JP4091722B2 - Endless belt and method of forming the same - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、無端状ベルト及びその成形方法に関し、特に、抵抗の膜厚方向のバラツキがない画像形成装置用の中間転写ベルトと、その成形方法に関するものである。本発明が応用できる技術分野としては、抵抗が膜厚方向に均一な各種抵抗制御膜及びその製造技術が挙げられる。
【０００２】
【従来の技術】
複写機、ファクシミリ、プリンタ等の画像形成装置において、最近多色特にフルカラーの再生画像の要求が高まっており、この要求に答えることができる画像形成装置として、中間転写体を使用した転写方式の画像形成装置が普及している。上記中間転写方式では、中間転写体としてローラを用いる場合と、ベルトを用いる場合とがある。
【０００３】
中間転写方式による画像形成方法は、感光体上に形成された潜像を電荷担持体トナーにより顕像化し、一次転写工程において上記感光体を中間転写体に転写色重ね（顕像化した画像の一次転写）した後、二次転写工程において上記顕像化画像を被転写体（複写紙）へ二次転写するものである。そして、この画像形成方法では中間転写体へ転写する際、電荷担持体（トナー）を移動転写させるために、感光体とこの中間転写体との間にバイアスの電圧を印加する必要があり、したがってこのバイアス電圧は、最適な画像が得られるように調整されている。
【０００４】
ところが、従来の中間転写体ベルトにおいては、画像形成装置を繰り返し使用していくと、初期印加バイアスのままでは画像品質が次第に劣化していくという不具合があった。この不具合は、バイアスを再調整することで、ある程度解消することはできるが、ベルト毎にいちいち微調整することは、メンテナンスの面から非常に煩わしく、不便でもあった。
【０００５】
そこで、本発明者らが上記不具合の原因を検討・解析した結果、従来の中間転写ベルトでは、熱可塑性樹脂中に抵抗制御剤が不均一に分散しているため、膜（ベルト）の厚み方向に抵抗バラツキが発生していることが明らかになった。
【０００６】
これについて更に具体的に説明すると、繰り返し使用するうちに中間転写ベルトが駆動ローラ等により摩耗して、その裏面側から膜厚が次第に減少し、その時の裏面の表面抵抗を測定すると初期値の１０8 Ωから、１０μｍの膜厚減少で１０11Ωまで増加していることが判明した。このように抵抗がベルトの膜厚方向に不均一になった（膜厚方向の抵抗分布が生じた、すなわち膜厚方向の抵抗バラツキが発生した）のは、ベルト中の抵抗制御剤が膜厚方向に均一に分布していないことや、ベルト裏面の摩耗による抵抗制御剤の欠落が原因していることが判った。また、これらの問題が生じるのは、ベルトの基材である樹脂の結晶構造が膜厚方向で異なっているためであり、さらに、この結晶構造が不均一になったのは、所定膜厚のベルトを形成する際にベルト膜厚方向で熱分布（温度分布すなわち温度バラツキ）が発生し、樹脂の微細構造が異なってくるためであることが判明した。
【０００７】
【発明が解決しようとする課題】
本発明は、従来技術の上記問題点に鑑みなされてもので、その目的は、抵抗が膜厚方向に均一な無端状ベルト、特に画像形成装置用の中間転写ベルトおよび、その成形方法を提供すること、そして、これにより画像形成装置において、高品位な画像が長期間継続して得られるようにすることにある。すなわち本発明は、中間転写ベルト（ベルト状中間転写体）を用いる画像形成装置において、良好な画像を継続して形成することができるように、上記中間転写ベルトの特性を改善することを目的としたものである。
【０００８】
【課題を解決するための手段】
前述のような、抵抗のベルト膜厚方向のバラツキ（膜厚方向の分布不均一）が生じる原因が、ベルト中に抵抗制御剤が膜厚方向に均一に分布していないことにあり、その理由が基材樹脂の結晶構造が膜厚方向で異なっていることにあるならば、基材樹脂の結晶構造を均質にすることで、抵抗バラツキの問題を解決することができる。また、そのためには、ベルト成形時（膜形成時）の熱分布（温度分布）を均一にすれば良い。
【０００９】
本発明では、ベルトの基材として結晶性の熱可塑性樹脂を使用する。ベルト成形のための薄膜形成は、一般に（１）融解液の塗布、あるいは（２）溶液の塗布により行われる。これらの場合、
（１）融解液の塗布では原料樹脂を融解温度まで加熱しなければならないが、融解樹脂は温度低下の際に凝固発熱して結晶化する。
（２）また、溶液の塗布においては、塗布液を乾燥して溶剤を除去していくときに樹脂分が濃縮されて過飽和液となり、樹脂分が析出して結晶化する。
【００１０】
基材中に分散した抵抗制御剤の分布状態が、これらの結晶化による凝固で膜厚方向に不均一になる理由は下記の通りである。
上記（１）に関しては、ゾーンメルティングでの不純物除去で知られているように、凝固（固化）するときに異物が押し出され、これが未凝固の残液部に濃縮されていく。またベルト成形用の金型である金属素管の成型物では大抵の場合、その表面は微結晶が多く、内部は粗大結晶になっており、結晶界面に異元素成分が析出していることが知られていることから分かるように、融解液冷却時の熱分布が成形物の結晶構造に影響を与える。
【００１１】
また、上記（２）では、基材樹脂成分が表面付近で溶剤蒸発により析出・結晶化する際に、分散成分が絞り出されて残液中の分散成分が濃縮されることになる。これは、あたかも海水結氷時の氷の真水化現象、つまり元々各種成分が含まれている海水が凍ると、氷の中では塩分が排斥されて減少し、残りの海水の濃度が増加していくことに似ている。
本発明は、上記考察をもとに完成されたものである。
【００１２】
請求項１に記載の無端状ベルトは、熱可塑性樹脂からなる無端状ベルトにおいて、結晶質の熱可塑性樹脂中に抵抗制御剤が均一に分散していることを特徴とする。
【００１３】
また、請求項１に記載の無端状ベルトは、前記熱可塑性樹脂の結晶化度及び／又は結晶形態が、ベルト全体にわたって均一であることを特徴とする。
さらに、請求項２に記載の無端状ベルトは、ポリフッ化ビニリデンを含むことを特徴とする。
【００１４】
請求項３に記載の無端状ベルトの成形方法は、請求項１または２に記載の無端状ベルトの成形方法であって、熱可塑性樹脂の液状溶液を成形型の表面に塗布して塗布膜を形成した後、成形型の裏面側から加熱するか、または成形型の裏面側および表面側から同時に加熱することにより、前記塗布膜を乾燥させることを特徴とする。
【００１５】
請求項４に記載の無端状ベルトの成形方法は、請求項３において、前記塗布膜を乾燥した後に、該乾燥膜を成形型から剥離することを特徴とする。
【００１６】
請求項５に記載の無端状ベルトの成形方法は、請求項３または４において、前記成形型として熱伝導性の高い材料（熱の良導体）からなるものを用いることを特徴とする。このような成形型としては金属材料、例えばアルミからなるものが挙げられる。
【００１７】
請求項６に記載の無端状ベルトの成形方法は、請求項１に記載の無端状ベルトを成形する方法であって、抵抗制御剤を分散させた熱可塑性樹脂の液状溶液を、成形型の表面に膜厚１〜１０μｍの薄膜として塗布したのち乾燥する操作を複数回繰り返すことを特徴とする。
【００１８】
請求項７に記載の無端状ベルトの成形方法は、請求項１に記載の無端状ベルトを成形する方法であって、熱可塑性樹脂を、沸点８０℃以上の溶剤に分散させた分散液を遠心成形用の成形型に塗布した後、乾燥することを特徴とする。
【００１９】
【実施例】
以下、本発明の実施例について説明する。
実施例１
メチルエチルケトンＭＥＫ（溶剤）にポリフッ化ビニリデンＰＶＤＦ２０ｗｔ％と、導電剤（抵抗制御剤）としてカーボンブラック４ｗｔ％とを混合攪拌することにより、上記溶剤中に上記成分を分散させた塗布液を作製した。この塗布液を容器に入れ、塗布型（成形型）を容器内に漬けて徐々に引き上げる、いわゆるディッピング法により膜厚約１００μｍの塗布膜を形成した後、溶剤を加熱乾燥して膜を形成した。また塗布型としては、表面に膜厚１μｍ以下のフッ素樹脂膜を被覆したアルミの型と、ポリフェニレンスルフィドＰＰＳを成形して作製した型を用いた。
【００２０】
上記溶剤を除去するための加熱乾燥条件は、
１．（塗布液を塗布した）型を、単に炉内に入れて乾燥（外部乾燥）、
２．型の内部に加熱体を挿入し、型の内部から加熱（内部乾燥）、
３．型内部の加熱と、型外部の加熱とを同時併用、
の３条件とし、ＰＶＤＦの結晶融点（１７０℃）以下の１３０℃で加熱乾燥を行った。
【００２１】
その後、形成された膜（中間転写ベルト）を脱型剥離し、膜の厚さ方向の抵抗と結晶化度、結晶粒径を測定するとともに、この膜ベルトを実機（リコー製プリテール）に搭載して画像評価を行った。結果を下記［表１］〜［表３］に示す。これらの表において、サンプルＮｏ．５の膜形成条件は、従来のベルト作製条件である。結晶性の分析では、マイクロＸ線回折および微小部ラーマン分光を用いて観察した。
【００２２】
【表１】
【表２】
【表３】
実施例２
実施例１と同一の分散液（塗布液）を容器に入れ、アルミの塗布型で膜厚約１０μｍの塗布膜を形成した後、溶剤を加熱乾燥して膜を形成した。この作業を１０回繰り返して膜厚１００μｍの膜を作製した。実施例１と同様に膜の抵抗、結晶性、および実機での画像特性を評価した。膜の抵抗は膜厚方向に変化がなく、１０9 Ωの表面抵抗が得られ、結晶形態や結晶化度のバラツキがなく、繰り返し画像特性も変化なく、バイアスの調整は必要なかった。
【００２６】
実施例３
ジメチルアセトアミドにポリフッ化ビニリデンＰＶＤＦ２０ｗｔ％を溶解した溶液であるカイナー２０３（巴工業株式会杜）に、導電剤としてカーボンブラックを固形分比率２０ｗｔ％で混合攪拌して塗布液を作製した。この塗布液を回転するアルミ製の塗布型に注入塗布して高速回転させた後、外部加熱方式により溶剤を加熱乾燥して膜厚約１００μｍの膜を形成した。
【００２７】
脱型剥離後、実施例１，２と同様に膜の抵抗、結晶性および実機での画像特性を評価した。膜の抵抗は膜厚方向に変化なく、１０9 Ωの表面抵抗が得られ、結晶形態や結晶化度のバラツキがなく、繰り返し画像特性も変化なく、バイアスの調整は必要なかった。
なお、低沸点溶剤であるエタノールにポリフッ化ビニリデンＰＶＤＦを２０ｗｔ％（導電剤として、カーボンブラックを固形分比率２０ｗｔ％で混合）溶解した溶液を同様に遠心成形したが、注液して成膜する際の溶剤乾燥が早すぎ、膜厚が均一になる前に乾燥してしまうため、均一な膜を形成することはできなかった。
【００２８】
実施例４
ポリアミドをメタノールに溶解し、抵抗制御剤としてカーボンブラックを固形分比率２０％で分散させ、この分散液を、実施例１のアルミ型を用いてディッピング塗布した。この塗布膜を外部加熱単独で乾燥して得た膜と、内部加熱単独で乾燥して得た膜とを作製し、それぞれの膜の抵抗を測定した。
【００２９】
外部加熱のみで乾燥した膜では、その裏面から削って深さ方向（膜厚方向）の表面抵抗を測定すると抵抗が次第に上昇していくのに対して、内部加熱単独による膜では深さ方向の抵抗変化は生じなかった。また、膜厚方向の微細構造を分析した結果、外部加熱のみで形成した膜は表面付近に微細な結晶が多数あるが内部に行くほど大きな結晶粒となっていた。これに対し内部加熱のみによる膜では表面側と裏面側とで、ほぼ同一径の結晶粒であった。
【００３０】
実施例５
ポリカーボネートをテトラヒドロフランＴＨＦに溶解し、抵抗制御剤としてカーボンブラックを固形分比率２０％で分散させ、この分散液を実施例１のアルミ型を用いてディッピング塗布した。この塗布膜を外部加熱単独で乾燥して得た膜と、内部加熱単独で乾燥して得た膜とを作製し、それぞれの膜の抵抗を測定した。
【００３１】
外部加熱のみで乾燥した膜は、その裏面から削って深さ方向（膜厚方向）の表面抵抗を測定すると抵抗が次第に上昇していくのに対して、内部加熱のみによる膜では深さ方向の抵抗変化は生じなかった。また、膜厚方向の微細構造を分析した結果、外部加熱のみで形成した膜は表面付近に微細な結晶が多数あるが内部に行くほど大きな結晶粒となり、内部加熱のみによる膜では表面側と裏面側とで、ほぼ同一径の結晶粒であった。
【００３２】
【発明の効果】
以上の説明で明らかなように、本発明によれば以下の効果が得られる。
（１）請求項１の無端状ベルトによる効果
この無端状ベルトでは、結晶質の熱可塑性樹脂中に抵抗制御剤が均一に分散している。これを画像形成装置における中間転写方式の中間転写ベルトとして用いた場合、繰り返し使用によりベルト裏面が摩耗してすり減って行くが、抵抗制御剤が膜中に均一に分散しており、膜厚方向に抵抗変化がないため、ベルトの摩耗があってもバイアス調整の必要がなく、長期間継続して良好な画像を得ることができる。
【００３３】
（２）請求項１の無端状ベルトによる効果
この無端状ベルトでは、熱可塑性樹脂の結晶化度及び／又は結晶形態が、ベルト全体にわたって均一となっている。ベルト抵抗のバラツキの原因は、これを形成する熱可塑性樹脂の膜の構造差により、この熱可塑性樹脂中の抵抗制御剤が不均一な状態で分散することにある。また、膜の構造差は膜樹脂の結晶化の差で生じる。したがって、結晶化特性（結晶化度、結晶形態）を均質にすることで、抵抗分布の不均一をなくすことができ、これによりベルトの摩耗があってもバイアス調製の必要がなく、長期間継続して良好な画像を得ることができる。
また、上記（１）項及び（２）項に記載の請求項１の無端状ベルトによる効果は、請求項２の無端状ベルトによっても同様の効果が得られる。
【００３４】
（３）請求項３の無端状ベルト成形方法による効果
この無端状ベルト成形方法では、熱可塑性樹脂の液状溶液を成形型の表面に塗布した後、成形型の裏面側から加熱するか、または成形型の裏面側及び表面側から同時に加熱することにより、上記塗布膜を乾燥する。上記した結晶状態の差は、上記液状溶液からの析出結晶時の乾燥条件が異なってくることで発生する。すなわち、乾燥が早すぎると微小結晶が多発し、ゆっくりした乾燥では粗大結晶が形成される。したがって、塗布型内部（裏面）からの加熱（内部加熱）を行い、膜表面側と塗布膜の深部を同時に加熱することで、乾燥時に膜表面のみが早く乾燥することに起因して微小結晶と残部濃縮液が発生する問題を解決することができる。
【００３５】
（４）請求項４の無端状ベルト成形方法による効果
この成形方法では、塗布膜を乾燥した後に、該乾燥膜を成形型から剥離することを特徴とする。これにより、中間転写方式の中間転写ベルトとして用いることができる無端状ベルトが得られる。
【００３６】
（５）請求項５の無端状ベルト成形方法による効果
この成形方法では、成形型として熱伝導性の高い、金属材料からなるものを用いる。これにより、成形型上の塗布膜を均一、かつ迅速に乾燥することができ、本発明の所期の目的が達成される。成形型が熱の不良導体（断熱材）であると、内部加熱をしても熱が良好に伝わらないため、膜の表裏間で乾燥状態にムラが生じて結晶状態の差異、ひいては抵抗バラツキが生じるので、成形型は熱の良導体を用いなければならない。
【００３７】
（６）請求項６の無端状ベルト成形方法による効果
この成形方法では、抵抗制御剤を分散させた熱可塑性樹脂の液状溶液を１〜１０μｍの薄膜で成形型の表面に塗布したのち乾燥する操作を複数回繰り返す。塗布膜が薄い場合、表裏の乾燥の差が小さくなるため、薄膜を複数回形成して積層することで、膜厚方向の抵抗バラツキが発生しなくなる。
【００３８】
（７）請求項７の無端状ベルト成形方法による効果
この成形方法では、熱可塑性樹脂を、沸点８０℃以上の溶剤に分散させた分散液を遠心成形型に注入塗布したのち乾燥する。遠心成形で膜を形成して外部加熱する際、ベルト表面の乾燥は裏面より遅くなり、結晶状態の差が生じにくくなる。特に、高沸点の溶剤を用いることで、溶液からの析出結晶化の速度が抑えられるので、結晶化状態のバラツキが小さくなる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an endless belt and a forming method thereof, and more particularly to an intermediate transfer belt for an image forming apparatus having no variation in resistance in the film thickness direction and a forming method thereof. Technical fields to which the present invention can be applied include various resistance control films having uniform resistance in the film thickness direction and manufacturing techniques thereof.
[0002]
[Prior art]
In image forming apparatuses such as copiers, facsimiles, and printers, there has recently been a growing demand for multi-color, especially full-color reconstructed images. As an image forming apparatus that can meet these demands, a transfer-type image using an intermediate transfer member. Forming devices are widespread. In the intermediate transfer method, there are cases where a roller is used as an intermediate transfer member and a belt is used.
[0003]
In the image forming method using the intermediate transfer method, the latent image formed on the photosensitive member is visualized with a charge carrier toner, and the photosensitive member is superimposed on the intermediate transfer member in the primary transfer step (transfer of the visualized image). After the primary transfer, the visualized image is secondarily transferred to a transfer target (copy paper) in a secondary transfer step. In this image forming method, it is necessary to apply a bias voltage between the photosensitive member and the intermediate transfer member in order to move and transfer the charge carrier (toner) when transferring to the intermediate transfer member. This bias voltage is adjusted so as to obtain an optimum image.
[0004]
However, the conventional intermediate transfer belt has a problem that when the image forming apparatus is repeatedly used, the image quality gradually deteriorates with the initial applied bias. This problem can be solved to some extent by readjusting the bias, but fine adjustment for each belt is very troublesome and inconvenient from the viewpoint of maintenance.
[0005]
Therefore, as a result of the inventors examining and analyzing the cause of the above-described problem, in the conventional intermediate transfer belt, since the resistance control agent is unevenly dispersed in the thermoplastic resin, the thickness direction of the film (belt) It became clear that there was resistance variation.
[0006]
More specifically, when the intermediate transfer belt is repeatedly used, the intermediate transfer belt is worn by the driving roller and the film thickness gradually decreases from the back surface side. When the surface resistance of the back surface at that time is measured, an initial value of 10 is obtained. It was found that the thickness increased from 8 Ω to 10 11 Ω with a decrease in film thickness of 10 μm. As described above, the resistance becomes uneven in the film thickness direction of the belt (the resistance distribution in the film thickness direction occurs, that is, the resistance variation in the film thickness direction occurs). It was found that the distribution was not uniformly distributed in the direction and the resistance control agent was missing due to wear on the back of the belt. In addition, these problems occur because the crystal structure of the resin that is the base material of the belt is different in the film thickness direction. When forming the belt, it was found that heat distribution (temperature distribution, that is, temperature variation) occurs in the belt film thickness direction, and the fine structure of the resin differs.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide an endless belt having uniform resistance in the film thickness direction, particularly an intermediate transfer belt for an image forming apparatus, and a molding method thereof. In this way, an image forming apparatus can continuously obtain high-quality images for a long period of time. That is, an object of the present invention is to improve the characteristics of the intermediate transfer belt so that a good image can be continuously formed in an image forming apparatus using an intermediate transfer belt (belt-shaped intermediate transfer member). It is a thing.
[0008]
[Means for Solving the Problems]
The reason why the resistance variation in the film thickness direction (uneven distribution in the film thickness direction) occurs as described above is that the resistance control agent is not uniformly distributed in the film thickness direction in the belt. If the crystal structure of the base resin is different in the film thickness direction, the problem of resistance variation can be solved by making the crystal structure of the base resin uniform. For this purpose, the heat distribution (temperature distribution) at the time of belt molding (film formation) may be made uniform.
[0009]
In the present invention, a crystalline thermoplastic resin is used as the base material of the belt. Formation of a thin film for forming a belt is generally performed by (1) application of a melt or (2) application of a solution. In these cases,
(1) In the application of the melt, the raw material resin must be heated to the melting temperature, but the molten resin crystallizes due to solidification heat generation when the temperature is lowered.
(2) In the application of the solution, when the coating solution is dried to remove the solvent, the resin component is concentrated to become a supersaturated solution, and the resin component is precipitated and crystallized.
[0010]
The reason why the distribution state of the resistance control agent dispersed in the base material becomes non-uniform in the film thickness direction due to solidification by crystallization is as follows.
As for (1) above, as is known in the removal of impurities by zone melting, foreign matters are pushed out during solidification (solidification), and this is concentrated in an unsolidified residual liquid portion. In addition, in most cases of molded metal base tubes, which are molds for belt molding, the surface has many fine crystals, the inside is coarse crystals, and foreign element components are precipitated at the crystal interface. As is known from the above, the heat distribution during cooling of the melt affects the crystal structure of the molded product.
[0011]
In (2) above, when the base resin component is precipitated and crystallized by solvent evaporation near the surface, the dispersed component is squeezed out to concentrate the dispersed component in the residual liquid. This is as if the seawater was frozen, that is, when the seawater that originally contained various components was frozen, the salinity was excreted and decreased in the ice, and the concentration of the remaining seawater increased. Similar to that.
The present invention has been completed based on the above consideration.
[0012]
The endless belt according to claim 1 is characterized in that in the endless belt made of a thermoplastic resin, the resistance control agent is uniformly dispersed in the crystalline thermoplastic resin.
[0013]
The endless belt according to claim 1 is characterized in that the thermoplastic resin has a uniform crystallinity and / or crystal form throughout the belt.
Furthermore, the endless belt according to claim 2 is characterized by containing polyvinylidene fluoride.
[0014]
A method for forming an endless belt according to claim 3 is the method for forming an endless belt according to claim 1 or 2 , wherein a liquid solution of a thermoplastic resin is applied to the surface of a mold to form a coating film. After the formation, the coating film is dried by heating from the back side of the mold or by simultaneously heating from the back side and the front side of the mold.
[0015]
According to a fourth aspect of the present invention, there is provided the endless belt molding method according to the third aspect , wherein the dry film is peeled off from the mold after the coating film is dried.
[0016]
According to a fifth aspect of the present invention, there is provided an endless belt molding method according to the third or fourth aspect , wherein the molding die is made of a material having a high thermal conductivity (a good thermal conductor). Examples of such a mold include a metal material such as aluminum.
[0017]
A method for forming an endless belt according to claim 6 is a method for forming the endless belt according to claim 1, wherein a liquid solution of a thermoplastic resin in which a resistance control agent is dispersed is applied to the surface of the mold. An operation of applying a thin film having a film thickness of 1 to 10 μm and then drying it is repeated a plurality of times.
[0018]
Method of molding an endless belt according to claim 7, centrifuged to a method of forming an endless belt according to claim 1, the thermoplastic resin, a dispersion prepared by dispersing the boiling point 80 ° C. or more solvents It is characterized by being dried after being applied to a molding die.
[0019]
【Example】
Examples of the present invention will be described below.
Example 1
By mixing and stirring methyl ethyl ketone MEK (solvent) with 20 wt% of polyvinylidene fluoride PVDF and 4 wt% of carbon black as a conductive agent (resistance control agent), a coating liquid in which the above components were dispersed in the solvent was prepared. This coating solution is placed in a container, and a coating mold (molding mold) is dipped in the container and gradually pulled up. After forming a coating film having a film thickness of about 100 μm by a so-called dipping method, the solvent is heated and dried to form a film. . As the coating mold, an aluminum mold having a surface coated with a fluororesin film having a thickness of 1 μm or less and a mold produced by molding polyphenylene sulfide PPS were used.
[0020]
The heat drying conditions for removing the solvent are as follows:
1. The mold (with the coating solution applied) is simply placed in a furnace and dried (external drying).
2. Insert a heating element inside the mold and heat it from inside the mold (internal drying)
3. Simultaneous use of heating inside the mold and heating outside the mold,
And drying under heat at 130 ° C. below the crystal melting point (170 ° C.) of PVDF.
[0021]
After that, the formed film (intermediate transfer belt) is demolded and peeled off, the resistance in the thickness direction of the film, the crystallinity, and the crystal grain size are measured, and this film belt is mounted on an actual machine (Ricoh Pretail). Image evaluation. The results are shown in [Table 1] to [Table 3] below. In these tables, sample no. The film forming conditions of No. 5 are conventional belt manufacturing conditions. In the analysis of crystallinity, observation was performed using micro X-ray diffraction and micro-part Raman spectroscopy.
[0022]
[Table 1]
[Table 2]
[Table 3]
Example 2
The same dispersion (coating liquid) as in Example 1 was put in a container to form a coating film having a film thickness of about 10 μm with an aluminum coating mold, and then the solvent was heated and dried to form a film. This operation was repeated 10 times to produce a film having a thickness of 100 μm. In the same manner as in Example 1, the resistance of the film, crystallinity, and image characteristics with an actual machine were evaluated. The film resistance did not change in the film thickness direction, a surface resistance of 10 9 Ω was obtained, there was no variation in crystal form or crystallinity, image characteristics were not changed repeatedly, and bias adjustment was not necessary.
[0026]
Example 3
A coating solution was prepared by mixing and stirring carbon black as a conductive agent at a solid content ratio of 20 wt% to Kyner 203 (Sakai Industrial Co., Ltd.), which is a solution of 20 wt% of polyvinylidene fluoride PVDF dissolved in dimethylacetamide. This coating solution was injected and applied to a rotating aluminum coating mold and rotated at a high speed, and then the solvent was heated and dried by an external heating method to form a film having a thickness of about 100 μm.
[0027]
After demolding and peeling, the film resistance, crystallinity, and image characteristics with an actual machine were evaluated in the same manner as in Examples 1 and 2. The film resistance did not change in the film thickness direction, a surface resistance of 10 9 Ω was obtained, there was no variation in crystal form or crystallinity, image characteristics did not change repeatedly, and bias adjustment was not necessary.
A solution obtained by dissolving 20 wt% of polyvinylidene fluoride PVDF in ethanol which is a low boiling point solvent (mixed with carbon black as a conductive agent at a solid content ratio of 20 wt%) was similarly centrifugally molded, but it was injected to form a film. Since the solvent drying at that time was too early and the film was dried before the film thickness became uniform, a uniform film could not be formed.
[0028]
Example 4
Polyamide was dissolved in methanol, carbon black was dispersed as a resistance control agent at a solid content ratio of 20%, and this dispersion was dipped using the aluminum mold of Example 1. A film obtained by drying this coating film by external heating alone and a film obtained by drying by internal heating alone were prepared, and the resistance of each film was measured.
[0029]
In the film dried only by external heating, the resistance gradually increases when the surface resistance in the depth direction (film thickness direction) is measured by scraping from the back surface, whereas in the film by internal heating alone, the resistance in the depth direction is increased. There was no change in resistance. Further, as a result of analyzing the fine structure in the film thickness direction, the film formed only by external heating has a large number of fine crystals near the surface but becomes larger as it goes inside. On the other hand, in the film formed only by internal heating, the surface side and the back side were crystal grains having substantially the same diameter.
[0030]
Example 5
Polycarbonate was dissolved in tetrahydrofuran THF, carbon black was dispersed as a resistance control agent at a solid content ratio of 20%, and this dispersion was dipped using the aluminum mold of Example 1. A film obtained by drying this coating film by external heating alone and a film obtained by drying by internal heating alone were prepared, and the resistance of each film was measured.
[0031]
A film dried only by external heating is scraped from the back side and measured for surface resistance in the depth direction (film thickness direction), while the resistance gradually increases, whereas in the film only by internal heating, the depth direction There was no change in resistance. Also, as a result of analyzing the fine structure in the film thickness direction, the film formed only by external heating has many fine crystals near the surface, but becomes larger as it goes to the inside. On the side, the crystal grains had almost the same diameter.
[0032]
【The invention's effect】
As is apparent from the above description, the present invention provides the following effects.
(1) Effect of the endless belt according to claim 1 In this endless belt, the resistance control agent is uniformly dispersed in the crystalline thermoplastic resin. When this is used as an intermediate transfer belt of an intermediate transfer system in an image forming apparatus, the back surface of the belt is worn away and worn away by repeated use, but the resistance control agent is uniformly dispersed in the film, and in the film thickness direction. Since there is no resistance change, there is no need to adjust the bias even if the belt is worn, and a good image can be obtained continuously for a long time.
[0033]
(2) Effect of the endless belt according to claim 1 In this endless belt, the crystallinity and / or crystal form of the thermoplastic resin is uniform throughout the belt. The cause of the belt resistance variation is that the resistance control agent in the thermoplastic resin is dispersed in a non-uniform state due to the difference in the structure of the thermoplastic resin film forming the belt resistance. Further, the difference in the structure of the film is caused by the difference in crystallization of the film resin. Therefore, by homogenizing the crystallization characteristics (crystallinity, crystal form), it is possible to eliminate non-uniform resistance distribution, which eliminates the need for bias preparation even if there is belt wear, and continues for a long period of time. And a good image can be obtained.
The effect of the endless belt according to claim 1 described in the above items (1) and (2) can be obtained by the endless belt according to claim 2.
[0034]
(3) Effect of the endless belt molding method of claim 3 In this endless belt molding method, a liquid solution of a thermoplastic resin is applied to the surface of the mold and then heated from the back side of the mold or molded. The coating film is dried by simultaneously heating from the back side and the front side of the mold. The difference in the crystal state described above occurs due to different drying conditions at the time of precipitation crystal from the liquid solution. That is, if drying is too early, microcrystals occur frequently, and if dried slowly, coarse crystals are formed. Therefore, by heating (internal heating) from the inside of the coating mold (back surface) and simultaneously heating the film surface side and the deep part of the coating film, only the film surface dries quickly during drying. The problem that the remaining concentrated liquid is generated can be solved.
[0035]
(4) Effect of Endless Belt Forming Method of Claim 4 This forming method is characterized in that after the coating film is dried, the dry film is peeled off from the mold. Thereby, an endless belt that can be used as an intermediate transfer belt of an intermediate transfer system is obtained.
[0036]
(5) Effect of Endless Belt Forming Method of Claim 5 In this forming method, a mold made of a metal material having high thermal conductivity is used. Thereby, the coating film on the mold can be dried uniformly and rapidly, and the intended object of the present invention is achieved. If the mold is a poor heat conductor (heat insulating material), heat will not be transmitted well even if it is internally heated, resulting in unevenness in the dry state between the front and back of the film, resulting in differences in the crystalline state and consequently resistance variations. As a result, the mold must use a good thermal conductor.
[0037]
(6) Effect of Endless Belt Molding Method of Claim 6 In this molding method, a liquid solution of a thermoplastic resin in which a resistance control agent is dispersed is applied to the surface of the mold with a thin film of 1 to 10 μm and then dried. Repeat several times. When the coating film is thin, the difference in drying between the front and back surfaces becomes small. Therefore, resistance variation in the film thickness direction does not occur by forming and laminating the thin film a plurality of times.
[0038]
(7) Effect of Endless Belt Molding Method of Claim 7 In this molding method, a dispersion liquid in which a thermoplastic resin is dispersed in a solvent having a boiling point of 80 ° C. or more is poured and applied to a centrifugal mold and then dried. When a film is formed by centrifugal molding and externally heated, drying of the belt surface is slower than the back surface, and the difference in crystal state is less likely to occur. In particular, by using a high boiling point solvent, the rate of precipitation crystallization from the solution can be suppressed, so that the variation in the crystallization state is reduced.
Claims (7)
結晶質の熱可塑性樹脂中に抵抗制御剤が均一に分散しており、
前記熱可塑性樹脂の結晶化度および／又は結晶形態が、ベルト全体にわたって均一であることを特徴とする無端状ベルト。In an endless belt made of thermoplastic resin,
The resistance control agent is uniformly dispersed in the crystalline thermoplastic resin,
An endless belt, wherein the thermoplastic resin has a uniform crystallinity and / or crystal form throughout the belt.
熱可塑性樹脂の液状溶液を成形型の表面に塗布して塗布膜を形成した後、
成形型の裏面側から加熱するか、または成形型の裏面側および表面側から同時に加熱することにより、前記塗布膜を乾燥することを特徴とする無端状ベルトの成形方法。A method for forming an endless belt according to claim 1 or 2 ,
After applying a liquid solution of thermoplastic resin to the surface of the mold to form a coating film,
A method for molding an endless belt, wherein the coating film is dried by heating from the back side of the mold or simultaneously heating from the back side and the front side of the mold.
抵抗制御剤を分散させた熱可塑性樹脂の液状溶液を、成形型の表面に膜厚１〜１０μｍの薄膜として塗布したのち乾燥する操作を複数回繰り返すことを特徴とする無端状ベルトの成形方法。An endless belt comprising a thermoplastic resin, wherein the resistance control agent is uniformly dispersed in the crystalline thermoplastic resin, and the crystallinity and / or crystal form of the thermoplastic resin is uniform throughout the belt. A molding method,
A method for molding an endless belt, wherein a liquid solution of a thermoplastic resin in which a resistance control agent is dispersed is applied as a thin film having a film thickness of 1 to 10 μm on the surface of a mold and then dried a plurality of times.
熱可塑性樹脂を、沸点８０℃以上の溶剤に分散させた分散液を遠心成形用の成形型に塗布した後、乾燥することを特徴とする無端状ベルトの成形方法。An endless belt comprising a thermoplastic resin, wherein the resistance control agent is uniformly dispersed in the crystalline thermoplastic resin, and the crystallinity and / or crystal form of the thermoplastic resin is uniform throughout the belt. A molding method,
A method for forming an endless belt, comprising: applying a dispersion obtained by dispersing a thermoplastic resin in a solvent having a boiling point of 80 ° C or higher to a mold for centrifugal molding, and then drying.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35436199A JP4091722B2 (en) | 1999-12-14 | 1999-12-14 | Endless belt and method of forming the same |
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| JP35436199A JP4091722B2 (en) | 1999-12-14 | 1999-12-14 | Endless belt and method of forming the same |
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| JP4799214B2 (en) * | 2006-03-02 | 2011-10-26 | キヤノン株式会社 | Seamless belt and image forming apparatus using the same |
| JP5102058B2 (en) * | 2007-08-30 | 2012-12-19 | 株式会社リコー | A method for measuring an electrical resistance distribution in a film thickness direction of a conductive polymer sheet, and an intermediate transfer medium and an intermediate transfer medium made of the conductive polymer sheet. |
| JP5084412B2 (en) * | 2007-09-07 | 2012-11-28 | キヤノン株式会社 | Image forming apparatus and intermediate transfer belt |
| JP6780399B2 (en) * | 2016-09-16 | 2020-11-04 | コニカミノルタ株式会社 | Intermediate transfer belt manufacturing equipment and manufacturing method |
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