化鉄を用いても、トナーを一般的な粉砕法で製造した場合、トナー表面からの酸化鉄の露出が防ぎきれず、転写残トナーが帯電ローラーによる摺擦時に感光体を削ってしまったためと思われる。さらに、円形度も低いためトナー粒子のエッジ部による削れも加わり、感光体の劣化が早まったものと考えられる。
【０３９５】
（比較例１２）
トナーとしてトナーＪＪを使用し、実施例１３と同様の画像形成方法で画出し試験を行った。その結果、印字枚数２５００枚目からハーフトーン画像上に感光体の削れに起因する黒点が発生し、３０００枚目からはトナー融着に起因する白抜けが発生し、３５００枚目からは転写残トナーによる帯電ムラも発生しだした。トナー表面の球形化処理の際、トナー表面からの酸化鉄の露出は改良されたものの、円形度が未だ十分でないため、トナー粒子のエッジ部による感光体の削れの改良が不十分だったことが考えられる。
【０３９６】
（比較例１３）
トナーとしてトナーＫＫを使用し、実施例１３と同様の画像形成方法で画出し試験を行った。その結果、表８に示した様に、感光体の削れに起因する画像不良に関しては問題の無い結果が得られた。但し、印字枚数が増すにつれ、画像濃度が低下していき、印字枚数５０００枚後は画像濃度が０．７１まで低下した。さらに、耐久４０００枚以降に裏汚れが発生しだした。これは、Ｄ／Ｃ≦０．０２である粒子数が４４％と低いため、すなわち現像剤中の酸化鉄の分散性が悪いため、粒径が大きく酸化鉄を多く含んでいて現像性及び定着性の低いトナーだけが残ってしまったことが原因と思われる。
【０３９７】
（比較例１４）
トナーとしてトナーＬＬを使用し、実施例１３と同様の画像形成方法で画出し試験を行った。その結果、感光体の削れに起因する画像不良に関しては特に問題の無い結果が得られた。但し、印字枚数が増すにつれ、画像濃度が低下していき、印字枚数５０００枚後は画像濃度が０．６７まで低下した。また、耐久３５００枚以降に裏汚れも発生しだした。これは、トナーＫＫを用いた比較例１３の場合と同様に、現像性および定着性の低いトナーだけが残ってしまったためと思われる。更に、耐久４０００枚目からは転写残トナーによる帯電ムラが発生した。これはトナーの円形度が不十分なため転写残トナー量が多いことによるものと思われる。いずれの現象も、表面が疎水化処理されていない酸化鉄を用いてトナーを製造したことに起因しているものと考えられる。
【０３９８】
【表８】

【０３９９】
【発明の効果】
本発明によれば、一成分系現像剤を用いた画像形成方法において、表面における鉄元素含有量／炭素元素含有量の比が０．００１未満であり、トナーの投影面積相当径をＣとし、酸化鉄とトナー表面との距離の最小値をＤとしたとき、Ｄ／Ｃ≦０．０２の関係を満足するトナーが５０個数％以上存在しており、平均円形度が０．９７０以上である現像剤を用いることにより、感光体の削れやトナー融着が発生せず、低湿下においても高品位で解像性に優れた画像が長期間安定して得られる。
【図面の簡単な説明】
【図１】非接触現像方式を用いた画像形成装置の一例を示す図である。
【図２】図１に示した画像形成装置の現像器部分の拡大図である。
【図３】接触現像方式を用いた画像形成装置の一例を示す図である。
【図４】図３に示した画像形成装置の現像器部分の拡大図である。
【図５】接触転写部材の一例を示す図である。
【図６】画像形成装置の現像バイアスのパターンを示す図である。
【図７】トナーの現像特性を試験するためのチェッカー模様の説明図である。
【図８】感光体の構成の一例を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a toner and an image forming method used in a recording method using an electrophotographic method, an electrostatic recording method, a magnetic recording method, a toner jet recording method, or the like. More specifically, the present invention relates to a toner and an image forming method used in a copying machine, a printer, and a fax machine in which a toner image is previously formed on an electrostatic latent image carrier and then transferred onto a transfer material to form an image.
[0002]
[Prior art]
Conventionally, a number of methods are known as electrophotographic methods. In general, an electric latent image is formed on an electrostatic image bearing member (hereinafter referred to as a “photosensitive member”) using a photoconductive substance by various means. Then, the latent image is developed with toner to form a visible image. If necessary, the toner image is transferred to a transfer material such as paper, and then the toner image is fixed on the transfer material by heat and pressure. To obtain a copy.
[0003]
As a method for visualizing an electric latent image, a cascade development method, a magnetic brush development method, a pressure development method, and the like are known.
[0004]
U.S. Pat. No. 3,909,258 proposes a developing method using electrically conductive magnetic toner. In this method, a conductive magnetic toner is supported on a cylindrical conductive sleeve having magnetism inside, and this is brought into contact with an electrostatic image for development. At this time, a conductive path is formed by toner particles between the surface of the recording member and the sleeve surface in the developing unit, and electric charges are guided from the sleeve to the toner particles through this conductive path, and between the image part of the electrostatic image. The toner particles adhere to the image area and are developed by the Coulomb force. The developing method using the conductive magnetic toner is an excellent method that avoids the problems associated with the conventional two-component developing method. However, since the toner is conductive, the developed image is transferred from the recording medium to plain paper or the like. There is a problem that it is difficult to electrostatically transfer to the final support member.
[0005]
As a developing method using a high-resistance magnetic toner that can be electrostatically transferred, there is a developing method using dielectric polarization of toner particles. However, this method has problems such as a slow development speed and insufficient density of the developed image, and is difficult in practical use.
[0006]
As another developing method using a high-resistance insulating magnetic toner, the toner particles are frictionally charged by friction between the toner particles, friction between the toner particles and the sleeve, and the like, and then contact the electrostatic image holding member. A developing method is known. However, this method requires less contact between the toner particles and the friction member, and the magnetic toner used has a large amount of magnetic material exposed on the surface of the toner particles. There were problems such as.
[0007]
For example, in Japanese Patent Application Laid-Open Nos. 54-43027 and 55-18656, a magnetic developer is thinly applied on a developer carrier, and this is triboelectrically charged, and then subjected to a magnetic field. And a so-called jumping development method is disclosed in which the electrostatic latent image is brought very close to each other and opposed to each other without contact. According to this method, the magnetic developer is thinly coated on the developer carrying member to enable sufficient frictional charging of the developer, and the developer is supported without being in contact with the electrostatic latent image while being magnetically supported. Therefore, the transfer of the developer to the non-image area, so-called fogging, is suppressed, and a high-definition image can be obtained.
[0008]
Such a one-component development method does not require carrier particles such as glass beads or iron powder as in the two-component method, and therefore the development device itself can be reduced in size and weight. Furthermore, since the two-component development method needs to keep the toner concentration in the developer constant, a device for detecting the toner concentration and supplying a necessary amount of toner is necessary. Therefore, the developing device is also large and heavy here. The one-component development method is preferable because such an apparatus is not necessary, and can be made small and light.
[0009]
However, the developing method using the insulating magnetic toner has unstable elements related to the insulating magnetic toner to be used. This is because a considerable amount of fine powdery magnetic material is mixed and dispersed in the insulating magnetic toner, and a part of the magnetic material is exposed on the surface of the toner particles. As a result, various characteristics required for the magnetic toner, such as development characteristics and durability of the magnetic toner, are changed or deteriorated.
[0010]
When the magnetic toner containing the conventional magnetic body is used, the above-mentioned problem occurs because the magnetic body is exposed on the surface of the magnetic toner. That is, by exposing magnetic fine particles having a relatively low resistance compared to the resin constituting the toner to the surface of the magnetic toner, the toner charging performance is lowered, the toner fluidity is lowered, and a long-term In use, the deterioration of the developer, such as a decrease in image density due to the separation of the magnetic material due to the rubbing between the toners or the regulating member, and the occurrence of shading unevenness called sleeve ghost, is caused.
[0011]
Conventionally, proposals regarding magnetic iron oxide contained in a magnetic toner have been made, but there are still points to be improved.
[0012]
For example, JP-A-62-279352 proposes a magnetic toner containing magnetic iron oxide containing silicon element. Such magnetic iron oxide intentionally has silicon element present inside the magnetic iron oxide, but still has a point to be improved in the fluidity of the magnetic toner containing the magnetic iron oxide.
[0013]
In Japanese Patent Publication No. 3-9045, there is a proposal to control the shape of magnetic iron oxide to be spherical by adding silicate. The magnetic iron oxide obtained by this method uses silicate to control the particle shape, so that a large amount of silicon element is distributed inside the magnetic iron oxide, and the amount of silicon element present on the magnetic iron oxide surface is small. Since the smoothness of the magnetic iron oxide is high, the fluidity of the magnetic toner is improved to some extent, but the adhesion between the binder resin constituting the magnetic toner and the magnetic iron oxide is insufficient.
[0014]
Japanese Patent Laid-Open No. 61-34070 proposes a method for producing ferric tetroxide by adding a hydrosilicate silicate solution during the oxidation reaction to triiron tetroxide. Although the iron tetroxide by this method has Si element near the surface, the Si element exists in a layer near the iron tetroxide surface, and the surface is weak against mechanical impact such as friction. Has a point.
[0015]
On the other hand, the toner is manufactured as a toner having a desired particle size by melting and mixing a binder resin, a colorant, and the like, uniformly dispersing, pulverizing with a fine pulverizer, and classifying with a classifier (pulverization method). However, there is a limit to the range of materials that can be used to reduce the toner particle size. For example, the resin colorant dispersion must be sufficiently brittle and capable of being finely pulverized by an economically usable production apparatus. From this requirement, in order to make the resin colorant dispersion brittle, when the resin colorant dispersion is actually finely pulverized at a high speed, particles having a wide particle size range are easily formed, and in particular, a relatively large proportion of fine particles ( There arises a problem that excessively pulverized particles) are included therein. Further, such highly brittle materials are often further pulverized or powdered when used as developing toners in copying machines and the like.
[0016]
Also, in the pulverization method, it is difficult to completely disperse solid fine particles such as magnetic powder or colorant into the resin, and depending on the degree of dispersion, fogging may increase and image density may decrease. . Furthermore, the pulverization method inherently exposes the magnetic iron oxide particles on the surface of the toner, so that problems still remain in the fluidity of the toner and the charging stability in a harsh environment.
[0017]
That is, in the pulverization method, there is a limit to finer toner particles required for high definition and high image quality, and accordingly, powder characteristics, particularly toner uniform chargeability and fluidity, are significantly attenuated.
[0018]
In order to overcome the problems of the toner by the pulverization method as described above, and further to satisfy the above-described requirements, a toner production method by a suspension polymerization method has been proposed.
[0019]
The toner by suspension polymerization (hereinafter referred to as polymerized toner) can be easily made into fine particles of toner, and further, since the shape of the obtained toner is spherical, it has excellent fluidity and is advantageous for high image quality. It becomes.
[0020]
However, when the polymerized toner contains a magnetic substance, its fluidity and charging characteristics are significantly lowered. This is because magnetic particles are generally hydrophilic and thus easily exist on the toner surface. In order to solve this problem, it is important to modify the surface characteristics of the magnetic material.
[0021]
Many proposals have been made regarding surface modification for improving the dispersibility of a magnetic substance in a polymerized toner. For example, various silane coupling agent treatment techniques for magnetic materials are disclosed in Japanese Patent Application Laid-Open Nos. 59-200254, 59-2000025, 59-200277, and 59-224102. Japanese Laid-Open Patent Publication No. 63-250660 discloses a technique for treating silicon element-containing magnetic particles with a silane coupling agent, and Japanese Laid-Open Patent Publication No. 7-72654 discloses magnetic iron oxide as an alkyl. Techniques for treating with trialkoxysilanes are disclosed.
[0022]
However, although the dispersibility in the toner is improved to some extent by these treatments, there is a problem that it is difficult to uniformly hydrophobize the surface of the magnetic material. The generation of non-magnetic particles cannot be avoided, and this is insufficient to improve the dispersibility in the toner to a good level.
[0023]
Further, a special toner in which magnetic particles are contained only in specific portions inside the particles has already been disclosed in Japanese Patent Application Laid-Open No. 7-209904.
[0024]
However, Japanese Patent Laid-Open No. 7-209904 does not mention the circularity of the disclosed toner.
[0025]
Furthermore, to summarize the toner configuration disclosed in Japanese Patent Application Laid-Open No. 7-209904, the toner layer has a structure in which a resin layer having no magnetic particles is formed with a certain thickness or more in the vicinity of the toner particle surface. Yes, this means that there is a considerable proportion of the toner surface layer where no magnetic particles are present. However, in other words, when the average particle size is as small as 10 μm, for example, such a developer has a small volume in which magnetic particles can exist, and therefore it is difficult to enclose a sufficient amount of magnetic particles. In addition, in such a developer, the ratio of the surface resin layer in which the magnetic particles do not exist is different between the developer particles having a large particle size and the developer particles having a small particle size in the particle size distribution of the developer. The content of the magnetic substance contained in the developer is different, and the developability and transferability are also different depending on the particle size of the developer, that is, selective developability depending on the particle size is easily observed. Therefore, if printing is performed for a long time with a magnetic developer with a non-uniform particle size, particles that contain a large amount of magnetic material and are difficult to develop, that is, developer particles with a large particle size are likely to remain, and the image density and image quality are lowered. It also leads to deterioration.
[0026]
Also, LED and LBP printers are the mainstream in the recent market as printer devices, and the direction of technology is higher resolution, that is, what was conventionally 240, 300 dpi is 400, 600, 800 dpi. Accordingly, with this development, higher definition has been demanded. In addition, copiers are also becoming more sophisticated, and therefore are moving toward digitalization. This direction is mainly due to the method of forming an electrostatic latent image with a laser, so it is also proceeding in the direction of high resolution. Again, a high-resolution and high-definition development method is required as in the case of a printer. Yes. For this reason, the toner particle size has been reduced, and Japanese Patent Application Laid-Open Nos. 1-112253, 1-1191156, 2-214156, 2-284158, and 3-181955. No. 4, JP-A-4-162048, etc. propose a toner having a specific particle size distribution and a small particle size.
[0027]
In recent years, from the viewpoint of environmental protection, primary charging and transfer processes using a photoreceptor contact member are becoming mainstream from primary charging and transfer processes using corona discharge.
[0028]
In the primary charging and transfer process using corona discharge, a large amount of ozone is generated when generating corona discharge, particularly negative corona. Therefore, it is necessary to equip the electrophotographic apparatus with a filter for capturing ozone. There are problems such as an increase in size and an increase in running cost. Further, image problems caused by such a corona charging method include, for example, so-called image flow caused by a decrease in surface resistance of the photoreceptor due to adhesion of nitrogen oxide or the like, or the electrophotographic apparatus is stopped. Examples include a memory phenomenon of a photoconductor caused by ions remaining in the charger.
[0029]
As a technique for solving such a problem, a charging member such as a roller or a blade or a transfer member is brought into contact with the surface of the photosensitive member to form a narrow space near the contact portion, which can be interpreted according to the so-called Paschen's law. A contact charging method or a contact transfer method that suppresses the generation of ozone as much as possible by forming such a discharge has been developed. For example, JP-A-57-178257, JP-A-56-104351, JP-A-58. No. 40566, Japanese Patent Laid-Open No. 58-139156, and Japanese Patent Laid-Open No. 58-150975 are known techniques. Among these, a charging method and a transfer method using a conductive elastic roller as described in JP-A Nos. 63-149669 and 2-123385 are preferably used from the viewpoint of stability. ing.
[0030]
However, it has been found that the use of the contact charging method or the contact transfer method has an alarming problem, unlike the case of using corona discharge.
[0031]
Specifically, in the case of the contact transfer method, since the transfer member is brought into contact with the photosensitive member via the transfer member at the time of transfer, the toner image is formed when the toner image formed on the photosensitive member is transferred to the transfer material. Are in contact with each other, and a problem of partial transfer failure called so-called transfer omission occurs. Furthermore, as a recent technical direction, higher resolution and higher definition development methods have been required, and in order to meet such demands, progress has been made toward reducing the particle size of toner. Thus, as the toner particle size becomes smaller, the adhesion force (mirror image force, van der Waals force, etc.) of the toner particles to the photosensitive member becomes larger than the Coulomb force applied to the toner particles in the transfer process, and as a result, the residual transfer remains. The toner increases, and the transfer defect tends to be further deteriorated.
[0032]
On the other hand, in the contact charging method, the charging member is pressed against the surface of the photoreceptor with a pressing pressure. For this reason, residual toner that has not been transferred, that is, transfer residual toner, is pressed against the surface of the photoconductor, so that wear due to abrasion or a portion of the photoconductor surface is likely to cause toner fusion. The more toner remaining, the more pronounced it appears.
[0033]
Such scraping of the photosensitive member and toner fusion cause a serious defect in the formation of an electrostatic latent image on the electrostatic charge image carrier. Specifically, since the photoconductor scraping makes primary charging impossible, the shaved portion appears black on the halftone image. Further, since toner fusion makes it impossible to form a latent image by exposure, the fused portion appears white on the halftone image. Furthermore, the transferability of the toner is also deteriorated. For this reason, coupled with the above-mentioned transfer failure, a significant image defect appears, and in some cases, the image quality deteriorates synergistically.
[0034]
Such problems of photoconductor scraping and transfer failure are likely to occur when a developer composed of irregularly shaped toner particles is used. This is presumably because the edge of the toner particles easily scratches the surface of the photosensitive member in addition to the low transferability of the irregular shaped toner. Further, the problem of abrasion becomes particularly noticeable when a magnetic developer having a magnetic substance exposed on the toner particle surface is used. This is easily convinced considering that the exposed magnetic material is directly pressed against the photoreceptor.
[0035]
Furthermore, when the amount of transfer residual toner increases, it becomes difficult to maintain sufficient contact between the contact charging member and the photosensitive member, and chargeability deteriorates. Therefore, in reversal development, toner transfer to non-image areas, that is, fogging. Is likely to occur. This phenomenon is often seen under low humidity where the resistance of the member tends to increase.
[0036]
As described above, in the image forming method using the contact charging method and the contact transfer method which are very preferable in consideration of the environment, the development of a magnetic developer that has high transferability and is less likely to cause photoconductor scraping and toner fusion. It is desired.
[0037]
On the other hand, when the toner image formed on the photoconductor in the development process is transferred to the transfer material in the transfer process, if residual transfer toner remains on the photoconductor as described above, the toner is cleaned in the cleaning process and is used as waste toner. It needs to be stored in a container. Conventionally, blade cleaning, fur brush cleaning, roller cleaning, and the like have been used for this cleaning process. In either method, the transfer residual toner is mechanically scraped off or damped and collected in a waste toner container. However, when such a member is pressed against the surface of the photoconductor, the photoconductor is worn away, resulting in a problem of shortening the life. Further, from the standpoint of the apparatus, the apparatus is inevitably increased in size to have such a cleaning apparatus, which has been a bottleneck when aiming to make the apparatus compact. Furthermore, from the viewpoint of ecology, a system that does not generate waste toner is desired in the sense of effective use of toner.
[0038]
Here, technologies relating to cleanerless are disclosed in Japanese Patent Application Laid-Open Nos. 59-133573, 62-203182, 63-133179, and 64-20587. No. 2, JP-A-2-302277, JP-A-5-2289, JP-A-5-53482, JP-A-5-61383, and the like, but a desirable toner configuration is not mentioned.
[0039]
Japanese Patent Application Laid-Open No. 61-279864 proposes a toner that defines shape factors SF-1 and SF-2. However, this publication does not describe anything about transfer. Further, as a result of additional examples, the transfer efficiency is low and further improvement is required.
[0040]
Further, Japanese Patent Laid-Open No. 63-235953 proposes a magnetic toner that has been spheroidized by a mechanical impact force. However, the transfer efficiency is still insufficient and further improvement is necessary.
[0041]
In a developing and cleaning configuration that essentially does not have a cleaning device, the surface of the photosensitive member is rubbed with toner and a toner carrier, the toner of the non-image portion is collected with the toner carrier, and the image portion is developed with toner. Configuration is required. If the reversely charged toner such as the transfer residual toner or fog toner can be easily reversed to the positive charge during the rubbing, the potential recovery becomes easy.
[0042]
Conventionally, when a toner containing a magnetic material is used in a developing and cleaning configuration, the magnetic material is exposed on the surface of the toner, so that there is a partial continuity between the photoconductor and the toner carrier through the toner during development. As a result, the electrostatic charge image on the photoreceptor is disturbed and it is difficult to obtain a high-definition image. Further, the magnetic toner having a magnetic body exposed on the toner surface is insufficiently charged with the transfer residual toner, so that the smooth recovery of the toner on the photoconductor in the developing process is hindered. Furthermore, when the photoconductor is rubbed with the toner and the toner carrier, the photoconductor is abraded by the magnetic material exposed on the surface of the toner, and the life of the photoconductor is shortened. As a result, an area without an image becomes a printed image that is smeared with toner by a toner image, a so-called ghost image.
[0043]
As described above, it is desirable that the magnetic material-containing toner used in the development and cleaning configuration is not exposed to the magnetic material on the toner surface.
[0044]
In addition, if the pressing force of the cleaning member is weakened to extend the life of the photosensitive member, the amount of residual toner that passes through the cleaning member increases by that amount. It can be said that it is very important in the system.
[0045]
When the magnetic toner containing the conventional magnetic material is used, the above-mentioned problems occur because the magnetic material is exposed on the surface of the toner. is there. In the case of a magnetic toner in which a magnetic material is exposed on the toner surface, the resistance of the magnetic material is lower than the resistance of the resin of the toner, so that the charging characteristics under high humidity are likely to be poor, the fog suppression is deteriorated, the transfer This causes undesired adverse effects such as ghosting due to lowering of the transferability, recovery of the transfer residual toner, and deterioration of the photoreceptor performance due to rubbing with the photoreceptor.
[0046]
That is, in reality, no magnetic toner having good initial characteristics and stability in the developing and cleaning configuration has been found so far.
[0047]
[Problems to be solved by the invention]
An object of the present invention is to provide a toner and an image forming method that solve the above-mentioned problems of the prior art.
[0048]
An object of the present invention is to provide a toner that is less influenced by the environment, has a stable charging performance, has a high image density even during long-time use, suppresses fogging, and has excellent image reproducibility. is there.
[0049]
The object of the present invention is to solve the above-mentioned various problems in the contact development type image forming process that can also correspond to a cleaner-less configuration, and the occurrence of fog and ghost is suppressed without being influenced by the environment. An object is to provide an image forming method excellent in resolution, transferability and durability.
[0050]
It is an object of the present invention to provide an image forming method that combines a contact charging process with less ozone generation and a non-contact development process with less fog using a one-component developer. It is an object of the present invention to provide an image forming method in which image defects are less likely to occur even when used for a long period of time by using a magnetic developer that has a small amount of untransferred toner and the like, and that the surface of the photoreceptor is hard to be scraped.
[0051]
An object of the present invention is to provide an image forming method capable of forming a stable electrostatic latent image even in a low humidity environment and having less image defects such as fog due to a decrease in chargeability during durability.
[0052]
[Means for Solving the Problems]
The present invention has toner particles containing at least a binder resin and iron oxide, and i) iron with respect to the carbon element content (A) present on the toner surface measured by X-ray photoelectron spectroscopy. The ratio (B / A) of the element content (B) is less than 0.001, ii) the projected area equivalent diameter of the toner is C, and the oxidation in cross-sectional observation of the toner using a transmission electron microscope (TEM) When the minimum distance between the iron and the toner surface is D, 50% or more of the toners satisfy the relationship of D / C ≦ 0.02, and iii) the average circularity of the toner is 0.970 or more. It is related with the toner characterized by being.
[0053]
The present invention further includes a charging step of charging the electrostatic image carrier with a charging member to which a voltage is applied from the outside; an exposure step of forming an electrostatic latent image on the electrostatic image carrier by exposure; An image forming method comprising: developing a latent image with a toner carried on a toner carrier to form a toner image; and a transfer step for transferring the toner image onto a transfer material, wherein the toner is at least bonded. A toner particle containing an adhesion resin and iron oxide; i) the content of iron element (B) relative to the content of carbon element (A) present on the toner surface measured by X-ray photoelectron spectroscopy ) Ratio (B / A) is less than 0.001, ii) the projected area equivalent diameter of the toner is C, and the iron oxide and the toner surface in the cross-sectional observation of the toner using a transmission electron microscope (TEM) D is the minimum distance In this case, the present invention relates to an image forming method, wherein the toner satisfying the relationship of D / C ≦ 0.02 is 50% by number or more, and iii) the average circularity of the toner is 0.970 or more.
[0054]
DETAILED DESCRIPTION OF THE INVENTION
As a result of intensive studies on the homogenization and stabilization of the charging of the magnetic toner so far, the present inventors have found that the content (A) of the carbon element present on the surface of the magnetic toner measured by X-ray photoelectron spectroscopy analysis. The ratio of iron element content (B) (B / A) is less than 0.001, and the following formula
[0055]
[Outside 1]

(Where L₀Indicates the perimeter of a circle having the same projected area as the particle image, and L indicates the perimeter of the projected image of the particle. )
The average circularity of the toner calculated from the circularity obtained by the above is found to be 0.970 or more, which is very effective for uniformizing and stabilizing the chargeability of the toner, and the present invention has been achieved. It is.
[0056]
In addition, by using the toner as described above, a cleanerless structure in which a ghost image is likely to be generated due to poor toner collection, an image forming method combining contact charging, a contact charging process, a one-component non-contact development process, and contact transfer. In the image forming method including the steps, the photoconductor is scraped, the charging failure and the transfer failure are remarkably suppressed, and a high-definition image free from fogging and other image defects can be stably obtained even after long-term use. The headline, the present invention has been reached.
[0057]
This is difficult to achieve with a magnetic toner using magnetic iron oxide that has been generally used.
[0058]
The reason is that the magnetic iron oxide used was not sufficiently and uniformly hydrophobized.
[0059]
When manufacturing magnetic toner, the use of magnetic iron oxide whose surface has been hydrophobized can improve the dispersibility of the magnetic iron oxide particles in the toner binder resin. Even when a large amount of iron oxide is exposed, it is difficult to impair the charging performance of the toner in any environment as long as the surface of the magnetic iron oxide is uniformly hydrophobized.
[0060]
Therefore, various methods for hydrophobizing the surface of magnetic iron oxide particles have been proposed. However, it has been difficult to obtain magnetic iron oxide that has been sufficiently and uniformly hydrophobized by conventional methods. Also, when a large amount of treatment agent or the like is used, or when a highly viscous treatment agent or the like is used, the degree of hydrophobicity is certainly increased, but coalescence of particles occurs, and compatibility between hydrophobicity and dispersibility is not necessarily achieved. It was not achieved.
[0061]
Generally, since the untreated iron oxide surface has hydrophilicity, it is necessary to hydrophobize the hydrophilic iron oxide in order to obtain hydrophobic iron oxide. However, the conventional toner using such an iron oxide has a poor chargeability because its chargeability fluctuates depending on humidity and the like.
[0062]
On the other hand, the iron oxide used as a magnetic material in the toner of the present invention has a very high level of uniformity of hydrophobicity. For example, when hydrophobizing, it is in an aqueous medium. The iron oxide obtained by surface treatment while hydrolyzing the coupling agent while dispersing the iron oxide to have a primary particle size. Compared with treatment in the gas phase, the hydrophobization method in an aqueous medium is less likely to cause coalescence between the iron oxide particles, and the repulsive action between the iron oxide particles due to the hydrophobization treatment works. Since the surface treatment is performed almost in the state of primary particles, highly uniform hydrophobicity is achieved.
[0063]
The method of treating the surface of iron oxide while hydrolyzing the coupling agent in an aqueous medium does not require the use of a coupling agent that generates a gas, such as chlorosilanes and silazanes. In the phase, the iron oxide particles can be easily combined with each other, and a highly viscous coupling agent which has been difficult to be treated can be used, so that the hydrophobizing effect is great.
[0064]
Examples of the coupling agent that can be used in the present invention include a silane coupling agent and a titanium coupling agent. More preferably used is a silane coupling agent having a general formula
R_mSiY_n
[Wherein, R represents an alkoxy group, m represents an integer of 1 to 3, Y represents a hydrocarbon group such as an alkyl group, a vinyl group, a glycidoxy group, or a methacryl group, and n represents an integer of 1 to 3. Show. ]. For example, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethyl Mention may be made of methoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-hexadecyltrimethoxysilane and n-octadecyltrimethoxysilane.
[0065]
In particular, the formula
C_pH_{2p + 1}-Si- (OC_qH_{2q + 1})_Three
[Wherein p represents an integer of 2 to 20 and q represents an integer of 1 to 3], and the iron oxide is hydrophobized in an aqueous medium using an alkyltrialkoxysilane coupling agent represented by Is good.
[0066]
When p in the above formula is smaller than 2, the hydrophobic treatment is easy, but it is difficult to impart sufficient hydrophobicity. When p is larger than 20, the hydrophobicity is sufficient, but iron oxide The coalescence of the particles increases and it becomes difficult to sufficiently disperse the iron oxide particles in the toner.
[0067]
On the other hand, when q is larger than 3, the reactivity of the silane coupling agent is lowered and the hydrophobicity is not sufficiently performed.
[0068]
In particular, p in the formula represents an integer of 2 to 20 (more preferably an integer of 3 to 15), and q represents an integer of 1 to 3 (more preferably an integer of 1 or 2). A coupling agent should be used.
[0069]
The treatment amount is 0.05 to 20 parts by mass, preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of iron oxide.
[0070]
In the present invention, the aqueous medium is a medium containing water as a main component. Specific examples of the aqueous medium include water itself, water added with a small amount of a surfactant, water added with a pH adjusting agent, and water added with an organic solvent. As the surfactant, a nonionic surfactant such as polyvinyl alcohol is preferable. The surfactant is preferably added in an amount of 0.1 to 5% by mass with respect to water. Examples of the pH adjuster include inorganic acids such as hydrochloric acid.
[0071]
Stirring is sufficiently performed, for example, with a mixer having a stirring blade (specifically, a high shear force mixing device such as an attritor or a TK homomixer) so that the iron oxide fine particles become primary particles in the aqueous medium. Is good.
[0072]
Since the surface of the iron oxide particles thus obtained has been uniformly hydrophobized, when used as a toner material, the dispersibility in the toner is very good and there is no exposure from the toner surface. Therefore, by using such iron oxide, the ratio (B / A) of the content (B) of the iron element to the content (A) of the carbon element present on the surface of the toner measured by X-ray photoelectron spectroscopy analysis. ) Of less than 0.001 can be obtained, and the uniformity and stabilization of charging of the toner can be achieved. By using this toner, high image quality and high durability stability can be achieved. Furthermore, by making (B / A) less than 0.0005, the chargeability and stability are further improved.
[0073]
The iron oxide used in the toner of the present invention is produced, for example, by the following method.
[0074]
An aqueous solution containing ferrous hydroxide is prepared by adding an alkali such as sodium hydroxide in an amount equivalent to or greater than the iron component to the ferrous sulfate aqueous solution. Air was blown in while maintaining the pH of the prepared aqueous solution at pH 7 or higher (preferably pH 8 to 10), the ferrous hydroxide oxidation reaction was performed while heating the aqueous solution to 70 ° C. or higher, and the core of magnetic iron oxide particles First, a seed crystal is formed.
[0075]
Next, an aqueous solution containing about 1 equivalent of ferrous sulfate is added to the slurry-like liquid containing seed crystals based on the amount of alkali added previously. While maintaining the pH of the liquid at 6 to 10, the reaction of ferrous hydroxide is promoted while blowing air, and magnetic iron oxide particles are grown with the seed crystal as the core. As the oxidation reaction proceeds, the pH of the liquid shifts to the acidic side, but the pH of the liquid is preferably not less than 6. Adjust the pH of the solution at the end of the oxidation reaction, stir well so that the magnetic iron oxide becomes primary particles, add the coupling agent, stir well, stir, filter, dry, and lightly crush after stirring By doing so, hydrophobic treated magnetic iron oxide particles can be obtained. Alternatively, after the oxidation reaction is completed, the iron oxide particles obtained by washing and filtering are redispersed in another aqueous medium without drying, and then the pH of the redispersion is adjusted and sufficiently stirred. A silane coupling agent may be added to perform the coupling treatment.
[0076]
In any case, it is important that the untreated iron oxide particles generated in the aqueous solution be hydrophobized in the state of the water-containing slurry before passing through the drying step. This is because if untreated iron oxide particles are dried as they are, coalescence between the particles cannot be avoided, and even if wet-hydrophobic treatment is performed on such agglomerated powder, uniform hydrophobization treatment is possible. This is because it is difficult to achieve B / A <0.001 with the toner using the surface-treated iron oxide as in the toner according to the present invention.
[0077]
As the ferrous salt, iron sulfate generally produced as a by-product in the production of sulfuric acid titanium, iron sulfate produced as a by-product with the surface cleaning of the steel sheet can be used, and iron chloride or the like can be used.
[0078]
In the method for producing magnetic iron oxide by the aqueous solution method, an iron concentration of 0.5 to 2 mol / liter is generally used from the viewpoint of preventing an increase in viscosity during the reaction and the solubility of iron sulfate. Generally, the lower the iron sulfate concentration, the finer the particle size of the product. Further, in the reaction, the larger the amount of air and the lower the reaction temperature, the easier the atomization.
[0079]
By using the thus produced hydrophobic iron oxide particles for the toner, it is possible to obtain the toner of the present invention having excellent image characteristics and stability.
[0080]
Japanese Patent Publication No. 60-3181 also discloses a method of producing a magnetic polymer toner containing magnetic fine particles whose surface is wet-treated with a silane coupling agent.
[0081]
However, Japanese Patent Publication No. 60-3181 discloses a wet surface treatment of a dry powdery untreated magnetic material with a silane coupling agent.
[0082]
Since these untreated dry magnetic powders cannot avoid particle coalescence due to primary agglomeration during drying, it is difficult to make individual magnetic particles uniformly hydrophobic even if wet surface treatment is performed. . Therefore, even when a polymerized toner is produced using such a surface-treated magnetic material, it is difficult to achieve B / A <0.001 which is a characteristic of the toner according to the present invention.
[0083]
When the projected area equivalent diameter of the toner is C and the minimum distance between the iron oxide and the toner surface in the cross-sectional observation of the toner using a transmission electron microscope (TEM) is D, D / C ≦ 0.02. That the number of toners satisfying the relationship is 50% or more is also one of the necessary aspects of the toner of the present invention.
[0084]
In the present invention, the number of toners satisfying the relationship of D / C ≦ 0.02 needs to be 50% or more, preferably 65% or more, and more preferably 75% or more.
[0085]
When the number of toners satisfying the relationship of D / C ≦ 0.02 is less than 50%, in the majority of toners, there is no magnetic particle at least outside the boundary line of D / C = 0.02. . If such particles are assumed to be spherical, at least 11.5% of the space in which no iron oxide exists is present on the surface of the toner when one toner is used as the entire space. Actually, the iron oxide does not exist uniformly at the closest position so as to form an inner wall inside the toner, so that it is obvious that it becomes 12% or more. In the toner composed of such particles, various problems as described above are likely to occur.
[0086]
In the present invention, as a specific method for measuring D / C by TEM, particles to be observed can be sufficiently dispersed in a room temperature curable epoxy resin and then cured in an atmosphere at a temperature of 40 ° C. for 2 days. The cured product is preferably observed as it is or as a flaky sample with a microtome equipped with diamond teeth after freezing.
[0087]
A specific method for determining the ratio of the number of corresponding particles is as follows. Particles for determining D / C by TEM are obtained by calculating the equivalent circle diameter from the cross-sectional area in the micrograph, and the value is a width of ± 10% of the number average particle diameter obtained by the method described later using a Coulter counter. The particles contained in the above are regarded as applicable particles, and for the corresponding 100 particles, the minimum value (D) of the distance from the magnetic particle surface is measured, D / C is obtained, and the particles having a D / C value of 0.02 or less are obtained. Calculate the percentage. In this case, a magnification of 10,000 to 20,000 times is suitable for the microphotograph to perform measurement with high accuracy. In the present invention, a transmission electron microscope (Hitachi model H-600) was used as an apparatus, observed at an accelerating voltage of 100 kV, and observed and measured using a photomicrograph with a magnification of 10,000.
[0088]
A toner in which the number of toners satisfying B / A <0.001 and satisfying the relationship of D / C ≦ 0.02 is 50% or more means that the magnetic material is localized on the toner surface, On the other hand, the magnetic substance is not uniformly contained in the toner and is unevenly distributed inside the toner, but the magnetic substance is substantially uniformly dispersed in the toner, and the exposure of the magnetic substance to the toner surface is suppressed. The toner that is being used. If the dispersion of the magnetic material is not uniform, it is difficult to satisfy the provisions of the present invention.
[0089]
Further, if a magnetic developer in which iron oxide is hardly exposed on the surface of the toner particles is used, even in an image forming method in which the toner is pressed against the surface of the electrostatic charge image carrier by a charging member, a transfer member, etc. The surface of the image carrier is hardly scraped off, and the electrostatic charge image carrier scraping and toner fusion can be significantly reduced over a long period of time.
[0090]
The iron oxide used in the toner of the present invention is preferably used in an amount of 10 to 200 parts by weight, more preferably 20 to 180 parts by weight, with respect to 100 parts by weight of the binder resin. When the blending amount of iron oxide is less than 10 parts by mass, the coloring power of the developer is poor, and it is difficult to suppress fogging. Not only makes it difficult to uniformly disperse iron oxide into individual toner particles, but also lowers the fixability.
[0091]
Next, the circularity of the toner, which is another feature of the present invention, will be described. In order to reduce the toner adhesion to the non-image area on the electrostatic image bearing member and the amount of residual toner, it is necessary that the chargeability of the toner particles is sufficient and uniform. Furthermore, when using a toner having a small particle diameter from the viewpoint of improving the image quality, the adhesion force of the toner particles increases, so the shape of the toner particles has a great influence on the toner adhesion to the non-image area on the electrostatic charge image carrier. Effect. In other words, the closer the toner particles are to a spherical shape and the more uniform the shape, the smaller the adhesion area of the particles, the less toner adhesion to the non-image area on the electrostatic image bearing member and the residual toner transfer amount, high image quality and durability Stability is achieved.
[0092]
In addition, the toner particles according to the present invention are sufficiently charged, and as described above, the adhesion of the toner particles is reduced, so that the toner particles from the electrostatic charge image carrier to the transfer material such as paper can be transferred. Transfer efficiency is also greatly improved. This can be said to be an important toner performance for achieving high resolution as well as reproducibility of a minute dot image.
[0093]
Therefore, in the toner of the present invention, the average circularity of the toner needs to be 0.970 or more, thereby achieving high image quality and high stability.
[0094]
Therefore, since the residual toner after transfer is greatly reduced by using such a developer, the amount of toner present in the pressure contact portion between the charging member and the photosensitive member is very small, and even in an image forming method having a contact charging step. It is considered that the photoconductor scraping and toner fusion are prevented, and image defects are remarkably suppressed. Furthermore, since the toner having an average circularity of 0.970 or more has almost no edge portion on the surface, the surface of the photoconductor is not scratched at the pressure contact portion between the charging member and the photoconductor, thereby suppressing the abrasion of the surface of the photoconductor. It can also be mentioned.
[0095]
These effects are conspicuous even in an image forming method including a contact transfer process in which transfer loss tends to occur.
[0096]
In the toner of the present invention, the weight average particle diameter is preferably 2 to 10 μm.
[0097]
When the weight average particle size of the toner exceeds 10 μm, the reproducibility of the fine dot image is lowered, and the charging stability of the toner under the severe environment obtained by the present invention cannot be sufficiently exhibited. On the other hand, when the weight average particle diameter of the toner is smaller than 2 μm, even if the special iron oxide of the present invention is used, the fluidity of the toner is remarkably lowered, and problems such as fogging and density thinning due to poor charging are likely to occur. Become.
[0098]
That is, in the toner of the present invention, a remarkable effect on the image such as improvement in charging stability and fluidity appears on the image when the weight average particle diameter is 2 to 10 μm (more preferably 3 to 10 μm). Furthermore, 3.5 to 8.0 μm is preferable in terms of further improving the image quality.
[0099]
Next, a method for producing toner according to the present invention will be described.
[0100]
The toner of the present invention can be manufactured by a pulverization method, but in the pulverization method, it is necessary to perform mechanical, thermal, or some special treatment in order to set the average circularity of the toner to 0.970 or more. Therefore, it is preferable to produce by suspension polymerization. Even when a toner is produced by suspension polymerization using a normal magnetic material, the magnetic material is inferior in dispersibility, so that the magnetic material is unevenly distributed on the toner surface, or the magnetic material is confused during granulation in an aqueous medium. The toner has an average circularity of 0.970 or more, and the iron oxide used in the present invention is at a high level. Since uniform hydrophobicization is performed, a toner having an average circularity of 0.970 or more can be easily obtained.
[0101]
The following are mentioned as a polymerizable monomer which comprises the polymerizable monomer type | system | group used for this invention.
[0102]
Examples of the polymerizable monomer include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, and p-ethylstyrene; methyl acrylate, ethyl acrylate, Acrylic esters such as n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate Class: Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenolic methacrylate , Dimethylaminoethyl methacrylate, such as methacrylic acid esters of diethylaminoethyl methacrylate; acrylonitrile, methacrylonitrile, acrylamide.
[0103]
These monomers can be used alone or in combination. Among the above-mentioned monomers, styrene or a styrene derivative is preferably used alone or mixed with other monomers from the viewpoint of the developing characteristics and durability of the toner.
[0104]
In addition, the toner of the present invention preferably contains 0.5 to 50% by mass of a release agent with respect to the binder resin. Usually, a toner image is transferred onto a transfer material in a transfer process, and the toner image is then fixed on the transfer material with energy such as heat and pressure to obtain a semi-permanent image. As a fixing method at this time, a heat roll type fixing is generally used. As described above, if a toner having a weight average particle diameter of 10 μm or less is used, a very high-definition image can be obtained. When a transfer material such as paper is used, the toner particles having a small diameter enter the gap between the fibers of the paper, and heat reception from the heat fixing roller becomes insufficient, and low temperature offset tends to occur. However, in the toner of the present invention, by containing an appropriate amount of wax as a release agent, it is possible to prevent the photoconductor from being scraped while achieving both high resolution and offset resistance.
[0105]
Examples of the wax usable in the toner of the present invention include paraffin wax, microcrystalline wax, petroleum wax such as petrolactam and derivatives thereof, montan wax and derivatives thereof, hydrocarbon wax and derivatives thereof by Fischer-Tropsch method, and polyethylene. Polyolefin waxes and derivatives thereof, natural waxes such as carnauba wax and candelilla wax, and derivatives thereof. Derivatives here include oxides, block copolymers with vinyl monomers, and graft modified products. Furthermore, higher fatty alcohols, fatty acids such as stearic acid and palmitic acid or compounds thereof, acid amide waxes, ester waxes, ketones, hydrogenated castor oil and derivatives thereof, plant waxes and animal waxes can also be used.
[0106]
Among these wax components, the DSC curve measured by a differential scanning calorimeter preferably has a maximum endothermic peak in the region of 40 to 110 ° C. when the temperature is raised, and has a maximum endothermic peak in the region of 45 to 90 ° C. What has it is still more preferable. By having the maximum endothermic peak in the above temperature range, it is possible to effectively exhibit releasability while greatly contributing to low-temperature fixing. When this maximum endothermic peak is less than 40 ° C., the self-cohesive force of the wax component becomes weak, and as a result, the high temperature offset resistance deteriorates. On the other hand, if the maximum endothermic peak exceeds 110 ° C., the fixing temperature becomes high and low temperature offset is likely to occur, which is not preferable. Further, in the case where granulation / polymerization is carried out in an aqueous medium and a toner is directly obtained by the polymerization method, a high maximum endothermic peak temperature is not preferable because a problem such as precipitation of a wax component mainly occurs during granulation.
[0107]
The maximum endothermic peak temperature of the wax component is measured according to “ASTM D 3418-8”. For the measurement, for example, DSC-7 manufactured by PerkinElmer is used. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of heat uses the heat of fusion of indium. An aluminum pan is used as a measurement sample, an empty pan is set as a control, and measurement is performed at a heating rate of 10 ° C./min.
[0108]
In the toner of the present invention, the content of the wax component is preferably in the range of 0.5 to 50% by mass with respect to the binder resin. If the content of the wax component is less than 0.5% by mass, the effect of suppressing the low temperature offset is poor, and if it exceeds 50% by mass, the long-term storage stability is deteriorated and the dispersibility of other toner materials is deteriorated. Lead to deterioration of fluidity and image characteristics.
[0109]
In the present invention, polymerization may be carried out by adding a resin to the monomer system. For example, hydrophilic functional groups such as amino groups, carboxylic acid groups, hydroxyl groups, sulfonic acid groups, glycidyl groups, and nitrile groups cannot be used because monomers are water-soluble and dissolve in aqueous suspension to cause emulsion polymerization. When it is desired to introduce the monomer component contained in the toner, it may be in the form of a copolymer such as a random copolymer of these and a vinyl compound such as styrene or ethylene, a block copolymer, or a graft copolymer, or It can be used in the form of a polycondensate such as polyester or polyamide, or a polyaddition polymer such as polyether or polyimine. When such a polymer containing a polar functional group is allowed to coexist in the toner, the above-mentioned wax component is phase-separated and the encapsulation becomes stronger, and a toner having good offset resistance, blocking resistance, and low-temperature fixability can be obtained. Obtainable. As the usage-amount, 1-20 mass parts is preferable with respect to 100 mass parts of polymerizable monomers. If the amount used is less than 1 part by mass, the effect of addition is small, whereas if it is used in excess of 20 parts by mass, it becomes difficult to design various physical properties of the polymerized toner. Moreover, the average molecular weight of the high molecular polymer containing these polar functional groups is preferably 3000 or more. When the molecular weight is less than 3000, particularly 2000 or less, the present polymer is likely to concentrate near the surface, which is unfavorable because it tends to adversely affect developability, blocking resistance and the like. In addition, if a polymer having a molecular weight different from the molecular weight range of the toner obtained by polymerizing the monomer is dissolved in the monomer and polymerized, a toner having a wide molecular weight distribution and high offset resistance can be obtained. it can.
[0110]
The toner of the present invention may contain a charge control agent in order to stabilize the charge characteristics. As the charge control agent, known ones can be used, but a charge control agent that has a high charging speed and can stably maintain a constant charge amount is particularly preferable.
[0111]
Further, when the toner is produced using a direct polymerization method, a charge control agent having a low polymerization inhibitory property and substantially free from a solubilized product in an aqueous dispersion medium is particularly preferable. Specific compounds include, as negative charge control agents, metal compounds of aromatic carboxylic acids such as salicylic acid, alkylsalicylic acid, dialkylsalicylic acid, naphthoic acid, dicarboxylic acid, metal salts or metal complexes of azo dyes or azo pigments, sulfones Examples thereof include a polymer compound having an acid or carboxylic acid group in the side chain, a boron compound, a urea compound, a silicon compound, and a calixarene. Examples of the positive charge control agent include a quaternary ammonium salt, a polymer compound having the quaternary ammonium salt in the side chain, a guanidine compound, a nigrosine compound, and an imidazole compound. These charge control agents are preferably used in an amount of 0.5 to 10 parts by mass with respect to 100 parts by mass of the polymerizable monomer. However, the developer involved in the image forming method of the present invention does not require the addition of a charge control agent, and the toner in the toner is positively utilized by frictional charging of the developer with the layer pressure regulating member or the developer carrier. It is not always necessary to include a charge control agent.
[0112]
The iron oxide used as the magnetic material in the toner of the present invention may contain elements such as phosphorus, cobalt, nickel, copper, magnesium, manganese, aluminum, and silicon, and is mainly composed of iron trioxide and γ-iron oxide. These are used as components, and these may be used alone or in combination of two or more. These iron oxides preferably have a BET specific surface area by nitrogen adsorption method of 2 to 30 m.²/ G, especially 3 to 28m²/ G and a Mohs hardness of 5 to 7 is preferred.
[0113]
The shape of iron oxide includes octahedrons, hexahedrons, spheres, needles, scales, etc., but those with low anisotropy such as octahedrons, hexahedrons, spheres, and irregular shapes increase the image density. Preferred above. Such a shape can be confirmed by SEM or the like. As the particle size of iron oxide, the volume average particle size is 0.1 to 0.3 μm and 0.03 to 0.1 μm in the measurement of particle size targeting particles having a particle size of 0.03 μm or more. The number of particles is preferably 40% by number or less.
[0114]
When an image is obtained from a magnetic toner using iron oxide having an average particle size of less than 0.1 μm, the color of the image shifts to red, and the blackness of the image is insufficient, or the halftone image is more reddish. Generally, it is not preferable, such as a strong tendency to feel strongly. Further, since the surface area of iron oxide is increased, dispersibility is lowered, energy required for production is increased, and it is not efficient. Further, the effect of iron oxide as a colorant is weakened, and the image density may be insufficient, which is not preferable.
[0115]
On the other hand, if the average particle size of iron oxide exceeds 0.3 μm, the mass per particle increases, so the probability of exposure to the toner surface increases due to the difference in specific gravity with the binder during production, or the wear of the production equipment This is not preferable because the possibility that it becomes remarkable will increase or the sedimentation stability of the dispersion will decrease.
[0116]
In addition, when the number of particles of 0.1 μm or less of the iron oxide in the toner exceeds 40% by number, the surface area of the iron oxide is increased, the dispersibility is lowered, and agglomerates are easily formed in the toner. In order to increase the possibility of impairing the chargeability or reducing the coloring power, the number is preferably 40% by number or less. Furthermore, when it is 30% by number or less, the tendency becomes smaller, which is more preferable.
[0117]
It should be noted that iron oxide of less than 0.03 μm has a low probability of appearing on the surface of the toner particles because the stress applied during toner production is small due to the small particle diameter. Furthermore, even if it is exposed to the particle surface, it hardly acts as a leak site and is not substantially a problem. Therefore, in the present invention, attention is paid to particles of 0.03 to 0.1 μm, and the number% is defined.
[0118]
Further, if the number of particles of 0.3 μm or more in iron oxide exceeds 10% by number, the coloring power tends to decrease and the image density tends to decrease. It is not preferable that the toner particles exist in the vicinity of the surface of the toner particles and that a uniform number is included in each toner particle. More preferably, it is 5% or less.
[0119]
In the present invention, it is preferable to use a product in which iron oxide production conditions are set or the particle size distribution is adjusted in advance such as pulverization and classification so as to satisfy the conditions of the particle size distribution described above. As the classification method, for example, a method using sedimentation separation such as centrifugal separation or thickener, or a wet classification device using a cyclone is suitable.
[0120]
The volume average particle size and particle size distribution of iron oxide are determined by the following measurement method. With the particles sufficiently dispersed, the projection area of each of the 100 iron oxide particles in the field of view was measured with a transmission electron microscope (TEM) at a magnification of 30,000 times, and each of the measured particles was measured. The equivalent diameter of a circle equal to the projected area was determined as each particle diameter. Furthermore, based on the result, the volume average particle diameter was calculated, and the number% of particles having a size of 0.03 to 0.1 μm and particles having a size of 0.3 μm or more was calculated. The particle size was measured for particles having a particle size of 0.03 μm or more. It is also possible to measure the particle size with an image analyzer.
[0121]
When determining the volume average particle size and particle size distribution of iron oxide in the toner particles, the following measurement method is used.
[0122]
After sufficiently dispersing the toner particles to be observed in the epoxy resin, the cured product obtained by curing in an atmosphere at a temperature of 40 ° C. for 2 days was used as a flaky sample by a microtome, and a transmission electron microscope (TEM). , The projected area of each of the 100 iron oxide particles in the field of view is measured with a photograph with a magnification of 10,000 to 40,000 times, and the equivalent diameter of a circle equal to the measured projected area of each particle is The particle diameter was obtained. Further, based on the results, the number% of particles having a size of 0.03 to 0.1 μm and particles having a size of 0.3 μm or more was calculated. It is also possible to measure the particle size with an image analyzer.
[0123]
Furthermore, other colorants may be used in combination with iron oxide. Examples of coloring materials that can be used in combination include magnetic or nonmagnetic inorganic compounds, and known dyes and pigments. Specifically, for example, ferromagnetic metal particles such as cobalt and nickel, or alloys obtained by adding chromium, manganese, copper, zinc, aluminum, rare earth elements to these, hematite, titanium black, nigrosine dye / pigment, carbon black, Examples include phthalocyanine. These may also be used after treating the surface.
[0124]
The polymerization initiator used in the present invention has a half-life of 0.5 to 30 hours during the polymerization reaction. When the polymerization reaction is carried out with an addition amount of 0.5 to 20% by mass of the polymerizable monomer, the molecular weight A polymer having a maximum between 10,000 and 100,000 can be obtained, and the toner can be provided with desirable strength and suitable melting characteristics. Examples of polymerization initiators include 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile ), 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, azo or diazo polymerization initiators such as azobisisobutyronitrile; benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate , Peroxide polymerization initiators such as cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide.
[0125]
In the present invention, a crosslinking agent may be added, and a preferable addition amount is 0.001 to 15% by mass of the polymerizable monomer.
[0126]
In the production of toner by suspension polymerization, generally, the above-described toner composition, that is, a polymerizable monomer, contains iron oxide, a colorant, a release agent, a plasticizer, a binder, a charge control agent, a crosslinking agent, and the like. Components necessary for the toner and other additives such as an organic solvent and a dispersant added to lower the viscosity of the polymer produced by the polymerization reaction, as appropriate, homogenizer, ball mill, colloid mill, ultrasonic disperser, etc. The monomer system uniformly dissolved or dispersed by the dispersing machine is suspended in an aqueous medium containing a dispersion stabilizer. At this time, the particle size of the obtained toner particles becomes sharper by using a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser to obtain a desired toner particle size at a stretch. The polymerization initiator may be added at the same time when other additives are added to the polymerizable monomer, or may be mixed immediately before being suspended in the aqueous medium. Also, a polymerization initiator dissolved in a polymerizable monomer or solvent can be added immediately after granulation and before starting the polymerization reaction.
[0127]
After granulation, stirring may be performed using a normal stirrer to such an extent that the particle state is maintained and particle floating and sedimentation are prevented.
[0128]
In the suspension polymerization method of the present invention, known surfactants and organic / inorganic dispersants can be used as dispersion stabilizers. In particular, inorganic dispersants are less likely to produce harmful ultrafine powders, and their steric hindrance prevents dispersion stability. Therefore, even if the reaction temperature is changed, the stability is not easily lost, the cleaning is easy, and the toner is not adversely affected. Examples of such inorganic dispersants include polyvalent metal phosphates such as calcium phosphate, magnesium phosphate, aluminum phosphate and zinc phosphate; carbonates such as calcium carbonate and magnesium carbonate; calcium metasuccinate, calcium sulfate and barium sulfate. Inorganic salts; inorganic oxides such as calcium hydroxide, magnesium hydroxide, aluminum hydroxide, silica, bentonite and alumina can be mentioned.
[0129]
These inorganic dispersants are preferably used alone or in combination of two or more kinds in an amount of 0.2 to 20 parts by mass with respect to 100 parts by mass of the polymerizable monomer. When aiming at a more finely divided toner having an average particle diameter of 5 μm or less, 0.001 to 0.1 parts by mass of a surfactant may be used in combination.
[0130]
Examples of the surfactant include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, sodium stearate, and potassium stearate.
[0131]
When these inorganic dispersants are used, they may be used as they are, but in order to obtain finer particles, the inorganic dispersant particles can be generated in an aqueous medium. For example, in the case of calcium phosphate, a sodium phosphate aqueous solution and a calcium chloride aqueous solution can be mixed with high-speed stirring to produce water-insoluble calcium phosphate, which enables more uniform and fine dispersion. At the same time, a water-soluble sodium chloride salt is produced as a by-product. However, if a water-soluble salt is present in the aqueous medium, dissolution of the polymerizable monomer in water is suppressed, and an ultrafine toner based on emulsion polymerization is produced. Since it becomes difficult to generate | occur | produce, it is more convenient. Since it becomes an obstacle when removing the remaining polymerizable monomer at the end of the polymerization reaction, it is better to replace the aqueous medium or desalinate with an ion exchange resin. The inorganic dispersant can be almost completely removed by dissolution with an acid or alkali after completion of the polymerization.
[0132]
In the polymerization step, the polymerization is performed at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. When the polymerization is carried out in this temperature range, the release agent and wax to be sealed inside are precipitated by phase separation, and the encapsulation is more complete. In order to consume the remaining polymerizable monomer, the reaction temperature can be increased to 90 to 150 ° C. at the end of the polymerization reaction.
[0133]
The toner of the present invention is preferably mixed with an inorganic fine powder or a hydrophobic inorganic fine powder as a fluidity improver. For example, titanium oxide fine powder, silica fine powder, and alumina fine powder are preferably added and used, and silica fine powder is particularly preferred.
[0134]
The inorganic fine powder used for the developer has a specific surface area of 30 m by nitrogen adsorption measured by the BET method.²/ G or more, especially 50-400m²Those in the range of / g are preferable because good results can be obtained.
[0135]
As the silica fine powder used in the present invention, both a so-called dry method produced by vapor phase oxidation of a silicon halogen compound or a so-called wet silica produced from water glass or the like, or dry silica called fumed silica can be used. However, dry silica that has few silanol groups on the surface and inside and no production residue is preferably used.
[0136]
Further, the silica fine powder used in the present invention is preferably hydrophobized. The hydrophobizing treatment is performed by chemically treating with an organosilicon compound that reacts or physically adsorbs with silica fine powder. As a preferable method, a dry silica fine powder produced by vapor phase oxidation of a silicon halide compound is treated with a silane coupling agent or with a silane coupling agent and simultaneously with an organosilicon compound such as silicone oil. Is mentioned.
[0137]
Examples of silane coupling agents used for hydrophobizing treatment include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, and allylphenyldichlorosilane. , Benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilane mercaptan, trimethylsilyl mercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, Dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyl Examples thereof include tetramethyldisiloxane and 1,3-diphenyltetramethyldisiloxane.
[0138]
Examples of the organosilicon compound include silicone oil. As a preferable silicone oil, the viscosity at 25 ° C. is about 30 to 1,000 mm.²/ S (cSt) is used, and for example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, and fluorine modified silicone oil are preferable.
[0139]
Silicone oil treatment can be performed by, for example, mixing silica fine powder treated with a silane coupling agent and silicone oil directly using a mixer such as a Henschel mixer, or injecting silicone oil onto the base silica. Depending on how you do it. Alternatively, the silicone oil may be dissolved or dispersed in an appropriate solvent, and then mixed with the base silica fine powder to remove the solvent.
[0140]
If necessary, an external additive other than the fluidity improver may be added to the toner in the present invention.
[0141]
For example, the primary particle size exceeds 30 nm (preferably the specific surface area is 50 m for the purpose of improving the cleaning property).²/ G) fine particles, more preferably a primary particle size of 50 nm or more (preferably a specific surface area of 30 m)²It is also one of preferable modes to add inorganic fine particles or organic fine particles that are nearly spherical at a rate of less than / g). For example, spherical silica particles, spherical polymethylsilsesquioxane particles, and spherical resin particles are preferably used.
[0142]
Still other additives such as lubricant powders such as Teflon powder, zinc stearate powder, polyvinylidene fluoride powder; or abrasives such as cerium oxide powder, silicon carbide powder, strontium titanate powder; anti-caking agents; or such as carbon black Conductivity imparting agents such as powder, zinc oxide powder and tin oxide powder; organic fine particles having opposite polarity and inorganic fine particles can be added in small amounts as a developability improver. These additives can also be used after hydrophobizing the surface.
[0143]
As described above, the external additive may be used in an amount of 0.1 to 5 parts by mass (preferably 0.1 to 3 parts by mass) with respect to 100 parts by mass of the toner.
[0144]
When the toner of the present invention is produced by a pulverization method, a known method can be used. Known methods include, for example, a binder resin, a magnetic material, a release agent, a charge control agent, and in some cases, a component such as a colorant and other additives necessary for the toner and other additives, etc., a mixer such as a Henschel mixer or a ball mill. After thoroughly mixing, melt and knead using a heat kneader such as a heating roll, a kneader, and an extruder to disperse other toner materials such as a magnetic material while the resins are mutually melted. After dissolution, cooling and solidification, and pulverization, classification and surface treatment as necessary are performed to obtain toner particles. If necessary, a fine powder or the like can be added and mixed to obtain a developer. Either the classification or the surface treatment may be performed first. In the classification step, it is preferable to use a multi-division classifier from the viewpoint of production efficiency.
[0145]
The pulverization step can be performed using a known pulverizer such as a mechanical impact type or a jet type. In order to obtain a developer having a specific circularity according to the present invention, it is preferable to further pulverize by applying heat or to add a mechanical impact in an auxiliary manner. Further, a hot water bath method in which finely pulverized (classified as necessary) toner particles are dispersed in hot water, a method of passing in a hot air stream, or the like may be used.
[0146]
As a method of applying a mechanical impact force, for example, there is a method using a mechanical impact type pulverizer such as a kryptron system manufactured by Kawasaki Heavy Industries, Ltd. or a turbo mill manufactured by Turbo Industry. Also, like devices such as Hosokawa Micron's Mechano-Fusion System and Nara Machinery's Hybridization System, the toner is pressed against the inside of the casing by centrifugal force with high-speed rotating blades, and the force of compression force, friction force, etc. A method of applying a mechanical impact force to the toner may be used.
[0147]
In the case of performing a process of applying mechanical impact, the atmosphere temperature during the process is set to a temperature near the glass transition point Tg of the toner (that is, a temperature in the range of ± 30 ° C. of the glass transition point Tg) to prevent aggregation. From the viewpoint of productivity. More preferably, the treatment at a temperature in the range of ± 20 ° C. of the glass transition point Tg of the toner is particularly effective for improving the transfer efficiency.
[0148]
Furthermore, the toner of the present invention is a method for obtaining a spherical toner by atomizing a molten mixture into air using a disk or a multi-fluid nozzle described in JP-B-56-13945, etc. Represented by a dispersion polymerization method in which a toner is directly produced using an aqueous organic solvent in which the polymer obtained in 1 is insoluble, or a soap-free polymerization method in which a toner is produced by direct polymerization in the presence of a water-soluble polar polymerization initiator. The toner can also be produced by a method of producing toner using an emulsion polymerization method or the like.
[0149]
When the toner of the present invention is produced by a pulverization method, the binder resin may be a styrene such as polystyrene or polyvinyltoluene or a homopolymer of a substituted product thereof; a styrene-propylene copolymer, a styrene-vinyltoluene copolymer, or styrene. -Vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate Copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether Copolymer, styrene-vinyl ethyl acetate Styrene copolymer such as styrene copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer Combined; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic acid resin, rosin, modified rosin, temper resin, phenol resin, fat Aromatic or alicyclic hydrocarbon resins, aromatic petroleum resins, paraffin waxes and carnauba waxes can be used alone or in combination. In particular, a styrene copolymer and a polyester resin are preferable in terms of development characteristics, fixing properties, and the like.
[0150]
Next, a developing method using the toner of the present invention will be described.
[0151]
First, a system in which the toner carrier and the electrostatic image carrier are not in contact will be described.
[0152]
In the non-contact developing method, a magnetic toner is applied on the toner carrier with a layer thickness smaller than the closest distance (between S and D) of the toner carrier-photosensitive body (electrostatic charge image carrier), Development is performed by applying an electric field. That is, the layer thickness regulating member for regulating the magnetic toner on the toner carrying member is used by setting the closest gap between the photosensitive member and the toner carrying member to be wider than the toner layer thickness on the toner carrying member. At this time, the layer thickness regulating member that regulates the magnetic toner on the toner carrying member is an elastic member, and is preferably in contact with the toner carrying member via the toner from the viewpoint of uniformly charging the magnetic toner. .
[0153]
Further, it is preferable that the toner carrying member is disposed opposite to the photosensitive member with a separation distance of 100 to 500 μm, and is further disposed to be opposed to the photosensitive member with a separation distance of 120 to 500 μm. preferable. If the separation distance of the toner carrier from the photosensitive member is less than 100 μm, the change in the development characteristics of the toner with respect to the fluctuation of the separation distance becomes large, so that it is difficult to mass-produce an image forming apparatus that satisfies stable image quality. . When the separation distance of the toner carrying member from the photosensitive member is larger than 500 μm, the recoverability of the transfer residual toner to the developing device is lowered, and fogging due to poor collection tends to occur. Further, since the followability of the toner with respect to the latent image on the photosensitive member is lowered, the image quality is lowered such as a lower resolution and a lower image density.
[0154]
In the present invention, 5 to 30 g / m on the toner carrier.²The toner layers are preferably laminated so as to form a toner layer. The amount of toner on the toner carrier is 5 g / m.²If it is smaller than 1, a sufficient image density is difficult to obtain, and the toner layer becomes uneven due to excessive charging of the toner. The amount of toner on the toner carrier is 30 g / m.²If the amount is larger than that, toner scattering tends to occur.
[0155]
The surface roughness Ra (JIS centerline average roughness) of the toner carrier used in the present invention is preferably in the range of 0.2 to 3.5 μm. If Ra is less than 0.2 μm, the charge amount on the toner carrying member becomes high, and the developability becomes insufficient. On the other hand, if Ra exceeds 3.5 μm, unevenness of toner stacking on the toner carrier occurs, resulting in uneven density on the image. The surface roughness Ra is more preferably in the range of 0.5 to 3.0 μm.
[0156]
In the present invention, the surface roughness Ra of the toner carrier is measured using a surface roughness measuring instrument (Surfcoder SE-30H, manufactured by Kosaka Laboratory Co., Ltd.) based on JIS surface roughness “JIS B 0601”. This corresponds to the centerline average roughness. Specifically, a 2.5 mm portion as the measurement length a is extracted from the roughness curve in the direction of the center line, the center line of this extraction portion is the X axis, the direction of the vertical magnification is the Y axis, and the roughness curve is When represented by y = f (x), the value obtained by the following formula is represented in micrometers (μm).
[0157]
[Outside 2]

[0158]
Furthermore, since the magnetic toner according to the present invention has a high charging ability, it is preferable to control the total charge amount of the toner during development. The surface of the toner carrier according to the present invention is preferably coated with a resin layer in which conductive fine particles and / or a lubricant are dispersed.
[0159]
As the conductive fine particles contained in the resin layer covering the surface of the toner carrier, conductive metal oxides and metal double oxides such as carbon black, graphite, and conductive zinc oxide are used alone or in combination of two or more. Is preferred. Examples of the resin in which the conductive fine particles and / or the lubricant are dispersed include phenol resins, epoxy resins, polyamide resins, polyester resins, polycarbonate resins, polyolefin resins, silicone resins, fluorine resins, styrene resins. Known resins such as resins and acrylic resins are used. A thermosetting resin or a photocurable resin is particularly preferable.
[0160]
In the non-contact developing method, it is preferable that the moving speed of the toner carrying member that carries the toner in the developing process and transports it to the developing unit is different from the moving speed of the photosensitive member. By providing such a speed difference, toner particles and conductive fine powder can be sufficiently supplied from the toner carrying member side to the photosensitive member side, and a good image can be obtained.
[0161]
The surface of the toner carrying member that carries the toner may move in the same direction as the movement direction of the photosensitive member surface, or may move in the opposite direction. As the speed at that time, it is preferable that one of the surfaces of the toner carrying member and the surface of the photosensitive member is moving at a speed 1.02 to 3.0 times that of the other, rather than the moving speed being constant.
[0162]
In the developing unit, an AC bias is applied in order to transfer the magnetic toner to an electrostatic latent image for development. At this time, the AC bias has an electric field strength of at least peak-to-peak of 3 × 10.⁶~ 1x10⁷It is V / m, and it is preferable that it is a frequency of 100-5000 Hz. It is also a preferred form that a DC bias is further superimposed.
[0163]
On the other hand, a system that performs development by bringing a toner carrier and an electrostatic charge image carrier into contact with each other will be described.
[0164]
In the contact development method, it is preferable to use reversal development.
[0165]
Furthermore, it is also a preferable form to use a cleaner-less process together, and the apparatus can be greatly downsized. At this time, during development or when blank before and after development, a DC or AC component bias is applied to control the potential so that the remaining toner on the development and photoreceptor can be recovered. And between the dark potential.
[0166]
An elastic roller is preferably used as the toner carrier, and the surface is coated with toner and brought into contact with the surface of the photoreceptor. In this case, since development is performed by an electric field acting between the photosensitive member and the elastic roller facing the surface of the photosensitive member via toner, the elastic roller surface or the vicinity of the surface has a potential, and the surface of the photosensitive member and the surface of the toner carrying member are narrow. There is a need to have an electric field in the gap. For this reason, it is possible to use a method in which the elastic rubber of the elastic roller is resistance controlled to the middle resistance region to keep the electric field while preventing conduction with the surface of the photoreceptor, or a method of providing a thin insulating layer on the surface layer of the conductive roller. . Furthermore, a conductive resin sleeve in which the side facing the surface of the photoreceptor is covered with an insulating material on the conductive roller, or a conductive layer is provided on the side not facing the photoreceptor with the insulating sleeve is also possible. Further, a configuration in which a rigid roller is used as the toner carrying member and the photosensitive member is a flexible material such as a belt is possible. The resistance of the elastic roller as the toner carrier is 10²-10⁹A range of Ω · cm is preferred.
[0167]
As the surface shape of the toner carrier, when the surface roughness Ra (μm) is set to 0.2 to 3.0, both high image quality and high durability can be achieved. The surface roughness Ra correlates with the toner conveying ability and the toner charging ability. If the surface roughness Ra of the toner carrier exceeds 3.0, it is difficult not only to make the toner layer on the toner carrier thin, but also the chargeability of the toner is not improved, so that improvement in image quality cannot be expected. . Since the toner carrying ability on the surface of the toner carrier is suppressed by setting it to 3.0 or less, the toner layer on the toner carrier is thinned, and the number of contact between the toner carrier and the toner increases. Since the chargeability of the toner is also improved, the image quality is synergistically improved. On the other hand, when the surface roughness Ra is smaller than 0.2, it becomes difficult to control the toner coat amount.
[0168]
In the contact development method, the toner carrier may be rotated in the same direction as the peripheral speed of the photosensitive member, or may be rotated in the opposite direction. When the rotation is in the same direction, it is preferable to set the peripheral speed of the toner carrier to be 1.05 to 3.0 times the peripheral speed of the photosensitive member.
[0169]
When the peripheral speed of the toner carrier is less than 1.05 times the peripheral speed of the photoreceptor, the stirring effect received by the toner on the photoreceptor is insufficient, and good image quality cannot be expected. In addition, when developing an image that requires a large amount of toner over a wide area, such as a solid black image, the amount of toner supplied to the electrostatic latent image is insufficient and the image density becomes low. The higher the peripheral speed ratio, the more toner is supplied to the development site, the more frequent the toner is desorbed from the latent image, and the unnecessary part is collected and applied to the necessary part. An image faithful to the latent image can be obtained. However, if the peripheral speed ratio exceeds 3.0, on the other hand, in addition to various problems caused by excessive charging of the toner as described above (image density reduction due to excessive charging of the toner, etc.), mechanical Deterioration of toner due to stress and toner adhesion to the toner carrier are generated and promoted, which is not preferable.
[0170]
Next, the charging process will be described.
[0171]
In the present invention, a non-contact charging step such as a charging step using a charging device using corona discharge may be used, but a contact charging method in which a charging member is brought into contact with the photosensitive member is a preferable charging method. In this case, it is preferable to use a charging roller as the contact charging member.
[0172]
As a preferable process condition when using a charging roller, a contact pressure of the roller is 4.9 to 490 N / m (5 to 500 g / cm), and a DC voltage or a DC voltage superimposed with an AC voltage is used. . In the case of using a DC voltage superimposed with an AC voltage, AC voltage = 0.5 to 5 kVpp, AC frequency = 50 to 5 kHz, and DC voltage = ± 0.2 to ± 5 kV are preferable.
[0173]
Other charging means include a method using a charging blade and a method using a conductive brush. Even when these contact charging means are used, there is an effect that a high voltage becomes unnecessary and generation of ozone is reduced.
[0174]
The material of the charging roller and charging blade as the contact charging means is preferably conductive rubber, and a release coating may be provided on the surface thereof. As the releasable coating, nylon resin, PVdF (polyvinylidene fluoride), PVdC (polyvinylidene chloride), and fluorine acrylic resin are applicable.
[0175]
Next, the transfer process will be described.
[0176]
In the present invention, a non-contact transfer step such as a transfer step using a transfer device using corona discharge may be used, but preferably the contact is performed by bringing the transfer means into contact with the photoconductor via a transfer material. This is a transfer method.
[0177]
The contact pressure of the transfer means is preferably a linear pressure of 2.9 N / m (3 g / cm) or more, and more preferably 19.6 N / m (20 g / cm) or more. If the linear pressure as the contact pressure is less than 2.9 N / m (3 g / cm), it is not preferable because transfer of the transfer material and transfer failure are likely to occur.
[0178]
Further, as a transfer means in the contact transfer process, an apparatus having a transfer roller or a transfer belt is used. FIG. 5 shows an example of the configuration of the transfer roller. The transfer roller 34 includes at least a metal core 34a and a conductive elastic layer 34b. The conductive elastic layer has a volume resistance 10 such as urethane or EPDM in which a conductive material such as carbon is dispersed.⁶-10^TenIt is made of an elastic body of about Ωcm, and a transfer bias is applied by a transfer bias power source 35.
[0179]
Next, the photoreceptor used in the present invention will be described below.
[0180]
As a photoreceptor, a-Se, CdS, ZnO₂A photosensitive drum or a photosensitive belt having a photoconductive insulating material layer such as OPC (organic photoreceptor) or a-Si is preferably used.
[0181]
In particular, in the present invention, it is preferable to use a photoreceptor whose surface is composed mainly of a polymer binder. For example, when a protective film (protective layer) mainly composed of a resin is provided on an inorganic photoreceptor such as selenium or amorphous silicon, or as a charge transport layer of a function-separated organic photoreceptor, a charge transport material and a resin are used. In some cases, a surface layer is provided, or a protective layer mainly composed of a resin is provided on the surface layer. These surface layers (or protective layers) preferably have releasability, and as means for actually imparting releasability,
(1) Use a resin having a low surface energy as the resin itself constituting the film.
(2) Add additives that impart water repellency and lipophilicity.
(3) A material having high releasability is dispersed in powder form.
Means etc. are mentioned. Examples of (1) include the introduction of functional groups such as fluorine-containing groups and silicone-containing groups into the structure of the structural unit of the resin. Examples of the additive (2) that imparts water repellency and lipophilicity include surfactants. Examples of the material having high releasability (3) include compounds containing fluorine atoms, that is, polytetrafluoroethylene, polyvinylidene fluoride, and carbon fluoride.
[0182]
By these means, the contact angle of water on the surface of the photoconductor can be 85 degrees or more, and the toner transferability and the photoconductor durability can be further improved. The contact angle of water on the surface of the photoreceptor is preferably 90 degrees or more. In the present invention, among the above means (1) to (3), it is preferable to disperse in the outermost surface layer of the fluororesin releasable powder as in (3). It is particularly preferable to use polytetrafluoroethylene as the powder.
[0183]
In order to contain these powders on the surface, a layer in which a releasable powder is dispersed in a binder resin is provided on the outermost surface of the photoconductor, or the photoconductor itself is mainly composed of a resin. In the case of an organic photoreceptor, a releasable powder may be dispersed in the uppermost layer without newly providing a surface layer. 1-60 mass% is preferable with respect to the surface layer total amount, and, as for the addition amount of releasable powder, 2-50 mass% is still more preferable. If the addition amount of the release powder is less than 1% by mass, the effect of improving the transferability of the toner and the durability of the photoreceptor is insufficient, and if it exceeds 60% by mass, the strength of the protective film is reduced, This is not preferable because the amount of light incident on the body is significantly reduced.
[0184]
In the present invention, the contact charging method in which the charging means abuts the charging member on the photosensitive member is a preferable charging method. However, compared to the method using corona discharge or the like in which the charging means does not contact the photosensitive member, Since the load is large, providing a protective layer (protective film) on the surface of the photoconductor has a remarkable effect of improving durability, and is one of the preferable application forms.
[0185]
In the present invention, it is preferable to apply a contact charging method or a contact transfer method, so that the present invention is particularly effective for an image forming apparatus having a photoconductor with a diameter of 50 mm or less. That is, when the diameter of the photoconductor used in image formation is small, the curvature with respect to the same linear pressure is large, and pressure concentration tends to occur at the contact portion. Although it is considered that the same phenomenon occurs in the belt photoreceptor, the present invention is also effective for an image forming apparatus having a radius of curvature of 25 mm or less at the transfer portion.
[0186]
One preferred embodiment of the photoreceptor used in the present invention will be described below.
[0187]
As the conductive substrate, metal such as aluminum and stainless steel, aluminum alloy, plastic with a coating layer of indium oxide-tin oxide alloy, paper impregnated with conductive particles, plastic, plastic with conductive polymer, cylindrical shape Cylinders and films are used.
[0188]
On these conductive substrates, the adhesion of the photosensitive layer is improved, the coating property is improved, the substrate is protected, the defects on the substrate are coated, the charge injection from the substrate is improved, and the photosensitive layer is protected from electrical breakdown. For the purpose, an undercoat layer may be provided. Undercoat layer is polyvinyl alcohol, poly-N-vinylimidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenol resin, casein, polyamide, copolymer nylon, glue, gelatin, polyurethane , Formed of a material such as aluminum oxide. The thickness of the undercoat layer is usually 0.1 to 10 μm, preferably about 0.1 to 3 μm.
[0189]
The charge generation layer is composed of azo pigments, phthalocyanine pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, squarylium dyes, pyrylium salts, thiopyrylium salts, triphenylmethane dyes, selenium, amorphous silicon, etc. A charge generating material such as an inorganic material is dispersed in a suitable binder and applied, or formed by vapor deposition. Examples of the binder include polycarbonate resin, polyester resin, polyvinyl butyral resin, polystyrene resin, acrylic resin, methacrylic resin, phenol resin, silicon resin, epoxy resin, and vinyl acetate resin. A binder can be arbitrarily selected. The amount of the binder contained in the charge generation layer is preferably 80% by mass or less, and more preferably 0 to 60% by mass with respect to the entire charge generation layer. The film thickness of the charge generation layer is preferably 5 μm or less, particularly preferably 0.05 to 2 μm.
[0190]
The charge transport layer has a function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting them. The charge transport layer is formed by dissolving a charge transport material in a solvent together with a binder resin, if necessary, and coating. The thickness of the charge generation layer is generally 5 to 40 μm. Examples of charge transport materials include polycyclic aromatic compounds having a structure such as biphenylene, anthracene, pyrene, and phenanthrene in the main chain or side chain, nitrogen-containing cyclic compounds such as indole, carbazole, oxadiazole, and pyrazoline, hydrazone compounds, Examples include styryl compounds, selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide.
[0191]
In addition, binder resins for dispersing these charge transport materials include polycarbonate resins, polyester resins, polymethacrylic acid esters, polystyrene resins, acrylic resins, polyamide resins, and organic materials such as poly-N-vinylcarbazole and polyvinylanthracene. A photoconductive polymer is mentioned.
[0192]
Furthermore, you may provide a protective layer separately as a surface layer. As the resin for the protective layer, polyester, polycarbonate, acrylic resin, epoxy resin, phenol resin, or curing agents for these resins can be used alone or in combination of two or more.
[0193]
Moreover, you may disperse | distribute electroconductive fine particles in resin of a protective layer. Examples of the conductive fine particles include metals and metal oxides, and preferably zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin oxide-coated titanium oxide, tin-coated indium oxide, and antimony. Examples thereof include ultrafine particles of coated tin oxide and zirconium oxide. These conductive fine particles may be used alone or in combination of two or more. In general, when particles are dispersed in a protective layer, it is necessary that the particle diameter of the particles is smaller than the wavelength of incident light in order to prevent scattering of incident light by the dispersed particles, and the particles are dispersed in the protective layer in the present invention. The particle diameter of the conductive fine particles is preferably 0.3 μm or less. Moreover, 2-90 mass% is preferable with respect to the protective layer total weight, and, as for content of the electroconductive fine particles in a protective layer, 5-80 mass% is more preferable. The thickness of the protective layer is preferably from 0.1 to 10 μm, more preferably from 1 to 7 μm.
[0194]
The surface layer can be applied by spray coating, beam coating or penetration (dipping) coating of the resin dispersion.
[0195]
Next, the image forming method of the present invention will be specifically described with reference to the drawings.
[0196]
In the image forming apparatus of FIG. 1, reference numeral 100 denotes a photosensitive drum, and a primary charging roller 117, a developing device 140, a transfer charging roller 114, a cleaner 116, a register roller 124, and the like are provided around the photosensitive drum. The photoreceptor 100 is charged to, for example, −700 V by the primary charging roller 117. (Applied voltage is AC voltage −2.0 k Vpp, DC voltage −700 Vdc) Then, exposure is performed by irradiating photoconductor 100 with laser beam 123 by laser generator 121. The electrostatic latent image on the photoconductor 100 is developed with a one-component magnetic developer by the developing device 140 and transferred onto the transfer material by the transfer roller 114 in contact with the photoconductor via the transfer material. The transfer material on which the toner image is placed is conveyed to the fixing device 126 by the conveyance belt 125 or the like and fixed on the transfer material. In addition, toner remaining on a part of the photoconductor is cleaned by the cleaning unit 116. As shown in FIG. 2, the developing device 140 is provided with a cylindrical toner carrier 102 (hereinafter referred to as a developing sleeve) made of a nonmagnetic metal such as aluminum or stainless steel in the vicinity of the photosensitive member 100. The gap between 100 and the developing sleeve 102 is maintained at about 300 μm by a sleeve / photoreceptor gap holding member (not shown). A magnet roller 104 is fixed and arranged concentrically with the developing sleeve 102 in the developing sleeve. However, the developing sleeve 102 is rotatable. The magnet roller 104 is provided with a plurality of magnetic poles as shown in the figure, and S1 influences development, N1 regulates the amount of toner coating, S2 takes in / conveys toner, and N2 affects toner blowout prevention. The toner is applied to the developing sleeve 102 by the toner application roller 141, and is adhered and conveyed. An elastic blade 103 is provided as a member for regulating the amount of toner conveyed, and the amount of toner conveyed to the development area is controlled by the contact pressure of the elastic blade 103 against the developing sleeve 102. In the development region, a DC and AC development bias is applied between the photoconductor 100 and the development sleeve 102, and the developer on the development sleeve flies onto the photoconductor 100 in accordance with the electrostatic latent image to become a visible image. .
[0197]
Next, the image forming method of the present invention will be described below with reference to FIGS.
[0198]
FIG. 3 shows an outline of an image forming apparatus using a cleanerless process. 40 is a developing device, 1 is a photosensitive member, 27 is a transfer target (transfer material) such as paper, 14 is a transfer member, and 26 is a transfer member. A fixing pressure roller, 28 is a fixing heating roller, and 17 is a primary charging member that contacts the photoreceptor 1 and performs direct charging. A bias power source 31 is connected to the primary charging member 17 so as to uniformly charge the surface of the photoreceptor 1.
[0199]
The developing device 40 contains toner 42 and includes a toner carrier 4 that contacts the photoreceptor 1 and rotates in the direction of the arrow. Further, a developing blade 43 and a toner 42 for toner amount regulation and charging are attached to the toner carrier 4, and the application roller 41 that rotates in the direction of the arrow in order to charge the toner by friction with the toner carrier 4 is applied. It also has. A developing bias power source 33 is connected to the toner carrier 4. A bias power source 32 is also connected to the application roller 41, and a voltage is set on the negative side of the developing bias when using negatively charged toner, and on the positive side of the developing bias when using positively charged toner. Is done.
[0200]
A transfer bias power supply 34 having a polarity opposite to that of the photosensitive member 1 is connected to the transfer member 14.
[0201]
Here, the length in the rotation direction at the contact portion between the photosensitive member 1 and the toner carrying member 4, that is, the so-called development nip width is preferably 0.2 to 8.0 mm. If the thickness is less than 0.2 mm, the development amount is insufficient and a satisfactory image density cannot be obtained, and the transfer residual toner is not sufficiently collected. If it exceeds 8.0 mm, the amount of toner supplied becomes excessive, fog suppression is likely to deteriorate, and the wear of the photoreceptor 1 is also adversely affected.
[0202]
As the toner carrier 4, a so-called elastic roller having an elastic layer on the surface is preferably used.
[0203]
The hardness of the material of the elastic layer used is preferably 20 to 65 degrees (JIS A).
[0204]
The resistance of the toner carrier 4 is 10 in terms of volume resistance.²-10⁹A range of about Ω · cm is preferable. 10²If it is lower than Ω · cm, for example, if there is a pinhole or the like on the surface of the photoreceptor 1, an overcurrent may flow. Conversely, 10⁹When it is higher than Ω · cm, the toner is likely to be charged up due to frictional charging, and the image density is likely to be lowered.
[0205]
The toner coat amount on the toner carrier 4 is 0. l2.0mg / cm²Is preferred. 0. lmg / cm²If it is less, it is difficult to obtain a sufficient image density, and 2.0 mg / cm²If it exceeds the upper limit, it becomes difficult to uniformly triboelectrically charge all of the individual toner particles, which causes deterioration of fog suppression. Furthermore, 0.2 to 1.2 mg / cm²Is more preferable.
[0206]
The toner coating amount is controlled by the developing blade 143, and the developing blade 143 is in contact with the toner carrier 104 through the toner layer. The contact pressure at this time is preferably in the range of 5 to 50 g / cm. If it is less than 5 g / cm, in addition to controlling the toner coating amount, uniform frictional charging becomes difficult, which causes deterioration of fog suppression. On the other hand, if it exceeds 50 g / cm, the toner particles are subjected to an excessive load, so that the deformation of the particles and the fusion of the toner to the developing blade 143 or the toner carrier 104 are likely to occur.
[0207]
As the toner coating amount regulating member, a metal blade or a roller may be used in addition to the elastic blade for applying the toner by pressure contact.
[0208]
For the elastic regulating member, it is preferable to select a frictional charging material suitable for charging the toner to a desired polarity. A rubber elastic body such as silicone rubber, urethane rubber or NBR, or a synthetic resin such as polyethylene terephthalate. A metal elastic body such as an elastic body, stainless steel, copper, or phosphor bronze can be used. Moreover, those composites may be sufficient.
[0209]
Further, when durability is required for the elastic regulating member and the toner carrying member, it is preferable that the metal elastic member is bonded or coated with a resin or rubber so as to contact the sleeve contact portion.
[0210]
Furthermore, an organic substance or an inorganic substance may be added to the elastic regulating member, and it may be melt-mixed or dispersed. For example, the chargeability of the toner can be controlled by adding a metal oxide, metal powder, ceramics, carbon allotrope, whisker, inorganic fiber, dye, pigment, or surfactant. In particular, when the elastic body is a molded body such as rubber or resin, a metal oxide fine powder such as silica, alumina, titania, tin oxide, zirconia, and zinc oxide, carbon black, and a charge control agent generally used for toners are used. It is also preferable to contain.
[0211]
Furthermore, by applying a DC electric field and / or an AC electric field to the regulating member, the uniform thin layer coating property and the uniform charging property are further improved due to the loosening action on the toner, and sufficient image density can be achieved and a good quality can be achieved. An image can be obtained.
[0212]
In FIG. 3, the primary charging member 17 uniformly charges the photoreceptor 1 rotating in the direction of the arrow.
[0213]
The primary charging member used here is a charging roller having a basic configuration of a central core 17b and a conductive elastic layer 17a formed on the outer periphery thereof. The charging roller 17 is brought into contact with the entire surface of the electrostatic latent image carrier with a pressing force, and is driven to rotate as the photosensitive member 1 rotates.
[0214]
As a preferable process condition when the charging roller 117 is used, the contact pressure of the roller is 5 to 500 g / cm, and the applied voltage is a DC voltage or a DC voltage superposed with an AC voltage. Although not limited, in the present invention, an applied voltage of only a DC voltage is preferably used, and a voltage value in this case is used in a range of ± 0.2 to ± 5 kV.
[0215]
Other charging means include a method using a charging blade and a method using a conductive brush. These contact charging means have an effect that a high voltage is unnecessary and generation of ozone is reduced as compared with non-contact corona charging. The material of the charging roller and charging blade as the contact charging means is preferably conductive rubber, and a release coating may be provided on the surface thereof. As the releasable coating, nylon resin, PVDF (polyvinylidene fluoride), PVDC (polyvinylidene chloride) can be applied.
[0216]
Following the primary charging step, an electrostatic latent image corresponding to the information signal is formed on the photosensitive member 1 by exposure 23 from the light emitting element 21, and the electrostatic latent image is developed with toner at a position in contact with the toner carrier 4. Visualize. Furthermore, in the image forming method of the present invention, particularly in combination with a developing system in which a digital latent image is formed on a photoreceptor, it becomes possible to develop the dot latent image faithfully without disturbing the latent image. . Next, the visible image is transferred onto the transfer member 27 by the transfer member 14 having the core 14a and the conductive elastic layer 14b forming the outer periphery as a basic configuration, and the transfer toner 29 is transferred to the transfer member 27. At the same time, the conveying roller 25 conveys and fixes the image to a fixing device having a fixing pressure roller 26 and a fixing pressure roller 28 to obtain a permanent image. The heating and pressure fixing means is not limited to the heating roller system having a heating roller having a built-in heating element such as a halogen heater and an elastic pressure roller pressed against the heating roller with a pressing force. A system in which heat is fixed by a heater through a film is also used.
[0217]
On the other hand, the untransferred toner remaining on the photosensitive member 1 without being transferred passes through between the photosensitive member 1 and the primary charging member 17 and reaches the developing nip portion again. To be recovered.
[0218]
The method for measuring various physical property data in the present invention is described in detail below.
[0219]
(1) Ratio of iron element content (B) to carbon element content (A) present on the toner surface (B / A)
The ratio (B / A) of the iron element content (B) to the carbon element content (A) present on the toner surface in the present invention was calculated by performing surface composition analysis by ESCA (X-ray photoelectron spectroscopy). .
[0220]
In the present invention, the ESCA apparatus and measurement conditions are as follows.
Equipment used: 1600S type X-ray photoelectron spectrometer manufactured by PHI (Physical Electronics Industries, Inc.)

[0221]
In the present invention, the surface atomic concentration (atomic%) was calculated from the measured peak intensity of each element using a relative sensitivity factor provided by PHI.
[0222]
As the measurement sample, toner is used. When an external additive is added to the toner, the toner is washed with a solvent that does not dissolve the toner, such as isopropanol, and the measurement is performed after removing the external additive. Do.
[0223]
(2) Average circularity of toner
The circularity in the present invention is used as a simple method for quantitatively expressing the particle shape. In the present invention, the particle shape is measured using a flow particle image analyzer FPIA-1000 manufactured by Toa Medical Electronics. And the circularity is obtained by the following formula. Furthermore, as shown by the following equation, a value obtained by dividing the total roundness of all the measured particles by the total number of particles is defined as the average circularity.
[0224]
[Outside 3]

[0225]
In addition, “FPIA-1000” which is a measuring apparatus used in the present invention calculates the circularity of each particle, and then calculates the average circularity, and the circularity is 0.400 depending on the circularity obtained. 1.000 divided at intervals of 0.010 at intervals of 0.400 or more and less than 0.410, 0.410 or more and less than 0.420 ... 0.990 or more and less than 1.000 and 1.000 A calculation method is used in which the average circularity is calculated using the center value and frequency of the dividing points.
[0226]
There is very little error between each value of the average circularity calculated by this calculation method and each value of the average circularity calculated by the calculation formula that directly uses the circularity of each particle described above. Since it is negligible, the present invention uses the concept of the calculation formula that directly uses the circularity of each particle described above for reasons of handling data such as shortening the calculation time and simplifying the calculation calculation formula. However, such a calculation method which is partially changed is used.
[0227]
The circularity in the present invention is an index indicating the degree of unevenness of particles, and is 1.000 when the particles are completely spherical, and the circularity becomes smaller as the surface shape becomes more complicated.
[0228]
As a specific method for measuring the degree of circularity, about 5 mg of toner is dispersed in 10 ml of water in which about 0.1 mg of a nonionic surfactant is dissolved, and a dispersion is prepared, and ultrasonic waves (20 kHz, 50 W) are applied to the dispersion. And the dispersion concentration is set to 5000 to 20000 particles / μl, and the circularity distribution of particles having a circle-equivalent diameter of 3 μm or more is measured using the flow type particle image measuring apparatus.
[0229]
The outline of the measurement is described in the catalog (June 1995 edition) of FPIA-1000 published by Toa Medical Electronics Co., Ltd., the operation manual of the measuring apparatus, and JP-A-8-136439. It is.
[0230]
The sample dispersion is passed through a flat and flat transparent flow cell (thickness: about 200 μm) flow path (spread along the flow direction). The strobe and the CCD camera are mounted on the flow cell so as to be opposite to each other so as to form an optical path that passes through the thickness of the flow cell. While the sample dispersion is flowing, strobe light is irradiated at 1/30 second intervals to obtain an image of the particles flowing through the flow cell, so that each particle has a certain range parallel to the flow cell 2. Taken as a dimensional image. From the area of the two-dimensional image of each particle, the diameter of a circle having the same area is calculated as the equivalent circle diameter. The circularity of each particle is calculated from the projected area of the two-dimensional image of each particle and the perimeter of the projected image using the above circularity calculation formula.
[0231]
(3) Toner particle size distribution
As a measuring device, a Coulter counter TA-II type (manufactured by Coulter) was connected to an interface (manufactured by Nikkaki) that outputs number distribution and volume distribution, and a CX-1 personal computer (manufactured by Canon). Prepare 1% NaCl aqueous solution using grade sodium chloride. For example, ISOTON R-II (manufactured by Coulter Scientific Japan) can be used. As a measuring method, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolyte in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the volume and the number of toners are measured by measuring the volume and number of toners using the Coulter counter TA-II type with a 100 μm aperture as the aperture. Calculate the volume distribution and number distribution of particles of ˜40 μm. Then, the weight-based weight average diameter D4 obtained from the number average particle diameter (D1) volume distribution (the median value of each channel is the representative value for each channel), and the weight-based weight of 12.7 μm or more obtained from the volume distribution. Find the distribution.
[0232]
【Example】
Hereinafter, the present invention will be specifically described with reference to production examples and examples, but this does not limit the present invention in any way. The number of parts or% described in an Example shows a mass part or mass%.
[0233]
(Production Example 1 of hydrophobic iron oxide)
An aqueous solution containing ferrous hydroxide was prepared by mixing 1.0 to 1.1 equivalents of a caustic soda solution with respect to iron ions in an aqueous ferrous sulfate solution.
[0234]
While maintaining the aqueous solution at pH 9, air was blown and an oxidation reaction was performed at 80 to 90 ° C. to prepare a slurry liquid for generating seed crystals.
[0235]
Subsequently, after adding ferrous sulfate aqueous solution so that it may become 0.9-1.2 equivalent with respect to the original alkali amount (sodium component of caustic soda) to this slurry liquid, the slurry liquid is maintained at pH 8 and air is supplied. Oxidation reaction is promoted while blowing, pH is adjusted to about 6 at the end of the oxidation reaction, and silane coupling agent [n-C_FourH₉Si (OCH_Three)_Three] Was added to 100 parts of magnetic iron oxide and stirred sufficiently. The produced hydrophobic iron oxide particles were washed, filtered and dried by a conventional method, and then the agglomerated particles were crushed to obtain hydrophobic iron oxide 1. The physical properties of the hydrophobic iron oxide 1 are shown in Table 1.
[0236]
(Production Example 2 of hydrophobic iron oxide)
The oxidation reaction proceeds in the same manner as in Production Example 1, and the magnetic iron oxide particles generated after the oxidation reaction are washed, filtered, taken out once, redispersed in another water without drying, and then the pH of the redispersion is adjusted. The silane coupling agent [n-C₆H₁₃Si (OCH_Three)_Three] Was added and a coupling treatment was performed. The produced hydrophobic iron oxide particles were washed, filtered and dried by a conventional method, and then the aggregated particles were lightly crushed to obtain hydrophobic iron oxide 2.
[0237]
(Production Example 3 of hydrophobic iron oxide)
N-C as silane coupling agent_TenH_{twenty one}Si (OCH_Three)_ThreeA hydrophobic iron oxide 3 was obtained in the same manner as in Production Example 2 except that.
[0238]
(Production Example 4 of Hydrophobic Iron Oxide)
Hydrophobic iron oxide 4 was obtained in the same manner as in Production Example 2 except that γ-glycidyltrimethoxysilane was used as the silane coupling agent.
[0239]
(Production Example 5 of hydrophobic iron oxide)
An aqueous solution containing ferrous hydroxide was prepared by mixing 1.0 to 1.1 equivalents of a caustic soda solution with respect to iron ions in an aqueous ferrous sulfate solution.
[0240]
While maintaining the aqueous solution at pH 9, air was blown and an oxidation reaction was performed at 80 to 90 ° C. to prepare a slurry liquid for generating seed crystals.
[0241]
Subsequently, after adding ferrous sulfate aqueous solution so that it may become 0.9-1.2 equivalent with respect to the original alkali amount (sodium component of caustic soda) to this slurry liquid, the slurry liquid is maintained at pH 8 and air is supplied. The oxidation reaction was promoted while blowing, the pH was adjusted at the end of the oxidation reaction, and the oxidation reaction was completed. The generated particles were washed, filtered and dried by a conventional method, and then the aggregated particles were crushed to obtain iron oxide particles a. Silane coupling agent obtained by diluting the obtained iron oxide particles a 10 times with methanol in the gas phase [n-C₆H₁₃Si (OCH_Three)_ThreeHydrophobic iron oxide 5 was obtained by hydrophobizing (adjusted so that the coupling agent would be 0.5 parts with respect to 100 parts of iron oxide).
[0242]
(Production Example 6 of hydrophobic iron oxide)
The iron oxide particles a obtained in Production Example 5 of hydrophobic iron oxide are dispersed in water, the pH of the aqueous iron oxide dispersion is adjusted, and a silane coupling agent [n-C₆H₁₃Si (OCH_Three)_Three] 0.5 parts was added and mixed and stirred thoroughly. The produced hydrophobic iron oxide particles were washed, filtered and dried by a conventional method, and then the agglomerated particles were pulverized to obtain hydrophobic iron oxide 6.
[0243]
Table 1 shows the physical properties of the above hydrophobic iron oxides 2-6.
[0244]
[Table 1]

[0245]
Next, the image forming apparatus used in the following Examples 1 to 6 and Comparative Examples 1 to 4 will be described.
[0246]
A commercially available laser beam printer LBP-SX (manufactured by Canon) that performs development using a non-contact development method was modified as shown below. That is, the toner layer thickness regulating member in the process cartridge portion is changed to an elastic blade made of urethane rubber, a toner application roller and a cleaning magnet roller are installed, and the magnet contained in the toner carrier (developing sleeve) 15 is removed. An LBP printer was used.
[0247]
The image output conditions are shown below.
[0248]
FIG. 6 illustrates the alternating voltage used. V_dcIndicates the DC power supply voltage, V_dIs the dark potential on the electrostatic latent image carrier, V_LRepresents the light portion potential. f is the frequency of the alternating voltage, V_ppIndicates the voltage between the peaks of the alternating voltage.
[0249]
V_dIs set to −600 V, an electrostatic latent image is formed, and a gap (300 μm) is set between the photosensitive drum 3 and the developer layer on the developing sleeve 15 in a non-contact manner. f = 3200Hz V_pp= 1800V) and DC bias (V_dc= −400V) and V_LWas set to -150 V and imaged.
[0250]
The peripheral speed ratio of the developing sleeve to the photosensitive drum was set to 200%.
[0251]
<Example 1>
0.1 mol / liter-Na in 709 parts by mass of ion-exchanged water_ThreePO_FourAfter adding 451 parts by mass of the aqueous solution and heating to 60 ° C., 1.0 mol / liter-CaCl₂Gradually add 67.7 parts by weight of aqueous solution and add Ca._Three(PO_Four)₂An aqueous medium containing was obtained.
[0252]
on the other hand,
・ Styrene 82 parts
・ 18 parts of n-butyl acrylate
・ Polyester resin 5 parts
・ Negative charge control agent (monoazo dye-based Fe compound) 2 parts
・ Hydrophobic iron oxide 1 100 parts
The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.).
[0253]
This monomer composition was heated to 60 ° C., 20 parts of ester wax (mp.70 ° C.) was mixed and dissolved therein, and polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was added thereto. [T_1/2= 140 minutes at 60 ° C] 8 parts by mass and dimethyl-2,2'-azobisisobutyrate [t_1/2= 270 minutes, at 60 ° C; t_1/2= 80 minutes, at 80 ° C.] 2 parts by mass were dissolved.
[0254]
The polymerizable monomer system is charged into the aqueous medium, and 60 ° C., N₂In an atmosphere, the mixture was stirred for 15 minutes at 10,000 rpm with a TK homomixer (Special Machine Industries Co., Ltd.) and granulated. Thereafter, the mixture was reacted at 60 ° C. for 1 hour while stirring with a paddle stirring blade. Thereafter, the liquid temperature was raised to 80 ° C., and stirring was further continued for 10 hours. After completion of the reaction, the suspension is cooled, hydrochloric acid is added and Ca is added._Three(PO_Four)₂Was dissolved, filtered, washed with water, and dried to obtain toner particles.
[0255]
After 100 parts of the toner particles were treated with hexamethyldisilazane and then treated with silicone oil, the BET specific surface area after treatment was 120 m.²Toner A (weight average particle diameter 6.2 μm) was prepared by mixing 1.4 parts of / g hydrophobic silica fine powder with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.).
[0256]
Here, the dispersion state of the hydrophobic iron oxide inside the toner A particles was evaluated by observing the tomographic surface of the toner particles using a transmission electron microscope (TEM).
[0257]
As a specific evaluation method using TEM, the same method as that for determining the volume average particle size and particle size distribution of iron oxide in the toner particles described above was used.
[0258]
The specific evaluation of the dispersion state of the hydrophobic iron oxide inside the toner particles was performed as follows. Extract a particle fault plane having a diameter of ± 10% of the number average particle diameter of the toner, and write a similar figure with the same center as the fault plane and half the diameter (the area of the similar figure is 1 of the particle fault plane area). / 4).
[0259]
Next, the number of 0.03 μm or more hydrophobic iron oxide powders present in the particle tomographic plane (including the similar figure) is counted, and the number is defined as a. Similarly, the number of 0.03 μm or more hydrophobic iron oxide powders present in the similar figure is counted, and the number is b. The ratio b / a is calculated for a and b thus obtained.
[0260]
The closer the ratio b / a is to 1/4 of the area ratio of each surface, the more the hydrophobic iron oxide powder is present from the center of the toner particle to the vicinity of the surface layer, that is, within the toner particle. This means that the state of dispersion of the hydrophobic iron oxide is uniform. If the value of b / a is in the range of 3/8 to 1/5, it can be said that almost good dispersion is achieved.
[0261]
When b / a was determined for toner A, it was found to be about 1/4, and it was found that the dispersion state of hydrophobic iron oxide in the toner particles was very uniform.
[0262]
Using toner A, an image printing test was performed on 5000 sheets in a normal temperature and humidity environment (23 ° C., 65% RH). As a result, a good image without scattering was obtained even after continuous printing of 5000 sheets. Further, the toner on the sleeve was removed with air and then visually observed, but the developer was not fixed on the sleeve at all. Table 3 shows the evaluation results of the image density, the fog amount, and the dot reproducibility according to the evaluation method described later.
[0263]
In the same manner, the image-drawing test was performed in a high temperature and high humidity environment (32.5 ° C., 85% RH) and in a low temperature and low humidity environment (10 ° C., 15% RH). The results are shown in Table 2.
[0264]
<Example 2>
Magnetic toner particles were obtained in the same manner except that the hydrophobic iron oxide 1 of Example 1 was changed to 100 parts of hydrophobic iron oxide 2 and the stirring speed during granulation was changed. In the same manner as in Example 1, 1.7 parts of hydrophobic colloidal silica was externally added to 100 parts of the obtained toner particles to prepare toner B (weight average particle diameter 4.9 μm).
[0265]
Using the obtained toner B, an image output test was conducted in the same manner as in Example 1.
[0266]
<Example 3>
Toner particles were obtained in the same manner except that the hydrophobic iron oxide 1 of Example 1 was changed to 150 parts of hydrophobic iron oxide 3. In the same manner as in Example 1, 0.7 parts of hydrophobic colloidal silica was externally added to 100 parts of the obtained toner particles to prepare toner C (weight average particle diameter 9.7 μm).
[0267]
Using the obtained toner C, an image output test was conducted in the same manner as in Example 1.
[0268]
<Example 4>
Toner particles were obtained in the same manner except that the hydrophobic iron oxide 1 of Example 1 was changed to 190 parts of hydrophobic iron oxide 4. In the same manner as in Example 1, 2.0 parts of hydrophobic colloidal silica was externally added to 100 parts of the obtained toner particles to prepare toner D (weight average particle diameter 3.5 μm).
[0269]
Using the obtained toner D, an image output test was conducted in the same manner as in Example 1.
[0270]
<Examples 5 and 6>
Change the amount of hydrophobic iron oxide 3 used to 40 parts or 200 parts,_ThreePO_FourAqueous solution and CaCl₂Toner particles were obtained in the same manner as in Example 3 except that the amount of the aqueous solution was changed. In the same manner as in Example 1, 1.0 part and 3.0 part of hydrophobic colloidal silica were externally added to 100 parts of the obtained toner particles, and toners E (weight average particle diameter 10.5 μm) and F (weight average) were added. A particle size of 1.9 μm) was prepared.
[0271]
Using the obtained toners E and F, an image output test was conducted in the same manner as in Example 1.
[0272]
<Comparative Example 1>
0.1 mol / liter-Na in 709 parts by mass of ion-exchanged water_ThreePO_FourAfter adding 451 parts by mass of the aqueous solution and heating to 60 ° C., 1.0 mol / liter-CaCl₂Gradually add 67.7 parts by weight of aqueous solution and add Ca._Three(PO_Four)₂An aqueous medium containing was obtained.
[0273]
on the other hand,
・ Styrene 82 parts
・ 18 parts of n-butyl acrylate
・ Polyester resin 5 parts
・ Hydrophobic iron oxide 1 100 parts
The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.).
[0274]
The monomer composition was heated to 60 ° C., and the polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile [t_1/2= 140 minutes, at 60 ° C] 8 parts by mass and dimethyl-2,2'-azobisisobutyrate [t_1/2= 270 minutes, below 60 ° C; t_1/2= 80 minutes, at 80 ° C.] 2 parts by mass were dissolved.
[0275]
The polymerizable monomer system is charged into the aqueous medium, and 60 ° C., N₂In an atmosphere, the mixture was stirred for 15 minutes at 10,000 rpm with a TK homomixer (Special Machine Industries Co., Ltd.) and granulated. Thereafter, the mixture was reacted at 60 ° C. for 1 hour while stirring with a paddle stirring blade. Thereafter, the liquid temperature was raised to 80 ° C., and stirring was further continued for 10 hours. After completion of the reaction, the suspension is cooled, hydrochloric acid is added and Ca is added._Three(PO_Four)₂Was dissolved, filtered, washed with water, and dried to obtain an iron oxide-containing resin powder having a weight average particle size of 10.0 μm.
[0276]
Next,
・ 205 parts of the above iron oxide-containing resin powder
Negative charge control agent (monoazo dye-based Fe compound) 0.8 parts
・ Ethylene-propylene copolymer (Mw = 6000) 3 parts
The mixture is melt kneaded with a twin screw extruder heated to 140 ° C., the kneaded product is cooled, coarsely pulverized with a hammer mill, and the coarsely pulverized product is finely pulverized with a jet mill. Classification was performed to obtain toner particles a. A mixture obtained by adding 1.2 parts of the hydrophobic colloidal silica used in Example 1 to 100 parts of the toner particles a was mixed with a Henschel mixer to prepare toner G (weight average particle diameter 7.4 μm).
[0277]
Using the obtained toner G, an image output test was conducted in the same manner as in Example 1.
[0278]
<Comparative example 2>
The toner particles a obtained in Comparative Example 1 were surface-treated with a mechanical impact force to obtain toner particles b. Toner H was prepared by mixing a mixture obtained by adding 1.2 parts of hydrophobic colloidal silica used in Example 1 to 100 parts of the toner particles b with a Henschel mixer.
[0279]
Using the obtained toner H, an image output test was conducted in the same manner as in Example 1.
[0280]
<Comparative Example 3>
Toner particles were obtained in the same manner except that the hydrophobic iron oxide 1 of Example 1 was changed to 100 parts of hydrophobic iron oxide 5. In the same manner as in Example 1, 1.2 parts of hydrophobic colloidal silica was externally added to 100 parts of the obtained toner particles to prepare toner I (weight average particle diameter 6.9 μm).
[0281]
For this toner I, the state of iron oxide dispersion in the particles was evaluated by TEM observation as in the case of toner A. The b / a was about 1/6, and the state of iron oxide dispersion in the toner particles. Was non-uniform, and was found to be present especially on the toner particle surface. This is presumably because iron oxide powder having low hydrophobicity gathered on the surface of the toner particles during suspension polymerization because of the non-uniform hydrophobicity of iron oxide.
[0282]
Using the obtained toner I, an image output test was conducted in the same manner as in Example 1.
[0283]
<Comparative example 4>
Toner particles were obtained in the same manner except that the hydrophobic iron oxide 1 of Example 1 was changed to 150 parts of hydrophobic iron oxide 6. In the same manner as in Example 1, 1.7 parts of hydrophobic colloidal silica was externally added to 100 parts of the obtained toner particles to prepare toner J (weight average particle diameter 4.8 μm).
[0284]
Using the obtained toner J, an image output test was conducted in the same manner as in Example 1.
[0285]
Table 2 shows the physical properties of the obtained toners. In addition, Table 3 shows the image output test results of each toner. The evaluation method is as follows.
[0286]
a) Image density was measured with a Macbeth densitometer RD918 (manufactured by Macbeth).
[0287]
b) The fog was measured using a REFECTMETER MODELTC-6DS manufactured by Tokyo Denshoku. The filter was calculated from the following formula using a green filter.
[0288]
Fog (reflectance) (%) = reflectance on standard paper (%) − reflectance of sample non-image area (%)
[0289]
If the fog is 2.0% or less, a good image is obtained.
[0290]
c) The dot reproducibility was evaluated by conducting an image printing test using a checker pattern of 80 μm × 50 μm shown in FIG.
A: Less than 2 defects in 100
B: 3-5 defects in 100
C: 6 to 10 defects in 100
D: 11 or more defects in 100
[0291]
d) The transfer efficiency at the initial stage of durability (at 100 sheets) is determined by tapering the transfer residual toner on the photoconductor after transfer of the solid black image by taping with Mylar tape and pasting it on the paper. When the Macbeth density of the paper on which the Mylar tape was affixed on the paper on which the toner was fixed before fixing was E, and the Macbeth density of the Mylar tape affixed on the unused paper was D, the calculation was approximately made by the following equation.
[0292]
[Outside 4]

[0293]
If the transfer efficiency is 90% or more, there is no problem.
[0294]
[Table 2]

[0295]
[Table 3]

[0296]
(Toner Production Example 1)
0.1 mol / liter-Na in 709 parts by mass of ion-exchanged water_ThreePO_FourAfter adding 451 parts by mass of the aqueous solution and heating to 60 ° C., 1.0 mol / liter-CaCl₂Gradually add 67.7 parts by weight of aqueous solution and add Ca._Three(PO_Four)₂An aqueous medium containing was obtained.
[0297]
on the other hand,
・ Styrene 82 parts
・ 18 parts of n-butyl acrylate
・ Polyester resin 5 parts
・ Negative charge control agent (monoazo dye-based Fe compound) 2 parts
・ Hydrophobic iron oxide 1 100 parts
The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.).
[0298]
This monomer composition was heated to 60 ° C., 20 parts of ester wax (mp.70 ° C.) was mixed and dissolved therein, and polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was added thereto. [T_1/2= 140 minutes at 60 ° C] 8 parts by mass and dimethyl-2,2'-azobisisobutyrate [t_1/2= 270 minutes, at 60 ° C; t_1/2= 80 minutes, at 80 ° C.] 2 parts by mass were dissolved.
[0299]
The polymerizable monomer system is charged into the aqueous medium, and 60 ° C., N₂In an atmosphere, the mixture was stirred for 15 minutes at 10,000 rpm with a TK homomixer (Special Machine Industries Co., Ltd.) and granulated. Thereafter, the mixture was reacted at 60 ° C. for 1 hour while stirring with a paddle stirring blade. Thereafter, the liquid temperature was raised to 80 ° C., and stirring was further continued for 10 hours. After completion of the reaction, the suspension is cooled, hydrochloric acid is added and Ca is added._Three(PO_Four)₂Was dissolved, filtered, washed with water, and dried to obtain toner particles.
[0300]
After 100 parts of the toner particles were treated with hexamethyldisilazane and then treated with silicone oil, the BET value after the treatment was 120 m.²Toner K (weight average particle size 6.1 μm) was prepared by mixing 1.4 parts of / g hydrophobic silica fine powder with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.).
[0301]
(Toner Production Example 2)
Magnetic toner particles were obtained in the same manner except that the hydrophobic iron oxide 1 of Production Example 1 was changed to 100 parts of hydrophobic iron oxide 2. In the same manner as in Production Example 1, 1.7 parts of hydrophobic colloidal silica was externally added to 100 parts of the obtained toner particles to prepare toner L (weight average particle diameter 5.0 μm).
[0302]
(Toner Production Example 3)
Toner particles were obtained in the same manner except that the hydrophobic iron oxide 1 of Production Example 1 was changed to 150 parts of hydrophobic iron oxide 3. In the same manner as in Production Example 1, 0.7 parts of hydrophobic colloidal silica was externally added to 100 parts of the obtained toner particles to prepare Toner M (weight average particle diameter 9.8 μm).
[0303]
(Toner Production Example 4)
Toner particles were obtained in the same manner except that the hydrophobic iron oxide 1 of Production Example 1 was replaced with 190 parts of hydrophobic iron oxide 4. In the same manner as in Production Example 1, 2.0 parts of hydrophobic colloidal silica was externally added to 100 parts of the obtained toner particles to prepare toner N (weight average particle diameter 3.6 μm).
[0304]
(Toner Production Examples 5 and 6)
Change the amount of hydrophobic iron oxide 3 used to 10 parts or 200 parts,_ThreePO_FourAqueous solution and CaCl₂Toner particles were obtained in the same manner as in Production Example 3 except that the amount of the aqueous solution was changed. In the same manner as in Production Example 1, 1.0 part and 3.0 parts of hydrophobic colloidal silica were externally added to 100 parts of the obtained toner particles, and toners O (weight average particle diameter 10.9 μm) and P (weight average) were added. A particle size of 2.4 μm) was prepared.
[0305]
(Comparative Production Example 1 of Toner)
0.1 mol / liter-Na in 709 parts by mass of ion-exchanged water_ThreePO_FourAfter adding 451 parts by mass of the aqueous solution and heating to 60 ° C., 1.0 mol / liter-CaCl₂Gradually add 67.7 parts by weight of aqueous solution and add Ca._Three(PO_Four)₂An aqueous medium containing was obtained.
[0306]
on the other hand,
・ Styrene 82 parts
・ 18 parts of n-butyl acrylate
・ Polyester resin 5 parts
・ Hydrophobic iron oxide 1 100 parts
The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.).
[0307]
The monomer composition was heated to 60 ° C., and the polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile [t_1/2= 140 minutes, at 60 ° C] 8 parts by mass and dimethyl-2,2'-azobisisobutyrate [t_1/2= 270 minutes, below 60 ° C; t_1/2= 80 minutes, at 80 ° C.] 2 parts by mass were dissolved.
[0308]
The polymerizable monomer system is charged into the aqueous medium, and 60 ° C., N₂In an atmosphere, the mixture was stirred for 15 minutes at 10,000 rpm with a TK homomixer (Special Machine Industries Co., Ltd.) and granulated. Thereafter, the mixture was reacted at 60 ° C. for 1 hour while stirring with a paddle stirring blade. Thereafter, the liquid temperature was raised to 80 ° C., and stirring was further continued for 10 hours. After completion of the reaction, the suspension is cooled, hydrochloric acid is added and Ca is added._Three(PO_Four)₂Was dissolved, filtered, washed with water, and dried to obtain an iron oxide-containing resin powder having a weight average particle size of 10.0 μm.
[0309]
Next,
・ 205 parts of the above iron oxide-containing resin powder
Negative charge control agent (monoazo dye-based Fe compound) 0.8 parts
・ Ethylene-propylene copolymer (Mw = 6000) 3 parts
The mixture is melt-kneaded with a twin screw extruder heated to 140 ° C., the kneaded product is cooled, coarsely pulverized with a hammer mill, and the coarsely pulverized product is finely pulverized with a jet mill. Classification was performed to obtain toner particles c. To 100 parts of the toner particles c, a mixture obtained by adding 1.2 parts of hydrophobic colloidal silica used in Production Example 1 was mixed with a Henschel mixer to prepare toner Q (weight average particle diameter 7.2 μm).
[0310]
(Toner Comparative Production Example 2)
The toner particles c obtained in Comparative Production Example 1 were surface-treated with a mechanical impact force to obtain toner particles d. Toner R was prepared by mixing a mixture of 100 parts of the toner particles d with 1.2 parts of hydrophobic colloidal silica used in Production Example 1 with a Henschel mixer.
[0311]
(Toner Comparative Production Example 3)
Toner particles were obtained in the same manner except that the hydrophobic iron oxide 1 of Production Example 1 was changed to 100 parts of hydrophobic iron oxide 5. In the same manner as in Production Example 1, 1.2 parts of hydrophobic colloidal silica was externally added to 100 parts of the obtained toner particles to prepare toner S (weight average particle diameter 7.0 μm).
[0312]
(Toner Comparative Production Example 4)
Toner particles were obtained in the same manner except that the hydrophobic iron oxide 1 of Production Example 1 was changed to 150 parts of hydrophobic iron oxide 6. In the same manner as in Production Example 1, 1.7 parts of hydrophobic colloidal silica was externally added to 100 parts of the obtained toner particles to prepare toner T (weight average particle diameter 4.6 μm).
[0313]
Table 4 shows the physical properties of the obtained toners.
[0314]
[Table 4]

[0315]
[Examples 7 to 12 and Comparative Examples 5 to 8]
A 600 dpi laser beam printer (manufactured by Canon: LBP-860) was prepared as an electrophotographic apparatus having the configuration shown in FIGS. The process speed is modified to 60 mm / s.
[0316]
The cleaning blade in this process cartridge was removed, the charging method of the apparatus was direct charging performed by contacting a rubber roller, and the applied voltage was only the DC component (-1200 V).
[0317]
Next, the development part in the process cartridge was modified. Instead of a stainless steel sleeve as a toner carrier, a medium resistance rubber roller (diameter 16 mm, hardness ASKER C 45 degrees, resistance 10) made of silicone rubber dispersed with carbon black^Five(Ω · cm) was used to contact the photoreceptor. The developing contact width at this time was set to about 3 mm. The rotation speed of the toner carrier is the same in the contact portion with the photoconductor, and is driven to be 140% of the rotation speed of the photoconductor.
[0318]
The photoconductor used here is an Al cylinder having a diameter of 30 mm and a length of 254 mm as a base, and layers having the following constitutions are sequentially laminated by dip coating to produce a photoconductor.
(1) Conductive coating layer: Mainly composed of a powder of tin oxide and titanium oxide dispersed in a phenolic resin. Film thickness 15 μm.
(2) Undercoat layer: Mainly composed of modified nylon and copolymer nylon. Film thickness 0.6 μm.
(3) Charge generation layer: Mainly composed of a titanyl phthalocyanine pigment having absorption in a long wavelength region dispersed in a butyral resin. Film thickness 0.6 μm.
(4) Charge transport layer: Mainly composed of a hole transportable triphenylamine compound dissolved in a polycarbonate resin (molecular weight 20,000 by Ostwald viscosity method) at a mass ratio of 8:10. Film thickness 20 μm.
[0319]
As a means for applying the toner to the toner carrier, an application roller made of urethane foam rubber was provided in the developing device and brought into contact with the toner carrier. A voltage of about −550 V is applied to the application roller. Further, a stainless steel blade coated with resin for controlling the coat layer of the toner on the toner carrier was attached so that the contact pressure with the toner carrier was about 20 g / cm. The outline is shown in FIG. Further, the applied voltage at the time of development was only a direct current component (−450 V).
[0320]
The electrophotographic apparatus was remodeled and process conditions were set as follows in order to conform to the remodeling of these process cartridges.
[0321]
The modified device uses a roller charger (applying only direct current) to uniformly charge the photoreceptor. After charging, an image portion is exposed with a laser beam to form an electrostatic latent image and developed with toner to form a visible image, and then a process of transferring the toner image to a transfer material with a roller to which a voltage of +700 V is applied. Have.
[0322]
The photosensitive member charging potential was -580V for the dark portion potential and -150V for the bright portion potential. As a transfer material, 75 g / m²Paper was used.
[0323]
Using the toners K to T, the image forming test was performed by the image forming apparatus in a normal temperature and humidity environment (23 ° C., 65% RH). In addition, durability evaluation was evaluated as follows.
[0324]
a) The charging member contamination of the developer was determined by the number of durable sheets in which charging unevenness due to the charging member contamination occurred on the halftone image and the solid white image in which the image defect due to the charging failure was likely to appear. The greater the number of sheets generated, the better the durability of the developer.
[0325]
b) The method for measuring the transfer efficiency at the initial stage of durability is the same as that shown in Table 3 above.
[0326]
c) The toner recoverability in the development process was determined by whether or not an image (so-called ghost image) in the non-printing portion was generated on the obtained image sample. That is, if the toner remaining on the photoconductor without being transferred is recovered in the development process, an image is not generated in the non-printed portion, but if the toner recoverability is not good, the unrecovered toner is subjected to the transfer process again. It passes and is transferred onto the paper, and a ghost image is generated.
[0327]
A: No ghost is generated
B: Good (a level that cannot be confirmed without staring at the image)
C: Ghost is generated, but practically usable level
[0328]
When ghosting and charging unevenness did not occur, printing was continued up to 5000 sheets (5K).
[0329]
d) The resolving power at the end of durability (at the time of 100 sheets) was evaluated by the reproducibility of a small isolated dot (diameter 60 μm) at 600 dpi, which is easy to close due to the latent electric field and difficult to reproduce.
[0330]
A: Less than 5 defects in 100
B: 6-10 defects in 100
C: 11-20 defects in 100
D: 21 or more defects in 100
[0331]
e) The measurement of fog is the same as that shown in Table 3 above.
[0332]
In the same manner, the image-drawing test was performed in a high temperature and high humidity environment (32.5 ° C., 85% RH) and in a low temperature and low humidity environment (10 ° C., 15% RH). The results are shown in Table 5.
[0333]
[Table 5]

[0334]
(Production Example 7 of hydrophobic iron oxide)
In ferrous sulfate aqueous solution, l. An aqueous solution containing ferrous hydroxide was prepared by mixing 0 to 1.1 equivalents of caustic soda solution.
[0335]
While maintaining the pH of the aqueous solution at around 9, air was blown and an oxidation reaction was performed at 80 to 90 ° C. to prepare a slurry liquid for generating seed crystals.
[0336]
Subsequently, after adding ferrous sulfate aqueous solution so that it may become 0.9-1.2 equivalent with respect to the original alkali amount (sodium component of caustic soda) to this slurry liquid, the slurry liquid is maintained at pH 8 and air is supplied. The oxidation reaction was promoted while blowing, and the magnetic iron oxide particles produced after the oxidation reaction were washed, filtered, and taken out once. At this time, a small amount of a water-containing sample was collected and the water content was measured. Next, this water-containing sample was re-dispersed in another aqueous medium without drying, and then the pH of the re-dispersed liquid was adjusted to about 6, and the silane coupling agent (n-C_TenH_{twenty one}Si (OCH_Three)_Three) Was added to 100 parts of magnetic iron oxide (the amount of magnetic iron oxide was calculated as a value obtained by subtracting the water content from the water-containing sample) and subjected to a coupling treatment. The produced hydrophobic iron oxide particles were washed, filtered and dried by a conventional method, and then the slightly agglomerated particles were pulverized to obtain hydrophobic iron oxide 7.
[0337]
(Production Example 1 of magnetic material)
The oxidation reaction was advanced in the same manner as in Production Example 7 of magnetic iron oxide. The magnetic iron oxide particles produced after the oxidation reaction were washed, filtered and dried, and the aggregated particles were crushed to obtain a magnetic body 1.
[0338]
(Production Example 8 of hydrophobic iron oxide)
After re-dispersing the magnetic substance 1 obtained in Production Example 1 of the magnetic substance in another aqueous medium, the pH of the re-dispersed liquid was adjusted to about 6, and the silane coupling agent (n- C_TenH_{twenty one}Si (OCH_Three)_Three) Was added to 0.5 parts of magnetic iron oxide and subjected to coupling treatment. The produced hydrophobic iron oxide particles were washed, filtered and dried by a conventional method, and then the aggregated particles were crushed to obtain hydrophobic iron oxide 8.
[0339]
(Production Example 9 of hydrophobic iron oxide)
In Production Example 7 of hydrophobic iron oxide, hydrophobic iron oxide 9 was obtained by reducing the aqueous ferrous sulfate solution during the synthesis of magnetic iron oxide particles and increasing the amount of air blown.
[0340]
(Production Example 10 of hydrophobic iron oxide)
Hydrophobic iron oxide 10 was obtained in the same manner as in Production Example 7 of hydrophobic iron oxide except that the aqueous ferrous sulfate solution was increased during the synthesis of magnetic iron oxide particles and the amount of air blown was reduced.
[0341]
(Production Example 11 of hydrophobic iron oxide)
In Production Example 1 of hydrophobic iron oxide 7, hydrophobic iron oxide 11 was obtained by increasing the amount of air blown during the synthesis of magnetic iron oxide particles.
[0342]
Table 6 shows the physical properties of the hydrophobic iron oxides 7 to 11 and the magnetic body 1 obtained as described above.
[0343]
[Table 6]

[0344]
<Toner Production Example 7>
0.1 mol / liter-Na in 709 parts by mass of ion-exchanged water_ThreePO_FourAfter adding 451 parts by mass of the aqueous solution and heating to 60 ° C., 1.0 mol / liter-CaCl₂Gradually add 67.7 parts by weight of aqueous solution and add Ca._Three(PO_Four)₂An aqueous medium containing was obtained.
[0345]
80 parts of styrene
20 parts of n-butyl acrylate
2 parts unsaturated polyester resin obtained by condensation reaction of propylene oxide adduct of bisphenol A and ethylene oxide adduct and fumaric acid
Negative charge control agent (monoazo dye-based Fe compound represented by the following formula) 4 parts
Hydrophobic iron oxide 1 80 parts
The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.).
[0346]
[Outside 5]

[0347]
This monomer composition was heated to 60 ° C., and 10 parts of ester wax having an endothermic peak temperature in DSC of 75 ° C. was added and mixed therewith, to which polymerization initiator 2,2′-azobis (2,4- Dimethylvaleronitrile) [t_1/2= 140 minutes at 60 ° C] 8 parts by mass and dimethyl-2,2'-azobisisobutyrate [t_1/2= 270 minutes, at 60 ° C; t_1/2= 80 minutes, at 80 ° C.] 2 parts by mass were dissolved.
[0348]
The polymerizable monomer system is charged into the aqueous medium, 60 ° C., N₂In an atmosphere, the mixture was stirred for 15 minutes at 10,000 rpm with a TK homomixer (Special Machine Industries Co., Ltd.) and granulated. Thereafter, the mixture was reacted at 60 ° C. for 1 hour while stirring with a paddle stirring blade. Thereafter, the liquid temperature was raised to 80 ° C., and stirring was further continued for 10 hours. After completion of the reaction, the suspension is cooled, hydrochloric acid is added and Ca is added._Three(PO_Four)₂Was dissolved, filtered, washed with water, and dried to obtain magnetic toner particles having a weight average particle diameter of 7.0 μm.
[0349]
The surface is treated with 100 parts of the magnetic toner particles and hexamethyldisilazane, and the BET specific surface area after the treatment is 200 m.²Toner U was prepared by mixing 1.2 parts of / g hydrophobic silica fine powder with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 7 shows the physical properties of Toner U.
[0350]
For this toner U, the state of dispersion of iron oxide inside the particles was evaluated by TEM observation as in the case of toner A. As a result, b / a was almost 1/4, and the state of dispersion of iron oxide in the toner particles. Was found to be very uniform.
[0351]
<Toner Production Example 8>
Magnetic toner particles having a weight average particle diameter of 6.9 μm were obtained in the same manner as in Toner Production Example 7.
[0352]
After 100 parts of the magnetic toner particles were treated with hexamethyldisilazane and then treated with silicone oil, the BET specific surface area after treatment was 180 m.²Toner V was prepared by mixing 1.2 parts of / g hydrophobic silica fine powder with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 7 shows the physical properties of Toner V.
[0353]
<Toner Production Example 9>
In Toner Production Example 7, Na_ThreePO_FourAqueous solution and CaCl₂The amount of the aqueous solution input was changed, and magnetic toner particles having a weight average particle diameter of 3.8 μm were obtained using sodium dodecylbenzenesulfonate. Toner W was prepared by mixing 100 parts of the magnetic toner particles and 2.5 parts of hydrophobic silica fine powder used in Toner Production Example 8 with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 7 shows the physical properties of Toner W.
[0354]
<Toner Production Example 10>
In Toner Production Example 7, Na_ThreePO_FourAqueous solution and CaCl₂The amount of the aqueous solution charged was changed to obtain magnetic toner particles having a weight average particle diameter of 10.4 μm. Toner X was prepared by mixing 100 parts of the magnetic toner particles and 0.8 part of the hydrophobic silica fine powder used in Toner Production Example 8 with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 7 shows the physical properties of Toner X.
[0355]
<Toner Production Example 11>
Magnetic toner particles having a weight average particle diameter of 8.2 μm were obtained in the same manner as in Toner Production Example 7 except that the amount of ester wax used was 51 parts. Toner Y was prepared by mixing 100 parts of the magnetic toner particles and 1.1 parts of the hydrophobic silica fine powder used in Toner Production Example 8 with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 7 shows the physical properties of Toner Y.
[0356]
<Toner Production Example 12>
Magnetic toner particles having a weight average particle diameter of 6.8 μm were obtained in the same manner as in Toner Production Example 7 except that the amount of ester wax used was 0.4 parts. Toner Z was prepared by mixing 100 parts of the magnetic toner particles and 1.2 parts of hydrophobic silica fine powder used in Toner Production Example 8 with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 7 shows the physical properties of Toner Z.
[0357]
<Toner Production Example 13>
Magnetic toner particles having a weight average particle diameter of 8.4 μm were obtained in the same manner as in Toner Production Example 7 except that 10 parts of low molecular weight polyethylene wax having an endothermic peak temperature of 115 ° C. in DSC was used instead of ester wax. . Toner AA was prepared by mixing 100 parts of the magnetic toner particles and 1.1 parts of the hydrophobic silica fine powder used in Toner Production Example 8 with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 7 shows the physical properties of Toner AA.
[0358]
<Toner Production Example 14>
Magnetic toner particles having a weight average particle diameter of 6.9 μm were obtained in the same manner as in Toner Production Example 7 except that the amount of hydrophobic iron oxide 7 used was 30 parts. Toner BB was prepared by mixing 100 parts of the magnetic toner particles and 1.2 parts of the hydrophobic silica fine powder used in Toner Production Example 8 with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 7 shows the physical properties of Toner BB.
[0359]
<Toner Production Example 15>
Magnetic toner particles having a weight average particle diameter of 7.9 μm were obtained in the same manner as in Toner Production Example 7 except that 205 parts of hydrophobic iron oxide 7 was used. Toner CC was prepared by mixing 100 parts of the magnetic toner particles and 1.1 parts of hydrophobic silica fine powder used in Toner Production Example 8 with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 7 shows the physical properties of Toner CC.
[0360]
<Toner Production Examples 16-18>
A magnetic toner was obtained in the same manner as in Toner Production Example 7 except that hydrophobic iron oxides 9 to 11 were used instead of hydrophobic iron oxide 7. 100 parts of these magnetic toner particles and 1.2 parts of hydrophobic silica fine powder used in Toner Production Example 8 are mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.), and toners DD to FF are mixed. Prepared. Table 7 shows the physical properties of Toners DD to FF.
[0361]
<Toner Comparative Production Example 5>
Magnetic toner particles having a weight average particle diameter of 8.8 μm were obtained in the same manner as in Toner Production Example 7 except that 80 parts of the magnetic material 1 was used in place of the hydrophobic iron oxide 7. Toner GG prepared by mixing 100 parts of the magnetic toner particles and 1.0 part of hydrophobic silica fine powder used in Toner Production Example 8 with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 7 shows the physical properties.
[0362]
For this toner GG, when the state of iron oxide dispersion in the particles was evaluated by TEM observation as in the case of toner A, the b / a was about 1/8 and the state of iron oxide dispersion in the toner particles. Was non-uniform, and it was found that a large amount was present especially on the toner particle surface.
[0363]
<Comparative Production Example 6 of Toner>
Magnetic toner particles having a weight average particle size of 8.1 μm were obtained in the same manner as in Toner Production Example 7 except that 80 parts of hydrophobic iron oxide 8 was used instead of hydrophobic iron oxide 7. Toner HH was prepared by mixing 100 parts of the magnetic toner particles and 1.1 parts of hydrophobic silica fine powder used in Toner Production Example 8 with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 7 shows the physical properties of Toner HH.
[0364]
For this toner HH, the state of iron oxide dispersion in the particles was evaluated by TEM observation as in the case of toner A. The b / a was about 1/6, and the state of iron oxide dispersion in the toner particles. Was non-uniform, and it was found that a large amount was present especially on the toner particle surface.
[0365]
<Toner Comparative Production Example 7>

The above materials are mixed in a blender, melt kneaded with a biaxial extruder heated to 110 ° C., the cooled kneaded product is coarsely pulverized with a hammer mill, and the coarsely pulverized product is finely pulverized with a jet mill. The pulverized product was subjected to air classification to obtain magnetic toner particles having a weight average particle size of 10.4 μm. Toner II was prepared by mixing a mixture of 100 parts of the magnetic toner particles with 0.8 part of hydrophobic silica fine powder used in Toner Production Example 8 using a Henschel mixer. Table 7 shows the physical properties of Toner II.
[0366]
<Toner Comparative Production Example 8>
Magnetic toner particles were obtained in the same manner as in Comparative Toner Production Example 7 except that the coarsely pulverized product was finely pulverized with a turbo mill (manufactured by Turbo Kogyo Co., Ltd.). Thereafter, a spheroidized toner having a weight average particle diameter of 10.3 μm was obtained using an impact surface treatment apparatus (treatment temperature 50 ° C., rotary treatment blade peripheral speed 90 m / sec.).
[0367]
Next, a mixture obtained by adding 0.8 part of hydrophobic silica fine powder used in Toner Production Example 8 to 100 parts of the resulting spheroidized toner was mixed with a Henschel mixer to prepare toner JJ. Table 7 shows the physical properties of Toner JJ.
[0368]
<Toner Comparative Production Example 9>
0.1 mol / liter-Na in 709 parts by mass of ion-exchanged water_ThreePO_FourAfter adding 451 parts by mass of the aqueous solution and heating to 60 ° C., 1.0 mol / liter-CaCl₂Gradually add 67.7 parts by weight of aqueous solution and add Ca._Three(PO_Four)₂An aqueous medium containing was obtained.
[0369]

The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.).
[0370]
This monomer composition was heated to 60 ° C., and 12 parts of ester wax used in Toner Production Example 7 was added and mixed therewith, and polymerization initiator 2,2′-azobis (2,4-dimethyl) was added thereto. Valeronitrile) [t_1/2= 140 minutes at 60 ° C] 8 parts by mass and dimethyl-2,2'-azobisisobutyrate [t_1/2= 270 minutes, at 60 ° C; t_1/2= 80 minutes, at 80 ° C.] 2 parts by mass were dissolved.
[0371]
The polymerizable monomer system is charged into the aqueous medium, 60 ° C., N₂In an atmosphere, the mixture was stirred for 15 minutes at 10,000 rpm with a TK homomixer (Special Machine Industries Co., Ltd.) and granulated. Thereafter, the mixture was reacted at 60 ° C. for 1 hour while stirring with a paddle stirring blade. Thereafter, the liquid temperature was raised to 80 ° C., and stirring was further continued for 10 hours.
[0372]
Next, in this aqueous suspension
16 parts of styrene
4 parts of n-butyl acrylate
0.4 part of 2,2'-azobis (2,4-dimethylvaleronitrile)
Sodium behenate 0.1 part
20 parts of water
The mixture was added again, and the liquid temperature was changed to 80 ° C., and stirring was continued for 10 hours.
After completion of the reaction, the suspension is cooled, hydrochloric acid is added and Ca is added._Three(PO_Four)₂Was dissolved, filtered, washed with water, and dried to obtain toner particles having a weight average particle diameter of 8.5 μm.
[0373]
Toner KK was prepared by mixing 100 parts of the toner particles and 1.0 part of the hydrophobic silica fine powder used in Toner Production Example 8 with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 7 shows the physical properties of Toner KK.
[0374]
<Toner Comparative Production Example 10>
Magnetic toner particles having a weight average particle diameter of 8.3 μm were obtained in the same manner as in Toner Production Example 9 except that 96 parts of the magnetic material 1 was used in place of the hydrophobic iron oxide 7. Toner LL was prepared by mixing 100 parts of the magnetic toner particles and 1.0 part of hydrophobic silica fine powder used in toner production example 8 with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 7 shows the physical properties.
[0375]
[Table 7]

[0376]
(Photoreceptor Production Example 1)
As a photoreceptor, an Al cylinder having a diameter of 30 was used as a base. A layer having a structure as shown in FIG. 8 was sequentially laminated thereon by dip coating to prepare a photoreceptor.
(1) Conductive coating layer: Mainly composed of a powder of tin oxide and titanium oxide dispersed in a phenolic resin. Film thickness 15 μm.
(2) Undercoat layer: Mainly composed of modified nylon and copolymer nylon. Film thickness 0.6 μm.
(3) Charge generation layer: Mainly composed of an azo pigment having absorption in a long wavelength region dispersed in a butyral resin. Film thickness 0.6 μm.
(4) Charge transport layer: Mainly composed of a hole-transporting triphenylamine compound dissolved in a polycarbonate resin (molecular weight of 20,000 by the Ostwald viscosity method) at a mass ratio of 8:10, and polytetrafluoroethylene powder ( 10% by weight of the total solid content was added and dispersed uniformly. The film thickness was 25 μm and the contact angle with water was 95 degrees.
[0377]
The contact angle was measured using pure water and a contact angle meter CA-X type apparatus manufactured by Kyowa Interface Science Co., Ltd.
[0378]
Example 1
As the image forming apparatus, an apparatus generally shown in FIG. 1 was used.
[0379]
As the electrostatic charge image carrier, an organic photoreceptor (OPC) drum of (Photoreceptor Production Example 1) was used. A rubber roller charger in which conductive carbon is dispersed as a primary charging member and coated with nylon resin is brought into contact with this photoreceptor (contact pressure 60 g / cm), and an AC voltage of 2.0 kVpp is superimposed on a DC voltage of −700 Vdc. The bias is applied to uniformly charge the photosensitive member. Subsequent to primary charging, an electrostatic latent image is formed by exposing the image portion with laser light. At this time, the dark portion potential Vd = −700 V and the bright portion potential VL = −200 V.
[0380]
The gap between the photosensitive drum and the developing sleeve is 280 μm, and a resin layer having a layer thickness of about 7 μm and a JIS centerline average roughness (Ra) of 1.3 μm having the following configuration is used as a toner carrier. Using a developing sleeve formed on an aluminum cylinder, a developing magnetic pole of 95 mT (950 gauss), a toner regulating member having a thickness of 1.0 mm and a free length 10 mm urethane rubber blade of 14.7 N / m (15 kg / m) The contact was made by pressure.
[0381]
100 parts of phenolic resin
90 parts of graphite (particle size about 7μm)
10 parts of carbon black
[0382]
Next, a DC bias component Vdc = −400 V as a development bias, and an overlapping AC bias component V_pp= 1600 V, f = 2000 Hz was used. The peripheral speed of the developing sleeve was 110% (88 mm / sec) in the forward direction with respect to the peripheral speed of the photoreceptor (80 mm / sec).
[0383]
Further, a transfer roller as shown in FIG. 5 (made of ethylene-propylene rubber in which conductive carbon is dispersed, the volume resistance value of the conductive elastic layer is 10).⁸Ωcm, surface rubber hardness of 24 °, diameter of 20 mm, and contact pressure of 59 N / m (6 kg / m)) are set at a constant speed relative to the circumferential speed of the photosensitive member (80 mm / sec) in the direction A in FIG. The direct current was 1.5 kV.
[0384]
As a fixing method, a heat roller fixing device was used.
[0385]
First, toner U was used as a toner, and an image printing test was performed in an environment of 15 ° C. and 10% RH. 90g / m as transfer material²Paper was used. As a result, a good image was obtained that showed high transferability in the initial stage, no back-fouling due to transfer loss of characters and lines and fixing offset, and no fogging on non-image areas.
[0386]
Next, durability was evaluated with an image pattern consisting of only vertical lines with a printing area ratio of 5%.
[0387]
Image evaluation was performed as follows.
[0388]
The evaluation of the abrasion of the photosensitive member and the toner fusion was judged by the durable number in which the image defect due to the abrasion or the toner fusion, that is, the black spot or the white spot occurred on the halftone image in which the image defect is likely to appear. It means that the durability of the image forming method is better as the number of the durable sheets is increased. In addition, image defects due to primary charging failure due to transfer residual toner, that is, charging unevenness were also evaluated on the halftone image. When these image defects did not occur, the durability test was continued up to 5000 printed sheets.
a) The method for measuring the transfer efficiency is the same as that shown in Table 3 above.
b) The evaluation method of the resolving power at the initial stage of durability is the same as that shown in Table 5 above.
c) The image density measurement method is the same as that shown in Table 3 above.
d) Fog evaluation is the same as that shown in Table 3 above.
e) The fixing offset property was determined by observing dirt generated on the back side of the image sample from the initial stage to 100 durability sheets and counting the number of generated sheets.
[0389]
Table 8 shows the obtained results.
[0390]
(Example 14)
When toner V was used as the toner and an image forming test was conducted by the same image forming method as in Example 13, a very good result as shown in Table 8 was obtained up to 5000 printed sheets.
[0390]
(Examples 15 to 24)
Using toners W to FF as toners, an image output test was performed by the same image forming method as in Example 13. As a result, as shown in Table 8, a practically satisfactory result was obtained.
[0392]
(Comparative Example 9)
Using toner GG as a toner, an image output test was performed by the same image forming method as in Example 13. As a result, from the 2500th printed sheet, black spots were generated on the halftone image due to the scraping of the photoconductor, and from the 3000th sheet, white spots due to toner fusion began to occur. This is presumably because the untreated magnetic material was used, so that much of the iron oxide was exposed from the toner surface, and the photoconductor was scraped off when the transfer residual toner was rubbed by the charging roller.
[0393]
(Comparative Example 10)
Using the toner HH as the toner, an image output test was performed by the same image forming method as in Example 13. As a result, black spots were generated on the halftone images from the 3500th printed sheet, and white spots were generated from the 4000th sheet due to toner fusion. It seems that the hydrophobic treatment of the used hydrophobic iron oxide is not uniform, so that the exposure of the iron oxide from the toner surface cannot be prevented, and the transfer residual toner has scraped off the photosensitive member at the time of rubbing with the charging roller.
[0394]
(Comparative Example 11)
Using toner II as the toner, an image forming test was conducted by the same image forming method as in Example 13. As a result, black spots are generated on the halftone image on the halftone image from the 1000th printed sheet, white spots due to toner fusion are generated from the 1500th sheet, and transfer residuals are generated from the 2000th sheet. Uneven charging due to toner started to occur. Even when iron oxide with a hydrophobic surface uniformly applied is used, if the toner is manufactured by a general pulverization method, the exposure of iron oxide from the toner surface cannot be prevented, and the transfer residual toner is rubbed by the charging roller. This is probably due to the fact that the photoconductor has been scraped. Furthermore, since the degree of circularity is low, it is considered that the edge of the toner particle is scraped and the photoreceptor is deteriorated quickly.
[0395]
(Comparative Example 12)
Toner JJ was used as the toner, and an image output test was conducted by the same image forming method as in Example 13. As a result, black spots are generated on the halftone image on the halftone image from the 2500th printed sheet, white spots are generated from the 3000th sheet due to toner fusion, and transfer residual is generated from the 3500th sheet. Uneven charging due to toner started to occur. During the spheroidization of the toner surface, the iron oxide exposure from the toner surface was improved, but the degree of circularity was not sufficient, so the improvement of the photoconductor shaving due to the edge of the toner particles was insufficient. Conceivable.
[0396]
(Comparative Example 13)
Using toner KK as the toner, an image output test was conducted by the same image forming method as in Example 13. As a result, as shown in Table 8, there was obtained a problem-free result with respect to image defects caused by the photoconductor scraping. However, the image density decreased as the number of printed sheets increased, and after 5000 printed sheets, the image density decreased to 0.71. In addition, backside contamination began to occur after 4000 sheets of durability. This is because the number of particles satisfying D / C ≦ 0.02 is as low as 44%, that is, the dispersibility of iron oxide in the developer is poor, so that the particle size is large and contains a large amount of iron oxide. This is probably because only low-quality toner remained.
[0397]
(Comparative Example 14)
Using toner LL as a toner, an image forming test was performed by the same image forming method as in Example 13. As a result, there was obtained a problem with no particular problem with respect to image defects caused by photoconductor scraping. However, the image density decreased as the number of printed sheets increased, and after 5000 printed sheets, the image density decreased to 0.67. In addition, backside stains began to occur after the durability of 3500 sheets. This is probably because only the toner having low developability and fixability remained as in Comparative Example 13 using the toner KK. Further, charging unevenness due to residual toner was generated from the 4000th endurance sheet. This seems to be due to the large amount of residual toner due to insufficient toner circularity. Both phenomena are considered to result from the production of toner using iron oxide whose surface is not hydrophobized.
[0398]
[Table 8]

[0399]
【The invention's effect】
According to the present invention, in the image forming method using a one-component developer, the ratio of the iron element content / carbon element content on the surface is less than 0.001, the projected area equivalent diameter of the toner is C, When the minimum distance between the iron oxide and the toner surface is D, there are 50% or more of toners satisfying the relationship of D / C ≦ 0.02, and the average circularity is 0.970 or more. By using the developer, the photoconductor is not scraped off or the toner is fused, and an image having high quality and excellent resolution can be stably obtained for a long period of time even under low humidity.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of an image forming apparatus using a non-contact developing method.
FIG. 2 is an enlarged view of a developing unit portion of the image forming apparatus shown in FIG.
FIG. 3 is a diagram illustrating an example of an image forming apparatus using a contact development method.
4 is an enlarged view of a developing unit portion of the image forming apparatus shown in FIG.
FIG. 5 is a diagram illustrating an example of a contact transfer member.
FIG. 6 is a diagram illustrating a development bias pattern of the image forming apparatus.
FIG. 7 is an explanatory diagram of a checker pattern for testing development characteristics of toner.
FIG. 8 is a diagram illustrating an example of a configuration of a photoconductor.

Claims (34)

Having toner particles containing at least a binder resin and iron oxide;
i) The ratio (B / A) of the iron element content (B) to the carbon element content (A) present on the toner surface as measured by X-ray photoelectron spectroscopy is less than 0.001;
ii) When the equivalent diameter of the projected area of the toner is C and the minimum value of the distance between the iron oxide and the toner surface in the cross-sectional observation of the toner using a transmission electron microscope (TEM) is D, D / C ≦ 0. The toner satisfying the relationship of 02 is 50% by number or more,
iii) A toner having an average circularity of 0.970 or more.   The toner according to claim 1, wherein the ratio (B / A) is less than 0.0005.   The toner according to claim 1, wherein the toner satisfying the relationship of D / C ≦ 0.02 is 65% by number or more.   The toner according to claim 1, wherein the toner satisfying the relationship of D / C ≦ 0.02 is 75% by number or more.   The toner according to any one of claims 1 to 4, wherein the iron oxide is contained in an amount of 10 to 200 parts by mass with respect to 100 parts by mass of the binder resin.   The toner according to any one of claims 1 to 4, wherein the iron oxide is contained in an amount of 20 to 180 parts by mass with respect to 100 parts by mass of the binder resin.   The toner according to claim 1, wherein the toner has a weight average particle diameter of 2 to 10 μm.   The toner according to claim 1, wherein the toner has a weight average particle diameter of 3.5 to 8 μm.   The toner according to claim 1, wherein the toner contains hydrophobic silica treated with silicone oil.   The toner according to claim 1, wherein the iron oxide is surface-treated with a coupling agent in an aqueous medium.   The toner according to claim 10, wherein the coupling agent is an alkyltrialkoxysilane coupling agent.   The iron oxide is a magnetic iron oxide produced by adding an alkali to a ferrous salt aqueous solution, performing an oxidation reaction of ferrous hydroxide while heating, and adding a ferrous sulfate aqueous solution thereto. The toner according to claim 1, wherein:   13. The iron oxide according to claim 1, wherein the iron oxide has a volume average particle size of 0.1 to 0.3 [mu] m, and 0.03 to 0.1 [mu] m of particles are 40% by number or less. Toner.   The iron oxide contains 30% by number or less of 0.03-0.1 μm particles, and contains 10% by number or less of 0.3 μm or more particles. toner.   The iron oxide contains 30% by number or less of particles of 0.03 to 0.1 μm, and contains 5% by number or less of particles of 0.3 μm or more. toner.   The toner according to claim 1, wherein the toner contains 0.5 to 50% by mass of wax with respect to the binder resin.   The toner according to claim 16, wherein the wax has a maximum endothermic peak in a region of 40 to 110 ° C. when the temperature rises in a DSC curve measured by a differential scanning calorimeter.   The toner according to claim 1, wherein the toner is a toner produced by a suspension polymerization method. A charging step of charging the electrostatic image carrier with a charging member to which a voltage is applied from the outside; an exposure step of forming an electrostatic latent image on the electrostatic image carrier by exposure; and carrying the electrostatic latent image with toner An image forming method comprising: a developing step of developing with toner carried on a body to form a toner image; and a transfer step of transferring the toner image to a transfer material,
An image forming method, wherein the toner is the toner according to claim 1 .   20. The image formation according to claim 19, wherein the development step is a contact development step in which development is performed while bringing an electrostatic charge image on the electrostatic charge image carrier into contact with toner carried on the toner carrier. Method.   21. The image forming method according to claim 20, wherein the toner carrier is an elastic roller.   21. In the developing step, the moving speed of the toner carrier surface in the developing region is 1.05 to 3.0 times the moving speed of the electrostatic image carrier surface. 22. The image forming method according to item 21.   23. The image forming method according to claim 20, wherein the toner carrying member has a surface roughness Ra of 0.2 to 3.0 [mu] m.   24. The image forming method according to claim 20, wherein in the developing step, the transfer residual toner remaining on the electrostatic charge image carrier after the transfer step is collected by the toner carrier.   In the developing step, the electrostatic charge image carrier and the toner carrier are arranged with a certain interval, a toner layer is formed on the surface of the toner carrier with a thickness smaller than the interval, and an AC bias is applied. The image forming method according to claim 19, wherein the developing is performed by transferring the toner to an electrostatic latent image in a developing unit.   26. The image forming method according to claim 25, wherein a distance between the electrostatic charge image carrier and the toner carrier is 100 to 500 [mu] m.   27. The image forming method according to claim 25 or 26, wherein, in the development step, a speed difference between the surface of the electrostatic image carrier and the surface of the toner carrier in the development region is 1.02 to 3.0 times. .   28. The image forming method according to claim 25, wherein the toner carrier has a surface roughness Ra of 0.2 to 3.5 [mu] m.   29. The image forming method according to claim 25, wherein the AC bias is 3 × 10 6 to 1 × 10 7 V / m and a frequency of 100 to 5000 Hz in terms of a peak-to-peak electric field intensity.   30. The image forming method according to claim 19, wherein the charging step is a step of charging by bringing a charging member into contact with an electrostatic charge image carrier.   31. The image according to claim 19, wherein the transfer step is a step of transferring the toner image to the transfer material by a transfer member that contacts the electrostatic charge image carrier via the transfer material. Forming method.   The charging step is a step of charging by bringing a charging member into contact with the electrostatic charge image carrier, and the development step is a step of arranging the electrostatic charge image carrier and the toner carrier at a predetermined interval to carry the toner. The developing step is characterized in that a toner layer is formed on the surface of the body with a thickness smaller than the interval, and development is performed by transferring the toner to an electrostatic latent image in a developing portion to which an AC bias is applied. Item 20. The image forming method according to Item 19.   The thickness of the toner carried on the toner carrier is regulated by a toner layer thickness regulating member, and the toner layer thickness regulating member is in contact with the toner carrier via the toner. The image forming method according to claim 32.   34. The image forming method according to claim 33, wherein the toner layer thickness regulating member is an elastic member.

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