JP4072444B2 - Magnetic toner and image forming method using the same - Google Patents

Description

【００４８】
該磁性トナーの個数平均粒径（Ｄ１）は、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水溶液を調製して求めた。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、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。
【００４９】
さらに本発明者等は、本発明の磁性トナーは、磁性トナー粒子と逆極性の無機微粉体（無機微粉体α）と該磁性トナー粒子と同極性の無機微粉体（無機微粉体β）を含有し、該無機微粒体αの粉体帯電量をＱ（μＣ／ｇ）、比表面積Ｈ（ｍ²／ｇ）とした時、０．１≦Ｑ／Ｈ≦１０．０であり、該無機微粉体αと該無機微粉体βの含有量の比κ（κ＝αの含有量／βの含有量）が０．００３≦κ≦１．０であることが、様々な環境下において長期間放置し、繰り返し使用を行なっても磁性トナーを安定に帯電させるために非常に有効であることを見出した。
【００５０】
その原因の詳細についてはよく分かっていないが、本発明の構成要件である磁性粉体が存在しないと効果が発揮されないこと、また磁性トナー粒子の球形度が高いほどより効果を発揮することなどから、本発明者らは、磁性トナー粒子の表面に外添混合された無機微粉体α及び無機微粉体βと磁性体の間で静電的な相互作用、具体的には電荷の授受があると考えている。そして、その磁性トナー粒子との電荷授受と、お互いに逆極性である無機微粉体α及びβの二種の外添剤を添加することによる電荷反発が常にお互いの粒子を活性化させることにより磁性トナー粒子への埋め込みを抑制しているものと考えている。そして、それが磁性トナー粒子と逆極性の無機微粉体αの単位面積あたりの粉体帯電量（Ｑ／Ｈ）及び、該無機微粉体αとβの含有量の比（κ）と密接に関係していることが明らかとなった。
【００５１】
上記条件を満足する本発明の磁性トナーは、高湿環境下においてもトリボの立ち上がりが早く、また該環境において長期間放置後、再度画出し試験を行ってもトリボの低下を生じることなく高濃度の画像を得ることができる。さらに、低温低湿環境下においても、該条件を満たす本発明の磁性トナーはトリボの安定性に優れ、過剰帯電を起すことなく長期連続使用においても定着飛び散りのない高精細な画像を得ることができる。
【００５２】
ここで０．１＞Ｑ／Ｈでは、高湿環境下においてトリボの立ち上がりが遅く、耐久初期や放置後における画像濃度の低下やかぶりが発生してしまい、Ｑ／Ｈ＞１０．０では特に低湿環境下において磁性トナーの帯電性が不安定となり過剰帯電となってしまう。
【００５３】
また、０．００３＞κでは磁性トナーは過剰に帯電してしまい定着時における飛び散りやブロッチの発生を抑制することができず、κ＞１．０では磁性トナーのトリボ低下を抑制することができない。
【００５４】
また、磁性トナー粒子の円形度との関連性については、円形度の低い磁性トナー粒子では、その凸部に電荷が集中することにより、何れかの極性の無機微粉体のみが局在し、各々の粒子の活性化は行なわれず、無機微粉体の磁性トナーへの埋め込みを抑制できないため、磁性トナーの均一帯電性を得ることができないと考えられる。
【００５５】
さらに、比（Ｂ／Ａ）との関係については、Ｂ／Ａが０．００１以上、つまり磁性トナー粒子表面に磁性体が露出している場合では、磁性体がトナー粒子の過剰な帯電リークサイトとして機能することにより電荷が磁性トナー粒子から逃げてしまい、無機微粉体α及び無機微粉体βに対して十分な電荷授受を行なうことができず、結果として無機微粉体α及びβの二種類の外添剤の電荷反発が生じず、お互いの粒子が活性化できないために、耐久性や、均一な帯電安定性を得ることができないと考えられる。つまり、無機微粉体α及びβと磁性体の間には適度な電荷授受が必要であり、そのためには比（Ｂ／Ａ）が０．００１未満であることが必須であると考えられる。
【００５６】
本発明における無機微粉体α及びβとしては、例えばカーボンブラック、グラファイトなどの炭素微粉末；銅、金、銀、アルミニウム、ニッケルなどの金属微粉末；酸化亜鉛、酸化チタン、酸化スズ、酸化アルミニウム、酸化インジウム、酸化ケイ素、酸化マグネシウム、酸化バリウム、酸化モリブデン、酸化鉄、酸化タングステンなどの金属酸化物；硫化モリブデン、硫化カドミウム、チタン酸カリ、チタン酸バリウムなどの金属化合物、或いはこれらの複合酸化物、ハイドロタルサイト類似化合物などが必要に応じてアミノシランなどの有機処理を用いるなどして無機微粉体の帯電極性及び帯電量を調整して無機微粉体α或いは無機微粉体βとして使用することができる。これらの中でも無機微粉体αとしてはハイドロタルサイト類似化合物、及びアミノシラン化合物で処理した酸化チタン化合物、或いはその複合酸化物が、また無機微粉体βとしては、酸化スズ及び酸化チタン等の無機酸化物が好ましく、また該粉体の抵抗値を制御する等の目的で、該無機微粉体の主金属元素と異なるアンチモン、アルミニウムなどの元素を０．１〜５質量％含有した金属酸化物、導電性材料を表面に有する微粒子なども使用できる。例えば酸化スズ・アンチモンで表面処理された酸化チタン微粒子、アンチモンでドープされた酸化第二スズ微粒子、或いは酸化第二スズ微粒子などが好ましい。
【００５７】
また、無機微粉体βは粉体抵抗が１×１０⁹Ω・ｃｍ以下の導電性微粉体であることが好ましい。無機微粉体βの抵抗が１×１０⁹Ω・ｃｍを超えると、特に低温低湿下において磁性トナーの帯電量が過剰になる傾向があり、定着飛び散りやブロッチを発生しやすくなる。
【００５８】
本発明において、無機微粉体の抵抗測定は、錠剤法により測定し正規化して求めた。即ち、底面積２．２６ｃｍ²の円筒内におよそ０．５ｇの粉体試料を入れ、上下電極に１５ｋｇの加圧を行うと同時に１００Ｖの電圧を印加し抵抗値を計測、その後正規化して比抵抗を算出した。尚、抵抗を行なうにあたっては、測定試料を３日間低湿（１０％）環境下に放置してから行なった。
【００５９】
次に本発明におけるトナーの製造方法を説明する。
【００６０】
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、粉砕法ではトナー粒子の平均円形度を０．９７０以上とするために機械的、熱的或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。通常の磁性粉体を用いて懸濁重合によりトナーを製造したとしても、磁性粉体が分散性に劣るために磁性体粒子がトナー粒子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粒子が乱雑に動き、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難いものであったが、本発明において用いられる磁性粉体は、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。
【００６１】
本発明において、結着樹脂の構成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。
【００６２】
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。
【００６３】
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、或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。
【００６４】
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。
【００６５】
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、モンタンワックス及びその誘導体、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。
【００６６】
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。
【００６７】
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、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、これらとスチレン或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、或いはグラフト共重合体の如き共重合体の形にして、或いはポリエステル、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。
【００６８】
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。
【００６９】
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、ジ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、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においては、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。
【００７０】
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。
【００７１】
また、本発明のトナーにおいて磁性粉体として用いられる酸化鉄は、リン、コバルト、ニッケル、銅、マグネシウム、マンガン、アルミニウム、ケイ素の如き元素を含んでもよく、四三酸化鉄、γ−酸化鉄を主成分とするものであり、これらを１種または２種以上を併用して用いられる。これら酸化鉄は、窒素吸着法によるＢＥＴ比表面積が好ましくは２〜３０ｍ²／ｇ、特に３〜２８ｍ²／ｇであり、さらにモース硬度が５〜７のものが好ましい。
【００７２】
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（走査型電子顕微鏡）などによって確認することができる。
【００７３】
本発明のトナーに用いられる磁性粉体は、例えば下記方法で製造される。
【００７４】
硫酸第一鉄水溶液に、鉄成分に対して当量または当量以上の水酸化ナトリウムの如きアルカリを加え、水酸化第一鉄を含む水溶液を調製する。調製した水溶液のｐＨを７以上（好ましくは８〜１０）に維持しながら空気を吹き込み、水溶液を７０℃以上に加温しながら水酸化第一鉄の酸化反応をおこない、磁性酸化鉄粒子の芯となる種晶をまず生成する。
【００７５】
次に、種晶を含むスラリー状の液に、前に加えたアルカリの添加量を基準として約１当量の硫酸第一鉄を含む水溶液を加える。液のｐＨを６〜１０に維持しながら空気を吹込みながら水酸化第一鉄の反応をすすめ種晶を芯にして磁性酸化鉄粒子を成長させる。酸化反応が進むにつれて液のｐＨは酸性側に移行していくが、液のｐＨは６未満にしない方が好ましい。酸化反応の終期に液のｐＨを調整し、磁性酸化鉄が一次粒子になるよう十分に撹拌し、カップリング剤を添加して十分に混合撹拌し、撹拌後に濾過し、乾燥し、軽く解砕することで疎水性処理磁性酸化鉄粒子が得られる。或いは、酸化反応終了後、洗浄、濾過して得られた酸化鉄粒子を、乾操せずに別の水系媒体中に再分散させた後、再分散液のｐＨを調整し、十分撹拌しながらシランカップリング剤を添加し、カップリング処理を行っても良い。
【００７６】
第一鉄塩としては、一般的に硫酸法チタン製造に副生する硫酸鉄、鋼板の表面洗浄に伴って副生する硫酸鉄の利用が可能であり、さらに塩化鉄等が可能である。
【００７７】
水溶液法による磁性酸化鉄の製造方法は一般に反応時の粘度の上昇を防ぐこと、及び、硫酸鉄の溶解度から鉄濃度０．５〜２モル／リットルが用いられる。硫酸鉄の濃度は一般に薄いほど製品の粒度が細かくなる傾向を有する。また、反応に際しては、空気量が多いほど、そして反応温度が低いほど微粒化しやすい。
【００７８】
このようにして製造された疎水性酸化鉄粒子をトナーに使用することにより、画像特性及び安定性に優れた本発明のトナーを得ることが可能となる。
【００７９】
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、磁性或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。
【００８０】
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。
【００８１】
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。
【００８２】
懸濁重合法によるトナーの製造では、一般に上述の重合性単量体中に、磁性粉体、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或いは溶媒に溶解した重合開始剤を加えることもできる。
【００８３】
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。
【００８４】
また、本発明のトナーは、さらに高画質のため、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。
【００８５】
本発明のトナーの懸濁重合においては、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、リン酸カルシウム、リン酸マグネシウム、リン酸アルミニウム、リン酸亜鉛の如きリン酸多価金属塩；炭酸カルシウム、炭酸マグネシウムの如き炭酸塩；メタケイ酸カルシウム、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。
【００８６】
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。
【００８７】
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。
【００８８】
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、リン酸カルシウムの場合、高速撹拌下、リン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、水不溶性のリン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、重合終了後酸或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。
【００８９】
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。
【００９０】
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、さら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。
【００９１】
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γが混合されていることが好ましく、該無機微粉体γを本発明の磁性トナーに外添混合することにより、本発明の磁性トナーの流動性が向上し、前述の無機微粉体α及び無機微粉体βの活性化が促進される。
【００９２】
本発明に用いられる無機微粉体γは、一次平均粒径が４〜２５ｎｍ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γの一次平均粒径が２５ｎｍ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、画像濃度の低下或いは耐久性の低下等の問題を生じやすい。無機微粉体γの一次平均粒径が４ｎｍよりも小さい場合には、無機微粉体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γの一次平均粒径は６〜２０ｎｍであることがより良い。
【００９３】
無機微粉体γの一次平均粒径の測定法は、走査型電子顕微鏡により拡大撮影したトナーの写真で、さら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γ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γの一次粒子を１００個以上測定し、個数平均一次粒径を求めることができる。
【００９４】
本発明のトナーに用いられる無機微粉体γとしてはシリカまたはその複酸化物の微粉体が好ましい。
【００９５】
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。
【００９６】
さらに本発明に用いられる無機微粉体γは疎水化処理されていることが好ましく、特に疎水化処理されたシリカ微粉体は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或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、或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。
【００９７】
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。
【００９８】
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。
【００９９】
シリコーンオイル処理の方法は、例えばシランカップリング剤で処理されたシリカ微粉体とシリコーンオイルとをヘンシェルミキサー等の混合機を用いて直接混合しても良いし、ベースとなるシリカへシリコーンオイルを噴射する方法によっても良い。或いは適当な溶剤にシリコーンオイルを溶解或いは分散せしめた後、ベースのシリカ微粉体と混合し、溶剤を除去して作製しても良い。
【０１００】
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。
【０１０１】
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。
【０１０２】
尚、上記外部添加剤とトナー粒子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。
【０１０３】
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、磁性粉体、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または溶解させ、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できる。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。
【０１０４】
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。
【０１０５】
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。
【０１０６】
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（即ち、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。
【０１０７】
さらにまた、本発明のトナーは、ディスクまた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、また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。
【０１０８】
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。
【０１０９】
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、１は感光ドラムで、その周囲に一次帯電ローラー２、現像器３、転写ローラー４、クリーニング手段５、レジスタローラー６等が設けられている。そして感光体１は一次帯電ローラー２によって−６４０Ｖに帯電される（印加電圧は交流電圧−２．０ｋＶ_pp、直流電圧−６４０Ｖ_dc）。そして、レーザー発生装置７によりレーザー光８を感光体１に照射することによって露光される。感光体１上の静電潜像は現像器３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４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９等により定着器１０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１上に残されたトナーはクリーニング手段５によりクリーニングされる。現像器３は感光体１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１１（以下、現像スリーブと称す）が配設され、感光体１と現像スリーブ１１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２６５μｍに維持されている。現像スリーブ１１内にはマグネットローラー１３が現像スリーブ１１と同心的に固定、配設されている。但し現像スリーブ１１は回転可能である。図２に示すマグネットローラー１３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１１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１４が配設され弾性ブレード１４の現像スリーブ１１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１と現像スリーブ１１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１１上トナーは静電潜像に応じて感光体１上に飛翔し可視像となる。
【０１１０】
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。
【０１１１】
（１）トナー粒子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（Ｃ_i）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）で除した値を平均円形度（Ｃ_av）と定義する。
【０１１２】
【数２】

【０１１３】
尚、本発明で用いられる測定装置である「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、実質的には無視でき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。
【０１１４】
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。
【０１１５】
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。
【０１１６】
尚、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。
【０１１７】
（２）トナー粒子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粒子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。
【０１１８】
本発明では、ＥＳＣＡの装置及び測定条件は、下記の通りである。

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。
【０１１９】
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。
【０１２０】
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。
【０１２１】
（３）無機微粉体及びトナー粒子の粉体帯電量の測定
測定には図７に示す帯電量測定装置を用いる。温度２３℃、相対湿度６０％環境下、鉄粉キャリアとして粒径１０６〜１５０μｍの範囲に５０〜７０質量％、粒径７５〜１０６μｍの範囲に２０〜５０質量％の分布を持つような鉄粉キャリア（例えばＤＳＰ１３８（同和鉄粉社製））を用い、鉄粉キャリア９．０ｇに無機微粉体或いはトナー粒子１．０ｇを加えた混合物を５０〜１００ｍｌ容量のポリエチレン製の瓶に入れ５０回手で振盪する。
【０１２２】
次いで、底に５００メッシュのスクリーン７３のある金属製の測定容器７２に前記混合物１．０〜１．２ｇを入れ、金属製のフタ７４をする。この時の測定容器７２全体の重量を秤りＷ₁（ｇ）とする。次に吸引機７１（測定容器７２と接する部分は少なくとも絶縁体）において、吸引口７７から吸引し風量調節弁７６を調節して真空計７５の圧力を２ｋＰａとする。
【０１２３】
この状態で１分間吸引を行ない、現像剤を吸引除去する。この時の電位計７９の電位をＶ（ボルト）とする。ここで７８はコンデンサーであり容量をＣ（μＦ）とする。また、吸引後の測定機全体の質量を秤りＷ₂（ｇ）とする。無機微粉体或いはトナー粒子の摩擦帯電量Ｑ（μＣ／ｇ）は下式の如く計算される。
【０１２４】
Ｑ＝ＣＶ／（Ｗ₁−Ｗ₂）
【０１２５】
（４）無機微粉体の比表面積（ＢＥＴ）の測定
ＢＥＴ比表面積の測定は、ＱＵＡＮＴＡＣＨＲＯＭＥ社製比表面積計オートソープ１を使用し以下の通り行う。
【０１２６】
測定サンプル約０．１ｇをセル中に秤取し温度４０℃、真空度１．０×１０^-3ｍｍＨｇ以下で１２時間以上脱気処理を行う。その後、液体窒素により冷却した状態で窒素ガスを吸着し多点法により値を求める。
【０１２７】
以下に本発明の実施態様を示す。
【０１２８】
〔実施態様１〕
少なくとも結着樹脂と磁性粉体を含有する磁性トナー粒子と、無機微粉体α、無機微粉体βを含有する磁性トナーにおいて、
該磁性トナー粒子の平均円形度が、０．９７０以上であり、
該無機微粉体αの帯電極性が磁性トナー粒子と逆極性であり、
該無機微粉体βの帯電極性が磁性トナー粒子と同極性であり、
該無機微粒体αの粉体帯電量をＱ（μＣ／ｇ）、比表面積をＨ（ｍ²／ｇ）とした時、
０．１≦Ｑ／Ｈ≦１０．０であり、
無機微粉体αと無機微粉体βの含有量の比（κ＝αの含有量／βの含有量）が
０．００３≦κ≦１．０であり、
該磁性トナー粒子のＸ線光電子分光分析により測定されるトナー表面に存在する炭素元素の含有量（Ａ）に対する鉄元素の含有量（Ｂ）の比（Ｂ／Ａ）が０．００１未満であることを特徴とする磁性トナー。
【０１２９】
〔実施態様２〕
静電潜像を担持する像担持体に現像剤を供給することにより前記静電潜像を顕像化し、顕像化した像を記録材に定着させることにより画像を形成する画像形成方法において、前記現像剤が実施態様１の磁性トナーを含むことを特徴とする。
【０１３０】
〔実施態様３〕
実施態様１または２において、Ｂ／Ａが０．０００５未満である。
【０１３１】
〔実施態様４〕
実施態様１〜３のいずれかにおいて、無機微粉体αがハイドロタルサイト類似化合物である。
【０１３２】
〔実施態様５〕
実施態様１〜３のいずれかにおいて、無機微粉体αがアミノシラン化合物で処理した酸化チタン化合物である。
【０１３３】
〔実施態様６〕
実施態様１〜５のいずれかにおいて、無機微粉体βが酸化スズを含有している。
【０１３４】
〔実施態様７〕
実施態様１〜６のいずれかにおいて、無機微粉体βが粉体抵抗が１×１０⁹Ω・ｃｍ以下の導電性微粉体である。
【０１３５】
〔実施態様８〕
実施態様１〜７のいずれかにおいて、磁性トナー粒子の投影面積円相当径をＣとし、透過型電子顕微鏡（ＴＥＭ）を用いたトナーの断面観察における酸化鉄とトナー表面との距離の最小値をＤとしたとき、Ｄ／Ｃ≦０．０２の関係を満足する磁性トナー粒子が５０個数％以上である。
【０１３６】
〔実施態様９〕
実施態様１〜８のいずれかにおいて、磁性トナーは、一次平均粒径４〜２５ｎｍの無機微粉体γを含有する。
【０１３７】
〔実施態様１０〕
実施態様９において、無機微粉体γは、シリカまたはその複酸化物である。
【０１３８】
〔実施態様１１〕
実施態様９または１０において、無機微粉体γは疎水化処理されている。
【０１３９】
〔実施態様１２〕
実施態様１〜１１のいずれかにおいて、磁性トナー粒子が、結着樹脂１００質量部に対し、磁性粉体を１０〜１６０質量部含有する。
【０１４０】
〔実施態様１３〕
実施態様１〜１２のいずれかにおいて、磁性トナー粒子が、結着樹脂１００質量部に対し、ワックスを０．５〜５０質量部含有する。
【０１４１】
〔実施態様１４〕
実施態様１〜１３のいずれかにおいて、磁性トナー粒子のモード円形度が０．９９以上である。
【０１４２】
〔実施態様１５〕
実施態様１〜１４のいずれかにおいて、磁性トナー中のトナー粒子が重合法によって得られる。
【０１４３】
【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。尚、以下の配合における部数は全て質量部である。
【０１４４】
（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秒で酸化反応を行い、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、空気を吹き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−Ｃ₉Ｈ₁₇Ｓｉ（ＯＣＨ₃）₃）を磁性酸化鉄１００部に対し１．２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。
【０１４５】
（磁性粉体の製造例１）
疎水性酸化鉄の製造例１と同様に酸化反応を進め、酸化反応後に生成した磁性酸化鉄粒子を洗浄、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。
【０１４６】
（疎水性酸化鉄の製造例２）
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２を得た。
【０１４７】
次に、トナーの製造例及び、比較製造例について説明する。
【０１４８】
〈トナーの製造例１〉
イオン交換水７０６部に０．１ｍｏｌ／リットル−Ｎａ₃ＰＯ₄水溶液４４７部を投入し６０℃に加温した後、１．０ｍｏｌ／リットル−ＣａＣｌ₂水溶液６７．７部を徐々に添加してリン酸カルシウム塩を含む水系媒体を得た。

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。得られた重合性単量体組成物を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）５部を溶解した。
【０１４９】
前記水系媒体中に上記重合性単量体系を投入し、６０℃、Ｎ₂雰囲気下においてＴＫ式ホモミキサー（特殊機化工業（株））にて１０，０００ｒｐｍで１５分間撹拌して造粒を行なった。その後パドル撹拌翼で撹拌しつつ、８０℃で１０時間反応させた。反応終了後、懸濁液を冷却し、塩酸を加えてリン酸カルシウム塩を溶解し、濾過、水洗、乾燥してトナー粒子を得た。得られたトナー粒子の粉体帯電量を測定したところ、ネガ帯電性を示した。
【０１５０】
このトナー粒子１００部と、無機微粉体αとしてアミノシラン及び酸化スズで表面処理を行なった酸化チタン粒子０．３部と、無機微粉体βとして粉体抵抗が３．０×１０⁴Ω・ｃｍのｎ−プロピルトリメトキシシランで表面処理を行なった酸化スズ粒子（ネガ帯電性）０．８部及び、無機微粉体γとしてヘキサメチルジシラザン処理した後シリコーンオイルで処理し、処理後の一次平均粒径が１５ｎｍの疎水性シリカ微粉体１．１部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＡを調製した。
【０１５１】
得られたトナーＡの物性を、以下のトナーの製造例にて得られたトナーのものと併せ、表１に示す。
【０１５２】
〈トナーの製造例２〉
トナーの製造例１において、無機微粉体αをハイドロタルサイト粒子（ＴＯＭ−８４（戸田工業社製））に変えてさらに添加量を０．２部とし、無機微粉体βの添加量を１．０部に変更する以外は同様の手法により、トナーＢを得た。
【０１５３】
〈トナーの製造例３〉
トナーの製造例１において、無機微粉体αの表面処理をチタンカップリング剤により行い、該無機微粉体の帯電量を調節する以外は同様の手法により、トナーＣを得た。
【０１５４】
〈トナーの製造例４〉
トナーの製造例１において、無機微粉体βをｎ−ヘキシルトリメトキシシランで表面処理した酸化チタン（粉体抵抗＝２．０×１０⁵Ω・ｃｍ、ネガ帯電性）に変更する以外は同様の手法により、トナーＤを得た。
【０１５５】
〈トナーの製造例５〉
トナーの製造例１において、無機微粉体βを粉体抵抗２．０×１０⁹Ω・ｃｍのチタン酸バリウム微粉体（前述（３）の粉体帯電量の測定方法を用いて測定したところ、ネガ帯電性を示した。）に変更する以外は同様の手法により、トナーＥを得た。
【０１５６】
〈トナーの製造例６〉
トナーの製造例１において、無機微粉体αの比表面積及び、帯電量を酸化チタン粒子母体の粒径及び、アミノシランカップリング剤や酸化スズの量により調整し、Ｑ／Ｈ＝９．５０とした以外は同様の手法により、トナーＦを得た。
【０１５７】
〈トナーの製造例７〉
トナーの製造例２において、無機微粉体αの添加量を０．０１２部、無機微粉体βの添加量を３部とする以外は同様の手法により、トナーＧを得た。
【０１５８】
〈トナーの製造例８〉
トナーの製造例１において、無機微粉体αの添加量を０．４部、無機微粉体βの添加量を０．５部とする以外は同様の手法により、トナーＨを得た。
【０１５９】
〈トナーの製造例９〉
トナーの製造例１において、疎水性酸化鉄１を疎水性酸化鉄２に変更する以外は同様の手法により、トナーＩを得た。
【０１６０】
〈トナーの製造例１０〉
トナーの製造例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Ｊを得た。
【０１６１】
〈トナーの製造例１１〉
トナーの製造例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Ｋを得た。
【０１６２】
〈トナーの製造例１２〉
トナーの製造例１において、疎水性酸化鉄の添加量を９部に変更する以外は同様の手法によりトナーＬを得た。
【０１６３】
〈トナーの製造例１３〉
トナーの製造例１において、疎水性酸化鉄の添加量を１６１部に変更する以外は同様の手法によりトナーＭを得た。
【０１６４】
〈トナーの製造例１４〉
トナーの製造例１の処方の中で、磁性粉体を除き、さらにＮａ₃ＰＯ₄水溶液とＣａＣｌ₂水溶液の投入量を変更し、重量平均粒径０．６μｍ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、球形化トナー粒子を得た。得られたトナー粒子の粉体帯電量を測定したところ、ネガ帯電性を示した。
【０１６５】
このトナー粒子１００部と、無機微粉体αとしてアミノシラン及び酸化スズで表面処理を行なった酸化チタン粒子０．３部と、無機微粉体βとして抵抗が３．０×１０⁴Ω・ｃｍのｎ−プロピルトリメトキシシランで表面処理を行なった酸化スズ粒子０．８部及び、無機微粉体γとしてヘキサメチルジシラザン処理した後シリコーンオイルで処理し、処理後の一次平均粒径が１５ｎｍの疎水性シリカ微粉体１．１部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＮを調製した。
【０１６６】
〈トナーの製造例１５〉
トナーの製造例１において、疎水性シリカ微粉体を添加しない以外は同様の手法により、トナーＯを得た。
【０１６７】
〈トナーの製造例１６〉
トナーの製造例１において、疎水性シリカ微粉体を未処理シリカにする以外は同様の手法により、トナーＰを得た。
【０１６８】
〈トナーの比較製造例１〉
・スチレン／ｎ−ブチルアクリレート共重合体（質量比８０／２０） １００部
・アゾ系負帯電性荷電制御剤 １部
・疎水性酸化鉄１ ８５部
・トナー粒子の製造例１で使用したエステルワックス ５部
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トナー粒子を得た。得られたトナー粒子の粉体帯電量を測定したところ、ネガ帯電性を示した。
【０１６９】
このトナー粒子１００部と、無機微粉体αとしてアミノシラン及び酸化スズで表面処理を行なった酸化チタン粒子０．３部と、無機微粉体βとして抵抗が３．０×１０⁴Ω・ｃｍのｎ−プロピルトリメトキシシランで表面処理を行なった酸化スズ粒子（ネガ帯電性）０．８部及び、無機微粉体γとしてヘキサメチルジシラザン処理した後シリコーンオイルで処理し、処理後の一次平均粒径が１５ｎｍの疎水性シリカ微粉体１．１部とをヘンシェルミキサー（三井三池化工機（株））で混合して、トナーＱを調製した。
【０１７０】
〈トナーの比較製造例２〉
トナーの製造例１において、疎水性酸化鉄１を磁性粉体１に変更する以外は同様の手法により、トナーＲを得た。
【０１７１】
〈トナーの比較製造例３〉
トナーの製造例１において、無機微粉体αの比表面積及び、帯電量を酸化チタン粒子母体の粒径及び、アミノシランカップリング剤や酸化スズの量により調整し、Ｑ／Ｈ＝０．０８にした以外は同様の手法により、トナーＳを得た。
【０１７２】
〈トナーの比較製造例４〉
トナーの製造例１において、無機微粉体αの比表面積及び、帯電量を酸化チタン粒子母体の粒径及び、アミノシランカップリング剤や酸化スズの量により調整し、Ｑ／Ｈ＝１０．３０にした以外は同様の手法により、トナーＴを得た。
【０１７３】
〈トナーの比較製造例５〉
トナーの製造例２において、無機微粉体αの添加量を０．００７部及び、無機微粉体βの添加量を３部とした以外は同様の手法により、トナーＵを得た。
【０１７４】
〈トナーの比較製造例６〉
トナーの製造例１において、無機微粉体αの添加量を０．４部及び、無機微粉体βの添加量を０．３部とした以外は同様の手法により、トナーＶを得た。
【０１７５】
〈トナーの比較製造例７〉
トナーの製造例１において、無機微粉体βをトナーの製造例３で用いたチタンカップリング処理酸化チタンにする以外は同様の手法により、トナーＷを得た。
【０１７６】
〈トナーの比較製造例８〉
トナーの製造例１において、無機微粉体αをトナーの製造例４で用いたｎ−ヘキシルトリメトキシシラン処理酸化チタンにする以外は同様の手法により、トナーＸを得た。
【０１７７】
【表１】

【０１７８】
（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：酸化スズ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°であった。
【０１７９】
尚、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。
【０１８０】
［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に示される構造の装置を用いた。
【０１８１】
静電荷像担持体としては感光体製造例１の有機感光体（ＯＰＣ）ドラムを用いた。この感光体に、一次帯電部材として導電性カーボンを分散しナイロン樹脂で被覆されたゴムローラー帯電器を当接させ（当接圧５８．８Ｎ／ｍ（６０ｇ／ｃｍ））、直流電圧−６４０Ｖ_dcに交流電圧２．０ｋＶ_pp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Ｖ_d＝−６３０Ｖ、明部電位Ｖ_L＝−２２０Ｖとした。
【０１８２】
感光ドラムと現像スリーブとの間隙は２６５μｍ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）１．１μｍ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１．０ｍｍのシリコーンゴム製ブレードを１４．７Ｎ／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
次いで、現像バイアスとして直流バイアス成分Ｖ_dc＝−５００Ｖ、重畳する交流バイアス成分Ｖ_pp＝１８００Ｖ、ｆ＝２４００Ｈｚを用いた。また、現像スリーブの周速は感光体周速（２１６ｍｍ／ｓｅｃ）に対して順方向に１０５％のスピード（２２６．８ｍｍ／ｓｅｃ）とした。
【０１８３】
また、図４のような転写ローラー（導電性カーボンを分散したエチレン−プロピレンゴム製、導電性弾性層の体積抵抗値１０⁸Ωｃｍ、表面ゴム硬度２４゜、直径２０ｍｍ、当接圧５９Ｎ／ｍ（６ｋｇ／ｍ））を図４中Ａ方向の感光体周速（２１６ｍｍ／ｓｅｃ）に対して等速とし、転写バイアスは直流１．３ｋＶとした。図４中、１は感光体、４は転写ローラー、４１は芯金、４２は導電性弾性層、４３は転写バイアス電源を示す。
【０１８４】
定着方法としては、図５、図６に示す定着フィルム加熱方式の定着装置を用いた。図中、５０はステー、５１は加熱体、５１ａはヒーター基板、５１ｂは通電発熱抵抗体（発熱体）、５１ｃは表面保護層、５１ｄは検温素子、５２は耐熱性エンドレスフィルム、５３は加圧ローラー、５４はコイルばね、５５はフィルム端部規制フランジ、５６は給電コネクター、５７は断熱部材、５８は出口ガイド（分離ガイド）、５９は入口ガイドである。
【０１８５】
まず、トナーとしてトナーＡを使用し、常温常湿（２３℃、６５％ＲＨ）環境下において画出し試験を行った。転写材としては９０ｇ／ｍ²の紙を使用した。その結果、初期において高い濃度や転写性を示し、非画像部へのカブリもなくブロッチのない良好な画像が得られた。
【０１８６】
次に、印字面積比率３％の横ラインのみからなる画像パターンを印字枚数６０００枚まで印字し、その後３０日間放置して、再び初期評価及び６０００枚の印字を行い、耐久性の評価を行った。
【０１８７】
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。
【０１８８】
ａ）画像濃度
初期及び６０００枚のプリントアウトを終了した後、及び３０日放置して再び電源を入れた１枚目の画像濃度及び６０００枚のプリント後により評価した。尚、画像濃度は「マクベス反射濃度計」（マクベス社製）を用いて、原稿濃度が０．００の白地部分のプリントアウト画像に対する相対濃度を測定した。画像濃度の値は１．４０以上であれば実用上問題のない値である。
【０１８９】
ｂ）カブリ
カブリの測定は、東京電色社製のＲＥＦＬＥＣＴＭＥＴＥＲ ＭＯＤＥＬＴＣ−６ＤＳを使用して測定した。フィルターは、グリーンフィルターを用い、下記の式より算出した。
【０１９０】
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（％）
カブリは以下のような判定基準で行なった。
Ａ：０．５％未満
Ｂ：０．５％以上１．０％未満
Ｃ：１．０％以上１．５％未満
Ｄ：１．５％以上２．０％以下
Ｅ：２．０％＜カブリ（反射率）
Ａ〜Ｄであれば実用上問題のない画像である。
【０１９１】
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。
【０１９２】
転写効率（％）＝｛（Ｅ−Ｃ）／（Ｅ−Ｄ）｝×１００
転写性は以下のような判定基準で行なった。
Ａ：９７．５％以上
Ｂ：９５．０％以上９７．５％未満
Ｃ：９２．５％以上９５．０％未満
Ｄ：９０．０％以上９２．５％未満
Ｅ：９０．０％未満
Ａ〜Ｄであれば実用上問題のない画像である。
【０１９３】
ｅ）定着性
非オフセット性は、耐久１２０００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。
【０１９４】
また、定着こすり試験として、Ａ４の複写機用普通紙（１０５ｇ／ｍ²）に単位面積あたりのトナー質量を１．０ｍｇ／ｃｍ²になるように調整し、濃度測定用の１０ｍｍ×１０ｍｍ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／ｃｍ²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
Ａ〜Ｃならば実用上問題は無い。
【０１９５】
ｆ）ブロッチ
ブロッチの評価は、べた黒画像を目視にて観察し、その発生を以下のような基準で評価した。
Ａ：優秀
Ｂ：良好
Ｃ：実用上問題なし
Ｄ：実用上問題あり
【０１９６】
ｈ）定着飛び散り
定着飛び散りは、トナーの帯電量が上がる傾向にある低温低湿環境における耐久終了時に、２００μｍの横線画像を１ｃｍおきに引いた画像を出力し、定着画像と未定着画像の画像の飛び散り箇所の数の差で評価した。未定着画像は、無風オーブンで１２０℃、１分で定着した後に評価に供した。
Ａ：飛び散り箇所が１０箇所未満
Ｂ：飛び散り箇所が１０〜２０箇所未満
Ｃ：飛び散り箇所が２０〜３０箇所未満
Ｄ：飛び散り箇所が３０箇所以上
Ａ〜Ｃならば実用上問題のない画像である。
【０１９７】
得られた結果を表２及び表３に示す。表２及び３から分かるように、トナーＡは初期の画像評価が良好であり、また耐久前半６０００枚後でも耐久後半６０００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。
【０１９８】
次に、同様にして高温高湿（３２．５℃、８５％ＲＨ）環境下及び、低温低湿（１５℃、１０％ＲＨ）環境下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、高温高湿環境下は表４及び表５に、低温低湿環境下は表６及び表７に示す。
【０１９９】
［実施例２］
トナーとして、トナーＢ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３及び表４に示したように、画像特性ならびに耐久性について、良好な結果が得られた。
【０２００】
［実施例３及び４］
トナーとしてトナーＣ及びＤ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、表３及び表４に示すように実用上問題のない結果が得られた。
【０２０１】
［実施例５〜７］
トナーとして、トナーＥ〜Ｇ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３及び表４に示したように、画像特性ならびに耐久性について、良好な結果が得られた。
【０２０２】
［実施例８〜１６］
トナーとしてトナーＨ〜Ｐ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、表３及び表４に示すように実用上問題のない結果が得られた。
【０２０３】
［比較例１〜１０］
トナーとしてトナーＱ〜Ｘ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、表３及び表４に示すように画像特性は悪く、実用上耐えうるものではなかった。
【０２０４】
【表２】

【０２０５】
【表３】

【０２０６】
【表４】

【０２０７】
【表５】

【０２０８】
【表６】

【０２０９】
【表７】

【０２１０】
【発明の効果】
本発明によれば、高温高湿下で長期間放置されても、トナーの帯電量が損なわれず、帯電安定性に優れ、長期の使用においても画像濃度が高く、カブリの抑制された高精細な画像を得ることのでき、且つ低温低湿下においてもトナーの過剰な帯電を抑制することができる磁性トナーを提供することにある。
【図面の簡単な説明】
【図１】本発明の画像形成方法を実現する画像形成装置の一例を示す概略図である。
【図２】図１に示す現像器を示す図である。
【図３】本発明の画像形成方法に用いられる像担持体の一例を示す概略図である。
【図４】本発明の画像形成方法における転写工程で用いられる転写ローラーの一例を示す図である。
【図５】本発明の実施例、比較例に用いた定着装置の要部の分解傾斜図である。
【図６】本発明の実施例、比較例に用いた定着装置の非駆動時のフィルム状態を示した要部の拡大横断面図である。
【図７】本発明において無機微粉体の粉体帯電量の測定に用いた装置の概略図である。
【符号の説明】
１ 感光ドラム
２ 一次帯電ローラー
３ 現像器
４ 転写ローラー
５ クリーニング手段
６ レジスタローラー
７ レーザー発生装置
８ レーザー光
９ 搬送ベルト
１０ 定着器
１１ トナー担持体（現像スリーブ）
１２ 攪拌部材
１３ マグネットローラー
１４ 弾性ブレード
４１ 芯金
４２ 導電性弾性層
４３ 転写バイアス電源
５０ ステー
５１ 加熱体
５１ａ ヒーター基板
５１ｂ 通電発熱抵抗体（発熱体）
５１ｃ 表面保護層
５１ｄ 検温素子
５２ 耐熱エンドレスフィルム
５３ 加圧ローラー
５４ コイルばね
５５ フィルム端部規制フランジ
５６ 給電コネクター
５７ 断熱部材
５８ 出口ガイド（分離ガイド）
５９ 入口ガイド
７１ 吸引機
７２ 測定容器
７３ スクリーン
７４ フタ
７５ 真空計
７６ 風量調節弁
７７ 吸引口
７８ コンデンサー
７９ 電位計[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 recording method, and the like, and an image forming method using the magnetic toner. .
[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]
Also, LED and LBP printers have become the mainstream in the recent market as printer devices, and the direction of technology is higher resolution, that is, what was conventionally 240 dpi, 300 dpi has become 400 dpi, 600 dpi, 800 dpi. Accordingly, the development method is also required to have higher definition. 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 a means for satisfying this requirement, toner particle size reduction is progressing, and Patent Documents 1 to 6 propose a toner having a specific particle size distribution and a small particle size.
[0004]
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, a developer such as a charge control agent or a release agent is used to draw out the necessary properties. Contains the additive. 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.
[0005]
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 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 the development characteristics (particularly fog characteristics) 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.
[0006]
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. In recent years, both printers and copiers have been moving toward higher speeds. As a result, not only is the above charging property important, but toner such as CRG can be left in the machine for a long time and used repeatedly. Therefore, durability has been important especially when left in a harsh environment such as high temperature and high humidity or low temperature and low humidity.
[0007]
Attempts have also been made to solve these problems by improving the magnetic powder. Although proposals have been made regarding magnetic iron oxide contained in the magnetic toner, there are still points to be improved.
[0008]
For example, in patent document 7, the proposal which controls the shape of magnetic iron oxide to a spherical shape by adding a silicate is made. 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.
[0009]
Patent Document 8 discloses a technique for prescribing the presence state of iron oxide on the surface of a magnetic toner by surface-treating iron oxide with a coupling agent in an aqueous medium. Certainly, in the technology of this publication, the charging property of the magnetic toner is improved, and the image density, fog, and image reproducibility are excellent, but the above-mentioned long-term durability in a harsh environment is insufficient and still improved. It turns out that there is plenty of room.
[0010]
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.
[0011]
Further, in the pulverization method, it is difficult to completely disperse solid fine particles such as magnetic powder or a colorant into the resin, and depending on the degree of dispersion, it may cause an increase in fog and a decrease in image density. . 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. .
[0012]
On the other hand, for the purpose of preventing the exposure or separation of the magnetic substance contained in the toner on the surface of the toner particle and improving such a concern, in Patent Document 9, the exposure of the magnetic substance particle from the surface of the toner particle is completely performed. The technology of the developer suppressed in the above is disclosed.
[0013]
However, in such a toner, the magnetic particles are completely covered, so that the triboelectric charge amount does not moderate moderately. Therefore, the charge amount tends to be excessive in a low-humidity environment. 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.
[0014]
In other words, although some fluidity can be obtained even if the magnetic material is improved or the magnetic toner manufacturing method is improved, it is still insufficient from the viewpoint of frictional chargeability and transferability due to durability. It is.
[0015]
Further, a method of adding inorganic fine particles as external additives to toner base particles has been proposed and widely used in order to improve the above problems and to obtain good toner flow characteristics, charging characteristics, and the like.
[0016]
For example, many methods have been proposed for adjusting the chargeability as a toner by adding conductive fine particles as an external additive. Specifically, carbon black as conductive fine particles adheres to or adheres to the toner surface for the purpose of imparting conductivity to the toner, or to suppress excessive charging of the toner and to make the tribo distribution uniform. It is widely known to use it as an external additive. Patent Documents 10 to 12 disclose a technique for securing charging stability and fluidity of a toner by externally adding and mixing inorganic fine powders having the same polarity and opposite polarity as the toner. Furthermore, Patent Documents 13 to 15 disclose that conductive fine particles of tin oxide, zinc oxide, and titanium oxide are externally added to the high-resistance magnetic toner, respectively.
[0017]
However, there is no detailed description of the magnetic material in such an improvement means, and when such a magnetic material is used, a large amount of magnetic iron oxide particles are released on the surface of the toner. There remains a problem with tribocharging in harsh environments such as high humidity. In addition, it has been found that excessive charging of the toner cannot be suppressed even under low temperature and low humidity, and the tribo distribution cannot be made uniform, and as a result, the image characteristics and durability are sufficiently improved. It's hard to say.
[0018]
[Patent Document 1]
Japanese Patent Laid-Open No. 1-112253
[Patent Document 2]
JP-A-1-191156
[Patent Document 3]
JP-A-2-214156
[Patent Document 4]
JP-A-2-284158
[Patent Document 5]
Japanese Patent Laid-Open No. 3-181952
[Patent Document 6]
JP-A-4-162048
[Patent Document 7]
Japanese Patent Publication No. 3-9045
[Patent Document 8]
JP 2000-312097 A
[Patent Document 9]
In JP-A-7-209904
[Patent Document 10]
JP-A-5-204183
[Patent Document 11]
JP-A-5-343416
[Patent Document 12]
Japanese Patent Laid-Open No. 9-204065
[Patent Document 13]
JP 2001-318488 A
[Patent Document 14]
JP 7-168388 A
[Patent Document 15]
JP-A-8-202081
[0019]
[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 and an image forming method using the magnetic toner.
[0020]
That is, the object of the present invention is that even when left for a long time under high temperature and high humidity, the charge amount of the toner is not impaired, the charging stability is excellent, the image density is high even in long-term use, and the fog is suppressed. An object of the present invention is to provide a magnetic toner capable of obtaining a fine image and suppressing excessive charging of the toner even under low temperature and low humidity.
[0021]
[Means for Solving the Problems]
  The present invention relates to a magnetic toner containing at least a binder resin and a magnetic powder, an inorganic fine powder α, and an inorganic fine powder β.
The magnetic toner particles are produced by a suspension polymerization method,
The average circularity of the magnetic toner particles is 0.970 or more,
The charging polarity of the inorganic fine powder α is opposite to that of the magnetic toner particles,
The charging polarity of the inorganic fine powder β is the same as that of the magnetic toner particles,
The inorganic fine powder β has a powder resistance of 1 × 10 ⁹ Conductive fine powder of Ω · cm or less,
The powder charge amount of the inorganic fine particles α is Q (μC / g), and the specific surface area is H (m²/ G),
    0.1 ≦ Q / H ≦ 10.0,
Ratio of content of inorganic fine powder α and inorganic fine powder β (κ = α content / β content)
    0.003 ≦ κ ≦ 1.0,
Toner measured by X-ray photoelectron spectroscopic analysis of the magnetic toner particlesparticleA magnetic toner characterized in that the ratio (B / A) of the content (B) of iron element to the content (A) of carbon element present on the surface is less than 0.001.
[0022]
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 method, the developer contains the magnetic toner of the present invention.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is characterized in that the toner particle shape is a sphere in order to obtain excellent transferability and good charge uniformity. Specifically, it is necessary that the average circularity of the magnetic toner particles be 0.970 or more, and by doing so, the contact area between the toner particles and the photosensitive member is reduced, and the mirror image force, van der Waals force, etc. Since the adhesion of toner particles to the photoreceptor due to the toner is reduced, the toner particles are easily transferred. Furthermore, since the circularity is high and the shape is close to a sphere, compared to an irregular toner having a convex portion, the toner slides well and it is easy to rub the entire surface uniformly. Excellent charging uniformity. However, when the average circularity of the magnetic toner particles is less than 0.970, the above effects cannot be obtained, and the transferability and charging uniformity are insufficient.
[0024]
At this time, the mode circularity is more preferably 0.99 or more in the circularity distribution of the toner particles. 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 divided into 61 from 0.01 to 0.40 to 1.00, and the measured circularity of the toner particles is assigned to each divided range according to the circularity. The lower limit value of the division range in which the frequency value is maximum in the circularity frequency distribution.
[0025]
  In the present invention, the magnetic substance is substantially a toner.particleIt is preferable that the surface is not exposed. In the present invention, the magnetic substance is substantially a toner.particle“Not exposed to the surface” means the ratio (B / A) of the content (B) of the iron element to the content (A) of the carbon element present on the surface of the toner particles measured by X-ray photoelectron spectroscopy. , Less than 0.001, and the magnetic substance is not substantially exposed, thereby improving the fluidity and tribocharging properties of the small particle size magnetic toner, and developing characteristics of the magnetic toner (especially fog suppression), Various performances required for toner such as transferability are satisfied.
[0026]
In this regard, in order to obtain magnetic toner particles satisfying B / A, the production method can be performed by a pulverization method. However, in the pulverization method, the above-described average circularity of the toner particles is set to 0.970 or more. Since it is necessary to carry out thermal or some special treatment, it is preferable to produce by suspension polymerization.
[0027]
However, even if a normal magnetic powder is contained in the polymerized toner, the above-mentioned (B / A) is controlled to be less than 0.001, that is, the toner particles are not substantially exposed on the surface of the toner particles. It is difficult to obtain the fluidity and uniform triboelectric chargeability. Furthermore, due to the strong interaction between the magnetic powder and water during the production of the suspension polymerization toner, it is difficult to obtain toner particles having an average circularity of 0.970 or more. This is because (1) the magnetic powder is generally hydrophilic and thus easily present on the surface of the toner particles, and as described above, (2) the magnetic powder moves randomly when stirring with the aqueous solvent, The cause is thought to be that the surface of the suspended particles composed of the monomer is dragged, and the shape is distorted and is not easily rounded. In order to solve these problems, it is important to modify the surface characteristics of the magnetic powder.
[0028]
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.
[0029]
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.
[0030]
The method of treating the surface of magnetic particles while hydrolyzing the coupling agent in an aqueous medium does not require the use of a coupling agent that generates gas, such as chlorosilanes and silazanes, Among them, the magnetic particles are easily united with each other, and a highly viscous coupling agent, which has been difficult to be processed satisfactorily, can be used. Therefore, the hydrophobizing effect is very large.
[0031]
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_m-Si-Y_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, vinyl group, glycidoxy group, and 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.
[0032]
In particular, the following formula
C_pH_{2p + 1}-Si- (OC_qH_{2q + 1})_Three
(In the formula, 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
[0033]
  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 the magnetic particles are uniformly distributed in the toner.ScatteredThe fogging, transferability, and selective developability tend to deteriorate.
[0034]
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.
[0035]
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.
[0036]
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.
[0037]
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.
[0038]
Stirring is sufficiently performed by, for example, 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. It is good.
[0039]
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. Polymerized toner particles that are very good, have substantially no exposure from the surface of the toner particles, have a B / A of less than 0.001, and have an average circularity of 0.970 or more, which are nearly spherical, are obtained. Further, by setting B / A to less than 0.0005, the chargeability and stability are further improved.
[0040]
In the present invention, the projected area equivalent circle diameter of the magnetic toner particle 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) When D is D, the number of toner particles satisfying the relationship of D / C ≦ 0.02 or less is preferably 50% by number or more, and more preferably 65% by number or more. The reason is as follows.
[0041]
  When the conditions of the present invention are not satisfied, there are 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, the space where no magnetic material exists when one toner particle is the entire space is at least 11.5%Will exist. Actually, the magnetic particles do not exist so as to be uniformly aligned at the closest position to form an inner wall inside the toner particle.2%It is clear that this is the case.
[0042]
If there are no magnetic particles in such a space per particle,
{Circle around (1)} The magnetic particles are biased inside the toner particles, and the possibility of aggregation of the magnetic particles 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 likely to be embedded. In addition, the durability of the toner deteriorates.
The risk of causing such harmful effects increases.
[0043]
If the number of particles satisfying D / C ≦ 0.02 is less than 50% by number, such adverse effects as a decrease in coloring power, a deterioration in blocking resistance, and a deterioration in durability tend to become remarkable. Therefore, in the present invention, the number of particles satisfying D / C ≦ 0.02 is preferably 50% by number or more.
[0044]
  TAs a specific observation method by EM, 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.
[0045]
A specific method for determining the ratio of the number of corresponding particles is as follows.
[0046]
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.
[0047]
[Expression 1]

[0048]
The number average particle diameter (D1) of the magnetic toner was measured using a Coulter Multisizer (manufactured by Coulter) and connected to an interface (manufactured by Nikkiki) that outputs the number distribution and volume distribution and a PC9801 personal computer (manufactured by NEC). The electrolyte was obtained by preparing a 1% NaCl aqueous solution using first grade sodium chloride. 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 number-based number average particle diameter (D1) obtained from the number distribution was obtained.
[0049]
Furthermore, the inventors of the present invention include an inorganic fine powder (inorganic fine powder α) having a polarity opposite to that of the magnetic toner particles, and an inorganic fine powder (inorganic fine powder β) having the same polarity as the magnetic toner particles. The powder charge amount of the inorganic fine particles α is Q (μC / g) and the specific surface area H (m²/ G), 0.1 ≦ Q / H ≦ 10.0, and the ratio κ of the content of the inorganic fine powder α and the content of the inorganic fine powder β (κ = α content / β content) ) Of 0.003 ≦ κ ≦ 1.0 was found to be extremely effective for stably charging the magnetic toner even after repeated use in various environments for a long period of time. .
[0050]
  Although the details of the cause are not well understood, the effect is not exhibited unless the magnetic powder, which is a constituent of the present invention, is present, and the effect is exhibited more as the sphericity of the magnetic toner particles is higher.AndThe inventors of the present invention have found that electrostatic interaction, specifically, charge transfer between the inorganic fine powder α and the inorganic fine powder β externally mixed on the surface of the magnetic toner particles and the magnetic material. I think there is. Then, charge transfer with the magnetic toner particles and charge repulsion by adding two kinds of external additives, inorganic fine powders α and β, which are opposite in polarity to each other, always activate each other's magnetic properties. This is considered to suppress the embedding in the toner particles. It is closely related to the amount of charge (Q / H) per unit area of the inorganic fine powder α having the opposite polarity to the magnetic toner particles and the ratio (κ) of the content of the inorganic fine powder α and β. It became clear that
[0051]
The magnetic toner of the present invention satisfying the above conditions has a rapid start-up even in a high-humidity environment. A density image can be obtained. Further, the magnetic toner of the present invention satisfying the above condition is excellent in the stability of the tribo even under a low temperature and low humidity environment, and can obtain a high-definition image without fixing scattering even in long-term continuous use without causing excessive charging. .
[0052]
Here, when 0.1> Q / H, the start-up of the tribo is slow in a high-humidity environment, causing a decrease in image density and fogging at the initial stage of durability and after standing, and when Q / H> 10.0, particularly low humidity Under the environment, the chargeability of the magnetic toner becomes unstable and excessively charged.
[0053]
Further, when 0.003> κ, the magnetic toner is excessively charged and it is not possible to suppress the occurrence of scattering and blotch at the time of fixing, and when κ> 1.0, it is not possible to suppress the decrease in magnetic toner tribo. .
[0054]
In addition, regarding the relationship with the circularity of the magnetic toner particles, in the magnetic toner particles having a low circularity, only the inorganic fine powder of any polarity is localized due to the concentration of electric charges on the convex portions. The particles are not activated, and the embedding of the inorganic fine powder in the magnetic toner cannot be suppressed, so that it is considered that the uniform chargeability of the magnetic toner cannot be obtained.
[0055]
Further, regarding the relationship with the ratio (B / A), when B / A is 0.001 or more, that is, when the magnetic material is exposed on the surface of the magnetic toner particles, the magnetic material is excessively charged leakage sites of the toner particles. As a result, the charge escapes from the magnetic toner particles, and sufficient charge transfer cannot be performed for the inorganic fine powder α and the inorganic fine powder β. As a result, two types of inorganic fine powder α and β are obtained. The charge repulsion of the external additive does not occur, and the mutual particles cannot be activated. Therefore, it is considered that durability and uniform charging stability cannot be obtained. In other words, moderate charge exchange is required between the inorganic fine powders α and β and the magnetic material, and for that purpose, it is considered essential that the ratio (B / A) is less than 0.001.
[0056]
Examples of the inorganic fine powder α and β in the present invention include carbon fine powder such as carbon black and graphite; metal fine powder such as copper, gold, silver, aluminum, and nickel; zinc oxide, titanium oxide, tin oxide, aluminum oxide, Metal oxides such as indium oxide, silicon oxide, magnesium oxide, barium oxide, molybdenum oxide, iron oxide, tungsten oxide; metal compounds such as molybdenum sulfide, cadmium sulfide, potassium titanate, barium titanate, or composite oxides thereof Hydrotalcite-like compounds can be used as inorganic fine powder α or inorganic fine powder β by adjusting the charge polarity and charge amount of the inorganic fine powder by using an organic treatment such as aminosilane as necessary. . Among these, the inorganic fine powder α is a hydrotalcite-like compound and a titanium oxide compound treated with an aminosilane compound, or a composite oxide thereof, and the inorganic fine powder β is an inorganic oxide such as tin oxide and titanium oxide. In addition, for the purpose of controlling the resistance value of the powder, a metal oxide containing 0.1 to 5% by mass of an element such as antimony or aluminum different from the main metal element of the inorganic fine powder, conductivity Fine particles having a material on the surface can also be used. For example, titanium oxide fine particles surface-treated with tin oxide / antimony, stannic oxide fine particles doped with antimony, or stannic oxide fine particles are preferable.
[0057]
The inorganic fine powder β has a powder resistance of 1 × 10.⁹A conductive fine powder of Ω · cm or less is preferable. Resistance of inorganic fine powder β is 1 × 10⁹If it exceeds Ω · cm, the charge amount of the magnetic toner tends to be excessive, particularly under low temperature and low humidity, and fixing scattering and blotches are likely to occur.
[0058]
In the present invention, the resistance of the inorganic fine powder was measured by the tablet method and normalized. That is, the bottom area 2.26cm²Approximately 0.5 g of a powder sample was placed in the cylinder, and 15 kg of pressure was applied to the upper and lower electrodes. At the same time, a voltage of 100 V was applied to measure the resistance value, and then normalized to calculate the specific resistance. The resistance was measured after the measurement sample was left in a low humidity (10%) environment for 3 days.
[0059]
Next, a method for producing toner according to the present invention will be described.
[0060]
  The toner of the present invention can be manufactured by a pulverization method, but in the pulverization method, mechanical, thermal, or some special treatment may be performed in order to make the average circularity of toner particles 0.970 or more. Since it is necessary, it is preferable to produce it by suspension polymerization. Even if toner is produced by suspension polymerization using ordinary magnetic powder, the magnetic powder is inferior in dispersibility, so the magnetic particles are used in the toner.particleA toner having an average circularity of 0.970 or more is difficult to obtain because the magnetic particles are unevenly distributed on the surface or the magnetic particles move randomly during granulation in an aqueous medium and are dragged by the particles. However, since the magnetic powder used in the present invention is uniformly hydrophobized at a high level, a toner having an average circularity of 0.970 or more can be easily obtained.
[0061]
In the present invention, examples of the polymerizable monomer constituting the polymerizable monomer system used for the constitution of the binder resin include the following.
[0062]
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.
[0063]
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 developing characteristics and durability of the toner.
[0064]
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.
[0065]
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.
[0066]
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.
[0067]
In the present invention, polymerization may be carried out by adding a resin to the monomer system. For example, a monomer containing a water-soluble functional group such as an amino group, a carboxylic acid group, a hydroxyl group, a glycidyl group or a nitrile group cannot be used because it dissolves in an aqueous suspension and causes emulsion polymerization. When it is desired to introduce the body component into the toner, it is 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 a polyester or polyamide. Such polycondensates, polyethers, polyimines such as polyimines can be used. 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.
[0068]
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.
[0069]
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, alkyl salicylic acid, dialkyl salicylic acid, naphthoic acid, dicarboxylic acid, metal salts or metal complexes of azo dyes or azo pigments, boron compounds , Urea compounds, silicon compounds, 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, in the developer related to the image forming method of the present invention, it is not essential to add a charge control agent, and toner is obtained by positively utilizing frictional charging with the developer layer thickness regulating member or the developer carrier. It is not always necessary to include a charge control agent therein.
[0070]
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.
[0071]
Further, the iron oxide used as the magnetic powder in the toner of the present invention may contain elements such as phosphorus, cobalt, nickel, copper, magnesium, manganese, aluminum and silicon, and includes iron trioxide and γ-iron oxide. These are the main components, and these are 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 5-7 is preferred.
[0072]
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 (scanning electron microscope) or the like.
[0073]
The magnetic powder used for the toner of the present invention is produced, for example, by the following method.
[0074]
An aqueous solution containing ferrous hydroxide is prepared by adding an alkali such as sodium hydroxide in an amount equivalent to or greater than the iron component to the ferrous sulfate aqueous solution. Air is blown while maintaining the pH of the prepared aqueous solution at 7 or more (preferably 8 to 10), and iron oxide is oxidized while the aqueous solution is heated to 70 ° C. or more, and the core of the magnetic iron oxide particles First, a seed crystal is formed.
[0075]
Next, an aqueous solution containing about 1 equivalent of ferrous sulfate is added to the slurry-like liquid containing seed crystals based on the amount of alkali added previously. While maintaining the pH of the liquid at 6 to 10, the reaction of ferrous hydroxide is promoted while blowing air, and magnetic iron oxide particles are grown with the seed crystal as the core. As the oxidation reaction proceeds, the pH of the liquid shifts to the acidic side, but the pH of the liquid is preferably not less than 6. Adjust the pH of the solution at the end of the oxidation reaction, stir well so that the magnetic iron oxide becomes primary particles, add the coupling agent, stir well, stir, filter, dry, and lightly crush after stirring By doing so, hydrophobic treated magnetic iron oxide particles can be obtained. Alternatively, after the oxidation reaction is completed, the iron oxide particles obtained by washing and filtering are redispersed in another aqueous medium without drying, and then the pH of the redispersion is adjusted and sufficiently stirred. A silane coupling agent may be added to perform the coupling treatment.
[0076]
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.
[0077]
In general, a method for producing magnetic iron oxide by an aqueous solution method uses an iron concentration of 0.5 to 2 mol / liter from the viewpoint of preventing the viscosity from increasing during the reaction and the solubility of iron sulfate. Generally, the lower the iron sulfate concentration, the finer the particle size of the product. Further, in the reaction, the larger the amount of air and the lower the reaction temperature, the easier the atomization.
[0078]
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.
[0079]
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, 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.
[0080]
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.
[0081]
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.
[0082]
In the production of toners by suspension polymerization, the above-mentioned polymerizable monomers are generally required as toners such as magnetic powders, colorants, release agents, plasticizers, binders, charge control agents, and crosslinking agents. Components and other additives, for example, an organic solvent to be added to reduce the viscosity of the polymer produced by the polymerization reaction, a dispersing agent, etc. are added as appropriate to a disperser such as a homogenizer, ball mill, colloid mill, or ultrasonic disperser. The monomer system thus uniformly dissolved or dispersed 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.
[0083]
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.
[0084]
Further, 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.
[0085]
In the suspension polymerization of the toner of the present invention, known surfactants and organic / inorganic dispersants can be used as dispersion stabilizers. In particular, inorganic dispersants are unlikely 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 washing 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 metasilicate, calcium sulfate, and barium sulfate. And inorganic salts such as calcium hydroxide, magnesium hydroxide, aluminum hydroxide, silica, bentonite and alumina.
[0086]
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.
[0087]
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.
[0088]
When these inorganic dispersants are used, they may be used as they are, but in order to obtain finer particles, the inorganic dispersant particles can be generated in an aqueous medium. For example, in the case of calcium phosphate, a sodium phosphate aqueous solution and a calcium chloride aqueous solution can be mixed with high-speed stirring to produce water-insoluble calcium phosphate, which enables more uniform and fine dispersion. At the same time, a water-soluble sodium chloride salt is produced as a by-product. However, if a water-soluble salt is present in the aqueous medium, dissolution of the polymerizable monomer in water is suppressed, and an ultrafine toner based on emulsion polymerization is produced. Since it becomes difficult to generate | occur | produce, it is more convenient. Since it becomes an obstacle when removing the remaining polymerizable monomer at the end of the polymerization reaction, it is better to replace the aqueous medium or desalinate with an ion exchange resin. The inorganic dispersant can be almost completely removed by dissolution with an acid or alkali after completion of the polymerization.
[0089]
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.
[0090]
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.
[0091]
The toner of the present invention is preferably mixed with an inorganic fine powder γ as a fluidity improver. By adding the inorganic fine powder γ to the magnetic toner of the present invention, the toner of the present invention is mixed. The fluidity of the magnetic toner is improved, and the activation of the inorganic fine powder α and the inorganic fine powder β is promoted.
[0092]
As the inorganic fine powder γ used in the present invention, those having a primary average particle size in the range of 4 to 25 nm are preferable because good results can be obtained. When the primary average particle size of the inorganic fine powder γ is larger than 25 nm, good toner fluidity cannot be obtained, the toner particles are likely to be non-uniformly charged, and the triboelectric chargeability under low humidity is non-uniform. Therefore, problems such as an increase in fog, a decrease in image density, and a decrease in durability are likely to occur. When the primary average particle size of the inorganic fine powder γ is smaller than 4 nm, the cohesiveness between the inorganic fine powders is increased, and the aggregates having a wide particle size distribution having strong cohesiveness that is difficult to be solved by the pulverization treatment instead of the primary particles. It tends to behave as an aggregate, and image defects are likely to occur due to development of the aggregate, damage to the image carrier or toner carrier, and the like. In order to make the charge distribution of the toner particles more uniform, the primary average particle diameter of the inorganic fine powder γ is preferably 6 to 20 nm.
[0093]
The measurement method of the primary average particle size of the inorganic fine powder γ is a photograph of the toner magnified by a scanning electron microscope, and further contains the inorganic fine powder γ by an elemental analysis means such as XMA attached to the scanning electron microscope. The number average primary particle size can be determined by measuring 100 or more primary particles of the inorganic fine powder γ adhering to or leaving the toner surface while contrasting the photograph of the toner mapped with the element.
[0094]
The inorganic fine powder γ used in the toner of the present invention is preferably a fine powder of silica or a double oxide thereof.
[0095]
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.
[0096]
Furthermore, the inorganic fine powder γ used in the present invention is preferably hydrophobized, and the hydrophobized silica fine powder is particularly preferred because of its properties 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 applied 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 treated with a silane coupling agent and simultaneously with an organosilicon compound such as silicone oil. Is mentioned.
[0097]
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.
[0098]
Examples of the organosilicon compound include silicone oil. As a preferable silicone oil, the viscosity at 25 ° C. is about 30 to 1,000 mm.²/ S (cSt) is used, and for example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, and fluorine modified silicone oil are preferable.
[0099]
Silicone oil treatment can be performed by, for example, mixing silica fine powder treated with a silane coupling agent and silicone oil directly using a mixer such as a Henschel mixer, or injecting silicone oil onto the base silica. Depending on how you do it. Alternatively, it may be prepared by dissolving or dispersing silicone oil in a suitable solvent and then mixing with the base silica fine powder to remove the solvent.
[0100]
If necessary, an external additive other than the fluidity improver may be added to the toner in the present invention.
[0101]
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.
[0102]
The mixing of the external additive and the toner particles can be performed by using one kind or a plurality of kinds of known various methods.
[0103]
When the toner of the present invention is produced by a pulverization method, a known method can be used. As a known method, for example, binder resin, magnetic powder, release agent, charge control agent, and in some cases, necessary components such as a colorant and other additives are mixed with a Henschel mixer, a ball mill or the like. Mix thoroughly in the container, then melt and knead using a heat kneader such as a heating roll, kneader, or extruder to disperse other toner materials such as magnetic materials while the resins are compatible with each other. Alternatively, after dissolving, cooling, solidifying, and pulverizing, classification and surface treatment as necessary are performed to obtain toner particles, and 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.
[0104]
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.
[0105]
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.
[0106]
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.
[0107]
Furthermore, the toner of the present invention is a method for obtaining a spherical toner by atomizing a molten mixture into the air using a disk or a multi-fluid nozzle, or an aqueous organic solvent that is soluble in a monomer and insoluble in a polymer obtained. The toner is produced using a dispersion polymerization method in which toner is directly produced by using emulsion, or an emulsion polymerization method represented by a soap-free polymerization method in which toner is produced by direct polymerization in the presence of a water-soluble polar polymerization initiator. This method can also be manufactured.
[0108]
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.
[0109]
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 1 denotes a photosensitive drum, and a primary charging roller 2, a developing device 3, a transfer roller 4, a cleaning unit 5, a register roller 6 and the like are provided around the photosensitive drum. The photoreceptor 1 is charged to −640 V by the primary charging roller 2 (the applied voltage is AC voltage −2.0 kV)._ppDC voltage -640V_dc). And it exposes by irradiating the photoreceptor 1 with the laser beam 8 with the laser generator 7. FIG. The electrostatic latent image on the photoreceptor 1 is developed with a one-component magnetic toner by the developing device 3 and transferred onto the transfer material P by the transfer roller 4 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 10 by the conveyance belt 9 or the like, and the image is fixed on the transfer material P. In addition, toner remaining on a part of the photoreceptor 1 is cleaned by the cleaning unit 5. In the developing unit 3, a cylindrical toner carrier 11 (hereinafter referred to as a developing sleeve) made of a nonmagnetic metal such as aluminum or stainless steel is disposed in the vicinity of the photosensitive member 1. This gap is maintained at about 265 μm by a sleeve / photoreceptor gap holding member (not shown). A magnet roller 13 is fixed and disposed concentrically with the developing sleeve 11 in the developing sleeve 11. However, the developing sleeve 11 is rotatable. As shown in FIG. 2, the magnet roller 13 shown in FIG. 2 has a plurality of magnetic poles. 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 14 is provided as a member for regulating the amount of magnetic toner that adheres to the developing sleeve 11 and is conveyed, and the amount of toner conveyed to the developing region is controlled by the contact pressure of the elastic blade 14 against the developing sleeve 11. . In the developing region, a DC and AC developing bias is applied between the photosensitive member 1 and the developing sleeve 11, and the toner on the developing sleeve 11 flies onto the photosensitive member 1 according to the electrostatic latent image to become a visible image. .
[0110]
The method for measuring various physical property data in the present invention will be described below.
[0111]
(1) Average circularity and mode circularity of toner particles
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 of each particle measured for a group of particles having an equivalent circle diameter of 3 μm or more (C_i) Is obtained by the following equation (1), and the value obtained by dividing the total circularity of all particles measured by the following equation (2) by the total number of particles (m) is calculated as the average circularity (C_av).
[0112]
[Expression 2]

[0113]
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. .40 to 1.00 are divided into 61 divided classes, and a calculation method is used in which the average circularity is calculated using the center value and frequency of the dividing 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 data handling 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.
[0114]
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.
[0115]
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.
[0116]
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.
[0117]
  (2) TonerparticleRatio of iron element content (B) to carbon element content (A) on the surface (B / A)
  Toner in the present inventionparticleThe ratio (B / A) of the content (B) of the iron element to the content (A) of the carbon element present on the surface was calculated by performing surface composition analysis by ESCA (X-ray photoelectron spectroscopy).
[0118]
In the present invention, the ESCA apparatus and measurement conditions are as follows.

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.
[0119]
As the range of peak top of each element used for measurement,
Carbon element: 283-293 eV
Iron element: 706-730eV
It is.
[0120]
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.
[0121]
(3) Measurement of powder charge amount of inorganic fine powder and toner particles
For the measurement, a charge amount measuring apparatus shown in FIG. 7 is used. Iron powder having a distribution of 50 to 70% by mass in a particle size range of 106 to 150 μm and a distribution of 20 to 50% by mass in a particle size range of 75 to 106 μm as an iron powder carrier in an environment of a temperature of 23 ° C. and a relative humidity of 60% Using a carrier (for example, DSP138 (manufactured by Dowa Iron Powder Co., Ltd.)), a mixture of 9.0 g of iron powder carrier and 1.0 g of inorganic fine powder or toner particles is placed in a 50-100 ml polyethylene bottle and handed 50 times. Shake with.
[0122]
Next, 1.0 to 1.2 g of the mixture is put into a metal measuring container 72 having a 500-mesh screen 73 at the bottom, and a metal lid 74 is formed. Weigh the entire measurement container 72 at this time W₁(G). Next, in the suction machine 71 (at least the part in contact with the measurement container 72 is suctioned), the pressure of the vacuum gauge 75 is set to 2 kPa by suctioning from the suction port 77 and adjusting the air volume control valve 76.
[0123]
In this state, suction is performed for 1 minute to remove the developer by suction. The potential of the electrometer 79 at this time is set to V (volt). Here, 78 is a capacitor, and the capacity is C (μF). Also, weigh the whole measuring machine after suction₂(G). The triboelectric charge quantity Q (μC / g) of the inorganic fine powder or toner particles is calculated as follows.
[0124]
Q = CV / (W₁-W₂)
[0125]
(4) Measurement of specific surface area (BET) of inorganic fine powder
The BET specific surface area is measured as follows using a specific surface area meter auto soap 1 manufactured by QUANTACHROME.
[0126]
About 0.1 g of a measurement sample is weighed in a cell, temperature is 40 ° C., and the degree of vacuum is 1.0 × 10.^-3Deaeration treatment is performed for 12 hours or more at a mmHg or less. Thereafter, nitrogen gas is adsorbed while being cooled with liquid nitrogen, and a value is obtained by a multipoint method.
[0127]
Embodiments of the present invention are shown below.
[0128]
[Embodiment 1]
In a magnetic toner particle containing at least a binder resin and magnetic powder, an inorganic fine powder α, and an inorganic fine powder β,
The average circularity of the magnetic toner particles is 0.970 or more,
The charging polarity of the inorganic fine powder α is opposite to that of the magnetic toner particles,
The charging polarity of the inorganic fine powder β is the same as that of the magnetic toner particles,
The powder charge amount of the inorganic fine particles α is Q (μC / g), and the specific surface area is H (m²/ G),
0.1 ≦ Q / H ≦ 10.0,
Ratio of content of inorganic fine powder α and inorganic fine powder β (κ = α content / β content)
0.003 ≦ κ ≦ 1.0,
The ratio (B / A) of the iron element content (B) to the carbon element content (A) present on the toner surface as measured by X-ray photoelectron spectroscopy of the magnetic toner particles is less than 0.001. Magnetic toner characterized by the above.
[0129]
[Embodiment 2]
In an image forming method of forming an image by developing the electrostatic latent image by supplying a developer to an image carrier that carries the electrostatic latent image, and fixing the visualized image on a recording material. The developer includes the magnetic toner according to the first embodiment.
[0130]
[Embodiment 3]
In Embodiment 1 or 2, B / A is less than 0.0005.
[0131]
[Embodiment 4]
In any one of Embodiments 1 to 3, the inorganic fine powder α is a hydrotalcite-like compound.
[0132]
[Embodiment 5]
In any one of Embodiments 1-3, the inorganic fine powder α is a titanium oxide compound treated with an aminosilane compound.
[0133]
[Embodiment 6]
In any one of Embodiments 1-5, the inorganic fine powder (beta) contains a tin oxide.
[0134]
[Embodiment 7]
In any one of Embodiments 1 to 6, the inorganic fine powder β has a powder resistance of 1 × 10⁹Conductive fine powder of Ω · cm or less.
[0135]
[Embodiment 8]
In any one of Embodiments 1 to 7, the projected area equivalent circle diameter of the magnetic toner particles is C, and the minimum value of the distance between the iron oxide and the toner surface in the cross-sectional observation of the toner using a transmission electron microscope (TEM) is When D, the number of magnetic toner particles satisfying the relationship of D / C ≦ 0.02 is 50% by number or more.
[0136]
[Embodiment 9]
In any one of Embodiments 1 to 8, the magnetic toner contains an inorganic fine powder γ having a primary average particle diameter of 4 to 25 nm.
[0137]
[Embodiment 10]
In Embodiment 9, the inorganic fine powder γ is silica or a double oxide thereof.
[0138]
[Embodiment 11]
In Embodiment 9 or 10, the inorganic fine powder γ is hydrophobized.
[0139]
[Embodiment 12]
In any one of Embodiments 1 to 11, the magnetic toner particles contain 10 to 160 parts by mass of magnetic powder with respect to 100 parts by mass of the binder resin.
[0140]
[Embodiment 13]
In any one of Embodiments 1 to 12, the magnetic toner particles contain 0.5 to 50 parts by mass of wax with respect to 100 parts by mass of the binder resin.
[0141]
[Embodiment 14]
In any one of Embodiments 1 to 13, the mode circularity of the magnetic toner particles is 0.99 or more.
[0142]
[Embodiment 15]
In any one of Embodiments 1 to 14, toner particles in the magnetic toner are obtained by a polymerization method.
[0143]
【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.
[0144]
(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 in 80 to 90 seconds 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. While blowing, the oxidation reaction was promoted, and the magnetic iron oxide particles produced after the oxidation reaction were washed, filtered and once taken out. 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-C₉H₁₇Si (OCH_Three)_Three) Was added to 100 parts of magnetic iron oxide (the amount of magnetic iron oxide was calculated as a value obtained by subtracting the water content from the water-containing sample) and subjected to a coupling treatment. The produced hydrophobic iron oxide particles were washed, filtered and dried by a conventional method, and then the slightly agglomerated particles were pulverized to obtain hydrophobic iron oxide 1.
[0145]
(Production example 1 of magnetic powder)
The oxidation reaction proceeds in the same manner as in Production Example 1 of hydrophobic iron oxide, and 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.
[0146]
(Production Example 2 of hydrophobic iron oxide)
Hydrophobic iron oxide 2 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.
[0147]
Next, toner production examples and comparative production examples will be described.
[0148]
<Toner Production Example 1>
0.1 mol / liter-Na in 706 parts of ion-exchanged water_ThreePO_FourAfter adding 447 parts of the aqueous solution and heating to 60 ° C., 1.0 mol / liter-CaCl₂An aqueous medium containing calcium phosphate was obtained by gradually adding 67.7 parts of an aqueous solution.

The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.). The obtained polymerizable monomer composition was heated to 60 ° C., and 10 parts of an ester wax mainly composed of behenyl behenate (maximum endothermic peak 72 ° C. in DSC) was added and mixed therewith. 5 parts of a polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved.
[0149]
The polymerizable monomer system is charged into the aqueous medium, 60 ° C., N₂In an atmosphere, granulation was carried out by stirring for 15 minutes at 10,000 rpm with a TK homomixer (Special Machine Industries Co., Ltd.). Thereafter, the mixture was reacted at 80 ° C. for 10 hours while stirring with a paddle stirring blade. After completion of the reaction, the suspension was cooled, hydrochloric acid was added to dissolve the calcium phosphate salt, filtered, washed with water, and dried to obtain toner particles. When the powder charge amount of the obtained toner particles was measured, it showed negative chargeability.
[0150]
100 parts of the toner particles, 0.3 parts of titanium oxide particles surface-treated with aminosilane and tin oxide as the inorganic fine powder α, and powder resistance of 3.0 × 10 6 as the inorganic fine powder β^FourAfter treating with 0.8 parts of tin oxide particles (negative chargeability) surface treated with Ω · cm n-propyltrimethoxysilane and hexamethyldisilazane as inorganic fine powder γ, treated with silicone oil, after treatment Toner A was prepared by mixing 1.1 parts of hydrophobic silica fine powder having a primary average particle size of 15 nm with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.).
[0151]
The physical properties of the obtained toner A are shown in Table 1 together with those of the toner obtained in the following toner production examples.
[0152]
<Toner Production Example 2>
In Toner Production Example 1, the inorganic fine powder α is changed to hydrotalcite particles (TOM-84 (manufactured by Toda Kogyo Co., Ltd.)), the addition amount is 0.2 parts, and the addition amount of the inorganic fine powder β is 1. Toner B was obtained in the same manner except that the amount was changed to 0 part.
[0153]
<Toner Production Example 3>
Toner C was obtained in the same manner as in Toner Production Example 1 except that the surface treatment of inorganic fine powder α was performed with a titanium coupling agent and the charge amount of the inorganic fine powder was adjusted.
[0154]
<Toner Production Example 4>
In Toner Production Example 1, the inorganic fine powder β was surface-treated with n-hexyltrimethoxysilane titanium oxide (powder resistance = 2.0 × 10^FiveToner D was obtained in the same manner except that it was changed to (Ω · cm, negative chargeability).
[0155]
<Toner Production Example 5>
In Toner Production Example 1, the inorganic fine powder β was changed to a powder resistance of 2.0 × 10⁹Toner E was prepared in the same manner except that it was changed to Ω · cm barium titanate fine powder (showing negative chargeability when measured using the method of measuring the amount of powder charge described in (3) above). Obtained.
[0156]
<Toner Production Example 6>
In Toner Production Example 1, the specific surface area and charge amount of the inorganic fine powder α were adjusted by the particle size of the titanium oxide particle matrix and the amount of aminosilane coupling agent and tin oxide to obtain Q / H = 9.50. A toner F was obtained in the same manner except that.
[0157]
<Toner Production Example 7>
Toner G was obtained in the same manner as in Toner Production Example 2 except that the addition amount of inorganic fine powder α was 0.012 part and the addition amount of inorganic fine powder β was 3 parts.
[0158]
<Toner Production Example 8>
Toner H was obtained in the same manner as in Toner Production Example 1 except that the addition amount of inorganic fine powder α was 0.4 part and the addition amount of inorganic fine powder β was 0.5 part.
[0159]
<Toner Production Example 9>
Toner I was obtained in the same manner as in Toner Production Example 1 except that hydrophobic iron oxide 1 was changed to hydrophobic iron oxide 2.
[0160]
<Example 10 of toner production>
Toner J was obtained in the same manner except that the amount of ester wax used in toner production example 1 was changed to 51 parts.
[0161]
<Toner Production Example 11>
Toner K was obtained in the same manner as in Toner Production Example 1 except that the amount of ester wax used was changed to 0.4 part.
[0162]
<Toner Production Example 12>
Toner L was obtained in the same manner as in Toner Production Example 1 except that the amount of hydrophobic iron oxide added was changed to 9 parts.
[0163]
<Toner Production Example 13>
Toner M was obtained in the same manner as in Toner Production Example 1 except that the amount of hydrophobic iron oxide added was changed to 161 parts.
[0164]
<Toner Production Example 14>
In the formulation of Toner Production Example 1, except for magnetic powder, Na_ThreePO_FourAqueous solution and CaCl₂The amount of the aqueous solution charged was changed to obtain toner particles having a weight average particle diameter of 0.6 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 Non-magnetic toner particles were fixed on the surface to obtain spherical toner particles. When the powder charge amount of the obtained toner particles was measured, it showed negative chargeability.
[0165]
100 parts of the toner particles, 0.3 part of titanium oxide particles surface-treated with aminosilane and tin oxide as the inorganic fine powder α, and a resistance of 3.0 × 10 6 as the inorganic fine powder β^Four0.8 parts of tin oxide particles surface-treated with Ω · cm of n-propyltrimethoxysilane and hexamethyldisilazane as inorganic fine powder γ, then treated with silicone oil, and the primary average particle size after treatment Toner N was prepared by mixing 1.1 parts of hydrophobic silica fine powder of 15 nm with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.).
[0166]
<Toner Production Example 15>
Toner O was obtained in the same manner as in Toner Production Example 1 except that the hydrophobic silica fine powder was not added.
[0167]
<Toner Production Example 16>
Toner P was obtained in the same manner as in Toner Production Example 1 except that the hydrophobic silica fine powder was changed to untreated silica.
[0168]
<Toner Comparative Production Example 1>
-Styrene / n-butyl acrylate copolymer (mass ratio 80/20) 100 parts
・ Azo negative charge control agent 1 part
・ 85 parts of hydrophobic iron oxide 1
-5 parts of ester wax used in Production Example 1 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 Co., Ltd.). The resulting finely pulverized product was subjected to air classification to obtain toner particles. When the powder charge amount of the obtained toner particles was measured, it showed negative chargeability.
[0169]
100 parts of the toner particles, 0.3 part of titanium oxide particles surface-treated with aminosilane and tin oxide as the inorganic fine powder α, and a resistance of 3.0 × 10 6 as the inorganic fine powder β^FourAfter treating with 0.8 parts of tin oxide particles (negative chargeability) surface treated with Ω · cm n-propyltrimethoxysilane and hexamethyldisilazane as inorganic fine powder γ, treated with silicone oil, after treatment Toner Q was prepared by mixing 1.1 parts of hydrophobic silica fine powder having a primary average particle size of 15 nm with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.).
[0170]
<Toner Comparative Production Example 2>
Toner R was obtained in the same manner as in Toner Production Example 1 except that the hydrophobic iron oxide 1 was changed to the magnetic powder 1.
[0171]
<Toner Comparative Production Example 3>
In Toner Production Example 1, the specific surface area and charge amount of the inorganic fine powder α were adjusted by the particle size of the titanium oxide particle matrix and the amount of aminosilane coupling agent and tin oxide to obtain Q / H = 0.08. A toner S was obtained in the same manner except that.
[0172]
<Toner Comparative Production Example 4>
In Toner Production Example 1, the specific surface area and charge amount of the inorganic fine powder α were adjusted by the particle size of the titanium oxide particle matrix and the amount of aminosilane coupling agent and tin oxide to obtain Q / H = 10.30. A toner T was obtained in the same manner except that.
[0173]
<Toner Comparative Production Example 5>
Toner U was obtained in the same manner as in Toner Production Example 2 except that the addition amount of inorganic fine powder α was 0.007 part and the addition amount of inorganic fine powder β was 3 parts.
[0174]
<Comparative Production Example 6 of Toner>
Toner V was obtained in the same manner as in Toner Production Example 1 except that the addition amount of inorganic fine powder α was 0.4 part and the addition amount of inorganic fine powder β was 0.3 part.
[0175]
<Toner Comparative Production Example 7>
Toner W was obtained in the same manner as in Toner Production Example 1 except that the inorganic fine powder β was changed to the titanium coupling-treated titanium oxide used in Toner Production Example 3.
[0176]
<Toner Comparative Production Example 8>
Toner X was obtained in the same manner as in Toner Production Example 1 except that the inorganic fine powder α was changed to the n-hexyltrimethoxysilane-treated titanium oxide used in Toner Production Example 4.
[0177]
[Table 1]

[0178]
(Photoreceptor Production Example 1)
As the photoreceptor, an Al cylinder having a diameter of 30 mm was used as a base. To this, layers having a structure as shown in FIG. 3 were sequentially laminated by dip coating to produce a photoreceptor.
(1) Conductive coating layer: Mainly composed of a powder of tin oxide and titanium oxide dispersed in a phenol 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 °.
[0179]
The contact angle was measured using pure water and a contact angle meter CA-X type apparatus manufactured by Kyowa Interface Science Co., Ltd.
[0180]
[Example 1]
As an image forming apparatus, LBP-1760 (manufactured by Canon) was remodeled, and an apparatus having a structure generally shown in FIG. 1 was used.
[0181]
As the electrostatic charge image carrier, the organic photoreceptor (OPC) drum of Production Example 1 of the photoreceptor was used. A rubber roller charger in which conductive carbon is dispersed as a primary charging member and coated with a nylon resin is brought into contact with this photoreceptor (contact pressure 58.8 N / m (60 g / cm)), and a DC voltage of −640 V is applied._dcAC voltage 2.0kV_ppIs applied to the photosensitive member to uniformly charge the photosensitive member. Subsequent to primary charging, an electrostatic latent image is formed by exposing the image portion with laser light. At this time, dark part potential V_d= -630V, bright part potential V_L= −220V.
[0182]
The gap between the photosensitive drum and the developing sleeve is 265 μm, and a resin layer having a layer thickness of about 7 μm and a JIS centerline average roughness (Ra) of 1.1 μm is used as a toner carrier, and the surface is a mirror surface with a diameter of 20 mm. Using a developing sleeve formed on an aluminum cylinder, a developing magnetic pole of 95 mT (950 gauss), a toner regulating member having a thickness of 1.0 mm and a free length of 1.0 mm of a silicone rubber blade of 14.7 N / m (1.5 kg / m) The contact was made with the linear pressure of m).
・ Phenolic resin 100 parts
・ 90 parts of graphite (particle size: about 7μm)
・ 10 parts of carbon black
Next, a DC bias component V as a developing bias_dc= -500V, superimposed AC bias component V_pp= 1800 V, f = 2400 Hz was used. The peripheral speed of the developing sleeve was 105% (226.8 mm / sec) in the forward direction with respect to the peripheral speed of the photoreceptor (216 mm / sec).
[0183]
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 circumferential speed of the photosensitive member (216 mm / sec) in the direction A in FIG. It was 1.3 kV. In FIG. 4, 1 is a photoconductor, 4 is a transfer roller, 41 is a metal core, 42 is a conductive elastic layer, and 43 is a transfer bias power source.
[0184]
As a fixing method, a fixing device of a fixing film heating system shown in FIGS. 5 and 6 was used. In the figure, 50 is a stay, 51 is a heating element, 51a is a heater substrate, 51b is an energization heating resistor (heating element), 51c is a surface protection layer, 51d is a temperature measuring element, 52 is a heat-resistant endless film, and 53 is a pressure. A roller, 54 is a coil spring, 55 is a film end regulating flange, 56 is a power supply connector, 57 is a heat insulating member, 58 is an outlet guide (separation guide), and 59 is an inlet guide.
[0185]
First, toner A was used as a toner, and an image printing test was performed in a normal temperature and normal humidity (23 ° C., 65% RH) environment. 90g / m as transfer material²Paper was used. As a result, a high image with high density and transferability in the initial stage, no fogging on non-image areas, and no blotch was obtained.
[0186]
Next, an image pattern consisting only of horizontal lines with a printing area ratio of 3% was printed up to 6000 printed sheets, and then left for 30 days to perform initial evaluation and 6000 printing again to evaluate durability. .
[0187]
Image evaluation and toner durability evaluation were performed as follows.
[0188]
a) Image density
After the initial and 6000 printouts were completed, and after 30 days, the image density of the first sheet that was turned on again and turned on was evaluated. The image density was measured by using a “Macbeth reflection densitometer” (manufactured by Macbeth Co., Ltd.) to measure a relative density with respect to a printout image of a white background portion having a document density of 0.00. If the value of the image density is 1.40 or more, there is no practical problem.
[0189]
b) fog
The fog was measured using a REFECTMETER MODELTC-6DS manufactured by Tokyo Denshoku. The filter was calculated from the following formula using a green filter.
[0190]
Fog (reflectance) (%)
= Reflectance on standard paper (%)-reflectance of sample non-image area (%)
The fogging was performed according to the following criteria.
A: Less than 0.5%
B: 0.5% or more and less than 1.0%
C: 1.0% or more and less than 1.5%
D: 1.5% or more and 2.0% or less
E: 2.0% <fogging (reflectance)
If it is AD, it is an image with no problem in practical use.
[0191]
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.
[0192]
Transfer efficiency (%) = {(EC) / (ED)} × 100
Transferability was determined according to the following criteria.
A: 97.5% or more
B: 95.0% or more and less than 97.5%
C: 92.5% or more and less than 95.0%
D: 90.0% or more and less than 92.5%
E: Less than 90.0%
If it is AD, it is an image with no problem in practical use.
[0193]
e) Fixability
The non-offset property was evaluated on the basis of the following with respect to the degree of the back stain of the printout image obtained by observing the stain on the back side of the image sample after 12,000 sheets of durability.
A: Not generated
B: Almost no occurrence.
C: Slightly generated, but no problem in practical use.
D: It occurs considerably and has a problem in practical use.
[0194]
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 / cm²Was 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
If it is AC, there is no problem in practical use.
[0195]
f) Blotch
The blotch was evaluated by visually observing a solid black image and evaluating the occurrence according to the following criteria.
A: Excellent
B: Good
C: No problem in practical use
D: Practical problem
[0196]
h) Fixed scattering
At the end of endurance in a low-temperature and low-humidity environment where the toner charge amount tends to increase, fixing splattering outputs an image in which 200 μm horizontal line images are drawn every 1 cm, and the number of splattered points between the fixed image and the unfixed image. The difference was evaluated. The unfixed image was subjected to evaluation after being fixed in a windless oven at 120 ° C. for 1 minute.
A: Less than 10 scattered points
B: Less than 10 to 20 scattered points
C: Spattering points are less than 20-30
D: 30 or more scattered points
If it is A to C, the image has no practical problem.
[0197]
The obtained results are shown in Tables 2 and 3. As can be seen from Tables 2 and 3, the toner A had good initial image evaluation, and had no problem both after the first 6000 sheets and after the last 6000 sheets, indicating a very good durability result. .
[0198]
Next, the image formation test was conducted in the same manner under high temperature and high humidity (32.5 ° C., 85% RH) environment and low temperature and low humidity (15 ° C., 10% RH) environment. Image characteristics and durability. The obtained results are shown in Tables 4 and 5 under a high temperature and high humidity environment, and Tables 6 and 7 under a low temperature and low humidity environment.
[0199]
[Example 2]
The toner B was used as the toner, and an image forming test and a durability test were performed by the same image forming method as in Example 1. As a result, as shown in Tables 3 and 4, good results were obtained with respect to image characteristics and durability.
[0200]
[Examples 3 and 4]
Toners C and D were used as toners, and an image formation test was performed by the same image forming method as in Example 1. As a result, as shown in Tables 3 and 4, results with no practical problems were obtained.
[0201]
[Examples 5 to 7]
As toners, toners E to G 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, as shown in Tables 3 and 4, good results were obtained with respect to image characteristics and durability.
[0202]
[Examples 8 to 16]
Toners H to P were used as toners, and an image output test was performed by the same image forming method as in Example 1. As a result, as shown in Tables 3 and 4, results with no practical problems were obtained.
[0203]
[Comparative Examples 1 to 10]
Toners Q to X were used as toners, and an image output test was performed by the same image forming method as in Example 1. As a result, as shown in Tables 3 and 4, the image characteristics were poor and were not practically tolerable.
[0204]
[Table 2]

[0205]
[Table 3]

[0206]
[Table 4]

[0207]
[Table 5]

[0208]
[Table 6]

[0209]
[Table 7]

[0210]
【The invention's effect】
According to the present invention, even when left at high temperature and high humidity for a long time, the charge amount of the toner is not impaired, the charging stability is excellent, the image density is high even in long-term use, and high-definition with suppressed fogging. An object of the present invention is to provide a magnetic toner capable of obtaining an image and suppressing excessive charging of the toner even under low temperature and low humidity.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus that implements an image forming method of the present invention.
FIG. 2 is a diagram showing the developing device shown in FIG. 1;
FIG. 3 is a schematic view showing an example of an image carrier used in the image forming method of the present invention.
FIG. 4 is a diagram illustrating an example of a transfer roller used in a transfer step in the image forming method of the present invention.
FIG. 5 is an exploded tilt view of a main part of a fixing device used in an example of the present invention and a comparative example.
FIG. 6 is an enlarged cross-sectional view of a main part showing a film state when the fixing device used in the examples and comparative examples of the present invention is not driven.
FIG. 7 is a schematic view of an apparatus used for measuring a powder charge amount of an inorganic fine powder in the present invention.
[Explanation of symbols]
1 Photosensitive drum
2 Primary charging roller
3 Developer
4 Transfer roller
5 Cleaning means
6 Register roller
7 Laser generator
8 Laser light
9 Conveyor belt
10 Fixing device
11 Toner carrier (developing sleeve)
12 Stirring member
13 Magnet roller
14 Elastic blade
41 cored bar
42 Conductive elastic layer
43 Transfer bias power supply
50 stays
51 Heating body
51a Heater board
51b Energizing heating resistor (heating element)
51c Surface protective layer
51d Temperature sensor
52 heat resistant endless film
53 Pressure roller
54 Coil spring
55 Film end regulating flange
56 Power connector
57 Thermal insulation
58 Exit guide (separation guide)
59 Entrance Guide
71 Suction machine
72 Measuring container
73 screen
74 Lid
75 Vacuum gauge
76 Air volume control valve
77 Suction port
78 condenser
79 Electrometer

Claims (13)

In a magnetic toner particle containing at least a binder resin and magnetic powder, an inorganic fine powder α, and an inorganic fine powder β,
The magnetic toner particles are produced by a suspension polymerization method,
The average circularity of the magnetic toner particles is 0.970 or more,
The charging polarity of the inorganic fine powder α is opposite to that of the magnetic toner particles,
The charging polarity of the inorganic fine powder β is the same as that of the magnetic toner particles,
The inorganic fine powder β is a conductive fine powder having a powder resistance of 1 × 10 ⁹ Ω · cm or less,
When the powder charge amount of the inorganic fine particles α is Q (μC / g) and the specific surface area is H (m ² / g),
0.1 ≦ Q / H ≦ 10.0,
The ratio of the content of the inorganic fine powder α and the inorganic fine powder β (κ = α content / β content) is 0.003 ≦ κ ≦ 1.0,
The ratio (B / A) of the iron element content (B) to the carbon element content (A) present on the toner particle surface as measured by X-ray photoelectron spectroscopy of the magnetic toner particles is less than 0.001. A magnetic toner characterized by being.   The magnetic toner according to claim 1, wherein the B / A is less than 0.0005.   The magnetic toner according to claim 1, wherein the inorganic fine powder α is a hydrotalcite-like compound.   The magnetic toner according to claim 1, wherein the inorganic fine powder α is a titanium oxide compound treated with an aminosilane compound.   The magnetic toner according to claim 1, wherein the inorganic fine powder β contains tin oxide. The projected area equivalent circle diameter of the magnetic toner particles is C, and the minimum distance between the magnetic particles and the toner particle surface in the cross-sectional observation of the toner using a transmission electron microscope (TEM) is D / C. a magnetic toner according to any one of claims 1 to 5 the magnetic toner particles satisfying the relationship of ≦ 0.02 is 50% by number or more. The magnetic toner, magnetic toner according to any one of claims 1 to 6 containing an inorganic fine powder γ of an average primary particle size 4～25Nm. The magnetic toner according to claim 7 , wherein the inorganic fine powder γ is silica or a double oxide thereof. The magnetic toner of the inorganic fine powder γ according to claim 7 or 8 has been subjected to hydrophobic treatment. The magnetic toner particles, 100 parts by mass of the binder resin, the magnetic toner according to any one of claims 1 to 9 containing 10 to 160 parts by weight of magnetic powder. The magnetic toner particles, 100 parts by mass of the binder resin, the magnetic toner according to any one of claims 1 to 10 containing 0.5 to 50 parts by weight of wax. A magnetic toner according to any one of the magnetic toner according to claim mode circularity of particles is 0.99 or more 1 to 11. In an image forming method of forming an image by developing the electrostatic latent image by supplying a developer to an image carrier that carries the electrostatic latent image, and fixing the visualized image on a recording material. an image forming method wherein the developer is characterized in that it comprises a magnetic toner according to any one of claims 1 to 12.

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