JP3644788B2 - Capacitance measuring device for electrophotographic photoreceptor - Google Patents

Description

ｄ：コロナ帯電器（チャージワイヤー）がつくる電流露曝領域の周方向の幅（ｄ・Ｌ）は露曝領域の面積
ｑ：開口部がコロナ帯電器を１回通過する際に露曝する単位面積当たりの電荷量
Ｉ₀：ターンテーブルを静止させた状態で開口部に流れる静止コロナ電流値
ｖ：ターンテーブルの線速（線速は径方向で異なるので開口部径方向の中央部の値とする）
Ｌ：ターンテーブル開口部径方向の長さ
ターンテーブルの中心から開口部径方向の一端までの長さをｒ₁、他端をｒ₂（ｒ₁＞ｒ₂）とすると（ｒ₁−ｒ₂）
単位時間当たりの回転数（Ｎ）は次の（２）式で与えられる。
【００１３】
【数２】

Ｒ：ターンテーブルの中心から開口部径方向中央部までの長さ
ターンテーブルの中心から開口部方向の一端までの長さをｒ₁、他端をｒ₂とするとＲ＝（ｒ₁＋ｒ₂）／２
開口部がコロナ帯電器を単位時間当たりＮ回通過するときの開口部が受ける電荷量（Ｑ）は、次の（３）式で与えられる。
【００１４】
【数３】

（３）式の分母は、前記開口部がターンテーブルの全周に設けられると仮定したときの面積（Ａ）であって、図３の斜線部面積になる。
本件で取り上げているターンテーブル方式の測定では、開口部は限定された窓となり、試料を充電する電流は試料が帯電器の上を通過したときだけ流れるパルス電流であり、この電流信号は電気回路上で平滑化されたＤＣ信号になり、これを測定することになるので（図２）、ターンテーブル回転時測定されるＤＣ電流信号をＩとするとＩ₀との間に次の（４）式の関係が成立するなら、
【００１５】
【数４】

Ａ：π(ｒ₁ ²−Ｒ₂ ²）
Ｓ：開口部の面積
（３）式は次の（５）式のように書き換えられる。
【００１６】
【数５】

開口部が受ける電荷量をターンテーブル回転時の電流計測で評価できることになる。
すなわち、感光体試料の静電容量測定では、コロナ放電中、感光体試料表面が帯電上昇（チャージアップ）するため、前記（Ｉ）は刻々と変化する信号となる。このＩを測定し、開口部面積で割ることで、単位面積、単位時間当たりの充電電荷が算出され、任意の時間まで積算するとその時点までの充電電荷が求められる。ターンテーブル方式の静電容量測定でも、感光体試料に流れる充電電流をパルス電流の状態で測定する場合は、（３）式で充電電荷を算出することになるが、平滑化されたＤＣ信号として測定する場合は、（５）式で算出することになる。（５）式は（４）式が成立することが前提になる。したがって、ターンテーブルが静止した状態で開口部に流れる電流（Ｉ₀）とターンテーブルが高速回転している状態で開口部に流れる電流（Ｉ）との間で（４）式からの乖離が大きくなると、コロナ帯電法による静電容量測定の精度を悪くする。
【００１７】
（４）式からの乖離を生じさせる原因として、ターンテーブル開口部の形状（これは感光体試料のサイズにより変えることが多い）、回転体から電流をとるための接触帯電部で発生するノイズの影響、パルス電流をＤＣ電流にする平滑化回路の素子の特性、等のマッチング上の問題が関係すると思われるが判然としない。
【００１８】
本発明は上記の点に鑑み、コロナ帯電法で静電容量の測定を行なう装置において、ターンテーブル開口部に導電性試料をセットし、ターンテーブル静止状態でのコロナ電流値とコロナ放電の条件は同一でターンテーブル高速回転状態での平滑化されたＤＣ電流を計測し、両電流値の比Ｋｍ＝Ｉ／Ｉ₀と、（４）式の係数Ｋ＝Ｓ／Ａを用いて、次にターンテーブル開口部に感光体試料をセットして高速回転状態でのＤＣ電流（充電電流）を計測したとき、この計測された充電電流にＫ／Ｋｍを乗じて得られる電流値は（４）式を成立させる電流Ｉとなり、この値を開口部面積で割り、積算することで、正確な単位面積、単位時間当たりの充電電荷量を得ようとするものである。
【００１９】
ここで開口部が回転でつくる面積Ａの補足説明をしておく。
図３の面積Ａは開口部径方向の最大半径と最小半径がつくる面積である。これは開口部がターンテーブル中心から見て扇形になっているときに意味を持つ。
開口部が四角形の場合には、図４において（ｒ₁＋ｒ'₁)／２、（ｒ₂＋ｒ'₂)／２がつくる面積となる。
【００２０】
【実施例】
以下に本発明の実施例を示す。
実施例１
ターンテーブルをもつ測定器として、川口電機製作所（株）製の静電気帯電試験装置（型式ｓｐ−４２８）を利用した。測定システムの概略は図７に示すとおりである。なお、ターンテーブル静止状態でのコロナ帯電器よりターンテーブル開口部へ流れる電流計測値の正しさは国家標準にトレースされた基準電流発生器で校正されている。
上記測定器のターンテーブル開口部は扇形で、中心からみて５２°の開口角度を持ち、面積は３３．４ｃｍ²である。ターンテーブル開口部の径方向の最小半径と最大半径のつくる面積は２３１．２ｃｍ²でその面積比は０．１４４である。
実施例１ではＡ／Ｄ変換で測定システムに取り込まれた信号に演算処理を施し、静電容量測定値をアウトプットしている。
【００２１】
▲１▼ターンテーブルに付属するサンプル押さえ板（導電性金属板）で開口部をふさぎ、開口部をコロナ帯電器の真上に静止させる。放電をオンにし、開口部サンプル押さえ板に流れる電流値を読む。放電出力を調整し、１０．０μＡの電流値を得た。
次にターンテーブルを１０００ｒ．ｐ．ｍ．で回転させ、回転が安定したところで放電をオンにし、開口部サンプル押さえ板に流れる電流値を読んだ。この時の電流値は１．３μＡであった。この比は０．１３である。次に誘電体フィルム（裏面アルミ蒸着されたもの）を３種類（１０、２５、５０μｍ）用意し、ターンテーブル開口部にセットし、サンプル押さえ板で押さえ回転させた。回転が安定したところで放電を開始させ、表面電位と誘電体フィルムに流れ込む充電電流を同時測定した。計測された表面電位と充電電流から静電容量を求めた。同様にして同種の誘電体フィルムに対し表面電位と充電電流の同時測定を行ない、計測された充電電流に０．１４４／０．１３を乗じて得られた充電電流値から充電電荷を計算し、静電容量値を得た。結果を表１に示す。
【００２２】
【表１】

【００２３】
▲２▼図５に示すようにターンテーブル開口部に正方形（縦４．４ｃｍ×横４．４ｃｍ、面積１９．３６ｃｍ²）のマスクを置き試料の露出面積、露出形状を変えた開口部を用意した。この開口部の径方向の長さが回転でつくる面積は２２３ｃｍ²と計算された。したがって、面積比は１９．３６／２２３＝０．０８６８である。▲１▼と同様にしてこの開口部に流れ込む静止時の電流と回転時の電流を計測した。その結果は各々、１０．７μＡ、０．９１μＡで、比は０．０８５であった。次に誘電体フィルムを用いて静電容量の測定を行なった。結果を表２に示す。
【００２４】
【表２】

【００２５】
▲３▼図６に示すようにターンテーブル開口部に面積が１９．３６ｃｍ²になるように扇形の開口部を形成した。面積比は１９．３６／２３１．２＝０．０８３７である。この開口部に流れ込む電流は静止電流が１０．５μＡのとき回転時の電流が０．８５μＡで、比は０．０８１であった。▲１▼、▲２▼と同様にして静電容量の測定を行なった。結果を表３に示す。
【００２６】
【表３】

ここまでの例で同じ測定器であっても開口部の面積（サンプルの面積）が異なると、静電容量の値が異なるが、本発明によれば、サイズにかかわらず再現性のよい測定を行なうことができることがわかる。
【００２７】
▲４▼上記▲１▼、▲２▼、▲３▼で使用した測定器と同型の別測定器を用意し、測定器同士の比較を行なった。▲１▼、▲２▼、▲３▼で使用した測定器をＡ、ここで用意した測定器をＢと呼ぶことにする。Ｂは静止電流１９．４μＡに対し、回転時の電流は２．４μＡで、その比は０．１２４であった。したがって、Ａでは計測される充電電流に乗ぜられる定数は０．１４４／０．１３３、Ｂで計測される充電電流に乗ぜられる定数は０．１４４／０．１２４である。使用されたサンプルはリコーのアナログ複写機用の感光体を切り出したものである。結果を表４に示す。
【００２８】
【表４】

同型でターンテーブル開口部の形も面積も同じであるが、測定値に機差が生じていることが確認された。しかしながら、本発明によれば、同じ測定値が得られることが分かる。
【００２９】
実施例２
実施例１の▲１▼において計測される充電電流に乗ずべき定数０．１４４／０．１３＝１．１１が求められた段階で直流アナログアンプ（横河電機製 ３１３１）を用いて設定した。調節は基準電圧・電流発生器で信号を入力し、アンプの出力が１．１１倍になるよう微調節した。アンプ出力の確認はデジタルマルチメータ（フルーク製 ８７）を使用した。このアンプをＡ／Ｄ変換器の前段に設置し、誘電体フィルムで静電容量の測定を行なった。結果を表５に示す。
【００３０】
【表５】

【００３１】
【発明の効果】
以上、詳細かつ具体的に説明したように、本発明によれば、測定器が異なると測定値が異なる等の問題を解決でき、また、同一の測定器であっても、サンプルサイズを変えた時に測定値が異なる等の問題が生じることなく、測定の再現精度を高めることができる。さらに測定器毎で測定値が異なるとき、従来は１つを基準に対応関係を求め、換算係数で対処していたが、これでは基準とした測定器の正しさを保証する方法が抜けており、また対応関係も経時で変化しても気づかない等、測定器の管理としては時間がかかる割に効率も精度も悪い方法であったが、これらの問題は本発明により一気に解決される。また、測定システムに取り込まれた信号をデジタル演算するため特別の機器を設置することなく、安価に本発明を適用した測定システムをつくることができる。必要であれば、測定の度に乗ずべき定数を求め、測定システムに反映させることができ、測定器としての信頼性を向上させることができる。さらに、従来測定システムに１つ機器を入れるだけでソフトウエアの変更等なく、そのまま測定システムの測定確度向上をはかることができるという極めて優れた効果を発揮する。
【図面の簡単な説明】
【図１】本発明の基礎となる静電容量の測定原理を説明する図である。
【図２】本発明の測定装置におけるターンテーブル開口部に流れる電流を説明する図である。
【図３】本発明の測定装置におけるターンテーブル開口部の１例がつくる帯電露曝領域を説明する図である。
【図４】本発明の測定装置におけるターンテーブル開口部の他の１例（四角形）がつくる帯電露曝領域を説明する図である。
【図５】本発明の測定装置におけるターンテーブルの扇形開口部に四角形のマスクを設置した状態を説明する図である。
【図６】本発明の扇形開口部に四角形と同一面積のマスクを設置した状態を説明する図である。
【図７】本発明の測定装置の１例を示す概略図である。
【符号の説明】
１ ターンテーブル
２ 試料片押え板
３ 開口部
４ コロナ帯電器
５ 表面電位計電極部
６ 充電電流取り出し部
７ 電流計測・平滑化回路、他
８ 表面電位計・アンプ回路、他
９ インターフェース（Ａ／Ｄ変換）
１０ コントローラ（マイクロプロセッサ）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a capacitance measuring device for an electrophotographic photoreceptor. This capacitance measuring device is applicable to the measurement of a general dielectric non-destructive and non-contact capacitance.
[0002]
[Prior art]
Since the characteristics such as charging ability, charge retention ability, and sensitivity required for the electrophotographic photoreceptor are characteristics required in the electrophotographic process, corona charging is used in the measurement of these characteristics as in the electrophotographic process. And the above properties are often evaluated. Charging performance is evaluated by how many volts the corona charger is charged under a fixed condition and the sample piece passes through the corona charger once at the same speed as the actual machine. The However, with this method, details such as the rising profile of charging are not known. Therefore, the sample piece may be rotated at high speed, passed through the charger many times (reducing the charging potential per time), and gradually charged to observe the rising state of charging. At this time, it is generally evaluated how many volts it has become in seconds from the start of charging. However, even in these evaluation methods, if the output of the corona charger changes, the charged potential as an evaluation item naturally changes, and there is also a problem with the repeatability of measurement.・ There were many restrictions.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide a measuring apparatus with improved measurement accuracy in a measuring instrument that measures the electrostatic capacity of a photoreceptor by a non-contact, non-destructive corona charging method.
[0004]
[Means for Solving the Problems]
The object is (1) “a turntable having an opening for setting a sample piece of an electrophotographic photosensitive member, means for setting the sample piece in the opening, and a conductive metal. A sample holding plate made of a plate and electrically connected to the charging current extraction unit, a means for rotating the turntable , and a corona charger arranged to face the turntable and charging the photoconductor sample piece And means for simultaneously measuring the average charged potential of the surface of the photoconductor test piece mounted on the opening of the turntable and the charging current flowing into the photoconductor sample piece, and the charging current is integrated and charged over time. The electrostatic capacity of the photoconductor sample piece is nondestructive and non-destructive from the relational expression of Q = C · V (Q is the charge charge, V is the charge potential of the photoconductor, and C is the electrostatic capacity of the photoconductor). A device for measuring by contact, Quiescent corona current flowing through the conductive sample piece is set to the opening of the serial turntable conductive work piece by the high voltage when a high voltage is applied to the counter still be allowed the corona charger to the corona charger (I ₀ ), and a dynamic corona current that flows into the conductive sample piece when a high voltage is applied to the corona charger under the same charging output condition as that for measuring the static corona current by rotating the turntable at a predetermined speed. (I) is measured, the ratio of the two currents and the I ₀ from the I (K m) is computed as K m = I / I _0, also, when the opening portion is provided on the entire circumference of the turntable The assumed area (A) and the opening area (S) on the turntable are actually measured, and the ratio (K) of the area A and the area S is calculated from the A and S as K = S / A. As a result, When measuring capacitance, 'true charging current to, (K / K m) × I charge current (I)' flowing into the photoreceptor test piece of the turntable that rotates the electrostatic capacity measuring device for processing a), (2 ) “Capacitance measuring device according to item (1), wherein the K / Km magnification setting process is performed by digital arithmetic processing after A / D conversion of charging current is taken in”, (3) “ K / K This is achieved by the “capacitance measuring device according to the item (1)” in which the magnification setting process of m is performed by adjusting the gain of the analog amplifier and the charging current is captured.
The present invention will be described in detail below.
[0005]
The inventors of the present invention have tried to measure capacitance by a non-destructive, non-contact corona charging method using a capacitance as a characteristic value of charging ability as a characteristic item that is not easily affected by the setting of charging conditions during measurement. It was.
[0006]
An outline of the principle will be described with reference to FIG. In order to use the corona charging method, it is necessary to consider a model in which the photoreceptor is a capacitor. In the photoconductor capacitor model, the charging current flowing through the photoconductor sample rotating at a high speed by corona charging and the surface potential at this time are measured simultaneously. The charging current is integrated over time and treated as the charging charge. The lower graph in FIG. As shown in FIG. 4, the electrostatic capacity (C) is obtained from the relationship of Q = C · V (Q is the charged charge, V is the charging potential of the photoconductor, and C is the electrostatic capacity of the photoconductor). That is, when corona discharge is applied to the photoreceptor, the charging potential usually rises as shown in the upper graph in FIG. During this time, the charge on the photoreceptor changes as shown by the middle graph in FIG. That is, the charge charge (Q) is represented by an integrated value of the charge charges (q1), (q2), (q3),... (Qn) per time (Δt) and increases. Each charged charge (q1), (q2), (q3),... (Qn) is an integral value represented by the product of time (Δt) and current (I), and current (I ) Is determined by the measured sample passing current value / S (S is the area of the charged sample).
[0007]
For the charge charge, an integral ammeter may be used, or the current may be measured and integrated calculation processing may be performed later. At present, it is convenient to incorporate a current into an A / D converter and to perform calculation processing on a computer at low cost, and the upper limit of the amount of charge that can be measured is almost free and the degree of freedom in measurement is high. In any case, since the magnitude of the measured current (charge) depends on the measurement opening (sample size), the measured current (I) is divided by the area of the measurement opening to obtain a value per unit area. There is a need. This charge amount (Q) and the corresponding surface potential (V) are plotted to draw a straight line, and the capacitance (C) is calculated from this slope. In this way, a value obtained by averaging the correspondence relationship between the Q value and the V value at the initial stage of charging is obtained, and the measurement accuracy is increased.
[0008]
In this way, the capacitance of the photoconductor can be measured. Even if the output voltage of the corona charger slightly changes, there is almost no change in the capacitance value. In comparison, a dramatically stable evaluation of charging ability is performed. However, even if this method sometimes changes the shape, area, etc. of the opening according to the size of the sample, the capacitance value may change by several percent even though it is the same sample, and another measuring device of the same type There were some problems with the accuracy of the measuring instrument, such as different measurement values. In addition, when the measured values differ for each measuring instrument, in order to ensure consistency between the measuring instruments, conventionally, the corresponding relationship between the measured values was calculated based on one and handled by the conversion factor. There is no way to guarantee the correctness of the measuring instrument, and it is difficult to manage the measuring instrument because it is not noticed even if the correspondence changes over time. It was only taken.
[0009]
One factor is accuracy in current measurement. This is as follows. In other words, for the accuracy of static current measurement, it goes without saying that the measurement system is calibrated using a highly accurate current generator, but as shown in FIG. In the table type measurement, the current for charging the sample is a pulse current that flows only when the sample passes over the charger, and this current signal is smoothed on the electric circuit to become a DC signal. Confirmation of the correctness of the value has not been performed conventionally because the reference signal cannot be applied to the dynamic opening. In order to improve the measurement accuracy, it was desired to elucidate the cause and make further improvements.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
With reference to FIG. 7, an example of the principle of charge current measurement in a measuring instrument of the present invention that performs electrostatic capacity measurement by corona charging method by rotating a turntable at high speed will be described.
In the apparatus example of FIG. 7, after the sample piece of the electrophotographic photosensitive member is mounted in the opening (3) of the turntable (1) with the photosensitive surface facing downward and set by the sample piece pressing plate (2), the corona The photosensitive surface of the sample piece is charged by the charger (4). During the charging process, the turntable (1) can be stopped at a position where the photoconductor sample piece is kept stationary against the corona charger (4) and can be rotated at the same speed as the actual machine. In addition, to charge the sample piece and observe the rising state of the charge, etc., the sample piece is rotated at a high speed and the sample piece is passed through the charger many times (the charged potential per time is reduced). Can do. The pulse current applied to the sample piece from the corona charger (4) and charged by the sample piece is monitored by the charging current extraction unit (6) and sent to the charging ammeter (7) and smoothed by the smoothing circuit therein. After the above, the A / D conversion interface (9) performs A / D conversion, and the output signal is processed in the controller (10) comprising a microcomputer. On the other hand, the surface potential of the sample piece is monitored by the surface electrometer electrode (5) which is a monitor unit of the surface electrometer (8) arranged at a position different from the corona charger (4), and the monitored signal is After being sent to the surface electrometer (8) and amplified by an amplifier therein, it is A / D converted by an A / D conversion interface (9), and the output signal of the measured charging current is Along with the output signal, it is processed in a controller (10) comprising a microcomputer.
[0011]
Here, it is assumed that the charge wire of the corona charger (4) is stretched at right angles to the moving direction of the opening (3) of the turntable (1) and completely covers the opening radial direction.
When the opening (3) passes through the corona charger (charge wire) (4) once, the charge (q) per unit area to which one point in the opening (3) is exposed is (1).
Current per unit area x transit time of exposure area, ie
[Expression 1]

d: Circumferential width (d · L) of the current exposure area created by the corona charger (charge wire) is the area of the exposure area q: Unit of exposure when the opening passes once through the corona charger Charge amount per area I ₀ : static corona current value flowing through the opening with the turntable stationary v: linear velocity of the turntable (the linear velocity differs in the radial direction, so the value at the center in the radial direction of the opening To do)
L: Length in turn table opening radial direction When the length from the center of the turn table to one end in the opening radial direction is r ₁ and the other end is r ₂ (r ₁ > r ₂ ), (r ₁ −r ₂₎ )
The number of rotations (N) per unit time is given by the following equation (2).
[0013]
[Expression 2]

R: length from the center of the turntable to the center in the radial direction of the opening, where R _{1 is} the length from the center of the turntable to one end in the direction of the opening, and r ₂ is the other end, R = (r ₁ + r ₂ ) / 2
The amount of charge (Q) received by the opening when the opening passes through the corona charger N times per unit time is given by the following equation (3).
[0014]
[Equation 3]

The denominator of equation (3) is the area (A) when the opening is assumed to be provided on the entire circumference of the turntable, and is the hatched area in FIG.
In the turntable-type measurement taken up in this case, the opening becomes a limited window, and the current that charges the sample is a pulsed current that flows only when the sample passes over the charger. Since the DC signal smoothed above is measured and measured (FIG. 2), if the DC current signal measured during the turntable rotation is I, the following equation (4) is set between I ₀ and I _0. If the relationship of
[0015]
[Expression 4]

A: π (r ₁ ² −R ₂ ² )
S: The area (3) of the opening is rewritten as the following expression (5).
[0016]
[Equation 5]

The amount of charge received by the opening can be evaluated by measuring the current when the turntable rotates.
That is, in the measurement of the capacitance of the photoconductor sample, the surface of the photoconductor sample is charged up during the corona discharge, so that the signal (I) changes every moment. By measuring this I and dividing by the opening area, the charge charge per unit area and unit time is calculated, and when charging is performed up to an arbitrary time, the charge charge up to that point is obtained. Even in the turntable type capacitance measurement, when the charging current flowing through the photoconductor sample is measured in the state of a pulse current, the charging charge is calculated by the equation (3), but as a smoothed DC signal In the case of measurement, it is calculated by equation (5). Equation (5) is premised on that equation (4) holds. Therefore, there is a large divergence from the equation (4) between the current (I ₀ ) flowing through the opening when the turntable is stationary and the current (I) flowing through the opening while the turntable is rotating at high speed. Then, the accuracy of capacitance measurement by the corona charging method is deteriorated.
[0017]
As a cause of the deviation from the equation (4), the shape of the turntable opening (this often changes depending on the size of the photoconductor sample), and the noise generated in the contact charging unit for taking a current from the rotating body It seems to be related to the matching problems such as the influence, the characteristics of the elements of the smoothing circuit that changes the pulse current to DC current, but it is not clear.
[0018]
In view of the above points, the present invention is an apparatus for measuring capacitance by the corona charging method. A conductive sample is set in the opening of the turntable, and the corona current value and corona discharge conditions when the turntable is stationary are as follows. Measure the smoothed DC current in the same turntable high-speed rotation state, then use the ratio Km = I / I _{0 of} both current values and the coefficient K = S / A in equation (4) to turn When the photoconductor sample is set in the table opening and the DC current (charge current) in the high speed rotation state is measured, the current value obtained by multiplying the measured charge current by K / Km is expressed by the following equation (4). The current I to be established is obtained, and this value is divided by the opening area and integrated to obtain an accurate unit area and charge amount per unit time.
[0019]
Here, a supplementary explanation of the area A formed by the rotation of the opening will be given.
The area A in FIG. 3 is an area formed by the maximum radius and the minimum radius in the opening radial direction. This is meaningful when the opening is fan-shaped when viewed from the center of the turntable.
When the opening is a quadrangle, the area formed by (r ₁ + r ′ ₁ ) / 2 and (r ₂ + r ′ ₂ ) / 2 in FIG.
[0020]
【Example】
Examples of the present invention are shown below.
Example 1
As a measuring instrument having a turntable, an electrostatic charge test apparatus (model sp-428) manufactured by Kawaguchi Electric Mfg. Co., Ltd. was used. The outline of the measurement system is as shown in FIG. The correctness of the measured current value flowing from the corona charger to the turntable opening when the turntable is stationary is calibrated by a reference current generator traced to the national standard.
The measuring device has a fan-shaped turntable opening with an opening angle of 52 ° when viewed from the center and an area of 33.4 cm ² . The area formed by the minimum radius and the maximum radius in the radial direction of the turntable opening is 231.2 cm ² and the area ratio is 0.144.
In the first embodiment, arithmetic processing is performed on a signal taken into the measurement system by A / D conversion, and a capacitance measurement value is output.
[0021]
(1) The opening is closed with a sample pressing plate (conductive metal plate) attached to the turntable, and the opening is stopped immediately above the corona charger. Turn on the discharge and read the value of the current flowing through the opening sample holding plate. The discharge output was adjusted to obtain a current value of 10.0 μA.
Then turn the turntable to 1000r. p. m. When the rotation was stable, the discharge was turned on, and the value of the current flowing through the opening sample holding plate was read. The current value at this time was 1.3 μA. This ratio is 0.13. Next, three types (10, 25, 50 μm) of dielectric films (those deposited with aluminum on the back surface) were prepared, set in the turntable opening, and rotated by pressing with a sample pressing plate. When the rotation was stabilized, discharge was started, and the surface potential and the charging current flowing into the dielectric film were measured simultaneously. The capacitance was obtained from the measured surface potential and charging current. Similarly, the surface potential and the charging current are simultaneously measured for the same kind of dielectric film, and the charging charge is calculated from the charging current value obtained by multiplying the measured charging current by 0.144 / 0.13, Capacitance values were obtained. The results are shown in Table 1.
[0022]
[Table 1]

[0023]
( ² ) As shown in FIG. 5, a square (4.4 cm x 4.4 cm, area 19.36 cm ² ) mask is placed at the opening of the turntable to prepare an opening with a different exposed area and exposed shape. did. The area formed by rotation of the radial length of the opening was calculated to be 223 cm ² . Therefore, the area ratio is 19.36 / 223 = 0.0868. In the same manner as in (1), the current at rest and the current at rotation flowing into this opening were measured. The results were 10.7 μA and 0.91 μA, respectively, and the ratio was 0.085. Next, the capacitance was measured using the dielectric film. The results are shown in Table 2.
[0024]
[Table 2]

[0025]
(3) A fan-shaped opening was formed in the turntable opening so as to have an area of 19.36 cm ² as shown in FIG. The area ratio is 19.36 / 231.2 = 0.0837. When the quiescent current was 10.5 μA, the current flowing into the opening was 0.85 μA during rotation, and the ratio was 0.081. The capacitance was measured in the same manner as (1) and (2). The results are shown in Table 3.
[0026]
[Table 3]

Even if the same measuring instrument is used in the examples so far, the capacitance value is different if the opening area (sample area) is different. However, according to the present invention, measurement with good reproducibility can be performed regardless of the size. You can see that it can be done.
[0027]
(4) Another measuring device of the same type as the measuring device used in (1), (2) and (3) above was prepared, and the measuring devices were compared. The measuring instrument used in (1), (2), and (3) is called A, and the measuring instrument prepared here is called B. B had a quiescent current of 19.4 μA, while the rotating current was 2.4 μA, and the ratio was 0.124. Therefore, in A, the constant multiplied by the measured charging current is 0.144 / 0.133, and the constant multiplied by the charging current measured in B is 0.144 / 0.124. The sample used was a cut-out photoconductor for Ricoh's analog copier. The results are shown in Table 4.
[0028]
[Table 4]

Although the shape and area of the opening of the turntable are the same, it was confirmed that there was a machine difference in the measured values. However, it can be seen that the same measurement is obtained according to the present invention.
[0029]
Example 2
When a constant of 0.144 / 0.13 = 1.11 to be multiplied by the charging current measured in (1) of Example 1 was obtained, it was set using a DC analog amplifier (Yokogawa 3131). Adjustment was performed by inputting a signal with a reference voltage / current generator and finely adjusting the output of the amplifier to 1.11 times. A digital multimeter (87 manufactured by Fluke) was used to check the amplifier output. This amplifier was placed in front of the A / D converter, and the capacitance was measured with a dielectric film. The results are shown in Table 5.
[0030]
[Table 5]

[0031]
【The invention's effect】
As described above in detail and concretely, according to the present invention, it is possible to solve problems such as different measurement values when different measuring instruments are used, and the sample size is changed even with the same measuring instrument. The measurement reproducibility can be improved without causing problems such as sometimes different measurement values. Furthermore, when the measured values differ for each measuring instrument, conventionally, the corresponding relationship was calculated based on one and dealt with by a conversion factor. However, there is no way to guarantee the correctness of the measuring instrument based on this. In addition, although it takes time to manage the measuring instrument, such as the correspondence relationship is not noticed even if it changes over time, the efficiency and accuracy are poor, but these problems are solved at once by the present invention. Further, a measurement system to which the present invention is applied can be made at low cost without installing a special device for digitally calculating a signal taken into the measurement system. If necessary, a constant to be multiplied for each measurement can be obtained and reflected in the measurement system, and the reliability as a measuring instrument can be improved. Furthermore, it is possible to improve the measurement accuracy of the measurement system as it is without changing the software and the like by simply putting one device into the conventional measurement system.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining the principle of capacitance measurement that is the basis of the present invention.
FIG. 2 is a diagram for explaining a current flowing through a turntable opening in a measuring apparatus according to the present invention.
FIG. 3 is a diagram for explaining a charged exposure area created by an example of a turntable opening in the measurement apparatus of the present invention.
FIG. 4 is a diagram for explaining a charged exposure area formed by another example (square) of the turntable opening in the measurement apparatus of the present invention.
FIG. 5 is a diagram illustrating a state in which a square mask is installed in a fan-shaped opening of a turntable in the measurement apparatus of the present invention.
FIG. 6 is a diagram illustrating a state where a mask having the same area as a quadrangle is installed in the fan-shaped opening of the present invention.
FIG. 7 is a schematic view showing an example of a measuring apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Turntable 2 Sample piece holding plate 3 Opening part 4 Corona charger 5 Surface potential meter electrode part 6 Charging current extraction part 7 Current measurement / smoothing circuit, others 8 Surface potential meter / amplifier circuit, others 9 Interface (A / D conversion)
10 Controller (microprocessor)

Claims (3)

A turntable having an opening for setting a sample piece of an electrophotographic photosensitive member , and means for setting the sample piece in the opening, and is made of a conductive metal plate and is electrically connected to a charging current extracting portion. A sample holding plate, means for rotating the turntable, a corona charger arranged to face the turntable and charging the photoconductor sample piece, and a photoconductor mounted on an opening of the turntable Means for simultaneously measuring the average charging potential on the surface of the test piece and the charging current flowing into the photoconductor sample piece, the charging current is integrated over time and processed as a charge charge, and Q = C · V (Q is A charge charge, V is a charge potential of the photoconductor, and C is a capacitance of the photoconductor). Set in the opening The conductive specimen to the corona charger is opposed stationary to the corona charger high voltage quiescent corona current flowing through the conductive work piece by the high voltage upon application of (I _0), and the turntable When a high voltage is applied to the corona charger under the same charging output conditions as those for rotating at a predetermined speed and measuring the static corona current, the dynamic corona current (I) flowing into the conductive sample piece is measured, area when the ratio of the two currents from the said I ₀ I (K m) is computed as K m = I / I _0, also, the opening portion is assumed to be provided on the entire circumference of the turntable (a) And the opening area (S) on the turntable is actually measured, and the ratio (K) of the area A to the area S is calculated from the A and S as K = S / A, thereby obtaining a photoconductor sample. When measuring the capacitance of a piece, the rotating turntable 'True charging current to, (K / K m) × charge current (I)' flowing into the photoreceptor test piece of the cable capacitance measuring device for processing a. The capacitance measuring apparatus according to claim 1, wherein the K / Km magnification setting process is performed by digital arithmetic processing after taking in A / D conversion of charging current. 2. The capacitance measuring apparatus according to claim 1, wherein the K / Km magnification setting process is performed by adjusting the gain of an analog amplifier to perform a charging current capturing process.

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