JPH07295341A - Method for electrostatically charging photoreceptor and method for forming image - Google Patents

Abstract

PURPOSE:To provide an electrostatic charging method suitable for improving a faulty image while solving such a problem that the life of the photoreceptor is shortened by a direct electrostatic charge method. CONSTITUTION:This is a method for electrostatically charging the photoreceptor as for an electrophotographic device constituted so that the photoreceptor can be exchanged. The method is provided with such a process that the surface of the photoreceptor is electrostatically charged by directly receiving electric discharge generated at a very small space between an electrostatic charge member by the surface of the photoreceptor. Besides, the relation of 1<(Ig<1/2>XTg+In<1/2>XTn)/(Ig<1/2>XTg)<=(D0+D1)/D0. (Ig is the electrostatic charge current of an image part, Tg is the electrostatic charge time thereof, In is the electrostatic charge current of a non-image part, Tn is the electrostatic charge time thereof, DO is the photoreceptive layer thickness of the photoreceptor required for being exchanged and D1 is the photoreceptive layer thickness of the photoreceptor exchanged and integrated in the electrophotographic device) is satisfied by this method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for charging the surface of an electrostatic charge carrier in an image forming method such as electrophotography.
Particularly, the present invention relates to a charging method and an image forming method for a photoconductor that is repeatedly used.

[0002]

2. Description of the Related Art Conventionally, a number of methods are known as electrophotography, but generally, a photoconductive substance is used to form an electric latent image on a photoconductor by various means, and then the electrophotographic image is formed. The latent image is developed with toner to form a visible image, and if necessary, the toner image is transferred to a transfer material such as paper, and then the toner image is fixed on the transfer material by heat or pressure to obtain a copy. It is a thing. In addition, the toner particles remaining on the photoconductor without being transferred onto the transfer material are removed from the photoconductor by a cleaning process.

As a charging means in such an electrophotographic method, a so-called corotron or a scorotron which utilizes a corona discharge has been used, but a large amount of ozone is generated when corona discharge, particularly negative corona is generated. Therefore, it is necessary to equip the electrophotographic apparatus with a filter for trapping ozone, which causes problems such as an increase in the size of the apparatus and an increase in running cost. As a technique for solving such a problem, a charging member such as a roller or a blade is brought into contact with the surface of the photoconductor (hereinafter referred to as direct charging in the present invention) to form a narrow space near the contact portion. A charging method in which ozone generation is suppressed as much as possible by forming a discharge that can be interpreted by the so-called Paschen's law has been developed. For example, JP-A-57-178257, JP-A-56-104351, and JP-A-58-40566. JP-A-58-139156 and JP-A-58-150975 disclose known techniques.

The reason why the ozone generation amount is smaller in the direct charging than in the corona discharge is considered to be that the charging mechanism of the surface of the photoconductor is different due to the difference in the discharge region. In corona discharge, it is considered that air molecules are ionized in the discharge area to control the charging of the surface of the photoconductor as ions, whereas in direct charging, a large number of electrons are generated in the discharge area due to the multiplication of electrons. It is charged by reaching the surface.

Conventionally, the problems in the image caused by the corona charging method are, for example, so-called image flow caused by the decrease of the surface resistance due to the adhesion of nitrogen oxides, and the charger while the electrophotographic apparatus is stopped. There was a memory phenomenon of the photoconductor caused by the ions remaining inside. It has been found that the direct charging has another problem to be solved in addition to the problem in the corona charging method described above.

[0006]

Since a large number of electrons directly reach the surface of the photoconductor, the surface layer is physically and chemically deteriorated. Therefore, the life of the photoconductor used in the direct charging method is longer than that in the case of corona charging. The life is significantly shorter than that of. That is, the photosensitive layer is greatly worn during repeated use. There is a dilemma that if the amount of wear is simply suppressed in order to improve the life expectancy, image defects will occur due to the influence of the deterioration products of the surface layer of the photoconductor, which is suitable for the electrophotographic process and direct charging method that satisfy both requirements. An image forming method using an electrophotographic photoreceptor is desired.

In the direct charging method, the absolute value of abrasion on the surface of the photoconductor is large, but in addition to that, when a cylindrical photoconductor is used in an electrophotographic apparatus, the location of the photoconductor is specifically scraped. There is a phenomenon in which the actual life of the photoconductor is further shortened because the phenomenon occurs more remarkably than in the corona charging method. If such so-called uneven scraping occurs, the uniformity of the image will be lost, so this means for solving the problem is desired.

An object of the present invention is to provide a charging method suitable for improving image defects while solving the problem of shortening the life of the photoconductor by the direct charging method.

[0009]

SUMMARY OF THE INVENTION The present invention utilizes a charging sequence suitable for improving image defects while solving the problem of shortening the life of the photoconductor, and using a charging sequence that maximizes the characteristics of this sequence. The configuration is provided as an image forming method.

In the direct charging method, the damage on the surface of the photoconductor is more severe than in the corona charging method and the amount of abrasion of the photoconductor is large. Therefore, the inventor first studied the mechanism in detail. As a result, the following things became clear.

Direct charging causes a chemical change on the surface of the photoreceptor.

Photoconductor wear is due to two factors. One is that molecular chains are broken on the chemically deteriorated surface and are easily peeled off by a rubbing member such as a cleaning blade. The surface layer is vaporized by the charging itself.

FIG. 1 shows the result of actually observed decrease in the molecular weight of the surface layer by gel permeation chromatography.

Regarding the relationship between the charging current and the wear of the photoconductor, in the region where the current amount is small, in the present study, as shown in FIG. 2, the result obtained is approximately proportional to the square root of the current amount. It was found that the relationship between the charging time and the wear of the photoconductor is almost proportional as shown in FIG.

As a result of the above results, as well as earnest studies of the durable image and charging conditions, the present invention has been completed.

That is, according to the results of this study, the present invention provides an electrophotographic apparatus in which the photoconductor is replaceable, and in the electrophotographic apparatus in which the photoconductor is replaceable, the photoconductor is in a small space with a contact member or a non-contact charging member. Having a step of directly receiving the discharge on the surface of the photoconductor and charging the surface of the photoconductor,
It has a function of detecting the charging current while keeping the charging voltage or detecting the charging voltage while keeping the charging current, and when each of the image portion charging current Ig increases or when the image portion charging voltage Vg increases, a non-image It is a method of charging a photoconductor, which is characterized by controlling a partial charging current In and / or a non-image part charging time Tn.

In a preferred embodiment of the present invention, the photosensitive member has a step of directly receiving on the surface of the photosensitive member a discharge in a minute space with a contacting or non-contacting charging member and charging the surface of the photosensitive member. Relational expression 1 <(Ig ^1/2 × Tg + In ^1/2 × Tn) / (Ig ^1/2 × Tg) ≦ (D0 + D1) / D0 (1) (where Ig is the image area charging current) , Tg is the charging time of the image area, In is the charging current of the non-image area, Tn is the charging time of the non-image area, D0 is the thickness of the photosensitive layer of the photoconductor that needs to be replaced,
The charging of the photoconductor is performed under the condition that D1 is the film thickness of the photoconductive layer of the photoconductor to be replaced and incorporated in the electrophotography.

Further, according to the present invention, at least the step of charging the photoconductor, the step of exposing the photoconductor to form a latent image, the step of developing the latent image, and the surface of the photoconductor cleaned physically or electrostatically. In the step of charging the photoreceptor of an electrophotographic apparatus in which the photoreceptor is repeatedly used, the photoreceptor is a function-separated photoreceptor in which at least a charge generation layer and a charge transport layer are laminated in this order, and An image forming method is provided, wherein the above-mentioned photoreceptor charging method is applied.

It has been found that the above-mentioned charging method is a basic condition that can sufficiently satisfy the requirements for abrasion of the photoconductor and sufficiently prevent image defects.

The photoconductor charging current means a current component that contributes to the charging of the photoconductor, and in the case of direct current, the amount of current flowing from the charging member to the photoconductor is the charging current amount. On the other hand, in the case of using a direct current in which alternating current is superposed, the direct current component can be directly used as the charging current amount. But,
Regarding the AC current, it means that the charging member and the photoconductor are interpreted as a capacitor, and the AC current amount is measured as the sum of the amount of current flowing through the capacitor and the amount of discharge current that contributes to actual charging. There is. As will be described later, the charging current amount in the present invention is represented by the sum of the direct current component and the discharge current amount component that contributes to the alternating charging when the alternating current is superposed. The advantages of superimposing alternating current are that pre-exposure before charging is not required, and that electrostatic history on the surface of the photoconductor is erased and charging stability is improved, which leads to downsizing of the electrophotographic apparatus and cost reduction. That is, the abrasion of the photoconductor is larger than that when only the direct current is applied.

The parameters of the above equation will be described in detail below.
Ig is an image portion charging current, and its meaning is as follows.
For example, when a copying machine and a cylindrical photosensitive member, that is, a so-called photosensitive drum are used, an image or a latent image to be copied is formed on the photosensitive drum. In order to provide the latent image to be formed, the photosensitive image is previously formed. The drum must be charged.
In order to provide the latent image to be formed, the current value at the time of charging the photosensitive drum in advance is set to Ig, that is, the image portion charging current, and the time required for charging that area is Tg. That is, the charging time is set to the image area.

Further, In and Tn mean that, when the photosensitive drum is repeatedly used, its surface layer must be electrostatically and physically cleaned so as to be suitable for charging, exposure latent image formation, development and transfer. Therefore, it is the charging current and the charging time on the sequence prepared for charging and exposure in addition to the actual image forming portion. From the standpoint of simply reducing the abrasion of the photoconductor surface layer, I
It is sufficient if n or Tn is zero. However, when the photoconductor is used repeatedly, when the photoconductor surface used once is used for the next use, the previous usage history remains mechanically and electrically, and the photoconductor and other contacts There is an undesired history on the surface of the photoreceptor due to frictional charging with the member. In order to eliminate these undesirable histories, In or Tn cannot often be zero at all times. From this point of view, it is desirable that the charging in the non-image area before the image area is at least one cycle of the photoconductor.

When only direct current is used as charging current
The difference between when the AC component and
The uniformity is easier to obtain when AC components are superimposed.
Have signs. However, the charging voltage of the AC component
Current contributes to charging uniformity, but its discharge current is
If an AC component is superimposed, it will damage the surface,
It has the other side that the abrasion of the photoconductor is accelerated. Tsuma
As one of the desirable modes of the present invention, the band of the image part is
AC superimposes AC, and non-image parts are charged with DC only.
One way is to do it. Also the preferred form of the invention
As a state, (Ig ^1/2 × Tg + In^1/2 × Tn) / (I
g^1/2 XTg) is 2 or less.

In the definition of the method in the present invention, the transfer material which is frequently used in the electrophotographic apparatus is kept in mind.
The charging sequence from start to stop of the electrophotographic apparatus when copying or printing one sheet is intended for transfer paper sizes of 3, A4, LTR, and 11 × 17.
Further, it is desirable to be within the scope of the present invention even when a plurality of sheets are continuously copied or printed.

D0 is replaced with a new one because the photoconductor that has been used up does not have a sufficient charging potential due to abrasion in the photosensitive layer, or it is charged but does not fall sufficiently due to exposure. It shows the film thickness of the photosensitive layer when it must be replaced with the photoconductor. As a method of determining how much abrasion has caused the life of the photoconductor, the phenomenon as described above occurs, or regarding the life of the photoconductor of the electrophotographic device put on the market, the standard of the yield of the photoconductor in the specifications is used. For reference, 22-27 ° C, 40-60% R
Under an environment of H, A4 or LTR size paper is copied or printed by the photoconductor yield, and the abrasion amount of the photoconductive layer is measured, which is designated as D0. As the original image to be used, an image mainly composed of characters having a printing ratio of 3 to 5% is selected.

In the case of a photoreceptor in which a charge generating layer and a charge transporting layer are laminated in this order on a conductive substrate, the charge generating layer is usually negligible in thickness as compared with the charge transporting layer.
The thickness of the charge transport layer, which corresponds to D1 in this case, is usually about 5 to 50 μm, and among them, 10 to 10 μm.
A material having a size of about 30 μm is often used. Further, in many cases, a photoconductor that needs to be replaced due to being used up becomes unusable due to the above problems when the film thickness is reduced to about 1/2 to 2/3.

Further, due to the direct charging mechanism, as the photosensitive member is repeatedly used, the surface layer thereof is gradually scraped off. Therefore, in order to charge the surface potential to a constant potential, more charging potential is applied. As it is needed, more and more charging current is required as it is scraped, and the wear amount of the photoconductor increases as it is used. Therefore, in order to suppress an excessive amount of wear of the photoconductor from the new state of the photoconductor to the end of its life, in an electrophotographic apparatus in which the photoconductor is replaceable, a small amount of contact between the photoconductor and the charging member It has a process of directly receiving the discharge in space on the surface of the photoconductor and charging the surface of the photoconductor, and has the function of detecting the charging current while maintaining the charging voltage or detecting the charging voltage while maintaining the charging current. A photoconductor charging method controlled to decrease the non-image part charging current In or the non-image part charging time Tn when the image part charging current is increased by Ig or the image part charging voltage Vg is increased. suggest. This charging sequence allows the photoconductor provided in the electrophotographic apparatus to be used with an appropriate life.

The operation and effect of such control will be described. The details will be described in the embodiments of the invention, and therefore the outline will be described here. Fig. 4 shows the transitions of the photoconductor charging current amount and the thickness of the photosensitive layer when the electrophotographic apparatus was used for the duration of the photoconductor without adding any control to Ig, In, Tg, and Tn, and the transitions when the control was added. Indicated. It can be seen that the amount of abrasion is smaller with respect to the number of copies when control is added, and in this case, the amount of abrasion is controlled to be almost equal in any section. Further, according to a detailed study by the present inventors, when the photoconductor is new, that is, when the photoconductor layer is not largely shaved, when the photoconductor is repeatedly used as described above, the photoconductor surface used once is When used for the next use, the previous use history remains mechanically and electrically, and an undesired history remains on the surface of the photoconductor due to frictional charging between the photoconductor and other contact members. As the photosensitive layer becomes thinner as the photosensitive layer is used, an undesired history, that is, electric charge remains on the surface of the photosensitive layer due to frictional charging with the contact member, but the photosensitive layer becomes thin. It was found that In or Tn can be made zero in some cases without affecting the potential of the photosensitive layer surface. As will be described in detail in the examples of the invention, a process is possible in which the abrasion of the photosensitive layer can be gradually reduced with use.

Since the amount of wear of the photosensitive member depends on the amount of charging current, if the wear of a part of the photoconductor is severe for some reason, the film thickness of that part becomes thin. A large amount of current flows into the thin portion, and the thin portion becomes thinner. This phenomenon often appears mainly in the rotation period of the photosensitive drum, and the cause thereof is related to the roundness of the cylindrical conductive substrate, the eccentricity of the photosensitive drum drive system, etc. As a result, the inventors of the present invention have found that the frequency of charging the surface of the photosensitive drum is also related to some extent. When using a gear etc., the drive system itself is made to be a random combination of prime numbers, but as mentioned above, it is affected by the accelerating phenomenon that the thinner part becomes thinner. it is conceivable that. The present inventors have found that there is an improvement in the method of charging a photoconductor, which is characterized in that the photoconductor is charged substantially in the cycle of the photoconductor. Here, the photoconductor cycle is substantially the photoconductor cycle even if a deviation of about ± 5% occurs with respect to one cycle.

The photoconductor used in the present invention includes
A photoreceptor in which at least a charge generation layer and a charge transport layer are laminated in this order on a conductive substrate is preferably used. The reason is that the surface layer of the photoreceptor is formed by the direct charging method as described above. This is because the discharge is directly received, which causes abrasion.However, such a layered type photoreceptor has a surface layer film thickness larger than that of other types of photoreceptors, and therefore, the This photosensitive member is preferable in the image forming method.

The constitution, material and manufacturing method of the member used in the present invention will be exemplified below.

The charging member is brought into contact with the surface of the photosensitive member to utilize the discharge in the vicinity of the contacting portion. As a form of the charging member, an elastic roller, an elastic blade, a brush or the like is used. As the material, for example, in the case of a roller, it is disclosed in, for example, Japanese Patent Application Laid-Open No. 1-211799, but as the conductive substrate, metal such as iron, copper, stainless steel, carbon dispersed resin, metal or metal oxide. A dispersion resin or the like is used, and the shape thereof may be a rod shape, a plate shape, or the like. For example, as the constitution of the elastic roller, one having an elastic layer, a conductive layer and a resistance layer provided on a conductive substrate is used, and as the roller elastic layer, chloroprene rubber, isoprene rubber, EPDM rubber, polyurethane rubber, epoxy rubber is used. , Rubber such as butyl rubber or sponge, styrene-butadiene thermoplastic elastomer, polyurethane thermoplastic elastomer, polyester thermoplastic elastomer,
It can be formed of a thermoplastic elastomer such as ethylene-vinyl acetate thermoplastic elastomer, and the conductive layer has a volume resistivity of 10 ⁷ Ω-cm or less, preferably 10 ⁶ Ω-cm or less. For example,
A metal vapor deposition film, a conductive particle-dispersed resin, a conductive resin, or the like is used, and specific examples include a vapor deposition film of aluminum, indium, nickel, copper, iron, or the like, and examples of the conductive particle-dispersed resin include carbon or aluminum. , Nickel, titanium oxide and the like, conductive particles dispersed in a resin such as urethane, polyester, vinyl acetate-vinyl chloride copolymer polymethylmethacrylate.

Examples of the conductive resin include polymethylmethacrylate containing quaternary ammonium salt, polyvinylaniline, polyvinylpyrrole, polydiacetylene and polyethyleneimine. The resistance layer is, for example, a layer having a volume resistivity of 10 ⁶ to 10 ¹² Ω-cm, and a semiconductive resin, a conductive particle-dispersed insulating resin, or the like can be used. As the semiconductive resin, ethyl cellulose, nitrocellulose,
Resins such as methoxymethylated nylon, ethoxymethylated nylon, copolymerized nylon, polyvinylhydrin, and casein are used. As an example of the conductive particle dispersion resin, a small amount of conductive particles such as carbon, aluminum, indium oxide, and titanium oxide are dispersed in an insulating resin such as urethane, polyester, vinyl acetate-vinyl chloride copolymer polymethylmethacrylate. The ones that have been done are listed.

The photoconductor used in the present invention includes:
A photoreceptor in which at least a charge generation layer and a charge transport layer are laminated in this order on a conductive substrate is preferably used. The reason is that the surface layer of the photoreceptor is formed by the direct charging method as described above. This is because the discharge is directly received, which causes abrasion.However, such a layered type photoreceptor has a surface layer film thickness larger than that of other types of photoreceptors, and therefore, the This photoreceptor is preferable in the image forming method. Examples of the photoconductor that can be used in the present invention include, as the conductive substrate, a metal such as aluminum and stainless steel, a plastic having a coating layer of aluminum alloy / indium oxide-tin oxide alloy, and conductive particles impregnated. Cylindrical cylinders and films of paper / plastics, plastics with conductive polymers, etc. are used.

On these conductive substrates, the adhesion of the photosensitive layer is improved, the coatability is improved, the substrate is protected, and the defects are covered on the substrate.
An undercoat layer may be provided for the purpose of improving the charge injection property from the substrate and protecting the photosensitive layer against electrical breakdown. The subbing layer is polyvinyl alcohol, poly-N-vinylimidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenolic resin, casein, polyamide, copolymerized nylon, glue.
It is made of materials such as gelatin, polyurethane, and aluminum oxide. The film thickness is usually 0.1 to 10 μm,
It is preferably about 0.1 to 3 μm. The charge generation layer is
Azo pigments, phthalocyanine pigments, isodigo pigments,
Perylene pigments, polycyclic quinone pigments, squarylium dyes, pyrylium salts, thiopyrylium salts, triphenylmethane dyes, charge generating substances such as selenium, amorphous silicon, and other inorganic substances are dispersed in a suitable binder and coated. It is formed by working or vapor deposition. The binder can be selected from a wide range of binder resins, for example, polycarbonate resin, polyester resin, polyvinyl butyral resin, polystyrene resin, acrylic resin, methacrylic resin,
Examples thereof include phenol resin, silicone resin, epoxy resin, vinyl acetate resin and the like. The amount of the binder contained in the charge generation layer is 80% by weight or less, preferably 0-40% by weight.
Choose to. The film thickness of the charge generation layer is preferably 5 μm or less, and particularly preferably 0.05 to 2 μm.

The charge transport layer has a function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting them. The charge transport layer is formed by dissolving a charge transport material in a solvent together with a binder resin, if necessary, and applying it, and the film thickness thereof is generally 5 to 50 μm. As a charge transport material, biphenylene
Polycyclic aromatic compounds having a structure such as anthracene, pyrene, phenanthrene, nitrogen-containing cyclic compounds such as indole, carbazole, oxadiazole, pyrazoline, hydrazone compounds, styryl compounds, selenium, selenium-tellurium, amorphous silicon, sulfurized Examples thereof include cadmium.

As the binder resin in which these charge transporting substances are dispersed, polycarbonate resin, polyester resin, polyarylate resin, polymethacrylic acid ester,
Examples thereof include resins such as polystyrene resin, acrylic resin, polyamide resin, and organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene. Among these, polycarbonate resin, polyester resin, polyarylate resin, and polyamide resin are preferably used in the present invention.

[0038]

EXAMPLES The production examples and examples of the present invention will be described in detail below in comparison with comparative examples. (Photoreceptor Manufacturing Example 1) 60φ × 36 as a conductive support
Prepare a 0 mm aluminum cylinder and use antimony oxide 1
Tin oxide containing 0% by weight, based on titanium oxide, is 75
100 parts by weight of the conductive powder coated so as to have a weight% was added to a solution consisting of 100 parts by weight of a resol-based phenol resin, 30 parts by weight of methanol, and 100 parts by weight of metal cellosolve, and dispersed by a ball mill to obtain a coating material. This coating material was applied onto the above support by dip coating and heat-cured at 140 ° C. for 30 minutes to form a conductive undercoat layer having a thickness of 20 μm. On top of this, 1 part of polyamide resin (6-66-610-12 quaternary nylon copolymer) and 8-nylon resin (methoxymethylated 6 nylon, methoxymethylated 30%) 3
Part by dissolving in a solvent composed of 50 parts by mass of methanol and 40 parts by mass of butanol by a dipping method and applied at 70 ° C. for 1
After drying for 0 minutes, an undercoat layer of 0.5 μm was provided.

Next, 10 parts by mass of bisazo pigment, 5 parts by mass of polyvinyl butyral resin and 10 parts of cyclohexanone.
0 part by mass was dispersed for 20 hours in a sand mill using 1φ glass beads. Tetrahydrofuran was appropriately added (50 to 100 parts by mass) to this dispersion liquid to apply it to the undercoat layer, followed by drying at 100 ° C. for 5 minutes to form a 0.12 μm charge generation layer.

Next, tetrafluoroethylene resin powder, a fluorinated acrylic oligomer as a dispersant, and a charge transport agent
A bisphenol Z type polycarbonate resin was prepared as a binder for the hydrazone compound. First, 20 parts by mass of a polycarbonate resin, 20 parts by mass of a hydrazone compound, and 0.6 parts by mass of a fluorinated acrylic oligomer are dissolved in a monochlorobenzene solution, and then, a tetrafluoroethylene resin powder (having a relative dielectric constant of 2. 0) 6 parts by mass was added and dispersed for 40 hours with a stainless steel ball mill, and 20 parts by mass of dichloromethane was added to prepare a coating liquid for the charge transport layer. This solution is applied on the charge generation layer and the temperature is 120 ° C.
Drying was carried out with hot air to form a 25 μm charge transport layer. The photosensitive layer of this photoreceptor is 25 μm because the charge transport layer is so thin that it can be ignored.

(Photoreceptor Production Example 2) In preparing the charge transport layer coating solution in Example 1, tetrafluoroethylene was added in an amount of 10
A photoconductor was manufactured in the same manner except that 1.0 part by mass of a fluorine-based acrylic oligomer was added. At this time, the film thickness of the photosensitive layer was 25 μm.

(Production Example 1 of toner) Styrene acrylic resin 100 parts by mass Magnetic substance 80 parts by mass Nigrosine dye 2 parts by mass Low molecular weight polypropylene 3 parts by mass After the above materials are dry-mixed, a twin-screw kneading extruder set at 140 ° C. Kneaded in. The obtained kneaded product was cooled, finely pulverized by an air flow type pulverizer, and then air-classified to obtain a toner composition having a controlled particle size distribution. This toner composition is provided with colloidal silica (BE
T300 m ^{2 /} g) 1.0 Wt% was externally added to prepare a toner having a weight average particle diameter of 7.6 μm (content of particles of 5 μm or less: 41 number%).

(Production Example 2 of Toner) Styrene acrylic resin 100 parts by mass Magnetic substance 80 parts by mass Monoazo dye chromium complex 2 parts by mass Low molecular weight polypropylene 3 parts by mass Biaxial kneading set at 140 ° C. after dry-mixing the above materials It was kneaded with an extruder. The obtained kneaded product was cooled, finely pulverized by an air flow type pulverizer, and then air-classified to obtain a toner composition having a controlled particle size distribution. Hydrophobic colloidal silica (BET 300 m ² / g) was added to this toner composition.
1.0 Wt% is added externally, and the weight average particle diameter is 7.6 μm (5
A toner having a content of particles of not more than μm: 41% by number) was prepared.

(Example 1) An NP6030 machine manufactured by Canon Inc. was used with a process speed of 267 mm / sec and modified so that 40 sheets of A4 could be laterally fed per minute. The charging member is a roller and rotates following the rotation of the photoconductor. A programmable arbitrary waveform generator and a high voltage amplifier are prepared for the charging sequence, and the charging current is measured by incorporating a 10KΩ resistor in the connection between the high voltage amplifier and the photoconductor charging member of the modified NP6030 machine and monitoring the voltage across it. did. To charge the photoconductor, a DC voltage was applied to the charging member, and the applied voltage was changed by a program of the arbitrary waveform generator as needed.

That is, this is to compensate for fluctuations in the surface potential of the photoconductor due to abrasion of the photoconductive layer. The photoconductor charging method and the initial numerical values of the respective parameters are programmed, the photoconductor uses (photoconductor production example 1), and the toner uses (toner production example 1).
Was used. The thickness of the charge transport layer of the photoreceptor is D1
Was adjusted to 25 μm. The thickness of the photosensitive layer of the photosensitive member is 8 points in the circumferential direction and 8 points in the longitudinal direction. The difference between the initial film thickness and the film thickness at the end of the life of 64 points is taken, and the unevenness is reduced ΔD with the maximum and minimum differences of the film thickness.
And At this time, it goes without saying that the initial film thickness and the film thickness at the end of life are measured at the same place and the difference at the same place is taken.

FIG. 5 shows the photosensitive member charging method and the initial values of the respective parameters. Under this condition, an endurance test was performed with one A4 transverse feed intermittently. The photoconductor potential was measured every 1000 sheets, and the applied voltage was controlled so that the charging potential was within the range of ± 20 V as the initial setting. The environment is 24 ° C and the humidity is 5
The original used was 5% RH, and when a character chart having a printing ratio of 4% was used, it was judged that the drum life had reached due to the so-called background fog, because the potential hitting the white background could not be removed at 90,000 sheets. . Until then, the image defect due to the abrasion of the photoreceptor, which is a particular problem, did not occur, and the result was satisfactory. At this time, the thickness of the charge transport layer is D0
Was 10.6 μm.

Calculation is performed for the above relational expression (1). When there are a plurality of conditions in the charging process of the non-image area, the product for each of them may be obtained and the sum thereof may be taken.

In the case of this initial condition, the values of the respective parameters are Ig = 71 μA, Tg = 0.79 sec In1 = 44 μA, Tn1 = 0.70 sec In2 = 44 μA, Tn2 = 0.35 sec, and the dark part potential is −650 V. , -400V is charged as the non-image portion potential. Where In1 and Tn
1 is the charging before the image part is charged, and In2 and Tn2 are
The charge after the image portion is charged is shown.

Since there are two charging steps for the non-image area, the sum of the two is taken and In ^1/2 × Tn = In1 ^1/2 × Tn1 + In2 ^1/2
Calculate as × Tn2.

That is, (Ig ^1/2 × Tg + In ^1/2 × Tn) / (Ig ^1/2 × T
g) = 2.0 is obtained.

That is, (D0 + D1) /D0=3.4.

Table 1 collectively shows the results during the durability test. Here, the calculated value 1 is (Ig ^1/2 × Tg + In ^1/2 × Tn) / (Ig ^1/2 × T
g) and the calculated value 2 is (D0 + D1) / D0.

As shown in Table 1, the calculated value 1 is smaller than the calculated value 2 of the 90,000th sheet.

Example 2 The same test as in Example 1 was conducted except that the charging sequence was changed as shown in Table 2.

Comparative Example 1 The same test as in Example 1 was conducted except that the charging sequence was changed as shown in Table 2.

(Comparative Example 2) The same test as in Example 1 was conducted except that the charging sequence was changed as shown in Table 2.

(Comparative Example 3) The same test as in Example 1 was conducted except that the charging sequence was changed as shown in Table 2.

Explaining the examples 1 and 2 and the comparative examples 1 to 3 together, Table 2 shows each parameter and the calculated values 1 and 2 at the initial stage and at the life of the photoconductor. Examples 1 and 2 set the charging sequence such that the calculated value 1 was always smaller than the calculated value at the end of life, and Comparative Examples 1 and 2 set to exceed the charging sequence. Is
The service life is only half, which is significantly inferior to the examples.
For Comparative Example 3, a halftone uneven charge image was generated in the initial image, so the test was terminated. This is because the history of the previous rotation of the copying machine was picked up.

Example 3 A durability test was conducted under the same initial settings as in Example 1. However, for every 10,000 sheets, the calculated value is 1
In was controlled so that the molecular part (Ig ^1/2 × Tg + In ^1/2 × Tn) was maintained constant.

The results are shown in Table 3. As an effect of such control, the scraped amount per unit number of sheets is 1 as compared with the first embodiment.
It was possible to reduce it by about 0%, and the amount of scraping remained almost constant from the beginning to the life of 110,000 sheets.

(Embodiment 4) With the same configuration as in Embodiment 1, T
n2 was set to 0.96 sec, and the sum of the charging times of the image area and the non-image area was set to be charged for 6 cycles of the photoconductor cycle.

Table 4 shows the results of the durability test at that time. It can be seen that the abrasion amount is slightly increased as compared with the first embodiment, but the uneven abrasion is reduced, so that the photoreceptor can be used up to a region where the photosensitive layer film thickness of the photoreceptor is thinner than that of the first embodiment. .

(Embodiment 5) With the same configuration as in Embodiment 1, T
n2 is set to 0.96 sec, and the sum of the charging time of the image portion and the non-image portion is charged for 6 cycles of the photoconductor, and the molecular portion (Ig ^1/2 Control was performed such that In was changed so that (× Tg + In ^1/2 × Tn) was decreased. In this way, the amount of uneven wear can be reduced as compared with the first embodiment.

(Embodiment 6) A Canon NP6030 machine was modified so that a process speed was 267 mm / sec and 40 A4 sheets could be copied laterally per minute, and further development and transfer bias were reversed, and The charging exposure apparatus was removed, and the negative toner (Toner Production Example 2) was modified so as to be subjected to reversal development. A programmable arbitrary waveform generator and a high voltage amplifier are prepared for the charging sequence, and the charging current is measured by incorporating a 10KΩ resistor in the connection between the high voltage amplifier and the photoconductor charging member of the modified NP6030 machine and monitoring the voltage across it. did.

The charging of the photoreceptor is 1.4 KH to the charging member.
A DC voltage having a z and 2000 Vpp sinusoidal AC component superimposed thereon was applied, and the applied voltage was changed by a program of the arbitrary waveform generator as needed. The photoconductor charging method and the initial numerical values of the respective parameters are programmed, the photoconductor is (Production example 2 of the photoconductor), and the toner is (Production example 2 of the toner).
Was used. The thickness of the charge transport layer of the photoreceptor is D1
Was adjusted to 25 μm. The thickness of the photosensitive layer of the photosensitive member is 8 points in the circumferential direction and 8 points in the longitudinal direction. The difference between the initial film thickness and the film thickness at the end of the life of 64 points is taken, and the unevenness is reduced ΔD with the maximum and minimum differences of the film thickness.
And At this time, it goes without saying that the initial film thickness and the film thickness at the end of life are measured at the same place and the difference at the same place is taken.

FIG. 6 shows the photoconductor charging method and the initial numerical values of each parameter. The measuring method of the charging current of AC component is
By changing the peak-to-peak voltage of the AC component and plotting the AC effective current value observed at this time, as shown in FIG. 7, the portion deviated from the straight line is the discharge current of the AC component, that is, the charging current of the AC component. is there. Under this condition, an endurance test was performed with one A4 transverse feed intermittently.

The photoconductor potential was measured every 1000 sheets, and the applied voltage was controlled so that the charging potential was within the range of ± 20 V as the initial setting. The environment was 24 ° C., the humidity was 55% RH, and the original used was a character chart having a print ratio of 4% (white character part against a black background). At 40,000 sheets, it was judged that the potential of hitting the black background could not be removed and the drum life had reached due to the decrease in density. Until then, a satisfactory result was obtained in which no image defect caused by the problematic scraping occurred. At this time, the film thickness of the charge transport layer, that is, D0 was 9.9 μm.

The relational expression of the relational expression (1) is calculated. When there are a plurality of conditions in the charging process of the non-image area, the product for each of them may be obtained and the sum thereof may be taken. In the case of this initial condition, the value of each parameter is: Ig = Ig (DC component) + Ig (AC component) = 71 μA + 180 μA = 251 μA Tg = 0.79 sec In1 = In1 (DC component) + In1 (AC component) = 44 μA + 180 μA = 224 μA Tn1 = 0.70 sec Ig = Ig (DC component) + Ig (AC component) = 71 μA + 180 μA = 251 μA Tg = 0.79 sec In2 = In2 (DC component) + In2 (AC component) = 44 μA + 180 μA = 224 μA Tn2 = 0.35 sec, and the dark portion. The potential is −650 V and the non-image portion potential is −400 V. Where In1 and Tn
1 is the charging before the image part is charged, and In2 and Tn2 are
The charge after the image portion is charged is shown.

Since there are two charging steps for the non-image area, the sum of the two is taken and In ^1/2 × Tn = In ^{1 1/2} × Tn ¹ + In ^{2 1/2}
Calculate as × Tn2.

That is, (Ig ^1/2 × Tg + In ^1/2 × Tn) / (Ig ^1/2 × T
g) = 2.3 is obtained.

That is, (D0 + D1) /D0=3.5.

Table 6 collectively shows the results of the durability test. Here, the calculated value 1 is (Ig ^1/2 × Tg + In ^1/2
× Tn) / (Ig ^1/2 × Tg), and the calculated value 2 is
(D0 + D1) / D0.

As shown in Table 1, the calculated value 1 is smaller than the calculated value 2 of the 40,000th sheet. (Example 7) The same test as in Example 1 was conducted except that the non-image area was charged with only the DC component and the charging sequence was changed as shown in Table 7.

Example 8 The same test as in Example 1 was conducted, except that the non-image area was charged only with the DC component and the charging sequence was changed as shown in Table 7.

(Comparative Example 4) The same test as in Example 1 was conducted except that the charging sequence was changed as shown in Table 7.

As is clear from the above results, according to the photoconductor charging method of the present invention, as compared with the conventional method, a remarkable effect can be obtained in preventing abrasion of the photoconductor and image defects.

[0077]

As described above, according to the present invention, the image portion charging current, the image portion charging time, the non-image portion charging current, the non-image portion charging time, the photosensitive layer thickness of the photosensitive member which needs to be replaced. , And by controlling so that each parameter of the photosensitive layer thickness of the photoconductor to be incorporated into the electrophotography after replacement is satisfied so as to satisfy the predetermined relation, the requirements for the wear of the photoconductor are sufficiently satisfied and the image defects are sufficiently satisfied. It becomes possible to prevent it.

[0078]

[Table 1]

[0079]

[Table 2]

[0080]

[Table 3]

[0081]

[Table 4]

[0082]

[Table 5]

[0083]

[Table 6]

[0084]

[Table 7]

[Brief description of drawings]

FIG. 1 is a gel permeation chromatograph showing the result of the actually observed decrease in the molecular weight of the surface layer.

FIG. 2 is a graph showing the relationship between charging current and the amount of photoconductor surface abrasion.

FIG. 3 is a graph showing a relationship between charging time and a photoconductor.

FIG. 4 is a graph showing a change in the charging current amount of the photoconductor and the film thickness of the photosensitive layer when the electrophotographic apparatus is used for the life of the photoconductor without adding any control to Ig, In, Tg, and Tn and a change when the control is added. The graph showing.

FIG. 5 is a graph showing a method of charging a photoconductor in Example 1 and initial numerical values of respective parameters.

FIG. 6 is a graph showing a method of charging a photoconductor in Example 6 and initial numerical values of respective parameters.

FIG. 7 is a graph plotting an AC effective current value observed when the peak-to-peak voltage of the AC component is changed.

Claims (6)

[Claims] 1. An electrophotographic apparatus in which a photoconductor is replaceable, wherein the photoconductor directly receives on the surface of the photoconductor a discharge in a minute space between the photoconductor and a charging member which is in contact or non-contact, and the surface of the photoconductor is charged. And has a function of detecting the charging current while keeping the charging voltage or detecting the charging voltage while keeping the charging current, respectively when the image portion charging current Ig increases or when the image portion charging voltage Vg increases. To the non-image portion charging current In and / or the non-image portion charging time Tn
A method of charging a photoconductor, which is characterized by controlling so that 2. A step of charging a photoconductor of an electrophotographic apparatus, which comprises repeatedly using the photoconductor, comprising at least a step of charging the photoconductor and a step of physically or electrostatically cleaning the surface of the photoconductor. The method according to claim 1, wherein the charging is performed substantially in the cycle of the photoreceptor. 3. An electrophotographic apparatus having a replaceable photoconductor, wherein the photoconductor directly receives the discharge in a minute space between the photoconductor and a charging member which is in contact with or out of contact with the photoconductor, and the photoconductor surface is charged. And the following relational expression 1 <(Ig ^1/2 × Tg + In ^1/2 × Tn) / (Ig ^1/2 × Tg) ≦ (D0 + D1) / D0 (1) (where Ig is Image part charging current, Tg is image part charging time, In is non-image part charging current, Tn is non-image part charging time, D0 is the photosensitive layer thickness of the photoconductor that needs to be replaced,
D1 is a photoconductor charging method in which the photoconductor layer thickness of the photoconductor to be replaced and incorporated in the electrophotography is satisfied. 4. A step of charging a photoconductor of an electrophotographic apparatus, wherein the photoconductor is repeatedly used, including at least a step of charging the photoconductor and a step of physically or electrostatically cleaning the surface of the photoconductor. The method according to claim 3, wherein the charging is performed substantially in the cycle of the photoconductor. 5. A step of charging a photoconductor of an electrophotographic apparatus, wherein the photoconductor is repeatedly used, including at least a step of charging the photoconductor and a step of physically or electrostatically cleaning the surface of the photoconductor. 4. The method according to claim 3, wherein the charging is performed substantially in the photoconductor cycle. 6. A step of charging at least a photoreceptor, a step of exposing the photoreceptor to form a latent image, a step of developing the latent image, and a step of physically or electrostatically cleaning the photoreceptor surface, 7. A function-separated type photoreceptor in which at least a charge generation layer and a charge transport layer are laminated in this order in the step of charging the photoreceptor of an electrophotographic apparatus in which the photoreceptor is repeatedly used, and One of
An image forming method, wherein the photosensitive member charging method according to claim 1 is applied.