JP2006003614A - Image forming apparatus, image forming method of same, and process cartridge for image formation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus preventing deterioration of a surface of a photoreceptor due to short range discharge in the image forming apparatus adapting an electrifying method by the short range discharge. <P>SOLUTION: The image forming apparatus is provided in which a surface of a body to be electrified 1 is continuously and uniformly coated with necessary quantity of protective substance in a discharge range in a specified electrifying condition during repetition of an image forming process. A coating means consists of a pre-coating means and the coating means, the protective substance is coated on the coating means through the pre-coating means and element percentage [%] of the protective substance existing on the surface of the body to be electrified 1 in the discharge range is ≥ 6.23×10<SP>-3</SP>×(Vpp-2×Vth)×f/v[%] with the measurement by XPS. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, an image forming method using the image forming apparatus, and a process cartridge for the image forming apparatus, and more particularly, in an image forming apparatus employing a charging method using contact or non-contact proximity discharge. Deterioration of the photoreceptor surface due to discharge is prevented.

  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 a photoreceptor as an image carrier (hereinafter also referred to as a charged body or a photoreceptor). One of the charging methods used in the charging means is a charging method using proximity discharge. This is a system in which a charging member is brought into contact with the surface of the photoconductor or brought close to it in a non-contact manner to charge the surface of the photoconductor by proximity discharge.

  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 photoconductor because the discharge concentrates in the vicinity of the surface of the photoconductor. Unlike the mechanical rubbing, deterioration of the surface of the photoreceptor due to the proximity discharge occurs even when there is no contact member to the image carrier.

  FIG. 1 shows the surface of a photoconductor when a charging member is placed in close proximity to the surface of the photoconductor in a non-contact state in order to investigate the deterioration state of the photoconductor surface due to proximity discharge, and a charging experiment is performed for about 150 hours continuously. It is the result of having measured the change of film thickness.

  The photoconductor used in the experiment is an organic photoconductor using polycarbonate as the charge transport layer, and all the members in contact with the photoconductor are removed, and a non-contact charging roller to which a voltage in which an AC bias is superimposed on a DC bias is applied. Was used for charging. As a result, it was found that the amount of abrasion of the film on the surface of the photoconductor gradually increased and the film thickness of the photoconductor gradually decreased. The mechanism of film thickness reduction has not been clarified at the moment, but analysis of a photoconductor with a reduced film thickness revealed that carboxylic acids, etc., that are thought to have decomposed the polycarbonate constituting the photoconductor were detected. It was done. As described above, since the substance that is considered to have decomposed the components constituting the photoconductor was detected by the proximity discharge, the following may be considered as a mechanism for reducing the film thickness of the photoconductor.

  2A and 2B, the state of the surface of the photoconductor 1 when the surface of the photoconductor 1 deteriorates due to proximity discharge, and the state where the charging roller 2a is opposed to the surface of the photoconductor with a minute gap are taken as an example. It is explanatory drawing shown.

  When the proximity discharge is performed, the energy of particles (ozone, electrons, excited molecules, ions, plasma, etc.) generated by the discharge is irradiated to the charge transport layer 1a on the surface of the photoreceptor in the discharge region on the surface of the photoreceptor. This energy is resonated and absorbed by the binding energy of the molecules constituting the surface of the photoreceptor, and as shown in FIG. 2A, the charge transport layer 1a has a decrease in molecular weight due to the breakage 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 photoreceptor gradually decreases due to such chemical deterioration of the photoreceptor due to the proximity discharge.

  As described above, in addition to the countermeasure against the film thickness reduction due to mechanical rubbing, which has been conventionally taken, a countermeasure against the film thickness reduction due to the chemical deterioration of the photoreceptor surface caused by the proximity discharge is necessary. I understood that.

  Note that the decrease in the film thickness on the surface of the photoreceptor due to the proximity discharge is considered to occur due to the energy of the particles generated by the discharge, and is therefore considered to occur even when a photoreceptor of another material is used in addition to polycarbonate.

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

In Patent Documents 3 and 4, an image forming apparatus provided with means for applying zinc stearate to the surface of an image carrier as in a specific embodiment of discharge deterioration preventing means in means for solving the problems described below. Is described. However, this means for applying zinc stearate is applied for the purpose of reducing the coefficient of friction of the photoreceptor surface in order to prevent poor cleaning of the photoreceptor surface.
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 technologies have the problem that the characteristics of the photoconductor change due to discharge, specifically, that foreign matters are likely to adhere to the surface of the photoconductor, and that zinc stearate is used to prevent hazards due to discharge. In the above, the present invention is approximated.
JP 2002-207308 A JP 2002-229227 A JP 2002-55580 A JP 2002-244487 A JP 2002-244516 A JP 2002-156877 A

  According to the examination by the present applicant, it has been clarified that the conditions required for preventing the photoreceptor surface deterioration due to the proximity discharge are different from the conditions required for reducing the friction of the photoreceptor surface. . For example, as will be described later, there are conditions in which deterioration due to discharge cannot be prevented even if the surface of the photoconductor can be reduced in friction.

  In the prior art, there has been no deep study on the existence state of the protective substance on the surface of the photoreceptor in the discharge region. However, the applicant's investigation has revealed that the presence of a protective substance necessary to prevent a reduction in film thickness on the surface of the photoreceptor due to discharge depends on charging conditions and the like. In other words, even if a protective substance is present on the surface of the photoconductor in the discharge region without considering the charging conditions, the thickness of the photoconductor is reduced or the protective film is protected more than necessary because the protective material is not properly present. There is a substance. In addition, as disclosed in Patent Document 3, a method for preparing a supply source of a protective substance obtained by solidifying a protective substance into a rod shape and supplying it to a member to be cleaned (photosensitive member) via a brush-shaped roller is a small size of the apparatus. However, it has been found that it is not suitable for a coating state over the entire surface of the member to be cleaned, which is essential for the purpose of the present invention. Accordingly, an object of the present invention is to provide a mechanism for always supplying a necessary amount of a protective member continuously and uniformly to a member to be cleaned when the image forming process is repeated.

  In addition, the image forming apparatus may perform control to change the charging voltage according to environmental conditions, etc., but is necessary when the charging voltage is changed unless the relationship between the charging conditions and the presence state of the protective substance is known. Thus, there is a risk that the amount of a protective substance cannot be determined and deterioration of the photoreceptor cannot be prevented sufficiently.

  Accordingly, 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 the photoreceptor due to proximity discharge in an image forming apparatus employing a charging method by proximity discharge. It is an object of the present invention to provide an image forming apparatus capable of performing the above.

That is, the object is as described in claim 1,
At least a moving object to be charged;
A charging means for charging the member to be charged using a discharge generated by applying a DC voltage containing an AC component to a charging member provided in contact with or close to the member to be charged;
A latent image forming means for forming a latent image on the surface of the object to be charged charged by the charging means;
Developing means for attaching and developing toner on the image portion of the electrostatic latent image formed by the latent image forming means;
A coating means for applying a protective substance for protecting the surface of the body to be charged to the surface of the body to be charged;
In an image forming apparatus having
The coating means comprises a pre-coating means and a coating means, the protective substance is applied to the coating means via the pre-coating means, and the element ratio [%] of the protective substance present on the surface of the object to be charged in the discharge region is , Measured by XPS,
6.23 × 10 ⁻³ × (Vpp−2 × Vth) × f / v [%]
This is achieved by the image forming apparatus characterized by the above.

(Wherein, Vpp is the amplitude [V] of the alternating current component applied to the charging member, f is the frequency [Hz] of the alternating current component applied to the charging member, and Gp is the closest distance between the surface of the charging member and the surface of the object to be charged [ [mu] m], v is the moving speed [mm / sec] of the surface of the member to be charged facing the charging member, Vth is the discharge start voltage, and the value of Vth is the film thickness of the member to be charged d [[mu] m] When the relative dielectric constant of the charged body is εopc and the relative dielectric constant in the space between the charged body and the charging member is εair, 312 + 6.2 × (d / εopc + Gp / εair) + √ (7737.6 × d / ε )
According to the first aspect of the present invention, during the repeated image forming process, side effects are prevented by a specially-applied coating means for the protective substance, and the surface of the charged object, that is, the surface of the photosensitive member is prevented from being deteriorated, so-called white turbidity. It becomes possible to do.

The invention according to claim 2 is the invention according to claim 1, wherein the element ratio [%] of the protective substance present on the surface of the charged body in the discharge region is measured by XPS.
9.10 × 10 ⁻³ × (Vpp−2 × Vth) × f / v [%]
It is the above.

  According to the second aspect of the present invention, it is possible to prevent a decrease in the film thickness of the charged object, that is, the surface of the photosensitive member due to the proximity discharge.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the protective substance is a lamellar crystal powder.

  According to the invention described in claim 3, since the lamellar crystal has a layered structure in which the amphiphilic molecules are self-organized, when the shear force is applied, the lamellar crystal is cleaved between the layers and spreads on the surface of the object to be charged. Therefore, the surface of the photoreceptor can be effectively covered with a small amount of protective material.

The invention according to claim 4 is:
A moving object to be charged;
A charger that charges the object to be charged using a discharge generated by applying a DC voltage containing an AC component to a charging member provided in contact with or close to the object to be charged;
A latent image forming means for forming an electrostatic latent image on the surface of an object to be charged charged by a charger;
Developing means for attaching toner to the image portion of the electrostatic latent image formed by the latent image forming means;
A coating means for applying a protective substance for protecting the surface of the body to be charged to the surface of the body to be charged;
In an image forming apparatus having
The application means comprises a pre-application means and an application means, and the protective substance is applied to the application means via the pre-application means,
The protective substance is a fatty acid metal salt of a lamellar crystal,
In the discharge region, the element ratio [%] of the metal element contained in the fatty acid metal salt present on the surface of the charged body is measured by XPS.
1.52 × 10 ⁻⁴ × (Vpp−2 × Vth) × f / v [%]
This is achieved by the image forming apparatus characterized by the above.

(Wherein, Vpp is the amplitude [V] of the alternating current component applied to the charging member, f is the frequency [Hz] of the alternating current component applied to the charging member, and Gp is the closest distance between the surface of the charging member and the surface of the object to be charged [ [mu] m], v is the moving speed [mm / sec] of the surface of the member to be charged facing the charging member, Vth is the discharge start voltage, and the value of Vth is the film thickness of the member to be charged d [[mu] m] When the relative dielectric constant of the charged body is εopc and the relative dielectric constant in the space between the charged body and the charging member is εair, 312 + 6.2 × (d / εopc + Gp / εair) + √ (7737.6 × d / ε )
According to the fourth aspect of the present invention, side effects are prevented by a specially-applied means for applying a protective substance, and so-called white turbidity is prevented, that is, the surface of a charged body, that is, the surface of the photosensitive body, is prevented. It becomes possible.

The invention according to claim 5 is the invention according to claim 4, wherein the element ratio [%] of the metal element contained in the fatty acid metal salt present on the surface of the member to be charged in the discharge region is measured by XPS.
2.22 × 10 ⁻⁴ × (Vpp−2 × Vth) × f / v [%]
It is characterized by the above.

  According to the fifth aspect of the present invention, it is possible to prevent a decrease in film thickness on the surface of the member to be charged, that is, the surface of the photoreceptor due to the proximity discharge.

  The invention according to claim 6 is the invention according to claim 4 or 5, characterized in that the fatty acid metal salt is zinc stearate.

  According to the invention described in claim 6, since the zinc stearate that is the fatty acid metal salt forms a very thin and uniform coating state of lamellar crystals that are easily atomized on the entire surface of the charged photoreceptor, It is possible to provide an excellent protective effect.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, characterized in that the closest distance between the charging member and the member to be charged is 1 to 100 [μm].

  According to the seventh aspect of the present invention, since the non-contact charging is difficult for the protective substance to adhere to the charging member, the amount of the protective substance present in the discharge region can be stabilized.

  The invention according to claim 8 is the invention according to claim 7, wherein the surface layer of the charging member is a resin material.

  According to the eighth aspect of the invention, the deformation of the charging member is suppressed, and the amount of the protective substance present can be suppressed from being disturbed locally and suddenly.

  According to a ninth aspect of the present invention, in the invention according to any one of the third to sixth aspects, the coating means for applying the protective substance to the surface of the body to be charged and the portion to be charged are in contact with each other. The speed of the coating means is different from the moving speed of the charged body surface.

  According to the ninth aspect of the present invention, the lamellar crystal is cleaved and spreads on the surface of the member to be charged, so that it is possible to efficiently supply the protective substance.

  The invention according to claim 10 is the invention according to any one of claims 1 to 6, wherein the detector detects an environmental condition around the charging member, and the surface of the object to be charged based on the detected environmental condition. And a control unit for controlling the supply amount of the protective substance to the device.

  According to the invention described in claim 10, even when the discharge start voltage changes according to the environmental state such as temperature and humidity, the optimum amount of the protective substance can be determined adaptively.

The invention according to claim 11 is the invention according to any one of claims 1 to 6,
The developing means also serves as a means for removing transfer residual toner remaining on the surface of the charged body,
The charger is a contact charging type charger in which the closest distance Gp between the charging member and the object to be charged is 0 [μm],
Toner for charging the transfer residual toner remaining on the surface of the charged body on the downstream side in the moving direction of the surface of the charged body with respect to the developing unit and on the upstream side of the surface of the charged body in the moving direction with respect to the charger. It has a charging means.

  According to the eleventh aspect of the present invention, by fixing the transfer residual toner on the member to be charged with a mirror image force in a cleanerless system, the protection effect from the discharge by the protective substance can be effectively functioned.

  The invention according to claim 12 is the invention according to any one of claims 1 to 11, wherein the application means in contact with the member to be charged and the pre-application means in contact with the application means comprise an elastic roller, and It has a regulation means which regulates the protective substance on the pre-coating means.

  According to the twelfth aspect of the present invention, when the pre-coating means and the regulating means are provided, the protective material on the coating means is easily uniformed, so that the protective material layer can be more uniformly formed on the object to be charged. .

  The invention according to claim 13 is the invention according to claim 12, wherein the protective substance is in the form of powder or bar.

  According to the thirteenth aspect of the present invention, there is a pre-coating means for once transferring the protective substance, and there is a process in which the protective substance is formed on the object to be charged by the next applying means. Easy to homogenize. As a result, a uniform application state can be formed regardless of the shape of the protective substance, whether it is powder or bar.

  The invention according to claim 14 is the invention according to claim 13, wherein the moving speed of the surface of the member to be charged and the moving speed of the surface of the coating means in contact with the member to be charged are the same or different. To do.

  According to the fourteenth aspect of the present invention, since there is a uniform application state of the protective substance on the application means, a uniform protective substance can be applied to the surface of the object to be charged simply by transferring a part or all of this to the object to be charged. A coating state can be formed. Further, if a speed difference is made between the two, a force (shearing force) for rubbing the protective substance against the nip works, so that fine particles of the protective substance become finer and a uniform application state of the protective substance can be formed on the object to be charged.

  The invention according to claim 15 is the invention according to claim 14, wherein the moving speed of the surface of the pre-coating means and the moving speed of the surface of the applying means in contact with the pre-coating means are the same or different. To do.

According to the fifteenth aspect of the present invention, once the pre-transfer means is coated with a protective substance, when the speed is the same, the protective substance fine particles are finely divided by pressure, and the speed is different. By making the fine particles of the protective substance fine by shearing force, the application state of the protective substance can be densely and uniformly formed on the application means. As a result, a uniform state of the protective substance can be formed on the surface of the charged body simply by transferring the protective substance.

  According to a sixteenth aspect of the present invention, there is provided an image forming apparatus according to any one of the first to fifteenth aspects. Latent image formation, development of the electrostatic latent image with toner, transfer of a toner image visualized by the development to a recording medium, cleaning of transfer residual toner on the surface of the charged body, and on the charged body The required amount of protective substance is continuously applied uniformly on the surface of the object to be charged in the discharge region under predetermined charging conditions while the image forming process including the charge removal of the residual charge is repeated. This can be achieved by an image forming method.

  According to the invention described in claim 16, while the repeated image forming steps are performed, side effects are prevented by a specially applied protective substance applying means, and the charged object due to proximity discharge, that is, the surface of the photoreceptor is degenerated. So-called white turbidity can be prevented, and an image method capable of preventing a decrease in film thickness on the surface of the photoreceptor can be provided.

The invention according to claim 17 is:
A moving object to be charged;
A charger that charges the object to be charged using a discharge generated by applying a voltage containing an AC component to a charging member provided in contact with or close to the object to be charged;
A developing unit that attaches toner to an image portion of an electrostatic latent image formed by discharging the surface of an object to be charged charged by a charger according to image information;
The element ratio [%] of the protective substance present on the surface of the object to be charged in the discharge region is measured by XPS.
6.23 * 10 <-3> * {Vpp-2 * Vth} * f / v [%]
A feeder for supplying a protective substance to the surface of the member to be charged,
This is achieved by a process cartridge integrally configured.

(Wherein, Vpp is the amplitude [V] of the alternating current component applied to the charging member, f is the frequency [Hz] of the alternating current component applied to the charging member, and Gp is the closest distance between the surface of the charging member and the surface of the object to be charged [ [mu] m], v is the moving speed [mm / sec] of the surface of the member to be charged facing the charging member, Vth is the discharge start voltage, and the value of Vth is the film thickness of the member to be charged d [[mu] m] When the relative dielectric constant of the charged body is εopc and the relative dielectric constant in the space between the charged body and the charging member is εair, 312 + 6.2 × (d / εopc + Gp / εair) + √ (7737.6 × d / ε )
According to the seventeenth aspect of the present invention, during the repeated image forming process, side effects are prevented by the specially-applied means for the protective substance, and the surface of the charged object, that is, the surface of the photosensitive member, is prevented from being so-called white turbidity. It is possible to provide a process cartridge that can be used.

The invention according to claim 18 is the invention according to claim 17, wherein the element ratio [%] of the protective substance present on the surface of the member to be charged in the discharge region is measured by XPS.
9.10 × 10 ⁻³ × (Vpp−2 × Vth) × f / v [%]
It is the above.

  According to the eighteenth aspect of the present invention, it is possible to provide a process cartridge that can prevent a decrease in the film thickness of the charged object, that is, the surface of the photoreceptor due to the proximity discharge.

  According to the present invention, in an image forming apparatus that employs a charging method using contact or non-contact proximity discharge, there is an excellent effect that deterioration of the surface of the photoreceptor due to proximity discharge can be prevented. In addition, since an application means that can apply the protective agent thinly and uniformly to the photoreceptor is used, waste and side effects due to excessive application can be suppressed. Further, it has an effect of suppressing the wear of the organic photoreceptor that is often generated when a hard fur brush is used.

  Hereinafter, an image forming apparatus to which the present invention is applied will be described in an embodiment.

[Embodiment 1]
Referring to FIG. 3, an example of an image forming apparatus having a configuration common to each example described later is shown and will be described as an embodiment 1. This image forming apparatus includes a photoreceptor 1 as an image carrier made of an organic photoreceptor.

  In FIG. 3, the photosensitive member 1 is driven to rotate by a driving device (not shown), and the surface thereof is charged to a predetermined polarity by the charging roller 2a of the charging means 2 of the proximity charging method. The charged surface of the photoreceptor 1 is exposed by the exposure means 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 unit 4 to the surface of the photoreceptor 1 to be visualized as a toner image.

  On the other hand, a transfer sheet P as a recording medium is fed toward the photosensitive member 1 from a sheet feeding unit (not shown). On the transfer paper P, the toner image on the photoconductor 1 is transferred onto the transfer paper P by the transfer means 5 disposed opposite to the photoconductor 1. The transfer paper P onto which the toner image has been transferred is separated from the photosensitive member 1 and then conveyed to the fixing unit 6 along the transfer material conveyance path to fix the toner image.

  Transfer residual toner as residual toner remaining on the photosensitive member 1 after the toner image is transferred to the transfer paper is removed from the photosensitive member 1 by the cleaning device 7. Further, the residual charge on the surface of the photosensitive member after the transfer residual toner is removed is removed by the charge eliminating unit 9. In this way, the photoreceptor 1 is used repeatedly.

  The image forming apparatus according to the present exemplary embodiment includes a protective substance applying unit 10. This protective substance applying means 10 is an example in which a powdery protective substance is mounted inside. The protective substance in powder form is supplied to the photosensitive member via the transfer means 11 via the pre-transfer means 12.

  Details will be described later.

  In the image forming apparatus according to the present embodiment, the photosensitive member, the charging member, the developing device, and the cleaning device are integrally configured, and configured as a process cartridge that is detachable from the image forming apparatus main body. Since such a process cartridge is replaced as a unit, it is easy to set the amount of the protective substance contained in the coating apparatus 10 and the initial film thickness of the photoreceptor to appropriate amounts, which is suitable for the present invention. Yes.

  Next, the charging unit 2 used in the image forming apparatus according to the first embodiment will be described. The charging device 2 charges the photoconductor using proximity discharge. As a method of charging the photosensitive member using proximity discharge, a contact charging method in which a rotatable roller-shaped charging member (hereinafter referred to as a charging roller) 2a is placed in contact with the photosensitive member, and the charging roller is connected to the photosensitive member. There is a non-contact charging system that is arranged in a non-contact manner. In the first 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 photoreceptor and does not apply mechanical stress to the photoreceptor. However, when an elastic member is used, the charging nip width is widened, 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 first exemplary embodiment, a non-contact charging method in which the charging roller 2a is disposed so as to face at least an image forming area on the surface of the photoreceptor with a predetermined charging gap 14 is adopted.

  FIG. 4 is an explanatory diagram of the charging device 2 used in the image forming apparatus according to the first embodiment.

  The charging roller 2a includes a shaft portion 21a and a roller portion 21b. The roller portion 21 b can be rotated by the rotation of the shaft portion 21 a, and a portion of the surface of the photoreceptor 1 that faces the image forming region 11 where an image is formed is not in contact with the photoreceptor 1. The length of the charging roller in the longitudinal direction (axial direction) is set slightly longer than the image forming area, and spacers 22 are provided at both ends in the longitudinal direction. These two spacers are brought into contact with the non-image forming regions 18 at both ends of the photosensitive member surface, thereby forming a minute gap 19 between the photosensitive member 1 and the charging roller. The minute gap 19 is configured such that the distance at the closest portion between the charging roller and the photosensitive member 1 can be maintained at 5 to 100 [μm]. A more preferable range of the gap 19 is 30 to 65 [μm], and is set to 50 μm in the apparatus of the first embodiment. Further, the shaft portion 21a is pressed against the photosensitive member side by a pressing spring 15 made of a spring. Thereby, the minute gap 19 can be accurately maintained. Further, the charging roller rotates along with the surface of the photoreceptor via the spacer 22.

  A charging power source 16 is connected to the charging roller 2a. As a result, the surface of the photoconductor is uniformly charged by proximity discharge in a minute gap between the surface of the photoconductor and the surface of the charging roller. In the first embodiment, the applied voltage is an alternating voltage obtained by superimposing an AC voltage that is an AC component on a DC voltage that is a DC component. When an alternating voltage obtained by superimposing an AC voltage on a DC voltage is applied as an application voltage to be applied to the charging roller 2a, influences such as variations in charging potential due to minute gap fluctuations are 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 member is easily deformed, such as a rubber member, it is difficult to maintain the minute gap 19 between the photosensitive member 1 and the central portion of the charging roller 2a depending on image forming conditions. There is a possibility that only the surface of the photoconductor suddenly contacts. Since it is difficult to cope with the disturbance of the protective substance caused by the charging roller 2a being in contact with the surface of the photosensitive member locally or suddenly, a hard member with less deflection is used when the non-contact charging method is used. 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 photosensitive member 1 of the present embodiment is a negatively charged organic photosensitive member, in which a photosensitive layer is 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 10 10 Ω · cm or less, such as metals such as aluminum, nickel, chromium, nichrome, copper, gold, silver, platinum, and metal oxides such as tin oxide and indium oxide. After material is deposited by vapor deposition or sputtering, film or cylindrical plastic, paper coated, or a plate of aluminum, aluminum alloy, nickel, stainless steel, etc. Pipes that have been surface-treated 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-vinyl carbazole, 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.

  Furthermore, it is electrically conductive 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, chlorinated rubber, Teflon (registered trademark) on a suitable cylindrical substrate. Those provided with a conductive layer 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. Known charge generation materials 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 the 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- Vinyl carbazole, polyacrylamide, polyvinyl benzal, polyester, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyphenylene oxide, polyamide, polyvinyl pyridine, cellulose resin, casein, polyvinyl alcohol, polyvinyl pyrrolidone, etc. It is done. 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.

  Examples of the solvent used here include isopropanol, acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethyl cellosolve, ethyl acetate, methyl acetate, dichloromethane, dichloroethane, monochlorobenzene, cyclohexane, toluene, xylene, ligroin and the like. In particular, ketone solvents, ester solvents, and ether solvents are 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 may contain any additive such as a sensitizer, a dispersant, a surfactant, and silicone oil. good.

  As a coating method for the coating solution, a dip coating method, spray coating, beat coating, nozzle coating, spinner coating, ring coating, or the like can be used.

  The 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. Further, if necessary, two or more kinds of plasticizers, leveling agents, antioxidants and the like can be added.

  Charge transport materials include hole transport materials and electron transport materials.

  Examples of the electron transporting material include chloroanil, 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] thiophen-4-one, 1,3,7-tri Examples thereof include electron-accepting substances such as nitrodibenzothiophene-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, pyrazolines Derivatives, divinylbenzene derivatives, hydrazone derivatives, indene derivatives, butadiene derivatives, pyrene derivatives, bisstilbene derivatives, enamine derivatives, etc. Other known materials may be used. 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-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin And thermoplastic or thermosetting resins such as phenol resins and alkyd resins.

  The amount of the charge transport material is appropriately 20 to 300 parts by weight, preferably 40 to 150 parts by weight, based on 100 parts by weight of the binder resin. The thickness of the charge transport layer is preferably 25 μm or less from the viewpoint of resolution and responsiveness. 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 a photoreceptor having a single-layer photosensitive layer. As such a photoreceptor, a photoreceptor in which the above-described charge generating material 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. Of course, the polymer charge transport materials mentioned above can also be used favorably. The amount of the charge generating material with respect to 100 parts by weight of the binder resin is preferably 5 to 40 parts by weight, and the amount of the charge transporting 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 photoreceptor 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, the resin may be a resin having 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. Further, a metal oxide fine powder pigment 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, for the undercoat layer of the present invention, a vacuum thin film made of Al2O3 provided by anodic oxidation, organic substances such as polyparaxylylene (parylene), and inorganic substances such as SiO2, SnO2, TiO2, ITO, CeO2 is prepared. Those provided by the law 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 photosensitive member, which is effective in improving the wear resistance. For example, it is possible to use a photoreceptor whose surface is coated with amorphous silicon in order to improve wear resistance, or an organic photoreceptor 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. it can.

  As described above, the configuration of the photoreceptor 1 that can be used in the present invention is not limited to a specific configuration. A single 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 is applicable to photoreceptors having various layer configurations such as configurations.

  According to the applicant's research, it has been found that when proximity discharge is used as the charging device, the surface of the photoreceptor is deteriorated. It has been found that this deterioration occurs because the surface of the photoreceptor is directly exposed to the proximity discharge, and occurs even when there is no contact member on the surface of the photoreceptor. That is, it has been found that the photoreceptor surface deterioration due to proximity discharge occurs by a mechanism different from mechanical rubbing. Therefore, in the present embodiment, as a feature thereof, discharge deterioration preventing means for preventing the photoreceptor surface deterioration due to the proximity discharge is provided. Details of the specific configuration will be described below.

  Next, a description will be given of experimental results showing that the protective material acts to suppress the deterioration of the image carrier due to discharge. However, a conventional method in which a protective material is applied to the surface of the photoreceptor via a fur brush using a rod-shaped protective material as a supply source is taken as an example.

  FIG. 5A is a schematic configuration diagram of an experimental apparatus for confirming that deterioration of the photoreceptor due to proximity discharge is suppressed by the presence of the protective material 32 on the photoreceptor. FIG. 5B is an explanatory diagram of a state in which the surface of the photosensitive member 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 unit 30 were removed in advance, and the protective substance applying unit 30 was configured to apply the protective substance 32 to the surface area in the axial direction half of the photoconductor 1. . Then, the driving of the charging unit 2 and the protective substance applying unit 30 together with the photosensitive member 1 was continuously performed, and the deterioration state of the photosensitive member surface was examined. The experimental conditions are as follows.
・ Charging conditions:
Vpp (peak-to-peak value of AC voltage) = 2.12 [kV]
f (frequency of AC voltage) = 877.2 [Hz]
DC voltage value = −660 [V]
・ Moving speed of photoconductor surface v = 125 [mm / s]
-Protective substance: Zinc stearate-Linear speed of fur brush 31 = 216 [mm / sec]
As shown in FIG. 5B, the surface of the photoreceptor 1 is coated with zinc stearate as a protective material in the half area A in the longitudinal direction, and the surface of the photoreceptor 1 is exposed as it is in the remaining half area B. It has become. Further, the film abrasion amount of the photosensitive layer was measured as an index of the surface degradation of the photoreceptor 1.

  FIG. 6 is a graph showing the results of performing the experiment 1 continuously for 200 hours.

  In the region B where the protective substance 32 is not present, the film scraping amount increased with the passage of time, and after 200 hours, the film thickness decreased by about 2.5 [μm]. On the other hand, in the region A where the protective substance 32 is present, the decrease in the film thickness was suppressed to 1/8 or less. Further, when the surface of the photoconductor used in the experiment was visually observed after 200 hours, in the region B without the protective material 32, the surface of the photoconductor was discolored and deteriorated in white, whereas the region with the protective material 32 was present. In A, the mirror surface was maintained in the same manner as the new photoreceptor 1.

  From the above experimental results, it has been clarified that the presence of the protective substance 32 suppresses deterioration of the surface of the photoreceptor due to discharge.

  Next, an experiment conducted to clarify the difference from the prior art and to set an appropriate amount of protective substance will be described.

  First, as in Patent Documents 3 and 4, differences from the prior art using zinc stearate for the purpose of reducing the friction coefficient will be described.

  In the present embodiment, zinc stearate is used as the protective substance 32. Zinc stearate was applied to the surface of the photoreceptor for the purpose of reducing the friction coefficient even in conventional image forming apparatuses. However, according to the study of the present applicant, the presence of zinc stearate necessary for obtaining a low friction coefficient action is present. It has been clarified that the state and the presence state of zinc stearate necessary for preventing the deterioration of the surface of the photoreceptor due to discharge are different.

  As a countermeasure against the phenomenon in which the film thickness of the photoreceptor 1 is reduced by the discharge itself, the applicant of the present application has thought that the film thickness reduction can be prevented by applying something on the surface that alleviates the deterioration caused by the discharge. When the coating was repeated on the surface of the photoreceptor using zinc stearate under various conditions, the conditions for preventing the film thickness from being reduced became clear.

  In order to clarify the difference from the prior art, zinc stearate is applied to the surface of the photoreceptor as a lubricant, and it is applied to the surface of the photoreceptor as a protective material 32 for preventing deterioration of the surface of the photoreceptor due to discharge. The difference between and will be described below.

  Table 1 shows the photoconductor surface when the amount of zinc stearate applied to the photoconductor surface per unit area was changed between 0.0002 [mg / mm2] and 0.0016 [mg / mm2]. It is the result of examining the presence or absence of occurrence of deterioration. FIG. 7 is a graph showing changes in the coefficient of friction of the photoreceptor surface with time when zinc stearate is applied with these two application amounts. The measurement of the friction coefficient is based on the Euler belt method.

表１の結果より、ステアリン酸亜鉛を０．０００２[ｍｇ/ｍｍ２]塗布した場合には、感光体表面の膜厚が減少しており表面が劣化していた。ステアリン酸亜鉛を０．００１６[ｍｇ/ｍｍ２]塗布した場合には、感光体表面の膜厚は減少しておらず表面が劣化していなかった。この結果から、塗布量が０．０００２[ｍｇ/ｍｍ２]では、近接放電による感光体表面劣化を防止可能な保護物質５０を形成するには塗布量が不足しており、塗布量が０．００１６[ｍｇ/ｍｍ２]ではそのための塗布量を満たしていると言える。

From the results shown in Table 1, when 0.0002 [mg / mm 2] zinc stearate was applied, the film thickness on the surface of the photoreceptor decreased and the surface deteriorated. When 0.0016 [mg / mm 2] zinc stearate was applied, the film thickness of the photoreceptor surface was not reduced and the surface was not deteriorated. From this result, when the coating amount is 0.0002 [mg / mm 2], the coating amount is insufficient to form the protective material 50 capable of preventing the photoreceptor surface deterioration due to the proximity discharge, and the coating amount is 0.0016. It can be said that [mg / mm2] satisfies the coating amount for that purpose.

  Further, from the results of FIG. 7, m is obtained when zinc stearate is applied by 0.0002 [mg / mm2] and M is applied by 0.0016 [mg / mm2]. After the lapse of time, the coefficient of friction on the surface of the photoreceptor became about 0.1.

  With such a low coefficient of friction, film abrasion on the surface of the photoreceptor due to mechanical wear can be prevented. From the results shown in Table 1 and FIG. 7, a coating amount of 0.0002 [mg / mm2] is sufficient to apply zinc stearate as a lubricant to reduce the coefficient of friction on the surface of the photoreceptor. It can be seen that the coating amount needs to be greater than 0.0016 [mg / mm 2] in order to protect the body surface from deterioration due to proximity discharge. That is, the conditions for reducing the coefficient of friction of the photoconductor and the conditions for protecting the photoconductor surface from deterioration due to proximity discharge are different, and the conditions for protecting from deterioration due to proximity discharge cannot be derived from the prior art. .

  Next, as in Patent Documents 5 and 6, the difference from the prior art with respect to the problem that foreign matters are likely to adhere to the surface of the photoreceptor due to discharge will be described.

  The technology for applying zinc stearate or the like to the surface of the photoconductor to prevent changes in the photoconductor characteristics due to electric discharge has been disclosed in the past, but the conditions for the presence of a protective substance on the surface of the photoconductor have been extensively studied. It was not.

  The applicant's examination has revealed that the conditions for protecting the photoreceptor surface from deterioration due to proximity discharge are closely related to the charging conditions. The experimental results showing this fact will be described.

  Three experiments were conducted using an experimental system composed only of a charging roller and a photoreceptor, and the deterioration state of the surface of the photoreceptor was examined. All experiments were carried out in an experimental system composed only of the photoreceptor 1, the charging roller 2a, and the coating device 30.

  In the first experiment, the peak-to-peak voltage value Vpp of the AC voltage applied to the charging roller is changed to 2.2 [kV], 2.6 [kV], and 3.0 [kV], and the frequency f of the AC voltage is changed. Was fixed at 1350 [Hz], and the DC voltage was -600 [V]. The moving speed v of the photosensitive member surface was 113 [mm / s].

  FIG. 8 shows the results of this experiment plotted with the change in Vpp on the horizontal axis and the decrease in the film thickness of the photoreceptor on the vertical axis.

  From FIG. 8, the decrease in the photoreceptor film thickness is clearly proportional to Vpp.

  Further, when Vpp is about 1.9 [kV], the decrease in film thickness is zero. The applicant considers this point as follows.

  It is known that when an AC voltage is applied, if the voltage applied to the charging member does not exceed a predetermined value, a discharge is started between the charging member surface and the photoreceptor surface. According to the research of the present applicant, in the case of non-contact charging, when the closest distance between the charging member surface and the surface to be charged is Gp [μm], the charging is performed when the voltage applied to the charging member becomes equal to or higher than the following value. Discharge is started between the member surface and the photoreceptor surface. Hereinafter, this value is referred to as a discharge start voltage Vth.

Vth = 312 + 6.2 × (d / εopc + Gp / εair) + √ (7737.6 × d / ε) [V]
Here, the film thickness of the photoreceptor is d [μm], the relative permittivity of the photoreceptor is εopc, and the relative permittivity in the space between the photoreceptor and the charging member is εair.

  When the AC voltage Vpp is equal to or more than twice the above Vth, a bidirectional discharge occurs between the charging member and the photosensitive member.

  In this example, the gap between the charging roller and the photosensitive member was 50 μm, the relative dielectric constant of the photosensitive member was about 3, the film thickness was 30 μm, and the relative dielectric constant in the space between the photosensitive member and the charging member was about 1. Therefore, when applied to the above equation, Vth = 962 [V], and when the voltage applied to the charging member is 962 [V] or higher, discharge is started between the charging member surface and the photoreceptor surface, and Vpp is about 1924. If it exceeds [V], it is considered that discharge by AC voltage is started. The dominant discharge phenomenon is bi-directional discharge caused by the AC voltage. For this reason, it is considered that when the Vpp exceeds about 1.9 [kV], the reduction of the photoreceptor film thickness starts.

  In the second experiment, the frequency f of the AC voltage applied to the charging roller is changed to 500 [Hz], 900 [Hz], 1400 [Hz], 2000 [Hz], and 4000 [Hz], and the AC voltage peak to peak is changed. The peak voltage value Vpp was fixed at 2.2 [kV], and the DC voltage was −600 [V]. The moving speed v of the photosensitive member surface was 104 [mm / s].

  FIG. 9 shows the results of this experiment plotted with the change of f on the horizontal axis and the film thickness reduction amount of the photoreceptor on the vertical axis.

  From FIG. 9, the decrease in the photoreceptor film thickness is clearly proportional to f. As described above, the decrease in the photosensitive member film thickness depends on the charging condition, and is specifically proportional to Vpp and f.

  Therefore, the applicant of the present invention is that the reduction of the photosensitive member film thickness is proportional to Vpp−2 × Vth, proportional to f, and when the moving speed of the photosensitive member is slow, the discharge energy irradiated per unit area is the same even under the same charging condition. Since it is predicted to be large, it was predicted to be inversely proportional to the moving speed v of the photosensitive member surface. As a third experiment, as an experiment for obtaining the amount of protective material necessary for preventing deterioration due to discharge on the surface of the photoconductor, the presence or absence of deterioration of the surface of the photoconductor while changing the amount of Vpp, f, and protective material. I investigated. The results are shown in Table 2.

但しＸ＝{Ｖｐｐ−２×Ｖｔｈ}×ｆ／ｖである。

However, X = {Vpp−2 × Vth} × f / v.

  In this experiment, the amount of the protective substance is represented by the element ratio [%] of zinc stearate. Although it is difficult to measure the amount of a small amount of protective substance present on the surface of the photoconductor, the present applicant has measured the characteristic element (Zn) in the protective substance and required the protective substance on the surface of the photoconductor. We succeeded in obtaining knowledge about. The element ratio [%] of zinc stearate was measured using a Quantum 2000 scanning X-ray electron spectrometer (XPS) manufactured by PHI under the conditions of an X-ray source AlKα and an analysis region of 100 μmφ.

  The measured value (element ratio) of Zn is a value obtained when the surface of the photoconductor is measured after 5 hours have elapsed after applying zinc stearate without applying a voltage to the charging member. That is, an image forming apparatus is used for 5 hours under the same conditions except that an experiment with a voltage applied to the charging member is first conducted to check for the presence or absence of cloudiness and the amount of film thickness reduction, and then no voltage is applied to the charging member. And the amount of zinc present was measured.

  In the photoreceptor 1 used in this embodiment, since zinc is not present in the surface layer (charge transport layer), all measured Zn is derived from zinc stearate which is a protective substance. In that sense, Zn can be said to be a characteristic element representing the amount of the protective substance. Even when a protective material other than zinc stearate is used, knowledge about the amount of the protective material can be obtained if the protective material contains a characteristic element that does not exist in the photoreceptor.

  Next, considering that the molecular formula of zinc stearate is [CH 3 (CH 2) 16 COO] 2 Zn, 36 C, 4 O, and 70 H exist for 1 Zn. Among these, since H is not detected by XPS, the element ratio of the protective substance detected by XPS is 41 times the element ratio of Zn.

When the relationship between X and Zn is plotted from the results in Table 2 to obtain a straight line representing the boundary of the presence or absence of cloudiness, the amount of zinc stearate necessary to prevent deterioration (white cloudiness) of the photosensitive surface due to discharge is the element ratio. 1.52 × 10 −4 × {Vpp-2 × Vth} × f / v [%]
It turns out that it is above. Here, Vpp [V] is the peak-to-peak voltage of the AC voltage applied to the charging member (difference between the maximum value and the minimum value of the AC voltage), f [Hz] is the frequency of the AC voltage applied to the charging member, and v [ mm / s] is the moving speed of the photoreceptor surface. Further, when the relationship between X and Zn is plotted from the results shown in Table 2 to obtain a straight line representing the boundary of whether or not the film thickness is reduced, the amount of zinc stearate is 2.22 × 10 −4 × {Vpp-2 × Vth} × f / v [%]
It can be seen that the film thickness hardly decreases when the above is true.

  The relationship between X and Zn described above is shown in FIG.

When the element ratio of the whole protective substance measured by XPS is calculated based on the zinc element content thus obtained, the element ratio is 6.23 × 10 −3 × {Vpp−2 × Vth} × f / v [ %]
Can prevent deterioration (white turbidity) of the photoreceptor,
9.10 × 10 −3 × {Vpp-2 × Vth} × f / v [%]
From the above, it can be seen that the film thickness hardly decreases.

  The reason why the surface of the photoreceptor cannot be protected from deterioration due to proximity discharge depending on the coating amount of zinc stearate can be considered as follows. When charging the photoreceptor 1 by proximity discharge, the energy of particles (electrons, excited molecules, ions, plasma, etc.) generated by the discharge is irradiated to the photoreceptor surface layer in the discharge region of the photoreceptor surface. This energy resonates and is absorbed by the binding energy of the molecules that make up the surface of the photoconductor, and the charge transport layer undergoes chemical degradation such as a decrease in molecular weight due to breakage of the resin molecular chain and a decrease in the degree of entanglement of the polymer chain. It is thought that it will decrease.

  On the other hand, if a protective substance is present on the surface of the photoreceptor, it is the protective substance that is directly irradiated with the energy of the particles generated by the discharge, so that the photoreceptor itself is free from direct irradiation of the particles generated by the discharge. Therefore, it is considered that the protective substance itself absorbs the energy of the particles generated by the discharge and alleviates chemical deterioration of the surface of the photoreceptor. In the experiment shown in FIG. 4 as well, the surface of the photoreceptor B in the region B where no protective substance is present on the photoreceptor 1 is detected from the analysis of the molecular debris constituting the photoreceptor, whereas the region A where the protective substance is present. However, molecular debris constituting the photoconductor was not detected, and the photoconductor surface under the protective material was not deteriorated. And in this area | region A, the substance which the zinc stearate supplied as a protective substance changed chemically and decomposed | disassembled was detected.

  According to such examination, various substances can be used as the protective substance 32. In the image forming apparatus of the present embodiment, zinc stearate is used as the protective substance 32. However, zinc stearate is an example of the protective substance 32, and other substances such as various fatty acid salts, waxes, silicone oils and the like are used as the protective substance. 32 can also be used.

  Among the fatty acid salts, the fatty acid metal salt is easily a characteristic element in which the metal element is measured by XPS, and is easy to measure in setting conditions such as the coating amount. Therefore, it is suitable for designing an apparatus for supplying an optimal amount of a protective substance to the surface of the photosensitive member according to the charging conditions as in this embodiment.

  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 the 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 for lowering the coefficient of friction, but when viewed from the viewpoint of protecting the photoreceptor surface from electric discharge, the characteristics of lamellar crystals that uniformly cover the photoreceptor surface under shearing force are as follows: Since the surface of the photoreceptor can be effectively covered with a small amount of protective material, it is desirable as a protective material.

  In order to fully protect the surface of the photoreceptor from electric discharge by fully utilizing the properties of the lamellar crystals, the protective material coating device 30 has a linear velocity difference from the surface of the photoreceptor, and the protective material while acting a shearing force. It is desirable to apply.

  In addition, when the object is to protect the surface of the photoreceptor from deterioration due to discharge as in the present invention, it is desirable to provide the protective substance coating device 30 between the cleaning device and the charging device. This is to prevent the protective material from being removed by the cleaning device before reaching the discharge region.

  For example, when the protective material applied on the photoreceptor is zinc stearate, viscosity is generated when the protective material is deteriorated due to proximity discharge. Even when other various protective substances are used, it is generally considered desirable to quickly remove the deteriorated protective substance from the photoreceptor. From such a viewpoint, it is desirable to provide a removing member for removing the deteriorated protective substance 32 from the surface of the photoreceptor. In addition, the deteriorated protective member may be mixed in the developing device in the developing region. Since mixing of such protective substances may cause fluctuations in the toner charge amount, it is desirable to use a two-component magnetic brush development that is resistant to fluctuations.

  Here, the image forming apparatus of the present embodiment includes a temperature / humidity detector for detecting the environment around the charging roller. Further, the image forming apparatus according to the present embodiment includes a first table that associates the rotation speed of the fur brush with the amount of the protective substance supplied to the surface of the photoreceptor, and a temperature / humidity detector in a controller (not shown). According to the charging condition, the second table that matches the detected environment around the charging roller and the charging condition, the application control unit that controls the rotation speed of the fur brush, the charging control unit that controls the charging condition, A computer for calculating the amount of the protective member required is included.

  More specifically, the first table has a table in which the rotation speed of the fur brush is associated with the Zn element ratio obtained as a result of the measurement by XPS. Also, the second table shows the temperature and humidity values and the Vpp value necessary for the discharge in order to reliably generate an AC voltage discharge even when the discharge start voltage changes due to changes in the environment around the charging roller. It is a corresponding table.

  Further, in order to calculate the amount of the protective member required according to the charging condition, the computer calculates 1.52 × 10 −4 × {Vpp−2 × Vth} × f / v [%] from the charging condition, or 2. The element ratio of zinc stearate required is calculated according to the formula of 22 × 10 −4 × {Vpp−2 × Vth} × f / v [%].

  In such a configuration, when an image formation start command is input, the image forming apparatus of the present embodiment first detects the temperature and humidity (environmental conditions) by the temperature / humidity detector, and then detects the second table from the detected temperature and humidity. To obtain the charging condition (Vpp value), calculate the necessary Zn element ratio using a computer based on the charging condition, and calculate the rotation speed of the fur brush from the first table based on the calculated Zn element ratio. Ask. In accordance with the charging condition (Vpp value) thus obtained, the application control unit rotates the fur brush at an optimum rotation speed, and the charging control unit starts charging while controlling the voltage applied to the charging member.

  By such control, even when the charging condition changes according to the environment, it is possible to prevent the photoconductor from being deteriorated by supplying an optimal protective substance to the photoconductor surface.

  When the element ratio of zinc stearate required according to the formula of 1.52 × 10 −4 × {Vpp−2 × Vth} × f / v [%] is calculated, the film thickness of the photoreceptor decreases. It is necessary to calculate Vth in consideration of the fact. Therefore, the controller further has storage means for storing the accumulated discharge time and a third table for deriving the film thickness of the photoreceptor from the accumulated discharge time, and the photoreceptor film corresponding to the accumulated discharge time by the third table. The thickness is derived and Vth is calculated.

[Embodiment 2]
Note that the present invention is not applied only to the image forming apparatus as shown in FIG. 3, but can be used in general for an apparatus for charging the surface of an object to be charged using discharge.

  As an example, the present invention can also be applied to a cleanerless image forming apparatus in which the dedicated cleaning device 7 is removed from the image forming apparatus of FIG. In this cleanerless image forming apparatus, the charging roller 2a is made of a rubber material, and is a contact charging roller (Gp = 0 [μm]) that is brought into contact with the photosensitive member 1.

In such an image forming apparatus, a large amount of transfer residual toner exists on the photosensitive member when the protective material is applied by the coating device 30, and therefore, a protective substance is applied to the surface of the photosensitive member where the transfer residual toner exists. I can't. However, in order to protect the surface of the photoreceptor from electric discharge, it is sufficient that some substance exists on the surface of the photoreceptor. Therefore, even if toner exists on the surface of the photoreceptor instead of the protective substance, the effect of the present invention can be exhibited. That is, the element ratio [%] of zinc stearate is 1.52 × 10 −4 × {Vpp−2 × Vth} × f / v [%] without considering the influence of the residual toner.
If it is above, deterioration (white turbidity) of the photoreceptor can be prevented,
2.22 × 10 −4 × {Vpp−2 × Vth} × f / v [%]
If it is set as the above, the film thickness reduction of a photoreceptor can be prevented.

  However, if there is a transfer residual toner, the coating device 30 or the contact charging roller and the photosensitive member have a speed difference (an intentional speed difference or an unintentional speed difference caused by eccentricity of the photosensitive member). When the toner comes in contact, the untransferred toner may move. When the toner moves, the protective material 32 and the toner do not exist in the area where the toner has existed until then, and the discharge is performed when the conditions defined in the present invention are not satisfied due to the increase of such areas. Deterioration due to will worsen. Therefore, in this embodiment, a negative voltage is applied to the coating apparatus 30. For example, when a voltage of about −1000 {V} is applied to the coating device 30, the toner on the photoconductor is strongly negatively charged and the adhesion force (mirror image force) to the photoconductor is increased. This makes it difficult for the toner position to move even in the contact charging method, and it is easy to protect the surface of the photoreceptor from electric discharge.

[Embodiment 3]
As shown in FIG. 3, the image forming apparatus according to the present embodiment is provided with a protective substance applying unit 10 for supplying a powdery protective substance 14 to the surface of the photoreceptor. This protective substance applying means 10 comprises a pre-applying means 12 as an applying member, an applying means 11 and a restricting means 13, and a powdery protective substance in the protective substance applying means 10 is passed through two applying means. Apply a powdery protective substance to the photoreceptor (once a uniform application state of the protective substance is formed by the pre-coating means, and at least a part of it is moved to the applying means. There is something to do.

  That is, since the powdery protective substance may have a large particle size distribution or may be agglomerated, another application may be applied to these powdery protective substances once applied on the pre-coating means. A shearing force is applied by the means 11, and the fine particles are more uniformly pulverized and applied to the photoreceptor. At this time, the powder regulating means 13 prevents the coating amount from becoming sparse in the length direction of the pre-coating means 12 and also has a role of scraping off excess powdery protective substance.

  As described above, a typical example of the surface protective material of the present invention is a fine lamella crystal. This material has a layered structure called a lamellar layered layered structure. . Specific compounds include zinc stearate.

  When a shearing force is applied to the crystal, the crystal tends to break along the interlayer. Therefore, it is known to have a lubricating effect against sliding friction. It is also known that extremely finely divided crystals have the effect of concealing surface irregularities. In addition, it is also known that the zinc stearate crystals are highly transparent, which is advantageous for the present invention.

  That is, for example, if the surface roughness of the photoreceptor is expressed by peaks and valleys, the lubrication effect is that, if there is zinc stearate at least at the peaks, the zinc stearate is present between the contacting member surfaces. The effect is manifested. On the other hand, with regard to the protective effect of the surface, the desired effect will be realized only when there is zinc stearate in both the mountain and the valley. This difference is important. Furthermore, this difference becomes clearer when the surface roughness of the photoreceptor increases with long-term use. The means of the present invention for supplying an appropriate amount of zinc stearate to both the enlarged peaks and valleys at the same time becomes essential.

  The present invention is characterized mainly by the latter effect on concavity and convexity by supplying zinc stearate fine powder. Since the surface is effectively concealed by forming a very thin and uniform coating state (may be called a coating film) of lamellar crystals that are easily pulverized on the entire surface of the charged photoreceptor, the object of the present invention On the other hand, an excellent protective effect appears.

  In the case of commercially available zinc stearate, it is known that there is a particle size distribution as described above. In general, the particle size is several to several tens of μm, and it is said that the properties, particle size, and shape change depending on the production method, purity of raw materials, and thermal history. If the coating means 10 of this invention is used, there also exists an effect that it can be used without extra processing.

  In the present invention, this protective material is applied thinly and uniformly on the surface of the photoreceptor, but it is a preferred embodiment to use a powdery protective material. By combining the pre-coating means and the subsequent coating means, it is possible to supply the protective material to the entire surface of the photoreceptor in a minimum and uniform manner even for long-term use. Even if it is in the shape of a solid bar, it can be applied to the surface of the image carrier, but the conventional method is exclusively for the purpose of the above-mentioned lubrication action, so there are excessive application locations in some places than necessary. On the contrary, there are few or there are irregularities on the surface, and the protective material is not supplied to the valley part, but this was sufficient. However, since the object of the present invention was extremely insufficient, various devices were applied to the coating means.

  The pre-coating means 12 is usually preferably an elastic body such as rubber. Hard materials such as plastic and metal may be used. It may be a rod-like body in which fibers are implanted in the core like a fur brush. However, when a fur brush is used as the pre-coating means 12, the main role is to supply a protective substance to the transferring means 11, and the shearing force is applied between the transferring means 11 and the photosensitive member.

  The applying means 11 usually uses an elastic body such as a roller-like rubber. A hard material such as plastic can be used, but an elastic material such as a nip portion in contact with the photosensitive member is preferable. There should be an appropriate amount of bite. An elastic body that is capable of supplying a small amount of a powdery protective substance in contact with the photoreceptor, corresponding to fine irregularities on the surface, or even when there is slight undulation is preferable.

  The material used for the coating means 11 is preferably urethane rubber because of durability. As described later, when a voltage is applied for use, a conductive control material such as an ion conductive material may be contained.

  The application means 11 is a material having an appropriate elastic deformation so that a protective substance can be applied to a valley formed by these peaks even when there are irregularities due to the surface shape of the photoreceptor or when there is a slight undulation. Is preferred. The hardness is 40 ° to 90 ° (Asker C hardness meter, load 1 kg).

  Moreover, it is preferable that the application means 11 operates to rub a powdery protective substance. Therefore, it is preferable that the surface of the coating means 11 has an appropriate surface roughness. The surface roughness is 5 μm or less, usually 0.01 μm to 4 μm, in terms of Rz. Preferably, it is 0.1-3 micrometers. When Rz is 5 μm or more, the photoreceptor is scratched. When Rz is 0.01 μm or less, it is difficult to apply a protective substance.

  Furthermore, there may be a groove-like structure on the surface of the coating means 11. The depth of the groove is 0.01 to 1 mm, and the width is 0.01 to 1 mm. For example, when a spiral periodic groove having a depth of 0.5 mm and a width of 0.5 mm is provided, depending on the material of the coating unit 11, when the coating unit 11 is in contact with the surface of the photosensitive member, the spiral is caused by the pressing force. This is preferable because the structure is elastically deformed and has an effect of supplying the protective substance held in the groove at the same time by rubbing the surface or removing excess protective substance. Further, for example, an elastic body having a foam structure may be used. In a structure in which individual bubbles appear on the surface, a protective substance is retained in the bubbles, which is convenient.

  These surface structures can also be applied to pre-coating means.

  Further, the coating means 11 may have a bite on the photoreceptor. The amount of biting differs depending on the material of the coating means 11 and the photosensitive member, but if there is an appropriate amount of biting, the surface protective substance can be effectively rubbed. The amount of biting is 1 mm or less, preferably 0.1 to 0.5 mm. In short, it is sufficient that the elastic body is deformed or has an operation of rubbing the protective substance in the returning operation.

  And about the operation | movement which rubs a surface protection substance, there may be a speed difference in the movement of the application means 11, the pre-application means 12, and the surface of a photoreceptor. The surface protective substance can be rubbed more effectively than when there is no speed difference. The speed of the surface of the coating means 11 is 0.1 to 10 times the photosensitive member linear velocity. The speed of the surface of the coating unit 12 is 0.1 to 10 times that of the surface of the coating unit 11. However, when the amount of wear of the photoconductor is large, it is preferable to carry around with no speed difference. There is almost no difference in speed when traveling around.

  In FIG. 11, the roller of the pre-coating means 12 and the roller of the coating means 11 rotate in opposite directions and have the same roller diameter, and the rotational speed of the pre-coating means 12 is increased, so that the linear velocity of both rollers at the nip is different. The case where is attached is shown. The powder of the protective substance mainly receives pressure from both rollers, and at the same time, the action of rubbing increases, and the effect of applying a small amount of finely pulverized protective substance increases. As a result, it is considered that the fine powder is supplied to the surface of the photoreceptor, and at the same time, the effect of forming a thin coating state in a layer shape is increased, which is preferable. Further, if the linear velocity of the coating means 11 and the photosensitive member is made different, the operation of rubbing the protective substance can be performed, and a small amount of protective substance can be effectively transferred to the surface of the photosensitive member.

  FIG. 12 shows a case where the roller of the pre-coating unit 12 and the roller of the coating unit 11 rotate in the same direction and have the same roller diameter, thereby making a difference in linear velocity at the nip. The powder of the protective substance mainly receives pressure from both rollers, and at the same time, the action of rubbing increases, and the effect of applying a small amount of finely pulverized protective substance increases. As a result, it is considered that a finer powder is supplied to the surface of the photoreceptor, and at the same time, the effect of forming and transferring the thin coating state in layers is increased. This is also preferable. Further, when the moving direction of the surface of the coating means 11 and the surface of the photoconductor is rotated in the same direction and a speed difference is made, an operation of rubbing the protective material can be performed and a small amount of the protective material can be effectively transferred to the surface of the photoconductor.

  Further, in FIG. 13, when the roller of the pre-coating means 12 and the roller of the applying means 11 rotate in the opposite directions and there is no speed difference between the nips of the two, the protective substance powder receives pressure mainly from both rollers to protect it. The effect of finely pulverizing the substance is increased. As a result, a finer powder is preferably supplied to the surface of the photoreceptor. When the coating unit 11 and the surface of the photosensitive member are rotated in the same direction, even when the rotation speed of the coating unit is small, the speed difference can be increased and the operation of rubbing the protective substance becomes effective.

  As illustrated, it is preferable to create a speed difference so that the surface protective material is evenly rubbed against the surface of the photoreceptor. The lamellar crystal that can be used in the present invention can be micronized to prevent excessive adhesion.

  In the combination of the application means 11 and the pre-application means 12, both are preferably elastic bodies such as rubber. Further, although the transfer means 11 is an elastic body such as rubber and the pre-transfer means 12 can be a combination of fur brushes, it is difficult to uniformly and uniformly apply the protective substance as compared with the roller. Further, the application means 11 can be a fur brush, but if the brush fibers are not hard, the durability is insufficient, and if it is hard, the abrasion of the photoreceptor is often promoted, which is disadvantageous.

  Examples of the present invention are shown below, but the present invention is not limited thereto.

  A coating means having the configuration shown in FIG. 11 and having the following conditions was prepared, and the photoreceptor, charging means, and coating means shown in FIG. However, X = 8000. The results are shown in Tables 3 and 4 and FIG.

1. Roller-shaped coating means / urethane rubber roller (outer diameter 20 mm, surface roughness 3 μm or less, Asker C hardness 70 (1 kg load))
・ Freight / cylindricity: 0.05 / 0.06
・ Depression, swelling: 4 μm or less ・ Linear speed ratio (to photoconductor): 1.5
・ Rotation speed: 90rpm (Rotate in the same direction as the photoconductor)
-Amount of biting into the photoconductor: 0.3 mm
2. Roller-shaped pre-coating means / Polyurethane polyurethane roller (outer diameter 20 mm, surface roughness 3 μm or less, Asker FP hardness 70)
-Number of meshes: 60 pieces / inch (foam diameter of about 200 μm)
-Linear speed ratio (vs. coating means): 1.5
・ Rotation speed: 100 rpm (rotates in the opposite direction to the coating means)
-Amount of biting into the application means: 1.0 mm
Further, a regulating means urethane rubber plate was provided in the pre-coating means. When the amount of regulation was applied to the tip of the tail in the trailing direction, a large lump of zinc stearate particles could be regulated. Commercially available zinc stearate (volume average particle size 2.2 μm) was supplied to the coating means. The coating thickness on the pre-coating means was about 0.2 mg / cm ² .

In a conventional image forming apparatus, a graph showing changes in film thickness on the surface of a photoconductor when only a charging member is placed in close proximity to the surface of the photoconductor and charging is performed for about 150 hours continuously. is there. In the conventional image forming apparatus, it is a diagram illustrating a state of the photoreceptor surface when the photoreceptor surface deteriorates due to proximity discharge. 1 is a schematic diagram illustrating an example of an image forming apparatus of the present invention. 1 is a conceptual diagram illustrating a charging device in an image forming apparatus of the present invention. (A) is a schematic diagram of an experimental apparatus for confirming suppression of photoreceptor deterioration due to proximity discharge by making a protective substance present on the photoreceptor in the image forming apparatus of the present invention, and (b) It is a figure which shows the state which divided the photoreceptor surface of the image forming apparatus of invention into the protection substance presence part and the non-existence part. It is a figure which shows the graph of the result of having performed charging conditions continuously for 200 hours, in order to test the deterioration state of the photoreceptor surface of the image forming apparatus of this invention. It is a figure which shows the graph of the friction coefficient of the photoreceptor surface after the time progress by discharge by the difference in the coating amount of the zinc stearate with respect to the photoreceptor surface of the image forming apparatus of this invention. FIG. 6 is a graph showing the relationship between the amount of decrease in the thickness of the photoconductor and the voltage applied to the charging roller in order to test the deterioration state of the surface of the photoconductor of the image forming apparatus of the present invention. FIG. 6 is a graph showing a relationship between a decrease in film thickness of a photoconductor and a frequency of a voltage applied to a charging roller in order to test a deterioration state of the surface of the photoconductor of the image forming apparatus of the present invention. FIG. 3 is a diagram showing a graph of an element ratio of zinc stearate necessary for preventing deterioration of the surface of the photoreceptor due to electric discharge in the image forming apparatus of the present invention. FIG. 2 is a diagram illustrating a method in which a protective material is applied to the surface of a photoconductor when a roller of a pre-coating unit and a roller of a coating unit rotate in opposite directions in the image forming apparatus of the present invention and a speed difference is created between the two rollers. FIG. 2 shows a view in which a protective substance is applied to the surface of a photoreceptor when a roller of a pre-coating unit and a roller of a coating unit rotate in the same direction in the image forming apparatus of the present invention, and a speed difference is created between the two nips. FIG. 2 is a diagram illustrating a case in which a protective material is applied to the surface of a photoreceptor when a roller of a pre-coating unit and a roller of a coating unit rotate in opposite directions in the image forming apparatus of the present invention and there is no speed difference between the nips of the two. In the Example of this invention, it is a figure which shows the graph of the relationship between the film thickness change of a photoreceptor, and the abundance of zinc stearate on the surface of a photoreceptor.

Explanation of symbols

1 Charged body (photoconductor)
DESCRIPTION OF SYMBOLS 2 Charging means 2a Charging roller 3 Exposure means 4 Developing means 5 Transfer means 6 Fixing means 7 Cleaning 8 Cleaning blade 9 Gradation means 10 Protective substance application means 11 Application means 12 Pre-application means 13 Regulation means 14 Powdery protection means 15 Pressurization Spring 16 Power supply 17 Image forming area 18 Non-image forming area 19 Minute gap 21a Shaft portion 21b Roller portion 22 Spacer 30 Protective substance application means 31 Fur brush 32 Protective substance 50 Photoreceptor surface

Claims (18)

At least a moving object to be charged;
A charging means for charging the member to be charged using a discharge generated by applying a DC voltage containing an AC component to a charging member provided in contact with or close to the member to be charged;
A latent image forming means for forming a latent image on the surface of the object to be charged charged by the charging means;
Developing means for attaching and developing toner on the image portion of the electrostatic latent image formed by the latent image forming means;
A coating means for applying a protective substance for protecting the surface of the body to be charged to the surface of the body to be charged;
In an image forming apparatus having
The coating means comprises a pre-coating means and a coating means, the protective substance is applied to the coating means via the pre-coating means, and the element ratio [%] of the protective substance present on the surface of the object to be charged in the discharge region is , Measured by XPS,
6.23 × 10 ⁻³ × (Vpp−2 × Vth) × f / v [%]
An image forming apparatus characterized by the above.
(Wherein, Vpp is the amplitude [V] of the alternating current component applied to the charging member, f is the frequency [Hz] of the alternating current component applied to the charging member, and Gp is the closest distance between the surface of the charging member and the surface of the object to be charged [ [mu] m], v is the moving speed [mm / sec] of the surface of the member to be charged facing the charging member, Vth is the discharge start voltage, and the value of Vth is the film thickness of the member to be charged d [[mu] m] When the relative dielectric constant of the charged body is εopc and the relative dielectric constant in the space between the charged body and the charging member is εair, 312 + 6.2 × (d / εopc + Gp / εair) + √ (7737.6 × d / ε ) The element ratio [%] of the protective substance present on the surface of the charged body in the discharge region is measured by XPS.
9.10 × 10 ⁻³ × (Vpp−2 × Vth) × f / v [%]
The image forming apparatus according to claim 1, wherein:   The image forming apparatus according to claim 1, wherein the protective substance is a lamellar crystal powder. A moving object to be charged;
A charger that charges the object to be charged using a discharge generated by applying a DC voltage containing an AC component to a charging member provided in contact with or close to the object to be charged;
A latent image forming means for forming an electrostatic latent image on the surface of an object to be charged charged by a charger;
Developing means for attaching toner to the image portion of the electrostatic latent image formed by the latent image forming means;
A coating means for applying a protective substance for protecting the surface of the body to be charged to the surface of the body to be charged;
In an image forming apparatus having
The application means comprises a pre-application means and an application means, and the protective substance is applied to the application means via the pre-application means,
The protective substance is a fatty acid metal salt of a lamellar crystal,
In the discharge region, the element ratio [%] of the metal element contained in the fatty acid metal salt present on the surface of the charged body is measured by XPS.
1.52 × 10 ⁻⁴ × (Vpp−2 × Vth) × f / v [%]
An image forming apparatus characterized by the above.
(Wherein, Vpp is the amplitude [V] of the alternating current component applied to the charging member, f is the frequency [Hz] of the alternating current component applied to the charging member, and Gp is the closest distance between the surface of the charging member and the surface of the object to be charged [ [mu] m], v is the moving speed [mm / sec] of the surface of the member to be charged facing the charging member, Vth is the discharge start voltage, and the value of Vth is the film thickness of the member to be charged d [[mu] m] When the relative dielectric constant of the charged body is εopc and the relative dielectric constant in the space between the charged body and the charging member is εair, 312 + 6.2 × (d / εopc + Gp / εair) + √ (7737.6 × d / ε ) In the discharge region, the element ratio [%] of the metal element contained in the fatty acid metal salt present on the surface of the member to be charged is measured by XPS.
2.22 × 10 ⁻⁴ × (Vpp−2 × Vth) × f / v [%]
The image forming apparatus according to claim 4, which is as described above.   The image forming apparatus according to claim 4, wherein the fatty acid metal salt is zinc stearate.   The image forming apparatus according to claim 1, wherein the closest distance between the charging member and the member to be charged is 1 to 100 [μm].   The image forming apparatus according to claim 7, wherein a surface layer of the charging member is a resin material.   The moving speed of the surface of the charged body is different from the moving speed of the surface of the charged body, wherein the speed of the coating means at a portion where the coating means for applying the protective substance on the surface of the charged body and the charged body is in contact with each other is different. The image forming apparatus according to any one of 3 to 6.   2. The apparatus according to claim 1, further comprising: a detector that detects an environmental condition around the charging member; and a control unit that controls a supply amount of a protective substance to the surface of the object to be charged based on the detected environmental condition. 7. The image forming apparatus according to any one of items 1 to 6. The developing means also serves as a means for removing transfer residual toner remaining on the surface of the charged body,
The charger is a contact charging type charger in which the closest distance Gp between the charging member and the object to be charged is 0 [μm],
Toner for charging the transfer residual toner remaining on the surface of the charged body on the downstream side in the moving direction of the surface of the charged body with respect to the developing unit and on the upstream side of the surface of the charged body in the moving direction with respect to the charger. The image forming apparatus according to claim 1, further comprising a charging unit.   The coating means in contact with the member to be charged and the pre-coating means in contact with the coating means are made of an elastic roller, and further have regulation means for regulating a protective substance on the pre-coating means. 11. The image forming apparatus according to 11.   The image forming apparatus according to claim 12, wherein the protective substance is powdery or bar-shaped.   14. The image forming apparatus according to claim 13, wherein the moving speed of the surface of the member to be charged is the same as or different from the moving speed of the surface of the coating means in contact with the member to be charged.   15. The image forming apparatus according to claim 14, wherein the moving speed of the surface of the pre-coating means and the moving speed of the surface of the applying means in contact with the pre-coating means are the same or different.   The image forming apparatus according to claim 1, wherein at least the surface of a charged body is charged by a proximity charging method, the electrostatic latent image is formed by image exposure on the surface of the charged body, the electrostatic latent An image comprising development of an image with toner, transfer of a toner image visualized by the development to a recording medium, cleaning of transfer residual toner on the surface of the charged body, and charge removal of residual charge on the charged body An image forming method, wherein a required amount of a protective substance is continuously and uniformly applied to a surface of a member to be charged under a predetermined charging condition while a forming process is repeated. A moving object to be charged;
A charger that charges the object to be charged using a discharge generated by applying a voltage containing an AC component to a charging member provided in contact with or close to the object to be charged;
A developing unit that attaches toner to an image portion of an electrostatic latent image formed by discharging the surface of an object to be charged charged by a charger according to image information;
The element ratio [%] of the protective substance present on the surface of the charged body in the discharge region is measured by XPS.
6.23 * 10 <-3> * {Vpp-2 * Vth} * f / v [%]
A feeder for supplying a protective substance to the surface of the member to be charged,
A process cartridge that is constructed as a unit.
(Wherein, Vpp is the amplitude [V] of the alternating current component applied to the charging member, f is the frequency [Hz] of the alternating current component applied to the charging member, and Gp is the closest distance between the surface of the charging member and the surface of the object to be charged [ [mu] m], v is the moving speed [mm / sec] of the surface of the member to be charged facing the charging member, Vth is the discharge start voltage, and the value of Vth is the film thickness of the member to be charged d [[mu] m] When the relative dielectric constant of the charged body is εopc and the relative dielectric constant in the space between the charged body and the charging member is εair, 312 + 6.2 × (d / εopc + Gp / εair) + √ (7737.6 × d / ε ) The element ratio [%] of the protective substance present on the surface of the charged body in the discharge region is measured by XPS.
9.10 × 10 ⁻³ × (Vpp−2 × Vth) × f / v [%]
The process cartridge according to claim 17, which is as described above.

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