JP2005017976A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method by which it is made possible to reconcile chargeability with the service life of an apparatus in a developing-concurrent cleaning system using a direct injection charging mechanism in which a small diameter photoreceptor is adopted for apparatus miniaturization. <P>SOLUTION: In the image forming method including at least a step of charging a rotatable image carrier by a rotatable charging member which comes in contact with the image carrier while forming a nip section and a step in which electroconductive particles are carried on the image carrier and conveyed to the nip section, when the diameter of the image carrier is represented by LD (mm), LD≤28 (mm), the charging member is an elastic body, and when the surface roughness of the charging member is represented by Ra (μm), the amount of inroad upon the image carrier by δ (μm) and the volume-base 90% diameter of the electroconductive particles by D<SB>90</SB>(μm), the expression: 2×D<SB>90</SB><Ra≤δ is satisfied. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０１６５】
（式中Ｒはエチレンまたはプロピレン基であり、ｘ，ｙはそれぞれ０以上の整数であり、かつ、ｘ＋ｙの平均値は０〜１０である。）又（Ｆ）式で示されるジオール類；
【０１６６】
【化２】

【０１６７】
２価の酸成分としては、例えばフタル酸、テレフタル酸、イソフタル酸、無水フタル酸などのベンゼンジカルボン酸類又はその無水物、低級アルキルエステル；こはく酸、アジピン酸、セバシン酸、アゼライン酸などのアルキルジカルボン酸類又はその無水物、低級アルキルエステル；ｎ−ドデセニルコハク酸、ｎ−ドデシルコハク酸などのアルケニルコハク酸類もしくはアルキルコハク酸類、又はその無水物、低級アルキルエステル；フマル酸、マレイン酸、シトラコン酸、イタコン酸などの不飽和ジカルボン酸類又はその無水物、低級アルキルエステル；等のジカルボン酸類及びその誘導体が挙げられる。
【０１６８】
また架橋成分として働く３価以上のアルコール成分と３価以上の酸成分を併用することが好ましい。
【０１６９】
３価以上の多価アルコール成分としては、例えばソルビトール、１，２，３，６−ヘキサンテトロール、１，４−ソルビタン、ペンタエリスリトール、ジペンタエリスリトール、トリペンタエリスリトール、１，２，４−ブタントリオール、１，２，５−ペンタントリオール、グリセロール、２−メチルプロパントリオール、２−メチル−１，２，４−ブタントリオール、トリメチロールエタン、トリメチロールプロパン、１，３，５−トリヒドロキシベンゼン等が挙げられる。
【０１７０】
また、三価以上の多価カルボン酸成分としては、例えばトリメリット酸、ピロメリット酸、１，２，４−ベンゼントリカルボン酸、１，２，５−ベンゼントリカルボン酸、２，５，７−ナフタレントリカルボン酸、１，２，４−ナフタレントリカルボン酸、１，２，４−ブタントリカルボン酸、１，２，５−ヘキサントリカルボン酸、１，３−ジカルボキシル−２−メチル−２−メチレンカルボキシプロパン、テトラ（メチレンカルボキシル）メタン、１，２，７，８−オクタンテトラカルボン酸、エンポール三量体酸、及びこれらの無水物、低級アルキルエステル；次式
【０１７１】
【化３】

【０１７２】
（式中Ｘは炭素数３以上の側鎖を１個以上有する炭素数５〜３０のアルキレン基又はアルケニレン基）で表わされるテトラカルボン酸等、及びこれらの無水物、低級アルキルエステル等の多価カルボン酸類及びその誘導体が挙げられる。
【０１７３】
アルコール成分としては４０〜６０ｍｏｌ％、好ましくは４５〜５５ｍｏｌ％、酸成分としては６０〜４０ｍｏｌ％、好ましくは５５〜４５ｍｏｌ％であることが好ましい。また三価以上の多価の成分は、全成分中の５〜６０ｍｏｌ％であることが好ましい。
【０１７４】
該ポリエステル樹脂も通常一般に知られている縮重合によって得られる。
【０１７５】
本発明に係る現像剤に用いられるワックスには次のようなものがある。例えば低分子量ポリエチレン、低分子量ポリプロピレン、ポリオレフィン共重合物、ポリオレフィンワックス、マイクロクリスタリンワックス、パラフィンワックス、フィッシャートロプシュワックスの如き脂肪族炭化水素系ワックス；酸化ポリエチレンワックスの如き脂肪族炭化水素系ワックスの酸化物；又は、それらのブロック共重合物；キャンデリラワックス、カルナバワックス、木ろう、ホホバろうの如き植物系ワックス；みつろう、ラノリン、鯨ろうの如き動物系ワックス；オゾケライト、セレシン、ペトロラクタムの如き鉱物系ワックス；モンタン酸エステルワックス、カスターワックスの如き脂肪族エステルを主成分とするワックス類；脱酸カルナバワックスの如き脂肪族エステルを一部又は全部を脱酸化したものが挙げられる。更に、パルミチン酸、ステアリン酸、モンタン酸、或いは更に長鎖のアルキル基を有する長鎖アルキルカルボン酸類の如き飽和直鎖脂肪酸；ブラシジン酸、エレオステアリン酸、バリナリン酸の如き不飽和脂肪酸；ステアリルアルコール、エイコシルアルコール、ベヘニルアルコール、カウナビルアルコール、セリルアルコール、メリシルアルコール、或いは更に長鎖のアルキル基を有するアルキルアルコールの如き飽和アルコール；ソルビトールの如き多価アルコール；リノール酸アミド、オレイン酸アミド、ラウリン酸アミドの如き脂肪族アミド；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の如き飽和脂肪族ビスアミド；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の如き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の如き芳香族系ビスアミド；ステアリン酸カルシウム、ラウリン酸カルシウム、ステアリン酸亜鉛、ステアリン酸マグネシウムの如き脂肪族金属塩（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の如きビニル系モノマーを用いてグラフト化させたワックス；ベヘニン酸モノグリセリドの如き脂肪酸と多価アルコールの部分エステル化物；植物性油脂を水素添加すること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が挙げられる。
【０１７６】
また、これらのワックスを、プレス発汗法、溶剤法、再結晶法、真空蒸留法、超臨界ガス抽出法又は融液晶析法を用いて分子量分布をシャープにしたものや低分子量固形脂肪酸、低分子量固形アルコール、低分子量固形化合物、その他の不純物を除去したものも好ましく用いられる。
【０１７７】
本発明に係る現像剤の着色剤としては磁性酸化鉄を用いても良く、その場合磁性現像剤として用いることが出来、磁性酸化鉄としては、マグネタイト，マグヘマイト，フェライト等の酸化鉄が用いられ、その磁性酸化鉄表面あるいは内部に非鉄元素を含有するものが好ましい。
【０１７８】
本発明の画像形成方法に磁性現像剤を適用する場合には、そこに使用される磁性酸化鉄は、鉄元素基準で異種元素を０．０５〜１０質量％含有することが好ましい。とくに好ましくは、０．１〜５質量％である。
【０１７９】
また、これら磁性酸化鉄は、結着樹脂１００質量部に対して２０〜２００質量部含有されていることが好ましい。更に好ましくは、５０〜１２０質量部含有されていることが好ましい。
【０１８０】
異種元素としては、マグネシウム、アルミニウム、ケイ素、リン、イオウから選択される元素であることが好ましい。また、以下の、リチウム，ベリリウム，ボロン，ゲルマニウム，チタン，ジルコニウム，錫，鉛，亜鉛，カルシウム，バリウム，スカンジウム，バナジウム，クロム，マンガン，コバルト，銅，ニッケル，ガリウム，カドミウム，インジウム，銀元素，パラジウム，金，水銀，白金，タングステン，モリブデン，ニオブ，オスミウム，ストロンチウム，イットリウム，テクネチウム等の金属も挙げられる。
【０１８１】
これらの磁性酸化鉄は個数平均粒径が０．０５〜１．０μｍが好ましく、更には０．１〜０．５μｍのものが好ましい。磁性酸化鉄はＢＥＴ比表面積は２〜４０ｍ^２／ｇ（より好ましくは、４〜２０ｍ^２／ｇ）のものが好ましく用いられる。形状には特に制限はなく、任意の形状のものが用いられる。磁気特性としては、磁場７９５．８ｋＡ／ｍ下で飽和磁化が１０〜２００Ａｍ^２／ｋｇ（より好ましくは、７０〜１００Ａｍ^２／ｋｇ）、残留磁化が１〜１００Ａｍ^２／ｋｇ（より好ましくは、２〜２０Ａｍ^２／ｋｇ）、抗磁力が１〜３０ｋＡ／ｍ（より好ましくは、２〜１５ｋＡ／ｍ）であるものが好ましく用いられる。
【０１８２】
また、本発明の画像形成方法に磁性現像剤を用いる場合は該磁性現像剤の密度が、１．３〜２．２ｇ／ｃｍ^３であることが望ましい。更には、１．５〜２．０ｇ／ｃｍ^３の範囲であることが好ましい。磁性現像剤の質量（密度）は磁性トナー粒子に働く磁気力、静電気力、重力の作用に相関があり、磁性現像剤の密度がこの範囲である場合磁性酸化鉄の作用が適正であるため、帯電と磁気力とのバランスが良く、優れた現像力を示すことが出来る。
【０１８３】
また、磁性現像剤の密度が１．３ｇ／ｃｍ^３未満の場合、磁性トナー粒子に対する磁性酸化鉄の作用が弱いため、磁気力が低くなる。このため、現像時に感光体へ飛翔するための静電気力が勝り、現像過多の状態となり、かぶりや、消費量の増加につながる。反対に磁性現像剤密度が２．２ｇ／ｃｍ^３超である場合、磁性トナー粒子に対する磁性酸化鉄の作用が強くなり磁気力が静電気力に勝るようになり、その強い磁気力作用が大きく比重も重くなるため、現像時にスリーブから飛翔しにくく、現像不足の状態となり、画像濃度薄や画像劣化につながる。
【０１８４】
また、上記の磁性酸化鉄は、場合により、シランカップリング剤、チタンカップリング剤、チタネート、アミノシラン等で処理しても良い。
【０１８５】
現像剤は荷電制御剤を含有することが好ましい。
【０１８６】
現像剤を負荷電性に制御するものとして下記化合物が挙げられる。
【０１８７】
有機金属錯体、キレート化合物が有効であり、モノアゾ金属錯体、アセチルアセトン金属錯体、芳香族ハイドロキシカルボン酸、芳香族ダイカルボン酸の金属錯体が挙げられる。他には、芳香族ハイドロキシカルボン酸、芳香族モノ及びポリカルボン酸及びその金属塩、無水物、エステル類、ビスフェノールのフェノール誘導体類が挙げられる。
【０１８８】
中でも、下記式（Ｉ）で表されるアゾ系金属錯体が好ましい。
【０１８９】
【化４】

【０１９０】
〔式中、Ｍは配位中心金属を表し、Ｓｃ，Ｔｉ，Ｖ，Ｃｒ，Ｃｏ，Ｎｉ，Ｍｎ又はＦｅ等が挙げられる。Ａｒはアリール基であり、フェニル基、ナフチル基の如きアリール基であり、置換基を有してもよい。この場合の置換基としては、ニトロ基、ハロゲン基、カルボキシル基、アニリド基及び炭素数１〜１８のアルキル基、炭素数１〜１８のアルコキシ基がある。Ｘ，Ｘ’，Ｙ及びＹ’は−Ｏ−，−ＣＯ−，−ＮＨ−，−ＮＲ−（Ｒは炭素数１〜４のアルキル基）である。Ｃ^＋はカウンターイオンを示し、水素、ナトリウム、カリウム、アンモニウム、脂肪族アンモニウム或いはそれらの混合イオンを示す。〕
特に中心金属としてはＦｅ又はＣｒが好ましく、置換基としてはハロゲン、アルキル基又はアニリド基が好ましく、カウンターイオンとしては水素、アルカリ金属、アンモニウム又は脂肪族アンモニウムが好ましい。カウンターイオンの異なる錯塩の混合物も好ましく用いられる。
【０１９１】
現像剤を正荷電性に制御するものとして下記の化合物がある。
【０１９２】
ニグロシン及び脂肪酸金属塩等によるニグロシン変成物；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、及びこれらの類似体であるホスホニウム塩の如きオニウム塩及びこれらのレーキ顔料；トリフェニルメタン染料及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、フェリシアン化物、フェロシアン化物など）；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の如き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の如きジオルガノスズボレート類；グアニジン化合物；イミダゾール化合物が挙げられる。これらを単独で或いは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、トリフェニルメタン化合物、カウンターイオンがハロゲンでない四級アンモニウム塩が好ましく用いられる。下記式（ＩＩ）
【０１９３】
【化５】

【０１９４】
〔式中Ｒ_１はＨ又はＣＨ_３を示し、Ｒ_２及びＲ_３は置換または未置換のアルキル基（好ましくは、Ｃ１〜Ｃ４）を示す〕
で表されるモノマーの単重合体；前述したスチレン、アクリル酸エステル、メタクリル酸エステルの如き重合性モノマーとの共重合体を正荷電性制御剤として用いることができる。この場合、この単重合体及び共重合体は荷電制御剤としての機能と、結着樹脂（の全部または一部）としての機能を有する。
【０１９５】
荷電制御剤を現像剤に含有させる方法としては、トナー粒子内部に添加する方法と外添する方法がある。これらの荷電制御剤の使用量としては、結着樹脂の種類、他の添加剤の有無、分散方法を含めたトナー製造方法によって決定されるもので、一義的に限定されるものではないが、好ましくは結着樹脂１００質量部に対して０．１〜１０質量部、より好ましくは０．１〜５質量部の範囲で用いられる。
【０１９６】
現像剤を製造する方法としては、上述したような現像剤の構成材料をボールミルその他の混合機により十分混合した後、熱ロールニーダー、エクストルーダーの如き熱混練機を用いてよく混練し、冷却固化後、機械的に粉砕し、粉砕粉を分級することによってトナーを得る方法が好ましい。他には、結着樹脂を構成すべき単量体に所定の材料を混合して乳化懸濁液とした後に、重合させてトナーを得る重合法；コア材及びシェル材から成るいわゆるマイクロカプセルトナーにおいて、コア材あるいはシェル材、あるいはこれらの両方に所定の材料を含有させる方法；結着樹脂溶液中に構成材料を分散した後、噴霧乾燥することによりトナーを得る方法が挙げられる。更に必要に応じ所望の添加剤とトナーとを混合機により前述した各種方法を用いて十分に混合し、現像剤を製造することができる。
【０１９７】
例えば混合機としては、ヘンシェルミキサー（三井鉱山社製）；スーパーミキサー（カワタ社製）；リボコーン（大川原製作所社製）；ナウターミキサー、タービュライザー、サイクロミックス（ホソカワミクロン社製）；スパイラルピンミキサー（太平洋機工社製）；レーディゲミキサー（マツボー社製）が挙げられ、混練機としては、ＫＲＣニーダー（栗本鉄工所社製）；ブス・コ・ニーダー（Ｂｕｓｓ社製）；ＴＥＭ型押し出し機（東芝機械社製）；ＴＥＸ二軸混練機（日本製鋼所社製）；ＰＣＭ混練機（池貝鉄工所社製）；三本ロールミル、ミキシングロールミル、ニーダー（井上製作所社製）；ニーデックス（三井鉱山社製）；ＭＳ式加圧ニーダー、ニダールーダー（森山製作所社製）；バンバリーミキサー（神戸製鋼所社製）が挙げられ、粉砕機としては、カウンタージェットミル、ミクロンジェット、イノマイザ（ホソカワミクロン社製）；ＩＤＳ型ミル、ＰＪＭジェット粉砕機（日本ニューマチック工業社製）；クロスジェットミル（栗本鉄工所社製）；ウルマックス（日曹エンジニアリング社製）；ＳＫジェット・オー・ミル（セイシン企業社製）；クリプトロン（川崎重工業社製）；ターボミル（ターボ工業社製）が挙げられ、分級機としては、クラッシール、マイクロンクラッシファイアー、スペディッククラシファイアー（セイシン企業社製）；ターボクラッシファイアー（日清エンジニアリング社製）；ミクロンセパレータ、ターボプレックス（ＡＴＰ）、ＴＳＰセパレータ（ホソカワミクロン社製）；エルボージェット（日鉄鉱業社製）、ディスパージョンセパレータ（日本ニューマチック工業社製）；ＹＭマイクロカット（安川商事社製）が挙げられ、粗粒などをふるい分けるために用いられる篩い装置としては、ウルトラソニック（晃栄産業社製）；レゾナシーブ、ジャイロシフター（徳寿工作所社製）；バイブラソニックシステム（ダルトン社製）；ソニクリーン（新東工業社製）；ターボスクリーナー（ターボ工業社製）；ミクロシフター（槙野産業社製）；円形振動篩い等が挙げられる。
【０１９８】
（実施例）
以下、本発明に係る帯電装置、プロセスカートリッジ及び画像形成装置を図面に則して更に詳しく説明する。
【０１９９】
図１は、本発明の画像形成方法を用いた画像形成装置の概略構成を示す。この画像形成装置１００は、転写式電子写真プロセスを利用した、直接注入帯電方式、トナーリサイクルプロセス（クリーナレスシステム）のレーザビームプリンタである。
【０２００】
（１）画像形成装置１００の全体的な構成
画像形成装置１００は、感光体として、回転ドラム型の負極性ＯＰＣ感光体（ネガ感光体；以下、「感光ドラム」と呼ぶ。）１を有する。感光ドラム１は図中矢印の時計方向に一定速度をもって回転駆動される。感光ドラム１についてはさらに別項で詳述する。
【０２０１】
そして、画像形成装置１００は、本発明に従う粒子帯電型（粉末塗布型）の接触帯電部材である帯電ローラ２と、この帯電ローラ２に対する帯電バイアス印加電源Ｓ１とを備える帯電装置２Ａを有している。
【０２０２】
帯電ローラ２は、芯金２ａと、この芯金２ａの外周に同心一体にローラ状に形成したゴム或いは発泡体の弾性・中抵抗層（以下、「弾性層」と呼ぶ。）２ｂからなり、更に、弾性層２ｂの外周面に導電粒子ｍを担持させて構成される。本実施例では、ローラ外径φ１８ｍｍ、芯金径φ６ｍｍである。この帯電ローラ２は感光ドラム１に所定の侵入量をもって押圧当接させて、所定幅の帯電接触部（帯電ニップ部）ｎを形成させている。帯電ローラ２に担持させた導電粒子ｍが、帯電ニップ部ｎにおいて感光ドラム１の表面に接触する。帯電ローラの当接条件については、さらに別項で詳述する。
【０２０３】
帯電ローラ２は、感光ドラム１と同じ図中矢印の時計方向に回転駆動され、帯電ニップ部ｎにおいて感光ドラム１の回転方向と逆方向（カウンター）で回転することで、導電粒子ｍを介して感光ドラム１の表面に対して速度差をもって接触する。本実施例では、感光ドラム１と帯電ローラ２とは、帯電ニップ部ｎにおいて、互いに逆方向に等速（周速度）で回転駆動される。本実施例では、帯電ローラ２と感光ドラム１とを、感光ドラム１の周速度を１００％として、帯電ローラ２を７０％の周速度にて回転駆動している。周速度については、さらに別項で詳述する。
【０２０４】
画像形成装置１００の画像形成時には、帯電ローラ２の芯金２ａに帯電バイアス印加電源Ｓ１から所定の帯電バイアス電圧が印加される。これにより、感光ドラム１の周面が直接注入帯電方式で、所定の極性・電位に一様に接触帯電処理される。本実施例では帯電ローラ２の芯金２ａに帯電バイアス印加電源Ｓ１から−６４０Ｖの帯電バイアスを印加して、感光ドラム１の表面にその印加帯電バイアスとほぼ同じ帯電電位（−６２０Ｖ）を得た。
【０２０５】
帯電ローラ２の外周面に塗布されている導電粒子ｍは、帯電ローラ２による感光ドラム１の帯電とともに感光ドラム１の表面に付着して持ち去られる。そして、一部は転写材Ｐに転写される。従って、それを補うために帯電ローラ２に対する導電粒子の供給手段を必要とする。後述するように、本実施例では、現像装置４が導電粒子ｍの供給手段として機能する。
【０２０６】
画像形成装置１００は、像露光を行う露光装置（光学系）として、レーザダイオード、ポリゴンミラーなどを備えるレーザビームスキャナ３を有する。このレーザビームスキャナ３は、目的の画像情報の時系列電気ディジタル画素信号に対応して強度変調されたレーザ光Ｌを出力し、このレーザ光Ｌで感光ドラム１の一様帯電面を走査露光する。この走査露光により感光ドラム１の表面に目的の画像情報に対応した静電潜像が形成される。
【０２０７】
感光ドラム１上に形成された静電潜像は、次いで現像装置４によって現像される。本実施例では、現像装置４は、負帯電性の一成分磁性現像剤を用いた反転現像装置である。現像装置４の現像容器（現像装置本体）４ｅ内には、詳しくは後述するように、現像剤としてのトナーｔ（無機微粉体も含む）と導電粒子ｍとの混合剤ｔ＋ｍを収容させてある。
【０２０８】
現像装置４は、現像剤担持体として、マグネットロール４ｂを内包させた、非磁性回転現像スリーブで構成される現像ローラ４ａを有する。現像容器４ｅ内に備える混合剤ｔ＋ｍ内のトナーｔは、現像ローラ４ａ上を搬送される過程において、現像剤層厚規制部材である現像ブレード４ｅで層厚規制及び電荷付与を受ける。又、現像装置４は、現像容器４ｅ内の混合剤ｔ＋ｍの循環を行い、順次現像ローラ４ａの周辺に混合剤ｔ＋ｍを搬送する攪拌部材４ｄを有する。
【０２０９】
現像ローラ４ａにコートされたトナーｔは、現像ローラ４ａの回転により、感光ドラム１と現像ローラ４ａとの対向部である現像部位（現像領域）ａに搬送される。又、現像ローラ４ａには現像バイアス印加電源Ｓ２より現像バイアス電圧が印加される。本実施例では、現像バイアス電圧は、ＤＣ電圧とＡＣ電圧の重畳電圧とした。これにより、感光ドラム１に形成された静電潜像がトナーｔにより反転現像される。
【０２１０】
図２に現像ローラ４ａから感光ドラム１に導電性粒子ｍを供給する電位の関係を示す。例えば現像ローラ４ａに現像バイアスとして直流電圧Ｖｄｃ＝−４００Ｖに交流電圧１．２ｋＶを重畳印加した場合、トナーｔから離脱した導電性粒子ｍでポジ性のものは、非画像部（露光暗部）電位ＶＤ（−６２０Ｖ）に対し、交流電圧のＶｍｉｎにより８２０Ｖ（｜Ｖｍｉｎ−ＶＤ｜＝｜２００−（−６２０）｜）のコントラストをもって現像ローラ４ａから感光ドラム１へ飛翔する。
【０２１１】
又、導電性粒子ｍでトナーｔに付着しているものもあり、感光ドラム１上の画像部（露光明部）電位ＶＬに対し、交流電圧のＶｍａｘにより９００Ｖ（｜ＶＬ−Ｖｍａｘ｜＝｜−１００−（−１０００）｜）のコントラストをもって現像ローラ４ａから感光ドラム１へ飛翔する。このようにして、現像ローラ４ａ上から感光ドラム１へ導電性粒子ｍの供給を行う。
【０２１２】
感光ドラム１に形成されたトナー像は、次いで接触転写手段としての中抵抗の転写ローラ６により被記録材としての転写材Ｐに転写される。転写ローラ６は、感光ドラム１に所定の押圧力で圧接させて転写ニップ部ｂを形成させてある。この転写ニップ部ｂに給紙部（図示せず）から所定のタイミングで転写材Ｐが給紙され、且つ、転写ローラ６に転写バイアス印加電源Ｓ３から所定の転写バイアス電圧が印加されることで、感光ドラム１に形成されたトナー像が転写ニップ部ｂに給紙された転写材Ｐの表面に順次に転写されていく。
【０２１３】
本実施例で使用した転写ローラ６は、芯金６ａに中抵抗発砲層６ｂを形成した、ローラ抵抗値５×１０^８Ωのものであり、＋２．０ｋＶの電圧を芯金６ａに印加して転写を行った。転写ニップ部ｂに導入された転写材Ｐは、この転写ニップ部ｂを挟持搬送されて、その表面側に感光ドラム１の表面に形成担持されているトナー像が順次に静電気力と押圧力にて転写されていく。
【０２１４】
転写ニップ部ｂに給紙されて感光ドラム１からトナー像の転写を受けた転写材Ｐは、感光ドラム１の表面から分離されて、本実施例では熱定着方式とされる定着装置７に導入され、トナー像の定着を受けて画像形成物（プリント、コピー）として装置外へ排出される。
【０２１５】
そして、感光ドラム１は再度帯電ローラ２により帯電され、繰り返して画像形成に用いられる。
【０２１６】
本実施例では、導電粒子ｍは現像装置４のトナーｔに添加してあり、感光ドラム１上の静電潜像の現像時にトナーｔと共に感光ドラム１の表面に付着し、感光ドラム１の回転で帯電ニップ部ｎに持ち運ばれる。つまり、導電粒子ｍは、感光ドラム１を介して帯電ローラ２に供給される。
【０２１７】
即ち、本実施例の画像形成装置１００はトナーリサイクルプロセスを採用しており、画像転写後の感光ドラム１の表面上に残留した転写残トナーｔは専用のクリーニング装置（クリーナ）で除去されることなく、感光ドラム１の回転に伴い帯電ニップ部ｎに持ち運ばれて、帯電ニップ部ｎにおいて感光ドラム１の回転に対してカウンター回転する帯電ローラ２に一時的に回収される。そして、このトナーｔは、帯電ローラ２の外周を周回するにつれて、反転したトナー電荷が正規化（本実施例では負極性に）され、順次に感光ドラム１に吐き出される。そして、このトナーｔは、感光ドラム１の回転に伴って現像部位ａに至り、現像装置４により現像同時クリーニングにて回収・再利用される。つまり、次工程以降の現像時、即ち、引き続き感光ドラム１を帯電ローラ２によって帯電し、露光して潜像を形成し、この潜像を現像する時に、かぶり取りバイアス（現像装置に印加する直流電圧と感光体の表面電位間の電位差であるかぶり取り電位差Ｖｂａｃｋ）によって回収する。本実施例のように反転現像方式の場合では、この現像同時クリーニングは、感光ドラム１の暗部電位から現像ローラ４ａにトナーを回収する電界と、現像ローラ４ａから感光ドラム１の明部電位へトナーを付着させる電界の作用でなされる。
【０２１８】
（２）感光ドラム１
感光ドラム１について更に詳しく説明する。図３は感光ドラム１の層構成の模式図である。図３（ａ）は電荷注入層付きの感光ドラム１ａ、図３（ｂ）は電荷注入層のない感光ドラム１ｂの層構成の模式図である。
【０２１９】
図３（ｂ）に示す電荷注入層のない感光ドラム１ｂは、アルミドラム基体（Ａｌドラム基体）１１上に、下引き層１２、電荷発生層１３、電荷輸送層１４の順に重ねて塗工された一般的な有機感光体ドラムである。
【０２２０】
図３（ａ）に示す電荷注入層付きの感光ドラム１ａは、上記の図３（ｂ）に示す感光ドラム１ｂに、更に電荷注入層１５を塗布することにより、帯電性能を向上したものである。
【０２２１】
後に説明するが、本実施例における電荷注入層１５は、バインダーとしての硬化型のフェノール樹脂に、導電性粒子（導電フィラー、例えば粒径約０．０３μｍのＳｎＯ_２超微粒子）１５ａ、重合開始剤などを混合分散し、塗工後、光硬化法により膜形成したものである。
【０２２２】
又、加えて４フッ化エチレン樹脂などの滑剤も内包させることにより、感光ドラム１の表面の表面エネルギーを抑えて、導電粒子ｍの付着を全般的に抑える効果がある。その表面エネルギーは、水の接触角で表すと、好ましくは８５度以上、更に好ましくは９０度以上とする。
【０２２３】
又、帯電性能の観点から表層の抵抗は重要なファクターとなる。直接注入帯電方式においては、感光体側の抵抗を下げることで、１つの注入ポイント（接触ポイント）あたり、帯電できる感光体表面の面積が広くなると考えられる。従って、帯電ローラ２が同じ接触状態であっても、感光体表面の抵抗が低い場合、効率よく電荷の授受が可能となる。一方、感光体としては、静電潜像を一定時間保持する必要があるため、電荷注入層１５の体積抵抗値としては１×１０^９〜１×１０^１４（Ω・ｃｍ）の範囲が適当である。
【０２２４】
（３）帯電ローラ２
本実施例にて用いる帯電ローラ２は、次の特性を有する。
【０２２５】
（３）−１表面構造及び粗さ特性
本実施例にて接触帯電部材として用いた帯電ローラ２は、導電粒子ｍを高密度に担持する必要から、ある程度の粗さが要求される。平均粗さＲａにして、１μｍ〜５００μｍが好ましい。さらに、粒子の保持量を最適にして、ドラム表面に緻密に接触させて帯電均一性を安定化するには、１５μｍ〜１５０μｍが最適である。
【０２２６】
なお、例えば現像剤のような絶縁物などが帯電ローラ２の表面に付着した場合にはその周辺が浮いてしまい感光ドラム１に接触できなくなり、帯電性能が低下する。こういった現像剤の異物混入の害を減らすには、用いる現像剤の質量平均粒径よりも大きいＲａが好ましい。
【０２２７】
逆に、上記平均粗さＲａが５００μｍよりも大きいと、帯電ローラ２の表面の凹凸が、像担持体表面内の帯電均一性を低下させることになる。
【０２２８】
尚、平均粗さＲａの測定には、キーエンス社製表面形状測定顕微鏡ＶＦ−７５００、ＶＦ７５１０を用い、対物レンズ２５０倍から１２５０倍を用いた。そして、非接触にて帯電ローラ２の表面の形状及びＲａの測定を行った。
【０２２９】
（３）−２抵抗特性
直接注入帯電方式においては、低電圧による帯電を可能とするため、接触帯電部材の表層を高抵抗にする必要がなく、帯電ローラ２を単層で構成することができる。
【０２３０】
体積抵抗については、１０^４〜１０^７Ωの範囲であることが好ましい。１０^４Ωよりも小さい場合は、ピンホールリークによる電源の電圧降下を生じ易くなる。一方、１０^７Ωよりも大きい場合は、帯電に必要な電流が確保できなくなり、帯電電圧が低下する。
【０２３１】
（３）−３帯電ローラの材質、構造、寸法
帯電ローラ２の弾性層２ｂの材質としては、ＥＰＤＭ、ウレタン、ＮＢＲ、シリコーンゴムや、ＩＲなどに抵抗調整のためのカーボンブラックや金属酸化物などの導電性物質を分散したゴム材があげられる。導電性物質を分散せずにイオン導電性の材料を用いて抵抗調整をすることも可能である。その後必要に応じて表面の粗さ調整、研磨などによる成型を行う。又、機能分離した複数層による構成も可能である。
【０２３２】
しかし、帯電ローラ２の弾性層２ｂの形態としては、先述したように多孔体構造が好ましい。前述の表面粗さをローラの成型と同時に得られるという点で製造的にも有利である。発泡体のセル径としては、１〜５００μｍが適切である。更には、３０〜３００μｍが望ましい。発泡成形した後に、その表面を研磨することにより多孔体表面を露出させ、前述の粗さを持った表面構造を作製することができる。
【０２３３】
（３）−４その他のローラ特性
直接注入帯電方式において、接触帯電部材は柔軟な電極として機能することが重要である。本実施例においては、帯電ローラ２の弾性層２ｂの弾性特性を調整して達成している。アスカーＣ硬度としては５０度以下が好ましく、５〜４０度がより好ましい範囲である。４度以下ではセットが悪化する場合がある。一方、５０度を越えると適正なニップ幅の確保が難しくなり、帯電性が低下する場合がある。
【０２３４】
硬度が高すぎると、加圧力を大きくしないと必要な侵入量が得られず、像担持体との間に帯電ニップ部ｎを確保できないため、帯電性能が低下する。
【０２３５】
一方、硬度が低すぎると、形状が安定しないために、像担持体との接触圧にムラを生じ、帯電ムラを生じる。或いは、長期放置による帯電ローラ２の永久ひずみによる帯電不良を生じる。
【０２３６】
（３）−５ローラのドラムに対する当接構成
図５は帯電ローラ２と感光ドラム１の当接構成を示したものである。（ａ）は側面図、（ｂ）は途中部分省略の正面図である。
【０２３７】
帯電ローラ２は、その芯金２ａの両端部の芯金２ａをそれぞれフォーク状軸受２ｄに回転自由に軸受させて感光ドラム１に並行に配列するとともに、両側のフォーク状軸受２ｄをそれぞれ加圧ばね２ｅにより感光ドラム方向に加圧することで、感光ドラム１に圧接した状態に保持させている。
【０２３８】
帯電ローラ２の感光ドラム１ヘの侵入量は、感光ドラム、帯電ローラの径を固定すると、加圧バネの圧力と帯電ローラの硬度との関係から決まり、所定幅の帯電接触部ｎが形成される。両端部のフォーク状軸受２ｄはそれぞれ不図示の装置側板に設けたガイド溝に嵌め込まれていて、感光ドラム１方向にスライド移動自由である。Ｇは帯電ローラ２の芯金２ａの一端側に固着したドライブギヤであり、このドライブギヤＧに不図示の駆動系から回転力が伝達されて帯電ローラ２の回転駆動がなされる。
【０２３９】
（４）導電粒子担持量
帯電部材の表面粗さと感光体に対する侵入量、並びに導電粒子ｍのＤ９０、より好ましくはＤ１０、Ｄ５０、及びＢＥＴを厳密に制御することにより帯電性能は向上するが、比較的小径の導電粒子ｍを用いているため感光ドラム１への脱落は顕著になる。帯電ローラ２上に導電粒子ｍを保持し得る力は弱い付着力であるので、多くの粒子を供給しても、粒子を拘束することは困難であり、感光ドラム１に脱落して、その後の現像工程や転写材Ｐ上への転写工程において、画像不良の影響を与える。従って、理想的には、帯電ローラ２の表層に一層、均一に塗布することが望ましい。しかし、実際には担持量を調整することにより、帯電性を確保するとともに、付着する粒子を弊害のないレベルで減らすことが可能となる。
【０２４０】
導電粒子ｍの担持量は、帯電ローラ２の表面の平均粗さＲａにより適切に保つ必要がある。つまり、担持量を平均粗さＲａで除した値（以下、単に「担持量／Ｒａ」という。）が１ｍｇ／ｃｍ^２／μｍ以下、更に好ましくは０．３ｍｇ／ｃｍ^２／μｍ以下であるようにすると良好な結果が得られる。
【０２４１】
（粒子担持量及び抵抗測定）
帯電ローラ２に担持している粒子を洗浄し、粒子の重量及び抵抗の測定を行った。超音波洗浄機内にエタノールと水（１：２）によりなる洗浄液を調合し、その中に帯電ローラ２を浸し洗浄を行った。帯電ローラ２の表面を光学顕微鏡などで確認しながら、又必要に応じて帯電ローラ２の表面をブレードなどにより摺擦しながら洗浄を繰り返し行うことにより、帯電ローラ２上の付着物を除去することができる。
【０２４２】
得られた洗浄液は１〜２時間静置し、明らかに上澄みと分離できる場合は、上澄みを除去する。その後、１０５℃で充分乾燥して帯電ローラ２の担持物を抽出した。
【０２４３】
粒子抵抗の測定は先述した方法に従う。
【０２４４】
担持量は、得られた粒子の総重量と帯電ローラ８の表面積（帯電ローラ８の長手長さ及び外径から算出される）から、単位面積当たりの担持量として求める。
【０２４５】
（５）導電粒子被覆率
更に、導電粒子ｍの帯電における実効的な存在量を把握するために、導電粒子ｍの被覆率を調整することが更に重要となる。導電粒子ｍが白色に近ければ、通常のトナーの色と区別可能である。顕微鏡での観察において、白色を呈している領域を面積率として求める。被覆率が０．１以下の場合は、帯電ローラ２の周速度を高めても帯電性能としては不十分であることから、導電粒子ｍの被覆率を０．２〜１の範囲に保つことが重要となる。
【０２４６】
担持量の調整は、基本的には導電粒子ｍのトナーｔへの添加量の調整により行うことができる。
【０２４７】
（被覆率の測定）
被覆率の測定に関しては、帯電ローラ２の当接条件に近い状態で顕微鏡観察し、導電粒子ｍに覆われている面積を計測した。具体的には、帯電バイアスを印加しない状態で感光ドラム１及び帯電ローラ２の回転を停止し、感光ドラム１及び帯電ローラ２の表面をビデオマイクロスコープ（ＯＬＹＭＰＵＳ製ＯＶＭ１０００Ｎ）及びデジタルスチルレコーダ（ＤＥＬＴＳ製ＳＲ−３１００）で撮影した。帯電ローラ２については、帯電ローラ２を感光ドラム１に当接するのと同じ条件でスライドガラスに当接させ、スライドガラスの背面からビデオマイクロスコープにてその接触面を１０００倍の対物レンズで撮影した。その後、事前に計測した導電粒子ｍの色或いは輝度をもって、粒子で被覆されている領域を分離し、面積率を求めて被覆率とした。又、色による判別が困難な場合は、帯電ローラ２の最表面の物質を蛍光Ｘ線分析装置ＳＹＳＴＥＭ３０８０（理学電機工業（株）製）により行った。先ず、初期状態において導電粒子ｍに覆われた帯電ローラ２と感光ドラム１との間に、ポリエステルテープ（ニチバン製Ｎｏ．５５０（＃２５））の粘着面を帯電ローラ２に向けてはさみ、感光ドラム１と帯電ローラ２を従動回転させて、帯電ローラ２と感光ドラム１との帯電ニップ部ｎを一度通過させる。このとき、テープ面には、帯電ローラ２の最表面の粒子を一層サンプリングすることになる。一方、印字テストを終えた帯電ローラ２についても同様にサンプリングを行う。導電粒子ｍ中に含まれる特定の元素について、含有量を定量することにより、被覆率を求めることができる。つまり、導電粒子ｍのみを担持した初期状態の帯電ローラ２のテープ試料の含有量を１として、印字テスト後の試料の含有量の割合を算出し、その比より被覆率を求めることが可能となる。
【０２４８】
以下、本発明に係る現像剤、感光体、帯電部材の製造例、転写部材、現像装置の説明を行い、実施例により本発明を具体的に説明するが、これは本発明をなんら限定するものではない。尚、以下の配合における部数は全て質量部である。
【０２４９】
［導電粒子の製造例１］
塩化スズと塩化アンチモンを、スズとアンチモンのモル比が１００：７となるよう混合溶解したｐＨ約１の塩酸水溶液を８０℃とし、そこに水酸化ナトリウム水溶液を添加して、共沈物を生成させ、ろ過、洗浄して導電性微粒子のスラリーを得た。得られたスラリーを乾燥、解砕した後、５００℃で３時間焼成し、再度解砕して導電粒子１を得た。得られた導電粒子１の物性は、比表面積１６×１０^５ｃｍ^２／ｃｍ^３、体積抵抗６×１０^１Ωｃｍ、Ｄ_５０＝１．９μｍ、Ｄ_９０＝３．６μｍ、Ｄ_１０＝０．７μｍであり、酸化スズの含有量は９３質量％であった。
【０２５０】

上記化合物を、１３０℃に加熱された二軸エクストルーダーで溶融混練し、冷却した混練物をハンマーミルで祖粉砕した。粉砕はターボミル（ターボ工業社製）を用い、機械式粉砕を行った。得られた微粉砕物をコアンダ効果を利用した多分割分級装置（日鉄鉱業社製エルボジェット分級機）で、超微粉および粗粉を厳密に分級除去して黒色粉１を得た。得られた黒色粉１の重量平均径は７．８μｍであった。
【０２５１】
次に、
・上記黒色粉１ １００質量部
・一次粒径８ｎｍの疎水性シリカ
（ジメチルシリコーンオイルとヘキサメチルジシラザンで疎水化処理された、Ｂ
ＥＴ１００ｍ^２／ｇのもの） １．０質量部
・導電粒子１ ０．４質量部
上記の材料をヘンシェルミキサーＦＭ１０Ｃ／ｌ（三井鉱山株式会社製）にて１８０秒間混合処理を行い、現像剤１を得た。得られた現像剤１の噴流性指数は８６であった。
【０２５２】
［感光体の製造例１］
φ２４ｍｍ×２６０．５ｍｍのアルミニウムシリンダーを支持体として、この上にポリアミド樹脂のメタノール溶液を浸漬法で塗布し、膜厚が０．５μｍの下引き層を設けた。
【０２５３】
オキシチタニウムフタロシアニン顔料４部、ポリビニルブチラール樹脂２部及びシクロヘキサノン８０部を、サンドミル装置で４時間ほど分散した。この分散液を前記下引き層上に塗布し、０．２μｍの電荷発生層を形成した。
【０２５４】
次いで、トリフェニルアミン化合物１０部、及びポリカーボネート樹脂１０部を、モノクロロベンゼン１００部に溶解した。この溶液を、前記電荷発生層上に塗布し、熱風乾燥し、膜厚が２０μｍの電荷輸送層を形成した。
【０２５５】
次に、電荷注入層として、シリコーンオイルで表面処理したアンチモンドープ酸化スズ微粒子５０部をエタノール１５０部中に分散し、更に、ポリテトラフルオロエチレン微粒子２０部を加えて分散した。その後、レゾール型熱硬化型フェノール樹脂を樹脂成分として１５０部を溶解し、調合液とした。
【０２５６】
この調合液を用いて、先の電荷輸送層上に浸漬塗布法により、膜を形成し、熱風乾燥して電荷注入層を形成して感光体１得た。この時、感光体１の電荷注入層の膜厚測定は、薄膜のため光の干渉による瞬間マルチ測光システムＭＣＰＤ−２０００（大塚電子（株）製）を用いて測定し、その膜厚は２μｍであった。その他の膜厚測定法としては、感光体の膜の断面をＳＥＭ等で直接観察測定することもできる。
【０２５７】
［帯電部材の製造例１］
直径６ｍｍ、長さ２６４ｍｍのＳＵＳローラを芯金とし、芯金上にウレタン樹脂、導電性物質としてのカーボンブラック、硫化剤、発泡剤等を処方した中抵抗の発泡ウレタン層をローラ状に形成し、さらに切削研磨し形状及び表面性を整え、可撓性部材として直径１８ｍｍ、長さ２２０ｍｍの帯電部材１を作製した。
【０２５８】
得られた帯電部材１は、抵抗値が１０^５Ωｃｍであり、硬度がアスカーＣ硬度で２２度であった。また、セル径は１５０μｍ、表面粗さＲａは５０μｍであった。
【０２５９】
＜実施例１＞
本例の画像形成装置の全体的な概略構成を図１に示す。先述したように、図１は転写式電子写真プロセスを利用した現像同時クリーニングプロセス（クリーナレスシステム）のレーザプリンタ（記録装置）である。クリーニングブレード等のクリーニング部材を有するクリーニング手段を除去したプロセスカードリッジを有し、現像剤としては現像剤１を使用し、現像剤担持体上のトナー層と像担持体が非接触となるよう配置される非接触現像法を用いる。
【０２６０】
像担持体としての、前記感光体１は、回転ドラム型ＯＰＣ感光体であり、矢印の方向に９４ｍｍ／ｓｅｃの周速度（プロセススピード）をもって回転駆動される。
【０２６１】
帯電部材としては、上記帯電部材の製造例１で得られた帯電部材１が帯電ローラ２として用いられ、図に示すように帯電ローラ２は感光体１に対して弾性に抗して所定の押圧力で圧接させて配設してある。ｎは感光体１と帯電ローラ２の当接部である帯電当接部である。本実施例では、バネ加圧力５００〜１０００ｇ、帯電ローラの単位長手長当りｆ＝２．２５〜４．５ｇ／ｍｍの圧力が好適であった。帯電ローラの硬度が１５〜４０゜の場合に、ニップ巾約２〜４ｍｍに設定できた。
【０２６２】
本例では、帯電ローラ２は感光体１との接触面である帯電当接部ｎにおいて対向方向（矢印方向）に６０％の周速で回転駆動されている。帯電ローラ２の表面は感光体１の表面に対して、相対移動速度比１６０％の相対速度差を有している。また、本実施例では、導電粒子ｍの担持量は凡そ２ｍｇ／ｃｍ^２で、Ｒａは４０μｍであり、担持量／Ｒａは０．０５ｍｇ／ｃｍ^２／μｍであった。
【０２６３】
また帯電ローラ２の芯金２ａには、帯電バイアス印加電源Ｓ１から−６４０Ｖの直流電圧を帯電バイアスとして印加するようにした。本例では感光体１の表面は帯電ローラ２に対する印加電圧とほぼ等しい電位（−６２０Ｖ）に直接注入帯電方式にて一様に帯電処理される。
【０２６４】
露光手段であるレーザダイオード・ポリゴンミラー等を含むレーザビームスキャナ（露光器）３は、目的の画像情報の時系列電気デジタル画素信号に対応して強度変調されたレーザ光Ｌを出力し、該レーザ光Ｌで上記感光体１の一様帯電面を走査露光する。この走査露光により回転感光体１の面に目的の画像情報に対応した静電潜像が形成される。現像手段としての現像装置４により、感光体１の表面の静電潜像はトナー像として現像される。
【０２６５】
本例の現像装置４は、現像剤として現像剤１を用いた、非接触型の反転現像装置である。
【０２６６】
現像剤担持体として、下記の構成の層厚約７μｍ、ＪＩＳ中心線平均粗さ（Ｒａ）１．０μｍの樹脂層を、表面をブラストした直径１２ｍｍのアルミニウム円筒上に形成した現像スリーブ４ａを使用し、現像磁極８０ｍＴ（８００ガウス）のマグネットロールを内包し、現像剤層厚規制部材として厚み１．０ｍｍ、自由長１．５ｍｍのウレタン製の弾性ブレード４ｃを２９．４Ｎ／ｍ（３０ｇ／ｃｍ）の線圧で当接させた。感光体１と現像スリーブ４ａとの間隙は２９０μｍとした。
・フェノール樹脂 １００部
・グラファイト（体積平均粒径約７μｍ） ９０部
・カーボンブラック １０部
また、現像スリーブ４ａは、感光体１との対向部である現像部ａ（現像領域部）にて感光体１の回転方向と順方向（矢印方向）に感光体１の周速の１２０％の周速で回転させる。
【０２６７】
この現像スリーブ４ａに弾性ブレード４ｃで現像剤が薄層にコートされる。現像剤は弾性ブレード４ｃで現像スリーブ４ａに対する層厚が規制され、また電荷が付与される。この時、現像スリーブ４ａにコートされた現像剤量は、１６ｇ／ｍ^２であった。
【０２６８】
現像スリーブ４ａにコートされた現像剤は、現像スリーブ４ａの回転により、感光体１と現像スリーブ４ａの対向部である現像部ａに搬送される。また、スリーブ４ａには現像バイアス印加電源Ｓ２より現像バイアス電圧が印加される。現像バイアス電圧は、−４４０Ｖの直流電圧と、周波数１６００Ｈｚ、ピーク間電圧１５００Ｖ（電界強度５×１０^６Ｖ／ｍ）の矩形の交流電圧を重畳したものを用い、現像スリーブ４ａと感光体１の間、現像部ａで１成分ジャンピング現像を行わせた。
【０２６９】
接触転写手段としての中抵抗の転写ローラ５は、感光体１に９８Ｎ／ｍ（１００ｇ／ｃｍ）の線圧で圧接させて転写当接部ｂを形成させてある。この転写当接部ｂに不図示の給紙部から所定のタイミングで転写材Ｐが給紙され、かつ転写ローラ５に転写バイアス印加電源Ｓ３から所定の転写バイアス電圧が印加されることで、感光体１側のトナー像が転写当接部ｂに給紙された転写材Ｐの面に順次に転写されていく。
【０２７０】
本例では転写ローラ５の体積抵抗値は５×１０^８Ωｃｍのものを用い、＋１８００Ｖの直流電圧を印加して転写を行った。即ち、転写当接部ｂに導入された転写材Ｐはこの転写当接部ｂを挟持搬送されて、その表面側に感光体１の表面に形成担持されているトナー像が順次に静電気力と押圧力にて転写されていく。転写当接部ｂに給紙されて感光体１側のトナー像の転写を受けた転写材Ｐは感光体の表面から分離されて、定着手段である熱定着方式等の定着装置６に導入され、トナー像の定着を受けて画像形成物（プリント、コピー）として装置外へ排出される。
【０２７１】
本例の画像形成装置はクリーニング手段を除去しており、転写材Ｐに対するトナー像転写後の感光体１の表面に残留の転写残トナーはクリーナで除去されることなく、感光体１の回転にともない帯電当接部ｎを経由して現像部ａに至り、現像装置４において現像同時クリーニング（回収）される。
【０２７２】
従来、トナーは絶縁体であるため帯電当接部ｎへの転写残トナーの混入は感光体の帯電において帯電不良を生じさせる因子である。しかしながら本発明においては、帯電部材の表面粗さと感光体への侵入量及び導電粒子のＤ_９０の関係を適正に制御しているため、帯電ローラ２の感光体１への緻密な接触性と接触抵抗を維持でき、帯電ローラ２の転写残トナーによる汚染にかかわらず、均一な帯電性を長期に渡り安定に維持させることができ、さらに感光体の磨耗量も低減される。
【０２７３】
本実施例では、上記画像形成装置に１２０ｇの現像剤１を充填して、印字面積比率２％の横ラインのみからなる画像パターンにより、一枚間欠で２０００枚のプリントを行った。転写材としては７５ｇ／ｍ^２のＡ４コピー紙を用いた。
【０２７４】
［評価］
転写効率は、ベタ黒画像転写後の感光体上の転写残トナーをマイラーテープによりテーピングしてはぎ取り、紙上に貼ったもののマクベス濃度の値をＣ、転写後定着前のトナーの載った紙上にマイラーテープを貼ったもののマクベス濃度をＤ、未使用の紙上に貼ったマイラーテープのマクベス濃度をＥとした時、近似的に以下の式で計算した。転写効率は８０％以上であれば実用上問題の無い画像である。
【０２７５】
転写効率（％）＝（Ｄ−Ｃ／Ｄ−Ｅ）×１００
耐久終了時の解像力は、静電潜像電界によって電界が閉じやすく、再現しにくい６００ｄｐｉにおける小径孤立１ドットの再現性によって評価した。
◎：非常に良好、１００個中の欠損が５個以下
○：良好、１００個中の欠損が６〜１０個
△：実用可、１００個中の欠損が１１〜２０個
×：実用不可、１００個中の欠損が２０個以上
紙上カブリの測定は、東京電色社製のＲＥＦＬＥＣＴＭＥＴＥＲ ＭＯＤＥＬＴＣ−６ＤＳを使用して測定した。フィルターは、グリーンフィルターを用いた。カブリの数値は、べた白画像で下記の式より算出した。紙上カブリは、２．０％以下であれば良好な画像である。
【０２７６】
カブリ（反射率）（％）＝標準紙上の反射率（％）−サンプル非画像部の反射率（％）
画像濃度はマクベス濃度計ＲＤ９１８（マクベス社製）で測定した。初期濃度は画だし２０枚目の濃度とした。
【０２７７】
帯電性は、２０００枚のプリント後に次のような画像により評価した。上端部（画像先端部から３ｃｍ幅）がベタ画像及び非画像の混合画像で、画像先端部から３ｃｍ以降が均一な中間調である画像パターン、即ち帯電ゴーストの発生しやすいゴースト画像を印字して評価した。中間調部において、非画像対応部の画像濃度と、帯電性が不良でより濃く現像されるベタ画像対応部の画像濃度を測定し、両者の差を求めた。帯電性が良好なほど、両者の差が小さい。また、両者の濃度差が０．２０を超えるとゴースト画像が顕著となり、実用上問題がある。
【０２７８】
実験は低温低湿（１５℃／１０％）環境で、まずプリント耐久試験を行ったが、２０００枚プリント後も画質の低下は見られなかった。
【０２７９】
次に、２０００枚のプリント終了後、前述のゴースト画像を連続して５枚印字し、５枚目の画像で帯電性を評価した。その結果、ゴースト部の濃度差が０．０５という良好な帯電性が得られた。
【０２８０】
この後、感光体１の電荷注入層の膜厚を測定した。プリント前の未使用段階での膜厚が２μｍであるのに対し、２０００枚印字後の膜厚は１．２μｍであり、感光体の磨耗量は２．０―１．２＝０．８（μｍ）であった。
【０２８１】
得られた結果を表３に示す。
【０２８２】
［導電粒子の製造例２〜１７］
導電粒子の製造例１において、塩化スズ濃度、スズとアンチモンのモル比、水酸化ナトリウム水溶液の添加速度、焼成温度及び焼成時間を適宜調整して導電粒子２〜１７を製造した。得られた粒子の諸物性を表１に示す。
【０２８３】
［金属化合物微粒子の製造例１８］
酸性の塩化スズ水溶液を６０〜８０℃に制御し、そこにアンモニア水溶液を添加して沈殿物を生成させ、ろ過、洗浄して導電性微粒子のスラリーを得た。得られたスラリーを乾燥、解砕した後、窒素雰囲気下で５００℃で２時間、さらに窒素／水素混合ガス雰囲気下で５００℃で１時間焼成し、再度解砕して導電粒子１７を得た。得られた導電粒子１７の物性は、比表面積３１×１０^５ｃｍ^２／ｃｍ^３、体積抵抗７×１０^２Ωｃｍ、Ｄ_５０＝１．２μｍ、Ｄ_９０＝２．６μｍ、Ｄ_１０＝０．７μｍであり、酸化スズの含有量は１００質量％であった。
【０２８４】
［導電粒子の製造例１９］
炭酸アンモニウム水溶液と硫酸アルミニウム水溶液を混合し、酸化亜鉛を分散した水溶液中に入れて６０℃にて１時間撹拌後、ろ過して水洗し、スラリーを得た。このスラリーをイオン交換水中に分散して３０℃に保ちながら炭酸ガスを４時間吹き込んだ。しばらく静置した後、上澄みを捨て、残ったスラリーをスプレードライヤーで噴霧乾燥し、乾燥粉体を得た。この粉体を２５０℃で５時間加熱分解し、導電性酸化亜鉛微粒子からなる導電粒子１９を得た。
【０２８５】
［導電粒子の製造例２０］
加熱型混合機中、１００質量部の導電粒子１に対し、エタノール１００部に変性シリコーンオイル２部を加えた溶液を噴霧しながら８０℃で撹拌混合し、噴霧終了後さらに１５０℃に昇温して３０分間の加熱処理を行った。取り出し後、室温まで冷却し、解砕して表面処理を施した導電粒子２０を得た。
【０２８６】
［現像剤の製造例２〜２０］
黒色粉体１を用い、現像剤の製造例１において導電粒子１に代えて導電粒子２〜２０を使用して、現像剤２〜２０を製造した。得られた現像剤の物性を表２に示す。
【０２８７】
［現像剤の製造例２１、２２］
現像剤の製造例１において、疎水性シリカ代えてｉｓｏ−ブチルトリメトキシシランで表面処理された一次粒径５０ｎｍ、ＢＥＴ１００の酸化チタン、及び、ｉｓｏ−ブチルトリメトキシシランで表面処理された一次粒径７ｎｍ、ＢＥＴ１１０の酸化アルミナを用いて、現像剤２１、２２を製造した。得られた現像剤の物性を表２に示す。
【０２８８】
［現像剤の製造例２３］
現像剤の製造例１において、一次粒径８ｎｍの疎水性シリカに代えて一次粒径９０ｎｍの疎水性シリカを用いて、現像剤２３を製造した。得られた現像剤の物性を表２に示す。
【０２８９】
［現像剤の製造例２４］
現像剤の製造例１において、ヘンシェルミキサーＦＭ１０Ｃ／ｌ（三井鉱山株式会社製）での混合処理時間を３００秒間とし、現像剤２４を得た。得られた現像剤の物性を表２に示す。
【０２９０】
＜比較例１＞
トナー１４を用い、実施例１と同様の条件で評価を行ったところ、ゴースト部の濃度差が０．３４と帯電性が悪く、感光体の磨耗量は２μｍで電荷注入層が無くなっていた。
２×導電粒子のＤ_９０＜帯電部材の表面粗さＲａ
という条件を満たしていないため、帯電性及び感光体磨耗性が悪化したものと考えられる。転写性やカブリも良くなかった。
【０２９１】
＜実施例２＞
トナー１４を用い、セル径１２０μｍ、表面粗さＲａ４０μｍの帯電部材を用いる以外は実施例１と同様の条件で評価を行った。その結果、ゴースト部の濃度差は０．２０と実用に耐えうるレベルであり、感光体の磨耗量は１．．８μｍで電荷注入層が０．２μｍ残っていた。これは帯電部材の表面粗さＲａを変更して
２×導電粒子のＤ_９０＜帯電部材の表面粗さＲａ
という条件を満たしたため、レベルが改良されたものと思われる。
【０２９２】
＜実施例３〜２３＞
現像剤２〜１３、１５〜２３を用い、実施例１と同様の条件で評価を行った。結果を表３に示す。
【０２９３】
＜比較例２＞
現像剤１を用い、帯電部材の感光体への侵入量δを４０μと変更する以外は実施例１と同様の条件で評価を行ったところ、ゴースト部の濃度差が０．３１と帯電性が悪かった。
帯電部材の表面粗さＲａ≦δ
という条件を満たしていないため、帯電性が悪化したものと考えられる。
【０２９４】
実施例１、２、及び比較例１、２の結果より、直径が２８ｍｍ以下の小径感光体を用いた接触帯電の場合でも、
２×導電粒子のＤ_９０＜帯電部材の表面粗さＲａ≦感光体に対する侵入量δの設定とすれば、帯電性の向上と感光体の磨耗軽減が両立できる。
【０２９５】
実施例１、５、１０、１３、１４の結果より、使用する導電粒子のＤ_５０及びＤ_１０が小さいと画像濃度が低く帯電性も低下気味の傾向が見られる。Ｄ_５０は０．４μｍ以上が好ましく、０．５μｍ以上なら一層好ましいことが分かる。またＤ_１０は０．３μｍ以上が好ましく、０．４μｍ以上が一層好ましい範囲であることが分かる。一方、実施例１、２、３、７、８、９、１６、１７の結果より、Ｄ_５０及びＤ_９０が大きいとカブリが悪化し解像力が低下する傾向が見られ、Ｄ_５０は４．０μｍ以下が好ましく、３．５μｍ以下が一層好ましいことが分かる。また、Ｄ_９０については６．０μｍ以下が好ましく、４．０μｍ以下が一層好ましい範囲であることが分かる。
【０２９６】
実施例１、２、３、４、１１、１２の結果より、使用する導電粒子の比表面積が５×１０^５ｃｍ^２／ｃｍ^３以上であれば良好な帯電性を維持できることが分かる。好ましくは１０×１０^５以上であり、より好ましくは１２×１０^５以上であることも分かる。一方、実施例１、５、６、１０、１４の結果より、使用する導電粒子の比表面積が大きくなるにつれ感光体表面の磨耗量が増加気味となっており、好ましくは８０×１０^５ｃｍ^２／ｃｍ^３以下、より好ましくは４０×１０^５以下であることも分かる。なお、磨耗量が１．５μｍ以下であれば、耐久性に余裕があると判断できる。
【０２９７】
実施例１、１５の結果より、導電粒子の抵抗が高くなると帯電性が低下する傾向となるが、１×１０^９以下であれば十分であることも分かる。
【０２９８】
実施例１、１８、１９の結果より、導電粒子中に酸化スズが含有されていない場合、感光体の磨耗量が増加気味となることが分かる。
【０２９９】
実施例１と２０の結果より、導電粒子はシラン化合物によって表面処理を施した方が帯電性と感光体磨耗軽減、さらには画像特性にも良い結果をもたらすことが分かる。
【０３００】
実施例１、２３、２４の結果より、トナーの噴流性指数が低くなると帯電性が低下する傾向が見られるが、７４％を下回らなければ良好であることが分かる。また、そのようなトナーを得るためには、流動化剤として平均一次粒径が９０ｎｍを超える無機微粉体を用いることは好ましくないことも分かる。
実施例２１、２２の結果より、無機微粉体として酸化チタンやアルミナも使用可能であることが分かる。
【０３０１】
【表１】

【０３０２】
【表２】

【０３０３】
【表３】

【０３０４】
［現像剤の製造例２５〜２８］
現像剤の製造例１と同様にして、平均粒径２．８μｍ、３．０μｍ、１２．０μｍ、１２．５μｍの黒色粉体を製造した。得られたそれぞれの黒色粉体に１次粒径８ｎｍの疎水性シリカを、２．８μｍ及び３．０μｍの粉体には２．５部、１２．０μｍ及び１２．５μｍの粉体には０．７部処理し、現像剤２５〜２８を製造した。導電粒子として、いずれの現像剤にも導電粒子１を０．４部混合した。現像剤の処方を表４に示す。
【０３０５】
＜実施例２５〜２８＞
トナー２５〜２８を用い、実施例１と同様の条件で評価を行った。結果を表５に示す。
【０３０６】
実施例２５、２６の結果より、トナーの質量平均粒径が小さくなると転写性やカブリと共に帯電性が低下し、感光体磨耗量が増加することが分かるが、質量平均粒径が３μｍ以上であれば、ゴースト部の濃度差は０．２０以下に抑えられることが分かる。
【０３０７】
実施例２７、２８結果より、トナーの質量平均粒径が大きくなると解像力が低下することが分かるが、質量平均粒径が１２μｍ以下であれば、解像力に問題は無いことが分かる。
【０３０８】
【表４】

【０３０９】
【表５】

【０３１０】
【発明の効果】
以上説明したように、本発明によれば、小型化のために小径の像担持体を採用した接触帯電工程を含む画像形成方法において、帯電部材の表面粗さ（μｍ）、該像担持体に対する侵入量δ（μｍ）、帯電ニップ部に存在する導電粒子の体積基準の９０％径Ｄ_９０（μｍ）を適正に設定することにより、良好な帯電性を長期に渡って維持でき、さらに感光体表面の磨耗量が低減される。また、直接注入帯電機構を用いた現像同時クリーニングシステムにおいても、帯電性と装置寿命の両立が可能となる。
【図面の簡単な説明】
【図１】本発明で使用される画像形成装置の一例の概略図を示す。
【図２】現像ローラ４ａから感光ドラム１に導電性粒子ｍを供給する電位の関係を示す図。
【図３】感光ドラム１の層構成の模式図である。
【符号の説明】
１ 感光体
２ 帯電ローラ
２ａ 帯電ローラ芯金
２ｂ 可撓性層
３ 露光器
４ 現像装置
４ａ 現像スリーブ
４ｂ マグネットロール
４ｃ 弾性ブレード
４ｄ トナー
６ 転写ローラ
７ 定着装置
Ｓ１ 帯電部材用電源
Ｓ２ 現像用電源
Ｓ３ 転写用電源[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming method used for an electrophotographic apparatus, an electrostatic recording apparatus, a magnetic recording apparatus, and the like.
[0002]
[Prior art]
Conventionally, as an image forming method, many methods such as an electrostatic recording method, a magnetic recording method, and a toner jet method are known. For example, electrophotography generally forms an electrical latent image on an image carrier such as a photoconductor using a photoconductive material by various means, and then develops the latent image with toner. A visible toner image is formed, and the toner image is transferred to a recording medium such as paper as necessary, and then the toner image is fixed on the recording medium by heat, pressure, or the like to obtain an image.
[0003]
Generally, in such a method, after the transfer, the toner remaining without being transferred to the recording medium on the image carrier is cleaned by various methods and stored in a waste toner container as waste toner, and the above-described steps are performed. Repeated image forming methods have been used. However, since this image forming method requires a waste toner container, it is disadvantageous for downsizing of the apparatus, which is one of the current market needs.
[0004]
On the other hand, as a system that does not generate waste toner, a technique called simultaneous development cleaning or cleanerless has been proposed, and is expected to be a very effective means for downsizing the apparatus. JP-A-59-133573, JP-A-62-203182, JP-A-63-133179, JP-A-64-20587 are disclosed to disclose techniques related to the cleanerless. JP-A-2-302277, JP-A-5-2289, JP-A-5-53482, JP-A-5-61383, etc., but detailed and specific configuration of the entire system is mentioned. Not.
[0005]
In the simultaneous development cleaning that essentially does not have a cleaning device, it has become essential to rub the surface of the image carrier with toner and the toner carrier. Therefore, as a preferred development method, toner or toner is applied to the image carrier. Many contact development methods that come into contact have been studied. This is because it is considered that a configuration in which the toner or toner contacts and rubs the image carrier in order to collect the transfer residual toner in the developing unit is advantageous. However, the simultaneous development cleaning or the cleaner-less process using the contact development method causes toner deterioration, toner carrier surface deterioration, image carrier surface deterioration or wear, etc. due to long-term use, and is a sufficient solution to durability characteristics. Not done.
[0006]
On the other hand, a direct injection charging mechanism has been proposed as a new environment-friendly new technique that enables simultaneous development cleaning not only in a contact development system but also in a non-contact development system and does not generate active ions such as ozone.
[0007]
This direct injection charging mechanism will be briefly described.
[0008]
The direct injection charging mechanism is a mechanism in which the surface of the charged body is charged by directly injecting charges from the contact charging member to the charged body. It is also called direct charging, injection charging, or charge injection charging. More specifically, a medium-resistance contact charging member comes into contact with the surface of the member to be charged, and charge is directly injected into the surface of the member to be charged without going through a discharge phenomenon, that is, basically using no discharge. Therefore, even if the applied voltage to the contact charging member is an applied voltage that is equal to or lower than the discharge threshold, the object to be charged can be charged to a potential corresponding to the applied voltage. Since this charging system is not accompanied by the generation of ions, there is no adverse effect caused by the discharge products. However, since it is direct injection charging, the number of contact points and the contact area of the contact charging member to the member to be charged greatly affect the charging property. Therefore, in order to take a configuration in which the charged body is contacted more frequently, a configuration is required in which the contact charging member has a denser contact point, and the contact time with the charged body is maintained longer.
[0009]
Among them, as a method for increasing the density of the contact points between the charging member and the charged body, there is a high efficiency by providing conductive charge-promoting particles at the contact portion between the charging member and the charged body, so-called image carrier. A method for ensuring a good injection chargeability has been proposed.
[0010]
For example, in Japanese Patent Application Laid-Open No. 10-307456, a developer-cum-cleaning image using a direct injection charging mechanism with a developer containing toner particles and electrically conductive charge accelerating particles having a particle size of ½ or less of the toner particle size. An image forming apparatus applied to a forming method is disclosed. According to this proposal, it is possible to obtain a developing and cleaning image forming apparatus which can greatly reduce the amount of waste toner without generating a discharge product and is advantageous for downsizing at low cost. Alternatively, a good image that does not cause diffusion can be obtained.
[0011]
Further, according to Japanese Patent Laid-Open No. 10-307456, conductive fine particles are externally added to the toner, and at least the conductive portion contained in the toner at the contact portion between the flexible contact charging member and the image carrier. Fine particles adhere to the image carrier during the development process and remain on the image carrier after the transfer process and are carried and intervened, thereby obtaining a good image that does not cause charging failure or light exposure. A developing and cleaning image forming apparatus is disclosed.
[0012]
In JP-A-10-307421, a developer containing conductive fine particles having a particle size of 1/50 to 1/2 of the toner particle size is used as a developing and cleaning image forming method using a direct injection charging mechanism. An image forming apparatus in which conductive fine particles are applied to have a transfer promoting effect is disclosed.
[0013]
Further, in Japanese Patent Laid-Open No. 10-307455, the particle size of the metal fine particles is set to 10 nm in order to make the particle size of the conductive fine particles less than the size of one constituent pixel and to obtain better charging uniformity. It is described that it is set to ˜50 μm.
[0014]
In JP-A-10-307457, in consideration of human visual characteristics, the conductive fine particles are about 5 μm or less, preferably 20 nm to 5 μm in order to make it difficult to visually recognize the influence on the image of the poorly charged portion. It is described that.
[0015]
Further, according to Japanese Patent Laid-Open No. 10-307458, by setting the particle size of the conductive fine particles to be equal to or smaller than the toner particle size, the development of the toner is inhibited during development, or the development bias leaks through the conductive fine particles. By preventing the image defects and eliminating the defects in the image, and setting the particle size of the conductive fine particles to be larger than 0.1 μm, the adverse effect of shielding the exposure light by embedding the conductive fine particles in the image carrier can be solved. A developing and cleaning image forming method using a direct injection charging mechanism that realizes excellent image recording is described.
[0016]
Japanese Patent Application Laid-Open No. 2001-235891 discloses a technique for strictly controlling the particle size distribution of a developer containing conductive fine powder and improving not only direct injection charging properties but also image characteristics.
[0017]
However, in any of these methods, it is necessary to secure a contact portion between the charging member and the image carrier, that is, a so-called charging nip portion, to a certain width (preferably 1 mm or more). For this reason, it is necessary to use an elastic material as the charging member, and use a material having a large diameter for both the charging member and the image carrier, and there is a limit to downsizing the apparatus.
[0018]
On the other hand, many methods for adding conductive fine powder as an external additive have been proposed. For example, carbon black as a conductive fine powder adheres to or adheres to the toner surface for the purpose of imparting conductivity to the toner, or for suppressing excessive charging of the toner and making the tribo distribution uniform. It is widely used as an external additive. In JP-A-57-151952, JP-A-59-168458, and JP-A-60-69660, conductive powders of tin oxide, zinc oxide, and titanium oxide are respectively added to high-resistance magnetic toners. External addition is disclosed. Japanese Patent Application Laid-Open No. 56-142540 discloses that a conductive magnetic powder such as iron oxide, iron powder, and ferrite is added to a high-resistance magnetic toner to promote charge induction to the magnetic toner. Toners that have both developability and transferability have been proposed. Further, in JP-A-61-275864, JP-A-62-258472, JP-A-61-114152, and JP-A-02-120865, the toner is graphite, magnetite, polypyrrole conductive powder, polyaniline. In addition to the disclosure of adding conductive powder, it is known to add a wide variety of conductive fine powders to toner.
[0019]
[Problems to be solved by the invention]
However, in JP-A-10-307456, JP-A-10-307421, JP-A-10-307455, JP-A-10-307457, and JP-A-10-307458, preferred conductive fine powders. Although the particle size is described to some extent, the particle size distribution or components are not described, and there is room for further improvement in order to always obtain stable performance.
[0020]
Japanese Patent Application Laid-Open No. 2001-235891 does not always provide sufficient performance, and it is necessary to look at the material on a different scale from the past, and there is still room for improvement.
[0021]
Further, in these proposals, in order to ensure uniform and sufficient chargeability, it is preferable that the charging member and the image carrier are in contact with each other at a higher frequency, and the relative movement speed ratio between the two is set high. Alternatively, a technique such as increasing the amount of conductive particles in the contact portion between the two is described.
[0022]
However, such a method in the contact charging mechanism tends to promote wear between the charging member and the image carrier, and it is difficult to avoid shortening the life of the apparatus. In particular, securing the charging nip width is an obstacle to downsizing the apparatus.
[0023]
As described above, the contact charging method including the direct injection charging mechanism is still sufficient from the viewpoint of ensuring uniform and sufficient chargeability, extending the life of the apparatus, and further realizing the downsizing of the apparatus. It is hard to say that it is a serious level.
[0024]
In addition, when conductive fine particles are added as an external additive to the toner to improve the image characteristics, the additive is often selected mainly focusing on the average particle diameter. However, considering the interaction between the toner particles and these conductive fine particles, the density of the contact points between them is actually significant and, like the direct injection charging mechanism, has a great influence on the image characteristics. However, there are few examples that have been examined in detail in this regard.
[0025]
[Means for Solving the Problems]
The present invention relates to an image forming method characterized by the following configuration for solving the above-mentioned problems.
[0026]
That is, the present invention relates to a charging step of an image carrier by a charging member that forms a nip portion in contact with the rotatable image carrier and can rotate by rotation and carries conductive particles on the surface, and the conductive particles are the image carrier. In the image forming method having at least a step of being carried on the nip and being conveyed to the nip portion, when the diameter of the image carrier is LD (mm),
LD ≦ 28 (mm)
The charging member is an elastic body, the surface roughness of the charging member is Ra (μm), the amount of penetration into the image carrier is δ (μm), and the volume-based 90% diameter of the conductive particles is D. ₉₀ (Μm)
2 x D ₉₀ <Ra ≦ δ
It is characterized by being.
[0027]
Preferably, the specific surface area (cm ² / Cm ³ ) Is 5 × 10 ⁵ 100 × 10 or more ⁵ It is characterized by the following.
[0028]
More preferably, the specific surface area (cm ² / Cm ³ ) Is 10x10 ⁵ 80 × 10 or more ⁵ It is characterized by the following.
[0029]
More preferably, the specific surface area (cm ² / Cm ³ ) Is 12x10 ⁵ 40 × 10 or more ⁵ It is characterized by the following.
[0030]
Preferably, the volume resistivity of the conductive particles is 1 × 10 ^-1 ~ 1x10 ⁹ It is Ωcm.
[0031]
Preferably, the volume-based median diameter D of the conductive particles ₅₀ Is 0.4 μm or more and 4.0 μm or less.
[0032]
More preferably, the volume-based median diameter D of the conductive particles ₅₀ Is 0.5 μm or more and 3.5 μm or less.
Preferably, the volume-based D of the conductive particles ₉₀ Is 6.0 μm or less.
[0033]
More preferably, the volume-based D of the conductive particles ₉₀ Is 4.0 μm or less.
[0034]
Preferably, the volume-based D of the conductive particles ₁₀ Is 0.3 μm or more.
[0035]
More preferably, the volume-based D of the conductive particles ₁₀ Is 0.4 μm or more.
[0036]
Preferably, the conductive particles contain at least tin oxide.
[0037]
Preferably, the conductive particles have been surface-treated with a silane compound.
[0038]
Preferably, the charging member has a porous body surface.
[0039]
Preferably, the charging member is a roller member having an Asker C hardness of 5 to 40 degrees.
[0040]
Preferably, the diameter LD (mm) of the image carrier and the diameter LC (mm) of the charging member satisfy LC ≦ LD.
[0041]
Preferably, the supplying step of supplying conductive particles to the image carrier is a developing step of developing an electrostatic image formed on the image carrier with a developer, and the developer includes at least toner particles and the conductive particles. Further, the toner particles remaining on the image carrier can be collected in a development process.
[0042]
Preferably, the toner particles are formed of at least a binder resin and a colorant, and the developer has a mass average particle size of 3 μm or more and 12 μm or less, and the median diameter (D ₅₀ ) Is less than the mass average particle size of the developer.
[0043]
Preferably, the toner particles are externally added with an inorganic fine powder selected from at least silica, titanium oxide, alumina, a composite thereof, or a mixture thereof and having an average primary particle size of 4 nm to 80 nm. It is characterized by being.
[0044]
Preferably, the developer has a Carr jetting index greater than 80.
[0045]
Preferably, the image carrier is charged by the charging member, an image exposure surface of the image carrier is image-exposed by an image exposure device to form an electrostatic image, and the electrostatic image on the image carrier is An image is formed by an image forming process including a step of developing with the developer by a developing unit, and then transferring the developer image on the image carrier to a transfer target, and the surface of the image carrier after the transfer step is formed. The remaining developer is temporarily carried on at least the charging member, transferred to the surface of the image carrier again, and collected by the developing means.
[0046]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0047]
<Volume-based D of conductive particles ₁₀ , D ₅₀ , D ₉₀ , Charging member>
The main roles of the conductive particles in the image forming method of the present invention are a charging aid in the charging step and a developing aid in the development step.
[0048]
In the charging step in the image forming method of the present invention, an elastic body is used as the charging member. As a result, an appropriate contact area can be secured when the image carrier is brought into contact with a so-called photoreceptor, and uniform charging can be achieved.
[0049]
Further, since it is necessary to carry the conductive particles, which are also charging aids, at a high density, a certain degree of roughness is also required. Here, the surface roughness of the charging member is Ra (μm), and the volume-based 90% diameter of the conductive particles is D. ₉₀ (Μm)
2 x D ₉₀ <Ra
It is necessary to set.
[0050]
With the above setting, there are almost a plurality of conductive particles as charging aids in one recess on the surface of the charging member, and the contact point between the charging member and the photosensitive member is dramatically increased. Uniformity is greatly improved. In addition, since the rotation of the particles inside the recess is facilitated, the photosensitive member is prevented from being scraped by the charging member at the contact portion, so-called nip portion. This effect becomes more prominent when the charging member rotates with a speed difference from the photosensitive member.
[0051]
On the other hand, when the penetration amount of the charging member into the photosensitive member is δ (μm),
Ra ≦ δ
If this relationship is not satisfied, the conductive particles inside the recesses cannot reliably contact the photoconductor, and a significant improvement in chargeability cannot be expected.
[0052]
That is,
2 x D ₉₀ <Ra ≦ δ
By satisfying this relationship, the carrying amount of the conductive particles on the surface of the charging member becomes appropriate, the photoconductor is prevented from being scraped at the nip portion, and close contact with the photoconductor is possible, thereby stabilizing the charging uniformity.
[0053]
In this sense, the charging member according to the present invention preferably has a porous body surface for supporting conductive particles.
[0054]
In order to maintain the nip width while suppressing the wear of the photoreceptor, the charging member according to the present invention is preferably a roller member having an Asker C hardness of 40 degrees or less. If the hardness is too high, a charging nip portion cannot be secured between the photosensitive member and the micro contact property to the surface of the photosensitive member is deteriorated. If the hardness of the roller member is too low, the shape of the roller member is not stable, so that the contact with the member to be charged is deteriorated, and stable chargeability cannot be obtained. Therefore, the Asker C hardness is 10 to 40 degrees. This is a preferred range.
[0055]
Here, assuming that the drum diameter is LD (mm), in the present invention, LD ≦ 28 (mm) makes it easy to reduce the size of the apparatus while expanding the degree of freedom of arrangement of development, exposure, and transfer. did it. Further, when the charging roller diameter is LC (mm), LC ≦ LD is more preferable. However, when LC <0.2 × LD, it is difficult to ensure a sufficient nip width for chargeability. Therefore, 0.2 × LD ≦ LC is preferable. Furthermore, if LD ≦ 25, the cost can be reduced and the size of the apparatus can be designed more easily. Even with the configuration of the present invention, the effect of improving the charging uniformity and suppressing the wear of the photosensitive member can be sufficiently expected.
[0056]
The conductive particles described above have a volume-based median diameter (D ₅₀ ) Is preferably 0.4 μm or more and 4.0 μm or less, more preferably 0.5 μm or more and 3.5 μm or less, and even more preferably less than the mass average particle diameter of the toner. D ₉₀ Is preferably 6.0 μm or less, and more preferably 4.0 μm or less.
[0057]
In general, the greater the difference in particle size between particles, the stronger the adhesive force due to the interaction between particles. As described above, in order for the conductive particles according to the present invention to act as a charging aid, it is necessary to separate the toner particles from the toner particles after the transfer step and positively transport only the conductive particles to the charging member. This is difficult if the interaction with the particles is too strong. In addition, as one of the main roles of the conductive particles according to the present invention, there is also an auxiliary development effect from the improvement of triboelectric charging characteristics in contact friction with the toner particles in the development process, and the conductive particles and the toner particles adhere strongly. Therefore, the effect is difficult to be expressed. Taking these into account, preferred D of the conductive particles according to the present invention ₅₀ Is 0.4 μm or more, and more preferably 0.5 μm or more. D ₅₀ The conductive particles having a particle size of less than 0.4 μm are difficult to separate from the toner particles, and the action as a charging aid and further as a development aid is insufficient.
[0058]
On the other hand, D ₅₀ As the value increases, the interaction with the toner becomes weaker, and the effect of improving the frictional charging characteristics and the like decreases. Especially for conductive particles D ₅₀ When the particle diameter exceeds the mass average particle diameter of the developer, the effect of the interaction is hardly seen, and it also acts as an electrode under the developing electric field, which rather inhibits the movement of the toner. It deteriorates or the resolution decreases. Deterioration of fog leads to contamination of the charging member, leading to a decrease in chargeability. Therefore, D of conductive particles ₅₀ Is less than the mass average particle diameter of the developer and is preferably 4.0 μm or less, more preferably 3.5 μm or less. For this reason, it is preferable that the conductive particles have few large particles, and D is used as an indicator of the distribution on the coarse powder side. ₉₀ Is used, the conductive particle D ₉₀ Is preferably 6.0 μm or less, and more preferably 4.0 μm or less.
[0059]
In this sense, it is preferable that the conductive particles have a smaller particle size in the particle size distribution. As an index of the fine particle side distribution in the particle size distribution, D on a volume basis is used. ₁₀ This D can be used ₁₀ Is preferably 0.3 μm or more, more preferably 0.4 μm or more.
[0060]
Here, D of the conductive particles ₁₀ , D ₅₀ , D ₉₀ Is measured as follows.
[0061]
A liquid module is attached to a laser diffraction type particle size distribution measuring device “LS-230 type” (manufactured by Coulter), and a particle size of 0.04 to 2000 μm is set as a measuring range, and the particle size distribution based on the obtained volume-based particle size distribution ₁₀ , D ₅₀ , D ₉₀ Is calculated. In the measurement, about 10 mg of particles are added to 10 ml of methanol and dispersed for 2 minutes with an ultrasonic disperser, and then measured under the conditions of a measurement time of 90 seconds and a single measurement.
[0062]
<Specific surface area of conductive particles>
Further, the conductive particles have a specific surface area of 5E5 (cm ² / Cm ³ ) And 100E5 or less is preferable.
[0063]
The inventors of the present invention have made various studies in order to improve the techniques disclosed so far in relation to ensuring the chargeability and extending the life of the apparatus in the contact charging method. ₁₀ , D ₅₀ , D ₉₀ It was clarified that variation in charging performance was observed only by controlling only, and variation in device life occurred when the charging performance was kept constant. Therefore, as a result of repeated studies focusing on various particle properties that are necessary for contact chargeability and should have been overlooked so far, there is a physical property parameter in which the specific surface area of the conductive particles is important. It was found that controlling the value makes it possible to stabilize the charging performance and the life of the apparatus, and to achieve both.
[0064]
Here, the contact density between the conductive particles and the toner particles and between the conductive particles and the surface of the photosensitive member will be considered, and the background of reaching the technical point of controlling the specific surface area will be described.
[0065]
The number of contacts is 1 when a particle that is generally assumed to be spherical contacts a member that is assumed to be substantially planar. This also applies to the contact between the conductive particles according to the present invention and the photoreceptor or toner particles. Therefore, in order to increase the number of contact points between the conductive particles and the photoconductor for improving the charging property, if a large number of irregularities are formed in the contact portion, the convexity to be contacted increases, and the number of contact points can be increased. However, it is not preferable to form a large number of irregularities on the surface of the photoreceptor, for example, when a latent image is formed on the surface of the photoreceptor by light exposure, because the image quality deteriorates due to the scattering effect. Furthermore, when using an apparatus for cleaning the transfer residual toner remaining on the surface of the photoreceptor after the transfer process, the transfer residual toner slips out, which is not preferable. On the other hand, if irregularities are formed on the surface of the conductive particles, the number of contact points with the photosensitive member is increased, so that the charging property is expected to be improved and the above-described problem does not occur.
[0066]
Thus, the present inventors focused on the irregularities on the surface of the conductive particles and continued to improve the chargeability.
[0067]
As an index of the number of irregularities on the particle surface, the specific surface area of the particle powder is usually used. However, the specific surface area generally used is the unit "cm ² As can be seen from “/ g”, it is the surface area per unit mass, and it is not easy to compare or optimize materials having different specific gravities in the discussion using this numerical value.
[0068]
Therefore, the present inventors have a physical property corresponding to the surface area per particle as the specific surface area, “cm ² / Cm ³ The unit was adopted, and the relationship between the number of contact points between the conductive particles, the photoconductor and the toner, the charging property and the image characteristics was intensively studied.
[0069]
As a result, in the image forming method including the contact charging step, the specific surface area (cm) of the conductive particles contained in the developer used. ² / Cm ³ ) 5 × 10 ⁵ 100 × 10 or more ⁵ It has been found that the chargeability and image characteristics can be greatly improved by controlling the following, and in addition, this good chargeability can be maintained with good reproducibility. Furthermore, it has been clarified that wear due to contact between the charging member and the photosensitive member is reduced.
[0070]
The effect of improving the charging property is not only the effect of increasing the number of contact points between the conductive particles and the photosensitive member, but also the separation property of the toner increases due to the decrease in the contact area due to the increase of the contact points between the conductive particles and the toner. The effect of increasing the number of conductive particles conveyed to the charging member after the process is considered to be included. Further, the effect of improving the image characteristics seems to be due to the increase in the interaction due to the increase in the contact point between the conductive particles and the toner.
[0071]
On the other hand, there are many unclear parts regarding the reason for the effect of reducing the wear of the photoconductor, but due to the decrease in the contact area between the conductive particles, the individual particles in the concave portion of the charging member surface can easily move independently. Since it becomes easy to roll in accordance with the movement, wear due to friction may be reduced while maintaining the number of contact points.
[0072]
However, if the specific surface area is too large, that is, if there are too many surface projections, the cohesiveness between the particles becomes strong and individual particles within the charging member surface recesses are difficult to roll independently. It has fallen. More preferably 10 × 10 ⁵ 80 × 10 or more ⁵ More preferably, by the following, 12 × 10 ⁵ 40 × 10 or more ⁵ By making the following, the effect of improving the chargeability and the effect of reducing the wear on the surface of the photoreceptor are manifested simultaneously and greatly.
[0073]
Here, the specific surface area of the conductive particles was determined as follows.
[0074]
First, according to the BET method, nitrogen gas is adsorbed on the sample surface using a specific surface area measuring device “Gemini 2375 Vre. 5.0” (manufactured by Shimadzu Corporation), and the BET specific surface area (cm ² / G).
[0075]
Next, true density (g / cm) using a dry automatic densimeter “Acupyc 1330” (manufactured by Shimadzu Corporation) ³ ) At this time, 10cm ³ As a sample pretreatment, helium gas purge is performed 10 times at a maximum pressure of 19.5 psig. After that, as a pressure equilibrium judgment value as to whether or not the pressure in the container has reached equilibrium, the pressure fluctuation in the sample chamber is 0.0050 / min as a guide. Start and automatically measure true density. The measurement is performed 5 times, the average value is obtained, and the true density is obtained.
[0076]
Here, the specific surface area of the powder is obtained as follows.
[0077]
Specific surface area (cm ² / Cm ³ ) = BET specific surface area (cm ² / G) x true density (g / cm ³ )
<Resistance of conductive particles>
The preferred volume resistance of the conductive particles according to the present invention is 1 × 10. ^-1 ~ 1x10 ⁹ Ωcm. 1 × 10 ⁹ If it exceeds Ωcm, the effect of improving the chargeability is not expected when used in an image forming method including a contact charging step. Meanwhile, 1 × 10 ^-1 When it is less than Ωcm, the triboelectric charging characteristics of the toner under high humidity are inhibited, and in addition to the deterioration in developability, fogging and transferability are deteriorated.
[0078]
Here, the resistance of the conductive particles is measured as follows.
[0079]
A cylindrical metal cell is filled with a sample, and electrodes are arranged up and down so as to contact the sample. A load of 686 kPa (7 kgf / cm) is applied to the upper electrode. ² ). In this state, a voltage V is applied between the electrodes, and the resistance (volume resistivity RV) of the present invention is measured from the current I (A) flowing at that time. At this time, the electrode area is S (cm ² ) When the sample thickness is M (cm)
RV (Ωcm) = 100 V × S (cm ² ) / I (A) / M (cm).
[0080]
In the present invention, the contact area between the electrode and the sample is 2.26 cm. ² And measured at a voltage V = 100V.
[0081]
<Material of conductive particles>
Examples of the conductive particles in the present invention include fine metal powders such as copper, gold, silver, aluminum, and nickel; zinc oxide, titanium oxide, tin oxide, aluminum oxide, indium oxide, silicon oxide, magnesium oxide, barium oxide, and oxidation. Metal oxides such as molybdenum, iron oxide, and tungsten oxide; metal compounds such as molybdenum sulfide, cadmium sulfide, and potassium titanate, or conductive fine powders of these composite oxides can be used.
[0082]
Among these, the inclusion of at least one oxide selected from zinc oxide, tin oxide, and titanium oxide can set the resistance of the conductive particles low, is white or light, and is transferred onto the transfer material. This is preferable in that the conductive particles are not noticeable as fog.
[0083]
For the purpose of controlling the resistance value of the conductive particles, metal oxide fine particles containing elements such as antimony and aluminum, fine particles having a conductive material on the surface, and the like can also be used as the conductive particles. For example, zinc oxide fine particles containing an aluminum element, tin oxide fine particles containing an antimony element, and the like.
[0084]
However, resistance control by introducing an antimony element is generally not preferred because the blue-black color of the powder increases.
[0085]
In the present invention, when particles containing tin oxide are used as the conductive particles, the effect of reducing the wear of the photoreceptor is amplified. The reason for this is unclear, but it is also considered that the hardness, adhesion, and surface irregularity of the tin oxide appropriately matched the conditions under which the load on the surface of the photoreceptor was small. Therefore, it is preferable that the conductive particles contain at least tin oxide, and the higher the content, the better.
[0086]
However, resistance control is not sufficient with conductive particles containing about 100% by mass of ordinary tin oxide.
[0087]
Therefore, in the present invention, it is more preferable to use, as the conductive particles, reduction-treated tin oxide that is light in color and capable of appropriate resistance control.
The conductive particles are preferably substantially non-magnetic.
[0088]
When the particles are magnetic, for example, when they are added to the magnetic toner, the particles released from the toner often adhere to the toner carrier and become contaminated, which adversely affects the triboelectric charging characteristics of the toner and the image characteristics as they are. There is a fear.
[0089]
On the other hand, it is preferable to use the conductive particles after applying an appropriate surface treatment from the viewpoint of reducing the wear of the photoreceptor and improving the characteristics in a high-humidity environment. If the surface treatment is performed with a processing agent having high releasability, the frictional force between the charging member and the photoconductor can be reduced by the conductive particles, so that the life of the photoconductor is further extended. Further, if the hygroscopic property of the conductive particles is suppressed by the water repellency treatment, the triboelectric charging characteristics of the conductive particles are improved, and the conductive particles are less likely to be detached from the charging member by the Coulomb force, thereby improving the chargeability improving effect. In that sense, a silicon compound is preferred as the surface treatment agent because of its high releasability and water repellency.
[0090]
<Developer particle size>
The developer according to the present invention preferably has a mass average particle diameter of 3 μm or more and 12 μm or less. If the thickness is less than 3 μm, transferability is deteriorated and fogging is deteriorated. For example, in simultaneous development cleaning employing a direct injection charging mechanism, deterioration of chargeability due to contamination of the charging member with residual transfer toner is inevitable. On the other hand, when the mass average particle diameter exceeds 12 μm, the resolution on the image is lowered.
[0091]
The mass average particle size and the particle size distribution of the developer are determined using a Coulter counter method. For example, a Coulter Multisizer (manufactured by Coulter Inc.) can be used. As the electrolytic solution, a 1% NaCl aqueous solution is prepared using primary sodium chloride. For example, ISOTON R-II (manufactured by Coulter Scientific Japan) can be used. As a measurement method, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the volume and the number of magnetic toner particles of 2.00 μm or more are measured using the 100 μm aperture as the aperture by the measuring device. The volume distribution and the number distribution are calculated. Then, the weight-based weight average particle diameter (D4) obtained from the volume distribution according to the present invention is calculated. As channels, 2.00 to less than 2.52 μm; 2.52 to less than 3.17 μm; 3.17 to less than 4.00 μm; 4.00 to less than 5.04 μm; 5.04 to less than 6.35 μm; 6 Less than 35 to 8.00 μm; less than 8.00 to less than 10.08 μm; less than 10.08 to less than 12.70 μm; less than 12.70 to less than 16.00 μm; less than 16.00 to less than 20.20 μm; Use 13 channels less than 40 μm; 25.40 to less than 32.00 μm; 32.00 to less than 40.30 μm.
[0092]
<External additive for developer>
In the developer used in the present invention, an inorganic fine powder having an average primary particle size of 4 to 80 nm is preferably added as a fluidizing agent and a transfer aid. Inorganic fine powder is added to improve developer fluidity, uniform triboelectric charge of toner particles, and improve transferability. It is also a preferred form to provide functions such as adjustment of charge amount and improvement of environmental stability.
[0093]
When the average primary particle size of the inorganic fine powder is larger than 80 nm, the image density is lowered, and it is difficult to stably obtain a good image. Also, good developer fluidity cannot be obtained, charging to toner particles tends to be non-uniform, fog increases, and transfer residual toner increases. Further, as will be described later, the developer jet property index is low, and in the cleanerless system, the charging member is significantly contaminated. Therefore, it is difficult to improve the chargeability and image characteristics even when the conductive particles according to the present invention are used. On the other hand, when the average primary particle size of the inorganic fine powder is smaller than 4 nm, the cohesiveness of the inorganic fine powder is increased, and the aggregate has a wide particle size distribution with strong cohesiveness that is difficult to be broken by the pulverization treatment instead of the primary particles. It tends to behave as an aggregate, and image defects are likely to occur due to development of aggregates and damage to the photoreceptor or developer carrier. In order to make the triboelectric charge amount distribution of the toner particles more uniform, the average primary particle size of the inorganic fine powder is more preferably 6 to 70 nm.
[0094]
In the present invention, the average primary particle size of the inorganic fine powder is measured by a photograph of the developer magnified by a scanning electron microscope, and further by an elemental analysis means such as XMA attached to the scanning electron microscope. The number average particle diameter can be obtained by measuring 100 or more primary particles of the inorganic fine powder adhering to or liberating from the toner surface while contrasting the photograph of the developer mapped with the element contained in I can do it.
[0095]
As the inorganic fine powder used in the present invention, silica, alumina, titanium oxide, or a composite oxide thereof can be used.
[0096]
For example, both silica, so-called fine silica powder, so-called dry process produced by vapor phase oxidation of silicon halide or dry silica called fumed silica, and so-called wet silica produced from water glass, etc. Although it can be used, there are few silanol groups on the surface and inside the silica fine powder, and Na ₂ O, SO ^3- For example, dry silica with less production residue is preferred. In dry silica, it is also possible to obtain composite fine powders of silica and other metal oxides by using other metal halogen compounds such as aluminum chloride and titanium chloride together with silicon halogen compounds in the production process. Is also included.
[0097]
The addition amount of the inorganic fine powder having an average primary particle size of 4 to 80 nm is preferably 0.1 to 3.0% by mass with respect to the toner. However, if it exceeds 3.0% by mass, the fixing property is deteriorated.
[0098]
Here, the inorganic fine powder is preferably a hydrophobized product in view of characteristics in a high temperature and high humidity environment. When the inorganic fine powder mixed with the toner absorbs moisture, the triboelectric charge amount of the toner is remarkably reduced, fogging, transferability is deteriorated, and toner scattering is likely to occur.
[0099]
As treatment agents for hydrophobizing treatment, treatment agents such as silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane compounds, silane coupling agents, other organic silicon compounds, and organic titanium compounds may be used alone or You may process together.
[0100]
Among these, those treated with silicone oil are preferable, and more preferably, the inorganic fine powder is treated with silicone oil at the same time or after hydrophobizing with a silane compound, and then treated with silicone oil. It is good for keeping the amount high and preventing toner scattering.
[0101]
The conditions for hydrophobizing the inorganic fine powder are as follows. For example, a silylation reaction is performed with a silane compound as a first-stage reaction, and silanol groups are eliminated by chemical bonding, and then a hydrophobic thin film is formed on the surface with silicone oil as a second-stage reaction.
[0102]
The silicone oil has a viscosity at 25 ° C. of 10 to 200,000 mm. ² / S, even 3,000-80,000mm ² / S is preferred. 10mm ² If it is less than / s, the inorganic fine powder is not stable and the image quality tends to deteriorate due to heat and mechanical stress. 200,000mm ² If it exceeds / s, uniform processing tends to be difficult.
[0103]
As the silicone oil used, for example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, fluorine modified silicone oil and the like are particularly preferable.
[0104]
As a method for treating the silicone oil, for example, the inorganic fine powder treated with the silane compound and the silicone oil may be directly mixed using a mixer such as a Henschel mixer, or the silicone oil is sprayed onto the inorganic fine powder. A method may be used.
[0105]
Alternatively, after dissolving or dispersing silicone oil in an appropriate solvent, inorganic fine powder may be added and mixed to remove the solvent. A method using a sprayer is more preferable in that the formation of inorganic fine powder aggregates is relatively small.
[0106]
The treatment amount of the silicone oil is 1 to 23 parts by mass, preferably 5 to 20 parts by mass with respect to 100 parts by mass of the inorganic fine powder. If the amount of silicone oil is too small, good hydrophobicity cannot be obtained, and if it is too large, problems such as fogging occur.
[0107]
Next, the behavior when the developer adheres to the charging member will be considered.
[0108]
When the developer adheres to the contact charging member, if the developer remains attached without being removed, problems such as fusion to the charging member and wear of the photosensitive member are caused. The charging member to which the developer has been fused has a high resistance on its own surface, so that it is difficult to say that the effect of the image forming method of the present invention alone is sufficient. As a more preferable situation, the adhesive force between the developer contaminated by the vibration when the contact charging member is driven and the surface of the charging member is loosened, and the developer contaminated by the electric field due to the potential difference between the charging member surface and the photosensitive member is used. To be eliminated on the photoreceptor. For this purpose, it is preferable to use a developer that smoothly transitions from a static state to a fluid state.
[0109]
There are many ways to evaluate the fluidity that is one of the characteristics of the developer, but it is an index for comprehensively evaluating the fluidity of powders based on data on several phenomena and characteristics related to fluidity. There is Carr's jetability index.
[0110]
The jetability index is a measure of the likelihood of the flushing phenomenon. Flushing means that a fluid whose fluidity has been lowered in a stationary state becomes a fluid state like a liquid when it starts to flow due to vibration.
[0111]
This means that the higher the jet performance index value, the higher the jet performance of the developer.
[0112]
In the present invention, the jetability index was measured by the following method.
[0113]
Using a powder tester P-100 (manufactured by Hosokawa Micron Corporation), parameters of repose angle, collapse angle, difference angle, degree of compression, degree of aggregation, spatula angle and degree of dispersion are measured. The values obtained for each were applied to the Carr jetability index table, converted into respective indices of 25 or less, and the sum of the indices obtained from each parameter was calculated as the fluidity index / jetability index. The measurement method of each parameter is shown below.
[0114]
▲ 1 angle of repose
150 g of developer is deposited on a circular table of direct 8 cm through a mesh having a mesh opening of 710 μm. At this time, the developer is deposited so as to overflow from the end of the table. The angle of repose was determined by measuring the angle formed between the edge of the developer deposited on the table and the circular table surface with a laser beam.
[0115]
(2) Compression degree
The degree of compression can be determined from the loosely packed bulk density (loose apparent specific gravity A) and the tapping bulk density (hardened apparent specific gravity P).
[0116]
Compressibility (%) = 100 × (PA) / P
○ Spacious Apparent Specific Gravity Measurement Method 150 g of developer is gently poured into a cup having a diameter of 5 cm, a height of 5.2 cm, and a capacity of 100 cc. When the developer is filled in the measuring cup, the surface of the developer is ground, and the loose apparent specific gravity is calculated from the amount of the developer filled in the cup.
[0117]
○ Measurement method of solid apparent specific gravity Add the attached cap to the measuring cup used for loose apparent specific gravity. Fill the cup with developer and tap the cup 180 times. When tapping is finished, remove the cap and scrape off the excess developer that is piled up in the cup. The apparent apparent specific gravity is calculated from the amount of developer filled in the cup.
[0118]
The apparent specific gravity value is inserted into the compression degree formula to obtain the compression degree.
[0119]
▲ 3 ▼ Spatula corner
Place the bottom of the 10 cm x 15 cm bat against the 3 cm x 8 cm spatula. Deposit developer on the spatula. At this time, the developer is deposited so as to rise on the spatula. Then, only the bat is gently lowered, and the inclination angle of the developer side surface remaining on the spatula is measured with a laser beam. Then, after applying an impact once with a shocker attached to the spatula, the spatula angle is measured again. The average of this measured value and the measured value before giving an impact was calculated as a spatula angle.
[0120]
(4) Degree of aggregation
On the shaking table, sieves are set in the order of 250 μm, 150 μm, and 75 μm from the top. The vibration amplitude is set to 1 mm, the vibration time is set to 20 seconds, and 5 g of the developer is gently put on it to vibrate. After the vibration stops, measure the weight remaining on each sieve.
(Amount of developer remaining on upper screen) ÷ 5 (g) × 100...
(Amount of developer remaining on the middle screen) ÷ 5 (g) × 100 × 0.6... B
(Amount of developer remaining on the lower screen) ÷ 5 (g) × 100 × 0.2... C
a + b + c = calculation degree (%)
[0121]
The value obtained from the parameters is converted into an index of 25 or less according to the Carr's flowability index and jetability index table (Chemical Engineering. Jan. 18.1965), and if these values are summed, the Carr's fluidity index and Become.
[0122]
(1) + (2) + (3) + (4) = (Carr's liquidity index)
(5) Collapse angle
After measuring the angle of repose, shock is applied three times with a shocker to the bat on which the circular table for measurement is placed. Thereafter, the angle of the developer remaining on the table is measured using a laser beam to obtain a collapse angle.
[0123]
▲ 6 ▼ Difference angle
The difference between the angle of repose and the collapse angle is the difference angle.
[0124]
(7) degree of dispersion
10 g of developer is dropped as a lump onto a watch glass having a diameter of 10 cm from a height of about 60 cm. Then, the developer remaining on the watch glass is measured, and the degree of dispersion is obtained by the following equation.
[0125]
Dispersity (%) = ((10− (amount of developer remaining on the plate)) × 10
The sum of the index that can be converted from the values of (5), (6), and (7) and the index corresponding to the fluidity index value obtained above can be obtained as the jetability index from the aforementioned Carr table.
[0126]
If the developer has a good jet property such that the jetability index is greater than 80 when this measurement is performed, the developer can be fused to the charging member even in a cleanerless system including a contact charging step. Since it is difficult to occur, the effect of maintaining the chargeability and the effect of reducing photoreceptor wear by the image forming method of the present invention are sufficiently exhibited.
[0127]
When the jetability index is 80 or less, if a number of developer layers are stacked on the surface of the charging member, it is difficult to flow even if force is applied. Therefore, if the printer is used as it is, the developer will be fused. As a result, photoconductor wear is promoted and it is difficult to maintain chargeability.
[0128]
In order to achieve the above-described developer jettability index, the jettability index is changed by changing the particle size of the fluidizing agent added to the developer and the processing conditions (mixing time, etc.) of the mixing device used during the addition. Can be changed.
[0129]
For example, Henschel mixer (manufactured by Mitsui Mining); Super mixer (manufactured by Kawata); Ribocorn (manufactured by Okawara Seisakusho); Nauter mixer, turbulizer, cyclomix (manufactured by Hosokawa Micron) A spiral pin mixer (manufactured by Taiheiyo Kiko Co., Ltd.);
[0130]
The developer according to the present invention will be further described.
[0131]
The developer according to the present invention has a glass transition temperature (Tg) of 45 to 80 ° C, preferably 50 to 70 ° C, from the viewpoint of storage stability. If Tg is lower than 45 ° C., it may cause deterioration of the developer in a high temperature atmosphere and offset at the time of fixing. On the other hand, when Tg exceeds 80 ° C., fixability tends to decrease.
[0132]
As a method for measuring the glass transition temperature of the developer, a differential thermal analysis measuring device (DSC measuring device), DSC-7 (manufactured by Perkin Elmer), EXSTAR6000, SSC / 5200 (manufactured by Seiko Instruments Inc.), DSC2920MDSC (TA Instruments) Etc.) and the like can be measured under the following conditions.
[0133]
<Method for Measuring Glass Transition Temperature of Developer>
Sample: 0.5-2 mg, preferably 1 mg
Temperature curve: Temperature increase I (20 ° C. to 180 ° C., temperature increase rate 10 ° C./min)
Temperature drop I (180 ° C to 10 ° C, temperature drop rate 10 ° C / min)
Temperature increase II (10 ° C to 180 ° C, temperature increase rate 10 ° C / min)
Measurement method: Place the sample in an aluminum pan, and use an empty aluminum pan as a reference. The point of intersection between the line of the midpoint of the base line before and after the endothermic peak and the differential heat curve was defined as the glass transition point Tg.
[0134]
The binder resin component used for the developer material has a Mn (number average molecular weight) of 3000 to 20000 and a Mw (weight average molecular weight) of 50,000 in the molecular weight measured by GPC of the THF soluble component of the developer. It is preferably in the range of ~ 500,000. Within this range, the balance between fixability and durability is very good.
[0135]
These binder resin components can be mixed and dispersed in advance in the production of the developer. By mixing the wax component in advance, phase separation in the micro region is relaxed, and a good dispersion state is obtained.
[0136]
The molecular weight distribution by GPC using THF (tetrahydrofuran) as a solvent for the THF soluble component of the developer is measured under the following conditions.
[0137]
The column is stabilized in a 40 ° C. heat chamber, and THF as a solvent is allowed to flow through the column at this temperature at a flow rate of 1 ml per minute, and about 100 μl of a sample THF solution is injected and measured. In measuring the molecular weight of a sample, the molecular weight distribution of the sample is calculated from the relationship between the logarithmic value of a calibration curve prepared from several types of monodisperse polystyrene standard samples and the number of counts. As a standard polystyrene sample for preparing a calibration curve, for example, a molecular weight of 10 manufactured by Tosoh Corporation or Showa Denko KK is 10 ² -10 ⁷ It is appropriate to use a standard polystyrene sample of about 10 points. An RI (refractive index) detector is used as the detector. As the column, it is preferable to combine a plurality of commercially available polystyrene gel columns. For example, a combination of shodex GPC KF-801, 802, 803, 804, 805, 806, 807, and 800P manufactured by Showa Denko KK or TSKgel G1000H (H _XL ), G2000H (H _XL ), G3000H (H _XL ), G4000H (H _XL ), G5000H (H _XL ), G6000H (HH _XL ), G7000H (H _XL ), A combination of TSK guard column.
[0138]
The sample is prepared as follows.
[0139]
Put the sample in THF, leave it for several hours, then shake well and mix well with THF (until the sample is no longer united) and let stand for more than 12 hours. At this time, the sample is left in THF for 24 hours or longer. Thereafter, a sample processing filter (pore size 0.45 to 0.5 μm, for example, Mysori Disc H-25-5 manufactured by Tosoh Corp., Excro Disc 25CR manufactured by Gelman Science Japan Co., Ltd., etc.) can be used. This is a measurement sample. The sample concentration is adjusted so that the resin component is 0.5 to 5 mg / ml.
[0140]
The types of binder resins described above include styrene resins, styrene copolymer resins, polyester resins, polyol resins, polyvinyl chloride resins, phenol resins, natural modified phenol resins, natural resin modified maleic acid resins, acrylic resins, methacrylic resins. Examples thereof include resins, polyvinyl acetate, silicone resins, polyurethane resins, polyamide resins, furan resins, epoxy resins, xylene resins, polyvinyl butyral, terpene resins, coumarone indene resins, and petroleum resins.
[0141]
As a comonomer for the styrene monomer of the styrene copolymer, styrene derivatives such as vinyltoluene, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, acrylic Acrylic acid ester such as phenyl acid; Methacrylic acid ester such as methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate; Maleic acid; Double such as butyl maleate, methyl maleate, dimethyl maleate Dicarboxylic acid ester having a bond; acrylamide, acrylonitrile, methacrylonitrile, butadiene; vinyl chloride; vinyl ester such as vinyl acetate and vinyl benzoate; ethylene, propylene, butylene Such ethylenic olefins, vinyl methyl ketone, such as vinyl vinyl hexyl ketone, vinyl methyl ether, vinyl ethyl ether, vinyl propionate ether. These vinyl monomers are used alone or in combination of two or more.
[0142]
The binder resin in the present invention preferably has an acid value in the range of 1 to 100 mgKOH / g. Particularly preferred is a resin having an acid value of 1 to 70 mgKOH / g. If it exceeds 70 mgKOH / g, the triboelectric charge amount under high humidity is insufficient, and if it is less than 1 mgKOH / g, the triboelectric charging rate under low humidity becomes slow.
[0143]
Examples of the monomer for adjusting the acid value of the binder resin include acrylic acid such as acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, cinnamic acid, vinyl acetic acid, isocrotonic acid, and angelic acid, and α- β-alkyl derivatives, fumaric acid, maleic acid, citraconic acid, alkenyl succinic acid, itaconic acid, mesaconic acid, dimethyl maleic acid, dimethyl fumaric acid and other unsaturated dicarboxylic acids and monoester derivatives or anhydrides thereof, etc. Such a monomer can be made alone or mixed and copolymerized with other monomers to produce a desired polymer. Among these, it is particularly preferable to use a monoester derivative of an unsaturated dicarboxylic acid in order to control the acid value.
[0144]
More specifically, for example, monomethyl maleate, monoethyl maleate, monobutyl maleate, monooctyl maleate, monoallyl maleate, monophenyl maleate, monomethyl fumarate, monoethyl fumarate, monobutyl fumarate, monophenyl fumarate Monoesters of α, β-unsaturated dicarboxylic acids such as: monobutyl n-butenyl succinate, monomethyl n-octenyl succinate, monoethyl n-butenylmalonate, monomethyl n-dodecenyl glutarate, monobutyl n-butenyl adipate And monoesters of alkenyldicarboxylic acid such as
[0145]
The carboxyl group-containing monomer as described above may be added in an amount of 0.1 to 20 parts by mass, preferably 0.2 to 15 parts by mass, with respect to 100 parts by mass of all monomers constituting the binder resin.
[0146]
Examples of the polymerization method that can be used for the developer according to the present invention as a binder resin synthesis method include a solution polymerization method, an emulsion polymerization method, and a suspension polymerization method.
[0147]
Among them, the emulsion polymerization method is a method in which a monomer (monomer) almost insoluble in water is dispersed as small particles in an aqueous phase with an emulsifier, and polymerization is performed using a water-soluble polymerization initiator. In this method, the reaction heat can be easily adjusted, and the termination reaction rate is low because the phase in which the polymerization is carried out (the oil phase consisting of the polymer and the monomer) and the aqueous phase are separate, resulting in a high polymerization rate. A product having a high degree of polymerization is obtained. Furthermore, the reason is that the polymerization process is relatively simple, and that the polymerization product is fine particles, so that it can be easily mixed with colorants, charge control agents and other additives in the production of toner. Therefore, there is an advantage as a method for producing a binder resin for toner.
[0148]
However, the added polymer is likely to be impure due to the added emulsifier, and an operation such as salting out is necessary to take out the polymer. Suspension polymerization is convenient to avoid this inconvenience.
[0149]
In suspension polymerization, it is good to carry out by 100 mass parts or less (preferably 10-90 mass parts) of monomers with respect to 100 mass parts of aqueous solvents. Examples of the dispersant that can be used include polyvinyl alcohol, partially saponified polyvinyl alcohol, calcium phosphate, and the like, and generally 0.05 to 1 part by mass with respect to 100 parts by mass of the aqueous solvent. The polymerization temperature is suitably 50 to 95 ° C., but is appropriately selected depending on the initiator used and the target polymer.
[0150]
Further, the binder resin is preferably produced by using a polyfunctional polymerization initiator alone or in combination with a monofunctional polymerization initiator as exemplified below.
[0151]
Specific examples of the polyfunctional polymerization initiator having a polyfunctional structure include 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, 1,3-bis- (t-butylperoxy Isopropyl) benzene, 2,5-dimethyl-2,5- (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di- (t-butylperoxy) hexane, tris- (t-butyl) Peroxy) triazine, 1,1-di-t-butylperoxycyclohexane, 2,2-di-t-butylperoxybutane, 4,4-di-t-butylperoxyvaleric acid-n-butyl ester , Di-t-butylperoxyhexahydroterephthalate, di-t-butylperoxyazelate, di-t-butylperoxytrimethyladipate, 2,2-bis- ( , 4-di-t-butylperoxycyclohexyl) propane, 2,2-t-butylperoxyoctane and various polymer oxides, etc., a functional group having a polymerization initiating function such as two or more peroxide groups in one molecule. And a polyfunctional polymerization initiator having a peroxide group in one molecule such as diallyl peroxydicarbonate, t-butylperoxymaleic acid, t-butylperoxyallylcarbonate and t-butylperoxyisopropyl fumarate And a polyfunctional polymerization initiator having both a functional group having a polymerization initiating function and a polymerizable unsaturated group.
[0152]
Of these, more preferred are 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, 1,1-di-t-butylperoxycyclohexane, di-t-butylperoxy. Hexahydroterephthalate, di-t-butylperoxyazelate and 2,2-bis- (4,4-di-t-butylperoxycyclohexyl) propane, and t-butylperoxyallyl carbonate.
[0153]
These polyfunctional polymerization initiators are preferably used in combination with a monofunctional polymerization initiator in order to satisfy various performances required as a binder for toner. In particular, it is preferable to use in combination with a polymerization initiator having a decomposition temperature of a half-life of 10 hours which is lower than the decomposition temperature for obtaining a half-life of 10 hours of the polyfunctional polymerization initiator.
[0154]
Specifically, benzoyl peroxide, 1,1-di (t-butylperoxy) -3,3,5-trimethylcyclohexane, n-butyl-4,4-di (t-butylperoxy) valerate, dichroic Organic peroxides such as milperoxide, α, α'-bis (t-butylperoxydiisopropyl) benzene, t-butylperoxycumene, di-t-butylperoxide, azobisisobutyronitrile, diazoamino Examples include azo and diazo compounds such as azobenzene.
[0155]
These monofunctional polymerization initiators may be added to the monomer at the same time as the polyfunctional polymerization initiator, but in order to keep the efficiency of the polyfunctional polymerization initiator appropriate, in the polymerization step, It is preferably added after the half-life indicated by the polyfunctional polymerization initiator has elapsed.
[0156]
These initiators are preferably used in an amount of 0.05 to 2 parts by mass with respect to 100 parts by mass of the monomer from the viewpoint of efficiency.
[0157]
It is also preferable that the binder resin is crosslinked with a crosslinking monomer.
[0158]
As the crosslinkable monomer, a monomer having two or more polymerizable double bonds is mainly used. Specific examples include aromatic divinyl compounds (eg, divinylbenzene, divinylnaphthalene, etc.); diacrylate compounds linked by alkyl chains (eg, ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4 -Butanediol diacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, and acrylates of the above compounds replaced with methacrylate); alkyl chain containing an ether bond Diacrylate compounds (eg, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol # 400 diacrylate, Ethylene glycol # 600 diacrylate, dipropylene glycol diacrylate, and acrylates of the above compounds in place of methacrylate); diacrylate compounds linked by a chain containing an aromatic group and an ether bond (eg, polyoxyethylene) (2) -2,2-bis (4-hydroxyphenyl) propane diacrylate, polyoxyethylene (4) -2,2-bis (4-hydroxyphenyl) propane diacrylate, and methacrylates of the above compounds Furthermore, polyester-type diacrylate compounds (for example, trade name MANDA (Nippon Kayaku)) are mentioned. As polyfunctional crosslinking agents, pentaerythritol acrylate, trimethylol ethane triacrylate, trimethylol propane triacrylate, tetramethylol propane triacrylate, tetramethylol methane tetraacrylate, oligoester acrylate, and acrylates of the above compounds are replaced with methacrylate. Triallyl cyanurate, triallyl trimellitate; and the like.
[0159]
These crosslinking agents are preferably used in the range of 0.00001 to 1 part by mass, preferably 0.001 to 0.05 part by mass, with respect to 100 parts by mass of the other monomer components.
[0160]
Among these crosslinkable monomers, aromatic divinyl compounds (especially divinylbenzene), diethers linked by a chain containing an aromatic group and an ether bond are preferably used from the viewpoint of toner fixing properties and offset resistance. Examples include acrylate compounds.
[0161]
As other synthesis methods, a bulk polymerization method and a solution polymerization method can be used. However, in the bulk polymerization method, a polymer having a low molecular weight can be obtained by polymerizing at a high temperature to increase the termination reaction rate, but there is a problem that the reaction is difficult to control. In that respect, the solution polymerization method can easily obtain a polymer with a desired molecular weight under mild conditions by utilizing the difference in chain transfer of radicals by a solvent and adjusting the amount of initiator and reaction temperature. Is preferable. In particular, a solution polymerization method under a pressurized condition is also preferable in that the amount of the initiator used is minimized and the influence of the remaining initiator is minimized.
[0162]
The composition of the polyester resin used in the developer according to the present invention is as follows.
[0163]
Examples of the divalent alcohol component include 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, and bisphenol represented by the formula (E) and derivatives thereof;
[0164]
[Chemical 1]

[0165]
(Wherein R is an ethylene or propylene group, x and y are each an integer of 0 or more, and the average value of x + y is 0 to 10) and diols represented by the formula (F);
[0166]
[Chemical 2]

[0167]
Examples of the divalent acid component include benzene dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and phthalic anhydride or anhydrides thereof, lower alkyl esters; alkyl dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid. Acids or anhydrides thereof, lower alkyl esters; alkenyl succinic acids or alkyl succinic acids such as n-dodecenyl succinic acid and n-dodecyl succinic acid, or anhydrides, lower alkyl esters thereof; fumaric acid, maleic acid, citraconic acid, itaconic acid Dicarboxylic acids such as unsaturated dicarboxylic acids or anhydrides thereof, lower alkyl esters;
[0168]
Moreover, it is preferable to use together the trihydric or more alcohol component and trivalent or more acid component which work as a crosslinking component.
[0169]
Examples of the trihydric or higher polyhydric alcohol component include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butane. Triol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxybenzene, etc. Is mentioned.
[0170]
Examples of the trivalent or higher polyvalent carboxylic acid component include trimellitic acid, pyromellitic acid, 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, and 2,5,7-naphthalene. Tricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, Tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, empole trimer acid, and their anhydrides, lower alkyl esters;
[0171]
[Chemical 3]

[0172]
(Wherein X is an alkylene group or alkenylene group having 5 to 30 carbon atoms having one or more side chains having 3 or more carbon atoms) and the like, and their anhydrides, lower alkyl esters and the like polyvalent Examples thereof include carboxylic acids and derivatives thereof.
[0173]
The alcohol component is 40 to 60 mol%, preferably 45 to 55 mol%, and the acid component is 60 to 40 mol%, preferably 55 to 45 mol%. Moreover, it is preferable that the polyvalent component more than trivalence is 5-60 mol% in all the components.
[0174]
The polyester resin can also be obtained by a generally known condensation polymerization.
[0175]
Examples of the wax used in the developer according to the present invention are as follows. For example, low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, aliphatic hydrocarbon wax such as Fischer-Tropsch wax; oxide of aliphatic hydrocarbon wax such as oxidized polyethylene wax Or block copolymers thereof; plant waxes such as candelilla wax, carnauba wax, wax wax, jojoba wax; animal waxes such as beeswax, lanolin, spermaceti; mineral systems such as ozokerite, ceresin, petrolactam Waxes; waxes mainly composed of aliphatic esters such as montanic acid ester wax and castor wax; those obtained by partially or fully deoxidizing aliphatic esters such as deoxidized carnauba wax . Further, saturated linear fatty acids such as palmitic acid, stearic acid, montanic acid, or long-chain alkyl carboxylic acids having a long-chain alkyl group; unsaturated fatty acids such as brassic acid, eleostearic acid, and valinal acid; stearyl alcohol Saturated alcohol such as eicosyl alcohol, behenyl alcohol, cannavir alcohol, seryl alcohol, melyl alcohol, or alkyl alcohol having a long chain alkyl group; polyhydric alcohol such as sorbitol; linoleic acid amide, oleic acid amide, lauric acid Aliphatic amides such as acid amides; saturated aliphatic bisamides such as methylene bisstearic acid amide, ethylene biscapric acid amides, ethylene bislauric acid amides, hexamethylene bisstearic acid amides; Unsaturated fatty acid amides such as inamide, hexamethylenebisoleic acid amide, N, N′-dioleyl adipic acid amide, N, N′-dioleyl sebacic acid amide; m-xylene bisstearic acid amide, N, Aromatic bisamides such as N'-distearylisophthalamide; aliphatic metal salts such as calcium stearate, calcium laurate, zinc stearate and magnesium stearate (commonly referred to as metal soap); aliphatic hydrocarbons Wax grafted with a vinyl monomer such as styrene or acrylic acid; Partial esterified product of fatty acid and polyhydric alcohol such as behenic acid monoglyceride; Hydroxyl group obtained by hydrogenating vegetable oil Examples include methyl ester compounds That.
[0176]
In addition, these waxes have a sharp molecular weight distribution using a press sweating method, a solvent method, a recrystallization method, a vacuum distillation method, a supercritical gas extraction method or a melt liquid crystal deposition method, a low molecular weight solid fatty acid, a low molecular weight A solid alcohol, a low molecular weight solid compound, and other impurities are preferably used.
[0177]
Magnetic iron oxide may be used as the colorant of the developer according to the present invention, in which case it can be used as a magnetic developer, and as the magnetic iron oxide, iron oxide such as magnetite, maghemite, and ferrite is used. Those containing non-ferrous elements on or inside the magnetic iron oxide are preferred.
[0178]
When a magnetic developer is applied to the image forming method of the present invention, the magnetic iron oxide used therein preferably contains 0.05 to 10% by mass of a different element based on the iron element. Especially preferably, it is 0.1-5 mass%.
[0179]
Moreover, it is preferable that these magnetic iron oxides contain 20-200 mass parts with respect to 100 mass parts of binder resin. More preferably, 50 to 120 parts by mass are contained.
[0180]
The different element is preferably an element selected from magnesium, aluminum, silicon, phosphorus, and sulfur. The following lithium, beryllium, boron, germanium, titanium, zirconium, tin, lead, zinc, calcium, barium, scandium, vanadium, chromium, manganese, cobalt, copper, nickel, gallium, cadmium, indium, silver element, Examples of the metal include palladium, gold, mercury, platinum, tungsten, molybdenum, niobium, osmium, strontium, yttrium, and technetium.
[0181]
These magnetic iron oxides preferably have a number average particle diameter of 0.05 to 1.0 μm, more preferably 0.1 to 0.5 μm. Magnetic iron oxide has a BET specific surface area of 2-40m ² / G (more preferably 4 to 20 m ² / G) is preferably used. There is no restriction | limiting in particular in a shape, The thing of arbitrary shapes is used. As magnetic characteristics, saturation magnetization is 10 to 200 Am under a magnetic field of 795.8 kA / m. ² / Kg (more preferably 70-100 Am ² / Kg), residual magnetization 1-100 Am ² / Kg (more preferably 2-20 Am ² / Kg) and a coercive force of 1 to 30 kA / m (more preferably 2 to 15 kA / m) are preferably used.
[0182]
When a magnetic developer is used in the image forming method of the present invention, the density of the magnetic developer is 1.3 to 2.2 g / cm. ³ It is desirable that Furthermore, 1.5 to 2.0 g / cm ³ It is preferable to be in the range. The mass (density) of the magnetic developer has a correlation with the magnetic force acting on the magnetic toner particles, the electrostatic force, and the action of gravity. When the density of the magnetic developer is within this range, the action of magnetic iron oxide is appropriate. The balance between charging and magnetic force is good, and excellent developing power can be exhibited.
[0183]
The density of the magnetic developer is 1.3 g / cm. ³ If it is less than 1, the action of magnetic iron oxide on the magnetic toner particles is weak, so the magnetic force is low. For this reason, the electrostatic force for flying to the photosensitive member at the time of development is superior, resulting in an excessive development state, leading to fogging and an increase in consumption. Conversely, the magnetic developer density is 2.2 g / cm. ³ If it is super, the magnetic iron oxide has a strong action on the magnetic toner particles and the magnetic force is superior to the electrostatic force. The strong magnetic force action is large and the specific gravity is heavy. Insufficient state leads to low image density and image degradation.
[0184]
The magnetic iron oxide may be treated with a silane coupling agent, a titanium coupling agent, titanate, aminosilane, or the like depending on circumstances.
[0185]
The developer preferably contains a charge control agent.
[0186]
The following compounds can be cited as examples of controlling the developer to be negatively charged.
[0187]
Organic metal complexes and chelate compounds are effective, and examples include monoazo metal complexes, acetylacetone metal complexes, aromatic hydroxycarboxylic acids, and aromatic dicarboxylic acid metal complexes. Others include aromatic hydroxycarboxylic acids, aromatic mono- and polycarboxylic acids and their metal salts, anhydrides, esters, and phenol derivatives of bisphenol.
[0188]
Among these, an azo metal complex represented by the following formula (I) is preferable.
[0189]
[Formula 4]

[0190]
[In the formula, M represents a coordination center metal, and examples thereof include Sc, Ti, V, Cr, Co, Ni, Mn, and Fe. Ar is an aryl group, which is an aryl group such as a phenyl group or a naphthyl group, and may have a substituent. In this case, examples of the substituent include a nitro group, a halogen group, a carboxyl group, an anilide group, an alkyl group having 1 to 18 carbon atoms, and an alkoxy group having 1 to 18 carbon atoms. X, X ′, Y and Y ′ are —O—, —CO—, —NH—, —NR— (R is an alkyl group having 1 to 4 carbon atoms). C ⁺ Represents a counter ion, and represents hydrogen, sodium, potassium, ammonium, aliphatic ammonium, or a mixed ion thereof. ]
In particular, Fe or Cr is preferred as the central metal, halogen, alkyl group or anilide group is preferred as the substituent, and hydrogen, alkali metal, ammonium or aliphatic ammonium is preferred as the counter ion. A mixture of complex salts having different counter ions is also preferably used.
[0191]
The following compounds are used to control the developer to be positively charged.
[0192]
Nigrosine modified products such as nigrosine and fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylammonium tetrafluoroborate, and analogs such as phosphonium salts Onium salts and lake pigments thereof; triphenylmethane dyes and lake pigments thereof (as rake agents, phosphotungstic acid, phosphomolybdic acid, phosphotungsten molybdic acid, tannic acid, lauric acid, gallic acid, ferricyanide, Ferrocyanide, etc.); metal salt of higher fatty acid; diorganotin oxide such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide; dibutyltin borate, dioctyltin borate, di Black hexyl scan such diorgano tin borate such tin borate; guanidine compounds; imidazole compounds. These can be used alone or in combination of two or more. Among these, triphenylmethane compounds and quaternary ammonium salts whose counter ions are not halogen are preferably used. The following formula (II)
[0193]
[Chemical formula 5]

[0194]
[In the formula, R ₁ Is H or CH ₃ R ₂ And R ₃ Represents a substituted or unsubstituted alkyl group (preferably C1-C4)]
A copolymer with a polymerizable monomer such as styrene, acrylic acid ester or methacrylic acid ester described above can be used as a positive charge control agent. In this case, the homopolymer and copolymer have a function as a charge control agent and a function as a binder resin (all or a part thereof).
[0195]
As a method of adding the charge control agent to the developer, there are a method of adding the toner inside the toner particles and a method of adding it externally. The amount of these charge control agents used is determined by the toner production method including the type of binder resin, the presence or absence of other additives, and the dispersion method, and is not uniquely limited. Preferably, it is used in the range of 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the binder resin.
[0196]
As a method for producing the developer, after sufficiently mixing the constituent materials of the developer as described above with a ball mill or other mixer, the mixture is thoroughly kneaded using a heat kneader such as a hot roll kneader or an extruder, and solidified by cooling. Thereafter, a method of obtaining toner by mechanically pulverizing and classifying the pulverized powder is preferable. In addition, a polymerization method in which a predetermined material is mixed with a monomer that constitutes the binder resin to obtain an emulsion suspension, followed by polymerization to obtain a toner; a so-called microcapsule toner comprising a core material and a shell material In which a predetermined material is contained in the core material, the shell material, or both of them; and a method of obtaining the toner by dispersing the constituent materials in the binder resin solution and then spray-drying. Further, if necessary, a desired additive and toner can be sufficiently mixed by a mixer to use the various methods described above to produce a developer.
[0197]
For example, as a mixer, Henschel mixer (Mitsui Mining Co., Ltd.); Super mixer (Kawata Co., Ltd.); Ribocorn (Okawara Seisakusho Co., Ltd.); Nauter mixer, Turbulizer, Cyclomix (Hosokawa Micron Co., Ltd.); Spiral pin mixer (Pacific Kiko Co., Ltd.); Ladige mixer (Matsubo Co., Ltd.), and KRC kneader (Kurimoto Iron Works Co.); Bus Co Kneader (Buss Co.); TEM type extruder (Manufactured by Toshiba Machine Co., Ltd.); TEX twin-screw kneader (manufactured by Nippon Steel Works); PCM kneader (manufactured by Ikegai Iron Works Co., Ltd.); three roll mill, mixing roll mill, kneader (manufactured by Inoue Seisakusho Co., Ltd.); Mining company); MS pressure kneader, Nider Ruder (Moriyama Seisakusho); Banbury mixer (Kobe Steel) As a pulverizer, a counter jet mill, a micron jet, an inomizer (manufactured by Hosokawa Micron Co.); an IDS type mill, a PJM jet pulverizer (manufactured by Nippon Pneumatic Industry Co., Ltd.); a cross jet mill (manufactured by Kurimoto Iron Works Co., Ltd.); ULMAX (manufactured by Nisso Engineering Co., Ltd.); SK Jet O Mill (manufactured by Seishin Enterprise Co., Ltd.); Kryptron (manufactured by Kawasaki Heavy Industries Co., Ltd.); turbo mill (manufactured by Turbo Kogyo Co., Ltd.). , Micron Classifier, Spedick Classifier (manufactured by Seishin Enterprise Co., Ltd.); Turbo Classifier (Nisshin Engineering Co., Ltd.); Micron Separator, Turboplex (ATP), TSP Separator (manufactured by Hosokawa Micron Corporation); ), Disper Separator separator (manufactured by Nippon Pneumatic Industrial Co., Ltd.); YM micro cut (manufactured by Yaskawa Shoji Co., Ltd.), and as a sieving device used for sieving coarse particles, Ultrasonic (manufactured by Sakae Sangyo Co., Ltd.); Gyroshifter (manufactured by Deoksugaku Kosakusha); Vibrasonic system (manufactured by Dalton); Soniclean (manufactured by Shinto Kogyo); Turbo screener (manufactured by Turbo Kogyo); Micro shifter (manufactured by Hadano Sangyo); Circular vibration A sieve etc. are mentioned.
[0198]
(Example)
Hereinafter, a charging device, a process cartridge, and an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.
[0199]
FIG. 1 shows a schematic configuration of an image forming apparatus using the image forming method of the present invention. This image forming apparatus 100 is a laser beam printer of a direct injection charging system and a toner recycling process (cleanerless system) using a transfer type electrophotographic process.
[0200]
(1) Overall configuration of image forming apparatus 100
The image forming apparatus 100 includes a rotating drum type negative-polarity OPC photosensitive member (negative photosensitive member; hereinafter referred to as “photosensitive drum”) 1 as a photosensitive member. The photosensitive drum 1 is rotationally driven at a constant speed in the clockwise direction indicated by an arrow in the drawing. The photosensitive drum 1 will be described in detail in another section.
[0201]
The image forming apparatus 100 includes a charging device 2A including a charging roller 2 that is a particle charging type (powder coating type) contact charging member according to the present invention and a charging bias application power source S1 for the charging roller 2. Yes.
[0202]
The charging roller 2 includes a metal core 2a and a rubber or foam elastic / medium resistance layer (hereinafter referred to as "elastic layer") 2b formed concentrically on the outer periphery of the metal core 2a. Further, the conductive particles m are supported on the outer peripheral surface of the elastic layer 2b. In this embodiment, the outer diameter of the roller is 18 mm and the core diameter is 6 mm. The charging roller 2 is pressed and brought into contact with the photosensitive drum 1 with a predetermined penetration amount to form a charging contact portion (charging nip portion) n having a predetermined width. The conductive particles m carried on the charging roller 2 come into contact with the surface of the photosensitive drum 1 at the charging nip n. The contact condition of the charging roller will be described in detail in another section.
[0203]
The charging roller 2 is rotationally driven in the clockwise direction indicated by the arrow in the same figure as the photosensitive drum 1 and rotates in the opposite direction (counter) to the rotational direction of the photosensitive drum 1 in the charging nip n, via the conductive particles m. It contacts the surface of the photosensitive drum 1 with a speed difference. In this embodiment, the photosensitive drum 1 and the charging roller 2 are rotationally driven at a constant speed (circumferential speed) in opposite directions at the charging nip n. In this embodiment, the charging roller 2 and the photosensitive drum 1 are rotationally driven at a peripheral speed of 70% with the peripheral speed of the photosensitive drum 1 being 100%. The peripheral speed will be described in detail in another section.
[0204]
When the image forming apparatus 100 forms an image, a predetermined charging bias voltage is applied to the cored bar 2a of the charging roller 2 from the charging bias application power source S1. As a result, the peripheral surface of the photosensitive drum 1 is uniformly contact-charged to a predetermined polarity and potential by the direct injection charging method. In this embodiment, a charging bias of -640 V is applied to the cored bar 2a of the charging roller 2 from the charging bias application power source S1, and a charging potential (-620 V) substantially equal to the applied charging bias is obtained on the surface of the photosensitive drum 1. .
[0205]
The conductive particles m applied to the outer peripheral surface of the charging roller 2 are attached to the surface of the photosensitive drum 1 along with the charging of the photosensitive drum 1 by the charging roller 2 and are carried away. A part is transferred to the transfer material P. Accordingly, a means for supplying conductive particles to the charging roller 2 is necessary to compensate for this. As will be described later, in this embodiment, the developing device 4 functions as a means for supplying the conductive particles m.
[0206]
The image forming apparatus 100 includes a laser beam scanner 3 including a laser diode, a polygon mirror, and the like as an exposure apparatus (optical system) that performs image exposure. The laser beam scanner 3 outputs a laser beam L whose intensity is modulated in accordance with a time-series electric digital pixel signal of target image information, and scans and exposes the uniformly charged surface of the photosensitive drum 1 with the laser beam L. . By this scanning exposure, an electrostatic latent image corresponding to target image information is formed on the surface of the photosensitive drum 1.
[0207]
The electrostatic latent image formed on the photosensitive drum 1 is then developed by the developing device 4. In this embodiment, the developing device 4 is a reversal developing device using a negatively chargeable one-component magnetic developer. In the developing container (developing device main body) 4e of the developing device 4, as will be described in detail later, a mixture t + m of toner t (including inorganic fine powder) as a developer and conductive particles m is accommodated. .
[0208]
The developing device 4 includes a developing roller 4a configured as a non-magnetic rotating developing sleeve including a magnet roll 4b as a developer carrying member. The toner t in the mixture t + m provided in the developing container 4e is subjected to layer thickness regulation and charge application by the developing blade 4e which is a developer layer thickness regulating member in the process of being conveyed on the developing roller 4a. Further, the developing device 4 includes a stirring member 4d that circulates the mixed agent t + m in the developing container 4e and sequentially conveys the mixed agent t + m to the periphery of the developing roller 4a.
[0209]
The toner t coated on the developing roller 4a is transported to a developing site (developing area) a which is a facing portion between the photosensitive drum 1 and the developing roller 4a by the rotation of the developing roller 4a. A developing bias voltage is applied to the developing roller 4a from a developing bias applying power source S2. In this embodiment, the developing bias voltage is a superimposed voltage of a DC voltage and an AC voltage. As a result, the electrostatic latent image formed on the photosensitive drum 1 is reversely developed with the toner t.
[0210]
FIG. 2 shows the relationship of potentials for supplying the conductive particles m from the developing roller 4a to the photosensitive drum 1. For example, when an AC voltage of 1.2 kV is superimposed on a DC voltage Vdc = −400 V as a developing bias to the developing roller 4a, the positive conductive particles m detached from the toner t have a non-image portion (exposure dark portion) potential. With respect to VD (−620 V), the AC voltage Vmin causes the image to fly from the developing roller 4 a to the photosensitive drum 1 with a contrast of 820 V (| Vmin−VD | = | 200 − (− 620) |).
[0211]
Some of the conductive particles m adhere to the toner t, and the image portion (exposed bright portion) potential VL on the photosensitive drum 1 is 900 V (| VL−Vmax | = | −) by the AC voltage Vmax. 100 − (− 1000) |) with the contrast of the developing roller 4a to the photosensitive drum 1. In this way, the conductive particles m are supplied from the developing roller 4a to the photosensitive drum 1.
[0212]
The toner image formed on the photosensitive drum 1 is then transferred to a transfer material P as a recording material by a medium resistance transfer roller 6 as a contact transfer means. The transfer roller 6 is pressed against the photosensitive drum 1 with a predetermined pressing force to form a transfer nip portion b. The transfer material P is fed to the transfer nip b from a paper feed unit (not shown) at a predetermined timing, and a predetermined transfer bias voltage is applied to the transfer roller 6 from the transfer bias application power source S3. Then, the toner image formed on the photosensitive drum 1 is sequentially transferred onto the surface of the transfer material P fed to the transfer nip portion b.
[0213]
The transfer roller 6 used in this example has a roller resistance value of 5 × 10, in which a medium resistance firing layer 6b is formed on a cored bar 6a. ⁸ The transfer was carried out by applying a voltage of +2.0 kV to the cored bar 6a. The transfer material P introduced into the transfer nip portion b is nipped and conveyed by the transfer nip portion b, and the toner image formed and supported on the surface of the photosensitive drum 1 on the surface side is sequentially subjected to electrostatic force and pressing force. Will be transcribed.
[0214]
The transfer material P, which is fed to the transfer nip b and receives the transfer of the toner image from the photosensitive drum 1, is separated from the surface of the photosensitive drum 1 and introduced into the fixing device 7 which is a heat fixing system in this embodiment. Then, after the toner image is fixed, it is discharged out of the apparatus as an image formed product (print, copy).
[0215]
The photosensitive drum 1 is again charged by the charging roller 2 and repeatedly used for image formation.
[0216]
In this embodiment, the conductive particles m are added to the toner t of the developing device 4, and adhere to the surface of the photosensitive drum 1 together with the toner t when developing the electrostatic latent image on the photosensitive drum 1. Is carried to the charging nip n. That is, the conductive particles m are supplied to the charging roller 2 through the photosensitive drum 1.
[0217]
That is, the image forming apparatus 100 of the present embodiment employs a toner recycling process, and the transfer residual toner t remaining on the surface of the photosensitive drum 1 after image transfer is removed by a dedicated cleaning device (cleaner). Instead, it is carried to the charging nip n with the rotation of the photosensitive drum 1 and is temporarily collected by the charging roller 2 that counter-rotates with respect to the rotation of the photosensitive drum 1 at the charging nip n. Then, as the toner t circulates around the outer periphery of the charging roller 2, the inverted toner charge is normalized (in this embodiment, negative polarity) and sequentially discharged onto the photosensitive drum 1. The toner t reaches the development site a as the photosensitive drum 1 rotates, and is collected and reused by the development device 4 in the simultaneous development cleaning. That is, at the time of development after the next step, that is, when the photosensitive drum 1 is continuously charged by the charging roller 2 and exposed to form a latent image, and this latent image is developed, the fog removal bias (direct current applied to the developing device). It is recovered by a fog removal potential difference Vback, which is a potential difference between the voltage and the surface potential of the photoreceptor. In the case of the reversal development method as in this embodiment, this simultaneous development cleaning is performed by using an electric field for collecting toner from the dark portion potential of the photosensitive drum 1 to the developing roller 4a and from the developing roller 4a to the bright portion potential of the photosensitive drum 1. It is made by the action of an electric field that adheres.
[0218]
(2) Photosensitive drum 1
The photosensitive drum 1 will be described in more detail. FIG. 3 is a schematic diagram of the layer structure of the photosensitive drum 1. 3A is a schematic diagram of the layer structure of the photosensitive drum 1a with a charge injection layer, and FIG. 3B is a schematic diagram of the layer structure of the photosensitive drum 1b without the charge injection layer.
[0219]
The photosensitive drum 1b without the charge injection layer shown in FIG. 3B is coated on an aluminum drum base (Al drum base) 11 in the order of an undercoat layer 12, a charge generation layer 13, and a charge transport layer. It is a common organic photosensitive drum.
[0220]
The photosensitive drum 1a with a charge injection layer shown in FIG. 3A is obtained by further improving the charging performance by further applying a charge injection layer 15 to the photosensitive drum 1b shown in FIG. 3B. .
[0221]
As will be described later, the charge injection layer 15 in this example is formed by adding conductive particles (conductive filler, for example, SnO having a particle size of about 0.03 μm) to a curable phenol resin as a binder. ₂ Ultrafine particles) 15a, a polymerization initiator and the like are mixed and dispersed, and after coating, a film is formed by a photocuring method.
[0222]
In addition, by including a lubricant such as tetrafluoroethylene resin, the surface energy of the surface of the photosensitive drum 1 is suppressed, and the adhesion of the conductive particles m is generally suppressed. The surface energy is preferably 85 degrees or more, and more preferably 90 degrees or more, when expressed by the contact angle of water.
[0223]
Further, the resistance of the surface layer is an important factor from the viewpoint of charging performance. In the direct injection charging method, it is considered that the area of the photosensitive member surface that can be charged per one injection point (contact point) is widened by reducing the resistance on the photosensitive member side. Accordingly, even when the charging roller 2 is in the same contact state, if the resistance on the surface of the photoreceptor is low, it is possible to efficiently transfer and receive charges. On the other hand, since the electrostatic latent image needs to be held for a certain time as the photoconductor, the volume resistance value of the charge injection layer 15 is 1 × 10. ⁹ ~ 1x10 ¹⁴ A range of (Ω · cm) is appropriate.
[0224]
(3) Charging roller 2
The charging roller 2 used in this embodiment has the following characteristics.
[0225]
(3) -1 Surface structure and roughness characteristics
The charging roller 2 used as the contact charging member in this embodiment is required to have a certain degree of roughness because it is necessary to carry the conductive particles m at a high density. The average roughness Ra is preferably 1 μm to 500 μm. Furthermore, 15 μm to 150 μm is optimal for optimizing the amount of particles retained and bringing them into close contact with the drum surface to stabilize charging uniformity.
[0226]
For example, when an insulator such as a developer adheres to the surface of the charging roller 2, the periphery thereof floats and cannot contact the photosensitive drum 1, and the charging performance is deteriorated. In order to reduce the harmful effects of foreign substances mixed in the developer, Ra larger than the mass average particle diameter of the developer to be used is preferable.
[0227]
On the contrary, when the average roughness Ra is larger than 500 μm, the unevenness on the surface of the charging roller 2 decreases the charging uniformity in the surface of the image carrier.
[0228]
The average roughness Ra was measured using a surface shape measuring microscope VF-7500, VF7510 manufactured by Keyence Corporation, and an objective lens having a magnification of 250 to 1250 times. Then, the shape of the surface of the charging roller 2 and Ra were measured without contact.
[0229]
(3) -2 Resistance characteristics
In the direct injection charging method, charging by a low voltage is possible, so that the surface layer of the contact charging member does not need to have a high resistance, and the charging roller 2 can be configured as a single layer.
[0230]
For volume resistance, 10 ⁴ -10 ⁷ A range of Ω is preferable. 10 ⁴ If it is smaller than Ω, a voltage drop of the power supply due to pinhole leakage tends to occur. Meanwhile, 10 ⁷ If it is larger than Ω, the current required for charging cannot be secured, and the charging voltage decreases.
[0231]
(3) -3 Material, structure and dimensions of charging roller
Examples of the material of the elastic layer 2b of the charging roller 2 include EPDM, urethane, NBR, silicone rubber, and a rubber material in which a conductive substance such as carbon black and metal oxide for resistance adjustment is dispersed in IR. It is also possible to adjust the resistance by using an ion conductive material without dispersing the conductive substance. Thereafter, molding is performed by adjusting the surface roughness, polishing, or the like, if necessary. Moreover, the structure by the function-separated multiple layer is also possible.
[0232]
However, the form of the elastic layer 2b of the charging roller 2 is preferably a porous structure as described above. This is also advantageous in terms of manufacturing in that the aforementioned surface roughness can be obtained simultaneously with the molding of the roller. The cell diameter of the foam is suitably 1 to 500 μm. Furthermore, 30-300 micrometers is desirable. After foam molding, the surface of the porous body is exposed by polishing the surface, and a surface structure having the above-mentioned roughness can be produced.
[0233]
(3) -4 Other roller characteristics
In the direct injection charging method, it is important that the contact charging member functions as a flexible electrode. In the present embodiment, this is achieved by adjusting the elastic characteristics of the elastic layer 2 b of the charging roller 2. The Asker C hardness is preferably 50 degrees or less, more preferably 5 to 40 degrees. Below 4 degrees, the set may get worse. On the other hand, if it exceeds 50 degrees, it is difficult to secure an appropriate nip width, and the chargeability may be lowered.
[0234]
If the hardness is too high, the necessary penetration amount cannot be obtained unless the applied pressure is increased, and the charging nip n cannot be secured between the image carrier and the charging performance is deteriorated.
[0235]
On the other hand, if the hardness is too low, the shape is not stable, so that the contact pressure with the image carrier is uneven and charging unevenness occurs. Alternatively, charging failure occurs due to permanent deformation of the charging roller 2 due to long-term standing.
[0236]
(3) -5 roller contact structure with drum
FIG. 5 shows a contact structure between the charging roller 2 and the photosensitive drum 1. (A) is a side view, (b) is a front view with a part omitted.
[0237]
The charging roller 2 is arranged such that the cores 2a at both ends of the cored bar 2a are rotatably supported by the fork-shaped bearings 2d and arranged in parallel with the photosensitive drum 1, and the fork-shaped bearings 2d on both sides are respectively pressed springs. By pressing in the direction of the photosensitive drum by 2e, the state is held in pressure contact with the photosensitive drum 1.
[0238]
The amount of penetration of the charging roller 2 into the photosensitive drum 1 is determined by the relationship between the pressure of the pressure spring and the hardness of the charging roller when the diameters of the photosensitive drum and the charging roller are fixed, and a charging contact portion n having a predetermined width is formed. The The fork-like bearings 2d at both ends are respectively fitted in guide grooves provided in a device side plate (not shown) and are slidable in the direction of the photosensitive drum 1. G is a drive gear fixed to one end side of the cored bar 2a of the charging roller 2, and a rotational force is transmitted to the drive gear G from a drive system (not shown) to drive the charging roller 2 to rotate.
[0239]
(4) Amount of conductive particles supported
The charging performance is improved by strictly controlling the surface roughness of the charging member and the amount of penetration into the photoreceptor, and D90 of the conductive particles m, more preferably D10, D50, and BET. Since it is used, the dropout to the photosensitive drum 1 becomes remarkable. Since the force capable of holding the conductive particles m on the charging roller 2 is weak adhesion force, it is difficult to restrain the particles even if many particles are supplied. In the development process and the transfer process onto the transfer material P, an image defect is affected. Therefore, ideally, it is desirable that the surface layer of the charging roller 2 be uniformly applied. However, in practice, by adjusting the loading amount, it is possible to ensure the charging property and reduce the adhering particles at a level that is not harmful.
[0240]
The carrying amount of the conductive particles m needs to be appropriately maintained by the average roughness Ra of the surface of the charging roller 2. That is, the value obtained by dividing the carrying amount by the average roughness Ra (hereinafter simply referred to as “carrying amount / Ra”) is 1 mg / cm. ² / Μm or less, more preferably 0.3 mg / cm ² Good results can be obtained when the thickness is not more than / μm.
[0241]
(Particle loading and resistance measurement)
The particles carried on the charging roller 2 were washed, and the weight and resistance of the particles were measured. A cleaning liquid composed of ethanol and water (1: 2) was prepared in an ultrasonic cleaning machine, and the charging roller 2 was immersed therein to perform cleaning. The deposit on the charging roller 2 is removed by repeatedly cleaning the surface of the charging roller 2 with an optical microscope or the like, and if necessary, while washing the surface of the charging roller 2 with a blade or the like. Can do.
[0242]
The obtained washing liquid is allowed to stand for 1 to 2 hours, and when it can be clearly separated from the supernatant, the supernatant is removed. Thereafter, it was sufficiently dried at 105 ° C. to extract the support on the charging roller 2.
[0243]
The particle resistance is measured according to the method described above.
[0244]
The carrying amount is obtained as a carrying amount per unit area from the total weight of the obtained particles and the surface area of the charging roller 8 (calculated from the longitudinal length and outer diameter of the charging roller 8).
[0245]
(5) Conductive particle coverage
Furthermore, in order to grasp the effective abundance in charging of the conductive particles m, it is further important to adjust the coverage of the conductive particles m. If the conductive particles m are close to white, it can be distinguished from a normal toner color. In observation with a microscope, a white area is obtained as an area ratio. When the coverage is 0.1 or less, the charging performance is insufficient even if the peripheral speed of the charging roller 2 is increased. Therefore, the coverage of the conductive particles m can be kept in the range of 0.2 to 1. It becomes important.
[0246]
The adjustment of the carrying amount can be basically performed by adjusting the addition amount of the conductive particles m to the toner t.
[0247]
(Measurement of coverage)
Regarding the measurement of the coverage, the area covered by the conductive particles m was measured by observing under a microscope close to the contact condition of the charging roller 2. Specifically, the rotation of the photosensitive drum 1 and the charging roller 2 is stopped in a state where no charging bias is applied, and the surfaces of the photosensitive drum 1 and the charging roller 2 are video microscope (OLYMPUS OVM1000N) and digital still recorder (made by DELTS). SR-3100). As for the charging roller 2, the charging roller 2 is brought into contact with the slide glass under the same conditions as in contact with the photosensitive drum 1, and the contact surface is photographed with a 1000 × objective lens from the back surface of the slide glass with a video microscope. . Then, the area | region coat | covered with particle | grains was isolate | separated with the color or brightness | luminance of the electroconductive particle m measured in advance, and the area rate was calculated | required and it was set as the coverage rate. In addition, when it was difficult to distinguish by color, the material on the outermost surface of the charging roller 2 was measured with a fluorescent X-ray analyzer SYSTEM 3080 (manufactured by Rigaku Corporation). First, an adhesive surface of a polyester tape (Nichiban No. 550 (# 25)) is sandwiched between the charging roller 2 covered with the conductive particles m and the photosensitive drum 1 in the initial state, and the photosensitive roller 1 is exposed. The drum 1 and the charging roller 2 are driven to rotate to pass once through the charging nip n between the charging roller 2 and the photosensitive drum 1. At this time, particles on the outermost surface of the charging roller 2 are further sampled on the tape surface. On the other hand, the charging roller 2 that has finished the printing test is similarly sampled. About a specific element contained in the electroconductive particle m, a coverage can be calculated | required by quantifying content. That is, assuming that the content of the tape sample of the charging roller 2 in the initial state carrying only the conductive particles m is 1, the ratio of the content of the sample after the printing test is calculated, and the coverage can be obtained from the ratio. Become.
[0248]
Hereinafter, a developer, a photoreceptor, a charging member manufacturing example, a transfer member, and a developing device according to the present invention will be described, and the present invention will be specifically described by way of examples. However, this is not intended to limit the present invention. is not. In addition, all the parts in the following mixing | blending are a mass part.
[0249]
[Production Example 1 of Conductive Particles]
A hydrochloric acid aqueous solution having a pH of about 1 in which tin chloride and antimony chloride are mixed and dissolved so that the molar ratio of tin and antimony is 100: 7 is brought to 80 ° C., and an aqueous sodium hydroxide solution is added thereto to form a coprecipitate. Then, filtration and washing were performed to obtain a slurry of conductive fine particles. The obtained slurry was dried and crushed, then calcined at 500 ° C. for 3 hours, and crushed again to obtain conductive particles 1. The physical properties of the obtained conductive particles 1 are as follows: specific surface area 16 × 10 ⁵ cm ² / Cm ³ Volume resistance 6 × 10 ¹ Ωcm, D ₅₀ = 1.9 μm, D ₉₀ = 3.6 μm, D ₁₀ = 0.7 μm, and the tin oxide content was 93% by mass.
[0250]

The above compound was melt-kneaded with a biaxial extruder heated to 130 ° C., and the cooled kneaded product was ground by a hammer mill. The pulverization was performed by mechanical pulverization using a turbo mill (manufactured by Turbo Kogyo Co., Ltd.). The resulting finely pulverized product was subjected to strict classification and removal of ultrafine powder and coarse powder with a multi-division classifier (Elbow Jet Classifier manufactured by Nittetsu Mining Co., Ltd.) using the Coanda effect to obtain black powder 1. The obtained black powder 1 had a weight average diameter of 7.8 μm.
[0251]
next,
・ 100 parts by mass of the above black powder 1
-Hydrophobic silica with a primary particle size of 8 nm
(B hydrophobized with dimethyl silicone oil and hexamethyldisilazane, B
ET100m ² / G) 1.0 parts by weight
・ Conductive particles 1 0.4 parts by mass
The above materials were mixed for 180 seconds with a Henschel mixer FM10C / l (manufactured by Mitsui Mining Co., Ltd.) to obtain developer 1. The obtained developer 1 had a jetability index of 86.
[0252]
[Photoconductor Production Example 1]
An aluminum cylinder having a diameter of 24 mm × 260.5 mm was used as a support, and a methanol solution of polyamide resin was applied thereon by a dipping method to provide an undercoat layer having a thickness of 0.5 μm.
[0253]
4 parts of oxytitanium phthalocyanine pigment, 2 parts of polyvinyl butyral resin and 80 parts of cyclohexanone were dispersed in a sand mill apparatus for about 4 hours. This dispersion was applied onto the undercoat layer to form a 0.2 μm charge generation layer.
[0254]
Next, 10 parts of a triphenylamine compound and 10 parts of a polycarbonate resin were dissolved in 100 parts of monochlorobenzene. This solution was applied onto the charge generation layer and dried with hot air to form a charge transport layer having a thickness of 20 μm.
[0255]
Next, as a charge injection layer, 50 parts of antimony-doped tin oxide fine particles surface-treated with silicone oil were dispersed in 150 parts of ethanol, and further 20 parts of polytetrafluoroethylene fine particles were added and dispersed. Thereafter, 150 parts of a resole thermosetting phenol resin was dissolved as a resin component to prepare a preparation solution.
[0256]
Using this prepared solution, a film was formed on the previous charge transport layer by a dip coating method, followed by drying with hot air to form a charge injection layer, whereby a photoreceptor 1 was obtained. At this time, the film thickness of the charge injection layer of the photosensitive member 1 is measured using an instantaneous multi-photometry system MCPD-2000 (manufactured by Otsuka Electronics Co., Ltd.) due to light interference because of the thin film, and the film thickness is 2 μm. there were. As another method for measuring the film thickness, the cross section of the film of the photoreceptor can be directly observed and measured with an SEM or the like.
[0257]
[Production Example 1 of Charging Member]
A SUS roller with a diameter of 6 mm and a length of 264 mm is used as a core, and a medium-resistance foamed urethane layer is formed on the core as a roller. Further, the charged member 1 having a diameter of 18 mm and a length of 220 mm was produced as a flexible member by cutting and polishing to adjust the shape and surface properties.
[0258]
The obtained charging member 1 has a resistance value of 10 ⁵ The hardness was Ωcm and the hardness was 22 degrees in Asker C hardness. The cell diameter was 150 μm and the surface roughness Ra was 50 μm.
[0259]
<Example 1>
FIG. 1 shows an overall schematic configuration of the image forming apparatus of this example. As described above, FIG. 1 shows a laser printer (recording apparatus) of a simultaneous development cleaning process (cleanerless system) using a transfer type electrophotographic process. It has a process cartridge from which a cleaning means such as a cleaning blade has been removed, a developer 1 is used as a developer, and the toner layer on the developer carrier and the image carrier are placed in non-contact with each other. The non-contact development method is used.
[0260]
The photosensitive member 1 as an image carrier is a rotating drum type OPC photosensitive member, and is driven to rotate in the direction of an arrow at a peripheral speed (process speed) of 94 mm / sec.
[0261]
As the charging member, the charging member 1 obtained in the charging member production example 1 is used as the charging roller 2, and as shown in the figure, the charging roller 2 resists elasticity against the photoreceptor 1 with a predetermined pressure. They are placed in pressure contact with each other. Reference numeral n denotes a charging contact portion which is a contact portion between the photosensitive member 1 and the charging roller 2. In this embodiment, a spring pressure of 500 to 1000 g and a pressure of f = 2.25 to 4.5 g / mm per unit longitudinal length of the charging roller were suitable. When the charging roller had a hardness of 15 to 40 °, the nip width could be set to about 2 to 4 mm.
[0262]
In this example, the charging roller 2 is rotationally driven at a peripheral speed of 60% in the opposite direction (arrow direction) at the charging contact portion n which is a contact surface with the photoreceptor 1. The surface of the charging roller 2 has a relative speed difference of 160% relative to the surface of the photoreceptor 1. In this embodiment, the amount of the conductive particles m supported is about 2 mg / cm. ² Ra is 40 μm, and the supported amount / Ra is 0.05 mg / cm. ² / Μm.
[0263]
Further, a DC voltage of −640 V is applied as a charging bias to the cored bar 2a of the charging roller 2 from the charging bias application power source S1. In this example, the surface of the photoreceptor 1 is uniformly charged by a direct injection charging method to a potential (−620 V) substantially equal to the voltage applied to the charging roller 2.
[0264]
A laser beam scanner (exposure device) 3 including a laser diode, a polygon mirror, etc., which is an exposure means, outputs a laser beam L whose intensity is modulated in accordance with a time-series electrical digital pixel signal of target image information, and the laser The uniformly charged surface of the photoreceptor 1 is scanned and exposed with the light L. By this scanning exposure, an electrostatic latent image corresponding to target image information is formed on the surface of the rotating photosensitive member 1. The electrostatic latent image on the surface of the photoreceptor 1 is developed as a toner image by the developing device 4 as a developing unit.
[0265]
The developing device 4 of this example is a non-contact type reversal developing device using the developer 1 as a developer.
[0266]
As the developer carrying member, a developing sleeve 4a in which a resin layer having a layer thickness of about 7 μm and a JIS center line average roughness (Ra) of 1.0 μm having the following configuration is formed on an aluminum cylinder having a diameter of 12 mm blasted on the surface is used. Then, a magnetic roll of 80 mT (800 gauss) of development magnetic pole is included, and an elastic blade 4c made of urethane having a thickness of 1.0 mm and a free length of 1.5 mm as a developer layer thickness regulating member is 29.4 N / m (30 g / cm). ). The gap between the photoreceptor 1 and the developing sleeve 4a was 290 μm.
・ Phenolic resin 100 parts
・ Graphite (volume average particle size approx. 7μm) 90 parts
・ 10 parts of carbon black
Further, the developing sleeve 4a is 120% of the peripheral speed of the photosensitive member 1 in the rotation direction and the forward direction (arrow direction) of the photosensitive member 1 at a developing portion a (developing region portion) which is a portion facing the photosensitive member 1. Rotate at peripheral speed.
[0267]
The developing sleeve 4a is coated with a thin layer of developer by an elastic blade 4c. The layer thickness of the developer with respect to the developing sleeve 4a is regulated by the elastic blade 4c, and an electric charge is given. At this time, the amount of developer coated on the developing sleeve 4a is 16 g / m. ² Met.
[0268]
The developer coated on the developing sleeve 4a is conveyed to the developing portion a, which is a facing portion between the photosensitive member 1 and the developing sleeve 4a, by the rotation of the developing sleeve 4a. A developing bias voltage is applied to the sleeve 4a from a developing bias applying power source S2. The development bias voltage is a DC voltage of −440V, a frequency of 1600 Hz, a peak-to-peak voltage of 1500 V (electric field strength of 5 × 10 ⁶ V / m) rectangular alternating voltage was superimposed, and one-component jumping development was performed between the developing sleeve 4a and the photoreceptor 1 at the developing portion a.
[0269]
The transfer roller 5 having a medium resistance as a contact transfer means is brought into contact with the photosensitive member 1 with a linear pressure of 98 N / m (100 g / cm) to form a transfer contact portion b. The transfer contact portion b is fed with a transfer material P at a predetermined timing from a paper supply unit (not shown), and a predetermined transfer bias voltage is applied to the transfer roller 5 from a transfer bias application power source S3. The toner image on the body 1 side is sequentially transferred onto the surface of the transfer material P fed to the transfer contact portion b.
[0270]
In this example, the volume resistance value of the transfer roller 5 is 5 × 10. ⁸ Transferring was performed using a Ωcm one and applying a DC voltage of + 1800V. That is, the transfer material P introduced into the transfer contact portion b is nipped and conveyed by the transfer contact portion b, and the toner image formed and supported on the surface of the photosensitive member 1 on the surface side is successively subjected to electrostatic force. It is transferred by pressing force. The transfer material P that has been fed to the transfer contact portion b and has received the transfer of the toner image on the photosensitive member 1 side is separated from the surface of the photosensitive member, and is introduced into a fixing device 6 such as a heat fixing method as a fixing means. The toner image is fixed and discharged as an image formed product (print, copy) to the outside of the apparatus.
[0271]
In the image forming apparatus of this example, the cleaning means is removed, and residual toner remaining on the surface of the photoconductor 1 after the transfer of the toner image onto the transfer material P is not removed by the cleaner, and the photoconductor 1 is rotated. At the same time, it reaches the developing portion a via the charging contact portion n and is simultaneously cleaned (collected) by the developing device 4.
[0272]
Conventionally, since the toner is an insulator, the mixing of the untransferred toner into the charging contact portion n is a factor that causes a charging failure in charging the photosensitive member. However, in the present invention, the surface roughness of the charging member, the amount of penetration into the photoreceptor, and the D of the conductive particles ₉₀ Therefore, the charging roller 2 can be maintained in close contact with the photosensitive member 1 and the contact resistance can be maintained. In addition, the amount of wear of the photosensitive member can be reduced.
[0273]
In this example, 120 g of developer 1 was filled in the image forming apparatus, and 2000 sheets were printed intermittently with an image pattern consisting only of horizontal lines with a printing area ratio of 2%. 75g / m as transfer material ² A4 copy paper was used.
[0274]
[Evaluation]
The transfer efficiency is determined by taping the transfer residual toner on the photoconductor after the solid black image is transferred with a Mylar tape and pasting it on the paper. When the Macbeth concentration of the tape affixed was D, and the Macbeth concentration of Mylar tape affixed on unused paper was E, the following formula was used for approximation. If the transfer efficiency is 80% or more, the image has no practical problem.
[0275]
Transfer efficiency (%) = (DC / DE) × 100
The resolving power at the end of the durability was evaluated based on the reproducibility of a small-diameter isolated single dot at 600 dpi, which is easy to close due to the electrostatic latent image electric field and difficult to reproduce.
◎: Very good, less than 5 defects in 100
○: Good, 6 to 10 defects in 100
Δ: Practical use, 11-20 defects in 100
X: Not practical, 20 or more defects in 100
The fog on paper was measured using a REFECTMETER MODELTC-6DS manufactured by Tokyo Denshoku. A green filter was used as the filter. The fog value was calculated from the following formula using a solid white image. If the fog on paper is 2.0% or less, a good image is obtained.
[0276]
Fog (reflectance) (%) = reflectance on standard paper (%) − reflectance of sample non-image area (%)
The image density was measured with a Macbeth densitometer RD918 (manufactured by Macbeth). The initial density is the density of the 20th image.
[0277]
The chargeability was evaluated by the following images after printing 2000 sheets. The upper end (3 cm wide from the image front end) is a mixed image of a solid image and a non-image, and the image pattern having a uniform halftone from the front end of the image is a uniform halftone, that is, a ghost image that is likely to generate a charging ghost is printed. evaluated. In the halftone part, the image density of the non-image corresponding part and the image density of the solid image corresponding part developed to be darker due to poor chargeability were measured, and the difference between them was obtained. The better the chargeability, the smaller the difference between the two. Further, when the density difference between the two exceeds 0.20, the ghost image becomes remarkable, which causes a problem in practical use.
[0278]
In the experiment, a print durability test was first conducted in a low-temperature and low-humidity (15 ° C./10%) environment, but no deterioration in image quality was observed even after printing 2000 sheets.
[0279]
Next, after the end of printing 2000 sheets, the above-mentioned ghost images were continuously printed on 5 sheets, and the chargeability was evaluated on the 5th sheet. As a result, a good charging property with a ghost density difference of 0.05 was obtained.
[0280]
Thereafter, the thickness of the charge injection layer of the photoreceptor 1 was measured. The film thickness in the unused stage before printing is 2 μm, whereas the film thickness after printing 2000 sheets is 1.2 μm, and the wear amount of the photosensitive member is 2.0−1.2 = 0.8 ( μm).
[0281]
The obtained results are shown in Table 3.
[0282]
[Production Examples 2-17 of Conductive Particles]
In Production Example 1 of conductive particles, conductive particles 2 to 17 were produced by appropriately adjusting the tin chloride concentration, the molar ratio of tin and antimony, the addition rate of the sodium hydroxide aqueous solution, the firing temperature, and the firing time. Table 1 shows various physical properties of the obtained particles.
[0283]
[Production Example 18 of Metal Compound Fine Particles]
The acidic tin chloride aqueous solution was controlled at 60 to 80 ° C., and an aqueous ammonia solution was added thereto to generate a precipitate, followed by filtration and washing to obtain a slurry of conductive fine particles. The obtained slurry was dried and crushed, and then calcined at 500 ° C. for 2 hours in a nitrogen atmosphere and further at 500 ° C. for 1 hour in a nitrogen / hydrogen mixed gas atmosphere, and crushed again to obtain conductive particles 17. . The physical properties of the obtained conductive particles 17 are as follows: specific surface area 31 × 10 ⁵ cm ² / Cm ³ , Volume resistance 7 × 10 ² Ωcm, D ₅₀ = 1.2 μm, D ₉₀ = 2.6 μm, D ₁₀ = 0.7 μm, and the tin oxide content was 100% by mass.
[0284]
[Production Example 19 of Conductive Particles]
An aqueous ammonium carbonate solution and an aqueous aluminum sulfate solution were mixed, put into an aqueous solution in which zinc oxide was dispersed, stirred at 60 ° C. for 1 hour, filtered and washed with water to obtain a slurry. This slurry was dispersed in ion-exchanged water, and carbon dioxide gas was blown in for 4 hours while maintaining the temperature at 30 ° C. After standing for a while, the supernatant was discarded, and the remaining slurry was spray-dried with a spray dryer to obtain a dry powder. This powder was thermally decomposed at 250 ° C. for 5 hours to obtain conductive particles 19 composed of conductive zinc oxide fine particles.
[0285]
[Production Example 20 of Conductive Particles]
In a heating type mixer, 100 parts by mass of conductive particles 1 are stirred and mixed at 80 ° C. while spraying a solution obtained by adding 2 parts of modified silicone oil to 100 parts of ethanol. For 30 minutes. After taking out, it cooled to room temperature, crushed, and obtained the electroconductive particle 20 which gave the surface treatment.
[0286]
[Developer Production Examples 2 to 20]
Using black powder 1, developer 2-20 was produced using conductive particles 2-20 in place of conductive particles 1 in Developer Production Example 1. Table 2 shows the physical properties of the developer thus obtained.
[0287]
[Developer Production Examples 21 and 22]
In the production example 1 of the developer, the primary particle size of 50 nm primary surface treated with iso-butyltrimethoxysilane instead of hydrophobic silica, the titanium oxide of BET100, and the primary particle size surface treated with iso-butyltrimethoxysilane Developers 21 and 22 were produced using 7 nm alumina oxide of BET110. Table 2 shows the physical properties of the developer thus obtained.
[0288]
[Developer Production Example 23]
In Developer Production Example 1, developer 23 was produced using hydrophobic silica having a primary particle size of 90 nm instead of hydrophobic silica having a primary particle size of 8 nm. Table 2 shows the physical properties of the developer thus obtained.
[0289]
[Developer Production Example 24]
In Developer Production Example 1, the developer 24 was obtained by setting the mixing processing time in the Henschel mixer FM10C / 1 (made by Mitsui Mining Co., Ltd.) to 300 seconds. Table 2 shows the physical properties of the developer thus obtained.
[0290]
<Comparative Example 1>
When the toner 14 was used and evaluated under the same conditions as in Example 1, the density difference in the ghost part was 0.34, the charging property was poor, the wear amount of the photoconductor was 2 μm, and the charge injection layer disappeared.
2 x D of conductive particles ₉₀ <Surface roughness Ra of charging member
Therefore, it is considered that the chargeability and the photoreceptor wear resistance deteriorated. Transferability and fog were not good.
[0291]
<Example 2>
Evaluation was performed under the same conditions as in Example 1 except that the toner 14 was used and a charging member having a cell diameter of 120 μm and a surface roughness Ra of 40 μm was used. As a result, the density difference of the ghost part is 0.20, which is a level that can withstand practical use, and the wear amount of the photoreceptor is 1. . The charge injection layer remained at 0.2 μm at 8 μm. This is because the surface roughness Ra of the charging member is changed
2 x D of conductive particles ₉₀ <Surface roughness Ra of charging member
The level seems to have been improved.
[0292]
<Examples 3 to 23>
Evaluation was performed under the same conditions as in Example 1 using Developers 2-13 and 15-23. The results are shown in Table 3.
[0293]
<Comparative example 2>
Evaluation was performed under the same conditions as in Example 1 except that the developer 1 was used and the amount δ of penetration of the charging member into the photosensitive member was changed to 40 μm. It was bad.
Charging member surface roughness Ra ≦ δ
It is considered that the chargeability has deteriorated because the above condition is not satisfied.
[0294]
From the results of Examples 1 and 2 and Comparative Examples 1 and 2, even in the case of contact charging using a small diameter photoreceptor having a diameter of 28 mm or less,
2 x D of conductive particles ₉₀ If the surface roughness Ra of the charging member ≦ the penetration amount δ with respect to the photoconductor is set, both improvement in chargeability and reduction in wear of the photoconductor can be achieved.
[0295]
From the results of Examples 1, 5, 10, 13, and 14, D of the conductive particles to be used ₅₀ And D ₁₀ If the value is small, the image density is low and the chargeability tends to decrease. D ₅₀ Is preferably 0.4 μm or more, and more preferably 0.5 μm or more. D ₁₀ Is preferably 0.3 μm or more, and more preferably 0.4 μm or more. On the other hand, from the results of Examples 1, 2, 3, 7, 8, 9, 16, and 17, D ₅₀ And D ₉₀ If the value is large, fog tends to deteriorate and the resolution tends to decrease. ₅₀ It is understood that 4.0 is preferably 4.0 μm or less, and more preferably 3.5 μm or less. D ₉₀ It is found that the thickness is preferably 6.0 μm or less, and more preferably 4.0 μm or less.
[0296]
From the results of Examples 1, 2, 3, 4, 11, and 12, the specific surface area of the conductive particles used is 5 × 10. ⁵ cm ² / Cm ³ It can be seen that good chargeability can be maintained as described above. Preferably 10 × 10 ⁵ Or more, more preferably 12 × 10 ⁵ It can also be seen that this is the case. On the other hand, according to the results of Examples 1, 5, 6, 10, and 14, the amount of wear on the surface of the photosensitive member tends to increase as the specific surface area of the conductive particles used increases, and preferably 80 × 10. ⁵ cm ² / Cm ³ Or less, more preferably 40 × 10 ⁵ You can also see that: If the wear amount is 1.5 μm or less, it can be determined that there is a margin in durability.
[0297]
From the results of Examples 1 and 15, as the resistance of the conductive particles increases, the chargeability tends to decrease. ⁹ It can also be seen that the following is sufficient.
[0298]
From the results of Examples 1, 18, and 19, it can be seen that when the conductive particles do not contain tin oxide, the wear amount of the photosensitive member tends to increase.
[0299]
From the results of Examples 1 and 20, it can be seen that the surface treatment of the conductive particles with a silane compound gives good results in chargeability, reduction of photoreceptor wear, and good image characteristics.
[0300]
From the results of Examples 1, 23, and 24, it can be seen that the chargeability tends to decrease as the jetability index of the toner decreases, but it is good if it does not fall below 74%. It can also be seen that in order to obtain such a toner, it is not preferable to use an inorganic fine powder having an average primary particle size exceeding 90 nm as a fluidizing agent.
From the results of Examples 21 and 22, it can be seen that titanium oxide and alumina can also be used as the inorganic fine powder.
[0301]
[Table 1]

[0302]
[Table 2]

[0303]
[Table 3]

[0304]
[Developer Production Examples 25 to 28]
Black powders having an average particle diameter of 2.8 μm, 3.0 μm, 12.0 μm, and 12.5 μm were produced in the same manner as in Production Example 1 of the developer. Hydrophobic silica having a primary particle size of 8 nm was added to each black powder obtained, 2.5 parts for 2.8 μm and 3.0 μm powders, and 0 for 12.0 μm and 12.5 μm powders. 7 parts were processed to produce developer 25-28. As conductive particles, 0.4 parts of conductive particles 1 were mixed in any developer. Table 4 shows the formulation of the developer.
[0305]
<Examples 25 to 28>
Evaluation was performed under the same conditions as in Example 1 using toners 25 to 28. The results are shown in Table 5.
[0306]
From the results of Examples 25 and 26, it can be seen that as the mass average particle diameter of the toner decreases, the transferability and fogging as well as the chargeability decrease, and the photoreceptor wear increases, but the mass average particle diameter should be 3 μm or more. For example, it can be seen that the density difference in the ghost portion is suppressed to 0.20 or less.
[0307]
From the results of Examples 27 and 28, it can be seen that when the mass average particle diameter of the toner increases, the resolving power decreases, but when the mass average particle diameter is 12 μm or less, there is no problem in the resolving power.
[0308]
[Table 4]

[0309]
[Table 5]

[0310]
【The invention's effect】
As described above, according to the present invention, in an image forming method including a contact charging process that employs a small-diameter image carrier for miniaturization, the surface roughness (μm) of the charging member, Intrusion amount δ (μm), volume-based 90% diameter D of conductive particles present in charging nip ₉₀ By properly setting (μm), good chargeability can be maintained over a long period of time, and the amount of wear on the surface of the photoreceptor is reduced. Further, in the simultaneous development cleaning system using the direct injection charging mechanism, both charging property and apparatus life can be achieved.
[Brief description of the drawings]
FIG. 1 is a schematic view of an example of an image forming apparatus used in the present invention.
FIG. 2 is a diagram showing a relationship between potentials for supplying conductive particles m from the developing roller 4a to the photosensitive drum 1.
3 is a schematic diagram of a layer structure of the photosensitive drum 1. FIG.
[Explanation of symbols]
1 Photoconductor
2 Charging roller
2a Charging roller core
2b Flexible layer
3 Exposure unit
4 Development device
4a Development sleeve
4b Magnet roll
4c Elastic blade
4d toner
6 Transfer roller
7 Fixing device
S1 Power supply for charging member
S2 Development power supply
S3 Power supply for transfer

Claims (23)

A charging step for charging the image carrier with a charging member which is in contact with the rotatable image carrier to form a nip and is rotatable and carries conductive particles on the surface, and the conductive particles are carried on the image carrier. In the image forming method including at least a step of transporting to the nip portion, when the diameter of the image carrier is LD (mm),
LD ≦ 28 (mm)
The charging member is an elastic body, the surface roughness of the charging member is Ra (μm), the amount of penetration into the image carrier is δ (μm), and the volume-based 90% diameter of the conductive particles is D. ₉₀ (μm)
2 × D ₉₀ <Ra ≦ δ
An image forming method characterized by that. ^2. The image forming method according to claim 1, wherein the conductive particles have a specific surface area (cm ² / cm ³ ) of 5 × 10 ⁵ or more and 100 × 10 ⁵ or less. The image forming method according to claim 1, wherein the conductive particles have a volume resistance of 1 × 10 ⁻¹ to 1 × 10 ⁹ Ωcm. 4. The image forming method according to claim 1, wherein a volume-based median diameter D ₅₀ of the conductive particles is 0.4 μm or more and 4.0 μm or less. 4. The image forming method according to claim 1, wherein a volume-based median diameter D ₅₀ of the conductive particles is from 0.5 μm to 3.5 μm. 6. The image forming method according to claim 1, wherein the volume-based D ₉₀ of the conductive particles is 6.0 μm or less. The image forming method according to claim 1, wherein the volume-based D ₉₀ of the conductive particles is 4.0 μm or less. The image forming method according to claim 1, wherein the volume-based D ₁₀ of the conductive particles is 0.3 μm or more. 9. The image forming method according to claim 1, wherein the conductive particles have a specific surface area (cm ² / cm ³ ) of 10 × 10 ⁵ or more and 80 × 10 ⁵ or less. The image forming method according to claim 1, wherein the conductive particles have a specific surface area (cm ² / cm ³ ) of 12 × 10 ⁵ or more and 40 × 10 ⁵ or less. The image forming method according to claim 1, wherein the volume-based D ₁₀ of the conductive particles is 0.4 μm or more. 12. The image forming method according to claim 1, wherein the conductive particles contain at least tin oxide. 13. The image forming method according to claim 1, wherein the conductive particles are subjected to a surface treatment with a silane compound. The image forming method according to claim 1, wherein the charging member has a porous body surface. 15. The image forming method according to claim 1, wherein the charging member is a roller member having an Asker C hardness of 5 to 40 degrees. 16. The image forming method according to claim 1, wherein a diameter LD (mm) of the image carrier and a diameter LC (mm) of the charging member satisfy LC ≦ LD. The supplying step of supplying conductive particles to the image carrier is a developing step of developing an electrostatic image formed on the image carrier with a developer, and the developer includes at least toner particles and the conductive particles. The image forming method according to any one of claims 1 to 16, wherein toner particles remaining on the image carrier can be recovered in a developing step. The toner particles are formed of at least a binder resin and a colorant, and the developer has a mass average particle diameter of 3 μm or more and 12 μm or less, and the conductive particles have a median diameter (D ₅₀ ) of the developer. The image forming method according to claim 17, wherein the image forming method is less than the diameter. The toner particles are externally added with an inorganic fine powder selected from at least silica, titanium oxide, alumina, a composite thereof, or a mixture thereof and having an average primary particle size of 4 nm to 80 nm. The image forming method according to claim 17 or 18, characterized in that: 20. The image forming method according to claim 16, wherein the Carr jet property index of the developer is greater than 80. A charging step for charging the image carrier with a charging member that forms a nip portion in contact with the rotatable image carrier and rotates and carries conductive particles on the surface, and the conductive particles are carried on the image carrier and A developer used in an image forming method having at least a step of being conveyed to a nip portion,
When the diameter of the image carrier is LD (mm),
LD ≦ 28 (mm)
The charging member is an elastic body, the surface roughness of the charging member is Ra (μm), the amount of penetration into the image carrier is δ (μm), and the volume-based 90% diameter of the conductive particles is D. ₉₀ (μm)
2 × D ₉₀ <Ra ≦ δ
14. A developer for use in an image forming method, wherein the developer has at least toner particles and conductive particles, and the conductive particles have the characteristics according to any one of claims 2 to 13. The developer according to claim 21, wherein the developer has the characteristics according to any one of claims 18 to 20. The image carrier is charged by the charging member, the image carrying surface of the image carrier is exposed by an image exposure device to form an electrostatic image, and the electrostatic image on the image carrier is developed by the developing unit. Developing with the developer, and then forming the image by an image forming process including the steps of transferring the developer image on the image carrier to the transfer target, and the development remaining on the surface of the image carrier after the transfer step 21. The image forming method according to claim 1, wherein an agent is temporarily carried on at least the charging member, transferred to the surface of the image carrier again, and collected by the developing unit.

Images