JP2004125936A - Image forming method, developer and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which prevents toner fusion on a developer restricting member, thereby preventing a low density of an image and a vertical streak and ensuring steady image formation over a long period of time. <P>SOLUTION: In an image forming method having a development process in which developer is transferred to an electrostatic latent image on an image carrier by a developing means, thereby rendering the electrostatic latent image visible, control is exerted so that the potential of a developer carrier and the potential of the developer restricting member are almost equal during image formation and that the potential of the developer restricting member is at least temporarily higher toward the same polarity as electrified toner particles than the potential of the developer carrier during image non-formation in which the developer carrier is rotated but image formation is not carried out. Images are formed using the developer that contains the toner particles and silica particles having the same polarity as the toner particles and a BET specific surface area of 20 to 250 m<SP>2</SP>/g, the content of the silica fine particles being 0.5 to 2 pts. mass based on 100 pts. mass of the toner. <P>COPYRIGHT: (C)2004,JPO

Description

【００７５】
また、本発明で用いられるシリカ微粒子の数平均一次粒子径は、５〜１００ｎｍであることが好ましい。シリカ微粒子の数平均一次粒子径は、７〜６０ｎｍであることがより好ましい。数平均一次粒子径が５ｎｍ未満では、非常に帯電性が高いため、特に低湿環境下において現像剤規制部材に付着し易く、融着塊に発展して定着画像にスジを発生する。また、耐久的使用に伴いシリカ微粒子がトナー粒子中に埋め込まれやすく、特に高湿環境下における耐久後半にかぶりを生じる。また数平均一次粒子径が１００ｎｍ以上では帯電付与性に劣ることがある。
【００７６】
なお、シリカ微粒子の数平均一次粒子径は、ＦＥ−ＳＥＭ（日立製作所製Ｓ−４７００）により５万倍に拡大したトナー粒子表面の写真を撮影し、中心付近に存在するシリカ微粒子の長径を１０視野にわたり測定し、その平均値を数平均粒子径とすることにより求める。
【００７７】
シリカ微粒子は、ケイ素ハロゲン化合物の蒸気相酸化により生成されたいわゆる乾式法又はヒュームドシリカ微粒子と称される乾式シリカ、及び水ガラス等から製造されるいわゆる湿式シリカの両方が使用可能である。
【００７８】
粒径の小さなシリカ微粒子の母体としては、表面及びケイ酸微粉体の内部にあるシラノール基が少なく、またＮａ_２Ｏ、ＳＯ_３ ^２−等の製造残査のない乾式シリカの方が好ましい。
【００７９】
また、乾式シリカにおいては、製造工程において例えば、塩化アルミニウム又は塩化チタンの如き他の金属ハロゲン化合物をケイ素ハロゲン化合物と共に用いることによってシリカと他の金属酸化物の複合微粉体を得ることも可能であり、前記乾式シリカはそれらも包含する。
【００８０】
本発明に用いられるシリカ微粒子は、予めシランカップリング剤及び／又はシリコーンオイルで疎水化処理することにより、高温高湿環境下においても所望の帯電量を得ることができ、好ましい。
【００８１】
シランカップリング剤としては、下記一般式で示されるもので、例えば代表的にはジメチルジクロルシラン、トリメチルクロルシラン、アリルジメチルクロルシラン、ヘキサメチルジシラザン、アリルフェニルジクロルシラン、ベンジルジメチルクロルシラン、ビニルトリエトキシシラン、γ−メタクリルオキシプロピルトリメトキシシラン、ビニルトリアセトキシシラン、ジビニルクロルシラン、ジメチルビニルクロルシランが挙げられる。
【００８２】
【化１】
Ｒ_ｍＳｉＹ_ｎ
（式中、Ｒはアルコキシ基又は塩素原子を示し、Ｙはアルキル基、又はビニル基、グリシドキシ基、メタクル基を含む炭化水素基を示し、ｍは１〜３の整数を示し、ｎは３〜１の整数を示す。）
【００８３】
上記シリカ微粉体のシランカップリング剤処理は、シリカ微粉体を撹拌によりクラウド状としたものに気化したシランカップリング剤を反応させる乾式処理又は、シリカ微粒子を溶媒中に分散させたシランカップリング剤を滴下反応させる湿式法のような一般に知られた方法で処理することができる。
【００８４】
シリコーンオイルは、一般に次の式で示されるものである。
【化２】

（式中、Ｒは炭素数１〜３のアルキル基を示し、Ｒ’はアルキル、ハロゲン変性アルキル、フェニルおよび変性フェニルから選ばれるシリコーンオイル変性基を示し、Ｒ”は炭素数１〜３のアルキル基またはアルコキシ基を示し、ｍは０〜１０００の整数を示し、ｎは０〜１０００の整数を示す。）
【００８５】
このようなシリコーンオイルとしては、例えば、ジメチルシリコーンオイル、アルキル変性シリコーンオイル、α−メチルスチレン変性シリコーンオイル、クロルフェニルシリコーンオイル、フッ素変性シリコーンオイルが挙げられる。
【００８６】
シリコーンオイル処理の方法としては公知の技術が用いられ、例えばシリカ微粉体とシリコーンオイルとをヘンシェルミキサー等の混合機を用いて直接混合しても良いし、ベースシリカ微粒子へシリコーンオイルを噴霧する方法によっても良い。あるいは適当な溶剤にシリコーンオイルを溶解あるいは分散せしめた後、ベースのシリカ微粉体とを混合した後、溶剤を除去して作製しても良い。
【００８７】
処理量が０．１質量％未満であると、高温高湿環境下において著しく帯電量が落ち、かぶりやボタ落ちの原因となる。一方、処理量が３０質量％以上であると、シリコーンオイルが厚く塗られたシリカ微粒子や二次凝集シリカ微粒子量が相対的に増えるため、それらが現像剤規制部材への融着物のきっかけになりやすく好ましくない。
【００８８】
疎水化処理と同様の理由から、本発明で用いられるシリカ微粒子は解砕処理工程を設けることにより、ブレード融着へのラチチュードが更に広がり、より高寿命な現像装置に対応できる。
【００８９】
本発明の現像剤は、個数基準の粒度分布において粒径が４μｍ以下の粒子が３５％以下であることが好ましい。４μｍ以下の粒径の粒子が個数基準の粒度分布において３５％を超えると、粒径が４μｍ以下の小粒径のトナーは非常に高い帯電量を持つために、現像剤規制部材に強く付着し、低温低湿環境下において高いブレードバイアスを現像剤規制部材に印加しても十分にリフレッシュすることができず、現像剤担持体の回転摺擦によりトナー融着を生じる。
【００９０】
チャージアップによる現像剤規制部材へのトナー粒子の付着力を抑制する同様の理由から、現像剤の体積平均粒径は４〜１２μｍであることが好ましく、４μｍ以下の粒径の粒子が個数分布で２０％以下であることがより好ましい。
【００９１】
本発明の現像剤は、あらゆる環境において、現像剤担持体上での帯電量を絶対値で１５〜９０μＣ／ｇに制御することが好ましい。所望の帯電量に制御する手段としては、複数の補助粒子を使用することが可能である。流動性及び帯電能付与手段として上述のシリカ微粒子を添加するほかに、酸化チタンや酸化マグネシウム等を添加して帯電分布を調整したり、負帯電トナーに対してはハイドロタルサイトやチタン酸ストロンチウム等の正帯電性微粒子を添加することによりチャージアップを抑制することができる。また、補助粒子の一つにトナーの極性と逆極性の外添剤（トナーが負帯電性である場合には正極性の外添剤）を用いると、現像剤担持体の回転動作と相まって、現像剤規制部材に付着した負極性外添剤を擦り落とす効果も期待できる。
【００９２】
現像剤の現像剤担持体上における帯電量が絶対値で１５に満たない場合、高温高湿環境下でかぶりやボタ落ち等の画像不良を発生する。また、帯電量が絶対値で９０を超えると、高いブレードバイアスを現像剤規制部材に印加しても、該現像剤規制部材にチャージアップしたトナーやシリカ微粒子が強力に静電付着する為に、耐久的使用に伴なう融着スジを回避することができなくなる。
【００９３】
前記現像剤の帯電量は、例えば図８に示すファラデー・ケージ（Ｆａｒａｄａｙ−Ｃａｇｅ）によって測定することができる。ファラデー・ケージとは、同軸の２重筒のことで内筒と外筒は絶縁されている。この内筒の中に電荷量Ｑの帯電体を入れたとすると、静電誘導によりあたかも電気量Ｑの金属円筒が存在するのと同様になる。この誘起された電荷量をＫＥＩＴＨＬＥＹ　６１６　ＤＩＧＩＴＡＬ　ＥＬＥＣＴＲＯＭＥＴＥＲで測定し、内筒中のトナー重量Ｍで電荷量Ｑを割ったもの（Ｑ／Ｍ）を帯電量とする。現像剤は現像剤担持体より直接、ａｉｒ吸引によりフィルター中にとり入れる。
【００９４】
現像剤の帯電量は、トナー材料に適当な荷電制御剤を用いる等の材料面で調整することができるほか、現像剤担持体の材質や、現像剤規制部材の現像剤担持体への当接圧等を調整することにより、現像剤への摩擦帯電量付与能を制御することができる。
【００９５】
なお、外添剤の帯電量（μｃ／ｇ）はブローオフ測定法により次のように求められる。
図９は外添剤の摩擦帯電量を測定する装置の説明図である。先ず、摩擦帯電量を測定しようとする外添剤とキャリアの重量比１：５００の混合物を５０〜１００ｍｌ容量のポリエチレン製のビンに入れ、ターブラミキサーで２分間振とうする。底に５００メッシュのスクリーン５３のある金属製の測定容器５２に、該混合物０．１〜０．７ｇを入れ金属製のフタ５４をする。次に吸引機５１（測定容器５２と接する部分は少なくとも絶縁体）において、吸引口５７から吸引し風量調節弁を調整して真空計５５の圧力を２ｋＰａとする。この状態で充分（約一分間）吸引を行う。このときの電位計５９の電圧をＶ（ボルト）とする。ここで５８はコンデンサーであり、容量はＣ（μＦ）である。これらから得られる電荷量を、吸引除去した外添剤量で除したものが摩擦帯電量（μｃ／ｇ）である。
【００９６】
また、本発明の現像剤のメルトインデックス（ＭＩ）は３５以下であることが好ましい。現像剤のＭＩは２５以下であることがより好ましい。ＭＩが３５を超える現像剤を用いると、シリカ微粒子が現像剤規制部材に融着して現像剤規制部材が荒らされた場合に、摩擦熱によって現像剤規制部材へのトナー融着を誘発しやすく、早期の段階から酷いスジが発生する傾向がある。
【００９７】
なお、本発明におけるＭＩの測定は、ＪＩＳ　Ｋ　７２１０のＡ法に準じて測定を行い、試験温度１３５℃、試験荷重２．１６Ｋｇｆにおける値をＭＩ値とする。
【００９８】
以下、本発明の現像剤について更に詳しく述べる。
前述したように、本発明の現像剤はトナー粒子と、このトナー粒子と同極性の帯電極性を有する上記のシリカ微粒子とを含有する。本発明の現像剤に含有されるトナー粒子は非磁性及び絶縁性を有するものであり、正の極性に帯電する正極性のトナー粒子であっても負の極性に帯電する負極性のトナー粒子であってもよい。本発明のトナー粒子は、結着樹脂、着色剤、ワックス、荷電制御剤、前記シリカ微粒子以外の外添剤等、公知のトナー材料によって製造することができる。
【００９９】
トナー粒子に用いられる結着樹脂としては、例えばポリスチレン；ポリ−ｐ−クロルスチレン、ポリビニルトルエンなどのスチレン置換体の単重合体；スチレン−ｐ−クロルスチレン共重合体、スチレン−ビニルトルエン共重合体、スチレン−ビニルナフタリン共重合体、スチレン−アクリル酸エステル共重合体、スチレン−メタクリル酸エステル共重合体、スチレン−α−クロルメタクリル酸メチル共重合体、スチレン−アクリロニトリル共重合体、スチレン−ビニルメチルエーテル共重合体、スチレン−ビニルエチルエーテル共重合体、スチレン−ビニルメチルケトン共重合体、スチレン−ブタジエン共重合体、スチレン−イソプレン共重合体、スチレン−アクリロニトリル−インデン共重合体などのスチレン系共重合体；アクリル樹脂；メタクリル樹脂；ポリ酢酸ビニール；シリコーン樹脂；ポリエステル樹脂；ポリアミド樹脂；フラン樹脂；エポキシ樹脂；キシレン樹脂等が挙げられる。
【０１００】
これらの樹脂は、単独で又は２種以上を混合して使用される。結着樹脂の主成分としては、スチレンと他のビニルモノマーとの共重合体であるスチレン共重合体であることが現像性や定着性の点で好ましい。
【０１０１】
本発明では、適当なモノマーを重合させることによって結着樹脂を生成し、これを用いても良い。例えば、スチレン共重合体のスチレンモノマーに対するコモノマーとしては、アクリル酸、アクリル酸メチル、アクリル酸エチル、アクリル酸ブチル、アクリル酸ドジテル、アクリル酸オクチル、アクリル酸−２−エチルヘキシル、アクリル酸フェニル、メタクリル酸、メタクリル酸メチル、メタクリル酸エチル、メタクリル酸ブチル、メタクリル酸オクチル、アクリロニトリル、メタクリロニトリル、アクリルアミドのような二重結合を有するモノカルボン酸及びその置換体；マレイン酸、マレイン酸ブチル、マレイン酸メチル、マレイン酸ジメチルのような二重結合を有するジカルボン酸及びその置換体；塩化ビニル、酢酸ビニル、安息香酸ビニルのようなビニルエステル；エチレン、プロピレン、ブチレンのようなエチレン系オレフィン；ビニルメチルケトン、ビニルヘキシルケトンのようなビニルケトン；ビニルメチルエーテル、ビニルエチルエーテル、ビニルイソブチルエーテルのようなビニルエーテルが挙げられる。これらビニル単量体は単独で又は二種以上を混合して用いられる。
【０１０２】
スチレン共重合体は、ジビニルベンゼンのような架橋剤で架橋されていることが現像剤の定着温度領域を広げ、耐オフセット性を向上させる上で好ましい。
【０１０３】
また、本発明に用いられるトナー粒子を重合方法で製造する際に用いられる重合性単量体としては、ラジカル重合が可能なビニル系重合性単量体が用いられる。該ビニル系重合性単量体としては、単官能性重合性単量体或いは多官能性重合性単量体を使用することができる。
【０１０４】
単官能性重合性単量体としては、スチレン；α−メチルスチレン、β−メチルスチレン、ｏ−メチルスチレン、ｍ−メチルスチレン、ｐ−メチルスチレン、２，４−ジメチルスチレン、ｐ−ｎ−ブチルスチレン、ｐ−ｔｅｒｔ−ブチルスチレン、ｐ−ｎ−ヘキシルスチレン、ｐ−ｎ−オクチルスチレン、ｐ−ｎ−ノニルスチレン、ｐ−ｎ−デシルスチレン、ｐ−ｎ−ドデシルスチレン、ｐ−メトキシスチレン、ｐ−フェニルスチレンなどのスチレン誘導体；メチルアクリレート、エチルアクリレート、ｎ−プロピルアクリレート、ｉｓｏ−プロピルアクリレート、ｎ−ブチルアクリレート、ｉｓｏ−ブチルアクリレート、ｔｅｒｔ−ブチルアクリレート、ｎ−アミルアクリレート、ｎ−ヘキシルアクリレート、２−エチルヘキシルアクリレート、ｎ−オクチルアクリレート、ｎ−ノニルアクリレート、シクロヘキシルアクリレート、ベンジルアクリレート、ジメチルフォスフェートエチルアクリレート、ジエチルフォスフェートエチルアクリレート、ジブチルフォスフェートエチルアクリレート、２−ベンゾイルオキシエチルアクリレートなどのアクリル系重合性単量体；メチルメタクリレート、エチルメタクリレート、ｎ−プロピルメタクリレート、ｉｓｏ−プロピルメタクリレート、ｎ−ブチルメタクリレート、ｉｓｏ−ブチルメタクリレート、ｔｅｒｔ−ブチルメタクリレート、ｎ−アミルメタクリレート、ｎ−ヘキシルメタクリレート、２−エチルヘキシルメタクリレート、ｎ−オクチルメタクリレート、ｎ−ノニルメタクリレート、ジエチルフォスフェートエチルメタクリレート、ジブチルフォスフェートエチルメタクリレートなどのメタクリル系重合性単量体；メチレン脂肪族モノカルボン酸エステル；酢酸ビニル、プロピオン酸ビニル、酪酸ビニル、安息香酸ビニル、ギ酸ビニルなどのビニルエステル；ビニルメチルエーテル、ビニルエチルエーテル、ビニルイソブチルエーテルなどのビニルエーテル；ビニルメチルケトン、ビニルヘキシルケトン、ビニルイソプロピルケトンなどのビニルケトンが挙げられる。
【０１０５】
多官能性重合性単量体としては、ジエチレングリコールジアクリレート、トリエチレングリコールジアクリレート、テトラエチレングリコールジアクリレート、ポリエチレングリコールジアクリレート、１，６−ヘキサンジオールジアクリレート、ネオペンチルグリコールジアクリレート、トリプロピレングリコールジアクリレート、ポリプロピレングリコールジアクリレート、２，２’−ビス（４−（アクリロキシ・ジエトキシ）フェニル）プロパン、トリメチロールプロパントリアクリレート、テトラメチロールメタンテトラアクリレート、エチレングリコールジメタクリレート、ジエチレングリコールジメタクリレート、トリエチレングリコールジメタクリレート、テトラエチレングリコールジメタクリレート、ポリエチレングリコールジメタクリレート、１，３−ブチレングリコールジメタクリレート、１，６−ヘキサンジオールジメタクリレート、ネオペンチルグリコールジメタクリレート、ポリプロピレングリコールジメタクリレート、２，２’−ビス（４−（メタクリロキシ・ジエトキシ）フェニル）プロパン、２，２’−ビス（４−（メタクリロキシ・ポリエトキシ）フェニル）プロパン、トリメチロールプロパントリメタクリレート、テトラメチロールメタンテトラメタクリレート、ジビニルベンゼン、ジビニルナフタリン、ジビニルエーテル等が挙げられる。
【０１０６】
本発明においては、上記した単官能性重合性単量体を単独で或いは二種以上組み合わせて、又は上記した単官能性重合性単量体と多官能性重合性単量体とを組み合わせて使用する。多官能性重合性単量体は架橋剤として使用することも可能である。
【０１０７】
上記した重合性単量体の重合の際に用いられる重合開始剤としては、油溶性開始剤及び水溶性開始剤のいずれか一方又は両方が用いられる。例えば、油溶性開始剤としては、２，２’−アゾビスイソブチロニトリル、２，２’−アゾビス−２，４−ジメチルバレロニトリル、１，１’−アゾビス（シクロヘキサン−１−カルボニトリル）、２，２’−アゾビス−４−メトキシ−２，４−ジメチルバレロニトリルなどのアゾ化合物；アセチルシクロヘキシルスルホニルパーオキサイド、ジイソプロピルパーオキシカーボネート、デカノニルパーオキサイド、ラウロイルパーオキサイド、ステアロイルパーオキサイド、プロピオニルパーオキサイド、アセチルパーオキサイド、ｔ−ブチルパーオキシ−２−エチルヘキサノエート、ベンゾイルパーオキサイド、ｔ−ブチルパーオキシイソブチレート、シクロヘキサノンパーオキサイド、メチルエチルケトンパーオキサイド、ジクミルパーオキサイド、ｔ−ブチルヒドロパーオキサイド、ジ−ｔ−ブチルパーオキサイド、クメンヒドロパーオキサイドの如きパーオキサイド系開始剤が挙げられる。
【０１０８】
水溶性開始剤としては、過硫酸アンモニウム、過硫酸カリウム、２，２’−アゾビス（Ｎ，Ｎ’−ジメチレンイソブチロアミジン）塩酸塩、２，２’−アゾビス（２−アミノジプロパン）塩酸塩、アゾビス（イソブチルアミジン）塩酸塩、２，２’−アゾビスイソブチロニトリルスルホン酸ナトリウム、硫酸第一鉄及び過酸化水素等が挙げられる。
【０１０９】
本発明においては、重合性単量体の重合度を制御するために、連鎖移動剤、重合禁止剤等をさらに添加し用いることも可能である。
【０１１０】
上記トナー粒子に用いられる架橋剤としては、二個以上の重合可能な二重結合を有する化合物が用いられる。例えば、ジビニルベンゼン、ジビニルナフタレンのような芳香族ジビニル化合物；エチレングリコールジアクリレート、エチレングリコールジメタクリレート、１，３−ブタンジオールジメタクリレートのような二重結合を二個有するカルボン酸エステル；ジビニルアニリン、ジビニルエーテル、ジビニルスルフィド、ジビニルスルホンの如きジビニル化合物；及び三個以上のビニル基を有する化合物が挙げられる。これらは単独で又は２種以上の混合物として用いられる。
【０１１１】
なお、上記本発明で用いられるトナー粒子が重合法により製造される場合にはトナー粒子に縮合系樹脂を添加しても良い。縮合系樹脂としては、例えば、ポリエステル、ポリカーボネート、フェノール樹脂、エポキシ樹脂、ポリアミド、セルロース等が挙げられる。より好ましくは、材料の多様性からポリエステルが望まれる。前記縮合系樹脂は、その種類等によって異なるが、結着樹脂１００質量部当たり０．０１〜２０質量部、より好ましくは０．５〜１０質量部使用するのが良い。
【０１１２】
上記トナー粒子に用いられる着色剤は、非磁性のものであれば特に限定されず、黒色着色剤としては、例えばカーボンブラックや、以下に示すイエロー、マゼンタ、及びシアン着色剤を用いて黒色に調色したもの等が挙げられる。
【０１１３】
イエロー着色剤としては、顔料系としては、縮合アゾ化合物、イソインドリノン化合物、アンスラキノン化合物、アゾ金属錯体メチン化合物、アリルアミド化合物に代表される化合物が用いられる。具体的には、Ｃ．Ｉ．Ｐｉｇｍｅｎｔ　Ｙｅｌｌｏｗ３、７、１０、１２、１３、１４、１５、１７、２３、２４、６０、６２、７４、７５、８３、９３、９４、９５、９９、１００、１０１、１０４、１０８、１０９、１１０、１１１、１１７、１２３、１２８、１２９、１３８、１３９、１４７、１４８、１５０、１６６、１６８、１６９、１７７、１７９、１８０、１８１、１８３、１８５、１９１：１、１９１、１９２、１９３、１９９等が好適に用いられる。染料系としては、例えば、Ｃ．Ｉ．ｓｏｌｖｅｎｔＹｅｌｌｏｗ３３、５６、７９、８２、９３、１１２、１６２、１６３、Ｃ．Ｉ．ｄｉｓｐｅｒｓｅ　Ｙｅｌｌｏｗ４２、６４、２０１、２１１等が挙げられる。
【０１１４】
マゼンタ着色剤としては、縮合アゾ化合物、ジケトピロロピロール化合物、アントラキノン、キナクリドン化合物、塩基染料レーキ化合物、ナフトール化合物、ベンズイミダゾロン化合物、チオインジゴ化合物、ペリレン化合物が用いられる。具体的には、Ｃ．Ｉ．ピグメントレッド２、３、５、６、７、２３、４８：２、４８：３、４８：４、５７：１、８１：１、１２２、１４６、１５０、１６６、１６９、１７７、１８４、１８５、２０２、２０６、２２０、２２１、２５４、Ｃ．Ｉ．ピグメントバイオレッド１９が特に好ましい。
【０１１５】
シアン着色剤としては、フタロシアニン化合物及びその誘導体、アントラキノン化合物、塩基染料レーキ化合物等が利用できる。具体的には、Ｃ．Ｉ．ピグメントブルー１、７、１５、１５：１、１５：２、１５：３、１５：４、６０、６２、６６等が特に好適に利用される。
【０１１６】
これらの着色剤は、単独で又は混合して、さらには固溶体の状態で用いることができる。着色剤は、色相角、彩度、明度、耐候性、ＯＨＰ透明性、トナー中への分散性の点から選択される。着色剤の添加量は、着色剤の種類によって異なるが、結着樹脂１００質量部に対し１〜２０質量部であることが好ましい。
【０１１７】
上記本発明で用いられるトナー粒子は、示差熱分析における昇温時の吸熱曲線において、吸熱ピークが５０〜１２０℃の範囲に少なくともひとつあるものが好ましい。５０〜１２０℃に吸熱ピークを有するトナーは、上記シリカ粒子の添加量や他の外添剤の種類および量を調整することによって、より効果的にトナー帯電性をコントロールでき、より好ましい結果が得られる。
【０１１８】
トナー粒子の吸熱ピークが５０℃未満にあると、保存安定性が損なわれブロッキング等の問題が発生しやすい。また、吸熱ピークが１２０℃を超える温度にあると、定着時における離型効果が十分に発揮されない。５０〜１２０℃に吸熱ピークがあれば、１２０℃を超える温度域にさらに吸熱ピークがあってもかまわない。
【０１１９】
前記示差熱分析における吸熱ピークは、高精度の内熱式入力補償型の示差走査熱量計で測定することができる。前記示差熱分析における吸熱ピークの測定には、例えばパーキンエルマー社製のＤＳＣ−７が使用できる。測定方法は、ＡＳＴＭ　Ｄ３４１８−８２に準じて行う。
【０１２０】
本発明において吸熱ピーク温度とは、ＤＳＣ曲線において、プラスの方向のピーク温度のことであり、即ち、ピーク曲線の微分値が正から負にかわる際の０になる点を言う。ＤＳＣ曲線には、１回昇温させて前履歴をとった後、温度速度１０℃／ｍｉｎ、温度０〜２００℃の範囲で降温および昇温させたときに測定されるＤＳＣ曲線を用いる。
【０１２１】
トナー粒子の示差熱分析における吸熱ピークを５０〜１２０℃の範囲に有するように調整する手段としては、示差熱分析における吸熱ピークを５０〜１２０℃に有する化合物をトナー粒子中に内添させる手段が好ましい。示差熱分析における吸熱ピークを５０〜１２０℃に一つ以上有する物質としては、ワックスが好ましく用いられる。
【０１２２】
前記ワックスとしては、例えばパラフィンワックス、マイクロクリスタリンワックス、ペトロラクタムなどの石油系ワックス及びその誘導体；モンタンワックス及びその誘導体；フィシャートロプシュ法による炭化水素ワックス及びその誘導体；ポリエチレンに代表されるポリオレフィンワックス及びその誘導体；カルナバワックス、キャンデリラワックスなどの天然ワックス及びそれらの誘導体、高級脂肪族アルコールのアルコールワックス；ステアリン酸、パルミチン酸などの脂肪酸或いはその化合物；酸アミド及びその誘導体；エステル及びその誘導体；ケトン及びその誘導体；硬化ヒマシ油及びその誘導体；植物ワックス；及び動物ワックスが挙げられる。誘導体は酸化物や、ビニルモノマーとのブロック共重合物、グラフト変性物を含む。本発明に用いられるトナー粒子中におけるワックスの含有量は、離型効果と帯電阻害性のバランスを考慮して、０．３〜３０質量％が好ましく、より好ましくは０．５〜２０質量％である。
【０１２３】
本発明に用いられるトナー粒子には、荷電制御剤を併用することによってさらに好ましい効果を加えることができる。
【０１２４】
トナー粒子を負荷電性に制御するものとしては、例えば、有機金属化合物、キレート化合物が有効であり、モノアゾ金属化合物、アセチルアセトン金属化合物、芳香族オキシカルボン酸、芳香族ダイカルボン酸、オキシカルボン酸及びダイカルボン酸系の金属化合物がある。他には、芳香族オキシカルボン酸、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、ビスフェノール等のフェノール誘導体類等がある。さらに、尿素誘導体、含金属サリチル酸系化合物、含金属ナフトエ酸系化合物、ホウ素化合物、４級アンモニウム塩、カリックスアレーン、樹脂系帯電制御剤等が挙げられる。これらを単独で又は二種類以上を組み合わせて用いることができる。
【０１２５】
トナー粒子を正荷電性に制御するものとしては、例えば、ニグロシン及び脂肪酸金属塩等によるニグロシン変性物、グアニジン化合物、イミダゾール化合物、トリブチルベンジルアンモニウム−１−ヒドロキシ−４−ナフトスルホン酸塩、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４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などの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、リンタングステン酸、リンモリブデン酸、リン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、フェロシアン化物等）、高級脂肪酸の金属塩；ジブチルスズオキサイド、ジオクチルスズオキサイド、ジシクロヘキシルスズオキサイドなどのジオルガノスズオキサイド；ジブチルスズボレート、ジオクチルスズボレート、ジシクロヘキシルスズボレートなどのジオルガノスズボレート類、樹脂系帯電制御剤等が挙げられる。これらを単独で又は二種類以上を組み合わせて用いることができる。
【０１２６】
なお荷電制御剤の使用量は、用いる荷電制御剤の種類によって異なるが、結着樹脂１００質量部当たり０．０１〜２０質量部であることが好ましく、０．５〜１０質量部であることがより好ましい。荷電制御剤は、トナー粒子に配合（内添）しても良いし、又はトナー粒子と混合（外添）しても良い。
【０１２７】
トナー粒子および現像剤の平均粒径及び粒度分布は、例えばコールターカウンターＴＡ−ＩＩ型あるいはコールターマルチサイザー（コールター社製）等を用い、個数分布、体積分布を出力するインターフェイス（日科機製）及びＰＣ９８０１パーソナルコンピューター（ＮＥＣ製）を接続した測定装置で測定することができる。この測定では電解液が用いられるが、この電解液には、例えば１級塩化ナトリウムを用いて調製された１％ＮａＣｌ水溶液や、ＩＳＯＴＯＮ　Ｒ−ＩＩ（コールターサイエンティフィックジャパン社製）が使用できる。
【０１２８】
測定法としては、前記電解水溶液１００〜１５０ｍｌ中に分散剤として界面活性剤（好ましくはアルキルベンゼンスルホン酸塩）を０．１〜５ｍｌ加え、さらに測定試料を２〜２０ｍｇ加える。試料を懸濁した電解液は超音波分散器で約１〜３分間分散処理を行い、アパーチャーとして１００μｍアパーチャーを用いて、前記コールターカウンターＴＡ−ＩＩ型により２μｍ以上のトナーの体積、個数を測定して体積分布と個数分布とを算出する。それから、本発明に係わる体積分布から求めた体積基準の重量平均粒径（Ｄ４）、個数分布から求めた個数基準の長さ平均粒径（Ｄ１）を求める。
【０１２９】
以下に本発明で用いられるトナー粒子の製造方法を示す。
前記非磁性一成分トナーの製造方法としては、少なくとも結着樹脂、着色剤を、加圧ニーダーやエクストルーダー、或いはメディア分散機等を用いて混練し、均一に分散させた後、機械的又はジェット気流下でターゲットに衝突させて所望のトナー粒径に微粉砕化させ、分級工程を経てトナー粒子を得る粉砕法が挙げられる。さらに円形度を高くする目的で、機械的手段を用いて所望の円形度にしトナー粒子を製造する製造方法や、上記微粉砕化の後に湿式又は乾式の熱球形化処理をする方法等が挙げられる。
【０１３０】
前記非磁性一成分トナーの製造方法としては重合法が挙げられる。前記非磁性一成分トナーの製造方法が重合法である場合には、特に制約を受けるものではないが、特公昭３６−１０２３１号公報、特開昭５９−５３８５６号公報、特開昭５９−６１８４２号公報に述べられている懸濁重合法を用いて直接トナーを生成する方法；単量体には可溶で水溶性重合開始剤の存在下で直接重合させてトナー粒子を生成するソープフリー重合法に代表される乳化重合法、等の製造方法によるトナー粒子の製造が挙げられる。また、マイクロカプセル製法のような界面重合法、ｉｎ−ｓｉｔｕ重合法、コアセルベーション法等の製造方法も挙げられる。さらに、特開昭６２−１０６４７３号公報や特開昭６３−１８６２５３号公報に開示されているような、少なくとも一種以上の微粒子を凝集させ所望の粒径のものを得る界面会合法等が挙げられる。
【０１３１】
懸濁重合を行う場合には、通常単量体組成物１００質量部に対して水３００〜３０００質量部を分散媒体として使用するのが好ましい。用いる分散剤として例えば無機系酸化物として、リン酸三カルシウム、リン酸マグネシウム、リン酸アルミニウム、リン酸亜鉛、炭酸カルシウム、炭酸マグネシウム、水酸化カルシウム、水酸化マグネシウム、水酸化アルミニウム、メタケイ酸カルシウム、硫酸カルシウム、硫酸バリウム、ベントナイト、シリカ、アルミナ、ドデシル硫酸ナトリウム等が挙げられる。
【０１３２】
有機系化合物としては例えばポリビニルアルコール、ゼラチン、メチルセルロース、メチルヒドロキシプロピルセルロース、エチルセルロース、カルボキシメチルセルロースのナトリウム塩、デンプン等が使用されている。これら分散剤あるいは分散助剤は、重合性単量体１００質量部に対して０．１〜５．０質量部を使用することが好ましい。
【０１３３】
これら分散剤の微細化のために０．００１〜０．１質量％の界面活性剤を併用しても良い。具体的には市販のノニオン、アニオン、カチオン型の界面活性剤が利用できる。より具体的には、例えばドデシル硫酸ナトリウム、テトラデシル硫酸ナトリウム、ペンタデシル硫酸ナトリウム、オクチル硫酸ナトリウム、オレイン酸ナトリウム、ラウリル酸ナトリウム、ステアリン酸カリウム、オレイン酸カルシウム等が好ましく用いられる。
【０１３４】
本発明の現像剤は、前述したトナー粒子とシリカ微粒子の他に、他の公知の外添剤をさらに含有していても良い。シリカ微粒子のような小粒径微粒子と併用してトナーと逆極性の微粒子を外添剤として用いる場合には、互いの粒子同士による凝集塊の発生を防止する目的と、耐久的使用時の後半において外添剤のトナー粒子中への埋没を防ぐスペーサー粒子の効果を狙って、前記微粒子は８０ｎｍ以上の粒径であることが特に好ましい。
【０１３５】
上記外添剤としての微粒子は、その性能を確実に発揮し、安定な帯電性を有するためには、トナー粒子に対して０．０５〜５．０質量％添加されることが好ましい。また、本発明に用いる逆極性微粒子は一種類だけを用いることに限定されるものではなく、複数の種類を併用することができる。
【０１３６】
前記微粒子としては、トナー粒子への帯電付与均一性から金属酸化物が好ましく用いられる。上記の金属酸化物の中でも、マグネシウム、アルミニウム、チタン、亜鉛、ジルコニウム、ストロンチウム、マンガンから選ばれる酸化物、及び前記金属の複合酸化物が、トナーへの帯電付与均一性において特に優れている。上記金属酸化物は、単独で用いても良いし、二種以上のものを併用して用いても良い。
【０１３７】
これらの中でも特に、ハイドロタルサイト類化合物、酸化チタン、酸化マグネシウム、酸化アルミニウム、酸化亜鉛、酸化ジルコニウム、チタン酸ストロンチウム、酸化マンガンに代表される金属酸化物のいずれかは、トナーの帯電コントロール効果が高く、また、静電潜像担持体表面に微小な傷をつけ難く好ましい。
【０１３８】
特に、前記微粒子は、帯電コントロール性、静電潜像担持体表面への傷つけにくさ、帯電部材の汚染による画像不良防止の点で、ハイドロタルサイト化合物、酸化チタン、酸化アルミニウムのいずれかの酸化物であることがより好ましい。
【０１３９】
上記金属酸化物の帯電量は、絶対値で３０ｍＣ／ｋｇ以下であることが、トナーの帯電コントロール性がより高くなることから好ましい。
【０１４０】
上記金属酸化物は、表面が高級脂肪酸類、エステル類、カップリング剤又はオイルのような有機化合物により疎水化処理されたものを用いることができるが、帯電量の絶対値を低く抑えるために、未処理の親水性の金属酸化物も好ましく用いられる。
【０１４１】
上記金属酸化物の比表面積は、２．０〜１５０ｍ^２／ｇであることが好ましい。２．０ｍ^２／ｇ未満では十分な効果が得られず、１５０ｍ^２／ｇを超えるとトナーの流動性が悪化し画像濃度ムラを起こすため好ましくない。ＢＥＴ比表面積の測定は、脱ガス装置バキュプレップ０６１（マイクロメソティック社製）を備えたＢＥＴ測定装置ジェミニ２３７５（マイクロメソティック社製）等公知の装置を用いて行う。
【０１４２】
また前記微粒子は、樹脂微粒子であっても良い。具体例としては、スチレン樹脂、アクリル樹脂、アクリレート樹脂、及びそれらの共重合体や、シリコーン樹脂、メラミン−ホルムアルデヒド樹脂、ベンゾグアナミン−ホルムアルデヒド樹脂共重合体、フェノール樹脂等を挙げることができる。
【０１４３】
本発明の現像剤は、現像性や耐久性を向上させるために、無機粉体をさらに含有してもよい。このような無機粉体としては、例えばマグネシウム、亜鉛、アルミニウム、セリウム、コバルト、鉄、ジルコニウム、クロム、マンガン、ストロンチウム、錫、アンチモン等の金属酸化物；チタン酸カルシウム、チタン酸マグネシウム、チタン酸ストロンチウム等の複合金属酸化物；硫酸バリウム、炭酸カルシウム、炭酸マグネシウム、炭酸アルミニウム等の金属塩；カオリン等の粘土鉱物；アパタイト等のリン酸化合物；シリカ、炭化ケイ素、窒化ケイ素等のケイ素化合物が挙げられる。
【０１４４】
同様の目的で、本発明の現像剤には、有機粒子や複合粒子を添加することもできる。このような有機粒子や複合粒子としては、例えばポリアミド樹脂粒子、シリコーン樹脂粒子、シリコーンゴム粒子、ウレタン粒子、メラミン−ホルムアルデヒド粒子、アクリル粒子等の樹脂粒子；ゴム、ワックス、脂肪酸系化合物、樹脂等と金属、金属酸化物、塩、カーボンブラック等の無機粒子とからなる複合粒子；ポリフッ化エチレン、ポリフッ化ビニリデン等のフッ素樹脂；フッ化カーボン等のフッ素化合物；ステアリン酸亜鉛等の脂肪酸金属塩；脂肪酸、脂肪酸エステル等の脂肪酸誘導体；硫化モリブデン、アミノ酸及びアミノ酸誘導体等が挙げられる。
【０１４５】
上記したシリカ微粒子以外の外添剤、無機粉体、有機粒子および複合粒子は、単独で用いても、また、複数併用しても良い。さらに必要に応じ疎水化処理（オイル、カップリング）をしてもかまわない。
【０１４６】
シリカ微粒子や他の添加剤をトナー粒子に添加する際の撹拌方法としては、前記添加剤を外添したときに前記トナー粒子に機械的に付着させるものであれば特に限定するものでなく、公知の撹拌装置を用いて行うことができる。好ましくは、ヘンシェルミキサーやホモジナイザー等が用いられ、より好ましくは、ヘンシェルミキサーが用いられる。外添強度は回転数、バッフル版の角度、及び攪拌時間を制御して行い、他の外添剤との相互作用も十分に考慮して、シリカ微粒子の遊離率をコントロールすることが好ましい。
【０１４７】
以下、図面を参照して上記本発明の現像剤を用いた本発明の画像形成方法をより具体的に説明する。図１および図２は、本発明の画像形成方法が好適に用いられる画像形成装置の第１の実施形態を表す図である。
【０１４８】
図２は本実施形態の画像形成装置の構成を示す概略断面図である。まず、図２を用いて本実施形態の画像形成装置の構成を説明する。本実施形態の画像形成装置は、像担持体の被露光部に現像剤を付着させて可視化する反転現像系であり、負帯電性の現像剤を担持した現像剤担持体を像担持体に当接させて現像を行う一成分画像形成装置である。
【０１４９】
本発明で用いる画像形成装置は、像担持体としての感光ドラム１、この感光ドラム１表面を一様帯電する帯電ローラ２、帯電ローラ２によって一様帯電された感光ドラム１表面を露光して静電潜像を形成する露光器３、感光ドラム１表面の静電潜像に現像剤を転移させる現像手段としての現像器４、感光ドラム１表面に転移された現像剤を転写紙に転写する転写ローラ５、転写紙に転写された現像剤を転写紙に定着する定着器７、および転写紙への現像剤の転写が行われた後に感光ドラム１表面に残留した現像剤を除去するクリーニング手段６を有する。
【０１５０】
図２において、像担持体としての感光ドラム１は矢印ｘ方向に回転可能である。感光ドラム１は一次帯電器である帯電ローラ２により、表面が負極性に一様帯電される。そして、感光ドラム１の回転に伴って、一様に帯電された表面は露光器３により露光される。被露光部の電荷が消失することで、感光ドラム１上に静電潜像が形成される。
【０１５１】
４は現像手段としての現像器であり、静電潜像の被露光部に現像剤を転移させ、静電潜像を可視像化する現像手段である。用いられる現像剤は非磁性一成分現像剤を用いる。また、本実施形態は被露光部に現像剤を転移させる所謂反転現像系である。
【０１５２】
感光ドラム１上に転移した現像剤は転写帯電器としての転写ローラ５により転写紙Ｐに転移される。転写されずに感光ドラム１上に残った現像剤はクリーニング手段６により感光ドラム１上より除去される。一方、転写紙Ｐ上の現像剤は定着器７により熱溶融され転写紙Ｐ上に固着し、永久画像となる。
【０１５３】
現像器４は現像剤担持体としての現像ローラ８、現像ローラ８に現像剤を供給する供給ローラ１２、現像剤規制部材としての現像ブレード９、供給ローラ１２側にトナーを搬送する撹拌部材１３、現像ローラ８を回転させるモータ１５、現像ローラ８に電圧を印加する電圧印加手段としての現像バイアス電源１０、現像ブレード９に電圧を印加する電圧印加手段としてのブレードバイアス電源１１、現像バイアス電源１０およびブレードバイアス電源１１の動作を制御する電圧制御手段としての制御装置１４を有する。
【０１５４】
現像ローラ８は駆動装置としてのモータ１５により矢印ｙ方向に回転可能である。現像ローラ８は感光ドラム１表面に当接して現像を行う所謂接触現像を用いるものであることから、現像ローラ８はゴム等の弾性を有することが望ましい。本実施形態では、現像ローラ８には現像バイアス電源１０から約−４００Ｖの電圧が供給される。感光ドラム１上の被露光部電位と現像バイアス電源１０から供給される電位差により現像ローラ８上の現像剤が感光ドラム１上の被露光部に転移する。
【０１５５】
現像ブレード９は金属薄板からなり、薄板のバネ弾性を利用して現像ローラ８に接触当接される。金属薄板の材質は、ステンレス鋼、リン青銅等が使用可能であるが、本実施形態においては、厚さ０．１ｍｍのリン青銅薄板を用いる。現像ブレード９と現像ローラ８の摺擦によりトナーは摩擦帯電されて電荷を付与されると同時に層厚規制される。現像ブレード９には、ブレードバイアス電源１１から所定の電圧が供給される。なお、現像ブレード９に印加される電圧については後述する。
【０１５６】
１４は制御装置（制御手段）である。制御装置１４は現像ローラ８の回転駆動の制御、並びに電圧印加手段としての現像バイアス電源１０およびブレードバイアス電源１１の電圧値等の制御などを行う。
【０１５７】
図１は本実施形態に係るシーケンスを示す図である。図１は図２の画像形成装置を用いて２枚を連続プリントした場合を示したものである。図１において、感光ドラム回転のグラフおよび現像ローラ回転のグラフはそれぞれ、上に凸のとき（すなわちＯＮの時）に感光ドラム１または現像ローラ８が回転駆動されることを示している。
【０１５８】
なお、本実施形態においては、感光ドラム１と現像ローラ８が常時当接した状態であるため、感光ドラム１の回転と現像ローラ８の回転が同期して行われる。しかし、感光ドラムと現像ローラが常時離間している所謂非接触現像の場合や、接触現像であっても離間可能な機構を有している場合には、感光ドラム１と現像ローラ８の回転は非同期で行われる。本発明で用いられる現像方式は上記いずれのものであってもよく、現像方式に求められる特性に応じて適宜選択される。
【０１５９】
図１において、不図示のパーソナルコンピュータ等からプリント出力の要請がされると、感光ドラム１及び現像ローラ８の回転開始に伴って現像バイアス電源１０及びブレードバイアス電源１１から約−４００Ｖの同電位がそれぞれ印加される。現像ローラ８等の回転開始当初は、まだ画像を描き出す前の準備回転の時間であり、非画像形成時である。
【０１６０】
画像形成時とは、転写紙Ｐの余白領域を除いた部分にトナー像を形成するための各工程の時間をいう。また、非画像形成時とは、画像形成時を除き、かつ現像ローラが回転しているときをいう。たとえば、準備前回転、準備後回転、または、プリントとプリントの間に相当する所謂「紙間」などが非画像形成時に該当する。
【０１６１】
準備前回転が開始され、現像バイアス電源１０及びブレードバイアス電源１１から約−４００Ｖの電圧が印加された後、ブレードバイアス電源１１には現像ローラ８に印加される電圧よりもトナー粒子の帯電極性側に高い電圧が一瞬、印加される。前述したようにこのときの現像ローラ８に印加される電圧と現像ブレード９に印加される電圧の差（現像ローラ８と現像ブレード９との電位差）は６０〜５００Ｖであることが好ましい。本実施形態ではこの電位差を２００Ｖとし、現像ブレード９に約−６００Ｖの電圧を印加する。また、この非画像形成時に現像ブレード９に印加される、現像ローラよりも高い電圧の印加時間は画像形成に悪影響を及ぼさない範囲で、画像形成装置のプロセススピードや現像剤の現像ブレード９への付着のしやすさ等により適宜選択されるものであり、特に限定されるものではないが、５ｍｓｅｃ〜数秒の範囲であることが好ましい。なお、本実施形態ではこの印加時間を３００ｍｓｅｃとする。
【０１６２】
このように、転写紙Ｐ上の画像に影響を及ぼさない時間である非画像形成時に、現像ブレード９に−６００Ｖを、現像ローラ８には−４００Ｖを印加する。すなわち、本実施形態では負帯電性の粒子（トナー及び外添剤）にとって現像ブレード側から現像ローラ側へ転移可能な電位差が供給されることになる。従って、現像ローラの回転開始直後に現像ブレード９に付着する（現像ローラと現像ブレード当接部から固定端側：図７中ａ部）負極性外添剤は現像ローラ８側へ転移されることになる。
【０１６３】
現像ブレード９に−６００Ｖを、現像ローラ８には−４００Ｖを一瞬印加した後は、現像バイアス電源１０とブレードバイアス電源１１の電圧はほぼ同電位の−４００Ｖとなり、１枚目の画像形成領域となり画像形成が行われる（画像形成時）。この画像形成時は、現像ローラ８及び現像ブレード９は略同電位であるため、現像ローラ８の回転動作により現像ブレード９の当接部から固定端側に、トナー層のもつ電荷によって負極性の外添剤が転移する。しかしながら、反転トナーや正極性外添剤等が現像ブレード９に付着することはない。
【０１６４】
１枚目の画像形成時が終了すると、次の画像形成との間の所謂「紙間」といわれる領域になる。この紙間において、準備前回転と同様に３００ｍｓｅｃ間、現像ブレード９に−６００Ｖの電圧が印加される。この現像ブレード９に印加された電圧により、１枚目の画像形成中に現像ブレード９の当接部から固定端側に付着した負極性外添剤は現像ローラ８側に転移することとなる。これは、現像ローラ８が回転している間に行われていることから、再び現像ブレード９側に負極性外添剤が戻ることはない。
【０１６５】
そして、１枚目の画像形成と同様に２枚目の画像形成が行われる。画像形成時においては、前述同様に負極性外添剤が現像ブレード９の当接部から自由端先端に付着堆積していく。
【０１６６】
２枚目の画像形成が終了すると、次回のプリントのための準備後回転になる。このときも準備前回転及び紙間と同様に３００ｍｓｅｃ間、現像ブレード９に−６００Ｖの電圧が印加される。この現像ブレード９に印加された電圧により、１枚目の画像形成中に現像ブレード９の当接部から固定端側付着した負極性外添剤は現像ローラ８側に転移することとなる。これは、現像ローラ８が回転している間に行われていることから、再び現像ブレード９側に負極性外添剤が戻ることはない。
【０１６７】
そして準備後回転動作が終了して、現像ローラ８と感光ドラム１の回転が停止する。
【０１６８】
このように、画像形成時に現像ブレード９の当接部から固定端側付着した負極性外添剤を、非画像形成時に現像ブレード９と現像ローラ８間に一瞬電位差を設けて現像ローラ８側に戻すことで、現像ブレード９をリフレッシュすることが可能となる。その結果、現像ブレード当接部から固定端側に付着した負極性外添剤を堆積させることがないため、現像ブレード９へのトナー融着を防止することが可能となる。
【０１６９】
また、現像ブレード９と現像ローラ８間に一瞬電位差をもうけるタイミングとして、非画像形成時としているのは、同電位から電位差を付けるようにした場合に、現像ローラ８上に規制されるトナー担持量が変化してしまい、画像上では濃度の段差が発生するためである。
【０１７０】
また、非画像形成時において、現像ブレード９に現像ローラ８よりも高い電圧を印加する時間は毎回設ける必要はなく、例えば画像形成前の準備前回転時に行う、準備後回転時のみ行う等、適宜行うことが可能である。また、この電圧印加の回数は本実施形態においては３００ｍｓｅｃの１回のみであるが、例えば準備前回転中に複数回の電位差を設けることも可能である。
【０１７１】
なお、本実施形態では現像剤規制部材（現像ブレード９）および現像剤担持体（現像ローラ８）のそれぞれに別個の電圧印加手段（現像バイアス電源１０およびブレードバイアス電源１１）を設けた構成としているが、同一の電圧印加手段によって現像剤規制部材および現像剤担持体に電圧を印加する構成であってもよく、特に限定されるものではない。
【０１７２】
また本発明の画像形成方法で用いられる現像手段を画像形成装置本体に着脱自在なカートリッジとして構成することも好ましい。この場合、現像手段のみをカートリッジ化した現像カートリッジとしてもよいし、現像手段に加えて像担持体、帯電手段、クリーニング手段などを一体化したプロセスカートリッジとしてもよい。これにより、トナー補給や寿命を過ぎた現像器の交換等、諸々メンテナンス作業に係わる使用者の労力を軽減し、簡単な操作で安定した出力画像が得られる様になる。
【０１７３】
図３〜図５は本発明の画像形成方法を好適に用いられる画像形成装置の第２の実施形態を示す図である。以下これらの図を参照して、本発明の画像形成方法の第２実施形態について説明する。なお、この第２実施形態の画像形成装置において第１実施形態で用いた部材と同一部材には同一の番号を付して説明を省略する。
【０１７４】
図３は本第２実施形態に係る画像形成装置の概略断面図である。この画像形成装置は、カラー画像形成装置であり、像担持体としての感光ドラム１、この感光ドラム１表面を一様帯電する帯電ローラ２、帯電ローラ２によって一様帯電された感光ドラム１表面を露光して静電潜像を形成する露光器３、感光ドラム１表面の静電潜像に現像剤を転移させる現像手段としての現像器２２、感光ドラム１表面に転移された現像剤が転写される中間転写体２４を有する。
【０１７５】
現像器２２は回転支持体としてのロータリ２２ｘとイエロー現像カートリッジ２２ａとマゼンタ現像カートリッジ２２ｂとシアン現像カートリッジ２２ｃとブラック現像カートリッジ２２ｄとからなる。
【０１７６】
本実施形態にて画像形成装置は、電子写真方式のカラープリンタであり、不図示のパーソナルコンピュータやワークステーション等からの画像データを基にイエローＹ、マゼンタＭ、シアンＣ、ブラックＢｋの４色に分解し、分解された画像データにより順次各色のトナー像を感光ドラム１表面に形成し、それらを中間転写体２４上に重ね合わせ、紙などの転写材（記録媒体）に一括転写してフルカラー画像を得る。本実施形態の画像形成装置は、ロータリ２２ｘ内に複数の現像手段、即ち、現像カートリッジ２２ａ、２２ｂ、２２ｃ、２２ｄを搭載して構成される現像装置を採用した、所謂、ロータリ方式のカラープリンタとされる。
【０１７７】
図３において、画像形成装置は、像担持体としての光導電性の有機感光ドラム１を備える。画像形成動作に入ると、感光ドラム１は矢印ｑの方向に回転駆動される。この感光ドラム１表面は、接触帯電手段としての帯電ローラ２の芯金にバイアスを印加することによって、所定の暗部電位に一様に帯電される。次に、第１色目のイエロー（Ｙ）の画像データに応じて、露光器３によりＯＮ／ＯＦＦ制御されたレーザビームにより走査露光が施され、明部電位として第１の静電潜像が形成される。
【０１７８】
このように形成された静電潜像は、現像器２２のロータリ２２ｘ内に装着された現像手段（現像カートリッジ）により現像され、可視化される。このロータリ２２ｘは、第１色目の現像剤としてイエロー（Ｙ）トナーが収容された第１の現像カートリッジ２２ａ、第２色目の現像剤としてマゼンタ（Ｍ）トナーが収容された第２の現像カートリッジ２２ｂ、第３色目の現像剤としてシアン（Ｃ）トナーが収容された第３の現像カートリッジ２２ｃ、第４色目の現像剤としてブラック（Ｂｋ）トナーが収容された第４の現像カートリッジ２２ｄを搭載して一体化した構成となっている。このロータリ２２ｘは矢印ｒの方向に回転移動することにより、それぞれの色のトナー画像形成時に対応する現像カートリッジが感光ドラム１に対向する構成となっている。
【０１７９】
感光ドラム１と対向する現像位置に位置された現像カートリッジ（２２ａ、２２ｂ、２２ｃまたは２２ｄ）は、所定の層厚に規制された現像剤を担持する現像剤担持体としての現像ローラがモータ２３によりそれぞれ回転駆動され、この現像ローラの芯金に所定の電圧（現像バイアス）が印加されることにより現像が行われる。また、Ｙ、Ｍ、Ｃ、Ｂｋの各現像カートリッジ２２ａ、２２ｂ、２２ｃ、２２ｄは、それぞれ一つのカートリッジ（現像カートリッジ）として、その消耗度合いにより個々に交換可能となっている。
【０１８０】
先ず、前記第１の静電潜像は、第１色目の現像剤としてＹトナーが内包された第１の現像カートリッジ２２ａにより現像、可視化される。現像方法としては、接触／非接触を問わず用いることができるが、本実施形態ではイメージ露光と反転現像とを組み合わせた非磁性１成分トナーによる接触現像法を用いている。
【０１８１】
この可視化された第１色目のトナー像は、第２の像担持体としての中間転写体２４とのニップ部である第１の転写部位において、中間転写体２４の表面に静電転写（１次転写）される。中間転写体２４は、シリンダー上に導電弾性層と離型性を有する表層とを順次積層して形成されている。
【０１８２】
中間転写体２４は、通紙可能な最大転写材の長さよりも長い周長を有し、感光ドラム１に対して所定の押圧力をもって圧接されつつ、感光ドラム１の周速度と略等速の周速度をもって感光ドラム１の回転方向に対して逆方向（図３の矢印ｓの方向）に回転駆動される（接触部位では感光ドラム１表面と中間転写体２４表面は同方向に移動する）。
【０１８３】
そして、前記のように感光ドラム１表面に形成されたトナー像は、中間転写体２４のシリンダー部に対して現像剤の帯電極性とは逆極性の電圧（１次転写バイアス）が印加されることにより、中間転写体２４表面に静電転写（１次転写）される。なお、１次転写が終了した感光ドラム１表面に残留するトナーは、クリーニング手段６によって除去され、次の潜像形成に備える。
【０１８４】
引き続き同様な工程を繰り返し、その都度、Ｍトナーにより現像された第２色目のトナー像、Ｃトナーにより現像された第３色目のトナー像、Ｂｋトナーにより現像された第４色目のトナー像が順次中間転写体２４表面に転写、積層されることによりカラートナー像が形成される。
【０１８５】
その後、中間転写体２４表面に対して離間状態にあった転写ベルト１８が所定の押圧力をもって中間転写体２４表面に圧接、駆動回転される。前記転写ベルト１８は、転写ローラ１７を内包する。前記転写ローラ１７に対しては、トナーの帯電極性とは逆極性の電圧（２次転写バイアス）が印加されることにより、所定のタイミングで搬送されてくる転写紙Ｐ表面に、中間転写体２４表面に積層されているカラートナー像が一括転写（２次転写）され、この転写紙Ｐは定着器７へと搬送される。転写紙Ｐは、トナー像が定着器７にて永久画像として定着された後機外へと排出され、所望のカラープリント画像が得られる。
【０１８６】
また、２次転写が終了した中間転写体２４表面に残存するトナーは、所定のタイミングで中間転写体２４表面に対して当接状態となる中間転写体クリーニング装置１６により除去される。
【０１８７】
図５は、本実施形態で用いる現像手段であるＹ，Ｍ，Ｃ，Ｂｋのトナーをそれぞれ収容した現像カートリッジ２２ａ，２２ｂ，２２ｃ，２２ｄの構成を示す概略断面図であり、この現像カートリッジ２２ａ〜２２ｄは、図３に示した画像形成装置であるロータリ方式のカラープリンタに対し、不図示の現像カートリッジ交換用カバーを開閉することで着脱可能な構成とされ、図３中では、取り出し位置にあるシアン現像カートリッジ２２ｃを上方の矢印Ｄ方向に取り出すことができる。
【０１８８】
図３に示すロータリ方式のカラープリンタにおいては、取り出し位置にて現像カートリッジの着脱を行う必要があり、図中シアン現像カートリッジ２２ｃ以外のイエロー、マゼンタ、ブラック現像カートリッジである２２ａ、２２ｂ、２２ｄを交換する際には、ロータリ２２ｘを回転させて取り出したいカートリッジを着脱位置（図３中２２ｃの位置）に移動させる必要がある。
【０１８９】
以下、説明を簡略化するためＹトナーの現像カートリッジ２２ａについて説明するが、他色の現像カートリッジ２２ｂ，２２ｃ，２２ｄについても同様である。
【０１９０】
図５に示す本実施形態の現像カートリッジ２２ａは、現像剤として非磁性一成分のＹトナーを収容させてある反転現像手段である。この現像カートリッジ２２ａは、図中矢印ｅ方向に回転しながら感光ドラム１に接触して現像を行う現像ローラ８ａ、図中ｆ方向に回転することによって現像ローラ８ａに現像剤を供給する現像剤供給手段としての供給ローラ１２ａ、現像ローラ８ａ上の現像剤の塗布量及び帯電量を規制する現像剤規制部材としての現像ブレード９ａ、現像剤を供給ローラ１２ａに供給すると共に撹拌する撹拌部材１３ａを備えている。
【０１９１】
図４は本実施形態に係るシーケンスを示す図である。図４は上記４色のカラートナーによってフルカラー画像が１枚プリントされる場合を示したものである。図４において、不図示のパーソナルコンピュータ等からプリント出力の要請がされると、感光ドラム１が回転するとともに、１色目の現像カートリッジ２２ａを感光ドラム１の対向位置に移動させるためにロータリ２２ｘが回転を開始する。
【０１９２】
１色目（イエロー）の現像カートリッジ２２ａが感光ドラム１の対向位置にくると、現像ローラ８ａが準備前回転を始める。それと同時に、制御部（制御手段）２１の制御に従って電圧印加手段としての現像バイアス電源１９とブレードバイアス電源２０から電圧が供給される。このとき、現像バイアス電源１９からは現像ローラ８ａに約−４００Ｖの電圧が印加され、ブレードバイアス電源２０からは現像ブレード９ａに−６００Ｖをピークとした鋸波状の電圧が印加される。ブレードバイアス電源２０から印加される鋸波状の電圧は２波印加され、その周期は１波あたり２００ｍｓｅｃである。
【０１９３】
転写紙Ｐ上の画像に影響を及ぼさない時間である非画像形成時に、現像ブレード９ａに−６００Ｖをピークとした鋸波状の電圧を、現像ローラ８ａには−４００Ｖの電圧を印加する。すなわち、本実施形態では負帯電性の粒子（トナー及び外添剤）にとって現像ブレード９ａ側から現像ローラ８ａ側へ転移可能な電位差が供給されることになる。従って、現像ローラ８ａの回転開始直後に現像ブレード９ａに付着する負極性外添剤は現像ローラ８ａ側へ転移されることになる。
【０１９４】
現像ブレード９ａに−６００Ｖ（鋸波）が、現像ローラ８ａには−４００Ｖが一瞬印加された後は、現像バイアス電源１９とブレードバイアス電源２０とから印加される電圧はほぼ同電位の−４００Ｖとなり、１色目の画像形成領域に対して画像形成が行われる（画像形成時）。この画像形成時においては、現像ローラ８ａ及び現像ブレード９ａは略同電位であるため、現像ローラ８ａの回転動作により現像ブレード９ａの当接部から固定端側に、現像剤層のもつ電荷によって負極性の外添剤が転移する。しかしながら、反転トナーや正極性外添剤等が現像ブレード９ａに付着することはない。
【０１９５】
１色目の画像形成が終了すると、現像カートリッジ２２ａの準備後回転となり、このときにブレードバイアス電源２０からは−６００Ｖをピークとした鋸波状の電圧が現像ブレード９に１波印加される。この動作により、画像形成中にイエロー現像カートリッジ２２ａの現像ブレード９ａに付着した負極性外添剤を現像ローラ８ａ側に転移させ、現像ブレード９ａをリフレッシュ可能である。
【０１９６】
現像ローラ８ａの回転はオフされ、次の色（マゼンタ）の画像形成との間にロータリ２２ｘが回転を行う。このロータリ２２ｘの回転時においては、現像バイアス電源１９及びブレードバイアス電源２０からの電圧供給はオフされる。２色目（マゼンタ）の現像カートリッジ２２ｂが感光ドラム１の対向位置まで移動すると、ロータリ２２ｘの回転が終了し、現像カートリッジ２２ｂはこの対向位置で停止する。
【０１９７】
そして、１色目（イエロー）の時と同様に、現像ローラ８ｂが準備前回転を始める。それと同時に、現像バイアス電源１９とブレードバイアス電源２０から電圧が供給される。このとき、現像バイアス電源１９からは約−４００Ｖの電圧が印加され、ブレードバイアス電源２０からは−６００Ｖをピークとした鋸波状の電圧が印加される。ブレードバイアス電源２０から印加される鋸波状の電圧は２波印加され、周期は１波あたり２００ｍｓｅｃ印加である。そして、１色目の画像形成と同様に２色目の画像形成が行われる。画像形成時においては、前述同様に負極性外添剤が現像ブレード９ｂの当接部から自由端先端に付着堆積していく。上記動作を４色目まで行う。
【０１９８】
このように、各色の準備前回転時に前回の画像形成時に現像ブレード上に付着した負極性外添剤を現像ローラ側に転移させることで、現像ブレードへの外添剤の堆積を防止し、安定した画像形成装置を提供できる。
【０１９９】
４色目まで画像形成が終了すると、４色目の準備後回転となり、前記同様ブレードバイアス電源２０からは−６００Ｖをピークとした鋸波状の電圧が１波印加される。その後、現像ローラ８ｄの回転はオフされ、ロータリ２２ｘが回転する。このロータリ２２ｘの回転前に、現像バイアス電源１９及びブレードバイアス電源２０からの電圧供給はオフされる。
【０２００】
画像形成が終了し、ロータリ２２ｘの回転が終了すると、中間転写体２４や感光ドラム１等が次回のプリントのための本体後回転になり、本体後回転が終了すると感光ドラム１は停止する。
【０２０１】
【実施例】
以下に実施例を挙げてより具体的に本発明を説明するが、これは本発明を何ら限定するものではない。
まず、実施例で用いられる現像剤の製造方法を説明する。
〈現像剤の製造例１〉
高速撹拌装置ＴＫ−ホモミキサーを具備した２リットル用四つ口フラスコ中に、イオン交換水９１０質量部とＮａ_３ＰＯ_４水溶液を添加し、回転数を９０００ｒｐｍに調整し、６３℃に加温した。ここにＣａＣｌ_２水溶液を徐々に添加し、微小な難水溶性分散剤Ｃａ_３（ＰＯ_４）_２を含む水系分散媒体を調製した。
【０２０２】
・スチレン単量体　　　　　　　　　　　　　　　　　　８０質量部
・２−エチルヘキシルアクリレート単量体　　　　　　　２０質量部
・ジビニルベンゼン単量体　　　　　　　　　　　　０．２５質量部
・飽和ポリエステル樹脂　　　　　　　　　　　　　　　１０質量部
（テレフタル酸−プロピレンオキサイド変性ビスフェノールＡ、酸価１５ｍｇＫＯＨ／ｇ）
・カーボンブラック（一次粒子径４０ｎｍ）　　　　　　　８質量部
・離型剤（ベヘン酸ベヘニル）　　　　　　　　　　　　１０質量部
・ベンジル酸金属錯体　　　　　　　　　　　　　　　２．０質量部
【０２０３】
ボールミルを用い上記材料を３時間分散させた後、ボールミルより内容物を単離した。この内容物に対して、重合開始剤である２、２’−アゾビス（２、４−ジメチルバレロニトリル）３質量部を添加して重合性単量体組成物とし、これを上記水系分散媒体中に投入し、回転数９０００ｒｐｍを維持しつつ造粒した。その後、パドル撹拌翼で撹拌しつつ６５℃で４時間反応させ、その後に８０℃で５時間重合させ、更に８０℃で１３．３ｋＰａ（１００Ｔｏｒｒ）以下の圧力で減圧蒸留した。
【０２０４】
反応終了後、懸濁液を冷却し、塩酸を加えて難水溶性分散剤Ｃａ_３（ＰＯ_４）_２を溶解し、濾過、水洗、乾燥し、その後に風力分級によって所望の粒度に分級し、トナー粒子（１）を得た。
【０２０５】
上記トナー粒子（１）１００質量部に対して、流動性向上剤として原体に対して２０％のシリコーンオイルで処理した、ＢＥＴ比表面積が１３０ｍ^２／ｇの疎水性シリカ微粒子１を１．３質量部と、一次粒子径が３００ｎｍの酸化チタン化合物０．２質量部を加え、ヘンシェルミキサー（三井三池化工機社製）にて周速４３ｍ／ｓの回転速度で３分間混合し、上記各粉体をトナー粒子（１）表面に均一に固着させ、現像剤Ｎｏ．１を得た。現像剤Ｎｏ．１の平均粒子径は６．５μｍ、粒径が４μｍ以下の粒子の個数％が７．５％、シリカ微粒子の遊離率が２．７％であった。その他の物性値は表２に示す。
【０２０６】
〈現像剤の製造例２、３〉
現像剤の製造例１において、添加するシリカ微粒子の種類と添加量を表２に示すように変えた以外は上記製造例１と同様の方法を用いて現像剤Ｎｏ．２および現像剤Ｎｏ．３を得た。各現像剤Ｎｏ．２およびＮｏ．３の物性値を表２に示す。なお、表２中で用いた各シリカ微粒子の物性は表１に示す。
【０２０７】
〈現像剤の製造例４〉
現像剤の製造例１において、難水溶性分散剤の量を調整することにより、平均粒径が５．５μｍであり、粒径が４μｍ以下の粒子の個数％が２０％のトナー粒子（４）を得た。このトナー粒子（４）１００質量部に対して、シリカ微粒子４および酸化チタン化合物を表２に示す添加量で添加し、ヘンシェルミキサーにて周速２０ｍ／ｓの回転速度で３分間混合した以外は、製造例１と同様の方法を用いて現像剤Ｎｏ．４を得た。現像剤Ｎｏ．４の物性値を表２に示す。なお、表２中で用いたシリカ微粒子４の物性は表１に示す。
【０２０８】
〈現像剤の製造例５〉
・スチレン−ブチルアクリレート共重合体（８０／２０）　　　　　　　　　　１００部
・カーボンブラック（一次粒子径４０ｎｍ）　　　　　　　　　　　　　８部
・低分子量ポリプロピレン　　　　　　　　　　　　　　　　　　　　　５部
・ベンジル酸金属錯体　　　　　　　　　　　　　　　　　　　　　　　２部
上記成分をバンバリーミキサーにより溶融混練し、冷却後、ジエットミルにより微粉砕を行い、さらに、微粉砕物を風力分級によって所望の粒度に分級し、トナー粒子（５）を得た。
【０２０９】
上記トナー粒子（５）１００質量部に対して、流動性向上剤として原体に対して２０％のシリコーンオイルで処理した、ＢＥＴ比表面積が１３０ｍ^２／ｇの疎水性シリカ微粒子１を１．３質量部と、一次粒子径が４００ｎｍのハイドロタルサイト化合物０．２質量部を加え、ヘンシェルミキサーにて周速４３ｍ／ｓの回転速度で３分間混合し、上記各粉体をトナー粒子（５）表面に均一に固着させ、現像剤Ｎｏ．５を得た。現像剤Ｎｏ．５の平均粒子径は６．７μｍ、粒径が４μｍ以下の粒子の個数％が８．９％、シリカ微粒子の遊離率が２．４％であった。その他の物性値は表２に示す。
【０２１０】
〈現像剤の製造例６、７〉
現像剤の製造例５において、添加するシリカ微粒子及びその他の外添剤の種類と添加量を表２に示すように変え、さらに混合装置をサイクロミックス（ホソカワミクロン社製）に変更し、現像剤の製造例６は周速２５ｍ／ｓの回転速度で３分間、現像剤の製造例７は周速１５ｍ／ｓの回転速度で３分間混合した以外は上記製造例５と同様の方法を用いて現像剤Ｎｏ．６および現像剤Ｎｏ．７を得た。各現像剤Ｎｏ．６およびＮｏ．７の物性値を表２に示す。
【０２１１】
〈現像剤の製造例８〉
・ポリエステル樹脂（１）　　　　　　　　　　　　　　７０質量部
［ポリオキシプロピレン（２．２）−２，２−ビス（４−ヒドロキシフェニル）プロパン／ポリオキシエチレン（２．２）−２，２−ビス（４−ヒドロキシフェニル）プロパン／テレフタル酸／フマール酸／トリメリット酸から生成されたポリエステル樹脂（酸価１０．８ｍｇＫＯＨ／ｇ、Ｔｇ＝６５℃、Ｍｗ＝４５０００、Ｔｍ＝１０５℃）］
・カーボンブラック（一次粒子径４０ｎｍ）　　　　　　３０質量部
【０２１２】
上記材料をニーダー型ミキサーに仕込み、混合しながら非加圧下で１２０℃に昇温し、十分に前混合した。その後、三本ロールで二回混練し、第一の混練物を得た。
【０２１３】
・第一の混練物　　　　　　　　　　　　　　　　　１６．７質量部
（混練物１００質量部中の着色剤の含有量３０質量部）
・ポリエステル樹脂（１）　　　　　　　　　　　　８８．３質量部
・離型剤　　　　　　　　　　　　　　　　　　　　　　　５質量部
［ポリエチレン誘導体、Ｍｎ１０００、酸価０．６ｍｇＫＯＨ／ｇ］
・ジ−アルキルサリチル酸のアルミニウム錯体　　　　　　４質量部
上記材料をヘンシェルミキサーにより十分予備混合し、二軸式押し出し機で溶融混練し、溶融混練物を冷却し、冷却後ハンマーミルを用いて固化物を約１〜２ｍｍ程度に粗粉砕し、次いでエアージェット方式による微粉砕機で微粉砕した。、さらに、微粉砕物を風力分級によって所望の粒度に分級し、トナー粒子（８）を得た。
【０２１４】
このトナー粒子（８）１００質量部に対し、流動性向上剤として原体に対して３５％のシリコーンオイルで処理した、ＢＥＴ比表面積が１５０ｍ^２／ｇの疎水性シリカ微粉体４を１．０質量部と、一次粒子径が３０ｎｍの酸化チタン化合物０．１質量部を加え、ヘンシェルミキサーにて周速２０ｍ／ｓの回転速度で３分間混合し、上記各粉体をトナー粒子（８）に均一に固着させ、現像剤Ｎｏ．８を得た。
【０２１５】
現像剤Ｎｏ．８の円相当個数平均径は５．７μｍであり、粒径が４μｍ以下の粒子の個数％が１８％であった。その他の物性値を表２に示す。
【０２１６】
〈現像剤の製造例９〉
現像剤の製造例８において、添加するポリエステル樹脂を、［ポリオキシプロピレン（２．２）−２，２−ビス（４−ヒドロキシフェニル）プロパン／テレフタル酸／フマール酸／トリメリット酸から生成されたポリエステル樹脂（酸価１５．２ｍｇＫＯＨ／ｇ、Ｔｇ＝６３、Ｍｗ＝１８０００、Ｔｍ＝１０３℃）］に変更した以外は上記製造例８と同様の方法を用いて微粉砕物を得た。得られた微粉砕物を、ローターを回転して機械的衝撃力を与える方式の表面改質装置を用いて、１６００ｒｐｍ（周速８０ｍ／ｓｅｃ）で３分間、バッチ式により表面処理した。次いで風力分級によって所望の粒度に分級し、トナー粒子（９）を得た。
【０２１７】
このトナー粒子（９）に対して、添加するシリカ微粒子および酸化チタン化合物の種類と添加量を表２に示すように変え、ヘンシェルミキサー（三井三池化工機社製）にて周速２５ｍ／ｓの回転速度で３分間混合した以外は上記製造例８と同様の方法を用いて現像剤Ｎｏ．９を得た。各現像剤９の物性値を表２に示す。
【０２１８】
〈現像剤の製造例１０〜１２〉
現像剤の製造例１において、添加する着色剤を製造例１０ではＣ．Ｉ．ピグメントイエロー９３に、製造例１１ではＣ．Ｉ．ピグメントレッド５３に、製造例１２ではＣ．Ｉ．ピグメントブルー１５：３に変更した以外は製造例１と同様の方法を用いて現像剤Ｎｏ．１０〜Ｎｏ．１２を得た。各現像剤の物性値を表２に示す。
【０２１９】
〈現像剤の製造例１３〜１５〉
現像剤の製造例５において、添加する着色剤を製造例１３はＣ．Ｉ．ピグメントイエロー９３に、製造例１４はＣ．Ｉ．ピグメントレッド５３に、製造例１５はＣ．Ｉ．ピグメントブルー１５：３に変更する以外は製造例５と同様の方法を用いて現像剤Ｎｏ．１３〜Ｎｏ．１５を得た。各現像剤の物性値を表２に示す。
【０２２０】
〈現像剤の製造例１６〉
現像剤の製造例１において、添加するシリカ微粒子の種類を表２に示すように変えた以外は上記製造例１と同様の方法を用いて現像剤Ｎｏ．１６を得た。現像剤Ｎｏ．１６の物性値を表２に示す。なお、表２中で用いた各シリカ微粒子の物性は表１に示す。
【０２２１】
〈現像剤の製造例１７、１８〉
現像剤の製造例１において、添加するシリカ微粒子又は酸化チタンの種類及び量を表２に示すように変え、混合装置をレーディゲミキサー（マツボウ社製）に変更し、現像剤の製造例１７は周速１４ｍ／ｓの回転速度で２分間、現像剤の製造例１８は周速５０ｍ／ｓで３分間混合する以外は製造例１と同様の製造方法を用いて現像剤Ｎｏ．１７及びＮｏ．１８を得た。現像剤Ｎｏ．１７及びＮｏ．１８の物性値を表２に示す。なお、表２中で用いた各シリカ微粒子の物性は表１に示す。
【０２２２】
〈現像剤の製造例１９〉
現像剤の製造例５において、添加するシリカ微粒子の量を表２に示すように変えた以外は上記製造例５と同様の方法を用いて現像剤Ｎｏ．１９を得た。現像剤Ｎｏ．１９の物性値を表２に示す。
【０２２３】
〈現像剤の製造例２０〉
現像剤の製造例８において、添加するシリカ微粒子の種類および添加量を表２に示すように変えた以外は上記製造例８と同様の方法を用いて現像剤Ｎｏ．２０を得た。現像剤Ｎｏ．２０の物性値を表２に示す。
【０２２４】
【表１】

【０２２５】
【表２】

【０２２６】
次に、実施例で用いた画像形成装置について説明する。
〈画像形成装置の例１〉
図１および図２に示す第１実施形態の画像形成装置を画像形成装置Ｎｏ．１とした。この装置の説明は上述した通りである。
【０２２７】
〈画像形成装置の例２〉
図３〜図５に示す第２実施形態の画像形成装置を画像形成装置Ｎｏ．２とした。この装置の説明は上述した通りである。
【０２２８】
〈画像形成装置の例３〉
画像形成装置１において、画像形成時および非画像形成時を通して現像ローラ８と現像ブレード９に同電位（−４００Ｖ）のバイアスを印加した。すなわち非画像形成時に現像ローラ８と現像ブレード９との間に電位差を設けない構成とした。これを画像形成装置３とした。
【０２２９】
〈画像形成装置の例４〉
画像形成装置１において、画像形成時および非画像形成時を通して現像ローラ８には−４００Ｖの電位のバイアスを、現像ブレード９には−５００Ｖの電位の電圧をそれぞれ印加した。すなわち、画像形成時にも現像ローラ８と現像ブレード９との間に電位差を設ける構成とした。これを画像形成装置４とした。
各画像形成装置１〜４の電圧印加方法および現像方法を表３に示す。
【０２３０】
【表３】

【０２３１】
〈実施例１〉
画像形成装置１および現像剤Ｎｏ．１を用い、高温高湿環境（３０℃；相対湿度８０％）と低温低湿環境（１５℃；相対湿度１０％）で所定印字率のパターンを約１００００枚出力した場合の、高温高湿環境におけるカブリと低温低湿環境における縦スジの発生を評価した。評価は５００枚ごとにベタ画像と中間調画像を出力して行った。
【０２３２】
かぶり評価は、高温高湿環境下で出力された画像上のカブリ値が３％以上にった時点を画像不良とみなし、画像不良発生時期で以下のようにランクわけを行った。
・１００００枚耐久印字しても３％以上のかぶりを発生しない　　　：Ａ
・９０００枚耐久印字以降に、画像不良発生　　　　　　　　　　　：Ｂ
・８０００枚耐久印字以降に、画像不良発生　　　　　　　　　　　：Ｃ
・耐久初期〜５０００枚耐久印字までに画像不良発生　　　　　　　：Ｄ
【０２３３】
低温低湿環境下のスジの発生の評価は、以下の評価基準によりランク分けを行い評価した。
・１００００枚耐久印字しても均一な中間調を再現し、現像ブレードを観察しても融着物は見られない　　　　　　　　　　　　　　　　　　　　　：Ａ
・１００００枚耐久印字しても均一な中間調を再現するが、現像ブレードを観察すると、軽微な融着物あり　　　　　　　　　　　　　　　　　　　：Ｂ
・８０００枚耐久印字以降に、中間調画像に濃いスジが発生　　　　：Ｃ
・初期〜８０００枚耐久印字までに目立った濃淡スジ発生　　　　　：Ｄ
評価結果を表４に示す。
【０２３４】
〈実施例２〜９〉
実施例１において、現像剤を表４に示すように変えた以外は上記実施例１と同様の方法を用いて耐久印字を行い、高温高湿環境におけるカブリと低温低湿環境における縦スジの発生について評価した。評価結果を表４に示す。
【０２３５】
〈実施例１０〉
実施例１において、画像形成装置をＮｏ．２に変更し、カートリッジ２２ａに現像剤Ｎｏ．１０を、カートリッジ２２ｂに現像剤Ｎｏ．１１を、カートリッジ２２ｃに現像剤Ｎｏ．１２を、カートリッジ２２ｄに現像剤Ｎｏ．１をそれぞれ充填した以外は、上記実施例１と同様の方法を用いてフルカラー画像で耐久印字を行い、高温高湿環境におけるカブリと低温低湿環境における縦スジの発生について評価した。評価結果を表４に示す。
【０２３６】
〈実施例１１〉
実施例１において、画像形成装置をＮｏ．２に変更し、カートリッジ２２ａに現像剤Ｎｏ．１３を、カートリッジ２２ｂに現像剤Ｎｏ．１４を、カートリッジ２２ｃに現像剤Ｎｏ．１５を、カートリッジ２２ｄに現像剤Ｎｏ．５をそれぞれ充填した以外は、上記実施例１と同様の方法を用いてフルカラー画像で耐久印字を行い、高温高湿環境におけるカブリと低温低湿環境における縦スジの発生について評価した。評価結果を表４に示す。
【０２３７】
〈比較例１〉
実施例１において、現像剤を現像剤Ｎｏ．１６に変えた以外は上記実施例１と同様の方法を用いて耐久印字を行い、高温高湿環境におけるカブリと低温低湿環境における縦スジの発生について評価した。結果は表４に示すように、ＢＥＴ比表面積の大きいシリカ微粒子を用いたために、ブレードへのシリカの静電付着が強く、バイアス印加によるリフレッシュ効果が十分に得られず、Ｌ／Ｌ環境において耐久寿命を待たずして、目立ったスジ画像が発生した。
【０２３８】
〈比較例２〉
実施例１において、現像剤を現像剤Ｎｏ．１７に変えた以外は上記実施例１と同様の方法を用いて耐久評価を行った。結果は表４に示すように、ＢＥＴ比表面積の小さいシリカ微粒子を用いたために、Ｈ／Ｈ環境においては帯電不良によるカブリが耐久に伴い顕著に悪化し、Ｌ／Ｌ環境においては遊離率したシリカ微粒子がブレードへ蓄積され耐久初期からスジ画像が発生し、実用に耐えなかった。
【０２３９】
〈比較例３〉
実施例１において、現像剤を現像剤Ｎｏ．１８に変えた以外は上記実施例１と同様の方法を用いて耐久評価を行った。結果は表４に示すように、シリカ微粒子の添加量が少ないため、現像剤の耐久劣化に伴って良好な摩擦帯電が行えず、Ｈ／Ｈ環境で顕著にカブリが悪化した。
【０２４０】
〈比較例４〉
実施例１において、現像剤を現像剤Ｎｏ．１９に変えた以外は上記実施例１と同様の方法を用いて耐久評価を行った。結果は表４に示すように、シリカ微粒子の添加量が多いため、遊離シリカのブレードへの付着量が増え、バイアス印加によるリフレッシュ効果が十分に得られず、耐久寿命を待たずして、目立ったスジ画像が発生した。
【０２４１】
〈比較例５〉
実施例１において、現像剤を現像剤Ｎｏ．２０に変えた以外は上記実施例１と同様の方法を用いて耐久評価を行った。結果は表４に示すように、シリカ微粒子の添加量が多く、更に現像剤の粒径が４μｍ以下の粒子の含有量が多いために、帯電量の高いこれらのシリカ微粒子及び現像剤の微粉が強固にブレードに付着し、この付着によってブレード当接部による摩擦力が大きくなり、現像剤の融着が促進されて比較例４よりも初期からスジ画像が発生した。
【０２４２】
〈比較例６〉
実施例１において、画像形成装置を画像形成装置Ｎｏ．３に変えた以外は上記実施例１と同様の方法を用いて耐久評価を行った。結果は表４に示すように、ブレードと現像剤担持体の間に電位差が無いために、帯電量の高いシリカ微粒子がブレードに蓄積する一方で、耐久寿命を待たずして劣悪なスジ画像が発生した。
【０２４３】
〈比較例７〉
実施例１１において、画像形成装置を画像形成装置Ｎｏ．４に変更した以外は、上記実施例１１と同様の方法を用いてフルカラー画像で耐久評価を行った。結果は表４に示すように、ブレードと現像剤担持体の間に常時電位差があるためにニップ下流部へのシリカ微粒子の付着は抑制されるものの、ハイドロタルサイトや反転帯電現像剤がブレード当接部のニップ上流側に電位に引きつけられて蓄積していくため、耐久に伴ってＬ／Ｌ環境においては現像スジ、Ｈ／Ｈ環境においては帯電不良によるカブリが悪化し、実用に耐えなかった。
【０２４４】
【表４】

【０２４５】
この結果、本発明の画像形成方法を用いることにより、低温低湿環境においても現像ブレードへのトナー融着が生じることなく、長期にわたって安定した画像形成を行うことが可能であることがわかった。また、高温高湿環境でも画像不良が生じることが無く、あらゆる環境に対応した画像形成方法であることがわかった。
【０２４６】
以上述べたように、現像ローラ回転中の現像ローラ８および現像ブレード９に印加される電圧の電位関係を、画像形成時には各々を略同電位とし、非画像形成時には少なくとも一時的に現像ローラ８の電位より現像ブレード９の電位の方をトナー粒子の帯電極性と同極性側に高くすることと、特定のシリカ微粒子を含有する本発明の現像剤を用いることで、現像ブレード９へのトナー付着・堆積・融着を防ぎ、画像濃度不良及び縦スジを防止することが可能となる。
【０２４７】
また、フルカラー画像形成装置においても、現像ローラ回転中の現像ローラ８（８ａ〜８ｄ）と現像ブレード９（９ａ〜９ｄ）の電位関係を、画像形成時には各々を略同電位とし、非画像形成時には少なくとも一時的に現像ローラ８の電位より現像ブレード９の電位の方をトナー粒子の帯電極性と同極性側に高くすることと、特定のシリカ微粒子を含有する本発明の現像剤を用いることにより、現像ブレード９へのトナー付着・堆積・融着を防ぎ、画像濃度不良及び縦スジを防止することが可能となる。
【０２４８】
併せて、画像形成要素の内、比較的消耗の激しい、現像剤を含む現像手段を、画像形成装置本体に着脱可能なプロセスカートリッジとすることで、諸々のメンテナンス作業に係わる使用者の労力軽減を図ることが可能となった。
【０２４９】
【発明の効果】
本発明によれば、低温低湿環境においても現像剤規制部材への現像剤の融着を防止することができる。また、高温高湿環境においもかぶり等の画像不良が発生しない。これにより、あらゆる環境においてかぶりや縦スジなどの画像不良の発生を防ぎ、長期にわたって安定した画像形成を行うことが可能となる。
【図面の簡単な説明】
【図１】本発明の画像形成方法が好適に用いられる第１実施形態の画像形成装置のシーケンスを説明する図
【図２】本発明の画像形成方法が好適に用いられる第１実施形態の画像形成装置の構成を示す概略断面図
【図３】本発明の画像形成方法が好適に用いられる第２実施形態の画像形成装置の構成を示す概略断面図
【図４】本発明の画像形成方法が好適に用いられる第２実施形態の画像形成装置のシーケンスを説明する図
【図５】第２実施形態の画像形成装置に装着される現像カートリッジの概略断面図
【図６】従来技術の画像形成装置の構成を示す概略断面図
【図７】現像剤規制部材へのトナー融着を説明するための図
【図８】現像剤の帯電量測定に用いられるファラデー・ケージを示す図
【図９】外添剤の帯電量測定に用いられる測定機を示す図
【符号の説明】
１　感光ドラム（像担持体）
２　帯電ローラ
３　露光器
４　現像器（現像手段）
５　転写ローラ
６　クリーニング手段
７　定着器
８、８ａ、８ｂ、８ｃ、８ｄ　現像ローラ（現像剤担持体）
９、９ａ、９ｂ、９ｃ、９ｄ　現像ブレード（現像剤規制部材）
１０　現像バイアス電源（電圧印加手段）
１１　ブレードバイアス電源（電圧印加手段）
１２、１２ａ、１２ｂ、１２ｃ、１２ｄ　供給ローラ
１３、１３ａ、１３ｂ、１３ｃ、１３ｄ　撹拌部材
１４　制御回路（制御手段）
１５　モータ
１６　中間転写体クリーニング装置
１７　転写ローラ
１８　転写ベルト
１９　現像バイアス電源（電圧印加手段）
２０　ブレードバイアス電源（電圧印加手段）
２１　制御部（制御手段）
２２　現像器
２２ａ、２２ｂ、２２ｃ、２２ｄ　現像カートリッジ（現像手段）
２２ｘ　ロータリ
２３　モータ
２４　中間転写体
Ｐ　転写紙[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming method such as an electrophotographic method or an electrostatic recording method used for a copying machine or a printer, and a developer and a process cartridge used for the image forming method.
[0002]
[Prior art]
In recent years, the shift from two-component development to non-magnetic one-component development has been progressing due to the trend toward lower cost and more compact printers, and common use of printers and engines has been achieved even in low-speed digital copiers. As a result, those using the non-magnetic one-component system are increasing. For the same reason, a non-magnetic one-component system has become mainstream in color printers. In order to cope with the global expansion of the non-magnetic one-component system, which has become increasingly widespread, there has been a demand for a less expensive image forming apparatus capable of guaranteeing stable image quality under any environment.
[0003]
2. Description of the Related Art Conventionally, as an image forming apparatus of this type, for example, one having a configuration shown in FIG. 6 is known. FIG. 6 schematically shows an example of a basic configuration of a conventional image forming apparatus. In this example, a photosensitive drum 100 is used as an image carrier. The photosensitive drum 100 has a photosensitive material layer (for example, an organic photosensitive material layer) formed on the surface of a cylindrical base made of, for example, aluminum, and is driven to rotate. Around the photosensitive drum 100, a charging roller 101, a laser beam scanning optical system (not shown), a developing device 102 as a developing unit, a transfer roller 111, and a cleaner 109 are arranged in this order from the upstream side in the rotation direction.
[0004]
After uniformly charging the photosensitive drum 100 with the charging roller 101, an electrostatic latent image is formed on the photosensitive drum 100 by laser beam scanning light. Then, the toner in the developing device is transferred onto the photosensitive drum 100 according to the electrostatic latent image, so that the electrostatic latent image is visualized.
[0005]
The recording medium, that is, the transfer paper P, receives the transfer of the visible image (toner image) at a substantially contact portion between the photosensitive drum 100 and the transfer roller 111, and the image on the transfer paper P is fused and fixed by the fixing device 110.
[0006]
The developing device 102 includes a developing roller 103 serving as a developer carrier, a supply roller 105 that supplies a non-magnetic one-component toner (negative polarity) to the developing roller 103, and a stirring member 106 that conveys the toner in the container to a vicinity of the supply roller 105. And a developing blade 104 as a developer regulating member that regulates the amount of toner on the developing roller 103. The developing roller 103 is formed of an elastic body so as to be in contact with the photosensitive drum 100. The developing blade 104 is lightly contacted with the developing roller 103 by utilizing the spring elasticity of a thin metal plate.
[0007]
To the developing roller 103, a predetermined potential is supplied from a developing bias power supply 107 to transfer toner from the developing roller 103 to the photosensitive drum 100 side. Further, a blade bias power supply 108 may be connected to the developing blade 104 in order to stabilize the charge amount of the toner (for example, see Patent Document 1). There are various types of blade bias power supplies 108, such as those having the same potential as the developing bias power supply 107 and those supplying different potentials.
[0008]
The non-magnetic one-component developing method is a very simple and excellent developing method suitable for downsizing of the device.However, since the formation of a thin layer of developer needs to be directly pressed by a regulating member, the biggest bottleneck is developing. Fusion of the developer to the developer regulating member. To avoid fusing, approaches from developing device design such as reducing the blade contact pressure and approaches from developer designing such as using a non-fusible developer with controlled softening point Various studies have been made. To solve the above-mentioned problem, a non-magnetic one-component developing method has been proposed in which the softening point of the toner is 95 ° C. or more and 120 ° C. or less and toner particles of 5 μm or less are 10% by number or less (for example, see Patent Document 2) ).
[0009]
However, when the present inventors conducted additional tests using the developing device shown in FIG. 6, the effect of improving fusion to the developer regulating blade was recognized in a normal temperature and normal humidity environment. After forming about 800 sheets of image, density unevenness in the form of vertical stripes occurred in the halftone image due to fusion of the blade. Further, in order to respond to the demand for higher definition, which is increasingly required in the electrophotographic process, it is necessary to use toner particles having a small average particle diameter. The developing system used has a low yield in toner production and is uneconomical.
[0010]
Observing the developing blade 104 in order to investigate the cause of the vertical stripes generated in the low-temperature and low-humidity environment, a part a of the developing blade 104 (in the vicinity of the contact portion between the developing blade 104 and the developing roller 103 and when the developing roller rotates (On the downstream side in the direction), a fused mass was generated. In the portion where the fused mass exists, the developer could not be charged satisfactorily, the amount of toner on the developing roller 103 became thick, and vertical stripe-shaped density unevenness occurred on the image.
[0011]
The reason for this will be described with reference to the schematic diagram of toner fusion in FIG. In FIG. 7, T is a non-magnetic one-component toner having a negative polarity, and the toner T is composed of toner particles and an external additive as auxiliary particles.
[0012]
The toner carried on the developing roller 103 has a negative polarity, and in a normal environment, the toner layer carried on the developing roller 103 passing through the developing blade 104 has a potential of about −20 to −60 V (Trec (Measured with a surface potentiometer model 334 manufactured by KK) At the contact portion between the developing roller 103 and the developing blade 104, the surface of the developing blade 104 is constantly rubbed by the toner, so that the external additive hardly adheres.
[0013]
However, on the downstream side (part a in the figure) of the contact portion between the developing roller 103 and the developing blade 104, a potential gradient is generated because the toner layer gradually separates from the surface of the developing blade. That is, even if the developing roller 103 and the developing blade 104 have the same electric potential, the negatively charged toner layer carried on the developing roller 103 has an electric potential. It becomes larger in the negative polarity than the blade 104.
[0014]
Therefore, the negative external additive G1 adhering to the toner on the outermost surface of the toner layer is separated from the toner surface and adheres to the developing blade surface a. The external additive adhering to the surface a of the developing blade gradually increases as the image formation proceeds, and the adhering external additive is fused by friction. When the adhering external additive was analyzed by EDAX, Si was detected with high intensity, so it was confirmed that the fused external additive was mainly composed of silica fine particles. Since the fusion is performed in a non-uniform manner in the longitudinal direction, the portion of the blade 104 to which the external additive is adhered cannot be triboelectrically satisfactorily compared to the non-contaminated portion, and the toner having a small charge amount. Is thickly coated, so that only the fused portion is developed deeply on the vertical stripes. The fused mass due to the external additive gradually grows, and in a severe case, the vertical streak-shaped light and dark line deteriorates to a band shape. When the amount of fusion of the external additive is further increased, the surface of the blade 104 is roughened, and the toner is fused by frictional heat. Density does not appear
[0015]
The amount of fusion of the external additive depends on the amount of triboelectric charge of the developer depending on the environment in which the external additive is used. In addition, by controlling the type and amount of silica fine particles to be externally added to the toner and the state of adhesion to the toner, and controlling the amount of charge by controlling the particle size distribution of the toner, a streak-like image due to fusion is generated. It turns out that it is possible to delay.
[0016]
On the other hand, in the conventional image forming apparatus, for example, the developing roller 103 is constantly supplied with a voltage of −300 V from the developing bias power supply 107, and the developing blade 104 is supplied with −400 V from the blade bias power supply 108. And a developing blade 104, a potential difference of about 100 V is generated. Therefore, the external additive G1 having the negative polarity does not separate from the surface of the toner layer from the surface of the toner layer even when the charge of the toner layer is added. (For example, see Patent Document 1)
[0017]
However, in a low-temperature and low-humidity environment, when the image forming method provided with a potential difference described in the related art is used, the following problems occur. After the formation of about 1,300 sheets, the solid image had low density and vertical stripes. This also appeared on the developing roller 103 passing through the developing blade 104.
[0018]
As a result of observing the developing blade 104, the toner was adhered to one surface of the developing blade 104 at a portion b (near the contact portion between the developing blade 104 and the developing roller 103 and on the upstream side in the developing roller rotation direction). The attached toner was not melted, but was fixed to such an extent that the toner was not blown off even when air was blown with an air brush. The toner flow on the developing roller 103 is reduced because the flow of the toner is blocked by the fixation of the toner in the portion b, and the density unevenness in the form of vertical stripes occurs on the image.
[0019]
FIG. 7 illustrates a case where the potentials of the developing roller 103 (−300 V) and the developing blade 104 (−400 V) are changed. When the toner triboelectrically charged by the supply roller 105 reaches a position in front of the contact portion between the developing roller 103 and the developing blade 104 (near portion b), the reverse toner (positively charged toner) mixed in the toner layer is removed. The surface of the developing blade 104 is attracted to the portion b by the influence of the potential difference. In particular, as the potential difference between the developing roller 103 and the developing blade 104 is increased, the reverse toner is attracted, so that the toner is firmly fixed to the developing blade 104b.
[0020]
When the toner adhesion increases, the amount of toner entering before the contact portion (near the portion b) between the developing roller 103 and the developing blade 104 is damped, so that the thickness of the toner layer decreases. As a result, the density of the solid image becomes low. Further, since the amount of toner adhered to the portion b of the developing blade 104 differs in the longitudinal direction, vertical stripes occur in addition to the low density.
[0021]
This phenomenon occurs particularly remarkably when a positive external additive G2 is mixed in addition to the negative external additive G1 as the auxiliary particles of the toner. The positive external additive G2 may be added in addition to the toner particles and the negative external additive for stabilizing the charging property and adjusting the fluidity of the toner. Since the positive external additive G2 moves in the same manner as the above-described reversal toner, the positive external additive G2 adheres to the portion b which is the free end tip of the developing blade 104. The adhered positive external additive G2 generates low concentration and vertical stripes in the same manner as described above.
[0022]
Also, regarding the voltage applied to the developing blade 104, fine control is required because the surface potential of the toner layer changes depending on the environment in which it is used. Particularly, the surface potential of the toner layer tends to be high in a low humidity environment and low in a high humidity environment.
[0023]
Also, an image forming method in which an AC bias is constantly applied to the developing blade 104 has been proposed (for example, see Patent Document 3). However, when an AC bias is constantly applied, a toner cloud due to the AC bias is generated on the downstream side (a portion in the drawing) of the contact portion between the developing roller 103 and the developing blade 104. The generation of the toner cloud causes the toner to be scattered unnecessarily, and contaminates the inside of the machine. When an AC bias is applied to the developing blade 104, an attack sound is generated by the AC bias because the developing roller 103 and the developing blade 104 are in contact with each other.
[0024]
[Patent Document 1]
JP 05-011599 A
[Patent Document 2]
JP 2001-350285 A
[Patent Document 3]
JP-A-58-153972
[0025]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and in an image forming method for regulating the thickness of a developer layer on a developer carrying member using a developer regulating member, the present invention relates to It is an object of the present invention to provide an image forming method capable of preventing a low density image and vertical stripes by preventing fusion and performing stable image formation for a long period of time even in a low-temperature and low-humidity environment.
[0026]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above problems, and as a result, focused on the potential of the developer carrying member and the developer regulating member and the configuration of the developer, and during non-image formation, the developer carrying member and the developer regulating member The use of a developer containing a silica fine particle having a specific particle size by providing a potential difference therebetween suppresses the generation of a fusion product on the developer regulating member even in a low-temperature and low-humidity environment, and provides good image formation over a long period of time. And found that the present invention can be performed, and completed the present invention.
[0027]
That is, the present invention is as follows.
(1) An image forming method including a developing step of visualizing the electrostatic latent image by transferring a developer to the electrostatic latent image carried on the image carrier by a developing unit.
The developing unit is disposed to face the image carrier, a rotatable developer carrier that carries a developer, a developer regulating member that regulates the amount of developer on the developer carrier, Voltage applying means for applying a voltage to the developer carrier and the developer regulating member, and a voltage control means for controlling the operation of the voltage applying means,
The voltage control unit controls the amount of voltage applied by the voltage application unit so that the potentials of the developer carrier and the developer regulating member are substantially the same during image formation. At the time of non-image formation in which image formation is not performed during rotation, the potential of the developer regulating member is at least temporarily higher than the potential of the developer carrier to the same polarity as the charged polarity of the toner particles. Controlling the voltage application amount of the voltage application means as described above,
The developer has toner particles and the same polarity as the toner particles, and has a BET specific surface area of 20 to 250 m.²/ G of silica fine particles, wherein the silica fine particles are contained in an amount of 0.5 to 2 parts by mass based on 100 parts by mass of the toner.
[0028]
(2) The image forming method according to (1), wherein particles having a particle size of 4 μm or less are 35% or less in the number-based particle size distribution of the developer.
[0029]
(3) The image forming method according to (1) or (2), wherein the developer has a release rate of the silica fine particles with respect to the toner particles of 20% or less as measured by a particle analyzer.
[0030]
(4) The silica fine particles are subjected to hydrophobic treatment with a silane coupling agent and / or silicone oil, and have a number average primary particle diameter of 5 to 100 nm (1) to (3). Any one of the image forming methods.
[0031]
(5) The image forming method according to any one of (1) to (4), wherein the potential difference between the developer carrier and the developer regulating member during non-image formation is 60 to 500 V.
[0032]
(6) The image forming method according to any one of (1) to (5), wherein the charge amount of the developer is 15 to 90 μC / g in absolute value.
[0033]
(7) The image forming method according to any one of (1) to (6), wherein the melt index value of the developer is 35 or less.
[0034]
(8) a developer for visualizing the electrostatic latent image carried on the image carrier, wherein the developer is transferred to the electrostatic latent image on the latent image carrier by a developing means, Used in an image forming method having a developing step of visualizing an electrostatic latent image,
The developing unit is disposed to face the image carrier, a rotatable developer carrier that carries a developer, a developer regulating member that regulates the amount of developer on the developer carrier, Voltage applying means for applying a voltage to the developer carrier and the developer regulating member, and a voltage control means for controlling the operation of the voltage applying means,
The voltage control unit controls the amount of voltage applied by the voltage application unit so that the potentials of the developer carrier and the developer regulating member are substantially the same during image formation. At the time of non-image formation in which image formation is not performed during rotation, at least temporarily, the potential of the developer regulating member is higher than the potential of the developer carrier to the same polarity as the charging polarity of the toner. Controlling the voltage application amount of the voltage application means,
The developer has toner particles and the same polarity as the toner particles, and has a BET specific surface area of 20 to 250 m.²/ G of silica fine particles, wherein the silica fine particles are contained in an amount of 0.5 to 2 parts by mass with respect to 100 parts by mass of the toner.
[0035]
(9) The developer according to (8), wherein particles having a particle size of 4 μm or less are 35% or less in a number-based particle size distribution.
[0036]
(10) The developer according to (8) or (9), wherein the release rate of the silica fine particles with respect to the toner particles is 20% or less, as measured by a particle analyzer.
[0037]
(11) The silica fine particles are subjected to a hydrophobic treatment with a silane coupling agent and / or silicone oil, and have a number average primary particle diameter of 5 to 100 nm (8) to (10). Any of the developers.
[0038]
(12) The developer according to any one of (8) to (11), wherein the potential difference between the developer carrier and the developer regulating member during non-image formation is 60 to 500 V.
[0039]
(13) The developer according to any one of (8) to (12), wherein the charge amount is 15 to 90 μC / g in absolute value.
[0040]
(14) The developer according to any one of (8) to (13), wherein the melt index value is 35 or less.
[0041]
(15) A process cartridge detachable from an image forming apparatus for visualizing an electrostatic latent image carried on an image carrier with a developer,
A developer carrying member arranged to face the image carrying member for carrying a developer, a developer regulating member for regulating an amount of developer on the developer carrying member, a developer carrying member and a developer regulating member; A voltage application unit that applies a voltage to the member, and a voltage control unit that controls an operation of the voltage application unit, including a developing unit having:
The voltage control unit controls the amount of voltage applied by the voltage application unit so that the potentials of the developer carrier and the developer regulating member are substantially the same during image formation. At the time of non-image formation in which image formation is not performed during rotation, the potential of the developer regulating member is at least temporarily higher than the potential of the developer carrier to the same polarity as the charged polarity of the toner particles. Controlling the voltage application amount of the voltage application means as described above,
The developer has toner particles and the same polarity as the toner particles, and has a BET specific surface area of 20 to 250 m.²/ G of silica fine particles, wherein the silica fine particles are contained in an amount of 0.5 to 2 parts by mass with respect to 100 parts by mass of the toner.
[0042]
(16) The process cartridge according to (15), wherein particles having a particle size of 4 μm or less are 35% or less in the particle size distribution based on the number of the developer.
[0043]
(17) The process cartridge according to (15) or (16), wherein the developer has a release rate of the silica fine particles with respect to the toner particles of 20% or less, as measured by a particle analyzer.
[0044]
(18) The silica fine particles are subjected to a hydrophobic treatment with a silane coupling agent and / or silicone oil, and have a number average primary particle diameter of 5 to 100 nm (15) to (17). Any of the process cartridges.
[0045]
(19) The process cartridge according to any one of (15) to (18), wherein the potential difference between the developer carrier and the developer regulating member during non-image formation is 60 to 500 V.
[0046]
(20) The process cartridge according to any one of (15) to (19), wherein the charge amount of the developer is 15 to 90 μC / g in absolute value.
[0047]
(21) The process cartridge according to any one of (15) to (20), wherein a melt index value of the developer is 35 or less.
[0048]
BEST MODE FOR CARRYING OUT THE INVENTION
In a conventional image forming apparatus using an image forming method in which the thickness of a developer layer on a developer carrying member is regulated using a developer regulating member, a fixed DC (DC) bias or an AC (AC) bias is applied. By applying a voltage to the developer carrying member and / or the developer regulating member, charging properties to the toner or stabilization of the toner coat and the like have been achieved. However, as described above, it is difficult for the conventional image forming apparatus to stabilize the toner coat while preventing toner scattering, inversion toner sticking to the developing blade, and toner fusion to the developing blade.
[0049]
An image forming method according to the present invention includes a rotatable developer carrier that carries a developer, which is disposed to face an image carrier, and a developer regulating member that regulates an amount of the developer on the developer carrier. Voltage applying means for applying a voltage to the developer carrier and the developer regulating member; and voltage controlling means for controlling the operation of the voltage applying means. The voltage application amount of the voltage application unit is controlled so that the potential of the carrier and the potential of the developer regulating member are substantially the same, and the image forming is not performed while the developer carrier is rotating. At the time of image formation, the voltage application amount of the voltage application unit is controlled so that the potential of the developer regulating member is at least temporarily higher than the potential of the developer carrier on the same polarity side as the charging polarity of the toner. And developing means. Further, the image forming method of the present invention is characterized in that the toner particles have the same polarity as the toner particles and a BET specific surface area of 20 to 250 m.²/ G, and 0.5 to 2 parts by mass of the silica particles with respect to 100 parts by mass of the toner.
[0050]
That is, the developing means used in the image forming method of the present invention is such that the potential relationship between the developer carrier and the developer regulating member during rotation of the developer carrier is substantially the same during image formation, and at least during non-image formation. Controlling the potentials of the developer carrying member and the developer regulating member such that the potential of the developer regulating member temporarily becomes higher than the potential of the developer carrying member on the same polarity side as the charging polarity of the toner. It is characterized by the following. This makes it possible to remove the external additive having the same polarity as the charge polarity of the toner particles that easily adheres to the developer regulating member during non-image formation and to refresh the developer regulating member. Even in this case, it is possible to stably form the developer layer on the developer carrying member without generating a fused material on the developer regulating member, and it is possible to form a good image over a long period of time.
[0051]
Further, the developer of the present invention used in the image forming method of the present invention has a charge polarity of the same polarity as the charge polarity of the toner particles, and has a BET specific surface area of 20 to 250 m which is not easily fused to the developer regulating member.²/ G of silica fine particles in an amount of 0.5 to 2 parts by mass with respect to 100 parts by mass of the toner. By using such a developer together with the above-mentioned developing means, even in a low-temperature and low-humidity environment, no fused matter is generated on the developer regulating member, and it is possible to guarantee good image quality in any environment for a long period of time. it can.
[0052]
Here, at the time of image formation, the developing unit develops an electrostatic latent image to be transferred to an image forming area (a part excluding a blank area) of the transfer paper to form a visible image on the image carrier. The time while you are there. The non-image forming time is a time other than the image forming time and a time during which the developer carrying member is rotating. For example, a time during which a portion corresponding to a blank area of the transfer paper is subjected to the developing process (during this time) (A visible image is not actually formed.), At the time of rotation before preparation before image formation, at the time of rotation after preparation after completion of image formation, the time between transfer sheets (sheet interval) when printing a plurality of sheets, and when the power is turned on. Pre-preparation refers to multiple rotations.
[0053]
That is, in the present invention, at each printing, the developer regulating member is set to substantially the same potential as the developer carrying member at the time of image formation, and an external additive such as silica fine particles adhered to the developer regulating member (a portion in FIG. 7). Is transferred to the developer carrying member during non-image formation to refresh the developer regulating member, thereby preventing the external additive and the toner from being fused to the developer regulating member.
[0054]
This refresh operation is performed during non-image formation, that is, during the time when the portion corresponding to the blank area of the transfer paper is being used for development, during pre-preparation rotation before image formation, during post-preparation rotation after image formation is completed, and For example, when a developer containing negatively charged toner particles is used and a voltage of -400 V is applied to the developer carrier, a voltage of -600 V is applied to the developer regulating member for a short time. This acts to return the negative external additive adhering during image formation to the developing roller side.
[0055]
By using the above-mentioned refreshing operation and an external additive (silica fine particles used in the present invention) which is hardly adhered to the blade, the developer is applied to the developer carrying member and the developer regulating member during image formation in a low-temperature and low-humidity environment. Even when the voltage is set to substantially the same potential, the external additive does not accumulate on the developer regulating member, so that the toner is not captured by the developer regulating member. As a result, it is possible to prevent the generation of the fused material on the developer regulating member (a portion in FIG. 7).
[0056]
In the present invention, the substantially same potential means a range of about ± 60 V with respect to the applied developing bias. For example, when a developer containing a negatively charged toner is used and the developing bias is −400 V, when the voltage applied to the developer regulating member becomes −340 V or less, the amount of toner passing through the developer regulating member is reduced. And it becomes difficult to obtain a sufficient image density. Conversely, when the voltage applied to the developer regulating member is -460 V or more, the reversal toner and the positive external additive easily adhere to the developing blade, and the free end side of the developer regulating member (b in FIG. 7) This is because the toner that enters the contact portion between the developer regulating member and the developer carrying member is easily blocked by the inverted toner or the positive external additive attached to the portion (a), thereby causing vertical stripe-shaped density unevenness. .
[0057]
Since the toner layer passing through the developer regulating member on the developer carrier has a potential range of ± several tens of volts, the substantially same potential is determined to be approximately ± 60 volts in consideration of this value.
[0058]
Further, since this refresh operation is performed in a short time during non-image formation, even during the refresh operation, the charge polarity of the reversal toner or the toner particles is applied to the free end of the developer regulating member (portion b in FIG. 7). Even if a polar external additive adheres, it acts to return to the developer carrier during the next image formation, so that the external additive does not accumulate on the developer regulating member in the same manner as described above, so that vertical stripes and light Does not occur.
[0059]
In particular, in the present invention, when applying a potential difference between the developer carrying member and the developer regulating member during the non-image formation, it is important that the developer carrying member is rotating. Even if the above-mentioned potential difference is applied in a state where the developer carrier is stopped, the inverted toner once returned to the developer carrier from the developer regulating member and the external additive having the opposite polarity are reattached to the developer regulating member. This is because there are cases. By performing the above-described refresh operation while the developer carrier is rotating, the reverse toner or the external additive having the opposite polarity returned to the developer carrier side is brought into contact with the developer regulating member and the developer carrier. In this case, the developer carrier can be kept away from the downstream side in the rotational direction of the developer carrier (portion a in FIG. 7), and re-adhesion can be prevented.
[0060]
It is preferable that the potential difference between the developer carrying member and the developer regulating member during the non-image formation is 60 to 500 V in order to effectively remove the reversal toner and the external additive attached to the developer regulating member. This potential difference is more preferably 100 to 450V. This is because if the potential difference is 60 V or less, the negative external additive adhered to the developing blade cannot be transferred to the developing roller side, and the effect of preventing fusion of the developing blade cannot be obtained. Further, the reason why the potential difference is set to 500 V or less is that if the potential difference exceeds 500 V, a discharge is likely to occur between the developing roller and the developing blade, and a current flowing between the developing blade and the developing roller becomes large. Is required.
[0061]
The developer of the present invention used in the image forming method of the present invention contains toner particles and silica fine particles. In this specification, the term “toner” is used to refer to an aggregate of toner particles, or to a toner that is fixed on transfer paper, or when the toner particles become a fused material and cannot maintain their shape as particles. Sometimes.
[0062]
The silica fine particles used in the present invention have the same polarity as the charged polarity of the toner particles, and have a BET specific surface area of 20 to 250 m.²/ G. The BET specific surface area of the silica fine particles is 25 to 170 m²/ G, preferably 30 to 150 m²/ G is more preferable. In the present invention, the silica fine particles are contained in the developer in a ratio of 0.5 to 2 parts by mass with respect to 100 parts by mass of the toner particles. The content of the silica fine particles is preferably 0.6 to 1.9 parts by mass, more preferably 0.7 to 1.8 parts by mass.
[0063]
The present inventors have studied the external stability of the toner particles by adding all kinds of inorganic fine particles effective for environmental stability, fluidity and tribo-attractive property to the toner particles. It has been clarified that the fine particles are remarkably electrostatically attached to the developer regulating member and grow a fused mass. However, silica fine particles having excellent transferability, fluidity and tribo-impartability are essential components of the developer. As a result of extensive studies by the present inventors, the BET specific surface area was 20 to 250 m.²When a developer containing 0.5 to 2 parts by weight of silica fine particles with respect to toner particles is used in combination with the above-mentioned refreshing function, no fused mass is generated on the developer regulating member even in a low-temperature and low-humidity environment. Heading, the present invention has been reached.
[0064]
BET specific surface area is 20m²When a developer containing silica fine particles of less than 1 g / g is used, the charge-imparting ability is small, and an image defect such as fogging or blurring occurs when used in a high temperature and high humidity environment. On the other hand, the BET specific surface area is 250 m²When using a developer containing silica fine particles exceeding 10 g / g, the developer adheres strongly to the developer regulating member when used in a low-temperature and low-humidity environment, and therefore does not return to the developer carrier even when a high bias is applied to the developer regulating member. However, as the durable use progresses, the fused mass grows and a streak image is generated.
[0065]
The measurement of the BET specific surface area of the silica fine particles is performed by using a known device such as a degassing device VacuPrep 061 (manufactured by MicroMestic) and a BET measuring device Gemini 2375 (manufactured by MicroMestic). The BET specific surface area in the present invention is a value of the one-point method BET specific surface area. Specifically, the following procedure is performed.
[0066]
After measuring the weight of the empty sample cell, the measurement sample is filled so as to be between 0.01 and 0.002 g. Further, the sample cell filled with the sample is set in the degassing device, and degassing is performed at room temperature for 3 hours. After the degassing, the mass of the entire sample cell is measured, and the accurate mass of the sample is calculated from the difference from the empty sample cell. Next, an empty sample cell is set in the balance port and the analysis port of the BET measuring device. A Dewar bottle containing liquid nitrogen is set at a predetermined position, and P0 is measured by a saturated vapor pressure (P0) measurement command. After the P0 measurement is completed, the degas-prepared sample cell is set in the analysis port, the sample mass and P0 are input, and the measurement is started by the BET measurement command. Thereafter, the BET specific surface area is automatically calculated.
[0067]
When a developer containing less than 0.5 part of silica fine particles with respect to 100 parts by mass of toner particles is used, the coverage of the silica particles with the toner particles is not sufficient, so that it is difficult to obtain a sufficient effect of imparting charge and fluidity. In addition, fogging and drooling are likely to occur in a high-temperature and high-humidity environment, and the durability deteriorates quickly. When a developer containing more than 2.0 parts of silica fine particles per 100 parts by mass of toner particles is used, excessive silica fine particles are likely to strongly adhere to the developer regulating member, and are durable in a low temperature and low humidity environment. Development streaks occur from the beginning of the process.
[0068]
Further, the silica fine particles contained in the developer of the present invention preferably have a release rate of the silica fine particles with respect to the toner particles of 20% or less, as measured by a particle analyzer. If the release rate of the silica fine particles exceeds 20%, the silica fine particles are fused to the developer regulating member from the early stage of the durable use, and a dark streak becomes conspicuous on an intermediate tone image at an early stage. The release rate of the silica fine particles is more preferably 10% or less in order to guarantee a further long life of the developing device.
[0069]
In order to make the release rate of the silica fine particles within an appropriate range, a known external addition method can be used. That is, a suitable stirring method for producing the developer of the present invention having the above-mentioned liberation ratio is not particularly limited as long as silica fine particles are mechanically externally attached to toner particles. It can be performed using an apparatus. Preferably, a Henschel mixer or a homogenizer is used, and more preferably, a Henschel mixer can be used. It is necessary to control the number of rotations, the angle of the baffle plate and the stirring time to adjust the external addition strength, and to sufficiently control the liberation rate of the silica fine particles in consideration of the interaction with other external additives.
[0070]
The method of measuring the release rate of Si atoms from carbon atoms of toner particles is described in the Annual Meeting of the Society of Electrophotography (95 times in total), "Japan @ Hardcopy '97", "New External Evaluation Method-Toner Analysis by Particle Analyzer" − ”, Toshiyuki Suzuki, Toshio Takahara, sponsored by the Society of Electrographic Photography, July 9-11, 1997. In this toner analysis method, toner particles are excited by introducing the toner particles into plasma, and an analysis is performed by detecting an emission spectrum accompanying the excitation. According to this analysis method, it is possible to simultaneously detect the emission spectra accompanying the excitation of a plurality of elements, and it is also possible to measure the periodicity of the emission spectra.
[0071]
In the present invention, the liberation rate of Si atoms with respect to carbon atoms of toner particles measured using this periodicity is defined as the liberation rate of silica fine particles. The elements contained in the same particle generate an excitation emission spectrum (synchronous spectrum) at the same period, while the element present as a single substance, such as a free substance of silica fine particles, is synchronized with the carbon atom in the toner particles. Without generating an excited emission spectrum (asynchronous spectrum) alone. In the present invention, based on the periodic difference between the emission spectrum associated with the excitation of carbon atoms derived from toner particles and the emission spectrum associated with the excitation of Si atoms derived from silica fine particles, unsynchronized atoms are converted into free silica fine particles. The ratio is defined as the release rate of the silica fine particles.
[0072]
As a specific measuring method, after measuring under the following conditions using PT1000 manufactured by Yokogawa Electric Corporation, the liberation rate is determined by applying the synchronization of light emission of Si atoms with reference to C atoms to the following equation.
[0073]
<Measurement conditions of PT1000 manufactured by Yokogawa Electric Corporation>
-Number of detected C atoms in one measurement: 500 to 2500
・ Noise cut level: 1.5 or less
・ Sort time: 20 digits
・ Gas: O₂0.1%, He gas
・ Analysis wavelength
C atom: 247.860 nm
Si atom: 288.160 nm
・ Use channel
C atom: 1 or 2
Si atom: 1 or 2
[0074]
(Equation 1)

[0075]
Further, the number average primary particle diameter of the silica fine particles used in the present invention is preferably 5 to 100 nm. The number average primary particle diameter of the silica fine particles is more preferably from 7 to 60 nm. When the number average primary particle diameter is less than 5 nm, the chargeability is extremely high, so that the toner easily adheres to the developer regulating member particularly in a low humidity environment, develops into a fused mass, and generates streaks in a fixed image. Further, the silica fine particles are easily embedded in the toner particles with the durable use, and fogging occurs in the latter half of the endurance particularly in a high humidity environment. When the number average primary particle diameter is 100 nm or more, the charge-imparting property may be poor.
[0076]
The number average primary particle diameter of the silica fine particles was determined by taking a photograph of the surface of the toner particles magnified 50,000 times with an FE-SEM (S-4700 manufactured by Hitachi, Ltd.). It is measured over a visual field, and the average value is determined as the number average particle size.
[0077]
As the silica fine particles, both a so-called dry method produced by vapor phase oxidation of a silicon halide and a so-called fumed silica fine particle, and a so-called wet silica produced from water glass or the like can be used.
[0078]
As a base of the silica fine particles having a small particle diameter, there are few silanol groups on the surface and in the inside of the fine silica powder.₂O, SO₃ ^2-Dry silica without production residue such as is preferred.
[0079]
In the case of fumed silica, it is also possible to obtain a composite fine powder of silica and another metal oxide by using another metal halide such as aluminum chloride or titanium chloride together with a silicon halide in the production process. The above-mentioned fumed silica also includes them.
[0080]
The silica fine particles used in the present invention are preferably hydrophobized with a silane coupling agent and / or silicone oil in advance so that a desired charge amount can be obtained even in a high-temperature and high-humidity environment.
[0081]
The silane coupling agent is represented by the following general formula, for example, typically, dimethyldichlorosilane, trimethylchlorosilane, allyldimethylchlorosilane, hexamethyldisilazane, allylphenyldichlorosilane, benzyldimethylchlorosilane , Vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, divinylchlorosilane, and dimethylvinylchlorosilane.
[0082]
Embedded image
R_mSiY_n
(Wherein, R represents an alkoxy group or a chlorine atom, Y represents an alkyl group, or a hydrocarbon group containing a vinyl group, a glycidoxy group, and a methacle group, m represents an integer of 1 to 3, and n represents 3 to Shows an integer of 1.)
[0083]
The above-mentioned silane coupling agent treatment of the silica fine powder is a dry treatment in which a vaporized silane coupling agent is reacted with a cloud of silica fine powder by stirring, or a silane coupling agent in which silica fine particles are dispersed in a solvent. Can be treated by a generally known method such as a wet method of reacting the compound dropwise.
[0084]
The silicone oil is generally represented by the following formula.
Embedded image

(Wherein, R represents an alkyl group having 1 to 3 carbon atoms, R ′ represents a silicone oil-modified group selected from alkyl, halogen-modified alkyl, phenyl and modified phenyl, and R ″ represents an alkyl group having 1 to 3 carbon atoms. Represents a group or an alkoxy group, m represents an integer of 0 to 1000, and n represents an integer of 0 to 1000.)
[0085]
Examples of such silicone oils include dimethyl silicone oil, alkyl-modified silicone oil, α-methylstyrene-modified silicone oil, chlorophenyl silicone oil, and fluorine-modified silicone oil.
[0086]
A known technique is used as a method of treating the silicone oil. For example, silica fine powder and silicone oil may be directly mixed using a mixer such as a Henschel mixer, or a method of spraying the silicone oil onto the base silica fine particles. Is also good. Alternatively, it may be prepared by dissolving or dispersing a silicone oil in an appropriate solvent, mixing with a base silica fine powder, and removing the solvent.
[0087]
When the processing amount is less than 0.1% by mass, the charge amount is significantly reduced in a high-temperature and high-humidity environment, which causes fogging and dropping. On the other hand, when the processing amount is 30% by mass or more, the amount of silica fine particles or secondary aggregated silica fine particles coated with a thick silicone oil relatively increases, and these trigger the fused material to the developer regulating member. It is not preferred because it is easy
[0088]
For the same reason as the hydrophobizing treatment, the silica fine particles used in the present invention are provided with a crushing treatment step, whereby the latitude for blade fusion is further expanded, and it is possible to cope with a developing device having a longer life.
[0089]
In the developer of the present invention, particles having a particle size of 4 μm or less in a number-based particle size distribution are preferably 35% or less. If the particles having a particle diameter of 4 μm or less exceed 35% in the number-based particle size distribution, the toner having a small particle diameter of 4 μm or less has a very high charge amount, and thus strongly adheres to the developer regulating member. However, even if a high blade bias is applied to the developer regulating member in a low-temperature and low-humidity environment, the developer cannot be sufficiently refreshed, and toner is fused by rotational sliding of the developer carrier.
[0090]
For the same reason as described above, which suppresses the adhesion of toner particles to the developer regulating member due to charge-up, the volume average particle diameter of the developer is preferably 4 to 12 μm, and particles having a particle diameter of 4 μm or less have a number distribution. More preferably, it is 20% or less.
[0091]
In the developer of the present invention, it is preferable to control the charge amount on the developer carrier to 15 to 90 μC / g in absolute value in any environment. As means for controlling to a desired charge amount, a plurality of auxiliary particles can be used. In addition to the above-mentioned silica fine particles as a means for imparting fluidity and charging ability, titanium oxide and magnesium oxide are added to adjust the charge distribution, and for negatively charged toners, hydrotalcite and strontium titanate are used. By adding the positively-chargeable fine particles, charge-up can be suppressed. When an external additive having a polarity opposite to the polarity of the toner (a positive external additive when the toner is negatively charged) is used as one of the auxiliary particles, the rotation of the developer carrier is combined with the rotation of the developer carrier. An effect of scraping off the negative external additive adhered to the developer regulating member can also be expected.
[0092]
When the charge amount of the developer on the developer carrying member is less than 15 in absolute value, image defects such as fogging and dropping occur in a high temperature and high humidity environment. Further, when the charge amount exceeds 90 in absolute value, even if a high blade bias is applied to the developer regulating member, the toner and silica fine particles charged up on the developer regulating member strongly adhere to the developer regulating member. It becomes impossible to avoid the fusion streak accompanying the durable use.
[0093]
The charge amount of the developer can be measured by, for example, a Faraday-Cage shown in FIG. The Faraday cage is a coaxial double cylinder in which the inner cylinder and the outer cylinder are insulated. Assuming that a charged body having a charge amount of Q is placed in the inner cylinder, it is as if a metal cylinder having an electric quantity of Q exists by electrostatic induction. The amount of the induced charge is measured with KEITHLEY 616 DIGITAL ELECTROMETHER, and the charge amount is obtained by dividing the charge amount Q by the toner weight M in the inner cylinder (Q / M). The developer is taken into the filter by air suction directly from the developer carrier.
[0094]
The charge amount of the developer can be adjusted in terms of the material, such as by using an appropriate charge control agent for the toner material, and the material of the developer carrier, or the contact of the developer regulating member with the developer carrier. By adjusting the pressure and the like, the ability to impart a triboelectric charge to the developer can be controlled.
[0095]
The charge amount (μc / g) of the external additive can be obtained as follows by a blow-off measurement method.
FIG. 9 is an explanatory view of an apparatus for measuring the triboelectric charge amount of the external additive. First, a mixture having a weight ratio of an external additive and a carrier to be measured of a triboelectric charge of 1: 500 is put into a polyethylene bottle having a volume of 50 to 100 ml, and shaken with a turbula mixer for 2 minutes. 0.1 to 0.7 g of the mixture is placed in a metal measuring container 52 having a 500-mesh screen 53 at the bottom, and a metal lid 54 is placed. Next, in the suction device 51 (at least a portion in contact with the measurement container 52 is at least an insulator), the pressure of the vacuum gauge 55 is adjusted to 2 kPa by adjusting the air volume control valve by suctioning from the suction port 57. In this state, suction is sufficiently performed (about one minute). The voltage of the electrometer 59 at this time is set to V (volt). Here, 58 is a capacitor, and the capacity is C (μF). The triboelectric charge (μc / g) is obtained by dividing the amount of charge obtained from these by the amount of the external additive removed by suction.
[0096]
Further, the melt index (MI) of the developer of the present invention is preferably 35 or less. The MI of the developer is more preferably 25 or less. When a developer having an MI of more than 35 is used, when the silica fine particles are fused to the developer regulating member and the developer regulating member is roughened, toner fusion to the developer regulating member is easily induced by frictional heat. However, severe streaks tend to occur from an early stage.
[0097]
In the present invention, the MI is measured according to the method A of JIS K 7210, and the value at a test temperature of 135 ° C. and a test load of 2.16 Kgf is defined as the MI value.
[0098]
Hereinafter, the developer of the present invention will be described in more detail.
As described above, the developer of the present invention contains toner particles and the above-mentioned silica fine particles having the same charge polarity as the toner particles. The toner particles contained in the developer of the present invention have non-magnetic and insulating properties, and are negative toner particles charged to a negative polarity even if they are positive toner particles charged to a positive polarity. There may be. The toner particles of the present invention can be manufactured using known toner materials such as a binder resin, a colorant, a wax, a charge control agent, and an external additive other than the silica fine particles.
[0099]
Examples of the binder resin used for the toner particles include polystyrene; styrene-substituted homopolymers such as poly-p-chlorostyrene and polyvinyltoluene; styrene-p-chlorostyrene copolymer and styrene-vinyltoluene copolymer. Styrene-vinyl naphthalene copolymer, styrene-acrylate copolymer, styrene-methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl Styrene copolymers such as ether copolymers, styrene-vinyl ethyl ether copolymers, styrene-vinyl methyl ketone copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-acrylonitrile-indene copolymers Polymer; acrylic resin Methacrylic resins; polyvinyl acetate; silicone resins; polyester resins; polyamide resin; furan resins, epoxy resins, xylene resins.
[0100]
These resins are used alone or in combination of two or more. The main component of the binder resin is preferably a styrene copolymer, which is a copolymer of styrene and another vinyl monomer, from the viewpoint of developability and fixability.
[0101]
In the present invention, a binder resin may be produced by polymerizing an appropriate monomer, and this may be used. For example, comonomers for the styrene monomer of the styrene copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodite acrylate, octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, methacrylic acid Monocarboxylic acid having a double bond such as methacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide and its substituted products; maleic acid, butyl maleate, methyl maleate , Dicarboxylic acids having a double bond such as dimethyl maleate and substituted products thereof; vinyl esters such as vinyl chloride, vinyl acetate and vinyl benzoate; ethylene-based olefins such as ethylene, propylene and butylene ; Vinyl methyl ketone, vinyl ketones such as vinyl hexyl ketone, vinyl methyl ether, vinyl ethyl ether, vinyl ethers such as vinyl isobutyl ether. These vinyl monomers are used alone or in combination of two or more.
[0102]
The styrene copolymer is preferably crosslinked with a crosslinking agent such as divinylbenzene in order to widen the fixing temperature range of the developer and improve the offset resistance.
[0103]
As the polymerizable monomer used when the toner particles used in the present invention are produced by a polymerization method, a vinyl polymerizable monomer capable of radical polymerization is used. As the vinyl polymerizable monomer, a monofunctional polymerizable monomer or a polyfunctional polymerizable monomer can be used.
[0104]
As the monofunctional polymerizable monomer, styrene; α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, pn-butyl Styrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p Styrene derivatives such as phenylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, n-amyl acrylate, n-hexyl acrylate, 2 -Ethylhexyl acrylate Acrylic polymerizable monomers such as n-octyl acrylate, n-nonyl acrylate, cyclohexyl acrylate, benzyl acrylate, dimethyl phosphate ethyl acrylate, diethyl phosphate ethyl acrylate, dibutyl phosphate ethyl acrylate, and 2-benzoyloxyethyl acrylate Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl Methacrylate, n-nonyl methacrylate, diethyl phosphate ethyl methacrylate Methacrylic polymerizable monomers such as phosphate and dibutyl phosphate ethyl methacrylate; methylene aliphatic monocarboxylic acid esters; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate and vinyl formate; vinyl methyl ether And vinyl ethers such as vinyl ethyl ether and vinyl isobutyl ether; and vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropyl ketone.
[0105]
Examples of polyfunctional polymerizable monomers include diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, and tripropylene glycol. Diacrylate, polypropylene glycol diacrylate, 2,2'-bis (4- (acryloxydiethoxy) phenyl) propane, trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol Dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol Dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2′-bis (4- (methacryloxy diethoxy) phenyl) propane, 2,2′-bis (4- (methacryloxypolyethoxy) phenyl) propane, trimethylolpropane trimethacrylate, tetramethylolmethanetetramethacrylate, divinylbenzene, divinylnaphthalene, divinyl ether, and the like.
[0106]
In the present invention, the above-mentioned monofunctional polymerizable monomers are used alone or in combination of two or more, or the above-mentioned monofunctional polymerizable monomers and polyfunctional polymerizable monomers are used in combination. I do. Polyfunctional polymerizable monomers can also be used as crosslinking agents.
[0107]
As the polymerization initiator used in the polymerization of the polymerizable monomer, one or both of an oil-soluble initiator and a water-soluble initiator are used. For example, examples of the oil-soluble initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, and 1,1′-azobis (cyclohexane-1-carbonitrile). And azo compounds such as 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile; acetylcyclohexylsulfonyl peroxide, diisopropylperoxycarbonate, decanolyl peroxide, lauroyl peroxide, stearoyl peroxide, propionyl peroxide Oxide, acetyl peroxide, t-butylperoxy-2-ethylhexanoate, benzoyl peroxide, t-butylperoxyisobutyrate, cyclohexanone peroxide, methyl ethyl ketone peroxide, dicumylper Kisaido, t- butyl hydroperoxide, di -t- butyl peroxide, include peroxide initiators such as cumene hydroperoxide.
[0108]
Examples of the water-soluble initiator include ammonium persulfate, potassium persulfate, 2,2′-azobis (N, N′-dimethyleneisobutyroamidine) hydrochloride, 2,2′-azobis (2-aminodipropane) hydrochloride Salts, azobis (isobutylamidine) hydrochloride, sodium 2,2′-azobisisobutyronitrile sulfonate, ferrous sulfate and hydrogen peroxide.
[0109]
In the present invention, in order to control the degree of polymerization of the polymerizable monomer, a chain transfer agent, a polymerization inhibitor and the like may be further added and used.
[0110]
As the crosslinking agent used for the toner particles, a compound having two or more polymerizable double bonds is used. For example, aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; carboxylic acid esters having two double bonds such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, and 1,3-butanediol dimethacrylate; divinylaniline; Divinyl compounds such as divinyl ether, divinyl sulfide and divinyl sulfone; and compounds having three or more vinyl groups. These are used alone or as a mixture of two or more.
[0111]
When the toner particles used in the present invention are produced by a polymerization method, a condensation resin may be added to the toner particles. Examples of the condensation resin include polyester, polycarbonate, phenol resin, epoxy resin, polyamide, and cellulose. More preferably, polyester is desired from the diversity of materials. The condensed resin varies depending on the type and the like, but is preferably used in an amount of 0.01 to 20 parts by mass, more preferably 0.5 to 10 parts by mass per 100 parts by mass of the binder resin.
[0112]
The colorant used in the toner particles is not particularly limited as long as it is non-magnetic. Examples of the black colorant include black using carbon black or the following yellow, magenta, and cyan colorants. And colored ones.
[0113]
As the yellow colorant, as a pigment, a compound represented by a condensed azo compound, an isoindolinone compound, an anthraquinone compound, an azo metal complex methine compound, or an allylamide compound is used. Specifically, C.I. I. Pigment Yellow 3, 7, 10, 12, 13, 14, 15, 17, 23, 24, 60, 62, 74, 75, 83, 93, 94, 95, 99, 100, 101, 104, 108, 109, 110 , 111, 117, 123, 128, 129, 138, 139, 147, 148, 150, 166, 168, 169, 177, 179, 180, 181, 183, 185, 191: 1, 191, 192, 193, 199 Etc. are preferably used. As the dye system, for example, C.I. I. solvent Yellow 33, 56, 79, 82, 93, 112, 162, 163, C.I. I. disperse @ Yellow42, 64, 201, 211 and the like.
[0114]
As the magenta colorant, a condensed azo compound, a diketopyrrolopyrrole compound, an anthraquinone, a quinacridone compound, a basic dye lake compound, a naphthol compound, a benzimidazolone compound, a thioindigo compound, and a perylene compound are used. Specifically, C.I. I. Pigment Red 2, 3, 5, 6, 7, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 146, 150, 166, 169, 177, 184, 185, 202, 206, 220, 221, 254, C.I. I. Pigment Violet 19 is particularly preferred.
[0115]
As the cyan coloring agent, phthalocyanine compounds and derivatives thereof, anthraquinone compounds, basic dye lake compounds and the like can be used. Specifically, C.I. I. Pigment Blue 1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, 66 and the like are particularly preferably used.
[0116]
These colorants can be used alone or as a mixture, or in the form of a solid solution. The colorant is selected from the viewpoints of hue angle, saturation, lightness, weather resistance, OHP transparency, and dispersibility in the toner. The amount of the coloring agent varies depending on the type of the coloring agent, but is preferably 1 to 20 parts by mass with respect to 100 parts by mass of the binder resin.
[0117]
The toner particles used in the present invention preferably have at least one endothermic peak in the range of 50 to 120 ° C. in the endothermic curve at the time of temperature rise in the differential thermal analysis. The toner having an endothermic peak at 50 to 120 ° C. can more effectively control the toner chargeability by adjusting the amount of the silica particles and the type and amount of other external additives, and more preferable results can be obtained. Can be
[0118]
When the endothermic peak of the toner particles is less than 50 ° C., storage stability is impaired, and problems such as blocking are likely to occur. If the endothermic peak is at a temperature higher than 120 ° C., the releasing effect at the time of fixing is not sufficiently exhibited. If there is an endothermic peak at 50 to 120 ° C, there may be an additional endothermic peak in a temperature range exceeding 120 ° C.
[0119]
The endothermic peak in the differential thermal analysis can be measured by a high-precision internal heating input compensation type differential scanning calorimeter. For the measurement of the endothermic peak in the differential thermal analysis, for example, DSC-7 manufactured by Perkin Elmer Co., Ltd. can be used. The measurement is performed according to ASTM D3418-82.
[0120]
In the present invention, the endothermic peak temperature is a peak temperature in a positive direction in the DSC curve, that is, a point at which the differential value of the peak curve becomes 0 when the value changes from positive to negative. As the DSC curve, a DSC curve measured when the temperature is raised once, a pre-history is obtained, and then the temperature is decreased and raised at a temperature rate of 10 ° C./min and a temperature range of 0 to 200 ° C. is used.
[0121]
As means for adjusting the endothermic peak in the differential thermal analysis of the toner particles to have a range of 50 to 120 ° C., means for internally adding a compound having an endothermic peak in the differential thermal analysis at 50 to 120 ° C. in the toner particles is used. preferable. As the substance having one or more endothermic peaks at 50 to 120 ° C. in differential thermal analysis, wax is preferably used.
[0122]
Examples of the wax include petroleum waxes such as paraffin wax, microcrystalline wax and petrolactam and derivatives thereof; montan wax and derivatives thereof; hydrocarbon waxes and derivatives thereof by the Fischer-Tropsch method; polyolefin waxes represented by polyethylene and polyolefin waxes thereof. Derivatives; natural waxes and derivatives thereof such as carnauba wax and candelilla wax; alcohol waxes of higher aliphatic alcohols; fatty acids and compounds thereof such as stearic acid and palmitic acid; acid amides and derivatives thereof; esters and derivatives thereof; Hydrogenated castor oil and its derivatives; vegetable waxes; and animal waxes. Derivatives include oxides, block copolymers with vinyl monomers, and graft-modified products. The content of the wax in the toner particles used in the present invention is preferably from 0.3 to 30% by mass, more preferably from 0.5 to 20% by mass, in consideration of the balance between the releasing effect and the charge inhibiting property. is there.
[0123]
Further advantageous effects can be added by using a charge control agent in combination with the toner particles used in the present invention.
[0124]
For controlling the toner particles to be negatively charged, for example, organometallic compounds and chelate compounds are effective, monoazo metal compounds, acetylacetone metal compounds, aromatic oxycarboxylic acids, aromatic dicarboxylic acids, oxycarboxylic acids and There are dicarboxylic acid-based metal compounds. Other examples include aromatic oxycarboxylic acids, aromatic mono- and polycarboxylic acids and their metal salts, anhydrides, esters, and phenol derivatives such as bisphenol. Furthermore, urea derivatives, metal-containing salicylic acid-based compounds, metal-containing naphthoic acid-based compounds, boron compounds, quaternary ammonium salts, calixarenes, resin-based charge control agents and the like can be mentioned. These can be used alone or in combination of two or more.
[0125]
Examples of the toner particles that control the toner particles to be positively charged include, for example, a modified nigrosine with nigrosine and a fatty acid metal salt, a guanidine compound, an imidazole compound, tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, and tetrabutylammonium. Onium salts such as quaternary ammonium salts such as tetrafluoroborate, and their analogs such as phosphonium salts, and their lake pigments, triphenylmethane dyes and these lake pigments (phosphor tungstic acid, phosphorus Molybdic acid, phosphotungsten molybdic acid, tannic acid, lauric acid, gallic acid, ferricyanide, ferrocyanide, etc.), metal salts of higher fatty acids; dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide Diorganotin oxides such as id; dibutyl tin borate, dioctyl tin borate, diorgano tin borate such as dicyclohexyl tin borate, resin charge control agent and the like. These can be used alone or in combination of two or more.
[0126]
The amount of the charge control agent varies depending on the type of the charge control agent used, but is preferably 0.01 to 20 parts by mass, and more preferably 0.5 to 10 parts by mass per 100 parts by mass of the binder resin. More preferred. The charge control agent may be blended (internally added) to the toner particles, or may be mixed (externally added) with the toner particles.
[0127]
The average particle size and the particle size distribution of the toner particles and the developer can be determined by using, for example, a Coulter Counter TA-II or a Coulter Multisizer (manufactured by Coulter), etc., and an interface (manufactured by Nikkaki) for outputting a number distribution and a volume distribution, and PC9801 It can be measured with a measuring device connected to a personal computer (manufactured by NEC). In this measurement, an electrolytic solution is used. As the electrolytic solution, for example, a 1% aqueous NaCl solution prepared using primary sodium chloride or ISOTON® R-II (manufactured by Coulter Scientific Japan) can be used.
[0128]
As a measuring method, 0.1 to 5 ml of a surfactant (preferably an alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the aqueous electrolytic solution, and 2 to 20 mg of a measurement sample is further added. The electrolyte in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes using an ultrasonic disperser, and the volume and number of toner particles of 2 μm or more were measured using the Coulter Counter TA-II using an aperture of 100 μm. To calculate a volume distribution and a number distribution. Then, a volume-based weight average particle diameter (D4) determined from the volume distribution according to the present invention and a number-based length average particle diameter (D1) determined from the number distribution are determined.
[0129]
Hereinafter, a method for producing the toner particles used in the present invention will be described.
As a method for producing the non-magnetic one-component toner, at least a binder resin, a colorant, kneading using a pressure kneader or an extruder, or a media disperser and the like, uniformly dispersed, and then mechanically or jetted A pulverization method in which the particles are pulverized into a desired toner particle size by colliding with a target under an air current to obtain toner particles through a classification step, may be mentioned. For the purpose of further increasing the degree of circularity, a method of producing toner particles with a desired degree of circularity by using mechanical means, a method of performing a wet or dry thermal spheroidizing treatment after the above-mentioned pulverization, and the like can be mentioned. .
[0130]
The non-magnetic one-component toner may be produced by a polymerization method. When the method for producing the non-magnetic one-component toner is a polymerization method, there is no particular limitation, but Japanese Patent Publication Nos. 36-10231, 59-53856, and 59-61842. US Patent No. 6,064,059, a method for producing a toner directly using a suspension polymerization method described in Japanese Patent Application Laid-Open Publication No. H10-209,972; a soap-free polymer which is soluble in a monomer and is directly polymerized in the presence of a water-soluble polymerization initiator to produce toner particles. Production of toner particles by a production method such as an emulsion polymerization method typified by a legal method. In addition, production methods such as an interfacial polymerization method such as a microcapsule production method, an in-situ polymerization method, a coacervation method, and the like can also be mentioned. Further, an interface association method of aggregating at least one kind of fine particles to obtain a particle having a desired particle size, as disclosed in JP-A-62-106473 and JP-A-63-186253, may be mentioned. .
[0131]
When performing suspension polymerization, it is usually preferable to use 300 to 3000 parts by mass of water as a dispersion medium with respect to 100 parts by mass of the monomer composition. Examples of dispersants used include inorganic oxides such as tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, and calcium metasilicate. Examples thereof include calcium sulfate, barium sulfate, bentonite, silica, alumina, and sodium dodecyl sulfate.
[0132]
As the organic compound, for example, polyvinyl alcohol, gelatin, methyl cellulose, methyl hydroxypropyl cellulose, ethyl cellulose, sodium salt of carboxymethyl cellulose, starch and the like are used. It is preferable to use 0.1 to 5.0 parts by mass of these dispersants or dispersing aids with respect to 100 parts by mass of the polymerizable monomer.
[0133]
A surfactant of 0.001 to 0.1% by mass may be used in combination for miniaturization of these dispersants. Specifically, commercially available nonionic, anionic and cationic surfactants can be used. More specifically, for example, sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, potassium stearate, calcium oleate and the like are preferably used.
[0134]
The developer of the present invention may further contain other known external additives in addition to the toner particles and silica fine particles described above. When fine particles of the opposite polarity to the toner are used as an external additive in combination with small-sized fine particles such as silica fine particles, the purpose is to prevent the generation of agglomerates due to the mutual particles, It is particularly preferable that the fine particles have a particle size of 80 nm or more in view of the effect of the spacer particles for preventing the external additive from being embedded in the toner particles.
[0135]
It is preferable that the fine particles as the external additive be added in an amount of 0.05 to 5.0% by mass based on the toner particles in order to surely exhibit the performance and to have a stable charging property. Further, the reverse polarity fine particles used in the present invention are not limited to using only one kind, and a plurality of kinds can be used in combination.
[0136]
As the fine particles, metal oxides are preferably used from the viewpoint of uniformity of charge application to toner particles. Among the above-mentioned metal oxides, oxides selected from magnesium, aluminum, titanium, zinc, zirconium, strontium, and manganese, and composite oxides of the above-mentioned metals are particularly excellent in charging uniformity to the toner. The metal oxides described above may be used alone or in combination of two or more.
[0137]
Among these, in particular, any one of metal oxides represented by hydrotalcite compounds, titanium oxide, magnesium oxide, aluminum oxide, zinc oxide, zirconium oxide, strontium titanate, and manganese oxide has a toner charge control effect. This is preferable because it is high and it is difficult to make a minute scratch on the surface of the electrostatic latent image carrier.
[0138]
In particular, the fine particles are oxidized by a hydrotalcite compound, titanium oxide, or aluminum oxide in terms of charge controllability, difficulty in damaging the surface of the electrostatic latent image carrier, and prevention of image defects due to contamination of the charging member. It is more preferable that it is a substance.
[0139]
The charge amount of the metal oxide is preferably 30 mC / kg or less in absolute value, because the charge controllability of the toner becomes higher.
[0140]
The metal oxide, the surface of which may be subjected to a hydrophobic treatment with an organic compound such as higher fatty acids, esters, a coupling agent or oil can be used, but in order to suppress the absolute value of the charge amount low, Untreated hydrophilic metal oxides are also preferably used.
[0141]
The specific surface area of the metal oxide is 2.0 to 150 m²/ G. 2.0m²/ G does not provide a sufficient effect.²/ G is not preferred because the fluidity of the toner deteriorates and image density unevenness occurs. The measurement of the BET specific surface area is performed by using a known device such as a BET measuring device Gemini 2375 (manufactured by Micro Mesotic) equipped with a degassing device VacuPrep 061 (manufactured by Micro Mesotic).
[0142]
Further, the fine particles may be resin fine particles. Specific examples include a styrene resin, an acrylic resin, an acrylate resin, and a copolymer thereof, a silicone resin, a melamine-formaldehyde resin, a benzoguanamine-formaldehyde resin copolymer, and a phenol resin.
[0143]
The developer of the present invention may further contain an inorganic powder in order to improve developability and durability. Examples of such inorganic powders include metal oxides such as magnesium, zinc, aluminum, cerium, cobalt, iron, zirconium, chromium, manganese, strontium, tin, and antimony; calcium titanate, magnesium titanate, and strontium titanate. Metal salts such as barium sulfate, calcium carbonate, magnesium carbonate and aluminum carbonate; clay minerals such as kaolin; phosphoric acid compounds such as apatite; and silicon compounds such as silica, silicon carbide and silicon nitride. .
[0144]
For the same purpose, organic particles or composite particles can be added to the developer of the present invention. Examples of such organic particles and composite particles include resin particles such as polyamide resin particles, silicone resin particles, silicone rubber particles, urethane particles, melamine-formaldehyde particles, and acrylic particles; rubber, wax, fatty acid compounds, resins, and the like. Composite particles composed of metals, metal oxides, salts, and inorganic particles such as carbon black; fluororesins such as polyfluoroethylene and polyvinylidene fluoride; fluorine compounds such as carbon fluoride; fatty acid metal salts such as zinc stearate; And fatty acid derivatives such as fatty acid esters; molybdenum sulfide, amino acids and amino acid derivatives.
[0145]
The external additives, inorganic powder, organic particles and composite particles other than the silica fine particles described above may be used alone or in combination. Further, if necessary, a hydrophobic treatment (oil, coupling) may be performed.
[0146]
The method of stirring when adding the silica fine particles and other additives to the toner particles is not particularly limited as long as the additive mechanically adheres to the toner particles when the additive is externally added. Can be carried out using a stirring device described above. Preferably, a Henschel mixer, a homogenizer or the like is used, and more preferably, a Henschel mixer is used. The external addition strength is preferably controlled by controlling the rotation speed, the angle of the baffle plate, and the stirring time, and the liberation rate of the silica fine particles is preferably controlled in consideration of the interaction with other external additives.
[0147]
Hereinafter, the image forming method of the present invention using the developer of the present invention will be described more specifically with reference to the drawings. FIGS. 1 and 2 are views showing a first embodiment of an image forming apparatus in which the image forming method of the present invention is suitably used.
[0148]
FIG. 2 is a schematic sectional view illustrating the configuration of the image forming apparatus according to the present embodiment. First, the configuration of the image forming apparatus of the present embodiment will be described with reference to FIG. The image forming apparatus according to the present embodiment is a reversal developing system in which a developer is adhered to an exposed portion of an image carrier to visualize the image carrier, and a developer carrier carrying a negatively charged developer is applied to the image carrier. This is a one-component image forming apparatus that performs development by contacting.
[0149]
An image forming apparatus used in the present invention includes a photosensitive drum 1 as an image carrier, a charging roller 2 for uniformly charging the surface of the photosensitive drum 1, and a photosensitive drum 1 uniformly charged by the charging roller 2 to expose and statically expose the surface. Exposure device 3 for forming an electrostatic latent image, developing device 4 as a developing means for transferring a developer to the electrostatic latent image on the surface of photosensitive drum 1, transfer for transferring the developer transferred to the surface of photosensitive drum 1 to transfer paper A roller 5, a fixing device 7 for fixing the developer transferred to the transfer paper to the transfer paper, and a cleaning unit 6 for removing the developer remaining on the surface of the photosensitive drum 1 after the transfer of the developer to the transfer paper is performed. Having.
[0150]
In FIG. 2, a photosensitive drum 1 as an image carrier is rotatable in an arrow x direction. The surface of the photosensitive drum 1 is uniformly charged to a negative polarity by a charging roller 2 as a primary charger. Then, as the photosensitive drum 1 rotates, the uniformly charged surface is exposed by the exposure device 3. As the charges in the exposed portion disappear, an electrostatic latent image is formed on the photosensitive drum 1.
[0151]
Reference numeral 4 denotes a developing unit as a developing unit, which transfers a developer to a portion to be exposed of the electrostatic latent image to visualize the electrostatic latent image. The developer used is a non-magnetic one-component developer. Further, the present embodiment is a so-called reversal developing system for transferring a developer to a portion to be exposed.
[0152]
The developer transferred onto the photosensitive drum 1 is transferred to the transfer paper P by a transfer roller 5 as a transfer charger. The developer remaining on the photosensitive drum 1 without being transferred is removed from the photosensitive drum 1 by the cleaning unit 6. On the other hand, the developer on the transfer paper P is heat-melted by the fixing device 7 and is fixed on the transfer paper P to form a permanent image.
[0153]
The developing device 4 includes a developing roller 8 as a developer carrier, a supply roller 12 for supplying a developer to the developing roller 8, a developing blade 9 as a developer regulating member, a stirring member 13 for conveying toner to the supply roller 12 side, A motor 15 for rotating the developing roller 8, a developing bias power supply 10 as a voltage applying means for applying a voltage to the developing roller 8, a blade bias power supply 11 as a voltage applying means for applying a voltage to the developing blade 9, a developing bias power supply 10 It has a control device 14 as voltage control means for controlling the operation of the blade bias power supply 11.
[0154]
The developing roller 8 is rotatable in the direction of arrow y by a motor 15 as a driving device. Since the developing roller 8 uses what is called contact development in which development is performed by contacting the surface of the photosensitive drum 1, the developing roller 8 desirably has elasticity such as rubber. In the present embodiment, a voltage of about −400 V is supplied to the developing roller 8 from the developing bias power supply 10. The developer on the developing roller 8 is transferred to the exposed portion on the photosensitive drum 1 by the difference between the exposed portion potential on the photosensitive drum 1 and the potential supplied from the developing bias power supply 10.
[0155]
The developing blade 9 is made of a thin metal plate, and is brought into contact with the developing roller 8 by utilizing the elasticity of the thin plate. As the material of the metal thin plate, stainless steel, phosphor bronze, or the like can be used. In this embodiment, a phosphor bronze thin plate having a thickness of 0.1 mm is used. The toner is frictionally charged by the rubbing between the developing blade 9 and the developing roller 8 to be charged, and the layer thickness is regulated at the same time. A predetermined voltage is supplied to the developing blade 9 from a blade bias power supply 11. The voltage applied to the developing blade 9 will be described later.
[0156]
Reference numeral 14 denotes a control device (control means). The control device 14 controls the rotation of the developing roller 8 and controls the voltage values of the developing bias power supply 10 and the blade bias power supply 11 as voltage applying means.
[0157]
FIG. 1 is a diagram showing a sequence according to the present embodiment. FIG. 1 shows a case where two sheets are continuously printed using the image forming apparatus of FIG. In FIG. 1, the graph of the rotation of the photosensitive drum and the graph of the rotation of the developing roller respectively indicate that the photosensitive drum 1 or the developing roller 8 is driven to rotate when it is convex upward (that is, when it is ON).
[0158]
In this embodiment, since the photosensitive drum 1 and the developing roller 8 are always in contact with each other, the rotation of the photosensitive drum 1 and the rotation of the developing roller 8 are performed in synchronization. However, in the case of so-called non-contact development where the photosensitive drum and the developing roller are always separated, or in the case where a mechanism capable of separating the photosensitive drum 1 and the developing roller 8 is provided, the rotation of the photosensitive drum 1 and the developing roller 8 is It is done asynchronously. The developing method used in the present invention may be any of the above-mentioned methods, and is appropriately selected according to the characteristics required for the developing method.
[0159]
In FIG. 1, when a print output is requested from a personal computer or the like (not shown), the same potential of about −400 V is applied from the developing bias power supply 10 and the blade bias power supply 11 with the start of rotation of the photosensitive drum 1 and the developing roller 8. Each is applied. At the beginning of the rotation of the developing roller 8 and the like, it is a preparatory rotation time before an image is still drawn, that is, at the time of non-image formation.
[0160]
The time of image formation refers to the time of each process for forming a toner image on a portion of the transfer paper P excluding a blank area. In addition, non-image formation refers to when the developing roller is rotating except during image formation. For example, the rotation before preparation, the rotation after preparation, or the so-called “sheet interval” between prints corresponds to the time of non-image formation.
[0161]
After the pre-preparation rotation is started and a voltage of about −400 V is applied from the developing bias power supply 10 and the blade bias power supply 11, the blade bias power supply 11 has a charging polarity side of the toner particles higher than the voltage applied to the developing roller 8. A high voltage is applied for a moment. As described above, the difference between the voltage applied to the developing roller 8 and the voltage applied to the developing blade 9 (potential difference between the developing roller 8 and the developing blade 9) at this time is preferably 60 to 500V. In this embodiment, the potential difference is set to 200 V, and a voltage of about -600 V is applied to the developing blade 9. Further, the application time of a voltage higher than that of the developing roller, which is applied to the developing blade 9 during the non-image formation, does not adversely affect the image formation, and the process speed of the image forming apparatus and the developer applied to the developing blade 9 are not affected. It is appropriately selected depending on the ease of adhesion and the like, and is not particularly limited, but is preferably in the range of 5 msec to several seconds. In this embodiment, the application time is 300 msec.
[0162]
As described above, during the non-image forming time during which the image on the transfer paper P is not affected, −600 V is applied to the developing blade 9 and −400 V is applied to the developing roller 8. That is, in the present embodiment, a potential difference that can be transferred from the developing blade side to the developing roller side is supplied to the negatively charged particles (toner and external additive). Therefore, the negative external additive that adheres to the developing blade 9 immediately after the start of rotation of the developing roller (the fixed end side from the developing roller and the developing blade contact portion: a portion in FIG. 7) is transferred to the developing roller 8 side. become.
[0163]
After a momentary application of -600 V to the developing blade 9 and -400 V to the developing roller 8, the voltages of the developing bias power supply 10 and the blade bias power supply 11 become almost the same potential, -400 V, which is the first image forming area. Image formation is performed (at the time of image formation). During the image formation, the developing roller 8 and the developing blade 9 have substantially the same potential, and the rotation of the developing roller 8 causes the charge of the toner layer to move the negative polarity from the contact portion of the developing blade 9 to the fixed end. External additives transfer. However, the reversal toner and the positive external additive do not adhere to the developing blade 9.
[0164]
When the image formation for the first sheet is completed, a so-called “paper interval” is formed between the image formation and the next image formation. During this sheet interval, a voltage of -600 V is applied to the developing blade 9 for 300 msec as in the pre-preparation rotation. Due to the voltage applied to the developing blade 9, the negative external additive adhered to the fixed end side from the contact portion of the developing blade 9 during the first image formation is transferred to the developing roller 8 side. Since this is performed while the developing roller 8 is rotating, the negative external additive does not return to the developing blade 9 side again.
[0165]
Then, the second image formation is performed in the same manner as the first image formation. At the time of image formation, the negative external additive adheres and accumulates from the contact portion of the developing blade 9 to the free end tip as described above.
[0166]
When the image formation for the second sheet is completed, the rotation starts after preparation for the next print. At this time, a voltage of -600 V is applied to the developing blade 9 for 300 msec in the same manner as the pre-preparation rotation and the sheet interval. Due to the voltage applied to the developing blade 9, the negative external additive adhered from the contact portion of the developing blade 9 to the fixed end side during the first image formation is transferred to the developing roller 8 side. Since this is performed while the developing roller 8 is rotating, the negative external additive does not return to the developing blade 9 side again.
[0167]
Then, after the preparation, the rotation operation ends, and the rotation of the developing roller 8 and the photosensitive drum 1 stops.
[0168]
In this manner, the negative external additive attached to the fixed end from the contact portion of the developing blade 9 during image formation is applied to the developing roller 8 side by momentarily providing a potential difference between the developing blade 9 and the developing roller 8 during non-image formation. By returning, the developing blade 9 can be refreshed. As a result, since the negative external additive attached to the fixed end side from the developing blade contact portion is not deposited, it is possible to prevent the toner from being fused to the developing blade 9.
[0169]
The timing when an electric potential difference is generated between the developing blade 9 and the developing roller 8 at the time of non-image formation is that the toner carrying amount regulated on the developing roller 8 when the electric potential difference is applied from the same electric potential. Is changed, and a density step occurs on the image.
[0170]
In addition, during non-image formation, it is not necessary to provide a time for applying a voltage higher than that of the developing roller 8 to the developing blade 9 every time. For example, it is performed during pre-preparation rotation before image formation, or only during post-preparation rotation. It is possible to do. In this embodiment, the voltage is applied only once, for example, 300 msec. However, for example, a plurality of potential differences can be provided during the pre-preparation rotation.
[0171]
In this embodiment, separate voltage applying means (developing bias power supply 10 and blade bias power supply 11) are provided for each of the developer regulating member (developing blade 9) and the developer carrier (developing roller 8). However, the configuration may be such that a voltage is applied to the developer regulating member and the developer carrying member by the same voltage applying unit, and there is no particular limitation.
[0172]
It is also preferable that the developing means used in the image forming method of the present invention is configured as a cartridge which is detachable from the main body of the image forming apparatus. In this case, a developing cartridge in which only the developing unit is formed into a cartridge may be used, or a process cartridge in which an image carrier, a charging unit, a cleaning unit and the like are integrated in addition to the developing unit may be used. As a result, the user's labor involved in various maintenance operations such as toner replenishment and replacement of the developing device after the end of its life can be reduced, and a stable output image can be obtained with a simple operation.
[0173]
3 to 5 show a second embodiment of an image forming apparatus in which the image forming method of the present invention is suitably used. Hereinafter, a second embodiment of the image forming method of the present invention will be described with reference to these drawings. In the image forming apparatus according to the second embodiment, the same members as those used in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0174]
FIG. 3 is a schematic sectional view of the image forming apparatus according to the second embodiment. This image forming apparatus is a color image forming apparatus, and includes a photosensitive drum 1 as an image carrier, a charging roller 2 for uniformly charging the surface of the photosensitive drum 1, and a surface of the photosensitive drum 1 uniformly charged by the charging roller 2. Exposure device 3 that forms an electrostatic latent image by exposing, developing device 22 as a developing unit that transfers a developer to the electrostatic latent image on the surface of photosensitive drum 1, and developer that has been transferred to the surface of photosensitive drum 1 is transferred. Intermediate transfer member 24.
[0175]
The developing unit 22 includes a rotary 22x as a rotating support, a yellow developing cartridge 22a, a magenta developing cartridge 22b, a cyan developing cartridge 22c, and a black developing cartridge 22d.
[0176]
In the present embodiment, the image forming apparatus is an electrophotographic color printer, and converts the image data into four colors of yellow Y, magenta M, cyan C, and black Bk based on image data from a personal computer or a workstation (not shown). A toner image of each color is sequentially formed on the surface of the photosensitive drum 1 based on the decomposed image data, and the toner images are superimposed on the intermediate transfer body 24, and are collectively transferred to a transfer material (recording medium) such as paper to form a full-color image. Get. The image forming apparatus according to the present exemplary embodiment includes a so-called rotary type color printer that employs a developing device including a plurality of developing units, that is, developing cartridges 22a, 22b, 22c, and 22d mounted in a rotary 22x. Is done.
[0177]
In FIG. 3, the image forming apparatus includes a photoconductive organic photosensitive drum 1 as an image carrier. When the image forming operation starts, the photosensitive drum 1 is driven to rotate in the direction of arrow q. The surface of the photosensitive drum 1 is uniformly charged to a predetermined dark area potential by applying a bias to a core of the charging roller 2 as a contact charging unit. Next, according to the first color yellow (Y) image data, scanning exposure is performed by a laser beam whose ON / OFF control is performed by the exposure device 3, and a first electrostatic latent image is formed as a light portion potential. Is done.
[0178]
The electrostatic latent image thus formed is developed and visualized by a developing unit (developing cartridge) mounted in the rotary 22x of the developing unit 22. The rotary 22x includes a first developing cartridge 22a containing yellow (Y) toner as a first color developer and a second developing cartridge 22b containing magenta (M) toner as a second color developer. A third developing cartridge 22c containing cyan (C) toner as a third color developer, and a fourth developing cartridge 22d containing black (Bk) toner as a fourth color developer. It has an integrated configuration. The rotary 22x is configured to rotate and move in the direction of the arrow r so that the developing cartridges corresponding to the respective color toner images are opposed to the photosensitive drum 1.
[0179]
The developing cartridge (22a, 22b, 22c, or 22d) positioned at the developing position facing the photosensitive drum 1 has a motor 23 as a developing roller as a developer carrier for carrying a developer regulated to a predetermined layer thickness. Each is driven to rotate, and development is performed by applying a predetermined voltage (development bias) to the core metal of the developing roller. Each of the Y, M, C, and Bk developing cartridges 22a, 22b, 22c, and 22d is individually replaceable as a single cartridge (developing cartridge) depending on the degree of wear.
[0180]
First, the first electrostatic latent image is developed and visualized by a first developing cartridge 22a containing Y toner as a developer of a first color. The developing method can be used irrespective of contact / non-contact, but in the present embodiment, a contact developing method using a non-magnetic one-component toner combining image exposure and reversal development is used.
[0181]
The visualized toner image of the first color is electrostatically transferred (primary) to the surface of the intermediate transfer member 24 at a first transfer portion which is a nip portion with the intermediate transfer member 24 as a second image carrier. Transfer). The intermediate transfer member 24 is formed by sequentially laminating a conductive elastic layer and a surface layer having releasability on a cylinder.
[0182]
The intermediate transfer body 24 has a circumferential length longer than the maximum length of the transfer material that can be passed, and is pressed against the photosensitive drum 1 with a predetermined pressing force while maintaining a substantially constant speed with the circumferential speed of the photosensitive drum 1. The photosensitive drum 1 is rotationally driven at a peripheral speed in a direction opposite to the rotational direction of the photosensitive drum 1 (the direction of arrow s in FIG. 3) (at the contact portion, the surface of the photosensitive drum 1 and the surface of the intermediate transfer body 24 move in the same direction).
[0183]
The toner image formed on the surface of the photosensitive drum 1 as described above is applied to the cylinder portion of the intermediate transfer body 24 with a voltage (primary transfer bias) having a polarity opposite to the polarity of the charged developer. As a result, electrostatic transfer (primary transfer) is performed on the surface of the intermediate transfer body 24. The toner remaining on the surface of the photosensitive drum 1 after the primary transfer is removed by the cleaning unit 6 to prepare for the next latent image formation.
[0184]
Subsequently, the same process is repeated, and each time, the toner image of the second color developed with the M toner, the toner image of the third color developed with the C toner, and the toner image of the fourth color developed with the Bk toner are sequentially formed. A color toner image is formed by being transferred and laminated on the surface of the intermediate transfer member 24.
[0185]
Thereafter, the transfer belt 18 that has been separated from the surface of the intermediate transfer member 24 is pressed against the surface of the intermediate transfer member 24 with a predetermined pressing force and is driven to rotate. The transfer belt 18 includes the transfer roller 17. By applying a voltage (secondary transfer bias) having a polarity opposite to the charging polarity of the toner to the transfer roller 17, the intermediate transfer member 24 is applied to the surface of the transfer paper P conveyed at a predetermined timing. The color toner images stacked on the surface are collectively transferred (secondary transfer), and the transfer paper P is conveyed to the fixing device 7. The transfer paper P is discharged out of the apparatus after the toner image is fixed as a permanent image by the fixing device 7, and a desired color print image is obtained.
[0186]
The toner remaining on the surface of the intermediate transfer body 24 after the completion of the secondary transfer is removed by the intermediate transfer body cleaning device 16 which comes into contact with the surface of the intermediate transfer body 24 at a predetermined timing.
[0187]
FIG. 5 is a schematic cross-sectional view showing the configuration of developing cartridges 22a, 22b, 22c, and 22d containing toners of Y, M, C, and Bk, respectively, which are developing units used in the present embodiment. Reference numeral 22d denotes a structure which can be attached to and detached from the rotary color printer, which is the image forming apparatus shown in FIG. 3, by opening and closing a cover for replacing a developing cartridge (not shown). The cyan developing cartridge 22c can be taken out in the upward arrow D direction.
[0188]
In the rotary type color printer shown in FIG. 3, it is necessary to attach and detach the developing cartridge at the take-out position, and replace the yellow, magenta, and black developing cartridges 22a, 22b, and 22d other than the cyan developing cartridge 22c in the drawing. In this case, it is necessary to move the cartridge to be removed by rotating the rotary 22x to the attachment / detachment position (the position 22c in FIG. 3).
[0189]
Hereinafter, the developing cartridge 22a for the Y toner will be described for simplicity, but the same applies to the developing cartridges 22b, 22c, and 22d for the other colors.
[0190]
The developing cartridge 22a of the present embodiment shown in FIG. 5 is a reversal developing unit that contains a non-magnetic one-component Y toner as a developer. The developing cartridge 22a rotates in a direction indicated by an arrow e in the drawing to contact the photosensitive drum 1 to perform development, and rotates in a direction f to supply a developer to the developing roller 8a. A supply roller 12a as a means, a developing blade 9a as a developer regulating member for regulating an application amount and a charge amount of the developer on the developing roller 8a, and a stirring member 13a for supplying and agitating the developer to the supply roller 12a. ing.
[0191]
FIG. 4 is a diagram showing a sequence according to the present embodiment. FIG. 4 shows a case where one full-color image is printed with the four color toners. In FIG. 4, when a print output is requested from a personal computer or the like (not shown), the photosensitive drum 1 rotates and the rotary 22x rotates to move the first color developing cartridge 22a to a position facing the photosensitive drum 1. To start.
[0192]
When the first color (yellow) developing cartridge 22a comes to a position facing the photosensitive drum 1, the developing roller 8a starts pre-preparation rotation. At the same time, a voltage is supplied from a developing bias power supply 19 and a blade bias power supply 20 as voltage applying means under the control of a control unit (control means) 21. At this time, a voltage of about −400 V is applied to the developing roller 8 a from the developing bias power supply 19, and a sawtooth voltage having a peak at −600 V is applied to the developing blade 9 a from the blade bias power supply 20. Two sawtooth-wave voltages applied from the blade bias power supply 20 are applied, and the cycle is 200 msec per wave.
[0193]
During non-image formation, which is a time that does not affect the image on the transfer paper P, a sawtooth voltage having a peak of −600 V is applied to the developing blade 9 a and a −400 V voltage is applied to the developing roller 8 a. That is, in the present embodiment, a potential difference that can transfer from the developing blade 9a to the developing roller 8a is supplied to the negatively charged particles (toner and external additive). Therefore, the negative external additive adhering to the developing blade 9a immediately after the rotation of the developing roller 8a is transferred to the developing roller 8a side.
[0194]
After an instantaneous application of -600 V (saw wave) to the developing blade 9a and -400 V to the developing roller 8a, the voltage applied from the developing bias power supply 19 and the blade bias power supply 20 becomes -400 V, which is almost the same potential. First, image formation is performed on the first color image formation area (at the time of image formation). At the time of image formation, the developing roller 8a and the developing blade 9a have substantially the same potential, so that the rotating operation of the developing roller 8a causes the charge of the developer layer to move the negative electrode from the contact portion of the developing blade 9a to the fixed end. The external additive of the nature is transferred. However, the reversal toner and the positive external additive do not adhere to the developing blade 9a.
[0195]
When the image formation for the first color is completed, the developing cartridge 22 a is rotated after preparation, and at this time, a single sawtooth voltage having a peak of −600 V is applied to the developing blade 9 from the blade bias power supply 20. By this operation, the negative external additive attached to the developing blade 9a of the yellow developing cartridge 22a is transferred to the developing roller 8a side during image formation, and the developing blade 9a can be refreshed.
[0196]
The rotation of the developing roller 8a is turned off, and the rotary 22x rotates between the next color (magenta) image formation. During the rotation of the rotary 22x, the voltage supply from the developing bias power supply 19 and the blade bias power supply 20 is turned off. When the second color (magenta) developing cartridge 22b moves to the position facing the photosensitive drum 1, the rotation of the rotary 22x ends, and the developing cartridge 22b stops at this position.
[0197]
Then, as in the case of the first color (yellow), the developing roller 8b starts rotating before preparation. At the same time, voltages are supplied from the developing bias power supply 19 and the blade bias power supply 20. At this time, a voltage of about −400 V is applied from the developing bias power supply 19, and a sawtooth voltage having a peak of −600 V is applied from the blade bias power supply 20. The sawtooth voltage applied from the blade bias power supply 20 is applied in two waves, and the cycle is 200 msec per wave. Then, the second color image formation is performed in the same manner as the first color image formation. At the time of image formation, as described above, the negative external additive adheres and accumulates from the contact portion of the developing blade 9b to the free end tip. The above operation is performed up to the fourth color.
[0198]
In this way, by transferring the negative external additive adhered on the developing blade during the previous image formation to the developing roller side during the pre-preparation rotation of each color, the accumulation of the external additive on the developing blade is prevented, and stable. Image forming apparatus can be provided.
[0199]
When the image formation for the fourth color is completed, the rotation starts after the preparation for the fourth color, and a single sawtooth voltage having a peak of -600 V is applied from the blade bias power supply 20 as described above. Thereafter, the rotation of the developing roller 8d is turned off, and the rotary 22x rotates. Before the rotation of the rotary 22x, the voltage supply from the developing bias power supply 19 and the blade bias power supply 20 is turned off.
[0200]
When the image formation is completed and the rotation of the rotary 22x is completed, the intermediate transfer body 24 and the photosensitive drum 1 are rotated after the main body for the next printing, and the photosensitive drum 1 stops when the post-body rotation is completed.
[0201]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto.
First, a method for manufacturing a developer used in the examples will be described.
<Development example 1>
In a 2-liter four-necked flask equipped with a high-speed stirrer TK-homomixer, 910 parts by mass of ion-exchanged water and Na₃PO₄An aqueous solution was added, the rotation speed was adjusted to 9000 rpm, and the mixture was heated to 63 ° C. Here CaCl₂The aqueous solution is gradually added, and a fine hardly water-soluble dispersant Ca is added.₃(PO₄)₂The aqueous dispersion medium containing was prepared.
[0202]
・ Styrene monomer 80 parts by mass
・ 2-ethylhexyl acrylate monomer 20 parts by mass
・ Divinylbenzene monomer 0.25 parts by mass
・ Saturated polyester resin 10 parts by mass
(Terephthalic acid-propylene oxide modified bisphenol A, acid value 15 mgKOH / g)
・ Carbon black (primary particle diameter 40nm) 8 parts by mass
・ Release agent (behenyl behenate) 10 parts by mass
・ Benzyl acid metal complex 2.0 parts by mass
[0203]
After dispersing the above material for 3 hours using a ball mill, the contents were isolated from the ball mill. To this content, 3 parts by mass of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator was added to form a polymerizable monomer composition, which was added to the aqueous dispersion medium. And granulated while maintaining the rotation number at 9000 rpm. Thereafter, the mixture was reacted at 65 ° C. for 4 hours while stirring with a paddle stirring blade, then polymerized at 80 ° C. for 5 hours, and further distilled at 80 ° C. under reduced pressure of 13.3 kPa (100 Torr) or less.
[0204]
After the completion of the reaction, the suspension was cooled, and hydrochloric acid was added thereto to add a poorly water-soluble dispersant Ca.₃(PO₄)₂Was dissolved, filtered, washed with water, dried, and then classified to a desired particle size by air classification to obtain toner particles (1).
[0205]
100 parts by mass of the toner particles (1) were treated with a 20% silicone oil based on the base material as a fluidity improver, and the BET specific surface area was 130 m.²/ G of hydrophobic silica fine particles 1 of 1.3 parts by mass and 0.2 parts by mass of a titanium oxide compound having a primary particle diameter of 300 nm are added, and the peripheral speed is 43 m / s by a Henschel mixer (manufactured by Mitsui Miike Kakoki Co., Ltd.). , And the above powders were uniformly fixed on the surface of the toner particles (1). 1 was obtained. Developer No. The average particle diameter of No. 1 was 6.5 μm, the number% of particles having a particle diameter of 4 μm or less was 7.5%, and the liberation rate of silica fine particles was 2.7%. Table 2 shows other physical property values.
[0206]
<Development Examples 2 and 3>
The developer No. 1 was prepared in the same manner as in Production Example 1 except that the type and amount of the silica fine particles to be added were changed as shown in Table 2 in Production Example 1 of the developer. 2 and developer No. 2 3 was obtained. Each developer No. 2 and No. Table 2 shows the physical property values of No. 3. The physical properties of each silica fine particle used in Table 2 are shown in Table 1.
[0207]
<Production Example 4 of Developer>
By adjusting the amount of the poorly water-soluble dispersant in Production Example 1 of the developer, toner particles (4) having an average particle diameter of 5.5 μm and 20% of the number% of particles having a particle diameter of 4 μm or less were used. Got. Silica fine particles 4 and a titanium oxide compound were added in the amounts shown in Table 2 to 100 parts by mass of the toner particles (4), and mixed at a rotational speed of 20 m / s for 3 minutes using a Henschel mixer. Using the same method as in Production Example 1, the developer No. 4 was obtained. Developer No. Table 2 shows the physical property values of Sample No. 4. Table 1 shows the physical properties of the silica fine particles 4 used in Table 2.
[0208]
<Development example 5>
・ Styrene-butyl acrylate copolymer (80/20) 100 parts
・ Carbon black (primary particle diameter 40nm) 8 parts
・ 5 parts of low molecular weight polypropylene
・ 2 parts of metal benzyl acid complex
The above components were melt-kneaded by a Banbury mixer, cooled, and then finely pulverized by a jet mill, and the finely pulverized product was classified to a desired particle size by air classification to obtain toner particles (5).
[0209]
100 parts by mass of the toner particles (5) were treated with a 20% silicone oil based on the base material as a fluidity improver, and the BET specific surface area was 130 m.²/ G of hydrophobic silica fine particles 1 of 1.3 parts by mass and 0.2 parts by mass of a hydrotalcite compound having a primary particle diameter of 400 nm are mixed with a Henschel mixer at a rotation speed of 43 m / s for 3 minutes. Then, the respective powders are uniformly fixed on the surface of the toner particles (5), and the developer No. 5 was obtained. Developer No. The average particle diameter of No. 5 was 6.7 μm, the number% of particles having a particle diameter of 4 μm or less was 8.9%, and the release rate of silica fine particles was 2.4%. Table 2 shows other physical property values.
[0210]
<Development Production Examples 6 and 7>
In Production Example 5 of the developer, the types and amounts of the silica fine particles and other external additives to be added were changed as shown in Table 2, and the mixing device was changed to Cyclomix (manufactured by Hosokawa Micron Corporation). Production Example 6 was developed using the same method as in Production Example 5 except that mixing was performed at a peripheral speed of 25 m / s for 3 minutes at a rotation speed of 25 m / s. Agent No. 6 and developer no. 7 was obtained. Each developer No. 6 and no. Table 2 shows the physical property values of No. 7.
[0211]
<Development Example 8>
・ Polyester resin (1) 70 parts by mass
[Polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane / polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane / terephthalic acid / fumaric acid / Polyester resin produced from trimellitic acid (acid value 10.8 mgKOH / g, Tg = 65 ° C, Mw = 45000, Tm = 105 ° C)]
・ Carbon black (primary particle diameter 40 nm) 30 parts by mass
[0212]
The above-mentioned materials were charged into a kneader-type mixer, and while mixing, the temperature was raised to 120 ° C. under no pressure, and the mixture was sufficiently premixed. Thereafter, the mixture was kneaded twice with three rolls to obtain a first kneaded material.
[0213]
・ First kneaded material: 16.7 parts by mass
(30 parts by mass of the colorant in 100 parts by mass of the kneaded material)
・ Polyester resin (1): 88.3 parts by mass
・ Release agent 5 parts by mass
[Polyethylene derivative, Mn1000, acid value 0.6 mgKOH / g]
.Aluminum complex of di-alkylsalicylic acid 4 parts by mass
The above materials are sufficiently premixed with a Henschel mixer, melt-kneaded with a twin screw extruder, the melt-kneaded material is cooled, and after cooling, the solidified material is roughly pulverized to about 1 to 2 mm using a hammer mill, and then air-cooled. It was pulverized with a jet pulverizer. Further, the finely pulverized product was classified into a desired particle size by air classification to obtain toner particles (8).
[0214]
100 parts by mass of the toner particles (8) were treated with a 35% silicone oil based on the base material as a fluidity improver, and the BET specific surface area was 150 m.²/ G of hydrophobic silica fine powder 4 and 0.1 parts by mass of a titanium oxide compound having a primary particle diameter of 30 nm are mixed with a Henschel mixer at a peripheral speed of 20 m / s for 3 minutes. Then, the above-mentioned respective powders are uniformly fixed to the toner particles (8), and the developer No. 8 was obtained.
[0215]
Developer No. The average number-equivalent diameter of the circle of No. 8 was 5.7 μm, and the number% of particles having a particle diameter of 4 μm or less was 18%. Table 2 shows other physical property values.
[0216]
<Development example 9>
In Production Example 8 of the developer, the polyester resin to be added was [polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane / terephthalic acid / fumaric acid / trimellitic acid. A finely pulverized product was obtained using the same method as in Production Example 8 except that the polyester resin was changed to an acid value (15.2 mgKOH / g, Tg = 63, Mw = 18000, Tm = 103 ° C.). The obtained finely pulverized product was subjected to a surface treatment by a batch method at 1600 rpm (peripheral speed: 80 m / sec) for 3 minutes using a surface reforming apparatus of a type in which a rotor is rotated to apply a mechanical impact force. Next, the particles were classified into a desired particle size by air classification to obtain toner particles (9).
[0219]
With respect to the toner particles (9), the types and amounts of the silica fine particles and the titanium oxide compound to be added were changed as shown in Table 2, and a Henschel mixer (manufactured by Mitsui Miike Koki Co., Ltd.) was used at a peripheral speed of 25 m / s. Except for mixing at a rotation speed for 3 minutes, the same method as in Production Example 8 was used to make the developer No. 9 was obtained. Table 2 shows the physical property values of each developer 9.
[0218]
<Development Examples 10 to 12>
In Production Example 1 of the developer, the coloring agent to be added is C.I. I. Pigment Yellow 93, and in Production Example 11, C.I. I. Pigment Red 53 and C.I. I. Pigment Blue 15: 3, and using the same method as in Production Example 1, the developer No. 10-No. 12 was obtained. Table 2 shows the physical property values of each developer.
[0219]
<Development Examples 13 to 15>
In Production Example 5 of the developer, the coloring agent to be added was prepared in C.I. I. Pigment Yellow 93, Production Example 14 is C.I. I. Pigment Red 53, Production Example 15 is C.I. I. Pigment Blue 15: 3, and using the same method as in Production Example 5, except that the developer No. 13-No. 15 was obtained. Table 2 shows the physical property values of each developer.
[0220]
<Development Example 16>
In Developer Production Example 1, except that the type of silica fine particles to be added was changed as shown in Table 2, a developer No. 16 was obtained. Developer No. Table 2 shows the physical property values of No. 16. The physical properties of each silica fine particle used in Table 2 are shown in Table 1.
[0221]
<Development Production Examples 17, 18>
In Production Example 1 of the developer, the type and amount of the silica fine particles or titanium oxide to be added were changed as shown in Table 2, and the mixing device was changed to a Ledige mixer (manufactured by Matsubo Co., Ltd.). Is mixed at a rotation speed of 14 m / s for 2 minutes, and in Production Example 18 of the developer, developer No. 1 is mixed using the same production method as in Production Example 1 except that mixing is performed at a peripheral speed of 50 m / s for 3 minutes. 17 and No. 18 was obtained. Developer No. 17 and No. Table 2 shows the physical property values of No. 18. The physical properties of each silica fine particle used in Table 2 are shown in Table 1.
[0222]
<Production Example 19 of Developer>
The developer No. 5 was prepared in the same manner as in Production Example 5 except that the amount of the added silica fine particles was changed as shown in Table 2 in Production Example 5 of the developer. 19 was obtained. Developer No. Table 2 shows the physical property values of No. 19.
[0223]
<Development Example 20>
In Production Example 8 of the developer, except that the kind and amount of the silica fine particles to be added were changed as shown in Table 2, the same method as in Production Example 8 was used to make the developer No. 20 was obtained. Developer No. Table 2 shows the physical property values of Sample No. 20.
[0224]
[Table 1]

[0225]
[Table 2]

[0226]
Next, the image forming apparatus used in the embodiment will be described.
<Example 1 of image forming apparatus>
The image forming apparatus of the first embodiment shown in FIGS. It was set to 1. The description of this device is as described above.
[0227]
<Example 2 of image forming apparatus>
The image forming apparatus according to the second embodiment shown in FIGS. And 2. The description of this device is as described above.
[0228]
<Example 3 of Image Forming Apparatus>
In the image forming apparatus 1, a bias of the same potential (−400 V) was applied to the developing roller 8 and the developing blade 9 throughout image formation and non-image formation. That is, the configuration is such that no potential difference is provided between the developing roller 8 and the developing blade 9 during non-image formation. This was designated as image forming apparatus 3.
[0229]
<Example 4 of image forming apparatus>
In the image forming apparatus 1, a bias having a potential of -400 V was applied to the developing roller 8 and a voltage having a potential of -500 V was applied to the developing blade 9 throughout image formation and non-image formation. That is, a configuration is adopted in which a potential difference is provided between the developing roller 8 and the developing blade 9 even during image formation. This was designated as an image forming apparatus 4.
Table 3 shows the voltage applying method and the developing method of each of the image forming apparatuses 1 to 4.
[0230]
[Table 3]

[0231]
<Example 1>
The image forming apparatus 1 and the developer No. 1 in a high-temperature and high-humidity environment when about 10,000 patterns of a predetermined printing rate are output in a high-temperature and high-humidity environment (30 ° C .; 80% relative humidity) and a low-temperature and low-humidity environment (15 ° C .; 10% relative humidity) The generation of fog and vertical streaks in low-temperature and low-humidity environment was evaluated. The evaluation was performed by outputting a solid image and a halftone image every 500 sheets.
[0232]
In the fog evaluation, a point in time when the fog value on an image output in a high-temperature and high-humidity environment became 3% or more was regarded as an image defect, and ranks were classified according to the image defect occurrence time as follows.
-No fog of 3% or more occurs even when printing for 10,000 sheets.
・ Image failure occurs after 9000 sheets durability printing.
・ Image defects occur after 8000 sheets of durable printing △: C
・ Image failure occurs from the end of the endurance to the endurance printing of 5000 sheets.
[0233]
The evaluation of the occurrence of streaks in a low-temperature and low-humidity environment was evaluated by ranking according to the following evaluation criteria.
・ Even when printing on 10,000 sheets, uniform halftone is reproduced, and no fused matter is observed even when the developing blade is observed.
・ Even when printing for 10,000 sheets, uniform halftone is reproduced. However, when the developing blade is observed, there is a slight fused matter.
-Dark streaks occur in halftone images after 8000 sheets of durable printing.
・ Conspicuous dark and streak generation from the initial to 8,000 sheets of durable printing: D
Table 4 shows the evaluation results.
[0234]
<Examples 2 to 9>
In Example 1, durable printing was performed using the same method as in Example 1 except that the developer was changed as shown in Table 4, and generation of fog in a high-temperature and high-humidity environment and vertical stripes in a low-temperature and low-humidity environment evaluated. Table 4 shows the evaluation results.
[0235]
<Example 10>
In the first embodiment, the image forming apparatus is no. 2 and developer No. 2 in the cartridge 22a. 10 in the cartridge 22b. 11 into the cartridge 22c. 12 in the cartridge 22d. Durability printing was performed with a full-color image using the same method as in Example 1 except that each of No. 1 was filled, and the occurrence of fog in a high-temperature and high-humidity environment and the occurrence of vertical stripes in a low-temperature and low-humidity environment were evaluated. Table 4 shows the evaluation results.
[0236]
<Example 11>
In the first embodiment, the image forming apparatus is no. 2 and developer No. 2 in the cartridge 22a. 13 in the cartridge 22b. 14 in the cartridge 22c. 15 into the cartridge 22d. The same method as in Example 1 described above was used to carry out durable printing with a full-color image except that each of No. 5 was filled, and the fog in a high-temperature and high-humidity environment and the generation of vertical stripes in a low-temperature and low-humidity environment were evaluated. Table 4 shows the evaluation results.
[0237]
<Comparative Example 1>
In Example 1, the developer was changed to the developer No. Durability printing was performed using the same method as in Example 1 except that the number was changed to 16, and the occurrence of fog in a high-temperature and high-humidity environment and the generation of vertical stripes in a low-temperature and low-humidity environment were evaluated. As shown in Table 4, the silica fine particles having a large BET specific surface area were used, so that the silica was strongly adhered to the blade, the refresh effect was not sufficiently obtained by applying a bias, and the blade was durable in an L / L environment. A noticeable streak image occurred without waiting for the life.
[0238]
<Comparative Example 2>
In Example 1, the developer was changed to the developer No. The durability was evaluated by using the same method as in Example 1 except that the durability was changed to 17. The results are shown in Table 4. As shown in Table 4, the silica fine particles having a small BET specific surface area were used, so that fog due to poor charging was significantly deteriorated with durability in an H / H environment, and a released silica was obtained in an L / L environment. Fine particles were accumulated on the blade and a streak image was generated from an early stage of the durability, which was not practical.
[0239]
<Comparative Example 3>
In Example 1, the developer was changed to the developer No. The durability was evaluated by using the same method as in Example 1 except that the durability was changed to 18. As shown in Table 4, as the amount of the added silica fine particles was small, good triboelectric charging could not be performed with the deterioration of the durability of the developer, and the fog was significantly deteriorated in an H / H environment.
[0240]
<Comparative Example 4>
In Example 1, the developer was changed to the developer No. The durability was evaluated using the same method as in Example 1 except that the number was changed to 19. As shown in Table 4, as the amount of added silica fine particles was large, the amount of free silica adhering to the blade was increased, and the refresh effect by bias application was not sufficiently obtained. A streak image occurred.
[0241]
<Comparative Example 5>
In Example 1, the developer was changed to the developer No. The durability was evaluated by using the same method as in Example 1 except that the value was changed to 20. As shown in Table 4, as shown in Table 4, the addition amount of the silica fine particles was large and the content of the particles having a particle size of the developer of 4 μm or less was large. The toner adhered firmly to the blade, and the adhesion increased the frictional force at the blade contacting portion, promoting the fusion of the developer and generating a streak image from an earlier stage than in Comparative Example 4.
[0242]
<Comparative Example 6>
In the first embodiment, the image forming apparatus is designated as the image forming apparatus No. The durability was evaluated using the same method as in Example 1 except that the number was changed to 3. As shown in Table 4, since there is no potential difference between the blade and the developer carrier, the silica fine particles having a high charge amount accumulate on the blade, and a poor streak image without waiting for the durability life. Occurred.
[0243]
<Comparative Example 7>
In the eleventh embodiment, the image forming apparatus is designated as image forming apparatus No. The durability was evaluated with a full-color image using the same method as in Example 11 except that the evaluation was changed to 4. The results are shown in Table 4. As shown in Table 4, although there is always a potential difference between the blade and the developer carrier, the adhesion of the silica fine particles to the downstream portion of the nip is suppressed, but the hydrotalcite or the reversal charging developer is not applied to the blade. Because the potential is attracted to the nip upstream of the contact portion and accumulates, the development streak in the L / L environment and fog due to poor charging in the H / H environment deteriorated with durability, and the device was not practical. .
[0244]
[Table 4]

[0245]
As a result, it was found that by using the image forming method of the present invention, even in a low-temperature and low-humidity environment, it was possible to perform stable image formation for a long period without causing toner fusion to the developing blade. Further, it was found that the image forming method did not cause image defects even in a high-temperature and high-humidity environment, and was suitable for any environment.
[0246]
As described above, the potential relationship between the voltages applied to the developing roller 8 and the developing blade 9 during the rotation of the developing roller is set to be substantially the same during image formation, and at least temporarily during non-image formation. By making the potential of the developing blade 9 higher than the potential on the same polarity side as the charged polarity of the toner particles, and by using the developer of the present invention containing specific silica fine particles, toner adhesion to the developing blade 9 is improved. Deposition and fusion can be prevented, and defective image density and vertical stripes can be prevented.
[0247]
Also in the full-color image forming apparatus, the potential relationship between the developing roller 8 (8a to 8d) and the developing blade 9 (9a to 9d) during the rotation of the developing roller is set to substantially the same potential at the time of image formation, and at the time of non-image formation. By making the potential of the developing blade 9 at least temporarily higher than the potential of the developing roller 8 to the same polarity as the charging polarity of the toner particles, and by using the developer of the present invention containing specific silica fine particles, It is possible to prevent toner from adhering, accumulating, and fusing to the developing blade 9, thereby preventing image density defects and vertical streaks.
[0248]
At the same time, the developing means including the developer, which is relatively worn out of the image forming elements, is a process cartridge detachable from the image forming apparatus main body, thereby reducing the user's labor involved in various maintenance operations. It became possible to plan.
[0249]
【The invention's effect】
According to the present invention, it is possible to prevent the developer from fusing to the developer regulating member even in a low temperature and low humidity environment. Further, image defects such as fogging and the like in a high temperature and high humidity environment do not occur. Thus, it is possible to prevent image defects such as fogging and vertical stripes from occurring in any environment, and to perform stable image formation over a long period of time.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a sequence of an image forming apparatus according to a first embodiment in which an image forming method of the present invention is preferably used.
FIG. 2 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus according to a first embodiment in which the image forming method of the present invention is preferably used.
FIG. 3 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus according to a second embodiment in which the image forming method of the present invention is preferably used.
FIG. 4 is a diagram illustrating a sequence of an image forming apparatus according to a second embodiment in which the image forming method of the present invention is preferably used.
FIG. 5 is a schematic sectional view of a developing cartridge mounted on the image forming apparatus according to the second embodiment.
FIG. 6 is a schematic sectional view showing the configuration of a conventional image forming apparatus.
FIG. 7 is a diagram for explaining toner fusion to a developer regulating member;
FIG. 8 is a diagram showing a Faraday cage used for measuring a charge amount of a developer.
FIG. 9 is a diagram showing a measuring device used for measuring the charge amount of the external additive.
[Explanation of symbols]
1 Photosensitive drum (image carrier)
2 charging roller
3 Exposure device
4 Developer (developing means)
5 transfer roller
6 Cleaning means
7 Fixing unit
8, 8a, 8b, 8c, 8d Developing roller (developer carrier)
9, 9a, 9b, 9c, 9d Developing blade (developer regulating member)
10 ° developing bias power supply (voltage applying means)
11 blade bias power supply (voltage applying means)
12, 12a, 12b, 12c, 12d supply roller
13, 13a, 13b, 13c, 13d stirrer
14 control circuit (control means)
15 motor
16 intermediate transfer body cleaning device
17 transfer roller
18 transfer belt
19 ° developing bias power supply (voltage applying means)
20 ° blade bias power supply (voltage applying means)
21 Control unit (control means)
22 developer
22a, 22b, 22c, 22d Developing cartridge (developing means)
22x @ rotary
23 motor
24 intermediate transfer member
P transfer paper

Claims (21)

An image forming method having a developing step of visualizing the electrostatic latent image by transferring a developer by a developing unit to the electrostatic latent image carried on the image carrier,
The developing unit is disposed to face the image carrier, a rotatable developer carrier that carries a developer, a developer regulating member that regulates the amount of developer on the developer carrier, Voltage applying means for applying a voltage to the developer carrier and the developer regulating member, and a voltage control means for controlling the operation of the voltage applying means,
The voltage control unit controls the amount of voltage applied by the voltage application unit so that the potentials of the developer carrier and the developer regulating member are substantially the same during image formation. At the time of non-image formation in which image formation is not performed during rotation, the potential of the developer regulating member is at least temporarily higher than the potential of the developer carrier to the same polarity as the charged polarity of the toner particles. Controlling the voltage application amount of the voltage application means as described above,
The developer contains toner particles and silica fine particles having the same polarity as the toner particles and a BET specific surface area of 20 to 250 m ² / g. An image forming method comprising 2 parts by mass. 2. The image forming method according to claim 1, wherein particles having a particle size of 4 [mu] m or less are 35% or less in a particle size distribution of the developer. The image forming method according to claim 1, wherein the developer has a release rate of the silica fine particles with respect to the toner particles of 20% or less, as measured by a particle analyzer. The silica fine particles are subjected to a hydrophobizing treatment with a silane coupling agent and / or silicone oil, and have a number average primary particle diameter of 5 to 100 nm. 2. The image forming method according to 1., The image forming method according to any one of claims 1 to 4, wherein a potential difference between the developer carrier and the developer regulating member during the non-image formation is 60 to 500V. The image forming method according to any one of claims 1 to 5, wherein the charge amount of the developer is 15 to 90 C / g in absolute value. The image forming method according to claim 1, wherein a melt index value of the developer is 35 or less. A developer for visualizing the electrostatic latent image carried on the image carrier,
By transferring the developer to the electrostatic latent image on the latent image carrier by a developing unit, used in an image forming method having a developing step of visualizing the electrostatic latent image,
The developing unit is disposed to face the image carrier, a rotatable developer carrier that carries a developer, a developer regulating member that regulates the amount of developer on the developer carrier, Voltage applying means for applying a voltage to the developer carrier and the developer regulating member, and a voltage control means for controlling the operation of the voltage applying means,
The voltage control unit controls the amount of voltage applied by the voltage application unit so that the potentials of the developer carrier and the developer regulating member are substantially the same during image formation. At the time of non-image formation in which image formation is not performed during rotation, at least temporarily, the potential of the developer regulating member is higher than the potential of the developer carrier to the same polarity as the charging polarity of the toner. Controlling the voltage application amount of the voltage application means,
The developer contains toner particles and silica fine particles having the same polarity as the toner particles and a BET specific surface area of 20 to 250 m ² / g. 2 parts by mass of a developer. 9. The developer according to claim 8, wherein in the number-based particle size distribution, particles having a particle size of 4 μm or less are 35% or less. 10. The developer according to claim 8, wherein a release rate of the silica fine particles with respect to the toner particles measured by a particle analyzer is 20% or less. The silica fine particles are subjected to a hydrophobic treatment with a silane coupling agent and / or silicone oil, and have a number average primary particle diameter of 5 to 100 nm. The developer according to item 1. The developer according to any one of claims 8 to 11, wherein a potential difference between the developer carrier and the developer regulating member during non-image formation is 60 to 500V. The developer according to any one of claims 8 to 12, wherein the charge amount is 15 to 90 µC / g in absolute value. The developer according to any one of claims 8 to 13, wherein the melt index value is 35 or less. A process cartridge detachable from an image forming apparatus that visualizes an electrostatic latent image carried on an image carrier by a developer,
A developer carrying member arranged to face the image carrying member for carrying a developer, a developer regulating member for regulating an amount of developer on the developer carrying member, a developer carrying member and a developer regulating member; A voltage application unit that applies a voltage to the member, and a voltage control unit that controls an operation of the voltage application unit, including a developing unit having:
The voltage control unit controls the amount of voltage applied by the voltage application unit so that the potentials of the developer carrier and the developer regulating member are substantially the same during image formation. At the time of non-image formation in which image formation is not performed during rotation, the potential of the developer regulating member is at least temporarily higher than the potential of the developer carrier to the same polarity as the charged polarity of the toner particles. Controlling the voltage application amount of the voltage application means as described above,
The developer contains toner particles and silica fine particles having the same polarity as the toner particles and a BET specific surface area of 20 to 250 m ² / g. A process cartridge containing 2 parts by mass. 16. The process cartridge according to claim 15, wherein particles having a particle size of 4 [mu] m or less are 35% or less in the particle size distribution of the developer. 17. The process cartridge according to claim 15, wherein the developer has a release rate of the silica fine particles with respect to the toner particles of 20% or less, as measured by a particle analyzer. The silica fine particles are subjected to a hydrophobic treatment with a silane coupling agent and / or silicone oil, and have a number average primary particle diameter of 5 to 100 nm. 4. The process cartridge according to 1. The process cartridge according to any one of claims 15 to 18, wherein a potential difference between the developer carrier and the developer regulating member during non-image formation is 60 to 500V. 20. The process cartridge according to claim 15, wherein the charge amount of the developer is 15 to 90 [mu] C / g in absolute value. 21. The process cartridge according to claim 15, wherein the melt index value of the developer is 35 or less.

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