Image forming apparatus

Abstract

To prevent the occurrence of an increase in torque due to insufficient supply of metal soap to a surface of a photoreceptor.SOLUTION: An image forming apparatus comprises: a photoconductor drum 1; an electrifying roller 2; a developing roller 4; a cleaning blade 8; a toner storage unit 3b; and a control unit 202 that controls a metal soap application operation of applying, with the developing roller 4, metal soap stored in the toner storage unit 3b to a surface of the photoconductor drum 1. When performing the metal soap application operation, the control unit 202 performs control so that the moving speed of the surface of the photoconductor drum 1 becomes larger than the moving speed of the surface of the photoconductor drum 1 when performing an image forming operation.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an image forming apparatus. Here, the image forming apparatus forms an image on a recording material (recording medium) using an electrophotographic image forming method. Examples of the image forming apparatus include a copying machine, a printer (laser beam printer, LED printer, etc.), a facsimile apparatus, a word processor, and a multifunction machine (multifunction printer) thereof.

Background Art

[0002] As an electrophotographic photoreceptor (hereinafter, also simply referred to as "photoreceptor") used in an electrophotographic image forming apparatus, organic photoreceptors are widespread due to the advantages of low cost and high productivity. This is composed of a photosensitive layer (organic photosensitive layer) using an organic material as a photoconductive substance (charge generating substance or charge transporting substance) provided on a support. In the photoreceptor, electric and mechanical external forces are directly applied in each of the processes of charging, exposure, development, transfer, and cleaning, so durability against these external forces is required. Specifically, durability against the occurrence of surface scratches and wear due to these external forces, that is, scratch resistance and abrasion resistance are required.

[0003] However, when the surface of the photoreceptor is made to have high hardness in order to obtain abrasion resistance, the surface becomes difficult to be shaved, so that discharge products such as ozone and NOx generated by discharge on the photoreceptor surface due to charging are difficult to be removed from the photoreceptor surface. As a result, the friction coefficient of the photoreceptor surface becomes high and the torque becomes high. When the torque becomes high, the load on the drive motor increases, the power consumption increases, or the motor becomes difficult to start, so it is desirable to suppress the increase in torque. As a method for suppressing the increase in torque of a photoreceptor with high hardness, for example, Patent Document 1 describes a method of containing a metal soap in a developer and supplying the metal soap from a developer carrier to the photoreceptor surface. Specifically, zinc stearate, which is a metal soap, is supplied to the surface of the photoreceptor by a developer carrier, and the surface of the photoreceptor is coated with zinc stearate to suppress the adhesion of discharge products. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-006839 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in conventional technology, if the rotation speed of the photoreceptor and the developing roller is slower than the rotation speed of the metal soap supply during the image formation operation, the lubrication of the metal soap supplied to the photoreceptor surface may be insufficient. This insufficient lubrication of the metal soap is particularly noticeable when the friction coefficient of the photoreceptor surface is high in the initial stages, requiring a large supply of metal soap, or when the metal soap is consumed and the supply of metal soap decreases towards the end of its lifespan. Insufficient supply of metal soap may lead to an increase in torque.

[0006] This invention was made under such circumstances and aims to suppress the occurrence of torque increase due to insufficient supply of metal soap to the photoreceptor surface. [Means for solving the problem]

[0007] To solve the above-mentioned problems, the present invention has the following configuration. (1) An image forming apparatus comprising: a rotatable image carrier on which an electrostatic latent image is formed; a charging member for charging the surface of the image carrier before the electrostatic latent image is formed; a developing member that contacts the image carrier and develops the electrostatic latent image formed on the surface of the image carrier with a developer to form a developer image; a cleaning member that contacts the image carrier and scrapes off the developer from the image carrier; a storage section for storing the developer containing metal soap; and a control means for controlling the execution of an image forming operation in which an image forming operation is formed on a recording material, and a coating operation in which the metal soap stored in the storage section is applied to the surface of the image carrier by the developing member, wherein the control means controls the speed of movement of the surface of the image carrier when performing the coating operation to be greater than the speed of movement of the surface of the image carrier when performing the image forming operation. [Effects of the Invention]

[0008] According to the present invention, it is possible to suppress the occurrence of torque increase due to insufficient supply of metal soap to the photoreceptor surface. [Brief explanation of the drawing]

[0009] [Figure 1] Schematic cross-sectional view of the image forming apparatus in Examples 1 and 2, and cross-sectional view of the process cartridge. [Figure 2] Schematic block diagram showing the control mode of the image forming apparatus in Examples 1 and 2. [Figure 3] Schematic diagrams of the toners in Examples 1 and 2, and a diagram illustrating ΔVr and the amount of metal soap transferred in Example 1. [Figure 4] Flowchart showing the metal soap application operation in Example 1 [Figure 5] Diagram illustrating the DD peripheral speed ratio and the amount of metal soap transferred in Example 2; Diagram illustrating the DD peripheral speed ratio and the amount of fogging on the photosensitive drum. [Figure 6] Flowchart showing the metal soap application operation in Example 2 [Modes for carrying out the invention]

[0010] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments are illustrative and do not limit the present invention to the content of these embodiments. Furthermore, in the following figures, components not necessary for describing the embodiments have been omitted. [Examples]

[0011] [1. Image forming apparatus] The overall configuration of the electrophotographic image forming apparatus of Example 1 will now be described. Figure 1(a) is a schematic cross-sectional view of the image forming apparatus 100 of Example 1. The image forming apparatus 100 of Example 1 is a full-color laser printer employing an in-line method and an intermediate transfer method. The image forming apparatus 100 can form a full-color image on a recording material S (for example, recording paper, plastic sheet, cloth, etc.) according to image information. Image information is input to the image forming apparatus 100 from an image reading device (not shown) connected to the image forming apparatus 100, or from a host device (not shown) such as a personal computer that is communicatively connected to the image forming apparatus 100.

[0012] The image forming apparatus 100 has a plurality of image forming units, namely the first, second, third, and fourth image forming units SY, SM, SC, and SK, each for forming images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Hereinafter, components that contribute to the formation of toner images of each color will be denoted by the subscripts Y, M, C, and K to distinguish the colors, although the subscripts Y, M, C, and K may be omitted except when describing a specific color. In Example 1, the image forming apparatus 100 has a plurality of image carriers, namely four drum-type electrophotographic photoreceptors 1 arranged in a direction intersecting the vertical direction. The photoreceptor drums 1 are integrated with the image forming unit S to form a process cartridge 7.

[0013] The rotatable photosensitive drum 1, which is an image carrier on which an electrostatic latent image is formed on its surface, is driven to rotate in the direction of arrow A in Figure 1(b) by a drive motor 80 (see Figure 2), which is a driving means. The charging roller 2, which is a charging member, is a single-layer roller consisting of a conductive core metal and a conductive rubber layer, for example, with an outer diameter of φ7.5 mm and a volume resistivity of 10 3 ~10 6 The coefficient of force is Ω·cm. Then, by applying a charging voltage of, for example, -1000V to the charging roller 2 using the charging voltage power supply 71 (see Figure 2), which is the first voltage application means described later, the surface of the photosensitive drum 1 is uniformly charged to -500V. A DC voltage consisting of Vd + Vth is applied to the charging roller 2, and the photosensitive drum 1 (image carrier) is uniformly charged with a charging potential Vd by discharge. Vd at this time is called the dark area potential, and is, for example, -500V. Vth is the discharge initiation voltage, and when the applied charging voltage is small, the surface potential on the photosensitive drum 1 does not increase by discharge, but from the discharge initiation voltage Vth onwards, the surface potential begins to increase by discharge. In other words, the discharge initiation voltage Vth in Example 1 is -500V.

[0014] After the surface of the photosensitive drum 1 is charged by the charging roller 2, the surface of the photosensitive drum 1 is irradiated with laser light from the exposure unit 30. The exposure unit 30 is an exposure means that irradiates laser light based on image information to form an electrostatic latent image on the surface of the photosensitive drum 1. The surface potential of the surface of the photosensitive drum 1 irradiated with laser light changes to, for example, -100V as the bright area potential Vl, and an electrostatic latent image is formed.

[0015] (Process cartridge) Figure 1(b) is a cross-sectional view of the process cartridge 7 of Embodiment 1, viewed along the longitudinal direction (rotation axis direction) of the photosensitive drum 1. The process cartridge 7 consists of a developing unit 3 and a photosensitive drum unit 13. The developing unit 3 is equipped with a developing roller 4, which is a developing member, and a toner supply roller (hereinafter referred to as "supply roller") 5, which is a supply member. The developing unit 3 is provided with a developing chamber 3a, a toner storage section 3b, a developing blade 6, and a toner transport member 22 that transports the toner 10, which is a developer, to the developing chamber 3a by rotating in the direction of arrow G. By receiving the driving force of a drive motor (not shown), the developing roller 4 starts to rotate in the direction of arrow D in Figure 1(b), and the supply roller 5 starts to rotate in the direction of arrow R in Figure 1(b). Then, a voltage of, for example, -300V is applied to the developing roller 4 as a developing voltage from a developing voltage power supply 72 (see Figure 2), which is a second voltage application means. As a result, toner 10 is supplied by the developing roller 4 to the electrostatic latent image formed on the surface of the photosensitive drum 1, that is, the portion with the bright area potential Vl described above, and developed. In this embodiment, the drive motors for the developing roller 4 and the supply roller 5 are configured separately from the drive motor for the photosensitive drum 1, but a common drive motor 80 may be used.

[0016] The process cartridge 7 has a non-volatile memory 70, which is a memory unit used during the metal soap coating operation (coating operation) described later. The non-volatile memory 70 stores the usage history of the process cartridge 7, for example, information of a new product flag that indicates whether the process cartridge 7 is new or not. The new product flag, for example, indicates that the process cartridge 7 is new if it is 0, and that the process cartridge 7 is not new and is in use if it is 1. However, the form of information on whether the process cartridge 7 is new or not stored in the non-volatile memory 70 is not limited to this. Also, although the developing unit 3 is depicted as having the non-volatile memory 70 in Figure 1(b), the photosensitive drum unit 13 may also have the non-volatile memory 70. The non-volatile memory 70 only needs to be arranged so that it can communicate with the control unit 202 described later when the process cartridge 7 is installed in the image forming apparatus 100.

[0017] The developer image (toner image) developed on the surface of the photosensitive drum 1 is transferred to the intermediate transfer belt 31 which is the intermediate transfer member shown in Fig. 1(a). The endless belt-shaped intermediate transfer belt 31 formed as the intermediate transfer member is a member for transferring the toner image on the photosensitive drum 1 to the recording material S facing the photosensitive drum 1 of each image forming unit S. The intermediate transfer belt 31 abuts against the photosensitive drum 1 of each image forming unit S and circulates (rotates) in the direction of arrow B (counterclockwise) in Fig. 1(a). Note that the intermediate transfer belt 31 may be configured to be able to abut against or separate from the photosensitive drum 1.

[0018] On the inner peripheral surface side of the intermediate transfer belt 31, transfer rollers 32 as primary transfer means (transfer members) are respectively arranged so as to face each photosensitive drum 1. And a voltage having a polarity opposite to the normal charging polarity of the toner is applied to the transfer roller 32 from the primary transfer voltage power source 73 which is the fourth voltage applying means. Thereby, the toner image on the photosensitive drum 1 is transferred (primary transfer) onto the intermediate transfer belt 31. The polarity of the toner in Example 1 has the normal polarity as the negative polarity. Therefore, primary transfer can be performed by applying a positive-polarity voltage as the primary transfer voltage (transfer voltage).

[0019] Furthermore, a secondary transfer roller 33 is positioned on the outer circumferential surface of the intermediate transfer belt 31 as a secondary transfer means. A voltage with the opposite polarity to that of the toner is applied to the secondary transfer roller 33 from a secondary transfer voltage power supply 74, which acts as a secondary transfer voltage application unit. This transfers the toner image on the intermediate transfer belt 31 to the recording material S (secondary transfer). Hereinafter, the position where the toner image is secondary transferred to the recording material S will be referred to as the secondary transfer section. For example, during full-color image formation, the above process is performed sequentially in the image formation units SY, SM, SC, and SK, and the toner images of each color are sequentially superimposed on the intermediate transfer belt 31 for primary transfer. Subsequently, the recording material S is transported to the secondary transfer section in synchronization with the movement of the intermediate transfer belt 31. Then, through the action of the secondary transfer roller 33, which is in contact with the intermediate transfer belt 31 via the recording material S, the four-color toner images on the intermediate transfer belt 31 are collectively secondary transferred to the recording material S. The recording material S onto which the unfixed toner image has been transferred is transported to the fixing device 34. In the fixing device 34, heat and pressure are applied to the recording material S, fixing the toner image to the recording material S, and the recording material S is discharged outside the image forming apparatus 100.

[0020] On the other hand, the surface potential of the photosensitive drum 1 after toner has been transferred to the intermediate transfer belt 31 is non-uniform due to the primary transfer voltage. Therefore, the surface potential of the photosensitive drum 1, which has become non-uniform due to the previous image formation, is uniformly leveled by exposing the entire surface of the photosensitive drum 1 (entire surface light irradiation) using the pre-exposure unit 27, which is a pre-exposure means. In other words, light is irradiated onto the surface of the photosensitive drum 1 to remove any residual charge on its surface. The pre-exposure unit 27 is positioned downstream of the primary transfer section, which is the contact point between the intermediate transfer belt 31 and the photosensitive drum 1, in the rotational direction of the photosensitive drum 1, and upstream of the charging section, which is the contact point between the charging roller 2 and the photosensitive drum 1, in the rotational direction of the photosensitive drum 1. The pre-exposure unit 27 exposes the surface of the photosensitive drum 1, which is the opposing part. As the light source for the pre-exposure unit 27, for example, an LED or a halogen lamp can be used. While there are no particular limitations on the light source used, LEDs are preferred because they have a low driving voltage and are easy to miniaturize. Therefore, in Example 1, LEDs are used as the light source for the pre-exposure unit 27.

[0021] Furthermore, toner that remains on the surface of the photosensitive drum 1 without being transferred by the primary transfer roller 32 is scraped off from the surface of the photosensitive drum 1 by a cleaning blade 8, which is a cleaning member that comes into contact with the photosensitive drum 1 (see Figure 1(b)). The toner scraped off by the cleaning blade 8 is collected in a waste toner storage chamber 9 located below the cleaning blade 8. Toner that remains on the intermediate transfer belt 31 without being transferred to the recording material S by the secondary transfer roller 33 is transported to a belt cleaning device 35 for the intermediate transfer belt 31, which acts as a cleaning device, and is removed. The control unit 202 will be described later. Note that the image forming apparatus in which the metal soap coating operation of Example 1 is performed is not limited to the image forming apparatus 100 shown in Figure 1(a).

[0022] [2. Control Modes of Image Forming Apparatus] Figure 2 is a block diagram illustrating the schematic control configuration of the main components of the image forming apparatus 100 in Embodiment 1. The control unit 202 is a control means that controls the operation of the image forming apparatus 100 and exchanges various electrical information signals. The control unit 202 also processes electrical information signals input from various process equipment and sensors, and processes command signals to various process equipment. The controller 200 exchanges various electrical information with the host device (not shown) and comprehensively controls the image forming operation of the image forming apparatus 100 via the interface 201 to the control unit 202 according to a predetermined control program and reference table. The control unit 202 is composed of a CPU 155, which is a central element that performs various calculations, a memory 15 such as RAM and ROM, which are memory elements, and a timer 156 for measuring time. The RAM stores sensor detection results, counter count results, calculation results, etc., and the ROM stores control programs, data tables obtained in advance through experiments, etc. Various control targets, sensors, counters, etc. in the image forming apparatus 100 are connected to the control unit 202.

[0023] The control unit 202 controls the transmission and reception of various electrical information signals and the timing of the drive of each part, thereby controlling a predetermined image formation sequence. For example, to form a toner image on the surface of the photosensitive drum 1, it controls the following high-voltage power supplies and devices. The control unit 202 controls the charging voltage power supply 71 that applies the charging voltage, the developing voltage power supply 72 that applies the developing voltage, and the supply voltage power supply 75, which is the third voltage application means for the supply roller 5 that supplies the toner supply voltage. The control unit 202 also controls the developing blade voltage power supply 76, which is the power supply for the developing blade 6, which is a toner regulating member. The control unit 202 also controls the exposure unit 30 and other components. Furthermore, the control unit 202 controls the primary transfer voltage power supply 73, the secondary transfer voltage power supply 74, and other components for forming a toner image on the recording material S. The control unit 202 controls the contact / separation mechanism 50 that controls the contact / separation between the developing roller 4 and the photosensitive drum 1, the torque detection mechanism 51 which is a detection means for the drive motor 80 of the photosensitive drum 1, and the cartridge memory communication mechanism 52 which communicates with the non-volatile memory 70. In Example 1, the control unit 202 controls the voltage power supply and the like in order to perform the metal soap coating operation, which will be described in more detail later. The control unit 202 controls the image forming operation to form a toner image on the recording material S, and the metal soap coating operation to apply the metal soap 45c contained in the toner storage section 3b to the surface of the photosensitive drum 1 using the developing roller 4.

[0024] [3. Overview of the Process Cartridge Configuration] The overall configuration of the process cartridge 7 installed in the image forming apparatus 100 of Example 1 will be explained using Figure 1(b). The process cartridge 7 is detachable from the image forming apparatus 100 via mounting means such as mounting guides (not shown) and positioning members (not shown) provided on the image forming apparatus 100. In other words, the process cartridge 7 is insertable into and removeable from the image forming apparatus 100. In Example 1, all process cartridges 7 for each color have the same shape. Each process cartridge 7 contains toner 10 of yellow (Y), magenta (M), cyan (C), and black (K), respectively. In Example 1, the process cartridge 7 is described, but the developing unit 3 may also have a developing cartridge that can be independently attached to and removed from the image forming apparatus 100. In Example 1, the configuration and operation of the process cartridge 7 for each color are substantially the same, except for the type (color) of toner 10 contained.

[0025] The process cartridge 7 comprises a developing unit 3 equipped with a developing roller 4, etc., and a photosensitive drum unit 13 equipped with a photosensitive drum 1. In Embodiment 1, the developing unit 3 and the photosensitive drum unit 13 are integrated to form the process cartridge 7, but the invention is not limited to this configuration. For example, they may be configured to be detachably attached to the image forming apparatus 100 as a developing cartridge and a photosensitive drum cartridge, respectively.

[0026] The developing unit 3 is broadly divided into a developing chamber 3a and a toner storage section 3b. The toner storage section 3b is provided with a toner transport member 22 for transporting toner 10 to the developing chamber 3a. The toner transport member 22 transports the toner 10 to the developing chamber 3a by rotating in the direction of arrow G in the figure. The developing chamber 3a is provided with a developing roller 4, which acts as a toner carrier and rotates in the direction of arrow D in the figure in contact with the photosensitive drum 1. In Embodiment 1, the developing roller 4 and the photosensitive drum 1 rotate so that their surfaces move in the same direction in the opposing developing sections. Also, a supply roller 5 and a developing blade 6 are arranged inside the developing chamber 3a. The supply roller 5 supplies toner 10 transported from the toner storage section 3b to the developing roller 4. The developing blade 6 is a toner regulating member that regulates the amount of toner 10 coated on the developing roller 4 supplied by the supply roller 5 and applies charge.

[0027] Independent voltages are applied from the power supply to the developing roller 4, the supply roller 5, and the developing blade 6 (see Figure 2). The toner 10 supplied to the developing roller 4 by the supply roller 5 is charged by friction between the developing roller 4 and the developing blade 6, and its layer thickness is regulated. The regulated toner 10 on the developing roller 4 is transported to the part opposite the photosensitive drum 1 by the rotation of the developing roller 4, and the electrostatic latent image on the photosensitive drum 1 is developed and visualized as a toner image.

[0028] During the image formation operation, a predetermined DC voltage (developing voltage: Vdc) is applied to the developing roller 4, which is set to -300V. Additionally, by applying a voltage (supply voltage: Vr = -350V) to the supply roller 5, the potential difference (ΔVr) between the supply roller 5 and the developing roller 4 is adjusted, thereby adjusting the amount of toner 10 supplied to the developing roller 4. In Example 1, ΔVr = Vdc - Vr is set to +50V (= -300V - (-350V)), setting the potential to facilitate the movement of negatively charged toner from the supply roller 5 to the developing roller 4.

[0029] When developing and visualizing the electrostatic latent image on the photosensitive drum 1 as a toner image, the developing roller 4 is rotated in contact with the circumferential surface of the photosensitive drum 1. This is to facilitate the supply of the metal soap added to the toner, as described later, onto the photosensitive drum 1. The configuration is not limited to the developing roller 4 and the photosensitive drum 1 being in contact, as long as a configuration that can supply the metal soap is available.

[0030] In the following explanation, with respect to potential and applied voltage, a large absolute value on the negative side (for example, -1000V compared to -500V) will be referred to as "high potential," and a small absolute value on the negative side (for example, -300V compared to -500V) will be referred to as "low potential." This is because we are considering the negatively charged toner 10 in Example 1 as the reference. Also, the voltage in Example 1 is expressed as a potential difference with respect to the earth potential (0V). Therefore, the developing voltage = -300V is interpreted as having a potential difference of -300V with respect to the earth potential due to the developing voltage applied to the core metal of the developing roller 4. The same applies to other voltages such as the charging voltage.

[0031] The photosensitive drum unit 13 is rotatably mounted to the photosensitive drum unit 13 via bearings (not shown). The photosensitive drum 1 is driven to rotate in the direction of arrow A in Figure 1(b) by the driving force of the drive motor 80. The photosensitive drum unit 13 also has a charging roller 2 and a cleaning blade 8 as a plate-shaped elastic body arranged so as to contact the circumferential surface of the photosensitive drum 1. One end of the cleaning blade 8 is fixed to a plate-shaped metal sheet, and the other free end abuts in a counter-direction relative to the rotation of the photosensitive drum 1, forming a cleaning nip portion which is the contact point with the photosensitive drum 1. The cleaning blade 8 rubs the surface of the photosensitive drum 1, scraping off toner 10 and fine particles remaining from the transfer process and collecting them in the waste toner storage chamber 9. This prevents contamination of the charging roller 2 and image damage caused by toner 10 being carried along with the photosensitive drum 1.

[0032] [4. Configuration of the photosensitive drum] The photosensitive drum 1 consists of a cylindrical, conductive metal support, a conductive layer as an undercoat for the support, a photosensitive layer (charge generation layer, charge transport layer) formed on the undercoat layer, and a protective layer formed on the photosensitive layer. The photosensitive drum 1 is constructed by providing a photosensitive material such as OPC (organic photopolymer), amorphous selenium, or amorphous silicon on a drum base in the shape of a cylinder, which serves as a support with an outer diameter of φ24 mm and is made of aluminum, nickel, or the like. Furthermore, the photosensitive drum 1 in Example 1 has a wear-resistant protective layer on the outermost layer to improve wear resistance. By providing a protective layer, durability can be improved.

[0033] The protective layer preferably contains conductive particles and / or charge transport material and a resin. Examples of conductive particles include metal oxide particles such as titanium dioxide, zinc oxide, tin oxide, and indium oxide. Examples of charge transport material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these substances. Among these, triarylamine compounds and benzidine compounds are preferred. Examples of resins include polyester resins, acrylic resins, phenoxy resins, polycarbonate resins, polystyrene resins, phenolic resins, melamine resins, and epoxy resins. Among these, polycarbonate resins, polyester resins, and acrylic resins are preferred.

[0034] Furthermore, the protective layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. Examples of reactions in this case include thermal polymerization, photopolymerization, and radiation polymerization. Examples of polymerizable functional groups in monomers having a polymerizable functional group include acrylic groups and methacrylic groups. Materials with charge transport ability may be used as monomers having a polymerizable functional group.

[0035] The protective layer may contain additives such as antioxidants, UV absorbers, plasticizers, leveling agents, lubrication agents, and wear resistance enhancers. Specifically, examples include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles. The average film thickness of the protective layer is preferably 0.5 μm to 10 μm, and more preferably 1 μm to 7 μm.

[0036] The protective layer can be formed by preparing a protective coating solution containing the above-mentioned materials and solvents, forming this coating film, and then drying and / or curing it. Examples of solvents used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, sulfoxide-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. In Example 1, the average film thickness of the protective layer was 3 μm.

[0037] [5. Toner Configuration] A schematic diagram of the toner 10 used in Example 1 is shown in Figure 3(a). In Example 1, inorganic particle toner 45 is used, in which inorganic silicon 45b, indicated by the white circle, is added to the mother particle 45a to ensure fluidity and improve chargeability. The toner used in Example 1 is a non-magnetic, one-component particle polymerization toner with negative charge polarity, and the average particle size is 7 μm.

[0038] Furthermore, in order to reduce the coefficient of friction on the surface of the photosensitive drum 1, a metal soap 45c, indicated by a black circle, is added in addition to the inorganic silicon 45b. Note that only a portion of the inorganic silicon 45b and metal soap 45c are labeled with symbols. Originally, discharge products are highly adhesive and increase the coefficient of friction on the surface of the photosensitive drum 1, but by supplying the metal soap 45c to the surface of the photosensitive drum 1, the adhesion of discharge products to the surface of the photosensitive drum 1 can be suppressed, and the increase in the coefficient of friction can be suppressed.

[0039] Metal soap 45c is a general term for long-chain fatty acids and metal salts other than sodium and potassium. Specifically, examples include metal salts of fatty acids such as stearic acid, myristic acid, lauric acid, ricinoleic acid, and octic acid, and metal species such as lithium, magnesium, calcium, barium, and zinc. For example, metal soap 45c may contain at least one of zinc, calcium, and magnesium as the metal species. In Example 1, zinc stearate is added as metal soap 45c. However, the type of metal soap 45c is not limited to this, and lead stearate, cadmium stearate, barium stearate, calcium stearate, aluminum stearate, zinc stearate, magnesium stearate, zinc lauryl stearate, and zinc myristate may also be used as appropriate, and at least one of these should be selected. For example, metal soap 45c may contain at least one of zinc stearate, calcium stearate, and magnesium stearate.

[0040] The amount of metal soap 45c added externally should preferably be 0.6 wt% (weight percentage) or less. A higher amount of external addition is more effective in suppressing the adhesion of discharge products to the photosensitive drum 1, but excessive addition reduces the fluidity of the toner, resulting in lower image density in the latter half of the image. This is a phenomenon called poor tracking performance, where tracking performance decreases as you approach the trailing edge when outputting a solid black image. Here, the trailing edge of the image refers to the upstream edge in the transport direction of the recording material S in the image formed on the recording material S. On the other hand, the amount of metal soap 45c added externally should preferably be 0.05 wt% or more. If the amount of external addition is too low, the effect of metal soap 45c will not be easily realized.

[0041] The average particle size of the metal soap 45c is preferably 0.15 μm or more and 2.0 μm or less. If the average particle size of the metal soap 45c is smaller than 0.15 μm, it becomes difficult to coat the surface of the photosensitive drum 1. This is particularly noticeable when there are grooves on the surface of the photosensitive drum 1, as described later. On the other hand, if the particle size is larger than 2.0 μm, it cannot pass through the developing blade 6 in the developing unit 3 and is left behind in the developing chamber 3a, making it difficult to supply to the surface of the photosensitive drum 1. Hereafter, in Example 1, "toner" refers to the general term for the combination of the mother particles 45a and the external additives (inorganic silicon 45b, metal soap 45c).

[0042] This document describes the method for measuring the average particle size of metal soap 45c. 0.5 g of metal soap 45c was mixed with 10 mL of ethanol and ultrasonically dispersed for 5 minutes using an ultrasonic disperser manufactured by Nippon Seiki Co., Ltd. Next, ethanol was circulated as the measurement solvent. Then, the resulting dispersion of metal soap 45c was added to a Nikkiso Co., Ltd. Microtrac laser diffraction / scattering particle size distribution analyzer (SPA type) until the DV (diffractive light intensity), a value related to the integrated scattered light intensity of the particles, reached 0.6 to 0.8. The particle size distribution in this state was then measured, and the median diameter, obtained as the cumulative median diameter (50% diameter), was defined as the average particle size.

[0043] The metal soap 45c with the above average particle size may be manufactured, for example, by a double decomposition method in which an aqueous solution of a fatty acid salt is reacted with an aqueous solution or dispersion of an inorganic metal salt. In Example 1, zinc stearate with an average particle size of 0.60 μm was used. The zinc stearate, as the metal soap 45c, is attached to the toner particles by being charged with opposite polarity to the toner, and is supplied onto the photosensitive drum 1 when not forming an image.

[0044] Next, a method for producing toner particles will be described. Known methods can be used to produce toner particles, including the kneading and grinding method and the wet manufacturing method. From the viewpoint of uniform particle size and shape control, the wet manufacturing method is preferred. Furthermore, as a wet manufacturing method, methods such as suspension polymerization, dissolution and suspension, emulsion polymerization and agglutination, and emulsion agglutination may be used.

[0045] Example 1 describes the suspension polymerization method. In the suspension polymerization method, first, a polymerizable monomer composition is prepared by uniformly dissolving or dispersing polymerizable monomers for generating a binder resin, and other additives such as colorants as needed, using a disperser such as a ball mill or ultrasonic disperser. This step is called the preparation step of the polymerizable monomer composition. At this time, polyfunctional monomers, chain transfer agents, and release agents such as wax, charge control agents, and plasticizers can be added as needed. The following vinyl polymerizable monomers are suitable examples of polymerizable monomers used in the suspension polymerization method.

[0046] Styrene; styrene derivatives such as α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-phenylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, n-amyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n-nonyl acrylate, cyclohexyl acrylate, benzyl acrylate, dimethyl phosphate ethyl acrylate, diethyl phosphate ethyl acrylate, dibutyl phosphate ethyl acrylate Acrylic polymerizable monomers such as acrylate and 2-benzoyloxyethyl acrylate; methacrylic polymerizable monomers such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, n-nonyl methacrylate, diethyl phosphate ethyl methacrylate, and dibutyl phosphate ethyl methacrylate; methylene aliphatic monocarboxylic acid esters; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, vinyl benzoate, and vinyl formate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether; vinyl methyl ketone, vinyl hexyl ketone, and vinyl isopropyl ketone.

[0047] Next, the polymerizable monomer composition is added to a pre-prepared aqueous medium, and droplets of the polymerizable monomer composition are formed to the desired toner particle size using a stirrer or disperser with high shear force. This process is called the granulation process. It is preferable that the aqueous medium in the granulation process contains a dispersion stabilizer in order to control the particle size of the toner particles, sharpen the particle size distribution, and suppress the coalescence of toner particles during the manufacturing process. Dispersion stabilizers are generally broadly classified into polymers that exhibit repulsive force due to steric hindrance and poorly water-soluble inorganic compounds that stabilize dispersion through electrostatic repulsion. Fine particles of poorly water-soluble inorganic compounds are suitable for use because they dissolve in acids and alkalis, and can be easily removed by washing with an acid or alkali after polymerization.

[0048] For dispersion stabilizers of poorly water-soluble inorganic compounds, those containing magnesium, calcium, barium, zinc, aluminum, or phosphorus are preferably used. More preferably, those containing magnesium, calcium, aluminum, or phosphorus are desired. Specifically, the following are examples: magnesium phosphate, tricalcium phosphate, aluminum phosphate, zinc phosphate, magnesium carbonate, calcium carbonate, magnesium hydroxide, calcium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, and hydroxyapatide.

[0049] Organic compounds, such as polyvinyl alcohol, gelatin, methylcellulose, methylhydroxypropylcellulose, ethylcellulose, sodium salts of carboxymethylcellulose, and starch, may be used in combination with the above-mentioned dispersion stabilizers. It is preferable to use these dispersion stabilizers in an amount of 0.01 parts by mass to 2.00 parts by mass per 100 parts by mass of polymerizable monomer.

[0050] Furthermore, in order to further refine these dispersion stabilizers, a surfactant may be added in an amount of 0.001 parts by mass or more and 0.1 parts by mass or less per 100 parts by mass of polymerizable monomer. Specifically, commercially available nonionic, anionic, and cationic surfactants can be used. For example, sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium lauryl sulfate, potassium stearate, and calcium oleate are preferably used.

[0051] After the granulation process, or while the granulation process is being carried out, the polymerizable monomers contained in the polymerizable monomer composition are polymerized at a temperature preferably between 50°C and 90°C to obtain a toner particle dispersion. This process is called the polymerization process. During the polymerization process, it is preferable to stir the mixture to ensure a uniform temperature distribution within the container. When a polymerization initiator is added, it can be added at any timing and for any required time. Furthermore, the temperature may be raised in the latter half of the polymerization reaction to obtain a desired molecular weight distribution. In addition, to remove unreacted polymerizable monomers, by-products, etc., from the system, a portion of the aqueous medium may be removed by distillation in the latter half of the reaction or after the reaction is completed. The distillation operation can be carried out at atmospheric pressure or under reduced pressure.

[0052] Oil-soluble initiators are generally used as polymerization initiators in suspension polymerization. Examples include the following: Azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 1,1'-azobis(cyclohexane-1-carbonitride), and 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile; peroxide initiators such as acetylcyclohexylsulfonyl peroxide, diisopropyl peroxycarbonate, decanonyl peroxide, lauroyl peroxide, stearoyl peroxide, propionyl peroxide, acetyl peroxide, tert-butylperoxy-2-ethylhexanoate, benzoyl peroxide, tert-butylperoxyisobutyrate, cyclohexanone peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, tert-butylhydroperoxide, di-tert-butyl peroxide, tert-butylperoxypivalate, and cumenehydroperoxide.

[0053] Polymerization initiators may be used in combination with water-soluble initiators as needed, including the following: ammonium persulfate, potassium persulfate, 2,2'-azobis(N,N'-dimelenisobutyroamidine) hydrochloride, 2,2'-azobis(2-aminodinopropane) hydrochloride, azobis(isobutylamidine) hydrochloride, 2,2'-azobisisobutyronitrile sulfonate sodium, ferrous sulfate, or hydrogen peroxide.

[0054] These polymerization initiators can be used individually or in combination, and chain transfer agents, polymerization inhibitors, etc., can be further added to control the degree of polymerization of the polymerizable monomers. The toner of the present invention may contain an organosilicon polymer, and the organosilicon polymer may have one to three carbon atoms directly bonded to the silicon atoms. The organosilicon polymer may also have a substructure represented as R-SiO3 / 2, where R is a hydrocarbon group having one to six carbon atoms, or R may be a hydrocarbon group having one to three carbon atoms.

[0055] The amount of inorganic silica transferred during water washing was controlled using a Henschel mixer (manufactured by Nippon Coke Industries Co., Ltd.) by changing the external additive conditions: the amount of external additive, the rotation speed of the nozzle tip (peripheral speed), and the rotation time of the nozzle (duration). Table 1 below shows the external additive conditions for toner a. Details regarding the peripheral speed and duration of the external additive conditions are as described in Japanese Patent Publication No. 2016-38591. In addition, 0.20 wt% zinc stearate was added externally to the toner used in Example 1. [Table 1] Table 1 shows the conditions for inorganic silicon particles and metal soaps. For inorganic silicon particles, the conditions for the first and second stages of external addition are shown, indicating the silica content (wt%) (e.g., 0.8), equipment (e.g., surface modification equipment), peripheral speed (m / s) (e.g., 40), and time (sec) (e.g., 300, 60). For metal soaps, the type (e.g., zinc stearate) and the amount added (wt%) (e.g., 0.2) are shown.

[0056] [6. Effects of discharge products on the photosensitive drum] When performing an image forming operation using the image forming apparatus 100, discharge is generated by the charging roller 2, which may produce discharge products such as ozone and NOx that adhere to the surface of the photosensitive drum 1. These discharge products are scraped off by the cleaning blade 8 that contacts the photosensitive drum 1, but if the amount of discharge exceeds the amount that is scraped off, they gradually accumulate on the surface of the photosensitive drum 1 with repeated image forming operations. In the contact charging method, the amount of discharge is less and the amount of discharge products generated is less compared to the corona charging method using a corona charger. However, because there is a tiny gap between the photosensitive drum 1 and the charging roller 2, even if only a small amount of discharge products are generated, they tend to adhere to the surface of the photosensitive drum 1 due to physical friction between the photosensitive drum 1 and the charging roller 2. When discharge products adhere to the surface of the photosensitive drum 1, the coefficient of friction between the surface of the photosensitive drum 1 and the cleaning blade 8 increases. As a result, the driving torque of the photosensitive drum 1 increases, increasing the load on the drive motor 80, which can lead to increased power consumption and starting failure of the drive motor 80. Therefore, in order to reduce the influence of discharge products, in Example 1, metal soap 45c is supplied to the surface of the photosensitive drum 1, and a film of metal soap 45c is formed on the surface of the photosensitive drum 1, thereby suppressing the adhesion of discharge products.

[0057] [7. Metal soap application process] In Example 1, a metal soap coating operation is performed separately from the normal image forming operation. The timing for performing the metal soap coating operation is determined to be when the process cartridge is new, a predetermined number of prints have been made, and the torque during driving is high, and it is performed during non-image forming operations when no image forming operation is being performed. For example, in this example, it is performed while the photosensitive drum 1 is rotating before the image forming operation, or while the photosensitive drum 1 is rotating after the image forming operation. It may also be performed at a timing specified by the user. In Example 1, the metal soap coating operation is performed only when the process cartridge 7 is new. In other words, the control unit 202 performs the metal soap coating operation when a new photosensitive drum 1 is installed in the image forming apparatus 100.

[0058] In the metal soap coating operation, when the process cartridge 7 is in its initial state of use, the friction coefficient of the surface of the photosensitive drum 1 is high, so metal soap 45c is quickly and actively supplied to the surface of the photosensitive drum 1 to reduce the friction coefficient. On the other hand, since the blocking layer made of the external additive has not yet been sufficiently formed between the photosensitive drum 1 and the cleaning blade 8, and the cleaning performance is unstable, it is necessary to control the supply of toner 10.

[0059] Therefore, in the metal soap coating operation, it is desirable to actively supply only the metal soap 45c and to reduce the coefficient of friction on the surface of the photosensitive drum 1 by setting the potential difference ΔVr (=Vdc-Vr) of the supply roller 5 with respect to the developing roller 4 to the opposite polarity of the metal soap 45c. By setting ΔVr to the opposite polarity of the charged metal soap 45c, it is possible to move the metal soap 45c towards the developing roller 4 and suppress its movement towards the supply roller 5. As a result, a large amount of metal soap 45c can be supplied onto the surface of the photosensitive drum 1.

[0060] In Example 1, during the metal soap coating operation, Vdc = -300V, Vr = -100V, and ΔVr = -200V are set. As a result, the metal soap 45c is positively charged, causing the metal soap 45c itself to actively move towards the developing roller 4. That is, when performing the metal soap coating operation, the control unit 202 controls the developing voltage power supply 72 and the supply voltage power supply 75 so that a second potential difference is formed at the contact point between the supply roller 5 and the developing roller 4. Here, the second potential difference refers to a potential difference such that an electrostatic force acts on the metal soap in the direction from the supply roller 5 to the developing roller 4.

[0061] Furthermore, a charging voltage is applied to control the photosensitive drum 1 to a dark area potential Vd, and the development voltage is set to the same as during the image formation operation. In other words, when the metal soap coating operation is performed, the control unit 202 controls the first potential difference (back contrast), which is the difference between the potential of the surface of the photosensitive drum 1 charged by the charging roller 2 and the development voltage, to be greater than the first potential difference during the image formation operation. This enables so-called solid white printing, so that only the metal soap 45c is developed on the surface of the photosensitive drum 1.

[0062] In fact, when the amount of metal soap 45c transferred to the surface of the photosensitive drum 1 was measured, it was found that the amount of metal soap 45c transferred increases when ΔVr is small (when Vr is on the positive polarity side of Vdc), as shown in Figure 3(b). Figure 3(b) is a graph showing ΔVr [V] on the horizontal axis and the amount of metal soap 45c transferred [atom% (atomic percentage)] on the vertical axis. As shown by the black circles in the graph of Figure 3(b), it can be seen that the amount of metal soap 45c transferred increases as ΔVr increases on the negative polarity side. The amount of metal soap 45c transferred to the surface of the photosensitive drum 1 was measured using a scanning X-ray photoelectron spectroscopy analyzer.

[0063] <<Measurement conditions for scanning X-ray photoelectron spectroscopy>> Analyzer: Scanning X-ray photoelectron spectrometer (ESCA system) ULVAC PHI 5700 (manufactured by ULVAC-PHI) Vacuum degree: 3.99×10-5Pa or less X-ray source: Mg source Scan: Narrow scan Measured elements: C1s, O1s, Mg2s, Si2p, Zn2p3 X-ray incident angle: 45 degrees. Measurement method: Electron beam or ultraviolet irradiation area with a wavelength of 125-260 nm and For any one location in the area that has not been irradiated with electron beam or ultraviolet light. It was measured. Analysis software: “PHI MultiPak” (trademark) (ULVAC-PHI Using (company-made) Smoothing correction: Point 9, Background correction: OFF SET The spectra of each element were displayed and a baseline was drawn. Spectral area The elemental concentration values ​​(atom%) were calculated from the data.

[0064] [8. Control procedure for metal soap application operation] The control procedure for the metal soap coating operation will be explained with reference to the flowchart in Figure 4. In Embodiment 1, when the process cartridge 7 is detected as new, the control unit 202 executes the metal soap coating operation from step 1 onwards (hereinafter referred to as S). In S1, the control unit 202 detects that the process cartridge 7 has been installed in the image forming apparatus 100. When the process cartridge 7 is installed in the image forming apparatus 100, the non-volatile memory 70 of the process cartridge 7 communicates with the control unit 202 through a contact (not shown) with the image forming apparatus 100. In S2, the control unit 202 communicates with the non-volatile memory 70 of the process cartridge 7 using the cartridge memory communication mechanism 52. Here, the control unit 202 obtains new product flag information (for example, 0 for new product, 1 for used product) through data communication. In S3, based on the information obtained in S2, the control unit 202 determines whether the installed process cartridge 7 is new (a new process cartridge) or not. In S3, if the control unit 202 determines that the process cartridge 7 is not new, the metal soap coating operation is not necessary and the process is terminated.

[0065] In S3, if the control unit 202 determines that the process cartridge 7 is new, it proceeds to S4. In S4, the control unit 202 performs the metal soap application operation. In S5, the control unit 202 applies (turns on) the charging voltage using the charging voltage power supply 71, the developing voltage using the developing voltage power supply 72, the developing blade voltage using the developing blade voltage power supply 76, and the supply voltage using the supply voltage power supply 75. Along with these controls, the control unit 202 starts driving the developing roller 4 and the photosensitive drum 1, brings the developing roller 4 into contact with the photosensitive drum 1 using the contact / separation mechanism 50, and further starts measuring the metal soap application operation time T using the timer 156.

[0066] In S6, the control unit 202 determines whether the metal soap application time T is greater than or equal to a predetermined time by referring to the timer 156. If the control unit 202 determines in S6 that the metal soap application time T is less than the predetermined time, it returns to S6 and continues to execute the metal soap application operation. If the control unit 202 determines in S6 that the metal soap application time T is greater than or equal to the predetermined time, it proceeds to S7. In S7, the control unit separates the developing roller 4 from the photosensitive drum 1 using the contact / separation mechanism 50 and stops the driving of the developing roller 4 and the photosensitive drum 1. The control unit 202 also turns OFF the charging voltage with the charging voltage power supply 71, the developing voltage with the developing voltage power supply 72, the developing blade voltage with the developing blade voltage power supply 76, and the supply voltage with the supply voltage power supply 75, thereby ending the metal soap application operation. In Embodiment 1, the predetermined time was set to 120 seconds, for example. The predetermined time is not limited to 120 seconds and can be set as appropriate. The predetermined time should be set to the amount of time required to supply enough metal soap 45c to reduce the frictional force between the photosensitive drum 1 and the cleaning blade 8. Alternatively, the primary transfer roller 32 may be configured to allow for contact and separation, and the primary transfer roller 32 may be separated during the metal soap application operation.

[0067] [9. Verification of the effects of Example 1] The experiment conducted to demonstrate the effects of Example 1 will be described. In this experiment, 1000 sheets of low-intermittent printing endurance were performed under low-temperature, low-humidity conditions (temperature 15°C, humidity 10%) where contamination of the charging roller 2 is likely to occur, and the torque and contamination of the charging roller 2 were evaluated. In this low-intermittent printing endurance test, horizontal lines with an image ratio of 1% were printed on the recording material S. In the metal soap coating operation of Example 1, the following surface movement speed difference was provided between the surface of the developing roller 4 and the surface of the photosensitive drum 1. The surface movement speed difference refers to the difference between the rotational speed on the surface of the developing roller 4 (hereinafter referred to as surface movement speed) and the surface movement speed of the photosensitive drum 1. Hereinafter, the ratio of the surface movement speed of the developing roller 4 to the surface movement speed of the photosensitive drum 1 will be referred to as the DD peripheral speed ratio.

[0068] The rotation speed of the photosensitive drum 1 was set to 1.2 times that of the image forming operation (a multiplier relative to the maximum rotation speed of multiple image forming operations), and the rotation speed of the developing roller 4 was set to the same as that of the image forming operation (a multiplier relative to the maximum rotation speed of multiple image forming operations), and the DD peripheral speed ratio was set to 75%. In other words, in Example 1, the control unit 202 controls the movement speed of the surface of the photosensitive drum 1 when performing the metal soap coating operation so that it is greater than the movement speed of the surface of the photosensitive drum 1 when performing the image forming operation. As an example to compare the effect of Example 1, in Comparative Example 1-1, the metal soap coating operation was not performed when the drum was new. In the metal soap coating operation of Comparative Example 1-2, the rotation speed of the photosensitive drum 1 was set to 1 / 4 times that of the image forming operation, the rotation speed of the developing roller 4 was set to 1 / 3 times that of the image forming operation, and the DD peripheral speed ratio was set to 120%. In the metal soap coating operation of Comparative Examples 1-3, the rotation speed of the photosensitive drum 1 was set to 1 / 4 times that of the image forming operation, and the rotation speed of the developing roller 4 was set to the same as that of the image forming operation, with the DD peripheral speed ratio set to 360%.

[0069] <Verification Result 1> Table 2 shows the verification results. [Table 2] Table 2 shows Example 1 in the second column, Comparative Example 1-1 in the third column, Comparative Example 1-2 in the fourth column, and Comparative Example 1-3 in the fifth column. The first column shows various conditions during the metal soap coating operation, initial torque, contamination status (○, ×, etc.), and torque and contamination status after printing 1000 sheets (1K). The various conditions are the rotation speed of the photosensitive drum 1, the rotation speed of the developing roller 4, and the DD peripheral speed ratio. ○ indicates a situation where the torque is high or contamination of the charging roller 2 does not occur or can be considered not to occur. △ indicates a situation where the torque is high or contamination of the charging roller 2 occurred, but it is within an acceptable range. × indicates a situation where the torque is high or contamination of the charging roller 2 occurred. ×× indicates a situation where the torque is high or contamination of the charging roller 2 occurred, and the degree of occurrence was significant.

[0070] In Example 1, no torque increase or image defects due to contamination of the charging roller 2 occurred up to 1000 sheets. The reason for this is explained below. When the process cartridge 7 is new, the rotation speed of the photosensitive drum 1 is 1.2 times that of the image formation operation. Therefore, the contact pressure of the cleaning blade 8, which is in contact with the photosensitive drum 1 in the counter direction, is higher than that during image formation. Because the metal soap 45c is pressed firmly against the photosensitive drum 1, a film can be effectively formed on the surface of the photosensitive drum 1, suppressing the torque increase after the metal soap application operation and preventing image defects.

[0071] On the other hand, in Comparative Example 1-1, the metal soap coating operation was not performed when the process cartridge 7 was new, resulting in a high coefficient of friction on the surface of the photosensitive drum 1 and an increase in initial torque. In addition, the inhibitory layer consisting of the external additive had not yet been sufficiently formed between the photosensitive drum 1 and the cleaning blade 8, resulting in unstable cleaning performance and contamination of the charging roller 2. Although the torque decreased slightly after 1000 prints, the initial effects caused contamination of the charging roller 2, resulting in poorly charged images.

[0072] In Comparative Examples 1-2, the DD peripheral speed ratio during the metal soap coating operation was 120%, resulting in increased toner rolling, which increased the contact opportunities between the metal soap 45c and the photosensitive drum 1, making transfer more likely. However, because the rotation speed of the developing roller 4 was 1 / 3 that of the image formation operation, even if the metal soap coating operation was performed for 120 seconds, the number of rotations (travel distance) of the developing roller 4 was 1 / 3 that of Example 1. Therefore, if the friction coefficient of the surface of the photosensitive drum 1 was high initially, the supply of the external additive was insufficient, and the initial torque increased, similar to Comparative Examples 1-1. In addition, the blocking layer was not sufficiently formed, resulting in unstable cleaning performance and contamination of the charging roller 2.

[0073] In Comparative Examples 1-3, when the metal soap coating operation was performed for 120 seconds, the DD peripheral speed ratio was high at 360%, resulting in a large amount of fouled toner being developed on the photosensitive drum 1 and passing through the cleaning blade 8. A large amount of toner 10 adhered to the charging roller 2, causing poorly charged images due to contamination of the charging roller 2. Although the contamination of the charging roller 2 stopped after 1000 prints, poorly charged images still occurred due to the initial effects.

[0074] In Example 1, during the metal soap coating operation, increasing the rotation speed of the photosensitive drum 1 to 1.2 times that of the image forming operation temporarily increased the contact pressure, effectively forming a coating. However, increasing the rotation speed of the photosensitive drum 1 to the same speed as during the image forming operation resulted in excessively high torque, causing the rotation of the photosensitive drum 1 to become unstable and resulting in image defects. Therefore, increasing the rotation speed of the photosensitive drum 1 only during the metal soap coating operation allows for a balance between image quality and torque. Furthermore, in Example 1, the rotation speed of the developing roller 4 during the metal soap coating operation was set to 1x, but this is not always the case; a faster rotation speed of the developing roller 4 allows for a greater supply of metal soap 45c, so a speed of 1x or higher is desirable. As explained above, in this verification, by performing the metal soap coating operation described in Example 1, it was possible to suppress the increase in torque and prevent contamination of the charging roller 2.

[0075] As described above, according to Example 1, it is possible to suppress the occurrence of torque increase due to insufficient supply of metal soap to the photoreceptor surface. [Examples]

[0076] In Example 2, as one method for more effectively applying metal soap during the metal soap application operation of Example 1, the optimal range for the surface movement speed difference between the surface of the developing roller 4 and the surface of the photosensitive drum 1 is described. In Example 2, the non-volatile memory 70 stores information regarding the usage history of the process cartridge 7, in other words, the photosensitive drum 1. The usage history information includes the number of rotations of the photosensitive drum 1 or the number of recording materials S on which the image forming operation was performed.

[0077] [1. Surface movement speed during metal soap application] The developing roller 4 contacts the photosensitive drum 1 to form a developing nip in the developing section. By creating a difference in surface movement speed between the surface of the developing roller 4 and the surface of the photosensitive drum 1, the toner 10 rotates in the developing nip and supplies metal soap 45c to the photosensitive drum 1. Increasing the DD peripheral speed ratio increases the rolling of the toner 10, which increases the contact opportunities between the metal soap 45c and the photosensitive drum 1, making it easier to form a film of metal soap 45c on the surface of the photosensitive drum 1. Therefore, it is desirable to have a large difference between the surface movement speed of the developing roller 4 and the surface movement speed of the photosensitive drum 1.

[0078] In fact, when the amount of metal soap 45c transferred to the surface of the photosensitive drum 1 was measured, it was found that the amount of metal soap 45c transferred increased as the DD peripheral speed ratio increased (as the developing roller 4 rotated faster than the photosensitive drum 1), as shown in Figure 5(a). Figure 5(a) shows the DD peripheral speed ratio [%] on the horizontal axis and the amount of metal soap 45c transferred [atom%] on the vertical axis. As shown in Figure 5(a), the amount of metal soap 45c transferred increases as the DD peripheral speed ratio increases. The amount of metal soap 45c transferred to the surface of the photosensitive drum 1 was measured using a scanning X-ray photoelectron spectroscopy analyzer, as in Example 1.

[0079] The DD peripheral speed ratio is one indicator that expresses the difference in surface movement speed between the surface of the photosensitive drum 1 and the surface of the developing roller 4. For example, the difference in surface movement speed (DD peripheral speed difference) may be used as an indicator instead of the DD peripheral speed ratio. When changing the DD peripheral speed ratio or the DD peripheral speed difference, the rotation speed of the developing roller 4 may be changed, or the rotation speed of the photosensitive drum 1 may be changed.

[0080] However, it has been found that if the image forming operation is constantly performed at a high DD peripheral speed ratio, the occurrence of fogging increases due to toner degradation. Toner degradation occurs when an excessive amount of metal soap 45c is supplied in the early stages of using the process cartridge 7, causing the metal soap 45c to be depleted from the developing chamber 3a and toner storage section 3b. Furthermore, toner degradation also causes the following phenomenon: as the use of the process cartridge 7 progresses (durability), the number of times the toner 10 is rubbed increases, the toner 10 degrades, the non-electrostatic adhesion force increases, and the amount of toner on the developing roller 4 rises. When the amount of toner on the developing roller 4 rises, the apparent potential difference with the photosensitive drum 1 decreases, which increases the occurrence of fogging.

[0081] Figure 5(b) shows the relationship between the DD peripheral speed ratio and the amount of fogging in the process cartridge 7 of Example 2 at the initial and final stages. In Figure 5(b), the horizontal axis shows the DD peripheral speed ratio [%], and the vertical axis shows the amount of fogging [%] generated on the photosensitive drum 1. In Figure 5(b), black circles indicate the value in the initial state of the process cartridge 7, and × indicates the value in the final state where use has progressed and replacement is approaching (close to the end of life). As shown in Figure 5(b), the amount of fogging increases as the DD peripheral speed ratio increases, and even at the same DD peripheral speed ratio, it increases from the initial stage to the final stage. If a large amount of toner due to fogging is developed on the photosensitive drum 1, it may lead to cleaning failure. In the configuration of Example 2, it is desirable to use a DD peripheral speed ratio between 60% and 140% so that the amount of fogging on the photosensitive drum 1 is approximately 4% or less. Furthermore, similar to Example 1, a charging voltage is applied to control the photosensitive drum 1 to a dark area potential Vd, and the development voltage is set to the same as during the image formation operation, thereby performing so-called solid white printing.

[0082] [2. Control procedure for metal soap application operation] Referring to the flowchart in Figure 6, the control procedure for the metal soap coating operation in Example 2 will be explained. In Example 2, in addition to the new condition as in Example 1, the control unit 202 executes the metal soap coating operation from S12 onward when the number of printed sheets exceeds a predetermined cumulative number, or when it is determined that the torque during driving is high. That is, the control unit 202 performs the metal soap coating operation when the information regarding the usage history stored in the non-volatile memory 70 exceeds a predetermined number, or when the torque detected by the torque detection mechanism 51 exceeds a predetermined torque. In the following explanation, the control unit 202 counts the number of recording materials S printed by the image forming operation since the completion of the previous metal soap coating operation (hereinafter also referred to as the cumulative number of prints) using a counter.

[0083] In S12, the control unit 202 executes the image forming operation when the image forming apparatus 100 is ready for image forming and a print signal is input by the user. In S13, when the image forming operation is completed, the control unit 202 stops the drive by separating the developing roller 4 from the photosensitive drum 1 using the contact / separation mechanism 50. The control unit 202 also turns OFF the charging voltage from the charging voltage power supply 71, the developing voltage from the developing voltage power supply 72, the developing blade voltage from the developing blade voltage power supply 76, and the supply voltage from the supply voltage power supply 75.

[0084] In S14, the control unit 202 checks the usage history from the non-volatile memory 70 of the process cartridge 7 via the cartridge memory communication mechanism 52. The non-volatile memory 70 of the process cartridge 7 stores information such as the usage history of the process cartridge 7, for example, the number of prints (cumulative number) for which image forming operations were performed using that process cartridge 7. The non-volatile memory 70 of the process cartridge 7 may also store the rotation speed of the photosensitive drum 1. In other words, the usage history of the process cartridge 7, or in other words the usage history of the photosensitive drum 1, includes the number of prints and the rotation speed of the photosensitive drum 1.

[0085] In S15, the control unit 202 determines, based on the information read in S14, whether the cumulative number of prints since the previous metal soap coating operation is equal to or greater than a predetermined number. If the control unit 202 determines in S15 that the cumulative number of prints is less than the predetermined number, it proceeds to S16; if it determines that the cumulative number is equal to or greater than the predetermined number, it proceeds to S18. In S16, the control unit 202 proceeds to the torque detection operation of the drive motor 80 of the photosensitive drum 1. The control unit 202 detects the torque of the drive motor 80 of the photosensitive drum 1 using the torque detection mechanism 51. The torque detection of the drive motor 80 by the torque detection mechanism 51 may be performed using a known method. In Embodiment 2, the predetermined number was set to 1000. The setting of the predetermined number may be determined based on the number of prints at which overprinting occurs, etc., depending on the individual image forming apparatus.

[0086] In S17, the control unit 202 determines whether the torque value of the drive motor 80 detected by the torque detection mechanism 51 is equal to or greater than a predetermined threshold. If the control unit 202 determines in S17 that the detected torque value is equal to or greater than the predetermined threshold, it proceeds to S18. If it determines that the torque value is less than the predetermined threshold, it terminates the printing operation. In Embodiment 2, the predetermined threshold used for the determination in S17 was set to 2.0 kgf·cm. The setting of the predetermined threshold may be determined based on the torque value at which fouling occurs, etc., depending on the individual image forming apparatus.

[0087] In S18, the control unit 202 starts the metal soap application operation. In S19, the control unit 202 applies (turns on) the charging voltage using the charging voltage power supply 71, the developing voltage using the developing voltage power supply 72, the developing blade voltage using the developing blade voltage power supply 76, and the supply voltage using the supply voltage power supply 75. The control unit 202 also starts driving the developing roller 4 and the photosensitive drum 1, brings the developing roller 4 into contact with the photosensitive drum 1 using the contact / separation mechanism 50, and starts measuring the metal soap application operation time T using the timer 156.

[0088] In S20, the control unit 202 refers to the timer 156 and determines whether the metal soap application operation time T is equal to or greater than a predetermined time. If the control unit 202 determines in S20 that the metal soap application operation time T is less than the predetermined time, it returns to S20 and continues to execute the metal soap application operation. If the control unit 202 determines in S20 that the metal soap application operation time T is equal to or greater than the predetermined time, it proceeds to S21. In S21, the control unit 202 separates the developing roller 4 from the photosensitive drum 1 using the contact / separation mechanism 50 and stops the driving of the developing roller 4 and the photosensitive drum 1. The control unit 202 also turns OFF the charging voltage with the charging voltage power supply 71, the developing voltage with the developing voltage power supply 72, the developing blade voltage with the developing blade voltage power supply 76, and the supply voltage with the supply voltage power supply 75, and terminates the metal soap application operation in S22.

[0089] In S23, the control unit 202 determines whether there is a request for continuous printing. If it determines that there is no request, it proceeds to the print termination operation and terminates the printing operation. In S23, if the control unit 202 determines that there is a request for continuous printing, it returns to processing in S12 and repeats the operations in S12 to S23 until there are no more requests for continuous printing. In Embodiment 2, the predetermined time was set to 5 seconds. The predetermined time is not limited to 5 seconds and can be set as appropriate. The metal soap application operation in S18 may be performed immediately after the image forming operation in S12 without separating the developing roller 4, or it may be performed while the various voltages are applied and driven as is.

[0090] [3. Verification of the effects of Example 2] The experiment conducted to demonstrate the effects of Example 2 will now be described. In this experiment, a low-intermittent printing endurance test was performed for 30,000 sheets under low-temperature, low-humidity conditions (temperature 15°C, humidity 10%) where contamination of the charging roller 2 is likely to occur, and the torque and contamination of the charging roller 2 were evaluated. In this low-intermittent printing endurance test, horizontal lines with an image ratio of 1% were printed on the recorded image.

[0091] In the metal soap coating operation of Example 2, the rotation speed of the photosensitive drum 1 was set to 1.2 times the maximum rotation speed of the multiple image forming operations, and the rotation speed of the developing roller 4 was set to 1.6 times, with the DD peripheral speed ratio set to 120%. That is, the control unit 202 controls the rotation speed on the surface of the developing roller 4 to be greater than the rotation speed on the surface of the photosensitive drum 1 when performing the metal soap coating operation. As an example to compare the effect of Example 2, in Comparative Example 2-1, the rotation speed of the photosensitive drum 1 was set to 1.2 times, the rotation speed of the developing roller 4 was set to 2.4 times, and the DD peripheral speed ratio was set to 180%. In the metal soap coating operation of Comparative Example 2-2, the rotation speed of the photosensitive drum 1 was set to 1.2 times, the rotation speed of the developing roller 4 was set to 0.6 times, and the DD peripheral speed ratio was set to 45%. In Example 2, the rotation speed of the developing roller 4 was 1.6 times that of Example 1, and the predetermined time for new equipment was set to 75 seconds so that the rotation speed of the developing roller 4 was the same as in Example 1.

[0092] <Verification Result 2> Table 3 shows the verification results. [Table 3] Table 3 is the same as Table 2 in Example 1. Note that Example 2 shows the torque and contamination status of the charged roller 2 at 30,000 (30K) sheets.

[0093] In Example 2, no torque increase or image defects due to contamination of the charging roller 2 occurred up to 30,000 sheets. On the other hand, Comparative Example 2-1 was initially good with no torque increase or contamination of the charging roller 2. However, because the DD peripheral speed ratio was large at 180%, as the toner deteriorated with durability, a large amount of fouled toner was developed on the photosensitive drum 1 and slipped through the cleaning blade 8. As a result, a large amount of toner 10 adhered to the charging roller 2, causing poorly charged images due to contamination of the charging roller 2.

[0094] In Comparative Example 2-2, the DD peripheral speed ratio was low at 45%, resulting in reduced rolling of the toner 10 and decreased contact opportunities between the metal soap 45c and the photosensitive drum 1. This made it difficult to form a film of metal soap 45c on the surface of the photosensitive drum 1. Furthermore, a sufficient inhibitory layer consisting of the external additive had not yet formed between the photosensitive drum 1 and the cleaning blade 8, resulting in unstable cleaning performance. Consequently, the torque was high initially, and poorly charged images occurred due to contamination of the charging roller 2.

[0095] In Example 2, the effect was achieved by increasing the rotation speed of the photosensitive drum 1 during the metal soap coating operation to 1.2 times and setting the DD peripheral speed ratio to 120%. However, this is not the only option; the DD peripheral speed ratio can be appropriately set to 120% or higher if the toner fouling can be cleaned during the metal soap coating operation, depending on the configuration of the process cartridge 7. Furthermore, during the metal soap coating operation, it is preferable to reduce the light intensity of the pre-exposure unit 27 compared to the image forming operation, and it is especially preferable to turn it OFF (no illumination). That is, when the metal soap coating operation is performed, the control unit 202 controls the exposure amount of the pre-exposure unit 27 to be less than the exposure amount of the pre-exposure unit 27 in the image forming operation. The control unit 202 may also choose not to perform exposure by the pre-exposure unit 27 when the metal soap coating operation is performed. If the intermediate transfer belt 31 can be separated from the photosensitive drum 1, separating the intermediate transfer belt 31 from the photosensitive drum 1 will prevent the metal soap 45c from being recovered by physical adhesion to the intermediate transfer belt 31. The contact and separation of the intermediate transfer belt 31 may be performed in conjunction with the contact and separation of the primary transfer roller 32. Furthermore, by setting the transfer voltage from the primary transfer voltage power supply 73 to 0V, it is possible to reduce the amount recovered by electrostatic adhesion to the intermediate transfer belt 31. In other words, when performing the metal soap coating operation, the control unit 202 may control the intermediate transfer belt 31 to be separated, or it may control the transfer voltage to 0V. As explained above, by setting the DD peripheral speed ratio during the metal soap coating operation within the range described in Example 2 (60% to 140%), it was possible to suppress the increase in torque and prevent contamination of the charging roller 2. In other words, the control unit 202 controls the ratio of the rotation speed on the surface of the developing roller 4 to the rotation speed on the surface of the photosensitive drum 1 to be between 60% and 140%.

[0096] As described above, according to Example 2, it is possible to suppress the occurrence of torque increase due to insufficient supply of metal soap to the photoreceptor surface. [Explanation of Symbols]

[0097] 1 Photosensitive drum 3b Toner storage section 4. Developing roller 8 Cleaning blades 10 Toners 45c Metal soap 202 Control Unit

Claims

1. a rotatable image carrier on whose surface an electrostatic latent image is formed; a charging member for charging the surface of the image carrier before the electrostatic latent image is formed; a developing member that is in contact with the image carrier and develops the electrostatic latent image formed on the surface of the image carrier with a developer to form a developer image; a cleaning member that comes into contact with the image carrier and scrapes off the developer on the image carrier; a container for containing the developer containing a metal soap; a control means for controlling an image forming operation of forming the developer image on a recording material and an application operation of applying the metal soap contained in the container to a surface of the image carrier by the developing member; Equipped with The image forming apparatus is characterized in that the control means controls the moving speed of the surface of the image carrier when performing the coating operation so that it is faster than the moving speed of the surface of the image carrier when performing the image forming operation.

2. 2. The image forming apparatus according to claim 1, wherein the control means controls the moving speed of the surface of the developing member so as to be faster than the moving speed of the surface of the image carrier when the application operation is performed.

3. 3. The image forming apparatus according to claim 1, wherein the control means controls the ratio of the moving speed of the surface of the developing member to the moving speed of the surface of the image carrier to be in the range of 60% to 140%.

4. a first voltage applying means for applying a charging voltage to the charging member; a second voltage applying means for applying a developing voltage to the developing member; Equipped with The image forming apparatus according to claim 1 or claim 2, characterized in that the control means controls so that, when performing the coating operation, a first potential difference, which is the difference between the potential of the surface of the image carrier charged by the charging member and the developing voltage, is larger than the first potential difference in the image forming operation.

5. a supply member for supplying the developer contained in the container to the developing member; a third voltage applying means for applying a supply voltage to the supply member; Equipped with The image forming apparatus described in claim 1 or claim 2, characterized in that the control means controls the second voltage application means and the third voltage application means so that a second potential difference is formed at the contact point between the supply member and the developing member, such that an electrostatic force acts on the metal soap in a direction from the supply member toward the developing member, when the application operation is performed.

6. an intermediate transfer member onto which the developer image on the image carrier is transferred; a transfer member for transferring the developer image on the image carrier to the intermediate transfer member; a pre-exposure unit that is provided downstream of the transfer member and upstream of the charging member in a rotation direction of the image carrier and that exposes a surface of the image carrier; Equipped with 3. The image forming apparatus according to claim 1, wherein the control means controls the exposure amount of the pre-exposure means during the application operation so as to be smaller than the exposure amount of the pre-exposure means during the image forming operation.

7. 7. The image forming apparatus according to claim 6, wherein the control means prevents exposure by the pre-exposure means when the coating operation is performed.

8. the intermediate transfer body is capable of contacting the image carrier or being separated from the image carrier, 7. The image forming apparatus according to claim 6, wherein the control unit controls the intermediate transfer body to be spaced apart when the application operation is performed.

9. a fourth voltage application means for applying a transfer voltage to the transfer member; 7. The image forming apparatus according to claim 6, wherein the control means controls the transfer voltage to 0 V when the application operation is performed.

10. the image carrier is insertable into and removable from the image forming apparatus; 3. The image forming apparatus according to claim 1, wherein the control unit performs the application operation when the image carrier is a new one and is attached to the image forming apparatus.

11. the developer comprises an organosilicon polymer; 3. An image forming apparatus according to claim 1, wherein the number of carbon atoms directly bonded to silicon atoms in said organosilicon polymer is from 1 to 3.

12. 12. The image forming apparatus according to claim 11, wherein the organosilicon polymer has a partial structure represented by R-SiO3 / 2. Here, R is a hydrocarbon group having 1 to 6 carbon atoms.

13. 12. The image forming apparatus according to claim 11, wherein the organosilicon polymer has a partial structure represented by R-SiO3 / 2. Here, R is a hydrocarbon group having 1 to 3 carbon atoms.

14. 3. The image forming apparatus according to claim 1, wherein the metal soap contains at least one metal selected from the group consisting of zinc, calcium, and magnesium.

15. 15. The image forming apparatus according to claim 14, wherein the metal soap is at least one of zinc stearate, calcium stearate, and magnesium stearate.

16. 3. The image forming apparatus according to claim 1, wherein the metal soap has a particle size of 0.15 [mu]m or more and 2.0 [mu]m or less.

17. 3. The image forming apparatus according to claim 1, wherein the image carrier has a protective layer made of an acrylic resin as an outermost layer.

18. a storage unit that stores information regarding a usage history of the image carrier; A driving means for driving the image carrier; A detection means for detecting the torque of the driving means; Equipped with The image forming apparatus according to claim 1 or claim 2, characterized in that the control means performs the coating operation when the information regarding the usage history stored in the memory unit reaches a predetermined number of sheets or when the torque detected by the detection means reaches a predetermined torque or greater.

19. 20. The image forming apparatus according to claim 18, wherein the information regarding the usage history includes the number of rotations of the image carrier or the number of sheets of the recording material on which the image forming operation has been performed.

Images