JP4875352B2 - Image forming method - Google Patents

Description

  The present invention relates to an electrophotographic image forming method. More specifically, an electrophotographic photosensitive member is used to charge the photosensitive member, a charging step for charging the photosensitive member, an information writing step for forming an electrostatic latent image on the charging surface of the photosensitive member, and a developer carried on the developer carrier. The present invention relates to an image forming method comprising: a developing step of developing the electrostatic latent image of the toner as a toner image; and a transfer step of transferring the toner image of the photosensitive member to the transferred member side by applying an electric field between the photosensitive member and the transferred member. .

  In an image forming method used for an electrophotographic apparatus, an electrostatic recording apparatus, and the like, various methods are known as a method for forming a latent image on a photosensitive member such as an electrophotographic photosensitive member or an electrostatic recording dielectric.

  For example, in electrophotography, an electrical latent image is formed by uniformly charging a photoconductor using a photoconductive material as a latent photoconductor to the required polarity and potential, and then performing image pattern exposure. In general, the toner is developed and visualized, and this is transferred and fixed to a transfer medium such as paper.

  2. Description of the Related Art In recent years, multifunction devices compatible with a network that include all output terminals such as copying machines, printers, and facsimiles are widely accepted in the market.

  As such a network-compatible output terminal, an electrophotographic system is widely accepted, but one of the major problems is the duty cycle of the main body. The duty cycle is a limit number of sheets in which the main body continues to operate normally without requiring maintenance by an operator.

  One of the biggest factors that control the duty cycle is the life of the photosensitive drum. If the life of the photosensitive drum can be extended, it is possible to reduce waste, that is, reduce consumables, extend the life of consumables, and improve reliability. From the viewpoint of environmental protection, development of such a technology is required.

Under such circumstances, amorphous silicon (a-Si) photoreceptors are increasingly used as photoreceptors. This amorphous silicon photoreceptor has an extremely hard Vickers hardness of 500 or more (500 Kg / m ² or more, JIS standard), and is excellent in durability, heat resistance, and environmental stability. For this reason, it has become indispensable particularly for high-speed machines that require high reliability. (For example, refer to Patent Document 1.)

  However, according to the knowledge of the present inventors, in these apparatuses, it is not limited to the toner that adheres to the surface of the photoreceptor and affects the image quality.

  That is, it adheres to the surface of the photosensitive member and affects the image quality because fine paper dust generated from a piece of paper that is often used as a transfer material, organic components precipitated from this, and high-pressure members in the apparatus Corona products generated due to the presence.

  And, these fine paper powder, organic component or corona product adheres to the surface of the photoreceptor and becomes a foreign substance, particularly lowering the resistance in a high humidity environment, preventing the formation of a clear electrostatic latent image, This is considered to be a factor causing image quality degradation.

  It is known that the above-described image deterioration phenomenon is likely to occur particularly in the case of an amorphous silicon (amorphous silicon) photoreceptor having a film formed by glow discharge decomposition of silanes.

  As described above, a corona charger (corona discharger) is often used as a charging device that uniformly charges a latent image carrier to a required polarity and potential (including charge removal processing). The corona charger is a non-contact type charging device, and includes a discharge electrode such as a wire electrode and a shield electrode surrounding the discharge electrode, and is disposed in a non-contact manner with the discharge opening facing the image carrier that is a charged body. The image carrier surface is charged to a predetermined level by exposing the image carrier surface to a discharge current (corona shower) generated by applying a high voltage to the discharge electrode and the shield electrode.

  In recent years, as charging devices for charged objects such as latent image carriers, contact charging devices have been proposed and put to practical use because they have advantages such as low ozone and low power compared to corona chargers.

  The contact charging device contacts a charged object such as an image carrier with a conductive charging member (contact charging member / contact charger) such as a roller type (charging roller), a fur brush type, a magnetic brush type, or a blade type. Then, a predetermined charging bias is applied to the contact charging member to charge the charged body surface to a predetermined polarity and potential.

  The contact charging mechanism (charging mechanism, charging principle) has two types of charging mechanisms: a discharge charging mechanism and a direct injection charging mechanism, and each characteristic appears depending on which is dominant.

Discharge Charging Mechanism This is a mechanism for charging the surface of the object to be charged by a discharge phenomenon that occurs in a minute gap between the contact charging member and the object to be charged. Since the discharge charging mechanism has a constant discharge threshold value for the contact charging member and the member to be charged, it is necessary to apply a voltage larger than the charging potential to the contact charging member. Moreover, although the amount of generation is much smaller than that of a corona charger, the generation of discharge products is unavoidable in principle, so that harmful effects due to active ions such as ozone are unavoidable.

Direct injection charging mechanism
In this system, the surface of the charged body is charged by directly injecting the charge from the contact charging member to the charged body. It is also called direct charging, injection charging, or charge injection charging. More specifically, a medium-resistance contact charging member comes into contact with the surface of the member to be charged, and charge is directly injected into the surface of the member to be charged without going through a discharge phenomenon, that is, basically using no discharge. Therefore, even if the applied voltage to the contact charging member is an applied voltage that is equal to or lower than the discharge threshold, the object to be charged can be charged to a potential corresponding to the applied voltage. Since this charging system is not accompanied by the generation of ions, there is no adverse effect caused by the discharge products. However, since direct injection charging is used, the contact property of the contact charging member to the member to be charged greatly affects the charging property. Therefore, in order to take a configuration that comes into contact with the charged body at a higher frequency, a configuration in which the contact charging member has a denser contact point and a large speed difference from the charged body is required. (For example, see Patent Document 2.)
By charging the surface of the photosensitive member mainly using this injection charging mechanism, the number of discharge products can be reduced, and deterioration of the photosensitive member due to the discharge products can be suppressed.

JP-A-60-67951 JP-A-8-106200

However, the above-described image forming apparatus has the following problems.
That is, the generation of discharge products is reduced by charging mainly by the injection charging mechanism as described above, but a slight discharge phenomenon occurs, and in the amorphous silicon photoconductor whose surface resistance tends to be low, In some cases, an image flow phenomenon may occur. Further, the place where the discharge product is generated is not limited to the charging device, but the discharge product is also generated at a place where a high voltage is applied such as development, pre-transfer charging, and transfer process.

  Further, as a factor that causes image flow in addition to the discharge generation source, when fine paper dust generated from toner or paper used as a transfer material in most cases adheres to the surface of the photoreceptor, it is easily changed by the discharge product. This absorbs moisture and lowers the resistance, thereby causing image flow.

  As described above, not only the charging device but also various devices and members are involved as factors that cause the image flow, and this tends to cause a problem particularly when an amorphous silicon photoconductor is used.

  In addition, when charging the surface of the photoconductor with a contact charging brush, the flow-causing substances accumulated on the surface of the amorphous silicon photoconductor adhere to and accumulate on the charging brush, resulting in poor charging performance and image defects due to image flow. cause.

  Therefore, in order to solve the above-described problems, the object of the present invention is that a high-hardness amorphous silicon photoconductor does not generate image flow over a long period of time and has excellent durability performance without image deterioration due to filming. An object is to provide an image forming method capable of outputting an image.

  As a result of intensive studies, the present inventors have found a method for solving the above-mentioned problems by carrying out rubbing polishing with a charging device on the surface of an amorphous silicon photoreceptor.

  Specifically, by using the following image forming method, it is possible to perform high-quality and long-life image formation without causing image flow.

(1) a silicon atom having a photoconductive layer composed of a non-monocrystalline material as a matrix, the surface of the electrophotographic photosensitive member the volume resistivity of the surface is not more than 10 ⁸ Ω · cm or more 10 ¹⁵ Ω · cm a charging step of Ru is charged by using a charging device having a charging magnetic particles, an exposure step of forming an electrostatic latent image by exposing the surface of the electrophotographic photosensitive member charged by the charging process, the toner of the toner carrying A development process for developing the electrostatic latent image formed by applying the toner from the toner support to the surface of the electrophotographic photosensitive member to form a toner image, and the development process. in the image forming method and a transfer step of transferring to a transfer material the toner image on the surface of the electrophotographic photosensitive member, in the charging step, a charging bias is applied to the charging device, and a magnetic brush by the band electromagnetic particles The surface of the electrophotographic photoreceptor By rubbing, the surface of the electrophotographic photosensitive member is charged, and the charged magnetic particles have a volume resistance of 10 ⁴ Ω · cm or more and 10 ¹⁰ Ω · cm or less. It particles a cubic and / or rectangular particle shape and an average particle size of 500nm hereinafter more 30nm inorganic powder abrasive particles of primary particles, with respect to the band electromagnetic particles, 0.01 % is present 8 mass% or more, the image forming method of the inorganic powder abrasive particles, characterized that you have adhered to the band electromagnetic particles.

(2) The image forming method according to (1), wherein the inorganic powder abrasive particles are externally added to a toner, and are supplied from a developing device to a charging device to be adhered to the charged magnetic particles.

(3) The inorganic powder abrasive particles are ejected by applying a voltage having the same polarity as the abrasive particles in the charging device to the charging device in accordance with the image ratio during non-image formation. Image forming method.

(4) 1-3 image forming method, wherein the volume resistivity of the inorganic powder abrasive particles is less than 10 ³ times 10 ^-3 times the volume resistivity of the band electromagnetic particles.

(5) The image forming method according to any one of (1) to (4), wherein the inorganic powder abrasive particles are strontium titanate, barium titanate or calcium titanate.

(6) The image forming method according to any one of 1 to 5, wherein the charged magnetic particles are ferrite particles.

(7) The image forming method according to any one of claims 1 to 6, wherein when the charged magnetic particles and the inorganic powder abrasive particles are rubbed, the inorganic powder abrasive particles are charged with a polarity opposite to that of the toner particles. .

(8) The method further includes a step of cleaning the transfer residual toner from the photosensitive member by an elastic body in contact with the electrophotographic photosensitive member, wherein an average primary particle diameter of the inorganic powder abrasive particles is 30 nm or more and 300 nm or less. 7. The image forming method according to 1 to 6, which is characterized in that

(9) The image forming method according to any one of 1 to 8, wherein the transfer residual toner on the electrophotographic photosensitive member is returned to the developing means and used again for development.

(10) When the surface roughness of the electrophotographic photoreceptor is Rz, the groove interval is Sm, and the average particle diameter of the charged magnetic particles is D, the following formula:
2 × D / 3 ≦ Sm / Rz
10. The image forming method according to 1 to 9, wherein:

  As described above, according to the present invention, when the surface of the amorphous silicon photosensitive member is rubbed with a charging device to solve the above problems, the injection charging device has cubic and / or cuboid abrasive particles (hereinafter referred to as a cuboid shape). By adding an appropriate amount of (abrasive) and properly combining the surface roughness and shape of the photoreceptor with the charged magnetic particle size and abrasive particle size and shape, image flow can be prevented, and high-quality and long-life images. Formation can be performed.

  Furthermore, not only the surface of the photoconductor but also the surface of the conductive particles can be rubbed to remove contaminants such as discharge products, and the life of the charging device can be extended.

  In addition, since the small-diameter abrasive particles function as spacer particles, the cleaner-less mechanism that does not have a cleaning process can be achieved by suppressing toner deterioration due to contact between the charged magnetic particles and the toner and improving the toner recovery performance from the photoreceptor. In this case, toner reuse is facilitated.

<Image forming process>
FIG. 1 shows an example of an image forming apparatus according to the present invention. FIG. 2 is a longitudinal sectional view showing a schematic configuration of a digital copying machine. The copying machine shown in the figure includes a drum-type electrophotographic photosensitive member 101 as a photosensitive member. The photosensitive member 101 is rotationally driven in the direction of an arrow by a driving unit (not shown). Around the photosensitive member 101, a charging roller 102, which is a primary charging unit, an exposure unit 103, a developing unit (developing unit) 104, and a transfer charging unit (transfer unit) 105 are arranged almost sequentially along the rotation direction. ing. Further, a fixing device 106 is disposed on the downstream side (left side in the figure) of the transfer charger 105 in the conveyance direction (arrow direction) of the transfer material 111. The surface of the photoreceptor 101 is charged by the primary charger 102. Next, image exposure is performed by the laser beam emitted from the exposure means 103, the electric charge of the laser beam irradiated portion is removed, and an electrostatic latent image is formed. The electrostatic latent image on the photoconductor 101 is developed with the charged toner of the developing device 104. The developed toner image on the photoreceptor 101 is transferred by the transfer charger 105 to the transfer material 111 conveyed in the direction of the arrow. After the toner image is transferred, the transfer material 111 is conveyed to a fixing device 106 where the toner image is fixed on the surface by being heated and pressurized. The transfer residual toner remaining on the photoconductor after the transfer is collected by the developing device and again used for development.

<Injection charging device>
The injection charging method is a medium-resistance contact charging member that charges a charge injection layer of a photoreceptor having a medium resistance surface resistance by charging the charge.
A charging device 102 in FIG. 1 is a conductive magnetic brush as a contact charging member in contact with the photosensitive member 101, a nonmagnetic conductive charging sleeve having an outer diameter of 16 mm, a magnet roll included therein, and a charging sleeve. The magnet roll is fixed, and the charging sleeve can be driven to rotate. The magnetic flux density by the magnet on the surface of the charging sleeve is 800 × 10 ⁻⁴ T (Tesla). The charged magnetic particles are coated on the charging sleeve with a thickness of 1 mm and a longitudinal width of 220 mm to form a charging nip with a width of about 5 mm between the photosensitive member 101 and contact with the photosensitive member. A DC charging bias of −700 V is applied to the sleeve from a charging bias application power source, and the charging surface of the photosensitive member 101 is uniformly charged to approximately −700 V.

  In order to obtain uniform and sufficient charging performance, the rotation speed of the charging sleeve is preferably 100% or more with respect to the photoreceptor in the forward direction, but if the charging sleeve is rotated slightly in the reverse direction from the brush stopped state, Good.

  Here, as the charged magnetic particles of the magnetic brush as the contact charging member, (1) a magnetic powder such as resin and magnetite is kneaded and formed into particles, or conductive carbon or the like is used for adjusting the resistance value. (2) Sintered magnetite, ferrite, or those whose resistance value is adjusted by reduction or oxidation treatment, (3) Coating material with resistance adjustment of the above charged magnetic particles (on phenol resin) It is conceivable that the volume resistance value is adjusted to an appropriate value by plating with a metal such as a coat or Ni, etc. in which carbon is dispersed. If the volume resistance value of these charged magnetic particles is too high, the charge cannot be uniformly injected into the photoconductor, resulting in a fogged image due to minute charging failure. On the other hand, if there is a pinhole on the surface of the photoconductor if it is too low, the current concentrates on the pinhole, the charging voltage drops, and the photoconductor surface cannot be charged, resulting in a charging failure in a charging nip shape. Usually, the volume resistance value of the charged magnetic particles is measured at one or two points with a low applied voltage (1 V or more and 100 V or less). However, the volume resistance value of the charged magnetic particles depends on the voltage, which causes a problem. Sometimes.

Pinhole leakage is determined by the volume resistance value when a high voltage is applied to the charging member. Specifically, when the pinhole on the photoconductor comes to the nip, the difference between the voltage applied to the ground of the photoconductor substrate in the pinhole and the charged magnetic particle of the charging member is the charged magnetic particle of the pinhole. Therefore, it is preferable that an excessive current does not flow at this time. Therefore, for that purpose, it is desirable that the volume resistance value of the charged magnetic particles at the maximum applied voltage Vmax (V) applied to the charging member is 1 × 10 ⁴ Ω or more. This is because if the volume resistance value of the charged magnetic particles at Vmax (V) is smaller than 1 × 10 ⁴ Ω, leakage occurs at Vmax (V).

On the other hand, the charging failure is determined by the volume resistance value when a low voltage is applied to the charging member. In the injection charging method, as shown in FIG. 2, the photosensitive member potential (Vd) approaches the applied voltage (Vdc) of the charging member when the contact time elapses after the charging member starts to contact the photosensitive member. Specifically, assuming that the photoreceptor potential is initially 0V, at time t = 0, Vd = 0V and Vdc = −700V, so the voltage (Vdc−Vd) applied to the substantially charged magnetic particles is −700V. Therefore, at this time, the volume resistance of the charged magnetic particles when 700 V is applied determines the chargeability. At time t = t1, when a certain amount of time has elapsed, Vd = -500V and Vdc = -700V, so the voltage applied to the substantially charged magnetic particles is -200V. At this time, the volume resistance of the charged magnetic particles when -200 V is applied determines the chargeability. As described above, the voltage applied to the substantially charged magnetic particles becomes smaller as the photoreceptor potential (Vd) approaches the charging member applied voltage (Vdc), and the volume resistance of the charged magnetic particles at that time is charged. Have decided. If the volume resistance of the charged magnetic particles when 1 V is applied is higher than 1 × 10 ¹⁰ Ω, the charged magnetic particles cannot pass the charge to the photosensitive member within a certain charging time, resulting in poor charging. The volume resistance of the particles is preferably 1 × 10 ¹⁰ Ω or less. The volume resistance value on the low voltage side is an important characteristic in the injection charging method, and the conventional contact charging member discharges a minute gap to charge the photosensitive member. Since the potential difference between the potential and the charging member must be equal to or greater than the discharge threshold, the volume resistance value at a voltage so low has not been a problem.

  The voltage applied to the charging member may be only a DC voltage or a DC / AC component superimposed voltage. As the AC component, in the case of the injection charging method, although depending on the process speed of the apparatus, the peak-to-peak voltage of the applied AC component is preferably about 1000 V or less at a frequency of about 100 Hz to 10 kHz. When the voltage exceeds 1000 V, the photoreceptor potential is obtained with respect to the applied voltage, so that the latent image surface may be wavy in potential, resulting in fogging and thin density.

  In the case of a charging method using discharge, the alternating current component has a frequency of about 100 Hz to 10 kHz depending on the process speed of the apparatus, and the peak-to-peak voltage of the applied alternating current component is about 1000 V or more, and more than twice the discharge start voltage. Is preferred. As the waveform of the alternating current component to be applied, a sine wave, a rectangular wave, a sawtooth wave or the like can be used.

  In the present invention, a photosensitive member having a charge injection layer must be used for a method of charging by directly injecting charges into the photosensitive member.

  When a magnetic brush using charged magnetic particles is used as a charging member and only a DC voltage is applied, since a discharge start voltage exists, the potential on the photosensitive member due to discharge is not charged up to the applied voltage, and the charging member accordingly Therefore, it is preferable to use the injection charging method because the potential difference between the photosensitive member and the photosensitive member increases and the charged magnetic particles as the charging member tend to leak onto the photosensitive member.

  In addition, charging by discharge has a problem that the surface of the photoreceptor is damaged by the discharge product, and is liable to cause deterioration or image flow under high temperature and high humidity. In this respect, it is preferable to use the injection charging method. .

The present invention provides good chargeability due to charge injection, which could not be produced without using a low-resistance contact charging member, and leakage due to pinholes on the photoconductor that could not be prevented with a low-resistance contact charging member. In order to satisfy the above characteristics at the same time and obtain sufficient potential convergence, the volume resistance value of a magnetic brush made of charged magnetic particles of a contact charging member that is charged by injection in contact with a photoreceptor having a charge injection layer However, the contact charging member in the range of 10 ⁴ Ωcm or more and 10 ¹⁰ Ωcm or less is used.

  By sufficiently bringing the magnetic brush, which is a charging member, into contact with the photoconductor, the chargeability is improved, and the transfer residual toner can be taken into the charger, and the toner mixed in the charger is placed on the photoconductor. It is preferable that the magnetic brush be moved with respect to the photosensitive member with a difference in the speed of collection because the chance of ejection increases.

  The volume average particle size of the charged magnetic particles used for the charging member is preferably 10 μm or more and 60 μm or less. If it is smaller than 10 μm, the magnetic brush is likely to adhere to the photoreceptor, and the transportability of the charged magnetic particles when it is used as a magnetic brush is poor. If it exceeds 60 μm, the contact point between the charged magnetic particles and the photosensitive member decreases, and the charging uniformity of the injection charging method tends to deteriorate. More preferably, the volume average particle diameter of the charged magnetic particles is 15 μm or more and 40 μm or less.

  The gap between the holding member that holds the charged magnetic particles and the photosensitive member is preferably in the range of 0.2 mm to 2 mm. If the gap is smaller than 0.2 mm, it becomes difficult for the charged magnetic particles to pass through the gap, the charged magnetic particles are not smoothly conveyed on the holding member, and charging failure occurs, and excessively charged magnetic particles accumulate in the nip portion. Adhesion to the body tends to occur, and a thickness of 2 mm or more is not preferable because it is difficult to form a wide nip width between the photosensitive member and the charged magnetic particles. More preferably, the gap is 0.2 mm or more and 1 mm or less, and more preferably 0.3 mm or more and 0.7 mm or less.

  As the charged magnetic particles according to the present invention, for example, an element exhibiting ferromagnetism such as iron, cobalt, nickel, etc. is used as a material for causing the magnetic brush to come into contact with the photoconductor to be charged. An alloy or a compound to be contained, ferrite having a volume resistance adjusted by oxidation treatment, reduction treatment, or the like, for example, a composition-adjusted ferrite, a hydrogen-reduced Zn-Cu ferrite, or the like is used. In order to keep the volume resistance value of ferrite in the above range, it is achieved by adjusting the metal composition.

  The charged magnetic particles constituting the magnetic brush used as the contact charging member used in the present invention may have a surface layer for the purpose of adjusting the resistance. The surface layer is formed by coating the surfaces of the charged magnetic particles with a vapor deposition film, a conductive resin film, a conductive pigment-dispersed resin film, or the like. This surface layer does not necessarily have to completely cover the charged magnetic particles, and the charged magnetic particles may be exposed within a range where the effects of the present invention can be obtained. That is, the surface layer may be formed discontinuously.

  Binder resins used for coating charged magnetic particles include styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene and isobutylene; vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, etc. Α-methylene aliphatic such as methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate Monocarboxylic acid ester; Vinyl ether such as vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether; Homopolymer or copolymer of vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone Body and the like. Particularly representative binder resins include polystyrene, styrene-alkyl acrylate copolymers, styrene-acrylonitrile copolymers, from the viewpoints of dispersibility of conductive fine particles, film formability as a coating layer, and productivity. Examples thereof include styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyethylene, and polypropylene. Further, polycarbonate, phenol resin, polyester, polyurethane, epoxy resin, polyolefin, fluororesin, silicone resin, polyamide and the like can be mentioned.

  Examples of fluororesins include solvents in which other monomers are copolymerized with polyvinyl fluoride, polyvinylidene fluoride, polytrifluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, polytetrafluoroethylene, polyhexafluoropropylene, and the like. A soluble copolymer is mentioned.

  Examples of the silicone resin include KR271, KR282, KR311, KR255, KR155 (straight silicone varnish), KR211, KR212, KR216, KR213, KR217, KR9218 (modified silicone varnish), SA-4, KR206, manufactured by Shin-Etsu Silicone. , KR5206 (silicone alkyd varnish), ES1001, ES1001N, ES1002T, ES1004 (silicone epoxy varnish), KR9706 (silicone acrylic varnish), KR5203, KR5221 (silicone polyester varnish), SR2100, SR2101, SR2107, SR2110 manufactured by Toray Silicone SR2108, SR2109, SR2400, SR2410, SR2411, SH805, SH8 6A, SH840 and the like are used.

  Further, a resin film in which a conductive pigment is dispersed may be formed for resistance adjustment. The conductive fine particles according to the present invention include metals such as copper, nickel, iron, aluminum, gold and silver, or metal oxides such as iron oxide, ferrite, zinc oxide, tin oxide, antimony oxide and titanium oxide, and carbon black. Examples of the ionic conductive agent include lithium perchlorate, quaternary ammonium salt, and the like.

  Further, from the viewpoint of controlling resistance change due to the environment, the surface of the charged magnetic particles may be coated with a coupling agent that is a compound having a hydrophilic group and a hydrophobic group and subjected to a hydrophobic treatment. In the case of a coupling agent, an extremely thin film (at the molecular level) is formed on the surface of the charged magnetic particle, so there is little influence on the volume resistance value of the charged magnetic particle, and if only the resistance of the core that is the charged magnetic particle is adjusted, It is not necessary to perform resistance adjustment processing on the coating layer.

  Examples of coupling agents include titanate-based, aluminum-based, and silane-based coupling agents, and various functional groups such as amino groups and fluorine may be introduced to control the triboelectric charge polarity of the toner.

<Electrophotographic photoreceptor>
When the charged magnetic particles are used for injection charging, the electrophotographic photosensitive member used in the present invention has a charge injection layer as a layer farthest from the support, that is, a surface layer. The volume resistance value of the charge injection layer is preferably 1 × 10 ⁸ Ωcm or more and 1 × 10 ¹⁵ Ωcm or less so that sufficient chargeability can be obtained and image flow is less likely to occur. From the viewpoint of flow, it is preferably 1 × 10 ¹⁰ Ωcm or more and 1 × 10 ¹⁵ Ωcm or less, and further considering environmental fluctuations, it is preferably 1 × 10 ¹² Ωcm or more and 1 × 10 ¹⁵ Ωcm or less. And a charging member charges the volume resistivity of the injection layer charge in a high-humidity environment is less than 1 × 10 ⁸ Ωcm is sometimes easily occurs smeared images because they are not retained on the surface direction, whereas exceeding 1 × 10 ¹⁵ Ωcm The charged electric charge cannot be sufficiently injected and held, and there is a tendency to cause a charging failure. By providing such a functional layer on the surface of the photoconductor, it plays the role of holding the charged charge injected from the charging member, and also plays the role of releasing this charge to the photoconductor support during light exposure, reducing the residual potential. Let In addition, by using the charging member and the photoconductor according to the present invention, the charging start voltage Vth is small and the photoconductor charging potential is converged to almost 90% or more of the voltage applied to the charging member. It became possible.

  When an amorphous silicon photoreceptor is used, the photosensitive layer and the injection layer can be used together, and if the injection layer is within the above volume resistivity range, the conductive filler need not be added.

FIG. 3 shows an example of an amorphous silicon electrophotographic photosensitive member according to the present invention.
The electrophotographic photosensitive member of this example is obtained by sequentially laminating a photoconductive layer 302 and a surface protective layer 303 on a base 301 made of a conductive material such as Al or stainless steel (see FIG. 3A).

  In addition to these layers, various functional layers such as a lower charge injection blocking layer 304, an upper charge injection blocking layer 305, a charge injection layer, and an antireflection layer can be provided as necessary. For example, by providing a lower charge injection blocking layer 304, an upper charge injection blocking layer 305, and the like, and selecting a group 13 element and a group 15 element in the periodic table as a dopant, the charging polarity such as positive charging and negative charging can be controlled. This is possible (see FIG. 3B).

  The shape of the substrate used in the present invention may be as desired depending on the driving method of the electrophotographic photosensitive member. As the base material, it is common to use conductive materials such as Al and stainless steel. For example, these conductive materials are deposited on non-conductive materials such as various plastics and ceramics. In addition, those imparted with conductivity can also be used. A typical example of the photoconductive layer 302 is an amorphous material (also abbreviated as “a-Si (H, X)”) containing, for example, silicon atoms and hydrogen atoms or halogen atoms. Further, the layer thickness of the photoconductive layer 302 is not particularly limited, but about 15 to 50 μm is appropriate in consideration of the manufacturing cost. Further, in order to improve the characteristics, a plurality of layer structures such as a lower photoconductive layer 306 and an upper photoconductive layer 307 may be used (see FIG. 3B).

  The surface protective layer 303 is generally a non-single-crystal (preferably amorphous) material a-SiC (H, X) containing a silicon atom as a base and containing a carbon atom and, if necessary, a hydrogen atom or a halogen atom. A non-single crystal (preferably amorphous) material a-SiN (H, X) containing a silicon atom as a base, a nitrogen atom and a hydrogen atom or a halogen atom as necessary, or a carbon atom as a base, If necessary, it is formed of non-single crystal carbon (preferably amorphous carbon) a-C (H, X) containing a hydrogen atom or a halogen atom.

  Alternatively, the interface between the photoconductive layer 302 and the surface protective layer 303 may be continuously changed, and an antireflection layer may be provided to control the interface reflection of the portion.

The Vickers hardness of the photoreceptor is measured by a measuring method according to JIS standard B7774. When the Vickers hardness is 500 kg / m ² or more, it is sufficiently hard and the fine surface shape described above can be maintained for a long time. On the other hand, when the Vickers hardness is less than 500 kg / m ² , the growth of wear and scratches is fast, and it becomes difficult to maintain the surface shape.

<Abrasive particles>
As a result of intensive studies by the present inventors, an inorganic fine powder that is a rectangular parallelepiped crystal having an average primary particle size of 30 nm to 500 nm and a particle shape of approximately cubic or cuboid is charged with the surface of the photoreceptor. By interposing between the members and rubbing, it is possible to remove deposits such as discharge products, paper dust, and toner on the high-hardness photoreceptor, and to prevent image flow and adhesion of foreign matter onto the photoreceptor. I found it.

  The abrasive particles used in the present invention preferably have a rectangular parallelepiped crystal. Among the rectangular parallelepiped abrasive particles, more preferable are strontium titanate, barium titanate, and calcium titanate, and strontium titanate is particularly preferable.

  The rectangular parallelepiped abrasive particles used in the present invention preferably have an average primary particle size of 30 nm to 500 nm. When the average particle size of the rectangular parallelepiped abrasive particles is less than 30 nm, the abrasive particles are liable to adhere to the charged magnetic particles and the surface of the photoreceptor, and the polishing effect is insufficient. It is enough.

  In addition, when the image forming method includes a cleaning process using a cleaning blade, if the average particle size of the rectangular parallelepiped abrasive particles exceeds 300 nm, the photoreceptor is easily damaged, which is not suitable.

  In addition, about the particle size of the rectangular parallelepiped abrasive | polishing particle | grains in this invention, it calculated | required by measuring 100 particle size from the photograph image | photographed with the magnification of 50,000 times with the electron microscope. The particle diameter was determined by (a + b) / 2, where a is the longest side of the primary particles and b is the shortest side.

When the cuboid abrasive particles are externally added to the toner, in order to prevent the influence of the moisture absorption of the inorganic fine powder in a high-humidity environment on the development process, for example, a reduction in toner charge amount, the cuboid abrasive particles of the present invention The specific surface area is preferably 45 m ² / g or less. By setting the specific surface area of the rectangular parallelepiped abrasive particles to 45 m ² / g or less, the absolute amount of water adsorbed on the surface of the inorganic fine powder can be kept small, so that the influence on the toner charge imparted by frictional charging can be reduced. .

  In addition, the specific surface area of this invention was computed using the BET multipoint method using the autosorb 1 (made by Yuasa Ionics).

  The rectangular parallelepiped abrasive particles used in the present invention are prepared by adding strontium hydroxide to a titania sol dispersion obtained by adjusting the pH of a hydrous titanium oxide slurry obtained by hydrolyzing a titanyl sulfate aqueous solution, for example. It can be synthesized by heating up to.

  By setting the pH of the hydrous titanium oxide slurry to 0.5 or more and 1.0 or less, a titania sol having a good crystallinity and a particle size can be obtained.

  For the purpose of removing ions adsorbed on the titania sol particles, it is preferable to add an alkaline substance such as sodium hydroxide to the titania sol dispersion. At this time, it is preferable that the pH of the slurry is not 7 or higher so that sodium ions and the like are not adsorbed on the surface of the hydrous titanium oxide.

  The reaction temperature is preferably about 60 ° C. to 100 ° C., the temperature rising rate is preferably 30 ° C./hour or less in order to obtain a desired particle size distribution, and the reaction time is 3 hours or more and 7 hours or less. preferable.

  The inorganic particles thus produced can be obtained as perovskite crystals having a substantially cubic or cuboid particle shape. When the particle shape is approximately a cube or a rectangular parallelepiped, the contact area with the surface of the photoreceptor can be increased, and a good scraping property due to the solid ridgeline can be obtained. Further, by effectively using the particle size and the three-dimensional ridgeline and corner according to the surface shape of the photoconductor, it is possible to prevent deposits from depositing on fine irregularities when the photoconductor is particularly difficult to wear.

  Further, at the same time as removing the adhering matter on the photosensitive member, it is possible to contribute to refreshing of the charged magnetic particles even in the charging device, thereby preventing a decrease in charging ability and an image flow.

The volume resistance of the rectangular parallelepiped abrasive particles in the present invention is desirably 10 ⁻³ times or more and 10 ³ times or less of the volume resistance of the charged magnetic particles. When the volume resistivity of the rectangular parallelepiped abrasive particles is less than 10 ³ times 10 ^-3 times the volume resistivity of the magnetic brush, charging irregularity due to the difference in volume resistivity even when attached to the charging magnetic particles it is unlikely to occur.

An example of an electron micrograph (magnification of 20,000 times) of the rectangular parallelepiped abrasive particles of the present invention is shown in FIG.
Further, it is desirable that the abrasive particles in the present invention are charged with a polarity opposite to that of the toner used in frictional charging with the charged magnetic particles in the charging device. By charging with a polarity opposite to that of the toner, it is easy to control the discharge of the toner from the charging device and the holding of the abrasive by the charging bias, and the deterioration of the toner can be suppressed particularly in the cleanerless system.

<Toner>
The method for producing the toner of the present invention is not particularly limited, and a suspension polymerization method, an emulsion polymerization method, an associative polymerization method, a kneading pulverization method, and the like are used.

A method for producing toner in the kneading and pulverizing method will be described below.
Examples of the binder resin used in the pulverized toner of the present invention include polystyrene, poly-α-methylstyrene, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, and styrene-vinyl acetate. Copolymers, styrene-acrylic acid ester copolymers, styrene-methacrylic acid acrylic copolymers, vinyl chloride resins, polyester resins, epoxy resins, phenol resins, polyurethane resins, etc. can be used alone or in combination. -Acrylic, styrene-methacrylic copolymer resin and polyester resin are preferred.

  Further, when the pulverized toner of the present invention is controlled to be positively charged, a modified product of a fatty acid metal salt or the like; 4 such as tributylbenzidyl ammonium-1-hydroxy-4-naphthosulfonate, tetrabutylammonium tetrafluoroborate, etc. Onium salts such as quaternary ammonium salts and their analogs such as phosphonium salts; amines and polyamine compounds; metal salts of higher fatty acids; acetylacetone metal complexes; diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, and dicyclohexyltin oxide Adding a charge control agent such as diorganotin borate such as dibutyltin borate, dioctyltin borate, dicyclohexyltin borate; When controlling to negative charge, organometallic complexes and chelate compounds are effective, and monoazo metal complexes, acetylacetone metal complexes, aromatic hydroxycarboxylic acid, aromatic dicarboxylic acid metal complexes should be used as charge control agents. Can do. The amount of the charge control agent used is 0.1 to 15 parts by mass, preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the binder resin.

  A release agent can be added to the pulverized toner of the present invention as necessary. Examples of the release agent include aliphatic hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, paraffin wax, and Fischer-Tropsch wax or oxides thereof; and aliphatic esters such as carnauba wax and montanic ester wax as main components. And wax obtained by deoxidizing a part or all of the wax. In addition, saturated linear fatty acids such as palmitic acid, stearic acid, and montanic acid; unsaturated fatty acids such as brassic acid, eleostearic acid, and valinalic acid; stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnauvir alcohol, and seryl alcohol , Saturated alcohols such as melyl alcohol; polyhydric alcohols such as sorbitol; fatty acid amides such as linoleic acid amide; saturated fatty acid bisamides such as methylene bis stearic acid amide; unsaturated fatty acid amides such as ethylene bisoleic acid amide Aromatic bisamides such as N, N′-distearylisophthalic acid amide; fatty acid metal salts such as zinc stearate; waxes grafted to a hydrocarbon hydrocarbon wax using a vinyl monomer such as styrene; Fatty acids with polyhydric alcohols partial esters of such Henin acid monoglyceride; and methyl ester having a hydroxyl group obtained by and hydrogenated vegetable oils can be used as the releasing agent. The addition amount of the release agent is 0.1 to 20 parts by mass, preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the binder resin.

Colorants used in the pulverized toner of the present invention include known dyes and pigments such as carbon black, graphite, nigrosine, monoazo dye metal complexes, phthalocyanine blue, indanthrene blue, peacock blue, permanent red, lake red, rhodamine. Rake, Hansa Yellow, Permanent Yellow, Benzine Yellow and the like. The addition amount of the colorant is 0.5 part by mass or more and 20 parts by mass or less, preferably 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin.

  Next, in the case of non-magnetic toners, these binder resins, mold release agents, charge control agents, colorants, etc., and in the case of magnetic toners, magnetic substances are used in place of the above colorants, or colorants as required. And a magnetic material are sufficiently mixed by a mixer such as a Henschel mixer or a ball mill, and then melted and kneaded using a heat kneader such as a heating roll, a kneader or an extruder to charge the resin while the resins are compatible with each other. A control agent and a colorant are dispersed or dissolved, and after cooling and solidification, the particles are mechanically pulverized to a desired particle size, and the particle size distribution is sharpened by classification. Alternatively, after cooling and solidification, a finely pulverized product obtained by colliding with a target under a jet stream is spheroidized by heat or mechanical impact force.

Fine particles having a specific surface area of 100 m ² / g or more and 350 m ² / g or less are externally added to the colored particles thus obtained. The fine particles are inorganic particles such as metal oxides such as silicon, magnesium, zinc, aluminum, titanium, iron and zirconium; metal salts such as barium sulfate, calcium carbonate, magnesium carbonate and aluminum carbonate; clay minerals such as kaolin; apatite Phosphoric acid compounds such as silicon compounds such as silicon carbide and silicon nitride; and carbon powders such as carbon black and graphite. Organic particles and composite particles include polyamide resin particles, silicone resin particles, silicone rubber particles, urethane particles, melamine-formaldehyde particles, acrylic particles, etc .; rubber, wax, fatty acid compounds, resins, etc., metals, metals Composite particles composed of inorganic particles such as oxides, salts, carbon black, etc .; fluorine resins such as polyfluorinated ethylene and polyvinylidene fluoride; fluorine compounds such as carbon fluoride; fatty acid metal salts such as zinc stearate; Examples include fatty acid derivatives such as fatty acid esters; molybdenum sulfide, amino acids and amino acid derivatives.

The toner of the present invention is prepared by adding fine particles having a specific surface area of 100 m ² / g or more and 350 m ² / g or less to colored particles comprising at least a colorant and a binder resin. This is necessary for imparting appropriate fluidity and chargeability to the toner. If the specific surface area of the fine particles is less than 100 m ² / g, sufficient fluidity cannot be obtained, which is not preferable. Further, if the specific surface area of the fine particles exceeds 350 m ² / g, the charging becomes too high particularly in a low humidity environment, and filming on the photosensitive member is likely to occur, which is not preferable. The development method using the toner of the present invention is not particularly limited. For example, a two-component development method using a nonmagnetic toner produced by the above production method mixed with a carrier, a nonmagnetic one using only a nonmagnetic toner without using a carrier. Examples thereof include a component developing method and a magnetic one-component developing method using a magnetic toner.

<Relationship between charged magnetic particles and photoreceptor surface shape>
In the present invention, as shown in FIG. 5, an image forming method is used in which the photosensitive member surface 503 is rubbed in the direction of the arrow with charged magnetic particles 501 having rectangular parallelepiped abrasive particles 502 attached thereto. However, the surface of the photoreceptor may have a fine roughness, and according to the study by the present inventors, the concave portion due to the roughness is small and the charged magnetic particles of the charged magnetic brush are not large enough to enter. In this case, it was found that the surface of the photoreceptor is not easily polished with the charged magnetic particles carrying the abrasive particles, and the polishing effect is hardly exhibited.

  FIG. 6 shows an enlarged schematic view of a contact portion between the photoreceptor surface 603 and the charged particles 601. As is apparent from FIG. 6, unless the curvature of the charged particles 601 is sufficiently small with respect to the roughness of the photoreceptor surface 603, the abrasive particles 602 cannot be rubbed to the concave portion of the roughness of the photoreceptor surface 603. , More parts that can not be polished.

As a result of investigation, as a result of examining the relationship between the surface roughness of the photoreceptor and the charged magnetic particles, the surface roughness of the photoreceptor is Rz, the groove interval is Sm, and the average particle diameter of the charged magnetic particles is D. formula:
2 × D / 3 ≦ Sm / Rz
Satisfying good results.
By satisfying the above formula, polishing and injection charging with charged magnetic particles carrying an abrasive can be performed efficiently.

<Method of attaching abrasive to charged magnetic particles>
The adhesion of the abrasive to the charged magnetic particles includes a method of providing a supply means in addition to the method of adding the abrasive to the charged magnetic particles in advance.

  The most convenient method is to add an abrasive to the charged magnetic particles in advance and use it as it is.However, in the method of providing supply means, it is possible to suppress the decrease in abrasive or supply new abrasive to improve the polishing performance. Can be maintained over a long period of time, and the service life of the charged magnetic particles can be further improved.

  The simplest method for supplying the abrasive is to externally add the abrasive to the toner, and when the abrasive attached to the toner remaining on the photoreceptor as the transfer residual toner reaches the charging device, In this method, the abrasive is taken into the charging device. According to this method, it is not necessary to provide a new abrasive supply member. However, because it is necessary to devise to discharge the old abrasive from the charging device, and depending on the size of the output image ratio, the amount of abrasive supply to the charging device may not be constant, It is necessary to control the amount of abrasive in the charging device. For example, there are a method of electrostatic discharge by applying a bias for discharging the abrasive from the charging device during non-image formation such as between papers, and a method of mechanical discharge by increasing the rotation speed of the charging sleeve. In the case of applying the discharge bias, it is preferable to apply a DC bias having the same polarity as the charging polarity of the abrasive, and the AC bias may be superimposed within a range where the image flow does not deteriorate.

<Example of photoconductor preparation>
Using an apparatus for manufacturing a photoconductor for electrophotographic apparatus by high-frequency plasma CVD method using a VHF band, a charge injection blocking layer, a photoconductive layer, a surface are formed on an aluminum cylinder of ψ30 which has been roughened by cutting the surface. An a-Si photoconductor composed of layers was prepared. Photoconductors A to F having different cylinder substrate surface shapes were obtained by changing the cutting conditions. The obtained photoreceptor had a Vickers hardness (JIS standard) of 1200 kg / m ² . Table 1 shows values of the surface roughness Rz (μm) and the groove interval Sm (μm). The photoreceptor surface roughness was measured with a Keyence color laser microscope VK-8500.

<Production example of charging member>
Fe ₂ O ₃ : 51.2 mol%
CuO: 24.4 mol%
ZnO: 24.4 mol%
The above materials were pulverized and mixed in a ball mill, and a dispersant, a binder and water were added to form a slurry, followed by granulating operation with a spray dryer and classification as appropriate, followed by firing at 1120 ° C.

The obtained charged magnetic particles were crushed and then classified to obtain charged magnetic particles A, B, and C having volume average particle sizes of 30, 50, and 60 μm. The volume resistance values of the charged magnetic particles A, B, and C were 4 × 10 ⁷ Ωcm, 1 × 10 ⁷ Ωcm, and 8 × 10 ⁶ Ωcm, respectively.

<Example of production of rectangular parallelepiped abrasive particles>
The hydrous titanium oxide slurry obtained by hydrolyzing the aqueous titanyl sulfate solution was washed with an alkaline aqueous solution. Next, hydrochloric acid was added to the hydrous titanium oxide slurry to adjust the pH to 0.65 to obtain a titania sol dispersion. NaOH was added to the titania sol dispersion, the pH of the dispersion was adjusted to 4.5, and washing was repeated until the electrical conductivity of the supernatant reached 70 μS / cm.

0.97-fold molar amount of Sr (OH) ₂ .8H ₂ O was added to the hydrous titanium oxide, and the mixture was placed in a SUS reaction vessel and purged with nitrogen gas. Further, distilled water was added so as to be 0.1 mol / liter or more and 2.0 mol / liter or less in terms of SrTiO ₃ .

  The slurry was heated to 83 ° C. at a rate of 5 to 30 ° C./hour in a nitrogen atmosphere, and reacted for 3 to 7 hours after reaching 83 ° C. After the reaction, the mixture was cooled to room temperature, the supernatant was removed, and washing was repeated with pure water.

Further, in a nitrogen atmosphere, the slurry was placed in an aqueous solution in which 6.5% by mass of sodium stearic acid (18 carbon atoms) was dissolved with respect to the solid content of the slurry. Zinc stearate was deposited on the mold crystal surface. This surface treatment changed the chargeability of the particles. When the charge polarity was measured by triboelectric charging with the charged magnetic particles A, the positive electrode was charged at +12.2 μC / g. The volume resistance of the powder was 1.8 × 10 ⁸ Ω · cm.

  The slurry was washed repeatedly with pure water and then filtered with Nutsche, and the resulting cake was dried to obtain strontium titanate surface-treated with zinc stearate.

  Various strontium titanates A, B, C, and D having different average particle diameters were obtained by changing the heating rate and reaction time of the slurry. The obtained strontium titanate had an average primary particle size of 75, 110, 165, and 190 nm, respectively, and an aggregate content of 800 nm or more was 0.5% by number. In addition, the content of particles having an approximately cubic or rectangular parallelepiped shape was 80% by number or more.

<Examples of colored particle production>
Styrene acrylic resin 100 parts Carbon black 8 parts Salicylic acid metal compound 5 parts Paraffin wax 2 parts The above materials are mixed using a Henschel mixer, melt-kneaded with a twin screw extruder kneader, coarsely ground with a hammer mill, jet mill And then classified to obtain colored particles having an average particle diameter of 7 μm.
With respect to 100 parts by mass of the colored particles, 1.0 part by mass of hydrophobic silica (BET = 220 m ^{2 /} g) surface-treated with 20 parts by mass of dimethyl silicone oil on 100 parts by mass of silica was measured with a Henschel mixer FM10B. Toner A was obtained by external addition under conditions of 66S ⁻¹ , time: 3 minutes.
100 parts by mass of colored particles, 100 parts by mass of silica, 1.0 part by mass of hydrophobic silica (BET = 220 m ^{2 /} g) surface-treated with 20 parts by mass of dimethyl silicone oil, and 1.0 parts by mass of rectangular parallelepiped abrasive particles B The toner B was externally added with a Henschel mixer FM10B under the conditions of a rotational speed of 66S ⁻¹ and a time of 3 minutes.
For 100 parts by mass of colored particles, 1.2 parts by mass of hydrophobic silica (BET = 220 m ^{2 /} g) surface-treated with 20 parts by mass of dimethyl silicone oil on 100 parts by mass of silica, and 1.0 mass of rectangular parallelepiped abrasive particles B The toner C was externally added using a Henschel mixer FM10B under the conditions of a rotational speed of 66 S ⁻¹ and a time of 3 minutes.
When these toners were triboelectrically charged with the charged magnetic particles A, the toners A, B, and C were negatively charged at −20.0 μC / g, −18.0 μC / g, and −21.0 μC / g, respectively.

<Image forming system configuration>
The configuration of the image forming system in this embodiment is such that the toners A to C described above are developers, the photoconductors A to F are image carriers, the charged magnetic particles A to C are charge injection media, and the cuboidal abrasive particles A to C are used. D was included in the charging device. Charged particles having cuboid abrasive particles carried on the surface are carried by a magnetic force on a charging sleeve provided with a gap of about 500 μm from the photosensitive member in the charging device. Further, the charged magnetic particles are transported to the gap with the photoreceptor after the thickness of the charged magnetic particles is regulated by a blade approaching with a gap of about 180 μm. The charged magnetic particle magnetic brush rotates counterclockwise at a peripheral speed ratio of about 120% with respect to the rotation of the photosensitive member, and rubs the surface of the photosensitive member to inject and charge the photosensitive member. Polish and refresh.
When there is no photoconductor cleaning process using a blade, the transfer residual toner is taken into the charging device, charged negatively by frictional charging with the charged magnetic particles, discharged onto the photoconductor, and then collected by the developing device. And reused for development.

<Evaluation method>
Evaluation of image flow was made by using a Canon digital color copier CP2150 in an environment of 30 ° C. and 85% RH in a black cartridge only for an amorphous silicon photoconductor and an image forming apparatus with a modified exposure device. Ten thousand images were printed, and after the 100,000 images were printed, the main body was turned off, and the digital halftone image and the 5-point character image after being left in the same environment for 36 hours were evaluated. The evaluation results were ranked as follows.
◎: No image flow ○: Halftone highlight skipping is slight, but there is no problem with text △: Text line is slightly thin but readable enough ×: Halftone highlight is completely skipped and text is blurred Cannot read

Durability evaluation of charging unevenness is 100,000 images of 5% image with an image forming apparatus in which only Canon black color cartridge is modified for use with amorphous silicon photoconductor under the environment of temperature 23 ° C and humidity 5% RH. The image was drawn out, and the image at that time was evaluated by evaluating the texture.
For evaluation of the texture, the output halftone image was observed and evaluated according to the following criteria.
◎: No roughening ○: Slightly rough but not conspicuous ×: There is roughness and is conspicuous in the image

The development durability is 30 ° C and humidity 80% RH. Canon's digital color copier CP2150 is an image forming device in which only a black cartridge is modified for an amorphous silicon photoreceptor. The solid images at that time were evaluated according to the following criteria.
A: Almost no decrease in image density relative to the initial level B: A decrease in image density is less than 0.2 relative to the initial level
Δ: Image density decrease from 0.2 to less than 0.4 relative to the initial stage (thin but no problem)
×: Image density drop is 0.4 or more from the initial stage (recognized as clearly thin)

The durability of the charging device is an image forming device in which a digital color copier CP2150 made by Canon is modified for an amorphous silicon photoconductor in an environment of a temperature of 25 ° C. and a humidity of 50% RH. Then, the photoreceptor surface potential charged by the charging device at that time was evaluated according to the following criteria.
◎: Potential drop below 5V with respect to initial stage ○: Potential drop with respect to initial stage at 5V or more and less than 10V
X: Potential drop 30 V or more relative to the initial stage (image density reduction, fogging deterioration)

(Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-9)
To charged magnetic particles A, 0.1% by mass of silica for imparting fluidity and rectangular parallelepiped abrasive particles B and D were mixed and added externally by a turbo mill. Tables 2 and 3 show the results of evaluating the image flow and charging unevenness by changing the external additive amount of the abrasive. Photoreceptor A was used as the image carrier, and developer A was used as the toner. In addition, Table 4 shows the results of evaluation in the case of mixing strontium titanate having an irregular primary average particle diameter of 190 nm with charged magnetic particles.
The charging application voltage and the photosensitive member exposure intensity were set so that the potential of the photosensitive member was −450 V in the background portion potential and −50 V in the image portion (writing portion potential).

  As can be seen from the results of Tables 2, 3 and 4, the rectangular parallelepiped abrasive particles have the effect of preventing image flow and inhibiting development deterioration as compared with the case of using amorphous abrasive particles. When the rectangular parallelepiped or cubic shaped abrasive is present in the injection charging device in an amount of 0.01% by mass or more and 8% by mass or less, there is no image flow, and an image can be formed with high durability in charging performance. If the amount of the abrasive is too small relative to the charged magnetic particles, there is no effect on the image flow. Conversely, too much abrasive has no effect on image flow, and charging performance has also deteriorated. When the charging device was investigated, the magnetic brush ears were shortened. It is considered that since a large amount of abrasive particles are present on the surface of the conductive particles, the magnetic binding force between the conductive particles is reduced to inhibit the formation of the magnetic brush spike.

  The deterioration of the charged magnetic particles is also suppressed by the presence of the rectangular parallelepiped abrasive particles, and the durability of the charging device is improved.

  Furthermore, the transfer residual toner is smoothly discharged from the charging device due to the spacer effect of the abrasive particles, and is collected and reused in the developing device without deterioration of the developer in the charging device. Degradation of developability due to collection / reuse is suppressed. Further, even when the transfer residual toner is collected by the developing device and reused, the deterioration of the developer in the charging device can be suppressed, and both reduction in toner consumption and image quality can be achieved.

(Examples 2-1 to 2-18)
<Example in which abrasive particles are externally added to toner and supplied to a charging device>
In this embodiment, an abrasive is externally added to the toner, and the toner is supplied to the charging device so as to function effectively in the charging device. The abrasive externally added to the toner moves to the photosensitive member during image formation or during rotation of the photosensitive member during non-image formation, and moves from the photosensitive member to the charging device.
As the toner, toner B to which the above-described rectangular abrasive particles B were externally added was used. As the charged magnetic particles in the charging device, charged magnetic particles A, B, and C having different particle diameters of 30 μm, 50 μm, and 60 μm were used. Table 5 shows the results of image formation evaluation using the photoreceptors A to F and the charged magnetic particles A to C.
The charging application voltage and the photosensitive member exposure intensity were set so that the potential of the photosensitive member was −450 V in the background portion potential and −50 V in the image portion (writing portion potential).

  The amount of the inorganic powder in the charging device was calculated from the image ratio × transfer efficiency (determined from the temperature / humidity sensor measurement value) and controlled to be 2.0% by mass with respect to the charged magnetic particles. The amount of inorganic powder was controlled by changing the abrasive particle discharge bias application time during non-image formation. That is, the bias application is lengthened when an image with a high image ratio continues, and the bias application time is shortened when the image ratio is low.

  In this embodiment, since the rectangular parallelepiped abrasive is charged to + polarity in the charging device, by applying a + polarity DC bias to the charging device, discharge from the charging device is promoted, and the charging device has an inside. This reduces the number of rectangular parallelepiped abrasive particles. After continuous image formation in an environment of temperature 25 ° C. and humidity 50%, when the image ratio of black toner used is 2%, 10%, 50%, and 80%, respectively between 10 msec, 30 msec, 130 msec, and 205 msec, It was set to apply + 50V DC.

As described above, the presence of a rectangular parallelepiped or cubic shaped abrasive having a mass of 0.01% by mass or less and 8% by mass or less in the injection charging device eliminates image flow and enables image formation with high durability of charging performance. By supplying the cuboidal abrasive particles from the developing device, the abrasive itself is easily refreshed, and the polishing effect can be maintained for a long period of time. When the surface roughness of the photoreceptor is Rz, the groove interval is Sm, and the average particle diameter of the charged magnetic particles is D, the following formula:
2 × D / 3 ≦ Sm / Rz
By satisfying the above, it is possible to obtain better image flow prevention performance.

  Further, even when the transfer residual toner is collected by the developing device and reused, the deterioration of the developer in the charging device can be suppressed, and both reduction in toner consumption and image quality can be achieved.

(Examples 3-1 to 3-18)
<Example with a cleaning blade>
In this example, after the above-described photoconductor transfer process of the main body of the evaluation machine, evaluation was performed by installing a member for cleaning the residual toner on the photoconductor by scraping with a urethane rubber blade. Since Canon digital color copier CP2150 does not have a photoreceptor cleaning process, a cleaning blade was newly attached after the transfer process and before the injection charging process. The blade was made of the same material as the Canon copier GP405, and the cleaning contact pressure was set at a linear pressure of about 20 mN / mm and the contact angle was 25 °. Waste toner generated by the cleaning blade is sent to a waste toner box provided outside the main body by providing a conveyor belt.

  Toner C was used as a developer. The abrasive particles are externally added to the toner, and the toner is blocked and removed by the cleaning blade, but some of the externally added abrasive particles are released from the toner and pass through the cleaning blade to be supplied to the charging device. And subjected to a polishing process.

As in Examples 2-1 to 2-18, the amount of inorganic powder in the charging device is calculated from image ratio × transfer efficiency (determined from temperature and humidity sensor measurement values), and abrasive particle discharge bias application during non-image formation is applied. The time was controlled so as to be 2.0% with respect to the charged magnetic particles.
After continuous image formation in an environment with a temperature of 25 ° C. and a humidity of 50%, + 50V between 0 msec, 15 msec, 55 msec, and 85 msec when the image ratio of black toner used is 2%, 10%, 50%, and 80%, respectively. Was set to perform DC application. As for the potential of the photoconductor, the charging application voltage and the photoconductor exposure intensity were set so that the background portion potential was −450 V and the image portion (writing portion potential) was −50 V.

  In the same manner as in Examples 1-1 to 1-6, the actual machine image was evaluated according to the evaluation method. The evaluation results are shown in Table 6.

  As described above, the presence of a rectangular parallelepiped or cubic shaped abrasive having a mass of 0.01% by mass or less and 8% by mass or less in the injection charging device eliminates image flow and enables image formation with high durability of charging performance. By supplying the cuboidal abrasive particles from the developing device, the abrasive itself is easily refreshed, and the polishing effect can be maintained for a long period of time.

When the surface roughness of the photoreceptor is Rz, the groove interval is Sm, and the average particle diameter of the charged magnetic particles is D, the following formula:
2 × D / 3 ≦ Sm / Rz
By satisfying the above, it is possible to obtain better image flow prevention performance.

  Furthermore, by having an independent toner cleaning step, deterioration due to adhesion of toner colored particles to charged magnetic particles can be further reduced, and image formation with a longer life can be performed.

  In the above embodiment, strontium titanate was used as the abrasive particles, but the same effect can be obtained with barium titanate and calcium titanate.

1 is a schematic cross-sectional view showing an image forming apparatus according to the present invention. It is a graph showing the relationship between charging time, applied voltage, and charging potential. 1 is a cross-sectional view of an electrophotographic photosensitive member according to the present invention. It is an enlarged photograph of the abrasive particle concerning this invention by an electron microscope. FIG. 3 is a schematic diagram showing a contact state between abrasive particles present on charged magnetic particles and the surface of a photoreceptor. FIG. 3 is an enlarged schematic view showing a contact state between abrasive particles present on charged magnetic particles and the surface of a photoreceptor.

Explanation of symbols

101, photosensitive member 102, charging roller 103, exposure device 104, developing device 105, transfer member 106, fixing device 111, transfer material 501, charged magnetic particles 502, rectangular parallelepiped abrasive particles 503, photosensitive member surface 601, charged magnetic particles 602. , Cuboidal abrasive particles 603, photoreceptor surface

Claims (10)

Silicon atoms have a photoconductive layer composed of a non-monocrystalline material as a matrix, the surface of the electrophotographic photosensitive member the volume resistivity of the surface is not more than 10 ⁸ Ω · cm or more 10 ¹⁵ Ω · cm, charged magnetic a charging step of Ru is charged with the charging device having the particle,
An exposure step of forming an electrostatic latent image on the surface of the electrophotographic photosensitive member charged by the charging step by exposure;
A developing step of carrying a toner on a toner carrier and developing the electrostatic latent image formed by supplying the toner from the toner carrier to the surface of the electrophotographic photosensitive member to form a toner image;
In the image forming method and a transfer step of transferring to a transfer material the toner image on the surface of the developing step said electrophotographic photosensitive member formed by,
In the charging step, the surface of the electrophotographic photosensitive member is charged by applying a charging bias to the charging device and rubbing the surface of the electrophotographic photosensitive member with a magnetic brush made of the charged magnetic particles. ,
The charged magnetic particles have a volume resistance of 10 ⁴ Ω · cm to 10 ¹⁰ Ω · cm,
In the charging the device, and the primary particles was cubic and / or rectangular particle shape and an average particle size of 500nm hereinafter more 30nm inorganic powder abrasive particles of primary particles, the belt-electromagnetic particles On the other hand, it is present in an amount of 0.01% to 8% by weight ,
Inorganic powder abrasive particles, an image forming method characterized that you have adhered to the band electromagnetic particles.   The image forming method according to claim 1, wherein the inorganic powder abrasive particles are externally added to the toner, and are supplied from the developing device to the charging device to adhere to the charged magnetic particles.   3. The abrasive particles are discharged by applying a voltage having the same polarity as that of the abrasive particles in the charging device to the charging device in accordance with the image ratio during non-image formation. Image forming method. The image forming method according to any one of claims 1 to 3, characterized in that the volume resistivity of the inorganic powder abrasive particles is less than 10 ³ times 10 ^-3 times the volume resistivity of the band electromagnetic particles.   5. The image forming method according to claim 1, wherein the inorganic powder abrasive particles are strontium titanate, barium titanate, or calcium titanate.   The image forming method according to claim 1, wherein the charged magnetic particles are ferrite particles.   The inorganic powder abrasive particles are charged with a polarity opposite to that of the toner particles when the charged magnetic particles and the inorganic powder abrasive particles are rubbed with each other. Image forming method.   The method further comprises a step of cleaning the transfer residual toner from the photosensitive member by an elastic member that contacts the electrophotographic photosensitive member, wherein the average particle size of the primary particles of the inorganic powder abrasive particles is 30 nm to 300 nm. The image forming method according to claim 1.   9. The image forming method according to claim 1, wherein the transfer residual toner on the electrophotographic photosensitive member is returned to the developing unit and used again for development. When the surface roughness of the electrophotographic photosensitive member is Rz, the groove interval is Sm, and the average particle diameter of the charged magnetic particles is D, the following formula:
2 × D / 3 ≦ Sm / Rz
The image forming method according to claim 1, wherein:

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