JP2004062169A - Seamless belt and method for manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a seamless belt which makes high-quality transferred images obtainable because of its high modulus of elasticity and small bending hardness even when the belt is used for an intermediate transfer member of an image forming apparatus of a tandem intermediate transfer type and a method for manufacturing the same, and the image forming apparatus provided with such seamless belt. <P>SOLUTION: The seamless belt is characterized by ≥5,000 MPa in tensile modulus of elasticity in a circumferential direction measured pursuant to JIS (Japanese Industrial Standards) K 7127 and ≤1.5 g/mm in bending hardness per 10 mm in width when one end thereof is fixed and a vertical load is applied to a position of 10 mm on the other end side. <P>COPYRIGHT: (C)2004,JPO

Description

（一般式（１）中、Ｒは４価の有機基であり、芳香族、脂肪族、環状脂肪族、芳香族と脂肪族を組み合わせたもの、またはそれらの置換された基である。）
テトラカルボン酸二無水物として具体的には、ピロメリット酸二無水物、３，３’，４，４’−ベンゾフェノンテトラカルボン酸二無水物、３，３’，４，４’−ビフェニルテトラカルボン酸二無水物、２，３，３’，４−ビフェニルテトラカルボン酸二無水物、２，３，６，７−ナフタレンテトラカルボン酸二無水物、１，２，５，６−ナフタレンテトラカルボン酸二無水物、１，４，５，８−ナフタレンテトラカルボン酸二無水物、２，２’−ビス（３，４−ジカルボキシフェニル）スルホン酸二無水物、ペリレン−３，４，９，１０−テトラカルボン酸二無水物、ビス（３，４−ジカルボキシフェニル）エーテル二無水物、エチレンテトラカルボン酸二無水物等が挙げられる。特に、高弾性率のポリイミドを作成するために３，３’，４，４’−ビフェニルテトラカルボン酸二無水物を用いる事が好ましい。
【００２３】
一方、ジアミンの具体例としては、４，４’−ジアミノジフェニルエーテル、４，４’−ジアミノジフェニルメタン、３，３’−ジアミノジフェニルメタン、３，３’−ジクロロベンジジン、４，４’−ジアミノジフェニルスルフイド、３，３’−ジアミノジフェニルスルフォン、１，５−ジアミノナフタレン、ｍ−フェニレンジアミン、ｐ−フェニレンジアミン、３，３’−ジメチル−４，４’−ビフェニルジアミン、ベンジジン、３，３’−ジメチルベンジジン、３，３’−ジメトキシベンジジン、４，４’−ジアミノジフェニルスルフオン、４，４’−ジアミノジフェニルプロパン、２，４−ビス（β−アミノ第三ブチル）トルエン、ビス（ｐ−β−アミノ−第三ブチルフェニル）エーテル、ビス（ｐ−β−メチル−δ−アミノフェニル）ベンゼン、ビス−ｐ−（１，１−ジメチル−５−アミノ−ベンチル）ベンゼン、１−イソプロピル−２，４−ｍ−フェニレンジアミン、ｍ−キシリレンジアミン、ｐ−キシリレンジアミン、ジ（ｐ−アミノシクロヘキシル）メタン、ヘキサメチレンジアミン、ヘプタメチレンジアミン、オクタメチレンジアミン、ノナメチレンジアミン、デカメチレンジアミン、ジアミノプロピルテトラメチレン、３−メチルへプタメチレンジアミン、４，４−ジメチルヘプタメチレンジアミン、２，１１−ジアミノドデカン、１，２−ビス−３−アミノプロポキシエタン、２，２−ジメチルプロピレンジアミン、３−メトキシヘキサメチレンジアミン、２，５−ジメチルヘプタメチレンジアミン、３−メチルへプタメチレンジアミン、５−メチルノナメチレンジアミン、２，１７−ジアミノエイコサデカン、１，４−ジアミノシクロヘキサン、１，１０−ジアミノ−１，１０−ジメチルデカン、１２−ジアミノオクタデカン、２，２−ビス〔４−（４−アミノフェノキシ）フェニル〕プロパン、ピペラジン、Ｈ_２　Ｎ（ＣＨ_２　）_３　Ｏ（ＣＨ_２　）_２　Ｏ（ＣＨ_２　）ＮＨ_２　、Ｈ_２　Ｎ（ＣＨ_２　）_３　Ｓ（ＣＨ_２　）_３　ＮＨ_２　、Ｈ_２　Ｎ（ＣＨ_２　）_３　Ｎ（ＣＨ_３　）_２　（ＣＨ_２　）_３　ＮＨ_２　等が挙げられる。
【００２４】
テトラカルボン酸二無水物とジアミンを重合反応させる際の溶媒としては、溶解性等の点より極性溶媒が好適に挙げられる。極性溶媒としては、Ｎ，Ｎ−ジアルキルアミド類が好ましく、具体的には、例えば、これの低分子量のものであるＮ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジメチルアセトアミド、Ｎ，Ｎ−ジエチルホルムアミド、Ｎ，Ｎ−ジエチルアセトアミド、Ｎ，Ｎ−ジメチルメトキシアセトアミド、ジメチルスルホキシド、ヘキサメチルホスホルトリアミド、Ｎ−メチル−２−ピロリドン、ピリジン、テトラメチレンスルホン、ジメチルテトラメチレンスルホン等が挙げられる。これらは単数または複数併用することができる。
【００２５】
ポリアミド酸を得る際のモノマー濃度は、５〜３０重量％が好ましい。また、反応温度は８０℃以下に設定することが好ましく、特に好ましくは５〜５０℃であり、反応時間は約０．５〜１０時間が好ましい。
【００２６】
本発明のシームレスベルトは、半導電性を得るために樹脂中に各種導電材料を添加するのが好ましい。その場合、表面抵抗率が１０^８　〜１０^１４Ω／□の範囲であるのが好ましい。具体的には、カーボンブラック、アルミニウム、ニッケル、酸化錫、チタン酸カリウム等の無機化合物やポリアニリンやポリピロールなどに代表される導電性高分子を用いることができる。特に、抵抗制御や抵抗低下の観点からカーボンブラックを用いることが望ましく、特に酸化処理されたカーボンブラックを用いることが更に望ましい。
【００２７】
酸化処理カーボンブラックは、カーボンブラックを酸化処理することで、表面に酸素含有官能基（例えば、カルボキシル基、キノン基、ラクトン基、水酸基等）を付与して得ることができるものである。この酸化処理は、高温雰囲気下で、空気と接触、反応させる空気酸化法、常温下で窒素酸化物やオゾン等と反応させる方法、及び高温下での空気酸化後、低温下でオゾン酸化する方法等により行うことができる。このようにして得られる酸化処理カーボンブラックは、一部に過剰な電流が流れ、繰返しの電圧印加による酸化の影響を受けにくく、さらに、その表面に付着する酸素含有官能基の効果で、ポリイミド中への分散性が高く、抵抗バラツキを小さくすることができるとともに、電界依存性も小さくなり、転写電圧による電界集中が起き難くなる。その結果、転写電圧による抵抗低下を防止し、電気抵抗の均一性を改善し、電界依存性が少なく、さらに環境による抵抗の変化の少ない、用紙走行部が白く抜けること等の画質欠陥の発生が抑制された高画質を得ることができる中間転写体となる。
【００２８】
これら酸化処理カーボンブラックの含有量は、ポリイミド樹脂に対して１０〜５０重量％程度が好ましく、より好ましくは１２〜３０重量％である。この含有量が１０重量％未満であると、電気抵抗の均一性が低下し、耐久使用時の表面抵抗率の低下が大きくなる場合があり、一方、５０重量％を超えると、所望の抵抗値が得られ難く、また、成型物として脆くなるため好ましくない。
【００２９】
本発明のシームレスベルトは、少なくとも、溶媒にポリアミド酸が溶解した原料液を円筒状金型内面に展開する工程、前記溶媒を蒸発させる工程、及びポリアミド酸のイミド転化を行う工程を経ることで得ることができる。このとき、原料液に導電剤を分散させることで、半導電性のシームレスベルトを得ることができる。
【００３０】
導電剤を分散させたポリアミド酸溶液の製造方法については、溶媒中に導電剤を予め分散した分散液中に上記酸二無水物成分及びジアミン成分を溶解・重合する方法、導電剤を溶媒中に分散させた分散液とポリアミド酸溶液を混合する方法、ポリアミド酸溶液に導電剤を分散させる方法等が考えられ、適宜選択して導電剤を分散したポリアミド酸溶液を作製する。
【００３１】
本発明のシームレスベルトは、このようにして得られたポリアミド酸溶液を円筒状金型内面に供給・展開し被膜とし、加熱によりポリアミド酸をイミド転化させることにより得られる。以下詳細に説明する。
【００３２】
本発明では、前記ポリアミド酸溶液を円筒状金型内面に供給する。この供給方法は、ディスペンサーによる方法、ダイスによる方法等適宜選択して行うことができる。
【００３３】
この時用いる円筒金型の内周面の表面状態は、本発明では鏡面仕上げしたものが好ましい。また、金型内周面に離型処理を施すこともできる。このようにして供給したポリアミド酸溶液を、加熱しながら遠心成形する方法、弾丸状走行体を用いて成形する方法、回転成形する方法等適宜選択して均一な膜厚の被膜を形成する。続いて内周面に被膜を形成した金型ごと乾燥機中で加温を行ない、イミド転化まで昇温する方法、もしくはベルトとして形状を保持できるまで溶媒の除去を行った後、金型内面から剥離し金属製シリンダ外面に差し替えた後、該シリンダごと加熱してイミド転化を行う方法等が考えられる。好適な引張弾性率のシームレスベルトを得るためには、後者の方法が望ましい。
【００３４】
また、好適な曲げ硬さのシームレスベルトを得るためには、初期のポリアミド酸溶液中に含まれる溶媒の乾燥をイミド化が開始する温度以下（具体的には、ポリアミド酸溶液の温度が６０〜１３０℃で０．１〜２時間）で少なくとも６０％以上を蒸発させる事が望ましい。更に好ましくは７０％以上であることが望ましい。即ち、本発明の製造方法は、加熱温度１３０℃以下の条件で前記溶媒を６０％以上を蒸発させることを特徴とする。これとは逆に、初期の溶媒蒸発率が低い状態で、更に溶媒の除去を行うために短時間で高温に昇温すると、フィルムが硬くなるばかりでなく脆くなる。
【００３５】
次にベルトとして保持できるまで溶媒の除去を行うために初期乾燥温度より高い温度（具体的には１５０〜３００℃範囲で行う）で乾燥を行ないベルトとして保持できる温度まで溶媒の除去を行う。その後、金属製シリンダに差し替えてイミド転化を行う方法が好ましい。この時用いる金属製シリンダは、線膨張係数がポリイミド樹脂よりも大きいものが好ましく、シリンダの外径をポリイミド成形物の内径より所定量小さくすることで、ヒートセットを行うことができ、均一な膜厚でムラのない無端ベルトを得ることができる。この時用いる金属製シリンダ外面の表面粗度（Ｒａ）は、１．２〜２．０μｍであるのが好ましい。金属製シリンダ外面の表面粗度（Ｒａ）が１．２μｍより小さいと、金属製シリンダ自身が平滑過ぎるために得られるシームレスベルトがベルトの軸方向に対する収縮による滑りが発生しないため、延伸がこの工程で行われ、これにより膜厚のバラツキや平面度の精度の低下が発生する。また、金属製シリンダ外面の表面粗度（Ｒａ）が２．０μｍより大きいと金属製シリンダ外面がシームレスベルトの内面に転写し、さらには外面に凹凸を発生させ、これにより画像不良を発生させる。このようにして得られたポリイミド樹脂から成るシームレスベルトの外面の表面粗さ（Ｒａ）は、１．５μｍ以下である。本発明における表面粗度はＪＩＳ　Ｂ　６０１に準じ測定したものである。シームレスベルト外面の表面粗度（Ｒａ）が１．５μｍより大きいと白抜け等の画像欠陥が発生する。この理由としては転写の際に印加する電圧や剥離放電による電界が、ベルト表面の凸部に集中することにより、この部分の表面が変質して、新しい導電経路ができて抵抗が低下することが考えられる。
【００３６】
本発明のシームレスベルトの厚さは、フィルム幅１０ｍｍ当りの曲げ硬さが１．５ｇ／ｍｍ以下であれば特に限定されるものではないが、２０〜８５μｍ程度が好ましく、特に好ましくは４０〜７５μｍである。フィルム厚みが２０μｍ未満であるとフィルム強度が弱く耐久性の問題が生じる。一方、フィルムの厚みが厚くなるとフィルムの曲げ硬さが硬くなり過ぎる。
【００３７】
このようなシームレスベルトは、引張弾性率及び曲げ硬さが良好であるため、タンデム式画像形成装置に好適に用いることができる。タンデム式画像形成装置は、従来から知られている転写ドラム方式や中間転写方式のように、各色毎に潜像形成・現像・転写・除電・クリーニングを繰り返すことがなく、複数の像担持体が直列に配置したものであるため、格段に画像形成速度が向上するというメリットがある。この時、本発明のシームレスベルトを用いると、その引張弾性率及び曲げ硬さが良好であるため、良好な画像を得ることができる。
【００３８】
（画像形成装置）
本発明の画像形成装置は、前記本発明のシームレスベルトを中間転写体として備えている。本発明の画像形成装置は、像担持体に形成したトナー像が一時的に転写される中間転写体を有するもので有ればよく、白黒画像、カラー画像、フルカラー画像など、何れの画像を形成する装置でもよい。但し、各色毎の現像器を備えた複数の像担持体を中間転写体に沿って直列に配置したタンデム式カラー画像形成装置である場合が好ましい。
【００３９】
タンデム式カラー画像形成装置は、例えば図２に示すように、４色（ブラック、イエロー、マゼンタ、シアン）の現像器１５を備えた各色毎の感光体９が中間転写体１６に沿って直列に配置している。本発明の中間転写体を備えることで、高画質の転写画像を得ることができる。
【００４０】
具体的には、感光体９表面を均一に帯電する帯電装置１３、感光体９表面を露光し静電潜像を形成する露光装置８、感光体９表面に形成された潜像を現像剤を用いて現像し、トナー像を形成する現像装置１５、感光体に付着したトナーやゴミ等を除去するクリーニング装置１４、被転写材上のトナー像を定着する定着する装置２等、必要に応じて公知の方法で任意に備えることができる。
【００４１】
感光体９としては、従来未知のものを用いることができ、感光体９は通常、導電性基体の上に感光層を有している。その感光体層としては、有機系、アモルファスシリコン等公知のものを用いることができる。前記感光体９が円筒状の場合は、導電性基体はアルミニウム又はアルミニウム含金を押出し成型後、表面加工する等の公知の製法により得られる。またベルト状の感光体を用いることも可能である。
【００４２】
帯電手段１３としては、特に制限はなく、例えば、導電性又は半導電性のローラ、ブラシ、フィルム、ゴムブレード等を用いた接触型帯電器、コロナ放電を利用したスコロトロン帯電器やコロトロン帯電器などのそれ自体公知の帯電器が挙げられる。これらの中でも、帯電補償能力に優れる点で接触型帯電器が好ましい。前記帯電手段は、前記電子写真感光体に対し、通常、直流電流を印加するが、交流電流をさらに重畳させてもよい。
【００４３】
露光装置８としては、特に制限はなく、例えば、前記電子写真感光体表面に、半導体レーザ光、ＬＥＤ光、液晶シャッタ光等の光源、或いはこれらの光源からポリゴンミラーを介して所望の像様に露光できる光学系器機等が挙げられる。
【００４４】
現像装置１５としては、目的に応じて適宣選択することができるが、例えば、一成分系現像剤又は二成分系現像剤をブラシ、ローラ等を用い接触或いは非接触させて現像する公知の現像器機等が挙げられる。
【００４５】
第一転写手段１０としては、例えば、ベルト、ローラ、フィルム、ゴムブレードを等を用いた接触型転写帯電器、コロナ放電を利用したスコロトロン転写帯電器やコロトロン転写帯電器などのそれ自体公知の転写帯電器が挙げられる。これらの中でも、転写帯電補償能力に優れる点で接触型転写帯電器が好ましい。なお、本発明においては、前記転写帯電器の他、剥離帯電器等を併用することもできる。
【００４６】
第二転写手段５としては、前記第一転写手段１０として例示した転写ローラ等の接触型転写帯電器、スコロトロン転写帯電器やコロトロン転写帯電器が挙げられる。これらの中でも、前記第一転写手段と同様に接触型転写帯電器が好ましい。転写ローラ等の接触型転写帯電器により強く押圧するようにすると、画像の転写状態を良好な状態に維持させることができる。また、中間転写体を案内するローラの位置で転写ローラ等の接触型転写帯電器を押圧すると、中間転写体から被転写体に対してトナー像を移転させる作用を良好な状態で行うことが可能になる。
【００４７】
転写後の感光体表面に残留する電位を除電することが必要な場合に使用する光除電手段としては、例えば、タングステンランプ、ＬＥＤ等が挙げられ、該光除電プロセスに用いる光質としては、例えば、タングステンランプ等の白色光、ＬＥＤ光等の赤色光等が挙げられる。該光除電プロセスにおける照射光強度としては、通常、電子写真感光体の半減露光感度を示す光量の数倍から３０倍程度になるよう出力設定される。
【００４８】
感光体９のクリーニング装置１４としては、特に制限はなく、それ自体公知のクリーニング装置等を用いればよい。また、中間転写体１６に対する転写クリーナー１２としては、特に制限はなく、それ自体公知のクリーニング装置等を用いればよい。
【００４９】
定着装置２としては、特に制限はなく、それ自体公知の定着器、例えばローラ定着器、ベルト式定着器、オーブン定着器等が挙げられる。
【００５０】
【実施例】
以下、本発明の構成と効果を具体的に示す実施例等について説明する。なお、実施例等における評価項目は下記のようにして測定を行った。
【００５１】
１．引張弾性率
ＪＩＳ　Ｋ　７１２７に準じて測定を行った。試験片は、ＪＩＳ　Ｋ　６３０１（３号ダンベル）を用いた。
【００５２】
２．曲げ硬さ
試験片は、周方向に５０ｍｍ・幅方向に１０ｍｍの大きさとした。試料台に先端を２０ｍｍ出して試験片を固定した。試験装置は、カトーテック株式会社製ハンディ圧縮試験機ＫＥＳ−Ｇ５を使用した。この試験片の先端から１０ｍｍの位置に先端径φｌｍｍの芯を速度０．１ｍｍ／ｓｅｃの速度で押し込みそのときの荷重をロードセルで読み取った（図１参照）。曲げ硬さは、この時の押し込み量と押し込み荷重の傾きから単位押し込み量当りの押し込み荷重を曲げ硬さとした。
【００５３】
３．ベルトの厚み
ベルトの周方向１０点、幅方向５点の計５０点を測定しその平均値を求めた。
【００５４】
４．表面抵抗率
半導電性ベルトの２４点（周方向８点、幅方向３点）の表面について、ハイレスタＵＰ、ＭＣＰ−ＨＴＰ１６（三菱化学社製、プローブ：ＵＲ−１００）にて印加電圧１００Ｖ、１０秒後、測定条件２５℃、６０％ＲＨでの表面抵抗率を調べ、その表面抵抗率を常用対数値にて示した。
【００５５】
５．溶媒の蒸発率
塗布した原料液の重量と、乾燥後の塗膜重量の差から蒸発量を計算し、これを塗布した原料液中の溶媒量で除して百分率で求めた。
【００５６】
実施例１
Ｎ−メチル−２−ピロリドン（ＮＭＰ）３８９ｇ中に、カーボンブラック（ＳＰＥＣＩＡＬ　ＢＬＡＣＫ４、デグサ社製）２３ｇを添加し、ボールミルで８時間攪拌してカーボンブラック分散ＮＭＰ液を得た。このカーボンブラック分散ＮＭＰ液に３，３’，４，４’−ビフェニルテトラカルボン酸二無水物６５ｇと、ｐ−フェニレンジアミン２４ｇ（等モル数）を溶解し、窒素雰囲気下において室温で５時間攪拌しながら反応させた後、粘度調整を行い、カーボンブラックを分散したポリアミド酸溶液（固形分２０重量％、２３℃におけるＢ型粘度計による溶液粘度２００Ｐａ・ｓ）を得た。
【００５７】
このポリアミド酸溶液４２０ｇを円筒状金型（内径３００ｍｍ、長さ８００ｍｍ）の内面にディスペンサーによりスパイラル状に供給した。次に１５００ｒｐｍで１０分間回転させた後、１３０℃で２０分間加熱する事により初期の溶媒の８５％を除去した後、２５０℃まで３０分で昇温し溶媒を除去し、金型内面の塗膜自身が皮膜として支持できるまで乾燥、硬化させた。この皮膜を金型内面より離型した後、金属製シリンダ（皮膜支持部の長さが８００ｍｍ）に差し替え、残存溶媒の除去、閉環水の除去、およびイミド転化の完結反応を行うために３６０℃まで昇温加熱した後、室温まで冷却した。得られたベルトの両端と中央部の不要部分を切断し、半導電性ベルトを２本得た。これらのベルトをタンデム式中間転写型画像形成装置の中間転写ベルトとして搭載し画像形成を行ったところ、画像ムラもなく良好な画像が得られた。
【００５８】
実施例２
金型内面へのポリアミド酸溶液の供給量を３３０ｇにした以外は実施例１と同様の方法でシームレスベルトを作製した。この時の初期乾燥時の溶媒の蒸発率は８６％であった。得られたベルトをタンデム式中間転写型画像形成装置の中間転写ベルトとして搭載し画像形成を行ったところ、画像ムラもなく良好な画像が得られた。
【００５９】
比較例１
ポリアミド酸溶液の初期乾燥を１３０℃で５分間行なった以外は、実施例１と同様の方法でシームレスベルトを作製した。この時の初期乾燥時の溶媒の蒸発率は５５％であった。得られたベルトをタンデム式中間転写型画像形成装置の中間転写ベルトとして搭載し画像形成を行ったところ、画像ムラが発生した。
【００６０】
以上のシームレスベルトの物性と画像評価の結果を表１に示す。
【００６１】
【表１】

表１の結果が示すように、引張弾性率と曲げ硬さが適切な実施例１〜２では、画像評価の結果、画像ムラが生じなかった。これに対して、曲げ硬さが硬すぎる比較例１では、画像ムラが生じた。
【図面の簡単な説明】
【図１】実施例等における曲げ硬さの測定方法を説明するための説明図
【図２】本発明の画像形成装置の一例を示す概略図
【符号の説明】
１　　トナーカートリッジ
２　　定着ロール（定着装置）
３　　バックアップロール
４　　テンションロール
５　　２次転写ロール（第二転写手段）
６　　用紙経路
７　　用紙トレイ
８　　レーザー発生装置（露光装置）
９　　感光体
１０　１次転写ロール（第一転写手段）
１１　駆動ロール
１２　転写クリーナー
１３　帯電ロール（帯電装置）
１４　感光体クリーナー（クリーニング装置）
１５　現像器（現像装置）
１６　中間転写体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a seamless belt having a tensile elastic modulus and a bending hardness in a circumferential range within a predetermined range, a method for manufacturing the same, and an image forming apparatus including the seamless belt, and a plurality of image carriers having a developing device for each color. Especially useful as an intermediate transfer member, an intermediate transfer fixing member, and a fixing member for use in an electrophotographic copying machine, a printer, a facsimile, and a multifunction machine equipped with a tandem-type color image forming apparatus in which the members are arranged in series on an intermediate transfer member It is.
[0002]
[Prior art]
An image forming apparatus using an electrophotographic method forms a uniform charge on a latent image carrier made of an inorganic or organic photoconductive photoconductor, and modulates an image signal with a laser or a light emitting diode light to form an electrostatic latent image. After the image is formed, the electrostatic latent image is developed with the charged toner to obtain a visualized toner image. Then, the required reproduced image is obtained by electrostatically transferring the toner image via an intermediate transfer member or directly to a transfer material such as recording paper. In particular, there is known an intermediate transfer method in which a toner image formed on the image carrier is primarily transferred to an intermediate transfer member, and a toner image of the intermediate transfer member is secondarily transferred to recording paper.
[0003]
As the material of the endless belt used in the image forming apparatus using the intermediate transfer system, a blend material of a polycarbonate resin (PC), polyvinylidene fluoride (PVDF), polyalkylene phthalate, PC / polyalkylene phthalate (PAT) And a semiconductive endless belt made of a thermoplastic resin such as ethylene tetrafluoroethylene copolymer (ETFE).
[0004]
Further, an intermediate transfer body in which ordinary carbon black is dispersed as a conductive fine powder in a polyimide resin has been proposed (for example, see Patent Documents 1 and 2).
[0005]
[Patent Document 1]
Japanese Patent No. 2560727 (page 1)
[Patent Document 2]
JP-A-5-77252 (page 2)
[0006]
[Problems to be solved by the invention]
On the other hand, as a new image forming apparatus using such an intermediate transfer member, a plurality of image carriers provided with a developing device for each color are arranged in series along the intermediate transfer member, and each image carrier on the photosensitive member is provided for each color. A tandem-type intermediate transfer type color image forming apparatus for transferring an image onto a recording material such as paper after transferring the image onto an intermediate transfer body has been studied. Conventionally, in a color image forming apparatus, as a method of transferring a visible image to a recording material, a recording material such as paper is wound around a transfer drum, and a developed image on a photoconductor is transferred to the recording material for each color. There is known an intermediate transfer method in which a developed image on a photoconductor is transferred to an intermediate transfer body for each color, and then the developed image on the intermediate transfer body is collectively transferred to a recording material.
[0007]
The tandem-type intermediate transfer method has been studied as a promising transfer method in the future because it can achieve an improvement in image forming speed as compared with the transfer method described above, and has the merit that a transfer target is not selected unlike the transfer drum method. However, since the intermediate transfer body in this transfer method is larger in diameter than the conventional intermediate transfer belt and has four independent color developing units, it is necessary to design a high-precision device such as the accuracy of color misregistration for each color. It becomes. A high elastic modulus is required for the intermediate transfer member mounted on such an image forming apparatus. Further, with the miniaturization and high speed of the image forming apparatus, the components inside the recent image forming apparatus are close to each other, and when the bending hardness of the intermediate transfer body becomes hard, the followability to the transfer roll becomes poor, Causes phenomena such as missing colors.
[0008]
An object of the present invention is to solve the above-mentioned problems in the prior art and achieve the following objects. That is, an object of the present invention is to provide a seamless belt that can obtain a high-quality transferred image even when used for an intermediate transfer member of a tandem-type intermediate transfer image forming apparatus because of its high elastic modulus and small bending hardness. And an image forming apparatus provided with the seamless belt.
[0009]
[Means for Solving the Problems]
Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above problems, and as a result, have found that the above object can be achieved by the following semiconductive belt, and have completed the present invention.
[0010]
That is, the seamless belt of the present invention has a tensile modulus in the circumferential direction measured in accordance with JIS K 7127 of 5000 MPa or more, and a width when one end is fixed and a vertical load is applied to a position of 10 mm on the other end. The flexural hardness in the circumferential direction per 10 mm is not more than 1.5 g / mm. In the present invention, the physical properties such as the tensile elastic modulus are values specifically measured by the measuring methods described in Examples.
[0011]
The seamless belt of the present invention is preferably used as an intermediate transfer member of a tandem-type color image forming apparatus in which a plurality of image carriers having developing units for each color are arranged in series along the intermediate transfer member.
[0012]
Further, it is preferable to contain a polyimide resin as a resin component. In addition, it contains carbon black as a conductive agent and has a surface resistivity of 10%. ⁸ -10 ¹⁴ It is preferably in the range of Ω / □.
[0013]
On the other hand, the method for producing a seamless belt of the present invention includes a step of developing a raw material liquid in which polyamic acid is dissolved in a solvent on the inner surface of a cylindrical mold, a step of evaporating the solvent, and a step of performing imide conversion of the polyamic acid. The method for producing a seamless belt is characterized in that the solvent is evaporated at a rate of 60% or more at a heating temperature of 130 ° C. or less.
[0014]
On the other hand, an image forming apparatus of the present invention includes any one of the above-described seamless belts as an intermediate transfer member. This is preferably the case of a tandem-type color image forming apparatus in which a plurality of image carriers having developing units for each color are arranged in series along the intermediate transfer member.
[0015]
[Effects]
According to the seamless belt of the present invention, even when it is used for an intermediate transfer member of a tandem type intermediate transfer type image forming apparatus, it has a high elastic modulus and a small bending hardness in the circumferential direction, so that a high quality transfer image can be obtained. it can. Therefore, it can be suitably used as an intermediate transfer member of a tandem type color image forming apparatus.
[0016]
Such physical properties can be realized more reliably by including a polyimide resin as a resin component. It contains carbon black as a conductive agent and has a surface resistivity of 10%. ⁸ -10 ¹⁴ When it is in the range of Ω / □, since it has appropriate conductivity, image unevenness hardly occurs.
[0017]
On the other hand, according to the production method of the present invention, 60% or more of the solvent is evaporated under the condition of a heating temperature of 130 ° C. or less. A belt can be obtained, and a high-quality transfer image can be obtained even when used for an intermediate transfer member of a tandem-type intermediate transfer image forming apparatus.
[0018]
On the other hand, according to the image forming apparatus of the present invention, since a seamless belt having a high elastic modulus and a small bending hardness in the circumferential direction is provided as an intermediate transfer body, even in the case of a tandem-type intermediate transfer image forming apparatus, Color shift can be suppressed with high accuracy. Further, even in the case of a device structure in which components in recent years are close to each other, followability to a transfer roll is improved, and color omission and the like can be suitably prevented. Therefore, a high-quality transfer image can be obtained.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
(Seamless belt)
The seamless belt of the present invention has a tensile modulus in the circumferential direction measured according to JIS K 7127 of 5,000 MPa or more, and preferably 6000 MPa or more. If the tensile modulus in the circumferential direction is lower than 5000 MPa, color matching becomes difficult when used in a tandem-type intermediate transfer image forming apparatus, and a large-scale control device is required to cause color shift and prevent it.
[0020]
Further, the seamless belt of the present invention has a bending hardness per 10 mm width of 1.5 g / mm or less when one end is fixed and a vertical load is applied to a position of 10 mm on the other end side. 0 g / mm or less. When the bending hardness in the circumferential direction is higher than 1.5 g / mm, the ability to follow the transfer roll is deteriorated, causing phenomena such as color omission and image unevenness.
[0021]
The seamless belt of the present invention may use any polymer as a resin component as long as it has the above-mentioned physical properties. For example, it is also possible to increase the elastic modulus by stretching and orienting. However, it is desirable to use an aromatic polyimide resin in order to exhibit a high elastic modulus without stretching. The polyimide resin is usually obtained as a polyamic acid solution by subjecting substantially equimolar tetracarboxylic dianhydride or a derivative thereof and a diamine to a polymerization reaction in a solvent. Examples of the tetracarboxylic dianhydride include those represented by the following general formula (1).
[0022]
Embedded image

(In the general formula (1), R is a tetravalent organic group, which is aromatic, aliphatic, cycloaliphatic, a combination of aromatic and aliphatic, or a substituted group thereof.)
Specific examples of the tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic acid Acid dianhydride, 2,3,3 ', 4-biphenyltetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic acid Dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) sulfonic dianhydride, perylene-3,4,9,10 -Tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, ethylenetetracarboxylic dianhydride and the like. In particular, it is preferable to use 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride to prepare a polyimide having a high elastic modulus.
[0023]
On the other hand, specific examples of the diamine include 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 3,3'-dichlorobenzidine, and 4,4'-diaminodiphenylsulfur. Id, 3,3'-diaminodiphenylsulfone, 1,5-diaminonaphthalene, m-phenylenediamine, p-phenylenediamine, 3,3'-dimethyl-4,4'-biphenyldiamine, benzidine, 3,3'- Dimethylbenzidine, 3,3′-dimethoxybenzidine, 4,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylpropane, 2,4-bis (β-aminotert-butyl) toluene, bis (p-β -Amino-tert-butylphenyl) ether, bis (p-β-methyl-δ-aminophenyl) benzene, bis p- (1,1-dimethyl-5-amino-bentyl) benzene, 1-isopropyl-2,4-m-phenylenediamine, m-xylylenediamine, p-xylylenediamine, di (p-aminocyclohexyl) methane , Hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, diaminopropyltetramethylene, 3-methylheptamethylenediamine, 4,4-dimethylheptamethylenediamine, 2,11-diaminododecane, 1,2-bis-3-aminopropoxyethane, 2,2-dimethylpropylenediamine, 3-methoxyhexamethylenediamine, 2,5-dimethylheptamethylenediamine, 3-methylheptamethylenediamine, 5-methylnonamethylenediamine , 2, 17-diaminoeicosadecane, 1,4-diaminocyclohexane, 1,10-diamino-1,10-dimethyldecane, 12-diaminooctadecane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, Piperazine, H ₂ N (CH ₂ ) ₃ O (CH ₂ ) ₂ O (CH ₂ ) NH ₂ , H ₂ N (CH ₂ ) ₃ S (CH ₂ ) ₃ NH ₂ , H ₂ N (CH ₂ ) ₃ N (CH ₃ ) ₂ (CH ₂ ) ₃ NH ₂ And the like.
[0024]
As the solvent for the polymerization reaction of the tetracarboxylic dianhydride and the diamine, a polar solvent is preferably mentioned from the viewpoint of solubility and the like. As the polar solvent, N, N-dialkylamides are preferable. Specifically, for example, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylformamide, which are low-molecular-weight ones thereof, are used. , N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, dimethylsulfoxide, hexamethylphosphortriamide, N-methyl-2-pyrrolidone, pyridine, tetramethylenesulfone, dimethyltetramethylenesulfone and the like. These can be used alone or in combination.
[0025]
The monomer concentration for obtaining the polyamic acid is preferably 5 to 30% by weight. The reaction temperature is preferably set to 80 ° C. or lower, particularly preferably 5 to 50 ° C., and the reaction time is preferably about 0.5 to 10 hours.
[0026]
In the seamless belt of the present invention, it is preferable to add various conductive materials to the resin in order to obtain semi-conductivity. In that case, the surface resistivity is 10 ⁸ -10 ¹⁴ It is preferably in the range of Ω / □. Specifically, an inorganic compound such as carbon black, aluminum, nickel, tin oxide, or potassium titanate, or a conductive polymer represented by polyaniline, polypyrrole, or the like can be used. In particular, it is desirable to use carbon black from the viewpoint of resistance control and resistance reduction, and it is more desirable to use oxidized carbon black.
[0027]
Oxidized carbon black can be obtained by oxidizing carbon black to provide an oxygen-containing functional group (for example, a carboxyl group, a quinone group, a lactone group, a hydroxyl group, etc.) on the surface. This oxidation treatment is carried out in a high-temperature atmosphere by contacting with air and reacting with air, a method of reacting with nitrogen oxide or ozone at room temperature, and a method of oxidizing air at high temperature and then oxidizing ozone at low temperature. And the like. The oxidized carbon black obtained in this way is partially affected by excessive current flowing, is less susceptible to oxidation due to repeated voltage application, and furthermore, due to the effect of oxygen-containing functional groups attached to its surface, polyimide In addition to being highly dispersible to the substrate, the variation in resistance can be reduced, the dependence on the electric field is reduced, and the electric field concentration due to the transfer voltage is less likely to occur. As a result, resistance reduction due to transfer voltage is prevented, uniformity of electric resistance is improved, electric field dependence is small, and there is little change in resistance due to the environment, and image quality defects such as a white paper running out of the paper running section are generated. An intermediate transfer member capable of obtaining suppressed high image quality is obtained.
[0028]
The content of these oxidized carbon blacks is preferably about 10 to 50% by weight, more preferably 12 to 30% by weight, based on the polyimide resin. When the content is less than 10% by weight, the uniformity of the electric resistance is reduced, and the decrease in the surface resistivity during the durable use may be large. On the other hand, when the content exceeds 50% by weight, a desired resistance value is obtained. Is difficult to obtain, and it is not preferable because it becomes brittle as a molded product.
[0029]
The seamless belt of the present invention is obtained at least through a step of developing a raw material liquid in which a polyamic acid is dissolved in a solvent on the inner surface of a cylindrical mold, a step of evaporating the solvent, and a step of performing imide conversion of the polyamic acid. be able to. At this time, a semiconductive seamless belt can be obtained by dispersing the conductive agent in the raw material liquid.
[0030]
For the method for producing a polyamic acid solution in which a conductive agent is dispersed, a method in which the acid dianhydride component and the diamine component are dissolved and polymerized in a dispersion in which the conductive agent is previously dispersed in a solvent, and the conductive agent is dissolved in the solvent A method of mixing the polydispersed solution with the polyamic acid solution, a method of dispersing the conductive agent in the polyamic acid solution, and the like are considered. A polyamic acid solution in which the conductive agent is dispersed is prepared by appropriately selecting the method.
[0031]
The seamless belt of the present invention is obtained by supplying and developing the polyamic acid solution thus obtained on the inner surface of the cylindrical mold to form a coating film, and heating the polyamic acid to imide conversion. The details will be described below.
[0032]
In the present invention, the polyamic acid solution is supplied to the inner surface of a cylindrical mold. This supply method can be performed by appropriately selecting a method using a dispenser, a method using a die, or the like.
[0033]
The surface condition of the inner peripheral surface of the cylindrical mold used at this time is preferably mirror finished in the present invention. Further, a mold release treatment can be performed on the inner peripheral surface of the mold. The thus-supplied polyamic acid solution is subjected to centrifugal molding while heating, a method of molding using a bullet-shaped traveling body, a method of rotational molding, or the like, and a film having a uniform film thickness is formed as appropriate. Subsequently, the mold with the coating formed on the inner peripheral surface is heated in a dryer together with the mold, and the solvent is removed until the shape can be maintained as a belt or a method of raising the temperature until the imide conversion, and then from the mold inner surface. After exfoliation and replacement with the outer surface of the metal cylinder, a method of heating the entire cylinder to perform imide conversion can be considered. In order to obtain a seamless belt having a suitable tensile modulus, the latter method is desirable.
[0034]
In addition, in order to obtain a seamless belt having a suitable bending hardness, drying of the solvent contained in the initial polyamic acid solution is performed at a temperature equal to or lower than the temperature at which imidization starts (specifically, the temperature of the polyamic acid solution is 60 to 60). It is desirable to evaporate at least 60% or more at 130 ° C. for 0.1 to 2 hours. More preferably, it is desirable to be 70% or more. That is, the production method of the present invention is characterized in that the solvent is evaporated by 60% or more under the condition of a heating temperature of 130 ° C. or less. Conversely, if the temperature is raised to a high temperature in a short time to further remove the solvent in a state where the initial solvent evaporation rate is low, the film becomes not only hard but also brittle.
[0035]
Next, in order to remove the solvent until it can be held as a belt, drying is performed at a temperature higher than the initial drying temperature (specifically, in a range of 150 to 300 ° C.), and the solvent is removed to a temperature that can be held as a belt. Thereafter, a method of performing imide conversion by replacing the cylinder with a metal cylinder is preferable. The metal cylinder used at this time preferably has a coefficient of linear expansion larger than that of the polyimide resin.The outer diameter of the cylinder is smaller than the inner diameter of the polyimide molded article by a predetermined amount, so that heat setting can be performed, and a uniform film can be formed. An endless belt having a uniform thickness can be obtained. The surface roughness (Ra) of the outer surface of the metal cylinder used at this time is preferably 1.2 to 2.0 μm. If the surface roughness (Ra) of the outer surface of the metal cylinder is less than 1.2 μm, the metal cylinder itself is too smooth, and the resulting seamless belt does not slip due to contraction in the axial direction of the belt. This causes variations in film thickness and a decrease in accuracy of flatness. On the other hand, if the surface roughness (Ra) of the outer surface of the metal cylinder is larger than 2.0 μm, the outer surface of the metal cylinder is transferred to the inner surface of the seamless belt, and furthermore, irregularities are generated on the outer surface, thereby causing image defects. The outer surface of the seamless belt made of the polyimide resin thus obtained has a surface roughness (Ra) of 1.5 μm or less. The surface roughness in the present invention is measured according to JIS B 601. If the surface roughness (Ra) of the outer surface of the seamless belt is larger than 1.5 μm, image defects such as white spots occur. The reason for this is that the voltage applied during transfer and the electric field due to peeling discharge are concentrated on the convex parts of the belt surface, and the surface of this part is deteriorated, a new conductive path is formed, and the resistance decreases. Conceivable.
[0036]
The thickness of the seamless belt of the present invention is not particularly limited as long as the bending hardness per 10 mm of the film width is 1.5 g / mm or less, but is preferably about 20 to 85 μm, and particularly preferably 40 to 75 μm. It is. When the film thickness is less than 20 μm, the film strength is weak and a problem of durability occurs. On the other hand, when the thickness of the film increases, the bending hardness of the film becomes too hard.
[0037]
Such a seamless belt has good tensile elasticity and bending hardness, and thus can be suitably used for a tandem-type image forming apparatus. The tandem image forming apparatus does not repeat the latent image formation, development, transfer, charge removal, and cleaning for each color as in the conventionally known transfer drum method and intermediate transfer method, and a plurality of image carriers are used. Since they are arranged in series, there is an advantage that the image forming speed is remarkably improved. At this time, when the seamless belt of the present invention is used, since a tensile elastic modulus and a bending hardness thereof are good, a good image can be obtained.
[0038]
(Image forming device)
An image forming apparatus of the present invention includes the seamless belt of the present invention as an intermediate transfer member. The image forming apparatus of the present invention only needs to have an intermediate transfer member to which a toner image formed on an image carrier is temporarily transferred, and can form any image such as a black and white image, a color image, and a full color image. May be used. However, it is preferable that the image forming apparatus be a tandem type color image forming apparatus in which a plurality of image carriers having developing units for each color are arranged in series along the intermediate transfer member.
[0039]
In the tandem type color image forming apparatus, for example, as shown in FIG. 2, a photoconductor 9 for each color provided with a developing device 15 of four colors (black, yellow, magenta, cyan) is serially arranged along an intermediate transfer body 16. Are placed. By providing the intermediate transfer member of the present invention, a high-quality transfer image can be obtained.
[0040]
Specifically, a charging device 13 for uniformly charging the surface of the photoconductor 9, an exposing device 8 for exposing the surface of the photoconductor 9 to form an electrostatic latent image, and a developing device for applying the latent image formed on the surface of the photoconductor 9 to a developer A developing device 15 for developing and using the toner image to form a toner image, a cleaning device 14 for removing toner and dust adhering to the photoreceptor, a fixing device 2 for fixing the toner image on the transfer material, and the like. It can be arbitrarily provided by a known method.
[0041]
As the photoconductor 9, a conventionally unknown photoconductor can be used, and the photoconductor 9 generally has a photosensitive layer on a conductive substrate. As the photoconductor layer, a known material such as an organic material or amorphous silicon can be used. When the photoreceptor 9 has a cylindrical shape, the conductive substrate is obtained by a known manufacturing method such as extruding aluminum or aluminum-containing metal and processing the surface. It is also possible to use a belt-shaped photoconductor.
[0042]
The charging unit 13 is not particularly limited, and may be, for example, a contact type charger using a conductive or semiconductive roller, brush, film, rubber blade, or the like, a scorotron charger using corona discharge, a corotron charger, or the like. Is known per se. Among these, a contact-type charger is preferable because of its excellent charge compensation ability. The charging unit normally applies a direct current to the electrophotographic photosensitive member, but may further superimpose an alternating current.
[0043]
The exposure device 8 is not particularly limited. For example, a light source such as a semiconductor laser light, an LED light, a liquid crystal shutter light, or a light source such as a semiconductor laser light, an LED light, or a liquid crystal shutter light may be provided on a surface of the electrophotographic photosensitive member through a polygon mirror. An optical device capable of exposure can be used.
[0044]
The developing device 15 can be appropriately selected according to the purpose. For example, a known developing method in which a one-component developer or a two-component developer is brought into contact or non-contact with a brush or a roller to perform development. Equipment and the like.
[0045]
As the first transfer unit 10, for example, a transfer device known per se such as a contact type transfer charger using a belt, a roller, a film, a rubber blade, or the like, a scorotron transfer charger using a corona discharge, or a corotron transfer charger. And a charger. Among these, a contact-type transfer charger is preferable because of its excellent transfer charge compensation ability. In the present invention, in addition to the transfer charger, a peeling charger and the like can be used in combination.
[0046]
Examples of the second transfer unit 5 include a contact-type transfer charger such as a transfer roller exemplified as the first transfer unit 10, a scorotron transfer charger, and a corotron transfer charger. Among these, a contact-type transfer charger is preferable as in the first transfer unit. When the contact type transfer charger such as a transfer roller is pressed strongly, an image transfer state can be maintained in a good state. Also, when a contact-type transfer charger such as a transfer roller is pressed at the position of the roller for guiding the intermediate transfer member, the operation of transferring the toner image from the intermediate transfer member to the transfer target member can be performed in a good state. become.
[0047]
Examples of the light removing means used when it is necessary to remove the potential remaining on the surface of the photoreceptor after transfer include, for example, a tungsten lamp and an LED, and the light quality used in the light removing process includes, for example, , A white light such as a tungsten lamp, and a red light such as an LED light. The irradiation light intensity in the photostatic process is usually set so as to be several times to about 30 times the light amount indicating the half-life exposure sensitivity of the electrophotographic photosensitive member.
[0048]
The cleaning device 14 for the photoconductor 9 is not particularly limited, and a known cleaning device or the like may be used. The transfer cleaner 12 for the intermediate transfer member 16 is not particularly limited, and a known cleaning device or the like may be used.
[0049]
The fixing device 2 is not particularly limited, and includes a fixing device known per se, for example, a roller fixing device, a belt-type fixing device, an oven fixing device, and the like.
[0050]
【Example】
Hereinafter, examples and the like specifically illustrating the configuration and effects of the present invention will be described. The evaluation items in Examples and the like were measured as follows.
[0051]
1. Tensile modulus
The measurement was performed according to JIS K7127. The test piece used was JIS K 6301 (No. 3 dumbbell).
[0052]
2. Bending hardness
The test piece had a size of 50 mm in the circumferential direction and 10 mm in the width direction. The test piece was fixed by projecting the tip of the sample table by 20 mm. As a test device, a handy compression tester KES-G5 manufactured by Kato Tech Co., Ltd. was used. A core having a tip diameter of φ1 mm was pushed into the test piece at a position 10 mm from the tip end at a speed of 0.1 mm / sec, and the load at that time was read by a load cell (see FIG. 1). The bending hardness was defined as the bending load as the indentation load per unit indentation amount based on the indentation amount and the gradient of the indentation load at this time.
[0053]
3. Belt thickness
A total of 50 points of 10 points in the circumferential direction and 5 points in the width direction of the belt were measured, and the average value was obtained.
[0054]
4. Surface resistivity
About 24 surfaces (8 points in the circumferential direction, 3 points in the width direction) of the surface of the semiconductive belt, an applied voltage of 100 V was applied by Hiresta UP, MCP-HTP16 (produced by Mitsubishi Chemical Corporation, probe: UR-100) for 10 seconds. The surface resistivity at a measurement condition of 25 ° C. and 60% RH was examined, and the surface resistivity was represented by a common logarithmic value.
[0055]
5. Evaporation rate of solvent
The amount of evaporation was calculated from the difference between the weight of the applied raw material liquid and the weight of the dried coating film, and this was divided by the amount of solvent in the applied raw material liquid to obtain a percentage.
[0056]
Example 1
23 g of carbon black (SPECIAL BLACK4, manufactured by Degussa) was added to 389 g of N-methyl-2-pyrrolidone (NMP), and the mixture was stirred with a ball mill for 8 hours to obtain a carbon black-dispersed NMP solution. In this carbon black-dispersed NMP solution, 65 g of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and 24 g (equimolar number) of p-phenylenediamine are dissolved and stirred at room temperature for 5 hours under a nitrogen atmosphere. After the reaction, the viscosity was adjusted to obtain a polyamic acid solution in which carbon black was dispersed (solid content: 20% by weight, solution viscosity at 23 ° C. by a B-type viscometer at 200 Pa · s).
[0057]
420 g of this polyamic acid solution was spirally supplied to the inner surface of a cylindrical mold (inner diameter 300 mm, length 800 mm) by a dispenser. Next, after rotating at 1500 rpm for 10 minutes, 85% of the initial solvent is removed by heating at 130 ° C. for 20 minutes, then the temperature is raised to 250 ° C. for 30 minutes to remove the solvent, and the coating on the inner surface of the mold is performed. The film was dried and cured until the film itself could be supported as a film. After the film was released from the inner surface of the mold, it was replaced with a metal cylinder (length of the film support portion was 800 mm), and 360 ° C. was performed to remove the residual solvent, remove the ring-closing water, and complete the imide conversion. After heating to, the mixture was cooled to room temperature. Unnecessary portions at both ends and the center of the obtained belt were cut to obtain two semiconductive belts. When these belts were mounted as an intermediate transfer belt of a tandem type intermediate transfer type image forming apparatus to form an image, good images were obtained without image unevenness.
[0058]
Example 2
A seamless belt was produced in the same manner as in Example 1, except that the supply amount of the polyamic acid solution to the inner surface of the mold was 330 g. At this time, the evaporation rate of the solvent in the initial drying was 86%. When the obtained belt was mounted as an intermediate transfer belt of a tandem type intermediate transfer type image forming apparatus to form an image, a good image was obtained without image unevenness.
[0059]
Comparative Example 1
A seamless belt was produced in the same manner as in Example 1, except that the polyamic acid solution was initially dried at 130 ° C. for 5 minutes. At this time, the evaporation rate of the solvent in the initial drying was 55%. When the obtained belt was mounted as an intermediate transfer belt of a tandem-type intermediate transfer type image forming apparatus and an image was formed, image unevenness occurred.
[0060]
Table 1 shows the physical properties of the seamless belt and the results of the image evaluation.
[0061]
[Table 1]

As shown in the results of Table 1, in Examples 1 and 2 in which the tensile modulus and the bending hardness were appropriate, no image unevenness occurred as a result of the image evaluation. On the other hand, in Comparative Example 1 in which the bending hardness was too hard, image unevenness occurred.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram for explaining a method of measuring bending hardness in Examples and the like.
FIG. 2 is a schematic diagram illustrating an example of the image forming apparatus of the present invention.
[Explanation of symbols]
1 Toner cartridge
2 Fixing roll (fixing device)
3 backup roll
4 tension roll
5 Secondary transfer roll (second transfer means)
6 Paper path
7 Paper tray
8 Laser generator (exposure device)
9 Photoconductor
10 Primary transfer roll (first transfer means)
11 Drive roll
12 Transfer cleaner
13 Charging roll (charging device)
14 Photoreceptor cleaner (cleaning device)
15 Developing device (developing device)
16 Intermediate transfer member

Claims (6)

The circumferential tensile modulus measured in accordance with JIS K7127 is 5000 MPa or more, and the circumferential bending hardness per 10 mm width when one end is fixed and a vertical load is applied to a position of 10 mm on the other end. Is 1.5 g / mm or less. 2. The seamless belt according to claim 1, wherein the seamless belt is used as an intermediate transfer member of a tandem-type color image forming apparatus in which a plurality of image carriers having developing units for each color are arranged in series along the intermediate transfer member. The seamless belt according to claim 1, wherein the seamless belt contains a polyimide resin as a resin component. The seamless belt according to any one of claims 1 to 3, which contains carbon black as a conductive agent and has a surface resistivity in a range of 10 ⁸ to 10 ¹⁴ Ω / □. In a method for producing a seamless belt including a step of developing a raw material liquid in which a polyamic acid is dissolved in a solvent on the inner surface of a cylindrical mold, a step of evaporating the solvent, and a step of performing imide conversion of the polyamic acid, a heating temperature of 130 ° C. or less A method for producing a seamless belt, comprising evaporating 60% or more of the solvent under the following conditions. An image forming apparatus comprising the seamless belt according to claim 1 as an intermediate transfer member.

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