JP2008216704A - Method and device for evaluating characteristic of electrophotographic photoreceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for calculating electrostatic capacitance of electrophotographic photoreceptor capable of precisely calculating the electrostatic capacitance without being affected by the rotation, and to provide a device for evaluating characteristic of electrophotographic photoreceptor using the method for evaluating the characteristic. <P>SOLUTION: The method for calculating electrostatic capacitance of electrophotographic photoreceptor has: a step of rotating a sample as a photoreceptor drum 1; a static electricity charging step of electrifying a photosensitive surface of the sample by discharge from a corona electrifier 6; a photoemission step of performing photoemission by exposing the photosensitive surface of the sample after electrification; and an electrostatic capacitance calculation step of determining electrostatic capacitance of the sample based on a detection result of the surface potential and the amount of charged electric charge of the sample, wherein a discharge current I of the corona electrifier 6 satisfies the following relation. ¾I¾≥148.5/r[nA/cm<SP>2</SP>], therein, r presents a drum radius (unit:cm) of the sample. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and apparatus for evaluating characteristics of an electrophotographic photoreceptor used in an image forming apparatus such as a laser printer or a copying machine.

  In Patent Document 1, a turntable having an opening for setting a sample piece of an electrophotographic photosensitive member, a means for rotating the turntable at a high speed, and a photoconductor sample piece arranged opposite to the turntable. A corona charger for gradually charging, 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 current flowing into the photoconductor sample piece, This is a device that integrates with time and processes as a charged charge, and measures the electrostatic capacity of the photoconductor sample piece in a non-destructive and non-contact manner according to the relation Q = C · V. There is described a measuring apparatus that calculates the true current with respect to the current flowing into the photosensitive drum sample piece of the turntable that rotates at high speed during the measurement, thereby improving the capacitance measurement accuracy.

  As other conventional techniques, Patent Document 2 discloses a step of rotating an electrophotographic photosensitive member at a high speed, an electrostatic charging step of charging the photosensitive surface of the electrophotographic photosensitive member, and a photosensitive surface of the electrophotographic photosensitive member. A photodischarge step for photodischarging the electrophotographic photosensitive member, detecting a current signal of a current flowing into the electrophotographic photosensitive member and performing A / D conversion, and calculating the charge amount of the electrophotographic photosensitive member, and the electrophotography Capacitance calculation of the electrophotographic photosensitive member for detecting the electrostatic potential of the electrophotographic photosensitive member from the obtained charging potential of the electrophotographic photosensitive member by detecting a potential signal of the surface potential of the photosensitive member and performing A / D conversion. A method for calculating the electrostatic capacity of an electrophotographic photosensitive member is described, wherein the charge amount of the electrophotographic photosensitive member is obtained by adding a correction value to a value obtained by integrating a current value with time. Here, “high speed” is used to mean 1000 rpm or more, and “low speed” means 200 rpm or less.

  However, it has been found that when charging characteristics are measured in order to calculate the electrostatic capacity of the photosensitive member, if the set discharge current of the charging device is reduced, the electrostatic capacity calculation results differ. In addition, it was found that when the set discharge current of the charging device is reduced at low speed rotation, the difference in the capacitance calculation result appears significantly. Further, it was found that when the electrostatic capacity was calculated with the rotational speed decreased, the difference in the electrostatic capacity calculation result was greater as the rotational speed was decreased, regardless of the magnitude of the set discharge current. However, the conventional patent document does not describe this problem and has not been recognized as a problem.

  In addition, as described in the conventional patent documents, the chargeability, charge retention ability, sensitivity, and the like are given as the characteristics required for the electrophotographic photosensitive member. In the measurement of these electrical and optical characteristics, the above characteristics are often evaluated by performing corona charging / exposure in the same manner as in the electrophotographic process. As one of characteristic values for evaluating these characteristics, there is a method in which the electrophotographic photosensitive member is regarded as a capacitor and the capacitance is obtained and evaluated.

  FIG. 2 shows the principle of this method. In the model in which the electrophotographic photosensitive member is considered as a capacitor, the current I flowing through the photosensitive member sample by corona charging and the surface potential V at this time are simultaneously measured, and the passing current is integrated at time t, and the graph of FIG. As shown, Q = C · V (Q is the charge amount, V is the charge potential of the photoconductor, and C is the capacitance of the photoconductor). When corona discharge is applied to the photoreceptor, its surface potential (V) usually rises as shown in the upper graph of FIG. During this time, the charge amount of the photoreceptor changes as shown in the graph of FIG. That is, the charge amount (Q) is represented by an integrated value of each charge amount (q1), (q2), (q3),... (Qn) per each time (Δt) and increases. . Each charge amount (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 charging current value / S (S is the area of the charged sample). The charge amount (Q) obtained from these and the surface potential (V) corresponding thereto are plotted, a straight line is drawn, and the capacitance (C) is calculated from this slope (FIG. 2 (c)). As described in the conventional patent literature, in this calculation method, it is necessary to calculate the capacitance by rotating at a high speed in order to create and measure a state of gradually charging.

  When the photoconductor to be measured was a test piece such as a flat plate, there was no particular problem when calculating the capacitance by rotating at high speed because the sample size was small. Also, when the object to be measured is a photosensitive drum and the drum diameter of the photosensitive member is small, even if the support has a non-uniform thickness portion, the shake is so great that a large problem occurs during rotation. Since it does not increase, it was possible to calculate the capacitance by rotating at high speed. However, when the drum diameter is large and the support has a non-uniform thickness portion, a very large vibration occurs during rotation due to poor weight balance. In addition, it has been found that a situation in which accurate measurement cannot be performed also occurs because the distance from the charging device, the exposure device, and the surface potential detection device arranged around the photosensitive member is not stable.

  In addition, when the shake is large, the charging device, exposure device, and surface potential detection device placed around the photoconductor come into contact with the device and damage the photoconductor. There is a method to check the position where the position is bad and to suppress the shake amount by attaching a weight to the position, but when a mechanism or device to measure the unbalanced part is required or when measuring Had the problem of being troublesome for the measurer. For this reason, there has been a demand for a method for accurately measuring the capacitance at a low speed rotation without taking the trouble of the measurer with a conventional apparatus.

Japanese Patent Laid-Open No. 10-282057 JP 2003-279608 A

  The present invention has been made in view of the above problems in the prior art, and is a method for calculating the capacitance of an electrophotographic photoreceptor capable of accurately calculating the capacitance without being affected by the rotational speed, and a method for evaluating the characteristics. An object of the present invention is to provide an apparatus for evaluating characteristics of an electrophotographic photoreceptor using the above.

The present invention provided to solve the above problems is as follows.
(1) A step of rotating a sample which is a drum-shaped electrophotographic photosensitive member, an electrostatic charging step of charging the photosensitive surface of the sample by discharge from a charging device, and an exposure of the photosensitive surface of the sample after charging Capacitance calculation of an electrophotographic photoreceptor having a photodischarge process for photodischarge, and a capacitance calculation process for obtaining a capacitance of the sample based on a detection result of a surface potential and a charge amount of the sample A method for calculating the capacitance of an electrophotographic photoreceptor, characterized in that the discharge current I of the charging device satisfies the following formula:
| I | ≧ 148.5 / r [nA / cm ² ]
(R: drum radius of the sample (unit: cm))
(2) In the electrostatic capacity calculation method for the electrophotographic photoreceptor according to (1), in the electrostatic capacity calculation step, the surface potential and the charge of the sample collected at a time interval equal to or greater than the rotation period of the sample. An electrostatic capacity calculation method for an electrophotographic photosensitive member, wherein the electrostatic capacity of the sample is obtained based on a charge amount detection result.
(3) In the electrostatic capacity calculation method for the electrophotographic photoreceptor according to (2), in the electrostatic capacity calculation step, the surface potential and the charge of the sample collected at an integer multiple of the rotation period of the sample. An electrostatic capacity calculation method for an electrophotographic photosensitive member, wherein the electrostatic capacity of the sample is obtained based on a charge amount detection result.
(4) In the method of calculating the electrostatic capacity of the electrophotographic photoreceptor according to (3), the charge amount of the sample is obtained by integrating the passing current value of the sample with the elapsed charging time. A method for calculating the capacitance of an electrophotographic photoreceptor, wherein the value is a value based on correction based on signal responsiveness.
(5) In the method for calculating the electrostatic capacity of the electrophotographic photosensitive member according to (4), the charge amount of the sample is calculated by a method of multiplying a passing current value of the sample by a coefficient. A method for calculating the capacitance of an electrophotographic photoreceptor.
(6) The electrostatic capacity calculation method for an electrophotographic photoreceptor according to (5), wherein the coefficient is a positive value.
(7) A sample rotating device that is a drum-shaped electrophotographic photosensitive member, a charging device that charges the photosensitive surface of the sample by discharge, an exposure device that exposes the photosensitive surface of the sample, and charging of the sample surface A charge potential detection device for detecting a potential, a charge amount detection device for detecting a charge amount of the sample, and a method for calculating the capacitance of the electrophotographic photoreceptor according to any one of (1) to (6) And an electrostatic capacity calculating means for determining the electrostatic capacity of the sample.

According to the method for calculating the capacitance of the electrophotographic photoreceptor of the present invention, it is possible to calculate the capacitance of the electrophotographic photoreceptor (sample) with high accuracy from the high speed rotation to the low speed rotation without being influenced by the rotational speed. It becomes possible. In particular, conventionally, it has been difficult to accurately calculate the capacitance when the rotational speed is low, but according to the present invention, the capacitance can be calculated with high accuracy. In addition, it is possible to provide an electrophotographic photoreceptor characteristic evaluation apparatus that realizes the electrophotographic photoreceptor electrostatic capacity calculation method of the present invention.
That is, according to the first aspect of the present invention, the condition of the set discharge current I of the charging device is defined for the sample to be charged, the charge potential of the sample and the amount of charge flowing through the sample are measured, and the capacitance is calculated. Thus, the capacitance can be calculated with high accuracy.
According to the second aspect of the present invention, the graph is obtained by plotting the result at a time interval equal to or greater than the drum rotation period and calculating the capacitance by using a graph of the charge amount and the surface potential used for calculating the capacitance. The variation of the points to be eliminated is eliminated, and a straight line for calculating the capacitance can be easily drawn, and the capacitance can be calculated with high accuracy.
According to the third aspect of the present invention, by plotting the result at intervals of integer multiples of the drum rotation period on the correspondence graph between the charge amount used and the surface potential used when calculating the capacitance, and calculating the capacitance, Even during rotation, there is no variation in points to be plotted, and it is possible to easily draw a straight line for calculating the capacitance, and the capacitance can be calculated with high accuracy.
According to the fourth aspect of the present invention, the charge amount applied to the photosensitive member is measured by measuring the flowing current and integrating the charge amount over time. By calculating the capacitance as a value obtained by integrating the passing current with time and taking into account the signal response of the current measurement system, the signal delay caused by the signal processing circuit is corrected and static It is possible to accurately calculate the electric capacity.
According to the fifth aspect of the present invention, since the correction value at the time of calculating the charge amount is calculated by multiplying the passing current at the time of calculation by a coefficient, it is easy to correct a signal delay caused by signal processing or the like. It is possible to provide a feasible method.
According to the invention of claim 6, since the correction value at the time of calculating the charge amount is a positive value, it is possible to correct the signal delay caused by signal processing or the like and calculate the capacitance with high accuracy. Become.
According to the invention of claim 7, the characteristics of the electrophotographic photoreceptor capable of accurately calculating the electrostatic capacity of the electrophotographic photoreceptor (sample) from high speed rotation to low speed rotation without being influenced by the rotational speed. An evaluation device can be provided.

  Embodiments of the present invention will be described below with reference to the drawings. In the present invention, the term “discharge current” is used. This is a value for determining the discharge conditions of the charging device, and has the same shape (diameter, total length, and thickness) as the photoconductor (sample) to be measured. It means the current that flows to the aluminum tube side by discharging the same tube (no photosensitive layer applied). The output of the charging device is set by this discharge current.

In the present invention, discharge is performed so that the condition of the set discharge current I of the charging device for the photoreceptor sample satisfies the following formula (1), the charge potential of the sample and the amount of charge flowing through the sample are measured, There is a feature in the electrostatic capacity calculation method of the electrophotographic photoreceptor for calculating the electrical capacity.
| I | ≧ 148.5 / r [nA / cm ² ] (1)
(R: drum radius of photoconductor sample (unit: cm))
Hereinafter, a method for calculating the capacitance of an electrophotographic photoreceptor according to the present invention and an apparatus for evaluating characteristics of an electrophotographic photoreceptor to which this method is applied will be described.

FIG. 1 is a schematic view of an electrophotographic photoreceptor characteristic evaluation apparatus (hereinafter, characteristic evaluation apparatus) according to the present invention. The characteristic evaluation apparatus will be described with reference to FIG.
The characteristic evaluation apparatus includes an exposure lamp 11 that exposes the photosensitive drum 1, a surface potential meter probe 3 that measures the potential of the photosensitive drum 1, a corona charger 6 that charges the photosensitive drum 1, and a voltage applied to the corona charger 6. A power supply 7 for supplying, a switch 13 for the power supply 7, a light source 8 for neutralizing the photosensitive drum 1, a lamp box 10 for covering the exposure lamp 11, and an exposure for guiding the exposed light to the irradiation surface of the electrophotographic photosensitive member. It has a guide box 2 and a diaphragm 12 for adjusting the illuminance.

  In this characteristic evaluation apparatus, the photosensitive drum 1 has a mechanism that is rotated by a motor 14, and rotates in the direction of the arrow in FIG. At this time, a high voltage is output from the power source 7 and the photosensitive drum 1 is charged by the corona charger 6. The current (passing current) passing through the photosensitive drum 1 at the time of charging is measured and sent to a signal processing circuit 5. Note that a smoothing circuit (not shown) is incorporated in the signal processing circuit, and the smoothing circuit smoothes the passing current. Thereafter, it is converted into a digital signal by the A / D converter 16 and sent to the controller 15 where the digital signal is processed.

  Further, the surface potential of the photosensitive drum 1 is sent from the surface potential meter probe 3 to the surface potential meter 4 as a monitor unit, monitored, and sent to the signal processing circuit 9. Thereafter, the data is converted by the A / D converter 16 and then sent to the controller 15 for arithmetic processing. The controller 15 is connected to a motor driver in the motor 14 that rotates the photosensitive drum 1. In the motor driver, a function for outputting the rotation speed and a function for remotely controlling the rotation speed are added, so that the rotation speed control and the rotation speed recognition are possible.

  The units around the photosensitive drum 1 are ON / OFF controlled by a digital relay output. Further, the post-exposure potential of the photosensitive drum 1 can be measured by using the exposure lamp 11, and when the surface potential of the photosensitive drum 1 is removed, it can be removed by using the light source 8 for static elimination. It is possible to evaluate characteristics such as charging characteristics and light attenuation characteristics of the photosensitive drum 1.

  For the exposure apparatus (exposure lamp 11), it is possible to use a general luminescent material such as a fluorescent lamp, a tungsten lamp, a halogen lamp, a mercury lamp, a sodium lamp, a light emitting diode (LED), a semiconductor laser (LD), and an electroluminescence (EL). it can. And to irradiate only light in the desired wavelength range, various filters such as sharp cut filter, band pass filter, near infrared cut filter, dichroic filter, interference filter, color temperature conversion filter can be used, A neutral density filter can be used to lower the value. The diaphragm 12 for adjusting the illuminance can be a neutral density filter capable of adjusting the illuminance without using the diaphragm.

  The charging device power supply circuit control means for charging the surface of the sample to be tested (photosensitive drum 1) and the light source power supply circuit control means for irradiating the sample to be tested are not shown. As these, conventionally known ones can be used as they are.

  FIG. 3 shows the principle of a method for calculating the electrostatic capacity of the photosensitive drum 1. This is a method of calculating the electrostatic capacity with a model in which the electrophotographic photosensitive member is regarded as a capacitor, and simultaneously measures the current flowing through the photosensitive member sample (photosensitive drum 1) by corona charging and the surface potential at this time, The passing current is integrated over time, and as shown in the graph of FIG. 3C, Q = C · V (Q is the charge amount, V is the charge potential of the photoconductor, and C is the electrostatic capacitance of the photoconductor). The capacitance (C) is obtained from the relationship. When corona discharge is applied to the photosensitive drum 1, its surface potential (V) usually rises as shown in the graph of FIG. During this time, the charge amount of the photosensitive drum 1 changes as shown in the graph of FIG. That is, the charge amount (Q) is represented by an integrated value of each charge amount (q1), (q2), (q3),... (Qn) per each time (Δt) and increases. . Each charge amount (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 charging current value / S (S is the area of the charged sample), but in order to correct the current delay, when calculating the charge amount at each point, a correction coefficient N is added to the current value. The charged items (Q) are calculated by adding the multiplied items. The charge amount (Q) obtained from these and the surface potential (V) (FIG. 3 (a)) corresponding thereto are plotted, a straight line is drawn, and the capacitance (C) is calculated from this slope (FIG. 3). (C)). This capacitance calculation itself is a mechanism in which processing is performed by the controller 15 using the surface potential and current data stored in the storage area of the controller 15 to calculate the capacitance (C). ing. Further, when calculating the capacitance (C), the time interval and the number of points for plotting the charge amount (Q) and the surface potential (V) can be freely changed.

  The characteristic evaluation device is affected by the external environment (wind, light, temperature) during the test if it is covered with a dark box that does not transmit light, or with a dark curtain, etc. It becomes difficult. However, objects that do not affect the evaluation of the photosensitive drum, such as a controller / signal processing circuit, do not need to be covered with a dark box or a black curtain.

  The photosensitive drum 1 as an evaluation sample used in the practice of the present invention has a charge generating layer and a charge transport layer formed on a conductive support, and further has a protective layer formed on the charge transport layer. Etc. are used. As the conductive support, the charge generation layer, and the charge transport layer, any known ones can be used.

(Experimental example)
Photosensitive drum with the same material and prescription structure as the Ricoh IPSIO CX8000 photoconductor on a drum with a drum diameter of 30 mm, a drum total length of 340 mm, and a drum thickness of 0.75 mm, using the characteristic evaluation apparatus shown in FIG. 1 was used to evaluate the characteristics. Here, the set discharge current I of the charging device (corona charger 6) was set to −127.3 [nA / cm ² ], and the rotational speed of the photosensitive drum 1 was measured at two levels of 1800 rpm and 200 rpm. The surface potential / passing current sampling interval was set to 0.01 sec, and the capacitance calculation method was performed by the method shown in FIG.

A transition result of the surface potential of the photosensitive drum 1 is shown in FIG. 4, and a transition result of the passing current is shown in FIG.
From the results shown in FIGS. 4 and 5, it can be confirmed that the surface potential / passing current gradually changes when measured at a high speed of 1800 rpm, but the surface potential / passing current is measured when measured at a low speed of 200 rpm. In both cases, the discharge state does not change until one revolution, so that it can be confirmed only by the result of the step change. It can also be seen that the measurement results at 200 rpm are delayed in the signal due to the problem of responsiveness in both the surface potential and the passing current.
FIG. 6 is an enlarged graph (schematic graph) of the passing current at 200 rpm, and a region drawn with diagonal lines corresponds to a current delay.

  Further, as a graph of the result of the correspondence relationship between the charged charge amount and the surface potential plotted for calculating the capacitance, FIG. 7 shows the case of 1800 rpm and FIG. 8 shows the case of 200 rpm. Here, the plotted points plot the charge charge amount and surface potential correspondence relationship of all measurement data. Here, from the result of FIG. 7, when calculating the electrostatic capacity at a high speed of 1800 rpm, the same electrostatic capacity result can be obtained by drawing a regression line at any point of the result graph of the charge amount and the surface potential. Can be calculated. On the other hand, the results shown in FIG. 8 show that it is difficult to select points for drawing a regression line when calculating the capacitance at a low speed of 200 rpm. As can be seen from the results of FIGS. 4 and 5, since the charging device and the surface potential probe are not at the same position, the surface potential and the passing current do not change at the same time. Therefore, it can be seen that if the correspondence between the surface potential and the passing current at the time of calculating the capacitance is wrong, the correct capacitance cannot be calculated.

  Next, among the surface potential / passing current sampling data, only the value closest to the value obtained by dividing the surface potential of the Y axis by 26 (-1200 V divided by 26) was plotted on the graph. FIG. 9 shows a result graph of the charge amount and surface potential when the electrostatic capacity is calculated at 1800 rpm, and FIG. 10 shows the result of charge amount and surface potential when the electrostatic capacity is calculated at 200 rpm. A graph is shown.

  From the results shown in FIG. 9, when the capacitance is calculated at a high speed of 1800 rpm, even if only the value closest to the value obtained by dividing the surface potential of the Y axis by 26 is plotted, the charge amount and the surface potential can be obtained without any problem. As a result, a straight line could be drawn from the graph and the capacitance could be calculated. However, as shown in FIG. 10, only the value closest to the value obtained by dividing the surface potential of the Y axis by 26 at a low speed of 200 rpm as in the prior art. It can be seen that it is difficult to draw a straight line by the method of plotting and calculating the capacitance, and it is difficult to calculate the capacitance with high accuracy.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited at all by these Examples.

(Example 1)
Using the characteristic evaluation device shown in Fig. 1 (using an evaluation device designed and manufactured in-house), a drum with a drum diameter of 30 mm, a drum total length of 340 mm, and a drum wall thickness of 0.75 mm, the same materials and materials as the Ricoh IPSIO CX8000 photoconductor Characteristic evaluation was performed using a photosensitive drum coated with a photosensitive layer having a prescribed composition. The drum rotation speed was 1800 rpm, the surface potential / passing current sampling interval was 0.01 sec, and the set discharge current was changed as follows to evaluate the characteristics (calculation of capacitance). Moreover, the method shown in FIG. 2 was used for the capacitance calculation method.

(Example 1a) Set discharge current: -127.3 [nA / cm ² ] (−191.0 / r [nA / cm ² ])
(Example 1b) Set discharge current: -99.0 [nA / cm ² ] (-148.5 / r [nA / cm ² ])
(Comparative Example 1a) Set discharge current: −70.7 [nA / cm ² ] (−106.1 / r [nA / cm ² ])
(Comparative Example 1b) Set discharge current: −42.4 [nA / cm ² ] (−63.7 / r [nA / cm ² ])
(R: Radius of photosensitive drum)

The characteristic evaluation results are shown in Table 1. Here, the electrostatic capacity calculation result when implemented under each set discharge current condition is shown by the electrostatic capacity result (1), and the electrostatic capacity when measured at the set discharge current-127.3 [nA / cm ² ]. The capacitance calculation result is indicated by a capacitance result (2). Moreover, in the characteristic evaluation apparatus used this time, a PET film whose capacitance is known in advance under the condition of a set discharge current of 127.3 [nA / cm ² ] and a rotation speed of 1800 [rpm] is applied to the aluminum base tube. When the electrostatic capacity was calculated by winding, since the same level of electrostatic capacity was obtained, measurement was performed under this condition (set discharge current-127.3 [nA / cm ² ] · rotation speed 1800 [rpm]). Using the calculated capacitance value as a reference, the difference from the result calculated under each set discharge current condition was obtained and shown as the result in the rightmost column of Table 1.

From the results in Table 1, it can be seen that a difference occurs from the reference value when the set discharge current changes. Further, the allowable difference is ± 3% as the difference in capacitance, but the set discharge current is −99.0 [nA / cm ² ] (when the drum radius is r, −148.5 / r [nA / Cm ² ]) or more (both absolute values), it can be seen that the allowable range is not satisfied.

(Examples 2 to 4)
Next, using the characteristic evaluation apparatus shown in FIG. 1, a photosensitive layer having the same material and formulation as the Ricoh IPSIO CX8000 photoreceptor is applied to a drum having a drum diameter of 30 mm, a drum total length of 340 mm, and a drum wall thickness of 0.75 mm. The photosensitive drum 1 was used for property evaluation. The set discharge current is -127.3 [nA / cm ² ], the drum rotation speed is 1800 rpm (rotation cycle 1/30 sec), and the discharge is started when the rotation of the photosensitive drum 1 is stabilized. Passing current sampling interval: The surface potential and the passing current were measured at 0.01 sec, and the charge amount was calculated from the measured passing current using the method shown in FIG. In addition, when plotting the charge charge amount and the surface potential value on the graph, it was determined whether it was possible to draw a straight line in the result graph of the charge charge amount and the surface potential by shifting the time interval of the points to be plotted ( Example 2). In addition, the drum rotation speed was set to 400 rpm (rotation cycle 3/20 sec), and the same evaluation was performed under the same conditions as in Example 2 except for the other conditions. Furthermore, the drum rotation speed was set to 200 rpm (rotation cycle 3/10 sec), and the same evaluation was performed with the other conditions being the same as in Example 2, and Example 4 was obtained.
The determination results are shown in Table 2.

  From the results in Table 2, in the result graph of charge amount and surface potential used when calculating the capacitance, plotting at intervals longer than the drum rotation period at the time of measurement is a straight line from the result graph of charge charge and surface potential. It can be seen that it is a necessary condition for drawing. Further, when the rotational speed is low (Example 4; 200 rpm), it becomes difficult to draw a straight line with high accuracy even when plotted at an interval longer than the rotational cycle. It can be seen that it becomes possible to draw a straight line with high accuracy.

(Example 5)
Using the characteristic evaluation apparatus shown in FIG. 1, a photoconductor in which a drum having a drum diameter of 30 mm, a total drum length of 340 mm, and a drum thickness of 0.75 mm is coated with a photoconductive layer having the same material and composition as the photoconductor for Ricoh IPSIO CX8000. The drum 1 was used for property evaluation. The set discharge current was -127.3 [nA / cm ² ], the drum rotation speed was 200 rpm, the surface potential and the passing current were measured at a sampling interval of 0.01 sec, and the passing potential was measured. Thus, as shown in FIG. 3, the charge charge amount was calculated by a method of adding a value obtained by multiplying the passing current by the correction coefficient N as shown in FIG. The points plotted in the result graph of the charge amount and the surface potential were plotted at 0.3 sec intervals, and the capacitance was calculated by drawing a straight line.

  As described above, a signal delay occurs at a drum rotation speed of 200 rpm (FIG. 6). When there is no signal delay, the passing current should drop at 0.3 sec. However, since the signal response of the current measurement system is delayed, the passing current gradually decreases. Therefore, when plotting at intervals of 0.3 sec, it is also necessary to add the amount of charge corresponding to the region drawn with diagonal lines in FIG. However, since the delay does not change linearly, as a method of approximately correcting the charge amount, a method of adding a value obtained by multiplying the passing current at the time of calculation by the correction coefficient N is performed.

Table 3 shows the electrostatic capacity calculation result a when the level of the correction coefficient N is changed, and the static electricity measured and calculated under the conditions of the set discharge current-127.3 [nA / cm ² ] and the rotation speed 1800 [rpm]. Table 3 shows the results of obtaining the difference (| ab− ÷ b × 100 (%)) based on the electric capacity b (described as a reference sample in the table). Here, since it is the characteristic evaluation apparatus used in Example 1, it was measured and calculated under the same conditions as Example 1 (set discharge current-127.3 [nA / cm ² ] · rotation speed 1800 [rpm]). The difference was calculated based on the capacitance value. Further, the result of the amount of charge charge deviation (charge amount deviation amount) at the charging start potential in the straight line used for the capacitance calculation and the set discharge current of 127.3 [nA / cm ² ]. Table 3 also shows the results of the difference in the amount of charge charge deviation (difference from the reference value of the amount of charge charge amount deviation) at the charging start potential of the straight line used for calculating the capacitance at a rotation speed of 1800 [rpm]. Show.

  From the results in Table 3, since the influence of the signal delay caused by the problem of responsiveness affects the passing current, the electrostatic capacity must be calculated without adding a correction term when calculating the charge amount. It was found that the calculated results differed from the original results (reference sample). It can also be seen that the amount of deviation of the charge charge amount at the charging start potential of the straight line used for calculating the capacitance differs from the reference value, and therefore accurate calculation cannot be made unless a correction term is entered. Furthermore, since the result in the case of the correction coefficient N = 0.1 is a value close to the value of the reference sample, it can be calculated by correcting the influence of the delay by multiplying the charging current at the time of calculation by the coefficient. I understand that. As for the correction term, in order to correct the delay of the signal, it can also be understood from the results of Table 3 that it has no meaning unless it is a positive value.

(Example 6)
Next, using the characteristic evaluation device shown in FIG. 1 (using an evaluation device designed and manufactured in-house), a drum having a drum diameter of 30 mm, a drum total length of 340 mm, and a drum wall thickness of 0.75 mm, a Ricoh IPSIO CX8000 photoconductor and The characteristics were evaluated using a photosensitive drum coated with a photosensitive layer of the same material and composition. The drum rotation speed is 200 rpm, the set discharge current is changed under the following conditions, the surface potential / passing current sampling interval: 0.01 sec, the surface potential and the passing current are measured, and the result graph of the charge amount and the surface potential is shown in the graph. The points to be plotted were plotted at intervals of 0.3 sec. When the charge amount was calculated by the method shown in FIG. 3, the correction coefficient N was corrected to 0.1, and the capacitance was calculated.

(Example 6a) Set discharge current: -127.3 [nA / cm ² ] (−191.0 / r [nA / cm ² ])
(Example 6b) Set discharge current: -99.0 [nA / cm ² ] (-148.5 / r [nA / cm ² ])
(Comparative Example 6a) Set discharge current: −70.7 [nA / cm ² ] (−106.1 / r [nA / cm ² ])
(Comparative Example 6b) Set discharge current: −42.4 [nA / cm ² ] (−63.7 / r [nA / cm ² ])
(R: Radius of photosensitive drum)

The characteristic evaluation results are shown in Table 4. Here, the electrostatic capacity calculation result when implemented under each set discharge current condition is shown by an electrostatic capacity result (1), and the same photoconductor is rotated at 1800 rpm and set discharge current-127.3 [nA / cm ^2. ] Shows the capacitance calculation result when measured in [Capacitance Result (2)]. In addition, since the characteristic evaluation apparatus used this time uses the same characteristic evaluation apparatus as in Example 1, the measurement was performed under the conditions of the set discharge current of 127.3 [nA / cm ² ] and the rotation speed of 1800 [rpm]. Using the calculated capacitance value as a reference, the difference from the result calculated under each set discharge current condition was obtained and shown as the result in the rightmost column of Table 4.

From the results in Table 4, it can be seen that the result at 200 rpm is different from the reference value by changing the set discharge current in the same manner as the result of Example 1 measured at the rotation speed of 1800 rpm. Although the allowable range is ± 3% as the difference in capacitance, the set discharge current is -99.0 [nA / cm ² ] from the results shown in Table 4 (when the drum radius is r, -148.5 / r [nA / cm ² ]) or more (both absolute values), it can be seen that the allowable range is not satisfied. It can also be seen that the difference in electrostatic capacity is larger in the low-speed rotation than in the high-speed rotation results in Table 1.

  Although the present invention has been described with the embodiments shown in the drawings, the present invention is not limited to the embodiments shown in the drawings, and other embodiments, additions, modifications, deletions, etc. Can be changed within the range that can be conceived, and any embodiment is included in the scope of the present invention as long as the effects and advantages of the present invention are exhibited.

It is the schematic which shows the structural example of the characteristic evaluation apparatus of the electrophotographic photoreceptor based on this invention. It is explanatory drawing of an electrostatic capacitance calculation method. It is explanatory drawing of the electrostatic capacitance calculation method at the time of putting a correction coefficient at the time of electrostatic capacitance calculation. It is a surface potential transition comparison graph at the time of high speed rotation (1800 rpm) and low speed rotation (200 rpm). It is a passage current transition comparison graph at the time of high speed rotation (1800rpm) and low speed rotation (200rpm). It is a passage current transition enlarged graph (schematic graph) at the time of low speed rotation (200 rpm). It is the graph which plotted the result of charge amount and surface potential using all the measurement data measured at 1800rpm. It is the graph which plotted the charge amount of charge and the result of surface potential using all the measurement data measured at 200 rpm. It is a result graph (a plot which divides the Y-axis into 26) from the result of measurement at 1800 rpm and the charge amount and surface potential. It is a result graph (plotted by dividing the Y-axis into 26) from the result of measurement at 200 rpm and the charge amount and surface potential.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Exposure guide box 3 Surface potential meter probe 4 Surface potential meter 5 Signal processing circuit 6 Corona charger 7 Power supply 8 Light source for static elimination 9 Signal processing circuit 10 Lamp box 11 Exposure lamp 12 Aperture 13 Power switch 14 Motor 15 Controller 16 A / D converter

Claims (7)

A step of rotating a sample which is a drum-shaped electrophotographic photoreceptor;
An electrostatic charging step of charging the photosensitive surface of the sample by discharging from a charging device;
A photo-discharge step of photo-discharge the photosensitive surface of the sample after charging by exposure;
A method for calculating the capacitance of an electrophotographic photoreceptor, comprising: a capacitance calculating step for obtaining a capacitance of the sample based on a detection result of a surface potential and a charge amount of the sample;
A method for calculating the capacitance of an electrophotographic photoreceptor, wherein the discharge current I of the charging device satisfies the following formula:
| I | ≧ 148.5 / r [nA / cm ² ]
(R: drum radius of the sample (unit: cm)) In the method for calculating the capacitance of the electrophotographic photoreceptor according to claim 1,
In the capacitance calculating step, the capacitance of the sample is obtained based on the detection result of the surface potential and charge amount of the sample collected at a time interval equal to or greater than the rotation period of the sample. A method for calculating the capacitance of an electrophotographic photoreceptor. In the method for calculating the capacitance of the electrophotographic photoreceptor according to claim 2,
In the capacitance calculating step, the capacitance of the sample is obtained based on the detection result of the surface potential and charge amount of the sample collected at an integer multiple of the rotation period of the sample. A method for calculating the capacitance of an electrophotographic photoreceptor. In the method for calculating the electrostatic capacity of the electrophotographic photoreceptor according to claim 3,
The charged amount of charge of the sample is a value obtained by adding the correction based on the signal response of the current measurement system to the value obtained by integrating the passing current value of the sample with the elapsed charging time. Capacitance calculation method. In the method for calculating the electrostatic capacity of the electrophotographic photoreceptor according to claim 4,
The method for calculating the capacitance of an electrophotographic photoreceptor, wherein the charge amount of the sample is calculated by a method of multiplying a passing current value of the sample by a coefficient. In the method for calculating the capacitance of the electrophotographic photoreceptor according to claim 5,
The coefficient is a positive value, and the electrostatic capacity of the electrophotographic photoreceptor is calculated.   A sample rotating device that is a drum-shaped electrophotographic photosensitive member, a charging device that charges the photosensitive surface of the sample by discharging, an exposure device that exposes the photosensitive surface of the sample, and a charged potential on the sample surface is detected. An electrostatic charge detection device for detecting the charge amount of the sample, a charge amount detection device for detecting a charge amount of the sample, and a method for calculating the electrostatic capacity of the electrophotographic photoreceptor according to claim 1. An apparatus for evaluating characteristics of an electrophotographic photoreceptor, comprising: an electrostatic capacity calculating means for obtaining a capacity.

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