JP2008089771A - Cleaning method, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning method that ensures stable formation of an image of high image quality for a long time without causing any trouble arising from nonuniform quantity of lubricant, by applying an appropriate quantity of lubricant to a photoreceptor and controlling the quantity of application in the lengthwise direction of the photoreceptor, and to provide a process cartridge and an image forming apparatus. <P>SOLUTION: The image forming method includes: forming an electrostatic latent image on an image carrier 1; conveying developer to a developing area opposite the image carrier by means of a developer carrier 5a by holding the developer on the surface thereof; transferring a developer image on the image carrier 1 to transfer paper; applying a lubricant to the image carrier 1; and removing residual developer on the image carrier 1 by using a cleaning means 7. The method further includes applying charged developer to the surface of the image carrier 1 by a difference between the surface potential of the image carrier 1 and the potential of a bias applied to the lubricant application means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cleaning method in a copying machine, a printer, a facsimile, or the like using an electrophotographic system, a process cartridge, and an image forming apparatus to which these are applied.

Conventional image forming apparatuses using electrophotography such as copying machines, facsimiles, and printers include a charging device that uniformly charges the surface of a photoconductor as an image carrier, and an electrostatic latent image on the surface of the uniformly charged photoconductor. A writing device for forming a developer, a developer carrying member for carrying the developer on the surface and transporting the developer to a developing region which is opposite to the image carrying member, and a developer on the developer carrying member. There are various types constituted by a developing device that visualizes the latent image above, a voltage power supply unit that applies a developing bias voltage to the developer carrying member, and a cleaning device that removes the developer remaining on the photosensitive member. Known (for example, see Patent Documents 1 and 2).
In such an image forming apparatus, in recent years, the degree of demand for higher reliability and higher image quality of the formed image has also increased. For this reason, a device for realizing high image quality efficiently has been demanded.

For example, it is conceivable to make the developer easy to fix on the transfer paper or to reduce the average particle size of the developer in order to improve the image quality. However, if the toner particle size is reduced in order to improve the image quality of the formed image, the fluidity of the developer tends to decrease as the average particle size of the toner decreases.
When the toner having lowered fluidity is used, background stains and transfer defects due to toner charging failure are likely to occur. Therefore, conventionally, an additive such as silica is added to the toner in order to improve the fluidity of the developer.
However, it has been found that this causes side effects such as abrasion of the cleaning blade and filming phenomenon in which the toner adheres to the surface of the photoreceptor in the form of a film. When toner filming on the surface of the photoconductor occurs, the adhesion force between the surface of the photoconductor and the toner increases, so that the toner is not transferred well to the transfer paper, which may cause the characters in the transfer image to be lost. turn into.

In order to improve these, conventionally, a method of applying zinc stearate to a photoreceptor has been proposed in order to reduce the adhesion between the surface of the photoreceptor and the toner, and has already been put into practical use.
As a method that is generally put into practical use, a fur brush brought into contact with solid zinc stearate is rotated to scrape off the stearic acid, and the scraped powdered zinc stearate is applied onto the photoreceptor. There is a method of forming a film with a blade.
Thereby, since the frictional force on the surface of the photosensitive member can be reduced, the sliding of the cleaning member on the surface of the photosensitive member is improved, and the background dirt and transferability can be improved. It is also possible to prevent the wear of the photoreceptor itself over time.

Patent Document 1 discloses a developer in which zinc stearate is added to toner together with silica. According to the image forming apparatus using this developer, during development, zinc stearate is moved onto the photoconductor together with the toner, or zinc stearate is developed on the background portion of the photoconductor to develop stearin on the surface of the photoconductor. A zinc oxide film is formed.
In this disclosure, since zinc stearate is contained in the developer, zinc stearate is supplied to the photoreceptor only during development. Therefore, it is effective in that it is not necessary to specially apply zinc stearate after development is started. However, when using a new photoconductor, the surface of the photoconductor generally does not have a zinc stearate film, so the frictional force is large. An abnormal image such as this may occur.

In Patent Document 2, separately from the image forming mode, an electric field that moves the zinc stearate supported on the photosensitive member and charged to the opposite polarity to the charging polarity of the toner from the photosensitive member toward the developer roller is photosensitive. It is disclosed that a zinc stearate coating mode is provided which is formed between a body and a developing roller and is moved onto an image carrier by an electric field.
As a result, even when a new image carrier is used, it is possible to maintain a good cleaning performance of the image carrier and obtain a good image free from background stains and transfer defects from the initial stage of output.
Japanese Patent Laid-Open No. 10-20123 Japanese Patent Laid-Open No. 10-307163

However, these conventional methods have a problem that the coating amount of zinc stearate on the photosensitive member is constant, and the coating amount on the photosensitive member becomes excessive or small depending on the use environment and usage method of the machine. .
When the amount of lubricant applied becomes excessive, the amount of zinc stearate that rubs through the blade increases, and the zinc stearate that rubs through adheres to the charging roller and increases the resistance of the charging roller. The problem of appearing as vertical stripes occurs.
On the other hand, if the coating amount is too small, there is a concern that blade deflection or cleaning failure may occur due to filming on the photoreceptor or an increase in the friction coefficient on the photoreceptor. Furthermore, it has been found that the application efficiency of zinc stearate depends on the amount of residual toner remaining on the photoreceptor, and the longitudinal ratio on the photoreceptor depends on the area ratio of the image to be formed and the image / non-image area. It is known that uneven coating in the longitudinal direction occurs when the transfer residual toner is unevenly distributed in the direction.

  Accordingly, an object of the present invention is to provide an appropriate amount of the lubricant to be applied on the photoconductor in consideration of the above-described situation, and further to control the amount of the lubricant applied in the longitudinal direction of the photoconductor, thereby causing uneven coating of the lubricant. It is an object of the present invention to provide an image forming method, a process cartridge, and an image forming apparatus capable of forming a high-quality image stably over a long period of time without causing the above-described problems.

In order to solve the above-mentioned problems, the invention according to claim 1 develops an electrostatic latent image formed on an image carrier, transfers a toner image obtained by the development to a transfer paper, and then a lubricant. In a cleaning method in which a lubricant is applied to the image carrier by an application unit and toner remaining on the image carrier is removed by a cleaning unit, the potential on the surface of the image carrier and the lubricant application unit are applied. An image forming method is characterized in that the lubricant is applied to the image carrier by a potential difference from a bias.
According to a second aspect of the present invention, in the image forming method according to the first aspect, the amount of the lubricant applied is controlled by a potential difference between the potential of the surface of the image carrier and a bias applied to the lubricant applying means. It is characterized by.

According to a third aspect of the present invention, the potential difference between the potential of the surface of the image carrier and the bias applied to the lubricant applying means is controlled in the longitudinal direction of the image carrier. It features an image forming method.
According to a fourth aspect of the present invention, there is provided the method according to any one of the first to third aspects, wherein the surface of the image carrier is charged on the upstream side in the rotation direction of the image carrier itself from the position where the lubricant is applied. The image forming method is characterized.
According to a fifth aspect of the present invention, the potential difference between the potential on the surface of the image carrier and the bias applied to the lubricant application unit is controlled according to temperature or humidity. The image forming method described in the item is characterized.

According to a sixth aspect of the present invention, there is provided at least an image carrier used in the image forming method according to any one of the first to fifth aspects and a lubricant applying unit, and the image carrier is attached to and detached from the main body of the image forming apparatus. Features a process cartridge that is possible.
According to a seventh aspect of the invention, an image carrier capable of forming an electrostatic latent image and a toner image developed from the electrostatic latent image are transferred onto a transfer paper, and then a lubricant is applied to the image carrier. In the image forming apparatus having a lubricant applying unit that performs cleaning and a cleaning unit that removes toner remaining on the image carrier, the lubricant applying unit applies the charged lubricant to the potential of the surface of the image carrier. An image forming apparatus that coats on the image carrier by a potential difference of a bias applied to the lubricant coating unit.
The invention according to claim 8 is characterized in that the image forming apparatus according to claim 7, further comprising a potential difference control means for controlling the potential difference and changing a coating amount of the lubricant.

The invention according to claim 9 further comprises a potential difference control means for controlling a potential difference between the surface potential of the image carrier and the bias applied to the lubricant applying means in the longitudinal direction of the image carrier. Alternatively, the image forming apparatus described in 8 is characterized.
The invention according to claim 10 further comprises charging means for charging the surface of the image carrier on the upstream side in the rotation direction of the image carrier with respect to the lubricant applying means. The image forming apparatus described in 1. is characterized.
The invention according to claim 11 is characterized in that the potential difference control means changes the potential difference according to temperature or humidity, according to any one of claims 7 to 10.
According to a twelfth aspect of the present invention, there is provided an image forming apparatus including the process cartridge according to the sixth aspect.

  According to the present invention, in order to achieve the above object, a charged lubricant is applied onto the image carrier using a difference in potential between the surface potential of the image carrier and a bias applied on the lubricant side. Therefore, the amount of the lubricant to be applied to the image carrier is adjusted according to the magnitude of the potential difference, and the application can be performed in a timely manner by generating the potential difference only when application is required.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus according to an embodiment of the present invention. Here, an embodiment applied to an electrophotographic image forming apparatus A will be described.
The image forming apparatus A is yellow (hereinafter referred to as “Y”), cyan (hereinafter referred to as “C”), magenta (hereinafter referred to as “M”), and black (hereinafter referred to as “K”). ) Is a tandem type image forming apparatus that forms a color image from the four color toners.
The image forming apparatus A includes four photoconductors 1Y, 1C, 1M, and 1K as latent image carriers. Here, the drum-shaped photosensitive member 1 is taken as an example, but a belt-shaped photosensitive member can also be adopted. Each of the photoreceptors 1Y, 1C, 1M, and 1K is rotationally driven in the direction of the arrow in the drawing while being in contact with the intermediate transfer belt 6a that is a surface moving member.

FIG. 2 is a schematic diagram showing the configuration of an image forming unit in which a photoconductor is disposed. In addition, since the configuration around each of the photoreceptors 1Y, 1C, 1M, and 1K in the image forming units 2Y, 2C, 2M, and 2K is the same, only one image forming unit 2 is illustrated, and the reference symbols Y, C, M, and K are omitted.
Around the photoconductor 1, along the surface movement direction, a developing device 5 that visualizes a latent image to form a toner image, and a pre-cleaning static elimination device (hereinafter, PCL) 20 that neutralizes the charged potential of the photoconductor 1. A cleaning device 7 for cleaning residual toner on the photosensitive member 1, a charging device 22 for charging the photosensitive member 1 for applying a lubricant, a lubricant applying device 21 for applying a lubricant to the photosensitive member 1 by a potential difference, and a photosensitive member. The coating blade 24 for acclimatizing the lubricant applied on the body 1 and the charging device 3 for charging the photoreceptor 1 are arranged in this order.
Further, although the application of the lubricant in the longitudinal direction of the photoreceptor 1 cannot be controlled, a configuration without the charging device 22 for charging the photoreceptor 1 for the lubricant application is also conceivable. In this case, the lubricant is applied by the potential difference between the bias applied to the photoreceptor 1 and the lubricant applying device 21 that have been neutralized by the PCL 20.

The configuration of the image forming apparatus A of the present invention will be described with reference to FIGS.
The charging device 3 in FIG. 2 charges the surface of the photoreceptor 1 to a negative polarity. The charging device 3 in the present embodiment includes a charging roller 3a as a charging member that performs a charging process by a so-called contact / proximity charging method.
That is, the charging device 3 charges or charges the surface of the photosensitive member 1 by bringing the charging roller 3a into contact with or close to the surface of the photosensitive member 1 and applying a negative bias to the charging roller 3a. A DC charging bias is applied to the charging roller 3a so that the surface potential of the photoreceptor 1 is -400 to -500V. Note that a charging bias in which an AC bias is superimposed on a DC bias can also be used.

Further, the charging device 3 is provided with a cleaning unit 3b for cleaning the surface of the charging roller 3a. The cleaning roller 3b as a cleaning means is formed of a metal roller shaft and a melamine resin foam provided on the outer periphery of the roller shaft, and has a function of removing foreign matters adhering to the surface of the charging roller 3a.
As the charging device 3, a thin film may be wound around both end portions in the axial direction on the peripheral surface of the charging roller 3 a and installed so as to contact the surface of the photoreceptor 1. As a result, the surface of the charging roller 3a and the surface of the photoreceptor 1 are extremely close to each other with a distance corresponding to the thickness of the film. Thereby, contact with the residual toner on the photoreceptor 1 can be reduced.
The surface of the photosensitive member 1 thus charged is exposed by an exposure device 4 (only arrows in FIGS. 1 and 2 to 4), and an electrostatic latent image is formed based on image information corresponding to each color. The
The exposure apparatus 4 of the present embodiment is a laser type exposure apparatus, but other types of exposure apparatuses such as an exposure apparatus composed of an LED array and an image forming means can also be adopted.

In the developing device 5, a developing roller 5a as a developer carrying member is partially exposed from an opening of a casing (not shown). Further, although a two-component developer composed of toner and carrier is used here, a one-component developer not containing a carrier may be used. The developing device 5 receives toner of a corresponding color from a toner bottle (not shown) and accommodates it inside.
Although not shown, the developing roller 5a is composed of a magnet roller as magnetic field generating means and a developing sleeve that rotates coaxially therearound. The carrier in the developer is brought up on the developing roller 5a by the magnetic force generated by the magnet roller, and is conveyed to a region facing the photoreceptor 1 (hereinafter, a developing region).

Here, the developing roller 5a moves in the same direction at a linear velocity faster than the surface of the photoreceptor 1 in the developing region. Then, the carrier spiked on the developing roller 5a supplies the toner adhered to the carrier surface to the surface of the photosensitive member 1 and develops it while sliding on the surface of the photosensitive member 1. At this time, a developing bias of −300 V is applied to the developing roller 5a from a power source (not shown), whereby a developing electric field is formed in the developing region.
The intermediate transfer belt 6a in the transfer device 6 is stretched around three support rollers 6b, 6c, and 6d, and is configured to endlessly move in the direction of the arrow in the figure. On the intermediate transfer belt 6a, the toner images on the photoreceptors 1Y, 1C, 1M, and 1K are transferred so as to overlap each other by an electrostatic transfer method.

Although there is a configuration using a transfer charger in the electrostatic transfer system, a configuration using a transfer roller 6e that generates less transfer dust is adopted here. Specifically, the primary transfer rollers 6eY, 6eC, 6eM, and 6eK as the transfer devices 6 are arranged on the back surface of the portion of the intermediate transfer belt 6a that is in contact with the photoreceptors 1Y, 1C, 1M, and 1K, respectively. Yes.
Here, the primary transfer region is formed by the portion of the intermediate transfer belt 6 a pressed by the primary transfer roller 6 e and the photosensitive member 1. When the toner images on the photoreceptors 1Y, 1C, 1M, and 1K are transferred onto the intermediate transfer belt 6a, a positive bias is applied to the primary transfer roller 6e.
As a result, a transfer electric field is formed in each primary transfer area (hereinafter referred to as a transfer area), and the toner images on the photoreceptors 1Y, 1C, 1M, and 1K are electrostatically transferred onto the intermediate transfer belt 6a. Attached and transferred.

A belt cleaning device 15 for removing toner remaining on the surface of the intermediate transfer belt 6a is provided around the intermediate transfer belt 6a. The belt cleaning device 15 is configured to collect unnecessary toner adhering to the surface of the intermediate transfer belt 6a with a fur brush and a cleaning blade.
The collected unnecessary toner is transported from the belt cleaning device 15 to a waste toner tank (not shown) by a transport means (not shown). The transfer belt 6a is a high-resistance endless single-layer belt having a volume resistivity of 10 ⁹ to 10 ¹¹ Ωcm, and the material thereof is preferably PVDF (polyvinylidene fluoride). It may be a resin layer.
Further, the secondary transfer roller 16 is disposed in contact with the portion of the intermediate transfer belt 6a stretched around the support roller 6d. A secondary transfer region is formed between the intermediate transfer belt 6a and the secondary transfer roller 16, and a transfer sheet as a recording member is fed into this portion at a predetermined timing.

The transfer paper is accommodated in a paper feed cassette 9 below the exposure device 4 in the drawing, and is conveyed to the secondary transfer region by a pickup roller 10, a registration roller pair 11, and the like. The toner images superimposed on the intermediate transfer belt 6a are collectively transferred onto the transfer paper in the secondary transfer area.
At the time of the secondary transfer, a positive bias is applied to the secondary transfer roller 16, and the toner image on the intermediate transfer belt 6a is transferred onto the transfer paper by the transfer electric field formed thereby.
The charging device 22 charges the surface of the photoreceptor 1 to a negative polarity. On the surface of the photoreceptor 1 charged in this way, writing corresponding to each color is performed on the photoreceptor 1 by the exposure device 23 based on image information corresponding to each color.

The portion where the remaining amount of transfer toner on the photoconductor 1 is large, the application efficiency of the lubricant is deteriorated due to the presence of the transfer residual toner. Therefore, the photoconductor 1 in the portion where the image area ratio of the image created previously by writing is high and low. Manipulate the upper charging potential.
Here, the lubricant application device 21 is in a position facing the photoreceptor 1 by winding the powder-like lubricant 21b accommodated in the case and contacting the powder-like lubricant 21b while frictionally charging the lubricant. It is mainly composed of a conveying brush 21a that conveys to the conveying brush 21a and a pressure spring 21c that presses the powdery lubricant 21b against the conveying brush 21a. The powdery lubricant 21b conveyed to a position facing the photoconductor 1 is sensitized by the potential difference between the bias applied to the core of the conveyance brush 21a by the power pack (not shown) and the surface potential of the photoconductor 1. Adhere on the body 1. The amount of adhesion is controlled by the potential difference.

Further, the bias applied to the conveying brush 21a is corrected depending on the environment in which the image is formed because the charge amount of the lubricant varies depending on the environment (temperature / humidity) at that time. As a result, a target amount of lubricant can be efficiently adhered onto the photoreceptor 1.
In this way, by correcting the potential difference applied to the lubricant depending on the environment (temperature / humidity), fluctuations in the coating amount on the photoreceptor 1 caused by fluctuations in the charging amount of the lubricant due to environmental fluctuations are suppressed, and photosensitivity is always achieved. A target amount of lubricant can be efficiently applied to the body 1.
The conveying brush 21a may be a roller having a shape. Further, in this configuration, the powdery lubricant 21b is transported by the transport brush 21a and is attached on the photoreceptor 1 using a potential difference. However, the powdery lubricant 21b may be a lubricant molded body. At this time, the lubricant molded body is scraped off by the transport brush 21 a and transported to a position facing the photoreceptor 1.

The lubricant application device 21 applies the charged lubricant onto the photoconductor 1 using the difference between the surface potential of the photoconductor 1 and the bias potential applied on the lubricant application device 21 side. By applying the lubricant using the potential difference, the potential difference is generated only when the application is required, so that the application can be performed in a timely manner.
For example, when charging on the photoreceptor 1 is not performed, the lubricant applied on the photoreceptor 1 does not deteriorate. For this reason, since it will become overcoating if it apply | coats at this time, I want to avoid applying. In the always-contact coating method, coating is always performed when the photosensitive member 1 is driven, but in this method, coating can be turned on / off.

In FIG. 2, potential difference control means 25, which is simply shown as a block, is used to control the amount of lubricant applied according to the surface potential of the photoreceptor 1 and the magnitude of the potential difference between the bias applied to the lubricant application device 21. By controlling the amount of lubricant applied on the photoreceptor 1 with the magnitude of the potential difference, an appropriate amount of lubricant can always be applied on the photoreceptor 1, resulting in coating unevenness such as excessive and too small application amounts. Can be suppressed.
The potential difference control means 25 is used in the longitudinal direction of the photoconductor 1 to control the surface potential of the photoconductor 1 and the potential difference between the bias applied on the lubricant side. Thus, by controlling the potential difference between the image carrier surface potential and the bias applied on the lubricant application device 21 side in the longitudinal direction of the photoreceptor 1, the amount of lubricant applied in the longitudinal direction on the photoreceptor 1 can be controlled. It is possible to control, and it is possible to reduce longitudinal coating unevenness caused by the difference in the remaining amount of transfer depending on the image area / non-image area and the image area ratio.

  FIG. 3 is a schematic view showing another embodiment of the lubricant coating apparatus. FIG. 4 is a schematic view showing another embodiment of the lubricant coating device having the same configuration as that of the developing device. FIG. 3 shows a configuration in which the possible conveying brush 21a is removed, and the powdered lubricant 21b is stirred with a stirring member such as an agitator, and the stirred powdered lubricant 21b is directly applied to the photoreceptor 1. Deposit on the surface using a potential difference.

In FIG. 4, the lubricant application device has the same configuration as the developing device 5, and the transport roller 21 a includes a magnet roller as a magnetic field generating unit and a transport sleeve that rotates coaxially therearound. The carrier in the lubricant is brought up on the developing roller by the magnetic force generated by the magnet roller, and is conveyed to the coating region facing the photoreceptor 1.
Here, the transport roller 21 a moves in the same direction at a linear velocity faster than the surface of the photoreceptor 1 in a region facing the photoreceptor 1. Then, the carrier spiked on the transport roller 21 a supplies and applies the lubricant adhering to the carrier surface to the surface of the photoreceptor 1 while rubbing the surface of the photoreceptor 1. At this time, a bias is applied to the transport roller 21a from a power source (not shown), thereby forming a potential difference in the adhesion region.
The housing case is urged by a pressure spring 21c with respect to the brush-like conveying roller 21a so that almost all of the powdery lubricant 21b can be used up. Since the powdery lubricant 21b is a consumable item, its amount decreases with time, but since it is pressurized by the pressure spring 21c, it is always in contact with the conveying brush 21a. The pressure applied by the pressure spring 21c in the present embodiment is 500 mN.

Examples of the lubricant include fatty acid metal salts, silicone oils, fluororesins, and the like, and these can be used alone or in combination of two or more. In particular, fatty acid metal salts are preferred. As the fatty acid metal salt, as the fatty acid, a linear hydrocarbon is preferable, and for example, myristic acid, palmitic acid, stearic acid, oleic acid and the like are preferable, and stearic acid is more preferable.
Examples of the metal include lithium, magnesium, calcium, strontium, zinc, cadmium, aluminum, cerium, titanium, and iron. Of these, zinc stearate, magnesium stearate, aluminum stearate, iron stearate and the like are preferred, and zinc stearate is most preferred.

Referring to FIG. 2, the cleaning device 7 and the coating device 24 include cleaning (application) blades 7a and 24a, support members 7b and 24b, and blade pressure springs 7c and 24c. The cleaning blade 7a removes the toner on the photoreceptor 1 remaining after the transfer.
The coating blade 24a functions to uniformly acclimate the lubricant adhering to the photoreceptor 1. The support members 7b and 24b are attached to the cleaning device 7 and the coating device 24, but the support members 7b and 24b are not particularly limited, but metals, plastics, ceramics, and the like can be used.

For the cleaning (coating) blades 7a and 24a, examples of the elastic body having a low coefficient of friction include urethane elastomer, silicone elastomer, and fluorine elastomer among urethane resin, silicone resin, and fluorine resin.
As the cleaning (coating) blades 7a and 24a, thermosetting urethane resins are preferable, and urethane elastomers are particularly preferable from the viewpoints of wear resistance, ozone resistance, and contamination resistance. The elastomer includes rubber. The cleaning blade 7a preferably has a hardness (JIS-A) in the range of 65 to 85 degrees.
The cleaning blade 7a preferably has a thickness of 0.8 to 3.0 mm and a protrusion amount of 3 to 15 mm. Further, as other conditions, the contact pressure, the contact angle, the amount of biting, and the like can be determined as appropriate.

Here, the image forming operation of the image forming apparatus A of the present invention will be described in more detail with reference to FIGS. 3 and 4, the same parts as those in FIG. 2 are denoted by the same reference numerals, and descriptions other than those necessary are omitted.
When the image forming operation starts, first, the photosensitive member 1 is uniformly charged to the negative polarity by the charging device 3. At this time, dirt such as toner and lubricant adhering to the charging roller 3a is cleaned by the cleaning roller 3b.
Next, the exposure device 4 irradiates the surface of the photoconductor 1 with laser light based on the image data to form a latent image. The latent image is developed with toner by the developing device 5 to form a toner image. As the toner, a two-component developer used together with a magnetic carrier is preferable because it can easily handle color toners.
At this time, the photosensitive member 1 on which the toner image is formed rotates to enter the transfer region, and contacts the intermediate transfer belt 6a that has moved at the same time in the transfer region. In the transfer area, the toner image developed on the photoreceptor 1 is transferred to the intermediate transfer belt 6a under the action of a transfer electric field and nip pressure.

By this transfer, a toner image is formed on the intermediate transfer belt 6a. In the case of the tandem type in which the photoreceptor 1 includes a plurality of color toners, a color toner image is formed on the intermediate transfer belt 6a by repeating this transfer a plurality of times.
On the other hand, the toner image on the intermediate transfer belt 6a is transferred onto the transfer paper in the secondary transfer region under the action of a transfer electric field or nip pressure. At the same time, the transfer paper is fed from the paper feed unit 9, conveyed by a conveyance roller while being guided by a conveyance guide (not shown), conveyed to the registration roller pair 11, and sent to the nip at a predetermined timing.
By this transfer, a full color toner image is formed on the transfer paper. The transfer sheet on which the full-color toner image is formed is discharged onto the discharge tray of the image forming apparatus A after the full-color toner image is fixed by the fixing device 8 (see FIG. 1).

The surface potential of the photoreceptor 1 before transfer is −500 V at the background portion (white background portion) and −50 V at the image portion exposed by the laser beam. A negative toner is developed on the image area with a developing bias of -500 V direct current and 0.5 to 2 kV alternating voltage. In the transfer region, the toner image is transferred to the intermediate transfer belt 6a with a transfer bias of positive polarity of +400 to 450 V and an AC voltage of 0.5 to 2 kV.
After the transfer, due to the influence of the transfer electric field, the surface potential of the photoreceptor 1 is about −200 V at the background portion (white background portion) and about −10 V at the image portion. The toner on the photoconductor 1 after transfer is strongly adhered to the surface of the photoconductor 1 due to the electric field of −200 V and −10 V, and passes through the cleaning blade 7a. Since it remains charged, it becomes an abnormal image such as background fog or white spot.

The electric field remaining on the photosensitive member 1 is irradiated with light by the PCL 20 to change the potential of the background portion without toner from −200 V to 0 V, thereby forming an electric field with an image portion of −10 V, and the toner photosensitive member 1 Reduces the adhesion force to the surface and suppresses the occurrence of poor cleaning.
Thereafter, the charging device 22 charges the surface potential of the photosensitive member 1 to −500 V, and irradiates the surface of the photosensitive member 1 while scanning the surface of the photosensitive member 1 on the basis of the image data formed last time. A potential pattern is formed.

The lubricant application device 21 for applying the lubricant is wound with the powdery lubricant 21b accommodated in the case and the powdery lubricant 21b coming into contact with the powdery lubricant 21b while frictionally charging the lubricant. Transport to the position where
The lubricant in the present embodiment uses powdered zinc stearate, and the zinc stearate particles are charged to −2 to 8 μC / g. The powdery lubricant 21b conveyed to a position facing the photoreceptor 1 is biased (−350V) applied to the core of the conveying brush and the surface potential of the photoreceptor 1 (applying part −50V, non-applying part). It is adhered on the photoreceptor 1 by a potential difference of −500 V). This adhesion amount is controlled by the potential difference.

FIG. 5 is a graph showing the coating amount control on the photosensitive member by the potential difference. FIG. 6 is a graph showing the lubricant application amount control in the longitudinal direction of the photoreceptor. FIG. 5A shows a case where the coating amount is large, and the potential difference between the photoreceptor surface potential and the bias applied to the lubricant coating device 21 side is large. FIG. 5B shows a case where the coating amount is small, and the potential difference between the image carrier surface potential and the bias applied to the lubricant side is small.
In FIG. 6, the surface potential in the longitudinal direction of the photoreceptor 1 can be controlled before applying the lubricant by controlling the charging potential in the longitudinal direction of the photoreceptor by the potential difference control means 25, and as a result, the photoreceptor 1. It is possible to control the amount of lubricant applied in the longitudinal direction.

Next, the lubricant is pressed by the coating blade 24 a that is in contact with the photosensitive member 1 to form a thin film. This thin film reduces the friction coefficient of the photoreceptor 1. At this time, the friction coefficient μ of the photosensitive member 1 is preferably set to 0.4 or less.
The toner on the photosensitive member 1 forming the lubricant film is easily cleaned, and the adhesive force with the potential of the surface of the photosensitive member 1 is also reduced. Therefore, the residual toner having a circularity of 0.94 or more. Even it can be cleaned. The friction coefficient μ can be controlled by a bias applied to the powdery lubricant 21b.
The photosensitive member 1 has a friction coefficient of 0.4 or less, thereby suppressing an increase in friction with the cleaning blade 7a or the coating blade 24a, and suppressing the deformation or twisting of the cleaning blade 7a or the coating blade 24a. 7a or the application blade 24a can be prevented from slipping through and the occurrence of defective cleaning can be suppressed. Further, 0.4 or less, and further preferably 0.3 or less.

FIG. 7 is a schematic view for explaining a method of measuring the friction coefficient of the photosensitive member. The coefficient of friction of the photoreceptor 1 was measured by the Euler belt method as follows. In this case, medium-quality high-quality paper as a belt is stretched around the drum circumference ¼ of the photosensitive member 1 so that the paper scissors are in the longitudinal direction, and one of the belts has, for example, 0.98 N (100 gr). A load is applied.
On the other side of the belt, a force gauge is installed, the force gauge is pulled, the load at the time when the belt moves is read, and the friction coefficient μs = 2 / π × 1n (F / 0.98) (where μ: Substitutive coefficient of friction, F: measured value) Note that the coefficient of friction of the photosensitive member 1 in the image forming apparatus A is a value when a steady state is obtained by image formation.
This is because the coefficient of friction of the photosensitive member 1 is affected by other devices provided in the image forming apparatus A, and therefore changes from the value of the coefficient of friction immediately after image formation. However, the value of the friction coefficient becomes a substantially constant value by forming about 1,000 images on A4 size recording paper. Therefore, the friction coefficient referred to here is the friction coefficient when it becomes constant in the steady state.

In the image forming apparatus A of the present invention, the photosensitive member 1 and one or more devices selected from the coating device 21, the charging device 3, the developing device 5, and the cleaning device 7 are integrally supported and detachable. A process cartridge is provided. Further, the image forming apparatus A can clean even toner having a circularity of 0.94 or more by disposing the PCL 20 as a light emitting unit in the main body.
In addition, the photosensitive member 1 and one or more devices selected from the lubricant application device 21, the charging device 3, the developing device 5, and the cleaning device 7 are integrally supported to be detachable from the image forming apparatus A. Further, a process cartridge including a PCL 20 that is a light emitting member for discharging the photosensitive member 1 can be used on the upstream side of the cleaning device 7 with respect to the rotation direction of the photosensitive member 1.

  By providing the PCL 20 in the process cartridge, the residual potential of the photosensitive member is attenuated, and in particular, by reducing the electric field at the white background portion and the edge portion of the image portion, the adhesion force between the toner and the photosensitive member 1 is reduced. Occurrence of cleaning failure can be suppressed. Thus, by applying the lubricant using the potential difference, the potential difference is generated only when the application is required, so that the application can be performed in a timely manner.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a configuration of an image forming unit in which a photoconductor is disposed. Schematic which shows other embodiment of a lubricant coating device. Schematic which shows other embodiment of the lubricant coating device made the same structure as a developing device. The figure which shows the coating amount control on the image carrier by a potential difference with a graph. The figure which shows the lubricant application amount control of the longitudinal direction of an image carrier with a graph. Schematic for demonstrating the measuring method of the friction coefficient of a photoreceptor.

Explanation of symbols

  A image forming apparatus, 1 image carrier (photosensitive member), 2 image forming unit, 3 charging device, 3a charging roller, 3b cleaning roller, 4 latent image forming means (exposure device), 5 developing device, 5a developer carrying member (Developing roller), 6 transfer means (transfer device), 6a intermediate transfer belt, 6e primary transfer roller, 7 cleaning means (cleaning device), 7a cleaning blade, 7b support member, 7c pressure spring, 8 fixing device, 15 Belt cleaning device, 16 secondary transfer roller, 20 light emitting means (PCL), 21 lubricant application device, 21a conveying brush, 21b powdered lubricant, 21c pressure spring, 22 charging device (for lubricant application) , 23 Coating device, 24a Coating blade, 24b Support member, 24c Blade pressure spring

Claims (12)

  The electrostatic latent image formed on the image carrier is developed, and a toner image obtained by development is transferred to transfer paper, and then a lubricant is applied to the image carrier by a lubricant coating unit, and the image carrier is In the cleaning method in which the toner remaining on the surface is removed by a cleaning unit, the lubricant is applied to the image carrier by a potential difference between the potential of the surface of the image carrier and a bias applied to the lubricant application unit. A characteristic cleaning method.   The cleaning method according to claim 1, wherein the application amount of the lubricant is changed by controlling the potential difference.   The cleaning method according to claim 1, wherein the potential difference is changed in a longitudinal direction of the image carrier.   4. The cleaning method according to claim 1, wherein the surface of the image carrier is charged on the upstream side in the rotation direction of the image carrier from a position where the lubricant is applied.   5. The cleaning method according to claim 1, wherein a potential difference between a potential on the surface of the image carrier and a bias applied to the lubricant application unit is controlled according to temperature or humidity. .   An image carrier used in the cleaning method according to claim 1, a lubricant applying unit, and a cleaning unit are provided at least, and can be attached to and detached from the main body of the image forming apparatus. Process cartridge.   An image carrier capable of forming an electrostatic latent image, a lubricant application means for applying a lubricant to the image carrier after the toner image developed from the electrostatic latent image is transferred to transfer paper, and the image carrier In the image forming apparatus having a cleaning unit that removes toner remaining on the surface, the lubricant application unit applies the charged lubricant to a potential of the surface of the image carrier and a bias applied to the lubricant application unit. An image forming apparatus, wherein a lubricant is applied on the image carrier by a potential difference.   The image forming apparatus according to claim 7, further comprising a potential difference control unit that controls the potential difference and changes a coating amount of the lubricant.   9. The image forming apparatus according to claim 7, wherein the potential difference control unit changes the potential difference in a longitudinal direction of the image carrier.   The image forming apparatus according to claim 7, further comprising a charging unit that charges the surface of the image carrier on the upstream side in the rotation direction of the image carrier with respect to the lubricant application unit. .   The image forming apparatus according to claim 7, wherein the potential difference control unit changes the potential difference according to temperature or humidity.   An image forming apparatus comprising the process cartridge according to claim 6.

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