JP3977159B2 - Magnetic toner - Google Patents

Description

【００５１】
本発明のトナーの重量平均粒径及び数平均粒径はコールターカウンターＴＡ−ＩＩ型あるいはコールターマルチサイザー（コールター社製）等種々の方法で測定される。具体的には、下記のように測定できる。コールターマルチサイザー（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ＰＣ９８０１パーソナルコンピューター（ＮＥＣ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。たとえば、ＩＳＯＴＯＮ Ｒ−ＩＩ（コールターサイエンティフィックジャパン社製）が使用できる。測定手順は以下の通りである。前記電解水溶液を１００〜１５０ｍｌ加え、更に測定試料を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マルチサイザーによりアパーチャーを用いて、２μｍ以上のトナー粒子の体積、個数を測定して体積分布と個数分布とを算出する。それから、本発明に係わる体積分布から求めた体積基準の重量平均粒径（Ｄ４）及び個数分布から求めた個数基準の平均粒径、すなわち個数平均粒径（Ｄ１）を求める。
【００５２】
次に、本発明の磁性トナーに好適な平均円形度の範囲について説明する。
【００５３】
本発明の磁性トナーは、平均円形度が、０．９７０以上であるのが好ましい。平均円形度が０．９７０以上のトナー（トナー粒子群で構成される粉体）から構成されるトナーは転写性に非常に優れている。これはトナー粒子と感光体との接触面積が小さく、鏡像力やファンデルワールス力等に起因するトナー粒子の感光体への付着力が低下するためと考えられる。従って、本発明の比重分布を有するトナーに前述の平均円形度を組み合わせることで、転写率が高く、トナー消費量の低減に寄与する。
【００５４】
さらに、平均円形度が０．９７０以上のトナー粒子は表面のエッジ部がほとんど無いため、一つの粒子内での電荷の局在化が起こりにくいため、帯電量分布も狭くなる傾向にあり、潜像に対して忠実に現像される。しかし、平均円形度が高い場合でも主として存在する粒子の円形度が低いと効果が不十分な場合もあるため、特に、後に説明するモード円形度が０．９９以上であると、円形度が０．９９以上の粒子が主として存在することから、上記の効果が顕著に表れるので好ましい。
【００５５】
本発明における平均円形度は、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製フロー式粒子像分析装置「ＦＰＩＡ−１０００」を用いて測定を行い、３μｍ以上の円相当径の粒子群について測定された各粒子の円径度（ａｉ）を下式（１）によりそれぞれもとめ、さらに下式（２）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（ｍ）で除した値を平均円形度（ａ）と定義する。
【００５６】
【数２】

【００５７】
【数３】

【００５８】
また、モード円形度とは、円形度を０．４０から１．００まで０．０１毎に６１分割し、測定した各粒子の円形度をそれぞれ各分割範囲に割り振り、円形度頻度分布において頻度値が最大となるピークの円形度である。
【００５９】
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、平均円形度およびモード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０．４０〜１．００を６１分割したクラスに分け、分割点の中心値と頻度を用いて平均円形度及びモード円形度の算出を行う算出を行う算出法を用いている。しかしながら、この算出式で算出される平均円形度及びモード円形度の各値との誤差は、非常に少なく、実質的に無視出来る程度のものであり、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、一部変更したこのような算出式を用いても良い。
【００６０】
測定手段としては以下の通りである。界面活性剤を約０．１ｍｇ溶解している水１０ｍｌに現像剤５ｍｇを分散させて分散液を調製し、超音波（２０ｋＨｚ、５０Ｗ）を分散液に５分間照射し、分散液濃度を５０００〜２万個／μｌとして前記装置により測定を行い、３μｍ以上の円相当径の粒子群の平均円形度及びモード円形度を求める。
【００６１】
本発明における平均円形度とは、現像剤の凹凸の度合いの指標であり、現像剤が完全な球形の場合１．０００を示し、表面形状が複雑になるほど円形度は小さな値となる。
【００６２】
なお、本測定において３μｍ以上の円相当径の粒子群についてのみ円形度を測定する理由は、３μｍ未満の円相当径の粒子群にはトナー粒子とは独立して存在する外部添加剤の粒子群も多数含まれるため、その影響によりトナー粒子群についての円形度が正確に見積もれないからである。
【００６３】
本発明において、トナーの平均円形度を０．９７０以上とする方法としては、前述した懸濁重合法により直接トナー粒子を製造する方法、単量体は溶解するがその樹脂は溶解しない溶媒中で、分散安定剤の存在下に単量体の重合を行う分散重合法により球形のトナーを得る方法、粉砕法により製造したトナー粒子を熱により球形化する方法、トナー原料の溶融混合物あるいは溶液を空気中に噴霧して球形のトナーを製造する方法など様々な方法で達成可能である。これらのトナーの製造方法のうち、噴霧による方法は球形のトナーが容易に得られるものの、得られたトナーの粒度分布が広くなりやすい。他方、分散重合法は、球形のトナーが容易に得られ、得られるトナーは極めてシャープな粒度分布を示すが、使用する材料の選択が狭いことや有機溶剤の利用が廃溶剤の処理や溶剤の引火性に関する観点から製造装置が複雑で煩雑化しやすい。また、粉砕トナーの平滑化および球形化処理による製造方法では、平均円形度を０．９７０以上とすることは必ずしも容易ではなく、球形化処理に多大なコストが生じたり、処理工程によりトナー性能の低下が生じる場合がある。一方、懸濁重合法により本発明のトナーを製造する方法は、トナー粒子の円形度や円形度標準偏差の制御が非常に容易であり、特に好ましい製造方法である。また、本発明のトナーに磁性酸化鉄粒子を含有させ磁性トナーとする場合には、均一に表面が疎水化処理された磁性酸化鉄粒子をトナー原料として用いれば、トナー粒子表面に実質的に磁性酸化鉄粒子が露出していない、磁性酸化鉄粒子がトナー粒子内部に内包化されたトナーを得やすいため、トナーと接触する部材、例えば感光ドラムや定着ローラー、定着フィルムなどの削れや磨耗が抑制されるという点でも、懸濁重合法は特に有利な製造方法である。
【００６４】
本発明のトナーは、ヘッドスペース法によるトナーの有機揮発成分分析において、トナーの加熱温度が１５０℃におけるトナー質量を基準としたトルエン換算の有機揮発成分量が１０〜４００ｐｐｍであることが好ましい。
【００６５】
本発明のトナーの有機揮発成分量の定量は、ヘッドスペース法を用いて行われる。ヘッドスペース法とは、トナーを密閉容器中に封入して一定温度で、一定時間加熱して試料と気相間を平衡状態にした後、密閉容器内の気相部のガスをガスクロマトグラフに注入し、揮発成分を定量するというものである。この際、ガスクロマトグラフの検出器としてＦＩＤを用いて有機揮発成分を検出する。従来よりトナー中の揮発成分の分析方法として、トナーを溶媒に溶解してガスクロマトグラフに注入し定量する方法が知られているが、この方法では溶媒ピークに揮発成分のピークが埋没してしまうため、トナーの有機揮発成分の定量法としては不適である。
【００６６】
本発明のトナーにおいて、トナーの加熱温度が１５０℃におけるトナー質量を基準としたトルエン換算の有機揮発成分量がトナー粒子と外添剤の付着に関係しており、外添剤の付着状態が変化することにより、多数枚印字の差異に画質が低下することが判明した。即ち、１０ｐｐｍ未満であると、低湿環境下ではトナー表面の有機揮発成分が少なくなることによりトナー粒子と外添剤との付着力が弱くなり外添剤が遊離し、印字枚数の増加に伴い帯電量が変化し細線再現性が低下し、画質が悪化する。４００ｐｐｍを超えると、高温環境下においてトナー粒子表面の弾性が低下し外添剤の埋め込みが促進されることにより、前記同様にトナーの帯電量が変化しベタ画像均一性が低下し、画質が悪化する。
【００６７】
そのため、有機揮発成分量はトルエンに換算して１０〜４００ｐｐｍの範囲にあることが好ましく、２０〜２００ｐｐｍが特に好ましい範囲である。
【００６８】
本発明のトナーは、トナーの加熱温度が１５０℃におけるトナー質量を基準としたトルエン換算の有機揮発成分量が１０〜４００ｐｐｍであることが好ましいが、これは様々な方法により達成可能である。例えば重合トナーの製造の場合には、重合条件の調整により残留モノマー、ベンズアルデヒド、重合開始剤残渣等の残存量を調節する。また、重合終了後に蒸留を行ないトナー中のこれらの揮発成分を水とともに留去して残存量を調節する。さらに、気流乾燥や真空乾燥によりトナー中の揮発成分量を調整する等、従来から知られている方法に加えて、溶剤によりトナー粒子を洗浄することによりトナー中の揮発成分量を調整するという方法等、様々な方法が採用できる。
【００６９】
尚、ヘッドスペース法によるトナーの有機揮発成分量の定量は以下のようにして測定すればよい。
【００７０】
ヘッドスペース用バイアル瓶（容積２２ｍｌ）にトナー３００ｍｇを精秤し、クリンパーを用いてクリンプキャップとフッ素樹脂コーティングされた専用セプタムでシールする。このバイアルをヘッドスペースサンプラーにセットし、以下の条件で分析を行う。そして、得られたＧＣチャートのピークの総面積値をデータ処理により算出する。尚この際、トナーを封入していない空のバイアルもブランクとして同時に測定し、例えばセプタムから揮発する有機揮発成分等、ブランクの値についてはトナー測定データから差し引く。尚、トナー質量を基準としたトルエン換算の有機揮発成分量は、バイアルの中にトルエンのみを精秤したものを数点（例えば０．１μｌ、０．５μｌ、１．０μｌ）準備し、トナーサンプルの測定を行う前に下記分析条件にてそれぞれ測定を行った後、トルエンの仕込み量とトルエン面積値から検量線を作成し、この検量線を元にトナーの有機揮発成分の面積値をトナー質量を基準としたトルエンの質量に換算すればよい。
【００７１】
＜測定装置＞
ヘッドスペースサンプラー：ＨＥＷＬＥＴＴ ＰＡＣＫＡＲＤ ７６９４
オーブン温度：１５０℃
サンプル加熱時間：６０分
サンプル ループ（Ｎｉ）：１ｍｌ
ループ温度：１７０℃
トランスファーライン温度：１９０℃
加圧時間：０．５０分
ＬＯＯＰ ＦＩＬＬ ＴＩＭＥ：０．０１分
ＬＯＯＰ ＥＱ ＴＩＭＥ：０．０５分
ＩＮＪＥＣＴ ＴＩＭＥ：１．００分
ＧＣサイクル時間：８０分
キャリアーガス：Ｈｅ
ＧＣ：ＨＥＷＬＥＴＴ ＰＡＣＫＡＲＤ ６８９０ＧＣ（検出器：ＦＩＤ）
カラム：ＨＰ−１（内径０．２５μｍ×３０ｍ）、キャリアーガス：Ｈｅ
オーブン：３５℃で２０分ホールド、２０℃／分で３００℃まで昇温２０分ホールド。
ＩＮＪ：３００℃
ＤＥＴ：３２０℃
スプリットレス、コンスタントプレッシャー（２０ｐｓｉ）モード
【００７２】
次に、磁性トナーの粒径について説明する。
【００７３】
本発明のトナーは、更に高画質化およびベタ画像均一性と細線再現性の両立のため、より微小な潜像ドットを忠実に現像するためには、本発明の磁性トナーの重量平均径は３〜１０μｍであることが必要である。この磁性トナーの重量平均径は、４〜８μｍであることが好ましい。重量平均径が３μｍ未満のトナーにおいては、転写効率の低下から感光体上の転写残トナーが多くなり、接触帯電工程での感光体の削れやトナー融着の抑制が難しくなる。さらに、トナー全体の表面積が増えることに加え、粉体としての流動性及び撹拌性が低下し、個々のトナー粒子を均一に帯電させることが困難となることからカブリや転写性が悪化傾向となり、削れや融着以外にも画像の不均一ムラの原因となりやすいため、本発明で使用するトナーには好ましくない。また、トナーの重量平均径が１０μｍを超える場合には、文字やライン画像に飛び散りが生じやすく、高解像度が得られにくい。さらに装置が高解像度になっていくと８μｍ以上のトナーは１ドットの再現が悪化する傾向にある。
【００７４】
更に、本発明の磁性トナーに好適な態様として、硫黄元素を含有する樹脂を使用することによりトナーの比重分布と、酸化鉄の分散状態を効果的に両立することが可能となる。さらに、硫黄元素を有する樹脂は極性が高いため、このような樹脂をトナーに含有させることにより、トナー粒子の摩擦帯電時の電荷移動速度が向上し、低湿下でのチャージアップや高湿下での帯電量の低下が抑制する効果も発現される。但し、該樹脂がトナー粒子表面近傍に多く存在し、かつ、トナー粒子表面全体が均一に摩擦帯電部材と接触する条件が加わらないと、こういった効果はあまり期待できない。例えば不定形トナーに対して該結着樹脂を含有させても、トナー粒子表面のうち主に凸部だけが摩擦帯電部材と接触するだけなので、電荷移動速度の向上はあまり望めない。また、該結着樹脂がトナー粒子の内部にのみ存在しているような状況では、摩擦帯電部材と接触することが難しい。
【００７５】
本発明は硫黄元素を有する樹脂を含有することが好ましい態様として、挙げられる。その中でも、スルホン酸を有する樹脂がより好ましい態様である。
【００７６】
本発明に使用される硫黄元素を有する樹脂を構成する単量体としては、スチレンスルホン酸、２−アクリルアミド−２−メチルプロパンスルホン酸、２−メタクリルアミド−２−メチルプロパンスルホン酸ビニルスルホン酸、メタクリルスルホン酸等或いは、下記構造を有するマレイン酸アミド誘導体、マレイミド誘導体、スチレン誘導体がある。
【００７７】
【化１】

【００７８】
本発明に係る硫黄元素を有する樹脂は、上記単量体の単重合体であっても構わないが、上記単量体と他の単量体との共重合体であっても構わない。上記単量体と共重合体をなす単量体としては、ビニル系重合性単量体があり、単官能性重合性単量体或いは多官能性重合性単量体を使用することが出来る。
【００７９】
単官能性重合性単量体としては、スチレン；α−メチルスチレン、β−メチルスチレン、ｏ−メチルスチレン、ｍ−メチルスチレン、ｐ−メチルスチレン、２，４−ジメチルスチレン、ｐ−ｎ−ブチルスチレン、ｐ−ｔｅｒｔ−ブチルスチレン、ｐ−ｎ−ヘキシルスチレン、ｐ−ｎ−オクチルスチレン、ｐ−ｎ−ノニルスチレン、ｐ−ｎ−デシルスチレン、ｐ−ｎ−ドデシルスチレン、ｐ−メトキシスチレン、ｐ−フェニルスチレンの如きスチレン誘導体；メチルアクリレート、エチルアクリレート、ｎ−プロピルアクリレート、ｉｓｏ−プロピルアクリレート、ｎ−ブチルアクリレート、ｉｓｏ−ブチルアクリレート、ｔｅｒｔ−ブチルアクリレート、ｎ−アミルアクリレート、ｎ−ヘキシルアクリレート、２−エチルヘキシルアクリレート、ｎ−オクチルアクリレート、ｎ−ノニルアクリレート、シクロヘキシルアクリレート、ベンジルアクリレート、ジメチルフォスフェートエチルアクリレート、ジエチルフォスフェートエチルアクリレート、ジブチルフォスフェートエチルアクリレート、２−ベンゾイルオキシエチルアクリレートの如きアクリル系重合性単量体；メチルメタクリレート、エチルメタクリレート、ｎ−プロピルメタクリレート、ｉｓｏ−プロピルメタクリレート、ｎ−ブチルメタクリレート、ｉｓｏ−ブチルメタクリレート、ｔｅｒｔ−ブチルメタクリレート、ｎ−アミルメタクリレート、ｎ−ヘキシルメタクリレート、２−エチルヘキシルメタクリレート、ｎ−オクチルメタクリレート、ｎ−ノニルメタクリレート、ジエチルフォスフェートエチルメタクリレート、ジブチルフォスフェートエチルメタクリレートの如きメタクリル系重合性単量体；メチレン脂肪族モノカルボン酸エステル；酢酸ビニル、プロピオン酸ビニル、酪酸ビニル、安息香酸ビニル、ギ酸ビニルの如きビニルエステル；ビニルメチルエーテル、ビニルエチルエーテル、ビニルイソブチルエーテルの如きビニルエーテル；ビニルメチルケトン、ビニルヘキシルケトン、ビニルイソプロピルケトンの如きビニルケトンが挙げられる。
【００８０】
多官能性重合性単量体としては、ジエチレングリコールジアクリレート、トリエチレングリコールジアクリレート、テトラエチレングリコールジアクリレート、ポリエチレングリコールジアクリレート、１，６−ヘキサンジオールジアクリレート、ネオペンチルグリコールジアクリレート、トリプロピレングリコールジアクリレート、ポリプロピレングリコールジアクリレート、２，２’−ビス（４−（アクリロキシ・ジエトキシ）フェニル）プロパン、トリメチロールプロパントリアクリレート、テトラメチロールメタンテトラアクリレート、エチレングリコールジメタクリレート、ジエチレングリコールジメタクリレート、トリエチレングリコールジメタクリレート、テトラエチレングリコールジメタクリレート、ポリエチレングリコールジメタクリレート、１，３−ブチレングリコールジメタクリレート、１，６−ヘキサンジオールジメタクリレート、ネオペンチルグリコールジメタクリレート、ポリプロピレングリコールジメタクリレート、２，２’−ビス（４−（メタクリロキシ・ジエトキシ）フェニル）プロパン、２，２’−ビス（４−メタクリロキシ・ポリエトキシ）フェニル）プロパン、トリメチロールプロパントリメタクリレート、テトラメチロールメタンテトラメタクリレート、ジビニルベンゼン、ジビニルナフタリン、ジビニルエーテル等が挙げられる。
【００８１】
硫黄元素を有する樹脂としては、上述の如き単量体を用いることができるが、スチレン誘導体を単量体として含有していることが、より好ましい。
【００８２】
含硫黄樹脂の製造方法は、塊状重合、溶液重合、乳化重合、懸濁重合、分散重合、イオン重合等があるが、操作性などの面から溶液重合が好ましい。
【００８３】
該硫黄元素を有する樹脂は、スルホン酸基のような
Ｘ（ＳＯ₃ ^-）_n・ｍＹ^k+
（Ｘ：前記重合性単量体に由来する重合体部位を表し、Ｙ⁺：カウンターイオンを表し、ｋはカウンターイオンの価数であり、ｍ及びｎは整数であり、ｎ＝ｋ×ｍである。）
の如き構造を有する。カウンターイオンとしては、水素イオン、ナトリウムイオン、カリウムイオン、カルシウムイオン、アンモニウムイオンなどであることが良い。
【００８４】
該硫黄元素を有する樹脂を構成する官能基は前述のようにスルホン酸基が好適であり、さらにスルホン酸基含有単量体としては、（メタ）アクリルアミドが本発明の目的を達成する上で好ましい。その含有量は共重合体中０．０１〜２０質量％が好ましく、０．０５〜１０質量％がより好ましく、０．１〜５質量％がさらに好ましい。
【００８５】
該硫黄元素を有する樹脂の酸価（ｍｇＫＯＨ／ｇ）は３乃至５０が好ましい。
【００８６】
酸価が３未満の場合には、本発明で言及するような良好な酸化鉄の分散状態と十分な電荷制御作用の両立が得られず、かつ環境特性が悪い。酸価が５０を超える場合には、この様な重合体を含有する組成物を用いて、懸濁重合で粒子を造る場合、トナー粒子がいびつな形状を有する様になり、円形度が小さくなってしまい、転写効率が低下し、画質の離型剤を含有する場合には離型剤がトナー表面に現れ、現像性の低下をひきおこす。
【００８７】
該硫黄元素を有する樹脂はその他の結着樹脂１００質量部当り０．０５乃至２０質量部含有されていることが良い。好ましくは０．２乃至１０質量部が良い。
【００８８】
該硫黄元素を有する樹脂の含有量が０．０５質量部未満の場合には、本発明で言及するような良好な酸化鉄の分散状態と十分な電荷制御作用を両立させることが困難となり、２０質量部を超えると、粒度分布がブロードとなりカブリの増大や転写性の低下を引き起こす。
【００８９】
該硫黄元素を有する樹脂の分子量は重量平均分子量（Ｍｗ）が２０００乃至１０００００が好ましい。重量平均分子量（Ｍｗ）が２０００未満の場合には、トナーのブロッキング性が悪くなる。１０００００を超える場合には、単量体への溶解に時間がかかることに加え、顔料の分散性も悪くなり、トナーの着色力が低下してしまう。特開平１１−２８８１２９号公報において、重量平均分子量が２０００〜１５０００の範囲では着色剤の分散性が不十分であることが記載されているが、本発明の磁性トナーにおいては必ずしも所望の分散状態を得ることが困難であるとは限らない。
【００９０】
＜ゲルパーミエーションクロマトグラフィーによる分子量分布の測定＞
本発明において、トナー中の樹脂の分子量は、ゲルパーミエーションクロマトグラフィー（ＧＰＣ）における分子量分布からポリスチレン換算分子量として求めた。ＧＰＣの測定方法としては、以下のとおりである。
【００９１】
まず、サンプルの調製として、試料中の樹脂成分が０．４〜０．６ｍｇ／ｍｌとなるように、トナーを室温でテトラヒドロフラン（ＴＨＦ）に溶解せしめ、得られた溶液をポア径が０．２μｍの耐溶剤性メンブランフィルターでろ過する。
【００９２】
次に、４０℃のヒートチャンバー中でカラムを安定化させ、溶媒としてＴＨＦを毎分１ｍｌの流速で流し、ＴＨＦ試料溶液を約１００μｌ注入して測定する。試料の分子量測定にあたっては、試料の有する分子量分布を、数種の単分散ポリスチレン標準試料により作成された検量線の対数値とカウント数との関係から算出した。検量線作成用の標準ポリスチレン試料として、東ソー社製ＴＳＫ スタンダード ポリスチレン Ｆ−８５０、Ｆ−４５０、Ｆ−２８８、Ｆ−１２８、Ｆ−８０、Ｆ−４０、Ｆ−２０、Ｆ−１０、Ｆ−４、Ｆ−２、Ｆ−１、Ａ−５０００、Ａ−２５００、Ａ−１０００、Ａ−５００を用いて検量線を作成した。また、検出器は、ＲＩ（屈折率）検出器とＵＶ（紫外線）検出器とを直列に配列し用いた。なおカラムとしては、市販のポリスチレンジェルカラムを複数本組み合わせるのが良く、本発明では、昭和電工社製のｓｈｏｄｅｘ ＧＰＣ ＫＦ−８０１，８０２，８０３，８０４，８０５，８０６，８０７，８００Ｐの組み合わせにて測定した。
【００９３】
装置は、高速ＧＰＣ ＨＬＣ８１２０ ＧＰＣ（東ソー社製）を使用した。
【００９４】
該硫黄元素を有する重合体のガラス転移点（Ｔｇ）は５０℃乃至１００℃が好ましい。ガラス転移点が５０℃未満の場合には、トナーの流動性、保存性に劣り、さらに転写性も劣るようになる。ガラス転移点が１００℃を超える場合には、トナー印字率の多い画像の時の定着性に劣る。
【００９５】
本発明において該硫黄元素を有する樹脂のガラス転移温度は、示差走査熱量計（ＤＳＣ）により測定した。測定方法は、後述する。
【００９６】
また、本発明の磁性トナーにおいては、硫黄元素量を元素分析などの既存の分析方法などにより定量することが可能である。さらに、前述のＸ線光電子分光分析によりトナー粒子表面に存在する硫黄元素量の好適な範囲を規定することが可能である。具体的には、Ｘ線光電子分光分析により測定されるトナー表面に存在する結合エネルギー２８３〜２９３ｅＶ炭素元素の含有量（Ａ）に対する結合エネルギー１６７〜１７２ｅＶにピークを有する硫黄元素の含有量（Ｅ）の比（Ｅ／Ａ）が０．０００３〜０．００５０の範囲が好ましく、用いられる酸化鉄の平均粒径や、結着樹脂中に含まれる硫黄元素量、用いられる硫黄元素を有する樹脂量により好適な範囲に制御することが可能である。０．０００３では十分な電荷制御作用を得られない傾向が強まり、０．００５０未満では帯電量の環境安定性を得られにくくなる。
【００９７】
本発明の磁性トナーに用いられる好ましい磁性粉体（酸化鉄）の粒度としては、体積平均粒径が０．１〜０．３μｍであり、かつ０．０３μｍ以上０．１μｍ未満の粒子の個数％が４０％以下であることが好ましい。
【００９８】
平均粒径が０．１μｍ未満の磁性粉体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、このようなトナーをカラー画像に用いた場合には、色再現性が得られにくくなったり、色空間の形状がいびつになる傾向があるため好ましくない。さらに、磁性粉体の表面積が増大するために分散性が悪化し、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、磁性粉体の添加量から得られるべき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。
【００９９】
一方、磁性粉体の平均粒径が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。
【０１００】
また、トナー中において該磁性粉体の０．０３μｍ以上０．１μｍ未満の粒子の個数％が４０％を超えると、磁性粉体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量が広がり、ベタ画像均一性と細線再現性のバランスがとりにくくなるために４０％以下が好ましい。さらに、３０％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。
【０１０１】
なお、０．０３μｍ未満の磁性粉体は、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影響は無い。そのため、本発明では、０．０３μｍ以上０．１μｍ未満の粒子に注目し、その個数％を定義するものである。
【０１０２】
また、磁性粉体中の０．３μｍ超の粒子が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となるので、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。
【０１０３】
本発明においては、前述の粒度分布の条件を満たすよう、磁性体の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りし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。
【０１０４】
磁性粉体の粒度の決定方法としては、エポキシ樹脂中へ観察すべき磁性体粉末あるいは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上のサンプルとして、透過型電子顕微鏡（ＴＥＭ）において１万倍ないしは４万倍の拡大倍率の写真で視野中の１００個の磁性体粒子を観察し、その投影面積を求め、得られた面積の円相当径を計算して体積平均粒径を求めることが好ましい。さらに、その結果を元に０．０３μｍ以上０．１μｍ未満の粒子と、０．３μｍ超の粒子の個数％を計算する。
【０１０５】
このような磁性粉体は、コバルト、ニッケル、銅、マグネシウム、マンガン、アルミニウムなどの元素を含んでもよく、四三酸化鉄、γ−酸化鉄等、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種以上併用して用いられる。
【０１０６】
本発明の磁性トナー粒子は重合法によって得られる粒子であることが好ましい。本発明に係わるトナーは、粉砕法によって製造することも可能であるが、この粉砕法で得られるトナー粒子は一般に不定形のものであり、本発明に係わるトナーの必須要件である平均円形度が０．９７０以上、（好ましくはモード円形度が０．９９０以上）という物性を得るためには機械的・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。さらに粉砕法は、本質的にトナー粒子表面に磁性酸化鉄粒子が露出してしまうため、本発明に好適な実質上表面に磁性体が存在しないトナーを得るためにも、表面改質などが必要となる。
【０１０７】
そこで、上述の諸問題を解決するため、本発明においては、トナー粒子を重合法により製造することが好ましい。トナーの重合法としては、直接重合法、懸濁重合法、乳化重合法、乳化会合重合法、シード重合法等が挙げられるが、これらの中では、粒径と粒子形状のバランスのとりやすさという点で、特に懸濁重合法により製造することが好ましい。この懸濁重合法においては重合性単量体および着色剤（更に必要に応じて重合開始剤、架橋剤、荷電制御剤、その他の添加剤）を均一に溶解または分散せしめて単量体組成物とした後、この単量体組成物を分散安定剤を含有する連続層（例えば水相）中に適当な撹拌器を用いて分散し同時に重合反応を行わせ、所望の粒径を有するトナーを得るものである。この懸濁重合法で得られるトナー（以後重合トナー）は、個々のトナー粒子形状がほぼ球形に揃っているため、平均円形度が０．９７０以上、特にモード円形度が０．９９以上という物性要件を満たすトナーが得られやすく、さらにこういったトナーは帯電量の分布も比較的均一となるため高い転写性を有している。
【０１０８】
さらに、懸濁重合して得られた微粒子に再度、重合性単量体と重合開始剤を添加して表面層を設けるコア・シェル構造も必要に応じて設計することが可能である。
【０１０９】
しかしながら、重合トナー中に通常の磁性体を含有させても、粒子表面からの磁性体の露出を抑えることは難しい。さらにはトナー粒子の流動性及び帯電特性が著しく低下するだけでなく、懸濁重合トナーの製造時に磁性体と水との相互作用が強いことにより、平均円形度が０．９７０以上のトナーが得られ難い。これは、▲１▼磁性体粒子は一般的に親水性であるためにトナー表面に存在しやすいこと、▲２▼水溶媒撹拌時に磁性体が乱雑に動き、それに単量体から成る懸濁粒子表面が引きずられ、形状が歪んで円形になりにくいこと、等が原因と考えられる。こういった問題を解決するためには磁性体粒子の有する表面特性の改質が重要である。
【０１１０】
そこで、本発明の画像形成方法に関わる磁性トナーに使用される磁性体においては、その粒子表面を疎水化する際、水系媒体中で、磁性体粒子を一次粒径となるよう分散しつつカップリング剤を加水分解しながら表面処理する方法を用いることが特に好ましい。この疎水化処理方法は気相中で処理するより、磁性体粒子同士の合一が生じにくく、また疎水化処理による磁性体粒子間の帯電反発作用が働き、磁性体はほぼ一次粒子の状態で表面処理される。
【０１１１】
カップリング剤を水系媒体中で加水分解しながら磁性体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磁性体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、疎水化の効果は非常に大きい。
【０１１２】
本発明に係わる磁性体の表面処理において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等が挙げられる。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、下記の一般式（Ｉ）で示されるものである。
【０１１３】
Ｒ_m−Ｓｉ−Ｙ_n （Ｉ）
［式中、Ｒはアルコオキシ基を示し、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。］
【０１１４】
具体的には、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−メタクリロイ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、ヒドロキシプロピリ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等を挙げることができる。
【０１１５】
特に、下記の一般式（ＩＩ）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磁性粒子を疎水化処理するのが良い。
Ｃ_pＨ_2p+1−Ｓｉ−（ＯＣ_qＨ_2q+1）₃ （ＩＩ）
［式中、ｐは２〜２０の整数を示し、ｑは１〜３の整数を示す。］
【０１１６】
上記式（ＩＩ）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、トナー粒子からの磁性粒子の露出を抑制するのが難しくなる。またｐが２０より大きいと、疎水性は十分になるが、磁性体粒子同士の合一が多くなり、トナー中へ磁性体粒子を十分に分散性させることが困難になり、カブリや転写性が悪化傾向となる。
【０１１７】
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。
【０１１８】
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。
【０１１９】
その処理量は磁性体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。
【０１２０】
ここで、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、特に限定されるものではないが、ポリビニルアルコール等のノンイオン系界面活性剤を使用するのが好ましい。界面活性剤は、水に対して０．１〜５質量％添加するのが好ましい。ｐＨ調整剤としては、例えば、塩酸のような無機酸が挙げられる。有機溶剤としては、例えば、メタノール等が挙げられ、水に対して０〜５００質量％添加するのが好ましい。
【０１２１】
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、磁性体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。
【０１２２】
こうして得られる磁性体は粒子の凝集が見られず、個々の粒子表面が均一に疎水化処理されているため、本発明の硫黄元素を含有する重合体と組み合わせるとそれぞれの相乗効果により、特に重合トナー用の材料として用いた場合、トナー粒子中への分散性が極めて良好となる。しかもトナー粒子表面からの露出が非常に少なく、ほぼ球形に近い、粒度分布の非常に狭い重合トナー粒子が得られる。従って、こういった磁性体を用いることにより、平均円形度が０．９７０以上、特にはモード円形度が０．９９以上で、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未満という磁性トナーを得ることが可能となる。
【０１２３】
これらの磁性体の磁気特性としては、磁場７９５．８ｋＡ／ｍ下で飽和磁化が１０〜２００Ａｍ²／ｋｇ、残留磁化が１〜１００Ａｍ²／ｋｇ、抗磁力が１〜３０ｋＡ／ｍであるものが用いられる。これらの磁性体は結着樹脂１００質量部に対し、２０〜２００質量部で用いられる。このような磁性体の中でもマグネタイトを主とするものが特に好ましい。
【０１２４】
本発明において磁性トナーの磁化の強さは、振動型磁力計ＶＳＭ Ｐ−１−１０（東英工業社製）を用いて、２５℃の室温にて外部磁場７９．６ｋＡ／ｍで測定した。また、磁性体の磁気特性は、２５℃の室温にて外部磁場７９６ｋＡ／ｍで測定した。
【０１２５】
また、本発明の磁性トナーは、磁場７９．６ｋＡ／ｍ（１０００エルステッド）における磁化の強さが１０〜５０Ａｍ²／ｋｇ（ｅｍｕ／ｇ）である磁性トナーであることが必要である。
【０１２６】
本発明において磁場７９．６ｋＡ／ｍにおける磁化の強さを規定する理由は、磁性体の磁気特性を表わす量としては、磁気飽和における磁化の強さ（飽和磁化）が用いられるが、本発明においては画像形成装置内で実際に磁性トナーに作用する磁場における磁性トナーの磁化の強さが重要であるためである。画像形成装置に磁性トナーが適用される場合、磁性トナーに作用する磁場は、画像装置外への磁場の漏洩を大きくしないため或いは磁場発生源のコストを低く抑えるために、市販されている多くの画像形成装置において数十から百数十ｋＡ／ｍであり、画像形成装置内で実際に磁性トナーに作用する磁場の代表的な値として磁場７９．６ｋＡ／ｍ（１０００エルステッド）を選択し、磁場７９．６ｋＡ／ｍにおける磁化の強さを規定した。
【０１２７】
現像装置内に磁気力発生手段を設けることで、磁性トナーではトナーの漏れを防止でき、トナーの搬送性或いは撹拌性を高められるばかりでなく、トナー担持体上に磁力が作用するように磁気力発生手段を設けることで、転写残トナーの回収性が更に向上し、また磁性トナーが穂立ちを形成するためにトナーの飛散を防止することが容易となる。しかし、トナーの磁場７９．６ｋＡ／ｍにおける磁化の強さが１０Ａｍ²／ｋｇ未満であると、上記の効果が得られず、トナー担持体上に磁力を作用させるとトナーの穂立ちが不安定となり、トナーへの帯電付与が均一に行えないことによるカブリ、画像濃度ムラ、転写残トナーの回収不良等の画像不良を生じる易くなる。また、磁気力によるトナーのトナー担持体への搬送も不十分になりやすい。トナーの磁場７９．６ｋＡ／ｍにおける磁化の強さが５０Ａｍ²／ｋｇよりも大きいと、トナーに磁力を作用させると磁気凝集によりトナーの流動性が著しく低下し、転写性が低下することで転写残トナーが増加し、画質の低下を生じ易くなる。さらに磁化の強さを大きくする為に磁性体量を増量すると定着性の悪化を引き起こし易い。また、本発明のトナーのように０．９７０以上の平均円形度、０．９９以上のモード円形度を有することによって、トナー担持体上でのトナーの穂立ちが細く密になることによって、帯電が均一化され更にカブリが大幅に減少する。
【０１２８】
本発明の磁性トナーに用いられる酸化鉄（磁性体）は、例えばマグネタイトの場合、下記方法で製造される。
【０１２９】
第一鉄塩水溶液に、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、鉄元素に対して０．０５〜５．０質量％のリン元素となるよう水溶性リン化合物（例えばヘキサメタリン酸ソーダ、第一リン酸アンモニウム等のリン酸塩、正リン酸塩、亜リン酸塩等のリン酸塩）水溶液、場合によって鉄元素に対して０〜５．０質量％の珪素元素となるよう水溶性珪素化合物（例えば水ガラス、珪酸ソーダ、珪酸カリウム）水溶液を加え、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ｐＨ７〜１０）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、磁性粒子を生成する。
【０１３０】
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表面処理磁性粉体が得られる。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。
【０１３１】
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。
【０１３２】
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／ｌ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。
【０１３３】
このようにして製造された表面処理磁性粉末を用いることにより、本発明の優れた磁性トナーが得られ高画質及び高安定性が可能となる。
【０１３４】
さらにまた、磁性体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、ニッケルなどの強磁性金属粒子、またはこれらにクロム、マンガン、銅、亜鉛、アルミニウム、希土類元素などを加えた合金、ヘマタイトなどの粒子、チタンブラック、ニグロシン染料／顔料、カーボンブラック、フタロシアニン等が挙げられる。これらもまた、表面を処理して用いても良い。
【０１３５】
本発明の磁性トナーは、結着樹脂に対して０．５〜４０質量％の離型剤を含有することも好ましい。結着樹脂としては、後述するように例えば、各種のワックス等が例示できる。
【０１３６】
転写材上に転写されたトナー像はその後、熱・圧力等のエネルギーにより転写材上に定着され、半永久的画像が得られる。この際、熱ロール式定着やフィルム式定着が一般に良く用いられる。
【０１３７】
前述のように、重量平均粒径が１０μｍ以下のトナー粒子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、本発明に係わるトナーにおいて、適正量の離型剤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ることが可能となる。
【０１３８】
本発明に係わるトナーに使用可能な離型剤としては、パラフィンワックス、マイクロクリスタリンワックス、ペトロラクタム等の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等天然ワックス及びその誘導体などである。これら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、グラフト変性物を含む。さらには、高級脂肪族アルコール、ステアリン酸、パルミチン酸等の脂肪酸、あるいはその化合物、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、動物性ワックス等が挙げられる。これらのワックスの中では、示差熱分析における吸熱ピークが４０〜１１０℃であるものが好ましく、更には４５〜９０℃であるものが好ましい。
【０１３９】
離型剤を使用する際の含有量としては、結着樹脂に対して０．５〜４０質量％の範囲が好ましい。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、４０質量％を超えてしまうと長期間の保存性が悪化すると共に、他のトナー材料の分散性が悪くなり、トナーの流動性の悪化や画像特性の低下につながる。
【０１４０】
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。
【０１４１】
また、硫黄元素を含有する重合体のガラス転移温度（Ｔｇ）は、２度目の昇温時のＤＳＣカーブより、吸熱ピーク前の基線と吸熱ピーク後の基線の中線と、立ち上がり曲線での交点をもってしてＴｇとした。
【０１４２】
本発明の磁性トナーには、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、特に帯電スピードが速く、かつ、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。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。
【０１４３】
次に本発明の磁性トナーの懸濁重合法による製造方法を説明する。
【０１４４】
本発明のトナーを懸濁重合法で製造する場合、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。
【０１４５】
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−エチルスチレン等のスチレン系単量体、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等の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等のメタクリル酸エステル類その他のアクリロニトリル・メタクリロニトリル・アクリルアミド等の単量体が挙げられる。
【０１４６】
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。
【０１４７】
本発明に係わる重合トナーの製造においては、単量体系に樹脂を添加して重合しても良い。
【０１４８】
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、グリシジル基、ニトリル基等、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等、共重合体の形にして、あるいはポリエステル、ポリアミド等の重縮合体、ポリエーテル、ポリイミン等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。
【０１４９】
また、材料の分散性や定着性、あるいは画像特性の改良等を目的として上記以外の樹脂を単量体系中に添加しても良く、用いられる樹脂としては、例えば、ポリスチレン、ポリビニルトルエンなどの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−メタクリル酸メチル共重合体、スチレン−メタクリル酸エチル共重合体、スチレン−メタ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などの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、シリコーン樹脂、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、テルペン樹脂、フェノール樹脂、脂肪族または脂環族炭化水素樹脂、芳香族系石油樹脂などが単独或いは混合して使用できる。
【０１５０】
これら樹脂の添加量としては、単量体１００質量部に対し１〜２０質量部が好ましい。１質量部未満では添加効果が小さく、一方２０質量部を超えると重合トナーの種々の物性設計が難しくなる。
【０１５１】
さらに、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。
【０１５２】
本発明に係わる重合トナーの製造において使用され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１００質量部に対し０．５〜２０質量部の添加量で重合反応を行うと、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等の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、ｔ−ブチルパーオキシ２−エチルヘキサノエート、ｔ−ブチルパーオキシピバレート、ｔ−ブチルパーオキシイソブチレート、ｔ−ブチルパーオキシネオデカノエート、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等の過酸化物系重合開始剤が挙げられる。
【０１５３】
本発明に係わる重合トナーを製造する際は、架橋剤を添加しても良く、好ましい添加量としては、０．００１〜１５質量％である。
【０１５４】
本発明に関わる重合トナーを製造する際は、分子量調整剤を使用することができる。分子量調整剤としては、例えば、ｔ−ドデシルメルカプタン、ｎ−ドデシルメルカプタン、ｎ−オクチルメルカプタンなどのメルカプタン類；四塩化炭素、四臭化炭素などのハロゲン化炭化水素類；α−メチルスチレンダイマーなどを挙げることができる。これらの分子量調整剤は、重合開始前あるいは重合途中に添加することができる。分子量調整剤は、重合性単量体１００質量部に対して、通常、０．０１〜１０質量部、好ましくは０．１〜５質量部の割合で用いられる。
【０１５５】
本発明に関わる重合トナーの製造方法では、一般に上述のトナー組成物、すなわち重合性単量体中に、磁性酸化鉄、離型剤、可塑剤、荷電制御剤、架橋剤、場合によって着色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、高分子重合体、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よ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。
【０１５６】
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えば良い。
【０１５７】
本発明に係わる重合トナーを製造する場合には、分散安定剤として公知の界面活性剤や有機あるいは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、燐酸亜鉛等の燐酸多価金属塩、炭酸カルシウム、炭酸マグネシウム等の炭酸塩、メタ硅酸カルシウム、硫酸カルシウム、硫酸バリウム等の無機塩、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、アルミナ等の無機酸化物が挙げられる。
【０１５８】
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質量部を単独で使用しても良く、粒度分布を調整する目的で０．００１〜０．１質量部の界面活性剤を併用しても良い。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等が挙げられる。
【０１５９】
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、乳化重合によ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。
【０１６０】
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う。この温度範囲で重合を行うと、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。重合トナー粒子は重合終了後、公知の方法によって濾過、洗浄、乾燥を行い、無機微粉体を混合し表面に付着させることで、トナーを得ることができる。また、製造工程に分級工程を入れ、粗粉や微粉をカットすることも、望ましい形態の一つである。
【０１６１】
本発明のトナーにおいては、必要に応じて荷電制御剤をトナー粒子と混合して用いることも可能である。この手法によっても、現像システムに応じた最適の摩擦帯電量のコントロールが可能となる。
【０１６２】
本発明のトナーは、流動性向上剤として平均一次粒子径４〜８０ｎｍの無機微粉末が、トナー全体に対し０．１〜４質量％添加されていることも非常に好ましい使用形態である。無機微粉末は、トナーの流動性改良及びトナー母粒子の帯電均一化のために添加されるが、無機微粉末を疎水化処理するなどの処理によってトナーの帯電量の調整、環境安定性の向上等の機能を付与することも好ましい。
【０１６３】
無機微粉末の平均一次粒子径が８０ｎｍよりも大きい場合、良好なトナーの流動性が得られず、トナー粒子への帯電付与が不均一になり易く、低湿下での摩擦帯電性の不均一化につながるため、カブリの増大、画像濃度の低下あるいは耐久性の低下等の問題を避けられない。無機微粉末の平均一次粒径が４ｎｍよりも小さい場合には、無機微粒子どうしの凝集性が強まり、一次粒子ではなく解砕処理によっても解れ難い強固な凝集性を持つ粒度分布の広い凝集体として挙動し易く、この凝集体の現像、像担持体或いはトナー担持体等を傷つけること、などによる画像欠陥を生じ易くなる。トナー粒子の帯電分布をより均一とするためには、無機微粉末の平均一次粒径は６〜３５ｎｍであることがより良い。
【０１６４】
無機微粉末の平均一次粒子径は、走査型電子顕微鏡により拡大撮影したトナーの写真で、更に走査型電子顕微鏡に付属させたＸＭＡ等の元素分析手段によって無機微粉末の含有する元素でマッピングされたトナーの写真を対照しつつ、トナー表面に付着或いは遊離して存在している無機微粉末の一次粒子を１００個以上測定し、個数平均径を求めることで測定法できる。
【０１６５】
また、無機微粉末の含有量は、蛍光Ｘ線分析を用い、標準試料から作成した検量線を用いて定量できる。
【０１６６】
本発明のトナーに添加する無機微粉末としては、シリカ，アルミナ，チタニアなどが使用できる。
【０１６７】
こういった平均一次粒径が４〜８０ｎｍの無機微粉末の添加量は、トナー母粒子１００質量部に対して０．１〜４．０質量部であることが好ましく、添加量が０．１質量部未満ではその効果が十分ではなく、４．０質量部を超えると定着性が悪くなる。
【０１６８】
無機微粉末は、疎水化処理されたものであることが高湿環境下での特性を向上させる点から好ましい。トナーに添加された無機微粉末が吸湿すると、トナーとしての帯電量が著しく低下し、現像性や転写性の低下が生じ易くなる。
【０１６９】
疎水化処理の処理剤としては、シリコーンワニス、各種変性シリコーンワニス、シリコーンオイル、各種変性シリコーンオイル、シラン化合物、シランカップリング剤、その他有機硅素化合物、有機チタン化合物の如き処理剤を単独で或いは併用して処理しても良い。
【０１７０】
その中でも、シリコーンオイルにより処理したものが好ましく、より好ましくは、無機微粉末を疎水化処理すると同時或いは処理した後に、シリコーンオイルにより処理したものが高湿環境下でもトナー粒子の帯電量を高く維持し、選択現像性を低減する上でよい。
【０１７１】
無機微粉末の処理条件としては、例えば第一段反応としてシリル化反応を行い表面の活性水素基を化学結合により消失させた後、第二段反応としてシリコーンオイルにより表面に疎水性の薄膜を形成することができる。シリル化剤の使用量としては、無機微粉末１００質量部に対し５〜５０質量部が好ましい。５質量部未満では無機微粒子表面の活性水素基を消失させるのに十分でなく、５０質量部を超えると余分なシリル化剤どうしの反応で生成するシロキサン化合物が糊の役割となって無機微粒子どうしの凝集が起こり、画像欠陥を生じ易くなる。
【０１７２】
上記シリコーンオイルは、２５℃における粘度が１０〜２００，０００ｍｍ²／ｓのものが、さらには３，０００〜８０，０００ｍｍ²／ｓのものが好ましい。１０ｍｍ²／ｓ未満では、無機微粉末に安定性が無く、熱および機械的な応力により、画質が劣化する傾向がある。２００，０００ｍｍ²／ｓを超える場合は、均一な処理が困難になる傾向がある。
【０１７３】
シリコーンオイルの処理方法としては、例えばシラン化合物で処理された無機微粉末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よいし、無機微粉末にシリコーンオイルを噴霧する方法を用いてもよい。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、無機微粉末を加え混合し溶剤を除去する方法でもよい。無機微粉末の凝集体の生成が比較的少ない点で噴霧機を用いる方法がより好ましい。
【０１７４】
シリコーンオイルの処理量は無機微粉末１００質量部に対し１〜２３質量部、好ましくは５〜２０質量部が良い。シリコーンオイルの量が少なすぎると良好な疎水性が得られず、多すぎるとやはり無機微粒子の凝集が起こりやすい。
【０１７５】
本発明の磁性トナーには、クリーニング性向上等の目的で、一次粒径３０ｎｍを超える（好ましくは比表面積が５０ｍ²／ｇ未満）、より好ましくは一次粒径５０ｎｍ以上（好ましくは比表面積が３０ｍ²／ｇ未満）の無機又は有機の球状に近い微粒子をさらに添加することも好ましい形態のひとつである。例えば球状シリカ粒子、球状ポリメチルシルセスキオキサン粒子、球状樹脂粒子等が好ましく用いられる。
【０１７６】
本発明に用いられる現像剤には、実質的な悪影響を与えない範囲内で更に他の添加剤、例えばフッ素樹脂粉末、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；あるい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などの研磨剤；あるいは例えば酸化チタン粉末、酸化アルミニウム粉末などの流動性付与剤；ケーキング防止剤；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用いることもできる。これらの添加剤も表面を疎水化処理して用いることも可能である。
【０１７７】
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。
【０１７８】
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−２．０ｋＶｐｐ、直流電圧−７００Ｖｄｃ）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。
【０１７９】
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。
【０１８０】
図５は本発明に従う画像形成装置の一例の概略構成模型図である。
【０１８１】
この画像形成装置は、転写式電子写真プロセスを利用した現像同時クリーニングプロセス（クリーナーレスシステム）のレーザープリンター（記録装置）である。クリーニングブレードのようにクリーニング部材を有するクリーニングユニットを除去したプロセスカートリッジを有し、現像剤としては磁性一成分系現像剤を使用し、現像剤担持体上の現像剤層と像担持体が非接触となるよう配置される非接触現像の例を示す。
【０１８２】
２１は像担持体としての回転ドラム型ＯＰＣ感光体であり、矢印の時計方向に一定速度の周速度（プロセススピード）をもって回転駆動される。
【０１８３】
２２は接触帯電部材としての帯電ローラーである。
【０１８４】
帯電ローラー２２は感光体２１に対して弾性に抗して所定の押圧力で圧接させて配設してある。ｎは感光体２１と帯電ローラ２２の当接部である帯電当接部である。帯電ローラー２２は感光体２１との接触面である帯電当接部ｎにおいて対向方向（感光体表面の移動方向と逆方向）に回転駆動される。即ち接触帯電部材としての帯電ローラーの表面は、感光体２１の表面に対して速度差を持たせてある。また、帯電ローラー２２の表面には、塗布量が均一になるように導電性微粉末を塗布している。
【０１８５】
また帯電ローラー２２の芯金２２ａには帯電バイアス印加電源から直流電圧を帯電バイアスとして印加してある。ここで、感光体２１の表面は、帯電ローラー２２に対する印加電圧とほぼ等しい電位に直接注入帯電方式にて一様に帯電処理される。
【０１８６】
２３は露光器である。この露光器により回転感光体２１の面に目的の画像情報に対応した静電潜像が形成される。２４は現像装置である。感光体２１の表面の静電潜像はこの現像装置によりトナー画像として現像される。
【０１８７】
この現像装置２４は、非接触型の反転現像装置である。また、感光体２１との対向部である現像部ａ（現像領域部）にて感光体２１の回転方向と順方向に一定速度の周速で回転させる。この現像スリーブ２４ａに弾性ブレード２４ｃで現像剤が薄層にコートされる。現像剤は弾性ブレード２４ｃで現像スリーブ２４ａに対する層厚が規制され、また電荷が付与される。現像スリーブ２４ａにコートされた現像剤はスリーブ２４ａの回転により、感光体２１とスリーブ２４ａの対向部である現像部ａに搬送される。また、スリーブ２４ａには現像バイアス印加電源より現像バイアス電圧が印加される。そして、現像スリーブ２４ａと感光体２１の間ａで一成分ジャンピング現像を行わせる。
【０１８８】
２５は接触転写手段としての転写ローラーであり、感光体２１に一定の線圧で圧接させて転写当接部ｂを形成させてある。この転写当接部ｂに、不図示の給紙部から所定のタイミングで記録媒体としての転写材Ｐが給紙され、かつ転写ローラー２５に転写バイアス印加電源から所定のバイアス電圧が印加されることで、感光体２１側のトナー像が転写当接部ｂに給紙された転写材Ｐの面に順次に転写されていく。そして、一定のローラ抵抗値のものを用いＤＣ電圧を印加して転写を行う。即ち、転写当接部ｂに導入された転写材Ｐはこの転写当接部ｂを挟持搬送されて、その表面側に感光体２１の表面に形成担持されているトナー画像が順次に静電気力と押圧力にて転写されていく。
【０１８９】
２６は熱定着方式等の定着装置である。転写当接部ｂに給紙されて感光体２１側のトナー像の転写を受けた転写材Ｐは、感光体２１の表面から分離されてこの定着装置２６に導入され、トナー像の定着を受けて画像形成物（プリント、コピー）として装置外へ排出される。
【０１９０】
このプリンターはクリーニングユニットを除去しており、転写材Ｐに対するトナー像転写後の感光体２１の表面に残留の転写残トナーはクリーナーで除去されることなく、感光体２１の回転にともない帯電部ｎを経由して現像部ａに至り、現像装置２４において現像同時クリーニング（回収）される。
【０１９１】
２７はプリンター本体に対して着脱自在の画像形成装置及びプロセスカートリッジである。このプリンターは、感光体２１、帯電ローラー２２、現像装置２４の３つのプロセス機器を一括してプリンター本体に対して着脱自在のプロセスカートリッジとして構成してある。プロセスカートリッジ化するプロセス機器の組み合わせ等は上記に限られるものではなく任意である。例えば、現像装置と感光体の組み合わせ、現像装置と帯電ローラーの組み合わせ、現像装置と感光体と帯電ローラーの組み合わせ等が考えられる。２８はプロセスカートリッジの着脱案内・保持部材である。
【０１９２】
【実施例】
以下、本発明を製造例及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。なお、以下の配合における部数は全て質量部である。
【０１９３】
（含硫黄樹脂の製造例１）
還流管，撹拌機，温度計，窒素導入管，滴下装置及び減圧装置を備えた加圧可能な反応容器に、溶媒としてメタノール２５０部、２−ブタノン１５０部及び２−プロパノール１００部、モノマーとしてスチレン８４部、アクリル酸２−エチルヘキシル１３部、２−アクリルアミド−２−メチルプロパンスルホン酸３部を添加して撹拌しながら還流温度まで加熱した。重合開始剤である２，２’−アゾビス（２−メチルブチロニトリル）４部を２−ブタノン２０部で希釈した溶液を３０分かけて滴下して５時間撹拌を継続し、更に２，２’−アゾビス（２−メチルブチロニトリル）０．４部を２−ブタノン２０部で希釈した溶液を３０分かけて滴下して、更に５時間撹拌して重合を終了した。
【０１９４】
重合溶媒を減圧留去した後に得られた重合体を１００μｍのスクリーンを装着したカッターミルを用いて１００μｍ以下に粗粉砕した。得られた含硫黄樹脂はＴｇ約６９℃であった。得られた樹脂を含硫黄樹脂１とする。
【０１９５】
（含硫黄樹脂の製造例２〜５）
含硫黄樹脂の製造例１において、使用するモノマーを表１に示す内容に変更し、重合開始剤の量あるいは重合温度・時間を調節することにより分子量を制御する以外は同様の手法により、含硫黄樹脂２〜５を製造した。
【０１９６】
（含硫黄樹脂の比較製造例１）
含硫黄樹脂の製造例１において、使用するモノマーを表１に示す内容に変更する以外は同様の手法により、樹脂１を製造した。
【０１９７】
【表１】

【０１９８】
（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。
【０１９９】
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、磁性粒子のスラリー液を得た。洗浄・濾過した後この含水スラリー液を一旦取り出した。この時、含水サンプルを少量採取し、含水量を計っておいた。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、十分撹拌しながらシランカップリング剤（ｎ−Ｃ₆Ｈ₁₃Ｓｉ（ＯＣＨ₃）₃）を磁性酸化鉄１００部に対し２．０部（磁性粒子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。生成した疎水性磁性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１を得た。得られた磁性粉体の物性を、以下の製造例で得られた磁性粉体のものと併せて表２に示す。
【０２００】
（疎水性酸化鉄の製造例２）
上記磁性粉体の製造例１で得られた磁性粉体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、十分撹拌しながらシランカップリング剤（ｎ−Ｃ₄Ｈ₉Ｓｉ（ＯＣＨ₃）₃）を１００部の磁性粉体１に対し０．８部添加し、カップリング処理を行った。得られた磁性粒子スラリーを常法により洗浄・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２を得た。
【０２０１】
（疎水性酸化鉄の製造例３）
上記磁性粉体の製造例１で得られた磁性粉体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、十分撹拌しながらシランカップリング剤（ｎ−Ｃ₄Ｈ₉Ｓｉ（ＯＣＨ₃）₃）を１００部の磁性粉体１に対し０．６部添加し、カップリング処理を行った。得られた磁性粒子スラリーを常法により洗浄・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３を得た。
【０２０２】
（疎水性酸化鉄の製造例４）
上記磁性粉体の製造例１で得られた磁性粉体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、十分撹拌しながらシランカップリング剤（ｎ−Ｃ₁₀Ｈ₂₁Ｓｉ（ＯＣＨ₃）₃）を１００部の磁性粉体１に対し２．５部添加し、カップリング処理を行った。得られた磁性粒子スラリーを常法により洗浄・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４を得た。
【０２０３】
（疎水性酸化鉄の製造例５）
上記磁性粉体の製造例１で得られた磁性粉体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、十分撹拌しながらシランカップリング剤（ｎ−Ｃ₁₀Ｈ₂₁Ｓｉ（ＯＣＨ₃）₃）を１００部の磁性粉体１に対し３．０部添加し、カップリング処理を行った。得られた磁性粒子スラリーを常法により洗浄・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４を得た。
【０２０４】
（疎水性酸化鉄の製造例６）
疎水性酸化鉄の製造例１において、磁性酸化鉄粒子の合成時の硫酸第一鉄水溶液量を増やし、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６を得た。
【０２０５】
（疎水性酸化鉄の製造例７）
上記磁性粉体の製造例１で得られた磁性粉体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、十分撹拌しながらシランカップリング剤（ｎ−Ｃ₁₀Ｈ₂₁Ｓｉ（ＯＣＨ₃）₃）を１００部の磁性粉体１に対し５．０部添加し、カップリング処理を行った。得られた磁性粒子スラリーを常法により洗浄・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７を得た。
【０２０６】
（疎水性酸化鉄の製造例８）
疎水性酸化鉄の製造例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たのちに１００ｍｍ²／ｓ（ｃＳｔ）のジメチルシリコーンオイルを５．０部添加し、ヘンシェルミキサー（三井三池化工機（株））で混合して、疎水性酸化鉄８を得た。
【０２０７】
（酸化鉄の製造例１）
疎水性酸化鉄の製造例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て酸化鉄１を得た。
【０２０８】
【表２】

【０２０９】
（導電性微粉末１）
体積平均粒径３．７μｍ、粒度分布における０．５μｍ未満が６．６体積％、５μｍ超が８個数％の微粒子酸化亜鉛（抵抗８０Ω・ｃｍ、一次粒子径０．１〜０．３μｍの酸化亜鉛一次粒子を圧力により造粒して得られたもの、白色）を導電性微粉末１とする。
【０２１０】
この導電性微粉末１は、走査型電子顕微鏡にて３０００倍及び３万倍で観察したところ、０．１〜０．３μｍの酸化亜鉛一次粒子と１〜１０μｍの凝集体からなっていた。
【０２１１】
実施例１の画像形成装置で画像露光に用いられるレーザーの露光光波長７４０ｎｍにあわせて、波長７４０ｎｍの光源を用いて、この波長域における透過率をＸ−Ｒｉｔｅ社製３１０Ｔ透過型濃度計を用い測定したところ、この導電性微粉末１の透過率はおよそ３５％であった。
【０２１２】
（導電性微粉末２）
導電性微粒末１を風力分級して得られた、体積平均粒径２．４μｍ、粒度分布における０．５μｍ未満が４．１体積％、５μｍ超が１個数％の微粒子酸化亜鉛（抵抗１５００Ω・ｃｍ、透過率３５％）を導電性微粉末２とする。
【０２１３】
この導電性微粉末２は、走査型電子顕微鏡にて観察したところ、０．１〜０．３μｍの酸化亜鉛一次粒子と１〜５μｍの凝集体からなっていたが、導電性微粉末１と比較すると、一次粒子は減少していた。
【０２１４】
（導電性微粉末３）
導電性微粒末１を風力分級して得られた、体積平均粒径１．５μｍ、粒度分布における０．５μｍ未満が３５体積％、５μｍ超が０個数％の微粒子酸化亜鉛（抵抗１５００Ω・ｃｍ、透過率３５％）を導電性微粉末３とする。
【０２１５】
この導電性微粉末３は、走査型電子顕微鏡にて観察したところ、０．１〜０．３μｍの酸化亜鉛一次粒子と１〜４μｍの凝集体からなっていたが、導電性微粉末２と比較すると、一次粒子は増加していた。
【０２１６】
（導電性微粉末４）
体積平均粒径０．３μｍ、粒度分布における０．５μｍ未満が８０体積％、５μｍ超が０個数％の微粒子酸化亜鉛（抵抗１００Ω・ｃｍ、一次粒子径０．１〜０．３μｍ、白色、透過率３５％、純度９９％以上）を導電性微粉末４とする。
【０２１７】
この導電性微粉末４は、走査型電子顕微鏡にて観察したところ、凝集体の少ない０．１〜０．３μｍの酸化亜鉛一次粒子からなっていた。
【０２１８】
（導電性微粉末５）
酸化スズ・アンチモンで表面処理された体積平均粒径２．８μｍのホウ酸アルミニウムを風力分級によって粗粒子を除いた後に、水系に分散して濾過を繰り返し行うことで微粒子を除き、体積平均粒径３．２μｍ、粒度分布における０．５μｍ未満が０．４体積％、５μｍ超が１個数％の灰白色の導電性粒子を得た。これを導電性微粉末５とする。
【０２１９】
導電性微粉末１〜５の代表的物性値を下記表３に示す。
【０２２０】
【表３】

【０２２１】
（磁性トナー粒子の製造例１）
イオン交換水７１０部に０．１ｍｏｌ／リットル−Ｎａ₃ＰＯ₄水溶液４５０部を投入し６０℃に加温した後、塩化カルシウム投入後のｐＨが５．５となるよう１Ｎ塩酸を加え、１．０ｍｏｌ／リットル−ＣａＣｌ₂水溶液６７．７部を徐々に添加してリン酸カルシウム塩を含む水系媒体を得た。
【０２２２】
・スチレン ８０部
・ｎ−ブチルアクリレート ２０部
・含硫黄樹脂１ ５部
・疎水性酸化鉄１ ９０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。
【０２２３】
この単量体組成物を６０℃に加温し、そこにベヘニン酸ベヘニルを主体とするエステルワックス（ＤＳＣにおける吸熱ピークの極大値７２℃）６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］４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部を溶解した。
【０２２４】
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７時間反応させた。その後液温を８０℃とし更に３時間撹拌を続けた。反応終了後、懸濁液を冷却し、塩酸を加えてリン酸カルシウム塩を溶解し、濾過，水洗し、０．３ｋＰａ（２．３ｔｏｒｒ）の圧力下５０℃にて１０日間乾燥して重量平均粒径７．０μｍの磁性トナー粒子１を得た。
【０２２５】
（磁性トナー粒子の製造例２）
磁性トナー粒子の製造例１において、含硫黄樹脂１に代えて含硫黄樹脂２を４部用いる以外は同様の手法により、磁性トナー粒子２を得た。
【０２２６】
（磁性トナー粒子の製造例３）
磁性トナー粒子の製造例１において、含硫黄樹脂１の添加量を３．５部に変える以外は同様の手法により、磁性トナー粒子３を得た。
【０２２７】
（磁性トナー粒子の製造例４）
磁性トナー粒子の製造例１において、含硫黄樹脂１の添加量を２部に変える以外は同様の手法により、磁性トナー粒子４を得た。
【０２２８】
（磁性トナー粒子の製造例５）
磁性トナー粒子の製造例１において、疎水性酸化鉄１に代えて疎水性酸化鉄２を用いる以外は同様の手法により、磁性トナー粒子５を得た。
【０２２９】
（磁性トナー粒子の製造例６）
磁性トナー粒子の製造例１において、疎水性酸化鉄１に代えて疎水性酸化鉄３を用いる以外は同様の手法により、磁性トナー粒子６を得た。
【０２３０】
（磁性トナー粒子の製造例７）
磁性トナー粒子の製造例１において、疎水性酸化鉄１に代えて疎水性酸化鉄４を用いる以外は同様の手法により、磁性トナー粒子７を得た。
【０２３１】
（磁性トナー粒子の製造例８）
磁性トナー粒子の製造例１において、疎水性酸化鉄１に代えて疎水性酸化鉄５を用いる以外は同様の手法により、磁性トナー粒子８を得た。
【０２３２】
（磁性トナー粒子の製造例９）
磁性トナー粒子の製造例１において、含硫黄樹脂１に代えて含硫黄樹脂３を９部用いる以外は同様の手法により、磁性トナー粒子９を得た。
【０２３３】
（磁性トナー粒子の製造例１０）
磁性トナー粒子の製造例１において、含硫黄樹脂１に代えて含硫黄樹脂４を５部用いる以外は同様の手法により、磁性トナー粒子１０を得た。
【０２３４】
（磁性トナー粒子の製造例１１）
磁性トナー粒子の製造例１において、含硫黄樹脂１に代えて含硫黄樹脂３を５部用いる以外は同様の手法により、磁性トナー粒子１１を得た。
【０２３５】
（磁性トナー粒子の製造例１２）
磁性トナー粒子の製造例１において、含硫黄樹脂１に代えて含硫黄樹脂５を２部用いる以外は同様の手法により、磁性トナー粒子１２を得た。
【０２３６】
（磁性トナー粒子の製造例１３）
磁性トナー粒子の製造例１において、Ｎａ₃ＰＯ₄水溶液の投入量及びＣａＣｌ₂水溶液の添加量を調整して水系媒体中のリン酸カルシウム塩量を増量する以外は同様の手法により、磁性トナー粒子１３を得た。
【０２３７】
（磁性トナー粒子の製造例１４）
磁性トナー粒子の製造例１において、Ｎａ₃ＰＯ₄水溶液の投入量及びＣａＣｌ₂水溶液の添加量を調整して水系媒体中のリン酸カルシウム塩量を減量する以外は同様の手法により、磁性トナー粒子１４を得た。
【０２３８】
（磁性トナー粒子の製造例１５）
磁性トナー粒子の製造例１において、ＴＫ式ホモミキサー（特殊機化工業（株））にて８，０００ｒｐｍで１０分間撹拌し、造粒する以外は同様の手法により、磁性トナー粒子１５を得た。
【０２３９】
（磁性トナー粒子の製造例１６）
磁性トナー粒子の製造例１において、ＴＫ式ホモミキサー（特殊機化工業（株））にて７，０００ｒｐｍで８分間撹拌し、造粒する以外は同様の手法により、磁性トナー粒子１６を得た。
【０２４０】
（磁性トナー粒子の製造例１７）
磁性トナー粒子の製造例１において、疎水性酸化鉄１の部数を６０部に代える以外は同様の手法により、磁性トナー粒子１７を得た。
【０２４１】
（磁性トナー粒子の製造例１８）
磁性トナー粒子の製造例１において、疎水性酸化鉄１に代えて疎水性酸化鉄６を１２０部用いる以外は同様の手法により、磁性トナー粒子１８を得た。
【０２４２】
（磁性トナー粒子の製造例１９）
磁性トナー粒子の製造例１において、ワックスの部数を１部に代える以外は同様の手法により、磁性トナー粒子１９を得た。
【０２４３】
（磁性トナー粒子の製造例２０）
磁性トナー粒子の製造例１において、ワックスの部数を３５部に代える以外は同様の手法により、磁性トナー粒子２０を得た。
【０２４４】
（磁性トナー粒子の製造例２１）
磁性トナー粒子の製造例１において、エステルワックスをポリエチレンを主体とするワックス（ＤＳＣにおける吸熱ピークの極大値１１０℃）に代える以外は同様の手法により、磁性トナー粒子２１を得た。
【０２４５】
（処理ワックス１の製造方法）
スチレンモノマー２２質量部に重合開始剤としてジクミルパーオキサイド３部を添加した後、加熱溶融した融点７９℃のパラフィンワックス７５部中に撹拌しながら滴下し、４時間反応させ、１段階の処理によって処理ワックス１を得た。処理ワックス１の軟化点は７９．４℃であった。
【０２４６】
（磁性トナー粒子の製造例２２）
イオン交換水２９２部に１．０ｍｏｌ／リットル−Ｎａ₃ＰＯ₄水溶液４６部を投入し６０℃に加温した後、塩化カルシウム投入後のｐＨが５．５となるよう１Ｎ塩酸を加え、１．０ｍｏｌ／リットル−ＣａＣｌ₂水溶液６７部を徐々に添加してリン酸カルシウム塩を含む水系媒体を得、そこへドデシルベンゼンスルホン酸ナトリウムを０．１部添加した。
【０２４７】
・スチレン ８０部
・ｎ−ブチルアクリレート ２０部
・含硫黄樹脂１ ５部
・疎水性酸化鉄１ ９０部
上記処方をアトライター（三井三池工機(株)）を用いて均一に分散混合した。
【０２４８】
この単量体組成物を６０℃に加温し、そこに処理ワックス１を６部添加混合し、これに、重合開始剤としてベンゾイルパーオキサイド５部を溶解した。
【０２４９】
前記水系媒体中に上記重合性単量体系を投入し、６０℃，Ｎ₂雰囲気下においてクレアミックス０．８Ｓ（エム・テクニック(株)）にて１５，０００ｒｐｍで１０分間撹拌し、造粒した。その後パドル撹拌翼で撹拌しつつ、３０分で８０℃まで昇温し、８０℃で４時間反応させ、無水炭酸ナトリウム４部を系内に添加した。
【０２５０】
その後、系内を−５０ｋＰａに減圧しして４時間蒸留を行った。蒸留終了後、懸濁液を冷却し、アルカリ性の懸濁液のろ過を行った。次いでトナー粒子の水洗を３回繰り返し、含水磁性トナー粒子を得た。
【０２５１】
その後、室温下１０００部の希塩酸（ｐＨ１．０）の中に撹拌しながら含水磁性トナー粒子を投入し、３時間撹拌を継続した。さらに、この懸濁液をろ過し、トナーの水洗を５回行った。その後、この含水磁性トナーを０．３ｋＰａ（２．３ｔｏｒｒ）の圧力下、５０℃で５日間真空乾燥して重量平均粒径６．０μｍの磁性トナー粒子２２を得た。
【０２５２】
（磁性トナー粒子の比較製造例１）
磁性トナー粒子の製造例１において、疎水性酸化鉄１に代えて疎水性酸化鉄７を用いる以外は同様の手法により、磁性トナー粒子２３を得た。
【０２５３】
（磁性トナー粒子の比較製造例２）
・スチレン／ｎ−ブチルアクリレート共重合体（質量比８０／２０）１００部
（Ｍｎ＝２４３００ Ｍｗ／Ｍｎ＝３．０）
・含硫黄樹脂１ ５部
・酸化鉄１ ９０部
・製造例１で用いたエステルワックス ６部
上記材料をブレンダーにて混合し、９０℃に加熱した二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し、得られた微粉砕物を風力分級して重量平均粒径７．９μｍの磁性トナー粒子２４を得た。
【０２５４】
（磁性トナー粒子の比較製造例３）
撹拌翼、冷却器をとりつけた５００ｍｌの四つ口フラスコに、メチルビニルエーテル−無水マレイン酸共重合体（分子量４００００、ＧＡＦ社製）３．０部とメタノール１００部を入れ、６０℃で２時間撹拌し、メチルビニルエーテル−無水マレイン酸共重合体を完全に溶解させ分散安定剤を調製した。その後、室温まで冷却し次のものを仕込んだ。
・スチレン ８０部
・アクリル酸ブチル ４０部
・ｔ−ドデシルメルカプタン ０．０６部
・含硫黄樹脂１ ５部
【０２５５】
これらを撹拌しながら、フラスコ内を窒素ガスでパージし、系内の残存酸素濃度が０．１％になるまで約１時間ゆるやかに撹拌（１０００ｒｐｍ）を続けた。その後、恒温槽の温度を６０℃まで上昇させた後、２，２’−アゾビスイソブチロニトリル０．２部を開始剤に用い、２４時間重合を続けた。加熱後、１５分すると液は白濁し始め、２４時間重合後も白濁した安定な分散液であった。一部サンプリングしてガスクロマトグラフィーで内部標準法による測定を行った結果、重合率９５％であることが確認できた。得られた分散液を冷却し遠心分離器にて２０００ｒｐｍで遠心分離すると、重合体粒子は完全に沈殿し上部の液は透明であった。上澄み液を除き、新たにメタノール２００部を加え、１時間撹拌洗浄した。遠心分離しメタノールで洗浄する操作を繰り返し濾過した。瀘別したものを５０℃にて２４時間減圧乾燥し、９０％の収率で白色粉末の樹脂粒子を得た。
【０２５６】
次に、得られた粒子１００部に対して１５部の疎水化酸化鉄１をハイブリタイザー（奈良機械製作所）にてトナー中に含有させる処理を６回繰り返した。次に、着色樹脂粒子１００部をメタノール１０００部に分散させ、５０℃で１時間撹拌加熱した。その後、分散液を室温まで冷却し瀘別し着色樹脂粒子分散液を得た。
【０２５７】
続いて、含硫黄樹脂１をトルエン溶媒に溶解させ、着色樹脂粒子１００部に対して０．５部加えた。１時間撹拌後瀘過し、乾燥させて磁性トナー粒子２５を得た。
【０２５８】
（磁性トナー粒子の比較製造例４）
磁性トナー粒子の製造例１において、含硫黄樹脂１を樹脂１に代える以外は同様の手法により、磁性トナー粒子２６の製造を行った。
【０２５９】
（磁性トナー粒子の比較製造例５）
磁性トナー粒子の製造例１において、含硫黄樹脂１に代えて含硫黄樹脂１を０．０３部用いる以外は同様の手法により、磁性トナー粒子２７を得た。
【０２６０】
（磁性トナー粒子の比較製造例６）
磁性トナー粒子の製造例１において、含硫黄樹脂１に代えて含硫黄樹脂１を２３部用いる以外は同様の手法により、磁性トナー粒子２８を得た。
【０２６１】
（磁性トナー粒子の比較製造例７）
磁性トナー粒子の製造例１において、ワックスの部数を４５部に代える以外は同様の手法により、磁性トナー粒子２９を得た。
【０２６２】
（磁性トナー粒子の比較製造例８）
磁性トナー粒子の製造例１において、エステルワックスをパラフィンを主体とするワックス（ＤＳＣにおける吸熱ピークの極大値３５℃）に代える以外は同様の手法により、磁性トナー粒子３０を得た。
【０２６３】
（磁性トナー粒子の比較製造例９）
磁性トナー粒子の製造例１において、疎水性酸化鉄１に代えて疎水性酸化鉄８を用いる以外は同様の手法により、磁性トナー粒子３１を得た。
【０２６４】
（磁性トナー粒子の比較製造例１０）
・スチレン／ｎ−ブチルアクリレート共重合体（質量比８０／２０）
（Ｍｎ＝３１５００ Ｍｗ／Ｍｎ＝２．８） １００部
・含硫黄樹脂１ ５部
・酸化鉄１ ９０部
・処理ワックス１ ６部
上記材料をブレンダーにて混合し、１２０℃に加熱した二軸エクストルーダーで溶融混練し、冷却した混合物をハンマーミルで粗粉砕し、その後粗粉砕物をジェットミルで微粉砕し、得られた微粉砕物で風力分級して重量平均粒径７．３μｍの磁性トナー粒子３２を得た。
【０２６５】
（磁性トナー粒子の比較製造例１１）
磁性トナー粒子３２の製造において、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手法により、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７．２μｍの球形化処理された磁性トナー粒子３３を得た。
【０２６６】
実施例１
磁性トナー粒子１の１００部に対し、一次粒径１２ｎｍのシリカに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１４０ｍ²／ｇの疎水性シリカ微粉体１部を、ヘンシェルミキサー（三井三池化工機（株））で混合して、磁性トナー１を調製した。
【０２６７】
実施例２〜１９、参考例２０、実施例２１
磁性トナー粒子２〜２１の１００部に対し、実施例１で用いた疎水性シリカ微粉体を実施例１３においては磁性トナー粒子１００部に対して１．５部、実施例１４においては磁性トナー粒子１００部に対して０．６部、実施例１７においては磁性トナー粒子１００部に対して０．８部、それ以外は１部を混合して、磁性トナー２〜２１を調製した。
【０２６８】
実施例２２
磁性トナー粒子２２の１００部に対し、実施例１で用いた疎水性シリカ微粉体を１．２部混合して、磁性トナー２２を調製した。
【０２６９】
実施例２３〜２７
磁性トナー粒子１の１００部に対し、実施例１で用いた疎水性シリカ微粉体を１部及び導電性微粉末１〜５を２部混合して、磁性トナー２３〜２７を調製した。
【０２７０】
実施例２８
磁性トナー粒子２２の１００部に対し、実施例１で用いた疎水性シリカ微粉体を１．２部及び導電性微粉末１を２部混合して、磁性トナー２８を調製した。
【０２７１】
比較例１〜９
磁性トナー粒子２３〜３１の１００部に対し、実施例１で用いた疎水性シリカ微粉体１部を混合して、比較用磁性トナー１〜９を調製した。
【０２７２】
比較例１０
磁性トナー粒子３２の１００部に対し、実施例１で用いた疎水性シリカ微粉体１．２部を混合して、比較用磁性トナー１２を調製した。
【０２７３】
比較例１１
磁性トナー粒子３３の１００部に対し、実施例１で用いた疎水性シリカ微粉体１．２部を混合して、比較用磁性トナー１３を調製した。
【０２７４】
比較例１２
磁性トナー粒子３２の１００部に対し、実施例１で用いた疎水性シリカ微粉体１．２部及び導電性微粉末１を２部を混合して、比較用磁性トナー１４を調製した。
【０２７５】
比較例１３
磁性トナー粒子３３の１００部に対し、実施例１で用いた疎水性シリカ微粉体１．２部及び導電性微粉末１を２部を混合して、比較用磁性トナー１５を調製した。
【０２７６】
本発明における比重分布の測定方法を説明する。
【０２７７】
本発明では、比重分布の基準を決定するために乾式比重を測定する。乾式比重は、乾式密度計アキュピック１３３０（島津製作所製）を用いて測定した。
【０２７８】
次に、乾式比重の値を（Ａ）とし、その比重を基準として２．５％刻みで（Ａ）の値に対して（Ａ）×０．９００、（Ａ）×０．９２５、（Ａ）×０．９５０、（Ａ）×０．９７５、（Ａ）×１．０００、（Ａ）×１．０２５まで６水準の水溶液を準備する。前記の各水溶液中には、ノニオン性界面活性剤（コンタミノン）を０．０１％程度添加した。この水溶液５０ｇに精秤したトナーを１００ｍｇ添加し、超音波分散して一次粒子にまで分散されたことをコールターカウンター、あるいは光学顕微鏡にて確認した後に２４時間静置し分離させた。そののちに、上澄みをデカンテーションしイオン交換水を添加して洗浄する工程を３回繰り返して沈降したトナーを真空乾燥し、乾燥したトナーの重量を精秤した。
【０２７９】
本発明では、各比重の水溶液にて沈降するトナーはその水溶液以上の比重を有することを利用し、前述したように隣接する比重を有する水溶液にて沈降するトナー重量比率の差から比重の分布を求めた。
【０２８０】
得られた磁性トナーの物性を表４及び５に示す。
【０２８１】
【表４】

【０２８２】
【表５】

【０２８３】
（感光体製造例１）
感光体としては３０φのＡｌシリンダーを基体とした。これに、図３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２５μｍ。水に対する接触角は９５度であった。
【０２８４】
なお、接触角の測定は、純水を用い、装置は、協和界面科学（株）、接触角計ＣＡ−Ｘ型を用いた。
【０２８５】
＜実施例Ａ１＞
画像形成装置として、ＬＢＰ−１７６０（キヤノン社製）を改造し、図１に概略的に示されるものを用いた。
【０２８６】
静電荷像担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、５８．８Ｎ／ｍ（６０ｇ／ｃｍ）の線圧で当接させ、直流電圧−７００Ｖｄｃに交流電圧１．２ｋＶｐｐ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＝−１８０Ｖとした。
【０２８７】
感光ドラムと現像スリーブとの間隙は１８０μｍ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）１．０μｍの樹脂層を、表面をブラストした直径１６φ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１．０ｍｍのウレタンゴム製ブレードを２９．４Ｎ／ｍ（３０ｇ／ｃｍ）の線圧で当接させた。
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
【０２８８】
次いで、現像バイアスとして直流バイアス成分Ｖｄｃ＝−５００Ｖ、重畳する交流バイアス成分Ｖｐｐ＝９００Ｖ、ｆ＝２１００Ｈｚを用いた。また、現像スリーブの周速は感光体周速（９４ｍｍ／ｓｅｃ）に対して順方向に１１０％のスピード（１０３ｍｍ／ｓｅｃ）とした。
【０２８９】
また、図４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５９Ｎ／ｍ（６０ｇ／ｃｍ））を、図４中Ａ方向の感光体周速（９４ｍｍ／ｓｅｃ）に対して順方向に１０５％（９９ｍｍ／ｓｅｃ）とし、転写バイアスは直流１．４ｋＶとした。
【０２９０】
定着方法としてはＬＢＰ−１７６０のオイル塗布機能のない、フィルムを介してヒーターにより加熱加圧定着する方式の定着装置を用いた。この時加圧ローラーはフッ素系樹脂の表面層を有するものを使用し、ローラーの直径は３０ｍｍであった。また、定着温度は１７０℃、ニップ幅を７ｍｍに設定した。
【０２９１】
まず、磁性トナーとして実施例１で得られた磁性トナーを使用し、常温常湿（２３℃，５０％ＲＨ）環境下において印字面積比率４％の横線画像にて連続モードで８０００枚の画出し試験および耐久試験を行い、画像濃度、画像カブリおよび転写性について評価した。転写材としては７５ｇ／ｍ²の紙を使用した。以下の評価基準に従って、画像評価した。併せて、トナーの消費量も算出した。
【０２９２】
また、高温高湿（３０℃，８０％ＲＨ）環境下および低温低湿（１５℃，１０％ＲＨ）環境下においても同様に８０００枚の画出し試験を行い、高温高湿下においては画像濃度と転写性、ベタ画像の濃度均一性について、低温低湿下においては画像濃度と画像カブリ、細線再現性について評価した。
【０２９３】
いずれの環境下においても、終始、画像濃度が高く、カブリが少なく、また、高温高湿下でのベタ画像の濃度均一性は良好であり、低温低湿下での細線再現性にも優れていた。
【０２９４】
結果を表６に示す。
【０２９５】
画像評価は以下のように行った。
【０２９６】
（１）画像濃度
通常の複写機用普通紙（７５ｇ／ｍ²）の転写材を用いて、画出し試験８０００枚終了後にベタ黒画像を出力し、その濃度を測定することにより評価した。尚、画像濃度は「マクベス反射濃度計 ＲＤ９１８」（マクベス社製）を用いて、原稿濃度が０．００の白地部分の画像に対する相対濃度を測定した。
Ａ：非常に良好 １．４０以上
Ｂ：良好 １．３５以上、１．４０未満
Ｃ：実用上問題なし １．００以上、１．３５未満
Ｄ：やや難あり １．００未満
【０２９７】
（２）画像カブリ
「ＲＥＦＬＥＣＴＭＥＴＥＲ ＭＯＤＥＬ ＴＣ−６ＤＳ」（東京電色社製）により測定したプリントアウト画像の白地部分の白色度と転写紙の白色度の差から、カブリ濃度（％）を算出し、画像カブリを評価した。フィルターは、グリーンフィルターを用いた。
Ａ：非常に良好 １．０％未満
Ｂ：良好 １．０％以上乃至２．０％未満
Ｃ：実用上問題なし ２．０％以上乃至３．０％未満
Ｄ：やや難あり ３．０％以上
【０２９８】
（３）転写性
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Ｄ、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Ｅとした時、近似的に以下の式で計算した。
【０２９９】
【数４】

転写効率は９０％以上であれば問題の無い画像である。
Ａ：非常に良好（９７％以上）
Ｂ：良好 （９４〜９７％未満）
Ｃ：実用可 （９０〜９４％未満）
Ｄ：実用不可 （９０％未満）
【０３００】
（４）ベタ画像の濃度均一性
ベタ画像の濃度均一性は、８０００枚出力後の画像上、最も透過濃度の高い部分と最も低い部分との差により以下の基準で評価した。
Ａ：非常に良好 ０．０３未満
Ｂ：良好 ０．０３以上、０．０６未満
Ｃ：実用上問題なし ０．０６以上、０．１５未満
Ｄ：やや難あり ０．１５以上
【０３０１】
（５）細線再現性
本発明において、細線再現性は次に示すような方法によって測定を行った。すなわち、潜像が幅１００μｍとなるようにレーザー露光して、得られた定着画像を測定用サンプルとし、測定装置として、ルーゼックス４５０粒子アナライザーを用いて、拡大したモニター画像から、インジケーターによって線幅の測定を行なう。この時、線幅の測定位置はトナーの細線画像の幅方向に凹凸があるため、凹凸の平均的線幅をもって測定点とする。これより、細線再現性の値（％）は、下記式によって算出する。
【０３０２】
【数５】

Ａ：非常に良好 １０５未満
Ｂ：良好 １０５以上、１１０未満
Ｃ：実用上問題なし １１０以上、１２０未満
Ｄ：やや難あり １２０以上
【０３０３】
＜実施例Ａ２〜Ａ１９、参考例Ａ２０、実施例Ａ２１〜Ａ２８＞
磁性トナーとして、実施例２〜２８で得られた磁性トナーを使用し、実施例Ａ１と同様の画像形成方法で画出し試験及び耐久性評価を行った。その結果、初期の画像特性も問題無く、耐久８０００枚時まで特に問題の無い結果が得られた。実施例Ａ１９においては、低温低湿下において耐久５０００枚を超えると、画像の裏汚れがわずかに発生した。
【０３０４】
結果を表６に示す。
【０３０５】
＜比較例Ａ１〜Ａ１３＞
磁性トナーとして、比較例１〜１３で得られた磁性トナーを使用し、実施例Ａ１と同様の画像形成方法で画出し試験及び耐久性評価を行った。その結果、初期から画像特性が良くなく、耐久試験と共に画像不良が発生した。
【０３０６】
結果を表６に示す。
【０３０７】
【表６】

【０３０８】
また本発明のトナーは、クリーナレス画像形成方法あるいは現像同時回収画像形成方法にも、適用可能である。本発明では、図５に示すような画像形成装置を使用した。
【０３０９】
以下、具体的実施例によって本発明を説明するが本発明はなんらこれに限定されるものではない。
【０３１０】
まず、本発明の実施例に用いる像担持体としての感光体の製造例について述べる。
【０３１１】
（感光体製造例２）
感光体は負帯電用の有機光導電性物質を用いた感光体（以下ＯＰＣ感光体）であり、φ３０ｍｍのアルミニウム製のシリンダーを基体とした。これに、図６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。
【０３１２】
第１層は導電層であり、アルミニウムシリンダーの欠陥等をならすため、またレーザ露光の反射によるモアレの発生を防止するために設けられている厚さ約２０μｍの導電性粒子分散樹脂層（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）である。
【０３１３】
第２層は正電荷注入防止層（下引き層）であり、アルミニウム支持体から注入された正電荷が感光体表面に帯電された負電荷を打ち消すのを防止する役割を果し、メトキシメチル化ナイロンによって１０⁶Ω・ｃｍ程度に抵抗調整された厚さ約１μｍの中抵抗層である。
【０３１４】
第３層は電荷発生層であり、ジスアゾ系の顔料をブチラール樹脂に分散した厚さ約０．３μｍの層であり、レーザ露光を受けることによって正負の電荷対を発生する。
【０３１５】
第４層は電荷輸送層であり、ポリカーボネート樹脂にヒドラゾン化合物を分散した厚さ約２５μｍの層であり、Ｐ型半導体である。従って、感光体表面に帯電された負電荷はこの層を移動することはできず、電荷発生層で発生した正電荷のみを感光体表面に輸送することができる。第５層は電荷注入層であり、光硬化性のアクリル樹脂に導電性酸化スズ超微粒子及び粒径約０．２５μｍの四フッ化エチレン樹脂粒子を分散したものである。具体的には、アンチモンをドーピングし低抵抗化した粒径約０．０３μｍの酸化スズ粒子を樹脂に対して１００質量％、更に四フッ化エチレン樹脂粒子を２０質量％、分散剤を１．２質量％分散したものである。このようにして調製した塗工液をスプレー塗工法にて厚さ約２．５μｍに塗工して電荷注入層とした。得られた感光体の表面の抵抗値は、５×１０¹²Ω・ｃｍ、感光体表面の水に対する接触角は、１０２度であった。
【０３１６】
次に、本発明の実施例に用いる帯電部材の製造例について述べる。
【０３１７】
（帯電部材の製造例１）
６φ、２６４ｍｍのＳＵＳローラーを芯金とし、芯金上にウレタン樹脂、導電性粒子としてのカーボンブラック、硫化剤、発泡剤等を処方した中抵抗の発泡ウレタン層をローラ状に形成し、さらに切削研磨し形状及び表面性を整え、可撓性部材として１２φ、２３４ｍｍの帯電ローラーを作製した。
【０３１８】
得られた帯電ローラーは、抵抗値が１０⁵Ω・ｃｍであり、硬度は、アスカーＣ硬度で３０度であった。また、この帯電ローラー表面を走査型電子顕微鏡で観察したところ、平均セル径は約１００μｍで、空隙率は６０％であった。
【０３１９】
＜実施例Ｂ１＞
図５は本発明に従う画像形成装置の一例の概略構成模型図である。実施例Ｂ１本例の画像形成装置は、転写式電子写真プロセスを利用した現像同時クリーニングプロセス（クリーナーレスシステム）のレーザープリンター（記録装置）である。クリーニングブレードの如きクリーニング部材を有するクリーニングユニットを除去したプロセスカートリッジを有し、現像剤としては磁性一成分系現像剤を使用し、現像剤担持体上の現像剤層と像担持体が非接触となるよう配置される非接触現像の例である。
【０３２０】
（ａ）本例プリンターの全体的な概略構成
２１は像担持体としての、感光体製造例２の回転ドラム型ＯＰＣ感光体であり、矢印の時計方向に９４ｍｍ／ｓｅｃの周速度（プロセススピード）をもって回転駆動される。
【０３２１】
２２は接触帯電部材としての帯電部材製造例１の帯電ローラーである。帯電ローラー２２は感光体２１に対して弾性に抗して所定の押圧力で圧接させて配設してある。ｎは感光体２１と帯電ローラー２２の当接部である帯電当接部である。本例では、帯電ローラー２２は感光体２１との接触面である帯電当接部ｎにおいて対向方向（感光体表面の移動方向と逆方向）に１００％の周速で回転駆動されている。即ち接触帯電部材としての帯電ローラー２の表面は感光体２１の表面に対して相対移動速度比２００％の相対速度差を有している。また、帯電ローラー２２の表面には、塗布量がおよそ１×１０⁴個／ｍｍ²で均一になるように前記導電性微粉末１を塗布した。
【０３２２】
また帯電ローラー２の芯金２２ａには帯電バイアス印加電源から−７００Ｖの直流電圧を帯電バイアスとして印加するようにした。本例では感光体２１の表面は帯電ローラー２２に対する印加電圧とほぼ等しい電位（−６８０Ｖ）に直接注入帯電方式にて一様に帯電処理される。これについては後述する。
【０３２３】
２３はレーザーダイオード・ポリゴンミラー等を含むレーザービームスキャナ（露光器）である。このレーザービームスキャナは目的の画像情報の時系列電気ディジタル画素信号に対応して強度変調されたレーザー光を出力し、該レーザー光で上記感光体２１の一様帯電面を走査露光Ｌする。この走査露光Ｌにより回転感光体２１の面に目的の画像情報に対応した静電潜像が形成される。
【０３２４】
２４は現像装置である。感光体２１の表面の静電潜像はこの現像装置によりトナー画像として現像される。
【０３２５】
本例の現像装置２４は、現像剤として磁性トナー２３を用いた、非接触型の反転現像装置である。磁性トナー２３には導電性微粉末を外添添加してある。
【０３２６】
感光ドラム２１と現像スリーブ２４ａとの間隙は１８０μｍとし、トナー担持体２４ａとして下記の構成の層厚約７μｍ、ＪＩＳ中心線平均粗さ（Ｒａ）１．０μｍの樹脂層を、表面をブラストした直径１６φ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９０ｍＴ（９００ガウス）のマグネットロールを内包し、トナー規制部材として厚み１．０ｍｍ、自由長１．５ｍｍのウレタン製ブレードを２９．４Ｎ／ｍ（３０ｇ／ｃｍ）の線圧で当接させた。
フェノール樹脂 １００部
グラファイト（体積平均粒径約７μｍ） ９０部
カーボンブラック １０部
【０３２７】
また、感光体２１との対向部である現像部ａ（現像領域部）にて感光体２１の回転方向と順方向に感光体２１の周速の１２０％の周速で回転させる。この現像スリーブ２４ａに弾性ブレード２４ｃで現像剤が薄層にコートされる。現像剤は弾性ブレード２４ｃで現像スリーブ２４ａに対する層厚が規制され、また電荷が付与される。この時、現像スリーブ２４ａにコートされた現像剤量は、１５ｇ／ｍ²であった。現像スリーブ２４ａにコートされた現像剤はスリーブ２４ａの回転により、感光体２１とスリーブ２４ａの対向部である現像部ａに搬送される。また、スリーブ２４ａには現像バイアス印加電源より現像バイアス電圧が印加される。現像バイアス電圧は、−４２０ＶのＤＣ電圧と、周波数１６００Ｈｚ、ピーク間電圧１５００Ｖ（電界強度５．２×１０⁶Ｖ／ｍ）の矩形のＡＣ電圧を重畳したものを用い、現像スリーブ２４ａと感光体２１の間ａで一成分ジャンピング現像を行わせた。
【０３２８】
２５は接触転写手段としての中抵抗の転写ローラーであり、感光体１に９８Ｎ／ｍ（１００ｇ／ｃｍ）の線圧で圧接させて転写当接部ｂを形成させてある。この転写当接部ｂに不図示の給紙部から所定のタイミングで記録媒体としての転写材Ｐが給紙され、かつ転写ローラー２５に転写バイアス印加電源から所定の転写バイアス電圧が印加されることで、感光体２１側のトナー像が転写当接部ｂに給紙された転写材Ｐの面に順次に転写されていく。
【０３２９】
本例ではローラ抵抗値は５×１０⁸Ωｃｍのものを用い、＋３０００ＶのＤＣ電圧を印加して転写を行なった。即ち、転写当接部ｂに導入された転写材Ｐはこの転写当接部ｂを挟持搬送されて、その表面側に感光体２１の表面に形成担持されているトナー画像が順次に静電気力と押圧力にて転写されていく。
【０３３０】
２６は熱定着方式等の定着装置である。転写当接部ｂに給紙されて感光体２１側のトナー像の転写を受けた転写材Ｐは感光体１の表面から分離されてこの定着装置２６に導入され、トナー像の定着を受けて画像形成物（プリント、コピー）として装置外へ排出される。
【０３３１】
本例のプリンターはクリーニングユニットを除去しており、転写材Ｐに対するトナー像転写後の感光体２１の表面に残留の転写残トナーはクリーナーで除去されることなく、感光体２１の回転にともない帯電部ｎを経由して現像部ａに至り、現像装置２４において現像同時クリーニング（回収）される。
【０３３２】
２７はプリンター本体に対して着脱自在の画像形成装置及びプロセスカートリッジである。本例のプリンターは、感光体２１、帯電ローラー２２、現像装置２４の３つのプロセス機器を一括してプリンター本体に対して着脱自在の画像形成装置及びプロセスカートリッジとして構成してある。
【０３３３】
２８はプロセスカートリジの着脱案内・保持部材である。
【０３３４】
本画像形成装置を使用し、耐久枚数を３０００枚とする以外は、実施例Ａ１と同様の項目について評価した。結果を表７に示した。
【０３３５】
＜実施例Ｂ２〜Ｂ６＞
磁性トナー２３に代えて磁性トナー２４〜２８を用い、帯電ローラーに、トナーに使用している導電性微粉末を同じ導電性微粉末を塗布する以外は実施例Ｂ１と同様の画像形成方法で画出し試験及び耐久性評価を行った。その結果、初期の画像特性も問題無く、耐久３０００枚時まで特に問題の無い結果が得られた。
【０３３６】
＜比較例Ｂ１、Ｂ２＞
磁性トナー２３に代えて比較用磁性トナー１２、１３を用いる以外は実施例Ｂ１と同様の画像形成方法で画出し試験及び耐久性評価を行った。その結果、初期の画像特性は問題なかったが、高温高湿環境下にて比較用磁性トナー１２は１５００枚頃から、比較用磁性トナー１３は２０００枚頃からベタ画像の濃度均一性が悪化した。低温低湿環境下にて比較用磁性トナー１２は２０００枚頃から、比較用磁性トナー１３は２５００枚頃から細線の再現性が悪化した。
【０３３７】
【表７】

【０３３８】
【発明の効果】
上記構成の本発明の磁性トナーは、高画質の画像を得ることが出来る。さらに、高温高湿下や低温低湿下においても、ベタ画像の均一性および細線再現性など高解像度であり高画質の画像を長期間安定して与えることができる。
【図面の簡単な説明】
【図１】本発明の実施例に用いた画像形成装置の一例を示す図である。
【図２】一成分現像用現像器の一例を示す図である。
【図３】本発明に用いる感光体の構成の一例を示す図である。
【図４】接触転写部材の一例を示す図である。
【図５】本発明の一態様における画像形成装置の概略構成図である。
【図６】感光体の層構成模型図である。
【符号の説明】
１１ アルミ基体
１２ 導電層
１３ 注入防止層
１４ 電荷発生層
１５ 電荷輸送層
１６ 電荷注入層
１６ａ 導電粒子（導電フィラー）
２１ 感光体
２２ 帯電部材
２２ａ 芯金
２３ レーザービームスキャナー（潜像形成手段、露光装置）
２４ 現像装置
２４ａ 現像スリーブ（現像剤担持体）
２４ｂ 撹拌部材
２４ｃ 弾性ブレード（層規制部材）
２５ 転写ローラ
２６ 定着装置
２６ａ ヒータ
２６ｂ 定着フィルム
２６ｃ 加圧ローラ
２７ プロセスカートリッジ
２８ カートリッジ保持部材
３４ａ 芯金
３４ｂ 弾性層
３５ 転写バイアス電源
１００ 感光ドラム
１０２ 現像スリーブ
１０３ 弾性ブレード
１０４ マグネットローラー
１１４ 転写ローラー
１１６ クリーニング手段
１１７ 一次帯電ローラー
１２１ レーザー発生装置
１２３ レーザー光
１２４ レジスタローラー
１２５ 搬送ベルト
１２６ 定着器
１４０ 現像器
１４１ 現像剤撹拌部材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic toner for visualizing an electrostatic latent image using electrophotography, electrostatic recording, magnetic recording, toner jet recording, or the like.
[0002]
[Prior art]
Conventionally, many methods are known as electrophotographic methods. In general, a photoconductive substance is used to form an electrostatic charge latent image on an electrostatic image carrier (hereinafter also referred to as a photoreceptor) by various means, and then the latent image is developed with toner to form a toner image. If necessary, the toner image is transferred to a transfer material such as plain paper, and then the toner image is fixed on the transfer material by heat and pressure such as heat and pressure to obtain a copy or printed matter.
[0003]
As a method for visualizing an electrostatic latent image with a toner, a cascade developing method, a magnetic brush developing method, a pressure developing method, a magnetic brush developing method using a two-component developer composed of a carrier and a toner, a toner carrier is a photoreceptor. Non-contact one-component development method that causes toner to fly from the toner carrier to the photoconductor in a non-contact manner, a contact one-component development method in which the toner carrier is pressed against the photoconductor and the toner is transferred by an electric field, and magnetic toner is used. A so-called jumping method is also used in which a rotating sleeve having a magnetic pole at the center is used to fly between the photosensitive member and the sleeve by an electric field.
[0004]
The electrophotographic apparatus such as a printer apparatus has a higher resolution as a technical direction, that is, what has been conventionally 300 or 600 dpi has become 1200 or 2400 dpi. Accordingly, the development method is also required to have higher definition. In addition, copying machines are becoming more sophisticated, and therefore are moving toward digitalization. Since this method is mainly a method of forming an electrostatic charge image with a laser, it is also proceeding in the direction of high resolution, and here again, a high-resolution and high-definition developing method is required as in the case of a printer. .
[0005]
Magnetic developer used in the jumping method (hereinafter referred to as magnetic toner) is a magnetic material such as iron tetroxide (magnetite) that is uniformly dispersed in the binder resin together with wax for improving fixability. Is. Conventionally, in order to make the dispersion state of the magnetic material uniform, manufacturing conditions, surface properties and shape of the magnetic material, type of binder resin, viscoelasticity, and the like have been proposed. However, as described above, even if high resolution is satisfied using the toner in which the magnetic material is uniformly dispersed, a problem occurs when a durability test for printing a large number of sheets is performed in a high-temperature and high-humidity or low-humidity environment. For example, if a durability test using an image with a high printing ratio is performed under high temperature and high humidity, the reproducibility of fine lines deteriorates due to a decrease in resolution, or if a durability test at a low printing ratio is performed under low humidity, the resolution is maintained. There remains room for improvement in achieving both resolution and solid image uniformity, such as loss of image density uniformity. In order to improve the image quality, it is known as an effective means to reduce the particle size and the spherical shape of the toner. JP-A-9-62029 and EP1058157 are disclosed as such toner. . However, further environmental stability and improvement in image quality are expected.
[0006]
Furthermore, Japanese Patent Application Laid-Open No. 2002-148853 also describes that there is an effect of improving the developability by defining the saturation magnetization amount on the fine powder side and the coarse powder side. Long-awaited.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a magnetic toner that solves the above-mentioned problems of the prior art.
[0008]
That is, the object of the present invention is to maintain high image quality over a long period of time, with high coloring power, and compatibility between fine line reproducibility and solid image density uniformity without being affected by the use environment and image printing ratio. It is an object of the present invention to provide a magnetic toner that can be used.
[0009]
[Means for Solving the Problems]
The inventors have various environments and conditions in which the toner is used, and as a result of intensive studies on stabilizing the image quality even when the usage environment and the usage condition change, the toner having a specific gravity distribution has been obtained. As a result, it was found that this can be solved, and the present invention has been completed.
[0010]
  That is, the present invention is a toner containing at least iron oxide,
  In the components fractionated by the wet method based on the dry specific gravity (A) of the toner
15% by mass or less of toner having a specific gravity of (A) × 1.000 and (A) × 1.025 or less,
0.1 to 20% by mass of a toner having a specific gravity of (A) × 0.975 and (A) × 1.000 or less,
30% or more by weight of toner having a specific gravity of (A) × 0.950 and (A) × 0.975 or less,
0.1 to 20% by mass of a toner having a specific gravity exceeding (A) × 0.925 and not more than (A) × 0.950,
The toner having a specific gravity of (A) × 0.900 and (A) × 0.925 or less is 15% by mass or less,
AndThe average circularity of the toner is 0.970 or moreThe present invention relates to a magnetic toner.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the magnetic toner of the present invention will be described.
[0012]
The magnetic toner of the present invention is
15% by mass or less of toner having a specific gravity of (A) × 1.000 and (A) × 1.025 or less,
0.1 to 20% by mass of a toner having a specific gravity of (A) × 0.975 and (A) × 1.000 or less,
30% or more by weight of toner having a specific gravity of (A) × 0.950 and (A) × 0.975 or less,
0.1 to 20% by mass of a toner having a specific gravity exceeding (A) × 0.925 and not more than (A) × 0.950,
The toner having a specific gravity of (A) × 0.900 and (A) × 0.925 or less is 15% by mass or less,
Thus, it is possible to achieve both fine line reproducibility and solid image density uniformity even under high temperature and high humidity and (low temperature) and low humidity.
[0013]
As a preferable range,
10% by mass or less of toner having a specific gravity of (A) × 1.000 and (A) × 1.025 or less,
0.5 to 15% by mass of a toner having a specific gravity of (A) × 0.975 and (A) × 1.000 or less,
The toner having a specific gravity of (A) × 0.950 and (A) × 0.975 or less is 40% by mass or more,
0.5 to 15% by mass of a toner having a specific gravity of (A) × 0.925 and (A) × 0.950 or less,
10% by mass or less of toner having a specific gravity of (A) × 0.900 and (A) × 0.925 or less,
As a more preferable range,
1 to 5% by mass of a toner having a specific gravity of (A) × 1.000 and (A) × 1.025 or less,
(A) 3 to 10% by mass of toner having a specific gravity exceeding 0.975 and not exceeding (A) 1.000;
40-90% by mass of a toner having a specific gravity of (A) × 0.950 and (A) × 0.975 or less,
3 to 10% by mass of a toner having a specific gravity of (A) × 0.925 and (A) × 0.950 or less,
1 to 5% by mass of toner having a specific gravity exceeding (A) × 0.900 and not more than (A) × 0.925
Is mentioned.
[0014]
First, the specific gravity distribution measuring method in the present invention will be described.
[0015]
In the present invention, the dry specific gravity is measured in order to determine the above-mentioned standard of specific gravity distribution. The dry specific gravity was measured using a dry density meter Accupic 1330 (manufactured by Shimadzu Corporation).
[0016]
Next, assuming that the dry specific gravity value is (A), 6 levels of aqueous solution are prepared from -10% to + 2.5% with respect to the value of (A) in increments of 2.5% on the basis of the specific gravity. About 0.01-0.1% of nonionic surfactant (contaminone) is added in each said aqueous solution. Toner precisely weighed in this aqueous solution was added to a concentration of about 0.1 to 1%, and it was ultrasonically dispersed to confirm that it was dispersed to primary particles. Then, after separating by means such as using a centrifugal separator, the supernatant is decanted, the settled toner is washed with ion-exchanged water, and the mass of the dried toner is precisely weighed.
[0017]
According to this principle, particles having a specific gravity larger than that of the aqueous solution will settle. Accordingly, particles that settle in an aqueous solution having a specific gravity of (A) × 0.900 have a specific gravity exceeding (A) × 0.900. The mass of the particles that settled at this time is defined as W1. Similarly, particles that settle in an aqueous solution with a specific gravity of (A) × 0.925 have a specific gravity greater than (A) × 0.925, while floating particles have a specific gravity of 0.925 or less. . The mass of the particles that settled at this time is defined as W2.
[0018]
The difference between W1 and W2 described above represents a component that settles in an aqueous solution of (A) × 0.900 and floats in an aqueous solution of (A) × 0.925. That is, it has a specific gravity exceeding (A) × 0.900 and not more than (A) × 0.925.
[0019]
In the present invention, utilizing the fact that the toner that settles in the aqueous solution of each specific gravity has a specific gravity higher than that of the aqueous solution, the distribution of specific gravity is obtained from the difference in the mass ratio of the toner that settles in the aqueous solution having the adjacent specific gravity. Here, an aqueous solution having a high specific gravity can be prepared from sodium iodide, zinc chloride, zinc bromide, and tin chloride. In the present invention, an aqueous zinc chloride solution and zinc bromide are suitable.
[0020]
In the distribution of specific gravity of the present invention, the present inventors consider the following as the reason why the above-described effect can be obtained.
[0021]
In the specific gravity distribution defined in the present invention, particles (low specific gravity) existing in a specific gravity range (hereinafter referred to as channel) having a smaller specific gravity centering on a channel that is a mode of distribution (mode) obtained by a wet method. Component) has a slightly lower amount of magnetic iron oxide (hereinafter abbreviated as a magnetic substance) than particles contained in a channel having a central specific gravity, so that the mass per toner particle is small when the particle size is the same. Small. On the other hand, since toners having the same particle diameter have the same surface area, the charging opportunities due to friction with the sleeve and the blade are almost equal, and as a result, the amount of charge given is usually almost the same. In that case, as the value of the charge amount per unit mass, that is, the charge amount (tribo), particles having a small specific gravity are slightly higher, and as a secondary effect, the charge speed tends to be faster. Further, in the case of jumping development, the influence of the magnetic poles arranged in the toner carrier (sleeve), that is, the magnetic binding force received from the sleeve tends to be slightly reduced. For this reason, the toner in the channel on the low specific gravity side has a slightly higher charge amount even under high temperature and high humidity, and rises slightly faster than the particles in the central channel. Further, since the magnetic restraining force is slightly small, it contributes to increase the development efficiency even in the same environment. The toner that is actually developed is mainly the toner of the mode channel of specific gravity, but if there is a certain amount of low specific gravity component there, for the reasons described above, under high temperature and high humidity (solid image It is possible to obtain density uniformity even if images with a high printing ratio are continuously output. However, if the amount of the low specific gravity component is within the range of the present invention, image defects such as scattering and fogging caused by the slightly high charge amount will not occur even in a low humidity environment. The reason for this is that the low specific gravity component and the central channel component within the scope of the present invention are not a large difference in the abundance of the magnetic material but an appropriate difference, so that the difference in charge amount is also appropriate. In addition, the inventors consider that the lower limit range of specific gravity and the abundance of low specific gravity components are greatly involved. On the other hand, a certain amount of particles (high specific gravity component) existing in a channel having a specific gravity greater than the mode value, that is, a toner having a slightly larger amount of magnetic substance, is formed on the sleeve by a magnetic brush. The present inventors consider that the magnetic restraint force easily spreads to the tip of the toner ear, and the necessary magnetic restraint force acts on the low specific gravity component to suppress the above-mentioned problems.
[0022]
On the other hand, particles (high specific gravity components) present in the channel with a higher specific gravity centering on the channel that has a specific gravity distribution mode (mode) obtained by the wet method have a slightly larger amount of magnetic substance. Therefore, when the same particle diameter is compared, the charge amount is slightly lowered due to the large toner particle mass, while the magnetic restraining force received from the sleeve in jumping development tends to be slightly increased. For this reason, it tends to be difficult to charge up even when outputting an image with a low printing ratio under low temperature and low humidity, and since the magnetic restraint force is somewhat large, it tends to suppress scattering on the image even in the same environment. Further, as described above, since the scattering of the low specific gravity component is also suppressed, the effect of reproducing the fine line faithfully with respect to the latent image can be exhibited. Furthermore, as long as the abundance of such high specific gravity components is within the range defined by the present invention, the density unevenness of a solid image caused by insufficient charge amount or slow charging speed in a high temperature and high humidity environment. Is suppressed. That is, the toner of the present invention achieves high image quality over a long period of time by satisfying both the reproducibility of fine lines and the density uniformity of solid images without being affected by the use environment and image printing ratio, if the above-mentioned specific gravity distribution is used. It is possible to maintain.
[0023]
As described above, the toner of the present invention has good image quality stability within the above-mentioned specific gravity distribution range, and the difference in the amount of magnetic substance in the toner due to the specific gravity distribution affects the coloring power of each toner particle. Does not cause deterioration in image quality such as density unevenness.
[0024]
When the low specific gravity component exceeds the range of the present invention, the possibility that the toner is charged up under low humidity and fogging or scattering occurs on the image becomes extremely high. On the other hand, if the high specific gravity component exceeds the range of the present invention, none of them is preferable because the possibility of uneven density in the solid image becomes extremely high under high temperature and high humidity.
[0025]
In order to obtain such a specific gravity distribution, when a toner is obtained by a pulverization method, it is necessary to adjust the shape of the magnetic material such as iron oxide, the pressure density, the polarity and viscoelasticity of the binder, or the conditions of melt kneading. Is possible. When a toner is obtained by a polymerization method, it can be adjusted by the shape and surface chemical composition of a magnetic material such as iron oxide, the composition and polarity of a polymerizable monomer, and the polymerization rate.
[0026]
Furthermore, it depends greatly on the interaction between the surface state of the magnetic material such as iron oxide and the components constituting the toner. In iron oxide, not only the chemical composition of the surface but also the particle size and particle size distribution have a great influence. In particular, it is possible to adjust the specific gravity distribution of the toner within the scope of the present invention by combining the surface treatment agent as described later, the surface-treated iron oxide obtained by the production method, and the iron oxide having a particle size distribution. It becomes.
[0027]
Addition of a sulfur-containing polymer, which will be described later, is more suitable for adjusting the specific gravity distribution within the range of the present invention. The inventors consider that the reason is that the sulfur element interacts with iron element, oxygen element, silicon element, etc., and the degree thereof is appropriate.
[0028]
The toner of the present invention is preferably produced by suspension polymerization in order to achieve the average circularity described later. At this time, in order to form droplets of the polymerizable monomer composition consisting of a polymerizable monomer and a raw material having a large specific gravity difference, such as iron oxide, by shearing force in water, the distribution of specific gravity and a Coulter described later are used. Between the weight average particle diameter measured by the counter, the weight average particle diameter of the low specific gravity component is smaller than the weight average particle diameter of the entire toner, or the weight average particle diameter of the high specific gravity component is the weight average of the entire toner. The possibility of becoming larger than the particle size arises. When such a phenomenon becomes prominent, the image quality varies greatly between environments. However, the weight average particle diameter of the component having a specific gravity smaller than 0.950 × (A) is (D4L), and the weight average particle diameter of the component having a specific gravity larger than 0.975 × (A) is (D4H). When the weight average particle diameter is (D4A), if the following relationship is satisfied, the above-described adverse effects are extremely difficult to occur.
(D4L) / (D4A) ≧ 0.8
(D4H) / (D4A) ≦ 1.1
[0029]
The present inventors consider that the reason is due to the relationship between the specific surface area of the toner and the chargeability.
[0030]
In the above relationship, for the same reason,
(D4L) / (D4A) ≧ 0.9
(D4H) / (D4A) ≦ 1.05
It is preferable to satisfy
(D4L) / (D4A) ≧ 0.95
(D4H) / (D4A) ≦ 1.03
Is more preferable.
[0031]
Further, if the iron oxide that becomes a leak site is not substantially exposed on the toner surface, the charge amount of the toner is stabilized and the latent image is developed faithfully. As a result, it is possible to increase the resolution of the image and obtain a good image with a high image density.
[0032]
Furthermore, since the average circularity and mode circularity are very high, the magnetic toner forms thin spikes at the developing portion, and the charging of each magnetic toner is made uniform. It is possible to obtain an image and to achieve both solid image uniformity and fine line reproducibility. Furthermore, since transferability is also improved, an image faithful to the latent image can be obtained on the transfer material.
[0033]
These will be described in detail below.
[0034]
The magnetic toner particles of the present invention contain at least magnetic iron oxide as a magnetic material. In the present invention, however, the binding energy 283 to 293 eV present on the surface of the toner measured by X-ray photoelectron spectroscopy analysis of the magnetic toner is used. The ratio (B / A) of the content (B) of the iron element having the peak top to the binding energy 706 to 730 eV with respect to the content (A) of the carbon element having the peak top is less than 0.001. It is preferable in order to maintain the charge amount. This ratio (B / A) is more preferably less than 0.0005, and even more preferably less than 0.0003.
[0035]
In the toner of the present invention, it is preferable that the charge amount of the toner particles is stable, and for this purpose, it is preferable that iron oxide serving as a charge leakage site is not exposed on the surface.
[0036]
Normally, when a magnetic toner having iron oxide exposed on the toner particle surface is used, charge discharge due to the exposed iron oxide occurs. If the charge is released before development, that is, if the amount of charge is extremely low, the image is developed in the non-image area and image fogging occurs. On the other hand, if charge release occurs after development, it is not transferred from the image carrier to the transfer member and remains on the image carrier, which leads to deterioration in image quality such as transfer loss. However, as described above, when a magnetic toner having a (B / A) of less than 0.001, that is, an iron oxide exposure amount on the toner particle surface is extremely low, a high-quality image faithful to low image fog and latent image is used. Can be obtained.
[0037]
The ratio (B / A) of the content of iron element (B) to the content of carbon element (A) present on the toner particle surface (B / A) was analyzed by ESCA (X-ray photoelectron spectroscopy) as follows. It can be measured by doing.
[0038]
In the present invention, the ESCA apparatus and measurement conditions are as follows.
Equipment used: 1600S type X-ray photoelectron spectrometer manufactured by PHI
Measurement conditions: X-ray source MgKα (400W)
Spectral region 800μmφ
[0039]
In the present invention, the surface atom concentration was calculated from the measured peak intensity of each element using a relative sensitivity factor provided by PHI.
[0040]
This measurement is preferably performed by ultrasonically washing the toner, removing the external additive adhering to the surface of the toner particles, separating by magnetic force, and drying.
[0041]
In the present invention, the preferable iron oxide dispersion state in the toner particles is a state in which the iron oxide particles are present uniformly throughout the toner particles as much as possible without aggregation. That is, when the projected area equivalent circle diameter of the magnetic toner is C, and the minimum value of the distance between the iron oxide and the toner particle surface is D in the cross-sectional observation of the magnetic toner using a transmission electron microscope (TEM), One of the preferred embodiments of the magnetic toner of the present invention is that the number of toner particles satisfying the relationship of D / C ≦ 0.02 is 50% or more.
[0042]
In the present invention, the projected area equivalent circle diameter of the magnetic toner is C, and the minimum value of the distance between the magnetic particle surface and the toner particle surface in the cross-sectional observation of the magnetic toner using a transmission electron microscope (TEM) is D. The toner particle number satisfying the relationship of D / C ≦ 0.02 is preferably 50% or more, more preferably 65% or more, and even more preferably 75% or more.
[0043]
The reason is as follows.
[0044]
If the conditions of the present invention are not satisfied, there will be no magnetic particles at least outside the boundary line of D / C = 0.02 in the toner particles. Assuming that the above-mentioned particles are spherical, when one toner particle is the entire space, at least 11.5% of the space where no iron oxide exists is present on the surface of the toner particle. Actually, the magnetic particles do not exist so as to be uniformly aligned at the closest position so as to form an inner wall inside the toner particles.
[0045]
If there are no magnetic particles in such a space per particle,
(1) The possibility that iron oxide is biased inside toner particles and iron oxide agglomerates is extremely increased. As a result, the coloring power is reduced.
(2) Although the specific gravity of the toner particles increases according to the content of the magnetic powder, the binder resin and the wax component are unevenly distributed on the surface of the toner particles. For this reason, even if a surface layer is provided on the surface of the toner particles by some means, if the toner particles or stress is applied to the toner particles during the manufacture of the toner, fusion or deformation is likely to occur. However, there is a high possibility that the toner will have a complicated distribution or a distribution in the powder characteristics of the toner obtained by deformation, which will adversely affect the electrophotographic characteristics, and that the blocking resistance during storage of the toner will deteriorate.
(3) In the particle structure in which the toner particle surface is only the binder resin and the wax, and the magnetic particles are unevenly distributed inside, the toner particle exterior is soft and the interior is hard, so that external additives are very easily embedded. The durability of the toner is deteriorated.
The risk of causing such harmful effects increases.
[0046]
If the number of particles satisfying D / C ≦ 0.02 is less than 50%, the adverse effects such as the reduction in coloring power, the deterioration in blocking resistance, and the deterioration in durability tend to become remarkable.
[0047]
Therefore, in the present invention, the number of particles satisfying D / C ≦ 0.02 is preferably 50% or more.
[0048]
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.
[0049]
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 ± 10% of the number average particle diameter (D1) measured by a Coulter counter described later. The particle included in the width is regarded as the corresponding particle, and the minimum value (D) of the distance from the magnetic particle surface is measured for the corresponding particle, and D / C is calculated. The ratio of particles having a D / C value calculated in this way of 0.02 or less is defined as being determined by the following formula. 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 (H-600 type manufactured by Hitachi) was used as an apparatus, observed at an accelerating voltage of 100 kV, and observed / measured using a micrograph having a magnification of 10,000 times.
[0050]
[Expression 1]

[0051]
The weight average particle diameter and number average particle diameter of the toner of the present invention are measured by various methods such as Coulter Counter TA-II type or Coulter Multisizer (manufactured by Coulter Co.). Specifically, it can be measured as follows. Using Coulter Multisizer (manufactured by Coulter), an interface (manufactured by Nikka) and a PC9801 personal computer (manufactured by NEC) that output number distribution and volume distribution are connected, and the electrolyte is 1% NaCl using first grade sodium chloride. Prepare an aqueous solution. For example, ISOTON R-II (manufactured by Coulter Scientific Japan) can be used. The measurement procedure is as follows. 100 to 150 ml of the electrolytic aqueous solution is added, and 2 to 20 mg of a measurement sample is further added. The electrolyte in which the sample is suspended is dispersed for about 1 to 3 minutes with an ultrasonic disperser, and the volume and number distribution of toner particles of 2 μm or more are measured by using the aperture with the Coulter Multisizer. And calculate. Then, the volume-based weight average particle diameter (D4) obtained from the volume distribution according to the present invention and the number-based average particle diameter obtained from the number distribution, that is, the number average particle diameter (D1) are obtained.
[0052]
Next, the range of the average circularity suitable for the magnetic toner of the present invention will be described.
[0053]
The magnetic toner of the present invention preferably has an average circularity of 0.970 or more. A toner composed of toner (powder composed of a group of toner particles) having an average circularity of 0.970 or more is very excellent in transferability. This is presumably because the contact area between the toner particles and the photoconductor is small, and the adhesion force of the toner particles to the photoconductor due to mirror image force, van der Waals force, or the like is reduced. Therefore, by combining the above-mentioned average circularity with the toner having the specific gravity distribution of the present invention, the transfer rate is high, which contributes to a reduction in toner consumption.
[0054]
Furthermore, toner particles having an average circularity of 0.970 or more have almost no edge portion on the surface, so that the charge localization within one particle hardly occurs, and therefore the charge amount distribution tends to be narrowed, and the latent particle size is low. Developed faithfully to the image. However, even when the average circularity is high, the effect may be insufficient if the circularity of the existing particles is low. In particular, when the mode circularity described later is 0.99 or more, the circularity is 0. .99 or more particles are mainly present, and therefore the above effect is remarkably exhibited, which is preferable.
[0055]
The average circularity in the present invention is used as a simple method for quantitatively expressing the shape of the particles. In the present invention, the average circularity is measured using a flow type particle image analyzer “FPIA-1000” manufactured by Toa Medical Electronics. The circularity degree (ai) of each particle measured for a particle group having a circle-equivalent diameter of 3 μm or more was determined by the following equation (1), and the total particle size measured by the following equation (2) A value obtained by dividing the sum of the circularity by the total number of particles (m) is defined as the average circularity (a).
[0056]
[Expression 2]

[0057]
[Equation 3]

[0058]
Further, the mode circularity means that the circularity is divided into 61 parts every 0.01 from 0.40 to 1.00, and the measured circularity of each particle is assigned to each divided range, and the frequency value in the circularity frequency distribution. Is the maximum circularity of the peak.
[0059]
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 mode circularity. A calculation method is used in which 0.40 to 1.00 is divided into 61 classes, and the average circularity and the mode circularity are calculated using the center value and frequency of the dividing points. However, the errors with the average circularity and mode circularity values calculated by this calculation formula are very small and can be substantially ignored.In the present invention, the calculation time can be shortened and For reasons of handling data such as simplification of the calculation formula, such a calculation formula partially modified by using the concept of the calculation formula that directly uses the circularity of each particle described above may be used.
[0060]
Measuring means are as follows. A dispersion is prepared by dispersing 5 mg of a developer in 10 ml of water in which about 0.1 mg of a surfactant is dissolved, and the dispersion is irradiated with ultrasonic waves (20 kHz, 50 W) for 5 minutes. Measurement is performed with the above apparatus at 20,000 particles / μl, and average circularity and mode circularity of a particle group having a circle-equivalent diameter of 3 μm or more are obtained.
[0061]
The average circularity in the present invention is an index of the degree of unevenness of the developer, and is 1.000 when the developer is a perfect sphere, and the circularity becomes smaller as the surface shape becomes more complicated.
[0062]
In this measurement, the reason why the circularity is measured only for the particle group having an equivalent circle diameter of 3 μm or more is that the particle group of the external additive existing independently of the toner particles in the particle group having an equivalent circle diameter of less than 3 μm. This is because the circularity of the toner particle group cannot be accurately estimated due to the influence of such a large amount.
[0063]
In the present invention, as a method of setting the average circularity of the toner to 0.970 or more, a method of directly producing toner particles by the suspension polymerization method described above, in a solvent in which the monomer is dissolved but the resin is not dissolved. , A method of obtaining a spherical toner by a dispersion polymerization method in which a monomer is polymerized in the presence of a dispersion stabilizer, a method of spheroidizing toner particles produced by a pulverization method, a molten mixture or a solution of a toner raw material in air It can be achieved by various methods such as a method of producing a spherical toner by spraying inside. Among these toner production methods, the spray method is easy to obtain a spherical toner, but the particle size distribution of the obtained toner tends to be wide. On the other hand, in the dispersion polymerization method, a spherical toner can be easily obtained, and the obtained toner shows a very sharp particle size distribution. However, the selection of materials to be used is narrow, and the use of organic solvents makes it possible to treat waste solvents or remove solvents. From the viewpoint of flammability, the manufacturing apparatus is complicated and complicated. In addition, in the manufacturing method by smoothing and spheroidizing the pulverized toner, it is not always easy to set the average circularity to 0.970 or more. Decrease may occur. On the other hand, the method for producing the toner of the present invention by the suspension polymerization method is a particularly preferred production method because it is very easy to control the circularity and circularity standard deviation of the toner particles. In addition, in the case where the toner of the present invention contains magnetic iron oxide particles to form a magnetic toner, if magnetic iron oxide particles whose surface is uniformly hydrophobized are used as the toner material, the surface of the toner particles is substantially magnetic. Since it is easy to obtain a toner in which the iron oxide particles are not exposed and the magnetic iron oxide particles are encapsulated in the toner particles, the wear and wear of the members that come into contact with the toner, such as the photosensitive drum, the fixing roller, and the fixing film, are suppressed. In view of this, the suspension polymerization method is a particularly advantageous production method.
[0064]
In the toner of the present invention, the amount of organic volatile component in terms of toluene based on the toner mass when the toner heating temperature is 150 ° C. is preferably 10 to 400 ppm in the analysis of the organic volatile component of the toner by the headspace method.
[0065]
The amount of the organic volatile component of the toner of the present invention is quantified using a headspace method. In the headspace method, the toner is sealed in a sealed container and heated at a constant temperature for a certain time to equilibrate between the sample and the gas phase, and then the gas in the gas phase in the sealed container is injected into the gas chromatograph. Quantify volatile components. At this time, an organic volatile component is detected using FID as a detector of the gas chromatograph. Conventionally, as a method for analyzing a volatile component in a toner, a method in which a toner is dissolved in a solvent and injected into a gas chromatograph and quantified is known. However, in this method, the peak of the volatile component is buried in the solvent peak. It is not suitable as a method for quantifying organic volatile components of toner.
[0066]
In the toner of the present invention, the amount of organic volatile component in terms of toluene based on the toner mass when the heating temperature of the toner is 150 ° C. is related to the adhesion between the toner particles and the external additive, and the adhesion state of the external additive changes. As a result, it has been found that the image quality deteriorates due to the difference in printing of a large number of sheets. That is, if it is less than 10 ppm, the organic volatile components on the toner surface decrease in a low-humidity environment, so that the adhesion between the toner particles and the external additive is weakened and the external additive is liberated. The amount changes, the fine line reproducibility decreases, and the image quality deteriorates. If it exceeds 400 ppm, the elasticity of the toner particle surface will decrease under high temperature environment and the embedding of the external additive will be promoted, so that the charge amount of the toner will change in the same manner as described above, the solid image uniformity will deteriorate, and the image quality will deteriorate. To do.
[0067]
Therefore, the amount of organic volatile components is preferably in the range of 10 to 400 ppm in terms of toluene, and 20 to 200 ppm is particularly preferable.
[0068]
The toner of the present invention preferably has a toluene-converted organic volatile component amount of 10 to 400 ppm based on the toner mass when the toner heating temperature is 150 ° C. This can be achieved by various methods. For example, in the production of polymerized toner, the residual amount of residual monomer, benzaldehyde, polymerization initiator residue, etc. is adjusted by adjusting the polymerization conditions. Further, distillation is performed after the completion of polymerization, and these volatile components in the toner are distilled off together with water to adjust the residual amount. Furthermore, in addition to the conventionally known methods such as adjusting the amount of volatile components in the toner by airflow drying or vacuum drying, a method of adjusting the amount of volatile components in the toner by washing the toner particles with a solvent. Various methods can be adopted.
[0069]
The amount of organic volatile components in the toner by the headspace method may be measured as follows.
[0070]
In a headspace vial (volume: 22 ml), 300 mg of toner is precisely weighed and sealed with a crimper and a special septum coated with fluororesin using a crimper. This vial is set in a headspace sampler and analyzed under the following conditions. And the total area value of the peak of the obtained GC chart is calculated by data processing. At this time, an empty vial in which no toner is sealed is simultaneously measured as a blank, and the blank value such as an organic volatile component volatilized from the septum is subtracted from the toner measurement data. The amount of organic volatile component in terms of toluene based on the toner mass is prepared by preparing several points (for example, 0.1 μl, 0.5 μl, 1.0 μl) in which only toluene is precisely weighed in a vial. After measuring each of the following analysis conditions before making a measurement, a calibration curve is created from the amount of toluene charged and the toluene area value, and the area value of the organic volatile component of the toner is calculated based on the calibration curve. Can be converted to the mass of toluene based on the above.
[0071]
<Measurement device>
Headspace sampler: HEWLETT PACKARD 7694
Oven temperature: 150 ° C
Sample heating time: 60 minutes
Sample loop (Ni): 1ml
Loop temperature: 170 ° C
Transfer line temperature: 190 ° C
Pressurization time: 0.50 minutes
LOOP FILL TIME: 0.01 min
LOOP EQ TIME: 0.05 minutes
INJECT TIME: 1.00 minutes
GC cycle time: 80 minutes
Carrier gas: He
GC: HEWLETT PACKARD 6890GC (detector: FID)
Column: HP-1 (inner diameter 0.25 μm × 30 m), carrier gas: He
Oven: Hold at 35 ° C. for 20 minutes, hold at 20 ° C./min up to 300 ° C. for 20 minutes.
INJ: 300 ° C
DET: 320 ° C
Splitless, constant pressure (20 psi) mode
[0072]
Next, the particle size of the magnetic toner will be described.
[0073]
The toner of the present invention has a weight average diameter of 3 for faithfully developing finer latent image dots in order to further improve image quality and achieve both solid image uniformity and fine line reproducibility. It is necessary to be 10 μm. The weight average diameter of the magnetic toner is preferably 4 to 8 μm. In a toner having a weight average diameter of less than 3 μm, the transfer residual toner on the photoconductor increases due to a decrease in transfer efficiency, and it becomes difficult to suppress the photoconductor shaving and toner fusion in the contact charging step. Furthermore, in addition to an increase in the entire surface area of the toner, the fluidity and agitation as a powder decrease, and it becomes difficult to uniformly charge individual toner particles, so fog and transferability tend to deteriorate, In addition to scraping and fusing, it tends to cause non-uniform image unevenness, which is not preferable for the toner used in the present invention. When the weight average diameter of the toner exceeds 10 μm, the characters and the line image are likely to be scattered and high resolution is difficult to obtain. Furthermore, as the apparatus becomes higher in resolution, toner of 8 μm or more tends to deteriorate the reproduction of one dot.
[0074]
Furthermore, as a preferred embodiment for the magnetic toner of the present invention, it is possible to effectively balance the specific gravity distribution of the toner and the dispersed state of iron oxide by using a resin containing sulfur element. Furthermore, since a resin containing elemental sulfur has a high polarity, by incorporating such a resin into the toner, the charge transfer speed at the time of triboelectric charging of the toner particles is improved, so that charge up under low humidity or under high humidity. The effect of suppressing the decrease in the charge amount is also exhibited. However, if the resin is present in a large amount in the vicinity of the toner particle surface and the condition that the entire toner particle surface is in contact with the frictional charging member is not added, such an effect cannot be expected. For example, even if the binder resin is contained in the irregular toner, only the convex portion of the toner particle surface is in contact with the frictional charging member, so that the charge transfer speed cannot be improved much. Further, in a situation where the binder resin is present only inside the toner particles, it is difficult to contact the friction charging member.
[0075]
In the present invention, it is preferable that the resin containing a sulfur element is contained. Among these, a resin having a sulfonic acid is a more preferable embodiment.
[0076]
As monomers constituting the resin having elemental sulfur used in the present invention, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid vinylsulfonic acid, There are methacrylsulfonic acid and the like, or maleic acid amide derivatives, maleimide derivatives, and styrene derivatives having the following structures.
[0077]
[Chemical 1]

[0078]
The resin having a sulfur element according to the present invention may be a homopolymer of the above monomer, or may be a copolymer of the above monomer and another monomer. As a monomer that forms a copolymer with the above monomer, there is a vinyl polymerizable monomer, and a monofunctional polymerizable monomer or a polyfunctional polymerizable monomer can be used.
[0079]
Monofunctional polymerizable monomers include styrene; α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, pn-butyl. Styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, p-methoxy styrene, p -Styrene derivatives such as phenylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, n-amyl acrylate, n-hexyl acrylate, 2 -Ethylhexyl acrylate , N-octyl acrylate, n-nonyl acrylate, cyclohexyl acrylate, benzyl acrylate, dimethyl phosphate ethyl acrylate, diethyl phosphate ethyl acrylate, dibutyl phosphate ethyl acrylate, 2-benzoyloxyethyl acrylate Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl Methacrylate, n-nonyl methacrylate, diethyl phosphate ethyl methacrylate Methacrylic polymerizable monomers such as dibutyl phosphate ethyl methacrylate; methylene aliphatic monocarboxylic acid esters; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, vinyl formate; vinyl methyl ether Vinyl ether such as vinyl ethyl ether and vinyl isobutyl ether; vinyl ketone such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropyl ketone.
[0080]
As polyfunctional polymerizable monomers, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, tripropylene glycol Diacrylate, polypropylene glycol diacrylate, 2,2′-bis (4- (acryloxydiethoxy) phenyl) propane, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol Dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol Dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2'-bis (4- (methacryloxy-diethoxy) phenyl) propane, 2,2′-bis (4-methacryloxy / polyethoxy) phenyl) propane, trimethylolpropane trimethacrylate, tetramethylolmethane tetramethacrylate, divinylbenzene, divinylnaphthalene, divinyl ether, and the like.
[0081]
As the resin having elemental sulfur, the monomers as described above can be used, but it is more preferable to contain a styrene derivative as a monomer.
[0082]
The method for producing the sulfur-containing resin includes bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, dispersion polymerization, ionic polymerization, etc., but solution polymerization is preferable from the viewpoint of operability.
[0083]
The resin having the sulfur element is a sulfonic acid group such as
X (SO_Three ^-)_n・ MY^{k +}
(X: represents a polymer site derived from the polymerizable monomer, Y⁺: Represents a counter ion, k is the valence of the counter ion, m and n are integers, and n = k × m. )
It has the following structure. Counter ions are preferably hydrogen ions, sodium ions, potassium ions, calcium ions, ammonium ions, and the like.
[0084]
As described above, the functional group constituting the resin having sulfur element is preferably a sulfonic acid group, and as the sulfonic acid group-containing monomer, (meth) acrylamide is preferable for achieving the object of the present invention. . The content of the copolymer is preferably 0.01 to 20% by mass, more preferably 0.05 to 10% by mass, and further preferably 0.1 to 5% by mass.
[0085]
The acid value (mgKOH / g) of the resin containing sulfur element is preferably 3 to 50.
[0086]
When the acid value is less than 3, it is not possible to achieve both a good iron oxide dispersion state and sufficient charge control action as mentioned in the present invention, and the environmental characteristics are poor. When the acid value exceeds 50, when particles are produced by suspension polymerization using a composition containing such a polymer, the toner particles have an irregular shape and the circularity decreases. As a result, the transfer efficiency is lowered, and when a release agent having an image quality is contained, the release agent appears on the toner surface, causing a decrease in developability.
[0087]
The resin containing sulfur element is preferably contained in an amount of 0.05 to 20 parts by mass per 100 parts by mass of the other binder resin. 0.2 to 10 parts by mass is preferable.
[0088]
When the content of the resin having sulfur element is less than 0.05 parts by mass, it becomes difficult to achieve both a good iron oxide dispersion state and sufficient charge control action as referred to in the present invention. When it exceeds the mass part, the particle size distribution becomes broad, causing an increase in fog and a decrease in transferability.
[0089]
The molecular weight of the resin containing sulfur element is preferably 2000 to 100,000 in terms of weight average molecular weight (Mw). When the weight average molecular weight (Mw) is less than 2,000, the toner has poor blocking properties. When it exceeds 100,000, in addition to taking time to dissolve in the monomer, the dispersibility of the pigment also deteriorates and the coloring power of the toner decreases. In JP-A-11-288129, it is described that the dispersibility of the colorant is insufficient when the weight average molecular weight is in the range of 2000 to 15000. However, the magnetic toner of the present invention does not necessarily have a desired dispersion state. It is not always difficult to obtain.
[0090]
<Measurement of molecular weight distribution by gel permeation chromatography>
In the present invention, the molecular weight of the resin in the toner was determined as a polystyrene-converted molecular weight from the molecular weight distribution in gel permeation chromatography (GPC). The GPC measurement method is as follows.
[0091]
First, as a sample preparation, the toner was dissolved in tetrahydrofuran (THF) at room temperature so that the resin component in the sample was 0.4 to 0.6 mg / ml, and the resulting solution had a pore diameter of 0.2 μm. Filter with a solvent resistant membrane filter.
[0092]
Next, the column is stabilized in a heat chamber at 40 ° C., THF as a solvent is allowed to flow at a flow rate of 1 ml / min, and about 100 μl of THF sample solution is injected for measurement. In measuring the molecular weight of the sample, the molecular weight distribution of the sample was calculated from the relationship between the logarithmic value of the calibration curve prepared from several monodisperse polystyrene standard samples and the number of counts. As standard polystyrene samples for creating a calibration curve, TSK standard polystyrene F-850, F-450, F-288, F-128, F-80, F-40, F-20, F-20, F-10, F- manufactured by Tosoh Corporation 4, F-2, F-1, A-5000, A-2500, A-1000, A-500 was used to create a calibration curve. The detector used was an RI (refractive index) detector and a UV (ultraviolet) detector arranged in series. As the column, it is preferable to combine a plurality of commercially available polystyrene gel columns. In the present invention, a combination of shodex GPC KF-801, 802, 803, 804, 805, 806, 807, and 800P manufactured by Showa Denko KK It was measured.
[0093]
A high-speed GPC HLC8120 GPC (manufactured by Tosoh Corporation) was used as the apparatus.
[0094]
The glass transition point (Tg) of the polymer containing sulfur element is preferably 50 ° C to 100 ° C. When the glass transition point is less than 50 ° C., the fluidity and storage stability of the toner are inferior, and the transferability is also inferior. When the glass transition point exceeds 100 ° C., the fixability at the time of an image having a high toner printing rate is poor.
[0095]
In the present invention, the glass transition temperature of the resin containing the elemental sulfur was measured by a differential scanning calorimeter (DSC). The measuring method will be described later.
[0096]
In the magnetic toner of the present invention, the amount of sulfur element can be quantified by an existing analysis method such as elemental analysis. Furthermore, it is possible to define a suitable range of the amount of sulfur element existing on the toner particle surface by the above-mentioned X-ray photoelectron spectroscopic analysis. Specifically, the content (E) of sulfur element having a peak at a binding energy of 167 to 172 eV with respect to the content (A) of the binding energy 283 to 293 eV on the toner surface as measured by X-ray photoelectron spectroscopy. The ratio (E / A) is preferably in the range of 0.0003 to 0.0050, depending on the average particle size of the iron oxide used, the amount of sulfur element contained in the binder resin, and the amount of resin having the sulfur element used. It is possible to control within a suitable range. If 0.0003, there is a tendency that sufficient charge control action cannot be obtained, and if it is less than 0.0050, it becomes difficult to obtain the environmental stability of the charge amount.
[0097]
As a particle size of a preferable magnetic powder (iron oxide) used in the magnetic toner of the present invention, the volume average particle size is 0.1 to 0.3 μm and the number% of particles having a particle size of 0.03 μm or more and less than 0.1 μm. Is preferably 40% or less.
[0098]
When an image is obtained from a magnetic toner using a magnetic powder having an average particle size of less than 0.1 μm, the color of the image shifts to reddish, and the blackness of the image is insufficient, or the halftone image is more reddish. In general, this is not preferable, such as a strong tendency to be felt. In addition, when such a toner is used for a color image, it is not preferable because color reproducibility becomes difficult to obtain or the shape of the color space tends to be distorted. Further, since the surface area of the magnetic powder is increased, dispersibility is deteriorated, energy required for production is increased, and it is not efficient. Further, the density of an image to be obtained from the amount of magnetic powder added is insufficient, which is not preferable.
[0099]
On the other hand, if the average particle size of the magnetic powder 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, This is not preferable because the possibility of significant wear increases and the sedimentation stability of the dispersion decreases.
[0100]
In addition, when the number percentage of particles of 0.03 μm or more and less than 0.1 μm in the magnetic powder exceeds 40% in the toner, the surface area of the magnetic powder increases and the dispersibility decreases, causing aggregation in the toner. The amount is preferably 40% or less in order to easily generate a lump, increase the charge amount of the toner, and make it difficult to balance solid image uniformity and fine line reproducibility. Furthermore, if it is 30% or less, the tendency becomes smaller, which is more preferable.
[0101]
Note that the magnetic powder 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 has virtually no effect. Therefore, in the present invention, attention is given to particles having a size of 0.03 μm or more and less than 0.1 μm, and the number% is defined.
[0102]
On the other hand, if the number of particles exceeding 0.3 μm in the magnetic powder exceeds 10% by number, the coloring power tends to decrease and the image density tends to decrease, such being undesirable. More preferably, it is 5% or less.
[0103]
In the present invention, it is preferable to use a magnetic material whose production conditions are set so as to satisfy the above-mentioned condition of the particle size distribution or whose particle size distribution is adjusted in advance such as pulverization and classification. 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.
[0104]
As a method for determining the particle size of the magnetic powder, after sufficiently dispersing the magnetic powder or toner particles to be observed in the epoxy resin, a cured product obtained by curing in an atmosphere at a temperature of 40 ° C. for 2 days, As a sample on a thin piece by a microtome, a magnetic transmission particle (TEM) is used to observe 100 magnetic particles in the field of view at a magnification of 10,000 to 40,000 times, and the projection area is obtained. It is preferable to calculate the volume average particle diameter by calculating the equivalent circle diameter of the area. Further, based on the result, the number% of particles of 0.03 μm or more and less than 0.1 μm and particles of more than 0.3 μm is calculated.
[0105]
Such a magnetic powder may contain elements such as cobalt, nickel, copper, magnesium, manganese, and aluminum, and is composed mainly of iron oxide such as triiron tetroxide and γ-iron oxide. Are used alone or in combination of two or more.
[0106]
The magnetic toner particles of the present invention are preferably particles obtained by a polymerization method. The toner according to the present invention can also be produced by a pulverization method, but the toner particles obtained by this pulverization method are generally amorphous, and the average circularity, which is an essential requirement of the toner according to the present invention, is required. In order to obtain a physical property of 0.970 or more (preferably a mode circularity of 0.990 or more), it is necessary to perform mechanical / thermal or some special treatment. Furthermore, the pulverization method inherently exposes the magnetic iron oxide particles on the surface of the toner particles, so surface modification is required to obtain a toner that is substantially free of magnetic material and is suitable for the present invention. It becomes.
[0107]
Therefore, in order to solve the above-described problems, in the present invention, it is preferable to produce toner particles by a polymerization method. Examples of the toner polymerization method include a direct polymerization method, a suspension polymerization method, an emulsion polymerization method, an emulsion association polymerization method, and a seed polymerization method. Among these, the balance between the particle size and the particle shape is easy to balance. In this respect, it is particularly preferable to produce the suspension by a suspension polymerization method. In this suspension polymerization method, a monomer composition is prepared by uniformly dissolving or dispersing a polymerizable monomer and a colorant (and, if necessary, a polymerization initiator, a crosslinking agent, a charge control agent, and other additives). After that, the monomer composition is dispersed in a continuous layer containing a dispersion stabilizer (for example, an aqueous phase) using a suitable stirrer and simultaneously subjected to a polymerization reaction to obtain a toner having a desired particle size. To get. The toner obtained by this suspension polymerization method (hereinafter referred to as polymerized toner) has an average circularity of 0.970 or more, particularly a mode circularity of 0.99 or more, because the individual toner particle shapes are substantially spherical. It is easy to obtain toner that satisfies the requirements, and such toner has high transferability because the distribution of charge amount is relatively uniform.
[0108]
Furthermore, a core / shell structure in which a surface layer is provided by adding a polymerizable monomer and a polymerization initiator again to the fine particles obtained by suspension polymerization can be designed as necessary.
[0109]
However, even if a normal magnetic substance is contained in the polymerized toner, it is difficult to suppress the exposure of the magnetic substance from the particle surface. Furthermore, not only the fluidity and charging characteristics of the toner particles are remarkably lowered, but also the toner having an average circularity of 0.970 or more is obtained due to the strong interaction between the magnetic substance and water during the production of the suspension polymerization toner. It's hard to be done. This is because (1) the magnetic particles are generally hydrophilic and are therefore likely to be present on the toner surface, and (2) the magnetic particles move randomly when the aqueous solvent is stirred, and suspended particles composed of monomers. It is considered that the surface is dragged, the shape is distorted, and it is difficult to form a circle. In order to solve these problems, it is important to modify the surface properties of the magnetic particles.
[0110]
Therefore, in the magnetic material used in the magnetic toner related to the image forming method of the present invention, when the particle surface is hydrophobized, coupling is performed while dispersing the magnetic particles so as to have a primary particle size in an aqueous medium. It is particularly preferable to use a method of surface treatment while hydrolyzing the agent. This hydrophobic treatment method is less likely to cause coalescence between the magnetic particles than the treatment in the gas phase, and the repulsive action between the magnetic particles due to the hydrophobic treatment works, so that the magnetic material is almost in the state of primary particles. Surface treated.
[0111]
The method of treating the surface of the magnetic material 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, and further, In the phase, the magnetic particles are easily united with each other, and a highly viscous coupling agent that has been difficult to be processed can be used, so that the hydrophobizing effect is very large.
[0112]
Examples of the coupling agent that can be used in the surface treatment of the magnetic material according to the present invention include a silane coupling agent and a titanium coupling agent. More preferably used is a silane coupling agent, which is represented by the following general formula (I).
[0113]
R_m-Si-Y_n      (I)
[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. ]
[0114]
Specifically, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldi Examples include ethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-hexadecyltrimethoxysilane, and n-octadecyltrimethoxysilane.
[0115]
In particular, it is preferable to hydrophobize the magnetic particles in an aqueous medium using an alkyltrialkoxysilane coupling agent represented by the following general formula (II).
C_pH_{2p + 1}-Si- (OC_qH_{2q + 1})_Three      (II)
[In formula, p shows the integer of 2-20, q shows the integer of 1-3. ]
[0116]
When p in the formula (II) is smaller than 2, the hydrophobization treatment is easy, but it is difficult to sufficiently impart hydrophobicity, and it is difficult to suppress exposure of the magnetic particles from the toner particles. Become. On the other hand, when p is larger than 20, the hydrophobicity is sufficient, but the coalescence between the magnetic particles increases, and it becomes difficult to sufficiently disperse the magnetic particles in the toner. Deteriorating.
[0117]
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.
[0118]
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.
[0119]
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 the magnetic material.
[0120]
Here, 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. Although it does not specifically limit as surfactant, It is preferable to use nonionic surfactants, such as polyvinyl alcohol. The surfactant is preferably added in an amount of 0.1 to 5% by mass relative to water. Examples of the pH adjuster include inorganic acids such as hydrochloric acid. As an organic solvent, methanol etc. are mentioned, for example, and it is preferable to add 0-500 mass% with respect to water.
[0121]
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 magnetic particles become primary particles in the aqueous medium. Is good.
[0122]
In the magnetic material thus obtained, no aggregation of particles is observed, and the surface of each particle is uniformly hydrophobized. Therefore, when combined with the polymer containing sulfur element of the present invention, each polymer has a special effect. When used as a toner material, the dispersibility in toner particles is extremely good. In addition, it is possible to obtain polymerized toner particles that have very little exposure from the surface of the toner particles, are almost spherical, and have a very narrow particle size distribution. Therefore, by using such a magnetic material, the carbon element present on the surface of the toner having an average circularity of 0.970 or more, particularly a mode circularity of 0.99 or more and measured by X-ray photoelectron spectroscopy analysis. It is possible to obtain a magnetic toner in which the ratio (B / A) of the iron element content (B) to the iron content (A) is less than 0.001.
[0123]
As magnetic characteristics of these magnetic materials, the saturation magnetization is 10 to 200 Am under a magnetic field of 795.8 kA / m.²/ Kg, residual magnetization 1-100Am²/ Kg and a coercive force of 1 to 30 kA / m are used. These magnetic materials are used in an amount of 20 to 200 parts by mass with respect to 100 parts by mass of the binder resin. Among such magnetic materials, those mainly composed of magnetite are particularly preferable.
[0124]
In the present invention, the strength of magnetization of the magnetic toner was measured with a vibrating magnetometer VSM P-1-10 (manufactured by Toei Kogyo Co., Ltd.) at a room temperature of 25 ° C. and an external magnetic field of 79.6 kA / m. The magnetic properties of the magnetic material were measured at a room temperature of 25 ° C. with an external magnetic field of 796 kA / m.
[0125]
The magnetic toner of the present invention has a magnetization intensity of 10 to 50 Am in a magnetic field of 79.6 kA / m (1000 oersted).²It is necessary that the magnetic toner be / kg (emu / g).
[0126]
In the present invention, the reason why the strength of magnetization at a magnetic field of 79.6 kA / m is defined is that the amount of magnetization (saturation magnetization) in magnetic saturation is used as the quantity representing the magnetic properties of the magnetic material. This is because the strength of magnetization of the magnetic toner in the magnetic field actually acting on the magnetic toner in the image forming apparatus is important. When magnetic toner is applied to an image forming apparatus, the magnetic field acting on the magnetic toner is not limited to the leakage of the magnetic field to the outside of the image apparatus or in order to keep the cost of the magnetic field generation source low. In the image forming apparatus, a magnetic field of 79.6 kA / m (1000 oersted) is selected as a representative value of the magnetic field actually acting on the magnetic toner in the image forming apparatus. The strength of magnetization at 79.6 kA / m was defined.
[0127]
By providing magnetic force generating means in the developing device, magnetic toner can prevent leakage of the toner, and not only can the toner transportability or agitation be improved, but also magnetic force can be exerted on the toner carrier. By providing the generating means, the recovery performance of the transfer residual toner is further improved, and it becomes easy to prevent toner scattering because the magnetic toner forms spikes. However, when the magnetic field of the toner is 79.6 kA / m, the magnetization strength is 10 Am.²If it is less than / kg, the above-mentioned effects cannot be obtained, and if magnetic force is applied to the toner carrier, the rising of the toner becomes unstable and fogging and image density due to inability to uniformly apply charging to the toner. Image defects such as unevenness and poor recovery of transfer residual toner are likely to occur. Further, the conveyance of the toner to the toner carrier by the magnetic force tends to be insufficient. The magnetic strength of the toner at a magnetic field of 79.6 kA / m is 50 Am.²If it is greater than / kg, when a magnetic force is applied to the toner, the fluidity of the toner is remarkably reduced due to magnetic aggregation, and the transfer residual toner is increased due to a decrease in transferability, which tends to cause a reduction in image quality. Further, if the amount of the magnetic material is increased in order to increase the strength of magnetization, the fixing property is liable to be deteriorated. Further, since the toner has an average circularity of 0.970 or more and a mode circularity of 0.99 or more like the toner of the present invention, the rising of the toner on the toner carrier becomes fine and dense. Becomes uniform and fog is greatly reduced.
[0128]
For example, in the case of magnetite, the iron oxide (magnetic material) used in the magnetic toner of the present invention is produced by the following method.
[0129]
A water-soluble phosphorus compound is added to an aqueous ferrous salt solution by adding an alkali such as sodium hydroxide in an amount equivalent to or greater than the iron component to a concentration of 0.05 to 5.0% by mass of the phosphorus element with respect to the iron element. (For example, phosphates such as sodium hexametaphosphate and primary ammonium phosphate, phosphates such as normal phosphate and phosphite) Aqueous solution, optionally 0 to 5.0 mass% silicon with respect to iron element An aqueous solution containing ferrous hydroxide is prepared by adding an aqueous solution of a water-soluble silicon compound (for example, water glass, sodium silicate, potassium silicate) so as to be an element. Air is blown while maintaining the pH of the prepared aqueous solution at pH 7 or higher (preferably pH 7 to 10), and ferrous hydroxide is oxidized while heating the aqueous solution to 70 ° C. or higher to generate magnetic particles.
[0130]
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, a surface-treated magnetic powder is 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 the silane is stirred well. A coupling agent may be added to perform the coupling treatment.
[0131]
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.
[0132]
In the method for producing magnetic iron oxide by the aqueous solution method, an iron concentration of 0.5 to 2 mol / l is generally used from the viewpoint of preventing the viscosity from increasing 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.
[0133]
By using the surface-treated magnetic powder thus produced, the excellent magnetic toner of the present invention can be obtained, and high image quality and high stability are possible.
[0134]
Furthermore, other colorants may be used in combination with the magnetic substance. 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, particles such as hematite, titanium black, nigrosine dye / pigment , Carbon black, phthalocyanine and the like. These may also be used after treating the surface.
[0135]
The magnetic toner of the present invention preferably contains 0.5 to 40% by mass of a release agent with respect to the binder resin. Examples of the binder resin include various waxes as will be described later.
[0136]
The toner image transferred onto the transfer material is then fixed on the transfer material with energy such as heat and pressure to obtain a semi-permanent image. At this time, heat roll type fixing and film type fixing are generally used.
[0137]
As described above, if toner particles having a weight average particle size of 10 μm or less can be used, an extremely high-definition image can be obtained. It enters into the gaps between the fibers, and heat reception from the heat fixing roller becomes insufficient, so that low temperature offset is likely to occur. However, in the toner according to the present invention, by including an appropriate amount of the release agent, it is possible to achieve both high resolution and offset resistance.
[0138]
Release agents usable for the toner according to the present invention include petroleum waxes such as paraffin wax, microcrystalline wax, petrolactam and derivatives thereof, montan wax and derivatives thereof, hydrocarbon waxes and derivatives thereof according to the Fischer-Tropsch method, polyethylene And natural waxes such as carnauba wax and candelilla wax and derivatives thereof. These derivatives 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, animal waxes and the like can be mentioned. Among these waxes, those having an endothermic peak in differential thermal analysis of 40 to 110 ° C. are preferred, and those having a temperature of 45 to 90 ° C. are more preferred.
[0139]
As content when using a mold release agent, the range of 0.5-40 mass% with respect to binder resin is preferable. If the content is less than 0.5% by mass, the effect of suppressing low temperature offset is poor, and if it exceeds 40% by mass, the long-term storage stability deteriorates and the dispersibility of other toner materials deteriorates, and the fluidity of the toner. Leading to deterioration and deterioration of image characteristics.
[0140]
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.
[0141]
In addition, the glass transition temperature (Tg) of the polymer containing elemental sulfur is the intersection of the baseline between the baseline before the endothermic peak and the baseline after the endothermic peak and the rising curve from the DSC curve at the second temperature rise. To Tg.
[0142]
The magnetic toner of the present invention may contain a charge control agent in order to stabilize the charge characteristics. As the charge control agent, a known one can be used, and a charge control agent that has a high charging speed and can stably maintain a constant charge amount is particularly preferable. 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.
[0143]
Next, a method for producing the magnetic toner of the present invention by suspension polymerization will be described.
[0144]
When the toner of the present invention is produced by the suspension polymerization method, examples of the polymerizable monomer constituting the polymerizable monomer system to be used include the following.
[0145]
Examples of the polymerizable monomer include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, 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, etc. , Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, Methacrylic acid dimethyl aminoethyl methacrylate esters such as diethylaminoethyl methacrylate and other acrylonitrile-methacrylonitrile-monomer acrylamide.
[0146]
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.
[0147]
In the production of the polymerized toner according to the present invention, a resin may be added to the monomer system for polymerization.
[0148]
For example, a monomer containing a hydrophilic functional group such as an amino group, a carboxylic acid group, a hydroxyl group, a glycidyl group, or a nitrile group that cannot be used because it is soluble in an aqueous suspension and causes emulsion polymerization by dissolving in an aqueous suspension. When it is desired to introduce a body component into the toner, a random copolymer of these with a vinyl compound such as styrene or ethylene, a block copolymer, a graft copolymer, or the like, or in the form of a copolymer, or polyester, polyamide, etc. It can be used in the form of a polyaddition polymer such as a polycondensate, a polyether or a 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.
[0149]
In addition, resins other than those described above may be added to the monomer system for the purpose of improving the dispersibility and fixing properties of the material or image characteristics. Examples of the resin used include styrene such as polystyrene and polyvinyltoluene. And styrene-propylene copolymer, styrene-vinyltoluene copolymer, 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-methacrylic acid Acid butyl copolymer, styrene-dimethylaminoethyl methacrylate copolymer Polymer, Styrene-vinyl methyl ether copolymer, Styrene-vinyl ethyl ether copolymer, Styrene-vinyl methyl ketone copolymer, Styrene-butadiene copolymer, Styrene-isoprene copolymer, Styrene-maleic acid copolymer Styrene copolymers such as styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacryl Acid resins, rosins, modified rosins, terpene resins, phenol resins, aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins and the like can be used alone or in combination.
[0150]
As addition amount of these resin, 1-20 mass parts is preferable with respect to 100 mass parts of monomers. If the amount is less than 1 part by mass, the effect of addition is small, while if it exceeds 20 parts by mass, it becomes difficult to design various physical properties of the polymerized toner.
[0151]
Furthermore, 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.
[0152]
The polymerization initiator used in the production of the polymerized toner according to the present invention has a half-life of 0.5 to 30 hours at the time of the polymerization reaction, and 0.5 to 20 mass per 100 mass parts of the polymerizable monomer. When the polymerization reaction is carried out with a part addition amount, a polymer having a maximum between 10,000 and 100,000 in molecular weight can be obtained, and the toner can have 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) Azo or diazo polymerization initiators such as 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile; benzoyl peroxide, t-butylperoxy 2-ethylhexa Noate, t-butyl peroxypivalate, t-butyl peroxyisobutyrate, t-butyl peroxyneodecanoate, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl Peroxide polymerization such as peroxide and lauroyl peroxide Agents.
[0153]
When the polymerized toner according to the present invention is produced, a crosslinking agent may be added, and a preferable addition amount is 0.001 to 15% by mass.
[0154]
In producing the polymerized toner according to the present invention, a molecular weight modifier can be used. Examples of the molecular weight modifier include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, and n-octyl mercaptan; halogenated hydrocarbons such as carbon tetrachloride and carbon tetrabromide; α-methylstyrene dimer, and the like. Can be mentioned. These molecular weight regulators can be added before the polymerization starts or during the polymerization. The molecular weight modifier is usually used in a proportion of 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the polymerizable monomer.
[0155]
In the method for producing a polymerized toner according to the present invention, generally, the above-described toner composition, that is, a polymerizable monomer, includes magnetic iron oxide, a release agent, a plasticizer, a charge control agent, a crosslinking agent, and optionally a colorant. Components necessary for the toner and other additives such as an organic solvent, a high molecular weight polymer, a dispersing agent, etc., which are added to reduce the viscosity of the polymer produced by the polymerization reaction, are added as appropriate, and a homogenizer, ball mill, colloid mill, A monomer system uniformly dissolved or dispersed by a dispersing machine such as an ultrasonic 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.
[0156]
After granulation, stirring may be performed using a normal stirrer to such an extent that the particle state is maintained and the particles are prevented from floating and settling.
[0157]
In the production of the polymerized toner according to the present invention, known surfactants and organic or inorganic dispersants can be used as dispersion stabilizers. Among them, inorganic dispersants are unlikely to produce harmful ultra fine powders, and due to their steric hindrance. Since the dispersion stability is obtained, the stability is not easily lost even if the reaction temperature is changed, and the toner can be preferably used because it is easily washed and does not adversely affect the toner. 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 oxides such as inorganic salts, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, silica, bentonite and alumina can be mentioned.
[0158]
These inorganic dispersants may be used alone in an amount of 0.2 to 20 parts by mass with respect to 100 parts by mass of the polymerizable monomer, and 0.001 to 0.1 parts by mass for the purpose of adjusting the particle size distribution. These surfactants may be used in combination. Examples of the surfactant include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, sodium stearate, potassium stearate and the like.
[0159]
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, water-soluble sodium chloride salt is produced as a by-product. However, if water-soluble salt is present in the aqueous medium, dissolution of the polymerizable monomer in water is suppressed, and ultrafine toner is generated by emulsion polymerization. This 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.
[0160]
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 or wax to be sealed inside is precipitated by phase separation, and the encapsulation becomes 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. The polymerized toner particles are filtered, washed, and dried by a known method after the polymerization is completed, and the toner can be obtained by mixing and adhering the inorganic fine powder to the surface. Moreover, it is also one of desirable forms that a classification process is included in the manufacturing process to cut coarse powder and fine powder.
[0161]
In the toner of the present invention, a charge control agent can be mixed with toner particles and used as necessary. This technique also makes it possible to control the optimum triboelectric charge amount according to the development system.
[0162]
In the toner of the present invention, an inorganic fine powder having an average primary particle size of 4 to 80 nm is added as a fluidity improver in an amount of 0.1 to 4% by mass based on the whole toner. Inorganic fine powder is added to improve the fluidity of the toner and to make the toner base particles evenly charged. However, the inorganic chargeable powder is treated to make it hydrophobic and adjust the toner charge amount and improve the environmental stability. It is also preferable to provide such functions.
[0163]
When the average primary particle size of the inorganic fine powder is larger than 80 nm, good toner fluidity cannot be obtained, and the toner particles are likely to be non-uniformly charged, and the triboelectric chargeability under low humidity is not uniform. Therefore, problems such as an increase in fog, a decrease in image density, and a decrease in durability cannot be avoided. When the average primary particle size of the inorganic fine powder is smaller than 4 nm, the cohesiveness between the inorganic fine particles is increased, and the aggregate is not a primary particle but an aggregate having a wide particle size distribution having a strong cohesive property that is difficult to break even by crushing treatment. It is easy to behave, and image defects due to development of the aggregate, damage to the image carrier or toner carrier, and the like are likely to occur. In order to make the charge distribution of the toner particles more uniform, the average primary particle size of the inorganic fine powder is preferably 6 to 35 nm.
[0164]
The average primary particle diameter of the inorganic fine powder is a photograph of the toner magnified by a scanning electron microscope, and is further mapped with the elements contained in the inorganic fine powder by an elemental analysis means such as XMA attached to the scanning electron microscope. The method can be measured by measuring 100 or more primary particles of inorganic fine powder present on the toner surface while adhering to or separating from the toner image, and determining the number average diameter.
[0165]
The content of the inorganic fine powder can be quantified using a calibration curve prepared from a standard sample using fluorescent X-ray analysis.
[0166]
As the inorganic fine powder added to the toner of the present invention, silica, alumina, titania and the like can be used.
[0167]
The addition amount of such inorganic fine powder having an average primary particle size of 4 to 80 nm is preferably 0.1 to 4.0 parts by mass with respect to 100 parts by mass of the toner base particles, and the addition amount is 0.1. If the amount is less than part by mass, the effect is not sufficient.
[0168]
The inorganic fine powder is preferably hydrophobized from the viewpoint of improving characteristics in a high humidity environment. When the inorganic fine powder added to the toner absorbs moisture, the charge amount as the toner is remarkably lowered, and the developability and transferability are easily lowered.
[0169]
As treatment agents for hydrophobic treatment, treatment agents such as silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane compounds, silane coupling agents, other organic silicon compounds, and organic titanium compounds may be used alone or in combination. And may be processed.
[0170]
Among them, those treated with silicone oil are preferable, and more preferably, the inorganic fine powder treated with silicone oil at the same time as or after hydrophobizing treatment maintains a high charge amount of toner particles even in a high humidity environment. In addition, the selective developability may be reduced.
[0171]
The processing conditions for the inorganic fine powder include, for example, a silylation reaction as the first stage reaction to eliminate active hydrogen groups on the surface by chemical bonding, and then a hydrophobic thin film is formed on the surface with silicone oil as the second stage reaction. can do. As a usage-amount of a silylating agent, 5-50 mass parts is preferable with respect to 100 mass parts of inorganic fine powder. If it is less than 5 parts by mass, it is not sufficient to eliminate the active hydrogen groups on the surface of the inorganic fine particles, and if it exceeds 50 parts by mass, the siloxane compound produced by the reaction of the excess silylating agent serves as a paste to serve as the inorganic fine particles. Aggregation occurs and image defects are likely to occur.
[0172]
The silicone oil has a viscosity at 25 ° C. of 10 to 200,000 mm.²/ S, even 3,000-80,000mm²/ S is preferred. 10mm²If it is less than / s, the inorganic fine powder is not stable and the image quality tends to deteriorate due to heat and mechanical stress. 200,000mm²If it exceeds / s, uniform processing tends to be difficult.
[0173]
As a method for treating silicone oil, for example, an inorganic fine powder treated with a silane compound and silicone oil may be directly mixed using a mixer such as a Henschel mixer, or a method in which silicone oil is sprayed onto the inorganic fine powder. May be used. Alternatively, after dissolving or dispersing silicone oil in an appropriate solvent, inorganic fine powder may be added and mixed to remove the solvent. A method using a sprayer is more preferable in that the formation of aggregates of inorganic fine powder is relatively small.
[0174]
The treatment amount of silicone oil is 1 to 23 parts by mass, preferably 5 to 20 parts by mass with respect to 100 parts by mass of the inorganic fine powder. If the amount of the silicone oil is too small, good hydrophobicity cannot be obtained, and if it is too large, aggregation of inorganic fine particles tends to occur.
[0175]
The magnetic toner of the present invention has a primary particle size exceeding 30 nm (preferably having a specific surface area of 50 m for the purpose of improving the cleaning property)²/ G), more preferably the primary particle size is 50 nm or more (preferably the specific surface area is 30 m).²It is also one of preferable modes to add inorganic or organic fine particles close to spherical shape (less than / g). For example, spherical silica particles, spherical polymethylsilsesquioxane particles, spherical resin particles and the like are preferably used.
[0176]
The developer used in the present invention may further contain other additives, for example, a lubricant powder such as a fluororesin powder, a zinc stearate powder, a polyvinylidene fluoride powder, or a cerium oxide powder within a range that does not substantially adversely affect the developer. Abrasives such as silicon carbide powder and strontium titanate powder; or fluidity-imparting agents such as titanium oxide powder and aluminum oxide powder; anti-caking agents; and small amounts of organic and inorganic fine particles of reverse polarity as developability improvers It can also be used. These additives can also be used after hydrophobizing the surface.
[0177]
Next, the image forming method of the present invention will be specifically described with reference to the drawings.
[0178]
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 kVpp, DC voltage -700 Vdc) Then, exposure is performed by irradiating the photoconductor 100 with laser light 123 by the 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.
[0179]
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. .
[0180]
FIG. 5 is a schematic structural model diagram of an example of an image forming apparatus according to the present invention.
[0181]
This image forming apparatus is a laser printer (recording apparatus) of a development simultaneous cleaning process (cleanerless system) using a transfer type electrophotographic process. It has a process cartridge from which a cleaning unit having a cleaning member such as a cleaning blade is removed, a magnetic one-component developer is used as a developer, and the developer layer on the developer carrier and the image carrier are not in contact with each other. An example of non-contact development arranged to be as follows.
[0182]
Reference numeral 21 denotes a rotary drum type OPC photoconductor as an image carrier, which is driven to rotate at a constant peripheral speed (process speed) in the clockwise direction of an arrow.
[0183]
Reference numeral 22 denotes a charging roller as a contact charging member.
[0184]
The charging roller 22 is disposed in pressure contact with the photoreceptor 21 with a predetermined pressing force against elasticity. Reference numeral n denotes a charging contact portion that is a contact portion between the photosensitive member 21 and the charging roller 22. The charging roller 22 is rotationally driven in a facing direction (a direction opposite to the moving direction of the photosensitive member surface) at a charging contact portion n that is a contact surface with the photosensitive member 21. That is, the surface of the charging roller as the contact charging member has a speed difference with respect to the surface of the photoreceptor 21. Further, conductive fine powder is applied to the surface of the charging roller 22 so that the amount of application is uniform.
[0185]
Further, a DC voltage is applied as a charging bias from a charging bias application power source to the cored bar 22a of the charging roller 22. Here, the surface of the photosensitive member 21 is uniformly charged by a direct injection charging method to a potential substantially equal to the voltage applied to the charging roller 22.
[0186]
Reference numeral 23 denotes an exposure unit. By this exposure device, an electrostatic latent image corresponding to the target image information is formed on the surface of the rotating photoreceptor 21. Reference numeral 24 denotes a developing device. The electrostatic latent image on the surface of the photoreceptor 21 is developed as a toner image by the developing device.
[0187]
The developing device 24 is a non-contact type reversal developing device. Further, the photosensitive drum 21 is rotated at a constant peripheral speed in the forward direction and the rotational direction of the photosensitive member 21 at a developing portion a (developing region portion) which is a portion facing the photosensitive member 21. The developing sleeve 24a is coated with a thin layer of developer by an elastic blade 24c. The developer is restricted in layer thickness with respect to the developing sleeve 24a by the elastic blade 24c, and is given an electric charge. The developer coated on the developing sleeve 24a is conveyed to the developing portion a which is a portion opposite to the photosensitive member 21 and the sleeve 24a by the rotation of the sleeve 24a. A developing bias voltage is applied to the sleeve 24a from a developing bias applying power source. Then, one-component jumping development is performed between the developing sleeve 24a and the photosensitive member 21a.
[0188]
Reference numeral 25 denotes a transfer roller as contact transfer means, which is in contact with the photosensitive member 21 with a constant linear pressure to form a transfer contact portion b. A transfer material P as a recording medium is supplied to the transfer contact portion b from a paper supply unit (not shown) at a predetermined timing, and a predetermined bias voltage is applied to the transfer roller 25 from a transfer bias application power source. Thus, the toner image on the photosensitive member 21 side is sequentially transferred onto the surface of the transfer material P fed to the transfer contact portion b. Then, transfer is performed by applying a DC voltage using a roller having a constant roller resistance value. That is, the transfer material P introduced into the transfer contact portion b is nipped and conveyed by the transfer contact portion b, and the toner images formed and supported on the surface of the photoreceptor 21 on the surface side are sequentially subjected to electrostatic force. It is transferred by pressing force.
[0189]
Reference numeral 26 denotes a fixing device such as a heat fixing method. The transfer material P that has been fed to the transfer contact portion b and has received the transfer of the toner image on the photoconductor 21 side is separated from the surface of the photoconductor 21 and introduced into the fixing device 26 to receive the toner image fixing. Then, it is discharged out of the apparatus as an image formed product (print, copy).
[0190]
In this printer, the cleaning unit is removed, and residual toner remaining on the surface of the photoconductor 21 after the transfer of the toner image to the transfer material P is not removed by the cleaner, and the charging unit n is rotated as the photoconductor 21 rotates. To the developing section a, and the development device 24 performs simultaneous cleaning (collection) of development.
[0191]
Reference numeral 27 denotes an image forming apparatus and a process cartridge which are detachable from the printer main body. In this printer, the three process devices of the photosensitive member 21, the charging roller 22, and the developing device 24 are collectively configured as a process cartridge that is detachable from the printer body. The combination of process devices to be processed into a process cartridge is not limited to the above, and is arbitrary. For example, a combination of a developing device and a photoreceptor, a combination of a developing device and a charging roller, a combination of a developing device, a photoreceptor and a charging roller, and the like can be considered. Reference numeral 28 denotes a process cartridge attaching / detaching guide / holding member.
[0192]
【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. In addition, all the parts in the following mixing | blending are mass parts.
[0193]
(Sulfur-containing resin production example 1)
In a pressurizable reaction vessel equipped with a reflux tube, a stirrer, a thermometer, a nitrogen introduction tube, a dropping device and a decompression device, 250 parts of methanol as a solvent, 150 parts of 2-butanone and 100 parts of 2-propanol, styrene as a monomer 84 parts, 13 parts of 2-ethylhexyl acrylate, and 3 parts of 2-acrylamido-2-methylpropanesulfonic acid were added and heated to reflux temperature with stirring. A solution prepared by diluting 4 parts of 2,2′-azobis (2-methylbutyronitrile) as a polymerization initiator with 20 parts of 2-butanone was added dropwise over 30 minutes, and stirring was continued for 5 hours. A solution prepared by diluting 0.4 part of '-azobis (2-methylbutyronitrile) with 20 parts of 2-butanone was added dropwise over 30 minutes, and the mixture was further stirred for 5 hours to complete the polymerization.
[0194]
The polymer obtained after the polymerization solvent was distilled off under reduced pressure was coarsely pulverized to 100 μm or less using a cutter mill equipped with a 100 μm screen. The obtained sulfur-containing resin had a Tg of about 69 ° C. The obtained resin is referred to as a sulfur-containing resin 1.
[0195]
(Production Examples 2 to 5 of sulfur-containing resin)
In the production example 1 of the sulfur-containing resin, the monomer used was changed to the contents shown in Table 1, and the sulfur-containing resin was subjected to the same method except that the molecular weight was controlled by adjusting the amount of the polymerization initiator or the polymerization temperature / time. Resins 2-5 were produced.
[0196]
(Sulfur-containing resin comparative production example 1)
In Production Example 1 of sulfur-containing resin, Resin 1 was produced by the same method except that the monomer used was changed to the contents shown in Table 1.
[0197]
[Table 1]

[0198]
(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.
[0199]
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 obtain a slurry solution of magnetic particles. After washing and filtering, the water-containing slurry was once taken out. At this time, a small amount of water-containing sample was collected and the water content was measured. Next, the 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-C₆H₁₃Si (OCH_Three)_Three) Was added to 100 parts of magnetic iron oxide (the amount of magnetic particles 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 magnetic particles were washed, filtered and dried by a conventional method, and then the slightly agglomerated particles were pulverized to obtain hydrophobic iron oxide 1. The physical properties of the obtained magnetic powder are shown in Table 2 together with those of the magnetic powder obtained in the following production examples.
[0200]
(Production Example 2 of hydrophobic iron oxide)
After re-dispersing the magnetic powder 1 obtained in Production Example 1 of the magnetic powder in another aqueous medium, the pH of the re-dispersed liquid is adjusted to about 6, and the silane coupling agent is sufficiently stirred. (N-C_FourH₉Si (OCH_Three)_Three) Was added to 100 parts of the magnetic powder 1 to perform a coupling treatment. The obtained magnetic particle slurry was washed, filtered and dried by a conventional method, and then the agglomerated particles were pulverized to obtain hydrophobic iron oxide 2.
[0201]
(Production Example 3 of hydrophobic iron oxide)
After re-dispersing the magnetic powder 1 obtained in Production Example 1 of the magnetic powder in another aqueous medium, the pH of the re-dispersed liquid is adjusted to about 6, and the silane coupling agent is sufficiently stirred. (N-C_FourH₉Si (OCH_Three)_Three) Was added to 100 parts of the magnetic powder 1 and subjected to a coupling treatment. The obtained magnetic particle slurry was washed, filtered and dried by a conventional method, and then the agglomerated particles were pulverized to obtain hydrophobic iron oxide 3.
[0202]
(Production Example 4 of Hydrophobic Iron Oxide)
After re-dispersing the magnetic powder 1 obtained in Production Example 1 of the magnetic powder in another aqueous medium, the pH of the re-dispersed liquid is adjusted to about 6, and the silane coupling agent is sufficiently stirred. (N-C_TenH_{twenty one}Si (OCH_Three)_Three) Was added to 100 parts of magnetic powder 1 and subjected to coupling treatment. The obtained magnetic particle slurry was washed, filtered, and dried by a conventional method, and then the agglomerated particles were pulverized to obtain hydrophobic iron oxide 4.
[0203]
(Production Example 5 of hydrophobic iron oxide)
After re-dispersing the magnetic powder 1 obtained in Production Example 1 of the magnetic powder in another aqueous medium, the pH of the re-dispersed liquid is adjusted to about 6, and the silane coupling agent is sufficiently stirred. (N-C_TenH_{twenty one}Si (OCH_Three)_Three) Was added in an amount of 3.0 parts to 100 parts of the magnetic powder 1 to perform a coupling treatment. The obtained magnetic particle slurry was washed, filtered, and dried by a conventional method, and then the agglomerated particles were pulverized to obtain hydrophobic iron oxide 4.
[0204]
(Production Example 6 of hydrophobic iron oxide)
Hydrophobic iron oxide 6 was obtained in the same manner as in Production Example 1 of hydrophobic iron oxide, except that the amount of ferrous sulfate aqueous solution during the synthesis of magnetic iron oxide particles was increased and the amount of air blown was decreased.
[0205]
(Production Example 7 of hydrophobic iron oxide)
After re-dispersing the magnetic powder 1 obtained in Production Example 1 of the magnetic powder in another aqueous medium, the pH of the re-dispersed liquid is adjusted to about 6, and the silane coupling agent is sufficiently stirred. (N-C_TenH_{twenty one}Si (OCH_Three)_Three) Was added to 100 parts of magnetic powder 1 and subjected to coupling treatment. The obtained magnetic particle slurry was washed, filtered and dried by a conventional method, and then the agglomerated particles were pulverized to obtain hydrophobic iron oxide 7.
[0206]
(Production Example 8 of hydrophobic iron oxide)
The oxidation reaction proceeds in the same manner as in Production Example 1 of hydrophobic iron oxide, and the magnetic particles generated after the oxidation reaction are washed, filtered and dried, and the aggregated particles are crushed and then 100 mm²5.0 parts of dimethyl silicone oil of / s (cSt) was added and mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.) to obtain hydrophobic iron oxide 8.
[0207]
(Iron oxide production example 1)
The oxidation reaction was advanced in the same manner as in Production Example 1 of hydrophobic iron oxide, and the magnetic particles produced after the oxidation reaction were washed, filtered and dried, and the aggregated particles were crushed to obtain iron oxide 1.
[0208]
[Table 2]

[0209]
(Conductive fine powder 1)
Fine particle zinc oxide with a volume average particle size of 3.7 μm, particle size distribution of less than 0.5 μm is 6.6% by volume, and more than 5 μm is 8% by number (resistance 80 Ω · cm, oxidation with primary particle size of 0.1 to 0.3 μm) Conductive fine powder 1 is obtained by granulating zinc primary particles by pressure, white).
[0210]
When the conductive fine powder 1 was observed with a scanning electron microscope at 3000 times and 30,000 times, it was composed of 0.1 to 0.3 μm primary particles of zinc oxide and 1 to 10 μm aggregates.
[0211]
In accordance with the exposure light wavelength 740 nm of the laser used for image exposure in the image forming apparatus of Example 1, using a light source with a wavelength of 740 nm, the transmittance in this wavelength region is measured using a 310T transmission densitometer made by X-Rite. When measured, the transmittance of the conductive fine powder 1 was approximately 35%.
[0212]
(Conductive fine powder 2)
Fine particles of zinc oxide (resistance: 1500 Ω · resistance) obtained by air classification of conductive fine particles 1 and having a volume average particle size of 2.4 μm, a particle size distribution of less than 0.5 μm is 4.1% by volume, and more than 5 μm is 1% by number. cm, transmittance 35%) is defined as conductive fine powder 2.
[0213]
When the conductive fine powder 2 was observed with a scanning electron microscope, it was composed of zinc oxide primary particles of 0.1 to 0.3 μm and aggregates of 1 to 5 μm, but compared with the conductive fine powder 1. Then, the primary particles were decreased.
[0214]
(Conductive fine powder 3)
Finely divided zinc oxide (resistance: 1500 Ω · cm, with a volume average particle size of 1.5 μm, a particle size distribution of less than 0.5 μm is 35% by volume and 0 μm is greater than 5 μm, obtained by air classification of the conductive fine particles 1 Conductivity fine powder 3 is defined as a transmittance of 35%).
[0215]
When this conductive fine powder 3 was observed with a scanning electron microscope, it was composed of 0.1 to 0.3 μm zinc oxide primary particles and 1 to 4 μm aggregates. Then, the primary particles increased.
[0216]
(Conductive fine powder 4)
Fine particle zinc oxide with a volume average particle size of 0.3 μm, particle size distribution of less than 0.5 μm is 80% by volume, and more than 5 μm is 0% by number (resistance 100 Ω · cm, primary particle size 0.1 to 0.3 μm, white, transmission The rate is 35% and the purity is 99% or more).
[0217]
When the conductive fine powder 4 was observed with a scanning electron microscope, it was composed of 0.1 to 0.3 μm zinc oxide primary particles with few aggregates.
[0218]
(Conductive fine powder 5)
After removing coarse particles of aluminum borate with a volume average particle size of 2.8 μm surface-treated with tin oxide / antimony by air classification, fine particles are removed by dispersing in an aqueous system and repeating filtration to remove the volume average particle size. As a result, grayish white conductive particles having a particle size distribution of 3.2 μm, less than 0.5 μm in 0.4% by volume, and more than 5 μm in 1% by number were obtained. This is designated as conductive fine powder 5.
[0219]
Table 3 shows typical physical property values of the conductive fine powders 1 to 5.
[0220]
[Table 3]

[0221]
(Production Example 1 of Magnetic Toner Particles)
0.1 mol / liter-Na in 710 parts of ion-exchanged water_ThreePO_FourAfter 450 parts of an aqueous solution was added and heated to 60 ° C., 1N hydrochloric acid was added so that the pH after addition of calcium chloride was 5.5, and 1.0 mol / liter-CaCl was added.₂An aqueous medium containing calcium phosphate was obtained by gradually adding 67.7 parts of an aqueous solution.
[0222]
・ 80 parts of styrene
・ N-butyl acrylate 20 parts
・ Sulfur-containing resin 1 5 parts
・ 90 parts of hydrophobic iron oxide 1
The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.).
[0223]
This monomer composition was heated to 60 ° C., and 6 parts of an ester wax mainly composed of behenyl behenate (maximum endothermic peak value of 72 ° C. in DSC) was added and mixed therewith. , 2′-azobis (2,4-dimethylvaleronitrile) [t_1/2= 140 minutes at 60 ° C] 4 parts and dimethyl-2,2'-azobisisobutyrate [t_1/2= 270 minutes, at 60 ° C; t_1/2= 80 minutes, at 80 ° C.] 2 parts were dissolved.
[0224]
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 7 hours while stirring with a paddle stirring blade. Thereafter, the liquid temperature was raised to 80 ° C., and stirring was further continued for 3 hours. After completion of the reaction, the suspension was cooled, hydrochloric acid was added to dissolve the calcium phosphate salt, filtered, washed with water, dried at 50 ° C. under a pressure of 0.3 kPa (2.3 torr) for 10 days, and the weight average particle size. 7.0 μm of magnetic toner particles 1 were obtained.
[0225]
(Production example 2 of magnetic toner particles)
Magnetic toner particles 2 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that 4 parts of sulfur-containing resin 2 was used instead of sulfur-containing resin 1.
[0226]
(Production Example 3 of Magnetic Toner Particles)
Magnetic toner particles 3 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that the amount of sulfur-containing resin 1 added was changed to 3.5 parts.
[0227]
(Magnetic toner particle production example 4)
Magnetic toner particles 4 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that the amount of sulfur-containing resin 1 added was changed to 2 parts.
[0228]
(Magnetic toner particle production example 5)
Magnetic toner particles 5 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that hydrophobic iron oxide 2 was used instead of hydrophobic iron oxide 1.
[0229]
(Magnetic toner particle production example 6)
Magnetic toner particles 6 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that hydrophobic iron oxide 3 was used instead of hydrophobic iron oxide 1.
[0230]
(Production Example 7 of magnetic toner particles)
Magnetic toner particles 7 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that hydrophobic iron oxide 4 was used instead of hydrophobic iron oxide 1.
[0231]
(Production Example 8 of Magnetic Toner Particles)
Magnetic toner particles 8 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that hydrophobic iron oxide 5 was used instead of hydrophobic iron oxide 1.
[0232]
(Production Example 9 of magnetic toner particles)
Magnetic toner particles 9 were obtained in the same manner as in magnetic toner particle production example 1 except that 9 parts of sulfur-containing resin 3 was used instead of sulfur-containing resin 1.
[0233]
(Production Example 10 of Magnetic Toner Particles)
Magnetic toner particles 10 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that 5 parts of sulfur-containing resin 4 was used instead of sulfur-containing resin 1.
[0234]
(Production Example 11 of Magnetic Toner Particles)
Magnetic toner particles 11 were obtained in the same manner as in magnetic toner particle production example 1 except that 5 parts of sulfur-containing resin 3 was used instead of sulfur-containing resin 1.
[0235]
(Production Example 12 of magnetic toner particles)
Magnetic toner particles 12 were obtained in the same manner as in Production Example 1 of magnetic toner particles except that 2 parts of sulfur-containing resin 5 was used instead of sulfur-containing resin 1.
[0236]
(Manufacturing Example 13 of Magnetic Toner Particles)
In Production Example 1 of magnetic toner particles, Na_ThreePO_FourAmount of aqueous solution and CaCl₂Magnetic toner particles 13 were obtained by the same method except that the amount of the aqueous solution was adjusted to increase the amount of calcium phosphate in the aqueous medium.
[0237]
(Production Example 14 of Magnetic Toner Particles)
In Production Example 1 of magnetic toner particles, Na_ThreePO_FourAmount of aqueous solution and CaCl₂Magnetic toner particles 14 were obtained by the same method except that the amount of calcium phosphate in the aqueous medium was reduced by adjusting the amount of aqueous solution added.
[0238]
(Production Example 15 of magnetic toner particles)
Magnetic toner particles 15 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that the mixture was stirred for 10 minutes at 8,000 rpm with a TK homomixer (Special Machine Industries Co., Ltd.) and granulated. .
[0239]
(Production Example 16 of magnetic toner particles)
Magnetic toner particles 16 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that the mixture was stirred for 8 minutes at 7,000 rpm with a TK homomixer (Special Machine Industries Co., Ltd.) and granulated. .
[0240]
(Production Example 17 of magnetic toner particles)
Magnetic toner particles 17 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that the number of parts of hydrophobic iron oxide 1 was changed to 60 parts.
[0241]
(Production Example 18 of magnetic toner particles)
Magnetic toner particles 18 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that 120 parts of hydrophobic iron oxide 6 was used instead of hydrophobic iron oxide 1.
[0242]
(Manufacturing Example 19 of Magnetic Toner Particles)
Magnetic toner particles 19 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that the number of waxes was changed to 1 part.
[0243]
(Manufacturing Example 20 of Magnetic Toner Particles)
Magnetic toner particles 20 were obtained in the same manner as in Production Example 1 of magnetic toner particles except that the number of waxes was changed to 35 parts.
[0244]
(Manufacturing Example 21 of Magnetic Toner Particles)
Magnetic toner particles 21 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that the ester wax was replaced with a wax mainly composed of polyethylene (maximum value of endothermic peak in DSC 110 ° C.).
[0245]
(Method for producing treated wax 1)
After adding 3 parts of dicumyl peroxide as a polymerization initiator to 22 parts by mass of a styrene monomer, the mixture was dropped into 75 parts of heated and melted paraffin wax having a melting point of 79 ° C. with stirring and reacted for 4 hours. Treated wax 1 was obtained. The softening point of the treated wax 1 was 79.4 ° C.
[0246]
(Manufacturing Example 22 of Magnetic Toner Particles)
1.0 mol / liter-Na in 292 parts of ion-exchanged water_ThreePO_FourAfter 46 parts of the aqueous solution was added and heated to 60 ° C., 1N hydrochloric acid was added so that the pH after addition of calcium chloride was 5.5, and 1.0 mol / liter-CaCl was added.₂67 parts of the aqueous solution was gradually added to obtain an aqueous medium containing a calcium phosphate salt, and 0.1 part of sodium dodecylbenzenesulfonate was added thereto.
[0247]
・ 80 parts of styrene
・ N-butyl acrylate 20 parts
・ Sulfur-containing resin 1 5 parts
・ 90 parts of hydrophobic iron oxide 1
The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Koki Co., Ltd.).
[0248]
This monomer composition was heated to 60 ° C., 6 parts of treated wax 1 was added and mixed therewith, and 5 parts of benzoyl peroxide was dissolved therein as a polymerization initiator.
[0249]
The polymerizable monomer system is charged into the aqueous medium, and 60 ° C., N₂In an atmosphere, the mixture was stirred at 15,000 rpm for 10 minutes with CLEARMIX 0.8S (M Technique Co., Ltd.) and granulated. Then, while stirring with a paddle stirring blade, the temperature was raised to 80 ° C. in 30 minutes, the reaction was carried out at 80 ° C. for 4 hours, and 4 parts of anhydrous sodium carbonate was added to the system.
[0250]
Thereafter, the system was depressurized to -50 kPa and distilled for 4 hours. After completion of the distillation, the suspension was cooled, and the alkaline suspension was filtered. The toner particles were then washed three times with water to obtain water-containing magnetic toner particles.
[0251]
Thereafter, the water-containing magnetic toner particles were added to 1000 parts of dilute hydrochloric acid (pH 1.0) at room temperature while stirring, and stirring was continued for 3 hours. Further, this suspension was filtered, and the toner was washed with water five times. Thereafter, the water-containing magnetic toner was vacuum-dried at 50 ° C. for 5 days under a pressure of 0.3 kPa (2.3 torr) to obtain magnetic toner particles 22 having a weight average particle diameter of 6.0 μm.
[0252]
(Comparative Production Example 1 of Magnetic Toner Particles)
Magnetic toner particles 23 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that hydrophobic iron oxide 7 was used instead of hydrophobic iron oxide 1.
[0253]
(Comparative Production Example 2 of Magnetic Toner Particles)
・ Styrene / n-butyl acrylate copolymer (mass ratio 80/20) 100 parts
(Mn = 24300 Mw / Mn = 3.0)
・ Sulfur-containing resin 1 5 parts
・ 90 parts of iron oxide 1
-6 parts of ester wax used in Production Example 1
The above materials are mixed in a blender, melt kneaded with a biaxial extruder heated to 90 ° 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 24 having a weight average particle diameter of 7.9 μm.
[0254]
(Comparative Production Example 3 of Magnetic Toner Particles)
A 500 ml four-necked flask equipped with a stirring blade and a condenser is charged with 3.0 parts of methyl vinyl ether-maleic anhydride copolymer (molecular weight 40000, manufactured by GAF) and 100 parts of methanol, and stirred at 60 ° C. for 2 hours. Then, a methyl vinyl ether-maleic anhydride copolymer was completely dissolved to prepare a dispersion stabilizer. Then, it cooled to room temperature and prepared the following.
・ 80 parts of styrene
・ 40 parts of butyl acrylate
・ 0.06 parts of t-dodecyl mercaptan
・ Sulfur-containing resin 1 5 parts
[0255]
While stirring these, the inside of the flask was purged with nitrogen gas, and stirring (1000 rpm) was continued gently for about 1 hour until the residual oxygen concentration in the system reached 0.1%. Thereafter, the temperature of the thermostatic bath was raised to 60 ° C., and then 0.2 part of 2,2′-azobisisobutyronitrile was used as an initiator, and polymerization was continued for 24 hours. After heating for 15 minutes, the liquid started to become cloudy and became a cloudy and stable dispersion after 24 hours of polymerization. As a result of partial sampling and measurement by gas chromatography using an internal standard method, it was confirmed that the polymerization rate was 95%. When the obtained dispersion was cooled and centrifuged at 2000 rpm in a centrifuge, the polymer particles were completely precipitated and the upper liquid was transparent. The supernatant was removed, and 200 parts of methanol was newly added, followed by stirring and washing for 1 hour. The operation of centrifuging and washing with methanol was repeatedly filtered. The material separated was dried under reduced pressure at 50 ° C. for 24 hours to obtain white powdery resin particles in a yield of 90%.
[0256]
Next, the treatment of incorporating 15 parts of hydrophobized iron oxide 1 into the toner with a hybridizer (Nara Machinery Co., Ltd.) was repeated 6 times with respect to 100 parts of the obtained particles. Next, 100 parts of colored resin particles were dispersed in 1000 parts of methanol and heated with stirring at 50 ° C. for 1 hour. Thereafter, the dispersion was cooled to room temperature and separated to obtain a colored resin particle dispersion.
[0257]
Subsequently, the sulfur-containing resin 1 was dissolved in a toluene solvent, and 0.5 part was added to 100 parts of the colored resin particles. After stirring for 1 hour, the mixture was filtered and dried to obtain magnetic toner particles 25.
[0258]
(Comparative Production Example 4 of Magnetic Toner Particles)
In magnetic toner particle production example 1, magnetic toner particles 26 were produced in the same manner except that sulfur-containing resin 1 was replaced with resin 1.
[0259]
(Comparative Production Example 5 of Magnetic Toner Particles)
Magnetic toner particles 27 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that 0.03 part of sulfur-containing resin 1 was used instead of sulfur-containing resin 1.
[0260]
(Comparative Production Example 6 of Magnetic Toner Particles)
Magnetic toner particles 28 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that 23 parts of sulfur-containing resin 1 was used instead of sulfur-containing resin 1.
[0261]
(Comparative Production Example 7 of Magnetic Toner Particles)
Magnetic toner particles 29 were obtained in the same manner as in Production Example 1 of magnetic toner particles except that the number of parts of wax was changed to 45 parts.
[0262]
(Comparative Production Example 8 of Magnetic Toner Particles)
Magnetic toner particles 30 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that the ester wax was replaced with wax mainly composed of paraffin (maximum value of endothermic peak in DSC: 35 ° C.).
[0263]
(Comparative Production Example 9 of Magnetic Toner Particles)
Magnetic toner particles 31 were obtained in the same manner as in Production Example 1 of magnetic toner particles, except that hydrophobic iron oxide 8 was used instead of hydrophobic iron oxide 1.
[0264]
(Comparative Production Example 10 of Magnetic Toner Particles)
・ Styrene / n-butyl acrylate copolymer (mass ratio 80/20)
(Mn = 31500 Mw / Mn = 2.8) 100 parts
・ Sulfur-containing resin 1 5 parts
・ 90 parts of iron oxide 1
・ Processing wax 1 6 parts
The above materials are mixed in a blender, melt-kneaded with a twin screw extruder heated to 120 ° C., the cooled mixture is coarsely pulverized with a hammer mill, and then the coarsely pulverized product is finely pulverized with a jet mill. Air pulverization with the pulverized product gave magnetic toner particles 32 having a weight average particle size of 7.3 μm.
[0265]
  (Comparative Production Example 11 of Magnetic Toner Particles)
  Magnetic toner particles32In the production of toner particles, toner particles were obtained by the same method except that the coarsely pulverized product was finely pulverized with a turbo mill (manufactured by Turbo Kogyo Co., Ltd.). Thereafter, magnetic toner particles 33 subjected to spheroidizing treatment having a weight average particle diameter of 7.2 μm were obtained using an impact surface treatment apparatus (treatment temperature: 50 ° C., rotary treatment blade peripheral speed: 90 m / sec.).
[0266]
Example 1
100 parts of the magnetic toner particles 1 were treated with hexamethyldisilazane on silica having a primary particle size of 12 nm and then with silicone oil, and the BET value after treatment was 140 m.²A magnetic toner 1 was prepared by mixing 1 part of / g hydrophobic silica fine powder with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.).
[0267]
  Examples 2 to 19, Reference Example 20, Example 21
  The hydrophobic silica fine powder used in Example 1 is 1.5 parts with respect to 100 parts of magnetic toner particles in Example 13, and the magnetic toner particles in Example 14 with respect to 100 parts of magnetic toner particles 2 to 21. Magnetic toners 2 to 21 were prepared by mixing 0.6 parts with respect to 100 parts, 0.8 parts with respect to 100 parts of magnetic toner particles in Example 17, and 1 part other than that.
[0268]
Example 22
Magnetic toner 22 was prepared by mixing 1.2 parts of the hydrophobic silica fine powder used in Example 1 with 100 parts of magnetic toner particles 22.
[0269]
Examples 23-27
Magnetic toners 23 to 27 were prepared by mixing 1 part of the hydrophobic silica fine powder used in Example 1 and 2 parts of the conductive fine powders 1 to 5 with respect to 100 parts of the magnetic toner particles 1.
[0270]
Example 28
Magnetic toner 28 was prepared by mixing 1.2 parts of the hydrophobic silica fine powder used in Example 1 and 2 parts of the conductive fine powder 1 with 100 parts of the magnetic toner particles 22.
[0271]
Comparative Examples 1-9
Comparative magnetic toners 1 to 9 were prepared by mixing 100 parts of the magnetic toner particles 23 to 31 with 1 part of the hydrophobic silica fine powder used in Example 1.
[0272]
Comparative Example 10
The comparative magnetic toner 12 was prepared by mixing 1.2 parts of the hydrophobic silica fine powder used in Example 1 with 100 parts of the magnetic toner particles 32.
[0273]
Comparative Example 11
Comparative magnetic toner 13 was prepared by mixing 1.2 parts of hydrophobic silica fine powder used in Example 1 with 100 parts of magnetic toner particles 33.
[0274]
Comparative Example 12
Magnetic toner 14 for comparison was prepared by mixing 1.2 parts of hydrophobic silica fine powder used in Example 1 and 2 parts of conductive fine powder 1 with 100 parts of magnetic toner particles 32.
[0275]
Comparative Example 13
Magnetic toner 15 for comparison was prepared by mixing 1.2 parts of hydrophobic silica fine powder used in Example 1 and 2 parts of conductive fine powder 1 with 100 parts of magnetic toner particles 33.
[0276]
A method for measuring the specific gravity distribution in the present invention will be described.
[0277]
In the present invention, the dry specific gravity is measured in order to determine the standard of the specific gravity distribution. The dry specific gravity was measured using a dry density meter Accupic 1330 (manufactured by Shimadzu Corporation).
[0278]
Next, the value of the dry specific gravity is (A), and the value of (A) × 0.900, (A) × 0.925, (A ) × 0.950, (A) × 0.975, (A) × 1.000, and (A) × 1.025 to prepare 6 levels of aqueous solution. About 0.01% of nonionic surfactant (contaminone) was added to each aqueous solution. 100 mg of toner precisely weighed in 50 g of this aqueous solution was added, and it was allowed to stand for 24 hours for separation after confirming that it was dispersed by ultrasonic dispersion into primary particles using a Coulter counter or an optical microscope. After that, the process of decanting the supernatant, adding ion-exchanged water and washing it was repeated three times, the precipitated toner was vacuum dried, and the weight of the dried toner was precisely weighed.
[0279]
In the present invention, utilizing the fact that the toner that settles in the aqueous solution of each specific gravity has a specific gravity higher than that of the aqueous solution, as described above, the distribution of specific gravity is determined from the difference in the weight ratio of the toner that settles in the aqueous solution having an adjacent specific gravity. Asked.
[0280]
The physical properties of the obtained magnetic toner are shown in Tables 4 and 5.
[0281]
[Table 4]

[0282]
[Table 5]

[0283]
(Photoreceptor Production Example 1)
As a photoreceptor, a 30φ Al cylinder was used as a base. To this, layers having a structure as shown in FIG. 3 were sequentially laminated by dip coating to produce 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 a dispersion of an azo pigment having absorption in a long wavelength region in a butyral resin. Film thickness 0.6 μm.
(4) Charge transport layer: Mainly composed of a hole-transporting triphenylamine compound dissolved in polycarbonate resin (molecular weight 20,000 by Ostwald viscosity method) at a mass ratio of 8:10, and further polytetrafluoroethylene powder ( 10% by weight of the total solid content was added and dispersed uniformly. Film thickness 25 μm. The contact angle with water was 95 degrees.
[0284]
In addition, the measurement of the contact angle used pure water, and the apparatus used Kyowa Interface Science Co., Ltd. and the contact angle meter CA-X type.
[0285]
<Example A1>
As the image forming apparatus, LBP-1760 (manufactured by Canon Inc.) was remodeled and the one schematically shown in FIG. 1 was used.
[0286]
As the electrostatic charge image carrier, the organic photoreceptor (OPC) drum of Production Example 1 of the photoreceptor was used. A rubber roller charger in which conductive carbon is dispersed as a primary charging member and coated with a nylon resin is brought into contact with this photosensitive member at a linear pressure of 58.8 N / m (60 g / cm), and the DC voltage is set to −700 Vdc. A bias superimposed with an alternating voltage of 1.2 kVpp is applied to uniformly charge the surface of the photoconductor. 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 = −180 V.
[0287]
The gap between the photosensitive drum and the developing sleeve is 180 μm, and the toner carrying member has a layer thickness of about 7 μm and a JIS center line average roughness (Ra) of 1.0 μm. Using a developing sleeve formed on a 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 of 1.0 mm urethane rubber blade of 29.4 N / m (30 g / cm). The contact was made with linear pressure.
100 parts of phenolic resin
90 parts of graphite (particle size approx. 7μm)
10 parts of carbon black
[0288]
Next, a DC bias component Vdc = −500 V, an overlapping AC bias component Vpp = 900 V, and f = 2100 Hz were used as the developing bias. The peripheral speed of the developing sleeve was 110% (103 mm / sec) in the forward direction with respect to the peripheral speed of the photosensitive member (94 mm / sec).
[0289]
Further, a transfer roller as shown in FIG. 4 (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, contact pressure of 59 N / m (60 g / cm)) is 105% (99 mm in the forward direction) with respect to the circumferential speed of the photoreceptor (94 mm / sec) in FIG. / Sec), and the transfer bias was DC 1.4 kV.
[0290]
As a fixing method, there was used a fixing device of LBP-1760 which does not have an oil application function and which is fixed by heating and pressing with a heater through a film. At this time, a pressure roller having a fluororesin surface layer was used, and the diameter of the roller was 30 mm. The fixing temperature was set to 170 ° C. and the nip width was set to 7 mm.
[0291]
First, the magnetic toner obtained in Example 1 was used as a magnetic toner, and 8000 images were printed in a continuous mode in a horizontal line image with a printing area ratio of 4% in a normal temperature and normal humidity (23 ° C., 50% RH) environment. And an endurance test were performed to evaluate image density, image fog, and transferability. 75g / m as transfer material²Paper was used. The image was evaluated according to the following evaluation criteria. In addition, toner consumption was also calculated.
[0292]
In addition, a 8000-sheet image print test was performed in a high temperature and high humidity (30 ° C., 80% RH) environment and a low temperature and low humidity (15 ° C., 10% RH) environment. In addition, the image density, image fogging, and fine line reproducibility were evaluated under low temperature and low humidity conditions for the transferability and solid image density uniformity.
[0293]
In any environment, the image density was high from beginning to end, there was little fogging, the density uniformity of the solid image under high temperature and high humidity was good, and the fine line reproducibility under low temperature and low humidity was also excellent. .
[0294]
The results are shown in Table 6.
[0295]
Image evaluation was performed as follows.
[0296]
(1) Image density
Ordinary paper for ordinary copying machines (75 g / m²) Was used to output a solid black image after the completion of the image printing test 8000 sheets, and the density was measured for evaluation. The image density was measured by using a “Macbeth reflection densitometer RD918” (manufactured by Macbeth Co., Ltd.) to measure the relative density with respect to an image of a white background portion having a document density of 0.00.
A: Very good 1.40 or more
B: Good 1.35 or more and less than 1.40
C: No problem in practical use 1.00 or more and less than 1.35
D: Somewhat difficult, less than 1.00
[0297]
(2) Image fog
The fog density (%) was calculated from the difference between the whiteness of the white background portion of the printout image and the whiteness of the transfer paper measured by “REFLECTMETER MODEL TC-6DS” (manufactured by Tokyo Denshoku Co., Ltd.), and the image fogging was evaluated. . A green filter was used as the filter.
A: Very good, less than 1.0%
B: Good 1.0% or more to less than 2.0%
C: No problem in practical use 2.0% or more to less than 3.0%
D: Somewhat difficult 3.0% or more
[0298]
(3) Transferability
The transfer efficiency is determined by tapering the transfer residual toner on the photoconductor after the solid black image is transferred with a Mylar tape and pasting it on the paper. The Macbeth density value is C. When the Macbeth concentration of the tape was affixed to D and the Macbeth concentration of the Mylar tape affixed on unused paper was assumed to be E, it was approximately calculated by the following formula.
[0299]
[Expression 4]

If the transfer efficiency is 90% or more, the image has no problem.
A: Very good (over 97%)
B: Good (less than 94 to 97%)
C: Practical use possible (less than 90-94%)
D: Not practical (less than 90%)
[0300]
(4) Solid image density uniformity
The density uniformity of the solid image was evaluated according to the following criteria based on the difference between the highest transmission density portion and the lowest transmission portion on the image after 8000 sheets were output.
A: Very good, less than 0.03
B: Good 0.03 or more and less than 0.06
C: No problem in practical use 0.06 or more and less than 0.15
D: Somewhat difficult 0.15 or more
[0301]
(5) Fine line reproducibility
In the present invention, fine line reproducibility was measured by the following method. That is, the latent image is laser-exposed so as to have a width of 100 μm, and the obtained fixed image is used as a measurement sample. Measure. At this time, since the measurement position of the line width is uneven in the width direction of the fine line image of the toner, the average line width of the unevenness is used as the measurement point. From this, the fine line reproducibility value (%) is calculated by the following equation.
[0302]
[Equation 5]

A: Very good, less than 105
B: Good 105 or more, less than 110
C: No problem in practical use 110 or more, less than 120
D: Somewhat difficult 120 or more
[0303]
  <Example A2To A19, Reference Example A20, Example A21~ A28>
  As the magnetic toner, the magnetic toner obtained in Examples 2 to 28 was used, and an image formation test and durability evaluation were performed by the same image forming method as in Example A1. As a result, there was no problem in the initial image characteristics, and no problem was obtained until the end of 8000 sheets. In Example A19, when the durability exceeded 5000 sheets under low temperature and low humidity, the back side of the image was slightly stained.
[0304]
The results are shown in Table 6.
[0305]
<Comparative Examples A1 to A13>
As the magnetic toner, the magnetic toner obtained in Comparative Examples 1 to 13 was used, and an image formation test and durability evaluation were performed by the same image forming method as in Example A1. As a result, the image characteristics were not good from the beginning, and an image defect occurred along with the durability test.
[0306]
The results are shown in Table 6.
[0307]
[Table 6]

[0308]
The toner of the present invention is also applicable to a cleanerless image forming method or a simultaneous development image forming method. In the present invention, an image forming apparatus as shown in FIG. 5 is used.
[0309]
Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited thereto.
[0310]
First, a production example of a photoconductor as an image carrier used in an embodiment of the present invention will be described.
[0311]
(Photoreceptor Production Example 2)
The photoconductor is a photoconductor using an organic photoconductive substance for negative charging (hereinafter referred to as OPC photoconductor), and an aluminum cylinder having a diameter of 30 mm was used as a base. To this, layers having a structure as shown in FIG. 6 were sequentially laminated by dip coating to produce a photoreceptor.
[0312]
The first layer is a conductive layer, and is provided with a conductive particle-dispersed resin layer (tin oxide) having a thickness of about 20 μm, which is provided in order to smooth out defects in the aluminum cylinder and prevent the occurrence of moire due to reflection of laser exposure. And mainly titanium oxide powder dispersed in a phenol resin.
[0313]
The second layer is a positive charge injection prevention layer (undercoat layer), which plays a role in preventing the positive charge injected from the aluminum support from canceling the negative charge charged on the surface of the photoreceptor. 10 by nylon⁶This is a medium resistance layer having a thickness of about 1 μm, the resistance of which is adjusted to about Ω · cm.
[0314]
The third layer is a charge generation layer, which is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a butyral resin, and generates positive and negative charge pairs upon receiving laser exposure.
[0315]
The fourth layer is a charge transport layer, which is a layer having a thickness of about 25 μm in which a hydrazone compound is dispersed in a polycarbonate resin, and is a P-type semiconductor. Accordingly, negative charges charged on the surface of the photoreceptor cannot move through this layer, and only positive charges generated in the charge generation layer can be transported to the surface of the photoreceptor. The fifth layer is a charge injection layer, in which conductive tin oxide ultrafine particles and tetrafluoroethylene resin particles having a particle diameter of about 0.25 μm are dispersed in a photocurable acrylic resin. Specifically, tin oxide particles having a particle diameter of about 0.03 μm, doped with antimony and reduced in resistance, are 100% by mass with respect to the resin, further 20% by mass of tetrafluoroethylene resin particles, and 1.2% of the dispersant. Dispersed in mass%. The coating solution thus prepared was applied to a thickness of about 2.5 μm by a spray coating method to form a charge injection layer. The resistance value of the surface of the obtained photoreceptor is 5 × 10¹²The contact angle with respect to water on the surface of the photoreceptor was 102 degrees.
[0316]
Next, a manufacturing example of the charging member used in the embodiment of the present invention will be described.
[0317]
(Production example 1 of charging member)
A 6-mm, 264 mm SUS roller is used as a core, and a medium-resistance foamed urethane layer formulated with urethane resin, carbon black as a conductive particle, sulfurizing agent, foaming agent, etc. is formed into a roller shape on the core, and further cut. The shape and surface properties were polished to prepare a charging roller of 12φ, 234 mm as a flexible member.
[0318]
The resulting charging roller has a resistance value of 10^FiveThe hardness was 30 degrees in terms of Asker C hardness. Further, when the surface of the charging roller was observed with a scanning electron microscope, the average cell diameter was about 100 μm and the porosity was 60%.
[0319]
<Example B1>
FIG. 5 is a schematic structural model diagram of an example of an image forming apparatus according to the present invention. Example B1 The image forming apparatus of this example is a laser printer (recording apparatus) of a simultaneous development cleaning process (cleanerless system) using a transfer type electrophotographic process. It has a process cartridge from which a cleaning unit having a cleaning member such as a cleaning blade is removed, a magnetic one-component developer is used as a developer, and the developer layer on the developer carrier and the image carrier are not in contact with each other. It is an example of non-contact development arranged so that.
[0320]
(A) Overall schematic configuration of this example printer
Reference numeral 21 denotes a rotary drum type OPC photoconductor of the photoconductor production example 2 as an image carrier, which is rotationally driven at a peripheral speed (process speed) of 94 mm / sec in the clockwise direction of an arrow.
[0321]
Reference numeral 22 denotes a charging roller of the charging member production example 1 as a contact charging member. The charging roller 22 is disposed in pressure contact with the photoreceptor 21 with a predetermined pressing force against elasticity. Reference numeral n denotes a charging contact portion that is a contact portion between the photosensitive member 21 and the charging roller 22. In this example, the charging roller 22 is rotationally driven at a peripheral speed of 100% in a facing direction (a direction opposite to the moving direction of the surface of the photoconductor) at a charging contact portion n that is a contact surface with the photoconductor 21. That is, the surface of the charging roller 2 as the contact charging member has a relative speed difference of 200% relative to the surface of the photoreceptor 21. Further, the surface of the charging roller 22 has a coating amount of about 1 × 10^FourPiece / mm²The conductive fine powder 1 was applied so as to be uniform.
[0322]
Further, a DC voltage of −700 V was applied as a charging bias to the cored bar 22a of the charging roller 2 from a charging bias application power source. In this example, the surface of the photosensitive member 21 is uniformly charged by a direct injection charging method at a potential (−680 V) substantially equal to the voltage applied to the charging roller 22. This will be described later.
[0323]
Reference numeral 23 denotes a laser beam scanner (exposure device) including a laser diode, a polygon mirror, and the like. This laser beam scanner outputs a laser beam whose intensity is modulated in accordance with the time-series electric digital pixel signal of the target image information, and scans and exposes the uniformly charged surface of the photosensitive member 21 with the laser beam. By this scanning exposure L, an electrostatic latent image corresponding to target image information is formed on the surface of the rotary photosensitive member 21.
[0324]
Reference numeral 24 denotes a developing device. The electrostatic latent image on the surface of the photoreceptor 21 is developed as a toner image by the developing device.
[0325]
The developing device 24 of this example is a non-contact type reversal developing device using magnetic toner 23 as a developer. The magnetic toner 23 is externally added with conductive fine powder.
[0326]
The clearance between the photosensitive drum 21 and the developing sleeve 24a is 180 μm, and the toner carrier 24a is a resin layer having a layer thickness of about 7 μm and a JIS center line average roughness (Ra) of 1.0 μm as described below. A developing sleeve formed on a 16φ aluminum cylinder is used, and a magnetic roll of 90 mT (900 gauss) of developing magnetic pole is included, and a urethane blade having a thickness of 1.0 mm and a free length of 1.5 mm as a toner regulating member is 29.4N. / M (30 g / cm) for contact.
100 parts of phenolic resin
Graphite (volume average particle size of about 7 μm) 90 parts
10 parts of carbon black
[0327]
In addition, the developing unit a (developing region unit) which is a portion facing the photoconductor 21 is rotated at a peripheral speed of 120% of the peripheral speed of the photoconductor 21 in the rotation direction and the forward direction of the photoconductor 21. The developing sleeve 24a is coated with a thin layer of developer by an elastic blade 24c. The developer is restricted in layer thickness with respect to the developing sleeve 24a by the elastic blade 24c, and is given an electric charge. At this time, the amount of developer coated on the developing sleeve 24a is 15 g / m.²Met. The developer coated on the developing sleeve 24a is conveyed to the developing portion a which is a portion opposite to the photosensitive member 21 and the sleeve 24a by the rotation of the sleeve 24a. A developing bias voltage is applied to the sleeve 24a from a developing bias applying power source. The development bias voltage is a DC voltage of −420 V, a frequency of 1600 Hz, a peak-to-peak voltage of 1500 V (electric field strength of 5.2 × 10⁶A one-component jumping development was performed between the developing sleeve 24a and the photosensitive member 21 using a rectangular AC voltage of V / m).
[0328]
Reference numeral 25 denotes a medium-resistance transfer roller as a contact transfer unit, which is in contact with the photoreceptor 1 with a linear pressure of 98 N / m (100 g / cm) to form a transfer contact portion b. A transfer material P as a recording medium is fed to the transfer contact portion b from a paper feed unit (not shown) at a predetermined timing, and a predetermined transfer bias voltage is applied to the transfer roller 25 from a transfer bias application power source. Thus, the toner image on the photosensitive member 21 side is sequentially transferred onto the surface of the transfer material P fed to the transfer contact portion b.
[0329]
In this example, the roller resistance value is 5 × 10.⁸Transferring was performed by applying a DC voltage of +3000 V using an Ωcm one. That is, the transfer material P introduced into the transfer contact portion b is nipped and conveyed by the transfer contact portion b, and the toner images formed and supported on the surface of the photoreceptor 21 on the surface side are sequentially subjected to electrostatic force. It is transferred by pressing force.
[0330]
Reference numeral 26 denotes a fixing device such as a heat fixing method. The transfer material P that has been fed to the transfer contact portion b and has received the transfer of the toner image on the side of the photoconductor 21 is separated from the surface of the photoconductor 1 and introduced into the fixing device 26, where the toner image is fixed. It is discharged out of the apparatus as an image formed product (print, copy).
[0331]
In the printer of this example, the cleaning unit is removed, and the residual toner remaining on the surface of the photoconductor 21 after the transfer of the toner image onto the transfer material P is not removed by the cleaner, and is charged as the photoconductor 21 rotates. The developing unit a is reached via the part n and is simultaneously cleaned (collected) by the developing device 24.
[0332]
Reference numeral 27 denotes an image forming apparatus and a process cartridge which are detachable from the printer main body. In the printer of this example, three process devices including the photosensitive member 21, the charging roller 22, and the developing device 24 are collectively configured as an image forming apparatus and a process cartridge that are detachable from the printer main body.
[0333]
Reference numeral 28 denotes an attachment / detachment guide / holding member for the process cartridge.
[0334]
The same items as in Example A1 were evaluated except that this image forming apparatus was used and the durable number was 3000 sheets. The results are shown in Table 7.
[0335]
<Examples B2 to B6>
An image is formed by the same image forming method as in Example B1, except that the magnetic toners 24 to 28 are used in place of the magnetic toner 23, and the same conductive fine powder as that used for the toner is applied to the charging roller. A dispensing test and durability evaluation were conducted. As a result, there was no problem in the initial image characteristics, and no problem was obtained until the end of 3000 sheets.
[0336]
<Comparative Examples B1, B2>
An image forming test and durability evaluation were performed by the same image forming method as in Example B1 except that the comparative magnetic toners 12 and 13 were used instead of the magnetic toner 23. As a result, there was no problem in the initial image characteristics, but the density uniformity of the solid image deteriorated from about 1500 sheets of the comparative magnetic toner 12 and about 2000 sheets of the comparative magnetic toner 13 in a high temperature and high humidity environment. . In a low temperature and low humidity environment, the reproducibility of fine lines deteriorated from about 2000 sheets of the comparative magnetic toner 12 and about 2500 sheets of the comparative magnetic toner 13.
[0337]
[Table 7]

[0338]
【The invention's effect】
The magnetic toner of the present invention having the above configuration can obtain a high-quality image. Further, even under high temperature and high humidity and low temperature and low humidity, it is possible to stably provide a high-resolution and high-quality image such as solid image uniformity and fine line reproducibility for a long period of time.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of an image forming apparatus used in an embodiment of the present invention.
FIG. 2 is a diagram illustrating an example of a developing unit for one-component development.
FIG. 3 is a diagram illustrating an example of a configuration of a photoconductor used in the present invention.
FIG. 4 is a diagram illustrating an example of a contact transfer member.
FIG. 5 is a schematic configuration diagram of an image forming apparatus according to an aspect of the present invention.
FIG. 6 is a layer configuration model diagram of a photoreceptor.
[Explanation of symbols]
11 Aluminum base
12 Conductive layer
13 Injection prevention layer
14 Charge generation layer
15 Charge transport layer
16 Charge injection layer
16a Conductive particles (conductive filler)
21 photoconductor
22 Charging member
22a cored bar
23 Laser beam scanner (latent image forming means, exposure device)
24 Development device
24a Development sleeve (developer carrier)
24b Stirring member
24c Elastic blade (layer regulating member)
25 Transfer roller
26 Fixing device
26a heater
26b fixing film
26c Pressure roller
27 Process cartridge
28 Cartridge holding member
34a cored bar
34b Elastic layer
35 Transfer bias power supply
100 photosensitive drum
102 Development sleeve
103 Elastic blade
104 Magnet roller
114 Transfer roller
116 Cleaning means
117 Primary charging roller
121 Laser generator
123 Laser light
124 register roller
125 Conveyor belt
126 Fixing device
140 Developer
141 Developer stirring member

Claims (28)

A toner containing at least iron oxide,
15% by mass or less of a toner having a specific gravity of (A) × 1.000 and (A) × 1.025 or less in a component fractionated by a wet method based on the dry specific gravity (A) of the toner;
0.1 to 20% by mass of a toner having a specific gravity of (A) × 0.975 and (A) × 1.000 or less,
30% or more by weight of toner having a specific gravity of (A) × 0.950 and (A) × 0.975 or less,
0.1 to 20% by mass of a toner having a specific gravity exceeding (A) × 0.925 and not more than (A) × 0.950,
The toner having a specific gravity of (A) × 0.900 and (A) × 0.925 or less is 15% by mass or less,
Der is, the magnetic toner having an average circularity of the toner is characterized in that 0.970 or more. (A) × 0.950 or less The weight average particle diameter of the component having a small specific gravity is (D4L), and (A) × 0.975 is the weight average particle diameter of the component having a specific gravity larger than (D4H). The magnetic toner according to claim 1, wherein the particle size is (D4A) and the following formula is satisfied.
(D4L) / (D4A) ≧ 0.8
(D4H) / (D4A) ≦ 1.1   2. The organic volatile component analysis of the toner by the headspace method, wherein the amount of organic volatile component in terms of toluene based on the toner mass when the heating temperature of the toner is 150 ° C. is 10 to 400 ppm. The magnetic toner according to 2. i) The ratio (B / A) of the content (B) of the iron element to the content (A) of the carbon element present on the toner surface measured by X-ray photoelectron spectroscopy is less than 0.001, and ii) When the projected area equivalent circle diameter of the toner is C and D is 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), D / C ≦ 0.02. a magnetic toner according to any one of claims 1 to 3 toner satisfying the relationship is characterized in that 50% by number or more. The ratio (E / A) of the atomic number% (E) of the sulfur element to the atomic number% (A) of the carbon element present on the toner surface measured by X-ray photoelectron spectroscopy is 0.0003 to 0.0050. a magnetic toner according to any one of claims 1 to 4, characterized in that. The average particle size of the iron oxide is is 0.1 to 0.3 [mu] m, and any one of claims 1 to 5, wherein the% by number of 0.03~0.1μm of the particles are greater than 40% The magnetic toner described in 1. Number% 1 to 30% of 0.03~0.1μm smaller particles of the iron oxide, in any one of claims 1 to 6, characterized in that 0.3μm or more of the particles is 10% by number or less The magnetic toner described. A magnetic toner according to claim 1 to 7, wherein the 0.3μm or more particles of the iron oxide is 5% by number or less. A magnetic toner according to any one of claims 1 to 8, characterized in that the intensity of magnetization in the toner of the magnetic field 79.6 kA / m (1000 oersted) is ^{10~50Am 2 / kg (emu / g} ) . A magnetic toner according to any one of claims 1 to 9 ratio (B / A) is characterized in that it is less than 0.0005. A magnetic toner according to any one of claims 1 to 9 ratio (B / A) is characterized in that it is less than 0.0003. A magnetic toner according to any one of claims 1 to 11 toner satisfies the relationship D / C ≦ 0.02 is characterized in that 65% by number or more. A magnetic toner according to any one of claims 1 to 11 toner satisfies the relationship D / C ≦ 0.02 is characterized in that 75% by number or more. 10% by mass or less of toner having a specific gravity of (A) × 1.000 and (A) × 1.025 or less,
The toner having a specific gravity of (A) × 0.975 and (A) × 1.000 or less is 0.5 to 15% by mass or less,
The toner having a specific gravity of (A) × 0.950 and (A) × 0.975 or less is 40% by mass or more,
The toner having a specific gravity of (A) × 0.925 and (A) × 0.950 or less is 0.5 to 15% by mass or less,
10% by mass or less of toner having a specific gravity of (A) × 0.900 and (A) × 0.925 or less,
A magnetic toner according to any one of claims 1 to 13, characterized in that. 1 to 5% by mass of a toner having a specific gravity of (A) × 1.000 and (A) × 1.025 or less,
(A) 3 to 10% by mass of toner having a specific gravity exceeding 0.975 and not exceeding (A) 1.000;
40-90% by mass of a toner having a specific gravity of (A) × 0.950 and (A) × 0.975 or less,
3 to 10% by mass of a toner having a specific gravity of (A) × 0.925 and (A) × 0.950 or less,
1 to 5% by mass of toner having a specific gravity exceeding (A) × 0.900 and not more than (A) × 0.925
A magnetic toner according to any one of claims 1 to 13, characterized in that. A magnetic toner according to any one of claims 1 to 15, characterized in that it contains a resin containing a sulfur element. The magnetic toner according to claim 16 , wherein the resin is a polymer containing sulfonic acid groups. The magnetic toner according to claim 16 , wherein the resin contains (meth) acrylamide containing a sulfonic acid group (—SO ₃ X: X═H, alkali metal). A magnetic toner according to any one of claims 16 to 18 glass transition temperature of the resin (Tg) of characterized in that it is a 50 to 100 ° C.. A magnetic toner according to any one of claims 16 to 18 weight average molecular weight of the resin is characterized by a 2,000 to 100,000. A magnetic toner according to any one of claims 16 to 20, wherein the resin is contained 0.05 to 20 parts by weight per 100 parts by weight other binder resin. 21. The sulfonic acid group (—SO ₃ X: X═H, alkali metal) -containing (meth) acrylamide is contained in the resin in an amount of 0.01 to 20 % by mass. 21. Magnetic toner. A magnetic toner according to any one of claims 1 to 22 wherein the toner is characterized by containing a 0.5 to 40 wt% wax of the binder resin. 24. The magnetic toner according to claim 23 , wherein the wax has a maximum endothermic peak in a region of 40 to 110 [deg.] C. when the temperature rises in a DSC curve measured by a differential scanning calorimeter. 24. The magnetic toner according to claim 23 , wherein the wax has a maximum endothermic peak in a region of 45 to 90 [deg.] C. when a temperature rises in a DSC curve measured by a differential scanning calorimeter. The iron oxide is in an aqueous medium, the magnetic toner according to any one of claims 1 to 25, characterized in that surface-treated with a coupling agent. A magnetic toner according to any one of claims 1 to 26 mode circularity is characterized in that at least 0.99. The iron oxide obtained by subjecting magnetic particles obtained by oxidizing the ferrous hydroxide in an aqueous medium to surface treatment with a coupling agent in another aqueous medium without drying. 27. The magnetic toner according to claim 26 , wherein:

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