Image forming device

Abstract

To effectively supply fine particles to a surface of a photoconductor drum to improve transfer efficiency.SOLUTION: An image forming apparatus has a rotatable developer carrier that carries a developer composed of a toner particle and carrier particles adhered to the surface of the toner particle. When a pressing force for pressing the developer carrier against an image carrier is F, and the total number of carrier particles interposed between the 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.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus that utilizes an electrophotographic process or the like. [Background technology]

[0002] 2. Description of the Related Art Image forming apparatuses that form images using an electrophotographic process, such as copying machines and laser printers, are known.

[0003] In the transfer process, this image forming apparatus applies a voltage from a voltage power source to a transfer member disposed opposite the photosensitive drum as an image carrier, thereby electrostatically transferring the toner image formed on the surface of the photosensitive drum onto an intermediate transfer body or a recording material. When forming a toner image of multiple colors, this transfer process is repeatedly performed for the toner images of multiple colors, thereby forming a toner image of multiple 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 a cleaning member and is stored as waste toner in a waste toner storage section in the cleaning unit.

[0004] However, in recent years, a cleanerless system has been proposed in which the cleaning system for the photosensitive drum surface is omitted in order to reduce the size of the device. In order to achieve a cleanerless system, it is preferable to improve the transfer efficiency of the toner image from the photosensitive drum to the intermediate transfer body and reduce the amount of transfer residual toner remaining on the photosensitive drum surface after the toner image is transferred by the transfer member.

[0005] Patent document 1 proposes a configuration for achieving a cleanerless system in which fine particles are attached to the surface of a photosensitive drum in advance and interposed between the photosensitive drum and the toner image to reduce the adhesive force between the photosensitive drum and the toner, thereby improving transfer efficiency.

[0006] Furthermore, Patent Document 1 proposes a configuration in which, as a means for adhering fine particles to the surface of the photosensitive drum, a toner to which fine particles are externally added is used, and the fine particles are supplied onto the photosensitive drum from a developing device. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 10-63027 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in order to supply only fine particles from the toner of the developing device to the photosensitive drum surface as in Patent Document 1, it is necessary to detach the fine particles adhering to the toner from the toner and transfer them to the drum side. In the case of commonly used toner with externally added fine particles such as silica, the adhesive force between the toner and the fine particles is large, so it is difficult to supply a sufficient amount of fine particles to the surface of the photosensitive drum to improve transfer efficiency.

[0009] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to improve transfer efficiency by effectively supplying fine particles from a developing device to the surface of a photosensitive drum. [Means for solving the problem]

[0010] Therefore, the image forming apparatus according to the present invention includes a rotatable image carrier, a charging member that contacts the image carrier and charges the surface of the image carrier, a charging voltage power source that applies a charging voltage to the charging member, an exposure unit that exposes the surface of the image carrier charged by the charging member to form an electrostatic latent image, a rotatable developer carrier that carries a developer composed of toner particles and carrier particles adhering to the surfaces of the toner particles, the developer carrier forming a development section in contact with the image carrier and supplying the developer to the surface of the image carrier in the development section, a developer storage section that stores the developer, a control section that controls the charging voltage power source and the exposure unit, and in a state where the image carrier is rotated, a toner carried on the surface of the developer carrier and stored in the developer storage section is charged in the development section. an image forming apparatus capable of supplying the carrier particles having been subjected to the above-mentioned treatment to a surface of the image carrier, wherein, when a pressing force with which the developer carrier is pressed onto the image carrier is F and a total number of the carrier particles interposed between the toner particles and the image carrier is N, a relationship between an adhesive force Ft formed between the carrier particles and the toner particles, which is measured when the carrier particles are pressed onto the toner particles with a pressing force per unit carrier particle, F / N, and an adhesive force Fdr formed between the carrier particles and the image carrier, which is measured when the carrier particles are pressed onto the image carrier with the above-mentioned F / N, satisfies Ft≦Fdr, and the control unit controls to execute an image forming mode in which the developer is developed onto the electrostatic latent image and a supply mode in which the carrier particles are supplied from the developer carrier to the image carrier. Effect of the Invention

[0011] As described above, according to the present invention, the transfer efficiency can be improved by effectively supplying fine particles from the developing device to the surface of the photosensitive drum. [Brief description of the drawings]

[0012] [Figure 1] 1 is an outline of an image forming apparatus according to a first embodiment. [Diagram 2] FIG. 2 is a control block diagram according to the first embodiment. [Diagram 3] FIG. 2 is a schematic diagram of a toner surface in Example 1. [Figure 4] 3 is a schematic diagram of a convex shape on a toner surface in Example 1. FIG. [Diagram 5] 3 is a schematic diagram of a convex shape on a toner surface in Example 1. FIG. [Figure 6] 3 is a schematic diagram of a convex shape on a toner surface in Example 1. FIG. [Figure 7] FIG. 2 is a schematic diagram of a toner and a transfer carrier in the first embodiment. [Figure 8] FIG. 4 is a schematic diagram illustrating a transfer carrier supply time in the first embodiment. [Figure 9] FIG. 2 is a schematic diagram illustrating primary transfer in the first embodiment. [Figure 10] 4 is a timing chart of an image forming operation in the first embodiment. [Figure 11] 5A and 5B are diagrams illustrating a contact state of toner in a developing unit in Example 1. FIG. [Figure 12] FIG. 4 is a diagram showing the state of toner and transfer carrier particles in a developing section in the first embodiment. [Figure 13] 5A and 5B are diagrams illustrating the state of transfer carrier particles in a development section in Example 1. FIG. [Figure 14] 1 shows the results of confirming the effect of Example 1. [Figure 15] 1 shows the results of adhesion measurement in Example 1. [Figure 16] 10 is a timing chart of an image forming operation in the second embodiment. [Figure 17] 13A and 13B are diagrams illustrating a transfer carrier supply mechanism during a non-image forming operation in a development unit according to a second embodiment. [Figure 18] 11A and 11B are diagrams illustrating a transfer carrier supply mechanism in an image forming operation in a development unit according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the following embodiments may be changed as appropriate depending on the configuration of the device to which the present invention is applied and various conditions. Therefore, unless otherwise specified, it is not intended to limit the scope of the present invention to only those. EXAMPLES

[0014] 1. Image forming device In particular, the present invention relates to an image forming apparatus using a so-called drum cleanerless system that does not have a cleaning means for an image carrier.

[0015] FIG. 1 is a schematic diagram showing an example of a color image forming apparatus, and the configuration and operation of the image forming apparatus of this embodiment will be described with reference to FIG. The image forming apparatus of this embodiment is a so-called tandem type printer having image forming stations a to d. The first image forming station a forms an image of each color, yellow (Y), the second image forming station b forms an image of magenta (M), the third image forming station c forms an image of cyan (C), and the fourth image forming station d forms an image of black (Bk). The configuration of each image forming station is the same except for the color of the toner contained therein, and the following description will be given using the first image forming station a. In addition, hereinafter, unless a distinction is particularly required, a to d in Y, M, C, and K will be omitted and a general description will be given.

[0016] The first image forming station a includes a drum-shaped electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 1a, a charging roller 2a serving as a charging means, an exposure unit 3a, and a developing device 4a.

[0017] The photosensitive drum 1a is an image carrier that is rotationally driven in the direction of the arrow at a peripheral speed (process speed) of 150 mm / sec by a photosensitive drum drive unit 110 and carries a toner image. The photosensitive drum 1a is made of an aluminum tube having a diameter of φ20 mm on which a photosensitive layer and a surface layer are provided, and the surface layer is a thin film layer having a thickness of 20 μm formed from polyarylate.

[0018] When a control unit 200 such as a controller receives an image signal, an image forming operation is started, and the photosensitive drum 1a is rotated. During the rotation process, the photosensitive drum 1a is uniformly charged to a predetermined potential with a predetermined polarity (in this embodiment, the normal polarity is negative) by the charging roller 2a, and is exposed to light by the exposure unit 3a according to the image signal. As a result, an electrostatic latent image corresponding to the yellow color component image of the target color image is formed. Next, the electrostatic latent image is developed by a developer (yellow developer) 4a at the development position, and visualized as a yellow toner image.

[0019] The charging roller 2a as a charging member is in contact with the surface of the photosensitive drum 1a at a charging portion with a predetermined pressure contact force, and rotates relative to the photosensitive drum 1a due to friction with the surface of the photosensitive drum 1a. A predetermined DC voltage is applied to the rotating shaft of the charging roller 2a from a charging voltage power source 120 in accordance with the image forming operation. In this embodiment, the charging roller 2a is a 1.5 mm thick, 1×10 specific volume resistivity roller mounted on a metal shaft with a diameter of φ5.5 mm. 6 The charging roller 2a is provided with an elastic layer made of a conductive elastic material of about Ωcm. In response to the image forming operation, the control unit 200 applies a DC voltage of −1050V as a charging voltage to the rotating shaft of the charging roller 2a to charge the surface of the photosensitive drum 1a to a predetermined potential of −500V. The surface potential of the photosensitive drum 1a is measured using a Trek surface potential meter Model 344. The surface potential of the photosensitive drum 1a at this time, −500V, is the surface potential of the photosensitive drum 1 when no image is formed, and is a dark potential (Vd) where no toner image is developed. In addition, a large number of convex portions are provided on the surface layer of the charging roller 2a, and the average height of the convex portions is about 10 μm. The convex portions provided on the surface layer of the charging roller 2a serve as spacers between the charging roller 2a and the photosensitive drum 1a in the charging section. When residual toner, which is toner that remains on the photosensitive drum 1a without being transferred in the primary transfer section described later, enters the charging section, it serves to prevent areas other than the convex parts from coming into contact with the residual toner, causing the charging roller 2a to become dirty with the residual toner.

[0020] The exposure unit 3a includes a laser driver, a laser diode, a polygon mirror, an optical lens system, etc. As shown in Fig. 2, the exposure unit 3 receives a time-series electric digital pixel signal of image information that is input from the controller 202 to the control unit 200 via an interface 201 and image-processed. In this embodiment, the exposure amount is adjusted so that the image formation potential Vl of the photosensitive drum 1 in the electrostatic latent image portion after exposure by the exposure unit 3a is -100V. The image formation potential is also called the bright area potential.

[0021] The developing unit 4a includes a developing roller 41a as a developing member (developer carrier) and a non-magnetic one-component developer composed of toner and transfer carrier particles described later. The developing unit 4a is a developing means that performs a developing action on the photosensitive drum 1 in order to develop an electrostatic latent image into a toner image, and is a developer container that contains the developer. The developing unit 4a and the image forming apparatus main body 100 include a contact / separation mechanism 40 that controls the contact / separation (development / separation) state of the developing roller 41a and the photosensitive drum 1a as shown in FIG. 2. The control unit 200 causes the developing roller 41a and the photosensitive drum 1a to contact and separate in response to the image forming operation, etc. When the developing roller 41a and the photosensitive drum 1a are in contact with each other, the developing roller 41a is in contact with the photosensitive drum 1a with a pressing force of 200 gf. The width of the development nip portion, which is the contact portion between the development roller 41a and the photosensitive drum 1a, is 2 mm in the rotation direction of the photosensitive drum 1 and 220 mm in the longitudinal direction of the photosensitive drum. The development roller 41a is rotationally driven by a development roller drive unit 130 in the forward direction to the surface movement direction of the photosensitive drum 1a so that the surface movement speed (hereinafter, circumferential speed) in the development nip portion becomes equal to the circumferential speed of the photosensitive drum 1a.

[0022] The pre-exposure unit 5a as a charge removing means removes electricity by exposing the surface of the photosensitive drum 1a to light before the surface of the photosensitive drum 1a is charged by the charging roller 2a. By removing electricity from the surface of the photosensitive drum 1a, the pre-exposure unit 5a has the role of leveling the surface potential formed on the photosensitive drum 1 and the role of controlling the amount of discharge caused by discharge occurring in the charging section.

[0023] Furthermore, when the developing roller 41a and the photosensitive drum 1a are in contact with each other during the image forming operation, the control unit 200 controls the developing voltage power supply 140 to apply a DC voltage of −300 V as the developing voltage Vdc to the core metal of the developing roller 41a. During image formation, the toner carried on the developing roller 41a is developed at the image forming potential Vl portion of the photosensitive drum 1a by electrostatic force generated by the potential difference between the developing voltage Vdc=−300 V and the image forming potential Vl=−100 V of the photosensitive drum 1a.

[0024] In the following description, regarding potential and applied voltage, a larger absolute value on the negative polarity side (e.g., -1000V compared to -500V) is referred to as a high potential, and a smaller absolute value on the negative polarity side (e.g., -300V compared to -500V) is referred to as a low potential. This is because the toner having negative charging properties in this embodiment is considered as the standard.

[0025] In this embodiment, the voltage is expressed as a potential difference with respect to the earth potential (0 V). Therefore, the developing voltage Vdc=-300 V is interpreted as having a potential difference of -300 V with respect to the earth potential due to the developing voltage applied to the core metal of the developing roller 41a. This is the same for the charging voltage, the transfer voltage, and the like.

[0026] Next, the control unit 200 will be described. FIG. 2 is a control block diagram showing a schematic control mode of the main parts of the image forming apparatus 100 in this embodiment. The controller 202 exchanges various electrical information with the host device, and controls the image forming operation of the image forming apparatus 100 via the interface 201 in accordance with a predetermined control program and a reference table. The control unit 202 is configured with a CPU 155, which is a central element that performs various arithmetic processing, and a memory 154 such as a ROM and a RAM, which are storage elements. The RAM stores the detection results of the sensor, the count results of the counter, and the results of arithmetic operations, and the ROM stores the control program, a data table obtained in advance by experiments, and the like. The control unit 200 is connected to each control target, sensor, counter, and the like in the image forming apparatus 100. The control unit 200 controls the exchange of various electrical information signals and the timing of driving each part, and controls a predetermined image forming sequence. For example, the control unit 200 controls the voltages and exposure amounts applied by the charging voltage power supply 120, the developing voltage power supply 140, the exposure unit 3, the primary transfer voltage power supply 160, and the secondary transfer voltage power supply 150. In addition, the control unit 200 also controls the photosensitive drum drive unit 110, the developing roller drive unit 130, and the developing contact / separation mechanism 40. The image forming apparatus 100 forms an image on the recording material P based on an electrical image signal input from a host device to the controller 202. Examples of the host device include an image reader, a personal computer, a facsimile, and a smartphone.

[0027] The toner in this embodiment is a negatively charged non-magnetic toner produced by suspension polymerization, has a volume average particle diameter of 7.0 μm, and is negatively charged when carried on the developing roller 41a. The volume average particle diameter of the toner was measured using a laser diffraction particle size distribution measuring instrument LS-230 manufactured by Beckman Coulter, Inc. The toner will be described in detail later.

[0028] The intermediate transfer belt 10 as an intermediate transfer body is stretched by a plurality of stretching members 11, 12, and 13, and is rotated at the same peripheral speed as the photosensitive drum 1a in a direction moving in the circumferential direction at a portion facing the photosensitive drum 1a where the intermediate transfer belt 10 abuts against the photosensitive drum 1a. A DC voltage of 200 V is applied from a primary transfer voltage power source 160 to the primary transfer roller 14a as a primary transfer member during primary transfer during image forming operation. The yellow toner image formed on the photosensitive drum 1a is electrostatically transferred onto the intermediate transfer belt 10 in the process of passing through a primary transfer portion, which is the portion where the photosensitive drum 1a abuts against the primary transfer roller 14a via the intermediate transfer belt 10.

[0029] The primary transfer roller 14a is a cylindrical metal roller with a diameter of 6 mm, and is made of nickel-plated SUS. The primary transfer member 14a is disposed at a position offset by 8 mm downstream in the moving direction of the intermediate transfer belt 10 from the center position of the photosensitive drum 1a, and the intermediate transfer belt 10 is configured to wrap around the photosensitive drum 1a. The primary transfer roller 14a is disposed at a position raised by 1 mm from the horizontal plane formed by the photosensitive drum 1a and the intermediate transfer belt 10 so that the amount of winding of the intermediate transfer belt 10 around the photosensitive drum 1a can be secured. The primary transfer roller 14a presses the intermediate transfer belt 10 with a force of about 200 gf. The primary transfer roller 14a rotates in accordance with the rotation of the intermediate transfer belt 10. The primary transfer roller 14b disposed in the second image forming station b, the primary transfer roller 14c disposed in the third image forming station c, and the primary transfer roller 14d disposed in the fourth image forming station d are also configured similarly to the primary transfer roller 14a.

[0030] Similarly, a magenta toner image as a second color, a cyan toner image as a third color, and a black toner image as a fourth color are formed by the second, third, and fourth image forming stations b, c, and d, respectively, and are transferred in a superimposed manner onto the intermediate transfer belt 10. Thus, a composite color image corresponding to the desired color image is obtained.

[0031] The four color toner images on the intermediate transfer belt 10 are transferred collectively onto the surface of the recording material P fed by paper feeding means 50 during a secondary transfer process in which the recording material P passes through a secondary transfer nip formed by the intermediate transfer belt 10 and a secondary transfer roller 15 as a secondary transfer member. The secondary transfer roller 15 contacts the intermediate transfer belt 10 with a pressure of 50 N to form the secondary transfer nip. The secondary transfer roller 15 is rotated relative to the intermediate transfer belt 10, and a voltage of 1500 V is applied to the secondary transfer roller 15 from a secondary transfer voltage power source 150 when the toner on the intermediate transfer belt 10 is secondarily transferred onto the recording material P such as paper.

[0032] Thereafter, the recording material P carrying the four color toner images is introduced into the fixing device 30. The four color toners are melted, mixed, and fixed to the recording material P by being heated and pressurized by the fixing device 30. Any toner remaining on the intermediate transfer belt 10 after the secondary transfer is cleaned and removed by a cleaning device 17.

[0033] The cleaning device 17 has a cleaning blade or the like that comes into contact with the outer peripheral surface of the intermediate transfer belt 10 to scrape off the toner remaining on the intermediate transfer belt 10 and collect it in the intermediate transfer belt cleaning device 17. The intermediate transfer belt cleaning device 17 is disposed downstream of the secondary transfer portion of the intermediate transfer belt 10 in the rotation direction of the intermediate transfer belt 10 so as to collect the toner adhering to the intermediate transfer belt 10.

[0034] Through the above operations, a full-color print image is formed.

[0035] 2. Developers, toners, transfer carrier particles Next, the developer, toner, and transfer carrier particles used in this embodiment will be described in detail.

[0036] In this embodiment, a mixture of toner and external additive A, which is transfer carrier particles, is used as the developer. Here, the transfer carrier particles refer to particles that are present 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 improving the primary transfer efficiency of the toner image. The toner is toner particles that contain toner base particles containing a release agent and an organosilicon polymer on the surface of the toner base particles.

[0037] The organosilicon polymer is R-Si(O 1 / 2 )3, in which R represents an alkyl group or a phenyl group having 1 to 6 carbon atoms, and the organosilicon polymer forms convex portions on the surface of the toner base particle.

[0038] The protrusions are characterized by being in surface contact with the surface of the toner base particle, and this surface contact is expected to have a significant effect in inhibiting the movement, detachment, and embedding of the protrusions.

[0039] The degree of surface contact will be explained with reference to schematic diagrams of protrusions shown in Figs.

[0040] 3, 61 is a cross-sectional image of a toner particle in which about 1 / 4 of the toner particle can be seen, 62 is a toner particle, 63 is the surface of a toner base particle, and 64 is a protrusion. The cross section of a toner particle can be observed using a scanning transmission electron microscope (hereinafter also referred to as STEM) described later.

[0041] A cross-sectional image of the toner is observed, and a line is drawn along the periphery of the surface of the toner base particle. The image is converted into a horizontal image based on the line along the periphery. In the horizontal image, the length of the line along the periphery at the portion where the convex portion and the toner base particle form a continuous interface is defined as the convex width w.

[0042] Furthermore, the maximum length of the convex portion in the normal direction to the convex width w is defined as the convex diameter D, and the length from the apex of the convex portion to a line along the circumference in the line segment forming the convex diameter D is defined as the convex height H.

[0043] 4 and 6, the convex diameter D and the convex height H are the same, while in FIG.

[0044] FIG. 6 is a schematic diagram showing the adhesion state of particles similar to bowl-shaped particles, which are semi-spherical particles with a concave center, obtained by crushing or breaking hollow particles.

[0045] In Figure 6, the convex width W is the total length of the organosilicon polymer in contact with the surface of the toner base particle, i.e., the convex width W in Figure 6 is the sum of W1 and W2.

[0046] 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 occurs between the surface of the toner base particle and the transfer member, and the transferability is significantly improved. On the other hand, when the number average value of the convex height H is 300 nm or less, the effect of suppressing the movement, detachment, and embedding is remarkable, and high transferability is maintained even in long-term use. A cumulative distribution of the convex height H is taken for the convex portion having a convex height H of 30 nm or more and 300 nm or less. When the convex height H that corresponds to 80 number % by integrating from the smallest convex height H is H80, H80 is preferably 65 nm or more and 120 nm or less, and more preferably 75 nm or more and 100 nm or less. By setting H80 in the above range, the transferability can be further improved.

[0047] The number-average particle diameter 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 exerted between the transfer member and the toner, and high transferability is exhibited. In addition, the larger R is, the more the transferability tends to improve. On the other hand, when R is more than 1200 nm, the fluidity of the toner decreases, and image unevenness is easily generated.

[0048] 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 is preferably 1.00 or more and 4.00 or less. When the ratio [(number average particle diameter R of the primary particles of the external additive A) / (number average value of the convex height H)] is in the above range, it is possible to achieve both excellent transferability and low-temperature fixability that can withstand a long life.

[0049] 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 is exerted between the transfer member and the transferability can be improved. This is thought to be because the external additive A is substituted in the places where there are no convex parts due to the influence of detachment, etc., and the spacer effect is exerted. In other words, if R is less than 30 nm, the spacer effect is difficult to exert.

[0050] The adhesion rate of the external additive A to the toner particle surface is preferably 0% to 20%, more preferably 0% to 10%. When the adhesion rate is within the above range, the external additive A can move easily on the surface of the toner particles, and the transferability can be further improved by the protrusion substitution effect. In the fixing process in which the toner is fixed to the fixing member, an appropriate amount of release agent seeps out from the toner base particles, improving the separation performance between the fixing member and the paper.

[0051] A 1.5 μm square backscattered electron image of the toner surface is obtained by observing the surface of the toner using a scanning electron microscope. When an image is obtained by binarizing the backscattered electron image so that the organosilicon polymer portion in the backscattered electron image becomes a bright portion, the area ratio of the bright portion area of ​​the image to the total area of ​​the image (hereinafter also simply referred to as the area ratio of the bright portion area) is 30.0% or more and 75.0% or less. In addition, the area ratio of the bright portion area of ​​the image is preferably 35.0% or more and 70.0% or less. The higher the area ratio of the bright portion area, the higher the proportion of the organosilicon polymer present on the surface of the toner base particle. When the area ratio of the bright portion area is higher than 75.0%, the proportion of the components originating from the toner base particle on the surface of the toner base particle is low, so that the exudation of the release agent from the toner base particle is difficult to occur, and the thin paper tends to wrap around the fixing device during low-temperature fixing. On the other hand, when the area ratio of the bright portion area of ​​the image is less than 30.0%, the proportion of the components originating from the toner base particle on the surface of the toner base particle is high. In other words, the exposed area of ​​the components derived from the toner base particles on the toner base particle surface is large, and the transferability is reduced in the initial stage of use. The area ratio of the bright area of ​​the image is hereinafter also referred to as the coverage rate of the organosilicon polymer on the surface of the toner base particle.

[0052] The external additive A is not particularly limited as long as the number average particle diameter R of the primary particles is 30 nm or more and 1000 nm or less, and various organic or inorganic fine particles can be used. From the viewpoint of easily imparting fluidity and being easily negatively charged like the toner mother particles, it is preferable that the external additive A contains silica fine particles. The content of the silica fine particles in the external additive A is preferably 50 mass% or more, and it is more preferable that the external additive A is silica fine particles. The content of the external additive A in the toner is preferably 0.02 mass% or more and 5.00 mass% or less, and more preferably 0.05 mass% or more and 3.00 mass% or less.

[0053] Examples of organic or inorganic fine particles other than silica fine particles include the following. (1) Fluidity imparting agents: alumina fine particles, titanium oxide fine particles, carbon black and carbon fluoride. (2) Abrasives: fine particles of metal oxides (fine particles of strontium titanate, cerium oxide, alumina, magnesium oxide, chromium oxide, etc.), fine particles of nitrides (fine particles of silicon nitride, etc.), fine particles of carbides (fine particles of silicon carbide, etc.), fine particles of metal salts (fine particles of calcium sulfate, barium sulfate, calcium carbonate, etc.). (3) Lubricants: fine particles of fluororesin (fine particles of vinylidene fluoride, polytetrafluoroethylene, etc.), fine particles of fatty acid metal salts (fine particles of zinc stearate, calcium stearate, etc.). (4) Charge-controlling fine particles: fine particles of metal oxides (fine particles of tin oxide, titanium oxide, zinc oxide, alumina, etc.), carbon black.

[0054] The silica fine particles and the organic or inorganic fine particles may be subjected to a hydrophobic treatment in order to improve the flowability of the toner and to uniformly charge the toner particles.

[0055] 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. These treatment agents may be used alone or in combination.

[0056] The silica fine particles may be any known silica fine particles, and may be either dry silica fine particles or wet silica fine particles. Preferably, the silica fine particles are wet silica fine particles obtained by a sol-gel method (hereinafter, also referred to as sol-gel silica).

[0057] Fig. 7 is an enlarged view of the developer used in this embodiment. As shown in Fig. 7, the developer in this embodiment has a toner surface on which many protrusions of an organosilicon polymer are formed, and external additive A, which is a transfer carrier particle, is disposed on the toner surface.

[0058] The convex interval G and convex height H on the toner surface shown in Figure 7 can be measured using a scanning transmission electron microscope (hereinafter also referred to as STEM), which will be described later. The convex interval G and convex height H can also be measured with a scanning probe microscope (hereinafter referred to as SPM). A scanning probe microscope (hereinafter referred to as 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 detects the atomic force (attractive or repulsive force) between the probe and the sample to observe the shape of the sample surface.

[0059] If the convex interval G is larger than the transfer carrier, when the transfer carrier particles are arranged between the convex portions, they come into contact with the toner matrix, and the adhesive force Ft between the transfer carrier particles and the toner increases, making it difficult for the transfer carrier particles to transfer from the toner to the photosensitive drum 1. For this reason, it is preferable that the number average value of the convex interval G is smaller than the number average particle size of the transfer carrier particles.

[0060] Furthermore, if the convex height H is larger than the particle size of the transfer carrier particles, the convex portions come into contact with the photosensitive drum 1 before the transfer carrier particles, making it difficult for the transfer carrier particles to come into contact with the photosensitive drum 1, and making it difficult for the transfer carrier particles to be transferred from the toner to the photosensitive drum 1. For this reason, 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.

[0061] 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, it is preferable to select a material for the transfer carrier particles that reduces the adhesive force Ft of the transfer carrier particles to the toner. For example, as in this embodiment, when the convex portions on the toner surface are formed of a silica-based material such as an organic silica polymer, it is preferable to select a silica-based material having a similar material composition to the convex portions as the material for the transfer carrier particles in order to reduce the adhesive force between the convex portions and the transfer carrier particles.

[0062] A larger number of transfer carrier particles covering the toner is preferable from the viewpoint of supplying the transfer carrier particles from the developing roller 41 to the photosensitive drum 1. However, if the amount of transfer carrier particles added is too large, the risk of contamination of members inside the image forming apparatus 100 increases, so it is preferable to adjust the amount according to the desired primary transferability.

[0063] The primary transferability improves with an increase in the coverage of the transfer carrier particles on the photosensitive drum 1, and in order to obtain sufficient primary transferability, it is preferable that the coverage of the transfer carrier particles on the photosensitive drum 1 is 10% or more. 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 within the image forming apparatus by the transfer carrier particles increases. Therefore, it is preferable to keep the coverage of the transfer carrier particles on the photosensitive drum 1 within 50%.

[0064] 3. Measurement method of developer physical properties Various measurement methods will be described below.

[0065] <Method of observing the cross section of a toner using a scanning transmission electron microscope (STEM)> A cross section of a toner to be observed with a scanning transmission electron microscope (STEM) is prepared as follows.

[0066] The procedure for preparing a cross section of a toner will be described below. When organic or inorganic fine particles are externally added to the toner, the organic or inorganic fine particles are removed by the following method or the like and the toner is used as a sample.

[0067] Add 160 g of sucrose (Kishida Chemical) to 100 mL of ion-exchanged water and dissolve in a hot water bath to prepare a concentrated sucrose solution. In a centrifuge tube (50 mL capacity), add 31 g of the concentrated sucrose solution and 6 mL of Contaminon N (a 10% by weight aqueous solution of a neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, with a pH of 7, manufactured by Wako Pure Chemical Industries, Ltd.). Add 1.0 g of toner to the tube and break up the toner clumps with a spatula or the like. Shake the centrifuge tube at 300 strokes per minute (strokes per minute) for 20 minutes in a shaker (AS-1N, sold by AS ONE Corporation). After shaking, transfer the solution to a glass tube (50 mL) for a swing rotor and separate it in a centrifuge (H-9R, manufactured by Kokusan Corporation) at 3500 rpm for 30 minutes. This operation separates the toner particles from the external additives. Visually check that the toner particles and the aqueous solution are sufficiently separated, and collect the toner particles that have separated to the top layer with a spatula, etc. The collected toner particles are filtered through a vacuum filter, and then dried in a dryer for at least one hour to obtain a sample for measurement. This operation is repeated several times to ensure the required amount.

[0068] Furthermore, whether or not the convex portions contain an organosilicon polymer is confirmed by combining this with elemental analysis using energy dispersive X-ray analysis (EDS).

[0069] The toner is spread on a cover glass (Matsunami Glass Co., Ltd., square cover glass; square No. 1) to form a single layer, and an osmium (Os) plasma coater (filgen, OPC80T) is used to apply an Os film (5 nm) and a naphthalene film (20 nm) to the toner as a protective film. Next, a PTFE tube (outer diameter 3 mm (inner diameter 1.5 mm) x 3 mm) is filled with photocurable resin D800 (JEOL Ltd.), and the cover glass is gently placed on top of the tube so that the toner is in contact with the photocurable resin D800. After irradiating light in this state to harden the resin, the cover glass and the tube are removed to form a cylindrical resin with the toner embedded in the outermost surface. Using an ultrasonic ultramicrotome (Leica, UC7), a cutting speed of 0.6 mm / s is used to cut from the outermost surface of the cylindrical resin to the length of the toner radius (for example, 4.0 μm when the weight average particle size (D4) is 8.0 μm) to expose a cross section of the center of the toner.

[0070] Next, the toner is cut to a thickness of 100 nm to prepare a thin sample of the toner cross section. By cutting in this manner, a cross section of the central part of the toner can be obtained.

[0071] As a scanning transmission electron microscope (STEM), JEM-2800 manufactured by JEOL was used. The probe size of the STEM was 1 nm, and an image was acquired at an image size of 1024×1024 pixels. Also, the contrast of the Detector Control panel of the bright-field image was adjusted to 1425, the brightness to 3750, the contrast of the Image Control panel to 0.0, the brightness to 0.5, and the gamma to 1.00 to acquire the image. The image magnification was 100,000 times, and the image was acquired so that it covered approximately one-fourth to one-half of the circumference of the cross-section in one toner particle as shown in Figure 3. For the obtained STEM image, image analysis was performed using image processing software (ImageJ (available from https: / / imagej.nih.gov / ij / )), and convex portions containing the organosilicon polymer were measured. This measurement was performed for 30 convex portions arbitrarily selected from the STEM image. Whether the convex portion contains an organosilicon polymer or not was confirmed by a combination of scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDS). First, a line was drawn along the circumference of the toner mother particle using the line drawing tool (select Segmented line in the Straght tab). For portions where the convex portion of the organosilicon polymer is buried in the toner mother particle, the line was smoothly connected as if there was no such burial. Based on that line, conversion to a horizontal image (select Selection in the Edit tab, change the line width to 500 pixels in properties, then select Selection in the Edit tab and perform Straightener) was performed. In the horizontal image, the following measurement was performed for one convex portion containing the organosilicon polymer. The length of the line along the circumference at the portion where the convex portion and the toner mother particle form a continuous interface was defined as the convex width w. The maximum length of the convex portion in the normal direction of the convex width w was defined as the convex diameter D, and the length from the vertex of the convex portion to the line along the circumference in the line segment forming the convex diameter D was defined as the convex height H. This measurement was performed for 30 arbitrarily selected convex portions, and the arithmetic mean value of each measurement value was defined as the number average value of the convex height H.

[0072] <Method for calculating H80> In the STEM image of the cross section of the toner obtained by the above-mentioned scanning transmission electron microscope (STEM), the cumulative distribution of the convex height H is taken for convex portions having a convex height H of 30 nm or more and 300 nm or less. The convex height H that is integrated from the smallest convex height H and accounts for 80% by number is defined as H80 (unit: nm).

[0073] <Calculation method for the ratio of bright area in a 1.5 μm square reflected electron image of a toner surface> The bright area ratio is determined by observing the toner surface using a scanning electron microscope. A backscattered electron image of a 1.5 μm square of the toner surface is obtained. An image is then obtained that is binarized so that the organosilicon polymer portion in the backscattered electron image becomes the bright area, and the ratio of the bright area of ​​the image to the total area of ​​the image is determined. When organic or inorganic fine particles are externally added to the toner, the organic or inorganic fine particles are removed by the following method or the like, and the sample is used.

[0074] Add 160 g of sucrose (Kishida Chemical) to 100 mL of ion-exchanged water and dissolve in a hot water bath to prepare a concentrated sucrose solution. In a centrifuge tube (50 mL capacity), add 31 g of the concentrated sucrose solution and 6 mL of Contaminon N (a 10% by weight aqueous solution of a neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, with a pH of 7, manufactured by Wako Pure Chemical Industries, Ltd.). Add 1.0 g of toner to the tube and break up the toner clumps with a spatula or the like. Shake the centrifuge tube at 300 strokes per minute (strokes per minute) for 20 minutes in a shaker (AS-1N, sold by AS ONE Corporation). After shaking, transfer the solution to a glass tube (50 mL) for a swing rotor and separate it in a centrifuge (H-9R, manufactured by Kokusan Corporation) at 3500 rpm for 30 minutes. This operation separates the toner particles from the external additives. Visually check that the toner particles and the aqueous solution are sufficiently separated, and collect the toner particles that have separated to the top layer with a spatula or similar. After filtering the collected toner particles with a vacuum filter, dry them in a dryer for at least one hour to obtain a sample for measurement. This operation is repeated several times to ensure the required amount.

[0075] Whether or not the convex portions contain an organosilicon polymer is confirmed by combining this with elemental analysis by energy dispersive X-ray analysis (EDS) as described below.

[0076] The SEM equipment and observation conditions are as follows. Equipment used: Carl Zeiss Microscopy ULTRA PLUS Acceleration voltage: 1.0 kV WD:2.0mm Aperture Size: 30.0μm Detection signal: EsB (energy selective backscattered electrons) ESB Grid: 800V Magnification: 50,000x Contrast: 63.0±5.0% (reference value) Brightness: 38.0±5.0% (reference value) Resolution: 1024 x 768 Pretreatment: Toner particles are scattered onto carbon tape (no deposition is performed)

[0077] The accelerating voltage and EsB Grid are set to achieve the following: obtaining structural information on the outermost surface of the toner particles, preventing charging up of undeposited samples, and selectively detecting high-energy reflected electrons. The observation field is selected to be near the apex where the curvature of the toner particles is smallest. It was confirmed that the bright areas in the reflected electron image were derived from the organosilicon polymer by overlaying the reflected electron image with an element mapping image obtained by energy dispersive X-ray analysis (EDS) that can be obtained with a scanning electron microscope (SEM).

[0078] 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): Thermo Fisher Scientific NORAN System 7, Ultra Dry EDS Detector Accelerating voltage: 5.0 kV WD:7.0mm Aperture Size: 30.0μm Detection signal: SE2 (secondary electrons) Magnification: 50,000x Mode:Spectral Imaging Pretreatment: Toner particles are scattered on carbon tape and platinum sputtered.

[0079] The mapping image of silicon element obtained by this method is superimposed on the backscattered electron image, and it is confirmed that the silicon atom parts of the mapping image coincide with the bright parts of the backscattered electron image.

[0080] The ratio of the bright area to the total area of ​​the reflected electron image was calculated by analyzing the reflected electron image of the toner particle surface obtained by the above method using the image processing software ImageJ (developed by Wayne Rashand). The procedure is as follows:

[0081] First, convert the backscattered electron image to 8-bit from Type in the Image menu. Next, set the Median diameter to 2.0 pixels from Filters in the Process menu to reduce image noise. Estimate the image center after excluding the observation condition display area displayed at the bottom of the backscattered electron image, and select a 1.5 μm square area from the center of the backscattered electron image using the Rectangle Tool on the toolbar. Next, select Threshold from Adjust in the Image menu. Select Default, click Auto, and then click Apply to obtain a binarized image. This operation displays the bright areas of the backscattered electron image in white. Again, estimate the image center after excluding the observation condition display area displayed at the bottom of the backscattered electron image, and select a 1.5 μm square area from the center of the backscattered electron image using the Rectangle Tool on the toolbar. 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 to read the Count value when the brightness is 0 (corresponding to the area of ​​the bright areas of the backscattered electron image). From the above value, the area ratio of the bright area to the total area of ​​the reflected electron image is calculated. The above procedure is carried out for 10 visual fields for the toner particles to be evaluated, and the number average value is calculated, which is the area ratio (%) of the bright area of ​​the image to the total area of ​​the image that has been binarized so that the organosilicon polymer portion in the reflected electron image becomes the bright area.

[0082] <Method of Identifying Organosilicon Polymers> The organosilicon polymer is identified by a combination of observation with a scanning electron microscope (SEM) and elemental analysis by energy dispersive X-ray analysis (EDS).

[0083] Using a scanning electron microscope "Hitachi Ultra High Resolution Field Emission Scanning Electron Microscope S-4800" (Hitachi High-Technologies Corporation), the toner is observed in a field of view magnified up to 50,000 times. The surface is observed by focusing on the surface of the toner particle. An EDS analysis is performed on the particles present on the surface, and it is determined whether or not the particles are organosilicon polymers based on the presence or absence of an Si element peak. If the toner particle surface contains both organosilicon polymers and silica fine particles, the organosilicon polymer is identified by comparing the ratio of the elemental contents (atomic%) of Si and O (Si / O ratio) with a standard. An EDS analysis is performed under the same conditions on each standard of the organosilicon polymer and silica fine particles, and the elemental contents (atomic%) of Si and O are obtained. The Si / O ratio of the organosilicon polymer is designated as A, and the Si / O ratio of the silica fine particles is designated as B. Measurement conditions under which A is significantly larger than B are selected. Specifically, 10 measurements are performed on the standard under the same conditions, and the arithmetic mean values ​​of A and B are obtained. Select the measurement conditions that result in an average value of A / B > 1.1. If the Si / O ratio of the particle to be identified is on the A side of [(A+B) / 2], the particle is determined to be an organosilicon polymer.

[0084] Tospearl 120A (Momentive Performance Materials Japan, LLC) was used as a sample of organosilicon polymer particles, and HDK V15 (Asahi Kasei) was used as a sample of silica microparticles.

[0085] <Method for measuring number average particle size R of primary particles of external additives> This is performed in combination with a scanning electron microscope, "Hitachi Ultra-High Resolution Field Emission Scanning Electron Microscope S-4800" (Hitachi High-Technologies Corporation), and elemental analysis using energy dispersive X-ray analysis (EDS).

[0086] In a field of view magnified up to 50,000 times, the external additive particles are randomly photographed using the elemental analysis method by EDS described above. From the photographed image, 100 external additive particles are randomly selected, the major axis of the primary particle of the target external additive particles is measured, and the arithmetic average value is taken as the number-average particle size R. The observation magnification is appropriately adjusted depending on the size of the external additive particles.

[0087] <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. If the toner contains external additives such as silica particles in addition to the organosilicon polymer, the following procedure is carried out.

[0088] 1 g of toner is placed in a vial, dissolved in 31 g of chloroform, and dispersed in an ultrasonic homogenizer for 30 minutes to produce a dispersion liquid. Ultrasonic processing device: Ultrasonic homogenizer VP-050 (manufactured by Taitec Co., Ltd.) Microchip: Step type microchip, tip diameter φ2mm Microchip tip position: Center of glass vial, 5 mm above the bottom of the vial Ultrasonic conditions: 30% intensity, 30 minutes

[0089] At this time, ultrasonic waves are applied while cooling the vial with ice water to prevent the temperature of the dispersion from increasing. The dispersion is transferred to a glass tube for a swing rotor (50 mL) and centrifuged at 58.33 S in a centrifuge (H-9R; manufactured by Kokusan Co., Ltd.). -1 Centrifugation is carried out under conditions of 100°C for 30 minutes. After centrifugation, the bottom layer of the glass tube contains particles with a high specific gravity, such as silica fine particles. The chloroform solution containing the organosilicon polymer in the top layer is collected and the chloroform is removed by vacuum drying (40°C / 24 hours) to prepare a sample. Using the above sample or the organosilicon polymer, the abundance ratio of the constituent compounds of the organosilicon polymer and the R-Si(O 1 / 2 )3, the proportion of T3 unit structures represented by solid 29Measured and calculated by Si-NMR.

[0090] First, the hydrocarbon group represented by R above is 13 Confirm by C-NMR. << 13 C-NMR (solid) measurement conditions≫ Equipment: JEOL RESONANCE JNM-ECX500II Sample tube: 3.2mmφ Specimen: Sample or organosilicon polymer Measurement temperature: room temperature Pulse mode: CP / MAS Measurement nuclear frequency: 123.25MHz ( 13 C) Reference substance: Adamantane (external standard: 29.5ppm) Sample rotation speed: 20kHz Contact time: 2ms Delay time: 2s Number of times accumulated: 1024

[0091] In this method, methyl groups (Si-CH3), ethyl groups (Si-C2H5), propyl groups (Si-C3H7), butyl groups (Si-C4H9), pentyl groups (Si-C5H 11 ), hexyl group (Si-CH 13 The presence or absence of signals due to the phenyl group (Si-C6H5-) or the like confirms the presence of the hydrocarbon group represented by R. 29 In Si-NMR, peaks are detected in different shift regions depending on the structure of the functional group that bonds to the Si of the constituent compounds of the organosilicon polymer. The structure that bonds to the Si can be identified by identifying the position of each peak using a standard sample. 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.

[0092] solid 29 Specifically, the Si-NMR measurement conditions are as follows: Equipment: JNM-ECX5002 (JEOL RESONANCE) Temperature: room temperature Measurement method: DDMAS method 29 Si 45° Sample tube: Zirconia 3.2mmφ Sample: Powdered material filled into test tube Sample rotation speed: 10kHz Relaxation delay: 180s Scan:2000

[0093] After the measurement, the peaks of multiple silane components with different substituents and bonding groups of the sample or organosilicon polymer are separated into the following X1, X2, X3, and X4 structures by curve fitting, and the peak areas of each are calculated.

[0094] 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)

[0095] [ka]

[0096] In the formulae (A1), (A2) and (A3), Ri, Rj, Rk, Rg, Rh and Rm each represent an organic group such as a hydrocarbon group having 1 to 6 carbon atoms, a halogen atom, a hydroxyl group, an acetoxy group or an alkoxy group, which is bonded to a silicon atom. 13 C-NMR and 29 Along with the Si-NMR measurement results 1 The identification may be performed by the results of H-NMR measurement.

[0097] <Method for quantifying organosilicon polymer or silica fine particles contained in toner> The toner is dispersed in chloroform as described above, and then centrifugal separation is used to separate the external additives such as the organosilicon polymer and silica fine particles based on the difference in specific gravity to obtain samples, and the content of the external additives such as the organosilicon polymer or silica fine particles is determined.

[0098] The following describes an example in which the external additive is silica fine particles, but other fine particles can also be quantified in the same manner.

[0099] First, the pressed toner is measured by fluorescent X-rays, and the silicon content in the toner is determined by analytical processing such as the calibration curve method or FP method. Next, the silicon content in the toner is determined by the solid content of each of the constituent compounds that form the organosilicon polymer and the silica fine particles. 29 The structure is identified using Si-NMR and pyrolysis GC / MS, and the silicon content in the organosilicon polymer and silica particles is determined. The silicon content in the toner determined by fluorescent X-rays and the solid 29 The contents of the organosilicon polymer and the silica fine particles in the toner are calculated from the relationship between the silicon contents in the organosilicon polymer and the silica fine particles determined by Si-NMR and pyrolysis GC / MS.

[0100] <Method of measuring the adhesion rate of external additives such as organosilicon polymers or silica fine particles to toner base particles or toner particles by water washing method> (Water washing process) 20g of 30% by weight aqueous solution of "Contaminon N" (a neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, with a pH of 7) is weighed out and placed in a 50mL vial, and mixed with 1g of toner. The vial is set in a "KM Shaker" (model: V.SX) manufactured by Iwaki Sangyo Co., Ltd., and shaken at a speed of 50 for 120 seconds. Depending on the adhesion state of the organosilicon polymer or silica fine particles, the external additives such as the organosilicon polymer or silica fine particles will migrate from the toner base particles or the toner particle surface to the dispersion liquid. Then, the toner and the external additives such as the organosilicon polymer or silica fine particles that have migrated to the supernatant liquid are separated using a centrifuge (H-9R; manufactured by Kokusan Co., Ltd.) (16.67S-1 for 5 minutes). The precipitated toner is dried by vacuum drying (40°C / 24 hours) and washed to obtain the toner.

[0101] Next, a Hitachi ultra-high resolution field emission scanning electron microscope S-4800 (Hitachi High-Technologies Corporation) is used to photograph the toner that has not been subjected to the above-mentioned washing process (toner before washing) and the toner obtained through the above-mentioned washing process (toner after washing).

[0102] Additionally, the measurement target is identified by elemental analysis using energy dispersive X-ray analysis (EDS).

[0103] The photographed toner surface image is then analyzed using image analysis software Image-Pro Plus ver. 5.0 (Nippon Roper Co., Ltd.) to calculate the coverage rate.

[0104] The imaging conditions for the S-4800 are as follows:

[0105] (1) Sample preparation Apply a thin layer of conductive paste to a sample stage (aluminum sample stage 15 mm x 6 mm) and spray toner onto it. Then use air to remove excess toner from the sample stage and dry thoroughly. Set the sample stage in the sample holder and adjust the sample stage height to 36 mm using the sample height gauge.

[0106] (2) Setting the S-4800 observation conditions When measuring the coverage, first perform elemental analysis by the energy dispersive X-ray analysis (EDS) described above to distinguish external additives such as organosilicon polymers or silica fine particles on the toner surface before carrying out the measurement. Pour liquid nitrogen into the anti-contamination trap attached to the S-4800 housing until it overflows, and leave it for 30 minutes. Start the S-4800's "PC-SEM" and perform flushing (cleaning the FE chip, which is the electron source). Click the accelerating voltage display area on the control panel on the screen, and press the [Flushing] button to open the flushing execution dialog. Check that the flushing intensity is 2 and execute it. Check 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.

[0107] Click the accelerating voltage display to open the HV setting dialog, and set the accelerating voltage to [1.1kV] and the emission current to [20μA]. In the [Basic] tab of the operation panel, set the signal selection to [SE], select the SE detector to [Upper (U)] and [+BSE], and select [LA100] in the selection box to the right of [+BSE] to set the mode to observation with backscattered electron images. In the same [Basic] tab of the operation panel, set the probe current in the electron optical system condition block to [Normal], the focus mode to [UHR], and the WD to [4.5mm]. Press the [ON] button in the accelerating voltage display of the control panel to apply the accelerating voltage.

[0108] (3) Calculation of the number-average particle size (D1) of toner Drag within the magnification display area on the control panel to set the magnification to 5000 (5k). Rotate the focus knob [COARSE] on the operation panel to adjust the aperture alignment once the image is in focus to a certain extent. Click [Align] on the control panel to display the alignment dialog and select [Beam]. Rotate the STIGMA / ALIGNMENT knobs (X, Y) on the operation panel to move the displayed beam to the center of the concentric circles. Next, select [Aperture] and rotate the STIGMA / ALIGNMENT knobs (X, Y) one by one to stop the image movement or adjust it so that it moves as little as possible. Close the aperture dialog and use autofocus to adjust the focus. Repeat this operation two more times to adjust the focus.

[0109] Thereafter, the particle diameters of 300 toner particles are measured to obtain the number average particle diameter (D1). The particle diameter of each particle is the maximum diameter observed when the toner particles are observed.

[0110] (4) Focus adjustment For the particles with a number average particle diameter (D1) of ±0.1 μm obtained in (3), align the midpoint of the maximum diameter with the center of the measurement screen, and drag within the magnification display section of the control panel to set the magnification to 10,000 (10k).

[0111] Rotate the focus knob [COARSE] on the operation panel, and adjust the aperture alignment once the image is in focus to a certain extent. Click [Align] on the control panel to display the alignment dialog, and select [Beam]. Rotate the STIGMA / ALIGNMENT knobs (X, Y) on the operation panel to move the displayed beam to the center of the concentric circles. Next, select [Aperture], and rotate the STIGMA / ALIGNMENT knobs (X, Y) one by one to stop the image movement or to minimize its movement. Close the aperture dialog, and adjust the focus using autofocus. After that, set the magnification to 50,000 (50k), and adjust the focus using the focus knob and STIGMA / ALIGNMENT knob in the same way as above, and then adjust the focus using autofocus again. Repeat this operation to adjust the focus. Here, if the inclination angle of the observation surface is large, the measurement accuracy of the coverage rate is likely to be low, so when adjusting the focus, select an observation surface with as little surface inclination as possible for analysis by selecting one that can simultaneously bring the entire observation surface into focus.

[0112] (5) Image storage Adjust the brightness in ABC mode, take a photo with a size of 640 x 480 pixels, and save it. Use this image file to perform the following analysis. Take one photo for each toner to obtain an image of the toner particles.

[0113] (6) Image analysis The image obtained by the above method is binarized using the following analysis software to calculate the coverage rate. At this time, the above screen is divided into 12 squares and each is analyzed. The analysis conditions for the image analysis software Image-Pro Plus ver.5.0 are as follows. However, if an external additive such as an organosilicon polymer with a particle size of less than 30 nm and more than 300 nm, or silica fine particles with a particle size of less than 30 nm and more than 1200 nm is included in a divided section, the coverage rate is not calculated for that section.

[0114] In the image analysis software Image-Pro Plus5.0, select "Count / Size" from "Measurement" on the toolbar, and then "Options" to set the binarization conditions. In the object extraction options, select 8 connectivity and set smoothing to 0. In addition, do not select pre-selection, fill holes, or inclusion lines, and set "Exclude borders" to "None." Select "Measurement item" from "Measurement" on the toolbar, and set the selection range for area to 2 to 10. 7 Enter:

[0115] The coverage rate is calculated by enclosing a square region. In this case, the area of ​​the region (C) should be 24,000 to 26,000 pixels. Automatic binarization is performed using "Processing"-Binarization, and the total area (D) of regions free of external additives such as organosilicon polymers or silica microparticles is calculated. The coverage rate can be calculated using the following formula from the area C of the square region and the total area D of regions free of external additives such as organosilicon polymers or silica microparticles. Coverage rate (%)=100-(D / C×100)

[0116] The arithmetic mean value of all the data obtained is taken as the coverage rate.

[0117] Then, the coverage of the toner before and after washing is calculated, [Toner coverage after washing] / [Toner coverage before washing]×100 is defined as the “adhesion rate” in the present invention.

[0118] 4. Manufacturing methods for toner particles, additives, and developers Next, examples of the production of the toner particles, the external additive A, and the developer of this embodiment will be described.

[0119] <Toner particle manufacturing example> (Preparation of aqueous medium 1) In a reaction vessel equipped with a stirrer, thermometer, and reflux tube, 650.0 parts of ion-exchanged water and 14.0 parts of sodium phosphate (Rasa Kogyo Co., Ltd., 12-hydrate) were added, and the mixture was kept at 65°C for 1.0 hour while purging with nitrogen. An aqueous calcium chloride solution in which 9.2 parts of calcium chloride (dihydrate) was dissolved in 10.0 parts of ion-exchanged water was added all at once while stirring at 15,000 rpm using a TK homomixer (Tokushu Kika Kogyo Co., Ltd.) to prepare an aqueous medium containing a dispersion stabilizer. Furthermore, 10% by mass of hydrochloric acid was added to the aqueous medium to adjust the pH to 5.0, and aqueous medium 1 was obtained.

[0120] (Preparation of Polymerizable Monomer Composition) Styrene: 60.0 parts CI Pigment Blue 15:3: 6.5 parts

[0121] The material was placed in an attritor (manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) and further dispersed using zirconia particles having a diameter of 1.7 mm at 220 rpm for 5.0 hours, after which the zirconia particles were removed to prepare a colorant dispersion. Styrene: 20.0 parts n-Butyl acrylate: 20.0 parts Crosslinking agent (divinylbenzene): 0.3 parts Saturated polyester resin: 5.0 parts (Polycondensation product of propylene oxide modified bisphenol A (2 mole adduct) and 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

[0122] This material was added to the colorant dispersion and heated to 65° C., after which it was uniformly dissolved and dispersed at 500 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to prepare a polymerizable monomer composition.

[0123] (granulation process) The temperature of the aqueous medium 1 was adjusted to 70° C., and the polymerizable monomer composition was added to the aqueous medium 1 while maintaining the rotation speed of the TK homomixer at 15,000 rpm, and 10.0 parts of t-butyl peroxypivalate as a polymerization initiator was added. Granulation was continued for 10 minutes while maintaining the rotation speed at 15,000 rpm with the stirring device.

[0124] (Polymerization process and distillation process) After the granulation step, the agitator was replaced with a propeller agitator blade, and polymerization was carried out for 5.0 hours while stirring at 150 rpm and maintaining the temperature at 70°C, and then the temperature was raised to 85°C and maintained at that temperature for 2.0 hours. Thereafter, the reflux tube of the reaction vessel was replaced with a cooling tube, and the obtained slurry was heated to 100°C, and distilled for 6 hours to remove the unreacted polymerizable monomer, thereby obtaining a resin particle dispersion.

[0125] (Organosilicon Polymer Formation Process) 60.0 parts of ion-exchanged water was weighed into a reaction vessel equipped with a stirrer and a thermometer, and the pH was adjusted to 4.0 using 10% by mass hydrochloric acid. This was heated with stirring to a temperature of 40°C. Then, 40.0 parts of methyltriethoxysilane, an organosilicon compound, was added and stirred for 2 hours or more to carry out hydrolysis. The end point of hydrolysis was confirmed by visual observation when the oil and water did not separate and became one layer, and the mixture was cooled to obtain a hydrolyzed liquid of an organosilicon compound.

[0126] The temperature of the resin particle dispersion obtained above was adjusted to 55°C, and then 25.0 parts of the hydrolyzed solution of the organosilicon compound (addition amount of the organosilicon compound was 10.0 parts) was added to initiate polymerization of the organosilicon compound. After maintaining the mixture for 0.25 hours, the pH was adjusted to 5.5 with a 3.0% aqueous sodium hydrogen carbonate solution. After maintaining the mixture for 1.0 hours (condensation reaction 1) while continuing stirring at 55°C, the pH was adjusted to 9.5 with a 3.0% aqueous sodium hydrogen carbonate solution, and the mixture was maintained for another 4.0 hours (condensation reaction 2) to obtain a toner particle dispersion.

[0127] (Washing process and drying process) After the organosilicon polymer formation process was completed, the toner particle dispersion was cooled, and hydrochloric acid was added to the toner particle dispersion to adjust the pH to 1.5 or less, and the dispersion was left to stand for 1.0 hour with stirring. The toner cake was then separated into solid and liquid using a pressure filter. The toner cake was reslurried in ion-exchanged water to make a dispersion again, and then separated into solid and liquid using the filter to obtain a toner cake. The toner cake was transferred to a thermostatic chamber at 40°C, and dried and classified for 72 hours to obtain toner particles.

[0128] <Production Example of External Additive A> The external additive A was produced as follows. 150 parts of 5% aqueous ammonia was added to a 1.5L glass reaction vessel equipped with a stirrer, a dropping nozzle, and a thermometer to prepare an alkaline catalyst solution. After adjusting the alkaline catalyst solution to 50°C, 100 parts of tetraethoxysilane and 50 parts of 5% aqueous ammonia were dropped simultaneously while stirring, and reacted for 8 hours to obtain a silica microparticle dispersion. The obtained silica microparticle dispersion was then dried by spray drying and crushed with a pin mill to obtain silica microparticles with a number average particle size of 100 nm as the external additive A.

[0129] <Developer manufacturing example> 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 & Engineering Co., Ltd.) with 7°C water passing through the jacket. Next, after the water temperature in the jacket stabilized at 7°C ± 1°C, the mixture was mixed for 10 minutes with the peripheral speed of the rotating blade set to 38 m / sec. During the mixing, the amount of water passing through the jacket was appropriately adjusted so that the temperature inside the Henschel mixer tank did not exceed 25°C. The resulting mixture was sieved through a mesh with an opening of 75 μm to obtain a developer.

[0130] The physical properties of the developer are shown in Table 1.

[0131] [Table 1]

[0132] In the table, "X" represents the ratio of the number average particle diameter R of the primary particles of external additive A to the number average value of the convex height H. When the manufactured developer was observed using an SEM, it was confirmed that external additive A was arranged as transfer carrier particles on the convex portions of the organosilicon polymer of the toner particles, and the average number of external additive A particles coated per toner particle was about 500.

[0133] 5. Supply of transfer carrier Next, a description will be given of a means for supplying transfer carrier particles onto the photosensitive drum 1, which is a feature of this embodiment. As described above, the transfer carrier particles refer to particles that are present 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 improving the primary transfer efficiency of the toner image.

[0134] In this embodiment, before the toner image is developed, transfer carrier particles are supplied in advance to the surface of the photosensitive drum 1 by using the toner carried on the developing roller 41. By coating the surface of the photosensitive drum 1 with transfer carrier particles in advance, the transfer carrier particles are interposed between the toner image and the photosensitive drum 1.

[0135] FIG. 8(a) is a schematic diagram of the development nip portion when the development roller 41 and the photosensitive drum 1 are in contact with each other. As shown in FIG. 8(a), in the development nip portion, the toner carried on the development roller 41 and the photosensitive drum 1 are in contact with each other via the transfer carrier particles. FIG. 8(b) is a schematic diagram showing the state after the toner carried on the development roller 41 and the photosensitive drum 1 shown in FIG. 8(a) have passed through the development nip portion. As shown in FIG. 8(b), the transfer carrier particles that were interposed between the toner and the photosensitive drum 1 in the development nip portion are transferred from the surface of the toner carried on the development roller 41 to the surface of the photosensitive drum 1 after passing through the development nip portion, and are supplied.

[0136] 8(a), when the adhesive force Ft between the transfer carrier particles and the toner present between the toner and the photosensitive drum 1 in the development nip portion is larger than the adhesive force Fdr between the transfer carrier particles and the photosensitive drum 1, the transfer carrier particles are difficult to transfer onto the photosensitive drum 1. Therefore, it is preferable that Ft is smaller than Fdr.

[0137] Fig. 9(a) is a schematic diagram of the primary transfer section when a toner image is carried on the surface of the photosensitive drum 1. Fig. 9(b) is a schematic diagram 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. 9(a) is completed. When Ft is smaller than Fdr, when the toner image is primarily transferred from the photosensitive drum 1 onto the surface of the intermediate transfer belt 10, only the toner image is primarily transferred onto the intermediate transfer belt 10, and the transfer carrier particles interposed between the toner image and the photosensitive drum 1 remain on the photosensitive drum 1.

[0138] Let us consider a case where the transfer carrier particles present between the toner image and the photosensitive drum 1 are primarily transferred to the intermediate transfer belt 10 together with the toner image, and the transfer carrier particles are lost from the surface of the photosensitive drum 1. In that case, the transfer carrier particles are not present between the toner image developed next 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, resulting in a decrease in the primary transferability.

[0139] Therefore, it is preferable that Ft is smaller than Fdr not only to facilitate the supply of transfer carrier particles from the toner carried on the developing roller 41 to the photosensitive drum 1, but also from the viewpoint of maintaining the transfer carrier particles coated on the photosensitive drum 1.

[0140] Fig. 10 is a timing chart of the print operation of the image forming apparatus 100 used in this embodiment. As shown in Fig. 10, during an image forming operation, the image forming apparatus 100 of this embodiment rotates while the developing roller 41 and the photosensitive drum 1 are in contact with each other before starting to develop the toner from the developing roller 41 to the photosensitive drum 1. This provides a timing for supplying transfer carrier particles from the developing roller 41 to the photosensitive drum 1 (transfer carrier supply mode).

[0141] 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 start of development of the toner image. For this purpose, it is preferable to set the time for supplying the transfer carrier particles to a time required for the photosensitive drum 1 to rotate one revolution or more. For this reason, in this embodiment, the length of the transfer carrier particle supply timing shown in FIG. 10 is set to 500 msec, which is approximately the same as the time required for the photosensitive drum 1 to rotate one revolution, so that the entire surface of the photosensitive drum 1 can be coated with the transfer carrier particles.

[0142] 10, the surface potential of the photosensitive drum 1 is set to a non-image forming potential Vd=-500V at which the toner charged to the normal polarity is not developed. Therefore, at the timing of supplying the transfer carrier particles in this embodiment, the toner whose normal polarity is negative is not developed on the surface of the photosensitive drum 1 from the developing roller 41, and only the transfer carrier particles are supplied from the developing roller 41 onto the photosensitive drum 1.

[0143] When the transfer carrier particles are supplied from the toner on the developing roller 41 to the photosensitive drum 1 in a state where there is a potential difference between the developing roller 41 and the photosensitive drum 1 as in this embodiment, the following problem occurs. If the particle size of the transfer carrier particles is too large, the transfer carrier particles are easily affected by electrostatic forces generated by the potential difference between the developing roller 41 and the photosensitive drum 1. Therefore, it becomes difficult to control the supply of the transfer carrier particles from the toner on the developing roller 41 to the photosensitive drum 1. For example, in a configuration in which the 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 41 side by electrostatic forces. Therefore, it becomes difficult to supply the transfer carrier particles from the toner on the developing roller 41 to the photosensitive drum 1. Here, it is preferable that the particle size of the transfer carrier particles is 1000 nm or less, which is less susceptible to electrostatic forces. In this embodiment, in order to stably supply the transfer carrier particles from the toner on the developing roller 41 to the surface of the photosensitive drum 1 regardless of the potential difference between the developing roller 41 and the photosensitive drum 1, particles with a particle size of 100 nm are used as the transfer carrier particles.

[0144] The developer used in this embodiment is a mixture of the toner and transfer carrier particles described above. Figure 7 is an enlarged view of the developer used in this embodiment. As shown in Figure 7, the developer in this embodiment is a toner surface on which a large number of convex portions of an organosilicon polymer are formed, and transfer carrier particles are arranged on the toner surface. The convex interval G and convex height H on the toner surface shown in Figure 7 can be measured by a scanning probe microscope (hereinafter SPM). A scanning probe microscope (hereinafter 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 detects the atomic force (attractive or repulsive force) between the probe and the sample to observe the shape of the sample surface.

[0145] If the convex interval G is larger than the transfer carrier, when the transfer carrier particles are arranged between the convex portions, they come into contact with the toner matrix, and the adhesive force Ft between the transfer carrier particles and the toner increases, making it difficult for the transfer carrier particles to transfer from the toner to the photosensitive drum 1. For this reason, it is preferable that the convex interval G is narrower than the particle size of the transfer carrier particles. Therefore, when the closest distance between adjacent convex portions is defined as the convex interval G, it is preferable that the average of the convex interval G is equal to or smaller than the average particle size of the transfer carrier particles.

[0146] Furthermore, if the convex height H is higher than the particle size of the transfer carrier particles, the convex portions will come into contact with the photosensitive drum 1 before the transfer carrier particles, making it difficult for the transfer carrier particles to come into contact with the photosensitive drum 1. For this reason, it is preferable that the convex height H is lower than the particle size of the transfer carrier particles, since it becomes difficult for the transfer carrier particles to be transferred from the toner to the photosensitive drum 1. Therefore, when the height of the convex portions from the surface of the toner particles is defined as the convex height H, it is preferable that the average of the convex height H is equal to or smaller than the average particle size of the transfer carrier particles.

[0147] When the convex portions on the toner surface in this embodiment were measured, the average convex spacing G on the toner surface was approximately 30 nm, the average convex height H was 50 nm, and both the convex spacing G and the convex height H were smaller than the particle size of the transfer carrier, 100 nm.

[0148] The transfer carrier particles used in this embodiment are silica particles with a particle size of 100 nm manufactured by the sol-gel method. In this embodiment, silica is used as the transfer carrier particles, but the material of the transfer carrier particles is not limited to silica and may be various organic or inorganic fine powders. However, as described above, it is preferable that the adhesion force Ft between the transfer carrier particles and the toner is smaller than the adhesion force Fdr between the transfer carrier particles and the photosensitive drum 1. Therefore, it is preferable to select a material for the transfer carrier particles that reduces the adhesion force Ft of the transfer carrier particles to the toner. For example, as in this embodiment, when the convex parts on the toner surface are formed of a silica-based material such as an organic silica polymer, it is preferable to select a silica-based material with a material composition similar to that of the convex parts as the material for the transfer carrier particles. It is preferable to select a silica-based material with a material composition similar to that of the convex parts from the viewpoint of reducing the adhesion force between the convex parts and the transfer carrier particles.

[0149] In this embodiment, the amount of transfer carrier particles added was adjusted so that the number of transfer carrier particles coated per toner particle was about 500. The more the number of transfer carrier particles that coat the toner, the more the transfer carrier particles can be transferred from the developing roller 41 to the surface of the photosensitive drum 1. However, if the amount of transfer carrier particles added is too large, the risk of contamination of members inside the image forming apparatus 100 increases, so it is preferable to adjust the amount according to the desired primary transferability.

[0150] Furthermore, the primary transferability improves to a certain extent with an increase in the coverage of the transfer carrier particles occupying the surface of the photosensitive drum 1. 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 within the image forming apparatus by the transfer carrier particles increases. Therefore, it is preferable to keep the coverage of the transfer carrier particles occupying the surface of the photosensitive drum 1 within 80%.

[0151] 6. Effect of transfer carrier particles Next, an effect confirmation experiment conducted to confirm the effect of the means for supplying transfer carrier particles to the photosensitive drum 1 of this embodiment will be described.

[0152] First, a yellow patch image with a density of 100% was formed using the image forming apparatus 100 equipped with a brand new photosensitive drum 1 not coated with transfer carrier particles. Then, immediately after the primary transfer of the formed yellow patch image was completed, the image forming apparatus 100 was stopped. At that time, the transfer residual toner density of the patch image portion remaining on the surface of the photosensitive drum 1a of the yellow station was confirmed.

[0153] The measurement of the residual toner density was carried out by the following method. First, a transparent tape (polyester tape 5511, Nichiban) was applied to the residual toner portion of the yellow patch image on the surface of the photosensitive drum 1a, and the residual toner was collected on the transparent tape. Then, the transparent tape that had collected the residual toner peeled off from the surface of the photosensitive drum 1a and a new transparent tape were each applied on a high whiteness paper (GFC081, Canon). Then, the density D1 of the transparent tape at the residual toner collection portion and the density D0 of the new transparent tape portion were each measured using a reflection densitometer (Reflectometer Model TC-6DS, Tokyo Denshoku Co., Ltd.). The difference "D0-D1" obtained by the measurement was taken as the residual toner density. The smaller the value of the residual toner density, the less the residual toner is. If the value is 1.0 or less, it can be determined that there is almost no residual toner, and no image defects caused by adhesion to the charging roller 2a will occur.

[0154] In addition, the surface of the photosensitive drum 1a where the transfer residual toner concentration was measured was observed with a microscope, and the coverage rate of the surface of the photosensitive drum 1a occupied by the transfer carrier particles was calculated. Specifically, the coverage rate was calculated using the following procedure for an observation image of the surface of the photosensitive drum 1a at a magnification of 3000 times using a laser microscope (VK-X200, Keyence). A binarization process was performed on the area of ​​the transfer carrier particles and the other areas, and the total area rate of the transfer carrier particles occupied on the surface of the photosensitive drum 1 was calculated as the coverage rate of the transfer carrier particles on the surface of the photosensitive drum 1.

[0155] In addition, the adhesive force between the transfer carrier particles and the toner used in this embodiment was measured using an SPM. Specifically, a cantilever was created with a transfer carrier particle fixed to the tip of the lever, and the cantilever was pressed against the toner with a predetermined pressure. After that, the force required to detach the cantilever from the toner was measured as the adhesive force Ft between the transfer carrier particles and the toner.

[0156] The predetermined pressing force for pressing the cantilever against the toner during adhesion measurement is preferably set to the force with which the transfer carrier particles interposed between the toner and the photosensitive drum 1 in the development nip are pressed against the toner. The pressing force was calculated using the calculation method described below. Here, "the transfer carrier is interposed between the toner and the photosensitive drum 1 in the development nip" refers to a state in which the transfer carrier particles are in contact with both the toner and the photosensitive drum 1 at the same time.

[0157] First, the conditions assumed for the calculation will be explained with reference to Figs. 11 and 12. Fig. 11(a) is a schematic diagram of the development nip portion, and it is assumed that the development roller 41 and the photosensitive drum 1 are in contact with each other through the toner in the development nip portion. Fig. 11(b) shows a cross section parallel to the surface of the photosensitive drum 1 at the dotted line AB in Fig. 11(a), and it is assumed that the toner in contact with the photosensitive drum 1 is closest packed as shown in the hatched area. Fig. 12 is a schematic diagram showing an enlarged contact area between the toner and the photosensitive drum 1 surrounded by the dotted line in Fig. 11. As shown in Fig. 12, it is assumed that the toner and the photosensitive drum 1 are in contact with each other through the transfer carrier particles. It is assumed that the transfer carrier particles have not yet been supplied onto the surface of the photosensitive drum 1, and that no transfer carrier particles are present on the surface of the photosensitive drum 1 in advance.

[0158] Based on the above assumptions, the total number N of transfer carrier particles present between the toner and the photosensitive drum 1 in the development nip was calculated as follows: From the calculated N and the contact force F between the development roller 41 and the photosensitive drum 1, F / N, which is the pressing force on the toner per transfer carrier particle in the development section, was calculated, and the calculated F / N was used as the predetermined pressing force of the cantilever on the toner when measuring the adhesion force.

[0159] First, a method for calculating the total number N of transfer carrier particles present between the toner and the photosensitive drum 1 in the development nip portion will be described.

[0160] FIG. 13(a) is a schematic diagram showing the contact state of the toner, transfer carrier particles, and photosensitive drum 1 in the developing section in two dimensions. As shown in FIG. 13(b), if the particle size of the transfer carrier particles is r, when the distance between the photosensitive drum 1 and the toner surface exceeds r, the transfer carrier particles on the toner are almost out of contact with the photosensitive drum 1. Therefore, the toner circumferential portion where the transfer carrier particles arranged on the toner circumference can contact the photosensitive drum 1 is on an arc connecting A to B. In reality, it is necessary to consider the toner as a sphere as shown in FIG. 13(b), and it is necessary to find the ratio of the surface area (shaded area in FIG. 13(b)) obtained by integrating the arc AB in the circumferential direction to the toner surface area. The surface area of ​​the shaded area can generally be found as the surface area of ​​a spherical crown, as shown in formula (2). Therefore, the ratio of the toner surface area is shown in formula (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.

[0161]

number

[0162] From the above calculation, the ratio of the arc AB to the toner circumferential portion in the configuration of this embodiment is calculated to be approximately 1.43%.

[0163] Therefore, it can be considered that the area of ​​the transfer carrier particles present between the toner and the photosensitive drum 1 in the development nip portion is approximately 1.43% of the entire toner surface. Since the number of transfer carrier particles covering one toner particle is 500, the number M of transfer carrier particles present between the toner and the photosensitive drum 1 per toner particle is calculated as "500 particles x 1.43%", which is approximately 7.2 particles.

[0164] Then, the number of transfer carrier particles between the toner and the photosensitive drum 1 per toner particle, 7.2, is multiplied by the total number of toner particles in contact with the photosensitive drum 1 in the development section, and the total number N of transfer carrier particles between the toner and the photosensitive drum 1 in the development nip section can be calculated.

[0165] The total amount of toner particles L in contact with the photosensitive drum 1 in the developing nip can be calculated by (area of ​​the developing nip) x (fullness of toner) / (maximum cross-sectional area of ​​toner). (Total amount of toner in contact with photosensitive drum 1 in the development nip) =(220[mm]×2.0[mm]×π / √12) / (π×(7.0 / 2) 2 ) = approx. 10.37×10 6 pieces (The closest packing ratio of two-dimensional circles, π / √12 ≒ 0.9069, was used.)

[0166] Therefore, the "total number N of transfer carrier particles present between the toner and the photosensitive drum 1 in the development nip" is calculated as follows: The total number N is calculated by multiplying the "total number of toner particles in contact with the photosensitive drum 1 in the development nip" by the "number of transfer carrier particles present between the toner and the photosensitive drum 1 per toner particle", and is approximately 7.47 x 10 7 It becomes an individual.

[0167] In this embodiment, the pressing force of the developing roller 41 on the photosensitive drum 1 is F=200 gf, so F / N, which is the "pressure on the toner per transfer carrier particle in the developing section," is calculated to be 26.3 nN. The value of F / N calculated above was used as the predetermined pressing force for pressing the cantilever on the toner when measuring the adhesion force by SPM. In addition, a similar adhesion force measurement was also performed on the photosensitive drum 1, and the adhesion force Fdr between the transfer carrier particle fixed to the tip of the cantilever and the photosensitive drum 1 was measured.

[0168] The results of the experiment to confirm the effect of this embodiment will be described. As shown in FIG. 14, in the configuration of this embodiment, the transfer residual toner concentration was 0.8%, and it was confirmed that there was almost no transfer residual toner, and that the transfer performance was high. In addition, the transfer carrier coverage on the surface of the photosensitive drum 1 of this embodiment was 61.7%, and it was confirmed that the photosensitive drum 1 was sufficiently covered with the transfer carrier particles. In addition, as shown in FIG. 15, the adhesion force between the transfer carrier particles and the toner of this embodiment was 32.8 (nN), and the adhesion force between the transfer carrier particles and the photosensitive drum 1 was 210.1 (nN). In other words, it was confirmed that the adhesion force between the transfer carrier particles and the toner in this embodiment was smaller than the adhesion force between the transfer carrier particles and the photosensitive drum 1.

[0169] On the other hand, in Comparative Example 1, a developer configuration was adopted in which the adhesive force between the transfer carrier particles and the photosensitive drum 1 was greater than the adhesive force between the transfer carrier particles and the toner. Specifically, the toner surface was not covered with an organic silica polymer or the like as in the configuration of Example 1, and the transfer carrier particles were directly added to the toner surface. When the developer of Comparative Example 1 was used, the transfer residual toner concentration was 4.1%. The more the transfer residual toner, the more image defects occur due to poor charging caused by the charging roller 2 becoming dirty. In addition, as shown in FIG. 15, the adhesive force between the transfer carrier particles and the toner in Comparative Example 1 was 304.6 (nN), and the adhesive force between the transfer carrier particles and the photosensitive drum 1 was 210.1 (nN). In other words, it was confirmed that the adhesive force between the transfer carrier particles and the toner in Comparative Example 1 was greater than the adhesive force between the transfer carrier particles and the photosensitive drum 1.

[0170] From the above results, this embodiment has the following features.

[0171] The image forming apparatus includes a rotatable photosensitive drum 1 and a rotatable developing roller 41 carrying a developer composed of toner particles and transfer carrier particles adhering to the surface of the toner particles. The developing roller 41 contacts the photosensitive drum 1 to form a development nip portion, and supplies the developer to the surface of the photosensitive drum 1 in the development nip portion. The image forming apparatus includes a developer storage portion 4 for storing the developer. The image forming apparatus includes a transfer roller 14 for transferring the developer supplied to the surface of the photosensitive drum 1 to an intermediate transfer belt 10 as a transfer medium, a photosensitive drum driving portion 110 for driving the photosensitive drum 1, and a control portion 200 for controlling the photosensitive drum driving portion 110. In the configuration of this embodiment, the transfer carrier particles carried on the surface of the developing roller 41 can be supplied to the surface of the photosensitive drum 1 in the development nip portion while the photosensitive drum 1 is rotating. The pressing force for pressing the developing roller 41 against the photosensitive drum 1 is defined as F, and the total number of transfer carrier particles interposed between the toner particles and the photosensitive drum 1 is defined as N. The adhesive force formed between the carrier particles and the toner particles is defined as Ft, which is measured when the transfer carrier particles are pressed against the toner particles with F / N, which is the pressing force per unit carrier particle. The adhesive force formed between the transfer carrier particles and the photosensitive drum 1 is defined as Fdr, which is measured when the transfer carrier particles are pressed against the photosensitive drum 1 with F / N. The relationship between the adhesive forces Ft and Fdr satisfies Ft≦Fdr. The image forming apparatus 100 is capable of executing an image forming mode in which the electrostatic latent image is developed with developer, and a supply mode in which the transfer carrier particles are supplied from the developing roller 41 to the photosensitive drum 1.

[0172] As described above, in the configuration of this embodiment, by effectively supplying transfer carrier particles to the surface of the photosensitive drum 1, the transfer efficiency can be improved. EXAMPLES

[0173] In Example 1, the developing roller 41 was rotationally driven in the forward direction of the surface movement direction of the photosensitive drum 1 so that the peripheral speed of the developing roller 41 in the developing nip portion was equal to the peripheral speed of the photosensitive drum 1. This example is characterized in that a peripheral speed difference is provided between the developing roller 41 and the photosensitive drum 1 by rotating the developing roller 41 at a peripheral speed 40% faster than that of the photosensitive drum 1 in the developing nip portion.

[0174] In this embodiment, as shown in Fig. 16, the developing operation is set to start immediately after the developer contact in the image forming operation, and the timing for supplying transfer carrier particles before the start of development is not provided. The other configurations are the same as those in the first embodiment, and therefore will be omitted.

[0175] The operation of this embodiment will be described below.

[0176] FIG. 17(a) is a schematic diagram showing the behavior of the toner and transfer carrier particles in the development nip when the developing roller 41 and the photosensitive drum 1 are set to a non-image forming potential relationship. As shown in FIG. 17(a), by providing a peripheral speed difference between the developing roller 41 and the photosensitive drum 1, the following phenomenon occurs. The force that the toner interposed between the developing roller 41 and the photosensitive drum 1 receives from the developing roller 41, which is parallel to the rotation direction of the developing roller 41, is defined as f1. The force that the toner interposed between the developing roller 41 and the photosensitive drum 1 receives from the photosensitive drum 1, which is parallel to the rotation direction of the photosensitive drum 1, is defined as f2. In the conditions described in the first embodiment, f1 and f2 were balanced, whereas in the configuration of this embodiment, the balance between f1 and f2 is lost, and the toner rolls in the development nip. 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 toner rolling. Therefore, by being able to come into contact with the photosensitive drum 1, the opportunity for supplying transfer carrier particles from the toner to the surface of the photosensitive drum 1 increases. Therefore, as shown in Fig. 17(b), more transfer carrier particles can be supplied from the toner on the developing roller 41 to the surface of the photosensitive drum 1 after passing through the development nip, even compared to Example 1.

[0177] FIG. 18(a) is a schematic diagram showing the behavior of the toner and transfer carrier particles in the development nip when the potential relationship between the development roller 41 and the photosensitive drum 1 is set to the image formation potential relationship. As shown in FIG. 18(a), even when the potential relationship between the development roller 41 and the photosensitive drum 1 is set to the image formation potential relationship, the following phenomenon occurs due to the difference in peripheral speed between the development roller 41 and the photosensitive drum 1. The toner rolls in the development nip, and the efficiency of supplying the transfer carrier particles from the surface of the toner in the development nip to the surface of the photosensitive drum 1 is improved. Then, as shown in FIG. 18(b), since the potential relationship between the development roller 41 and the photosensitive drum 1 is set to the image formation potential relationship, the toner is developed from the development roller 41 onto the surface of the photosensitive drum 1 after passing through the development nip. However, since the efficiency of supplying the transfer carrier particles from the surface of the toner to the surface of the photosensitive drum 1 when passing through the development nip is improved, it is possible to interpose a large number of transfer carrier particles between the toner developed on the surface of the photosensitive drum 1 and the photosensitive drum 1.

[0178] Therefore, in this embodiment, even if the timing for supplying the transfer carrier particles is not set before the image formation operation as in embodiment 1, the transfer carrier particles can be coated on the surface of the photosensitive drum 1 at the same time as development, and the transfer carrier particles can be interposed between the toner image and the photosensitive drum 1.

[0179] In this embodiment, a cleaning member is not provided on the surface of the photosensitive drum 1, but since transfer carrier particles can be supplied simultaneously with development, the transfer efficiency can be suitably improved even if a cleaning member is provided on the surface of the photosensitive drum 1. Even in a configuration in which the transfer carrier particles coated on the surface of the photosensitive drum 1 are collected by the cleaning member every time the photosensitive drum 1 rotates, the effect of improving the primary transfer efficiency by the transfer carrier particles can be obtained. Of course, a configuration in which a cleaning member is provided in the case of a driven rotation with no peripheral speed difference between the developing roller 41 and the photosensitive drum 1 as in the first embodiment is not excluded as long as the transfer carrier particles are sufficiently supplied.

[0180] Next, in the configuration of this embodiment, the residual toner concentration of the yellow patch image was measured in a manner similar to that of embodiment 1, and the coverage rate of the transfer carrier particles on the surface of the photosensitive drum 1 was measured, and the results of confirming the effects of this embodiment will be described.

[0181] As shown in Fig. 14, even in the configuration of this embodiment, the transfer residual toner concentration was 0.7%, and it was confirmed that there was almost no transfer residual toner and that the transfer performance was high. Also, as shown in Fig. 14, the transfer carrier coverage on the surface of the photosensitive drum 1 in this embodiment was 62.2%, and it was confirmed that the surface of the photosensitive drum 1 was sufficiently covered with transfer carrier particles.

[0182] From the above results, the second embodiment is characterized by an image forming apparatus having the following configuration.

[0183] When the photosensitive drum driving unit 110 is defined as a first driving unit, the developing roller driving unit 130 that drives the developing roller 41 is defined as a second driving unit. The control unit 200 controls the second driving unit so that the surface movement speed of the developing roller 41 and the surface movement speed of the photosensitive drum 1 are different from each other in the development nip portion.

[0184] As described above, in the configuration of this embodiment, the transfer carrier particles can be more effectively supplied to the surface of the photosensitive drum 1, thereby improving the transfer efficiency.

[0185] In the configuration of this embodiment, an intermediate transfer method using the intermediate transfer belt 10 is adopted, but a direct transfer method in which the image is directly transferred to the recording material P may also be adopted. For example, the recording material P may be placed on the transfer belt and the image may be directly transferred from the photosensitive drum 1, or a belt configuration may not be used. [Explanation of symbols]

[0186] 1 Photosensitive drum 2. Charge roller 3 Exposure unit 4 Development Unit 14 Transfer roller 41 Developing roller 62 Toner particles

Claims

1. A rotatable image carrier; a charging member that contacts the image carrier and charges the surface of the image carrier; a charging voltage power source that applies a charging voltage to the charging member; an exposure unit that exposes the surface of the image carrier charged by the charging member to form an electrostatic latent image; a rotatable developer carrier that carries a developer composed of toner particles and carrier particles adhering to the surfaces of the toner particles, the developer carrier being in contact with the image carrier to form a development section and supplying the developer to the surface of the image carrier in the development section; a developer container that contains the developer; a control unit that controls the charging voltage power supply and the exposure unit; having an image forming apparatus capable of supplying the carrier particles carried on the surface of the developer carrier and accommodated in the developer accommodating section to the surface of the image carrier in the developing section while the image carrier is rotating, the image forming apparatus comprising: When the pressing force with which the developer carrying body is pressed against the image carrying body is F and the total number of the carrier particles interposed between the toner particles and the image carrying body is N, an adhesive force Ft formed between the carrier particles and the toner particles, the adhesive force Ft being measured when the carrier particles are pressed against the toner particles with a pressing force F / N per unit carrier particle; and an adhesive force Fdr formed between the carrier particles and the image carrier, the adhesive force Fdr being measured when the carrier particles are pressed against the image carrier at the F / N, Ft≦Fdr Fulfilling The control unit is characterized by controlling to be able to execute an image formation mode in which the developer is developed onto the electrostatic latent image, and a supply mode in which the carrier particles are supplied from the developer carrier to the image carrier.

2. 2. The image forming apparatus according to claim 1, wherein the developer has convex portions formed of fine particles containing an organosilicon polymer having a structure represented by the following formula (1) present on the surfaces of the toner particles, and the carrier particles are disposed on the convex portions: R-Si(O １／２ ) ３ (1) (The above R represents a hydrocarbon group having 1 to 6 carbon atoms.)

3. 3. The image forming apparatus according to claim 1, further comprising a transfer member that transfers the developer supplied to the surface of the image carrier to a transferee, and the developer remaining on the image carrier without being transferred to the transferee is collected by the developer carrier.

4. 4. The image forming apparatus according to claim 3, wherein the developer is a one-component developer.

5. A first drive unit that drives the image carrier; A second drive unit that drives the developer carrier; a control unit that controls the first drive unit and the second drive unit, 5. The image forming apparatus according to claim 1, wherein the control unit controls the second drive unit so that a surface movement speed of the developer carrier and a surface movement speed of the image carrier are different in the development unit.

6. The image forming apparatus according to claim 5 , wherein the control unit controls the first drive unit so as to rotate the image carrier at least one revolution in the supply mode.

7. a developing voltage power source that applies a developing voltage to the developer carrier; The image forming apparatus according to any one of claims 1 to 6, characterized in that in the supply mode, the control unit controls so that the surface potential formed on the surface of the image carrier in the developing unit is greater on the normal polarity side than the development voltage applied to the developer carrier in the developing unit, so that the developer charged to the normal polarity is not developed from the developer carrier to the image carrier.

8. 3. The image forming apparatus according to claim 2, wherein, when a closest distance between adjacent convex portions is defined as a convex interval G, an average of the convex interval G is equal to or smaller than an average particle size of the carrier particles.

9. 3. The image forming apparatus according to claim 2, wherein, when a height H of the convex portion from the surface of the toner particle is taken as a convex height, an average of the convex height H is equal to or smaller than an average particle size of the carrier particles.

10. 10. The image forming apparatus according to claim 1, wherein the carrier particles are silica.

11. 11. The image forming apparatus according to claim 1, wherein the carrier particles are made of an organic silica polymer.

12. 12. The image forming apparatus according to claim 1, wherein the average particle size of the carrier particles is 30 nm or more and 1000 nm or less.

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