Developing apparatus and image forming apparatus equipped therewith

Abstract

To provide a developing device that can prevent a reduction in developing performance while preventing the occurrence of an image defect, and an image forming apparatus including the same.SOLUTION: A developing device comprises a developing device housing, a developer carrier, a regulation blade, a magnet member, and a blade magnet. The regulation blade forms a regulation part. The magnet member has a plurality of magnetic poles. A toner includes a toner base particle including a binder resin and magnetic powder, and silica particles and alumina particles attached to the surface of the toner base particle. The alumina particles have a primary particle diameter of 150 nm or more and 400 nm or less, and a resistivity of 0.1 Ωm or more and 2 Ωm or less. The developing device can execute a developer removing mode for rotating the developer carrier in a reverse direction being a direction opposite to a normal direction being the direction of rotation during image formation within a range of 1 / 18 or more and 1 / 5 or less of the outer circumferential length of the developer carrier, thereby removing a developer remaining on the regulation part.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a developing device and an image forming apparatus including the same.

Background Art

[0002] Conventionally, as a developing method in an image forming apparatus using an electrophotographic process, mainly a powder developer is used. An electrostatic latent image formed on an image carrier such as a photoreceptor drum is visualized by the developer, and after the visible image (toner image) is transferred onto a recording medium, a fixing process is generally performed...

[0003] Among developers, there is a magnetic one-component developer composed only of magnetized toner. As a developing method using a magnetic one-component developer, there is a jumping one-component developing method. In the jumping one-component developing method, a developing roller having a fixed magnet body provided with a plurality of magnetic poles inside the roller is used. Utilizing the magnetic carrying force of this fixed magnet body, the toner in the developing container is carried onto the developing roller, and layer thickness regulation is performed using a regulating blade. As a result, a thin toner layer is formed on the surface of the developing roller, and the toner is made to fly from the developing roller to the photoreceptor drum at the developing position.

[0004] In the magnetic one-component developing method as described above, in order to ensure the stability of the toner layer on the developing roller and improve the charging performance to the toner, sufficient magnetic force is required at the tip of the regulating blade. Therefore, there is a technique of increasing the magnetic force at the tip of the regulating blade by attaching a blade magnet to the side surface of the regulating blade.

[0005] However, when a blade magnet is attached, aggregated toner is likely to occur around the blade magnet and at the blade tip inside the developing device. As a result, the toner layer on the developing roller becomes disturbed, and image defects such as white streaks are likely to occur.

[0006] Therefore, Patent Document 1 discloses an image forming apparatus that can suppress image defects such as white streaks by performing a first removal mode and a second removal mode to allow the developer that aggregates between the regulating blade and the developing roller to flow. In the first removal mode, a repulsive magnetic field is generated between the regulating blade and the developing roller when not forming an image, and the developing roller is rotated in the forward direction (the same direction as the rotation direction of the developing roller during development). In the second removal mode, the repulsive magnetic field is generated, and the developing roller is rotated in the reverse direction (the opposite direction to the forward direction). This eliminates clogging around the blade tip due to the aggregation of the developer, making the aforementioned image defects less likely to occur. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-95085 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, in image forming apparatuses like the one described in Patent Document 1, it is difficult to maintain a relatively thin and stable toner layer thickness over a long period of time. As a result, when an image forming apparatus is used for a long period of time, variations in the toner layer thickness gradually occur, which may lead to a decrease in development performance, such as image unevenness and white streaks.

[0009] The present invention aims to provide a developing apparatus capable of suppressing the occurrence of image defects while suppressing a decrease in developing performance, and an image forming apparatus equipped therewith. [Means for solving the problem]

[0010] To achieve the above objective, the first configuration of the present invention is a developing apparatus comprising a housing, a developer carrier, a regulating blade, a magnetic member, and a blade magnet. The housing houses a magnetic one-component developer consisting only of magnetic toner. The developer carrier is rotatably supported by the housing and carries the developer on its outer circumferential surface. The regulating blade is positioned at a predetermined distance from the developer carrier and is made of a magnetic material that forms a regulating portion that regulates the thickness of the developer layer carried on the developer carrier. The magnetic member is fixed non-rotatably inside the developer carrier and has a plurality of magnetic poles arranged along the circumferential direction of the developer carrier. The blade magnet is fixed to the regulating blade and induces a magnetic pole at the tip of the regulating blade. The developing apparatus develops an electrostatic latent image formed on an image carrier. The toner comprises toner matrix particles containing a binder resin and magnetic powder, and silica particles and alumina particles adhering to the surface of the toner matrix particles. The alumina particles have a primary particle diameter of 150 nm or more and 400 nm or less, and a resistivity of 0.1 Ωm or more and 2 Ωm or less. The developing apparatus is capable of performing a developer removal mode to remove the developer accumulated in the regulated area by rotating the developing image carrier in the reverse direction, which is the opposite direction to the forward direction of rotation during image formation, within a range of 1 / 18 or more and 1 / 5 or less of the outer circumference of the developing image carrier. [Effects of the Invention]

[0011] According to the first configuration of the present invention, by setting the resistivity of the alumina particles to 0.1 Ωm or more and 2 Ωm, the permeability of the toner becomes more suitable. This makes it possible to stably maintain a low toner transport amount (layer thickness) on the developing roller (developer carrier), and improve the development efficiency during development (a value indicating how much of the toner in the toner layer has flown to the electrostatic latent image on the photoreceptor). This makes it possible to improve development performance. Furthermore, by setting the primary particle diameter of the alumina particles to 150 nm or more and 400 nm or less, the dependence of development efficiency on particle diameter is reduced. As a result, the particle diameter distribution is maintained constant over a long period of time, and the deterioration of development performance can be suppressed for a long period of time.

[0012] Furthermore, by executing the toner removal mode, the toner around the regulated area can be fluidized. This allows the toner around the regulated area to be replaced appropriately, preventing toner from accumulating around the regulated area and reducing its regulatory force. By suppressing the reduction in the regulatory force of the regulated area, the amount of toner transported on the developing roller is stabilized. As a result, the thickness of the toner layer on the developing roller can be maintained relatively thin and stably, improving development efficiency. In addition, by suppressing the reduction in the regulatory force of the regulated area, the toner layer on the developing roller is less likely to become disordered, and the occurrence of image defects can also be suppressed.

[0013] Therefore, it is possible to provide a developing apparatus that can suppress the occurrence of image defects while suppressing a decrease in developing performance. [Brief explanation of the drawing]

[0014] [Figure 1] Schematic cross-sectional view of an image forming apparatus 100 equipped with a developing device 4 according to one embodiment of the present invention. [Figure 2] Plan view of a developing apparatus 4 according to an embodiment of the present invention [Figure 3] Front view of the developing apparatus 4 according to an embodiment of the present invention [Figure 4] Side cross-sectional view of the developing apparatus 4 of the embodiment [Figure 5] Enlarged view of the area around the developing roller 25 in the developing apparatus 4 of the embodiment. [Figure 6] Cross-sectional view of the developing roller 25 in Figure 4, viewed from a direction perpendicular to the axial direction. [Figure 7] Block diagram showing an example of a control path used in the image forming apparatus 100. [Figure 8] Plan view showing a magnified view of toner Tn. [Figure 9] A flowchart showing an example of controlling the developer removal mode in the developing apparatus 4 of the embodiment. [Modes for carrying out the invention]

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of an image forming apparatus 100 including a developing device 4 according to an embodiment of the present invention. In an image forming apparatus (for example, a monochrome printer) 100, when performing a printing operation, in an image forming unit 9 in the image forming apparatus 100, an electrostatic latent image is formed based on manuscript image data transmitted from a host device (not shown) such as a personal computer (hereinafter referred to as a personal computer). Then, toner Tn is attached to the electrostatic latent image by the developing device 4 to form a toner image. The supply of toner Tn to the developing device 4 is performed from a toner container 5 (developer storage unit). In the image forming apparatus 100, an image forming process on the photosensitive drum 1 is executed while rotating the photosensitive drum 1 in the clockwise direction in FIG. 1.

[0016] In the image forming unit 9, along the rotation direction (clockwise direction) of the photosensitive drum 1, a charging device 2, an exposure unit 3, a developing device 4, a transfer roller 6, a cleaning device 7, and a charge removing device (not shown) are provided. The photosensitive drum 1 is, for example, an aluminum drum with a photosensitive layer laminated thereon, and the surface is uniformly charged by the charging device 2. Then, an electrostatic latent image with reduced charge is formed on the surface that receives the light beam from the exposure unit 3 described later. The photosensitive layer is not particularly limited, but for example, amorphous silicon (a-Si) with excellent durability is preferable.

[0017] The charging device 2 uniformly charges the surface of the photosensitive drum 1. The charging device 2 uses a corona discharge device that discharges by applying a high voltage using a thin wire as an electrode. Instead of the corona discharge device, a contact charging device that applies a voltage in a state where a charging member typified by a charging roller is in contact with the surface of the photosensitive drum 1 may be used. The exposure unit 3 irradiates the photosensitive drum 1 with a light beam based on image data to form an electrostatic latent image on the surface of the photosensitive drum 1.

[0018] The developing device 4 forms a toner image by attaching toner Tn to the electrostatic latent image on the photoreceptor drum 1. The developing device 4 contains a magnetic one-component developer composed of magnetic toner (hereinafter referred to as toner Tn). Details of the developing device 4 and details of the components of the toner Tn will be described later.

[0019] The cleaning device 7 includes a cleaning roller, a cleaning blade, etc. that are in line contact with the photoreceptor drum 1 in the longitudinal direction (the direction perpendicular to the plane of FIG. 1), and removes the toner Tn remaining on the surface of the photoreceptor drum 1 after the toner image has been transferred (transferred) to the paper.

[0020] Towards the photoreceptor drum 1 on which the toner image has been formed as described above, the paper is conveyed from the paper storage unit 10 to the image forming unit 9 at a predetermined timing via the paper conveyance path 11 and the resist roller pair 13. The transfer roller 6 transfers the toner image formed on the surface of the photoreceptor drum 1 to the paper conveyed through the paper conveyance path 11. Thereafter, in preparation for the formation of a new electrostatic latent image that will be carried out subsequently, the cleaning device 7 removes the residual toner Tn on the surface of the photoreceptor drum 1, and the charge removal device removes the residual charge.

[0021] The paper onto which the toner image has been transferred is separated from the photoreceptor drum 1 and conveyed to the fixing device 8, where it is heated and pressurized to fix the toner image to the paper. The paper that has passed through the fixing device 8 passes through the discharge roller pair 14 and is discharged to the paper discharge unit 15.

[0022] FIG. 2 and FIG. 3 are a plan view and a front view of the developing device 4 according to an embodiment of the present invention, and FIG. 4 is a side cross-sectional view of the developing device 4 of the embodiment. In FIGS. 2 and 3, for the sake of convenience, the upper cover is removed to show the internal state. As shown in FIGS. 2 to 4, the inside of the housing 20 is partitioned by a partition wall 20a integrally formed with the housing 20 into a first storage chamber 21 and a second storage chamber 22. A first stirring screw 23 is provided in the first storage chamber 21, and a second stirring screw 24 (stirring and conveying member) is provided in the second storage chamber 22.

[0023] The first agitation screw 23 and the second agitation screw 24 each have spiral blades around a support shaft (rotation axis) and are rotatably supported in the housing 20 in a parallel manner to each other. There are no partition walls 20a at both ends in the longitudinal direction of the housing 20, which is the axial direction of the first agitation screw 23 and the second agitation screw 24. The first agitation screw 23 conveys the toner Tn in the first storage chamber 21 in the direction of arrow P while agitating it, and then conveys it to the second storage chamber 22. The second agitation screw 24 conveys the toner Tn that has been conveyed to the second storage chamber 22 in the direction of arrow Q while agitating it, and then supplies it to the developing roller 25 (developer carrier).

[0024] The developing roller 25 rotates in accordance with the rotation of the photoreceptor drum 1 (see Figure 1), thereby supplying toner Tn to the photosensitive layer of the photoreceptor drum 1. A fixed magnet body 27 (magnetic member) consisting of a permanent magnet having multiple magnetic poles is fixed inside the developing roller 25. The magnetic force of the fixed magnet body 27 causes toner Tn to adhere (carry) to the surface of the developing roller 25, forming a magnetic brush. The developing roller 25 is rotatably supported in the housing 20 in a state parallel to the first agitation screw 23 and the second agitation screw 24.

[0025] Here, the straight line L1 is defined as the line passing through the rotation center P1 (first rotation center) of the developing roller 25 and the rotation center P2 (second rotation center) of the second agitation screw 24. The angle θ between the horizontal line L2 passing through the rotation center P1 and the reference straight line L1 is such that, with the rotation center P1 as the center and the horizontal line L2 being positive (+) and the opposite direction (-), it is 0 degrees or greater and 75 degrees or less. under This is the result.

[0026] The regulating blade 29 is formed so that its longitudinal direction (left-right direction in Figure 2) is larger than the maximum development width. The regulating blade 29 is positioned at a predetermined distance from the development roller 25. The regulating blade 29 has a regulating section 30 formed in the gap between the tip of the regulating blade 29 and the outer surface of the photoreceptor drum 1. The regulating section 30 regulates the amount of toner (toner layer thickness) supplied to the photoreceptor drum 1. Magnetic materials such as SUS (stainless steel) are used as the material for the regulating blade 29.

[0027] A toner quantity detection sensor (not shown) is provided on the bottom surface of the second storage chamber 22, which faces the second stirring screw 24, to detect the amount of toner stored in the housing 20. According to the detection result of this toner quantity detection sensor, the toner Tn stored in the toner container 5 (see Figure 1) is supplied into the housing 20 via the developer supply port 20b (developer supply unit) located at the top of the housing 20. The toner container 5 is empty at the time of factory shipment. Therefore, it is necessary to fill the empty toner container 5 with toner Tn before use. This initial filling is called "toner installation".

[0028] DS rollers 31a and 31b are rotatably externally mounted on the rotation axis of the developing roller 25. The DS rollers 31a and 31b strictly regulate the distance between the developing roller 25 and the photoreceptor drum 1 by contacting both axial ends of the outer surface of the photoreceptor drum 1. The DS rollers 31a and 31b have built-in bearings and can prevent wear on the drum surface by rotating in conjunction with the photoreceptor drum 1. In addition, magnetic sealing members 33a and 33b are provided at both axial ends of the developing roller 25 to prevent toner Tn leakage from the gap between the housing 20 and the developing roller 25.

[0029] Figure 5 is an enlarged view of the area around the developing roller 25 in the developing apparatus 4 of the embodiment. Figure 6 is a cross-sectional view of the developing roller 25 in Figure 5, viewed from a direction perpendicular to the axial direction. As shown in Figures 5 and 6, the fixed magnet body 27 has four magnetic poles 27a to 27d, consisting of S1 pole 27a, S2 pole 27c and N1 pole 27b and N2 pole 27d, fixed to a metal shaft 27e.

[0030] Flange portions 25a and 25b are attached to both longitudinal ends of the developing roller 25, and a drive input shaft 25c is fixed to flange portion 25a. One end (the right end in Figure 6) of the shaft 27e of the fixed magnet body 27 is fixed to the housing 20 (see Figure 3), and bearings 26a and 26b are positioned between the flange portions 25a and 25b and the shaft 27e. When rotational driving force is input to the drive input shaft 25c from the developing drive motor 41 (see Figure 7) via a drive input gear (not shown), the developing roller 25 rotates together with the flange portions 25a and 25b, but the fixed magnet body 27 does not rotate.

[0031] A blade magnet 35 is provided near the tip of the regulating blade 29 via a magnet support stay 36. The magnet support stay 36 is supported on the rear side of the regulating blade 29 (right side in Figure 5).

[0032] During image formation, the blade magnet 35 has its tip edge of the opposing magnetic pole 35a positioned inward (radially outward from the developing roller 25) of the tip of the regulating blade 29.

[0033] As shown in Figure 2, the blade magnet 35 is provided between the magnetic sealing members 33a and 33b, extending over almost the entire length of the regulating blade 29 (left-right direction in Figure 2). The blade magnet 35 is in contact with the regulating blade 29 with its south pole facing downwards, and a north pole is induced at the tip of the regulating blade 29. As a result, a magnetic field is generated between the S2 pole (regulating pole) 27c of the fixed magnet body 27 and the magnet, which attracts the regulating portion 30.

[0034] This magnetic field causes a magnetic brush, in which toner particles are linked together, to form between the regulating blade 29 and the developing roller 25. As the magnetic brush passes through the regulating section 30, the toner is layered to a desired height. Meanwhile, the toner Tn that was not used to form the magnetic brush accumulates along the upstream (right) side of the regulating blade 29. Subsequently, as the developing roller 25 rotates counterclockwise and the magnetic brush moves to the region (developing region) facing the photoreceptor drum 1, a magnetic field is applied by the N1 pole (main pole) 27b, causing the magnetic brush to come into contact with the surface of the photoreceptor drum 1 and develop the electrostatic latent image.

[0035] As the developing roller 25 rotates counterclockwise, the S1 pole (transport pole) 27a applies a magnetic field along the outer surface of the developing roller 25, and the toner Tn that was not used to form the toner image is collected on the developing roller 25 along with the magnetic brush. Furthermore, the magnetic brush detaches from the developing roller 25 in the gap between the S1 pole 27a and the N2 pole 27d and falls into the housing 20. After being agitated and transported by the second agitation screw 24, the magnetic field of the N2 pole (pumping pole) 27d causes the magnetic brush to be formed on the developing roller 25 again.

[0036] Magnetic sealing members 33a and 33b are positioned in the housing 20 surrounding both ends of the developing roller 25. Note that only magnetic sealing member 33a is shown in Figure 5. The magnetic sealing members 33a and 33b are positioned at both ends of the developing roller 25 in a non-contact state, that is, at a predetermined distance (gap) from the outer surface of the developing roller 25. The magnetic sealing members 33a and 33b are also provided on the opposite side of the photoreceptor drum 1 from the developing roller 25.

[0037] Figure 7 is a block diagram showing an example of a control path used in the image forming apparatus 100. Since various controls are performed on different parts of the apparatus during operation, the overall control path of the image forming apparatus 100 is complex. Therefore, this section will focus on explaining the parts of the control path that are necessary for implementing the present invention.

[0038] The developing drive unit 40 includes a developing drive motor 41 and a developing clutch 42. The developing drive motor 41 rotates the first agitation screw 23, the second agitation screw 24, and the developing roller 25. The developing clutch 42 turns the rotational driving force input from the developing drive motor 41 to the first agitation screw 23, the second agitation screw 24, and the developing roller 25 ON and OFF.

[0039] The voltage control circuit 51 is connected to the charging voltage power supply 52, the developing voltage power supply 53, and the transfer voltage power supply 54, and operates each of these power supplies by output signals from the control unit 90. Each of these power supplies applies a predetermined voltage to the wires in the charging device 2 (charging voltage power supply 52), to the developing roller 25 in the developing device 4 (developing voltage power supply 53), and to the transfer roller 6 (transfer voltage power supply 54) in response to a control signal from the voltage control circuit 51.

[0040] The image input unit 60 is a receiving unit that receives image data transmitted to the image forming apparatus 100 from a personal computer or the like. The image signal input from the image input unit 60 is converted into a digital signal and then sent to the temporary storage unit 94.

[0041] The control unit 70 is equipped with a liquid crystal display unit 71 and LEDs 72 that indicate various statuses, showing the status of the image forming apparatus 100, the image forming status, and the number of copies to be printed. Various settings for the image forming apparatus 100 are made using the printer driver on a personal computer.

[0042] The control unit 90 includes a CPU (Central Processing Unit) 91 as a central processing unit, a ROM (Read Only Memory) 92 as a read-only memory, a RAM (Random Access Memory) 93 as a read-write memory, a temporary memory 94 for temporarily storing image data, etc., a counter 95, a timer 97, and at least a plurality (two in this case) of I / F (interfaces) 96 for transmitting control signals to each device in the image forming apparatus 100 and receiving input signals from the operation unit 70.

[0043] ROM 92 stores control programs for the image forming apparatus 100, necessary control values, and other data that should not be changed while the image forming apparatus 100 is in use. RAM 93 stores necessary data generated during the control of the image forming apparatus 100, as well as data temporarily required for the control of the image forming apparatus 100. RAM 93 (or ROM 92) also stores the cumulative number of prints made by the developing apparatus 4, as measured by the timer 97 described later.

[0044] The temporary storage unit 94 receives image data transmitted from a personal computer or the like from the image input unit 60, and temporarily stores the image signal that has been converted into a digital signal. The counter 95 accumulates and counts the number of printed pages.

[0045] Furthermore, the control unit 90 transmits control signals from the CPU 91 to each part and device of the image forming apparatus 100 via the I / F 96. In addition, signals indicating their status and input signals are transmitted from each part and device to the CPU 91 via the I / F 96. Examples of parts and devices controlled by the control unit 90 include the fixing device 8, the image forming unit 9, the development drive unit 40, the voltage control circuit 51, the image input unit 60, and the operation unit 70.

[0046] Figure 8 is a magnified plan view of toner Tn. Toner Tn is composed of toner matrix particles Tn1 and an external additive Tn2. Toner matrix particles Tn1 contain a binder resin and magnetic powder. The binder resin is a styrene-acrylic acid copolymer or polyester.

[0047] The external additive Tn2 contains silica particles Tn21 and alumina particles Tn22. The particle size of the alumina particles Tn22 is 150 nm or larger and 400 nm or smaller. The m-resistivity of the alumina particles Tn22 is 0.1 Ωm or larger and 2 Ωm or smaller.

[0048] Here, if the fluidity of the toner Tn around the regulating unit 30 deteriorates, the toner Tn will concentrate around the regulating unit 30, reducing the regulating force of the regulating unit 30. This reduction in the regulating force of the regulating unit 30 can lead to disturbances in the amount of toner Tn transported on the developing roller 25, which can also be a cause of image defects. Therefore, in this embodiment, the developer removal mode can be executed when no image is being formed. The developer removal mode is executed at least one of the following: a first timing from the supply of toner Tn from the toner container 5 to the next print command, and a second timing from the end of the printing operation to the next print command. The developer removal mode will be described in detail below.

[0049] Figure 9 is a flowchart showing an example of control of the developer removal mode in the developing apparatus 4 of the embodiment. The procedure for executing the developer removal mode will be described according to the steps in Figure 9.

[0050] When a print command is input from a higher-level device such as a PC (step S1), it is determined whether or not toner Tn was supplied from the toner container 5 after the last print (step S2). If it was supplied (Yes in step S2), step S3 is skipped and the developer removal mode is executed (steps S4-S7). If it was not supplied (No in step S2), it is determined whether or not the cumulative number of printed pages since the last execution of the developer removal mode has reached a specified number (step S3). If the cumulative number of printed pages is equal to or greater than the specified value (Yes in step S3), the developer removal mode is executed (steps S4-S7).

[0051] In developer removal mode, first, paper feeding from the paper storage unit 10 is stopped (step S4). Also, the application of the development bias from the development voltage power supply 53 (see Figure 7) to the development roller 25 is stopped (step S5), and the development clutch 42 (see Figure 7) is turned OFF to stop the rotation of the development roller 25 (step S6). Then, the development roller 25 is rotated in the opposite direction to the rotation direction during development (step S7). At this time, the development roller 25 is rotated within a range of 1 / 18 or more and 1 / 5 or less of the outer circumference of the development roller 25.

[0052] After the developing roller 25 is rotated in reverse (step S7), printing is performed (step S8). Also, if the specified number of pages has not been reached in step S3 (No in step S3), printing is performed without performing the developer removal mode (step S). Then, it is determined whether or not printing is continuing (step S9).

[0053] If printing is continuing (Yes in step S9), return to step S1. If printing has finished (No in step S9), turn off the developing clutch 42 and end the process.

[0054] As described above, by setting the resistivity of the alumina particles to 0.1 Ωm or higher, and specifically to 2 Ωm, the permeability of the toner Tn becomes more favorable. This makes it possible to stably maintain a low toner transport amount (layer thickness) on the developing roller 25, thereby improving the development efficiency during development (a value indicating how much of the toner in the toner layer has flown to the electrostatic latent image on the photoreceptor). This makes it possible to improve the development performance.

[0055] Generally, magnetic toner particles are more likely to fly away the smaller their diameter, and less likely to fly away the larger their diameter. Therefore, if there is variation in the particle diameter of the toner particles that make up the toner, the smaller particles that are more likely to fly away will actively fly away, while the larger particles will tend to remain in the toner. As a result, the particle diameter distribution of the toner (the distribution of the particle diameter of each toner particle contained in the toner) will increase as the cumulative number of printed pages increases, with a larger proportion of larger toner particles taking up more space. This leads to a decrease in development efficiency and a decline in development performance.

[0056] On the other hand, in this invention, the primary particle diameter of the alumina particles is set to be 150 nm or more and 400 nm or less, resulting in a relatively small bias in the particle size distribution (variation of alumina particles in toner Tn). Therefore, the dependence of development efficiency on particle size is reduced. In other words, even if printing operations are repeated over a long period of time, the particle size distribution is maintained at a constant level, and the deterioration of development performance can be suppressed for a long period of time.

[0057] Furthermore, by executing the toner removal mode, the toner Tn around the restricting unit 30 can be fluidized. This allows the toner Tn around the restricting unit 30 to be replaced appropriately, thus preventing the concentration of toner Tn around the restricting unit 30 and the resulting decrease in the restricting force of the restricting unit 30. By suppressing the decrease in the restricting force of the restricting unit 30, the amount of toner Tn transported on the developing roller 25 is stabilized. As a result, the thickness of the toner layer on the developing roller 25 can be maintained relatively thin and stably, improving the development efficiency. In addition, by suppressing the decrease in the restricting force of the restricting unit 30, the layer on the developing roller 25 is less likely to be disturbed, and the occurrence of image defects can also be suppressed.

[0058] Therefore, it is possible to provide a developing apparatus that can suppress the occurrence of image defects while suppressing a decrease in developing performance.

[0059] Furthermore, as mentioned above, the angle θ between the reference line L1 and the horizontal line L2 must be 0 degrees or greater and 75 degrees or less. under This allows the toner Tn to be supplied more effectively to the developing roller 25 by the second stirring screw 24. As a result, the developing performance of the developing roller 25 is stably maintained.

[0060] Next, the effects of the present invention will be described in more detail using examples. [Examples]

[0061] The presence or absence of image defects caused by differences in the composition of toner Tn, the amount of reverse rotation of the developing roller 25, and the positional relationship between the developing roller 25 and the second stirring screw 24 was experimentally evaluated. In the experiment, eight types of toner Tn according to the above embodiment (Invention 1 to 8) and seven types of conventional toner Tn different from the toner Tn according to the present invention (Comparative Examples 1 to 7) were filled into the toner container, and images were formed using a monochrome printer, which is a type of image forming apparatus 100 shown in Figure 1. The image density values, presence or absence of image fringing, presence or absence of white streaks, and presence or absence of toner drop were checked. This monochrome printer is controlled to rotate the developing roller 45° in the reverse direction at the end of toner installation and at the end of each job.

[0062] Table 1 shows the configurations of Inventions 1-8 and Comparative Examples 1-7. First, the toner Tn, the reverse rotation amount of the developing roller 25, and the developing roller 25 and the second stirring screw 24 of Inventions 1-8 will be explained using Table 1. First, the preparation of the toner used in the experiment will be explained.

[0063] [Table 1]

[0064] [Production of silica particles] The silica particles contained in the toner used in this example were prepared as follows. First, 30 g of dimethylpolysiloxane and 15 g of 3-aminopropyltrimethoxysilane (both manufactured by Shin-Etsu Chemical Co., Ltd.) were dissolved in 200 g of toluene and diluted 10 times. Next, 200 g of fumed silica particles (AERSIL® 130, manufactured by Nippon Aerosil Co., Ltd.) were stirred, and the resulting diluted solution was gradually added dropwise. The mixture was then ultrasonically irradiated and stirred for 30 minutes to obtain a mixture. After heating this mixture in a constant temperature bath at 150°C, the toluene was removed using a rotary evaporator, and the resulting solid was dried in a vacuum dryer at a set temperature of 50°C until no further weight loss occurred. Furthermore, it was heat-treated in an electric furnace under a nitrogen stream at 200°C for 3 hours. The resulting powder was crushed using a jet mill and collected with a bag filter to obtain silica.

[0065] As shown in Table 1, the binder resins of Invention 1 to 8 are polyester.

[0066] The alumina particles of Inventions 1 to 5 each have different primary particle diameters or electrical resistivity. The alumina particles of Inventions 1 to 5 are designated A to E, respectively. Inventions 1 and 6 to 8 use the same alumina particle A. Alumina particle A has a primary particle diameter of 180 nm and an electrical resistivity of 1.22 Ωm. Alumina particle B has a primary particle diameter of 360 nm and an electrical resistivity of 0.95 Ωm. Alumina particle C has a primary particle diameter of 250 nm and an electrical resistivity of 0.79 Ωm. Alumina particle D has a primary particle diameter of 210 nm and an electrical resistivity of 1.87 Ωm. Alumina particle E has a primary particle diameter of 200 nm and an electrical resistivity of 0.13 Ωm.

[0067] Next, we will explain how to prepare alumina particles A to I.

[0068] [Preparation of alumina particles A] (Manufacturing of alumina seed crystal slurry) Intermediate alumina, obtained by calcining aluminum hydroxide from the hydrolysis of aluminum isopropoxide, was pulverized in a jet mill and calcined at a maximum temperature of 1200°C to obtain α-alumina particles. 300g of these alumina particles were mixed with 3g of propylene glycol as a grinding aid, and 2mm diameter alumina beads were added as a grinding medium. The mixture was then ground in a vibratory mill for 8 hours to obtain α-alumina particles with a primary particle size of 180nm. 100g of this mixture was added to 400g of a 0.01M aluminum chloride aqueous solution and dispersed. Then, 500g of the mixture was wet-dispersed over 24 hours using a ball mill filled with 4kg of 2mm diameter alumina beads to obtain an alumina slurry.

[0069] (Manufacturing of alumina microparticles) 300g of this slurry was added to 2L of 1M aluminum chloride aqueous solution, and then 350g of 13.3N aqueous ammonia was added over approximately 1 hour using a micro-rotary pump while stirring at 25°C. The pH of the aluminum hydrolysate slurry after the addition was 3.8. This slurry was allowed to stand at 25°C to gel, and then the water was evaporated using a 60°C constant temperature bath to obtain a dry powder mixture. This hydrolysis precipitate was crushed in a mortar and placed in an alumina crucible, and heated in a box-type electric furnace in the air at a heating rate of 300°C / h from room temperature to 900°C, and calcined at 900°C for 3 hours to obtain fine α-alumina.

[0070] (Manufacturing of surface-treated alumina microparticles) 100g of the obtained alumina was dispersed in 1 liter of water to form a slurry, which was heated and maintained at 70°C. To this slurry, an aqueous solution of 10.5g of tin chloride pentahydrate dissolved in 100ml of 2N hydrochloric acid and 6.7N ammonia water were simultaneously added over approximately 40 minutes to maintain the slurry's pH at 7-8. Subsequently, a solution of 34.4g of antimony chloride and 5.3g of tin chloride pentahydrate dissolved in 450ml of 2N hydrochloric acid and 6.7N ammonia water were simultaneously added dropwise over approximately 1 hour to maintain the slurry's pH at 7-8. The slurry was then filtered and washed, and dried at 110°C. Finally, it was heat-treated at 500°C in a nitrogen gas stream of 1 L / min for 1 hour to obtain conductive alumina fine particles. The volume resistivity of the alumina fine particles was 1.22 Ωm The following was done. 2.5 g of isopropyltriisostearoyl titanate (KR-TTS, Ajinomoto Co., Ltd.'s "PlenAct®") was dissolved in 40 ml of toluene to 50 g of the obtained alumina fine particles, and the mixed slurry was mixed in a ball mill for 2 hours. Then it was dried to obtain surface-treated alumina fine particles A with a primary particle size of 180 nm.

[0071] [Preparation of alumina particles B-I] The following describes only the differences between the preparation of alumina particles B-I and the preparation of alumina particle A.

[0072] [Preparation of alumina particles B] For alumina particle B, instead of the 2 mm diameter alumina beads mentioned above, 5 mm diameter alumina beads were used and the particles were ground in a vibratory mill for 8 hours. Furthermore, 8.4 g of tin chloride pentahydrate was added to 100 ml of 2N hydrochloric acid, and 4.2 g of tin chloride pentahydrate was added to 450 ml of 2N hydrochloric acid. Additionally, 38.3 g of antimony chloride was added to 450 ml of 2N hydrochloric acid. Other aspects were the same as for alumina particle A, resulting in alumina particle B with a primary particle size of 360 nm and an electrical resistivity of 0.95 Ωm.

[0073] [Preparation of alumina particles C] For alumina particle C, the grinding time using 2 mm diameter alumina beads in a vibratory mill, as in the preparation of alumina particle A, was changed from 8 hours to 2 hours. Other aspects were the same as for alumina particle A, and alumina particle C with a primary particle size of 250 nm and an electrical resistivity of 0.79 Ωm was obtained.

[0074] [Preparation of alumina particles D] For alumina particle D, the grinding time using 2 mm diameter alumina beads in a vibratory mill, as in the preparation of alumina particle A, was changed from 8 hours to 4 hours. Additionally, the amount of tin chloride pentahydrate added to 100 ml of 2N hydrochloric acid was set to 8.4 g, and the amount added to 450 ml of 2N hydrochloric acid was set to 4.2 g. Furthermore, the amount of antimony chloride added to 450 ml of 2N hydrochloric acid was set to 38.3 g. Other aspects were the same as for alumina particle A, resulting in alumina particle D with a primary particle size of 210 nm and an electrical resistivity of 1.87 Ωm.

[0075] [Preparation of alumina particles E] For alumina particle E, the grinding time using 2 mm diameter alumina beads in a vibratory mill, as in the preparation of alumina particle A, was changed from 8 hours to 4 hours. Additionally, the amount of tin chloride pentahydrate added to 100 ml of 2N hydrochloric acid was changed from 10.5 g to 12.6 g. Furthermore, the amount of tin chloride pentahydrate added to 450 ml of 2N hydrochloric acid was changed from 5.3 g to 6.3 g. Finally, the amount of antimony chloride added to 450 ml of 2N hydrochloric acid was changed from 34.4 g to 30.6 g. Other aspects were the same as for alumina particle A, resulting in alumina particle E with a primary particle size of 200 nm and an electrical resistivity of 0.13 Ωm.

[0076] [Preparation of alumina particles F] For alumina particles F, 1 mm diameter alumina beads were used instead of the 2 mm diameter alumina beads used in the preparation of alumina particles A. Additionally, the amount of tin chloride pentahydrate added to 34.4 g of antimony chloride and 100 ml of 2N hydrochloric acid was changed from 10.5 g to 12.6 g. Furthermore, the amount of tin chloride pentahydrate added to 450 ml of 2N hydrochloric acid was changed from 5.3 g to 6.3 g. Also, the amount of antimony chloride added to 450 ml of 2N hydrochloric acid was changed from 34.4 g to 30.6 g. Other aspects were the same as for alumina particles A, resulting in alumina particles F with a primary particle size of 140 nm and an electrical resistivity of 0.88 Ωm.

[0077] [Preparation of alumina particles G] For alumina particle G, instead of grinding 2 mm diameter alumina beads in a vibratory mill for 8 hours as in the preparation of alumina particle A, the process was changed to grinding 5 mm diameter alumina beads in a vibratory mill for 4 hours. Additionally, the amount of tin chloride pentahydrate added to 100 ml of 2N hydrochloric acid was changed from 10.5 g to 8.4 g. Furthermore, the amount of tin chloride pentahydrate added to 450 ml of 2N hydrochloric acid was changed from 5.3 g to 4.2 g. Finally, the amount of antimony chloride added to 450 ml of 2N hydrochloric acid was changed from 34.4 g to 38.3 g. Other aspects were the same as for alumina particle A, resulting in alumina particle G with a primary particle size of 430 nm and an electrical resistivity of 0.93 Ωm.

[0078] [Preparation of alumina particles H] For alumina particle H, the amount of tin chloride pentahydrate added to 100 ml of 2N hydrochloric acid in the preparation of alumina particle A was changed from 10.5 g to 12.6 g. Also, the amount of tin chloride pentahydrate added to 450 ml of 2N hydrochloric acid was changed from 5.3 g to 6.3 g. Furthermore, the amount of antimony chloride added to 450 ml of 2N hydrochloric acid was changed from 34.4 g to 30.6 g. Except for the addition of 12.6 g and 6.3 g of tin chloride pentahydrate, alumina particle H with a primary particle size of 200 nm and an electrical resistivity of 0.08 Ωm was obtained in the same manner as alumina particle A.

[0079] [Preparation of alumina particles I] For alumina particle I, the amount of tin chloride pentahydrate added to 100 ml of 2N hydrochloric acid in the preparation of alumina particle A was changed from 10.5 g to 8.4 g. Also, the amount of tin chloride pentahydrate added to 450 ml of 2N hydrochloric acid was changed from 5.3 g to 4.2 g. Furthermore, the amount of antimony chloride added to 100 ml of 2N hydrochloric acid was changed from 34.4 g to 38.3 g. Other aspects were the same as for alumina particle A, resulting in alumina particle I with a primary particle size of 190 nm and an electrical resistivity of 2.23 Ωm.

[0080] [Toner production] Next, the preparation of toners according to Inventions 1-8 and Comparative Examples 1-7 will be described.

[0081] The toner of the present invention 1 was manufactured as follows: 1100g of polyester binder resin (manufactured by Kao Corporation, Mw: 6500, acid value: 8.2 mg KOH / g, Tm: 96.3℃, Tg: 54.4℃), 1090g of binder resin (manufactured by Kao Corporation, acid value: 11.8 mg KOH / g, Tm: 118.5℃, Tg: 59.6℃, gel content 36%), 1450g of magnetic powder X (2 × 10⁵ Ωcm, manufactured by Toda Kogyo Co., Ltd., "MRO-15A"), 200g of electrostatic control agent (manufactured by Fujikura Kasei Co., Ltd., "FCA-482PLV"), and 160g of mold release agent (manufactured by Kato Yoko Co., Ltd., "Carnauba Wax Characteristics No. 1") were mixed at 2000 rpm for 5 minutes using a mixer (manufactured by Nippon Coke Co., Ltd., "FM-20B").

[0082] The obtained mixture was melt-kneaded using a twin-screw extruder (Toshiba Machine Co., Ltd. "TEM-26SS") under the conditions of a cylinder temperature of 120°C, a shaft rotation speed of 100 rpm, and a flow rate of 75 g / min. After the resulting mixture was cooled, it was coarsely ground using a pulverizer (Hosokawa Micron Corporation "Rotoplex 16 / 8 type"). The resulting coarsely ground material was finely ground using a powder turbo mill TA (Freund Turbo Corporation). Subsequently, it was fed into a jet mill (Hosokawa Micron Corporation "MJT-1") for fine grinding and classification to obtain toner mother particles Tn1.

[0083] To 1 kg of the obtained toner matrix particles, 12 g of silica particles and 11 g of alumina particles A obtained by the method described above were added as external additives and mixed for 5 minutes at 3200 rpm using a mixer (FM-10C manufactured by Nippon Coke Industries). The mixture was then sieved using a 100-mesh (150 μm opening) sieve to obtain the toner according to Invention 1.

[0084] The toner of the second invention uses alumina particle B instead of alumina particle A. Other aspects are the same as the toner of the first invention.

[0085] The toner of the third invention uses alumina particle C instead of alumina particle A. Other aspects are the same as the toner of the first invention.

[0086] The toner of the fourth invention uses alumina particles D instead of alumina particles A. Other aspects are the same as the toner of the first invention.

[0087] The toner of the present invention 5 uses alumina particle E instead of alumina particle A. Other aspects are the same as the toner of the present invention 1.

[0088] The toners of Invention 6-7 and Comparative Examples 5-7 are the same as the toner of Invention 1.

[0089] The toner of the present invention 8 replaces magnetic powder X with magnetic powder Y (3 × 10 7 A toner cartridge (Ωcm, Toda Kogyo Co., Ltd. "MTS-D3") was used. Other aspects are the same as those of the toner in Invention 1.

[0090] The toner in Comparative Example 1 used alumina particle F instead of alumina particle A. Other aspects are the same as the toner in Invention 1.

[0091] The toner in Comparative Example 2 used alumina particle G instead of alumina particle A. Other aspects are the same as the toner in Example 1 of the present invention.

[0092] The toner in Comparative Example 3 used alumina particle H instead of alumina particle A. Other aspects are the same as the toner in Invention 1.

[0093] The toner in Comparative Example 4 used alumina particle I instead of alumina particle A. Other aspects are the same as the toner in Invention 1.

[0094] For Inventions 1 to 5 and Invention 8, the amount of reverse rotation of the developing roller 25 when the developer removal mode is executed is set to 1 / 8 the length of the circumference of the outer surface of the developing roller 25. For Invention 6, the amount of reverse rotation is set to 5 / 72 the length of the circumference of the outer surface of the developing roller 25. For Invention 7, the amount of reverse rotation is set to 13 / 72 the length of the circumference of the outer surface of the developing roller 25.

[0095] The positional relationship between the developing roller 25 and the second stirring screw 24 in inventions 1 to 8 is such that the angle θ between the reference line L1 and the horizontal line L2 is 20 degrees (see Figure 3).

[0096] Next, the toner Tn, the reverse rotation amount of the developing roller 25, and the developing roller 25 and the second stirring screw 24 of Comparative Examples 1 to 7 will be described. As shown in Table 1, the binder resin of Comparative Examples 1 to 7 is all polyester. Comparative Examples 1 to 7 all use magnetic powder X.

[0097] The alumina particles in Comparative Examples 5-7 are alumina particle A, the same as in Invention 1 and Inventions 6-7. The alumina particles in Comparative Examples 1-3 are all different and also different from alumina particles A-E. The alumina particles in Comparative Examples 1-3 are denoted as particle F, particle G, and particle H, respectively. Alumina particle F has a primary particle diameter of 140 nm and an electrical resistivity of 0.88 Ωm. Alumina particle G has a primary particle diameter of 430 nm and an electrical resistivity of 0.93 Ωm. Alumina particle H has a primary particle diameter of 200 nm and an electrical resistivity of 0.08.

[0098] For Comparative Examples 1 to 4 and Comparative Example 7, the amount of reverse rotation of the developing roller 25 when the developer removal mode is executed is set to 1 / 8 the length of the circumference of the outer surface of the developing roller 25. For Comparative Example 5, the amount of reverse rotation is set to 1 / 24 the length of the circumference of the outer surface of the developing roller 25. For Comparative Example 6, the amount of reverse rotation of the developing roller 25 is set to 5 / 72 the length of the circumference of the outer surface of the developing roller 25.

[0099] In Comparative Examples 1 to 6, the positional relationship between the developing roller 25 and the second agitation screw 24 is such that the angle θ between the reference line L1 and the horizontal line L2 is 20 degrees (see Figure 3). In Comparative Example 7, the positional relationship between the developing roller 25 and the second agitation screw 24 is such that the angle θ between the reference line L1 and the horizontal line L2 is -45 degrees (see Figure 3).

[0100] Table 2 shows the experimental results of the experiments described above. The experimental results of Inventions 1-8 and Comparative Examples 1-7 will be explained using Table 2.

[0101] [Table 2]

[0102] The experiment checked image density values, the presence or absence of image fringing, the presence or absence of white streaks, and the presence or absence of toner loss. Image density was evaluated after toner installation (before output) in a normal temperature and humidity environment (temperature 23°C, humidity 50%, N / N environment), at the end of 50,000 prints in a normal temperature and humidity environment (N / N environment), and at the end of 50,000 prints in a high temperature and high humidity environment (temperature 32.5°C, humidity 80%, RH environment). Output was performed using three intermittent prints of an LSA chart as specified in ISO / IEC 19752 (printed in sets of three with intervals in between). The evaluation method involved measuring the ID (image density) of the output solid image using a reflectance densitometer. A measured value of 1.2 or less was considered insufficient image density.

[0103] As shown in Table 2, in all of Inventions 1 to 8 and Comparative Examples 1 to 7, the initial image density under normal temperature and humidity conditions exceeds 1.2. Furthermore, in all of Inventions 1 to 8, the image density after 100,000 prints under normal temperature and humidity conditions, and after 5,000 prints under high temperature and high humidity conditions, exceeds 1.2. On the other hand, in Comparative Examples 1 and 4, the image density after 100,000 prints under normal temperature and humidity conditions was 1.2 or less, confirming insufficient image density. Furthermore, in Comparative Examples 3 and 7, the image density after 5,000 prints under high temperature and high humidity conditions was 1.2 or less, confirming insufficient image density.

[0104] The toner in Comparative Example 1 has smaller alumina particle size compared to the toners of Invention 1 to 8, and therefore contributes relatively little to the toner's electrical properties. Furthermore, the toner in Comparative Example 4 has a higher electrical resistivity compared to the toners of Invention 1 to 8, and therefore contributes relatively little to the toner's dielectric properties. As a result, Comparative Examples 1 and 4 have a relatively large amount of toner transported by the developing roller 25, meaning the layer thickness of the developing roller 25 is relatively thick. This is thought to have resulted in reduced developability and insufficient image density in Comparative Examples 1 and 4.

[0105] Furthermore, the toner in Comparative Example 3 has a lower electrical resistivity compared to the toners of Inventions 1 to 8. Therefore, it is believed that the amount of charge decreased in a high-temperature, high-humidity environment, resulting in reduced developability and consequently, insufficient image density.

[0106] In contrast, the toners of the present invention 1 to 8 have a primary particle diameter of alumina particles of 150 nm and 400 nm or less, and an electrical resistivity of 0.1 Ωm or more and 2 Ωm or less. As a result, the layer thickness of the developing roller 25 is relatively thin, which suppresses a decrease in developability and prevents image density deficiency.

[0107] Next, we also checked for image overlap. To check for image overlap, we printed 50,000 LSA charts in a normal temperature and humidity environment using intermittent output of three images each. Every 5,000 images, we printed a white background image and recorded the maximum value of the ID measured using a reflectance densitometer. If this maximum value is 0.008 or higher, image overlap is considered to have occurred.

[0108] In all of Inventions 1 to 8, the maximum value was less than 0.008. On the other hand, in Comparative Example 2, the maximum value was 0.012, and the occurrence of image blur was confirmed.

[0109] Generally, poor charging can occur when toners with different residence times (degraded toner and new toner) are mixed. This is because changes in the state of silica particles, which are external additives on the toner surface (embedding in the toner, or peeling of the surface treatment of the silica particles, etc.), lead to changes in the toner's charging ability (changes in the work function), which can cause the toners to come into contact with each other, resulting in reversed or undercharged toner. If the external additive has sufficient dielectric properties, it becomes less likely for reversed or undercharged toner to occur due to contact between toners (silica particles). This is because the dielectric properties of the external additive reduce the frequency of contact between silica particles and extend the charge transfer time during contact. The toner in Comparative Example 2 has a larger primary particle size of alumina particles, which are external additives, and contains relatively fewer alumina particles than the toners in Inventions 1 to 8. Therefore, it becomes impossible to secure sufficient dielectric properties to mitigate the aforementioned insufficient charging. Consequently, it is thought that in Comparative Example 2, the toner was undercharged, resulting in image fringing.

[0110] In contrast, the toners of the present invention 1 to 8 have a primary particle diameter of alumina particles of 150 nm and 400 nm or less. As a result, the number of toner particles contained in the toner is suitable, and sufficient dielectric properties are ensured to alleviate the aforementioned charge deficiency, so it is thought that no image fringing occurred.

[0111] Next, we checked for the occurrence of white streaks and toner dropouts. After printing 100,000 pages under normal temperature and humidity conditions, we printed a halftone image and checked whether white streaks or toner dropouts occurred in the image. White streaks were evaluated by marking an image density difference of 0.1 or more for multiple adjacent image areas along the axial direction of the photoreceptor drum 1 in the halftone image, and an image density difference of less than 0.1, with a mark of ×. In other words, × indicates the presence of white streaks, and ○ indicates the absence of white streaks. For toner dropouts, we visually checked whether there were any black spots on the image caused by toner aggregates or other fallout. If toner dropouts were confirmed, we marked an image of ×, and if not, we marked an image of ○.

[0112] In all of Inventions 1 to 8, no white streaks or toner loss were observed. On the other hand, white streaks were observed in Comparative Examples 5 and 7. In addition, toner loss was observed in Comparative Example 6.

[0113] Comparative Example 5 has a relatively small amount of reverse rotation compared to Inventions 1-8, resulting in less toner exchange around the regulating section 30 during reverse rotation. This causes toner to concentrate around the regulating section 30, increasing the amount of toner accumulated there. As a result, the magnetic field around the regulating section 30 weakens, reducing the effect of the regulating section 30 on regulating the layer thickness. Consequently, the amount of toner transported by the developing roller 25 (the layer thickness of the developing roller 25) increases. This is thought to have caused uneven toner transport along the axial direction of the developing roller 25, resulting in the formation of white streaks. In addition, Comparative Example 7 has a smaller angle θ than Inventions 1-8. Therefore, the toner supply pressure supplied by the second stirring screw 24 to the developing roller 25 is relatively small. This makes it difficult for toner to be exchanged around the regulating section 30, causing toner to concentrate there. This is thought to have resulted in the formation of white streaks, similar to Comparative Example 5.

[0114] In Comparative Example 6, the amount of reverse rotation is greater than in Inventions 1 to 8. Generally, toner drop is a phenomenon in which clumps of toner, which have been transformed into magnetic brushes by the magnetic force of the fixed magnet body 27, fall due to the centrifugal force when the developing roller 25 rotates in reverse. During reverse rotation, the layer thickness is not restricted by the regulating section 30, and the amount of toner transported on the developing roller 25 increases. When the amount of reverse rotation is large, as in Comparative Example 6, the increase in the amount of toner transported also increases, making it easier for clumps of toner to fall due to centrifugal force. For this reason, it is thought that toner drop occurred in Comparative Example 6.

[0115] In contrast, in inventions 1 to 8, the angle θ described above is set to 0 degrees or more and 75 degrees or less. This is thought to result in a relatively large toner supply pressure from the second stirring screw 24 to the developing roller 25, suppressing toner aggregation around the regulating section 30 and thus suppressing the occurrence of white streaks. Furthermore, in inventions 1 to 8, the amount of reverse rotation of the developing roller 25 is set to 1 / 18 or more and 1 / 5 or less of the outer circumference of the developing roller 25. This is thought to stabilize the amount of toner transported by the developing roller 25 during reverse rotation and suppress toner dropping.

[0116] From the above, it has been confirmed that by employing the developing apparatus 4 of the present invention, it is possible to suppress image defects (insufficient image density, image fringing, occurrence of white streaks, and toner drop) while suppressing a decrease in developing performance.

[0117] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. For example, in the above embodiments, the fixed magnet body 27 has a four-pole configuration with two north poles and two south poles, but the present invention is similarly applicable to a fixed magnet body 27 with a five-pole configuration or a three-pole configuration. [Industrial applicability]

[0118] The present invention is applicable to developing apparatuses that use a magnetic single-component developer, and to developer carriers used therein. By utilizing the present invention, it is possible to provide a developing apparatus that can suppress the deterioration of developing performance over a long period of time, and an image forming apparatus equipped therewith. [Explanation of Symbols]

[0119] 1. Photosensitive drum (image carrier) 4. Developing device 5. Toner container (developer storage section) 9 Image forming unit 20 Housing (Enclosure) 20b Developer supply port (developer supply section) 24 Agitation screw 24. Second stirring screw (stirring and conveying member) 25. Developing roller (developer carrier) 27 Fixed magnet body (magnetic component) 27a~27d magnetic pole 29 Regulatory Blade 30 Regulatory Department 35 Blade Magnets 90 Control Unit 100 Image forming apparatus L1 reference straight line L2 horizontal line P1: Center of rotation (first center) P2 Center of rotation (second center) Q Arrow Tn Toner Tn1 Toner matrix particles Tn2 external additive Tn21 Silica Particles Tn22 Alumina Particles θ is the angle between the reference line L1 and the horizontal line L2.

Claims

1. A housing for a magnetic single-component developer consisting only of magnetic toner, A developer carrier that is rotatably supported in the housing and carries the developer on its outer surface, A restricting blade made of a magnetic material is positioned at a predetermined distance from the developer carrier and forms a restricting portion that restricts the thickness of the developer layer supported on the developer carrier. A magnetic member having multiple magnetic poles fixed immovably inside the developer carrier and arranged along the circumferential direction of the developer carrier, A blade magnet fixed to the regulating blade and inducing a magnetic pole at the tip of the regulating blade, A developing apparatus comprising, for developing an electrostatic latent image formed on an image carrier, The aforementioned toner is Toner matrix particles containing binder resin and magnetic powder, Silica particles and alumina particles adhering to the surface of the toner matrix particles, Includes, The alumina particles have a conductive treatment applied to their surface, and have a primary particle diameter of 150 nm or more and 400 nm or less, and a resistivity of 0.1 Ωm or more and 2 Ωm or less. The developer carrier can be rotated in the opposite direction to the forward direction of rotation during image formation, within a range of 1 / 18 to 1 / 5 of the outer circumference of the developer carrier, to perform a developer removal mode to remove the developer accumulated in the regulating section. The system includes an agitation and conveying member that is parallel to the developer carrier and rotatably supported by the housing, which supplies the developer to the developer carrier while agitating and conveying it, A developing apparatus characterized in that the angle between a horizontal line passing through a first rotation center, which is the rotation center of the developer carrier, and a reference straight line passing through a second rotation center, which is the rotation center of the agitation conveying member, and the first rotation center, is 0 degrees or more and 75 degrees or less when the positive direction is considered positive and the opposite direction is considered negative relative to the horizontal line.

2. The developing apparatus according to claim 1, characterized in that the binder resin is a styrene-acrylic acid copolymer or polyester.

3. The image carrier having a photosensitive layer laminated on its surface, A developing apparatus according to claim 1 or 2, which develops the electrostatic latent image formed on the photosensitive layer of the image carrier into a toner image, An image forming apparatus characterized by comprising:

4. A developer container for containing the developer, A developer supply unit that supplies the developer from the developer storage unit to the housing, A control unit capable of controlling the supply of the developer from the developer supply unit and the rotation of the developer carrier, Equipped with, The control unit, A supply mode in which the developer is supplied from the developer storage section to the housing, A development mode for developing the electrostatic latent image on the image carrier, The developer removal mode and, The image forming apparatus according to claim 3, which is capable of performing the developer removal mode at at least one of a first timing from the end of the supply mode to the execution of the next development mode, and a second timing from the end of the development mode to the execution of the next development mode.

Images