JP2001356568A - Electrifying device and device for image formation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrifying device in which electrification at a low voltage in a non-contact state is possible without producing ozone or NOx. SOLUTION: The electrifying roller 1 as the electrifying device consists of a conductive substrate 11, conductive elastic body 12 and medium resistance layer 13 containing CNT, and electrification is carried out by the field emission.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charger and an image forming apparatus, and more particularly to a charger having improved charging efficiency and an image forming apparatus using the same.

[0002]

BACKGROUND OF THE INVENTION The present invention relates to a charger for use in an image recording apparatus such as an electrophotographic copying machine, a printer, a facsimile or the like. Application is possible. For example, in a liquid crystal factory or the like, there is an ionizer or the like used for performing antistatic. Conventional ionizers utilize the aerial phenomenon. For this reason, foreign matter is generated from the electrodes, which is a factor that lowers the yield. By using the charger of the present invention, it is possible to eliminate static electricity without generating foreign matter. When removing the normal substrate charge,
The thin line portion of the charger of the present invention is brought into contact with a charged substrate or the like. Although the effect of the present invention is to positively charge the battery, it can be expected that a static elimination effect can be expected by placing it on the ground without applying a voltage. Basically, no foreign matter is generated from the charger. At the same time, it can be expected that foreign substances existing on the substrate are adsorbed to the charger. In this case, it is necessary to configure a device for removing foreign matter on the charger side.

Here, let us return to the contact type charger used in the image recording apparatus. In the conventional charging system, a corotron using a corona discharge and a scorotron were mainly used.
However, corona discharge applies an electric field in the air,
Producing harmful substances such as ozone and NOx in large quantities,
High power consumption due to low charging efficiency, and 4k-6k
Since a high-voltage power supply of V is required, there are disadvantages that the cost is high and there is a danger to the human body. Due to recent environmental considerations, it is urgent to improve such a charging system, and there is a shift to roller charging.

[0004] Roller charging means that in the case of an image recording apparatus, a conductive rubber roller is brought into contact with a member to be charged such as a photoreceptor, and discharge is caused in a minute gap between the member and the charging roller to charge the surface of the member. Method, in which the generation of ozone is significantly reduced as compared with a corotron (1/100 to 1/100).
500). Such a method is disclosed in, for example, JP-A-7-92617 and JP-A-64-733.
No. 65, JP-A-64-54471, and the like. However, since the charging roller also applies a voltage to the minute gap between the member to be charged and the charging roller to cause corona discharge, the generation of ozone cannot be reduced to zero in principle.
Further, since ozone is generated near the member to be charged, deterioration of the member to be charged due to ozone still remains as a problem.

There are various causes for the deterioration of the member to be charged. One of the causes is unnecessary products (ozone and NOx) due to discharge.
There is a theory that these are due to chemical bonding with the surface of the member to be charged. It is considered that the chemical bond is caused by a strong oxidizing power of ozone or a nitride formed by NOx or the like. Also from such a thing, it is desired that unnecessary substances are not generated as much as possible in the charging step. Further, since the roller type generates the ozone much closer to the member to be charged than the corona, the deterioration of the member to be charged by ozone still remains as a problem. In recent years, a high electric field near the photoconductor has been suspected as a factor that deteriorates the photoconductor. In order to eliminate such concerns, a charging method at a low voltage is desired. Further, in principle, there is a certain threshold value due to discharge, and charging cannot be performed unless a voltage is applied more than that. For this reason, for example, when it is desired to charge to 100 V, it is necessary to apply several hundred volts for discharging, while 150 V for charging. Even if future low-voltage development is realized, a voltage higher than the threshold must be applied, and the merit is diminished. If possible, a method that satisfies the condition with an applied voltage approximately equal to the required surface potential is desired.

[0006] Minolta has proposed a film-type blade-type charger. This also causes a discharge in the gap between the blade and the photoconductor. A feature of this is the flexibility of the film. Thereby, it is considered that the adhesion can be improved, and uneven charging due to roughness of the photoconductor can be reduced. However, the flexibility of the film has a trade-off relationship with its durability, and there remains a problem in practical use.

Accordingly, charge injection which does not generate ozone at all has recently attracted attention. The charge injection is a method of injecting charges directly from a contact-type charger into a photosensitive layer without causing discharge. This method therefore does not generate ozone in principle. In charge injection, the lower the contact resistance, the better the contact resistance between the contact-type charger and the member to be charged and the capacity of the minute voids. For that purpose, Japanese Patent Laid-Open Publication No.
Japanese Patent No. 5449 discloses tetracyanoquinodimethane (TCN).
Q) and an electron accepting compound such as tetrathiafulvalene (T
A charge roller is made of a conductive rubber made of a polymer material having conductivity provided by replacing a charge transfer complex composed of an electron donating compound such as TF) with a polymer network.

However, J by Kagawa, Furukawa, Shinkawa and others
Apan Hardcopy 92, pp. 287-29
According to the report of No. 0, a sufficient charging voltage can be obtained for an organic photoconductor (hereinafter abbreviated as OPC) under a high humidity of 80% RH,
It is known that under a humidity of 50% RH, only half of the applied voltage is charged, and the injection speed is low. This is probably because the contact area (nip width) of the charging roller is small and the resistance of the conductive rubber is not sufficiently reduced.

That is, in order to obtain a conductive rubber having a low resistance, it is necessary to dope a large amount of the charge transfer complex. However, as the doping amount increases, the flexibility of the network of the polymer itself decreases and the rubber hardness increases. I think it is. For example, the resistance of the conductive rubber in Japanese Patent Application Laid-Open No. 6-75459 is 10 Ω · cm, and lowering the resistance of the conductive rubber while maintaining an appropriate rubber hardness is a matter of selecting a polymer material. It is not expected that this will be easy. Moreover, since the charging potential of a conductive rubber made of a polymer material having conductivity as a whole is sensitive to humidity, it is necessary to strictly control the environment, and the structure of the contact-type charger becomes complicated.

On the other hand, in Japanese Patent Application Laid-Open No. 7-140729, an electric charge is injected into a photosensitive member using a water-absorbing sponge roller. When a water-absorbing sponge roller is used, the water content of the roller greatly affects the roller resistance and the charge injection speed, and thus the charging potential may fluctuate due to evaporation of water from the roller. In order to suppress the fluctuation of the charging potential, it is necessary to strictly control the evaporation of water from the roller over a long period of time, and the structure of the contact-type charger becomes complicated and cannot be manufactured at low cost. Also, in Japanese Patent Application Laid-Open No. 9-101649, the contact area between the conductive fiber and the photoconductor is increased by making the conductive fiber of the charging brush an etching fiber or a split fiber,
It has been proposed to increase the speed of charge injection. The etching fiber is a fiber obtained by dissolving a part of the conductive fiber component with a chemical solution and dividing one conductive fiber into a plurality of fibers in the thickness direction. In addition, the split fiber is a fiber obtained by splitting one conductive fiber in the thickness direction by utilizing a difference in heat shrinkage of each part at the time of heating. By these treatments, the conductive fibers having a substantially smaller diameter are used, and the contact area with the photoconductor can be increased.

However, the tensile strength of the divided fiber is smaller than that of the conductive fiber before the division by an amount corresponding to the division. As a result, when it comes into contact with the photoreceptor, the split fibers are easily cut, and when used for a long period of time, the charging potential varies, which causes a reduction in the life of the contact type charger. Conversely, when trying to obtain a long-life contact-type charger, the number of conductive fibers cannot be increased, so that a remarkable increase in the contact area cannot be expected, and the charge injection speed does not seem to be significantly improved. As described above, some problems still remain in the charge injection method, and there are not many examples of application to an actual device.

In recent years, a charging method that is non-contact and does not use discharge has been studied under such a background. This possibility has also been reported by Professor Nakayama of Osaka Prefectural University (Japan HardCopy 97 (Preliminary Collection P221), Osaka Prefectural University Akita, Nakayama). In this method, non-contact charging that does not conform to the ordinary Paschen's rule can be performed by forming minute projections on the charger surface.
It is stated that this makes it possible to perform charging at a Paschen threshold or less, reduce by-products such as ozone in terms of cost, and reduce damage to the photoconductor.

In view of the above, it is an object of the present invention to employ a charge injection method free from problems of ozone and NOx and to solve the problems of the conventional charging brush. Another object of the present invention is to minimize the wear of the charging brush and improve the mechanical life. Furthermore, not only increase the density of the fine wires, but also provide a configuration that enables efficient charging by increasing the contact area between the fine wires and the member to be charged,
It is an object of the present invention to provide a configuration which can improve the charging ability and can solve the problems relating to pinholes and discharge.

[0014]

Here, the problems of the conventional charger and the necessity of dealing with them will be enumerated. (1) Risk of High Voltage In an electrophotographic process, corona discharge or roller-type discharge has been used as a method for charging a photoreceptor. In this case, it was necessary to apply a large voltage of several kV as a voltage required for discharging. A large potential on the order of kV is a very dangerous voltage for humans. The existence of such a large voltage in an office or the like where a copying machine is used must be avoided as much as possible. In addition, it is undeniable that electromagnetic waves are generated to some extent by using such a large voltage as an alternating current. Although scientific evidence is poor, health damage due to electromagnetic waves has been attempted in recent years. This tendency to be cautious about electromagnetic waves is expected to spread further in the future. In this sense, it is necessary to avoid using as large a voltage as possible in a space where a person works nearby.

(2) Cost and design problems In order to obtain a high voltage required for a charger, a power supply 10
0V is set to a desired voltage by a booster. This booster is a major problem in design in terms of cost. Therefore, various researches have been conducted to enable the electrophotographic process to be performed with as small a voltage as possible. In recent years, such results have been achieved, and low potential development and the like have been realized little by little. Thus, once the low potential electrophotographic process is completed, a lower charging potential in the charging process will be better. However, in the current charging using the discharge, unless at least a voltage up to the Paschen threshold is applied, no discharge occurs and charging is impossible. In such a situation, even if low-potential development can be realized in the future, a large voltage is required for charging, and the effect of low-potential development is diminished. 5 if possible
When a surface potential of 00 V is required, it is equivalent to that, for example, 5 V
A charging device that requires an applied voltage of about 50 V is desired.

(3) Photoconductor Damage In the current electrophotographic process, a photoconductor is used as a member to be charged. The photoreceptor has a role of reducing the resistance only at the portion irradiated with light, eliminating surface charges contributing to charging, and forming a latent image. In recent years, many organic substances have been used for the photoreceptor, but organic substances deteriorate much faster than inorganic substances and the like. The deterioration of the photoreceptor is much faster than other parts, and maintenance and replacement of parts are necessary to use a copier or a printer for a long time. Such a short-life component is an important improvement item in view of maintenance costs, and development of a photoconductor having a long life is eagerly desired. In addition, there is a need for an electrophotographic process that does not deteriorate the photoconductor. This deterioration phenomenon is evaluated by a decrease in the photo-charge speed, a decrease in photo-generated carriers, an increase in dark current, and the like. At present, no clear data has been collected on the cause of this deterioration, but one of the factors is considered to be the charging process. In the charging process, ionized molecules are
It is accelerated by the charging voltage. The accelerated ions collide with the photoconductor. This is very similar to surface degradation due to plasma etching in a semiconductor manufacturing process.

Hereinafter, the deterioration of the surface in the semiconductor process will be considered. Deterioration in a semiconductor process or the like is regarded as very important in the process, and a great deal of research has been made so far, and its mechanism has been largely clarified. Among the well-known research results are the correlation between the kinetic energy of the colliding ion and the atomic defect formed by it. These have been confirmed experimentally, and also verified by methods such as Monte Carlo and first-principles calculations. Atomic defects formed by such collisions cause interstitial atoms, Frenkel defects, etc.
In band theory, an inter-band level is formed. Such impurity levels reduce the mobility of electrons in the substance or serve as recombination centers. This has been confirmed and recognized experimentally. Such experiments and calculation results have been performed on compound semiconductors such as Si and GaAs. However, it is easily imagined that such physical phenomena also occur in a photoconductor made of an organic semiconductor. That is, an impurity level is formed on the photoconductor depending on the momentum of the colliding ions. As a result, electron mobility is reduced and recombination centers are formed, and hopping conduction is increased. This leads to a reduction in the photo-elimination speed, a reduction in photo-generated carriers, or an increase in dark current, which are the above-mentioned phenomena of photoconductor deterioration.
From the above, it can be seen that it is necessary to charge the member to be charged using ions (electrons) having low kinetic energy as much as possible. The kinetic energy of a charged particle is generally governed by the electric field in its vicinity, and it is therefore desirable to reduce its electric field and voltage.

(4) Limitation in Conventional Discharge It is difficult to perform charging at a low voltage with a conventional roller charger. This is because this charging process utilizes discharge according to Paschen's rule. That is, the threshold is present in the Paschen rule, and discharge does not start unless a voltage exceeding the threshold is applied. Therefore, for example, 500
Even when a charging potential of about V was required, a voltage close to 1 kV had to be applied. This can be easily understood from the relationship between the charging potential and the applied voltage shown in FIG. Although it is desired to reduce the applied voltage from the above-described problems, it is impossible to reduce the voltage when a conventional discharge phenomenon is used.

(5) Requirement of non-discharge In the field emission charging method, there is a possibility that discharge occurs even though the voltage is low. When a discharge occurs between the charger and the member to be charged, positive and negative charges are generated, respectively.
Each is moved by an electric field. Originally, the charge required in the present invention is only one polarity charge that charges the member to be charged. In other words, it is only necessary that the diode has the monopolar property of a diode, and it need not be a bipolar. Field emission is monopolar, whereas discharge is bipolar. If it is bipolar, charges unnecessary for charging will collide with the charger surface. The collision may cause deterioration of the charger surface and heat generation. This is the same as that exposed in the plasma, and the chemical reaction etching and the sputtering effect are considered. In order to eliminate such a problem, it is desired that even when a voltage is applied, the gas is ionized and a discharge phenomenon does not occur.

(6) Problems of ozone In the conventional charging by electric discharge, air is ionized to supply electric charges. Therefore, generation of active oxygen generated at that time and ozone which is a by-product thereof is inevitable. It is well known that ozone affects the human body. Therefore, it is desired to realize a charging process that does not generate ozone by examining the generation mechanism and removing the cause. As described above, in a roller charger or the like, charging is performed by applying an electric field higher than a discharge threshold given by Paschen's law. With such a high electric field, hazard (deterioration) of the member to be charged and generation of ozone are inevitable. If possible, it is desired to perform charging at a low voltage.
The charge injection method is effective as a method for charging at a low voltage. In this method, the charger and the member to be charged need to be in contact with each other. The problem with this method is that the charging speed depends on the contact resistance, and a sufficient charging speed cannot be obtained with a conventional charge injection type charger. Further, since a stable contact is an absolute condition for a contact-type charger, it is necessary to adopt a method of using a flexible member having rubber elasticity on the surface of the charger. However, it is difficult to select a material having ionic conductivity and rubber elasticity and capable of controlling the resistance. In addition, problems such as poor charge injection due to the particle size and the like have been reported for lowering resistance by fillers and the like (Kagawa: Japan).
n Hard Copy (1992) p31).

For this reason, it seems that adoption of the charge injection method to an actual machine is difficult unless such problems are solved. Against this background, there is a demand for a new type of charging that is neither a contact-type charge injection nor a quasi-parallel plate type discharge based on Paschen's rule. Under such conditions, the possibility of electrification due to field emission has been reported (Japan Hard Copy 1997 (Preliminary Collection P221), Osaka Prefecture University Akita, Nakayama). In this report, the current-voltage characteristics in the atmosphere are measured, and a sufficient current is obtained for charging. The threshold value is also about 200 V, which is smaller than the threshold value of about 400 V (the gap length is set to 10 μm or more) which can be considered from Paschen's rule. However, their report only mentions the possibility of application to the charging process in the field emission, but does not present the problem as in the present invention. The present invention presents a problem different from this report, in which the use of this field emission phenomenon (or non-Paschen discharge) reduces the generation of ozone and NOx, and reduces the hazards to the photoreceptor. . In addition, the necessary driving range is determined.

(7) Shape of Micro Protrusions In a conventional parallel flat plate, Paschen's law is established, and it is difficult to sufficiently charge at a voltage lower than that. For this reason, a structure deviating from Paschen's rule is required for charging by discharging. Further, even in the case of assuming a field emission that does not cause a discharge, an ordinary parallel flat plate has a very high threshold value, and sufficient charging cannot be performed with an applied voltage. Therefore, microscopically, the realization of a configuration that breaks the parallel flat plate is considered. The microprojection shape is one option for that.

(8) Insufficient Amount of Charge Supply Conventionally, a method has been attempted in which minute projections are formed on the surface of a charger to reduce the discharge threshold voltage in Paschen. The presence of the microprojections causes the electric field concentration there,
Compared to a parallel plate, a higher electric field region can be formed around the microprojections. Discharge occurs in this region, and the generated charge is transferred to the member to be charged, whereby charging can be performed. As a result, the normal discharge threshold can be slightly reduced, and damage to the photoconductor, generation of ozone, and the like can be reduced. However, at present, even if minute projections are formed, the amount of electric charge generated there is small, and such an effect does not appear remarkably. One of the problems here is to generate a sufficient charge around the microprojections. Currently possible solutions include the following:

In this way, the high electric field region can be increased. However, even if the amount of electric charge is obtained, if the voltage becomes higher than the threshold value, the battery will fall over. Also, no matter how high the voltage,
Since the mean free path does not change, it is unlikely that the charge generation efficiency is improved even with the high electric field. Miniaturization of micro-projections By miniaturizing micro-projections, the electric field concentration increases strongly,
Conversely, the high electric field region formed thereby is reduced. That is, in the shape of the minute protrusion, there is a trade-off relationship between the electric field strength and the area size. Therefore, an increase in generated charge cannot be expected only by miniaturization. Reducing the gap between the microprojections and the member to be charged This makes it possible to obtain a high electric field with a low voltage. Although the applied voltage can be reduced, the electric field generated near the member to be charged also increases. This leads to an increase in the momentum of the colliding ions, and the damage to the photoconductor increases. Further, since the charged body functions as a capacity, the gap becomes a series capacity of the charged body. For this reason, the applied voltage is distributed by this series capacitance. When the size of the gap is smaller than the thickness of the member to be charged, a larger applied voltage is applied to the member to be charged. Therefore, the smaller the gap is, the more the voltage applied to the gap is saturated. Increasing the number of microprojections There is a method of increasing the number of microprojections per unit area, that is, increasing the surface area of the microprojections. Thus, the formed high electric field region increases. However, there is a limit in the case of minute projections projecting from the parallel plate. Further, when the distance between the projections is reduced, the projections work as if they were parallel plates, and the electric field concentration does not occur. Therefore, it is desired to increase the amount of the fine protrusions without increasing the density of the fine protrusions.

(9) Incorporation of Foreign Substances In a non-contact type charger having a structure in which minute projections are formed, a gap control of several μm units is required between the surface of the charger and the member to be charged. As a method for solving this, a blade-type or roller-type charger has been conventionally considered. In the charger having such a shape, when minute foreign matter such as toner enters between the charger and the member to be charged, it is difficult to control the gap. For this reason, in the case of the roller type, measures such as providing a device that can always be cleaned and installing a cleaner on the member to be charged have been considered. However, such measures are difficult in principle with a blade-type charger. Further, it is impossible to completely remove foreign matters such as toner by using only the cleaner. The conventional cleaner has only a stance function of reducing a large amount of residual toner and the like. In comparison, the level of foreign matter removal required here is much higher. Regarding the blade type, if even one toner remains, the gap between the blade type charger and the member to be charged is widened by at least the toner in the toner portion, and accurate gap control cannot be performed. Necessary gap control is on the order of several μm, whereas the particle size of the toner is as large as about 10 μm. Therefore, the portion where such residual toner exists cannot be sufficiently charged. The same can be said for the roller type.
With respect to the blade type, a roller that does not rotate in the same cycle as the member to be charged can be expected to have a slight improvement, but not a fundamental improvement. As described above, the gap control of the non-contact non-Paschen type charger, which is based on the conventional surface roughness, has a problem from the viewpoint of foreign matter and the like.

(10) Brush Structure In the uneven structure as described above, there is a limit in improving the surface area. A method of more positively increasing the unevenness is desired. The shape of the structure, which can be considered at several thousand dpi, is on the order of μm. Difficulties of such order are accompanied by difficulties. For example, in a method such as resin molding, it is very difficult to produce the mold alone. As described above, as a method of molding this structure, a simple method and a structural shape capable of taking such a method are desired. One of the methods is a brush structure.

(11) Deformation of Brush The distance between the minute projections formed on the brush surface and the member to be charged must be within a certain range. And
The order is desirably about several μm. If the brush is made non-contact, the distance between the brush and the member to be charged must be accurately controlled. Further, in the case of a simple uneven shape, the uneven shape may be changed due to the friction and wear. A certain degree of wear on the charger side is necessary so that the member to be charged does not wear. For this reason, even if it has an uneven shape, its surface may become flat due to wear. If possible, a structure is desired that does not significantly reduce the surface area even if it is worn. The force of the pressing force related to friction also requires fine adjustment. In order to create such a delicate adjustment mechanism, we would like to avoid it, if possible, due to cost and other problems. It is desired to control the pressing pressure and the distance between the minute projection and the member to be charged by a method as simple as possible.

(12) Microprojection material When microprojections are used, it is necessary to reduce the field emission threshold with a structure having a very small size. It is theoretically said to be on the order of several nm, but such a phenomenon has been confirmed experimentally on the order of several tens of nm.
This means that even if a structure on the order of tens of nanometers is made experimentally,
This is because the structure at the tip is on the order of several nm. As a method for forming a structure on the order of nm or several tens of nm, there is a method using a photoresist / mask cultivated in semiconductor technology or the like. However, forming by such a method is very costly. The present invention does not require the accuracy of size and shape. In view of this, a low-cost manufacturing method is desired. In the present invention, a method for realizing this using nanotubes and whiskers is considered.

(13) Requirements for microprojection substance A structure satisfying such conditions must be formed, but this structure has further conditions that must be satisfied. The surface of the charged body receives a mechanical shock such as contact with the charged body. Also, since a structure is considered in which a part of the charger moves so as to slide on the surface of the member to be charged,
Slidability is also required. Considering various situations, demands for microprojections include fineness (high aspect ratio), conductivity, friction resistance (mechanical strength), flexibility, chemical stability, and cost.

(14) Gap formation In the non-contact type charger described above, it is considered that charging will not occur unless the distance from the member to be charged is kept to about 100 μm or less. This can be seen from the results of previous Osaka Prefectural University experiments. As the gap distance was increased, the charging start threshold value was increased, and it was confirmed that the gap distance was about 100 μm, which was almost the same as the threshold value of Paschen's rule. That is, if the gap distance is not controlled to be less than that, discharge occurs and the object of the present invention cannot be achieved.
However, it is difficult to accurately control the distance of the gap between the surface of the charger and the charged object to about several tens of μm due to roughness of the charged object and fluctuation of rotational driving. Also,
It is expected that the charging potential greatly depends on the gap and that the control changes over time due to friction and wear. Therefore, a mechanism that can generate a desired gap by changing the viewpoint and performing control as roughly as possible is desired.

(15) Charge Injection and Combination In the non-contact type charger described above, charging in the contact area cannot be performed. For this reason, in the contact area, charging failure may occur, and image damage such as whitening may occur. In a charger which requires a contact point, it is necessary to charge the contact point by some method.

(16) Countermeasures against pinholes It is also important to consider the resistance value of the charger. Since the member to be charged is a very thin film of several tens of μm, there may be a case where a pinhole with a hole partially exists. When a pinhole is present, when a charger contacts the area, charge concentration occurs at this point, and a short circuit occurs. When a short circuit occurs, no voltage is applied to other areas. In addition, since a large current flows in the short-circuited portion, problems such as deterioration of the peripheral member to be charged due to heat generation and enlargement of the pinhole region occur. Therefore, it is necessary to take measures against pinholes. As an optimal method of this measure, a method of controlling the resistance of the charger can be considered.

(17) Charge-Controlling Resistance Value It is effective to increase the resistance value Rb of the charger surface as a measure against pinholes. However, the charging speed decreases by increasing the surface resistance Rb. This can be understood from an equivalent circuit as shown in FIG. 3, and it is necessary to suppress the resistance to a certain fixed value or less. From this equivalent circuit, not limited to charge injection,
Sum of the resistance value Rb of the charger and the contact resistance value Rc, Rb + Rc
= Rd indicates that the charging speed is determined. The charging speed and the charging capability must maintain the capability required from the electrophotographic process. That is, there is a resistance value Rd determined from the required charging speed, and the resistance value on the charger surface needs to be smaller.

(18) Relationship between Friction Speed When a gap is formed due to surface roughness, a charged body and a charged body come into contact with each other in a certain region. When the member to be charged is driven in the state of contact, friction occurs at the interface. The friction causes the charged object and the charger surface to be worn. Normally, the object to be charged is very thin, several tens of μm.
Therefore, there is a problem in the image formation including the life of the surface that is worn out and scraped off even at several μm. If it can be removed by about several μm, the effect is smaller if the surface on the charger side is removed.

(19) Blade In the conventional roller-type charger, an arbitrary point on the charger-side surface comes into contact with only one fixed point on the member to be charged. If the point is a contact area, it is a contact point area, and if it is a gap area, it is a gap area. Even in the gap region, the surface potential varies depending on the size of the gap. That is, when the charger and the member to be charged come into contact with each other without slipping, unevenness in potential occurs due to the size of the gap. Potential non-uniformity causes image non-uniformity as it is, which is a major problem. In addition, by using a blade type, the applied voltage can be applied stepwise, the potential difference between the charger and the charged object in each block can be kept low, and the potential difference can be made equal to or lower than the discharge threshold voltage. In addition, the problem caused by the discharge can be solved.

(20) Since there is no cleaner device in the polishing roller blade type, there is a possibility that toner or other fine dust may enter between the charger and the member to be charged. In such a state, formation of a uniform gap is hindered, which is a serious problem in image formation. Therefore, a process design that is as resistant to such contamination as possible is required. Further, CNTs (carbon nanotubes) are provided on the blade surface, but wear thereof is inevitable. In the case of a blade as well, contact with the member to be charged causes C
There is a possibility that the resin fixing the NT is scraped and the CNT is constantly exposed. The control is determined only by the member to be charged and the fixed resin. In this regard, a configuration that is easier to control is desired.

(21) Diversion to Transfer, etc. In a copying machine or a printer using an electrophotographic process, a charging phenomenon is used for various purposes other than the charging device for charging the photosensitive member. For example, a transfer process for transferring the toner from the photoconductor to the paper corresponds to this. An object of the present invention is to remove ozone, high voltage, and the like in an apparatus using an electrophotographic process. In other words, even if the present invention is used only for the charger for charging the photosensitive member, if the conventional charger is used for other parts, the above problem can be solved as a final device. Not. In order to achieve the object of the present invention, charging in other parts must be considered. From the above perspective,
The present invention solves the problem of the conventional charger, and uses a non-contact type low-voltage charger that does not generate ozone or NOx without using a discharge according to Paschen's law and this charger. It is an object of the present invention to realize an efficient image forming apparatus in which the present invention is applied to charging, transfer, static elimination and the like.

The problems to be solved by the present invention, that is, the problems of the prior art are specifically listed as follows. The conventional charger requires a high voltage, and the following three problems are caused by the high voltage. Danger to human body due to high voltage Cost problem of high voltage device Damage to charged body due to high voltage flying charge However, there is a limit to the conventional charging by Paschen's law.

According to the second aspect of the present invention (non-discharge) In the discharge, charges unnecessary for charging collide with the surface of the charger. The collision may cause deterioration of the charger surface and heat generation.

According to the third aspect of the invention (ozone / NOx), in the conventional charging by electric discharge, air is ionized to supply electric charges. Therefore, generation of active oxygen generated at that time and ozone which is a by-product thereof is inevitable. It is well known that ozone affects the human body. Similarly, damage to the charged object due to NOx has been reported.

The invention of claim 4 (projection shape) In order to have the features described in claims 1 to 3, Paschen's law is established in a conventional parallel flat plate, and it is difficult to achieve sufficient charging below that.

The invention of claim 5 (irregularities, lack of charge supply amount) At present, even if minute projections are formed, the amount of charge generated there is small. Increasing the number of microprojections per unit area, that is, increasing the surface area of the microprojections.

The invention according to claim 6 (Ra> 10 μm: entry of foreign matter) When minute foreign matter such as toner enters between the charger and the member to be charged, it becomes difficult to control the gap.

The invention of claim 7 (brush) In the above uneven structure, there is a limit to the improvement of the surface area. A method of more positively increasing the unevenness is desired. As a method for molding this structure, a simple method and a structural shape that can be used for the method are desired.

The invention according to claim 8 (brush structure) It is desired to have a structure that does not significantly reduce the surface area even if it is worn. The force of the pressing force related to friction also requires fine adjustment. It is desired to control the pressing pressure and the distance between the minute projection and the member to be charged by a method as simple as possible.

The invention of claim 9 (projection substance) As a method for forming a projection, a low-cost manufacturing method is desired.

The tenth invention (CNT) In order to satisfy the above-mentioned functions, it is necessary to realize fineness and conductivity. The surface of the charger is subjected to a mechanical shock such as contact with the member to be charged. Therefore, friction resistance, flexibility, chemical stability, slidability, and the like are required.

According to the eleventh aspect (space shaping), in order to realize as low a cost as possible, rough control is performed.
A mechanism for forming a space is desired.

In the twelfth aspect of the present invention, a contact point is required for forming a space. At this contact point, the contact point is required to be improved in order to improve the charging efficiency due to white spots without charging. It is necessary to perform charging at this contact point.

The invention of claim 13 (measures against pinholes) It is necessary to take measures against pinholes present in the member to be charged.

The charging speed is reduced by increasing the surface resistance. This can be understood from the equivalent circuit shown in FIG. 4, and it is necessary to suppress the resistance to a certain value.

The invention according to the fifteenth aspect (relationship of the wear rate) Normally, the charged body is very thin and several tens of μm in size. There is.

Inventions of Claims 16 to 18 (Sliding) In a conventional sliding roller type charger, potential unevenness directly causes image unevenness, which is a major problem. Further, the voltage cannot be changed stepwise.

The invention according to claim 19 (polishing apparatus) The projections are shaved due to wear, and new projection forming means is required.

Even if the present invention is applied only to the charging device for charging the preceding photoreceptor, if the conventional charging device is used in other portions,
As a final device, the above problem has not been solved.
In order to achieve the object of the present invention, charging in other parts must be considered.

Next, the objects of the present invention are listed as follows. It is an object of the invention of claim 1 to provide an electric device using a charging method at a low voltage, and an object of the invention (non-discharge) of claim 2 is to provide a charging device using a charging method that does not rely on discharging. The invention of claim 3 (ozone / NO
The purpose of x) is to provide a charger using a charging method that does not emit ozone or NOx.

The objects of claims 4 and 5 are as follows.
A third object of the present invention is to provide a charger having a structure capable of realizing the characteristics described in the third aspect, and to provide a charger without uneven charging. It is an object of the present invention to provide a charger which realizes manufacturing the structures of Nos. 4 to 6 at low cost, and to provide a charger free from uneven charging.

The object of claims 9 to 11 is that of claim 4
To provide a charger that realizes the manufacturing of the structures of (1) to (6) at a low cost; It is an object of the invention (countermeasures against pinholes) to provide a charger in which measures against pinholes present in an object to be charged are provided. An object of the present invention is to provide a charger capable of charging a potential.

It is an object of the present invention to provide a charger for improving the life of a member to be charged. The object of the invention (polishing apparatus) of claim 18 is to provide a charger having a long life, and the purpose of the invention (diverted to transfer, etc.) is to provide a long life. Accordingly, an object of the present invention is to provide an image forming apparatus that does not emit ozone or NOx.

[0060]

According to the present invention, at least a space is provided between the surface of a charger and a member to be charged, and a voltage is applied between the surface of the charger and the member to be charged. Then, in the charger for charging the object to be charged and transferring the charge, the charging is performed at least by a field emission phenomenon. In the image forming apparatus,
It is characterized in that such a charger is used in an electrophotographic process. As a result, it is possible to realize a charger capable of charging at a low voltage without generating ozone or NOx without using discharge in accordance with the Paschen's rule, and to realize a safer and more efficient image forming apparatus. .

[0061]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a charger according to the present invention will be described in detail with reference to the accompanying drawings. As a measure to solve the problems of high voltage danger, cost, design problems, and photoconductor damage problems mentioned above and to overcome the limitations of the conventional discharge method, the A voltage is applied to charge the object to be charged, and charging is performed using at least a field emission phenomenon in a charger having at least a space gap between the surface of the charger and the object to be charged in a region where the charge is transferred. It is characterized by the following.

FIG. 14 is a schematic diagram of the above equation. For example, when there is a protrusion, an electric field concentration occurs, and a high electric field is generated near the protrusion. This high electric field region becomes smaller as the distance from the electrode increases. The dotted line shown in FIG. 14 illustrates the interface where the electric field is 3.5E7 (V / m). Also,
The broken line indicates the interface at a distance of 8 μm from the electrode. Under the condition that the positional relationship between these two interfaces is the above equation, no discharge occurs according to the ordinary Paschen's rule. This will be described below.

Usually, in the discharge phenomenon, electrons accelerated by an electric field collide with gas molecules, and new charges are generated there. By repeating this, electrons are avalanche amplified. To accelerate the accelerated ionization of gas molecules, 1
It is said that 2.06 eV (oxygen molecule) or more is required. To accelerate the electrons by this energy during the mean free path (0.36 μm), an electric field of 3.5E7
(V / m) or more is required. That is, if this electric field does not exist, no discharge occurs.

Conditions necessary for forming a discharge include:
There is a distance between the electrodes. It is said that if there is some distance, avalanche does not occur sufficiently and the discharge does not last. This distance is set to 8 μm. In other words, even if a necessary electric field exists under the above conditions, discharge is not established unless the electric field exists in a sufficient region.

As a condition that does not cause a discharge, the electric field K1 (x) in the space satisfies the following condition. That is, in the range of x> 8 μm,

It is assumed that K1 (x) <3.5E7 (V / m). Here, K1 (x) is an electric field depending on the distance x from the charger electrode, and x is the distance from the electrode. Further, as a condition of the field emission phenomenon that does not generate ozone, K2 (x) satisfies the following condition in an electric field in the gap space. That is, x> 0.
In the range of 34 μm,

It is assumed that K2 (x) <1.5E7 (V / m). Here, K2 (x) is an electric field depending on the distance x from the charger electrode, and x is the distance from the electrode. In order to prevent deterioration of the photoreceptor, generation of ozone and NOx must be completely prevented. Further, even if the amount is very small, the influence becomes large as long as the place of occurrence is near the photoconductor surface. Ozone and NOx are rarely present in the atmosphere. It is a principle part of the subject of the present invention that such substances are generated by charging. In other words, it is necessary to have an approach that physically captures the generation phenomena such as ozone and solves them from the generation mechanism.

The generation of ozone is believed to occur through several processes. The main ones are described below.

E + O ₂ → e + (O ₂ *) → e + 2O O + O ₂ + M → O ₃ + M By reducing electrons occurring in such a process, generation of ozone can be reduced. However, these electrons are a necessary factor for charging the photoreceptor, and reducing them alone will overturn. Therefore, it is sufficient that the above equation does not hold even if electrons exist. Here, attention was focused on activated oxygen (O ₂
*) Is the kinetic energy of the electrons needed to produce The energy is set to 5.1 eV. That is, even if an electron exists, its kinetic energy is 5.
What is necessary is that it does not become 1 eV or more. Then, the following calculation can be performed.

W = L * K where L is the mean free path and L = 0.34 μm W is the energy obtained by the electric field K. From this, if the electric field K is K = 1.5E7 (V / m) or less, 5 It turns out that it does not become .1 eV. From this, if the electric field is set to 1.5E7 (V / m) or less, no ozone is generated. Next, a method that can be drastically reduced even in the case of some occurrence will be examined. The electrons in the electric field
The kinetic energy is obtained only after running μm. That is,
This electric field must occupy a region that is at least 0.34 μm or longer. As described above, generation of ozone can be reduced by setting the electric field region of 1.5E7 V / m or more to a distance of 0.34 μm or less from the electrode.

Next, conditions for breaking a parallel plate will be considered. For this purpose, minute projections are formed on the surface of the flat plate. Even if the surface shape is not a parallel plate, no discharge is generated within the conditions described above. At the same time, mass production of ozone and the like can be avoided. However, at the same time, with such a shape, the electric field at the tip is 7E
May exceed 9 V / m. Field emission occurs under such a strong electric field. Further, there is a possibility that a discharge phenomenon that cannot be explained by the ordinary Paschen's rule or the like may occur.

Next, consideration will be given to a measure to cope with the shortage of the charge supply amount which occurs when the condition for breaking the parallel plate is adopted. There is at least a space between the area to be charged and the charger,
A non-contact type charger having a micro-projection structure on the surface, which is non-contact type which charges in that area, is characterized in that the surface of the charger is not at least flat but has irregularities.
This is because, as shown in FIG. 12, the member for supporting the fine projection is usually formed of a flat surface, but the portion is intentionally provided with irregularities. If these irregularities are not flat,
A material that can exhibit the effect and that is accidentally formed in production may be used. In addition, as a method for coping with the problem such as mixing of foreign matters, the radius Ra of the unevenness on the charger surface is set to 10 μm or more.

This depends on the size of the toner mixed as a foreign substance. The toner is at most about 10 μm,
By setting Ra to a value higher than that, the toner is pushed into the concave portion. This can be confirmed by experiments performed with different roughness. When Ra is about 5 μm, the white spot defect image of the image increases. This was solved by setting Ra to 10 μm.

Further, in the case of the ordinary uneven shape, there is a limit in improving the surface area. As one solution to this, a brush in which fine wires are bundled is formed on the charger surface. As a result, the unevenness as shown in FIG. 12 can be realized with a high aspect ratio of the brush. FIG. 13 is a diagram imagining this.
As a method for controlling the distance between the minute projections and the member to be charged, the brush is configured to be in contact with the member to be charged and bend.
A part of the brush makes contact, but in a part other than the contact area, a predetermined space is formed between the brush and the member to be charged. This space is used as a charging area. When the brush bends, it becomes as shown in FIG. This sectional view is FIG.
The distance from the minute protrusion to the member to be charged depends on the brush diameter. By controlling the brush diameter, the distance from the minute projection to the member to be charged can be easily controlled.

[0075] A nano-sized nano material or a whisker having a nanometer order is used as a micro-super-super material constituting a micro-projection. As a method that has recently attracted attention, there is a method that utilizes self-organization and self-assembly phenomena in vapor phase growth and the like. In this method, one formed by a method such as quantum dot formation with GaAs, NaCl or the like,
There are other well-known substances, such as fullerenes and zeolites, which are on the extension of macromolecules. The microstructure obtained by such a method generally has n
It is of the order of m, and can be synthesized in large quantities at very low cost from its production method.

In the present invention, since the field emission is performed from the fine projections, it is desirable that the aspect ratio be some extent. The electric field is concentrated by having a sharp pointed structure, and the field emission occurs. As such elongated structures, for example, whiskers, C (carbon; the following Roman letters are element symbols) nanotubes, CB nanotubes, WS nanotubes, SiC nanotubes, and CNB nanotubes are well known. All of these have a diameter on the order of nanometers, are optimal for the purpose of the present invention, and can be formed at very low cost. In the present invention, the size of the elongated structure indicates the diameter of the distal end, but does not indicate the length.

In the present invention, as the fine projections, CN
T (carbon nanotube) is used. Generally, a resin, a rubber, or the like is used for the surface member of the charger due to its processing advantage. Since such an advantage is also required in the present invention, such a member is desired. Further, in order to satisfy the above conditions, it is desired to form fine projections on the surface. The microprojections need to be resistant to mechanical friction such as contacting the photoreceptor. It is optimal to use CNT from such a request.

As the name suggests, CNT is known to have a diameter on the order of nm and a length on the order of μm.
It was discovered in 1991 by Sumio Iijima of the NEC Basic Research Laboratory. CNT has a tip diameter on the order of nm and is liable to cause field emission. Because of its seamless structure even at the atomic level, cracks and the like are unlikely to occur even under external stress. In addition, since it is also excellent in flexibility, stress can be reduced. The material is made of a carbon graphite layer that is seamlessly formed into a cylindrical shape, and the layer also has various types from a single layer to several hundred layers. Further, there are various types, such as a closed end including a five-membered ring of carbon or the like, and an open end as it is. Initially, its production method was based on the arc discharge method, but it has been made in large quantities by a CVD method or a laser ablation method using a more efficient metal catalyst, and is becoming a familiar material. .

Research on basic physical properties has also been made energetically since its discovery from the peculiar shape. In particular, its electrical characteristics are metallic or semiconductor-like.
Predicted from first-principles calculations. In addition, various things have been studied in spite of its small size and difficult to evaluate, such as its extremely high mechanical strength and its ability to return to its original state without breaking even when bent sharply. I understand. Also,
Since the surface is formed of a graphite layer, it is also known that the surface is very chemically stable. On the other hand, it is appropriately dispersed in an epoxy resin or the like, has very high adhesion at the interface, and can be fixed firmly. For this reason, handling, etc., has been becoming easy, for example, by embedding the resin in a resin having a nm size.

Further, since the material is close to graphite, it has a potential as a solid lubricant. In addition, in previous reports, it has been reported that the coefficient of friction in the nm order is smaller for sliding friction than for rolling friction. Although there have not been many reports on the lubricity of CNTs, they are also expected to have high potential as a lubricant. From the aspect of application, a high non-uniform electric field can be generated due to the size of the aspect and the conductivity, and it is attracting attention as a field emission source of a field emission type display. In addition, due to its high surface properties, it has also attracted attention as a battery electrode or a gas-adsorbing substance, which has conventionally used activated carbon or the like. Further, as an example utilizing mechanical strength, there is a report of dispersing in a resin to strengthen the resin (0. Louri).
e A. P. L. 73 (1998) 3527) and reports on application to actuators in the micro world (Ray)
H. Baughman SCIENCE 284 (19
99) 1340).

As described above, the CNT generally satisfies the requirements for the above-described fine wire, and the present invention considers that this material is optimal. However, in the present invention, it is not necessary to clear all of the above requirements. Can be used. Examples of a method for manufacturing a charger using CNT include a resin dispersion type, an electrophoresis type flocking type, and a surface growth type by CVD.

The gap is formed by the surface roughness of the charger and the surface roughness of the member to be charged as described above. In addition, a charge injection method is used together so that charging can be performed even in the contact area.

As a countermeasure against pinholes, the specific resistance Rb of the surface member is set so that the following equation is satisfied.

Ro * Lo * f / 100 <Rb * Lb * S1 Here, ratio of pinhole area to charged area = 1: S1 f: ratio of allowable voltage drop (%) Ro: specific resistance of member to be charged (Ω · m) Lo: thickness of the member to be charged (m) Rb: specific resistance of the surface member of the charger (Ω · m) Lb: thickness of the surface member of the charger (m) This is shown in FIG. As shown, the voltage distribution based on the ratio of the resistances is calculated.

The pinhole part is as if the resistance Ro of the photoreceptor is
An equivalent circuit without p is obtained. At this time, if Rb is small, the current concentrates on the pinhole portion and the current flows on the non-pinhole portion, so that charging cannot be performed. Therefore, by designing the resistance value on the charger side as described above, a design is made so that current does not concentrate only on the pinhole. That is, if the resistance of the non-pinhole portion is smaller than the resistance value of the pinhole portion, the current flowing therethrough increases and charging can be performed. If this is written down into an equation, it suffices if the formula is “pinhole portion resistance <non-pinhole portion resistance”. In addition, since resistance = specific resistance * thickness * area, the form is as shown in the above equation.

In order to improve the effect of preventing pinholes without lowering the charging speed, the sum Rd of the resistance Rb of the charger and the contact resistance Rc should satisfy the following expression.

Vss <Vs (Rd) Vs (Rd) = Va ｛1-exp (-w1 / v1C1R
d)｝ Here, Vss: required charging potential Vs (Rd): charging potential determined by the resistance of the charger w1: nip width (m) v1: charging linear velocity (m / sec) C1: charged body capacity (F Va: applied voltage (V) As shown in the left branch of the equivalent circuit in FIG. 3, the equivalent circuit of the charging ability is a series circuit of a resistor and a capacitor. By expressing equivalently in this way, it is possible to solve analytically. However, the resistance Ro of the member to be charged was omitted because it was sufficiently large.
From this equation, it is clear that the charging potential depends on the resistance of the charger, and by controlling this, sufficient charging can be performed.

A current flows through the charger to perform charging. There is a resistance Rb of the charger as a physical value that defines the amount of current.
It is the current value that is controlled by the resistance value. Since the current is the amount of electric charge flowing per unit time, when the current value is determined, the charging potential and the linear velocity (this is determined by the specifications of the image forming apparatus, and is determined by how many images are created per minute. ) Are regulated. Conversely, when the linear velocity and the required potential are determined in the product specifications, the current value and the resistance value Rb are determined correspondingly. I wrote this down in the equation. The value of the flowing current is determined by CR from the above equivalent circuit. C
C in R is the charged body capacity C1, and R is Rb of the charger.
It is. In a series CR equivalent circuit, a time change of a current value flowing therethrough can be described by a logarithm. Further, since the charging potential charged by the current is proportional to the current value, it can be written in the same form. Therefore, the surface potential at a certain time T1 can be expressed as Vs (t) = Va {1-exp (-t / C1Rd)}. Here, the time is the charging time,
Since the charging time T1 is equal to a value obtained by dividing the nip width by the linear velocity, the charging time T1 is multiplied by T1 = W1 / V1. Substituting this gives the above equation.

In the magnitude relationship between the mechanical strength of the charged object and the mechanical strength of the charger, the mechanical elasticity (strength) of the member on the surface of the charged device is made smaller than that of the charged object. The shape of the charger is a blade-type shape, so that the surface of the member to be charged slides to increase the contact area. The shape of the blade type has the advantage of a large contact area as described above. It is susceptible to minute dust. The shape of the charger is a roller type, and the charger is provided with a cleaner for polishing the surface of the charger. When diverted to a transfer device or the like, the above-described charger is used in at least one of the processes using static electricity in the electrophotographic process, such as charging, transferring, and discharging.

[0090]

The present invention will be described below with reference to specific examples of the present invention. Embodiment 1 In this embodiment, a roller-type charger and a member to be charged adapted thereto will be described for a roller-type charger, and thereafter, an operation method thereof will be described.

(1) Charger (Roller Type) FIG. 1 is a configuration diagram of an image forming apparatus using the charger of the present embodiment. In FIG. 1, reference numeral 1 denotes a charging roller which is a charger of the present embodiment, reference numeral 2 denotes a cleaner, reference numeral 3 denotes a photosensitive member which is a member to be charged, reference numeral 4 denotes a voltage application step, and reference numeral 5
Denotes an exposure step, 6 denotes a development step, 7 denotes a transfer step, 8 denotes a fixing step, and 9 denotes a light irradiation step. In this embodiment, a roller type charger (charging roller) as shown in FIG.
Use 1. The charging roller type is characterized by having CNTs on its surface. As shown in FIG. 1, the charger 1 of the present embodiment is in the form of a roller and has a function of applying a voltage. As shown in FIG. A laminated structure composed of the elastic body 12 and the medium resistance layer 13 containing CNT on the surface is formed.

The base 11 of the charging roller 1 is made of aluminum, SU
It is preferable that a conductor film is formed on the surface of a metal conductor such as S or Fe, or an insulator such as plastic (eg, acrylic resin). If the volume resistance is 1E-2 Ω · cm or less, resins and rubbers mixed with various conductive materials can also be used. This time, aluminum was adopted because of the manufacturing costs of the manufacturing process. After processing aluminum into a cylindrical shape having a diameter of 20 mm and a thickness of 2 mm, the surface is roughened to the order of 0.1 mm with a grinder so as to improve adhesion. On top of this, a conductive elastic body 12 having a thickness of 5 mm is attached as shown in FIG.

The conductive elastic body 12 is obtained by dispersing conductive particles in a base material having elasticity. Various thermoplastic elastomers such as polyester-based elastomer, polyamide-based elastomer, polyurethane-based elastomer, soft vinyl chloride resin, styrene-butadiene-styrene block copolymer elastomer, and acrylic elastomer are suitable for the base material. 6, nylon 6,
6, polyamides, copolyamides such as nylon 6-nylon 6,6 copolymer, nylon 6,6-nylon 6,10 copolymer, and alkoxymethylated nylon such as methoxymethylated nylon, or modified products thereof, silicone Resins, acetal resins such as polyvinyl butyral, polyvinyl acetate, ethylene-vinyl acetate copolymer, ionomer, and the like can also be used. Examples of the rubber include natural rubber, butadiene rubber, styrene rubber, butadiene-styrene rubber, nitrile-butadiene rubber, ethylene-propylene copolymer rubber, ethylene-propylene-nonconjugated diene copolymer rubber, chloroprene rubber, butyl rubber, and silicone rubber. , Urethane rubber, acrylic rubber and the like are preferable. This time, we adopted silicone resin.

As the dispersed conductive particles, conductive carbon black, metal powders such as silver, gold, copper, brass, nickel, aluminum, and stainless steel, and powdered conductive agents such as tin oxide-based conductive agents may be used. In addition, organic conductive agents such as nonionic, anionic, cationic, and amphoteric conductive agents, and organic tin conductive agents can also be used. Further, in order to effectively perform uniform dispersion of the conductive agent, it is also possible to partially use an acid-modified resin or rubber obtained by copolymerizing an ethylenically unsaturated carboxylic acid such as acrylic acid, methacrylic acid, and maleic anhydride. It is valid. This time, conductive carbon black was adopted. The conductive particle carbon black is dispersed in the heat-melted silicone resin of the base material, which is molded and cooled to obtain a solid having a desired shape. The conductivity of the material obtained in this manner can be appropriately adjusted depending on the material ratio. This time, the resistance was adjusted to about 10Ω · cm.

On the surface of the conductive elastic body 12 thus formed, one layer of a medium-resistance layer 13 containing CNT is formed.
A protruding shape is formed on the surface. The conductive elastic body 12
As the medium resistance film provided thereon, a resin or rubber adjusted to have an appropriate resistance value according to the composition of the conductive agent and the layer thickness is used. The types of the resin and rubber may be the same as those described above, but other than these, a fluorine-based resin or rubber, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTF)
E), a tetrafluoroethylene-hexafluoropropylene copolymer (PTFE / HFP), a perfluoroalkoxy-based fluororesin, or the like is preferably used. In particular, when these fluorine-based resins and rubbers are used, they are inactive and have a small coefficient of friction, so that there is a great merit in terms of the service life of the photoreceptor and the charging roller as the object to be charged. This time PVD
F was adopted. The mechanical strength of PVDF is
Adjust so that it becomes smaller. The resistance value of the middle resistance layer 13 is 1E1 to 1E10 Ω · cm, particularly 1E6 to 1E7 Ω.
Cm. CNT is contained in this resin. Since this CNT also acts as a filler, the resistance was controlled by the CNT and carbon black.
CNT concentration is 10wt%, carbon black is 5wt%
%, A desired resistance value was obtained.

For this resistance control, a value based on the following calculation as a measure against pinholes was used.

Ratio of pinhole area to charged area = 1: 1E5 where pinhole area is 100 μm and charged area is 2 * 300
mm. That is, in the equivalent circuit of FIG.

It is assumed that Rb '= Rb * 1E5. If you want to reduce the effects of shorts by 10%,

It is sufficient to set 10 * (Rb + Rc + Ro) = Rb '. Substituting Rb '= Rb * 1E5

From Rb + Rc + Ro = Rb * 1E4 Ro >> Rb + Rc

Ro = Rb * 1E4 The volume resistivity of the member to be charged is 1E12 Ω · cm (dark resistance) and the thickness is 50 μm.

Rb = 5E6Ω · cm (about 1 mm thick)

As described above, the arc discharge method, the CVD method, the laser ablation method, and the like have been devised as the CNT generation method. In this case, CNTs prepared by an arc discharge method were used (multi-walled carbon nanotubes BU201 (Bucky USA)). Obtained C
Since NT is in the form of powder substantially the same as carbon black, it is mixed into a resin and stirred. Thereafter, a film having a thickness of 1 mm is formed on the surface of the low-resistance silicone roller by the dipping method. Next, the CNTs thus dispersed in the resin are projected from the surface. Ashing methods, polishing methods, and the like have been devised as such methods. This time, the method by polishing was selected. For polishing, abrasive particles of silica were used. Resin surface roughness is μ
Polishing is performed to the order of m. This gives C
NT protrudes with a length of about 1 μm. It was confirmed that the protrusion density of the CNTs was about 1 / μm ² depending on the amount previously dispersed in the resin. It has been reported that the breakdown current of each CNT is 1E-12A. In this embodiment, the number of CNTs was controlled so that current breakdown did not occur. In addition, it is necessary that the surface roughness of the resin be on the order of μm and that a gap region be formed between the resin and the member to be charged. In this gap region, non-contact charging is performed.

(2) Cleaner The roller charger 1 is provided with a cleaner 2 capable of performing a polishing step as shown in FIG. The role of the cleaner 2 is to constantly polish the surface of the roller charger 1, maintain the surface at an appropriate roughness, and allow fresh CNTs to protrude from the surface. For this reason, the above-mentioned polishing step can be performed by the cleaner 2. As the cleaner 2, a member having high mechanical strength and capable of always maintaining an appropriate projection state is used. Its applications include Al, SUS,
A metal or alloy such as Fe, a resin having high mechanical strength such as acryl or epoxy, or an inorganic material such as silica, glass or other oxide is suitable. This time, SUS was used. This cleaner is also roller-shaped, SUS
When the resin of the charger adheres to the surface, it can be removed. The surface of the SUS has a roughness on the order of μm, and the SUS comes in contact with the charger at a different rotation speed, thereby polishing the surface of the charger roller. By adjusting the pressing pressure, the shaving amount can be controlled. Since the thickness of the roller is about 1 mm, the roller is adjusted to about 1 mm / rotation in order to have a life of about 500 k sheets.

(3) Charged Member (Photosensitive Member) As shown in FIG.
1, a charge transport layer 32, a charge generation layer 33, an undercoat layer 34, and a base 35. This will be described below in order. Surface protective layer Use a transparent and high mechanical strength material. As a material,
Commercially available resins such as polyester, polycarbonate, polyurethane, acrylic, epoxy, silicone, alkyd, and vinyl chloride-vinyl acetate copolymer can be used. Investigations were made to further improve the strength and dispersibility. As a result, the conductive particles were dispersed in a photocurable acrylic monomer having three or more acryloyl groups in one molecule. By using a surface layer formed by coating and photocuring on the layer, the film strength was dramatically improved.

Charge Transport Layer For the charge transport layer 32 of this example, a material for transporting holes which has been conventionally used was used. As the charge transport agent,
Oxadiazole derivatives, pyrazoline derivatives, hydrazone derivatives, triphenylmethane derivatives, oxazole derivatives, triarylamine derivatives, diphenylmethane derivatives, stilbene derivatives, butadiene derivatives, polyvinylcarbazole, polysilane derivatives, and the like are used.
As the binder, a polycarbonate resin or a polyester resin was used. The concentration of the transfer agent was about 50%.
The film thickness was about 20 μm and formed by dipping coating.

Charge generation layer This layer is a long-wavelength (7
80 nm). Examples of the CGM include a squarylium dye, a metal-free phthalocyanine dye, a metal phthalocyanine dye, an azurenium salt dye, a thiapyrylium salt, a polycyclic quinone dye, a perylene dye, an azo pigment dye, and an azo pigment. These were put into a binder material such as polyvinyl butyral resin. The film thickness was about 1 μm to 10 μm, and formed by spray coating.

Undercoat Layer The undercoat layer 34 improves the chargeability of the photoreceptor 3,
The purpose is to improve the adhesiveness and applicability of the photosensitive layer to the substrate 35. As the material used, for example, in a single-layer configuration, polyethylene, polystyrene, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyurethane, epoxy resin, polyester, melanin resin, silicone resin, polyvinyl butyral, polyimide resin, or the like, or And the like. In addition, casein, gelatin, polyvinyl alcohol, ethyl cellulose and the like are also used. Ag, C
A film in which conductive particles realized by a metal such as u, Ni, Au, and Bi or carbon are dispersed in an adhesive is also effective. A layer containing titanium oxide surface-treated with tin oxide or alumina is also effective. A layer in which titanium oxide fine particles coated with alumina, titanium oxide surface-treated with a titanate coupling agent, a metal oxide particle surface-treated with a silane compound, or a fluorine-containing silane compound dispersed in an adhesive is used. Can be

Substrate The substrate 35 preferably has characteristics such as conductivity, high mechanical strength, low manufacturing cost, and good film adhesion. Therefore, general metals are used, for example, Al,
SUS, Fe, Ni, Cu, Mg, Ag and the like can be mentioned, but Al was used in this case. Alternatively, a metal film can be formed on an insulating material such as acrylic to be used as a substitute.

(4) Driving Method The operating method is similar to that of a normal roller charger. The applied voltage was DC, and the applied voltage was 300 V. This value satisfies the K1 condition of claim 2. Therefore, normal discharge does not occur, and generation of ozone can be prevented. This can be checked with an ozone detector or the like. The rotation speed of the photoreceptor was designed to be compatible with 60 cpm. In this embodiment, satisfactory charging ability was obtained even at this speed.

Embodiment 2 In this embodiment, a blade type was used for the charger. As described above, the contact area can be increased by sliding on the surface as compared with the roller. FIG. 6 shows a configuration diagram of an image forming apparatus using the blade-shaped charger of this embodiment.
In FIG. 6, reference numeral 1-1 denotes a blade-type charger, and reference numerals 3 to 9 of other parts have substantially the same configuration as that of the roller-type charger shown in FIG. The same applies. The nip width is designed to be 2 mm, and the resistance value, thickness, surface roughness, and the like are the same as in Example 1. As in the case of the roller, the blade was processed so that the CNT protruded from the surface of the blade.

Embodiment 3 In this embodiment, not only the charging of the photosensitive member but also the charging of
It was also used for the transfer process. In the transfer process, the image developed on the photoconductor is moved onto paper. At this time, the reverse polarity charge of the electrode charged with the toner is charged on the back surface of the paper. The charging area can be made smaller than that of a conventional corona charger. This time, assuming a nip width of 2 mm,
In other areas, the blade was shaped so that no voltage was applied. As a result, an image could be formed with less blur without toner scattering.

Embodiment 4 In this embodiment, a blade type was adopted. Gap control in a non-contact non-Paschen type charger is easily realized by making the surface brush-like. The CNTs protrude from the brush surface. The brush tip is pressed against the member to be charged and bends. Thus, a gap having a brush diameter of about 10 μm can be formed between the CNT and the member to be charged.
FIGS. 7 and 9 show schematic diagrams of the configuration of this embodiment. FIG. 8 shows the positional relationship between the supporting thin wire and the member to be charged in the charger of this embodiment. 7 to 9, reference numeral 1-2 denotes a base of the charger, reference numeral 3 denotes an object to be charged, reference numeral 14 denotes a support fine wire (brush), and reference numeral 15 denotes CNT. These are configured by combining the elements described above. As a manufacturing method, CNT15 is formed by an arc discharge method and a CVD method.
The fact that it can be synthesized by a method or the like has been described above. This time, the one formed by the arc discharge method was used (Bucky-US
A). This is crushed appropriately in a mortar or the like, and mixed with the nylon solution as the brush material. At this time, the resistance of the nylon is controlled by doping.

The CNTs 15 were mixed so that the concentration became about 10 wt%. This is adjusted by a trade-off between the protrusion density and the strength of the nylon brush. The nylon resin mixed in this way is formed into fibers by a jetting method. At this time, the diameter of the nylon fiber was controlled to about 15 μm.
After that, it is brushed with a pile. Each brush 14 is fixed by a fixing cloth. The density at this time was 120 lines / mm ² . The length is about 2 mm.
In this state, the brush 14 is exposed to oxygen plasma. The oxygen plasma oxidizes the nylon resin. At this time, CN
Although T15 also slightly oxidizes, selective etching can be performed because its speed is greatly different. This plasma exposure is performed for about 30 minutes, and the brush diameter is changed from 15 μm to 10 μm.
Thinning to about μm. At this time, the CNTs 15 are exposed as minute projections from the brush surface. This density is about 1 / μm ² . The protrusion length is about 1 μm. Thereafter, the brush cloth is fixed to the base 1-2 to complete the brush cloth.

Basic Specifications Base 1-2 Material: ABS resin Width: 3 mm Pushing into charged object: 0.5 mm Fixed layer Nylon resin doped with TCNQ and TTF Brush 14 Diameter: 10 μm Length: 2 mm Density: 120 / mm ² Material: Nylon fiber CNT15 doped with TCNQ and TTF Diameter: 10 to 25 nm Length: 10 μm or more Material: Multi-walled carbon nanotube Synthesis method: Arc discharge Projection method: Oxygen plasma ashing method Conductive adhesive Material: Thermosetting epoxy System conductive adhesive Applied voltage -500V Charging capacity 30cpm

As a result, it was confirmed with a surface voltmeter that sufficient charging was achieved. In addition, it was confirmed that there was no uneven charging by forming an image.

Embodiment 5 This embodiment is an example in which the applied voltage is divided into three blocks. FIG. 10 shows a schematic diagram of the configuration viewed from the side. 10, reference numeral 1-3 denotes a base of the three-block charger, reference numeral 3 denotes an object to be charged, reference numeral 14 denotes a brush, and reference numeral 16 denotes a resistor. A PET film is interposed between the blocks to prevent short circuits between the blocks. The respective potentials were adjusted by changing the resistance 16 to -200V, -400V, and -500V. Thereby, it can be charged without discharging. Basic Specifications Base material 1-3 Material: ABS resin Width: 3 blocks of 2 mm indentation into charged object: 0.5 mm Insulation film PET film: 0.5 mm Fixed layer NCN resin doped with TCNQ and TTF Brush 14 Diameter: 10 μm Length: 2 mm Density: 120 fibers / mm ² Material: Nylon fiber CNT doped with TCNQ and TTF Diameter: 10 to 25 nm Length: 10 μm or more Material: Multi-walled carbon nanotube Synthesis method: arc discharge Purification: centrifugal separation method and limit Combination of external filtration method Projection method: Oxygen plasma ashing method Conductive adhesive Material: Thermosetting epoxy-based conductive adhesive Applied voltage -200V, -400V, -500V Charging capacity 30 cpm

As a result, it was confirmed that the surface was sufficiently charged by a surface voltmeter. In addition, it was confirmed that there was no uneven charging by forming an image.

Example 6 In this example, a roller type as shown in FIG. 11 was used.
In FIG. 11, reference numeral 1-4 denotes a base of the charger, reference numeral 14 denotes a brush, and reference numeral 15 denotes CNT. The above-mentioned brush cloth is wound around this charging roller. The rotation speed of the roller was set to three times the rotation speed of the member to be charged, and the rotation direction was reversed. As a result, a charging ability of 60 cpm was obtained. Basic Specifications Base 1-4 Material: SUS Radius: 10 mm Pushing into charged object: 0.5 mm Fixed layer Nylon resin doped with TCNQ and TTF Brush 14 Diameter: 10 μm Length: 2 mm Density: 120 / mm ² Material: Nylon fiber CNT15 doped with TCNQ and TTF Diameter: 10 to 25 nm Length: 10 μm or more Material: Multi-walled carbon nanotube Synthesis method: Arc discharge Purification: Combined use of centrifugation method and ultrafiltration method Projection method: Oxygen plasma ashing method Conductivity Adhesive Material: Mature hardened epoxy-based conductive adhesive Applied voltage -500V Charging roller operation Three times the number of rotations of charged body Charging capacity 60 cpm

As a result, it was confirmed with a surface voltmeter that sufficient charging was achieved. In addition, it was confirmed that there was no uneven charging by forming an image.

[0121]

As described above, according to the first aspect of the present invention, charging is performed at least by a field emission phenomenon.
By utilizing the field emission phenomenon, there is no longer a high threshold as in the conventional discharge according to Paschen's rule. That is, charging at a low voltage becomes possible. This reduces the risk of high voltage. When a low voltage such as a developing process is realized, the present invention enables charging at a low voltage in accordance with the low voltage. In the conventional discharge, a voltage equal to or higher than a threshold determined by Paschen's rule is required even when charging at a low potential. As a result, in the present invention, there is no need to provide an expensive device such as a booster, and there is a great merit in terms of cost. From the viewpoint of damage to the photoconductor, charging at a lower voltage is desired. The present invention enables charging at a much lower voltage than a conventional roller charger, so that damage to the photoconductor can be reduced.

According to the invention of claim 2 of the present invention, the electric field K1 (x) in the space formed between the surface of the charger and the member to be charged is defined as x>
It is assumed that K1 (x) <3.5E7 (V / m) in the range of 8 μm. As a result, discharge that takes over the normal Paschen rule does not occur. Normally, in the discharge phenomenon, electrons accelerated by an electric field collide with gas molecules, where charges are newly generated. By repeating this, electrons are avalanche amplified. To ionize this accelerated gas molecule, 1
It is said that 2.06 eV (oxygen molecule) or more is required. To accelerate the electrons by this energy during the mean free path (0.36 μm), an electric field of 3.5E7
(V / m) or more is required. That is, if this electric field does not exist, no discharge occurs. A condition necessary for forming a discharge is a distance between electrodes. It is said that if there is some distance, avalanche does not occur sufficiently and the discharge does not last. This distance is set to 8 μm. That is,
Under the above conditions, even if a necessary electric field exists, if the electric field does not exist in a sufficient region, discharge is not established. From the above, when the above expression holds, no discharge occurs.

According to a third aspect of the present invention, the electric field K2 (x) in the space formed between the surface of the charger and the member to be charged is defined as x>
In the range of 0.34 μm, K2 (x) <1.5E7 (V /
m). Thereby, generation of ozone and the like can be reduced. By performing charging at a lower voltage than conventional roller chargers and blade-type chargers, deterioration of the member to be charged and generation of unnecessary products such as NOx and ozone can be suppressed. Further, the charging speed is not slow as in the case of charge injection, and factors such as contact instability can be eliminated.

[0124] The invention of claim 4 of the present invention is characterized in that the charger has fine projections on the surface. Thus, by forming a sharp projection, a strong electric field can be formed at the tip. As a result, a phenomenon such as field emission occurs, and electrons can be emitted into the air. The electrons can be charged by reaching the member to be charged without causing avalanche in a large area. Therefore, no stable discharge occurs and no ozone is generated. At the same time, a sufficient charging ability can be obtained.

The invention of claim 5 of the present invention is characterized in that the surface of the charger supporting the minute projections has irregularities. Thus, by making the surface uneven, the surface area is much larger than that of a normal flat plate. Due to the increase in the surface area, the area in which the minute projection can be formed increases. Thus, the number of the fine protrusions can be increased without increasing the density of the fine protrusions. In addition, by supporting the charger with the projections, the distance between the surface of the charger and the member to be charged can be appropriately maintained.

According to the invention of claim 6 of the present invention, the average radius of curvature Ra of the unevenness of the charger surface is set to 10 μm or more.
As a result, the foreign matter of about 10 μm is pushed into the concave region of the surface roughness, and it is possible to prevent the spatial gap between the surface of the charger and the member to be charged from fluctuating largely due to the mixing of toner.

According to the invention of claim 7 of the present invention, the unevenness of the charger surface is realized by forming a brush on which fine wires are bundled on the charger surface. In this way, by using a brush as the surface, the unevenness can be created by diverting the brush manufacturing method and the like. The manufacture of brushes has a long manufacturing history and is technically proficient compared to a method of simply forming irregularities. Therefore, by diverting such a method, manufacturing costs can be reduced. In addition, the brush has an application example in a charger and the like, and various conditions such as a material and a shape of the brush can be selected based on results.

According to the eighth aspect of the present invention, the brush has flexibility and bends when it comes into contact with the member to be charged. Thus, the distance from the surface of the brush to the object to be charged is determined to some extent by the bending of the brush in contact with the object to be charged. That is, if the brush diameter is determined, the two are separated only by such a distance. This generally allows for control of the gap. In addition, the brush touches,
By bending, the force due to the pressing force can be appropriately adjusted. This size can be finely adjusted by changing parameters such as the material and thickness of the brush.

The invention according to a ninth aspect of the present invention is characterized in that the size of the fine projections is on the order of nm and is formed of nanotubes or whiskers. Thus, a large-scale structure on the order of nm can be obtained at low cost. In addition, since the tube formed in this way is made to order, a tube suitable for the purpose can be obtained.

According to the tenth aspect of the present invention, CNTs (carbon nanotubes) are used for the fine projections. CNTs are known to be very thin due to their shape. It is also known that the structure has high mechanical strength and, at the same time, sufficiently bends due to its large aspect ratio. Also, it is known that even if it bends sharply, it does not break easily.
The production method has been improved in recent years, and it has become possible to make it very easily, and it has become easier to obtain than other thin wires. Further, since CNT is made of carbon alone, it is more environmentally friendly than a thin wire such as a whisker made of a noble metal. In addition, since graphite is cylindrical in structure, no dangling bond exists on the surface. Thereby, it is chemically stable, and no oxide or the like is formed on the surface. Because of these features, many examples have been reported as field emission element members, and they have excellent stability. In addition, it has the properties of graphite used as a solid lubricant, and has excellent lubricity.

According to the eleventh aspect of the present invention, the space between the surface of the charger and the member to be charged is formed by the surface roughness of the charger and the member to be charged. This eliminates the need for minute position control. In the gap control by the roughness, a narrow area or a wide area may be formed. However, by suppressing the areas having different gap widths to the order of μm, it is possible to obtain substantially the same average potential in a macro order in which an image is visually recognized. As a result, problems such as uneven charging potential due to the difference in gap can be solved.

A twelfth aspect of the present invention is characterized in that charging is performed even in a region where the surface of the charger contacts the member to be charged. By keeping the surface of the charger low, charge injection occurs in the contact area. In the charge injection, a charging potential of almost 100% with respect to the applied voltage can be obtained. As a result, the non-contact area is charged by field emission (or non-Paschen discharge), and the charge injection occurs in the contact area.

According to a thirteenth aspect of the present invention, the surface resistance of the member to be charged is set to be equal to or higher than the surface resistance of the surface member of the charger.
As a result, even if charge concentration occurs in the pinhole portion, at least charge can be supplied to other regions. This can be calculated from a simple formula for voltage distribution.

According to a fourteenth aspect of the present invention, a predetermined relationship is established between the resistance of the surface member of the charger and the sum of the contact resistance between the charger and the member to be charged. By setting these resistance values in this way, it is possible to have a sufficient charging ability with respect to the charging speed.

The invention of claim 15 of the present invention is characterized in that the wear rate of the surface member of the charger is faster than the wear rate of the surface of the member to be charged. Wear due to friction is determined by the mechanical strength of the material, which of which is predominantly cut. Therefore, by making the mechanical strength of the surface of the charger smaller than that of the member to be charged, the charger is shaved.
By designing the charger to be a thicker member on the surface, the influence can be reduced even if the charger is slightly shaved.

According to the sixteenth aspect of the present invention, it is possible to provide a charger in which charging unevenness is reduced by sliding the charger on the surface of the member to be charged.

According to the seventeenth aspect of the present invention, the shape of the charger is a blade type. By using the blade type, the charger surface slides on the surface of the member to be charged. As a result, an arbitrary point on the surface of the member to be charged comes into contact with a plurality of regions on the surface of the charger. In other words, in the conventional roller type,
Any point on the charger side only comes into contact with an area of the same size as that point. On the other hand, by making the blade type and sliding the surface, the area where any point comes into contact is greatly expanded. Thereby, even if the contact area and the non-contact area are formed with the surface roughness, the respective areas are alternately switched by sliding on the surface, thereby enabling uniform charging.

According to an eighteenth aspect of the present invention, the shape of the charger is a blade type, and the applied voltage is applied in a plurality of voltage steps. By dividing the voltage into a plurality of stages in this manner, the potential difference in each region can be reduced. For example, even if 500 V is applied, 100 V, 2
It is divided into five blocks of 00V, 300V, 400V, and 500V. As a result, the potential of the member to be charged rises to the respective potential in each block. After the potential rises, the process moves to the next block, and the potential difference between the charged object and the charger in that block is 100 V. The discharge phenomenon is understood by Paschen's law, and the discharge phenomenon has a threshold voltage, which is about 350V. That is, when the potential difference does not exceed the threshold value, occurrence of discharge can be prevented.

According to an eighteenth aspect of the present invention, the shape of the charger is a roller type, and a cleaner for polishing the surface of the charger is provided. By making the charger a roller type, a portion in contact with the member to be charged and a portion other than the portion can be formed, and the two portions are interchanged by rotation. Accordingly, cleaning can be performed on a portion not in contact with the member to be charged. This cleaning step can be sufficiently exerted by a simple blade-type cleaner. At the same time, the surface of the charger can be polished by a cleaner. Although the CNT protrudes from the surface of the roller charger, this manufacturing process is performed by the polishing process as described above. By incorporating this polishing step into the charging process, the charger surface can be constantly polished, a fresh surface can be created, and the CNT can be constantly projected. This can prevent the CNT from deteriorating due to the operation. Further, by designing the roller to have a sufficient thickness, a long service life can be endured. Furthermore, instead of rotating at the same speed as the object to be charged as in the conventional roller type,
By changing the rotation speed and sliding the mutual surfaces, the same effect as the blade type can be obtained. This makes it possible to compensate for the shortage of the contact area, which is a problem with a normal roller charger, and also to solve the problem of a problem such as uneven charging.

According to a twentieth aspect of the present invention, in the image forming apparatus, the above-described charger of the present invention is used in at least one part of an electrophotographic process using static electricity such as charging, transferring, and discharging. Thus, even when the image forming apparatus is considered as a whole, it is possible to reduce problems caused by charging.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an image forming apparatus using an embodiment of a charger of the present invention.

FIG. 2 is a diagram illustrating a relationship between a surface charging potential of an object to be charged and an applied voltage based on Paschen's rule.

FIG. 3 is an equivalent circuit when a member to be charged has a pinhole.

FIG. 4 is a configuration diagram of a charging roller in the embodiment of FIG.

FIG. 5 is a configuration diagram of a photosensitive member that is a member to be charged.

FIG. 6 is a configuration diagram of an image forming apparatus using another embodiment of the charger of the present invention.

FIG. 7 is a configuration diagram of still another embodiment of the charger of the present invention.

FIG. 8 is a view showing a positional relationship between a support fine line and a member to be charged in the embodiment shown in FIG. 7;

FIG. 9 is a configuration diagram of the embodiment shown in FIG. 7;

FIG. 10 is a configuration diagram of still another embodiment of the charger of the present invention.

FIG. 11 is a configuration diagram of still another embodiment of the charger of the present invention.

FIG. 12 is a diagram showing an image of a surface uneven structure.

FIG. 13 is a diagram showing an image when the surface unevenness structure is realized by a brush.

FIG. 14 is a conceptual diagram of an electric field intensity showing an outline of the invention according to claims 2 and 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1-1, 1-2, 1-3, 1-4 Charger 2 Cleaner 3 To-be-charged object 4 Voltage application process 5 Exposure process 6 Development process 7 Transfer process 8 Fixing process 9 Light irradiation process 11 Conductive substrate 12 Conductive elastic body 13 CNT-containing medium resistance layer 14 Brush (support fine wire) 15 CNT 16 Resistance 31 Protective layer 32 Charge transport layer 33 Charge generation layer 34 Undercoat layer 35 Base

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyoshi Shoko 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Shuichi Hikichi 1-3-6 Nakamagome, Ota-ku, Tokyo Stock F-term in Ricoh Company (reference) 2H200 FA07 HA13 HA30 HB07 HB12 HB14 HB45 HB46 HB47 LA06 MA11 MA12 MB05 MC06 NA02 NA09 PB02 PB03 PB08 PB14

Claims (20)

[Claims] At least a space is provided between the surface of a charger and a member to be charged, and a voltage is applied between the surface of the charger and the member to be charged to charge the member to be charged and to transfer charges. A charger, wherein charging is performed at least by a field emission phenomenon. 2. An electric field K1 (x) depending on a distance x from a charger electrode with respect to an electric field in the space formed between the surface of the charger and the member to be charged in the range of x> 8 μm. 2. The charging device according to claim 1, wherein a condition is satisfied. K1 (x) <3.5E7 (V / m) 3. An electric field in the space formed between the surface of the charger and the member to be charged, wherein an electric field K2 (x) depending on a distance x from the charger electrode is within a range of x> 0.34 μm. The charging device according to claim 1, wherein the following condition is satisfied. K2 (x) <1.5E7 (V / m) 4. The charging device according to claim 1, further comprising minute projections on a surface of the charging device. 5. The charging device according to claim 4, wherein a surface of the charging device supporting the minute projection has irregularities. 6. The charger according to claim 5, wherein an average radius of curvature Ra of the unevenness of the charger surface is 10 μm or more. 7. The charger according to claim 5, wherein the unevenness on the charger surface is realized by forming a brush on which fine wires are bundled on the charger surface. 8. The charger according to claim 7, wherein the brush has flexibility, and bends when the brush contacts the member to be charged. 9. The charging device according to claim 4, wherein the size of the fine projection is on the order of nm, and the projection is made of nanotubes or whiskers. 10. The charger according to claim 9, wherein CNTs (carbon nanotubes) are used for the minute projections. 11. The device according to claim 1, wherein the space between the surface of the charger and the member to be charged is formed by the surface roughness of the charger and the member to be charged.
0. The charger according to any one of 0. 12. The charging device according to claim 1, wherein charging is performed even in a region where the surface of the charging device and the member to be charged are in contact with each other. 13. The charging device according to claim 1, wherein the resistance value Rb of the surface member of the charging device satisfies the following condition. Ro * Lo * f / 100 <Rb * Lb * S1 where the ratio of the pinhole area to the charged area of the object to be charged = 1: S1 f: Permissible voltage drop ratio (%) Ro: Resistance of the object to be charged (Ω · m) Lo: thickness of the above-mentioned charged body (m) Rb: resistance of the charger surface member (Ω · m) Lb: thickness of the charger surface member (m) 14. The method according to claim 1, wherein the sum Rd of the resistance Rb of the surface member of the charger and the contact resistance Rc between the charger and the member to be charged satisfies the following expression. A charger according to any of the above. Vss <Vs (Rd) Vs (Rd) = Va ｛1-exp (−w1 / v1C1R
d)｝, where Vss: required charging potential Vs (Rd): charging potential determined by resistance Rd w1: nip width (m) v1: charging linear velocity (m / sec) C1: charged body capacity (F) Va: Applied voltage (V) 15. The charger according to claim 1, wherein a wear rate of the surface member of the charger is faster than a wear rate of the surface of the member to be charged. 16. The charging device according to claim 1, wherein the charging device slides on a surface of the member to be charged. 17. The charging device according to claim 1, wherein the charging device has a blade shape. 18. The charger according to claim 17, wherein the shape of the charger is a blade type, and the applied voltage is applied in a plurality of voltage steps. 19. The charger according to claim 1, wherein the shape of the charger is a roller type, and the charger includes a cleaner for polishing a surface of the charger. 20. An image forming apparatus, wherein the charger according to claim 1 is used in at least one part of an electrophotographic process using static electricity such as charging, transferring, and discharging. .