JP2022024874A - Image forming apparatus - Google Patents

Abstract

To prevent a harmful influence on an image caused by fine particles while supplying a sufficient amount of fine particles to a surface of a photoconductor drum to improve transfer efficiency.SOLUTION: When a pressing force for pressing a developer carrier against an image carrier is F, and the total number of carrier particles interposed between a toner particle and the image carrier is N, the relationship between an adhesion force Ft formed between the carrier particles and the toner particle measured when the carrier particles are pressed against the toner particle with F/N being a pressing force per unit carrier particle and an adhesion force Fdr formed between the carrier particles and the image carrier measured when the carrier particles are pressed against the image carrier with F/N satisfies Ft≤Fdr. In the direction of movement of a surface of an intermediate transfer body, the adhesion area of carrier particles adhered to a surface of an image carrier included in a second image forming unit arranged downstream of a secondary transfer unit and upstream of the second image forming unit is larger than the adhesion area of carrier particles adhered to a surface of an image carrier included in a first image forming unit.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image forming apparatus using an electrophotographic process or the like.

Conventionally, an image forming apparatus such as a copier or a laser printer that forms an image by using an electrophotographic process has been known.

As a transfer step, this image forming apparatus applies a voltage from a voltage power source to a transfer member arranged on a portion facing the photosensitive drum as an image carrier, whereby a toner image formed on the surface of the photosensitive drum is transferred to an intermediate transfer body or the transfer member. Electrostatic transfer onto the recording material. When forming a toner image of a plurality of colors, this transfer step is repeatedly executed for the toner images of the plurality of colors to form a toner image of the plurality of colors on the surface of the intermediate transfer body or the recording material. The developer (toner) that has not been transferred from the photosensitive drum to the intermediate transfer body or the recording material is removed from the photosensitive drum by the cleaning member, and is stored as waste toner in the waste toner accommodating portion in the cleaning unit.

However, in recent years, a cleanerless system that omits the cleaning system for the surface of the photosensitive drum has been proposed for the purpose of downsizing the apparatus. In order to achieve a cleanerless system, it is necessary to improve the transfer efficiency of the toner image from the photosensitive drum to the intermediate transfer body and reduce the residual transfer toner remaining on the surface of the photosensitive drum after the toner image is transferred by the transfer member. preferable.

In Patent Document 1, in order to achieve a cleanerless system, fine particles are previously adhered to the surface of the photosensitive drum, and the fine particles are interposed between the photosensitive drum and the toner image to reduce the adhesive force between the photosensitive drum and the toner. A configuration for improving transfer efficiency has been proposed.

Further, Patent Document 1 proposes a configuration in which fine particles are supplied from a developing device onto a photosensitive drum by using a toner externally added with fine particles as a means for adhering fine particles to the surface of the photosensitive drum.

Japanese Patent Application Laid-Open No. 10-63027

However, as in Patent Document 1, when toner with fine particles externally added onto a photosensitive drum is supplied from a developing device and a toner image is transferred to a recording material in order to improve transfer efficiency, the toner image is transferred to the surface of the recording material. Fine particles are transferred together with the toner image. In particular, in order to improve the transfer efficiency of a plurality of colors for high printing, it is necessary to supply more fine particles to the surface of the photosensitive drum. Then, a large amount of fine particles may be transferred to the surface of the recording material together with the transferred toner. As a result, when fixing the toner to the recording material, a large amount of fine particles may hinder heat conduction to the toner and deteriorate the fixability.

Therefore, it is an object of the present invention to supply a sufficient amount of fine particles to the surface of the photosensitive drum in order to improve the transfer efficiency, and to suppress the image harmful effect caused by the fine particles.

Therefore, the image forming apparatus according to the present invention is a first developer composed of a rotatable first image carrier, first toner particles, and carrier particles adhering to the surface of the first toner particles. A rotatable first developer carrier that carries the image, and is in contact with the first image carrier to form a first developing section, and the first image carrier carries the first image. A first image forming unit having a first developer carrier for supplying the first developer to form a first developer image on the surface of the body, and a rotatable second image. A rotatable second developer carrier that carries a second developer composed of a carrier and carrier particles that adhere to the surface of the second toner particles and the second toner particles. The second developer image is formed on the surface of the second image carrier in the second developing section by contacting with the second image carrier to form the second developing section. The second image forming portion having the second developing agent carrier for supplying the developing agent of the above and the second image forming portion are contacted with the first image carrier to form the first contact portion, and the second image forming portion is formed. An intermediate transfer body that comes into contact with an image carrier to form a second contact portion, wherein the first developer image is transferred to the first contact portion and the second contact portion is used. The first developer formed on the surface of the intermediate transfer body in contact with the intermediate transfer body on which the second developer image is transferred to form a transfer portion. The first developing unit has the image and the transfer member for transferring the second developer image to the recording material, and the first developing unit rotates the first image carrier. The carrier particles carried on the surface of the agent carrier can be supplied to the surface of the first image carrier, and the second development is carried out in a state where the second image carrier is rotated. An image forming apparatus capable of supplying the carrier particles carried on the surface of the second developer carrier to the surface of the second image carrier, and is a surface of the intermediate transfer body. Is movable so that the first contact portion is formed downstream of the transfer portion and upstream of the second contact portion in the moving direction of the surface of the intermediate transfer body. , The first image forming portion and the second image forming portion are arranged, and the pressing force for pressing the first developer carrier against the first image carrier is F1, the first. When the total number of the carrier particles interposed between the toner particles and the first image carrier is N1, the carrier particles are pressed per unit carrier particle. The adhesive force Ft1 formed between the carrier particles and the first toner particles, which is measured when the first toner particles are pressed by the force F1 / N1, and the carrier particles are the F1 /. The relationship between the carrier particles measured when pressed against the first image carrier with N1 and the adhesive force Fdr1 formed between the first image carrier satisfies Ft1 ≦ Fdr1. The pressing force for pressing the second developer carrier against the second image carrier is F2, and the total number of the carrier particles interposed between the second toner particles and the second image carrier is the total number of the carrier particles. When N2, the carrier particles and the second toner particles measured when the carrier particles are pressed against the second toner particles with F2 / N2, which is a pressing force per unit carrier particle, The adhesive force Ft2 formed between the carrier particles and the carrier particles formed between the carrier particles and the second image carrier measured when the carrier particles are pressed against the second image carrier by the F2 / N2. The relationship between the adhesive force Fdr2 and Ft2≤Fdr2 satisfies Ft2≤Fdr2, and the first image carrier and the first developer carrier, and the second image carrier and the second developer The carrier particles adhering to the surface of the second image carrier after the first image carrier and the second image carrier have each rotated in a state where the carriers are in contact with each other. It is characterized in that the adhesion area is larger than the adhesion area of the carrier particles adhered to the surface of the first image carrier.

As described above, according to the present invention, it is possible to supply a sufficient amount of fine particles to the surface of the photosensitive drum in order to improve the transfer efficiency, and to suppress image damage caused by the fine particles.

It is a timing chart of the transfer carrier supply operation in Example 1. It is an outline of the image forming apparatus in Example 1. It is a control block diagram in Example 1. FIG. It is a figure explaining the development cartridge in Example 1. FIG. It is a figure explaining the setting of the development blade in Example 1. FIG. It is a figure explaining the contact portion between the developing roller and a photosensitive drum in Example 1. FIG. It is a schematic diagram of the toner surface in Example 1. FIG. It is a schematic diagram of the convex shape of the toner surface in Example 1. FIG. It is a schematic diagram of the convex shape of the toner surface in Example 1. FIG. It is a schematic diagram of the convex shape of the toner surface in Example 1. FIG. It is a schematic diagram of the toner and the transfer carrier in Example 1. FIG. It is a schematic diagram at the time of the transfer carrier supply in Example 1. It is a schematic diagram at the time of the primary transfer in Example 1. FIG. It is a timing chart of the image formation operation in Example 1. It is a figure which shows the contact state of the toner in the developing part in (a), (b) Example 1. FIG. It is a figure which shows the existence state of the toner and the transfer carrier particle in the developing part in Example 1. FIG. It is a figure which shows the state of the transfer carrier particle in the developing part in (a), (b) Example 1. FIG. It is a timing chart explaining the supply operation of the transfer carrier particles in Example 1. FIG. It is a timing chart explaining the supply operation of the transfer carrier particles in Example 2. FIG. It is a figure explaining (a), (b) the supply mechanism of the transfer carrier in the non-image formation operation in the developing part in Example 2. FIG. It is a figure explaining (a), (b) the supply mechanism of the transfer carrier in the image formation operation in the developing part in Example 2. It is a figure explaining the transfer carrier supply member in other examples.

Hereinafter, preferred embodiments of the present invention will be exemplified in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the following embodiments should be appropriately changed depending on the configuration of the apparatus to which the present invention is applied and various conditions. Therefore, unless otherwise specified, the scope of the present invention is not intended to be limited to them.

1. 1. Image Forming Device First, the overall configuration of the electrophotographic image forming device (hereinafter referred to as an image forming device) according to the present invention will be described. FIG. 2 is a schematic cross-sectional view of the image forming apparatus 100 of this embodiment. FIG. 3 is a diagram showing a configuration of a control unit 200 that controls the image forming apparatus 100. The configuration, operation, and control of the image forming apparatus 100 of this embodiment will be described with reference to FIGS. 2 and 3.

The image forming apparatus 100 of this embodiment is a full-color laser printer that employs an in-line method and an intermediate transfer method. The first embodiment particularly relates to an image forming apparatus using a so-called drum cleanerless method which does not have a cleaning means for an image carrier.

The image forming apparatus 100 can form a full-color image on the recording material P (for example, recording paper, plastic sheet) according to the image information. The image information is input to the image forming apparatus 100 from an image reading device or a host device such as a personal computer communicably connected to the image forming apparatus 100.

The image forming apparatus 100 is a first, second, and third image forming unit for forming an image of each color of yellow (Y), magenta (M), cyan (C), and black (K), respectively. , Has a fourth process cartridge Sa, Sb, Sc, Sd. In this embodiment, the first to fourth process cartridges Sa, Sb, Sc, and Sd are arranged in a row in a direction intersecting the vertical direction. In this embodiment, the configurations and operations of the first to fourth process cartridges Sa, Sb, Sc, and Sd are substantially the same except that the colors of the formed images are different. Therefore, in the following, if no particular distinction is required, the subscripts a, b, c, and d given to the code to indicate that the element is provided for any of the colors are omitted and collectively. explain.

In this embodiment, the image forming apparatus 100 has four drum-type electrophotographic photosensitive members arranged side by side in a direction intersecting the vertical direction as a plurality of image carriers, that is, photosensitive drums 1 (1a, 1b, It has 1c and 1d). The photosensitive drum 1 is rotationally driven by the photosensitive drum driving unit (drive source) 110. Around the photosensitive drum 1, a charging roller 2 (2a, 2b, 2c, 2d), a scanner unit (exposure device) 3 (3a, 3b, 3c, 3d), a developing unit (developing device) 4 (4a, 4b,) 4c, 4d) and a precharge pre-exposure device 5 (5a, 5b, 5c, 5d) are arranged. The charging roller 2 is a charging means for uniformly charging the surface of the photosensitive drum 1. Further, the scanner unit 3 irradiates a laser to form an electrostatic image (electrostatic latent image) on the photosensitive drum 1 based on the output calculated by the CPU 150 from the image information input from the host device such as a personal computer. It is an exposure means to be used. The developing unit 4 is a developing means for developing an electrostatic image as a toner image. The precharge pre-exposure device 5 is an exposure means for eliminating the non-uniformity of the surface potential of the photosensitive drum 1 after the primary transfer. The photosensitive drum 1, the charging roller 2 as a process means acting on the photosensitive drum 1, and the developing unit 4 are integrated to form the process cartridge S. The process cartridge S can be attached to and detached from the image forming apparatus 100 via an attachment means such as a attachment guide and a positioning member provided in the image forming apparatus 100.

Further, an intermediate transfer belt 10 as an intermediate transfer body for transferring the toner image on the photosensitive drum 1 to the recording material P is arranged facing the four photosensitive drums 1. The intermediate transfer belt 10 formed of the endless belt abuts on each photosensitive drum 1 and circulates (rotates) in the direction (clockwise) of the arrow R3 shown in the figure. The intermediate transfer belt 10 is hung on the secondary transfer facing roller 13, the drive roller 11, and the tension roller 12 as a plurality of support members. In order to move the surface of the intermediate transfer belt 10, the drive roller 11 is rotationally driven in the direction of arrow R2 shown in the figure.

On the inner peripheral surface side of the intermediate transfer belt 10, four primary transfer rollers 14 (14a, 14b, 14c, 14d) as primary transfer means are arranged side by side so as to face each photosensitive drum 1. .. The primary transfer roller 14 presses the intermediate transfer belt 10 toward the photosensitive drum 1 to form a primary transfer portion in which the intermediate transfer belt 10 and the photosensitive drum 1 come into contact with each other.

Further, a secondary transfer roller 20 as a secondary transfer means is arranged at a position facing the secondary transfer facing roller 13 on the outer peripheral surface side of the intermediate transfer belt 10. The secondary transfer roller 20 presses against the secondary transfer opposed roller 13 via the intermediate transfer belt 10 to form a secondary transfer portion in which the intermediate transfer belt 10 and the secondary transfer roller 13 come into contact with each other.

The recording material P to which the toner image is transferred is conveyed to the fixing device 30 as a fixing means. When heat and pressure are applied to the recording material P in the fixing device 30, the toner image is fixed to the recording material P.

It should be noted that the image forming apparatus 100 may form a monochromatic or multicolor image using only one desired image forming portion or using only some (but not all) image forming portions. You can do it.

The image forming apparatus 100 in this embodiment is a printer compatible with a process speed of 148 mm / sec and A4 size paper.

The configuration of the control unit 200 that controls the entire image forming apparatus will be described with reference to FIG. As shown in FIG. 3, the control unit 200 includes a CPU circuit unit 150, a ROM 151, and a RAM 152. The CPU circuit unit 150 collectively controls the primary transfer control unit 201, the secondary transfer control unit 202, the development control unit 203, the exposure control unit 204, and the charge control unit 205 according to the control program stored in the ROM 151. .. The environment table and the paper thickness correspondence table are stored in the ROM 151, and are called and reflected by the CPU 150. The RAM 152 temporarily holds the control data and is used as a work area for arithmetic processing associated with the control. The primary transfer control unit 201 and the secondary transfer control unit 202 control the primary transfer voltage power supply 15 and the secondary transfer voltage power supply 21, respectively, and the primary transfer voltage power supply 15 is based on the current value detected by a current detection circuit (not shown). And the secondary transfer voltage The voltage output from the power supply 21 is controlled. When the control unit 200 receives image information and a print command from a host computer (not shown), each control unit (primary transfer control unit 201, secondary transfer control unit 202, development control unit 203, exposure control unit 204, charge control) Part 205) is controlled to execute the image forming operation required for the printing operation.
2. 2. Image formation process Next, the image formation process in Example 1 will be described. At the time of image formation, first, the surface of the photosensitive drum 1 is uniformly charged by the charging roller 2 to which a charging voltage of −1000 V is applied by the charging voltage power supply 132. Next, the surface of the photosensitive drum 1 charged with laser light (La, Lb, Lc, Ld) emitted from the scanner unit 3 based on the output calculated by the CPU 150 from the image information input from the host device is scanned and exposed. do. As a result, an electrostatic image according to the image information is formed on the photosensitive drum 1. Next, the electrostatic image formed on the photosensitive drum 1 is developed as a toner image by the developing unit 4. Then, a voltage having a polarity opposite to the normal charging polarity of the toner is applied to the primary transfer roller 14 from the primary transfer voltage power supply 15 (high voltage power supply) as the primary transfer voltage applying means. As a result, the toner image on the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 10. At the time of forming a full-color image, the above-mentioned processes are sequentially performed in the first to fourth process cartridges Sa, Sb, Sc, and Sd, and the toner images of each color are then superposed on the intermediate transfer belt 10 for primary transfer. Will be done.

The primary transfer roller 14 is a cylindrical metal roller having an outer diameter of φ6 mm, and a nickel-plated SUS is used as the material. The primary transfer roller 14 is arranged at a position offset by 8 mm on the downstream side in the moving direction of the intermediate transfer belt 10 with respect to the center position of the photosensitive drum 1, so that the intermediate transfer belt 10 is wound around the photosensitive drum 1. It is configured. The primary transfer roller 14 is arranged at a position raised by 1 mm with respect to the horizontal plane formed by the photosensitive drum 1 and the intermediate transfer belt 10 so as to secure the amount of winding of the intermediate transfer belt 10 around the photosensitive drum 1. The transfer belt 10 is pressed with a force of about 200 gf. The primary transfer roller 14 is driven and rotated as the intermediate transfer belt 10 rotates.

After that, the recording material P is transferred to the secondary transfer unit in synchronization with the movement of the intermediate transfer belt 10. Then, a voltage having a polarity opposite to the normal charging polarity of the toner is applied to the secondary transfer roller 20 from the secondary transfer voltage power supply 21 (high voltage power supply) as the secondary transfer voltage applying means. As a result, the four-color toner image on the intermediate transfer belt 10 is transferred on the recording material P by the feeding means by the action of the secondary transfer roller 20 which is in contact with the intermediate transfer belt 10 via the recording material P. It is secondarily transferred to all at once.

The secondary transfer roller 20 as the secondary transfer member abuts on the intermediate transfer belt 10 with a pressure of 50 N to form a secondary transfer portion (secondary transfer nip). The secondary transfer roller 20 is driven to rotate with respect to the intermediate transfer belt 10, and when the toner on the intermediate transfer belt 10 is secondarily transferred to the recording material P such as paper, the secondary transfer voltage power supply 21 is used. A voltage of 1500 V is applied.

The recording material P to which the toner image is transferred is conveyed to the fixing device 30 as a fixing means. In the fixing device 30, when heat and pressure are applied to the recording material P, the transferred toner image is fixed and discharged from the image forming device 100.

The primary transfer residual toner remaining on the surface of the photosensitive drum 1 in the primary transfer step is recovered by the developing roller 22 (described later) and reused. The transfer residual toner on the surface of the photosensitive drum 1 remaining in the primary transfer step is charged to the negative electrode property having the normal charging polarity when passing through the charging roller 2. After that, the primary transfer residual toner is generated by the electric field due to the potential difference between the potential of the photosensitive drum 1 formed by the charging roller 2 and the potential of the developing roller 22 (described later) formed by applying a DC voltage to the developing roller 22. It is collected at 22 and reused.

Further, the secondary transfer residual toner remaining on the surface of the intermediate transfer belt 10 in the secondary transfer step is cleaned and removed by the intermediate transfer belt cleaning device 16.
3. 3. Configuration of Process Cartridge Next, the overall configuration of the process cartridge S mounted on the image forming apparatus 100 of this embodiment will be described. The process cartridge S for each color has the same shape except for an identification portion and the like (not shown). The development unit (developer) 4 of the process cartridge S for each color contains toners of each color of yellow (Y), magenta (M), cyan (C), and black (K), respectively. The developing unit 4, which is a developing agent accommodating portion, accommodates a negative electrode non-magnetic one-component developer (toner) produced by a suspension polymerization method.

The process cartridge S is configured by integrating a photoconductor unit including a photosensitive drum 1, a rotatable charging roller 2, and a developing unit 4 including a rotatable developing roller 22 and the like.

The photosensitive drum 1 is rotatably supported via a bearing (not shown). The photosensitive drum 1 rotates in the direction of arrow R1 (counterclockwise) shown in the figure according to the image forming operation by transmitting the driving force of the photosensitive drum driving means 110 (driving source), which is the photosensitive drum driving unit, to the photoconductor unit. It is configured to be driven.

The photosensitive drum 1 was provided with a photosensitive layer and a surface layer on an aluminum raw tube having an outer diameter of φ20 mm, and a thin film layer having a film thickness of 20 mm formed by polyarylate was used as the surface layer.

The charging roller 2 has a roller portion having an elastic layer made of a conductive rubber having a thickness of 1.5 mm and a volume resistivity of about 1 × 10 ⁶ Ω cm on a metal shaft having a diameter of 5.5 mm. It is configured to be in contact with pressure and to rotate in a driven manner. Further, a large number of convex portions are provided on the surface layer of the charging roller 2, and the average height of the convex portions is about 10 μm. The convex portion provided on the surface layer of the charging roller 2 has a role as a spacer between the charging roller 2 and the photosensitive drum 1 in the charging portion. When the primary transfer residual toner on the photosensitive drum 1 invades the charged portion, the portion other than the convex portion touches the primary transfer residual toner to prevent the charging roller 2 from being contaminated with the transfer residual toner.

On the other hand, as shown in FIG. 4, the developing unit 4 includes a developing roller 22 for supporting the toner T, a developing blade 23 (toner regulating member), a supply roller 26 for supplying the toner T, and a developing frame for fixing these. It has a body 24 and. The developing frame body 24 includes a developing chamber 24a in which a developing roller 22 is arranged, and a balloon prevention sheet 24b for sealing a developing opening (opening) connected to the outside from the developing chamber 24a.

Toner is supplied to the developing roller 22 by the supply roller 26 in contact with the developing roller 22. The supply roller 26 is in contact with the developing roller 22 (in the direction of arrow R4 in the figure) and rotates (in the direction of arrow R5 in the figure). The supply roller 26 also has a function of transporting the toner T from the inside of the developing chamber 24a, adhering it to the developing roller 22, and temporarily removing the toner T remaining in the developing roller 22. Further, the toner T adhering to the supply roller 26 is given a preliminary triboelectric charge by rubbing against the developing roller 22.

One end of the developing blade 23 is fixed to the fixing member 25 fixed to the developing frame body 24, and the other end of the developing blade 23 is brought into contact with the developing roller 22, so that the toner coating amount on the developing roller 22 is regulated and the electric charge is applied. It is a possible configuration. The developing roller 22 is arranged in the developing opening so that it can come into contact with the photosensitive drum 1.

As shown in FIG. 4, the developing roller 22 is a roller having a structure in which, for example, a base layer 22b made of silicon and a surface layer 22c made of urethane are sequentially laminated on a metal core metal 22a. It is arranged so as to be rotationally driven in the direction R4 of the arrow in the figure by the driving force of the developing roller driving means 130 (driving source) which is the developing roller driving unit.

In this embodiment, a predetermined DC voltage (development voltage Vdc) is applied to the developing roller 22 from the developing voltage power supply 131, and a negatively charged toner due to triboelectric charging comes into contact with the photosensitive drum 1 in an electrostatic latent image. Is visualized to form a toner image.

The supply roller 26 is provided with a urethane foam layer 26b around a core metal electrode 26a having an outer diameter of φ5.5 (mm), which is a conductive support. The outer diameter of the entire supply roller 26 including the urethane foam layer 26b is φ11 (mm). The amount of penetration of the developing roller 22 into the supply roller 26 is 1.2 mm. The supply roller 26 rotates in a direction (in the direction of arrow R5 in the figure) so that the supply rollers 26 have speeds in opposite directions at the contact portion with the developing roller 22. The powder pressure of the toner T existing around the urethane foam layer 26b acts on the urethane foam layer 26b, and the supply roller 26 rotates, so that the toner T is taken into the urethane foam layer 26b. A predetermined DC voltage (supply voltage Vrs) is applied to the supply roller 26 from the supply voltage power supply 136. Then, the toner supply amount and the preliminary triboelectric charge amount are controlled by controlling the potential difference (supply roller contrast ΔVrs = Vrs-Vdc) with the voltage (development voltage Vdc) applied to the developing roller 22.

In this embodiment, the supply voltage Vrs = −500V is applied to the supply roller 26, and the development voltage Vdc = −300V is applied to the development roller 22 from the supply voltage power supply 136 and the development voltage power supply 131, respectively. As a result, the supply roller 26 is controlled by the control unit 200 so that a potential difference of −200 V is formed with respect to the developing roller 22, and the toner supply amount and the preliminary triboelectric charge amount are stabilized.

Here, in the following description, with respect to the potential and the applied voltage, a large absolute value on the negative electrode side (for example, -1000 V with respect to -500 V) is referred to as a high potential, and an absolute value is small on the negative electrode side (for example, -1000 V). For example, -300V with respect to -500V) is referred to as low potential. This is because the toner having a negative charge property in this embodiment is considered as a reference.

Further, the voltage in this embodiment is expressed as a potential difference from the ground potential (0V). Therefore, it is interpreted that the developing voltage Vdc = −300V has a potential difference of −300V with respect to the ground potential due to the developing voltage applied to the core metal of the developing roller 22. This also applies to the charging voltage, transfer voltage, and the like.

As shown in FIG. 4, the developing blade 23 is in contact with the developing roller 22 so as to face the counter direction, and regulates the coating amount of the toner and applies charge.

In this embodiment, as the developing blade 23 which is a toner regulating member, a supporting member of a leaf spring-shaped SUS plate having a thickness of 50 to 120 μm is used, and the surface of the blade portion is developed by the developing roller 22 by utilizing the spring elasticity of the supporting member. Is in contact with. Specifically, they are in contact with each other as shown in FIG. When the center of the cross section of the developing roller 22 is set to the zero point, the XY coordinate axes are defined as shown in FIG. 5, and the contact position is defined by the XY coordinates (x, y). In this embodiment, x = 3. It is 86 mm and y = −0.60 mm. The blade portion of the developing blade 23 has a blade portion formed at one end thereof and the other end fixed to the developing frame body 24 in the lateral direction to be supported. On the other hand, the blade portion is formed by coating the surface of the support member with a thin film made of a conductive urethane resin. Further, a predetermined DC voltage is applied to the developing blade 23 from the developing blade voltage power supply 133 (development blade voltage Vb), and a potential difference from the voltage applied to the developing roller 22 (development voltage Vdc) (development blade contrast ΔVb = Vb-Vdc). To control. Thereby, the toner charge amount and the toner coat amount are controlled.

In this embodiment, the developing blade voltage Vb = −500V is applied to the developing blade 23, and the developing voltage Vdc = −300V is applied to the developing roller 22. A potential difference of −200 V (development blade contrast) is applied to the developing blade 23 with respect to the developing roller 22 to stabilize the toner charging amount and the toner coating amount.

The toner layer formed on the developing roller 22 by the developing blade 23 is conveyed to the developing section in contact with the photosensitive drum 1, and the developing section performs reverse development. At the contact position A shown in FIG. 6, the amount of penetration of the developing roller 22 into the photoconductor 1 is set to 40 μm by a roller (not shown) at the end of the developing roller 22. The surface of the developing roller 22 is deformed by being pressed against the photosensitive drum 1. As a result, a developing nip can be formed and development can be performed in a stable contact state. The pressing force of the developing roller 22 on the photosensitive drum 1 in this embodiment is 200 gf. The width of the developing section (hereinafter referred to as the developing nip section), which is the contact portion between the developing roller 22 and the photosensitive drum 1, is 2.0 mm in the rotational direction of the photosensitive drum 1 and 220 mm in the longitudinal direction of the photosensitive drum 1. Is.

The toner in this embodiment is a non-magnetic toner having a negative charge property produced by a suspension polymerization method, has a volume average particle size of 7.0 μm, and is charged negatively when supported on a developing roller 22. do. The volume average particle size of the toner was measured by a laser diffraction type particle size distribution measuring instrument LS230 manufactured by Beckman Coulter Co., Ltd. The toner will be described later.
4. The primary transfer will be described in detail with respect to the primary transfer process described in the section on image formation process.

First, the surface of the photosensitive drum 1 is uniformly charged to a charging potential Vd, which is a predetermined potential, by the charging roller 2. Next, the surface of the photosensitive drum 1 charged with the laser beam emitted from the scanner unit 3 is scanned and exposed based on the output calculated by the CPU 150 from the image information input from the host device, and the image information is displayed on the photosensitive drum 1. An electrostatic image is formed according to the above. At this time, the post-exposure potential Vl, which is the potential at which the electrostatic image is formed, is formed. Next, the electrostatic image formed on the photosensitive drum 1 is developed as a toner image by the potential difference between the development voltage Vdc and the post-exposure potential Vl (development contrast ΔVcont = Vl−Vdc). Then, a primary transfer voltage Vtr, which is a predetermined DC voltage having a polarity opposite to the normal charging polarity of the toner, is applied to the primary transfer roller 14 from the primary transfer voltage power supply 15 (high voltage power supply) as the primary transfer voltage applying means. .. At this time, the potential difference between Vtr and Vl (primary transfer contrast ΔVtr = Vtr−Vl) becomes the primary transfer electric field, and the toner image on the photosensitive drum 1 is primary transferred onto the intermediate transfer belt 10.

Each potential setting during the image forming operation in this embodiment is a charging potential Vd = −500V, a developing voltage Vdc = −300V, a post-exposure potential Vl = −100V, and a primary transfer voltage Vtr = 200V.

The surface potential of the photosensitive drum 1 was measured with a surface electrometer Model 344 manufactured by Trek Corporation.
5. Developer, Toner, Transfer Carrier Particles Next, the developer, toner, and transfer carrier particles used in this example will be described in detail.

In this example, a mixture of toner and external additive A, which is a transfer carrier particle, was used as a developer. Here, the transfer carrier particles are interposed between the toner image developed on the photosensitive drum 1 and the photosensitive drum 1, thereby reducing the adhesive force between the toner image and the photosensitive drum 1 and reducing the toner. It refers to fine particles that have a role of improving the primary transfer efficiency of an image. The toner is a toner mother particle containing a mold release agent and a toner particle containing an organic silicon polymer on the surface of the toner mother particle.

The organic silicon polymer has a T3 unit structure represented by R—Si (O _1/2 ) ₃ , and R represents an alkyl group or a phenyl group having 1 or more and 6 or less carbon atoms, and has an organic silicon weight. The coalescence forms a convex portion on the surface of the toner matrix particles.

The convex portion is characterized in that it is in surface contact with the surface of the toner matrix particles, and the surface contact can be expected to have a remarkable effect of suppressing the movement, desorption, and burial of the convex portion.

The degree of surface contact will be described with reference to the schematic views of the convex portions shown in FIGS. 7, 8, 9, and 10.

61 shown in FIG. 7 is a cross-sectional image of the toner particles showing about 1/4 of the toner particles, 62 is the toner particles, 63 is the surface of the toner mother particles, and 64 is the convex portion. The cross section of the toner particles can be observed using a scanning transmission electron microscope (hereinafter, also referred to as STEM), which will be described later.

Observe the cross-sectional image of the toner and draw a line along the circumference of the toner matrix particle surface. Conversion is performed to a horizontal image based on the line along the circumference. In the horizontal image, the length of the line along the circumference in the portion where the convex portion and the toner mother particle form a continuous interface is defined as the convex width w.

Further, the maximum length of the convex portion in the normal direction of the convex width w is defined as the convex diameter D, and the length from the apex of the convex portion to the line along the circumference in the line segment forming the convex diameter D is defined as the convex diameter D. The convex height is H.

In FIGS. 8 and 10, the convex diameter D and the convex height H are the same, and in FIG. 9, the convex diameter D is larger than the convex height H.

Further, FIG. 10 schematically shows a fixed state of particles similar to bowl-shaped particles in which the central portion of the hemispherical particles is recessed, which is obtained by crushing or breaking the hollow particles.

In FIG. 10, the convex width W is the total length of the organosilicon polymers in contact with the surface of the toner mother particles. That is, the convex width W in FIG. 10 is the sum of W1 and W2.

The number average value of the convex height H is 30 nm or more and 300 nm or less, and preferably 30 nm or more and 200 nm or less. When the number average value of the convex height H is 30 nm or more, a spacer effect is generated between the surface of the toner mother particles and the transfer member, and the transferability is remarkably improved. On the other hand, when the number average value of the convex height H is 300 nm or less, the effect of suppressing migration, desorption, and burial is remarkable, and high transferability is maintained even in long-term use. A cumulative distribution of the convex height H is taken in the convex portion where the convex height H is 30 nm or more and 300 nm or less. When the convex height corresponding to 80% by total from the smaller convex height H is H80, the H80 is preferably 65 nm or more and 120 nm or less, and more preferably 75 nm or more and 100 nm or less. When H80 is in the above range, the transferability can be further improved.

The number average particle size R of the primary particles of the external additive A is preferably 30 nm or more and 1200 nm or less. When R is 30 nm or more, a spacer effect is exhibited between the R and the transfer member, and high transferability is exhibited. Further, the larger the R, the better the transfer performance tends to be. On the other hand, when R exceeds 1200 nm, the fluidity of the toner is lowered and image unevenness is likely to occur.

The ratio of the number average particle size R of the primary particles of the external additive A to the number average value of the convex height H is preferably 1.00 or more and 4.00 or less. When the ratio [(the number average particle size R of the primary particles of the external additive A) / (the number average value of the convex height H)] is within the above range, excellent transferability and low temperature fixing that can withstand a long life are achieved. It is possible to achieve both sex.

When the number average value of the convex height H is 30 nm, which is the minimum value, if R is 30 nm or more, a spacer effect can be exhibited between the convex height H and the transfer member, and the transferability can be improved. It is considered that the external additive A is substituted in a place where the convex portion does not exist due to the influence of desorption or the like, and the spacer effect is exhibited. That is, if R is less than 30 nm, the spacer effect is unlikely to be exhibited.

The adhesion rate of the external additive A to the surface of the toner particles is preferably 0% or more and 20% or less, and more preferably 0% or more and 10% or less. When the adhesion rate is within the above range, the external additive A can easily move on the surface of the toner particles, and the transferability can be further improved by the convex portion substitution action. In the fixing step of fixing the toner to the fixing member, an appropriate amount of the mold release agent exudes from the toner mother particles, thereby improving the separation performance between the fixing member and the paper.

By observing the surface of the toner with a scanning electron microscope, a 1.5 μm square backscattered electron image of the toner surface is obtained. When an image obtained by binarization so that the organic silicon polymer portion in the backscattered electron image becomes a bright part, the area ratio of the bright part area of the image to the total area of the image (hereinafter, simply, the bright part). The area ratio of the area) is 30.0% or more and 75.0% or less. Further, the area ratio of the bright area of the image is preferably 35.0% or more and 70.0% or less. The higher the area ratio of the bright area, the higher the abundance ratio of the organosilicon polymer on the surface of the toner matrix particles. When the area ratio of the bright area is higher than 75.0%, the abundance ratio of the component derived from the toner mother particles on the surface of the toner mother particles is small, the exudation of the mold release agent from the toner mother particles is less likely to occur, and the temperature is low. Thin paper wrapping around the fuser tends to occur during fixing. On the other hand, when the area ratio of the bright area of the image is less than 30.0%, the abundance ratio of the component derived from the toner mother particles on the surface of the toner mother particles is large. That is, the exposed area of the component derived from the toner mother particles on the surface of the toner mother particles is large, and the transferability at the initial stage of use is lowered. The area ratio of the bright area of the image is also referred to as the coverage of the organic silicon polymer on the surface of the toner matrix particles.

The external additive A is not particularly limited as long as the number average particle size R of the primary particles is 30 nm or more and 1000 nm or less, and various organic fine particles or inorganic fine particles can be used. The external additive A preferably contains silica fine particles from the viewpoint of easily imparting fluidity and being easily negatively charged like the toner mother particles. The content of the silica fine particles in the external additive A is preferably 50% by mass or more, and more preferably the external additive A is silica fine particles. The content of the external additive A in the toner is preferably 0.02% by mass or more and 5.00% by mass or less, and more preferably 0.05% by mass or more and 3.00% by mass or less.

Examples of the organic fine particles or the inorganic fine particles other than the silica fine particles include the following.
(1) Fluidity-imparting agent: alumina fine particles, titanium oxide fine particles, carbon black and carbon fluoride.
(2) Abrasive: Fine particles of metal oxide (fine particles such as strontium titanate, cerium oxide, alumina, magnesium oxide, and chromium oxide), fine particles of nitride (fine particles such as silicon nitride), fine particles of carbide (silicon carbide) Fine particles such as), fine particles of metal salts (fine particles such as calcium sulfate, barium sulfate, and calcium carbonate).
(3) Lubricants: Fine particles of fluororesin (fine particles such as vinylidene fluoride and polytetrafluoroethylene) and fine particles of fatty acid metal salts (fine particles such as zinc stearate and calcium stearate).
(4) Charge control fine particles: Metal oxide fine particles (fine particles such as tin oxide, titanium oxide, zinc oxide, and alumina), carbon black.

As the silica fine particles and the organic fine particles or the inorganic fine particles, those which have been subjected to a hydrophobic treatment for improving the fluidity of the toner and making the charge uniform of the toner particles may be used.

Examples of the treatment agent for the hydrophobic treatment include unmodified silicone varnish, various modified silicone varnishes, unmodified silicone oil, various modified silicone oils, silane compounds, silane coupling agents, other organosilicon compounds, and organotitanium compounds. Can be mentioned. These treatment agents may be used alone or in combination.

As the silica fine particles, known silica fine particles can be used, and either dry silica fine particles or wet silica fine particles may be used. It is preferable that the particles are wet silica fine particles (hereinafter, also referred to as sol-gel silica) obtained by the sol-gel method.

FIG. 11 is an enlarged view of the developer used in this embodiment. As shown in FIG. 11, the developer of this embodiment has an external additive A, which is a transfer carrier particle, arranged on a toner surface on which a large number of convex portions of an organosilicon polymer are formed.

The convex spacing G and the convex height H of the toner surface shown in FIG. 11 can be measured by using a scanning transmission electron microscope (hereinafter, also referred to as STEM) described later. Further, the convex spacing G and the convex height H can also be measured by a scanning probe microscope (hereinafter referred to as SPM). The scanning probe microscope (SPM) is equipped with a probe, a cantilever that supports the probe, and a displacement measurement system that detects the bending of the cantilever, and is equipped with an atomic force (attractive force or repulsive force) between the probe and the sample. Is detected, and the shape of the sample surface is observed.

If the convex spacing G is larger than the transfer carrier, the transfer carrier particles come into contact with the toner base when the transfer carrier particles are arranged between the convex portions, and the adhesive force Ft between the transfer carrier particles and the toner increases, so that the toner is transferred to the photosensitive drum 1. Transfer carrier particles are less likely to transfer. Therefore, it is preferable that the number average value of the convex spacing G is smaller than the number average particle size of the transfer carrier particles.

Further, when the convex height H is higher than the particle size of the transfer carrier particles, the convex portion comes into contact with the photosensitive drum 1 before the transfer carrier particles, and it becomes difficult for the transfer carrier particles to come into contact with the photosensitive drum 1. Transfer carrier particles are less likely to transfer from the toner to the photosensitive drum 1. Therefore, it is preferable that the number average value of the convex height H is smaller than the number average particle size of the transfer carrier particles.

However, as described above, it is preferable that the adhesive force Ft between the transfer carrier particles and the toner is smaller than the adhesive force Fdr between the transfer carrier particles and the photosensitive drum 1. Therefore, as the material of the transfer carrier particles, it is preferable to select a material in which the adhesive force Ft of the transfer carrier particles to the toner is small. For example, when the convex portion of the toner surface is formed of a silica-based material such as an organic silica polymer as in this embodiment, the material of the transfer carrier particles is also a silica-based material having a material composition similar to that of the convex portion. Is preferable because the adhesive force between the convex portion and the transfer carrier particles is low.

It is preferable that the number of transfer carrier particles covering the toner is large from the viewpoint of supplying the transfer carrier particles from the developing roller 22 to the photosensitive drum 1. However, if the amount of the transfer carrier particles added is too large, the risk of contamination of the members in the image forming apparatus 100 increases, so it is preferable to adjust the transfer carrier particles according to the desired primary transferability.

The primary transferability improves as the coverage of the transfer carrier particles on the photosensitive drum 1 increases, and in order to obtain sufficient primary transferability, the coverage of the transfer carrier particles on the photosensitive drum 1 is 10% or more. Is preferable. However, as the coverage of the transfer carrier particles on the photosensitive drum 1 increases, the degree of improvement in the primary transferability slows down, and the risk of contamination of various members in the image forming apparatus by the transfer carrier particles increases. Therefore, the coverage of the transfer carrier particles on the photosensitive drum 1 is preferably kept within 50%.
6. Methods for Measuring Physical Properties of Developers Various measuring methods will be described below.

<Method of observing the cross section of toner with a scanning transmission electron microscope (STEM)>
The cross section of the toner observed with a scanning transmission electron microscope (STEM) is prepared as follows.

Hereinafter, the procedure for producing the cross section of the toner will be described. When organic fine particles or inorganic fine particles are externally added to the toner, the toner from which the organic fine particles or the inorganic fine particles have been removed by the following method or the like is used as a sample.

Add 160 g of sucrose (manufactured by Kishida Chemical) to 100 mL of ion-exchanged water and dissolve in a water bath to prepare a sucrose concentrate. 31 g of the above sucrose concentrate in a centrifuge tube (capacity 50 mL), and a neutral detergent for cleaning a precision measuring instrument with a pH of 7 consisting of Contaminone N (nonionic surfactant, anionic surfactant, and organic builder). Add 6 mL of 10% by mass aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.). Add 1.0 g of toner to this and loosen the toner lumps with a spatula or the like. The centrifuge tube is shaken with a shaker (sold by AS-1N AS ONE Corporation) at 300 spm (strokes per min) for 20 minutes. After shaking, the solution is replaced with a glass tube for a swing rotor (50 mL), and the solution is separated by a centrifuge (H-9R, manufactured by Kokusan Co., Ltd.) at 3500 rpm for 30 minutes. By this operation, the toner particles and the external additive are separated. Visually confirm that the toner particles and the aqueous solution are sufficiently separated, and collect the toner particles separated in the uppermost layer with a spatula or the like. The collected toner particles are filtered with a vacuum filter and then dried with a dryer for 1 hour or more to obtain a sample for measurement. Perform this operation multiple times to secure the required amount.

Whether or not the convex portion contains an organic silicon polymer is confirmed by combining elemental analysis by energy dispersive X-ray analysis (EDS).

Toner is sprayed on a cover glass (Matsunami Glass Co., Ltd., square cover glass; square No. 1) so as to form a single layer, and an osmium (Os) plasma coater (filgen Co., Ltd., OPC80T) is used as a protective film on the toner. An Os film (5 nm) and a naphthalene film (20 nm) are applied. Next, a PTFE tube (outer diameter 3 mm (inner diameter 1.5 mm) x 3 mm) is filled with a photocurable resin D800 (JEOL Ltd.), and the cover glass is placed on the tube with a toner photocurable resin D800. Place it quietly so that it touches the surface. After irradiating light in this state to cure the resin, the cover glass and the tube are removed to form a cylindrical resin in which toner is embedded in the outermost surface. 4 when the radius of the toner from the outermost surface of the cylindrical resin (for example, weight average particle size (D4)) is 8.0 μm at a cutting speed of 0.6 mm / s by an ultrasonic ultramicrotome (Leica, UC7). Cut to a length of .0 μm) to obtain a cross section of the toner center.

Next, cutting is performed so that the film thickness is 100 nm, and a flaky sample of the cross section of the toner is prepared. By cutting by such a method, a cross section of the toner center portion can be obtained.

As a scanning transmission electron microscope (STEM), JEM-2800 manufactured by JEOL Ltd. was used. Images are acquired with a STEM probe size of 1 nm and an image size of 1024 x 1024 pixels. Further, the contrast of the Director Control panel of the bright field image is adjusted to 1425, the Brightness is adjusted to 3750, the Contrast of the Image Control panel is adjusted to 0.0, the Brightness is adjusted to 0.5, and the Gammma is adjusted to 1.00 to acquire an image. The image magnification is 100,000 times, and the image is acquired so as to fit in about one-fourth to one-half of the circumference of the cross section in one toner particle as shown in FIG. The obtained STEM image is image-analyzed using image processing software (image J (available from images: //imagej.nih.gov/ij/)), and the convex portion containing the organic silicon polymer is measured. .. The measurement is performed on 30 convex portions arbitrarily selected from the STEM image. Whether or not the convex portion contains an organic silicon polymer is confirmed by a combination of elemental analysis by a scanning electron microscope (SEM) and an energy dispersive X-ray analysis (EDS). First, draw a line along the circumference of the toner matrix particle with the line drawing tool (select the Line segmented line on the Line tab). The portion where the convex portion of the organosilicon polymer is buried in the toner matrix particles is smoothly connected with the line assuming that the convex portion is not buried. Convert to a horizontal image based on the line (select Selection on the Edit tab, change the line width to 500 pixels in the properties, select Selection on the Edit tab, and perform Struggener). In the horizontal image, the following measurement is carried out for one of the convex portions containing the organosilicon polymer. The length of the line along the circumference in the portion where the convex portion and the toner mother particle form a continuous interface is defined as the convex width w. In the normal direction of the convex width w, the maximum length of the convex portion is defined as the convex diameter D, and the length from the apex of the convex portion to the line along the circumference in the line segment forming the convex diameter D is the convex height. Let's say H. The measurement is carried out for 30 arbitrarily selected convex portions, and the arithmetic mean value of each measured value is taken as the number average value of the convex height H.

<Calculation method of H80>
In the STEM image of the cross section of the toner using the scanning transmission electron microscope (STEM), the cumulative distribution of the convex height H is taken in the convex portion where the convex height H is 30 nm or more and 300 nm or less. The convex height corresponding to 80% by total from the smaller convex height H is defined as H80 (unit: nm).

<Calculation method of the area ratio of the bright area in the 1.5 μm square backscattered electron image on the toner surface>
For the area ratio of the bright area, the surface of the toner is observed using a scanning electron microscope. Then, a 1.5 μm square backscattered electron image of the toner surface is acquired. Then, an image obtained by binarizing the organosilicon polymer portion in the backscattered electron image so as to be a bright part is obtained, and the ratio of the bright part area of the image to the total area of the image is obtained. When organic fine particles or inorganic fine particles are externally attached to the toner, the toner from which the organic fine particles or the inorganic fine particles have been removed by the following method or the like is used as a sample.

Add 160 g of sucrose (manufactured by Kishida Chemical) to 100 mL of ion-exchanged water and dissolve in a water bath to prepare a sucrose concentrate. 31 g of the above sucrose concentrate in a centrifuge tube (capacity 50 mL), and a neutral detergent for cleaning a precision measuring instrument with a pH of 7 consisting of Contaminone N (nonionic surfactant, anionic surfactant, and organic builder). Add 6 mL of 10% by mass aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.). Add 1.0 g of toner to this and loosen the toner lumps with a spatula or the like. The centrifuge tube is shaken with a shaker (sold by AS-1N AS ONE Corporation) at 300 spm (strokes per min) for 20 minutes. After shaking, the solution is replaced with a glass tube for a swing rotor (50 mL), and the solution is separated by a centrifuge (H-9R, manufactured by Kokusan Co., Ltd.) at 3500 rpm for 30 minutes. By this operation, the toner particles and the external additive are separated. Visually confirm that the toner particles and the aqueous solution are sufficiently separated, and collect the toner particles separated in the uppermost layer with a spatula or the like. The collected toner particles are filtered with a vacuum filter and then dried with a dryer for 1 hour or more to obtain a sample for measurement. Perform this operation multiple times to secure the required amount.

Further, whether or not the convex portion contains the organic silicon polymer is confirmed by combining elemental analysis by energy dispersive X-ray analysis (EDS) described later.

The SEM device and observation conditions are as follows.
Equipment used: ULTRA PLUS manufactured by Carl Zeiss Microscopy Co., Ltd.
Acceleration voltage: 1.0kV
WD: 2.0mm
Aperture Size: 30.0 μm
Detection signal: EsB (energy selective reflected electron)
EsB Grid: 800V
Observation magnification: 50,000 times Contrast: 63.0 ± 5.0% (reference value)
Brightness: 38.0 ± 5.0% (reference value)
Resolution: 1024 x 768
Pretreatment: Toner particles are sprayed on carbon tape (no vapor deposition)
The acceleration voltage and EsB Grid are set to achieve items such as acquisition of structural information on the outermost surface of toner particles, prevention of charge-up of undeposited samples, and selective detection of high-energy backscattered electrons. For the observation field, select the vicinity of the apex where the curvature of the toner particles is the smallest. The bright part of the backscattered electron image is derived from the organic silicon polymer by superimposing the element mapping image by energy dispersive X-ray analysis (EDS) that can be obtained by a scanning electron microscope (SEM) and the backscattered electron image. confirmed.

The SEM / EDS equipment and observation conditions are as follows.
Equipment used (SEM): ULTRA PLUS manufactured by Carl Zeiss Microscopy Co., Ltd.
Equipment used (EDS): NORAN System 7, Ultra Dry EDS Detector manufactured by Thermo Fisher Scientific Co., Ltd.
Acceleration voltage: 5.0kV
WD: 7.0 mm
Aperture Size: 30.0 μm
Detection signal: SE2 (secondary electron)
Observation magnification: 50,000 times Mode: Spectral Imaging
Pretreatment: Toner particles are sprayed on carbon tape and platinum spatter. The mapping image of the silicon element obtained by this method and the backscattered electron image are superimposed, and the silicon atom part of the mapping image and the bright part of the backscattered electron image match. Make sure you do.

The area ratio of the bright area to the total area of the backscattered electron image is calculated by analyzing the backscattered electron image on the surface of the toner particles obtained by the above method using the image processing software ImageJ (developer Wayne Rashand). Obtained. The procedure is shown below.

First, the backscattered electron image is converted into 8-bit from the Type of the Image menu. Next, from Filters in the Process menu, set the Median diameter to 2.0 pixels to reduce image noise. Estimate the center of the image after removing the observation condition display part displayed at the bottom of the backscattered electron image, and use the rectangle tool (Rectangle Tool) on the toolbar to select a range of 1.5 μm square from the center of the backscattered electron image. .. Next, select Thrashold from Adjust in the Image menu. Select Default, click Auto, and then click Apply to get a binarized image. By this operation, the bright part of the reflected electron image is displayed in white. Estimate the image center again after removing the observation condition display part displayed at the bottom of the backscattered electron image, and use the rectangular tool (Rectangle Tool) on the toolbar to cover a range of 1.5 μm square from the image center of the backscattered electron image. select. Next, select Histogram from the Analyze menu. Read the Count value from the newly opened Histogram window (corresponding to the total area of the backscattered electron image). Also, click List and read the Count value when the brightness is 0 (corresponding to the bright area of the backscattered electron image). From the above values, the area ratio of the bright area to the total area of the backscattered electron image is calculated. The above procedure is performed for 10 fields of toner particles to be evaluated, the number average value is calculated, and the entire area of the image obtained by binarizing so that the organic silicon polymer portion in the backscattered electron image becomes a bright part. The area ratio (%) of the bright area of the image to the image.

<Method for identifying organosilicon polymers>
The method for identifying the organic silicon polymer is a combination of observation with a scanning electron microscope (SEM) and elemental analysis with energy dispersive X-ray analysis (EDS).

Using a scanning electron microscope "Hitachi ultra-high resolution field emission scanning electron microscope S-4800" (Hitachi High-Technologies Corporation), observe the toner in a field magnified up to 50,000 times. Focus on the surface of the toner particles and observe the surface. EDS analysis is performed on the particles and the like existing on the surface, and it is determined whether or not the analyzed particles and the like are organosilicon polymers based on the presence or absence of the Si element peak. When the surface of the toner particles contains both an organosilicon polymer and silica fine particles, compare the ratio (Si / O ratio) of the element content (atomic%) of Si and O with the standard. The organosilicon polymer is identified in. EDS analysis is performed on each of the organosilicon polymer and silica fine particles under the same conditions to obtain the element content (atomic%) of Si and O respectively. The Si / O ratio of the organosilicon polymer is A, and the Si / O ratio of the silica fine particles is B. Select a measurement condition in which A is significantly larger than B. Specifically, the standard is measured 10 times under the same conditions, and the arithmetic mean values of A and B are obtained. Select the measurement conditions for which the obtained average value is A / B> 1.1. When the Si / O ratio of the particles to be discriminated is on the A side of [(A + B) / 2], the particles or the like are judged to be organosilicon polymers.

Tospearl 120A (Momentive Performance Materials Japan GK) is used as a standard for organosilicon polymer particles, and HDK V15 (Asahi Kasei) is used as a standard for silica fine particles.

<Measuring method of number average particle size R of primary particles of external additive>
Element analysis by scanning electron microscope "Hitachi ultra-high resolution field emission scanning electron microscope S-4800" (Hitachi High Technologies America, Inc.) and energy dispersive X-ray analysis (EDS) is performed.

In the field of view magnified up to 50,000 times, the elemental analysis method by EDS described above is used in combination, and the external additive particles are randomly photographed. 100 external additive particles are randomly selected from the captured image, the major axis of the primary particle of the target external additive particle is measured, and the arithmetic average value is defined as the number average particle size R. The observation magnification is appropriately adjusted according to the size of the external additive particles.

<Method for identifying the composition and ratio of constituent compounds of organosilicon polymers>
NMR is used to identify the composition and ratio of the constituent compounds of the organosilicon polymer contained in the toner. When the toner contains an external additive such as silica fine particles in addition to the organosilicon polymer, the following operation is performed.

1 g of toner is placed in a vial, dissolved in 31 g of chloroform, and dispersed. For dispersion, an ultrasonic homogenizer is used for 30 minutes to prepare a dispersion.
Sonication device: Ultrasonic homogenizer VP-050 (manufactured by TIETECH Co., Ltd.)
Microchip: Step type microchip, tip diameter φ2 mm
Microchip tip position: Central part of glass vial and height 5 mm from the bottom of the vial Ultrasonic conditions: Intensity 30%, 30 minutes At this time, ultrasonic waves while cooling the vial with ice water so that the dispersion liquid does not rise in temperature. Hang. The dispersion is replaced with a glass tube for a swing rotor (50 mL), and a centrifuge (H-9R; manufactured by Kokusan Co., Ltd.) is used to centrifuge under the conditions of 58.33S ^-1 for 30 minutes. In the glass tube after centrifugation, the lower layer contains particles having a heavy specific density, for example, silica fine particles. A chloroform solution containing the upper layer organosilicon polymer is collected, and the chloroform is removed by vacuum drying (40 ° C./24 hours) to prepare a sample. Using the above sample or organosilicon polymer, the abundance ratio of the constituent compounds of the organosilicon polymer and the ratio of the T3 unit structure represented by R—Si (O _1/2 ) ₃ in the organosilicon polymer are determined. , Solid ²⁹ Measured and calculated by Si-NMR.

First, the hydrocarbon group represented by R is confirmed by ¹³ C-NMR.
<< ¹³ C-NMR (solid-state) measurement conditions >>
Equipment: JNM-ECX500II manufactured by JEOL RESONANCE
Sample tube: 3.2 mmφ
Sample: Sample or organosilicon polymer Measurement temperature: Room temperature Pulse mode: CP / MAS
Measured nuclear frequency: 123.25 MHz ( ¹³ C)
Reference substance: Adamantane (external standard: 29.5 ppm)
Sample rotation speed: 20 kHz
Contact time: 2ms
Delay time: 2s
Number of integrations: 1024 times By this method, a methyl group (Si-CH ₃ ), an ethyl group (Si-C ₂ H ₅ ), a propyl group (Si-C ₃ H ₇ ), and a butyl group bonded to a silicon atom. Depending on the presence or absence of signals due to (Si—C ₄ H ₉ ), pentyl group (Si—C ₅ H ₁₁ ), hexyl group (Si—C ₆ H ₁₃ ) or phenyl group (Si—C ₆ H ₅ −). , Confirm the hydrocarbon group represented by R above. On the other hand, in solid ²⁹ Si-NMR, peaks are detected in different shift regions depending on the structure of the functional group bonded to Si of the constituent compound of the organic silicon polymer. By specifying each peak position using a standard sample, the structure bound to Si can be specified. In addition, the abundance ratio of each constituent compound can be calculated from the obtained peak area. The ratio of the peak area of the T3 unit structure to the total peak area can be calculated.

Specifically, the measurement conditions for the solid ²⁹ Si-NMR are as follows.
Equipment: JNM-ECX5002 (JEOL RESONANCE)
Temperature: Room temperature Measurement method: DDMAS method ²⁹ Si 45 °
Sample tube: Zirconia 3.2 mmφ
Sample: Filled in a test tube in powder form Sample rotation speed: 10 kHz
relaxation delay: 180s
Scan: 2000
After the measurement, a plurality of silane components having different substituents and bonding groups of the sample or organosilicon polymer are peak-separated into the following X1 structure, X2 structure, X3 structure, and X4 structure by curve fitting, and each peak is obtained. Calculate the area.

The following X3 structure is a T3 unit structure.
X1 structure: (Ri) (Rj) (Rk) SiO _1/2 (A1)
X2 structure: (Rg) (Rh) Si (O _1/2 ) ₂ (A2)
X3 structure: RmSi (O _1/2 ) ₃ (A3)
X4 structure: Si (O _1/2 ) ₄ (A4)

Ri, Rj, Rk, Rg, Rh and Rm in the formulas (A1), (A2) and (A3) are organic groups such as hydrocarbon groups having 1 to 6 carbon atoms and halogen atoms bonded to silicon. , A hydroxy group, an acetoxy group or an alkoxy group. If it is necessary to confirm the structure in more detail, it may be identified by the measurement result of ¹ H-NMR together with the measurement results of ¹³ C-NMR and ²⁹ Si-NMR.

<Method for quantifying organosilicon polymer or silica fine particles contained in toner>
The toner is dispersed in chloroform as described above, and then centrifugation is used to separate the organic silicon polymer and the external additives such as silica fine particles by the difference in specific gravity, and each sample is obtained to obtain the organic silicon polymer or silica. Obtain the content of an external additive such as fine particles.

Hereinafter, the case where the external additive is silica fine particles will be illustrated. Even other fine particles can be quantified by the same method.

First, the pressed toner is measured by fluorescent X-rays, and the content of silicon in the toner is determined by performing an analysis process such as a calibration curve method or an FP method. Next, the structures of the organic silicon polymer and each constituent compound forming the silica fine particles were specified by using solid ²⁹ Si-NMR and pyrolysis GC / MS, and the silicon content in the organic silicon polymer and the silica fine particles was specified. Find the quantity. From the relationship between the silicon content in the toner determined by fluorescent X-rays and the silicon content in the organosilicon polymer and silica fine particles determined by solid ²⁹ Si-NMR and thermal decomposition GC / MS, it is calculated in the toner. The content of the organosilicon polymer and silica fine particles is determined.

<Method of measuring the adhesion rate to toner matrix particles or toner particles by washing with an external agent such as an organosilicon polymer or silica fine particles>
(Washing process)
Weigh 20 g of a 30 mass% aqueous solution of "Contaminone N" (a neutral detergent for cleaning a pH 7 precision measuring instrument consisting of a nonionic surfactant, an anionic surfactant, and an organic builder) into a vial having a capacity of 50 mL, and add 1 g of toner. Mix. Set in "KM Shaker" (model: V.SX) manufactured by Iwaki Sangyo Co., Ltd., set speed to 50 and shake for 120 seconds. Depending on the above, an external additive such as an organic silicon polymer or silica fine particles moves from the toner mother particles or the surface of the toner particles to the dispersion liquid side. After that, a centrifuge (H-9R; manufactured by Kokusan Co., Ltd.) ) (At 16.67S-1 for 5 minutes), the toner and the external additive such as the organic silicon polymer or silica fine particles transferred to the supernatant are separated. The precipitated toner is vacuum-dried (40 ° C.). (24 hours) to dry and wash with water to make toner.

Next, using a Hitachi ultra-high resolution field emission scanning electron microscope S-4800 (Hitachi High-Technologies Corporation), a toner that does not undergo the water washing step (toner before washing) and a toner obtained through the water washing step. Take a picture of the toner (toner after washing with water).

The measurement target is identified by elemental analysis using energy dispersive X-ray analysis (EDS).

Then, the photographed toner surface image is subjected to image analysis software Image-Pro Plus ver. Analysis is performed using 5.0 (Nippon Roper Co., Ltd.), and the coverage is calculated.

The image shooting conditions of S-4800 are as follows.
(1) Sample preparation A thin layer of conductive paste is applied to a sample table (aluminum sample table 15 mm x 6 mm), and toner is sprayed on it. Further air blow to remove excess toner from the sample table and allow it to dry sufficiently. Set the sample table on the sample holder and adjust the sample table height to 36 mm with the sample height gauge.
(2) Setting of S-4800 observation conditions When measuring the coverage, elemental analysis by the above-mentioned energy dispersive X-ray analysis (EDS) is performed in advance, and an external agent such as an organic silicon polymer or silica fine particles on the toner surface is used. The measurement is performed after distinguishing between. Inject liquid nitrogen into the anti-contamination trap attached to the housing of S-4800 until it overflows, and leave it for 30 minutes. Start the "PC-SEM" of S-4800 and perform flushing (cleaning of the FE chip which is an electron source). Click the acceleration voltage display part of the control panel on the screen and press the [Flushing] button to open the flushing execution dialog. Confirm that the flushing intensity is 2, and execute. Confirm that the emission current due to flushing is 20 to 40 μA. Insert the sample holder into the sample chamber of the S-4800 housing. Press [Origin] on the control panel to move the sample holder to the observation position.

Click the acceleration voltage display to open the HV setting dialog, and set the acceleration voltage to [1.1 kV] and the emission current to [20 μA]. In the [Basic] tab of the operation panel, set the signal selection to [SE], select [Top (U)] and [+ BSE] for the SE detector, and select [+ BSE] in the selection box to the right of [+ BSE]. L. A. 100] is selected to set the mode for observing with a backscattered electron image. Similarly, in the [Basic] tab of the operation panel, set the probe current of the electro-optical system condition block to [Normal], the focal mode to [UHR], and the WD to [4.5 mm]. Press the [ON] button on the acceleration voltage display of the control panel to apply the acceleration voltage.
(3) Number of toners Average particle size (D1) calculation Drag the inside of the magnification display section of the control panel to set the magnification to 5000 (5k) times. Rotate the focus knob [COARSE] on the operation panel to adjust the aperture alignment when the focus is reached to some extent. Click [Align] in the control panel to display the alignment dialog, and select [Beam]. Rotate the STIGMA / ALIGNMENT knobs (X, Y) on the control panel to move the displayed beam to the center of the concentric circles. Next, select [Aperture] and turn the STIGMA / ALIGNMENT knobs (X, Y) one by one to stop the movement of the image or adjust it to the minimum movement. Close the aperture dialog and focus with autofocus. Repeat this operation twice more to focus.

Then, the particle size of 300 toners is measured to obtain the number average particle size (D1). The particle size of each particle is the maximum diameter when the toner particles are observed.
(4) Focus adjustment For particles with a number average particle size (D1) of ± 0.1 μm obtained in (3), the inside of the magnification display section of the control panel is displayed with the midpoint of the maximum diameter aligned with the center of the measurement screen. Drag to set the magnification to 10000 (10k) times.

Rotate the focus knob [COARSE] on the operation panel to adjust the aperture alignment when the focus is reached to some extent. Click [Align] in the control panel to display the alignment dialog, and select [Beam]. Rotate the STIGMA / ALIGNMENT knobs (X, Y) on the control panel to move the displayed beam to the center of the concentric circles. Next, select [Aperture] and turn the STIGMA / ALIGNMENT knobs (X, Y) one by one to stop the movement of the image or adjust it to the minimum movement. Close the aperture dialog and focus with autofocus. After that, the magnification is set to 50,000 (50k) times, the focus is adjusted using the focus knob and the STIGMA / ALIGNMENT knob in the same manner as above, and the focus is adjusted again by autofocus. Repeat this operation again to focus. Here, if the tilt angle of the observation surface is large, the measurement accuracy of the coverage tends to be low, so by selecting the one that focuses on the entire observation surface at the same time when adjusting the focus, select the one with the least inclination of the surface. And analyze.
(5) Image saving Perform brightness adjustment in ABC mode, take a picture with a size of 640 x 480 pixels, and save it. The following analysis is performed using this image file. One photograph is taken for each toner and an image is obtained for the toner particles.
(6) Image analysis Using the following analysis software, the coverage is calculated by binarizing the image obtained by the above method. At this time, the above screen is divided into 12 squares and analyzed. Image analysis software Image-Pro Plus ver. The analysis conditions for 5.0 are as follows. However, if an organosilicon polymer having a particle size of less than 30 nm and more than 300 nm or an external additive such as silica fine particles having a particle size of less than 30 nm and more than 1200 nm is contained in the divided compartment, the coverage is calculated in that compartment. Will not be done.

In the image analysis software Image-Pro Plus5.0, select "Measurement"-"Count / Size"-"Options" on the toolbar and set the binarization conditions. Select 8 concatenations in the object extraction options and set the smoothing to 0. In addition, pre-sort, fill holes, do not select envelopes, and "exclude borders" is "none". Select "Measurement item" from "Measurement" on the toolbar, and enter 2 to ¹⁰⁷ in the area selection range.

The coverage is calculated by enclosing a square area. At this time, the area (C) of the area is set to be 24,000 to 26,000 pixels. "Treatment" -Automatically binarize by binarization, and calculate the total area (D) of the area without an external agent such as an organosilicon polymer or silica fine particles. The coverage can be determined by the following formula from the total area C of the square region and the total area D of the region without an external agent such as an organosilicon polymer or silica fine particles.

Coverage (%) = 100- (D / C x 100)
The arithmetic mean value of all the obtained data is used as the coverage ratio.

Then, the coverage of each of the toner before washing and the toner after washing is calculated.
[Coverage of toner after washing with water] / [Coverage of toner before washing with water] × 100 is defined as the “sticking rate” of the present invention.
7. Methods for Manufacturing Toner Particles, External Additives, and Developers Next, examples of manufacturing the toner particles, external additive A, and developer of this example will be described.

<Manufacturing example of toner particles>
(Preparation of water-based medium 1)
650.0 parts of ion-exchanged water and 14.0 parts of sodium phosphate (12-hydrate manufactured by Rasa Industries, Ltd.) were put into a reaction vessel equipped with a stirrer, a thermometer, and a return pipe, and purged with nitrogen. While keeping the temperature at 65 ° C. for 1.0 hour. T. K. Using a homomixer (manufactured by Tokushu Kagaku Kogyo Co., Ltd.), while stirring at 15,000 rpm, a calcium chloride aqueous solution in which 9.2 parts of calcium chloride (dihydrate) is dissolved in 10.0 parts of ion-exchanged water is collectively added. Then, an aqueous medium containing a dispersion stabilizer was prepared. Further, 10% by mass hydrochloric acid was added to the aqueous medium to adjust the pH to 5.0 to obtain the aqueous medium 1.

(Preparation of polymerizable monomer composition)
・ Styrene: 60.0 parts ・ C.I. I. Pigment Blue 15: 3: 6.5 parts After putting the above material into an attritor (manufactured by Mitsui Miike Machinery Co., Ltd.) and further dispersing it at 220 rpm for 5.0 hours using zirconia particles with a diameter of 1.7 mm. Zirconia particles were removed to prepare a colorant dispersion.
-Styline: 20.0 parts-n-butyl acrylate: 20.0 parts-Crosslinking agent (divinylbenzene): 0.3 parts-Saturated polyester resin: 5.0 parts (propylene oxide-modified bisphenol A (2 mol adduct) Polycondensate of terephthalic acid (molar ratio 10:12), glass transition temperature (Tg) 68 ° C., weight average molecular weight (Mw) 10,000, molecular weight distribution (Mw / Mn) 5.12)
Fischer-Tropsch wax (melting point 78 ° C.): 7.0 parts After adding the material to the above colorant dispersion and heating to 65 ° C., T.I. K. A polymerizable monomer composition was prepared by uniformly dissolving and dispersing at 500 rpm using a homomixer (manufactured by Tokushu Kagaku Kogyo Co., Ltd.).

(Granulation process)
The temperature of the aqueous medium 1 was adjusted to 70 ° C., and T.I. K. The polymerizable monomer composition was put into the aqueous medium 1 while keeping the rotation speed of the homomixer at 15,000 rpm, and 10.0 parts of t-butylperoxypivalate as a polymerization initiator was added. As it was, granulation was carried out for 10 minutes while maintaining 15,000 rpm with the stirring device.

(Polymerization process and distillation process)
After the granulation step, the stirrer is replaced with a propeller stirring blade, and the polymerization is carried out at 70 ° C. for 5.0 hours while stirring at 150 rpm, and further, the temperature is raised to 85 ° C. and the polymerization is carried out for 2.0 hours. Was done. After that, the return pipe of the reaction vessel was replaced with a cooling pipe, and the obtained slurry was heated to 100 ° C. to carry out distillation for 6 hours, and the unreacted polymerizable monomer was distilled off to distill off the unreacted polymerizable monomer. Got

(Step of forming organosilicon polymer)
60.0 parts of ion-exchanged water was weighed in a reaction vessel equipped with a stirrer and a thermometer, and the pH was adjusted to 4.0 with 10% by mass of hydrochloric acid. This was heated with stirring to bring the temperature to 40 ° C. Then, 40.0 parts of methyltriethoxysilane, which is an organosilicon compound, was added and stirred for 2 hours or more for hydrolysis. The end point of the hydrolysis was visually confirmed that the oil and water did not separate and became one layer, and the mixture was cooled to obtain a hydrolyzed solution of an organosilicon compound.

After adjusting the temperature of the resin particle dispersion obtained above to 55 ° C., 25.0 parts (the amount of the organosilicon compound added is 10.0 parts) of the hydrolyzed solution of the organosilicon compound is added to make it organic. The polymerization of the silicon compound was started. After holding as it was for 0.25 hours, the pH was adjusted to 5.5 with a 3.0% aqueous sodium hydrogen carbonate solution. After holding for 1.0 hour (condensation reaction 1) while continuing stirring at 55 ° C., adjust the pH to 9.5 using a 3.0% aqueous sodium hydrogen carbonate solution, and hold for 4.0 hours (condensation reaction 1). Reaction 2) was carried out to obtain a toner particle dispersion.

(Washing process and drying process)
After the step of forming the organic silicon polymer was completed, the toner particle dispersion was cooled, hydrochloric acid was added to the toner particle dispersion to adjust the pH to 1.5 or less, and the mixture was left to stand for 1.0 hour with stirring. Then, solid-liquid separation was performed with a pressure filter to obtain a toner cake. The obtained toner cake was reslurried with ion-exchanged water to form a dispersion liquid again, and then solid-liquid separated with the above-mentioned filter to obtain a toner cake. The obtained toner cake was transferred to a constant temperature bath at 40 ° C., dried and classified over 72 hours to obtain toner particles.

<Manufacturing example of external additive A>
The external additive A was manufactured as follows. 150 parts of 5% ammonia water was placed in a 1.5 L glass reaction vessel equipped with a stirrer, a dropping nozzle and a thermometer to prepare an alkaline catalyst solution. After adjusting the alkali catalyst solution to 50 ° C., 100 parts of tetraethoxysilane and 50 parts of 5% aqueous ammonia were added dropwise at the same time with stirring, and the mixture was reacted for 8 hours to obtain a silica fine particle dispersion. Then, the obtained silica fine particle dispersion was dried by spray drying and crushed by a pin mill to obtain silica fine particles having an average number of primary particles of 100 nm as an external additive A.

<Manufacturing example of developer>
100.00 parts of toner particles 1 and 1.00 parts of external additive A were put into a Henschel mixer (FM10C type manufactured by Nippon Coke Industries Co., Ltd.) in which water at 7 ° C. was passed through the jacket. Next, after the water temperature in the jacket became stable at 7 ° C. ± 1 ° C., the peripheral speed of the rotary blade was set to 38 m / sec, and the mixture was mixed for 10 minutes. In the mixing, the amount of water flowing through the jacket was appropriately adjusted so that the temperature inside the tank of the Henschel mixer did not exceed 25 ° C. The obtained mixture was sieved with a mesh having an opening of 75 μm to obtain a developer.

Table 1 shows the physical characteristics of the developer.

In the table, "X" represents the ratio of the number average particle diameter R of the primary particles of the external additive A to the number average value of the convex height H. When the developed developer was observed using SEM, it was confirmed that the external additive A was arranged as the transfer carrier particles on the convex portion of the organosilicon polymer of the toner particles, and one toner particle was observed. The average number of coated external particles A per particle was about 500.

As the developer used in this example, as described above, a mixture of toner and transfer carrier particles was used. The primary transferability is improved to some extent as the coverage of the transfer carrier particles occupying the surface of the photosensitive drum 1 increases. However, as the coverage of the transfer carrier particles occupying the surface of the photosensitive drum 1 increases, the degree of improvement in the primary transferability slows down, and the risk of contamination of various members in the image forming apparatus by the transfer carrier particles increases. Therefore, it is preferable that the coverage of the transfer carrier particles occupying the surface of the photosensitive drum 1 is 80% or less.
8. Regarding the supply of the transfer carrier Next, the means for supplying the transfer carrier particles onto the photosensitive drum 1 will be described.

As described above, the transfer carrier particles are interposed between the toner image developed on the photosensitive drum 1 and the photosensitive drum 1, thereby reducing the adhesive force between the toner image and the photosensitive drum 1. Particles that have the role of improving the primary transfer efficiency of the toner image.

In this embodiment, the transfer carrier particles are supplied to the surface of the photosensitive drum 1 in advance by using the toner supported on the developing roller 22 before the toner image is developed. By coating the photosensitive drum 1 with the transfer carrier particles in advance, the transfer carrier particles are interposed between the toner image and the photosensitive drum 1.

FIG. 12A is a schematic view of the developing nip portion when the developing roller 22 and the photosensitive drum 1 are in contact with each other. As shown in FIG. 12A, in the developing nip portion, the toner carried on the developing roller 22 and the photosensitive drum 1 are in contact with each other via the transfer carrier particles. FIG. 12B is a schematic view showing a state after the toner and the photosensitive drum 1 carried on the developing roller 22 shown in FIG. 12A have passed through the developing nip portion. As shown in FIG. 12B, the transfer carrier particles interposed between the toner and the photosensitive drum 1 in the developing nip portion are photosensitive from the surface of the toner carried on the developing roller 22 after passing through the developing nip portion. It is supplied by transferring to the surface of the drum 1.

As shown in FIG. 12A, the adhesive force Ft between the transfer carrier particles and the toner interposed between the toner and the photosensitive drum 1 at the developing nip portion is higher than the adhesive force Fdr between the transfer carrier particles and the photosensitive drum 1. When the size is large, the transfer carrier particles are difficult to transfer onto the photosensitive drum 1. Therefore, it is preferable that Ft is smaller than Fdr.

FIG. 13A is a schematic view of the primary transfer portion when the toner image is supported on the surface of the photosensitive drum 1. FIG. 13B is a schematic view of a state in which the photosensitive drum 1 and the intermediate transfer belt 10 are separated after the primary transfer of the toner image shown in FIG. 13A is completed. When Ft is smaller than Fdr, when the toner image is first transferred from the photosensitive drum 1 onto the surface of the intermediate transfer belt 10, only the toner image is first transferred onto the intermediate transfer belt 10, and the toner image and the photosensitive drum 1 are transferred. The transfer carrier particles intervening between them remain on the photosensitive drum 1.

Suppose that the transfer carrier particles interposed between the toner image and the photosensitive drum 1 together with the toner image are primarily transferred to the intermediate transfer belt 10, and the transfer carrier particles are lost from the surface of the photosensitive drum 1. In that case, the transfer carrier particles do not intervene between the toner image to be developed on the surface of the photosensitive drum 1 and the photosensitive drum 1, and the adhesive force between the toner image and the photosensitive drum 1 is large. The transferability will be reduced.

Therefore, not only is it easy to supply the transfer carrier particles from the toner supported on the developing roller 22 to the photosensitive drum 1, but also from the viewpoint of maintaining the transfer carrier particles coated on the photosensitive drum 1, Ft is Fdr. It is preferably smaller than.

FIG. 14 is a timing chart of the printing operation of the image forming apparatus 100 used in this embodiment. As shown in FIG. 14, in the image forming apparatus 100 of this embodiment, the developing roller 22 and the photosensitive drum 1 come into contact with each other before starting the toner development from the developing roller 22 to the photosensitive drum 1 during the image forming operation. It is driven to rotate in the state. As a result, a timing (transfer carrier supply mode) for supplying transfer carrier particles from the developing roller 22 to the photosensitive drum 1 is provided. The transfer carrier supply mode may be executed at a timing other than the timing of image formation, and is executed, for example, in a pre-rotation operation performed before the image formation operation or a post-rotation operation performed after the image formation operation.

In order to improve the primary transfer efficiency of the toner image over the entire surface of the photosensitive drum 1, the entire surface of the photosensitive drum 1 is coated with transfer carrier particles before the development of the toner image is started. Therefore, it is preferable to set the time for supplying the transfer carrier particles to the time for rotating the photosensitive drum 1 by one or more turns. Therefore, in this embodiment, the length of the transfer carrier particle supply timing shown in FIG. 14 is set to 500 msec, which is substantially the same as the time for the photosensitive drum 1 to make one round, so that the transfer carrier particles can be coated on the entire surface of the photosensitive drum 1. is doing.

Further, in this embodiment, at the transfer carrier particle supply timing shown in FIG. 14, the surface potential of the photosensitive drum 1 is set to a non-image forming potential Vd = −500V in which the toner charged with the normal polarity does not develop. Therefore, at the supply timing of the transfer carrier particles of this embodiment, the toner having a negative normal polarity is not developed from the developing roller 22 onto the surface of the photosensitive drum 1, and only the transfer carrier particles are transferred from the developing roller 22 onto the photosensitive drum 1. Is supplied to.

As in this embodiment, when the transfer carrier particles are supplied from the toner on the developing roller 22 to the photosensitive drum 1 in a state where there is a potential difference between the developing roller 22 and the photosensitive drum 1, there are the following problems. If the particle size of the transfer carrier particles is too large, the transfer carrier particles are susceptible to the electrostatic force generated by the potential difference between the developing roller 22 and the photosensitive drum 1. Therefore, it becomes difficult to control the supply of transfer carrier particles from the toner on the developing roller 22 to the photosensitive drum 1. For example, in a configuration in which transfer carrier particles are supplied at a non-image forming potential as in this embodiment, when the transfer carrier particles are negatively charged, the transfer carrier particles are attracted to the developing roller 22 side by electrostatic force. Be done. Therefore, it becomes difficult to supply the transfer carrier particles from the toner on the developing roller 22 to the photosensitive drum 1. Here, the particle size of the transfer carrier particles is preferably set to 1000 nm or less, which is not easily affected by electrostatic force. In this embodiment, since the transfer carrier particles are stably supplied from the toner on the developing roller 22 to the surface of the photosensitive drum 1 regardless of the potential difference between the developing roller 22 and the photosensitive drum 1, the particle size is used as the transfer carrier particles. Particles of 100 nm are used.
9. Features and effects Next, the features of this example will be described below. Ft <Fdr in the Ft, which is the adhesive force between the transfer carrier particles and the toner, and the adhesive force Fdr between the transfer carrier particles and the photosensitive drum 1. Then, the supply amount of the transfer carrier particles to the photosensitive drum 1 according to the above relationship is controlled as follows. Between at least two process cartridges, the supply of transfer carrier particles in the process cartridge downstream of the upstream process cartridge with respect to the transport direction of the intermediate transfer body 10 is increased. The first embodiment is characterized in that the contact time between the developing roller 22 and the photosensitive drum 1 during the preparatory operation accompanying the activation of the image forming apparatus 100 is changed for each process cartridge. The operation of supplying the transfer carrier particles to the surface of the photosensitive drum 1 is called a transfer carrier supply operation.

The larger the transfer carrier particles that coat the photosensitive drum 1, the smaller the number of direct contacts between the toner and the photosensitive drum 1, and the more preferable the transfer carrier particles are, from the viewpoint of improving the primary transferability. In particular, in order to improve the primary transfer efficiency of a plurality of colors with high printing, it is preferable that a large amount of transfer carrier particles are attached to the photosensitive drum 1. By using the developer of this example, many transfer carrier particles remain largely on the photosensitive drum 1 due to the relationship of Ft <Fdr in the primary transfer step. However, when a larger amount of transfer carrier particles are attached to the surface of the photosensitive drum 1, the destination of the transfer carrier particles is determined not by the adhesive force with the photosensitive drum 1 but by the adhesive force between the transfer carriers. It ends up. That is, in some cases, the relationship between Ft and Fdr apparently becomes Ft ≧ Fdr, and the primary transfer and the secondary transfer together with the toner may be transferred to the recording material P. Further, when the toner matrix between the convex portions containing the organosilicon polymer having the partial structure represented by the above-mentioned formula (1) and the transfer carrier particles come into contact with each other, Ft ≧ Fdr may be satisfied. be. Then, the transfer carrier particles are primary and secondary transferred together with a part of the toner, and are transferred onto the recording material P. In particular, when the number of transfer carrier particles on the photosensitive drum 1 is large, the chances of contact with the toner base increase, so that more particles are transferred onto the recording material P. As a result, when fixing the high-printing multi-color toner on the recording material, there arises a problem that the transfer carrier particles inhibit the heat conduction to the toner and deteriorate the fixability.

Therefore, in this embodiment, the supply amount (that is, the adhesion amount) of the transfer carrier particles to the photosensitive drum 1 is set to the process cartridge downstream of the process cartridge upstream in the transport direction of the intermediate transfer body 10 between the process cartridges. Do more. Thereby, the amount of transfer carrier particles transferred onto the recording material P can be suppressed to reduce the influence on the fixability, and the primary transferability required for each process cartridge can be satisfied. Since the downstream process cartridge needs to transfer the toner onto the toner layer on the intermediate transfer belt 10 printed by the upstream process cartridge, it is more difficult to transfer the toner than the upstream process cartridge. Therefore, the downstream process cartridge requires transfer carrier particles to improve the primary transferability. If the transfer carrier particles are supplied according to the required transferability, it is possible to achieve both primary transferability and fixability.

In this embodiment, the following control is performed in order to realize the surface state of the photosensitive drum 1. During the pre-rotation operation, which is the preparatory operation at the time of starting the image forming apparatus 100, the process cartridge downstream from the process cartridge upstream in the transport direction of the intermediate transfer body 10 abuts on the photosensitive drum 1 of the developing roller 22. Increase the time. This will be described in detail with reference to FIG.

FIG. 1 is a timing chart of rotational drive and development contact of the developing rollers 22 of each process cartridge during the preparatory operation accompanying the activation of the image forming apparatus 100, and the contact time of the developing rollers 22 is T _{before many} . Represents.

First, the contents common to each process cartridge will be described. In any of the process cartridges, the rotation of the developing roller 22 starts after the image forming apparatus 100 is started. During the start-up of the rotary drive, the rotational speeds of the motors, which are the photosensitive drum drive unit 110 and the developing drive unit 130, are unstable. Therefore, after the rotation of the motor and the rotation of the developing roller 22 are stable, the developing roller 22 is subjected to the photosensitive drum. It is in contact with 1. The toner layer on the developing roller 22 is stabilized at this development contact time _T. After that, the developing roller 22 is separated from the photosensitive drum 1 to end the rotational drive of the developing roller 22.

The contact time T of the developing roller 22 is increased by increasing the contact time of the developing roller 22 of _Sd with respect to Sa, Sb, and Sc. Thereby, the adhesion area (amount) of the transfer carrier particles on the photosensitive drum 1 can be increased in the downstream side in the transport direction of the intermediate transfer belt 10 as compared with the upstream side. The time for supplying the transfer carrier particles is preferably set to a time equal to or longer than one round of the photosensitive drum 1. In this embodiment, the transfer carrier particles are supplied by contacting Sa, Sb, and _Sc with Sa, Sb, and Sc for 500 ms (one or more rounds of the photosensitive drum 1) and 1000 ms (two or more rounds of the photosensitive drum 1) with Sd. is doing.

In this embodiment, the surface of the photosensitive drum 1 is prevented from developing the toner charged to the normal charging polarity during the development contact time T _before the development contact time T during the front rotation operation of the image forming apparatus 100, which is the transfer carrier particle supply timing. The potential is being adjusted. The surface potential of the photosensitive drum 1 in the transfer carrier supply operation is set to a non-image forming potential Vd = −500V and a developing voltage Vdc = −300V applied to the developing roller 22. Therefore, in the transfer carrier supply operation of this embodiment, the toner is not developed from the developing roller 22 to the photosensitive drum 1, and only the transfer carrier particles are supplied from the developing roller 22 onto the photosensitive drum 1.

In this embodiment, when the case where the transfer carrier particles are attached to the entire surface of the photosensitive drum 1 is 100%, the following adhesion area ratio is used. By the transfer carrier supply operation, the adhesion area ratio of the transfer carrier particles on the photosensitive drum 1 in Sa, Sb, and Sc is controlled to 15 to 25%, and the adhesion area ratio of Sd is controlled to about 45%.

The ratio of the adhered area of the transfer carrier particles to the photosensitive drum 1 has been described above. Here, it is desirable that the transfer carrier particles are substantially uniformly adhered to the photosensitive drum 1. Even if the adhesion area ratio itself is within the range of the above-mentioned values, if it is locally adhered, a portion that does not satisfy the desired primary transferability will occur, so that the adhered state is substantially uniform. There is a need. Therefore, in this embodiment, the Clark Evans Index (CEI) is used for evaluation as a numerical value of the adhesion state. The Clark Evans index in this example was in the range of 0.80 to 1.30 at all stations.

If the CEI is smaller than 1, it will be a concentrated distribution (the degree of aggregation is large), if the CEI is equal to 1, it will be a Poisson distribution (random distribution), and if the CEI is larger than 1, it will be a regular distribution (distributed at regular intervals). .. The limit value of CEI is about 2.1.

The Clark-Evans index is preferably 0.60 or more in order to satisfy the desired primary transferability at any position on the photosensitive drum 1. If it is less than that, it will be in a locally attached state, and the primary transferability will be deteriorated in some parts, which is not preferable.

The adhesion area ratio, adhesion state (Clark Evans index), adhesion force measurement method, and adhesion force verification results will be described later.
10. Measurement and verification method of various parameters Next, the measurement and verification method of parameters will be described.
(1) Adhesion area ratio of transfer carrier particles on the photosensitive drum 1 The surface of the photosensitive drum 1 was observed with a microscope, and the coating ratio of the transfer carrier particles on the surface of the photosensitive drum 1 was calculated. Specifically, the surface of the photosensitive drum 1 is observed with a laser microscope (VK-X200 KEYENCE) at a magnification of 3000 times. The image to be observed is binarized with a contrast that clearly shows a difference between the transfer carrier particles and the other portions, and the total area ratio of the transfer carrier particles on the surface of the photosensitive drum 1 is determined by the photosensitive drum 1. It was calculated as the film ratio of the transfer carrier particles on the surface of.
(2) Adhesion state of transfer carrier particles on the photosensitive drum 1 (Clark Evans index)
The surface of the photosensitive drum 1 was observed with a microscope, and the adhesion state (Clark Evans index) of the transfer carrier particles on the surface of the photosensitive drum 1 was calculated. Specifically, as in (1), the surface of the photosensitive drum 1 is observed with a laser microscope (VK-X200 Keyence) at a magnification of 3000 times. The image to be observed is binarized with a contrast that clearly shows a difference between the portion of the transfer carrier particles and the portion other than the transfer carrier particles. After calculating the coordinates for each particle in the binarized image, the average r of the distance between the closest centers of gravity of all the particles is calculated. The Clark Evans index (CEI) is defined by CEI = r / E (r), where E (r) is the expected value of the distance between the closest centers of gravity of particles with a Poisson distribution, and that value is Clark.・ Calculated as the Evans index.
(3) Adhesive force measuring method The adhesive force between the transfer carrier particles and the toner used in this example was measured using SPM. Specifically, a cantilever in which transfer carrier particles are fixed to the tip of the lever is created, and the cantilever is pressed against the toner with a predetermined pressing force. Then, the force required to separate the cantilever from the toner was measured as the adhesive force Ft between the transfer carrier particles and the toner.

It is preferable that the predetermined pressing force for pressing the cantilever against the toner at the time of measuring the adhesive force is set to the force at which the transfer carrier particles interposed between the toner and the photosensitive drum 1 in the developing nip portion are pressed against the toner. .. The pressing force was calculated by the calculation method described below. Here, "the transfer carrier is interposed between the toner and the photosensitive drum 1 in the developing nip portion" means a state in which the transfer carrier particles are in contact with both the toner and the photosensitive drum 1 at the same time.

First, in performing the calculation, the assumed conditions will be described with reference to FIGS. 15 and 16. FIG. 15A is a schematic view of the developing nip portion, and it is assumed that the developing roller 22 and the photosensitive drum 1 are in contact with each other via the toner in the developing nip portion. Further, FIG. 15B shows a cross section parallel to the surface of the photosensitive drum 1 in the dotted line AB of FIG. 15A, and the toner in contact with the photosensitive drum 1 is the most as shown in the shaded area. It was assumed to be tightly packed. FIG. 16 is an enlarged schematic view of a contact portion between the toner and the photosensitive drum 1 surrounded by the dotted line in FIG. As shown in FIG. 16, it is assumed that the toner and the photosensitive drum 1 are in contact with each other via the transfer carrier particles. Further, the transfer carrier particles were not yet supplied on the surface of the photosensitive drum 1, and the transfer carrier particles were not present on the surface of the photosensitive drum 1 in advance.

After making the above assumptions, the total number N of transfer carrier particles interposed between the toner and the photosensitive drum 1 in the developing nip portion was calculated as follows. From the calculated N, the contact force F between the developing roller 22 and the photosensitive drum 1, the F / N, which is the pressing force against the toner per transfer carrier in the developing unit, is calculated, and the calculated F / N is used when measuring the adhesive force. It was adopted as a predetermined pressing force against the toner of the cantilever.

First, a method of calculating the total number N of transfer carrier particles interposed between the toner and the photosensitive drum 1 in the developing nip portion will be described.

FIG. 17A is a two-dimensional schematic view showing the contact state of the toner, the transfer carrier particles, and the photosensitive drum 1 in the developing unit. As shown in FIG. 17B, assuming that the particle size of the transfer carrier particles is r, the transfer carrier particles on the toner hardly come into contact with the photosensitive drum 1 when the distance between the photosensitive drum 1 and the toner surface exceeds r. .. Therefore, the toner circumferential portion where the transfer carrier particles arranged on the toner circumference can come into contact with the photosensitive drum 1 is on an arc connecting A and B. Actually, it is necessary to think of the toner as a sphere as shown in FIG. 17 (b), and it is necessary to obtain the ratio of the surface area obtained by integrating the arc AB in the circumferential direction (the shaded portion in FIG. 17 (b)) to the toner surface area. .. The surface area of the shaded area can be generally obtained as the surface area of the spherical cap, and is as shown in Eq. (2). Therefore, the ratio to the toner surface area is as shown in the equation (3). The actual value can be calculated from the average particle size R of the toner and the particle size r of the transfer carrier particles.

By the above calculation, the ratio of the arc AB to the toner circumference in the configuration of this embodiment is calculated to be about 1.43%.

Therefore, it can be assumed that the transfer carrier particles intervene between the toner and the photosensitive drum 1 in the developing nip portion in a region of about 1.43% of the entire surface of the toner. The number of transfer carrier particles coated per toner is 500. From the above, the number M of transfer carrier particles interposed between the toner and the photosensitive drum 1 per toner is calculated as "500 x 1.43%" and is about 7.2.

Then, the number of transfer carrier particles interposed between the toner and the photosensitive drum 1 per toner is 7.2, and the total number of toners in contact with the photosensitive drum 1 in the developing unit is multiplied. Then, the total number N of the transfer carrier particles interposed between the toner and the photosensitive drum 1 in the developing nip portion can be calculated.

The total number L of toner in contact with the photosensitive drum 1 in the developing nip portion can be calculated by "area of developing nip portion x toner filling rate) / maximum cross-sectional area of toner".

(Total number of toners in contact with photosensitive drum 1 at the developing nip)
= (220 [mm] × 2.0 [mm] × π / √12) / (π × (7.0/2) ² )
= Approximately 10.37 × 10 ⁶ (using π / √12 ≈ 0.9069, which is the closest filling factor of a two-dimensional circle)
Therefore, "the total number N of transfer carriers interposed between the toner and the photosensitive drum 1 in the developing nip portion" is calculated as follows. Calculated from the multiplication of "the total number of toners in contact with the photosensitive drum 1 at the developing nip" and "the number of transfer carrier particles intervening between the toner and the photosensitive drum 1 per toner". , The total number N is about 7.47 × ¹⁰⁷ .

Since the pressing force of the developing roller 22 on the photosensitive drum 1 in this embodiment is F = 200 gf, the F / N, which is the "pressing pressure on the toner per transfer carrier in the developing unit", is 26.3 nN. The F / N value obtained above was adopted as a predetermined pressing force for pressing the cantilever against the toner when measuring the adhesive force by SPM. The adhesive force between the transfer carrier particles and the convex portion of the toner at a predetermined pressure of pressing the cantilever against the toner was 32.8 (nN). Further, the adhesive force between the transfer carrier particles and the photosensitive drum 1 was 210.1 (nN), and the adhesive force between the transfer carrier particles and the toner matrix was 250.7 (nN). That is, the adhesive force between the transfer carrier particles and the convex portion of the toner is smaller than the adhesive force between the transfer carrier particles and the photosensitive drum 1, and the adhesive force between the transfer carrier particles and the toner matrix is the transfer carrier particles. It was confirmed that the adhesive force with the photosensitive drum 1 was larger than that of the adhesive force.
11. Effect Confirmation For the purpose of confirming the effect of this example, the primary transferability and fixability of the configuration of the example and the configuration of Comparative Example 1 were verified under the following conditions. HP Color LaserJet Pro M452dw (HP Company, trade name) was used for the image forming apparatus 100, and CS-680 (Canon Marketing Japan, trade name) was used for the recording material P.

The verification of the primary transferability was performed by removing the cleaning blade of the process cartridge included in the HP Color LaserJet Pro M452dw. This is because the evaluation is performed based on the presence or absence of image defects (hereinafter referred to as cleanerless ghosts) that cannot be completely recovered when the primary transfer residual toner passes through the developing roller 22 and becomes apparent as a ghost image after one round of the photosensitive drum 1. .. In the verification of the fixability, the evaluation was made based on the presence or absence of an image defect (hereinafter referred to as cold offset) in which the toner was not completely fixed to the recording material P and was offset. In both cases, in order to simplify the verification, evaluation was performed using a solid black image of a secondary color using a cyan (Sc) station and a black (Sd) station.

As described above, in the configuration of the first embodiment, the adhesion area ratio of the transfer carrier particles on the photosensitive drum 1 of Sc, which is a process cartridge relatively upstream with respect to the transport direction of the intermediate transfer belt 10, is 20%. It is supposed to be. The transfer carrier particles on the photosensitive drum 1 of Sd, which is a downstream process cartridge, have an adhesion area ratio of 45%.

On the other hand, in the configuration of Comparative Example 1, the adhesion area ratio of the transfer carrier particles on the photosensitive drum 1 of Sc, which is an upstream process cartridge, is 45%, and the transfer carrier particles on the photosensitive drum 1 of Sd, which is a downstream process cartridge, are attached. The adhesion area ratio is 20%. In Comparative Example 2, the adhesion area ratio of the transfer carrier particles on the photosensitive drum 1 was 45% for both Sc and Sd.

Table 2 summarizes the presence / absence of cleanerless ghost (primary transferability) and the occurrence of cold offset (fixability) in Example 1 and Comparative Example 1. OK in the table indicates that no image defect has occurred, and NG indicates that an image defect has occurred.

In Example 1, as shown in Table 2, transfer on the photosensitive drum 1 of Sd downstream from the adhesion area ratio of the transfer carrier particles on the photosensitive drum 1 of Sc upstream in the transport direction of the intermediate transfer belt 10. The adhesion area ratio of carrier particles is increased. The upstream process cartridge Sc may be capable of primary transfer of 100% of the print amount of a single cyan color. Therefore, cleanerless ghost did not occur even if the adhesion area ratio was lower than that of the downstream process cartridge Sd, and the primary transferability was good. On the other hand, the downstream process cartridge Sd needs to transfer the black toner onto the cyan solid black image already formed on the intermediate transfer belt 10. Therefore, the adhesion area ratio of the downstream process cartridge is higher than that of the upstream process cartridge Sc. As a result, cleanerless ghost did not occur as in Sc, and the primary transferability was good. Further, in Example 1, the transfer carrier particles were suppressed from being transferred in terms of fixability, so that cold offset did not occur.

On the other hand, in the configuration of Comparative Example 1, the transfer carrier particles on the photosensitive drum 1 of Sd downstream from the adhesion area ratio of the transfer carrier particles on the photosensitive drum 1 of Sc upstream in the transport direction of the intermediate transfer belt 10 The adhesion area ratio is low. First, regarding the fixability, since the total amount of adhesion was the same as that of Example 1, no cold offset occurred. Further, since Sc having a high adhesion area ratio of the transfer carrier particles had a higher adhesion area ratio than that of Example 1, cleanerless ghost did not occur and the primary transferability was good. However, since Sd has a lower adhesion area ratio than that of Example 1, it cannot exhibit sufficient primary transferability, resulting in the occurrence of cleanerless ghost.

Further, in the configuration of Comparative Example 2, the adhesion area ratio of the transfer carrier particles on the photosensitive drum 1 of Sc upstream and the transfer carrier particles on the photosensitive drum 1 of Sd downstream with respect to the transport direction of the intermediate transfer belt 10 The adhesion area ratio of is the same. Further, since the adhesion area ratio is set to 45%, it can be said that the structure enhances the transferability. From the results in Table 2, Comparative Example 2 had no problem of transferability, but cold offset occurred in fixability. It is considered that this is because the transfer carrier particles were transferred to the recording material P in an allowable amount or more and the fixation was hindered.

The configuration of Example 1 has the features described below.

The yellow station, which is the first image forming unit, is a first developer composed of a rotatable first photosensitive drum 1a, first toner particles, and carrier particles adhering to the surface of the first toner particles. It has a rotatable first developing roller 22a carrying the above. The developing roller 22a comes into contact with the first photosensitive drum 1a to form a first developing portion, and in the first developing portion, in order to form a first developer image on the surface of the first photosensitive drum 1a. A first developer is supplied.

The magenta station, which is the second image forming unit, is a second developer composed of a rotatable second photosensitive drum 1b, second toner particles, and carrier particles adhering to the surface of the second toner particles. Has a rotatable second developing roller 22b that carries. In order for the developing roller 22b to come into contact with the second photosensitive drum 1b to form a second developing portion and to form a second developer image on the surface of the second photosensitive drum 1b in the second developing portion. A second developer is supplied.

An intermediate that contacts the first photosensitive drum 1a to form a primary transfer portion that is a first contact portion, and contacts the second photosensitive drum 1b to form a primary transfer portion that is a second contact portion. It has a transfer belt 10. In the intermediate transfer belt 10, the first developer image is transferred at the first contact portion, and the second developer image is transferred at the second contact portion.

A secondary transfer portion is formed in contact with the intermediate transfer belt 10, and the first developer image and the second developer image formed on the surface of the intermediate transfer belt 10 in the secondary transfer portion are transferred to the recording material. It has a secondary transfer roller 20 to be processed.

In the state where the first photosensitive drum 1a is rotated, the carrier particles supported on the surface of the first developing roller 22a can be supplied to the surface of the first photosensitive drum 1 in the first developing unit. .. In the state where the second photosensitive drum 1b is rotated, the carrier particles supported on the surface of the second developing roller 22b can be supplied to the surface of the second photosensitive drum 1b in the second developing section. ..

The surface of the intermediate transfer belt 10 is movable, and in the moving direction of the intermediate transfer belt 10, the first contact portion is formed downstream of the secondary transfer portion and upstream of the second contact portion. As such, the first image forming portion and the second image forming portion are arranged.

Let F be the pressing force for pressing the developing roller 22 against the photosensitive drum 1, and N be the total number of carrier particles interposed between the toner particles and the photosensitive drum 1.

Let Ft be the adhesive force formed between the carrier particles and the toner particles, which is measured when the carrier particles are pressed against the toner particles with F / N, which is the pressing force per unit carrier particle. The adhesive force Fdr formed between the carrier particles and the photosensitive drum 1 measured when the carrier particles are pressed against the photosensitive drum 1 by F / N. The relationship between Ft and Fdr in this embodiment satisfies Ft ≦ Fdr.

After the photosensitive drum 1 is rotated in a state where the photosensitive drum 1 and the developing roller 22 are in contact with each other, the adhesion area of the carrier particles adhering to the surface of the second photosensitive drum 1b is the adhesion area of the first photosensitive drum 1a. It is larger than the adhesion area of the carrier particles adhering to the surface.

Further, in a state where the photosensitive drum 1 and the second developing roller 22 are in contact with each other, the distribution state of the carrier particles after the photosensitive drum 1 is rotated is uniform, and the Clark Evans index is 0.6 or more.

Therefore, as described above, in the configuration of the present embodiment, it is possible to supply a sufficient amount of fine particles to the surface of the photosensitive drum 1 in order to improve the transfer efficiency, and to suppress the inhibition of fixation by the fine particles.

In this embodiment, the contact time of the developing roller 22 with the photosensitive drum 1 is lengthened downstream with respect to the upstream in the transport direction of the intermediate transfer belt 10 during the preparatory operation accompanying the activation of the image forming apparatus. Not limited to examples. Specifically, it is not limited to (a) the preparatory operation (pre-rotation operation) accompanying the activation of the image forming apparatus of this embodiment, (b) the rotation operation before image formation during the print operation, and (c) print. The development contact time may be controlled in the rotation operation (post-rotation operation) after image formation during operation. Alternatively, all or combinations of (a), (b), and (c) may be used.

For example, FIG. 18 shows a timing chart of rotation drive and development contact when controlling the development contact time in (c) rotation operation after image formation during printing operation. Specifically, the timing chart of the rotational drive of the developing rollers 22 of the Sc station and the Sd station and the development contact during the printing operation is shown. In each station, the rotational drive of the developing roller 22 starts after a certain period of time after receiving the print signal. Development contact is started after the rotational drive of the motor is stabilized, and the toner layer on the developing roller 22 is stabilized by the start of image formation ( _before T). After that, the image formation is started and the image formation is completed (T _{image formation} ). Since the state of the toner layer on the developing roller 22 after image formation differs depending on the image pattern in terms of both the charge amount and the coating amount, the developing roller 22 is rotated for a certain period of time even after the image drawing is completed in order to return to a uniform state (T). _Later ). By changing the time of the rotation operation after this image formation, the adhered state of the transfer carrier particles on the photosensitive drum 1 may be controlled. In FIG. 18, _after T of Sc is set to 500 ms (one or more laps of the photosensitive drum 1), and _after T of Sd is set to 1000 ms (two or more laps of the photosensitive drum 1). As a result, the amount of transfer carrier particles on the photosensitive drum 1 is larger in the downstream than in the upstream with respect to the transport direction of the intermediate transfer belt 10. In this way, the same action and effect as in this embodiment can be obtained.

In this embodiment, although the adhesion area ratio of the transfer carrier particles of Sd is higher than that of Sa, Sb, and Sc, the configuration is not limited to that of the above embodiment. Between at least two process cartridges of Sa to Sd according to the transfer performance of each color toner alone (transfer carrier particle adhesion area ratio of the upstream process cartridge) <(transfer carrier particle adhesion area ratio of the downstream process cartridge) You just have to satisfy the relationship. The adhesion area ratio of the transfer carrier particles may be gradually increased from the upstream to the downstream, or Sa <Sb <Sc <Sd may be set.

Regarding the configuration in the second embodiment, the same reference numerals are given to the members and parts common to the first embodiment, and the description thereof will be omitted again.

The feature of this embodiment is that the amount of transfer carrier particles adhering to the toner is changed at each station. The means for supplying the toner by changing the amount of the transfer carrier adhering to the toner, which is a feature of the second embodiment, and the specific action and effect in the second embodiment will be described in detail below.
1. 1. Features and effects There are three features and effects in Example 2.

The first feature is the same as in Example 1, in which Ft <Fdr in "adhesion force Ft between the transfer carrier particles and the toner" and "adhesion force Fdr between the transfer carrier particles and the photosensitive drum 1". Depending on the relationship, the transfer carrier particles are supplied to the surface of the photosensitive drum 1. By doing so, the transfer carrier particles can be interposed on the surface of the photosensitive drum 1, and the toner is not brought into contact with the photosensitive drum 1 to reduce the adhesive force of the toner. As a result, the effect of improving the primary transferability in the primary transfer step is obtained.

The second feature is to adjust the supply amount (adhesion amount) of the transfer carrier so that the number of the downstream station is larger than that of the upstream station in the transport direction of the intermediate transfer belt 10. In the downstream station where high primary transferability is required, more transfer carrier particles are supplied as compared with the upstream stay station to improve the primary transferability. On the other hand, in the upstream station where such high primary transferability is not required, the supply amount of transfer carrier particles is reduced. As a result, the total amount of transfer carrier particles in the toner on the recording material P can be minimized, and the effect of reducing the influence of fixability is obtained.

Since the above two features and effects are the same as in Example 1, detailed description thereof will be omitted.

The third feature is that the means for changing the supply of transfer carrier particles from station to station changes the amount of transfer carrier particles adhering to the toner from station to station. In Example 1, the amount of transfer carrier particles added was adjusted so that the number of coated transfer carrier particles per toner was about 500 regardless of the station. In the second embodiment, as shown in Table 3 below, the number of Sa stations is 300, the number of Sb stations is 400, the number of Sc stations is 500, and the number of Sd stations is about 600. The amount of transfer carrier particles added was adjusted. At this time, as described in Example 1, the transfer carrier particles intervene between the toner and the photosensitive drum 1 in the developing nip portion in about 1.43% of the entire surface of the toner. Therefore, Table 3 also shows the number M of transfer carrier particles interposed between the toner and the photosensitive drum 1 per toner. As a result, the amount of transfer carrier particles supplied onto the photosensitive drum 1 can be increased at the downstream station than at the upstream station in the transport direction of the intermediate transfer belt 10.

In this embodiment, the execution timing of the transfer carrier supply operation is the development contact time during the printing operation as shown in FIG. 19, which is common to each station.

The action and effect regarding the third feature in this example will be described.

In this embodiment, the amount of the transfer carrier particles supplied onto the photosensitive drum 1 is adjusted to the downstream station rather than the upstream station in the transport direction of the intermediate transfer belt 10 without changing the supply time of the transfer carrier particles for each station. Do more. Therefore, the supply operation time of the transfer carrier particles in one printing operation can be minimized. As a result, it is possible to reduce the time required for one printing operation and improve the productivity.

As described above, it is possible to suppress the inhibition of fixation by the fine particles while supplying a sufficient amount of fine particles to the surface of the photosensitive drum 1 in order to improve the transfer efficiency.

In Examples 1 and 2, although a peripheral speed difference is not provided in the rotation of the developing roller 22 and the photosensitive drum 1 at the time of contact, the present invention is not limited to the above embodiment, and the developing roller 22 is rotated with respect to the rotation of the photosensitive drum 1. A peripheral speed difference may be provided for rotation. Such a peripheral speed difference has a role of stabilizing the amount of toner to be developed and a role of hiding the minute non-uniformity of the coat on the developing roller 22 on the photosensitive drum 1 and making it difficult to see. It also has the following effects in the supply of the transfer carrier particles of this embodiment.

FIG. 20A is a schematic diagram showing the behavior of the toner and the transfer carrier particles in the developing nip portion when the development roller 22 and the photosensitive drum 1 are set to have a non-image forming potential relationship. As shown in FIG. 20A, the following phenomenon occurs by providing a peripheral speed difference between the developing roller 22 and the photosensitive drum 1. The force parallel to the rotation direction of the developing roller 22 received from the developing roller 22 by the toner interposed between the developing roller 22 and the photosensitive drum 1 is defined as f1. The force f2 parallel to the rotation direction of the photosensitive drum 1 received from the photosensitive drum 1 by the toner interposed between the developing roller 22 and the photosensitive drum 1. Under the conditions described in Examples 1, 2 and 3, f1 and f2 were balanced, whereas in the configurations of Examples 1, 2 and 3, the balance between f1 and f2 was lost, and the developing nip portion. Toner rolls. Then, as the toner rolls, the transfer carrier particles on the toner that are not in contact with the photosensitive drum 1 also move with the rolling of the toner. Therefore, the contact with the photosensitive drum 1 increases the chances of supplying the transfer carrier particles from the toner to the surface of the photosensitive drum 1. Therefore, as shown in FIG. 18B, more transfer carrier particles are put on the surface of the photosensitive drum 1 after passing through the developing nip as compared with Examples 1, 2 and 3, and the toner of the developing roller 22 is applied. It can be supplied from above.

FIG. 21A is a schematic diagram showing the behavior of the toner and the transfer carrier particles in the developing nip portion when the space between the developing roller 22 and the photosensitive drum 1 is set to have an image forming potential relationship. As shown in FIG. 21A, even when the image forming potential relationship is set between the developing roller 22 and the photosensitive drum 1, the peripheral speed difference is provided between the developing roller 22 and the photosensitive drum 1. , The following phenomena occur. The toner rolls in the developing nip portion, and the efficiency of supplying transfer carrier particles from the surface of the toner in the developing nip portion to the surface of the photosensitive drum 1 is improved. Then, as shown in FIG. 21B, since the image forming potential relationship is set between the developing roller 22 and the photosensitive drum 1, the toner is transferred from the developing roller 22 to the photosensitive drum 1 after passing through the developing nip portion. Is developed on the surface of. However, since the efficiency of supplying transfer carrier particles from the surface of the toner to the surface of the photosensitive drum 1 when passing through the developing nip portion is improved, transfer is performed between the toner developed on the surface of the photosensitive drum 1 and the photosensitive drum 1. Many carrier particles can be intervened.

From the above, in the second embodiment, the first drive unit 110 for driving the photosensitive drum 1, the second drive unit 130 for driving the developing roller 22, the first drive unit, and the second drive unit are used. It has a control unit 200 for controlling the above. The control unit 200 controls the first drive unit and the second drive unit so that the surface movement speed of the developing roller 22 and the surface movement speed of the photosensitive drum 1 have different surface movement speeds in the developing unit. It is characterized by doing.

Regarding the configuration in the third embodiment, the same reference numerals are given to the members and parts common to the first and second embodiments, and the description thereof will be omitted again.

A feature of this embodiment is that the amount of toner coated on the developing roller 22 after passing through the developing blade 23 is changed for each station while providing a difference in development peripheral speed. In Example 3, the mechanism capable of controlling the supply amount of the transfer carrier and the action and effect of Example 3 will be described in detail below.
1. 1. Features and effects In Example 3, there are three features and effects.

The first feature is the same as in Example 1, in which Ft <Fdr in "adhesion force Ft between the transfer carrier particles and the toner" and "adhesion force Fdr between the transfer carrier particles and the photosensitive drum 1". Depending on the relationship, the transfer carrier particles are supplied to the surface of the photosensitive drum 1. By doing so, the transfer carrier particles can be interposed on the surface of the photosensitive drum 1, and the toner is not brought into contact with the photosensitive drum 1 to reduce the adhesive force of the toner. As a result, the effect of improving the primary transferability in the primary transfer step is obtained.

The second feature is to adjust the supply amount (adhesion amount) of the transfer carrier so that the number of the downstream station is larger than that of the upstream station in the transport direction of the intermediate transfer belt 10. In the downstream station where high primary transferability is required, more transfer carrier particles are supplied as compared with the upstream stay station to improve the primary transferability. On the other hand, in the upstream station where such high primary transferability is not required, the supply amount of transfer carrier particles is reduced. As a result, the total amount of transfer carrier particles in the toner on the recording material P can be minimized, and the effect of reducing the influence of fixability is obtained.

Since the above two features and effects are the same as in Examples 1 and 2, detailed description thereof will be omitted.

The third feature is that the amount of toner coated on the surface of the developing roller 22 after passing through the developing blade 23 is changed for each station while providing a difference in development peripheral speed. The amount of toner coated on the surface of the developing roller 22 is increased at the downstream station rather than at the upstream station in the transport direction of the intermediate transfer belt 10. At this time, the supply amount (adhesion amount) of the transfer carrier can be increased at the downstream station rather than at the upstream station in the transport direction of the intermediate transfer belt 10.

As described in the second embodiment, when the peripheral speed difference is provided between the developing roller 22 and the photosensitive drum 1, the following phenomenon occurs. Let f1 be a force parallel to the rotation direction of the developing roller 22 received from the developing roller 22 by the toner interposed between the developing roller 22 and the photosensitive drum 1. Let f2 be a force parallel to the rotation direction of the photosensitive drum 1 that the toner interposed between the developing roller 22 and the photosensitive drum 1 receives from the photosensitive drum 1. The balance between f1 and f2 is lost due to the difference in development peripheral speed, and the toner rolls in the developing nip portion. Then, when the toner rolls, the transfer carrier particles on the toner that are not in contact with the photosensitive drum 1 also move with the rolling of the toner, and can come into contact with the photosensitive drum 1. Therefore, the chance of supplying the transfer carrier particles from the toner to the photosensitive drum 1 increases. The movement of the transfer carrier particles on the toner that is not in contact with the photosensitive drum 1 due to rolling increases depending on the amount of toner coated on the developing roller 22. Therefore, by controlling the amount of toner coated on the developing roller 22 while rolling the toner by providing a peripheral speed difference between the developing roller 22 and the photosensitive drum 1, the supply amount of the transfer carrier particles can be increased. It can be controlled.

In Example 3, as shown in Table 4, the amounts of toner on the developing rollers 22 from Sa to Sd are Sa: 0.28, Sb: 0.30, Sc: 0.32, Sd: 0.34 [, respectively. It was adjusted to be mg / cm ² ]. As the adjusting means, the force for regulating the toner by the developing blade 23 is adjusted by changing the contact position between the developing blade 23 and the developing roller 22. Specifically, as shown in Table 4, the developing blades are located at positions Sa: 0.70, Sb: 0.60, Sc: 0.50, Sd: 0.40 [mm] from the center of the developing roller 22, respectively. It was adjusted so that the tip of 23 was arranged.

Further, in the third embodiment, the developing roller 22 rotates in the same direction with the photosensitive drum 1 and the developing nip portion thereof having a peripheral speed ratio of 140% with respect to the photosensitive member 1. That is, the moving speed of the surface of the developing roller 22 is 1.4 times faster than the moving speed of the surface of the photosensitive drum 1.

In Example 3, the execution timing of the transfer carrier supply operation is the development contact time during the printing operation as shown in FIG. 14, which is common to each station. Further, regardless of the station, the amount of transfer carrier particles added was adjusted so that the number of coated transfer carrier particles per toner was about 500.

Next, the action and effect in Example 3 will be described.

In Example 3, the transfer carrier particles are supplied to the surface of the photosensitive drum 1 at a station downstream of the upstream station in the transport direction of the intermediate transfer belt 10 without changing the supply time of the transfer carrier particles for each station. You can do a lot. Therefore, it is possible to minimize the supply operation time of the transfer carrier particles in one printing operation. As a result, it is possible to reduce the time required for one printing operation and improve the productivity. Moreover, since the amount of transfer carrier particles added can be suppressed, the risk of contamination due to the transfer of transfer carrier particles to parts in the developing device (for example, the developing blade 23 and the supply roller 26) can be reduced. ..

As described above, it is possible to suppress the inhibition of fixation by the fine particles while supplying a sufficient amount of fine particles to the surface of the photosensitive drum in order to improve the transfer efficiency.

Further, in Examples 1, 2 and 3, the case of four colors of yellow (Y), magenta (M), cyan (C) and black (K) has been described, but the present invention is not limited to the above examples, and for example, It may be the case of four or more stations including white toner, metallic color toner, and the like. In this case as well, it is effective if the relationship of (transfer carrier particle adhesion area ratio of the upstream process cartridge) <(transfer carrier particle adhesion area ratio of the downstream process cartridge) is satisfied between at least two process cartridges.

In Examples 1, 2 and 3, although the characteristics are described in the "adhesion area ratio" of the transfer carrier particles, the "adhesion force Fc between the transfer carrier particles" is the "adhesion force Ft between the toner and the transfer carrier". If it is smaller than (Fc <Ft), it may be the "adhesion amount". That is, the relationship of (amount of transfer carrier particles attached to the upstream process cartridge) <(amount of transfer carrier particles attached to the downstream process cartridge) may be established. When Fc <Ft, no further transfer carrier particles are supplied on the transfer carrier particles supplied on the photosensitive drum 1. Therefore, the transfer carrier particles on the photosensitive drum 1 become one layer, and the magnitude relation of the "adhesion area ratio" is synonymous with the magnitude relation of the "adhesion amount".

Therefore, after the photosensitive drum 1 is rotated in a state where the photosensitive drum 1 and the developing roller 22 are in contact with each other, the amount of carrier particles adhering to the surface of the second photosensitive drum 1b is applied to the surface of the first photosensitive drum 1a. This means that it is larger than the amount of adhered carrier particles.

In Examples 1, 2 and 3, the cleaning member is not provided on the photosensitive drum 1, but the present invention is not limited to the above embodiment, and the photosensitive drum cleaning member may be provided. When the cleaning member is provided on the photosensitive drum 1, the transfer carrier particles coated on the photosensitive drum 1 are collected by the cleaning member every one round of the photosensitive drum 1. However, since the transfer carrier particles can be supplied at the same time as the development, the adhesion area (or amount) of the transfer carrier particles on the photosensitive drum 1 from the start of the development to the primary transfer may be controlled. For example, the peripheral speed difference in the rotation of the developing roller 22 with respect to the rotation of the photosensitive drum 1 is larger in the downstream process cartridge than in the upstream process cartridge in the transport direction of the intermediate transfer belt 10. Then, the downstream process cartridge can roll more toner than the upstream process cartridge. As a result, the chances of supplying the transfer carrier particles to the photosensitive drum 1 downstream in the transport direction of the intermediate transfer belt 10 are increased as compared with the upstream process cartridge. It is possible to obtain the same action and effect as in Examples 1, 2 and 3.

In Examples 1, 2 and 3, the transfer carrier particles were supplied to the photosensitive drum 1 via the toner because of the relationship of Ft <Fdr. It may be provided. In that case, the relationship between "adhesive force Fs between the transfer carrier particles and the transfer carrier particle supply member" and "Fdr" may be set to Fs <Fdr, and the transfer carrier particles may be supplied to the photosensitive drum 1. The transfer carrier particle supply member may satisfy this adhesive force relationship. For example, as shown in FIG. 22, the transfer carrier particles may be supplied onto the photosensitive drum 1 using the brush member as the transfer carrier supply member. In FIG. 22, the transfer carrier particles are supplied via the transfer carrier particle supply roller 6. The transfer carrier particle supply roller 6 has a role of supplying transfer carrier particles onto the photosensitive drum 1, and is a brush roller having a brush layer on the surface. The transfer carrier particle supply roller 6 is rotationally driven in a direction opposite to the rotation direction of the photosensitive drum 1, and the transfer carrier is supplied onto the brush from the transfer carrier particle container on which the transfer carrier particles are mounted. Then, the transfer carrier particles are supplied from the brush onto the photosensitive drum 1 at the contact portion between the transfer carrier particle supply roller 6 and the photosensitive drum 1.

In Examples 1, 2 and 3, the developing blade 23 uses a SUS plate as a support member, but the present invention is not limited to the above embodiment, and a thin metal plate such as phosphor bronze or aluminum may be used. Further, in the above embodiment, the surface of the support member is coated with a thin film made of a conductive urethane resin to form a thin film, but the present invention is not limited to the above embodiment, and the conductive resin made of a polyamide elastomer or urethane rubber is used. The one formed by coating a thin film made of is used. Alternatively, the conductive support member itself may be brought into contact with the developing roller 22 as the developing blade 23.

In Examples 1, 2 and 3, the supply roller 26 and the developing blade 23 are provided with a potential difference of −200V with respect to the developing roller 22 to stabilize the toner charging amount, the toner supply amount and the toner coating amount. , Not limited to the above embodiment. If the toner charge amount, the toner supply amount, and the toner coat amount are stable regardless of the voltage, it is not necessary to provide a potential difference. In that case, by making the potential the same as that of the developing roller 22, it is possible to reduce the high-voltage power supply, and it is possible to realize miniaturization and cost reduction of the apparatus.

In Examples 1, 2 and 3, the primary transferability of each station can be controlled by the adhered state of the transfer carrier particles. Therefore, it is not necessary to change the primary transfer voltage at each station, and the primary transfer power supply to which the primary transfer voltage is applied can be shared at each station, and the device can be miniaturized and the cost can be reduced. ..

Even if each station has its own primary transfer power supply, the optimum primary transfer voltage can be set according to the primary transferability required for each station. Therefore, it is possible to suppress image scattering and re-transfer in the primary transfer unit. Retransfer refers to a phenomenon in which an image formed at an upstream station is transferred to an intermediate transfer belt 10, is discharged by passing through a primary transfer portion of the downstream station, and is transferred again to a photosensitive drum 1 of the downstream station. ..

1 Photosensitive drum (photoreceptor)
2 Charging roller 3 Exposure unit 4 Development unit 10 Intermediate transfer belt 14 Primary transfer roller 22 Development roller 62 Toner particles 100 Image forming device

Claims (19)

A rotatable first developer that carries a first developer composed of a rotatable first image carrier and carrier particles that adhere to the surface of the first toner particles and the first toner particles. The carrier is in contact with the first image carrier to form a first developing section, and the first developing agent image is formed on the surface of the first image carrier in the first developing section. A first image forming unit having a first developer carrier for supplying the first developer for forming, and a first image forming portion.
A rotatable second developer that carries a second developer composed of a rotatable second image carrier and carrier particles that adhere to the surface of the second toner particles and the second toner particles. The carrier is in contact with the second image carrier to form a second developing section, and the second developer image is formed on the surface of the second image carrier in the second developing section. A second image forming unit having a second developer carrier for supplying the second developer for forming, and a second image forming portion.
An intermediate transfer body that is in contact with the first image carrier to form a first contact portion and is in contact with the second image carrier to form a second contact portion. An intermediate transfer body to which the first developer image is transferred at the contact portion 1 and the second developer image is transferred at the second contact portion.
A transfer portion is formed in contact with the intermediate transfer body, and the first developer image and the second developer image formed on the surface of the intermediate transfer body in the transfer portion are transferred to a recording material. With a transfer member,
In the state where the first image carrier is rotated, the carrier particles supported on the surface of the first developer carrier are supplied to the surface of the first image carrier in the first developing unit. In the state where the second image carrier is rotated, the carrier particles supported on the surface of the second developer carrier in the second developing section are subjected to the second carrier particles. An image forming apparatus capable of supplying the surface of an image carrier of
The surface of the intermediate transfer body is movable, and in the moving direction of the surface of the intermediate transfer body, the first contact portion is downstream of the transfer portion and upstream of the second contact portion. The first image forming portion and the second image forming portion are arranged so that
The pressing force for pressing the first developer carrier against the first image carrier is F1, and the total number of carrier particles interposed between the first toner particles and the first image carrier is the total number of carrier particles. When N1,
Adhesive force formed between the carrier particles and the first toner particles measured when the carrier particles are pressed against the first toner particles with F1 / N1, which is a pressing force per unit carrier particle. Ft1 and
The relationship between the carrier particles and the adhesive force Fdr1 formed between the carrier particles and the first image carrier, which is measured when the carrier particles are pressed against the first image carrier with F1 / N1. ,
Ft1 ≤ Fdr1
The filling,
The pressing force for pressing the second developer carrier against the second image carrier is F2, and the total number of carrier particles interposed between the second toner particles and the second image carrier is the total number of carrier particles. When N2,
Adhesive force formed between the carrier particles and the second toner particles, which is measured when the carrier particles are pressed against the second toner particles with F2 / N2, which is a pressing force per unit carrier particle. Ft2 and
The relationship between the carrier particles and the adhesive force Fdr2 formed between the carrier particles and the second image carrier, which is measured when the carrier particles are pressed against the second image carrier with F2 / N2, is ,
Ft2 ≤ Fdr2
The filling,
The first image carrier is in contact with the first image carrier and the first developer carrier, and the second image carrier and the second developer carrier are in contact with each other. After the body and the second image carrier have each rotated, the adhesion area of the carrier particles attached to the surface of the second image carrier is the attachment area of the carrier particles attached to the surface of the first image carrier. An image forming apparatus characterized in that it is larger than the adhered area of carrier particles. The first developer and the second developer have a structure represented by the following formula (1), which is present on both the surface of the first toner particles and the surface of the second toner particles. The image forming apparatus according to claim 1, wherein the image forming apparatus has a convex portion formed of fine particles containing an organic silicon polymer, and the carrier particles are arranged on the convex portion.
R-Si (O _1/2 ) ₃ (1)
(The R represents a hydrocarbon group having 1 or more and 6 or less carbon atoms.) The first developer remaining on the first image carrier without being transferred to the intermediate transfer body is recovered by the first developer carrier, and the second developer is recovered without being transferred to the intermediate transfer body. The image forming apparatus according to claim 1 or 2, wherein the second developer remaining on the image carrier is recovered by the second developer carrier. The image forming apparatus according to claim 3, wherein the first developer and the second developer are one-component developing agents. The first image carrier is in contact with the first image carrier and the first developer carrier, and the second image carrier and the second developer carrier are in contact with each other. After each rotation of the body and the second image carrier, the first distribution of the carrier particles adhering to the surface of the first image carrier on the surface of the first image carrier and the said. Claims 1 to 4, wherein the carrier particles attached to the surface of the second image carrier are both uniformly distributed with the second distribution on the surface of the second image carrier. The image forming apparatus according to any one item. The image forming apparatus according to claim 5, wherein the state of the first distribution and the state of the second distribution are 0.6 or more in a Clark-Evans index. The first image carrier is in contact with the first image carrier and the first developer carrier, and the second image carrier and the second developer carrier are in contact with each other. After the body and the second image carrier have each rotated, the amount of the carrier particles attached to the surface of the second image carrier is the amount of the carrier particles attached to the surface of the first image carrier. The image forming apparatus according to any one of claims 1 to 6, wherein the amount is larger than the amount of adhered carrier particles. An image forming mode in which the first developer is developed by the first developer carrier and the second developer is developed by the second developer carrier, and the first developer carrier. 1 to 7 capable of executing a supply mode in which the carrier particles are supplied from the first image carrier to the second image carrier and the carrier particles are supplied from the second developer carrier to the second image carrier. The image forming apparatus according to any one of the above items. A first driving unit that drives the first image carrier, and
A second driving unit that drives the first developer carrier, and
It has a control unit that controls the first drive unit and the second drive unit.
The control unit has the first development unit so that the surface movement speed of the first developer carrier and the surface movement speed of the first image carrier are different from each other. The image forming apparatus according to claim 8, wherein the driving unit 1 and the second driving unit are controlled. The ninth aspect of the present invention is characterized in that, in the supply mode, the first drive unit is controlled so as to rotate the first image carrier and the second image carrier one or more turns. Image forming device. In the supply mode, the first drive unit and the second drive unit are used so that the rotation time of the second image carrier is longer than the rotation time of the first image carrier. The image forming apparatus according to claim 9 or 10, wherein the image forming apparatus is controlled. The image forming apparatus according to any one of claims 8 to 11, wherein the supply mode is performed during a pre-rotation operation performed before the image forming mode. The image forming apparatus according to any one of claims 8 to 12, wherein the supply mode is performed during a post-rotation operation performed after the image forming mode. One of claims 1 to 13, wherein the amount of carrier particles adhering to the surface of the second toner particles is larger than the amount of carrier particles adhering to the surface of the first toner particles. The image forming apparatus according to. The image forming apparatus according to claim 2, wherein when the closest distance between the adjacent convex portions is the convex interval G, the average of the convex intervals G is equal to or less than the average particle size of the carrier particles. The claim is characterized in that, when the height of the convex portion from the surface of the first toner particles is the convex height H, the average of the convex height H is equal to or less than the average particle size of the carrier particles. 2. The image forming apparatus according to 2. The image forming apparatus according to any one of claims 1 to 16, wherein the carrier particles are silica. The image forming apparatus according to any one of claims 1 to 17, wherein the carrier particles are an organic silica polymer. The image forming apparatus according to any one of claims 1 to 18, wherein the average particle size of the carrier particles is 30 nm or more and 1000 nm or less.

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