JP4086487B2 - Magnetic toner and image forming apparatus - Google Patents

Description

【００９９】
該磁性トナーの個数平均粒径（Ｄ１）は、後述するコールターカウンターにて決定するのが良い。
【０１００】
更に、トナー表面における無機微粉体の個数遊離率Ｆが０．１０％≦Ｆ≦６０．００％の関係をみたすことも、本発明のトナーに必要な態様の一つである。
【０１０１】
先述したように、球形のトナーにスルホン酸基を有する重合体を含有させることにより、スルホン酸基を含有する重合体の特性を十分に発揮させることができ、磁性トナーとして良好な摩擦帯電性を得ることができる。
【０１０２】
しかし、トナー形状が球形であるが故に、さらには流動性が向上するスルホン酸基を有する重合体を含有する磁性トナーにおいては、過度のすべりが生じ、現像スリーブとトナー規制ブレードとの圧接間隙をトナーが通過することにより帯電が付与される一成分現像方式においては、この過度の流動性に起因して、該ブレードによるトナーの帯電付与が不均一になりやすく、またトナーのチャージアップが生じやすくなり画像上、ゴーストといった現象が生じやすくなる。更に、本発明の球形形状を有するトナーは放置によって特にトナーがパッキングされやすいために、長期放置後に帯電規制部等での過度の規制が生じやすく、現像剤担持体上のトナーのり量が少なくなり、結果として放置初期画像濃度が低下しやすしやすい。なお、上記の現象は低温低湿下で特に顕著となることから、本発明者らは帯電量によって現像剤担持体上でのすべり性も変化していると考えている。
【０１０３】
そこで、本発明者らが最適な流動性についてトナー粒子に外添混合する無機微粉体について鋭意検討したところ、トナー表面における無機微粉体の個数遊離率Ｆが０．１０％≦Ｆ≦６０．００％の関係をみたすときに、磁性トナーの帯電性が均一となり、画像上、ゴースト抑制も良好なものとなる。更に、既述した転写性やカブリ特性も良好であり、長期使用においても画像劣化のない磁性トナーを得ることができる。
【０１０４】
ここで、無機微粉体の遊離率が０．１０％より少ないと、トナー表面の摩擦が大きくなるために放置特性については問題ないもののトナー表面に外添された無機微粉体は、特に高温高湿環境下において長期使用することにより、トナー粒子へ埋め込まれ易くなり、そして、表面が露出されたトナー粒子による静電凝集を生じ、トナー担持体上で帯電制御ができなくなりトナー飛散を生じさせやすく、画像出力時、特に紙上の先端付近において、カブリが著しくなる。
【０１０５】
また、無機微粉体の遊離率が６０．００％より多い場合には、遊離無機微粉体が必要以上に生じていることを意味し、トナー全体として過度の流動性を示す。これにより、トナーの帯電も不均一なものになってしまい、ゴーストの発生が著しくなるばかりでなく、トナー担持体上のトナー量を規制させることができず、カブリも増大してしまう。また、帯電部材と現像剤担持体間でのすべりも過大となるために、長期放置後の画像濃度低下が大きくなる。
【０１０６】
つまり、無機微粉体は適度な量の遊離粒子として存在している必要があり、その為に無機微粉体の遊離率Ｆが０．１０％≦Ｆ≦６０．００％の関係を示すことが重要なのである。
【０１０７】
また、無機微粉体の遊離率Ｆが上記関係を満たすためには、無機微粉体とトナーを混合する際に用いられる、公知の様々な混合機の混合強度が重要であり、具体的には混合機の回転数や混合時間などを調整することにより、遊離率Ｆを０．１０％≦Ｆ≦６０．００％の関係にすることができる。更には複数の無機微粉体を磁性トナーに外添混合した場合には、各無機微粉体の中で最も遊離率の数値が高いものに流動性や摩擦帯電性が支配されることが明らかとなった。
【０１０８】
また、磁性トナー粒子表面における無機微粉体の遊離率とは、パーティクルアナライザー（ＰＴ１０００：横河電機（株）製）により測定されるものである。
【０１０９】
パーティクルアナライザーはＪａｐａｎ Ｈａｒｄｃｏｐｙ ９７論文集の６５〜６８ページに記載の原理で測定を行なう。具体的には、該装置はトナー等の微粒子を一個ずつ、電子密度５×１０^１３ｃｍ^−３、励起温度３，３００Ｋ、２０，０００Ｋを超える高い電子温度を持つ高温の非熱平衡型プラズマへ導入し、この励起に伴う微粒子の発光スペクトルから発光物の元素、粒子数、粒子の粒径を知ることが出来る。
【０１１０】
この中で、遊離率とは、結着樹脂の構成元素である炭素原子の発光と、無機微粉体を構成する主要原子の発光の同時性から下記に示す式により求めたものと定義する。
【０１１１】
無機微粉体の遊離率（％）＝１００×（無機微粉体を構成する主要原子のみの発光回数／炭素原子と同時に発光した無機微粉体を構成する主要原子のみの発光回数＋無機微粉体を構成する主要原子のみの発光回数）
【０１１２】
ここで、炭素原子と無機微粉体を構成する主要原子の同時発光とは、炭素原子の発光から２．６ｍｓｅｃ以内に発光した無機微粉体を構成する主要原子の発光を同時発光とし、それ以降の無機微粉体を構成する主要原子の発光は無機微粉体を構成する主要原子のみの発光とする。本発明では無機微粉体をトナー粒子表面へ外添付着せしめている為、炭素原子と無機微粉体を構成する主要原子が同時発光すると言うことは、トナー粒子表面に無機微粉体が付着している事を意味し、無機微粉体を構成する主要原子のみの発光は、無機微粉体がトナー粒子表面から遊離離脱している事を意味すると言い換えることも可能である。
【０１１３】
具体的な測定方法としては、０．１％酸素含有のヘリウムガスを用い、２３℃で湿度６０％の環境にて測定を行ない、チャンネル１で炭素原子（測定波長２４７．８６０ｎｍ、Ｋファクターは本体推奨値）を測定し、チャンネル２〜チャンネル４を用いて無機微粉体を構成する主要原子を測定し、（使用したチャンネルや波長、Ｋファクターは本体推奨のものを用いた）、一回のスキャンで炭素原子の発光数が１０００±２００個となる様にサンプリングを行い、炭素原子の発光数が総数で１００００以上となるまでスキャンを繰り返し、発光数を積算する。このデータを元に、上記計算式を用い、無機微粉体の遊離率を算出する。本発明に係る無機微粉体の発光強度の測定はＰＴ１０００にて推奨されるチャンネルを選択すればなんら構わない。
【０１１４】
尚、本発明に係る遊離率の算出に至ってはノイズレベルを１は１．５Ｖ設定で行った。
【０１１５】
また、本発明のトナーは、更に高画質のため、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粒径は３〜１０μｍであることが好ましい。重量平均粒径が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攪拌性が低下し、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しやすく、削れや融着以外にも画像の均一ムラの原因となりやすい。また、トナーの重量平均粒径が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。
【０１１６】
更に、本発明ではトナー表面にマグネシウム、カルシウム、バリウム、アルミニウム、亜鉛から選ばれる少なくとも一種以上の元素を積極的に５〜１０００ｐｐｍ、より好ましくは１０〜５００ｐｐｍ存在させることにより一層帯電特性、特に帯電速度が向上する。
【０１１７】
この現象が生じる原因について詳細は分からないが、本発明の構成である磁性体が存在しないと効果が発揮されにくいこと、また本発明の特徴の一つであるＤ／Ｃ＜０．０２を満足するトナーが多いほどより効果を発揮することなどから
【０１１８】
本発明者らは、上記のマグネシウム、カルシウム、バリウム、アルミニウム、亜鉛等の２価或いは３価の元素と磁性体の間で電荷の受け渡しがあり、結果として本発明の硫黄重合体との間の帯電助剤としての効果があると考えている。
【０１１９】
また本発明では特定の磁性体構造を有するため上記元素の存在位置や量が課題となるが、本発明者らの検討の結果では、トナー内部よりはるかにトナー表層での存在によって効果を発揮することを見出し、具体的にはトナー表面にマグネシウム、カルシウム、バリウム、アルミニウム、亜鉛から選ばれる少なくとも一種以上の元素を積極的に５〜１０００ｐｐｍ、より好ましくは１０〜５００ｐｐｍ存在させる事で帯電量、転写性、カブリ等に効果を発揮する。
【０１２０】
これら元素が５ｐｐｍ未満であると本発明の効果が発揮されず、１０００ｐｐｍより多く存在すると、トナーの帯電量が必要以上に低くなってしまい、転写効率の低下、カブリの増大を招き、好ましくない。
【０１２１】
このように、磁性トナー表面における無機微粉体の個数遊離率を特定の値の範囲に制御し、且つ特定の元素を磁性トナー表面に特定量存在させることの相乗効果によりチャージアップの抑制や帯電均一性といった磁性トナーの帯電特性がより優れたものになり、ゴーストやカブリ特性、更には転写性にも優れた画像を得ることができると考えている。
【０１２２】
なお、トナー表面に存在するマグネシウム、カルシウム、バリウム、アルミニウム、亜鉛のうち、複数の元素が存在する場合、それらの総量が５〜１０００ｐｐｍであることが必要である。また、このような元素のうち、マグネシウムとカルシウムが特にゴーストの抑制に効果があり、好ましい。
【０１２３】
本発明において、トナー表面に存在するマグネシウム、カルシウム、バリウム、アルミニウム、亜鉛とは、イソプロパノールの如きトナーを溶かさない溶媒中にトナーを入れ、超音波洗浄機にて１０分振動を与え、外添剤を除いた状態で存在する元素の事を意味する。
【０１２４】
また、それら元素の存在量については、外添剤を取り除いた後、トナー粒子に対して蛍光Ｘ線分析やプラズマ発光分析（ＩＣＰ）やＥＳＣＡなどの公知の分析方法を用いて上記元素の定量を行うことが出来る。
【０１２５】
後述の実施例において、各元素の測定は、蛍光Ｘ線分析を用いて行い、その詳細はＪＩＳ−ＫＯ１１９に準ずる。
【０１２６】
（１）使用装置について
蛍光Ｘ線分析装置３０８０（理学電気（株））
試料プレス成型機ＭＡＥＫＡＷＡ Ｔｅｓｔｉｎｇ Ｍａｃｈｉｎｅ（ＭＦＧＣｏ，ＬＴＤ製）
【０１２７】
（２）検量線の作成について
定量目的の複合化合物を、コーヒーミルを用いて５水準外添することによりサンプルを作製する。上記サンプルを試料プレス成型機を用いてプレス成形する。２θテーブルより複合化合物中〔Ｍ〕Ｋαピーク角度（ａ）を決定する。蛍光Ｘ線分析装置中へ検量線サンプルを入れ、資料室を減圧し真空にする。以下の条件にて各々のサンプルのＸ線強度を求め検量線（質量比：ｐｐｍ表示）を作成する。
【０１２８】
（３）測定条件について
測定電位、電圧 ５０ｋＶ、５０〜７０ｍＡ
２θ角度 ａ
結晶板 ＬｉＦ
測定時間 ６０秒
【０１２９】
（４）トナー粒子中の上記元素の定量について
上記検量線と同様の方法でサンプル成形した後、同じ測定条件にてＸ線強度をもとめ、検量線より含有量を算出する。
【０１３０】
なお、トナー表面以外にマグネシウム、カルシウム、バリウム、アルミニウム、亜鉛の各元素を有する化合物が存在しない場合は上記方法にて各元素の存在量を求めるものの、トナー表面以外にこれら元素のいずれかを有する場合は、次の様にしてトナー表面の存在量を求める。
【０１３１】
まず、上記方法にて各元素の存在量を求める：これを存在量Ａとする。次に、外添剤を除いたトナー粒子を濃硝酸中にて１時間攪拌し、純水にて十分に洗浄した後、乾燥し、上記方法にて各元素の存在量を求める：これを存在量Ｂとする。トナー表面の各元素の存在量はＡとＢの差、即ち（Ａ−Ｂ）にて求めることが出来る。なお、マグネタイト等に上記元素が含まれる場合でも、マグネタイトは濃硝酸と不動体を形成し、溶出する事はないので、トナー粒子表面のみの存在量の測定が可能となる。
【０１３２】
次に本発明におけるトナーの製造方法を説明する。
【０１３３】
本発明のトナーは、粉砕法によって製造することも可能であるが、粉砕法ではトナーの平均円形度を０．９７０以上とするために機械的、熱的あるいは何らかの特殊な処理を行うことが必要となることから、懸濁重合法により製造することが好ましい。通常の磁性体を用いて懸濁重合によりトナーを製造したとしても、磁性体が分散性に劣るために磁性体がトナー表面に偏在してしまったり、水系媒体中における造粒時に磁性体が乱雑に動き、それに引きずられて粒子形状がゆがんだりするために、平均円形度が０．９７０以上のトナーは得られがたいものであったが、本発明において用いられる酸化鉄は、高いレベルでの均一な疎水化が行われているため、平均円形度が０．９７０以上のトナーを容易に得ることができる。
【０１３４】
本発明に使用される重合性単量体系を構成する重合性単量体としては以下のものが挙げられる。
【０１３５】
重合性単量体としては、スチレン、ｏ−メチルスチレン、ｍ−メチルスチレン、ｐ−メチルスチレン、ｐ−メトキシスチレン、ｐ−エチルスチレンの如きスチレン系単量体；アクリル酸メチル、アクリル酸エチル、アクリル酸ｎ−ブチル、アクリル酸イソブチル、アクリル酸ｎ−プロピル、アクリル酸ｎ−オクチル、アクリル酸ドデシル、アクリル酸２−エチルヘキシル、アクリル酸ステアリル、アクリル酸２−クロルエチル、アクリル酸フェニルの如きアクリル酸エステル類；メタクリル酸メチル、メタクリル酸エチル、メタクリル酸ｎ−プロピル、メタクリル酸ｎ−ブチル、メタクリル酸イソブチル、メタクリル酸ｎ−オクチル、メタクリル酸ドデシル、メタクリル酸２−エチルヘキシル、メタクリル酸ステアリル、メタクリル酸フェニル、メタクリル酸ジメチルアミノエチル、メタクリル酸ジエチルアミノエチルの如きメタクリル酸エステル類；アクリロニトリル、メタクリロニトリル、アクリルアミドが挙げられる。
【０１３６】
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。
【０１３７】
また、本発明のトナーは、離型剤を含有することも好ましい使用形態の一つである。通常、トナー像は、転写工程で転写材上に転写され、そして、このトナー像はその後、熱・圧力等のエネルギーにより転写材上に定着され、半永久的な画像が得られる。この際の定着方法としては、熱ロール式定着が一般に良く用いられるが、上記のように、重量平均粒径が１０μｍ以下のトナーを用いれば非常に高精細な画像を得ることができるが、粒径の細かいトナー粒子は紙等の転写材を使用した場合に紙の繊維の隙間に入り込み、熱定着用ローラーからの熱の受け取りが不十分となり、低温オフセットが発生しやすい。しかしながら、本発明のトナーにおいて、離型剤として適正量のワックスを含有させることにより、高解像性と耐オフセット性を両立させつつ感光体の削れを防止することが可能となる。
【０１３８】
本発明のトナーに使用可能なワックスとしては、パラフィンワックス、マイクロクリスタリンワックス、ペトロラクタムの如き石油系ワックス及びその誘導体、モンタンワックスびその誘導体、フィッシャートロプシュ法による炭化水素ワックス及びその誘導体、ポリエチレンに代表されるポリオレフィンワックス及びその誘導体、カルナバワックス、キャンデリラワックスの如き天然ワックス及びその誘導体などが含まれる。ここでの誘導体には酸化物や、ビニル系モノマーとのブロック共重合物、グラフト変性物が含まれる。さらに、高級脂肪族アルコール、ステアリン酸、パルミチン酸の如き脂肪酸またはその化合物、酸アミドワックス、エステルワックス、ケトン、硬化ヒマシ油及びその誘導体、植物系ワックス、動物性ワックスも使用できる。
【０１３９】
本発明のトナーにおいて、上記のワックス成分の含有量は、結着樹脂１００質量部に対して０．５〜５０質量部の範囲であるのが好ましい。ワックス成分の含有量が０．５質量部未満では低温オフセット抑制効果に乏しく、５０質量部を超えてしまうと長期間の保存性が低下すると共に、他のトナー材料の分散性が悪くなり、トナーの流動性の劣化や画像特性の低下につながる。
【０１４０】
本発明では、単量体系に樹脂を添加して重合しても良い。例えば、単量体では水溶性のため水性懸濁液中では溶解して乳化重合を起こすため使用できないアミノ基、カルボン酸基、水酸基、スルフォン酸基、グリシジル基、ニトリル基の如き親水性官能基含有の単量体成分をトナー中に導入したい時には、これらとスチレンあるいはエチレン等ビニル化合物とのランダム共重合体、ブロック共重合体、あるいはグラフト共重合体の如き共重合体の形にして、あるいはポリエステル、ポリアミドの如き重縮合体、ポリエーテル、ポリイミンの如き重付加重合体の形で使用が可能となる。その使用量としては、重合性単量体１００質量部に対して１〜２０質量部が好ましい。使用量が１質量部未満では添加効果が小さく、一方２０質量部を超えて使用された場合には、重合トナーの種々の物性設計が難しくなってしまう。また、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。
【０１４１】
本発明のトナーには、荷電特性を安定化するために荷電制御剤を配合しても良い。荷電制御剤としては、公知のものが利用できるが、特に帯電スピードが速く、且つ、一定の帯電量を安定して維持できる荷電制御剤が好ましい。
【０１４２】
さらに、トナーを直接重合法を用いて製造する場合には、重合阻害性が低く、水系分散媒体への可溶化物が実質的にない荷電制御剤が特に好ましい。具体的な化合物としては、ネガ系荷電制御剤としてサリチル酸、アルキルサリチル酸、ジアルキルサリチル酸、ナフトエ酸、ダイカルボン酸の如き芳香族カルボン酸の金属化合物、アゾ染料もしくはアゾ顔料の金属塩または金属錯体、スルホン酸又はカルボン酸基を側鎖に持つ高分子型化合物、ホウ素化合物、尿素化合物、ケイ素化合物、カリックスアレーンが挙げられる。ポジ系荷電制御剤として四級アンモニウム塩、その四級アンモニウム塩を側鎖に有する高分子型化合物、グアニジン化合物、ニグロシン系化合物、イミダゾール化合物が挙げられる。これらの荷電制御剤は、重合性単量体１００質量部に対して０．５〜１０質量部使用することが好ましい。しかしながら、本発明の画像形成方法に関わる現像剤は、荷電制御剤の添加は必須ではなく、現像剤の層厚規制部材や現像剤担持体との摩擦帯電を積極的に利用することでトナー中に必ずしも荷電制御剤を含む必要はない。
【０１４３】
本発明のトナーに用いられる磁性粉体は、結着樹脂１００質量部に対して１０〜１６０質量部を用いることが好ましい。１０質量部未満ではトナーの着色力が乏しく、カブリの抑制も困難である。一方、１６０質量部を超えると、トナー担持体への磁力による保持力が強まり現像性が低下したり、個々のトナー粒子への磁性粉体の均一な分散が難しくなるだけでなく、定着性が低下してしまう。
【０１４４】
また、本発明のトナーにおいて磁性体として用いられる酸化鉄は、リン、コバルト、ニッケル、銅、マグネシウム、マンガン、アルミニウム、ケイ素の如き元素を含んでもよく、四三酸化鉄、γ−酸化鉄を主成分とするものであり、これらを１種または２種以上を併用して用いられる。これら酸化鉄は、窒素吸着法によるＢＥＴ比表面積が好ましくは２〜３０ｍ^２／ｇ、特に３〜２８ｍ^２／ｇであり、更にモース硬度が５〜７のものが好ましい。
【０１４５】
また、酸化鉄の形状としては、８面体、６面体、球状、針状、鱗片状などがあるが、８面体、６面体、球状、不定形の如き異方性の少ないものが画像濃度を高める上で好ましい。こういった形状は、ＳＥＭなどによって確認することができる。
【０１４６】
さらにまた、酸化鉄以外に他の着色剤を併用しても良い。併用し得る着色材料としては、磁性あるいは非磁性無機化合物、公知の染料及び顔料が挙げられる。具体的には、例えば、コバルト、ニッケルの如き強磁性金属粒子、またはこれらにクロム、マンガン、銅、亜鉛、アルミニウム、希土類元素を加えた合金、ヘマタイト、チタンブラック、ニグロシン染料／顔料、カーボンブラック、フタロシアニンが挙げられる。これらもまた、表面を処理して用いても良い。
【０１４７】
本発明に使用する重合開始剤としては重合反応時に半減期０．５〜３０時間であるものを、重合性単量体の０．５〜２０質量％の添加量で重合反応を行なうと、分子量１万〜１０万の間に極大を有する重合体を得、トナーに望ましい強度と適当な溶融特性を与えることができる。重合開始剤の例としては、２，２’−アゾビス−（２，４−ジメチルバレロニトリル）、２，２’−アゾビスイソブチロニトリル、１，１’−アゾビス（シクロヘキサン−１−カルボニトリル）、２，２’−アゾビス−４−メトキシ−２，４−ジメチルバレロニトリル、アゾビスイソブチロニトリルの如きアゾ系またはジアゾ系重合開始剤；ベンゾイルパーオキサイド、メチルエチルケトンパーオキサイド、ジイソプロピルパーオキシカーボネート、クメンヒドロパーオキサイド、２，４−ジクロロベンゾイルパーオキサイド、ラウロイルパーオキサイドの如き過酸化物系重合開始剤が挙げられる。
【０１４８】
本発明では、架橋剤を添加しても良く、好ましい添加量としては、重合性単量体の０．００１〜１５質量％である。
【０１４９】
懸濁重合法によるトナーの製造では、一般に上述のトナー組成物、すなわち重合性単量体中に、酸化鉄、着色剤、離型剤、可塑剤、結着剤、荷電制御剤、架橋剤等トナーとして必要な成分及びその他の添加剤、例えば重合反応で生成する重合体の粘度を低下させるために入れる有機溶媒、分散剤等を適宜加えて、ホモジナイザー、ボールミル、コロイドミル、超音波分散機等の分散機に依って均一に溶解または分散せしめた単量体系を、分散安定剤を含有する水系媒体中に懸濁する。この時、高速撹拌機もしくは超音波分散機のような高速分散機を使用して一気に所望のトナー粒子のサイズとするほうが、得られるトナー粒子の粒径がシャープになる。重合開始剤添加の時期としては、重合性単量体中に他の添加剤を添加する時同時に加えても良いし、水系媒体中に懸濁する直前に混合しても良い。また、造粒直後、重合反応を開始する前に重合性単量体あるいは溶媒に溶解した重合開始剤を加えることもできる。
【０１５０】
造粒後は、通常の撹拌機を用いて、粒子状態が維持され且つ粒子の浮遊・沈降が防止される程度の撹拌を行なえば良い。
【０１５１】
本発明の懸濁重合法においては、分散安定剤として公知の界面活性剤や有機・無機分散剤が使用でき、中でも無機分散剤が有害な超微粉を生じ難く、その立体障害性により分散安定性を得ているので反応温度を変化させても安定性が崩れ難く、洗浄も容易でトナーに悪影響を与え難いので、好ましく使用できる。こうした無機分散剤の例としては、燐酸カルシウム、燐酸マグネシウム、燐酸アルミニウム、燐酸亜鉛の如き燐酸多価金属塩；炭酸カルシウム、炭酸マグネシウムの如き炭酸塩；メタ硅酸カルシウム、硫酸カルシウム、硫酸バリウムの如き無機塩；水酸化カルシウム、水酸化マグネシウム、水酸化アルミニウム、シリカ、ベントナイト、アルミナの如き無機酸化物が挙げられる。
【０１５２】
これらの無機分散剤は、重合性単量体１００質量部に対して、０．２〜２０質量部を単独でまたは２種類以上組み合わせて使用することが好ましい。
【０１５３】
平均粒径が５μｍ以下である様な、より微粒化されたトナーを目的とする場合には、０．００１〜０．１質量部の界面活性剤を併用しても良い。界面活性剤としては、例えばドデシルベンゼン硫酸ナトリウム、テトラデシル硫酸ナトリウム、ペンタデシル硫酸ナトリウム、オクチル硫酸ナトリウム、オレイン酸ナトリウム、ラウリル酸ナトリウム、ステアリン酸ナトリウム、ステアリン酸カリウムが挙げられる。
【０１５４】
これら無機分散剤を用いる場合には、そのまま使用しても良いが、より細かい粒子を得るため、水系媒体中にて該無機分散剤粒子を生成させることができる。例えば、燐酸カルシウムの場合、高速撹拌下、燐酸ナトリウム水溶液と塩化カルシウム水溶液とを混合して、水不溶性の燐酸カルシウムを生成させることができ、より均一で細かな分散が可能となる。この時、同時に水溶性の塩化ナトリウム塩が副生するが、水系媒体中に水溶性塩が存在すると、重合性単量体の水への溶解が抑制されて、乳化重合に依る超微粒トナーが発生し難くなるので、より好都合である。重合反応終期に残存重合性単量体を除去する時には障害となることから、水系媒体を交換するか、イオン交換樹脂で脱塩したほうが良い。無機分散剤は、重合終了後酸あるいはアルカリで溶解して、ほぼ完全に取り除くことができる。
【０１５５】
前記重合工程においては、重合温度は４０℃以上、一般には５０〜９０℃の温度に設定して重合を行なう。この温度範囲で重合を行なうと、内部に封じられるべき離型剤やワックスの類が、相分離により析出して内包化がより完全となる。残存する重合性単量体を消費するために、重合反応終期ならば、反応温度を９０〜１５０℃にまで上げることは可能である。
【０１５６】
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、乾燥を行うが、更に該製造工程後に分級工程を入れ、粗粉や微粉をカットすることも、本発明の望ましい形態の一つである。
【０１５７】
また、本発明のトナーには、流動性向上剤として、無機微粉体または疎水性無機微粉体が混合されることが好ましい。例えば、酸化チタン微粉末、シリカ微粉末、アルミナ微粉末を添加して用いることが好ましく、特にシリカ微粉末を用いることが好ましい。
【０１５８】
本発明の現像剤に用いられる無機微粉体は、一次平均粒径が４〜８０ｎｍの範囲のものが良好な結果を与えることができるため好ましい。無機微粉体の一次平均粒径が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。無機微粉体の一次平均粒径が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、無機微粉体の一次平均粒径は６〜３５ｎｍであることがより良い。
【０１５９】
無機微粉体の一次平均粒子径の測定法は、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体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体の一次次粒子を１００個以上測定し、個数平均一次粒径を求めることが出来る。
【０１６０】
本発明に用いられるシリカ微粉体は、ケイ素ハロゲン化合物の蒸気相酸化により生成されたいわゆる乾式法またはヒュームドシリカと称される乾式シリカ及び水ガラス等から製造されるいわゆる湿式シリカの両方が使用可能であるが、表面及び内部にあるシラノール基が少なく、製造残渣のない乾式シリカが好ましく用いられる。
【０１６１】
さらに本発明に用いるシリカ微粉体は疎水化処理されているものが高温高湿環境下での特性から好ましい。トナー粒子に添加された無機微粉体が吸湿すると、トナー粒子の帯電量が低下し、画像濃度が低下する。疎水化処理するには、シリカ微粉体と反応あるいは物理吸着する有機ケイ素化合物などで化学的に処理することによって付与される。好ましい方法としては、ケイ素ハロゲン化合物の蒸気相酸化により生成された乾式シリカ微粉体をシランカップリング剤で処理した後、あるいはシランカップリング剤で処理すると同時にシリコーンオイルの如き有機ケイ素化合物で処理する方法が挙げられる。
【０１６２】
疎水化処理に使用されるシランカップリング剤としては、例えばヘキサメチルジシラザン、トリメチルシラン、トリメチルクロルシラン、トリメチルエトキシシラン、ジメチルジクロルシラン、メチルトリクロルシラン、アリルジメチルクロルシラン、アリルフェニルジクロルシラン、ベンジルジメチルクロルシラン、ブロムメチルジメチルクロルシラン、α−クロルエチルトリクロルシラン、β−クロルエチルトリクロルシラン、クロルメチルジメチルクロルシラン、トリオルガノシランメルカプタン、トリメチルシリルメルカプタン、トリオルガノシリルアクリレート、ビニルジメチルアセトキシシラン、ジメチルエトキシシラン、ジメチルジメトキシシラン、ジフェニルジエトキシシラン、ヘキサメチルジシロキサン、１，３−ジビニルテトラメチルジシロキサン、１，３−ジフェニルテトラメチルジシロキサンが挙げられる。
【０１６３】
有機ケイ素化合物としては、シリコーンオイルが挙げられる。好ましいシリコーンオイルとしては、２５℃における粘度がおよそ３０〜１，０００ｍｍ２／ｓ（ｃＳｔ）のものが用いられ、例えばジメチルシリコーンオイル、メチルフェニルシリコーンオイル、α−メチルスチレン変性シリコーンオイル、クロルフェニルシリコーンオイル、フッ素変性シリコーンオイルが好ましい。
【０１６４】
シリコーンオイル処理の方法は、例えばシランカップリング剤で処理されたシリカ微粉体とシリコーンオイルとをヘンシェルミキサー等の混合機を用いて直接混合しても良いし、ベースとなるシリカヘシリコーンオイルを噴射する方法によっても良い。あるいは適当な溶剤にシリコーンオイルを溶解あるいは分散せしめた後、ベースのシリカ微粉体とを混合し、溶剤を除去して作製しても良い。
【０１６５】
本発明中のトナーには、必要に応じて流動性向上剤以外の外部添加剤を添加してもよい。
【０１６６】
例えば、クリーニング性や凝集性を向上させる等の目的で、一次粒径が３０ｎｍを超える微粒子、より好ましくは一次粒径が５０ｎｍ以上で球状に近い無機微粒子または有機微粒子をさらに添加することも好ましい形態の一つである。例えば球状のシリカ粒子、球状のポリメチルシルセスキオキサン粒子、球状の樹脂粒子を用いるのが好ましい。
【０１６７】
尚、上記外部添加剤と磁性トナーの混合は公知の様々な手法の一種或いは、複数種を用いることにより行なうことができる。
【０１６８】
本発明のトナーを粉砕法により製造する場合は、公知の方法が用いることができる。公知の方法としては、例えば、結着樹脂、磁性体、離型剤、荷電制御剤、場合によっては着色剤等のトナーとして必要な成分及びその他の添加剤等をヘンシェルミキサー、ボールミル等の混合器中で十分混合した後、加熱ロール、ニーダー、エクストルーダーのような熱混練機を用いて溶融混練して、樹脂類をお互いに相溶させた中に磁性体等の他のトナー材料を分散又は溶解させ、冷却固化、粉砕後に、分級、必要に応じて表面処理を行なってトナー粒子を得、必要に応じて微粉体等を添加して混合することによって現像剤を得ることが出来る。分級及び表面処理の順序はどちらが先でもよい。分級工程においては生産効率の点からは、多分割分級機を用いることが好ましい。
【０１６９】
粉砕工程は、機械衝撃式、ジェット式等の公知の粉砕装置を用いて行うことができる。本発明に係わる特定の円形度を有する現像剤を得るためには、さらに熱をかけて粉砕したり、または補助的に機械的衝撃を加える処理をすることが好ましい。また、微粉砕（必要に応じて分級）されたトナー粒子を熱水中に分散させる湯浴法，熱気流中を通過させる方法などを用いてもよい。
【０１７０】
機械的衝撃力を加える方法としては、例えば川崎重工社製のクリプトロンシステムやターボ工業社製のターボミル等の機械衝撃式粉砕機を用いる方法がある。また、ホソカワミクロン社製のメカノフージョンシステムや奈良機械製作所製のハイブリダイゼーションシステム等の装置のように、高速回転する羽根によりトナーをケーシングの内側に遠心力により押しつけ、圧縮力、摩擦力等の力によりトナーに機械的衝撃力を加える方法を用いてもよい。
【０１７１】
機械的衝撃を加える処理をする場合には、処理時の雰囲気温度をトナーのガラス転移点Ｔｇ付近の温度（すなわち、ガラス転移点Ｔｇの±３０℃の範囲の温度）とすることが、凝集防止と生産性の観点から好ましい。さらに好ましくは、トナーのガラス転移点Ｔｇの±２０℃の範囲の温度で処理を行うことが、転写効率を向上させるのに特に有効である。
【０１７２】
さらにまた、本発明のトナーは、特公昭５６−１３９４５号公報等に記載のディスク又は多流体ノズルを用いて溶融混合物を空気中に霧化し球状トナーを得る方法や、単量体には可溶で得られる重合体が不溶な水系有機溶剤を用いて直接トナーを生成する分散重合方法、又は水溶性の極性重合開始剤の存在下で直接重合させてトナーを生成するソープフリー重合方法に代表される乳化重合方法等を用いてトナーを製造する方法でも製造が可能である。
【０１７３】
本発明のトナーを粉砕法により製造する場合の結着樹脂としては、ポリスチレン、ポリビニルトルエンの如きスチレン及びその置換体の単重合体；スチレン−プロピレン共重合体、スチレン−ビニルトルエン共重合体、スチレン−ビニルナフタリン共重合体、スチレン−アクリル酸メチル共重合体、スチレン−アクリル酸エチル共重合体、スチレン−アクリル酸ブチル共重合体、スチレン−アクリル酸オクチル共重合体、スチレン−アクリル酸ジメチルアミノエチル共重合体、スチレン−メタアクリル酸メチル共重合体、スチレン−メタアクリル酸エチル共重合体、スチレン−メタアクリル酸ブチル共重合体、スチレン−メタクリル酸ジメチルアミノエチル共重合体、スチレン−ビニルメチルエーテル共重合体、スチレン−ビニルエチルエーテル共重合体、スチレン−ビニルメチルケトン共重合体、スチレン−ブタジエン共重合体、スチレン−イソプレン共重合体、スチレン−マレイン酸共重合体、スチレン−マレイン酸エステル共重合体の如きスチレン系共重合体；ポリメチルメタクリレート、ポリブチルメタクリレート、ポリ酢酸ビニル、ポリエチレン、ポリプロピレン、ポリビニルブチラール、シリコーン樹脂、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、パラフィンワックス、カルナバワックスを単独または混合して使用できる。特に、スチレン系共重合体及びポリエステル樹脂が現像特性、定着性等の点で好ましい。
【０１７４】
次に、本発明のトナーを適用するのに好ましい画像形成方法を図１及び図２に沿って具体的に説明する。図１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−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トナーで現像され、転写材Ｐ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Ｐ上へ転写される。トナー画像をのせた転写材Ｐは搬送ベルト１２５等により定着器１２６へ運ばれ、転写材Ｐ上に画像が定着される。また、一部感光体上に残されたトナーはクリーニング手段１１６によりクリーニングされる。現像器１４０は感光体１００に近接してアルミニウム，ステンレス等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２７０μｍ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。図２に示すマグネットローラー１０４には図示の如く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。現像スリーブ１０２に付着して搬送される磁性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、現像スリーブ上トナーは静電潜像に応じて感光体１００上に飛翔し可視像となる。
【０１７５】
本発明における各種物性データの測定方法を以下に既述する。
【０１７６】
（１）現像剤の平均円形度とモード円形度
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、本発明では東亞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形度（Ｃｉ）を下式（１）によりそれぞれ求め、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

【０１７７】
【数２】

【０１７８】
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、平均円形度及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の算出を行う算出法を用いている。しかしながら、この算出法で算出される平均円形度の各値と、上述した各粒子の円形度を直接用いる算出式によって算出される平均円形度の各値との誤差は、非常に少なく、実質的には無視出来る程度のものであり、本発明においては、算出時間の短絡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法を用いても良い。
【０１７９】
具体的な測定方法としては、界面活性剤を約０．１ｍｇ溶解している水１０ｍｌに現像剤約５ｍｇを分散させて分散液を調整し、超音波（２０ｋＨｚ、５０Ｗ）を分散液に５分間照射し、分散液濃度を５０００〜２万個／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を求める。
【０１８０】
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１．００を示し、現像剤の表面形状が複雑になるほど平均円形度は小さな値となる。
【０１８１】
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。
【０１８２】
（２）トナー表面に存在する炭素元素の含有量（Ａ）に対する鉄元素の含有量（Ｂ）の比（Ｂ／Ａ）
本発明におけるトナー表面に存在する炭素元素の含有量（Ａ）に対する鉄元素の含有量（Ｂ）の比（Ｂ／Ａ）は、ＥＳＣＡ（Ｘ線光電子分光分析）により表面組成分析を行い算出した。
【０１８３】
本発明では、ＥＳＣＡの装置および測定条件は、下記の通りである。
使用装置：ＰＨＩ社（Ｐｈｙｓｉｃａｌ Ｅｌｅｃｔｒｏｎｉｃｓ Ｉｎｄｕｓｔｒｉｅｓ，Ｉｎｃ．）製 １６００Ｓ型 Ｘ線光電子分光装置
測定条件：Ｘ線源 ＭｇＫα（４００Ｗ）
分光領域８００μｍφ
【０１８４】
本発明では、測定された各元素のピーク強度から、ＰＨＩ社提供の相対感度因子を用いて表面原子濃度（原子％）を算出した。測定に用いる各元素のピークトップの範囲としては、炭素元素：２８３−２９３ｅＶ、鉄元素：７０６〜７３０ｅＶである。
【０１８５】
測定試料としては、トナーを用いるが、トナーに外添剤が添加されている場合には、イソプロパノールの如きトナーを溶解しない溶媒を用いて、トナーを洗浄し、外添剤を取り除いた後に測定を行う。
【０１８６】
（３）トナーの粒度分布
本実施例においてトナーの重量平均粒径は、以下のようにして求めた。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。測定方法としては、前記電解水溶液１００〜１５０ｍｌ中に分散剤として界面活性剤、好ましくはアルキルベンゼンスルフォン酸塩を０．１〜５ｍｌ加え、さらに測定試料を２〜２０ｍｇ加える。試料を懸濁した電解液は超音波分散器で約１〜３分間分散処理を行い前記コールターマルチサイザーによりアパーチャーとして１００μｍ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した。それから、本発明に関わる所の体積分布から求めた体積基準の重量平均粒径（Ｄ４）、個数分布から求めた個数基準の個数平均粒径（Ｄ１）を求めた。
【０１８７】
（４）スルホン酸基含有重合体の分子量測定
含硫黄重合体の重量平均分子量は、テトラヒドロフランを用いたゲルパーミエーションクロマトグラフィー（ＧＰＣ）によって測定されるポリスチレン換算値として求めた。具体的には、以下の方法に従った。検出器としてＲＩを用いた。＜試料調製＞試料約１０ｍｇを５ｍｌのテトラヒドロフラン溶媒に溶解し、２５℃，１６時間放置後、孔径０．４５μｍのメンブランフィルターで濾過し、試料とした。
【０１８８】
＜測定条件＞
温度：３５℃
溶媒：テトラヒドロフラン
流速：１．０ｍｌ／ｍｉｎ
濃度：０．２重量％
試料注入量：１００μｌ
カラム：昭和電工（株）製、ショウデックス ＧＰＣ ＫＦ８０６Ｍ（３０ｃｍ×２本）
【０１８９】
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。装置は、高速ＧＰＣ ＨＰＬＣ８１２０ ＧＰＣ（東ソー社製）を使用した。
【０１９０】
【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。
【０１９１】
（極性重合体の製造例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８９部、アクリル酸２−エチルヘキシル７部、２−アクリルアミド−２−メチルプロパンスルホン酸４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ｔ−ブチルペルオキシ−２−エチルヘキサノエート０．３５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ｔ−ブチルペルオキシ−２−エチルヘキサノエート０．１８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。
【０１９２】
重合溶媒を減圧留去した後に得られた重合体を１５０メッシュ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。得られた極性重合体はＴｇ約８３℃であった。得られた極性重合体を極性重合体１とする。
【０１９３】
（極性重合体の製造例２〜６）
極性重合体の製造例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、重合温度や重合時間を調整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極性重合体２〜６を製造した。
【０１９４】
【表１】

【０１９５】
（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。水溶液のｐＨを９前後に維持しながら空気を吹き込み、８０〜９０℃で酸化反応を行い、種晶を生成させるスラリー液を調製した。次いでこのスラリー液に、当初のアルカリ量（苛性ソーダのナトリウム成分）に対し０．９〜１．２当量となるよう硫酸第一鉄水溶液を加えた後、スラリー液をｐＨ８に維持して、空気を吹込みながら酸化反応をすすめ、酸化反応後に生成した磁性酸化鉄粒子を洗浄、濾過して一旦取り出した。この時、含水サンプルを少量採取し、含水量を計っておいた。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、十分攪拌しながらシランカップリング剤（ｎ−Ｃ_１０Ｈ_２１Ｓｉ（ＯＣＨ_３）_３）を磁性酸化鉄に対し１．０質量部（磁性酸化鉄の量は含水サンプルから含水量を引いた値として計算した）添加し、カップリング処理を行った。生成した疎水性酸化鉄粒子を常法により洗浄、濾過、乾燥し、次いで若干凝集している粒子を解砕処理して疎水性酸化鉄１を得た。
【０１９６】
（磁性粉体の製造例１）
表面処理磁性粉体の製造例１と同様に酸化反応を進め、酸化反応後に生成した磁性酸化鉄粒子を洗浄、濾過後、表面処理を行わずに乾燥し、凝集している粒子を解砕処理して磁性粉体１を得た。
【０１９７】
（疎水性酸化鉄の製造例２）
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、十分攪拌しながらシランカップリング剤（ｎ−Ｃ_１０Ｈ_２１Ｓｉ（ＯＣＨ_３）_３）を磁性酸化鉄に対し１．０部添加し、カップリング処理を行った。生成した疎水性酸化鉄粒子を常法により洗浄、濾過、乾燥し、次いで凝集している粒子を解砕処理して疎水性酸化鉄２を得た。
【０１９８】
（疎水性酸化鉄の製造例３）
疎水性酸化鉄の製造例１においてシランカップリング剤の処理量を０．０４部とする以外は同様にして疎水性酸化鉄３を得た。
【０１９９】
次に、トナー粒子の製造例及び比較製造例について説明する。
【０２００】
〈トナー粒子の製造例１〉
イオン交換水７０９部に０．１ｍｏｌ／リットル−Ｎａ_３ＰＯ_４水溶液４５１部、１Ｎ塩酸を１９質量部投入し６０℃に加温した後、１．０ｍｏｌ／リットル−ＣａＣｌ_２水溶液６７．７部を徐々に添加して分散安定剤を含む水系媒体を得た。
【０２０１】
一方、
・スチレン ７８部
・ｎ−ブチルアクリレート ２２部
・ビスフェノールＡのＰ．Ｏ．及びＥ．Ｏ．付加物とテレフタル酸の縮合反応より得られる不飽和ポリエステル樹脂 １部
・極性重合体１ ３部
・負荷電性制御剤（モノアゾ染料系のＦｅ化合物） １部
・ジビニルベンゼン ０．４部
・疎水性酸化鉄１ ８０部
上記処方をアトライター（三井三池化工機（株））を用いて均一に分散混合した。
【０２０２】
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℃）１０部を添加混合し、これに、重合開始剤２，２’−アゾビス（２，４−ジメチルバレロニトリル）［ｔ_１／２＝１４０分，６０℃条件下］７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。
【０２０３】
前記水系媒体中に上記重合性単量体系を投入し、６０℃，Ｎ_２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、１０％塩酸を加えてｐＨ＝１以下の状態で２時間攪拌しながら洗浄した。そのエマルジョンを加圧濾過し、さらに２０００質量部以上のイオン交換水で３回洗浄し、十分通気した後、乾燥して重量平均粒径７．２μｍのトナー粒子Ａを得た。
【０２０４】
得られたトナー粒子Ａの物性を、以下のトナー粒子の製造例にて得られたトナー粒子のものと併せ、表２に示す。
【０２０５】
〈トナー粒子の製造例２〜６〉
トナー粒子の製造例１において、極性重合体１に代えて極性重合体２〜６を用いる以外は同様の手法により、トナー粒子Ｂ〜Ｆを得た。
【０２０６】
〈トナー粒子の製造例７〉
トナー粒子の製造例１において、極性重合体１を１７部加える以外は同様の手法により、トナー粒子Ｇを得た。
【０２０７】
〈トナー粒子の製造例８〉
トナーの製造例１の処方の中で、磁性粉体を除き、さらにＮａ_３ＰＯ_４水溶液とＣａＣｌ_２水溶液の投入量を変更し、重量平均粒径０．５μｍのトナー粒子（レーザー回折型粒度分布計ＬＳ−２３０にて測定）を得た。このトナー粒子５部と、トナーの製造例１で得られたトナー粒子１００部を衝撃式表面処理装置（処理温度６０℃、回転式処理ブレード周速９０ｍ／ｓｅｃ．）を用いて、磁性トナー粒子上に非磁性トナー粒子を固着皮膜化させた重量平均粒径８．３μｍの球形化トナー粒子Ｈを得た。
【０２０８】
〈トナー粒子の製造例９及び１０〉
トナー粒子の製造例１において疎水性酸化鉄１を疎水性酸化鉄２及び３に変更した以外は同様の手法により、トナー粒子Ｉ及びＪを得た。
【０２０９】
〈トナー粒子の製造例１１〉
トナー粒子の製造例１においてエステルワックスの使用量を５１部に変更する以外は同様の手法により、トナー粒子Ｋを得た。
【０２１０】
〈トナー粒子の製造例１２〉
トナー粒子の製造例１においてエステルワックスの使用量を０．４部に変更する以外は同様の手法により、トナー粒子Ｌを得た。
【０２１１】
〈トナー粒子の製造例１３〉
トナー粒子の製造例１において疎水性酸化鉄の使用量を１７０部に変更する以外は同様の手法により、トナー粒子Ｍを得た。
【０２１２】
〈トナー粒子の製造例１４〉
トナー粒子の製造例１において、Ｎａ_３ＰＯ_４水溶液とＣａＣｌ_２水溶液の投入量を変更する以外は同様の手法により、重量平均粒径１０．３μｍのトナー粒子Ｎを得た。
【０２１３】
＜トナー粒子の製造例１５＞
イオン交換水１０７０部に塩化マグネシウム１０．２部を溶解させ、これにイオン交換水１７０部に水酸化ナトリウム７．０部を溶解した溶液を徐々に添加して分散安定剤２を得た。トナー粒子の製造例１において用いた分散安定剤を、上記にて得られた分散安定剤２に変えたこと以外はトナー粒子Ａと同様にして、トナー粒子Ｏを製造した。
【０２１４】
＜トナー粒子の製造例１６＞
イオン交換水１０７０部に硫酸アルミニウム１４．２部を溶解させ、これにイオン交換水１７０部に水酸化ナトリウム８．２部を溶解した溶液を徐々に添加して分散安定剤３を得た。トナー粒子の製造例１において用いた分散安定剤を、上記にて得られた分散安定剤３に変えたこと以外はトナー粒子Ａと同様にして、トナー粒子Ｐを製造した。
【０２１５】
＜トナー粒子の製造例１７＞
イオン交換水１２００部に燐酸亜鉛２８部を溶解させ、分散安定剤４を得た。トナー粒子の製造例１において用いた分散安定剤を、上記にて得られた分散安定剤４に変えたこと以外はトナー粒子Ａと同様にして、トナー粒子Ｑを製造した。
【０２１６】
＜トナー粒子の製造例１８＞
イオン交換水１２００部に硫酸バリウム３０質量部を溶解させ、分散安定剤５を得た。トナー粒子の製造例１において用いた分散安定剤を、上記にて得られた分散安定剤５に変えた事以外はトナー粒子Ａと同様にして、トナー粒子Ｒを製造した。
【０２１７】
＜トナー粒子の製造例１９＞
１０％塩酸を加えて５時間攪拌しながら洗浄し、そのエマルジョンを加圧濾過し、さらに２０００部以上のイオン交換水で７回洗浄したこと以外はトナー粒子Ａの製造と同様にしてトナー粒子Ｓを製造した。
【０２１８】
＜トナー粒子の製造例２０＞
３％塩酸を加えて４時間攪拌しながら洗浄し、そのエマルジョンを加圧濾過し、さらに２０００部以上のイオン交換水で３回洗浄したこと以外はトナー粒子Ａの製造と同様にしてトナー粒子Ｔを製造した。
【０２１９】
＜トナー粒子の製造例２１＞
２％塩酸を加えて６時間攪拌しながら洗浄し、そのエマルジョンを加圧濾過し、さらに２０００部以上のイオン交換水で３回洗浄したこと以外はトナー粒子Ａの製造と同様にしてトナー粒子Ｕを製造した。
【０２２０】
＜トナー粒子の製造例２２＞
１０％塩酸を加えて７時間攪拌しながら洗浄し、そのエマルジョンを加圧濾過し、さらに２０００部以上のイオン交換水で７回洗浄したこと以外はトナー粒子Ａの製造と同様にしてトナー粒子Ｖを製造した。
【０２２１】
〈トナー粒子の比較製造例１〉
トナー粒子の製造例１において、極性重合体１を使用しない以外は同様の手法により、トナー粒子Ｗを得た。
【０２２２】
〈トナー粒子の比較製造例２〉
トナー粒子の製造例１において、疎水性酸化鉄１を磁性体１に変更する以外は同様の手法により、トナー粒子Ｘを得た。
【０２２３】
〈トナー粒子の比較製造例３〉
上記材料をブレンダーにて混合し、１１０℃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、粗粉砕物をターボミル（ターボ工業社製）で微粉砕後、得られた微粉砕物を風力分級して重量平均粒径１０．６μｍのトナー粒子Ｙを得た。
【０２２４】
【表２】

【０２２５】
〈磁性トナーの製造例１〉
トナー粒子Ａの１００部に対し、一次粒径１５ｎｍのシリカにヘキサメチルジシラザン（ＨＭＤＳ）処理した後、シリコーンオイルで処理した疎水性シリカ微粉体１．２部をヘンシェルミキサー（三井三池化工機（株））にて２０００ｒｐｍの回転数で３分間混合し、磁性トナー１を得た。
【０２２６】
磁性トナー１の外添条件及び、無機微粉体の遊離率、トナー表面に存在する元素及び量を、以下に示す磁性トナーの製造例及び比較例で得られた磁性トナーのものと併せて、表３に示す。尚、表３の無機微粉体の遊離率について複数の無機微粉体を磁性トナーに対して外添混合した場合には、最も数値の高いものを掲載した。
【０２２７】
〈磁性トナーの製造例２〉
トナー粒子Ａの１００部に対し、一次粒径８２ｎｍのチタンにヘキサメチルジシラザンで表面を処理した後、シリコーンオイルで処理した疎水性チタン微粉体１．２部をハイブリダイザー（奈良機械（株））にて２０００ｒｐｍの回転数で２分間混合し、磁性トナー２を得た。
【０２２８】
〈磁性トナーの製造例３〉
トナー粒子Ａの１００部に対し、一次粒径８ｎｍの未処理シリカ微粉体１．２部をＶ型ブレンダー（（株）徳寿工作所）にて１５ｒｐｍの回転数で６分間混合し、磁性トナー３を得た。
【０２２９】
〈磁性トナーの製造例４〉
トナー粒子Ａの１００部に対し、一次粒径１５ｎｍ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た疎水性シリカ微粉体０．６部及び、一次粒径８２ｎｍのチタンにヘキサメチルジシラザンで表面を処理した後、シリコーンオイルで処理した疎水性チタン微粉体０．５部をヘンシェルミキサー（三井三池化工機（株））にて２０００ｒｐｍの回転数で２分間混合し、磁性トナー４を得た。
【０２３０】
〈磁性トナーの製造例５〉
トナー粒子Ｂの１００部に対し、一次粒径１５ｎｍのシリカにヘキサメチルジシラザンで表面を処理した後、シリコーンオイルで処理した疎水性シリカ微粉体１．２部をヘンシェルミキサー（三井三池化工機（株））にて１５００ｒｐｍの回転数で２分間混合し、磁性トナー５を得た。
【０２３１】
〈磁性トナーの製造例６〉
トナー粒子Ｃの１００部に対し、一次粒径８２ｎｍのチタンにヘキサメチルジシラザンで表面を処理した後、シリコーンオイルで処理した疎水性チタン微粉体１．２部をハイブリダイザー（奈良機械（株））にて２０００ｒｐｍの回転数で２分間混合し、磁性トナー６を得た。
【０２３２】
〈磁性トナーの製造例７〉
トナー粒子Ｄの１００部に対し、一次粒径８２ｎｍのチタンにヘキサメチルジシラザンで表面を処理した後、シリコーンオイルで処理した疎水性チタン微粉体１．２部をハイブリダイザー（奈良機械（株））にて２０００ｒｐｍの回転数で２分間混合し、磁性トナー７を得た。
【０２３３】
〈磁性トナーの製造例８〉
トナー粒子Ｅの１００部に対し、一次粒径１５ｎｍのシリカにヘキサメチルジシラザンで表面を処理した後、シリコーンオイルで処理した疎水性シリカ微粉体１．２部をヘンシェルミキサー（三井三池化工機（株））にて２０００ｒｐｍの回転数で３分間混合し、磁性トナー８を得た。
【０２３４】
〈磁性トナーの製造例９〜２５〉
トナー粒子Ｆ〜Ｖの１００部に対し、一次粒径１５ｎｍのシリカにヘキサメチルジシラザンで表面を処理した後、シリコーンオイルで処理した疎水性シリカ微粉体１．２部をヘンシェルミキサー（三井三池化工機（株））にて２０００ｒｐｍの回転数で３分間混合し、磁性トナー９〜２５を得た。
【０２３５】
〈磁性トナーの比較製造例１〉
トナー粒子Ａの１００部に対し、一次粒径１５ｎｍのシリカにヘキサメチルジシラザンで表面を処理した後、シリコーンオイルで処理した疎水性シリカ微粉体０．６部及び、一次粒径８２ｎｍのチタンにヘキサメチルジシラザンで表面を処理した後、シリコーンオイルで処理した疎水性チタン微粉体０．６部をヘンシェルミキサー（三井三池化工機（株））にて５００ｒｐｍの回転数で２分間混合し、磁性トナー２６を得た。
【０２３６】
〈磁性トナーの比較製造例２〉
トナー粒子Ａの１００部に対し、一次粒径１５ｎｍのシリカにヘキサメチルジシラザンで表面を処理した後、シリコーンオイルで処理した疎水性シリカ微粉体１．２部をヘンシェルミキサー（三井三池化工機（株））にて２０００ｒｐｍの回転数で８分間混合し、磁性トナー２７を得た。
【０２３７】
〈磁性トナーの比較製造例３〜５〉
トナー粒子Ｗ〜Ｙの１００部に対し、一次粒径１５ｎｍのシリカにヘキサメチルジシラザンで表面を処理した後、シリコーンオイルで処理した疎水性シリカ微粉体１．２部をヘンシェルミキサー（三井三池化工機（株））にて２０００ｒｐｍの回転数で３分間混合し、磁性トナー２８〜３０を得た。
【０２３８】
【表３】

【０２３９】
（感光体製造例１）
感光体としては直径３０ｍｍのＡｌシリンダーを基体とした。これに、図３に感光体としては直径３０ｍｍ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。膜厚は２５μｍであり、水に対する接触角は９５度であった。
【０２４０】
なお、接触角は、純水を用い、協和界面科学（株）製の接触角計ＣＡ−Ｘ型装置を用いて測定した。
【０２４１】
［実施例１］
画像形成装置として、ＬＢＰ−１７６０（キヤノン製）を改造し、概ね図１及び２に示されるものを用いた。
【０２４２】
静電荷像担持体１００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１１７を、当接圧５８．８Ｎ／ｍ（６０ｇ／ｃｍ）で当接させ、直流電圧−７００Ｖｄｃに交流電圧２．０ｋＶｐｐを重畳したバイアスを印加して感光体上を一様に帯電する。一次帯電に次いで、レーザー光で画像部分を露光することにより静電潜像を形成する。この時、暗部電位Ｖｄ＝−７００Ｖ、明部電位ＶＬ＝−２００Ｖとした。
【０２４３】
感光ドラムと現像スリーブとの間隙は２７０μｍとし、トナー担持体として下記の構成の層厚約７μｍ、ＪＩＳ中心線平均粗さ（Ｒａ）１．３μｍの樹脂層を、表面が鏡面である直径２０ｍｍのアルミニウム円筒上に形成した現像スリーブを使用し、現像磁極９５ｍＴ（９５０ガウス）、トナー規制部材として厚み１．０ｍｍ、自由長１０ｍｍのシリコーンゴム製ブレードを１４７Ｎ／ｍ（１．５ｋｇ／ｍ）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
【０２４４】
次いで、現像バイアスとして直流バイアス成分Ｖｄｃ＝−５３０Ｖ、重畳する交流バイアス成分Ｖｐｐ＝１６００Ｖ、ｆ＝２０００Ｈｚを用いた。また、現像スリーブの周速は感光体周速（８０ｍｍ／ｓｅｃ）に対して順方向に１１０％のスピード（８８ｍｍ／ｓｅｃ）とした。
【０２４５】
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１０^８Ωｃｍ、表面ゴム硬度２４°、直径２０ｍｍ、当接圧５９Ｎ／ｍ（６ｋｇ／ｍ））を図４中Ａ方向の感光体周速（８０ｍｍ／ｓｅｃ）に対して等速とし、転写バイアスは直流１．５ｋＶとした。
【０２４６】
定着方法としては熱ローラー定着装置を用いた。
【０２４７】
まず、トナーとしてトナー１を使用し、２３℃，６０％ＲＨ環境下において画出し試験を行った。転写材としては９０ｇ／ｍ^２の紙を使用した。その結果、初期において高い濃度や転写性を示し、定着オフセットによる裏汚れ及び画像上、ゴーストの発生もなく、非画像部へのカブリもない良好な画像が得られた。
【０２４８】
次に、印字面積比率４％の横ラインのみからなる画像パターンを印字枚数５０００枚まで印字することにより耐久性の評価を行った。
【０２４９】
画像評価及びトナー耐久性の評価は以下のように行った。
【０２５０】
ａ）濃度
画像濃度の測定はマクベス濃度計ＲＤ９１８（マクベス社製）で測定した。
【０２５１】
ｂ）カブリ
カブリの測定は、東京電色社製のＲＥＦＬＥＣＴＭＥＴＥＲ ＭＯＤＥＬ ＴＣ−６ＤＳを使用して測定した。フィルターは、グリーンフィルターを用い、下記の式より算出した。
【０２５２】
カブリ（反射率）（％）＝標準紙上の反射率（％）−サンプル非画像部の反射率（％）
【０２５３】
カブリは、２．０％以下であれば良好な画像である。
【０２５４】
ｃ）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Ｅ、未使用の紙上に貼ったマイラーテープのマクベス濃度をＤとし、近似的に以下の式で計算した。
【０２５５】
【数３】

【０２５６】
転写効率は９０％以上であれば問題のない画像である。
【０２５７】
ｄ）ゴースト
ゴーストの評価は、べた黒画像上先端のスリーブ一周目の画像濃度と二週目以降の画像濃度の差で評価した。
【０２５８】
ゴーストの評価
Ａ： ０≦｜（スリーブ一周目の画像濃度）−（スリーブ二週目以降の画像濃度）｜≦０．０２
Ｂ：０．０２＜｜（スリーブ一周目の画像濃度）−（スリーブ二週目以降の画像濃度）｜≦０．０４
Ｃ：０．０４＜｜（スリーブ一周目の画像濃度）−（スリーブ二週目以降の画像濃度）｜≦０．０６
Ｄ：０．０６＜｜（スリーブ一周目の画像濃度）−（スリーブ二週目以降の画像濃度）｜
【０２５９】
Ａ〜Ｃならば実用上問題の無い画像である。
【０２６０】
ｅ）解像性
解像性は耐久初期１００枚後において、潜像電界によって電界が閉じやすく、再現しにくい６００ｄｐｉにおける小径孤立１ドットの再現性によって評価した。
Ａ：１００個中の欠損が５個以下
Ｂ：１００個中の欠損が６〜１０個
Ｃ：１００個中の欠損が１１〜２０個
Ｄ：１００個中の欠損が２０個超
【０２６１】
ｆ）定着性
オフセット性は、耐久２０００枚後の画像サンプルの裏側に発生する汚れを観察し、得られたプリントアウト画像の裏汚れの程度について、以下に基づいて評価した。
Ａ：未発生
Ｂ：ほとんど発生せず
Ｃ：若干発生したが、実用的に問題がない
Ｄ：かなり発生し、実用的に問題がある
【０２６２】
また、定着こすり試験として、Ａ４の複写機用普通紙（１０５ｇ／ｍ^２）に単位面積あたりのトナー質量を１．０ｍｇ／ｃｍ^２になるように調整し、濃度測定用の１０ｍｍｘ１０ｍｍベタ画像を多数有する画像を出力し、得られた定着画像を５０ｇ／ｃｍ^２の加重をかけたシルボン紙で５回摺擦し、摺擦後の画像濃度低下率から以下に基づいて評価した。
Ａ：２％未満
Ｂ：２％以上、５％未満
Ｃ：５％以上、１０％未満
Ｄ：１０％以上
【０２６３】
Ｇ）トナー融着
トナー融着の評価は、画像不良が現れやすいハーフトーン画像上にトナー融着による画像不良、即ち白抜けが発生した時点での耐久枚数で判断した。発生するまでの耐久枚数が多いほど、トナーの耐久性が良好なことを意味する。
【０２６４】
得られた結果を表４に示す。表４から分かるように、磁性トナー１は初期の画像評価が良好であり、また耐久５０００枚後でも問題の無い値を示し、非常に良好な耐久結果を示した。
【０２６５】
次に、同様にして低温低湿環境下（１５℃，１０％ＲＨ）及び、高温高湿環境下（３２．５℃，８０％ＲＨ）においても画出し試験を行なったが、やはり同様に良好な画像特性及び耐久性を示した。得られた結果を表５及び表６に示す。
【０２６６】
［実施例２〜２５］
磁性トナーとして、磁性トナー２〜２５を使用し、実施例１と同様の画像形成方法で画出し試験及び耐久試験を行なった。その結果、表４〜表６に示したように、画像特性ならびに耐久性について、特に実用的に問題の無い結果が得られた。
【０２６７】
［比較例１］
トナーとしてトナー２６を使用し、実施例１と同様の画像形成方法で画出し試験を行った。その結果、初期よりカブリとゴーストが悪く、耐久により更に悪化し、転写効率も低いものとなった。
【０２６８】
［比較例２］
トナーとしてトナー２７を使用し、実施例１と同様の画像形成方法で画出し試験を行った。その結果、耐久によりカブリは悪化し、特に高温高湿環境下においてトナー飛散による、画像出力時に紙上の先端付近におけるカブリが著しく、転写効率も低いものとなった。
【０２６９】
［比較例３］
トナーとしてトナー２８を使用し、実施例１と同様の画像形成方法で画出し試験を行った。その結果、初期よりカブリは悪く、耐久により、特に低温低湿環境下ではゴーストが悪化し、また、高温高湿環境下では濃度が低下した。
【０２７０】
［比較例４］
トナーとしてトナー２９を使用し、実施例１と同様の画像形成方法で画出し試験を行った。その結果、画像濃度は低く、耐久によりカブリは悪化し、転写効率も低いものとなった。
【０２７１】
［比較例５］
トナーとしてトナー３０を使用し、実施例１と同様の画像形成方法で画出し試験を行った。その結果、画像濃度は低く、耐久によりカブリは悪化し、転写効率も低いものとなった。
【０２７２】
【表４】

【０２７３】
【表５】

【０２７４】
【表６】

【０２７５】
【発明の効果】
本発明によれば、一成分現像剤を用いた画像形成方法において、平均円形度が０．９７０以上であり、表面に実質上磁性粉体が露出していなく、表面の無機微粉体の個数遊離率Ｆが０．１０％≦Ｆ≦６０．００％の関係を満たすことを特徴とする磁性トナーを用いることにより、良好な帯電均一性及び良好な現像性、高転写性を示し、環境に左右されない高画質画像を長期間安定して得られる。
【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概略図である。
【図２】本発明の実施例に用いた画像形成装置の一例を示す概略図である。
【図３】感光体の構成の一例を示す説明図である。
【図４】接触転写部材の一例を示す説明図である。
【符号の説明】
３４ａ 芯金
３４ｂ 弾性層
３５ バイアス
１００ 感光体（像担持体、被帯電体）
１０２ 現像スリーブ（トナー担持体）
１０３ 磁性トナー
１１４ 転写ローラー（転写部材）
１１６ クリーナー
１１７ 帯電ローラー（接触帯電部材）
１２１ レーザービームスキャナー（潜像形成手段、露光装置）
１２４ 給紙ローラー
１２５ 搬送部材
１２６ 定着装置
１４０ 現像装置
１４１ 撹拌部材
Ｐ 転写材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic toner for developing an electrostatic latent image using an electrophotographic method, an electrostatic recording method, a magnetic recording method, a toner jet method recording, and the like, and an image forming apparatus using the same.
[0002]
[Prior art]
Conventionally, a number of methods are known as electrophotographic methods. In general, an electric latent image is formed on an electrostatic image carrier (hereinafter also referred to as a photoreceptor) by various means using a photoconductive substance. Then, the latent image is developed with toner to form a visible image. If necessary, the toner image is transferred to a transfer material such as paper, and then the toner image is fixed on the transfer material by heat and pressure. To obtain a copy.
[0003]
As a method of visualizing an electric latent image with toner, a cascade development method, a magnetic brush development method, a pressure development method, a magnetic brush development 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]
As a jumping method, for example, in Japanese Patent Application Laid-Open No. 54-43027, an insulating magnetic developer is thinly applied on a developer carrier, and this is triboelectrically charged. A method is disclosed in which the image is developed in close proximity to the image and facing without contact. According to this method, the insulating magnetic developer is thinly coated on the developer carrying member, thereby enabling sufficient frictional charging of the developer, and in contact with the electrostatic latent image while supporting the developer by magnetic force. Since the development is performed without any problem, the transfer of the developer to the non-image portion, so-called fogging, is suppressed, and a high-definition image can be obtained.
[0005]
Such a one-component development method does not require carrier particles such as glass beads or iron powder as in the two-component method, and therefore the development device itself can be reduced in size and weight. Furthermore, since the two-component development method needs to keep the toner concentration in the developer constant, an apparatus that detects the toner concentration and replenishes the necessary amount of toner is required. Therefore, the developing device is also large and heavy here. Since such a device is not necessary in the one-component development method, it is preferable because it can be made small and light.
[0006]
Also, LED and LBP printers are the mainstream in the recent market as printer devices, and the direction of technology is higher resolution, that is, what was conventionally 240, 300 dpi is 400, 600, 800 dpi. Accordingly, with this development, higher definition has been demanded. In addition, copiers are also becoming more sophisticated, and therefore are moving toward digitalization. Since this method is mainly a method of forming an electrostatic latent image with a laser, it is also proceeding in the direction of high resolution, and here again, a high-resolution and high-definition development method is required as in the case of a printer. Yes. As one means for satisfying this requirement, the toner particle size has been reduced. JP-A-1-112253, JP-A-1-191156, JP-A-2-214156, and JP-A-2-284158. JP-A-3-181952 and JP-A-4-162048 propose a toner having a specific particle size distribution and a small particle size.
[0007]
On the other hand, the toner image formed on the photoconductor in the development process is transferred to the transfer material in the transfer process, but the transfer residual toner in the image area and the fog toner in the non-image area remaining on the photoconductor are cleaned in the cleaning process. Then, the toner is stored in the waste toner container. For this cleaning process, blade cleaning, fur brush cleaning, roller cleaning, and the like have been conventionally used. From the standpoint of the apparatus, since the apparatus is inevitably enlarged in order to have such a cleaning apparatus, it has become a bottleneck when aiming to make the apparatus compact. Furthermore, from the viewpoint of ecology, a system with little waste toner is desired in the sense of effective use of toner, and a toner having high transfer efficiency and low fog has been demanded.
[0008]
The developer used in such an image forming process is composed of a toner mainly composed of a binder resin and a colorant. In addition, the developer has characteristics necessary for a toner such as a charge control agent and a release agent. Contains additives to pull out. As a colorant for the magnetic toner, a magnetic material is used as it is, or carbon black or a nonmagnetic inorganic compound, an organic pigment, a dye, or the like is used together with the magnetic material.
[0009]
However, the developing method using the insulating magnetic toner has unstable elements related to the insulating magnetic toner to be used. One of them is that a considerable amount of fine powder magnetic material is mixed and dispersed in the insulating magnetic toner, and a part of the magnetic material is exposed or released on the surface of the toner particles. As a result, the photosensitive properties after transfer are unsatisfactory because various properties required for the toner such as development characteristics (particularly fog suppression) and transferability of the magnetic toner are still unsatisfactory. A lot of toner tends to remain on the body. Such a problem appears particularly conspicuously under high humidity where the triboelectric charge amount tends to decrease. Although means for incorporating a charge control agent is commonly used for improving the triboelectric chargeability, it cannot be said that the adverse effects of the free magnetic powder can be sufficiently excluded.
[0010]
In addition, as described above, as a recent technology direction, there has been a demand for a higher resolution and higher definition development method, and in order to meet these demands, progress has been made in the direction of reducing the toner particle size. However, as the toner particle size becomes smaller in this way, stable tribocharging of the toner powder becomes an important technique. In other words, unless the fine individual toner particles have a uniform charge amount, the above-described decrease in image stability is more likely to appear. This is because the toner particle size is simply reduced, and the adhesion force (mirror image force, van der Waals force, etc.) of the toner particles to the photoreceptor is larger than the Coulomb force applied to the toner particles in the transfer process. As a result, in addition to the increase in the residual toner, the reduction in the toner diameter is accompanied by a deterioration in fluidity, so that the charge amount of individual toner particles tends to be non-uniform, resulting in fog and toner particles having poor transferability. This is because it increases.
[0011]
From the viewpoint of improving the triboelectric chargeability, further improvement of the charge control agent is desired. For example, as a negative charge control agent, an aromatic carboxylic acid such as salicylic acid, alkylsalicylic acid, dialkylsalicylic acid, naphthoic acid, dicarboxylic acid is used. Metal compounds of acids, metal salts or metal complexes of azo dyes or azo pigments, polymer compounds having sulfonic acid or carboxylic acid groups in the side chain, boron compounds, urea compounds, silicon compounds, calixarene. Also, various charge control agents such as quaternary ammonium salts, polymer compounds having quaternary ammonium salts in the side chain, guanidine compounds, nigrosine compounds, imidazole compounds as positive charge control agents are disclosed in JP-B-45. No. 26478, JP-A 59-62870, JP-A 62-262055, and the like.
[0012]
Among them, polar polymer charge control agents have attracted attention in recent years because they are highly compatible with other components and can be uniformly charged. For example, Japanese Patent Application Laid-Open Nos. 63-184762 and 3-56974. , JP-A-8-179564, JP-A-11-184165, JP-A-11-28126, JP-A-11-327208, and JP-A-2000-56518. It is disclosed as a toner using a monomer containing a group as an essential component. However, although these charge control agents have a certain level of performance in charging, the control agent itself also affects the dispersibility of the colorant in the toner and the toner fluidity, so that the amount sufficient for charging is sufficient. It has been found that excessive addition of toner causes a toner having a wide charge distribution. This phenomenon is prominent in development configurations with few opportunities for charging, such as blade coating and magnetic cutting.
[0013]
For this reason, when a polymer having a sulfonic acid group is combined with a spherical toner having excellent fluidity like the above-described polymerization method toner, the slip at the charging portion is further increased, and the charging of the toner becomes uneven. A phenomenon such as ghost on the image occurs.
[0014]
In addition, when the image is left for a long period of time, in which toner packing is likely to occur, the amount of toner on the developer bearing member is extremely likely to be extremely low even when there is almost no decrease in charge amount due to toner slippage. I understand that too. For this reason, the initial image density after standing tends to be lowered, and there is still a point to be improved.
[0015]
Attempts have also been made to solve these problems by improving magnetic powder. Although proposals have been made regarding magnetic iron oxide contained in the magnetic toner, there are still points to be improved.
[0016]
For example, JP-A-62-279352 proposes a magnetic toner containing magnetic iron oxide containing silicon element. Such magnetic iron oxide intentionally has silicon element present inside the magnetic iron oxide, but still has a point to be improved in the fluidity of the magnetic toner containing the magnetic iron oxide.
[0017]
In Japanese Patent Publication No. 3-9045, there is a proposal to control the shape of magnetic iron oxide to be spherical by adding silicate. The magnetic iron oxide obtained by this method uses silicate to control the particle shape, so that a large amount of silicon element is distributed inside the magnetic iron oxide, and the amount of silicon element present on the magnetic iron oxide surface is small. Since the smoothness of the magnetic iron oxide is high, the fluidity of the magnetic toner is improved to some extent, but the adhesion between the binder resin constituting the magnetic toner and the magnetic iron oxide is insufficient.
[0018]
Japanese Patent Application Laid-Open No. 61-34070 proposes a method for producing triiron tetroxide in which a hydroxysilicate solution is added during an oxidation reaction to triiron tetroxide. Although the iron trioxide by this method has Si element near the surface, the Si element exists in a layer near the iron tetraoxide surface, and the surface is vulnerable to mechanical impact such as friction. have.
[0019]
On the other hand, the toner is manufactured as a toner having a desired particle size by melting and mixing a binder resin, a colorant, and the like, uniformly dispersing, pulverizing with a fine pulverizer, and classifying with a classifier (pulverization method). However, there is a limit to the range of materials that can be used to reduce the particle size of the toner. For example, the resin colorant dispersion must be sufficiently brittle and capable of being finely pulverized by an economically usable production apparatus. From this requirement, in order to make the resin colorant dispersion brittle, when the resin colorant dispersion is actually finely pulverized at a high speed, particles having a wide particle size range are easily formed, and in particular, a relatively large proportion of fine particles ( There arises a problem that excessively pulverized particles) are included therein. Further, such highly brittle materials are often further pulverized or powdered when used as developing toners in copying machines and the like. In addition, as described above, the adhesion between the pulverized particle surface and the photosensitive member is also large.
[0020]
Also, in the pulverization method, it is difficult to completely disperse solid fine particles such as magnetic powder or colorant into the resin, and depending on the degree of dispersion, fogging may increase and image density may decrease. . Furthermore, since the pulverization method essentially releases a large amount of magnetic iron oxide particles on the surface of the toner, problems still remain in the triboelectric charging stability under harsh environments such as toner fluidity and high humidity. .
[0021]
That is, in the pulverization method, there is a limit to finer toner particles required for high definition and high image quality, and the powder characteristics, particularly the uniform chargeability and fluidity of the toner are significantly attenuated.
[0022]
In order to overcome the problems of the toner by the pulverization method as described above, and further to satisfy the above-described requirements, a toner production method by a suspension polymerization method has been proposed.
[0023]
The toner by suspension polymerization (hereinafter referred to as polymerized toner) can be easily finely divided into toner particles. Furthermore, since the shape of the obtained toner is spherical, it has excellent transferability and fluidity, and high image quality. It will be advantageous.
[0024]
However, by including a magnetic substance in the polymerized toner, its shape is easily changed from a spherical shape to a distorted one, and fluidity and charging characteristics are greatly reduced, and transferability and frictional charging uniformity are reduced. There is a tendency. This is because suspended particles are easily distorted when a magnetic material having a large specific gravity moves in the polymer material.
[0025]
In addition, since magnetic particles are generally hydrophilic, they are easily released from the toner surface during suspension polymerization, and the shape of the surface is distorted, making it difficult to obtain spherical particles. To do.
[0026]
Therefore, in order to solve these problems, it is important to modify the surface characteristics of the magnetic material.
[0027]
Many proposals have been made regarding surface modification for improving the dispersibility of a magnetic substance in a polymerized toner. For example, various silane coupling agent treatment techniques for magnetic materials are disclosed in Japanese Patent Application Laid-Open Nos. 59-200254, 59-2000025, 59-200277, and 59-224102. Japanese Laid-Open Patent Publication Nos. 63-250660 and 10-239897 disclose techniques for treating silicon element-containing magnetic particles with a silane coupling agent.
[0028]
However, although the dispersibility in the toner is improved to some extent by these treatments, there is a problem that it is difficult to uniformly hydrophobize the surface of the magnetic material. The generation of the magnetic particles cannot be avoided, and the toner particles are insufficient to make the shape of the toner particles into a good level, and it is also difficult to suppress the release of the magnetic particles from the surface.
[0029]
On the other hand, Japanese Patent Application Laid-Open No. 7-209904 discloses a developer technique that completely suppresses exposure of magnetic particles from the surface of toner particles.
[0030]
However, in such a toner, the magnetic particles are completely covered, so that the triboelectric charge amount is not moderated moderately. Therefore, the charge amount is likely to be excessive in a low humidity environment, so that it is caused by so-called charge-up. Deterioration of image density and deterioration of fog are likely to occur. In addition, since the charge control agent that should be present on the surface of the toner particles is also completely covered, it is still difficult to control the toner charge amount under high humidity.
[0031]
Also, a method of adding inorganic fine particles as external additives to toner base particles has been proposed and widely used for the purpose of improving toner flow characteristics, charging characteristics, and the like.
[0032]
For example, as an attempt to improve the flow characteristics using specific inorganic fine particles, inorganic fine particles that have been subjected to a hydrophobizing treatment in JP-A-5-66608, JP-A-4-9860, etc. Or a method of adding hydrophobized inorganic particles and silicone oil-treated inorganic fine particles together in JP-A-61-249059, JP-A-4-264453, and JP-A-5-346682 It has been known.
[0033]
In addition, in JP-A-11-258847, JP-A-2000-47417, JP-A-2000-47418, JP-A-2000-47425, JP-A-2000-47426, and JP-A-2000-47479. Attempts have been made to improve the toner carrying amount and image density on the sleeve surface by defining the release rate and release state of the external additive from the toner base particles.
[0034]
However, these techniques relate to non-magnetic toners, and there is still room for examination regarding magnetic development methods in which conveyance is performed by magnetic force, and characteristics such as image density after being left.
[0035]
Furthermore, many methods have been proposed for adjusting the chargeability of the toner by adding conductive fine particles as an external additive. For example, carbon black as conductive fine particles is used to attach or adhere to the toner surface for the purpose of imparting conductivity to the toner, or for the purpose of suppressing excessive charging of the toner and making the tribo distribution uniform. It is widely known to use as an external additive. In JP-A-57-151952, JP-A-59-168458 and JP-A-60-69660, conductive fine particles of tin oxide, zinc oxide, and titanium oxide are respectively added to the high-resistance magnetic toner. The addition is disclosed. Japanese Patent Application Laid-Open No. 56-142540 discloses that conductive magnetic particles such as iron oxide, iron powder, and ferrite are added to a high-resistance magnetic toner to promote charge induction to the magnetic toner. Toners that have both developability and transferability have been proposed. Further, in JP-A-61-275864, JP-A-62-258472, JP-A-61-114152, and JP-A-2-120865, the toner is graphite, magnetite, polypyrrole conductive particles, polyaniline. In addition to the disclosure of adding conductive particles, it is known to add a wide variety of conductive fine particles to the toner.
[0036]
However, even if such improvement means is used, it is not sufficient to sufficiently bring out the performance in terms of both the fluidity and the chargeability, and as a result, there is a sufficient improvement effect in image characteristics and durability. Is hard to say.
[0037]
As described above, there is still much room for improvement in improving transferability, triboelectric chargeability, and fluidity of the magnetic toner.
[0038]
[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.
[0039]
That is, an object of the present invention is to provide a magnetic toner having high transfer efficiency, no fog, good fluidity even in long-term use, and stable image characteristics even when left for a long time.
[0040]
Another object of the present invention is to provide a magnetic toner having uniform triboelectric charging properties and no ghost.
[0041]
Furthermore, an object of the present invention is to provide an image forming apparatus that can obtain a high-quality image over a long period of time regardless of the environment.
[0042]
[Means and Actions for Solving the Problems]
  The present invention relates to a magnetic toner having magnetic toner particles containing at least a binder resin and iron oxide, and inorganic fine powder mixed in the magnetic toner particles.
  The magnetic toner has a sulfur-containing polymer, and the average circularity of the magnetic toner is 0.970 or more,
  The sulfur-containing polymer is a polymer having a sulfonic acid group and has a weight average molecular weight of 27,000 to 40,000.
  The iron oxide is not substantially exposed on the toner surface,
  The present invention relates to a magnetic toner characterized in that the number free rate F of the inorganic fine powder on the toner particle surface satisfies a relationship of 0.10% ≦ F ≦ 60.00%.
[0043]
The present invention also provides a developer to an image carrier that carries an electrostatic latent image to visualize the electrostatic latent image, and forms the image by fixing the visualized image on a recording material. In the image forming apparatus, the developer includes the magnetic toner.
[0044]
As described above, the control of the shape of the toner and the amount of the magnetic substance existing on the surface of the magnetic toner particles, or the toner fluidity can be said to be an important technique that influences the triboelectric chargeability of the small particle size toner. These controls can improve the developability and transferability of the toner.
[0045]
Therefore, as a result of various studies on the physical properties and materials of the magnetic toner by the present inventors, it has iron oxide and a sulfur-containing polymer, has an average circularity of 0.970 or more, and iron oxide is on the toner surface. A magnetic toner that is substantially unexposed and has a number free rate F of inorganic fine powder on the toner particle surface of 0.10 ≦ F ≦ 60.00 has good charge uniformity, good developability, and high transferability. I found that I have. Further, it has been found that even when the magnetic toner is used for a long period of time, the image density is hardly lowered due to packing, and it is possible to achieve long-term maintenance of a high-quality image, and the present invention has been completed.
[0046]
DETAILED DESCRIPTION OF THE INVENTION
Sulfur-containing polymers, especially polymers having sulfonic acid groups, have high polarity. By incorporating such a polymer into the toner, the charge transfer speed during frictional charging of the toner particles is improved, so that it can be used at low humidity. Charge reduction and decrease in charge amount under high humidity can be suppressed. However, such an effect cannot be expected unless there is a large amount of polar polymer in the vicinity of the surface of the toner particle and the condition that the entire surface of the toner particle is uniformly contacted with the frictional charging member. For example, it is preferable that the toner shape is spherical because it is easy to perform tribocharging uniformly. On the other hand, even if a polar polymer is added to the amorphous toner, only the convex portion of the toner particle surface is in contact with the frictional charging member, so that the toner surface is non-uniformly charged and the charge transfer speed is increased. I cannot expect much improvement. Further, in a situation where the polar polymer exists only inside the toner particles, it is difficult to even contact the friction charging member.
[0047]
Next, the circularity of the magnetic toner will be described.
[0048]
A magnetic toner having an average circularity of 0.970 or more is very excellent in transferability. The reason for this is that the contact area between the toner particles and the photoconductor is small due to the extremely high degree of circularity, and the adhesion of the toner particles to the photoconductor due to mirror image force, van der Waals force, etc. is reduced. Easy to be. Furthermore, when an alternating electric field is applied between the toner carrier and the image carrier, and the development on the image carrier is performed by the reciprocating flying motion of the magnetic toner, the above-described properties act and suppress fogging. It also leads to.
[0049]
At this time, the mode circularity is more preferably 0.99 or more in the circularity distribution of the toner. When the mode circularity is 0.99 or more, it means that most of the toner particles have a shape close to a true sphere, and the above action becomes more remarkable, and the triboelectric charging characteristics and transferability are further improved. . Here, the “mode circularity” means that the circularity is 0.40 to 1.00 divided by 61 every 0.01, and the measured circularity of the toner is assigned to each divided range according to the circularity. This is the lower limit value of the division range in which the frequency value is maximum in the circularity frequency distribution.
[0050]
The sulfur-containing polymer used in the present invention is particularly preferably a polymer containing a sulfonic acid group from the viewpoint of chargeability, and the monomer having a sulfonic acid group for producing this polymer is a styrene sulfone. Acid, 2-acrylamido-2-methylpropane sulfonic acid, 2-methacrylamide-2-methylpropane sulfonic acid, vinyl sulfonic acid, methacryl sulfonic acid and the like, or maleic acid amide derivatives, maleimide derivatives, and styrene derivatives.
[0051]
The polymer containing a sulfonic acid group 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. Absent. 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.
[0052]
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.
[0053]
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.
[0054]
As the polymer having a sulfonic acid group, the monomers as described above can be used, but it is more preferable that the polymer contains a styrene derivative.
[0055]
There are bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, ionic polymerization, and the like as the method for producing the polymer having a sulfonic acid group, but the production is simple and the monomer containing the sulfonic acid group is uniformly formed. Solution polymerization is preferred because it can be easily mixed.
[0056]
The polymer having a sulfonic acid group is
X (SO₃ ⁻) 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 more preferably hydrogen ions.
[0057]
The polymer having a sulfonic acid group is styrene and / or styrene (meth) acrylic containing 0.1 to 5% by mass of a component derived from a sulfonic acid group-containing (meth) acrylamide monomer in the copolymer. When the toner is incorporated in the toner, it is preferable that the compound is a polymer compound composed of an acid copolymer, and if it exceeds the above range, the above-described effects are difficult to obtain.
[0058]
The polymer having a sulfonic acid group is preferably contained in an amount of 0.01 to 15 parts by mass per 100 parts by mass of the binder resin. 0.1 to 10 parts by mass is preferable.
[0059]
When the content of the polar group-containing monomer is less than 0.01 parts by mass, it is difficult to obtain a sufficient charge control action as mentioned in the present invention. It tends to cause a decrease in developability and transferability.
[0060]
The content of the polymer having a sulfonic acid group in the toner can be measured using a capillary electrophoresis method or the like.
[0061]
The polymer having a sulfonic acid group preferably has a weight average molecular weight (Mw) of 27,000 to 40,000. When the weight average molecular weight (Mw) is less than 27000, the fluidity of the toner may be deteriorated, and not only the transferability is likely to deteriorate, but also in long-term continuous use particularly in a high temperature and high humidity environment, Embedding of external additives tends to occur. If it exceeds 40,000, it tends to take time to dissolve in the monomer, and the dispersibility of the pigment tends to be insufficient. Furthermore, not only the coloring power of the toner tends to be lowered but also the possibility of impairing the fixing performance is increased.
[0062]
The molecular weight of the polymer having a sulfonic acid group is measured using gel permeation chromatography (GPC), and details thereof will be described later.
[0063]
The glass transition point (Tg) of the polymer having a sulfonic acid group is preferably 70 ° C. <Tg ≦ 110 ° C. When the glass transition point does not exceed 70 ° C., the storage stability is poor, and embedding of the external additive tends to occur, and the toner fluidity and transferability are further improved by continuous use in a high temperature and high humidity environment. Become inferior. When the glass transition point exceeds 110 ° C., not only is the fixing property at the time of an image having a high toner printing ratio, but also the adhesion of the inorganic fine powder added externally to the toner particles is hindered and the release ratio is high. Become.
[0064]
In addition, the measurement of the glass transition temperature (Tg) of the polymer having a sulfonic acid group was performed using a DSC-7 (manufactured by Perkin Elmer) at a temperature setting pattern of ASTM (D3418-82) at a temperature rate of 10 ° C./min. According to the same procedure. From the DSC curve at the second temperature increase, Tg is defined as Tg, which is the intersection of the baseline before the endothermic peak, the baseline between the baseline after the endothermic peak and the rising curve.
[0065]
The extraction of the polymer having a sulfonic acid group from the toner is not particularly limited, and any method can be used.
[0066]
Next, it will be described that in the present invention, it is preferable that the magnetic material is not substantially exposed on the toner surface.
[0067]
In the present invention, “substantially no magnetic substance is exposed on the toner surface” means that the amount of iron element relative to the content (A) of carbon element present on the surface of the toner particles measured by X-ray photoelectron spectroscopy analysis. The ratio (B / A) of the content (B) is defined as being less than 0.001, and the magnetic substance is not substantially exposed, thereby improving the fluidity and triboelectric chargeability of the magnetic toner, and increasing the magnetic properties. Various performances required for the toner such as development characteristics (particularly, fog suppression) and transferability of the toner are satisfied. Moreover, such an effect shows a further effect by combining with the sulfonic acid group containing polymer mentioned above.
[0068]
Further, in the image forming method including the contact charging step, when the magnetic toner having the magnetic powder exposed on the toner particle surface is used, the photosensitive drum is more prominently scraped by the exposed magnetic powder. However, if (B / A) as described above is less than 0.001, that is, if magnetic toner in which the magnetic powder is substantially not exposed on the surface of the toner particles is used, the toner particles are transferred to the photosensitive drum by a charging member or the like. Even when pressed against the surface, the surface of the photosensitive drum is hardly scraped off, and the shaving of the photosensitive drum and toner fusion can be remarkably reduced. Of course, the image forming method combined with the contact transfer process is also extremely effective, and a very high-definition image can be obtained over a long period of time.
[0069]
However, even when a normal magnetic powder is contained in the polymerized toner, the aforementioned (B / A) is controlled to be less than 0.001, that is, the magnetic powder is not substantially exposed on the toner surface, and the toner particles It is difficult to obtain fluidity and uniform triboelectric charging. Furthermore, since the interaction between the magnetic powder and water is strong during the production of the suspension polymerization toner, it is difficult to obtain a toner having an average circularity of 0.970 or more. This is because (1) the magnetic powder is generally hydrophilic and therefore easily present on the toner surface, and as described above, (2) the magnetic powder moves randomly when the aqueous solvent is stirred, This is probably because the surface of suspended particles composed of the body 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 characteristics of the magnetic powder.
[0070]
Therefore, various methods for hydrophobizing the surface of magnetic iron oxide particles have been proposed. However, it has been difficult to obtain magnetic iron oxide that has been sufficiently and uniformly hydrophobized by conventional methods. Also, when a large amount of treatment agent or the like is used, or when a highly viscous treatment agent or the like is used, the degree of hydrophobicity is certainly increased, but coalescence of particles occurs, and compatibility between hydrophobicity and dispersibility is not necessarily achieved. It was not achieved.
[0071]
Therefore, in the magnetic powder used in the magnetic toner of the present invention, when the particle surface is hydrophobized, the coupling agent is hydrolyzed while dispersing the magnetic particles in the aqueous medium so as to have a primary particle size. It is particularly preferable to use a surface treatment method. 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.
[0072]
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. In this case, since the magnetic particles can be easily combined with each other and a highly viscous coupling agent that has been difficult to be treated can be used, the effect of hydrophobization is very large.
[0073]
Examples of the coupling agent that can be used in the surface treatment of the magnetic powder according to the present invention include a silane coupling agent and a titanium coupling agent. More preferably used is a silane coupling agent having a general formula
R_mSiY_n
[In the formula, 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. ]
It is shown by. For example, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethyl Examples include methoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-hexadecyltrimethoxysilane, and n-octadecyltrimethoxysilane.
[0074]
In particular, the formula
C_pH_{2p + 1}-Si- (OC_qH_{2q + 1})₃
[Wherein p represents an integer of 2 to 20, and q represents an integer of 1 to 3]
It is preferable to hydrophobize the magnetic powder in an aqueous medium using an alkyltrialkoxysilane coupling agent represented by
[0075]
When p in the above formula is smaller than 2, the hydrophobization treatment is easy, but it is difficult to sufficiently impart hydrophobicity, and it becomes difficult to suppress the exposure of the magnetic powder from the toner particles. 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 uniformly disperse the magnetic particles in the toner. Tends to deteriorate the selective developability.
[0076]
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.
[0077]
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.
[0078]
The amount of the treatment 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 powder from the viewpoint of the effect of the treatment and productivity.
[0079]
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. As the surfactant, a nonionic surfactant such as polyvinyl alcohol is preferable. The surfactant is preferably added in an amount of 0.1 to 5% by mass with respect to water. Examples of the pH adjuster include inorganic acids such as hydrochloric acid.
[0080]
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.
[0081]
In the surface-treated magnetic powder thus obtained, no particle aggregation is observed, and the surface of each particle is uniformly hydrophobized. Therefore, when used as a material for polymerized toner, the surface-treated magnetic powder has a dispersibility in toner particles. A polymer toner that is very good, has substantially no exposure from the toner surface, and has an average circularity of 0.970 or more, which is almost spherical, is obtained.
[0082]
More interestingly, when the suspension-polymerized toner is produced using the uniformly hydrophobized magnetic powder and the above-mentioned polymer having a sulfonic acid group at the same time, the affinity between the two is very low. It was found that highly magnetic powders are likely to be present inside toner particles, and conversely, highly polar polymers are likely to be present in the vicinity of toner particle surfaces. As a result, it became clear that the polar polymer and the friction charging member can always come into contact with each other, and the effect of improving the charge transfer rate appears more remarkably.
[0083]
The iron oxide used in the toner of the present invention is produced, for example, by the following method.
[0084]
An aqueous solution containing ferrous hydroxide is prepared by adding an alkali such as sodium hydroxide in an amount equivalent to or greater than the iron component to the ferrous sulfate aqueous solution. Air was blown in while maintaining the pH of the prepared aqueous solution at pH 7 or higher (preferably pH 8 to 10), the ferrous hydroxide oxidation reaction was performed while heating the aqueous solution to 70 ° C. or higher, and the core of magnetic iron oxide particles First, a seed crystal is formed.
[0085]
Next, an aqueous solution containing about 1 equivalent of ferrous sulfate is added to the slurry-like liquid containing seed crystals based on the amount of alkali added previously. While maintaining the pH of the liquid at 6 to 10, the reaction of ferrous hydroxide is promoted while blowing air, and magnetic iron oxide particles are grown with the seed crystal as the core. As the oxidation reaction proceeds, the pH of the liquid shifts to the acidic side, but the pH of the liquid is preferably not less than 6. Adjust the pH of the solution at the end of the oxidation reaction, stir well so that the magnetic iron oxide becomes primary particles, add the coupling agent, stir well, stir, filter, dry, and lightly crush after stirring By doing so, hydrophobic treated magnetic iron oxide particles can be obtained. Alternatively, after the oxidation reaction is completed, the iron oxide particles obtained by washing and filtering are redispersed in another aqueous medium without drying, and then the pH of the redispersion is adjusted and sufficiently stirred. A silane coupling agent may be added to perform the coupling treatment.
[0086]
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.
[0087]
In the method for producing magnetic iron oxide by the aqueous solution method, an iron concentration of 0.5 to 2 mol / liter is generally used from the viewpoint of preventing an increase in viscosity during the reaction and the solubility of iron sulfate. Generally, the lower the iron sulfate concentration, the finer the particle size of the product. Further, in the reaction, the larger the amount of air and the lower the reaction temperature, the easier the atomization.
[0088]
By using the thus produced hydrophobic iron oxide particles for the toner, it is possible to obtain the toner of the present invention having excellent image characteristics and stability.
[0089]
Further, 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 cross-sectional observation of the magnetic toner using a transmission electron microscope (TEM) is used. When D is set, the number of toner particles satisfying the relationship of D / C ≦ 0.02 is preferably 50% or more, and more preferably 65% or more.
[0090]
The reason is as follows.
[0091]
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-described particles are spherical, when one toner particle is the entire space, at least 11.5% of the space in which no magnetic material 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.
[0092]
If there are no magnetic particles in such a space per particle,
{Circle around (1)} The magnetic substance is biased inside the toner particles, and the possibility of aggregation of the magnetic substance 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.
[0093]
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.
[0094]
Therefore, in the present invention, the number of particles satisfying D / C ≦ 0.02 is preferably 50% or more.
[0095]
As a specific observation method by TEM, a cured product obtained by sufficiently dispersing particles to be observed in a room temperature curable epoxy resin and then curing in an atmosphere at a temperature of 40 ° C. as it is, or A method of observing as a flaky sample with a microtome having frozen and diamond teeth is preferred.
[0096]
A specific method for determining the ratio of the number of corresponding particles is as follows.
[0097]
Particles for determining D / C by TEM are obtained by obtaining the equivalent circle diameter from the cross-sectional area in the micrograph and including the value within ± 10% of the number average particle diameter (D1). For the corresponding particles, the minimum value (D) of the distance between the magnetic particle surface and the magnetic toner particle surface is measured, 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.
[0098]
[Expression 1]

[0099]
The number average particle diameter (D1) of the magnetic toner is preferably determined by a Coulter counter described later.
[0100]
Further, it is one of the necessary aspects of the toner of the present invention that the number free rate F of the inorganic fine powder on the toner surface satisfies the relationship of 0.10% ≦ F ≦ 60.00%.
[0101]
As described above, by adding a polymer having a sulfonic acid group to a spherical toner, the characteristics of the polymer having a sulfonic acid group can be sufficiently exerted, and a good triboelectric charging property as a magnetic toner can be obtained. Obtainable.
[0102]
However, since the toner shape is spherical, the magnetic toner containing a polymer having a sulfonic acid group that further improves the fluidity causes excessive sliding, and the pressure contact gap between the developing sleeve and the toner regulating blade is reduced. In the one-component development system in which charging is imparted by passing toner, due to this excessive fluidity, toner charging by the blade is likely to be non-uniform and toner charge-up is likely to occur. Therefore, a phenomenon such as ghost is likely to occur on the image. Further, since the toner having a spherical shape of the present invention is particularly easily packed by being left to stand, excessive restriction at the charge regulating portion or the like is likely to occur after being left for a long period of time, and the amount of toner on the developer carrier is reduced. As a result, the neglected initial image density tends to decrease. Since the above phenomenon becomes particularly remarkable at low temperature and low humidity, the present inventors consider that the sliding property on the developer carrying member also changes depending on the charge amount.
[0103]
Therefore, the present inventors diligently studied about the inorganic fine powder externally added to the toner particles for optimum fluidity. As a result, the number free rate F of the inorganic fine powder on the toner surface is 0.10% ≦ F ≦ 60.00. %, The magnetic toner has uniform chargeability, and ghost suppression is also good on the image. Furthermore, the above-described transferability and fog characteristics are good, and a magnetic toner can be obtained without image deterioration even after long-term use.
[0104]
Here, if the liberation rate of the inorganic fine powder is less than 0.10%, the friction on the toner surface is increased, and there is no problem with the leaving characteristics, but the inorganic fine powder added to the toner surface is particularly high temperature and high humidity. Long-term use in the environment makes it easy to be embedded in toner particles, and causes electrostatic aggregation due to the exposed toner particles on the surface, making it impossible to control charging on the toner carrier and causing toner scattering. When an image is output, fog is particularly noticeable near the leading edge of the paper.
[0105]
Further, when the liberation rate of the inorganic fine powder is more than 60.00%, it means that the free inorganic fine powder is generated more than necessary, and the toner as a whole exhibits excessive fluidity. As a result, the toner becomes non-uniformly charged, and not only the ghost is remarkably generated, but also the amount of toner on the toner carrier cannot be regulated, and the fog increases. In addition, since the slip between the charging member and the developer carrying member becomes excessive, a decrease in image density after being left for a long time becomes large.
[0106]
That is, the inorganic fine powder must be present as an appropriate amount of free particles, and for that purpose, it is important that the free rate F of the inorganic fine powder exhibits a relationship of 0.10% ≦ F ≦ 60.00%. That's it.
[0107]
Further, in order for the liberation rate F of the inorganic fine powder to satisfy the above relationship, the mixing strength of various known mixers used when mixing the inorganic fine powder and the toner is important. By adjusting the number of rotations of the machine, mixing time, etc., the liberation rate F can be in a relationship of 0.10% ≦ F ≦ 60.00%. Furthermore, when a plurality of inorganic fine powders are externally added to the magnetic toner, it becomes clear that the fluidity and triboelectricity are governed by the highest free fraction value among the inorganic fine powders. It was.
[0108]
Further, the liberation rate of the inorganic fine powder on the surface of the magnetic toner particles is measured by a particle analyzer (PT1000: manufactured by Yokogawa Electric Corporation).
[0109]
The particle analyzer performs measurement according to the principle described on pages 65-68 of the Japan Hardcopy 97 papers. Specifically, the device has fine particles such as toner one by one with an electron density of 5 × 10.¹³cm^-3Introduced into a high-temperature non-thermal equilibrium plasma with high electron temperatures exceeding excitation temperatures of 3,300K and 20,000K and knowing the element, number of particles, and particle size of the luminescent material from the emission spectrum of the fine particles accompanying this excitation I can do it.
[0110]
Among these, the liberation rate is defined as a value obtained by the following formula from the simultaneous emission of carbon atoms, which are constituent elements of the binder resin, and emission of main atoms constituting the inorganic fine powder.
[0111]
Free rate of inorganic fine powder (%) = 100 × (Number of light emission only of main atom constituting inorganic fine powder / Number of light emission number of main atom constituting inorganic fine powder simultaneously emitted with carbon atom + Inorganic fine powder The number of times of emission of only the main atoms
[0112]
Here, the simultaneous light emission of the carbon atom and the main atom constituting the inorganic fine powder means that the light emission of the main atom constituting the inorganic fine powder emitted within 2.6 msec from the light emission of the carbon atom is the simultaneous light emission. The light emission of the main atoms constituting the inorganic fine powder is the light emission of only the main atoms constituting the inorganic fine powder. In the present invention, since the inorganic fine powder is externally attached to the toner particle surface, the fact that the main atoms constituting the carbon atom and the inorganic fine powder emit light simultaneously means that the inorganic fine powder is attached to the toner particle surface. In other words, the light emission of only the main atoms constituting the inorganic fine powder can be paraphrased as meaning that the inorganic fine powder is liberated from the toner particle surface.
[0113]
As a specific measurement method, helium gas containing 0.1% oxygen is used, and measurement is performed in an environment of 60% humidity at 23 ° C., and carbon atoms are measured in channel 1 (measurement wavelength 247.860 nm, K factor is the main body) (Recommended value) is measured, and the main atoms constituting the inorganic fine powder are measured using channels 2 to 4 (the channel, wavelength, and K factor used are those recommended by the main unit), and one scan is performed. Then, sampling is performed so that the number of light emission of carbon atoms is 1000 ± 200, and scanning is repeated until the total number of light emission of carbon atoms reaches 10,000 or more, and the light emission number is integrated. Based on this data, the liberation rate of the inorganic fine powder is calculated using the above formula. The light emission intensity of the inorganic fine powder according to the present invention can be measured by selecting a channel recommended by PT1000.
[0114]
In the calculation of the liberation rate according to the present invention, the noise level was set at 1.5V for 1 noise level.
[0115]
In addition, since the toner of the present invention has a higher image quality, the magnetic toner of the present invention preferably has a weight average particle diameter of 3 to 10 μm in order to faithfully develop finer latent image dots. In a toner having a weight average particle size 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 scraping and toner fusion in the contact charging step. Furthermore, in addition to an increase in the surface area of the whole toner, the fluidity and agitation as a powder decrease, and it becomes difficult to uniformly charge individual toner particles, so fog and transferability are likely to deteriorate. In addition to shaving and fusing, it tends to cause uneven image uniformity. When the weight average particle diameter of the toner exceeds 10 μm, the characters and line images are likely to be scattered and high resolution is difficult to obtain.
[0116]
Furthermore, in the present invention, the toner surface is further charged with at least one element selected from magnesium, calcium, barium, aluminum, and zinc by positively presenting 5 to 1000 ppm, more preferably 10 to 500 ppm. Will improve.
[0117]
Although the details of the cause of this phenomenon are not known, it is difficult to achieve the effect unless the magnetic material of the present invention is present, and D / C <0.02 which is one of the features of the present invention is satisfied. The more toner you use, the more effective
[0118]
The present inventors transfer charges between the divalent or trivalent elements such as magnesium, calcium, barium, aluminum, zinc and the magnetic material, and as a result, between the sulfur polymer of the present invention. We believe that it is effective as a charging aid.
[0119]
Further, since the present invention has a specific magnetic structure, the position and amount of the above elements are problems. However, as a result of the study by the present inventors, the effect is exhibited by the presence on the toner surface layer far from the inside of the toner. Specifically, the amount of charge and transfer can be determined by positively allowing 5-1000 ppm, more preferably 10-500 ppm of at least one element selected from magnesium, calcium, barium, aluminum, and zinc to be present on the toner surface. It is effective for sex, fog, etc.
[0120]
If the content of these elements is less than 5 ppm, the effect of the present invention is not exhibited. If the content is more than 1000 ppm, the charge amount of the toner is unnecessarily low, leading to a decrease in transfer efficiency and an increase in fog.
[0121]
In this way, the charge release is suppressed and the charge is evenly controlled by the synergistic effect of controlling the number release rate of the inorganic fine powder on the surface of the magnetic toner within a specific value range and the presence of a specific amount of a specific element on the magnetic toner surface. It is considered that the charging characteristics of the magnetic toner such as the property can be improved, and an image having excellent ghost and fog characteristics and transfer characteristics can be obtained.
[0122]
In addition, when a plurality of elements are present among magnesium, calcium, barium, aluminum, and zinc existing on the toner surface, the total amount thereof needs to be 5 to 1000 ppm. Of these elements, magnesium and calcium are particularly preferable because they are effective in suppressing ghosts.
[0123]
In the present invention, magnesium, calcium, barium, aluminum, and zinc existing on the toner surface are placed in a solvent that does not dissolve the toner, such as isopropanol, and subjected to vibration for 10 minutes with an ultrasonic cleaner, and external additives. It means an element that exists in a state excluding.
[0124]
As for the abundance of these elements, after removing the external additives, the above elements are quantified using a known analysis method such as fluorescent X-ray analysis, plasma emission analysis (ICP) or ESCA on the toner particles. Can be done.
[0125]
In the examples described later, the measurement of each element is performed using fluorescent X-ray analysis, and the details are in accordance with JIS-KO119.
[0126]
(1) Equipment used
X-ray fluorescence analyzer 3080 (Rigaku Corporation)
Sample press molding machine MAEKAWA Testing Machine (manufactured by MFGCo, LTD)
[0127]
(2) Creating a calibration curve
Samples are prepared by externally adding 5 levels of complex compounds for quantitative determination using a coffee mill. The sample is press molded using a sample press molding machine. [M] Kα peak angle (a) in the composite compound is determined from the 2θ table. Place the calibration curve sample in the X-ray fluorescence analyzer and depressurize and vacuum the data chamber. The X-ray intensity of each sample is obtained under the following conditions, and a calibration curve (mass ratio: expressed in ppm) is created.
[0128]
(3) Measurement conditions
Measurement potential, voltage 50kV, 50-70mA
2θ angle a
Crystal plate LiF
Measurement time 60 seconds
[0129]
(4) Determination of the above elements in toner particles
After forming a sample by the same method as the calibration curve, the X-ray intensity is obtained under the same measurement conditions, and the content is calculated from the calibration curve.
[0130]
If there is no compound having each element of magnesium, calcium, barium, aluminum, and zinc other than the toner surface, the amount of each element is obtained by the above method, but any of these elements is present in addition to the toner surface. In this case, the abundance on the toner surface is obtained as follows.
[0131]
First, the abundance of each element is determined by the above method: this is abundance A. Next, the toner particles excluding the external additive are stirred in concentrated nitric acid for 1 hour, thoroughly washed with pure water, dried, and the abundance of each element is determined by the above method: The amount is B. The abundance of each element on the toner surface can be determined by the difference between A and B, that is, (A−B). Even when the above elements are contained in magnetite or the like, magnetite forms a non-moving substance with concentrated nitric acid and does not elute, so that it is possible to measure the abundance only on the toner particle surface.
[0132]
Next, a method for producing toner according to the present invention will be described.
[0133]
The toner of the present invention can be manufactured by a pulverization method, but in the pulverization method, it is necessary to perform mechanical, thermal, or some special treatment in order to set the average circularity of the toner to 0.970 or more. Therefore, it is preferable to produce by suspension polymerization. Even when a toner is produced by suspension polymerization using a normal magnetic material, the magnetic material is inferior in dispersibility, so that the magnetic material is unevenly distributed on the toner surface, or the magnetic material is confused during granulation in an aqueous medium. The toner has an average circularity of 0.970 or more, and the iron oxide used in the present invention is at a high level. Since uniform hydrophobicization is performed, a toner having an average circularity of 0.970 or more can be easily obtained.
[0134]
The following are mentioned as a polymerizable monomer which comprises the polymerizable monomer type | system | group used for this invention.
[0135]
Examples of the polymerizable monomer include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, and p-ethylstyrene; methyl acrylate, ethyl acrylate, Acrylic esters such as n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate Class: Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenolic methacrylate , Dimethylaminoethyl methacrylate, such as methacrylic acid esters of diethylaminoethyl methacrylate; acrylonitrile, methacrylonitrile, acrylamide.
[0136]
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.
[0137]
In addition, the toner of the present invention also contains a release agent, which is one of preferable usage forms. Usually, a toner image is transferred onto a transfer material in a transfer process, and the toner image is then fixed on the transfer material with energy such as heat and pressure to obtain a semi-permanent image. As a fixing method at this time, a heat roll type fixing is generally used. As described above, if a toner having a weight average particle diameter of 10 μm or less is used, a very high-definition image can be obtained. When a transfer material such as paper is used, the toner particles having a small diameter enter the gap between the fibers of the paper, and heat reception from the heat fixing roller becomes insufficient, and low temperature offset tends to occur. However, in the toner of the present invention, by containing an appropriate amount of wax as a release agent, it is possible to prevent the photoconductor from being scraped while achieving both high resolution and offset resistance.
[0138]
Examples of the wax that can be used in the toner of the present invention include paraffin wax, microcrystalline wax, petroleum wax such as petrolactam and derivatives thereof, montan wax and derivatives thereof, hydrocarbon wax and derivatives thereof by Fischer-Tropsch method, and polyethylene. Polyolefin waxes and derivatives thereof, natural waxes such as carnauba wax and candelilla wax, and derivatives thereof. Derivatives here include oxides, block copolymers with vinyl monomers, and graft modified products. Furthermore, higher fatty alcohols, fatty acids such as stearic acid and palmitic acid or compounds thereof, acid amide waxes, ester waxes, ketones, hydrogenated castor oil and derivatives thereof, plant waxes and animal waxes can also be used.
[0139]
In the toner of the present invention, the content of the wax component is preferably in the range of 0.5 to 50 parts by mass with respect to 100 parts by mass of the binder resin. When the content of the wax component is less than 0.5 parts by mass, the effect of suppressing the low temperature offset is poor, and when it exceeds 50 parts by mass, the long-term storage stability is lowered and the dispersibility of other toner materials is deteriorated. Lead to deterioration of fluidity and image characteristics.
[0140]
In the present invention, polymerization may be carried out by adding a resin to the monomer system. For example, hydrophilic functional groups such as amino groups, carboxylic acid groups, hydroxyl groups, sulfonic acid groups, glycidyl groups, and nitrile groups cannot be used because monomers are water-soluble and dissolve in aqueous suspension to cause emulsion polymerization. When it is desired to introduce the monomer component contained in the toner, it may be in the form of a copolymer such as a random copolymer of these and a vinyl compound such as styrene or ethylene, a block copolymer, or a graft copolymer, or It can be used in the form of a polycondensate such as polyester or polyamide, or a polyaddition polymer such as polyether or polyimine. As the usage-amount, 1-20 mass parts is preferable with respect to 100 mass parts of polymerizable monomers. If the amount used is less than 1 part by mass, the effect of addition is small, whereas if it is used in excess of 20 parts by mass, it becomes difficult to design various physical properties of the polymerized toner. In addition, if a polymer having a molecular weight different from the molecular weight range of the toner obtained by polymerizing the monomer is dissolved in the monomer and polymerized, a toner having a wide molecular weight distribution and high offset resistance can be obtained. it can.
[0141]
The toner of the present invention may contain a charge control agent in order to stabilize the charge characteristics. As the charge control agent, known ones can be used, but a charge control agent that has a high charging speed and can stably maintain a constant charge amount is particularly preferable.
[0142]
Further, when the toner is produced using a direct polymerization method, a charge control agent having a low polymerization inhibitory property and substantially free from a solubilized product in an aqueous dispersion medium is particularly preferable. Specific compounds include, as negative charge control agents, metal compounds of aromatic carboxylic acids such as salicylic acid, alkylsalicylic acid, dialkylsalicylic acid, naphthoic acid and dicarboxylic acid, metal salts or metal complexes of azo dyes or azo pigments, sulfones Examples thereof include a polymer compound having an acid or carboxylic acid group in the side chain, a boron compound, a urea compound, a silicon compound, and a calixarene. Examples of the positive charge control agent include a quaternary ammonium salt, a polymer compound having the quaternary ammonium salt in the side chain, a guanidine compound, a nigrosine compound, and an imidazole compound. These charge control agents are preferably used in an amount of 0.5 to 10 parts by mass with respect to 100 parts by mass of the polymerizable monomer. However, the developer related to the image forming method of the present invention does not necessarily include the addition of a charge control agent, and the toner in the toner is positively utilized by frictional charging with the developer layer thickness regulating member or the developer carrier. It is not always necessary to include a charge control agent.
[0143]
The magnetic powder used in the toner of the present invention is preferably used in an amount of 10 to 160 parts by mass with respect to 100 parts by mass of the binder resin. If it is less than 10 parts by mass, the coloring power of the toner is poor, and it is difficult to suppress fogging. On the other hand, when the amount exceeds 160 parts by mass, not only the retention by the magnetic force on the toner carrier is increased and the developability is lowered, but it is difficult not only to uniformly disperse the magnetic powder into individual toner particles, but also the fixability. It will decline.
[0144]
The iron oxide used as the magnetic material in the toner of the present invention may contain elements such as phosphorus, cobalt, nickel, copper, magnesium, manganese, aluminum, and silicon, and is mainly composed of iron trioxide and γ-iron oxide. These are used as components, and these may be used alone or in combination of two or more. These iron oxides preferably have a BET specific surface area by nitrogen adsorption method of 2 to 30 m.²/ G, especially 3 to 28m²/ G and a Mohs hardness of 5 to 7 is preferred.
[0145]
The shape of iron oxide includes octahedrons, hexahedrons, spheres, needles, scales, etc., but those with low anisotropy such as octahedrons, hexahedrons, spheres, and irregular shapes increase the image density. Preferred above. Such a shape can be confirmed by SEM or the like.
[0146]
Furthermore, other colorants may be used in combination with iron oxide. Examples of coloring materials that can be used in combination include magnetic or nonmagnetic inorganic compounds, and known dyes and pigments. Specifically, for example, ferromagnetic metal particles such as cobalt and nickel, or alloys obtained by adding chromium, manganese, copper, zinc, aluminum, rare earth elements to these, hematite, titanium black, nigrosine dye / pigment, carbon black, Examples include phthalocyanine. These may also be used after treating the surface.
[0147]
The polymerization initiator used in the present invention has a half-life of 0.5 to 30 hours during the polymerization reaction. When the polymerization reaction is carried out with an addition amount of 0.5 to 20% by mass of the polymerizable monomer, the molecular weight A polymer having a maximum between 10,000 and 100,000 can be obtained, and the toner can be provided with desirable strength and suitable melting characteristics. Examples of polymerization initiators include 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile ), 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, azo or diazo polymerization initiators such as azobisisobutyronitrile; benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate , Peroxide polymerization initiators such as cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide.
[0148]
In the present invention, a crosslinking agent may be added, and a preferable addition amount is 0.001 to 15% by mass of the polymerizable monomer.
[0149]
In the production of toner by suspension polymerization, generally, the above-described toner composition, that is, a polymerizable monomer, contains iron oxide, a colorant, a release agent, a plasticizer, a binder, a charge control agent, a crosslinking agent, and the like. Components necessary for the toner and other additives such as an organic solvent and a dispersant added to lower the viscosity of the polymer produced by the polymerization reaction, as appropriate, homogenizer, ball mill, colloid mill, ultrasonic disperser, etc. The monomer system uniformly dissolved or dispersed by the dispersing machine is suspended in an aqueous medium containing a dispersion stabilizer. At this time, the particle size of the obtained toner particles becomes sharper by using a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser to obtain a desired toner particle size at a stretch. The polymerization initiator may be added at the same time when other additives are added to the polymerizable monomer, or may be mixed immediately before being suspended in the aqueous medium. Also, a polymerization initiator dissolved in a polymerizable monomer or solvent can be added immediately after granulation and before starting the polymerization reaction.
[0150]
After granulation, stirring may be performed using a normal stirrer to such an extent that the particle state is maintained and particle floating and sedimentation are prevented.
[0151]
In the suspension polymerization method of the present invention, known surfactants and organic / inorganic dispersants can be used as dispersion stabilizers. In particular, inorganic dispersants are less likely to produce harmful ultrafine powders, and their steric hindrance prevents dispersion stability. Therefore, even if the reaction temperature is changed, the stability is not easily lost, the cleaning is easy, and the toner is not adversely affected. Examples of such inorganic dispersants include polyvalent metal phosphates such as calcium phosphate, magnesium phosphate, aluminum phosphate and zinc phosphate; carbonates such as calcium carbonate and magnesium carbonate; calcium metasuccinate, calcium sulfate and barium sulfate. Inorganic salts; inorganic oxides such as calcium hydroxide, magnesium hydroxide, aluminum hydroxide, silica, bentonite and alumina can be mentioned.
[0152]
These inorganic dispersants are preferably used alone or in combination of two or more kinds in an amount of 0.2 to 20 parts by mass with respect to 100 parts by mass of the polymerizable monomer.
[0153]
When aiming at a more finely divided toner having an average particle diameter of 5 μm or less, 0.001 to 0.1 parts by mass of a surfactant may be used in combination. Examples of the surfactant include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, sodium stearate, and potassium stearate.
[0154]
When these inorganic dispersants are used, they may be used as they are, but in order to obtain finer particles, the inorganic dispersant particles can be generated in an aqueous medium. For example, in the case of calcium phosphate, a sodium phosphate aqueous solution and a calcium chloride aqueous solution can be mixed with high-speed stirring to produce water-insoluble calcium phosphate, which enables more uniform and fine dispersion. At the same time, a water-soluble sodium chloride salt is produced as a by-product. However, if a water-soluble salt is present in the aqueous medium, dissolution of the polymerizable monomer in water is suppressed, and an ultrafine toner based on emulsion polymerization is produced. Since it becomes difficult to generate | occur | produce, it is more convenient. Since it becomes an obstacle when removing the remaining polymerizable monomer at the end of the polymerization reaction, it is better to replace the aqueous medium or desalinate with an ion exchange resin. The inorganic dispersant can be almost completely removed by dissolving with an acid or alkali after completion of the polymerization.
[0155]
In the polymerization step, the polymerization is performed at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. When the polymerization is carried out in this temperature range, the release agent and wax to be sealed inside are precipitated by phase separation, and the encapsulation is more complete. In order to consume the remaining polymerizable monomer, the reaction temperature can be increased to 90 to 150 ° C. at the end of the polymerization reaction.
[0156]
The polymerized toner particles are filtered, washed and dried by a known method after the polymerization is completed, and further, a classification process is performed after the production process to cut coarse powder and fine powder. is there.
[0157]
The toner of the present invention is preferably mixed with an inorganic fine powder or a hydrophobic inorganic fine powder as a fluidity improver. For example, titanium oxide fine powder, silica fine powder, and alumina fine powder are preferably added and used, and silica fine powder is particularly preferred.
[0158]
The inorganic fine powder used in the developer of the present invention is preferably one having a primary average particle size in the range of 4 to 80 nm because good results can be obtained. When the primary average 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 becomes non-uniform. Therefore, problems such as an increase in fog, a decrease in image density, and a decrease in durability cannot be avoided. When the primary average particle size of the inorganic fine powder is smaller than 4 nm, the agglomeration property 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 agglomeration 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 primary average particle diameter of the inorganic fine powder is preferably 6 to 35 nm.
[0159]
The measurement method of the primary average particle diameter of the inorganic fine powder is a photograph of the toner magnified by a scanning electron microscope, and further the element contained in the inorganic fine powder by an elemental analysis means such as XMA attached to the scanning electron microscope. While contrasting the photograph of the mapped toner, 100 or more primary particles of the inorganic fine powder that are attached to or separated from the toner surface can be measured to determine the number average primary particle size.
[0160]
As the silica fine powder used in the present invention, both a so-called dry process produced by vapor phase oxidation of a silicon halide compound or a so-called wet silica produced from water glass or the like can be used. However, dry silica with few silanol groups on the surface and inside and no production residue is preferably used.
[0161]
Furthermore, the silica fine powder used in the present invention is preferably hydrophobized because of its characteristics in a high temperature and high humidity environment. When the inorganic fine powder added to the toner particles absorbs moisture, the charge amount of the toner particles decreases and the image density decreases. The hydrophobizing treatment is performed by chemically treating with an organosilicon compound that reacts or physically adsorbs with silica fine powder. As a preferable method, a dry silica fine powder produced by vapor phase oxidation of a silicon halogen compound is treated with a silane coupling agent or with a silane coupling agent and simultaneously with an organosilicon compound such as silicone oil. Is mentioned.
[0162]
Examples of silane coupling agents used for hydrophobizing treatment include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, and allylphenyldichlorosilane. , Benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilane mercaptan, trimethylsilyl mercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, Dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyl Examples thereof include tetramethyldisiloxane and 1,3-diphenyltetramethyldisiloxane.
[0163]
Examples of the organosilicon compound include silicone oil. Preferred silicone oils are those having a viscosity at 25 ° C. of about 30 to 1,000 mm 2 / s (cSt), such as dimethyl silicone oil, methyl phenyl silicone oil, α-methyl styrene modified silicone oil, chlorophenyl silicone oil. Fluorine-modified silicone oil is preferred.
[0164]
Silicone oil treatment methods include, for example, mixing silica fine powder treated with a silane coupling agent and silicone oil directly using a mixer such as a Henschel mixer, or injecting silica silicone oil as a base. Depending on how you do it. Alternatively, the silicone oil may be dissolved or dispersed in an appropriate solvent, and then mixed with the base silica fine powder to remove the solvent.
[0165]
If necessary, an external additive other than the fluidity improver may be added to the toner in the present invention.
[0166]
For example, for the purpose of improving cleaning properties and cohesiveness, it is also preferable to further add fine particles having a primary particle size exceeding 30 nm, more preferably inorganic fine particles or organic fine particles having a primary particle size of 50 nm or more and nearly spherical. one of. For example, spherical silica particles, spherical polymethylsilsesquioxane particles, and spherical resin particles are preferably used.
[0167]
The mixing of the external additive and the magnetic toner can be performed by using one kind or a plurality of kinds of known various methods.
[0168]
When the toner of the present invention is produced by a pulverization method, a known method can be used. Known methods include, for example, a binder resin, a magnetic material, a release agent, a charge control agent, and in some cases, a component such as a colorant and other additives necessary for the toner and other additives, etc., a mixer such as a Henschel mixer or a ball mill. After thoroughly mixing, melt or knead using a heat kneader such as a heating roll, kneader, or extruder to disperse other toner materials such as a magnetic material in a resin that is mutually compatible. After dissolution, cooling and solidification, and pulverization, classification and surface treatment as necessary are performed to obtain toner particles. If necessary, a fine powder or the like can be added and mixed to obtain a developer. Either the classification or the surface treatment may be performed first. In the classification step, it is preferable to use a multi-division classifier from the viewpoint of production efficiency.
[0169]
The pulverization step can be performed using a known pulverizer such as a mechanical impact type or a jet type. In order to obtain a developer having a specific circularity according to the present invention, it is preferable to further pulverize by applying heat or to add a mechanical impact in an auxiliary manner. Further, a hot water bath method in which finely pulverized (classified as necessary) toner particles are dispersed in hot water, a method of passing in a hot air stream, or the like may be used.
[0170]
As a method of applying a mechanical impact force, for example, there is a method using a mechanical impact type pulverizer such as a kryptron system manufactured by Kawasaki Heavy Industries, Ltd. or a turbo mill manufactured by Turbo Industry. In addition, like the mechano-fusion system manufactured by Hosokawa Micron Co., Ltd. and the hybridization system manufactured by Nara Machinery Co., Ltd., the toner is pressed against the inside of the casing by centrifugal force with high-speed rotating blades, and the force of compression force, friction force, etc. A method of applying a mechanical impact force to the toner may be used.
[0171]
In the case of performing a process of applying mechanical impact, the atmosphere temperature during the process is set to a temperature near the glass transition point Tg of the toner (that is, a temperature in the range of ± 30 ° C. of the glass transition point Tg) to prevent aggregation. From the viewpoint of productivity. More preferably, the treatment at a temperature in the range of ± 20 ° C. of the glass transition point Tg of the toner is particularly effective for improving the transfer efficiency.
[0172]
Furthermore, the toner of the present invention is a method for obtaining a spherical toner by atomizing a molten mixture into air using a disk or a multi-fluid nozzle described in JP-B-56-13945, etc. Represented by a dispersion polymerization method in which a toner is directly produced using an aqueous organic solvent in which the polymer obtained in 1 is insoluble, or a soap-free polymerization method in which a toner is produced by direct polymerization in the presence of a water-soluble polar polymerization initiator. The toner can also be produced by a method of producing toner using an emulsion polymerization method or the like.
[0173]
When the toner of the present invention is produced by a pulverization method, the binder resin may be a styrene such as polystyrene or polyvinyltoluene or a homopolymer of a substituted product thereof; a styrene-propylene copolymer, a styrene-vinyltoluene copolymer, or styrene. -Vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate Copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether Copolymer, styrene-vinyl ethyl acetate Styrene copolymer such as styrene copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer Combined; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, fat Aromatic or alicyclic hydrocarbon resins, aromatic petroleum resins, paraffin waxes and carnauba waxes can be used alone or in combination. In particular, a styrene copolymer and a polyester resin are preferable in terms of development characteristics, fixing properties, and the like.
[0174]
Next, a preferred image forming method for applying the toner of the present invention will be specifically described with reference to FIGS. In 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 −700 V by the primary charging roller 117 (applied voltages are AC voltage −2.0 kVpp, DC voltage −700 Vdc). Then, exposure is performed by irradiating the photosensitive member 100 with a laser beam 123 by the laser generator 121. The electrostatic latent image on the photoreceptor 100 is developed with a one-component magnetic toner by the developing device 140 and is transferred onto the transfer material P by the transfer roller 114 in contact with the photoreceptor via the transfer material P. The transfer material P on which the toner image is placed is conveyed to the fixing device 126 by the conveyance belt 125 or the like, and the image is fixed on the transfer material P. In addition, toner remaining on a part of the photoreceptor is cleaned by the cleaning unit 116. 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, and the photosensitive member 100, the developing sleeve 102, and the like. This gap is maintained at about 270 μm by a sleeve / photoreceptor gap holding member (not shown). A magnet roller 104 is fixed and disposed concentrically with the developing sleeve 102 in the developing sleeve. However, the developing sleeve 102 is rotatable. The magnet roller 104 shown in FIG. 2 has a plurality of magnetic poles as shown in the figure. S1 is development, N1 is toner coating amount regulation, S2 is toner intake / conveyance, and N2 is influence on toner blowout prevention. Yes. An elastic blade 103 is provided as a member for regulating the amount of magnetic toner that adheres to the developing sleeve 102 and is conveyed, and the amount of toner conveyed to the developing region is controlled by the contact pressure of the elastic blade 103 against the developing sleeve 102. . In the developing region, a DC and AC developing bias is applied between the photoconductor 100 and the developing sleeve 102, and the toner on the developing sleeve flies onto the photoconductor 100 in accordance with the electrostatic latent image and becomes a visible image.
[0175]
The method for measuring various physical property data in the present invention will be described below.
[0176]
(1) Average circularity and mode circularity of developer
The average circularity in the present invention is used as a simple method for quantitatively expressing the shape of particles. In the present invention, the average circularity is measured using a flow type particle image analyzer “FPIA-1000” manufactured by Toago Medical Electronics. The circularity (Ci) 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 circularity of all particles measured as shown by the following equation (2): Divide the sum of degrees by the total number of particles (m)

[0177]
[Expression 2]

[0178]
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 is calculated using the center value and frequency of the division points. However, there is very little error between each value of the average circularity calculated by this calculation method and each value of the average circularity calculated by the above-described calculation formula that directly uses the circularity of each particle. In the present invention, the calculation formula that directly uses the circularity of each particle described above for reasons of handling data such as a short calculation time and simplification of the calculation formula. Such a calculation method that is partially changed using the concept may be used.
[0179]
As a specific measurement method, about 5 mg of a developer is dispersed in 10 ml of water in which about 0.1 mg of a surfactant is dissolved to prepare a dispersion, and ultrasonic waves (20 kHz, 50 W) are applied to the dispersion for 5 minutes. Irradiation is performed, the dispersion concentration is set to 5000 to 20,000 / μl, and measurement is performed by the above-described apparatus to determine the average circularity of a group of particles having an equivalent circle diameter of 3 μm or more.
[0180]
The average circularity in the present invention is an index of the degree of unevenness of the developer, and indicates 1.00 when the developer is a perfect sphere, and the average circularity becomes smaller as the developer surface shape becomes more complex. Become.
[0181]
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.
[0182]
(2) Ratio of iron element content (B) to carbon element content (A) present on the toner surface (B / A)
The ratio (B / A) of the iron element content (B) to the carbon element content (A) present on the toner surface in the present invention was calculated by performing surface composition analysis by ESCA (X-ray photoelectron spectroscopy). .
[0183]
In the present invention, the ESCA apparatus and measurement conditions are as follows.
Equipment used: 1600S type X-ray photoelectron spectrometer manufactured by PHI (Physical Electronics Industries, Inc.)
Measurement conditions: X-ray source MgKα (400W)
Spectral region 800μmφ
[0184]
In the present invention, the surface atomic concentration (atomic%) was calculated from the measured peak intensity of each element using a relative sensitivity factor provided by PHI. The peak top ranges of each element used for measurement are carbon element: 283-293 eV and iron element: 706 to 730 eV.
[0185]
As the measurement sample, toner is used. When an external additive is added to the toner, the toner is washed with a solvent that does not dissolve the toner, such as isopropanol, and the measurement is performed after removing the external additive. Do.
[0186]
(3) Toner particle size distribution
In this example, the weight average particle diameter of the toner was determined as follows. Using Coulter Multisizer (manufactured by Coulter), an interface (manufactured by Nikka) and PC9801 personal computer (manufactured by NEC) for outputting number distribution and volume distribution were connected, and the electrolyte was 1% NaCl using first grade sodium chloride. Prepare an aqueous solution. As a measuring method, 0.1 to 5 ml of a surfactant, preferably alkylbenzene sulfonate is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolyte in which the sample is suspended is dispersed for about 1 to 3 minutes using an ultrasonic disperser, and the volume distribution is determined by measuring the volume and number of toner particles of 2 μm or more using the 100 μm aperture as the aperture by the Coulter Multisizer. And the number distribution were calculated. Then, the volume-based weight average particle diameter (D4) obtained from the volume distribution in the present invention and the number-based number average particle diameter (D1) obtained from the number distribution were obtained.
[0187]
(4) Measurement of molecular weight of sulfonic acid group-containing polymer
The weight average molecular weight of the sulfur-containing polymer was determined as a polystyrene conversion value measured by gel permeation chromatography (GPC) using tetrahydrofuran. Specifically, the following method was followed. RI was used as a detector. <Sample preparation> About 10 mg of a sample was dissolved in 5 ml of a tetrahydrofuran solvent, allowed to stand at 25 ° C. for 16 hours, and then filtered through a membrane filter having a pore size of 0.45 μm to prepare a sample.
[0188]
<Measurement conditions>
Temperature: 35 ° C
Solvent: Tetrahydrofuran
Flow rate: 1.0 ml / min
Concentration: 0.2% by weight
Sample injection volume: 100 μl
Column: Showa Denko K.K., Shodex GPC KF806M (2 x 30 cm)
[0189]
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. A high-speed GPC HPLC8120 GPC (manufactured by Tosoh Corporation) was used as the apparatus.
[0190]
【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 a mass part.
[0191]
(Production Example 1 of Polar Polymer)
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 89 parts, 7 parts of 2-ethylhexyl acrylate and 4 parts of 2-acrylamido-2-methylpropanesulfonic acid were added and heated to reflux temperature with stirring. A solution obtained by diluting 0.35 part of t-butylperoxy-2-ethylhexanoate as a polymerization initiator with 20 parts of 2-butanone was added dropwise over 30 minutes, and stirring was continued for 5 hours. Further, t-butylperoxy was further added. A solution prepared by diluting 0.18 part of 2-ethylhexanoate 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.
[0192]
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 150 mesh screen. The obtained polar polymer had a Tg of about 83 ° C. The obtained polar polymer is designated as polar polymer 1.
[0193]
(Production Examples 2 to 6 of polar polymer)
In the production example 1 of the polar polymer, the monomers used are changed to the contents shown in Table 1, and the polarities are obtained by the same method except that the molecular weight is controlled by adjusting the amount of the polymerization initiator or the polymerization temperature and the polymerization time. Polymers 2-6 were produced.
[0194]
[Table 1]

[0195]
(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. Air was blown in while maintaining the pH of the aqueous solution at around 9, and an oxidation reaction was performed at 80 to 90 ° C. to prepare a slurry liquid for generating seed crystals. Subsequently, after adding ferrous sulfate aqueous solution to this slurry liquid so that it may become 0.9-1.2 equivalent with respect to the original amount of alkalis (sodium component of caustic soda), the slurry liquid is maintained at pH 8, and air is supplied. The oxidation reaction was promoted while blowing, and the magnetic iron oxide particles produced after the oxidation reaction were washed, filtered, and taken out once. At this time, a small amount of water-containing sample was collected and the water content was measured. Next, this water-containing sample was re-dispersed in another aqueous medium without drying, and then the pH of the re-dispersed liquid was adjusted to about 6, and the silane coupling agent (n-C₁₀H₂₁Si (OCH₃)₃) Was added to the magnetic iron oxide in an amount of 1.0 part by mass (the amount of the magnetic iron oxide was calculated as a value obtained by subtracting the water content from the water-containing sample), and the coupling treatment was performed. The produced hydrophobic iron oxide particles were washed, filtered and dried by a conventional method, and then the slightly agglomerated particles were pulverized to obtain hydrophobic iron oxide 1.
[0196]
(Production example 1 of magnetic powder)
As in Production Example 1 of surface-treated magnetic powder, the oxidation reaction proceeds, the magnetic iron oxide particles generated after the oxidation reaction are washed, filtered, dried without surface treatment, and the aggregated particles are crushed Thus, magnetic powder 1 was obtained.
[0197]
(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 ( n-C₁₀H₂₁Si (OCH₃)₃) Was added to 1.0 parts of magnetic iron oxide and subjected to coupling treatment. The produced hydrophobic iron oxide particles were washed, filtered and dried by a conventional method, and then the agglomerated particles were pulverized to obtain hydrophobic iron oxide 2.
[0198]
(Production Example 3 of hydrophobic iron oxide)
Hydrophobic iron oxide 3 was obtained in the same manner as in Production Example 1 of hydrophobic iron oxide, except that the treatment amount of the silane coupling agent was 0.04 part.
[0199]
Next, a toner particle manufacturing example and a comparative manufacturing example will be described.
[0200]
<Production Example 1 of Toner Particles>
0.1 mol / liter-Na in 709 parts of ion-exchanged water₃PO₄After adding 451 parts of aqueous solution and 19 parts by mass of 1N hydrochloric acid and heating to 60 ° C., 1.0 mol / liter-CaCl₂An aqueous medium containing a dispersion stabilizer was obtained by gradually adding 67.7 parts of an aqueous solution.
[0201]
on the other hand,
・ 78 parts of styrene
・ 22 parts of n-butyl acrylate
-P. of bisphenol A O. And E. O. 1 part of unsaturated polyester resin obtained by condensation reaction of adduct and terephthalic acid
・ Polar polymer 1 3 parts
・ Negative charge control agent (monoazo dye-based Fe compound) 1 part
・ 0.4 parts of divinylbenzene
・ 80 parts of hydrophobic iron oxide 1
The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.).
[0202]
This monomer composition was heated to 60 ° C., and 10 parts of ester wax (because of the endothermic peak maximum value of 72 ° C. in DSC) was added and mixed therewith. , 2′-azobis (2,4-dimethylvaleronitrile) [t_1/2= 140 minutes at 60 ° C] 7 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.
[0203]
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, washed with 10% hydrochloric acid and stirring for 2 hours at pH = 1 or lower. The emulsion was filtered under pressure, further washed three times with 2000 parts by mass or more of ion-exchanged water, sufficiently aerated, and dried to obtain toner particles A having a weight average particle diameter of 7.2 μm.
[0204]
The physical properties of the obtained toner particles A are shown in Table 2 together with those of the toner particles obtained in the following toner particle production examples.
[0205]
<Production Examples 2 to 6 of Toner Particles>
Toner particles B to F were obtained in the same manner as in toner particle production example 1 except that polar polymers 2 to 6 were used instead of polar polymer 1.
[0206]
<Toner particle production example 7>
Toner particles G were obtained in the same manner as in Toner Particle Production Example 1 except that 17 parts of polar polymer 1 was added.
[0207]
<Production Example 8 of Toner Particles>
In the formulation of Toner Production Example 1, except for magnetic powder, Na₃PO₄Aqueous solution and CaCl₂The amount of the aqueous solution charged was changed to obtain toner particles having a weight average particle size of 0.5 μm (measured with a laser diffraction particle size distribution analyzer LS-230). Using 5 parts of the toner particles and 100 parts of the toner particles obtained in Toner Production Example 1 using an impact surface treatment apparatus (treatment temperature 60 ° C., rotary treatment blade peripheral speed 90 m / sec.), Magnetic toner particles Spherical toner particles H having a weight average particle diameter of 8.3 μm were obtained by forming a non-magnetic toner particle as a fixed film thereon.
[0208]
<Toner particle production examples 9 and 10>
Toner particles I and J were obtained in the same manner except that the hydrophobic iron oxide 1 was changed to the hydrophobic iron oxides 2 and 3 in the toner particle production example 1.
[0209]
<Production Example 11 of Toner Particles>
Toner particles K were obtained in the same manner except that the amount of ester wax used in toner particle production example 1 was changed to 51 parts.
[0210]
<Toner Particle Production Example 12>
Toner particles L were obtained in the same manner except that the amount of ester wax used in toner particle production example 1 was changed to 0.4 parts.
[0211]
<Production Example 13 of Toner Particles>
Toner particles M were obtained by the same method except that the amount of hydrophobic iron oxide used in Toner Particle Production Example 1 was changed to 170 parts.
[0212]
<Toner Particle Production Example 14>
In Production Example 1 of toner particles, Na₃PO₄Aqueous solution and CaCl₂A toner particle N having a weight average particle size of 10.3 μm was obtained in the same manner except that the amount of the aqueous solution was changed.
[0213]
<Toner Particle Production Example 15>
Dispersion stabilizer 2 was obtained by gradually adding 10.2 parts of magnesium chloride in 1070 parts of ion-exchanged water and gradually adding a solution of 7.0 parts of sodium hydroxide in 170 parts of ion-exchanged water. Toner particles O were produced in the same manner as toner particles A, except that the dispersion stabilizer used in Toner Particle Production Example 1 was changed to the dispersion stabilizer 2 obtained above.
[0214]
<Toner Particle Production Example 16>
Dispersion stabilizer 3 was obtained by slowly adding 14.2 parts of aluminum sulfate in 1070 parts of ion-exchanged water and gradually adding a solution of 8.2 parts of sodium hydroxide in 170 parts of ion-exchanged water. Toner particles P were produced in the same manner as toner particles A, except that the dispersion stabilizer used in Toner Particle Production Example 1 was changed to the dispersion stabilizer 3 obtained above.
[0215]
<Toner Particle Production Example 17>
Dispersion stabilizer 4 was obtained by dissolving 28 parts of zinc phosphate in 1200 parts of ion-exchanged water. Toner particles Q were produced in the same manner as toner particles A, except that the dispersion stabilizer used in Toner Particle Production Example 1 was changed to the dispersion stabilizer 4 obtained above.
[0216]
<Toner Particle Production Example 18>
Dispersion stabilizer 5 was obtained by dissolving 30 parts by mass of barium sulfate in 1200 parts of ion-exchanged water. Toner particles R were produced in the same manner as toner particles A, except that the dispersion stabilizer used in toner particle production example 1 was changed to the dispersion stabilizer 5 obtained above.
[0217]
<Toner Particle Production Example 19>
Toner particles S were prepared in the same manner as in the production of toner particles A, except that 10% hydrochloric acid was added and washed with stirring for 5 hours, and the emulsion was filtered under pressure and further washed 7 times with 2000 parts or more of ion-exchanged water. Manufactured.
[0218]
<Toner Particle Production Example 20>
Toner particles T were washed in the same manner as in the production of toner particles A, except that 3% hydrochloric acid was added and washed with stirring for 4 hours, the emulsion was filtered under pressure, and further washed three times with 2000 parts or more of ion-exchanged water. Manufactured.
[0219]
<Toner Particle Production Example 21>
Toner particles U were prepared in the same manner as in the production of toner particles A, except that 2% hydrochloric acid was added and washed with stirring for 6 hours, and the emulsion was filtered under pressure and further washed three times with 2000 parts or more of ion-exchanged water. Manufactured.
[0220]
<Toner Particle Production Example 22>
Toner particles V were prepared in the same manner as in the production of toner particles A, except that 10% hydrochloric acid was added and washed with stirring for 7 hours, the emulsion was filtered under pressure, and further washed seven times with 2000 parts or more of ion-exchanged water. Manufactured.
[0221]
  <Comparative Production Example 1 of Toner Particles>
  In the toner particle production example 1, the polar polymer 1 isdo not useExcept for toner particles, the same method is used.WGot.
[0222]
  <Comparative Production Example 2 of Toner Particles>
  Toner particles are produced in the same manner as in Production Example 1 of toner particles except that the hydrophobic iron oxide 1 is changed to the magnetic material 1.XGot.
[0223]
  <Comparative Production Example 3 of Toner Particles>
  The above materials are mixed with a blender, melt-kneaded with a biaxial extruder heated to 110 ° C., the cooled kneaded product is coarsely pulverized with a hammer mill, and the coarsely pulverized product is finely pulverized with a turbo mill (manufactured by Turbo Kogyo). The resulting finely pulverized product was air-classified to produce toner particles having a weight average particle size of 10.6 μm.YGot.
[0224]
[Table 2]

[0225]
<Production Example 1 of Magnetic Toner>
After 100 parts of toner particles A were treated with hexamethyldisilazane (HMDS) on silica having a primary particle diameter of 15 nm, 1.2 parts of hydrophobic silica fine powder treated with silicone oil was added to a Henschel mixer (Mitsui Miike Chemical Industries, Ltd.). The magnetic toner 1 was obtained by mixing at 2000 rpm for 3 minutes.
[0226]
The external addition conditions of the magnetic toner 1, the liberation rate of the inorganic fine powder, the elements and amounts present on the toner surface are shown together with those of the magnetic toners obtained in the following magnetic toner production examples and comparative examples. 3 shows. When the inorganic fine powders in Table 3 were externally added and mixed with a plurality of inorganic fine powders, the one with the highest numerical value was listed.
[0227]
<Production Example 2 of Magnetic Toner>
After 100 parts of toner particles A were treated with hexamethyldisilazane on titanium having a primary particle diameter of 82 nm, 1.2 parts of hydrophobic titanium fine powder treated with silicone oil was added to a hybridizer (Nara Machinery Co., Ltd.). The magnetic toner 2 was obtained by mixing at 2,000 rpm for 2 minutes.
[0228]
<Production Example 3 of Magnetic Toner>
To 100 parts of toner particles A, 1.2 parts of untreated silica fine powder having a primary particle size of 8 nm were mixed for 6 minutes at a rotation speed of 15 rpm in a V-type blender (Tokuju Kogyo Co., Ltd.) to obtain magnetic toner 3 Got.
[0229]
<Example 4 of magnetic toner production>
To 100 parts of toner particles A, silica having a primary particle diameter of 15 nm is treated with hexamethyldisilazane, and then 0.6 parts of hydrophobic silica fine powder treated with silicone oil and titanium with a primary particle diameter of 82 nm are coated with hexamethyldisilazane. After treating the surface with silazane, 0.5 part of hydrophobic titanium fine powder treated with silicone oil was mixed for 2 minutes with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.) at a rotational speed of 2000 rpm. Obtained.
[0230]
<Production Example 5 of Magnetic Toner>
After 100 parts of toner particles B were treated with hexamethyldisilazane on silica having a primary particle diameter of 15 nm, 1.2 parts of hydrophobic silica fine powder treated with silicone oil was added to a Henschel mixer (Mitsui Miike Chemical Industries ( The magnetic toner 5 was obtained by mixing at 1500 rpm for 2 minutes.
[0231]
<Manufacture example 6 of magnetic toner>
For 100 parts of toner particles C, titanium having a primary particle diameter of 82 nm was treated with hexamethyldisilazane, and then 1.2 parts of hydrophobic titanium fine powder treated with silicone oil was added to a hybridizer (Nara Machinery Co., Ltd.). The magnetic toner 6 was obtained by mixing at 2000 rpm for 2 minutes.
[0232]
<Magnetic toner production example 7>
After 100 parts of toner particles D were treated with hexamethyldisilazane on titanium having a primary particle size of 82 nm, 1.2 parts of hydrophobic titanium fine powder treated with silicone oil was added to a hybridizer (Nara Machinery Co., Ltd.). The magnetic toner 7 was obtained by mixing at 2000 rpm for 2 minutes.
[0233]
<Magnetic toner production example 8>
After 100 parts of toner particles E were treated with hexamethyldisilazane on silica having a primary particle diameter of 15 nm, 1.2 parts of hydrophobic silica fine powder treated with silicone oil was added to a Henschel mixer (Mitsui Miike Chemical Industries, Ltd.). The magnetic toner 8 was obtained by mixing at a rotational speed of 2000 rpm for 3 minutes.
[0234]
<Production Examples 9-25 of Magnetic Toner>
After 100 parts of toner particles F to V are treated with hexamethyldisilazane on silica having a primary particle diameter of 15 nm, 1.2 parts of hydrophobic silica fine powder treated with silicone oil is added to a Henschel mixer (Mitsui Miike Chemical Industries). Machine) for 3 minutes at a rotational speed of 2000 rpm to obtain magnetic toners 9 to 25.
[0235]
<Comparative Production Example 1 of Magnetic Toner>
To 100 parts of toner particles A, silica having a primary particle diameter of 15 nm was treated with hexamethyldisilazane, and then 0.6 parts of hydrophobic silica fine powder treated with silicone oil and titanium having a primary particle diameter of 82 nm After treating the surface with hexamethyldisilazane, 0.6 parts of hydrophobic titanium fine powder treated with silicone oil was mixed for 2 minutes at a rotation speed of 500 rpm with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Toner 26 was obtained.
[0236]
<Comparative Production Example 2 of Magnetic Toner>
After 100 parts of toner particles A were treated with hexamethyldisilazane on silica having a primary particle diameter of 15 nm, 1.2 parts of hydrophobic silica fine powder treated with silicone oil was added to a Henschel mixer (Mitsui Miike Chemical Industries ( The magnetic toner 27 was obtained by mixing for 8 minutes at a rotational speed of 2000 rpm.
[0237]
<Comparative Production Examples 3-5 of Magnetic Toner>
After 100 parts of toner particles W to Y were treated with hexamethyldisilazane on silica having a primary particle diameter of 15 nm, 1.2 parts of hydrophobic silica fine powder treated with silicone oil was added to a Henschel mixer (Mitsui Miike Chemical Industries). Machine) for 3 minutes at a rotational speed of 2000 rpm to obtain magnetic toners 28-30.
[0238]
[Table 3]

[0239]
(Photoreceptor Production Example 1)
As the photoreceptor, an Al cylinder having a diameter of 30 mm was used as a base. In FIG. 3, an Al cylinder having a diameter of 30 mm was used as the substrate as the photoreceptor. 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 an azo pigment having absorption in a long wavelength region dispersed in a butyral resin. Film thickness 0.6 μm.
(4) Charge transport layer: Mainly composed of a hole-transporting triphenylamine compound dissolved in a polycarbonate resin (molecular weight of 20,000 by the Ostwald viscosity method) at a mass ratio of 8:10, and polytetrafluoroethylene powder ( 10% by weight of the total solid content was added and dispersed uniformly. The film thickness was 25 μm and the contact angle with water was 95 degrees.
[0240]
The contact angle was measured using pure water and a contact angle meter CA-X type apparatus manufactured by Kyowa Interface Science Co., Ltd.
[0241]
[Example 1]
As the image forming apparatus, LBP-1760 (manufactured by Canon Inc.) was remodeled, and an apparatus generally shown in FIGS. 1 and 2 was used.
[0242]
As the electrostatic image carrier 100, the organic photoreceptor (OPC) drum of Production Example 1 of the photoreceptor was used. A rubber roller charger 117 in which conductive carbon is dispersed as a primary charging member and coated with a nylon resin is brought into contact with this photoreceptor at a contact pressure of 58.8 N / m (60 g / cm), and a DC voltage of −700 Vdc. A bias superposed with an alternating voltage of 2.0 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 = −200 V.
[0243]
The gap between the photosensitive drum and the developing sleeve is 270 μm, and a resin layer having a layer thickness of about 7 μm and a JIS centerline average roughness (Ra) of 1.3 μm having the following configuration is used as a toner carrier, and the surface has a mirror surface of 20 mm in diameter. Using a developing sleeve formed on an aluminum cylinder, a developing magnetic pole of 95 mT (950 gauss), a toner regulating member having a thickness of 1.0 mm, a free length 10 mm silicone rubber blade of 147 N / m (1.5 kg / m) The contact was made by pressure.
・ Phenolic resin 100 parts
・ 90 parts of graphite (particle size: about 7μm)
・ 10 parts of carbon black
[0244]
Next, a DC bias component Vdc = −530 V, an overlapping AC bias component Vpp = 1600 V, and f = 2000 Hz were used as the developing bias. The peripheral speed of the developing sleeve was 110% (88 mm / sec) in the forward direction with respect to the peripheral speed of the photoreceptor (80 mm / sec).
[0245]
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 (6 kg / m)) are set at a constant speed with respect to the peripheral speed of the photoconductor in the direction A in FIG. 4 (80 mm / sec), and the transfer bias is DC. The voltage was 1.5 kV.
[0246]
As a fixing method, a heat roller fixing device was used.
[0247]
First, toner 1 was used as a toner, and an image printing test was performed in an environment of 23 ° C. and 60% RH. 90g / m as transfer material²Paper was used. As a result, a high image having high density and transferability in the initial stage, no back stain due to fixing offset, no ghosting on the image, and no fogging on the non-image area was obtained.
[0248]
Next, durability was evaluated by printing an image pattern consisting of only horizontal lines with a printing area ratio of 4% up to 5000 printed sheets.
[0249]
Image evaluation and toner durability evaluation were performed as follows.
[0250]
a) Concentration
The image density was measured with a Macbeth densitometer RD918 (manufactured by Macbeth).
[0251]
b) fog
The fog was measured using a REFECTMETER MODEL TC-6DS manufactured by Tokyo Denshoku. The filter was calculated from the following formula using a green filter.
[0252]
Fog (reflectance) (%) = reflectance on standard paper (%) − reflectance of sample non-image area (%)
[0253]
If the fog is 2.0% or less, a good image is obtained.
[0254]
c) Transcription
The transfer efficiency is determined by tapering the transfer residual toner on the photoconductor after the solid black image transfer with a Mylar tape and pasting it on the paper. The Macbeth density value is C, and the Mylar is applied on the paper with the toner after the fixing before the transfer. The Macbeth density of the tape with the tape applied was E, and the Macbeth density of the Mylar tape affixed on the unused paper was D, and approximately calculated by the following formula.
[0255]
[Equation 3]

[0256]
If the transfer efficiency is 90% or more, there is no problem.
[0257]
d) Ghost
The ghost was evaluated by the difference between the image density of the first round of the sleeve on the top of the solid black image and the image density after the second week.
[0258]
Ghost rating
A: 0 ≦ | (Image density at the first round of the sleeve) − (Image density after the second week of the sleeve) | ≦ 0.02
B: 0.02 <| (image density in the first round of the sleeve) − (image density after the second week of the sleeve) | ≦ 0.04
C: 0.04 <| (Image density of the first round of the sleeve) − (Image density of the second and subsequent weeks of the sleeve) | ≦ 0.06
D: 0.06 <| (image density in the first round of the sleeve) − (image density in the second and subsequent weeks of the sleeve) |
[0259]
If it is A to C, the image has no practical problem.
[0260]
e) Resolution
The resolution was evaluated based on the reproducibility of a small-diameter isolated 1 dot at 600 dpi, which is easy to close due to the latent image electric field and difficult to reproduce after 100 sheets at the initial durability.
A: Less than 5 defects in 100
B: 6-10 defects in 100
C: 11-20 defects in 100
D: More than 20 defects in 100
[0261]
f) Fixability
The offset property was evaluated by observing the stains occurring on the back side of the image sample after 2000 durability sheets and evaluating the degree of back stains of the obtained printout image based on the following.
A: Not generated
B: Almost no occurrence
C: Slightly generated, but practically no problem
D: It occurs considerably and has a problem in practical use
[0262]
Also, as a fixing rubbing test, A4 copier plain paper (105 g / m²) 1.0 mg / cm of toner mass per unit area²Output an image having a large number of 10 mm × 10 mm solid images for density measurement, and obtain a fixed image obtained by 50 g / cm.²Was rubbed 5 times with the Sylbon paper to which the above weight was applied, and the image density reduction rate after the rubbing was evaluated based on the following.
A: Less than 2%
B: 2% or more and less than 5%
C: 5% or more and less than 10%
D: 10% or more
[0263]
G) Toner fusion
The evaluation of the toner fusion was judged by the durable number at the time when the image defect due to the toner fusion, that is, the white spot occurred on the halftone image where the image defect is likely to appear. It means that the greater the number of durable sheets until the toner is generated, the better the durability of the toner.
[0264]
The results obtained are shown in Table 4. As can be seen from Table 4, the magnetic toner 1 had good initial image evaluation, and showed no problem even after 5,000 sheets of durability, indicating very good durability results.
[0265]
Next, the image formation test was conducted in the same way under a low temperature and low humidity environment (15 ° C., 10% RH) and a high temperature and high humidity environment (32.5 ° C., 80% RH). Image characteristics and durability. The obtained results are shown in Tables 5 and 6.
[0266]
  [Examples 2 to 25]
  As the magnetic toner, magnetic toners 2 to 25 were used, and an image forming test and an endurance test were performed by the same image forming method as in Example 1. As a result, Table 4~As shown in Table 6, there were obtained practically no problems with respect to image characteristics and durability.
[0267]
[Comparative Example 1]
The toner 26 was used as the toner, and an image output test was performed by the same image forming method as in Example 1. As a result, fog and ghost were poor from the beginning, further deteriorated by durability, and transfer efficiency was low.
[0268]
[Comparative Example 2]
The toner 27 was used as the toner, and an image output test was performed by the same image forming method as in Example 1. As a result, the fog deteriorated due to durability, and the fog in the vicinity of the leading edge on the paper during image output due to toner scattering particularly in a high temperature and high humidity environment was low, and the transfer efficiency was low.
[0269]
[Comparative Example 3]
The toner 28 was used as the toner, and an image forming test was performed by the same image forming method as in Example 1. As a result, fog was poor from the beginning, and ghosts deteriorated due to durability, particularly in a low temperature and low humidity environment, and the concentration decreased in a high temperature and high humidity environment.
[0270]
[Comparative Example 4]
Using toner 29 as the toner, an image output test was performed by the same image forming method as in Example 1. As a result, the image density was low, the fog deteriorated due to durability, and the transfer efficiency was low.
[0271]
[Comparative Example 5]
The toner 30 was used as the toner, and an image output test was performed by the same image forming method as in Example 1. As a result, the image density was low, the fog deteriorated due to durability, and the transfer efficiency was low.
[0272]
[Table 4]

[0273]
[Table 5]

[0274]
[Table 6]

[0275]
【The invention's effect】
According to the present invention, in an image forming method using a one-component developer, the average circularity is 0.970 or more, the magnetic powder is not substantially exposed on the surface, and the number of inorganic fine powders on the surface is free. By using a magnetic toner characterized in that the rate F satisfies the relationship of 0.10% ≦ F ≦ 60.00%, it exhibits good charging uniformity, good developability, and high transferability, and depends on the environment. High-quality images that are not used can be obtained stably over a long period of time.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus used in an embodiment of the present invention.
FIG. 2 is a schematic diagram illustrating an example of an image forming apparatus used in an embodiment of the present invention.
FIG. 3 is an explanatory diagram illustrating an example of a configuration of a photoconductor.
FIG. 4 is an explanatory view showing an example of a contact transfer member.
[Explanation of symbols]
34a cored bar
34b Elastic layer
35 bias
100 photoconductor (image carrier, charged body)
102 Development sleeve (toner carrier)
103 Magnetic toner
114 Transfer roller (transfer member)
116 Cleaner
117 Charging roller (contact charging member)
121 Laser beam scanner (latent image forming means, exposure device)
124 Paper feed roller
125 Conveying member
126 Fixing device
140 Developer
141 Stirring member
P transfer material

Claims (17)

In a magnetic toner having magnetic toner particles containing at least a binder resin and iron oxide, and inorganic fine powder mixed in the magnetic toner particles,
The magnetic toner has a sulfur-containing polymer, and the average circularity of the magnetic toner is 0.970 or more,
The sulfur-containing polymer is a polymer having a sulfonic acid group and has a weight average molecular weight of 27,000 to 40,000.
The iron oxide is not substantially exposed on the toner surface,
A magnetic toner, wherein the number free rate F of the inorganic fine powder on the surface of the toner particles satisfies a relationship of 0.10% ≦ F ≦ 60.00%. 2. The magnetic toner according to claim 1 , wherein a relationship of 70 ° C. <Tg ≦ 110 ° C. is satisfied, where Tg is a glass transition temperature of the polymer having a sulfonic acid group. Polymer having the sulfonic acid group, according to claim 1, characterized in that the component derived from a sulfonic acid group-containing (meth) acrylamide monomer is a polymer type compound containing more than 2 wt% in the copolymer Or the magnetic toner according to 2 . A magnetic toner according to the polymer having a sulfonic acid group, any one of claims 1 to 3, characterized in that it is contained 0.01 to 15 parts by weight per 100 parts by weight of the binder resin. When the projected area equivalent circle diameter of the magnetic 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. a magnetic toner according to any one of claims 1 to 4 toner satisfying the 02 relationship is characterized in that 50% by number or more. The magnetic toner according to claim 5 , wherein the toner satisfying the relationship of D / C ≦ 0.02 is 65% by number or more. The magnetic toner has at least one element selected from the group consisting of magnesium, calcium, barium and aluminum, and the abundance of the element on the toner surface is 5 to 1000 ppm based on the toner particle mass. a magnetic toner according to billed claims 1 to 6 that. A magnetic toner according to any one of claims 1 to 7 weight average particle diameter determined from the volume distribution of the magnetic toner (D4) is characterized in that it is a 3 to 10 [mu] m. Magnetic toner is magnetic toner according to any one of claims 1 to 8, characterized in that it contains an inorganic fine powder of average primary particle diameter 4～80Nm. The magnetic toner according to claim 9 , wherein the inorganic fine powder is at least one inorganic powder selected from silica, titanium oxide, and alumina, or a double oxide thereof. The magnetic toner according to claim 9 or 10 , wherein the inorganic fine powder is hydrophobized. 100 parts by mass of the binder resin, the magnetic toner according to any one of claims 1 to 11, characterized in that it contains 10 to 160 parts by weight of magnetic powder. 100 parts by mass of the binder resin, the magnetic toner according to any one of claims 1 to 12, characterized in that it contains 0.5 to 50 parts by weight of wax. A magnetic toner according to any one of claims 1 to 13 mode circularity is characterized in that at least 0.99. A magnetic toner according to any one of claims 1 to 14 toner particles in the magnetic toner is characterized in that it is obtained by polymerization. In an image forming apparatus that visualizes the electrostatic latent image by supplying a developer to an image carrier that carries the electrostatic latent image, and forms an image by fixing the visualized image on a recording material. an image forming apparatus wherein the developer is characterized in that it comprises a magnetic toner according to any one of the claims 1 to 15. The image forming apparatus includes: an image carrier that carries an electrostatic latent image; a charging unit that charges the image carrier; a latent image forming unit that forms an electrostatic latent image on the charged image carrier; A developing device that visualizes the electrostatic latent image by supplying a developer to the image carrier on which the latent image is formed, a transfer unit that transfers the visualized image to the transfer material, and the image transferred to the transfer material At least a fixing means for fixing the image to the transfer material, and the means for charging the developer in the developing device is performed by an elastic member or a magnetic blade that is in contact with the developer carrier via the developer. The image forming apparatus according to claim 16 .

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