JP2005301201A - Image forming apparatus with refacing mode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus, capable of preventing the generation of an abnormal image by performing refacing operation for the surface of an image carrier, before the generation of the abnormal image by using a means for detecting deterioration in image quality, in order to prevent the turning into abnormal image, when a protective substance, supplied to the surface of the image carrier in order to prevent deterioration on the surface of the image carrier due to proximity discharge, accumulates on the surface of the image carrier in the image forming apparatus which uses an electrostatic charging system based on the proximity discharge. <P>SOLUTION: By detecting the surface deterioration state of the image carrier 1, determining the removal operation condition of deteriorated protection substance 9b stuck on the surface of the image carrier 1, on the basis of an output value from a sensor and removing the deteriorated protection substance 9b by using a removing means, the generation of an abnormal image can be suppressed, even after repeated image forming operation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a method for removing a deteriorated surface protective substance from an image carrier used for image formation by an electrostatic copying process such as a copying machine, a facsimile machine, a printer, etc., and an image forming method and an image forming apparatus using the same.

2. Description of the Related Art Conventionally, an image forming apparatus that employs an electrophotographic process has a charging unit that charges the surface of an object to be charged as an image carrier. One of the charging methods used in the charging means is a charging method using proximity discharge. In this method, the surface of the image carrier is charged by proximity discharge by bringing a charging member into contact with the surface of the image carrier or bringing the charging member into contact with each other without contact.
In recent years, high image quality and miniaturization of devices are increasingly desired, and charging devices are also required to have high image quality and miniaturization. For such a problem, a charging device using a proximity discharge method using a charging member in contact with or close to the image carrier is effective because it does not require a large charging device.

However, it was found that the charging method using proximity discharge deteriorates the surface of the charged body because the discharge concentrates on the surface of the image carrier. The deterioration of the surface of the image carrier due to the proximity discharge occurs even when there is no contact member to the image carrier, unlike mechanical rubbing.
FIG. 9 shows a state in which only a charging member is placed close to the surface of the image carrier in a non-contact state in order to investigate the deterioration state of the surface of the image carrier due to proximity discharge, and a charging experiment is performed for about 150 hours continuously. It is the result of measuring the change of the film thickness of the charged body surface.
The image carrier used in the experiment is an organic image carrier using polycarbonate for the charge transport layer,
All members contacting the image carrier were removed, and charging was performed using a non-contact charging roller to which a voltage in which an AC bias was superimposed on a DC bias was applied. As a result, it was found that the amount of film scraping on the surface of the image carrier gradually increased and the film thickness of the image carrier gradually decreased. When the image carrier having a reduced film thickness was analyzed, carboxylic acid and the like that were considered to have decomposed the polycarbonate constituting the image carrier were detected. As described above, since the substance that is considered to have decomposed the components constituting the image carrier is detected by the proximity discharge, the following may be considered as a mechanism for reducing the film thickness of the image carrier.

10A and 10B show an example of the state of the surface of the image carrier 1 when the surface of the image carrier 1 is deteriorated by proximity discharge, and the state where the charging roller 2a is opposed to the surface of the image carrier with a minute gap. It is explanatory drawing shown for.
As shown in FIG. 10A, when proximity discharge is performed, the energy of particles (ozone, electrons, excited molecules, ions, plasma, etc.) generated by the discharge is generated on the surface of the charged body in the discharge region of the image carrier surface. The charge transport layer 1a is irradiated. This energy is resonated and absorbed by the binding energy of the molecules constituting the surface of the image bearing member, and as shown in FIG. 10B, the charge transport layer 1a has a decrease in molecular weight due to the cleavage of the resin molecular chain, and the entanglement of the polymer chain. This causes chemical deterioration such as a decrease in the degree of evaporation and resin evaporation. It is considered that the film thickness of the charge transport layer 1a on the surface of the image carrier gradually decreases due to such chemical deterioration of the image carrier due to the proximity discharge.

In this way, apart from measures to reduce film thickness due to mechanical rubbing, which had been taken before, measures to reduce film thickness due to chemical degradation of the image carrier surface due to proximity discharge are necessary. I found out.
Note that the decrease in the film thickness on the surface of the image carrier due to the proximity discharge is considered to occur due to the energy of the particles generated by the discharge. Therefore, it is considered to occur even when an image carrier made of another material is used.

The following measures have been taken so far to prevent the film thickness on the surface of the image carrier from being reduced. For example, there is an image bearing member whose surface is coated with amorphous silicon carbide to improve wear resistance. Further, for example, an organic image carrier in which an inorganic material such as alumina is dispersed in a charge transport (CTR) layer on the surface layer of the image carrier to improve wear resistance is used (see Patent Documents 1 and 2). ). However, in such a configuration, durability against mechanical wear can be improved, but chemical deterioration of the image carrier surface due to proximity discharge cannot be prevented.

In Patent Documents 3 and 4, image formation is provided with means for applying zinc stearate to the surface of the image bearing member in the same manner as a specific embodiment of discharge deterioration prevention means in means for solving the problems described later. An apparatus is described. However, this zinc stearate is applied for the purpose of reducing the coefficient of friction on the surface of the image bearing member in order to prevent poor cleaning of the surface of the charged body.

Patent Documents 5 and 6 describe an image forming apparatus provided with a means for applying zinc stearate to the surface of an image carrier, as in a specific example of the discharge deterioration preventing means. These techniques have the problem that the characteristics of the image carrier change due to discharge, specifically, that foreign matter is likely to adhere to the surface of the image carrier, and zinc stearate is used to prevent hazards due to discharge. In this respect, the present invention is approximated.
On the other hand, when the protective material is supplied to the surface of the image carrier, the protective material that has been repeatedly discharged deteriorates itself to protect the image carrier. The deteriorated protective substance accumulates on the surface of the image carrier after repeated image forming operations. In particular, by applying protective substances
When preventing the image carrier from being deteriorated by discharge and extending the life of the image carrier, a protective material sufficiently deteriorated to form an abnormal image is deposited on the surface of the image carrier.
Therefore, it is necessary to remove the deteriorated protective substance accumulated on the surface of the image carrier before an abnormal image is obtained. In the present invention, a change in the surface of the image carrier due to the accumulation of the deteriorated protective substance is detected by the detection means, and the deteriorated protective substance is removed based on the detection result.

Japanese Patent Application Laid-Open No. H10-228707 describes that the surface of an image carrier is detected by a sensor to prevent filming growth.
Patent Document 8 discloses a control means for detecting a reference toner image and background density on an image carrier by an optical image density sensor and controlling the amount of lubricant applied based on the detected reference toner image and background density value. Is provided. The point that a reference toner image is formed on the surface of the image carrier and detected by the optical image density sensor is similar to the present invention, but the purpose is to apply a lubricant to prevent filming. This is an optimization of the amount, which prevents a decrease in the amount of toner adhering to excessive supply of the lubricant and a decrease in the filming suppression effect due to insufficient supply.

On the other hand, according to the present invention, the reference toner image formed on the surface of the image carrier is detected by the optical image density sensor, and the image carrier is prevented from being deteriorated due to the proximity discharge deposited on the surface of the image carrier based on the detection result. Therefore, it is different in that the purpose is to remove the deteriorated protective substance applied.
Moreover, in patent documents 1 thru | or 8, there is no description about the zinc stearate which receives a discharge and deteriorates and it becomes an abnormal image, and the description about the solution.

When charging the image carrier using discharge generated by applying a voltage containing an alternating current component to the charging member, the polymer constituting the image carrier is deteriorated, resulting in a reduction in the film thickness of the image carrier. There is a problem in promoting the service life of the image carrier, and the toner component and the like easily adhere to the image carrier. In order to prevent such a problem, the image carrier can be prevented from being deteriorated by supplying a protective substance to the surface of the image carrier at least in the discharge region in order to prevent the image carrier from being deteriorated by discharge. .
However, since the protective substance that has been discharged in the discharge region is deteriorated, the protective substance itself becomes an abnormal image when accumulated on the surface of the image carrier. Therefore, the protective substance deteriorated in the discharge area needs to be quickly removed from the surface of the image carrier after passing through the discharge area.
It is considered that a part of the deteriorated protective substance is removed from the surface of the image carrier during the transfer process and cleaning process together with the developer in the normal image forming process. And reaches the discharge region again. Such a deteriorated protective substance that could not be removed repeatedly passes through the discharge region and gradually accumulates on the surface of the image carrier.

As described above, since a part of the deteriorated protective substance is removed from the surface of the image carrier during the repeated image forming operation, an abnormal image is generated due to accumulation of the deteriorated protective substance in a low-life apparatus. Accumulation of deteriorated protective substances has not been a problem because the lifetime of the device will be reached before this occurs.
On the other hand, when the life of the image carrier can be extended by supplying a protective substance to at least the discharge region of the surface of the image carrier and preventing the image carrier from being deteriorated by proximity discharge, as in the present invention, The accumulated amount of the deteriorated protective member on the surface of the carrier may reach an amount that causes an abnormal image.

An abnormal image will be described. An abnormal image means that a desired image cannot be obtained as a result of the toner image not being normally formed due to the deteriorated protective substance adhering to the surface of the image carrier. As a mechanism in which a normal toner image is not formed, the surface energy on the surface of the image carrier changes due to the attachment of a deteriorated protective substance, and even when the development conditions are the same, the toner adhesion amount changes or the deterioration This is because the charging by the charging device is not correctly performed due to the adhesion of the protective material, or the latent image is not correctly formed.
In addition, in the normal image forming process, a part of the deteriorated protective substance is removed, but the removal amount largely depends on the image pattern and the image area ratio. In this case, the deteriorated protective substance accumulates unevenly.
Therefore, before becoming an abnormal image, it is necessary to remove at once the protective material deteriorated from the entire surface of the image carrier by the removing operation.

JP 2002-207308 A JP 2002-229227 A JP 2002-55580 A JP 2002-244487 A JP 2002-244516 A JP 2002-156877 A Japanese Patent Laid-Open No. 10-312143 JP-A-8-137354

The present invention has been made in view of the above background, and an object of the present invention is to prevent deterioration of the surface of an image carrier due to proximity discharge in an image forming apparatus that employs a charging method using proximity discharge. In order to prevent the protective material supplied to the surface of the image carrier from accumulating on the surface of the image carrier and forming an abnormal image, a means for detecting image quality degradation is used to prevent the image carrier from generating an abnormal image. An object of the present invention is to provide an image forming apparatus capable of preventing the occurrence of abnormal images by performing a surface reface operation.

As means for solving the above problems, the present invention has the following features.
The removal method according to claim 1 utilizes a discharge generated by applying a voltage containing an AC component to a moving image carrier and a charging member provided in contact with or close to the image carrier. A charging device for charging the image carrier, a latent image forming device for forming an electrostatic latent image on the surface of the image carrier charged by the charging device, and an image portion of the electrostatic latent image formed by the latent image forming device In an image forming apparatus in which a protective material is present at least on the image carrier in the discharge area, and sticking that occurs due to deposition of deteriorated protective material accumulated on the surface of the image carrier. A detecting means for detecting a change in sex and refreshing the surface of the image carrier to a state in which no abnormal image occurs based on the detection result.

According to a second aspect of the present invention, the toner image formed on the surface of the image carrier is detected using an optical sensor.
According to a third aspect of the present invention, when applied to an image forming apparatus having an intermediate transfer member, the toner image on the intermediate transfer member is detected using an optical sensor.
According to a fourth aspect of the present invention, there is provided a configuration for detecting a torque when the image carrier is driven.
The removal method described in claim 5 is configured to detect the distortion of the blade-like member disposed in contact with the image carrier.

The removal method according to claim 6 is the removal method according to claim 1, wherein the removal means is a magnetic brush of a developing device, and a relational expression: | P-Pref | (Pref is for reference) The operating condition of the magnetic brush is determined based on the sensor output value).
In the removing method according to claim 7, the removing means is a toner removing means,
The operating condition of the toner removing unit is determined based on the relational expression: | P-Pref |.
9. The removal method according to claim 8, wherein the removing means is an intermediate transfer member that mediates toner movement from the image carrier to paper, and the intermediate transfer member and the image based on the relational expression: | P-Pref |. The removal operation condition of the carrier is determined.
The removing method according to claim 9, wherein the removing means is a polishing means provided with a separation / contact mechanism with respect to the image carrier, and the polishing means is based on an output value P of a sensor that detects the surface of the image carrier. A contact state is established with the carrier, and the contact time is determined based on the relational expression: | P-Pref |.
The removal method according to claim 10 is characterized in that, in the removal method, the protective material is not supplied to the surface of the image carrier during the removal operation.

The charging member according to claim 11 is the charging member according to any one of claims 1, 2, 6 to 9, wherein the charging member includes a shaft portion and a main body portion covering the shaft portion. A spacer member is provided in the main body corresponding to the outside of the image forming area of the image carrier, and a gap is formed between the image carrier and the image carrier.
The charging member according to claim 12 is characterized in that the charging member is made of a resin material having a roller shape and a hard surface layer.
The charging device according to claim 13 is characterized in that the charging member according to claim 11 or 12 is used.

15. The image forming apparatus according to claim 14, wherein the charging member according to any one of claims 1, 2, 6 to 9, and 11 to 13 is used. The closest distance to the image carrier is 1 to 100 [μm].
The removal method according to claim 15, wherein the removal method according to claim 1, wherein at least the protective substance present in the discharge region is lamellar crystal powder. It is characterized by.
In the removing method according to claim 16, the protective substance according to claim 15 is zinc stearate.

The image forming method according to claim 17 is characterized in that the removing method according to any one of claims 1 to 10 is used as the image forming method.
The image forming apparatus according to claim 18 is characterized in that the image forming apparatus uses the removal method according to any one of claims 1 to 10.

According to the present invention, in an image forming apparatus employing a charging method using proximity discharge, a protective substance applied to prevent deterioration of the surface of the image carrier due to proximity discharge is deteriorated due to proximity discharge, and repeatedly. In the case of accumulating on the surface of the photoreceptor after the image forming operation, occurrence of an abnormal image can be suppressed by removing it appropriately before it becomes an abnormal image.

Hereinafter, a first embodiment of an image forming apparatus to which the present invention is applied will be described.
FIG. 1 shows an example of an image forming apparatus having a configuration common to the embodiments described later. The image forming apparatus includes an image carrier 1 as an image carrier made of an organic image carrier.
In FIG. 1, an image carrier 1 is rotated by a driving device (not shown), and the surface thereof is charged to a predetermined polarity by a charging roller 2a of a charging device 2 of a proximity charging type. The surface of the charged object 1 is exposed by the exposure device 3 to form an electrostatic latent image corresponding to the image information.
The electrostatic latent image is developed with toner as a developer supplied from the developing device 4 to the surface of the image carrier 1 to be visualized as a toner image.

On the other hand, a transfer sheet as a recording medium is fed toward the image carrier 1 from a sheet feeding unit (not shown). On the transfer paper, the toner image on the image carrier 1 is transferred onto the transfer paper by the transfer device 5 disposed opposite to the image carrier 1. The transfer paper onto which the toner image has been transferred is separated from the image carrier 1 and then conveyed to the fixing device 6 along the transfer material conveyance path 10 to fix the toner image. Transfer residual toner as residual toner remaining on the image carrier 1 after the toner image is transferred to the transfer paper is removed from the image carrier 1 by the cleaning device 7. Further, the residual charge on the surface of the image carrier after the transfer residual toner is removed is removed by the static eliminator 9. In this way, the image carrier 1 is used repeatedly. Note that the image forming apparatus of the present embodiment includes a coating device 9, which will be described later.

In the image forming apparatus to which the present invention is applied, the adhesiveness of the surface of the image carrier is detected by the detection unit, and the cause of the abnormal image accumulated on the surface of the image carrier before the abnormal image is generated according to the detection result It has a removal operation to remove the material. Hereinafter, a method for detecting the surface of the image carrier with a sensor and a method for removing a deteriorated protective substance on the surface of the image carrier will be described.
In the present invention, an optical sensor is used as a means for detecting the surface of the image carrier. A method for detecting the adhesiveness of the surface of the image carrier using an optical sensor will be described.
In the detection method of the present invention, instead of directly detecting the amount of deteriorating substances accumulated on the image carrier, the reference image is detected by the optical image density sensor, and the image carrier is determined depending on whether the image density is normal or not. A method is used to detect the accumulation state of deteriorating substances on the body surface.

The optical sensor is an optical image density sensor composed of a light emitting element and a light receiving element. A control means having a CPU is provided, and the image density sensor detects the image density of the reference toner image formed on the surface of the image carrier. The output is input to the control means, and the control means determines a removal operation for removing the deteriorated protective substance on the surface of the image carrier according to a program set in advance corresponding to this input.
Here, Pref is a sensor output value for reference when a reference image is formed on a normal image carrier and the toner adhesion amount is detected by an image density sensor (in this embodiment, a photosensor). Is recorded in the program. On the other hand, P is an output value when a reference image is formed after repeated image formation and the toner adhesion amount is detected by an image density sensor.

As shown in FIG. 3, the optical sensor detects reflected light of the reference image. Therefore, the higher the image density, the smaller the intensity of the reflected light, and the smaller the sensor output value. On the other hand, when the image density is low, the sensor output value takes a large value because the intensity of the reflected light is high.
In FIG. 3, the horizontal axis represents potential (surface potential-development bias), and the vertical axis represents image density sensor output. Let VC be the potential at the time of reference image creation. At this time, the image density detected by the image density sensor of the reference image formed on the normal image carrier becomes Pref.
On the other hand, the image density P1 indicates a case where the reference image has a low image density. Image density P
2 shows a case where the reference image has a high image density.
The image density of the reference image varies depending on the protective substance accumulated on the surface of the image carrier, but the allowable range of the image density that does not become an abnormal image is determined in advance by | P-Pref | ≦ α × Pref (0 <α <1). Determine. The allowable range is determined by a constant α, and it is desirable that the allowable range is set so as not to cause an abnormal image even when | P-Pref | = αPref.

In the operation of removing the deteriorated protective substance, the output value P of the optical image density sensor is input to the control means, and the presence or absence of the removal operation is determined according to the flowchart shown in FIG.
As described above, when the deteriorated protective substance exists on the surface of the image carrier, the reflection density measurement value P of the reference image shows a value different from Pref. By using such a relationship, it is possible to determine whether the removal operation is necessary based on the difference between the measured reflection density values P and Pref of the reference image, instead of directly detecting the amount of the protective substance that has deteriorated. The image formation of the reference pattern may be performed for every 50 copies, for example, but may be appropriately set depending on the model configuration.

Next, a second embodiment will be described.
In the first embodiment, a reference pattern on the surface of the image carrier, which is uniformly charged by a charging device, an electrostatic latent image is formed by an exposure device, and a visible image is formed by a developing device is formed by an optical sensor. Detected. On the other hand, the detection method of the second embodiment is not the reference pattern formed on the image carrier but the reference pattern formed on the image carrier in the image forming apparatus having the intermediate transfer member to which the toner image is transferred from the image carrier. As shown, the reference pattern transferred onto the intermediate transfer member is detected by the optical image density sensor. In this case, in an image forming apparatus having a plurality of image carriers, it is not necessary to provide an optical image density sensor for each of the plurality of image carriers, so that the number of parts can be reduced, the cost can be reduced, and the space can be reduced.

Next, a third embodiment will be described.
In the third embodiment, as shown in FIG. 12, torque detecting means for detecting a change in frictional force between the image carrier and a torque detecting blade-like member disposed in contact with the image carrier is used. In this configuration, the torque fluctuation of the image carrier is detected, and the removal operation is performed based on the detection result.
“Rotation driving torque of image carrier” = “driving force of image carrier alone” + “friction force between blade member for torque detection / image carrier”
Therefore, the tackiness of the surface of the image carrier due to the deposition of the deteriorated protective substance can be detected by the fluctuation of the rotational driving torque of the image carrier.
When the torque value exceeds a certain value, the reface operation is performed. By doing so, the surface of the image carrier can be refreshed before the occurrence of an abnormal image.

FIG. 13 shows the time change of the image carrier driving torque. In section (1) of FIG. 13A, there is no accumulation of deteriorated protective material on the surface of the image carrier, and no abnormal image is generated, and the output value by the detection means is Tref. On the other hand, in the section (2), the deposited protective substance is deposited on the surface of the image carrier, and the detected torque value is increased as a result of the change in adhesiveness. When the torque value reaches T1, an abnormal image is generated.
FIG. 13B shows the change over time in the torque value when the reface operation of the surface of the image carrier is performed before the occurrence of an abnormal image based on the torque detection result. In the section (3), the torque value increases due to the deposition of the deteriorated protective substance, but at the time (point A) when the torque value reaches T2 before reaching T1 where the abnormal image occurs, the image carrier. Perform surface reface operation. The reface operation is performed until the detection value Tref at which no abnormal image occurs is reached, and is terminated when the Tref is reached. In this way, by repeating the reface operation based on the torque detection result, it is possible to suppress the occurrence of an abnormal image due to the application of the protective substance for a long time while protecting the image carrier from the discharge of the charging device.

Next, a fourth embodiment will be described.
In the fourth embodiment, as shown in FIG. 14, a strain sensor is installed on a blade-like member disposed in contact with the surface of the image carrier, and the adhesiveness of the surface of the image carrier is determined based on the detection result of the strain sensor. Is detected, and removal is performed based on the detection result.
When the deteriorated protective substance accumulates on the surface of the image carrier, the surface state of the image carrier changes, so that the frictional force with the blade-like member changes. As the frictional force changes, the amount of distortion of the blade-like member varies. A reface operation is performed on the surface of the image carrier so that this distortion is in a range where no abnormal image occurs.

FIGS. 15A and 15B show the change over time (the number of copies) of the distortion of the blade-like member disposed in contact with the image carrier. FIG. 15A shows that as a result of repeated image forming operations, the protective material supplied to the surface of the image carrier deteriorates and accumulates due to discharge, resulting in an increase in the coefficient of friction on the surface of the image carrier and an increase in the amount of distortion. It shows how to do. In addition, an abnormal image is generated in a region where the distortion amount is ε1 or more.
FIG. 15B shows a change in the distortion amount when the reface operation is performed based on the detection result of the distortion amount. That is, in the section (1), as a result of repeated image forming operations, the amount of distortion increases while the deteriorated protective substance is deposited. Before reaching the distortion amount ε1 at which the abnormal image occurs, an operation of removing the deteriorated protective substance deposited on the surface of the image carrier at the time when the distortion amount ε2 is reached (point A) is started. The section (2) shows the distortion change in the section in which the removal operation is performed, and the removal operation is stopped when the distortion value returns to the point where no abnormal image is generated.

A specific configuration of the strain sensor is shown in FIG. As shown in FIG. 16, the strain sensor is configured to be attached to a blade-like member. As the blade-like member, an elastic member such as a urethane rubber blade conventionally used for a cleaning blade or the like is used. In addition, the strain sensor is attached to the blade surface in FIG. 16, but it may be the back surface. If the distortion of the blade due to the image carrier surface can be detected, the attachment position, the number of attachments, etc. are arbitrary. Just do it. In FIG. 16, the blade-like member is in a so-called counter direction with respect to the rotation direction of the image carrier, but may be in the trailing direction. Further, as shown in FIG. 16A, the blade-like member to which the strain sensor is attached may be disposed anywhere as long as it exists in the image forming region with respect to the main scanning direction of the image carrier. Further, the blade-shaped member may be brought into contact with the entire width of the image forming area in FIG.

Next, a fifth embodiment will be described.
The above embodiment relates to a means for detecting a change in adhesiveness on the surface of the image carrier. Hereinafter, a reface for refreshing the surface of the image carrier based on the detection result obtained by the detection means. An embodiment relating to the operation will be described.
In this embodiment, a magnetic brush of a developing device is used as a first method for removing a deteriorated protective substance on the surface of an image carrier.
The removal operation is performed during non-image formation. During the removal operation, only the image carrier and the developing device are in a movable state, and by the rotation of the magnetic brush of the developing device, the surface of the image carrier is rubbed and rubbed on the surface of the image carrier, and the deteriorated protective substance accumulated. Remove. In order to perform the removal operation corresponding to the amount of the deteriorated protective substance on the surface of the image carrier, the removal operation condition is determined based on the sensor output value | P-Pref |. Specifically, there is a method of making the linear velocity difference between the developing roller and the image carrier larger than that during the image forming operation based on | P-Pref |. Alternatively, when the rotation direction of the developing roller and the image carrier at the time of image formation is the trailing direction, there is a method in which the rotation direction of the developing roller and the image carrier is set to the counter direction during the removal operation. As another removal operation, there is a method in which the removal operation time is adjusted based on | P-Pref | while the rotation speeds of the developing roller and the image carrier are constant. As described above, by determining the removal operation condition according to the surface state of the non-charged body, it is possible to prevent the occurrence of an abnormal image due to insufficient removal and the excessive shaving of the surface of the non-charged body.

Next, a sixth embodiment will be described.
As a second method for removing the deteriorated protective substance, toner removing means is used.
A cleaning blade is usually used as the toner removing means. There is a method in which abrasive particles for polishing the surface of the image carrier are retained between the cleaning blade and the image carrier during the removal operation, and the deteriorated protective material is removed from the surface of the image carrier by the abrasive particles.
Specifically, there are the following removal methods. During the removal operation, only the image carrier and the developing device are in a movable state, and transfer is not performed. During the removing operation, a toner image is formed on the surface of the image carrier by the developing device. The toner image reaches the cleaning blade as it is without being transferred, stays between the cleaning blade and the rotating image carrier, acts as an abrasive, and removes a deteriorated protective material on the surface of the image carrier. .
In order to perform the removal operation according to the amount of the deteriorated protective substance on the surface of the image carrier, the removal condition is determined based on the sensor output value | P-Pref |. The removal amount can be adjusted by adjusting the toner development amount on the surface of the image carrier based on | P-Pref | and adjusting the amount of toner reaching the cleaning unit. When the removal operation time is constant, the amount of abrasion on the surface of the image carrier increases as the amount of toner in the cleaning unit increases.
As another adjustment method, there is a method in which the toner image developed on the surface of the image carrier during the removal operation is made constant, and the removal operation time is set based on | P-Pref |.

Next, a seventh embodiment will be described.
As a third method for removing the deteriorated protective substance, an intermediate transfer member is used.
The removal operation is performed during non-image formation. At the time of the removal operation, only the image carrier and the intermediate transfer member are in a movable state, and the intermediate transfer member rubs the surface of the image carrier to remove the deteriorated protective substance attached and accumulated on the surface of the image carrier. In order to perform the removal operation according to the amount of the deteriorated protective substance on the surface of the image carrier, the removal condition is determined based on the sensor output value | P-Pref |.
The difference between the rotation speed of the intermediate transfer body and the rotation speed of the image carrier is made larger than in the image forming operation based on | P-Pref |, and the rubbing force between the intermediate transfer body and the image carrier is changed. There is a way to do that. As another method, there is a method of determining the removal operation time, that is, the rotation time of the intermediate transfer member, based on | P-Pref |. As described above, by determining the removal operation condition in accordance with the surface state of the image carrier, it is possible to prevent the occurrence of an abnormal image due to insufficient removal and the excessive shaving of the image carrier surface.

Finally, an eighth embodiment will be described.
As a fourth method for removing the deteriorated protective substance, a polishing means is used.
Examples of the polishing means include a roller form and a blade form. FIG. 7 shows a polishing blade in the form of a blade as an example of the polishing means.
In the removing operation, the surface of the image carrier is polished by bringing a polishing blade into contact with the surface of the image carrier during non-image formation. At the time of image formation, a separation / contact mechanism is provided so that the polishing blade is not in contact with the surface of the image carrier. The polishing amount is adjusted by the contact time determined by | P-Pref |. As described above, by determining the removal operation condition in accordance with the surface state of the image carrier, it is possible to prevent the occurrence of an abnormal image due to insufficient removal and the excessive shaving of the image carrier surface.

Next, an embodiment common to the above embodiments will be described.
First, the protective material on the surface of the image carrier will be described.
Various materials can be used as the protective material 9b that protects the image carrier from deterioration from electric discharge. In the image forming apparatus of the present embodiment, zinc stearate is used as the protective substance 9b. However, zinc stearate is an example of the protective substance 9b, and other substances such as various fatty acid salts, waxes, silicone oils and the like are used as the protective substance. It can also be used as 9b.
Examples of fatty acids include undecyl acid, lauric acid, tridecyl acid, myristic acid, palmitic acid, pendadecyl acid, stearic acid, heptadecyl acid, arachidic acid, montanic acid, oleic acid, arachidonic acid, caprylic acid, capric acid, caproic acid, etc. Examples of the metal salt include salts with metals such as zinc, iron, copper, magnesium, aluminum, and calcium.

It is preferable to use a lamellar crystal powder such as zinc stearate as a protective substance.
A lamellar crystal has a layered structure in which amphiphilic molecules are self-organized, and when a shearing force is applied, the crystal breaks along the layers and is slippery. This action is effective in reducing the friction coefficient. However, from the viewpoint of protecting the surface of the image carrier from discharge, the lamellar crystals that uniformly cover the surface of the object to be charged are also subjected to shear force. The characteristic is desirable as a protective material because the surface of the image carrier can be effectively covered with a small amount of the protective material.
In order to fully utilize the properties of the lamella crystals to protect the surface of the image carrier from electric discharge, the protective substance coating device 9 has a linear velocity difference from the surface of the image carrier, and a shearing force is applied. It is desirable to apply protective substances.

Next, a method for supplying a protective substance will be described.
As shown in FIG. 1, the image forming apparatus of the present embodiment is provided with a protective substance coating device 9 as a protective substance supply means for supplying the protective substance 9b to the surface of the image carrier. The protective substance applying device 9 includes a fur brush 9a as an application member, a protective substance 9b, and a pressure spring 9c for pressing the protective substance in the fur brush direction. The protective substance 9b is a solid protective substance 9b formed into a bar shape. The fur brush 9a has a brush tip abutting on the surface of the image carrier. The fur brush 9a is rotated about an axis to pump up the protective substance 9b to one end of the brush, and is carried on the brush to a contact position with the image carrier surface. To apply to the surface of the image carrier.
Further, even if the protective material 9b is scraped off by the fur brush 9a with time, the protective material 9b is pressed against the fur brush 9a with a predetermined pressure by the pressurizing spring 9c so that it does not come into contact with the fur brush 9a. Has been. As a result, even a small amount of protective substance 9b is always uniformly pumped up to the fur brush 9a.

In addition, there is a method of transferring the protective substance 9b to the surface of the image carrier by adding or externally adding the protective substance 9b to the toner. In this case, the presence of the protective substance 9b on the surface of the image carrier is determined depending on the image density or image pattern. Unevenness is likely to occur in the amount, and it is necessary to apply a protective substance 9b more than necessary to compensate for this. Since the protective material 9b is directly applied to the surface of the image carrier as in the present embodiment, the protective material can be stably distributed on the surface of the image carrier without changing depending on various conditions such as image density and image pattern. Can do.
Further, as will be described later, it is important that the protective substance is present in an appropriate state on the surface of the image carrier, and means for transferring the protective substance to the surface of the image carrier is not limited to coating.

Next, protection of image carrier deterioration will be described.
An experimental result showing that the protective substance 9b functions to suppress the deterioration of the image carrier due to discharge will be described.
FIG. 5A is a schematic configuration diagram of an experimental apparatus for confirming that deterioration of the image carrier due to proximity discharge is suppressed by the presence of the protective substance 9b on the image carrier. FIG.
) Is an explanatory diagram of a state in which the surface of the image carrier is divided into a protective substance existence part A and a non-existence part B.
In order to perform this experiment, all members other than the charging roller 2a and the protective substance applying device 9 are removed in advance, and the protective substance applying device 9 is configured to apply the protective substance 9b to the half surface area of the image carrier 1 in the axial direction. did. Then, the charging device 2 and the protective substance coating device 9 were continuously driven together with the image carrier 1, and the deterioration state of the image carrier surface was examined. The experimental conditions are as follows.
Charging conditions:
Vpp (peak-to-peak voltage value of AC voltage) = 2.12 [kV]
f (frequency of AC voltage) = 877.2 [Hz]
DC voltage value = −660 [V]
Moving speed of image carrier surface v = 125 [mm / s]
Protective substance: Zinc stearate fur brush 9a linear velocity = 216 [mm / sec]

As shown in FIG. 5B, zinc stearate as a protective substance is applied to the surface of the half area A in the longitudinal direction of the image carrier 1, and the surface of the image carrier 1 is exposed as it is in the remaining half area B. It has become a state. Further, the amount of film abrasion of the photosensitive layer was measured as an index of the surface deterioration of the image carrier 1.
FIG. 6 is a graph showing the results of carrying out the above experiment for 200 hours.
In the region B where the protective substance 9b is not present, the amount of film scraping increases with the passage of time.
After a lapse of time, the film thickness decreased by about 2.5 [μm]. On the other hand, in the region A where the protective substance 9b is present, the decrease in the film thickness was suppressed to 1/8 or less. Further, when the surface of the image carrier used in the experiment was visually observed after 200 hours had elapsed, in the region B where the protective material 9b was not present, the surface of the charged body turned white and changed in quality. In a certain area A, the mirror surface was kept as in the case of the new image carrier 1.

In addition, from the surface of the image carrier in the region B where the protective material 9b is not present, molecular debris constituting the image carrier is detected from the analysis, whereas in the region A where the protective material 9b is present, the image carrier is constructed. No molecular debris was detected, and the surface of the image carrier under the protective substance 9b was not deteriorated. In region A, the zinc stearate supplied as a protective substance in this experiment was chemically changed, and a decomposed substance was detected.
From the above experimental results, it has been clarified that the presence of the protective substance 9b suppresses deterioration of the surface of the image carrier due to discharge.

Next, the effect of removing the deteriorated protective substance 9b will be described.
An experimental result that confirms that the occurrence of abnormal images is suppressed by removing the deteriorated protective substance 9b will be described.
As shown in FIG. 5, all members other than the charging roller 2 a and the protective substance applying device 9 are removed in advance, and the protective substance applying device 9 is configured to apply the protective substance 9 b to the surface area of the image carrier 1.
Then, the driving of the charging device 2 and the protective material coating device 9 together with the image carrier 1 was continued for about 5 hours under the following conditions.
Charging conditions:
Vpp (peak-to-peak voltage value of AC voltage) = 2.20 [kV]
f (frequency of AC voltage) = 900 [Hz]
DC voltage value = −660 [V]
Image carrier surface moving speed v = 125 [mm / sec]
Protective substance: Zinc stearate fur brush 9a linear velocity = 216 [mm / sec]

As a result, a sticky object having a viscosity adhered to the surface of the image carrier. When the deposits were removed, the image carrier was protected from deterioration due to discharge by the protective substance 9b, as described in "Protection of image carrier deterioration" (column 37). As a result of analyzing this deposit by IR analysis, a substance that was considered to have been broken in the molecular chain of zinc stearate was detected. In addition, adhesion of NOx and ammonium nitrate as discharge products was also observed.
When the image carrier on which the deteriorated zinc stearate was adhered was put in the image forming apparatus and the image was output, an abnormal image was obtained.
On the other hand, an image carrier to which the deteriorated zinc stearate adhered was separately prepared under the same conditions, and the deteriorated zinc stearate was removed by the following method (see FIG. 8).

Next, an example of a method for removing deteriorated zinc stearate will be described.
As an example of removing the deteriorated zinc stearate, the following experiment was performed.
In an experimental machine comprising an image carrier to which deteriorated zinc stearate is adhered and a cleaning blade, toner is retained as abrasive particles at the contact portion between the image carrier and the cleaning blade, and the image carrier is moved to a linear velocity of 185 [mm]. / S].
When the image carrier after removing the deteriorating substance was put in an image forming apparatus and the image was taken out, the occurrence of abnormal images was dramatically improved.
Therefore, from the above experiment, the deposited amount of deteriorated zinc stearate is small, and by performing the removal operation while it can be removed, the deteriorated zinc stearate is removed from the surface of the image carrier,
The image carrier can be returned to a state where no abnormal image occurs.

Next, the charging device will be described.
FIG. 2 is an explanatory diagram of the charging device 2 used in the image forming apparatus of the present embodiment.
The charging device 2 charges the image carrier using proximity discharge. As a method of charging the image carrier 1 using proximity discharge, a rotatable roller-shaped charging member (hereinafter referred to as a charging roller) is used.
A contact charging method in which 2a is placed in contact with the image carrier 1 and a charging roller 2a is connected to the image carrier 1;
There is a non-contact charging system that is arranged in a non-contact manner. In this embodiment, a non-contact charging method is used.

The present invention can also be applied to a contact charging method. However, in the contact charging method, it is preferable to use an elastic member that improves the contact property with the surface of the image carrier and does not apply mechanical stress to the image carrier. However, when an elastic member is used, the charging nip width becomes wide, which may cause the protective material to easily adhere to the charging roller side. Therefore, it is more advantageous to adopt a non-contact charging method for high durability. In the present embodiment, the charging roller 2 is opposed to at least the image forming area on the surface of the image carrier with a predetermined charging gap 14.
A non-contact charging method in which a is arranged was adopted.

The charging roller 2a includes a shaft portion 21a and a roller portion 21b. The roller portion 21b is a shaft portion 2
The portion of the surface of the image carrier 1 facing the image forming area 11 where the image is formed is not in contact with the image carrier 1. The charging roller 2a is set to have a length in the longitudinal direction (axial direction) slightly longer than the image forming area, and spacers 22 are provided at both ends in the longitudinal direction. By bringing these two spacers 22 into contact with the non-image forming regions 12 at both ends of the surface of the image carrier, a minute gap 14 is formed between the image carrier 1 and the charging roller 2a. The minute gap 14 is configured such that the distance at the closest portion between the charging roller 2a and the image carrier 1 can be maintained at 1 to 100 [μm]. A more preferable range of the gap 14 is 30 to 65 [μm].
Set to 0 μm. Further, the shaft portion 21a is pressed against the charged body side by a pressing spring 15 made of a spring. Thereby, the minute gap 14 can be accurately maintained. The charging roller rotates along with the surface of the image carrier via the spacer 22.

A charging power source is connected to the charging roller 2a. Thereby, the surface of the image carrier is uniformly charged by the proximity discharge in the minute gap between the surface of the image carrier and the surface of the charging roller. In this embodiment, an alternating voltage obtained by superimposing an AC voltage that is an AC component on a DC voltage that is a DC component is used as the applied voltage. A DC voltage as the applied voltage applied to the charging roller 2a is A.
When an alternating voltage on which the C voltage is superimposed is applied, the influence of variations in charging potential due to a minute gap fluctuation is suppressed, and uniform charging becomes possible.
The charging roller 2a has a cored bar as a conductive support having a cylindrical shape and a resistance adjusting layer formed on the outer peripheral surface of the cored bar. The surface of the charging roller 2a is preferably hard. A rubber member can also be used as the roller member. However, if the rubber member is also a member that is easily deformed, it is difficult to maintain the minute gap 14 between the charged body 1 and the center of the charging roller 2a depending on image forming conditions. Only the portion may suddenly contact the surface of the image carrier. Since it is difficult to cope with the disturbance of the protective substance caused when the charging roller 2a comes into contact with the surface of the object to be charged locally / suddenly, a hard member with less deflection when using the non-contact charging method Is desirable.

Specific examples of the charging roller 2a having a hard surface include, for example, a thermoplastic resin composition (polyethylene, polypropylene, polymethyl methacrylate, polystyrene, and a copolymer thereof, etc.) in which a polymer ion conductive agent is dispersed in a resistance adjustment layer. ), And the surface of the resistance adjustment layer is cured with a curing agent. The cured film treatment is performed, for example, by immersing the resistance adjustment layer in a treatment solution containing an isocyanate-containing compound, but may be performed by forming a cured treatment film layer on the surface of the resistance adjustment layer. In the present embodiment, the charging roller 2a is formed with a diameter of 10 mm (diameter 10 mm).

The image carrier 1 of the present embodiment is a negatively chargeable organic image carrier having a photosensitive layer provided on a drum-like conductive support having a diameter of 30 mm.
Examples of the conductive support include those having a volume resistance of 1010 Ω · cm or less, for example, metals such as aluminum, nickel, chromium, nichrome, copper, gold, silver, and platinum, metals such as tin oxide and indium oxide. Oxide is deposited or sputtered on a film or cylindrical plastic, paper, or a plate of aluminum, aluminum alloy, nickel, stainless steel, etc. Later, pipes that have been subjected to surface treatment such as cutting, superfinishing, and polishing can be used.
Further, endless nickel belts and endless stainless steel belts disclosed in JP-A-52-36016 can also be used as the conductive support.

In addition, those obtained by dispersing and coating conductive powder in an appropriate binder resin on the support can also be used as the conductive support of the present invention. Examples of the conductive powder include carbon black, acetylene black, metal powder such as aluminum, nickel, iron, nichrome, copper, zinc and silver, or metal oxide powder such as conductive tin oxide and ITO. It is done. The binder resin used at the same time is polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer. , Polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinylcarbazole, acrylic resin, silicone resin, epoxy resin, Examples thereof include thermoplastic, thermosetting resins, and photocurable resins such as melamine resin, urethane resin, phenol resin, and alkyd resin. Such a conductive layer can be provided by dispersing and coating these conductive powder and binder resin in a suitable solvent such as tetrahydrofuran, dichloromethane, methyl ethyl ketone, and toluene.
Further, a conductive layer is provided on a suitable cylindrical substrate by a heat shrinkable tube in which the conductive powder is contained in a material such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, and chlorinated rubber. Those can also be used favorably as the conductive support of the present invention.

Next, the photosensitive layer will be described. The photosensitive layer may be a single layer or a laminated layer, but for convenience of explanation, the case where it is composed of a charge generation layer and a charge transport layer will be described first.
The charge generation layer is a layer mainly composed of a charge generation material. A known charge generation material can be used for the charge generation layer, and representative examples thereof include monoazo pigments, disazo pigments, trisazo pigments, perylene pigments, perinone pigments, quinacridone pigments, quinone condensed polycyclic compounds, Squalic acid dyes, other phthalocyanine pigments, naphthalocyanine pigments, azulenium salt dyes and the like are used. These charge generation materials may be used alone or in combination of two or more.
For the charge generation layer, the charge generation material is dispersed in a suitable solvent together with a binder resin as necessary using a ball mill, attritor, sand mill, ultrasonic wave, etc., and this is applied onto a conductive support and dried. It is formed by doing.

As a binder resin used for the charge generation layer as necessary, polyamide, polyurethane,
Epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polysulfone, poly-N-vinylcarbazole, polyacrylamide, polyvinyl benzal, polyester, phenoxy resin, vinyl chloride-vinyl acetate Examples of the copolymer include polyvinyl acetate, polyphenylene oxide, polyamide, polyvinyl pyridine, cellulose resin, casein, polyvinyl alcohol, and polyvinyl pyrrolidone. The amount of the binder resin is suitably 0 to 500 parts by weight, preferably 10 to 300 parts by weight with respect to 100 parts by weight of the charge generating material. The binder resin may be added before or after dispersion.
As the solvent used here, isopropanol, acetone, methyl ethyl ketone,
Cyclohexanone, tetrahydrofuran, dioxane, ethyl cellosolve, ethyl acetate,
Methyl acetate, dichloromethane, dichloroethane, monochlorobenzene, cyclohexane,
Toluene, xylene, ligroin and the like can be mentioned, and ketone solvents, ester solvents, and ether solvents are particularly preferably used. These may be used alone or in combination of two or more.

The charge generation layer is mainly composed of a charge generation material, a solvent, and a binder resin, and any additive such as a sensitizer, a dispersant, a surfactant, or silicone oil may be contained therein. good.
Coating methods for coating liquids include dip coating, spray coating, beat coating, nozzle coating,
Methods such as spinner coating and ring coating can be used.
The film thickness of the charge generation layer is suitably about 0.01 to 5 μm, preferably 0.1 to 2 μm.

The charge transport layer can be formed by dissolving or dispersing a charge transport material and a binder resin in an appropriate solvent, and applying and drying the solution on the charge generation layer. If necessary, alone or 2
More than one kind of plasticizer, leveling agent, antioxidant and the like can also be added.
Charge transport materials include hole transport materials and electron transport materials.

Examples of the electron transport material include chloranil, bromoanil, tetracyanoethylene,
Tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,
7-tetranitro-9-fluorenone, 2,4,5,7-tetranitroxanthone, 2,
4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2
-B] Electron accepting substances such as thiophen-4-one, 1,3,7-trinitrodibenzothiophene-5,5-dioxide, and benzoquinone derivatives.
Examples of hole transport materials include poly-N-vinylcarbazole and derivatives thereof, poly-γ-carbazolylethyl glutamate and derivatives thereof, pyrene-formaldehyde condensates and derivatives thereof, polyvinylpyrene, polyvinylphenanthrene, polysilane, oxazole derivatives, Oxadiazole derivatives, imidazole derivatives, monoarylamine derivatives,
Diarylamine derivatives, triarylamine derivatives, stilbene derivatives, α-phenylstilbene derivatives, benzidine derivatives, diarylmethane derivatives, triarylmethane derivatives, 9-styrylanthracene derivatives, pyrazoline derivatives, divinylbenzene derivatives,
Other known materials such as hydrazone derivatives, indene derivatives, butadiene derivatives, pyrene derivatives, bisstilbene derivatives, enamine derivatives, and the like can be given. These charge transport materials may be used alone or in combination of two or more.

As the binder resin, polystyrene, styrene-acrylonitrile copolymer, styrene-
Butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, Ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N
-Vinylcarbazole, acrylic resin, silicone resin, epoxy resin, melamine resin,
Thermoplastic or thermosetting resins such as urethane resin, phenol resin, alkyd resin and the like can be mentioned.

The amount of the charge transport material is 20 to 300 parts by weight, preferably 4 with respect to 100 parts by weight of the binder resin.
0 to 150 parts by weight is appropriate. The thickness of the charge transport layer is 2 in terms of resolution and responsiveness.
The thickness is preferably 5 μm or less. Regarding the lower limit, although it differs depending on the system to be used (particularly the charging potential), it is preferably 5 μm or more.
As the solvent used here, tetrahydrofuran, dioxane, toluene, dichloromethane, monochlorobenzene, dichloroethane, cyclohexanone, methyl ethyl ketone, acetone and the like are used. These may be used alone or in combination of two or more.

The present invention can also be applied to an image carrier having a single photosensitive layer. As such an image carrier, an image carrier in which the above-described charge generating substance is dispersed in a binder resin can be used. The photosensitive layer can be formed by dissolving or dispersing a charge generating substance, a charge transporting substance, and a binder resin in a suitable solvent, and applying and drying them. Moreover, a plasticizer, a leveling agent, antioxidant, etc. can also be added as needed.
As the binder resin, in addition to the binder resin previously mentioned in the charge transport layer, the binder resin mentioned in the charge generation layer may be mixed and used. The amount of the charge generating material is 5 to 4 with respect to 100 parts by weight of the binder resin.
0 part by weight is preferable, and the amount of the charge transport material is preferably 0 to 190 parts by weight, and more preferably 50 to 150 parts by weight. The photosensitive layer is formed by dip coating, spray coating, bead coating, a coating solution in which a charge generating material and a binder resin are dispersed together with a charge transporting material using a solvent such as tetrahydrofuran, dioxane, dichloroethane, and cyclohexane. It can be formed by coating with a ring coat or the like. The film thickness of the photosensitive layer is suitably about 5 to 25 μm.

In the image carrier of the present invention, an undercoat layer can be provided between the conductive support and the photosensitive layer. In general, the undercoat layer is mainly composed of a resin. However, considering that the photosensitive layer is coated with a solvent on these resins, it may be a resin having a high solvent resistance with respect to a general organic solvent. desirable. Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine resin, phenol resin, alkyd-melamine resin, and epoxy. Examples thereof include a curable resin that forms a three-dimensional network structure such as a resin. In addition, a fine powder pigment of a metal oxide which can be exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide and the like may be added to the undercoat layer in order to prevent moire and reduce residual potential.
These undercoat layers can be formed using an appropriate solvent and a coating method like the above-mentioned photosensitive layer. Furthermore, a silane coupling agent, a titanium coupling agent, a chromium coupling agent, or the like can be used as the undercoat layer of the present invention. In addition, the undercoat layer of the present invention includes A
l2O3 provided by anodic oxidation, organic substances such as polyparaxylylene (parylene), S
What provided inorganic substances, such as iO2, SnO2, TiO2, ITO, CeO2, by the vacuum thin film preparation method can also be used satisfactorily. In addition, known ones can be used. The thickness of the undercoat layer is suitably from 0 to 5 μm.

Further, it is possible to provide a protective layer on the outermost surface layer of the image carrier, which is effective in improving wear resistance. For example, an image carrier coated with amorphous silicon to improve wear resistance, or an organic image carrier provided with an outermost surface layer in which alumina, tin oxide, or the like is further dispersed on the surface of the charge transport layer is used. You can also do things.

As described above, the configuration of the image carrier 1 that can be used in the present invention is not limited to a specific configuration. A one-layer configuration in which only a photosensitive layer mainly composed of a charge generation material and a charge transport material is provided on a conductive support, or a charge generation layer and a charge mainly composed of a charge generation material on a conductive support. A structure in which a charge transport layer mainly composed of a transport material is laminated, or a photosensitive layer mainly composed of a charge generation material and a charge transport material is provided on a conductive support, and a protective layer is further provided on the surface of the photosensitive layer. A charge generation layer mainly composed of a charge generation material and a charge transport layer mainly composed of a charge transport material are laminated on a conductive support, and a protective layer is further provided on the charge transport layer. A charge transport layer mainly composed of a charge transport material and a charge generation layer mainly composed of a charge generation material were laminated on a conductive support, and a protective layer was further provided on the charge generation layer. The present invention can be applied to image carriers having various layer configurations such as configurations.
For examples of removal means,

1 is a schematic configuration diagram of an image forming apparatus showing an embodiment of the present invention. It is explanatory drawing of the charging device used for the image forming apparatus of this invention. It is a figure which shows the relationship between the potential of the image carrier surface, and the output value of a photosensor. It is a flowchart for determining the necessity of removal operation and determining removal operation conditions. (A) is a schematic diagram of a configuration of an experimental apparatus for confirming that deterioration of an image carrier due to proximity discharge is suppressed by the presence of a protective substance. (B) is an explanatory diagram of a state in which the surface of the image carrier is divided into a protective substance existence part A and a non-existence part B. 6 is a graph showing the results of a deterioration experiment on the surface of an image carrier. 1 is a schematic configuration diagram of an image forming apparatus showing an embodiment in which a polishing means is used as a method for removing a deteriorated protective substance. It is a figure which shows an example of the removal method of the deteriorated zinc stearate. It is a graph which shows the deterioration state by proximity discharge by the change of the film thickness of the image carrier surface. It is a figure which shows the surface state of the image carrier in case the surface deteriorates by proximity discharge. FIG. 4 is a diagram illustrating a configuration in which a toner image formed on an intermediate transfer member is detected by an optical sensor. It is a figure which shows the structure which detects the torque fluctuation of an image carrier. (A) is a figure which shows the time change of an image carrier drive torque value. (B) is a figure which shows the time change of the torque value at the time of performing the reface operation | movement of the image carrier surface. FIG. 3 is a diagram showing a configuration in which the adhesiveness of the image carrier surface is detected by a strain sensor installed on a blade-like member disposed in contact with the image carrier surface. (A) is a figure which shows the time change (the number of copies) of distortion of a blade-shaped member. (B) is a diagram showing the time change (number of copies) of the distortion when performing the reface operation on the surface of the image carrier. (A) is a figure which shows the structure which affixes a distortion sensor to the braided member contact | abutted to the image carrier. (B) is a diagram showing a configuration in which a blade-like member is brought into contact with the entire image forming region of the image carrier.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image carrier 1a Charge transport layer 2 Charging device 2a Charging roller 3 Exposure device 4 Developing device 5 Intermediate transfer member 6 Fixing device 7 Cleaning device 8 Static eliminating device 9 Coating device 9a Coating member 9b Protective substance 9c Pressure spring 10 for coating device Transfer material conveyance path 11 Image forming area 12 Non-image forming area 14 Fine gap 15 Pressure spring 16 for charging device Drive motor 21a Roller shaft portion 21b Roller portion 22 Spacer

Claims (18)

A moving image carrier;
A charging device for charging the image carrier using a discharge generated by applying a voltage containing an AC component to a charging member provided in contact with or close to the image carrier;
A latent image forming device that forms an electrostatic latent image on the surface of the image carrier charged by the charging device;
A developing device that attaches toner to the image portion of the electrostatic latent image formed by the latent image forming device;
In an image forming apparatus in which a protective substance exists at least in the image carrier in the discharge area,
Deletion characterized by having a detecting means for detecting a change in adhesiveness due to the deposition of a deteriorated protective substance on the surface of the image carrier, and performing an operation for removing the deteriorated protective substance on the surface of the image carrier based on the detection result. Method. The removal method according to claim 1,
The removal method, wherein the detection means is an optical sensor for detecting a toner image formed on the surface of the image carrier. The removal method according to claim 2,
The removal method according to claim 1, wherein the detection means is an optical sensor for detecting a toner image on the intermediate transfer member. The removal method according to claim 1,
The removal method according to claim 1, wherein the detecting means is means for detecting torque when the image carrier is driven. The removal method according to claim 1,
The removal method according to claim 1, wherein the detection means is means for detecting distortion of a blade-like member disposed in contact with the image carrier. The removal method according to claim 1,
In the removing method, the removing means is a magnetic brush of a developing device,
A removal method characterized by determining an operating condition of the magnetic brush based on a relational expression: | P-Pref | (Pref is a reference sensor output value). The removal method according to claim 1,
In the removing method, the removing means is a toner removing means,
A removal method characterized in that the operating condition of the toner removing means is determined based on the relational expression: | P-Pref |. The removal method according to claim 1,
The removal method is an intermediate transfer body in which the removal means mediates the movement of toner from the image carrier to paper,
A removal method characterized in that the removal operation condition of the intermediate transfer member and the image carrier is determined based on the relational expression: | P-Pref |. The removal method according to claim 1,
The removing method is a polishing means in which the removing means is provided with a separation / contact mechanism with the image carrier,
Based on the output value P of the sensor that detects the surface of the image carrier, the polishing means comes into contact with the image carrier,
The contact method is determined based on the relational expression: | P-Pref |. The removal method according to any one of claims 1 to 9,
In the removing method, the protective material is not supplied to the surface of the image carrier during the removing operation. The charging member according to any one of claims 1, 2, 6 to 9,
The charging member includes a shaft portion and a main body portion covering the shaft portion,
A charging member, wherein a spacer member is provided in a main body portion corresponding to an outside of an image forming area of an image carrier to form a gap with the image carrier. A charging member according to any one of claims 1, 2, 6 to 9, 11.
The charging member is made of a resin material having a roller shape and a hard surface layer. A charging device using the charging member according to claim 11. An image forming apparatus using the charging member according to any one of claims 1, 2, 6 to 9, and 11 to 13,
In the image forming apparatus, the closest distance between the charging member and the image carrier is 1 to 100 [μm]. The removal method according to any one of claims 1, 2, 6 to 9,
The removal method is characterized in that at least the protective substance present in the discharge region is lamellar crystal powder. The removal method according to claim 15, wherein the protective substance is zinc stearate. An image forming method using the removing method according to claim 1. An image forming apparatus using the removal method according to claim 1.

Images