JP2010072056A - Conductive member evaluation device and conductive member evaluation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive member evaluation device that are used for correctly evaluating a conductive member that charges an electrostatic latent image carrier, and to provide a conductive member evaluation method. <P>SOLUTION: In the conductive member evaluation device, a charged member and the conductive member are supported so that their surfaces are disposed in contact with or close to each other. At least one of the charged member or conductive member is driven so that part of the surface of the charged member and that of the conductive member disposed in contact with or close to each other successively move on the respective surfaces. A predetermined evaluation voltage in which an AC voltage is superposed on a DC voltage is applied to the conductive member, and evaluation currents flowing in the charged member and conductive member are measured. Then, a potential difference between the evaluation voltage and the evaluation current is measured. On the basis of the measured potential difference, the conductive member is evaluated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a conductive member evaluation apparatus that evaluates a conductive member that charges an electrostatic latent image carrier provided in an electrophotographic image forming apparatus and the like, and a conductive member evaluation method.

  An electrophotographic image forming apparatus such as a copying machine, a laser beam printer, a facsimile or the like uniformly distributes the surface of a photosensitive member as an electrostatic latent image carrier (that is, an image carrier) on which an electrostatic latent image is formed. A charging member that performs a charging process for charging is provided. As such a charging member, a conductive member (hereinafter referred to as a charging roller) formed in a roller shape or the like is used. Conventionally, there has been known a contact charging method in which the charging process is performed by bringing the outer peripheral surface of the charging roller into contact with the surface of the photoreceptor (for example, Patent Document 1).

  However, in the contact charging method described above, (1) the substance constituting the charging roller oozes out from the charging roller and adheres to the surface of the contacted photoreceptor, and (2) the charging roller is AC. Vibration noise is generated when voltage is applied. (3) The toner on the photoconductor adheres to the charging roller and the charging performance deteriorates. (4) When the rotation of the photoconductor is stopped for a long period of time, charging occurs. There is a problem that the contact portion of the roller with the photoreceptor is permanently deformed.

  Therefore, in order to solve these problems, a proximity charging method has been proposed in which charging is performed by placing a charging roller close to the surface of the photoreceptor so as to have a predetermined gap (gap) (for example, Patent Document 2). In such a proximity charging method, the charging roller and the photoconductor are opposed to each other so that the closest distance of the gap is 50 to 300 μm, and a voltage is applied to the charging roller to perform charging processing of the photoconductor. Is. In this proximity charging method, the charging roller and the photosensitive member are not in contact with each other, so that the above-described problems caused in the contact charging method can be solved.

  Since the charging roller used in the contact charging method described above is required to uniformly contact the surface of the photosensitive member in order to uniformly charge the photosensitive member, an elastic body is used around the core shaft. Covered with some vulcanized rubber. On the other hand, the charging roller used in the proximity charging method is required to make the gap between the charging roller and the photosensitive member uniform in order to uniformly charge the photosensitive member. It is formed by coating with a thermoplastic resin or the like which is an elastic body with no sag. As described above, the charging roller used in the contact charging system and the charging roller used in the proximity charging system are different in the material constituting each charging roller.

  Regardless of the contact charging method or the proximity charging method, the charging mechanism to the surface of the photosensitive member by the charging roller described above greatly contributes to the discharge according to Paschen's law in the minute discharge generated between the charging roller and the photosensitive member. It is known. Therefore, in order to evaluate the basic function of the charging roller that uniformly charges the surface of the photoreceptor at a predetermined potential (that is, uniformly), it is important to evaluate the electrical characteristics (discharge characteristics) of the charging roller. It becomes.

Conventionally, as a method for evaluating electrical characteristics of a charging roller (ie, a conductive member evaluation method), as schematically shown in FIG. 13, each of an outer peripheral surface 101a of the charging roller 101 and a core shaft 106 of the charging roller 101 is provided. The resistance value of the charging roller 101 is calculated by measuring the current value flowing through the charging roller 101 by applying a DC voltage between the electrodes 302 and 303 from the DC power supply 301 and connecting the electrodes 302 and 303 to the An evaluation method for judging (evaluating) the quality of the charging roller using this resistance value has been used. According to this evaluation method, the lower the resistance value of the charging roller, the higher the conductivity, the more uniform discharge is possible, and the charging roller is evaluated as being capable of obtaining a good image.
JP-A-1-267667 JP-A-5-107871

  However, as the electrical characteristics of the charging roller, each component can be evaluated by dividing the current value into three components, ie, a resistance component, a capacitance component, and a discharge component. Is only the resistance component of these three components, and the discharge component related to the discharge characteristics has not been evaluated. Therefore, particularly in the charging roller used in the proximity charging method, depending on the prescription of the material constituting the charging roller, the evaluation result in the evaluation method described above and the image evaluation result of the image actually formed using the charging roller are There is a case where it does not correspond, and there is a problem that the quality of the charging roller cannot be accurately evaluated by the conventional evaluation method.

  The present invention aims to solve the above problems. That is, an object of the present invention is to provide a conductive member evaluation apparatus and a conductive member evaluation method that can accurately evaluate a conductive member that charges an electrostatic latent image carrier.

  The inventors pay attention to a current (evaluation current) that flows when a predetermined evaluation voltage is applied to the charging roller by placing a charging roller as a conductive member in contact with or close to the electrostatic latent image carrier. As a result of extensive studies, the following was found.

  When the electrostatic latent image carrier and the charging roller are placed in contact or close to each other so that Paschen's law is established, and a predetermined evaluation voltage in which an AC voltage is superimposed on a DC voltage is applied to the charging roller. Further, when the current waveform of the evaluation current flowing through the charging roller and the electrostatic latent image carrier is observed, the current waveform I shown in FIG. 8 is obtained in the charging roller having a good image evaluation result, and the image evaluation result is For the defective charging roller, a current waveform I shown in FIG. 9 was obtained. From these current waveforms I, a positive side waveform (waveform above 0A) and a negative side waveform (waveform below 0A) having a center value of 0A are symmetrical in a charging roller with good image evaluation results. It has been found that the positive side waveform and the negative side waveform tend to be asymmetric in a charging roller that tends to have a poor image evaluation result.

  Consider these current waveforms I. The current waveform I can be divided into three components, a resistance component A, a capacitance component B, and a discharge component C, as shown in FIG. Among these, regarding the resistance component A and the capacitance component B, the resistance and capacitance as electrical characteristics of the charging roller are electrically non-polar, and the plus side waveform and the minus side waveform in these components are considered to be symmetric. Therefore, whether or not the current waveform I is symmetric between the plus side waveform and the minus side waveform is considered to be due to the discharge component C.

  The positive waveform in the discharge component C indicates the state of discharge (positive discharge) from the charging roller to the electrostatic latent image carrier, and the negative waveform in the discharge component C is from the electrostatic latent image carrier to the charging roller. The state of discharge (reverse discharge) is shown. That is, if the positive waveform and the negative waveform of the current waveform I are symmetric, it indicates that the positive discharge and the reverse discharge are performed uniformly, and the positive waveform and the negative waveform of the current waveform I are If it is asymmetrical, it is considered that the forward discharge and the reverse discharge are performed unevenly.

  When the normal discharge and the reverse discharge are uniformly performed, the surface of the electrostatic latent image carrier is uniformly charged. On the other hand, if the positive discharge and the reverse discharge are performed non-uniformly, the charge from one discharge remains on the surface of the electrostatic latent image carrier at the time of the other discharge, and the electrostatic latent image carrier The surface is charged unevenly. It is considered that the quality of the image evaluation result depends on the difference in the charged state of the electrostatic latent image carrier. That is, if the positive waveform and the negative waveform of the current waveform I are symmetric, it can be determined that the charging roller can obtain a good image, and the positive waveform and the negative waveform of the current waveform I described above can be obtained. If it is asymmetric, it can be determined that the charging roller is a defective image.

  Further, the present inventors have conducted intensive studies on such a method for determining the symmetry / asymmetricity of the current waveform, and found the determination method.

  Since the predetermined evaluation voltage applied to the charging roller is a voltage obtained by superimposing a DC voltage on a sine wave AC voltage, the voltage waveform V is a positive waveform (above the DC voltage value) with the DC voltage value as the center value. Waveform) and the negative waveform (waveform below the DC voltage value) are symmetric. On the other hand, in the evaluation current I, the symmetry of the current waveform is determined by the state of the positive discharge and the reverse discharge, and when the normal discharge and the reverse discharge are performed unevenly, the discharge amount in each discharge Therefore, the heights of the peaks (points where the absolute value from the center value (0A) is maximum) of the plus-side waveform and the minus-side waveform are different, and therefore, the current waveform I passes through the center value. The time (phase) of the time slightly changes between a rising point at which the center value penetrates from the bottom to the top and a falling point at which the center value penetrates from the top to the bottom.

  Therefore, based on the phase difference between the voltage waveform V and the current waveform I, it can be determined whether or not the positive waveform and the negative waveform of the current waveform I are symmetric. Specifically, as shown in FIG. 11, the phase difference between the rising time Tvu at the center value of the voltage waveform V and the rising time Tiu at the center value of the current waveform I (hereinafter referred to as the rising phase difference α1), and the voltage waveform V The difference between the falling time Tvd at the center value and the phase difference (falling phase difference α2) between the falling time Tid at the center value of the current waveform I is obtained, and if this difference is small, the positive waveform of the current waveform I And the negative waveform can be determined to be symmetrical, that is, it can be determined (evaluated) that the charging roller can obtain a good image. If this difference is large, the positive waveform and the negative waveform of the current waveform I are asymmetric. That is, it can be determined (evaluated) that the charging roller is a defective image. Although the above describes a roller-shaped charging roller as the conductive member, the same evaluation can be performed for a belt-shaped, blade (plate) -shaped, and semi-cylindrical conductive member. In addition, the conductive member can be classified into an ion conductive conductive member or an electronic conductive conductive member depending on the material constituting the conductive member. Since the conductive member is evaluated based on the state (uniformity) between the positive discharge and the reverse discharge that are actually generated, regardless of the material constituting the conductive member, any ion conductivity, electronic conductivity, etc. It is possible to evaluate a conductive member using a material.

  Thus, it was found that the quality of the conductive member can be evaluated based on the phase difference between the predetermined evaluation voltage applied to the conductive member and the evaluation current that flows when the evaluation voltage is applied.

  In order to achieve the above object, the invention described in claim 1 includes: (a) a member to be charged; and (b) a portion of the surface of the conductive member as a portion of the surface of the member to be charged. A supporting means for supporting the conductive member in contact with or close to each other; (c) a part of the surface of the member to be charged and a part of the surface of the conductive member that are in contact with or close to each other; Driving means for driving at least one of the member to be charged and the conductive member so that the respective surfaces are sequentially moved, and (d) the member to be charged and the conductive member by the driving unit. Voltage application means for applying a predetermined evaluation voltage obtained by superimposing an alternating voltage on a direct current voltage to the conductive member when at least one of them is driven, and (e) the conductive member is applied to the conductive member by the voltage application means. When the evaluation voltage is applied, In a conductive member evaluation apparatus, comprising: a current measuring unit that measures an evaluation current flowing through the member to be charged and the conductive member; (a) the evaluation voltage applied by the voltage applying unit and the current measurement A phase difference measuring means for measuring a phase difference with the evaluation current measured by the means; and (b) the conductivity based on the phase difference between the evaluation voltage and the evaluation current measured by the phase difference measuring means. An evaluation means for evaluating a member is provided. The conductive member evaluation apparatus is provided.

  In order to achieve the above object, the invention described in claim 2 includes: (a) a cylindrical member to be charged that is rotatably supported; and (b) an outer peripheral surface of a roller-like conductive member. (C) a driving means for rotating the charged member and the conductive member in directions opposite to each other; and (c) a supporting means that rotatably supports the outer peripheral surface of the charged member. d) voltage applying means for applying a predetermined evaluation voltage obtained by superimposing an alternating voltage on a direct current voltage to the conductive member when the member to be charged and the conductive member are rotated by the driving means; (E) a current measuring means for measuring an evaluation current flowing through the member to be charged and the conductive member when the evaluation voltage is applied to the conductive member by the voltage applying means; In member evaluation equipment, (i) Phase difference measuring means for measuring a phase difference between the evaluation voltage applied by the voltage applying means and the evaluation current measured by the current measuring means; and (b) the evaluation measured by the phase difference measuring means. An evaluation means for evaluating the conductive member based on a phase difference between a voltage and the evaluation current is provided.

  The invention described in claim 3 is the invention described in claim 1 or 2, wherein in the phase difference measuring means, the waveform rises at the center value of the evaluation voltage and the waveform at the center value of the evaluation current. The phase difference between the rising point and the phase difference between the time point when the waveform falls at the center value of the evaluation voltage and the time point when the waveform falls at the center value of the evaluation current are measured, and the evaluation means The phase difference between the time when the waveform of the evaluation voltage rises and the time when the waveform of the evaluation current rises, the time when the waveform of the evaluation voltage falls, and the evaluation current measured by the phase difference measuring unit The conductive member is evaluated on the basis of the difference between the waveform and the time point when the waveform falls.

  In order to achieve the above-described object, the invention described in claim 4 includes: (a) a member to be charged; and (b) a part of the surface of the conductive member as a part of the surface of the member to be charged. A supporting means for supporting the conductive member in contact with or close to each other; (c) a part of the surface of the member to be charged and a part of the surface of the conductive member that are in contact with or close to each other; Driving means for driving at least one of the member to be charged and the conductive member so that the respective surfaces are sequentially moved, and (d) the member to be charged and the conductive member by the driving unit. Voltage application means for applying a predetermined evaluation voltage obtained by superimposing an alternating voltage on a direct current voltage to the conductive member when at least one of them is driven, and (e) the conductive member is applied to the conductive member by the voltage application means. When the evaluation voltage is applied, A current measuring means for measuring an evaluation current flowing through the member to be charged and the conductive member, and a conductive member evaluation method used in a conductive member evaluation apparatus comprising: (a) by the voltage applying means; A phase difference measuring step of measuring a phase difference between the applied evaluation voltage and the evaluation current measured by the current measuring means; and (b) the evaluation voltage and the evaluation current measured in the phase difference measuring step. And an evaluation process for evaluating the conductive member based on a phase difference between the conductive member and the conductive member.

  In order to achieve the above-mentioned object, the invention described in claim 5 includes: (a) a cylindrical member to be charged rotatably supported; and (b) an outer peripheral surface of a roller-like conductive member. (C) a driving means for rotating the charged member and the conductive member in directions opposite to each other; and (c) a supporting means that rotatably supports the outer peripheral surface of the charged member. d) voltage applying means for applying a predetermined evaluation voltage obtained by superimposing an alternating voltage on a direct current voltage to the conductive member when the member to be charged and the conductive member are rotated by the driving means; (E) a current measuring means for measuring an evaluation current flowing through the member to be charged and the conductive member when the evaluation voltage is applied to the conductive member by the voltage applying means; Conductivity used in member evaluation equipment (B) a phase difference measurement step of measuring a phase difference between the evaluation voltage applied by the voltage application unit and the evaluation current measured by the current measurement unit; A conductive member, wherein the conductive member is evaluated by sequentially evaluating the conductive member based on a phase difference between the evaluation voltage and the evaluation current measured in the phase difference measuring step. It is an evaluation method.

  In the invention described in claim 6, in the invention described in claim 4 or 5, in the phase difference measurement step, the waveform is generated at the time when the waveform rises at the center value of the evaluation voltage and at the center value of the evaluation current. The phase difference from the rising point and the phase difference between the time point when the waveform falls at the center value of the evaluation voltage and the time point when the waveform falls at the center value of the evaluation current are measured, and in the evaluation step, The phase difference between the time when the waveform of the evaluation voltage rises and the time when the waveform of the evaluation current rises, the time when the waveform of the evaluation voltage falls, and the evaluation current measured in the phase difference measurement step The conductive member is evaluated on the basis of the difference between the waveform and the time point when the waveform falls.

  According to the invention described in claims 1, 2, 4, and 5, the phase difference between the evaluation voltage applied to the conductive member and the evaluation current flowing through the conductive member is measured, and based on the phase difference. Therefore, the conductive member that charges the electrostatic latent image carrier can be accurately evaluated.

  According to the third and sixth aspects of the invention, the phase difference between the time when the waveform rises at the central value of the evaluation voltage and the time when the waveform rises at the central value of the evaluation current, and the waveform at the central value of the evaluation voltage. The phase difference between the time of falling and the time when the waveform falls at the center value of the evaluation current is measured, and the conductive member is evaluated based on the difference in the measured phase difference. The conductive member that charges the body can be accurately evaluated.

  Below, each embodiment of the electroconductive member evaluation apparatus which concerns on this invention, the electroconductive member evaluated in this electroconductive member evaluation apparatus, and an image forming apparatus provided with this electroconductive member is described in order. After that, verification contents of the present invention by the present inventors will be described.

(Conductive member evaluation device)
Below, one Embodiment of the electroconductive member evaluation apparatus which concerns on this invention is described with reference to FIGS. FIG. 1 is a configuration diagram of a conductive member evaluation apparatus according to the present invention. FIG. 2 is a diagram schematically illustrating an electrical connection relationship of the conductive member evaluation apparatus in FIG. 1. FIG. 3 is a flowchart illustrating an example of an evaluation process executed by a control unit included in the conductive member evaluation apparatus of FIG.

  As shown in FIG. 1, the conductive member evaluation apparatus 200 includes a base 201, a pair of support members 202 as support means, a drive unit 203 as drive means, a photoreceptor 204 as a member to be charged, a voltage A power supply unit 205 as an application unit, a measurement unit 206 as a current measurement unit, and a control unit 207 are provided.

  The base 201 is formed in a flat plate shape and is installed on a factory floor or table. The upper surface of the base 3 is kept parallel to the horizontal direction. The planar shape of the base 3 is formed in a rectangular shape.

  The pair of support members 202 are plate-shaped or bar-shaped members that are vertically arranged to be opposed to each other from the upper surface of the base 201. The pair of support members 202 pivotally support a roller-shaped charging member 101 as a conductive member and a photosensitive member 204 (described later) between them in a rotatable manner. The pair of support members 202 are not in contact (that is, close to each other) so that the outer peripheral surface of the charging member 101 and the outer peripheral surface of the photosensitive member 204 are in contact with each other, or a gap is provided between the outer peripheral surfaces. Further, the charging member 101 and the photosensitive member 204 are pivotally supported. With the pair of support members 202, the size of the gap between the outer peripheral surface of the charging member 101 and the outer peripheral surface of the photosensitive member 204 can be arbitrarily set. In addition, the pair of support members 202 are configured such that the charging member 101 can be easily attached and detached. In addition, since a high voltage is applied to the charging member 101, portions of the base 201 and the pair of supporting members 202 that are located in the vicinity of the charging member 101 and the photosensitive member 204 are made of an electrically insulating material. Yes.

  The drive unit 203 is disposed on one of the pair of support members 202, and includes a known motor 203a and a drive force transmission unit 203b including a plurality of gears combined with each other. The drive unit 203 transmits the rotation of the motor 203a to the charging member 101 and the photosensitive member 204 directly or via the plurality of gears of the driving force transmission unit 203b, and the charging member 101 and the photosensitive member 204 are opposite to each other. Rotate in the direction. In this way, a part of the outer surface of the charging member 101 and a part of the outer surface of the photosensitive member 204 that are in contact with or close to each other sequentially move on the respective outer surfaces. The locations do not always come into contact with or approach each other, and deterioration due to discharge or the like can be prevented from concentrating on some locations on the outer surface of the charging member 101 and the photoreceptor 204.

  In the driving unit 203, the linear velocity (peripheral velocity) of the charging member 101 is rotated so that the linear velocity (circumferential velocity) of the charging member 101 is equal to or higher than the linear velocity of the photosensitive member 204 by adjusting a gear ratio of the driving force transmission unit 203 b or the like. It is particularly preferable that the linear velocity of the charging member 101 and the linear velocity of the photosensitive member 204 are the same. When the linear velocity of the charging member 101 is lower than the linear velocity of the photosensitive member 204, the charging state of the charging member 101 becomes unstable depending on the voltage applied to the charging member 101 by the power supply unit 205, and the photosensitive member 204 is uniformly charged. It becomes difficult to make. In this evaluation apparatus, since a high voltage is applied to the charging member 101, when a high voltage is applied to the stationary charging member 101 as in the conventional evaluation method described above, the charging member 101 and the photoconductor. Leakage current is generated between the electrodes 204, making measurement impossible due to discharge breakdown. Therefore, it is necessary to apply a high voltage while the charging member 101 and the photosensitive member 204 are rotated. The drive unit 203 is connected to the control unit 207, and controls the number of rotations (that is, the linear velocity of the charging member 101 and the linear velocity of the photosensitive member 204) based on a control signal sent from the control unit 207. In the present embodiment, the driving unit 203 rotates the charging member 101 and the photosensitive member 204 by one motor. However, the driving unit 203 is not limited to this, and the charging member 101 and the photosensitive member 204 are respectively connected to each other by separate motors. You may make it rotate in the reverse direction.

  The photoreceptor 204 is a member to be charged whose surface (outer peripheral surface) is charged by the charging member 101. The photoreceptor 204 has a four-layer structure in which an undercoat layer, a charge generation layer, a charge transport layer, and a surface protective layer are sequentially laminated on an aluminum base tube. In the photoreceptor 204, a phthalocyanine pigment is used as a charge generation material. Further, a polycarbonate resin is used for the surface protective layer that becomes the surface layer of the photoreceptor 204, and silica having an average particle diameter of 0.05 to 0.8 μm is used as the filler. By using such a photoreceptor 204, it is possible to create a state close to the state in which the charging member 101 is actually mounted on the image forming apparatus. As shown in FIG. 2, the photosensitive element 204 has its aluminum tube grounded (grounded).

  As shown in FIG. 2, the power supply unit 205 includes a DC voltage source and a sine wave AC voltage source, and is a well-known device capable of generating a voltage (that is, an evaluation voltage) of an arbitrary frequency between a pair of terminals 205a and 206b. It is a power supply device. In the power supply unit 205, one terminal 205a is connected to a conductive support (core shaft) 106 (to be described later) of the charging member 101 via an ammeter 206b provided in the measurement unit 206, and the other terminal 205b is grounded. Yes. The power supply unit 205 is connected to the control unit 207, and controls voltage and frequency generated between the pair of terminals 205a and 206b based on a control signal sent from the control unit 207.

  The power supply unit 205 generates an evaluation voltage by superimposing an AC voltage that is a sine wave on the DC voltage Vdc. Since this evaluation voltage needs to generate a discharge component in the current waveform of the evaluation current in order to evaluate the discharge component (discharge characteristic) in the evaluation current flowing through the charging member 101 by the evaluation voltage, the superposition is performed. The peak-to-peak voltage Vpp (kV) of the alternating voltage to be applied is equal to or higher than the discharge start voltage in Paschen's law, and preferably the peak-to-peak voltage Vpp is set to be twice or more the discharge start voltage. The frequency f (Hz) of the AC voltage is set so that the frequency linear velocity ratio f / V is 7 or more with respect to the linear velocity V (mm / sec) of the charging member 101 and the photosensitive member 204. When the frequency linear velocity ratio is less than 7, the number of discharges per unit distance on the outer peripheral surface of the photoconductor 204 is small, and non-uniform charging (uneven discharge current) occurs as in the case of moiré image generation on an actual machine. It's easy to do.

  The measuring unit 206 is a well-known measuring instrument that includes a voltmeter 206a and an ammeter 206b. The voltmeter 206 a is connected between the pair of terminals 205 a and 205 b of the power supply unit 205 and measures a voltage (evaluation voltage) generated by the power supply unit 205. The ammeter 206 b is connected between one terminal 205 a of the power supply unit 205 and the charging member 101, and measures a current (evaluation current) flowing through the charging member 101 and the photosensitive member 204. The measurement unit 206 is connected to the control unit 207 and transmits measurement information regarding the evaluation voltage and the evaluation current to the control unit 207. In the measurement unit 206, the sampling rate for measuring the evaluation voltage and the evaluation current needs to be higher than the frequency of the AC voltage. This is because it is difficult to accurately capture the discharge component of the current waveform at a sampling rate below the frequency of the AC voltage.

  The control unit 207 is configured by a known computer such as a personal computer (PC). The control unit 207 is connected to each of the above-described drive unit 203, power supply unit 205, and measurement unit 206 via various external interfaces (USB, GPIB, etc.) included in the control unit 207, and controls between them. Send and receive signals and various information. The control unit 207 includes storage means such as a hard disk or a memory card. The storage means includes (1) information on the rotation speed (linear speed) of the charging member 101 and the photosensitive member 204, and (2) charging member. Information on evaluation voltage (DC voltage value, AC voltage value, AC frequency) applied to 101, and (3) phase difference (rising position) between the rising point at the central value of the evaluation voltage and the rising point at the central value of the evaluation current Phase difference), and phase difference (falling phase difference) between the falling time point at the center value of the evaluation voltage and the falling time point at the center value of the evaluation current, and the determination criterion information of the difference are stored in advance. The control unit 207 performs various controls in the conductive member evaluation apparatus 200 based on a program stored in advance in a ROM, a storage unit, or the like, and based on measurement information regarding the evaluation voltage and evaluation current received from the measurement unit 206. The phase difference between the evaluation voltage and the evaluation current is calculated, and the charging member 101 is evaluated based on the phase difference. That is, the control unit 207 corresponds to the phase difference measuring unit and the evaluation unit in the claims.

  The evaluation process according to the present invention performed by the control unit 207 will be described with reference to the flowchart of FIG.

  First, the charging member 101 to be evaluated is attached to the pair of support members 202 so as to be in contact with the photosensitive member 204 or close to the photosensitive member 204 with a predetermined gap therebetween, and the conductive member. The evaluation apparatus 200 is turned on. When power is turned on, the control unit 207 executes a predetermined initialization process and then starts an evaluation process. The control unit 207 reads information related to the rotation speed (linear velocity) of the charging member 101 and the photosensitive member 204 from the storage unit, and transmits a predetermined control signal to the driving unit 203 based on this information. And the photosensitive member 204 are rotated in the opposite directions at the same predetermined linear velocity (for example, 282 mm / sec) (S110). Then, the control unit 207 reads information on the evaluation voltage applied to the charging member 101 from the storage unit, transmits a predetermined control signal to the power supply unit 205 based on this information, and applies a predetermined evaluation voltage to the charging member 101. Apply (S120). The evaluation voltage is, for example, a DC voltage (Vdc = −0.7 kV) superimposed with an AC voltage (peak-to-peak voltage Vpp = 2.2 kV, frequency f = 2200 Hz).

  Then, the control unit 207 starts measuring the evaluation voltage and the evaluation current by the measurement unit 206, and sequentially receives measurement information regarding the evaluation voltage and the evaluation current from the measurement unit 206 (S130). Then, the measurement information received from the measurement unit 206 is analyzed, and the DC voltage value Vdc constituting the evaluation voltage is set as the central value, the rising time that penetrates the central value from the bottom to the top, and the evaluation current of 0 A is the central value. The rise time that penetrates the center value from the bottom to the top is obtained, and the phase difference between the rise time of the waveform at the center value of the evaluation voltage and the rise time of the waveform at the center value of the evaluation current is calculated from the difference between these times. The phase difference α1) is calculated, the falling time that penetrates the center value of the evaluation voltage from top to bottom, and the falling time that penetrates the center value of the evaluation current from top to bottom, and the evaluation voltage is calculated from the difference between these times The phase difference (falling phase difference α2) between the waveform falling point at the center value of the waveform and the waveform falling point at the center value of the evaluation current is calculated. (S140). Then, the difference (| α2−α1 |) between the rising phase difference α1 and the falling phase difference α2 is calculated, and compared with the determination reference information (for example, 4 °) stored in advance in the storage means. If the difference in phase difference is equal to or less than the determination reference information, the charging member 101 is determined to obtain a good image. If the difference between the phase differences is larger than the determination reference information, the charging member 101 is determined to be a defective image. These determination results are displayed on a display device such as a display provided in the control unit 207 (S150). And the process of this flowchart is complete | finished.

  The above-described step S140 corresponds to the phase difference measuring means and the phase difference measuring step in the claims, and step S150 corresponds to the evaluating means and the evaluation steps in the claims.

  As described above, according to the present invention, the phase difference (rising phase difference) between the time when the waveform rises at the central value of the evaluation voltage and the time when the waveform rises at the central value of the evaluation current, and the waveform at the central value of the evaluation voltage. Because the phase difference (falling phase difference) between the time point of falling and the time point when the waveform falls at the center value of the evaluation current is measured, and the conductive member is evaluated based on the difference in the measured phase difference. Thus, it is possible to accurately evaluate the conductive member that charges the electrostatic latent image carrier included in the image forming apparatus.

  In addition, the present invention can be used as long as Paschen's law is established in the atmosphere. Therefore, unlike the conventional evaluation method, the gap between the charging member and the photosensitive member can be arbitrarily set. The measurement can be performed by changing the value to. Therefore, the charging member can be evaluated in a state close to a state in which the charging member is mounted on an actual image forming apparatus adopting a proximity charging method. In addition, the conductive member evaluation apparatus of the present invention is used not only in the research and development of conductive members, but also by incorporating it into the above-mentioned mass production process of charging members, etc., so that a charging member that becomes a defective image can be detected at an early stage. Therefore, the productivity of an image forming apparatus provided with this charging member can be improved.

  In the evaluation of the conductive member described above, the measurement time of the evaluation voltage and the evaluation current (that is, the electrical characteristic evaluation) is not particularly limited. Even when there is a defective portion, it can be detected.

  In the present embodiment, the roller-shaped charging member 101 is a conductive member to be evaluated, but is not limited thereto, and is not limited to a belt-like shape, a blade (plate) shape, or a semi-cylindrical shape. Conductive members can also be evaluated. In that case, the support member (support means) supports the conductive member by bringing a part of the surface of the conductive member into contact with or close to a part of the surface (outer peripheral surface) of the photosensitive member 204, and The photosensitive member 204 is arranged such that a part of the surface of the photosensitive member 204 and a part of the surface of the conductive member which are brought into contact with or close to each other by the driving unit (driving means) sequentially move on the respective surfaces. And at least one of the conductive member is driven. In this state, an evaluation voltage is applied to measure an evaluation current, and a phase difference is obtained to evaluate the conductive member.

  Specifically, for example, when the conductive member is belt-shaped, a pair of support members are provided with a driving roller and a driven roller, and the conductive member can be stretched over both the driving roller and the driven roller to rotate. And the surface of the conductive member and the photosensitive member 204 are brought into contact with or close to each other (that is, since the photosensitive member 204 is cylindrical, a part of the surface of the conductive member and the surface of the photosensitive member 204). (A part of the (outer peripheral surface) abuts or approaches). Then, the driving member rotates the conductive member and the photosensitive member 204 in the opposite directions so that the linear velocities are the same. By doing so, a part of the surface of the photoreceptor 204 and a part of the surface of the conductive member that are in contact with or close to each other sequentially move on the respective surfaces. In this state, an evaluation voltage is applied to measure an evaluation current, and a phase difference is obtained to evaluate the conductive member.

  Further, in the present embodiment, the rising phase difference and the falling phase difference at the respective center values of the evaluation voltage and the evaluation current are measured, and the charging member is evaluated based on these phase differences. For example, the phase difference between the time when the evaluation voltage is maximized and the time when the evaluation current is maximized, and the phase difference between the time when the evaluation voltage is minimized and the time when the evaluation current is minimized are not limited thereto. On the voltage waveform where the phase difference between the evaluation voltage and the evaluation current occurs when the positive discharge and the reverse discharge are non-uniform, such as those that measure the charging member based on these phase differences As long as it is a location on the current waveform, the location where the phase difference is measured is arbitrary.

(Conductive member)
Below, the charging member which is one Embodiment of the electroconductive member evaluated by the electroconductive member evaluation apparatus and electroconductive member evaluation method which concern on this invention is demonstrated with reference to FIG. FIG. 4 is a diagram showing the configuration of the charging member, which is a conductive member evaluated according to the present invention, and the positional relationship between the photosensitive layer region, the image region, and the non-image region of the image carrier.

  A charging member 101 as a conductive member is a member that charges a photosensitive member 61 (that is, an image carrier 61 described later) as an electrostatic latent image carrier provided in an electrophotographic image forming apparatus. The charging member 101 is formed in a roller shape as shown in FIG. The configuration of the charging member 101 is not particularly limited, and either a single layer structure or a multilayer structure can be used. However, the electric resistance adjustment layer formed on the conductive support (core shaft) 106 is used. A two-layer structure in which a surface layer 105 to which toner and toner additives are difficult to adhere is formed on 104 is particularly preferable. In the case of using the proximity charging method, in addition to this configuration, a gap holding member 103 for providing a predetermined gap between the charging member 101 and the photoreceptor 61 is provided at both ends of the electric resistance adjusting layer 104. .

The electric resistance adjusting layer 104 is composed of a base material and a conductive agent dispersed in the base material, and the volume resistivity is preferably 10 ⁶ to 10 ⁹ Ωcm. If the volume resistivity of the electric resistance adjusting layer 104 exceeds 10 ⁹ Ωcm, the charging ability and the transfer capability are insufficient, and if the volume resistivity of the electric resistance adjusting layer 104 is lower than 10 ⁶ Ωcm, the entire photoreceptor 61 is obtained. Leakage due to voltage concentration occurs. If the volume resistivity of the electric resistance adjusting layer 104 is 10 ⁶ to 10 ⁹ Ωcm, an elastic composition and a thermoplastic resin composition can be used as the base material. When the charging member 101 is used for the proximity charging method, it is preferable to use a thermoplastic resin composition in order to make the gap between the photosensitive member 61 uniform.

  As the elastic composition, rubber materials such as ethylene propylene rubber (EPDM), urethane rubber, silicone rubber, and epichlorohydrin rubber can be used. Examples of the thermoplastic resin composition include olefin resins such as polyethylene (PE) and polypropylene (PP), styrene resins such as polystyrene (PS) and copolymers thereof (AS, ABS), polymethyl methacrylate (PMMA). A general-purpose resin with good processability such as an acrylic resin is preferred.

  Examples of the conductive agent dispersed in the base material include alkali metal salts such as lithium peroxide, perchlorates such as sodium perchlorate, quaternary ammonium salts such as tetrabutylammonium salts, and polymer ion conductive materials. A conductive agent having an ionic conduction mechanism can be used. In addition, it is possible to use a conductive agent having an electronic conductive mechanism such as carbon black such as ketjen black and acetylene black, graphite, and conductive metal oxide, but the conductive agent of the electronic conductive mechanism is used in the base material. Since it is difficult to uniformly disperse, it is most preferable to use a polymer type ion conductive material.

  Hereinafter, an example using a thermoplastic resin composition in which a polymer ion conductive material is dispersed will be described as the electric resistance adjusting layer 104.

  The polymer ion conductive material dispersed in the thermoplastic resin is preferably a polymer compound containing a polyether ester amide component. Polyether ester amide is an ion conductive polymer material, and is uniformly dispersed and immobilized at a molecular level in a matrix polymer. Therefore, there is no variation in resistance value due to poor dispersion as seen in a composition in which a conductive pigment is dispersed. In addition, since it is a polymer material, bleed-out hardly occurs. About a compounding quantity, since it is necessary to make resistance value into a desired value, it is preferable that a thermoplastic resin is 30 to 70 weight% and a polymeric ion conductive material is 70 to 30 weight%. The electric resistance adjusting layer 104 contains a thermoplastic resin (A) containing at least a polyamide elastomer and a polyolefin block polymer, a perchlorate, and a fluorine-containing organic anion salt in order to obtain a conduction mechanism by ionic conduction. Consists of resin material. The reason why ionic conductivity is necessary is that, in general, when an electron conductive conductive agent such as carbon black is used, the electric charge is discharged to the photoreceptor 61 through the carbon black, which is caused by the dispersion state of the carbon black. Minute discharge unevenness is likely to occur, which hinders high image quality. This is because this phenomenon becomes remarkable particularly when a high voltage is applied. As the ion conductive material, there are low molecular weight salts such as alkali metal salts and ammonium salts, but they are easily polarized and bleed out due to energization. Thus, solid polymer elastomers and polyolefin block polymers containing ether groups are used as the polymeric ion conductive material. By having an ether group in the molecule, the salt is stabilized by an oxygen atom or the like contained in the ether bond, and high conductivity can be obtained. In this configuration, since the polymer is uniformly dispersed and fixed at the molecular level in the matrix polymer, there is no variation in conductivity due to poor dispersion as seen in the composition in which the conductive pigment is dispersed. In addition, since it is a polymer material, bleed-out hardly occurs. Examples of the polymer type ion conductive material include polyether polyols such as liquid polyethylene oxide and polypropylene oxide having an ether group, but in the case of liquid, since they cannot be uniformly dispersed in the thermoplastic resin, It is necessary to use a solid polyamide elastomer or a polyolefin block polymer. Polyamide elastomers and polyolefin block polymers are generally roughly classified into hydrophilic and hydrophobic grades, and the characteristics are greatly different. Therefore, it is possible to blend multiple grades in order to obtain the desired properties. However, since only the thermoplastic resin material including the polyamide elastomer and the polyolefin block polymer cannot obtain the conductivity for use as the conductive member, the use of the electrolyte salt together can improve the conductivity. As the electrolyte salt, perchlorate is most common, and fluorine-containing organic anion salts, organic phosphonium salts, and the like can also be used.

  The perchlorate can be used as long as it is generally used, but considering conductivity, it is a salt selected from alkali metal salts and alkaline earth metal salts. It is desirable. Among these, lithium perchlorate and sodium perchlorate are particularly preferable.

  As the fluorine-containing organic anion salt, a salt having an anion having a fluoro group and a sulfonyl group is desirable. The salt having an anion described above is highly dissociated in a polymer composition in which the anion is stable because the charge is delocalized by the strong electron withdrawing effect of the fluoro group (-F) and the sulfonyl group (-SO2-). Show high ionic conductivity. Among these, alkali metal salts of bis (fluoroalkylsulfonyl) imide, alkali metal salts of tris (fluoroalkylsulfonyl) methide, alkali metal salts of fluoroalkylsulfonic acid, and the like are preferable because the resistance value can be easily lowered. In particular, lithium salts having high conductivity such as lithium trifluoromethanesulfonate, lithium bis (trifluoromethanesulfonyl) imide lithium, and tris (trifluoromethanesulfonyl) methide lithium are preferable.

Perchlorate and fluorine-containing organic anion salt can be added to a polymer type ion conductive material and kneaded, and can be blended at a predetermined ratio, each of which is blended with one or more electrolyte salts. It can also be added. In addition, as a polymer ion conductive material containing perchlorate, for example, “IRGASTAT P18” manufactured by Ciba Specialty Chemicals, as a polymer ion conductive material containing a fluorine-containing organic anion salt, for example, Sanko Chemical Industries It is possible to obtain as "Sanconol" series of Co., Ltd. As a compounding amount of the salt, it is desirable that the salt is blended in the polymer ion conductive material in a proportion of 0.01 to 20% by weight. When the blending amount is lower than 0.01% by weight, the electrical conductivity is insufficient. When the blending amount is higher than 20% by weight, it is difficult to uniformly disperse in the resin composition. If the volume resistivity of the electric resistance adjusting layer 104 exceeds 10 ⁹ Ωcm, the charging ability and the transfer capability are insufficient, and if the volume resistivity of the electric resistance adjusting layer 104 is lower than 10 ⁶ Ωcm, the entire photoreceptor 61 is obtained. Leakage due to voltage concentration occurs.

  In addition, the conductive member evaluated in the present invention requires machining such as cutting and grinding in order to achieve high precision of parts. Polyamide elastomers and polyolefin block polymers are soft and difficult to machine. Therefore, it is possible to blend with other thermoplastic resin (B) having a higher hardness than these resins, if necessary. By increasing the hardness, the machinability is improved. The high-hardness thermoplastic resin (B) is not particularly limited, but polyethylene (PE), polypropylene (PP), polymethyl methacrylate (PMMA), polystyrene (PS) and copolymers thereof (AS, ABS) Etc.) and engineering plastics such as polycarbonate and polyacetal are preferred because they are easy to mold. The blending amount can be set according to the target machinability as long as the conductivity of the electrical resistance adjusting layer 104 is not impaired.

  When improving the conductivity of the electrical resistance adjusting layer 104, it is important to control the dispersion state as well as the selection of the conductive resin material and the electrolyte salt. When the dispersion state of the electrolyte salt is rough, non-uniform discharge due to the dispersion state easily occurs in a low temperature and low humidity environment, resulting in an image defect. Therefore, it is desirable to add a compatibilizing agent for the purpose of densifying the dispersed state. Examples of such a compatibilizing agent include the above-mentioned polyamide elastomer and graft copolymer (C) having affinity for the thermoplastic resin (A) containing a polyolefin block polymer. Specifically, a graft copolymer having a polycarbonate resin in the main chain and an acrylonitrile-styrene-glycidyl methacrylate copolymer in the side chain is used. In this graft copolymer, an acrylonitrile-styrene-glycidyl methacrylate copolymer contained in a side chain is composed of an acrylonitrile component and a glycidyl methacrylate component which is a reactive group with the styrene component. The reactive group glycidyl methacrylate reacts with the ester group or amino group of (A) by heating when the components are melted and kneaded, so that it chemically bonds with (A). By doing so, the dispersion state of the electrolyte salt is made uniform and dense. Thereby, generation | occurrence | production of the nonuniform discharge accompanying the dispersion | distribution defect of electrolyte salt can be prevented. By setting the amount of the graft copolymer to 1 to 15% by weight with respect to (A), the dispersion state can be densified.

  In addition, when the thermoplastic resin (A) is blended with the high-hardness thermoplastic resin (B), the graft copolymer functions as a compatibilizing agent. Since the polycarbonate resin of the main chain has a molecular structure with a polar group and a chain of dioxy group, the attractive force between molecules is very strong. For this reason, it is excellent in mechanical strength, creep characteristics, etc., and especially impact strength is excellent compared with other plastics. In addition, since the water absorption is relatively low, there is little volume fluctuation due to water absorption fluctuation. Due to these characteristics, in a system using a polycarbonate resin as the main chain of the graft copolymer, cracks due to mechanical / electrical stress at the time of use, aging and volume fluctuations in the environment are unlikely to occur.

  Further, the acrylonitrile component and styrene component in the side chain have good compatibility with (B). Therefore, the graft copolymer (C) functions as a compatibilizing agent even when the affinity between (A) and (B) is low, and makes the dispersed state of (A) and (B) uniform and dense. As a result, (A) and (B) are caused in the weld portion of the electric resistance adjustment layer 104 due to uneven conductivity in the weld portion due to poor dispersion, electrical / mechanical stress during use, and volume variation over time and environment. Cracks can be suppressed. As a result, it is possible to form a kneading resin composition having excellent strength in combination with the effect of the main chain.

  There is no restriction | limiting in particular about the manufacturing method of an elastic body composition and a thermoplastic resin composition, It can manufacture easily by melt-kneading the mixture of each material with a biaxial kneader, a kneader, etc. The electric resistance adjusting layer 104 can be easily formed on the conductive support 106 by covering the conductive support 106 with the semiconductive resin composition by means of extrusion molding or injection molding. Can do.

  Even with a conductive member in which only the electric resistance adjusting layer 104 is formed on the conductive support 106, it is possible to apply the electric characteristic evaluation method of the present invention. In some cases, toner, toner additives, and the like adhere to each other and performance deteriorates. Such a problem can be prevented by forming the surface layer 105 on the electric resistance adjusting layer 104.

The surface layer 105 is formed so that its resistance value is larger than the resistance value of the electric resistance adjusting layer 104, thereby avoiding voltage concentration and excessive discharge (leakage) on the defective portion of the photoreceptor 61. it can. However, if the resistance value of the surface layer 105 is too high, the charging ability and the transfer ability are insufficient. Therefore, the difference in resistance value between the surface layer 105 and the electric resistance adjusting layer 104 is preferably 3 orders or less. . Specifically, the surface resistivity of the surface layer 105 is required to be 10 ⁶ to 10 ⁹ Ω / □.

  As a material for forming the surface layer 105, a thermoplastic resin composition is preferable in that the film-forming property is good. In particular, a fluorine-based resin, a silicone-based resin, a polyamide resin, a polyester resin, and the like are excellent in non-adhesiveness and are preferable in terms of preventing toner sticking. Further, since the resin material is electrically insulating, the resistance of the surface layer is adjusted by dispersing various conductive materials in the resin. The surface layer 105 is formed on the electric resistance adjusting layer 104 by dissolving the constituent material of the surface layer 105 in an organic solvent to prepare a paint, and performing various coating methods such as spray coating, dipping, roll coating and the like. . About a film thickness, about 10-30 micrometers is desirable.

  The material of the surface layer 105 can be either one-component or two-component, but it can improve environmental resistance, non-adhesiveness, and releasability by using a two-component coating with a curing agent. I can do it. In the case of a two-component paint, a method of crosslinking and curing the resin by heating the coating film is common. However, since the resistance adjustment layer is a thermoplastic resin, it cannot be heated at a high temperature. As the two-component paint, it is effective to use a main agent having a hydroxyl group in the molecule and an isocyanate-based resin that causes a crosslinking reaction with the hydroxyl group. By using an isocyanate resin, a crosslinking / curing reaction occurs at a relatively low temperature of 100 ° C. or lower. As a result of investigations from the non-adhesiveness of the toner, it was confirmed that the resin is a silicone-based resin having a high non-adhesiveness of the toner, and an acrylic silicone resin having an acrylic skeleton in the molecule is particularly good.

  Since the electrical characteristics of the conductive member are important, the surface layer 105 needs to be conductive. A conductive forming method is possible by dispersing a conductive agent in a resin material. Conductivity is not particularly limited, and conductive carbon such as ketjen black EC and acetylene black, rubber carbon such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT, oxidation treatment, etc. Carbon for color, pyrolytic carbon, indium-doped tin oxide (ITO), tin oxide, titanium oxide, zinc oxide, copper, silver, germanium and other conductive metals, metal oxide, polyaniline, polypyrrole, polyacetylene, etc. Include a functional polymer. In addition, there are ionic conductive materials as conductivity imparting materials, inorganic ionic conductive materials such as sodium perchlorate, lithium perchlorate, calcium perchlorate, lithium chloride, and further ethyltriphenylphosphonium tetrafluoroborate And organic ionic conductive substances such as quaternary phosphonium salts such as tetraphenylphosphonium bromide, modified fatty acid dimethylammonium ethosulphate, ammonium stearate acetate, and laurylammonium acetate.

  The gap holding member 103 is provided to provide a gap G between the charging member 101 and the photosensitive member 61, and the gap holding member 103 sets the gap to 100 μm or less, in particular, about 5 to 70 μm. Thereby, formation of an abnormal image at the time of operation of charging device 100 can be suppressed. When the gap G is 100 μm or more, the distance to reach the photoconductor 61 becomes long, so that the Paschen's law discharge start voltage in the atmosphere increases, and further, the discharge space to the photoconductor 61 increases. As a result, when the photosensitive member 61 is charged to a predetermined level, a large amount of discharge products are generated due to discharge, which remains in the discharge space even after image formation and adheres to the photosensitive member 61. Causes deterioration. If the gap G is small, the reach to the photoconductor 61 is short, and the photoconductor 61 can be charged even if the discharge energy is small. However, since the space formed by the charging member 101 and the photoconductor 61 is narrowed, the flow of air is deteriorated. Therefore, the discharge product formed in the discharge space stays in this space, so As in the case where G is large, a large amount remains in the discharge space after image formation and adheres to the photoreceptor 61, which causes the deterioration of the photoreceptor 61 over time. Accordingly, it is preferable to reduce the discharge energy to reduce the generation of discharge products and to form a space that does not retain air. Therefore, the space | gap G is 100 micrometers or less, Comprising: It is preferable to set it as the range of 5-70 micrometers. Thereby, the generation of streamer discharge can be prevented, the generation of discharge products can be reduced, the amount deposited on the photoreceptor 61 can be reduced, and spotted image spots / image flow can be prevented.

  Here, the toner remaining on the photosensitive member 61 after development is cleaned by a cleaning device 64 (described later) provided facing the photosensitive member 61, but it is difficult to completely remove the toner, and a very small amount of toner is removed. It passes through the cleaning device and is conveyed to the charging device 100. At this time, if the particle diameter of the toner is larger than the gap G, the toner may be rubbed by the rotating photoreceptor 61 or the charging member 101 to be heated and fused to the charging member 101. Since the portion where the toner is fused is close to the photosensitive member 61, abnormal discharge that causes preferential discharge occurs. Therefore, the gap G is preferably larger than the maximum particle size of the toner used in the image forming apparatus 1.

A necessary characteristic of the gap holding member 103 is that the gap with the photoreceptor 61 is stably formed over the environment and for a long time (time). For this purpose, a material with low hygroscopicity and wear resistance is used. Is desirable. It is also important that the toner and the toner additive do not easily adhere to each other, and that the photosensitive member 61 is not worn because it contacts and slides on the photosensitive member 61, and is appropriately selected according to various conditions. It is what is done. Specifically, general-purpose resins such as polyethylene (PE), polypropylene (PP), polyacetal (POM), polymethyl methacrylate (PMMA), polystyrene (PS) and copolymers thereof (AS, ABS), polycarbonate (PC ), Urethane, fluorine (PTFE) and the like. As long as the above characteristics are satisfied, the shape is not particularly limited, and a tape-like or sheet-like member can be wound around the resistance adjustment layer. Is preferably pressed into the end of the resistance adjusting tank because the gap can be held most stably. In order to securely fix the gap holding member, it is necessary to apply and bond an adhesive. The gap holding member is preferably an insulating material and preferably has a volume resistivity of 10 ¹³ Ωcm or more. The reason why insulation is necessary is to eliminate the occurrence of leakage current with the photoreceptor 61. The gap holding member 103 is preferably formed by molding.

  A part of the gap holding member 103 has a height difference from the electric resistance adjusting layer 104. As a method for forming the gap, the electrical resistance adjusting layer 104 and the gap holding member 103 can be formed simultaneously by removing processing such as cutting and grinding. By simultaneously processing the gap holding member 103 and the electric resistance adjusting layer 104, the gap can be formed with high accuracy.

  The contact width between the gap holding member 103 and the photoreceptor 61 is reduced by forming the height of the portion of the gap holding member 103 adjacent to the electric resistance adjustment layer 104 equal to or lower than the height of the electric resistance adjustment layer 104. Thus, the gap between the charging member 101 and the photoreceptor 61 can be made highly accurate. By doing so, it is possible to prevent the outer surface of the end portion of the gap holding member 103 on the side of the electric resistance adjusting layer 104 from coming into contact with the photosensitive member 61, and the electric resistance adjusting layer adjacent through the end portion. It is possible to prevent the leak current from occurring due to the contact of the photosensitive member 104 with the photoconductor 61. Further, by processing the end portion of the gap holding member 103 on the electric resistance adjusting layer 104 side to be low, this portion can be used as a clearance allowance (escape processing) of a cutting blade or the like when performing removal processing. The shape of the clearance allowance (relief processing) may be any shape as long as the outer surface of the end portion of the gap holding member 103 is not in contact with the photoreceptor 61.

  Furthermore, it is difficult to perform masking at the boundary between the electric resistance adjusting layer 104 and the gap holding member 103 when coating the surface layer 105 in consideration of variations, and when forming the step, the electric resistance adjusting layer 104 and By forming the surface layer 105 up to the gap holding member 103 that is the same or low, the surface layer 105 can be reliably formed on the electric resistance adjusting layer 104.

(Image forming device)
Hereinafter, an image forming apparatus including, as a charging member, a conductive member evaluated by a conductive member evaluation apparatus and a conductive member evaluation method according to the present invention will be described with reference to FIGS. FIG. 5 is a configuration diagram of a charging device including a charging member which is a conductive member evaluated according to the present invention, and an image forming apparatus including the charging device. FIG. 6 is a configuration diagram of an image forming unit of the image forming apparatus of FIG. FIG. 7 is a configuration diagram of the charging device and the process cartridge.

  As shown in FIGS. 5 and 6, the image forming apparatus 1 has a drum shape having a photosensitive layer on the surface, and has four colors of yellow (Y), magenta (M), cyan (C), and black (K). The number of electrostatic latent image carriers 61 corresponding to colors (hereinafter referred to as “image carriers”), the charging device 100 for charging each image carrier 61 substantially uniformly, and the charged image carriers An exposure device 70 for exposing the body 61 with a laser beam to form an electrostatic latent image and a developer of four colors, yellow, magenta, cyan, and black, are accommodated and correspond to the electrostatic latent image on the image carrier 61 A developing device 63 for forming a toner image, a primary transfer device 62 for transferring the toner image on the image carrier 61, a belt-like intermediate transfer member 50 to which the toner image on the image carrier 61 is transferred, A secondary transfer device 51 for transferring the toner image on the intermediate transfer member 50; A fixing device 80 which toner image to fix the toner image on the recording medium to be transferred, further comprising a cleaning device 64 for removing the toner remaining after transfer on the image carrier 61. The recording medium is conveyed from one of the paper feeding devices 21 and 22 that store the recording medium one by one to the registration roller 23 by a conveyance roller through the conveyance path. Here, the recording medium is synchronized with the toner image on the image carrier 61. To the transfer position.

  As shown in FIGS. 5 and 6, the exposure device 70 in the image forming apparatus 1 irradiates the image carrier 61 charged by the charging device 100 with the light L, and the image carrier 61 has photoconductivity on the image carrier 61. An electrostatic latent image is formed. The light L may be a lamp such as a fluorescent lamp or a halogen lamp, or a laser beam by a semiconductor element such as an LED or LD. Here, an LD element is used when irradiation is performed in synchronization with the rotation speed of the image carrier 61 by a signal from an image processing unit (not shown).

  The developing device 63 has a developer carrying member, and the toner stored in the developing device 63 is conveyed to a stirring unit by a supply roller, mixed and stirred with a developer containing a carrier, and faces the image carrying member 61. To the developing area. At this time, the positively or negatively charged toner is transferred to the electrostatic latent image on the image carrier 61 and developed. The developer may be a magnetic or non-magnetic one-component developer or a combination thereof, or a wet developer.

  The primary transfer device 62 transfers the developed toner image on the image carrier 61 to the intermediate transfer member 50 by forming an electric field having a polarity opposite to the polarity of the toner from the back side of the intermediate transfer member 50. The primary transfer device 62 may be any one of a corotron, a scorotron corona transfer device, a transfer roller, and a transfer brush. Thereafter, in synchronization with the recording medium conveyed from the paper feeding device 22, the toner image is transferred onto the recording medium again by the transfer by the secondary transfer device 51. Here, the first transfer may be performed directly on the recording medium instead of the intermediate transfer member 50.

  The fixing device 80 heats and / or presses the toner image on the recording medium to fix and fix the toner image on the recording medium. Here, the toner is passed through a pair of pressure and fixing rollers, and heat and pressure are applied at this time to fix the toner while melting the binder resin. The fixing device 80 may be in the form of a belt instead of a roller, or may be fixed by heat irradiation with a halogen lamp or the like. The cleaning device 64 for the image carrier 61 cleans and removes the toner remaining on the image carrier 61 without being transferred, thereby enabling the next image formation. The cleaning device 64 may be any system such as a blade made of rubber such as urethane or a fur brush made of fiber such as polyester.

  Hereinafter, the operation of the image forming apparatus 1 will be described. The reading unit 30 sets a document on the document table of the document transport unit 36, or opens the document transport unit 36 to set a document on the contact glass 31, closes the document transport unit 36, and presses the document. When a start switch (not shown) is pressed, the original is conveyed onto the contact glass 31 when the original is set on the original conveying section 36, and immediately after the original is set on the other contact glass 31, the first The first reading traveling body and the second reading traveling body 32, 33 travel. Then, the first reading traveling body 32 emits light from the light source, and the reflected light from the document surface is further reflected toward the second reading traveling body 33 and reflected by the mirror of the second reading traveling body 33 to form an image. The image information is read through the lens 34 into the CCD 35 which is a reading sensor. The read image information is sent to this control unit. Based on the image information received from the reading unit 30, the control unit controls an LD or LED (not shown) disposed in the exposure device 70 of the image forming unit 60, so that the outer surface is made uniform by the charging device 100. The laser beam L for writing is irradiated toward the charged image carrier 61. By this irradiation, an electrostatic latent image is formed on the surface of the image carrier 61.

  The paper feeding unit 20 feeds a recording medium from a multi-stage paper feeding cassette 21 by a paper feeding roller, separates the fed recording medium by a separation roller, sends it to a paper feeding path, and records it on the paper feeding path of the image forming unit 60. The medium is transported by a transport roller. In addition to the paper feeding unit 20, manual paper feeding is also possible, and a manual feed tray for manual feeding and a separation roller for separating the recording medium on the manual tray one by one toward the manual paper feed path are also provided on the side of the apparatus. I have. Each of the registration rollers 23 discharges only one recording medium placed on the paper feed cassette 21 and sends it to a secondary transfer unit positioned between the intermediate transfer member 50 and the secondary transfer device 51. When the image forming unit 60 receives image information from the reading unit 30, the image forming unit 60 forms a latent image on the image carrier 61 by performing the laser writing or the development process as described above.

  The developer in the developing device 63 is drawn up and held by a magnetic pole (not shown) to form a magnetic brush on the developer carrier. Further, the toner image is transferred to the image carrier 61 by a developing bias voltage applied to the developer carrier, and the electrostatic latent image on the image carrier 61 is visualized to form a toner image. As the developing bias voltage, an AC voltage and a DC voltage are superimposed. Next, one of the paper feed rollers of the paper feed unit 20 is operated to feed a recording medium having a size corresponding to the toner image. Along with this, one of the support rollers is driven to rotate by the drive motor, the other two support rollers are driven to rotate, and the intermediate transfer member 50 is rotated and conveyed. At the same time, the image carrier 61 is rotated by each image forming unit to form black, yellow, magenta, and cyan monochrome images on the image carrier 61, respectively. Then, along with the conveyance of the intermediate transfer member 50, these single color images are sequentially transferred to form a composite toner image on the intermediate transfer member 50.

  On the other hand, one of the paper feed rollers of the paper feed unit 20 is selectively rotated, the recording medium is fed out from one of the paper feed cassettes 21, separated one by one by the separation roller, and put into the paper feed path, and the image is taken by the transport roller. The recording medium is guided to the sheet feeding path in the image forming unit 60 of the forming apparatus 1 and the recording medium is abutted against the registration roller 23 and stopped. Then, the registration roller 23 is rotated in synchronization with the synthetic toner image on the intermediate transfer member 50, and the recording medium is sent to the secondary transfer portion which is a contact portion between the intermediate transfer member 50 and the secondary transfer device 51. The toner image is secondarily transferred by the influence of the secondary transfer bias and contact pressure formed in the secondary transfer portion, and the toner image is recorded on the recording medium. Here, the secondary transfer bias is preferably a direct current. The recording medium after the image transfer is sent to the fixing device 80 by the transport belt of the secondary transfer device, and the fixing device 80 fixes the toner image by applying pressure and heat by the pressure roller, and then the discharging roller 41. The paper is discharged onto the paper discharge tray 40.

  Here, the case where the conductive member is used as the charging member will be described in detail with reference to the charging device 100. FIG. 7 is a configuration diagram of the charging device and the process cartridge. The process cartridge includes at least the image carrier 61, the charging device 100, and the cleaning device 64, and may include a developing device 63 as shown in FIG. The process cartridge is an integral unit and can be freely attached to and detached from the image forming apparatus. Referring to FIG. 6, the surface of the image carrier 61 is uniformly charged by a charging member in which an image forming area is arranged in a non-contact manner, and is visualized by development after forming an image (latent image), and a toner image is recorded. Transferred to the medium. The toner remaining on the image carrier without being transferred to the recording medium is collected by the auxiliary cleaning member 64d. Thereafter, in order to prevent toner and toner constituent materials from adhering to the surface of the image carrier, the solid lubricant 64a is uniformly applied on the image carrier by the application member 64b to form a lubricant layer. Thereafter, the toner that could not be collected by the auxiliary cleaning member by the cleaning member 64c is collected and conveyed to the waste toner collecting unit. The auxiliary cleaning member has a roller shape and a brush shape, and solid lubricants such as fatty acid metal salts such as zinc stearate, polytetrafluoroethylene, etc., reduce the coefficient of friction on the image carrier, and make it non-adhesive. Anything can be given. Examples of the cleaning member include a blade made of rubber such as silicon and urethane, and a fur brush made of fiber such as polyester.

  The charging device 100 includes a cleaning member 102 for removing contamination of the charging member 101. The shape of the cleaning member may be a roller shape or a pad shape, but in this embodiment, it is a roller shape. The cleaning member 102 is fitted into a bearing provided in a housing (not shown) of the charging device 100 and is rotatably supported. The cleaning member 102 contacts the charging member 101 and cleans the outer peripheral surface. If foreign matter such as toner, paper dust, or a damaged member adheres to the surface of the charging member 101, abnormal electric discharge that preferentially generates discharge occurs because the electric field concentrates on the foreign matter portion. On the contrary, when an electrically insulating foreign material adheres to a wide range, no discharge occurs in that portion, and thus charging spots occur on the image carrier 61. For this reason, the charging device 100 is preferably provided with a cleaning member 102 for cleaning the surface of the charging member 101. As the cleaning member, a brush made of a fiber such as polyester or a porous material (sponge) such as a melamine resin can be used. The cleaning member may be rotated with the charging member, rotated with a linear speed difference, and separated and rotated in a intermittent manner.

  The charging device 100 includes a power source that applies a voltage to the charging member 101. The voltage is preferably a voltage obtained by superimposing a DC voltage and an AC voltage. When there is a portion where the layer configuration of the charging member 101 is non-uniform, the surface potential of the image carrier 61 may become non-uniform when only a DC voltage is applied. With the superimposed voltage, the surface of the charging member 101 becomes equipotential, so that the discharge is stable and the image carrier 61 can be charged uniformly. The alternating voltage in the superimposed voltage preferably has a peak-to-peak voltage that is at least twice the charging start voltage of the image carrier 61. The charging start voltage is an absolute value of a voltage when the image carrier 61 starts to be charged when only a direct current is applied to the charging member 101. Accordingly, reverse discharge from the image carrier 61 to the charging member 101 occurs, and the leveling effect enables the image carrier 61 to be uniformly charged in a more stable state. The frequency of the AC voltage is preferably 7 times or more the peripheral speed (process speed) of the image carrier. By setting the frequency to 7 times or more, the moire image cannot be recognized (visually).

  In this embodiment, the auxiliary cleaning member is a brush roller, the lubricant is zinc stearate in a block shape, and the application roller is pressed with a pressure member such as a spring to apply a solid lubricant to the application roller. The solid lubricant removed from the block is applied to the image carrier. The cleaning member was a counter type using a urethane blade. In addition, the cleaning member of the charging member can be cleaned well by using a melamine resin sponge roller and rotating together with the charging member.

  Hereinafter, a case where a charging member as a conductive member is used as a charging roller of a proximity charging type will be described. The conductive member is not limited to this. As shown in FIG. 4, the charging device 100 is provided with a charging member 101 facing the image carrier 61 and provided with a minute gap G, a cleaning member 102 for cleaning the charging member, and a voltage applied to the charging member 101. At least a power supply (not shown) and a pressure spring (not shown) that presses and contacts the charging member 101 to the image carrier 61. As shown in FIGS. 4 and 7, the charging member 101 is disposed to face the image carrier 61 with a minute gap G therebetween. The gap G between the charging member 101 and the image carrier 61 is formed by bringing the gap holding member 103 into contact with the non-image forming area of the charging member 101. By bringing the gap holding member 103 into contact with the photosensitive layer region, even if the coating thickness of the photosensitive layer varies, variation in the gap can be prevented.

  The shape of the charging member 101 is not particularly limited, and may be fixed and disposed in a belt shape, a blade (plate) shape, or a semi-columnar shape, but a cylindrical shape is most preferable.

  Further, both ends of the cylindrical charging member 101 may be rotatably supported by a gear or a bearing. As described above, when the charging member 101 is formed with a curved surface that gradually separates from the closest part to the image carrier 61 in the moving direction of the image carrier 61, the image carrier 61 is more uniformly charged. Can be made. If the charging member 101 facing the image carrier 61 has a sharp portion, the electric potential of that portion becomes high, so that discharge is preferentially started, and uniform charging of the image carrier 61 becomes difficult. Accordingly, the image carrier 61 can be charged uniformly by having a cylindrical shape and a curved surface. Further, the discharging surface of the charging member 101 is subjected to strong stress. Since the discharge always occurs on the same surface, its deterioration is promoted and may be scraped off. Therefore, if the entire surface of the charging member 101 can be used as a discharging surface, it can be used for a long period of time by rotating it to prevent early deterioration.

  Further, as shown in FIG. 4, the charging member 101 is fitted into a bearing provided on a side plate of a housing (not shown) of the charging device 100, and a compression spring 108 provided on the bearing 107 made of a resin having a low friction coefficient that is not driven by the bearing. Is pressed toward the surface of the image carrier 61. As a result, a constant gap G can be formed even if there is mechanical vibration or deviation of the core shaft 106. The pressing load is 4 to 25N. Preferably, it is 6-15N. Even if the charging member 101 is fixed by the bearing 107, the size of the gap G may fluctuate due to vibrations when rotating, eccentricity of the charging member 101, and unevenness of the surface, and the gap G may deviate from an appropriate range. For this reason, the deterioration of the image carrier 61 is promoted over time. Here, the load means all loads applied to the image carrier 61 through the gap holding member 103. This can be adjusted by the force of the compression springs 108 provided at both ends of the charging member 101, the weight of the charging member 101 and the cleaning member 102, and the like. When the load is small, fluctuation due to rotation of the charging member 101 and jumping up due to impact force of a driving gear or the like cannot be suppressed. When the load is large, the friction between the charging member 101 and the bearing 107 to be fitted increases, and the amount of wear over time is increased to promote fluctuation. Therefore, by setting the load in the range of 4 to 25 N, preferably 6 to 15 N, the gap G is set in an appropriate range, the generation of discharge products is reduced, and the amount deposited on the image carrier 61 is reduced. Thus, the life of the image carrier 61 can be extended, and spotted abnormal images / image streams can be prevented.

(Verification of the present invention)
The inventors have prepared a plurality of conductive members (charging rollers) with different image formation evaluation results in the image forming apparatus, and the evaluation methods shown in the following examples and comparative examples for these conductive members. Was evaluated. Then, the evaluation result was compared with the image formation evaluation result, and it was verified whether the conductive member could be accurately evaluated by the present invention described above.

For the verification, the following two types of charging rollers were used.
(Charging roller A)
A resin composition (volume resistivity: 2 × 10 ⁸ Ωcm) obtained by melting and kneading A, B, and C at 220 ° C. on a core shaft made of stainless steel (outer diameter: 8 mm) is coated by injection molding to adjust the electric resistance. (Overall length 300 mm) was formed.
A: IRGASTAT P18 (manufactured by Ciba Specialty Chemicals) 60 parts by weight (above, polyamide elastomer, A contains perchlorates)
B: ABS resin (Denka ABS GR-3000, manufactured by Denki Kagaku Kogyo Co., Ltd.) 40 parts by weight of A and B mixture 100 parts by weight,
C: Polycarbonate-glycidyl methacrylate-styrene-acrylonitrile copolymer (Modiper C L440-G, manufactured by NOF Corporation) 4.5 parts by weight (graft copolymer)

  Next, the outer diameter of the electric resistance adjusting layer was simultaneously finished to 12.7 mm by cutting.

  Next, on the surface of the electric resistance adjusting layer, a mixture of an acrylic-modified silicone resin (Mukicoat 3000VH, manufactured by Kawakami Paint Co., Ltd.), an ionic conductive agent (PEL20A, manufactured by Nippon Carlit Co., Ltd.), and an isocyanate resin (T4 curing agent, manufactured by Kawakami Paint Co., Ltd.) After the coating material to be diluted with a diluent solvent consisting of butyl acetate, toluene, and MEK, a surface layer having a film thickness of about 10 μm was formed by spray coating, and a charging roller A was manufactured through a baking process.

(Charging roller B)
A charging roller B (outer diameter 12.7 mm, total length 300 mm) having a three-layer structure was manufactured by sequentially laminating the following layers from the bottom on the outer periphery of a core shaft (outer diameter 8 mm) made of stainless steel.
Lower layer A: Foamed EPDM with carbon dispersion (volume resistivity 10 ⁹ Ωcm)
Intermediate layer B: carbon-dispersed NBR rubber (volume resistivity 10 ⁵ Ωcm)
Surface layer C: Fluorine-based resin resin in which tin oxide and carbon are dispersed (volume resistivity 10 ¹⁰ Ωcm)

  The above-described two types of charging roller A and charging roller B were incorporated in the image forming apparatus shown in FIG. 5, and image formation was actually performed in a low temperature and low humidity environment (10 ° C. and 15% RH). Then, the formed image was visually checked to confirm the presence or absence of an image defect due to non-uniform discharge. As a result, the charging roller A obtained a good image without causing image defects due to non-uniform discharge, but the charging roller B resulted in a defective image due to image defects due to non-uniform discharge. It was. That is, as an evaluation result of image formation, the charging roller A was determined to be a charging roller capable of obtaining a good image, and the charging roller B was determined to be a charging roller for forming a defective image.

Example 1
In the measurement environment of 23 ° C. and 50% RH in the atmosphere, the charging roller A and the charging roller B are attached to the conductive member evaluation apparatus shown in FIG. 1 as the charging member 101, and the photosensitive member 204 having an outer diameter of 40 mm and a total length of 320 mm. And a DC voltage Vdc = −0.7 kV from the power supply unit 205 (10 / 10B, manufactured by Trek Japan) to the charging member 101 in a state where they are rotated in opposite directions at a linear velocity of 282 mm / sec. Apply a voltage (that is, an evaluation voltage) with a peak-to-peak voltage Vpp = 2.2 kV and a frequency f = 2200 Hz, and measure unit 206 (USB type data collection system, NR-2000, manufactured by Keyence) to the monitoring terminal of power supply unit 205 Of the voltage value and current value output from the power supply unit 205 at a sampling rate of 200 kHz (that is, evaluation voltage and evaluation current) Was subjected to constant (sampling). Then, the control unit 207 takes in the data (information) about the evaluation voltage and the evaluation current measured by the measurement unit 206, and evaluates the evaluation voltage when the DC voltage Vdc of the evaluation voltage and 0A of the evaluation current are set to the respective center values. The rising phase difference α1 and the falling phase difference α2 with respect to the evaluation current are calculated, and the difference (that is, the measured value) between the rising phase difference α1 and the falling phase difference α2 is obtained. The charging roller A and the charging roller B were evaluated as a charging roller that can obtain a good image.

(Example 2)
The same evaluation as in Example 1 was performed with the peak-to-peak voltage of the evaluation voltage set to Vpp = 2.6 kV.

(Example 3)
The same evaluation as in Example 1 was performed with the peak-to-peak voltage of the evaluation voltage set to Vpp = 2.8 kV.

Example 4
The same evaluation as in Example 1 was performed with the frequency of the evaluation voltage being f = 3000 Hz.

(Example 5)
The same evaluation as in Example 1 was performed with the frequency of the evaluation voltage being f = 5000 Hz.

(Example 6)
The same evaluation as in Example 1 was performed in a state where the charging roller was disposed close to the photosensitive member 204 at a position of a gap of 30 μm.

(Example 7)
The same evaluation as in Example 1 was performed in a state where the charging roller was placed close to the photosensitive member 204 at a position of a gap of 50 μm.

(Example 8)
The same evaluation as in Example 1 was performed in a state where the charging roller was disposed close to the photosensitive member 204 at a position of a gap of 70 μm.

Example 9
The same evaluation as that in Example 1 was performed using an acceleration test apparatus in which the image forming apparatus shown in FIG. 5 was modified, and in a 23 ° C. and 50% RH environment, the electrification roller was idled without passing paper. The test was performed on each charging roller after 120 hours (corresponding to 150,000 copies).

(Comparative Example 1)
In a measurement environment of 23 ° C. and 50%, resistance measurement was performed with the conductive rubber electrode in contact with each charging roller as shown in FIG. A 0.7 kV DC voltage is applied to each charging roller from a digital ultra-high resistance / microammeter (R8340A, manufactured by Advantest), and the resistance value (ie, measured value) of each charging roller is determined from the current value after 15 seconds. ) Was calculated. The lower one of the calculated resistance values is determined as a charging roller capable of forming a good image, and the charging roller A and the charging roller B are evaluated.

(Comparative Example 2)
The same evaluation as in Comparative Example 1 was performed with each charging roller rotated at a linear velocity of 282 mm / sec and a 0.7 kV DC voltage applied, and the current value for a time corresponding to one cycle of the roller was measured. The roller resistance value (that is, measured value) was calculated from the average.

(Comparative Example 3)
The same evaluation as in Example 1 was performed in a stopped state (that is, a non-rotating state) for both the charging roller and the photosensitive member 204.

(Comparative Example 4)
The same evaluation as in Example 1 was performed by applying a DC voltage Vdc = −0.7 kV, a peak-to-peak voltage Vpp = 0 kV, and a voltage with a frequency f = 0 Hz (that is, only a DC voltage) as evaluation voltages.

(Comparative Example 5)
The same evaluation as in Example 1 was performed by applying a DC voltage Vdc = 0 kV, a peak-to-peak voltage Vpp = 2.2 kV, and a frequency f = 2200 Hz (that is, only an AC voltage) as evaluation voltages.

(Comparative Example 6)
The same evaluation as in Example 1 was performed by applying a DC voltage Vdc = −0.7 kV, a peak-to-peak voltage Vpp = 1.0 kV, and a frequency f = 2200 Hz as evaluation voltages.

(Comparative Example 7)
The same evaluation as in Example 1 was performed by applying a DC voltage Vdc = −0.7 kV, a peak-to-peak voltage Vpp = 2.2 kV, and a frequency f = 10000 Hz as evaluation voltages.

(Comparative Example 8)
The same evaluation as in Example 1 was performed in a state where the charging roller was disposed close to the photosensitive member 204 at a position of a gap of 120 μm.

(Comparative Example 9)
The same evaluation as in Example 1 was performed in a state where the charging roller and the photosensitive member 204 were rotated in the same direction.

(Comparative Example 10)
The same evaluation as in Example 1 was performed with the charging roller rotated at a linear velocity of 282 mm / sec and the photosensitive member 204 rotated at a linear velocity of 100 mm / sec.

The evaluation results of the charging roller A and the charging roller B in each of the above-described examples and comparative examples are compared with the evaluation results of image formation in which an image is actually formed using the charging roller A and the charging roller B. If they match, “Good” indicates that the quality of charging roller A and charging roller B can be accurately determined, and if they do not match, “No” indicates that quality of charging roller A and charging roller B cannot be determined. As a result, each example and each comparative example were determined.
○: The quality of the charging roller can be accurately determined.
×: The quality of the charging roller cannot be judged.
Tables 1 and 2 show tables comparing the respective examples and comparative examples, and Table 3 shows determination results in the above examples and comparative examples.

  From the determination results shown in the above tables, the following matters were found. In the conventional evaluation method (Comparative Examples 1 and 2) in which the resistance value is measured by applying an electrode to the charging roller, the quality of the charging roller A and the charging roller B cannot be determined. In comparison example 2, the evaluation result of the electrical characteristics and the image evaluation result in the actual machine are reversed and cannot be dealt with in the comparative example 2. The quality of the charging roller could be accurately judged with the conductive member evaluation apparatus (evaluation method) according to the present invention (accepting examples and comparative examples 1 and 2). In addition, it is necessary to perform evaluation by rotating the charging roller and the photosensitive member 204 in the opposite directions, and it is preferable that the respective linear velocities are the same (Example 1, Comparative Examples 3, 9, and 10). It is necessary to apply an evaluation voltage obtained by superimposing an AC voltage on a DC voltage to the charging roller. If the evaluation voltage is only a DC voltage, only an AC voltage, or even if an AC voltage is superimposed on the DC voltage, When the peak-to-peak voltage Vpp was too low or the frequency f was too high, the quality of the charging roller could not be determined (Comparative Examples 4 to 7). In addition, the gap between the charging roller and the photosensitive member 204 needs to be appropriately provided so as to satisfy Paschen's law. If the gap is too wide, discharge is not performed, and the quality of the charging roller cannot be determined (Example 6). To 8, Comparative Example 8). Further, in the conductive member evaluation apparatus (evaluation method) according to the present invention, the peak-to-peak voltage Vpp and the gap between the charging roller and the photoconductor 204 satisfy Paschen's law, and the gap between the charging roller and the photoconductor 204 is satisfied. If discharge can be generated, those values are arbitrary (Examples 1-3, 6-8). The conductive member evaluation apparatus (evaluation method) according to the present invention can both evaluate an unused charging roller and an aged charging roller (Examples 1 and 9). Moreover, in the conductive member evaluation apparatus (evaluation method) according to the present invention, when the frequency of the evaluation voltage is increased, the evaluation current cannot follow the evaluation voltage, and the evaluation becomes impossible (Examples 4 and 5). Example 7). In the frequency test of the evaluation voltage performed separately, as shown in FIG. 12, when the frequency of the evaluation voltage is increased, the difference between the rising phase difference α1 and the falling phase difference α2 between the evaluation voltage and the evaluation current decreases. Furthermore, when the frequency of the evaluation voltage is 7 kHz or more, the evaluation current flows excessively. Therefore, the frequency of the evaluation voltage needs to be in a range lower than 7 kHz.

  From the above verification, it was found that the conductive member evaluation apparatus and the conductive member evaluation method according to the present invention can accurately evaluate the conductive member that charges the electrostatic latent image carrier.

  In addition, embodiment mentioned above only showed the typical form of this invention, and this invention is not limited to embodiment. That is, various modifications can be made without departing from the scope of the present invention.

It is a block diagram of the electroconductive member evaluation apparatus of this invention. It is a figure which shows the electrical connection relationship of the electroconductive member evaluation apparatus of FIG. It is a flowchart which shows an example of the evaluation process which the control part with which the conductive member evaluation apparatus of FIG. 1 is provided. FIG. 3 is a diagram illustrating a configuration of a charging member that is a conductive member evaluated according to the present invention and a positional relationship between a photosensitive layer region, an image region, and a non-image region of an image carrier. FIG. 2 is a configuration diagram of a charging device including a charging member that is a conductive member evaluated according to the present invention, and an image forming apparatus including the charging device. FIG. 6 is a configuration diagram of an image forming unit of the image forming apparatus in FIG. 5. It is a block diagram of a charging device and a process cartridge. It is a figure which shows the voltage waveform and current waveform in the charging member in which a favorable image is formed. It is a figure which shows the voltage waveform and current waveform in the charging member in which a defective image is formed. It is a figure which shows typically each waveform of a resistance component, a capacity | capacitance component, and a discharge component in a voltage waveform, a current waveform, and a current waveform. It is a figure explaining the rising phase difference and falling phase difference of a voltage and an electric current. It is a figure which shows the relationship between the frequency of a voltage, and the phase difference of a voltage and an electric current. It is a figure which shows the conventional conductive member evaluation apparatus typically.

Explanation of symbols

1 Image forming apparatus 61 Image carrier, photoconductor (electrostatic latent image carrier)
101 Charging member (conductive member)
DESCRIPTION OF SYMBOLS 103 Space | gap holding member 104 Electrical resistance adjustment layer 105 Surface layer 106 Conductive support body, core shaft 200 Conductive member evaluation apparatus 202 A pair of support members (support means)
203 Drive part (drive means)
204 photoconductor (charged member)
205 Power supply (voltage application means)
206 Measuring unit (current measuring means)
207 Control unit (phase difference measuring means, evaluation means)
V Evaluation voltage waveform I Evaluation current waveform A Evaluation current resistance component waveform B Evaluation current capacitance component waveform C Evaluation current discharge component waveform α1 Rising phase difference α2 Falling phase difference

Claims (6)

(A) a member to be charged, and (b) a supporting means for supporting the conductive member by bringing a part of the surface of the conductive member into contact with or close to a part of the surface of the member to be charged. (C) the charged member and the charged member so that a part of the surface of the charged member and a part of the surface of the conductive member which are in contact with or close to each other are sequentially moved on the respective surfaces; Driving means for driving at least one of the conductive member; and (d) when at least one of the member to be charged and the conductive member is driven by the driving means, a DC voltage is applied to the conductive member. Voltage applying means for applying a predetermined evaluation voltage on which an alternating voltage is superimposed; and (e) the charged member and the conductive member when the evaluation voltage is applied to the conductive member by the voltage applying means. Measure the evaluation current flowing through In the conductive member evaluation device including a current measuring unit that, the,
(A) a phase difference measuring means for measuring a phase difference between the evaluation voltage applied by the voltage applying means and the evaluation current measured by the current measuring means;
(B) Evaluation means for evaluating the conductive member based on a phase difference between the evaluation voltage and the evaluation current measured by the phase difference measurement means;
A conductive member evaluation apparatus characterized in that is provided. (A) a cylindrical member to be charged rotatably supported; and (b) a roller-like conductive member that is rotatably supported by bringing the outer peripheral surface of the roller-like conductive member into contact with or close to the outer peripheral surface of the member to be charged. (C) a driving means for rotating the charged member and the conductive member in opposite directions, and (d) the charged member and the conductive member by the driving means, respectively. Voltage application means for applying a predetermined evaluation voltage obtained by superimposing an AC voltage on a DC voltage to the conductive member when rotating; and (e) applying the evaluation voltage to the conductive member by the voltage application means. In a conductive member evaluation apparatus comprising: a current measuring unit that measures an evaluation current flowing through the member to be charged and the conductive member.
(A) a phase difference measuring means for measuring a phase difference between the evaluation voltage applied by the voltage applying means and the evaluation current measured by the current measuring means;
(B) Evaluation means for evaluating the conductive member based on a phase difference between the evaluation voltage and the evaluation current measured by the phase difference measurement means;
A conductive member evaluation apparatus characterized in that is provided. In the phase difference measuring means, the phase difference between the time when the waveform rises at the central value of the evaluation voltage and the time when the waveform rises at the central value of the evaluation current, and the time when the waveform falls at the central value of the evaluation voltage A phase difference from the time point when the waveform falls at the center value of the evaluation current, respectively, and
In the evaluation means, the phase difference between the time point when the waveform of the evaluation voltage rises and the time point when the waveform of the evaluation current rises, and the time point when the waveform of the evaluation voltage falls, measured by the phase difference measurement means. 3. The conductive member evaluation apparatus according to claim 1, wherein the conductive member is evaluated based on a difference between a phase difference between the waveform and the time point when the waveform of the evaluation current falls. 4. (A) a member to be charged, and (b) a supporting means for supporting the conductive member by bringing a part of the surface of the conductive member into contact with or close to a part of the surface of the member to be charged. (C) the charged member and the charged member so that a part of the surface of the charged member and a part of the surface of the conductive member which are in contact with or close to each other are sequentially moved on the respective surfaces; Driving means for driving at least one of the conductive member; and (d) when at least one of the member to be charged and the conductive member is driven by the driving means, a DC voltage is applied to the conductive member. Voltage applying means for applying a predetermined evaluation voltage on which an alternating voltage is superimposed; and (e) the charged member and the conductive member when the evaluation voltage is applied to the conductive member by the voltage applying means. Measure the evaluation current flowing through A conductive member evaluation methods used in the conductive member evaluation device including a current measuring unit that, the,
(A) a phase difference measurement step of measuring a phase difference between the evaluation voltage applied by the voltage application unit and the evaluation current measured by the current measurement unit;
(B) an evaluation step for evaluating the conductive member based on a phase difference between the evaluation voltage and the evaluation current measured in the phase difference measurement step;
The conductive member evaluation method characterized by evaluating a conductive member through these. (A) a cylindrical member to be charged rotatably supported; and (b) a roller-like conductive member that is rotatably supported by bringing the outer peripheral surface of the roller-like conductive member into contact with or close to the outer peripheral surface of the member to be charged. (C) a driving means for rotating the charged member and the conductive member in opposite directions, and (d) the charged member and the conductive member by the driving means, respectively. Voltage application means for applying a predetermined evaluation voltage obtained by superimposing an AC voltage on a DC voltage to the conductive member when rotating; and (e) applying the evaluation voltage to the conductive member by the voltage application means. A current measuring means for measuring an evaluation current flowing through the member to be charged and the conductive member, and a conductive member evaluation method used in a conductive member evaluation apparatus comprising:
(A) a phase difference measurement step of measuring a phase difference between the evaluation voltage applied by the voltage application unit and the evaluation current measured by the current measurement unit;
(B) an evaluation step for evaluating the conductive member based on a phase difference between the evaluation voltage and the evaluation current measured in the phase difference measurement step;
The conductive member evaluation method characterized by evaluating a conductive member through these. In the phase difference measuring step, the phase difference between the time when the waveform rises at the central value of the evaluation voltage and the time when the waveform rises at the central value of the evaluation current, and the time when the waveform falls at the central value of the evaluation voltage A phase difference from the time point when the waveform falls at the center value of the evaluation current, respectively, and
In the evaluation step, the phase difference between the time point when the waveform of the evaluation voltage rises and the time point when the waveform of the evaluation current rises, and the time point when the waveform of the evaluation voltage falls, measured in the phase difference measurement step 6. The conductive member evaluation method according to claim 4, wherein the conductive member is evaluated based on a difference between a phase difference between the waveform and the time point when the waveform of the evaluation current falls.

Images