JP2005099133A - Method for accelerated testing of deterioration in electrophotographic photoreceptor and electrostatic charger used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for stable and accelerated testing of deterioration by the increase or the like of the current flowing 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 stretched in a mesh form. 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. On the other hand, the current passing through the electrophotographic photoreceptor when an A4 size sheet is printed out with an actual machine is determined by the electrostatic capacity C (value per unit area) of the photoreceptor and the charging potential V. The size of the photoreceptor is Assuming that the size of one A4 sheet can be printed on the photoconductor without duplication, it is obtained from C · V, and as a result, the life test time is made to correspond to the number of prints of the actual machine by the value of Q / (C · V). It is possible to do.
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, in such a conventional deterioration acceleration test apparatus, it takes a lot of time to determine the life of the photoconductor having a long life.

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 stretched in a mesh shape, and the casing surrounding the wires is not entirely casing on a surface parallel to the electrophotographic photoreceptor surface. Photoreceptor deterioration acceleration test method characterized by being ",
(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) This is achieved by the “photoconductor deterioration acceleration test method according to (1) or (2), wherein the electrostatic charging step and the exposure step are performed simultaneously”.

In addition, the above-described problem is solved by (4) the electrostatic charging step of the test method of the present invention in which a cycle including an electrostatic charging step and an exposure step is repeated on the electrophotographic photosensitive member to accelerate the deterioration of the electrophotographic photosensitive member. And a plurality of wires stretched in a mesh shape, and the casing surrounding the wires is entirely casing on a surface parallel to the surface of the electrophotographic photoreceptor. A charging device characterized in that it is not, "
(5) “Charging device according to item (4), wherein the surface of the casing portion is formed of an insulating member”;
(6) “A charging device according to the item (4) or (5), wherein the interval between the plurality of wires is larger than 2 mm”.

In the present invention, the electrophotographic photoreceptor is repeatedly subjected to a cycle including an electrostatic charging step and an exposure step, and has a plurality of wires as a charging device in the electrostatic charging step so that the wires are stretched in a mesh shape, and The test method for accelerating the deterioration of the electrophotographic photosensitive member using a casing that surrounds the wire and whose surface parallel to the photosensitive member surface is not casing is the current per unit area flowing on the photosensitive member surface. The amount 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.
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 clear from the above and the following detailed and specific explanation, in the test method for accelerating the deterioration of the electrophotographic photoreceptor by repeating the electrostatic charging process and the cycle including the exposure process on the electrophotographic photoreceptor, The charging device used for the electrostatic charging process has a plurality of wires so that the wires are stretched in a mesh shape, and the shape of the casing surrounding the wires is that all surfaces parallel to the photoreceptor surface are casing. Therefore, the amount of current per unit area flowing on the surface of the photoreceptor 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, when 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.
In addition, when AC is superimposed on the 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]
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 a wire in a mesh shape at intervals of 10 mm in the frame (material: gold-plated tungsten wire, wire diameter: 60 μm) The charging device frame uses a charging device using an insulating member (material: polytetrafluoroethylene-based fluororesin) (a schematic diagram of the charging device is shown in FIGS. 2-1 and 2-2). FIG. 6 shows the result of measuring the corona current when the distance between the sample and the wire is 5 mm and the aluminum plate is corona discharged. (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. FIG. 6 also shows the results of measuring the corona current when corona discharge is applied to an aluminum plate when two wires are stretched at intervals of 10 mm and the distance between the wire and the sample surface is 5 mm. (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 in a mesh shape, and the shape of the casing surrounding the wires is all casings parallel to the photoreceptor surface. By having no casing, the casing has an opening only on the surface facing the photoreceptor, and the amount of current can be increased with the same applied voltage as compared with a charging device stretched with a wire only in one direction inside the casing. I understand.

[Example 2 (corresponding to claim 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 a wire (material: gold-plated tungsten wire, wire diameter: 60 μm) is formed in the frame at intervals of 10 mm. The charging device frame was a corona discharge to an aluminum plate when 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. 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.)
As Comparative Example 2 corresponding to Example 2, the charging device has a casing of 50 × 50 (mm) on a surface parallel to the sample, and has an opening frame of 50 × 50 (mm). : Gold-plated tungsten wire, wire diameter: 60 μm), and the charging device frame uses a charging device using a conductive member (material: aluminum), and when the distance between the sample and the wire is 5 mm, the aluminum plate The results of measuring the corona current when corona discharge is 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. 3.)
From the result of FIG. 7, it can be seen that the amount of current flowing to the sample is increased by using an insulating member on the surface of the charging device.

Example 3
As a charging device, there is no casing on the 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) is stretched 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より大きくなければ、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 if the wire interval is not larger than 2 mm, the 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 an opening frame of 50 x 50 (mm), and wires (material: gold-plated tungsten wire, wire diameter: 60 μm) are formed in the frame at intervals of 10 mm. The charging device frame uses a charging device that uses an insulating member (material: polytetrafluoroethylene fluoropolymer), and corona discharge to the aluminum plate when the distance between the sample and the wire is varied. Table 2 shows the results of the discharge start voltage when the discharge is performed. (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 if the distance between the sample and the wire is not 2 mm or more, the 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 wires (material: gold-plated tungsten wire, wire diameter: 60 μm) are formed in the frame at intervals of 10 mm. A charging device using an insulating member (material: polytetrafluoroethylene-based fluororesin) was used as the frame of the charging device, and 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. (A schematic diagram of the charging device is shown in FIGS. 2-1 and 2-2 as in Examples 1 to 4, and a schematic diagram of the experimental device is shown in FIG. 3.)
As Comparative Example 3 corresponding to Example 5, the conventional deterioration acceleration test apparatus shown in FIG. 1 was used, and the charger had a casing having an opening only on the sample-facing surface. Uses a charger in which wires (material: gold-plated tungsten wire, wire diameter: 60 μm) are stretched at 10 mm intervals and the distance between the wires and the sample is 5 mm, and rotates in the same way as the deterioration acceleration test (1100 rpm) 8), the results of measuring the corona current when corona discharge is applied to the aluminum plate are also shown in FIG. (A schematic diagram of the charging device is shown in FIG. 3. In Comparative Example 3, 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 with 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 (6)

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 is meshed Photoconductor deterioration characterized in that it has a plurality of stretched wires and the shape of the casing surrounding the wires is not entirely casing on a plane parallel to the electrophotographic photoreceptor surface Accelerated test method. 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 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. A charging device comprising a plurality of wires mounted and having a casing surrounding the wires that is not entirely casing on a surface parallel to the surface of the electrophotographic photoreceptor. The charging device according to claim 4, wherein a surface of the casing portion is formed of an insulating member. The charging device according to claim 4, wherein an interval between the plurality of wires is larger than 2 mm.

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