JP2004093642A - Image forming apparatus and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus and a process cartridge having excellent characteristics of repeated output of images while keeping the developing property even when a toner having a small size and high circularity is used, and having high image quality and high precision of an image for a long time. <P>SOLUTION: The image forming apparatus has a cleaning mechanism for an intermediate transfer belt by arranging the intermediate transfer belt, a photoreceptor, the cleaning mechanism for the intermediate transfer belt, and a cleaning mechanism for the photoreceptor in one integrated unit in the image forming apparatus or the process cartridge. The mechanism works in such a manner that the residual developer is electrified into the opposite polarity to that in the primary transfer period and the developer is made to return to the photoreceptor at the time of primary transfer on the intermediate belt. The charge transfer layer of the photoreceptor shows the universal hardness (HU) of≥ 230 N/mm<SP>2</SP>and ≤260 N/mm<SP>2</SP>at 1 μm dent depth from the surface of the charge transfer layer, ≥35% elastic deformation rate, and shows ≥260 N/mm<SP>2</SP>HU at 5 μm dent depth from the surface and ≥30% elastic deformation rate. <P>COPYRIGHT: (C)2004,JPO

Description

【００２５】
ここで、「粒子投影面積」とは二値化されたトナー粒子像の面積であり、「粒子投影像の周囲長」とは該トナー粒子像のエッジ点を結んで得られる輪郭線の長さと定義する。
【００２６】
本発明における円形度はトナー粒子の凹凸の度合いを示す指標であり、トナー粒子が完全な球形の場合に１．０００を示し、表面形状が複雑になる程、円形度は小さな値となる。
【００２７】
本発明において、トナーの個数基準の粒径頻度分布の平均値を意味する円相当個数平均径ｄ_１と粒径標準偏差ＳＤｄは、粒度分布の分割点ｉでの粒径（中心値）をｄｉ、頻度をｆｉとすると次式から算出される。
【００２８】
【数２】

【００２９】
また、円形度頻度分布の平均値を意味する平均円形度ｃと円形度標準偏差ＳＤｃは、粒度分布の分割点ｉでの円形度（中心値）をｃｉ、頻度をｆ_ｃｉとすると、次式から算出される。
【００３０】
【数３】

【００３１】
具体的な測定方法としては、容器中に予め不純固形物等を除去したイオン交換水１０ｍｌを用意し、その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加えた後、更に測定試料を０．０２ｇ加え、均一に分散させる。分散させる手段としては、超音波分散機ＵＨ−５０型（エスエムテー社製）に振動子としてφ５ｍｍのチタン合金チップを装着したものを用い、５分間分散処理を用い、測定用の分散液とする。その際、該分散液の温度が４０℃以上とならない様に適宜冷却する。
【００３２】
トナー粒子の形状測定には、前記フロー式粒子像測定装置を用い、測定時のトナー粒子濃度が３０００〜１万個／μｌとなる様に該分散液濃度を再調整し、トナー粒子を１０００個以上計測する。計測後、このデータを用いて、トナーの円相当径や円形度頻度分布等を求める。
【００３３】
本発明においてトナーに使用されるワックス成分としては、パラフィンワックス、マイクロクリスタリンワックス、ペトロラクタム等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、フィッシャートロプシュ法による炭化水素ワックス及びその誘導体、ポリエチレンに代表されるポリオレフィンワックス及びその誘導体、カルナバワックス、キャンデリラワックス等の天然ワックス及びそれらの誘導体等で、誘導体には酸化物や、ビニルモノマーとのブロック共重合物、グラフト変性物も含み、また、高級脂肪族アルコール等のアルコール；ステアリン酸、パルミチン酸等の脂肪酸あるいはその化合物；酸アミド、エステル、ケトン、硬化ヒマシ油及びその誘導体、植物ワックス、動物ワックス等のスチレンモノマーへの溶解温度が４０〜８０℃のものであれば、どれでも用いることが可能である。
【００３４】
これらの中でもポリオレフィン、フィッシャートロプシュ法による炭化水素ワックス、石油系ワックス、高級アルコール、もしくは、高級エステルである場合、現像性や転写性の改善効果が更に高くなる。
【００３５】
上述したワックス成分は、結着樹脂１００質量部に対して１〜３０質量部使用するのが好ましい。
【００３６】
本発明においてトナーに用いられる結着樹脂としては、一般的に用いられているスチレン−（メタ）アクリル共重合体、ポリエステル樹脂、エポキシ樹脂及びスチレン−ブタジエン共重合体が挙げられる。重合法により直接トナー粒子を得る方法においては、それらを形成するための単量体が用いられる。具体的にはスチレン；ｏ−（ｍ−，ｐ−）メチルスチレン、ｍ−（ｐ−）エチルスチレンの如きスチレン系単量体；（メタ）アクリル酸メチル、（メタ）アクリル酸エチル、（メタ）アクリル酸プロピル、（メタ）アクリル酸ブチル、（メタ）アクリル酸オクチル、（メタ）アクリル酸ドデシル、（メタ）アクリル酸ステアリル、（メタ）アクリル酸ベヘニル、（メタ）アクリル酸２−エチルヘキシル、（メタ）アクリル酸ジメチルアミノエチル、（メタ）アクリル酸ジエチルアミノエチルの如き（メタ）アクリル酸エステル系単量体；ブタジエン、イソプレン、シクロヘキセン、（メタ）アクリロニトリル、アクリル酸アミドの如きエン系単量体が好ましく用いられる。これらは、単独、又は、一般的には出版物ポリマーハンドブック第２版ＩＩＩ−Ｐ１３９〜１９２（Ｊｏｈｎ　Ｗｉｌｅｙ＆Ｓｏｎｓ社製）に記載の理論ガラス転移温度（Ｔｇ）が、４０〜７５℃を示すように単量体を適宜混合して用いられる。理論ガラス転移温度が４０℃未満の場合にはトナーの保存安定性や耐久安定性の面から問題が生じ易く、一方７５℃を超える場合はトナーの定着点の上昇をもたらす。特に、フルカラー画像を形成するためのカラートナーの場合においては各色トナーまた、現像剤であるトナーの形状係数を特定の値とすることで、現像剤の電子写真感光体から転写媒体への転写効率を大きくすることができる。その結果、電子写真感光体上に転写残の現像剤が少なくなり、帯電部材への現像剤付着が減少する。また、仮に帯電部材に付着したとしても本発明のような形状係数を有する現像剤であれば帯電部材上から離脱し易いことがわかった。トナーの定着時の混色性が低下し色再現性に乏しく、更にＯＨＰ画像の透明性が低下するため好ましくない。
【００３７】
結着樹脂の分子量は、ゲルパーミエーションクロマトグラフィー（ＧＰＣ）により測定される。低軟化点物質を外殻樹脂で内包化した所謂コアーシェル構造を有するトナーの場合、具体的なＧＰＣの測定方法としては、予めトナーをソックスレー抽出器を用いトルエン溶剤で２０時間抽出を行った後、ロータリーエバポレーターでトルエンを留去せしめて抽出物を得て、更に低軟化点物質は溶解するが外殻樹脂は溶解しない有機溶剤（例えばクロロホルム等）を抽出物に加え十分洗浄を行った後、残留物をテトラヒドロフラン（ＴＨＦ）に溶解した溶液をポア径が０．３μｍの耐溶剤性メンブランフィルターでろ過したサンプル（ＴＨＦ溶液）をウォーターズ社製１５０Ｃを用いて測定する。カラム構成は昭和電工製Ａ−８０１、８０２、８０３、８０４、８０５、８０６及び８０７を連結し、標準ポリスチレン樹脂の検量線を用い分子量分布を測定し得る。結着樹脂の主たるピーク分子量は５０００〜１００万、重量平均分子量（Ｍｗ）と数平均分子量（Ｍｎ）との比（Ｍｗ／Ｍｎ）が２〜１００を示すものが本発明には好ましい。
【００３８】
本発明に使用されるトナーに用いられる着色剤は、以下に示すイエロー着色剤、マゼンタ着色剤及びシアン着色剤が挙げられ、黒色着色剤としてカーボンブラック、磁性体又は以下に示すイエロー着色剤／マゼンタ着色剤／シアン着色剤を混合して黒色に調色されたものが利用される。
【００３９】
イエロー着色剤としては、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、メチン化合物又はアリルアミド化合物が用いられる。具体的には、Ｃ．Ｉ．ピグメントイエロー１２、１３、１４、１５、１７、６２、７４、８３、９３、９４、９５、１０９、１１０、１１１、１２８、１２９、１４７、１６８又は１８０等が好適に用いられる。
【００４０】
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、アンスラキノン、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又は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、１４４、１４６、１６６、１６９、１７７、１８４、１８５、２０２、２０６、２２０、２２１又は２５４等が特に好適に用いられる。
【００４１】
シアン着色剤としては、銅フタロシアニン化合物及びその誘導体、アンスラキノン化合物又は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又は６６等が特に好適に用いられる。
【００４２】
これらの着色剤は、単独又は混合し更には固溶体の状態で用いることができる。着色剤は、色相、彩度、明度、耐候性、ＯＨＰ透明性、トナー粒子中への分散性の点から選択される。該着色剤の添加量は、樹脂成分１００質量部に対し１〜２０質量部使用するのが好ましい。
【００４３】
黒色着色剤として磁性体を用いた場合には、他の着色剤と異なり、樹脂１００質量部に対し４０〜１５０質量部使用するのが好ましい。
【００４４】
本発明に使用されるトナーには公知の荷電制御剤を併用することができ、特に帯電スピードが速く、かつ、一定の帯電量を安定して維持できる荷電制御剤が好ましい。更に、トナー粒子を直接重合法を用いる場合には、重合阻害性が無く水系分散媒体への可溶化物の無い荷電制御剤が好ましい。
【００４５】
具体的化合物としては、ネガ系荷電制御剤としてサリチル酸、ナフトエ酸、ダイカルボン酸の如き芳香族カルボン酸の金属化合物；スルホン酸又はカルボン酸基を側鎖に持つ高分子型化合物；ホウ素化合物；尿素化合物；ケイ素化合物；カリークスアレーン等が挙げられる。ポジ系荷電制御剤として、四級アンモニウム塩；該四級アンモニウム塩を側鎖に有する高分子型化合物；グアニジン化合物；イミダゾール化合物等が挙げられる。
【００４６】
しかしながら、本発明において荷電制御剤の添加は必須ではなく、二成分現像方法を用いた場合においては、キャリヤーとの摩擦帯電を利用し、非磁性一成分ブレードコーティング現像方法を用いた場合においては、ブレード部材やスリーブ部材との摩擦帯電を積極的に利用することでトナー粒子中に必ずしも荷電制御剤を含む必要はない。
【００４７】
本発明に使用されるトナーに無機微粉体を添加することは、現像性、転写性、帯電安定性、流動性及び耐久性向上のために好ましい実施形態である。該無機微粉体としては公知のものが使用可能であるが、特にシリカ、アルミナ、チタニアあるいはその複酸化物の中から選ばれることが好ましい。更には、シリカであることがより好ましい。例えば、かかるシリカは硅素ハロゲン化物やアルコキシド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と称される乾式シリカ及びアルコキシドや水ガラス等から製造されるいわゆる湿式シリカの両者が使用可能であるが、表面及びシリカ微粉体の内部にあるシラノール基が少なく、またＮａ_２ＯやＳＯ_３ ^２−等の製造残渣の少ない乾式シリカの方が好ましい。また、乾式シリカにおいては、製造工程において例えば、塩化アルミニウム及び塩化チタン等の他の金属ハロゲン化合物を硅素ハロゲン化合物と共に用いることによって、シリカと他の金属酸化物の複合微粉体を得ることも可能でありそれらも包含する。
【００４８】
本発明に使用されるトナーに用いられる無機微粉体は、ＢＥＴ法で測定した窒素吸着による比表面積が３０ｍ^２／ｇ以上、特に５０〜４００ｍ^２／ｇの範囲のものが良好な結果を与え、トナー１００質量部に対してシリカ微粉末０．１〜８質量部が好ましく、より好ましくは０．５〜５質量部、更に好ましくは１．０を超えて３．０質量部まで使用するのが特によい。
【００４９】
また、本発明に使用されるトナーに用いられる無機微粉体は、必要に応じ、疎水化や帯電性制御等の目的でシリコーンワニス、各種変性シリコーンワニス、シリコーンオイル、各種変性シリコーンオイル、シランカップリング剤、官能基を有するシランカップリング剤、その他の有機硅素化合物、有機チタン化合物等の処理剤で、あるいは、種々の処理剤で併用して処理されていることも可能であり好ましい。
【００５０】
比表面積はＢＥＴ法に従って、比表面積測定装置オートソーブ１（湯浅アイオニクス社製）を用いて試料表面に窒素ガスを吸着させ、ＢＥＴ多点法を用いて比表面積を算出した。
【００５１】
高い帯電量を維持し、低消費量及び高転写率を達成するためには、無機微粉体は少なくともシリコーンオイルで処理されることが更に好ましい。
【００５２】
本発明に使用するトナーにおいては、実質的な悪影響を与えない範囲内で更に他の添加剤、例えばポリテトラフルオロエチレン粉末、ステアリン酸亜鉛粉末、ポリフッ化ビニリデン粉末の如き滑剤粉末；酸化セリウム粉末、炭化硅素粉末、チタン酸ストロンチウム粉末等の研磨剤；例えば酸化チタン粉末、酸化アルミニウム粉末等の流動性付与剤；ケーキング防止剤、あるいは例えばカーボンブラック粉末、酸化亜鉛粉末、酸化スズ粉末等の導電性付与剤、また、逆極性の有機微粒子及び無機微粒子を現像性向上剤として少量用いることもできる。
【００５３】
本発明に使用するトナーを製造する方法としては、樹脂、低軟化点物質からなる離型剤、着色剤、荷電制御剤等を加圧ニーダーやエクストルーダー又はメディア分散機を用い均一に分散せしめた後、機械的又はジェット気流下でターゲットに衝突させ、所望のトナー粒径に微粉砕化せしめた後（必要により、トナー粒子の平滑化及び球形化の工程を付加）、更に分級工程を経て粒度分布をシャープにせしめトナーにする粉砕方法によるトナーの製造方法の他に、特公昭５６−１３９４５号公報等に記載のディスク又は多流体ノズルを用い溶融混合物を空気中に霧化し球状トナーを得る方法や、特公昭３６−１０２３１号公報、特開昭５９−５３８５６号公報及び特開昭５９−６１８４２号公報に開示されている懸濁重合方法を用いて直接トナーを生成する方法や、単量体には可溶で得られる重合体が不溶な水系有機溶剤を用い直接トナーを生成する分散重合方法又は水溶性極性重合開始剤存在下で直接重合しトナーを生成するソープフリー重合法に代表される乳化重合方法等を用いトナーを製造することが可能である。
【００５４】
粉砕法を用いてトナーを製造する方法においては、トナー粒子の形状を所望の円形度頻度分布の範囲に納めることが困難であり、溶融スプレー法においては、ある程度の円形度を得ることができるが、得られるトナーの粒度分布が広くなり易い傾向があると共に、トナーの表面状態をコントロールすることが困難である。他方、分散重合法においては、得られるトナーは極めてシャープな粒度分布を示すが、使用する材料の選択が狭いことや有機溶剤の利用が廃溶剤の処理や溶剤の引火性に関する観点から製造装置が複雑で煩雑化し易い。ソープフリー重合に代表される乳化重合方法は、トナーの粒度分布が比較的揃うため有効であるが、使用した乳化剤や重合開始剤末端がトナー粒子表面に存在し時に環境特性を悪化させ易い。
【００５５】
本発明においては、トナー粒子の円形度頻度分布のコントロールが重要であり、比較的容易に円相当個数平均径が２〜６μｍの微粒子トナーが得られる常圧下、又は、加圧下での乳化重合法又は懸濁重合方法を用い、予め得られた重合体にメディアを用い定形化したり、直接加圧衝突板に重合体を衝突せしめる方法や、更には得られた重合体を水系中にて凍結せしめたり、塩折や反対表面電荷を有する粒子をｐＨ等の条件を考慮することで合体し、凝集、合一せしめる凝集方法が特に好ましい。更に、一旦得られた重合粒子に更に単量体を吸着せしめた後、重合開始剤を用い重合せしめるシード重合方法も本発明に好適に利用することができる。中でも懸濁重合方法が本発明においては特に好ましい。
【００５６】
トナーの製造方法として直接重合方法を利用する場合、トナー粒子の円形度頻度分布及び粒径頻度分布の制御は、難水溶性の無機塩や保護コロイド作用をする分散剤の種類や添加量を変える方法や機械的装置条件（例えばローターの周速、パス回数、攪拌羽根形状等の攪拌条件や容器形状）又は、水溶液中での固形分濃度等を制御することにより所定のトナー粒子を得ることができる。また、前述の如くトナー粒子の乾燥に用いられる円錘型乾燥機の攪拌条件、処理時間を調整することによっても所定のトナー粒子を得ることができる。
【００５７】
また、トナーを加熱乾燥する際にもトナー粒子に球形化処理を施すことが可能で、例えば流動層乾燥機を用い、回転翼の攪拌条件と処理時間を調整することによりトナー粒子形状を好ましいものにすることができる。
【００５８】
本発明におけるトナーは、ワックス成分の物理特性を前述の如き特定することにより、上記の如きトナー粒子の球形化処理に対してもトナーの粗粒化やワックス成分による影響を最小限とすることができるので非常に有効なものとなる。
【００５９】
直接重合法によりトナーを製造する際、用いられる重合開始剤として例えば、２，２’−アゾビス−（２，４−ジメチルバレロニトリル）、２，２’−アゾビスイソブチロニトリル、１，１’−アゾビス（シクロヘキサン−１−カルボニトリル）、２，２’−アゾビス−４−メトキシ−２，４−ジメチルバレロニトリル及びアゾビスイソブチロニトリルの如きアゾ系又はジアゾ系重合開始剤；ベンゾイルペルオキシド、メチルエチルケトンペルオキシド、ジイソプロピルペルオキシカーボネート、クメンヒドロペルオキシド、２，４−ジクロロベンゾイルペルオキシド及びラウロイルペルオキシドの如き過酸化物系重合開始剤が用いられる。該重合開始剤の使用量は、目的とする重合度により変化するが一般的には重合性単量体に対し０．５〜２０質量％用いられる。重合開始剤の種類は、重合法により若干異なるが、十時間半減期温度を参考に、単独又は混合して使用される。重合度を制御するため公知の架橋剤、連鎖移動剤及び重合禁止剤等を更に添加し、用いてもよい。
【００６０】
トナーの製法として分散安定剤を用いた懸濁重合法を利用する場合、用いる分散安定剤としては、無機化合物として、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、シリカ及びアルミナ等が挙げられる。有機化合物としては、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、ポリアクリル酸及びその塩、デンプン等が挙げられる。これらを水相に分散させて使用できる。これら分散安定剤は、重合性単量体１００質量部に対して０．２〜２０質量部を使用することが好ましい。
【００６１】
分散安定剤として、無機化合物を用いる場合、市販のものをそのまま用いてもよいが、細かい粒子を得るために、分散媒体中にて該無機化合物の微粒子を生成してもよい。例えば、リン酸三カルシウムの場合、高速攪拌下において、リン酸ナトリウム水溶液と塩化カルシウム水溶液を混合するのが好ましい。
【００６２】
これら分散安定剤の微細な分散のために、０．００１〜０．１質量部の界面活性剤を併用してもよい。これは上記分散安定剤の所期の作用を促進するためのものであり、例えば、ドデシルベンゼン硫酸ナトリウム、テトラデシル硫酸ナトリウム、ペンタデシル硫酸ナトリウム、オクチル硫酸ナトリウム、オレイン酸ナトリウム、ラウリル酸ナトリウム、ステアリン酸カリウム及びオレイン酸カルシウム等が挙げられる。
【００６３】
本発明で使用するトナーの製造方法として直接重合法を用いる場合においては、以下の如き製造方法が可能である。
【００６４】
重合性単量体中に、低軟化点物質からなる離型剤、着色剤、荷電制御剤、重合開始剤その他の添加剤を加え、ホモジナイザーや超音波分散機等によって均一に溶解又は分散せしめた単量体組成物を、分散安定剤を含有する水相中に通常の攪拌機、ホモミキサー又はホモジナイザー等により分散せしめる。好ましくは、単量体組成物の液滴が所望のトナー粒子のサイズを有するように攪拌速度や攪拌時間を調整し、造粒する。その後は分散安定剤の作用により、粒子状態が維持され、かつ粒子の沈降が防止される程度の攪拌を行えばよい。重合温度は４０℃以上、一般的には５０〜９０℃の温度に設定して重合を行うのが好ましい。重合反応後半に昇温してもよく、更に、本発明における画像形成方法における耐久性向上の目的で、未反応の重合性単量体や副生成物等を除去するために反応後半、又は、反応終了後に一部水系媒体を反応系から留去してもよい。反応終了後、生成したトナー粒子を洗浄・濾過により回収し、乾燥する。懸濁重合法においては、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。
【００６５】
本発明の画像形成装置は、現像ローラとしての弾性ローラ表面に、一成分現像剤としてトナーをコーティングし、これを感光体表面と接触させる方法を採用している。トナーは非磁性トナーが好ましいが、磁性トナーでもよい。現像ローラ上のトナーと感光体表面が接触するようにすることが重要である。トナー担持体は実質的に感光体表面と接触しているが、これは、トナー担持体からトナーを除いた時に該トナー担持体が感光体と接触しているということを意味する。この時、トナーを介して、感光体と感光体表面に対向する現像ローラ間に働く電界によってエッジ効果のないトナー画像を得るためには、現像ローラ表面あるいは、現像ローラの表面近傍に電位をもち、感光体表面とトナー担持体表面間で電界を形成する必要がある。このため、現像ローラの弾性ゴムが中抵抗領域に抵抗制御されて感光体表面との導通を防ぎつつ電界を形成するか、又は導電性ローラの表面層に薄層の誘電層を設けるか、更には、導電性ローラ上に感光体表面に対向する側を絶縁性物質により被覆した導電性樹脂スリーブあるいは、絶縁性スリーブで感光体に対向しない側に導電層を設けたいずれの構成でも可能である。
【００６６】
本発明において、トナーを担持する現像ローラは感光体の周速同方向に回転していてもよいし、逆方向に回転していてもよい。その回転が同方向である場合感光体の周速に対して、周速比で１００％以上が好ましく、より好ましくは１２０〜３００％、更に好ましくは１４０〜２５０％にして周速差を生じさせるのがよい。１００％未満であると、ラインの切れが悪い等の画像品質に問題を生じ易い。周速比が高くなると、現像部位に供給されるトナーの量は多く、潜像に対しトナーの脱着頻度が多くなり、不要な部分は掻き落とされ必要な部分には付与されるという繰り返しにより、潜像に忠実な画像が得られる。
【００６７】
本発明は、トナーを磁性キャリヤーから形成される磁気ブラシを用いる二成分現像方法についてはこれを包含していない。
【００６８】
本発明に用いられるクリーニング部材としては、ブレード、ローラ、ファーブラシ、磁気ブラシ等を用いることができる。これらのクリーニング部材の２種類以上を組み合わせて使用してもよい。
【００６９】
本発明に用いられる電子写真感光体は、導電性支持体上に電荷発生材料を含有する電荷発生層と電荷輸送材料を含有する電荷輸送層とをこの順に積層した構成もしくは、導電性支持体上に電荷発生材料を含有する電荷発生層と電荷輸送材料を含有する電荷輸送層をこの順に積層した構成である。
【００７０】
本発明に用いる感光体の電荷輸送層は、表面から１μｍの押し込み深さにおけるユニバーサル硬度ＨＵが２３０Ｎ／ｍｍ^２以上２６０Ｎ／ｍｍ^２以下で弾性変形率が３５％以上かつ、表面から５μｍの押し込み深さにおけるユニバーサル硬度ＨＵが２６０Ｎ／ｍｍ^２以上で弾性変形率が３０％以上であるである必要がある。
【００７１】
本発明者らは鋭意検討の結果、電子写真感光体の電荷輸送層の硬度と変形率に着目し、表面皮膜硬度計を用いて得られるユニバーサル硬さ値（Ｈｕ）と弾性変形率（塑性変形率）の値が、ある数値以上の場合に、接触現像方法において球形トナーの現像性を維持しつつトナークリーニング性、感光体の耐久性を維持することが可能であることを見出した。
【００７２】
電子写真感光体における電荷輸送層の表面近傍のユニバーサル硬さ、すなわち表面から１μｍの押し込み深さにおけるユニバーサル硬度ＨＵが２３０Ｎ／ｍｍ^２未満では本発明の画像形成装置においては、感光体の機械的強度が十分でなく、また、表面から１μｍの押し込み深さにおける弾性変形率が３５％未満ではトナークリーニング性が十分でなく、トナー外添剤の埋め込み等に起因したトナー融着が引き起こる。また、表面から１μｍの押し込み深さにおけるユニバーサル硬度ＨＵが２６０Ｎ／ｍｍ^２より大きくなると、感光体電荷輸送層の摩耗量が少なくなるためにブレードめくれが発生する。
【００７３】
一方、電子写真感光体における電荷輸送層の内部のユニバーサル硬さ、すなわち表面から５μｍの押し込み深さにおけるユニバーサル硬度ＨＵが２６０Ｎ／ｍｍ^２未満であるか、弾性変形率が３０％未満である場合、本発明の画像形成装置においては、感光体の繰り返し使用時の電荷輸送層における傷、不均一な摩耗に対する耐久性が十分でなく、特にスジ状のトナークリーニング不良発生の原因となる傷がより深く成長する。
【００７４】
本発明における電子写真感光体の電荷輸送層の表面硬度は、計装化圧子圧入法（ｎａｎｏｉｎｄｅｎｔａｔｉｏｎ　ｍｅｔｈｏｄｓ）によるユニバーサル硬さ（ＨＵ：単位Ｎ／ｍｍ^２）で測定する。
【００７５】
本発明において、ユニバーサル硬さはＨｅｌｍｕｔ　Ｆｉｓｈｅｒ　ＧＭＢＨ＋Ｃｏ．製のＦＩＳＨＥＲＳＣＯＰＥ　Ｈ１００Ｖを用いて測定した。試料は、ガラス板上に１８μｍの膜厚で形成した。測定は圧子に一定の荷重をかけ圧子の押し込み深さを１μｍ、５μｍと代えて測定した。また、弾性変形率はユニバーサル硬度測定時に圧子の荷重を減少させることにより、膜の弾性エネルギー（塑性エネルギー）を解析することもできる。弾性変形率（塑性変形率）は圧子が膜に対して行った仕事量（エネルギー）、すなわち圧子の膜に対する荷重の増減によるエネルギーの変化より求めたものであり、下式からその値は求まる；
弾性変形率（％）＝弾性変形に要したエネルギー／（塑性変形に要したエネルギー＋弾性変形に要したエネルギー）
本発明における電子写真感光体の具体例を以下に説明する。
【００７６】
本発明における電子写真感光体に使用する支持体は、導電性を有するものであればよく、アルミニウムやステンレス等の金属、あるいは導電層を設けた金属、紙及びプラスチック等が挙げられ、形状はシート状や円筒状等が挙げられる。特に、ＬＢＰ等の画像入力がレーザー光の場合は、散乱による干渉縞防止、又は支持体の傷を被覆することを目的とした導電層を設けることが好ましい。これは、カーボンブラックや金属粒子等の導電性粉体を結着樹脂に分散させて形成することができる。導電層の膜厚は５〜４０μｍが好ましく、特には１０〜３０μｍが好ましい。
【００７７】
その上に必要に応じて接着機能及びバリアー機能を有する中間層を設けることができる。中間層の材料としては、ポリアミド、ポリビニルアルコール、ポリエチレンオキシド、エチルセルロース、カゼイン、ポリウレタン及びポリエーテルウレタン等が挙げられる。これらは、適当な溶剤に溶解して塗布される。中間層の膜厚は０．０５〜５μｍが好ましく、特には０．３〜１μｍが好ましい。
【００７８】
導電性支持体あるいは中間層の上には電荷発生層が形成される。用いられる電荷発生材料としては、セレン−テルル、ピリリウム、チアピリリウム系染料、フタロシアニン、アントアントロン、ジベンズピレンキノン、トリスアゾ、シアニン、ジスアゾ、モノアゾ、インジゴ、キナクリドン及び非対称キノシアニン系の各顔料が挙げられる。電荷発生層は前記電荷発生材料を０．３〜４倍量の結着樹脂及び溶剤と共にホモジナイザー、超音波分散、ボールミル、振動ボールミル、サンドミル、アトライター、ロールミル又は液衝突型高速分散機等を使用して十分に分散し、分散液を塗布、乾燥させて形成される。電荷発生層の膜厚は５μｍ以下が好ましく、特には０．１〜２μｍが好ましい。
【００７９】
電荷輸送層は、主として電荷輸送材料と結着樹脂とを溶剤中に溶解させた塗料を塗布、乾燥して形成する。用いられる電荷輸送材料としては、トリアリールアミン系化合物、ヒドラゾン化合物、スチルベン化合物、ピラゾリン系化合物、オキサゾール系化合物、トリアリルメタン系化合物及びチアゾール系化合物等が挙げられる。これらは、０．５〜２倍量の結着樹脂と組み合わされ、塗布、乾燥して電荷輸送層を形成する。
【００８０】
電荷輸送層の膜厚は５〜４０μｍであることが好ましく、１０〜３０μｍであることがより好ましい。
【００８１】
電荷輸送層に用いられる結着樹脂としては、ポリアリレート樹脂、ポリカーボネート樹脂、ポリエステル樹脂、ポリメタクリル酸エステル、ポリスチレン樹脂、アクリル樹脂及びポリアミド樹脂等の熱可塑性樹脂が挙げられる。熱可塑性樹脂の重量平均分子量（Ｍｗ）は、５００００以上２０００００以下が好ましい。５００００未満では結着樹脂として、機械的強度が十分でなく電荷輸送層の耐摩耗性が低下やトナー融着が発生し易く、２０００００を超えると電荷輸送層用塗料の粘度が高くなり過ぎ塗工性が極度に悪化し生産性低下の問題がある。
【００８２】
本発明に用いられる感光体の電荷輸送層は、表面から１μｍの押し込み深さにおけるユニバーサル硬度ＨＵが２３０Ｎ／ｍｍ^２以上２６０Ｎ／ｍｍ^２以下で弾性変形率が３５％以上かつ、表面から５μｍの押し込み深さにおけるユニバーサル硬度ＨＵが２６０Ｎ／ｍｍ^２以上で弾性変形率が３０％以上であればよいが、上記のような低分子量の電荷輸送材料を結着樹脂中に分散した電荷輸送層では、その膜の機械的強度及び変形率は結着樹脂の機械的強度及び電荷輸送材料の含有量に大きく依存する。しかも低分子量の電荷輸送材料を分子分散しているため、その分散状態により電荷輸送層の膜の機械的強度及び変形率は表面近傍と内部で異なる値となる。特に、電荷輸送層形成時の膜の乾燥条件により電荷輸送層中の電荷輸送材料の分散状態が異なってくる。従って、本発明に用いる電荷輸送層を、低分子量の電荷輸送材料を結着樹脂中に分散した膜によって得るためには、結着樹脂として、ポリアリレート樹脂やポリカーボネート樹脂等の硬度の高いかつ高分子量の樹脂を選択し、更に低分子量の電荷輸送材料の含有量を極力小さくする必要がある。更に、適当な乾燥条件を選択することにより、本発明のような膜の表面近傍と内部で硬度と弾性変形率が異なる電荷輸送層を形成することが可能である。
【００８３】
電荷輸送層の硬度は上述のように多くの因子で決まるため、一概には決定されないが、結着樹脂及び電荷輸送材料の組み合わせと混合比、更に乾燥条件の選択によっては表面から１μｍの押し込み深さにおけるユニバーサル硬度ＨＵが２３０Ｎ／ｍｍ^２以上２６０Ｎ／ｍｍ^２以下で弾性変形率が３５％以上かつ、表面から５μｍの押し込み深さにおけるユニバーサル硬度ＨＵが２６０Ｎ／ｍｍ^２以上で弾性変形率が３０％以上は達成される。
【００８４】
例えば重量平均分子量８００００以上のポリカーボネート樹脂と分子量４００〜５００程度のトリフェニルアミン誘導体又はスチルベン誘導体の電荷輸送材料を質量比１０：８以上の比率で混合し、１００℃で乾燥した場合には上述の電荷輸送層の硬度及び弾性率と成り得る。
【００８５】
本発明に使用される感光体の電荷輸送層には、各種添加剤を添加することができる。該添加剤とは酸化防止剤及び紫外線吸収剤等の劣化防止剤である。
【００８６】
本発明における中間転写体に用いられる成型用原料のうちの主たる材料である樹脂は、特に制約はないが、例えば、ポリエチレンやポリプロピレン等のオレフィン系樹脂やポリスチレン系樹脂、アクリル樹脂、ポリエステル樹脂、ポリカーボネート、ポリサルホンやポリエーテルサルホン及びポリフェニレンサルファイド等の硫黄含有樹脂、ポリフッ化ビニリデンやポリエチレン−四フッ化エチレン共重合体等のフッ素含有樹脂、ポリウレタン樹脂、シリコーン樹脂、ケトン樹脂、ポリ塩化ビニリデン、熱可塑性ポリイミド樹脂、ポリアミド樹脂、変性ポリフェニレンオキサイド樹脂等やこれらの各種変性樹脂や共重合体を１種類あるいは２種類以上を使用することができる。但し、上記材料に限定されるものではない。
【００８７】
次に、中間転写ベルトの電気抵抗値を調節するために混合する添加剤は、特に制限されるものではないが、抵抗を調整する導電性フィラーとしては、カーボンブラックや各種の導電性金属酸化物等があり、非フィラー系抵抗調整剤としてはエーテル結合や水酸基等を分子内に含んだ帯電防止樹脂又は電子導電性を示す有機高分子化合物等である。
【００８８】
各種金属塩やグリコール類等の低分子量のイオン導電材は、電子写真感光体への移行を生じ易いため、一般的には好ましくないが、必ずしも全ての材料が問題を生じるわけでは無いので、電子写真感光体に影響しない範囲にある材料であれば使用することができる。
【００８９】
つづいて本発明の中間転写ベルト−電子写真感光体一体カートリッジを用いた画像形成装置の１例を図１に示す。
【００９０】
図１は電子写真プロセスを利用したフルカラー画像形成装置（複写機あるいはレーザービームプリンター）である。
【００９１】
第１の画像担持体として繰り返し使用される回転ドラム型の電子写真感光体（以下感光ドラムと記す）１は、矢印方向に所定の周速度（プロセススピード）をもって回転駆動される。
【００９２】
感光ドラム１は回転過程で、一次帯電器２により所定の極性・電位に一様に帯電処理される。３２は一次帯電器の電源であり、ここでは直流に交流を重畳して印加しているが、直流のみでもよい。次いで不図示の露光手段（カラー原稿画像の色分解・結像露光光学系、画像情報の時系列電気デジタル画素信号に対応して変調されたレーザービームを出力するレーザースキャナによる走査露光系等）による露光光３を受けることにより目的のカラー画像の第１の色成分像（例えばイエロー色成分像）に対応した静電潜像が形成される。
【００９３】
次いで、その静電潜像が第１の現像器（イエロー色現像器４１）により第１色であるイエロートナーＹにより現像される。この時、第２〜第４の現像器（マゼンタ色現像器４２、シアン色現像器４３及びブラック色現像器４４）の各現像器は作動−オフになっていて感光ドラム１には作用せず、上記第１色のイエロートナー画像は上記第２〜第４の現像器による影響を受けない。
【００９４】
中間転写ベルト５は、矢印方向に感光ドラム１と同じ周速度をもって回転駆動されている。感光ドラム１上に形成担持された上記第１色のイエロートナー画像が、感光ドラム１と中間転写ベルト５とのニップ部を通過する過程で、一次転写ローラー６から中間転写ベルト５に印加される一次転写バイアスにより形成される電界により、中間転写ベルト５の外周面に順次一次転写されていく。
【００９５】
中間転写ベルト５に対応する第一色のイエロートナー画像の転写を終えた感光ドラム１の表面は、クリーニング装置１３により清掃される。
【００９６】
以下、同様に第２色のマゼンタトナー画像、第３色のシアントナー画像、第４色のブラックトナー画像が順次中間転写ベルト５上に重ね合わせて転写され、目的のカラー画像に対応した合成カラートナー画像が形成される。
【００９７】
二次転写ローラー７は、二次転写対向ローラー８に対応し平行に軸受させて中間転写ベルト５の下面部に離間可能な状態に配設してある。
【００９８】
感光ドラム１から中間転写ベルト５への第１〜第４色のトナー画像の順次重畳転写のための一次転写バイアスは、トナーとは逆極性（＋）でバイアス電源３０から印加される。その印加電圧は、例えば＋１００Ｖ〜２ｋＶの範囲である。
【００９９】
感光ドラム１から中間転写ベルト５への第１〜第３色のトナー画像の一次転写工程において、二次転写ローラー７は中間転写ベルト５から離間させることも可能である。
【０１００】
中間転写ベルト５上に転写された合成カラートナー画像の転写材Ｐへの転写は、二次転写ローラー７が中間転写ベルト５に当接されると共に、給紙ローラー１１から転写材ガイド１０を通って、中間転写ベルト５と二次転写ローラー７との当接ニップに所定のタイミングで転写材Ｐが給送され、二次転写バイアスが電源３１から二次転写ローラー７に印加される。この二次転写バイアスにより中間転写ベルト５から転写材Ｐへ合成カラートナー画像が二次転写される。トナー画像の転写を受けた転写材Ｐは、定着器１５へ導入され加熱定着される。
【０１０１】
転写材Ｐへの画像転写終了後、中間転写ベルト５には離接自在に配置されたクリーニング用帯電部材９が当接され、感光ドラム１とは逆極性のバイアスを印加することにより、転写材Ｐに転写されずに中間転写ベルト５上に残留している転写残トナーに一次転写時と逆極性の電荷が付与される。３３はバイアス電源である。ここでは、直流に交流を重畳して印加している。一次転写時と逆極性に帯電された前記転写残トナーは、感光ドラム１とのニップ部及びその近傍において感光ドラム１に静電的に転写されることにより、中間転写体がクリーニングされる。この工程は一次転写と同時に行うことができるため、スループットの低下を生じない。
【０１０２】
つづいて本発明の中間転写ベルト−電子写真感光体一体カートリッジについて説明する。本発明のカートリッジは、図２に示されるように少なくとも中間転写ベルト５と電子写真感光体１、中間転写ベルトクリーニング部材９及び電子写真感光体のクリーニング部材１３が一体のユニットとして構成され、画像形成装置本体と容易に着脱できるようになっている。中間転写ベルトのクリーニングは、前述のように転写残トナーを一次転写と逆の極性に帯電させ、一次転写部で電子写真感光体に戻すために必要な機構であり、本図では中抵抗の弾性体からなるクリーニングローラー９を装備している。電子写真感光体のクリーニングは、ブレードクリーニングである。本カートリッジには不図示の廃トナー容器も一体となっており、中間転写ベルト−電子写真感光体双方の転写残トナーもカートリッジ交換時に同時に廃棄されるため、メンテナンス性の向上に貢献している。また、中間転写ベルトは、８と１２の２本のローラーで張架され部品点数の削減と小型化を図っている。ここで、８は駆動ローラーであると同時にクリーニングローラーの対向ローラーとなっている。中間転写ベルトに従動して回転するテンションローラー１２は、スライドする機構を有しており、圧縮ばねにより矢印の方向に圧接され、中間転写ベルトに張力を与えている。そのスライド幅は１〜５ｍｍ程度で、ばねの圧力合計は５〜１００Ｎ程度である。また、電子写真感光体１と駆動ローラー８は不図示のカップリングを有し、本体から回転駆動力が伝達されるようになっている。
【０１０３】
【実施例】
以下、本発明を具体的な実施例を挙げてより詳細に説明する。但し、本発明はこれのみに限定されない。なお、実施例中の「部」は質量部を意味する。
【０１０４】
［トナーの製造例］
高速攪拌装置ＴＫ式ホモミキサー（特殊機化工業社製）を備えた２リットル用４ッ口フラスコ中にイオン交換水６５０ｇと０．１ｍｏｌ／リットル−Ｎａ_３ＰＯ_４水溶液５００ｇを投入し、回転数を１２０００ｒｐｍに調整し、７０℃に加温せしめた。ここに１．０ｍｏｌ／リットル−ＣａＣｌ_２水溶液７０部を徐々に添加し、微小な難水溶性分散安定剤Ｃａ_３（ＰＯ_４）_２を含む水系分散媒体を調製した。
【０１０５】
一方、分散質として、
スチレン　　　　　　　　　　　　　　　　　　　　７８部
２−エチルヘキシルアクリレート　　　　　　　　　２２部
ジビニルベンゼン　　　　　　　　　　　　　　　０．２部
カーボンブラック（粒径＝４５ｎｍ）　　　　　　　　５部
ポリカーボネート樹脂（ピーク分子量＝７０００）　　５部
ジ−ｔｅｒｔ−ブチルサリチル酸のクロム化合物　　　２部
エステルワックス（ｍｐ＝６２℃）　　　　　　　　１０部
からなる混合物をアトライター（三井金属社製）を用い３時間分散させた後、２，２’−アゾビス（２，４−ジメチルバレロニトリル）１０部を添加し重合性単量体組成物を調製した。
【０１０６】
次に、前記水系分散媒体中に該重合性単量体組成物を投入し、内温７０℃のＮ_２雰囲気下で、高速攪拌器の回転数を１２０００ｒｐｍに維持しつつ、１５分間攪拌し、該重合性単量体組成物を造粒した。その後、攪拌器をプロペラ攪拌羽根に換え５０ｒｐｍで攪拌しながら同温度に５時間保持し、更に８０℃に昇温して１０時間保持して重合を完了した。
【０１０７】
重合終了後、懸濁液を冷却し、次いで希塩酸を添加し分散安定剤を除去せしめた。更に、水洗浄を数回繰り返した後、流動層乾燥機（大川原製作所製）を用い、熱風中で攪拌しながら１０時間トナー粒子の球形化処理と乾燥処理を行い、重合体粒子（Ａ）を得た。
【０１０８】
該重合体粒子（Ａ）は、円相当個数平均径が４．１μｍで、円形度頻度分布における平均円形度が０．９９０で、円形度標準偏差が０．０３０で、ＧＰＣによる分子量分布で、ピーク分子量が１５０００、Ｍｗ／Ｍｎが１８であった。
【０１０９】
上記重合体粒子（Ａ）１００部と疎水性オイル処理シリカ微粉体（ＢＥＴ；２００ｍ^２／ｇ）２部をヘンシェルミキサー（三井金属社製）で乾式混合して、トナーを調製した。
【０１１０】
＜感光体の製造例１＞
直径４７ｍｍのアルミニウムシリンダーを支持体とし、これに、以下の材料より構成される塗料を支持体上に浸漬塗布し、１４０℃で３０分間熱硬化し、膜厚が１５μｍの導電層を形成した。
【０１１１】
導電性顔料：ＳｎＯ_２コート処理硫酸バリウム　　　　　　　１０部
抵抗調節用顔料：酸化チタン　　　　　　　　　　　　　　　　２部
結着樹脂：フェノール樹脂　　　　　　　　　　　　　　　　　６部
レベリング材：シリコーンオイル　　　　　　　　　　０．００１部
溶剤：メタノール／メトキシプロパノール＝０．２／０．８　２０部
【０１１２】
次に、この導電層上に、Ｎ−メトキシメチル化ナイロン３部及び共重合ナイロン３部をメタノール６５部／ｎ−ブタノール３０部の混合溶媒に溶解した溶液を浸漬法で塗布し、膜厚が０．７μｍの中間層を形成した。
【０１１３】
次に、ＣｕＫαの特性Ｘ線回折におけるブラッグ角（２θ±０．２°）の９．０°、１４．２°、２３．９°及び２７．１°に強いピークを有するＴｉＯＰｃ４部とポリビニルブチラール（商品名：エスレックＢＭ２、積水化学製）２部及びシクロヘキサノン６０部をφ１ｍｍガラスビーズを用いたサンドミル装置で４時間分散した後、エチルアセテート１００部を加えて電荷発生層用分散液を調製した。これを浸漬法で塗布し、膜厚が０．３μｍの電荷発生層を形成した。
【０１１４】
次に、電荷輸送層を形成するために、下記式で示される構成単位を有するポリアリレート樹脂（Ｍｗ＝１０１０００）１０部と
【０１１５】
【化１】

下記式で示されるアミン化合物７部
【０１１６】
【化２】

とモノクロロベンゼン５０部／ジクロロメタン３０部の混合溶媒中に溶解して調製した電荷輸送層用塗料を用いて、前記電荷発生層上にこの塗料を浸漬法で塗布し、１００℃で１時間乾燥し、膜厚が２４μｍの電荷輸送層を形成し、感光体１を作製した。この時電荷輸送層のユニバーサル硬度及び弾性変形率を表１に示す。
【０１１７】
＜感光体の製造例２＞
感光体製造例１において用いたアミン化合物を７部から５部に代えた以外は、感光体製造例１と同様にして感光体２を作製した。この時の電荷輸送層のユニバーサル硬度及び弾性変形率を表１に示す。
【０１１８】
＜感光体の製造例３＞
感光体製造例１と同様にして支持体、導電層、下引き層、電荷発生層を形成した。
【０１１９】
次に、下記式で示されるスチリル化合物７部
【０１２０】
【化３】

及び下記式で示される構成単位を有するポリカーボネート樹脂（Ｍｗ＝１０００００）１０部
【０１２１】
【化４】

をモノクロロベンゼン５０部／ジクロロメタン２０部の混合溶媒中に溶解して調製した電荷輸送層用塗料を用いて、前記電荷発生層上にこの塗料を浸漬法で塗布し、１００℃で１時間乾燥し、膜厚が２４μｍの電荷輸送層を形成し、感光体３を作製した。この時の電荷輸送層のユニバーサル硬度及び弾性変形率を表１に示す。
【０１２２】
＜感光体の製造例４＞
感光体の製造例３において用いたポリカーボネート樹脂の重量平均分子量１０００００を１８００００に代えた以外は、感光体の製造例３と同様にして感光体４を作製した。この時の電荷輸送層のユニバーサル硬度及び弾性変形率を表１に示す。
【０１２３】
＜感光体の比較製造例１＞
感光体製造例１と同様にして支持体、導電層、下引き層、電荷発生層を形成した。
【０１２４】
次に、製造例１で用いたポリアリレート樹脂に代え重量平均分子量Ｍｗが４００００のＺ型ポリカーボネート樹脂２５部をモノクロロベンゼン５０部／ジクロロメタン２０部の混合溶媒中に溶解して調製した電荷輸送層用塗料を用いて前記電荷発生層上に浸漬法で塗布し、１００℃で１時間乾燥し、膜厚が２４μｍの電荷輸送層を形成し、電子写真感光体５を得た。この時の電荷輸送層のユニバーサル硬度及び弾性変形率を表１に示す。
【０１２５】
＜感光体の比較製造例２＞
感光体製造例１において用いたアミン化合物を７部から１０部に代えた以外は、感光体製造例１と同様にして感光体６を作製した。この時の電荷輸送層のユニバーサル硬度及び弾性変形率を表１に示す。
【０１２６】
＜感光体の比較製造例３＞
感光体製造例１において電荷輸送層形成時の乾燥条件を１２５℃で１時間にした以外は、感光体製造例１と同様にして感光体７を作製した。この時の電荷輸送層のユニバーサル硬度及び弾性変形率を表１に示す。
【０１２７】
＜感光体の比較製造例４＞
感光体製造例４において電荷輸送層形成時の乾燥条件を１２５℃で１時間にした以外は、感光体製造例４と同様にして感光体８を作製した。この時の電荷輸送層のユニバーサル硬度及び弾性変形率を表１に示す。
【０１２８】
【表１】

【０１２９】
（実施例１）
画像形成装置として、ヒューレットパッカード製ＬＢＰ「カラーレーザージェット４５００」（プロセススピード１１７ｍｍ／秒）を改造して用いた。現像ローラの回転周速は、感光体との接触部分において同方向であり、該感光体回転周速に対し１５０％となるように駆動、クリーニング部材として、ウレタンブレードを、設定圧７０ｇ／ｃｍに設定した。
【０１３０】
感光体として製造例１の感光体１を用い、トナーとして前記製造例のトナーを用い、以下の条件を満足するようプロセス条件を設定した。
【０１３１】
感光体暗部電位　　−６００Ｖ
感光体明部電位　　−１３０Ｖ
現像バイアス　　　−３７５Ｖ
【０１３２】
本機を温湿度２３℃／６０％の環境に設置し、トナーを補給しつつ、Ａ４サイズ紙に面積比率４％印字の文字パターンで１００００枚の連続画出し試験を行い、評価を行った。また、耐久前後において、感光体の表面粗さを測定した。評価結果を表２に示す。
【０１３３】
（実施例２〜４及び比較例１〜４）
感光体として前記製造例の感光体２〜８を用いた以外は、実施例１と同様に評価を行った。結果を表２に示す。
【０１３４】
（実施例５、６及び比較例５、６）
実施例１の画像形成装置においてクリーニングブレードの設定圧は９０ｇ／ｃｍとし、感光体として感光体１、３及び５、７を用いて、実施例１と同様の評価を行った。結果を表３に示す。
【０１３５】
【表２】

【０１３６】
【表３】

【０１３７】
表２及び表３より明らかなように、本発明における実施例の画像形成装置は球形トナーを用いた接触現像方法においてトナーの現像性を維持しつつ、トナークリーニング性、感光体の耐久性を維持することが可能となり、高画質、高精細な画像を長期間安定して提供することができる。
【０１３８】
【発明の効果】
上述したように、本発明によれば、トナー現像性、トナークリーニング性を維持しつつ、繰り返し画像出力時の感光体の機械的摩耗を抑え、高画質、高安定な画像形成装置及びプロセスカートリッジを提供することが可能となった。
【図面の簡単な説明】
【図１】本発明の中間転写ベルト−電子写真感光体一体型プロセスカートリッジを備えた画像形成装置の概略構成を示す図である。
【図２】本発明の中間転写ベルト−電子写真感光体一体型プロセスカートリッジの概略構成を示す図である。
【符号の説明】
１　電子写真感光体
２　一次帯電器
３　露光光
５　中間転写ベルト
６　一次転写対向ローラー
７　二次転写ローラー
８　二次転写対向ローラー
９　クリーニングローラー
１０　転写材ガイド
１１　給紙ローラー
１２　テンションローラー
１３　クリーニング装置
１６　定着器
３０，３１，３２，３３　電源
４１　イエロー色現像器
４２　マゼンタ色現像器
４３　シアン色現像器
４４　ブラック色現像器[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus and a process cartridge such as a copying machine, a laser printer, and a plain paper facsimile, and more particularly, to an image forming apparatus and a process cartridge excellent in image quality and durability stability.
[0002]
[Prior art]
2. Description of the Related Art In recent years, with rapid development of the information industry, high-quality image recording has been desired for industrial or office use. To meet these demands, various methods such as an electrophotographic method, a thermal transfer method, and an ink-jet method have been proposed and put into practical use. Among them, electrophotography is widely used in offices because of its high-speed printability and high image quality.However, recently, the number of cases of recording graphic images has been increasing, and further improvement in image quality and definition has been required. Is being sought. In response to these market demands, the resolution of laser printers has been increased from the conventional 240 dpi to 600 and 1200 dpi, and the image quality of the image forming apparatus has been increased by promoting digitalization and higher resolution in copiers. And high definition are being promoted.
[0003]
In response to these movements, the development of precision processing technology, the development and use of high-precision control technology, etc. have been proposed and examined from the equipment development side. The development of high image quality due to image formation and high image quality and high definition using toner having a high degree of circularity are being actively developed. In reducing the diameter of these toners and improving the degree of circularity, conventional pulverization methods of kneading, pulverizing, and classifying a colorant and a binder resin to obtain toners include finer pulverization, classification means, and post-processing such as polishing. While studies on the reduction in diameter and spheroidization have been actively conducted, on the other hand, a polymerized toner obtained by dispersing an ethylenically unsaturated monomer containing a colorant in water in the presence of a dispersant and then polymerizing the same is known. Attention has been paid to research and development, and it has been confirmed that the polymerized toner is a powerful means for reducing the diameter of the toner and improving the circularity. Such a small-diameter, high-circularity toner develops an electrostatic latent image on a photoreceptor faithfully and accurately, and exhibits high transferability, which is enormous for high image quality and high definition. Bring effect.
[0004]
In recent years, a so-called contact one-component developing method has been proposed in which development is performed using an elastic roller having a semiconductive or dielectric layer on the surface as a developing roller while pressing the surface against the surface of the photoreceptor. For example, Japanese Hardcopy'89 Transactions 25-28, FUJITSU @ Sci. Tech. J. , 28,4, pp. 473-480 (December # 1992), JP-A-5-188756 and JP-A-5-188752 describe techniques relating to one-component contact development.
[0005]
In the contact one-component developing method, since the surface of the photoreceptor and the developing electrode are very close to each other, there is an advantage that the edge effect of the developing can be reduced. There is a possibility of higher image quality and higher definition.
[0006]
In the contact one-component developing method, an elastic roller such as a rubber roller or a sponge roller is pressed against the developing roller in order to stably maintain a uniform nip width in the axial direction between the developing roller and the photosensitive member. The peripheral speed of the developing roller needs to be set higher than the peripheral speed of the photoconductor in order to strongly press the roller against the photoconductor and develop more toner on the photoconductor than the surface of the developing roller. For this reason, the driving torque between the photosensitive member and the developing roller is increased, and the surface of the photosensitive member is scratched or worn due to long-term use, and the toner is fused.
[0007]
Further, when spherical toner is used as the toner, the toner layer formed on the developing roller becomes non-uniform, and there is a problem of image quality deterioration such as a decrease in image density and fog. For example, Japanese Patent Application Laid-Open No. 9-62085 discloses Japanese Patent Application Laid-Open No. 9-319208 discloses a method for forming a uniform toner layer on a developing roller by using a developing roller having a surface roughness of 10 μm or less. A method of defining the roughness and forming a uniform toner layer on the developing roller is disclosed.However, increasing the surface roughness increases the chance of contact between the toner and the surface of the developing roller. As a result, the contact pressure between the developing roller and the photosensitive drum is increased, and the driving torque of the developing roller is increased. Problems arise.
[0008]
In particular, in an organic laminated photoreceptor in which the photosensitive layer is composed of a charge generation layer and a charge transport layer, the charge transport layer comes into strong contact with the toner and the developing roller and slides. Wear out. Scratches and uneven wear of the photosensitive layer reduce the durability of the photosensitive member, make the contact of the developing roller with the photosensitive member surface uneven, and cause image defects such as streaks and fog. Reducing the contact pressure of the developing roller can solve problems such as scratches and abrasion of the initial photoconductor, but it is necessary to increase the peripheral speed ratio between the developing roller and the photoconductor considerably in order to prevent deterioration in developability. However, in repeated image output, scratches and abrasion of the photoreceptor increase, and furthermore, problems such as deterioration of toner tend to occur.
[0009]
As a method of reducing the abrasion amount of the photoreceptor, Japanese Patent Application Laid-Open No. 63-65449 discloses a method of reducing the abrasion amount by increasing the slipperiness of the photoreceptor surface by adding silicone resin fine particles or fluororesin particles in the photosensitive layer. However, even though these methods increase the slipperiness of the photoreceptor, the photosensitive layer still has low mechanical strength, and inorganic additives such as silica, alumina and titania, which are toner additives, dig deep grooves in the surface of the photosensitive layer. Such scratches are liable to occur, such as abrasive wear, and the above-mentioned toner additive is fused to the surface of the photosensitive layer, which may be a trigger to cause toner fusion, which is not a sufficient measure.
[0010]
On the other hand, the small-diameter, high-circularity toner, as described above, develops the electrostatic latent image on the photoreceptor faithfully and accurately, and exhibits high transferability to improve image quality and definition. Although it has a great effect, it has a drawback that cleaning properties are low and problems such as poor cleaning frequently occur in a printing test using a copying machine or a printer.
[0011]
In image forming apparatuses such as copiers and printers, after a toner image formed on the surface of a photoreceptor is transferred to a transfer material, untransferred toner remains on the surface of the photoreceptor, and the residual toner is a brush, a magnetic brush or a blade. Is removed from the surface of the photoreceptor. In brush cleaning, polyester or acrylic fibers are used, and the shapes such as loops and straight hairs, and the hardness and thickness of the fibers are changed to optimize the brush cleaning. However, cleaning with a brush alone cannot remove fine powder toner and does not lead to sufficient removal by slipping between fibers. The same holds true for the magnetic brush. Attempts have also been made to remove electrostatically by applying an electric field, but toner scattering is not sufficient. Therefore, at present, blade cleaning using an elastic blade is predominant from the viewpoint of removing residual toner, cost, and miniaturization. Many reports on improvements in blade cleaning are disclosed in patent publications. For example, Japanese Patent Application Laid-Open No. 5-35156 discloses the results of studies on physical properties such as hardness, elastic modulus and elongation of urethane rubber blades and cleaning properties.
[0012]
As described above, blade cleaning has higher cleaning performance than other methods.However, if the small-diameter and high-circularity toner is cleaned as described above, it is sufficient in any environment where a copier or a printer is used. It is difficult to exhibit the cleaning performance, and in particular, poor cleaning tends to occur in an environment of high temperature and high humidity or low temperature and low humidity. In particular, when a toner having a small diameter and a high degree of circularity is used, it is easy to cause a cleaning failure in a state where the toner slips between the cleaning blade and the surface of the photoreceptor at the initial stage. In addition, streak-like cleaning failure is likely to occur due to uneven contact between the cleaning blade and the surface of the photoconductor due to uneven wear. Increasing the contact pressure of the cleaning blade against the photoreceptor surface in order to improve the initial pass-through cleaning failure improves the initial cleaning performance, but in repeated image output, the photoreceptor surface is scratched and unevenly worn. However, as a result, there is a tendency that the cleaning property is liable to be deteriorated, and if the contact pressure of the cleaning blade with the surface of the photoreceptor is too high, the blade is easily turned up.
[0013]
Therefore, at present, it is difficult to maintain the toner cleaning property and the durability of the photoconductor while maintaining the developing property of the spherical toner in the contact developing method.
[0014]
Further, in the present invention, the electrostatic latent image formed on the electrophotographic photoreceptor is visualized by a developer, and the obtained image is further transferred to a primary transfer unit and an image transferred to the intermediate transfer belt. In an image forming apparatus having a secondary transfer unit for transferring to a transfer material, an intermediate transfer belt, an electrophotographic photosensitive member, a cleaning mechanism for the intermediate transfer belt, and a cleaning mechanism for the electrophotographic photosensitive member are arranged in an integrated unit. A mechanism for cleaning the intermediate transfer belt uses a mechanism that charges the remaining developer to a polarity opposite to that of the primary transfer and returns the developer to the electrophotographic photosensitive member simultaneously with the primary transfer from the intermediate transfer belt.
[0015]
In such a mechanism, not only the toner remaining on the electrophotographic photosensitive member at the time of the primary transfer but also the toner remaining on the intermediate transfer belt must be cleaned, and the amount of the residual toner increases. Further, the toner returned from the intermediate transfer belt to the electrophotographic photosensitive member contains a large amount of an external additive and a charge control agent used for increasing the fluidity, and thus has a configuration in which cleaning properties are more difficult.
[0016]
[Problems to be solved by the invention]
As described above, the electrostatic latent image formed on the electrophotographic photoreceptor is visualized with a developer, and the obtained image is transferred to an intermediate transfer belt. In an image forming apparatus having a secondary transfer unit for transferring to a transfer material, an intermediate transfer belt, an electrophotographic photosensitive member, a cleaning mechanism for the intermediate transfer belt, and a cleaning mechanism for the electrophotographic photosensitive member are arranged in an integrated unit. The intermediate transfer belt cleaning mechanism charges the remaining developer to the polarity opposite to that of the primary transfer, and returns the toner to the electrophotographic photosensitive member at the same time as the primary transfer from the intermediate transfer belt. The contact developing method used has a problem in maintaining the developability of the spherical toner, and in balancing the toner cleaning property and the durability of the photoreceptor, particularly the organic photoreceptor. It had been.
[0017]
An object of the present invention is to solve such a problem, and to maintain the developability even in an electrophotographic developing method using a small-diameter toner having a high circularity as a toner, to have excellent characteristics at the time of repeated image output, and to have a high An object of the present invention is to provide an image forming apparatus and a process cartridge capable of supplying a high-definition image with high image quality for a long period of time.
[0018]
[Means for Solving the Problems]
According to the present invention, an electrostatic latent image formed on an electrophotographic photoreceptor having a charge generation layer and a charge transport layer laminated thereon is visualized with a developer, and a primary transfer unit for transferring an obtained image to an intermediate transfer belt is provided. In an image forming apparatus having a secondary transfer unit that further transfers an image transferred to a transfer belt to a transfer material, a cleaning mechanism for an intermediate transfer belt, an electrophotographic photosensitive member, an intermediate transfer belt, and a cleaning mechanism for an electrophotographic photosensitive member is provided. A cleaning mechanism for the intermediate transfer belt, which is disposed in an integrated unit, charges the remaining developer to a polarity opposite to that of the primary transfer and returns the developer to the electrophotographic photosensitive member simultaneously with the primary transfer from the intermediate transfer belt. And a universal hardness HU of 230 N / mm at an indentation depth of 1 μm from the surface of the charge transport layer of the electrophotographic photosensitive member.²More than 260N / mm²The universal hardness HU at an indentation depth of 5 μm from the surface with an elastic deformation rate of 35% or more below is 260 N / mm²As described above, an image forming apparatus and a process cartridge having an elastic deformation rate of 30% or more are provided.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0020]
The toner used in the image forming apparatus of the present invention has a small particle diameter and a high circularity. The toner has a circle-equivalent number average diameter of 2 to 10 μm, preferably 5 to 8 μm, so that the reproducibility of the outline portion of an image, particularly a character image or a line pattern in developing is improved. However, in general, when the particle diameter of the toner is reduced, the existence ratio of the toner having a very small diameter necessarily increases, so that the adhesion of the toner to the photoconductor surface and the developing roller increases, and as a result, the residual toner of the transfer remains. This causes problems such as an increase and image fogging.
[0021]
However, the toner used in the present invention has a high circularity, an average circularity of 0.950 to 0.995, and a standard deviation of circularity of less than 0.040. Is greatly improved, and the developing ability for a low potential latent image is remarkably improved.
[0022]
Specifically, in the circle equivalent diameter-circularity scattergram based on the number of toners measured by the flow type particle image measuring device, the circle equivalent number average diameter of the toner is 2 to 10 μm, and the average circularity is This is a dry single-component toner having a circularity standard deviation of 0.950 to 0.995 and less than 0.040.
[0023]
The circle equivalent diameter, circularity, and their frequency distribution of the toner used in the present invention are used as a simple method for quantitatively expressing the shape of the toner particles. The measurement was performed using an apparatus FPIA-1000 (manufactured by Toa Medical Electronics Co., Ltd.), and calculated using the following equation.
[0024]
(Equation 1)

[0025]
Here, the “particle projection area” is the area of the binarized toner particle image, and the “perimeter of the particle projection image” is the length of the contour obtained by connecting the edge points of the toner particle image. Define.
[0026]
The circularity in the present invention is an index indicating the degree of unevenness of the toner particles, and is 1.000 when the toner particles are perfectly spherical, and the circularity becomes smaller as the surface shape becomes more complicated.
[0027]
In the present invention, the circle-equivalent number average diameter d means the average value of the particle size frequency distribution based on the number of toners.₁And the particle size standard deviation SDd are calculated from the following equation, where di is the particle size (center value) at the dividing point i of the particle size distribution and fi is the frequency.
[0028]
(Equation 2)

[0029]
The average circularity c and the circularity standard deviation SDc which mean the circularity frequency distribution mean the circularity (center value) at the dividing point i of the particle size distribution and the frequency f, respectively._ciThen, it is calculated from the following equation.
[0030]
(Equation 3)

[0031]
As a specific measuring method, 10 ml of ion-exchanged water from which impurity solids and the like have been removed in advance in a container is prepared, and a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersing agent thereto, and then further measured. Add 0.02 g of sample and disperse uniformly. As a means for dispersing, an ultrasonic dispersing machine UH-50 type (manufactured by SMT Co.) equipped with a titanium alloy chip having a diameter of 5 mm as a vibrator is used for a dispersion treatment for 5 minutes to prepare a dispersion for measurement. At this time, the dispersion is appropriately cooled so that the temperature of the dispersion does not exceed 40 ° C.
[0032]
To measure the shape of the toner particles, the flow particle image measuring apparatus was used, and the concentration of the dispersion was readjusted so that the concentration of the toner particles at the time of measurement was 3000 to 10,000 particles / μl. Measure above. After the measurement, using this data, the equivalent circle diameter and circularity frequency distribution of the toner are obtained.
[0033]
Examples of the wax component used in the toner of the present invention 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 Fischer-Tropsch method, and polyethylene. Representative polyolefin waxes and derivatives thereof, carnauba wax, natural waxes such as candelilla wax and derivatives thereof, and the like, including oxides, block copolymers with vinyl monomers, and graft-modified products, Alcohols such as higher aliphatic alcohols; fatty acids such as stearic acid and palmitic acid or compounds thereof; acid amides, esters, ketones, hydrogenated castor oil and derivatives thereof, and styrene monomers such as vegetable waxes and animal waxes As long as the melting temperature of 40 to 80 ° C., it is possible to use any.
[0034]
Among these, when polyolefin, hydrocarbon wax, petroleum wax, higher alcohol or higher ester by Fischer-Tropsch method is used, the effect of improving developability and transferability is further enhanced.
[0035]
The above-mentioned wax component is preferably used in an amount of 1 to 30 parts by mass based on 100 parts by mass of the binder resin.
[0036]
Examples of the binder resin used in the toner of the present invention include generally used styrene- (meth) acrylic copolymers, polyester resins, epoxy resins, and styrene-butadiene copolymers. In a method of directly obtaining toner particles by a polymerization method, a monomer for forming them is used. Specifically, styrene; styrene-based monomers such as o- (m-, p-) methylstyrene and m- (p-) ethylstyrene; methyl (meth) acrylate, ethyl (meth) acrylate, (meth) ) Propyl acrylate, butyl (meth) acrylate, octyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, ( (Meth) acrylate monomers such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate; ene monomers such as butadiene, isoprene, cyclohexene, (meth) acrylonitrile and acrylamide It is preferably used. These may be used alone or generally in such a manner that the theoretical glass transition temperature (Tg) described in the published Polymer Handbook, 2nd edition III-P139-192 (manufactured by John Wiley & Sons) is 40 to 75 ° C. The monomers are appropriately mixed and used. If the theoretical glass transition temperature is less than 40 ° C., problems tend to occur in terms of storage stability and durability stability of the toner, while if it exceeds 75 ° C., the fixing point of the toner increases. In particular, in the case of a color toner for forming a full-color image, the transfer efficiency of the developer from the electrophotographic photosensitive member to the transfer medium is set by setting the shape factor of each color toner and the toner as the developer to a specific value. Can be increased. As a result, the developer remaining on the electrophotographic photosensitive member after transfer is reduced, and the adhesion of the developer to the charging member is reduced. Further, it was found that even if the developer adhered to the charging member, the developer having the shape coefficient as in the present invention easily detached from the charging member. It is not preferable because the color mixing at the time of fixing the toner is reduced and the color reproducibility is poor, and the transparency of the OHP image is further reduced.
[0037]
The molecular weight of the binder resin is measured by gel permeation chromatography (GPC). In the case of a toner having a so-called core-shell structure in which a low softening point substance is encapsulated in an outer shell resin, as a specific GPC measurement method, the toner is previously extracted with a toluene solvent using a Soxhlet extractor for 20 hours. Toluene is distilled off using a rotary evaporator to obtain an extract. Further, an organic solvent (for example, chloroform, etc.) that dissolves the low softening point substance but does not dissolve the outer shell resin is added to the extract, and the extract is thoroughly washed. A sample (THF solution) obtained by filtering a solution obtained by dissolving the substance in tetrahydrofuran (THF) through a solvent-resistant membrane filter having a pore diameter of 0.3 μm is measured using 150C manufactured by Waters. The column configuration is such that A-801, 802, 803, 804, 805, 806 and 807 manufactured by Showa Denko are connected, and the molecular weight distribution can be measured using a calibration curve of a standard polystyrene resin. The binder resin preferably has a main peak molecular weight of 5,000 to 1,000,000 and a ratio (Mw / Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) of 2 to 100 is preferred in the present invention.
[0038]
The colorant used in the toner used in the present invention includes a yellow colorant, a magenta colorant, and a cyan colorant shown below. As a black colorant, carbon black, a magnetic substance, or a yellow colorant / magenta shown below A mixture of a colorant / cyan colorant and adjusted to black is used.
[0039]
As the yellow colorant, a condensed azo compound, an isoindolinone compound, an anthraquinone compound, an azo metal complex, a methine compound or an allylamide compound is used. Specifically, C.I. I. Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147, 168 or 180 are preferably used.
[0040]
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 or a perylene compound is used. Specifically, C.I. I. Pigment Red 2, 3, 5, 6, 7, 23, 48; 2, 48; 3, 48; 4, 57; 1, 81; 1, 144, 146, 166, 169, 177, 184, 185, 202, 206, 220, 221 or 254 are particularly preferably used.
[0041]
As the cyan colorant, a copper phthalocyanine compound and its derivative, an anthraquinone compound or a basic dye lake compound can be used. Specifically, C.I. I. Pigment Blue 1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62 or 66 are particularly preferably used.
[0042]
These colorants can be used alone or as a mixture or in the form of a solid solution. The colorant is selected from the viewpoint of hue, saturation, lightness, weather resistance, OHP transparency, and dispersibility in toner particles. The amount of the coloring agent to be added is preferably 1 to 20 parts by mass with respect to 100 parts by mass of the resin component.
[0043]
When a magnetic material is used as the black colorant, it is preferable to use 40 to 150 parts by mass with respect to 100 parts by mass of the resin, unlike other colorants.
[0044]
A known charge control agent can be used in combination with the toner used in the present invention. In particular, a charge control agent which has a high charging speed and can stably maintain a constant charge amount is preferable. Further, in the case where the toner particles are directly polymerized, a charge control agent having no polymerization inhibition and having no solubilized substance in an aqueous dispersion medium is preferable.
[0045]
Specific examples of the compound include a metal compound of an aromatic carboxylic acid such as salicylic acid, naphthoic acid, and dicarboxylic acid as a negative charge control agent; a polymer compound having a sulfonic acid or carboxylic acid group in a side chain; a boron compound; Compounds; silicon compounds; curryxarene and the like. Examples of the positive charge control agent include a quaternary ammonium salt; a polymer compound having the quaternary ammonium salt in a side chain; a guanidine compound; and an imidazole compound.
[0046]
However, the addition of a charge control agent is not essential in the present invention, and in the case of using a two-component developing method, utilizing triboelectric charging with a carrier, and in the case of using a non-magnetic one-component blade coating developing method, By positively utilizing frictional charging with the blade member or the sleeve member, it is not necessary to necessarily include a charge control agent in the toner particles.
[0047]
The addition of an inorganic fine powder to the toner used in the present invention is a preferred embodiment for improving developability, transferability, charging stability, fluidity and durability. As the inorganic fine powder, known ones can be used, but it is particularly preferable to be selected from silica, alumina, titania or a double oxide thereof. Furthermore, silica is more preferable. For example, as the silica, both a so-called dry method produced by vapor phase oxidation of a silicon halide or an alkoxide or a dry silica called a fumed silica and a so-called wet silica produced from an alkoxide or water glass can be used. However, there are few silanol groups on the surface and inside the silica fine powder.₂O or SO₃ ^2-Dry silica with a small production residue such as is preferred. 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 and titanium chloride together with a silicon halide in the production process. Yes, they are included.
[0048]
The inorganic fine powder used for the toner used in the present invention has a specific surface area of 30 m by nitrogen adsorption measured by the BET method.²/ G or more, especially 50 to 400 m²/ G gives good results, and preferably 0.1 to 8 parts by mass, more preferably 0.5 to 5 parts by mass, and still more preferably 1.0 to 10 parts by mass of the silica fine powder with respect to 100 parts by mass of the toner. It is particularly preferred to use more than 3.0 parts by mass.
[0049]
Further, the inorganic fine powder used in the toner used in the present invention may be, if necessary, silicone varnish, various modified silicone varnish, silicone oil, various modified silicone oil, various modified silicone oil, silane coupling, for the purpose of hydrophobicity or charge control. It is also possible and preferable to use a treating agent such as an agent, a silane coupling agent having a functional group, another organosilicon compound, an organotitanium compound, or a combination of various treating agents.
[0050]
According to the BET method, the specific surface area was determined by adsorbing nitrogen gas on the sample surface using a specific surface area measuring apparatus Autosorb 1 (manufactured by Yuasa Ionics) and calculating the specific surface area using the BET multipoint method.
[0051]
In order to maintain a high charge amount and achieve a low consumption and a high transfer rate, it is more preferable that the inorganic fine powder be treated with at least silicone oil.
[0052]
In the toner used in the present invention, other additives such as lubricant powders such as polytetrafluoroethylene powder, zinc stearate powder, and polyvinylidene fluoride powder; cerium oxide powder; Abrasives such as silicon carbide powder and strontium titanate powder; fluidity imparting agents such as titanium oxide powder and aluminum oxide powder; anti-caking agents; or conductivity imparting such as carbon black powder, zinc oxide powder and tin oxide powder. In addition, a small amount of an organic fine particle and an inorganic fine particle having the opposite polarity can be used as a developing property improver.
[0053]
As a method for producing the toner used in the present invention, a resin, a release agent composed of a substance having a low softening point, a colorant, a charge control agent, and the like were uniformly dispersed using a pressure kneader, an extruder, or a media disperser. After that, the particles are made to impinge on the target mechanically or under a jet stream to pulverize the particles to a desired toner particle diameter (if necessary, a step of smoothing and spheroidizing the toner particles is added). In addition to a method for producing a toner by a pulverization method in which the distribution is sharpened to obtain a toner, a method in which a molten mixture is atomized into air using a disk or a multi-fluid nozzle described in Japanese Patent Publication No. 56-13945 to obtain a spherical toner And the suspension polymerization method disclosed in JP-B-36-10231, JP-A-59-53856 and JP-A-59-61842. Or a dispersion polymerization method in which an aqueous organic solvent in which the obtained polymer is soluble in a monomer is insoluble and a polymer is insoluble, or a direct polymerization is performed in the presence of a water-soluble polar polymerization initiator to form a toner. The toner can be manufactured using an emulsion polymerization method represented by a soap-free polymerization method.
[0054]
In the method of producing a toner using a pulverization method, it is difficult to keep the shape of the toner particles within a desired range of the circularity frequency distribution. In the melt spraying method, a certain degree of circularity can be obtained. In addition, the obtained toner tends to have a wide particle size distribution, and it is difficult to control the surface state of the toner. On the other hand, in the dispersion polymerization method, the obtained toner has an extremely sharp particle size distribution, but the production equipment is not suitable from the viewpoints of narrow selection of materials to be used and the use of organic solvents in terms of waste solvent treatment and solvent flammability. It is complicated and easily complicated. Emulsion polymerization methods typified by soap-free polymerization are effective because the particle size distribution of the toner is relatively uniform, but when the used emulsifier and polymerization initiator terminal are present on the surface of the toner particles, environmental characteristics are likely to deteriorate.
[0055]
In the present invention, it is important to control the frequency distribution of the circularity of the toner particles, and the emulsion polymerization method under normal pressure or under pressure, in which a fine particle toner having a circle-equivalent number average diameter of 2 to 6 μm can be obtained relatively easily. Alternatively, a suspension polymerization method may be used to shape the polymer obtained in advance using a medium, or a method may be employed in which the polymer is caused to collide directly with a pressure impingement plate, or the obtained polymer may be frozen in an aqueous system. In particular, an aggregation method in which particles having a salt break or an opposite surface charge are united, aggregated, and united in consideration of conditions such as pH is particularly preferable. Furthermore, a seed polymerization method in which a monomer is further adsorbed onto the obtained polymer particles and then polymerized using a polymerization initiator can also be suitably used in the present invention. Among them, the suspension polymerization method is particularly preferred in the present invention.
[0056]
When a direct polymerization method is used as a method for producing a toner, the control of the circularity frequency distribution and the particle size frequency distribution of the toner particles is performed by changing the type and amount of a poorly water-soluble inorganic salt or a dispersant having a protective colloid action. The desired toner particles can be obtained by controlling the method and mechanical device conditions (for example, the peripheral speed of the rotor, the number of passes, the stirring conditions such as the shape of the stirring blades and the shape of the container), or the solid content concentration in the aqueous solution. it can. As described above, predetermined toner particles can also be obtained by adjusting the stirring conditions and the processing time of the conical dryer used for drying the toner particles.
[0057]
When the toner is dried by heating, the toner particles can be subjected to a spheroidizing treatment. For example, by using a fluidized-bed dryer, the stirring conditions of the rotating blades and the processing time are adjusted so that the toner particle shape is preferable. Can be
[0058]
In the toner of the present invention, by specifying the physical characteristics of the wax component as described above, it is possible to minimize the influence of the coarsening of the toner and the wax component on the spheroidization of the toner particles as described above. It is very effective because it can be done.
[0059]
When a toner is produced by a direct polymerization method, for example, 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1 Azo or diazo polymerization initiators such as' -azobis (cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile and azobisisobutyronitrile; benzoyl peroxide And peroxide polymerization initiators such as methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide and lauroyl peroxide. The amount of the polymerization initiator varies depending on the desired degree of polymerization, but is generally used in an amount of 0.5 to 20% by mass based on the polymerizable monomer. The type of the polymerization initiator varies slightly depending on the polymerization method, but is used alone or in combination with reference to the 10-hour half-life temperature. In order to control the degree of polymerization, a known crosslinking agent, chain transfer agent, polymerization inhibitor or the like may be further added and used.
[0060]
When utilizing a suspension polymerization method using a dispersion stabilizer as a toner production method, as the dispersion stabilizer to be used, as an inorganic compound, tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, calcium carbonate, Examples include magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, bentonite, silica and alumina. Examples of the organic compound include polyvinyl alcohol, gelatin, methyl cellulose, methyl hydroxypropyl cellulose, ethyl cellulose, sodium salts of carboxymethyl cellulose, polyacrylic acid and salts thereof, and starch. These can be used by dispersing them in an aqueous phase. It is preferable to use 0.2 to 20 parts by mass of these dispersion stabilizers with respect to 100 parts by mass of the polymerizable monomer.
[0061]
When an inorganic compound is used as the dispersion stabilizer, a commercially available one may be used as it is, but fine particles of the inorganic compound may be generated in a dispersion medium in order to obtain fine particles. For example, in the case of tricalcium phosphate, it is preferable to mix an aqueous sodium phosphate solution and an aqueous calcium chloride solution under high-speed stirring.
[0062]
For fine dispersion of these dispersion stabilizers, 0.001 to 0.1 parts by mass of a surfactant may be used in combination. This is to promote the intended action of the dispersion stabilizer, for example, sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, potassium stearate. And calcium oleate.
[0063]
When the direct polymerization method is used as the method for producing the toner used in the present invention, the following production methods are possible.
[0064]
In the polymerizable monomer, a release agent composed of a low softening point substance, a colorant, a charge control agent, a polymerization initiator, and other additives were added and uniformly dissolved or dispersed by a homogenizer or an ultrasonic disperser. The monomer composition is dispersed in an aqueous phase containing a dispersion stabilizer using a conventional stirrer, homomixer, homogenizer, or the like. Preferably, the granulation is performed by adjusting the stirring speed and the stirring time so that the droplets of the monomer composition have a desired size of the toner particles. After that, by the action of the dispersion stabilizer, stirring may be performed to such an extent that the particle state is maintained and the particles are prevented from settling. The polymerization is preferably performed at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. The temperature may be raised in the second half of the polymerization reaction, and further in the second half of the reaction to remove unreacted polymerizable monomers and by-products for the purpose of improving durability in the image forming method of the present invention, or After the completion of the reaction, a part of the aqueous medium may be distilled off from the reaction system. After the reaction, the generated toner particles are collected by washing and filtration, and dried. In the suspension polymerization method, 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.
[0065]
The image forming apparatus of the present invention employs a method in which a toner is coated as a one-component developer on a surface of an elastic roller as a developing roller, and the toner is brought into contact with the surface of a photoreceptor. The toner is preferably a non-magnetic toner, but may be a magnetic toner. It is important that the toner on the developing roller be in contact with the surface of the photoconductor. The toner carrier is substantially in contact with the photoreceptor surface, which means that the toner carrier is in contact with the photoconductor when the toner is removed from the toner carrier. At this time, in order to obtain a toner image having no edge effect by an electric field acting between the photosensitive member and the developing roller facing the photosensitive member via the toner, a potential is applied to the developing roller surface or in the vicinity of the developing roller surface. It is necessary to form an electric field between the surface of the photoconductor and the surface of the toner carrier. For this reason, the elastic rubber of the developing roller controls the resistance in the medium resistance region to form an electric field while preventing conduction with the photoconductor surface, or a thin dielectric layer is provided on the surface layer of the conductive roller, or It is possible to use any structure in which a conductive resin sleeve in which the side facing the photoreceptor surface is covered with an insulating material on a conductive roller, or a conductive layer is provided on the side not facing the photoreceptor with an insulating sleeve. .
[0066]
In the present invention, the developing roller carrying the toner may rotate in the same direction as the peripheral speed of the photoconductor, or may rotate in the opposite direction. When the rotation is in the same direction, the peripheral speed ratio is preferably 100% or more, more preferably 120 to 300%, and still more preferably 140 to 250% with respect to the peripheral speed of the photoreceptor. Is good. If it is less than 100%, problems tend to occur in image quality such as poor line breaks. As the peripheral speed ratio increases, the amount of toner supplied to the development site increases, the frequency of toner detachment from the latent image increases, and unnecessary portions are scraped off and repeatedly applied to necessary portions. An image faithful to the latent image can be obtained.
[0067]
The present invention does not cover a two-component developing method using a magnetic brush in which toner is formed from a magnetic carrier.
[0068]
As the cleaning member used in the present invention, a blade, a roller, a fur brush, a magnetic brush, or the like can be used. Two or more of these cleaning members may be used in combination.
[0069]
The electrophotographic photoreceptor used in the present invention has a structure in which a charge generating layer containing a charge generating material and a charge transporting layer containing a charge transporting material are laminated in this order on a conductive support, or on a conductive support. A charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material.
[0070]
The charge transport layer of the photoreceptor used in the present invention has a universal hardness HU of 230 N / mm at an indentation depth of 1 μm from the surface.²More than 260N / mm²The universal hardness HU at an indentation depth of 5 μm from the surface with an elastic deformation rate of 35% or more below is 260 N / mm²As described above, the elastic deformation rate needs to be 30% or more.
[0071]
As a result of intensive studies, the present inventors have focused on the hardness and deformation rate of the charge transport layer of the electrophotographic photoreceptor, and have obtained a universal hardness value (Hu) and an elastic deformation rate (plastic deformation) obtained using a surface film hardness meter. It has been found that, when the value of (ratio) is a certain value or more, it is possible to maintain the toner cleaning property and the durability of the photoreceptor while maintaining the developability of the spherical toner in the contact developing method.
[0072]
The universal hardness in the vicinity of the surface of the charge transport layer in the electrophotographic photosensitive member, that is, the universal hardness HU at an indentation depth of 1 μm from the surface is 230 N / mm.²If the elastic deformation rate at a pressing depth of 1 μm from the surface is less than 35%, the toner cleaning property is insufficient and the toner cleaning property is insufficient. Toner fusion occurs due to the embedding of additives. Further, the universal hardness HU at a pressing depth of 1 μm from the surface is 260 N / mm.²When it is larger, the blade is turned up because the abrasion amount of the photoconductor charge transport layer is reduced.
[0073]
On the other hand, the universal hardness inside the charge transport layer in the electrophotographic photosensitive member, that is, the universal hardness HU at a depth of 5 μm indentation from the surface is 260 N / mm.²If it is less than 30% or the elastic deformation rate is less than 30%, the image forming apparatus of the present invention does not have sufficient durability against scratches and uneven abrasion in the charge transport layer when the photoreceptor is repeatedly used, In particular, stripes that cause defective toner cleaning are grown deeper.
[0074]
The surface hardness of the charge transport layer of the electrophotographic photosensitive member in the present invention is determined by a universal hardness (HU: unit N / mm) by an instrumented indentation method (nanoindentation @ methods).²).
[0075]
In the present invention, the universal hardness is determined by Helmut Fisher GMBH + Co. The measurement was performed using FISHERSCOPE @ H100V manufactured by KK. The sample was formed with a thickness of 18 μm on a glass plate. The measurement was carried out by applying a constant load to the indenter and changing the indentation depth of the indenter to 1 μm and 5 μm. In addition, the elastic deformation rate can also analyze the elastic energy (plastic energy) of the film by reducing the load of the indenter when measuring the universal hardness. The elastic deformation rate (plastic deformation rate) is obtained from the work (energy) performed by the indenter on the film, that is, the change in energy due to the increase or decrease of the load of the indenter on the film, and the value is obtained from the following equation;
Elastic deformation rate (%) = energy required for elastic deformation / (energy required for plastic deformation + energy required for elastic deformation)
Specific examples of the electrophotographic photosensitive member according to the invention will be described below.
[0076]
The support used for the electrophotographic photoreceptor in the present invention may be any one having conductivity, such as a metal such as aluminum or stainless steel, or a metal provided with a conductive layer, paper and plastic, and the like. Shape and cylindrical shape. In particular, when an image input such as LBP is a laser beam, it is preferable to provide a conductive layer for the purpose of preventing interference fringes due to scattering or covering a scratch on the support. This can be formed by dispersing a conductive powder such as carbon black or metal particles in a binder resin. The thickness of the conductive layer is preferably from 5 to 40 μm, particularly preferably from 10 to 30 μm.
[0077]
An intermediate layer having an adhesive function and a barrier function can be provided thereon as needed. Examples of the material of the intermediate layer include polyamide, polyvinyl alcohol, polyethylene oxide, ethyl cellulose, casein, polyurethane, and polyether urethane. These are dissolved in an appropriate solvent and applied. The thickness of the intermediate layer is preferably from 0.05 to 5 μm, particularly preferably from 0.3 to 1 μm.
[0078]
A charge generation layer is formed on the conductive support or the intermediate layer. Examples of the charge generation material to be used include selenium-tellurium, pyrylium, thiapyrylium dyes, phthalocyanine, anthantrone, dibenzapyrene quinone, trisazo, cyanine, disazo, monoazo, indigo, quinacridone, and asymmetric quinocyanine pigments. For the charge generation layer, use a homogenizer, an ultrasonic dispersion, a ball mill, a vibration ball mill, a sand mill, an attritor, a roll mill, or a liquid collision type high-speed disperser with the charge generation material together with a binder resin and a solvent in an amount of 0.3 to 4 times. And sufficiently dispersed, and the dispersion is formed by applying and drying the dispersion. The thickness of the charge generation layer is preferably 5 μm or less, particularly preferably 0.1 to 2 μm.
[0079]
The charge transport layer is formed by applying a coating material in which a charge transport material and a binder resin are dissolved in a solvent and drying the coating material. Examples of the charge transport material used include a triarylamine compound, a hydrazone compound, a stilbene compound, a pyrazoline compound, an oxazole compound, a triallylmethane compound, and a thiazole compound. These are combined with 0.5 to 2 times the amount of the binder resin, applied and dried to form a charge transport layer.
[0080]
The thickness of the charge transport layer is preferably from 5 to 40 μm, more preferably from 10 to 30 μm.
[0081]
Examples of the binder resin used for the charge transport layer include thermoplastic resins such as polyarylate resin, polycarbonate resin, polyester resin, polymethacrylate, polystyrene resin, acrylic resin, and polyamide resin. The weight average molecular weight (Mw) of the thermoplastic resin is preferably from 50,000 to 200,000. When the molecular weight is less than 50,000, the mechanical strength of the binder resin is not sufficient, and the abrasion resistance of the charge transport layer is lowered, and the toner is easily fused. When the molecular weight exceeds 200,000, the viscosity of the paint for the charge transport layer becomes too high. There is a problem that productivity is extremely deteriorated and productivity is reduced.
[0082]
The charge transport layer of the photoreceptor used in the present invention has a universal hardness HU of 230 N / mm at an indentation depth of 1 μm from the surface.²More than 260N / mm²The universal hardness HU at an indentation depth of 5 μm from the surface with an elastic deformation rate of 35% or more below is 260 N / mm²As described above, the elastic deformation rate may be 30% or more. However, in the charge transport layer in which the low molecular weight charge transport material is dispersed in the binder resin, the mechanical strength and the deformation rate of the film are low. It largely depends on the mechanical strength of the resin and the content of the charge transport material. In addition, since the low molecular weight charge transporting material is molecularly dispersed, the mechanical strength and the deformation ratio of the film of the charge transporting layer differ depending on the state of dispersion between the vicinity of the surface and the inside. In particular, the dispersion state of the charge transport material in the charge transport layer differs depending on the drying conditions of the film when forming the charge transport layer. Therefore, in order to obtain the charge transporting layer used in the present invention by a film in which a low-molecular weight charge transporting material is dispersed in a binder resin, the binder resin may have a high hardness and a high hardness such as a polyarylate resin or a polycarbonate resin. It is necessary to select a resin having a high molecular weight and further reduce the content of the charge transporting material having a low molecular weight as much as possible. Further, by selecting appropriate drying conditions, it is possible to form a charge transporting layer having different hardness and elastic deformation ratio near and inside the surface of the film as in the present invention.
[0083]
Since the hardness of the charge transport layer is determined by many factors as described above, it cannot be unconditionally determined. Hardness HU at 230 N / mm²More than 260N / mm²The universal hardness HU at an indentation depth of 5 μm from the surface with an elastic deformation rate of 35% or more below is 260 N / mm²Thus, the elastic deformation rate of 30% or more is achieved.
[0084]
For example, when a polycarbonate resin having a weight average molecular weight of 80,000 or more and a charge transport material of a triphenylamine derivative or a stilbene derivative having a molecular weight of about 400 to 500 are mixed at a mass ratio of 10: 8 or more and dried at 100 ° C. It can be the hardness and elastic modulus of the charge transport layer.
[0085]
Various additives can be added to the charge transport layer of the photoreceptor used in the present invention. The additives are deterioration inhibitors such as antioxidants and ultraviolet absorbers.
[0086]
The resin which is the main material among the molding materials used for the intermediate transfer member in the present invention is not particularly limited, for example, olefin resins such as polyethylene and polypropylene and polystyrene resins, acrylic resins, polyester resins, polycarbonates Sulfur-containing resins such as polysulfone, polyethersulfone and polyphenylene sulfide, fluorine-containing resins such as polyvinylidene fluoride and polyethylene-tetrafluoroethylene copolymer, polyurethane resins, silicone resins, ketone resins, polyvinylidene chloride, thermoplastics One or two or more of a polyimide resin, a polyamide resin, a modified polyphenylene oxide resin and the like, and various modified resins and copolymers thereof can be used. However, it is not limited to the above materials.
[0087]
Next, the additives to be mixed to adjust the electric resistance value of the intermediate transfer belt are not particularly limited, but as the conductive filler for adjusting the resistance, carbon black or various conductive metal oxides may be used. Examples of the non-filler resistance adjuster include an antistatic resin containing an ether bond, a hydroxyl group, and the like in the molecule, and an organic polymer compound having electronic conductivity.
[0088]
Low molecular weight ionic conductive materials such as various metal salts and glycols are generally not preferred because they easily migrate to the electrophotographic photoreceptor, but not all materials cause problems. Any material can be used as long as it does not affect the photographic photoreceptor.
[0089]
FIG. 1 shows an example of an image forming apparatus using the intermediate transfer belt-electrophotographic photosensitive member integrated cartridge of the present invention.
[0090]
FIG. 1 shows a full-color image forming apparatus (copier or laser beam printer) using an electrophotographic process.
[0091]
A rotating drum type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) 1 repeatedly used as a first image carrier is rotationally driven at a predetermined peripheral speed (process speed) in the direction of an arrow.
[0092]
The photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by the primary charger 2 during the rotation process. Reference numeral 32 denotes a power supply for the primary charger. In this case, AC is superimposed on DC and applied. However, DC may be used. Next, exposure means (not shown) such as a color original image color separation / imaging exposure optical system, a scanning exposure system using a laser scanner that outputs a laser beam modulated in accordance with a time-series electric digital pixel signal of image information, and the like are used. By receiving the exposure light 3, an electrostatic latent image corresponding to a first color component image (for example, a yellow color component image) of a target color image is formed.
[0093]
Next, the electrostatic latent image is developed by the first developing device (yellow color developing device 41) with the yellow toner Y as the first color. At this time, the developing units of the second to fourth developing units (the magenta developing unit 42, the cyan developing unit 43, and the black developing unit 44) are turned off and do not act on the photosensitive drum 1. The first color yellow toner image is not affected by the second to fourth developing units.
[0094]
The intermediate transfer belt 5 is driven to rotate at the same peripheral speed as the photosensitive drum 1 in the direction of the arrow. The first color yellow toner image formed and carried on the photosensitive drum 1 is applied from the primary transfer roller 6 to the intermediate transfer belt 5 while passing through the nip between the photosensitive drum 1 and the intermediate transfer belt 5. The primary transfer is sequentially performed on the outer peripheral surface of the intermediate transfer belt 5 by the electric field generated by the primary transfer bias.
[0095]
After the transfer of the first color yellow toner image corresponding to the intermediate transfer belt 5, the surface of the photosensitive drum 1 is cleaned by the cleaning device 13.
[0096]
Hereinafter, similarly, the magenta toner image of the second color, the cyan toner image of the third color, and the black toner image of the fourth color are sequentially superimposed on the intermediate transfer belt 5 and transferred, so that the composite color corresponding to the target color image is obtained. A toner image is formed.
[0097]
The secondary transfer roller 7 is provided in parallel with the secondary transfer opposing roller 8 so as to be supported in parallel, and is disposed on the lower surface of the intermediate transfer belt 5 so as to be separated therefrom.
[0098]
A primary transfer bias for sequentially superimposing transfer of the first to fourth color toner images from the photosensitive drum 1 to the intermediate transfer belt 5 is applied from a bias power supply 30 with a polarity (+) opposite to that of the toner. The applied voltage is, for example, in the range of +100 V to 2 kV.
[0099]
In the primary transfer process of the toner images of the first to third colors from the photosensitive drum 1 to the intermediate transfer belt 5, the secondary transfer roller 7 can be separated from the intermediate transfer belt 5.
[0100]
The transfer of the composite color toner image transferred onto the intermediate transfer belt 5 to the transfer material P is performed by the secondary transfer roller 7 being in contact with the intermediate transfer belt 5 and passing from the paper feed roller 11 to the transfer material guide 10. The transfer material P is fed to the contact nip between the intermediate transfer belt 5 and the secondary transfer roller 7 at a predetermined timing, and a secondary transfer bias is applied to the secondary transfer roller 7 from the power supply 31. With this secondary transfer bias, the composite color toner image is secondarily transferred from the intermediate transfer belt 5 to the transfer material P. The transfer material P to which the toner image has been transferred is introduced into the fixing device 15 and is heated and fixed.
[0101]
After the image transfer to the transfer material P is completed, a cleaning charging member 9 arranged to be detachable from the intermediate transfer belt 5 is brought into contact with the intermediate transfer belt 5, and a bias having a polarity opposite to that of the photosensitive drum 1 is applied. The transfer residual toner remaining on the intermediate transfer belt 5 without being transferred to the P is given a charge having a polarity opposite to that of the primary transfer. 33 is a bias power supply. Here, alternating current is superimposed on direct current and applied. The transfer residual toner charged to a polarity opposite to that of the primary transfer is electrostatically transferred to the photosensitive drum 1 in a nip portion with the photosensitive drum 1 and in the vicinity thereof, thereby cleaning the intermediate transfer member. Since this step can be performed simultaneously with the primary transfer, a decrease in throughput does not occur.
[0102]
Next, the intermediate transfer belt-electrophotographic photosensitive member integrated cartridge of the present invention will be described. As shown in FIG. 2, the cartridge of the present invention comprises at least the intermediate transfer belt 5, the electrophotographic photosensitive member 1, the intermediate transfer belt cleaning member 9 and the cleaning member 13 for the electrophotographic photosensitive member as an integrated unit. It can be easily attached to and detached from the device body. As described above, the cleaning of the intermediate transfer belt is a mechanism necessary to charge the transfer residual toner to the polarity opposite to that of the primary transfer and return the toner to the electrophotographic photosensitive member at the primary transfer portion. A cleaning roller 9 composed of a body is provided. Cleaning of the electrophotographic photosensitive member is blade cleaning. A waste toner container (not shown) is also integrated with this cartridge, and the transfer residual toner of both the intermediate transfer belt and the electrophotographic photosensitive member is discarded at the same time when the cartridge is replaced, thereby contributing to an improvement in maintenance. Further, the intermediate transfer belt is stretched by two rollers 8 and 12 to reduce the number of parts and reduce the size. Here, reference numeral 8 denotes a driving roller and a roller opposite to the cleaning roller. The tension roller 12, which rotates following the intermediate transfer belt, has a sliding mechanism, and is pressed against the intermediate transfer belt by a compression spring in the direction of the arrow to apply tension to the intermediate transfer belt. The slide width is about 1 to 5 mm, and the total pressure of the spring is about 5 to 100 N. Further, the electrophotographic photosensitive member 1 and the driving roller 8 have a coupling (not shown) so that a rotational driving force is transmitted from the main body.
[0103]
【Example】
Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to this. In addition, "part" in an Example means a mass part.
[0104]
[Production Example of Toner]
650 g of ion-exchanged water and 0.1 mol / L-Na were placed in a two-liter four-necked flask equipped with a high-speed stirrer TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.).₃PO₄500 g of the aqueous solution was charged, the rotation speed was adjusted to 12000 rpm, and the mixture was heated to 70 ° C. 1.0 mol / liter-CaCl₂70 parts of an aqueous solution is gradually added, and a fine hardly water-soluble dispersion stabilizer Ca is added.₃(PO₄)₂The aqueous dispersion medium containing was prepared.
[0105]
On the other hand, as a dispersoid,
Styrene 78 parts
2-ethylhexyl acrylate 22 parts
Divinylbenzene 0.2 parts
Carbon black (particle size = 45 nm) 5 parts
Polycarbonate resin (peak molecular weight = 7000) 5 parts
Chromium compound of di-tert-butylsalicylic acid 2 parts
Ester wax (mp = 62 ℃) 10 parts
Is dispersed using an attritor (manufactured by Mitsui Kinzoku Co., Ltd.) for 3 hours, and then 10 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) is added to prepare a polymerizable monomer composition. did.
[0106]
Next, the polymerizable monomer composition was charged into the aqueous dispersion medium, and N 2 at an internal temperature of 70 ° C.₂Under an atmosphere, the mixture was stirred for 15 minutes while maintaining the rotation speed of the high-speed stirrer at 12,000 rpm, to granulate the polymerizable monomer composition. Thereafter, the agitator was replaced with a propeller stirring blade, the temperature was maintained at the same temperature for 5 hours while stirring at 50 rpm, and the temperature was further raised to 80 ° C. for 10 hours to complete the polymerization.
[0107]
After completion of the polymerization, the suspension was cooled, and then dilute hydrochloric acid was added to remove the dispersion stabilizer. Further, after repeating water washing several times, the toner particles are subjected to sphering treatment and drying treatment for 10 hours while stirring in hot air using a fluidized bed drier (manufactured by Okawara Seisakusho), and polymer particles (A) are obtained. Obtained.
[0108]
The polymer particles (A) have a circle-equivalent number average diameter of 4.1 μm, an average circularity in the circularity frequency distribution of 0.990, a circularity standard deviation of 0.030, and a molecular weight distribution by GPC. The peak molecular weight was 15,000 and Mw / Mn was 18.
[0109]
100 parts of the above polymer particles (A) and hydrophobic oil-treated silica fine powder (BET; 200 m²/ G) 2 parts were dry-mixed with a Henschel mixer (manufactured by Mitsui Kinzoku Co., Ltd.) to prepare a toner.
[0110]
<Production Example 1 of Photoconductor>
An aluminum cylinder having a diameter of 47 mm was used as a support, and a coating composed of the following materials was dip-coated on the support and thermally cured at 140 ° C. for 30 minutes to form a conductive layer having a thickness of 15 μm.
[0111]
Conductive pigment: SnO₂Coated barium sulfate 10 parts
Pigment for resistance adjustment: Titanium oxide 2 parts
Binder resin: phenol resin 6 parts
Leveling material: silicone oil 0.001 part
Solvent: methanol / methoxypropanol = 0.2 / 0.8 20 parts
[0112]
Next, a solution obtained by dissolving 3 parts of N-methoxymethylated nylon and 3 parts of copolymerized nylon in a mixed solvent of 65 parts of methanol / 30 parts of n-butanol was applied onto the conductive layer by an immersion method. An intermediate layer of 0.7 μm was formed.
[0113]
Next, 4 parts of TiOPc having strong peaks at 9.0 °, 14.2 °, 23.9 ° and 27.1 ° of Bragg angles (2θ ± 0.2 °) in characteristic X-ray diffraction of CuKα and polyvinyl butyral After 2 parts of (trade name: ESLEC BM2, manufactured by Sekisui Chemical) and 60 parts of cyclohexanone were dispersed in a sand mill using φ1 mm glass beads for 4 hours, 100 parts of ethyl acetate was added to prepare a dispersion for a charge generation layer. This was applied by an immersion method to form a charge generation layer having a thickness of 0.3 μm.
[0114]
Next, in order to form a charge transport layer, 10 parts of a polyarylate resin (Mw = 101000) having a structural unit represented by the following formula:
[0115]
Embedded image

7 parts of an amine compound represented by the following formula
[0116]
Embedded image

Using a paint for a charge transport layer prepared by dissolving in a mixed solvent of 50 parts of monochlorobenzene and 30 parts of dichloromethane, the paint is applied on the charge generation layer by a dipping method, and dried at 100 ° C. for 1 hour. Then, a charge transport layer having a thickness of 24 μm was formed, and a photoreceptor 1 was produced. Table 1 shows the universal hardness and the elastic deformation rate of the charge transport layer at this time.
[0117]
<Production Example 2 of Photoconductor>
Photoconductor 2 was produced in the same manner as in Photoconductor Production Example 1, except that the amine compound used in Photoconductor Production Example 1 was changed from 7 parts to 5 parts. Table 1 shows the universal hardness and the elastic deformation rate of the charge transport layer at this time.
[0118]
<Production Example 3 of Photoconductor>
A support, a conductive layer, an undercoat layer, and a charge generation layer were formed in the same manner as in Photoconductor Production Example 1.
[0119]
Next, 7 parts of a styryl compound represented by the following formula:
[0120]
Embedded image

And 10 parts of a polycarbonate resin (Mw = 100000) having a structural unit represented by the following formula:
[0121]
Embedded image

Was dissolved in a mixed solvent of 50 parts of monochlorobenzene / 20 parts of dichloromethane, and the paint was applied on the charge generating layer by a dipping method, and dried at 100 ° C. for 1 hour. Then, a charge transport layer having a thickness of 24 μm was formed, and a photoreceptor 3 was produced. Table 1 shows the universal hardness and the elastic deformation rate of the charge transport layer at this time.
[0122]
<Production Example 4 of Photoconductor>
Photoconductor 4 was produced in the same manner as in Production Example 3 of the photoconductor, except that the weight average molecular weight of the polycarbonate resin used in Production Example 3 of the photoconductor was changed to 180,000. Table 1 shows the universal hardness and the elastic deformation rate of the charge transport layer at this time.
[0123]
<Comparative Production Example 1 of Photoconductor>
A support, a conductive layer, an undercoat layer, and a charge generation layer were formed in the same manner as in Photoconductor Production Example 1.
[0124]
Next, a charge transport layer prepared by dissolving 25 parts of a Z-type polycarbonate resin having a weight average molecular weight Mw of 40,000 in a mixed solvent of 50 parts of monochlorobenzene / 20 parts of dichloromethane instead of the polyarylate resin used in Production Example 1 The charge generation layer was applied by a dipping method using a paint, and dried at 100 ° C. for 1 hour to form a charge transport layer having a thickness of 24 μm. Thus, an electrophotographic photoreceptor 5 was obtained. Table 1 shows the universal hardness and the elastic deformation rate of the charge transport layer at this time.
[0125]
<Comparative Production Example 2 of Photoconductor>
Photoconductor 6 was produced in the same manner as photoconductor production example 1, except that the amine compound used in photoconductor production example 1 was changed from 7 parts to 10 parts. Table 1 shows the universal hardness and the elastic deformation rate of the charge transport layer at this time.
[0126]
<Comparative Production Example 3 of Photoconductor>
Photoreceptor 7 was prepared in the same manner as in Photoreceptor Production Example 1, except that the drying conditions for forming the charge transport layer were changed to 125 ° C. for 1 hour. Table 1 shows the universal hardness and the elastic deformation rate of the charge transport layer at this time.
[0127]
<Comparative Production Example 4 of Photoconductor>
Photoreceptor 8 was prepared in the same manner as in Photoreceptor Production Example 4, except that the drying conditions for forming the charge transport layer were changed to 125 ° C. for 1 hour. Table 1 shows the universal hardness and the elastic deformation rate of the charge transport layer at this time.
[0128]
[Table 1]

[0129]
(Example 1)
As an image forming apparatus, a modified Hewlett-Packard LBP “Color Laser Jet 4500” (process speed of 117 mm / sec) was used. The rotational speed of the developing roller is in the same direction at the contact portion with the photoreceptor, and is driven so as to be 150% of the rotational speed of the photoreceptor. A urethane blade is used as a cleaning member at a set pressure of 70 g / cm. Set.
[0130]
The photoreceptor 1 of Production Example 1 was used as the photoreceptor, and the toner of the above Production Example was used as the toner. The process conditions were set so as to satisfy the following conditions.
[0131]
Photoconductor dark area potential -600V
Photoconductor light section potential -130V
Development bias -375V
[0132]
This machine was installed in an environment of a temperature and humidity of 23 ° C./60%, and a continuous image output test was performed on 10,000 sheets of A4 size paper with a character pattern of 4% area ratio while supplying toner. . In addition, before and after the endurance, the surface roughness of the photoconductor was measured. Table 2 shows the evaluation results.
[0133]
(Examples 2 to 4 and Comparative Examples 1 to 4)
The evaluation was performed in the same manner as in Example 1 except that the photoconductors 2 to 8 of the above Production Examples were used as the photoconductor. Table 2 shows the results.
[0134]
(Examples 5 and 6 and Comparative Examples 5 and 6)
In the image forming apparatus of the first embodiment, the same evaluation as in the first embodiment was performed using the photoconductors 1, 3, 5, and 7 as the photoconductors with the set pressure of the cleaning blade being 90 g / cm. Table 3 shows the results.
[0135]
[Table 2]

[0136]
[Table 3]

[0137]
As is clear from Tables 2 and 3, the image forming apparatus according to the embodiment of the present invention maintains the toner developing property, the toner cleaning property, and the durability of the photoreceptor in the contact developing method using the spherical toner. It is possible to stably provide high-quality, high-definition images for a long period of time.
[0138]
【The invention's effect】
As described above, according to the present invention, while maintaining the toner developing property and the toner cleaning property, the mechanical abrasion of the photoreceptor during repeated image output is suppressed, and a high-quality, high-stability image forming apparatus and a process cartridge are provided. It became possible to provide.
[Brief description of the drawings]
FIG. 1 is a view showing a schematic configuration of an image forming apparatus provided with an intermediate transfer belt-electrophotographic photosensitive member integrated type process cartridge of the present invention.
FIG. 2 is a diagram showing a schematic configuration of an intermediate transfer belt-electrophotographic photosensitive member integrated type process cartridge of the present invention.
[Explanation of symbols]
1. Electrophotographic photoreceptor
2 Primary charger
3 Exposure light
5 Intermediate transfer belt
6 Primary transfer facing roller
7 Secondary transfer roller
8 Secondary transfer facing roller
9 Cleaning roller
10 Transfer material guide
11 paper feed roller
12 tension roller
13 Cleaning device
16mm fuser
30, 31, 32, 33 power supply
41 yellow color developer
42 magenta color developing unit
43 cyan developing unit
44 black color developer

Claims (8)

The electrostatic latent image formed on the electrophotographic photosensitive member having the charge generation layer and the charge transport layer laminated thereon is visualized with a developer, and the obtained image is transferred to an intermediate transfer belt and to a primary transfer means and an intermediate transfer belt. An intermediate transfer belt, an electrophotographic photosensitive member, a cleaning mechanism for the intermediate transfer belt, and a cleaning mechanism for the electrophotographic photosensitive member in an integrated unit. A mechanism for charging the remaining developer to a polarity opposite to that of the primary transfer and returning the developer to the electrophotographic photosensitive member at the same time as the primary transfer from the intermediate transfer belt. The universal hardness HU at an indentation depth of 1 μm from the surface of the charge transport layer of the photoreceptor is 230 N / mm ² or more and 260 N / mm ² or less, and the elastic deformation rate is 3 An image forming apparatus characterized by having a universal hardness HU of not less than 5% and an indentation depth of 5 μm from the surface of not less than 260 N / mm ² and an elastic deformation rate of not less than 30%. Developing means forms a toner layer on the elastic roller and contacts the toner layer with the surface of the electrophotographic photosensitive member while rotating the elastic roller and the electrophotographic photosensitive member with respect to each other. Means for developing a toner image by developing the electrostatic latent image formed on the toner layer with the toner of the toner layer, wherein the toner is a circle-equivalent diameter-circle based on the number of toners measured by a flow type particle image measuring device. A dry one-component toner in which the toner has a circle-equivalent number average diameter of 2 to 10 μm, an average circularity of 0.950 to 0.995, and a circularity standard deviation of less than 0.040 in a degree scattergram. Item 2. The image forming apparatus according to Item 1. 3. The image forming apparatus according to claim 1, wherein the binder resin of the charge transport layer of the electrophotographic photosensitive member is a thermoplastic resin having a weight average molecular weight of 50,000 or more and 200,000 or less. The image forming apparatus according to claim 1, wherein the toner is manufactured using a suspension polymerization method. The electrostatic latent image formed on the electrophotographic photosensitive member having the charge generation layer and the charge transport layer laminated thereon is visualized with a developer, and the obtained image is transferred to an intermediate transfer belt and to a primary transfer means and an intermediate transfer belt. In an image forming apparatus having a secondary transfer means for further transferring the transferred image to a transfer material, an intermediate transfer belt, an electrophotographic photosensitive member, a cleaning mechanism for the intermediate transfer belt, and a cleaning mechanism for the electrophotographic photosensitive member are integrated in a unit. And an intermediate transfer belt and an electrophotographic photosensitive member integrated with the image forming apparatus main body, the cleaning mechanism of the intermediate transfer belt removes the remaining developer to a polarity opposite to that of the primary transfer. And the primary transfer from the intermediate transfer belt to the electrophotographic photosensitive member at the same time as the primary transfer. and the elastic deformation ratio of 35% or more universal hardness HU is 230N / mm ² or more 260 N / mm ² or less at an indentation depth of m, the elastic deformation at the universal hardness HU is 260 N / mm ² or more from the surface of the indentation depth of 5μm A process cartridge having a rate of 30% or more. Developing means forms a toner layer on the elastic roller and contacts the toner layer with the surface of the electrophotographic photosensitive member while rotating the elastic roller and the electrophotographic photosensitive member with respect to each other. Means for developing a toner image by developing the electrostatic latent image formed on the toner layer with the toner of the toner layer, wherein the toner is a circle-equivalent diameter-circle based on the number of toners measured by a flow type particle image measuring device. A dry one-component toner in which the toner has a circle-equivalent number average diameter of 2 to 10 μm, an average circularity of 0.950 to 0.995, and a circularity standard deviation of less than 0.040 in a degree scattergram. Item 6. A process cartridge according to item 5. 7. The process cartridge according to claim 5, wherein the binder resin of the charge transport layer of the electrophotographic photosensitive member is a thermoplastic resin having a weight average molecular weight of 50,000 or more and 200,000 or less. The process cartridge according to claim 5, wherein the toner is manufactured using a suspension polymerization method.

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