JP4479119B2 - Method for producing undercoat layer coating solution for electrophotographic photosensitive member, electrophotographic photosensitive member and image forming apparatus using the coating solution - Google Patents

Description

式中、Ａ、Ｂはそれぞれ、置換基を有してもよいシクロへキシル基を表し、Ｒ₁ 、Ｒ₂はそれぞれ、独立として水素、アルキル基、アリール基、アラルキル基あるいはアルコキシ基を表す。なお、これらの有機基には本発明の効果を損なわない限り置換基を有していてもよい。ここで、アルキル基としては、メチル基、エチル基、ｎ−プロピル基、イソプロピル基等の低級アルキル基が好ましく、アルコキシ基としてはメトキシ基、エトキシ基、ｎ−プロポキシ基、イソプロポキシ基等の低級アルコキシ基が好ましく、アリール基としてはフェニル基が好ましく、アラルキル基としてはベンジル基、フェネチル基等が挙げられるが、Ｒ₁ 、Ｒ₂ としてより好ましいのは、水素原子、メチル基、エチル基である。
【００１０】
かかる共重合ポリアミドの数平均分子量としては、１万〜５万、より好ましくは１．５万〜３．５万の範囲のものを用いるのがよい。これはかかる範囲外であると、塗布性や保存性に問題を生じ易いためである。
【００１１】
本発明で用いる溶媒としては、上記のようなバインダー樹脂を溶解しうる種々の溶媒であれば特に限定されるものではないが、アルコール類やエーテル類、ケトン類が好適に用いられる。これらの中でもメタノール、エタノール、プロパノール、ブタノール等の低級アルコール及びこれらの混合物を用いるのがより好ましい。
【００１２】
かかる溶媒に対するバインダー樹脂の使用量は、得られる下引き層塗布液として塗布できうる状態であれば、特に限定されるものではないが、通常、１wt％〜１０wt％の範囲、好ましくは１wt％〜８wt％の範囲、より好ましくは１wt％〜６wt％の範囲で混合される。
【００１３】
本発明で用いられる無機粒子としては、電子写真感光体用下引き層に用いられる種々の無機粒子であればよく、例えば、アルミナや酸化チタン等が好適に用いられる。本発明では、この方法によって調整された下引き層用塗布液との相性の観点からアルミナを用いるのが特に好ましい。
【００１４】
アルミナとしては公知のアルミナを用いることが出来るが、特に、含水量１wt％〜３wt％のアルミナ粒子を用いることが好ましい。アルミナ粒子の粒径はおよそ均一なものが好ましく、平均粒径が０．０１μｍ〜１μｍのものが好ましく、０．１μｍ〜０．８μｍであればより好ましく、０．３μｍ〜０．６μｍであれば特に好ましい。なお、ここで言う含水量とは３５℃、８５％ＲＨ環境下に４時間放置後の値を意味する。
【００１５】
バインダー樹脂に対する無機粒子の添加比は下引き層塗布液の特性を損なわない限り任意に選べるが、４０wt％から４００wt％の範囲で使用することが、下引き層塗布液の保存安定性、塗布性の面で好ましい。
【００１６】
本発明の下引き層塗布液は、例えば以下のようにして調整される。
まず、バインダー樹脂を溶媒と混合しバインダー樹脂が溶解された混合溶液を得る。次いで、一定の容積を有する容器にこの混合溶液を注入し、加圧状態で加熱する。ここで、加圧状態で加熱することによりバインダー樹脂の熱運動が盛んになる結果、絡み合ったバインダー樹脂がほどけ、安定化すると考えられる。このような工程により下引き層塗布液を製造すると、塗布するまでに下引き層塗布液の液温が低下しても、下引き層塗布液がゲル化する事態を効果的に防止することができる。
【００１７】
混合溶液に対する加圧状態とは、通常、１．５気圧〜１０気圧の範囲、好ましくは１．５気圧〜５気圧の範囲であり、更に好ましくは１．７気圧〜４気圧の範囲で加圧されておればよい。加熱温度としては、バインダー樹脂の熱運動を盛んとし、絡み合ったバインダー樹脂がほどけ安定化するような温度であれば、特に限定されるものではない。具体的には、用いる溶媒により異なるが、通常は用いる溶媒の沸点−１５℃以上の加熱温度、好ましくはその沸点−５℃以上、更に好ましくは沸点以上で加熱するのがよい。特に、溶媒の沸点以上で加熱する場合には、その溶媒の沸点〜沸点＋１０℃の範囲で加熱するのがより好ましく、当該沸点＋１℃〜当該沸点＋７℃の範囲であれば更に好ましく、当該沸点＋２℃〜当該沸点＋５℃の範囲であれば特に好ましい。ここで、溶媒として混合溶媒を用いる場合の溶媒の沸点とは沸点の最も低い溶媒の沸点を意味する。
【００１８】
本発明での加圧状態で加熱する方法としては、加熱時に加圧されていれば特に限定されるものではないが、例えば、バインダー樹脂と溶媒等からなる混合液を密封下で溶媒の沸点以上に加熱することにより溶媒蒸気による加圧状態で加熱する方法や外部から混合液に圧力を付加しながら加熱する方法等が挙げられる。何れの方法においても、少なくともバインダー樹脂と溶媒からなる混合液に対して、上述したような圧力が付加された状態で加熱するのが重要である。特に、本発明の加圧状態で加熱する工程は、密閉下で溶媒の沸点以上で加熱する方法、具体的には、密封容器内で加熱することにより装置的にも容易に加圧状態を作り出せるので好ましい。以下、密封容器内で加熱する場合について説明する。
【００１９】
密封容器は、完全に密封されているものの他に、完全に密封されている状態でなくともある程度容器内の圧力が高くなるものであればよい。加熱中の密封容器内の最大圧力としては、上述したような加圧状態、すなわち、１．５気圧〜１０気圧が好ましく、１．５気圧〜５気圧であれば、より好ましく、更に１．７圧〜４気圧であれば特に好ましい。加熱時間としては、十分に均一な下引き層塗布液が調整されればよく、具体的には、通常１分〜１０時間で加熱するのが好ましく、１０分〜３時間であればより好ましく、２０分〜２時間であれば更に好ましく、２５分〜１時間であれば特に好ましい。加熱温度としては、上述したように、溶媒の沸点以上の温度であり、その溶媒の沸点〜沸点＋１０℃の範囲で加熱するのがより好ましく、当該沸点＋１℃〜当該沸点＋７℃の範囲であれば更に好ましく、当該沸点＋２℃〜当該沸点＋５℃の範囲であれば特に好ましい。
【００２０】
このようにして調整した混合溶液に更に無機粒子を添加する場合においては、予め調整した無機粒子を加え分散処理を施すことが望ましい。分散処理の方法としては、サンドグラインドミルやボールミル、ホモジナイザー等による分散処理方法が挙げられるが、これらの中でもホモジナイザーによる分散処理を用いると均一に分散出来るので好ましい。分散後、上記と同様にして、かかる混合溶液を加圧状態で加熱する。この場合の加圧状態で加熱するのは上記と同様であり、バインダー樹脂の熱運動を盛んとし、絡み合ったバインダー樹脂をほどき安定化させるのである。なお、バインダー樹脂、無機粒子、溶媒を一度に混合してこれらの混合溶液を得た後、上記のように、加圧状態で加熱してもよい。
【００２１】
なお、本発明においては、上述のように下引き層塗布液を調整した後、濾過を施すことによってより好ましい下引き層塗布液が得られるので好ましい。濾過処理としては、コットンフィルター又はガラスフィルター等を用い調整後のかかる塗布液を濾過処理するのがよいが、更にかかる濾過処理した後にメンブランフィルターで再度濾過処理を行うのがより好ましい。このような濾過処理を行うことによりバインダー樹脂のゲル化をより効果的に防止できるからである。
【００２２】
下引き層塗布液を製造した後は、塗布液を５℃〜５５℃、好ましくは、１０℃〜４０℃、より好ましくは、１５℃〜２５℃に保つことが特に好ましい。あまりに液温を高くするとゲル化が始まるおそれがあり、液温を低くすると液の粘度が下がり、また結晶化が始まるからである。
【００２３】
次に、本発明の他の態様である電子写真感光体について説明する。かかる電子写真感光体は上述の製造方法で得られた下引き層塗布液を導電性支持体上に均一に塗布して下引き層を形成し、次いで、かかる下引き層の上層に感光層を形成したものである。下引き層の膜厚は、０．１μｍから１０μｍ、好ましくは０．２μｍから５μｍの範囲で使用されるのが最も効果的である。
【００２４】
感光層は導電性支持体上に設けられた下引き層の上層に設けられる。導電性支持体としては、アルミニウム、ステンレス綱、銅、ニッケル等の金属材料、表面にアルミニウム、銅、パラジウム、酸化すず、酸化インジウム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体が使用される。導電性支持体と電荷発生層の間には下引き層が設けられるが、下引き層と共に公知のアルマイト層が形成されていても良い。
【００２５】
感光層は、積層型、単層型のいずれであってもよいが、積層型が特に好適に用いられる。積層型の感光層には、電荷発生剤を含む電荷発生層と、その上に設けられ電荷輸送剤を含む電荷輸送層が形成されており、更にその上に表面層が設けられていても良い。
【００２６】
電荷発生剤としては、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、その他の無機光導電体、フタロシアニン、アゾ、キナクリドン、多環キノン、ペリレン、インジゴ、ベンズイミダゾールなどの有機顔料を使用することができる。特に銅、塩化インジウム、塩化カリウム、スズ、オキシチタニウム、亜鉛、バナジウムなどの金属、またはその酸化物や塩化物の配位したフタロシアニン類、無金属フタロシアニン類、または、モノアゾ、ビスアゾ、トリスアゾ、ポリアゾ類などのアゾ顔料が好ましい。これらのうち特にアゾ顔料又はフタロシアニン類がより好ましく、いわゆるＹ型オキシチタニウムフタロシアニンが特に好ましい。これは通常の顔料より熱による結晶変換が起きやすいためである。
【００２７】
いわゆるＹ型オキシチタニウムフタロシアニンとは、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ものである。この結晶型オキシチタニウムフタロシアニンは、一般にはＹ型あるいはＤ型と呼ばれているものであり、例えば特開昭６２−６７０９４号公報の第２図（同公報ではＩＩ型と称されている）、特開平２−８２５６号公報の第１図、特開昭６４−８２０４５号公報の第１図、電子写真学会誌第９２巻（１９９０年発行）第３号第２５０〜２５８頁（同刊行物ではＹ型と称されている）に示されたものである。この結晶型オキシチタニウムフタロシアニンは、２７．３°に最大回折ピークを示すことが特徴であるが、これ以外に通常７．４゜、９．７゜、２４．２゜にピークを示す。
【００２８】
なお、回折ピークの強度は、結晶性、試料の配向性及び測定法により変化する場合もあるが、粉末結晶のＸ線回折を行う場合に通常用いられるブラッグ−ブレンダーノの集中法による測定では、上記のＹ型オキシチタニウムフタロシアニンは２７．３°に最大回折ピークを有する。また、薄膜光学系（一般に薄膜法あるいは平行法とも呼ばれる）により測定された場合には、試料の状態によっては２７．３°が最大回折ピークとならない場合があるが、これは結晶粉末が特定の方向に配向しているためと考えられる。
【００２９】
分散媒としては種々の溶媒を用いてよい。例えば、ジエチルエーテル、ジメトキシエタン、テトラヒドロフラン、1,2−ジメトキシエタン等のエーテル類；アセトン、メチルエチルケトン等のケトン類；酢酸メチル、酢酸エチル等のエステル類；メタノール、エタノール、プロパノール等のアルコール類を単独あるいは２種以上混合して使用することができる。
【００３０】
用いる分散媒の量は分散が充分行え、且つ分散液中に有効量の電荷発生剤が含まれる限りいかなる量でもよく、通常は分散時の分散液中の電荷発生剤の濃度にして３〜20wt％、より好ましくは４〜20wt％程度が好ましい。
【００３１】
結着樹脂としてはポリビニルブチラール、ポリビニルアセタール、ポリエステル、ポリカーボネート、ポリスチレン、ポリエステルカーボネート、ポリスルホン、ポリイミド、ポリメチルメタクリレート、ポリ塩化ビニル等のビニル重合体、及びその共重合体、フェノキシ、エポキシ、シリコーン樹脂等またこれらの部分的架橋硬化物等を単独あるいは２種以上用いることができる。
【００３２】
結着樹脂と電荷発生剤粒子との混合方法としては例えば、電荷発生剤粒子を分散処理中に結着樹脂を粉末のまま或いはそのポリマー溶液を加え同時に分散する方法、分散液を結着樹脂のポリマー溶液中に混合する方法、或いは逆に分散液中にポリマー溶液を混合する方法等のいずれかの方法を用いてもかまわない。
【００３３】
次にここで得られた分散液は、塗布をするのに適した液物性にするために、種々の溶剤を用いて希釈してもかまわない。このような溶剤としては、例えば前記分散媒として例示した溶媒を使用することができる。電荷発生剤と結着樹脂との割合は特に制限はないが一般には樹脂１００重量部に対して電荷発生剤が５〜５００重量部の範囲より使用される。また必要に応じて電荷移動剤を含むことができる。電荷移動剤としては例えば、2,4,7−トリニトロフルオレノン、テトラシアノキシジメタンなどの電子吸引性物質、セルバゾール、インドール、イミダゾール、オキサゾール、ピラゾール、オキサジアゾール、ピラゾリン、チアジアゾール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、或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の電子供与性物質が挙げられる。電荷移動剤と結着樹脂との割合は結着樹脂１００重量に対して電荷移動物質が５〜５００重量部の範囲により使用される。
【００３４】
この様にして調製された分散液を用いて、導電性支持体上に電荷発生層を形成させ、その上に電荷移動層を積層させて感光層を形成する、或いは導電性支持体上に電荷移動層を形成しその上に前記分散液を用いて電荷発生層を形成し感光層を形成する、或いは導電性支持体上に前記分散液を用いて電荷発生層を形成させ感光層とする、のいずれかの構造で感光層を形成することが出来る。電荷発生層の膜厚は電荷移動層と積層させて感光層を形成する場合0.1μｍ〜10μｍの範囲が好適であり電荷移動層の膜厚は10〜40μｍが好適である。電荷発生層のみの単層構造で感光層を形成する場合の電荷発生層の膜厚は５〜40μｍの範囲が好適である。
【００３５】
電荷移動層を設ける場合、そこに使用される電荷移動剤としては、前記電荷移動剤として例示した材料を使用することが出来る。これらの電荷移動剤とともに必要に応じて結着樹脂が配合される。結着樹脂としては、例えば前記結着樹脂として例示した結着樹脂を使用することが出来る。感光層には、必要に応じて酸化防止剤、増感剤等の各種添加剤を含んでいてもよい。
【００３６】
次いで、本発明の他の態様である画像形成装置について説明する。かかる画像装置は電子写真方式の画像形成装置として既に種々知られており、基本的には、電子写真感光体の外周面に沿って帯電装置、露光装置、現像装置、転写装置及びクリーニング装置から構成される画像装置である。本発明においては、かかる画像形成装置における電子写真用感光体として、上述の製造方法で得られた下引き層塗布液を導電性支持体上に均一に塗布して形成した下引き層の上層に感光層を設けた電子写真用感光体を用いることを特徴としたものである。
【００３７】
【実施例】
以下、実施例を用いて本発明を具体的に説明する。なお、本発明は、以下の実施例に限定されるものではない。
実施例１
まず、下引き層用塗布液、電荷発生層用塗布液、電荷移動層用塗布液を調整した。
［下引き層用塗布液］
下記に示した共重合ポリアミド（数平均分子量３万５千）を混合アルコール（メタノール／ｎ−プロパノール＝７／３）溶液６０〜６５℃で密閉容器に入れ撹拌下にて３時間溶解した（工程１）。その後、溶液を６８℃〜７３℃で３０分間加熱した（工程２）。なお、混合溶媒中の沸点の低い溶媒であるメタノールの沸点は、約６６℃である。この際、加熱された容器内の圧力は、時間と共に高くなった。このようにして処理を施した溶液に、予め超音波分散したアルミナ〔昭和電工（株）製：ＵＡ−５３０５〕の混合アルコール（メタノール／ｎ−プロパノール＝７／３）溶液をホモミキサーにて混合した（工程３）。混合液を密封容器に入れ、６８℃〜７３℃で１時間加熱しながら拡散処理を施した（工程４）。その後、濾過を行った後、超音波で２時間分散処理を行った（工程５）。このようにして、ＵＡ−５３０５／共重合ポリアミド＝１／１組成（重量比）で、固形分濃度８％下引き層塗布液を調液した。
【００３８】
【化３】

【００３９】
［電荷発生層用塗布液］
Ｙ型オキシチタニウムフタロシアニン１０部、ポリビニルブチラール（電気化学工業（株）製、商品名＃６０００−Ｃ）５部に１、２−ジメトキシエタン５００部を加え、サンドグラインドミルで粉砕、分散処理を行い電荷発生層用塗布液を調整した。
［電荷移動層用塗布液］
次に示すヒドラゾン化合物５６重量部と
【００４０】
【化４】

次に示すヒドラゾン化合物１４重量部、
【００４１】
【化５】

及び下記のシアン化合物１．５重量部
【００４２】
【化６】

及び、特開平３−２２１９６２号公報の実施例中に記載された製造法により製造された、２つの繰り返し構造単位を有する下記ポリカーボネート樹脂（モノマーモル比１：１）１００重量部
【００４３】
【化７】

を１、４ジオキサン、テトラヒドロフランの混合溶媒に溶解して電荷移動層塗布液とした。
【００４４】
［導電性基体］
導電性基体として表面が鏡面仕上げされた外径６０ｍｍ、長さ３５０ｍｍ、肉厚１．０ｍｍの６０６３系アルミニウム製シリンダーを用意した。導電性基体上に以下のようにして塗膜を形成した。
【００４５】
［塗布工程］
導電性基体を予め調整した下引き層塗布液に浸漬した。塗布時の下引き層塗布液の液温は、約２５℃であった。目視によって、下引き層塗布液がゲル化している様子は見受けられなかった。次に、導電性基体を引き上げた。得られた下引き層の膜厚は、１．２５μｍであった。常温にて風乾を施し、下引き層を形成した。
【００４６】
［電荷発生層形成］
次に、下引き層が形成された導電性基体を予め調整した電荷発生層用塗布液に浸漬した。次に、導電性基体を引き上げた。得られた電荷発生層の膜厚は、１．５μｍであった。常温にて風乾を施し、電荷発生層を形成した。
【００４７】
［電荷移動層形成］
次に、電荷発生層が形成された導電性基体を予め調整した電荷移動層用塗布液に浸漬した。次に、導電性基体を引き上げた。得られた電荷発生層の膜厚は、１７μｍであった。１００℃湿度１０％の乾燥室にて１時間乾燥処理を施し、電荷移動層を乾燥した。このようにして電子写真感光体を４０本製造した。
得られた電子写真感光体を画像形成装置に組み込んだ。このようにして製造された画像形成装置は、いずれも均一な画像をえることができた。
【００４８】
【比較例１】
下引き層用塗布液製造過程において、工程２及び工程４を施さなかった以外は、実施例１と同様にして電子写真感光体を４０本製造し、画像形成装置に組み込んだ。
下引き層塗布液に導電性基体を浸漬する際、目視により下引き層用塗布液を観測したところ、塗布槽の底面にゲル化した下引き層塗布液が存在することが確認された。
このようにして製造された画像形成装置には、装置毎の画像濃度にムラが生じていた。
【００４９】
【発明の効果】
本発明によれば、電子写真感光体に用いられるバインダー樹脂を含んだ下引き層用塗布液において、下引き層塗布液のゲル化を防止し、収率の向上を図り、かつ、下引き層塗布液の均一性を保ち、電気特性等にばらつきのない電子写真感光体や、画像形成装置を得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an undercoat layer coating solution for an electrophotographic photoreceptor. Specifically, the present invention relates to a method for producing a specific undercoat layer coating solution, an electrophotographic photosensitive member using the same, and an image forming apparatus.
[0002]
[Prior art]
In general, an electrophotographic photosensitive member is formed by providing such a photosensitive layer on a conductive substrate such as aluminum. However, the influence of the substrate surface on the actual electrophotographic process is very large. For example, dirt, foreign matter adhesion, scratches, etc. present on the surface of the substrate more or less adversely affect the electrical characteristics, resulting in image defects. In order to remove such defects on the surface of the substrate as much as possible, secondary processing such as cutting and mirror polishing that leads to an increase in the cost of the photoreceptor and precise cleaning are required. On the other hand, it is known as a known technique to provide an undercoat layer between a substrate and a photosensitive layer as a means for obtaining a uniform and clean substrate surface without going through such steps. The undercoat layer is required to have a low electric resistance so as not to affect the electrophotographic characteristics. Further, it is required that the photosensitive layer has no carrier injection property. When an undercoat layer having carrier injectability is used for the photosensitive layer, the charging potential is decreased, resulting in a decrease in image contrast and fogging.
[0003]
Examples of the undercoat layer include inorganic layers such as aluminum anodic oxide coating, aluminum oxide, and aluminum hydroxide, organic layers such as polyvinyl alcohol, casein, polyvinyl pyrrolidone, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, and polyamide. Layers and mixed layers of inorganic particles and organic pigments and organic binders are known. Japanese Patent Application Laid-Open No. 10-90930 describes an electrophotographic photosensitive member containing polyamide and alumina in an undercoat layer. Japanese Patent Application Laid-Open No. 10-254150 describes that, in a method for producing an undercoat layer containing polyamide and titanium oxide, heating is performed after adjusting the undercoat layer coating solution. However, there is no description about heating the undercoat layer coating solution in a pressurized state.
[0004]
[Problems to be solved by the invention]
In general, a coating solution for an undercoat layer containing polyamide used for an electrophotographic photosensitive member has a problem that it easily gels. When the undercoat layer coating solution gels, not only does the yield deteriorate, but there is a problem that the uniformity of the coating solution cannot be maintained and the produced electrophotographic photosensitive member and the image forming apparatus vary. In addition, the undercoat coating liquid obtained by the adjustment method described in the above publication has a problem in long-term storage stability.
The present invention solves such problems, provides a uniform undercoat layer coating solution having excellent long-term storage stability, and a homogeneous electrophotographic photoreceptor using such an undercoat layer coating solution, and An object is to provide an image forming apparatus.
[0005]
[Means for Solving the Problems]
The above problems are solved by the following invention. That is, a method for producing an undercoat layer coating solution for an electrophotographic photoreceptor containing at least a binder resin and a solvent, wherein the binder resin is a polyamide resin, and after mixing the polyamide resin and the solvent, the mixed solution The above-mentioned problem is solved by a method for producing an undercoat layer coating solution for an electrophotographic photosensitive member, which comprises a step of heating in a pressurized state. This is because when the undercoat layer coating solution is prepared, the binder resin and the solvent are heated in a pressurized state, and the binder resin and the solvent are activated in a state where there is no risk of deterioration by touching the ambient atmosphere. This is because a preferable state is obtained. Moreover, the situation where a solvent evaporates and escapes from a liquid mixture system by heating in a pressurized state can be avoided.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The undercoat layer coating liquid in the present invention preferably contains at least a binder resin and a solvent, and further contains inorganic particles. Furthermore, known secondary materials such as known binder resins and antioxidants may be contained.
[0007]
The binder resin may be any of various binder resins used for the undercoat layer for an electrophotographic photoreceptor, such as polyvinyl alcohol, sodium caseinate, polyvinyl pyrrolidone, polyacrylic acid, methyl cellulose, nitrocellulose, polyvinyl acetal, phenoxy resin. Epoxy resin, polyurethane, polyimide, and polyamide can be preferably used. These may be used alone or in combination. Among these binder resins, polyamide is particularly preferable from the viewpoints of coatability, adhesion, solvent resistance, and the like.
[0008]
The polyamide is not particularly limited as long as it can be used as an undercoat layer coating solution for an electrophotographic photosensitive member. Among them, an alcohol-soluble copolymer polyamide, a modified polyamide, etc. have good dispersibility and coatability. Is preferable. More preferably, a copolyamide having a diamine represented by the following general formula (I) as a constituent component is used.
[0009]
[Chemical formula 2]

In the formula, A and B each represent a cyclohexyl group which may have a substituent, and R ₁ and R ₂ each independently represent hydrogen, an alkyl group, an aryl group, an aralkyl group or an alkoxy group. In addition, as long as the effect of this invention is not impaired, these organic groups may have a substituent. Here, the alkyl group is preferably a lower alkyl group such as a methyl group, an ethyl group, an n-propyl group, or an isopropyl group, and the alkoxy group is a lower group such as a methoxy group, an ethoxy group, an n-propoxy group, or an isopropoxy group. Alkoxy groups are preferred, aryl groups are preferably phenyl groups, and aralkyl groups include benzyl groups and phenethyl groups. R ₁ and R ₂ are more preferably hydrogen atoms, methyl groups, and ethyl groups. .
[0010]
The copolymer polyamide has a number average molecular weight of 10,000 to 50,000, more preferably 15,000 to 35,000. This is because if it is out of such a range, problems may occur in applicability and storage stability.
[0011]
The solvent used in the present invention is not particularly limited as long as it is a variety of solvents that can dissolve the binder resin as described above, but alcohols, ethers, and ketones are preferably used. Among these, it is more preferable to use lower alcohols such as methanol, ethanol, propanol and butanol, and mixtures thereof.
[0012]
The amount of the binder resin used with respect to the solvent is not particularly limited as long as it can be applied as the resulting undercoat layer coating solution, but is usually in the range of 1 wt% to 10 wt%, preferably 1 wt% to It is mixed in the range of 8 wt%, more preferably in the range of 1 wt% to 6 wt%.
[0013]
The inorganic particles used in the present invention may be various inorganic particles used for the undercoat layer for an electrophotographic photosensitive member. For example, alumina or titanium oxide is preferably used. In the present invention, it is particularly preferable to use alumina from the viewpoint of compatibility with the coating solution for the undercoat layer prepared by this method.
[0014]
Known alumina can be used as the alumina, but it is particularly preferable to use alumina particles having a water content of 1 wt% to 3 wt%. The particle size of the alumina particles is preferably approximately uniform, the average particle size is preferably 0.01 μm to 1 μm, more preferably 0.1 μm to 0.8 μm, and 0.3 μm to 0.6 μm. Particularly preferred. In addition, the water content here means a value after being left for 4 hours in an environment of 35 ° C. and 85% RH.
[0015]
The addition ratio of the inorganic particles to the binder resin can be arbitrarily selected as long as the properties of the undercoat layer coating solution are not impaired. However, the storage stability and the coatability of the undercoat layer coating solution can be selected within the range of 40 wt% to 400 wt%. It is preferable in terms of
[0016]
The undercoat layer coating solution of the present invention is prepared, for example, as follows.
First, a binder resin is mixed with a solvent to obtain a mixed solution in which the binder resin is dissolved. Next, the mixed solution is poured into a container having a constant volume and heated in a pressurized state. Here, as a result of the thermal motion of the binder resin becoming active by heating in a pressurized state, it is considered that the intertwined binder resin is unwound and stabilized. When the undercoat layer coating solution is produced by such a process, it is possible to effectively prevent the undercoat layer coating solution from gelling even if the temperature of the undercoat layer coating solution is reduced before coating. it can.
[0017]
The pressurized state for the mixed solution is usually in the range of 1.5 to 10 atm, preferably in the range of 1.5 to 5 atm, more preferably in the range of 1.7 to 4 atm. It only has to be done. The heating temperature is not particularly limited as long as the temperature is such that the thermal motion of the binder resin is active and the entangled binder resin is unwound and stabilized. Specifically, although it depends on the solvent to be used, it is usually preferable to heat at a heating temperature of the boiling point of the solvent used at −15 ° C. or higher, preferably at a boiling point of −5 ° C. or higher, more preferably at the boiling point or higher. In particular, when heating at a temperature equal to or higher than the boiling point of the solvent, the heating is preferably performed in the range of the boiling point of the solvent to the boiling point + 10 ° C, more preferably in the range of the boiling point + 1 ° C to the boiling point + 7 ° C. A range of + 2 ° C to the boiling point + 5 ° C is particularly preferable. Here, when the mixed solvent is used as the solvent, the boiling point of the solvent means the boiling point of the solvent having the lowest boiling point.
[0018]
The method of heating in a pressurized state in the present invention is not particularly limited as long as it is pressurized at the time of heating. For example, a mixed liquid composed of a binder resin and a solvent is hermetically sealed above the boiling point of the solvent. And a method of heating in a pressurized state by a solvent vapor, a method of heating while applying pressure to the liquid mixture from the outside, and the like. In any method, it is important to heat at least the mixed liquid composed of the binder resin and the solvent in a state where the pressure as described above is applied. In particular, the step of heating in a pressurized state of the present invention is a method of heating above the boiling point of the solvent in a sealed state, specifically, a pressurized state can be easily created in terms of equipment by heating in a sealed container. Therefore, it is preferable. Hereinafter, the case where it heats in a sealed container is demonstrated.
[0019]
The sealed container is not limited to a completely sealed container, but may be any container that does not have a completely sealed container but can increase the pressure in the container to some extent. The maximum pressure in the sealed container during heating is preferably a pressurized state as described above, that is, 1.5 to 10 atm, more preferably 1.5 to 5 atm, and more preferably 1.7. The pressure is particularly preferably 4 to 4 atm. As the heating time, it is sufficient that a sufficiently uniform undercoat layer coating solution is prepared. Specifically, heating is usually preferably performed for 1 minute to 10 hours, more preferably 10 minutes to 3 hours, More preferably, it is 20 minutes to 2 hours, and particularly preferably 25 minutes to 1 hour. As described above, the heating temperature is a temperature equal to or higher than the boiling point of the solvent, and it is more preferable to heat in the range of the boiling point of the solvent to the boiling point + 10 ° C. The boiling point is more preferably in the range of the boiling point + 2 ° C to the boiling point + 5 ° C.
[0020]
In the case of further adding inorganic particles to the mixed solution thus prepared, it is desirable to add inorganic particles prepared in advance and perform a dispersion treatment. Examples of the dispersion treatment method include a dispersion treatment method using a sand grind mill, a ball mill, a homogenizer, and the like. Among these, a dispersion treatment using a homogenizer is preferable because it can be uniformly dispersed. After the dispersion, the mixed solution is heated under pressure in the same manner as described above. In this case, heating in a pressurized state is the same as described above, and the thermal motion of the binder resin is stimulated to unwind and stabilize the entangled binder resin. In addition, after mixing binder resin, inorganic particle | grains, and a solvent at once and obtaining these mixed solutions, you may heat in a pressurized state as mentioned above.
[0021]
In the present invention, since the undercoat layer coating solution is prepared as described above and then subjected to filtration, a more preferable undercoat layer coating solution can be obtained. As the filtration treatment, it is preferable to perform filtration treatment of the adjusted coating solution using a cotton filter or a glass filter, but it is more preferable to perform filtration treatment again with a membrane filter after further filtration treatment. It is because gelling of binder resin can be prevented more effectively by performing such filtration processing.
[0022]
After the undercoat layer coating solution is produced, it is particularly preferable to keep the coating solution at 5 ° C to 55 ° C, preferably 10 ° C to 40 ° C, more preferably 15 ° C to 25 ° C. If the liquid temperature is too high, gelation may start, and if the liquid temperature is low, the viscosity of the liquid decreases and crystallization starts.
[0023]
Next, an electrophotographic photoreceptor which is another embodiment of the present invention will be described. In such an electrophotographic photoreceptor, the undercoat layer coating solution obtained by the above-described production method is uniformly coated on a conductive support to form an undercoat layer, and then the photosensitive layer is formed on the undercoat layer. Formed. It is most effective that the thickness of the undercoat layer is 0.1 to 10 μm, preferably 0.2 to 5 μm.
[0024]
The photosensitive layer is provided in the upper layer of the undercoat layer provided on the conductive support. Conductive supports include metal materials such as aluminum, stainless steel, copper, nickel, etc., polyester film with a conductive layer such as aluminum, copper, palladium, tin oxide, indium oxide on the surface, paper, glass, etc. A sex support is used. An undercoat layer is provided between the conductive support and the charge generation layer, but a known alumite layer may be formed together with the undercoat layer.
[0025]
The photosensitive layer may be either a laminated type or a single layer type, but a laminated type is particularly preferably used. In the laminated photosensitive layer, a charge generation layer containing a charge generation agent and a charge transport layer containing a charge transfer agent provided thereon are formed, and a surface layer may be further provided thereon. .
[0026]
As a charge generator, organic pigments such as selenium and its alloys, arsenic-selenium, cadmium sulfide, zinc oxide, other inorganic photoconductors, phthalocyanine, azo, quinacridone, polycyclic quinone, perylene, indigo, benzimidazole are used. can do. In particular, metals such as copper, indium chloride, potassium chloride, tin, oxytitanium, zinc, vanadium, or phthalocyanines coordinated with oxides or chlorides, metal-free phthalocyanines, or monoazo, bisazo, trisazo, polyazos Azo pigments such as are preferred. Of these, azo pigments or phthalocyanines are particularly preferable, and so-called Y-type oxytitanium phthalocyanine is particularly preferable. This is because crystal conversion by heat occurs more easily than ordinary pigments.
[0027]
The so-called Y-type oxytitanium phthalocyanine has a maximum diffraction peak at a Bragg angle (2θ ± 0.2) of 27.3 ° in X-ray diffraction by CuKα rays. This crystalline oxytitanium phthalocyanine is generally referred to as Y-type or D-type. For example, FIG. 2 of JP-A-62-67094 (referred to as type II in the same publication), Fig. 1 of JP-A-2-8256, Fig. 1 of JP-A-64-82045, Journal of Electrophotographic Society Vol. 92 (issued in 1990), No. 3, pages 250-258 (in the same publication) (Referred to as Y-type). This crystalline oxytitanium phthalocyanine is characterized by having a maximum diffraction peak at 27.3 °, but normally has peaks at 7.4 °, 9.7 °, and 24.2 °.
[0028]
The intensity of the diffraction peak may vary depending on the crystallinity, the orientation of the sample, and the measurement method, but in the measurement by the Bragg-Brendano concentration method usually used when performing X-ray diffraction of the powder crystal, The Y-type oxytitanium phthalocyanine has a maximum diffraction peak at 27.3 °. In addition, when measured by a thin film optical system (generally called thin film method or parallel method), 27.3 ° may not be the maximum diffraction peak depending on the state of the sample. This is probably because it is oriented in the direction.
[0029]
Various solvents may be used as the dispersion medium. For example, ethers such as diethyl ether, dimethoxyethane, tetrahydrofuran and 1,2-dimethoxyethane; ketones such as acetone and methyl ethyl ketone; esters such as methyl acetate and ethyl acetate; alcohols such as methanol, ethanol and propanol alone Alternatively, two or more kinds can be mixed and used.
[0030]
The amount of the dispersion medium to be used can be any amount as long as the dispersion can be sufficiently performed and an effective amount of the charge generating agent is contained in the dispersion, and is usually 3 to 20 wt as the concentration of the charge generating agent in the dispersion during dispersion. %, More preferably about 4 to 20 wt%.
[0031]
As binder resins, polyvinyl butyral, polyvinyl acetal, polyester, polycarbonate, polystyrene, polyester carbonate, polysulfone, polyimide, polymethyl methacrylate, polyvinyl chloride and other vinyl polymers, and copolymers thereof, phenoxy, epoxy, silicone resin, etc. These partially cross-linked cured products can be used alone or in combination of two or more.
[0032]
As a method for mixing the binder resin and the charge generating particles, for example, a method of dispersing the charge generating particles as a powder or a polymer solution at the same time while dispersing the charge generating particles, or dispersing the dispersion of the binder resin. Any method such as a method of mixing in a polymer solution, or a method of mixing a polymer solution in a dispersion, may be used.
[0033]
Next, the dispersion obtained here may be diluted with various solvents in order to obtain liquid properties suitable for coating. As such a solvent, the solvent illustrated as the said dispersion medium can be used, for example. The ratio between the charge generating agent and the binder resin is not particularly limited, but generally the charge generating agent is used in the range of 5 to 500 parts by weight with respect to 100 parts by weight of the resin. Moreover, a charge transfer agent can be included as needed. Examples of the charge transfer agent include electron-withdrawing substances such as 2,4,7-trinitrofluorenone and tetracyanoxydimethane, and heterocyclic rings such as selbazole, indole, imidazole, oxazole, pyrazole, oxadiazole, pyrazoline and thiadiazole. Examples thereof include an electron donating substance such as a compound, an aniline derivative, a hydrazone compound, an aromatic amine derivative, a stilbene derivative, or a polymer having a group composed of these compounds in the main chain or side chain. The ratio between the charge transfer agent and the binder resin is such that the charge transfer material is in the range of 5 to 500 parts by weight with respect to 100 weight of the binder resin.
[0034]
Using the dispersion thus prepared, a charge generation layer is formed on a conductive support and a charge transfer layer is laminated thereon to form a photosensitive layer, or a charge is formed on the conductive support. A moving layer is formed and a charge generation layer is formed thereon using the dispersion liquid to form a photosensitive layer, or a charge generation layer is formed using a dispersion liquid on a conductive support to form a photosensitive layer. The photosensitive layer can be formed with any of the following structures. When the charge generation layer is laminated with the charge transfer layer to form a photosensitive layer, the range of 0.1 μm to 10 μm is preferable, and the thickness of the charge transfer layer is preferably 10 to 40 μm. When the photosensitive layer is formed with a single layer structure having only the charge generation layer, the thickness of the charge generation layer is preferably in the range of 5 to 40 μm.
[0035]
When the charge transfer layer is provided, as the charge transfer agent used there, the materials exemplified as the charge transfer agent can be used. If necessary, a binder resin is blended with these charge transfer agents. As the binder resin, for example, the binder resin exemplified as the binder resin can be used. The photosensitive layer may contain various additives such as an antioxidant and a sensitizer as necessary.
[0036]
Next, an image forming apparatus according to another aspect of the present invention will be described. Such an image apparatus is already known as an electrophotographic image forming apparatus, and basically includes a charging device, an exposure device, a developing device, a transfer device, and a cleaning device along the outer peripheral surface of the electrophotographic photosensitive member. Image device. In the present invention, as an electrophotographic photoreceptor in such an image forming apparatus, an undercoat layer formed by uniformly applying the undercoat layer coating solution obtained by the above-described production method on a conductive support. An electrophotographic photoreceptor provided with a photosensitive layer is used.
[0037]
【Example】
Hereinafter, the present invention will be specifically described with reference to examples. The present invention is not limited to the following examples.
Example 1
First, an undercoat layer coating solution, a charge generation layer coating solution, and a charge transfer layer coating solution were prepared.
[Coating liquid for undercoat layer]
The following copolymer polyamide (number average molecular weight 35,000) was mixed in a mixed alcohol (methanol / n-propanol = 7/3) solution at 60 to 65 ° C. in a sealed container and dissolved under stirring for 3 hours (process) 1). Thereafter, the solution was heated at 68 ° C. to 73 ° C. for 30 minutes (step 2). In addition, the boiling point of methanol which is a low boiling point solvent in the mixed solvent is about 66 ° C. At this time, the pressure in the heated container increased with time. A mixed alcohol (methanol / n-propanol = 7/3) solution of alumina (manufactured by Showa Denko KK: UA-5305) that has been ultrasonically dispersed in advance is mixed with the solution thus treated with a homomixer. (Step 3). The mixed solution was put in a sealed container and subjected to diffusion treatment while being heated at 68 ° C. to 73 ° C. for 1 hour (step 4). Then, after filtering, the dispersion process was performed with ultrasonic waves for 2 hours (step 5). In this way, an undercoat layer coating solution with a solid content concentration of 8% was prepared with UA-5305 / copolymerized polyamide = 1/1 composition (weight ratio).
[0038]
[Chemical 3]

[0039]
[Coating liquid for charge generation layer]
Add 500 parts of 1,2-dimethoxyethane to 10 parts of Y-type oxytitanium phthalocyanine and 5 parts of polyvinyl butyral (trade name # 6000-C, manufactured by Denki Kagaku Kogyo Co., Ltd.), and grind and disperse in a sand grind mill. A coating solution for charge generation layer was prepared.
[Coating liquid for charge transfer layer]
56 parts by weight of the following hydrazone compound:
[Formula 4]

14 parts by weight of the following hydrazone compound,
[0041]
[Chemical formula 5]

And 1.5 parts by weight of the following cyanide compound:
[Chemical 6]

And 100 parts by weight of the following polycarbonate resin (monomer molar ratio 1: 1) having two repeating structural units produced by the production method described in Examples of JP-A-3-221196.
[Chemical 7]

Was dissolved in a mixed solvent of 1,4 dioxane and tetrahydrofuran to prepare a charge transfer layer coating solution.
[0044]
[Conductive substrate]
A 6063 series aluminum cylinder having an outer diameter of 60 mm, a length of 350 mm, and a wall thickness of 1.0 mm was prepared as a conductive substrate. A coating film was formed on the conductive substrate as follows.
[0045]
[Coating process]
The conductive substrate was immersed in a preliminarily prepared undercoat layer coating solution. The temperature of the undercoat layer coating solution at the time of coating was about 25 ° C. The appearance of gelation of the undercoat layer coating solution was not observed by visual inspection. Next, the conductive substrate was pulled up. The thickness of the obtained undercoat layer was 1.25 μm. Air drying was performed at room temperature to form an undercoat layer.
[0046]
[Charge generation layer formation]
Next, the conductive substrate on which the undercoat layer was formed was immersed in a charge generation layer coating solution prepared in advance. Next, the conductive substrate was pulled up. The resulting charge generation layer had a thickness of 1.5 μm. The charge generation layer was formed by air drying at room temperature.
[0047]
[Charge transfer layer formation]
Next, the conductive substrate on which the charge generation layer was formed was immersed in a charge transfer layer coating solution prepared in advance. Next, the conductive substrate was pulled up. The resulting charge generation layer had a thickness of 17 μm. A drying process was performed for 1 hour in a drying chamber at 100 ° C. and humidity of 10% to dry the charge transfer layer. In this way, 40 electrophotographic photoreceptors were produced.
The obtained electrophotographic photosensitive member was incorporated into an image forming apparatus. All of the image forming apparatuses manufactured in this way were able to obtain a uniform image.
[0048]
[Comparative Example 1]
40 electrophotographic photoreceptors were produced in the same manner as in Example 1 except that Steps 2 and 4 were not performed in the undercoat layer coating liquid production process, and were incorporated into an image forming apparatus.
When the conductive substrate was immersed in the undercoat layer coating solution, the undercoat layer coating solution was visually observed, and it was confirmed that the gelled undercoat layer coating solution was present on the bottom surface of the coating tank.
In the image forming apparatus manufactured as described above, the image density of each apparatus is uneven.
[0049]
【The invention's effect】
According to the present invention, in the coating solution for the undercoat layer containing the binder resin used for the electrophotographic photoreceptor, gelation of the undercoat layer coating solution is prevented, the yield is improved, and the undercoat layer is formed. It is possible to obtain an electrophotographic photosensitive member and an image forming apparatus that maintain the uniformity of the coating liquid and have no variation in electrical characteristics and the like.

Claims (6)

  A method for producing an undercoat layer coating solution for an electrophotographic photoreceptor comprising at least a binder resin and a solvent, wherein the binder resin is a polyamide resin, and the mixed solution is added after the polyamide resin and the solvent are mixed. A method for producing an undercoat layer coating solution for an electrophotographic photosensitive member, comprising a step of heating in a pressurized state.   The method for producing an undercoat layer coating solution for an electrophotographic photosensitive member according to claim 1, wherein the step of heating in a pressurized state is a step of heating above the boiling point of the solvent under sealing.   The method for producing an undercoat layer coating solution for an electrophotographic photosensitive member according to claim 1, wherein the undercoat layer coating solution further contains inorganic particles.   The method for producing an undercoat layer coating solution for an electrophotographic photosensitive member according to claim 3, wherein the inorganic particles are alumina. The said polyamide resin is a manufacturing method of the undercoat layer coating liquid for electrophotographic photoreceptors of any one of Claims 1-4 which contain following General formula (1) as a structural part.

(In the formula, A and B each represent a cyclohexyl ring which may have a substituent, R ¹ , R ² Each independently represents hydrogen, an alkyl group, an aryl group, an aralkyl group, or an alkoxy group. ) Characterized by using an undercoat layer coating solution prepared by the method for producing an electrophotographic photoreceptor subbing layer coating solution according to any one of claims 1 to 5, process for producing an electrophotographic photosensitive member .