JPH11249383A - Electrifying means, process cartridge and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent endurance boring while obtaining a stable image by appropriately keeping the thickness and the surface roughness of the outermost layer of an electrifying roller using substance including fluororesin. SOLUTION: The electrifying roller 1 is constituted of a shaft type conductive supporting body 2 made of metal or plastic, an urethane foam elastic layer 3 to which conductivity is imparted by dispersing carbon, a resistance layer 4 whose resistance is adjusted by dispersing the carbon in water dispersion acrylic resin and a protection layer 5 made of water dispersion fluororesin. The thickness of the layer 5 is set to >=2.5 μm and <=13 μm and the surface roughness thereof Rz is set to >=1 μm and <=8 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging means for charging by contacting an electrophotographic photosensitive member as an object to be charged, and an image forming apparatus using the electrophotographic method, such as a copying machine or a printer, having the charging means. The present invention relates to an apparatus and a process cartridge having the charging unit detachably mounted on the image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, a corona charger has been used as a charging means for electrophotography. In recent years, a contact charging device has been put to practical use instead. This is intended for low ozone and low power, and among them, a roller charging method using a conductive roller as a charging means is particularly preferable in terms of charging stability and widely used.

In the roller charging system, a conductive elastic roller is pressed against an object to be charged, and a voltage is applied thereto to charge the object by discharging. Specifically, the discharge starting voltage (about 550 when the charging roller is pressed against the OPC photosensitive member as the member to be charged).
V) plus the required photoreceptor surface potential Vd
As a DC charging system that performs charging by applying a voltage, and for the purpose of improving fluctuations in potential due to environmental and endurance fluctuations,
An AC charging method in which charging is performed by applying to a contact charging member a voltage obtained by superposing an AC component having a peak-to-peak voltage that is twice or more the discharge start voltage on a DC voltage corresponding to the required photoconductor surface potential Vd. is there.

However, even in this contact roller charging method, the surface of the charging roller is contaminated by fine powder toner and external additives adhered to the photoreceptor due to the nature of contact with the photoreceptor. Poor charging due to the rise may cause unevenness in density and adhesion (fogging) of toner to a white portion in some cases.

In particular, due to the recent demand for higher image quality in the market, toner particles have become smaller and the ratio of fine powder toner has increased, and accordingly, the degree of contamination of the charging roller has deteriorated. In addition, demands for longer life, colorization, and the like increase the target durability life value of a process cartridge including a charging roller and a photoconductor (this increases the operating time for obtaining one output by colorization). As a result, the amount of deposits increases, and image defects that did not occur with the previous number of durable sheets have become apparent in the latter half of the durable period.

[0006] Concerning the surface contamination of the charging roller, there is a problem in image output by improving the surface release of the charging roller, and in particular, by using a substance containing a fluorine resin having excellent antifouling properties as a material of the outermost layer of the charging roller. It has been found that it is possible to improve to a level without any.

[0007]

However, when a material containing a fluororesin is used for the outermost layer of the charging roller, it is difficult to uniformly disperse a conductive material such as carbon or metal oxide, and partial charging due to resistance unevenness is difficult. In order to prevent defects, it is preferable to form the outermost layer as thin as possible. However, if the outermost layer is formed extremely thin, the toner adheres to the surface of the charging roller and penetrates the outermost layer to form a hole as the durability increases (hereinafter referred to as “durable hole”). ) Is known to occur.

The following two mechanisms can be considered for the cause of the perforation.

1. If the thickness of the outermost layer of the charging roller is insufficient, the strength of the outermost layer of the charging roller is insufficient, and when the toner that has slipped out of the cleaning device adheres to the surface of the charging roller, the pressure contact force between the photosensitive drum and the charging roller is reduced. It is embedded in the charging roller and forms a hole.

[0010] 2. When the toner that has slipped from the cleaning device adheres to the charging roller, a force for embedding the toner in the charging roller is exerted by the pressure contact between the charging roller and the photosensitive drum. Since there is no escape place, the toner bites into the surface of the charging roller.

For the above-mentioned cause, it is possible to eliminate the durable hole by increasing the thickness of the outermost layer of the charging roller and increasing the surface roughness. When the thickness is increased, resistance unevenness easily occurs in the outermost layer of the charging roller as described above, and partial charging failure occurs. Further, when the surface roughness of the charging roller is increased, the charging roller is easily contaminated with toner, so that image defects due to contamination of the charging roller are likely to occur.

Accordingly, an object of the present invention is to provide a charging means capable of obtaining a stable image and preventing durable perforation by appropriately maintaining the thickness and surface roughness of the outermost layer using a substance containing a fluororesin. Another object of the present invention is to provide a process cartridge and an image forming apparatus having the charging unit.

[0013]

The above object is achieved by a charging member, a process cartridge and an image forming apparatus according to the present invention. In summary, the present invention provides a charging unit that contacts an image carrier and applies a voltage to the surface of the image carrier to charge the surface of the image carrier at a constant potential. The surface layer is made of a material containing at least a fluororesin, and has a thickness of 2.5 μm.
Charging means is provided, which has a surface roughness Rz of 1 μm or more and 8 μm or less.

According to another aspect of the present invention, there is provided a charging unit for charging a surface of the image bearing member to a constant potential by applying a voltage to the image bearing member. Wherein the surface layer is made of a substance containing at least an aqueous fluororesin, has a thickness of 2.5 μm or more and 13 μm or less, and has a surface roughness Rz of 1 μm or more and 8 μm or less. Is provided.

According to another aspect of the present invention, at least an image carrier and a charging means for contacting the image carrier and applying a voltage to charge the surface of the image carrier to a constant potential. And a developing unit containing a developer, wherein the charging unit has at least two layers of a base material and a surface layer, The layer is made of a substance containing at least a fluororesin, has a thickness of 2.5 μm to 13 μm, and has a surface roughness Rz of 1 μm to 8 μm.
m or less.

According to another aspect of the present invention, at least an image carrier, and charging means for contacting the image carrier and applying a voltage to charge the surface of the image carrier to a constant potential, A developing unit containing a developer, and in a process cartridge detachably mounted to the image forming apparatus, the charging unit has at least two layers of a base material and a surface layer, and the surface layer is , Composed of a substance containing at least an aqueous fluororesin, having a thickness of 2.5 μm or more and 13 μm or less, and a surface roughness Rz of 1 μm or more and 8 μm or less.
m or less.

According to another aspect of the present invention, at least an image bearing member and a charging means for contacting the image bearing member and applying a voltage to charge the surface of the image bearing member to a constant potential. And an image forming apparatus having a developing unit containing a developer, wherein the charging unit has at least two layers of a substrate and a surface layer, and the surface layer is made of a material containing at least a fluororesin. , Its thickness is 2.5
μm or more and 13 μm or less, and the surface roughness Rz is 1 μm
There is provided an image forming apparatus having a thickness of not less than 8 μm.

Further, according to another aspect of the present invention, there is provided:
Image formation comprising at least an image carrier, a charging unit that contacts the image carrier and applies a voltage to apply a voltage to the surface of the image carrier to a constant potential, and a developing unit that contains a developer. In the apparatus, the charging means has at least two layers of a base material and a surface layer, and the surface layer is made of a material containing at least an aqueous fluororesin, and has a thickness of 2.5 μm or more and 13 μm or less, and , Surface roughness Rz
Is not less than 1 μm and not more than 8 μm.

In the above invention, the charging means preferably has a roller shape. The volume average particle size of the developer is preferably 6 μm or less. At least, the image carrier and the charging means are integrally formed as a process cartridge so as to be detachably mountable to the image forming apparatus main body, and the plurality of developing means are each formed as a process cartridge so as to be detachably mountable to the image forming apparatus main body. preferable. [Detailed description of the invention]

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a charging means, a process cartridge and an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 A first embodiment of the present invention will be described with reference to FIGS.

First, an electrophotographic image forming apparatus to which the present invention is applied will be described with reference to FIG. In FIG. 1, an image forming apparatus includes a photosensitive drum 6 serving as an image carrier,
A charging roller 1 serving as a charging unit for uniformly charging the photosensitive drum 6; an exposure device 8 for forming an electrostatic latent image on the charged photosensitive drum 6; and a developing device for visualizing the electrostatic latent image as a toner image Developing device 9, a transfer device 11 for transferring the toner image on the photosensitive drum 6 to a transfer material 10 such as paper, and a fixing device 1 for fixing the toner image transferred to the transfer material 10
2. After the transfer of the toner image onto the transfer material 10, a cleaning device 13 is provided for scraping off a small amount of toner remaining on the photosensitive drum 6 and providing the same for the next image formation.

The photosensitive drum 6 has an undercoat layer on an aluminum cylinder having a diameter of 30 mm, a charge generation layer on the undercoat layer, and a charge transport layer on the charge generation layer using bisphenol Z type polycarbonate resin as a resin. It has an organic photoreceptor.

The charging roller 1 has a weight of 700 g on one side (total of 1400 g) with respect to the photosensitive drum 6 by a charging roller terminal and a spring (not shown) at both ends in the longitudinal direction.
Heavy) force.

In the present image forming apparatus, a magnetic one-component toner having a particle diameter of 5.8 μm is used.

In the image forming apparatus having the above structure, the surface of the photosensitive drum 6 rotating in the direction of the arrow is uniformly charged by the charging roller 1, and the exposure device 8 forms an electrostatic latent image corresponding to image information. You. The electrostatic latent image is visualized as a toner image by the developing device 9. The toner image is transferred by the transfer device 11 to the transfer material 10 fed to the transfer unit, and is fixed to the transfer material 10 by the fixing device 12.
After the fixing, the transfer material 10 is discharged outside the apparatus. On the other hand, the residual toner and the like are removed from the photosensitive drum 6 after the transfer by the cleaning device 13 and used for the next image formation.

Next, the charging roller 1 serving as the charging means of this embodiment will be described with reference to FIG.

As shown in FIG. 1, the charging roller 1 of this embodiment includes a metal or plastic shaft-shaped conductive support 2 also serving as a power supply electrode, and an elastic layer 3 is provided thereon.
Is provided. In this embodiment, urethane foam in which carbon is dispersed and conductivity is provided is used.

The resistance layer 4 on the elastic layer 3 is a layer provided to give an appropriate resistance to the charging roller 1. As a material of the resistance layer 4, carbon is dispersed in a water-dispersible acrylic resin. It is formed to a thickness of 200 μm by a dipping method using a paint whose resistance is adjusted.

The protective layer 5 on the resistance layer 4 is mainly used to ensure the surface properties of the charging roller 1 and to prevent the material of the resistance layer 4 from oozing and contaminating the photoreceptor surface. It is a layer provided.

As the protective layer 5, a layer obtained by adding a thickener to a water-dispersed fluororesin made of carbon-dispersed tetrafluoroethylene and having a thickness of 3.
It is formed to 5 μm.

As described above, by using a material containing a fluorine resin for the protective layer 5, the releasability of the surface of the charging roller 1 is improved, and the contamination of the charging roller 1 by toner can be effectively prevented. it can.

In particular, by using an aqueous fluororesin, that is, by using an aqueous material, deterioration of the surface properties of the charging roller 1 due to foam expansion due to the use of an organic solvent is prevented. In addition, there are additional advantages such as no cost for managing harmful organic solvents and no environmental pollution.

The surface roughness of the charging roller is JIS10
The point average roughness was 1.0 μm on an Rz scale.

Using this image forming apparatus, a temperature of 15 ° C.
When images were continuously output on 10,000 sheets in an environment with a relative humidity of 10%, no abnormalities were found on the character images and halftone images.

After the endurance test, the charging roller 1 was removed, the toner was wiped off, and the surface of the charging roller 1 was observed. As a result, some hole-like defects having a diameter of about 0.1 mm (hereinafter referred to simply as “holes”) were obtained. ) Was observed, but the image was not particularly affected.

Hereinafter, a comparative example with this embodiment will be described.

COMPARATIVE EXAMPLE 1 In a first comparative example, a material obtained by reducing the viscosity of the material of the protective layer 5 during dipping by reducing the amount of the thickener in the material of the protective layer 5 in the first example was used. used. The charging roller 1 is the same as the first embodiment up to the conductive support 2, the elastic layer 3, and the resistance layer 4, except that the thickness of the protective layer 5 is 2 μm.

The surface roughness of the charging roller 1 was 1.0 μm on the JIS 10-point average roughness scale, similarly to the charging roller 1 of the first embodiment.

As in the case of the first embodiment, the roller is continuously operated in an environment at a temperature of 15 ° C. and a relative humidity of 10%.
When 0000 sheets were passed, there was no particular abnormality with respect to the initial image, and no contamination of the entire surface of the charging roller was caused by the toner even after the sheet was passed. Many black spots were observed. Also, when the surface of the charging roller 1 was observed after the image was displayed,
A large number of "holes" having a diameter of about 0.1 to 0.2 mm were observed. The cause of the black spot is that the charging roller 1
This is because the charging ability was significantly impaired and the charging was insufficient.

COMPARATIVE EXAMPLE 2 In the second comparative example, the material obtained by increasing the viscosity of the material of the protective layer 5 during dipping by increasing the amount of the thickener in the material of the protective layer 5 in the first example was used. used. The charging roller 1 includes a conductive support 2, an elastic layer 3, and a resistance layer 4.
Up to the first embodiment, except that the thickness of the protective layer 5 is 1
4 μm.

The surface roughness of the charging roller 1 was 1.0 μm on the JIS 10-point average roughness Rz scale, similarly to the charging roller 1 of the first embodiment.

This charging roller is applied to an image forming apparatus using an electrophotographic method similar to that of the first embodiment, and a temperature of 15
When an image was formed in an environment at a temperature of 10 ° C. and a relative humidity of 10%, a haze-like image was observed on the halftone from the beginning. This is because the thickness of the protective layer 5 of the charging roller 1 is too large, so that the resistance of the charging roller 1 is increased, and the unevenness of the surface resistance of the charging roller 1 is more conspicuous, causing partial charging unevenness. Because it is.

Further, continuous image output was performed up to 10,000 sheets, but no trouble occurred except for the initial haze.

COMPARATIVE EXAMPLE 3 In the third comparative example, the surface roughness of the protective layer 5 is further reduced by selecting a material having a particularly low conductivity of carbon dispersed in the material of the protective layer 5 in the first example. Charging roller 1 was tried. It is known that the surface roughness of the completed charging roller 1 is reduced by dispersing a large amount of carbon having a low conductivity in the material.

In this comparative example, the charging roller 1 of the first embodiment is
In comparison with the above, a protective layer 5 having a carbon conductivity of about half was used.

The charging roller 1 of this comparative example is the same as that of the first embodiment up to the conductive support 2, the elastic layer 3, and the resistance layer 4, but the surface roughness of the protective layer 5 is JIS 10 points. Roughness R
The difference is 0.4 μm on the z-scale.

With respect to the charging roller 1, as in the first embodiment, 10,000 images were continuously output.
On about 7,000 sheets, black spots of the charging roller cycle occurred on the image. When the surface of the charging roller was observed after the image was formed, many "holes" having a diameter of about 0.1 to 0.2 mm were observed on the surface of the charging roller 1 at locations corresponding to black spots on the image.

This is because the surface roughness of the charging roller 1 is too small, so that when the toner adheres to the surface of the charging roller 1,
This is because, when toner particles enter between the charging roller 1 and the photosensitive drum 6, there is no place for the toner to escape, and the force of pressing the toner against the surface of the charging roller 1 is increased. .

Comparative Example 4 In a fourth comparative example, tin oxide was used instead of carbon as the conductive agent dispersed in the material of the protective layer 5 in the first example. Tin oxide is adjusted to a particle size of about 3 to 4 μm.

The charging roller 1 is the same as that of the first embodiment up to the conductive support 2, the elastic layer 3, and the resistance layer 4. However, the surface roughness of the protective layer 5 is JIS 10 point average roughness Rz scale. Was 8.0 μm.

This charging roller 1 is applied to an image forming apparatus using the same electrophotographic method as the first embodiment,
When an image of 10,000 sheets was continuously output in an environment of 5 ° C. and a relative humidity of 10%, although the initial image was not particularly abnormal,
When about 5,000 sheets of paper were passed, a haze-like image was generated on the halftone.

This is because the surface of the charging roller 1 has a large surface roughness, so that the toner tends to adhere thereto, and the surface of the charging roller 1 is contaminated with the toner. This is because it appeared uneven. However, even after passing 10,000 sheets, the degree of haze was slight, and there was no problem on practical images.

When the surface of the charging roller was observed after the image was formed, no "hole" was found.

Comparative Example 5 In the fifth comparative example, the protective layer 5 of the charging roller 1 of the fourth comparative example was used.
To which the urethane particles for further increasing the surface roughness were added. The urethane particles are adjusted to a particle size of about 5 to 6 μm.

The charging roller 1 is the same as the first embodiment up to the conductive support 2, the elastic layer 3, and the resistance layer 4. However, the surface roughness of the protective layer 5 is JIS 10 point average roughness Rz. 1
The difference is 0.0 μm.

This charging roller 1 is applied to an image forming apparatus using an electrophotographic method similar to that of the first embodiment, and a temperature of 1
When an image was output in an environment of 5 ° C. and a relative humidity of 10%, the initial image was not particularly abnormal, but when about 1000 sheets of paper were passed, a hazy image was generated on halftone.

This is because the surface roughness of the charging roller 1 is large, so that the toner easily adheres, and the surface of the charging roller is contaminated with the toner. Because it appeared.

Further, when the image output was further continued, 5
After passing about 000 sheets, the haze on the halftone became a mottled image, which was a level unusable for use.

When the surface of the charging roller was observed at the time when the image output of 10,000 continuous sheets was completed, no "hole" was found.

The above results are summarized in Table 1 below.

[0062]

[Table 1]

From Table 1, it can be seen that the charging roller 1 has a perforated hole, that the toner is contaminated, and that the charging roller 1 has a protective layer 5.
It can be seen that the condition for satisfying all the charging unevenness due to the large film thickness of the protective layer is as follows: protective layer thickness: 3.5 to 13 μm protective layer surface roughness: Rz 1 to 8 μm.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG.

Process cartridge 1 in this embodiment
Reference numeral 00 denotes a photosensitive drum 6, a charging device 1 for uniformly charging the photosensitive drum 6, a developing device 9 for forming a toner image on an electrostatic latent image, and a photosensitive drum after transferring the toner image to a transfer material 10. The cleaning device 13 for scraping off the remaining toner on the surface 6 and providing it for the next image formation is incorporated in an integral housing, and is configured to be detachable from the image forming apparatus.

As in the first embodiment, the toner in this embodiment is a magnetic one-component toner having a particle size of 5.8 μm.

The process cartridge 100 has the first
A charging roller 1 having the same configuration as that of the example was mounted.

In the present embodiment, the process cartridge 100 is mounted on the image forming apparatus, and is continuously operated in an environment at a temperature of 15 ° C. and a relative humidity of 10% as in the first embodiment.
00 images were output.

No particular problem occurred in the image. In addition, when the surface of the charging roller was observed after image formation, several "holes" having a diameter of about 0.1 mm were found. However, the holes were slight and had no problem in practical use.

Comparative Example 6 As a sixth comparative example, the same charging roller 1 as that of the first comparative example was mounted on the process cartridge of the second example, and a temperature of 15 ° C. and a relative humidity of 10 were set in the same manner as in the second example. When 10,000 sheets were continuously output in an environment of%, when 5000 sheets were passed, black spots having a diameter of about 0.1 to 0.2 mm of the charging roller cycle were generated on the image. Observation on the charging roller 1 shows that the portion corresponding to the black spot is a "hole".
Had become.

Comparative Example 7 As a seventh comparative example, the same charging roller 1 as that of the third comparative example was attached to a process cartridge, and an image was formed in an environment at a temperature of 15 ° C. and a relative humidity of 10%, as in the second embodiment. As a result, black spots having a diameter of about 0.1 to 0.2 mm were generated on the image when 5000 sheets were passed. Observation on the charging roller revealed that a portion corresponding to the black spot was a “hole”.

Embodiment 3 Next, a third embodiment of the present invention will be described with reference to FIG.

The present embodiment is characterized in that an electrophotographic full-color image forming apparatus is used as the image forming apparatus as shown in FIG.

The image forming apparatus according to the present embodiment has
A toner image of each color is sequentially formed based on image data separated into four colors of magenta M, cyan C, and black K, and these are superimposed on an intermediate transfer body and collectively transferred to a transfer material such as paper to obtain a full-color image. is there.

In FIG. 4, the photosensitive drum 6, which is the first image carrier, is driven to rotate at a predetermined peripheral speed (80 mm / s) in the direction of arrow A, and the surface thereof is rotated by the charging roller 1 as charging means. (To about -600 V).

Next, scanning is performed by the exposure means 8 which is ON / OFF controlled in accordance with the image data of the first color (Y), and an electrostatic latent image of the first color is formed (the exposure portion potential is about -100V).

The first-color electrostatic latent image is formed of the first-color Y electrostatic latent image.
The toner is developed and visualized by the first developing means 104a containing toner (polarity). The visualized first toner image is pressed against the photosensitive drum 6 with a predetermined pressing force, and is substantially at the same speed as the peripheral speed of the photosensitive drum 6 (80 mm / s).
An intermediate transfer member as a second image carrier that is driven to rotate in the direction of arrow B with a conductive elastic layer made of NBR rubber or the like on an aluminum cylinder made of urethane resin in which carbon, fluororesin or the like is dispersed on the surface A transfer layer (primary transfer) is formed on the surface of the intermediate transfer member 105 at a nip portion between the surface layer having releasability and an outer diameter of 153 mm.

At this time, a voltage VItr (+100 V) uniquely set in advance and having a polarity opposite to the charging polarity (−) of the toner is applied to the intermediate transfer member 105.

The photosensitive drum 6 is not transferred during the primary transfer.
The toner remaining on the photosensitive drum 6 is scraped off by a cleaning blade 15 which is a cleaning means pressed against the photosensitive drum 6, and is collected in a waste toner container 109.

Then, the above process is repeated for the remaining three colors (M, C,
K) is repeated in the same manner, and each time, a toner image of a different color contained in the second developing unit 104b, the third developing unit 104c, and the fourth developing unit 104d is transferred to the surface of the intermediate transfer member 105. Are successively electrostatically transferred and laminated to form a color image.

This color image has an intermediate transfer member 105 and
The intermediate transfer member 105 is pressed against this at a predetermined timing.
At a nip portion between the transfer device 11 and the transfer device 11, which is rotated at substantially the same peripheral speed as that of the transfer device 11, the transfer material 10 is batch-transferred (secondarily transferred) to the surface of the transfer material 10 conveyed from the paper supply unit 120.

At this time, a voltage Vtr (+1000 V) uniquely set in advance and having a polarity opposite to the charging polarity of the toner is applied to the transfer device 11.

Thereafter, the transfer material 10 is conveyed to the fixing means 12, where the four color toner images are permanently fixed, and discharged from the paper discharge section to the outside of the apparatus, thereby obtaining a desired print image.

The toner remaining on the intermediate transfer member 105 without being transferred at the time of the secondary transfer is a toner charge control member 1
20, after the charging polarity is controlled, the intermediate transfer body 10
The photosensitive drum 6 is returned to the photosensitive drum 6 due to a potential difference between the photosensitive drum 6 and the photosensitive drum 6, scraped off by a cleaning blade 15 provided on the photosensitive drum 6, and collected in a waste toner container 109.

The photosensitive drum 6, the charging roller 1, the cleaning blade 15, and the waste toner container 109 are configured as one process cartridge (photosensitive drum cartridge) so as to be detachable from the image forming apparatus.

Also, yellow Y, magenta M, cyan C
Each of the developing means 104a, 104b, and 104c is detachably supported as a single process cartridge (developing cartridge) by a developing rotary 111 serving as a rotating support, and can be separately replaced depending on the degree of wear.

The developing means 104d for black K is of a fixed type and is exchangeably mounted as a process cartridge (developing cartridge) in the apparatus main body, similarly to the developing means.

The charging roller 1 is constructed in the same manner as in the first embodiment, is pressurized by a bearing (not shown) and a pressing spring, comes into pressure contact with the photosensitive drum 6, and rotates following the rotation of the photosensitive drum 6. .

In the image forming apparatus of this embodiment, the second
In the same manner as in the embodiment, when an image is displayed in an environment of a temperature of 15 ° C. and a relative humidity of 10%, even if a full-color image of 3000 sheets is formed (equivalent to 12,000 sheets passed by a monochrome image forming apparatus), an image is not formed. No particular abnormality occurred.

When the surface of the charging roller was observed after image formation, several "holes" were observed, but this was not a problematic level.

In the above embodiment, the charging roller of the present invention has been described by taking a charging roller as an example. However, the charging member is not limited to this, and various other shapes such as a blade can be applied. The charging means of the present invention is not particularly limited as long as it is a contact charging means.

[0092]

As is apparent from the above description, according to the present invention, the charging means has at least two layers of the substrate and the surface layer, and the surface layer is formed of at least a fluororesin or an aqueous fluorine. It is composed of a substance containing a resin and has a thickness of 2.
5 μm or more and 13 μm or less, and a surface roughness Rz of 1 μm
When the thickness is not less than m and not more than 8 μm, the thickness of the outermost layer of the charging means can be appropriately maintained, there is no resistance unevenness, there is no toner stain, and therefore, it is possible to obtain a stable image and prevent durable holes. And a process cartridge and an image forming apparatus having the charging means.

[Brief description of the drawings]

FIG. 1 is a sectional view of a charging member according to the present invention.

FIG. 2 is a configuration diagram illustrating an image forming apparatus according to a first embodiment.

FIG. 3 is a configuration diagram illustrating a process cartridge according to a second embodiment.

FIG. 4 is a configuration diagram illustrating a full-color image forming apparatus according to a third embodiment.

[Explanation of symbols]

Reference Signs List 1 charging roller (charging means) 2 conductive support (substrate) 3 elastic layer 4 resistance layer 5 protective layer (surface layer) 6 photosensitive drum (image carrier) 9 developing device (developing means) 104a, 104b, 104c 104d developing device 100, 110 process cartridge

Continued on the front page. (72) Inventor Ken Sunahara 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (12)

[Claims] 1. A charging means for contacting an image carrier and applying a voltage to charge the surface of the image carrier to a constant potential, comprising at least two layers of a base material and a surface layer, The surface layer is made of a material containing at least a fluororesin, has a thickness of 2.5 μm or more and 13 μm or less, and has a surface roughness Rz
Is 1 μm or more and 8 μm or less. 2. A charging means for contacting an image carrier and applying a voltage to apply a voltage to the surface of the image carrier to a constant potential, comprising at least two layers of a substrate and a surface layer, Charging means characterized in that the layer is composed of a substance containing at least an aqueous fluororesin, has a thickness of 2.5 μm or more and 13 μm or less, and a surface roughness Rz of 1 μm or more and 8 μm or less. 3. The charging means according to claim 1, wherein said charging means has a roller shape. 4. At least an image carrier, a charging unit that contacts the image carrier, and applies a voltage to apply a voltage to the surface of the image carrier to a constant potential, and a developing unit containing a developer. Wherein the charging means has at least two layers of a base material and a surface layer, and the surface layer is made of a material containing at least a fluororesin. The thickness is 2.5μm or more and 13μm or less,
A process cartridge having a surface roughness Rz of 1 μm or more and 8 μm or less. 5. At least an image carrier, a charging unit that contacts the image carrier, and charges the surface of the image carrier to a constant potential by applying a voltage, and a developing unit containing a developer. In the process cartridge detachably mounted to the image forming apparatus, the charging means has at least two layers of a substrate and a surface layer, the surface layer is made of a material containing at least an aqueous fluororesin A process cartridge having a thickness of 2.5 μm to 13 μm and a surface roughness Rz of 1 μm to 8 μm. 6. The process cartridge according to claim 4, wherein said charging means has a roller shape. 7. The process cartridge according to claim 4, wherein the volume average particle diameter of the developer is 6 μm or less. 8. At least an image carrier, a charging unit that contacts the image carrier, and charges the surface of the image carrier to a constant potential by applying a voltage, and a developing unit containing a developer. In the image forming apparatus having the above, the charging means has at least two layers of a base material and a surface layer, and the surface layer is made of a material containing at least a fluororesin, and has a thickness of 2.5 μm or more and 13 μm or more. Below,
And an image forming apparatus having a surface roughness Rz of 1 μm or more and 8 μm or less. 9. At least an image carrier, a charging unit that contacts the image carrier, and charges the surface of the image carrier to a constant potential by applying a voltage, and a developing unit containing a developer. In the image forming apparatus, the charging unit has at least two layers of a base material and a surface layer, and the surface layer is made of a material containing at least an aqueous fluororesin, and has a thickness of 2.5 μm or more and 13 μm or more. Wherein the surface roughness Rz is 1 μm or more and 8 μm or less. 10. An image forming apparatus according to claim 8, wherein said charging means has a roller shape. 11. The developer has a volume average particle diameter of 6 μm.
The following is characterized in that:
Image forming apparatus. 12. At least the image carrier and the charging means are integrally detachable from the main body of the image forming apparatus as a process cartridge, and a plurality of the developing means are detachably mounted on the main body of the image forming apparatus as process cartridges. The image forming apparatus according to claim 8, wherein the image forming apparatus is free.