JP2005099111A - Method for accelerated testing of deterioration in electrophotographic photoreceptor and electrostatic charger used for it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for stable and accelerated testing of deterioration by increase or the like of the current flow per unit area of a sample. <P>SOLUTION: In the method for testing, the deterioration of an electrophotographic photoreceptor is accelerated by repetitively applying cycles including an electrostatic charging process and an exposure process to the electrophotographic photoreceptor. The electrostatic charger used for the electrostatic charging process has a plurality of wires to which a high voltage is applied and which are stretched only in one direction. The shape of a casing enclosing the wires is such that all of the surfaces parallel to the surface of the electrophotographic photoreceptor have no casing surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a deterioration acceleration test method for evaluating the characteristics of an electrophotographic photoreceptor and a charging device used therefor.

Conventionally, a method for evaluating the lifetime, which is one of the characteristics of an electrophotographic photoreceptor provided with a photoconductive layer, has been proposed.
Prepare at least one electrophotographic photoconductor having a confirmed cycle operation life of an image forming cycle, and repeat the electrophotographic photoconductor through a cycle including an electrostatic charging step and a photodischarge step. The dark decay of the photoconductive layer is measured until the dark attenuation reaches the maximum value. Based on the maximum value, the dark decay maximum value vs. the image formation cycle standard data is established, and then newly prepared. In the same manner for the electrophotographic photosensitive member, the cycle including the electrostatic charging step and the photodischarge step was repeated until the dark attenuation amount reached the maximum value that remained substantially constant even after the cycle operation, There is a method of confirming the estimated cycle life of the newly produced electrophotographic photoreceptor by comparing the dark decay maximum value of the fresh electrophotographic image forming member with the reference data (for example, Patent Document 1 reference.).
This method is repeated through a cycle including an electrostatic charging process and a light discharge process, and the newly prepared electrophotographic photoreceptor is compared with the dark decay of a deteriorated electrophotographic photoreceptor. This is characterized by the fact that the estimated cycle life is confirmed. Specifically, it is called corona charging / roller charging applied in an actual electrophotographic process by pressing a transparent glass and applying bias and irradiating light. Is a deterioration test performed by a different method.
In addition, in this method, it is necessary to confirm in advance the dark decay characteristics of a sample that has reached the end of its life. For this reason, a photosensitive member for electrophotography must be once mounted in a machine and a paper passing test must be performed. There was a problem that took a lot of time and effort.

Therefore, as a method for confirming the life without carrying out the paper passing test, the charging is arranged around the electrophotographic photosensitive member rotated at a high speed (1,000 to 2,000 rpm). There is a method of predicting the lifetime by repeatedly charging and exposing with a light source and an exposure apparatus. This method is further divided into two test methods.
The first method is to fix the output of the charger and the light intensity of the exposure device under predetermined conditions, perform the test within a predetermined time, and then perform the measurement to evaluate the characteristics of the electrophotographic photosensitive member. Determine the state.
The second method measures the post-exposure potential V of the electrophotographic photoreceptor under test and the passing current I flowing through the electrophotographic photoreceptor, and outputs the charger so that these two are always at a predetermined level. And adjusting the light quantity of the exposure apparatus.
The important point in these two methods is that the current passing through the electrophotographic photoreceptor during the test is measured, and this value is converted to obtain the charge amount (value per unit area) Q, while A4 The current passing through the electrophotographic photosensitive member when printing out one size with an actual machine is based on the electrostatic capacity C (value per unit area) of the photosensitive member and the charging potential V. The size of the photosensitive member is A4 paper 1 Assuming that the size of the sheet is such that it can be printed on the photoconductor without duplication, C · V is obtained. As a result, the life test time can be made to correspond to the number of printed sheets of the actual machine by the value of Q / (C · V). is there.
Yet another important point is that this test is an accelerated life test.
Specifically, when a 20-hour test is conducted by passing a sample-passing current of 5 μA / 10 cm ² through the electrophotographic photosensitive member (10 days a day for 2 days), 5/10 × 10 5 ⁻⁶ × 20 × 60 × 60 = 0.036 (C / cm ² ) of charge passed through the photoconductor. Assuming that printing is performed with A4 paper vertical feed, the electrostatic capacity of the electrophotographic photosensitive member is 100 (pF / cm ² ), the charging potential is −700 (V), and the post-exposure potential including after static elimination is set. Assuming 0 (V), 100 × 10 ⁻¹² × 700 = 7 × 10 ⁻⁸ (C / cm ² ) becomes a charge that passes through the photoconductor when the A4-1 sheet is printed out. This means that 036 / (7 × 10 ⁻⁸ ) ≈514,000 (sheets) has been printed out, which is a significant acceleration test.
For this reason, the life test is often performed by the second method. As can be seen from the specific calculation described above, if the current passing through the photoconductor is constant during the test, the number of printouts corresponding to It is easy to calculate whether the test was done.
Therefore, in general, the test is performed with a constant passing current. The essence is to know the passing charge amount. Depending on the level of the charged potential depending on the photosensitive member, the result of the life test may differ, and it is required to perform the test with the charged potential kept constant.
Thus, in order to make the charging potential and the passing current constant, a system for adjusting the high-voltage power supply output of the charger and adjusting the light amount of the exposure apparatus is required, and a conventional life test apparatus has been constructed.

In this conventional system, the relationship between the two measured quantities, the surface potential X, the passing current Y, the two manipulated variables, the output control value A of the charger high-voltage power supply, and the output control value B of the discharge lamp light quantity is X and Y increase when increasing, X and Y decrease when A decreases, X decreases when Y increases, Y increases, X decreases when B decreases, and Y decreases If X deviates from the target value and A or B is manipulated so as to be within the target range, another measured amount Y changes, and disturbances act on Y.
If A or B is operated to maintain this within the target range, X will change this time, and complicated control must be performed.
In addition, even if there is a momentary variation in the photoreceptor surface potential / passing current during the deterioration acceleration test, it is a system that does not reflect this in the calculation of the passing charge as an instantaneous error. Could not be done.

Thus, a method for solving these problems has been proposed (see, for example, Patent Document 2).
In Patent Document 2, the electrophotographic photosensitive member is rotated at high speed, and a cycle including an electrostatic charging process and a light discharge by a charging device is repeatedly executed to control and measure the surface potential of the photosensitive member at a constant condition. By calculating the passing charge amount from the passed current, a simple and accurate electrophotographic photosensitive member deterioration acceleration test apparatus is considered.
An outline of the deterioration acceleration test apparatus shown in Patent Document 2 is shown in FIG.
The photosensitive layer surface of the sample piece of the electrophotographic photosensitive member is mounted face down in the opening (3) of the turntable (1) and set by the sample piece holding plate (2), and then the sample is collected by the corona charger (4). The photosensitive layer surface of one piece is charged.
During the charging process, the turntable (1) can be stopped at a position where the electrophotographic photoconductor sample piece is placed stationary against the corona charger (4), and at the same speed as the actual machine. In addition, since the sample piece is charged and the state of the rising of the charge is observed, the sample piece can be passed through the charger many times by rotating at high speed.
The pulse current applied to the sample piece from the corona charger (4) and charged to the sample piece is sent to the ammeter (6) and smoothed by the smoothing circuit therein, and then the A / D converter ( In 8), it is converted and sent to the controller (9) for calculation processing.
Further, the surface potential of the sample piece is monitored by the surface electrometer electrode (5) which is a monitor unit of the surface electrometer (7) arranged at a position different from the corona charger (4), and the monitored signal is After being sent to the surface electrometer (7) and amplified by an amplifier therein, it is converted by the A / D converter (8), sent to the controller (9) and processed. In the deterioration acceleration test, the turntable is rotated at a high speed, the photosensitive surface of the sample piece is charged with the corona charger (4) for deterioration test, and then the photodischarge process is performed with the exposure device (5). By repeating this, the charge in the photosensitive layer is forcibly passed and the lifetime can be judged earlier than the actual machine.

  However, recent electrophotographic photoconductors have a long life, and when the above-described deterioration acceleration test apparatus is used, it takes much time to perform a test until the life is determined. Accordingly, there has been a demand for an accelerated deterioration test method that can further accelerate deterioration and judge the life in a short time. In order to realize this, it has been found that it is important to increase the amount of current to the electrophotographic photoreceptor surface per unit area.

Japanese Patent Laid-Open No. 5-1973 JP 2002-149005 A

  Accordingly, an object of the present invention is to provide a stable and accelerated accelerated acceleration test method by increasing the current flowing per unit area of a sample in view of the above prior art.

The above-described problem is (1) a test method for accelerating deterioration of an electrophotographic photosensitive member by repeating a cycle including an electrostatic charging step and an exposure step on the electrophotographic photosensitive member. The charging device used in the process has a plurality of wires to which a high voltage is applied, the wires are stretched in only one direction, and the shape of the casing that surrounds the wires is the shape of the casing that surrounds the wires. `` Photoconductor deterioration acceleration test method characterized in that the entire surface parallel to the electrophotographic photoreceptor surface is not casing ''
(2) “Electrophotographic photosensitive member deterioration acceleration test method according to item (1), wherein the distance between the electrophotographic photosensitive member surface and the charging device wire is 2 mm or more”;
(3) “The photoreceptor deterioration acceleration test method according to (1) or (2) above, wherein the high voltage applied to the wire of the charging device superimposes the AC voltage on the DC voltage”,
(4) “A photoreceptor deterioration acceleration test method according to any one of items (1) to (3), wherein the electrostatic charging step and the exposure step are performed simultaneously”. .

In addition, the above-described problem is solved by (5) the electrostatic charging step of the test method of accelerating the deterioration of the electrophotographic photosensitive member by repeating a cycle including the electrostatic charging step and the exposure step on the electrophotographic photosensitive member. A plurality of wires to which a high voltage is applied, the wires are stretched in only one direction, and the shape of the casing surrounding the wires is relative to the surface of the electrophotographic photoreceptor In addition, the charging device is characterized in that all the parallel surfaces are not casing "
(6) “Charging device according to item (5), wherein the surface of the casing portion is formed of an insulating member”;
(7) This is achieved by “the charging device according to (5) or (6) above, wherein the interval between the plurality of wires is 2 mm or more”.

In the test method for accelerating the deterioration of the electrophotographic photosensitive member of the present invention, a cycle including an electrostatic charging step and an exposure step is repeated on the electrophotographic photosensitive member, and a high voltage is applied as a charging device in the electrostatic charging step. If the wire is stretched in only one direction and the shape of the casing surrounding the wire is such that all surfaces parallel to the surface of the photoconductor are not casing, The amount of current per unit area that flows can be increased.
In addition, when the charging device used in the test method of the present invention is such that the surface of the casing portion is formed of an insulating member, it is possible to prevent a current from flowing to the casing portion, and a unit that flows on the surface of the photoreceptor. The amount of current per area can be further increased.
Further, when a charging device having a wire interval of more than 2 mm is used as the charging device used in the test method of the present invention, it is possible to prevent spark discharge on the surface of the photoreceptor.
In the test method of the present invention, if the distance between the photoreceptor surface and the wire of the charging device is 2 mm or more, it is effective to prevent spark discharge to the photoreceptor surface.
Further, in the test method of the present invention, it is preferable that the high voltage applied to the charging device superimposes AC on the DC voltage because the adjustment range of the current flowing to the photosensitive member is widened and easy to handle.
In the test method of the present invention, if the electrostatic charging step and the exposure step are performed simultaneously, the photoreceptor deterioration can be accelerated and the deterioration acceleration test time can be shortened.

As is apparent from the above and the following detailed and specific description, in the test method for accelerating the deterioration of the electrophotographic photosensitive member by repeating the cycle including the electrostatic charging step and the exposure step, The charging device used in the charging process has a plurality of wires to which a high voltage is applied, the wires are stretched in only one direction, and the shape of the casing surrounding the wires is all parallel to the photoreceptor surface. Since the charging device is not casing, the amount of current per unit area flowing on the surface of the photosensitive member can be increased, and the test time in the deterioration acceleration test can be shortened.
In addition, since the surface of the casing portion of the charging device is formed of an insulating member, it is possible to prevent current from flowing to the casing portion and increase the amount of current per unit area that flows to the surface of the photosensitive member. It is more effective to shorten the test time in the test.
Further, if the wire interval of the charging device is larger than 2 mm, it is possible to prevent spark discharge on the surface of the photosensitive member, and an accurate deterioration acceleration test can be performed.
Further, if the distance between the photosensitive member surface and the wire of the charging device is 2 mm or more, spark discharge to the photosensitive member surface can be prevented, and an accurate deterioration acceleration test can be performed.
Further, when AC is superimposed on the DC voltage by the high voltage applied to the charging device, the adjustment range of the current flowing to the photosensitive member is widened, and the handling becomes easy.
Further, if the electrostatic charging step and the exposure step are performed simultaneously, the photoreceptor deterioration can be accelerated and the deterioration acceleration test time can be shortened.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
[Example 1 (corresponding to claim 1)]
As a charging device, there is no casing on the surface parallel to the sample, and there is an opening frame of 50 x 50 (mm), and wires (material: gold-plated tungsten wire, wire diameter: 60 μm) are only in one direction at intervals of 10 mm within the frame. Using a charging device (charging device schematic diagram shown in FIGS. 2-1 and 2-2) using an insulating member (material: polytetrafluoroethylene-based fluororesin) for the frame of the tensioning and charging device, a sample FIG. 6 shows the results of measuring the corona current when corona discharge is performed on the aluminum plate when the distance between the wire and the wire is 5 mm. (A schematic diagram of the experimental apparatus is shown in FIG. 3.)
On the other hand, as Comparative Example 1 corresponding to Example 1, a casing having an opening only on the sample facing surface is provided, and a wire (material: gold-plated tungsten wire, wire diameter: 60 μm) is provided only in one direction inside the casing. When two wires are stretched at intervals of 10 mm and the distance between the wire and the sample surface is 5 mm, the corona current when corona discharge is performed on the aluminum plate is measured, and the results are also shown in FIG. (The schematic diagram of the charging device is shown in FIG. 3, and the schematic diagram of the experimental device is shown in FIG. 4.)
From the result of FIG. 6, the charging device has a plurality of wires, the wires are stretched only in one direction, and the shape of the casing surrounding the wires is that all surfaces parallel to the photoreceptor surface are casing. Therefore, it is possible to increase the amount of current with the same applied voltage as compared with a charging device having a casing having an opening only on the surface facing the photoconductor, and extending inside the casing with a wire only in one direction. I understand that.

[Example 2]
As a charging device, there is no casing on the surface parallel to the sample, and there is an opening frame of 50 x 50 (mm), and the wire is only in one direction at intervals of 10 mm within the frame (material: gold-plated tungsten wire, wire diameter: 60 μm) Using a charging device that uses an insulating member (material: polytetrafluoroethylene-based fluororesin) for the frame of the charging device, when the distance between the sample and the wire was 5 mm, corona discharge was applied to the aluminum plate. The result of measuring the corona current is shown in FIG. (Similar to Example 1, the schematic diagram of the charging device is shown in FIGS. 2-1 and 2-2, and the schematic diagram of the experimental device is shown in FIG. 3.)
On the other hand, as Comparative Example 2 corresponding to Example 2, the charging device has no casing on the surface parallel to the sample and has an opening frame of 50 × 50 (mm), and the frame is only in one direction at intervals of 5 mm in the frame. When a wire (material: gold-plated tungsten wire, wire diameter: 60 μm) is stretched, and the frame of the charging device uses a charging device using a conductive member (material: aluminum), and the distance between the sample and the wire is 5 mm, The corona current when corona discharge is applied to the aluminum plate is measured, and the results are also shown in FIG. (Similar to Example 2, the schematic diagram of the charging device is shown in FIGS. 2-1 and 2-2, and the schematic diagram of the experimental device is shown in FIG. 4.)
From the result of FIG. 7, it can be seen that when the surface of the charging device is an insulating member, the amount of current flowing to the sample increases.

Example 3
As a charging device, there is no casing on a surface parallel to the sample, and there is a 50 × 50 (mm) opening frame, and a wire (material: gold-plated tungsten wire, wire diameter: 60 μm) is stretched only in one direction in the frame, As the frame of the charging device, a charging device using an insulating member (material: polytetrafluoroethylene-based fluororesin) was used, and the distance between the sample and the wire was 5 mm.
Table 1 shows the results of the discharge start voltage when corona discharge is applied to the aluminum plate when the wire spacing level is varied. (A schematic diagram of the charging device is shown in FIGS. 2-1 and 2-2 as in Examples 1 and 2, and a schematic diagram of the experimental device is shown in FIG. 3.)

表１の結果から、ワイヤ間隔が２ｍｍ以下であると、火花放電が発生していることがわかる。このことから、ワイヤ間隔が２ｍｍ以上でなければ、サンプル面に均一にコロナ放電がされず、正確な劣化加速試験を行なうことが出来ないことがわかる。

From the results in Table 1, it can be seen that spark discharge is generated when the wire interval is 2 mm or less. From this, it can be seen that unless the wire interval is 2 mm or more, corona discharge is not uniformly applied to the sample surface, and an accurate deterioration acceleration test cannot be performed.

Example 4
As a charging device, there is no casing on the surface parallel to the sample, and there is a 50 × 50 (mm) opening frame, and wires (material: gold-plated tungsten wire, wire diameter: 60 μm) are formed in the frame at intervals of 10 mm. Use a charging device that uses an insulating material (material: polytetrafluoroethylene-based fluororesin) for the frame of the tensioning and charging device. When the distance between the sample and the wire is varied, corona discharge is applied to the aluminum plate. Table 2 shows the results of the discharge start voltage. (The schematic diagram of the charging device is the same as in Examples 1-3, and FIGS. 2-1 and 2-2, and the schematic diagram of the experimental device is shown in FIG. 3.)

表２の結果から、サンプルとワイヤ間の距離は２ｍｍ以上ないと、火花放電が発生していることがわかる。このことから、サンプルとワイヤ間の距離は２ｍｍ以上でなければ、サンプル面へ均一にコロナ放電がされず、正確な劣化加速試験を行なうことが出来ないことがわかる。

From the results in Table 2, it can be seen that spark discharge occurs when the distance between the sample and the wire is not 2 mm or more. From this, it can be seen that unless the distance between the sample and the wire is 2 mm or more, corona discharge is not uniformly applied to the sample surface, and an accurate deterioration acceleration test cannot be performed.

Example 5
As a charging device, there is no casing on the surface parallel to the sample, and there is an opening frame of 50 x 50 (mm), and within that frame, wires are arranged in only one direction at intervals of 10 mm (material: gold-plated tungsten wire, wire diameter: 60 μm) A charging device using an insulating member (material: polytetrafluoroethylene-based fluororesin) for the frame of the charging device is used, and the voltage applied to the charging device is superimposed on AC (AC superimposition condition: Vpp) = 2000 V, f = 500 Hz), when adjusting the distance between the sample and the wire, the adjustment range of the high voltage power supply when adjusting to 0 to -20 (μA / cm ² ) when corona discharge is applied to the aluminum plate Table 2 shows the results.
On the other hand, as Comparative Example 4 corresponding to Example 5, there is no casing on a surface parallel to the surface of the photosensitive member, and there is a 50 × 50 (mm) opening frame, and a wire (material) in a mesh shape at intervals of 10 mm in the frame. : Gold-plated tungsten wire, wire diameter: 60 μm) The charging device frame uses a charging device that uses an insulating material (material: polytetrafluoroethylene-based fluororesin), and the voltage applied to the charging device is DC only When the level of the distance between the sample and the wire is changed, the result of the adjustment range of the high voltage power supply when adjusting to 0 to −20 (μA / cm ² ) when corona discharge is applied to the aluminum plate (0 to −20 (μA / cm ² )) is shown in Table 3. (The schematic diagram of the charging device is shown in FIGS. 2-1 and 2-2 as in Examples 1 to 4, and the experimental device is shown in FIG. 3.)

表３の結果から帯電装置への印加電圧にＡＣを重畳することにより、サンプルに流れる電流の調整幅が広がり、劣化加速試験時に電流調整がし易くなることがわかる。

From the results in Table 3, it can be seen that by superimposing AC on the voltage applied to the charging device, the adjustment range of the current flowing through the sample is widened, and it is easy to adjust the current during the deterioration acceleration test.

Example 6
As a charging device, there is no casing on a surface parallel to the sample, and there is an opening frame of 50 × 50 (mm), and a wire (material: gold-plated tungsten wire, wire diameter: 60 μm) only in one direction at intervals of 10 mm within the frame. ) And using a charging device that uses an insulating material (material: polytetrafluoroethylene-based fluororesin) as the frame of the charging device. When the distance between the sample and the wire is 5 mm, corona discharge is applied to the aluminum plate. The result of measuring the corona current is shown in FIG. (A schematic diagram of the charging device is shown in FIGS. 2-1 and 2-2 as in Examples 1 to 5, and a schematic diagram of the experimental device is shown in FIG. 3.)
On the other hand, as Comparative Example 4 corresponding to Example 6, the conventional deterioration acceleration test apparatus shown in FIG. 1 was used, and the charger had a casing having an opening only on the surface facing the sample. Inside, only two wires (material: gold-plated tungsten wire, wire diameter: 60 μm) are stretched at 10 mm intervals, and a charger with a 5 mm gap between the wire and the sample is used. FIG. 8 also shows the results of measuring the corona current when the corona discharge is performed on the aluminum plate when rotating (1100 rpm). (A schematic diagram of the charging device is shown in FIG. 3. In Comparative Example 6, the corona current is smoothed by the smoothing circuit during the rotation, so that the current value does not change during the rotation and is constant.)
From the result of FIG. 8, the exposure process can be performed simultaneously with the charging process by using a charger without a casing on the surface parallel to the surface of the photoconductor, and further without the casing parallel to the surface of the photoconductor. It can be seen that a much larger current can be obtained compared to the accelerated deterioration test, leading to a reduction in the accelerated deterioration test time.

It is the schematic of the conventional deterioration acceleration test apparatus. It is the figure which showed the charging device schematic used in this invention. It is the figure which showed the experimental apparatus schematic used by this invention. It is another figure which showed the experimental apparatus schematic used by this invention. It is another figure which showed the experimental apparatus schematic used by this invention. It is the figure which showed the result of having measured the corona electric current when making an aluminum plate corona discharge in Example 1. FIG. It is the figure which showed the result of having measured the corona electric current when it was made to corona discharge to the aluminum plate in Example 2. FIG. It is the figure which showed the result of having measured the corona electric current when it was made to corona discharge to the aluminum plate in Example 6. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Turntable 2 Sample piece presser plate 3 Opening part 4 Corona charger 5 Surface potential meter electrode part and exposure apparatus 6 Ammeter 7 Surface potential meter 8 Interface (A / D conversion)
9 Controller 10 Casing 11 Wire 12 Aluminum plate 13 Sample stand 14 High voltage power supply

Claims (7)

A test method for accelerating deterioration of an electrophotographic photosensitive member by repeating a cycle including an electrostatic charging step and an exposure step on the electrophotographic photosensitive member, wherein the charging device used in the electrostatic charging step has a high voltage A plurality of wires to be applied are stretched in only one direction, and the shape of the casing surrounding the wires is parallel to the surface of the electrophotographic photoreceptor. A method for accelerating photoconductor degradation, characterized in that the entire surface is not casing. 2. The electrophotographic photoreceptor deterioration acceleration test method according to claim 1, wherein the distance between the electrophotographic photoreceptor surface and the wire of the charging device is 2 mm or more. 3. The photoreceptor deterioration acceleration test method according to claim 1, wherein the high voltage applied to the wire of the charging device superimposes an AC voltage on a DC voltage. 4. The method for accelerating a photoreceptor deterioration according to claim 1, wherein the electrostatic charging step and the exposure step are performed simultaneously. A charging device used in the electrostatic charging step of a test method for accelerating deterioration of an electrophotographic photosensitive member by repeating a cycle including an electrostatic charging step and an exposure step on the electrophotographic photosensitive member, and a high voltage is applied. The wire is stretched only in one direction, and the shape of the casing surrounding the wire is not entirely casing on a plane parallel to the surface of the electrophotographic photoreceptor. There is a charging device. The charging device according to claim 5, wherein a surface of the casing portion is formed of an insulating member. The charging device according to claim 5 or 6, wherein an interval between the plurality of wires is 2 mm or more.

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