JP4289860B2 - Toner and image forming apparatus - Google Patents

Description

【００５１】
【化２】

【００５２】
また、上記モノマーのうち酸成分としては、フタル酸、テレフタル酸、イソフタル酸、無水フタル酸等のベンゼンジカルボン酸類またはその無水物；コハク酸、アジピン酸、セバシン酸、アゼライン酸等のアルキルジカルボン酸類またはその無水物、またさらに炭素数６〜１８のアルキル基で置換されたコハク酸もしくはその無水物：フマル酸、マレイン酸、シトラコン酸、イタコン酸等の不飽和ジカルボン酸またはその無水物などが挙げられる。
【００５３】
また、グリセリン、ペンタエリスリトール、ソルビット、ソルビタン、さらには、例えばノボラック型フェノール樹脂のオキシアルキレンエーテル等の多価アルコール類；トリメリット酸、ピロメリット酸、ベンゾフェノンテトラカルボン酸やその無水物などの多価カルボン酸類等が挙げられる。
【００５４】
スチレン−アクリル系樹脂を生成するためのビニル系モノマーとしては次のようなものが挙げられる。
【００５５】
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−フェニルスチレン、ｐ−エチルスチレン、２，４−ジメチルスチレン、ｐ−ｎ−ブチルスチレン、ｐ−ｔｅｒｔ−ブチルスチレン、ｐ−ｎ−ヘキシルスチレン、ｐ−ｎ−オクチルスチレン、ｐ−ｎ−ノニルスチレン、ｐ−ｎ−デシルスチレン、ｐ−ｎ−ドデシルスチレン、ｐ−メトキシスチレン、ｐ−クロルスチレン、３，４−ジクロルスチレン、ｍ−ニトロスチレン、ｏ−ニトロスチレン、ｐ−ニトロスチレンなどのスチレンおよびその誘導体；エチレン、プロピレン、ブチレン、イソブチレンなどのエチレン不飽和モノオレフィン類；ブタジエン、イソプレンなどの不飽和ポリエン類；塩化ビニル、塩化ビニリデン、臭化ビニル、フッ化ビニルなどのハロゲン化ビニル類；酢酸ビニル、プロピオン酸ビニル、ベンゾエ酸ビニルなどのビニルエステル類；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などのα−メチレン脂肪族モノカルボン酸エステル類：アクリル酸メチル、アクリル酸エチル、アクリル酸プロピル、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−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などのアクリル酸エステル類；ビニルメチルエーテル、ビニルエチルエーテル、ビニルイソブチルエーテルなどのビニルエーテル類；ビニルメチルケトン、ビニルヘキシルケトン、メチルイソプロペニルケトンなどのビニルケトン類；Ｎ−ビニルピロール、Ｎ−ビニルカルバゾール、Ｎ−ビニルインドール、Ｎ−ビニルピロリドンなどのＮ−ビニル化合物；ビニルナフタリン類；アクリロニトリル、メタクリロニトリル、アクリルアミドなどのアクリル酸もしくはメタクリル酸誘導体等が挙げられる。
【００５６】
さらに、マレイン酸、シトラコン酸、イタコン酸、アルケニルコハク酸、フマル酸、メサコン酸などの不飽和二塩基酸；マレイン酸無水物、シトラコン酸無水物、イタコン酸無水物、アルケニルコハク酸無水物などの不飽和二塩基酸無水物；マレイン酸メチルハーフエステル、マレイン酸エチルハーフエステル、マレイン酸ブチルハーフエステル、シトラコン酸メチルハーフエステル、シトラコン酸エチルハーフエステル、シトラコン酸ブチルハーフエステル、イタコン酸メチルハーフエステル、アルケニルコハク酸メチルハーフエステル、フマル酸メチルハーフエステル、メサコン酸メチルハーフエステルなどの不飽和塩基酸のハーフエステル；ジメチルマレイン酸、ジメチルフマル酸などの不飽和塩基酸エステル；アクリル酸、メタクリル酸、クロトン酸、ケイヒ酸などのα、β−不飽和酸無水物；該α、β−不飽和酸と低級脂肪酸との無水物；アルケニルマロン酸、アルケニルグルタル酸、アルケニルアジピン酸、これらの酸無水物およびこれらのモノエステルの如きカルボキシル基を有するモノマーが挙げられる。
【００５７】
さらに、２−ヒドロキシルエチルアクリレート、２−ヒドロキシルエチルメタクリレート、２−ヒドロキシルプロピルメタクリレートなどのアクリル酸またはメタクリル酸エステル類、４−（１−ヒドロキシ−１−メチルブチル）スチレン、４−（１−ヒドロキシ−１−メチルヘキシル）スチレンなどのヒドロキシル基を有するモノマーが挙げられる。
【００５８】
また必要に応じて以下に例示するような架橋性モノマーで架橋された重合体であってもよい。芳香族ジビニル化合物として例えば、ジビニルベンゼン、ジビニルナフタレンが挙げられ；アルキル鎖で結ばれたジアクリレート化合物類として例えば、エチレングリコールジアクリレート、１，３−ブチレングリコールジアクリレート、１，４−ブタンジオールジアクリレート、１，５−ペンタンジオールジアクリレート、１，６−ヘキサンジオールジアクリレート、ネオペンチルグリコールジアクリレート、および以上の化合物のアクリレートをメタクリレートに代えたものが挙げられ；エーテル結合を含むアルキル鎖で結ばれたジアクリレート化合物類としては、例えばジエチレングリコールジアクリレート、トリエチレングリコールジアクリレート、テトラエチレングリコールジアクリレート、ポリエチレングリコール＃４００ジアクリレート、ポリエチレングリコール＃６００ジアクリレート、ジプロピレングリコールジアクリレート、および以上の化合物のアクリレートをメタアクリレートに代えたものが挙げられ；芳香族基およびエーテル結合を含む鎖で結ばれたジアクリレート化合物類として例えば、ポリオキシエチレン（２）−２，２−ビス（４−ヒドロキシフェニル）プロパンジアクリレート、ポリオキシエチレン（４）−２，２−ビス（４−ヒドロキシフェニル）プロパンジアクリレート、および以上の化合物のアクリレートをメタアクリレートに代えたものが挙げられ；ポリエステル型ジアクリレー卜類として例えば、商品名ＭＡＮＤＡ（日本化薬）が挙げられる。
【００５９】
多官能の架橋剤としては、ペンタエリスリトールトリアクリレート、トリメチロールエタントリアクリレート、トリメチロールプロパントリアクリレート、テトラメチロールメタンテトラアクリレート、オリゴエステルアクリレート、および以上の化合物のアクリレートをメタアクリレートに代えたもの；トリアリルシアヌレート、トリアリルトリメリテート；が挙げられる。
【００６０】
これらの架橋剤は、他のモノマー成分１００質量％に対して、０．０１〜１０質量％（さらに好ましくは０．０３〜５質量％）用いることができる。これらの架橋性モノマーのうち、トナー用樹脂に定着性、耐オフセット性の点から好適に用いられるものとして、芳香族ジビニル化合物（特にジビニルベンゼン）、芳香族基およびエーテル結合を含む鎖で結ばれたジアクリレート化合物類が挙げられる。
【００６１】
本発明におけるビニル系共重合体を製造する場合に用いられる重合開始剤としては、例えば、２，２'−アゾビスイソブチロニトリル、２，２'−アゾビス（４−メトキシ−２，４ジメチルバレロニトリル）、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（−２メチルブチロニトリル）、ジメチル−２，２'−アゾビスイソブチレート、１，１'−アゾビス（１−シクロヘキサンカルボニトリル）、２−（カーバモイルアゾ）−イソブチロニトリル、２，２'−アゾビス（２，４，４−トリメチルペンタン）、２−フェニルアゾ−２，４−ジメチル−４−メトキシバレロニトリル、２，２'−アゾビス（２−メチル−プロパン）、メチルエチルケトンパーオキサイド、アセチルアセトンパ−オキサイド、シクロヘキサノンパーオキサイドなどのケトンパーオキサイド類、２，２−ビス（ｔ−ブチルパーオキシ）ブタン、ｔ−ブチルハイドロパーオキサイド、クメンハイドロパーオキサイド、１，１，３，３−テトラメチルブチルハイドロパーオキサイド、ジ−ｔ−ブチルパーオキサイド、ｔ−ブチルクミルパーオキサイド、ジ−クミルパーオキサイド、α，α'−ビス（ｔ−ブチルパーオキシイソプロピル）ベンゼン、イソブチルパーオキサイド、オクタノイルパーオキサイド、デカノイルパーオキサイド、ラウロイルパーオキサイド、３，５，５−トリメチルヘキサノイルパーオキサイド、ベンゾイルパーオキサイド、ｍ−トリオイルパーオキサイド、ジ−イソプロピルパーオキシジカーボネート、ジ−２−エチルヘキシルパーオキシジカーボネート、ジ−ｎ−プロピルパーオキシジカーボネート、ジ−２−エトキシエチルパーオキシカーボネート、ジ−メトキシイソプロピルパーオキシジカーボネート、ジ（３−メチル−３−メトキシブチル）パーオキシカーボネート、アセチルシクロヘキシルスルホニルパーオキサイド、ｔ−ブチルパーオキシアセテート、ｔ−ブチルパーオキシイソブチレート、ｔ−ブチルパーオキシネオデカノエイト、ｔ−ブチルパーオキシ２−エチルヘキサノエイト、ｔ−ブチルパーオキシラウレート、ｔ−ブチルパーオキシベンゾエイト、ｔ−ブチルパーオキシイソプロピルカーボネート、ジ−ｔ−ブチルパーオキシイソフタレート、ｔ−ブチルパーオキシアリルカーボネート、ｔ−アミルパーオキシ２−エチルヘキサノエイト、ジ−ｔ−ブチルパーオキシヘキサハイドロテレフタレート、ジ−ｔ−ブチルパーオキシアゼレートが挙げられる。
【００６２】
本発明のトナーを磁性トナーとして用いる場合、磁性トナーに含まれる磁性材料としては、マグネタイト、マグヘマイト、フェライト等の酸化鉄、および他の金属酸化物を含む酸化鉄；Ｆｅ、Ｃｏ、Ｎｉのような金属、あるいはこれらの金属とＡｌ、Ｃｏ、Ｃｕ、Ｐｂ、Ｍｇ、Ｎｉ、Ｓｎ、Ｚｎ、Ｓｂ、Ｂｅ、Ｂｉ、Ｃｄ、Ｃａ、Ｍｎ、Ｓｅ、Ｔｉ、Ｗ、Ｖのような金属との合金、およびこれらの混合物等が挙げられる。
【００６３】
磁性材料としては、従来四三酸化鉄（Ｆｅ₃Ｏ₄）、三二酸化鉄（γ−Ｆｅ₂Ｏ₃）、酸化鉄亜鉛（ＺｎＦｅ₂Ｏ₄）、酸化鉄イットリウム（Ｙ₃Ｆｅ₅Ｏ₁₂）、酸化鉄カドミニウム（ＣｄＦｅ₂Ｏ₄）、酸化鉄ガドリニウム（Ｇｄ₃Ｆｅ₅Ｏ₁₂）、酸化鉄銅（ＣｕＦｅ₂Ｏ₄）、酸化鉄鉛（ＰｂＦｅ₁₂Ｏ₁₉）、酸化鉄ニッケル（ＮｉＦｅ₂Ｏ₄）、酸化鉄ネオジム（ＮｄＦｅ₂Ｏ₃）、酸化鉄バリウム（ＢａＦｅ₁₂Ｏ₁₉）、酸化鉄マグネシウム（ＭｇＦｅ₂Ｏ₄）、酸化鉄マンガン（ＭｎＦｅ₂Ｏ₄）、酸化鉄ランタン（ＬａＦｅＯ₃）、鉄粉（Ｆｅ）、コバルト粉（Ｃｏ）、ニッケル粉（Ｎｉ）等が知られているが、本発明によれば上述した磁性材料を単独であるいは２種以上の組み合わせで選択使用する。本発明の目的に特に好適な磁性材料は四三酸化鉄またはγ−三二酸化鉄の微粉末である。
【００６４】
これらの磁性材料は平均粒径が０．１〜２μｍ程度で、７９５．８ｋＡ／ｍ（１０ｋエルステッド）印加での磁気特性が抗磁力ｌ．５〜１２ｋＡ／ｍ、飽和磁化５０〜２００Ａｍ²／ｋｇ（好ましくは５０〜１００Ａｍ²／ｋｇ）、残留磁化２〜２０Ａｍ²／ｋｇのものが望ましい。結着樹脂１００質量部に対して、磁性体２０〜１５０質量部使用するのが良い。
【００６５】
また、本発明のトナーに用いられる着色剤としては、一成分、二成分を問わず、カーボンブラック、チタンホワイトやその他あらゆる顔料および／または染料を用いることができる。例えば本発明のトナーを磁性カラートナーとして使用する場合には、染料としては、Ｃ．Ｉ．ダイレクトレッド１、Ｃ．Ｉ．ダイレクトレッド４、Ｃ．Ｉ．アシッドレッド１、Ｃ．Ｉ．ベーシックレッド１、Ｃ．Ｉ．モーダントレッド３０、Ｃ．Ｉ．ダイレクトブルー１、Ｃ．Ｉ．ダイレクトブルー２、Ｃ．Ｉ．アシッドブルー９、Ｃ．Ｉ．アシッドブルー１５、Ｃ．Ｉ．ベーシックブルー３、Ｃ．Ｉ．ベーシックブルー５、Ｃ．Ｉ．モーダントブルー７、Ｃ．Ｉ．ダイレクトグリーン６、Ｃ．Ｉ．ベーシックグリーン４、Ｃ．Ｉ．ベーシックグリーン６等がある。顔料としては、黄鉛、カドミウムイエロー、ミネラルファストイエロー、ネーブルイエロー、ナフトールイエローＳ、ハンザイエローＧ、パーマネントイエローＮＣＧ、タートラジンレーキ、赤口黄鉛、モリブデンオレンジ、パーマネントオレンジＧＴＲ、ピラゾロンオレンジ、ベンジジンオレンジＧ、カドミウムレッド、パーマネントレッド４Ｒ、ウォッチングレッドカルシウム塩、エオシンレーキ、ブリリアントカーミン３Ｂ、マンガン紫、ファストバイオレットＢ、メチルバイオレットレーキ、紺青、コバルトブルー、アルカリブルーレーキ、ビクトリアブルーレーキ、フタロシアニンブルー、ファーストスカイブルー、インダンスレンブルーＢＣ、クロムグリーン、酸化クロム、ピグメントグリーンＢ、マラカイトグリーンレーキ、ファイナルイエローグリーンＧ等がある。
【００６６】
また、本発明のトナーを二成分フルカラー用トナーとして使用する場合には、次の様なものが挙げられる。マゼンタ用着色顔科としては、Ｃ．Ｉ．ピグメントレッド１，２，３，４，５．６，７，８，９，１０，１１，１２，１３，１４，１５，１６，１７，１８，１９，２１，２２，２３，３０，３１，３２，３７，３８，３９，４０，４１，４８，４９，５０，５１，５２，５３，５４，５５，５７，５８，６０，６３，６４，６８，８１，８３，８７，８８，８９，９０，１１２，１１４，１２２，１２３，１６３，２０２，２０６，２０７，２０９、Ｃ．Ｉ．ピグメントバイオレット１９、Ｃ．Ｉ．バットレッド１，２，１０，１３．１５，２３，２９，３５等が挙げられる。
【００６７】
上記顔料を単独で使用しても構わないが、染料と顔料と併用してその鮮明度を向上させた方がフルカラー画像の画質の点からより好ましい。かかるマゼンタ用染料としては、Ｃ．Ｉ．ソルベントレッド１，３，８，２３，２４，２５，２７，３０，４９，８１，８２，８３，８４，ｌ００，ｌ０９，１２１、Ｃ．Ｉ．ディスバースレッド９、Ｃ．Ｉ．ソルベントバイオレット８，１３，１４，２１，２７、Ｃ．Ｉ，ディスパースバイオレット１等の油溶染料、Ｃ．Ｉ．ベーシックレッド１，２，９，１２，１３，１４，１５，１７，１８，２２，２３，２４，２７，２９，３２，３４，３５，３６，３７，３８，３９，４０、Ｃ．Ｉ．ベーシックバイオレット１，３，７，１０，１４，１５，２１，２５，２６，２７，２８等の塩基性染料が挙げられる。
【００６８】
その他の着色顔料として、シアン用着色顔料としては、Ｃ．Ｉ．ピグメントブルー２，３，１５，１６，１７、Ｃ．Ｉ．バットブルー６、Ｃ．Ｉ．アシッドブルー４５または下記（ウ）式で示される構造を有するフタロシアニン骨格にフタルイミドメチル基を１〜５個置換した銅フタロシアニン顔料等が挙げられる。
【００６９】
【化３】

【００７０】
イエロー用着色顔科としては、Ｃ．Ｉ．ピグメントイエロー１，２，３，４，５，６，７，１０，１１，１２，１３，１４，１５，１６，１７，２３，６５，７３、８３、Ｃ．Ｉ．バットイエロー１，３，２０等が挙げられる，
尚、着色剤の使用量は結着樹脂１００質量部に対して、０．１〜６０質量部、好ましくは０．５〜５０質量部である。
【００７１】
本発明のトナーには、必要に応じて一種または二種以上の離型剤をトナー母粒子中に含有させてもかまわない。本発明に用いられる離型剤としては次のものが挙げられる。低分子量ポリエチレン、低分子量ポリプロピレン、マイクロクリスタリンワックス、パラフィンワックスなどの脂肪族炭化水素系ワックス、また酸化ポリエチレンワックスなどの脂肪族炭化水素系ワックスの酸化物、またはそれらのブロック共重合物；カルナバワックス、サゾールワックス、モンタン酸エステルワックスなどの脂肪酸エステルを主成分とするワックス類、および脱酸カルナバワックスなどの脂肪酸エステル類を一部または全部を脱酸化したものなどが挙げられる。さらに、パルミチン酸、ステアリン酸、モンタン酸などの飽和直鎖脂肪酸類；ブランジン酸、エレオステアリン酸、バリナリン酸などの不飽和脂肪酸類；ステアリルアルコール、アラルキルアルコール、ベヘニルアルコール、カルナウビルアルコール、セリルアルコール、メリシルアルコールなどの飽和アルコール類；ソルビトールなどの多価アルコール類；リノール酸アミド、オレイン酸アミド、ラウリン酸アミドなどの脂肪酸アミド類；メチレンビスステアリン酸アミド、エチレンビスカプリン酸アミド、エチレンビスラウリン酸アミド、ヘキサメチレンビスステアリン酸アミドなどの飽和脂肪酸ビスアミド類；エチレンビスオレイン酸アミド、ヘキサメチレンビスオレイン酸アミド、Ｎ，Ｎ'ジオレイルアジピン酸アミド、Ｎ，Ｎ'ジオレイルセバシン酸アミドなどの不飽和脂肪酸アミド類；ｍ−キシレンビスステアリン酸アミド、Ｎ，Ｎ'ジステアリルイソフタル酸アミドなどの芳香族系ビスアミド類；ステアリン酸カルシウム、ステアリン酸カルシウム、ステアリン酸亜鉛、ステアリン酸マグネシウムなどの脂肪族金属塩（一般に金属石けんといわれているもの）；脂肪族炭化水素系ワックスにスチレンやアクリル酸などのビニル系モノマーを用いてグラフト化させたワックス類；ベヘニン酸モノグリセリドなどの脂肪酸と多価アルコールの部分エステル化物；植物性油脂の水素添加などによって得られるヒドロキシル基を有するメチルエステル化合物などが挙げられる。
【００７２】
本発明において特に好ましく用いられる離型剤としては、脂肪族炭化水素系ワックスが挙げられる。例えば、アルキレンを高圧化でラジカル重合あるいは低圧化でチーグラー触媒で重合した低分子量のアルキレンポリマー；高分子量のアルキレンポリマーを熱分解して得られるアルキレンポリマー；一酸化炭素および水素を含む合成ガスからアーゲ法により得られる炭化水素の蒸留残分から、あるいはこれらを水素添加して得られる合成炭化水素ワックスがよい。さらにプレス発汗法、溶剤法、真空蒸留の利用や分別結晶方式により炭化水素ワックスの分別を行ったものがより好ましく用いられる。母体としての炭化水素は、金属酸化物系触媒（多くは２種以上の多元系）を使用した一酸化炭素と水素の反応によって合成されるもの［例えばジントール法、ヒドロコール法（流動触媒床を使用）によって合成された炭化水素化合物］；ワックス状炭化水素が多く得られるアーゲ法（同定触媒床を使用）により得られる炭素数が数百ぐらいまでの炭化水素；エチレンなどのアルキレンをチーグラー触媒により重合した炭化水素が、分岐が少なくて小さく、飽和の長い直鎖状炭化水素であるので好ましい。特にアルキレンの重合によらない方法により合成されたワックスがその分子量分布からも好ましいものである。
【００７３】
本発明において使用されるワックスは、ワックスを含有するトナーの示差走査熱量計で測定されるＤＳＣ曲線において、８０〜１３０℃の領域に吸熱メインピークを有することが、トナーの低温定着性および耐高温オフセット性の点で好ましい。
【００７４】
離型剤は結着樹脂１００質量部あたり０．１〜２０質量部、好ましくは０．５〜１０質量部使用するのが良い。離型剤は通常、樹脂を溶剤に溶解し樹脂溶液温度を上げ、撹拌しながら添加混合する方法や、混練時に混合する方法で結着樹脂に含有させられる。
【００７５】
本発明の静電荷像現像用トナーは、その帯電性をさらに安定化させる為に必要に応じて荷電制御剤を用いることができる。荷電制御剤は、樹脂成分１００質量部当たり０．１〜１０質量部、好ましくは０．１〜５質量部使用するのが好ましい。荷電制御剤としては、以下のものが挙げられる。
【００７６】
トナーを負帯電性に制御するものとして例えば有機金属錯体、キレート化合物が有効で、その例としてはモノアゾ金属錯体；アセチルアセトン金属錯体；芳香族ヒドロキシカルボン酸または芳香族ジカルボン酸の金属錯体または金属塩が挙げられる。他には、芳香族モノおよびポリカルボン酸およびその金属塩、無水物、エステル類やビスフェノールなどのフェノール誘導体が挙げられる。
【００７７】
トナーを正荷電性に制御するものとして、ニグロシンおよび脂肪酸金属塩などによる変性物；トリブチルベンジルアンモニウム−１−ヒドロキシ−４−ナフトスルフォン酸塩、テトラブチルアンモニウムテトラフルオロボレートなどの四級アンモニウム塩、およびこれらの類似体であるホスホニウム塩などのオニウム塩およびこれらのレーキ顔料；トリフェニルメタン染料およびこれらのレーキ顔料（レーキ化剤としては、りんタングステン酸、りんモリブデン酸、りんタングステンモリブデン酸、タンニン酸、ラウリン酸、没食子酸、フェリシアン酸、フェロシアン化合物など）；高級脂肪酸の金属塩；ジブチルスズオキサイド、ジオクチルスズオキサイド、ジシクロヘキシルスズオキサイドなどのジオルガノスズオキサイド；ジブチルスズボレート、ジオクチルスズボレート、ジシクロヘキシルスズボレートなどのジオルガノスズボレートが挙げられる。これらを単独であるいは２種類以上組み合わせて用いることができる。これらの中でもニグロシン系化合物、四級アンモニウム塩などの荷電制御剤が特に好ましく用いられる。
【００７８】
また、本発明のトナーは、粒径が３μｍ以下の微粒子を含有する。この微粒子の粒径は０．１〜２．９μｍであることが好ましく、０．３〜２．５μｍであることがより好ましい。また、上記微粒子は、チタン酸ストロンチウム、チタン酸マグネシウム、チタン酸カルシウム、酸化セリウム、酸化アルミニウム、酸化亜鉛から選ばれる１種類以上を含有することを特徴とし、これらのうち１種のみからなるものであっても、２種以上が混合されてなるものであっても良く、さらに他の材料を含有していても良い。これらの微粒子は、後述する流動化向上剤などの他の外添剤とともにトナー母粒子に外添される。
【００７９】
上記微粒子の平均円形度および平均粒径は、東亜医用電子製フロー式粒子像分析装置ＦＰＩＡ−１０００を用いて測定される平均円形度が０．９０以上であり、平均粒径が２．５μｍ以下であることが好ましい。
【００８０】
上記装置を用いた具体的な測定方法としては、容器中の予め不純固形物を除去した水１００〜１５０ｍｌ中に分散剤として界面活性剤、好ましくはアルキルベンゼンスルホン酸塩を０．１〜０．５ｍｌ加え、さらに測定試料を０．０５〜０．１ｇ程度加え、試料を分散した懸濁液に超音波分散器で約５分間分散処理を行い、分散液濃度を３０００〜１万個／μｌとして上記微粒子の形状、平均粒径および平均円形度を測定する。
【００８１】
微粒子の平均円形度および平均粒径を上記範囲に調整する方法は特に限定されないが、例えば平均円形度は湿式による造粒工程を用いたり機械式粉砕を行うことにより調整することができ、また平均粒径は風力分級やメッシュによる篩分けを行うことにより調整できる。
【００８２】
本発明のトナーは、流動性向上剤をトナー母粒子に外添して含んでいても良い。流動性向上剤は、トナー母粒子に外添することによりトナーの流動性を向上し得るものが挙げられる。例えばフッ化ビニリデン微粉末、ポリテトラフルオロエチレン微粉末などのフッ素系樹脂粉末；湿式製法シリカ、乾式製法シリカなどの微粉末シリカ、微粉末酸化チタン、微粉末アルミナ、それらをシランカップリング剤、チタンカップリング剤、シリコーンオイル等により表面処理を施した処理シリカ、処理酸化チタン、処理アルミナ等が挙げられる。
【００８３】
好ましい流動性向上剤としては、ケイ素ハロゲン化合物の蒸気相酸化により生成された微粉体であり、乾式法シリカまたはヒュームドシリカと称されるものである。例えば、四塩化ケイ素ガスの酸素、水素中における熱分解酸化反応を利用するもので、基礎となる反応式は次の様なものである。
【００８４】
【化４】
ＳｉＣｌ₄＋２Ｈ₂＋Ｏ₂ → ＳｉＯ₂＋４ＨＣｌ
【００８５】
この反応工程において、例えば塩化アルミニウムまたは塩化チタンなどの他の金属ハロゲン化合物をケイ素ハロゲン化合物と共に用いることによってシリカと他の金属酸化物の複合微粉体を得ることも可能であり、それらも包含する。その粒径は、平均の一次粒径として０．００１〜２μｍの範囲内であることが好ましく、特に好ましくは０．００２〜０．２μｍの範囲内のシリカ微粉体を使用するのが良い。
【００８６】
ケイ素ハロゲン化合物の蒸気相酸化により生成された市販のシリカ微粉体としては、例えば以下の様な商品名で市販されているものがある。
【００８７】

【００８８】
さらには、該ケイ素ハロゲン化合物の気相酸化により生成されたシリカ微粉体に疎水化処理した処理シリカ微粉体を用いることがより好ましい。該処理シリカ微粉体において、メタノール滴定試験によって測定された疎水化度が３０〜８０の範囲の値を示すようにシリカ微粉体を処理したものが特に好ましい。
【００８９】
疎水化方法としては、シリカ微粉体と反応あるいは物理吸着する有機珪素化合物および／またはシリコーンオイル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シリカ微粉体を有機ケイ素化合物で処理する。
【００９０】
有機ケイ素化合物としては、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、トリオルガノシリルメルカプタン、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および１分子当たり２から１２個のシロキサン単位を有し末端に位置する単位にそれぞれ１個宛のＳｉに結合した水酸基を含有するジメチルポリシロキサン等が挙げられる。これらは１種あるいは２種以上の混合物で用いられる。
【００９１】
窒素原子を有するアミノプロピルトリメトキシシラン、アミノプロピルトリエトキシシラン、ジメチルアミノプロピルトリメトキシシラン、ジエチルアミノプロピルトリメトキシシラン、ジプロピルアミノプロピルトリメトキシシラン、ジブチルアミノプロピルトリメトキシシラン、モノブチルアミノプロピルトリメトキシシラン、ジオクチルアミノプロピルジメトキシシラン、ジブチルアミノプロピルジメトキシシラン、ジブチルアミノプロピルモノメトキシシラン、ジメチルアミノフェニルトリエトキシシラン、トリメトキシシリル−γ−プロピルフェニルアミン、トリメトキシシリル−γ−プロピルベンジルアミンなどのシランカップリング剤も単独あるいは併用して使用される。好ましいシランカップリング剤としては、へキサメチルジシラザン（ＨＭＤＳ）が挙げられる。
【００９２】
本発明で用い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０．５〜１００００センチストークス、好ましくは１〜１０００センチストークス、さらに好ましくは１０〜２００センチストークスのものが用いられ、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特に好ましい。シリコーンオイル処理の方法としては、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などの混合機を用いて直接混合する方法；ベースとなるシリカ微粉体にシリコーンオイルを噴霧する方法；あるいは適当な溶剤にシリコーンオイルを溶解あるいは分散させた後、シリカ微粉体を加え混合し溶剤を除去する方法；を用いることが可能である。
【００９３】
シリコーンオイル処理シリカは、シリコーンオイルの処理後にシリカを不活性ガス中で２００℃以上（より好ましくは２５０℃以上）に加熱し表面のコートを安定化させることがより好ましい。
【００９４】
本発明においては、シリカをあらかじめ、カップリング剤で処理した後にシリコーンオイルで処理する方法、または、シリカをカップリング剤とシリコーンオイルで同時に処理する方法によって処理されたものが好ましい。
【００９５】
流動性向上剤は、ＢＥＴ法で測定した窒素吸着による比表面積が３０ｍ²／ｇ以上、好ましくは５０ｍ²／ｇ以上のものが良好な結果を与える。トナー１００質量部に対して流動性向上剤０．０１〜８質量部、好ましくは０．１〜４質量部使用するのが良い。
【００９６】
本発明で用いられるトナー母粒子を作製するには結着樹脂、着色剤および／または磁性体、荷電制御剤またはその他の添加剤をヘンシェルミキサー、ボールミルなどの混合機により充分混合し、ニーダー、エクストルーダーなどの熱混練機を用いて溶融、捏和および練肉して樹脂類を互いに相溶させ、溶融混練物を冷却固化後に固化物を粉砕し、粉砕物を分級して本発明に係わるトナー母粒子を得ることができる。
【００９７】
ここで、トナー母粒子、粒径が３μｍ以下の微粒子、および必要に応じた他の外添剤（流動性向上剤など）を含有する本発明のトナーは、上述したように、ＢＡＥによる露光方法における１ドット再現性を向上させるために、平均円形度Ｌ０が０．９００以上であり、且つ該平均円形度Ｌ０と粒径が３μｍ以上のトナーの平均円形度Ｌ３との関係が上記式（１）を満足することを特徴とする。また、本発明のトナーは、トナー全体の平均粒径Ｄ０が２．７μｍ以上であり、且つ該平均粒径Ｄ０と粒径が３μｍ以上のトナーの平均粒径Ｄ３との関係が上記式（２）を満足することを特徴とする。
【００９８】
本発明において、上記トナーのＬ０、Ｌ３、Ｄ０およびＤ３が上記関係を満足するためには、機械的衝撃力を加える処理を行うことが好ましい。機械的衝撃力を与える処理としては、例えば川崎重工業（株）製粉砕機ＫＴＭ、ターボ工業（株）製ターボミルのごとき機械式粉砕機を用いる方法、あるいはホソカワミクロン社製のメカノフュ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などの装置により処理する方法が挙げられる。これらの装置をそのまま、あるいは適宜改良して使用することが好ましいが、粉砕時の雰囲気温度（粉砕後の排気雰囲気温度）をトナーもしくは結着樹脂のガラス化転移温度（Ｔｇ）より１〜１５℃低い温度で制御することが好ましい。また、上記各装置により機械的衝撃力を与える場合、ローターのブレード幅を２００〜８００μｍにすることがトナーの平均円形度を調整する上で好ましい。
【００９９】
得られたトナー母粒子、粒径が３μｍ以下の微粒子、および必要に応じて流動性向上剤をヘンシェルミキサーなどの混合機により充分混合し、本発明のトナーを得ることができる。
【０１００】
以下に、本発明のトナーの平均円形度および粒度分布の測定について説明する。なお、後述の実施例もこの方法に基づいている。
【０１０１】
トナーの平均円形度（Ｌ０およびＬ３）と粒度分布（平均粒径Ｄ０およびＤ３）との両方を測定できる測定装置として、東亜医用電子製フロー式粒子像分析装置ＦＰＩＡ−１０００を用いる。
【０１０２】
上記装置を用いた具体的な測定方法としては、容器中の予め不純固形物を除去した水１００〜１５０ｍｌ中に分散剤として界面活性剤、好ましくはアルキルベンゼンスルホン酸塩を０．１〜０．５ｍｌ加え、さらに測定試料を０．１〜０．５ｇ程度加え、試料を分散した懸濁液に超音波分散器で約１分間分散処理を行い、分散液濃度を３０００〜１万個／μｌとして前記装置によりトナーの形状、平均粒径および平均円形度を測定する。
【０１０３】
本発明においてトナーの粒度測定は、従来のエレクトロゾーン法では細孔内容積に比べて粒子が小さいため正確に測定することは困難であり、フラットシースフローセルを通過したトナーを１／３０秒間隔でＣＣＤカメラで撮像された静止画像で画像解析するフロー式粒子像分析装置が適している。
【０１０４】
なお、トナー母粒子の粉砕、分級時の粒径を測定する場合はコールターカウンターのマルチサイザーを用いて行う。
【０１０５】
測定装置としてはコールターカウンターのマルチサイザーII型（コールター社製）を用い、個数分布、体積分布を出力するインターフェイス（日科機製）および解析用コンピューターを接続し、電解液は特級または１級塩化ナトリウムを用いて１％ＮａＣｌ水溶液を調整する。測定法としては前記電解水溶液ｌ００〜１５０ｍｌ中に分散剤として界面活性剤（好ましくはアルキルベンゼンスルホン酸塩）を０．１〜５ｍｌ加え、さらに測定試科を２〜２０ｍｇ加える。試料を懸濁した電解液は超音波分散器で約１〜３分間分散処理を行い、前記コールターカウンターのマルチサイザーII型により、アパーチャーとしてトナー粒径を測定するときは、１００μｍアパーチャーを用いて重量基準の重量平均径を求める。
【０１０６】
また、本発明のトナーはトナーのみからなる（キャリアを用いない）一成分現像剤として用いることもできるし、キャリアと混合して二成分現像剤として用いることもできる。二成分現像剤として用いる場合、キャリアの電流値はキャリア表面の凹凸度合い、被覆する樹脂の量を調整して２０〜２００μＡにするのが良い。
【０１０７】
キャリア表面を被覆する樹脂としては、スチレン−アクリル酸エステル共重合体、スチレン−メタクリル酸エステル共重合体、アクリル酸エステル共重合体、メタクリル酸エステル共重合体、シリコーン樹脂、フッ素含有樹脂、ポリアミド樹脂、アイオノマー樹脂、ポリフェニレンサルファイド樹脂など、或いはこれらの混合物を用いることができる。
【０１０８】
キャリアコアの磁性材料としては、フェライト、鉄過剰型フェライト、マグネタイト、γ−酸化鉄等の酸化物や、鉄、コバルト、ニッケルのような金属或いはこれらの合金を用いることができる。また、これらの磁性材料に含まれる元素としては、鉄、コバルト、ニッケル、アルミニウム、銅、鉛、マグネシウム、スズ、亜鉛、アンチモン、ベリリウム、ビスマス、カドミウム、カルシウム、マンガン、セレン、チタン、タングステン、バナジウム等が挙げられる。
【０１０９】
以下、上記本発明のトナーを用いた本発明の画像形成装置について説明する。図５は本発明の画像形成装置の好ましい実施形態の一例を示す概略構成図である。なお、この図に示す画像形成装置は、キヤノン製デジタル複写機ＩＲ６０００を基本構成として改造を施し、下記構造としたものである。
【０１１０】
１は感光層にアモルファスシリコン（以下ａ−Ｓｉと記載）を用いた直径８０ｍｍのドラム感光体（表面粗さＲａを２０μｍに研磨）、２は残留電荷を除去するための波長略６６０ｎｍのＬＥＤ発光素子から成る前露光装置、３は帯電電極としてタングステンワイヤーを用い、グリッドを有するいわゆるスコロトロン方式の帯電手段としての一次帯電器、４は内部に６極のマグネットローラーを配し、表面がフェノール等の樹脂にカーボングラファイト等の導電性粒子を分散させた直径２４ｍｍ径の現像スリーブに本発明のトナーを担持させ、ドラム感光体の画像情報部分にトナーを飛着させる現像手段としての現像装置である。
【０１１１】
５はドラム上のトナー電荷を上昇させ転写効率を上げるためのポスト帯電器、６は記録紙にトナーを転写するための転写帯電器、７はドラム感光体から記録紙を分離するための分離帯電器であり、これら５〜７により本発明における転写手段を構成する。また、８はドラム感光体上に残留したトナーを除去するためのクリーニング手段としてのクリーナー装置である。９はトナーが転写された記録紙を定着装置に搬送するための搬送ベルト、１０は記録紙上の未定着トナーを記録紙に加圧および加熱により固着させるための定着装置である。
【０１１２】
本実施形態において、静電潜像形成手段は、画像露光のための波長６５５ｎｍのレーザー半導体を発光駆動させるためのレーザードライバー回路１１；ドラム感光体の回転および画像位置に同期させレーザー光をドラム面上に照射するためのコリメーティングレンズ、ポリゴンミラー、ｆθレンズ等から構成されるレーザースキャナー装置１２；不図示の原稿台に置かれた原稿の画像情報を６００ｄｐｉ（Ｄｏｔ ｐｅｒ Ｉｎｃｈ）の解像度で読み取るための、ＣＣＤ等の撮像素子および光学レンズ等で構成される画像読取装置１３；画像読取装置から読み取った画像のシェーディング補正、濃度変換、データ圧縮伸長、２値化処理（誤差拡散）等を行う読み取り画像データ処理回路１４を含むものである。
【０１１３】
さらに、１５は外部ネットワークと接続し、ネットワークに接続されているコンピューターからの制御信号およびコンピュータで作成した画像データー信号を入出力するためのインターフェイス回路、１６は画像読取装置から読み取った画像データおよび外部から入力した画像を一時蓄えるためのＨＤＤ等で構成されるバッファーメモリ、１７は装置全体を制御するＣＰＵである。
【０１１４】
本発明の画像形成装置に用いられる感光体は、ａ−Ｓｉ感光体として公知のものを用いることができ、特に限定されない。上述したように、感光体表面の表面粗さＲａ＝２０〜０．５μｍとすることにより、ＢＡＥのドット再現性の向上およびトナーの転写性の点において本発明の効果がより顕著に発揮されるため好ましい。なお、この表面粗さＲａは１８〜１．０μｍであることがより好ましく、１５〜２．０μｍであることがさらに好ましい。
【０１１５】
本発明において、感光体の表面粗さＲａは、ＪＩＳ表面粗さ「ＪＩＳ Ｂ ０６０１」に基づき、表面粗さ測定器（サーフコーダＳＥ−３０Ｈ、株式会社小坂研究所社製）を用いて測定される中心線平均粗さに相当する。また、上記表面粗さＲａは感光体表面を研磨粒子を用いて表面研磨することによって調整することができるが、これに限定されず従来公知の任意の方法により調整しても良い。
【０１１６】
次に、本発明で用いられる潜像形成手段について説明する。本発明における潜像形成手段は、上述したように、ＢＡＥによる露光を行うものである。
本発明におけるＢＡＥによる露光は、露光光のＯＮ／ＯＦＦによる２値化法による露光方法であってもよいし、露光光のレーザービームの強度や照射時間等を変調して画素単位で複数レベルの階調表現を行う多値化法による露光方法であってもよい。このうち、２値化法による露光方法が、多値化法に比べて感光体やトナーの環境条件変動の影響を受けにくいため好ましい。
【０１１７】
また、本発明における露光方法において、ハイライト部（中間階調濃度）の画像を再現する方法は特に限定されず、ディザ法や誤差拡散法等を用いることができる。また２値化法を用いる場合には閾値法による画像処理を行うものであってもよい。これらのうち、ガサツキ感のないハイライト画像を再現することができる点から誤差拡散法を用いることが好ましい。
【０１１８】
また、本実施形態においては、ドラム感光体表面においてドラムの回転軸に平行な方向をレーザー光の主走査方向とし、この主走査方向に直交する方向（すなわち、ドラムの回転方向）を副走査方向とする。画像形成の最小画素サイズは主副走査方向共に６００ｄｐｉとし、主走査方向のレーザースポット径を４０μｍ、副走査方向のスポット径を５０μｍとする。
【０１１９】
この時のドラム感光体１の回転軸方向（レーザー主走査方向）に垂直な面の白地部（Ｖｌ）の潜像電位の電位分布は、図４に示された主走査方向に垂直な断面における潜像電位プロフィールの模式図のように、副走査ピッチのレーザー照射オーバーラップ部の消し残りがある程度残っているため（図中Ａ参照）、従来のトナーを用いた場合、カブリ取り電位Ｖｂａｃｋが小さくなるとこの部分にトナーが付着しはじめ、主走査方向に平行なスジ状のカブリが急激に目立ってくる。
【０１２０】
レーザーパワーを上げれば、レーザーパワーを強くした時の潜像電位における白地部の底の部分がつぶれた潜像電位となるため、副走査ピッチの境界部における電位が高い部分（消し残り）が低下するため更にカブリのマージンは大きく取れることになる。そのため副走査方向のビーム径を走査ピッチより大きくしなければならない。この場合、十分なドット、ライン幅が得られるようにすることは困難である。
【０１２１】
そこで、上述したような本発明のトナーを上記静電潜像形成手段に用いることにより、潜像ドットのエッジ部にもトナーを規則的に配列させて付着させることができるため、ドット再現性が向上し、従来のＢＡＥにおけるライン細りの問題が解決することができる。また、前述したように感光体表面の電位の消し残り部分には、トナーに含有されるトナー母粒子と逆極性に帯電した粒径が３μｍ以下の微粒子が付着するため、Ｖｂａｃｋが小さくなってもトナー粒子が付着することがなく、カブリの発生を抑制することができる。従って、本発明のトナーを用いれば、静電潜像形成の際のレーザーパワーを上げなくとも、カブリの発生しない、良好な画像を得ることができる。
【０１２２】
次に、現像手段について説明する。現像装置４の現像剤担持体（スリーブ）４ａは、現像部（現像スリーブにおいてトナーが感光体に移行する部分）において、感光体表面に対して一定の間隙を設けて対向されている。この間隙の大きさ（距離）は従来公知の方法により適宜設定され、特に限定されるものではないが、本実施形態では該現像部におけるドラム感光体１と現像スリーブ４ａとの間の距離は２３０μｍに設定されている。
【０１２３】
また、現像スリーブ４に印加される現像バイアスは図６に示すように、一定の高さを有する低電圧部分（Ｉ）および高電圧部分（III）と、低電圧部分から高電圧部分へ一定の割合で電圧が上昇するスロープ部分（II）とを有し、（Ｉ）〜（III）を繰り返すスロープ状の波形を有する交番電界であることが好ましい。本実施形態では（Ｉ）〜（III）の時間の比が３：４：３であり、周波数は３．３ｋＨｚ、振幅は１．７ｋＶである交番電界が現像バイアスとして用いられている。本発明においては、現像スリーブ４ａ上に上記本発明のトナーを前記感光体表面との間隙よりも薄い厚さに担持し、上記現像バイアスを現像スリーブ４ａに印加することにより、トナーを感光体表面に移行させてトナー像が形成される。なお、本実施形態におけるプロセススピードは３２０ｍｍ／ｓｅｃである。
【０１２４】
本発明は、このようなトレードオフの状態を解消させるトナーおよび画像形成装置である。プロセススピード、ドラム感光体の径、現像バイアス波形、Ｖｄ、Ｖｌ、および画像形成装置における他の手段（帯電手段、転写手段、クリーニング手段等）は上記実施の形態に何ら限定されるものではない。
【０１２５】
【実施例】
以下、実施例によって本発明をより具体的に説明するが、本発明はこれら実施例に限定されるものではない。
【０１２６】
〈トナーの製造例１〉
・ポリエステル樹脂 ：１００質量部
（テレフタル酸、フマル酸、トリメリット酸、上記式（ア）で表されるジオール（Ｒがプロピレン基、ｘ＋ｙ＝２．２）、式（ア）で表されるジオール（Ｒがエチレン基、ｘ＋ｙ＝２．０）の縮重合体、Ｔｇ：６０℃、軟化点：１２９℃、酸価：１５ｍｇＫＯＨ／ｇ）
・磁性酸化鉄 ： ９０質量部
（平均粒径：０．１６μｍ、Ｈｃ（保磁力）：１１．４ｋＡ／ｍ、σｓ（飽和磁化）：８１Ａｍ²／ｋｇ、σｒ（残留磁化）：１０Ａｍ²／ｋｇ）
・モノアゾ系鉄錯体 ： ２質量部
・低分子量ポリエチレン（融点：１００℃） ： ３質量部
上記混合物を、１４０℃に加熱された二軸エクストルーダーで溶融混練し、冷却した混合物をハンマーミルで粗粉砕した。この粗粉砕物をターボミル（ターボ工業社製）で微粉砕し（粉砕排気温度５０℃）、得られた微粉砕物を風力分級機で分級し、重量平均径が６．２１μｍの磁性トナー母粒子を得た。
【０１２７】
この磁性トナー母粒子１００質量部に、疎水性乾式シリカ（ＢＥＴ比表面積：２００ｍ²）１．０質量部、および平均径１．３μｍ、平均円形度０．９６のチタン酸ストロンチウム３．０質量部をヘンシェルミキサーにて外部添加しトナー１を得た。このトナー１の平均円形度Ｌ０は０．９６４、平均粒径Ｄ０は２．９０μｍであり、粒径が３μｍ以上の粒子における平均円形度Ｌ３は０．９６１、平均粒径Ｄ３は６．５３μｍであった。
【０１２８】
なお、トナー１のガラス化転移温度Ｔｇは６０℃であった。またＬ０／Ｌ３＝１．００３、Ｄ３／Ｄ０＝２．２５であった。トナー１の物性を表１に示す。
【０１２９】
〈トナーの製造例２〉
・スチレン／ｎ−ブチルアクリレート／アクリル酸共重合体 ：１００質量部
（Ｔｇ：６３℃、軟化点：１２０℃、酸価：１０ｍｇＫＯＨ／ｇ）
・磁性酸化鉄 ：１００質量部
（平均粒径：０．２５μｍ、Ｈｃ：８．１ｋＡ／ｍ、σｓ：７５Ａｍ²／ｋｇ、σｒ：７Ａｍ²／ｋｇ）
・ジ−ターシャリーブチルサリチル酸Ｚｎ錯体 ： ２質量部
・フィッシャー・トロプシュＷＡＸ（融点：１０５℃） ： ４質量部
上記混合物を、１４０℃に加熱された二軸エクストルーダーで溶融混練し、冷却した混合物をハンマーミルで粗粉砕した。この粗粉砕物をターボミル（ターボ工業社製）で微粉砕し（粉砕排気温度５５℃）、得られた微粉砕物を風力分級機で分級し、重量平均径が６．８１μｍの磁性トナー母粒子を得た。
【０１３０】
この磁性トナー母粒子１００質量部に、疎水性乾式シリカ（ＢＥＴ比表面積：２００ｍ²）１．０質量部、および平均径１．０μｍ、平均円形度０．９８のチタン酸カルシウム３．０質量部をヘンシェルミキサーにて外部添加しトナー２を得た。このトナー２の平均円形度Ｌ０は０．９７１、平均粒径Ｄ０は３．１０μｍであり、粒径が３μｍ以上の粒子の平均円形度Ｌ３は０．９６３、平均粒径Ｄ３は７．５５μｍであった。また、トナー２のガラス化転移温度Ｔｇは６２．５℃であった。トナー２の物性を表１に示す。
【０１３１】
〈トナーの製造例３〉
トナーの製造例１において、ターボミルで微粉砕する時の条件（ロータやライナーの材質およびロータとライナーのギャップなど）を変更した以外は上記製造例１と同様の方法を用いて、重量平均径が７．５μｍの磁性トナー母粒子を得た。
【０１３２】
この磁性トナー母粒子１００質量部に、疎水性乾式シリカ（ＢＥＴ比表面積：２００ｍ²）１．０質量部、および平均径１．０μｍ、平均円形度０．９５の酸化亜鉛１．０質量部、平均円形度０．９７のチタン酸マグネシウム１．０質量部をヘンシェルミキサーにて外部添加しトナー３を得た。このトナー３の平均円形度Ｌ０は０．９５７、平均粒径Ｄ０は４．７９μｍであり、粒径が３μｍ以上の粒子の平均円形度Ｌ３は０．９７１、平均粒径Ｄ３は７．１２μｍであった。トナー３の物性を表１に示す。
【０１３３】
〈トナーの製造例４〉
トナーの製造例１において、ターボミルで微粉砕する時の条件（ロータやライナーの材質およびロータとライナーのギャップなど）を変更した以外は上記製造例１と同様の方法を用いて、重量平均径が９．５μｍの磁性トナー母粒子を得た。
【０１３４】
この磁性トナー母粒子１００質量部に、疎水性乾式シリカ（ＢＥＴ比表面積：２００ｍ²）１．０質量部、および平均径１．９μｍ、平均円形度０．９５の酸化セリウム３．０質量部をヘンシェルミキサーにて外部添加しトナー４を得た。このトナー４の平均円形度Ｌ０は０．９４１、平均粒径Ｄ０は６．２７μｍであり、粒径が３μｍ以上の粒子の平均円形度Ｌ３は０．９２８、平均粒径Ｄ３は７．１１μｍであった。トナー４の物性を表４に示す。
【０１３５】
〈トナーの製造例５〉
トナーの製造例１において、ターボミルで微粉砕する時の条件（ロータやライナーの材質およびロータとライナーのギャップなど）を変更した以外は上記製造例１と同様の方法を用いて、重量平均径が６．７μｍの磁性トナー母粒子を得た。
【０１３６】
この磁性トナー母粒子１００質量部に、疎水性乾式シリカ（ＢＥＴ比表面積：２００ｍ²）１．０質量部、および平均径０．９μｍ、平均円形度０．９９の酸化アルミニウム３．０質量部をヘンシェルミキサーにて外部添加しトナー５を得た。このトナー５の平均円形度Ｌ０は０．９８２、平均粒径Ｄ０は２．８３μｍであり、粒径が３μｍ以上の粒子の平均円形度Ｌ３は０．９８１、平均粒径Ｄ３は８．３５μｍであった。トナー５の物性を表１に示す。
【０１３７】
〈トナーの比較製造例１〉
トナーの製造例２において、ターボミルで微粉砕する際の、ロータやライナーの材質およびロータとライナーのギャップを変更し、粉砕排気温度を３０℃に変更した以外は上記製造例２と同様の方法を用いて、重量平均径が７．８μｍの磁性トナー母粒子を得た。この磁性トナー母粒子１００質量部に、疎水性乾式シリカ（ＢＥＴ比表面積：２００ｍ²）１．０質量部、および平均径１．９μｍ、平均円形度０．８５の酸化チタン１．０質量部をヘンシェルミキサーにて外部添加してトナー６を得た。このトナー６の平均円形度Ｌ０は０．９７３、平均粒径Ｄ０は７．１２μｍであり、粒径が３μｍ以上の粒子の平均円形度Ｌ３は０．９２１、平均粒径Ｄ３は７．２３μｍであった。トナー６の物性を表１に示す。
【０１３８】
〈トナーの比較製造例２〉
トナーの製造例２において、ターボミルで微粉砕する際の、ロータやライナーの材質およびロータとライナーのギャップを変更し、粉砕排気温度を４０℃に変更した以外は上記製造例２と同様の方法を用いて、重量平均径が９．２μｍの磁性トナー母粒子を得た。この磁性トナー母粒子１００質量部に、疎水性乾式シリカ（ＢＥＴ比表面積：２００ｍ²）１．０質量部、および平均径０．５μｍ、平均円形度０．９８の酸化タングステン４．０質量部をヘンシェルミキサーにて外部添加してトナー７を得た。このトナー７の平均円形度Ｌ０は０．９３５、平均粒径Ｄ０は２．４９μｍであり、粒径が３μｍ以上の粒子の平均円形度Ｌ３は０．９５６、平均粒径Ｄ３は８．６３μｍであった。トナー７の物性を表１に示す。
【０１３９】
【表１】

【０１４０】
〈実施例１〉
得られたトナー１を用いて、通常環境（温度２３℃、湿度５０％）にて１００万枚の通紙耐久試験を行った。画像評価は以下の項目について検討した。評価機はキヤノン社製 ＩＲ-６０００を用い、Ａ４サイズ紙に画像印字面積５％のライン画像を連続複写した。また、現像バイアスとして、図６に示すスロープ状の交番電界（周波数３．３ｋＨｚ、振幅１．７ｋＶ）を現像スリーブに印加した。
【０１４１】
１．デジタル画像の鮮鋭さ
ラインおよび文字を含む原稿を使用し、耐久試験初期および１００万枚耐久試験後の画像を、目視または拡大顕微鏡を使用して、以下の基準で評価した。
【０１４２】
Ａ：文字画像およびライン画像ともに、細部まで忠実に再現している
Ｂ：細部に多少の乱れまたは中抜けが生じているが、目視では問題ないレベルである
Ｃ：目視でも乱れや中抜けがわかるレベルである
Ｄ：乱れ、中抜けが多数発生し、原稿を再現していない
【０１４３】
２．ハイライト画像の品位
１００万枚耐久試験後、反射画像濃度０．５のハーフトーン原稿（Ａ３サイズ）を用いハーフトーン（ハイライト）画像の評価を行った。Ａ３画像の出力における画像濃度の一様性を、マクベス反射濃度計（マクベス社製）を用いて最高画像濃度と最低画像濃度との差を測定した。また、拡大顕微鏡を使用して画像ドットの再現性を評価した。これらの結果から以下の基準に従って、ＢＡＥ現像による２値化処理されたドット潜像の現像性の品位を評価した。
【０１４４】
Ａ：最高画像濃度と最低画像濃度との差が０．０３以内で、ドット再現も良好Ｂ：最高画像濃度と最低画像濃度との差が０．０５以内で、若干のムラが見られドット再現もやや飛び散り気味
Ｃ：最高画像濃度と最低画像濃度との差が０．１以内で、多少のムラが見られドット再現も飛び散り気味
Ｄ：最高画像濃度と最低画像濃度との差が０．１を超え、顕著なムラがみられドット再現も不十分
【０１４５】
３．カブリの測定
カブリは「リフレクトメーター」（東京電色社製）により測定した複写画像の白地部分の白色度と転写紙の白色度の差からカブリ濃度（％）を算出して評価した。
【０１４６】
４．画像流れの評価
１００万枚耐久試験後、さらに温度３３℃、湿度９５％の高温高湿下に１週間放置した後に再度通紙試験を行い、以下の基準に従って目視により画出しし画像流れの評価を行った。
【０１４７】
Ａ：非常に良好（未発生）
Ｂ：良好（わずかに１〜３点の発生が見られるが、２〜３枚の通紙で消失）
Ｃ：普通（５〜１５点の発生が見られるが、１００枚の通紙で消失）
Ｄ：悪い（顕著な発生が見られる、１００枚の通紙でも消失しない）
評価結果を表２に示す。
【０１４８】
〈実施例２〜５〉
実施例１において、トナー１の代わりに表２に示すトナーをそれぞれ用いた以外は上記実施例１と同様の評価を行った。評価結果を表２に示す。
【０１４９】
表２に示すように、実施例１〜５においてはデジタル画像の鮮鋭さと高品位なハイライト画像を長期にわたり出力でき、且つ微小ビーム径を用いた場合ＢＡＥ特有のカブリを著しく改善できた。
【０１５０】
〈実施例６〉
実施例１において、表面粗さＲａを０．５μｍに研磨したアモルファスシリコン感光体を使用した以外は上記実施例１と同様の評価を行った。評価結果を表２に示す。表２から分かるように、本実施例においても実施例１と同様の良好な結果が得られた。
【０１５１】
〈比較例１、２〉
実施例１において、トナー１の代わりにトナー６およびトナー７をそれぞれ用いた以外は上記実施例１と同様の評価を行った。評価結果を表２に示す。比較例１、２ではデジタル画像の鮮鋭さがなく、ハイライト画像の品位がなく、且つ微小ビーム径を用いた場合のＢＡＥ特有のカブリが目立った。
【０１５２】
〈実施例７〉
実施例１において、トナー担持体に印加する現像バイアスを、一定電圧部分と立ち上がり時間の比（図６における（Ｉ）〜（III）の比）が５：５：５である矩形波に変更する以外はすべて実施例１と同様に評価した。評価結果を表２に示す。本実施例７では実施例１と比較してデジタル画像の鮮鋭さが劣り、カブリも若干ながら発生したが、実用可能範囲の結果が得られた。これより、本発明においては、図６に示すようなスロープ状の現像バイアスを用いることが好ましいことが分かった。
【０１５３】
【表２】

【０１５４】
【発明の効果】
本発明によれば、転写分離において有利なＢＡＥによる潜像形成方法を用いた画像形成装置において、カブリやライン細り等を防止し、長期にわたって高品位な画像を形成することが可能となる。
【図面の簡単な説明】
【図１】（ａ）ＢＡＥによるドット形成の様子、および（ｂ）ＩＡＥによるドット形成の様子を、それぞれ模式的に示した図
【図２】（ａ）ＢＡＥによる潜像ドットを本発明のトナーを用いて現像した様子、および（ｂ）（ａ）と同様の潜像ドットを従来技術のトナーを用いて現像した様子を、それぞれ模式的に表した図
【図３】（ａ）は本発明のトナーの感光体表面への付着状態、（ｂ）従来技術のトナーの感光体表面への付着状態を、それぞれ示す模式図
【図４】本発明の画像形成装置において、現像の際の感光体表面にトナーが付着する様子およびその時の感光体表面の帯電電位を模式的に示す図
【図５】本発明の画像形成装置の実施形態の一例を示す概略構成図
【図６】本発明で用いられる現像バイアスの波形の一例を示す図
【符号の説明】
１ 感光体
２ 前露光装置
３ 一次帯電器
４ 現像装置
５ ポスト帯電器
６ 転写帯電器
７ 分離帯電器
８ クリーナー装置
１０ 定着装置
１１ レーザードライバー回路
１２ レーザースキャナー装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine and a printer apparatus, and a toner used in the image forming apparatus.
[0002]
[Prior art]
In an image forming apparatus for forming an image by an electrophotographic method, an image forming apparatus such as a digital copying machine or a printer using a laser light source for forming a latent image is generally a laser after a photosensitive member is uniformly charged. A reversal development system is mainly employed in which the potential of the portion corresponding to the image information is lowered by light, and toner charged to the same polarity as the photosensitive member charging polarity is attached to the portion by a developing device to obtain image information. The latent image forming method in the reversal development method is generally called IAE (Image Area Exposuring), and the latent image forming method in the regular development method is called BAE (Background Area Exposuring).
[0003]
When nonlinearity is strong in the relationship between the exposure energy received by the photoconductor and the photoconductor surface potential, there is a drawback that the potential sagging increases at the edge, the line is thinned at BAE, and the sharpness is lowered at IAE. In this respect, the amorphous silicon (a-Si) photosensitive member is relatively faithful to the exposure energy distribution in the latent image formation, so that there is little difference in image quality between IAE and BAE, and both latent image forming modes can be adopted. .
[0004]
Considering the cleaning property after development, the potential of the photosensitive member is attenuated at the time of entering the cleaning. Therefore, in the IAE that develops in a portion having a low potential, a large amount of developer adheres to the photosensitive member at the cleaning portion. However, the electrostatic adhesion between the toner and the photoreceptor is relatively small. For this reason, with regard to cleaning, the latitude of IAE is wider than that of BAE, and many digital copiers and printers currently employ the IAE method. On the other hand, from the viewpoint of transfer separation, IAE has a higher potential in the non-image area (background area) than in the image area, so it is difficult to ensure a transfer separation latitude for various transfer media.
[0005]
The BAE method, which uses a laser as the light emitting element and forms a latent image by turning it ON / OFF, lowers the surface potential with laser light having a Gaussian light intensity distribution in the ON state to form a white background, and the potential in the OFF state In order to attach the toner charged in the reverse polarity to the portion where the decrease in the toner is not reduced, the fog removal potential Vback (Vdc−Vl) which is the difference between the developing bias DC potential Vdc and the white background portion potential Vl as shown in FIG. Is small, the toner tends to adhere to the remaining portion of the sub-scanning pitch potential.
[0006]
In this regard, the exposure light amount in units of pixels by the electrostatic latent image forming process means using the BAE method is set so that the potential of the photoconductor in the exposed portion is substantially equal to the residual potential, and in units of pixels. In the exposure, the spot diameter in the sub-scanning direction is 1.4 times or more the pitch in the sub-scanning direction, and the difference between the spot diameter in the main scanning direction and the spot diameter in the sub-scanning direction is ½ of the minimum pixel size. It has been proposed to set so as to be within (see, for example, Patent Document 1). However, if the spot diameter in the main scanning direction is reduced, the line width in the sub-scanning direction is increased, and the BAE is limited in miniaturizing the spot diameter in the main scanning direction, which is important for high-definition image formation.
[0007]
Further, in the cleaning property when the BAE method is used, when the surface property of the photosensitive member is smoothed by blade cleaning or the like, not only the electrostatic adhesion force of the transfer residual toner but also the cohesion force is increased, thereby causing problems such as poor cleaning. Is likely to occur.
[0008]
In addition, the reproduction of the highlight part is a so-called binary process in which a gradation process is expressed by the area density of toner-attached pixels to form an intermediate electrostatic latent image by modulating the light beam intensity, irradiation time, etc. for one dot. The one-dot multi-value process is not easily affected by fluctuations in environmental conditions of the photoconductor and developer. Among these binary processes, the error diffusion method is different from a dot concentration type called a dither method as a method of adjusting the density of the toner adhering pixels per area depending on the distance between the respective toner adhering pixels. The error diffusion method changes the interval pattern of the toner adhering pixels in accordance with the shade pattern of the image, so that it is possible to reproduce a highlight portion without a feeling of roughness without making the toner adhering pixel group conspicuous. In this case, since one dot shown in FIG. 1 is smaller than the dot pitch size, in the error diffusion method, the reproducibility of the toner-attached pixel with respect to one dot becomes a problem.
[0009]
However, since the transfer medium is not limited from the print-on-demand market and the digital small printing market, the BAE method, which is difficult to limit the transfer separation condition, is desired to be adopted.
[0010]
[Problems to be solved by the invention]
The present invention has been made to solve the problems of the conventional BAE technology as described above, achieves good highlight reproducibility even in various environments, and prevents fogging and line thinning, It is an object of the present invention to provide an image forming apparatus capable of ensuring good cleaning properties and stably forming a high-quality image, and a toner used in such an image forming apparatus.
[0011]
[Patent Document 1]
JP 2000-066488 A
[0012]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have made the toner contain specific fine particles and make the toner circularity distribution and particle size distribution specific so that the problems of the BAE technique can be solved. The inventors have found that this can be solved and completed the present invention.
[0013]
That is, the present invention is as follows.
[0014]
(1) A toner for visualizing an electrostatic latent image carried on the surface of a photoconductor, charging the surface of the photoconductor, and exposing and scanning the charged photoconductor surface in units of pixels by an electrostatic latent image forming unit. As a result, the charged potential on the surface of the photoreceptor corresponding to the white background portion of the image is lowered, and the toner is attached to the portion of the photoreceptor surface where the charged potential is not lowered by the developing means to form a toner image. Is transferred to a transfer material, and is used in an image forming method for removing toner remaining on the surface of the photoreceptor after the toner image is transferred,
The photoreceptor is an amorphous silicon photoreceptor,
The developing means has a toner carrier disposed so as to face the photosensitive member with a certain gap in the developing unit, and the toner carrier carries the toner to a thickness thinner than the gap, A means for developing an electrostatic latent image by applying an alternating electric field as a developing bias to a toner carrier to attach the toner to the surface of the photoreceptor.
The toner has at least toner base particles and fine particles having a particle size of 3 μm or less,
The average circularity L0 of the toner is 0.900 or more, and the relationship between the average circularity L0 and the average circularity L3 of the toner having a particle diameter of 3 μm or more is expressed by the following formula (1).
0.985 <L0 / L3 <1.015 (1)
Satisfied,
The average particle diameter D0 of the whole toner is 2.7 μm or more, and the relationship between the average particle diameter D0 and the average particle diameter D3 of the toner having a particle diameter of 3 μm or more is expressed by the following formula (2).
1.10 <D3 / D0 <3.00 (2)
Satisfied,
The toner, wherein the fine particles having a particle size of 3 μm or less contain one or more selected from strontium titanate, magnesium titanate, calcium titanate, cerium oxide, aluminum oxide, and zinc oxide.
[0015]
(2) The toner according to (1), wherein the surface roughness Ra of the photoreceptor is 20 to 0.5 μm.
[0016]
(3) The toner according to (1) or (2), wherein the exposure means forms a latent image by a binarization method by ON / OFF of exposure light.
[0017]
(4) The toner according to any one of (1) to (3), wherein the exposure means reproduces the gradation of an image by an error diffusion method.
[0018]
(5) The toner according to any one of (1) to (4), wherein the developing bias is an alternating electric field having a sloped waveform.
[0019]
A photosensitive member, a charging unit for charging the surface of the photosensitive member, and an electrostatic latent image for reducing the charged potential of the surface of the photosensitive member corresponding to a white background portion of an image by exposing and scanning the charged surface of the photosensitive member in units of pixels. An image forming unit; a developing unit that forms a toner image by attaching toner to a portion of the surface of the photoreceptor where the charged potential is not lowered; a transfer unit that transfers the toner image to a transfer material; and the toner image An image forming apparatus having cleaning means for removing toner remaining on the surface of the photoreceptor after being transferred,
The photoreceptor is Amorphous silicon photoconductor And
The developing means has a toner carrier disposed so as to face the photosensitive member with a certain gap in the developing unit, and the toner carrier carries the toner to a thickness thinner than the gap, A means for developing an electrostatic latent image by applying an alternating electric field as a developing bias to a toner carrier to attach the toner to the surface of the photoreceptor.
The toner has at least toner base particles and fine particles having a particle size of 3 μm or less,
The average circularity L0 of the toner is 0.900 or more, and the relationship between the average circularity L0 and the average circularity L3 of the toner having a particle diameter of 3 μm or more is expressed by the following formula (1).
0.985 <L0 / L3 <1.015 (1)
Satisfied,
The average particle diameter D0 of the whole toner is 2.7 μm or more, and the relationship between the average particle diameter D0 and the average particle diameter D3 of the toner having a particle diameter of 3 μm or more is Following formula (2)
1.10 <D3 / D0 <3.00 (2)
Satisfied,
The image forming apparatus, wherein the fine particles having a particle size of 3 μm or less contain one or more selected from strontium titanate, magnesium titanate, calcium titanate, cerium oxide, aluminum oxide, and zinc oxide.
[0020]
(7) The image forming apparatus according to (6), wherein the surface roughness Ra of the photoreceptor is 20 to 0.5 μm.
[0021]
(8) The image forming apparatus according to (6) or (7), wherein the exposure means forms a latent image by a binarization method by ON / OFF of exposure light.
[0022]
(9) The image forming apparatus according to any one of (6) to (8), wherein the exposure unit reproduces the gradation of an image by an error diffusion method.
[0023]
(10) The image forming apparatus according to any one of (6) to (9), wherein the developing bias is an alternating electric field having a sloped waveform.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
The image forming apparatus according to the present invention includes a photosensitive member, a charging unit that charges the surface of the photosensitive member, and exposure scanning of the charged surface of the photosensitive member in units of pixels. An electrostatic latent image forming unit that lowers the charging potential; a developing unit that forms a toner image by attaching toner to a portion of the surface of the photoreceptor where the charging potential is not decreased; and the toner image is transferred to a transfer material The present invention relates to an image forming apparatus that includes a transfer unit and a cleaning unit that removes toner remaining on the surface of the photoreceptor after the toner image is transferred.
[0025]
In the image forming apparatus of the present invention, the photoreceptor is Amorphous silicon It is a photoreceptor. Further, the developing means has a toner carrier disposed so as to face the photosensitive member with a certain gap in the developing portion, and the toner is carried on the toner carrier to a thickness smaller than the gap. The electrostatic latent image is developed by applying an alternating electric field to the toner carrying member as a developing bias so that the toner adheres to the surface of the photosensitive member.
[0026]
The toner of the present invention used in the image forming apparatus of the present invention has at least toner base particles and fine particles having a particle size of 3 μm or less, and the average circularity L0 of the toner is 0.900 or more, and The relationship between the average circularity L0 and the average circularity L3 of the toner having a particle diameter of 3 μm or more is expressed by the following formula (1).
[0027]
[Expression 1]
0.985 <L0 / L3 <1.015 (1)
[0028]
The average particle diameter D0 of the whole toner is 2.7 μm or more, and the relationship between the average particle diameter D0 and the average particle diameter D3 of the toner having a particle diameter of 3 μm or more is expressed by the following formula (2).
[0029]
[Expression 2]
1.10 <D3 / D0 <3.00 (2)
[0030]
Satisfied. In the toner of the present invention, the particles having a particle size of 3 μm or less contain at least one selected from strontium titanate, magnesium titanate, calcium titanate, cerium oxide, aluminum oxide, and zinc oxide.
[0031]
The image forming apparatus of the present invention uses a digital exposure unit that performs exposure scanning in units of pixels. The image forming apparatus of the present invention also includes an exposure method by BAE (Background Area Exposing) that reduces the charged potential of the photoreceptor surface corresponding to the white background portion of the image to be formed by exposure, and the charged potential of the photoreceptor surface. A regular development method is used in which toner is attached to a portion that has not decreased.
[0032]
FIG. 1A is a diagram schematically showing the formation of latent image dots by BAE corresponding to the regular development method, and FIG. 1B is a latent image by IAE (Image Area Exposing) corresponding to the reverse development method. It is the figure which showed the mode of image dot formation typically. FIG. 2A is a diagram schematically showing a state in which latent image dots by BAE (see FIG. 1A) are developed using the toner of the present invention, and FIG. It is a figure showing a mode that the latent image dot of this was developed using the toner of a prior art. FIG. 3A is a schematic view showing the state of adhesion of the toner of the present invention to the surface of the photoreceptor, and FIG. 3B is a schematic view showing the state of attachment of the conventional toner to the surface of the photoreceptor.
[0033]
As shown in FIG. 1, in the BAE that exposes the non-dot portion, the size of one dot is smaller than the dot pitch size compared to the IAE that exposes the dot portion. For this reason, in BAE, the reproducibility of the toner-attached pixel with respect to one dot becomes a problem. The shape of the latent image dots is not a circle or an ellipse, but is a square shape. When the toner of the present invention containing fine particles containing a specific inorganic compound and having a specific circularity distribution and particle size distribution is used, the inventors of the present invention are able to achieve such BAE-specific dots with respect to FIG. As shown in FIG. 3 (a) and FIG. 3 (a), it was found that the dots can be neatly arranged along the edge portion around the dots, and the reproducibility of the dots can be improved.
[0034]
That is, the toner containing the fine particles has an average circularity L0 of 0.900 or more, and the relationship between the L0 and the average circularity L3 of the toner having a particle diameter of 3 μm or more is expressed by the following formula (1).
[0035]
[Equation 3]
0.985 <L0 / L3 <1.015 (1)
[0036]
Is satisfied, the particle diameter of 3 μm containing strontium titanate, magnesium titanate, calcium titanate, cerium oxide, aluminum oxide, or zinc oxide around the electrostatic latent image (latent image dot) for one dot image The following fine particles adhere. This is because these fine particles are charged with a reverse polarity to the toner base particles that contribute to the visualization of the electrostatic latent image. Equation (1) indicates that the shape difference between the toner base particles forming the dot image and the particles having a particle diameter of 3 μm or less including the toner base particles and the fine particles is small. When L0 / L3 does not satisfy the above formula (1), as shown in FIGS. 2B and 3B, the dot shape is distorted and the toner adheres. The relationship between L0 and L3 is given by the following formula:
[0037]
[Expression 4]
0.990 <L0 / L3 <1.010
[0038]
Is preferably satisfied, and the value of L0 / L3 is preferably closer to 1.
[0039]
The toner of the present invention has an overall average particle diameter D0 of 2.7 μm or more, and the relationship between this D0 and the average particle diameter D3 of the toner having a particle diameter of 3 μm or more is expressed by the following formula (2).
[0040]
[Equation 5]
1.10 <D3 / D0 <3.00 (2)
[0041]
When satisfying the above, it has been found by experiments by the present inventors that it becomes possible to uniformly fill a one-dot image close to a square with toner as shown in FIG. The present inventors have found that, in order for fine particles having a particle diameter of 3 μm or less to adhere to the periphery of an electrostatic latent image for a one-dot image, it is important that the fine particles are present in the toner number distribution. Equation (2) was derived. In addition, it is preferable to use a developing method in which an alternating electric field having a waveform (developing bias waveform) having a slope shape is applied to the toner carrier as the developing bias, since the above-described effect is more exhibited. Details of the waveform of the developing bias will be described later.
[0042]
Such an effect is preferable because an amorphous silicon photoconductor is used and the surface roughness Ra of the photoconductor is 20 to 0.5 μm. When Ra exceeds 20 μm, the BAE latent image dots are likely to be disturbed due to surface irregularities, and when Ra is less than 0.5 μm, the image force on the surface of the photoreceptor is increased and toner transferability may be deteriorated.
[0043]
FIG. 4 is a diagram schematically showing how toner adheres to the surface of the photoreceptor during development and the charged potential of the surface of the photoreceptor at that time in the image forming apparatus of the present invention. FIG. 4 shows a cross section of the photoconductor perpendicular to the main scanning direction of exposure (that is, perpendicular to the rotation axis of the photoconductor). As shown in FIG. 4, toner mother particles adhered to the unexposed portion of the photoreceptor surface (the portion where the charged potential was not lowered), and the charged potential became lower than the developing bias potential Vdc due to the exposure. Fine particles with a particle size of 3 μm or less charged to the opposite polarity to the toner base particles adhere to the portion. Further, as indicated by A in FIG. 4, the fine particles adhere to the remaining portion of the potential near the boundary of the pitch in the sub-scanning direction (B in FIG. 4).
[0044]
As described above, in the present invention, the surface potential of the photoconductor changes due to variations in environmental temperature / humidity, charging current, etc., or the white background potential exposed in units of pixels by the electrostatic latent image forming means changes somewhat (absolute value). Even in the range of about 50 V), fine particles of 3 μm or less charged to the opposite polarity to the toner mother particles adhere to the portions other than the image area on the surface of the photosensitive member, and these fine particles have the opposite polarity to the toner mother particles. Since it is charged, it is not transferred onto the transfer paper. Therefore, coupled with the effect of the present invention in which the toner base particles uniformly adhere to the edge portion of the latent image dots, the trade-off between fogging and line thinning can be eliminated.
[0045]
These fine particles that are not transferred act as a cleaning agent for the a-Si drum, and can suppress the occurrence of “image flow” due to poor cleaning or generation of ozone under high humidity. As described above, the present invention can provide a toner that is excellent in highlight reproducibility and can always obtain an image with little fog, and a low-cost image forming apparatus with a simple configuration.
[0046]
Hereinafter, the toner of the present invention will be described in detail. The toner of the present invention has at least toner base particles and fine particles having a particle size of 3 μm or less.
[0047]
The toner base particles in the present invention contain at least a binder resin and a colorant, and appropriately contain other known components such as a charge control agent and a release agent.
[0048]
Examples of the binder resin used in the toner of the present invention include a polyester resin, a styrene-acrylic resin, an epoxy resin, a styrene-butadiene resin, a polyurethane resin, and the like. it can. Of these, polyester resins and styrene-acrylic resins are particularly preferable.
[0049]
The following are mentioned as a monomer of the polyester resin used for this invention. Among the monomers constituting the polyester resin, the alcohol component includes ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5 -Pentanediol, 1,6-hexanediol, neopentyl glycol, 2-ethyl 1,3-hexanediol, hydrogenated bisphenol A, bisphenol derivatives represented by the following formula (a), and the following formula (a) Diols.
[0050]
[Chemical 1]

[0051]
[Chemical formula 2]

[0052]
Among the above monomers, the acid component includes benzenedicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and phthalic anhydride or anhydrides thereof; alkyldicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid; The succinic acid substituted with an alkyl group having 6 to 18 carbon atoms or the anhydride thereof: unsaturated dicarboxylic acid such as fumaric acid, maleic acid, citraconic acid, itaconic acid or the anhydride thereof. .
[0053]
In addition, glycerin, pentaerythritol, sorbit, sorbitan, and polyhydric alcohols such as oxyalkylene ethers of novolak-type phenolic resins; Examples thereof include carboxylic acids.
[0054]
Examples of the vinyl monomer for producing the styrene-acrylic resin include the following.
[0055]
Styrene: o-methylstyrene, m-methylstyrene, p-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, p- n-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-chlorostyrene, 3,4-dichlorostyrene Styrene and derivatives thereof such as ethylene, propylene, butylene and isobutylene; unsaturated polyenes such as butadiene and isoprene; vinyl chloride , Halo such as vinylidene chloride, vinyl bromide, vinyl fluoride Vinyl esters; vinyl acetates such as vinyl acetate, vinyl propionate and vinyl benzoate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, methacrylic acid Α-methylene aliphatic monocarboxylic acid esters such as dodecyl acid, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate: methyl acrylate, ethyl acrylate, acrylic acid Propyl, n-butyl acrylate, isobutyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, acrylic Acrylic esters such as phenyl laurate; Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole, N- N-vinyl compounds such as vinyl carbazole, N-vinyl indole and N-vinyl pyrrolidone; vinyl naphthalenes; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide.
[0056]
Furthermore, unsaturated dibasic acids such as maleic acid, citraconic acid, itaconic acid, alkenyl succinic acid, fumaric acid, mesaconic acid; maleic anhydride, citraconic anhydride, itaconic anhydride, alkenyl succinic anhydride, etc. Unsaturated dibasic acid anhydride; maleic acid methyl half ester, maleic acid ethyl half ester, maleic acid butyl half ester, citraconic acid methyl half ester, citraconic acid ethyl half ester, citraconic acid butyl half ester, itaconic acid methyl half ester, Unsaturated basic acid half esters such as alkenyl succinic acid methyl half ester, fumaric acid methyl half ester, mesaconic acid methyl half ester; dimethylmaleic acid, dimethyl fumaric acid, etc .; acrylic acid, methacrylate Α, β-unsaturated acid anhydrides such as acids, crotonic acid and cinnamic acid; anhydrides of the α, β-unsaturated acids and lower fatty acids; alkenylmalonic acid, alkenylglutaric acid, alkenyladipic acid, these acids And monomers having a carboxyl group such as anhydrides and monoesters thereof.
[0057]
Further, acrylic acid or methacrylic acid esters such as 2-hydroxylethyl acrylate, 2-hydroxylethyl methacrylate, 2-hydroxylpropyl methacrylate, 4- (1-hydroxy-1-methylbutyl) styrene, 4- (1-hydroxy-1 -Methylhexyl) Monomers having a hydroxyl group such as styrene.
[0058]
Moreover, the polymer bridge | crosslinked with the crosslinkable monomer which is illustrated below may be sufficient as needed. Examples of aromatic divinyl compounds include divinylbenzene and divinylnaphthalene; examples of diacrylate compounds linked by an alkyl chain include ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, and 1,4-butanediol di Examples include acrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, neopentylglycol diacrylate, and those obtained by replacing acrylate of the above compound with methacrylate; Examples of the diacrylate compounds include diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, and polyethylene glycol # 400 dia. Relate, polyethylene glycol # 600 diacrylate, dipropylene glycol diacrylate, and those in which the acrylate of the above compound is replaced by methacrylate; as diacrylate compounds linked by a chain containing an aromatic group and an ether bond For example, polyoxyethylene (2) -2,2-bis (4-hydroxyphenyl) propane diacrylate, polyoxyethylene (4) -2,2-bis (4-hydroxyphenyl) propane diacrylate, and the above compounds Examples of the polyester-type diacryl derivatives include, for example, trade name MANDA (Nippon Kayaku Co., Ltd.).
[0059]
As polyfunctional crosslinking agents, pentaerythritol triacrylate, trimethylol ethane triacrylate, trimethylol propane triacrylate, tetramethylol methane tetraacrylate, oligoester acrylate, and acrylates of the above compounds are replaced with methacrylate; And allyl cyanurate and triallyl trimellitate.
[0060]
These crosslinking agents can be used in an amount of 0.01 to 10% by mass (more preferably 0.03 to 5% by mass) with respect to 100% by mass of other monomer components. Among these cross-linkable monomers, those that are preferably used for toner resins from the viewpoint of fixability and offset resistance are bonded with aromatic divinyl compounds (particularly divinylbenzene), chains containing aromatic groups and ether bonds. And diacrylate compounds.
[0061]
Examples of the polymerization initiator used for producing the vinyl copolymer in the present invention include 2,2′-azobisisobutyronitrile and 2,2′-azobis (4-methoxy-2,4dimethyl). Valeronitrile), 2,2′-azobis (-2,4-dimethylvaleronitrile), 2,2′-azobis (-2methylbutyronitrile), dimethyl-2,2′-azobisisobutyrate, 1 , 1′-azobis (1-cyclohexanecarbonitrile), 2- (carbamoylazo) -isobutyronitrile, 2,2′-azobis (2,4,4-trimethylpentane), 2-phenylazo-2,4-dimethyl -4-methoxyvaleronitrile, 2,2'-azobis (2-methyl-propane), methyl ethyl ketone peroxide, acetylacetone peroxide, cyclohexane Ketone peroxides such as non-peroxides, 2,2-bis (t-butylperoxy) butane, t-butyl hydroperoxide, cumene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide , Di-t-butyl peroxide, t-butyl cumyl peroxide, di-cumyl peroxide, α, α'-bis (t-butylperoxyisopropyl) benzene, isobutyl peroxide, octanoyl peroxide, decanoyl peroxide Oxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide, benzoyl peroxide, m-trioyl peroxide, di-isopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di- -Propyl peroxydicarbonate, di-2-ethoxyethyl peroxycarbonate, di-methoxyisopropyl peroxydicarbonate, di (3-methyl-3-methoxybutyl) peroxycarbonate, acetylcyclohexylsulfonyl peroxide, t-butyl Peroxyacetate, t-butylperoxyisobutyrate, t-butylperoxyneodecanoate, t-butylperoxy 2-ethylhexanoate, t-butylperoxylaurate, t-butylperoxybenzoate , T-butyl peroxyisopropyl carbonate, di-t-butyl peroxyisophthalate, t-butyl peroxyallyl carbonate, t-amyl peroxy 2-ethylhexanoate, di-t-butyl peroxyhexa high Roterefutareto, di -t- butyl peroxy azelate and the like.
[0062]
When the toner of the present invention is used as a magnetic toner, magnetic materials contained in the magnetic toner include iron oxides such as magnetite, maghemite, and ferrite, and iron oxides containing other metal oxides; Fe, Co, Ni, etc. Metals or alloys of these metals with metals such as Al, Co, Cu, Pb, Mg, Ni, Sn, Zn, Sb, Be, Bi, Cd, Ca, Mn, Se, Ti, W, V, And mixtures thereof.
[0063]
Conventionally, as a magnetic material, iron trioxide (Fe) _Three O _Four ), Iron sesquioxide (γ-Fe ₂ O _Three ), Zinc iron oxide (ZnFe ₂ O _Four ), Iron yttrium oxide (Y _Three Fe _Five O ₁₂ ), Iron cadmium oxide (CdFe ₂ O _Four ), Gadolinium oxide (Gd) _Three Fe _Five O ₁₂ ), Copper iron oxide (CuFe ₂ O _Four ), Lead iron oxide (PbFe ₁₂ O ₁₉ ), Nickel iron oxide (NiFe) ₂ O _Four ), Neodymium iron oxide (NdFe ₂ O _Three ), Iron barium oxide (BaFe) ₁₂ O ₁₉ ), Magnesium iron oxide (MgFe ₂ O _Four ), Iron manganese oxide (MnFe ₂ O _Four ), Iron lanthanum oxide (LaFeO) _Three ), Iron powder (Fe), cobalt powder (Co), nickel powder (Ni), and the like are known. According to the present invention, the above-described magnetic materials are selected and used alone or in combination of two or more. A magnetic material particularly suitable for the purposes of the present invention is a fine powder of iron trioxide or γ-iron trioxide.
[0064]
These magnetic materials have an average particle diameter of about 0.1 to 2 μm, and the magnetic properties when applied with 795.8 kA / m (10 k Oersted) are coercive force l. 5-12 kA / m, saturation magnetization 50-200 Am ² / Kg (preferably 50-100 Am ² / Kg), residual magnetization 2-20 Am ² / Kg is desirable. It is good to use 20-150 mass parts of magnetic bodies with respect to 100 mass parts of binder resin.
[0065]
Further, as the colorant used in the toner of the present invention, carbon black, titanium white and any other pigments and / or dyes can be used regardless of one component or two components. For example, when the toner of the present invention is used as a magnetic color toner, examples of the dye include C.I. I. Direct Red 1, C.I. I. Direct Red 4, C.I. I. Acid Red 1, C.I. I. Basic Red 1, C.I. I. Modern Tread 30, C.I. I. Direct Blue 1, C.I. I. Direct Blue 2, C.I. I. Acid Blue 9, C.I. I. Acid Blue 15, C.I. I. Basic Blue 3, C.I. I. Basic Blue 5, C.I. I. Modern Blue 7, C.I. I. Direct Green 6, C.I. I. Basic Green 4, C.I. I. Basic green 6 etc. As pigments, yellow lead, cadmium yellow, mineral fast yellow, navel yellow, naphthol yellow S, Hansa yellow G, permanent yellow NCG, tartra gin lake, red mouth yellow lead, molybdenum orange, permanent orange GTR, pyrazolone orange, benzidine orange G , Cadmium Red, Permanent Red 4R, Watching Red Calcium Salt, Eosin Lake, Brilliant Carmine 3B, Manganese Purple, Fast Violet B, Methyl Violet Lake, Bitumen, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Fast Sky Blue , Indanthrene Blue BC, Chrome Green, Chrome Oxide, Pigment Green B, Malachite Green Lake, There is § Lee Naru yellow green G and the like.
[0066]
Further, when the toner of the present invention is used as a two-component full color toner, the following may be mentioned. As a magenta coloring face department, C.I. I. Pigment Red 1, 2, 3, 4, 5.6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 163, 202, 206, 207, 209, C.I. I. Pigment violet 19, C.I. I. Vat red 1, 2, 10, 13.15, 23, 29, 35 etc. are mentioned.
[0067]
Although the above pigment may be used alone, it is more preferable from the viewpoint of the image quality of a full color image to improve the sharpness by using a dye and a pigment together. Such magenta dyes include C.I. I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, l00, l09, 121, C.I. I. Disbar thread 9, C.I. I. Solvent Violet 8, 13, 14, 21, 27, C.I. I. Disperse violet 1 and other oil-soluble dyes, C.I. I. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40, C.I. I. Basic dyes such as basic violet 1,3,7,10,14,15,21,25,26,27,28 are listed.
[0068]
As other coloring pigments, cyan pigments include C.I. I. Pigment blue 2, 3, 15, 16, 17, C.I. I. Bat Blue 6, C.I. I. Examples include Acid Blue 45 or a copper phthalocyanine pigment in which 1 to 5 phthalimidomethyl groups are substituted on a phthalocyanine skeleton having a structure represented by the following formula (c).
[0069]
[Chemical 3]

[0070]
Examples of the colored facial department for yellow include C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 65, 73, 83, C.I. I. Bat yellow 1, 3, 20, etc.
In addition, the usage-amount of a coloring agent is 0.1-60 mass parts with respect to 100 mass parts of binder resin, Preferably it is 0.5-50 mass parts.
[0071]
The toner of the present invention may contain one or two or more release agents in the toner base particles as necessary. Examples of the release agent used in the present invention include the following. Low molecular weight polyethylene, low molecular weight polypropylene, aliphatic hydrocarbon waxes such as microcrystalline wax, paraffin wax, and the like, or oxides of aliphatic hydrocarbon waxes such as oxidized polyethylene wax, or block copolymers thereof; carnauba wax; Examples thereof include waxes mainly composed of fatty acid esters such as sasol wax and montanic acid ester wax, and those obtained by partially or fully deoxidizing fatty acid esters such as deoxidized carnauba wax. In addition, saturated linear fatty acids such as palmitic acid, stearic acid, and montanic acid; unsaturated fatty acids such as brandic acid, eleostearic acid, and valinal acid; stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnauvir alcohol, and seryl alcohol , Saturated alcohols such as melyl alcohol; polyhydric alcohols such as sorbitol; fatty acid amides such as linoleic acid amide, oleic acid amide, and lauric acid amide; Saturated fatty acid bisamides such as acid amides and hexamethylene bis stearic acid amides; ethylene bis oleic acid amides, hexamethylene bis oleic acid amides, N, N′dioleyl adipic acid amides, N, N ′ geos Unsaturated fatty acid amides such as irsebacic acid amide; Aromatic bisamides such as m-xylene bis stearic acid amide, N, N ′ distearyl isophthalic acid amide; Calcium stearate, calcium stearate, zinc stearate, magnesium stearate, etc. Aliphatic metal salts (generally referred to as metal soaps); waxes grafted with aliphatic hydrocarbon waxes using vinyl monomers such as styrene and acrylic acid; fatty acids such as behenic acid monoglycerides and many others Examples include partially esterified products of monohydric alcohols; methyl ester compounds having a hydroxyl group obtained by hydrogenation of vegetable oils and the like.
[0072]
Examples of the release agent particularly preferably used in the present invention include aliphatic hydrocarbon waxes. For example, a low molecular weight alkylene polymer obtained by radical polymerization at a high pressure or a Ziegler catalyst at a low pressure; an alkylene polymer obtained by thermally decomposing a high molecular weight alkylene polymer; a synthesis gas containing carbon monoxide and hydrogen A synthetic hydrocarbon wax obtained from the distillation residue of hydrocarbons obtained by the method or by hydrogenation of these is preferred. Furthermore, the thing which fractionated hydrocarbon wax by the use of the press perspiration method, the solvent method, vacuum distillation, or a fractional crystallization system is used more preferably. The hydrocarbon as a base is synthesized by the reaction of carbon monoxide and hydrogen using a metal oxide catalyst (mostly two or more multi-component systems) [for example, the Jintol method, the Hydrocol method (the fluidized catalyst bed Hydrocarbon compounds synthesized by use); hydrocarbons with up to several hundred carbon atoms obtained by the age method (using the identified catalyst bed) from which a large amount of wax-like hydrocarbons can be obtained; alkylene such as ethylene by Ziegler catalyst Polymerized hydrocarbons are preferred because they are linear hydrocarbons with little branching, small and long saturation. In particular, a wax synthesized by a method that does not rely on polymerization of alkylene is also preferred from its molecular weight distribution.
[0073]
The wax used in the present invention has an endothermic main peak in the region of 80 to 130 ° C. in a DSC curve measured with a differential scanning calorimeter of the toner containing the wax. It is preferable in terms of offset property.
[0074]
The release agent is used in an amount of 0.1 to 20 parts by mass, preferably 0.5 to 10 parts by mass, per 100 parts by mass of the binder resin. The release agent is usually contained in the binder resin by a method in which the resin is dissolved in a solvent, the temperature of the resin solution is increased, and the mixture is added and mixed while stirring, or by mixing during kneading.
[0075]
In the electrostatic charge image developing toner of the present invention, a charge control agent can be used as necessary in order to further stabilize the chargeability. The charge control agent is used in an amount of 0.1 to 10 parts by mass, preferably 0.1 to 5 parts by mass, per 100 parts by mass of the resin component. Examples of the charge control agent include the following.
[0076]
For example, an organometallic complex or a chelate compound is effective for controlling the toner to be negatively charged. Examples thereof include a monoazo metal complex; an acetylacetone metal complex; a metal complex or metal salt of an aromatic hydroxycarboxylic acid or aromatic dicarboxylic acid. Can be mentioned. Others include aromatic mono- and polycarboxylic acids and their metal salts, anhydrides, esters and phenol derivatives such as bisphenol.
[0077]
Modified products with nigrosine and fatty acid metal salts, etc. for controlling the toner to be positively charged; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylammonium tetrafluoroborate, and the like These analogs such as onium salts such as phosphonium salts and lake pigments thereof; triphenylmethane dyes and lake lake pigments thereof (phosphotungstic acid, phosphomolybdic acid, phosphotungsten molybdic acid, tannic acid, Lauric acid, gallic acid, ferricyanic acid, ferrocyanic compound, etc.); metal salts of higher fatty acids; diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide; dibutyls Borate, dioctyl tin borate include diorgano tin borate such as dicyclohexyl tin borate. These can be used alone or in combination of two or more. Of these, charge control agents such as nigrosine compounds and quaternary ammonium salts are particularly preferably used.
[0078]
The toner of the present invention contains fine particles having a particle size of 3 μm or less. The particle size of the fine particles is preferably 0.1 to 2.9 μm, and more preferably 0.3 to 2.5 μm. The fine particles contain one or more selected from strontium titanate, magnesium titanate, calcium titanate, cerium oxide, aluminum oxide, and zinc oxide, and consist of only one of these. Even if it exists, 2 or more types may be mixed, and other materials may be contained. These fine particles are externally added to the toner base particles together with other external additives such as a fluidization improver described later.
[0079]
The average circularity and average particle size of the fine particles are 0.90 or more and the average particle size is 2.5 μm or less as measured using a flow type particle image analyzer FPIA-1000 manufactured by Toa Medical Electronics. It is preferable that
[0080]
As a specific measuring method using the above apparatus, a surfactant, preferably an alkylbenzene sulfonate, is added in an amount of 0.1 to 0.5 ml as a dispersant in 100 to 150 ml of water from which impure solids have been removed in advance. In addition, about 0.05 to 0.1 g of a measurement sample is further added, and the suspension in which the sample is dispersed is subjected to a dispersion treatment with an ultrasonic disperser for about 5 minutes, and the dispersion concentration is set to 3000 to 10,000 / μl. The shape, average particle diameter and average circularity of the fine particles are measured.
[0081]
The method for adjusting the average circularity and the average particle size of the fine particles to the above ranges is not particularly limited, but for example, the average circularity can be adjusted by using a wet granulation process or by mechanical pulverization. The particle size can be adjusted by air classification or sieving with a mesh.
[0082]
The toner of the present invention may contain a fluidity improver externally added to the toner base particles. Examples of the fluidity improver include those that can improve the fluidity of the toner by external addition to the toner base particles. For example, fluorine resin powder such as vinylidene fluoride fine powder and polytetrafluoroethylene fine powder; fine powder silica such as wet process silica and dry process silica, fine powder titanium oxide, fine powder alumina, silane coupling agent, titanium Examples include treated silica, treated titanium oxide, and treated alumina that have been surface-treated with a coupling agent, silicone oil, and the like.
[0083]
A preferred fluidity improver is a fine powder produced by vapor phase oxidation of a silicon halogen compound, and is referred to as dry process silica or fumed silica. For example, it utilizes a thermal decomposition oxidation reaction of silicon tetrachloride gas in oxygen and hydrogen, and the basic reaction formula is as follows.
[0084]
[Formula 4]
SiCl _Four + 2H ₂ + O ₂ → SiO ₂ + 4HCl
[0085]
In this reaction step, it is possible to obtain a composite fine powder of silica and other metal oxides by using other metal halogen compounds such as aluminum chloride or titanium chloride together with silicon halogen compounds. The particle size is preferably within the range of 0.001 to 2 μm as the average primary particle size, and particularly preferably silica fine powder within the range of 0.002 to 0.2 μm is used.
[0086]
Examples of commercially available silica fine powders produced by vapor phase oxidation of silicon halogen compounds include those sold under the following trade names.
[0087]

[0088]
Further, it is more preferable to use a treated silica fine powder obtained by hydrophobizing a silica fine powder produced by vapor phase oxidation of the silicon halide compound. Among the treated silica fine powders, those obtained by treating the silica fine powder so that the degree of hydrophobicity measured by a methanol titration test is in the range of 30 to 80 are particularly preferable.
[0089]
As a hydrophobizing method, it is given by chemically treating with an organosilicon compound and / or silicone oil that reacts or physically adsorbs with silica fine powder. As a preferred method, silica fine powder produced by vapor phase oxidation of a silicon halogen compound is treated with an organosilicon compound.
[0090]
Examples of organosilicon compounds include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, and bromomethyldimethyl. Chlorsilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyl Diethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3 -Diphenyltetramethyldisiloxane and dimethylpolysiloxane having 2 to 12 siloxane units per molecule and containing a hydroxyl group bonded to one Si atom in each terminal unit. These are used alone or in a mixture of two or more.
[0091]
Aminopropyltrimethoxysilane having nitrogen atom, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane, monobutylaminopropyltrimethoxy Silanes such as silane, dioctylaminopropyldimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-γ-propylphenylamine, trimethoxysilyl-γ-propylbenzylamine A coupling agent may be used alone or in combination. A preferred silane coupling agent is hexamethyldisilazane (HMDS).
[0092]
Preferred silicone oils used in the present invention are those having a viscosity at 25 ° C. of 0.5 to 10,000 centistokes, preferably 1 to 1000 centistokes, more preferably 10 to 200 centistokes, such as dimethyl silicone oil, Methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, and fluorine modified silicone oil are particularly preferred. As a method for treating the silicone oil, for example, a method in which silica fine powder treated with a silane coupling agent and silicone oil are directly mixed using a mixer such as a Henschel mixer; Or a method of dissolving or dispersing silicone oil in an appropriate solvent and then adding and mixing silica fine powder to remove the solvent.
[0093]
More preferably, the silicone oil-treated silica is heated to 200 ° C. or higher (more preferably 250 ° C. or higher) in an inert gas after the silicone oil is treated to stabilize the surface coating.
[0094]
In the present invention, the silica is preferably treated by a method in which silica is treated with a coupling agent and then treated with silicone oil, or a method in which silica is treated with a coupling agent and silicone oil at the same time.
[0095]
The fluidity improver has a specific surface area of 30 m by nitrogen adsorption measured by the BET method. ² / G or more, preferably 50 m ² / G or more gives good results. The flow improver is used in an amount of 0.01 to 8 parts by weight, preferably 0.1 to 4 parts by weight, based on 100 parts by weight of the toner.
[0096]
To prepare the toner base particles used in the present invention, the binder resin, colorant and / or magnetic substance, charge control agent or other additive is sufficiently mixed by a mixer such as a Henschel mixer or a ball mill, and then kneader, extender, etc. The toner according to the present invention is prepared by melting, kneading and kneading using a heat kneader such as a rudder to make the resins compatible with each other, cooling and solidifying the melt-kneaded product, pulverizing the solidified product, and classifying the pulverized product. Mother particles can be obtained.
[0097]
Here, as described above, the toner of the present invention containing toner base particles, fine particles having a particle size of 3 μm or less, and other external additives (fluidity improver, etc.) as required is an exposure method using BAE. In order to improve the 1-dot reproducibility, the relationship between the average circularity L0 is 0.900 or more and the average circularity L3 of the toner having a particle diameter of 3 μm or more is expressed by the above formula (1). ) Is satisfied. In the toner of the present invention, the average particle diameter D0 of the whole toner is 2.7 μm or more, and the relationship between the average particle diameter D0 and the average particle diameter D3 of the toner having a particle diameter of 3 μm or more is expressed by the above formula (2). ) Is satisfied.
[0098]
In the present invention, in order for L0, L3, D0 and D3 of the toner to satisfy the above relationship, it is preferable to perform a process of applying a mechanical impact force. Examples of the treatment that gives mechanical impact force include a method using a mechanical crusher such as a crusher KTM manufactured by Kawasaki Heavy Industries, Ltd., a turbo mill manufactured by Turbo Industry Co., Ltd., a mechano-fusion system manufactured by Hosokawa Micron Corporation, The method of processing with apparatuses, such as a manufactured hybridization system, is mentioned. It is preferable to use these apparatuses as they are or as they are appropriately modified. However, the atmospheric temperature during pulverization (exhaust atmospheric temperature after pulverization) is 1 to 15 ° C. from the vitrification transition temperature (Tg) of the toner or binder resin. It is preferable to control at a low temperature. In addition, when a mechanical impact force is applied by each of the above devices, the blade width of the rotor is preferably 200 to 800 μm for adjusting the average circularity of the toner.
[0099]
The toner of the present invention can be obtained by sufficiently mixing the obtained toner base particles, fine particles having a particle size of 3 μm or less, and, if necessary, a fluidity improver with a mixer such as a Henschel mixer.
[0100]
The measurement of the average circularity and particle size distribution of the toner of the present invention will be described below. In addition, the below-mentioned Example is also based on this method.
[0101]
As a measuring device capable of measuring both the average circularity (L0 and L3) and the particle size distribution (average particle size D0 and D3), Toa Medical Electronics' flow type particle image analyzer FPIA-1000 is used.
[0102]
As a specific measuring method using the above apparatus, a surfactant, preferably an alkylbenzene sulfonate, is added in an amount of 0.1 to 0.5 ml as a dispersant in 100 to 150 ml of water from which impure solids have been removed in advance. In addition, about 0.1 to 0.5 g of a measurement sample is further added, and the suspension in which the sample is dispersed is subjected to a dispersion treatment with an ultrasonic disperser for about 1 minute, and the dispersion concentration is set to 3000 to 10,000 / μl. The shape, average particle diameter and average circularity of the toner are measured by the apparatus.
[0103]
In the present invention, it is difficult to accurately measure the particle size of the toner by the conventional electrozone method because the particles are smaller than the pore volume, and it is difficult to accurately measure the toner passing through the flat sheath flow cell at 1/30 second intervals. A flow-type particle image analyzer that analyzes a still image captured by a CCD camera is suitable.
[0104]
In addition, when measuring the particle size at the time of pulverization and classification of toner base particles, a multisizer of a Coulter counter is used.
[0105]
The measuring device is a Coulter Counter Multisizer II (manufactured by Coulter), connected to an interface (manufactured by Nikkiki) that outputs number distribution and volume distribution, and a computer for analysis. The electrolyte is a special grade or first grade sodium chloride. Is used to prepare a 1% NaCl aqueous solution. As a measuring method, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the above electrolytic aqueous solution, and further 2 to 20 mg of a measurement trial is added. The electrolyte in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and when measuring the toner particle size as an aperture using the multisizer II type of the Coulter counter, the weight is measured using a 100 μm aperture. The standard weight average diameter is obtained.
[0106]
In addition, the toner of the present invention can be used as a one-component developer composed only of toner (without using a carrier), or can be mixed with a carrier and used as a two-component developer. When used as a two-component developer, the carrier current value is preferably adjusted to 20 to 200 μA by adjusting the degree of unevenness of the carrier surface and the amount of resin to be coated.
[0107]
Examples of the resin covering the carrier surface include styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, acrylic acid ester copolymer, methacrylic acid ester copolymer, silicone resin, fluorine-containing resin, and polyamide resin. , Ionomer resins, polyphenylene sulfide resins, and the like, or a mixture thereof can be used.
[0108]
As the magnetic material for the carrier core, oxides such as ferrite, iron-rich ferrite, magnetite and γ-iron oxide, metals such as iron, cobalt and nickel, or alloys thereof can be used. The elements contained in these magnetic materials are iron, cobalt, nickel, aluminum, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, vanadium. Etc.
[0109]
The image forming apparatus of the present invention using the toner of the present invention will be described below. FIG. 5 is a schematic configuration diagram showing an example of a preferred embodiment of the image forming apparatus of the present invention. Note that the image forming apparatus shown in this figure has the following structure, modified from a Canon digital copying machine IR6000 as a basic configuration.
[0110]
1 is a drum photoreceptor having a diameter of 80 mm using amorphous silicon (hereinafter referred to as a-Si) as a photosensitive layer (surface roughness Ra is polished to 20 μm), and 2 is LED light emission having a wavelength of about 660 nm for removing residual charges. Pre-exposure device composed of elements, 3 is a tungsten charger as a charging electrode, a primary charger as a so-called scorotron charging means having a grid, 4 has a 6-pole magnet roller inside, and the surface is phenol or the like This is a developing device as a developing means for carrying the toner of the present invention on a developing sleeve having a diameter of 24 mm in which conductive particles such as carbon graphite are dispersed in a resin and landing the toner on the image information portion of the drum photoreceptor.
[0111]
5 is a post charger for increasing the toner charge on the drum to increase transfer efficiency, 6 is a transfer charger for transferring the toner to the recording paper, and 7 is a separation charging for separating the recording paper from the drum photoreceptor. These 5 to 7 constitute transfer means in the present invention. Reference numeral 8 denotes a cleaner device as a cleaning means for removing toner remaining on the drum photoconductor. Reference numeral 9 denotes a conveyance belt for conveying the recording paper onto which the toner has been transferred to the fixing device, and reference numeral 10 denotes a fixing device for fixing unfixed toner on the recording paper to the recording paper by pressurization and heating.
[0112]
In this embodiment, the electrostatic latent image forming means includes a laser driver circuit 11 for driving the laser semiconductor having a wavelength of 655 nm for image exposure to emit light; the laser beam is synchronized with the rotation of the drum photosensitive member and the image position, Laser scanner device 12 including a collimating lens, a polygon mirror, an fθ lens, and the like for irradiating upward; reads image information of a document placed on a document table (not shown) at a resolution of 600 dpi (Dot per Inch) Image reading device 13 composed of an image sensor such as a CCD and an optical lens; shading correction, density conversion, data compression / decompression, binarization processing (error diffusion) of an image read from the image reading device, etc. A read image data processing circuit 14 is included.
[0113]
Further, 15 is connected to an external network, an interface circuit for inputting / outputting a control signal from the computer connected to the network and an image data signal created by the computer, 16 is an image data read from the image reading apparatus and an external Reference numeral 17 denotes a buffer memory composed of an HDD or the like for temporarily storing an image input from, and a CPU for controlling the entire apparatus.
[0114]
As the photoreceptor used in the image forming apparatus of the present invention, a known a-Si photoreceptor can be used and is not particularly limited. As described above, by setting the surface roughness Ra = 20 to 0.5 μm on the surface of the photosensitive member, the effects of the present invention are more remarkably exhibited in terms of improvement in BAE dot reproducibility and toner transferability. Therefore, it is preferable. The surface roughness Ra is more preferably 18 to 1.0 μm, and further preferably 15 to 2.0 μm.
[0115]
In the present invention, the surface roughness Ra of the photoreceptor is measured using a surface roughness measuring instrument (Surfcoder SE-30H, manufactured by Kosaka Laboratory Co., Ltd.) based on JIS surface roughness “JIS B 0601”. This corresponds to the centerline average roughness. The surface roughness Ra can be adjusted by polishing the surface of the photoreceptor with abrasive particles, but is not limited thereto, and may be adjusted by any conventionally known method.
[0116]
Next, the latent image forming means used in the present invention will be described. The latent image forming means in the present invention performs exposure by BAE as described above.
The exposure by BAE in the present invention may be an exposure method based on a binarization method by ON / OFF of exposure light, or the intensity of the laser beam of the exposure light, irradiation time, etc. are modulated, and a plurality of levels are obtained for each pixel. An exposure method based on a multi-value method that performs gradation expression may be used. Of these, the binarization exposure method is preferable because it is less susceptible to changes in the environmental conditions of the photoconductor and toner than the multivalue conversion method.
[0117]
In the exposure method of the present invention, a method for reproducing an image of a highlight portion (intermediate gradation density) is not particularly limited, and a dither method, an error diffusion method, or the like can be used. When the binarization method is used, image processing by a threshold method may be performed. Among these, it is preferable to use an error diffusion method from the viewpoint that a highlight image without a feeling of roughness can be reproduced.
[0118]
In this embodiment, the direction parallel to the rotation axis of the drum on the surface of the drum photoreceptor is the main scanning direction of the laser beam, and the direction orthogonal to the main scanning direction (that is, the rotation direction of the drum) is the sub-scanning direction. And The minimum pixel size for image formation is 600 dpi in both the main and sub scanning directions, the laser spot diameter in the main scanning direction is 40 μm, and the spot diameter in the sub scanning direction is 50 μm.
[0119]
At this time, the potential distribution of the latent image potential of the white background portion (Vl) on the surface perpendicular to the rotation axis direction (laser main scanning direction) of the drum photosensitive member 1 is in a cross section perpendicular to the main scanning direction shown in FIG. As shown in the schematic diagram of the latent image potential profile, since the unerased portion of the laser irradiation overlap portion at the sub-scanning pitch remains to some extent (see A in the figure), the fog removal potential Vback is small when the conventional toner is used. Then, toner begins to adhere to this portion, and streaky fog parallel to the main scanning direction becomes noticeable rapidly.
[0120]
If the laser power is increased, the latent image potential at the bottom of the white background in the latent image potential when the laser power is increased becomes a collapsed latent image potential, so that the portion where the potential at the boundary of the sub-scanning pitch is high (unerased) decreases. Therefore, the margin of fog is further increased. For this reason, the beam diameter in the sub-scanning direction must be larger than the scanning pitch. In this case, it is difficult to obtain a sufficient dot and line width.
[0121]
Therefore, by using the toner of the present invention as described above for the electrostatic latent image forming means, the toner can be regularly arranged and adhered to the edge portion of the latent image dots, so that the dot reproducibility is improved. The line narrowing problem in the conventional BAE can be solved. Further, as described above, fine particles having a particle size of 3 μm or less charged to the opposite polarity to the toner base particles contained in the toner adhere to the remaining portion of the surface of the photosensitive member where the potential is not erased. Toner particles do not adhere and the occurrence of fog can be suppressed. Therefore, by using the toner of the present invention, it is possible to obtain a good image without fogging without increasing the laser power for forming the electrostatic latent image.
[0122]
Next, the developing unit will be described. The developer carrying member (sleeve) 4a of the developing device 4 is opposed to the surface of the photosensitive member with a certain gap in the developing portion (portion where the toner moves to the photosensitive member in the developing sleeve). The size (distance) of the gap is appropriately set by a conventionally known method and is not particularly limited. In this embodiment, the distance between the drum photosensitive member 1 and the developing sleeve 4a in the developing unit is 230 μm. Is set to
[0123]
Further, as shown in FIG. 6, the developing bias applied to the developing sleeve 4 is constant from the low voltage portion (I) and the high voltage portion (III) having a certain height and from the low voltage portion to the high voltage portion. It is preferable that the electric field is an alternating electric field having a slope portion (II) in which the voltage rises at a rate and having a slope-like waveform repeating (I) to (III). In this embodiment, an alternating electric field having a time ratio of (I) to (III) of 3: 4: 3, a frequency of 3.3 kHz, and an amplitude of 1.7 kV is used as the developing bias. In the present invention, the toner of the present invention is carried on the developing sleeve 4a to a thickness thinner than the gap with the surface of the photosensitive member, and the developing bias is applied to the developing sleeve 4a, whereby the toner is transferred to the surface of the photosensitive member. Then, a toner image is formed. In this embodiment, the process speed is 320 mm / sec.
[0124]
The present invention is a toner and an image forming apparatus that eliminate such a trade-off state. The process speed, the diameter of the drum photoreceptor, the developing bias waveform, Vd, Vl, and other means (charging means, transfer means, cleaning means, etc.) in the image forming apparatus are not limited to the above embodiments.
[0125]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to these Examples.
[0126]
<Toner Production Example 1>
・ Polyester resin: 100 parts by mass
(Terephthalic acid, fumaric acid, trimellitic acid, diol represented by the above formula (A) (R is a propylene group, x + y = 2.2), diol represented by the formula (A) (R is an ethylene group, x + y = 2.0) condensation polymer, Tg: 60 ° C., softening point: 129 ° C., acid value: 15 mgKOH / g)
・ Magnetic iron oxide: 90 parts by mass
(Average particle diameter: 0.16 μm, Hc (coercive force): 11.4 kA / m, σs (saturation magnetization): 81 Am ² / Kg, σr (residual magnetization): 10 Am ² / Kg)
・ Monoazo iron complex: 2 parts by mass
・ Low molecular weight polyethylene (melting point: 100 ° C.): 3 parts by mass
The above mixture was melt-kneaded with a biaxial extruder heated to 140 ° C., and the cooled mixture was coarsely pulverized with a hammer mill. The coarsely pulverized product is finely pulverized with a turbo mill (manufactured by Turbo Kogyo Co., Ltd.) (pulverization exhaust temperature 50 ° C.), and the resulting finely pulverized product is classified with an air classifier to obtain magnetic toner base particles having a weight average diameter of 6.21 μm. Got.
[0127]
Hydrophobic dry silica (BET specific surface area: 200 m) was added to 100 parts by mass of the magnetic toner base particles. ² The toner 1 was obtained by adding 1.0 part by mass and 3.0 parts by mass of strontium titanate having an average diameter of 1.3 μm and an average circularity of 0.96 using a Henschel mixer. The toner 1 has an average circularity L0 of 0.964 and an average particle diameter D0 of 2.90 μm. The average circularity L3 of particles having a particle diameter of 3 μm or more is 0.961, and the average particle diameter D3 is 6.53 μm. there were.
[0128]
The vitrification transition temperature Tg of the toner 1 was 60 ° C. L0 / L3 = 1.003 and D3 / D0 = 2.25. Table 1 shows the physical properties of Toner 1.
[0129]
<Toner Production Example 2>
Styrene / n-butyl acrylate / acrylic acid copolymer: 100 parts by mass
(Tg: 63 ° C., softening point: 120 ° C., acid value: 10 mg KOH / g)
・ Magnetic iron oxide: 100 parts by mass
(Average particle diameter: 0.25 μm, Hc: 8.1 kA / m, σs: 75 Am ² / Kg, σr: 7 Am ² / Kg)
・ Di-tertiary butyl salicylate Zn complex: 2 parts by mass
Fischer-Tropsch WAX (melting point: 105 ° C.): 4 parts by mass
The above mixture was melt-kneaded with a biaxial extruder heated to 140 ° C., and the cooled mixture was coarsely pulverized with a hammer mill. The coarsely pulverized product is finely pulverized with a turbo mill (manufactured by Turbo Kogyo Co., Ltd.) (pulverization exhaust temperature 55 ° C.). Got.
[0130]
Hydrophobic dry silica (BET specific surface area: 200 m) was added to 100 parts by mass of the magnetic toner base particles. ² The toner 2 was obtained by externally adding 1.0 part by mass and 3.0 parts by mass of calcium titanate having an average diameter of 1.0 μm and an average circularity of 0.98 using a Henschel mixer. The toner 2 has an average circularity L0 of 0.971 and an average particle diameter D0 of 3.10 μm. The average circularity L3 of particles having a particle diameter of 3 μm or more is 0.963, and the average particle diameter D3 is 7.55 μm. there were. Further, the vitrification transition temperature Tg of the toner 2 was 62.5 ° C. Table 1 shows the physical properties of Toner 2.
[0131]
<Toner Production Example 3>
In Toner Production Example 1, the weight average diameter was changed using the same method as in Production Example 1 except that the conditions for fine pulverization with a turbo mill (such as the material of the rotor and liner and the gap between the rotor and the liner) were changed. Magnetic toner base particles of 7.5 μm were obtained.
[0132]
Hydrophobic dry silica (BET specific surface area: 200 m) was added to 100 parts by mass of the magnetic toner base particles. ² ) 1.0 part by mass, 1.0 part by mass of zinc oxide having an average diameter of 1.0 μm, an average degree of circularity of 0.95, and 1.0 part by weight of magnesium titanate having an average degree of circularity of 0.97 were externalized using a Henschel mixer. Toner 3 was obtained by addition. The toner 3 has an average circularity L0 of 0.957 and an average particle diameter D0 of 4.79 μm. The average circularity L3 of particles having a particle diameter of 3 μm or more is 0.971, and the average particle diameter D3 is 7.12 μm. there were. Table 1 shows the physical properties of Toner 3.
[0133]
<Toner Production Example 4>
In Toner Production Example 1, the weight average diameter was changed using the same method as in Production Example 1 except that the conditions for fine pulverization with a turbo mill (such as the material of the rotor and liner and the gap between the rotor and the liner) were changed. 9.5 μm magnetic toner mother particles were obtained.
[0134]
Hydrophobic dry silica (BET specific surface area: 200 m) was added to 100 parts by mass of the magnetic toner base particles. ² The toner 4 was obtained by adding 1.0 part by mass and 3.0 parts by mass of cerium oxide having an average diameter of 1.9 μm and an average circularity of 0.95 using a Henschel mixer. The toner 4 has an average circularity L0 of 0.941 and an average particle diameter D0 of 6.27 μm. The average circularity L3 of particles having a particle diameter of 3 μm or more is 0.928, and the average particle diameter D3 is 7.11 μm. there were. Table 4 shows the physical properties of Toner 4.
[0135]
<Toner Production Example 5>
In Toner Production Example 1, the weight average diameter was changed using the same method as in Production Example 1 except that the conditions for fine pulverization with a turbo mill (such as the material of the rotor and liner and the gap between the rotor and the liner) were changed. A magnetic toner base particle of 6.7 μm was obtained.
[0136]
Hydrophobic dry silica (BET specific surface area: 200 m) was added to 100 parts by mass of the magnetic toner base particles. ² The toner 5 was obtained by adding 1.0 part by mass and 3.0 parts by mass of aluminum oxide having an average diameter of 0.9 μm and an average circularity of 0.99 with a Henschel mixer. The toner 5 has an average circularity L0 of 0.982 and an average particle diameter D0 of 2.83 μm. The average circularity L3 of particles having a particle diameter of 3 μm or more is 0.981, and the average particle diameter D3 is 8.35 μm. there were. Table 1 shows the physical properties of Toner 5.
[0137]
<Toner Comparative Production Example 1>
In Toner Production Example 2, the same method as in Production Example 2 except that the material of the rotor and liner and the gap between the rotor and the liner were changed and the pulverization exhaust temperature was changed to 30 ° C. when finely pulverizing with a turbo mill. Thus, magnetic toner base particles having a weight average diameter of 7.8 μm were obtained. Hydrophobic dry silica (BET specific surface area: 200 m) was added to 100 parts by mass of the magnetic toner base particles. ² The toner 6 was obtained by externally adding 1.0 part by mass and 1.0 part by mass of titanium oxide having an average diameter of 1.9 μm and an average circularity of 0.85 using a Henschel mixer. The toner 6 has an average circularity L0 of 0.973 and an average particle diameter D0 of 7.12 μm. The average circularity L3 of particles having a particle diameter of 3 μm or more is 0.921, and the average particle diameter D3 is 7.23 μm. there were. Table 1 shows the physical properties of Toner 6.
[0138]
<Toner Comparative Production Example 2>
In Toner Production Example 2, the same method as in Production Example 2 except that the material of the rotor and liner and the gap between the rotor and the liner were changed and the pulverization exhaust temperature was changed to 40 ° C. when finely pulverizing with a turbo mill. Thus, magnetic toner base particles having a weight average diameter of 9.2 μm were obtained. Hydrophobic dry silica (BET specific surface area: 200 m) was added to 100 parts by mass of the magnetic toner base particles. ² The toner 7 was obtained by externally adding 1.0 part by mass and 4.0 parts by mass of tungsten oxide having an average diameter of 0.5 μm and an average circularity of 0.98 using a Henschel mixer. The toner 7 has an average circularity L0 of 0.935 and an average particle diameter D0 of 2.49 μm. An average circularity L3 of particles having a particle diameter of 3 μm or more is 0.956 and an average particle diameter D3 is 8.63 μm. there were. Table 1 shows the physical properties of Toner 7.
[0139]
[Table 1]

[0140]
<Example 1>
Using the toner 1 thus obtained, a paper passing durability test of 1 million sheets was performed in a normal environment (temperature 23 ° C., humidity 50%). The following items were examined for image evaluation. The evaluation machine used was IR-6000 manufactured by Canon Inc., and a line image having an image printing area of 5% was continuously copied on A4 size paper. As a developing bias, a slope-like alternating electric field (frequency: 3.3 kHz, amplitude: 1.7 kV) shown in FIG. 6 was applied to the developing sleeve.
[0141]
1. Sharpness of digital images
Using a manuscript including lines and letters, images at the beginning of the endurance test and after the endurance test for 1 million sheets were evaluated according to the following criteria using a visual observation or a magnifying microscope.
[0142]
A: Both character images and line images are faithfully reproduced in detail.
B: Some irregularities or hollows in the details occur, but at a level that is not a problem with visual inspection.
C: Level at which turbulence and voids can be seen visually
D: Many irregularities and voids occur, and the document is not reproduced
[0143]
2. Highlight image quality
After a 1 million sheet durability test, a halftone (highlight) image was evaluated using a halftone original (A3 size) having a reflection image density of 0.5. The uniformity of the image density in the output of the A3 image was measured by using a Macbeth reflection densitometer (manufactured by Macbeth) to measure the difference between the highest image density and the lowest image density. Moreover, the reproducibility of the image dots was evaluated using a magnifying microscope. From these results, the quality of developability of the binarized dot latent image by BAE development was evaluated according to the following criteria.
[0144]
A: The difference between the highest image density and the lowest image density is within 0.03, and the dot reproduction is also good. B: The difference between the highest image density and the lowest image density is within 0.05, and there is some unevenness and dot reproduction. Slightly scattered
C: The difference between the maximum image density and the minimum image density is within 0.1, some unevenness is seen, and the dot reproduction is scattered.
D: The difference between the highest image density and the lowest image density exceeds 0.1, remarkable unevenness is observed, and dot reproduction is insufficient.
[0145]
3. Measurement of fog
The fog was evaluated by calculating the fog density (%) from the difference between the whiteness of the white portion of the copied image and the whiteness of the transfer paper measured with a “reflectometer” (manufactured by Tokyo Denshoku).
[0146]
4). Image flow evaluation
After a 1 million-sheet durability test, the paper was passed again for a week at a high temperature and high humidity of 33 ° C. and 95% humidity, and then a paper passing test was performed again. .
[0147]
A: Very good (not generated)
B: Good (slight generation of 1 to 3 points is observed, but disappears by passing 2 to 3 sheets)
C: Normal (occurrence of 5 to 15 points is observed, but disappears after passing 100 sheets)
D: Poor (conspicuous occurrence is seen, it does not disappear even after passing 100 sheets)
The evaluation results are shown in Table 2.
[0148]
<Examples 2 to 5>
In Example 1, evaluation was performed in the same manner as in Example 1 except that the toner shown in Table 2 was used instead of toner 1. The evaluation results are shown in Table 2.
[0149]
As shown in Table 2, in Examples 1 to 5, sharpness of a digital image and a high-quality highlight image can be output over a long period of time, and fogging peculiar to BAE can be remarkably improved when a minute beam diameter is used.
[0150]
<Example 6>
In Example 1, the same evaluation as in Example 1 was performed except that an amorphous silicon photoconductor having a surface roughness Ra polished to 0.5 μm was used. The evaluation results are shown in Table 2. As can be seen from Table 2, the same good results as in Example 1 were also obtained in this example.
[0151]
<Comparative Examples 1 and 2>
In Example 1, evaluation was performed in the same manner as in Example 1 except that toner 6 and toner 7 were used instead of toner 1, respectively. The evaluation results are shown in Table 2. In Comparative Examples 1 and 2, there was no sharpness of the digital image, no quality of the highlight image, and fogging peculiar to BAE when a minute beam diameter was used was conspicuous.
[0152]
<Example 7>
In Example 1, the developing bias applied to the toner carrier is changed to a rectangular wave in which the ratio between the constant voltage portion and the rise time (ratio (I) to (III) in FIG. 6) is 5: 5: 5. All the evaluations were the same as in Example 1. The evaluation results are shown in Table 2. In Example 7, the sharpness of the digital image was inferior to that in Example 1, and a slight amount of fogging occurred. However, a result in a practical range was obtained. From this, it has been found that it is preferable to use a slope-shaped development bias as shown in FIG. 6 in the present invention.
[0153]
[Table 2]

[0154]
【The invention's effect】
According to the present invention, in an image forming apparatus using a latent image forming method by BAE which is advantageous in transfer separation, it is possible to prevent fogging and line thinning and form a high-quality image over a long period of time.
[Brief description of the drawings]
1A and 1B are diagrams schematically showing a state of dot formation by BAE and a state of dot formation by IAE, respectively.
FIGS. 2A and 2B show a state in which a latent image dot by BAE is developed using the toner of the present invention, and a state in which a latent image dot similar to that in FIG. 2B and FIG. Each diagram schematically
FIGS. 3A and 3B are schematic views showing the state of adhesion of the toner of the present invention to the surface of the photoreceptor, and FIG. 3B shows the state of adhesion of the toner of the prior art to the surface of the photoreceptor, respectively.
FIG. 4 is a diagram schematically showing how toner adheres to the surface of the photoconductor during development and the charged potential of the photoconductor surface at that time in the image forming apparatus of the present invention.
FIG. 5 is a schematic configuration diagram illustrating an example of an embodiment of an image forming apparatus according to the present invention.
FIG. 6 is a view showing an example of a developing bias waveform used in the present invention.
[Explanation of symbols]
1 Photoconductor
2 Pre-exposure equipment
3 Primary charger
4 Development device
5 Post charger
6 Transfer charger
7 Separation charger
8 Cleaner device
10 Fixing device
11 Laser driver circuit
12 Laser scanner device

Claims (4)

A photosensitive member, a charging unit for charging the surface of the photosensitive member, and an electrostatic latent image for reducing the charged potential of the surface of the photosensitive member corresponding to a white background portion of an image by exposing and scanning the charged surface of the photosensitive member in units of pixels. An image forming unit; a developing unit that forms a toner image by attaching toner to a portion of the surface of the photoreceptor where the charged potential is not lowered; a transfer unit that transfers the toner image to a transfer material; and the toner image An image forming apparatus having cleaning means for removing toner remaining on the surface of the photoreceptor after being transferred,
The photoreceptor is an amorphous silicon photoreceptor,
An exposure unit that exposes and scans the surface of the photoreceptor in the electrostatic latent image forming unit reproduces the gradation of an image by an error diffusion method,
The developing means has a toner carrier disposed so as to face the photosensitive member with a certain gap in the developing unit, and the toner carrier carries the toner to a thickness thinner than the gap, A means for developing an electrostatic latent image by applying an alternating electric field as a developing bias to a toner carrier to attach the toner to the surface of the photoreceptor.
The toner has at least toner base particles and fine particles having a particle size of 3 μm or less,
The average circularity L0 of the toner is 0.900 or more, and the relationship between the average circularity L0 and the average circularity L3 of the toner having a particle diameter of 3 μm or more is expressed by the following formula (1).
0.985 <L0 / L3 <1.015 (1)
Satisfied,
The average particle diameter D0 of the whole toner is 2.7 μm or more, and the relationship between the average particle diameter D0 and the average particle diameter D3 of the toner having a particle diameter of 3 μm or more is expressed by the following formula (2).
1.10 <D3 / D0 <3.00 (2)
Satisfied,
The image forming apparatus, wherein the fine particles having a particle size of 3 μm or less contain one or more selected from strontium titanate, magnesium titanate, calcium titanate, cerium oxide, aluminum oxide, and zinc oxide.   2. The image forming apparatus according to claim 1, wherein the surface roughness Ra of the photoconductor is 20 to 0.5 [mu] m. 3. The image forming apparatus according to claim 1, wherein the exposure unit forms a latent image by a binarization method by ON / OFF of exposure light. The image forming apparatus according to claim 1, wherein the developing bias is an alternating electric field having a sloped waveform.

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