JP3714838B2 - Coating liquid for undercoat layer of electrophotographic photosensitive member, method for producing electrophotographic photosensitive member using the same, and electrophotographic photosensitive member - Google Patents

Description

【００３１】
（式中、Ｒ₁ 〜Ｒ₆ は水素原子もしくはアルコキシ基、アシル基および／またはヒドロキシ基で置換されていてもよいアルキル基）
で表されるジオキソランおよびその誘導体が特に好ましい。
置換基Ｒ₁ 〜Ｒ₆ としては、何れかが水素原子であるものが好ましく、置換基Ｒ₁ 〜Ｒ₆ のすべてが水素原子である１，３−ジオキソランが特に好ましい。
【００３２】
置換基Ｒ₁ 〜Ｒ₆ のアルキル基が炭素数の大きな置換基を有する場合には、ジオキソラン誘導体の沸点が高くなり、沸点が１００℃を超える場合には、塗布形成した下引き層の乾燥時間が長くなり、生産性が低下するだけでなく、気流や湿度などの塗布環境により乾燥ムラが発生しやすくなるので好ましくない。
【００３３】
また、下引き層上に塗布する感光層用塗布液に使用される有機溶剤に溶解しない下引き層を作製するために、上記の水溶性かつ非プロトン性有機溶剤、特に環状エーテルに炭素数１〜４の低級アルコールを混合して用いることが好ましい。炭素数１〜４の低級アルコールとしては、メチルアルコール、エチルアルコール、イソプロピルアルコール、ｎ−プロピルアルコールおよびｎ−ブチルアルコールなどが挙げられ、中でも、メタノールが特に好ましい。
【００３４】
上記の混合溶剤を用いることにより、感光層用塗布液に使用される有機溶剤に対する下引き層の溶解性を低下させ、下引き層の溶解を防止することができる。また、混合溶剤を用いることにより、水溶性かつ非プロトン性有機溶剤単独よりも金属酸化物の分散性が改善され、保存安定性（下引き層用塗布液の調製後の経過日数を「ポットライフ」と称する）が向上し、下引き層を形成する際に非常に均一な塗布膜が得られる。しかもハロゲンを有する有機溶剤を用いないことから環境問題や健康問題の恐れがより少ない優れた特性を有する下引き層用塗布液を提供することができる
【００３５】
水溶性かつ非プロトン性有機溶剤と低級アルコールとの混合溶剤は、共沸組成にあるのが好ましい。ここで「共沸」とは、液体混合物が一定圧力下において、溶液の組成と蒸気の組成が一致し、定沸点混合物となる現象のことであり、その組成は混合溶剤の組み合わせにより決定される。例えば、テトラヒドロフランとメタノールの場合、テトラヒドロフラン６８．９重量部、メタノール３１．１重量部の割合が共沸組成である（「化学便覧基礎編 改訂３版」、社団法人日本化学会編 第II−１５１頁参照）。混合溶剤の重量割合が共沸組成であれば、均一な蒸発が起こるので、塗膜欠陥のない均一な下引き層を形成することができる。
【００３６】
水溶性かつ非プロトン性有機溶剤と低級アルコールとの混合溶剤との重量割合は、６０／４０〜５／９５が好ましく、５０／５０〜３０／７０が特に好ましい。この重量割合は、ジオキソラン化合物（特に１，３−ジオキソラン）と低級アルコール（特にメタノール）との混合溶剤の場合に特に適用される。
例えば、上記の重量割合において、１，３−ジオキソランの含有量が多い場合には、下引き層用塗布液中に分散された金属酸化物粒子と溶剤との親和性が低下し、分散液の粘度が上昇して下引き層用塗布液の保存安定性が悪くなるので好ましくない。また、１，３−ジオキソランの含有量が少ない場合には、混合溶剤としての効果が薄れ、金属酸化物の分散性が著しく低下し、均一な下引き層を形成することができなくなるので好ましくない。
【００３７】
より具体的には、本発明の下引き層用塗布液に用いられる有機溶剤としては、Ｎ，Ｎ−ジメチルホルムアミド、テトラヒドロフラン、１，３−ジオキソランまたは１，３−ジオキソランとメタノールとの混合溶剤が好適である。
【００３８】
本発明の下引き層用塗布液に用いられる樹脂（「バインダー樹脂」ともいう）としては、樹脂の単一層で下引き層を形成する場合と同様の樹脂を用いることができる。
【００３９】
具体的には、ポリエチレン、ポリプロピレン、ポリスチレン、アクリル樹脂、塩化ビニル樹脂、酢酸ビニル樹脂、ポリウレタン樹脂、エポキシ樹脂、ポリエステル樹脂、メラミン樹脂、シリコン樹脂、ブチラール樹脂およびポリアミド樹脂などの樹脂および繰り返し単位を２種以上含む共重合体樹脂、ならびにカゼイン、ゼラチン、ポリビニルアルコールおよびエチルセルロースなどが挙げられる。
【００４０】
これらの樹脂の中でも、アルコール可溶性の樹脂が好ましい。具体的には、ポリアミド樹脂、ブチラール樹脂および酢酸ビニル樹脂が挙げられ、中でもポリアミド樹脂およびブチラール樹脂が好ましく、ポリアミド樹脂が特に好ましい。
【００４１】
上記の樹脂は、下引き層用塗布液を構成する樹脂に要求される下記の特性を満足する。
▲１▼下引き層上に形成される感光体層用塗布液の溶媒に対して溶解や膨潤などが起こらないこと
▲２▼導電性支持体との接着性に優れていること
▲３▼可撓性を有すること
▲４▼金属酸化物との親和性がよいこと
▲５▼金属酸化物の分散性および分散液の保存安定性に優れていること
【００４２】
ポリアミド樹脂としては、アルコール可溶性ナイロン樹脂、例えば、６−ナイロン、６６−ナイロン、６１０−ナイロン、１１−ナイロンおよび１２−ナイロンおよびこれらを共重合させた共重合ナイロン、Ｎ−アルコキシメチル変性ナイロンおよびＮ−アルコキシエチル変性ナイロンのようなナイロンを化学的に変性させたものが挙げられる。
【００４３】
本発明の下引き層用塗布液に用いられる金属酸化物としては、酸化チタン、酸化ジルコニウム、酸化錫、酸化アルミニウムおよび酸化亜鉛などが挙げられ、これらの金属酸化物は２種以上の混合物であってもよい。
【００４４】
上記の金属酸化物の中でも酸化チタンが特に好ましく、その形状は粒状、針状および樹枝状のいずれであってもよいが、図３（Ａ）に示した針状もしくは図３（Ｂ）に示した樹枝状のものが特に好ましい。
【００４５】
ここで「針状」とは、棒状、柱状および紡錘状などを含む細長い形状を意味し、必ずしも極端に細長いものでなくてもよく、先端が鋭く尖っている必要もない。また「樹枝状」とは、棒状、柱状および紡錘状などを含む細長い形状が枝分かれした形状を意味する。
【００４６】
針状および樹枝状の酸化チタンの寸法は、図３に示すような採寸において、長軸ａが１００μｍ以下、短軸ｂが１μｍ以下が好ましく、長軸ａが１０μｍ以下、短軸ｂが０．５μｍ以下がより好ましい。
各軸長が上記の範囲を超える場合には、後述するような金属酸化物や有機化合物を用いた表面処理により分散安定性に優れた下引き層用塗布液が得られにくいので好ましくない。
【００４７】
「針状」とは、通常、長軸ａと短軸ｂとの比ａ／ｂ（アスペクト比）が１．５以上のものを意味する。本発明における針状の酸化チタンのアスペクト比としては、１．５〜３００の範囲が好ましく、２〜１０の範囲が特に好ましい
針状および樹枝状の酸化チタン粒子の大きさは、重量沈降法、光透過式粒度分布測定法などの公知の方法にて測定できるが、このアスペクト比は、電子顕微鏡観察などにより測定することができる。
【００４８】
本発明においては、針状もしくは樹枝状の酸化チタンと粒状の酸化チタン粒子とを混合したものを用いてもよい。酸化チタンには、アナターゼ型やルチル型などの結晶体と非晶質体（アモルファス）が存在するが、本発明においてはいずれを用いてもよく、また２種以上の混合体でもよい。
【００４９】
本発明の下引き層用塗布液に含有する酸化チタンにおける針状もしくは樹枝状の酸化チタンの含有率（酸化チタンと本発明の下引き層用塗布液に含有する樹脂との混合割合）は、１０〜９９重量％の範囲、好ましくは３０〜９９重量％の範囲、より好ましくは３５〜９５重量％の範囲である。
【００５０】
針状もしくは樹枝状の酸化チタンの含有率が１０重量％未満の場合には、下引き層中に電荷が蓄積され残留電位が増大して、感光体の感度が低下するので好ましくない。このような感度の低下は、低温低湿下での繰り返し特性において特に顕著に表れる。また、針状もしくは樹枝状の酸化チタンの含有率が９９重量％を超える場合には、下引き層用塗布液の保存安定性が悪くなり、針状もしくは樹枝状の酸化チタン粒子の沈降が起こりやすくなるので好ましくない。
【００５１】
酸化チタンの体積抵抗値は、１０⁵ 〜１０¹⁰Ωｃｍが好ましい。
酸化チタンの体積抵抗値が１０⁵ Ωｃｍ未満の場合には、下引き層の抵抗値が低下し、下引き層が電荷ブロッキング層として機能しなくなるので好ましくない。例えば、アンチモンをドープした酸化錫を用いて導電処理を施した酸化チタンの体積抵抗値は１０⁰ 〜１０¹ Ωｃｍと非常に低くなる。このような酸化チタンを用いた下引き層は電荷ブロッキング層として機能せず、感光体特性としての帯電性が悪化するために、画像にカブリや黒点が発生する。また、酸化チタンの体積抵抗値が１０¹⁰Ωｃｍを超える場合には、下引き層としての抵抗値が高過ぎるために、光照射時に生成したキャリアの輸送が抑制あるいは阻止され、残留電位が上昇し光感度が低下するので好ましくない。したがって、本発明の酸化チタンとしては、導電処理を施していないものが好ましい。
【００５２】
本発明で用いられる酸化チタンは、体積抵抗値を上記の範囲に維持しつつ、酸化ジルコニウムおよび／または酸化アルミニウムで表面を被覆され、さらに任意にシランカップリング剤、シリル化剤、アルミニウム系カップリング剤およびチタネート系カップリング剤などの有機化合物で表面を被覆されているものが好ましい。
【００５３】
表面処理を施していない酸化チタンの場合には、酸化チタンが微粒子であるために、十分に分散された下引き層用塗布液であっても長期間の使用や塗布液の保管時に酸化チタンの凝集が避けられない。このような凝集は下引き層の塗布膜の欠陥や塗布ムラを引き起こし、画像欠陥の原因となる。また、表面処理を施していない酸化チタンを含む下引き層を有する感光体では、導電性支持体からの電荷の注入が起こりやすくなるために、微小領域の帯電性が低下し黒点が発生することになる。
【００５４】
そこで、酸化チタン、特に針状もしくは樹枝状の酸化チタンの表面を酸化アルミニウムおよび／または酸化ジルコニウムなどの金属酸化物で被覆することにより酸化チタンの凝集を防止し、分散性や保存安定性に優れた下引き層用塗布液を得る。また、このような表面処理を施した酸化チタンを含む下引き層を有する感光体では、導電性支持体からの電荷の注入を防止することができるために、黒点のない優れた画像が得られる。
【００５５】
表面処理に用いる金属酸化物としては、酸化アルミニウムおよび／または酸化ジルコニウムが好ましい。優れた画像特性を有する感光体が得られる点で、酸化アルミニウムおよび酸化ジルコニウムの異なる金属酸化物の両方で表面処理を施すのがより好ましい。
【００５６】
金属酸化物として酸化ケイ素を用いた場合には、処理した酸化チタンの表面が親水性を示し、有機溶剤との相溶性が悪くなり、酸化チタンの分散性が低下して凝集を引き起こしやすくなるために、塗布液の長期間の使用には不適になる。
また、金属酸化物として酸化鉄（Ｆｅ₂ Ｏ₃ ）などの磁性をもつ金属酸化物を用いた場合には、感光層中に含有する顔料（例えば、フタロシアニン顔料）と化学的な相互作用が生じ、感光体特性、特に感度低下や帯電性の低下が生じるために好ましくない。
【００５７】
酸化チタンに対する酸化アルミニウムおよび／または酸化ジルコニウムの表面処理量は、０．１〜２０重量％程度が好ましい。
表面処理量が０．１重量％未満の場合には、酸化チタンの表面を十分に被覆できず、表面処理の効果が十分に得られないので好ましくない。また、２０重量％を超えて表面処理を施しても、処理コストがかかるだけでそれ以上の効果が期待できないので好ましくない。
【００５８】
下引き層用塗布液における酸化チタンの分散性や保存安定性を高めるために、酸化ジルコニウムおよび／または酸化アルミニウムで表面を被覆した酸化チタンを、さらに有機化合物で表面を被覆するのが好ましい。
【００５９】
有機化合物としては、一般的なカップリング剤を用いることができる。
具体的には、アルコキシシラン化合物などのシランカップリング剤、ハロゲン、窒素、硫黄のような原子がケイ素と結合したシリル化剤、アルミニウム系カップリング剤およびチタネート系カップリング剤などが挙げられる。
【００６０】
例えば、シランカップリング剤としては、テトラメトキシシラン、メチルトリメトキシシラン、ジメチルジメトキシシラン、エチルトリメトキシシラン、ジエチルジメトキシシラン、フェニルトリエトキシシラン、アミノプロピルトリメトキシシラン、γ−（２−アミノエチル）アミノプロピルメチルジメトキシシラン、アリルトリメトキシシラン、アリルトリエトキシシラン、３−（１−アミノプロポキシ）−３，３−ジメチル−１−プロペニルトリメトキシシラン、（３−アクリロキシプロピル）トリメトキシシラン、（３−アクリロキシプロピル）メチルジメトキシシラン、（３−アクリロキシプロピル）ジメチルメトキシシランおよびＮ−３−（アクリロキシ−２−ヒドロキシプロピル）−３−アミノプロピルトリエトキシシランなどのアルコキシシラン化合物、メチルトリクロロシラン、メチルジクロロシラン、ジメチルジクロロシランおよびフェニルトリクロロシランなどのクロロシラン類、ならびにヘキサメチルジシラザンおよびオクタメチルシクロテトラシラザンなどのシラザン類が挙げられる。
【００６１】
その他のカップリング剤としては、イソプロピルトリイソステアロイルチタネートおよびビス（ジオクチルパイロホフェート）などのチタネート系カップリング剤、アセトアルコキシアルミニウムジイソプロピレートなどのアルミニウム系カップリング剤などが挙げられる。
【００６２】
カップリング剤は上記の例示化合物に限定されず、これらのカップリング剤を併用してもよい。また、これらカップリング剤を下引き層用塗布液に分散剤として添加してもよい。
【００６３】
酸化チタンに表面処理を施す方法は、前処理法とインテグラルブレンド法に大別され、さらに前処理法は湿式法と乾式法に分けられる。
湿式法は水処理法と溶剤処理法に分けられ、水処理法には、直接溶解法、エマルジョン法およびアミンアダクト法などがある。
【００６４】
湿式法では、有機溶剤や水に表面処理剤を溶解または懸濁させたものに酸化チタンを添加するか、あるいは酸化チタンを有機溶剤や水に分散した懸濁液に表面処理剤を添加して、その溶液を数分から１時間程度撹拌混合し、任意に加熱処理を施した後に、濾過などの工程を経て乾燥する。
用いることができる表面処理剤は、用いる有機溶剤や水に溶解または懸濁しうるものに限られ、直接溶解法では水に溶解する品種、エマルジョン法では水中乳化可能型の品種、アミンアダクト法ではリン酸残基を有する品種が挙げられる。
【００６５】
アミンアダクト法では、トリアルキルアミンやトリアルキロールアミンなどの３級アミンを少量添加して調製液をｐＨ＝７〜１０に調整し、中和発熱反応による液温の上昇を抑えるために冷却しながら処理することが好ましく、その他の工程は他の湿式法と同様に行なうことができる。
【００６６】
乾式法では、酸化チタンに直接表面処理剤を添加し、ミキサーなどで撹拌混合する。一般的な方法としては、乾式法は予備乾燥により酸化チタンの表面水を除去した後に行なわれる。例えば、ヘイシャルミキサーなどのシェアの大きい混合機に酸化チタンを投入し、数１０ｒｐｍで回転しつつ、１００℃前後の温度で予備乾燥を行った後、表面処理剤を直接もしくは有機溶剤や水に溶解もしくは分散混合した溶液を添加する。その際、乾燥空気や窒素ガスで噴霧させて処理することにより、酸化チタンと表面処理剤をより均一に混合することができる。表面処理剤を添加する際には、８０℃前後の温度、１０００ｒｐｍ以上の回転数で数１０分間撹拌することが好ましい。
【００６７】
インテグラルブレンド法は、酸化チタンと樹脂を混練する際に表面処理剤を添加する方法であり、塗料の分野では一般的に用いられる方法である。
【００６８】
表面処理剤および添加剤としての表面処理剤の添加量は、金属酸化物の種類や形態によって異なるが、一般に酸化チタンの０．０１〜３０重量％程度、好ましくは０．１〜２０重量％程度である。表面処理剤の添加量が０．０１重量％未満の場合には、添加効果が発現しにくいので好ましくない。また、３０重量％を超えて表面処理剤を添加してもさらなる添加効果が得られず、コストの面で不利になるので好ましくない。
【００６９】
また、酸化チタンの表面を、カップリング剤で処理する場合には、その処理の前後において、また分散剤として有機溶剤中に添加する場合のいずれにおいても、酸化チタンの体積抵抗値を前述の範囲に維持する限り、酸化チタンの表面は未処理のものでもよく、さらに酸化アルミニウムおよび／または酸化ジルコニウムの金属酸化物を被覆させたものでもよい。
【００７０】
水溶性かつ非プロトン性有機溶剤もしくは水溶性かつ非プロトン性有機溶剤と低級アルコールとの混合溶剤と、樹脂と金属酸化物の合計量との重量割合は、３／９７〜２０／８０が好ましい。
【００７１】
塗布液中の固形分、すなわち樹脂と金属酸化物の合計量が上記の範囲より少ない場合には、所定の膜厚の下引き層を形成する際に、導電性支持体上に付着した直後の塗布膜から有機溶剤が蒸発して乾燥状態になるまでに多量の有機溶剤が蒸発することから、乾燥時間が非常に長くなり、周りの温湿度の影響から塗膜の乾燥の際に乾燥ムラが発生しやすくなるので好ましくない。また、樹脂と金属酸化物の合計量が上記の範囲より多い場合には、塗布液の粘度が高くなり導電性支持体上に均一な膜厚の下引き層を形成できなくなり、塗布液の保存安定性が悪くなり増粘してゲル化が起こりやすくなるので好ましくない。一方、溶剤と、樹脂と金属酸化物の合計量との重量割合が上記の範囲であれば、下引き層用塗布液中に分散された金属酸化物の凝集や沈降が抑制され、塗布液の粘度の増減が無く保存安定性に優れた塗布液を提供することができる。
下引き層用塗布液の粘度は、１〜２０ｍＰａ・ｓであることが好ましい。
【００７２】
本発明の下引き層用塗布液は、上記の水溶性かつ非プロトン性有機溶剤、低級アルコール、樹脂および金属酸化物を、ペイントシェーカー、ボールミル、サンドミル、アトライター、振動ミルおよび超音波分散機などを用いた公知の方法により混合し、均一に分散することにより得られる。
【００７３】
下引き層用塗布液中に分散された金属酸化物の分散性が悪ければ、金属酸化物の凝集や沈降が発生するために塗布液の粘度は著しく低下する。このため、導電性支持体上に浸漬塗布によって下引き層を形成する場合には、導電性支持体を非常に早い速度にて引き上げなければ所定の膜厚の下引き層を形成することはできない。さらに、有機溶剤の乾燥に長時間必要となるために、下引き層は塗布ムラが発生しやすくなり金属酸化物の凝集物が付着することから画像欠陥を生じる原因となる。
【００７４】
また、金属酸化物を過分散となるまで分散させた場合には、金属酸化物が粉砕されて表面積が増大し、塗布液の粘度が上昇して塗布性が著しく低下する。また、塗布液の粘度が経時的に上昇してゲル化するため、長期間の継続あるいは保存使用ができなくなる。
【００７５】
本発明は、上記のようにして得られた下引き層用塗布液を導電性支持体上に塗布し、自然乾燥して導電性支持体上に下引き層を形成し、次いで感光層用塗布液を前記下引き層上に塗布して感光層を形成して感光体を得ることを特徴とする感光体の製造方法を提供する。
【００７６】
下引き層用塗布液の塗布手段としては、通常、この分野で用いられる方法が適用できるが、浸漬塗布が特に好ましい。
図２は本発明において用いることができる浸漬塗布装置の概略模式図である。この装置は、導電性支持体２を上下移動させるための回転軸１０およびモーター１１、塗布液１２を攪拌しながら収容するための塗布液槽１３、攪拌槽１４、攪拌装置１５、モーター１６、循環経路１７ａおよび循環経路１７ｂからなる。
【００７７】
導電性支持体としては、通常、この分野で用いられるものが用いられ、例えばアルミニウム、アルミニウム合金、銅、亜鉛、ステンレスおよびチタンなどの金属製ドラムおよびシート、ポリエチレンテレフタレート、ナイロンおよびポリスチレンなどの高分子材料や硬質紙上に金属箔ラミネートや金属蒸着処理を施したドラム、シートおよびシームレスベルトなどが挙げられる。
【００７８】
本発明の感光体の製造方法においては、下引き層用塗布液の塗布が浸漬塗布で行なう場合には、２０℃での相対湿度が６０％ＲＨ以下であり、かつ風速が１ｍ／ｓである環境下に設置された浸漬塗布装置で行なうのが好ましい。
【００７９】
従来の下引き層用塗布液を高湿度下で塗布した場合には、結露により下引き層塗布膜が白濁し、その表面が著しく悪化して塗布ムラが発生し、画像欠陥が起こることがあった。この現象は、下引き層が導電性支持体上に形成された直後から有機溶剤が蒸発し、導電性支持体および塗布膜が気化熱を奪われて、温度が低下することにより起こる。しかし、本発明の下引き層用塗布液を用いた場合には、従来のように２０℃での相対湿度を２０％ＲＨ程度まで下げることなく塗布膜の白濁を抑制でき、製造条件の設定が非常に容易になり製造コストを下げることができる。
また、浸漬塗布装置を設置する環境として風速は１ｍ／ｓ以下が好ましい。風速が前記の範囲であれば、均一でムラのない塗布膜を形成することができる。
【００８０】
また、本発明の下引き層用塗布液は、従来の下引き層用塗布液のように塗布液中に分散された金属酸化物粒子が凝集することなく、溶剤の樹脂に対する溶解性も十分であるために分散液の粘度の経時変化がなく保存安定性に優れている。
したがって、塗布液の増粘によって導電性支持体の引き上げ速度を遅くする必要がないので生産性が向上し、下引き層の膜厚が導電性支持体の引き上げの上下方向で著しく異なるといった膜厚ムラが抑制される。
【００８１】
上記のことから、本発明の感光体の製造方法の浸漬塗布においては、下引き層用塗布液に導電性支持体を浸漬した後、０．５ｍｍ／ｓ以上の引き上げ速度で塗布しても、導電性支持体の上下方向で膜厚分布に変化のない均一な下引き層の塗布膜が得られる。
しかし、導電性支持体の引き上げ速度が０．５ｍｍ／ｓ未満の場合には、生産性が悪くなるので好ましくない。
【００８２】
下引き層の膜厚としては、０．０１〜２０μｍの範囲が好ましく、０．０５〜１０μｍの範囲がより好ましい。下引き層の膜厚が０．０１μｍ未満の場合には、実質的に下引き層として機能しなくなり、導電性支持体の欠陥を被覆して均一な表面性が得られず、導電性支持体からのキャリアの注入を防止することができなくなり、帯電性が低下するので好ましくない。また、下引き層の膜厚が２０μｍを超える場合には、感光体の感度が低下するので好ましくない。
【００８３】
このように本発明の感光体下引き層用塗布液を用いて製造された感光体は、その優れた塗布性と塗布液の安定性などから非常に優れた画像特性を有し、さらに高感度で、高耐久性を備える。
【００８４】
下引き層を形成した後、感光層用塗布液を前記下引き層上に塗布して感光層を形成する。感光層の塗布手段としては、通常、この分野で用いられる方法が適用できるが、浸漬塗布が特に好ましい。
【００８５】
下引き層上に形成される感光層の構造としては、電荷発生層と電荷輸送層との二層からなる機能分離型、およびこれらが分離されずに単一層で形成される単層型があるが、いずれを用いてもよい。
図１は、本発明の一実施形態である機能分離型の感光体（Ａ）および単層型の感光体（Ｂ）の模式断面図である。
【００８６】
図１（Ａ）の機能分離型の感光体１ａは、導電性支持体２、下引き層３および電荷発生層５と電荷輸送層６とからなる感光層４からなり、図１（Ｂ）の単層型の感光体１ｂは、導電性支持体２、下引き層３および感光層４からなる。
【００８７】
機能分離型の感光体の場合、下引き層上に電荷発生層が形成される。
電荷発生層に含有される電荷発生材料としては、通常、この分野で公知の化合物が用いられ、例えば、クロロダイアンブルーなどのビスアゾ系化合物、ジブロモアンサンスロンなどの多環キノン系化合物、ペリレン系化合物、キナクリドン系化合物、フタロシアニン系化合物およびアズレニウム塩系化合物などが挙げられる。
【００８８】
レーザー光やＬＥＤなどの光源を用いて反転現像プロセスにより画像形成を行う感光体において要求される感度は、６２０〜８００ｎｍの長波長の範囲であり、このような場合に用いられる電荷発生材料としては、高感度で耐久性に優れているフタロシアニン顔料やトリスアゾ顔料が挙げられる。これらの顔料は１種もしくは２種以上を併用することができ、中でもフタロシアニン顔料が特に好ましい。
【００８９】
本発明の下引き層塗布液を用いて形成した下引き層と、長波長に感度を有する電荷発生材料（例えばフタロシアニン顔料）を用いて形成した本発明の感光体は、反転現像方法を利用した画像形成装置に搭載することにより、微小領域での表面電荷の減少や消失による反転現像特有の白地に微小な黒点（黒ポチ）のない優れた画像特性を発揮する。
【００９０】
フタロシアニン顔料としては、無金属フタロシアニンおよび金属フタロシアニン、ならびにこれらの混合物や混晶化合物が挙げられる。金属フタロシアニン顔料における金属としては、酸化状態がゼロであるもの、その塩化物および臭化物などのハロゲン化金属、ならびに酸化物などが挙げられる。好ましい金属の具体例としては、Ｃｕ，Ｎｉ，Ｍｇ，Ｐｂ，Ｖ，Ｐｄ，Ｃｏ，Ｎｂ，Ａｌ，Ｓｎ，Ｚｎ，Ｃａ，Ｉｎ，Ｇａ，Ｆｅ，Ｇｅ，ＴｉおよびＣｒなどが挙げられる。
【００９１】
これらのフタロシアニン顔料の製造方法は種々の手法が提案されており、その製造方法は特に限定されず、また顔料化された後に各種精製や結晶型を変換させるために種々の有機溶剤で分散処理を行ったものでもよい。本発明において用いられるフタロシアニン顔料の結晶型としては、α型、β型、γ型、δ型、ε型、χ型およびτ型などの結晶型、ならびに非晶型が挙げられる。
【００９２】
これらのフタロシアニン顔料を用いた電荷発生層の作製方法としては、電荷発生材料、特にフタロシアニン顔料を真空蒸着することによって形成する方法、およびバインダー樹脂と有機溶剤と混合分散して成膜する方法がある。この混合分散の処理前には、ボールミル、サンドミル、アトライター、振動ミルおよび超音波分散機などの粉砕機を用いて予め粉砕処理を行ってもよい。
【００９３】
バインダー樹脂としては、メラミン樹脂、エポキシ樹脂、シリコン樹脂、ポリウレタン樹脂、アクリル樹脂、ポリカーボネート樹脂、ポリアリレート樹脂、フェノキシ樹脂およびブチラール樹脂、ならびに繰り返し単位を２種以上含む共重合体樹脂、例えば塩化ビニル−酢酸ビニル共重合体樹脂およびアクリロニトリル−スチレン共重合体樹脂などの絶縁性樹脂が挙げられる。
【００９４】
また、上記の樹脂を溶解させる溶剤としては、塩化メチレンおよび２塩化エタンなどのハロゲン化炭化水素、アセトン、メチルエチルケトンおよびシクロヘキサノンなどのケトン類、酢酸エチルおよび酢酸ブチルなどのエステル類、テトラヒドロフランおよびジオキサンなどのエーテル類、ベンゼン、トルエンおよびキシレンなどの芳香族炭化水素類、Ｎ，Ｎ−ジメチルホルムアミドおよびＮ，Ｎ−ジメチルアセトアミドなどの非プロトン性極性溶剤ならびにこれらの混合溶剤などが挙げられる。
【００９５】
フタロシアニン顔料とバインダー樹脂との配合割合は、フタロシアニン顔料が１０〜９９重量％の範囲が好ましい。フタロシアニン顔料が１０重量％未満の場合には感光体の感度が低下し、９９重量％を超える場合には感光体の耐久性が低下するばかりでなく、分散性が低下して粗大粒子が増大し、画像欠陥、特に黒ポチが多くなるので好ましくない。
【００９６】
電荷発生層用塗布液は、電荷発生材料、バインダー樹脂および溶剤を、ペイントシェーカー、ボールミル、サンドミル、アトライター、振動ミルおよび超音波分散機などを用いた公知の方法により混合し、均一に分散することにより得られる。用いる容器や分散メディアの摩耗などによって不純物の混入が起こらないように分散条件を選択する。
【００９７】
電荷発生材料としてフタロシアニン顔料を用いた電荷発生層用塗布液は、一次粒子および／またはその凝集粒子径が３μｍ以下の粒子径にまで分散を進めることが肝要である。一次粒子および／またはその凝集粒子径が３μｍを超える場合には、得られた感光体を反転現像に用いたとき、白地に黒ポチが非常に発生することになる。そのため電荷発生層用塗布液を調製する際には、各種分散機により分散条件を最適化し、フタロシアニン顔料を３μｍ以下、さらに好ましくはメジアン径で０．５μｍ以下、モード径で３μｍ以下にまで分散させる。
【００９８】
フタロシアニン顔料の粒子はその化学的構造から微粒子にするためには比較的強い分散条件と長時間の分散時間を必要とし、分散メディアの摩耗などによる不純物の混入が避けられないので、過分散はコスト的にも効率が悪く、好ましくない。また、分散時の熱や分散による衝撃などによってフタロシアニン顔料の結晶型が変化して、感光体の感度が大きく低下するので、フタロシアニン顔料の粒子径は、メジアン径で０．０１μｍ以下、モード径で０．１μｍ以下にすることは好ましくない。
【００９９】
また、分散処理した電荷発生層用塗布液に粒径３μｍを超えるフタロシアニン顔料が含まれている場合には、濾過処理を施すことにより３μｍよりも大きい一次粒子および／または凝集粒子を除去してもよい。濾過処理に用いられるフィルターの材質は分散の際に用いられた有機溶剤に膨潤や溶解しないものであれば一般的に用いられるものが使用されるが、好ましくは孔径が均一のテフロン製メンブランフィルターが好ましい。さらに遠心分離により粗大粒子や凝集物を除去してもよい。
【０１００】
電荷発生層用塗布液の塗布方法としては、スプレー法、バーコート法、ロールコート法、ブレード法、リング法および浸漬法などが挙げられ、生産性およびコストの点で浸漬法が好ましい。
図２に示した浸漬塗布装置を用いた浸漬法は、塗布液を満たした塗布槽に、導電性支持体を浸漬した後、一定速度または逐次変化する速度で引き上げることにより感光層を形成する方法であり、比較的簡単で、生産性およびコストの点で優れているために感光体を製造する場合に多く利用されている。
【０１０１】
電荷発生層の膜厚は、０．１〜１０μｍの範囲が好ましく、０．２〜２．０μｍの範囲が特に好ましい。
電荷発生層の膜厚が０．１μｍ未満の場合には、フタロシアニン顔料の分散過程においてその結晶型が変化することがあり、感光体の感度が低下するので好ましくない。また、電荷発生層の膜厚が１０μｍを超える場合には、均一な塗布が困難になるだけでなく、それ以上の感度の向上が期待できず、コスト的にも好ましくない。
【０１０２】
機能分離型の感光体の場合には、電荷発生層を形成した後、その上に電荷輸送層が形成される。
電荷輸送層に含有される電荷輸送材料としては、通常、この分野で公知の化合物が用いられ、例えば、ヒドラゾン系化合物、ピラゾリン系化合物、トリフェニルアミン系化合物、トリフェニルメタン系化合物、スチルベン系化合物およびオキサジアゾール系化合物などが挙げられ、これらの化合物は１種もしくは２種以上を併用して用いることができる。
【０１０３】
電荷輸送層用塗布液は、電荷輸送材料、バインダー樹脂を溶剤に混合し、溶解させることにより得られる。バインダー樹脂および溶剤としては、電荷発生層用塗布液のバインダー樹脂および溶剤として例示したものが挙げられる。
【０１０４】
電荷輸送層は、下引き層や電荷発生層と同様の方法で形成することができる。その膜厚は、５〜５０μｍの範囲が好ましく、１０〜４０μｍの範囲が好ましい。
【０１０５】
単層構造の感光体は、積層構造の感光体の場合に例示した電荷発生材料（例えば、フタロシアニン顔料）、電荷輸送材料、バインダー樹脂および溶剤をペイントシェーカー、ボールミル、サンドミル、アトライター、振動ミルおよび超音波分散機などを用いた公知の方法で混合・分散して感光層用塗布液を調製し、この塗布液を下引き層上に公知の方法で塗布することにより作製することができる。
感光層の膜厚は、５〜５０μｍの範囲が好ましく、１０〜４０μｍの範囲がより好ましい。
【０１０６】
単層構造および積層構造のいずれの感光体の場合であっても、下引き層が導電性支持体からのキャリア（ホール）注入に対して障壁となる。高感度、高耐久性の感光体を得るためには、感光層を負帯電性とするのが好ましい。
【０１０７】
感光体の感度向上および残留電位や繰り返し使用時の疲労低減などを目的として、感光層には少なくとも１種以上の電子受容性材料を添加してもよい。
電子受容性材料としては、例えば、パラベンゾキノン、クロラニル、テトラクロロ１，２−ベンゾキノン、ハイドロキノン、２，６−ジメチルベンゾキノン、メチル１，４−ベンゾキノン、α−ナフトキノンおよびβ−ナフトキノンなどのキノン系化合物、２，４，７−トリニトロ−９−フルオレノン、１，３，６，８−テトラニトロカルバゾール、ｐ−ニトロベンゾフェノン、２，４，５，７−テトラニトロ−９−フルオレノンおよび２−ニトロフルオレノンなどのニトロ化合物、テトラシアノエチレン、７，７，８，８−テトラシアノキノジメタン、４−（Ｐ−ニトロベンゾイルオキシ）−２’，２’−ジシアノビニルベンゼンおよび４−（ｍ−ニトロベンゾイルオキシ）−２’，２’−ジシアノビニルベンゼンなどのシアノ化合物などが挙げられる。これらの電子受容性材料の中でも、キノン系化合物やフルオレノン、Ｃｌ、ＣＮおよびＮＯ₂ などの電子吸引性置換基を有するベンゼン誘導体が特に好ましい。
【０１０８】
また、感光層には、安息香酸、スチルベン化合物およびその誘導体、トリアゾール化合物、イミダゾール化合物、オキサジアゾール化合物、チアゾール化合物およびその誘導体などの含窒素化合物類などの紫外線吸収剤や酸化防止剤を含有させてもよい。
【０１０９】
さらに、感光層には、必要に応じて感光層表面を保護するために保護層を設けてもよい。
表面保護層には、熱可塑性樹脂、光硬化性樹脂および熱硬化性樹脂が用いられ、この保護層は、前記の紫外線防止剤、酸化防止剤、金属酸化物などの無機材料、有機金属化合物および電子受容性材料などを含んでいてもよい。
【０１１０】
また、感光層および表面保護層には、必要に応じて二塩基酸エステル、脂肪酸エステル、リン酸エステル、フタル酸エステルおよび塩素化パラフィンなどの可塑剤を混合して、加工性および可撓性を付与するような機械的物性の改良を施してもよく、シリコン樹脂などのレベリング剤を添加してもよい。
【０１１１】
本発明によれば、上記の感光体の製造方法により得られる感光体が提供される。この感光体は、反転現像プロセスによる画像形成装置、例えば、電子写真複写機やレーザー、ＬＥＤなどを光源とする各種プリンターおよび電子写真製版システムなどに使用することができる。
【０１１２】
【実施例】
本発明を実施例および比較例により具体的に説明するが、これらの実施例により本発明が限定されるものではない。
【０１１３】
（実施例１）（参考例）
粒状の酸化亜鉛（堺化学製、ＦＩＮＥＸ−５０）１７．１重量部とブチラール樹脂（積水化学製、ＢＸ−１）０．９重量部を、Ｎ，Ｎ−ジメチルホルムアミド８２重量部に加え、ペイントシェーカーを用いて１２時間分散させ、固形分１８％の下引き層用塗布液を調製した。
【０１１４】
得られた下引き層用塗布液を厚さ２ｍｍのセルに入れ、調製直後の下引き層用塗布液の濁度を積分球式濁度計（三菱化学製、ＳＥＰ−ＰＴ−５０１Ｄ）を用いて測定し、下引き層用塗布液の分散性を評価した。
また、調製した下引き層用塗布液を９０日間静置した後、上記の測定と同様にして濁度を測定し、下引き層用塗布液の保存安定性を評価した。
得られた結果を表１に示す。
【０１１５】
（実施例２〜８）（参考例）
金属酸化物として粒状の酸化亜鉛に代えて、それぞれ以下に示す成分を用いた以外は、実施例１と同様して、下引き層用塗布液を調製し、調製直後および９０日後の濁度を測定し、下引き層用塗布液の分散性および保存安定性を評価した。
得られた結果を表１に示す。
【０１１６】
実施例２：粒状の酸化錫（三菱マテリアル製、Ｓ−１）
実施例３：粒状の酸化アルミニウム（日本アエロジル製、Aluminium Oxide Ｃ）
実施例４：未処理の粒状の酸化チタン（石原産業製、ＴＴＯ−５５Ｎ）
実施例５：酸化アルミニウムで表面処理した粒状の酸化チタン（石原産業製、ＴＴＯ−５５Ａ）
【０１１７】
実施例６：未処理の針状の酸化チタン（堺化学製、ＳＴＲ−６０Ｎ）
実施例７：酸化アルミニウムで表面処理した針状の酸化チタン（堺化学製、ＳＴＲ−６０）
実施例８：酸化アルミニウムおよび酸化ジルコニウムで表面処理した樹枝状の酸化チタン（石原産業製、ＴＴＯ−Ｄ−１）
【０１１８】
【表１】

【０１１９】
（実施例９）（参考例）
表面処理剤（カップリング剤）としてγ−（２−アミノエチル）アミノプロピルメチルジメトキシシラン０．０２重量部をｎ−ヘキサン５００重量部に加え、この混合物を攪拌しながら、未処理の針状の酸化チタン（堺化学製、ＳＴＲ−６０Ｎ）２０重量部を加えて１時間攪拌した。次いで、この混合物を濾過し、ろ取物を１００℃で３時間加熱乾燥して、カップリング剤で表面処理された針状の酸化チタンを得た。
【０１２０】
金属酸化物として粒状の酸化亜鉛に代えて、表面処理された針状の酸化チタンを用いた以外は、実施例１と同様して、下引き層用塗布液を調製し、調製直後および９０日後の濁度を測定し、下引き層用塗布液の分散性および保存安定性を評価した。
得られた結果を表１に示す。
【０１２１】
（実施例１０〜１３）（参考例）
表面処理剤（カップリング剤）としてγ−（２−アミノエチル）アミノプロピルメチルジメトキシシランに代えて、それぞれ以下に示す成分と使用量の表面処理剤を用いた以外は、実施例９と同様して、カップリング剤で表面処理された針状の酸化チタンを得た。
【０１２２】
実施例１０：γ−（２−アミノエチル）アミノプロピルメチルジメトキシシラン ４重量部
実施例１１：フェニルトリクロロシラン ０．１５重量部
実施例１２：ビス（ジオクチルパイロホフェート） ０．１５重量部
実施例１３：アセトアルコキシアルミニウムジイソプロピレート ０．１５重量部
【０１２３】
金属酸化物として粒状の酸化亜鉛に代えて、表面処理された針状の酸化チタンを用いた以外は、実施例１と同様して、下引き層用塗布液を調製し、調製直後および９０日後の濁度を測定し、下引き層用塗布液の分散性および保存安定性を評価した。
得られた結果を表１に示す。
【０１２４】
（実施例１４〜１５）（参考例）
金属酸化物として未処理の針状の酸化チタンに代えて、それぞれ以下に示す酸化チタンを用いた以外は、実施例９と同様して、カップリング剤でさらに表面処理された針状および樹枝状の酸化チタンを得た。
【０１２５】
実施例１４：酸化アルミニウムで表面処理した針状の酸化チタン（堺化学製、ＳＴＲ−６０）、
実施例１５：酸化アルミニウムおよび酸化ジルコニウムで表面処理した樹枝状の酸化チタン（石原産業製：ＴＴＯ−Ｄ−１）
【０１２６】
金属酸化物として粒状の酸化亜鉛に代えて、上記の表面処理された酸化チタンを用いた以外は、実施例１と同様して、下引き層用塗布液を調製し、調製直後および９０日後の濁度を測定し、下引き層用塗布液の分散性および保存安定性を評価した。
得られた結果を表１に示す。
【０１２７】
（比較例１〜１５）
水溶性・非プロトン性有機溶剤としてＮ，Ｎ−ジメチルホルムアミドに代えて、メチルアルコールを用いた以外は、それぞれ実施例１〜１５と同様にして、下引き層用塗布液を調製し、調製直後および９０日後の濁度を測定し、下引き層用塗布液の分散性および保存安定性を評価した。
得られた結果を表２に示す。
【０１２８】
【表２】

【０１２９】
表１の結果から、実施例１〜１５の下引き層用塗布液における調製直後の濁度はいずれも低い値を示し、これらの塗布液が非常に透明性の高い、分散性に優れたものであることがわかる。また、９０日後の濁度は、いずれも調製直後の濁度からやや増大しているものの、金属酸化物の凝集・沈降物は観察されず、これらの塗布液が保存安定性に優れたものであることがわかる。
【０１３０】
一方、表２の結果から、比較例１〜１５の下引き層用塗布液における調製直後の濁度はいずれも高い値を示し、これらの塗布液が非常に濁りのある、分散性に劣るものであることがわかる。また、比較例４および比較例６の下引き層用塗布液においては、調製直後から凝集・沈降が観察され、未処理の酸化チタンを含有する下引き層用塗布液が特に分散性に劣ることがわかる。このような酸化チタンの表面を酸化アルミニウムや酸化ジルコニウムなどの金属酸化物やカップリング剤で処理することにより比較的分散性が向上する。しかし、いずれの下引き層用塗布液も９０日後にゲル化あるいは金属酸化物の凝集・沈降物が観察され、保存安定性に劣ることがわかる。
【０１３１】
したがって、水溶性かつ非プロトン性有機溶剤を用いることにより、優れた分散性と長期保存安定性を有する下引き層用塗布液が得られることがわかる。
【０１３２】
（実施例１６〜１８）（参考例）
金属酸化物として粒状の酸化亜鉛に代えて、酸化アルミニウムおよび酸化ジルコニウムで表面処理した樹枝状の酸化チタン（石原産業製：ＴＴＯ−Ｄ−１）を用い、有機溶剤としてＮ，Ｎ−ジメチルホルムアミドに代えて、それぞれ以下に示す成分と使用量の有機溶剤を用いた以外は、実施例１と同様して、下引き層用塗布液を調製し、調製直後および９０日後の濁度を測定し、下引き層用塗布液の分散性および保存安定性を評価した。
得られた結果を表３に示す。
【０１３３】

【０１３４】
【表３】

【０１３５】
（実施例１９）（参考例）
樹脂としてブチラール樹脂に代えて、共重合ナイロン樹脂（東レ製、ＣＭ８０００）を用いた以外は、実施例１８と同様にして、下引き層用塗布液を調製し、調製直後および９０日後の濁度を測定した。
得られた結果を表３に示す。
【０１３６】
（実施例２０〜２２）
有機溶剤としてテトラヒドロフランに代えて、それぞれ以下に示す成分と使用量の有機溶剤を用いた以外は、実施例１６と同様して、下引き層用塗布液を調製し、調製直後および９０日後の濁度を測定し、下引き層用塗布液の分散性および保存安定性を評価した。
得られた結果を表３に示す。
【０１３７】

【０１３８】
（実施例２３）
酸化アルミニウムおよび酸化ジルコニウムで表面処理した樹枝状の酸化チタン（石原産業製：ＴＴＯ−Ｄ−１）６．３重量部と共重合ナイロン樹脂（東レ製、ＣＭ８０００）１１．７重量部を、１，３−ジオキソラン３２．８重量部とメチルアルコール４９．２重量部の混合溶剤に加え、ペイントシェーカーを用いて１２時間分散させ、下引き層用塗布液を調製した。
得られた下引き層用塗布液の調製直後および９０日後の濁度を測定し、下引き層用塗布液の分散性および保存安定性を評価した。
得られた結果を表３に示す。
【０１３９】
（実施例２４）
１，３−ジオキソランの使用量を２３２．８重量部、メチルアルコールの使用量を３４９．２重量部にした以外は、実施例２３と同様にして、固形分３％の下引き層用塗布液を調製した。
得られた下引き層用塗布液の調製直後および９０日後の濁度を測定し、下引き層用塗布液の分散性および保存安定性を評価した。
得られた結果を表３に示す。
【０１４０】
（実施例２５）
１，３−ジオキソランの使用量を１１２．８重量部、メチルアルコールの使用量を１６９．２重量部にした以外は、実施例２３と同様にして、固形分６％の下引き層用塗布液を調製した。
得られた下引き層用塗布液の調製直後および９０日後の濁度を測定し、下引き層用塗布液の分散性および保存安定性を評価した。
得られた結果を表３に示す。
【０１４１】
表３の結果から、実施例１６〜２５の下引き層用塗布液における調製直後の濁度はいずれも低い値を示し、これらの塗布液が非常に透明性の高い、分散性に優れたものであることがわかる。また、９０日後の濁度は、いずれも調製直後の濁度からあまり変化がなく、初期の分散性を維持しており、これらの塗布液が保存安定性に優れたものであることがわかる。
さらに、表１の実施例１〜１５の結果と比較して、水溶性かつ非プロトン性有機溶剤として環状エーテル、特にジオキソラン化合物を用いた実施例１６〜２５の方が、塗布液の分散性および保存安定性に優れていることがわかる。
【０１４２】
（実施例２６）
実施例２２で調製した下引き層用塗布液の粘度をＥ型粘度計（東機産業製、ＲＥ−１２５Ｌ）を用いて測定したところ、２０ｍＰａ・ｓであった。
図２に示した浸漬塗布装置を用いて、実施例２２で調製した塗布液１２を導電性支持体２（アルミニウム製、厚さ１ｍｍ（ｔ）×直径８０ｍｍ（φ）×長さ３４８ｍｍ）上に浸漬塗布し、次いで塗布層を自然乾燥して、乾燥膜厚１．０μｍの下引き層を形成した。下引き層を浸漬塗布する際に浸漬塗布装置を設置した環境は、室温２０℃、相対湿度６０％ＲＨでクリーンルーム内の風速が１．０ｍ／ｓであり、導電性支持体の引き上げ速度が０．５ｍｍ／ｓであった。
【０１４３】
さらに、下引き層上に電荷発生層および電荷輸送層からなる感光層を形成して図１（Ａ）に示した機能分離型の感光体を得た。具体的には、以下に示した化学構造のビスアゾ顔料（クロロダイアンブルー）１．５重量部とフェノキシ樹脂（ユニオンカーバイド製、ＰＫＨＨ）１．５重量部を、１，２−ジメトキシエタン９７重量部に加え、ペイントシェーカーを用いて１２時間分散させ、電荷発生層用塗布液を調製した。
図２に示した浸漬塗布装置を用いて、下引き層を形成した導電性支持体上に電荷発生層用塗布液を浸漬塗布し、次いで塗布層を９０℃で１０分間熱風乾燥して、乾燥膜厚１．０μｍの電荷発生層を形成した。
【０１４４】
次いで、電荷発生層上に電荷輸送層を形成した。具体的には、以下に示した化学構造のヒドラゾン系化合物１重量部とポリカーボネート樹脂（三菱瓦斯化学製、Ｚ−４００）１重量部を、テトラヒドロフラン８重量部に加え、攪拌・混合して、電荷輸送層用塗布液を調製した。
電荷発生層と同様にして、下引き層および電荷発生層を順次形成した導電性支持体上に電荷輸送層用塗布液を浸漬塗布し、次いで塗布層を１１０℃で１時間熱風乾燥して、乾燥膜厚２５．０μｍの電荷輸送層を形成した。
【０１４５】
以上のようにして作製した機能分離型の感光体を画像形成装置（シャープ製、ＳＦ−８８７０）の改造機に搭載し、３００００枚の耐刷試験を行った。
評価項目は、初期および３００００枚耐刷後における暗部電位Ｖ₀（−Ｖ）および明部電位Ｖ_L（−Ｖ）ならびに画像欠陥とした。
得られた結果を表４に示す。表４には下引き層の塗布欠陥を併記する。
【０１４６】
【表４】

【０１４７】
（比較例１６）
実施例２２の下引き層用塗布液に含有する樹枝状の酸化チタンに代えて、酸化錫（Ｓｂドープ）で導電処理を施した針状の酸化チタン（石原産業製：ＦＴＬ−１０００）を用いて下引き層用塗布液を調製し、下引き層を形成した以外は、実施例２６と同様にして、機能分離型の感光体を作製し、３００００枚の耐刷試験を行った。
得られた結果を表４に示す。
【０１４８】
（比較例１７）
実施例２６で下引き層を形成する際に、下引き層用塗布液の固形分を２５％に高め、かつ導電性支持体の引き上げ速度を０．２ｍｍ／ｓとして下引き層を形成した以外は、実施例２６と同様にして、機能分離型の感光体を作製し、３００００枚の耐刷試験を行った。Ｅ型粘度計を用いて調製した下引き層用塗布液の粘度を測定したところ、２５ｍＰａ・ｓであった。
得られた結果を表４に示す。
【０１４９】
形成した下引き層の膜厚を測定したところ、浸漬塗布において導電性支持体を引き上げる際の上端部と下端部とで膜厚差が０．８μｍもあり、下端部の膜厚が非常に薄かった。また、下引き層の表面に、下引き層用塗布液の溶剤に由来する、浸漬塗布における導電性支持体の引き上げ方向と同方向の多数の細い縦筋が観察された。
【０１５０】
（比較例１８）
実施例２６で下引き層を形成する際に、下引き層用塗布液の固形分を２％に低め、かつ導電性支持体の引き上げ速度を１０．０ｍｍ／ｓとして下引き層を形成した以外は、実施例２６と同様にして、機能分離型の感光体を作製し、３００００枚の耐刷試験を行った。Ｅ型粘度計を用いて調製した下引き層用塗布液の粘度を測定したところ、０．８ｍＰａ・ｓであった。
得られた結果を表４に示す。
【０１５１】
形成した下引き層の膜厚を測定したところ、その膜厚が所定の膜厚になる位置は、塗布をはじめた導電性支持体の上端から５０ｍｍの位置であった。このような事実から、用いた下引き層用塗布液の付着性が非常に悪いことがわかる。
【０１５２】
（比較例１９）
下引き層を浸漬塗布する浸漬塗布装置の設置環境であるクリーンルーム内の風速を２ｍ／ｓとした以外は、実施例２６と同様にして、機能分離型の感光体を作製し、３００００枚の耐刷試験を行った。
得られた結果を表４に示す。
【０１５３】
形成した下引き層の一部に白濁が観察された。この白濁は下引き層用塗布液中の有機溶剤の蒸発に由来するもので、白濁部分の膜厚を測定したところ、その膜厚は所定の下引き層の膜厚よりも０．５μｍ厚かった。
【０１５４】
（比較例２０）
下引き層を浸漬塗布する浸漬塗布装置の設置環境である室温と相対湿度を２０℃、７０％ＲＨとした以外は、実施例２６と同様にして、機能分離型の感光体を作製し、３００００枚の耐刷試験を行った。
得られた結果を表４に示す。
【０１５５】
形成した下引き層は全体的に白濁が観察された。その白濁した表面部分を光学顕微鏡で調べたところ、下引き層表面に非常に小さな凹凸が観察された。
【０１５６】
以上の比較例の結果から、次のようなことがわかる。
▲１▼下引き層用塗布液の金属酸化物として、導電処理を施した金属酸化物を用いた場合には、感光体の帯電性が著しく低下し、黒ベタの濃度が低下するという画像欠陥が生じる（比較例１６）。
▲２▼下引き層用塗布液を導電性支持体に浸漬塗布するときの導電性支持体の引き上げ速度が遅い場合には、導電性支持体の下端部に塗布ムラが発生する（比較例１７）。
【０１５７】
▲３▼下引き層用塗布液の粘度が非常に低い場合には、下引き層用塗布液の付着性が悪くなり、所望の膜厚の下引き層が得られず、画像欠陥が生じる（比較例１８）。
▲４▼下引き層を浸漬塗布する浸漬塗布装置の設置環境（室内の風速、室温および相対湿度）により下引き層の塗布膜にムラが発生し、ハーフトーン画像に影響する（比較例１９および比較例２０）。
【０１５８】
（実施例２７）
図２で示した浸漬塗布装置を用いて、実施例２５で調製した塗布液１２を導電性支持体２（アルミニウム製、厚さ１ｍｍ（ｔ）×直径６５ｍｍ（φ）×長さ３５０ｍｍ）上に浸漬塗布し、次いで塗布層を自然乾燥して、乾燥膜厚１．０μｍの下引き層を形成した。下引き層を浸漬塗布する際に浸漬塗布装置を設置した環境は、室温２０℃、相対湿度３０％ＲＨでクリーンルーム内の風速が０．１ｍ／ｓであり、導電性支持体の引き上げ速度が４．０ｍｍ／ｓであった。
【０１５９】
さらに、下引き層上に電荷発生層および電荷輸送層からなる感光層を形成して図１（Ａ）に示した機能分離型の感光体を得た。具体的には、下記の電荷発生層用塗布液の成分をボールミルを用いて１２時間分散させ、電荷発生層用塗布液を調製し、図２に示した浸漬塗布装置を用いて、下引き層を形成した導電性支持体上に電荷発生層用塗布液を浸漬塗布し、次いで塗布層を１２０℃で１０分間熱風乾燥して、乾燥膜厚０．８μｍの電荷発生層３を設けた。
【０１６０】
（電荷発生層用塗布液）
τ型無金属フタロシアニン
（東洋インキ製造製、Ｌｉｏｐｈｏｔｏｎ ＴＰＡ−８９１） ２重量部
塩化ビニル―酢酸ビニル―マレイン酸共重合体樹脂
（日信化学工業製 、ＳＯＬＢＩＮ Ｍ） ２重量部
メチルエチルケトン １００重量部
【０１６１】
次いで、電荷発生層上に電荷輸送層を形成した。具体的には、下記の電荷輸送層用塗布液の成分を攪拌・混合して、電荷輸送層用塗布液を調製した。
（電荷輸送層用塗布液）
ヒドラゾン系化合物（下記構造式(１)） ８重量部
ポリカーボネート樹脂（三菱瓦斯化学製、Ｚ−４００） １０重量部
シリコンオイル（信越化学製、ＫＦ５０） ０．００２重量部
テトラヒドロフラン １２０重量部
【０１６２】
【化２】

【０１６３】
電荷発生層と同様にして、下引き層および電荷発生層を順次形成した導電性支持体上に電荷輸送層用塗布液を浸漬塗布し、次いで塗布層を１１０℃で1時間熱風乾燥して、乾燥膜厚２５μｍの電荷輸送層を形成した。
【０１６４】
以上のようにして作製した機能分離型の感光体を画像形成装置（シャープ製、デジタル複写機 ＡＲ２０３０）の改造機に搭載し、３００００枚の耐刷試験を行った。
初期および３００００枚耐刷後の画像は、白地に微小の黒点（黒ポチ）や下引き層の塗布ムラなどに由来する画像欠陥のない非常に良好な画質であった。
【０１６５】
また、試験環境を高温高湿度（室温３５℃、相対湿度８５％ＲＨ）および低温低湿度（室温５℃、相対湿度２０％ＲＨ）とした以外は、上記と同様にして３００００枚の耐刷試験を行った。
初期および３００００枚耐刷後の画像は、いずれの環境でも感度の低下がなく、カブリや黒ポチ、塗布ムラなどに由来する画像欠陥のない良好な画質であった。
【０１６６】
（実施例２８）
実施例２５の下引き層用塗布液に含有するポリアミド樹脂に代えて、Ｎ−メトキシメチル化ナイロン樹脂（帝国化学製、ＥＦ−３０Ｔ）を用いて下引き層用塗布液を調製し、下引き層を形成した以外は、実施例２６と同様にして、機能分離型の感光体を作製し、３００００枚の耐刷試験を行った。
初期および３００００枚耐刷後の画像は、白地に微小の黒点（黒ポチ）や下引き層の塗布ムラなどに由来する画像欠陥のない非常に良好な画質であった。
【０１６７】
（実施例２９）
図２で示した浸漬塗布装置を用いて、導電性支持体２上に下引き層３および電荷発生材料と電荷輸送材料とを含有する感光層４を順次を形成して図１（Ｂ）に示した単層型の感光体を得た。
【０１６８】
具体的には、下記の下引き層用塗布液の成分をペイントシェーカーを用いて１０時間分散させ、下引き層用塗布液を調製した。
（下引き層塗布液）
未処理の粒状の酸化チタン（石原産業製、ＴＴＯ−５５Ｎ） ３重量部
共重合ナイロン樹脂（東レ製、ＣＭ８０００） ３重量部
メチルアルコール ５０重量部
１，３−ジオキソラン ５０重量部
【０１６９】
調製した下引き層用塗布液を導電性支持体（アルミニウム製、厚さ１００μｍ（ｔ）×２５０ｍｍ×１８０ｍｍ）上にベーカーアプリケーターによって塗布し、次いで塗布層を自然乾燥して、乾燥膜厚１．０μｍの下引き層２を形成した。
【０１７０】
次いで、下引き層上に感光層を形成した。具体的には、下記の感光層用塗布液の成分をボールミルを用いて１２時間分散させ、電荷輸送層用塗布液を調製した。

【０１７１】
【化３】

【０１７２】
【化４】

【０１７３】
下引き層と同様にして、下引き層を形成した導電性支持体上に感光層用塗布液をベーカーアプリケーターによって塗布し、次いで塗布層を１１０℃で1時間熱風乾燥して、乾燥膜厚２０μｍの感光層を形成した。
【０１７４】
以上のようにして作製した単層型の感光体を画像形成装置（シャープ製、デジタル複写機 ＡＲ２０３０）の改造機に搭載し、室温常湿（２０℃、相対湿度５０％ＲＨ）条件下で３００００枚の耐刷試験を行った。
初期および３００００枚耐刷後の画像は、白地に微小の黒点（黒ポチ）や下引き層の塗布ムラなどに由来する画像欠陥のない非常に良好な画質であった。
【０１７５】
【発明の効果】
本発明の下引き層用塗布液は、水溶性かつ非プロトン性有機溶剤または水溶性かつ非プロトン性有機溶剤と低級アルコールとの混合溶剤、樹脂および金属酸化物を含有することを特徴とする。
【０１７６】
本発明の下引き層用塗布液は、樹脂を溶解させた水溶性かつ非プロトン性有機溶剤中に金属酸化物を含有させるので、金属酸化物の分散性が非常によくなり、初期の分散性を長期間にわたって維持できる。また、近年の環境問題や毒性の問題からハロゲン含有の有機溶剤を使用することを避けることができる。
したがって、導電性支持体からのキャリア注入を抑制し黒ポチの発生を抑制する、安全性に優れた下引き層用塗布液を提供することができる。
【０１７７】
本発明の下引き層用塗布液は、水溶性かつ非プロトン性有機溶剤として環状エーテルを用いることにより、水や低級アルコールおよびハロゲンを含有する有機溶剤を用いた場合に生じるタレや乾燥ムラのない、均一な下引き層を形成することができ、かつ環境問題のない下引き層用塗布液を提供することができる。
【０１７８】
本発明の下引き層用塗布液は、水溶性かつ非プロトン性有機溶剤と低級アルコールとの重量割合を６０／４０〜５／９５にすることにより、さらに保存安定性や塗工性に優れた下引き層用塗布液を提供することができる。
【０１７９】
本発明の下引き層用塗布液は、溶剤としてＮ，Ｎ−ジメチルホルムアミド、テトラヒドロフラン、１，３−ジオキソランもしくは１，３−ジオキソランとメタノールとの混合溶剤、特に前記の混合溶剤を用いることにより、環境や健康問題が無く優れた塗工性を有する下引き層用塗布液を提供することができる。
【０１８０】
本発明の下引き層用塗布液は、樹脂としてアルコール可溶性の樹脂、特にポリアミド樹脂および／またはブチラール樹脂を用いることにより、金属酸化物と馴染みがよく、導電性支持体との接着性に優れた下引き層用塗布液を提供することができ、膜の可撓性を保持し得る下引き層を形成することができる。
また、本発明の下引き層用塗布液は、感光体塗布液用溶剤による膨潤や感光体塗布液用溶剤への溶解がないので、下引き層の塗布欠陥やムラの発生を防止し優れた画像特性を有する感光体を作製し得る下引き層用塗布液を提供することができる。
【０１８１】
本発明の下引き層用塗布液は、金属酸化物として酸化チタン、酸化ジルコニウム、酸化錫、酸化アルミニウムまたは酸化亜鉛、特に酸化チタンを用いることにより、導電性支持体からのキャリアの注入で表面電荷が微視的に消失もしくは減少することを防止し、種々の環境下でも優れた電子写真特性を安定して保つことができる下引き層を形成することができる。
【０１８２】
本発明の下引き層用塗布液は、金属酸化物として酸化チタン、特に針状および／または樹枝状の酸化チタンを用いることにより、酸化チタンの凝集が抑えられ、非常に分散性の優れた下引き層用塗布液を提供することができる。この下引き層用塗布液を用いて作製した感光体は、帯電性に優れ、残留電位が低く、繰り返し使用しても残留電位の蓄積が少なく、光感度の劣化が小さい。すなわち、繰り返し安定性と環境特性に優れた感光体を提供することができる。
【０１８３】
本発明の下引き層用塗布液は、金属酸化物としての酸化チタンの表面を酸化アルミニウムおよび／または酸化ジルコニウムで被覆することにより、さらに任意にシランカップリング剤、シリル化剤、アルミニウム系カップリング剤またはチタネート系カップリング剤で被覆することにより、酸化チタンを高い含有率で樹脂中に分散しても分散性および保存安定性の優れた下引き層用塗布液を提供することができる。したがって、導電性支持体の欠陥に由来する画像欠陥を防止し、感光層形成時に均一な塗膜を得ることができ、良好な画質特性を有する感光体を作製することができる。
上記の金属酸化物や有機化合物による被覆量（表面処理量）は、共に酸化チタンに対して２０重量％以下が効果的である。
【０１８４】
本発明の下引き層用塗布液は、金属酸化物（例えば、酸化チタン）の表面に導電性処理を施さなくても粒子同志の接触機会が多くなるので、針状および／または樹枝状の酸化チタンの含有量が少なくても感光体特性、特に感度および残留電位を悪化させることがない優れた帯電性を有する感光体を作製することができる。
すなわち、酸化チタン粒子が針状もしくは樹枝状であれば、粒子が細長いために、下引き層が形成されたときには、酸化チタン粒子どうしが接触しやすく接触面積が大きくなるので、粒状の酸化チタン粒子を使用する場合よりも、下引き層中の酸化チタン粒子の含有量を低下させても、同等の性能をもつ下引き層が容易に作製できる。酸化チタン粒子の含有率を少なくできることは、下引き層の膜強度及び導電性支持体との接着性の向上にも役立つ。そのうえ酸化チタン粒子どうしの接触が強固であるので、長期間の繰り返し使用によっても電気的特性及び画像特性の劣化が発生せず、優れた安定性をもつ電子写真感光体が得られる。
【０１８５】
また、酸化チタン粒子の含有率が同じ場合には、粒状よりも針状もしくは樹枝状の酸化チタン粒子を用いた方が下引き層の抵抗値が低くなり、下引き層の膜厚を厚くすることができる。このため、下引き層表面には導電性支持体の表面欠陥が現れず、平滑な下引き層表面を得るうえで有利である。
【０１８６】
本発明の下引き層用塗布液は、水溶性かつ非プロトン性有機溶剤または水溶性かつ非プロトン性有機溶剤と低級アルコールとの混合溶剤と、樹脂および金属酸化物の合計量との重量割合が３／９７〜２０／８０にすることにより、下引き層用塗布液中に分散された金属酸化物の凝集や沈降が抑制され、塗布液の粘度の増減がなく、塗工性および保存安定性に優れた下引き層用塗布液を提供することができる。
これは、下引き層の形成（塗布）後の乾燥過程において生ずる有機溶剤の蒸発による乾燥ムラを抑制し、および塗布液の増粘やゲル化を抑えて、塗布性を改善するものである。
【０１８７】
本発明の感光体の製造方法は、上記の下引き層用塗布液を導電性支持体上に塗布し、自然乾燥して導電性支持体上に下引き層を形成し、次いで感光層用塗布液を前記下引き層上に塗布して感光層を形成して感光体を得ることを特徴とする。
【０１８８】
したがって、導電性支持体からのキャリア注入を抑制し黒ポチの発生を抑制する感光体下引き層を有する感光体の製造方法を提供することができる。
本発明の下引き層用塗布液は分散性や保存安定性に優れているので、塗布欠陥のない均一な塗布膜が容易に形成でき、画像欠陥のない優れた画像特性を有する感光体を製造することができる。
【０１８９】
本発明の感光体の製造方法は、下引き層用塗布液の塗布を浸漬塗布で行ない、浸漬塗布装置の設置環境を２０℃での相対湿度が６０％ＲＨ以下、風速１ｍ／ｓ以下とすることにより、さらに優れた画像特性を有する感光体を製造することができる。また、塗布速度の低下による生産性の低下のない優れた塗布性と生産性を有し、塗布ムラや塗布欠陥のない優れた画像特性を有する感光体の製造方法を提供することができる。
浸漬塗布装置などの塗工装置周辺を無風状態に維持することなしに、クリーンルーム内を一定の気流で循環させて、塗布欠陥の原因となるチリを除去しつつ、導電性支持体上に下引き層を形成することができる。
【０１９０】
本発明の感光体は、上記の感光体の製造方法により得られるものであり、導電性支持体からのキャリア注入を抑制し黒ポチの発生を抑制する感光体下引き層を有する。
【０１９１】
したがって、帯電性に優れ、残留電位が低く、繰り返し使用しても残留電位の蓄積が少なく、光感度の劣化が小さい。すなわち、繰り返し安定性と環境特性に優れた感光体を提供することができる。
【０１９２】
本発明の感光体は、反転現像プロセスによる画像形成装置、例えば画像の加工処理やＦＡＸ、プリンターなどとの複合機種に好適に用いられる。
このような画像形成装置に用いても、導電性支持体や感光層の欠陥に由来する微少な領域での帯電性の低下による著しい画像欠陥が生じにくい。
【０１９３】
特に、本発明の感光体は、感光層の電荷発生材料として長波長に光感度を有する有機顔料（例えば、フタロシアニン顔料）を用いることにより、長波長に光源を有する半導体レーザーやＬＥＤを用いて反転現像方式による画像形成装置に反転現像プロセスを用いて画像を形成する場合に好適に用いられる。
【図面の簡単な説明】
【図１】本発明の一実施形態である機能分離型の電子写真感光体（Ａ）および単層型の電子写真感光体（Ｂ）の模式断面図である。
【図２】本発明において用いることができる浸漬塗布装置の概略模式図である。
【図３】本発明における金属酸化物として用いられる酸化チタンの形状を示す模式図である。
【符号の説明】
１ａ 機能分離型の電子写真感光体
１ｂ 単層型の電子写真感光体
２ 導電性支持体
３ 下引き層
４ 感光層
５ 電荷発生層
６ 電荷輸送層
１０ 回転軸
１１ モーター
１２ 塗布液
１３ 塗布液槽
１４ 攪拌槽
１５ 攪拌装置
１６ モーター
１７ａ 循環経路
１７ｂ 循環経路
ａ 長軸
ｂ 短軸[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coating solution for an undercoat layer of an electrophotographic photoreceptor comprising a conductive support, an undercoat layer and a photosensitive layer, a method for producing an electrophotographic photoreceptor using the same, and an electrophotographic photoreceptor.
[0002]
[Prior art]
In general, an electrophotographic process using a photoconductive electrophotographic photoreceptor (hereinafter referred to as “photoreceptor”) is one of information recording means utilizing the photoconductive phenomenon of the photoreceptor. In this process, first, the surface of a photoconductor is uniformly charged by corona discharge in a dark place, and then exposed to selectively discharge the charge in the exposed area to form a latent image, and then colored. Charged fine particles (toner) are attached to the latent image to form a visible image and form an image.
[0003]
In such a series of processes, the photoreceptor is required to have the following basic characteristics.
1) It can be uniformly charged to an appropriate potential in a dark place.
2) High charge retention capability in the dark and low charge discharge
3) It has excellent photosensitivity, and discharges electric charge quickly by light irradiation.
[0004]
The photoreceptor is also required to have the following characteristics.
4) The surface of the photoreceptor can be easily neutralized.
5) Low residual potential
6) Mechanical strength and excellent flexibility
7) It is stable, that is, when it is used repeatedly, its electrical characteristics, especially charging property, photosensitivity, residual potential, etc. do not fluctuate
8) Excellent durability, that is, resistance to heat, light, moisture, ozone, etc.
[0005]
Materials having a photoconductive phenomenon used for the photoreceptor can be roughly classified into inorganic materials and organic materials.
Examples of the photoreceptor using a known representative inorganic photoconductive material include selenium, cadmium sulfide, zinc oxide and the like dispersed in a binder resin, amorphous silicon, and the like.
[0006]
These photoconductors have many advantages, such as being able to be charged to an appropriate potential in the dark, having little charge dissipation in the dark, and being able to quickly dissipate charge by light irradiation. Has various drawbacks. For example, it is difficult to select manufacturing conditions for selenium-based photoconductors, which is expensive to manufacture, and is sensitive to heat and mechanical shock. Since it has, it is not preferable.
[0007]
In addition, with zinc oxide photoconductors, stable sensitivity cannot be obtained in a humid environment, and dyes added as sensitizers cause charging deterioration due to corona charging and photobleaching due to exposure. It has the disadvantage that it cannot be given.
[0008]
In this regard, a photoconductor using amorphous silicon has high sensitivity and excellent durability, but its manufacturing process is complicated, so that the manufacturing cost is high, and image defects such as image defects caused by film defects occurring during film formation Leaving a problem.
Therefore, a photoreceptor using an inorganic photoconductive material is hardly used at present.
[0009]
On the other hand, various organic photoconductive materials such as polyvinyl carbazole have been proposed, but these polymers are lighter and have better film formability than the inorganic photoconductive materials described above. However, it is inferior to inorganic photoconductive materials in terms of sensitivity, durability, and stability due to environmental changes.
[0010]
However, in general, there are a wide variety of organic materials, various arrangements can be made by synthesis, and by utilizing the advantages that toxicity and durability can be improved and manufacturing costs can be reduced by appropriately selecting materials, Various organic photoconductive materials have been developed.
[0011]
Further, as a method for solving the above-described drawbacks and problems from another viewpoint, a layered or dispersed function-separated photoreceptor in which a charge generation function and a charge transport function, which are photoconductive functions, are assigned to separate materials, respectively. Has been proposed.
[0012]
The functional separation type photoconductor has a wide selection range of each material, and provides a high-performance photoconductor by combining the best materials in electrophotographic characteristics such as charging characteristics, sensitivity, residual potential, repetitive characteristics and printing durability. can do. In addition, organic photoconductive materials can be produced using a simple coating process, so that they are extremely productive and can provide a photoconductor at a low cost. It can be controlled freely. Therefore, in recent years, organic photoconductive materials are more frequently used than inorganic photoconductive materials.
[0013]
At present, the photoreceptors in practical use have a photosensitive layer formed directly on the conductive support, so that carrier injection from the conductive support is likely to occur and the surface charge disappears microscopically. Decrease and image defects are likely to occur. For the purpose of preventing such image defects and coating defects on the surface of the conductive support, improving the charging property, improving the adhesion of the photosensitive layer and improving the coating property, the conductive support and the photosensitive layer An undercoat layer is provided between the two.
[0014]
On the other hand, electrophotographic copying machines and printers have been improved in functionality for image processing such as maintaining high image quality and image processing, and for combining with copying machines, printers, and facsimiles. . The reversal development method is often used for such high functionality. The reversal development method forms a toner image in the area where the surface charge of the exposed area has decreased. If the surface charge decreases due to factors other than exposure, fogging of the image, called minute black spots (black spots), where the toner adheres to the white background occurs. However, the image quality may be significantly degraded. In order to prevent such image defects, it is necessary to provide an undercoat layer in the reversal development method. That is, by providing an undercoat layer between the conductive support and the photosensitive layer, carrier injection from the conductive support is suppressed, and the occurrence of black spots is suppressed.
[0015]
  As the undercoat layer, various resins and those containing metal oxide particles such as metal particles and titanium oxide powder in various resins have been studied.
The resin that forms the undercoat layer in a single layer includes polyethylene, polypropylene, polystyrene, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyurethane, epoxy resin, polyester, melamine resin, silicon resin, polyvinyl butyral, and polyamide resin. Resins and copolymer resins containing two or more types of repeating units, as well as casein, gelatin, polyvinyl alcohol and ethyl cellulose are known, and among these, polyamide resins are particularly preferred (Japanese Patent Laid-Open No. 48-47344). See the official gazette).
[0016]
However, a photoreceptor using a single layer of polyamide resin as an undercoat layer has a drawback that it has a large amount of accumulated residual potential and causes a decrease in sensitivity. Such a tendency becomes particularly remarkable in a low humidity environment.
[0017]
Therefore, an undercoat layer containing titanium oxide powder has been proposed in order to prevent the occurrence of image defects due to the influence of the conductive support and to reduce the amount of accumulated residual potential (Japanese Patent Laid-Open No. 56-52757). See the official gazette).
However, the above prior art is still insufficient in characteristics as a photoreceptor, and further improvement is desired.
[0018]
In general, the undercoat layer is formed by applying an undercoat layer coating solution on a conductive support. As the resin for the undercoat layer, a resin that does not dissolve in the organic solvent used in the coating solution for the photosensitive layer formed on the undercoat layer or a resin having low solubility is often selected. As a solvent to be used, water or a lower alcohol is generally large.
[0019]
However, since these solvents have a large surface tension and are not well suited to the surface of a metal such as aluminum used as a conductive support, repelling or the like occurs in the undercoat layer, and a uniform undercoat layer is not formed. Problems with image defects occur. In addition, since these solvents have a high boiling point and a low evaporation rate, it is difficult to uniformly apply the undercoat layer, which causes problems such as a decrease in productivity and a high manufacturing cost.
[0020]
On the other hand, in the method of dispersing a metal oxide such as titanium oxide in the undercoat layer, it is important to dissolve the resin while maintaining good affinity between the solvent and the resin or metal oxide surface. The selection becomes very difficult.
[0021]
In order to solve these problems, the use of an organic solvent containing halogen has been proposed, but in recent years, from the viewpoint of environmental problems and the like, the use of an organic solvent containing halogen is in the direction of prohibiting use or reducing the amount of use.
[0022]
[Problems to be solved by the invention]
It is an object of the present invention to provide a photoreceptor undercoat layer coating solution that suppresses carrier injection from a conductive support and suppresses the occurrence of black spots, a method for producing a photoreceptor using the same, and a photoreceptor. To do.
[0023]
[Means for Solving the Problems]
As a result of diligent research to solve the above problems, the present inventors have determined that a specific water-soluble and aprotic organic solvent or a mixed solvent of a water-soluble and aprotic organic solvent and a lower alcohol, a resin and a metal The coating solution for the photoreceptor undercoat layer combined with the oxide has good dispersibility and storage stability, excellent coating properties and film formability, and the coating solution for the photoreceptor undercoat layer The present inventors have found that a photoreceptor having an undercoat layer formed by use has excellent electrophotographic characteristics such as electrical characteristics, and completed the present invention.
[0024]
  Thus, according to the present invention,1 whose weight ratio is 60/40 to 5/95, 3-Dioxolane and a mixed solvent of lower alcohol, a resin and a metal oxide are provided.
[0025]
Further, according to the present invention, the above-mentioned photosensitive subbing layer coating solution is applied onto a conductive support, naturally dried to form an undercoat layer on the conductive support, and then the photosensitive layer coating is applied. There is provided a method for producing a photoconductor, wherein a liquid is applied on the undercoat layer to form a photoconductive layer to obtain a photoconductor.
[0026]
Furthermore, according to the present invention, there is provided a photoreceptor obtained by the above-described method for producing a photoreceptor.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
The organic solvent used in the photoreceptor undercoat layer coating solution of the present invention (hereinafter referred to as “undercoat layer coating solution”) is a water-soluble and aprotic organic solvent or a water-soluble and aprotic organic solvent. It is a mixed solvent with lower alcohol.
[0028]
Examples of the water-soluble and aprotic organic solvent include substituted or unsubstituted formamide and derivatives thereof, substituted or unsubstituted tetrahydrofuran and derivatives thereof, and substituted or unsubstituted dioxolane compounds and derivatives thereof.
[0029]
By using the above water-soluble and aprotic organic solvent as the solvent for the coating solution for the undercoat layer, the affinity between the coating solution for the undercoat layer and the metal surface that is the conductive support is increased. The coatability of the layer coating solution is improved. Among these, cyclic ethers such as substituted or unsubstituted tetrahydrofuran and derivatives thereof, and substituted or unsubstituted dioxolane compounds and derivatives thereof are particularly preferable because they have a high evaporation rate and further improve coatability and productivity.
Among the cyclic ethers, the general formula (I):
[0030]
[Chemical 1]

[0031]
(Wherein R₁~ R₆Is a hydrogen atom or an alkoxy group, an acyl group and / or an alkyl group optionally substituted with a hydroxy group)
Particularly preferred are dioxolanes and derivatives thereof.
Substituent R₁~ R₆Is preferably any one of which is a hydrogen atom, and the substituent R₁~ R₆1,3-dioxolane in which all of is a hydrogen atom is particularly preferred.
[0032]
Substituent R₁~ R₆When the alkyl group has a substituent having a large number of carbon atoms, the boiling point of the dioxolane derivative is increased, and when the boiling point exceeds 100 ° C., the drying time of the subbing layer formed by coating is increased, and the productivity is increased. Not only does this decrease, but drying unevenness is likely to occur depending on the coating environment such as airflow and humidity, which is not preferable.
[0033]
Further, in order to produce an undercoat layer that does not dissolve in the organic solvent used in the coating solution for the photosensitive layer applied on the undercoat layer, the above water-soluble and aprotic organic solvent, particularly cyclic ether, has 1 carbon atom. It is preferable to use a mixture of -4 lower alcohols. Examples of the lower alcohol having 1 to 4 carbon atoms include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, and n-butyl alcohol. Among these, methanol is particularly preferable.
[0034]
By using the above mixed solvent, the solubility of the undercoat layer in the organic solvent used in the photosensitive layer coating solution can be reduced, and dissolution of the undercoat layer can be prevented. In addition, the use of a mixed solvent improves the dispersibility of the metal oxide compared to the water-soluble and aprotic organic solvent alone, and the storage stability (the elapsed time after preparation of the coating solution for the undercoat layer is expressed as “pot life. And a very uniform coating film can be obtained when the undercoat layer is formed. Moreover, since an organic solvent containing halogen is not used, it is possible to provide a coating solution for an undercoat layer having excellent characteristics with less fear of environmental problems and health problems.
[0035]
The mixed solvent of the water-soluble and aprotic organic solvent and the lower alcohol preferably has an azeotropic composition. Here, “azeotropic” is a phenomenon in which the composition of a solution and the composition of a vapor coincide with each other under a constant pressure to form a constant boiling point mixture, and the composition is determined by the combination of mixed solvents. . For example, in the case of tetrahydrofuran and methanol, the ratio of 68.9 parts by weight of tetrahydrofuran and 31.1 parts by weight of methanol is an azeotropic composition ("Chemical Handbook Basic Edition Revised 3rd Edition", Japan Chemical Society, II-151). Page). If the weight ratio of the mixed solvent is an azeotropic composition, uniform evaporation occurs, so that a uniform undercoat layer having no coating film defects can be formed.
[0036]
The weight ratio of the water-soluble and aprotic organic solvent and the mixed solvent of lower alcohol is preferably 60/40 to 5/95, particularly preferably 50/50 to 30/70. This weight ratio is particularly applicable in the case of a mixed solvent of a dioxolane compound (particularly 1,3-dioxolane) and a lower alcohol (particularly methanol).
For example, when the content of 1,3-dioxolane is large in the above weight ratio, the affinity between the metal oxide particles dispersed in the coating liquid for the undercoat layer and the solvent decreases, and the dispersion liquid This is not preferable because the viscosity increases and the storage stability of the coating solution for the undercoat layer deteriorates. Further, when the content of 1,3-dioxolane is small, the effect as a mixed solvent is reduced, the dispersibility of the metal oxide is remarkably lowered, and a uniform undercoat layer cannot be formed. .
[0037]
More specifically, the organic solvent used in the coating solution for the undercoat layer of the present invention includes N, N-dimethylformamide, tetrahydrofuran, 1,3-dioxolane, or a mixed solvent of 1,3-dioxolane and methanol. Is preferred.
[0038]
As the resin (also referred to as “binder resin”) used in the coating solution for the undercoat layer of the present invention, the same resin as in the case of forming the undercoat layer with a single resin layer can be used.
[0039]
Specifically, two resins and repeating units such as polyethylene, polypropylene, polystyrene, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyurethane resin, epoxy resin, polyester resin, melamine resin, silicon resin, butyral resin, and polyamide resin are used. Examples include copolymer resins containing at least species, and casein, gelatin, polyvinyl alcohol, and ethyl cellulose.
[0040]
Among these resins, alcohol-soluble resins are preferable. Specific examples include polyamide resins, butyral resins, and vinyl acetate resins. Among them, polyamide resins and butyral resins are preferable, and polyamide resins are particularly preferable.
[0041]
Said resin satisfies the following characteristic requested | required of resin which comprises the coating liquid for undercoat.
(1) No dissolution or swelling occurs in the solvent of the coating solution for the photoreceptor layer formed on the undercoat layer.
(2) Excellent adhesion to conductive support
(3) Have flexibility
(4) Good affinity with metal oxides
(5) Excellent dispersibility of the metal oxide and storage stability of the dispersion.
[0042]
Examples of the polyamide resin include alcohol-soluble nylon resins such as 6-nylon, 66-nylon, 610-nylon, 11-nylon and 12-nylon, copolymerized nylon obtained by copolymerizing these, N-alkoxymethyl-modified nylon, and N -Chemically modified nylon such as alkoxyethyl modified nylon.
[0043]
Examples of the metal oxide used in the coating solution for the undercoat layer of the present invention include titanium oxide, zirconium oxide, tin oxide, aluminum oxide and zinc oxide. These metal oxides are a mixture of two or more. May be.
[0044]
Among the above metal oxides, titanium oxide is particularly preferable, and the shape thereof may be any of granular, needle-like and dendritic shapes, but the needle-like shape shown in FIG. 3A or the shape shown in FIG. Particularly preferred is a dendritic one.
[0045]
Here, the “needle shape” means an elongated shape including a rod shape, a column shape, a spindle shape, and the like, and does not necessarily have to be extremely elongated, and the tip does not need to be sharp and sharp. The “dendritic shape” means a shape obtained by branching an elongated shape including a rod shape, a column shape, a spindle shape, and the like.
[0046]
With respect to the dimensions of acicular and dendritic titanium oxide, the major axis a is preferably 100 μm or less, the minor axis b is preferably 1 μm or less, the major axis a is 10 μm or less, and the minor axis b is 0. 5 μm or less is more preferable.
When each axial length exceeds the above range, it is not preferable because it is difficult to obtain a coating solution for an undercoat layer excellent in dispersion stability by a surface treatment using a metal oxide or an organic compound as described later.
[0047]
“Needle” generally means that the ratio a / b (aspect ratio) between the major axis “a” and the minor axis “b” is 1.5 or more. The aspect ratio of the acicular titanium oxide in the present invention is preferably in the range of 1.5 to 300, particularly preferably in the range of 2 to 10.
The size of the acicular and dendritic titanium oxide particles can be measured by a known method such as a weight sedimentation method or a light transmission particle size distribution measurement method, but this aspect ratio can be measured by observation with an electron microscope or the like. it can.
[0048]
In the present invention, a mixture of acicular or dendritic titanium oxide and granular titanium oxide particles may be used. Titanium oxide includes anatase-type and rutile-type crystals and amorphous (amorphous), and any of these may be used in the present invention, or a mixture of two or more types may be used.
[0049]
The content of needle-like or dendritic titanium oxide in the titanium oxide contained in the coating solution for the undercoat layer of the present invention (mixing ratio of titanium oxide and the resin contained in the coating solution for the undercoat layer of the present invention) is: The range is 10 to 99% by weight, preferably 30 to 99% by weight, and more preferably 35 to 95% by weight.
[0050]
When the content of needle-like or dendritic titanium oxide is less than 10% by weight, electric charges are accumulated in the undercoat layer, the residual potential increases, and the sensitivity of the photoreceptor decreases, which is not preferable. Such a decrease in sensitivity is particularly noticeable in the repetitive characteristics under low temperature and low humidity. In addition, when the content of needle-like or dendritic titanium oxide exceeds 99% by weight, the storage stability of the coating solution for the undercoat layer deteriorates, and the precipitation of needle-like or dendritic titanium oxide particles occurs. Since it becomes easy, it is not preferable.
[0051]
The volume resistance value of titanium oxide is 10^Five-10^TenΩcm is preferred.
The volume resistance value of titanium oxide is 10^FiveWhen it is less than Ωcm, the resistance value of the undercoat layer is lowered, and the undercoat layer does not function as a charge blocking layer, which is not preferable. For example, the volume resistance value of titanium oxide subjected to conductive treatment using tin oxide doped with antimony is 10⁰-10¹It becomes very low with Ωcm. Such an undercoat layer using titanium oxide does not function as a charge blocking layer, and chargeability as a photoreceptor characteristic deteriorates, so that fog and black spots are generated in an image. The volume resistance value of titanium oxide is 10^TenIf it exceeds Ωcm, the resistance value as the undercoat layer is too high, so that the transport of carriers generated during light irradiation is suppressed or prevented, the residual potential is increased, and the photosensitivity is lowered, which is not preferable. Accordingly, the titanium oxide of the present invention is preferably not subjected to a conductive treatment.
[0052]
The titanium oxide used in the present invention is coated on the surface with zirconium oxide and / or aluminum oxide while maintaining the volume resistance value in the above range, and optionally, a silane coupling agent, a silylating agent, and an aluminum-based coupling. Those whose surface is coated with an organic compound such as an agent and a titanate coupling agent are preferred.
[0053]
In the case of titanium oxide that has not been subjected to surface treatment, since titanium oxide is a fine particle, even if it is a sufficiently dispersed coating solution for the undercoat layer, the titanium oxide is not used during long-term use or storage of the coating solution. Aggregation is inevitable. Such agglomeration causes defects in the coating film of the undercoat layer and coating unevenness, and causes image defects. In addition, in a photoreceptor having an undercoat layer containing titanium oxide that has not been subjected to surface treatment, charge injection from the conductive support is likely to occur, so that the chargeability of a small region is reduced and black spots are generated. become.
[0054]
Therefore, the surface of titanium oxide, especially acicular or dendritic titanium oxide, is coated with a metal oxide such as aluminum oxide and / or zirconium oxide to prevent aggregation of titanium oxide, and is excellent in dispersibility and storage stability. An undercoat layer coating solution is obtained. In addition, in a photoreceptor having an undercoat layer containing titanium oxide that has been subjected to such surface treatment, it is possible to prevent the injection of charges from the conductive support, and thus an excellent image without black spots can be obtained. .
[0055]
As the metal oxide used for the surface treatment, aluminum oxide and / or zirconium oxide are preferable. In view of obtaining a photoreceptor having excellent image characteristics, it is more preferable to perform surface treatment with both aluminum oxide and metal oxides different in zirconium oxide.
[0056]
When silicon oxide is used as the metal oxide, the surface of the treated titanium oxide exhibits hydrophilicity, the compatibility with the organic solvent is deteriorated, and the dispersibility of the titanium oxide is lowered, which easily causes aggregation. In addition, it becomes unsuitable for long-term use of the coating solution.
In addition, iron oxide (Fe₂O_Three) And other magnetic metal oxides, chemically interact with the pigment (eg, phthalocyanine pigment) contained in the photosensitive layer, resulting in a decrease in photoreceptor characteristics, particularly sensitivity and chargeability. Is not preferable.
[0057]
The surface treatment amount of aluminum oxide and / or zirconium oxide with respect to titanium oxide is preferably about 0.1 to 20% by weight.
When the surface treatment amount is less than 0.1% by weight, it is not preferable because the surface of titanium oxide cannot be sufficiently coated and the effect of the surface treatment cannot be obtained sufficiently. Further, it is not preferable to perform the surface treatment exceeding 20% by weight because the processing cost is high and no further effect can be expected.
[0058]
In order to enhance the dispersibility and storage stability of the titanium oxide in the coating solution for the undercoat layer, it is preferable to coat the surface of the titanium oxide whose surface is coated with zirconium oxide and / or aluminum oxide and further with the organic compound.
[0059]
A common coupling agent can be used as the organic compound.
Specific examples include silane coupling agents such as alkoxysilane compounds, silylating agents in which atoms such as halogen, nitrogen, and sulfur are bonded to silicon, aluminum coupling agents, and titanate coupling agents.
[0060]
For example, as a silane coupling agent, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, ethyltrimethoxysilane, diethyldimethoxysilane, phenyltriethoxysilane, aminopropyltrimethoxysilane, γ- (2-aminoethyl) Aminopropylmethyldimethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, 3- (1-aminopropoxy) -3,3-dimethyl-1-propenyltrimethoxysilane, (3-acryloxypropyl) trimethoxysilane, ( 3-acryloxypropyl) methyldimethoxysilane, (3-acryloxypropyl) dimethylmethoxysilane and N-3- (acryloxy-2-hydroxypropyl) -3-aminopropyltriethoxysilane. Alkoxysilane compounds, methyltrichlorosilane, methyldichlorosilane, chlorosilanes such as dimethyldichlorosilane and phenyltrichlorosilane, and silazanes such as hexamethyldisilazane and octamethylcyclotetrasilazane and the like.
[0061]
Examples of other coupling agents include titanate coupling agents such as isopropyl triisostearoyl titanate and bis (dioctylpyrophosphate), and aluminum coupling agents such as acetoalkoxyaluminum diisopropylate.
[0062]
A coupling agent is not limited to said exemplary compound, You may use these coupling agents together. Further, these coupling agents may be added to the undercoat layer coating solution as a dispersant.
[0063]
Methods for surface treatment of titanium oxide are broadly classified into pretreatment methods and integral blend methods, and the pretreatment methods are further classified into wet methods and dry methods.
The wet method is divided into a water treatment method and a solvent treatment method. Examples of the water treatment method include a direct dissolution method, an emulsion method, and an amine adduct method.
[0064]
In the wet method, titanium oxide is added to a solution obtained by dissolving or suspending a surface treatment agent in an organic solvent or water, or a surface treatment agent is added to a suspension obtained by dispersing titanium oxide in an organic solvent or water. The solution is stirred and mixed for several minutes to 1 hour, optionally subjected to heat treatment, and then dried through a process such as filtration.
Surface treatment agents that can be used are limited to those that can be dissolved or suspended in the organic solvent or water used, varieties that dissolve in water in the direct dissolution method, varieties that can be emulsified in water in the emulsion method, and phosphorus in the amine adduct method. A variety having an acid residue is exemplified.
[0065]
In the amine adduct method, a small amount of a tertiary amine such as trialkylamine or trialkylolamine is added to adjust the prepared solution to pH = 7 to 10, and the mixture is cooled to suppress an increase in the liquid temperature due to the neutralization exothermic reaction. It is preferable to carry out the treatment while the other steps can be carried out in the same manner as other wet methods.
[0066]
In the dry method, a surface treatment agent is added directly to titanium oxide, and the mixture is stirred and mixed with a mixer or the like. As a general method, the dry method is performed after removing surface water of titanium oxide by preliminary drying. For example, after adding titanium oxide to a mixer with a large market share such as a halial mixer, rotating at a speed of several tens of rpm and performing preliminary drying at a temperature of about 100 ° C., the surface treatment agent is applied directly or to an organic solvent or water. Add dissolved or dispersed solution. At that time, titanium oxide and the surface treatment agent can be mixed more uniformly by spraying with dry air or nitrogen gas. When adding the surface treating agent, it is preferable to stir for several tens of minutes at a temperature of about 80 ° C. and a rotation speed of 1000 rpm or more.
[0067]
The integral blend method is a method of adding a surface treatment agent when kneading titanium oxide and a resin, and is a method generally used in the field of paints.
[0068]
The amount of the surface treatment agent and the surface treatment agent added as an additive varies depending on the type and form of the metal oxide, but is generally about 0.01 to 30% by weight of titanium oxide, preferably about 0.1 to 20% by weight. It is. When the addition amount of the surface treatment agent is less than 0.01% by weight, the effect of addition is hardly exhibited, which is not preferable. Further, even if the surface treatment agent is added in excess of 30% by weight, a further effect of addition cannot be obtained, which is disadvantageous in terms of cost.
[0069]
Further, when the surface of titanium oxide is treated with a coupling agent, the volume resistance value of titanium oxide is the above-mentioned range both before and after the treatment and when added to an organic solvent as a dispersant. The surface of the titanium oxide may be untreated as long as it is maintained, and may be further coated with a metal oxide of aluminum oxide and / or zirconium oxide.
[0070]
The weight ratio of the water-soluble and aprotic organic solvent or the mixed solvent of the water-soluble and aprotic organic solvent and the lower alcohol and the total amount of the resin and the metal oxide is preferably 3/97 to 20/80.
[0071]
When the solid content in the coating solution, that is, the total amount of the resin and the metal oxide is less than the above range, when forming the undercoat layer of a predetermined film thickness, it is immediately after adhering to the conductive support. Since a large amount of organic solvent evaporates from the coating film until the organic solvent evaporates to dryness, the drying time becomes very long, and drying unevenness occurs when the coating film is dried due to the influence of ambient temperature and humidity. Since it becomes easy to generate | occur | produce, it is not preferable. In addition, when the total amount of the resin and the metal oxide is larger than the above range, the viscosity of the coating solution becomes high, and it becomes impossible to form an undercoat layer having a uniform film thickness on the conductive support, and the coating solution is stored. It is not preferable because stability is deteriorated and viscosity is increased and gelation is likely to occur. On the other hand, if the weight ratio of the solvent and the total amount of the resin and the metal oxide is in the above range, aggregation and settling of the metal oxide dispersed in the coating solution for the undercoat layer is suppressed, and the coating solution It is possible to provide a coating solution having no increase or decrease in viscosity and excellent storage stability.
The viscosity of the undercoat layer coating solution is preferably 1 to 20 mPa · s.
[0072]
The undercoat layer coating solution of the present invention comprises the above water-soluble and aprotic organic solvent, lower alcohol, resin and metal oxide, paint shaker, ball mill, sand mill, attritor, vibration mill, ultrasonic disperser, etc. It is obtained by mixing and dispersing uniformly by a known method using.
[0073]
If the dispersibility of the metal oxide dispersed in the coating solution for the undercoat layer is poor, the viscosity of the coating solution is remarkably lowered due to the occurrence of aggregation and sedimentation of the metal oxide. For this reason, when the undercoat layer is formed on the conductive support by dip coating, the undercoat layer having a predetermined thickness cannot be formed unless the conductive support is pulled up at a very high speed. . Furthermore, since the organic solvent is required to dry for a long time, the undercoat layer is liable to cause coating unevenness, and agglomerates of metal oxides are attached, causing image defects.
[0074]
Further, when the metal oxide is dispersed until it is overdispersed, the metal oxide is pulverized to increase the surface area, the viscosity of the coating solution is increased, and the coating property is remarkably lowered. Further, since the viscosity of the coating solution increases with time and gels, it cannot be used for a long time or stored.
[0075]
In the present invention, the coating solution for the undercoat layer obtained as described above is applied on a conductive support, naturally dried to form an undercoat layer on the conductive support, and then applied to the photosensitive layer. There is provided a method for producing a photoreceptor, wherein a liquid is applied on the undercoat layer to form a photosensitive layer to obtain a photoreceptor.
[0076]
As a means for applying the coating solution for the undercoat layer, a method generally used in this field can be applied, but dip coating is particularly preferable.
FIG. 2 is a schematic diagram of a dip coating apparatus that can be used in the present invention. This apparatus includes a rotating shaft 10 and a motor 11 for moving the conductive support 2 up and down, a coating liquid tank 13 for containing the coating liquid 12 while stirring, a stirring tank 14, a stirring apparatus 15, a motor 16, and a circulation. It consists of a path 17a and a circulation path 17b.
[0077]
As the conductive support, those usually used in this field are used, for example, metal drums and sheets such as aluminum, aluminum alloys, copper, zinc, stainless steel and titanium, polymers such as polyethylene terephthalate, nylon and polystyrene. Examples thereof include drums, sheets, and seamless belts obtained by applying metal foil lamination or metal vapor deposition on the material or hard paper.
[0078]
In the method for producing a photoreceptor of the present invention, when the undercoat layer coating solution is applied by dip coating, the relative humidity at 20 ° C. is 60% RH or less and the wind speed is 1 m / s. It is preferable to carry out with a dip coating apparatus installed in an environment.
[0079]
When a conventional undercoat layer coating solution is applied at high humidity, the undercoat layer coating film may become cloudy due to condensation, and the surface of the undercoat layer may deteriorate significantly, resulting in uneven coating and image defects. It was. This phenomenon occurs when the organic solvent evaporates immediately after the undercoat layer is formed on the conductive support, and the conductive support and the coating film are deprived of heat of vaporization, resulting in a decrease in temperature. However, when the coating solution for the undercoat layer of the present invention is used, it is possible to suppress white turbidity of the coating film without lowering the relative humidity at 20 ° C. to about 20% RH as in the prior art, and the production conditions can be set. It becomes very easy and the manufacturing cost can be reduced.
Further, the wind speed is preferably 1 m / s or less as an environment for installing the dip coating apparatus. When the wind speed is within the above range, a uniform and uniform coating film can be formed.
[0080]
In addition, the undercoat layer coating solution of the present invention has sufficient solubility in the resin of the solvent without aggregation of the metal oxide particles dispersed in the coating solution unlike the conventional undercoat layer coating solution. For this reason, there is no change in the viscosity of the dispersion over time, and the storage stability is excellent.
Therefore, it is not necessary to slow down the lifting speed of the conductive support by increasing the viscosity of the coating solution, so that productivity is improved and the film thickness of the undercoat layer is significantly different in the vertical direction of lifting of the conductive support. Unevenness is suppressed.
[0081]
From the above, in the dip coating of the method for producing the photoreceptor of the present invention, after immersing the conductive support in the coating solution for the undercoat layer, it can be applied at a lifting speed of 0.5 mm / s or more, A uniform undercoat coating film having no change in film thickness distribution in the vertical direction of the conductive support can be obtained.
However, when the lifting speed of the conductive support is less than 0.5 mm / s, productivity is deteriorated, which is not preferable.
[0082]
The thickness of the undercoat layer is preferably in the range of 0.01 to 20 μm, and more preferably in the range of 0.05 to 10 μm. When the thickness of the undercoat layer is less than 0.01 μm, it does not substantially function as the undercoat layer, and the surface of the conductive support cannot be obtained by covering the defects of the conductive support. It is not possible to prevent the carrier from being injected, and the chargeability is lowered. Further, when the thickness of the undercoat layer exceeds 20 μm, the sensitivity of the photoreceptor is lowered, which is not preferable.
[0083]
Thus, the photoreceptor manufactured using the coating solution for the photoreceptor undercoat layer of the present invention has very excellent image characteristics due to its excellent coating properties and stability of the coating solution, and further has high sensitivity. With high durability.
[0084]
After forming the undercoat layer, a photosensitive layer coating solution is applied onto the undercoat layer to form a photosensitive layer. As a means for applying the photosensitive layer, a method generally used in this field can be applied, but dip coating is particularly preferable.
[0085]
As the structure of the photosensitive layer formed on the undercoat layer, there are a functional separation type consisting of two layers of a charge generation layer and a charge transport layer, and a single layer type in which they are formed as a single layer without being separated. Any of these may be used.
FIG. 1 is a schematic cross-sectional view of a function-separated photoreceptor (A) and a single-layer photoreceptor (B) according to an embodiment of the present invention.
[0086]
1A includes a conductive support 2, an undercoat layer 3, and a photosensitive layer 4 composed of a charge generation layer 5 and a charge transport layer 6, and includes a photosensitive layer 4 shown in FIG. 1B. The single-layer type photoreceptor 1 b includes a conductive support 2, an undercoat layer 3, and a photosensitive layer 4.
[0087]
In the case of the function separation type photoreceptor, a charge generation layer is formed on the undercoat layer.
As the charge generation material contained in the charge generation layer, generally known compounds in this field are used. For example, bisazo compounds such as chlorodian blue, polycyclic quinone compounds such as dibromoanthanthrone, and perylene compounds. Quinacridone compounds, phthalocyanine compounds, and azulenium salt compounds.
[0088]
Sensitivity required for a photoreceptor that forms an image by a reversal development process using a light source such as a laser beam or LED is in the range of a long wavelength of 620 to 800 nm. As a charge generation material used in such a case, And phthalocyanine pigments and trisazo pigments which are highly sensitive and excellent in durability. These pigments can be used alone or in combination of two or more. Among them, phthalocyanine pigments are particularly preferable.
[0089]
The photoreceptor of the present invention formed by using the undercoat layer formed using the undercoat layer coating solution of the present invention and a charge generation material (eg, phthalocyanine pigment) having sensitivity to a long wavelength utilizes a reversal development method. When mounted in an image forming apparatus, it exhibits excellent image characteristics with no small black spots (black spots) on a white background peculiar to reversal development due to reduction or disappearance of surface charge in a minute region.
[0090]
Examples of the phthalocyanine pigment include metal-free phthalocyanine and metal phthalocyanine, and mixtures and mixed crystal compounds thereof. Examples of the metal in the metal phthalocyanine pigment include those having an oxidation state of zero, metal halides such as chlorides and bromides thereof, and oxides. Specific examples of preferable metals include Cu, Ni, Mg, Pb, V, Pd, Co, Nb, Al, Sn, Zn, Ca, In, Ga, Fe, Ge, Ti, and Cr.
[0091]
Various methods have been proposed for the production methods of these phthalocyanine pigments, and the production method is not particularly limited, and after the pigmentation, various treatments with various organic solvents are performed in order to convert various types of purification and crystal forms. You may have done it. Examples of the crystal form of the phthalocyanine pigment used in the present invention include α-type, β-type, γ-type, δ-type, ε-type, χ-type and τ-type crystal types, and amorphous types.
[0092]
As a method for producing a charge generation layer using these phthalocyanine pigments, there are a method of forming a charge generation material, particularly a phthalocyanine pigment by vacuum deposition, and a method of forming a film by mixing and dispersing a binder resin and an organic solvent. . Prior to the mixing and dispersing process, a pulverizing process may be performed in advance using a pulverizer such as a ball mill, a sand mill, an attritor, a vibration mill, and an ultrasonic disperser.
[0093]
Examples of the binder resin include melamine resin, epoxy resin, silicone resin, polyurethane resin, acrylic resin, polycarbonate resin, polyarylate resin, phenoxy resin and butyral resin, and copolymer resins containing two or more kinds of repeating units, such as vinyl chloride- Examples thereof include insulating resins such as vinyl acetate copolymer resins and acrylonitrile-styrene copolymer resins.
[0094]
Solvents for dissolving the above resins include halogenated hydrocarbons such as methylene chloride and ethane dichloride, ketones such as acetone, methyl ethyl ketone and cyclohexanone, esters such as ethyl acetate and butyl acetate, tetrahydrofuran and dioxane, and the like. Examples include ethers, aromatic hydrocarbons such as benzene, toluene and xylene, aprotic polar solvents such as N, N-dimethylformamide and N, N-dimethylacetamide, and mixed solvents thereof.
[0095]
The blending ratio of the phthalocyanine pigment and the binder resin is preferably in the range of 10 to 99% by weight of the phthalocyanine pigment. When the phthalocyanine pigment is less than 10% by weight, the sensitivity of the photoreceptor decreases, and when it exceeds 99% by weight, not only the durability of the photoreceptor decreases but also the dispersibility decreases and coarse particles increase. This is not preferable because image defects, particularly black spots, increase.
[0096]
In the charge generation layer coating solution, the charge generation material, binder resin, and solvent are mixed and dispersed uniformly by a known method using a paint shaker, ball mill, sand mill, attritor, vibration mill, ultrasonic disperser, or the like. Can be obtained. Dispersion conditions are selected so that impurities are not mixed in due to wear of containers and dispersion media used.
[0097]
It is important that the charge generation layer coating liquid using a phthalocyanine pigment as a charge generation material is dispersed to primary particles and / or particle diameters of aggregated particles of 3 μm or less. When the primary particles and / or the aggregated particle diameter thereof exceeds 3 μm, when the obtained photoreceptor is used for reversal development, black spots are very generated on a white background. Therefore, when preparing the coating solution for the charge generation layer, the dispersion conditions are optimized by various dispersers, and the phthalocyanine pigment is dispersed to 3 μm or less, more preferably 0.5 μm or less in median diameter and 3 μm or less in mode diameter. .
[0098]
Due to its chemical structure, phthalocyanine pigment particles require relatively strong dispersion conditions and a long dispersion time in order to make fine particles, and it is inevitable to mix impurities due to wear of the dispersion media. The efficiency is also low, which is not preferable. In addition, since the crystal form of the phthalocyanine pigment changes due to heat during dispersion or impact due to dispersion, and the sensitivity of the photoreceptor is greatly reduced, the particle diameter of the phthalocyanine pigment is 0.01 μm or less in median diameter and mode diameter. It is not preferable to make it 0.1 μm or less.
[0099]
Further, when the phthalocyanine pigment having a particle size exceeding 3 μm is contained in the dispersion-generating charge generation layer coating solution, primary particles and / or aggregated particles larger than 3 μm can be removed by performing a filtration treatment. Good. As the filter material used for the filtration treatment, those commonly used are used as long as they do not swell or dissolve in the organic solvent used for dispersion. Preferably, a Teflon membrane filter having a uniform pore size is used. preferable. Further, coarse particles and aggregates may be removed by centrifugation.
[0100]
Examples of the coating method for the charge generation layer coating solution include a spray method, a bar coating method, a roll coating method, a blade method, a ring method, and a dipping method. The dipping method is preferable in terms of productivity and cost.
The dipping method using the dip coating apparatus shown in FIG. 2 is a method of forming a photosensitive layer by immersing a conductive support in a coating tank filled with a coating solution and then pulling it up at a constant rate or a rate that changes sequentially. Since it is relatively simple and excellent in terms of productivity and cost, it is often used in the production of a photoreceptor.
[0101]
The thickness of the charge generation layer is preferably in the range of 0.1 to 10 μm, particularly preferably in the range of 0.2 to 2.0 μm.
When the thickness of the charge generation layer is less than 0.1 μm, the crystal form may change during the dispersion process of the phthalocyanine pigment, which is not preferable because the sensitivity of the photoreceptor is lowered. Further, when the thickness of the charge generation layer exceeds 10 μm, not only uniform coating becomes difficult, but further improvement in sensitivity cannot be expected, which is not preferable in terms of cost.
[0102]
In the case of a function-separated type photoreceptor, after a charge generation layer is formed, a charge transport layer is formed thereon.
As the charge transport material contained in the charge transport layer, generally known compounds in this field are used, for example, hydrazone compounds, pyrazoline compounds, triphenylamine compounds, triphenylmethane compounds, stilbene compounds. And oxadiazole compounds and the like, and these compounds can be used alone or in combination of two or more.
[0103]
The coating liquid for charge transport layer is obtained by mixing a charge transport material and a binder resin in a solvent and dissolving them. Examples of the binder resin and the solvent include those exemplified as the binder resin and the solvent for the charge generation layer coating solution.
[0104]
The charge transport layer can be formed by the same method as the undercoat layer and the charge generation layer. The film thickness is preferably in the range of 5 to 50 μm, and more preferably in the range of 10 to 40 μm.
[0105]
A single-layer photoconductor includes a charge generating material (for example, a phthalocyanine pigment), a charge transport material, a binder resin and a solvent exemplified in the case of a laminated photoconductor, a paint shaker, a ball mill, a sand mill, an attritor, a vibration mill, and It can be prepared by mixing and dispersing by a known method using an ultrasonic disperser to prepare a coating solution for a photosensitive layer, and coating this coating solution on the undercoat layer by a known method.
The film thickness of the photosensitive layer is preferably in the range of 5 to 50 μm, more preferably in the range of 10 to 40 μm.
[0106]
In both cases of a single layer structure and a multilayer structure, the undercoat layer serves as a barrier against carrier (hole) injection from the conductive support. In order to obtain a highly sensitive and highly durable photoconductor, the photosensitive layer is preferably negatively charged.
[0107]
For the purpose of improving the sensitivity of the photoreceptor and reducing the residual potential and fatigue during repeated use, at least one electron accepting material may be added to the photosensitive layer.
Examples of the electron accepting material include quinone compounds such as parabenzoquinone, chloranil, tetrachloro1,2-benzoquinone, hydroquinone, 2,6-dimethylbenzoquinone, methyl 1,4-benzoquinone, α-naphthoquinone, and β-naphthoquinone. 2,4,7-trinitro-9-fluorenone, 1,3,6,8-tetranitrocarbazole, p-nitrobenzophenone, 2,4,5,7-tetranitro-9-fluorenone and 2-nitrofluorenone Nitro compounds, tetracyanoethylene, 7,7,8,8-tetracyanoquinodimethane, 4- (P-nitrobenzoyloxy) -2 ', 2'-dicyanovinylbenzene and 4- (m-nitrobenzoyloxy) Cyano compounds such as -2 ', 2'-dicyanovinylbenzene Can be mentioned. Among these electron accepting materials, quinone compounds, fluorenone, Cl, CN and NO₂Particularly preferred are benzene derivatives having an electron-withdrawing substituent.
[0108]
Further, the photosensitive layer contains ultraviolet absorbers and antioxidants such as benzoic acid, stilbene compounds and derivatives thereof, nitrogen-containing compounds such as triazole compounds, imidazole compounds, oxadiazole compounds, thiazole compounds and derivatives thereof. May be.
[0109]
Furthermore, a protective layer may be provided on the photosensitive layer as necessary to protect the surface of the photosensitive layer.
For the surface protective layer, a thermoplastic resin, a photocurable resin, and a thermosetting resin are used. This protective layer is composed of the above-mentioned inorganic materials such as ultraviolet ray inhibitors, antioxidants, metal oxides, organometallic compounds, and the like. An electron-accepting material may be included.
[0110]
In addition, a plasticizer such as dibasic acid ester, fatty acid ester, phosphoric acid ester, phthalic acid ester, and chlorinated paraffin is mixed in the photosensitive layer and the surface protective layer as necessary to improve workability and flexibility. The mechanical properties may be improved, and a leveling agent such as silicone resin may be added.
[0111]
According to the present invention, there is provided a photoreceptor obtained by the method for producing a photoreceptor. The photoreceptor can be used in an image forming apparatus using a reversal development process, for example, an electrophotographic copying machine, various printers using a laser, an LED, or the like as a light source and an electrophotographic plate making system.
[0112]
【Example】
The present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.
[0113]
  Example 1(Reference example)
  Add 17.1 parts by weight of granular zinc oxide (manufactured by Sakai Chemical, FINEX-50) and 0.9 parts by weight of butyral resin (manufactured by Sekisui Chemical, BX-1) to 82 parts by weight of N, N-dimethylformamide and paint The mixture was dispersed for 12 hours using a shaker to prepare a coating solution for an undercoat layer having a solid content of 18%.
[0114]
The obtained undercoat layer coating solution was placed in a 2 mm thick cell, and the turbidity of the undercoat layer coating solution immediately after preparation was measured using an integrating sphere turbidimeter (manufactured by Mitsubishi Chemical, SEP-PT-501D). And the dispersibility of the coating solution for the undercoat layer was evaluated.
Moreover, after leaving the prepared coating liquid for undercoat layers for 90 days, turbidity was measured similarly to said measurement, and the storage stability of the coating liquid for undercoat layers was evaluated.
The obtained results are shown in Table 1.
[0115]
  (Examples 2 to 8)(Reference example)
  A subbing layer coating solution was prepared in the same manner as in Example 1 except that the following components were used instead of granular zinc oxide as the metal oxide, and the turbidity immediately after preparation and after 90 days was measured. Measured to evaluate the dispersibility and storage stability of the coating solution for the undercoat layer.
  The obtained results are shown in Table 1.
[0116]
Example 2: Granular tin oxide (Mitsubishi Materials, S-1)
Example 3: Granular aluminum oxide (Aluminium Oxide C, manufactured by Nippon Aerosil Co., Ltd.)
Example 4: Untreated granular titanium oxide (Ishihara Sangyo, TTO-55N)
Example 5: Granular titanium oxide surface-treated with aluminum oxide (Ishihara Sangyo, TTO-55A)
[0117]
Example 6: Untreated acicular titanium oxide (manufactured by Sakai Chemical Industry, STR-60N)
Example 7: Needle-like titanium oxide surface-treated with aluminum oxide (STR-60, manufactured by Sakai Chemical)
Example 8: Dendritic titanium oxide surface-treated with aluminum oxide and zirconium oxide (Ishihara Sangyo, TTO-D-1)
[0118]
[Table 1]

[0119]
  Example 9(Reference example)
  As a surface treating agent (coupling agent), 0.02 part by weight of γ- (2-aminoethyl) aminopropylmethyldimethoxysilane was added to 500 parts by weight of n-hexane, and while stirring this mixture, untreated needle-like 20 parts by weight of titanium oxide (manufactured by Sakai Chemical Industry, STR-60N) was added and stirred for 1 hour. Subsequently, this mixture was filtered, and the filtered material was dried by heating at 100 ° C. for 3 hours to obtain acicular titanium oxide surface-treated with a coupling agent.
[0120]
A coating solution for the undercoat layer was prepared in the same manner as in Example 1 except that surface-treated needle-like titanium oxide was used instead of granular zinc oxide as the metal oxide, immediately after preparation and after 90 days. The turbidity was measured, and the dispersibility and storage stability of the coating solution for the undercoat layer were evaluated.
The obtained results are shown in Table 1.
[0121]
  (Examples 10 to 13)(Reference example)
  As in Example 9, except that γ- (2-aminoethyl) aminopropylmethyldimethoxysilane was used as the surface treatment agent (coupling agent), the following components and amounts of surface treatment agent were used. Thus, acicular titanium oxide surface-treated with a coupling agent was obtained.
[0122]
Example 10: 4 parts by weight of γ- (2-aminoethyl) aminopropylmethyldimethoxysilane
Example 11: 0.15 parts by weight of phenyltrichlorosilane
Example 12: 0.15 parts by weight of bis (dioctyl pyrophosphate)
Example 13: 0.15 parts by weight of acetoalkoxyaluminum diisopropylate
[0123]
A coating solution for the undercoat layer was prepared in the same manner as in Example 1 except that surface-treated needle-like titanium oxide was used instead of granular zinc oxide as the metal oxide, immediately after preparation and after 90 days. The turbidity was measured, and the dispersibility and storage stability of the coating solution for the undercoat layer were evaluated.
The obtained results are shown in Table 1.
[0124]
  (Examples 14 to 15)(Reference example)
  Instead of untreated acicular titanium oxide as a metal oxide, acicular and dendritic shapes further surface-treated with a coupling agent in the same manner as in Example 9 except that the following titanium oxides were used. Of titanium oxide was obtained.
[0125]
Example 14: Acicular titanium oxide surface-treated with aluminum oxide (STR-60, manufactured by Sakai Chemical)
Example 15: Dendritic titanium oxide surface-treated with aluminum oxide and zirconium oxide (Ishihara Sangyo: TTO-D-1)
[0126]
An undercoat layer coating solution was prepared in the same manner as in Example 1 except that the surface-treated titanium oxide was used in place of the granular zinc oxide as the metal oxide. Turbidity was measured, and the dispersibility and storage stability of the coating solution for the undercoat layer were evaluated.
The obtained results are shown in Table 1.
[0127]
(Comparative Examples 1-15)
Undercoat layer coating solutions were prepared in the same manner as in Examples 1 to 15 except that methyl alcohol was used in place of N, N-dimethylformamide as the water-soluble / aprotic organic solvent. The turbidity after 90 days was measured, and the dispersibility and storage stability of the coating solution for the undercoat layer were evaluated.
The obtained results are shown in Table 2.
[0128]
[Table 2]

[0129]
From the results of Table 1, the turbidity immediately after preparation in the coating solutions for the undercoat layers of Examples 1 to 15 all show low values, and these coating solutions are highly transparent and excellent in dispersibility. It can be seen that it is. In addition, although the turbidity after 90 days is slightly increased from the turbidity immediately after preparation, no aggregation or sedimentation of metal oxide is observed, and these coating solutions are excellent in storage stability. I know that there is.
[0130]
On the other hand, from the results of Table 2, the turbidity immediately after preparation in the coating solutions for the undercoat layer of Comparative Examples 1 to 15 shows a high value, and these coating solutions are very turbid and inferior in dispersibility. It can be seen that it is. Further, in the coating solution for the undercoat layer of Comparative Examples 4 and 6, aggregation / sedimentation was observed immediately after preparation, and the coating solution for the undercoat layer containing untreated titanium oxide was particularly inferior in dispersibility. I understand. Dispersibility is relatively improved by treating the surface of titanium oxide with a metal oxide such as aluminum oxide or zirconium oxide or a coupling agent. However, in any of the coating solutions for the undercoat layer, gelation or metal oxide agglomeration / precipitation is observed after 90 days, indicating that the storage stability is poor.
[0131]
Therefore, it can be seen that an undercoat layer coating solution having excellent dispersibility and long-term storage stability can be obtained by using a water-soluble and aprotic organic solvent.
[0132]
  (Examples 16 to 18)(Reference example)
  Instead of granular zinc oxide as the metal oxide, dendritic titanium oxide (Ishihara Sangyo: TTO-D-1) surface-treated with aluminum oxide and zirconium oxide was used, and N, N-dimethylformamide was used as the organic solvent. Instead, except that each of the components and the amount of organic solvent shown below was used, a coating solution for an undercoat layer was prepared in the same manner as in Example 1, and the turbidity immediately after preparation and after 90 days was measured. The dispersibility and storage stability of the coating solution for the undercoat layer were evaluated.
  The obtained results are shown in Table 3.
[0133]

[0134]
[Table 3]

[0135]
  (Example 19)(Reference example)
  A subbing layer coating solution was prepared in the same manner as in Example 18 except that a copolymer nylon resin (Toray, CM8000) was used in place of the butyral resin as a resin, and the turbidity immediately after preparation and after 90 days Was measured.
  The obtained results are shown in Table 3.
[0136]
(Examples 20 to 22)
An undercoat layer coating solution was prepared in the same manner as in Example 16 except that the following components and amounts of organic solvent were used in place of tetrahydrofuran as the organic solvent. The degree of dispersion was measured, and the dispersibility and storage stability of the coating solution for the undercoat layer were evaluated.
The obtained results are shown in Table 3.
[0137]

[0138]
(Example 23)
6.3 parts by weight of dendritic titanium oxide (Ishihara Sangyo: TTO-D-1) surface-treated with aluminum oxide and zirconium oxide and 11.7 parts by weight of a copolymer nylon resin (Toray, CM8000), In addition to a mixed solvent of 32.8 parts by weight of 3-dioxolane and 49.2 parts by weight of methyl alcohol, the mixture was dispersed for 12 hours using a paint shaker to prepare a coating solution for an undercoat layer.
The turbidity was measured immediately after the preparation of the obtained coating solution for the undercoat layer and after 90 days, and the dispersibility and the storage stability of the coating solution for the undercoat layer were evaluated.
The obtained results are shown in Table 3.
[0139]
(Example 24)
A coating solution for an undercoat layer having a solid content of 3% in the same manner as in Example 23, except that the amount of 1,3-dioxolane used was 232.8 parts by weight and the amount of methyl alcohol used was 349.2 parts by weight. Was prepared.
The turbidity was measured immediately after the preparation of the obtained coating solution for the undercoat layer and after 90 days, and the dispersibility and the storage stability of the coating solution for the undercoat layer were evaluated.
The obtained results are shown in Table 3.
[0140]
(Example 25)
A coating solution for an undercoat layer having a solid content of 6% in the same manner as in Example 23, except that the amount of 1,3-dioxolane used was 112.8 parts by weight and the amount of methyl alcohol used was 169.2 parts by weight. Was prepared.
The turbidity was measured immediately after the preparation of the obtained coating solution for the undercoat layer and after 90 days, and the dispersibility and the storage stability of the coating solution for the undercoat layer were evaluated.
The obtained results are shown in Table 3.
[0141]
From the results of Table 3, the turbidity immediately after preparation in the coating solutions for the undercoat layers of Examples 16 to 25 all show low values, and these coating solutions are very transparent and excellent in dispersibility. It can be seen that it is. In addition, the turbidity after 90 days did not change much from the turbidity immediately after preparation, and the initial dispersibility was maintained. It can be seen that these coating solutions have excellent storage stability.
Furthermore, compared with the results of Examples 1 to 15 in Table 1, Examples 16 to 25 using a cyclic ether, particularly a dioxolane compound, as the water-soluble and aprotic organic solvent are more dispersible in the coating solution. It can be seen that the storage stability is excellent.
[0142]
(Example 26)
It was 20 mPa * s when the viscosity of the coating liquid for undercoat prepared in Example 22 was measured using the E-type viscosity meter (the Toki Sangyo make, RE-125L).
Using the dip coating apparatus shown in FIG. 2, the coating solution 12 prepared in Example 22 is applied on the conductive support 2 (aluminum, thickness 1 mm (t) × diameter 80 mm (φ) × length 348 mm). Then, the coating layer was naturally dried to form an undercoat layer having a dry film thickness of 1.0 μm. The environment in which the dip coating apparatus is installed when the undercoat layer is dip coated is that the room temperature is 20 ° C., the relative humidity is 60% RH, the wind speed in the clean room is 1.0 m / s, and the lifting speed of the conductive support is 0. It was 5 mm / s.
[0143]
Further, a photosensitive layer composed of a charge generation layer and a charge transport layer was formed on the undercoat layer to obtain a function-separated type photoreceptor shown in FIG. Specifically, 1.5 parts by weight of a bisazo pigment (chlorodian blue) having the chemical structure shown below and 1.5 parts by weight of a phenoxy resin (PKHH manufactured by Union Carbide) are combined with 97 parts by weight of 1,2-dimethoxyethane. In addition, a coating solution for a charge generation layer was prepared by dispersing for 12 hours using a paint shaker.
Using the dip coating apparatus shown in FIG. 2, the charge generation layer coating solution is dip coated on the conductive support on which the undercoat layer is formed, and then the coating layer is dried with hot air at 90 ° C. for 10 minutes to dry. A charge generation layer having a thickness of 1.0 μm was formed.
[0144]
Next, a charge transport layer was formed on the charge generation layer. Specifically, 1 part by weight of a hydrazone compound having the chemical structure shown below and 1 part by weight of a polycarbonate resin (manufactured by Mitsubishi Gas Chemical Co., Ltd., Z-400) are added to 8 parts by weight of tetrahydrofuran, and are stirred and mixed. A transport layer coating solution was prepared.
In the same manner as the charge generation layer, a coating solution for charge transport layer is dip coated on a conductive support on which an undercoat layer and a charge generation layer are sequentially formed, and then the coating layer is dried with hot air at 110 ° C. for 1 hour, A charge transport layer having a dry film thickness of 25.0 μm was formed.
[0145]
The function-separated type photoconductor produced as described above was mounted on a remodeling machine of an image forming apparatus (manufactured by Sharp, SF-8870), and 30,000 printing durability tests were performed.
Evaluation item is dark portion potential V at initial stage and after 30,000 sheets printing.₀(-V) and light potential V_L(−V) as well as image defects.
Table 4 shows the obtained results. Table 4 also shows the coating defects of the undercoat layer.
[0146]
[Table 4]

[0147]
(Comparative Example 16)
Instead of the dendritic titanium oxide contained in the coating solution for the undercoat layer of Example 22, needle-like titanium oxide (Ishihara Sangyo: FTL-1000) subjected to conductive treatment with tin oxide (Sb dope) was used. Then, a functionally separated photoconductor was prepared in the same manner as in Example 26 except that an undercoat layer coating solution was prepared and an undercoat layer was formed, and a printing durability test for 30000 sheets was performed.
Table 4 shows the obtained results.
[0148]
(Comparative Example 17)
When the undercoat layer was formed in Example 26, the solid content of the undercoat layer coating liquid was increased to 25%, and the undercoat layer was formed at a lifting speed of 0.2 mm / s for the conductive support. In the same manner as in Example 26, a function-separated type photoconductor was prepared, and a printing durability test was conducted for 30000 sheets. It was 25 mPa * s when the viscosity of the coating liquid for undercoat layers prepared using the E-type viscosity meter was measured.
Table 4 shows the obtained results.
[0149]
When the film thickness of the formed undercoat layer was measured, there was a difference in film thickness of 0.8 μm between the upper end and the lower end when pulling up the conductive support in dip coating, and the film thickness at the lower end was very thin. It was. In addition, on the surface of the undercoat layer, a number of thin vertical streaks in the same direction as the direction of pulling up the conductive support in the dip coating derived from the solvent of the undercoat layer coating solution were observed.
[0150]
(Comparative Example 18)
When forming the undercoat layer in Example 26, except that the solid content of the coating solution for the undercoat layer was lowered to 2% and the pulling speed of the conductive support was 10.0 mm / s, the undercoat layer was formed. In the same manner as in Example 26, a function-separated type photoconductor was prepared, and a printing durability test was conducted for 30000 sheets. It was 0.8 mPa * s when the viscosity of the coating liquid for undercoat layers prepared using the E-type viscosity meter was measured.
Table 4 shows the obtained results.
[0151]
When the film thickness of the formed undercoat layer was measured, the position at which the film thickness reached a predetermined film thickness was a position 50 mm from the upper end of the conductive support including the coating. From these facts, it can be seen that the undercoat layer coating solution used has very poor adhesion.
[0152]
(Comparative Example 19)
A function-separated type photoconductor was prepared in the same manner as in Example 26 except that the wind speed in the clean room, which is the installation environment of the dip coating apparatus for dip coating the undercoat layer, was set to 30000 sheets. A printing test was conducted.
Table 4 shows the obtained results.
[0153]
White turbidity was observed in a part of the formed undercoat layer. This white turbidity originates from the evaporation of the organic solvent in the coating liquid for the undercoat layer. When the film thickness of the white turbid portion was measured, the film thickness was 0.5 μm thicker than the film thickness of the predetermined undercoat layer. .
[0154]
(Comparative Example 20)
A function-separated type photoconductor was prepared in the same manner as in Example 26 except that the room temperature and the relative humidity, which are the installation environment of the dip coating apparatus for dip coating the undercoat layer, were set to 20 ° C. and 70% RH. A plate life test was performed.
Table 4 shows the obtained results.
[0155]
The formed undercoat layer was observed to be entirely cloudy. When the clouded surface portion was examined with an optical microscope, very small irregularities were observed on the surface of the undercoat layer.
[0156]
From the results of the above comparative examples, the following can be understood.
(1) An image defect in which, when a metal oxide subjected to a conductive treatment is used as the metal oxide of the coating solution for the undercoat layer, the chargeability of the photoreceptor is remarkably lowered and the density of the black solid is lowered. (Comparative Example 16) occurs.
(2) If the conductive support is pulled up slowly when the coating solution for the undercoat layer is dip-coated on the conductive support, uneven coating occurs at the lower end of the conductive support (Comparative Example 17). ).
[0157]
(3) When the viscosity of the coating solution for the undercoat layer is very low, the adhesion of the coating solution for the undercoat layer is deteriorated, an undercoat layer having a desired film thickness cannot be obtained, and image defects occur ( Comparative Example 18).
(4) Depending on the installation environment (indoor wind speed, room temperature, and relative humidity) of the dip coating apparatus that dip coats the undercoat layer, unevenness occurs in the coating film of the undercoat layer, affecting the halftone image (Comparative Example 19 and Comparative Example 20).
[0158]
(Example 27)
Using the dip coating apparatus shown in FIG. 2, the coating solution 12 prepared in Example 25 is placed on the conductive support 2 (made of aluminum, thickness 1 mm (t) × diameter 65 mm (φ) × length 350 mm). Then, the coating layer was naturally dried to form an undercoat layer having a dry film thickness of 1.0 μm. The environment in which the dip coating apparatus is installed when the undercoat layer is dip-coated is that the room temperature is 20 ° C., the relative humidity is 30% RH, the wind speed in the clean room is 0.1 m / s, and the conductive support is pulled up at a speed of 4 0.0 mm / s.
[0159]
Further, a photosensitive layer composed of a charge generation layer and a charge transport layer was formed on the undercoat layer to obtain a function-separated type photoreceptor shown in FIG. Specifically, the components of the following charge generation layer coating solution are dispersed using a ball mill for 12 hours to prepare a charge generation layer coating solution, and the dip coating apparatus shown in FIG. The charge generation layer coating solution was dip coated on the conductive support on which the film was formed, and then the coating layer was dried with hot air at 120 ° C. for 10 minutes to provide a charge generation layer 3 having a dry film thickness of 0.8 μm.
[0160]
(Coating solution for charge generation layer)
τ-type metal-free phthalocyanine
(Toyo Ink Manufacturing, Liphophoton TPA-891) 2 parts by weight
Vinyl chloride-vinyl acetate-maleic acid copolymer resin
(Manufactured by Nissin Chemical Industry, SOLBIN M) 2 parts by weight
100 parts by weight of methyl ethyl ketone
[0161]
Next, a charge transport layer was formed on the charge generation layer. Specifically, the charge transport layer coating solution was prepared by stirring and mixing the following components of the charge transport layer coating solution.
(Coating liquid for charge transport layer)
Hydrazone compound (the following structural formula (1)) 8 parts by weight
Polycarbonate resin (Mitsubishi Gas Chemicals, Z-400) 10 parts by weight
Silicon oil (manufactured by Shin-Etsu Chemical, KF50) 0.002 parts by weight
120 parts by weight of tetrahydrofuran
[0162]
[Chemical 2]

[0163]
In the same manner as the charge generation layer, the charge transport layer coating solution is dip coated on the conductive support on which the undercoat layer and the charge generation layer are sequentially formed, and then the coating layer is dried with hot air at 110 ° C. for 1 hour, A charge transport layer having a dry film thickness of 25 μm was formed.
[0164]
The function-separated type photoconductor produced as described above was mounted on a modified machine of an image forming apparatus (manufactured by Sharp, digital copying machine AR2030), and 30,000 printing durability tests were performed.
The images at the initial stage and after the endurance printing of 30000 sheets had a very good image quality free from image defects due to fine black spots (black spots) on the white background or uneven coating of the undercoat layer.
[0165]
In addition, 30000 printing durability tests were performed in the same manner as above except that the test environment was high temperature and high humidity (room temperature 35 ° C., relative humidity 85% RH) and low temperature and low humidity (room temperature 5 ° C., relative humidity 20% RH). Went.
The initial image and the image after 30,000 sheets were printed had good image quality without image deterioration due to fog, black spots, coating unevenness, etc., without any decrease in sensitivity in any environment.
[0166]
(Example 28)
Example 25 An undercoat layer coating solution was prepared using N-methoxymethylated nylon resin (Teikoku Chemicals, EF-30T) instead of the polyamide resin contained in the undercoat layer coating solution. A function-separated type photoconductor was prepared in the same manner as in Example 26 except that the layer was formed, and a printing durability test for 30000 sheets was performed.
The images at the initial stage and after the endurance printing of 30000 sheets had a very good image quality free from image defects due to fine black spots (black spots) on the white background or uneven coating of the undercoat layer.
[0167]
(Example 29)
Using the dip coating apparatus shown in FIG. 2, an undercoat layer 3 and a photosensitive layer 4 containing a charge generating material and a charge transporting material are sequentially formed on the conductive support 2, and FIG. The single layer type photoreceptor shown was obtained.
[0168]
Specifically, the components of the undercoat layer coating solution described below were dispersed for 10 hours using a paint shaker to prepare an undercoat layer coating solution.
(Undercoat layer coating solution)
Untreated granular titanium oxide (Ishihara Sangyo, TTO-55N) 3 parts by weight
Copolymer nylon resin (Toray, CM8000) 3 parts by weight
50 parts by weight of methyl alcohol
1,3-dioxolane 50 parts by weight
[0169]
The prepared coating solution for the undercoat layer was applied onto a conductive support (made of aluminum, thickness 100 μm (t) × 250 mm × 180 mm) with a baker applicator, and then the coating layer was naturally dried to obtain a dry film thickness of 1. An undercoat layer 2 of 0 μm was formed.
[0170]
Next, a photosensitive layer was formed on the undercoat layer. Specifically, the components of the following photosensitive layer coating solution were dispersed for 12 hours using a ball mill to prepare a charge transport layer coating solution.

[0171]
[Chemical 3]

[0172]
[Formula 4]

[0173]
In the same manner as the undercoat layer, the photosensitive layer coating solution was applied by a baker applicator onto the conductive support on which the undercoat layer was formed, and then the applied layer was dried with hot air at 110 ° C. for 1 hour to obtain a dry film thickness of 20 μm. The photosensitive layer was formed.
[0174]
The single-layer type photoconductor produced as described above is mounted on a remodeling machine of an image forming apparatus (manufactured by Sharp, digital copying machine AR2030), and is 30,000 under conditions of room temperature and normal humidity (20 ° C., relative humidity 50% RH). A plate life test was performed.
The images at the initial stage and after the endurance printing of 30000 sheets had a very good image quality free from image defects due to fine black spots (black spots) on the white background or uneven coating of the undercoat layer.
[0175]
【The invention's effect】
The undercoat layer coating solution of the present invention comprises a water-soluble and aprotic organic solvent or a mixed solvent of a water-soluble and aprotic organic solvent and a lower alcohol, a resin and a metal oxide.
[0176]
The coating solution for the undercoat layer of the present invention contains a metal oxide in a water-soluble and aprotic organic solvent in which a resin is dissolved, so that the dispersibility of the metal oxide becomes very good and the initial dispersibility Can be maintained over a long period of time. In addition, it is possible to avoid the use of a halogen-containing organic solvent due to environmental problems and toxicity problems in recent years.
Therefore, it is possible to provide an undercoat layer coating liquid excellent in safety, which suppresses carrier injection from the conductive support and suppresses the occurrence of black spots.
[0177]
The coating solution for the undercoat layer of the present invention has no sagging or drying unevenness caused by using an organic solvent containing water, lower alcohol and halogen by using a cyclic ether as a water-soluble and aprotic organic solvent. A uniform undercoat layer can be formed, and an undercoat layer coating solution free from environmental problems can be provided.
[0178]
The coating solution for the undercoat layer of the present invention is further excellent in storage stability and coating properties by setting the weight ratio of the water-soluble and aprotic organic solvent and the lower alcohol to 60/40 to 5/95. An undercoat layer coating solution can be provided.
[0179]
The coating solution for the undercoat layer of the present invention is obtained by using N, N-dimethylformamide, tetrahydrofuran, 1,3-dioxolane or a mixed solvent of 1,3-dioxolane and methanol, particularly the above mixed solvent, as a solvent. It is possible to provide a coating solution for an undercoat layer having no environmental and health problems and having excellent coating properties.
[0180]
The coating solution for the undercoat layer of the present invention is well-familiar with the metal oxide and excellent in adhesion to the conductive support by using an alcohol-soluble resin, particularly a polyamide resin and / or a butyral resin as the resin. An undercoat layer coating solution can be provided, and an undercoat layer that can maintain the flexibility of the film can be formed.
In addition, the coating solution for the undercoat layer of the present invention is excellent in preventing the occurrence of coating defects and unevenness in the undercoat layer because it is not swollen by the solvent for the photoreceptor coating solution or dissolved in the solvent for the photoreceptor coating solution. An undercoat layer coating solution capable of producing a photoreceptor having image characteristics can be provided.
[0181]
The coating solution for the undercoat layer according to the present invention uses a titanium oxide, a zirconium oxide, a tin oxide, an aluminum oxide or a zinc oxide, particularly a titanium oxide as a metal oxide, so that a surface charge can be obtained by injecting carriers from a conductive support. Can be prevented from microscopically disappearing or decreasing, and an undercoat layer capable of stably maintaining excellent electrophotographic characteristics under various environments can be formed.
[0182]
The coating solution for the undercoat layer of the present invention uses titanium oxide, particularly acicular and / or dendritic titanium oxide, as the metal oxide, so that the aggregation of titanium oxide is suppressed and the dispersion has excellent dispersibility. A coating liquid for a pulling layer can be provided. A photoreceptor produced using this coating solution for the undercoat layer has excellent chargeability, a low residual potential, little accumulation of residual potential even after repeated use, and little deterioration in photosensitivity. That is, it is possible to provide a photoconductor excellent in repetitive stability and environmental characteristics.
[0183]
The coating solution for the undercoat layer of the present invention can be optionally coated with a silane coupling agent, a silylating agent, and an aluminum-based coupling by coating the surface of titanium oxide as a metal oxide with aluminum oxide and / or zirconium oxide. By coating with an agent or a titanate coupling agent, it is possible to provide an undercoat layer coating solution having excellent dispersibility and storage stability even when titanium oxide is dispersed in a resin at a high content. Therefore, it is possible to prevent image defects resulting from defects in the conductive support, to obtain a uniform coating film when forming the photosensitive layer, and to produce a photoreceptor having good image quality characteristics.
The effective coating amount (surface treatment amount) of the above metal oxide or organic compound is 20% by weight or less with respect to titanium oxide.
[0184]
The coating solution for the undercoat layer according to the present invention increases the chance of contact between particles without conducting a conductive treatment on the surface of a metal oxide (for example, titanium oxide), so that acicular and / or dendritic oxidation is performed. Even if the content of titanium is small, it is possible to produce a photoreceptor having excellent chargeability without deteriorating the photoreceptor characteristics, particularly sensitivity and residual potential.
That is, if the titanium oxide particles are needle-like or dendritic, the particles are elongated, and when the undercoat layer is formed, the titanium oxide particles are easy to contact with each other, and the contact area increases. Even when the content of titanium oxide particles in the undercoat layer is decreased, an undercoat layer having the same performance can be easily produced as compared with the case of using the above. The ability to reduce the content of titanium oxide particles is useful for improving the film strength of the undercoat layer and the adhesion to the conductive support. In addition, since the contact between the titanium oxide particles is strong, the electrophotographic photosensitive member having excellent stability can be obtained without deterioration of electrical characteristics and image characteristics even after repeated use over a long period of time.
[0185]
Further, when the content of titanium oxide particles is the same, the resistance value of the undercoat layer is lower when the needle-like or dendritic titanium oxide particles are used than the granular form, and the thickness of the undercoat layer is increased. be able to. For this reason, surface defects of the conductive support do not appear on the surface of the undercoat layer, which is advantageous in obtaining a smooth surface of the undercoat layer.
[0186]
The coating solution for the undercoat layer of the present invention has a weight ratio of a water-soluble and aprotic organic solvent or a mixed solvent of a water-soluble and aprotic organic solvent and a lower alcohol and the total amount of resin and metal oxide. By setting the ratio to 3/97 to 20/80, aggregation and sedimentation of the metal oxide dispersed in the coating solution for the undercoat layer is suppressed, and there is no increase or decrease in the viscosity of the coating solution, and coating properties and storage stability. It is possible to provide a coating solution for an undercoat layer excellent in the above.
This suppresses drying unevenness due to evaporation of the organic solvent that occurs in the drying process after the formation (application) of the undercoat layer, and suppresses thickening and gelation of the coating liquid, thereby improving coating properties.
[0187]
In the method for producing a photoreceptor of the present invention, the above undercoat layer coating solution is applied onto a conductive support, naturally dried to form an undercoat layer on the conductive support, and then applied to the photosensitive layer. A liquid is applied onto the undercoat layer to form a photosensitive layer to obtain a photoreceptor.
[0188]
Therefore, it is possible to provide a method for producing a photoconductor having a photoconductor undercoat layer that suppresses carrier injection from the conductive support and suppresses the occurrence of black spots.
Since the coating solution for the undercoat layer of the present invention is excellent in dispersibility and storage stability, a uniform coating film free from coating defects can be easily formed, and a photoreceptor having excellent image characteristics free from image defects is manufactured. can do.
[0189]
In the method for producing a photoreceptor according to the present invention, the coating solution for the undercoat layer is applied by dip coating, and the installation environment of the dip coating device is such that the relative humidity at 20 ° C. is 60% RH or less and the wind speed is 1 m / s or less. As a result, a photoreceptor having further excellent image characteristics can be produced. In addition, it is possible to provide a method for producing a photoconductor having excellent coating properties and productivity without causing a decrease in productivity due to a decrease in coating speed, and having excellent image characteristics free from coating unevenness and coating defects.
Without maintaining air around the coating device such as a dip coating device, it circulates in the clean room with a constant air flow, removing dust that causes coating defects, and subtracting it onto the conductive support. A layer can be formed.
[0190]
The photoreceptor of the present invention is obtained by the above-described method for producing a photoreceptor, and has a photoreceptor undercoat layer that suppresses carrier injection from the conductive support and suppresses black spots.
[0191]
Therefore, it has excellent chargeability, a low residual potential, little accumulation of residual potential even after repeated use, and little deterioration in photosensitivity. That is, it is possible to provide a photoconductor excellent in repetitive stability and environmental characteristics.
[0192]
The photoreceptor of the present invention is suitably used for an image forming apparatus using a reversal development process, for example, a composite model with image processing, a FAX, a printer, and the like.
Even when used in such an image forming apparatus, a remarkable image defect due to a decrease in chargeability in a minute region derived from a defect in the conductive support or the photosensitive layer is unlikely to occur.
[0193]
In particular, the photoreceptor of the present invention is inverted by using a semiconductor laser or LED having a light source at a long wavelength by using an organic pigment (for example, a phthalocyanine pigment) having a light sensitivity at a long wavelength as a charge generation material of the photosensitive layer. It is preferably used when an image is formed on a developing system image forming apparatus using a reversal development process.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a function-separated electrophotographic photoreceptor (A) and a single-layer electrophotographic photoreceptor (B) according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of a dip coating apparatus that can be used in the present invention.
FIG. 3 is a schematic view showing the shape of titanium oxide used as a metal oxide in the present invention.
[Explanation of symbols]
1a Function-separated electrophotographic photosensitive member
1b Single-layer type electrophotographic photosensitive member
2 Conductive support
3 Underlayer
4 Photosensitive layer
5 Charge generation layer
6 Charge transport layer
10 Rotating shaft
11 Motor
12 Coating liquid
13 Coating solution tank
14 Mixing tank
15 Stirrer
16 motor
17a Circulation route
17b Circulation route
a Long axis
b Short axis

Claims (11)

A coating solution for an undercoat layer of an electrophotographic photoreceptor, comprising a mixed solvent of 1,3 -dioxolane and lower alcohol having a weight ratio of 60/40 to 5/95, a resin and a metal oxide. The coating solution for an undercoat layer of an electrophotographic photosensitive member according to claim 1, wherein the resin is an alcohol-soluble resin. The coating solution for an undercoat layer of an electrophotographic photosensitive member according to claim 2 , wherein the alcohol-soluble resin is a polyamide resin and / or a butyral resin. The coating liquid for an undercoat layer for an electrophotographic photosensitive member according to any one of claims 1 to 3 , wherein the metal oxide is titanium oxide, zirconium oxide, tin oxide, aluminum oxide, or zinc oxide. The coating solution for an undercoat layer for an electrophotographic photosensitive member according to any one of claims 1 to 4 , wherein the metal oxide is titanium oxide. Titanium oxide, is a surface coated with a zirconium oxide and / or aluminum oxide, optionally further silane coupling agent, a silylating agent, claims are covered the surface with aluminum coupling agent or a titanate coupling agent 4 Or a coating solution for an undercoat layer of an electrophotographic photosensitive member according to 5 . 1, a mixed solvent of lower alcohol and 3-dioxolane, the weight ratio of the total amount of resin and metal oxide according to any one of claims 1 to 6 is a 3 / 97-20 / 80 Coating liquid for undercoat layer of electrophotographic photoreceptor. The electrophotographic photoreceptor undercoat layer coating solution according to any one of claims 1 to 7 is applied onto a conductive support, and is naturally dried to form an undercoat layer on the conductive support. Then, a photosensitive layer coating solution is applied on the undercoat layer to form a photosensitive layer to obtain an electrophotographic photosensitive member. The coating solution for the undercoat layer of the electrophotographic photosensitive member is applied by dip coating, and is immersed in an environment where the relative humidity at 20 ° C. is 60% RH or less and the wind speed is 1 m / s or less. The method for producing an electrophotographic photosensitive member according to claim 8 , wherein the method is performed by a coating apparatus. The electrophotographic photosensitive member obtained by the production method of the electrophotographic photosensitive member according to claim 8 or 9. The electrophotographic photosensitive member according to claim 10 , which is used in an image forming apparatus using a reversal development process.

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