JP2004341019A - Electrophotographic photoreceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor having excellent mechanical properties such as wear resistance, scratch resistance and smoothness for repeated use and having excellent electric characteristics under a whole environment from a low temperature and low humidity environment to a high temperature and high humidity environment. <P>SOLUTION: In the electrophotographic photoreceptor having a photosensitive layer on a conductive supporting body, the photosensitive layer contains a charge transport substance which has ≤0.1 mg/cm<SP>3</SP>solubility at 25 °C with respect to a mixture solvent having the ratio of tetrahydrofuran:toluene=8:2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

＜導電性支持体＞
本発明の電子写真感光体は、導電性支持体上に感光層を形成して構成される。感光層が形成される導電性支持体としては周知の電子写真感光体に採用されているものがいずれも使用できる。具体的には、例えばアルミニウム、ステンレス鋼、銅、ニッケル、亜鉛、インジウム、金、銀等の材料の金属材料からなるアルミニウム、銅、パラジウム、酸化スズ、酸化インジウム、導電性高分子等の導電性層を設けたポリエステルフィルム、紙、ガラス等の絶縁性支持帯が挙げられる。更に、金属粉末、カーボンブラック、ヨウ化銅、高分子電解質等の導電性物質を適当なバインダーとともに塗布して導電処理したプラスチックフィルム、プラスチックドラム、紙、紙管等は挙げられる。また、金属粉末、カーボンブラック、炭素繊維等の導電性物質を含有し、導電性となったプラスチックのシートやドラムが挙げられる。また、酸化スズ、酸化インジウム等の導電性金属酸化物で導電性処理したプラスチックフィルムやベルトが挙げられる。このような導電性支持体の表面は、画質に影響のない範囲で各種の処理、例えば、表面の酸化処理や薬品処理を行うことができる。形状はドラム、シート、ベルト、シームレスベルト等任意の形状を取ることができる。この中でも、金属のエンドレスパイプを適当な長さに切断したものが好ましく、アルミニウムが最も好適に用いられる。
＜ブロッキング層＞
導電性支持体と感光層との間には通常使用されるような公知のブロッキング層が設けられていてもよい。ブロッキング層としては、例えばアルミニウムの陽極酸化被膜、酸化アルミニウム、水酸化アルミニウム等の無機層、ポリビニルメチルエーテル、ポリ−Ｎ−ビニルイミダゾール、ポリエチレンオキシド、エチルセルロース、メチルセルロース、エチレン−アクリル酸共重合体、ポリエチレン、ポリエステル、フェノール樹脂、塩化ビニル−酢酸ビニル共重合体、エポキシ樹脂、ポリビニルピリジン、ポリウレタン、ポリグルタミン酸、ポリビニルアルコール、カゼイン、ポリビニルピロリドン、ポリアクリル酸、セルロース類、ゼラチン、デンプン、ポリウレタン、ポリイミド、ポリアミド等の有機層が使用される。有機層をブロッキング層として用いる場合には単独あるいはチタニア、アルミナ、シリカ、酸化ジルコニウム等の金属酸化物あるいは銅、銀、アルミニウム等の金属微粉末を分散させてもよい。
【００２０】
また、ブロッキング層には、特にレーザー露光における干渉縞を防ぐ目的で、アルミナ、チタニア、シリカ等の金属酸化物微粒子や、使用するレーザー光波長を吸収することのできる有機または無機の色素、顔料粒子等を含有させてもよい。
これらのブロッキング層の膜厚は便宜設定できるが、通常０．０５〜２０μｍ、好ましくは０．１〜１０μｍの範囲である。
【００２１】
バインダー樹脂に対する、金属酸化物粒子または、色素、顔料粒子の含有割合は特に制限はないが、バインダー１００重量部に対して、４０〜４００重量部の範囲で使用することが、下引き層を塗布する際の分散安定性、保存安定性、塗布性等の面で好ましい。
＜感光層の構成＞
有機系の光導電材料を使用した感光体としては、光導電性材料をバインダー樹脂中に分散させた、いわゆる単層型感光体、電荷発生層及び電荷輸送層を積層した積層型感光体などが知られている。
【００２２】
本発明の感光体は、最表面層に本発明の難溶性電荷輸送物質を含有するものであれば、単層型（分散型）感光層あるいは積層型感光層のいずれの形態も用いることができるが、感光体の機械的物性、電気特性、製造安定性など総合的に勘案して、それぞれ効率の高い電荷発生物質、および電荷輸送物質を組み合わせることにより高感度な感光体が得られること、材料選択範囲が広く安全性の高い感光体が得られること、また塗布の生産性が高く比較的コスト面でも有利なことから、順積層型の感光体が好ましい。
＜電荷発生物質＞
電荷発生層に用いられる電荷発生物質としては、公知のものをいずれも用いることができ、セレン及びその合金、ヒ素−セレン、硫化カドミウム、酸化亜鉛、酸化チタン等の酸化物系半導体、アモルファスシリコン等のシリコン系材料、その他の無機光導電性物質、フタロシアニン、アゾ色素、キナクドリン、多環キノン、ピリリウム塩、ペリレン、インジゴ、チオインジゴ、アントアントロン、ピラントロン、シアニン等の各種有機顔料、色素が使用できる。中でも、ペリレン、無金属フタロシアニン、銅、塩化インジウム、塩化ガリウム、シリコン、錫、オキシチタニウム、亜鉛、バナジウム等の金属、又は酸化物、塩化物、水酸化物の配位したフタロシアニン類、モノアゾ、ビスアゾ、トリスアゾ、ポリアゾ類等のアゾ顔料が好ましい。
【００２３】
このうち５５０〜８５０ｎｍの範囲の単色光による露光装置を備えた画像形成装置に使用する場合には、感度の点から、オキシチタニウムフタロシアニンが更に好ましく、中でもＣｕＫα線によるＸ線回折においてブラッグ角（２θ±０．２°）＝２７．３°に特徴的なピークを有するＹ型オキシチタニウムフタロシアニンが最も好ましい。白色光または３５０〜５５０ｎｍの範囲の単色光による露光装置を備えた画像形成装置に使用する場合には、感度の点から、アゾ顔料が好適に用いられる。
【００２４】
また、帯電性の改良、光疲労の低減、感度の調整といった目的で２種類以上の電荷発生物質を混合してもよい。
電荷発生層は上記の電荷発生物質とバインダーポリマーを溶剤あるいは分散して得られる塗布液を塗布乾燥して得ることができる。バインダーとしては、スチレン、酢酸ビニル、アクリル酸エステル、メタクリル酸エステル、ビニルアルコール、エチルビニルアルコール等のビニル化合物の重合体及び共重合体、ポリビニルアセタール、ポリカーボネート、ポリエステル、ポリアミド、ポリウレタン、セルロースエステル、フェノキシ樹脂、ケイ素樹脂、エポキシ樹脂等が挙げられる。
【００２５】
電荷輸送層を形成する上記電荷発生物質とバインダーの割合は、特に制限はないが、一般的には電荷発生物質１００重量部に対し、５〜５００重量部、好ましくは２０〜３００重量部のバインダーポリマーを使用する。
また、電荷発生層は上記電荷発生物質の蒸着膜であってもよい。電荷発生層の膜厚は０．０５〜５μｍ、好ましくは０．１〜２μｍになるようにする。
＜電荷輸送物質＞
本発明の感光層は、難溶性電荷輸送物質を含有するが、他の電荷輸送物質が併用されていても構わない。感光層に用いられる電荷輸送物質としては、ジフェノキノン誘導体、２，４，７−トリニトロフルオレノン等の芳香族ニトロ化合物、カルバゾール誘導体、インドール誘導体、イミダゾール誘導体、オキサゾール誘導体、ピラゾール誘導体、オキサジアゾール誘導体、ピラゾリン誘導体、チオジアゾール誘導体などの複素環化合物、アニリン誘導体、ヒドラゾン化合物、芳香族アミン誘導体、スチルベン誘導体、ブタジエン誘導体、エナミン化合物、これらの化合物が複数結合されたもの、あるいはこれらの化合物からなる基を主鎖もしくは側鎖に有する重合体などが挙げられる。
【００２６】
電荷輸送層はこれらの物質をバインダーとして優れた性能を有する公知のポリマーと共に適当な溶媒中に溶解または、分散し、必要に応じて電子受容性化合物、或いは可塑剤、無機粒子、有機顔料その他の添加剤を添加して得ることができる。
ポリメチルメタクリレート、ポリスチレン、ポリ塩化ビニル等のビニル重合体、及びその共重合体、ポリカーボネート、ポリエステル、ポリスルホン、フェノキシ、エポキシ、シリコーン樹脂等の熱可塑性樹脂や種々の熱硬化性樹脂が用いられてきている。数あるバインダー樹脂の中ではポリカーボネート樹脂が比較的優れた性能を有している。
【００２７】
ポリカーボネートの分子量は、低すぎると機械的強度が不足し、逆に分子量が高すぎると感光層形成のための塗布液の粘度が高すぎて生産性が低下するといった不具合が生じるため、粘度平均分子量で１０，０００以上、好ましくは２０，０００以上で、１００，０００以下、より好ましくは７０，０００以下の範囲で用いられる。
【００２８】
適用するポリカーボネートとしては、シート状に作製された感光体フィルムをテーバー摩耗試験機（東洋精機社性）により２３℃、５０％ＲＨの雰囲気下、摩耗輪ＣＳ−１０Ｆを用いて、荷重１００ｇで１０００回転させて試験した際の試験前後の重量減少が、６．０ｍｇ以下であるものが好ましい。
電荷輸送層の膜厚としては通常１０〜５０μｍ、好ましくは１３μｍ〜３５μｍの範囲で使用される。
【００２９】
＜感光層形成用塗布液＞
通常、電子写真感光体用の有機感光層は、導電性材料、バインダー樹脂および各種添加剤を特定の溶媒に溶解または分散させた塗布液を塗布、乾燥することにより形成される。
【００３０】
該溶媒としては、ブチルアミン、ジエチルアミン、エチレンジアミン、イソプロパノールアミン、トリエタノールアミン、トリエチレンジアミン等のアミン類、Ｎ−Ｎ−ジメチルホルムアミド等のアミド類、メチルアルコール、エチルアルコール、イソプロパノール等のアルコール類、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、クロロホルム、１，２−ジクロルエタン、トリクロロエチレン、テトラクロルエタン、ジクロルメタン等のハロゲン化アルキル類、テトラヒドロフラン等のシクロエーテル類、ジオキサン等のエーテル類、酢酸エチル、酢酸ブチル等のエステル類、ベンゼン、トルエン、キシレンなどの芳香族炭化水素類、酢酸エチル、酢酸ブチル、ジメチルスルホキシド、アニソール、メチルセルソルブ等が使用され、好ましくはトルエン、クロロホルム、テトラヒドロフラン、アニソール、ジオキサンを使用する。また、これらの溶媒は、１種類単独で使用しても２種類以上を混合して用いてもよい。
＜感光層形成方法＞
感光層の塗布方法としては、スプレー塗布法、スパイラル塗布法、リング塗布法、浸漬塗布法等がある。
【００３１】
スプレー塗布法としては、エアスプレー、エアレススプレー、静電エアスプレー、静電エアレススプレー、回転霧化式静電スプレー、ホットスプレー、ホットエアレススプレー等があるが、均一な膜厚を得るための微粒化度、付着効率等を考えると回転霧化式静電スプレーにおいて、再公表平１−８０５１９８号公報に開示されている搬送方法、すなわち円筒状ワークを回転させながらその軸方向に間隔を開けることなく連続して搬送することにより、総合的に高い付着効率で膜厚の均一性に優れた電子写真感光体を得ることができる。
【００３２】
スパイラル塗布法としては、特開昭５２−１１９６５１号公報に開示されている注液塗布機またはカーテン塗布機を用いた方法、特開平１−２３１９６６号公報に開示されている微小開口部から塗料を筋状に連続して飛翔させる方法、特開平３−１９３１６１号公報に開示されているマルチノズル体を用いた方法等がある。
【００３３】
浸漬塗布法は、一例としては以下のような電荷輸送層の塗布形成手段が挙げられる。
電荷輸送物質、バインダー樹脂、溶剤等を用いて、全固形分濃度が１５％以上あってより好ましくは４０％以下の、且つ粘度が通常５０センチポアーズ〜７００センチポアーズ以下、さらに好ましくは１００センチポアーズ〜５００センチポアーズ以下の電荷輸送層形成用の塗布液を調整する。
【００３４】
ここで実質的に塗布液の粘度はバインダーは樹脂の種類及びその分子量によりきまるが、あまり分子量が低い場合には感光層の機械的強度が低下するためこれを損なわない程度の分子量を持つバインダー樹脂を使用することが好ましい。この様にして調整された塗布液を用いて浸漬塗布法いより電荷輸送層または感光層が形成される。
【００３５】
その後塗布膜を乾燥するが、必要且つ充分な乾燥が行われる様に乾燥温度、時間を調整する。
乾燥温度は通常１００〜２５０℃、好ましくは１１０℃〜１７０℃、さらに好ましくは１１５℃〜１４０℃の範囲である。乾燥方法としては、熱風乾燥機、蒸気乾燥機、赤外線乾燥機及び遠赤外線乾燥機を用いることができる。
【００３６】
このようにして得られた本発明の電子写真感光体は長期間にわたって優れた耐刷性と滑り性を維持し、複写機、プリンター、ファックス、製版機等の電子写真分野に好適である。
＜画像形成方法＞
本発明の電子写真感光体を使用する複写機、プリンター等の電子写真装置は、少なくとも帯電、露光、現像、転写、除電の各プロセスを含むが、どのプロセスも通常用いられる方法のいずれを用いても良い。
【００３７】
帯電方法（帯電機）としては、例えばコロナ放電を利用したコロトロン、スコロトロン帯電、導電性ローラーあるいはブラシ、フィルムなどによる接触帯電などいずれを用いてもよい。このうち、コロナ放電を使用した帯電方法では暗部電位を一定に保つため、スコロトロン帯電が用いられることが多い。
また、最近では環境に鑑みて、オゾンレス型の複写機、プリンターが多くなりつつあり、帯電ローラーを用いることが多く、帯電方式としては、直流帯電、交流重畳直流帯電が用いられている。
【００３８】
本発明で使用している、難溶性電荷輸送物質を含有する感光体は、３７０〜８００ｎｍの波長領域で良好な光透過度を示すため、この樹脂を用いた電子写真感光体の露光手段としては、現在汎用されている７８０ｎｍのレーザー光による露光はもちろんのこと、６３０ｎｍ、６５０ｎｍ、６８０ｎｍ等の赤色レーザーや青色ＬＥＤ等のいずれの光源も使用可能である。
【００３９】
また、全可視光領域の光に対して良好な光透過度を示すため、カラー複写機やカラープリンター等の、カラー画像を形成するための電子写真装置にも好適である。
現像方法としては、磁性あるいは非磁性の１成分現像剤、２成分現像剤、重合トナー等を接触あるいは非接触させて現像する一般的な方法が用いられている。
【００４０】
本発明で使用している難溶性電荷輸送物質を添加すると、感光層の最表面の滑性、表面性を改質することから、転写性、解像度等が向上することが考えられる。特に粒径が小さく、均一性の良い重合トナーを使用する場合、上記の特性の向上が非常に見込まれる。
【００４１】
転写は、紙やＯＨＰ用フィルム等に対して直接行ってよいし、一旦中間転写（ベルト上あるいはドラム状）に転写したのちに、紙やＯＨＰ用フィルム上に転写しても良い。通常、転写の後、現像剤を紙などに定着させるプロセスが用いられ、定着手段としては一般的に用いられる熱定着、圧力定着などを用いることができる。
【００４２】
これらのプロセスのほかに、通常用いられるクリーニング、除電等のプロセスを有していてよい。
【００４３】
【実施例】
以下、実施例により本発明を更に具体的に説明するが、本発明はその要旨を超えない限り実施例に限定されるものではない。なお、以下において、特に記載しない限り、「部」とは「重量部」を示す。
合成例（従前の電荷輸送物質と本発明の難溶性電荷輸送物質の合成）
Ｎ，Ｎ’−ビス（４−ホルミルフェニル）−Ｎ，Ｎ’−ジフェニルベンジジン５４ｇとｔｒａｎｓ−３−フェニル−２−プロペニルトリフェニルホスフィニウムクロライド８７ｇをＴＨＦ５５０ｇに添加し、これにナトリウムメチラートの２８％メタノール溶液４１ｇを添加した。室温で２時間攪拌後、溶液を水中に放出し、有機層を抽出後、大量のメタノールに添加して、析出した固体を濾過、メタノールで洗浄後、乾燥し、粗製品７０ｇを得た。該粗製品４０ｇとトルエン３６０ｇを混合し粗製品電荷輸送物質溶液を作成した。粗製品電荷輸送物質溶液を活性炭２０ｇと混合し、２５〜６０℃の温度条件で３０分間攪拌した後、活性炭を濾別して精製電荷輸送物質溶液を得た。
【００４４】
精製電荷輸送物質溶液１５０ｇを１０００ｍｌメタノールと混合して析出した固体を濾別し乾燥して電荷輸送物質を得た。また、精製電荷輸送物質溶液２００ｇと、活性白土１０ｇを混合し、２５〜６０℃の温度条件で３０分間攪拌した後、活性白土を濾別して溶液を得る操作を５回繰り返し得られた溶液と、ｎ−ヘキサン３００ｍｌを混合し、析出した固体を濾過により回収して得られた固体５ｇと６０℃のトルエン１００ｇを３０分攪拌混合後さらに濾過し、濾紙上に濾別された不溶分を乾燥して目的の難溶性電荷輸送物質を得た。
【００４５】
得られた難溶性電荷輸送物質をテトラヒドロフラン：トルエン＝８：２の混合溶媒１００ｃｍ^３中に十分な量添加し、この溶液を６０℃になるまで昇温し、溶液の温度を６０℃に保ち１時間攪拌しながら電荷輸送物質を溶剤中に十分溶解させた。その後２５℃雰囲気に２４時間放置し、溶け残りが沈殿する２５℃飽和溶液を調整した。
【００４６】
上記操作を行った電荷輸送物質を溶解させた溶液を、ＪＩＳ Ｐ３８０１に規定される定量分析用５種Ｃの濾紙を用いて濾過した。この濾液１００ｃｍ^３を容器に取り、減圧乾燥器を使用して混合溶媒が十分揮発するまで乾燥を行った。乾燥後に残ったものの重量を測定し、最初に使用した溶液量の１００ｃｍ^３で除することにより、溶剤への溶解度（ｇ／ｃｍ^３）を求めた。
合成例１で得られた難溶性電荷輸送剤に対し、上記測定法を３回繰り返し行った時の溶解度を表１に示す。
【００４７】
【表１】

この結果から、合成例１で製造した難溶性電解同物質の溶解度は、０．１ｇ／ｃｍ^３以下であることが分かった。
【００４８】
得られた電荷輸送物質と難溶性電荷輸送物質を質量分析（ＥＩ法）したところ、いずれも分子量が７４５であり、下記構造式（ａ）に合致する化合物が得られたことが分かった。また、これらの化合物の粉末Ｘ線スペクトルから、電荷輸送物質に比し難溶性電荷輸送物質の結晶性が著しく高いことが分かった。これらの結果から、得られた難溶性電荷輸送物質は、電荷輸送物質と同じ構造を持つ（ａ）の化合物であるが、結晶性の著しく異なるものであることが分かった。
【００４９】
【化２】

実施例１
ＣｕＫα線によるＸ線回折においてブラッグ角（２θ±０．２）２７．３°に最大回折ピークを示すオキシチタニウムフタロシアニン１０部と、１，２−ジメトキシエタン１５０部を混合し、サンドグラインドミルにて粉砕分散処理を行い、顔料分散液を作製した。
【００５０】
また、ポリビニルブチラール（電気化学工業（株）製、商名デンカブチラール＃６０００Ｃ）５部を１，２−ジメトキシエタン９５部に溶解し、固形分濃度５％のバインダー溶液を作製した。
先に作製した顔料分散液１６０部、バインダー溶液１００部、適量の１，２−ジメトキシエタンと、適量の４−メトキシ−４−メチルペンタノン−２を混合し、固形分濃度４．０％、１，２−ジメトキシエタン：４−メトキシ−４−メチルペンタノン−２＝９：１の電荷発生層形成用塗布液を調整した。
【００５１】
表面が鏡面加工された外径３０ｍｍ、長さ２８５ｍｍ、肉厚１．０ｍｍのアルミニウム合金よりなるシリンダーの表面に、陽極酸化膜処理を行い、その後酢酸ニッケルを主成分とする封孔処理を行うことより、約６μｍの陽極酸化被膜（アルマイト被膜）を形成した。このシリンダーを電荷発生層形成用塗布液に浸漬塗布し、電荷発生層膜厚が０．３μｍとなるように電荷発生層を形成した。
【００５２】
次に、上記合成例で得られた電荷輸送物質３０部、難溶性電荷輸送物質２０部、下記構造式（ｃ）に示す酸化防止剤８部、下記構造式（ｄ）のポリカーボネート樹脂（粘度平均分子量約３００００）１００部をテトラヒドロフラン：トルエン＝８０：２０の混合溶媒に混合し得られた塗布液液に、電荷発生層を形成したシリンダーを浸漬塗布することにより、乾燥後の膜厚が１８μｍの電荷輸送層を設けた。このようにして得られた感光体を感光体Ａ１とする。
【００５３】
【化３】

比較例１
電荷輸送物質を、実施例１で用いた構造式（１）の電荷輸送物質５０部のみとする以外は、実施例１と同様にして感光体ドラムを作製した。これを比較感光体Ｂ１とする。
［ガラス転移点（Ｔｇ）の測定］
感光体Ａ１および比較感光体Ｂ１製造時に用いた電荷輸送液を、訴入れぞれガラス板上にキャストし、２０分風乾後、１５０℃、１時間乾燥させ液中の溶剤を十分揮発させ、電荷輸送層と同組成のフィルムを作製した。このフィルムをカッターで切り取り、約５ｍｇを精密天秤により秤取り、ＤＳＣ測定用アルミ試料容器に入れガラス転移温度測定用サンプルを作製した。このサンプルをＤＳＣ７（（株）パーキンエルマージャパン製）に導入し電荷輸送層のガラス転移温度を測定した。
【００５４】
測定は、窒素ガスをフローしながら、２０℃から２００℃まで１０℃／分の昇温速度で昇温させた。（第一昇温過程）この第一昇温過程では、サンプル作製時の乾燥等で受けるフィルム中の履歴を取り去ることを目的とする。
２００℃に昇温後、１分間保持し、２０℃まで５００℃／分の降温速度で温度を下げ、２０℃で５分間保持させた。
【００５５】
次に１０℃／分の昇温速度で温度２００℃まで昇温させた。（第二昇温過程）この第二昇温過程の吸発熱のピークを作製した感光体フィルムのガラス転移温度（Ｔｇ）とした。同一サンプルについてこの操作を３回行いその平均を電荷輸送層のＴｇとした。この結果を表２に示す。
【００５６】
【表２】

［電気特性評価］
感光体Ａ１、比較感光体Ｂ１を、感光体特性試験器（続電子写真技術の基礎と応用、電子写真学会編、コロナ社、４０４〜４０５頁記載）に装着し、帯電、露光、電位測定、除電のサイクルによる電気特性評価試験を行った。
【００５７】
初期表面電位は−８００Ｖとし、露光はハロゲンランプの光を干渉フィルターで７８０ｎｍの単色光としたものを用いて、表面電位が−８００Ｖから−４００Ｖに半減するのに要した露光量（以下、半減露光量またはＥ１／２ということがある）、１．４μＪ／ｃｍ２を照射した時の表面電位（以下、ＶＬということがある）を測定した。露光から電位測定までの時間は１００ｍｓとした。また、除電光には６６０ｎｍのＬＥＤ光を用いて、除電光照射後の残留電位（以下、Ｖｒということがある）を測定した。
【００５８】
測定は温度５℃、湿度１０％ＲＨ（以下、この環境をＬ／Ｌ環境と呼ぶことがある）、温度２５℃、湿度５０％ＲＨ（以下、この環境をＮ／Ｎ環境と呼ぶことがある）、温度３５℃、湿度８５％ＲＨ（以下、この環境をＨ／Ｈ環境と呼ぶことがある）の３環境下で行った。この結果を表３に示す。
また、Ｎ／Ｎ環境において、上記プロセスを３０Ｋ回転（Ｋは１０００を表す）繰り返し行い、１Ｋ回転毎にＶ０、ＶＬ、Ｖｒの測定を行った。この結果を表４に示す。
【００５９】
【表３】

【００６０】
【表４】

難溶性電荷輸送物質を含有する電子写真感光体は、該電荷輸送物質を含有しない電子写真感光体と同等、または、より優れた電気特性を示した。
［耐刷試験による感光層摩耗量測定］
次にこれらの感光体を市販のレーザープリンター（エプソン製 ＬＰ３０００Ｃ）に装着してＮ／Ｎ環境下において２４０００枚の画像形成を行った。
【００６１】
この際、プリントする前の感光層の厚さ、８０００枚プリント毎の厚さを測定し、その差から摩耗量を計算した。また、これらの４点（初期層厚さ、８０００枚後、１６０００枚後および２４０００枚後）の層厚さ値から最小自乗法により傾き値を算出して、プリント１００００枚当たりの感光層摩耗量を計算するとともに、比較感光体Ｂ１の感光層摩耗量を１００として、感光体Ａ１の感光層摩耗量を相対値で求めた。この結果を表５に示す。
【００６２】
【表５】

本発明の感光体Ａは、比較感光体に比し感光層の摩耗量が少なかった。
［滑り性の測定］
また、感光層摩耗量測定の前にあらかじめ感光体表面の滑り性を測定しておき、２４０００枚耐刷後に再度感光体の滑り性を測定して、滑り性の持続性を評価した。
【００６３】
感光体の滑り性評価は以下のように行った。
トルクモーターを５０ｒｐｍで回転させ、感光体に負荷がかからない状態でのトルクを測定する。このトルク値をＴ０とする。次に、長さ２３０ｍｍ、幅１４ｍｍ（うち自由長 ８ｍｍ）、厚さ２ｍｍのウレタンゴムよりなるブレードを、その先端が感光体の長手方向と平行になるよう、且つ感光体表面の接線とのなす角が２０°となるように、線圧２４．５ｇ／ｃｍで押しつける。この時、ブレードの先端には、筆を用いて若干トナーを付着させた。
【００６４】
感光体をトルクモーターにより、５０ｒｐｍで回転させ、トルクモーターから出力されるトルクを測定し、測定開始後１２０秒から１３０秒の間に得られたトルクを平均した値をＴｍとする。Ｔｍから先に求めた無付加でのトルク（Ｔ０）を引いた値が、感光体にブレードを押し当てたときに発生するトルク値とした。このトルク値を感光体の滑り性を表す指標とした。トルク値の小さい方が感光体の滑り性は良好である。
【００６５】
使用初期のトルクをＴｉｎｉ、３０Ｋ枚の画像形成後のトルクをＴｆｉｎ、その差をΔＴ（＝Ｔｆｉｎ−Ｔｉｎｉ）とした。
この結果を表６に示す。
【００６６】
【表６】

本発明の感光体Ａは、使用初期においても、また３０Ｋの画像形成後においても、従来の感光体より感光体を回転させる際のトルクが小さく、表面滑り性に優れたものであった。
【００６７】
感光体Ａの感光層は、比較感光体Ｂより高いガラス転移温度を示し、且つ難溶性電荷輸送物質を含有する感光体と含有しない感光体とのガラス転移温度の差は、２℃であった。
［接触角の測定］
感光体最表面層の接触角は、自動接触角計ＣＡ−ＶＰ型（協和界面科学社製）を使用して、感光体ドラムと純水との接触角を測定した。
【００６８】
測定はＮ／Ｎ環境において、純水を約１μＬガラスシリンダーから感光体上に滴下し、滴下１秒後の接触角を測定した。この測定を３回行いその平均値を感光体の接触角とした。
この結果を表７に示す。
【００６９】
【表７】

感光体Ａは、比較感光体Ｂに比し大きな接触角を有し、表面付着性が低かった。
【００７０】
【発明の効果】
本発明の、テトラヒドロフラン：トルエン＝８：２の混合溶媒に対して、２５℃での溶解度が０．１ｍｇ／ｃｍ^３以下である電荷輸送物質を含有する電子写真感光体は、耐摩耗性、表面滑り性優れ、なおかつ様々な環境下においても良好な電気特性を示す。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is an electrophotographic photosensitive material that has better electrical characteristics and slipperiness and good printing durability compared to conventional ones used in copiers, printers, faxes, etc. using an electrophotographic process by a dry development method. It is about the body.
[0002]
[Prior art]
2. Description of the Related Art In recent years, electrophotographic technology has been widely used and applied not only in the field of copying machines but also in the field of various printers because of its immediacy and high-quality images. Photoconductors, which are the core of electrophotographic technology, have recently been released from pollution-free inorganic photoconductors such as selenium, arsenic-selenium alloy, cadmium sulfide, and zinc oxide. An organic electrophotographic photoreceptor using an organic photoconductive material having advantages such as easy film formation and easy production has been developed.
[0003]
The electrophotographic photosensitive member is repeatedly used in an electrophotographic process, that is, in a cycle of charging, exposure, development, transfer, cleaning, charge elimination, and the like. Examples of such deterioration include chemical deterioration due to strong oxidizing ozone and NOx generated from the charger, carrier (current) generated by image exposure flowing in the photosensitive layer, static elimination light, and external light. This causes chemical and electrical deterioration due to decomposition of the photosensitive layer composition. Further, as other deteriorations, there are mechanical deteriorations such as abrasion and scratches on the photosensitive layer surface due to rubbing of a cleaning blade, a magnetic brush or the like, contact with a developer or paper, and peeling of a film.
[0004]
In particular, mechanical deterioration tends to appear on a copy image and directly impairs image quality, which is a major factor that limits the life of the photoconductor. That is, in order to develop a photoreceptor having a long life, it is an essential condition to increase the electrical and chemical durability as well as the mechanical strength.
It is the outermost surface layer that the photoreceptor receives a mechanical load, and in the case of an organic electrophotographic photoreceptor, it is the binder resin that binds the outermost surface layer that substantially determines the strength. Contains a conductive substance, and the doping amount is considerably large, so that sufficient mechanical strength has not been achieved, and an organic photoreceptor having higher durability is desired. Furthermore, in order to reduce the size and power consumption of the apparatus, it is necessary to improve the slipperiness of the surface of the photoconductor, reduce the frictional resistance with peripheral members such as a cleaning blade, and reduce the required rotational torque of the photoconductor. It is desired to prevent the occurrence of wear, abrasion and abnormal noise.
[0005]
As a binder resin for forming a photosensitive layer, various polycarbonate resins have been developed and put to practical use. However, conventional organic photoreceptors using polycarbonate do not have sufficient mechanical properties, so that the surface is worn or scratched by a practical load. In addition, the surface slipperiness is poor, and a large force is required for the operation of the photoreceptor, and there are defects such as poor toner cleaning performance and generation of abnormal noise. I was staying.
[0006]
On the other hand, it is known that an electrophotographic photosensitive member using a polyester resin having a specific kinematic viscosity range is particularly excellent in abrasion (abrasion) resistance among mechanical strengths (for example, see Patent Document 1). It is known that a photoreceptor for electrophotography using a polyester resin commercially available under the trade name "U-Polymer" as a binder has particularly excellent sensitivity as compared with polycarbonate (for example, Patent Document 2). reference). Further, an electrophotographic photoreceptor characterized by containing a polyester copolymer having a structure using tetramethylbisphenol F and bisphenol A in a bisphenol component is disclosed (for example, see Patent Document 3).
[0007]
However, although these photoconductors have improved mechanical strength, they have insufficient electrical characteristics as compared with conventional electrophotographic photoconductors using a polycarbonate resin.
[0008]
[Patent Document 1]
JP-A-10-288846
[Patent Document 2]
JP-A-56-135844
[Patent Document 3]
JP-A-3-6567
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electrophotographic photoreceptor having excellent mechanical properties such as friction resistance, scratch resistance, and slipperiness in repeated use, and also having excellent electrical properties. To provide.
[0010]
[Means for Solving the Problems]
The present inventor has conducted intensive studies to solve the above-described problems. As a result, in an electrophotographic photosensitive member having a photosensitive layer on a conductive support, the photosensitive layer has a charge having a specific solubility in an organic solvent. Completed the present invention by finding that by including a transport substance, it is possible to improve electrical properties such as charging characteristics, sensitivity, residual potential and the like, and to improve mechanical properties without impairing coatability and the like. did.
[0011]
That is, the present invention provides an electrophotographic photoreceptor comprising at least a photosensitive layer formed on a conductive support, wherein the photosensitive layer has a solubility at 25 ° C. in a mixed solvent of tetrahydrofuran: toluene = 8: 2. 0.1mg / cm ³ An electrophotographic photoreceptor comprising the following charge transport material:
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
Organic electrophotographic photoreceptors are usually formed by applying a coating solution obtained by dissolving or dispersing a conductive material in an organic solvent. In order to improve the physical properties, a binder resin is often contained in a high weight part, so that it has been considered that it is necessary to have high solubility in a solvent of a coating solution. On the other hand, the electrophotographic photoreceptor of the present invention contains a charge transport material having extremely low solubility in an organic solvent in the photosensitive layer.
[0013]
The electrophotographic photoreceptor of the present invention has a solubility in a photosensitive layer of 0.1 mg / ml at 25 ° C. in a typical solvent mixture of tetrahydrofuran: toluene = 8: 2 as a solvent for a coating solution for forming a photosensitive layer. cm ³ The following charge transport material (hereinafter sometimes referred to as a poorly soluble charge transport material) is contained.
Here, the solubility at 25 ° C. in a mixed solvent of tetrahydrofuran: toluene = 8: 2 means that a supersaturated solution is prepared by heating and dissolving a charge transport material in a mixed solvent of tetrahydrofuran: toluene = 8: 2. Then, the mixture was allowed to stand at 25 ° C. for a certain period of time. At this time, a part of the precipitated charge transporting material was separated by filtration with a filter paper, a fixed amount of the solution after filtration was measured, and the contained mixed solvent was distilled off. The weight of the remaining charge transporting material was determined, and a tetrahydrofuran: toluene = 8: 2 mixed solvent (1 cm) was obtained. ³ The weight value of the charge transport material contained in the mixture is defined as the solubility at 25 ° C. in a mixed solvent of tetrahydrofuran: toluene = 8: 2.
[0014]
The poorly soluble charge transporting substance can be selected from substances known up to now as electron-withdrawing substances and electron-donating substances, and has a solubility in a mixed solvent of tetrahydrofuran: toluene = 8: 2 at 25 ° C. of 0. .1 mg / cm ³ The following may be sufficient. In addition, a plurality of charge transporting substances can be used as a mixture, and the solubility in a mixed solvent of tetrahydrofuran: toluene = 8: 2 at 25 ° C. is 0.1 mg / cm. ³ It is preferable to use a mixture with the above charge transport materials. Particularly preferably, the solubility in a mixed solvent of tetrahydrofuran: toluene = 8: 2 at 25 ° C. is 1 mg / cm. ³ It is used in a mixture with the above charge transport materials.
When a plurality of charge transporting substances are used, the poorly soluble charge transporting substance is usually 5% by weight or more, preferably 10% by weight or more, more preferably 20% by weight, based on the total charge transporting substance, in order to obtain the effects of the present invention. It is used in an amount of at least 40% by weight, particularly preferably at least 40% by weight.
[0015]
Specific examples of the poorly soluble charge transporting material include, as described above, known electron-withdrawing materials such as 2,4,7-trinitrofluorenone and tetracyanoquinodimethane, carbazole, and the like. Heterocyclic compounds such as indole, imidazole, oxazole, pyrazole, oxadiazole, pyrazoline, thiadiazole, aniline derivatives, hydrazone compounds, aromatic amine derivatives, stilbene derivatives, or groups having these compounds in the main chain or side chains It can be selected from electron-withdrawing substances such as polymers and electron-donating substances.In general, materials with relatively good crystallinity, such as those showing a symmetric molecular structure, those showing a rigid molecular structure, and those showing a polar structure A compound having a group, a compound having a large molecular weight, or the like can be obtained. In the compound having such a structure, the molecules are strongly linked by stacking of aromatic rings in the molecule, and as a result, high crystallinity is obtained. In the case of low-molecular-weight organic compounds, in the case of compounds having a highly symmetric structure of molecules in which intermolecular force easily acts or a structure in which molecules are likely to overlap with each other, the molecules are not sufficiently released from the crystallinity and cohesiveness of the molecules. Causes poor solubility. The poorly soluble charge transporting material used in the present invention is developed and selected based on the above technical concept.
[0016]
On the other hand, in the case of an organic electrophotographic photoreceptor, the photosensitive layer is formed by binding a conductive material with a binder resin, but when the amount of the conductive material contained in the photosensitive layer is increased in order to improve the electric characteristics, In addition, since the conductive material functions as a plasticizer for the binder, the glass transition temperature of the photosensitive layer decreases, and the mechanical strength, particularly the abrasion resistance, decreases. That is, by using a conductive material that is hardly taken into the entanglement between the binder resins in the photosensitive layer, that is, hardly functions as a plasticizer, it is possible to prevent a decrease in the glass transition temperature and improve the mechanical strength. It becomes possible.
[0017]
Therefore, it is more preferable to use, among the hardly soluble charge transporting materials of the present invention, those that do not lower the glass transition temperature.
The content of the poorly soluble charge transporting material in the photosensitive layer is usually 2 parts by weight or more, preferably 20 parts by weight, based on 100 parts by weight of the binder resin, in order to obtain the effect when used in the charge transporting layer of the laminated photosensitive layer. In order to increase the transmittance of an exposure light source in the photosensitive layer, the amount is usually 50 parts by weight or less, preferably 30 parts by weight or less based on 100 parts by weight of the binder resin.
[0018]
In the case of a single-layer type photosensitive layer, the transmittance of the photosensitive layer after exposure does not significantly affect the photosensitive layer, so that it can be used in an amount of 1 to 200 parts by weight or 100 parts by weight or more with respect to 100 parts by weight of the binder resin.
The poorly soluble charge transport material used in the present invention has been designed and developed based on the above-mentioned concept, and has a solubility of 0.1 mg / cm at 25 ° C. in a mixed solvent of tetrahydrofuran: toluene = 8: 2. ³ Any charge transport material may be used as long as it is as follows. For example, compounds shown in the following (a) and (b) can be mentioned. More specifically, for example, a charge transport material synthesized by a conventional method is dissolved in toluene, and the solution is contacted with activated clay. The resulting solution is mixed with n-hexane, and the resulting solid is further mixed with toluene. The insoluble matter is filtered off and dried to obtain a poorly soluble charge transport material.
[0019]
Embedded image

<Conductive support>
The electrophotographic photoreceptor of the present invention is formed by forming a photosensitive layer on a conductive support. As the conductive support on which the photosensitive layer is formed, any one that has been used for a well-known electrophotographic photosensitive member can be used. Specifically, for example, conductive materials such as aluminum, copper, palladium, tin oxide, indium oxide, and conductive polymers made of metal materials such as aluminum, stainless steel, copper, nickel, zinc, indium, gold, and silver. Examples include an insulating support band such as a polyester film, paper, or glass provided with a layer. Further, plastic films, plastic drums, papers, paper tubes, and the like, which have been subjected to a conductive treatment by applying a conductive substance such as metal powder, carbon black, copper iodide, and a polymer electrolyte together with a suitable binder, may be mentioned. Further, a plastic sheet or drum containing a conductive substance such as a metal powder, carbon black, or carbon fiber to become conductive may be used. Further, a plastic film or a belt which is conductively treated with a conductive metal oxide such as tin oxide or indium oxide may be used. The surface of such a conductive support can be subjected to various kinds of treatments, for example, surface oxidation treatment and chemical treatment within a range that does not affect the image quality. The shape can be any shape such as a drum, a sheet, a belt, and a seamless belt. Among them, a metal endless pipe cut into an appropriate length is preferable, and aluminum is most preferably used.
<Blocking layer>
A known blocking layer, which is generally used, may be provided between the conductive support and the photosensitive layer. As the blocking layer, for example, anodized aluminum film, aluminum oxide, inorganic layers such as aluminum hydroxide, polyvinyl methyl ether, poly-N-vinyl imidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, ethylene-acrylic acid copolymer, polyethylene , Polyester, phenolic resin, vinyl chloride-vinyl acetate copolymer, epoxy resin, polyvinylpyridine, polyurethane, polyglutamic acid, polyvinyl alcohol, casein, polyvinylpyrrolidone, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, polyamide Etc. are used. When the organic layer is used as the blocking layer, a single metal oxide such as titania, alumina, silica, zirconium oxide, or a fine metal powder such as copper, silver, or aluminum may be dispersed.
[0020]
Further, in the blocking layer, especially for the purpose of preventing interference fringes in laser exposure, fine particles of metal oxides such as alumina, titania and silica, and organic or inorganic dyes and pigment particles capable of absorbing the laser light wavelength to be used. Etc. may be contained.
The thickness of these blocking layers can be set conveniently, but is usually in the range of 0.05 to 20 μm, preferably 0.1 to 10 μm.
[0021]
The content ratio of the metal oxide particles or the pigments and the pigment particles to the binder resin is not particularly limited, but it can be used in the range of 40 to 400 parts by weight with respect to 100 parts by weight of the binder to form the undercoat layer. This is preferred from the viewpoints of dispersion stability, storage stability, applicability and the like.
<Structure of photosensitive layer>
Examples of the photoconductor using an organic photoconductive material include a so-called single-layer photoconductor in which a photoconductive material is dispersed in a binder resin, and a stacked photoconductor in which a charge generation layer and a charge transport layer are stacked. Are known.
[0022]
The photoreceptor of the present invention may be in any form of a single-layer (dispersion type) photosensitive layer or a laminated type photosensitive layer as long as the outermost surface layer contains the poorly soluble charge transport material of the present invention. However, considering the mechanical properties, electrical properties, and manufacturing stability of the photoreceptor, a highly sensitive photoreceptor can be obtained by combining a highly efficient charge generating substance and a charge transporting substance. From the viewpoint that a photosensitive member having a wide selection range and high safety can be obtained, and coating productivity is high and the cost is relatively advantageous, a normally laminated photosensitive member is preferable.
<Charge generating substance>
As the charge generation material used for the charge generation layer, any of known materials can be used, and selenium and its alloys, oxide semiconductors such as arsenic-selenium, cadmium sulfide, zinc oxide, and titanium oxide, and amorphous silicon Various organic pigments and dyes such as silicon-based materials, other inorganic photoconductive substances, phthalocyanines, azo dyes, quinacdrine, polycyclic quinones, pyrylium salts, perylene, indigo, thioindigo, anthantrone, pyranthrone, and cyanine can be used. Among them, metals such as perylene, metal-free phthalocyanine, copper, indium chloride, gallium chloride, silicon, tin, oxytitanium, zinc, vanadium, or oxides, chlorides, phthalocyanines coordinated with hydroxides, monoazos, bisazos And azo pigments such as trisazo and polyazos.
[0023]
Of these, oxytitanium phthalocyanine is more preferable in terms of sensitivity when used in an image forming apparatus provided with an exposure device using monochromatic light in the range of 550 to 850 nm, and in particular, a Bragg angle (2θ) in X-ray diffraction using CuKα radiation. Y-type oxytitanium phthalocyanine having a characteristic peak at (± 0.2 °) = 27.3 ° is most preferred. When used in an image forming apparatus provided with an exposure device using white light or monochromatic light in the range of 350 to 550 nm, an azo pigment is preferably used in terms of sensitivity.
[0024]
Further, two or more kinds of charge generating substances may be mixed for the purpose of improving the charging property, reducing the light fatigue, and adjusting the sensitivity.
The charge generation layer can be obtained by applying and drying a coating solution obtained by dispersing the above-mentioned charge generation substance and the binder polymer in a solvent or dispersed therein. Examples of the binder include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, acrylic ester, methacrylic ester, vinyl alcohol, and ethyl vinyl alcohol, polyvinyl acetal, polycarbonate, polyester, polyamide, polyurethane, cellulose ester, and phenoxy. Resins, silicon resins, epoxy resins and the like can be mentioned.
[0025]
The ratio of the charge generating substance and the binder forming the charge transporting layer is not particularly limited, but is generally 5 to 500 parts by weight, preferably 20 to 300 parts by weight, per 100 parts by weight of the charge generating substance. Use a polymer.
Further, the charge generation layer may be a vapor-deposited film of the charge generation substance. The thickness of the charge generation layer is set to 0.05 to 5 μm, preferably 0.1 to 2 μm.
<Charge transport material>
The photosensitive layer of the present invention contains a poorly soluble charge transporting substance, but other charge transporting substances may be used in combination. Examples of the charge transport material used in the photosensitive layer include diphenoquinone derivatives, aromatic nitro compounds such as 2,4,7-trinitrofluorenone, carbazole derivatives, indole derivatives, imidazole derivatives, oxazole derivatives, pyrazole derivatives, oxadiazole derivatives, Heterocyclic compounds such as pyrazoline derivatives and thiodiazole derivatives, aniline derivatives, hydrazone compounds, aromatic amine derivatives, stilbene derivatives, butadiene derivatives, enamine compounds, those in which a plurality of these compounds are bonded, or groups composed of these compounds A polymer having a chain or a side chain is exemplified.
[0026]
The charge transport layer is dissolved or dispersed in a suitable solvent together with a known polymer having excellent performance using these substances as a binder, and if necessary, an electron-accepting compound, or a plasticizer, inorganic particles, an organic pigment, and the like. It can be obtained by adding additives.
Polymethyl methacrylate, polystyrene, vinyl polymers such as polyvinyl chloride, and copolymers thereof, polycarbonate, polyester, polysulfone, phenoxy, epoxy, silicone resins and other thermoplastic resins and various thermosetting resins have been used. I have. Among many binder resins, polycarbonate resins have relatively excellent performance.
[0027]
If the molecular weight of the polycarbonate is too low, the mechanical strength is insufficient, and if the molecular weight is too high, the viscosity of the coating solution for forming the photosensitive layer becomes too high, which causes a problem such as a decrease in productivity. In the range of 10,000 or more, preferably 20,000 or more, and 100,000 or less, more preferably 70,000 or less.
[0028]
As a polycarbonate to be applied, a photoreceptor film formed in a sheet shape was subjected to a Taber abrasion tester (manufactured by Toyo Seiki Co., Ltd.) under the atmosphere of 23 ° C. and 50% RH using a worn wheel CS-10F under a load of 100 g under a load of 100 g. It is preferable that the weight loss before and after the test when rotated and tested is 6.0 mg or less.
The thickness of the charge transport layer is usually in the range of 10 to 50 μm, preferably 13 to 35 μm.
[0029]
<Coating solution for forming photosensitive layer>
Usually, an organic photosensitive layer for an electrophotographic photosensitive member is formed by applying and drying a coating solution in which a conductive material, a binder resin and various additives are dissolved or dispersed in a specific solvent.
[0030]
Examples of the solvent include amines such as butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, amides such as N-N-dimethylformamide, methyl alcohol, ethyl alcohol, alcohols such as isopropanol, acetone, Ketones such as methyl ethyl ketone and cyclohexanone, alkyl halides such as chloroform, 1,2-dichloroethane, trichloroethylene, tetrachloroethane, and dichloromethane, cycloethers such as tetrahydrofuran, ethers such as dioxane, ethyl acetate, butyl acetate and the like Esters, benzene, toluene, aromatic hydrocarbons such as xylene, ethyl acetate, butyl acetate, dimethyl sulfoxide, anisole, methyl cellosolve, etc. It is used, preferably used toluene, chloroform, tetrahydrofuran, anisole, dioxane. These solvents may be used alone or as a mixture of two or more.
<Method of forming photosensitive layer>
Examples of the method for applying the photosensitive layer include a spray coating method, a spiral coating method, a ring coating method, and a dip coating method.
[0031]
Spray coating methods include air spray, airless spray, electrostatic air spray, electrostatic airless spray, rotary atomizing electrostatic spray, hot spray, hot airless spray, etc., but fine particles for obtaining a uniform film thickness In consideration of the degree of chemical conversion, adhesion efficiency, etc., in the case of a rotary atomizing electrostatic spray, the conveying method disclosed in Japanese Unexamined Patent Publication No. 1-805198, that is, the cylindrical workpiece is rotated and spaced apart in the axial direction. By continuously transporting the electrophotographic photoreceptors, it is possible to obtain an electrophotographic photoreceptor excellent in uniformity of film thickness with high overall adhesion efficiency.
[0032]
Examples of the spiral coating method include a method using a liquid coating machine or a curtain coating machine disclosed in JP-A-52-119651, and a method of coating a coating material through a fine opening disclosed in JP-A-1-231966. There is a method of continuously flying in a streak shape, a method using a multi-nozzle body disclosed in JP-A-3-193161, and the like.
[0033]
The dip coating method includes, for example, the following charge transport layer coating forming means.
Using a charge transport material, a binder resin, a solvent, and the like, the total solid content concentration is 15% or more, preferably 40% or less, and the viscosity is usually 50 centipoise to 700 centipoise or less, and further preferably 100 centipoise to 500 centipoise. The following coating liquid for forming a charge transport layer is prepared.
[0034]
Here, the viscosity of the coating liquid is substantially determined by the kind of the resin and the molecular weight of the binder, but if the molecular weight is too low, the mechanical strength of the photosensitive layer is reduced, so the binder resin having a molecular weight that does not impair the mechanical strength of the photosensitive layer. It is preferred to use The charge transport layer or the photosensitive layer is formed by a dip coating method using the coating solution thus adjusted.
[0035]
Thereafter, the coating film is dried. The drying temperature and time are adjusted so that necessary and sufficient drying is performed.
The drying temperature is usually in the range of 100 to 250 ° C, preferably 110 to 170 ° C, more preferably 115 to 140 ° C. As a drying method, a hot air dryer, a steam dryer, an infrared dryer, and a far infrared dryer can be used.
[0036]
The thus obtained electrophotographic photoreceptor of the present invention maintains excellent printing durability and slipperiness over a long period of time, and is suitable for electrophotographic fields such as copying machines, printers, fax machines, and plate making machines.
<Image forming method>
An electrophotographic apparatus such as a copier and a printer using the electrophotographic photoreceptor of the present invention includes at least charging, exposure, development, transfer, and each process of static elimination. Is also good.
[0037]
As a charging method (charging machine), for example, any of corotron and scorotron charging using corona discharge, contact charging using a conductive roller or a brush, a film, or the like may be used. Among them, scorotron charging is often used in the charging method using corona discharge in order to keep the dark area potential constant.
Recently, in view of the environment, the number of ozoneless copying machines and printers is increasing, and a charging roller is often used. As a charging method, DC charging and AC superimposed DC charging are used.
[0038]
The photoreceptor containing a poorly soluble charge transport material used in the present invention exhibits good light transmittance in a wavelength region of 370 to 800 nm. Therefore, as an exposure means for an electrophotographic photoreceptor using this resin, Any light source such as a red laser of 630 nm, 650 nm, 680 nm or the like, or a blue LED can be used, as well as exposure with a laser beam of 780 nm, which is currently widely used.
[0039]
Further, since it shows good light transmittance for light in the entire visible light region, it is suitable for an electrophotographic apparatus for forming a color image, such as a color copying machine or a color printer.
As a developing method, a general method of developing by contacting or non-contacting a magnetic or non-magnetic one-component developer, a two-component developer, a polymerized toner or the like is used.
[0040]
Addition of the poorly soluble charge transporting material used in the present invention improves the smoothness and surface properties of the outermost surface of the photosensitive layer, so that the transferability, resolution and the like may be improved. In particular, when a polymerized toner having a small particle size and good uniformity is used, the above characteristics are expected to be greatly improved.
[0041]
The transfer may be performed directly on paper, an OHP film, or the like, or may be temporarily transferred onto an intermediate transfer (on a belt or in a drum shape) and then transferred onto paper or an OHP film. Usually, after the transfer, a process of fixing the developer to paper or the like is used. As a fixing unit, generally used heat fixing, pressure fixing, or the like can be used.
[0042]
In addition to these processes, processes that are generally used, such as cleaning and static elimination, may be provided.
[0043]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples unless it exceeds the gist. In the following, “parts” means “parts by weight” unless otherwise specified.
Synthesis example (Synthesis of conventional charge transporting material and poorly soluble charge transporting material of the present invention)
54 g of N, N'-bis (4-formylphenyl) -N, N'-diphenylbenzidine and 87 g of trans-3-phenyl-2-propenyltriphenylphosphinium chloride were added to 550 g of THF, and sodium methylate was added thereto. 41 g of a 28% methanol solution were added. After stirring at room temperature for 2 hours, the solution was discharged into water, the organic layer was extracted, and added to a large amount of methanol. The precipitated solid was filtered, washed with methanol, and dried to obtain 70 g of a crude product. 40 g of the crude product and 360 g of toluene were mixed to prepare a crude charge transport material solution. The crude charge transport material solution was mixed with 20 g of activated carbon and stirred for 30 minutes at a temperature of 25 to 60 ° C., and then the activated carbon was filtered off to obtain a purified charge transport material solution.
[0044]
150 g of the purified charge transport material solution was mixed with 1000 ml of methanol, and the precipitated solid was separated by filtration and dried to obtain a charge transport material. Further, a solution obtained by mixing 200 g of the purified charge transport material solution and 10 g of activated clay, stirring the mixture for 30 minutes at a temperature of 25 to 60 ° C., and filtering the activated clay to obtain a solution, repeated five times, 300 ml of n-hexane was mixed, and the precipitated solid was collected by filtration. 5 g of the obtained solid and 100 g of toluene at 60 ° C. were stirred and mixed for 30 minutes, followed by further filtration. The insoluble matter filtered off on filter paper was dried. Thus, the desired poorly soluble charge transport material was obtained.
[0045]
The obtained poorly soluble charge transport material was mixed with tetrahydrofuran: toluene = 8: 2 mixed solvent of 100 cm. ³ The solution was heated to 60 ° C., and the charge transporting material was sufficiently dissolved in the solvent while stirring the solution at 60 ° C. for 1 hour. Thereafter, the mixture was allowed to stand in a 25 ° C. atmosphere for 24 hours to prepare a 25 ° C. saturated solution in which undissolved residue was precipitated.
[0046]
The solution in which the charge transporting material subjected to the above operation was dissolved was filtered using five kinds of C filter paper for quantitative analysis specified in JIS P3801. 100 cm of this filtrate ³ Was placed in a container, and dried using a vacuum dryer until the mixed solvent was sufficiently volatilized. The weight of the residue remaining after drying was measured, and the amount of the solution initially used was 100 cm. ³ , The solubility in the solvent (g / cm ³ ).
Table 1 shows the solubility of the poorly soluble charge transport agent obtained in Synthesis Example 1 when the above-mentioned measurement method was repeated three times.
[0047]
[Table 1]

From these results, the solubility of the poorly soluble electrolytic substance produced in Synthesis Example 1 was 0.1 g / cm. ³ It turned out that:
[0048]
The obtained charge transporting substance and the poorly soluble charge transporting substance were subjected to mass spectrometry (EI method). As a result, it was found that both had a molecular weight of 745, and a compound conforming to the following structural formula (a) was obtained. In addition, the powder X-ray spectrum of these compounds revealed that the crystallinity of the poorly soluble charge transport material was significantly higher than that of the charge transport material. From these results, it was found that the obtained poorly soluble charge transporting material was the compound (a) having the same structure as the charge transporting material, but had significantly different crystallinity.
[0049]
Embedded image

Example 1
In X-ray diffraction by CuKα ray, 10 parts of oxytitanium phthalocyanine showing a maximum diffraction peak at 27.3 ° at a Bragg angle (2θ ± 0.2) of 27.3 ° and 150 parts of 1,2-dimethoxyethane are mixed, and the mixture is mixed with a sand grind mill. A pulverization dispersion treatment was performed to prepare a pigment dispersion.
[0050]
In addition, 5 parts of polyvinyl butyral (trade name: Denkabutyral # 6000C, manufactured by Denki Kagaku Kogyo KK) was dissolved in 95 parts of 1,2-dimethoxyethane to prepare a binder solution having a solid content of 5%.
160 parts of the previously prepared pigment dispersion, 100 parts of the binder solution, and an appropriate amount of 1,2-dimethoxyethane and an appropriate amount of 4-methoxy-4-methylpentanone-2 were mixed, and the solid content concentration was 4.0%. A coating solution for forming a charge generation layer in which 1,2-dimethoxyethane: 4-methoxy-4-methylpentanone-2 = 9: 1 was prepared.
[0051]
The surface of a cylinder made of an aluminum alloy with an outer diameter of 30 mm, a length of 285 mm, and a wall thickness of 1.0 mm, whose surface is mirror-finished, is subjected to an anodic oxidation film treatment, and then a sealing treatment containing nickel acetate as a main component. As a result, an anodized film (alumite film) of about 6 μm was formed. This cylinder was dip-coated in a coating solution for forming a charge generation layer to form a charge generation layer having a thickness of 0.3 μm.
[0052]
Next, 30 parts of the charge transport material obtained in the above synthesis example, 20 parts of the poorly soluble charge transport material, 8 parts of the antioxidant represented by the following structural formula (c), and the polycarbonate resin of the following structural formula (d) (viscosity average) A cylinder having a charge generation layer formed thereon was immersed in 100 parts of a mixed solvent (molecular weight: about 30,000) in a mixed solvent of tetrahydrofuran: toluene = 80: 20 to obtain a coating liquid having a thickness of 18 μm. A charge transport layer was provided. The photoreceptor thus obtained is referred to as photoreceptor A1.
[0053]
Embedded image

Comparative Example 1
A photoconductor drum was prepared in the same manner as in Example 1, except that only 50 parts of the charge transport material of the structural formula (1) used in Example 1 were used. This is designated as Comparative Photoconductor B1.
[Measurement of glass transition point (Tg)]
The charge transport liquid used in the production of the photoreceptor A1 and the comparative photoreceptor B1 was cast on a glass plate, and air-dried for 20 minutes, then dried at 150 ° C. for 1 hour to sufficiently volatilize the solvent in the liquid, A film having the same composition as the transport layer was produced. This film was cut out with a cutter, and about 5 mg was weighed with a precision balance and placed in an aluminum sample container for DSC measurement to prepare a sample for glass transition temperature measurement. This sample was introduced into DSC7 (manufactured by Perkin Elmer Japan), and the glass transition temperature of the charge transport layer was measured.
[0054]
In the measurement, the temperature was increased from 20 ° C. to 200 ° C. at a rate of 10 ° C./min while flowing nitrogen gas. (First temperature rise process) The purpose of the first temperature rise process is to remove the history in the film received by drying or the like at the time of sample preparation.
After the temperature was raised to 200 ° C., the temperature was maintained for 1 minute, the temperature was lowered to 20 ° C. at a rate of 500 ° C./min, and the temperature was maintained at 20 ° C. for 5 minutes.
[0055]
Next, the temperature was raised to 200 ° C. at a rate of 10 ° C./min. (Second Temperature Rise Process) The peak of heat absorption and heat generation in the second temperature rise process was defined as the glass transition temperature (Tg) of the produced photosensitive film. This operation was performed three times for the same sample, and the average was defined as Tg of the charge transport layer. Table 2 shows the results.
[0056]
[Table 2]

[Electrical property evaluation]
The photoreceptor A1 and the comparative photoreceptor B1 were mounted on a photoreceptor characteristic tester (basic and application of continuous electrophotographic technology, edited by the Society of Electrophotography, Corona Co., pp. 404-405), and charged, exposed, and measured for potential. An electrical property evaluation test was performed using a cycle of static elimination.
[0057]
The initial surface potential was -800 V, and the exposure was performed by using a halogen lamp whose light was converted to monochromatic light of 780 nm by an interference filter, and the exposure amount required to reduce the surface potential from -800 V to -400 V by half (hereinafter referred to as half reduction). The surface potential (hereinafter, also referred to as VL) when irradiating 1.4 μJ / cm 2 was measured. The time from exposure to potential measurement was 100 ms. In addition, a residual potential (hereinafter, sometimes referred to as Vr) after irradiation of the neutralizing light was measured using LED light of 660 nm as the neutralizing light.
[0058]
The measurement is performed at a temperature of 5 ° C. and a humidity of 10% RH (hereinafter, this environment may be referred to as an L / L environment), a temperature of 25 ° C., a humidity of 50% RH (hereinafter, this environment may be referred to as an N / N environment). ), A temperature of 35 ° C. and a humidity of 85% RH (hereinafter, this environment may be referred to as an H / H environment). Table 3 shows the results.
In the N / N environment, the above process was repeated for 30K rotations (K represents 1000), and V0, VL, and Vr were measured every 1K rotations. Table 4 shows the results.
[0059]
[Table 3]

[0060]
[Table 4]

The electrophotographic photoreceptor containing the poorly soluble charge transport material exhibited the same or better electrical properties as the electrophotographic photoreceptor not containing the charge transport material.
[Measurement of wear amount of photosensitive layer by printing durability test]
Next, these photoconductors were mounted on a commercially available laser printer (LP3000C, manufactured by Epson) to form 24,000 images under an N / N environment.
[0061]
At this time, the thickness of the photosensitive layer before printing and the thickness of every 8,000 prints were measured, and the wear amount was calculated from the difference. The slope value was calculated by the least squares method from the layer thickness values at these four points (initial layer thickness, after 8,000 sheets, after 16,000 sheets and after 24,000 sheets), and the wear amount of the photosensitive layer per 10,000 sheets of prints was calculated. Was calculated, and the wear amount of the photosensitive layer of the photosensitive member A1 was calculated as a relative value, with the wear amount of the photosensitive layer of the comparative photosensitive member B1 as 100. Table 5 shows the results.
[0062]
[Table 5]

The photoreceptor A of the present invention had a smaller wear amount of the photosensitive layer than the comparative photoreceptor.
[Slidability measurement]
Further, before measuring the wear amount of the photosensitive layer, the slipperiness of the photoreceptor surface was measured in advance, and after the printing of 24,000 sheets, the slipperiness of the photoreceptor was measured again to evaluate the durability of the slipperiness.
[0063]
The evaluation of the slipperiness of the photoreceptor was performed as follows.
The torque motor is rotated at 50 rpm, and the torque is measured with no load applied to the photoconductor. This torque value is defined as T0. Next, a blade made of urethane rubber having a length of 230 mm, a width of 14 mm (including a free length of 8 mm) and a thickness of 2 mm is formed so that its tip is parallel to the longitudinal direction of the photoconductor and is tangential to the surface of the photoconductor. Press at a linear pressure of 24.5 g / cm so that the angle becomes 20 °. At this time, a small amount of toner was attached to the tip of the blade using a brush.
[0064]
The photoconductor is rotated at 50 rpm by a torque motor, the torque output from the torque motor is measured, and a value obtained by averaging the torque obtained from 120 seconds to 130 seconds after the start of the measurement is defined as Tm. The value obtained by subtracting the previously obtained torque (T0) without addition from Tm was defined as the torque value generated when the blade was pressed against the photoconductor. This torque value was used as an index representing the slipperiness of the photoconductor. The smaller the torque value, the better the slipperiness of the photoreceptor.
[0065]
The torque at the beginning of use was Tini, the torque after image formation of 30K sheets was Tfin, and the difference was ΔT (= Tfin−Tini).
Table 6 shows the results.
[0066]
[Table 6]

The photoreceptor A of the present invention had a smaller torque when rotating the photoreceptor than the conventional photoreceptor, and was excellent in surface slipperiness, both in the early stage of use and after image formation at 30K.
[0067]
The photosensitive layer of the photoconductor A showed a higher glass transition temperature than the comparative photoconductor B, and the difference in glass transition temperature between the photoconductor containing the poorly soluble charge transport material and the photoconductor not containing the same was 2 ° C. .
[Measurement of contact angle]
The contact angle of the outermost surface layer of the photoreceptor was measured by using an automatic contact angle meter CA-VP type (manufactured by Kyowa Interface Science Co., Ltd.) between the photoreceptor drum and pure water.
[0068]
For the measurement, in an N / N environment, about 1 μL of pure water was dropped on a photoreceptor from a glass cylinder, and a contact angle was measured one second after dropping. This measurement was performed three times, and the average value was defined as the contact angle of the photoconductor.
Table 7 shows the results.
[0069]
[Table 7]

Photoconductor A had a larger contact angle than Comparative Photoconductor B, and had low surface adhesion.
[0070]
【The invention's effect】
The solubility at 25 ° C. in a mixed solvent of tetrahydrofuran: toluene = 8: 2 of the present invention is 0.1 mg / cm. ³ An electrophotographic photoreceptor containing the following charge transport material has excellent abrasion resistance and surface slipperiness, and shows good electrical properties even in various environments.

Claims (4)

In an electrophotographic photosensitive member having a photosensitive layer on a conductive support, the photosensitive layer has a solubility of 0.1 mg / cm ³ or less at 25 ° C. in a mixed solvent of tetrahydrofuran: toluene = 8: 2. An electrophotographic photoreceptor containing a charge transport material. The photosensitive layer contains a plurality of charge transport materials, and at least one of the charge transport materials has a solubility at 25 ° C. in a mixed solvent of tetrahydrofuran: toluene = 8: 2 of greater than 0.1 mg / cm ^3. The electrophotographic photoconductor according to claim 1, wherein the electrophotographic photoconductor is a charge transport material. 3. The electrophotographic photoreceptor according to claim 1, wherein the charge transport material is a compound having alkenylene in a molecule. The glass transition temperature Tg2 of the photosensitive layer containing the charge transport material according to claim 1 and the glass transition temperature Tg1 of the same photosensitive layer except that the charge transport material is not contained are represented by the following formula (1). The electrophotographic photosensitive member according to claim 1, wherein the electrophotographic photosensitive member is satisfied.
Tg2-Tg1 ≤ 10 ° C (1)