JP2010066490A - Developing method, developing device, process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device using a two-component developer, which provides a high-quality image having high dot reproducibility and superior graininess while preventing a rough appearance of the image. <P>SOLUTION: It is found that the cumulative density of a magnetic brush in the vicinity of an image carrier (denoted as a dynamic developer density hereinafter) in a period from when a developer starts to be in contact the image carrier until to be apart is important for improving a rough appearance and dot reproducibility. Thereby, a state of the magnetic brush top of the two component developer is specified, that is, the dynamic developer density is specified as a characteristic value in a developing method, a developing device and an image forming apparatus. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention forms a latent image on a photoconductor such as a copying machine, a printer, a facsimile machine, etc., and attaches toner with a developing device to make the latent image visible, and transfers the obtained visible image onto a recording sheet. The developing method, the developing device, the image forming apparatus and the process cartridge having the developing device.

  In recent copying machines and laser printers, high image quality is demanded, and at the same time, high durability and high stability are desired. In other words, there is little change in image quality due to environmental fluctuations, and a stable image must be provided over time. Conventionally, a two-component developer composed of a non-magnetic toner and a magnetic carrier (hereinafter referred to as a developer) is held on a developer carrier (hereinafter referred to as a developing sleeve), and a magnetic brush is formed by a magnetic pole contained therein to develop. 2. Description of the Related Art A two-component development system that performs development by applying a development bias to a sleeve at a position facing a latent image carrier (hereinafter referred to as a photoreceptor) is widely known. This two-component development method is widely used because it is easy to colorize. In this system, the developer is transported to the developing area as the developing sleeve rotates. As the developer is transported to the development area, a large number of magnetic carriers in the developer gather together with the toner along the magnetic field lines of the development pole to form a magnetic brush.

  Further, an alternating electric field that alternately generates an electric field acting in the direction of biasing the toner to the photosensitive member and an electric field acting in the direction of moving the toner toward the developing sleeve by superimposing an alternating current component on the DC voltage as a developing electric field. The concentration stabilization technique used is also widely used. Due to the high developing ability by using an alternating electric field, a sufficient solid density can be secured even when the toner charge amount distribution shifts with time, and at the same time the toner has a relatively latent pattern such as a halftone. An electric field sufficient to deposit can be formed. For this reason, this technique is frequently used particularly in color image forming apparatuses and the like as having both sufficient developing ability and halftone stability. Of course, in a monochrome copying machine, it can be said to be an optimal technique for use in order to improve halftone graininess and achieve uniform solid filling.

However, when an alternating electric field is used as the developing electric field, a discharge is generated due to a local electric field strength increase caused by the density of the magnetic brush in the developing area (especially for a deep portion of the latent image), and the image is ringed. The phenomenon of falling white was generated. Therefore, the resistance value of the carrier used for development is limited, and it is difficult to use a so-called low resistance carrier. Furthermore, even in the case of a medium-high resistance carrier, it may break down locally due to non-uniformity of the coating film and discharge, so the uniformity of the carrier coating layer and the resistance value of the carrier core material (that is, the carrier core) There were also many constraints on the materials used for the materials.
In such a developing device, improvements have been made to obtain a high-quality image with high dot reproducibility and excellent graininess by eliminating the roughness of the image. As one of them, an electric field formed between the image carrier and the developing sleeve is used as an alternating electric field, and development is performed while urging toner rearrangement to eliminate the rough feeling. However, when an alternating electric field is formed, there is a problem that the maximum value of the electric field is increased and carrier adhesion to the image carrier is likely to occur as compared with the case of only a DC electric field. In addition, a power source for forming an alternating electric field is required, which increases costs. For this reason, even if the image is developed using a direct current electric field, a high-quality image that eliminates the roughness, has high dot reproducibility, and excellent graininess is desired.

As one of the causes of poor image roughness and dot reproducibility, it is known that the density of the magnetic brush in the development area is sparse and uniform development cannot be performed. Therefore, there has been proposed one that attempts to improve the image quality by defining the density of the magnetic brush in the development region using the volume ratio of the carrier in the development region (see, for example, Patent Document 1).
In addition, in order to carry the developer evenly and transport it to the development region, there has been proposed a method in which irregularities are formed on the surface of the developer carrying member by etching using a photoresist system (for example, see Patent Document 2). The arrangement of the recesses is staggered so that the conveyance unevenness does not occur in a direction perpendicular to the conveyance direction of the developer. In addition, since it is preferable that the unevenness is formed in a pattern that is continuous in a direction perpendicular to the developer transport direction, a corrugated or linear concave groove that is continuous in this direction is formed, and this is an equal pitch in the developer transport direction. Good results can be obtained even if they are arranged densely.

When surface irregularities of the developer carrier are formed by such a photoetching process, the developer carrier is hardly subjected to physical force during processing due to its processing characteristics utilizing chemical reaction. There is little risk of distortion and distortion on the outer periphery of the body. As a result, there is little possibility that an image defect corresponding to the rotation cycle of the developer carrier will occur.
However, although the technique described in Patent Document 2 certainly does not cause vibration or distortion on the outer periphery of the developer carrier, there is a possibility that image defects may occur due to the interval period of grooves formed on the surface. Therefore, in order to solve these problems, there has been proposed one that forms a continuous pattern densely and uniformly in a direction perpendicular to the developer conveyance direction (see, for example, Patent Document 3).

JP-A-8-146668 JP-A-5-46007 JP 2003-316146 A

However, the present inventors have found that even when the volume ratio of the carrier is the same, or even when the developer is not unevenly loaded, there is a difference in the roughness of the image and the dot reproducibility. It can be said that what defines the volume ratio of the carrier in order to express the density of the magnetic brush in the developing region has not fully explained the relationship with the rough feeling. This is considered to be due to the following reason. Considering the case where development is performed by forming a DC electric field between the image carrier and the developing sleeve, there is little toner flying from the base of the magnetic brush toward the image carrier, and the image carrier from the tip of the magnetic brush. Toner is supplied. That is, it is the magnetic brush tip that is mainly involved in the developing operation, and it is necessary to consider the arrangement state and density of the magnetic brush in order to improve the roughness and the dot reproducibility. Furthermore, the development does not end with only one contact of the magnetic brush, but particularly when there is a difference in linear velocity between the image carrier and the developer carrier, a plurality of magnetic brushes come into contact with the latent image. Since the development is performed, the roughness and dot reproducibility include the integration of the density of the magnetic brush in the vicinity of the image carrier (hereinafter referred to as dynamic developer density) from when the developer starts to contact until the developer leaves. It becomes important. In particular, it is important to suppress changes in the density of the dynamic developer when the pumping amount is reduced due to deterioration of the developer due to wear of the sleeve surface over time, carrier spent, toner embedding / detaching, etc.
The present invention has been made in view of the above-mentioned background. The state of the tip of the magnetic brush of the two-component developer, that is, the dynamic developer density is defined as a characteristic value, the roughness is eliminated, and the dot reproducibility is high. Another object of the present invention is to provide a developing method, a developing apparatus, and an image forming apparatus capable of obtaining a high-quality image having excellent graininess.

According to the first aspect of the present invention, a developer carrier having a magnet therein is disposed opposite to the image carrier, and a two-component developer containing toner and a magnetic carrier is layered on the surface of the developer carrier. In the developing method of developing the latent image formed on the surface of the image carrier with toner, with toner,
The diameter of the developer carrier is 15 to 20 mm, and the density of the developer that contacts the surface of the image carrier is integrated until one point of the image carrier contacts the two-component developer and leaves. The obtained image is subjected to two-dimensional FFT analysis, and the integrated value between 5 to 12 [cycle / mm] of the obtained power spectrum is defined as PS, and the PS between the upper and lower limits [10 mg / cm ² ] with respect to the standard pumping amount. The difference between the maximum value and the minimum value is 0.11 or less.
According to a second aspect of the present invention, in the developing method according to the first aspect, a plurality of wavy groove extending in the axial direction of the developer carrying member is formed, and the groove width and groove pitch of the wavy groove are determined in the rotation direction. It is characterized by being uniform.

According to a third aspect of the present invention, in the development method according to the first or second aspect, the carrier for an electrophotographic developer, wherein the magnetic carrier comprises magnetic core material particles and a resin layer covering the particle surface. And the weight average particle diameter Dw of this carrier is 20-40 micrometers, It is characterized by the above-mentioned.
According to a fourth aspect of the present invention, in the developing method according to any one of the first to third aspects, the magnetic carrier applies a magnetic field of 1000 · (10 ³ / 4π) [A / m]. The magnetic moment per carrier particle is 70 [A · m ² / kg] or less.

According to a fifth aspect of the present invention, there is provided a two-component component comprising a developer carrier having a magnet disposed inside and facing the image carrier, the developer carrier comprising a toner and a magnetic carrier for holding the toner. In a developing device that carries a developer on the surface, transports it to a development area, applies an electric field between the developer carrying body and the image carrying body, and develops a latent image formed on the surface of the image carrying body with toner. The developing device performs development by the developing method according to any one of claims 1 to 4.
In a process cartridge according to a sixth aspect of the present invention, the image carrier, the developing device, and either one or both of the charging device and the cleaning device are integrated, and the process cartridge is detachably formed on the image forming apparatus main body. The developing device is a developing device according to claim 5.

According to a seventh aspect of the present invention, an image carrier, a charging device that charges the surface of the image carrier, an exposure device that forms an electrostatic latent image by exposing the charged image carrier surface based on image information, and A developing device for supplying a developer to the electrostatic latent image formed on the image carrier to make it visible, a transfer device for transferring the obtained visible image to a recording medium, and an image after image transfer An image forming apparatus having a cleaning device for collecting the developer remaining on the carrier, wherein the developing device is a developing device according to claim 5 or a developing device as a part of a process cartridge according to claim 6. It is characterized by being.
According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, a plurality of the developing devices or process cartridges are provided.

According to the present invention, even if the pumping amount fluctuates over time, the maximum value and the minimum value of the PS value between the upper and lower limits of 10 [mg / cm ² ] with respect to the standard pumping amount are 0.11 or less. By doing so, it is possible to suppress a change in the dynamic developer density, and to form a high-quality image with good dot reproducibility that does not feel rough over time.
In addition, by using a wavy groove on the sleeve surface, it is possible to achieve a development state in which the dynamic developer density is unlikely to change even when the pumping amount fluctuates over time. High quality images can be formed.

FIG. 1 is a schematic sectional view of an image forming apparatus to which the present invention can be applied.
In the figure, reference numeral 1 is a photosensitive drum, 2 is a charging roller, 3 is a writing means, 4 is a developing means, 5 is an intermediate transfer belt, 6 is a registration roller pair, 7 is a paper transfer belt, 8 is a constant fixing means, 9 Denotes a cleaning blade, 10 denotes a toner bottle, 11 denotes a toner hopper, 12 denotes a transfer roller, 13 denotes a belt cleaning blade, 14 denotes a collected toner conveyance path, and 15 denotes a waste toner container.
Subscripts a to d are codes for distinguishing different development colors.
Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
An example of the embodiment of the present invention is shown below. In the figure, each of a plurality of photoconductors arranged side by side using an intermediate transfer belt is provided with a developing device, and a single color toner image is formed on each photoconductor, and the single color toner images are sequentially transferred to a sheet. Record a composite color image. This is an image forming part of a so-called tandem type color copier.

Explaining the configuration, the writing means 3 optically forms latent images on the photoreceptors 1a to 1d uniformly charged by the charging means (charging rollers 2a to 2d in the figure) (writing positions 3a to 3d). A visualized image of the toner is formed by the developing units 4a to 4d. The toner images formed on the photoreceptors 1a to 1d are temporarily transferred to the intermediate transfer belt 5 by the intermediate transfer belt transfer means 12a to 12d, and then transferred to the transfer paper conveyed through the registration roller pair 6 (paper transfer in the figure). The toner image of the intermediate transfer belt 5 is transferred to the transfer paper by the transfer belt 7. The toner image transferred to the transfer paper is conveyed to the fixing means 8 by the paper transfer belt 7, and the toner image on the transfer paper is fixed by heat. Discharged.
Untransferred toner that has not been transferred to the intermediate transfer belt on the photosensitive member is scraped off from the photosensitive member by the photosensitive member cleaning blades 9a to 9d. Residual charges on the photosensitive member are discharged by a discharging unit (not shown) to prepare for the next image forming operation.

The untransferred toner scraped off by the cleaning blades 9a to 9d passes through the recovered toner transport paths 14a to 14d, and the untransferred toner on the intermediate transfer belt and the pattern image for process control are transferred to the intermediate transfer belt by the intermediate transfer cleaning blade 13. The toner is scraped off from above and is stored in the waste toner storage container 15 through the recovered toner transport path 14e.
Next, replenishment of new toner to the developing devices 4a to 4d will be described. The new toner filled in the toner cartridge is supplied to the toner hoppers 11a to 11d on the rear side of the machine body by the toner supply devices 10a to 10d. When the toner stored in the toner hopper is judged to have a low toner concentration in the developing device by a toner concentration detecting means (described later) in the developing device, a toner supply screw (not shown) in the toner hopper is rotated, An appropriate amount of toner is supplied from the toner hopper to the developing device. To detect the remaining amount of toner in the toner bottle, a toner presence / absence sensor (not shown) is arranged in the toner hopper, and when the sensor detects the absence of toner, the toner supply device is requested to supply toner. If the presence of toner is not detected even if requested for a predetermined time, it is determined that there is no toner.

FIG. 2 is an enlarged cross-sectional view of the image forming unit of the device of the present invention.
In the figure, reference numeral 16 denotes a developing roller, 17 denotes a regulating member, 18 denotes a screw member, 19 denotes a screw member, 21 denotes a toner concentration sensor, 22 denotes a toner supply screw, 23 denotes a developing toner supply port, and 25 denotes a magnet of a magnet roller. Each is shown.
In the figure, the developing device 4 and the photosensitive member 1 are, for example, a process cartridge formed integrally. This process cartridge is formed so as to be detachable from the image forming apparatus main body by integrating the photosensitive member 1, the developing device 4, the charging roller 2, and the cleaning means 9 (cleaning blade in this embodiment). Yes.
The developing device 4 is provided with a developing roller (hereinafter also referred to as a developing sleeve) 16 for forming a toner image on the electrostatic latent image optically formed by the writing unit 3 on the photoreceptor 1. It has been. A regulating member (hereinafter also referred to as a developing doctor) 17 that restricts the amount of developer on the developing roller to a predetermined amount is disposed upstream of the developing area of the developing roller 16. A two-component developer in which toner particles and magnetic particles (carriers) are mixed is stored in a developing tank portion in the developing device 4, and this developer is stored in the developing device 4 by constant speed rotation of the screw members 18 and 19. The toner and the carrier are frictionally charged by stirring while circulating. The conveying screw 18 supplies a part of the developer to the developing sleeve 16, and the developing roller 16 carries the developer magnetically and conveys it. A toner concentration sensor 21 is disposed below the screw 19 to control the toner concentration in the developing tank as needed and to keep it within an appropriate value. The toner from the toner replenishing unit is once stored in a sub hopper (not shown), and then the toner concentration in the developing tank is detected to be low by the toner concentration sensor for the time converted according to a predetermined conversion formula. The supply screw 22 is rotated, whereby an appropriate amount of toner is supplied to the developing toner supply port 23.

  The developing roller 16 is composed of a cylindrical developing sleeve made of a non-magnetic material and a magnet 25 of a magnet roller as a magnetic field generating means fixed inside, and the developing sleeve rotates freely around this magnet. be able to. In the magnet, a main pole (P1 pole) is disposed at a position opposite to the photosensitive drum 1, and S poles and N poles are alternately arranged in the counterclockwise direction. In addition, a magnetic pole of the same polarity is disposed adjacent to the position facing the photosensitive drum at a position downstream of the developing sleeve in the rotational direction of the developing sleeve in order to peel the developer from the developing sleeve. The height (supported amount) of the developer on the developing roller 16 is regulated by a developer regulating member 17 disposed in the developing case. From the opening of the main body case, a developing roller serving as a developer carrying member for carrying a two-component developer (hereinafter referred to as developer) composed of toner and a magnetic powder carrier is partially exposed. . The electrostatic latent image on the photoreceptor 1 is developed with toner on the developing roller 16 to become a toner image.

In the present embodiment, the developing device is characterized in that the developer carrying amount per unit area on the developing sleeve at a position facing the photoconductor is 30 to 70 [mg / cm ² ], more preferably 40 to 60 [mg / cm ² ]. cm ² ] is preferable. When the developer carrying amount is less than 30 [mg / cm ² ], it is necessary to increase the electric field applied between the developing sleeve and the photoreceptor, which is disadvantageous for carrier adhesion. On the other hand, when the developer carrying amount is larger than 70 [mg / cm ² ], the developer filling density is increased in the space between the photosensitive member and the developing sleeve. There is a tendency for the stagnation to occur and the fluidity of the developer to decrease. Along with this decrease in fluidity, toner supply to the electrostatic latent image on the photoreceptor is not smoothly performed, and image density reduction and density unevenness are likely to occur.

In the present embodiment, the developing device is characterized in that the developer carrying amount per unit area on the developing sleeve at a position facing the photoconductor is preferably 30 to 70 [mg / cm ² ], more preferably 40. It is preferable that it is -60 [mg / cm < ² >]. When the developer carrying amount is less than 30 [mg / cm ² ], it is necessary to increase the electric field applied between the developing sleeve and the photoreceptor, which is disadvantageous for carrier adhesion. On the other hand, when the developer carrying amount is larger than 70 [mg / cm ² ], the developer filling density is increased in the space between the photosensitive member and the developing sleeve. There is a tendency for the stagnation to occur and the fluidity of the developer to decrease. Along with this decrease in fluidity, toner supply to the electrostatic latent image on the photoreceptor is not smoothly performed, and image density reduction and density unevenness are likely to occur.

  In this embodiment, the developer has a toner density in the range of 5.0 to 9.0 wt%, and an average charge amount Q / M of 15 to 60 [-μC / g], more preferably 20 to 40 [−μC. / G] is preferably used from the viewpoints of carrier coverage with toner and optimization of developer fluidity. When the toner concentration is lower than 5.0 wt%, the charge amount Q / M of the developer tends to increase, and the development potential for developing the electrostatic latent image on the photoreceptor needs to be set higher. There is a risk of reducing the life of the photoreceptor. Further, when the charge amount Q / M of the developer exceeds 60 [-μC / g], the possibility that the image density is lowered is increased. When the toner concentration is higher than 9.0 wt%, the developer charge amount Q / M tends to decrease. When the charge amount Q / M of the developer is less than 15 [-μC / g], toner scattering is likely to occur. As the level of toner scattering deteriorates, so-called background soiling occurs in which the image background becomes soiled with toner. Occurs and degrades image quality. Therefore, a developer having a toner concentration in the range of 5.0 to 9.0 [wt%] and an average charge amount Q / M of 15 to 60 [-μC / g] is used. As a result, a stable image quality can be obtained over a long period of time even with a developer using a small particle size carrier and a small particle size toner.

The coverage of the carrier with the toner is 10 to 80%, preferably 20 to 60%. The coverage is calculated by the following formula.
Coverage (%) = (Wt / Wc) × (ρc / ρt) × (Dc / Dw) × (1/4) × 100
In the above formula, Dc is the weight average particle diameter [μm] of the carrier,
Dw is the weight average particle diameter of the toner [μm],
Wt is the toner weight [g],
Wc is the weight of the carrier [g]
ρt is the true toner density [g / cm3],
ρc is the true carrier density [g / cm3]
Represents.
The weight average particle size is calculated based on the particle size distribution (relationship between the number frequency and the particle size) of the particles measured on the basis of the number. The weight average particle diameter Dw in this case is represented by the following formula.
Dw = {1 / Σ (nD3)} × {Σ (nD4)}
In the above formula, D represents a representative particle size [μm] of particles existing in each channel,
n represents the total number of particles present in each channel.
The channel indicates a length for equally dividing the particle size range in the particle size distribution diagram, and in the present embodiment, a length of 2 μm is adopted. Further, as the representative particle size of the particles existing in each channel, the lower limit value of the particle size that divides each channel was adopted.

  The developer applied to this embodiment has a toner weight average particle diameter of 4.0 to 8.0 μm, and a ratio (Dw) of the toner weight average particle diameter (Dw) to the number average particle diameter (Dn). / Dn) is desirably 1.20 or less. The reduction in toner particle size is indispensable for increasing the resolution, but as a side effect, fluidity and storage stability tend to deteriorate. When the toner particle diameter is less than 4.0 μm, the fluidity of the developer is extremely deteriorated, and it becomes difficult to ensure a uniform toner concentration in the developer. Further, the reduction in the toner particle diameter is a direction in which the coverage with respect to the carrier increases, and when the coverage is excessively high, there is a concern that the carrier contamination may be accelerated and toner scattering may be induced.

  As a means for improving the fluidity of the toner and the developer, there is a method of adding a large amount of additives to the toner. However, since a side effect occurs, an essential improvement cannot be expected. However, by making the particle size distribution of the toner uniform, the side effects associated with reducing the toner particle size are overcome. In other words, it is desirable that the weight average and number average particle diameter ratio Dw / Dn of the toner is close to 1. By making it 1.20 or less, the effect of suppressing the deterioration of fluidity can be obtained, and a small particle diameter toner is used. Even in this case, the toner density can be made uniform. As described above, the toner has a weight average particle diameter of 4.0 to 8.0 μm and a toner weight average / number average particle diameter ratio Dw / Dn of 1.20 or less, in addition to image density stability. Thus, the resolution is improved and a higher quality image can be obtained. Further, by making the ratio of the number of particles of 3 μm or less in the toner particle size distribution 5% or less, the quality improvement effect in the fluidity and storage stability is remarkable, and in the toner replenishment property in the developing device and the toner charge rising property. A good level is obtained.

The particle size distribution of the toner can be measured by various methods. In this embodiment, the toner particle size distribution is measured using a small hole passage method (Coulter counter method). As a measuring device, COULTERCOUNTERMODELA2 (manufactured by Coulter) was used, an interface for outputting number distribution and volume distribution was connected, and an aperture (pore) of 100 μm was used. As a measuring method, first, a toner measurement sample is dispersed in a surfactant added to an electrolytic aqueous solution. The dispersed sample is injected into another 1% NaCl electrolysis solution, and a current is passed between the electrodes through the electrolyte in which electrodes are placed on both sides of the aperture tube. The particle size distribution of 2 to 40 μm particles is measured from the resistance change at this time, and the number average particle diameter and the weight average particle diameter are obtained from the average distribution.
It is preferable to add a fluidity imparting agent to the toner. Various fluidity-imparting agents that can be used are listed, and it is preferable to use hydrophobic silica fine particles and hydrophobic titanium oxide fine particles in combination. In particular, when stirring and mixing are performed using particles having an average particle size of 50 nm or less, both electrostatic force and van der Waals force with the toner can be reduced, and toner fluidity can be improved. it can. As a result, a desired charge level of the developer can be obtained, good image quality can be obtained, and transfer residual toner can be reduced. Furthermore, the titanium oxide fine particles are excellent in environmental stability and image density stability, but tend to deteriorate the charge rising characteristics. Therefore, if the amount of titanium oxide fine particles added is larger than the amount of silica fine particles added, it is considered that the influence of deterioration of charging rise characteristics becomes large. However, when the addition amount of the hydrophobic silica fine particles is in the range of 0.3 to 1.5 wt% and the hydrophobic titanium oxide fine particles are in the range of 0.2 to 1.2 (wt%), the charge rising characteristics are not significantly impaired, Even when copying is repeated, stable image quality can be obtained and toner scattering can be suppressed.

Moreover, by adding hydrophobic silica having a large particle diameter of 80 to 140 nm, the performance is further improved with respect to transferability and developability. In particular, the effect of improving the quality is remarkable in a developer using a toner having a small particle diameter such that the average particle diameter of the toner is 7 μm or less. That is, the additive having a large particle size acts as a spacer between the toner particles, and it is possible to suppress the toner aggregation at the time of toner transfer compression and the embedding of the additive on the toner surface at the time of empty stirring of the developing machine. As a result, solid image density unevenness due to transfer failure and toner fluidity decrease due to additive embedding do not occur, and a high-quality image can be obtained over a long period of time.
The weight average particle diameter Dw of the carrier in the developer is 20 to 60 μm, more preferably 20 to 40 μm. As a result, the density of the dynamic developer can be made dense (the area where the developer does not come into contact with the photoreceptor can be reduced), and a high-quality image with good dot reproducibility and no roughness is formed. be able to.
When the weight average particle diameter Dw of the carrier is larger than 60 μm, the magnetic carrier holding power on the photoconductor is strong and the carrier adhesion hardly occurs, but the carrier surface area per unit weight is small, so that the high image density. When the toner concentration is increased in order to obtain the toner image, the scumming increases rapidly. In addition, when the dot diameter of the latent image is small, the variation in the dot diameter increases. On the other hand, when the weight average particle diameter Dw of the carrier is smaller than 20 μm, the magnetic moment per carrier particle is lowered, the magnetic carrier holding force on the developing sleeve is weakened, and carrier adhesion is likely to occur.

Magnetic moment per carrier particles 1000 · ⁽¹⁰ 3 / 4π) upon application of a magnetic field of [A / m] is ^{70 [A · m 2 / kg} ] or less. As a result, it is possible to form a high-quality image with good dot reproducibility that does not feel rough over time. If the height is higher than this, the magnetic brush becomes hard and tends to have a trace or a blurred image. The lower limit is not particularly limited, but is usually about 50 [A · m ² / kg]. When the magnetic moment is smaller than 50 [A · m ² / kg], the magnetic carrier holding force on the developing sleeve is reduced, and carrier adhesion tends to occur.
The magnetic moment of the carrier can be measured as follows. Using a BH tracer (BHU-60 / manufactured by Riken Denshi Co., Ltd.), 1.0 g of carrier particles are packed in a cylindrical cell and set in an apparatus. The magnetic field is gradually increased to 3000 oersteds, then gradually reduced to zero, and then the opposite magnetic field is gradually increased to 3000 oersteds. Further, after gradually reducing the magnetic field to zero, a magnetic field is applied in the same direction as the first. In this way, the BH curve is illustrated, and the magnetic moment of 1000 oersted is calculated from the figure.

Examples of carrier core particles include ferromagnetic materials such as iron and cobalt, magnetite, hematite, Li ferrite, Mn—Zn ferrite, Cu—Zn ferrite, Ni—Zn ferrite, Ba ferrite, and Mn. -Mg-Sr ferrite, Mn ferrite and the like. Ferrite is a sintered body generally represented by the following formula.
_{(MO) x (NO) y} (Fe 2 O 3) z
However, x + y + z = 100 mol%, and M and N are Ni, Cu, Zn, Li, Mg, Mn, Sr, Ca, etc., respectively, and the divalent metal oxide and the trivalent iron oxide Consists of a complete mixture.

Hereinafter, the carrier and toner materials used in this embodiment will be described. First, the carrier used in the present embodiment is composed of magnetic core particles and a resin layer covering the surface. As the resin for forming this resin layer, a known resin conventionally used in the production of carriers can be used. For example, a silicone resin containing a repeating unit represented by the following chemical formula 1 can be preferably used for the resin layer of the carrier.
In the formula, R1 represents a hydrogen atom, a halogen atom, a hydroxy group, a lower alkyl group having 1 to 4 carbon atoms, or an aryl group (such as a phenyl group or a tolyl group). R2 represents an alkylene group having 1 to 4 carbon atoms or an arylene group (such as a phenylene group).

  Examples of the straight silicone resin used for the resin layer of the carrier include KR271, KR272, KR282, KR252, KR255, KR152 (manufactured by Shin-Etsu Chemical Co., Ltd.), SR2400, SR2406 (manufactured by Toray Dow Corning Silicone). A modified silicone resin can be used for the resin layer of the carrier. Examples of such materials include epoxy-modified silicone, acrylic-modified silicone, phenol-modified silicone, urethane-modified silicone, polyester-modified silicone, and alkyd-modified silicone. Specific examples of the modified silicone resin include epoxy modified product: ES-1001N, acrylic modified silicone: KR-5208, polyester modified product: KR-5203, alkyd modified product: KR-206, urethane modified product: KR-305 ( As mentioned above, Shin-Etsu Chemical Co., Ltd.), epoxy modified product: SR2115, alkyd modified product: SR2110 (manufactured by Toray Dow Corning Silicone Co., Ltd.) and the like.

The silicone resin can contain an appropriate amount (0.001 to 30% by weight) of an aminosilane coupling agent. Examples of such a silicone resin include the following. However, MW represents molecular weight.
_{H 2 N (CH 2) 3} Si (OCH 3) 3: MW179.3
_{H 2 N (CH 2) 3} Si (OC 2 H 5) 3: MW221.4
_{H 2 NCH 2 CH 2 CH 2} Si (CH 3) 2 (OC 2 H 5): MW161.3
_{H 2 NCH 2 CH 2 CH 2} Si (CH 3) (OC 2 H 5) 2: MW191.3
_{H 2 NCH 2 CH 2 NHCH 2} Si (OCH 3) 3: MW194.3
_{H 2 NCH 2 CH 2 NHCH 2} CH 2 CH 2 Si (CH 3) (OCH 3) 2: MW206.4
_{H 2 NCH 2 CH 2 NHCH 2} CH 2 CH 2 Si (OCH 3) 3: MW224.4
_{(CH 3) 2 NCH 2 CH} 2 CH 2 Si (CH 3) (OC 2 H 5) 2: MW219.4
_{(C 4 H 9) 2 NC} 3 H 6 Si (OCH 3) 3: MW291.6

  Furthermore, it is also possible to use the following for the carrier resin layer alone or in combination with the silicone resin. Polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, Styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer) Polymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylate copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, Styrene-phenyl methacrylate copolymer, etc.) Styrene resins such as styrene-α-chloromethyl acrylate copolymer, styrene-acrylonitrile-acrylate ester copolymer, epoxy resin, polyester resin, polyethylene resin, polypropylene resin, ionomer resin, polyurethane resin, ketone resin, ethylene -Ethyl acrylate copolymer, xylene resin, polyamide resin, phenol resin, polycarbonate resin, melamine resin and the like.

As a method for forming the resin layer on the surface of the core particles of the carrier, a known method such as a spray drying method, a dipping method, or a powder coating method can be applied. In particular, the method using a fluidized bed type coating apparatus is effective for forming a uniform coated film.
The thickness of the resin layer formed on the surface of the carrier core particles is usually 0.02 to 1 μm, preferably 0.03 to 0.8 μm. Since the thickness of the resin layer is extremely small, the particle size distribution of the carrier made of core material particles covering the resin layer and the carrier core material particles is substantially the same.

Further, the resistivity of the carrier can be adjusted as necessary, and the resistivity of the carrier can be adjusted by adjusting the resistance of the coating resin on the core particle and controlling the film thickness. In order to adjust the carrier resistance, it is also possible to add conductive fine powder to the coating resin layer. As the conductive fine particles, conductive ZnO, metal or metal oxide powder such as Al, _SnO 2 doped with SnO ₂ or various elements that have been prepared in a variety of _{ways, TiB 2, ZnB 2, MoB} 2 , etc. Borides, silicon carbide, polyacetylene, polyparaphenylene, poly (para-phenylene sulfide) polypyrrole, conductive polymers such as polyethylene, carbon black such as furnace black, acetylene black, and channel black. These conductive fine powders are uniformly dispersed by using a dispersing machine using a medium such as a ball mill or a bead mill or a stirrer equipped with high-speed rotating blades after being put into a solvent used for coating or a resin solution for coating. can do.

The toner applied to the exemplary embodiment includes at least a binder resin, a colorant, a release agent, and a charge control agent. This toner is an amorphous or spherical toner prepared by various toner production methods such as a polymerization method and a granulation method. Either magnetic toner or non-magnetic toner can be used.
As the toner binder resin used here, all those conventionally used as toner binder resins are applicable. Specifically, homopolymers of styrene such as polystyrene, polychlorostyrene, polyvinyltoluene and the like; and styrene / p-chlorostyrene copolymers, styrene / propylene copolymers, styrene / vinyltoluene copolymers, styrene / Vinyl naphthalene copolymer, styrene / methyl acrylate copolymer, styrene / ethyl acrylate copolymer, styrene / butyl acrylate copolymer, styrene / octyl acrylate copolymer, styrene / methyl methacrylate copolymer Styrene / ethyl methacrylate copolymer, styrene / butyl methacrylate copolymer, styrene / α-chloromethyl methacrylate copolymer, styrene / acrylonitrile copolymer, styrene / vinyl ethyl ether copolymer, styrene / Vinyl methyl ketone copolymer, steel Styrene copolymers such as ethylene / butadiene copolymer, styrene / isoprene copolymer, styrene / acrylonitrile / indene copolymer, styrene / maleic acid copolymer, styrene / maleic acid ester copolymer; polymethyl methacrylate , Polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyvinyl butyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic A group petroleum resin, chlorinated paraffin, paraffin wax and the like can be mentioned, and these are used alone or in admixture of two or more.

  Here, as the colorant of the toner, dyes and pigments capable of obtaining toners of each color of yellow, magenta, cyan, and black can be used, and all pigments and dyes that have been conventionally used as toner colorants can be applied. It is. Specifically, nigrosine dye, aniline blue, calco oil blue, dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, phthalocyanine green, Hansa Yellow G, rhodamine 6C lake, chrome yellow, quinacridone, benzidine yellow, malachite green, Examples include malachite green hexalate, rose bengal, monoazo dye / pigment, disazo dye / pigment, and trisazo dye / pigment. The amount of these colorants to be used is generally 1-30 wt%, preferably 3-20 wt%, relative to the binder resin.

As the toner charge control agent, either a positive charge control agent or a negative charge control agent can be used. In the case of a color toner, a transparent to white one that does not impair the color tone is used. Is preferred. For example, quaternary ammonium salts, imidazole metal complexes, salts, and the like are used as positive polarity, and salicylic acid complexes, salts, organic boron salts, calixarene compounds, and the like as negative polarity.
Further, in order to give the toner releasability, plant waxes such as candelilla wax, carnauba wax, rice wax, wax, jojoba oil, as well as synthetic waxes such as low molecular weight polyethylene and polypropylene; Animal waxes such as beeswax, lanolin and whale wax; mineral waxes such as montan wax and ozokerite; fat waxes such as hardened castor oil, hydroxystearic acid, fatty acid amide, phenol fatty acid ester, etc. These can be used alone or in admixture of two or more.

  In addition to the above release agents, the toner contains various plasticizers (dibutyl phthalate, dioctyl phthalate, etc.), resistance, and the like for the purpose of adjusting the thermal, electrical and physical properties of the toner as required. It is also possible to add auxiliaries such as adjusting agents (tin oxide, lead oxide, antimony oxide, etc.). Furthermore, fluidity-imparting agents other than the above releasing agents and auxiliaries can be mixed with the toner as necessary. Examples of the fluidity-imparting agent include silica fine particles, titanium oxide fine particles, aluminum oxide fine particles, magnesium fluoride fine particles, silicon carbide fine particles, boron carbide fine particles, titanium carbide fine particles, zirconium carbide fine particles, boron nitride fine particles, titanium nitride fine particles, nitriding. Zirconium fine particles, magnetite fine particles, molybdenum disulfide fine particles, aluminum stearate fine particles, magnesium stearate fine particles, zinc stearate fine particles, fluororesin fine particles, acrylic resin fine particles, etc., are used alone or in combination of two or more. Is possible. The fluidity-imparting agent preferably has a primary particle size of less than 0.1 μm and a hydrophobization degree of 40 or more whose surface is hydrophobized with a silane coupling agent or silicon oil.

  A known method is used as a method for producing the toner. For example, a binder resin, a colorant and a pigment, a charge control agent, and if necessary, a release agent and the like are sufficiently mixed using a mixing machine such as a Henschel mixer and a ball mill at an appropriate ratio. Then, melt-kneading is performed using a screw-type extrusion continuous kneader, a two-roll mill, a three-roll mill, or a pressure and heating kneader. In the case of a color toner, for the purpose of improving the dispersibility of the pigment, it is common to use, as a colorant, a master batch pigment obtained by previously melt-kneading a part of the binder resin and the pigment. The kneaded product obtained by the above method is cooled and solidified, and then coarsely pulverized using a pulverizer such as a hammer mill. Further, the coarsely pulverized product is pulverized with a jet mill pulverizer and then subjected to surface treatment using a rotor pulverizer connected to an airflow classifier or the like. For example, examples of the collision pulverizer include a hammer mill, a ball mill, a tube mill, and a vibration mill. I-type and IDS type collision type pulverizers (manufactured by Nippon Pneumatic Industry Co., Ltd.) are preferably used as jet type pulverizers having compressed air and collision plates as main components. Examples of the rotor pulverizer include a roll mill, a pin mill, and a fluidized bed jet mill. In particular, as a rotor type pulverizer having a fixed container as an outer wall and a rotating piece having the same central axis as that of the fixed container, turbo mills (manufactured by Turbo Kogyo Co., Ltd.), kryptron (manufactured by Kawasaki Heavy Industries, Ltd.) Fine mill (manufactured by Nippon Pneumatic Industry Co., Ltd.) can be used. As the connected classifier, a dispersion separator (DS) classifier (manufactured by Nippon Pneumatic Kogyo Co., Ltd.), a multi-division classifier (Elbow Jet; manufactured by Nittetsu Mining Co., Ltd.) or the like can be used. Furthermore, fine powder classification can be performed using an airflow classifier or a mechanical classifier to obtain fine particles.

Furthermore, when adding a fluidity imparting agent to the fine particles obtained by the above method, known equipment such as a Henschel mixer, a supermixer, or a ball mill can be used. Alternatively, a toner may be directly produced from a monomer, a colorant and a fluidity imparting agent by a suspension polymerization method or a non-aqueous dispersion polymerization method.
Next, another embodiment of the present invention will be described.

FIG. 3 is a view showing a configuration of a main part (process cartridge) of an image forming apparatus having a process cartridge according to the low potential process of the present invention.
In this figure, this process cartridge is an integrated image carrier 31, charging device 32, developing device 34 and cleaning device 39. This process cartridge is detachable from the main body of the image forming apparatus, and the developing device 34 having the same configuration as that of the above embodiment is employed.
In the image forming apparatus having this process cartridge, the photosensitive member 31 is rotationally driven at a predetermined peripheral speed. In the rotation process, the photosensitive member 31 is uniformly charged with a predetermined positive or negative potential on its peripheral surface by the charging unit 32, and then receives image exposure light from an image exposure unit such as slit exposure or laser beam scanning exposure. An electrostatic latent image is sequentially formed on the peripheral surface of the photoconductor, and the formed electrostatic latent image is developed with toner by the developing unit 34, and the developed toner image is supplied from a paper supply unit (not shown) to the photoconductor 31. The transfer unit sequentially transfers the transfer material fed between the transfer unit and the transfer unit so as to be synchronized with the rotation of the photosensitive member 31.

The transfer material that has received the image transfer is separated from the surface of the photosensitive member, introduced into an image fixing means (not shown), and fixed on the image, and printed out as a copy (copy). The surface of the photoconductor after the image transfer is cleaned by removing the transfer residual toner by the cleaning unit 39, and after being further neutralized, it is repeatedly used for image formation.
According to the present embodiment, the process cartridge can be detached independently, and the life of the photosensitive unit and the developing device is extended according to the present invention. However, the lengths may not always coincide with each other, and at that time, each can be easily separated. It is possible to exchange it. In addition, since it can be arranged independently, a simple mechanism can be added, so that the developing roller can be retracted from the photosensitive member during non-development, thereby reducing the promotion of toner filming on the developing roller. The life of the developing device can be extended.

FIG. 4 is a schematic diagram showing a developing roller according to the present invention.
In the image forming apparatus according to this embodiment, aluminum is used as the material of the developing sleeve of the developing device, and the surface of the developing sleeve has a wavy groove processed in the axial direction of the developer carrier as shown in FIG. Using. The wavy groove has a uniform groove width and groove pitch in the rotational direction. As a result, the developer can be carried uniformly and transported to the development area.
Further, in order to eliminate unevenness in the longitudinal direction of the developing roller, a continuous pattern is formed in the longitudinal direction.
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

* Production Example of Polymerized Toner 710 g of ion-exchanged water was charged with 450 g of a 0.1 M Na ₃ PO ₄ aqueous solution, heated to 60 ° C., and then 12000 rpm using a TK homomixer (manufactured by Special Machine Industries). Was stirred. To this, 68 g of 1.0 M CaCl ₂ aqueous solution was gradually added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .
(Toner component)
170g of styrene
30g of n-butyl acrylate
Quinacridone magenta pigment 10g
Di-t-butylsalicylic acid metal compound 2g
Polyester resin 10g

The above formulation was heated to 60 ° C., and uniformly dissolved and dispersed at 12000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). In this, 10 g of polymerization initiators 2,2′-azobis (2,4-dimethylvaleronitrile) were dissolved to prepare a polymerizable monomer composition. Then, the aqueous medium a polymerizable monomer composition was charged in, forming 60 ° C., under N ₂ atmosphere, stirred for 20 minutes at 10000rpm in a TK homomixer, a polymerizable monomer composition Grained. Then, while stirring with a paddle stirring blade, the temperature was raised to 80 ° C. and reacted for 10 hours. After completion of the polymerization reaction, a part of the aqueous medium is distilled off under reduced pressure and cooled, and after adding hydrochloric acid to dissolve calcium phosphate, filtration, washing and drying are performed, and the weight average particle size is 7 μm, 3 μm or less. Colored suspended particles with a ratio of 1% were obtained. To 20 kg of the fine particles, 100 g of hydrophobic silica fine particles having an average particle diameter of 0.3 μm and 100 g of hydrophobic titanium fine particles having an average particle diameter of 0.3 μm were added and mixed by stirring to obtain a magenta electrophotographic toner A. .

Main characteristics of toner A Dv = 7.0 μm
Dn = 6.5 μm
Dv / Dn = 1.077
Particle number ratio of 3 μm or less = 1%

Production Example of Carrier A A silicone resin (solid content: 5%) was prepared by diluting a silicone resin (SR2411, manufactured by Toledo Corning Silicone). Then, using a fluidized bed type coating apparatus, the silicone resin solution is applied at a rate of about 40 g / min in an atmosphere of 100 ° C. on each particle surface of the carrier core material particles (1), and further 240 ° C. And a carrier having a film thickness of 0.53 μm and a true specific gravity of 5.0 g / cm ³ was obtained. The film thickness was adjusted depending on the amount of the coating solution.

The machine conditions for a full-color printer are as follows.
Photoconductor linear velocity 205 [mm / sec]
Photoconductor diameter 40 [mm]
Sleeve / photoreceptor linear velocity ratio 1.98
Gp 0.3 [mm]
Gd (Developing roller-Doctor Gap) 0.33 [mm]
Developer pumping amount 50 [mg / cm ² ]
Roller diameter φ18 [mm]
Roller surface Wavy groove: See Table 1 Main pole angle 6 °
Main pole magnetic flux density 105 [mT]
Doctor opposite pole magnetic flux density 71 [mT]
Charging potential V0-520 [V]
Post-exposure potential VL-50 [V]
Development bias VB (DC component) -400 [V]
Development bias VB DC

In Table 1, the cross-sectional area is an average value of the groove cross-sectional area in the circumference of the developing sleeve.
An image was formed under the above conditions, and the roughness and dot reproducibility of the image were evaluated. Granularity is used as an evaluation standard representing the degree of roughness. Here, the measurement principle of granularity will be described. For measurement of granularity, an image in a halftone area is read by a scanner, and a patch of about 1 cm ² is prepared. A frequency filter representing human visual characteristics is applied to the power spectrum obtained by Fourier transforming this image, and the power spectrum obtained by extracting a portion that is conspicuous to human eyes is integrated. The numerical value obtained for each patch in this way is called granularity. In the present embodiment, the average value of the granularity of the patch in the portion where the lightness is particularly 40 to 80 is used. It can be said that the smaller the granularity, the better the image without the feeling of roughness.
Next, a method for analyzing the dynamic developer density viewed from the photosensitive drum side in the development region in the present embodiment will be described.

FIG. 5 is a schematic diagram of the state of the magnetic brush observed through the development area and the photoreceptor.
Here, the developing area is an area where the magnetic brush on the developing sleeve and the photosensitive drum are in contact with each other as shown in FIG.
In order to obtain the developer density of the magnetic brush viewed from the photosensitive drum side, the magnetic brush in the development region is observed using a visualization device shown below.
The visualizing device includes a transparent glass drum having a diameter of 60 mm as a substitute for the photosensitive member, and a developing sleeve is disposed at a position separated by a predetermined developing gap. The glass drum is cut into ¼ so that the tip of the magnetic brush in the developing area can be observed from the cut portion. At this time, the glass drum can move at an actual machine linear speed. Further, a transparent electrode was prepared on the surface of the glass drum so that the toner did not adhere due to frictional charging, and a non-image area potential was applied by an external power source. Further, a surface layer of an image carrier is coated on the outermost surface of the glass drum in order to make the coefficient of friction the same as that of an actual photoconductor. Further, in order to always observe the same portion of the photosensitive member, a mirror that rotates synchronously with the photosensitive member is provided at the center of the glass drum, and the developer behavior is observed through this mirror.

FIG. 6 is an explanatory diagram of the dynamic developer density calculation method of the present invention.
The tip of the magnetic brush observed with this visualization device was magnified with a stereomicroscope (Olympus SZ60) and photographed at 6000 FPS using a high-speed camera (Fastron MAXcam-120KC). From the captured moving image data, a moving image from the position where the developer starts to contact the photosensitive member is cut out as an original image (FIG. (A)), moving image processing software (Image Pro Plus) and image analysis software ( NI Vision Assistant) is used to perform binarization processing with an appropriate threshold that can distinguish between a region where the developer is in contact with the photosensitive member and a region where the developer is not in contact [FIG. At this time, a portion where the developer is present is represented by 1 (white), and a portion where the developer is not present is represented by 0 (black). The image obtained by extracting the green luminance value of the binarized original image [FIG. (C)] is multiplied [(d)]. In this way, it is possible to obtain a plurality of image processed images until the developer is separated from the position where the developer starts to contact the photosensitive member [(e) in FIG. These images are integrated to obtain a single image (figure (f)), and this image is subjected to two-dimensional FFT analysis to obtain a power spectrum (figure (g)). A power spectrum integrated value of 5 to 12 [cycle / mm] (frequency (h)) having a frequency of 600 dpi and 2 × 2 dots or less was used as a substitute value of the dynamic developer density. The smaller the power spectrum integrated value, the higher the dynamic developer density, that is, the smaller the area where the developer does not contact the photoreceptor. Also, less than 5 [cycle / mm] was excluded because the shooting area is small and low frequency is meaningless.

  Example 2 was performed in the same manner as in Example 1 except that the groove on the sleeve surface shape was changed as shown in Table 1, and Example 2 was obtained.

  In Example 1, except that the groove on the sleeve surface shape was changed as shown in Table 1, it was performed in the same manner as in Example 1 under the same conditions as Example 1, and Example 3 was obtained.

FIG. 7 is a power spectrum diagram showing the analysis result of Example 1.
FIG. 7 shows a power spectrum (PS) at a standard pumping amount of 50 [mg / cm ² ] and its upper and lower limits of 10 [mg / cm ² ] (that is, 40, 60 [mg / cm ² ]).

<Comparative Example 1>
In Example 1, except that the sleeve surface shape was changed to sand blast as shown in Table 1, it was performed in the same manner as in Example 1 under the same conditions as in Example 1, and was set as Comparative Example 1.

FIG. 8 is a power spectrum diagram showing the analysis result of Comparative Example 1.
The power spectrum at the standard pumping amount [50 mg / cm ² ] and its upper and lower limits 10 [mg / cm ² ] (that is, 40, 60 [mg / cm ² ]) is shown in FIG. Table 2 shows the difference between the maximum and minimum values of PS between the upper and lower limits of 10 [mg / cm ² ] with respect to the standard pumping amount obtained from the same figure, judgment of roughness after initial and 75K running, and dot reproducibility Results are shown. In addition, the quality of the rough feeling was determined by setting the granularity less than 0.31 to ◯ and 0.31 or more to x.
From this table, it can be said that the quality of the granularity is determined by the difference between the maximum value and the minimum value of PS, that is, the width is 0.11. If said width | variety is 0.11 or less, a rough feeling will not worsen.

FIG. 9 is a power spectrum integrated value diagram showing the analysis results of Example 1 and Comparative Example 1.
FIG. 9 shows the power spectrum integrated value of 5 to 12 [cycle / mm] in FIGS. The difference between the maximum value and the minimum value of PS in the example was 0.068, and that in the comparative example was 0.112.

1 is a schematic configuration diagram of an image forming apparatus to which the present invention can be applied. It is an expanded sectional view of the image formation part of this invention apparatus. It is a figure which shows the process cartridge which concerns on this invention. It is a schematic block diagram which shows the developing roller which concerns on this invention. It is a schematic diagram of the state of the magnetic brush observed through the development area and the photoconductor. It is explanatory drawing of the dynamic developer density calculation method of this invention. 2 is a power spectrum diagram showing the analysis result of Example 1. FIG. 6 is a power spectrum diagram showing an analysis result of Comparative Example 1. FIG. It is a figure of the power spectrum integrated value which shows the analysis result of Example 1 and Comparative Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roller 4 Developing means 16 Developing roller 17 Developer control member

Claims (8)

A developer carrier having a magnet inside is disposed opposite the image carrier, and a two-component developer containing toner and a magnetic carrier is carried on the surface of the developer carrier in a layered manner on the surface of the image carrier. In the developing method of developing the latent image formed on the toner with toner,
The diameter of the developer carrier is 15 to 20 mm, and the density of the developer that contacts the surface of the image carrier is integrated until one point of the image carrier contacts the two-component developer and leaves. The obtained image is subjected to two-dimensional FFT analysis, and the integrated value between 5 and 12 [cycle / mm] of the obtained power spectrum is set as PS, and the upper and lower limits are 10 [mg / cm ² ] with respect to the standard pumping amount. A developing method characterized in that a difference between a maximum value and a minimum value of PS is 0.11 or less.   2. The developing method according to claim 1, wherein a plurality of wavy grooves extending in the axial direction of the developer carrier are formed, and the groove width and groove pitch of the wavy grooves are uniform in the rotation direction. Development method.   3. The developing method according to claim 1, wherein the magnetic carrier is a carrier for an electrophotographic developer comprising magnetic core material particles and a resin layer covering the particle surface, wherein the carrier has a weight average. A developing method wherein the particle diameter Dw is 20 to 40 μm. 4. The developing method according to claim 1, wherein the magnetic carrier has a magnetic moment per carrier particle when a magnetic field of 1000 · (10 ³ / 4π) [A / m] is applied. 70 development wherein the at [a ^· m 2 / kg] or less.   A developer carrier that is disposed opposite to the image carrier and has a magnet inside, and this developer carrier carries a two-component developer including a toner and a magnetic carrier that holds the toner on the surface, A developing device that transports to a developing region, applies an electric field between a developer carrier and an image carrier, and develops a latent image formed on the surface of the image carrier with toner. A developing apparatus, wherein the developing is performed by the developing method according to any one of claims 1 to 4.   In a process cartridge in which an image carrier, a developing device, and either or both of a charging device and a cleaning device are integrated and detachably formed on the image forming apparatus main body, the developing device is defined in claim 5. A process cartridge according to claim 1.   An image carrier, a charging device that charges the surface of the image carrier, an exposure device that forms an electrostatic latent image by exposing the charged surface of the image carrier based on image information, and the image carrier. A developing device for supplying a developer to the electrostatic latent image to make it visible, a transfer device for transferring the obtained visible image to a recording medium, and collecting the developer remaining on the image carrier after image transfer An image forming apparatus having a cleaning device that performs the developing device, wherein the developing device is a developing device according to claim 5 or a developing device as a part of a process cartridge according to claim 6. .   8. The image forming apparatus according to claim 7, comprising a plurality of the developing devices or process cartridges.

Images