JP7516149B2 - Image forming device - Google Patents

Description

The present invention relates to a color image forming apparatus that uses an electrophotographic process, etc.

Image forming devices that use an intermediate transfer body have been known for some time, including copying machines and laser printers.

In this image forming apparatus, in the primary transfer process, a toner image formed on the surface of a photosensitive drum serving as an image carrier is transferred onto an intermediate transfer body by applying a voltage from a voltage source to a primary transfer member arranged opposite the photosensitive drum. This primary transfer process is then repeated for multiple color toner images, forming multiple color toner images on the surface of the intermediate transfer body. Then, in the secondary transfer process, a voltage is applied to the secondary transfer member to transfer the multiple color toner images formed on the surface of the intermediate transfer body all at once onto the surface of a recording material such as paper. The collectively transferred toner images are then permanently fixed to the recording material by a fixing means, forming a color image.

In the image forming device described in Patent Document 1, the intermediate transfer belt as an intermediate transfer body contacts the photosensitive drum to form a primary transfer nip, where the toner image is transferred from the photosensitive drum to the intermediate transfer belt.

It is known that in the primary transfer nip area, if the peripheral speeds of the photosensitive drum and the intermediate transfer belt are made completely the same, the transfer efficiency decreases, and the central parts of the toner images, such as letters and lines, become blank, resulting in so-called hollows. Therefore, in Patent Document 1, a peripheral speed difference is actively imparted between the photosensitive drum and the intermediate transfer belt, thereby increasing the primary transfer efficiency and suppressing the occurrence of hollows, thereby improving image quality.

However, in the above image forming device, when the toner image formed on the photosensitive drum surface is primarily transferred to the intermediate transfer belt surface, sudden rotational fluctuations in the photosensitive drum may occur. This may cause uneven exposure in the laser exposure, and subsequently cause image streaks in the toner image formed on the photosensitive drum surface. This is because, when there is no toner in the primary transfer nip and the leading edge of the toner image developed on the photosensitive drum enters the primary transfer nip, the frictional force acting on the photosensitive drum surface by the intermediate transfer belt surface is suddenly reduced.

In response to this, it is known that by forming a small dot-type toner image using a yellow or other toner on the photosensitive drum in addition to the toner image of the image pattern, it is possible to suppress the rotational fluctuation of the photosensitive drum and intermediate transfer belt and prevent various image defects. For example, in the image forming device described in Patent Document 2, a small dot toner image is uniformly distributed and formed on the photosensitive drum, thereby preventing color shifts from occurring in the toner image that is primarily transferred onto the intermediate transfer belt.

JP 2016-1268 A Japanese Patent Application Publication No. 11-52758

However, the image forming apparatus described in Patent Document 2 has the following problems. When a dot toner image is added to print on recording materials such as highly white paper, coated paper, and glossy paper, the added dot toner image stands out on the recording material, making the recording material look yellowish overall, and reducing image quality. This is because recording materials such as highly white paper, coated paper, and glossy paper have high surface smoothness and good secondary transferability. The yellow dot toner image, which is primarily transferred onto the intermediate transfer belt and makes the surfaces of the photosensitive drum and intermediate transfer belt slippery against each other, reducing friction, is faithfully reproduced on the recording material.

The present invention aims to prevent image defects by suppressing rotational fluctuations of the photosensitive drum and intermediate transfer belt without adding dot toner images.

Therefore, the image forming apparatus according to the present invention includes a rotatable image carrier, a developer container for accommodating a developer composed of toner particles having toner base particles and contact portions formed on the surfaces of the toner base particles and in surface contact with the surfaces of the toner base particles, and fine particles as external additives in contact with the surfaces of the contact portions , a developer carrier that contacts the image carrier to form a development portion and supplies the developer to the surface of the image carrier in the development portion, an intermediate transfer body that contacts the image carrier to form a transfer portion and onto which a toner image formed by the developer supplied to the surface of the image carrier is transferred in the transfer portion, and a moving speed of the surface of the image carrier and a developer container for accommodating a developer composed of toner particles having toner base particles and contact portions formed on the surfaces of the toner base particles and in contact with the surfaces of the contact portions, and a drive unit which drives the image carrier and the intermediate transfer body so as to have a speed difference between the moving speed of the surface of the intermediate transfer body and the pressing force with which the developer carrier is pressed against the image carrier, and the total number of the microparticles present between the contact portion and the image carrier in the development unit is N, the relationship between an adhesive force Ft formed between the microparticle and the contact portion , which is measured when the microparticle is pressed against the contact portion with F/N, which is the pressing force per unit microparticle, and an adhesive force Fdr formed between the microparticle and the image carrier, which is measured when the microparticle is pressed against the image carrier with F/N, satisfies Ft≦Fdr.

As described above, according to the present invention, it is possible to suppress the occurrence of image defects by suppressing the rotational fluctuations of the photosensitive drum and intermediate transfer belt without adding dot toner images.

FIG. 1 is a diagram illustrating an image forming apparatus according to a first embodiment. FIG. 2 is a diagram illustrating a primary transfer portion in the first embodiment. FIG. 2 is a control block diagram according to the first embodiment. 5A to 5C are diagrams illustrating the behavior of toner in a drum nip portion in the first embodiment. 6 is a graph illustrating the relationship between the peripheral speed difference and the primary transfer residual toner amount in the first embodiment. 5A and 5B are diagrams illustrating the supply of fine particles to a photosensitive drum in the first embodiment. 5A to 5C are diagrams illustrating the state of fine particles during primary transfer in the first embodiment. 4 is a timing chart illustrating an image forming operation in the first embodiment. FIG. 2 is a schematic diagram of a toner surface in Example 1. 3 is a schematic diagram of a convex shape of a toner surface in Example 1. FIG. 3 is a schematic diagram of a convex shape of a toner surface in Example 1. FIG. 3 is a schematic diagram of a convex shape of a toner surface in Example 1. FIG. 5A and 5B are diagrams illustrating the state of toner and fine particles in the first embodiment. FIG. 11 is a diagram illustrating an image forming apparatus according to a second embodiment. FIG. 11 is a diagram illustrating an image forming apparatus according to a third embodiment. FIG. 11 is a diagram illustrating a primary transfer portion in a third embodiment.

The following describes in detail preferred embodiments of the present invention by way of example, with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the following embodiments should be modified as appropriate depending on the configuration and various conditions of the device to which the present invention is applied. Therefore, unless otherwise specified, it is not intended to limit the scope of the present invention to these alone.

Figure 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 Figure 1. The image forming apparatus of this embodiment is a so-called tandem type printer equipped with image forming stations a to d. 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). The configuration of each image forming station is the same except for the color of toner they contain, and the following description will be given using the first image forming station a. Furthermore, hereinafter, unless a distinction is particularly required, a to d in Y, M, C, and K will be omitted and a general description will be given.

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

When the control unit 200, such as a controller, receives an image signal, the image forming operation is started, and the photosensitive drum 1a is rotated. During the rotation process, the photosensitive drum 1a is uniformly charged to a predetermined potential with a predetermined polarity (negative polarity in this embodiment) by the charging roller 2a, and is exposed to light by the exposure unit 3a according to the image signal. This forms an electrostatic latent image corresponding to the yellow component image 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.

The photosensitive drum 1a is an image carrier that rotates in the direction of the arrow at a peripheral speed (process speed) of 100 mm/sec and carries a toner image. The photosensitive drum 1a is made of a φ20 mm aluminum tube on which a photosensitive layer and a surface layer are provided. The surface layer is a thin film layer made of polyarylate and has a thickness of 20 μm.

The charging roller 2a, which serves as a charging member, is in contact with the surface of the photosensitive drum 1a at the charging portion with a certain pressure contact force, and rotates relative to the photosensitive drum 1a due to friction with the surface of the photosensitive drum 1a. A DC voltage of -1100V is applied to the rotating shaft of the charging roller 2a from the charging high-voltage power supply 120 in response to the image formation operation. At this time, the surface potential of the photosensitive drum 1a was measured to be about -500V using a Trek Model 344 surface potential meter. The surface potential of the photosensitive drum 1a at this time, -500V, is the surface potential of the photosensitive drum 1 when no image is being formed, and is the dark potential (Vd) where no toner image is developed.

The exposure unit 3a is equipped with a laser driver, a laser diode, a polygon mirror, an optical lens system, etc. It is an exposure means that irradiates laser light based on image information input from a host computer (not shown) to form an electrostatic latent image on the uniformly charged surface of the photosensitive drum 1a. In this embodiment, the exposure amount is adjusted so that the image formation potential Vl of the photosensitive drum 1 surface after exposure with the maximum light amount of the exposure unit 3a is -100V. The image formation potential is also called the bright area potential.

The developing unit 4a has a developing roller 41a as a developing member (toner (developer) carrier) and a developer container that contains non-magnetic single-component toner (hereinafter, toner) as a developer. The developing unit 4a is a developing means that performs a developing action on the photosensitive drum 1 to develop an electrostatic latent image into a toner image. The developing roller 41a contacts the photosensitive drum 1a with a pressing force of 200 gf and a predetermined contact width depending on the image forming operation. The developing roller 41a is rotated at a circumferential speed faster than the circumferential speed of the photosensitive drum 1a so that the surface movement direction of the developing roller 41a at the opposing portion (contact portion) with the photosensitive drum 1a is the same as the surface movement direction of the photosensitive drum 1a.

Here, the developing roller 41a is provided so that it can be brought into contact with and separated from the photosensitive drum 1. That is, the developing unit 4a and the image forming apparatus main body 100 are provided with a mechanism 40 that controls the contact/separation (development/separation) state between the developing roller 41a and the photosensitive drum 1a. The developing roller 41a and the photosensitive drum 1a are brought into contact with each other depending on the image forming operation, etc., and are separated when the operation stops.

A specific DC voltage is applied to the core of the developing roller 41a from the high-voltage developing power supply 140 in response to the image forming operation. In this embodiment, a DC voltage of -300V is applied to the core of the developing roller 41a as the developing voltage Vdc. During image formation, the toner carried on the developing roller 41a is developed on the image forming potential Vl portion of the photosensitive drum 1a by the electrostatic force generated by the potential difference between the developing voltage Vdc = -300V and the image forming potential Vl = -100V of the photosensitive drum 1a.

In the following explanation, a high potential and applied voltage refers to an absolute value that is larger on the negative polarity side (e.g., -1000V compared to -500V), and a low potential refers to an absolute value that is smaller on the negative polarity side (e.g., -300V compared to -500V). This is because the negatively charged toner in this embodiment is considered as the standard.

In addition, the voltage in this embodiment is expressed as a potential difference with respect to the earth potential (0 V). Therefore, the development voltage Vdc = -300 V is interpreted as having a potential difference of -300 V with respect to the earth potential due to the development voltage applied to the core metal of the development roller 41a. The same applies to the charging voltage and transfer voltage. The toner in this embodiment is a non-magnetic toner with negative charging properties manufactured by the suspension polymerization method, and has a volume average particle size of 7.0 μm. The volume average particle size of the toner is the volume average particle size measured by a laser diffraction particle size distribution analyzer LS-230 manufactured by Beckman Coulter, Inc. Details of the toner will be described later.

The normal charging polarity of the toner contained in the developing unit is negative. In this embodiment, the electrostatic latent image is reversely developed using toner charged to the same polarity as the charging polarity of the photosensitive drum by the charging member, but the present invention can also be applied to electrophotographic devices in which the electrostatic latent image is positively developed using toner charged to the opposite polarity to the charging polarity of the photosensitive drum. The toner surface configuration and external additive configuration, which are the characteristics of this embodiment, will be described later.

The intermediate transfer belt 20 is stretched by a plurality of tension members 11, 12, and 13, and is driven to rotate at a constant peripheral speed difference with the photosensitive drum 1a in a direction in which it moves in the circumferential direction at the opposing portion where it abuts against the photosensitive drum 1a. As shown in FIG. 2, the intermediate transfer belt 20 is a two-layer structure consisting of a coat layer 21 and a base layer 22, and has a peripheral length of 700 mm. The coat layer 21 is made to have a high smoothness by applying an acrylic resin paint with a thickness of 2 μm to the surface. On the other hand, the base layer 22 is made of a material whose main component is polyester, and has a thickness of 100 μm. The above-mentioned coat layer 21 is thinner than the base layer 22, so it has a small effect on the resistance value of the intermediate transfer belt 20, but if necessary, a conductive agent such as carbon black may be added to adjust the resistance. In addition, the thickness of the coat layer 21 is preferably in the range of 0.5 to 4.0 μm from the viewpoints of smoothness and manufacturing.

The resin material applied to the coating layer 21 is not particularly limited, and may be, for example, polyester, polyether, polycarbonate, polyarylate, urethane, silicone, fluororesin, or other materials. The base layer 22 may be made of other thermoplastic resins. For example, polyimide, polycarbonate, polyarylate, acrylonitrile-butadiene-styrene copolymer (ABS), polyphenylene sulfide (PPS), polyvinylidene fluoride (PVdF), or other materials or mixtures of these materials.

The yellow toner image formed on the photosensitive drum 1a is transferred onto the intermediate transfer belt 20 (primary transfer) as it passes through the primary transfer section, which is the contact point between the photosensitive drum 1a and the primary transfer roller 14a via the intermediate transfer belt 20 as an intermediate transfer body. A DC voltage of 500V is applied to the primary transfer roller 14a as the primary transfer member from the primary transfer power supply 160 in accordance with the image forming operation. Then, the primary transfer residual toner remaining on the surface of the photosensitive drum 1a is cleaned and removed by the cleaning unit 5a, and is then charged and used in the image forming process that follows.

Similarly, the second, third and fourth image forming stations b, c and d form a magenta toner image as the second color, a cyan toner image as the third color and a black toner image as the fourth color. These are then transferred onto the intermediate transfer belt 20 in a superimposed manner, to obtain a composite color image corresponding to the desired color image.

The four-color toner image on the intermediate transfer belt 20 as described above is transferred collectively to the surface of the recording material P fed by the paper feed means 60 during the process of passing through the secondary transfer nip formed by the intermediate transfer belt 20 and the secondary transfer roller 15 as a secondary transfer member (secondary transfer). The secondary transfer roller 15 contacts the intermediate transfer belt 20 with a pressure of 5 kgf, forming a secondary transfer nip at the secondary transfer section. The secondary transfer roller 15 rotates in response to the intermediate transfer belt 20, and a voltage of 2500 V is applied from the secondary transfer power source 150 when the toner on the intermediate transfer belt 20 is secondarily transferred to the recording material P such as paper. The intermediate transfer belt 20 of this embodiment can reduce the minute space generated between the surface of the recording material P due to the coating layer 21 with high smoothness described above, so that the disturbance of the electric field at the secondary transfer nip can be suppressed and the secondary transfer efficiency can be improved.

Then, the recording material P carrying the four-color toner image is introduced into the fixing device 30, where it is heated and pressurized, melting and mixing the four colors of toner and fixing it to the recording material P. Any toner remaining on the intermediate transfer belt 20 after the secondary transfer is cleaned and removed by the cleaning unit 50.

Through the above steps, a full-color print image is created.

Next, the control unit 200 will be described. FIG. 3 is a control block diagram showing the 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 controls the image forming operation of the image forming apparatus 100 in a central manner via the interface 201 according to a predetermined control program and a reference table. The control unit 202 is configured with a CPU 155, which is a central element for performing various arithmetic processing, and a memory 154 such as a ROM and a RAM, which is a storage element. The RAM stores the detection results of the sensor, the count results of the counter, and the results of calculation, and the ROM stores the control program, a data table obtained in advance by experiments, and the like. The control unit 200 is connected to each control object, sensor, counter, and the like in the image forming apparatus 100. The control unit 200 controls the exchange of various electrical information signals and the timing of driving each part, and controls a predetermined image forming sequence. For example, the 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.
2. Difference in peripheral speed between intermediate transfer belt and photosensitive drum In this embodiment, in order to improve the efficiency of primary transfer, a difference in peripheral speed is provided between the photosensitive drums 1a, 1b, 1c, and 1d and the intermediate transfer belt 20. Details will be described below using the first image forming station a.

Figure 2 is an enlarged view of the primary transfer section in the first image forming station a.

The primary transfer roller 14a is configured by wrapping a 3 mm thick elastic body 142a having rubber-like elasticity around a metal core 141a with an outer diameter of φ6 mm. In the primary transfer section, the primary transfer roller 14a is disposed to face the photosensitive drum 1a with the intermediate transfer belt 20 sandwiched therebetween, and the primary transfer roller 14a presses the intermediate transfer belt 20 against the photosensitive drum 1a with a pressure of 500 gf. The intermediate transfer belt 20 is wrapped around the photosensitive drum 1a for a predetermined length and is in contact with the photosensitive drum 1a, and this contact area forms a drum nip portion in the transfer section. The drum nip width, which is the contact width of the drum nip portion at that time, is designated as Q.

The photosensitive drum 1a is rotated at a surface movement speed Vdr, which is a predetermined peripheral speed, and the intermediate transfer belt 20 is rotated at a movement speed Vb, which is a predetermined peripheral speed. In this state, the toner T is transferred sequentially to the intermediate transfer belt 20 at the drum nip portion. The primary transfer roller 14a rotates together with the intermediate transfer belt 20. The peripheral speeds Vdr and Vb of the photosensitive drum 1a and the intermediate transfer belt 20 are the movement speeds of the surface of the photosensitive drum 1 and the surface of the intermediate transfer belt 20, respectively. Here, in the configuration of this embodiment, the movement of the surface of the intermediate transfer belt 20 is performed by inputting from the photosensitive drum drive unit 110, generating a difference in the surface movement speed between the photosensitive drum 1 and the intermediate transfer belt 20. However, a drive unit for driving the intermediate transfer belt 20 may be provided separately from the photosensitive drum drive unit 110, or drive input may be received from another drive unit.

Next, referring to Figure 4, we will explain the mechanism by which the primary transfer efficiency is improved by applying a peripheral speed difference to the drum nip.

Figure 4 is a schematic diagram showing the inside of the drum nip portion described above, and explains the behavior of the toner T when a difference in peripheral speed is applied between the photosensitive drum 1a and the intermediate transfer belt 20.

At the drum nip, the photosensitive drum 1a rotates at a peripheral speed of Vdr, and the intermediate transfer belt 20 rotates at a peripheral speed of Vb, resulting in a peripheral speed difference of Vdr-Vb. In this embodiment, Vdr and Vb have a relationship of Vdr<Vb, and the primary transfer configuration is such that the peripheral speed Vb of the intermediate transfer belt 20 is greater than the peripheral speed Vdr of the photosensitive drum 1a.

Due to the development process, the bottom layer of toner T that adheres to the latent image forming portion on the photosensitive drum 1a comes into contact with the photosensitive drum 1a. The toner T that comes into contact with the photosensitive drum 1a is often in a stable state, with the contact points being the points on each surface where the adhesive force with the photosensitive drum 1a is greatest. Toner T tends to adhere to points where the adhesive force is greatest, which differs depending on the surface shape and surface charge state. In addition, toner T that adheres to points where the adhesive force is greatest is difficult to transfer, and in order to increase the primary transfer efficiency, transfer conditions that express a force greater than that adhesive force are required.

First, when the toner T circulates within the drum nip, the difference in peripheral speed causes the toner T to rotate like a bearing, moving from state A to state B. As the toner T moves, the contact point Pt between the toner T and the photosensitive drum 1a moves to point Pt'. Therefore, the toner T separates from the contact point Pt, which was in contact with the photosensitive drum 1a before entering the drum nip and had a relatively large adhesive force, and the adhesive force between the toner T and the photosensitive drum 1a decreases. Because the adhesion surface of the toner T separates from the photosensitive drum 1a at the contact point Pt due to the difference in peripheral speed, the magnitude relationship between the peripheral speed Vdr of the photosensitive drum 1a and the peripheral speed Vb of the intermediate transfer belt 20 does not need to follow the above-mentioned relationship of Vdr<Vb, and the effect can be achieved even if the two are reversed.

As explained above, by creating a peripheral speed difference between the photosensitive drum 1a and the intermediate transfer belt 20, the adhesion force between the toner T and the photosensitive drum 1a is reduced, making it easier to peel the toner T from the photosensitive drum 1a, thereby improving the primary transfer efficiency.

Next, the range of peripheral speed difference that realizes the above-mentioned improvement in primary transfer efficiency will be described. First, the amount of relative movement between the photosensitive drum 1a and the intermediate transfer belt 20 that occurs in the drum nip portion is defined as the amount of toner T rolling due to the peripheral speed difference. Then, the nip width Q of the drum nip portion and the peripheral speed difference rate are set so that the amount of rolling falls within a preset range, optimizing the balance between transfer efficiency and image quality degradation.

The following describes the relationship between the "rolling amount" of toner T, which is a unique parameter defined in this embodiment.

The rolling amount of the toner T is the amount of relative movement between the photosensitive drum 1a and the intermediate transfer belt 20 that occurs in the drum nip due to the difference in peripheral speed, and in this embodiment, is defined as follows:

Rolling amount (R) = peripheral speed difference rate (Vr) x drum nip width (Q) (Equation 1)
Peripheral speed difference rate (Vr) = |Vdr-Vb|/Vdr×100 (Formula 2)
Here, the peripheral speed difference rate (peripheral speed ratio, speed ratio) Vr in the above formula 1 is defined as a percentage of the peripheral speed difference |Vdr-Vb| between the peripheral speed Vdr and the peripheral speed Vb of the intermediate transfer belt 20 with respect to the peripheral speed Vdr of the photosensitive drum 1a.

Table 1 shows the amount of rolling R when the drum nip portion and the peripheral speed difference rate Vr are changed. As shown in Table 1, the amount of rolling R is a parameter that increases as the peripheral speed difference rate Vr increases or the drum nip width Q increases.

Figure 5 shows the results of measuring the amount of residual toner remaining on the surface of the photosensitive drum 1 after primary transfer when the above-mentioned drum nip width Q is 1500 μm, varying the peripheral speed difference rate Vr. The vertical axis in the graph shows the results of measuring the amount of residual toner after primary transfer based on the reflectance corresponding to the reflection density. A solid image is printed at the M color station, and the residual toner image after transfer on the surface of the C color photosensitive drum 1c after the solid image is printed (after transfer) at the downstream C color station is taped. Then, the reflectance of the taped result was measured using a reflection densitometer (Tokyo Densoku Co., Ltd.: model number TC-6DS). As a result, it can be seen that the larger the peripheral speed difference rate Vr, the smaller the amount of residual toner after primary transfer and the better the primary transfer efficiency. In addition, the effect of improving the primary transfer efficiency due to the peripheral speed difference rate Vr appears rapidly from around 0.75% of the peripheral speed difference rate Vr, and in the area where the peripheral speed difference rate Vr is 2% or more, there is almost no residual toner after primary transfer. This shows that the effect of providing a circumferential speed difference is fully realized. Since the drum nip width Q in the configuration of this embodiment is 1500 μm, the rolling amount (R) of the toner T at a circumferential speed difference rate (Vr) of 0.75%, at which the primary transfer efficiency improvement effect begins to appear, is 11.25 μm.

As described above, in this embodiment, toner T with a weight average particle diameter (D) of 7.0 μm is used, and if toner T is assumed to be spherical, the circumference of toner T is 21.98 μm. Here, the rolling amount R at which the primary transfer efficiency improvement effect begins to appear is 11.25 μm, which is an arc length of approximately half the circumference of toner T. In other words, by rolling approximately half a circumference, the initial contact point of toner T with photosensitive drum 1a moves to the intermediate transfer belt 20 side, and a distance from photosensitive drum 1a sufficient to reduce adhesion is secured, which is thought to improve primary transfer efficiency. From the above, in this embodiment, the lower limit of rolling amount R is set to half the average circumference calculated from the weight average particle diameter of toner T used.

Next, the upper limit of the rolling amount R will be explained. The upper limit of the rolling amount R was based on the amount of toner movement within the drum nip from the viewpoint of image quality degradation. As shown in FIG. 4, when the toner T is rotated by a distance L from state A to state B, the relative movement distance between the photosensitive drum 1a and the intermediate transfer belt 20 becomes L x 2 because the toner T moves the distance L. In other words, the toner T shifts in the drum nip by half its circumference relative to the relative movement distance between the photosensitive drum 1a and the intermediate transfer belt 20, i.e., the "rolling amount R." When the toner T shifts, the height and width of the toner image vary, causing the image to appear rougher.

Therefore, the allowable range of the amount of toner T shifting is considered to be a range of approximately 50 μm, which corresponds to the size of about 1 dot at 600 DPI, which is the resolution of a typical image forming device, so the upper limit of the rolling amount R is 100 μm.

From the above, the range of the rolling amount R that balances the primary transfer efficiency and image quality degradation is the range from the length of the arc that is half the circumference of the toner T to 100 μm. Using the toner weight average particle size D, the drum nip width Q, and the peripheral speed difference rate Vr, it is desirable to have a configuration that satisfies the range shown in the following formula 3.

1/2×D (μm)×π≦Vr (%)×Q (μm)/100≦100μm... (Formula 3)
In the configuration of this embodiment, the drum nip width Q was 1500 μm and the peripheral speed difference rate Vr was 2.5%.

In addition, in this embodiment, the toner is assumed to be spherical, but the toner is not limited to a sphere. As long as the toner has a shape that allows it to roll due to a difference in peripheral speed, the primary transfer property can be improved.
3. Image Blur Mechanism In the image forming apparatus 100 in which a peripheral speed difference is provided between the photosensitive drum 1 and the intermediate transfer belt 20 as described above, when the toner image formed on the surface of the photosensitive drum 1 is primarily transferred to the surface of the intermediate transfer belt 20, a sudden rotational fluctuation may occur in the photosensitive drum 1. It has been found that the rotational fluctuation causes exposure unevenness in the laser exposure, which subsequently causes image streaks in the toner image formed on the surface of the photosensitive drum 1, and this is a factor in degrading the image quality of the final image.

Details are provided below with reference to Figure 2, which shows an enlarged view of the primary transfer section in the first image forming station a.

During printing, the intermediate transfer belt 20 is rotated at a surface speed that is approximately 2.5% faster than the photosensitive drum 1a, which is rotated. This is because, as described above, by creating a difference in peripheral speed between the photosensitive drum 1a and the intermediate transfer belt 20, the adhesion force between the toner T and the photosensitive drum 1a decreases, making it easier to peel the toner T from the photosensitive drum 1a, and improving the primary transfer efficiency.

Under such circumstances, when there is no toner T in the drum nip, a frictional force F acts on the surface of the photosensitive drum 1a downstream in the tangential direction (sub-scanning direction) from the surface of the intermediate transfer belt 20. However, when the leading edge of the toner image developed on the surface of the photosensitive drum 1a enters the drum nip, this frictional force F decreases rapidly (F → F ≒ 0). This is because the surface of the photosensitive drum 1a and the surface of the intermediate transfer belt 20 become more slippery against each other when toner T is supplied into the drum nip. This causes sudden rotational fluctuations in the photosensitive drum 1a, causing writing unevenness in the laser exposure to the surface of the photosensitive drum 1a. This subsequently causes image streaks in the main scanning direction on the toner image formed on the surface of the photosensitive drum 1a, and also appears in the final image.

In the final image on the recording material P, the image streaks appear on the toner image at a position that has moved downstream in the sub-scanning direction from the laser exposure portion by the distance between the drum nips (for example, 30 mm in this embodiment) starting from the leading edge of the toner image in the sub-scanning direction arranged in the image pattern. In particular, when a halftone toner image portion, which is easily affected by uneven exposure of the laser, is present at the position, the image streaks appear prominently.

As described above, the friction force F varies intermittently over time depending on the image pattern the user wishes to obtain, resulting in image streaks on the final image due to fluctuations in the rotation of the photosensitive drum 1a.

As a countermeasure against image streaks, a method is known in which a dot-shaped tiny toner image made of yellow or other toner is added to the photosensitive drum in addition to the toner image of the image pattern that the user wishes to obtain, thereby suppressing the rotational fluctuation of the photosensitive drum 1a and the intermediate transfer belt 20. Although it is generally known that this method can prevent various image defects, there are cases in which the added dot toner image appears yellowish and stands out on the recording material P.

As described above, by reducing the friction force F between the photosensitive drum 1a and the intermediate transfer belt 20 at the drum nip portion using a means other than a dot toner image, image streaks caused by rotational fluctuations of the photosensitive drum 1 can be suppressed even when the leading edge of the toner image enters the drum nip portion. In addition, color fluctuations of the recording material P can be suppressed.

Therefore, in this embodiment, before the toner image is developed, fine particles are supplied from the toner T carried by the developing roller 41 to the photosensitive drum 1, and the fine particles are caused to adhere to the surface of the photosensitive drum 1. The frictional force F is reduced by interposing the fine particles between the photosensitive drum 1 and the intermediate transfer belt 20. Details are explained below.

Figure 6(a) is a schematic diagram of the development nip when the development roller 41a and the photosensitive drum 1a are in contact at the first image forming station a. As shown in Figure 6(a), in the development nip, the toner T carried on the development roller 41a and the photosensitive drum 1a are in contact with each other via fine particles. Figure 6(b) is a schematic diagram showing the state after the toner T carried on the development roller 41a and the photosensitive drum 1a shown in Figure 6(a) have passed through the development nip.

As shown in FIG. 6(b), the fine particles present between the toner T and the photosensitive drum 1a in the development nip are transferred from the toner T carried on the development roller 41a to the photosensitive drum 1a after passing through the development nip, and are supplied.

When the adhesive force Ft between the toner T and the fine particles present between the toner T and the photosensitive drum 1a in the development nip portion shown in FIG. 6(a) is greater than the adhesive force Fdr between the fine particles and the photosensitive drum 1a, the fine particles are less likely to transfer from the toner T to the photosensitive drum 1a. Therefore, it is preferable that Ft is smaller than Fdr.

Also, FIG. 7(a) is a schematic diagram of the primary transfer section when the toner image T is carried on the surface of the photosensitive drum 1a, and FIG. 7(b) is a schematic diagram of the state in which the primary transfer of the toner image T shown in FIG. 7(a) is completed and the photosensitive drum 1a and the intermediate transfer belt 20 are separated. When Ft is smaller than Fdr, as shown in FIG. 7(a) and FIG. 7(b), when the toner image T is primarily transferred from the photosensitive drum 1a to the intermediate transfer belt 20, only the toner image T is primarily transferred onto the intermediate transfer belt 20. Then, the fine particles that were present between the toner image T and the photosensitive drum 1a remain on the photosensitive drum 1a.

Figure 8 is a timing chart of the print operation of the image forming device used in this embodiment. As shown in Figure 8, during the print operation, the image forming device of this embodiment rotates the developing roller 41a before starting to develop the toner T from the developing roller 41a onto the photosensitive drum 1a. Then, at the timing when the developing roller 41a comes into contact with the photosensitive drum 1a, fine particles are supplied from the developing roller 41a to the photosensitive drum 1a.

In this embodiment, in order to suppress rotational fluctuations when the toner T enters the drum nip portion, it is necessary to supply fine particles to the drum nip portion between the photosensitive drum 1a and the intermediate transfer belt 20 before the development of the toner image T begins. Therefore, it is preferable to set the supply time of the fine particles to be equal to or longer than the time it takes for the contact portion of the developing roller 41a on the photosensitive drum 1a to reach the drum nip portion. In this embodiment, the length of the supply time of the fine particles shown in FIG. 8 is set to 200 msec, which is approximately the same as the time it takes for the contact portion of the developing roller 41a to reach the drum nip portion described above.

In addition, in this embodiment, at the timing of supplying the fine particles shown in FIG. 8, the surface potential of the photosensitive drum 1a is set to a non-image forming potential Vd = -500 V at which the toner charged to the normal polarity is not developed. Therefore, at the timing of supplying the fine particles in this embodiment, the toner T is not developed from the developing roller 41a to the photosensitive drum 1a, and only the fine particles are supplied from the developing roller 41a onto the photosensitive drum 1a.

In the case of supplying fine particles from the toner T on the developing roller 41a to the photosensitive drum 1a in a state where there is a potential difference between the developing roller 41a and the photosensitive drum 1a as in this embodiment, if the particle size of the fine particles is too large, the fine particles are easily affected by the electrostatic force generated by the potential difference. Therefore, it becomes difficult to control the supply of fine particles from the toner T on the developing roller 41a to the photosensitive drum 1a. For example, in a configuration in which fine particles are supplied at a non-image forming potential as in this embodiment, if the fine particles are negatively charged, the fine particles are attracted to the developing roller 41a side by electrostatic force. Therefore, it becomes difficult to supply the fine particles from the toner on the developing roller 41a to the photosensitive drum 1a. Therefore, it is preferable to set the particle size of the fine particles to 1000 nm or less, which is less susceptible to the electrostatic force. In this embodiment, in order to stably supply fine particles from the toner T on the developing roller 41a to the photosensitive drum 1a regardless of the potential difference between the developing roller 41a and the photosensitive drum 1a, particles with a particle size of 100 nm are used as the fine particles.
4. Developer, Toner, and Fine Particles Next, the developer, toner, and fine particles used in this embodiment will be described in detail.

In this embodiment, a mixture of toner and external additive A, which is a fine particle, was used as the developer. The toner is a toner particle that contains a release agent and an organosilicon polymer on the surface of the toner particle.

The organosilicon polymer has a T3 unit structure represented by R-Si(O _1/2 ) ₃ , where R represents an alkyl group or a phenyl group having 1 to 6 carbon atoms, and the organosilicon polymer forms convex portions on the surfaces of the toner base particles.

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

The degree of surface contact is explained using the schematic diagrams of the protrusions shown in Figures 9, 10, 11, and 12.

In FIG. 9, 61 is a cross-sectional image of a toner particle in which about 1/4 of the toner particle can be seen, 62 is a toner particle, 63 is the surface of the toner base particle, and 64 is a protrusion. The cross section of a toner particle can be observed using a scanning transmission electron microscope (hereinafter also referred to as STEM) described later.

Observe the cross-sectional image of the toner and draw a line along the periphery of the toner base particle surface. Convert the image into a horizontal image based on the line along the periphery. In the horizontal image, the length of the line along the periphery in the part where the convex portion and the toner base particle form a continuous interface is defined as the convex width w.

The maximum length of the convex portion in the normal direction of the convex width w is the convex diameter D, and the length from the apex of the convex portion to a line along the circumference on the line segment that forms the convex diameter D is the convex height H.

In Figures 10 and 12, the convex diameter D and the convex height H are the same, while in Figure 11, the convex diameter D is greater than the convex height H.

Figure 12 shows a schematic representation of the adhesion state of particles similar to bowl-shaped particles, which are hemispherical particles with a concave center, obtained by crushing or breaking hollow particles.

In Figure 12, the convex width W is the total length of the organosilicon polymer in contact with the surface of the toner base particle. In other words, the convex width W in Figure 12 is the sum of W1 and W2.

The number average value of the convex height H is 30 nm or more and 300 nm or less, and preferably 30 nm or more and 200 nm or less. When the number average value of the convex height H is 30 nm or more, a spacer effect occurs between the toner base particle surface and the transfer member. On the other hand, when the number average value of the convex height H is 300 nm or less, the effect of suppressing movement, detachment, and embedding is significant. A cumulative distribution of the convex height H is taken for the convex portion having a convex height H of 30 nm or more and 300 nm or less. When the convex height H that corresponds to 80% by number, calculated from the smallest convex height H, is H80, it is preferable that H80 is 65 nm or more and 120 nm or less, and more preferably 75 nm or more and 100 nm or less.

The number-average particle size R of the primary particles of the external additive A is preferably 30 nm or more and 1200 nm or less. When R is 30 nm or more, a spacer effect is exerted between the toner and the transfer member. On the other hand, when R exceeds 1200 nm, the fluidity of the toner decreases, and image unevenness is easily generated.

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

When the number average value of the convex height H is the minimum value of 30 nm, if R is 30 nm or more, a spacer effect can be achieved between the transfer member. This is thought to be because the external additive A is substituted in places where there are no convex portions due to the effects of detachment, etc., and the spacer effect is achieved. In other words, if R is less than 30 nm, the spacer effect is difficult to achieve.

The adhesion rate of external additive A to the toner particle surface is preferably 0% or more and 20% or less, and more preferably 0% or more and 10% or less. When the adhesion rate is in the above range, external additive A can easily move on the surface of the toner particles. In the fixing process in which the toner is fixed to the fixing member, an appropriate amount of release agent seeps out from the toner base particles, improving the separation performance between the fixing member and the paper.

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

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

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

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

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

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

Figure 13 is an enlarged view of the developer used in this embodiment. As shown in Figure 13, the developer in this embodiment has a toner surface on which many protrusions of an organosilicon polymer are formed, and external additive A, which is fine particles, is placed on the toner surface.

The convex spacing G and convex height H on the toner surface shown in Figure 13 can be measured using a scanning transmission electron microscope (hereinafter referred to as STEM), which will be described later. The convex spacing G and convex height H can also be measured with a scanning probe microscope (hereinafter referred to as SPM). A scanning probe microscope (hereinafter referred to as SPM) is equipped with a probe, a cantilever that supports the probe, and a displacement measurement system that detects the bending of the cantilever, and detects the atomic force (attractive or repulsive force) between the probe and the sample to observe the shape of the sample surface.

If the convex spacing G is larger than the microparticles, the microparticles will come into contact with the toner matrix when placed between the convex portions, and the adhesive force Ft between the microparticles and the toner will increase, making it difficult for the microparticles to transfer from the toner to the photosensitive drum 1. Therefore, it is preferable that the number-average convex spacing G is smaller than the number-average particle size of the microparticles.

Furthermore, if the convex height H is greater than the particle size of the microparticles, the convex portion will come into contact with the photosensitive drum 1 before the microparticles, making it difficult for the microparticles to come into contact with the photosensitive drum 1 and making it difficult for the microparticles to transfer from the toner to the photosensitive drum 1. Therefore, it is preferable that the number average value of the convex height H is smaller than the number average particle size of the microparticles.

However, as mentioned above, it is preferable that the adhesive force Ft between the fine particles and the toner is smaller than the adhesive force Fdr between the fine particles and the photosensitive drum 1. Therefore, it is preferable to select a material for the fine particles that reduces the adhesive force Ft of the fine particles to the toner. For example, as in this embodiment, when the convex portions on the toner surface are formed of a silica-based material such as an organic silica polymer, it is preferable to select a silica-based material for the fine particles that has a similar material composition to the convex portions, in order to reduce the adhesive force between the convex portions and the fine particles.

A larger number of fine particles covering the toner is preferable from the viewpoint of supplying the fine particles from the developing roller 41 to the photosensitive drum 1. However, if too many fine particles are added, the risk of contamination of components within the image forming device 100 increases, so it is preferable to adjust the amount.

In order to obtain a sufficient spacer effect, it is preferable that the coverage of the fine particles on the photosensitive drum 1 is 10% or more. However, as the coverage of the fine particles on the photosensitive drum 1 increases, the risk of the fine particles contaminating various members inside the image forming apparatus increases. Therefore, it is preferable that the coverage of the fine particles on the photosensitive drum 1 is kept within 50%.
5. Methods for Measuring Developer Properties Various measuring methods will be described below.

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

The procedure for preparing a cross section of a toner is explained below. If organic or inorganic fine particles are added to the toner, the toner from which the organic or inorganic fine particles have been removed using the method described below or similar is used as the sample.

160 g of sucrose (Kishida Chemical) is added to 100 mL of ion-exchanged water, and dissolved in a hot water bath to prepare a concentrated sucrose solution. 31 g of the concentrated sucrose solution and 6 mL of Contaminon N (a 10% aqueous solution of a neutral detergent for cleaning precision measuring instruments, pH 7, consisting of a nonionic surfactant, anionic surfactant, and organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) are placed in a centrifuge tube (50 mL capacity). 1.0 g of toner is added to this, and the toner clumps are loosened with a spatula or the like. The centrifuge tube is shaken at 300 spm (strokes per minute) for 20 minutes in a shaker (AS-1N, sold by AS ONE Corporation). After shaking, the solution is transferred to a glass tube for a swing rotor (50 mL) and separated at 3500 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 check that the toner particles and the aqueous solution are sufficiently separated, and collect the toner particles that have separated into the top layer with a spatula or similar. The collected toner particles are filtered through a vacuum filter, and then dried in a dryer for at least one hour to obtain a sample for measurement. This operation is carried out multiple times to ensure the required amount.

In addition, whether or not the convex portion contains an organosilicon polymer is confirmed by combining elemental analysis using energy dispersive X-ray analysis (EDS).

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

Next, the toner is cut to a thickness of 100 nm to produce a thin sample of the toner cross section. By cutting in this manner, a cross section of the center of the toner can be obtained.

A JEM-2800 manufactured by JEOL was used as the scanning transmission electron microscope (STEM). The probe size of the STEM was 1 nm, and images were acquired with an image size of 1024 x 1024 pixels. In addition, the contrast of the Detector Control panel for the bright field image was adjusted to 1425, the brightness to 3750, and the contrast of the Image Control panel to 0.0, the brightness to 0.5, and the gamma to 1.00, to acquire the image. The image magnification was 100,000 times, and the image was acquired so that it covered about one-quarter to one-half of the circumference of the cross section of one toner particle, as shown in Figure 9. The obtained STEM image is subjected to image analysis using image processing software (ImageJ (available from https://imagej.nih.gov/ij/)) and the convex portions containing the organosilicon polymer are measured. The measurement is performed on 30 convex portions arbitrarily selected from the STEM image. Whether or not the convex portions contain the organosilicon polymer is confirmed by a combination of elemental analysis using a scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDS). First, a line is drawn along the periphery of the toner base particle using a line drawing tool (select Segmented line in the Strong tab). Parts where the organosilicon polymer convex portions are buried in the toner base particle are connected smoothly with a line, assuming that they are not buried. The image is converted to a horizontal image based on that line (select Selection on the Edit tab, change line width to 500 pixels in properties, then select Selection on the Edit tab and perform Strengthener). In the horizontal image, the following measurements are performed on one of the convex parts containing the organosilicon polymer. The length of the line along the circumference in the part where the convex part and the toner base particle form a continuous interface is defined as the convex width w. The maximum length of the convex part in the normal direction of the convex width w is defined as the convex diameter D, and the length from the apex of the convex part to the line along the circumference in the line segment that forms the convex diameter D is defined as the convex height H. The measurements are performed on 30 arbitrarily selected convex parts, and the arithmetic average of each measurement value is defined as the number average of the convex height H.

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

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

160 g of sucrose (Kishida Chemical) is added to 100 mL of ion-exchanged water, and dissolved in a hot water bath to prepare a concentrated sucrose solution. 31 g of the concentrated sucrose solution and 6 mL of Contaminon N (a 10% aqueous solution of a neutral detergent for cleaning precision measuring instruments, pH 7, consisting of a nonionic surfactant, anionic surfactant, and organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) are placed in a centrifuge tube (50 mL capacity). 1.0 g of toner is added to this, and the toner clumps are loosened with a spatula or the like. The centrifuge tube is shaken at 300 spm (strokes per minute) for 20 minutes in a shaker (AS-1N, sold by AS ONE Corporation). After shaking, the solution is transferred to a glass tube for a swing rotor (50 mL) and separated at 3500 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 check that the toner particles and the aqueous solution are sufficiently separated, and collect the toner particles that have separated into the top layer with a spatula or similar. The collected toner particles are filtered through a vacuum filter, and then dried in a dryer for at least one hour to obtain a sample for measurement. This operation is carried out multiple times to ensure the required amount.

Whether or not the convex portions contain an organosilicon polymer will be confirmed by combining this with elemental analysis using energy dispersive X-ray analysis (EDS), which will be described later.

The SEM equipment and observation conditions are as follows.
Equipment used: ULTRA PLUS manufactured by Carl Zeiss Microscopy Co., Ltd.
Acceleration voltage: 1.0 kV
WD: 2.0 mm
Aperture Size: 30.0μm
Detection signal: EsB (energy selective backscattered electrons)
EsB Grid: 800V
Observation magnification: 50,000 times Contrast: 63.0±5.0% (reference value)
Brightness: 38.0±5.0% (reference value)
Resolution: 1024 x 768
Pretreatment: Toner particles are scattered onto carbon tape (no deposition is performed)
The accelerating voltage and EsB Grid are set to achieve the following: obtaining structural information on the outermost surface of the toner particles, preventing charging up of undeposited samples, and selectively detecting high-energy reflected electrons. The observation field is selected to be near the apex where the curvature of the toner particles is smallest. It was confirmed that the bright areas of the reflected electron image were derived from the organosilicon polymer by superimposing the reflected electron image on an element mapping image obtained by energy dispersive X-ray analysis (EDS) that can be obtained by a scanning electron microscope (SEM).

The SEM/EDS equipment and observation conditions are as follows.
Equipment used (SEM): ULTRA PLUS manufactured by Carl Zeiss Microscopy Co., Ltd.
Equipment used (EDS): NORAN System 7, Ultra Dry EDS Detector, manufactured by Thermo Fisher Scientific Co., Ltd.
Acceleration voltage: 5.0 kV
WD: 7.0 mm
Aperture Size: 30.0μm
Detection signal: SE2 (secondary electrons)
Observation 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 above-mentioned reflected electron image, and it is confirmed that the silicon atom parts of the mapping image match the bright parts of the reflected electron image.

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

First, convert the backscattered electron image to 8-bit from Type in the Image menu. Next, set the Median diameter to 2.0 pixels from Filters in the Process menu to reduce image noise. Estimate the image center after excluding the observation condition display section displayed at the bottom of the backscattered electron image, and select a 1.5 μm square range from the center of the backscattered electron image using the Rectangle Tool on the toolbar. Next, select Threshold from Adjust in the Image menu. Select Default, click Auto, and then click Apply to obtain a binarized image. This operation displays the bright areas of the backscattered electron image in white. Again, estimate the image center after excluding the observation condition display section displayed at the bottom of the backscattered electron image, and select a 1.5 μm square range from the center of the backscattered electron image using the Rectangle Tool on the toolbar. Next, select Histogram from the Analyze menu. Read the Count value from the newly opened Histogram window (corresponding to the total area of the reflected electron image). Also, click List and read the Count value when the brightness is 0 (corresponding to the bright area of the reflected electron image). From this value, calculate the area ratio of the bright area to the total area of the reflected electron image. 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 to obtain the area ratio (%) of the bright area of the image to the total area of the image that has been binarized so that the organosilicon polymer portion in the reflected electron image becomes the bright area.

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

Using a scanning electron microscope "Hitachi Ultra High Resolution Field Emission Scanning Electron Microscope S-4800" (Hitachi High-Technologies Corporation), the toner is observed in a field of view magnified up to 50,000 times. The surface is observed by focusing on the surface of the toner particles. EDS analysis is performed on the particles present on the surface, and the presence or absence of an Si element peak is used to determine whether the particles analyzed are organosilicon polymers. If the toner particle surface contains both organosilicon polymers and silica fine particles, the organosilicon polymer is identified by comparing the ratio of the elemental contents (atomic %) of Si and O (Si/O ratio) with a standard. EDS analysis is performed under the same conditions on standard samples of the organosilicon polymer and silica fine particles to obtain the elemental contents (atomic %) of Si and O. The Si/O ratio of the organosilicon polymer is designated as A, and the Si/O ratio of the silica fine particles is designated as B. Measurement conditions are selected under which A is significantly greater than B. Specifically, a standard sample is measured 10 times under the same conditions, and the arithmetic mean values for A and B are obtained. Measurement conditions are selected such that the obtained mean value is A/B>1.1. If the Si/O ratio of the particle to be identified is on the A side of [(A+B)/2], the particle is determined to be an organosilicon polymer.

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

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

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

<Method for identifying the composition and ratio of constituent compounds of organosilicon polymer>
The composition and ratio of the constituent compounds of the organosilicon polymer contained in the toner are identified using NMR. When the toner contains an external additive such as silica fine particles in addition to the organosilicon polymer, the following procedure is carried out.

1 g of the toner is placed in a vial, dissolved in 31 g of chloroform, and dispersed in the vial by treating with an ultrasonic homogenizer for 30 minutes to prepare a dispersion liquid.
Ultrasonic treatment device: Ultrasonic homogenizer VP-050 (manufactured by Taitec Co., Ltd.)
Microchip: Step type microchip, tip diameter φ2mm
Tip position of the microchip: Center of the glass vial, and 5 mm above the bottom of the vial. Ultrasonic conditions: Intensity 30%, 30 minutes. At this time, ultrasonic waves are applied while cooling the vial with ice water so that the temperature of the dispersion does not rise. The dispersion is transferred to a glass tube for a swing rotor (50 mL) and centrifuged in a centrifuge (H-9R; manufactured by Kokusan Co., Ltd.) at 58.33 S ^-1 for 30 minutes. After centrifugation, the lower layer of the glass tube contains particles with a high specific gravity, such as silica fine particles. The chloroform solution containing the organosilicon polymer in the upper layer is collected, and the chloroform is removed by vacuum drying (40°C/24 hours) to prepare a sample. Using the above sample or the organosilicon polymer, the abundance ratio of the constituent compounds of the organosilicon polymer and the proportion of the T3 unit structure represented by R-Si(O _1/2 ) ₃ in the organosilicon polymer are measured and calculated by solid-state ²⁹ Si-NMR.

First, the hydrocarbon group represented by R is confirmed by ¹³ C-NMR.
< ^13C -NMR (solid) measurement conditions>
Equipment: JEOL RESONANCE JNM-ECX500II
Sample tube: 3.2 mm diameter
Sample: Sample or organosilicon polymer Measurement temperature: Room temperature Pulse mode: CP/MAS
Measurement nuclear frequency: 123.25MHz ( ^13C )
Reference substance: Adamantane (external standard: 29.5 ppm)
Sample rotation speed: 20 kHz
Contact time: 2 ms
Delay time: 2s
Number of integrations: 1024 times. Using this method, the presence or absence of signals due to methyl groups (Si-CH ₃ ), ethyl groups (Si-C ₂ H ₅ ), propyl groups (Si-C ₃ H ₇ ), butyl groups (Si-C ₄ H ₉ ), pentyl groups (Si-C ₅ H ₁₁ ), hexyl groups (Si-C ₆ H ₁₃ ), or phenyl groups (Si-C ₆ H ₅ -) bonded to silicon atoms is used to confirm the presence or absence of the hydrocarbon group represented by R. On the other hand, in solid-state ²⁹ Si-NMR, peaks are detected in different shift regions depending on the structure of the functional groups bonded to Si in the constituent compounds of the organosilicon polymer. The structure bonded to Si can be identified by identifying the position of each peak using a standard sample. 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.

The specific measurement conditions for solid-state ^29Si -NMR are as follows.
Equipment: JNM-ECX5002 (JEOL RESONANCE)
Temperature: Room temperature measurement method: DDMAS method ²⁹ Si 45°
Sample tube: Zirconia 3.2 mm diameter
Sample: Powdered sample filled in test tube Sample rotation speed: 10 kHz
relaxation delay: 180s
Scan: 2000
After the measurement, the peaks of a plurality of silane components having different substituents and bonding groups of the sample or organosilicon polymer are separated into the following X1, X2, X3, and X4 structures by curve fitting, and the peak areas of each are calculated.

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

In the formulae (A1), (A2) and (A3), Ri, Rj, Rk, Rg, Rh and Rm each represent an organic group such as a hydrocarbon group having 1 to 6 carbon atoms, a halogen atom, a hydroxyl group, an acetoxy group or an alkoxy group, which is bonded to a silicon atom. When it is necessary to confirm the structure in more detail, it may be identified by the results of ¹ H-NMR measurement together with the results of ¹³ C-NMR and ²⁹ Si-NMR measurement.

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

The following is an example of an external additive that is silica microparticles. Other microparticles can also be quantified using the same method.

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

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

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

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

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

The image capturing conditions for the S-4800 are as follows.
(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 the paste. Then, use air to remove excess toner from the sample stage and allow it to dry thoroughly. Set the sample stage in the sample holder, and adjust the sample stage height to 36 mm using the sample height gauge.
(2) Setting the S-4800 observation conditions When measuring the coverage, perform elemental analysis by the energy dispersive X-ray analysis (EDS) described above in advance to distinguish between external additives such as organosilicon polymers or silica fine particles on the toner surface before carrying out the measurement. Pour liquid nitrogen into the anti-contamination trap attached to the S-4800 housing until it overflows, and leave it for 30 minutes. Start the S-4800's "PC-SEM" and perform flushing (cleaning the FE chip, which is the electron source). Click on the accelerating voltage display area on the control panel on the screen, press the [Flushing] button, and open the flushing execution dialog. Check that the flushing intensity is 2 and execute it. Check that the emission current due to flushing is 20 to 40 μA. Insert the sample holder into the sample chamber of the S-4800 housing. Press [Origin] on the control panel to move the sample holder to the observation position.

Click on the acceleration voltage display to open the HV setting dialog, and set the acceleration voltage to [1.1 kV] and the emission current to [20 μA]. In the [Basic] tab of the operation panel, set the signal selection to [SE], select the SE detector to [Upper (U)] and [+BSE], and select [L.A. 100] in the selection box to the right of [+BSE] to set the mode to observation with backscattered electron images. In the same [Basic] tab of the operation panel, set the probe current in the electron optical system condition block to [Normal], the focus mode to [UHR], and the WD to [4.5 mm]. Press the [ON] button on the acceleration voltage display of the control panel to apply the acceleration voltage.
(3) Calculation of toner number average particle diameter (D1) Drag within the magnification display area of the control panel to set the magnification to 5000 (5k). Rotate the focus knob [COARSE] on the operation panel to adjust the aperture alignment when the image is in focus to a certain extent. Click [Align] on the control panel to display the alignment dialog and select [Beam]. Rotate the STIGMA/ALIGNMENT knobs (X, Y) on the operation panel to move the displayed beam to the center of the concentric circle. Next, select [Aperture] and rotate the STIGMA/ALIGNMENT knobs (X, Y) one by one to stop the image movement or adjust it so that the movement is minimized. Close the aperture dialog and adjust the focus with autofocus. Repeat this operation two more times to adjust the focus.

Thereafter, the particle diameters of 300 toner particles are measured to obtain the number average particle diameter (D1). The particle diameter of each particle is the maximum diameter observed when the toner particles are observed.
(4) Focus Adjustment For the particles obtained in (3) with a number average particle diameter (D1) of ±0.1 μm, 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.

Rotate the focus knob [COARSE] on the operation panel, and adjust the aperture alignment when the image is in focus to some extent. Click [Align] on the control panel to display the alignment dialog, and select [Beam]. Rotate the STIGMA/ALIGNMENT knobs (X, Y) on the operation panel to move the displayed beam to the center of the concentric circle. 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 adjust the focus with autofocus. Then, set the magnification to 50,000 (50k) times, and adjust the focus using the focus knob and STIGMA/ALIGNMENT knob in the same way as above, and adjust the focus again with autofocus. Repeat this operation to adjust the focus. Here, if the inclination angle of the observation surface is large, the measurement accuracy of the coverage rate is likely to be low, so when adjusting the focus, select an observation surface with as little surface inclination as possible for analysis by selecting one that can simultaneously bring the entire observation surface into focus.
(5) Image storage Adjust the brightness in ABC mode, take a photograph with a size of 640 x 480 pixels, and save it. Use this image file to perform the following analysis. Take one photograph for each toner particle to obtain an image of the toner particles.
(6) Image Analysis The image obtained by the above-mentioned method is binarized using the following analysis software to calculate the coverage. At this time, the above screen is divided into 12 squares and each is analyzed. The analysis conditions for the image analysis software Image-Pro Plus ver. 5.0 are as follows. However, if an external additive such as an organosilicon polymer with a particle size of less than 30 nm and more than 300 nm, or silica fine particles with a particle size of less than 30 nm and more than 1200 nm is included in a divided section, the coverage is not calculated for that section.

In the image analysis software Image-Pro Plus 5.0, select "Count/Size" from "Measurement" on the toolbar, then "Options" to set the binarization conditions. Select 8 connectivity in the object extraction options and set smoothing to 0. Other options include not selecting in advance, not filling holes, and not including lines, and setting "Exclude boundaries" to "None." Select "Measurement item" from "Measurement" on the toolbar and enter 2 to ¹⁰⁷ as the selection range for area.

The coverage rate is calculated by enclosing a square region. In this case, the area (C) of the region should be between 24,000 and 26,000 pixels. Automatic binarization is performed using "Processing" - Binarization, and the total area (D) of regions free of external additives such as organosilicon polymers or silica microparticles is calculated. The coverage rate can be calculated using the following formula 4 from the area C of the square region and the total area D of regions free of external additives such as organosilicon polymers or silica microparticles.

Coverage rate (%) = 100 - (D / C × 100) (Equation 4)
The arithmetic mean value of all the data obtained is taken as the coverage rate.

Then, the coverage of the toner before and after washing is calculated,
[Toner coverage after washing]/[Toner coverage before washing]×100 is defined as the “adhesion rate” in the present invention.
6. Methods for Producing Toner Particles, External Additives, and Developer Next, examples of producing the toner particles, external additive A, and developer of this embodiment will be described.

<Production Example of Toner Particles>
(Preparation of aqueous medium 1)
In a reaction vessel equipped with a stirrer, a thermometer, and a reflux tube, 650.0 parts of ion-exchanged water and 14.0 parts of sodium phosphate (12-hydrate, manufactured by Rasa Kogyo Co., Ltd.) were charged, and the mixture was kept warm at 65 ° C. for 1.0 hours while purging with nitrogen. A calcium chloride aqueous solution in which 9.2 parts of calcium chloride (dihydrate) was dissolved in 10.0 parts of ion-exchanged water was charged all at once using a T.K. homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) while stirring at 15,000 rpm, to prepare an aqueous medium containing a dispersion stabilizer. Furthermore, 10% by mass of hydrochloric acid was charged into the aqueous medium, and the pH was adjusted to 5.0, to obtain aqueous medium 1.

(Preparation of Polymerizable Monomer Composition)
The above materials were put into an attritor (manufactured by Mitsui Miike Chemical Engineering Co., Ltd.), and further dispersed at 220 rpm for 5.0 hours using zirconia particles having a diameter of 1.7 mm, and then 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 (polycondensate of propylene oxide modified bisphenol A (2 mole adduct) and terephthalic acid (molar ratio 10:12), glass transition temperature (Tg) 68°C, weight average molecular weight (Mw) 10,000, molecular weight distribution (Mw/Mn) 5.12)
Fischer-Tropsch wax (melting point 78° C.): 7.0 parts This material was added to the colorant dispersion and heated to 65° C., and then dissolved and dispersed uniformly at 500 rpm using a T.K. homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to prepare a polymerizable monomer composition.

(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 T.K. 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.

(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. to carry out distillation for 6 hours, thereby distilling off the unreacted polymerizable monomer, and a resin particle dispersion was obtained.

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

After adjusting the temperature of the resin particle dispersion obtained above to 55°C, 25.0 parts of the hydrolyzed liquid of the organosilicon compound (addition amount of organosilicon compound was 10.0 parts) was added to initiate polymerization of the organosilicon compound. After holding for 0.25 hours, the pH was adjusted to 5.5 with a 3.0% aqueous sodium bicarbonate solution. With continued stirring at 55°C, the mixture was held for 1.0 hour (condensation reaction 1), after which the pH was adjusted to 9.5 with a 3.0% aqueous sodium bicarbonate solution and held for a further 4.0 hours (condensation reaction 2) to obtain a toner particle dispersion.

(Washing process and drying process)
After the organosilicon polymer formation process was completed, the toner particle dispersion was cooled, and hydrochloric acid was added to the toner particle dispersion to adjust the pH to 1.5 or less, and the mixture was left for 1.0 hour while stirring. Thereafter, the mixture was subjected to solid-liquid separation using a pressure filter to obtain a toner cake. The obtained toner cake was reslurried with ion-exchanged water to form a dispersion again, and then subjected to solid-liquid separation using the aforementioned filter to obtain a toner cake. The obtained toner cake was transferred to a thermostatic chamber at 40°C, and dried and classified for 72 hours to obtain toner particles.

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

<Production Example of Developer>
100.00 parts of toner particles 1 and 1.00 parts of external additive A were charged into a Henschel mixer (FM10C type manufactured by Nippon Coke & Engineering Co., Ltd.) with water at 7°C passing through the jacket. Next, after the water temperature in the jacket stabilized at 7°C ± 1°C, the mixture was mixed for 10 minutes with the peripheral speed of the rotating blade set to 38 m/sec. During the mixing, the amount of water passing through the jacket was appropriately adjusted so that the temperature inside the tank of the Henschel mixer did not exceed 25°C. The obtained mixture was sieved through a mesh with an opening of 75 μm to obtain a developer.

The physical properties of the developer are shown in Table 2.

In the table, "X" represents the ratio of the number average particle diameter R of the primary particles of external additive A to the number average value of the convex height H. When the produced developer was observed using an SEM, it was confirmed that external additive A was arranged as fine particles on the convex portions of the organosilicon polymer of the toner particles, and the average number of external additive A particles coated per toner particle was about 500.
7. Operation of the Present Example Next, the operation of the present example will be described using a comparative example.

In this embodiment, before the toner image is developed, fine particles are supplied from the toner carried on the developing roller 41 to the photosensitive drum 1 in advance, and the fine particles are caused to adhere to the photosensitive drum 1. To achieve this, the adhesion force Ft between the fine particles and the toner is made smaller than the adhesion force Fdr between the fine particles and the photosensitive drum 1. This reduces the friction force F between the photosensitive drum 1 and the intermediate transfer belt 20, thereby suppressing image streaks caused by rotational fluctuations of the photosensitive drum 1 while also suppressing color fluctuations in the recording material P.

The following explanation will be based on the configuration of the first image forming station a.

First, to demonstrate the effect of covering the photosensitive drum 1a with a certain amount of fine particles in this embodiment, the adhesion force Ft between the fine particles and the toner and the adhesion force Fdr between the fine particles and the photosensitive drum 1a were measured.

Specifically, the adhesion force was measured using an SPM. A cantilever with a microparticle fixed to the tip of the lever was created, and the cantilever was pressed against the toner with a specified pressure, after which the force required to detach the cantilever from the toner was measured as the adhesion force Ft between the microparticle and the toner.

The specified pressure with which the cantilever is pressed against the toner when measuring adhesion is preferably set to the force with which the fine particles present between the toner and the photosensitive drum 1a in the development nip are pressed against the toner, and was calculated using the calculation method described below. Here, the state in which the fine particles are present between the toner and the photosensitive drum 1a in the development nip refers to the state in which the fine particles are in contact with both the toner and the photosensitive drum at the same time.

Specifically, it is assumed that the developing roller 41a and the photosensitive drum 1a are in contact with each other via toner at the developing nip, and that the toner in contact with the photosensitive drum 1a is closest packed. In addition, it is assumed that the toner and the photosensitive drum 1a are in contact with each other via fine particles at the contact area between the toner and the photosensitive drum 1a.

After making the above assumptions, the total number N of microparticles present between the toner and the photosensitive drum 1a in the development nip was calculated. Then, F/N, which is the pressing force on the toner per microparticle in the development section, was calculated from the calculated N and the contact force F between the development roller 41a and the photosensitive drum 1a, and the calculated F/N was used as the specified pressing force of the cantilever on the toner when measuring the adhesion force.

In this embodiment, the pressing force F between the developing roller 41a and the photosensitive drum 1a is 200 gf, so the "pressure on the toner per microparticle in the developing nip" = F/N is approximately 4.5 (nN). Therefore, in this embodiment, this 4.5 (nN) was adopted as the predetermined pressing force of the cantilever on the toner when measuring adhesion force using the SPM.

A similar adhesion measurement was also performed on the photosensitive drum 1a, and the adhesion force Fdr between the fine particles fixed to the tip of the cantilever and the photosensitive drum 1a was measured.

As a result, in this embodiment, the adhesive force Ft between the particles and the toner was 32.8 (nN), and the adhesive force Fdr between the particles and the photosensitive drum 1a was 210.1 (nN), confirming that the adhesive force Ft between the particles and the toner was smaller than the adhesive force Fdr between the particles and the photosensitive drum 1a. Note that the magnitude relationship does not change even if the pressure of the cantilever is measured in the range from 3.0 (nN) to 50 (nN).

Next, we will explain the results of an evaluation conducted to confirm the effect of the means for supplying fine particles to the photosensitive drum 1a in this embodiment.

For the evaluation, the present embodiment, other embodiments, and Comparative Example 1, Comparative Example 2, and Comparative Example 3 were evaluated for the presence or absence of image streaks and the color variation of the recording material P.

Regarding image streaks, because they are easily affected by uneven laser exposure and tend to stand out in halftone toner image areas, a judgment was made using a halftone image with a density of 25%. A level where image streaks are clearly visible even in a halftone image was defined as rank C, a level where image streaks are faintly visible even in a halftone image was defined as rank B, and a level where image streaks are not visible even in a halftone image was defined as rank A.

Regarding the color variation of the recording material P, the density D1 of the white part after printing on high white paper (GFC081 Canon) and the density D0 of the high white paper on which no printing was performed were each measured using a reflection densitometer (Reflectometer Model TC-6DS manufactured by Tokyo Denshoku Co., Ltd.). The difference "D0-D1" was then defined as the color variation of the recording material P. When the reflection density difference value "D0-D1" was 3.5% or more, the recording material P was rated as C rank, in which the color variation was clearly visible. When it was 2.5% or more, the recording material P was rated as B rank, in which the color variation was faintly visible. When it was less than 2.5%, the recording material P was rated as A rank, in which the color variation was not visible.

In this embodiment, the photosensitive drum 1a is coated with fine particles to reduce the friction force F between the photosensitive drum 1a and the intermediate transfer belt 20. The amount of fine particles added is adjusted to about 0.5% of the toner weight, and the number of fine particles coated per toner particle is about 500. The coverage rate of the fine particles on the photosensitive drum 1a is 30%.

In another configuration, the photosensitive drum 1a is coated with fine particles to reduce the friction force F between the photosensitive drum 1a and the intermediate transfer belt 20. The amount of fine particles added is adjusted to about 0.2% of the toner weight, and the number of fine particles coated per toner particle is about 200. A fine particle coverage rate of 10% on the photosensitive drum 1a was used.

In the configuration of Comparative Example 1, the photosensitive drum 1a is coated with fine particles, and the amount of fine particles added is adjusted to about 0.1% of the toner weight, and the number of fine particles coated per toner particle is adjusted to about 100. A fine particle coverage rate of 5% on the photosensitive drum 1a was used.

Comparative example 2 uses a configuration that does not use fine particles or toner as a means for reducing the friction force F between the photosensitive drum 1a and the intermediate transfer belt 20.

In the configuration of Comparative Example 3, a yellow dot toner image was used as a means for reducing the friction force F between the photosensitive drum 1a and the intermediate transfer belt 20, and a toner coverage rate of 5% on the photosensitive drum 1a was used.

Next, the evaluation results are explained using Table 3.

In the configuration of Comparative Example 1, the coverage rate of the fine particles on the photosensitive drum 1a for reducing frictional force is 5%, and when there is no toner in the drum nip portion, a slight frictional force F acts on the surface of the photosensitive drum 1a downstream of the surface of the intermediate transfer belt 20 in the tangential direction (sub-scanning direction). Then, when the leading edge of the toner image of the halftone image developed on the photosensitive drum 1a enters the drum nip portion, this frictional force F decreases. As a result, slight but sudden rotation fluctuations occur on the photosensitive drum 1a, and writing unevenness occurs in the laser exposure to the surface of the photosensitive drum 1a. As a result, streaks in the main scanning direction are formed on the toner image formed on the surface of the photosensitive drum 1a subsequently, and image streaks occur on the halftone image. On the other hand, with regard to color fluctuations of the recording material P, no color fluctuations occur because fine particles, not toner, are used as a means for reducing the frictional force F between the photosensitive drum 1a and the intermediate transfer belt 20.

In the configuration of Comparative Example 2, since no fine particles or toner for reducing frictional force are present on the photosensitive drum 1a, when the leading edge of the toner image of the halftone image developed on the photosensitive drum 1a enters the drum nip, the frictional force F decreases rapidly. This causes sudden fluctuations in the rotation of the photosensitive drum 1a, resulting in uneven writing in the laser exposure to the surface of the photosensitive drum 1a. As a result, clearly visible image streaks are generated on the halftone image. On the other hand, with regard to color fluctuations in the recording material P, no color fluctuations occurred because neither toner nor fine particles are used as a means of reducing the frictional force F between the photosensitive drum 1a and the intermediate transfer belt 20.

In the configuration of Comparative Example 3, the photosensitive drum 1a is coated with 5% yellow dot toner to reduce friction. When the leading edge of the toner image of the halftone image developed on the photosensitive drum 1a enters the drum nip, image streaks occur on the halftone image, as in Comparative Example 1. Furthermore, with regard to the color variation of the recording material P, the reflection density difference value "D0-D1" was 2.5% or more, and the color variation was at a level where it was faintly visible. If the conditions of Comparative Example 3 were changed to increase the coverage rate, which is the direction in which image streaks are suppressed, the color variation would worsen, and conversely, if the coverage rate was changed to decrease the direction in which color variation is suppressed, the image streaks would worsen.

In contrast, in this embodiment and other implementation configurations (variations), the photosensitive drum 1a is coated with 30% and 10% of fine particles, respectively, to reduce frictional force. In either case, even if the leading edge of the toner image of the halftone image developed on the photosensitive drum 1a enters the drum nip portion, no sudden fluctuation in the rotation of the photosensitive drum 1a occurs, so no image streaks are generated. In addition, taking into account the results of Comparative Example 1, it is preferable that the coverage rate of the fine particles supplied to the photosensitive drum 1a required to reduce frictional force is 10% or more.

On the other hand, no color fluctuation occurred in the recording material P because fine particles, rather than toner, were used as a means for reducing the friction force F between the photosensitive drum 1a and the intermediate transfer belt 20.

As described above, in this embodiment, before the toner image is developed, fine particles are supplied from the toner carried on the developing roller 41 to the photosensitive drum 1 in advance, and the fine particles are adhered to the photosensitive drum 1. As a result, the fine particles are interposed between the photosensitive drum 1 and the intermediate transfer belt 20, reducing the frictional force F at the drum nip portion. Furthermore, with regard to the supply of fine particles to the photosensitive drum 1, the adhesion force Ft between the fine particles and the toner is made smaller than the adhesion force Fdr between the fine particles and the photosensitive drum 1, and the particle diameter of the fine particles is made 1000 nm or less. As a result, it is possible to supply fine particles to the photosensitive drum 1 without being affected by electrostatic forces.

This makes it possible to suppress image streaks caused by rotational fluctuations of the photosensitive drum 1 while also suppressing color fluctuations in the recording material P with a simple configuration.

In the configuration of the image forming device applied in this embodiment, the same components as those in the first embodiment are given the same reference numerals and the description is omitted.

In the configuration of Example 1, a method was described in which fine particles added to the toner are supplied to the photosensitive drum 1 in order to suppress image streaks caused by rotational fluctuations of the photosensitive drum 1 while also suppressing color fluctuations of the recording material P.

In contrast, in this embodiment, the cleaning units 5a, 5b, 5c, and 5d on the photosensitive drums 1a, 1b, 1c, and 1d are not provided, and a so-called drum cleanerless configuration is used. This is characterized by the fact that fine particles can be maintained on the photosensitive drums 1a, 1b, 1c, and 1d for a long period of time.

The configuration of this embodiment is explained below with reference to Figure 14.

In the drum cleanerless system described above, as shown in FIG. 14, no cleaning units are provided on the photosensitive drums 1a, 1b, 1c, and 1d. Therefore, the toner remaining on the photosensitive drums 1a, 1b, 1c, and 1d during the primary transfer must be collected in the developing units 4a, 4b, 4c, and 4d.

Below, we will explain how to recover the toner remaining on the photosensitive drums 1a, 1b, 1c, and 1d using the fourth image forming station d.

Among the toner (primary transfer residual toner and retransferred toner) remaining on the photosensitive drum 1d without being primarily transferred to the intermediate transfer belt 20 at the primary transfer section, the positive polarity toner adheres to the charging roller 2d. Then, as the photosensitive drum 1d rotates, the negative polarity toner is transported through the contact portion with the charging roller 2d to the opposing portion with the developing unit 4d. At this time, the surface of the photosensitive drum 1d is charged and exposed again, and an electrostatic latent image according to the image information is formed. The residual toner transported to the opposing portion with the developing unit 4d is almost negative polarity. Therefore, a part of the residual toner is collected by the developing unit 4d in the electric field formed by the difference between the surface potential of the photosensitive drum 1d (non-exposed portion is -500V, exposed portion is -100V) and the voltage applied to the developing roller 41d (-300V). In the non-exposed area, the direction of the electric field is such that the negative toner moves from the photosensitive drum 1d onto the developing roller 41d, so the remaining toner on the photosensitive drum 1d moves onto the developing roller 41d and is collected in the developing unit 4d.

Meanwhile, in the exposure section, the direction of the electric field is such that the negative toner moves from the developing roller 41d onto the photosensitive drum 1d, so the negative toner on the developing roller 41d moves onto the photosensitive drum 1d and develops the electrostatic latent image on the photosensitive drum 1d. At this time, the transfer residual toner on the photosensitive drum 1d is also used to develop the electrostatic latent image. In this way, the developing unit 4d is configured to develop the electrostatic latent image formed on the photosensitive drum 1d into a toner image and to collect the toner adhering to the photosensitive drum 1d.

The above operations are used to recover the remaining toner on the photosensitive drum 1d in the drum cleanerless system.

The rest of the configuration is the same as in Example 1, so the explanation will be omitted.

Next, we will explain the operation of this embodiment.

In the configuration of this embodiment, as in the first embodiment, before the toner image is developed, fine particles are supplied to the photosensitive drum 1 from the toner carried on the developing roller 41. In order to supply fine particles onto the photosensitive drum 1, the adhesion force Ft between the fine particles and the toner is made smaller than the adhesion force Fdr between the fine particles and the photosensitive drum 1. As a result, as shown in FIG. 7(a) and FIG. 7(b), when the toner image is primarily transferred from the photosensitive drum 1 to the intermediate transfer belt 20, only the toner image is primarily transferred onto the intermediate transfer belt 20. Then, the fine particles interposed between the toner image and the photosensitive drum 1 remain on the photosensitive drum 1. In this case, in the configuration of the first embodiment, the cleaning unit 5 arranged on the photosensitive drum 1 collects the fine particles remaining on the photosensitive drum 1. Therefore, fine particles must be supplied from the toner carried on the developing roller 41 every time an image is formed. On the other hand, in the configuration of this embodiment, since no cleaning unit is provided on the photosensitive drum 1, the fine particles supplied to the photosensitive drum 1 continue to remain on the photosensitive drum 1. The same is true when recovering toner in the developing unit 4 in the drum cleanerless system described above. In other words, because the particle size of the fine particles is 1000 nm or less, they are less susceptible to electrostatic effects, and the fine particles are not recovered by the developing unit 4 but remain on the photosensitive drum 1. This makes it possible to maintain the state in which the fine particles are attached to the photosensitive drum 1, and to provide stable images over a long period of time.

In the configuration of Example 1, the time for supplying the fine particles during the image formation operation had to be set to be longer than the time it takes for the part of the photosensitive drum 1 where the developing roller 41 contacts to reach the drum nip. In the drum cleaner-less configuration of this embodiment, as described above, the fine particles supplied to the photosensitive drum 1 can be maintained, so development can begin at the timing when the developing roller 41 contacts the photosensitive drum 1. This shortens the time from when the image forming device receives image data to when it prints it out, which reduces user stress.

As explained above, by adopting a so-called drum cleanerless configuration in which the cleaning unit 5 is not provided on the photosensitive drum 1, it is possible to stably maintain fine particles on the photosensitive drum 1. This makes it possible to provide stable images over a long period of time. In addition, the time from when image data is received until it is printed out can be shortened.

In the configuration of the image forming device applied in this embodiment, the same components as those in the first and second embodiments are given the same reference numerals and the description is omitted.

In the configuration of Example 1, a method was described in which fine particles added to the toner are supplied to the photosensitive drum 1 in order to suppress image streaks caused by rotational fluctuations of the photosensitive drum 1 while suppressing color fluctuations of the recording material P.

In contrast, in this embodiment, the metal roller 40 is offset by a predetermined amount between the intermediate transfer belt 20 and the photosensitive drum 1 in the transfer section. This makes it possible to reduce the friction force F between the photosensitive drum 1 and the intermediate transfer belt 20, and suppresses image streaks.

The configuration of this embodiment will be explained below with reference to Figures 15 and 16.

Figure 15 is a diagram of the image forming apparatus in this embodiment, and Figure 16 is an enlarged view of the configuration of the first image forming station a in Figure 15. In Figure 16, the metal roller 40a is disposed at a position offset by 8 mm downstream in the moving direction of the intermediate transfer belt 20 from the center position of the photosensitive drum 1a. Also, in order to ensure the amount of winding of the intermediate transfer belt 20 around the photosensitive drum 1a, it is disposed at a position raised by 1.0 mm from the horizontal plane formed by the photosensitive drum 1a and the intermediate transfer belt 20. The above-mentioned metal roller 40 is disposed as close as possible to the photosensitive drum 1 without contacting it in order to avoid scratches caused by contact with the photosensitive drum 1. Also, the reason for disposing it on the downstream side of the moving direction of the intermediate transfer belt 20 is that it is advantageous against the phenomenon of scattering caused by the generation of a transfer electric field on the upstream side of the primary transfer nip.

When the offset distance of the metal roller 40a is K, the lift height of the metal roller 40a relative to the intermediate transfer belt 20 is Z, and the drum nip width is Nk, in this embodiment, K = 8 mm, Z = 1.0 mm, and Nk = 1500 μm. The metal roller 40a is made of a straight nickel-plated SUS round bar with an outer diameter of 6 mm, and rotates in response to the rotation of the intermediate transfer belt 20. The metal roller 40b arranged in the second image forming station b, the metal roller 40c arranged in the third image forming station c, and the metal roller 40d arranged in the fourth image forming station d are also configured in the same way as the metal roller 40a.

The rest of the configuration is the same as in Example 2, so the explanation is omitted.

Next, we will explain the operation of this embodiment.

As described above, in this embodiment, the metal roller 40 is offset by a predetermined amount via the intermediate transfer belt 20 at a position facing the photosensitive drum 1 in the transfer section. Also, as described in the first embodiment, in order to realize the effect of improving the primary transfer efficiency due to the difference in peripheral speed between the photosensitive drum 1 and the intermediate transfer belt 20, the drum nip width Nk is set to 1500 μm, the same as in the first embodiment.

With this configuration, it is possible to reduce the pressure applied to the drum nip portion compared to the configuration in Example 1 in which the transfer roller 14 applies pressure directly to the photosensitive drum 1 via the intermediate transfer belt 20 to form the drum nip portion. In other words, the frictional force F is the product of the normal force and the friction coefficient, and reducing the pressure applied to the drum nip portion, which corresponds to the normal force, also leads to a reduction in the frictional force F of the drum nip portion.

In addition, to reduce the friction force F at the drum nip, the adhesion force Ft between the fine particles and the toner is made smaller than the adhesion force Fdr between the fine particles and the photosensitive drum 1. The effect of suppressing image streaks and color fluctuations on the recording material P caused by rotational fluctuations of the photosensitive drum 1 by supplying fine particles onto the photosensitive drum 1 is the same as in Examples 1 and 2.

As described above, in this embodiment, the metal roller 40 is offset by a predetermined amount between the intermediate transfer belt 20 and the photosensitive drum 1 in the transfer section. This makes it possible to reduce the friction force F between the photosensitive drum 1 and the intermediate transfer belt 20, and suppresses image streaks.

In addition, in this embodiment, a configuration has been described in which fine particles are supplied to and adhered to the photosensitive drum 1 corresponding to each color image forming station. For example, even when printing in a mono mode in which only black is printed in a single color, the friction force F between the photosensitive drum 1 and the intermediate transfer belt 20 can be maintained at a low state without separating the primary transfer members of the color image forming stations a, b, and c for the colors (yellow, magenta, and cyan). In other words, there is no need to provide a mechanism for contacting and separating the primary transfer members, making it possible to further reduce the size and cost of the main body.

1 Photosensitive drum 4 Development unit 20 Intermediate transfer belt 41 Development roller T Toner

Claims (11)

A rotatable image carrier;
a developer storage section for storing a developer including toner particles each having a toner base particle and a contact portion formed on the surface of the toner base particle and in surface contact with the surface of the toner base particle, and fine particles as an external additive in contact with the surface of the contact portion ;
a developer carrier that contacts the image carrier to form a development section and supplies the developer to a surface of the image carrier in the development section;
an intermediate transfer body that contacts the image carrier to form a transfer section, and onto which a toner image formed by the developer supplied to the surface of the image carrier is transferred in the transfer section;
a drive unit that drives the image carrier and the intermediate transfer body so that there is a speed difference between a moving speed of the surface of the image carrier and a moving speed of the surface of the intermediate transfer body;
When a pressing force for pressing the developer carrier against the image carrier is F and a total number of the fine particles present between the contact portion and the image carrier in the developing portion is N,
an adhesive force Ft formed between the particle and the contact portion , the adhesive force Ft being measured when the particle is pressed against the contact portion with a pressing force per unit particle, F/N;
and an adhesive force Fdr formed between the fine particle and the image carrier measured when the fine particle is pressed against the image carrier at the F/N ratio,
Ft≦Fdr
An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the developer has convex portions at the contact portion formed from fine particles containing an organosilicon polymer having a structure represented by the following formula (1) present on the surface of the toner base particle, and the fine particles are disposed on the convex portions:
R-Si(O1/2)3 (1)
(The R represents a hydrocarbon group having 1 to 6 carbon atoms.) The image forming apparatus according to claim 1 or 2, characterized in that the developer remaining on the image carrier without being transferred to the intermediate transfer body is collected by the developer carrier. The image forming apparatus according to claim 3, characterized in that the developer is a one-component developer. The speed ratio between the moving speed Vdr of the image carrier and the moving speed Vb of the intermediate transfer body is Vr=|Vdr-Vb|/Vdr×100.
The nip width of the nip formed between the image carrier and the intermediate transfer body in the transfer portion is Q,
When the weight average particle diameter of the toner particles is defined as D,
5. The image forming apparatus according to claim 1, wherein Vr and Q satisfy the following relational expression: Vr=V+Q/Q.
1/2 x D (μm) x π≦Vr (%) x Q (μm)/100≦100 (μm) The image forming device according to claim 2, characterized in that, when the closest distance between adjacent convex portions is defined as a convex interval G, the average of the convex interval G is equal to or smaller than the average particle size of the fine particles. 3. The image forming apparatus according to claim 2, wherein, when a height H of the convex portion from the surface of the toner base particle is taken as a convex height, the average of the convex height H is equal to or smaller than an average particle diameter of the fine particles. The image forming apparatus according to any one of claims 1 to 7, characterized in that the fine particles are silica. The image forming apparatus according to any one of claims 1 to 8, characterized in that the fine particles are organic silica polymers. The image forming apparatus according to any one of claims 1 to 9, characterized in that the average particle size of the fine particles is 30 nm or more and 1000 nm or less. a transfer member that transfers a toner image formed by the developer supplied to the surface of the image carrier to the intermediate transfer body in the transfer section;
11. The image forming apparatus according to claim 1, wherein the transfer member is disposed at a position offset from a position at which the image carrier is disposed with respect to a moving direction of the surface of the intermediate transfer body.

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