JP3638500B2 - Single layer type electrophotographic photosensitive member and image forming apparatus using the same - Google Patents

Description

（一般式（１）中、Ｒ¹およびＲ³は同一または異なって、置換基を有してもよいアルキル基、置換基を有してもよいアリール基、置換基を有してもよい、アラルキル基またはアルコキシ基を示し、Ｒ²およびＲ⁴は同一または異なって、水素原子、置換基を有してもよい、アルキル基またはアルコキシ基を示す。
但し、Ｒ²およびＲ⁴の置換位置がパラ位の場合、Ｒ²およびＲ⁴は水素原子である。）
【００１７】
【発明の作用】
請求項１記載のように、露光波長７８０ｎｍ、露光エネルギー１．０μＪ／ｃｍ²で測定した、プラス極性とマイナス極性の感度の絶対値差が５００Ｖ以下である単層型電子写真感光体を使用すると、露光メモリー及び転写メモリーが非常に小さい。これは、プラス極性とマイナス極性の感度の絶対値差が小さいほど、感光層中で発生したホールと電子の輸送バランスが良好となりメモリーが小さくなるためと考えられる。
【００１８】
請求項２記載のように、上記単層型電子写真感光体において、移動度の大きな電子輸送剤の材料設計が困難で、電子輸送材料の移動度がホール輸送材料の移動度に比較して小さいこと、画像形成装置内でのオゾンの発生が極めて少ないこと等の理由により、プラス極性感度の絶対値がマイナス極性感度の絶対値より小さい、すなわち正帯電型が主流となっている。
【００１９】
請求項１、３記載のように、正帯電単層型電子写真感光体において、ホール輸送剤として、一般式（１）で示される化合物を含有することが好ましく、電子輸送剤として、一般式（２）、（３）、（４）または（５）で示される化合物を、少なくとも１種以上含有することが好ましい。
これは、ホール輸送能力または電子輸送能力の高い前記化合物を使用することにより、正極性及び負極性に対する感度が良好となり、メモリー低減に非常に効果的なためである。
【００２０】
請求項４記載のように、除電工程を有さない反転現像式デジタル画像形成装置に使用しても、本発明の単層型電子写真感光体はメモリーが非常に小さいため、メモリー画像の発生は無い。
【００２１】
【発明の実施形態】
本発明の単層型電子写真感光体に用いられる種々の材料について詳細に説明する。
【００２２】
＜電荷発生剤＞デジタル画像形成装置において、レーザを光源とする場合、小型・安価・簡便さ等の点から、多くは半導体レーザ、ＬＥＤが使用される。従って、少なくとも７００〜８５０ｎｍの波長領域に感度を有する有機感光体が必要である。前記要求を満たす、有機感光体に使用される電荷発生剤として、例えば、多環キノン化合物、ピリリウム化合物、スクエアリウム化合物、フタロシアニン系化合物、アゾ化合物等が提案または実用化されているが、本発明の単層型電子写真感光体には、種々のフタロシアニン系化合物が使用される。
【００２３】
一般的にフタロシニン系化合物には、中心金属を有さないメタルフリーフタロシニン（ＣＧＭ−1）と、近年研究開発が活発に行われているチタニルフタロシアニン（ＣＧＭ−２）、及び、アルミニウムフタロシアニン、バナジウムフタロシニン、カドミウムフタロシアニン、アンチモンフタロシニン、クロムフタロシニン、銅４−フタロシニン、ゲルマニウムフタロシニン、鉄フタロシニン、クロロアルミニウムフタロシニン、クロロインジウムフタロシアニン、クロロガリウムフタロシニン、マグネシウムフタロシニン、ジアルキルフタロシニン、テトラメチルフタロシニン、テトラフェニルフタロシニン等の中心金属を有する金属フタロシアニンとがあり、またα型、β型、γ型、δ型、ε型、σ型、ｘ型、τ型等の結晶型のものがある。
【００２４】
＜ＣＧＭ−１＞
【化６】

【００２５】
＜ＣＧＭ−２＞
【化７】

【００２６】
上記フタロシアニン系化合物は、バインダー樹脂重量に対して０．０１〜５０ｗｔ％、更には０．１〜３０ｗｔ％含有することが好ましい。
【００２７】
＜ホール輸送剤＞本発明の単層型電子写真感光体に用いられるホール輸送剤としては、特に一般式（１）で示されるスチルベン系化合物が使用される。
また、ホール輸送剤として、該スチルベン系化合物は、単独、または少なくとも１種以上含有すればよい。
すなわち該スチルベン系化合物と共に、種々のホール輸送剤を含有していてもよい。
【００２８】
種々のホール輸送剤としては、例えば２，５−ジ（４−メチルアミノフェニル）−１，３，４−オキサジアゾール等のオキサジアゾール系の化合物、９−４（−ジエチルアミノスチリル）アントラセン等のスチリル系化合物、ポリビニルカルバゾール等のカルバゾール系化合物、有機ポリシラン化合物、１−フェニル−３（p−ジメチルアミノフェニル）ピラゾリン等のピラゾリン系化合物、ヒドラゾン系化合物、トリフェニルアミン系化合物、インドール系化合物、オキサゾール系化合物、イソオキサゾール系化合物、チアゾール系化合物、チアジアゾール系化合物、イミダゾール系化合物、ピラゾール系化合物、トリアゾール系化合物等の含窒素環式化合物等があげられる。
【００２９】
ホール輸送剤の含有量は、バインダー樹脂重量に対して５〜５００ｗｔ％、更には２５〜２００ｗｔ％が好ましい。
【００３０】
＜電子輸送剤＞本発明の単層型電子写真感光体に用いられる電子輸送剤としては、特に一般式（２）、（３）、（４）または（５）で示されるキノン系化合物が好適に使用される。また、電子輸送剤として、該キノン系化合物を使用する場合、単独、または少なくとも１種以上含有すればよい。すなわち該キノン系化合物と共に、種々の電子輸送剤を含有していてもよい。
【００３１】
種々の電子輸送剤としては、例えばピレン系化合物、カルバゾール系化合物、ヒドラゾン系化合物、Ｎ，Ｎ−ジアルキルアニリン系化合物、ジフェニルアミン系化合物、トリフェニルアミン系化合物、トリフェニルメタン系化合物、テトラシアノエチル、テトラシアノキノジメタン、クロルアニル、ブロモアニル、２,４,７−トリニトロ−９−フルオレノン、２,４,５,７−テトラニトロ−９−フルオレノン、２,４,７−トリニトロ−９−ジシアノメチレンフルオレノン、２,４,５,７−テトラニトロキサントン、２,４,８−トリニトロチオキサントン等の電子吸引性物質、あるいはこれらの電子吸引性物質を高分子化したもの等があげられる。
【００３２】
電子輸送剤の含有量は、バインダー樹脂重量に対して５〜１００ｗｔ％、更には１０〜８０ｗｔ％が好ましい。
【００３３】
＜バインダー樹脂＞前記各成分を分散させるためのバインダー樹脂は、従来から感光層に使用されている種々の樹脂を使用することができる。
【００３４】
例えば、スチレン−ブタジエン共重合体、スチレン−アクリロニトリル共重合体、スチレン−マレイン酸共重合体、アクリル共重合体、スチレン−アクリル酸共重合体、ポリエチレン、エチレン−酢酸ビニル共重合体、塩素化ポリエチレン、ポリ塩化ビニル、ポリプロピレン、アイオノマー、塩化ビニル−酢酸ビニル共重合体、ポリエステル、アルキド樹脂、ポリアミド、ポリウレタン、ポリカーボネート、ポリアリレート、ポリスルホン、ジアリルフタレート樹脂、ケトン樹脂、ポリビニルブチラール樹脂、ポリエーテル樹脂等の熱可塑性樹脂、シリコーン樹脂、エポキシ樹脂、フェノール樹脂、尿素樹脂、メラミン樹脂、その他架橋性の熱硬化性樹脂、エポキシアクリレート、ウレタン−アクリレート等の光硬化型樹脂等の樹脂が使用可能である。これらのバインダー樹脂は単独または二種類以上をブレンドして使用できる。
【００３５】
特に好適な樹脂は、帝人化成（株）社製パンライト、三菱瓦斯化学（株）社製ＰＣＺ等のビスフェノールＺ型モノマーとホスゲンとから誘導されるビスフェノールＺ型ポリカーボネートである。
【００３６】
前記例のバインダー樹脂の重量平均分子量は５，０００〜２００，０００、更には１５，０００〜１００，０００が好ましい。
【００３７】
本発明の単層型電子写真感光体には、前記各成分のほかに、電子写真特性に悪影響を与えない範囲で、従来公知の種々の添加剤、例えば、酸化防止剤、ラジカル補足剤、一重項クエンチャー、紫外線吸収剤等の劣化防止剤、軟化剤、可塑剤、表面改質剤、増量剤、増粘剤、分散安定剤、ワックス、アクセプター、ドナー等を配合することができる。また、感光層の感度を向上させるために、例えば、テルフェニル、ハロナフトナフトキノン類、アセナフチレン等の公知の増感剤を電荷発生剤と併用してもよい。
【００３８】
本発明の単層型電子写真感光体においては、導電性基体と感光層との間に、感光体の特性を阻害しない範囲でバリア層が形成されていてもよい。
【００３９】
本発明の単層型電子写真感光体の膜厚は５〜５０μｍ、特に１５〜３５μｍが好ましい。
【００４０】
単層型電子写真感光体は、導電性基体上に単一の感光層を設けたものである。この感光層は、電荷発生剤、ホール輸送剤、電子輸送剤、バインダー樹脂等を適当な溶媒に溶解または分散させ、得られた塗布液を導電性基体上に塗布し、乾燥させることで形成される。
【００４１】
上記感光層が形成される導電性基体としては、導電性を有する種々の材料を使用することができ、例えば、鉄、アルミニウム、銅、スズ、白金、銀、バナジウム、モリブデン、クロム、カドミウム、チタン、ニッケル、パラジウム、インジウム、ステンレス鋼、真鍮等の金属単体や、上記金属が蒸着またはラミネートされたプラスチック材料、ヨウ化アルミニウム、酸化スズ、酸化インジウム等で被覆されたガラス等があげられる。
【００４２】
導電性基体の形状は、使用する画像形成装置の構造に合わせて、シート状、ドラム状等のいずれであってもよく、基体自体が導電性を有するか、あるいは基体の表面が導電性を有していればよい。また、導電性基体は、使用に際して十分な機械的強度を有するものが好ましい。
【００４３】
前記感光層を塗布の方法により形成する場合には、前記例示のホール輸送剤、電荷発生剤、電子受容体、結着樹脂等を適当な溶剤とともに、公知の方法、例えば、ロールミル、ボールミル、アトライタ、ペイントシェーカー、超音波分散機等を用いて分散混合して分散液を調整し、これを公知の手段により塗布して乾燥させればよい。
【００４４】
上記分散液を作製するための溶剤としては、種々の有機溶剤が使用可能であり、例えば、メタノール、エタノール、イソプロパノール、ブタノール等のアルコール類、n−ヘキサン、オクタン、シクロヘキサン等の脂肪族系炭化水素、ベンゼン、トルエン、キシレン等の芳香族系炭化水素、ジクロロメタン、ジクロロエタン、クロロホルム、四塩化炭素、クロロベンゼン等のハロゲン化炭化水素、ジメチルエーテル、ジエチルエーテル、テトラヒドロフラン、エチレングリコールジメチルエーテル、ジエチレングリコールジメチルエーテル等のエーテル類、アセトン、メチルエチルケトン、シクロヘキサノン等のケトン類、酢酸エチル、酢酸メチル等のエステル類、ジメチルホルムアルデヒド、ジメチルホルムアミド、ジメチルスルホキシド等があげられる。これらの溶剤は単独で、または２種以上混合して用いられる。
【００４５】
更に、ホール輸送剤、電荷発生剤、電子受容体の分散性、感光層表面の平滑性を良くするために、界面活性剤、レベリング剤等を使用してもよい。
【００４６】
一方、本発明の画像形成装置は、請求項１記載の単層型電子写真感光体を使用し、該感光体の進行方向に沿って、少なくとも主帯電工程、露光工程、現像工程、転写工程とを備え、前記転写工程で印加される電圧は、帯電工程で印加される電圧とは逆極性であることを特徴とする除電工程を有さない反転現像式デジタル画像形成装置であり、デジタル複写機、ファクシミリ、レーザービームプリンタ等が挙げられる。
【００４７】
本発明の単層型電子写真感光体は、転写・露光メモリーが非常に小さいため、除電工程を有さない前記画像形成装置に使用してもメモリー画像が発生することはない。
【００４８】
また前述のように、画像形成装置の小型化やイニシャルコストダウン等のために、クリーニング工程は除電工程と同様に省略される場合がある。
【００４９】
【実施例】
以下、実施例、比較例をあげて本発明を説明する。なお、以下の実施形態は本発明を具体化した一例であって、本発明の技術的範囲を限定するものではない。
【００５０】
＜実施例１〜８＞電荷発生剤としてＸ型無金属フタロシアニン（ＣＧＭ−１）２．５重量部、一般式（１）で示されるホール輸送剤（ＨＴＭ−１）６５重量部、一般式（２）、（３）、（４）、（５）で示される電子輸送剤（ＥＴＭ−１〜ＥＴＭ−８）３５重量部、及びバインダー樹脂として重量平均分子量３０，０００のｂｉｓ−Ｚ型ポリカーボネート樹脂１００重量部、及びテトラヒドロフラン７５０重量部を、ボールミル中で２８時間分散あるいは溶解させ、単層型感光層用塗布液を調合した。そして、この塗布液を、支持体としてのアルミニウム素管上にディップコート法にて塗布し、１３０℃、３０分間の熱風乾燥を行い、膜厚２２μｍの単一感光層を有する単層型感光体を作製した。
【００５１】
＜比較例１〜３＞電子輸送剤としてＥＴＭ−９〜ＥＴＭ−１１を使用した以外は実施例１〜７と同様に単層型感光体を作製した。
【００５２】
＜ＨＴＭ−１＞
【化８】

【００５３】
＜ＥＴＭ−１＞
【化９】

【００５４】
＜ＥＴＭ−２＞
【化１０】

【００５５】
＜ＥＴＭ−３＞
【化１１】

【００５６】
＜ＥＴＭ−４＞
【化１２】

【００５７】
＜ＥＴＭ−５＞
【化１３】

【００５８】
＜ＥＴＭ−６＞
【化１４】

【００５９】
＜ＥＴＭ−７＞
【化１５】

【００６０】
＜ＥＴＭ−８＞
【化１６】

【００６１】
＜ＥＴＭ−９＞
【化１７】

【００６２】
＜ＥＴＭ−１０＞
【化１８】

【００６３】
＜ＥＴＭ−１１＞
【化１９】

【００６４】
＜実施例９〜１６＞電荷発生剤としてチタニルフタロシアニン（ＣＧＭ−２）を使用した以外は、実施例１〜８と同様に単層型感光体を作製した。
【００６５】
＜比較例４〜６＞電荷発生剤としてチタニルフタロシアニン（ＣＧＭ−２）を使用した以外は、比較例１〜３と同様に単層型感光体を作製した。
【００６６】
上記各実施例、比較例の単層型電子写真感光体について、下記の各特性を評価した。評価結果を表１、２に示した。また、これらのデータのうち、転写メモリー電位、露光メモリー電位と、プラス極性感度とマイナス極性感度の絶対値差との関係を図１に示した。
【００６７】
＜プラス極性感度評価＞ジェンテック（ＧＥＮＴＥＣ）社製のドラム感度試験機（商品名ジェンテックシンシア３０Ｍ）を用いて、各実施例、比較例の電子写真感光体に印加電圧を加えて、その表面を＋８００Ｖに帯電させた。次に、上記試験機の露光光源であるハロゲンランプの白色光からバンドパスフィルターを用いて取り出した波長７８０ｎｍの単色光（半値幅２０ｎｍ，光強度２０μＷ）を、上記帯電状態の感光体の表面に露光（露光時間１００ｍｓｅｃ）した（露光エネルギーは１．０μＪ／ｃｍ²）。そして、露光開始時点から５００ｍｓｅｃ経過した時点での表面電位を露光後電位Ｖ_LP（Ｖ）として測定した。すなわち、露光後電位が小さいほど感光体は高感度である。
【００６８】
＜マイナス極性感度評価＞ジェンテック（ＧＥＮＴＥＣ）社製のドラム感度試験機（商品名ジェンテックシンシア３０Ｍ）を用いて、各実施例、比較例の電子写真感光体に印加電圧を加えて、その表面を−８００Ｖに帯電させた以外は、前記＜プラス極性感度評価＞と同様に、露光開始時点から５００ｍｓｅｃ経過した時点での表面電位を露光後電位Ｖ_LN（Ｖ）として測定した。
【００６９】
＜転写メモリー電位評価＞除電ランプを取除いた京セラミタ（株）社製マルチファンクションプリンタＡｎｔｉｃｏ４０に、各実施例、比較例の電子写真感光体を搭載し、転写バイアスを印加しない時の表面電位、及び転写バイアス印加時の次帯電工程後の表面電位を測定し、その差異を転写メモリー電位とした。転写メモリー電位については、転写メモリー画像の発生しない４５Ｖ以下を可、４５Ｖより大きい場合を不可とした。
【００７０】
＜露光メモリー電位評価＞除電ランプを取除いた京セラミタ（株）社製マルチファンクションプリンタＡｎｔｉｃｏ４０に、各実施例、比較例の電子写真感光体を搭載し、未露光時の表面電位、及び露光時の次帯電工程後の表面電位を測定し、その差異を露光メモリー電位とした。露光メモリー電位については、転写メモリー電位と同様、露光メモリー画像の発生しない４５Ｖ以下を可、４５Ｖより大きい場合を不可とした。
【００７１】
＜転写メモリー画像評価＞除電ランプを取除いた京セラミタ（株）社製マルチファンクションプリンタＡｎｔｉｃｏ４０に、各実施例、比較例の電子写真感光体を搭載し、印写試験を実施し、転写メモリー画像が発生しているか否かを目視により判断した。転写メモリー画像とは、図２に示すように、前面グレー（マンセル値：Ｎ＝６．５）原稿を使用し印写試験を実施した場合、転写バイアスが印加された部分の感光体表面電位の低下により、ドラム長手方向に黒横帯が発生した画像を示す。
【００７２】
＜露光メモリー画像評価＞除電ランプを取除いた京セラミタ（株）社製マルチファンクションプリンタＡｎｔｉｃｏ４０に、各実施例、比較例の電子写真感光体を搭載し、印写試験を実施し、露光メモリー画像が発生しているか否かを目視により判断した。露光メモリー画像とは、図３に示すような原稿を使用し印写試験を実施した場合、強い露光部分（黒ベタ部）の感光体表面電位の低下により、露光部分のゴースト画像がグレー部に発生した画像を示す。
【００７３】
【表１】

【００７４】
【表２】

【００７５】
表１、２、図１より、プラス極性とマイナス極性の感度の絶対値差が５００Ｖ以下である場合、転写メモリー電位及び露光メモリー電位の両方が４５Ｖ以下となり、メモリー画像が発生しないことが明らかとなった。
【００７６】
【発明の効果】
本発明の単層型電子写真感光体は、露光メモリー及び転写メモリーが非常に小さいため、除電工程を有さない反転現像方式のデジタル画像形成装置に使用してもメモリー画像が発生しない。
【００７７】
【図面の簡単な説明】
【図１】各実施例、比較例の単層型電子写真感光体の転写メモリー電位・露光メモリー電位と、プラス極性とマイナス極性の感度の絶対値差との関係を示すグラフである。
【図２】転写メモリー画像評価用原稿と転写メモリー画像を示す図である。
【図３】露光メモリー画像評価用原稿と露光メモリー画像を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a single-layer type electrophotographic photosensitive member used in a digital image forming apparatus such as an electrophotographic copying machine, a facsimile, a laser beam printer, and the like, and a digital image forming method using the same.
[0002]
More specifically, a reversible development type digital image forming apparatus that does not have a static elimination process and does not generate a memory image even when used in a digital image forming apparatus, and a reverse development type that does not have a static elimination process using the same. The present invention relates to a digital image forming method.
[0003]
[Prior art]
Organic photoconductors are easier to manufacture than conventional inorganic photoconductors, are less expensive, have a wide range of options for photoconductor materials such as charge transport agents, charge generators, and binder resins. Has been widely used in recent years.
[0004]
The organic photoreceptor includes a single-layer type photoreceptor in which a charge transport agent (a hole transport agent, an electron transport agent) is dispersed in the same photosensitive layer together with a charge generator, a charge generation layer containing the charge generator, and a charge. In recent years, there are laminated type photoreceptors laminated with a charge transport layer containing a transport agent, which has the advantage that the layer structure is simple and excellent in productivity, and the optical properties can be improved because there are few interfaces between layers. Single layer type is getting the limelight.
[0005]
On the other hand, an image forming apparatus using an electrophotographic method charges a photosensitive member (main charging step), exposes an image to form an electrostatic latent image (exposure step), and develops the electrostatic latent image with a developing bias voltage. The toner is developed in the applied state (development process), and the formed toner image is transferred to transfer paper (transfer process) and fixed to perform image formation. The residual toner on the photoconductor is cleaned by a urethane blade or the like (cleaning process), and the residual charge on the photoconductor is erased by an LED or the like (static elimination process).
[0006]
Various attempts have been made to omit the cleaning process and the charge removal process in order to reduce the size of the image forming apparatus and reduce the initial cost.
[0007]
In addition, image forming apparatuses using the electrophotographic method include digital and analog copying machines, facsimiles, laser beam printers, and the like, and in particular, use toner having the same polarity as the charging voltage applied to the photoreceptor in the charging process. The reversal development method in which development is performed in this manner is widely used in digital image forming apparatuses.
[0008]
[Problems to be solved by the invention]
<Transfer memory> When an electrophotographic photosensitive member is used in a reversal development type digital image forming apparatus, the transfer voltage applied to the photosensitive member in the transfer process is not normally applied directly to the photosensitive member but via a transfer medium (paper). When the transfer medium does not pass through the transfer process, it is not applied.
[0009]
However, the transfer voltage on / off timing is very difficult, and a portion that is directly applied to the photoreceptor often occurs at the front and rear end portions of the transfer medium. That is, the transfer voltage starts to be applied before the leading edge of the transfer medium covers the transfer device, and the transfer voltage continues to be applied even if a part of the transfer device is exposed due to the passage of the rear end of the transfer medium. In this portion, a transfer voltage is directly applied to the photoconductor.
[0010]
For this reason, for example, in the case of a positively charged single layer type photoreceptor, since the polarity of the voltage applied by the transfer device is negative, negative space charges remain on the photoreceptor portion to which a negative voltage is applied. In general, a single-layer type photoreceptor has sensitivity in both polarities, so that negative space charges are erased in the next static elimination step.
[0011]
However, when the positively charged single layer type photoreceptor is very insensitive to the negative polarity (the mobility of the electron transfer agent is extremely small) or when used in an image forming apparatus that does not have a charge eliminating step, Even if the negative space charge is not sufficiently erased and is positively charged in the next charging step, the potential drop is caused by the effect of the space charge, and further appears as a difference in sensitivity in the development step, and this portion is displayed in the image. The problem of blackening (memory image) occurs.
[0012]
<Exposure memory> For example, a positively charged single-layer type photoreceptor is usually subjected to an exposure process and a development process, and after the positive charge on the surface of the photoreceptor has been erased uniformly in the neutralization process, Positively charged.
[0013]
However, as in the case of the transfer memory, when the sensitivity to the negative polarity of the positively charged single layer type photoreceptor is poor, or when used in an image forming apparatus that does not have a charge eliminating step, the exposed portion is non-exposed. The negative space charge density is larger than that of the exposed portion, and a potential difference is generated in the next charging step, so that a memory image is easily generated.
[0014]
Therefore, an object of the present invention is to provide a single-layer electrophotographic photosensitive member that has a very small exposure memory and transfer memory and does not generate a memory image even when used in a reversal development type digital image forming apparatus that does not have a static elimination process. Is to provide.
[0015]
Furthermore, the present invention is to provide a reversal development type digital image forming apparatus using the single layer type electrophotographic photosensitive member of the present invention and not having a charge eliminating step.
[0016]
[Means for Solving the Problems]
As a result of intensive studies, the inventors of the present invention formed a photosensitive layer on a conductive substrate in order to achieve the above object, and the photosensitive layer is represented by a phthalocyanine compound as a charge generating agent and the general formula (1). A hole transport agent and an electron transport agent contained in the binder resin, and
The photosensitive member is charged to a brass of 800 V, the post-exposure potential measured at an exposure wavelength of 780 nm and an exposure energy of 1.0 μJ / cm ² is a positive polarity sensitivity, the photosensitive member is charged to minus 800 V, an exposure wavelength of 780 nm, an exposure energy of 1 A single-layer electrophotographic photosensitive member in which the post-exposure potential measured at 0.0 μJ / cm ² has a negative polarity sensitivity and the absolute value difference between the positive polarity and the negative polarity is 500 V or less is extremely low in exposure memory and transfer memory. It has been found that a memory image is not generated in a reversal development digital image forming system that is small and does not have a charge eliminating step.
General formula (1):
[Chemical 1]

(In the general formula (1), R ¹ and R ³ are the same or different, and may have an alkyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. An aralkyl group or an alkoxy group, wherein R ² and R ⁴ are the same or different and each represents a hydrogen atom, an alkyl group or an alkoxy group which may have a substituent.
However, when the substitution positions of R ² and R ⁴ are para positions, R ² and R ⁴ are hydrogen atoms. )
[0017]
[Effects of the Invention]
When a single-layer electrophotographic photosensitive member having an absolute value difference between positive polarity and negative polarity sensitivity of 500 V or less, measured at an exposure wavelength of 780 nm and an exposure energy of 1.0 μJ / cm ² , is used. , Exposure memory and transfer memory are very small. This is presumably because the smaller the absolute value difference between the positive and negative polarities, the better the transport balance between holes and electrons generated in the photosensitive layer and the smaller the memory.
[0018]
As described in claim 2, in the single-layer electrophotographic photosensitive member, it is difficult to design a material of an electron transport agent having a high mobility, and the mobility of the electron transport material is smaller than the mobility of the hole transport material. In addition, the absolute value of the positive polarity sensitivity is smaller than the absolute value of the negative polarity sensitivity, that is, for the reason that ozone generation is extremely small in the image forming apparatus.
[0019]
In the positively charged single layer type electrophotographic photosensitive member as described in claims 1 and 3 , the hole transporting agent preferably contains a compound represented by the general formula (1). It is preferable to contain at least one compound represented by 2), (3), (4) or (5).
This is because by using the compound having a high hole transport ability or electron transport ability, the sensitivity to the positive polarity and the negative polarity becomes good, and it is very effective in reducing the memory.
[0020]
As in claim 4, also be used in a reversal development type digital image forming apparatus having no neutralization step, single-layer type electrophotosensitive material of the present invention, since memory is very small, the occurrence of memory images No.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Various materials used for the single-layer electrophotographic photosensitive member of the present invention will be described in detail.
[0022]
<Charge Generating Agent> In a digital image forming apparatus, when a laser is used as a light source, a semiconductor laser or an LED is often used from the viewpoints of small size, low cost, and simplicity. Therefore, an organic photoreceptor having sensitivity in a wavelength region of at least 700 to 850 nm is necessary. As charge generators used in organic photoreceptors that satisfy the above requirements, for example, polycyclic quinone compounds, pyrylium compounds, squalium compounds, phthalocyanine compounds, azo compounds and the like have been proposed or put into practical use. Various phthalocyanine compounds are used in the single-layer type electrophotographic photoreceptor.
[0023]
In general, phthalocinine compounds include metal-free phthalosinin (CGM-1) having no central metal, titanyl phthalocyanine (CGM-2), which has been actively researched and developed in recent years, and aluminum phthalocyanine and vanadium. Phthalocinine, Cadmium phthalocyanine, Antimony phthalocinine, Chromium phthalosinine, Copper 4-phthalosinine, Germanium phthalosinine, Iron phthalosinin, Chloroaluminum phthalosinine, Chloroindium phthalocyanine, Chlorogallium phthalosinine, Magnesium phthalosinine, Dialkylphthalosinine, Tetramethyl There are metal phthalocyanines having a central metal such as phthalosinine and tetraphenylphthalosinin, and crystal types such as α-type, β-type, γ-type, δ-type, ε-type, σ-type, x-type, τ-type, etc. is there.
[0024]
<CGM-1>
[Chemical 6]

[0025]
<CGM-2>
[Chemical 7]

[0026]
The phthalocyanine compound is preferably contained in an amount of 0.01 to 50 wt%, more preferably 0.1 to 30 wt%, based on the weight of the binder resin.
[0027]
<Hole Transfer Agent> As the hole transfer agent used in the single layer type electrophotographic photosensitive member of the present invention, a stilbene compound represented by the general formula (1) is used.
Moreover, what is necessary is just to contain this stilbene-type compound individually or at least 1 or more types as a hole transport agent.
That is, various hole transport agents may be contained together with the stilbene compound.
[0028]
Examples of various hole transporting agents include oxadiazole compounds such as 2,5-di (4-methylaminophenyl) -1,3,4-oxadiazole, 9-4 (-diethylaminostyryl) anthracene, and the like. Styryl compounds, carbazole compounds such as polyvinyl carbazole, organic polysilane compounds, pyrazoline compounds such as 1-phenyl-3 (p-dimethylaminophenyl) pyrazoline, hydrazone compounds, triphenylamine compounds, indole compounds, Examples thereof include nitrogen-containing cyclic compounds such as oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds.
[0029]
The content of the hole transport agent is preferably 5 to 500 wt%, more preferably 25 to 200 wt%, based on the binder resin weight.
[0030]
<Electron Transfer Agent> As the electron transfer agent used in the single layer type electrophotographic photoreceptor of the present invention, a quinone compound represented by the general formula (2), (3), (4) or (5) is particularly preferable. Used for. Moreover, when using this quinone type compound as an electron transport agent, what is necessary is just to contain individually or at least 1 sort (s) or more. That is, various electron transport agents may be contained together with the quinone compound.
[0031]
Examples of various electron transfer agents include pyrene compounds, carbazole compounds, hydrazone compounds, N, N-dialkylaniline compounds, diphenylamine compounds, triphenylamine compounds, triphenylmethane compounds, tetracyanoethyl, tetra Cyanoquinodimethane, chloroanil, bromoanil, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4,7-trinitro-9-dicyanomethylenefluorenone, 2 , 4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone and the like, or those obtained by polymerizing these electron withdrawing substances.
[0032]
The content of the electron transfer agent is preferably 5 to 100 wt%, more preferably 10 to 80 wt%, based on the binder resin weight.
[0033]
<Binder Resin> Various resins conventionally used in photosensitive layers can be used as the binder resin for dispersing each component.
[0034]
For example, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, acrylic copolymer, styrene-acrylic acid copolymer, polyethylene, ethylene-vinyl acetate copolymer, chlorinated polyethylene , Polyvinyl chloride, polypropylene, ionomer, vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyether resin, etc. Resin such as thermoplastic resin, silicone resin, epoxy resin, phenol resin, urea resin, melamine resin, other cross-linkable thermosetting resin, epoxy acrylate, urethane acrylate, etc. It is. These binder resins can be used alone or in combination of two or more.
[0035]
Particularly preferred resins are bisphenol Z-type polycarbonates derived from bisphenol Z-type monomers and phosgene, such as Panlite manufactured by Teijin Chemicals Ltd. and PCZ manufactured by Mitsubishi Gas Chemical Company, Inc.
[0036]
The weight average molecular weight of the binder resin in the above example is preferably 5,000 to 200,000, more preferably 15,000 to 100,000.
[0037]
In addition to the above-mentioned components, the single-layer electrophotographic photosensitive member of the present invention includes various conventionally known additives such as an antioxidant, a radical scavenger, a single layer within the range that does not adversely affect the electrophotographic characteristics. A terminator, a deterioration inhibitor such as an ultraviolet absorber, a softener, a plasticizer, a surface modifier, a bulking agent, a thickener, a dispersion stabilizer, a wax, an acceptor, a donor, and the like can be blended. In order to improve the sensitivity of the photosensitive layer, for example, a known sensitizer such as terphenyl, halonaphthoquinone, and acenaphthylene may be used in combination with the charge generator.
[0038]
In the single-layer electrophotographic photoreceptor of the present invention, a barrier layer may be formed between the conductive substrate and the photosensitive layer as long as the characteristics of the photoreceptor are not impaired.
[0039]
The film thickness of the single layer type electrophotographic photosensitive member of the present invention is preferably 5 to 50 μm, particularly preferably 15 to 35 μm.
[0040]
A single layer type electrophotographic photosensitive member is obtained by providing a single photosensitive layer on a conductive substrate. This photosensitive layer is formed by dissolving or dispersing a charge generator, a hole transport agent, an electron transport agent, a binder resin, etc. in an appropriate solvent, coating the resulting coating solution on a conductive substrate, and drying. The
[0041]
As the conductive substrate on which the photosensitive layer is formed, various materials having conductivity can be used. For example, iron, aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium Examples thereof include simple metals such as nickel, palladium, indium, stainless steel, and brass, plastic materials on which the above metals are vapor-deposited or laminated, glass coated with aluminum iodide, tin oxide, indium oxide, and the like.
[0042]
The shape of the conductive substrate may be any of a sheet shape and a drum shape according to the structure of the image forming apparatus to be used. The substrate itself has conductivity or the surface of the substrate has conductivity. If you do. The conductive substrate preferably has sufficient mechanical strength when used.
[0043]
When the photosensitive layer is formed by a coating method, the above-exemplified hole transporting agent, charge generating agent, electron acceptor, binder resin and the like together with a suitable solvent are known methods such as a roll mill, a ball mill, an attritor. A dispersion is prepared by dispersing and mixing using a paint shaker, an ultrasonic disperser, etc., and this is applied by a known means and dried.
[0044]
As the solvent for preparing the dispersion, various organic solvents can be used, for example, alcohols such as methanol, ethanol, isopropanol and butanol, and aliphatic hydrocarbons such as n-hexane, octane and cyclohexane. , Aromatic hydrocarbons such as benzene, toluene, xylene, halogenated hydrocarbons such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride, chlorobenzene, ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, Ketones such as acetone, methyl ethyl ketone and cyclohexanone, esters such as ethyl acetate and methyl acetate, dimethylformaldehyde, dimethylformamide, dimethyl sulfoxide, etc. Is given. These solvents are used alone or in combination of two or more.
[0045]
Further, a surfactant, a leveling agent or the like may be used in order to improve the dispersibility of the hole transporting agent, charge generating agent, electron acceptor, and surface of the photosensitive layer.
[0046]
On the other hand, an image forming apparatus according to the present invention uses the single-layer type electrophotographic photosensitive member according to claim 1, and includes at least a main charging step, an exposure step, a developing step, and a transfer step along the traveling direction of the photosensitive member. A reversible development type digital image forming apparatus having no charge eliminating step, wherein the voltage applied in the transfer step has a polarity opposite to that of the voltage applied in the charging step. Facsimile, laser beam printer and the like.
[0047]
Since the single layer type electrophotographic photosensitive member of the present invention has a very small transfer / exposure memory, a memory image is not generated even if it is used in the image forming apparatus having no charge eliminating step.
[0048]
In addition, as described above, the cleaning process may be omitted in the same manner as the charge removal process in order to reduce the size of the image forming apparatus and reduce the initial cost.
[0049]
【Example】
Hereinafter, the present invention will be described with reference to examples and comparative examples. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
[0050]
Examples 1 to 8 X-type metal-free phthalocyanine (CGM-1) 2.5 parts by weight as a charge generator, 65 parts by weight of a hole transport agent (HTM-1) represented by the general formula (1), 2), (3), (4), 35 parts by weight of an electron transport agent (ETM-1 to ETM-8) represented by (5), and a bis-Z type polycarbonate resin having a weight average molecular weight of 30,000 as a binder resin 100 parts by weight and 750 parts by weight of tetrahydrofuran were dispersed or dissolved in a ball mill for 28 hours to prepare a coating solution for a single-layer type photosensitive layer. Then, this coating solution is applied on an aluminum base tube as a support by a dip coating method, followed by hot-air drying at 130 ° C. for 30 minutes, and a single-layer photoreceptor having a single photosensitive layer with a thickness of 22 μm. Was made.
[0051]
<Comparative Examples 1-3> Single layer type photoreceptors were prepared in the same manner as in Examples 1-7, except that ETM-9 to ETM-11 were used as electron transport agents.
[0052]
<HTM-1>
[Chemical 8]

[0053]
<ETM-1>
[Chemical 9]

[0054]
<ETM-2>
[Chemical Formula 10]

[0055]
<ETM-3>
Embedded image

[0056]
<ETM-4>
Embedded image

[0057]
<ETM-5>
Embedded image

[0058]
<ETM-6>
Embedded image

[0059]
<ETM-7>
Embedded image

[0060]
<ETM-8>
Embedded image

[0061]
<ETM-9>
Embedded image

[0062]
<ETM-10>
Embedded image

[0063]
<ETM-11>
Embedded image

[0064]
Examples 9 to 16 Monolayer type photoreceptors were prepared in the same manner as in Examples 1 to 8, except that titanyl phthalocyanine (CGM-2) was used as the charge generator.
[0065]
<Comparative Examples 4 to 6> Monolayer type photoreceptors were prepared in the same manner as Comparative Examples 1 to 3, except that titanyl phthalocyanine (CGM-2) was used as the charge generator.
[0066]
The following characteristics were evaluated for the single-layer electrophotographic photoreceptors of the above Examples and Comparative Examples. The evaluation results are shown in Tables 1 and 2. Of these data, the relationship between the transfer memory potential, the exposure memory potential, and the absolute value difference between the positive polarity sensitivity and the negative polarity sensitivity is shown in FIG.
[0067]
<Positive polarity sensitivity evaluation> Using a drum sensitivity tester (trade name Gentec Cynthia 30M) manufactured by GENTEC, an applied voltage is applied to the electrophotographic photosensitive member of each example and comparative example, and the surface Was charged to + 800V. Next, monochromatic light having a wavelength of 780 nm (half-value width 20 nm, light intensity 20 μW) extracted from the white light of a halogen lamp, which is an exposure light source of the testing machine, using a band-pass filter is applied to the surface of the charged photoreceptor. Exposure (exposure time 100 msec) was performed (exposure energy was 1.0 μJ / cm ² ). Then, the surface potential after 500 msec from the exposure start time was measured as a post-exposure potential V _LP (V). That is, the smaller the post-exposure potential, the higher the sensitivity of the photoreceptor.
[0068]
<Negative polarity sensitivity evaluation> Using a drum sensitivity tester (product name Gentec Cynthia 30M) manufactured by GENTEC, an applied voltage is applied to the electrophotographic photosensitive member of each example and comparative example, and the surface The surface potential was measured as the post-exposure potential V _LN (V) at the time when 500 msec had elapsed from the start of exposure, in the same manner as in the above <Positive polarity sensitivity evaluation> except that was charged to −800V.
[0069]
<Evaluation of Transfer Memory Potential> The surface potential when no transfer bias is applied to the multi-function printer Antico40 manufactured by Kyocera Mita Co., Ltd., in which the static elimination lamp is removed, and the electrophotographic photosensitive member of each example and comparative example is mounted. The surface potential after the next charging step when applying the transfer bias was measured, and the difference was defined as the transfer memory potential. As for the transfer memory potential, 45 V or less at which no transfer memory image was generated was allowed, and when it was greater than 45 V, it was not allowed.
[0070]
<Evaluation of exposure memory potential> A multi-function printer Antico40 manufactured by Kyocera Mita Co., Ltd., from which the charge-removing lamp has been removed, is mounted with the electrophotographic photosensitive member of each example and comparative example, and the surface potential during unexposure and during exposure The surface potential after the subsequent charging step was measured, and the difference was taken as the exposure memory potential. As for the exposure memory potential, 45 V or less at which no exposure memory image is generated is allowed, and when it is higher than 45 V, the transfer memory potential is not allowed.
[0071]
<Evaluation of transfer memory image> A multi-function printer Antico40 manufactured by Kyocera Mita Co., Ltd., from which a static elimination lamp has been removed, was mounted with the electrophotographic photosensitive member of each example and comparative example, and a printing test was carried out. It was judged visually whether or not the above occurred. As shown in FIG. 2, the transfer memory image is the surface potential of the photoconductor in a portion to which a transfer bias is applied when a printing test is performed using a front gray (Munsell value: N = 6.5) document. An image in which a black horizontal band is generated in the drum longitudinal direction due to the decrease is shown.
[0072]
<Evaluation of exposure memory image> A multi-function printer Antico40 manufactured by Kyocera Mita Co., Ltd., from which the static elimination lamp was removed, was mounted with the electrophotographic photosensitive member of each example and comparative example, a printing test was performed, and an exposure memory image It was judged visually whether or not the above occurred. The exposure memory image means that when a printing test is carried out using a document as shown in FIG. 3, the ghost image in the exposed portion is changed to a gray portion due to a decrease in the photoreceptor surface potential in the strongly exposed portion (solid black portion). The generated image is shown.
[0073]
[Table 1]

[0074]
[Table 2]

[0075]
From Tables 1 and 2 and FIG. 1, it is clear that when the absolute value difference between the positive and negative polarities is 500 V or less, both the transfer memory potential and the exposure memory potential are 45 V or less, and no memory image is generated. became.
[0076]
【The invention's effect】
Since the single layer type electrophotographic photosensitive member of the present invention has very small exposure memory and transfer memory, a memory image is not generated even when used in a reversal development type digital image forming apparatus having no charge eliminating step.
[0077]
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the transfer memory potential / exposure memory potential of single layer type electrophotographic photosensitive members of each example and comparative example, and the absolute value difference between the positive and negative polarity sensitivities.
FIG. 2 is a diagram showing a transfer memory image evaluation document and a transfer memory image.
FIG. 3 is a view showing an exposure memory image evaluation document and an exposure memory image.

Claims (4)

Forming a photosensitive layer on a conductive substrate, the photosensitive layer containing a phthalocyanine compound as a charge generating agent, a hole transporting agent represented by the general formula (1), an electron transporting agent in a binder resin; and the photoreceptor is charged to a brass 800 V, the exposure wavelength 780 nm, the potential after exposure was measured at an exposure energy 1.0μJ / cm ² and the positive pole of the sensitivity, by charging the photosensitive member negatively 800 V, the exposure wavelength 780 nm, the exposure energy Inversion without a static elimination step , wherein the post-exposure potential measured at 1.0 μJ / cm ² is a negative polarity sensitivity, and the absolute value difference between the positive polarity and the negative polarity sensitivity is 500 V or less. A single-layer electrophotographic photosensitive member for development type digital image forming apparatus .
General formula (1):

(In the general formula (1), R ¹ and R ³ are the same or different, and may have an alkyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. An aralkyl group or an alkoxy group, wherein R ² and R ⁴ are the same or different and each represents a hydrogen atom, an alkyl group or an alkoxy group which may have a substituent.
However, when the substitution positions of R ² and R ⁴ are para positions, R ² and R ⁴ are hydrogen atoms. )   2. The single-layer electrophotographic photosensitive member according to claim 1, wherein the absolute value of the positive polarity sensitivity is smaller than the absolute value of the negative polarity sensitivity. The positively charged single-layer type electron according to claim 2, comprising at least one compound represented by the general formula (2), (3), (4) or (5) as an electron transport agent. Photoconductor.
General formula (2):

(In General Formula (2), R ⁵ represents a halogen atom, an alkyl group or an aryl group which may have a substituent, and R ⁶ represents an alkyl group or an aryl group, which may have a substituent, or Group: -O-R ^6a is shown.
R ^6a represents an alkyl group or an aryl group which may have a substituent. )
General formula (3):

(In the general formula (3), R ⁷ and R ⁸ are the same or different and are alkyl group, halogenated alkyl group, aryl group, aralkyl group, alkoxy group, aryloxy group, aralkyloxy group, acyl group, alkoxycarbonyl group. , Aryloxycarbonyl group, aralkyloxycarbonyl group or nitro group.
n represents an integer of 0 to 3. )
General formula (4):

(In the general formula (4), R ^9a , R ^9b , R ^9c and R ^9d are the same or different and represent a hydrogen atom or an alkyl group or an aryl group which may have a substituent.)
General formula (5):

(In the general formula (5), R ¹⁰ and R ¹¹ are the same or different and are an alkyl group, halogenated alkyl group, aryl group, aralkyl group, alkoxy group, aryloxy group, aralkyloxy group, acyl group, alkoxycarbonyl group. , Aryloxycarbonyl group, aralkyloxycarbonyl group or nitro group.
n represents an integer of 0 to 3. ) The single-layer electrophotographic photosensitive member according to claim 1 is used, and includes at least a main charging step, an exposure step, a development step, and a transfer step along the traveling direction of the photoconductor, and is applied in the transfer step. A reversal development type digital image forming apparatus having no charge eliminating step, wherein the voltage has a polarity opposite to that of the voltage applied in the charging step.

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