JP3868147B2

JP3868147B2 - Centrifugal forming method and apparatus

Info

Publication number: JP3868147B2
Application number: JP13475899A
Authority: JP
Inventors: 稔松尾; 亜希子田中
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 1999-05-14
Filing date: 1999-05-14
Publication date: 2007-01-17
Anticipated expiration: 2019-05-14
Also published as: JP2000317959A

Description

【０００１】
【発明の属する技術分野】
本発明は、液状物質を型内に注入し、該型を回転させながら該液状物質を乾燥させ、その遠心力により該型の内面形状にならった製品を形成する遠心形成方法及び装置に関するものである。
【０００２】
【従来の技術】
遠心形成方法は、ゴムおよびプラスチックをはじめとする製品の形成方法として、種々の工業分野において広範に用いられている技術である。例えば、電子写真複写機、ファクシミリ、あるいはプリンタ等の画像形成装置におけるトナー像又は転写材の担持体である無端状ベルトの形成方法にも用いられている。
【０００３】
上記遠心形成方法は、周知の如く円筒状の型内面に、製品の原料となる液状物質をスプレーで塗布、あるいはノズルから流し込み、該型を高速回転させながら該液状物質を乾燥させ、その遠心力により該型の内面形状にならった無端膜を形成するものである。液状物質として熱硬化性物質等を用いる場合には、遠心形成した無端膜を、さらに加熱により硬化反応を行う。
【０００４】
このような遠心形成方法における無端膜の成膜条件としては、上記型の内径をＤ、回転角速度をω（sec^-1)とすると、ω＝４２．３／（Ｄ）^１／２の関係を満たす必要があることが知られている。これは、塗布型の水平回転時に、該型上部の液状物質が重力によって落下しないぎりぎりの条件が、該型の回転による遠心力の加速度Ｄω^２と液状物質の重力加速度ｇ＝９８０とが釣り合うＤω^２＝９８０のときであり、これにより得られるω＝３１．３／（Ｄ）^１／２に安全係数をかけたものである（（株）高分子刊行会「ＦＲＰ成形の実際」参照）。また、該型の回転数Ｒ(rpm)は、ω＝２π×６０／Ｒの関係より求められる。
【０００５】
ところで、上記無端膜の乾燥後に上記型の回転を停止するときには、無端膜の乾燥が不充分であると、流動して液だれや膜厚ばらつきが生じてしまう。この問題を防ぐためには、無端膜が完全に乾燥固化した後に該型の回転を停止すればよいが、無端膜を完全に乾燥させるために加熱時間を必要以上に長くしすぎたり、加熱温度を高くしすぎたりすると、生産効率を低下させてしまう。また、無端膜を過剰に乾燥しすぎると、型の種類によっては、型面との接着力を増大させて膜の剥離脱型が困難になるという問題もある。
【０００６】
そこで、このような問題を解決するために、無端膜の乾燥状態を、過剰な乾燥による生産効率の低下や膜の剥離脱型不良がなく、且つ乾燥不足による無端膜の液だれや膜厚ばらつきのない最適な状態に制御することが望ましい。
【０００７】
ここで、無端膜が上記のような最適状態となるのは、経験的に、いわゆる指触乾燥と呼ばれる指で軽く触れたときに粘着性を感じる状態であることが判っている。また、この指触乾燥レベルにおける無端膜中の残留溶媒重量は、固形分重量に対して３対１以下であることも判っている。そこで、無端膜の乾燥状態を制御する方法の１つとして、予め単位面積当たりの塗布液重量と該塗布液重量の固形分の割合とを計測し、この計測結果に応じて、予め実験等で求めておいた加熱条件で加熱することにより、無端膜を指触乾燥状態に制御する方法が考えられる。ところが、この方法においては、加熱時の送風風量や加熱温度上昇のパターンなどの条件を常に一定に保つことは困難であり、完全に最適な状態に制御できるものではない。
【０００８】
【発明が解決しようとする課題】
本発明は以上の背景に鑑みなされたものであり、その目的とするところは、液状物質を型内に注入し、該型を回転させながら該液状物質を乾燥させ、その遠心力により該型の内面形状にならった製品を形成する遠心形成方法及び装置において、液状物質の乾燥状態を、過剰な乾燥による生産効率の低下や遠心成形後の剥離脱型不良がなく、且つ乾燥不足による液状物質の液だれや厚さばらつきのない最適な状態に制御可能にすることである。
【０００９】
【課題を解決するための手段】
上記目的を達成するために、請求項１の発明は、液状物質を型内に注入し、該型を回転させながら該液状物質を乾燥させ、その遠心力により該型の内面形状にならった製品を形成する遠心形成方法において、上記液状物質に対して光を発する発光部と、該発光部から発せられ該液状物質表面で反射した光を受光する受光部とを有する光学センサにより、上記液状物質の乾燥中に該液状物質の乾燥状態を検知し、該受光部で受光される反射光強度が減少から増加に転ずる時点で、該乾燥を停止するものである。
ここで、液状物質の乾燥は、上記型を回転させながら、自然乾燥させてもよいし、加熱して乾燥させてもよい。
請求項２の発明は、液状物質を注入した型を回転させる回転手段と、該液状物質を加熱する加熱手段とを備え、該型を回転させながら該液状物質を乾燥又は硬化させ、その遠心力により該型の内面形状にならった製品を形成する遠心形成装置において、上記液状物質に対して光を発する発光部と、該発光部から発せられ該液状物質表面で反射した光を受光する受光部とを有する光学センサと、該受光部で受光される反射光強度が減少から増加に転じた時点で報知を行う報知手段とを設けたことを特徴とするものである。ここで、報知手段は、表示による報知を行うものに限らず、音などによる報知を行うものでもよい。
請求項３の発明は、液状物質を注入した型を回転させる回転手段と、該液状物質を加熱する加熱手段とを備え、該型を回転させながら該液状物質を乾燥又は硬化させ、その遠心力により該型の内面形状にならった製品を形成する遠心形成装置において、上記液状物質に対して光を発する発光部と、該発光部から発せられ該液状物質表面で反射した光を受光する受光部とを有する光学センサと、該受光部で受光される反射光強度が減少から増加に転じた時点で回転手段による回転と上記加熱手段の加熱とを停止する手段とを設けたことを特徴とするものである。
【００１０】
発光部から発した光が、上記液状物質表面で反射し、反射光が受光部で受光され、この反射光強度から、該液状物質の乾燥状態を検知する。反射光強度は、該液状物質の乾燥状態に応じて次のように変化する。乾燥初期では、光沢のある液表面で光が反射するため反射光強度が大きく、乾燥が進むにつれて、液中の溶媒が蒸発して液表面がざらつき、光が乱反射するようになり、反射光強度が徐々に減少していく。乾燥が進むと、液状物質がいわゆる指触乾燥と呼ばれる指で軽く触れたときに粘着性を感じる程度に達し、表面が平滑化して少しずつ光沢をもつようになり、この時点で、反射光強度は再び増加傾向に転ずる。
そこで、請求項１の遠心形成方法においては、反射光強度が減少から増加に転ずる時点で乾燥を停止することにより、液状物質を指触乾燥状態に制御する。したがって、液状物質の乾燥状態を、過剰な乾燥による生産効率の低下や遠心成形後の剥離脱型不良がなく、且つ乾燥不足による液状物質の液だれや厚さばらつきのない最適な状態に制御することができる。
また、請求項２の遠心形成装置においては、反射光強度が減少から増加に転じたことを報知手段で報知する。この報知で、該液状物質の乾燥中に乾燥状態を作業者が認識できる。このことから、作業者が、上記回転手段を停止するといった所定の処置動作を行うことにより、該液状物質の乾燥状態を、過剰な乾燥による生産効率の低下や遠心成形後の剥離脱型不良がなく、且つ乾燥不足による液状物質の液だれや厚さばらつきのない最適な状態に制御することができる。
また、請求項３の遠心形成装置においては、受光部で受光される反射光強度が減少から増加に転じた時点で回転手段による回転を停止することにより、液状物質を指触乾燥状態に制御する。したがって、液状物質の乾燥状態を、過剰な乾燥による生産効率の低下や遠心成形後の剥離脱型不良がなく、且つ乾燥不足による液状物質の液だれや厚さばらつきのない最適な状態に制御することができる。
【００１１】
ここで、上記液状物質が熱硬化性物質である場合には、上記乾燥後に、さらに加熱して硬化反応を行う必要がある。硬化反応を行うための加熱方法としては、上記乾燥後に、型ごと別の加熱炉で加熱する方法と、上記乾燥後に、引き続き型を回転させながら、該液状物質が硬化し得る程度の温度に設定して加熱する方法とがあるが、乾燥に引き続いて硬化反応を行う場合には、上記乾燥と同様に、過剰な加熱による生産効率の低下や剥離脱型不良が発生するおそれがある。
【００１２】
そこで、請求項３の発明は、上記型に注入さした液状物質を加熱する加熱手段も備え、上記時点で該加熱手段の加熱を停止する。
【００１３】
上記時点で該加熱手段の加熱を停止することにより、乾燥に引き続いて硬化反応を行う場合においても、液状物質の乾燥及び硬化状態を、過剰な加熱による生産効率の低下や剥離脱型不良がない最適な状態に制御することができる。
【００２０】
【発明の実施の形態】
以下、本発明に係る遠心形成方法の一実施形態として、電子写真複写機、ファクシミリ、およびプリンター等の画像形成装置におけるトナー像又は転写材の担持体である無端状ベルトを形成する場合を例に説明する。
【００２１】
本実施形態においては、ポリイミドを基本素材とする無端状ベルトを形成する。
図１は、遠心形成用の円筒状の型１を、型１の内周面上に形成された無端状ベルト用無端膜２（以下、単に無端膜２と称する）とともに示す断面図である。図中の一点鎖線は遠心形成の工程における型１の回転軸線３を示している。本実施形態においては、型１としてアルミの金型を使用した。無端膜２は、ベルト原料である液状物質が遠心形成方法により型１内周面に形成されたものである。本実施形態においては、液状物質としてポリアミド酸溶液を用いた。ポリアミド酸は、熱又は触媒によってイミド閉環することによりポリイミドに変化する性質を有する。ポリアミド酸溶液は、市販のポリイミド前駆体溶液（東レ製：トレニース＃３０００）を、有機溶剤であるＮ−Ｎジメチルアセトアミド（以下、ＤＭＡＣと称する）によって３０％に希釈したものを使用した。なお、本実施形態においては、無端状ベルトの基本素材としてポリイミドを用いたが、これに限定されるものではない。
【００２２】
図１において、周知の遠心形成方法の技術により無端膜２を形成する。具体的には、上記液状物質としてのポリアミド酸溶液を型１に塗布し、該型１を１０００rpmで高速回転させて型内周面上に均一な所定膜厚の無端膜２を形成する。
【００２３】
次いで、型１を回転させながら、上記のように形成された無端膜２を図示を省略した加熱手段によって加熱し、無端膜中の溶剤ＤＭＡＣを蒸発させて無端膜２を乾燥固化させる。そして、無端膜２を最終的にポリイミドベルトに仕上げるために、さらに加熱して無端膜２を硬化させ、その後、冷却を経て、型１から剥離脱型することにより、ポリイミドを基本素材とする無端状ベルトを得る。
【００２４】
ここで、上記の遠心形成方法においては、無端膜２の乾燥後に型１の回転を停止するときには、無端膜２の乾燥が不充分であると、流動して液だれや膜厚ばらつきが生じてしまう。この問題を防ぐためには、無端膜２が完全に乾燥固化した後に型１の回転を停止すればよいが、無端膜２を完全に乾燥させるために加熱時間を必要以上に長くしすぎたり、加熱温度を高くしすぎたりすると、生産効率を低下させてしまう。また、無端膜２を過剰に乾燥しすぎると、型の種類によっては、型面との接着力を増大させて膜の剥離脱型が困難になるという問題もある。また、乾燥に引き続いて硬化反応を行う場合にも、同様に、過剰な加熱による生産効率の低下や剥離脱型不良が発生するおそれがある。したがって、このような問題を解決するためには、無端膜２の乾燥状態を、過剰な乾燥による生産効率の低下や膜の剥離脱型不良がなく、且つ乾燥不足による無端膜の液だれや膜厚ばらつきのない最適な状態に制御することが望ましい。
【００２５】
そこで、無端膜２を最適な状態に制御するために、本発明者等は、無端膜２を形成するポリアミド酸溶液を平板に塗布し、加熱しながら該溶液の表面を目視観察することにより、該溶液の乾燥・硬化が進むに従って、液表面の光沢や色調が変化することを見出した。そして、このポリアミド酸溶液表面の状態変化を利用して、光センサで液表面の反射光を測定することで、ポリアミド酸溶液の乾燥・硬化状態を検知できることが判明した。
【００２６】
図２は、平板に塗布したポリアミド酸溶液を加熱しながら、該溶液に対して光を照射し、液表面で反射された反射光強度を測定した結果を示すグラフである。縦軸に反射光強度Ｉを、横軸に加熱時間ｔを示す。
図２に示すように、加熱開始時はポリアミド酸溶液の光沢のある液表面で光が反射するため反射光強度Ｉが大きく、加熱が進むにつれて、液中の溶剤ＤＭＡＣが蒸発して表面がざらついた黄濁した乾燥膜となる。このとき、光が膜表面で乱反射するようになり、反射光強度が徐々に減少する。さらに加熱が進むと、乾燥膜がいわゆる指触乾燥と呼ばれる指で軽く触れたときに粘着性を感じる程度に達し、膜表面が平滑化して少しずつ光沢をもつようになり、この時点で、反射光強度は再び増加傾向に転ずる。そして、さらに加熱が進むと、硬化して膜表面の光沢が増していき反射光強度も増加するが、ある程度まで硬化が進んで膜表面の色調が濃くなっていくと、反射光強度は再び減少傾向に転ずる。さらに加熱が進むと、膜表面は褐黒化して反射光強度はさらに減少する。
【００２７】
このように、ポリアミド酸溶液の乾燥・硬化状態に応じて反射光強度が変化するため、反射光強度を測定することにより、例えば、反射光強度と該溶液の乾燥・硬化状態との関係を予めデータテーブルなどの形でもたせておくことで、該溶液の乾燥・硬化状態を検知できることができることがわかった。
【００２８】
次に、実際の遠心形成方法によるポリアミド酸溶液の乾燥・硬化処理において、反射光強度を測定する場合の具体例を説明する。
【００２９】
図３は、図１で示した型１の内部に、型１端部の図示しない保持治具の空洞部から、光センサを備えた支持体３を挿入した状態を示す図である。光学センサは、ポリアミド酸溶液が遠心形成された無端膜２に対して光を発する発光部としての発光素子４と、該発光素子４から発せられ無端膜２表面で反射した光を受光する受光部としての受光素子５から構成されている。
【００３０】
図３において、型１を回転させながら図示しない加熱手段により無端膜２を加熱する。そして無端膜２を加熱中に、型１に上記支持体３を挿入し、無端膜２に向かって発光素子４から光を照射すると、光は無端膜２表面で反射し、この反射光を受光素子５で受光して、無端膜２の反射光強度を測定する。
【００３１】
下表１に、塗布膜２の加熱時間及び加熱温度を種々変化させたときの、反射光強度の測定結果を示す。また、型１の回転及び加熱を停止した後、無端膜２が乾燥固化あるいは半硬化した状態の無端膜２を観察した結果を示す。また、その後、別の加熱炉で硬化処理を行って最終的な成膜状態を観察した結果、及び、型１からの剥離脱型状況も示す。
【表１】

【００３２】
表１より、無端膜２が、過剰な乾燥による生産効率の低下や剥離脱型不良がなく、且つ乾燥不足による流動変形のない最適な状態となるのは、反射光強度が減少から増加に転ずる時点付近であることがわかる。したがって、反射光強度が減少から増加に転ずる時点で、型１の回転及び無端膜２の加熱停止することにより、無端膜２を最適な状態に制御できる。具体的には、例えば、上記反射光強度を出力する報知手段としての表示モニターを設け、作業者がこれを監視して、反射光強度が減少から増加に転した時点で、型１の回転及び加熱を停止してもよいし、反射光強度が減少から増加に転した時点で、音などを発するように構成された報知手段を設けてもよい。また、反射光強度が減少から増加に転した時点で、型１の回転及び加熱を停止するように制御する制御手段を設け、型１の回転及び加熱の停止を自動的に行うようにしてもよい。
【００３３】
なお、上図２のグラフで示した、反射光強度は、ポリアミド酸溶液の濃度、液厚みなど、様々な要因で変化するが、反射光強度の増減の推移は、いづれの場合でも同様の傾向を示すので、乾燥・硬化状態の検知に使用可能である。また、溶剤蒸発と硬化反応の進行及び膜変質は、グラフ中で示したように明確に区別されるものではなく、同時進行していくものであるが、型１の回転及び加熱の継続あるいは停止を決定する手段として有効である。
【００３４】
以上、本実施形態においては、無端膜２の加熱中に該無端膜２の乾燥状態を検知し、この検知結果に基づいて、該乾燥を継続するか停止するかを決定するので、無端膜２を所望の乾燥状態に制御できる。したがって、過剰な乾燥による生産効率の低下や遠心成形後の剥離脱型不良がなく、且つ乾燥不足による無端膜２の液だれや厚さばらつきのない最適な状態に制御することができる。
【００３５】
なお、実施形態においては、電子写真複写機、ファクシミリ、およびプリンター等の画像形成装置におけるトナー像又は転写材の担持体である無端状ベルトを形成する場合を例に説明したが、液状物質を型内に注入し、該型を回転させながら該液状物質を乾燥させ、その遠心力により該型の内面形状にならった製品を形成する遠心形成方法であれば適用可能である。
【００３６】
【発明の効果】
請求項１乃至３の発明によれば、液状物質の過剰乾燥や乾燥不足を防止できるので、液状物質の乾燥状態を、過剰な乾燥による生産効率の低下や遠心成形後の剥離脱型不良がなく、且つ乾燥不足による液状物質の液だれや厚さばらつきのない最適な状態に制御することができるという優れた効果がある。
【図面の簡単な説明】
【図１】本実施形態に係る遠心形成方法を説明するための説明図。
【図２】ポリアミド酸溶液の加熱時間と該溶液に照射した光の反射光強度の関係を示すグラフ。
【図３】ポリアミド酸溶液の反射光強度を測定する方法を説明するための説明図。
【符号の説明】
１型
２無端膜
３支持体
４発光素子
５受光素子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a centrifugal forming method and apparatus for injecting a liquid substance into a mold, drying the liquid substance while rotating the mold, and forming a product having the shape of the inner surface of the mold by the centrifugal force. is there.
[0002]
[Prior art]
The centrifugal forming method is a technique widely used in various industrial fields as a method for forming products such as rubber and plastic. For example, it is also used in a method for forming an endless belt that is a carrier for a toner image or a transfer material in an image forming apparatus such as an electrophotographic copying machine, a facsimile machine, or a printer.
[0003]
As is well known, the above-mentioned centrifugal forming method is applied to a cylindrical mold inner surface by spraying a liquid substance as a raw material of a product, or pouring from a nozzle, and drying the liquid substance while rotating the mold at a high speed. Thus, an endless film having the inner shape of the mold is formed. When a thermosetting substance or the like is used as the liquid substance, the endless film formed by centrifugation is further subjected to a curing reaction by heating.
[0004]
As a film forming condition of the endless film in such a centrifugal forming method, assuming that the inner diameter of the mold is D and the rotational angular velocity is ω (sec ⁻¹ ), the relationship of ω = 42.3 / (D) ^1/2 is obtained. It is known that needs to be met. This is because, when the coating mold is rotated horizontally, the condition that the liquid material on the upper part of the mold does not fall due to gravity is balanced by the centrifugal force acceleration Dω ² due to the rotation of the mold and the gravity acceleration g = 980 of the liquid material. ² = 980, which is obtained by multiplying ω = 31.3 / (D) ^1/2 obtained by this by a safety factor (see “Actuals of FRP molding” by Kobunshi Publishing Co., Ltd.). The rotational speed R (rpm) of the mold is obtained from the relationship of ω = 2π × 60 / R.
[0005]
By the way, when the rotation of the mold is stopped after the endless film has been dried, if the endless film is not sufficiently dried, it will flow to cause dripping and variations in film thickness. In order to prevent this problem, it is only necessary to stop the rotation of the mold after the endless film is completely dried and solidified. However, in order to completely dry the endless film, the heating time is excessively longer than necessary, or the heating temperature is decreased. If it is too high, production efficiency will be reduced. Further, if the endless film is excessively dried, depending on the type of the mold, there is a problem in that the adhesive strength with the mold surface is increased and it is difficult to peel and remove the film.
[0006]
Therefore, in order to solve such problems, the dry state of the endless film is not reduced in production efficiency due to excessive drying, and there is no defective film peeling and demolding. It is desirable to control to an optimal state without any problem.
[0007]
Here, it has been empirically found that the endless film is in the optimum state as described above when it is lightly touched with a finger, so-called dry to touch. It has also been found that the residual solvent weight in the endless film at this dry-to-touch level is 3 to 1 or less with respect to the solid content weight. Therefore, as one of the methods for controlling the dry state of the endless film, the weight of the coating liquid per unit area and the ratio of the solid content of the weight of the coating liquid are measured in advance. A method is conceivable in which the endless film is controlled to be dry to the touch by heating under the required heating conditions. However, in this method, it is difficult to always keep the conditions such as the amount of blown air during heating and the heating temperature rise pattern constant, and it is not possible to completely control the conditions.
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of the above background. The object of the present invention is to inject a liquid substance into a mold, dry the liquid substance while rotating the mold, and use the centrifugal force of the mold. In a centrifuge forming method and apparatus for forming a product that conforms to the inner surface shape, there is no decrease in production efficiency due to excessive drying, there is no decrease in production efficiency due to excessive drying, and there is no defect in demolding after centrifugal molding. It is to be able to control to an optimal state without dripping or variation in thickness.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 is a product in which a liquid substance is poured into a mold, the liquid substance is dried while the mold is rotated, and the inner shape of the mold is obtained by centrifugal force. In the centrifugal forming method, the liquid substance is obtained by an optical sensor having a light emitting part that emits light to the liquid substance and a light receiving part that receives light emitted from the light emitting part and reflected by the surface of the liquid substance. of in dry detects the dryness of the liquid material, at the time when the reflected light intensity received by the light receiving portion starts to increase from decreasing, those that abolish stop the drying.
Here, the liquid substance may be dried naturally while rotating the mold, or may be dried by heating.
The invention of claim 2 includes a rotating means for rotating the mold into which the liquid material has been injected and a heating means for heating the liquid material, and the liquid material is dried or cured while rotating the mold, and the centrifugal force In the centrifugal forming apparatus for forming a product that conforms to the inner shape of the mold, a light emitting unit that emits light to the liquid material, and a light receiving unit that receives light emitted from the light emitting unit and reflected from the surface of the liquid material And an informing means for informing when the intensity of the reflected light received by the light receiving unit starts from decreasing to increasing. Here, the notification means is not limited to the notification by display, but may be notification by sound or the like.
The invention of claim 3 comprises a rotating means for rotating the mold into which the liquid material has been injected and a heating means for heating the liquid material, and the liquid material is dried or hardened while rotating the mold, and the centrifugal force thereof. In the centrifugal forming apparatus for forming a product that conforms to the inner shape of the mold, a light emitting unit that emits light to the liquid material, and a light receiving unit that receives light emitted from the light emitting unit and reflected from the surface of the liquid material And a means for stopping rotation by the rotating means and heating of the heating means when the intensity of the reflected light received by the light receiving portion starts from decreasing to increasing. Is.
[0010]
The light emitted from the light emitting part is reflected by the surface of the liquid material, and the reflected light is received by the light receiving part, and the dry state of the liquid substance is detected from the reflected light intensity. The reflected light intensity changes as follows according to the dry state of the liquid substance. At the initial stage of drying, the reflected light intensity is large because light is reflected from the glossy liquid surface. As the drying progresses, the solvent in the liquid evaporates and the liquid surface becomes rough, and the light is irregularly reflected. Gradually decreases. As drying progresses, the liquid material reaches a level where it feels sticky when touched lightly with the so-called finger touch drying, and the surface becomes smooth and gradually glossy. At this point, the reflected light intensity Will start to increase again.
Therefore, in the centrifugal forming method according to the first aspect, the liquid substance is controlled to be dry to the touch by stopping the drying when the reflected light intensity starts to increase from the decrease. Therefore, the dry state of the liquid material is controlled to an optimum state that does not cause a decrease in production efficiency due to excessive drying, peeling-off mold failure after centrifugal molding, and no liquid dripping or thickness variation due to insufficient drying. be able to.
Further, in the centrifugal forming apparatus according to the second aspect, the notifying means notifies that the reflected light intensity has changed from decreasing to increasing. By this notification, the operator can recognize the dry state during the drying of the liquid substance. From this, when the operator performs a predetermined treatment operation such as stopping the rotating means, the liquid material is dried to reduce the production efficiency due to excessive drying, and the peeling and demolding failure after centrifugal molding. In addition, it is possible to control to an optimum state in which there is no liquid dripping or thickness variation due to insufficient drying.
According to a third aspect of the present invention, the liquid material is controlled to be dry to the touch by stopping the rotation by the rotating means when the intensity of the reflected light received by the light receiving unit starts from decreasing to increasing. . Therefore, the dry state of the liquid material is controlled to an optimum state that does not cause a decrease in production efficiency due to excessive drying, peeling-off mold failure after centrifugal molding, and no liquid dripping or thickness variation due to insufficient drying. be able to.
[0011]
Here, when the liquid material is a thermosetting material, it is necessary to further heat and perform a curing reaction after the drying. As a heating method for performing the curing reaction, a method of heating in a separate heating furnace for each mold after the drying, and a temperature at which the liquid substance can be cured while continuing to rotate the mold after the drying is set. However, when the curing reaction is carried out subsequent to drying, there is a risk that production efficiency may be reduced due to excessive heating and peeling and demolding failure may occur as in the case of the drying described above.
[0012]
Accordingly, the invention of claim 3 is also provided with a heating means for heating the liquid material injected into the mold, and the heating of the heating means is stopped at the time point.
[0013]
By stopping heating of the heating means at the above point , even when a curing reaction is performed subsequent to drying, the drying and curing state of the liquid substance is not reduced by excessive heating and there is no deterioration in the peeling and demolding. It can be controlled to an optimum state.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, as an embodiment of the centrifugal forming method according to the present invention, an example of forming an endless belt which is a carrier for a toner image or a transfer material in an image forming apparatus such as an electrophotographic copying machine, a facsimile machine, and a printer is taken as an example. explain.
[0021]
In the present embodiment, an endless belt having polyimide as a basic material is formed.
FIG. 1 is a cross-sectional view showing a cylindrical mold 1 for centrifugal formation together with an endless belt endless film 2 (hereinafter simply referred to as endless film 2) formed on the inner peripheral surface of the mold 1. FIG. The one-dot chain line in the figure shows the rotation axis 3 of the mold 1 in the centrifugal forming process. In this embodiment, an aluminum mold is used as the mold 1. The endless film 2 is formed by forming a liquid material as a belt material on the inner peripheral surface of the mold 1 by a centrifugal forming method. In the present embodiment, a polyamic acid solution is used as the liquid substance. Polyamic acid has the property of changing to polyimide by ring closure of imide with heat or a catalyst. As the polyamic acid solution, a commercially available polyimide precursor solution (Toray Industries, Inc .: Torenice # 3000) diluted to 30% with an organic solvent NN dimethylacetamide (hereinafter referred to as DMAC) was used. In the present embodiment, polyimide is used as the basic material of the endless belt, but the present invention is not limited to this.
[0022]
In FIG. 1, an endless membrane 2 is formed by a known centrifugal forming technique. Specifically, the polyamic acid solution as the liquid material is applied to the mold 1 and the mold 1 is rotated at a high speed of 1000 rpm to form an endless film 2 having a uniform predetermined thickness on the inner peripheral surface of the mold.
[0023]
Next, while rotating the mold 1, the endless film 2 formed as described above is heated by a heating means (not shown), and the solvent DMAC in the endless film is evaporated to dry and solidify the endless film 2. Then, in order to finally finish the endless film 2 into a polyimide belt, the endless film 2 is further heated to cure the endless film 2, and then cooled and peeled off from the mold 1 to endlessly use polyimide as a basic material. Get a belt.
[0024]
Here, in the above-described centrifugal forming method, when the rotation of the mold 1 is stopped after the endless film 2 is dried, if the endless film 2 is insufficiently dried, it will flow, resulting in dripping and variation in film thickness. End up. In order to prevent this problem, it is only necessary to stop the rotation of the mold 1 after the endless film 2 is completely dried and solidified. However, in order to completely dry the endless film 2, the heating time is excessively longer than necessary, If the temperature is set too high, production efficiency will be reduced. Further, if the endless film 2 is excessively dried, depending on the type of the mold, there is a problem that the adhesive strength with the mold surface is increased and it becomes difficult to peel and remove the film. Similarly, when the curing reaction is carried out subsequent to drying, there is a possibility that production efficiency is reduced due to excessive heating and peeling and demolding failure may occur. Therefore, in order to solve such a problem, the endless film 2 is dried without causing a decrease in production efficiency due to excessive drying or a film peeling and demolding failure. It is desirable to control to an optimum state with no thickness variation.
[0025]
Therefore, in order to control the endless film 2 to an optimum state, the present inventors apply a polyamic acid solution forming the endless film 2 to a flat plate, and visually observe the surface of the solution while heating, It has been found that the gloss and color tone of the liquid surface change as the drying and curing of the solution proceeds. Then, it was found that the dry / cured state of the polyamic acid solution can be detected by measuring the reflected light on the liquid surface with an optical sensor using the change in the state of the polyamic acid solution surface.
[0026]
FIG. 2 is a graph showing the results of measuring the reflected light intensity reflected on the liquid surface by irradiating the solution with light while heating the polyamic acid solution applied to the flat plate. The vertical axis represents the reflected light intensity I, and the horizontal axis represents the heating time t.
As shown in FIG. 2, at the start of heating, light is reflected from the glossy liquid surface of the polyamic acid solution, so the reflected light intensity I is large. As the heating proceeds, the solvent DMAC in the liquid evaporates and the surface becomes rough. It becomes a yellowish dry film. At this time, light is diffusely reflected on the film surface, and the reflected light intensity gradually decreases. As the heating further progresses, the dry film reaches a level where it feels sticky when touched lightly with the so-called finger touch drying, and the film surface becomes smooth and gradually becomes glossy. The light intensity starts to increase again. As the heating proceeds further, the film is cured and the gloss of the film surface increases, and the reflected light intensity also increases. However, as the film progresses to a certain degree and the color of the film surface becomes dark, the reflected light intensity decreases again. Turn to the trend. As the heating further proceeds, the film surface becomes brown and the reflected light intensity further decreases.
[0027]
Thus, since the reflected light intensity changes depending on the dry / cured state of the polyamic acid solution, for example, by measuring the reflected light intensity, the relationship between the reflected light intensity and the dried / cured state of the solution is determined in advance. It was found that the dry / cured state of the solution can be detected by providing it in the form of a data table or the like.
[0028]
Next, a specific example in the case of measuring the reflected light intensity in the drying / curing treatment of the polyamic acid solution by an actual centrifugal forming method will be described.
[0029]
FIG. 3 is a view showing a state in which a support 3 having an optical sensor is inserted into the inside of the mold 1 shown in FIG. 1 from a cavity of a holding jig (not shown) at the end of the mold 1. The optical sensor includes a light emitting element 4 as a light emitting part that emits light to the endless film 2 in which the polyamic acid solution is formed by centrifugation, and a light receiving part that receives light emitted from the light emitting element 4 and reflected from the surface of the endless film 2. As a light receiving element 5.
[0030]
In FIG. 3, the endless film 2 is heated by a heating means (not shown) while rotating the mold 1. When the endless film 2 is heated and the support 3 is inserted into the mold 1 and light is emitted from the light emitting element 4 toward the endless film 2, the light is reflected on the surface of the endless film 2, and the reflected light is received. The light is received by the element 5 and the reflected light intensity of the endless film 2 is measured.
[0031]
Table 1 below shows the measurement results of the reflected light intensity when the heating time and the heating temperature of the coating film 2 are variously changed. Moreover, the result of observing the endless film 2 in a state where the endless film 2 is dried, solidified, or semi-cured after the rotation and heating of the mold 1 are stopped is shown. In addition, the result of observing the final film formation state after performing the curing process in another heating furnace and the state of demolding from the mold 1 are also shown.
[Table 1]

[0032]
From Table 1, the endless film 2 is in an optimum state in which there is no decrease in production efficiency due to excessive drying, poor peeling and demolding, and no flow deformation due to insufficient drying. It turns out that it is near the time. Therefore, the endless film 2 can be controlled to an optimum state by rotating the mold 1 and stopping the heating of the endless film 2 when the reflected light intensity starts to increase from the decrease. Specifically, for example, a display monitor is provided as an informing means for outputting the reflected light intensity, and when the operator monitors this and the reflected light intensity changes from decreasing to increasing, rotation of the mold 1 and The heating may be stopped, or a notification unit configured to emit a sound or the like may be provided when the reflected light intensity starts to increase from the decrease. In addition, when the reflected light intensity changes from decreasing to increasing, control means for controlling the rotation and heating of the mold 1 to stop is provided so that the rotation and heating of the mold 1 are automatically stopped. Good.
[0033]
The reflected light intensity shown in the graph of FIG. 2 changes depending on various factors such as the concentration of the polyamic acid solution and the liquid thickness, but the change in the reflected light intensity increases and decreases in any case. It can be used to detect dry / cured state. In addition, the progress of solvent evaporation and curing reaction and film alteration are not clearly distinguished as shown in the graph, but proceed at the same time. It is effective as a means for determining.
[0034]
As described above, in the present embodiment, the dry state of the endless film 2 is detected during the heating of the endless film 2, and it is determined whether to continue or stop the drying based on the detection result. Can be controlled to a desired dry state. Therefore, it is possible to control to an optimum state in which there is no decrease in production efficiency due to excessive drying, no peeling-off defect after centrifugal molding, and no liquid dripping or thickness variation of the endless film 2 due to insufficient drying.
[0035]
In the embodiment, the case where an endless belt that is a carrier for a toner image or a transfer material in an image forming apparatus such as an electrophotographic copying machine, a facsimile machine, and a printer has been described as an example. Any centrifugal forming method can be applied, in which the liquid material is dried while the mold is rotated, and a product having the shape of the inner surface of the mold is formed by the centrifugal force.
[0036]
【The invention's effect】
According to the first to third aspects of the invention, the liquid material can be prevented from being excessively dried or insufficiently dried, so that the liquid material can be dried without causing a reduction in production efficiency due to excessive drying or a peeling-off mold failure after centrifugal molding. In addition, there is an excellent effect that the liquid material can be controlled to an optimal state without dripping or variation in thickness due to insufficient drying.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram for explaining a centrifugal forming method according to an embodiment.
FIG. 2 is a graph showing the relationship between the heating time of a polyamic acid solution and the reflected light intensity of light irradiated on the solution.
FIG. 3 is an explanatory diagram for explaining a method of measuring the reflected light intensity of a polyamic acid solution.
[Explanation of symbols]
1 Type 2 Endless Film 3 Support 4 Light-Emitting Element 5 Light-Receiving Element

Claims

In a centrifugal forming method of injecting a liquid substance into a mold, drying the liquid substance while rotating the mold, and forming a product that has the shape of the inner surface of the mold by the centrifugal force.
An optical sensor having a light emitting part for emitting light to the liquid substance and a light receiving part for receiving light emitted from the light emitting part and reflected by the surface of the liquid substance, the dry detected, when the reflected light intensity received by the light receiving portion starts to increase from decreasing, the centrifugal forming method comprising the Turkey to abolish stop the drying.

Rotating means for rotating the mold into which the liquid material has been injected and heating means for heating the liquid material, the liquid substance is dried or cured while rotating the mold, and the inner surface of the mold is formed by the centrifugal force. In the centrifuge forming device that forms the ordered product,
An optical sensor having a light emitting unit that emits light to the liquid material, and a light receiving unit that receives light emitted from the light emitting unit and reflected by the surface of the liquid material ;
A centrifuge forming device characterized by comprising a notifying means for notifying when the intensity of the reflected light received by the light receiving portion starts from decreasing to increasing .

Rotating means for rotating the mold into which the liquid material has been injected and heating means for heating the liquid material, the liquid substance is dried or cured while rotating the mold, and the inner surface of the mold is formed by the centrifugal force. In the centrifuge forming device that forms the ordered product,
An optical sensor having a light emitting unit that emits light to the liquid material, and a light receiving unit that receives light emitted from the light emitting unit and reflected by the surface of the liquid material;
A centrifugal forming apparatus, comprising: means for stopping rotation by the rotating means and heating of the heating means when the intensity of reflected light received by the light receiving portion starts from decreasing to increasing .