JP2004341480A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent chemical deterioration of the surface of a photoreceptor caused by proximity electric discharge by forming a protective layer on the surface of an image carrying body in an image forming apparatus which uses an electrification system by proximity electric discharge. <P>SOLUTION: The image forming apparatus is equipped with a protecting agent applying means 30 as a protective agent supply means to supply a protecting agent 32 to the surface of a photoreceptor 1 so as to form a protective layer as a means to prevent deterioration by electric discharge . The protecting agent applying apparatus includes a fur brush 31 as a coating member, the protecting agent, and a pressurizing spring 33 to press the protecting agent in the direction to the fur brush. A protective layer comprising zinc stearate is formed on the surface of the photoreceptor by the protecting agent applying apparatus, and this protective layer prevents chemical deterioration of the photoreceptor surface due to proximity electric discharge. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer, and more particularly, to an image forming apparatus having a charging device using a proximity discharge method.

2. Description of the Related Art Conventionally, an image forming apparatus employing an electrophotographic process has a charging unit for charging a surface of a photoconductor as an image carrier. As one of the charging methods used in the charging means, there is a charging method by proximity discharge. This is a method in which a charging member is brought into contact with or non-contact with the surface of a photoconductor to charge the surface of the photoconductor by proximity discharge.
In recent years, while higher image quality and miniaturization of devices have been increasingly desired, charging devices have also been challenged to achieve higher image quality and smaller size. In order to solve such a problem, a charging device using a proximity discharge method using a charging member in contact with or in proximity to the image carrier is effective because a large-scale charging device is not required.

  However, it has been found that the charging method using the proximity discharge directly exposes the surface of the photoconductor to the proximity discharge, and thus chemically deteriorates the surface of the photoconductor. Unlike the mechanical rubbing, the deterioration of the photoconductor surface due to the proximity discharge occurs even when there is no contact member with the image carrier.

FIG. 16 shows a photoconductor surface when a charging experiment was performed for about 150 hours by continuously arranging only a charging member on the photoconductor surface in a non-contact state in order to examine a deterioration state of the photoconductor surface due to proximity discharge. 5 shows the results of measuring the change in the film pressure of Example 1. The photoreceptor used in the experiment is made of relatively hard material, polycarbonate, and all members that come into contact with the photoreceptor are removed, and a non-contact type in which a voltage in which an AC bias is superimposed on a DC bias is applied. Charging was performed using a charging roller. As a result, it was found that the shaving amount of the film on the surface of the photoconductor gradually increased, and the film thickness of the photoconductor gradually decreased. The mechanism of the decrease in film thickness has not been elucidated at this time, but analysis of the photoreceptor with reduced film thickness has detected carboxylic acids, etc., which are thought to have decomposed the polycarbonate constituting the photoreceptor. Was done. As described above, a substance that is considered to have a component constituting the photoconductor decomposed by the proximity discharge is detected, and the following is considered as a mechanism for reducing the thickness of the photoconductor.
FIGS. 17A and 17B illustrate the state of the surface of the photoconductor 1 when the surface of the photoconductor 1 is deteriorated due to the proximity discharge, with the charging roller 2a facing the photoconductor surface with a small gap as an example. FIG. When a proximity discharge is performed, the energy of particles (ozone, electrons, excited molecules, ions, plasma, etc.) generated by the discharge is applied to the charge transport (CTR) layer 1a on the photoconductor surface in the discharge region on the photoconductor surface. This energy is resonated and absorbed by the binding energy of the molecules constituting the photoreceptor surface, and as shown in FIG. 17A, the charge transport layer 1a has a reduced molecular weight due to the cleavage of the resin molecular chains and a degree of entanglement of the polymer chains. , And chemical deterioration such as evaporation of the resin. It is considered that the thickness of the charge transport (CTR) layer 1a on the surface of the photoconductor gradually decreases due to the chemical deterioration of the photoconductor due to such proximity discharge.

  In this way, apart from the conventional measures to prevent deterioration due to mechanical rubbing, there is a new obstacle to the reduction in durability and long life of the photoconductor due to chemical deterioration of the photoconductor surface caused by proximity discharge. Was found to occur.

  Since the deterioration of the photoconductor surface due to the proximity discharge is considered to be caused by the energy of the particles generated by the discharge, it is considered that the deterioration is caused not only by the polycarbonate but also when a photoconductor of another material is used. Further, even if the charging member is not disposed in a non-contact manner on the surface of the photoreceptor or the applied voltage is not set to the AC superimposed bias as used in the above experiment, if the charging method is based on proximity discharge, the surface of the photoreceptor can be used. It is believed that chemical degradation occurs more or less.

  Conventionally, the following measures have been taken to prevent the deterioration of the photoconductor surface. For example, there is a photoconductor whose surface is coated with amorphous silicon carbide to improve abrasion resistance. Further, for example, an organic photoreceptor having improved abrasion resistance by dispersing an inorganic substance such as alumina in a charge transport (CTR) layer on the surface of the photoreceptor is used (see Patent Documents 1 and 2).

  Patent Documents 3 to 6 disclose an image forming apparatus provided with a means for applying zinc stearate to the surface of an image carrier in the same manner as a specific embodiment of a means for preventing discharge deterioration in the means for solving the problems described below. An apparatus is described. However, the means for applying the zinc stearate is applied for the purpose of lowering the coefficient of friction on the surface of the photoreceptor in order to prevent toner filming and fusion of the toner and to prevent defective cleaning of the surface of the photoreceptor. Things. Therefore, it is not applied in order to prevent deterioration of the photosensitive member surface due to proximity discharge. Further, as will be described later, simply applying zinc stearate to reduce the friction coefficient of the surface of the photoreceptor does not necessarily prevent deterioration due to discharge.

JP 2002-207308 A JP 2002-229227 A JP 2002-244516 A JP 2002-156877 A JP-A-2002-55580 JP-A-2002-244487

  The above-described photoreceptor surface coated with amorphous silicon carbide or a photoreceptor surface layer in which an inorganic substance such as alumina is dispersed can prevent chemical deterioration of the photoreceptor surface due to proximity discharge, despite abrasion resistance. Not necessarily. Until now, only the problem of the decrease in the thickness of the photoreceptor caused by mechanical abrasion caused by the contact member has been regarded as a problem, and the problem of the chemical thickness decrease due to the proximity discharge during charging has been regarded as a problem. Because he did not come.

  The present invention has been made in view of the above background, and an object of the present invention is to prevent deterioration of a photoconductor surface due to proximity discharge in an image forming apparatus employing a charging method based on proximity discharge. An object of the present invention is to provide an image forming apparatus.

In order to achieve the above object, the invention according to claim 1 includes an image carrier and a charging member provided at a position close to or in contact with the surface of the image carrier and configured to charge the surface of the image carrier by a proximity discharge. In the image forming apparatus for forming an image on the image carrier, the surface of the image carrier is prevented from being chemically degraded due to a proximity discharge from the charging member to the surface of the image carrier. A protective layer is provided.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a protective agent for supplying the protective agent forming the protective layer to the surface of the image carrier by being supplied to the surface of the image carrier. It has a supply means.
According to a third aspect of the present invention, in the image forming apparatus of the second aspect, the protective agent supply means has a fur brush as an application member for applying the protective agent to the surface of the image carrier. Things.
According to a fourth aspect of the present invention, in the image forming apparatus of the second aspect, the protective agent supply means has an elastic roller as an application member for applying the protective agent to the surface of the image carrier. Things.
According to a fifth aspect of the present invention, in the image forming apparatus of the third or fourth aspect, the state before application of the protective agent applied to the surface of the image carrier via the application member is formed into a predetermined shape. Characterized in that it is a protected solid protective agent.
According to a sixth aspect of the present invention, in the image forming apparatus of the third or fourth aspect, a state before the application of the protective agent applied to the surface of the image carrier is internally added to the application member. It is a feature.
According to a seventh aspect of the present invention, in the image forming apparatus of the third, fourth, fifth, or sixth aspect, an application member contact / separation unit for bringing the application member into or out of contact with the surface of the image carrier is provided. It is characterized by the following.
According to an eighth aspect of the present invention, in the image forming apparatus of the second, third, fourth, fifth, sixth, or seventh aspect, the protective agent is zinc stearate, and the protective agent supply means supplies the zinc stearate. Is supplied to the surface of the image carrier in such a manner that chemical deterioration of the surface of the image carrier due to proximity discharge can be prevented.
According to a ninth aspect of the present invention, in the image forming apparatus of the eighth aspect, the protective layer is formed so that at least the image forming area of the surface of the image bearing member is not exposed. It is characterized by having done.
According to a tenth aspect of the present invention, in the image forming apparatus of the first, second, third, fourth, fifth, sixth, seventh, or ninth aspect, the charging member is provided in an image forming area on the surface of the image carrier. On the other hand, the image forming area is provided so as to be in non-contact with the surface of the image carrier so as to be opposed with a predetermined charging gap.
According to an eleventh aspect of the present invention, in the image forming apparatus of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, or tenth aspect, the charging member has a roller shape made of hard material. It is a hard charging roller.
According to a twelfth aspect of the present invention, in the image forming apparatus of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, or eleventh, the voltage applied to the charging member is a DC component. Characterized by a voltage obtained by superimposing an AC component on the voltage.
According to a thirteenth aspect of the present invention, in the image forming apparatus of the second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh or twelfth aspect, the protective layer is formed by the protective agent supply means. It is characterized in that it is applied intermittently on the image carrier.
According to a fourteenth aspect of the present invention, in the image forming apparatus of the thirteenth aspect, the intermittent application of the protective layer is performed by operating the image carrier and the protective agent supply means during non-image formation. By applying the above-mentioned protective agent.
According to a fifteenth aspect of the present invention, in the image forming apparatus of the thirteenth aspect, the intermittent application of the protective layer intermittently activates the protective agent supply means disposed in contact with the image carrier during image formation. And applying the protective agent to the image carrier.
According to a sixteenth aspect of the present invention, in the image forming apparatus of the thirteenth aspect, the intermittent application of the protective layer is performed by intermittently contacting the protective agent supply unit and the image carrier during image formation. It is characterized by being performed.
According to a seventeenth aspect of the present invention, in the image forming apparatus of the thirteenth aspect, the protective agent is applied to the surface of the image carrier via an application member that applies the surface of the image carrier. The previous state is an individual protective agent molded into a predetermined shape, and the intermittent application of the protective layer is performed by intermittently contacting the individual protective material and the application member. Things.
According to an eighteenth aspect of the present invention, in the image forming apparatus according to the thirteenth aspect, the intermittent application of the protective layer is performed by a coating member to which the protective agent is internally added and which is applied in contact with the image carrier. The internal addition ratio of the protective material is arbitrarily changed.
The invention according to claim 19 is the image forming apparatus according to claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18. In the image forming apparatus, the average circularity of the toner is 0.96 or more and less than 1.00.
The invention according to claim 20 is the invention according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19 The image forming apparatus is characterized in that it has an intermediate transfer member which is arranged in contact with the surface of the image carrier and temporarily carries an image formed on the image carrier.
The invention according to claim 21 is the invention according to claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20. The image forming apparatus according to claim 20, further comprising a process cartridge for integrally supporting at least the image carrier and the charging member detachably with respect to the image forming apparatus main body.
The invention according to claim 22 is based on claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20. Alternatively, in the image forming apparatus according to the twenty-first aspect, a plurality of the image carriers are provided.
The invention according to claim 23 is based on claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20. , 21 or 22, the image forming apparatus has at least a cleaning unit, the cleaning unit is a fur brush made of conductive fibers, and the cleaning unit is in contact with the fur brush. It is constituted by a roller and its scraper member, and by applying a voltage to the fur brush and / or the collecting roller, toner is collected from the image carrier using an electric field.
In these image forming apparatuses, the protective layer provided on the surface of the image carrier prevents the particles generated by the proximity discharge from the charging member from being directly irradiated on the surface of the image carrier. This prevents the surface of the image carrier from being chemically degraded by particles generated by the proximity discharge. Chemical deterioration refers to the reduction of molecular weight by breaking the molecular chains of the surface material of the image carrier that occurs when the energy of particles (electrons, excited molecules, ions, plasma, etc.) generated by proximity discharge is irradiated to the surface of the image carrier. These include reduction of entanglement of polymer chains, evaporation of resin, and the like. The coating layer for improving abrasion resistance, which is conventionally provided on the surface of the image carrier, cannot always prevent the chemical deterioration due to the above-described particle energy irradiation generated by the proximity discharge. For this reason, even if the coating layer is provided, if the surface portion of the image carrier is irradiated with particles generated by the proximity discharge, the surface of the image carrier may be directly chemically deteriorated. On the other hand, the protective layer of the present invention prevents the image carrier surface itself from deteriorating at least while the layer is present.

  According to these inventions, in an image forming apparatus employing a charging method based on proximity discharge, there is an excellent effect that deterioration of the photoconductor surface due to proximity discharge can be prevented.

[Embodiment 1]
Hereinafter, an embodiment 1 of an image forming apparatus to which the present invention is applied will be described. FIG. 1 shows an example of an image forming apparatus having a configuration common to each embodiment described later. This image forming apparatus includes a photoconductor 1 as an image carrier made of an organic photoconductor. In FIG. 1, a photoconductor 1 is driven to rotate by a driving device (not shown), and the surface thereof is uniformly charged to a predetermined polarity by a charging roller 2a of a main charging device 2 of a proximity charging system. A light image is exposed on the charged surface of the photoconductor 1 by the exposure device 3 to form a predetermined electrostatic latent image. This electrostatic latent image is developed by a toner as a developer supplied from the developing device 4 to the surface of the photoconductor 1, and is visualized as a toner image.

  On the other hand, transfer paper as a recording medium is fed toward the photoreceptor 1 from a paper supply unit (not shown). The toner image on the photoconductor 1 is transferred onto the transfer paper by the transfer device 5 arranged opposite to the photoconductor 1 on the transfer paper. The transfer paper on which the toner image has been transferred is separated from the photoreceptor 1 and then conveyed to the fixing device 6 along the transfer material conveyance path 10 where the toner image is fixed. The transfer residual toner 11 remaining on the photoconductor 1 after the transfer of the toner image to the transfer paper is removed from the photoconductor 1 by the cleaning device 7. Further, the residual charge on the photoconductor surface after the transfer residual toner 11 is removed is removed by the charge removing device 9. Thus, the photoconductor 1 is used repeatedly. The image forming apparatus according to the first embodiment includes a coating device, which will be described later in detail.

In the present embodiment, a coating layer is formed on the organic photosensitive layer in order to improve the abrasion resistance and electrical durability of the photosensitive member. The coating layer improves the durability of the photoreceptor by dispersing an appropriate amount of inorganic particles in a binder resin. Examples of the inorganic particles include titanium oxide, silica, alumina, zirconium oxide, indium oxide, and silicon nitride. Titanium oxide and alumina are particularly excellent in environmental stability and are suitable. On the other hand, as the binder resin, a polycarbonate resin, a polyethylene resin, a polyurethane resin, an acrylic resin, a polyamide resin or the like can be used by dispersing it. However, it has no polarity dependency and has a moderately high resistance (10 ¹⁶ to 10 ¹⁷ Ω · cm). Is preferred.
Note that, instead of the coating layer, a photosensitive member whose surface is coated with amorphous silicon or an inorganic substance such as alumina can be dispersed in the photosensitive layer. By using the photoconductor having such a configuration, cost reduction can be achieved in addition to abrasion resistance.

  Next, a main charging device (hereinafter referred to as a charging device) 2 used in the image forming apparatus of the first embodiment will be described. The charging device 2 charges the photoconductor using proximity discharge. As a method of charging the photoconductor using the 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 photoconductor, There is a non-contact charging system in which the charging is performed in a non-contact manner. In the first embodiment, a non-contact charging method is used. The reason is as follows.

  In the contact charging method among the methods of charging the photoconductor using the proximity discharge, the photoconductor is charged by bringing a charging roller into contact with the surface of the photoconductor and following the movement of the surface of the photoconductor 1. The charging roller is preferably made of an elastic material (for example, a rubber member) that can uniformly contact the surface of the photoconductor and does not give a mechanical stress to the photoconductor. In the case of the contact charging method, toner or paper powder adhering to the surface of the photoreceptor may be transferred and adhered to the charging roller due to defective cleaning. Deterioration may occur. Therefore, in order to increase the durability, it is more advantageous to adopt a non-contact charging system in which foreign matter is less likely to adhere to the charging roller. For the above reasons, the first embodiment employs the non-contact charging system in which the charging roller 2a is disposed so as to face at least the image forming area on the surface of the photosensitive member with a predetermined charging gap.

  FIG. 2 is an explanatory diagram of the main 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 21b is rotatable by rotation of the shaft portion 21a, and a portion of the surface of the photoconductor 1 facing the image forming area 11 where an image is formed is not in contact with the photoconductor 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. By bringing these two spacers into contact with the non-image forming areas 12 at both ends of the photoconductor surface, a minute gap 14 is formed between the photoconductor 1 and the charging roller. The minute gap 14 is configured so that the distance at the closest part between the charging roller and the photoconductor 1 can be maintained at 5 to 100 [μm]. A more preferable range of the gap 14 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 toward the photoreceptor by a pressing spring 15 formed of a spring. Thereby, the minute gap 14 can be maintained accurately. Further, the charging roller rotates around the surface of the photoconductor.

A charging power supply 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, an alternating voltage obtained by superimposing an AC voltage as an AC component on a DC voltage as a DC component is used as the applied voltage. However, the applied voltage is not limited to this, and only the DC voltage may be used.
When applying only the DC voltage as the applied voltage to the charging roller 2a is not suitable for uniformly charging the photoreceptor surface due to variations in charging potential due to minute gap fluctuations and problems in discharge stability. There is. When an alternating voltage in which an AC voltage is superimposed on a DC voltage is applied as in the present embodiment, more uniform charging can be performed, and higher image quality can be achieved.

The charging conditions are as follows: the photoreceptor surface potential after charging is about -700 V, the applied voltage is about 900 Hz with AC voltage superposition, the peak-to-peak voltage is about 2.2 kV, and the offset voltage is about -660 V.
An example of a roller member used for the charging roller 2a is a rubber member. In the case of a rubber member, it is difficult to maintain the minute gap 14 uniformly with the photoreceptor 1, and since rubber is a material that easily absorbs water, the electrical resistance greatly changes due to environmental changes. For this reason, poor charging may occur. In addition, due to the deflection of the charging roller 2a, the charging agent may come into contact with the photoreceptor 1 and adhere to the photoreceptor 1, and the uniformity of the protective layer on the photoreceptor may be lost. Therefore, in order to achieve high stability and high durability, it is more desirable to use a hard charging roller made of a hard resin member as the charging roller member 2a. Here, “hard” means that the hardness of the surface of the charging roller 2a is JIS-A85 ° or more.
In addition, by using a resin member that is hard enough not to cause bending, the gap between the charging roller 2a and the photoconductor 1 can be more accurately and uniformly maintained. Also in the present embodiment, the charging roller is made of a hard resin member that does not cause bending. Therefore, not only uniform charging is possible, but also there is no adhesion of foreign matter, and the life of the charging roller 2a can be extended.
The following shows the results of Experiment 1 in which the gap maintenance stability due to environmental changes was examined between a hard resin roller and a soft rubber roller.

[Experiment 1]
Considering the working environment, the working environment limit where moisture absorption is most promoted in the office is considered to be about 30 ° C. and about 80% RH. Similarly, the low humidity environment limit assumed in an office is considered to be about 20% RH at a high temperature of about 30 ° C. In the present embodiment, it is considered to provide a charging device having excellent temporal quality under such environmental conditions.

Under a condition of 30 ° C. and 20% RH where the influence of moisture absorption is small, when a small gap is formed as shown in FIG. 18, if a conventional rubber charging roller is used, the medium resistance layer of the middle resistance layer is absorbed as shown in FIG. Since the gap member cannot be stretched due to hygroscopic expansion, the charging member may come into contact with the photoconductor. Also, when a case where the moisture absorption portion is concentrated at the center due to the air flow design of the device is considered, contact may occur at that portion as shown in FIG. 18B. The occurrence of contact such as A can be reduced by imparting stretchability of the gap member. However, if contact such as B occurs, it cannot be reduced by the above method.
Table 1 shows the relationship between the environment and the gap when a rubber roller and a hard roller are used.

As a result, when the charging roller 2a is made of a hard material, the gap does not change even when the environment is changed, but when the charging roller 2a is a rubber roller, the gap becomes very narrow in a high humidity environment.
When the gap is narrowed, it is considered that there is a possibility that the gap is in contact with the gap, and therefore, there is a possibility that toner contamination occurs on the charging roller. Therefore, in order to maintain the charging uniformity, it is preferable that the charging roller 2a be of a hard type that ensures the maintenance of the gap.

[Experiment 2]
Next, a description will be given of an experimental example showing that a charging roller using a hard resin member that is more advantageous in maintaining a small gap than a rubber member is effective in suppressing abnormal images.
The occurrence frequency of an abnormal image called image deletion when the minute gap between the charging roller 2a and the photoconductor 1 fluctuated was examined.
The equipment used and the setting conditions are as follows. As the charging device, the proximity type roller charger of the present invention was used.

<< Conditions >>
Copy machine: imageio 4570 modified machine (linear speed: 230 mm / s)
Applied bias: DC (-950 V) + AC (2.2 kVpp, 10 kHz, sine wave)
Charging roller: a roller having a conductive resin layer. Method for maintaining a small gap: PET tape was wound around both ends of the charging roller. (Thickness: 30, 50, 80 μm).
Environmental conditions: 30 ° C, 90% RH
Mechanical conditions: No photoconductor cleaning member As a comparison, an experiment was performed under the condition that the charging roller was brought into contact.

The minute gap was intentionally changed in order to understand how the occurrence frequency of an abnormal image called image deletion depends on the change of the minute gap. As in the experimental conditions, the tape thickness for maintaining the small gap was changed. Then, continuous output of copy was performed under three kinds of small gap conditions, and the amount of hazardous substances was measured. For the evaluation of the hazard, 5,000 copies (A4 landscape) were continuously output, and the presence or absence of an abnormal image called an image deletion phenomenon at that time was confirmed by the image.
The result is shown in FIG. In the figure, the horizontal axis is the minute gap, and the vertical axis is the frequency of occurrence of the image deletion phenomenon.

As a result, although the image gap phenomenon is likely to occur when the small gap is increased, an abnormal image called the image stream phenomenon is less likely to occur at a certain small gap. That is, it has been found that an abnormal image called an image deletion phenomenon largely depends on a minute gap, and becomes the least when a certain gap is reached.
Consider that the plot of the frequency of occurrence of an abnormal image called a small gap and an image deletion phenomenon in FIG. 19 has a downwardly convex extreme value.

This graph shows that the frequency of occurrence of an abnormal image called an image deletion has a minimum value in a certain gap, as described above.
When the minute gap is widened to a certain extent or more, the frequency of occurrence of an abnormal image called an image deletion phenomenon increases in proportion to the minute gap. This is considered to be because, when the minute gap is widened, the voltage required for causing the discharge increases, and the ionization space due to the discharge increases.

First, the relationship between the small gap and the discharge voltage can be explained by Paschen's law.
In particular, when the gap is in a certain range, the discharge start voltage Vth (V) and the gap d (μm) are represented by Equation (1).
<Equation 1> Vth = 6.2 × d + 312 40 ≦ d ≦ 120 [μm]
From Equation 1, it can be seen that the larger the small gap, the higher the voltage for causing discharge.
It is considered that the fact that the discharge occurs at a high voltage means that the energy at the time of the discharge occurrence is large and many molecules can be ionized, so that more hazardous substances causing an abnormal image called an image deletion phenomenon are generated.
Next, regarding the discharge space, if the minute gap is large, the distance from the charging roller to the photoconductor increases. Therefore, the space region where the discharge starts from the charging roller and is ionized before reaching the photoreceptor becomes large, and as a result, the number of molecules to be ionized increases, and accordingly, more hazardous substances are generated. That is, the state where the charging roller is in contact with the photoconductor should minimize the hazard. However, actually, when a small gap is provided, the frequency of occurrence of an abnormal image called an image deletion phenomenon is reduced. It is considered that the reason is related to the airflow around the charging roller.

FIG. 20 shows a case of contact (or a gap in a substantially contact state). An air flow (or air flow) 705 is generated in a contact direction in the upstream wedge-shaped region 703 formed by the photoconductor 701 and the charging roller 702 by the rotation 704 of the charging roller. However, since the charging roller 702 and the photoconductor 701 are in contact, the air flow 705 stops at the contact portion.
Hazardous materials are also believed to move with this air flow 705. However, since the air flow 705 is blocked by the charging roller 702, the hazardous substance also stays at the contact portion of the charging roller 702. Therefore, it is considered that the concentration of the hazard substance in the wedge-shaped region 703 increases, and as a result, the amount of the hazard substance deposited on the photoconductor 701 increases.
However, as shown in FIG. 21, when the minute gap H becomes larger than a certain value, the air 805 flowing by the rotation 804 of the roller 802 passes through the minute gap. Since the hazard substance also moves on the air flow 805, the hazard substance does not stay in the wedge-shaped region 803, and the hazard substance deposited on the photoconductor 701 is reduced. When the minute gap H between the charging roller 802 and the photoconductor 701 increases, air flows further, so that the retention of the hazardous substance is reduced and the accumulation is further reduced.
However, the discharge voltage rises with the increase of the minute gap, a lot of hazardous materials are generated, and the reduction effect by the airflow cannot be made in time. Therefore, when the minute gap exceeds a certain size, the amount of hazardous substances increases.

Therefore, the relationship between the minute gap and the frequency of occurrence of an abnormal image called an image deletion phenomenon becomes minimum at a certain minute gap as shown in FIG. By maintaining the small gap at this time, occurrence of an abnormal image can be suppressed.
Next, the minute gap between the charging roller and the photoconductor when the charging roller rotates under various conditions during the image forming process will be considered.
If the finishing accuracy of the charging roller is poor, for example, if the straightness is poor, the minute gap fluctuates depending on the rotational position of the charging roller.
In addition, if the rigidity of the charging roller is low, there is a problem that the charging roller bends and deforms due to its own weight, and a certain minute gap cannot be maintained.
Based on the result of the relationship between the minute gap and the amount of the hazardous substance, the case where the above-described inferior charging roller is used will be considered.

Even if an appropriate minute gap is set at rest and the charging roller and the photoconductor are set, if the charging roller has poor elongation, the minute gap may increase or decrease during rotation. Since the amount of the hazardous substance changes greatly when the size of the minute gap changes, when a charging roller having poor straightness is used, image deletion is likely to occur.
Therefore, by using a hard resin member, the minute gap between the charging roller and the photoconductor can be maintained more accurately and uniformly over time, and not only can uniform charging be achieved, but also there is no adhesion of foreign matter. In addition, the service life of the charging roller 2 can be extended.

According to the study of the present inventors, the deterioration of the photoconductor surface due to the proximity discharge is caused by directly exposing the surface of the photoconductor to the proximity discharge, and occurs even when there is no abutting member on the photoconductor surface. I understood. That is, the deterioration of the photoconductor surface due to the proximity discharge occurs by a mechanism different from mechanical rubbing. In addition, it has been found that the deterioration caused by the proximity discharge cannot be prevented only by applying the lubricant to the surface of the photoconductor in order to prevent the surface deterioration caused by the mechanical rubbing of the surface of the photoconductor.
Therefore, in the present embodiment, as a feature, a discharge deterioration preventing means for preventing deterioration of the photoconductor surface due to proximity discharge is provided. Hereinafter, the specific configuration will be described in detail.

FIG. 3 is a cross-sectional view of the photoconductor 1, which is a feature of the present invention. The photoreceptor 1 has a protective layer 50 on its surface as a means for preventing discharge deterioration. In order to provide the protective layer 50, the image forming apparatus includes a protective agent applying device as a protective agent supply unit for supplying the protective agent 32 forming the protective layer 50 to the surface of the photoreceptor as shown in FIG. 30 are provided. This protective agent applying device has a fur brush 31A as an applying member, a protective agent 32, and a pressure spring 33 for pressing the protective agent in the fur brush direction.
The protective agent 32 is a bar-shaped solid protective agent 32 having a predetermined shape. The fur brush 31A has a brush tip in contact with the surface of the photoreceptor, and by rotating about a shaft, the protective agent 32 is once pumped up by the brush, and is carried on the brush to a position where it comes into contact with the surface of the photoreceptor. Apply to body surface.
Further, even if the protective agent 32 is scraped off by the fur brush 31A with the passage of time and decreases, the protective agent 32 is pressed at a predetermined pressure by the pressure spring 33 so that the protective agent 32 does not come into contact with the fur brush 31A. 31A is pressed. As a result, even a small amount of the protective agent 32 is constantly pumped up uniformly to the fur brush 31A.

Incidentally, there is a method of forming a protective layer on the surface of the photoreceptor by internally or externally adding the protective agent 32 to the toner. In this case, however, the amount of the protective agent 32 attached varies depending on the image density and the image pattern. It is considered that it is difficult to form a uniform protective layer on the surface of the photoconductor.
In the present embodiment, a protective agent applying device for directly applying the protective agent 32 to the surface of the photoconductor is provided as a protective agent supply unit. Therefore, the protective layer 50 can be stably formed on the surface of the photoreceptor without being changed by various conditions such as an image density and an image pattern.

There is also a method of supplying the protective agent to the surface of the photoreceptor without using a coating member such as the fur brush 31A, but in this case, the protective agent may not be uniformly spread on the photoreceptor. On the other hand, by using the application member as in the present embodiment, the protective agent 32 is stretched over the entire photoreceptor by the application member, and it is possible to apply the protective agent 32 more uniformly without coating unevenness than when directly applying the protective agent 32. it can. In order to obtain the lubricating action that is the purpose of coating conventional zinc stearate, the effect is exhibited even if applied in a sea-island shape to some extent, but in order to protect against energy irradiation by proximity discharge which is the object of the present invention, It is desirable that the surface of the photoreceptor be completely covered with the protective agent 32 so that the entire surface of the photoreceptor is not exposed, ideally, not in a sea-island shape. Therefore, it is required that the protective agent 32 is supplied and, at the same time, the protective agent 32 is uniformly spread over the entire surface of the photoconductor.
In the present embodiment, a fur brush 31A is used as a coating member. Since the protective agent 32 attached to the brush is supplied to the surface of the photoreceptor by rubbing the surface of the photoreceptor with a brush, the protective agent 32 can be stably and uniformly supplied over time to the photoreceptor.

  Various substances can be used as the protective agent 32. Therefore, in the image forming apparatus of the present embodiment, zinc stearate, which has been conventionally applied to the surface of the photoconductor as a lubricant, is used as the protective agent 32. However, zinc stearate is an example of the protective agent 32, and other substances such as wax and silicone oil can be used as the protective agent 32. The results of Experiment 3 in which the deterioration state of the photoreceptor surface was examined when zinc stearate was applied as a protective agent 32 to the photoreceptor surface and when no protective agent 32 was applied were shown.

[Experiment 3]
FIG. 4A is a schematic configuration diagram of an experimental apparatus for confirming that the formation of the protective layer 50 on the photoconductor suppresses deterioration of the photoconductor due to proximity discharge. FIG. 4B is an explanatory view showing a state where the surface of the photoconductor is divided into a protective layer forming portion A and a non-forming portion B.
In order to carry out this experiment, all members other than the charging roller 2a and the protective agent application device 30 were removed in advance, and the protective agent application device 30 was configured to apply the protective agent 32 to the half surface area of the photosensitive member 1 in the axial direction. . As the protective agent 32, zinc stearate was used. Then, the charging device 2 and the protective agent coating device 30 were continuously driven together with the photoconductor 1, and the deterioration state of the photoconductor surface was examined. The experimental conditions are as follows.
[Experiment conditions]
Charging conditions: Vpp: 2.12 [kV], f: 877.2 [Hz], offset: -660 [V]
・ Photoconductor linear velocity: 125 [mm / s]
As shown in FIG. 4B, a half-area A in the longitudinal direction of the photoreceptor 1 is provided with a protective layer 50 made of zinc stearate on the surface, and the other half is an area B. The surface of the photoconductor 1 is exposed as it is. Further, as an index of the deterioration of the surface of the photoconductor 1, the amount of film scraping of the photosensitive layer was measured.

FIG. 5 is a graph showing the result of performing the experiment 3 continuously for 200 hours. In the region B of the photoreceptor 1 where the protective layer is not provided, the amount of film scraping increased with the passage of time, and the film thickness decreased by about 2.5 [μm] after 200 hours. On the other hand, in the region A where the protective layer 50 exists, the film thickness was hardly reduced. After 200 hours, the surface of the photoreceptor used in the experiment was visually observed. In the area B without the protective layer, the filler was deposited and the white powder was sprayed. As in the case of the photoreceptor 1, the mirror surface was maintained, and the photoreceptor was not deteriorated.
From the above experimental results, it can be seen that the formation of the protective layer suppresses the deterioration of the photoconductor surface due to discharge.

Here, zinc stearate has conventionally been applied to the surface of the photoreceptor as a lubricant. Zinc stearate used as a lubricant has been applied to reduce the friction coefficient of the photoreceptor surface. The purpose was to lower the coefficient of friction of the photoreceptor surface to reduce the adhesion between the toner and the photoreceptor 1 to facilitate cleaning of the photoreceptor surface and to eliminate toner sticking.
Until now, the high durability of the photoreceptor 1 has been determined by how to maintain the strength against mechanical wear, or if the strength does not increase, how to reduce the wear rate by lowering the friction coefficient. I have been. However, it has not been clarified that the deterioration of the photoreceptor surface due to electric discharge as a problem to be solved by the present invention can be prevented by applying zinc stearate. That is, in the conventional zinc stearate coating, the effect of protecting the photoreceptor surface from energy irradiation by electric discharge has not been recognized.
In recent years, it has been clarified that the thickness of the photosensitive layer of the photoreceptor 1 is also reduced by electric discharge. As a countermeasure, if a material that reduces deterioration due to electric discharge is applied to the surface, it is possible to prevent the film thickness from being reduced due to electric discharge. Thus, it has been clarified that the present inventor can prevent this by using zinc stearate conventionally applied.
Here, the difference between the case of applying zinc stearate as a lubricant on the surface of the photoconductor as a lubricant and the case of applying the same on the surface of the photoconductor as a protective agent 32 for preventing deterioration of the surface of the photoconductor due to discharge will be described below. Will be described.

表２の結果より、ステアリン酸亜鉛を０．０００２［ｍｇ／ｍｍ^２］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／ｍｍ^２］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／ｍｍ^２］では、近接放電による感光体表面劣化を防止可能な保護層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／ｍｍ^２］ではそのための塗布量を満たしていると言える。
また、図６の結果より、ステアリン酸亜鉛を０．０００２［ｍｇ／ｍｍ^２］塗布した場合ｍと０．００１６［ｍｇ／ｍｍ^２］塗布した場合Ｍとは、何れの場合にも、ある程度の時間経過後には感光体表面の摩擦係数が０．１程度となった。この程度低い摩擦係数であれば、機械的磨耗による感光体表面の膜削れは防止することができる。この結果から、塗布量が０．０００２［ｍｇ／ｍｍ^２］以上あれば、感光体表面が機械的磨耗によって劣化することを防止することができると言える。
以上、表２及び図６の結果から、ステアリン酸亜鉛を潤滑剤として塗布して感光体表面を低摩擦係数化するためには、塗布量が０．０００２［ｍｇ／ｍｍ^２］で十分であるが、感光体表面を近接放電による劣化から保護するためには塗布量を０．００１６［ｍｇ／ｍｍ^２］より多くする必要があることがわかる。 Table 2 shows that when the amount of zinc stearate applied to the photoreceptor surface per unit area was changed in two ways: 0.0002 [mg / mm ² ] and 0.0016 [mg / mm ² ], It is a result of examining whether or not body surface deterioration has occurred. FIG. 6 is a graph showing the change with time of the friction coefficient of the photoreceptor surface when zinc stearate is applied with these two application amounts. The measurement of the coefficient of friction is based on the Euler belt method.

From the results shown in Table 2, when 0.0002 [mg / mm ² ] of zinc stearate was applied, the thickness of the surface of the photoreceptor was reduced and the surface was deteriorated. When 0.0016 [mg / mm ² ] of zinc stearate was applied, the film thickness of the photoreceptor surface did not decrease and the surface did not deteriorate. From this result, when the coating amount is 0.0002 [mg / mm ² ], the coating amount is insufficient to form the protective layer 50 capable of preventing the photoconductor surface from being deteriorated by the proximity discharge. It can be said that 0016 [mg / mm ² ] satisfies the application amount for that.
Further, from the results of FIG. 6, it can be seen that m when zinc stearate was applied at 0.0002 [mg / mm ² ] and M when 0.0016 [mg / mm ² ] were applied, After a lapse of time, the coefficient of friction of the photoreceptor surface became about 0.1. With such a low coefficient of friction, it is possible to prevent abrasion of the film on the photoconductor surface due to mechanical abrasion. From these results, it can be said that if the coating amount is 0.0002 [mg / mm ² ] or more, the photoreceptor surface can be prevented from being deteriorated due to mechanical abrasion.
As described above, from the results shown in Table 2 and FIG. 6, the amount of 0.0002 [mg / mm ² ] is sufficient to apply zinc stearate as a lubricant to reduce the friction coefficient of the photoconductor surface. However, it can be seen that in order to protect the surface of the photoreceptor from deterioration due to proximity discharge, it is necessary to increase the amount of coating to more than 0.0016 [mg / mm ² ].

The reason why the photoreceptor surface can be protected or not protected from deterioration due to proximity discharge depending on the amount of zinc stearate applied as described above can be considered as follows.
When the photoconductor 1 is charged by proximity discharge, the energy of particles (electrons, excited molecules, ions, plasma, etc.) generated by the discharge in the discharge region on the photoconductor surface is transferred to the charge transport (CTR) layer 1a on the photoconductor surface. Irradiated. This energy is resonated and absorbed by the binding energy of the molecules constituting the photoreceptor surface, and as shown in FIG. 17A, the charge transport layer 1a has a reduced molecular weight due to the cleavage of the resin molecular chains and a degree of entanglement of the polymer chains. It is considered that chemical deterioration such as reduction of the charge transport layer 1a occurs, and the film thickness for forming the charge transport layer 1a is reduced.
On the other hand, when the protective layer 50 is provided on the surface of the photoreceptor, since the energy of the particles generated by the discharge is directly irradiated by the protective layer 50 provided on the outermost layer of the photoreceptor 1, the photoreceptor itself is discharged by the discharge. This avoids direct irradiation of the generated particles. Therefore, it is considered that the protective layer itself absorbs the energy of the particles generated by the discharge, and alleviates the chemical deterioration of the photoconductor surface. Also in the experiments shown in FIGS. 4 and 5, the photoreceptor surface of the photoreceptor 1 in the region B where the protective layer is not provided has molecular debris constituting the photoreceptor detected by analysis, In a certain area A, no debris of the molecules constituting the photoconductor was detected, and the surface of the photoconductor under the protective layer 50 was not deteriorated. In this region A, a substance in which zinc stearate supplied as the protective layer 50 was chemically changed and decomposed was detected.
FIGS. 7A and 7B are explanatory diagrams showing a state in which the protective layer 50 is provided on the surface of the photoreceptor and the surface is irradiated with particles by proximity discharge. 17 (a) and 17 (b), when the protective layer 50 is provided on the surface of the photoreceptor (in this case, zinc stearate), the protective layer 50 discharges instead of the charge transport layer 1a on the surface of the photoreceptor. Absorb energy. Then, the protective layer 50 is decomposed. Since the energy of the discharge is absorbed by the protective layer, it cannot reach the charge transport layer 1a, thereby avoiding the chemical deterioration of the photoconductor surface. At this time, it is considered that the protective layer 50 needs to have a thickness that can absorb the energy of the discharge.

表３の結果より、表３に示すように、ステアリン酸亜鉛の塗布量が０．００１２［ｍｇ／ｍｍ^２］未満までは感光体表面の劣化が確認された。塗布量が０．００１２［ｍｇ／ｍｍ^２］以上で感光体が劣化しないことが確認された。従来技術では、感光体表面の摩擦係数を下げることによって機械的磨耗による感光体膜厚の減少を防ぎ、感光体１の高耐久化を図っていた。しかし、実験４の結果から、感光体表面の機械的磨耗を防ぐたけでは、感光体膜圧の減少を防止しきれるとは限らないことがわかる。また、感光体表面の低摩擦係数化の為に、潤滑剤としてステアリン酸亜鉛を感光体表面に塗布する場合と比べて、近接放電による劣化を防ぐ保護層５０として塗布する場合には、ある一定以上のステアリン酸亜鉛の塗布量が必要であることがわかる。
上記の結果より、実験４で用いたものと同じ条件の画像形成装置においては、およそ０．００１２［ｍｇ／ｍｍ^２］塗布すれば近接放電による劣化から感光体表面を保護することが可能であると言える。 [Experiment 4]
Based on the above results, the following experiment 4 was carried out in order to investigate the amount of coating required to protect the photoreceptor surface from chemical deterioration due to proximity discharge, that is, the amount that can prevent chemical deterioration. In Experiment 4, the coating amount was further finely changed using the apparatus configuration shown in FIG. 4, and the presence or absence of deterioration of the photoconductor surface due to the proximity discharge of the charging device 2 was examined. Table 3 shows the results.

From the results in Table 3, as shown in Table 3, deterioration of the photoreceptor surface was confirmed until the amount of zinc stearate applied was less than 0.0012 [mg / mm ² ]. It was confirmed that the photoreceptor did not deteriorate when the coating amount was 0.0012 [mg / mm ² ] or more. In the prior art, a reduction in the coefficient of friction of the surface of the photoreceptor prevents a reduction in the thickness of the photoreceptor due to mechanical abrasion, thereby improving the durability of the photoreceptor 1. However, from the results of Experiment 4, it can be seen that simply preventing the mechanical wear of the photoconductor surface does not always prevent the reduction of the photoconductor film pressure. Further, when zinc stearate is applied as a lubricant to the surface of the photoconductor as a protective layer 50 for preventing deterioration due to proximity discharge in order to reduce the friction coefficient of the surface of the photoconductor, a certain amount of It is understood that the above-mentioned zinc stearate application amount is necessary.
From the above results, in the image forming apparatus under the same conditions as those used in Experiment 4, it is possible to protect the photoreceptor surface from deterioration due to proximity discharge by applying approximately 0.0012 [mg / mm ² ]. It can be said.

As described above, the protective agent 32 for protecting the photoreceptor from being deteriorated due to proximity discharge is not limited to zinc stearate. For example, when zinc stearate is applied, it is necessary to act as the protective layer 50. It can be said that the amount of application is larger than when used as a lubricant. In the image forming apparatus under the same conditions as in Experiment 4 described above, the amount that can prevent chemical deterioration when zinc stearate is applied as the protective agent 32 is considered to be about 0.0012 [mg / mm ² ] or more. . However, when the type of the photoreceptor 1 and the applied voltage conditions of the charging device 2 are different from those in the above experiment, the amount of zinc stearate necessary for protecting the photoreceptor 1 is not limited to this, and changes. An amount that can protect the surface of the photoreceptor from chemical deterioration due to proximity discharge may be determined in accordance with the conditions of the apparatus actually used, and this amount may be applied to the surface of the photoreceptor.

Usually, the protective agent applied on the photoreceptor is gradually scraped off from the photoreceptor by volatilization due to the discharge or by contact with a developing roller, a transfer member or the like. Therefore, if the supply amount of the protective agent is appropriate, the photoconductor can be protected from deterioration due to discharge without adversely affecting the image.
However, when the supply amount is excessive, abnormal images such as image deletion, poor development due to a low friction coefficient, and image blurring at high temperature and high humidity are likely to occur. This occurs, for example, when the scraping amount of the developing roller or the transfer body or the amount of volatilization due to discharge is not sufficiently compared with the supply amount. In such a case, the protective agent stays on the photoreceptor for a long time, and the image is repeatedly discharged by the charging device during image formation. Further, since the protective agent newly supplied by the protective agent applying device is laminated on the protective agent already applied on the photoreceptor, the deposition of the protective agent is accelerated. Further, the protective agent that has passed under the charging roller repeatedly deteriorates and adheres to ozone, NOx, and the like, and becomes viscous, so that paper dust, toner additives, brush fibers, and the like easily adhere.
As a result, the minute gap between the charging roller disposed close to the photoconductor and the photoconductor fluctuates, causing an abnormal discharge, which causes a problem that the photoconductor cannot be uniformly charged. In particular, when the protective agent is continuously supplied onto the image bearing member while scraping off the protective agent with an application means such as a brush roller in contact with the protective agent formed into a bar, the supply tends to be excessive, and as described above. Problems easily occur.

  If the supply amount of the protective agent is excessive, the newly supplied protective agent and the deteriorated protective agent are deposited on the photoconductor 1, as shown in FIG. As a result, the minute gap between the charging roller 2a and the photoconductor 1 fluctuates, so that abnormal discharge occurs and it becomes impossible to uniformly charge the photoconductor 1. As a method of applying such a protective film in an appropriate amount to prevent such an excessive supply of the protective agent and prevent deterioration of the photoconductor 1 from discharging of the charging device, a method of intermittently applying the protective agent is effective. .

  Hereinafter, the intermittent coating method will be described. The intermittent application of the protective agent to the photoreceptor 1 is performed by operating only the photoreceptor 1 and the protective agent applying device 30 during non-image formation in which image formation is not performed. Specifically, as shown in FIG. 1, a protective agent 32 shaped like a bar is brought into contact with an application unit such as a fur brush 31A, and is supplied onto the photoreceptor 1 via the application unit. Since the application means such as the fur brush 31A does not rotate during image formation and is stopped, the protective agent 32 is not supplied during that time. However, the photoconductor 1 and the fur brush 31A are not supplied during non-image formation. By rotating only the protective agent 32, the protective agent 32 shaped into a bar is scraped off by the fur brush 31A and supplied onto the photoreceptor. The applying means is not limited to the fur brush 31A, but may be an elastic roller.

When the protective agent 32 is previously applied to the photoconductor 1 during non-image formation, the charging device operates during image formation, and when the electric charge is applied to the photoconductor 1 by discharging, the photoconductor 1 is directly discharged. Since it is not affected, deterioration of the photosensitive layer due to discharge is suppressed.
The interval at which the protective agent 32 is applied may be set so that, for example, when a certain number of copies are reached, the coating mechanism is activated during non-image formation, and the coating mechanism is activated for 30 seconds every 200 sheets are printed. It may be. In this way, by intermittently applying the protective agent, it becomes possible to apply the required amount of the protective agent 32, and it is possible to prevent the minute gap between the charging roller 2a and the photoconductor 1 from being changed due to excessive supply, and to achieve uniform charging. Can be performed.

When the protective agent applied on the photoreceptor is deteriorated while receiving the proximity discharge as described above, it generates viscosity. For this reason, it is desirable to quickly remove the deteriorated protective agent from the photoreceptor. Therefore, it is desirable to provide a removing member for removing the deteriorated protective agent 32 from the surface of the photoreceptor in order to exert a stable protective effect of the protective layer 50 and to have no other adverse effects. In the present embodiment, a cleaning device 7 is provided for removing the transfer residual toner from the photoconductor surface after passing through the transfer nip. The cleaning device 7 can also remove the deteriorated protective agent. In addition, providing a new cleaning device upstream of the transfer nip to the transfer paper is also effective in removing the deteriorated protective agent 32.
Next, a modified example of the image forming apparatus according to the first embodiment will be described.

[Modification 1]
In the first modification, the protective agent 32 is intermittently applied at the time of image formation. The other configuration is the same as the configuration of the first embodiment described above, and the description is omitted. The first modification is performed by intermittently performing the operation of the application unit disposed in contact with the photoconductor 1. Specifically, as shown in FIG. 1, a protective agent molded into a bar is brought into contact with an application unit such as a fur brush 31A and supplied onto the photoreceptor 1 via the application unit. In this case, the fur brush 31A, which is an application unit, is in a rotating or stopped state with respect to the photoreceptor 1 that rotates during image formation, and when the fur brush 31A rotates, the protective agent molded into a bar shape is scraped off. While supplying it onto the photosensitive member 1. There is a method of setting the rotation interval of the fur brush 31A such that the rotation is performed at the time of image formation when a certain number of copies is reached, for example. Alternatively, there is a method of repeating rotation and stop at a certain time interval during image formation. Thus, by intermittently applying the protective film, it becomes possible to apply a necessary amount of the protective agent. Therefore, it is possible to prevent the surface of the photoconductor from deteriorating due to the proximity discharge. In addition, it is possible to prevent a minute gap between the charging roller 2a and the photosensitive member 1 from fluctuating, thereby preventing abnormal discharge from occurring, and to perform uniform charging.

[Modification 2]
FIG. 8 is an explanatory diagram according to a second modification of the first embodiment. In the second modification, a moving device (not shown) is provided as an application member contacting / separating means for contacting / separating the fur brush 31A from / to the photoconductor surface. The configuration other than that the moving device is provided is the same as the configuration of the first embodiment described above, and the description is omitted. In Modification 2, the moving device causes the fur brush 31A to be in contact with the surface of the photoreceptor so that the protective agent 32 can be applied, and the retreat position 35b separated from the surface of the photoreceptor. Can move back and forth in the direction of arrow C. This makes it possible to intermittently apply the protective agent 32 to the photoconductor surface. Therefore, it is possible to prevent the surface of the photoconductor from deteriorating due to the proximity discharge. In addition, it is possible to prevent a minute gap between the charging roller 2a and the photosensitive member 1 from fluctuating, thereby preventing abnormal discharge from occurring, and to perform uniform charging.
Note that an elastic roller may be used as the application member instead of the fur brush 31A. Further, a fur brush or an elastic roller in which a protective agent is internally added may be used.

[Modification 3]
FIG. 9 is an explanatory diagram according to a third modification of the first embodiment. Hereinafter, only the characteristic portions of the third modification will be described, and the description of the same portions as those of the first embodiment will be omitted. In the third modification, the fur brush 31A is used as a member for applying the protective agent 32. However, in the third modification, a coating roller 36 made of an elastic roller is used as a coating member. Further, as the protective agent 32, a solid protective agent 32 molded in a bar shape in the same manner as described above is used. The application roller 36 is in contact with the protective agent 32 and is also in close contact with the photosensitive member 1. When the apparatus is driven, the application roller 36 also rotates, and reaches the contact position with the surface of the photoreceptor with the surface carrying the protective agent 32. The protective agent 32 is sandwiched between the application roller 36 and the photoconductor 1 at a contact position with the photoconductor surface, and adheres to the photoconductor surface. Thus, the protective agent 32 is applied to the surface of the photoconductor.
In the third modification, the contact area between the application roller 36 and the photoreceptor 1 is larger than when the application member is the fur brush 31A, and since the contact member is in close contact, the effect of extending the protective agent 32 is exhibited. You. Therefore, a uniform protective layer can be formed more effectively without newly providing a member for extending the protective agent 32 applied to the photoreceptor surface.

[Modification 4]
FIG. 10 is an explanatory diagram according to a fourth modification of the first embodiment. Hereinafter, only the characteristic portions of the modified example 4 will be described, and description of the same portions as those of the above-described first embodiment will be omitted. In this modified example 4, the protective agent internal brush 37 in which the protective agent 32 is preliminarily added to the fiber of the fur brush 31A is used, and the solid protective agent as shown in FIG. 1 is not provided. This eliminates the need for a space in which the solid protective agent 32 is provided, and can save space in the device.
In this modified example 4, the intermittent application of the protective film is performed by the contact between the photosensitive member 1 and the rotating roller member in which the protective agent is internally added. The ratio is arbitrarily changed at any position of the roller member. More specifically, as shown in FIG. 23, brush fibers in which a protective agent is partially added are implanted in a brush roller. In this way, when the brush is rotated, the contact between the brush fiber with the protective agent and the photoreceptor is performed intermittently, so that the supply of the protective agent is also performed intermittently. Will be. Therefore, it is possible to prevent the surface of the photoconductor from deteriorating due to the proximity discharge. In addition, it is possible to prevent a minute gap between the charging roller 2a and the photosensitive member 1 from fluctuating, thereby preventing abnormal discharge from occurring, and to perform uniform charging.

[Modification 5]
FIG. 11 is an explanatory diagram according to a fifth modification of the first embodiment. Hereinafter, only the characteristic portions of Modification Example 5 will be described, and description of the same portions as those of the configuration of Embodiment 1 will be omitted. In the fifth modification, as in the fifth modification, an application roller 36 made of an elastic roller is used as an application member. Further, in Modification Example 5, the protective agent 32 is a roller in which the protective agent 32 is previously added to the inside of the application roller 36, and the solid protective agent as shown in FIG. 1 is not provided. This eliminates the need for a space in which the solid protective agent 32 is provided, and can save space in the device.
In the fifth modification, the intermittent application of the protective film is performed by the contact between the rotating roller member with the protective agent and the photoreceptor 1 (see FIG. 23B). The ratio is arbitrarily changed at any position of the roller member. By internally adding the protective agent to a part of the elastic roller, the supply of the protective agent is performed intermittently. Therefore, it is possible to prevent the surface of the photoconductor from deteriorating due to the proximity discharge. In addition, it is possible to prevent a minute gap between the charging roller 2a and the photosensitive member 1 from fluctuating, thereby preventing abnormal discharge from occurring, and to perform uniform charging.
[Modification 6]
FIG. 24 is an explanatory diagram according to Modification 6 of Embodiment 1. Hereinafter, only the characteristic portions of the modified example 6 will be described, and the description of the same portions as those of the above-described first embodiment will be omitted. In this modified example 6, the intermittent application of the protective film is performed at the time of image formation via an application unit that comes into contact with a bar-shaped protective agent, and the contact between the bar-shaped protective agent and the application unit is performed. It is intermittent.
Specifically, a rotating brush having a partially different brush fiber density is used. FIG. 24 shows an example. FIG. 24 (a) shows a fur brush 31B obtained by cutting a half of the brush, and FIG. 24 (b) shows a fur brush 31C obtained by cutting a ／ of the brush. As shown in FIG. Due to the difference, the contact with the protective agent formed into a bar shape becomes intermittent, and as a result, the protective agent can be supplied to the photoconductor 1 intermittently. As the coating means, a partially cut elastic roller 38B as shown in FIG. 24C may be used other than the brush.
[Modification 7]
FIG. 25 is an explanatory diagram according to Modification 7 of Embodiment 1. Hereinafter, only the characteristic portions of the modified example 7 will be described, and the description of the same portions as those of the first embodiment will be omitted. In this modified example 7, the cleaning method is different from the above embodiment.
In recent years, spherical toners have been used for higher image quality. When spherical toner is used, there is a problem that cleaning failure occurs in the blade system. Further, since the blade and the image carrier are always in contact with each other, there is a problem in high durability. Instead of such a blade cleaning method, a fur brush 70 made of conductive fiber as shown in FIG. 25, a collection roller 71 in contact with the fur brush, and a scraper member 73 thereof are provided. Alternatively, when a method is used in which toner is collected from the photoreceptor 1 using an electric field by applying a voltage 75 to the collection roller, the spherical toner can be sufficiently cleaned, so that poor cleaning toner may reach the charging roller. And no charging failure occurs. Further, by using the fur brush 70 having a soft contact with the surface of the image carrier, stress on the photoconductor 1 is reduced and the durability of the photoconductor 1 is improved.

[Embodiment 2]
FIG. 12 is a schematic configuration diagram of a full-color image forming apparatus according to a second embodiment as another example of the image forming apparatus to which the present invention can be applied. Hereinafter, only the characteristic portions of the second embodiment will be described, and the description of the same components as those of the first embodiment will be omitted. In this image forming apparatus, the developing device 4 includes four developing devices 4 </ b> C that supply toner of each color of cyan (C), magenta (M), yellow (Y), and black (K) to one photoconductor 1. , 4M, 4Y, 4K. By switching the operation of each of the developing devices 4C, 4M, 4Y, and 4K, a plurality of toners of cyan (C), magenta (M), yellow (Y), and black (K) are formed on one photoconductor 1. The image is developed. Then, the full-color toner image formed on the photoreceptor is collectively transferred onto transfer paper by a transfer device 5 disposed opposite to the photoreceptor 1.
The full-color image forming apparatus according to the second embodiment having the above configuration also includes the protective agent applying device 30 according to the present invention, similarly to the image forming apparatus according to the first embodiment. Thereby, the same effect as in the first embodiment can be obtained. Further, the configurations of Modifications 1 to 7 of the first embodiment can be applied.

[Embodiment 3]
FIG. 13 is a schematic configuration diagram of a full-color image forming apparatus according to a third embodiment as an image forming apparatus to which the present invention can be applied. Hereinafter, only the features of the third embodiment will be described, and the description of the same components as those of the first embodiment will be omitted. The full-color image forming apparatus includes a plurality of image forming apparatuses (here, four images) formed on the intermediate transfer member 21 for forming images of different colors including portions excluding the fixing device 6 in the image forming apparatus shown in FIG. This is a tandem type full-color image forming apparatus configured by arranging the same. In this tandem-type full-color image forming apparatus, cyan (C), magenta (M), and yellow (Y) formed on the photoconductors 1C, M, Y, and K of the color image forming apparatuses 100C, M, Y, and K, respectively. , And black (K) toner images are sequentially superimposed on the intermediate transfer body 21 and primary-transferred. As a result, a full-color toner image is formed on the intermediate transfer member. Next, the full-color toner image (primary transfer image) on the intermediate transfer body 21 is secondarily transferred to the transfer paper P by the paper transfer unit 23.

The configuration according to the present invention can be applied to the full-color image forming apparatus according to the third embodiment having the above configuration, similarly to the image forming apparatuses according to the first and second embodiments.
In particular, in a configuration having a plurality of photoconductors 1C, M, Y, and K as in the image forming apparatus according to the third embodiment, the frequency of replacement on the photoconductors 1C, M, Y, and K increases by the number of photoconductors. In such an apparatus, increasing the durability on the photoconductors 1C, 1M, 1Y, and 1K can extend the replacement interval, and is therefore more useful than an apparatus having only one photoconductor. high. Therefore, by applying the present invention, the replacement intervals on the photoconductors 1C, M, Y, and K can be extended, and the replacement frequency can be reduced.
Further, the image forming apparatus according to the third embodiment includes the intermediate transfer body 21 that temporarily holds the image on the photoconductor. For this reason, the zinc stearate as the protective agent 32 applied on the photoconductors 1C, M, Y, and K is partially applied to the surface of the intermediate transfer body from the contact position between the photoconductors 1C, M, Y, and K and the intermediate transfer body. Transfer adheres. The zinc stearate transferred to the surface of the intermediate transfer member acts as a release agent when the image primarily transferred on the intermediate transfer member is secondarily transferred to the transfer paper, thereby improving the transfer rate to the transfer paper. Can be done.

[Embodiment 4]
FIG. 14 is a schematic configuration diagram of a full-color image forming apparatus according to a fourth embodiment as an image forming apparatus to which the present invention can be applied. Hereinafter, only the features of the fourth embodiment will be described, and the description of the same components as those of the first embodiment will be omitted. This full-color image forming apparatus has the same configuration as the full-color image forming apparatus of the second embodiment except that an intermediate transfer body 21 is provided between the photoconductor 1 and the paper transfer unit 23. The developing device 4 supplies toner of each color of cyan (C), magenta (M), yellow (Y), and black (K) to one photoconductor 1, and four developing devices 4C, 4M, 4Y, and 4K. It is composed of In this one-drum type full-color image forming apparatus, the operation of each of the developing devices 4C, 4M, 4Y, and 4K is switched so that cyan (C), magenta (M), yellow (Y), Black (K) color toner images are sequentially formed. Thereafter, similarly to the tandem-type image forming apparatus of the third embodiment, the toner images of the respective colors of cyan (C), magenta (M), yellow (Y), and black (K) formed on the photoreceptor 1. Are sequentially superimposed on the intermediate transfer member 21 to perform primary transfer. Next, the color toner image (primary transfer image) on the intermediate transfer body 21 is secondarily transferred to the transfer paper P by the paper transfer unit 23.

Various configurations according to the present invention can be applied to the full-color image forming apparatus according to the fourth embodiment having the above configuration, similarly to the image forming apparatuses according to the first to third embodiments.
Further, similarly to the third embodiment, the image forming apparatus includes an intermediate transfer body 21 that temporarily holds an image on a photoconductor. For this reason, zinc stearate as a protective agent 32 applied on the photoreceptor partially transfers and adheres to the surface of the intermediate transfer member, and the image primarily transferred on the intermediate transfer member is secondarily transferred to transfer paper. It can act as a release agent.

[Embodiment 5]
FIG. 15 is a schematic configuration diagram of an image forming apparatus according to a fifth embodiment as an image forming apparatus to which the present invention can be applied. In the image forming apparatus of the fifth embodiment, the latent image forming process cartridge 24 in which the photosensitive member 1 and the charging roller 2a are integrally detachable from the image forming apparatus main body, and the developing in which the developing apparatus is detachable from the image forming apparatus main body. The process cartridge 25 is used. For example, in the case of the latent image forming process cartridge 24, it is possible to remove the latent image forming process cartridge 24 from the main body of the image forming apparatus when replacing the photosensitive member 1 and replace the entire cartridge 24.

In the image forming apparatuses of the first to fifth embodiments, a charging method based on proximity discharge is used as a charging device. In addition, the above-described various features are provided in order to prevent the photoconductor from being deteriorated due to the proximity discharge.
Here, if a corona charging method using corona discharge is adopted as the charging device, chemical deterioration of the photoconductor due to collision of particles generated by the discharge with the surface of the photoconductor is suppressed as compared with proximity discharge. However, this corona charging method is not preferable because products such as ozone and nitrogen oxides are generated by corona discharge.
When ozone stays in the image forming apparatus at a high concentration, it oxidizes the surface of the photoreceptor, causing a decrease in photoreceptor photosensitivity and a reduction in charging ability, which may adversely affect image formation. In addition, deterioration of members other than the photoreceptor may be promoted, which may cause a problem such as shortening the life of components.
Nitrogen oxides generate various nitric acid compounds, such as reacting with moisture in the air or the like to generate nitric acid, or reacting with metals of peripheral members to generate metal nitrates. The nitric acid compound is a highly water-absorbing substance and therefore has a high resistance in a low humidity environment, but has a property of absorbing the moisture in the air and reducing the resistance in a high humidity environment. When such a nitric acid compound adheres to the surface of the photoreceptor to form a thin film, the resistance value of the surface of the photoreceptor decreases due to the hygroscopic action of the nitric acid compound. For this reason, if it exists over the image area and the non-image area on the surface of the photoconductor, the charge generated by the exposure may flow over the exposure area on the surface of the photoconductor, and an abnormal image may be generated.
The charging method using the proximity discharge employed in the first to fifth embodiments generates less ozone and nitrogen oxides than the corona charging method. High value.

In the image forming apparatuses of the first to fifth embodiments, a protective agent applying device is provided as a protective layer forming unit. Accordingly, it is possible to prevent the surface of the photoconductor from being deteriorated by the proximity discharge.
Further, since a protective agent applying device as a protective agent supply unit is provided, a uniform protective layer 50 can be formed on the surface of the photoconductor without being changed by various conditions such as an image density and an image pattern. .
Further, since the fur brush 31A is used as a coating member, it is possible to form a uniform protective layer 50 on the surface of the photoconductor.
It has also been proposed to use an application roller 36 made of an elastic roller as an application member. Thereby, the protective layer 50 can be formed uniformly.
Further, since the protective agent 32 is a bar-shaped solid protective agent 32 having a predetermined shape, it is easier to arrange the protective agent 32 in a device than when using a liquid or powder as the protective agent 32. Easy.
In addition, in Modification 4 of Embodiment 1 or Embodiments 2 to 5 to which this configuration is applied, a protective agent internally added brush 37 in which the protective agent 32 is previously added to the fibers of the fur brush is used. Similarly, in Modification Example 5 of Embodiment 1 or Embodiments 2 to 5 to which this configuration is applied, a protective agent internally added roller 38 in which the protective agent 32 is previously added inside the application roller 36 is used. This eliminates the need for a space in which the solid protective agent 32 is provided, and can save space in the device. Further, the internal ratio of the protective agent on the internal brush 37 (or the application roller 36) is arbitrarily different on the roller member. Thereby, when the brush (or the roller) is rotated, the brush fiber in which the protective agent is internally added and the photoconductor are intermittently contacted with each other, so that the occurrence of an abnormal image due to excessive supply can be prevented. Become. In addition, since an appropriate amount of the protective film can be supplied onto the image bearing member, uniform charging can be performed without changing the minute gap between the charging roller and the image bearing member. In addition, by appropriately controlling the supply amount of a substance that protects the photoreceptor from deterioration due to electric discharge to the image forming area, it is possible to prevent deterioration of the photoreceptor and improve durability without generating an abnormal image. Becomes possible.
Further, in Modification 2 of Embodiment 1 or Embodiments 2 to 5 to which this configuration is applied, a moving device (not shown) serving as an application member contacting / separating unit that contacts / separates the fur brush 31A with respect to the photoconductor surface. ) Is provided. As a result, it is possible to prevent adverse effects such as abnormal images due to excessive application of the protective agent.
Further, as a protective agent 32, zinc stearate is applied to the surface of the photoreceptor in such an amount as to prevent chemical deterioration of the photoreceptor surface. By applying zinc stearate, which has been conventionally used to prevent mechanical abrasion of the photoreceptor surface, to the photoreceptor, it is possible to further obtain the effect of preventing the photoreceptor surface deterioration due to proximity discharge. Therefore, with one coating apparatus for applying zinc stearate, both chemical deterioration due to proximity discharge on the surface of the photoreceptor and mechanical abrasion generated at a contact portion with a cleaning blade or the like can be reduced.
Further, as a protective agent 32, zinc stearate is formed in such a state that the surface of the photoreceptor is not exposed. This makes it possible to more reliably prevent chemical deterioration due to proximity discharge.
Further, the image forming apparatuses of the third and fourth embodiments have an intermediate transfer body 21 that temporarily holds an image on a photoconductor. Since zinc stearate applied to the surface of the photoreceptor as the protective agent 32 partially adheres to the surface of the intermediate transfer body, the transfer rate of the image on the intermediate transfer body to transfer paper can be improved. Further, the adhesion of paper powder to the photoconductor is suppressed, and the uniformity of charging is further improved.
In the image forming apparatuses according to the first to fifth embodiments, a non-contact charging method is used among methods of charging a photoconductor using a proximity discharge, and a minute charging is performed on an image forming area on the surface of the photoconductor. The charging roller 2a is opposed by the gap 14. As a result, it is possible to prevent poor charging due to adhesion of poor cleaning toner or paper dust and the like, and a reduction in the life of the charging roller 2a. Further, it is possible to prevent the life of the photoconductor 1 from shortening due to contact between the charging roller 2a and the photoconductor 1. Further, since zinc stearate is used as the protective agent 32, it is possible to prevent abnormal discharge that may occur when zinc stearate adheres to the charging roller 2a.
Further, in the image forming apparatuses of the first to fifth embodiments, a hard roller that does not cause bending of the charging roller 2a is used. As a result, not only uniform charging can be performed, but also a long life of the charging roller 2a can be achieved without adhesion of foreign matter. In addition, by preventing a gap change over time that occurs when a soft and weak rubber roller is used for environmental changes, stable charging can be performed.
In the image forming apparatus of the fifth embodiment, there is provided a latent image forming process cartridge 24 in which the photosensitive member 1 and the charging roller 2a are integrally detachable from the image forming apparatus main body. Accordingly, the charging gap between the photosensitive member 1 and the charging roller 2a of the main charging device 2 can be replaced while maintaining the fine gap accuracy. Further, since the precision of the charging gap can be maintained at a very small value, it is possible to prevent the protective agent 32 from adhering to the charging roller 2a when the apparatus is driven, and to prevent a charging failure caused by the protective agent 32 being erroneously attached to the charging roller 2a. Can be.
Further, in the image forming apparatuses of the first to fifth embodiments, the alternating voltage obtained by superimposing the DC voltage on the AC voltage is applied to the charging roller 2a. To be charged. Then, higher image quality can be achieved.
Further, the image forming apparatus of the third embodiment has a plurality of photoconductors 1C, M, Y, and K, and the frequency of replacement of the photoconductor 1 increases by the number of photoconductors. Since the present invention is applied to this apparatus, the replacement intervals on the photoconductors 1C, M, Y, and K can be extended and the frequency of replacement can be reduced, so that only one photoconductor is useful. Higher than equipment.
In the image forming apparatuses of the first to fifth embodiments, an appropriate amount of the protective substance is intermittently supplied to the surface of the photoconductor at a predetermined timing during non-image formation. As a result, the supply amount of the substance for protecting the photoreceptor from the deterioration due to the discharge becomes appropriate, and it becomes possible to prevent the occurrence of the abnormal image due to the excessive supply. In addition, since an appropriate amount of the protective film can be supplied onto the image bearing member, uniform charging can be performed without changing the minute gap between the charging roller and the image bearing member. In addition, by appropriately controlling the supply amount of a substance that protects the photoreceptor from deterioration due to electric discharge to the image forming area, it is possible to prevent deterioration of the photoreceptor and improve durability without generating an abnormal image. Becomes possible.
Further, in the image forming apparatuses according to the first modification of the first embodiment or the second to fifth embodiments to which this configuration is applied, an appropriate amount of the protective substance is intermittently supplied to the surface of the photoconductor at a predetermined timing during image formation. It has become. As a result, the supply amount of the substance for protecting the photoreceptor from the deterioration due to the discharge becomes appropriate, and it becomes possible to prevent the occurrence of the abnormal image due to the excessive supply. In addition, uniform charging can be performed for the same reason as described above. Further, the durability of the photoconductor can be improved for the same reason as described above.
In the modification 6 of the first embodiment or the image forming apparatuses of the second to fifth embodiments to which this configuration is applied, the brush density of the rotating brush is partially different. With this configuration, the supply of the protective agent to the photoconductor 1 can be performed intermittently. Therefore, the supply amount of the substance for protecting the photoreceptor from the deterioration due to the discharge becomes appropriate, and it becomes possible to prevent the occurrence of the abnormal image due to the excessive supply. In addition, uniform charging can be performed for the same reason as described above. Further, the durability of the photoconductor can be improved for the same reason as described above.
Further, in the image forming apparatuses according to the first to fifth embodiments, since sufficient cleaning is performed by using the spherical toner, toner contamination of the charging roller can be suppressed, and abnormal discharge can be suppressed.
Further, in the image forming apparatuses according to the modified example 7 of the first embodiment or the second to fifth embodiments to which this configuration is applied, by using the electrostatic brush cleaning which is more advantageous for cleaning the spherical toner than the raid cleaning, The cleaning property is improved, the amount of toner adhering to the charging roller is reduced, and abnormal discharge can be suppressed.

FIG. 2 is an explanatory diagram of a main part of the image forming apparatus according to the first embodiment. FIG. 2 is an explanatory diagram of a main charging device used in the image forming apparatus according to the first embodiment. FIG. 2 is a cross-sectional view of the photoconductor 1 that is a feature of the present invention. (A) is a schematic block diagram of an experimental device for confirming the effect of the present invention. (B) is an explanatory view of a state in which the surface of the photoreceptor is divided into a protective layer forming portion and a non-forming portion. The graph which showed the result of having performed an experiment continuously for 200 hours. 6 is a graph showing the change with time of the photoreceptor surface friction coefficient when zinc stearate is applied at two application amounts. 4A and 4B are explanatory diagrams showing a state in which a protective layer is provided on the surface of a photoreceptor and the surface is irradiated with particles by proximity discharge. FIG. 7 is an explanatory diagram according to a second modification of the first embodiment. FIG. 9 is an explanatory diagram according to a third modification of the first embodiment. FIG. 14 is an explanatory diagram according to a modification 4 of the first embodiment. FIG. 11 is an explanatory diagram according to a fifth modification of the first embodiment. FIG. 2 is a schematic configuration diagram of a full-color image forming apparatus according to a second embodiment. FIG. 9 is a schematic configuration diagram of a full-color image forming apparatus according to a third embodiment. FIG. 9 is a schematic configuration diagram of a full-color image forming apparatus according to a fourth embodiment. FIG. 9 is a schematic configuration diagram of a full-color image forming apparatus according to a fifth embodiment. The figure which shows the experimental result regarding the fault generation of a prior art. FIGS. 4A and 4B are explanatory diagrams showing a state of the photoconductor surface when the surface of the photoconductor is deteriorated by the proximity discharge. FIG. 4 is a diagram illustrating the hygroscopic expansion of the charging roller. FIG. 5 is a diagram illustrating a relationship between a minute gap and an image deletion phenomenon. FIG. 4 is a diagram illustrating a state in which a charging roller is in contact with a photoconductor. FIG. 3 is a diagram illustrating a state in which a minute gap is formed between a charging roller and a photoconductor. It is a figure showing the state where a protective agent has accumulated in a minute gap. It is a figure which shows the brush and elastic roller with which the protective agent was added internally. FIG. 3 is a diagram using a rotating brush as an application unit. FIG. 4 is a diagram illustrating a cleaning unit according to the embodiment of the present invention.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1, 1C, 1M, 1Y, 1K Photoconductor 2 Charging device 2a Charging roller 3 Exposure device 4, 4C, 4M, 4Y, 4K Developing device 5 Transfer device 6 Fixing device 7 Cleaning device 8 Cleaning blade 9 Static elimination device 10 Transfer material transfer Path 14 Charging gap 16 Power supply 21 Intermediate transfer member 22 Spacer 23 Paper transfer unit 24 Latent image forming process cartridge 25 Developing process cartridge 30 Protective agent application device 31 Fur brush 32 Protective agent 35a Application position 35b Retreat position 36 Application roller 37 Protective agent Auxiliary brush 38 Protective agent internal roller 50 Protective layer P Transfer paper

Claims (23)

An image forming apparatus comprising: an image carrier; and a charging member provided at a position close to or in contact with the surface of the image carrier, and charges the surface of the image carrier by a proximity discharge, and forms an image on the image carrier. At
An image forming apparatus, wherein a protective layer is provided on the surface of the image carrier to prevent chemical deterioration of the surface of the image carrier caused by a proximity discharge from the charging member to the surface of the image carrier. The image forming apparatus according to claim 1,
An image forming apparatus comprising: a protective agent supply unit for supplying a protective agent that forms the protective layer by being supplied to the surface of the image carrier to supply the protective agent to the surface of the image carrier. The image forming apparatus according to claim 2,
An image forming apparatus, wherein the protective agent supply means has a fur brush as an application member for applying the protective agent to the surface of the image carrier. The image forming apparatus according to claim 2,
An image forming apparatus, wherein the protective agent supply means includes an elastic roller as an application member for applying the protective agent to the surface of the image carrier. The image forming apparatus according to claim 3, wherein
An image forming apparatus, wherein a state before application of the protective agent applied to the surface of the image carrier via the application member is a solid protective agent molded into a predetermined shape. The image forming apparatus according to claim 3, wherein
An image forming apparatus, wherein a state before application of the protective agent applied to the surface of the image carrier is internally added to the application member. The image forming apparatus according to claim 3, 4, 5, or 6,
An image forming apparatus comprising: an application member contacting / separating means for bringing the application member into and out of contact with the surface of the image carrier. The image forming apparatus according to claim 2, 3, 4, 5, 6, or 7,
The protective agent is zinc stearate, and the protective agent supply means supplies the zinc stearate to the image carrier surface in an amount capable of preventing chemical deterioration of the image carrier surface due to proximity discharge. Image forming apparatus. The image forming apparatus according to claim 8,
An image forming apparatus, wherein the protective layer is formed in a state where the image forming area is completely covered so that at least the image forming area surface of the image carrier is not exposed. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, or 9,
The image forming apparatus is characterized in that the charging member is provided in a non-contact manner with the surface of the image carrier in the image forming area so as to face the image forming area on the surface of the image carrier with a predetermined charging gap. apparatus. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10,
An image forming apparatus, wherein the charging member is a roller-shaped hard charging roller made of a hard material. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11,
An image forming apparatus, wherein the voltage applied to the charging member is a voltage obtained by superimposing an AC component on a DC component. The image forming apparatus according to claim 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12,
An image forming apparatus, wherein the protective layer is intermittently provided on the image carrier by the protective agent supply means. The image forming apparatus according to claim 13,
An image forming apparatus, wherein the intermittent application of the protective layer is performed by applying the protective agent on the image carrier by operating the image carrier and the protective agent supply unit during non-image formation. . The image forming apparatus according to claim 13,
The intermittent application of the protective layer is performed by applying the protective agent on the image carrier by intermittently operating the protective agent supply unit disposed in contact with the image carrier during image formation. An image forming apparatus comprising: The image forming apparatus according to claim 13,
The image forming apparatus according to claim 1, wherein the intermittent application of the protective layer is performed by intermittently contacting the protective agent supply unit with the image carrier during image formation. The image forming apparatus according to claim 13,
The protective agent is an individual protective agent in which a state before application of the protective material applied to the surface of the image carrier through an application member applied to the surface of the image carrier is molded into a predetermined shape, The image forming apparatus according to claim 1, wherein the intermittent application of the protective layer is performed by intermittently bringing the individual protective material and the application member into contact with each other. The image forming apparatus according to claim 13,
The intermittent application of the protective layer is performed by an application member in which the protective agent is internally added and applied in contact with the image carrier, and the internal addition ratio of the protective material is arbitrarily changed. Image forming apparatus. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18,
The image forming apparatus is characterized in that the average circularity of the toner is 0.96 or more and less than 1.00. 20. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19.
An image forming apparatus, comprising: an intermediate transfer member that is arranged in contact with the surface of the image carrier and temporarily supports an image formed on the image carrier. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20,
An image forming apparatus, comprising: a process cartridge for integrally supporting at least the image carrier and the charging member detachably with respect to the image forming apparatus main body. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or 21,
An image forming apparatus comprising a plurality of the image carriers. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, or 22. At
The image forming apparatus has at least a cleaning unit, the cleaning unit is a fur brush made of conductive fiber, and includes a collection roller that contacts the fur brush of the cleaning unit and a scraper member thereof. An image forming apparatus, wherein a voltage is applied to a fur brush and / or a collection roller to collect toner from an image carrier using an electric field.

Images