Image forming device

Abstract

To suppress the occurrence of transfer residual toner over a long period when toners of a plurality of colors transferred on an intermediate transfer body are transferred to a recording material.SOLUTION: An image forming apparatus comprises: first and second image forming portions each including first and second photosensitive drums; and first and second development rollers that bear developers each composed of first and second toner particles and organosilicon protrusions formed on surfaces of the first and second toner particles, and supplies first and second developers in first and second developing portions each coming into contact with the first and second photosensitive drums; an intermediate transfer body to which a developer image is transferred in first and second contact portions each coming into contact with the first and second photosensitive drums; and a transfer member that transfers the developer image to a recording material in a transfer portion. The first contact portion is formed downstream of the transfer portion and upstream of the second contact portion in a movement direction of a surface of the intermediate transfer body, and the height of a protrusion formed on the second developer is lower than the height of a protrusion formed on the first developer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus that uses an electrophotographic recording method, such as a laser printer, a copying machine, or a facsimile machine. [Background technology]

[0002] Laser printers and copiers are typical examples of electrophotographic devices that use toner. In recent years, the rapid shift to color has led to demands for even higher image quality. One challenge facing toner-based electrophotography is improving transferability. For example, when a toner image formed on a photoreceptor (image carrier) is transferred to a transfer material during the transfer process, toner may remain on the photoreceptor. The toner remaining on the photoreceptor during the transfer process is called residual toner. To improve toner transferability, such as reducing residual toner, it is effective to reduce the adhesion of toner to the photoreceptor. One method for reducing toner adhesion is to attach external additives to the toner particle surface. In particular, a known method is known in which the addition of large-particle spherical external additives acts as a spacer, reducing the physical adhesion between the toner and the photoreceptor and improving transfer efficiency.

[0003] However, although this is an effective method for improving transfer efficiency, over a long period of image output, the large-particle spherical external additives move, fall off, or become embedded, and are no longer able to function as spacers. As a result, it has been difficult to consistently achieve the expected improvement in transfer efficiency.

[0004] Therefore, Patent Document 1 proposes a method of semi-burying large particle size external additives to suppress migration and detachment of the external additives, and Patent Document 2 proposes a method of using large particle size external additives with a hemispherical shape to suppress detachment and burying. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-36980 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-257217 Summary of the Invention [Problem to be solved by the invention]

[0006] However, Patent Documents 1 and 2 have the following problems: When forming an image using external additives as in Patent Documents 1 and 2, if toners of multiple colors stacked on an intermediate transfer body are transferred to a recording material all at once, the transferability may become insufficient as the toner specifications progress.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to suppress the generation of residual toner over a long period of time when toner of multiple colors transferred onto an intermediate transfer member is transferred onto a recording material. [Means for solving the problem]

[0008] As described above, the image forming apparatus of the present invention comprises a first image forming unit having a rotatable first image carrier and a first developer carrier that carries a first developer composed of first toner particles and convex portions made of organic silicon formed on the surfaces of the first toner particles, the first developer carrier contacting the first image carrier to form a first developing unit and supplying the first developer to form a first developer image on the surface of the first image carrier in the first developing unit; a rotatable second image carrier and a second developer carrier that carries a second developer composed of second toner particles and convex portions made of organic silicon formed on the surfaces of the second toner particles, the second developer carrier contacting the second image carrier to form a second developing unit and supplying the second developer to form a second developer image on the surface of the second image carrier in the second developing unit. a second image forming unit having a developer carrier and an intermediate transfer member that comes into contact with the first image carrier to form a first contact portion and that comes into contact with the second image carrier to form a second contact portion, wherein the first developer image is transferred at the first contact portion and the second developer image is transferred at the second contact portion; and a transfer member that comes into contact with the intermediate transfer member to form a transfer portion and transfers the first developer image and the second developer image formed on the surface of the intermediate transfer member at the transfer portion to a recording material, wherein the surface of the intermediate transfer member is movable, and the first image forming unit and the second image forming unit are arranged so that the first contact portion is formed downstream of the transfer portion and upstream of the second contact portion in a moving direction of the surface of the intermediate transfer member, and wherein a height of the convex portions formed in the second developer is smaller than a height of the convex portions formed in the first developer. and the adhesion rate of the organosilicon formed on the surface of the first toner particles in the first developer to the first toner particles is 85% or more. It is characterized by: [Effects of the Invention]

[0009] As described above, according to the present invention, high secondary transferability of toners of multiple colors can be maintained for a long period of time. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of an image forming apparatus according to a first embodiment. [Figure 2] FIG. 2 is a control block diagram according to the first embodiment. [Figure 3] FIG. 2 is a schematic diagram of a toner surface in Example 1. [Figure 4] 3 is a schematic diagram of the convex shape of the toner surface in Example 1. FIG. [Figure 5] 3 is a schematic diagram of the convex shape of the toner surface in Example 1. FIG. [Figure 6] FIG. 2 is a schematic diagram of another image forming apparatus according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following describes in detail exemplary embodiments of the present invention with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the embodiments may be changed as appropriate depending on the configuration of the device to which the invention is applied and various conditions. In other words, the scope of the present invention is not limited to the following embodiments. [Example]

[0012] 1. Image forming device 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 using Fig. 1. Note that the image forming apparatus 100 of this embodiment is a so-called tandem type printer provided with image forming stations a to d, which are image forming units. The first image forming station a forms images of yellow (Y), the second image forming station b forms images of magenta (M), the third image forming station c forms images of cyan (C), and the fourth image forming station d forms images of black (Bk).

[0013] The configuration of each image forming station is the same except for the color of toner they contain, and the following description will be made using the first image forming station a. Furthermore, unless a distinction is particularly required, the a to d in Y, M, C, and K will be omitted and the description will be generalized.

[0014] The first image forming station a includes a drum-shaped electrophotographic photosensitive member (hereinafter referred to as photosensitive drum) 1a, a charging roller 2a as charging means, an exposure unit 3a, a developing device 4a, and a cleaning device 5a as cleaning means.

[0015] The photosensitive drum 1a is an image carrier that carries a toner image and is driven to rotate in the direction of the arrow at a peripheral speed (process speed) of 150 mm / sec by a photosensitive drum drive unit 110. The photosensitive drum 1a is an aluminum tube with a diameter of 20 mm on which a photosensitive layer and a surface layer are provided, and the surface layer is a thin film layer made of polyarylate with a thickness of 20 μm.

[0016] The image forming operation is initiated when the control unit 200 shown in FIG. 2 receives an image signal via the controller 202 and interface 201, and the photosensitive drum 1a is driven to rotate. As the photosensitive drum 1a rotates, it is uniformly charged to a predetermined potential with a predetermined polarity (in this embodiment, normal polarity is negative) by the charging roller 2a, and is exposed to light by the exposure unit 3a in accordance with the image signal. This forms an electrostatic latent image corresponding to the yellow color component of the target color image. Next, the electrostatic latent image is developed by the developer (yellow developer) 4a at the development position and visualized as a yellow toner image.

[0017] The charging roller 2a, which serves as a charging member, contacts the surface of the photosensitive drum 1a at a charging section with a predetermined pressure 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 supply 120 in response to the image formation operation. In response to the image formation operation, the control unit 200 applies a DC voltage of −1050 V to the rotating shaft of the charging roller 2a as a charging voltage, thereby charging the surface of the photosensitive drum 1a to a predetermined potential of −500 V. The surface potential of the photosensitive drum 1a was measured using a Trek Model 344 surface potential meter. The surface potential of the photosensitive drum 1a at this time, −500 V, is the surface potential of the photosensitive drum 1a when no image is being formed, and is a dark potential (Vd) where no toner image is being developed.

[0018] 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 time-series electric digital pixel signals of image information that have been processed and input from the controller 202 to the control unit 200 via an interface 201. In this embodiment, the exposure amount is adjusted so that the image formation potential Vl of the electrostatic latent image portion of the photosensitive drum 1 after exposure by the exposure unit 3a is -100 V. The image formation potential is also called the bright area potential.

[0019] 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 to develop the electrostatic latent image into a toner image, and is also a developer container that contains the developer. As shown in FIG. 2, 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 between the developing roller 41a and the photosensitive drum 1a. The control unit 200 contacts and separates the developing roller 41a and the photosensitive drum 1a in accordance with the image formation operation, etc. When the developing roller 41a and the photosensitive drum 1a are in contact with each other, the developing roller 41a contacts them 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 1a and 220 mm in the longitudinal direction of the photosensitive drum. The development roller 41a is driven to rotate at a peripheral speed of 180 mm / sec by the development roller drive unit 130 in the forward direction of the surface movement direction of the photosensitive drum 1a so that the surface movement speed (hereinafter referred to as the peripheral speed) in the development nip portion is 120% of the peripheral speed of the photosensitive drum 1a. In other words, the development roller 41a and the photosensitive drum 1 are rotated such that the surface movement speed of the development roller 41a is 1.2 times faster than the surface movement speed of the photosensitive drum 1a.

[0020] Furthermore, when the developing roller 41a and the photosensitive drum 1a are in contact with each other during image formation, 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 of the developing roller 41a. During image formation, the toner carried on the developing roller 41a is developed at the image formation 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 formation potential Vl=−100 V of the photosensitive drum 1a.

[0021] In the following description, regarding potential and applied voltage, a large absolute value on the negative polarity side (for example, -1000V compared to -500V) is referred to as a high potential, and a small absolute value on the negative polarity side (for example, -300V compared to -500V) is referred to as a low potential. This is because the toner having negative chargeability in this embodiment is considered as the standard.

[0022] Furthermore, in this embodiment, the voltage is expressed as a potential difference from the earth potential (0 V). Therefore, the development voltage Vdc=-300 V is interpreted as a potential difference of -300 V from the earth potential due to the development voltage applied to the core metal of the development roller 41 a. This also applies to the charging voltage, transfer voltage, etc.

[0023] Next, the control unit 200 will be described. FIG. 2 is a control block diagram showing an outline of the 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 comprehensively controls the image forming operation of the image forming apparatus 100 via an interface 201 in accordance with a predetermined control program and lookup table. The control unit 202 includes a CPU 155, which is a central element that performs various arithmetic processing, and a memory 154, which is a storage element, such as a ROM and a RAM. The RAM stores sensor detection results, counter count results, and calculation results, while the ROM stores control programs and data tables obtained in advance through experiments. 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, thereby controlling a predetermined image formation sequence. For example, the controller 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 controller 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.

[0024] The toner used in this embodiment is a negatively charged non-magnetic toner produced by suspension polymerization, has a volume average particle size of 7.0 μm, and is negatively charged when carried on the developing roller 41a. The volume average particle size of the toner was measured using a laser diffraction particle size distribution analyzer LS-230 manufactured by Beckman Coulter, Inc. Details of the toner will be described later.

[0025] An intermediate transfer belt 10 serving as an intermediate transfer body is stretched by multiple stretching members 11, 12, and 13, and is driven to rotate at the same peripheral speed as the photosensitive drum 1a in a direction in which it moves circumferentially at a portion facing the photosensitive drum 1a where it abuts against the photosensitive drum 1a. A DC voltage of 200 V is applied to a primary transfer roller 14a serving as a primary transfer member from a primary transfer voltage power supply 160 during primary transfer during image formation. The yellow toner image formed on the photosensitive drum 1a is electrostatically transferred onto the intermediate transfer belt 10 as it passes through a primary transfer portion, which is the portion in contact between the photosensitive drum 1a and the primary transfer roller 14a via the intermediate transfer belt 10.

[0026] The primary transfer roller 14a is a cylindrical metal roller with a diameter of 6 mm and made of nickel-plated stainless steel. The primary transfer member 14a is positioned 8 mm downstream in the direction of movement of the intermediate transfer belt 10 relative to the center of the photosensitive drum 1a, so that the intermediate transfer belt 10 is wound around the photosensitive drum 1a. The primary transfer roller 14a is positioned 1 mm above the horizontal plane formed by the photosensitive drum 1a and the intermediate transfer belt 10 to ensure a sufficient amount of winding of the intermediate transfer belt 10 around the photosensitive drum 1a. The primary transfer roller 14a presses the intermediate transfer belt 10 with a force of approximately 200 gf. The primary transfer roller 14a rotates in response to the rotation of the intermediate transfer belt 10. The primary transfer roller 14b disposed at the second image forming station b, the primary transfer roller 14c disposed at the third image forming station c, and the primary transfer roller 14d disposed at the fourth image forming station d all have the same configuration as the primary transfer roller 14a.

[0027] Similarly, the second, third, and fourth image forming stations b, c, and d form a magenta toner image (second color), a cyan toner image (third color), and a black toner image (fourth color), which are then transferred onto the intermediate transfer belt 10 in a superimposed manner. A composite color image corresponding to the target color image is obtained. Any residual toner remaining on the surfaces of the photosensitive drums 1a, 1b, 1c, and 1d after the primary transfer is removed by cleaning blades (not shown) provided on the cleaning devices 5a, 5b, 5c, and 5d. This prepares the photosensitive drums 1a, 1b, 1c, and 1d for the next image formation.

[0028] The four color toner images on the intermediate transfer belt 10 are transferred all at once onto the surface of the recording material P fed by paper feeding means 50 during the 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 acting 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 supply 150 during the secondary transfer of the toner on the intermediate transfer belt 10 onto the recording material P, such as paper.

[0029] Thereafter, the recording material P bearing the four color toner images is introduced into the fixing device 30. The fixing device 30 applies heat and pressure to the four color toners, causing them to melt, mix, and be fixed to the recording material P. Any toner remaining on the intermediate transfer belt 10 after the secondary transfer is cleaned and removed by an intermediate transfer belt cleaning device 17, which serves as an intermediate transfer body cleaning device.

[0030] The intermediate transfer belt cleaning device 17 has a cleaning blade or the like that contacts the outer peripheral surface of the intermediate transfer belt 10 to scrape off 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 unit of the intermediate transfer belt 10 in the rotation direction of the intermediate transfer belt 10 so as to collect toner adhering to the intermediate transfer belt 10.

[0031] Through the above operations, a full-color print image is formed.

[0032] 2. Toner Next, the developer used in this embodiment will be described in detail.

[0033] The developers of this embodiment are all four colors of toner particles containing a release agent and an organosilicon polymer on the surface of the toner particles. The organosilicon polymer has a T3 unit structure represented by R-Si(O1 / 2)3, where R represents an alkyl group or phenyl group having 1 to 6 carbon atoms, and the organosilicon polymer forms convex portions 64 on the surface of the toner particles. The convex portions are characterized by being in surface contact with the surface of the toner particles, and this surface contact is expected to have a significant effect in inhibiting the migration, detachment, and embedding of the convex portions.

[0034] The degree of surface contact will be explained using the schematic diagrams of protrusions 64 shown in Figures 3, 4, and 5. In Figure 3, 61 is a cross-sectional image of a toner particle showing approximately one-quarter of the toner particle, with 62 being the toner particle and 63 being the surface of the toner base particle. The cross-section of the toner particle 62 can be observed using a scanning transmission electron microscope (hereinafter also referred to as STEM), which will be described later. The cross-sectional image of the toner is observed, and a line is drawn along the periphery of the toner base particle surface 63. A horizontal image is then created based on this periphery line. In the horizontal image, the length of the line along the periphery where the protrusion and the toner base particle form a continuous interface is defined as the protrusion width W. The maximum length of the protrusion in the normal direction to the protrusion width W is defined as the protrusion diameter D, and the length from the apex of the protrusion to the line along the periphery of the line segment forming the protrusion diameter D is defined as the protrusion height H. In Figure 4, the protrusion diameter D and the protrusion height H are the same, while in Figure 5, the protrusion diameter D is greater than the protrusion height H.

[0035] When considering primary and secondary transfer of only one color toner, the average convex height H is preferably 5 nm or more and 300 nm or less. The larger the number-average convex height H, the greater the spacer effect between the toner base particle surface and the transfer member, resulting in a weaker adhesive force. By setting the average convex height H to 5 nm or more, primary and secondary transfer performance can be improved for single-color toner. On the other hand, if the number-average convex height H exceeds 300 nm, the toner fluidity decreases, making image unevenness more likely to occur. As will be described later in Example 2, for the black toner at the fourth station, which is not stacked on the intermediate transfer belt 10, the spacer effect is not necessary, so convex portions may be omitted and transfer performance may be improved using external additives or the like. Here, the number-average value in this example is calculated by calculating the convex height H for an arbitrarily selected number of convex portions 64, and the arithmetic average of each measurement value is used as the number-average convex height H.

[0036] When considering the secondary transfer of toner of two or more colors, the toner loading amount is large, resulting in lower secondary transferability than when using toner of only one color. Therefore, among the toners that are primarily transferred onto the intermediate transfer belt 10 in a stacked manner, the number-average convex height H of the toner particles that are primarily transferred first is preferably greater than the number-average convex height H of the toner particles that are primarily transferred last, and is preferably at least 5 nm larger. More preferably, it is preferably at least 10 nm larger. This ensures that the adhesive force between the toner and the intermediate transfer belt 10 is sufficiently smaller than the adhesive force between the toner and the recording material P, thereby improving secondary transferability when toner particles of two or more colors on the intermediate transfer belt 10 are simultaneously transferred to the recording material P. In this embodiment, the ratio of the number-average convex height H (H1) of the toner particles that are primarily transferred first to the number-average convex height H (H2) of the toner particles that are primarily transferred last is preferably 0≦H2 / H1<1, more preferably 0≦H2 / H1<0.92, and even more preferably 0≦H2 / H1<0.83.

[0037] Furthermore, the adhesion rate of the convex portions of the first-transferred toner to the toner matrix is ​​85.0% or higher, and preferably 90.0% or higher. A convex adhesion rate of 85.0% or higher to the toner matrix minimizes peeling and detachment of the organosilicon polymer from the surface layer. Therefore, even with long-term use, the increase in adhesion between the toner and the intermediate transfer belt 10 can be suppressed when two or more colors of toner are simultaneously transferred to the recording material P. Furthermore, the adhesion force between the toner and the intermediate transfer belt 10 is maintained sufficiently smaller than the adhesion force between the toner and the recording material P. In this embodiment, the convex portions 64 are formed using an organosilicon polymer. However, other methods may be used to form the convex portions 64 as long as the above adhesion rate can be achieved. For example, some of the organosilicon particles may be partially embedded in the matrix surface as shown in Figure 5. However, in this case, the embedding of the particles may accelerate in the latter half of the durability test, resulting in a decrease in the convex height. Therefore, it is preferable for the convex portions 64 to be in surface contact with the toner matrix surface 63, as shown in Figure 4. In this embodiment, the convex portions 64 have this shape. The method for measuring the adhesion rate and its definition will be described later.

[0038] The toner surface is observed using a scanning electron microscope to obtain a backscattered electron image of a 1.5 μm square of the toner surface. When the backscattered electron image is binarized so that the organosilicon polymer portion becomes a bright area, the area ratio of the bright area of ​​the image to the total area of ​​the image (hereinafter simply referred to as the bright area ratio) is 30.0% or more and 75.0% or less. Furthermore, the area ratio of the bright area of ​​the image is preferably 35.0% or more and 70.0% or less.

[0039] The higher the area ratio of the bright area, the higher the proportion of organosilicon polymer present on the toner base particle surface. When the area ratio of the bright area is higher than 75.0%, the proportion of components derived from the toner base particles present on the toner base particle surface is low, which makes it difficult for the release agent to ooze from the toner base particles and increases the likelihood of thin paper wrapping around the fixing device (separation failure) during low-temperature fixing. On the other hand, when the area ratio of the bright area of ​​the image is less than 30.0%, the proportion of components derived from the toner base particles present on the toner base particle surface is high. In other words, the exposed area of ​​components derived from the toner base particles on the toner base particle surface is large, which reduces the effect of improving the transferability of primary and secondary transfers due to the height of the convex portions. Hereinafter, the area ratio of the bright area of ​​the image will also be referred to as the coverage rate of the organosilicon polymer on the surface of the toner base particle. The method for measuring the area ratio of the bright area, i.e., coverage rate, will be described later.

[0040] To improve the fluidity, chargeability, cleaning properties, etc., so-called external additives such as a fluidizing agent and a cleaning aid may be added to the toner.

[0041] Examples of external additives include inorganic oxide particles such as silica particles, alumina particles, and titanium oxide particles; inorganic stearic acid compound particles such as aluminum stearate particles and zinc stearate particles; and inorganic titanic acid compound particles such as strontium titanate and zinc titanate. These can be used alone or in combination of two or more. These inorganic particles are preferably gloss-treated with a silane coupling agent, a titanium coupling agent, a higher fatty acid, a silicone oil, or the like to improve heat-resistant storage stability and environmental stability. The BET specific surface area of ​​the external additive is 10 m 2 / g or more 450m 2 / g or less is preferable.

[0042] The BET specific surface area can be determined by a low-temperature gas adsorption method using a dynamic constant pressure method in accordance with the BET method (preferably the BET multipoint method). For example, a specific surface area measuring device (trade name: Gemini 2375 Ver. 5.0, manufactured by Shimadzu Corporation) is used to adsorb nitrogen gas onto the surface of a sample, and the BET multipoint method is used to measure the BET specific surface area (m 2 / g) can be calculated.

[0043] The total amount of these various external additives added is 0.05 to 5 parts by mass, preferably 0.1 to 3 parts by mass, per 100 parts by mass of toner. Various external additives may be used in combination.

[0044] 3.Method for measuring toner physical properties Various measurement methods will be explained below.

[0045] <Method for observing the cross section of toner using a scanning transmission electron microscope (STEM)> A cross section of the toner to be observed with a scanning transmission electron microscope (STEM) is prepared as follows.

[0046] The procedure for preparing a cross section of a toner is 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.

[0047] 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 50 mL centrifuge tube, add 31 g of the above concentrated sucrose solution and 6 mL of Contaminon N (a 10% aqueous solution of a pH 7 neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, anionic surfactant, and organic builder, manufactured by Wako Pure Chemical Industries, Ltd.). Add 1.0 g of toner to the tube and break up any clumps with a spatula or similar. Shake the centrifuge tube in a shaker (AS-1N, sold by AS ONE Corporation) at 300 strokes per minute (spm) for 20 minutes.

[0048] After shaking, the solution is transferred to a glass tube (50 mL) for a swing rotor and centrifuged at 3,500 rpm for 30 minutes in a centrifuge (H-9R, manufactured by Kokusan Co., Ltd.). This operation separates the toner particles from the external additives. Visually confirm that the toner particles and aqueous solution have been sufficiently separated, and collect the toner particles that have separated to the top layer with a spatula or similar. The collected toner particles are filtered using a vacuum filter and then dried in a dryer for at least one hour to obtain a sample for measurement. This operation is repeated multiple times to ensure the required amount.

[0049] 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).

[0050] Toner was sprayed onto a cover glass (Matsunami Glass Co., Ltd., square cover glass; No. 1) to form a single layer. Then, using an osmium (Os) plasma coater (Filgen, OPC80T), a protective layer of Os (5 nm) and naphthalene (20 nm) was applied to the toner. Next, a PTFE tube (3 mm outer diameter (1.5 mm inner diameter) x 3 mm) was filled with photocurable resin D800 (JEOL Ltd.), and the cover glass was gently placed on top of the tube so that the toner was in contact with the photocurable resin D800. After irradiating the resin with light to cure it, the cover glass and tube were removed, forming 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 diameter (D4) is 8.0 μm) to expose a cross section of the center of the toner.

[0051] Next, the toner is cut to a thickness of 100 nm to prepare a thin sample of the cross section of the toner.

[0052] By cutting in this manner, a cross section of the central part of the toner can be obtained.

[0053] A JEOL JEM-2800 scanning transmission electron microscope (STEM) was used. The STEM probe size was 1 nm, and images were acquired at an image size of 1024 x 1024 pixels. Furthermore, bright-field images were acquired by adjusting the contrast on the Detector Control panel to 1425, brightness to 3750, and the contrast on the Image Control panel to 0.0, brightness to 0.5, and gamma to 1.00. The image magnification was 100,000x, and the image was acquired so that it covered approximately one-quarter to one-half of the circumference of the cross section of one toner particle, as shown in Figure 3. The obtained STEM image was analyzed using image processing software (Image J (available from https: / / imagej.nih.gov / ij / )), and the protrusions 64 containing the organosilicon polymer were measured. The measurement was performed on 30 protrusions 64 randomly selected from the STEM image. Whether the protrusions 64 contain an organosilicon polymer is confirmed by a combination of scanning electron microscopy (SEM) and elemental analysis using energy dispersive X-ray analysis (EDS). First, a line is drawn along the periphery of the toner base particle 63 using the line drawing tool (select Segmented line on the Straight tab). Areas where the organosilicon polymer protrusions 64 are embedded in the toner base particle 63 are connected smoothly as if they are not embedded. A horizontal image is created based on this line (select Selection on the Edit tab, change the line width to 500 pixels in the properties, then select Selection on the Edit tab and perform Straightener). The following measurements are performed on one of the protrusions 64 containing the organosilicon polymer in the horizontal image. The length of the line along the periphery where the protrusion 64 and the toner base particle 63 form a continuous interface is defined as the protrusion width w. The maximum length of the convex portion 64 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 64 to a line along the circumference in the line segment forming the convex diameter D is defined as the convex height H. In this embodiment, the measurement is performed on 30 arbitrarily selected convex portions 64, and the arithmetic mean of the measurement values ​​is defined as the number-average value of the convex height H. Here, the method of calculating the number-average value is not limited to the above.For example, it does not have to be 30, and it does not have to be the arithmetic average value. Furthermore, for example, the height of the lowest 80% of the convex portions of 30 nm or more may be defined as the number average value. This is because convex portions of less than 30 nm do not contribute much to determining the magnitude of adhesive force.

[0054] <Method for calculating the area ratio of bright areas in a 1.5 μm square backscattered electron image of the toner surface> The area ratio of the bright area is determined by observing the toner surface using a scanning electron microscope. A backscattered electron image of a 1.5 μm square area of ​​the toner surface is then obtained. The backscattered electron image is then binarized so that the organosilicon polymer portion of the image becomes the bright area, and the ratio of the bright area area of ​​the image to the total area of ​​the image is determined. If organic or inorganic fine particles are externally added to the toner, the organic or inorganic fine particles are removed by the method described below, and the sample is used.

[0055] 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 50 mL centrifuge tube, add 31 g of the above concentrated sucrose solution and 6 mL of Contaminon N (a 10% aqueous solution of a pH 7 neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, anionic surfactant, and organic builder, manufactured by Wako Pure Chemical Industries, Ltd.). Add 1.0 g of toner to the tube and break up any clumps with a spatula or similar. Shake the centrifuge tube in a shaker (AS-1N, sold by AS ONE Corporation) at 300 strokes per minute (spm) for 20 minutes.

[0056] After shaking, the solution is transferred to a glass tube (50 mL) for a swing rotor and centrifuged at 3,500 rpm for 30 minutes in a centrifuge (H-9R, manufactured by Kokusan Co., Ltd.). This operation separates the toner particles from the external additives. Visually confirm that the toner particles and aqueous solution have been sufficiently separated, and collect the toner particles that have separated to the top layer using a spatula or similar. The collected toner particles are filtered using a vacuum filter and then dried in a dryer for at least one hour to obtain a sample for measurement. This operation is repeated multiple times to ensure the required amount.

[0057] Furthermore, whether or not the protrusions 64 contain an organosilicon polymer is confirmed by combining this with elemental analysis using energy dispersive X-ray analysis (EDS), which will be described later.

[0058] The SEM equipment and observation conditions are as follows: Equipment used: ULTRA PLUS manufactured by Carl Zeiss Microscopy Co., Ltd. Accelerating voltage: 1.0 kV WD: 2.0 mm Aperture Size: 30.0 μm 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 on carbon tape (no deposition is performed) The accelerating voltage and EsB grid were 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 backscattered electrons. The observation field was selected to be near the vertex where the curvature of the toner particles is smallest. The bright areas in the backscattered electron image were confirmed to be derived from the organosilicon polymer by overlaying the backscattered electron image with an elemental mapping image obtained by energy dispersive X-ray analysis (EDS) using a scanning electron microscope (SEM).

[0059] The SEM / EDS equipment and observation conditions are as follows: Equipment used (SEM): ULTRA PLUS manufactured by Carl Zeiss Microscopy Co., Ltd. Equipment used (EDS): NORAN manufactured by Thermo Fisher Scientific Co., Ltd. System 7, Ultra Dry EDS Detector Accelerating voltage: 5.0 kV WD: 7.0 mm Aperture Size: 30.0 μm Detection signal: SE2 (secondary electrons) Magnification: 50,000x Mode: Spectral Imaging Pretreatment: Toner particles are scattered on carbon tape and platinum sputtered. 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 part of the mapping image matches the bright part of the backscattered electron image.

[0060] The area ratio of the bright area to the total area of ​​the backscattered electron image was calculated by analyzing the backscattered 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:

[0061] First, convert the backscattered electron image to 8-bit resolution using Type in the Image menu. Next, set the Median diameter to 2.0 pixels using Filters in the Process menu to reduce image noise. Estimate the image center, excluding the observation condition display area at the bottom of the backscattered electron image, and use the Rectangle Tool on the toolbar to select a 1.5 μm square area from the center of the backscattered electron image. 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, excluding the observation condition display area at the bottom of the backscattered electron image, and use the Rectangle Tool on the toolbar to select a 1.5 μm square area from the center of the backscattered electron image. Next, select Histogram from the Analyze menu. Read the Count value (corresponding to the total area of ​​the backscattered electron image) from the newly opened Histogram window. Also, click List to read the Count value when brightness is 0 (corresponding to the area of ​​the bright areas in the backscattered electron image). From this value, the area ratio of the bright area to the total area of ​​the backscattered electron image is calculated. The above procedure is carried out for 10 fields of view 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 parts in the backscattered electron image become bright areas.

[0062] <Method for identifying organosilicon polymers> The organosilicon polymer is identified by a combination of observation using a scanning electron microscope (SEM) and elemental analysis using energy dispersive X-ray analysis (EDS).

[0063] Toner particles were observed at a magnification of up to 50,000x using a Hitachi Ultra-High Resolution Field Emission Scanning Electron Microscope S-4800 (Hitachi High-Technologies Corporation). The surface was focused and observed. EDS analysis was performed on the particles present on the surface, and the presence or absence of an Si element peak determined whether the particles were organosilicon polymers. If the toner particle surface contained both organosilicon polymers and silica microparticles, the organosilicon polymer was identified by comparing the ratio of the Si and O elemental contents (atomic %) (Si / O ratio) with those of standard specimens. EDS analysis was performed on standard specimens of the organosilicon polymer and silica microparticles under the same conditions to obtain the respective Si and O elemental contents (atomic %). The Si / O ratio of the organosilicon polymer was designated A, and the Si / O ratio of the silica microparticles was designated B. Measurement conditions were selected such that A was significantly greater than B. Specifically, 10 measurements were performed on the standard specimen under the same conditions, and the arithmetic mean values ​​of A and B were obtained. Select measurement conditions that result in an average value of A / B > 1.1. If the Si / O ratio of the particles being identified is on the A side of [(A+B) / 2], the particles are determined to be organosilicon polymers.

[0064] 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.

[0065] <Method for measuring the number average particle size R of primary particles of external additives> The analysis is performed using a scanning electron microscope, "Hitachi Ultra-High Resolution Field Emission Scanning Electron Microscope S-4800" (Hitachi High-Technologies Corporation), in combination with elemental analysis using energy dispersive X-ray analysis (EDS).

[0066] The external additive particles are randomly photographed in a field of view magnified up to 50,000 times, using the elemental analysis method using EDS described above. 100 external additive particles are randomly selected from the photographed image, and the major axis of the primary particles of the target external additive particles is measured, and the arithmetic average value thereof is taken as the number-average particle size R. The observation magnification is adjusted appropriately depending on the size of the external additive particles.

[0067] <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 performed.

[0068] 1 g of toner is placed in a vial and dissolved in 31 g of chloroform, and dispersed in an ultrasonic homogenizer for 30 minutes to produce a dispersion. Ultrasonic treatment device: Ultrasonic homogenizer VP-050 (manufactured by Taitec Co., Ltd.) Microchip: Stepped 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 The vial was cooled with ice water to prevent the dispersion from heating, while ultrasonic waves were applied. The dispersion was transferred to a 50 mL glass tube for a swing rotor and centrifuged in a centrifuge (H-9R; manufactured by Kokusan Co., Ltd.) at 58.33 S-1 for 30 minutes. After centrifugation, the bottom layer of the glass tube contained heavy particles, such as silica microparticles. The upper layer of the chloroform solution containing the organosilicon polymer was collected, and the chloroform was removed by vacuum drying (40°C / 24 hours) to prepare a sample. Using the sample or the organosilicon polymer, the abundance ratio of the constituent compounds of the organosilicon polymer and the proportion of T3 unit structures represented by R-Si(O1 / 2)3 in the organosilicon polymer were measured and calculated by solid-state 29Si-NMR.

[0069] First, the hydrocarbon group represented by R is confirmed by 13C-NMR.

[0070] <13C-NMR (solid state) measurement conditions> Equipment: JEOL RESONANCE JNM-ECX500II Sample tube: 3.2 mm diameter Specimen: Sample or organosilicon polymer Measurement temperature: room temperature Pulse mode: CP / MAS Measurement nuclear frequency: 123.25MHz (13C) Reference substance: Adamantane (external standard: 29.5ppm) Sample rotation speed: 20kHz Contact time: 2ms Delay time: 2 seconds Number of times accumulated: 1024 In this method, the hydrocarbon group represented by R above can be confirmed based on the presence or absence of signals attributable to groups such as methyl (Si-CH3), ethyl (Si-C2H5), propyl (Si-C3H7), butyl (Si-C4H9), pentyl (Si-C5H11), hexyl (Si-C6H13), or phenyl (Si-C6H5-) bonded to silicon atoms.

[0071] On the other hand, in solid-state 29Si-NMR, peaks are detected in different shift regions depending on the structure of the functional groups that bond to the silicon in the constituent compounds of the organosilicon polymer. By identifying the position of each peak using a standard sample, the structure that bonds to the silicon can be identified. Furthermore, 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.

[0072] The specific measurement conditions for solid-state 29Si-NMR are as follows: Equipment: JNM-ECX5002 (JEOL RESONANCE) Temperature: room temperature Measurement method: DDMAS method 29Si 45° Sample tube: zirconia 3.2 mm diameter Sample: Filled in powder form into a test tube Sample rotation speed: 10kHz Relaxation delay: 180s Scan:2000 After the measurement, the peaks of the sample or organosilicon polymer, which are composed of multiple silane components with different substituents and bonding groups, are separated into the following X1, X2, X3, and X4 structures by curve fitting, and the peak areas of each are calculated.

[0073] The following X3 structure is a T3 unit structure. X1 structure: (Ri)(Rj)(Rk)SiO1 / 2 (A1) X2 structure: (Rg)(Rh)Si(O1 / 2)2 (A2) X3 structure: RmSi(O1 / 2)3 (A3) X4 structure: Si(O1 / 2)4 (A4)

[0074] [ka]

[0075] [ka]

[0076] [ka]

[0077] [ka]

[0078] In the formulae (A1), (A2), and (A3), Ri, Rj, Rk, Rg, Rh, and Rm represent silicon-bonded organic groups such as hydrocarbon groups having 1 to 6 carbon atoms, halogen atoms, hydroxy groups, acetoxy groups, or alkoxy groups. If the structure needs to be confirmed in more detail, it may be identified by the results of H-NMR measurement in addition to the results of C-NMR and Si-NMR measurement.

[0079] <Method for quantifying organosilicon polymer or silica fine particles contained in toner> The toner is dispersed in chloroform as described above, and then centrifuged to separate the external additives such as organosilicon polymer and silica fine particles based on the difference in specific gravity, obtaining samples, and determining the content of the external additives such as organosilicon polymer or silica fine particles.

[0080] The following describes an example in which the external additive is silica fine particles. Other fine particles can also be quantified in the same manner.

[0081] First, the pressed toner is measured using X-ray fluorescence, and the silicon content in the toner is determined using analytical procedures such as the calibration curve method or FP method. Next, the structure of each component compound that makes up the organosilicon polymer and silica microparticles is identified using solid-state 29Si-NMR and pyrolysis GC / MS, and the silicon content in the organosilicon polymer and silica microparticles is determined. The silicon content in the toner is calculated from the relationship between the silicon content in the toner determined by X-ray fluorescence and the silicon content in the organosilicon polymer and silica microparticles determined by solid-state 29Si-NMR and pyrolysis GC / MS.

[0082] <Method for measuring the adhesion rate of external additives such as organosilicon polymers or silica fine particles to toner base particles 63 or toner particles by water washing method> (Water washing process) 20 g of a 30% by weight aqueous solution of "Contaminon N" (a neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, anionic surfactant, and organic builder, with a pH of 7) was weighed into a 50 mL vial and mixed with 1 g of toner. The vial was then placed in a "KM Shaker" (model: V.SX) manufactured by Iwaki Sangyo Co., Ltd., and shaken for 120 seconds at a speed of 50.

[0083] Depending on the adhesion state of the organosilicon polymer or silica particles, the external additives, such as the organosilicon polymer or silica particles, may migrate from the toner base particles 63 or the toner particle surface into the dispersion liquid. The toner is then separated from the external additives, such as the organosilicon polymer or silica particles, that have migrated to the supernatant liquid using a centrifuge (H-9R; manufactured by Kokusan Co., Ltd.) (16.67S-1 for 5 minutes). The precipitated toner is dried to dryness by vacuum drying (40°C / 24 hours), and is then washed with water to produce the toner.

[0084] 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).

[0085] Furthermore, the measurement target is identified by elemental analysis using energy dispersive X-ray analysis (EDS).

[0086] 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.

[0087] The imaging conditions for the S-4800 are as follows:

[0088] (1) Sample preparation Apply a thin layer of conductive paste to a sample stage (aluminum sample stage 15 mm x 6 mm), then spray toner onto it. Then, use air to remove excess toner from the sample stage and allow it to dry thoroughly. Place the sample stage in the sample holder and adjust the sample stage height to 36 mm using the sample height gauge.

[0089] (2) Setting the S-4800 observation conditions Before measuring the coverage, perform elemental analysis using the energy dispersive X-ray spectroscopy (EDS) described above to distinguish between external additives such as organosilicon polymers or silica particles on the toner surface before measuring. 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. Confirm that the flushing intensity is 2 and execute it. Confirm that the emission current due to flushing is 20 to 40 μA. Insert the sample holder into the sample chamber of the S-4800 housing. Press [Origin] on the control panel to move the sample holder to the observation position.

[0090] Click the accelerating voltage display to open the HV setting dialog, and set the accelerating voltage to [1.1 kV] and the emission current to [20 μA]. In the [Basic] tab of the operation panel, set the signal selection to [SE], select [Upper (U)] and [+BSE] for the SE detector, and select [LA100] in the selection box to the right of [+BSE] to set the mode for observation using backscattered electron images. Also in the [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 [4.5 mm]. Press the [ON] button in the accelerating voltage display on the control panel to apply the accelerating voltage.

[0091] (3) Calculation of the number average particle size (D1) of the 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 achieve a certain degree of focus, then adjust the aperture alignment. 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 twice more to adjust the focus.

[0092] Thereafter, the particle diameters of 300 toner particles are measured to determine the number average particle diameter (D1). The particle diameter of each particle is the maximum diameter observed when the toner particles are observed.

[0093] (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) times.

[0094] Rotate the focus knob [COARSE] on the control panel until the image is in focus to some extent, then adjust the aperture alignment. Click [Align] on the control panel to display the alignment dialog and select [Beam]. Rotate the STIGMA / ALIGNMENT knobs (X, Y) on the control panel to move the displayed beam to the center of the concentric circles. Next, select [Aperture] and rotate the STIGMA / ALIGNMENT knobs (X, Y) one by one to stop the image movement or minimize its movement. Close the aperture dialog and use autofocus to adjust the focus. Then, set the magnification to 50,000 (50k)x and adjust the focus using the focus knob and STIGMA / ALIGNMENT knob as above, then use autofocus to adjust the focus again. Repeat this process to adjust the focus. Here, if the tilt angle of the observation surface is large, the accuracy of measuring the coverage rate tends to be low, so when adjusting the focus, select an object that can simultaneously bring the entire observation surface into focus, and then select an object with as little surface tilt as possible for analysis.

[0095] (5) Save image Adjust the brightness in ABC mode, take a photo at a size of 640 x 480 pixels, and save it. Use this image file for the following analysis. Take one photo for each toner particle to obtain an image of the toner particles.

[0096] (6) Image analysis The image obtained using the above method is binarized using the following analysis software to calculate the coverage. The image is then 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 a divided section contains external additives such as organosilicon polymers with particle sizes less than 30 nm and more than 300 nm, or silica microparticles with particle sizes less than 30 nm and more than 1200 nm, coverage calculations for that section are not performed.

[0097] In the image analysis software Image-Pro Plus 5.0, select "Count / Size" from "Measurement" on the toolbar, then "Options," and set the binarization conditions. Select 8 connectivity in the object extraction options and set smoothing to 0. In addition, do not select pre-sort, fill holes, or encompass lines, and set "Exclude boundaries" to "None." Select "Measurement Items" from "Measurement" on the toolbar and enter 2 to 107 in the area selection range.

[0098] The coverage rate is calculated by enclosing a square area. The area (C) of the area should be 24,000 to 26,000 pixels. Automatic binarization is performed using "Processing" - Binarization, and the total area (D) of areas free of external additives such as organosilicon polymers or silica microparticles is calculated.

[0099] The coverage rate can be calculated using the following formula from the area C of the square region and the total area D of the region free of external additives such as organosilicon polymers or silica fine particles.

[0100] Coverage rate (%)=100-(D / C×100) The arithmetic mean value of all the data obtained is taken as the coverage rate.

[0101] Then, the coverage of the toner before washing and the toner after washing are calculated, and the "adhesion rate" of the present invention is defined as [coverage of toner after washing] / [coverage of toner before washing]×100.

[0102] 4. Manufacturing methods for toner particles, external additives, and developers Next, examples of the production of the toner particles, external additive A, and developer of this embodiment will be described.

[0103] <Example of toner particle production> (Preparation of aqueous medium 1) A reaction vessel equipped with a stirrer, thermometer, and reflux condenser was charged with 650.0 parts of ion-exchanged water and 14.0 parts of sodium phosphate (Rasa Kogyo Co., Ltd., 12-hydrate), and the mixture was kept at 65°C for 1.0 hour while purging with nitrogen. A calcium chloride solution prepared by dissolving 9.2 parts of calcium chloride (dihydrate) 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, yielding aqueous medium 1.

[0104] (Preparation of Polymerizable Monomer Composition) Styrene: 60.0 parts CI Pigment Blue 15:3: 6.5 parts 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-mol 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 The material was added to the colorant dispersion and heated to 65° C., and then uniformly dissolved and dispersed at 500 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to prepare a polymerizable monomer composition.

[0105] (granulation process) The temperature of the aqueous medium 1 was adjusted to 70°C, and the polymerizable monomer composition was charged into 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.

[0106] (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, whereby distillation was carried out for 6 hours to distill off the unreacted polymerizable monomer, thereby obtaining a resin particle dispersion.

[0107] (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 of hydrochloric acid. This was heated with stirring until the temperature reached 40°C. 40.0 parts of methyltriethoxysilane, an organosilicon compound, was then added and stirred for 2 hours or more to carry out hydrolysis. The end point of the hydrolysis was confirmed by visual inspection when the oil and water were no longer separated and a single layer was formed, and the mixture was cooled to obtain a hydrolyzed solution of the organosilicon compound.

[0108] The temperature of the resin particle dispersion obtained above was adjusted to 55°C, and 25.0 parts of the hydrolyzed solution of the organosilicon compound (10.0 parts of the organosilicon compound) 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 solution of sodium bicarbonate. While continuing stirring at 55°C, the mixture was maintained for 1.0 hour (condensation reaction 1), after which the pH was adjusted to 9.5 with a 3.0% aqueous solution of sodium bicarbonate and maintained for a further 4.0 hours (condensation reaction 2), yielding a toner particle dispersion.

[0109] (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. The mixture was then left to stand for 1.0 hour with stirring. The mixture was then subjected to solid-liquid separation using a pressure filter to obtain a toner cake. The resulting toner cake was reslurried in ion-exchanged water to form a dispersion again, and then subjected to solid-liquid separation using the same filter to obtain a toner cake. The resulting toner cake was transferred to a 40°C thermostatic chamber, where it was dried and classified for 72 hours to obtain toner particles.

[0110] 5. Effects of this Example Next, an effect confirmation experiment conducted to confirm the effect of this embodiment will be described.

[0111] First, using the image forming apparatus 100, a 50 mm square process black toner image with a 320% toner coverage was formed on the intermediate transfer belt 10. Specifically, a 50 mm square toner image with an 80% toner coverage formed with yellow toner was primarily transferred onto the intermediate transfer belt 10. Subsequently, 50 mm square toner images with 80% toner coverage each formed with magenta, cyan, and black toner were sequentially superimposed and primarily transferred onto the intermediate transfer belt 10. Immediately after secondary transfer of the formed process black toner image was completed, the image forming apparatus 100 was stopped. At this time, the amount of secondary transfer residual toner in the process black toner image area remaining on the surface of the intermediate transfer belt 10 was confirmed. In this example, a monochrome solid black image (FF gradation) was assumed to have a toner coverage of 100%.

[0112] The amount of secondary transfer residual toner was measured using the following method. First, the secondary transfer residual toner of the process black toner image on the intermediate transfer belt 10 was collected on the filter by vacuuming it through a filter with a mesh finer than the toner. Then, the weight of the filter was measured, and the increase from the initial weight was taken as the amount of secondary transfer residual toner. The amount of secondary transfer residual toner was measured when the value was 0.01 mg / cm. 2 If the value is less than 0.05 mg / cm, it can be determined that there is almost no residual toner remaining after secondary transfer. 2If the value was 0.05 mg / cm or less, no visible image defects such as a decrease in image density occurred. 2 More than 0.10 mg / cm 2 If the value is less than 0.10 mg / cm, a visually noticeable image defect such as a slight decrease in image density occurs, but this is at a level that does not pose a problem for practical images. 2 If the amount is larger, a visually noticeable image defect occurs, such as a decrease in image density.

[0113] The amount of residual toner after secondary transfer described above was checked in two configurations: one where the durability state of all color toners was at the initial stage (0 to 50 printed pages), and one where only yellow toner was used after printing 5,000 pages, and cyan, magenta, and black toners were at the initial stage.

[0114] Finally, the results of an experiment to confirm the effectiveness of this embodiment are shown.

[0115] (Example 1-a) The number average values ​​H1 and H2 of the convex height H of the toner used in Example 1-a are as follows: The yellow toner of the first image forming station a, the magenta toner of the second image forming station b, and the cyan toner of the third image forming station c were 60 nm, and the black toner of the fourth image forming station d was 15 nm. The measurement results of the amount of secondary transfer residual toner are shown in Table 1.

[0116] (Example 1-b) The same as Example 1-a except that the convex height H of the black toner was set to 15 nm. Table 1 shows the measurement results of the amount of secondary transfer residual toner.

[0117] (Example 1-c) The same as Example 1-a except that the convex height H of the black toner was set to 55 nm. Table 1 shows the measurement results of the amount of secondary transfer residual toner.

[0118] (Example 1-d) The same as Example 1-a except that the fixing rate of the yellow toner was set to 85%. Table 1 shows the measurement results of the amount of residual toner after secondary transfer.

[0119] (Comparative Example 1) The same as Example 1-a except that the convex height H of the black toner was set to 60 nm. Table 1 shows the measurement results of the amount of secondary transfer residual toner.

[0120] (Comparative Example 2) The same as Example 1-a except that the fixing rate of the yellow toner was set to 62%. Table 1 shows the measurement results of the amount of secondary transfer residual toner.

[0121] [Table 1]

[0122] As shown in Table 1, in Examples 1-a to 1-d having the above configuration, the secondary transfer performance can be maintained at a good level regardless of the durability state of the toner.

[0123] In particular, Examples 1-a and 1-b were able to maintain high secondary transferability throughout the test. This was because the number average value H2 of the convex height H of the black toner disposed downstream of the yellow image forming unit was smaller than the number average value H1 of the convex height H of the yellow toner disposed upstream of the black image forming unit. In other words, this was achieved by making the number average value H1 of the convex height H of the toner particles that are primarily transferred larger than the number average value H2 of the convex height H of the toner particles that are primarily transferred last. Furthermore, by setting the yellow toner adhesion rate at 98%, the convex portions of the toner particles were maintained on the toner particle surfaces throughout the test, thereby maintaining secondary transferability.

[0124] In Example 1-c, the number average value H2 of the convex height H of the black toner was set smaller than the number average value H1 of the convex height H of the yellow toner. Therefore, the difference was small, and the secondary transfer performance was slightly inferior to Examples 1-a and 1-b, but it was possible to achieve image output that was satisfactory for practical use.

[0125] In Example 1-d, the yellow toner adhesion rate was set to 85%, so that the protrusions of the toner particles were maintained on the toner particle surface throughout the durability test. However, compared with Examples 1-a and 1-b, the adhesion rate was slightly lower, and therefore the secondary transfer performance was slightly worse. However, it was possible to achieve image output that was satisfactory for practical use.

[0126] On the other hand, in Comparative Example 1, the number average value H1 of the convex height H of the yellow toner and the number average value H2 of the convex height H of the black toner were set to be the same. As a result, the secondary transfer performance was worse than in Example 1, resulting in image defects. In addition, in Comparative Example 2, the fixing rate of the yellow toner was set to 62%, so the convex portions of the toner particles could not be maintained on the toner particle surfaces throughout the durability test, and the secondary transfer performance after the durability test was worsened.

[0127] The configuration of the image forming apparatus according to the first embodiment is as follows.

[0128] The image forming unit has a rotatable first photosensitive drum 1 and a rotatable first developing roller 41 that carries a first developer composed of first toner particles and protrusions 64 made of organic silicon formed on the surfaces of the first toner particles. The first developing roller 41 contacts the first photosensitive drum 1 to form a first developing unit, and supplies the first developer to form a first developer image on the surface of the first photosensitive drum 1 in the first developing unit.

[0129] The second image forming unit has a rotatable second photosensitive drum 1 and a rotatable second developing roller 41 that carries a second developer composed of second toner particles and protrusions 64 made of organic silicon formed on the surfaces of the second toner particles. The second developing roller 41 contacts the second photosensitive drum 1 to form a second developing unit, and supplies the second developer to form a second developer image on the surface of the second photosensitive drum 1 in the second developing unit.

[0130] The intermediate transfer body 10 contacts the first photosensitive drum 1 to form a first contact portion and contacts the second photosensitive drum 1 to form a second contact portion, and has the intermediate transfer body 10 to which a first developer image is transferred at the first contact portion and a second developer image is transferred at the second contact portion.

[0131] The intermediate transfer member 10 contacts the secondary transfer roller 15 to form a transfer portion, and the secondary transfer roller 15 transfers the first developer image and the second developer image formed on the surface of the intermediate transfer member 10 to the recording material P in the transfer portion.

[0132] The surface of the intermediate transfer body 10 is movable, and the first image forming unit and the second image forming unit are arranged so that the first contact portion is formed downstream of the transfer unit and upstream of the second contact portion in the direction of movement of the surface of the intermediate transfer body 10. The height of the convex portions 64 formed in the second developer is smaller than the height of the convex portions 64 formed in the first developer.

[0133] The height of the protrusions 64 is expressed as the height from the surface of the toner particle to the apex of the protrusion 64. The height of the protrusions 64 is defined as follows using a cross-sectional image of the toner particle observed with a scanning transmission electron microscope. When a line is drawn along the circumferential surface of the surface of the toner particle, the line along the circumferential surface is used as a reference and converted into a horizontal image. Then, the maximum length of the protrusions 64 in the direction normal to the length of the line along the circumferential surface in the horizontal image at the portion where the protrusions 64 and the toner particles form a continuous interface is defined as the height of the protrusions 64. The height of the protrusions 64 is then calculated from the average number value of the protrusions 64 formed on the toner particle.

[0134] By making the number average value H1 of the convex height H of the toner that is first primarily transferred larger than the number average value H2 of the convex height H of the toner that is last primarily transferred, and by making the adhesion rate of the toner that is first primarily transferred 85% or more, it was possible to maintain good secondary transferability for a long period of time. [Example]

[0135] In this embodiment, the toner in the downstream image forming stations has the same configuration as in Example 1, except that it does not have convex features containing an organosilicon polymer on the surface of the toner particles and only contains an external additive. Specifically, only the black toner in the fourth image forming station d does not have convex features containing an organosilicon polymer on the surface of the toner particles and contains silica fine particles as an external additive. The spacer effect during transfer of toner that does not have convex features and contains an external additive is affected by the number-average particle size R of the external additive's primary particles. This is because, during transfer, secondary aggregates of the external additive interposed between the transfer member and the toner particle surface are broken down into primary particles by the transfer pressure. Therefore, when considering the secondary transfer of two or more colors of toner, the number-average particle size H1 of the convex height H of the toner first transferred onto the intermediate transfer belt 10 is larger than the number-average particle size R of the external additive's primary particles in the toner that is last transferred, preferably by 5 nm or more. More preferably, it is larger by 10 nm or more. In the configuration of this embodiment, the ratio of the number average value H1 of the convex height H of the toner particles that are first primarily transferred to the number average particle diameter R of the external additive particles of the toner particles that are last primarily transferred is preferably 0≦R / H1<1, and more preferably 0≦R / H1<0.92. Even more preferably, it is 0≦R / H1<0.83. As a result, as in the first embodiment, the adhesive force between the toner and the intermediate transfer belt 10 is sufficiently smaller than the adhesive force between the toner and the recording material P, improving the secondary transferability when two or more colors of toner on the intermediate transfer belt 10 are secondary transferred simultaneously to the recording material P.

[0136] In this example, the same effect confirmation experiment as in Example 1 was carried out, and the results are shown below.

[0137] (Example 2-a) The number average value H1 of the convex height H of the toner used in Example 2-a is as follows: The yellow toner of the first image forming station a, the magenta toner of the second image forming station b, and the cyan toner of the third image forming station c were 60 nm, and the black toner of the fourth image forming station d was 15 nm. The measurement results of the amount of secondary transfer residual toner are shown in Table 2.

[0138] (Example 2-b) The same as Example 1-a, except that the number average particle diameter R of the primary particles of the external additive of the black toner was set to 15 nm. Table 2 shows the measurement results of the amount of secondary transfer residual toner.

[0139] (Example 2-c) The same as Example 1-a, except that the number average particle diameter R of the primary particles of the external additive of the black toner was set to 55 nm. Table 2 shows the measurement results of the amount of secondary transfer residual toner.

[0140] (Example 2-d) The same as Example 1-a except that the fixing rate of the yellow toner was set to 85%. Table 2 shows the measurement results of the amount of residual toner after secondary transfer.

[0141] (Comparative Example 3) The same as Example 1-a, except that the number average particle diameter R of the primary particles of the external additive of the black toner was set to 60 nm. Table 2 shows the measurement results of the amount of secondary transfer residual toner.

[0142] Comparative Example 4 The same as Example 1-a except that the fixing rate of the yellow toner was set to 62%. Table 2 shows the measurement results of the amount of residual toner after secondary transfer.

[0143] [Table 2]

[0144] As shown in Table 2, in Examples 2-a to 2-d having the above configuration, the secondary transfer performance can be maintained at a good level regardless of the durability state of the toner.

[0145] In particular, Examples 2-a and 2-b were able to maintain high secondary transferability throughout the test. This was because the number-average particle size R of the primary particles of the external additive of the black toner disposed downstream of the yellow image forming unit was smaller than the number-average particle size H1 of the convex height H of the yellow toner disposed upstream of the black image forming unit. In other words, this was achieved by making the number-average particle size H1 of the convex height H of the toner to be primarily transferred larger than the number-average particle size R of the primary particles of the external additive of the toner to be primarily transferred last. Furthermore, by setting the yellow toner adhesion rate at 98%, the convex portions of the toner particles were maintained on the toner particle surface throughout the test, thereby maintaining secondary transferability.

[0146] In Example 2-c, the number average particle diameter R of the primary particles of the external additive of the black toner was set smaller than the number average value H1 of the convex height H of the yellow toner. Therefore, the difference was small, and although the secondary transfer performance was slightly inferior to Examples 2-a and 2-b, it was possible to achieve image output that had no practical problems.

[0147] In Example 2-d, the yellow toner adhesion rate was set to 85%, so that the protrusions of the toner particles were maintained on the toner particle surface throughout the durability test. However, compared to Examples 2-a and 2-b, the adhesion rate was slightly lower, and therefore the secondary transfer performance was slightly worse. However, it was possible to achieve image output that was satisfactory for practical use.

[0148] On the other hand, in Comparative Example 3, the number average value H1 of the convex height H of the yellow toner and the number average particle size R of the primary particles of the external additive of the black toner were set to the same value. As a result, the secondary transfer performance was worse than in Example 2, resulting in image defects. Also, in Comparative Example 4, the fixing rate of the yellow toner was set to 62%, so the convex portions of the toner particles could not be maintained on the toner particle surface throughout the durability test, and the secondary transfer performance after the durability test was worsened.

[0149] The configuration of the image forming apparatus according to the second embodiment has the following features.

[0150] The image forming unit has a rotatable first photosensitive drum 1 and a rotatable first developing roller 41 that carries a first developer composed of first toner particles and protrusions 64 made of organic silicon formed on the surfaces of the first toner particles. The first developing roller 41 contacts the first photosensitive drum 1 to form a first developing unit, and supplies the first developer to form a first developer image on the surface of the first photosensitive drum 1 in the first developing unit.

[0151] The second image forming unit has a rotatable second photosensitive drum 1 and a rotatable second developing roller 41 that carries a second developer that does not have second toner particles and protrusions 64 made of organic silicon formed on the surfaces of the second toner particles. The second developing roller 41 contacts the second photosensitive drum 1 to form a second developing unit, and supplies the second developer to form a second developer image on the surface of the second photosensitive drum 1 in the second developing unit.

[0152] The intermediate transfer body 10 contacts the first photosensitive drum 1 to form a first contact portion and contacts the second photosensitive drum 1 to form a second contact portion, and has the intermediate transfer body 10 to which a first developer image is transferred at the first contact portion and a second developer image is transferred at the second contact portion.

[0153] The intermediate transfer member 10 contacts the secondary transfer roller 15 to form a transfer portion, and the secondary transfer roller 15 transfers the first developer image and the second developer image formed on the surface of the intermediate transfer member 10 to the recording material P in the transfer portion.

[0154] The surface of the intermediate transfer body 10 is movable, and the first image forming unit and the second image forming unit are configured to be arranged so that the first contact portion is formed downstream of the transfer unit and upstream of the second contact portion in the direction of movement of the surface of the intermediate transfer body 10.

[0155] The number average particle size H1 of the convex height H of the toner that is primarily transferred first is made larger than the number average particle size R of the primary particles of the external additive of the toner that is primarily transferred last. In addition, by making the adhesion rate of the toner that is primarily transferred first 85% or more, it was possible to maintain good secondary transferability for a long period of time.

[0156] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the above-described embodiments.

[0157] In the above embodiment, the relationship between the convex heights of the toner in the first image station a and the toner in the fourth image station d was described. However, the combination of image stations is not limited to this embodiment. For example, to improve the secondary transfer performance of an image in which two colors, the toner in the second image station b and the toner in the third image station c, are superimposed, the relationship between the convex heights of the toner in these image stations may be configured as in the present invention. However, since the toner in the fourth image station d, which is the most downstream, is positioned on the recording material P side when superimposed with the toner from the other stations and then collectively secondary transferred, it is preferable that the toner in the fourth image station d has the highest adhesive strength of all the toners in the image stations. Furthermore, since the toner in the first image station a, which is the most upstream, is positioned on the intermediate transfer belt 10 side when superimposed with the toner from the other stations and then collectively secondary transferred, it is preferable that the toner in the first image station a has the lowest adhesive strength of all the toners in the image stations.

[0158] The order of toner colors in the image forming stations is not limited to that in this embodiment. During the secondary transfer of multi-colors, the toner in the downstream station comes into direct contact with the recording material P, and is therefore less likely to become residual toner after secondary transfer. For this reason, it is more preferable to arrange black toner, which has good visibility, in the most downstream image forming station, as in this embodiment, where it is less likely to become residual toner after secondary transfer, in order to maximize the effects of the present invention.

[0159] In this embodiment, the secondary transfer residual toner is scraped off within the intermediate transfer belt cleaning device 17, but the present invention is not limited to this. For example, the secondary transfer residual toner may be reversed in polarity using a brush or the like to which a voltage is applied, which is provided in the intermediate transfer belt cleaning device 17, and then collected by cleaning devices 5a, b, c, d, etc. In this configuration, if the amount of secondary transfer residual toner is large, it may not be possible to reverse the polarity of all the secondary transfer residual toner. The toner whose polarity is not reversed may not be collected by cleaning devices 5a, b, c, d, etc., and may be ejected onto the subsequent recording material P, resulting in a defective image. Because the present invention can improve this image defect, a configuration in which the polarity of the secondary transfer residual toner is reversed using a brush or the like to which a voltage is applied, which is provided in the intermediate transfer belt cleaning device 17, can more effectively demonstrate the effects of the present invention and is therefore more preferable.

[0160] Although the present embodiment employs a tandem-type configuration with image forming stations a to d, the present invention is not limited to this configuration. For example, as in the image forming apparatus 200 shown in FIG. 6, developing devices 4a, 4b, 4c, and 4d, each containing four color toners, may be sequentially moved to a developing position where they face and contact the photosensitive drum 1 of a common image station. In this manner, multiple toners may be layered on the intermediate transfer belt 10 by performing development and primary transfer. The configuration shown in FIG. 6 includes a rotatable photosensitive drum 1 and a rotatable first developing roller 41 carrying a first developer composed of first toner particles and protrusions made of organosilicon formed on the surface of the first toner particles. The developing roller 41 is included in a first developing unit 4 that contacts the photosensitive drum 1 to form a first developing section and supplies the first developer to form a first developer image on the surface of the photosensitive drum 1 in the first developing section. The second development roller 41 is rotatable and carries a second developer composed of second toner particles and protrusions made of organosilicon formed on the surface of the second toner particles. The development roller 41 contacts the photosensitive drum 1 to form a second development section and is included in a second development unit 4 that supplies the second developer to form a second developer image on the surface of the photosensitive drum 1 in the second development section. The second development roller 41 also includes an intermediate transfer body 10 that contacts the photosensitive drum 1 to form a contact section, at which the second developer image is transferred after the first developer image. The second development roller 41 also includes a secondary transfer roller 15 that contacts the intermediate transfer body 10 to form a transfer section and transfers the first and second developer images formed on the surface of the intermediate transfer body 10 to a recording material in the transfer section. The height of the protrusions formed on the second developer is smaller than the height of the protrusions formed on the first developer. As in the second embodiment, the second toner particles and the second toner particles do not necessarily need to have protrusions made of organosilicon formed on their surfaces. Therefore, as long as the developing devices 4a, 4b, 4c, and 4d, each having four colors of toner, are configured to face and contact the photosensitive drum 1 of a common image station, it is not necessary to configure the developing devices 4a, 4b, 4c, and 4d to move sequentially as in the image forming apparatus 200 of Figure 6. [Explanation of symbols]

[0161] 1 Photosensitive drum 10 Intermediate transfer belt 15 Secondary transfer roller 41 Developing roller 100 Image forming device a~d Image forming station P recording material

Claims

1. a first image forming section including a rotatable first image carrier and a rotatable first developer carrier that carries a first developer composed of first toner particles and protrusions made of organosilicon formed on the surfaces of the first toner particles, the first developer carrier coming into contact with the first image carrier to form a first developing section, and that supplies the first developer to form a first developer image on the surface of the first image carrier in the first developing section; a second image forming section including a rotatable second image carrier and a rotatable second developer carrier that carries a second developer composed of second toner particles and protrusions made of organosilicon formed on the surfaces of the second toner particles, the second developer carrier coming into contact with the second image carrier to form a second developing section and supplying the second developer to form a second developer image on the surface of the second image carrier in the second developing section; an intermediate transfer member that comes into contact with the first image carrier to form a first contact portion and that comes into contact with the second image carrier to form a second contact portion, the first developer image being transferred at the first contact portion and the second developer image being transferred at the second contact portion; a transfer member that contacts the intermediate transfer body to form a transfer section, and transfers the first developer image and the second developer image formed on the surface of the intermediate transfer body to a recording material at the transfer section; a surface of the intermediate transfer body is movable, and the first image forming unit and the second image forming unit are arranged so that the first contact portion is formed downstream of the transfer unit and upstream of the second contact portion in a moving direction of the surface of the intermediate transfer body; An image forming apparatus characterized in that the height of the convex portions formed in the second developer is smaller than the height of the convex portions formed in the first developer, and the adhesion rate of the organosilicon formed on the surface of the first toner particles in the first developer to the first toner particles is 85% or more.

2. 2. The image forming apparatus according to claim 1, wherein the height of the convex portion is expressed as a height from the surface of the toner particle to the apex of the convex portion.

3. The image forming apparatus according to claim 1 or 2, characterized in that the height of the convex portion is determined by converting a cross-sectional image of the toner particle observed using a scanning transmission electron microscope into a horizontal image based on a line drawn along the circumferential surface of the surface of the toner particle, and determining the maximum length of the convex portion in the direction normal to the length of the line along the circumferential surface in the portion of the horizontal image where the convex portion and the toner particle form a continuous interface.

4. 4. The image forming apparatus according to claim 1, wherein the height of the convex portion is calculated from an average value of the number of the convex portions formed on the toner particle.

5. the number average value of the heights of the convex portions of the first developer−the number average value of the heights of the convex portions of the second developer≧10 nm 5. The image forming apparatus according to claim 4, wherein the following relationship is satisfied:

6. a first image forming section including a rotatable first image carrier and a rotatable first developer carrier that carries a first developer composed of first toner particles and protrusions made of organosilicon formed on the surfaces of the first toner particles, the first developer carrier coming into contact with the first image carrier to form a first developing section, and that supplies the first developer to form a first developer image on the surface of the first image carrier in the first developing section; a second image forming section including a rotatable second image carrier, and a rotatable second developer carrier that carries a second developer that does not have second toner particles and convex portions made of organosilicon formed on the surfaces of the second toner particles, and that has an external additive externally added to the surfaces of the second toner particles, and that comes into contact with the second image carrier to form a second developing section, and that supplies the second developer to form a second developer image on the surface of the second image carrier in the second developing section; an intermediate transfer member that comes into contact with the first image carrier to form a first contact portion and that comes into contact with the second image carrier to form a second contact portion, the first developer image being transferred at the first contact portion and the second developer image being transferred at the second contact portion; a transfer member that contacts the intermediate transfer body to form a transfer section, and transfers the first developer image and the second developer image formed on the surface of the intermediate transfer body to a recording material at the transfer section; a surface of the intermediate transfer body is movable, and the first image forming unit and the second image forming unit are arranged so that the first contact portion is formed downstream of the transfer unit and upstream of the second contact portion in a moving direction of the surface of the intermediate transfer body; an image forming apparatus characterized in that the height of the convex portions of the first developer is larger than the average particle size of the external additive of the second developer, and the adhesion rate of the organosilicon formed on the surface of the first toner particles in the first developer to the first toner particles is 85% or more.

7. 7. The image forming apparatus according to claim 6, wherein the height of the convex portion is expressed as a height from the surface of the toner particle to the apex of the convex portion.

8. The image forming apparatus according to claim 6 or 7, characterized in that the height of the convex portion is determined by converting a cross-sectional image of the toner particle observed using a scanning transmission electron microscope into a horizontal image based on a line drawn along the circumferential surface of the surface of the toner particle, and determining the maximum length of the convex portion in the direction normal to the length of the line along the circumferential surface in the portion of the horizontal image where the convex portion and the toner particle form a continuous interface.

9. 9. The image forming apparatus according to claim 6, wherein the height of the convex portion is calculated from an average value of the number of the convex portions formed on the toner particle.

10. the number average value of the heights of the convex portions of the first developer−the number average particle diameter of the external additive of the second developer≧10 nm 10. The image forming apparatus according to claim 9, wherein the following relationship is satisfied:

11. a rotatable image carrier; a first developing unit including a rotatable first developer carrier that carries a first developer composed of first toner particles and protrusions made of organosilicon formed on the surfaces of the first toner particles, the first developer carrier contacting the image carrier to form a first developing section and supplying the first developer to form a first developer image on the surface of the image carrier in the first developing section; a second developing unit including a rotatable second developer carrier that carries a second developer composed of second toner particles and protrusions made of organosilicon formed on the surfaces of the second toner particles, the second developer carrier contacting the image carrier to form a second developing section and supplying the second developer to form a second developer image on the surface of the image carrier in the second developing section; an intermediate transfer member that contacts the image carrier to form a contact portion, and onto which the second developer image is transferred after the first developer image is transferred at the contact portion; a transfer member that contacts the intermediate transfer body to form a transfer section, and transfers the first developer image and the second developer image formed on the surface of the intermediate transfer body to a recording material at the transfer section; An image forming apparatus characterized in that the height of the convex portions formed in the second developer is smaller than the height of the convex portions formed in the first developer, and the adhesion rate of the organosilicon formed on the surface of the first toner particles in the first developer to the first toner particles is 85% or more.

12. a rotatable image carrier; a first developing unit including a rotatable first developer carrier that carries a first developer composed of first toner particles and protrusions made of organosilicon formed on the surfaces of the first toner particles, the first developer carrier contacting the image carrier to form a first developing section and supplying the first developer to form a first developer image on the surface of the image carrier in the first developing section; a second developing unit including: a rotatable second developer carrier that carries a second developer that does not have second toner particles and convex portions made of organosilicon formed on the surfaces of the second toner particles, and that has an external additive externally added to the surfaces of the second toner particles, the second developer carrier coming into contact with the image carrier to form a second developing section, and that supplies the second developer to form a second developer image on the surface of the image carrier in the second developing section; an intermediate transfer member that contacts the image carrier to form a contact portion, and onto which the second developer image is transferred after the first developer image is transferred at the contact portion; a transfer member that contacts the intermediate transfer body to form a transfer section, and transfers the first developer image and the second developer image formed on the surface of the intermediate transfer body to a recording material at the transfer section; an image forming apparatus characterized in that the height of the convex portions of the first developer is larger than the average particle size of the external additive of the second developer, and the adhesion rate of the organosilicon formed on the surface of the first toner particles in the first developer to the first toner particles is 85% or more.

13. 13. The image forming apparatus according to claim 1, wherein the convex portions have a surface containing an organosilicon polymer represented by the following formula (1): R-Si(O １／２ ) ３ (1) (The above R represents a hydrocarbon group having 1 to 6 carbon atoms.)

Images