JP2008139431A - Developing device, process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce toner deterioration even when using a developing device continuously and to prevent the occurrence of a so-called unclear image resulting from a transfer efficiency decrease. <P>SOLUTION: Particles are applied to a supply roller 104. The particles are such that if the supply roller 104 is insulative or conductive and has a potential same as a developing roller 106, the relationship between the mass m' per unit area of toner after passed along a regulating blade 105 on the developing roller 106 when the particles are applied to the supply roller 104 and the mass m per unit area of the toner when the particles are not applied to the supply roller 104 is m'<m. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a function of forming an image on a recording medium such as a recording material, such as a copying machine, a printer, a fax machine, and the like, and in particular, a developing device and a process provided in these apparatuses. This relates to the cartridge.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic printer or a copying machine, printing is performed by an electrophotographic process whose main processes are a charging process, an exposure process, a developing process, a transfer process, and a fixing process. Here, the charging process is a process for applying a charge on the photoreceptor. The exposure process is a process for forming an electrostatic latent image on the photoconductor based on image data. The development process is a process for visualizing the electrostatic latent image on the photoreceptor with toner as a developer. The transfer process is a process for transferring the toner image on the photoconductor to paper or the like as a recording medium. The fixing process is a process for fixing the toner image on the recording medium with heat or pressure.

  Various development process methods have been developed. Among them, there is a non-magnetic one-component development method as a small and inexpensive development method.

  A developing device using a general non-magnetic one-component developing system includes a developing roller as a developer carrier, a supply roller as a supply member, and a regulation blade as a regulation member. Here, the developing roller conveys toner as a developer to a portion in contact with or close to the photoreceptor. The supply roller supplies toner onto the developing roller. The regulating blade uniformly regulates the toner on the developing roller conveyed by the supply roller.

  In general, a developing roller having a base layer made of a thin layer of urethane or the like using silicon rubber as a base layer or a surface layer of a single layer of hydrin rubber is used. The regulation blade is configured to abut a metal sheet such as phosphor bronze or SUS or a sheet on which nylon or urethane rubber is attached to the developing roller with a predetermined pressure. The supply roller is composed of a sponge having a foam cell and a cored bar, and is capable of rotating with a speed difference to the developing roller by a predetermined amount of entry.

  By configuring the supply roller with the foamed sponge material as described above, a large amount of toner can be conveyed to the developing roller, and at the same time, the toner remaining on the developing roller without being developed can be peeled off. With these two functions, the toner developed on the photoreceptor can maintain a stable specific charge and a coating amount. However, a concern of this configuration is that the toner is easily rubbed because the supply roller rubs against the developing roller, and the external additive added to the toner base is embedded or peeled off. So-called toner deterioration is likely to occur.

In order to solve this problem, as described in Patent Document 1, a configuration in which the supply roller is arranged in non-contact with the developing roller has been devised.
JP 11-327291 A

However, when a supply roller arranged in a non-contact manner as in Patent Document 1 is used, it is necessary to provide a separate capability for peeling off the toner on the developing roller. There is a problem.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and has an object to reduce so-called edge images that occur due to reduction in toner deterioration and reduction in transfer efficiency even when a developing device is continuously used. To do.

In order to achieve the above object, the present invention provides:
A developer carrier;
A supply member for conveying the developer onto the developer carrying member;
A regulating member that regulates the developer on the developer carrying member conveyed from the supply member;
In a developing device comprising:
The supply member is pre-coated with particles,
The particles are
When the supply member is insulative or conductive and has the same potential as the developer carrier,
A mass m ′ per unit area of the developer after passing through the regulating member on the developer carrier when the particles are applied to the supply member;
The mass m per unit area of the developer after passing through the regulating member on the developer carrier when the particles are not applied to the supply member;
Is a particle in which the relationship of m ′ <m.

  According to the present invention, it is possible to reduce toner deterioration even when the developing device is continuously used, and to suppress a so-called edge image that occurs due to a decrease in transfer efficiency.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.

(Image forming device)
FIG. 2 is a schematic sectional view of the image forming apparatus 1. FIG. 3 is a schematic sectional view of the process cartridge.

  In FIG. 2, the image forming apparatus 1 has four process cartridges 2 that respectively form yellow, magenta, cyan, and black color images, which are sequentially attached and detached from the upstream side of the conveyance path of the recording material (recording medium) 3. Arranged to be possible. As shown in FIG. 3, the process cartridge 2 includes a photosensitive drum 4, a charging roller 5, a cleaning device 6, and a developing device 100. Various biases are applied to the process cartridge 2 from a high voltage power source (not shown).

  Hereinafter, the movement of the image forming apparatus 1 will be described.

  The recording material 3 conveyed from the feeding unit by the feeding roller and the feeding pad is adsorbed on the transfer belt 7 and conveyed upward to the discharge unit 9.

Meanwhile, the toner image formed on the photosensitive drum 4 of each color is transferred by the transfer bias. In the present embodiment, so-called negative toner, which is toner 101 as a developer having a negative polarity, is used, so that toner 101 is attracted to the transfer belt 7 with respect to the surface potential of the photosensitive drum 4. It is necessary to apply a positive bias. The toner attracted to the transfer bias adheres on the recording material 3 and is conveyed to the transfer portion of the next color.

  In this way, the colors are sequentially overlaid to form a color toner image. The so-called transfer residual toner remaining without being transferred onto the photosensitive drum 4 of each color is peeled off from the photosensitive drum 4 by the cleaning blade 6a disposed on the photosensitive drum 4 and collected in the waste toner container 6b. .

  The recording material 3 on which the color toner image is formed is conveyed to the fixing device 8. In the fixing device 8, the toner image is sandwiched between a pair of rollers whose temperature is adjusted to a predetermined temperature in the fixing nip portion, and receives heat and pressure simultaneously. At this time, the toner 101 melts and becomes entangled on the surface of the recording material fiber, and when it passes through the fixing nip portion and is cooled, it solidifies and fixes as it is. The recording material 3 on which the toner image has been fixed is discharged to the discharge unit 9, where one image forming process is completed. In the case where images are continuously formed, the above process is sequentially repeated.

(Process cartridge)
The process cartridge 2 in FIG. 3 includes a developing device 100, a photosensitive drum 4, a charging roller 5, and a cleaning device 6.

  The photosensitive drum 4 is composed of a semiconductor thin film of about 20 to 25 μm formed on the base layer of the aluminum base tube. On the surface of the photosensitive drum 4, a charging roller 5 is pressed and rotated. In order to charge the photosensitive drum 4 to a uniform potential, it is only necessary to apply a bias to the charging roller 5 to generate a discharge due to a potential difference from the conductive base layer of the photosensitive drum 4.

  The charging roller 5 is provided with a conductive foam sponge layer around the core metal, and a layer made of a rubber tube made of urethane or the like having higher resistance than the foam sponge. Further, the surface is covered with a thin rubber compounded with fluorine so that the toner 101 which has passed through the cleaning blade 6a and the external additive released from the toner are difficult to adhere.

  The photosensitive drum 4 charged by the charging roller 5 is driven to rotate and enters the exposure unit. In the exposure unit, the surface potential of the photosensitive drum 4 is partially lowered by exposure from the exposure apparatus 10, and electrostatic latent images of 600 dpi (dot / inch) and 1200 dpi are sequentially formed.

  The exposure apparatus 10 uses a semiconductor laser as a light source, and scans the photosensitive drum by reflecting the laser beam to a polygon mirror that rotates at high speed.

  The cleaning device 6 includes a cleaning blade 6a, a supporting metal plate thereof, and a waste toner container 6b. The cleaning blade 6a is made of hard urethane, silicone rubber or resin material, and is in contact with the photosensitive drum 4 at a predetermined angle and pressure. The cleaning blade 6a has a function of peeling off the transfer residual toner from the photosensitive drum 4 and storing it in a waste toner container 6b.

(Developer)
FIG. 1 is a schematic sectional view of a developing device 100 to which the present invention can be applied.

It is a function of the developing device 100 to visualize the electrostatic latent image as a toner image. The developing device 100 includes a toner container portion 102 filled with the toner 101, and the toner 101 is stirred while being conveyed to the vicinity of the supply roller 104 serving as a supply member by a stirring blade 103 that is rotationally driven. As members for forming a latent image on the photosensitive drum 4 with the toner 101 conveyed by the stirring blade 103, a supply roller 104, a regulating blade 105 as a regulating member, and a developing roller 106 as a developer carrier are provided. is there.

  The supply roller 104 is a so-called elastic sponge roller configured by a sponge such as urethane foam having ion conductivity or electronic conductivity and a cored bar at the center of rotation. As a material other than urethane, foamed silicon or the like may be used. A supply bias (supply roller bias) can be applied to the supply roller 104 from a power source Vc as a voltage application means. The resistance value of the supply roller 104 is preferably about 2 × 10 3 to 5 × 10 9 Ω. The measuring method of the resistance value is almost the same as that of the developing roller 106 described later.

  In Examples and Comparative Examples described later, particles are applied to the supply roller 104.

  FIG. 4 is a schematic sectional view of the supply roller 104 used in Examples and Comparative Examples described later. Urethane rubber was foamed on a SUS (stainless steel) core metal to produce a roller having a diameter of 16 mm. The foam cells may communicate with each other.

  FIG. 5 is a schematic view showing a state where the particles P are applied to the supply roller 104. If the particles P adhere to the supply roller 104 with almost no gap, the toner 101 cannot adhere. Selecting the particles P that improve the sliding of the toner 104 among the supply roller 104, the particles P, and the developing roller 106 leads to improvement in toner deterioration.

  The regulating blade 105 is a metal sheet such as phosphor bronze or SUS having a thickness of about 50 to 200 μm, and is supported by a sheet metal and fixed to the developing device casing. The surface of the regulating blade 105 preferably has a 10-point average roughness Rz measured based on JIS B0601 of 2 μm or less. In FIG. 1, the regulating blade 105 is supported in a so-called counter direction in which a force in the direction opposite to the rotation direction of the developing roller 106 is generated, and the unsupported end is a free end. The regulation blade 105 is configured to be able to apply a regulation blade bias from the power source Vb, but an insulating material may be used.

  The developing roller 106 is composed of one or more layers of rubber material having moderate conductivity around a metal core made of metal such as stainless steel. The rubber material is a commonly used rubber such as silicon rubber, urethane rubber, acrylic rubber, natural rubber, EPDM. The resistance value can be obtained by dispersing carbon, carbon resin particles, metal particles, an ionic conductive agent, or the like. The developing roller 106 is configured to be able to apply a bias from the power source Va.

  The resistance value of the developing roller 106 is preferably 2 × 10 4 to 5 × 10 8 Ω. Below this range, the current flowing through the elastic layer increases and the required electric capacity increases. On the other hand, if it exceeds this range, the current flowing during development tends to be hindered.

  FIG. 6 is a schematic diagram illustrating a method for measuring the resistance values of the developing roller 106 and the supply roller 104. FIG. 6 shows a roller to be measured, a cylindrical member 50 made of stainless steel, and a measurement circuit 51. The cylindrical member 50 has a diameter of 30 mm and rotates at a speed of about 48 mm / s. At this time, the roller to be measured rotates following the rotation of the cylindrical member 50. The end of the roller to be measured is an end that restricts the amount of entry into the cylindrical member 50 to 50 μm for the developing roller 106 and 1.5 mm for the supply roller 104 (measured by the amount of entry when incorporated in the developing device). A part roller 52 is attached.

The end roller 52 has a cylindrical shape smaller than the outer diameter of the roller to be measured. The load applied to both ends of the roller to be measured is pressed against the cylindrical member 50 by a load of 1 kg in total, weighing 500 g on each side. The measurement circuit 51 includes a power source Ein, a resistor Ro2, and a voltmeter Eout2. In this measurement, the voltage of Ein2 was 300V. The resistor Ro2 can use 100Ω to 10MΩ. With these measurement systems, the roller resistance value Rb is calculated by the following equation.
Rb = Ro2 {(Ein / Eout) -1}

  The arithmetic average roughness Ra, which is an index of the surface roughness of the developing roller 106, was measured using a surface roughness tester SE-30 manufactured by Kosaka Laboratory Co., Ltd. based on JIS B0601. The measurement points were measured at three points in the circumferential direction, ie, a portion close to the left and right end portions in the longitudinal direction, and the average value of a total of nine points was defined as the surface roughness in the present invention. The surface roughness has various values in the examples and comparative examples.

  The hardness of the developing roller 106 was an ASKER C rubber hardness meter. Since problems occur even if it is too hard or too soft, 30 to 90 ° is preferable. In particular, in the combination of the metal regulation blade 105 and the developing roller having a hardness exceeding 90 °, the toner 101 is not well regulated and the resistance value is difficult to control, so that current leakage occurs when a potential difference is provided. Cause image distortion.

  The supply roller 104 and the developing roller 106 are preferably disposed so that the amount of entry is 0.5 to 2 mm. The supply roller 104 and the developing roller 106 are rotated (moved) in the contact portion (hereinafter referred to as a supply nip) in a direction in which the surfaces (circumferential surfaces) rotate in the opposite direction (opposite direction). . Therefore, the toner 101 in the vicinity of the supply roller 104 is conveyed onto the developing roller 106 by the supply roller 104, and at the same time, the toner 101 remaining on the developing roller 106 without being developed is peeled off.

  The toner 101 supplied onto the developing roller 106 by the supply roller 104 enters the regulating portion by the rotation of the developing roller 106 and is regulated by the regulating blade 105 so as to become a uniform toner layer of about 1 to 3 layers. At the time of toner regulation, the toner is rubbed between the regulation blade 105 and the developing roller 106, so that it can have a charge.

  The uniform toner layer on the developing roller 106 formed by the regulating blade 105 develops the electrostatic latent image on the photosensitive drum 4 in the developing unit. Since the contact developing method is assumed in this embodiment, the developing roller 106 is pressed against the photosensitive drum 4, but the present invention is also effective in the non-contact developing method. Further, the developing roller 106 rotates with a circumferential speed ratio of about 1.3 times with respect to the photosensitive drum 4. The developing roller can transfer the charged toner 101 onto the photosensitive drum 4 by applying a potential about halfway between the exposed portion and the non-exposed portion on the photosensitive drum 4 from the power source Va to develop the latent image. it can.

(toner)
The toner 101 used in this exemplary embodiment has a volume average particle diameter containing a colorant or a charge control agent corresponding to each color using styrene-acryl, polyester, or the like produced by a polymerization method, a pulverization method, or the like as a binder resin. Is obtained by externally adding a so-called external additive to a base of about 5 to 10 μm. Here, the external additive is nano-micron order silica, metal oxide, easily charged resin, or the like. By externally adding particles having a chargeability opposite to that of the externally added toner as the external additive, the toner can be given cohesive properties or the toner can be charged stably.

The volume average particle diameter of the prepared toner 101 was measured with a Coulter Counter TA-II type manufactured by Coulter Inc. The measuring device is connected to an output device for volume average particle size and number average particle size and a personal computer. In the measurement using a Coulter counter, first, several g of the toner to be measured is dispersed in a 1% sodium chloride electrolyte, and a few drops of a surfactant are added. A good dispersion state can be obtained by using an ultrasonic cleaner. Thereafter, the particle size of the toner 101 is measured using a 100 μm aperture, and then processed by a computer to calculate the particle size distribution and the volume average particle size.

  Regarding the shape of the toner 101, the value of the shape factor SF-1 measured by the image analyzer is preferably 100 to 140, and the value of the shape factor SF-2 is preferably 100 to 130. Further, by satisfying the above conditions and setting the value of (SF-2) / (SF-1) to 1.0 or less, not only the characteristics of the toner 101 but also matching with the image analysis apparatus is extremely good. It will be something.

The shape factors SF-1 and SF-2 are parameters as shown below. First, using a FE-SEM (S-800) manufactured by Hitachi, 100 toner images enlarged at a magnification of 500 times are randomly extracted. Then, the image information is a parameter defined by a value obtained by introducing the image information into the image analysis apparatus (Luxex 3) manufactured by Nicole through an interface and performing analysis.
SF-1 = {(MXLNG) ² / AREA} × (π / 4) × 100
SF-2 = {(PERI) ² / AREA} × (1 / 4π) × 100
AREA: toner projected area MXLNG: absolute maximum length PERI: circumference

  The shape factor SF-1 indicates the degree of roundness of the toner particles, and the larger the value, the more spherical the shape becomes irregular. The shape factor SF-2 indicates the degree of unevenness of the toner particles, and the larger the value, the more prominent the unevenness of the toner surface. In particular, when the toner having SF-1 of 100 to 140 and SF-2 of 100 to 130 is used in terms of transferability and image quality, the effect of the present invention is raised.

  Various experiments were performed in the above configuration.

[Experiment 1]
The experiment was performed using only the cyan developing device and using the supply roller 104 as shown in FIGS. In this experiment, the different resistance values of the sponge layer of the supply roller 104 were prepared. A supply roller having a conductive sponge is a conductive supply roller (resistance value 2.0 × 10 ⁵ Ω), and an insulating supply roller is an insulating supply roller. First, various particles P were applied to the supply roller 104. Table 1 is a combination list of the particles P applied to the supply roller 104 and the conductive and insulating supply rollers.

Particle application example 1: Hydrotalcite having a volume average particle diameter of 0.4 μm was applied to a conductive supply roller.
-Particle application example 2: The particles of the particle application example 1 were applied to an insulating supply roller.
Particle application example 3: Tin oxide having a volume average particle diameter of 0.4 μm was applied to a conductive supply roller. Particle application example 4: Zinc oxide having a volume average particle diameter of 0.5 μm was applied to the conductive supply roller. Particle application example 5: The toner (particle diameter 7 μm) described in this embodiment was applied to a conductive supply roller. Here, in the particle application example 5, since the toner is applied, substantially nothing is applied except that the problem at the initial stage of use is solved.
Particle application example 6: Polyester resin particles having a volume average particle diameter of 0.4 μm were applied to a conductive supply roller. A so-called charge imparting agent is added to the polyester resin particles so as to have the same negative polarity as that of the toner.

  Note that SALD-2000 manufactured by Shimadzu Corporation was used to measure the particle size of the particles P.

  The application method to the supply roller 104 was such that each particle P was dispersed evenly on a flat surface as much as possible, the supply roller 104 was rotated several times and applied sufficiently, and then could not adhere to the supply roller 104. A method of blowing particles P with air was adopted. If blown off with air is insufficient, the particles P are separated from the supply roller 104 and mixed with the toner 101 in the developing device, and the physical properties of the toner change. In order to prevent this, a developing device different from the experimental developing device 100 is prepared, and first, a supply roller 104 coated with particles P in advance is attached thereto, and about 50 solid images are passed through. Then, the supply roller 104 is taken out. The taken-out supply roller 104 was once again blown with air and placed in the experimental developing device 100, and various experiments were performed.

  In the present embodiment, the mass per unit area of the toner after passing through the regulating blade 105 on the developing roller 106 is obtained by using a so-called suction type Faraday cage method. This suction type Faraday cage method includes a suction member having a suction port having a diameter of about 12 mm, a filter part for collecting the sucked toner, and a suction device for suctioning from the side opposite to the suction member of the filter part. . Lightly press the suction port so as not to damage the developing roller 106, suck all the toner 101 on a certain area, collect it on the filter, and calculate the weight per unit area of the developing roller 106 from the weight increase of the filter. Can be calculated. At the same time, the amount of charge per unit area on the developing roller can also be obtained by measuring the amount of charge accumulated in the externally electrostatically shielded filter.

FIG. 7 is a graph showing experimental results. The horizontal axis represents the supply bias, which is the difference (Vc−Va) between the voltage Vc applied to the supply roller 104 and the voltage Va applied to the developing roller 106. The vertical axis represents the mass M / S [mg / cm ² ] per unit area measured by the suction type Faraday gauge method.

  The regulation blade bias, which is the difference (Vc−Vb) between the voltage Vb applied to the regulation blade 105 and the voltage Va applied to the application developing roller 106, was Vc−Vb = −200V.

  In the particle application examples 1, 3, and 4, when the supply roller 104 was not biased (supply bias 0 V), the M / S of the toner layer on the developing roller in the developing unit was low. However, when the supply bias was increased, an M / S higher than that of the comparative example in which the toner 101 was applied could be obtained. Further, in the particle application example 2, since the supply roller is insulative, it hardly reacted to the supply bias.

  The reason for the above results can be considered as follows.

Since the friction between the toner 101 and the developing roller 106 can be reduced by applying the particles P of the particle application examples 1 to 4 on the supply roller 104, the supply amount of the toner 101 from the supply roller 104 to the developing roller 106 is reduced. M / S decreased. Further, in the particle application examples 1, 3, and 4, when the supply bias to the supply roller 104 is increased, the M / S increases because the toner charged by rubbing around the supply roller is applied to the developing roller. This is thought to be because the electric field in the direction in which it was pressed became easier to move. In the particle application example 2, since the electric field was not applied because the supply roller 104 was insulative, the M / S was not increased.

  On the other hand, in the particle application example 6, even when no bias was applied, the concentration was higher than in the particle application example 5, and the M / S was further increased by the bias.

  As described above, by using the conductive supply roller 104, the toner supply amount to the developing roller 106 can be increased if an appropriate bias is applied. Therefore, if it is necessary to compensate for the decrease in M / S when the particles P are applied to the supply roller 104, the supply bias may be increased to the same polarity as the toner 101.

[Experiment 2]
Using the supply roller 104 coated with each particle P, the toner deterioration was measured when the supply roller 104 was continuously used under the same conditions. Toner deterioration is indicated by transfer efficiency having a strong correlation with toner deterioration. Using a cyan developing device 100 filled with 150 g of toner 101, an intermittent endurance test was performed every two sheets (2 pages / 1 job) while taking a sample for calculating the transfer efficiency during printing at a printing rate of 1%.

  The regulated blade bias was set to Vc−Vb = −200 V as in Experiment 1.

  As a method for measuring the transfer efficiency, first, the image forming apparatus 1 is turned off during solid image formation, and the transfer residual toner on the photosensitive drum 4 is peeled off with a transparent tape. Adhere the tape and the tape with nothing attached on the same white recording material. The density of these two types of tapes is measured, and the difference between the two is taken to digitize the residual toner. This value is A.

  On the other hand, the toner 101 transferred onto the recording material is digitized by measuring the density of the solid image and the recording material and taking the difference. Let this value be B. When the transfer efficiency is expressed using A and B, transfer efficiency = B × 100 / (A + B). In all cases, a spectral densitometer / colorimeter 500 series manufactured by X-Rite was used for measuring the density.

  Table 2 shows the contents of Examples and Comparative Examples prepared by combining particle application examples and supply biases.

<Example 1> In the particle application example 1, the supply bias (Vc-Va) was set to -200V. <Example 2> In the particle application example 1, the supply bias (Vc-Va) was set to 0V.
<Example 3> In the particle application example 2, the supply bias (Vc-Va) was set to -200V. <Example 4> In the particle application example 3, the supply bias (Vc-Va) was set to -200V. <Example 5> In the particle application example 4, the supply bias (Vc-Va) was set to -200V. <Comparative example 1> In the particle application example 5, the supply bias (Vc-Va) was set to -200V. <Comparative Example 2> In the particle application example 6, the supply bias (Vc-Va) was set to -200V.

  FIG. 8 is a graph showing the result of using the supply roller 104 coated with various particles P in relation to the number of sheets and the transfer efficiency. The horizontal axis indicates the number of sheets passed [sheet], and the vertical axis indicates the transfer efficiency [%].

  In this experiment, the endurance test by continuous use of a total of 7 types of an Example and a comparative example was done, changing the coating particle P and bias conditions, and the transition of transfer efficiency was investigated.

  From FIG. 8, it can be seen that Examples 1 to 5 are less likely to have a lower transfer efficiency than Comparative Example 1. On the other hand, in Comparative Example 2, the transfer efficiency was lowered at an early stage as compared with Comparative Example 1, and when the transfer efficiency was about 80%, a so-called bulge image was generated. Since there is a strong relationship between the decrease in transfer efficiency and the deterioration of the toner 101, it can be said that the toner deterioration in Examples 1 to 5 is advanced as compared with Comparative Examples 1 and 2. This is considered to be due to the effect of suppressing toner deterioration by the particles P applied in Examples 1 to 5.

The difference between the first embodiment and the second embodiment is the supply bias. From Experiment 1, in Example 2, the amount of toner M / S [mg / cm ² ] on the developing roller is low because the supply bias is not applied. Further, although the supply bias is applied in the third embodiment, since an insulating sponge is used for the supply roller 104, there is almost no effect of the bias and the M / S is low.

  From the results of Examples 1 to 3, it can be considered that there is almost no correlation between the toner amount on the developing roller and the transfer efficiency. Accordingly, when the image density is insufficient due to the application of the particles P to the supply roller 104, a large bias may be applied as a supply bias on the same polarity side as the toner using the conductive supply roller 104. . If the image density is sufficient, even if the potential of the conductive supply roller is made equal to that of the developing roller 106 or an insulating supply roller is used, there is almost no influence on the transfer efficiency.

Thus, when the supply roller 104 is insulative or conductive and the supply bias is 0 V, toner deterioration can be suppressed by selecting the following particles. That is, the toner amount M / S [mg / cm ² ] on the developing roller when the particles P other than the toner 101 are applied to the supply roller 104 is lower than the M / S when the toner 101 is applied as the particles P. By selecting such particles P other than the toner, toner deterioration can be suppressed.

Since the durability does not change with the supply bias, the supply bias need not be applied if unnecessary. When the printed image density is low because M / S [mg / cm ² ] is low, toner deterioration is suppressed by applying a large amount to the developing roller 106 on the same polarity side as the toner 101 when the printed image density is low. In addition, the image density can be increased.

  In the embodiment, one type of particle P is applied to the supply roller 104 at the same time, but two or more types may be mixed and used. At that time, by mixing with the particles used in the comparative example, it is possible to prevent excessive application of the particles of the example even in a rough application method and to easily apply the particles of the example having no fluidity.

  From the above experimental results, the particles P having the characteristic that the toner layer weight M / S per unit area on the developing roller 106 decreases when the particles P are applied to the supply roller 104 in advance are advanced by continuous use of the developing device 100. Suppresses toner deterioration.

  Therefore, since the state in which the transfer efficiency is high can be maintained, so-called edge images due to a decrease in transfer efficiency can be suppressed. The decrease in image density due to the application of particles can be solved by applying a bias to the supply roller. Further, the M / S can be controlled higher by combining the supply bias and the particles of the example.

  As described above, in the present embodiment, as the particles applied to the supply roller 104, the mass m ′ per unit area in the developing unit when applied to the supply roller 104 and the mass m per unit area when not applied. Are applied such that m ′ <m. When specific particles are applied to the supply roller 104, m ′ <m is because the friction between the supply roller 104, the toner and the developing roller 106 is reduced, and the toner is conveyed from the supply roller 104 to the developing roller 106. This is because the ability has declined. This is considered to be because not only the so-called spacer effect in which the particles having a small particle size reduce the contact area between the members but also the properties of the particles are greatly effective.

  Experiments in the present embodiment have revealed that toner deterioration can be further suppressed when particles having a reduced ability to transport toner are applied.

  Further, when the mass m ′ per unit area is reduced, the reduced mass m ′ per unit area can be increased by applying a predetermined bias to the conductive supply roller 104. This is presumably because the toner that was frictionally charged due to the friction between the supply roller 104 and the developing roller 106 or the like was easily conveyed onto the developing roller 106 by the electric field. In addition, when the particles applied to the supply roller 104 are easily charged with a polarity opposite to that of the toner, it is considered that the particles are attracted to the supply roller 104 by an electric field and are not easily dropped during continuous use.

  Moreover, the ease of application | coating can be improved by apply | coating to the supply roller 104, after mixing multiple types of particle | grains.

  Considering from the viewpoint of particle size and adhesion, particles are more likely to adhere to the supply roller 104 than toner, so that the effect obtained by applying the particles to the supply roller 104 is higher.

It is a schematic sectional view showing a developing device. 1 is a schematic cross-sectional view showing an image forming apparatus. It is the schematic sectional drawing which showed the process cartridge. It is a schematic sectional drawing of a supply roller. It is an expanded sectional view of a supply roller. It is the schematic which showed the resistance measurement method of a roller. FIG. 6 is a diagram illustrating a relationship between a toner layer weight per unit area and a supply bias. FIG. 6 is a diagram illustrating a relationship between transfer efficiency and the number of sheets to be passed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Process cartridge 100 Developing device 101 Toner 104 Supply roller 105 Regulating blade 106 Developing roller

Claims (8)

A developer carrier;
A supply member for conveying the developer onto the developer carrying member;
A regulating member that regulates the developer on the developer carrying member conveyed from the supply member;
In a developing device comprising:
The supply member is pre-coated with particles,
The particles are
When the supply member is insulative or conductive and has the same potential as the developer carrier,
A mass m ′ per unit area of the developer after passing through the regulating member on the developer carrier when the particles are applied to the supply member;
The mass m per unit area of the developer after passing through the regulating member on the developer carrier when the particles are not applied to the supply member;
A developing device, wherein the relationship is m ′ <m. The supply member is electrically conductive;
Voltage supply means capable of applying a voltage to the supply member;
The developing device according to claim 1, wherein the voltage applying unit applies a voltage to the supply member that is larger than a voltage applied to the developer carrying member on a charging polarity side of the developer. The developing device according to claim 1, wherein the main component of the particles applied to the supply member is any one of hydrotalcite, tin oxide, and zinc oxide. The developing device according to claim 1, wherein the particles applied to the supply member are a mixture of two or more types of particles. 5. The developing device according to claim 1, wherein a volume average particle diameter of the particles is smaller than a volume average particle diameter of the developer. 6. The supply device according to claim 1, wherein the supply member and the developer carrying member are rotatably provided, and their peripheral surfaces are in contact with each other and rotate in opposite directions. Development device.   A process cartridge comprising the developing device according to claim 1.   An image forming apparatus comprising the developing device according to claim 1.

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