JP3902809B2

JP3902809B2 - Electrophotographic equipment

Info

Publication number: JP3902809B2
Application number: JP12767896A
Authority: JP
Inventors: 宜道三木; 秀樹穴山; 至山▲崎▼; 秀敏平野
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1996-04-25
Filing date: 1996-04-25
Publication date: 2007-04-11
Anticipated expiration: 2016-04-25
Also published as: JPH09292755A

Description

【０００１】
【発明の属する技術分野】
本発明は一次帯電部材を電子写真感光体に直接接触させる一次帯電系を有する電子写真装置に関する。
【０００２】
【従来の技術】
電子写真方法は米国特許第２２９７６９１号公報に示されるように画像露光の間に受けた照射量に応じて電気抵抗が変化し、かつ、暗所では絶縁性の物質をコーティングした支持体よりなる光導電性材料を用いる。この光導電性材料を用いた電子写真感光体に要求される基本的な特性としては（１）暗所で適当な電位に帯電できること、（２）暗所において電位の散逸が少ないこと、（３）光照射によって速やかに電荷を散逸せしめること等が挙げられる。
【０００３】
従来より電子写真感光体としてはセレン、酸化亜鉛、硫化カドミウム等の無機光導電性化合物を主成分とする感光層を有する無機感光体が広く使用されてきた。しかしこれ等は前記（１）〜（３）の条件は満足するが熱安定性、耐湿性、耐久性、生産性において必ずしも満足できるものではなかった。無機感光体の欠点を克服する目的で様々な有機光導電性化合物を主成分とする電子写真感光体の開発が近年盛んに行われている。例えば米国特許第３８３７８５１号公報にはトリアリルピラゾリンを含有する電荷輸送層を有する感光体、米国特許第３８７１８８０号公報にはペリレン顔料の誘導体からなる電荷発生層と３−プロピレンとホルムアルデヒドの縮合体からなる電荷輸送層とからなる感光体等が公知である。
【０００４】
さらに有機光導電性化合物はその化合物によって電子写真感光体の感光波長域を自由に選択することが可能であり、例えばアゾ顔料では特開昭６１−２７２７５４号公報、特開昭５６−１６７７５９号公報に示された物質は可視領域で高感度を示すものが開示されており、また、特開昭５７−１９５７６号公報、特開昭６１−２２８４５３号公報で示された化合物は赤外領域まで感度を有していることが示されている。これ等の材料のうち赤外領域に感度を示すものは近年進歩の著しいレーザービームプリンターやＬＥＤプリンターに使用されてその需要頻度は高くなっている。
【０００５】
現在、コンピューター、ワープロ、ファクシミリ等の出力装置としてレーザービームプリンター、ＬＥＤプリンター等の電子写真プリンターの重要が高い。これ等のプリンターに主に用いられている電子写真感光体は、有機光導電体を使用しており、その感光層の基本構成は材料選択の許容幅、耐久性、電位安定性、感度及び応答性等の様々な理由から電荷発生物質を含有する電荷発生層と電荷輸送物質を含有する電荷輸送層を有する、所謂機能分離型が多い。
【０００６】
また、感光ドラムを一次帯電させる方法も小エネルギー／エコロジーの観点から一次帯電部材を感光体の接触させる方式が多くなってきている。このように小径ローラーを帯電部材として直流電圧に交流電圧を重畳して印加し、感光体に従動して帯電させた場合、印加交流電圧が感光体上で凹凸の電位となり、その凹部のサイクルに近いピッチでレーザーを感光体に照射した場合、それがハーフトーン画像では顕著な濃淡のモアレとなって現れる。そして、モアレを発生させないためには感光体上の一次帯電電位の凹凸サイクルむらが小さくなるよう交流電圧の周波数を上げる必要があり、その結果、帯電音が許容範囲を超えるという問題があった。
【０００７】
また、この系に金属磁性体を含有する現像剤（トナー）を用いて連続出力を数千枚単位で行った場合、現像剤が感光ドラム上に固着し、デジタル方式のプリンターにおいては画像入力を反転で行うことが多いため、画像の黒地部分が白く抜けてしまうことが起こる。これは、現像剤粒子の表面に露出した金属磁性体が一次帯電部材を介して感光体表面を傷つけ、次に感光体表面に残った現像剤が一連の現像過程の中でその傷口に擦り込まれることが原因と考えられる。
【０００８】
これ等の問題を解決するため、感光体の表面物性の改良、現像剤の構成や一次帯電部材の構成、物性や表面形状の改良等各方面からのアプローチが試みられている。しかしながら、いずれの方法も十分な結果が得られていない。
【０００９】
【発明が解決しようとする課題】
本発明の目的は、一次帯電部材を感光体に接触させる一次帯電系において、交流帯電の帯電むらによるモアレ画像や許容範囲を超える帯電音を無くすための感光体構成と一次帯電部材形状を提供することである。また、併せて現像剤が感光体に固着しにくい構成にして、連続で画像出力しても白抜けが起こらないようにすることである。
【００１０】
【課題を解決するための手段】
本発明は、基体としての直径３０ｍｍのアルミニウムシリンダーおよび最表面に形成された水との接触角が９０度以上である保護層を有する電子写真感光体と、
該電子写真感光体に直接接触させた半径が１５ｍｍ以上で中心角が３０度以上６０度以下の扇柱状の一次帯電部材を有し、該一次帯電部材に直流電圧に交流電圧を重畳した電圧を印加することによって該電子写真感光体を一次帯電させる帯電装置と、
金属成分を含有しない現像剤粒子の表面にシリカ微粉体を有させてなる現像剤と
を有する電子写真装置であって、
該一次帯電部材は、扇の中心点を通る金属芯棒を中心として回動自在であり、かつ、加圧バネによって該電子写真感光体に対して押圧されるとともに別の加圧バネによって該電子写真感光体の回転方向の逆方向から押圧されることにより、該電子写真感光体上を摺動可能とされている電子写真装置から構成される。
【００１１】
本発明においては、ローラー状の一次帯電部材を用いた場合に顕著に見られる前記課題を解決するために、まず、円柱形の一次帯電部材の半径を従来の数倍に大径化することを試みた。これにより、一次帯電時の放電領域が広がり、交流電圧重畳時の帯電むら凹凸間の電位差を小さくできる。その結果、その凹凸のサイクルに近いピッチのレーザーを照射してもそれが目に見えるような濃淡となってハーフトーン画像に現れなくなる。従って、交流電圧の周波数でモアレ画像対策を施す必要がなく、帯電音が許容範囲を超えることがない。この帯電むら凹凸間の電位差はローラーの半径が大きくなると急激に減少するが、半径が１５ｍｍを超える辺りから緩やかに減少するため、半径が１５ｍｍ以上であればほぼ同様の効果が期待できる。
【００１２】
また、ローラー状の一次帯電部材の半径を大幅に大きくすると、設置スペースの確保や材料価格の面で不利なため、本発明においては、扇柱状の帯電部材を使う。この場合、ローラーのように感光体に従動できないため、帯電部材に感光体を摺動させる。そのため、バネ等を用いて、感光ドラムの回転と逆方向の力を帯電部材へ作用させて感光体上を摺動させる。
【００１３】
一次帯電部材の形状がローラーや扇柱状以外の場合、一次帯電部材が感光体上を従動もしくは摺動する際に一次帯電部材の支持点から感光体との接触地点までの距離が変化し、接触地点における機械的負担が増し、安定した帯電にも悪影響を与えるため好ましくない。
【００１４】
感光体は、表面層を低表面エネルギー状態の構成にして現像剤の転写効率や一次帯電部材の滑り性を良くする。例えば、熱や光硬化性の樹脂にフッ素系樹脂やシリコーン系樹脂をブレンドする方法や、硬化性樹脂そのものに含フッ素やシリコーンユニットを組み込む等の方法を用いることにより、表面エネルギーの指標となる水との接触角が初期、使用中とも９０度以上になるような薄い保護層を設ける。水との接触角が９０度未満になると現像剤の転写効率低下や一次帯電部材の滑り性低下等の弊害が顕著に現れてくる。
【００１５】
現像剤には、一成分現像方式に用いられる現像剤の構成成分である磁性体、即ち、金属酸化物微粒子を用いないことにより、現像剤粒子表面の高硬度成分を無くする（可能ならば、磁性体の存在を現像剤粒子の内部のみに留める方法でもよい）。その結果、感光体のクリーニング工程で除去されなかった現像剤が一次帯電部材と感光体の間に入り込んでも、滑剤として機能し、両者の摺動性を助けても傷つけることはない。
【００１６】
磁性体を少量含有する現像剤と低寿命用の感光体を組み合わせるならば、感光体に傷がつく前に寿命に至る場合があるが、そのような現像剤を長寿命用の感光体に組み合わせる場合、長寿命であるほど傷発生の可能性が大きくなり汎用性が限られるため、磁性体のような金属微粒子は現像剤粒子に含有されないことが好ましい。
【００１７】
上記の構成では、現像剤の感光体から複写紙への転写効率も高く、感光体のクリーニング後に感光体上に残る現像剤が少なく、また、現像剤粒子の表面に金属粒子が露出していないため感光体を傷つけにくく、感光体上に現像剤が固着して起こる黒地画像での白抜けが著しく起こりにくくなる。
【００１８】
【発明の実施の形態】
電子写真感光体の作成
リン含有の酸化スズからなるフィラーとレゾール型フェノール樹脂と２−メトキシ−１−プロパノールとからなる混合溶液をボールミルで分散して調製した塗料をアルミニウムシリンダー上に塗布して中間層を形成し、次に、共重合ナイロンと変性ナイロンをメタノール及び１−ブタノールの混合液に溶解して調製した塗料を中間層上に塗布してバリア層を形成し、次に、チタニルオキシフタロシアニン顔料とポリビニルブチラールとシクロヘキサノンからなる混合液をサンドミルで分散した後、酢酸エチルを加えて調製した電荷発生層用塗料をバリア層上に塗布して電荷発生層を形成し、次に、電荷輸送物質であるトリアリールアミン化合物とポリカーボネートをクロロベンゼンとジクロロメタン混合液に溶解して調製した電荷輸送層用塗料を電荷発生層上に塗布して電荷輸送層までを形成する。
【００１９】
次に、アンチモン含有酸化スズ微粒子、（３，３，３−トリフルオロプロピル）トリメトキシシラン、エタノールをミリング処理した後、溶液をろ過、エタノール洗浄後、乾燥により微粒子を表面処理し、次いで、結着樹脂としてアクリル系硬化性モノマー、光重合開始剤として２−メチルチオキサントン、前記表面処理を施したアンチモン含有酸化スズ微粒子及びトルエンを混合し、サンドミルで分散し、分散液に四フッ化エチレン樹脂粒子を混合して更にサンドミルで分散し、保護層用の塗料を調製する。この塗料を電荷輸送層上に塗布して成膜、乾燥後、高圧水銀灯にて紫外線照射して保護層を形成し、電子写真感光体を作成する。この電子写真感光体表面の水との接触角が本発明における所定の角度を有する。
【００２０】
現像剤の作成
スチレン−ブチルアクリレート−ジビニルベンゼン共重合体、低分子量エチレン−プロピレン共重合体、カーボンブラック及びサリチル酸クロム錯体をブレンダーでよく混合した後、２軸混練押出機にて混練し、得られた混練物を冷却し、粗粉砕した後、ジェット気流を用いた微粉砕機を用いて微粉砕し、得られた微粉砕粉を固定壁型風力分級機で分級して分級粉を生成する。得られた分級粉をコアンダ効果を利用した多分割分級装置で超微粉及び粗粉を、同時に厳密に分級除去して負帯電性絶縁性の黒色の現像剤粒子の粉体を製造する。得られた黒色の現像剤粒子の粉体と負帯電性疎水性乾式シリカ微粉体とを混合し、現像剤粒子表面にシリカ微粉体を有する現像剤を調製する。なお、この現像剤粒子は、磁性体等の金属成分を含有していないため、表面に金属粒子が露出することはない。
【００２１】
一次帯電部材の構成と形状
一次帯電部材の構成としては一般の製品に組み込まれる部材と同様であるが、例えば、半径が１５ｍｍの扇形柱を用いる。なお、一次帯電部材は扇の中心点で保持され、感光体に対して垂直方向及び感光体の回転方向と逆方向の２方向から軽く力が作用するようにバネが設置されている。
【００２２】
前記作成した電子写真感光体と前記作成した現像剤と前記構成形状の一次帯電部材を例えばレーザービームプリンターに装着して本発明の電子写真装置とする。
【００２３】
【実施例】
実施例１
電子写真感光体の作成
リン含有の酸化スズからなるフィラー（粉体抵抗２５Ωｃｍ）１４０重量部とレゾール型フェノール樹脂（商品名プライオーフェンＪ−３２５、大日本インキ化学工業（株）製、固形分７０％）７０重量部と２−メトキシ−１−プロパノール１００重量部とからなる混合溶液を約３時間ボールミルで分散し、調製した塗料を外径３０ｍｍ、長さ２５４ｍｍのアルミニウムシリンダー上に浸漬塗布し、１４０℃で３０分間加熱硬化し、厚み１０μｍの中間層を形成した。
【００２４】
次に、共重合ナイロン（商品名アミランＣＭ８０００、東レ（株）製）１２．５重量部と編成ナイロン（商品名トレジンＥＦ３０Ｔ−Ｐ）３７．５重量部をメタノール５６０重量部及び１−ブタノール２８０重量部の混合液に溶解し、調製した塗料を中間層上に浸漬塗布し、１００℃で１０分間加熱乾燥し、厚み１μｍのバリア層を形成した。
【００２５】
次に、チタニルオキシフタロシアニン顔料１８重量部、ポリビニルブチラール（商品名ＢＸ−１、積水化学工業（株）製）１５重量部とシクロヘキサノン５２０重量部からなる混合液をサンドミルで８時間分散した後、酢酸エチル４８０重量部を加えて電荷発生層用塗料を調製し、上記バリア層上に浸漬塗布し、９０℃で１０分間加熱乾燥し、厚み約０．２μｍの電荷発生層を形成した。
【００２６】
次に、下記構造式のトリアリールアミン化合物７０重量部
【００２７】
【外１】

とポリカーボネート（商品名ユーピロンＺ−２００、三菱瓦斯化学（株）製）１００重量部をクロロベンゼン／ジクロロメタン混合液５００重量部に溶解し、調製した電荷輸送層用塗料を電荷発生層上に浸漬塗布し、１００℃で３０分間乾燥し、厚み２０μｍの電荷輸送層を形成した。
【００２８】
次いで、平均粒径０．０２μｍのアンチモン含有酸化スズ微粒子（商品名Ｔ−１、三菱マテリアル（株）製）１００重量部、（３，３，３−トリフルオロプロピル）トリメトキシシラン（信越化学（株）製）３０部、９５％エタノール５％水溶液３００重量部をミリング装置で１時間ミリング処理した後、溶液をろ過、エタノール洗浄後、乾燥（１２０℃で１時間の加熱処理）により微粒子の表面処理を行った。
【００２９】
次いで、結着樹脂として下記構造式で示されるアクリル系硬化性モノマー２５部、
【００３０】
【外２】

光重合開始剤としての２−メチルチオキサントン０．１重量部、前記表面処理を施したアンチモン含有酸化スズ微粒子３５部、トルエン３００部を混合し、サンドミルで９６時間分散し、この分散液に四フッ化エチレン樹脂粒子（商品名ルブロンＬ−２、ダイキン工業（株）製）２５部を混合して更にサンドミルで８時間分散し、保護層用の塗料を調製した。この塗料を電荷輸送層上にスプレー塗工にて成膜、乾燥後、高圧水銀灯にて８００ｍＷ／℃ｍ^２の光強度で１５秒間紫外線照射して、厚み５μｍの保護層を形成し、電子写真感光体を作成した。この電子写真感光体表面の水との接触角を測定したところ、９５度であった。
【００３１】
現像剤の作成
スチレン−ブチルアクリレート−ジビニルベンゼン共重合体（モノマー重量比８０：１９．５：０．５、重量平均分子量（Ｍｗ）３０万）１００重量部、低分子量エチレン−プロピレン共重合体３重量部、カーボンブラック３重量部とサリチル酸クロム錯体２重量部をブレンダーでよく混合した後、１５０℃に設定した２軸混練押出機にて混練した。
【００３２】
得られた混練物を冷却し、カッターミルにて粗粉砕した後、ジェット気流を用いた微粉砕機を用いて微粉砕し、得られた微粉砕粉を固定壁型風力分級機で分級して分級粉を生成した。更に、得られた分級粉をコアンダ効果を利用した多分割分級装置（エルボジェット分級機、日鉄鉱業（株）製）で超微粉及び粗粉を、同時に厳密に分級除去して負帯電性絶縁性の黒色の現像剤粒子の粉体を得た。
【００３３】
得られた黒色の現像剤粒子の粉体１００部と負帯電性疎水性乾式シリカ微粉体（ＢＥＴ比表面積３００ｍ^２／ｇ）０．６部とをヘンシェルミキサーで混合し、現像剤粒子表面にシリカ微粉体を有する現像剤を調製した。なお、この現像剤粒子は、磁性体等の金属成分を含有していないため、表面に金属粒子が露出することはない。
【００３４】
一次帯電部材の構成と形状
一次帯電部材の構成は、一般の製品に組み込まれる部材と同様であるが（金属芯棒に低抵抗層、高抵抗層と表面層を塗布）、形状は中心角が６０度で半径が１５ｍｍの扇形柱とした。なお、一次帯電部材は扇の中心点で保持され、感光体に対して垂直方向及び感光体の回転方向と逆方向の２方向から軽く力が作用するようにバネが設置されている。なお、図１に帯電部材が扇柱状の場合の帯電装置と感光ドラムの組み合わせた例を掲げた。１は感光ドラム、２は帯電装置、３は感光層、４はアルミ基体、５はアース、６はドラム回転方向、７は金属芯棒、８は導電ゴム９は加圧バネ、１０は給電部を示す。
【００３５】
前記作成した電子写真感光体と前記作成した現像剤と前記構成形状の一次帯電部材を装着したレーザービームプリンター（ヒューレットパッカード社製ＬａｓｅｒＪｅｔ４）を直流電圧６５０Ｖ、交流電流５００μＡ、交流周波数２３０Ｈｚの一次帯電条件に設定した。
【００３６】
この本体を温度３０℃／湿度８０％の環境下で格子画像を連続して６０００枚出力した。そして連続出力の最後にベタ黒を出力し、白抜け画像欠陥の程度を評価し、また、連続出力の前後に横２ドット３スペースのレーザー照射パターンでハーフトーン画像を出力した。このように出力した画像のモアレと画像欠陥の程度を評価した。結果を表１に示す。
【００３７】
実施例２
実施例１における電子写真感光体と、実施例１における現像剤と、半径３０ｍｍで中心角が３０度である以外は実施例１における一次帯電部材と同様の一次帯電部材を組み合わせて、実施例１と同様に画像を出力し、評価した。結果を表１に示す。
【００３８】
比較例１
保護層を設けない他は、実施例１におけると同様にして作成された電子写真感光体（感光体表面での水との接触角は８０度）と現像剤粒子が磁性体粒子（Ｆｅ_３Ｏ_４）を３０ｗｔ％含有している他は、実施例１におけると同様にして作成された現像剤（現像剤粒子表面に磁性体微粒子が観察される）と半径６．２５ｍｍの一次帯電ローラーを感光体に従動させる構成を組み合わせて、実施例１と同様に画像を出力し、評価した。結果を表１に示す。
【００３９】
比較例２
保護層を設けない他は、実施例１におけると同様にして作成された感光体（感光体表面での水との接触角は８０度）と実施例１におけると同様にして作成された現像剤と実施例１におけると同様の一次帯電部材を組み合わせて、実施例１と同様に画像を出力し、評価した。結果を表１に示す。
【００４０】
比較例３
実施例１におけると同様にして作成された電子写真感光体と、現像剤粒子が磁性体粒子（Ｆｅ_３Ｏ_４）を３０ｗｔ％含有している他は実施例１における現像剤と同様にして作成された現像剤（現像剤粒子表面に磁性体微粒子が観察される）と、実施例１におけると同様の一次帯電部材を組み合わせて、実施例１と同様に画像を出力し、評価した。結果を表１に示す。
【００４１】
比較例４
実施例１におけると同様にして作成された電子写真感光体と、実施例１におけると同様にして作成された現像剤と、半径６．５ｍｍの一次帯電ローラーを感光体に従動させる構成を組み合わせて、実施例１と同様に画像を出力し、評価した。結果を表１に示す。
【００４２】
比較例５
実施例１におけると同様にして作成された電子写真感光体と、実施例１におけると同様にして作成された現像剤と、半径１３．５ｍｍで中心角が６０度である他は実施例１におけると同様の構成の一次帯電部材を組み合わせて、実施例１と同様に画像を出力し、評価した。結果を表１に示す。
【００４３】
比較例６
実施例１におけると同様にして作成された電子写真感光体と、実施例１におけると同様にして作成された現像剤と、半径１３．５ｍｍの一次帯電ローラーを感光体に従動させる構成を組み合わせて、実施例１と同様に画像を出力し、評価した。結果を表１に示す。
【００４４】
【表１】

【００４５】
【発明の効果】
本発明は、直流電圧に交流電圧を重畳した一次帯電部材を感光体に接触させて帯電する方式の電子写真装置において、低表面エネルギー感光体と従来より径が大きい一次帯電部材を組み合わせて用いることにより、ハーフトーン画像でのモアレをほぼ弊害なく防ぐことができ、また、このような系において感光体表面の傷や現像剤の感光体表面への固着が発生する場合でも、金属磁性体を含有しない現像剤を更に組み合わせることにより、これ等の問題を回避できるという顕著な効果を奏する。
【図面の簡単な説明】
【図１】帯電部材が扇柱状の場合の帯電装置と感光ドラムを組み合わせた装置の例である。
【符号の説明】
１感光ドラム
２帯電装置
３感光層
４アルミ基体
５アース
６ドラム回転方向
７金属芯棒
８導電ゴム
９加圧バネ
１０給電部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic apparatus having a primary charging system in which a primary charging member is brought into direct contact with an electrophotographic photosensitive member.
[0002]
[Prior art]
In the electrophotographic method, as shown in U.S. Pat. No. 2,297,691, the electric resistance changes in accordance with the amount of irradiation received during image exposure, and in the dark place, light comprising a support coated with an insulating material. A conductive material is used. Basic characteristics required for an electrophotographic photosensitive member using this photoconductive material are (1) that it can be charged to an appropriate potential in a dark place, (2) there is little potential dissipation in a dark place, (3 ) Quickly dissipate charges by light irradiation.
[0003]
Conventionally, as an electrophotographic photoreceptor, an inorganic photoreceptor having a photosensitive layer mainly composed of an inorganic photoconductive compound such as selenium, zinc oxide, cadmium sulfide and the like has been widely used. However, although these satisfy the conditions (1) to (3), they are not always satisfactory in terms of thermal stability, moisture resistance, durability and productivity. In order to overcome the disadvantages of inorganic photoreceptors, electrophotographic photoreceptors based on various organic photoconductive compounds as main components have been actively developed in recent years. For example, US Pat. No. 3,378,851 discloses a photoreceptor having a charge transport layer containing triallyl pyrazoline, and US Pat. No. 3,871,880 discloses a charge generation layer comprising a derivative of perylene pigment, and a condensate of 3-propylene and formaldehyde. A photoconductor comprising a charge transport layer comprising, is known.
[0004]
Further, the organic photoconductive compound can freely select the photosensitive wavelength range of the electrophotographic photosensitive member depending on the compound. For example, for azo pigments, Japanese Patent Application Laid-Open Nos. 61-272754 and 56-167759 are disclosed. Are disclosed that exhibit high sensitivity in the visible region, and the compounds disclosed in JP-A-57-19576 and JP-A-61-228453 are sensitive to the infrared region. Is shown. Among these materials, those showing sensitivity in the infrared region are used in laser beam printers and LED printers that have made remarkable progress in recent years, and the frequency of their demand is increasing.
[0005]
At present, the importance of electrophotographic printers such as laser beam printers and LED printers is high as output devices for computers, word processors and facsimiles. The electrophotographic photosensitive member mainly used in these printers uses an organic photoconductor, and the basic configuration of the photosensitive layer is an allowable range of material selection, durability, potential stability, sensitivity and response. There are many so-called functional separation types having a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material for various reasons such as properties.
[0006]
Further, as a method for primary charging the photosensitive drum, a method in which the primary charging member is brought into contact with the photosensitive member from the viewpoint of low energy / ecology is increasing. In this way, when a small diameter roller is used as a charging member and an AC voltage is superimposed on a DC voltage and is charged by being driven by the photoreceptor, the applied AC voltage becomes an uneven potential on the photoreceptor, and the cycle of the recess When the photosensitive member is irradiated with a laser at a close pitch, it appears as a remarkable shading in a halftone image. In order to prevent the generation of moire, it is necessary to increase the frequency of the AC voltage so that the unevenness of the unevenness of the primary charging potential on the photosensitive member is reduced. As a result, there is a problem that the charging sound exceeds the allowable range.
[0007]
In addition, when continuous output is performed in units of several thousand sheets using a developer (toner) containing a metal magnetic material in this system, the developer adheres to the photosensitive drum, and image input is performed in a digital printer. Since it is often performed by inversion, the black background portion of the image may be whitened. This is because the metal magnetic body exposed on the surface of the developer particles damages the surface of the photoreceptor through the primary charging member, and then the developer remaining on the surface of the photoreceptor is rubbed into the wound in a series of development processes. This is thought to be the cause.
[0008]
In order to solve these problems, approaches from various directions such as improvement of the surface physical properties of the photosensitive member, the constitution of the developer and the constitution of the primary charging member, and the improvement of the physical properties and the surface shape have been attempted. However, neither method has obtained sufficient results.
[0009]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a photosensitive member configuration and a primary charging member shape for eliminating moire images due to AC charging unevenness and charging sound exceeding an allowable range in a primary charging system in which a primary charging member is brought into contact with the photosensitive member. That is. In addition, it is to make it difficult for the developer to adhere to the photoreceptor so that white spots do not occur even when images are continuously output.
[0010]
[Means for Solving the Problems]
The present invention includes an electrophotographic photosensitive member having a protective layer having a contact angle of 90 ° or more with an aluminum cylinder having a diameter of 30 mm as a substrate and water formed on the outermost surface;
It has a fan-shaped primary charging member having a radius of 15 mm or more and a central angle of 30 degrees or more and 60 degrees or less that is in direct contact with the electrophotographic photosensitive member, and a voltage obtained by superimposing an AC voltage on a DC voltage is applied to the primary charging member. A charging device that primarily charges the electrophotographic photosensitive member by applying;
An electrophotographic apparatus having a developer having silica fine powder on the surface of developer particles not containing a metal component ,
The primary charging member is rotatable about a metal core rod passing through the center point of the fan, and is pressed against the electrophotographic photosensitive member by a pressure spring and the electron by another pressure spring. The electrophotographic apparatus is configured to be slidable on the electrophotographic photosensitive member by being pressed from the direction opposite to the rotation direction of the photographic photosensitive member .
[0011]
In the present invention, in order to solve the above-mentioned problem that is noticeable when a roller-shaped primary charging member is used, first, the radius of the cylindrical primary charging member is increased to several times the conventional diameter. Tried. Thereby, the discharge region at the time of primary charging is widened, and the potential difference between the uneven charging and unevenness at the time of alternating voltage alternating can be reduced. As a result, even if a laser having a pitch close to the concave / convex cycle is irradiated, the density becomes visible and does not appear in the halftone image. Therefore, it is not necessary to take a moire image countermeasure at the frequency of the AC voltage, and the charged sound does not exceed the allowable range. The potential difference between the uneven charging and unevenness decreases rapidly as the radius of the roller increases. However, since the radius gradually decreases from around 15 mm, almost the same effect can be expected if the radius is 15 mm or more.
[0012]
Further, if the radius of the roller-shaped primary charging member is greatly increased, it is disadvantageous in terms of securing the installation space and the material cost. Therefore, in the present invention, a fan-column-shaped charging member is used. In this case, since the photosensitive member cannot be driven like a roller, the photosensitive member is slid on the charging member. Therefore, using a spring or the like, a force opposite to the rotation of the photosensitive drum is applied to the charging member to slide on the photosensitive member.
[0013]
When the shape of the primary charging member is other than a roller or a fan column, the distance from the support point of the primary charging member to the contact point with the photoconductor changes when the primary charging member is driven or slid on the photoconductor, This is not preferable because the mechanical load at the contact point increases and adversely affects stable charging.
[0014]
The photoreceptor has a surface layer in a low surface energy state to improve the transfer efficiency of the developer and the sliding property of the primary charging member. For example, by using a method such as blending a fluororesin or silicone resin with a heat or photocurable resin, or incorporating a fluorine-containing or silicone unit into the curable resin itself, water serving as an index of surface energy can be obtained. A thin protective layer is provided so that the contact angle is 90 degrees or more at the initial stage and during use. When the contact angle with water is less than 90 degrees, adverse effects such as a decrease in the transfer efficiency of the developer and a decrease in the slipping property of the primary charging member become prominent.
[0015]
The developer eliminates the high hardness component on the surface of the developer particles by not using the magnetic substance that is a component of the developer used in the one-component development system, that is, metal oxide fine particles (if possible, Alternatively, the magnetic substance may be present only within the developer particles. As a result, even if the developer that has not been removed in the photosensitive member cleaning process enters between the primary charging member and the photosensitive member, it functions as a lubricant and does not hurt even if the slidability of both is assisted.
[0016]
If a developer containing a small amount of a magnetic material is combined with a low-life photoconductor, the photoconductor may reach the end of its life before being damaged. Such a developer is combined with a long-life photoconductor. In this case, the longer the life is, the greater the possibility of scratches and the limited versatility. Therefore, it is preferable that metal particles such as a magnetic material are not contained in the developer particles .
[0017]
In the above configuration, the transfer efficiency of the developer from the photoconductor to the copy paper is high, the developer remaining on the photoconductor is small after cleaning the photoconductor, and the metal particles are not exposed on the surface of the developer particles. Therefore, it is difficult to damage the photoconductor, and white spots in a black background image caused by the fixing of the developer on the photoconductor are extremely difficult to occur.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Preparation of electrophotographic photosensitive member A coating solution prepared by dispersing a mixed solution of a phosphorus-containing tin oxide filler, a resol type phenolic resin and 2-methoxy-1-propanol with a ball mill is applied onto an aluminum cylinder. Next, a coating prepared by dissolving copolymer nylon and modified nylon in a mixed solution of methanol and 1-butanol is applied on the intermediate layer to form a barrier layer, and then titanyloxyphthalocyanine After a mixture of pigment, polyvinyl butyral, and cyclohexanone is dispersed in a sand mill, a charge generation layer coating prepared by adding ethyl acetate is applied onto the barrier layer to form a charge generation layer, and then a charge transport material The triarylamine compound and polycarbonate are dissolved in a chlorobenzene and dichloromethane mixture to prepare. The produced charge transport layer coating is applied on the charge generation layer to form the charge transport layer.
[0019]
Next, after milling the antimony-containing tin oxide fine particles, (3,3,3-trifluoropropyl) trimethoxysilane, and ethanol, the solution is filtered, washed with ethanol, and then the fine particles are surface-treated by drying. Acrylic curable monomer as a resin, 2-methylthioxanthone as a photopolymerization initiator, antimony-containing tin oxide fine particles subjected to the above surface treatment and toluene are mixed, dispersed in a sand mill, and ethylene tetrafluoride resin particles in a dispersion. Are further dispersed with a sand mill to prepare a coating for the protective layer. This paint is applied onto the charge transport layer to form a film, dried, and then irradiated with ultraviolet light with a high-pressure mercury lamp to form a protective layer to produce an electrophotographic photoreceptor. The contact angle of the electrophotographic photosensitive member surface with water has a predetermined angle in the present invention.
[0020]
Preparation of developer Styrene-butyl acrylate-divinylbenzene copolymer, low molecular weight ethylene-propylene copolymer, carbon black and chromium salicylate complex were mixed well in a blender and then kneaded in a twin-screw kneading extruder. The kneaded product is cooled and coarsely pulverized, and then finely pulverized using a fine pulverizer using a jet stream, and the obtained finely pulverized powder is classified with a fixed wall type air classifier to produce classified powder. The resulting classified powder with a multi-division classifier utilizing the Coanda effect ultrafine and coarse powder, to produce simultaneously strictly powder classifying removed to negatively chargeable insulating black color developer particles. The resulting black powder product of a developing agent particles and the negatively chargeable hydrophobic dry-process silica fine powder were mixed to prepare a developer having a silica fine powder to the developer particle surfaces. Since the developer particles do not contain a metal component such as a magnetic material, the metal particles are not exposed on the surface.
[0021]
Configuration and shape of primary charging member The configuration of the primary charging member is the same as that of a member incorporated in a general product. For example, a fan-shaped column having a radius of 15 mm is used. The primary charging member is held at the center point of the fan, and a spring is installed so that a light force is applied to the photosensitive member in two directions, ie, the vertical direction and the direction opposite to the rotational direction of the photosensitive member.
[0022]
The produced electrophotographic photosensitive member, the produced developer, and the primary charging member having the configuration shape are mounted on, for example, a laser beam printer to form the electrophotographic apparatus of the present invention.
[0023]
【Example】
Example 1
Preparation of electrophotographic photoreceptor 140 parts by weight of a phosphorus-containing tin oxide (powder resistance: 25 Ωcm) and a resol type phenol resin (trade name: PRIOFEN J-325, manufactured by Dainippon Ink & Chemicals, Inc., solid content: 70 %) A mixed solution of 70 parts by weight and 100 parts by weight of 2-methoxy-1-propanol was dispersed by a ball mill for about 3 hours, and the prepared paint was dip-coated on an aluminum cylinder having an outer diameter of 30 mm and a length of 254 mm. Heat curing was performed at 140 ° C. for 30 minutes to form an intermediate layer having a thickness of 10 μm.
[0024]
Next, 12.5 parts by weight of copolymerized nylon (trade name: Amilan CM8000, manufactured by Toray Industries, Inc. ) and 37.5 parts by weight of knitted nylon (trade name: Resin EF30T- P) were added to 560 parts by weight of methanol and 280 parts by weight of 1-butanol. Part of the mixed solution was dissolved and applied to the intermediate layer by dip coating, followed by drying at 100 ° C. for 10 minutes to form a 1 μm thick barrier layer.
[0025]
Next, a mixed liquid consisting of 18 parts by weight of titanyloxyphthalocyanine pigment, 15 parts by weight of polyvinyl butyral (trade name BX-1, manufactured by Sekisui Chemical Co., Ltd.) and 520 parts by weight of cyclohexanone was dispersed in a sand mill for 8 hours. A charge generation layer coating material was prepared by adding 480 parts by weight of ethyl, dip-coated on the barrier layer, and heated and dried at 90 ° C. for 10 minutes to form a charge generation layer having a thickness of about 0.2 μm.
[0026]
Next, 70 parts by weight of a triarylamine compound having the following structural formula:
[Outside 1]

And 100 parts by weight of polycarbonate (trade name Iupilon Z-200, manufactured by Mitsubishi Gas Chemical Co., Ltd.) are dissolved in 500 parts by weight of a chlorobenzene / dichloromethane mixed solution, and the prepared charge transport layer coating material is dip-coated on the charge generation layer. And dried at 100 ° C. for 30 minutes to form a charge transport layer having a thickness of 20 μm.
[0028]
Subsequently, 100 parts by weight of antimony-containing tin oxide fine particles having an average particle diameter of 0.02 μm (trade name T-1, manufactured by Mitsubishi Materials Corporation), (3,3,3-trifluoropropyl) trimethoxysilane (Shin-Etsu Chemical ( Co., Ltd.) 30 parts, 300 parts by weight of 95% ethanol 5% aqueous solution was milled for 1 hour with a milling device, then the solution was filtered, washed with ethanol, and dried (heat treatment at 120 ° C. for 1 hour) to obtain fine particle surfaces. Processed.
[0029]
Next, 25 parts of an acrylic curable monomer represented by the following structural formula as a binder resin,
[0030]
[Outside 2]

0.1 part by weight of 2-methylthioxanthone as a photopolymerization initiator, 35 parts of antimony-containing tin oxide fine particles subjected to the above surface treatment, and 300 parts of toluene are mixed and dispersed in a sand mill for 96 hours. 25 parts of fluorinated ethylene resin particles (trade name: Lubron L-2, manufactured by Daikin Industries, Ltd.) were mixed and further dispersed for 8 hours by a sand mill to prepare a coating material for a protective layer. This paint is formed on the charge transport layer by spray coating, dried, and then irradiated with ultraviolet light at a light intensity of 800 mW / ° C. m ² for 15 seconds with a high-pressure mercury lamp to form a protective layer having a thickness of 5 μm. A photoconductor was prepared. The contact angle of the surface of this electrophotographic photosensitive member with water was measured and found to be 95 degrees.
[0031]
Preparation of developer Styrene-butyl acrylate-divinylbenzene copolymer (monomer weight ratio 80: 19.5: 0.5, weight average molecular weight (Mw) 300,000) 100 parts by weight, low molecular weight ethylene-propylene copolymer 3 Part by weight, 3 parts by weight of carbon black and 2 parts by weight of chromium salicylate complex were mixed well with a blender, and then kneaded in a twin-screw kneading extruder set at 150 ° C.
[0032]
The obtained kneaded product is cooled, coarsely pulverized by a cutter mill, finely pulverized using a fine pulverizer using a jet stream, and the obtained finely pulverized powder is classified by a fixed wall type air classifier. A classified powder was produced. Furthermore, the resulting classified powder is subjected to a multi-division classifier using the Coanda effect (elbow jet classifier, manufactured by Nittetsu Mining Co., Ltd.), and at the same time, the fine powder and coarse powder are strictly classified and removed at the same time to provide negatively charged insulation. to obtain a powder of sexual black color developer particles.
[0033]
Powder 100 parts of developer particles of the resulting black and negatively chargeable hydrophobic dry-process silica fine powder (the BET specific surface area 300m ² /g)0.6 parts were mixed in a Henschel mixer, silica developer particle surface A developer having a fine powder was prepared. Since the developer particles do not contain a metal component such as a magnetic material, the metal particles are not exposed on the surface.
[0034]
Configuration and shape of the primary charging member The configuration of the primary charging member is the same as that of a member incorporated in a general product (a metal core rod is coated with a low resistance layer, a high resistance layer and a surface layer), but the shape has a central angle. A sector column with a radius of 15 mm and a radius of 60 degrees was used. The primary charging member is held at the center point of the fan, and a spring is installed so that a light force is applied to the photosensitive member in two directions, ie, the vertical direction and the direction opposite to the rotational direction of the photosensitive member. FIG. 1 shows an example in which a charging device and a photosensitive drum are combined when the charging member is in the shape of a fan column. 1 is a photosensitive drum, 2 is a charging device, 3 is a photosensitive layer, 4 is an aluminum substrate, 5 is ground, 6 is a drum rotation direction, 7 is a metal core, 8 is a conductive rubber, 9 is a pressure spring, and 10 is a power supply unit. Indicates.
[0035]
A laser beam printer (Laser Jet4 manufactured by Hewlett Packard) equipped with the created electrophotographic photosensitive member, the created developer, and the primary charging member having the above-described configuration is subjected to primary charging with a DC voltage of 650 V, an AC current of 500 μA, and an AC frequency of 230 Hz. Set to conditions.
[0036]
6000 grid images were continuously output from the main body in an environment of a temperature of 30 ° C. and a humidity of 80%. Then, solid black was output at the end of continuous output, the degree of blank image defects was evaluated, and a halftone image was output with a laser irradiation pattern of 2 horizontal dots and 3 spaces before and after continuous output. The degree of moire and image defects in the output image was evaluated. The results are shown in Table 1.
[0037]
Example 2
Example 1 is combined with the electrophotographic photosensitive member in Example 1, the developer in Example 1, and the primary charging member similar to the primary charging member in Example 1 except that the radius is 30 mm and the central angle is 30 degrees. Images were output and evaluated in the same manner as described above. The results are shown in Table 1.
[0038]
Comparative Example 1
The electrophotographic photosensitive member (contact angle with water on the surface of the photosensitive member is 80 degrees) prepared in the same manner as in Example 1 except that the protective layer is not provided, and the developer particles are magnetic particles (Fe ₃ O ₄ ) Except that 30 wt% is contained, the developer prepared in the same manner as in Example 1 (magnetic particles are observed on the surface of the developer particles) and a primary charging roller having a radius of 6.25 mm are exposed to light. An image was output and evaluated in the same manner as in Example 1 by combining the configurations to follow the body. The results are shown in Table 1.
[0039]
Comparative Example 2
A developer prepared in the same manner as in Example 1 except that a protective layer is not provided, and a photoreceptor prepared in the same manner as in Example 1 (contact angle with water on the surface of the photoreceptor is 80 degrees). The same primary charging member as in Example 1 was combined, and an image was output and evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0040]
Comparative Example 3
An electronic photograph feeling light body that is produced in the same manner as in Example 1, the same except that the developer particles containing 30 wt% of the magnetic particles (Fe 3 _O ₄₎ is a developer in the actual Example 1 An image was output and evaluated in the same manner as in Example 1 by combining the developer prepared in this manner (magnetic particles are observed on the developer particle surface) and the primary charging member similar to that in Example 1. . The results are shown in Table 1.
[0041]
Comparative Example 4
By combining the electrophotographic photosensitive member was produced in the same manner as in Example 1, a developer was prepared in the same manner as in Example 1, a configuration in which the driven primary charging roller radius 6.5mm on the photoreceptor Images were output and evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0042]
Comparative Example 5
An electrophotographic photosensitive member which is produced in the same manner as in Example 1, Example and the developer was produced in the same manner as in 1, except central angle at a radius 13.5mm is 60 degrees the actual Example 1 An image was output and evaluated in the same manner as in Example 1 by combining primary charging members having the same configuration as in Example 1. The results are shown in Table 1.
[0043]
Comparative Example 6
By combining the electrophotographic photosensitive member was produced in the same manner as in Example 1, a developer was prepared in the same manner as in Example 1, a configuration in which the driven primary charging roller radius 13.5mm on the photoreceptor Images were output and evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0044]
[Table 1]

[0045]
【The invention's effect】
The present invention uses a combination of a low surface energy photosensitive member and a primary charging member having a diameter larger than that of a conventional one in an electrophotographic apparatus in which a primary charging member in which an alternating voltage is superimposed on a direct current voltage is brought into contact with the photosensitive member. Therefore, moire in halftone images can be prevented almost without harm, and even in such a system, even when scratches on the surface of the photoconductor or fixing of the developer to the photoconductor surface occurs, a metal magnetic material is contained. By further combining the developers that do not, it is possible to avoid these problems.
[Brief description of the drawings]
FIG. 1 is an example of an apparatus in which a charging device and a photosensitive drum are combined when a charging member has a fan-column shape.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging device 3 Photosensitive layer 4 Aluminum base | substrate 5 Ground 6 Drum rotation direction 7 Metal core stick 8 Conductive rubber 9 Pressure spring 10 Power supply part

Claims

基体としての直径３０ｍｍのアルミニウムシリンダーおよび最表面に形成された水との接触角が９０度以上である保護層を有する電子写真感光体と、
該電子写真感光体に直接接触させた半径が１５ｍｍ以上で中心角が３０度以上６０度以下の扇柱状の一次帯電部材を有し、該一次帯電部材に直流電圧に交流電圧を重畳した電圧を印加することによって該電子写真感光体を一次帯電させる帯電装置と、
金属成分を含有しない現像剤粒子の表面にシリカ微粉体を有させてなる現像剤と
を有する電子写真装置であって、
該一次帯電部材は、扇の中心点を通る金属芯棒を中心として回動自在であり、かつ、加圧バネによって該電子写真感光体に対して押圧されるとともに別の加圧バネによって該電子写真感光体の回転方向の逆方向から押圧されることにより、該電子写真感光体上を摺動可能とされている電子写真装置。An electrophotographic photosensitive member having a protective layer having a contact angle of 90 ° or more with an aluminum cylinder having a diameter of 30 mm as a substrate and water formed on the outermost surface;
It has a fan-shaped primary charging member having a radius of 15 mm or more and a central angle of 30 degrees or more and 60 degrees or less that is in direct contact with the electrophotographic photosensitive member, and a voltage obtained by superimposing an AC voltage on a DC voltage is applied to the primary charging member. A charging device that primarily charges the electrophotographic photosensitive member by applying;
An electrophotographic apparatus having a developer having silica fine powder on the surface of developer particles not containing a metal component ,
The primary charging member is rotatable about a metal core rod passing through the center point of the fan, and is pressed against the electrophotographic photosensitive member by a pressure spring and the electron by another pressure spring. An electrophotographic apparatus which is slidable on the electrophotographic photosensitive member by being pressed from a direction opposite to the rotation direction of the photographic photosensitive member .